typedef bfd
bfd_get_reloc_upper_bound
bfd_canonicalize_reloc
bfd_set_reloc
bfd_set_file_flags
bfd_get_arch_size
bfd_get_sign_extend_vma
bfd_set_start_address
bfd_get_gp_size
bfd_set_gp_size
bfd_scan_vma
bfd_copy_private_header_data
bfd_copy_private_bfd_data
bfd_set_private_flags
Other functions
bfd_alt_mach_code
bfd_emul_get_maxpagesize
bfd_emul_get_commonpagesize
bfd_demangle
bfd_update_compression_header
bfd_check_compression_header
bfd_get_compression_header_size
bfd_convert_section_size
bfd_convert_section_contents
struct bfd_iovec
bfd_get_mtime
bfd_get_size
bfd_get_file_size
bfd_mmap
bfd_section_list_clear
bfd_get_section_by_name
bfd_get_next_section_by_name
bfd_get_linker_section
bfd_get_section_by_name_if
bfd_get_unique_section_name
bfd_make_section_old_way
bfd_make_section_anyway_with_flags
bfd_make_section_anyway
bfd_make_section_with_flags
bfd_make_section
bfd_set_section_flags
bfd_rename_section
bfd_map_over_sections
bfd_sections_find_if
bfd_set_section_size
bfd_set_section_contents
bfd_get_section_contents
bfd_malloc_and_get_section
bfd_copy_private_section_data
bfd_generic_is_group_section
bfd_generic_group_name
bfd_generic_discard_group
bfd_get_symtab_upper_bound
bfd_is_local_label
bfd_is_local_label_name
bfd_is_target_special_symbol
bfd_canonicalize_symtab
bfd_set_symtab
bfd_print_symbol_vandf
bfd_make_empty_symbol
_bfd_generic_make_empty_symbol
bfd_make_debug_symbol
bfd_decode_symclass
bfd_is_undefined_symclass
bfd_symbol_info
bfd_copy_private_symbol_data
bfd_reloc_code_type
bfd_reloc_type_lookup
bfd_default_reloc_type_lookup
bfd_get_reloc_code_name
bfd_generic_relax_section
bfd_generic_gc_sections
bfd_generic_lookup_section_flags
bfd_generic_merge_sections
bfd_generic_get_relocated_section_contents
_bfd_generic_set_reloc
_bfd_unrecognized_reloc
bfd_printable_name
bfd_scan_arch
bfd_arch_list
bfd_arch_get_compatible
bfd_default_arch_struct
bfd_set_arch_info
bfd_default_set_arch_mach
bfd_get_arch
bfd_get_mach
bfd_arch_bits_per_byte
bfd_arch_bits_per_address
bfd_default_compatible
bfd_default_scan
bfd_get_arch_info
bfd_lookup_arch
bfd_printable_arch_mach
bfd_octets_per_byte
bfd_arch_mach_octets_per_byte
bfd_arch_default_fill
bfd_fopen
bfd_openr
bfd_fdopenr
bfd_fdopenw
bfd_openstreamr
bfd_openr_iovec
bfd_openw
bfd_close
bfd_close_all_done
bfd_create
bfd_make_writable
bfd_make_readable
bfd_alloc
bfd_zalloc
bfd_calc_gnu_debuglink_crc32
bfd_get_debug_link_info_1
bfd_get_debug_link_info
bfd_get_alt_debug_link_info
separate_debug_file_exists
separate_alt_debug_file_exists
find_separate_debug_file
bfd_follow_gnu_debuglink
bfd_follow_gnu_debugaltlink
bfd_create_gnu_debuglink_section
bfd_fill_in_gnu_debuglink_section
get_build_id
get_build_id_name
check_build_id_file
bfd_follow_build_id_debuglink
bfd_set_filename
bfd_link_split_section
bfd_section_already_linked
bfd_generic_define_common_symbol
_bfd_generic_link_hide_symbol
bfd_generic_define_start_stop
bfd_find_version_for_sym
bfd_hide_sym_by_version
bfd_link_check_relocs
_bfd_generic_link_check_relocs
bfd_merge_private_bfd_data
_bfd_generic_verify_endian_match
• Overview | Overview of BFD | |
• BFD front end | BFD front end | |
• BFD back ends | BFD back ends | |
• GNU Free Documentation License | GNU Free Documentation License | |
• BFD Index | BFD Index |
Next: BFD front end, Previous: Top, Up: Top [Contents][Index]
BFD is a package which allows applications to use the same routines to operate on object files whatever the object file format. A new object file format can be supported simply by creating a new BFD back end and adding it to the library.
BFD is split into two parts: the front end, and the back ends (one for each object file format).
• History | History | |
• How It Works | How It Works | |
• What BFD Version 2 Can Do | What BFD Version 2 Can Do |
Next: How It Works, Previous: Overview, Up: Overview [Contents][Index]
One spur behind BFD was the desire, on the part of the GNU 960 team at Intel Oregon, for interoperability of applications on their COFF and b.out file formats. Cygnus was providing GNU support for the team, and was contracted to provide the required functionality.
The name came from a conversation David Wallace was having with Richard Stallman about the library: RMS said that it would be quite hard—David said “BFD”. Stallman was right, but the name stuck.
At the same time, Ready Systems wanted much the same thing, but for different object file formats: IEEE-695, Oasys, Srecords, a.out and 68k coff.
BFD was first implemented by members of Cygnus Support; Steve
Chamberlain (sac@cygnus.com
), John Gilmore
(gnu@cygnus.com
), K. Richard Pixley (rich@cygnus.com
)
and David Henkel-Wallace (gumby@cygnus.com
).
Next: What BFD Version 2 Can Do, Previous: History, Up: Overview [Contents][Index]
To use the library, include bfd.h and link with libbfd.a.
BFD provides a common interface to the parts of an object file for a calling application.
When an application successfully opens a target file (object, archive, or
whatever), a pointer to an internal structure is returned. This pointer
points to a structure called bfd
, described in
bfd.h. Our convention is to call this pointer a BFD, and
instances of it within code abfd
. All operations on
the target object file are applied as methods to the BFD. The mapping is
defined within bfd.h
in a set of macros, all beginning
with ‘bfd_’ to reduce namespace pollution.
For example, this sequence does what you would probably expect:
return the number of sections in an object file attached to a BFD
abfd
.
#include "bfd.h" unsigned int number_of_sections (abfd) bfd *abfd; { return bfd_count_sections (abfd); }
The abstraction used within BFD is that an object file has:
Also, BFDs opened for archives have the additional attribute of an index and contain subordinate BFDs. This approach is fine for a.out and coff, but loses efficiency when applied to formats such as S-records and IEEE-695.
Previous: How It Works, Up: Overview [Contents][Index]
When an object file is opened, BFD subroutines automatically determine the format of the input object file. They then build a descriptor in memory with pointers to routines that will be used to access elements of the object file’s data structures.
As different information from the object files is required, BFD reads from different sections of the file and processes them. For example, a very common operation for the linker is processing symbol tables. Each BFD back end provides a routine for converting between the object file’s representation of symbols and an internal canonical format. When the linker asks for the symbol table of an object file, it calls through a memory pointer to the routine from the relevant BFD back end which reads and converts the table into a canonical form. The linker then operates upon the canonical form. When the link is finished and the linker writes the output file’s symbol table, another BFD back end routine is called to take the newly created symbol table and convert it into the chosen output format.
• BFD information loss | Information Loss | |
• Canonical format | The BFD canonical object-file format |
Next: Canonical format, Up: What BFD Version 2 Can Do [Contents][Index]
Information can be lost during output. The output formats
supported by BFD do not provide identical facilities, and
information which can be described in one form has nowhere to go in
another format. One example of this is alignment information in
b.out
. There is nowhere in an a.out
format file to store
alignment information on the contained data, so when a file is linked
from b.out
and an a.out
image is produced, alignment
information will not propagate to the output file. (The linker will
still use the alignment information internally, so the link is performed
correctly).
Another example is COFF section names. COFF files may contain an
unlimited number of sections, each one with a textual section name. If
the target of the link is a format which does not have many sections (e.g.,
a.out
) or has sections without names (e.g., the Oasys format), the
link cannot be done simply. You can circumvent this problem by
describing the desired input-to-output section mapping with the linker command
language.
Information can be lost during canonicalization. The BFD internal canonical form of the external formats is not exhaustive; there are structures in input formats for which there is no direct representation internally. This means that the BFD back ends cannot maintain all possible data richness through the transformation between external to internal and back to external formats.
This limitation is only a problem when an application reads one
format and writes another. Each BFD back end is responsible for
maintaining as much data as possible, and the internal BFD
canonical form has structures which are opaque to the BFD core,
and exported only to the back ends. When a file is read in one format,
the canonical form is generated for BFD and the application. At the
same time, the back end saves away any information which may otherwise
be lost. If the data is then written back in the same format, the back
end routine will be able to use the canonical form provided by the
BFD core as well as the information it prepared earlier. Since
there is a great deal of commonality between back ends,
there is no information lost when
linking or copying big endian COFF to little endian COFF, or a.out
to
b.out
. When a mixture of formats is linked, the information is
only lost from the files whose format differs from the destination.
Previous: BFD information loss, Up: What BFD Version 2 Can Do [Contents][Index]
The greatest potential for loss of information occurs when there is the least overlap between the information provided by the source format, that stored by the canonical format, and that needed by the destination format. A brief description of the canonical form may help you understand which kinds of data you can count on preserving across conversions.
Information stored on a per-file basis includes target machine
architecture, particular implementation format type, a demand pageable
bit, and a write protected bit. Information like Unix magic numbers is
not stored here—only the magic numbers’ meaning, so a ZMAGIC
file would have both the demand pageable bit and the write protected
text bit set. The byte order of the target is stored on a per-file
basis, so that big- and little-endian object files may be used with one
another.
Each section in the input file contains the name of the section, the section’s original address in the object file, size and alignment information, various flags, and pointers into other BFD data structures.
Each symbol contains a pointer to the information for the object file
which originally defined it, its name, its value, and various flag
bits. When a BFD back end reads in a symbol table, it relocates all
symbols to make them relative to the base of the section where they were
defined. Doing this ensures that each symbol points to its containing
section. Each symbol also has a varying amount of hidden private data
for the BFD back end. Since the symbol points to the original file, the
private data format for that symbol is accessible. ld
can
operate on a collection of symbols of wildly different formats without
problems.
Normal global and simple local symbols are maintained on output, so an
output file (no matter its format) will retain symbols pointing to
functions and to global, static, and common variables. Some symbol
information is not worth retaining; in a.out
, type information is
stored in the symbol table as long symbol names. This information would
be useless to most COFF debuggers; the linker has command-line switches
to allow users to throw it away.
There is one word of type information within the symbol, so if the format supports symbol type information within symbols (for example, COFF, Oasys) and the type is simple enough to fit within one word (nearly everything but aggregates), the information will be preserved.
Each canonical BFD relocation record contains a pointer to the symbol to relocate to, the offset of the data to relocate, the section the data is in, and a pointer to a relocation type descriptor. Relocation is performed by passing messages through the relocation type descriptor and the symbol pointer. Therefore, relocations can be performed on output data using a relocation method that is only available in one of the input formats. For instance, Oasys provides a byte relocation format. A relocation record requesting this relocation type would point indirectly to a routine to perform this, so the relocation may be performed on a byte being written to a 68k COFF file, even though 68k COFF has no such relocation type.
Object formats can contain, for debugging purposes, some form of mapping between symbols, source line numbers, and addresses in the output file. These addresses have to be relocated along with the symbol information. Each symbol with an associated list of line number records points to the first record of the list. The head of a line number list consists of a pointer to the symbol, which allows finding out the address of the function whose line number is being described. The rest of the list is made up of pairs: offsets into the section and line numbers. Any format which can simply derive this information can pass it successfully between formats.
Next: BFD back ends, Previous: Overview, Up: Top [Contents][Index]
• typedef bfd | ||
• Error reporting | ||
• Miscellaneous | ||
• Memory Usage | ||
• Initialization | ||
• Sections | ||
• Symbols | ||
• Archives | ||
• Formats | ||
• Relocations | ||
• Core Files | ||
• Targets | ||
• Architectures | ||
• Opening and Closing | ||
• Internal | ||
• File Caching | ||
• Linker Functions | ||
• Hash Tables |
Next: Error reporting, Previous: BFD front end, Up: BFD front end [Contents][Index]
typedef bfd
A BFD has type bfd
; objects of this type are the
cornerstone of any application using BFD. Using BFD
consists of making references though the BFD and to data in the BFD.
Here is the structure that defines the type bfd
. It
contains the major data about the file and pointers
to the rest of the data.
enum bfd_direction { no_direction = 0, read_direction = 1, write_direction = 2, both_direction = 3 }; enum bfd_plugin_format { bfd_plugin_unknown = 0, bfd_plugin_yes = 1, bfd_plugin_no = 2 }; struct bfd_build_id { bfd_size_type size; bfd_byte data[1]; }; struct bfd { /* The filename the application opened the BFD with. */ const char *filename; /* A pointer to the target jump table. */ const struct bfd_target *xvec; /* The IOSTREAM, and corresponding IO vector that provide access to the file backing the BFD. */ void *iostream; const struct bfd_iovec *iovec; /* The caching routines use these to maintain a least-recently-used list of BFDs. */ struct bfd *lru_prev, *lru_next; /* Track current file position (or current buffer offset for in-memory BFDs). When a file is closed by the caching routines, BFD retains state information on the file here. */ ufile_ptr where; /* File modified time, if mtime_set is TRUE. */ long mtime; /* A unique identifier of the BFD */ unsigned int id; /* Format_specific flags. */ flagword flags; /* Values that may appear in the flags field of a BFD. These also appear in the object_flags field of the bfd_target structure, where they indicate the set of flags used by that backend (not all flags are meaningful for all object file formats) (FIXME: at the moment, the object_flags values have mostly just been copied from backend to another, and are not necessarily correct). */ #define BFD_NO_FLAGS 0x0 /* BFD contains relocation entries. */ #define HAS_RELOC 0x1 /* BFD is directly executable. */ #define EXEC_P 0x2 /* BFD has line number information (basically used for F_LNNO in a COFF header). */ #define HAS_LINENO 0x4 /* BFD has debugging information. */ #define HAS_DEBUG 0x08 /* BFD has symbols. */ #define HAS_SYMS 0x10 /* BFD has local symbols (basically used for F_LSYMS in a COFF header). */ #define HAS_LOCALS 0x20 /* BFD is a dynamic object. */ #define DYNAMIC 0x40 /* Text section is write protected (if D_PAGED is not set, this is like an a.out NMAGIC file) (the linker sets this by default, but clears it for -r or -N). */ #define WP_TEXT 0x80 /* BFD is dynamically paged (this is like an a.out ZMAGIC file) (the linker sets this by default, but clears it for -r or -n or -N). */ #define D_PAGED 0x100 /* BFD is relaxable (this means that bfd_relax_section may be able to do something) (sometimes bfd_relax_section can do something even if this is not set). */ #define BFD_IS_RELAXABLE 0x200 /* This may be set before writing out a BFD to request using a traditional format. For example, this is used to request that when writing out an a.out object the symbols not be hashed to eliminate duplicates. */ #define BFD_TRADITIONAL_FORMAT 0x400 /* This flag indicates that the BFD contents are actually cached in memory. If this is set, iostream points to a bfd_in_memory struct. */ #define BFD_IN_MEMORY 0x800 /* This BFD has been created by the linker and doesn't correspond to any input file. */ #define BFD_LINKER_CREATED 0x1000 /* This may be set before writing out a BFD to request that it be written using values for UIDs, GIDs, timestamps, etc. that will be consistent from run to run. */ #define BFD_DETERMINISTIC_OUTPUT 0x2000 /* Compress sections in this BFD. */ #define BFD_COMPRESS 0x4000 /* Decompress sections in this BFD. */ #define BFD_DECOMPRESS 0x8000 /* BFD is a dummy, for plugins. */ #define BFD_PLUGIN 0x10000 /* Compress sections in this BFD with SHF_COMPRESSED from gABI. */ #define BFD_COMPRESS_GABI 0x20000 /* Convert ELF common symbol type to STT_COMMON or STT_OBJECT in this BFD. */ #define BFD_CONVERT_ELF_COMMON 0x40000 /* Use the ELF STT_COMMON type in this BFD. */ #define BFD_USE_ELF_STT_COMMON 0x80000 /* Put pathnames into archives (non-POSIX). */ #define BFD_ARCHIVE_FULL_PATH 0x100000 /* Flags bits to be saved in bfd_preserve_save. */ #define BFD_FLAGS_SAVED \ (BFD_IN_MEMORY | BFD_COMPRESS | BFD_DECOMPRESS | BFD_LINKER_CREATED \ | BFD_PLUGIN | BFD_COMPRESS_GABI | BFD_CONVERT_ELF_COMMON \ | BFD_USE_ELF_STT_COMMON) /* Flags bits which are for BFD use only. */ #define BFD_FLAGS_FOR_BFD_USE_MASK \ (BFD_IN_MEMORY | BFD_COMPRESS | BFD_DECOMPRESS | BFD_LINKER_CREATED \ | BFD_PLUGIN | BFD_TRADITIONAL_FORMAT | BFD_DETERMINISTIC_OUTPUT \ | BFD_COMPRESS_GABI | BFD_CONVERT_ELF_COMMON | BFD_USE_ELF_STT_COMMON) /* The format which belongs to the BFD. (object, core, etc.) */ ENUM_BITFIELD (bfd_format) format : 3; /* The direction with which the BFD was opened. */ ENUM_BITFIELD (bfd_direction) direction : 2; /* Is the file descriptor being cached? That is, can it be closed as needed, and re-opened when accessed later? */ unsigned int cacheable : 1; /* Marks whether there was a default target specified when the BFD was opened. This is used to select which matching algorithm to use to choose the back end. */ unsigned int target_defaulted : 1; /* ... and here: (``once'' means at least once). */ unsigned int opened_once : 1; /* Set if we have a locally maintained mtime value, rather than getting it from the file each time. */ unsigned int mtime_set : 1; /* Flag set if symbols from this BFD should not be exported. */ unsigned int no_export : 1; /* Remember when output has begun, to stop strange things from happening. */ unsigned int output_has_begun : 1; /* Have archive map. */ unsigned int has_armap : 1; /* Set if this is a thin archive. */ unsigned int is_thin_archive : 1; /* Set if this archive should not cache element positions. */ unsigned int no_element_cache : 1; /* Set if only required symbols should be added in the link hash table for this object. Used by VMS linkers. */ unsigned int selective_search : 1; /* Set if this is the linker output BFD. */ unsigned int is_linker_output : 1; /* Set if this is the linker input BFD. */ unsigned int is_linker_input : 1; /* If this is an input for a compiler plug-in library. */ ENUM_BITFIELD (bfd_plugin_format) plugin_format : 2; /* Set if this is a plugin output file. */ unsigned int lto_output : 1; /* Set if this is a slim LTO object not loaded with a compiler plugin. */ unsigned int lto_slim_object : 1; /* Do not attempt to modify this file. Set when detecting errors that BFD is not prepared to handle for objcopy/strip. */ unsigned int read_only : 1; /* Set to dummy BFD created when claimed by a compiler plug-in library. */ bfd *plugin_dummy_bfd; /* The offset of this bfd in the file, typically 0 if it is not contained in an archive. */ ufile_ptr origin; /* The origin in the archive of the proxy entry. This will normally be the same as origin, except for thin archives, when it will contain the current offset of the proxy in the thin archive rather than the offset of the bfd in its actual container. */ ufile_ptr proxy_origin; /* A hash table for section names. */ struct bfd_hash_table section_htab; /* Pointer to linked list of sections. */ struct bfd_section *sections; /* The last section on the section list. */ struct bfd_section *section_last; /* The number of sections. */ unsigned int section_count; /* The archive plugin file descriptor. */ int archive_plugin_fd; /* The number of opens on the archive plugin file descriptor. */ unsigned int archive_plugin_fd_open_count; /* A field used by _bfd_generic_link_add_archive_symbols. This will be used only for archive elements. */ int archive_pass; /* Stuff only useful for object files: The start address. */ bfd_vma start_address; /* Symbol table for output BFD (with symcount entries). Also used by the linker to cache input BFD symbols. */ struct bfd_symbol **outsymbols; /* Used for input and output. */ unsigned int symcount; /* Used for slurped dynamic symbol tables. */ unsigned int dynsymcount; /* Pointer to structure which contains architecture information. */ const struct bfd_arch_info *arch_info; /* Cached length of file for bfd_get_size. 0 until bfd_get_size is called, 1 if stat returns an error or the file size is too large to return in ufile_ptr. Both 0 and 1 should be treated as "unknown". */ ufile_ptr size; /* Stuff only useful for archives. */ void *arelt_data; struct bfd *my_archive; /* The containing archive BFD. */ struct bfd *archive_next; /* The next BFD in the archive. */ struct bfd *archive_head; /* The first BFD in the archive. */ struct bfd *nested_archives; /* List of nested archive in a flattened thin archive. */ union { /* For input BFDs, a chain of BFDs involved in a link. */ struct bfd *next; /* For output BFD, the linker hash table. */ struct bfd_link_hash_table *hash; } link; /* Used by the back end to hold private data. */ union { struct aout_data_struct *aout_data; struct artdata *aout_ar_data; struct coff_tdata *coff_obj_data; struct pe_tdata *pe_obj_data; struct xcoff_tdata *xcoff_obj_data; struct ecoff_tdata *ecoff_obj_data; struct srec_data_struct *srec_data; struct verilog_data_struct *verilog_data; struct ihex_data_struct *ihex_data; struct tekhex_data_struct *tekhex_data; struct elf_obj_tdata *elf_obj_data; struct mmo_data_struct *mmo_data; struct sun_core_struct *sun_core_data; struct sco5_core_struct *sco5_core_data; struct trad_core_struct *trad_core_data; struct som_data_struct *som_data; struct hpux_core_struct *hpux_core_data; struct hppabsd_core_struct *hppabsd_core_data; struct sgi_core_struct *sgi_core_data; struct lynx_core_struct *lynx_core_data; struct osf_core_struct *osf_core_data; struct cisco_core_struct *cisco_core_data; struct versados_data_struct *versados_data; struct netbsd_core_struct *netbsd_core_data; struct mach_o_data_struct *mach_o_data; struct mach_o_fat_data_struct *mach_o_fat_data; struct plugin_data_struct *plugin_data; struct bfd_pef_data_struct *pef_data; struct bfd_pef_xlib_data_struct *pef_xlib_data; struct bfd_sym_data_struct *sym_data; void *any; } tdata; /* Used by the application to hold private data. */ void *usrdata; /* Where all the allocated stuff under this BFD goes. This is a struct objalloc *, but we use void * to avoid requiring the inclusion of objalloc.h. */ void *memory; /* For input BFDs, the build ID, if the object has one. */ const struct bfd_build_id *build_id; }; static inline const char * bfd_get_filename (const bfd *abfd) { return abfd->filename; } static inline bool bfd_get_cacheable (const bfd *abfd) { return abfd->cacheable; } static inline enum bfd_format bfd_get_format (const bfd *abfd) { return abfd->format; } static inline flagword bfd_get_file_flags (const bfd *abfd) { return abfd->flags; } static inline bfd_vma bfd_get_start_address (const bfd *abfd) { return abfd->start_address; } static inline unsigned int bfd_get_symcount (const bfd *abfd) { return abfd->symcount; } static inline unsigned int bfd_get_dynamic_symcount (const bfd *abfd) { return abfd->dynsymcount; } static inline struct bfd_symbol ** bfd_get_outsymbols (const bfd *abfd) { return abfd->outsymbols; } static inline unsigned int bfd_count_sections (const bfd *abfd) { return abfd->section_count; } static inline bool bfd_has_map (const bfd *abfd) { return abfd->has_armap; } static inline bool bfd_is_thin_archive (const bfd *abfd) { return abfd->is_thin_archive; } static inline void * bfd_usrdata (const bfd *abfd) { return abfd->usrdata; } /* See note beside bfd_set_section_userdata. */ static inline bool bfd_set_cacheable (bfd * abfd, bool val) { abfd->cacheable = val; return true; } static inline void bfd_set_thin_archive (bfd *abfd, bool val) { abfd->is_thin_archive = val; } static inline void bfd_set_usrdata (bfd *abfd, void *val) { abfd->usrdata = val; } static inline asection * bfd_asymbol_section (const asymbol *sy) { return sy->section; } static inline bfd_vma bfd_asymbol_value (const asymbol *sy) { return sy->section->vma + sy->value; } static inline const char * bfd_asymbol_name (const asymbol *sy) { return sy->name; } static inline struct bfd * bfd_asymbol_bfd (const asymbol *sy) { return sy->the_bfd; } static inline void bfd_set_asymbol_name (asymbol *sy, const char *name) { sy->name = name; } static inline bfd_size_type bfd_get_section_limit_octets (const bfd *abfd, const asection *sec) { if (abfd->direction != write_direction && sec->rawsize != 0) return sec->rawsize; return sec->size; } /* Find the address one past the end of SEC. */ static inline bfd_size_type bfd_get_section_limit (const bfd *abfd, const asection *sec) { return (bfd_get_section_limit_octets (abfd, sec) / bfd_octets_per_byte (abfd, sec)); } /* Functions to handle insertion and deletion of a bfd's sections. These only handle the list pointers, ie. do not adjust section_count, target_index etc. */ static inline void bfd_section_list_remove (bfd *abfd, asection *s) { asection *next = s->next; asection *prev = s->prev; if (prev) prev->next = next; else abfd->sections = next; if (next) next->prev = prev; else abfd->section_last = prev; } static inline void bfd_section_list_append (bfd *abfd, asection *s) { s->next = 0; if (abfd->section_last) { s->prev = abfd->section_last; abfd->section_last->next = s; } else { s->prev = 0; abfd->sections = s; } abfd->section_last = s; } static inline void bfd_section_list_prepend (bfd *abfd, asection *s) { s->prev = 0; if (abfd->sections) { s->next = abfd->sections; abfd->sections->prev = s; } else { s->next = 0; abfd->section_last = s; } abfd->sections = s; } static inline void bfd_section_list_insert_after (bfd *abfd, asection *a, asection *s) { asection *next = a->next; s->next = next; s->prev = a; a->next = s; if (next) next->prev = s; else abfd->section_last = s; } static inline void bfd_section_list_insert_before (bfd *abfd, asection *b, asection *s) { asection *prev = b->prev; s->prev = prev; s->next = b; b->prev = s; if (prev) prev->next = s; else abfd->sections = s; } static inline bool bfd_section_removed_from_list (const bfd *abfd, const asection *s) { return s->next ? s->next->prev != s : abfd->section_last != s; }
Next: Miscellaneous, Previous: typedef bfd, Up: BFD front end [Contents][Index]
Most BFD functions return nonzero on success (check their
individual documentation for precise semantics). On an error,
they call bfd_set_error
to set an error condition that callers
can check by calling bfd_get_error
.
If that returns bfd_error_system_call
, then check
errno
.
The easiest way to report a BFD error to the user is to
use bfd_perror
.
bfd_error_type
The values returned by bfd_get_error
are defined by the
enumerated type bfd_error_type
.
typedef enum bfd_error { bfd_error_no_error = 0, bfd_error_system_call, bfd_error_invalid_target, bfd_error_wrong_format, bfd_error_wrong_object_format, bfd_error_invalid_operation, bfd_error_no_memory, bfd_error_no_symbols, bfd_error_no_armap, bfd_error_no_more_archived_files, bfd_error_malformed_archive, bfd_error_missing_dso, bfd_error_file_not_recognized, bfd_error_file_ambiguously_recognized, bfd_error_no_contents, bfd_error_nonrepresentable_section, bfd_error_no_debug_section, bfd_error_bad_value, bfd_error_file_truncated, bfd_error_file_too_big, bfd_error_sorry, bfd_error_on_input, bfd_error_invalid_error_code } bfd_error_type;
bfd_get_error
Synopsis
bfd_error_type bfd_get_error (void);
Description
Return the current BFD error condition.
bfd_set_error
Synopsis
void bfd_set_error (bfd_error_type error_tag);
Description
Set the BFD error condition to be error_tag.
error_tag must not be bfd_error_on_input. Use bfd_set_input_error for input errors instead.
bfd_set_input_error
Synopsis
void bfd_set_input_error (bfd *input, bfd_error_type error_tag);
Description
Set the BFD error condition to be bfd_error_on_input.
input is the input bfd where the error occurred, and
error_tag the bfd_error_type error.
bfd_errmsg
Synopsis
const char *bfd_errmsg (bfd_error_type error_tag);
Description
Return a string describing the error error_tag, or
the system error if error_tag is bfd_error_system_call
.
bfd_perror
Synopsis
void bfd_perror (const char *message);
Description
Print to the standard error stream a string describing the
last BFD error that occurred, or the last system error if
the last BFD error was a system call failure. If message
is non-NULL and non-empty, the error string printed is preceded
by message, a colon, and a space. It is followed by a newline.
Some BFD functions want to print messages describing the problem. They call a BFD error handler function. This function may be overridden by the program.
The BFD error handler acts like vprintf.
typedef void (*bfd_error_handler_type) (const char *, va_list);
_bfd_error_handler
Synopsis
void _bfd_error_handler (const char *fmt, ...) ATTRIBUTE_PRINTF_1;
Description
This is the default routine to handle BFD error messages.
Like fprintf (stderr, ...), but also handles some extra format
specifiers.
%pA section name from section. For group components, prints group name too. %pB file name from bfd. For archive components, prints archive too.
Beware: Only supports a maximum of 9 format arguments.
bfd_set_error_handler
Synopsis
bfd_error_handler_type bfd_set_error_handler (bfd_error_handler_type);
Description
Set the BFD error handler function. Returns the previous
function.
bfd_set_error_program_name
Synopsis
void bfd_set_error_program_name (const char *);
Description
Set the program name to use when printing a BFD error. This
is printed before the error message followed by a colon and
space. The string must not be changed after it is passed to
this function.
If BFD finds an internal inconsistency, the bfd assert handler is called with information on the BFD version, BFD source file and line. If this happens, most programs linked against BFD are expected to want to exit with an error, or mark the current BFD operation as failed, so it is recommended to override the default handler, which just calls _bfd_error_handler and continues.
typedef void (*bfd_assert_handler_type) (const char *bfd_formatmsg, const char *bfd_version, const char *bfd_file, int bfd_line);
bfd_set_assert_handler
Synopsis
bfd_assert_handler_type bfd_set_assert_handler (bfd_assert_handler_type);
Description
Set the BFD assert handler function. Returns the previous
function.
Next: Memory Usage, Previous: Error reporting, Up: BFD front end [Contents][Index]
bfd_get_reloc_upper_bound
Synopsis
long bfd_get_reloc_upper_bound (bfd *abfd, asection *sect);
Description
Return the number of bytes required to store the
relocation information associated with section sect
attached to bfd abfd. If an error occurs, return -1.
bfd_canonicalize_reloc
Synopsis
long bfd_canonicalize_reloc (bfd *abfd, asection *sec, arelent **loc, asymbol **syms);
Description
Call the back end associated with the open BFD
abfd and translate the external form of the relocation
information attached to sec into the internal canonical
form. Place the table into memory at loc, which has
been preallocated, usually by a call to
bfd_get_reloc_upper_bound
. Returns the number of relocs, or
-1 on error.
The syms table is also needed for horrible internal magic reasons.
bfd_set_reloc
Synopsis
void bfd_set_reloc (bfd *abfd, asection *sec, arelent **rel, unsigned int count);
Description
Set the relocation pointer and count within
section sec to the values rel and count.
The argument abfd is ignored.
#define bfd_set_reloc(abfd, asect, location, count) \ BFD_SEND (abfd, _bfd_set_reloc, (abfd, asect, location, count))
bfd_set_file_flags
Synopsis
bool bfd_set_file_flags (bfd *abfd, flagword flags);
Description
Set the flag word in the BFD abfd to the value flags.
Possible errors are:
bfd_error_wrong_format
- The target bfd was not of object format.
bfd_error_invalid_operation
- The target bfd was open for reading.
bfd_error_invalid_operation
-
The flag word contained a bit which was not applicable to the
type of file. E.g., an attempt was made to set the D_PAGED
bit
on a BFD format which does not support demand paging.
bfd_get_arch_size
Synopsis
int bfd_get_arch_size (bfd *abfd);
Description
Returns the normalized architecture address size, in bits, as
determined by the object file’s format. By normalized, we mean
either 32 or 64. For ELF, this information is included in the
header. Use bfd_arch_bits_per_address for number of bits in
the architecture address.
Returns
Returns the arch size in bits if known, -1
otherwise.
bfd_get_sign_extend_vma
Synopsis
int bfd_get_sign_extend_vma (bfd *abfd);
Description
Indicates if the target architecture "naturally" sign extends
an address. Some architectures implicitly sign extend address
values when they are converted to types larger than the size
of an address. For instance, bfd_get_start_address() will
return an address sign extended to fill a bfd_vma when this is
the case.
Returns
Returns 1
if the target architecture is known to sign
extend addresses, 0
if the target architecture is known to
not sign extend addresses, and -1
otherwise.
bfd_set_start_address
Synopsis
bool bfd_set_start_address (bfd *abfd, bfd_vma vma);
Description
Make vma the entry point of output BFD abfd.
Returns
Returns TRUE
on success, FALSE
otherwise.
bfd_get_gp_size
Synopsis
unsigned int bfd_get_gp_size (bfd *abfd);
Description
Return the maximum size of objects to be optimized using the GP
register under MIPS ECOFF. This is typically set by the -G
argument to the compiler, assembler or linker.
bfd_set_gp_size
Synopsis
void bfd_set_gp_size (bfd *abfd, unsigned int i);
Description
Set the maximum size of objects to be optimized using the GP
register under ECOFF or MIPS ELF. This is typically set by
the -G
argument to the compiler, assembler or linker.
bfd_scan_vma
Synopsis
bfd_vma bfd_scan_vma (const char *string, const char **end, int base);
Description
Convert, like strtoul
, a numerical expression
string into a bfd_vma
integer, and return that integer.
(Though without as many bells and whistles as strtoul
.)
The expression is assumed to be unsigned (i.e., positive).
If given a base, it is used as the base for conversion.
A base of 0 causes the function to interpret the string
in hex if a leading "0x" or "0X" is found, otherwise
in octal if a leading zero is found, otherwise in decimal.
If the value would overflow, the maximum bfd_vma
value is
returned.
bfd_copy_private_header_data
Synopsis
bool bfd_copy_private_header_data (bfd *ibfd, bfd *obfd);
Description
Copy private BFD header information from the BFD ibfd to the
the BFD obfd. This copies information that may require
sections to exist, but does not require symbol tables. Return
true
on success, false
on error.
Possible error returns are:
bfd_error_no_memory
-
Not enough memory exists to create private data for obfd.
#define bfd_copy_private_header_data(ibfd, obfd) \ BFD_SEND (obfd, _bfd_copy_private_header_data, \ (ibfd, obfd))
bfd_copy_private_bfd_data
Synopsis
bool bfd_copy_private_bfd_data (bfd *ibfd, bfd *obfd);
Description
Copy private BFD information from the BFD ibfd to the
the BFD obfd. Return TRUE
on success, FALSE
on error.
Possible error returns are:
bfd_error_no_memory
-
Not enough memory exists to create private data for obfd.
#define bfd_copy_private_bfd_data(ibfd, obfd) \ BFD_SEND (obfd, _bfd_copy_private_bfd_data, \ (ibfd, obfd))
bfd_set_private_flags
Synopsis
bool bfd_set_private_flags (bfd *abfd, flagword flags);
Description
Set private BFD flag information in the BFD abfd.
Return TRUE
on success, FALSE
on error. Possible error
returns are:
bfd_error_no_memory
-
Not enough memory exists to create private data for obfd.
#define bfd_set_private_flags(abfd, flags) \ BFD_SEND (abfd, _bfd_set_private_flags, (abfd, flags))
Other functions
Description
The following functions exist but have not yet been documented.
#define bfd_sizeof_headers(abfd, info) \ BFD_SEND (abfd, _bfd_sizeof_headers, (abfd, info)) #define bfd_find_nearest_line(abfd, sec, syms, off, file, func, line) \ BFD_SEND (abfd, _bfd_find_nearest_line, \ (abfd, syms, sec, off, file, func, line, NULL)) #define bfd_find_nearest_line_discriminator(abfd, sec, syms, off, file, func, \ line, disc) \ BFD_SEND (abfd, _bfd_find_nearest_line, \ (abfd, syms, sec, off, file, func, line, disc)) #define bfd_find_line(abfd, syms, sym, file, line) \ BFD_SEND (abfd, _bfd_find_line, \ (abfd, syms, sym, file, line)) #define bfd_find_inliner_info(abfd, file, func, line) \ BFD_SEND (abfd, _bfd_find_inliner_info, \ (abfd, file, func, line)) #define bfd_debug_info_start(abfd) \ BFD_SEND (abfd, _bfd_debug_info_start, (abfd)) #define bfd_debug_info_end(abfd) \ BFD_SEND (abfd, _bfd_debug_info_end, (abfd)) #define bfd_debug_info_accumulate(abfd, section) \ BFD_SEND (abfd, _bfd_debug_info_accumulate, (abfd, section)) #define bfd_stat_arch_elt(abfd, stat) \ BFD_SEND (abfd->my_archive ? abfd->my_archive : abfd, \ _bfd_stat_arch_elt, (abfd, stat)) #define bfd_update_armap_timestamp(abfd) \ BFD_SEND (abfd, _bfd_update_armap_timestamp, (abfd)) #define bfd_set_arch_mach(abfd, arch, mach)\ BFD_SEND ( abfd, _bfd_set_arch_mach, (abfd, arch, mach)) #define bfd_relax_section(abfd, section, link_info, again) \ BFD_SEND (abfd, _bfd_relax_section, (abfd, section, link_info, again)) #define bfd_gc_sections(abfd, link_info) \ BFD_SEND (abfd, _bfd_gc_sections, (abfd, link_info)) #define bfd_lookup_section_flags(link_info, flag_info, section) \ BFD_SEND (abfd, _bfd_lookup_section_flags, (link_info, flag_info, section)) #define bfd_merge_sections(abfd, link_info) \ BFD_SEND (abfd, _bfd_merge_sections, (abfd, link_info)) #define bfd_is_group_section(abfd, sec) \ BFD_SEND (abfd, _bfd_is_group_section, (abfd, sec)) #define bfd_group_name(abfd, sec) \ BFD_SEND (abfd, _bfd_group_name, (abfd, sec)) #define bfd_discard_group(abfd, sec) \ BFD_SEND (abfd, _bfd_discard_group, (abfd, sec)) #define bfd_link_hash_table_create(abfd) \ BFD_SEND (abfd, _bfd_link_hash_table_create, (abfd)) #define bfd_link_add_symbols(abfd, info) \ BFD_SEND (abfd, _bfd_link_add_symbols, (abfd, info)) #define bfd_link_just_syms(abfd, sec, info) \ BFD_SEND (abfd, _bfd_link_just_syms, (sec, info)) #define bfd_final_link(abfd, info) \ BFD_SEND (abfd, _bfd_final_link, (abfd, info)) #define bfd_free_cached_info(abfd) \ BFD_SEND (abfd, _bfd_free_cached_info, (abfd)) #define bfd_get_dynamic_symtab_upper_bound(abfd) \ BFD_SEND (abfd, _bfd_get_dynamic_symtab_upper_bound, (abfd)) #define bfd_print_private_bfd_data(abfd, file)\ BFD_SEND (abfd, _bfd_print_private_bfd_data, (abfd, file)) #define bfd_canonicalize_dynamic_symtab(abfd, asymbols) \ BFD_SEND (abfd, _bfd_canonicalize_dynamic_symtab, (abfd, asymbols)) #define bfd_get_synthetic_symtab(abfd, count, syms, dyncount, dynsyms, ret) \ BFD_SEND (abfd, _bfd_get_synthetic_symtab, (abfd, count, syms, \ dyncount, dynsyms, ret)) #define bfd_get_dynamic_reloc_upper_bound(abfd) \ BFD_SEND (abfd, _bfd_get_dynamic_reloc_upper_bound, (abfd)) #define bfd_canonicalize_dynamic_reloc(abfd, arels, asyms) \ BFD_SEND (abfd, _bfd_canonicalize_dynamic_reloc, (abfd, arels, asyms)) extern bfd_byte *bfd_get_relocated_section_contents (bfd *, struct bfd_link_info *, struct bfd_link_order *, bfd_byte *, bool, asymbol **);
bfd_alt_mach_code
Synopsis
bool bfd_alt_mach_code (bfd *abfd, int alternative);
Description
When more than one machine code number is available for the
same machine type, this function can be used to switch between
the preferred one (alternative == 0) and any others. Currently,
only ELF supports this feature, with up to two alternate
machine codes.
bfd_emul_get_maxpagesize
Synopsis
bfd_vma bfd_emul_get_maxpagesize (const char *);
Description
Returns the maximum page size, in bytes, as determined by
emulation.
Returns
Returns the maximum page size in bytes for ELF, 0 otherwise.
bfd_emul_get_commonpagesize
Synopsis
bfd_vma bfd_emul_get_commonpagesize (const char *, bool);
Description
Returns the common page size, in bytes, as determined by
emulation.
Returns
Returns the common page size in bytes for ELF, 0 otherwise.
bfd_demangle
Synopsis
char *bfd_demangle (bfd *, const char *, int);
Description
Wrapper around cplus_demangle. Strips leading underscores and
other such chars that would otherwise confuse the demangler.
If passed a g++ v3 ABI mangled name, returns a buffer allocated
with malloc holding the demangled name. Returns NULL otherwise
and on memory alloc failure.
bfd_update_compression_header
Synopsis
void bfd_update_compression_header (bfd *abfd, bfd_byte *contents, asection *sec);
Description
Set the compression header at CONTENTS of SEC in ABFD and update
elf_section_flags for compression.
bfd_check_compression_header
Synopsis
bool bfd_check_compression_header (bfd *abfd, bfd_byte *contents, asection *sec, bfd_size_type *uncompressed_size, unsigned int *uncompressed_alignment_power);
Description
Check the compression header at CONTENTS of SEC in ABFD and
store the uncompressed size in UNCOMPRESSED_SIZE and the
uncompressed data alignment in UNCOMPRESSED_ALIGNMENT_POWER
if the compression header is valid.
Returns
Return TRUE if the compression header is valid.
bfd_get_compression_header_size
Synopsis
int bfd_get_compression_header_size (bfd *abfd, asection *sec);
Description
Return the size of the compression header of SEC in ABFD.
Returns
Return the size of the compression header in bytes.
bfd_convert_section_size
Synopsis
bfd_size_type bfd_convert_section_size (bfd *ibfd, asection *isec, bfd *obfd, bfd_size_type size);
Description
Convert the size size of the section isec in input
BFD ibfd to the section size in output BFD obfd.
bfd_convert_section_contents
Synopsis
bool bfd_convert_section_contents (bfd *ibfd, asection *isec, bfd *obfd, bfd_byte **ptr, bfd_size_type *ptr_size);
Description
Convert the contents, stored in *ptr, of the section
isec in input BFD ibfd to output BFD obfd
if needed. The original buffer pointed to by *ptr may
be freed and *ptr is returned with memory malloc’d by this
function, and the new size written to ptr_size.
struct bfd_iovec
Description
The struct bfd_iovec
contains the internal file I/O class.
Each BFD
has an instance of this class and all file I/O is
routed through it (it is assumed that the instance implements
all methods listed below).
struct bfd_iovec { /* To avoid problems with macros, a "b" rather than "f" prefix is prepended to each method name. */ /* Attempt to read/write NBYTES on ABFD's IOSTREAM storing/fetching bytes starting at PTR. Return the number of bytes actually transfered (a read past end-of-file returns less than NBYTES), or -1 (settingbfd_error
) if an error occurs. */ file_ptr (*bread) (struct bfd *abfd, void *ptr, file_ptr nbytes); file_ptr (*bwrite) (struct bfd *abfd, const void *ptr, file_ptr nbytes); /* Return the current IOSTREAM file offset, or -1 (settingbfd_error
if an error occurs. */ file_ptr (*btell) (struct bfd *abfd); /* For the following, on successful completion a value of 0 is returned. Otherwise, a value of -1 is returned (andbfd_error
is set). */ int (*bseek) (struct bfd *abfd, file_ptr offset, int whence); int (*bclose) (struct bfd *abfd); int (*bflush) (struct bfd *abfd); int (*bstat) (struct bfd *abfd, struct stat *sb); /* Mmap a part of the files. ADDR, LEN, PROT, FLAGS and OFFSET are the usual mmap parameter, except that LEN and OFFSET do not need to be page aligned. Returns (void *)-1 on failure, mmapped address on success. Also write in MAP_ADDR the address of the page aligned buffer and in MAP_LEN the size mapped (a page multiple). Use unmap with MAP_ADDR and MAP_LEN to unmap. */ void *(*bmmap) (struct bfd *abfd, void *addr, bfd_size_type len, int prot, int flags, file_ptr offset, void **map_addr, bfd_size_type *map_len); }; extern const struct bfd_iovec _bfd_memory_iovec;
bfd_get_mtime
Synopsis
long bfd_get_mtime (bfd *abfd);
Description
Return the file modification time (as read from the file system, or
from the archive header for archive members).
bfd_get_size
Synopsis
ufile_ptr bfd_get_size (bfd *abfd);
Description
Return the file size (as read from file system) for the file
associated with BFD abfd.
The initial motivation for, and use of, this routine is not so we can get the exact size of the object the BFD applies to, since that might not be generally possible (archive members for example). It would be ideal if someone could eventually modify it so that such results were guaranteed.
Instead, we want to ask questions like "is this NNN byte sized
object I’m about to try read from file offset YYY reasonable?"
As as example of where we might do this, some object formats
use string tables for which the first sizeof (long)
bytes of the
table contain the size of the table itself, including the size bytes.
If an application tries to read what it thinks is one of these
string tables, without some way to validate the size, and for
some reason the size is wrong (byte swapping error, wrong location
for the string table, etc.), the only clue is likely to be a read
error when it tries to read the table, or a "virtual memory
exhausted" error when it tries to allocate 15 bazillon bytes
of space for the 15 bazillon byte table it is about to read.
This function at least allows us to answer the question, "is the
size reasonable?".
A return value of zero indicates the file size is unknown.
bfd_get_file_size
Synopsis
ufile_ptr bfd_get_file_size (bfd *abfd);
Description
Return the file size (as read from file system) for the file
associated with BFD abfd. It supports both normal files
and archive elements.
bfd_mmap
Synopsis
void *bfd_mmap (bfd *abfd, void *addr, bfd_size_type len, int prot, int flags, file_ptr offset, void **map_addr, bfd_size_type *map_len);
Description
Return mmap()ed region of the file, if possible and implemented.
LEN and OFFSET do not need to be page aligned. The page aligned
address and length are written to MAP_ADDR and MAP_LEN.
Next: Initialization, Previous: Miscellaneous, Up: BFD front end [Contents][Index]
BFD keeps all of its internal structures in obstacks. There is one obstack per open BFD file, into which the current state is stored. When a BFD is closed, the obstack is deleted, and so everything which has been allocated by BFD for the closing file is thrown away.
BFD does not free anything created by an application, but pointers into
bfd
structures become invalid on a bfd_close
; for example,
after a bfd_close
the vector passed to
bfd_canonicalize_symtab
is still around, since it has been
allocated by the application, but the data that it pointed to are
lost.
The general rule is to not close a BFD until all operations dependent
upon data from the BFD have been completed, or all the data from within
the file has been copied. To help with the management of memory, there
is a function (bfd_alloc_size
) which returns the number of bytes
in obstacks associated with the supplied BFD. This could be used to
select the greediest open BFD, close it to reclaim the memory, perform
some operation and reopen the BFD again, to get a fresh copy of the data
structures.
Next: Sections, Previous: Memory Usage, Up: BFD front end [Contents][Index]
These are the functions that handle initializing a BFD.
bfd_init
Synopsis
unsigned int bfd_init (void);
Description
This routine must be called before any other BFD function to
initialize magical internal data structures.
Returns a magic number, which may be used to check
that the bfd library is configured as expected by users.
/* Value returned by bfd_init. */ #define BFD_INIT_MAGIC (sizeof (struct bfd_section))
Next: Symbols, Previous: Initialization, Up: BFD front end [Contents][Index]
The raw data contained within a BFD is maintained through the section abstraction. A single BFD may have any number of sections. It keeps hold of them by pointing to the first; each one points to the next in the list.
Sections are supported in BFD in section.c
.
• Section Input | ||
• Section Output | ||
• typedef asection | ||
• section prototypes |
Next: Section Output, Previous: Sections, Up: Sections [Contents][Index]
When a BFD is opened for reading, the section structures are created and attached to the BFD.
Each section has a name which describes the section in the
outside world—for example, a.out
would contain at least
three sections, called .text
, .data
and .bss
.
Names need not be unique; for example a COFF file may have several
sections named .data
.
Sometimes a BFD will contain more than the “natural” number of
sections. A back end may attach other sections containing
constructor data, or an application may add a section (using
bfd_make_section
) to the sections attached to an already open
BFD. For example, the linker creates an extra section
COMMON
for each input file’s BFD to hold information about
common storage.
The raw data is not necessarily read in when
the section descriptor is created. Some targets may leave the
data in place until a bfd_get_section_contents
call is
made. Other back ends may read in all the data at once. For
example, an S-record file has to be read once to determine the
size of the data.
Next: typedef asection, Previous: Section Input, Up: Sections [Contents][Index]
To write a new object style BFD, the various sections to be
written have to be created. They are attached to the BFD in
the same way as input sections; data is written to the
sections using bfd_set_section_contents
.
Any program that creates or combines sections (e.g., the assembler
and linker) must use the asection
fields output_section
and
output_offset
to indicate the file sections to which each
section must be written. (If the section is being created from
scratch, output_section
should probably point to the section
itself and output_offset
should probably be zero.)
The data to be written comes from input sections attached
(via output_section
pointers) to
the output sections. The output section structure can be
considered a filter for the input section: the output section
determines the vma of the output data and the name, but the
input section determines the offset into the output section of
the data to be written.
E.g., to create a section "O", starting at 0x100, 0x123 long,
containing two subsections, "A" at offset 0x0 (i.e., at vma
0x100) and "B" at offset 0x20 (i.e., at vma 0x120) the asection
structures would look like:
section name "A" output_offset 0x00 size 0x20 output_section -----------> section name "O" | vma 0x100 section name "B" | size 0x123 output_offset 0x20 | size 0x103 | output_section --------|
The data within a section is stored in a link_order.
These are much like the fixups in gas
. The link_order
abstraction allows a section to grow and shrink within itself.
A link_order knows how big it is, and which is the next link_order and where the raw data for it is; it also points to a list of relocations which apply to it.
The link_order is used by the linker to perform relaxing on final code. The compiler creates code which is as big as necessary to make it work without relaxing, and the user can select whether to relax. Sometimes relaxing takes a lot of time. The linker runs around the relocations to see if any are attached to data which can be shrunk, if so it does it on a link_order by link_order basis.
Next: section prototypes, Previous: Section Output, Up: Sections [Contents][Index]
Here is the section structure:
typedef struct bfd_section { /* The name of the section; the name isn't a copy, the pointer is the same as that passed to bfd_make_section. */ const char *name; /* A unique sequence number. */ unsigned int id; /* A unique section number which can be used by assembler to distinguish different sections with the same section name. */ unsigned int section_id; /* Which section in the bfd; 0..n-1 as sections are created in a bfd. */ unsigned int index; /* The next section in the list belonging to the BFD, or NULL. */ struct bfd_section *next; /* The previous section in the list belonging to the BFD, or NULL. */ struct bfd_section *prev; /* The field flags contains attributes of the section. Some flags are read in from the object file, and some are synthesized from other information. */ flagword flags; #define SEC_NO_FLAGS 0x0 /* Tells the OS to allocate space for this section when loading. This is clear for a section containing debug information only. */ #define SEC_ALLOC 0x1 /* Tells the OS to load the section from the file when loading. This is clear for a .bss section. */ #define SEC_LOAD 0x2 /* The section contains data still to be relocated, so there is some relocation information too. */ #define SEC_RELOC 0x4 /* A signal to the OS that the section contains read only data. */ #define SEC_READONLY 0x8 /* The section contains code only. */ #define SEC_CODE 0x10 /* The section contains data only. */ #define SEC_DATA 0x20 /* The section will reside in ROM. */ #define SEC_ROM 0x40 /* The section contains constructor information. This section type is used by the linker to create lists of constructors and destructors used byg++
. When a back end sees a symbol which should be used in a constructor list, it creates a new section for the type of name (e.g.,__CTOR_LIST__
), attaches the symbol to it, and builds a relocation. To build the lists of constructors, all the linker has to do is catenate all the sections called__CTOR_LIST__
and relocate the data contained within - exactly the operations it would peform on standard data. */ #define SEC_CONSTRUCTOR 0x80 /* The section has contents - a data section could beSEC_ALLOC
|SEC_HAS_CONTENTS
; a debug section could beSEC_HAS_CONTENTS
*/ #define SEC_HAS_CONTENTS 0x100 /* An instruction to the linker to not output the section even if it has information which would normally be written. */ #define SEC_NEVER_LOAD 0x200 /* The section contains thread local data. */ #define SEC_THREAD_LOCAL 0x400 /* The section's size is fixed. Generic linker code will not recalculate it and it is up to whoever has set this flag to get the size right. */ #define SEC_FIXED_SIZE 0x800 /* The section contains common symbols (symbols may be defined multiple times, the value of a symbol is the amount of space it requires, and the largest symbol value is the one used). Most targets have exactly one of these (which we translate to bfd_com_section_ptr), but ECOFF has two. */ #define SEC_IS_COMMON 0x1000 /* The section contains only debugging information. For example, this is set for ELF .debug and .stab sections. strip tests this flag to see if a section can be discarded. */ #define SEC_DEBUGGING 0x2000 /* The contents of this section are held in memory pointed to by the contents field. This is checked by bfd_get_section_contents, and the data is retrieved from memory if appropriate. */ #define SEC_IN_MEMORY 0x4000 /* The contents of this section are to be excluded by the linker for executable and shared objects unless those objects are to be further relocated. */ #define SEC_EXCLUDE 0x8000 /* The contents of this section are to be sorted based on the sum of the symbol and addend values specified by the associated relocation entries. Entries without associated relocation entries will be appended to the end of the section in an unspecified order. */ #define SEC_SORT_ENTRIES 0x10000 /* When linking, duplicate sections of the same name should be discarded, rather than being combined into a single section as is usually done. This is similar to how common symbols are handled. See SEC_LINK_DUPLICATES below. */ #define SEC_LINK_ONCE 0x20000 /* If SEC_LINK_ONCE is set, this bitfield describes how the linker should handle duplicate sections. */ #define SEC_LINK_DUPLICATES 0xc0000 /* This value for SEC_LINK_DUPLICATES means that duplicate sections with the same name should simply be discarded. */ #define SEC_LINK_DUPLICATES_DISCARD 0x0 /* This value for SEC_LINK_DUPLICATES means that the linker should warn if there are any duplicate sections, although it should still only link one copy. */ #define SEC_LINK_DUPLICATES_ONE_ONLY 0x40000 /* This value for SEC_LINK_DUPLICATES means that the linker should warn if any duplicate sections are a different size. */ #define SEC_LINK_DUPLICATES_SAME_SIZE 0x80000 /* This value for SEC_LINK_DUPLICATES means that the linker should warn if any duplicate sections contain different contents. */ #define SEC_LINK_DUPLICATES_SAME_CONTENTS \ (SEC_LINK_DUPLICATES_ONE_ONLY | SEC_LINK_DUPLICATES_SAME_SIZE) /* This section was created by the linker as part of dynamic relocation or other arcane processing. It is skipped when going through the first-pass output, trusting that someone else up the line will take care of it later. */ #define SEC_LINKER_CREATED 0x100000 /* This section contains a section ID to distinguish different sections with the same section name. */ #define SEC_ASSEMBLER_SECTION_ID 0x100000 /* This section should not be subject to garbage collection. Also set to inform the linker that this section should not be listed in the link map as discarded. */ #define SEC_KEEP 0x200000 /* This section contains "short" data, and should be placed "near" the GP. */ #define SEC_SMALL_DATA 0x400000 /* Attempt to merge identical entities in the section. Entity size is given in the entsize field. */ #define SEC_MERGE 0x800000 /* If given with SEC_MERGE, entities to merge are zero terminated strings where entsize specifies character size instead of fixed size entries. */ #define SEC_STRINGS 0x1000000 /* This section contains data about section groups. */ #define SEC_GROUP 0x2000000 /* The section is a COFF shared library section. This flag is only for the linker. If this type of section appears in the input file, the linker must copy it to the output file without changing the vma or size. FIXME: Although this was originally intended to be general, it really is COFF specific (and the flag was renamed to indicate this). It might be cleaner to have some more general mechanism to allow the back end to control what the linker does with sections. */ #define SEC_COFF_SHARED_LIBRARY 0x4000000 /* This input section should be copied to output in reverse order as an array of pointers. This is for ELF linker internal use only. */ #define SEC_ELF_REVERSE_COPY 0x4000000 /* This section contains data which may be shared with other executables or shared objects. This is for COFF only. */ #define SEC_COFF_SHARED 0x8000000 /* This section should be compressed. This is for ELF linker internal use only. */ #define SEC_ELF_COMPRESS 0x8000000 /* When a section with this flag is being linked, then if the size of the input section is less than a page, it should not cross a page boundary. If the size of the input section is one page or more, it should be aligned on a page boundary. This is for TI TMS320C54X only. */ #define SEC_TIC54X_BLOCK 0x10000000 /* This section should be renamed. This is for ELF linker internal use only. */ #define SEC_ELF_RENAME 0x10000000 /* Conditionally link this section; do not link if there are no references found to any symbol in the section. This is for TI TMS320C54X only. */ #define SEC_TIC54X_CLINK 0x20000000 /* This section contains vliw code. This is for Toshiba MeP only. */ #define SEC_MEP_VLIW 0x20000000 /* All symbols, sizes and relocations in this section are octets instead of bytes. Required for DWARF debug sections as DWARF information is organized in octets, not bytes. */ #define SEC_ELF_OCTETS 0x40000000 /* Indicate that section has the no read flag set. This happens when memory read flag isn't set. */ #define SEC_COFF_NOREAD 0x40000000 /* Indicate that section has the purecode flag set. */ #define SEC_ELF_PURECODE 0x80000000 /* End of section flags. */ /* Some internal packed boolean fields. */ /* See the vma field. */ unsigned int user_set_vma : 1; /* A mark flag used by some of the linker backends. */ unsigned int linker_mark : 1; /* Another mark flag used by some of the linker backends. Set for output sections that have an input section. */ unsigned int linker_has_input : 1; /* Mark flag used by some linker backends for garbage collection. */ unsigned int gc_mark : 1; /* Section compression status. */ unsigned int compress_status : 2; #define COMPRESS_SECTION_NONE 0 #define COMPRESS_SECTION_DONE 1 #define DECOMPRESS_SECTION_SIZED 2 /* The following flags are used by the ELF linker. */ /* Mark sections which have been allocated to segments. */ unsigned int segment_mark : 1; /* Type of sec_info information. */ unsigned int sec_info_type:3; #define SEC_INFO_TYPE_NONE 0 #define SEC_INFO_TYPE_STABS 1 #define SEC_INFO_TYPE_MERGE 2 #define SEC_INFO_TYPE_EH_FRAME 3 #define SEC_INFO_TYPE_JUST_SYMS 4 #define SEC_INFO_TYPE_TARGET 5 #define SEC_INFO_TYPE_EH_FRAME_ENTRY 6 /* Nonzero if this section uses RELA relocations, rather than REL. */ unsigned int use_rela_p:1; /* Bits used by various backends. The generic code doesn't touch these fields. */ unsigned int sec_flg0:1; unsigned int sec_flg1:1; unsigned int sec_flg2:1; unsigned int sec_flg3:1; unsigned int sec_flg4:1; unsigned int sec_flg5:1; /* End of internal packed boolean fields. */ /* The virtual memory address of the section - where it will be at run time. The symbols are relocated against this. The user_set_vma flag is maintained by bfd; if it's not set, the backend can assign addresses (for example, ina.out
, where the default address for.data
is dependent on the specific target and various flags). */ bfd_vma vma; /* The load address of the section - where it would be in a rom image; really only used for writing section header information. */ bfd_vma lma; /* The size of the section in *octets*, as it will be output. Contains a value even if the section has no contents (e.g., the size of.bss
). */ bfd_size_type size; /* For input sections, the original size on disk of the section, in octets. This field should be set for any section whose size is changed by linker relaxation. It is required for sections where the linker relaxation scheme doesn't cache altered section and reloc contents (stabs, eh_frame, SEC_MERGE, some coff relaxing targets), and thus the original size needs to be kept to read the section multiple times. For output sections, rawsize holds the section size calculated on a previous linker relaxation pass. */ bfd_size_type rawsize; /* The compressed size of the section in octets. */ bfd_size_type compressed_size; /* Relaxation table. */ struct relax_table *relax; /* Count of used relaxation table entries. */ int relax_count; /* If this section is going to be output, then this value is the offset in *bytes* into the output section of the first byte in the input section (byte ==> smallest addressable unit on the target). In most cases, if this was going to start at the 100th octet (8-bit quantity) in the output section, this value would be 100. However, if the target byte size is 16 bits (bfd_octets_per_byte is "2"), this value would be 50. */ bfd_vma output_offset; /* The output section through which to map on output. */ struct bfd_section *output_section; /* The alignment requirement of the section, as an exponent of 2 - e.g., 3 aligns to 2^3 (or 8). */ unsigned int alignment_power; /* If an input section, a pointer to a vector of relocation records for the data in this section. */ struct reloc_cache_entry *relocation; /* If an output section, a pointer to a vector of pointers to relocation records for the data in this section. */ struct reloc_cache_entry **orelocation; /* The number of relocation records in one of the above. */ unsigned reloc_count; /* Information below is back end specific - and not always used or updated. */ /* File position of section data. */ file_ptr filepos; /* File position of relocation info. */ file_ptr rel_filepos; /* File position of line data. */ file_ptr line_filepos; /* Pointer to data for applications. */ void *userdata; /* If the SEC_IN_MEMORY flag is set, this points to the actual contents. */ unsigned char *contents; /* Attached line number information. */ alent *lineno; /* Number of line number records. */ unsigned int lineno_count; /* Entity size for merging purposes. */ unsigned int entsize; /* Points to the kept section if this section is a link-once section, and is discarded. */ struct bfd_section *kept_section; /* When a section is being output, this value changes as more linenumbers are written out. */ file_ptr moving_line_filepos; /* What the section number is in the target world. */ int target_index; void *used_by_bfd; /* If this is a constructor section then here is a list of the relocations created to relocate items within it. */ struct relent_chain *constructor_chain; /* The BFD which owns the section. */ bfd *owner; /* A symbol which points at this section only. */ struct bfd_symbol *symbol; struct bfd_symbol **symbol_ptr_ptr; /* Early in the link process, map_head and map_tail are used to build a list of input sections attached to an output section. Later, output sections use these fields for a list of bfd_link_order structs. The linked_to_symbol_name field is for ELF assembler internal use. */ union { struct bfd_link_order *link_order; struct bfd_section *s; const char *linked_to_symbol_name; } map_head, map_tail; /* Points to the output section this section is already assigned to, if any. This is used when support for non-contiguous memory regions is enabled. */ struct bfd_section *already_assigned; } asection; /* Relax table contains information about instructions which can be removed by relaxation -- replacing a long address with a short address. */ struct relax_table { /* Address where bytes may be deleted. */ bfd_vma addr; /* Number of bytes to be deleted. */ int size; }; static inline const char * bfd_section_name (const asection *sec) { return sec->name; } static inline bfd_size_type bfd_section_size (const asection *sec) { return sec->size; } static inline bfd_vma bfd_section_vma (const asection *sec) { return sec->vma; } static inline bfd_vma bfd_section_lma (const asection *sec) { return sec->lma; } static inline unsigned int bfd_section_alignment (const asection *sec) { return sec->alignment_power; } static inline flagword bfd_section_flags (const asection *sec) { return sec->flags; } static inline void * bfd_section_userdata (const asection *sec) { return sec->userdata; } static inline bool bfd_is_com_section (const asection *sec) { return (sec->flags & SEC_IS_COMMON) != 0; } /* Note: the following are provided as inline functions rather than macros because not all callers use the return value. A macro implementation would use a comma expression, eg: "((ptr)->foo = val, TRUE)" and some compilers will complain about comma expressions that have no effect. */ static inline bool bfd_set_section_userdata (asection *sec, void *val) { sec->userdata = val; return true; } static inline bool bfd_set_section_vma (asection *sec, bfd_vma val) { sec->vma = sec->lma = val; sec->user_set_vma = true; return true; } static inline bool bfd_set_section_lma (asection *sec, bfd_vma val) { sec->lma = val; return true; } static inline bool bfd_set_section_alignment (asection *sec, unsigned int val) { sec->alignment_power = val; return true; } /* These sections are global, and are managed by BFD. The application and target back end are not permitted to change the values in these sections. */ extern asection _bfd_std_section[4]; #define BFD_ABS_SECTION_NAME "*ABS*" #define BFD_UND_SECTION_NAME "*UND*" #define BFD_COM_SECTION_NAME "*COM*" #define BFD_IND_SECTION_NAME "*IND*" /* Pointer to the common section. */ #define bfd_com_section_ptr (&_bfd_std_section[0]) /* Pointer to the undefined section. */ #define bfd_und_section_ptr (&_bfd_std_section[1]) /* Pointer to the absolute section. */ #define bfd_abs_section_ptr (&_bfd_std_section[2]) /* Pointer to the indirect section. */ #define bfd_ind_section_ptr (&_bfd_std_section[3]) static inline bool bfd_is_und_section (const asection *sec) { return sec == bfd_und_section_ptr; } static inline bool bfd_is_abs_section (const asection *sec) { return sec == bfd_abs_section_ptr; } static inline bool bfd_is_ind_section (const asection *sec) { return sec == bfd_ind_section_ptr; } static inline bool bfd_is_const_section (const asection *sec) { return (sec >= _bfd_std_section && sec < _bfd_std_section + (sizeof (_bfd_std_section) / sizeof (_bfd_std_section[0]))); } /* Return TRUE if input section SEC has been discarded. */ static inline bool discarded_section (const asection *sec) { return (!bfd_is_abs_section (sec) && bfd_is_abs_section (sec->output_section) && sec->sec_info_type != SEC_INFO_TYPE_MERGE && sec->sec_info_type != SEC_INFO_TYPE_JUST_SYMS); } #define BFD_FAKE_SECTION(SEC, SYM, NAME, IDX, FLAGS) \ /* name, id, section_id, index, next, prev, flags, user_set_vma, */ \ { NAME, IDX, 0, 0, NULL, NULL, FLAGS, 0, \ \ /* linker_mark, linker_has_input, gc_mark, decompress_status, */ \ 0, 0, 1, 0, \ \ /* segment_mark, sec_info_type, use_rela_p, */ \ 0, 0, 0, \ \ /* sec_flg0, sec_flg1, sec_flg2, sec_flg3, sec_flg4, sec_flg5, */ \ 0, 0, 0, 0, 0, 0, \ \ /* vma, lma, size, rawsize, compressed_size, relax, relax_count, */ \ 0, 0, 0, 0, 0, 0, 0, \ \ /* output_offset, output_section, alignment_power, */ \ 0, &SEC, 0, \ \ /* relocation, orelocation, reloc_count, filepos, rel_filepos, */ \ NULL, NULL, 0, 0, 0, \ \ /* line_filepos, userdata, contents, lineno, lineno_count, */ \ 0, NULL, NULL, NULL, 0, \ \ /* entsize, kept_section, moving_line_filepos, */ \ 0, NULL, 0, \ \ /* target_index, used_by_bfd, constructor_chain, owner, */ \ 0, NULL, NULL, NULL, \ \ /* symbol, symbol_ptr_ptr, */ \ (struct bfd_symbol *) SYM, &SEC.symbol, \ \ /* map_head, map_tail, already_assigned */ \ { NULL }, { NULL }, NULL \ \ } /* We use a macro to initialize the static asymbol structures because traditional C does not permit us to initialize a union member while gcc warns if we don't initialize it. the_bfd, name, value, attr, section [, udata] */ #ifdef __STDC__ #define GLOBAL_SYM_INIT(NAME, SECTION) \ { 0, NAME, 0, BSF_SECTION_SYM, SECTION, { 0 }} #else #define GLOBAL_SYM_INIT(NAME, SECTION) \ { 0, NAME, 0, BSF_SECTION_SYM, SECTION } #endif
Previous: typedef asection, Up: Sections [Contents][Index]
These are the functions exported by the section handling part of BFD.
bfd_section_list_clear
Synopsis
void bfd_section_list_clear (bfd *);
Description
Clears the section list, and also resets the section count and
hash table entries.
bfd_get_section_by_name
Synopsis
asection *bfd_get_section_by_name (bfd *abfd, const char *name);
Description
Return the most recently created section attached to abfd
named name. Return NULL if no such section exists.
bfd_get_next_section_by_name
Synopsis
asection *bfd_get_next_section_by_name (bfd *ibfd, asection *sec);
Description
Given sec is a section returned by bfd_get_section_by_name
,
return the next most recently created section attached to the same
BFD with the same name, or if no such section exists in the same BFD and
IBFD is non-NULL, the next section with the same name in any input
BFD following IBFD. Return NULL on finding no section.
bfd_get_linker_section
Synopsis
asection *bfd_get_linker_section (bfd *abfd, const char *name);
Description
Return the linker created section attached to abfd
named name. Return NULL if no such section exists.
bfd_get_section_by_name_if
Synopsis
asection *bfd_get_section_by_name_if (bfd *abfd, const char *name, bool (*func) (bfd *abfd, asection *sect, void *obj), void *obj);
Description
Call the provided function func for each section
attached to the BFD abfd whose name matches name,
passing obj as an argument. The function will be called
as if by
func (abfd, the_section, obj);
It returns the first section for which func returns true,
otherwise NULL
.
bfd_get_unique_section_name
Synopsis
char *bfd_get_unique_section_name (bfd *abfd, const char *templat, int *count);
Description
Invent a section name that is unique in abfd by tacking
a dot and a digit suffix onto the original templat. If
count is non-NULL, then it specifies the first number
tried as a suffix to generate a unique name. The value
pointed to by count will be incremented in this case.
bfd_make_section_old_way
Synopsis
asection *bfd_make_section_old_way (bfd *abfd, const char *name);
Description
Create a new empty section called name
and attach it to the end of the chain of sections for the
BFD abfd. An attempt to create a section with a name which
is already in use returns its pointer without changing the
section chain.
It has the funny name since this is the way it used to be before it was rewritten....
Possible errors are:
bfd_error_invalid_operation
-
If output has already started for this BFD.
bfd_error_no_memory
-
If memory allocation fails.
bfd_make_section_anyway_with_flags
Synopsis
asection *bfd_make_section_anyway_with_flags (bfd *abfd, const char *name, flagword flags);
Description
Create a new empty section called name and attach it to the end of
the chain of sections for abfd. Create a new section even if there
is already a section with that name. Also set the attributes of the
new section to the value flags.
Return NULL
and set bfd_error
on error; possible errors are:
bfd_error_invalid_operation
- If output has already started for abfd.
bfd_error_no_memory
- If memory allocation fails.
bfd_make_section_anyway
Synopsis
asection *bfd_make_section_anyway (bfd *abfd, const char *name);
Description
Create a new empty section called name and attach it to the end of
the chain of sections for abfd. Create a new section even if there
is already a section with that name.
Return NULL
and set bfd_error
on error; possible errors are:
bfd_error_invalid_operation
- If output has already started for abfd.
bfd_error_no_memory
- If memory allocation fails.
bfd_make_section_with_flags
Synopsis
asection *bfd_make_section_with_flags (bfd *, const char *name, flagword flags);
Description
Like bfd_make_section_anyway
, but return NULL
(without calling
bfd_set_error ()) without changing the section chain if there is already a
section named name. Also set the attributes of the new section to
the value flags. If there is an error, return NULL
and set
bfd_error
.
bfd_make_section
Synopsis
asection *bfd_make_section (bfd *, const char *name);
Description
Like bfd_make_section_anyway
, but return NULL
(without calling
bfd_set_error ()) without changing the section chain if there is already a
section named name. If there is an error, return NULL
and set
bfd_error
.
bfd_set_section_flags
Synopsis
bool bfd_set_section_flags (asection *sec, flagword flags);
Description
Set the attributes of the section sec to the value flags.
Return TRUE
on success, FALSE
on error. Possible error
returns are:
bfd_error_invalid_operation
-
The section cannot have one or more of the attributes
requested. For example, a .bss section in a.out
may not
have the SEC_HAS_CONTENTS
field set.
bfd_rename_section
Synopsis
void bfd_rename_section (asection *sec, const char *newname);
Description
Rename section sec to newname.
bfd_map_over_sections
Synopsis
void bfd_map_over_sections (bfd *abfd, void (*func) (bfd *abfd, asection *sect, void *obj), void *obj);
Description
Call the provided function func for each section
attached to the BFD abfd, passing obj as an
argument. The function will be called as if by
func (abfd, the_section, obj);
This is the preferred method for iterating over sections; an alternative would be to use a loop:
asection *p; for (p = abfd->sections; p != NULL; p = p->next) func (abfd, p, ...)
bfd_sections_find_if
Synopsis
asection *bfd_sections_find_if (bfd *abfd, bool (*operation) (bfd *abfd, asection *sect, void *obj), void *obj);
Description
Call the provided function operation for each section
attached to the BFD abfd, passing obj as an
argument. The function will be called as if by
operation (abfd, the_section, obj);
It returns the first section for which operation returns true.
bfd_set_section_size
Synopsis
bool bfd_set_section_size (asection *sec, bfd_size_type val);
Description
Set sec to the size val. If the operation is
ok, then TRUE
is returned, else FALSE
.
Possible error returns:
bfd_error_invalid_operation
-
Writing has started to the BFD, so setting the size is invalid.
bfd_set_section_contents
Synopsis
bool bfd_set_section_contents (bfd *abfd, asection *section, const void *data, file_ptr offset, bfd_size_type count);
Description
Sets the contents of the section section in BFD
abfd to the data starting in memory at location.
The data is written to the output section starting at offset
offset for count octets.
Normally TRUE
is returned, but FALSE
is returned if
there was an error. Possible error returns are:
bfd_error_no_contents
-
The output section does not have the SEC_HAS_CONTENTS
attribute, so nothing can be written to it.
bfd_error_bad_value
-
The section is unable to contain all of the data.
bfd_error_invalid_operation
-
The BFD is not writeable.
This routine is front end to the back end function
_bfd_set_section_contents
.
bfd_get_section_contents
Synopsis
bool bfd_get_section_contents (bfd *abfd, asection *section, void *location, file_ptr offset, bfd_size_type count);
Description
Read data from section in BFD abfd
into memory starting at location. The data is read at an
offset of offset from the start of the input section,
and is read for count bytes.
If the contents of a constructor with the SEC_CONSTRUCTOR
flag set are requested or if the section does not have the
SEC_HAS_CONTENTS
flag set, then the location is filled
with zeroes. If no errors occur, TRUE
is returned, else
FALSE
.
bfd_malloc_and_get_section
Synopsis
bool bfd_malloc_and_get_section (bfd *abfd, asection *section, bfd_byte **buf);
Description
Read all data from section in BFD abfd
into a buffer, *buf, malloc’d by this function.
bfd_copy_private_section_data
Synopsis
bool bfd_copy_private_section_data (bfd *ibfd, asection *isec, bfd *obfd, asection *osec);
Description
Copy private section information from isec in the BFD
ibfd to the section osec in the BFD obfd.
Return TRUE
on success, FALSE
on error. Possible error
returns are:
bfd_error_no_memory
-
Not enough memory exists to create private data for osec.
#define bfd_copy_private_section_data(ibfd, isection, obfd, osection) \ BFD_SEND (obfd, _bfd_copy_private_section_data, \ (ibfd, isection, obfd, osection))
bfd_generic_is_group_section
Synopsis
bool bfd_generic_is_group_section (bfd *, const asection *sec);
Description
Returns TRUE if sec is a member of a group.
bfd_generic_group_name
Synopsis
const char *bfd_generic_group_name (bfd *, const asection *sec);
Description
Returns group name if sec is a member of a group.
bfd_generic_discard_group
Synopsis
bool bfd_generic_discard_group (bfd *abfd, asection *group);
Description
Remove all members of group from the output.
Next: Archives, Previous: Sections, Up: BFD front end [Contents][Index]
BFD tries to maintain as much symbol information as it can when
it moves information from file to file. BFD passes information
to applications though the asymbol
structure. When the
application requests the symbol table, BFD reads the table in
the native form and translates parts of it into the internal
format. To maintain more than the information passed to
applications, some targets keep some information “behind the
scenes” in a structure only the particular back end knows
about. For example, the coff back end keeps the original
symbol table structure as well as the canonical structure when
a BFD is read in. On output, the coff back end can reconstruct
the output symbol table so that no information is lost, even
information unique to coff which BFD doesn’t know or
understand. If a coff symbol table were read, but were written
through an a.out back end, all the coff specific information
would be lost. The symbol table of a BFD
is not necessarily read in until a canonicalize request is
made. Then the BFD back end fills in a table provided by the
application with pointers to the canonical information. To
output symbols, the application provides BFD with a table of
pointers to pointers to asymbol
s. This allows applications
like the linker to output a symbol as it was read, since the “behind
the scenes” information will be still available.
• Reading Symbols | ||
• Writing Symbols | ||
• Mini Symbols | ||
• typedef asymbol | ||
• symbol handling functions |
Next: Writing Symbols, Previous: Symbols, Up: Symbols [Contents][Index]
There are two stages to reading a symbol table from a BFD: allocating storage, and the actual reading process. This is an excerpt from an application which reads the symbol table:
long storage_needed; asymbol **symbol_table; long number_of_symbols; long i; storage_needed = bfd_get_symtab_upper_bound (abfd); if (storage_needed < 0) FAIL if (storage_needed == 0) return; symbol_table = xmalloc (storage_needed); ... number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table); if (number_of_symbols < 0) FAIL for (i = 0; i < number_of_symbols; i++) process_symbol (symbol_table[i]);
All storage for the symbols themselves is in an objalloc connected to the BFD; it is freed when the BFD is closed.
Next: Mini Symbols, Previous: Reading Symbols, Up: Symbols [Contents][Index]
Writing of a symbol table is automatic when a BFD open for
writing is closed. The application attaches a vector of
pointers to pointers to symbols to the BFD being written, and
fills in the symbol count. The close and cleanup code reads
through the table provided and performs all the necessary
operations. The BFD output code must always be provided with an
“owned” symbol: one which has come from another BFD, or one
which has been created using bfd_make_empty_symbol
. Here is an
example showing the creation of a symbol table with only one element:
#include "sysdep.h" #include "bfd.h" int main (void) { bfd *abfd; asymbol *ptrs[2]; asymbol *new; abfd = bfd_openw ("foo","a.out-sunos-big"); bfd_set_format (abfd, bfd_object); new = bfd_make_empty_symbol (abfd); new->name = "dummy_symbol"; new->section = bfd_make_section_old_way (abfd, ".text"); new->flags = BSF_GLOBAL; new->value = 0x12345; ptrs[0] = new; ptrs[1] = 0; bfd_set_symtab (abfd, ptrs, 1); bfd_close (abfd); return 0; } ./makesym nm foo 00012345 A dummy_symbol
Many formats cannot represent arbitrary symbol information; for
instance, the a.out
object format does not allow an
arbitrary number of sections. A symbol pointing to a section
which is not one of .text
, .data
or .bss
cannot
be described.
Next: typedef asymbol, Previous: Writing Symbols, Up: Symbols [Contents][Index]
Mini symbols provide read-only access to the symbol table. They use less memory space, but require more time to access. They can be useful for tools like nm or objdump, which may have to handle symbol tables of extremely large executables.
The bfd_read_minisymbols
function will read the symbols
into memory in an internal form. It will return a void *
pointer to a block of memory, a symbol count, and the size of
each symbol. The pointer is allocated using malloc
, and
should be freed by the caller when it is no longer needed.
The function bfd_minisymbol_to_symbol
will take a pointer
to a minisymbol, and a pointer to a structure returned by
bfd_make_empty_symbol
, and return a asymbol
structure.
The return value may or may not be the same as the value from
bfd_make_empty_symbol
which was passed in.
Next: symbol handling functions, Previous: Mini Symbols, Up: Symbols [Contents][Index]
An asymbol
has the form:
typedef struct bfd_symbol { /* A pointer to the BFD which owns the symbol. This information is necessary so that a back end can work out what additional information (invisible to the application writer) is carried with the symbol. This field is *almost* redundant, since you can use section->owner instead, except that some symbols point to the global sections bfd_{abs,com,und}_section. This could be fixed by making these globals be per-bfd (or per-target-flavor). FIXME. */ struct bfd *the_bfd; /* Use bfd_asymbol_bfd(sym) to access this field. */ /* The text of the symbol. The name is left alone, and not copied; the application may not alter it. */ const char *name; /* The value of the symbol. This really should be a union of a numeric value with a pointer, since some flags indicate that a pointer to another symbol is stored here. */ symvalue value; /* Attributes of a symbol. */ #define BSF_NO_FLAGS 0 /* The symbol has local scope;static
inC
. The value is the offset into the section of the data. */ #define BSF_LOCAL (1 << 0) /* The symbol has global scope; initialized data inC
. The value is the offset into the section of the data. */ #define BSF_GLOBAL (1 << 1) /* The symbol has global scope and is exported. The value is the offset into the section of the data. */ #define BSF_EXPORT BSF_GLOBAL /* No real difference. */ /* A normal C symbol would be one of:BSF_LOCAL
,BSF_UNDEFINED
orBSF_GLOBAL
. */ /* The symbol is a debugging record. The value has an arbitrary meaning, unless BSF_DEBUGGING_RELOC is also set. */ #define BSF_DEBUGGING (1 << 2) /* The symbol denotes a function entry point. Used in ELF, perhaps others someday. */ #define BSF_FUNCTION (1 << 3) /* Used by the linker. */ #define BSF_KEEP (1 << 5) /* An ELF common symbol. */ #define BSF_ELF_COMMON (1 << 6) /* A weak global symbol, overridable without warnings by a regular global symbol of the same name. */ #define BSF_WEAK (1 << 7) /* This symbol was created to point to a section, e.g. ELF's STT_SECTION symbols. */ #define BSF_SECTION_SYM (1 << 8) /* The symbol used to be a common symbol, but now it is allocated. */ #define BSF_OLD_COMMON (1 << 9) /* In some files the type of a symbol sometimes alters its location in an output file - ie in coff aISFCN
symbol which is alsoC_EXT
symbol appears where it was declared and not at the end of a section. This bit is set by the target BFD part to convey this information. */ #define BSF_NOT_AT_END (1 << 10) /* Signal that the symbol is the label of constructor section. */ #define BSF_CONSTRUCTOR (1 << 11) /* Signal that the symbol is a warning symbol. The name is a warning. The name of the next symbol is the one to warn about; if a reference is made to a symbol with the same name as the next symbol, a warning is issued by the linker. */ #define BSF_WARNING (1 << 12) /* Signal that the symbol is indirect. This symbol is an indirect pointer to the symbol with the same name as the next symbol. */ #define BSF_INDIRECT (1 << 13) /* BSF_FILE marks symbols that contain a file name. This is used for ELF STT_FILE symbols. */ #define BSF_FILE (1 << 14) /* Symbol is from dynamic linking information. */ #define BSF_DYNAMIC (1 << 15) /* The symbol denotes a data object. Used in ELF, and perhaps others someday. */ #define BSF_OBJECT (1 << 16) /* This symbol is a debugging symbol. The value is the offset into the section of the data. BSF_DEBUGGING should be set as well. */ #define BSF_DEBUGGING_RELOC (1 << 17) /* This symbol is thread local. Used in ELF. */ #define BSF_THREAD_LOCAL (1 << 18) /* This symbol represents a complex relocation expression, with the expression tree serialized in the symbol name. */ #define BSF_RELC (1 << 19) /* This symbol represents a signed complex relocation expression, with the expression tree serialized in the symbol name. */ #define BSF_SRELC (1 << 20) /* This symbol was created by bfd_get_synthetic_symtab. */ #define BSF_SYNTHETIC (1 << 21) /* This symbol is an indirect code object. Unrelated to BSF_INDIRECT. The dynamic linker will compute the value of this symbol by calling the function that it points to. BSF_FUNCTION must also be also set. */ #define BSF_GNU_INDIRECT_FUNCTION (1 << 22) /* This symbol is a globally unique data object. The dynamic linker will make sure that in the entire process there is just one symbol with this name and type in use. BSF_OBJECT must also be set. */ #define BSF_GNU_UNIQUE (1 << 23) /* This section symbol should be included in the symbol table. */ #define BSF_SECTION_SYM_USED (1 << 24) flagword flags; /* A pointer to the section to which this symbol is relative. This will always be non NULL, there are special sections for undefined and absolute symbols. */ struct bfd_section *section; /* Back end special data. */ union { void *p; bfd_vma i; } udata; } asymbol;
Previous: typedef asymbol, Up: Symbols [Contents][Index]
bfd_get_symtab_upper_bound
Description
Return the number of bytes required to store a vector of pointers
to asymbols
for all the symbols in the BFD abfd,
including a terminal NULL pointer. If there are no symbols in
the BFD, then return 0. If an error occurs, return -1.
#define bfd_get_symtab_upper_bound(abfd) \ BFD_SEND (abfd, _bfd_get_symtab_upper_bound, (abfd))
bfd_is_local_label
Synopsis
bool bfd_is_local_label (bfd *abfd, asymbol *sym);
Description
Return TRUE if the given symbol sym in the BFD abfd is
a compiler generated local label, else return FALSE.
bfd_is_local_label_name
Synopsis
bool bfd_is_local_label_name (bfd *abfd, const char *name);
Description
Return TRUE if a symbol with the name name in the BFD
abfd is a compiler generated local label, else return
FALSE. This just checks whether the name has the form of a
local label.
#define bfd_is_local_label_name(abfd, name) \ BFD_SEND (abfd, _bfd_is_local_label_name, (abfd, name))
bfd_is_target_special_symbol
Synopsis
bool bfd_is_target_special_symbol (bfd *abfd, asymbol *sym);
Description
Return TRUE iff a symbol sym in the BFD abfd is something
special to the particular target represented by the BFD. Such symbols
should normally not be mentioned to the user.
#define bfd_is_target_special_symbol(abfd, sym) \ BFD_SEND (abfd, _bfd_is_target_special_symbol, (abfd, sym))
bfd_canonicalize_symtab
Description
Read the symbols from the BFD abfd, and fills in
the vector location with pointers to the symbols and
a trailing NULL.
Return the actual number of symbol pointers, not
including the NULL.
#define bfd_canonicalize_symtab(abfd, location) \ BFD_SEND (abfd, _bfd_canonicalize_symtab, (abfd, location))
bfd_set_symtab
Synopsis
bool bfd_set_symtab (bfd *abfd, asymbol **location, unsigned int count);
Description
Arrange that when the output BFD abfd is closed,
the table location of count pointers to symbols
will be written.
bfd_print_symbol_vandf
Synopsis
void bfd_print_symbol_vandf (bfd *abfd, void *file, asymbol *symbol);
Description
Print the value and flags of the symbol supplied to the
stream file.
bfd_make_empty_symbol
Description
Create a new asymbol
structure for the BFD abfd
and return a pointer to it.
This routine is necessary because each back end has private
information surrounding the asymbol
. Building your own
asymbol
and pointing to it will not create the private
information, and will cause problems later on.
#define bfd_make_empty_symbol(abfd) \ BFD_SEND (abfd, _bfd_make_empty_symbol, (abfd))
_bfd_generic_make_empty_symbol
Synopsis
asymbol *_bfd_generic_make_empty_symbol (bfd *);
Description
Create a new asymbol
structure for the BFD abfd
and return a pointer to it. Used by core file routines,
binary back-end and anywhere else where no private info
is needed.
bfd_make_debug_symbol
Description
Create a new asymbol
structure for the BFD abfd,
to be used as a debugging symbol. Further details of its use have
yet to be worked out.
#define bfd_make_debug_symbol(abfd,ptr,size) \ BFD_SEND (abfd, _bfd_make_debug_symbol, (abfd, ptr, size))
bfd_decode_symclass
Description
Return a character corresponding to the symbol
class of symbol, or ’?’ for an unknown class.
Synopsis
int bfd_decode_symclass (asymbol *symbol);
bfd_is_undefined_symclass
Description
Returns non-zero if the class symbol returned by
bfd_decode_symclass represents an undefined symbol.
Returns zero otherwise.
Synopsis
bool bfd_is_undefined_symclass (int symclass);
bfd_symbol_info
Description
Fill in the basic info about symbol that nm needs.
Additional info may be added by the back-ends after
calling this function.
Synopsis
void bfd_symbol_info (asymbol *symbol, symbol_info *ret);
bfd_copy_private_symbol_data
Synopsis
bool bfd_copy_private_symbol_data (bfd *ibfd, asymbol *isym, bfd *obfd, asymbol *osym);
Description
Copy private symbol information from isym in the BFD
ibfd to the symbol osym in the BFD obfd.
Return TRUE
on success, FALSE
on error. Possible error
returns are:
bfd_error_no_memory
-
Not enough memory exists to create private data for osec.
#define bfd_copy_private_symbol_data(ibfd, isymbol, obfd, osymbol) \ BFD_SEND (obfd, _bfd_copy_private_symbol_data, \ (ibfd, isymbol, obfd, osymbol))
Next: Formats, Previous: Symbols, Up: BFD front end [Contents][Index]
Description
An archive (or library) is just another BFD. It has a symbol
table, although there’s not much a user program will do with it.
The big difference between an archive BFD and an ordinary BFD is that the archive doesn’t have sections. Instead it has a chain of BFDs that are considered its contents. These BFDs can be manipulated like any other. The BFDs contained in an archive opened for reading will all be opened for reading. You may put either input or output BFDs into an archive opened for output; they will be handled correctly when the archive is closed.
Use bfd_openr_next_archived_file
to step through
the contents of an archive opened for input. You don’t
have to read the entire archive if you don’t want
to! Read it until you find what you want.
A BFD returned by bfd_openr_next_archived_file
can be
closed manually with bfd_close
. If you do not close it,
then a second iteration through the members of an archive may
return the same BFD. If you close the archive BFD, then all
the member BFDs will automatically be closed as well.
Archive contents of output BFDs are chained through the
archive_next
pointer in a BFD. The first one is findable
through the archive_head
slot of the archive. Set it with
bfd_set_archive_head
(q.v.). A given BFD may be in only
one open output archive at a time.
As expected, the BFD archive code is more general than the archive code of any given environment. BFD archives may contain files of different formats (e.g., a.out and coff) and even different architectures. You may even place archives recursively into archives!
This can cause unexpected confusion, since some archive formats are more expressive than others. For instance, Intel COFF archives can preserve long filenames; SunOS a.out archives cannot. If you move a file from the first to the second format and back again, the filename may be truncated. Likewise, different a.out environments have different conventions as to how they truncate filenames, whether they preserve directory names in filenames, etc. When interoperating with native tools, be sure your files are homogeneous.
Beware: most of these formats do not react well to the presence of spaces in filenames. We do the best we can, but can’t always handle this case due to restrictions in the format of archives. Many Unix utilities are braindead in regards to spaces and such in filenames anyway, so this shouldn’t be much of a restriction.
Archives are supported in BFD in archive.c
.
bfd_get_next_mapent
Synopsis
symindex bfd_get_next_mapent (bfd *abfd, symindex previous, carsym **sym);
Description
Step through archive abfd’s symbol table (if it
has one). Successively update sym with the next symbol’s
information, returning that symbol’s (internal) index into the
symbol table.
Supply BFD_NO_MORE_SYMBOLS
as the previous entry to get
the first one; returns BFD_NO_MORE_SYMBOLS
when you’ve already
got the last one.
A carsym
is a canonical archive symbol. The only
user-visible element is its name, a null-terminated string.
bfd_set_archive_head
Synopsis
bool bfd_set_archive_head (bfd *output, bfd *new_head);
Description
Set the head of the chain of
BFDs contained in the archive output to new_head.
bfd_openr_next_archived_file
Synopsis
bfd *bfd_openr_next_archived_file (bfd *archive, bfd *previous);
Description
Provided a BFD, archive, containing an archive and NULL, open
an input BFD on the first contained element and returns that.
Subsequent calls should pass the archive and the previous return
value to return a created BFD to the next contained element. NULL
is returned when there are no more.
Note - if you want to process the bfd returned by this call be
sure to call bfd_check_format() on it first.
Next: Relocations, Previous: Archives, Up: BFD front end [Contents][Index]
A format is a BFD concept of high level file contents type. The formats supported by BFD are:
bfd_object
The BFD may contain data, symbols, relocations and debug info.
bfd_archive
The BFD contains other BFDs and an optional index.
bfd_core
The BFD contains the result of an executable core dump.
bfd_check_format
Synopsis
bool bfd_check_format (bfd *abfd, bfd_format format);
Description
Verify if the file attached to the BFD abfd is compatible
with the format format (i.e., one of bfd_object
,
bfd_archive
or bfd_core
).
If the BFD has been set to a specific target before the
call, only the named target and format combination is
checked. If the target has not been set, or has been set to
default
, then all the known target backends is
interrogated to determine a match. If the default target
matches, it is used. If not, exactly one target must recognize
the file, or an error results.
The function returns TRUE
on success, otherwise FALSE
with one of the following error codes:
bfd_error_invalid_operation
-
if format
is not one of bfd_object
, bfd_archive
or
bfd_core
.
bfd_error_system_call
-
if an error occured during a read - even some file mismatches
can cause bfd_error_system_calls.
file_not_recognised
-
none of the backends recognised the file format.
bfd_error_file_ambiguously_recognized
-
more than one backend recognised the file format.
bfd_check_format_matches
Synopsis
bool bfd_check_format_matches (bfd *abfd, bfd_format format, char ***matching);
Description
Like bfd_check_format
, except when it returns FALSE with
bfd_errno
set to bfd_error_file_ambiguously_recognized
. In that
case, if matching is not NULL, it will be filled in with
a NULL-terminated list of the names of the formats that matched,
allocated with malloc
.
Then the user may choose a format and try again.
When done with the list that matching points to, the caller should free it.
bfd_set_format
Synopsis
bool bfd_set_format (bfd *abfd, bfd_format format);
Description
This function sets the file format of the BFD abfd to the
format format. If the target set in the BFD does not
support the format requested, the format is invalid, or the BFD
is not open for writing, then an error occurs.
bfd_format_string
Synopsis
const char *bfd_format_string (bfd_format format);
Description
Return a pointer to a const string
invalid
, object
, archive
, core
, or unknown
,
depending upon the value of format.
Next: Core Files, Previous: Formats, Up: BFD front end [Contents][Index]
BFD maintains relocations in much the same way it maintains
symbols: they are left alone until required, then read in
en-masse and translated into an internal form. A common
routine bfd_perform_relocation
acts upon the
canonical form to do the fixup.
Relocations are maintained on a per section basis, while symbols are maintained on a per BFD basis.
All that a back end has to do to fit the BFD interface is to create
a struct reloc_cache_entry
for each relocation
in a particular section, and fill in the right bits of the structures.
• typedef arelent | ||
• howto manager |
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This is the structure of a relocation entry:
typedef enum bfd_reloc_status { /* No errors detected. Note - the value 2 is used so that it will not be mistaken for the boolean TRUE or FALSE values. */ bfd_reloc_ok = 2, /* The relocation was performed, but there was an overflow. */ bfd_reloc_overflow, /* The address to relocate was not within the section supplied. */ bfd_reloc_outofrange, /* Used by special functions. */ bfd_reloc_continue, /* Unsupported relocation size requested. */ bfd_reloc_notsupported, /* Unused. */ bfd_reloc_other, /* The symbol to relocate against was undefined. */ bfd_reloc_undefined, /* The relocation was performed, but may not be ok. If this type is returned, the error_message argument to bfd_perform_relocation will be set. */ bfd_reloc_dangerous } bfd_reloc_status_type; typedef const struct reloc_howto_struct reloc_howto_type; typedef struct reloc_cache_entry { /* A pointer into the canonical table of pointers. */ struct bfd_symbol **sym_ptr_ptr; /* offset in section. */ bfd_size_type address; /* addend for relocation value. */ bfd_vma addend; /* Pointer to how to perform the required relocation. */ reloc_howto_type *howto; } arelent;
Description
Here is a description of each of the fields within an arelent
:
sym_ptr_ptr
The symbol table pointer points to a pointer to the symbol
associated with the relocation request. It is the pointer
into the table returned by the back end’s
canonicalize_symtab
action. See Symbols. The symbol is
referenced through a pointer to a pointer so that tools like
the linker can fix up all the symbols of the same name by
modifying only one pointer. The relocation routine looks in
the symbol and uses the base of the section the symbol is
attached to and the value of the symbol as the initial
relocation offset. If the symbol pointer is zero, then the
section provided is looked up.
address
The address
field gives the offset in bytes from the base of
the section data which owns the relocation record to the first
byte of relocatable information. The actual data relocated
will be relative to this point; for example, a relocation
type which modifies the bottom two bytes of a four byte word
would not touch the first byte pointed to in a big endian
world.
addend
The addend
is a value provided by the back end to be added (!)
to the relocation offset. Its interpretation is dependent upon
the howto. For example, on the 68k the code:
char foo[]; main() { return foo[0x12345678]; }
Could be compiled into:
linkw fp,#-4 moveb @#12345678,d0 extbl d0 unlk fp rts
This could create a reloc pointing to foo
, but leave the
offset in the data, something like:
RELOCATION RECORDS FOR [.text]: offset type value 00000006 32 _foo 00000000 4e56 fffc ; linkw fp,#-4 00000004 1039 1234 5678 ; moveb @#12345678,d0 0000000a 49c0 ; extbl d0 0000000c 4e5e ; unlk fp 0000000e 4e75 ; rts
Using coff and an 88k, some instructions don’t have enough space in them to represent the full address range, and pointers have to be loaded in two parts. So you’d get something like:
or.u r13,r0,hi16(_foo+0x12345678) ld.b r2,r13,lo16(_foo+0x12345678) jmp r1
This should create two relocs, both pointing to _foo
, and with
0x12340000 in their addend field. The data would consist of:
RELOCATION RECORDS FOR [.text]: offset type value 00000002 HVRT16 _foo+0x12340000 00000006 LVRT16 _foo+0x12340000 00000000 5da05678 ; or.u r13,r0,0x5678 00000004 1c4d5678 ; ld.b r2,r13,0x5678 00000008 f400c001 ; jmp r1
The relocation routine digs out the value from the data, adds
it to the addend to get the original offset, and then adds the
value of _foo
. Note that all 32 bits have to be kept around
somewhere, to cope with carry from bit 15 to bit 16.
One further example is the sparc and the a.out format. The sparc has a similar problem to the 88k, in that some instructions don’t have room for an entire offset, but on the sparc the parts are created in odd sized lumps. The designers of the a.out format chose to not use the data within the section for storing part of the offset; all the offset is kept within the reloc. Anything in the data should be ignored.
save %sp,-112,%sp sethi %hi(_foo+0x12345678),%g2 ldsb [%g2+%lo(_foo+0x12345678)],%i0 ret restore
Both relocs contain a pointer to foo
, and the offsets
contain junk.
RELOCATION RECORDS FOR [.text]: offset type value 00000004 HI22 _foo+0x12345678 00000008 LO10 _foo+0x12345678 00000000 9de3bf90 ; save %sp,-112,%sp 00000004 05000000 ; sethi %hi(_foo+0),%g2 00000008 f048a000 ; ldsb [%g2+%lo(_foo+0)],%i0 0000000c 81c7e008 ; ret 00000010 81e80000 ; restore
howto
The howto
field can be imagined as a
relocation instruction. It is a pointer to a structure which
contains information on what to do with all of the other
information in the reloc record and data section. A back end
would normally have a relocation instruction set and turn
relocations into pointers to the correct structure on input -
but it would be possible to create each howto field on demand.
enum complain_overflow
Indicates what sort of overflow checking should be done when performing a relocation.
enum complain_overflow { /* Do not complain on overflow. */ complain_overflow_dont, /* Complain if the value overflows when considered as a signed number one bit larger than the field. ie. A bitfield of N bits is allowed to represent -2**n to 2**n-1. */ complain_overflow_bitfield, /* Complain if the value overflows when considered as a signed number. */ complain_overflow_signed, /* Complain if the value overflows when considered as an unsigned number. */ complain_overflow_unsigned };
reloc_howto_type
The reloc_howto_type
is a structure which contains all the
information that libbfd needs to know to tie up a back end’s data.
struct reloc_howto_struct { /* The type field has mainly a documentary use - the back end can do what it wants with it, though normally the back end's idea of an external reloc number is stored in this field. */ unsigned int type; /* The encoded size of the item to be relocated. This is *not* a power-of-two measure. Use bfd_get_reloc_size to find the size of the item in bytes. */ unsigned int size:3; /* The number of bits in the field to be relocated. This is used when doing overflow checking. */ unsigned int bitsize:7; /* The value the final relocation is shifted right by. This drops unwanted data from the relocation. */ unsigned int rightshift:6; /* The bit position of the reloc value in the destination. The relocated value is left shifted by this amount. */ unsigned int bitpos:6; /* What type of overflow error should be checked for when relocating. */ ENUM_BITFIELD (complain_overflow) complain_on_overflow:2; /* The relocation value should be negated before applying. */ unsigned int negate:1; /* The relocation is relative to the item being relocated. */ unsigned int pc_relative:1; /* Some formats record a relocation addend in the section contents rather than with the relocation. For ELF formats this is the distinction between USE_REL and USE_RELA (though the code checks for USE_REL == 1/0). The value of this field is TRUE if the addend is recorded with the section contents; when performing a partial link (ld -r) the section contents (the data) will be modified. The value of this field is FALSE if addends are recorded with the relocation (in arelent.addend); when performing a partial link the relocation will be modified. All relocations for all ELF USE_RELA targets should set this field to FALSE (values of TRUE should be looked on with suspicion). However, the converse is not true: not all relocations of all ELF USE_REL targets set this field to TRUE. Why this is so is peculiar to each particular target. For relocs that aren't used in partial links (e.g. GOT stuff) it doesn't matter what this is set to. */ unsigned int partial_inplace:1; /* When some formats create PC relative instructions, they leave the value of the pc of the place being relocated in the offset slot of the instruction, so that a PC relative relocation can be made just by adding in an ordinary offset (e.g., sun3 a.out). Some formats leave the displacement part of an instruction empty (e.g., ELF); this flag signals the fact. */ unsigned int pcrel_offset:1; /* src_mask selects the part of the instruction (or data) to be used in the relocation sum. If the target relocations don't have an addend in the reloc, eg. ELF USE_REL, src_mask will normally equal dst_mask to extract the addend from the section contents. If relocations do have an addend in the reloc, eg. ELF USE_RELA, this field should normally be zero. Non-zero values for ELF USE_RELA targets should be viewed with suspicion as normally the value in the dst_mask part of the section contents should be ignored. */ bfd_vma src_mask; /* dst_mask selects which parts of the instruction (or data) are replaced with a relocated value. */ bfd_vma dst_mask; /* If this field is non null, then the supplied function is called rather than the normal function. This allows really strange relocation methods to be accommodated. */ bfd_reloc_status_type (*special_function) (bfd *, arelent *, struct bfd_symbol *, void *, asection *, bfd *, char **); /* The textual name of the relocation type. */ const char *name; };
The HOWTO Macro
Description
The HOWTO macro fills in a reloc_howto_type (a typedef for
const struct reloc_howto_struct).
#define HOWTO(type, right, size, bits, pcrel, left, ovf, func, name, \ inplace, src_mask, dst_mask, pcrel_off) \ { (unsigned) type, size < 0 ? -size : size, bits, right, left, ovf, \ size < 0, pcrel, inplace, pcrel_off, src_mask, dst_mask, func, name }
Description
This is used to fill in an empty howto entry in an array.
#define EMPTY_HOWTO(C) \ HOWTO ((C), 0, 0, 0, false, 0, complain_overflow_dont, NULL, \ NULL, false, 0, 0, false)
bfd_get_reloc_size
Synopsis
unsigned int bfd_get_reloc_size (reloc_howto_type *);
Description
For a reloc_howto_type that operates on a fixed number of bytes,
this returns the number of bytes operated on.
arelent_chain
Description
How relocs are tied together in an asection
:
typedef struct relent_chain { arelent relent; struct relent_chain *next; } arelent_chain;
bfd_check_overflow
Synopsis
bfd_reloc_status_type bfd_check_overflow (enum complain_overflow how, unsigned int bitsize, unsigned int rightshift, unsigned int addrsize, bfd_vma relocation);
Description
Perform overflow checking on relocation which has
bitsize significant bits and will be shifted right by
rightshift bits, on a machine with addresses containing
addrsize significant bits. The result is either of
bfd_reloc_ok
or bfd_reloc_overflow
.
bfd_reloc_offset_in_range
Synopsis
bool bfd_reloc_offset_in_range (reloc_howto_type *howto, bfd *abfd, asection *section, bfd_size_type offset);
Description
Returns TRUE if the reloc described by HOWTO can be
applied at OFFSET octets in SECTION.
bfd_perform_relocation
Synopsis
bfd_reloc_status_type bfd_perform_relocation (bfd *abfd, arelent *reloc_entry, void *data, asection *input_section, bfd *output_bfd, char **error_message);
Description
If output_bfd is supplied to this function, the
generated image will be relocatable; the relocations are
copied to the output file after they have been changed to
reflect the new state of the world. There are two ways of
reflecting the results of partial linkage in an output file:
by modifying the output data in place, and by modifying the
relocation record. Some native formats (e.g., basic a.out and
basic coff) have no way of specifying an addend in the
relocation type, so the addend has to go in the output data.
This is no big deal since in these formats the output data
slot will always be big enough for the addend. Complex reloc
types with addends were invented to solve just this problem.
The error_message argument is set to an error message if
this return bfd_reloc_dangerous
.
bfd_install_relocation
Synopsis
bfd_reloc_status_type bfd_install_relocation (bfd *abfd, arelent *reloc_entry, void *data, bfd_vma data_start, asection *input_section, char **error_message);
Description
This looks remarkably like bfd_perform_relocation
, except it
does not expect that the section contents have been filled in.
I.e., it’s suitable for use when creating, rather than applying
a relocation.
For now, this function should be considered reserved for the assembler.
Previous: typedef arelent, Up: Relocations [Contents][Index]
When an application wants to create a relocation, but doesn’t know what the target machine might call it, it can find out by using this bit of code.
bfd_reloc_code_type
Description
The insides of a reloc code. The idea is that, eventually, there
will be one enumerator for every type of relocation we ever do.
Pass one of these values to bfd_reloc_type_lookup
, and it’ll
return a howto pointer.
This does mean that the application must determine the correct enumerator value; you can’t get a howto pointer from a random set of attributes.
Here are the possible values for enum bfd_reloc_code_real
:
Basic absolute relocations of N bits.
PC-relative relocations. Sometimes these are relative to the address of the relocation itself; sometimes they are relative to the start of the section containing the relocation. It depends on the specific target.
Section relative relocations. Some targets need this for DWARF2.
For ELF.
Size relocations.
Relocations used by 68K ELF.
Linkage-table relative.
Absolute 8-bit relocation, but used to form an address like 0xFFnn.
These PC-relative relocations are stored as word displacements – i.e., byte displacements shifted right two bits. The 30-bit word displacement (<<32_PCREL_S2>> – 32 bits, shifted 2) is used on the SPARC. (SPARC tools generally refer to this as <<WDISP30>>.) The signed 16-bit displacement is used on the MIPS, and the 23-bit displacement is used on the Alpha.
High 22 bits and low 10 bits of 32-bit value, placed into lower bits of the target word. These are used on the SPARC.
For systems that allocate a Global Pointer register, these are displacements off that register. These relocation types are handled specially, because the value the register will have is decided relatively late.
SPARC ELF relocations. There is probably some overlap with other relocation types already defined.
I think these are specific to SPARC a.out (e.g., Sun 4).
SPARC64 relocations
SPARC little endian relocation
SPARC TLS relocations
SPU Relocations.
Alpha ECOFF and ELF relocations. Some of these treat the symbol or "addend" in some special way. For GPDISP_HI16 ("gpdisp") relocations, the symbol is ignored when writing; when reading, it will be the absolute section symbol. The addend is the displacement in bytes of the "lda" instruction from the "ldah" instruction (which is at the address of this reloc).
For GPDISP_LO16 ("ignore") relocations, the symbol is handled as with GPDISP_HI16 relocs. The addend is ignored when writing the relocations out, and is filled in with the file’s GP value on reading, for convenience.
The ELF GPDISP relocation is exactly the same as the GPDISP_HI16 relocation except that there is no accompanying GPDISP_LO16 relocation.
The Alpha LITERAL/LITUSE relocs are produced by a symbol reference; the assembler turns it into a LDQ instruction to load the address of the symbol, and then fills in a register in the real instruction.
The LITERAL reloc, at the LDQ instruction, refers to the .lita section symbol. The addend is ignored when writing, but is filled in with the file’s GP value on reading, for convenience, as with the GPDISP_LO16 reloc.
The ELF_LITERAL reloc is somewhere between 16_GOTOFF and GPDISP_LO16. It should refer to the symbol to be referenced, as with 16_GOTOFF, but it generates output not based on the position within the .got section, but relative to the GP value chosen for the file during the final link stage.
The LITUSE reloc, on the instruction using the loaded address, gives information to the linker that it might be able to use to optimize away some literal section references. The symbol is ignored (read as the absolute section symbol), and the "addend" indicates the type of instruction using the register: 1 - "memory" fmt insn 2 - byte-manipulation (byte offset reg) 3 - jsr (target of branch)
The HINT relocation indicates a value that should be filled into the "hint" field of a jmp/jsr/ret instruction, for possible branch- prediction logic which may be provided on some processors.
The LINKAGE relocation outputs a linkage pair in the object file, which is filled by the linker.
The CODEADDR relocation outputs a STO_CA in the object file, which is filled by the linker.
The GPREL_HI/LO relocations together form a 32-bit offset from the GP register.
Like BFD_RELOC_23_PCREL_S2, except that the source and target must share a common GP, and the target address is adjusted for STO_ALPHA_STD_GPLOAD.
The NOP relocation outputs a NOP if the longword displacement between two procedure entry points is < 2^21.
The BSR relocation outputs a BSR if the longword displacement between two procedure entry points is < 2^21.
The LDA relocation outputs a LDA if the longword displacement between two procedure entry points is < 2^16.
The BOH relocation outputs a BSR if the longword displacement between two procedure entry points is < 2^21, or else a hint.
Alpha thread-local storage relocations.
The MIPS jump instruction.
The MIPS16 jump instruction.
MIPS16 GP relative reloc.
High 16 bits of 32-bit value; simple reloc.
High 16 bits of 32-bit value but the low 16 bits will be sign extended and added to form the final result. If the low 16 bits form a negative number, we need to add one to the high value to compensate for the borrow when the low bits are added.
Low 16 bits.
High 16 bits of 32-bit pc-relative value
High 16 bits of 32-bit pc-relative value, adjusted
Low 16 bits of pc-relative value
Equivalent of BFD_RELOC_MIPS_*, but with the MIPS16 layout of 16-bit immediate fields
MIPS16 high 16 bits of 32-bit value.
MIPS16 high 16 bits of 32-bit value but the low 16 bits will be sign extended and added to form the final result. If the low 16 bits form a negative number, we need to add one to the high value to compensate for the borrow when the low bits are added.
MIPS16 low 16 bits.
MIPS16 TLS relocations
Relocation against a MIPS literal section.
microMIPS PC-relative relocations.
MIPS16 PC-relative relocation.
MIPS PC-relative relocations.
microMIPS versions of generic BFD relocs.
MIPS ELF relocations.
MIPS ELF relocations (VxWorks and PLT extensions).
Moxie ELF relocations.
FT32 ELF relocations.
Fujitsu Frv Relocations.
This is a 24bit GOT-relative reloc for the mn10300.
This is a 32bit GOT-relative reloc for the mn10300, offset by two bytes in the instruction.
This is a 24bit GOT-relative reloc for the mn10300, offset by two bytes in the instruction.
This is a 16bit GOT-relative reloc for the mn10300, offset by two bytes in the instruction.
Copy symbol at runtime.
Create GOT entry.
Create PLT entry.
Adjust by program base.
Together with another reloc targeted at the same location, allows for a value that is the difference of two symbols in the same section.
The addend of this reloc is an alignment power that must be honoured at the offset’s location, regardless of linker relaxation.
Various TLS-related relocations.
This is a 32bit pcrel reloc for the mn10300, offset by two bytes in the instruction.
This is a 16bit pcrel reloc for the mn10300, offset by two bytes in the instruction.
i386/elf relocations
x86-64/elf relocations
ns32k relocations
PDP11 relocations
Picojava relocs. Not all of these appear in object files.
Power(rs6000) and PowerPC relocations.
PowerPC and PowerPC64 thread-local storage relocations.
IBM 370/390 relocations
The type of reloc used to build a constructor table - at the moment probably a 32 bit wide absolute relocation, but the target can choose. It generally does map to one of the other relocation types.
ARM 26 bit pc-relative branch. The lowest two bits must be zero and are not stored in the instruction.
ARM 26 bit pc-relative branch. The lowest bit must be zero and is not stored in the instruction. The 2nd lowest bit comes from a 1 bit field in the instruction.
Thumb 22 bit pc-relative branch. The lowest bit must be zero and is not stored in the instruction. The 2nd lowest bit comes from a 1 bit field in the instruction.
ARM 26-bit pc-relative branch for an unconditional BL or BLX instruction.
ARM 26-bit pc-relative branch for B or conditional BL instruction.
ARM 5-bit pc-relative branch for Branch Future instructions.
ARM 6-bit pc-relative branch for BFCSEL instruction.
ARM 17-bit pc-relative branch for Branch Future instructions.
ARM 13-bit pc-relative branch for BFCSEL instruction.
ARM 19-bit pc-relative branch for Branch Future Link instruction.
ARM 12-bit pc-relative branch for Low Overhead Loop instructions.
Thumb 7-, 9-, 12-, 20-, 23-, and 25-bit pc-relative branches. The lowest bit must be zero and is not stored in the instruction. Note that the corresponding ELF R_ARM_THM_JUMPnn constant has an "nn" one smaller in all cases. Note further that BRANCH23 corresponds to R_ARM_THM_CALL.
12-bit immediate offset, used in ARM-format ldr and str instructions.
5-bit immediate offset, used in Thumb-format ldr and str instructions.
Pc-relative or absolute relocation depending on target. Used for entries in .init_array sections.
Read-only segment base relative address.
Data segment base relative address.
This reloc is used for references to RTTI data from exception handling tables. The actual definition depends on the target. It may be a pc-relative or some form of GOT-indirect relocation.
31-bit PC relative address.
Low and High halfword relocations for MOVW and MOVT instructions.
ARM FDPIC specific relocations.
Relocations for setting up GOTs and PLTs for shared libraries.
ARM thread-local storage relocations.
ARM group relocations.
Annotation of BX instructions.
ARM support for STT_GNU_IFUNC.
Thumb1 relocations to support execute-only code.
These relocs are only used within the ARM assembler. They are not (at present) written to any object files.
Renesas / SuperH SH relocs. Not all of these appear in object files.
ARC relocs.
ADI Blackfin 16 bit immediate absolute reloc.
ADI Blackfin 16 bit immediate absolute reloc higher 16 bits.
ADI Blackfin ’a’ part of LSETUP.
ADI Blackfin.
ADI Blackfin 16 bit immediate absolute reloc lower 16 bits.
ADI Blackfin.
ADI Blackfin ’b’ part of LSETUP.
ADI Blackfin.
ADI Blackfin Short jump, pcrel.
ADI Blackfin Call.x not implemented.
ADI Blackfin Long Jump pcrel.
ADI Blackfin FD-PIC relocations.
ADI Blackfin GOT relocation.
ADI Blackfin PLTPC relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
ADI Blackfin arithmetic relocation.
Mitsubishi D10V relocs. This is a 10-bit reloc with the right 2 bits assumed to be 0.
Mitsubishi D10V relocs. This is a 10-bit reloc with the right 2 bits assumed to be 0. This is the same as the previous reloc except it is in the left container, i.e., shifted left 15 bits.
This is an 18-bit reloc with the right 2 bits assumed to be 0.
This is an 18-bit reloc with the right 2 bits assumed to be 0.
Mitsubishi D30V relocs. This is a 6-bit absolute reloc.
This is a 6-bit pc-relative reloc with the right 3 bits assumed to be 0.
This is a 6-bit pc-relative reloc with the right 3 bits assumed to be 0. Same as the previous reloc but on the right side of the container.
This is a 12-bit absolute reloc with the right 3 bitsassumed to be 0.
This is a 12-bit pc-relative reloc with the right 3 bits assumed to be 0.
This is a 12-bit pc-relative reloc with the right 3 bits assumed to be 0. Same as the previous reloc but on the right side of the container.
This is an 18-bit absolute reloc with the right 3 bits assumed to be 0.
This is an 18-bit pc-relative reloc with the right 3 bits assumed to be 0.
This is an 18-bit pc-relative reloc with the right 3 bits assumed to be 0. Same as the previous reloc but on the right side of the container.
This is a 32-bit absolute reloc.
This is a 32-bit pc-relative reloc.
DLX relocs
DLX relocs
DLX relocs
Renesas M16C/M32C Relocations.
Renesas M32R (formerly Mitsubishi M32R) relocs. This is a 24 bit absolute address.
This is a 10-bit pc-relative reloc with the right 2 bits assumed to be 0.
This is an 18-bit reloc with the right 2 bits assumed to be 0.
This is a 26-bit reloc with the right 2 bits assumed to be 0.
This is a 16-bit reloc containing the high 16 bits of an address used when the lower 16 bits are treated as unsigned.
This is a 16-bit reloc containing the high 16 bits of an address used when the lower 16 bits are treated as signed.
This is a 16-bit reloc containing the lower 16 bits of an address.
This is a 16-bit reloc containing the small data area offset for use in add3, load, and store instructions.
For PIC.
NDS32 relocs. This is a 20 bit absolute address.
This is a 9-bit pc-relative reloc with the right 1 bit assumed to be 0.
This is a 9-bit pc-relative reloc with the right 1 bit assumed to be 0.
This is an 15-bit reloc with the right 1 bit assumed to be 0.
This is an 17-bit reloc with the right 1 bit assumed to be 0.
This is a 25-bit reloc with the right 1 bit assumed to be 0.
This is a 20-bit reloc containing the high 20 bits of an address used with the lower 12 bits
This is a 12-bit reloc containing the lower 12 bits of an address then shift right by 3. This is used with ldi,sdi...
This is a 12-bit reloc containing the lower 12 bits of an address then shift left by 2. This is used with lwi,swi...
This is a 12-bit reloc containing the lower 12 bits of an address then shift left by 1. This is used with lhi,shi...
This is a 12-bit reloc containing the lower 12 bits of an address then shift left by 0. This is used with lbisbi...
This is a 12-bit reloc containing the lower 12 bits of an address then shift left by 0. This is only used with branch relaxations
This is a 15-bit reloc containing the small data area 18-bit signed offset and shift left by 3 for use in ldi, sdi...
This is a 15-bit reloc containing the small data area 17-bit signed offset and shift left by 2 for use in lwi, swi...
This is a 15-bit reloc containing the small data area 16-bit signed offset and shift left by 1 for use in lhi, shi...
This is a 15-bit reloc containing the small data area 15-bit signed offset and shift left by 0 for use in lbi, sbi...
This is a 16-bit reloc containing the small data area 16-bit signed offset and shift left by 3
This is a 17-bit reloc containing the small data area 17-bit signed offset and shift left by 2 for use in lwi.gp, swi.gp...
This is a 18-bit reloc containing the small data area 18-bit signed offset and shift left by 1 for use in lhi.gp, shi.gp...
This is a 19-bit reloc containing the small data area 19-bit signed offset and shift left by 0 for use in lbi.gp, sbi.gp...
for PIC
for relax
for PIC
for floating point
for dwarf2 debug_line.
for eliminate 16-bit instructions
for PIC object relaxation
NDS32 relocs. This is a 5 bit absolute address.
This is a 10-bit unsigned pc-relative reloc with the right 1 bit assumed to be 0.
If fp were omitted, fp can used as another gp.
relaxation relative relocation types
This is a 25 bit absolute address.
For ex9 and ifc using.
For TLS.
For floating load store relaxation.
This is a 9-bit reloc
This is a 22-bit reloc
This is a 16 bit offset from the short data area pointer.
This is a 16 bit offset (of which only 15 bits are used) from the short data area pointer.
This is a 16 bit offset from the zero data area pointer.
This is a 16 bit offset (of which only 15 bits are used) from the zero data area pointer.
This is an 8 bit offset (of which only 6 bits are used) from the tiny data area pointer.
This is an 8bit offset (of which only 7 bits are used) from the tiny data area pointer.
This is a 7 bit offset from the tiny data area pointer.
This is a 16 bit offset from the tiny data area pointer.
This is a 5 bit offset (of which only 4 bits are used) from the tiny data area pointer.
This is a 4 bit offset from the tiny data area pointer.
This is a 16 bit offset from the short data area pointer, with the bits placed non-contiguously in the instruction.
This is a 16 bit offset from the zero data area pointer, with the bits placed non-contiguously in the instruction.
This is a 6 bit offset from the call table base pointer.
This is a 16 bit offset from the call table base pointer.
Used for relaxing indirect function calls.
Used for relaxing indirect jumps.
Used to maintain alignment whilst relaxing.
This is a variation of BFD_RELOC_LO16 that can be used in v850e ld.bu instructions.
This is a 16-bit reloc.
This is a 17-bit reloc.
This is a 23-bit reloc.
This is a 32-bit reloc.
This is a 32-bit reloc.
This is a 16-bit reloc.
This is a 16-bit reloc.
Low 16 bits. 16 bit shifted by 1.
This is a 16 bit offset from the call table base pointer.
DSO relocations.
DSO relocations.
DSO relocations.
DSO relocations.
DSO relocations.
DSO relocations.
DSO relocations.
DSO relocations.
DSO relocations.
DSO relocations.
DSO relocations.
start code.
start data in text.
This is a 8bit DP reloc for the tms320c30, where the most significant 8 bits of a 24 bit word are placed into the least significant 8 bits of the opcode.
This is a 7bit reloc for the tms320c54x, where the least significant 7 bits of a 16 bit word are placed into the least significant 7 bits of the opcode.
This is a 9bit DP reloc for the tms320c54x, where the most significant 9 bits of a 16 bit word are placed into the least significant 9 bits of the opcode.
This is an extended address 23-bit reloc for the tms320c54x.
This is a 16-bit reloc for the tms320c54x, where the least significant 16 bits of a 23-bit extended address are placed into the opcode.
This is a reloc for the tms320c54x, where the most significant 7 bits of a 23-bit extended address are placed into the opcode.
TMS320C6000 relocations.
This is a 48 bit reloc for the FR30 that stores 32 bits.
This is a 32 bit reloc for the FR30 that stores 20 bits split up into two sections.
This is a 16 bit reloc for the FR30 that stores a 6 bit word offset in 4 bits.
This is a 16 bit reloc for the FR30 that stores an 8 bit byte offset into 8 bits.
This is a 16 bit reloc for the FR30 that stores a 9 bit short offset into 8 bits.
This is a 16 bit reloc for the FR30 that stores a 10 bit word offset into 8 bits.
This is a 16 bit reloc for the FR30 that stores a 9 bit pc relative short offset into 8 bits.
This is a 16 bit reloc for the FR30 that stores a 12 bit pc relative short offset into 11 bits.
Motorola Mcore relocations.
Toshiba Media Processor Relocations.
Imagination Technologies Meta relocations.
These are relocations for the GETA instruction.
These are relocations for a conditional branch instruction.
These are relocations for the PUSHJ instruction.
These are relocations for the JMP instruction.
This is a relocation for a relative address as in a GETA instruction or a branch.
This is a relocation for a relative address as in a JMP instruction.
This is a relocation for an instruction field that may be a general register or a value 0..255.
This is a relocation for an instruction field that may be a general register.
This is a relocation for two instruction fields holding a register and an offset, the equivalent of the relocation.
This relocation is an assertion that the expression is not allocated as a global register. It does not modify contents.
This is a 16 bit reloc for the AVR that stores 8 bit pc relative short offset into 7 bits.
This is a 16 bit reloc for the AVR that stores 13 bit pc relative short offset into 12 bits.
This is a 16 bit reloc for the AVR that stores 17 bit value (usually program memory address) into 16 bits.
This is a 16 bit reloc for the AVR that stores 8 bit value (usually data memory address) into 8 bit immediate value of LDI insn.
This is a 16 bit reloc for the AVR that stores 8 bit value (high 8 bit of data memory address) into 8 bit immediate value of LDI insn.
This is a 16 bit reloc for the AVR that stores 8 bit value (most high 8 bit of program memory address) into 8 bit immediate value of LDI insn.
This is a 16 bit reloc for the AVR that stores 8 bit value (most high 8 bit of 32 bit value) into 8 bit immediate value of LDI insn.
This is a 16 bit reloc for the AVR that stores negated 8 bit value (usually data memory address) into 8 bit immediate value of SUBI insn.
This is a 16 bit reloc for the AVR that stores negated 8 bit value (high 8 bit of data memory address) into 8 bit immediate value of SUBI insn.
This is a 16 bit reloc for the AVR that stores negated 8 bit value (most high 8 bit of program memory address) into 8 bit immediate value of LDI or SUBI insn.
This is a 16 bit reloc for the AVR that stores negated 8 bit value (msb of 32 bit value) into 8 bit immediate value of LDI insn.
This is a 16 bit reloc for the AVR that stores 8 bit value (usually command address) into 8 bit immediate value of LDI insn.
This is a 16 bit reloc for the AVR that stores 8 bit value (command address) into 8 bit immediate value of LDI insn. If the address is beyond the 128k boundary, the linker inserts a jump stub for this reloc in the lower 128k.
This is a 16 bit reloc for the AVR that stores 8 bit value (high 8 bit of command address) into 8 bit immediate value of LDI insn.
This is a 16 bit reloc for the AVR that stores 8 bit value (high 8 bit of command address) into 8 bit immediate value of LDI insn. If the address is beyond the 128k boundary, the linker inserts a jump stub for this reloc below 128k.
This is a 16 bit reloc for the AVR that stores 8 bit value (most high 8 bit of command address) into 8 bit immediate value of LDI insn.
This is a 16 bit reloc for the AVR that stores negated 8 bit value (usually command address) into 8 bit immediate value of SUBI insn.
This is a 16 bit reloc for the AVR that stores negated 8 bit value (high 8 bit of 16 bit command address) into 8 bit immediate value of SUBI insn.
This is a 16 bit reloc for the AVR that stores negated 8 bit value (high 6 bit of 22 bit command address) into 8 bit immediate value of SUBI insn.
This is a 32 bit reloc for the AVR that stores 23 bit value into 22 bits.
This is a 16 bit reloc for the AVR that stores all needed bits for absolute addressing with ldi with overflow check to linktime
This is a 6 bit reloc for the AVR that stores offset for ldd/std instructions
This is a 6 bit reloc for the AVR that stores offset for adiw/sbiw instructions
This is a 8 bit reloc for the AVR that stores bits 0..7 of a symbol in .byte lo8(symbol)
This is a 8 bit reloc for the AVR that stores bits 8..15 of a symbol in .byte hi8(symbol)
This is a 8 bit reloc for the AVR that stores bits 16..23 of a symbol in .byte hlo8(symbol)
AVR relocations to mark the difference of two local symbols. These are only needed to support linker relaxation and can be ignored when not relaxing. The field is set to the value of the difference assuming no relaxation. The relocation encodes the position of the second symbol so the linker can determine whether to adjust the field value.
This is a 7 bit reloc for the AVR that stores SRAM address for 16bit lds and sts instructions supported only tiny core.
This is a 6 bit reloc for the AVR that stores an I/O register number for the IN and OUT instructions
This is a 5 bit reloc for the AVR that stores an I/O register number for the SBIC, SBIS, SBI and CBI instructions
RISC-V relocations.
Renesas RL78 Relocations.
Renesas RX Relocations.
Direct 12 bit.
12 bit GOT offset.
32 bit PC relative PLT address.
Copy symbol at runtime.
Create GOT entry.
Create PLT entry.
Adjust by program base.
32 bit PC relative offset to GOT.
16 bit GOT offset.
PC relative 12 bit shifted by 1.
12 bit PC rel. PLT shifted by 1.
PC relative 16 bit shifted by 1.
16 bit PC rel. PLT shifted by 1.
PC relative 24 bit shifted by 1.
24 bit PC rel. PLT shifted by 1.
PC relative 32 bit shifted by 1.
32 bit PC rel. PLT shifted by 1.
32 bit PC rel. GOT shifted by 1.
64 bit GOT offset.
64 bit PC relative PLT address.
32 bit rel. offset to GOT entry.
64 bit offset to GOT.
12-bit offset to symbol-entry within GOT, with PLT handling.
16-bit offset to symbol-entry within GOT, with PLT handling.
32-bit offset to symbol-entry within GOT, with PLT handling.
64-bit offset to symbol-entry within GOT, with PLT handling.
32-bit rel. offset to symbol-entry within GOT, with PLT handling.
16-bit rel. offset from the GOT to a PLT entry.
32-bit rel. offset from the GOT to a PLT entry.
64-bit rel. offset from the GOT to a PLT entry.
s390 tls relocations.
Long displacement extension.
STT_GNU_IFUNC relocation.
Score relocations Low 16 bit for load/store
This is a 24-bit reloc with the right 1 bit assumed to be 0
This is a 19-bit reloc with the right 1 bit assumed to be 0
This is a 32-bit reloc for 48-bit instructions.
This is a 32-bit reloc for 48-bit instructions.
This is a 11-bit reloc with the right 1 bit assumed to be 0
This is a 8-bit reloc with the right 1 bit assumed to be 0
This is a 9-bit reloc with the right 1 bit assumed to be 0
Undocumented Score relocs
Scenix IP2K - 9-bit register number / data address
Scenix IP2K - 4-bit register/data bank number
Scenix IP2K - low 13 bits of instruction word address
Scenix IP2K - high 3 bits of instruction word address
Scenix IP2K - ext/low/high 8 bits of data address
Scenix IP2K - low/high 8 bits of instruction word address
Scenix IP2K - even/odd PC modifier to modify snb pcl.0
Scenix IP2K - 16 bit word address in text section.
Scenix IP2K - 7-bit sp or dp offset
Scenix VPE4K coprocessor - data/insn-space addressing
These two relocations are used by the linker to determine which of the entries in a C++ virtual function table are actually used. When the –gc-sections option is given, the linker will zero out the entries that are not used, so that the code for those functions need not be included in the output.
VTABLE_INHERIT is a zero-space relocation used to describe to the linker the inheritance tree of a C++ virtual function table. The relocation’s symbol should be the parent class’ vtable, and the relocation should be located at the child vtable.
VTABLE_ENTRY is a zero-space relocation that describes the use of a virtual function table entry. The reloc’s symbol should refer to the table of the class mentioned in the code. Off of that base, an offset describes the entry that is being used. For Rela hosts, this offset is stored in the reloc’s addend. For Rel hosts, we are forced to put this offset in the reloc’s section offset.
Intel IA64 Relocations.
Motorola 68HC11 reloc. This is the 8 bit high part of an absolute address.
Motorola 68HC11 reloc. This is the 8 bit low part of an absolute address.
Motorola 68HC11 reloc. This is the 3 bit of a value.
Motorola 68HC11 reloc. This reloc marks the beginning of a jump/call instruction. It is used for linker relaxation to correctly identify beginning of instruction and change some branches to use PC-relative addressing mode.
Motorola 68HC11 reloc. This reloc marks a group of several instructions that gcc generates and for which the linker relaxation pass can modify and/or remove some of them.
Motorola 68HC11 reloc. This is the 16-bit lower part of an address. It is used for ’call’ instruction to specify the symbol address without any special transformation (due to memory bank window).
Motorola 68HC11 reloc. This is a 8-bit reloc that specifies the page number of an address. It is used by ’call’ instruction to specify the page number of the symbol.
Motorola 68HC11 reloc. This is a 24-bit reloc that represents the address with a 16-bit value and a 8-bit page number. The symbol address is transformed to follow the 16K memory bank of 68HC12 (seen as mapped in the window).
Motorola 68HC12 reloc. This is the 5 bits of a value.
Freescale XGATE reloc. This reloc marks the beginning of a bra/jal instruction.
Freescale XGATE reloc. This reloc marks a group of several instructions that gcc generates and for which the linker relaxation pass can modify and/or remove some of them.
Freescale XGATE reloc. This is the 16-bit lower part of an address. It is used for the ’16-bit’ instructions.
Freescale XGATE reloc.
Freescale XGATE reloc.
Freescale XGATE reloc. This is a 9-bit pc-relative reloc.
Freescale XGATE reloc. This is a 10-bit pc-relative reloc.
Freescale XGATE reloc. This is the 16-bit lower part of an address. It is used for the ’16-bit’ instructions.
Freescale XGATE reloc. This is the 16-bit higher part of an address. It is used for the ’16-bit’ instructions.
Freescale XGATE reloc. This is a 3-bit pc-relative reloc.
Freescale XGATE reloc. This is a 4-bit pc-relative reloc.
Freescale XGATE reloc. This is a 5-bit pc-relative reloc.
Motorola 68HC12 reloc. This is the 9 bits of a value.
Motorola 68HC12 reloc. This is the 16 bits of a value.
Motorola 68HC12/XGATE reloc. This is a PCREL9 branch.
Motorola 68HC12/XGATE reloc. This is a PCREL10 branch.
Motorola 68HC12/XGATE reloc. This is the 8 bit low part of an absolute address and immediately precedes a matching HI8XG part.
Motorola 68HC12/XGATE reloc. This is the 8 bit high part of an absolute address and immediately follows a matching LO8XG part.
Freescale S12Z reloc. This is a 15 bit relative address. If the most significant bits are all zero then it may be truncated to 8 bits.
NS CR16 Relocations.
NS CRX Relocations.
These relocs are only used within the CRIS assembler. They are not (at present) written to any object files.
Relocs used in ELF shared libraries for CRIS.
32-bit offset to symbol-entry within GOT.
16-bit offset to symbol-entry within GOT.
32-bit offset to symbol-entry within GOT, with PLT handling.
16-bit offset to symbol-entry within GOT, with PLT handling.
32-bit offset to symbol, relative to GOT.
32-bit offset to symbol with PLT entry, relative to GOT.
32-bit offset to symbol with PLT entry, relative to this relocation.
Relocs used in TLS code for CRIS.
OpenRISC 1000 Relocations.
H8 elf Relocations.
Sony Xstormy16 Relocations.
Self-describing complex relocations.
Infineon Relocations.
Relocations used by VAX ELF.
Morpho MT - 16 bit immediate relocation.
Morpho MT - Hi 16 bits of an address.
Morpho MT - Low 16 bits of an address.
Morpho MT - Used to tell the linker which vtable entries are used.
Morpho MT - Used to tell the linker which vtable entries are used.
Morpho MT - 8 bit immediate relocation.
msp430 specific relocation codes
Relocations used by the Altera Nios II core.
PRU LDI 16-bit unsigned data-memory relocation.
PRU LDI 16-bit unsigned instruction-memory relocation.
PRU relocation for two consecutive LDI load instructions that load a 32 bit value into a register. If the higher bits are all zero, then the second instruction may be relaxed.
PRU QBBx 10-bit signed PC-relative relocation.
PRU 8-bit unsigned relocation used for the LOOP instruction.
PRU Program Memory relocations. Used to convert from byte addressing to 32-bit word addressing.
PRU relocations to mark the difference of two local symbols. These are only needed to support linker relaxation and can be ignored when not relaxing. The field is set to the value of the difference assuming no relaxation. The relocation encodes the position of the second symbol so the linker can determine whether to adjust the field value. The PMEM variants encode the word difference, instead of byte difference between symbols.
IQ2000 Relocations.
Special Xtensa relocation used only by PLT entries in ELF shared objects to indicate that the runtime linker should set the value to one of its own internal functions or data structures.
Xtensa relocations for ELF shared objects.
Xtensa relocation used in ELF object files for symbols that may require PLT entries. Otherwise, this is just a generic 32-bit relocation.
Xtensa relocations for backward compatibility. These have been replaced by BFD_RELOC_XTENSA_PDIFF and BFD_RELOC_XTENSA_NDIFF. Xtensa relocations to mark the difference of two local symbols. These are only needed to support linker relaxation and can be ignored when not relaxing. The field is set to the value of the difference assuming no relaxation. The relocation encodes the position of the first symbol so the linker can determine whether to adjust the field value.
Generic Xtensa relocations for instruction operands. Only the slot number is encoded in the relocation. The relocation applies to the last PC-relative immediate operand, or if there are no PC-relative immediates, to the last immediate operand.
Alternate Xtensa relocations. Only the slot is encoded in the relocation. The meaning of these relocations is opcode-specific.
Xtensa relocations for backward compatibility. These have all been replaced by BFD_RELOC_XTENSA_SLOT0_OP.
Xtensa relocation to mark that the assembler expanded the instructions from an original target. The expansion size is encoded in the reloc size.
Xtensa relocation to mark that the linker should simplify assembler-expanded instructions. This is commonly used internally by the linker after analysis of a BFD_RELOC_XTENSA_ASM_EXPAND.
Xtensa TLS relocations.
Xtensa relocations to mark the difference of two local symbols. These are only needed to support linker relaxation and can be ignored when not relaxing. The field is set to the value of the difference assuming no relaxation. The relocation encodes the position of the subtracted symbol so the linker can determine whether to adjust the field value. PDIFF relocations are used for positive differences, NDIFF relocations are used for negative differences. The difference value is treated as unsigned with these relocation types, giving full 8/16 value ranges.
8 bit signed offset in (ix+d) or (iy+d).
First 8 bits of multibyte (32, 24 or 16 bit) value.
Second 8 bits of multibyte (32, 24 or 16 bit) value.
Third 8 bits of multibyte (32 or 24 bit) value.
Fourth 8 bits of multibyte (32 bit) value.
Lowest 16 bits of multibyte (32 or 24 bit) value.
Highest 16 bits of multibyte (32 or 24 bit) value.
Like BFD_RELOC_16 but big-endian.
DJNZ offset.
CALR offset.
4 bit value.
Lattice Mico32 relocations.
Difference between two section addreses. Must be followed by a BFD_RELOC_MACH_O_PAIR.
Like BFD_RELOC_MACH_O_SECTDIFF but with a local symbol.
Pair of relocation. Contains the first symbol.
Symbol will be substracted. Must be followed by a BFD_RELOC_32.
Symbol will be substracted. Must be followed by a BFD_RELOC_64.
PCREL relocations. They are marked as branch to create PLT entry if required.
Used when referencing a GOT entry.
Used when loading a GOT entry with movq. It is specially marked so that the linker could optimize the movq to a leaq if possible.
Same as BFD_RELOC_32_PCREL but with an implicit -1 addend.
Same as BFD_RELOC_32_PCREL but with an implicit -2 addend.
Same as BFD_RELOC_32_PCREL but with an implicit -4 addend.
Used when referencing a TLV entry.
Addend for PAGE or PAGEOFF.
Relative offset to page of GOT slot.
Relative offset within page of GOT slot.
Address of a GOT entry.
This is a 32 bit reloc for the microblaze that stores the low 16 bits of a value
This is a 32 bit pc-relative reloc for the microblaze that stores the low 16 bits of a value
This is a 32 bit reloc for the microblaze that stores a value relative to the read-only small data area anchor
This is a 32 bit reloc for the microblaze that stores a value relative to the read-write small data area anchor
This is a 32 bit reloc for the microblaze to handle expressions of the form "Symbol Op Symbol"
This is a 64 bit reloc that stores the 32 bit pc relative value in two words (with an imm instruction). No relocation is done here - only used for relaxing
This is a 64 bit reloc that stores the 32 bit pc relative value in two words (with an imm instruction). The relocation is PC-relative GOT offset
This is a 64 bit reloc that stores the 32 bit pc relative value in two words (with an imm instruction). The relocation is GOT offset
This is a 64 bit reloc that stores the 32 bit pc relative value in two words (with an imm instruction). The relocation is PC-relative offset into PLT
This is a 64 bit reloc that stores the 32 bit GOT relative value in two words (with an imm instruction). The relocation is relative offset from _GLOBAL_OFFSET_TABLE_
This is a 32 bit reloc that stores the 32 bit GOT relative value in a word. The relocation is relative offset from
This is used to tell the dynamic linker to copy the value out of the dynamic object into the runtime process image.
Unused Reloc
This is a 64 bit reloc that stores the 32 bit GOT relative value of the GOT TLS GD info entry in two words (with an imm instruction). The relocation is GOT offset.
This is a 64 bit reloc that stores the 32 bit GOT relative value of the GOT TLS LD info entry in two words (with an imm instruction). The relocation is GOT offset.
This is a 32 bit reloc that stores the Module ID to GOT(n).
This is a 32 bit reloc that stores TLS offset to GOT(n+1).
This is a 32 bit reloc for storing TLS offset to two words (uses imm instruction)
This is a 64 bit reloc that stores 32-bit thread pointer relative offset to two words (uses imm instruction).
This is a 64 bit reloc that stores 32-bit thread pointer relative offset to two words (uses imm instruction).
This is a 64 bit reloc that stores the 32 bit pc relative value in two words (with an imm instruction). The relocation is PC-relative offset from start of TEXT.
This is a 64 bit reloc that stores the 32 bit offset value in two words (with an imm instruction). The relocation is relative offset from start of TEXT.
AArch64 pseudo relocation code to mark the start of the AArch64 relocation enumerators. N.B. the order of the enumerators is important as several tables in the AArch64 bfd backend are indexed by these enumerators; make sure they are all synced.
Deprecated AArch64 null relocation code.
AArch64 null relocation code.
Basic absolute relocations of N bits. These are equivalent to BFD_RELOC_N and they were added to assist the indexing of the howto table.
PC-relative relocations. These are equivalent to BFD_RELOC_N_PCREL and they were added to assist the indexing of the howto table.
AArch64 MOV[NZK] instruction with most significant bits 0 to 15 of an unsigned address/value.
AArch64 MOV[NZK] instruction with less significant bits 0 to 15 of an address/value. No overflow checking.
AArch64 MOV[NZK] instruction with most significant bits 16 to 31 of an unsigned address/value.
AArch64 MOV[NZK] instruction with less significant bits 16 to 31 of an address/value. No overflow checking.
AArch64 MOV[NZK] instruction with most significant bits 32 to 47 of an unsigned address/value.
AArch64 MOV[NZK] instruction with less significant bits 32 to 47 of an address/value. No overflow checking.
AArch64 MOV[NZK] instruction with most signficant bits 48 to 64 of a signed or unsigned address/value.
AArch64 MOV[NZ] instruction with most significant bits 0 to 15 of a signed value. Changes instruction to MOVZ or MOVN depending on the value’s sign.
AArch64 MOV[NZ] instruction with most significant bits 16 to 31 of a signed value. Changes instruction to MOVZ or MOVN depending on the value’s sign.
AArch64 MOV[NZ] instruction with most significant bits 32 to 47 of a signed value. Changes instruction to MOVZ or MOVN depending on the value’s sign.
AArch64 MOV[NZ] instruction with most significant bits 0 to 15 of a signed value. Changes instruction to MOVZ or MOVN depending on the value’s sign.
AArch64 MOV[NZ] instruction with most significant bits 0 to 15 of a signed value. Changes instruction to MOVZ or MOVN depending on the value’s sign.
AArch64 MOVK instruction with most significant bits 16 to 31 of a signed value.
AArch64 MOVK instruction with most significant bits 16 to 31 of a signed value.
AArch64 MOVK instruction with most significant bits 32 to 47 of a signed value.
AArch64 MOVK instruction with most significant bits 32 to 47 of a signed value.
AArch64 MOVK instruction with most significant bits 47 to 63 of a signed value.
AArch64 Load Literal instruction, holding a 19 bit pc-relative word offset. The lowest two bits must be zero and are not stored in the instruction, giving a 21 bit signed byte offset.
AArch64 ADR instruction, holding a simple 21 bit pc-relative byte offset.
AArch64 ADRP instruction, with bits 12 to 32 of a pc-relative page offset, giving a 4KB aligned page base address.
AArch64 ADRP instruction, with bits 12 to 32 of a pc-relative page offset, giving a 4KB aligned page base address, but with no overflow checking.
AArch64 ADD immediate instruction, holding bits 0 to 11 of the address. Used in conjunction with BFD_RELOC_AARCH64_ADR_HI21_PCREL.
AArch64 8-bit load/store instruction, holding bits 0 to 11 of the address. Used in conjunction with BFD_RELOC_AARCH64_ADR_HI21_PCREL.
AArch64 14 bit pc-relative test bit and branch. The lowest two bits must be zero and are not stored in the instruction, giving a 16 bit signed byte offset.
AArch64 19 bit pc-relative conditional branch and compare & branch. The lowest two bits must be zero and are not stored in the instruction, giving a 21 bit signed byte offset.
AArch64 26 bit pc-relative unconditional branch. The lowest two bits must be zero and are not stored in the instruction, giving a 28 bit signed byte offset.
AArch64 26 bit pc-relative unconditional branch and link. The lowest two bits must be zero and are not stored in the instruction, giving a 28 bit signed byte offset.
AArch64 16-bit load/store instruction, holding bits 0 to 11 of the address. Used in conjunction with BFD_RELOC_AARCH64_ADR_HI21_PCREL.
AArch64 32-bit load/store instruction, holding bits 0 to 11 of the address. Used in conjunction with BFD_RELOC_AARCH64_ADR_HI21_PCREL.
AArch64 64-bit load/store instruction, holding bits 0 to 11 of the address. Used in conjunction with BFD_RELOC_AARCH64_ADR_HI21_PCREL.
AArch64 128-bit load/store instruction, holding bits 0 to 11 of the address. Used in conjunction with BFD_RELOC_AARCH64_ADR_HI21_PCREL.
AArch64 Load Literal instruction, holding a 19 bit PC relative word offset of the global offset table entry for a symbol. The lowest two bits must be zero and are not stored in the instruction, giving a 21 bit signed byte offset. This relocation type requires signed overflow checking.
Get to the page base of the global offset table entry for a symbol as part of an ADRP instruction using a 21 bit PC relative value.Used in conjunction with BFD_RELOC_AARCH64_LD64_GOT_LO12_NC.
Unsigned 12 bit byte offset for 64 bit load/store from the page of the GOT entry for this symbol. Used in conjunction with BFD_RELOC_AARCH64_ADR_GOT_PAGE. Valid in LP64 ABI only.
Unsigned 12 bit byte offset for 32 bit load/store from the page of the GOT entry for this symbol. Used in conjunction with BFD_RELOC_AARCH64_ADR_GOT_PAGE. Valid in ILP32 ABI only.
Unsigned 16 bit byte offset for 64 bit load/store from the GOT entry for this symbol. Valid in LP64 ABI only.
Unsigned 16 bit byte higher offset for 64 bit load/store from the GOT entry for this symbol. Valid in LP64 ABI only.
Unsigned 15 bit byte offset for 64 bit load/store from the page of the GOT entry for this symbol. Valid in LP64 ABI only.
Scaled 14 bit byte offset to the page base of the global offset table.
Scaled 15 bit byte offset to the page base of the global offset table.
Get to the page base of the global offset table entry for a symbols tls_index structure as part of an adrp instruction using a 21 bit PC relative value. Used in conjunction with BFD_RELOC_AARCH64_TLSGD_ADD_LO12_NC.
AArch64 TLS General Dynamic
Unsigned 12 bit byte offset to global offset table entry for a symbols tls_index structure. Used in conjunction with BFD_RELOC_AARCH64_TLSGD_ADR_PAGE21.
AArch64 TLS General Dynamic relocation.
AArch64 TLS General Dynamic relocation.
AArch64 TLS INITIAL EXEC relocation.
AArch64 TLS INITIAL EXEC relocation.
AArch64 TLS INITIAL EXEC relocation.
AArch64 TLS INITIAL EXEC relocation.
AArch64 TLS INITIAL EXEC relocation.
AArch64 TLS INITIAL EXEC relocation.
bit[23:12] of byte offset to module TLS base address.
Unsigned 12 bit byte offset to module TLS base address.
No overflow check version of BFD_RELOC_AARCH64_TLSLD_ADD_DTPREL_LO12.
Unsigned 12 bit byte offset to global offset table entry for a symbols tls_index structure. Used in conjunction with BFD_RELOC_AARCH64_TLSLD_ADR_PAGE21.
GOT entry page address for AArch64 TLS Local Dynamic, used with ADRP instruction.
GOT entry address for AArch64 TLS Local Dynamic, used with ADR instruction.
bit[11:1] of byte offset to module TLS base address, encoded in ldst instructions.
Similar as BFD_RELOC_AARCH64_TLSLD_LDST16_DTPREL_LO12, but no overflow check.
bit[11:2] of byte offset to module TLS base address, encoded in ldst instructions.
Similar as BFD_RELOC_AARCH64_TLSLD_LDST32_DTPREL_LO12, but no overflow check.
bit[11:3] of byte offset to module TLS base address, encoded in ldst instructions.
Similar as BFD_RELOC_AARCH64_TLSLD_LDST64_DTPREL_LO12, but no overflow check.
bit[11:0] of byte offset to module TLS base address, encoded in ldst instructions.
Similar as BFD_RELOC_AARCH64_TLSLD_LDST8_DTPREL_LO12, but no overflow check.
bit[15:0] of byte offset to module TLS base address.
No overflow check version of BFD_RELOC_AARCH64_TLSLD_MOVW_DTPREL_G0
bit[31:16] of byte offset to module TLS base address.
No overflow check version of BFD_RELOC_AARCH64_TLSLD_MOVW_DTPREL_G1
bit[47:32] of byte offset to module TLS base address.
AArch64 TLS LOCAL EXEC relocation.
AArch64 TLS LOCAL EXEC relocation.
AArch64 TLS LOCAL EXEC relocation.
AArch64 TLS LOCAL EXEC relocation.
AArch64 TLS LOCAL EXEC relocation.
AArch64 TLS LOCAL EXEC relocation.
AArch64 TLS LOCAL EXEC relocation.
AArch64 TLS LOCAL EXEC relocation.
bit[11:1] of byte offset to module TLS base address, encoded in ldst instructions.
Similar as BFD_RELOC_AARCH64_TLSLE_LDST16_TPREL_LO12, but no overflow check.
bit[11:2] of byte offset to module TLS base address, encoded in ldst instructions.
Similar as BFD_RELOC_AARCH64_TLSLE_LDST32_TPREL_LO12, but no overflow check.
bit[11:3] of byte offset to module TLS base address, encoded in ldst instructions.
Similar as BFD_RELOC_AARCH64_TLSLE_LDST64_TPREL_LO12, but no overflow check.
bit[11:0] of byte offset to module TLS base address, encoded in ldst instructions.
Similar as BFD_RELOC_AARCH64_TLSLE_LDST8_TPREL_LO12, but no overflow check.
AArch64 TLS DESC relocation.
AArch64 TLS DESC relocation.
AArch64 TLS DESC relocation.
AArch64 TLS DESC relocation.
AArch64 TLS DESC relocation.
AArch64 TLS DESC relocation.
AArch64 TLS DESC relocation.
AArch64 TLS DESC relocation.
AArch64 TLS DESC relocation.
AArch64 TLS DESC relocation.
AArch64 TLS DESC relocation.
AArch64 TLS relocation.
AArch64 TLS relocation.
AArch64 TLS relocation.
AArch64 TLS relocation.
AArch64 TLS relocation.
AArch64 TLS relocation.
AArch64 TLS relocation.
AArch64 TLS relocation.
AArch64 support for STT_GNU_IFUNC.
AArch64 pseudo relocation code to mark the end of the AArch64 relocation enumerators that have direct mapping to ELF reloc codes. There are a few more enumerators after this one; those are mainly used by the AArch64 assembler for the internal fixup or to select one of the above enumerators.
AArch64 pseudo relocation code to be used internally by the AArch64 assembler and not (currently) written to any object files.
AArch64 unspecified load/store instruction, holding bits 0 to 11 of the address. Used in conjunction with BFD_RELOC_AARCH64_ADR_HI21_PCREL.
AArch64 pseudo relocation code for TLS local dynamic mode. It’s to be used internally by the AArch64 assembler and not (currently) written to any object files.
Similar as BFD_RELOC_AARCH64_TLSLD_LDST_DTPREL_LO12, but no overflow check.
AArch64 pseudo relocation code for TLS local exec mode. It’s to be used internally by the AArch64 assembler and not (currently) written to any object files.
Similar as BFD_RELOC_AARCH64_TLSLE_LDST_TPREL_LO12, but no overflow check.
AArch64 pseudo relocation code to be used internally by the AArch64 assembler and not (currently) written to any object files.
AArch64 pseudo relocation code to be used internally by the AArch64 assembler and not (currently) written to any object files.
AArch64 pseudo relocation code to be used internally by the AArch64 assembler and not (currently) written to any object files.
Tilera TILEPro Relocations.
Tilera TILE-Gx Relocations.
Linux eBPF relocations.
Adapteva EPIPHANY - 8 bit signed pc-relative displacement
Adapteva EPIPHANY - 24 bit signed pc-relative displacement
Adapteva EPIPHANY - 16 most-significant bits of absolute address
Adapteva EPIPHANY - 16 least-significant bits of absolute address
Adapteva EPIPHANY - 11 bit signed number - add/sub immediate
Adapteva EPIPHANY - 11 bit sign-magnitude number (ld/st displacement)
Adapteva EPIPHANY - 8 bit immediate for 16 bit mov instruction.
Visium Relocations.
WebAssembly relocations.
C-SKY relocations.
S12Z relocations.
typedef enum bfd_reloc_code_real bfd_reloc_code_real_type;
bfd_reloc_type_lookup
Synopsis
reloc_howto_type *bfd_reloc_type_lookup (bfd *abfd, bfd_reloc_code_real_type code); reloc_howto_type *bfd_reloc_name_lookup (bfd *abfd, const char *reloc_name);
Description
Return a pointer to a howto structure which, when
invoked, will perform the relocation code on data from the
architecture noted.
bfd_default_reloc_type_lookup
Synopsis
reloc_howto_type *bfd_default_reloc_type_lookup (bfd *abfd, bfd_reloc_code_real_type code);
Description
Provides a default relocation lookup routine for any architecture.
bfd_get_reloc_code_name
Synopsis
const char *bfd_get_reloc_code_name (bfd_reloc_code_real_type code);
Description
Provides a printable name for the supplied relocation code.
Useful mainly for printing error messages.
bfd_generic_relax_section
Synopsis
bool bfd_generic_relax_section (bfd *abfd, asection *section, struct bfd_link_info *, bool *);
Description
Provides default handling for relaxing for back ends which
don’t do relaxing.
bfd_generic_gc_sections
Synopsis
bool bfd_generic_gc_sections (bfd *, struct bfd_link_info *);
Description
Provides default handling for relaxing for back ends which
don’t do section gc – i.e., does nothing.
bfd_generic_lookup_section_flags
Synopsis
bool bfd_generic_lookup_section_flags (struct bfd_link_info *, struct flag_info *, asection *);
Description
Provides default handling for section flags lookup
– i.e., does nothing.
Returns FALSE if the section should be omitted, otherwise TRUE.
bfd_generic_merge_sections
Synopsis
bool bfd_generic_merge_sections (bfd *, struct bfd_link_info *);
Description
Provides default handling for SEC_MERGE section merging for back ends
which don’t have SEC_MERGE support – i.e., does nothing.
bfd_generic_get_relocated_section_contents
Synopsis
bfd_byte *bfd_generic_get_relocated_section_contents (bfd *abfd, struct bfd_link_info *link_info, struct bfd_link_order *link_order, bfd_byte *data, bool relocatable, asymbol **symbols);
Description
Provides default handling of relocation effort for back ends
which can’t be bothered to do it efficiently.
_bfd_generic_set_reloc
Synopsis
void _bfd_generic_set_reloc (bfd *abfd, sec_ptr section, arelent **relptr, unsigned int count);
Description
Installs a new set of internal relocations in SECTION.
_bfd_unrecognized_reloc
Synopsis
bool _bfd_unrecognized_reloc (bfd * abfd, sec_ptr section, unsigned int r_type);
Description
Reports an unrecognized reloc.
Written as a function in order to reduce code duplication.
Returns FALSE so that it can be called from a return statement.
Next: Targets, Previous: Relocations, Up: BFD front end [Contents][Index]
Description
These are functions pertaining to core files.
bfd_core_file_failing_command
Synopsis
const char *bfd_core_file_failing_command (bfd *abfd);
Description
Return a read-only string explaining which program was running
when it failed and produced the core file abfd.
bfd_core_file_failing_signal
Synopsis
int bfd_core_file_failing_signal (bfd *abfd);
Description
Returns the signal number which caused the core dump which
generated the file the BFD abfd is attached to.
bfd_core_file_pid
Synopsis
int bfd_core_file_pid (bfd *abfd);
Description
Returns the PID of the process the core dump the BFD
abfd is attached to was generated from.
core_file_matches_executable_p
Synopsis
bool core_file_matches_executable_p (bfd *core_bfd, bfd *exec_bfd);
Description
Return TRUE
if the core file attached to core_bfd
was generated by a run of the executable file attached to
exec_bfd, FALSE
otherwise.
generic_core_file_matches_executable_p
Synopsis
bool generic_core_file_matches_executable_p (bfd *core_bfd, bfd *exec_bfd);
Description
Return TRUE if the core file attached to core_bfd
was generated by a run of the executable file attached
to exec_bfd. The match is based on executable
basenames only.
Note: When not able to determine the core file failing command or the executable name, we still return TRUE even though we’re not sure that core file and executable match. This is to avoid generating a false warning in situations where we really don’t know whether they match or not.
Next: Architectures, Previous: Core Files, Up: BFD front end [Contents][Index]
Description
Each port of BFD to a different machine requires the creation
of a target back end. All the back end provides to the root
part of BFD is a structure containing pointers to functions
which perform certain low level operations on files. BFD
translates the applications’s requests through a pointer into
calls to the back end routines.
When a file is opened with bfd_openr
, its format and
target are unknown. BFD uses various mechanisms to determine
how to interpret the file. The operations performed are:
_bfd_new_bfd
, then call bfd_find_target
with the
target string supplied to bfd_openr
and the new BFD pointer.
bfd_find_target
,
look up the environment variable GNUTARGET
and use
that as the target string.
NULL
, or the target string is
default
, then use the first item in the target vector
as the target type, and set target_defaulted
in the BFD to
cause bfd_check_format
to loop through all the targets.
See bfd_target. See Formats.
bfd_error_invalid_target
to
bfd_openr
.
bfd_openr
attempts to open the file using
bfd_open_file
, and returns the BFD.
Once the BFD has been opened and the target selected, the file
format may be determined. This is done by calling
bfd_check_format
on the BFD with a suggested format.
If target_defaulted
has been set, each possible target
type is tried to see if it recognizes the specified format.
bfd_check_format
returns TRUE
when the caller guesses right.
• bfd_target |
Description
This structure contains everything that BFD knows about a
target. It includes things like its byte order, name, and which
routines to call to do various operations.
Every BFD points to a target structure with its xvec
member.
The macros below are used to dispatch to functions through the
bfd_target
vector. They are used in a number of macros further
down in bfd.h, and are also used when calling various
routines by hand inside the BFD implementation. The arglist
argument must be parenthesized; it contains all the arguments
to the called function.
They make the documentation (more) unpleasant to read, so if someone wants to fix this and not break the above, please do.
#define BFD_SEND(bfd, message, arglist) \ ((*((bfd)->xvec->message)) arglist) #ifdef DEBUG_BFD_SEND #undef BFD_SEND #define BFD_SEND(bfd, message, arglist) \ (((bfd) && (bfd)->xvec && (bfd)->xvec->message) ? \ ((*((bfd)->xvec->message)) arglist) : \ (bfd_assert (__FILE__,__LINE__), NULL)) #endif
For operations which index on the BFD format:
#define BFD_SEND_FMT(bfd, message, arglist) \ (((bfd)->xvec->message[(int) ((bfd)->format)]) arglist) #ifdef DEBUG_BFD_SEND #undef BFD_SEND_FMT #define BFD_SEND_FMT(bfd, message, arglist) \ (((bfd) && (bfd)->xvec && (bfd)->xvec->message) ? \ (((bfd)->xvec->message[(int) ((bfd)->format)]) arglist) : \ (bfd_assert (__FILE__,__LINE__), NULL)) #endif /* Defined to TRUE if unused section symbol should be kept. */ #ifndef TARGET_KEEP_UNUSED_SECTION_SYMBOLS #define TARGET_KEEP_UNUSED_SECTION_SYMBOLS true #endif
This is the structure which defines the type of BFD this is. The
xvec
member of the struct bfd
itself points here. Each
module that implements access to a different target under BFD,
defines one of these.
FIXME, these names should be rationalised with the names of the entry points which call them. Too bad we can’t have one macro to define them both!
enum bfd_flavour { /* N.B. Update bfd_flavour_name if you change this. */ bfd_target_unknown_flavour, bfd_target_aout_flavour, bfd_target_coff_flavour, bfd_target_ecoff_flavour, bfd_target_xcoff_flavour, bfd_target_elf_flavour, bfd_target_tekhex_flavour, bfd_target_srec_flavour, bfd_target_verilog_flavour, bfd_target_ihex_flavour, bfd_target_som_flavour, bfd_target_os9k_flavour, bfd_target_versados_flavour, bfd_target_msdos_flavour, bfd_target_ovax_flavour, bfd_target_evax_flavour, bfd_target_mmo_flavour, bfd_target_mach_o_flavour, bfd_target_pef_flavour, bfd_target_pef_xlib_flavour, bfd_target_sym_flavour }; enum bfd_endian { BFD_ENDIAN_BIG, BFD_ENDIAN_LITTLE, BFD_ENDIAN_UNKNOWN }; /* Forward declaration. */ typedef struct bfd_link_info _bfd_link_info; /* Forward declaration. */ typedef struct flag_info flag_info; typedef void (*bfd_cleanup) (bfd *); typedef struct bfd_target { /* Identifies the kind of target, e.g., SunOS4, Ultrix, etc. */ const char *name; /* The "flavour" of a back end is a general indication about the contents of a file. */ enum bfd_flavour flavour; /* The order of bytes within the data area of a file. */ enum bfd_endian byteorder; /* The order of bytes within the header parts of a file. */ enum bfd_endian header_byteorder; /* A mask of all the flags which an executable may have set - from the setBFD_NO_FLAGS
,HAS_RELOC
, ...D_PAGED
. */ flagword object_flags; /* A mask of all the flags which a section may have set - from the setSEC_NO_FLAGS
,SEC_ALLOC
, ...SET_NEVER_LOAD
. */ flagword section_flags; /* The character normally found at the front of a symbol. (if any), perhaps `_'. */ char symbol_leading_char; /* The pad character for file names within an archive header. */ char ar_pad_char; /* The maximum number of characters in an archive header. */ unsigned char ar_max_namelen; /* How well this target matches, used to select between various possible targets when more than one target matches. */ unsigned char match_priority; /* TRUE if unused section symbols should be kept. */ bool keep_unused_section_symbols; /* Entries for byte swapping for data. These are different from the other entry points, since they don't take a BFD as the first argument. Certain other handlers could do the same. */ bfd_uint64_t (*bfd_getx64) (const void *); bfd_int64_t (*bfd_getx_signed_64) (const void *); void (*bfd_putx64) (bfd_uint64_t, void *); bfd_vma (*bfd_getx32) (const void *); bfd_signed_vma (*bfd_getx_signed_32) (const void *); void (*bfd_putx32) (bfd_vma, void *); bfd_vma (*bfd_getx16) (const void *); bfd_signed_vma (*bfd_getx_signed_16) (const void *); void (*bfd_putx16) (bfd_vma, void *); /* Byte swapping for the headers. */ bfd_uint64_t (*bfd_h_getx64) (const void *); bfd_int64_t (*bfd_h_getx_signed_64) (const void *); void (*bfd_h_putx64) (bfd_uint64_t, void *); bfd_vma (*bfd_h_getx32) (const void *); bfd_signed_vma (*bfd_h_getx_signed_32) (const void *); void (*bfd_h_putx32) (bfd_vma, void *); bfd_vma (*bfd_h_getx16) (const void *); bfd_signed_vma (*bfd_h_getx_signed_16) (const void *); void (*bfd_h_putx16) (bfd_vma, void *); /* Format dependent routines: these are vectors of entry points within the target vector structure, one for each format to check. */ /* Check the format of a file being read. Return abfd_cleanup
on success or zero on failure. */ bfd_cleanup (*_bfd_check_format[bfd_type_end]) (bfd *); /* Set the format of a file being written. */ bool (*_bfd_set_format[bfd_type_end]) (bfd *); /* Write cached information into a file being written, atbfd_close
. */ bool (*_bfd_write_contents[bfd_type_end]) (bfd *);
The general target vector. These vectors are initialized using the BFD_JUMP_TABLE macros.
/* Generic entry points. */ #define BFD_JUMP_TABLE_GENERIC(NAME) \ NAME##_close_and_cleanup, \ NAME##_bfd_free_cached_info, \ NAME##_new_section_hook, \ NAME##_get_section_contents, \ NAME##_get_section_contents_in_window /* Called when the BFD is being closed to do any necessary cleanup. */ bool (*_close_and_cleanup) (bfd *); /* Ask the BFD to free all cached information. */ bool (*_bfd_free_cached_info) (bfd *); /* Called when a new section is created. */ bool (*_new_section_hook) (bfd *, sec_ptr); /* Read the contents of a section. */ bool (*_bfd_get_section_contents) (bfd *, sec_ptr, void *, file_ptr, bfd_size_type); bool (*_bfd_get_section_contents_in_window) (bfd *, sec_ptr, bfd_window *, file_ptr, bfd_size_type); /* Entry points to copy private data. */ #define BFD_JUMP_TABLE_COPY(NAME) \ NAME##_bfd_copy_private_bfd_data, \ NAME##_bfd_merge_private_bfd_data, \ _bfd_generic_init_private_section_data, \ NAME##_bfd_copy_private_section_data, \ NAME##_bfd_copy_private_symbol_data, \ NAME##_bfd_copy_private_header_data, \ NAME##_bfd_set_private_flags, \ NAME##_bfd_print_private_bfd_data /* Called to copy BFD general private data from one object file to another. */ bool (*_bfd_copy_private_bfd_data) (bfd *, bfd *); /* Called to merge BFD general private data from one object file to a common output file when linking. */ bool (*_bfd_merge_private_bfd_data) (bfd *, struct bfd_link_info *); /* Called to initialize BFD private section data from one object file to another. */ #define bfd_init_private_section_data(ibfd, isec, obfd, osec, link_info) \ BFD_SEND (obfd, _bfd_init_private_section_data, \ (ibfd, isec, obfd, osec, link_info)) bool (*_bfd_init_private_section_data) (bfd *, sec_ptr, bfd *, sec_ptr, struct bfd_link_info *); /* Called to copy BFD private section data from one object file to another. */ bool (*_bfd_copy_private_section_data) (bfd *, sec_ptr, bfd *, sec_ptr); /* Called to copy BFD private symbol data from one symbol to another. */ bool (*_bfd_copy_private_symbol_data) (bfd *, asymbol *, bfd *, asymbol *); /* Called to copy BFD private header data from one object file to another. */ bool (*_bfd_copy_private_header_data) (bfd *, bfd *); /* Called to set private backend flags. */ bool (*_bfd_set_private_flags) (bfd *, flagword); /* Called to print private BFD data. */ bool (*_bfd_print_private_bfd_data) (bfd *, void *); /* Core file entry points. */ #define BFD_JUMP_TABLE_CORE(NAME) \ NAME##_core_file_failing_command, \ NAME##_core_file_failing_signal, \ NAME##_core_file_matches_executable_p, \ NAME##_core_file_pid char *(*_core_file_failing_command) (bfd *); int (*_core_file_failing_signal) (bfd *); bool (*_core_file_matches_executable_p) (bfd *, bfd *); int (*_core_file_pid) (bfd *); /* Archive entry points. */ #define BFD_JUMP_TABLE_ARCHIVE(NAME) \ NAME##_slurp_armap, \ NAME##_slurp_extended_name_table, \ NAME##_construct_extended_name_table, \ NAME##_truncate_arname, \ NAME##_write_armap, \ NAME##_read_ar_hdr, \ NAME##_write_ar_hdr, \ NAME##_openr_next_archived_file, \ NAME##_get_elt_at_index, \ NAME##_generic_stat_arch_elt, \ NAME##_update_armap_timestamp bool (*_bfd_slurp_armap) (bfd *); bool (*_bfd_slurp_extended_name_table) (bfd *); bool (*_bfd_construct_extended_name_table) (bfd *, char **, bfd_size_type *, const char **); void (*_bfd_truncate_arname) (bfd *, const char *, char *); bool (*write_armap) (bfd *, unsigned, struct orl *, unsigned, int); void *(*_bfd_read_ar_hdr_fn) (bfd *); bool (*_bfd_write_ar_hdr_fn) (bfd *, bfd *); bfd *(*openr_next_archived_file) (bfd *, bfd *); #define bfd_get_elt_at_index(b,i) \ BFD_SEND (b, _bfd_get_elt_at_index, (b,i)) bfd *(*_bfd_get_elt_at_index) (bfd *, symindex); int (*_bfd_stat_arch_elt) (bfd *, struct stat *); bool (*_bfd_update_armap_timestamp) (bfd *); /* Entry points used for symbols. */ #define BFD_JUMP_TABLE_SYMBOLS(NAME) \ NAME##_get_symtab_upper_bound, \ NAME##_canonicalize_symtab, \ NAME##_make_empty_symbol, \ NAME##_print_symbol, \ NAME##_get_symbol_info, \ NAME##_get_symbol_version_string, \ NAME##_bfd_is_local_label_name, \ NAME##_bfd_is_target_special_symbol, \ NAME##_get_lineno, \ NAME##_find_nearest_line, \ NAME##_find_line, \ NAME##_find_inliner_info, \ NAME##_bfd_make_debug_symbol, \ NAME##_read_minisymbols, \ NAME##_minisymbol_to_symbol long (*_bfd_get_symtab_upper_bound) (bfd *); long (*_bfd_canonicalize_symtab) (bfd *, struct bfd_symbol **); struct bfd_symbol * (*_bfd_make_empty_symbol) (bfd *); void (*_bfd_print_symbol) (bfd *, void *, struct bfd_symbol *, bfd_print_symbol_type); #define bfd_print_symbol(b,p,s,e) \ BFD_SEND (b, _bfd_print_symbol, (b,p,s,e)) void (*_bfd_get_symbol_info) (bfd *, struct bfd_symbol *, symbol_info *); #define bfd_get_symbol_info(b,p,e) \ BFD_SEND (b, _bfd_get_symbol_info, (b,p,e)) const char * (*_bfd_get_symbol_version_string) (bfd *, struct bfd_symbol *, bool, bool *); #define bfd_get_symbol_version_string(b,s,p,h) \ BFD_SEND (b, _bfd_get_symbol_version_string, (b,s,p,h)) bool (*_bfd_is_local_label_name) (bfd *, const char *); bool (*_bfd_is_target_special_symbol) (bfd *, asymbol *); alent * (*_get_lineno) (bfd *, struct bfd_symbol *); bool (*_bfd_find_nearest_line) (bfd *, struct bfd_symbol **, struct bfd_section *, bfd_vma, const char **, const char **, unsigned int *, unsigned int *); bool (*_bfd_find_line) (bfd *, struct bfd_symbol **, struct bfd_symbol *, const char **, unsigned int *); bool (*_bfd_find_inliner_info) (bfd *, const char **, const char **, unsigned int *); /* Back-door to allow format-aware applications to create debug symbols while using BFD for everything else. Currently used by the assembler when creating COFF files. */ asymbol * (*_bfd_make_debug_symbol) (bfd *, void *, unsigned long size); #define bfd_read_minisymbols(b, d, m, s) \ BFD_SEND (b, _read_minisymbols, (b, d, m, s)) long (*_read_minisymbols) (bfd *, bool, void **, unsigned int *); #define bfd_minisymbol_to_symbol(b, d, m, f) \ BFD_SEND (b, _minisymbol_to_symbol, (b, d, m, f)) asymbol * (*_minisymbol_to_symbol) (bfd *, bool, const void *, asymbol *); /* Routines for relocs. */ #define BFD_JUMP_TABLE_RELOCS(NAME) \ NAME##_get_reloc_upper_bound, \ NAME##_canonicalize_reloc, \ NAME##_set_reloc, \ NAME##_bfd_reloc_type_lookup, \ NAME##_bfd_reloc_name_lookup long (*_get_reloc_upper_bound) (bfd *, sec_ptr); long (*_bfd_canonicalize_reloc) (bfd *, sec_ptr, arelent **, struct bfd_symbol **); void (*_bfd_set_reloc) (bfd *, sec_ptr, arelent **, unsigned int); /* See documentation on reloc types. */ reloc_howto_type * (*reloc_type_lookup) (bfd *, bfd_reloc_code_real_type); reloc_howto_type * (*reloc_name_lookup) (bfd *, const char *); /* Routines used when writing an object file. */ #define BFD_JUMP_TABLE_WRITE(NAME) \ NAME##_set_arch_mach, \ NAME##_set_section_contents bool (*_bfd_set_arch_mach) (bfd *, enum bfd_architecture, unsigned long); bool (*_bfd_set_section_contents) (bfd *, sec_ptr, const void *, file_ptr, bfd_size_type); /* Routines used by the linker. */ #define BFD_JUMP_TABLE_LINK(NAME) \ NAME##_sizeof_headers, \ NAME##_bfd_get_relocated_section_contents, \ NAME##_bfd_relax_section, \ NAME##_bfd_link_hash_table_create, \ NAME##_bfd_link_add_symbols, \ NAME##_bfd_link_just_syms, \ NAME##_bfd_copy_link_hash_symbol_type, \ NAME##_bfd_final_link, \ NAME##_bfd_link_split_section, \ NAME##_bfd_link_check_relocs, \ NAME##_bfd_gc_sections, \ NAME##_bfd_lookup_section_flags, \ NAME##_bfd_merge_sections, \ NAME##_bfd_is_group_section, \ NAME##_bfd_group_name, \ NAME##_bfd_discard_group, \ NAME##_section_already_linked, \ NAME##_bfd_define_common_symbol, \ NAME##_bfd_link_hide_symbol, \ NAME##_bfd_define_start_stop int (*_bfd_sizeof_headers) (bfd *, struct bfd_link_info *); bfd_byte * (*_bfd_get_relocated_section_contents) (bfd *, struct bfd_link_info *, struct bfd_link_order *, bfd_byte *, bool, struct bfd_symbol **); bool (*_bfd_relax_section) (bfd *, struct bfd_section *, struct bfd_link_info *, bool *); /* Create a hash table for the linker. Different backends store different information in this table. */ struct bfd_link_hash_table * (*_bfd_link_hash_table_create) (bfd *); /* Add symbols from this object file into the hash table. */ bool (*_bfd_link_add_symbols) (bfd *, struct bfd_link_info *); /* Indicate that we are only retrieving symbol values from this section. */ void (*_bfd_link_just_syms) (asection *, struct bfd_link_info *); /* Copy the symbol type and other attributes for a linker script assignment of one symbol to another. */ #define bfd_copy_link_hash_symbol_type(b, t, f) \ BFD_SEND (b, _bfd_copy_link_hash_symbol_type, (b, t, f)) void (*_bfd_copy_link_hash_symbol_type) (bfd *, struct bfd_link_hash_entry *, struct bfd_link_hash_entry *); /* Do a link based on the link_order structures attached to each section of the BFD. */ bool (*_bfd_final_link) (bfd *, struct bfd_link_info *); /* Should this section be split up into smaller pieces during linking. */ bool (*_bfd_link_split_section) (bfd *, struct bfd_section *); /* Check the relocations in the bfd for validity. */ bool (* _bfd_link_check_relocs)(bfd *, struct bfd_link_info *); /* Remove sections that are not referenced from the output. */ bool (*_bfd_gc_sections) (bfd *, struct bfd_link_info *); /* Sets the bitmask of allowed and disallowed section flags. */ bool (*_bfd_lookup_section_flags) (struct bfd_link_info *, struct flag_info *, asection *); /* Attempt to merge SEC_MERGE sections. */ bool (*_bfd_merge_sections) (bfd *, struct bfd_link_info *); /* Is this section a member of a group? */ bool (*_bfd_is_group_section) (bfd *, const struct bfd_section *); /* The group name, if section is a member of a group. */ const char *(*_bfd_group_name) (bfd *, const struct bfd_section *); /* Discard members of a group. */ bool (*_bfd_discard_group) (bfd *, struct bfd_section *); /* Check if SEC has been already linked during a reloceatable or final link. */ bool (*_section_already_linked) (bfd *, asection *, struct bfd_link_info *); /* Define a common symbol. */ bool (*_bfd_define_common_symbol) (bfd *, struct bfd_link_info *, struct bfd_link_hash_entry *); /* Hide a symbol. */ void (*_bfd_link_hide_symbol) (bfd *, struct bfd_link_info *, struct bfd_link_hash_entry *); /* Define a __start, __stop, .startof. or .sizeof. symbol. */ struct bfd_link_hash_entry * (*_bfd_define_start_stop) (struct bfd_link_info *, const char *, asection *); /* Routines to handle dynamic symbols and relocs. */ #define BFD_JUMP_TABLE_DYNAMIC(NAME) \ NAME##_get_dynamic_symtab_upper_bound, \ NAME##_canonicalize_dynamic_symtab, \ NAME##_get_synthetic_symtab, \ NAME##_get_dynamic_reloc_upper_bound, \ NAME##_canonicalize_dynamic_reloc /* Get the amount of memory required to hold the dynamic symbols. */ long (*_bfd_get_dynamic_symtab_upper_bound) (bfd *); /* Read in the dynamic symbols. */ long (*_bfd_canonicalize_dynamic_symtab) (bfd *, struct bfd_symbol **); /* Create synthetized symbols. */ long (*_bfd_get_synthetic_symtab) (bfd *, long, struct bfd_symbol **, long, struct bfd_symbol **, struct bfd_symbol **); /* Get the amount of memory required to hold the dynamic relocs. */ long (*_bfd_get_dynamic_reloc_upper_bound) (bfd *); /* Read in the dynamic relocs. */ long (*_bfd_canonicalize_dynamic_reloc) (bfd *, arelent **, struct bfd_symbol **);
A pointer to an alternative bfd_target in case the current one is not satisfactory. This can happen when the target cpu supports both big and little endian code, and target chosen by the linker has the wrong endianness. The function open_output() in ld/ldlang.c uses this field to find an alternative output format that is suitable.
/* Opposite endian version of this target. */ const struct bfd_target *alternative_target; /* Data for use by back-end routines, which isn't generic enough to belong in this structure. */ const void *backend_data; } bfd_target; static inline const char * bfd_get_target (const bfd *abfd) { return abfd->xvec->name; } static inline enum bfd_flavour bfd_get_flavour (const bfd *abfd) { return abfd->xvec->flavour; } static inline flagword bfd_applicable_file_flags (const bfd *abfd) { return abfd->xvec->object_flags; } static inline bool bfd_family_coff (const bfd *abfd) { return (bfd_get_flavour (abfd) == bfd_target_coff_flavour || bfd_get_flavour (abfd) == bfd_target_xcoff_flavour); } static inline bool bfd_big_endian (const bfd *abfd) { return abfd->xvec->byteorder == BFD_ENDIAN_BIG; } static inline bool bfd_little_endian (const bfd *abfd) { return abfd->xvec->byteorder == BFD_ENDIAN_LITTLE; } static inline bool bfd_header_big_endian (const bfd *abfd) { return abfd->xvec->header_byteorder == BFD_ENDIAN_BIG; } static inline bool bfd_header_little_endian (const bfd *abfd) { return abfd->xvec->header_byteorder == BFD_ENDIAN_LITTLE; } static inline flagword bfd_applicable_section_flags (const bfd *abfd) { return abfd->xvec->section_flags; } static inline char bfd_get_symbol_leading_char (const bfd *abfd) { return abfd->xvec->symbol_leading_char; } static inline enum bfd_flavour bfd_asymbol_flavour (const asymbol *sy) { if ((sy->flags & BSF_SYNTHETIC) != 0) return bfd_target_unknown_flavour; return sy->the_bfd->xvec->flavour; } static inline bool bfd_keep_unused_section_symbols (const bfd *abfd) { return abfd->xvec->keep_unused_section_symbols; }
bfd_set_default_target
Synopsis
bool bfd_set_default_target (const char *name);
Description
Set the default target vector to use when recognizing a BFD.
This takes the name of the target, which may be a BFD target
name or a configuration triplet.
bfd_find_target
Synopsis
const bfd_target *bfd_find_target (const char *target_name, bfd *abfd);
Description
Return a pointer to the transfer vector for the object target
named target_name. If target_name is NULL
,
choose the one in the environment variable GNUTARGET
; if
that is null or not defined, then choose the first entry in the
target list. Passing in the string "default" or setting the
environment variable to "default" will cause the first entry in
the target list to be returned, and "target_defaulted" will be
set in the BFD if abfd isn’t NULL
. This causes
bfd_check_format
to loop over all the targets to find the
one that matches the file being read.
bfd_get_target_info
Synopsis
const bfd_target *bfd_get_target_info (const char *target_name, bfd *abfd, bool *is_bigendian, int *underscoring, const char **def_target_arch);
Description
Return a pointer to the transfer vector for the object target
named target_name. If target_name is NULL
,
choose the one in the environment variable GNUTARGET
; if
that is null or not defined, then choose the first entry in the
target list. Passing in the string "default" or setting the
environment variable to "default" will cause the first entry in
the target list to be returned, and "target_defaulted" will be
set in the BFD if abfd isn’t NULL
. This causes
bfd_check_format
to loop over all the targets to find the
one that matches the file being read.
If is_bigendian is not NULL
, then set this value to target’s
endian mode. True for big-endian, FALSE for little-endian or for
invalid target.
If underscoring is not NULL
, then set this value to target’s
underscoring mode. Zero for none-underscoring, -1 for invalid target,
else the value of target vector’s symbol underscoring.
If def_target_arch is not NULL
, then set it to the architecture
string specified by the target_name.
bfd_target_list
Synopsis
const char ** bfd_target_list (void);
Description
Return a freshly malloced NULL-terminated
vector of the names of all the valid BFD targets. Do not
modify the names.
bfd_iterate_over_targets
Synopsis
const bfd_target *bfd_iterate_over_targets (int (*func) (const bfd_target *, void *), void *data);
Description
Call func for each target in the list of BFD target
vectors, passing data to func. Stop iterating if
func returns a non-zero result, and return that target
vector. Return NULL if func always returns zero.
bfd_flavour_name
Synopsis
const char *bfd_flavour_name (enum bfd_flavour flavour);
Description
Return the string form of flavour.
Next: Opening and Closing, Previous: Targets, Up: BFD front end [Contents][Index]
BFD keeps one atom in a BFD describing the
architecture of the data attached to the BFD: a pointer to a
bfd_arch_info_type
.
Pointers to structures can be requested independently of a BFD so that an architecture’s information can be interrogated without access to an open BFD.
The architecture information is provided by each architecture package.
The set of default architectures is selected by the macro
SELECT_ARCHITECTURES
. This is normally set up in the
config/target.mt file of your choice. If the name is not
defined, then all the architectures supported are included.
When BFD starts up, all the architectures are called with an initialize method. It is up to the architecture back end to insert as many items into the list of architectures as it wants to; generally this would be one for each machine and one for the default case (an item with a machine field of 0).
BFD’s idea of an architecture is implemented in archures.c.
Description
This enum gives the object file’s CPU architecture, in a
global sense—i.e., what processor family does it belong to?
Another field indicates which processor within
the family is in use. The machine gives a number which
distinguishes different versions of the architecture,
containing, for example, 68020 for Motorola 68020.
enum bfd_architecture { bfd_arch_unknown, /* File arch not known. */ bfd_arch_obscure, /* Arch known, not one of these. */ bfd_arch_m68k, /* Motorola 68xxx. */ #define bfd_mach_m68000 1 #define bfd_mach_m68008 2 #define bfd_mach_m68010 3 #define bfd_mach_m68020 4 #define bfd_mach_m68030 5 #define bfd_mach_m68040 6 #define bfd_mach_m68060 7 #define bfd_mach_cpu32 8 #define bfd_mach_fido 9 #define bfd_mach_mcf_isa_a_nodiv 10 #define bfd_mach_mcf_isa_a 11 #define bfd_mach_mcf_isa_a_mac 12 #define bfd_mach_mcf_isa_a_emac 13 #define bfd_mach_mcf_isa_aplus 14 #define bfd_mach_mcf_isa_aplus_mac 15 #define bfd_mach_mcf_isa_aplus_emac 16 #define bfd_mach_mcf_isa_b_nousp 17 #define bfd_mach_mcf_isa_b_nousp_mac 18 #define bfd_mach_mcf_isa_b_nousp_emac 19 #define bfd_mach_mcf_isa_b 20 #define bfd_mach_mcf_isa_b_mac 21 #define bfd_mach_mcf_isa_b_emac 22 #define bfd_mach_mcf_isa_b_float 23 #define bfd_mach_mcf_isa_b_float_mac 24 #define bfd_mach_mcf_isa_b_float_emac 25 #define bfd_mach_mcf_isa_c 26 #define bfd_mach_mcf_isa_c_mac 27 #define bfd_mach_mcf_isa_c_emac 28 #define bfd_mach_mcf_isa_c_nodiv 29 #define bfd_mach_mcf_isa_c_nodiv_mac 30 #define bfd_mach_mcf_isa_c_nodiv_emac 31 bfd_arch_vax, /* DEC Vax. */ bfd_arch_or1k, /* OpenRISC 1000. */ #define bfd_mach_or1k 1 #define bfd_mach_or1knd 2 bfd_arch_sparc, /* SPARC. */ #define bfd_mach_sparc 1 /* The difference between v8plus and v9 is that v9 is a true 64 bit env. */ #define bfd_mach_sparc_sparclet 2 #define bfd_mach_sparc_sparclite 3 #define bfd_mach_sparc_v8plus 4 #define bfd_mach_sparc_v8plusa 5 /* with ultrasparc add'ns. */ #define bfd_mach_sparc_sparclite_le 6 #define bfd_mach_sparc_v9 7 #define bfd_mach_sparc_v9a 8 /* with ultrasparc add'ns. */ #define bfd_mach_sparc_v8plusb 9 /* with cheetah add'ns. */ #define bfd_mach_sparc_v9b 10 /* with cheetah add'ns. */ #define bfd_mach_sparc_v8plusc 11 /* with UA2005 and T1 add'ns. */ #define bfd_mach_sparc_v9c 12 /* with UA2005 and T1 add'ns. */ #define bfd_mach_sparc_v8plusd 13 /* with UA2007 and T3 add'ns. */ #define bfd_mach_sparc_v9d 14 /* with UA2007 and T3 add'ns. */ #define bfd_mach_sparc_v8pluse 15 /* with OSA2001 and T4 add'ns (no IMA). */ #define bfd_mach_sparc_v9e 16 /* with OSA2001 and T4 add'ns (no IMA). */ #define bfd_mach_sparc_v8plusv 17 /* with OSA2011 and T4 and IMA and FJMAU add'ns. */ #define bfd_mach_sparc_v9v 18 /* with OSA2011 and T4 and IMA and FJMAU add'ns. */ #define bfd_mach_sparc_v8plusm 19 /* with OSA2015 and M7 add'ns. */ #define bfd_mach_sparc_v9m 20 /* with OSA2015 and M7 add'ns. */ #define bfd_mach_sparc_v8plusm8 21 /* with OSA2017 and M8 add'ns. */ #define bfd_mach_sparc_v9m8 22 /* with OSA2017 and M8 add'ns. */ /* Nonzero if MACH has the v9 instruction set. */ #define bfd_mach_sparc_v9_p(mach) \ ((mach) >= bfd_mach_sparc_v8plus && (mach) <= bfd_mach_sparc_v9m8 \ && (mach) != bfd_mach_sparc_sparclite_le) /* Nonzero if MACH is a 64 bit sparc architecture. */ #define bfd_mach_sparc_64bit_p(mach) \ ((mach) >= bfd_mach_sparc_v9 \ && (mach) != bfd_mach_sparc_v8plusb \ && (mach) != bfd_mach_sparc_v8plusc \ && (mach) != bfd_mach_sparc_v8plusd \ && (mach) != bfd_mach_sparc_v8pluse \ && (mach) != bfd_mach_sparc_v8plusv \ && (mach) != bfd_mach_sparc_v8plusm \ && (mach) != bfd_mach_sparc_v8plusm8) bfd_arch_spu, /* PowerPC SPU. */ #define bfd_mach_spu 256 bfd_arch_mips, /* MIPS Rxxxx. */ #define bfd_mach_mips3000 3000 #define bfd_mach_mips3900 3900 #define bfd_mach_mips4000 4000 #define bfd_mach_mips4010 4010 #define bfd_mach_mips4100 4100 #define bfd_mach_mips4111 4111 #define bfd_mach_mips4120 4120 #define bfd_mach_mips4300 4300 #define bfd_mach_mips4400 4400 #define bfd_mach_mips4600 4600 #define bfd_mach_mips4650 4650 #define bfd_mach_mips5000 5000 #define bfd_mach_mips5400 5400 #define bfd_mach_mips5500 5500 #define bfd_mach_mips5900 5900 #define bfd_mach_mips6000 6000 #define bfd_mach_mips7000 7000 #define bfd_mach_mips8000 8000 #define bfd_mach_mips9000 9000 #define bfd_mach_mips10000 10000 #define bfd_mach_mips12000 12000 #define bfd_mach_mips14000 14000 #define bfd_mach_mips16000 16000 #define bfd_mach_mips16 16 #define bfd_mach_mips5 5 #define bfd_mach_mips_loongson_2e 3001 #define bfd_mach_mips_loongson_2f 3002 #define bfd_mach_mips_gs464 3003 #define bfd_mach_mips_gs464e 3004 #define bfd_mach_mips_gs264e 3005 #define bfd_mach_mips_sb1 12310201 /* octal 'SB', 01. */ #define bfd_mach_mips_octeon 6501 #define bfd_mach_mips_octeonp 6601 #define bfd_mach_mips_octeon2 6502 #define bfd_mach_mips_octeon3 6503 #define bfd_mach_mips_xlr 887682 /* decimal 'XLR'. */ #define bfd_mach_mips_interaptiv_mr2 736550 /* decimal 'IA2'. */ #define bfd_mach_mipsisa32 32 #define bfd_mach_mipsisa32r2 33 #define bfd_mach_mipsisa32r3 34 #define bfd_mach_mipsisa32r5 36 #define bfd_mach_mipsisa32r6 37 #define bfd_mach_mipsisa64 64 #define bfd_mach_mipsisa64r2 65 #define bfd_mach_mipsisa64r3 66 #define bfd_mach_mipsisa64r5 68 #define bfd_mach_mipsisa64r6 69 #define bfd_mach_mips_micromips 96 bfd_arch_i386, /* Intel 386. */ #define bfd_mach_i386_intel_syntax (1 << 0) #define bfd_mach_i386_i8086 (1 << 1) #define bfd_mach_i386_i386 (1 << 2) #define bfd_mach_x86_64 (1 << 3) #define bfd_mach_x64_32 (1 << 4) #define bfd_mach_i386_i386_intel_syntax (bfd_mach_i386_i386 | bfd_mach_i386_intel_syntax) #define bfd_mach_x86_64_intel_syntax (bfd_mach_x86_64 | bfd_mach_i386_intel_syntax) #define bfd_mach_x64_32_intel_syntax (bfd_mach_x64_32 | bfd_mach_i386_intel_syntax) bfd_arch_l1om, /* Intel L1OM. */ #define bfd_mach_l1om (1 << 5) #define bfd_mach_l1om_intel_syntax (bfd_mach_l1om | bfd_mach_i386_intel_syntax) bfd_arch_k1om, /* Intel K1OM. */ #define bfd_mach_k1om (1 << 6) #define bfd_mach_k1om_intel_syntax (bfd_mach_k1om | bfd_mach_i386_intel_syntax) bfd_arch_iamcu, /* Intel MCU. */ #define bfd_mach_iamcu (1 << 8) #define bfd_mach_i386_iamcu (bfd_mach_i386_i386 | bfd_mach_iamcu) #define bfd_mach_i386_iamcu_intel_syntax (bfd_mach_i386_iamcu | bfd_mach_i386_intel_syntax) bfd_arch_romp, /* IBM ROMP PC/RT. */ bfd_arch_convex, /* Convex. */ bfd_arch_m98k, /* Motorola 98xxx. */ bfd_arch_pyramid, /* Pyramid Technology. */ bfd_arch_h8300, /* Renesas H8/300 (formerly Hitachi H8/300). */ #define bfd_mach_h8300 1 #define bfd_mach_h8300h 2 #define bfd_mach_h8300s 3 #define bfd_mach_h8300hn 4 #define bfd_mach_h8300sn 5 #define bfd_mach_h8300sx 6 #define bfd_mach_h8300sxn 7 bfd_arch_pdp11, /* DEC PDP-11. */ bfd_arch_powerpc, /* PowerPC. */ #define bfd_mach_ppc 32 #define bfd_mach_ppc64 64 #define bfd_mach_ppc_403 403 #define bfd_mach_ppc_403gc 4030 #define bfd_mach_ppc_405 405 #define bfd_mach_ppc_505 505 #define bfd_mach_ppc_601 601 #define bfd_mach_ppc_602 602 #define bfd_mach_ppc_603 603 #define bfd_mach_ppc_ec603e 6031 #define bfd_mach_ppc_604 604 #define bfd_mach_ppc_620 620 #define bfd_mach_ppc_630 630 #define bfd_mach_ppc_750 750 #define bfd_mach_ppc_860 860 #define bfd_mach_ppc_a35 35 #define bfd_mach_ppc_rs64ii 642 #define bfd_mach_ppc_rs64iii 643 #define bfd_mach_ppc_7400 7400 #define bfd_mach_ppc_e500 500 #define bfd_mach_ppc_e500mc 5001 #define bfd_mach_ppc_e500mc64 5005 #define bfd_mach_ppc_e5500 5006 #define bfd_mach_ppc_e6500 5007 #define bfd_mach_ppc_titan 83 #define bfd_mach_ppc_vle 84 bfd_arch_rs6000, /* IBM RS/6000. */ #define bfd_mach_rs6k 6000 #define bfd_mach_rs6k_rs1 6001 #define bfd_mach_rs6k_rsc 6003 #define bfd_mach_rs6k_rs2 6002 bfd_arch_hppa, /* HP PA RISC. */ #define bfd_mach_hppa10 10 #define bfd_mach_hppa11 11 #define bfd_mach_hppa20 20 #define bfd_mach_hppa20w 25 bfd_arch_d10v, /* Mitsubishi D10V. */ #define bfd_mach_d10v 1 #define bfd_mach_d10v_ts2 2 #define bfd_mach_d10v_ts3 3 bfd_arch_d30v, /* Mitsubishi D30V. */ bfd_arch_dlx, /* DLX. */ bfd_arch_m68hc11, /* Motorola 68HC11. */ bfd_arch_m68hc12, /* Motorola 68HC12. */ #define bfd_mach_m6812_default 0 #define bfd_mach_m6812 1 #define bfd_mach_m6812s 2 bfd_arch_m9s12x, /* Freescale S12X. */ bfd_arch_m9s12xg, /* Freescale XGATE. */ bfd_arch_s12z, /* Freescale S12Z. */ #define bfd_mach_s12z_default 0 bfd_arch_z8k, /* Zilog Z8000. */ #define bfd_mach_z8001 1 #define bfd_mach_z8002 2 bfd_arch_sh, /* Renesas / SuperH SH (formerly Hitachi SH). */ #define bfd_mach_sh 1 #define bfd_mach_sh2 0x20 #define bfd_mach_sh_dsp 0x2d #define bfd_mach_sh2a 0x2a #define bfd_mach_sh2a_nofpu 0x2b #define bfd_mach_sh2a_nofpu_or_sh4_nommu_nofpu 0x2a1 #define bfd_mach_sh2a_nofpu_or_sh3_nommu 0x2a2 #define bfd_mach_sh2a_or_sh4 0x2a3 #define bfd_mach_sh2a_or_sh3e 0x2a4 #define bfd_mach_sh2e 0x2e #define bfd_mach_sh3 0x30 #define bfd_mach_sh3_nommu 0x31 #define bfd_mach_sh3_dsp 0x3d #define bfd_mach_sh3e 0x3e #define bfd_mach_sh4 0x40 #define bfd_mach_sh4_nofpu 0x41 #define bfd_mach_sh4_nommu_nofpu 0x42 #define bfd_mach_sh4a 0x4a #define bfd_mach_sh4a_nofpu 0x4b #define bfd_mach_sh4al_dsp 0x4d bfd_arch_alpha, /* Dec Alpha. */ #define bfd_mach_alpha_ev4 0x10 #define bfd_mach_alpha_ev5 0x20 #define bfd_mach_alpha_ev6 0x30 bfd_arch_arm, /* Advanced Risc Machines ARM. */ #define bfd_mach_arm_unknown 0 #define bfd_mach_arm_2 1 #define bfd_mach_arm_2a 2 #define bfd_mach_arm_3 3 #define bfd_mach_arm_3M 4 #define bfd_mach_arm_4 5 #define bfd_mach_arm_4T 6 #define bfd_mach_arm_5 7 #define bfd_mach_arm_5T 8 #define bfd_mach_arm_5TE 9 #define bfd_mach_arm_XScale 10 #define bfd_mach_arm_ep9312 11 #define bfd_mach_arm_iWMMXt 12 #define bfd_mach_arm_iWMMXt2 13 #define bfd_mach_arm_5TEJ 14 #define bfd_mach_arm_6 15 #define bfd_mach_arm_6KZ 16 #define bfd_mach_arm_6T2 17 #define bfd_mach_arm_6K 18 #define bfd_mach_arm_7 19 #define bfd_mach_arm_6M 20 #define bfd_mach_arm_6SM 21 #define bfd_mach_arm_7EM 22 #define bfd_mach_arm_8 23 #define bfd_mach_arm_8R 24 #define bfd_mach_arm_8M_BASE 25 #define bfd_mach_arm_8M_MAIN 26 #define bfd_mach_arm_8_1M_MAIN 27 bfd_arch_nds32, /* Andes NDS32. */ #define bfd_mach_n1 1 #define bfd_mach_n1h 2 #define bfd_mach_n1h_v2 3 #define bfd_mach_n1h_v3 4 #define bfd_mach_n1h_v3m 5 bfd_arch_ns32k, /* National Semiconductors ns32000. */ bfd_arch_tic30, /* Texas Instruments TMS320C30. */ bfd_arch_tic4x, /* Texas Instruments TMS320C3X/4X. */ #define bfd_mach_tic3x 30 #define bfd_mach_tic4x 40 bfd_arch_tic54x, /* Texas Instruments TMS320C54X. */ bfd_arch_tic6x, /* Texas Instruments TMS320C6X. */ bfd_arch_v850, /* NEC V850. */ bfd_arch_v850_rh850,/* NEC V850 (using RH850 ABI). */ #define bfd_mach_v850 1 #define bfd_mach_v850e 'E' #define bfd_mach_v850e1 '1' #define bfd_mach_v850e2 0x4532 #define bfd_mach_v850e2v3 0x45325633 #define bfd_mach_v850e3v5 0x45335635 /* ('E'|'3'|'V'|'5'). */ bfd_arch_arc, /* ARC Cores. */ #define bfd_mach_arc_a4 0 #define bfd_mach_arc_a5 1 #define bfd_mach_arc_arc600 2 #define bfd_mach_arc_arc601 4 #define bfd_mach_arc_arc700 3 #define bfd_mach_arc_arcv2 5 bfd_arch_m32c, /* Renesas M16C/M32C. */ #define bfd_mach_m16c 0x75 #define bfd_mach_m32c 0x78 bfd_arch_m32r, /* Renesas M32R (formerly Mitsubishi M32R/D). */ #define bfd_mach_m32r 1 /* For backwards compatibility. */ #define bfd_mach_m32rx 'x' #define bfd_mach_m32r2 '2' bfd_arch_mn10200, /* Matsushita MN10200. */ bfd_arch_mn10300, /* Matsushita MN10300. */ #define bfd_mach_mn10300 300 #define bfd_mach_am33 330 #define bfd_mach_am33_2 332 bfd_arch_fr30, #define bfd_mach_fr30 0x46523330 bfd_arch_frv, #define bfd_mach_frv 1 #define bfd_mach_frvsimple 2 #define bfd_mach_fr300 300 #define bfd_mach_fr400 400 #define bfd_mach_fr450 450 #define bfd_mach_frvtomcat 499 /* fr500 prototype. */ #define bfd_mach_fr500 500 #define bfd_mach_fr550 550 bfd_arch_moxie, /* The moxie processor. */ #define bfd_mach_moxie 1 bfd_arch_ft32, /* The ft32 processor. */ #define bfd_mach_ft32 1 #define bfd_mach_ft32b 2 bfd_arch_mcore, bfd_arch_mep, #define bfd_mach_mep 1 #define bfd_mach_mep_h1 0x6831 #define bfd_mach_mep_c5 0x6335 bfd_arch_metag, #define bfd_mach_metag 1 bfd_arch_ia64, /* HP/Intel ia64. */ #define bfd_mach_ia64_elf64 64 #define bfd_mach_ia64_elf32 32 bfd_arch_ip2k, /* Ubicom IP2K microcontrollers. */ #define bfd_mach_ip2022 1 #define bfd_mach_ip2022ext 2 bfd_arch_iq2000, /* Vitesse IQ2000. */ #define bfd_mach_iq2000 1 #define bfd_mach_iq10 2 bfd_arch_bpf, /* Linux eBPF. */ #define bfd_mach_bpf 1 #define bfd_mach_xbpf 2 bfd_arch_epiphany, /* Adapteva EPIPHANY. */ #define bfd_mach_epiphany16 1 #define bfd_mach_epiphany32 2 bfd_arch_mt, #define bfd_mach_ms1 1 #define bfd_mach_mrisc2 2 #define bfd_mach_ms2 3 bfd_arch_pj, bfd_arch_avr, /* Atmel AVR microcontrollers. */ #define bfd_mach_avr1 1 #define bfd_mach_avr2 2 #define bfd_mach_avr25 25 #define bfd_mach_avr3 3 #define bfd_mach_avr31 31 #define bfd_mach_avr35 35 #define bfd_mach_avr4 4 #define bfd_mach_avr5 5 #define bfd_mach_avr51 51 #define bfd_mach_avr6 6 #define bfd_mach_avrtiny 100 #define bfd_mach_avrxmega1 101 #define bfd_mach_avrxmega2 102 #define bfd_mach_avrxmega3 103 #define bfd_mach_avrxmega4 104 #define bfd_mach_avrxmega5 105 #define bfd_mach_avrxmega6 106 #define bfd_mach_avrxmega7 107 bfd_arch_bfin, /* ADI Blackfin. */ #define bfd_mach_bfin 1 bfd_arch_cr16, /* National Semiconductor CompactRISC (ie CR16). */ #define bfd_mach_cr16 1 bfd_arch_crx, /* National Semiconductor CRX. */ #define bfd_mach_crx 1 bfd_arch_cris, /* Axis CRIS. */ #define bfd_mach_cris_v0_v10 255 #define bfd_mach_cris_v32 32 #define bfd_mach_cris_v10_v32 1032 bfd_arch_riscv, #define bfd_mach_riscv32 132 #define bfd_mach_riscv64 164 bfd_arch_rl78, #define bfd_mach_rl78 0x75 bfd_arch_rx, /* Renesas RX. */ #define bfd_mach_rx 0x75 #define bfd_mach_rx_v2 0x76 #define bfd_mach_rx_v3 0x77 bfd_arch_s390, /* IBM s390. */ #define bfd_mach_s390_31 31 #define bfd_mach_s390_64 64 bfd_arch_score, /* Sunplus score. */ #define bfd_mach_score3 3 #define bfd_mach_score7 7 bfd_arch_mmix, /* Donald Knuth's educational processor. */ bfd_arch_xstormy16, #define bfd_mach_xstormy16 1 bfd_arch_msp430, /* Texas Instruments MSP430 architecture. */ #define bfd_mach_msp11 11 #define bfd_mach_msp110 110 #define bfd_mach_msp12 12 #define bfd_mach_msp13 13 #define bfd_mach_msp14 14 #define bfd_mach_msp15 15 #define bfd_mach_msp16 16 #define bfd_mach_msp20 20 #define bfd_mach_msp21 21 #define bfd_mach_msp22 22 #define bfd_mach_msp23 23 #define bfd_mach_msp24 24 #define bfd_mach_msp26 26 #define bfd_mach_msp31 31 #define bfd_mach_msp32 32 #define bfd_mach_msp33 33 #define bfd_mach_msp41 41 #define bfd_mach_msp42 42 #define bfd_mach_msp43 43 #define bfd_mach_msp44 44 #define bfd_mach_msp430x 45 #define bfd_mach_msp46 46 #define bfd_mach_msp47 47 #define bfd_mach_msp54 54 bfd_arch_xc16x, /* Infineon's XC16X Series. */ #define bfd_mach_xc16x 1 #define bfd_mach_xc16xl 2 #define bfd_mach_xc16xs 3 bfd_arch_xgate, /* Freescale XGATE. */ #define bfd_mach_xgate 1 bfd_arch_xtensa, /* Tensilica's Xtensa cores. */ #define bfd_mach_xtensa 1 bfd_arch_z80, /* Zilog Z80 without undocumented opcodes. */ #define bfd_mach_z80strict 1 /* Zilog Z180: successor with additional instructions, but without halves of ix and iy. */ #define bfd_mach_z180 2 /* Zilog Z80 with ixl, ixh, iyl, and iyh. */ #define bfd_mach_z80 3 /* Zilog eZ80 (successor of Z80 & Z180) in Z80 (16-bit address) mode. */ #define bfd_mach_ez80_z80 4 /* Zilog eZ80 (successor of Z80 & Z180) in ADL (24-bit address) mode. */ #define bfd_mach_ez80_adl 5 /* Z80N */ #define bfd_mach_z80n 6 /* Zilog Z80 with all undocumented instructions. */ #define bfd_mach_z80full 7 /* GameBoy Z80 (reduced instruction set). */ #define bfd_mach_gbz80 8 /* ASCII R800: successor with multiplication. */ #define bfd_mach_r800 11 bfd_arch_lm32, /* Lattice Mico32. */ #define bfd_mach_lm32 1 bfd_arch_microblaze,/* Xilinx MicroBlaze. */ bfd_arch_tilepro, /* Tilera TILEPro. */ bfd_arch_tilegx, /* Tilera TILE-Gx. */ #define bfd_mach_tilepro 1 #define bfd_mach_tilegx 1 #define bfd_mach_tilegx32 2 bfd_arch_aarch64, /* AArch64. */ #define bfd_mach_aarch64 0 #define bfd_mach_aarch64_8R 1 #define bfd_mach_aarch64_ilp32 32 bfd_arch_nios2, /* Nios II. */ #define bfd_mach_nios2 0 #define bfd_mach_nios2r1 1 #define bfd_mach_nios2r2 2 bfd_arch_visium, /* Visium. */ #define bfd_mach_visium 1 bfd_arch_wasm32, /* WebAssembly. */ #define bfd_mach_wasm32 1 bfd_arch_pru, /* PRU. */ #define bfd_mach_pru 0 bfd_arch_nfp, /* Netronome Flow Processor */ #define bfd_mach_nfp3200 0x3200 #define bfd_mach_nfp6000 0x6000 bfd_arch_csky, /* C-SKY. */ #define bfd_mach_ck_unknown 0 #define bfd_mach_ck510 1 #define bfd_mach_ck610 2 #define bfd_mach_ck801 3 #define bfd_mach_ck802 4 #define bfd_mach_ck803 5 #define bfd_mach_ck807 6 #define bfd_mach_ck810 7 #define bfd_mach_ck860 8 bfd_arch_last };
Description
This structure contains information on architectures for use
within BFD.
typedef struct bfd_arch_info
{
int bits_per_word;
int bits_per_address;
int bits_per_byte;
enum bfd_architecture arch;
unsigned long mach;
const char *arch_name;
const char *printable_name;
unsigned int section_align_power;
/* TRUE if this is the default machine for the architecture.
The default arch should be the first entry for an arch so that
all the entries for that arch can be accessed via next
. */
bool the_default;
const struct bfd_arch_info * (*compatible) (const struct bfd_arch_info *,
const struct bfd_arch_info *);
bool (*scan) (const struct bfd_arch_info *, const char *);
/* Allocate via bfd_malloc and return a fill buffer of size COUNT. If
IS_BIGENDIAN is TRUE, the order of bytes is big endian. If CODE is
TRUE, the buffer contains code. */
void *(*fill) (bfd_size_type count, bool is_bigendian, bool code);
const struct bfd_arch_info *next;
/* On some architectures the offset for a relocation can point into
the middle of an instruction. This field specifies the maximum
offset such a relocation can have (in octets). This affects the
behaviour of the disassembler, since a value greater than zero
means that it may need to disassemble an instruction twice, once
to get its length and then a second time to display it. If the
value is negative then this has to be done for every single
instruction, regardless of the offset of the reloc. */
signed int max_reloc_offset_into_insn;
}
bfd_arch_info_type;
bfd_printable_name
Synopsis
const char *bfd_printable_name (bfd *abfd);
Description
Return a printable string representing the architecture and machine
from the pointer to the architecture info structure.
bfd_scan_arch
Synopsis
const bfd_arch_info_type *bfd_scan_arch (const char *string);
Description
Figure out if BFD supports any cpu which could be described with
the name string. Return a pointer to an arch_info
structure if a machine is found, otherwise NULL.
bfd_arch_list
Synopsis
const char **bfd_arch_list (void);
Description
Return a freshly malloced NULL-terminated vector of the names
of all the valid BFD architectures. Do not modify the names.
bfd_arch_get_compatible
Synopsis
const bfd_arch_info_type *bfd_arch_get_compatible (const bfd *abfd, const bfd *bbfd, bool accept_unknowns);
Description
Determine whether two BFDs’ architectures and machine types
are compatible. Calculates the lowest common denominator
between the two architectures and machine types implied by
the BFDs and returns a pointer to an arch_info
structure
describing the compatible machine.
bfd_default_arch_struct
Description
The bfd_default_arch_struct
is an item of
bfd_arch_info_type
which has been initialized to a fairly
generic state. A BFD starts life by pointing to this
structure, until the correct back end has determined the real
architecture of the file.
extern const bfd_arch_info_type bfd_default_arch_struct;
bfd_set_arch_info
Synopsis
void bfd_set_arch_info (bfd *abfd, const bfd_arch_info_type *arg);
Description
Set the architecture info of abfd to arg.
bfd_default_set_arch_mach
Synopsis
bool bfd_default_set_arch_mach (bfd *abfd, enum bfd_architecture arch, unsigned long mach);
Description
Set the architecture and machine type in BFD abfd
to arch and mach. Find the correct
pointer to a structure and insert it into the arch_info
pointer.
bfd_get_arch
Synopsis
enum bfd_architecture bfd_get_arch (const bfd *abfd);
Description
Return the enumerated type which describes the BFD abfd’s
architecture.
bfd_get_mach
Synopsis
unsigned long bfd_get_mach (const bfd *abfd);
Description
Return the long type which describes the BFD abfd’s
machine.
bfd_arch_bits_per_byte
Synopsis
unsigned int bfd_arch_bits_per_byte (const bfd *abfd);
Description
Return the number of bits in one of the BFD abfd’s
architecture’s bytes.
bfd_arch_bits_per_address
Synopsis
unsigned int bfd_arch_bits_per_address (const bfd *abfd);
Description
Return the number of bits in one of the BFD abfd’s
architecture’s addresses.
bfd_default_compatible
Synopsis
const bfd_arch_info_type *bfd_default_compatible (const bfd_arch_info_type *a, const bfd_arch_info_type *b);
Description
The default function for testing for compatibility.
bfd_default_scan
Synopsis
bool bfd_default_scan (const struct bfd_arch_info *info, const char *string);
Description
The default function for working out whether this is an
architecture hit and a machine hit.
bfd_get_arch_info
Synopsis
const bfd_arch_info_type *bfd_get_arch_info (bfd *abfd);
Description
Return the architecture info struct in abfd.
bfd_lookup_arch
Synopsis
const bfd_arch_info_type *bfd_lookup_arch (enum bfd_architecture arch, unsigned long machine);
Description
Look for the architecture info structure which matches the
arguments arch and machine. A machine of 0 matches the
machine/architecture structure which marks itself as the
default.
bfd_printable_arch_mach
Synopsis
const char *bfd_printable_arch_mach (enum bfd_architecture arch, unsigned long machine);
Description
Return a printable string representing the architecture and
machine type.
This routine is depreciated.
bfd_octets_per_byte
Synopsis
unsigned int bfd_octets_per_byte (const bfd *abfd, const asection *sec);
Description
Return the number of octets (8-bit quantities) per target byte
(minimum addressable unit). In most cases, this will be one, but some
DSP targets have 16, 32, or even 48 bits per byte.
bfd_arch_mach_octets_per_byte
Synopsis
unsigned int bfd_arch_mach_octets_per_byte (enum bfd_architecture arch, unsigned long machine);
Description
See bfd_octets_per_byte.
This routine is provided for those cases where a bfd * is not available
bfd_arch_default_fill
Synopsis
void *bfd_arch_default_fill (bfd_size_type count, bool is_bigendian, bool code);
Description
Allocate via bfd_malloc and return a fill buffer of size COUNT.
If IS_BIGENDIAN is TRUE, the order of bytes is big endian. If
CODE is TRUE, the buffer contains code.
Next: Internal, Previous: Architectures, Up: BFD front end [Contents][Index]
/* Set to N to open the next N BFDs using an alternate id space. */ extern unsigned int bfd_use_reserved_id;
bfd_fopen
Synopsis
bfd *bfd_fopen (const char *filename, const char *target, const char *mode, int fd);
Description
Open the file filename with the target target.
Return a pointer to the created BFD. If fd is not -1,
then fdopen
is used to open the file; otherwise, fopen
is used. mode is passed directly to fopen
or
fdopen
.
Calls bfd_find_target
, so target is interpreted as by
that function.
The new BFD is marked as cacheable iff fd is -1.
If NULL
is returned then an error has occured. Possible errors
are bfd_error_no_memory
, bfd_error_invalid_target
or
system_call
error.
On error, fd is always closed.
A copy of the filename argument is stored in the newly created BFD. It can be accessed via the bfd_get_filename() macro.
bfd_openr
Synopsis
bfd *bfd_openr (const char *filename, const char *target);
Description
Open the file filename (using fopen
) with the target
target. Return a pointer to the created BFD.
Calls bfd_find_target
, so target is interpreted as by
that function.
If NULL
is returned then an error has occured. Possible errors
are bfd_error_no_memory
, bfd_error_invalid_target
or
system_call
error.
A copy of the filename argument is stored in the newly created BFD. It can be accessed via the bfd_get_filename() macro.
bfd_fdopenr
Synopsis
bfd *bfd_fdopenr (const char *filename, const char *target, int fd);
Description
bfd_fdopenr
is to bfd_fopenr
much like fdopen
is to
fopen
. It opens a BFD on a file already described by the
fd supplied.
When the file is later bfd_close
d, the file descriptor will
be closed. If the caller desires that this file descriptor be
cached by BFD (opened as needed, closed as needed to free
descriptors for other opens), with the supplied fd used as
an initial file descriptor (but subject to closure at any time),
call bfd_set_cacheable(bfd, 1) on the returned BFD. The default
is to assume no caching; the file descriptor will remain open
until bfd_close
, and will not be affected by BFD operations
on other files.
Possible errors are bfd_error_no_memory
,
bfd_error_invalid_target
and bfd_error_system_call
.
On error, fd is closed.
A copy of the filename argument is stored in the newly created BFD. It can be accessed via the bfd_get_filename() macro.
bfd_fdopenw
Synopsis
bfd *bfd_fdopenw (const char *filename, const char *target, int fd);
Description
bfd_fdopenw
is exactly like bfd_fdopenr
with the exception that
the resulting BFD is suitable for output.
bfd_openstreamr
Synopsis
bfd *bfd_openstreamr (const char * filename, const char * target, void * stream);
Description
Open a BFD for read access on an existing stdio stream. When
the BFD is passed to bfd_close
, the stream will be closed.
A copy of the filename argument is stored in the newly created BFD. It can be accessed via the bfd_get_filename() macro.
bfd_openr_iovec
Synopsis
bfd *bfd_openr_iovec (const char *filename, const char *target, void *(*open_func) (struct bfd *nbfd, void *open_closure), void *open_closure, file_ptr (*pread_func) (struct bfd *nbfd, void *stream, void *buf, file_ptr nbytes, file_ptr offset), int (*close_func) (struct bfd *nbfd, void *stream), int (*stat_func) (struct bfd *abfd, void *stream, struct stat *sb));
Description
Create and return a BFD backed by a read-only stream.
The stream is created using open_func, accessed using
pread_func and destroyed using close_func.
Calls bfd_find_target
, so target is interpreted as by
that function.
Calls open_func (which can call bfd_zalloc
and
bfd_get_filename
) to obtain the read-only stream backing
the BFD. open_func either succeeds returning the
non-NULL
stream, or fails returning NULL
(setting bfd_error
).
Calls pread_func to request nbytes of data from
stream starting at offset (e.g., via a call to
bfd_read
). pread_func either succeeds returning the
number of bytes read (which can be less than nbytes when
end-of-file), or fails returning -1 (setting bfd_error
).
Calls close_func when the BFD is later closed using
bfd_close
. close_func either succeeds returning 0, or
fails returning -1 (setting bfd_error
).
Calls stat_func to fill in a stat structure for bfd_stat,
bfd_get_size, and bfd_get_mtime calls. stat_func returns 0
on success, or returns -1 on failure (setting bfd_error
).
If bfd_openr_iovec
returns NULL
then an error has
occurred. Possible errors are bfd_error_no_memory
,
bfd_error_invalid_target
and bfd_error_system_call
.
A copy of the filename argument is stored in the newly created BFD. It can be accessed via the bfd_get_filename() macro.
bfd_openw
Synopsis
bfd *bfd_openw (const char *filename, const char *target);
Description
Create a BFD, associated with file filename, using the
file format target, and return a pointer to it.
Possible errors are bfd_error_system_call
, bfd_error_no_memory
,
bfd_error_invalid_target
.
A copy of the filename argument is stored in the newly created BFD. It can be accessed via the bfd_get_filename() macro.
bfd_close
Synopsis
bool bfd_close (bfd *abfd);
Description
Close a BFD. If the BFD was open for writing, then pending
operations are completed and the file written out and closed.
If the created file is executable, then chmod
is called
to mark it as such.
All memory attached to the BFD is released.
The file descriptor associated with the BFD is closed (even
if it was passed in to BFD by bfd_fdopenr
).
Returns
TRUE
is returned if all is ok, otherwise FALSE
.
bfd_close_all_done
Synopsis
bool bfd_close_all_done (bfd *);
Description
Close a BFD. Differs from bfd_close
since it does not
complete any pending operations. This routine would be used
if the application had just used BFD for swapping and didn’t
want to use any of the writing code.
If the created file is executable, then chmod
is called
to mark it as such.
All memory attached to the BFD is released.
Returns
TRUE
is returned if all is ok, otherwise FALSE
.
bfd_create
Synopsis
bfd *bfd_create (const char *filename, bfd *templ);
Description
Create a new BFD in the manner of bfd_openw
, but without
opening a file. The new BFD takes the target from the target
used by templ. The format is always set to bfd_object
.
A copy of the filename argument is stored in the newly created BFD. It can be accessed via the bfd_get_filename() macro.
bfd_make_writable
Synopsis
bool bfd_make_writable (bfd *abfd);
Description
Takes a BFD as created by bfd_create
and converts it
into one like as returned by bfd_openw
. It does this
by converting the BFD to BFD_IN_MEMORY. It’s assumed that
you will call bfd_make_readable
on this bfd later.
Returns
TRUE
is returned if all is ok, otherwise FALSE
.
bfd_make_readable
Synopsis
bool bfd_make_readable (bfd *abfd);
Description
Takes a BFD as created by bfd_create
and
bfd_make_writable
and converts it into one like as
returned by bfd_openr
. It does this by writing the
contents out to the memory buffer, then reversing the
direction.
Returns
TRUE
is returned if all is ok, otherwise FALSE
.
bfd_alloc
Synopsis
void *bfd_alloc (bfd *abfd, bfd_size_type wanted);
Description
Allocate a block of wanted bytes of memory attached to
abfd
and return a pointer to it.
bfd_zalloc
Synopsis
void *bfd_zalloc (bfd *abfd, bfd_size_type wanted);
Description
Allocate a block of wanted bytes of zeroed memory
attached to abfd
and return a pointer to it.
bfd_calc_gnu_debuglink_crc32
Synopsis
unsigned long bfd_calc_gnu_debuglink_crc32 (unsigned long crc, const unsigned char *buf, bfd_size_type len);
Description
Computes a CRC value as used in the .gnu_debuglink section.
Advances the previously computed crc value by computing
and adding in the crc32 for len bytes of buf.
Returns
Return the updated CRC32 value.
bfd_get_debug_link_info_1
Synopsis
char *bfd_get_debug_link_info_1 (bfd *abfd, void *crc32_out);
Description
Extracts the filename and CRC32 value for any separate debug
information file associated with abfd.
The crc32_out parameter is an untyped pointer because
this routine is used as a get_func_type
function, but it
is expected to be an unsigned long pointer.
Returns
The filename of the associated debug information file, or NULL
if there is no such file. If the filename was found then the
contents of crc32_out are updated to hold the corresponding
CRC32 value for the file.
The returned filename is allocated with malloc
; freeing
it is the responsibility of the caller.
bfd_get_debug_link_info
Synopsis
char *bfd_get_debug_link_info (bfd *abfd, unsigned long *crc32_out);
Description
Extracts the filename and CRC32 value for any separate debug
information file associated with abfd.
Returns
The filename of the associated debug information file, or NULL
if there is no such file. If the filename was found then the
contents of crc32_out are updated to hold the corresponding
CRC32 value for the file.
The returned filename is allocated with malloc
; freeing
it is the responsibility of the caller.
bfd_get_alt_debug_link_info
Synopsis
char *bfd_get_alt_debug_link_info (bfd * abfd, bfd_size_type *buildid_len, bfd_byte **buildid_out);
Description
Fetch the filename and BuildID value for any alternate debuginfo
associated with abfd. Return NULL if no such info found,
otherwise return filename and update buildid_len and
buildid_out. The returned filename and build_id are
allocated with malloc
; freeing them is the responsibility
of the caller.
separate_debug_file_exists
Synopsis
bool separate_debug_file_exists (char *name, void *crc32_p);
Description
Checks to see if name is a file and if its contents
match crc32, which is a pointer to an unsigned
long
containing a CRC32.
The crc32_p parameter is an untyped pointer because
this routine is used as a check_func_type
function.
separate_alt_debug_file_exists
Synopsis
bool separate_alt_debug_file_exists (char *name, void *unused);
Description
Checks to see if name is a file.
find_separate_debug_file
Synopsis
char *find_separate_debug_file (bfd *abfd, const char *dir, bool include_dirs, get_func_type get, check_func_type check, void *data);
Description
Searches for a debug information file corresponding to abfd.
The name of the separate debug info file is returned by the get function. This function scans various fixed locations in the filesystem, including the file tree rooted at dir. If the include_dirs parameter is true then the directory components of abfd’s filename will be included in the searched locations.
data is passed unmodified to the get and check functions. It is generally used to implement build-id-like matching in the callback functions.
Returns
Returns the filename of the first file to be found which
receives a TRUE result from the check function.
Returns NULL if no valid file could be found.
bfd_follow_gnu_debuglink
Synopsis
char *bfd_follow_gnu_debuglink (bfd *abfd, const char *dir);
Description
Takes a BFD and searches it for a .gnu_debuglink section. If this
section is found, it examines the section for the name and checksum
of a ’.debug’ file containing auxiliary debugging information. It
then searches the filesystem for this .debug file in some standard
locations, including the directory tree rooted at dir, and if
found returns the full filename.
If dir is NULL, the search will take place starting at the current directory.
Returns
NULL
on any errors or failure to locate the .debug file,
otherwise a pointer to a heap-allocated string containing the
filename. The caller is responsible for freeing this string.
bfd_follow_gnu_debugaltlink
Synopsis
char *bfd_follow_gnu_debugaltlink (bfd *abfd, const char *dir);
Description
Takes a BFD and searches it for a .gnu_debugaltlink section. If this
section is found, it examines the section for the name of a file
containing auxiliary debugging information. It then searches the
filesystem for this file in a set of standard locations, including
the directory tree rooted at dir, and if found returns the
full filename.
If dir is NULL, the search will take place starting at the current directory.
Returns
NULL
on any errors or failure to locate the debug file,
otherwise a pointer to a heap-allocated string containing the
filename. The caller is responsible for freeing this string.
bfd_create_gnu_debuglink_section
Synopsis
struct bfd_section *bfd_create_gnu_debuglink_section (bfd *abfd, const char *filename);
Description
Takes a BFD and adds a .gnu_debuglink section to it. The
section is sized to be big enough to contain a link to the specified
filename.
Returns
A pointer to the new section is returned if all is ok. Otherwise
NULL
is returned and bfd_error is set.
bfd_fill_in_gnu_debuglink_section
Synopsis
bool bfd_fill_in_gnu_debuglink_section (bfd *abfd, struct bfd_section *sect, const char *filename);
Description
Takes a BFD and containing a .gnu_debuglink section SECT
and fills in the contents of the section to contain a link to the
specified filename. The filename should be relative to the
current directory.
Returns
TRUE
is returned if all is ok. Otherwise FALSE
is returned
and bfd_error is set.
get_build_id
Synopsis
struct bfd_build_id * get_build_id (bfd *abfd);
Description
Finds the build-id associated with abfd. If the build-id is
extracted from the note section then a build-id structure is built
for it, using memory allocated to abfd, and this is then
attached to the abfd.
Returns
Returns a pointer to the build-id structure if a build-id could be
found. If no build-id is found NULL is returned and error code is
set.
get_build_id_name
Synopsis
char * get_build_id_name (bfd *abfd, void *build_id_out_p)
Description
Searches abfd for a build-id, and then constructs a pathname
from it. The path is computed as .build-id/NN/NN+NN.debug where
NNNN+NN is the build-id value as a hexadecimal string.
Returns
Returns the constructed filename or NULL upon error.
It is the caller’s responsibility to free the memory used to hold the
filename.
If a filename is returned then the build_id_out_p
parameter (which points to a struct bfd_build_id
pointer) is set to a pointer to the build_id structure.
check_build_id_file
Synopsis
bool check_build_id_file (char *name, void *buildid_p);
Description
Checks to see if name is a readable file and if its build-id
matches buildid.
Returns
Returns TRUE if the file exists, is readable, and contains a
build-id which matches the build-id pointed at by
build_id_p (which is really a struct bfd_build_id **
).
bfd_follow_build_id_debuglink
Synopsis
char *bfd_follow_build_id_debuglink (bfd *abfd, const char *dir);
Description
Takes abfd and searches it for a .note.gnu.build-id section.
If this section is found, it extracts the value of the NT_GNU_BUILD_ID
note, which should be a hexadecimal value NNNN+NN (for
32+ hex digits). It then searches the filesystem for a file named
.build-id/NN/NN+NN.debug in a set of standard locations,
including the directory tree rooted at dir. The filename
of the first matching file to be found is returned. A matching
file should contain a .note.gnu.build-id section with the same
NNNN+NN note as abfd, although this check is currently
not implemented.
If dir is NULL, the search will take place starting at the current directory.
Returns
NULL
on any errors or failure to locate the debug file,
otherwise a pointer to a heap-allocated string containing the
filename. The caller is responsible for freeing this string.
bfd_set_filename
Synopsis
const char *bfd_set_filename (bfd *abfd, const char *filename);
Description
Set the filename of abfd, copying the FILENAME parameter to
bfd_alloc’d memory owned by abfd. Returns a pointer the
newly allocated name, or NULL if the allocation failed.
Next: File Caching, Previous: Opening and Closing, Up: BFD front end [Contents][Index]
Description
These routines are used within BFD.
They are not intended for export, but are documented here for
completeness.
bfd_malloc
Synopsis
extern void * bfd_malloc (bfd_size_type SIZE) ATTRIBUTE_HIDDEN;
Description
Returns a pointer to an allocated block of memory that is at least
SIZE bytes long. If SIZE is 0 then it will be treated as if it were
1. If SIZE is too big then NULL will be returned.
Returns NULL upon error and sets bfd_error.
bfd_realloc
Synopsis
extern void * bfd_realloc (void * MEM, bfd_size_type SIZE) ATTRIBUTE_HIDDEN;
Description
Returns a pointer to an allocated block of memory that is at least
SIZE bytes long. If SIZE is 0 then it will be treated as if it were
1. If SIZE is too big then NULL will be returned.
If MEM is not NULL then it must point to an allocated block of memory.
If this block is large enough then MEM may be used as the return
value for this function, but this is not guaranteed.
If MEM is not returned then the first N bytes in the returned block will be identical to the first N bytes in region pointed to by MEM, where N is the lessor of SIZE and the length of the region of memory currently addressed by MEM.
Returns NULL upon error and sets bfd_error.
bfd_realloc_or_free
Synopsis
extern void * bfd_realloc_or_free (void * MEM, bfd_size_type SIZE) ATTRIBUTE_HIDDEN;
Description
Returns a pointer to an allocated block of memory that is at least
SIZE bytes long. If SIZE is 0 then no memory will be allocated,
MEM will be freed, and NULL will be returned. This will not cause
bfd_error to be set.
If SIZE is too big then NULL will be returned and bfd_error will be set. If MEM is not NULL then it must point to an allocated block of memory. If this block is large enough then MEM may be used as the return value for this function, but this is not guaranteed.
If MEM is not returned then the first N bytes in the returned block will be identical to the first N bytes in region pointed to by MEM, where N is the lessor of SIZE and the length of the region of memory currently addressed by MEM.
bfd_zmalloc
Synopsis
extern void * bfd_zmalloc (bfd_size_type SIZE) ATTRIBUTE_HIDDEN;
Description
Returns a pointer to an allocated block of memory that is at least
SIZE bytes long. If SIZE is 0 then it will be treated as if it were
1. If SIZE is too big then NULL will be returned.
Returns NULL upon error and sets bfd_error.
If NULL is not returned then the allocated block of memory will have been cleared.
bfd_write_bigendian_4byte_int
Synopsis
bool bfd_write_bigendian_4byte_int (bfd *, unsigned int);
Description
Write a 4 byte integer i to the output BFD abfd, in big
endian order regardless of what else is going on. This is useful in
archives.
bfd_put_size
bfd_get_size
Description
These macros as used for reading and writing raw data in
sections; each access (except for bytes) is vectored through
the target format of the BFD and mangled accordingly. The
mangling performs any necessary endian translations and
removes alignment restrictions. Note that types accepted and
returned by these macros are identical so they can be swapped
around in macros—for example, libaout.h defines GET_WORD
to either bfd_get_32
or bfd_get_64
.
In the put routines, val must be a bfd_vma
. If we are on a
system without prototypes, the caller is responsible for making
sure that is true, with a cast if necessary. We don’t cast
them in the macro definitions because that would prevent lint
or gcc -Wall
from detecting sins such as passing a pointer.
To detect calling these with less than a bfd_vma
, use
gcc -Wconversion
on a host with 64 bit bfd_vma
’s.
/* Byte swapping macros for user section data. */ #define bfd_put_8(abfd, val, ptr) \ ((void) (*((unsigned char *) (ptr)) = (val) & 0xff)) #define bfd_put_signed_8 \ bfd_put_8 #define bfd_get_8(abfd, ptr) \ ((bfd_vma) *(const unsigned char *) (ptr) & 0xff) #define bfd_get_signed_8(abfd, ptr) \ ((((bfd_signed_vma) *(const unsigned char *) (ptr) & 0xff) ^ 0x80) - 0x80) #define bfd_put_16(abfd, val, ptr) \ BFD_SEND (abfd, bfd_putx16, ((val),(ptr))) #define bfd_put_signed_16 \ bfd_put_16 #define bfd_get_16(abfd, ptr) \ BFD_SEND (abfd, bfd_getx16, (ptr)) #define bfd_get_signed_16(abfd, ptr) \ BFD_SEND (abfd, bfd_getx_signed_16, (ptr)) #define bfd_put_24(abfd, val, ptr) \ do \ if (bfd_big_endian (abfd)) \ bfd_putb24 ((val), (ptr)); \ else \ bfd_putl24 ((val), (ptr)); \ while (0) bfd_vma bfd_getb24 (const void *p); bfd_vma bfd_getl24 (const void *p); #define bfd_get_24(abfd, ptr) \ (bfd_big_endian (abfd) ? bfd_getb24 (ptr) : bfd_getl24 (ptr)) #define bfd_put_32(abfd, val, ptr) \ BFD_SEND (abfd, bfd_putx32, ((val),(ptr))) #define bfd_put_signed_32 \ bfd_put_32 #define bfd_get_32(abfd, ptr) \ BFD_SEND (abfd, bfd_getx32, (ptr)) #define bfd_get_signed_32(abfd, ptr) \ BFD_SEND (abfd, bfd_getx_signed_32, (ptr)) #define bfd_put_64(abfd, val, ptr) \ BFD_SEND (abfd, bfd_putx64, ((val), (ptr))) #define bfd_put_signed_64 \ bfd_put_64 #define bfd_get_64(abfd, ptr) \ BFD_SEND (abfd, bfd_getx64, (ptr)) #define bfd_get_signed_64(abfd, ptr) \ BFD_SEND (abfd, bfd_getx_signed_64, (ptr)) #define bfd_get(bits, abfd, ptr) \ ((bits) == 8 ? bfd_get_8 (abfd, ptr) \ : (bits) == 16 ? bfd_get_16 (abfd, ptr) \ : (bits) == 32 ? bfd_get_32 (abfd, ptr) \ : (bits) == 64 ? bfd_get_64 (abfd, ptr) \ : (abort (), (bfd_vma) - 1)) #define bfd_put(bits, abfd, val, ptr) \ ((bits) == 8 ? bfd_put_8 (abfd, val, ptr) \ : (bits) == 16 ? bfd_put_16 (abfd, val, ptr) \ : (bits) == 32 ? bfd_put_32 (abfd, val, ptr) \ : (bits) == 64 ? bfd_put_64 (abfd, val, ptr) \ : (abort (), (void) 0))
bfd_h_put_size
Description
These macros have the same function as their bfd_get_x
brethren, except that they are used for removing information
for the header records of object files. Believe it or not,
some object files keep their header records in big endian
order and their data in little endian order.
/* Byte swapping macros for file header data. */ #define bfd_h_put_8(abfd, val, ptr) \ bfd_put_8 (abfd, val, ptr) #define bfd_h_put_signed_8(abfd, val, ptr) \ bfd_put_8 (abfd, val, ptr) #define bfd_h_get_8(abfd, ptr) \ bfd_get_8 (abfd, ptr) #define bfd_h_get_signed_8(abfd, ptr) \ bfd_get_signed_8 (abfd, ptr) #define bfd_h_put_16(abfd, val, ptr) \ BFD_SEND (abfd, bfd_h_putx16, (val, ptr)) #define bfd_h_put_signed_16 \ bfd_h_put_16 #define bfd_h_get_16(abfd, ptr) \ BFD_SEND (abfd, bfd_h_getx16, (ptr)) #define bfd_h_get_signed_16(abfd, ptr) \ BFD_SEND (abfd, bfd_h_getx_signed_16, (ptr)) #define bfd_h_put_32(abfd, val, ptr) \ BFD_SEND (abfd, bfd_h_putx32, (val, ptr)) #define bfd_h_put_signed_32 \ bfd_h_put_32 #define bfd_h_get_32(abfd, ptr) \ BFD_SEND (abfd, bfd_h_getx32, (ptr)) #define bfd_h_get_signed_32(abfd, ptr) \ BFD_SEND (abfd, bfd_h_getx_signed_32, (ptr)) #define bfd_h_put_64(abfd, val, ptr) \ BFD_SEND (abfd, bfd_h_putx64, (val, ptr)) #define bfd_h_put_signed_64 \ bfd_h_put_64 #define bfd_h_get_64(abfd, ptr) \ BFD_SEND (abfd, bfd_h_getx64, (ptr)) #define bfd_h_get_signed_64(abfd, ptr) \ BFD_SEND (abfd, bfd_h_getx_signed_64, (ptr)) /* Aliases for the above, which should eventually go away. */ #define H_PUT_64 bfd_h_put_64 #define H_PUT_32 bfd_h_put_32 #define H_PUT_16 bfd_h_put_16 #define H_PUT_8 bfd_h_put_8 #define H_PUT_S64 bfd_h_put_signed_64 #define H_PUT_S32 bfd_h_put_signed_32 #define H_PUT_S16 bfd_h_put_signed_16 #define H_PUT_S8 bfd_h_put_signed_8 #define H_GET_64 bfd_h_get_64 #define H_GET_32 bfd_h_get_32 #define H_GET_16 bfd_h_get_16 #define H_GET_8 bfd_h_get_8 #define H_GET_S64 bfd_h_get_signed_64 #define H_GET_S32 bfd_h_get_signed_32 #define H_GET_S16 bfd_h_get_signed_16 #define H_GET_S8 bfd_h_get_signed_8
bfd_log2
Synopsis
unsigned int bfd_log2 (bfd_vma x);
Description
Return the log base 2 of the value supplied, rounded up. E.g., an
x of 1025 returns 11. A x of 0 returns 0.
Next: Linker Functions, Previous: Internal, Up: BFD front end [Contents][Index]
The file caching mechanism is embedded within BFD and allows
the application to open as many BFDs as it wants without
regard to the underlying operating system’s file descriptor
limit (often as low as 20 open files). The module in
cache.c
maintains a least recently used list of
bfd_cache_max_open
files, and exports the name
bfd_cache_lookup
, which runs around and makes sure that
the required BFD is open. If not, then it chooses a file to
close, closes it and opens the one wanted, returning its file
handle.
bfd_cache_init
Synopsis
bool bfd_cache_init (bfd *abfd);
Description
Add a newly opened BFD to the cache.
bfd_cache_close
Synopsis
bool bfd_cache_close (bfd *abfd);
Description
Remove the BFD abfd from the cache. If the attached file is open,
then close it too.
Returns
FALSE
is returned if closing the file fails, TRUE
is
returned if all is well.
bfd_cache_close_all
Synopsis
bool bfd_cache_close_all (void);
Description
Remove all BFDs from the cache. If the attached file is open,
then close it too.
Returns
FALSE
is returned if closing one of the file fails, TRUE
is
returned if all is well.
bfd_open_file
Synopsis
FILE* bfd_open_file (bfd *abfd);
Description
Call the OS to open a file for abfd. Return the FILE *
(possibly NULL
) that results from this operation. Set up the
BFD so that future accesses know the file is open. If the FILE *
returned is NULL
, then it won’t have been put in the
cache, so it won’t have to be removed from it.
Next: Hash Tables, Previous: File Caching, Up: BFD front end [Contents][Index]
The linker uses three special entry points in the BFD target vector. It is not necessary to write special routines for these entry points when creating a new BFD back end, since generic versions are provided. However, writing them can speed up linking and make it use significantly less runtime memory.
The first routine creates a hash table used by the other routines. The second routine adds the symbols from an object file to the hash table. The third routine takes all the object files and links them together to create the output file. These routines are designed so that the linker proper does not need to know anything about the symbols in the object files that it is linking. The linker merely arranges the sections as directed by the linker script and lets BFD handle the details of symbols and relocs.
The second routine and third routines are passed a pointer to
a struct bfd_link_info
structure (defined in
bfdlink.h
) which holds information relevant to the link,
including the linker hash table (which was created by the
first routine) and a set of callback functions to the linker
proper.
The generic linker routines are in linker.c
, and use the
header file genlink.h
. As of this writing, the only back
ends which have implemented versions of these routines are
a.out (in aoutx.h
) and ECOFF (in ecoff.c
). The a.out
routines are used as examples throughout this section.
• Creating a Linker Hash Table | ||
• Adding Symbols to the Hash Table | ||
• Performing the Final Link |
Next: Adding Symbols to the Hash Table, Previous: Linker Functions, Up: Linker Functions [Contents][Index]
The linker routines must create a hash table, which must be
derived from struct bfd_link_hash_table
described in
bfdlink.c
. See Hash Tables, for information on how to
create a derived hash table. This entry point is called using
the target vector of the linker output file.
The _bfd_link_hash_table_create
entry point must allocate
and initialize an instance of the desired hash table. If the
back end does not require any additional information to be
stored with the entries in the hash table, the entry point may
simply create a struct bfd_link_hash_table
. Most likely,
however, some additional information will be needed.
For example, with each entry in the hash table the a.out
linker keeps the index the symbol has in the final output file
(this index number is used so that when doing a relocatable
link the symbol index used in the output file can be quickly
filled in when copying over a reloc). The a.out linker code
defines the required structures and functions for a hash table
derived from struct bfd_link_hash_table
. The a.out linker
hash table is created by the function
NAME(aout,link_hash_table_create)
; it simply allocates
space for the hash table, initializes it, and returns a
pointer to it.
When writing the linker routines for a new back end, you will generally not know exactly which fields will be required until you have finished. You should simply create a new hash table which defines no additional fields, and then simply add fields as they become necessary.
Next: Performing the Final Link, Previous: Creating a Linker Hash Table, Up: Linker Functions [Contents][Index]
The linker proper will call the _bfd_link_add_symbols
entry point for each object file or archive which is to be
linked (typically these are the files named on the command
line, but some may also come from the linker script). The
entry point is responsible for examining the file. For an
object file, BFD must add any relevant symbol information to
the hash table. For an archive, BFD must determine which
elements of the archive should be used and adding them to the
link.
The a.out version of this entry point is
NAME(aout,link_add_symbols)
.
• Differing file formats | ||
• Adding symbols from an object file | ||
• Adding symbols from an archive |
Next: Adding symbols from an object file, Previous: Adding Symbols to the Hash Table, Up: Adding Symbols to the Hash Table [Contents][Index]
Normally all the files involved in a link will be of the same
format, but it is also possible to link together different
format object files, and the back end must support that. The
_bfd_link_add_symbols
entry point is called via the target
vector of the file to be added. This has an important
consequence: the function may not assume that the hash table
is the type created by the corresponding
_bfd_link_hash_table_create
vector. All the
_bfd_link_add_symbols
function can assume about the hash
table is that it is derived from struct
bfd_link_hash_table
.
Sometimes the _bfd_link_add_symbols
function must store
some information in the hash table entry to be used by the
_bfd_final_link
function. In such a case the output bfd
xvec must be checked to make sure that the hash table was
created by an object file of the same format.
The _bfd_final_link
routine must be prepared to handle a
hash entry without any extra information added by the
_bfd_link_add_symbols
function. A hash entry without
extra information will also occur when the linker script
directs the linker to create a symbol. Note that, regardless
of how a hash table entry is added, all the fields will be
initialized to some sort of null value by the hash table entry
initialization function.
See ecoff_link_add_externals
for an example of how to
check the output bfd before saving information (in this
case, the ECOFF external symbol debugging information) in a
hash table entry.
Next: Adding symbols from an archive, Previous: Differing file formats, Up: Adding Symbols to the Hash Table [Contents][Index]
When the _bfd_link_add_symbols
routine is passed an object
file, it must add all externally visible symbols in that
object file to the hash table. The actual work of adding the
symbol to the hash table is normally handled by the function
_bfd_generic_link_add_one_symbol
. The
_bfd_link_add_symbols
routine is responsible for reading
all the symbols from the object file and passing the correct
information to _bfd_generic_link_add_one_symbol
.
The _bfd_link_add_symbols
routine should not use
bfd_canonicalize_symtab
to read the symbols. The point of
providing this routine is to avoid the overhead of converting
the symbols into generic asymbol
structures.
_bfd_generic_link_add_one_symbol
handles the details of
combining common symbols, warning about multiple definitions,
and so forth. It takes arguments which describe the symbol to
add, notably symbol flags, a section, and an offset. The
symbol flags include such things as BSF_WEAK
or
BSF_INDIRECT
. The section is a section in the object
file, or something like bfd_und_section_ptr
for an undefined
symbol or bfd_com_section_ptr
for a common symbol.
If the _bfd_final_link
routine is also going to need to
read the symbol information, the _bfd_link_add_symbols
routine should save it somewhere attached to the object file
BFD. However, the information should only be saved if the
keep_memory
field of the info
argument is TRUE, so
that the -no-keep-memory
linker switch is effective.
The a.out function which adds symbols from an object file is
aout_link_add_object_symbols
, and most of the interesting
work is in aout_link_add_symbols
. The latter saves
pointers to the hash tables entries created by
_bfd_generic_link_add_one_symbol
indexed by symbol number,
so that the _bfd_final_link
routine does not have to call
the hash table lookup routine to locate the entry.
Previous: Adding symbols from an object file, Up: Adding Symbols to the Hash Table [Contents][Index]
When the _bfd_link_add_symbols
routine is passed an
archive, it must look through the symbols defined by the
archive and decide which elements of the archive should be
included in the link. For each such element it must call the
add_archive_element
linker callback, and it must add the
symbols from the object file to the linker hash table. (The
callback may in fact indicate that a replacement BFD should be
used, in which case the symbols from that BFD should be added
to the linker hash table instead.)
In most cases the work of looking through the symbols in the
archive should be done by the
_bfd_generic_link_add_archive_symbols
function.
_bfd_generic_link_add_archive_symbols
is passed a function
to call to make the final decision about adding an archive
element to the link and to do the actual work of adding the
symbols to the linker hash table. If the element is to
be included, the add_archive_element
linker callback
routine must be called with the element as an argument, and
the element’s symbols must be added to the linker hash table
just as though the element had itself been passed to the
_bfd_link_add_symbols
function.
When the a.out _bfd_link_add_symbols
function receives an
archive, it calls _bfd_generic_link_add_archive_symbols
passing aout_link_check_archive_element
as the function
argument. aout_link_check_archive_element
calls
aout_link_check_ar_symbols
. If the latter decides to add
the element (an element is only added if it provides a real,
non-common, definition for a previously undefined or common
symbol) it calls the add_archive_element
callback and then
aout_link_check_archive_element
calls
aout_link_add_symbols
to actually add the symbols to the
linker hash table - possibly those of a substitute BFD, if the
add_archive_element
callback avails itself of that option.
The ECOFF back end is unusual in that it does not normally
call _bfd_generic_link_add_archive_symbols
, because ECOFF
archives already contain a hash table of symbols. The ECOFF
back end searches the archive itself to avoid the overhead of
creating a new hash table.
Previous: Adding Symbols to the Hash Table, Up: Linker Functions [Contents][Index]
When all the input files have been processed, the linker calls
the _bfd_final_link
entry point of the output BFD. This
routine is responsible for producing the final output file,
which has several aspects. It must relocate the contents of
the input sections and copy the data into the output sections.
It must build an output symbol table including any local
symbols from the input files and the global symbols from the
hash table. When producing relocatable output, it must
modify the input relocs and write them into the output file.
There may also be object format dependent work to be done.
The linker will also call the write_object_contents
entry
point when the BFD is closed. The two entry points must work
together in order to produce the correct output file.
The details of how this works are inevitably dependent upon
the specific object file format. The a.out
_bfd_final_link
routine is NAME(aout,final_link)
.
• Information provided by the linker | ||
• Relocating the section contents | ||
• Writing the symbol table |
Next: Relocating the section contents, Previous: Performing the Final Link, Up: Performing the Final Link [Contents][Index]
Before the linker calls the _bfd_final_link
entry point,
it sets up some data structures for the function to use.
The input_bfds
field of the bfd_link_info
structure
will point to a list of all the input files included in the
link. These files are linked through the link.next
field
of the bfd
structure.
Each section in the output file will have a list of
link_order
structures attached to the map_head.link_order
field (the link_order
structure is defined in
bfdlink.h
). These structures describe how to create the
contents of the output section in terms of the contents of
various input sections, fill constants, and, eventually, other
types of information. They also describe relocs that must be
created by the BFD backend, but do not correspond to any input
file; this is used to support -Ur, which builds constructors
while generating a relocatable object file.
Next: Writing the symbol table, Previous: Information provided by the linker, Up: Performing the Final Link [Contents][Index]
The _bfd_final_link
function should look through the
link_order
structures attached to each section of the
output file. Each link_order
structure should either be
handled specially, or it should be passed to the function
_bfd_default_link_order
which will do the right thing
(_bfd_default_link_order
is defined in linker.c
).
For efficiency, a link_order
of type
bfd_indirect_link_order
whose associated section belongs
to a BFD of the same format as the output BFD must be handled
specially. This type of link_order
describes part of an
output section in terms of a section belonging to one of the
input files. The _bfd_final_link
function should read the
contents of the section and any associated relocs, apply the
relocs to the section contents, and write out the modified
section contents. If performing a relocatable link, the
relocs themselves must also be modified and written out.
The functions _bfd_relocate_contents
and
_bfd_final_link_relocate
provide some general support for
performing the actual relocations, notably overflow checking.
Their arguments include information about the symbol the
relocation is against and a reloc_howto_type
argument
which describes the relocation to perform. These functions
are defined in reloc.c
.
The a.out function which handles reading, relocating, and
writing section contents is aout_link_input_section
. The
actual relocation is done in aout_link_input_section_std
and aout_link_input_section_ext
.
Previous: Relocating the section contents, Up: Performing the Final Link [Contents][Index]
The _bfd_final_link
function must gather all the symbols
in the input files and write them out. It must also write out
all the symbols in the global hash table. This must be
controlled by the strip
and discard
fields of the
bfd_link_info
structure.
The local symbols of the input files will not have been
entered into the linker hash table. The _bfd_final_link
routine must consider each input file and include the symbols
in the output file. It may be convenient to do this when
looking through the link_order
structures, or it may be
done by stepping through the input_bfds
list.
The _bfd_final_link
routine must also traverse the global
hash table to gather all the externally visible symbols. It
is possible that most of the externally visible symbols may be
written out when considering the symbols of each input file,
but it is still necessary to traverse the hash table since the
linker script may have defined some symbols that are not in
any of the input files.
The strip
field of the bfd_link_info
structure
controls which symbols are written out. The possible values
are listed in bfdlink.h
. If the value is strip_some
,
then the keep_hash
field of the bfd_link_info
structure is a hash table of symbols to keep; each symbol
should be looked up in this hash table, and only symbols which
are present should be included in the output file.
If the strip
field of the bfd_link_info
structure
permits local symbols to be written out, the discard
field
is used to further controls which local symbols are included
in the output file. If the value is discard_l
, then all
local symbols which begin with a certain prefix are discarded;
this is controlled by the bfd_is_local_label_name
entry point.
The a.out backend handles symbols by calling
aout_link_write_symbols
on each input BFD and then
traversing the global hash table with the function
aout_link_write_other_symbol
. It builds a string table
while writing out the symbols, which is written to the output
file at the end of NAME(aout,final_link)
.
bfd_link_split_section
Synopsis
bool bfd_link_split_section (bfd *abfd, asection *sec);
Description
Return nonzero if sec should be split during a
reloceatable or final link.
#define bfd_link_split_section(abfd, sec) \ BFD_SEND (abfd, _bfd_link_split_section, (abfd, sec))
bfd_section_already_linked
Synopsis
bool bfd_section_already_linked (bfd *abfd, asection *sec, struct bfd_link_info *info);
Description
Check if data has been already linked during a reloceatable
or final link. Return TRUE if it has.
#define bfd_section_already_linked(abfd, sec, info) \ BFD_SEND (abfd, _section_already_linked, (abfd, sec, info))
bfd_generic_define_common_symbol
Synopsis
bool bfd_generic_define_common_symbol (bfd *output_bfd, struct bfd_link_info *info, struct bfd_link_hash_entry *h);
Description
Convert common symbol h into a defined symbol.
Return TRUE on success and FALSE on failure.
#define bfd_define_common_symbol(output_bfd, info, h) \ BFD_SEND (output_bfd, _bfd_define_common_symbol, (output_bfd, info, h))
_bfd_generic_link_hide_symbol
Synopsis
void _bfd_generic_link_hide_symbol (bfd *output_bfd, struct bfd_link_info *info, struct bfd_link_hash_entry *h);
Description
Hide symbol h.
This is an internal function. It should not be called from
outside the BFD library.
#define bfd_link_hide_symbol(output_bfd, info, h) \ BFD_SEND (output_bfd, _bfd_link_hide_symbol, (output_bfd, info, h))
bfd_generic_define_start_stop
Synopsis
struct bfd_link_hash_entry *bfd_generic_define_start_stop (struct bfd_link_info *info, const char *symbol, asection *sec);
Description
Define a __start, __stop, .startof. or .sizeof. symbol.
Return the symbol or NULL if no such undefined symbol exists.
#define bfd_define_start_stop(output_bfd, info, symbol, sec) \ BFD_SEND (output_bfd, _bfd_define_start_stop, (info, symbol, sec))
bfd_find_version_for_sym
Synopsis
struct bfd_elf_version_tree * bfd_find_version_for_sym (struct bfd_elf_version_tree *verdefs, const char *sym_name, bool *hide);
Description
Search an elf version script tree for symbol versioning
info and export / don’t-export status for a given symbol.
Return non-NULL on success and NULL on failure; also sets
the output ‘hide’ boolean parameter.
bfd_hide_sym_by_version
Synopsis
bool bfd_hide_sym_by_version (struct bfd_elf_version_tree *verdefs, const char *sym_name);
Description
Search an elf version script tree for symbol versioning
info for a given symbol. Return TRUE if the symbol is hidden.
bfd_link_check_relocs
Synopsis
bool bfd_link_check_relocs (bfd *abfd, struct bfd_link_info *info);
Description
Checks the relocs in ABFD for validity.
Does not execute the relocs.
Return TRUE if everything is OK, FALSE otherwise.
This is the external entry point to this code.
_bfd_generic_link_check_relocs
Synopsis
bool _bfd_generic_link_check_relocs (bfd *abfd, struct bfd_link_info *info);
Description
Stub function for targets that do not implement reloc checking.
Return TRUE.
This is an internal function. It should not be called from
outside the BFD library.
bfd_merge_private_bfd_data
Synopsis
bool bfd_merge_private_bfd_data (bfd *ibfd, struct bfd_link_info *info);
Description
Merge private BFD information from the BFD ibfd to the
the output file BFD when linking. Return TRUE
on success,
FALSE
on error. Possible error returns are:
bfd_error_no_memory
-
Not enough memory exists to create private data for obfd.
#define bfd_merge_private_bfd_data(ibfd, info) \ BFD_SEND ((info)->output_bfd, _bfd_merge_private_bfd_data, \ (ibfd, info))
_bfd_generic_verify_endian_match
Synopsis
bool _bfd_generic_verify_endian_match (bfd *ibfd, struct bfd_link_info *info);
Description
Can be used from / for bfd_merge_private_bfd_data to check that
endianness matches between input and output file. Returns
TRUE for a match, otherwise returns FALSE and emits an error.
Previous: Linker Functions, Up: BFD front end [Contents][Index]
BFD provides a simple set of hash table functions. Routines are provided to initialize a hash table, to free a hash table, to look up a string in a hash table and optionally create an entry for it, and to traverse a hash table. There is currently no routine to delete an string from a hash table.
The basic hash table does not permit any data to be stored with a string. However, a hash table is designed to present a base class from which other types of hash tables may be derived. These derived types may store additional information with the string. Hash tables were implemented in this way, rather than simply providing a data pointer in a hash table entry, because they were designed for use by the linker back ends. The linker may create thousands of hash table entries, and the overhead of allocating private data and storing and following pointers becomes noticeable.
The basic hash table code is in hash.c
.
• Creating and Freeing a Hash Table | ||
• Looking Up or Entering a String | ||
• Traversing a Hash Table | ||
• Deriving a New Hash Table Type |
Next: Looking Up or Entering a String, Previous: Hash Tables, Up: Hash Tables [Contents][Index]
To create a hash table, create an instance of a struct
bfd_hash_table
(defined in bfd.h
) and call
bfd_hash_table_init
(if you know approximately how many
entries you will need, the function bfd_hash_table_init_n
,
which takes a size argument, may be used).
bfd_hash_table_init
returns FALSE
if some sort of
error occurs.
The function bfd_hash_table_init
take as an argument a
function to use to create new entries. For a basic hash
table, use the function bfd_hash_newfunc
. See Deriving a New Hash Table Type, for why you would want to use a
different value for this argument.
bfd_hash_table_init
will create an objalloc which will be
used to allocate new entries. You may allocate memory on this
objalloc using bfd_hash_allocate
.
Use bfd_hash_table_free
to free up all the memory that has
been allocated for a hash table. This will not free up the
struct bfd_hash_table
itself, which you must provide.
Use bfd_hash_set_default_size
to set the default size of
hash table to use.
Next: Traversing a Hash Table, Previous: Creating and Freeing a Hash Table, Up: Hash Tables [Contents][Index]
The function bfd_hash_lookup
is used both to look up a
string in the hash table and to create a new entry.
If the create argument is FALSE
, bfd_hash_lookup
will look up a string. If the string is found, it will
returns a pointer to a struct bfd_hash_entry
. If the
string is not found in the table bfd_hash_lookup
will
return NULL
. You should not modify any of the fields in
the returns struct bfd_hash_entry
.
If the create argument is TRUE
, the string will be
entered into the hash table if it is not already there.
Either way a pointer to a struct bfd_hash_entry
will be
returned, either to the existing structure or to a newly
created one. In this case, a NULL
return means that an
error occurred.
If the create argument is TRUE
, and a new entry is
created, the copy argument is used to decide whether to
copy the string onto the hash table objalloc or not. If
copy is passed as FALSE
, you must be careful not to
deallocate or modify the string as long as the hash table
exists.
Next: Deriving a New Hash Table Type, Previous: Looking Up or Entering a String, Up: Hash Tables [Contents][Index]
The function bfd_hash_traverse
may be used to traverse a
hash table, calling a function on each element. The traversal
is done in a random order.
bfd_hash_traverse
takes as arguments a function and a
generic void *
pointer. The function is called with a
hash table entry (a struct bfd_hash_entry *
) and the
generic pointer passed to bfd_hash_traverse
. The function
must return a boolean
value, which indicates whether to
continue traversing the hash table. If the function returns
FALSE
, bfd_hash_traverse
will stop the traversal and
return immediately.
Previous: Traversing a Hash Table, Up: Hash Tables [Contents][Index]
Many uses of hash tables want to store additional information which each entry in the hash table. Some also find it convenient to store additional information with the hash table itself. This may be done using a derived hash table.
Since C is not an object oriented language, creating a derived hash table requires sticking together some boilerplate routines with a few differences specific to the type of hash table you want to create.
An example of a derived hash table is the linker hash table.
The structures for this are defined in bfdlink.h
. The
functions are in linker.c
.
You may also derive a hash table from an already derived hash table. For example, the a.out linker backend code uses a hash table derived from the linker hash table.
• Define the Derived Structures | ||
• Write the Derived Creation Routine | ||
• Write Other Derived Routines |
Next: Write the Derived Creation Routine, Previous: Deriving a New Hash Table Type, Up: Deriving a New Hash Table Type [Contents][Index]
You must define a structure for an entry in the hash table, and a structure for the hash table itself.
The first field in the structure for an entry in the hash
table must be of the type used for an entry in the hash table
you are deriving from. If you are deriving from a basic hash
table this is struct bfd_hash_entry
, which is defined in
bfd.h
. The first field in the structure for the hash
table itself must be of the type of the hash table you are
deriving from itself. If you are deriving from a basic hash
table, this is struct bfd_hash_table
.
For example, the linker hash table defines struct
bfd_link_hash_entry
(in bfdlink.h
). The first field,
root
, is of type struct bfd_hash_entry
. Similarly,
the first field in struct bfd_link_hash_table
, table
,
is of type struct bfd_hash_table
.
Next: Write Other Derived Routines, Previous: Define the Derived Structures, Up: Deriving a New Hash Table Type [Contents][Index]
You must write a routine which will create and initialize an
entry in the hash table. This routine is passed as the
function argument to bfd_hash_table_init
.
In order to permit other hash tables to be derived from the hash table you are creating, this routine must be written in a standard way.
The first argument to the creation routine is a pointer to a
hash table entry. This may be NULL
, in which case the
routine should allocate the right amount of space. Otherwise
the space has already been allocated by a hash table type
derived from this one.
After allocating space, the creation routine must call the creation routine of the hash table type it is derived from, passing in a pointer to the space it just allocated. This will initialize any fields used by the base hash table.
Finally the creation routine must initialize any local fields for the new hash table type.
Here is a boilerplate example of a creation routine. function_name is the name of the routine. entry_type is the type of an entry in the hash table you are creating. base_newfunc is the name of the creation routine of the hash table type your hash table is derived from.
struct bfd_hash_entry * function_name (struct bfd_hash_entry *entry, struct bfd_hash_table *table, const char *string) { struct entry_type *ret = (entry_type *) entry; /* Allocate the structure if it has not already been allocated by a derived class. */ if (ret == NULL) { ret = bfd_hash_allocate (table, sizeof (* ret)); if (ret == NULL) return NULL; } /* Call the allocation method of the base class. */ ret = ((entry_type *) base_newfunc ((struct bfd_hash_entry *) ret, table, string)); /* Initialize the local fields here. */ return (struct bfd_hash_entry *) ret; }
Description
The creation routine for the linker hash table, which is in
linker.c
, looks just like this example.
function_name is _bfd_link_hash_newfunc
.
entry_type is struct bfd_link_hash_entry
.
base_newfunc is bfd_hash_newfunc
, the creation
routine for a basic hash table.
_bfd_link_hash_newfunc
also initializes the local fields
in a linker hash table entry: type
, written
and
next
.
Previous: Write the Derived Creation Routine, Up: Deriving a New Hash Table Type [Contents][Index]
You will want to write other routines for your new hash table, as well.
You will want an initialization routine which calls the
initialization routine of the hash table you are deriving from
and initializes any other local fields. For the linker hash
table, this is _bfd_link_hash_table_init
in linker.c
.
You will want a lookup routine which calls the lookup routine
of the hash table you are deriving from and casts the result.
The linker hash table uses bfd_link_hash_lookup
in
linker.c
(this actually takes an additional argument which
it uses to decide how to return the looked up value).
You may want a traversal routine. This should just call the
traversal routine of the hash table you are deriving from with
appropriate casts. The linker hash table uses
bfd_link_hash_traverse
in linker.c
.
These routines may simply be defined as macros. For example,
the a.out backend linker hash table, which is derived from the
linker hash table, uses macros for the lookup and traversal
routines. These are aout_link_hash_lookup
and
aout_link_hash_traverse
in aoutx.h.
Next: GNU Free Documentation License, Previous: BFD front end, Up: Top [Contents][Index]
• What to Put Where | ||
• aout | a.out backends | |
• coff | coff backends | |
• elf | elf backends | |
• mmo | mmo backend |
Next: aout, Previous: BFD back ends, Up: BFD back ends [Contents][Index]
All of BFD lives in one directory.
Next: coff, Previous: What to Put Where, Up: BFD back ends [Contents][Index]
Description
BFD supports a number of different flavours of a.out format,
though the major differences are only the sizes of the
structures on disk, and the shape of the relocation
information.
The support is split into a basic support file aoutx.h and other files which derive functions from the base. One derivation file is aoutf1.h (for a.out flavour 1), and adds to the basic a.out functions support for sun3, sun4, and 386 a.out files, to create a target jump vector for a specific target.
This information is further split out into more specific files for each machine, including sunos.c for sun3 and sun4, and demo64.c for a demonstration of a 64 bit a.out format.
The base file aoutx.h defines general mechanisms for
reading and writing records to and from disk and various
other methods which BFD requires. It is included by
aout32.c and aout64.c to form the names
aout_32_swap_exec_header_in
, aout_64_swap_exec_header_in
, etc.
As an example, this is what goes on to make the back end for a sun4, from aout32.c:
#define ARCH_SIZE 32 #include "aoutx.h"
Which exports names:
... aout_32_canonicalize_reloc aout_32_find_nearest_line aout_32_get_lineno aout_32_get_reloc_upper_bound ...
from sunos.c:
#define TARGET_NAME "a.out-sunos-big" #define VECNAME sparc_aout_sunos_be_vec #include "aoutf1.h"
requires all the names from aout32.c, and produces the jump vector
sparc_aout_sunos_be_vec
The file host-aout.c is a special case. It is for a large set of hosts that use “more or less standard” a.out files, and for which cross-debugging is not interesting. It uses the standard 32-bit a.out support routines, but determines the file offsets and addresses of the text, data, and BSS sections, the machine architecture and machine type, and the entry point address, in a host-dependent manner. Once these values have been determined, generic code is used to handle the object file.
When porting it to run on a new system, you must supply:
HOST_PAGE_SIZE HOST_SEGMENT_SIZE HOST_MACHINE_ARCH (optional) HOST_MACHINE_MACHINE (optional) HOST_TEXT_START_ADDR HOST_STACK_END_ADDR
in the file ../include/sys/h-XXX.h (for your host). These values, plus the structures and macros defined in a.out.h on your host system, will produce a BFD target that will access ordinary a.out files on your host. To configure a new machine to use host-aout.c, specify:
TDEFAULTS = -DDEFAULT_VECTOR=host_aout_big_vec TDEPFILES= host-aout.o trad-core.o
in the config/XXX.mt file, and modify configure.ac
to use the
XXX.mt file (by setting "bfd_target=XXX
") when your
configuration is selected.
Description
The file aoutx.h provides for both the standard
and extended forms of a.out relocation records.
The standard records contain only an address, a symbol index, and a type field. The extended records also have a full integer for an addend.
Description
aoutx.h exports several routines for accessing the
contents of an a.out file, which are gathered and exported in
turn by various format specific files (eg sunos.c).
aout_size_swap_exec_header_in
Synopsis
void aout_size_swap_exec_header_in, (bfd *abfd, struct external_exec *bytes, struct internal_exec *execp);
Description
Swap the information in an executable header raw_bytes taken
from a raw byte stream memory image into the internal exec header
structure execp.
aout_size_swap_exec_header_out
Synopsis
void aout_size_swap_exec_header_out (bfd *abfd, struct internal_exec *execp, struct external_exec *raw_bytes);
Description
Swap the information in an internal exec header structure
execp into the buffer raw_bytes ready for writing to disk.
aout_size_some_aout_object_p
Synopsis
const bfd_target *aout_size_some_aout_object_p (bfd *abfd, struct internal_exec *execp, const bfd_target *(*callback_to_real_object_p) (bfd *));
Description
Some a.out variant thinks that the file open in abfd
checking is an a.out file. Do some more checking, and set up
for access if it really is. Call back to the calling
environment’s "finish up" function just before returning, to
handle any last-minute setup.
aout_size_mkobject
Synopsis
bool aout_size_mkobject, (bfd *abfd);
Description
Initialize BFD abfd for use with a.out files.
aout_size_machine_type
Synopsis
enum machine_type aout_size_machine_type (enum bfd_architecture arch, unsigned long machine, bool *unknown);
Description
Keep track of machine architecture and machine type for
a.out’s. Return the machine_type
for a particular
architecture and machine, or M_UNKNOWN
if that exact architecture
and machine can’t be represented in a.out format.
If the architecture is understood, machine type 0 (default) is always understood.
aout_size_set_arch_mach
Synopsis
bool aout_size_set_arch_mach, (bfd *, enum bfd_architecture arch, unsigned long machine);
Description
Set the architecture and the machine of the BFD abfd to the
values arch and machine. Verify that abfd’s format
can support the architecture required.
aout_size_new_section_hook
Synopsis
bool aout_size_new_section_hook, (bfd *abfd, asection *newsect);
Description
Called by the BFD in response to a bfd_make_section
request.
Next: elf, Previous: aout, Up: BFD back ends [Contents][Index]
BFD supports a number of different flavours of coff format. The major differences between formats are the sizes and alignments of fields in structures on disk, and the occasional extra field.
Coff in all its varieties is implemented with a few common
files and a number of implementation specific files. For
example, the i386 coff format is implemented in the file
coff-i386.c. This file #include
s
coff/i386.h which defines the external structure of the
coff format for the i386, and coff/internal.h which
defines the internal structure. coff-i386.c also
defines the relocations used by the i386 coff format
See Relocations.
The recommended method is to select from the existing
implementations the version of coff which is most like the one
you want to use. For example, we’ll say that i386 coff is
the one you select, and that your coff flavour is called foo.
Copy i386coff.c to foocoff.c, copy
../include/coff/i386.h to ../include/coff/foo.h,
and add the lines to targets.c and Makefile.in
so that your new back end is used. Alter the shapes of the
structures in ../include/coff/foo.h so that they match
what you need. You will probably also have to add
#ifdef
s to the code in coff/internal.h and
coffcode.h if your version of coff is too wild.
You can verify that your new BFD backend works quite simply by
building objdump from the binutils directory,
and making sure that its version of what’s going on and your
host system’s idea (assuming it has the pretty standard coff
dump utility, usually called att-dump
or just
dump
) are the same. Then clean up your code, and send
what you’ve done to Cygnus. Then your stuff will be in the
next release, and you won’t have to keep integrating it.
The Coff backend is split into generic routines that are applicable to any Coff target and routines that are specific to a particular target. The target-specific routines are further split into ones which are basically the same for all Coff targets except that they use the external symbol format or use different values for certain constants.
The generic routines are in coffgen.c. These routines
work for any Coff target. They use some hooks into the target
specific code; the hooks are in a bfd_coff_backend_data
structure, one of which exists for each target.
The essentially similar target-specific routines are in coffcode.h. This header file includes executable C code. The various Coff targets first include the appropriate Coff header file, make any special defines that are needed, and then include coffcode.h.
Some of the Coff targets then also have additional routines in the target source file itself.
In the standard Coff object format, section names are limited to
the eight bytes available in the s_name
field of the
SCNHDR
section header structure. The format requires the
field to be NUL-padded, but not necessarily NUL-terminated, so
the longest section names permitted are a full eight characters.
The Microsoft PE variants of the Coff object file format add
an extension to support the use of long section names. This
extension is defined in section 4 of the Microsoft PE/COFF
specification (rev 8.1). If a section name is too long to fit
into the section header’s s_name
field, it is instead
placed into the string table, and the s_name
field is
filled with a slash ("/") followed by the ASCII decimal
representation of the offset of the full name relative to the
string table base.
Note that this implies that the extension can only be used in object files, as executables do not contain a string table. The standard specifies that long section names from objects emitted into executable images are to be truncated.
However, as a GNU extension, BFD can generate executable images that contain a string table and long section names. This would appear to be technically valid, as the standard only says that Coff debugging information is deprecated, not forbidden, and in practice it works, although some tools that parse PE files expecting the MS standard format may become confused; PEview is one known example.
The functionality is supported in BFD by code implemented under
the control of the macro COFF_LONG_SECTION_NAMES
. If not
defined, the format does not support long section names in any way.
If defined, it is used to initialise a flag,
_bfd_coff_long_section_names
, and a hook function pointer,
_bfd_coff_set_long_section_names
, in the Coff backend data
structure. The flag controls the generation of long section names
in output BFDs at runtime; if it is false, as it will be by default
when generating an executable image, long section names are truncated;
if true, the long section names extension is employed. The hook
points to a function that allows the value of the flag to be altered
at runtime, on formats that support long section names at all; on
other formats it points to a stub that returns an error indication.
With input BFDs, the flag is set according to whether any long section names are detected while reading the section headers. For a completely new BFD, the flag is set to the default for the target format. This information can be used by a client of the BFD library when deciding what output format to generate, and means that a BFD that is opened for read and subsequently converted to a writeable BFD and modified in-place will retain whatever format it had on input.
If COFF_LONG_SECTION_NAMES
is simply defined (blank), or is
defined to the value "1", then long section names are enabled by
default; if it is defined to the value zero, they are disabled by
default (but still accepted in input BFDs). The header coffcode.h
defines a macro, COFF_DEFAULT_LONG_SECTION_NAMES
, which is
used in the backends to initialise the backend data structure fields
appropriately; see the comments for further detail.
Each flavour of coff supported in BFD has its own header file
describing the external layout of the structures. There is also
an internal description of the coff layout, in
coff/internal.h. A major function of the
coff backend is swapping the bytes and twiddling the bits to
translate the external form of the structures into the normal
internal form. This is all performed in the
bfd_swap
_thing_direction routines. Some
elements are different sizes between different versions of
coff; it is the duty of the coff version specific include file
to override the definitions of various packing routines in
coffcode.h. E.g., the size of line number entry in coff is
sometimes 16 bits, and sometimes 32 bits. #define
ing
PUT_LNSZ_LNNO
and GET_LNSZ_LNNO
will select the
correct one. No doubt, some day someone will find a version of
coff which has a varying field size not catered to at the
moment. To port BFD, that person will have to add more #defines
.
Three of the bit twiddling routines are exported to
gdb
; coff_swap_aux_in
, coff_swap_sym_in
and coff_swap_lineno_in
. GDB
reads the symbol
table on its own, but uses BFD to fix things up. More of the
bit twiddlers are exported for gas
;
coff_swap_aux_out
, coff_swap_sym_out
,
coff_swap_lineno_out
, coff_swap_reloc_out
,
coff_swap_filehdr_out
, coff_swap_aouthdr_out
,
coff_swap_scnhdr_out
. Gas
currently keeps track
of all the symbol table and reloc drudgery itself, thereby
saving the internal BFD overhead, but uses BFD to swap things
on the way out, making cross ports much safer. Doing so also
allows BFD (and thus the linker) to use the same header files
as gas
, which makes one avenue to disaster disappear.
The simple canonical form for symbols used by BFD is not rich enough to keep all the information available in a coff symbol table. The back end gets around this problem by keeping the original symbol table around, "behind the scenes".
When a symbol table is requested (through a call to
bfd_canonicalize_symtab
), a request gets through to
coff_get_normalized_symtab
. This reads the symbol table from
the coff file and swaps all the structures inside into the
internal form. It also fixes up all the pointers in the table
(represented in the file by offsets from the first symbol in
the table) into physical pointers to elements in the new
internal table. This involves some work since the meanings of
fields change depending upon context: a field that is a
pointer to another structure in the symbol table at one moment
may be the size in bytes of a structure at the next. Another
pass is made over the table. All symbols which mark file names
(C_FILE
symbols) are modified so that the internal
string points to the value in the auxent (the real filename)
rather than the normal text associated with the symbol
(".file"
).
At this time the symbol names are moved around. Coff stores all symbols less than nine characters long physically within the symbol table; longer strings are kept at the end of the file in the string table. This pass moves all strings into memory and replaces them with pointers to the strings.
The symbol table is massaged once again, this time to create
the canonical table used by the BFD application. Each symbol
is inspected in turn, and a decision made (using the
sclass
field) about the various flags to set in the
asymbol
. See Symbols. The generated canonical table
shares strings with the hidden internal symbol table.
Any linenumbers are read from the coff file too, and attached to the symbols which own the functions the linenumbers belong to.
Writing a symbol to a coff file which didn’t come from a coff
file will lose any debugging information. The asymbol
structure remembers the BFD from which the symbol was taken, and on
output the back end makes sure that the same destination target as
source target is present.
When the symbols have come from a coff file then all the debugging information is preserved.
Symbol tables are provided for writing to the back end in a vector of pointers to pointers. This allows applications like the linker to accumulate and output large symbol tables without having to do too much byte copying.
This function runs through the provided symbol table and
patches each symbol marked as a file place holder
(C_FILE
) to point to the next file place holder in the
list. It also marks each offset
field in the list with
the offset from the first symbol of the current symbol.
Another function of this procedure is to turn the canonical
value form of BFD into the form used by coff. Internally, BFD
expects symbol values to be offsets from a section base; so a
symbol physically at 0x120, but in a section starting at
0x100, would have the value 0x20. Coff expects symbols to
contain their final value, so symbols have their values
changed at this point to reflect their sum with their owning
section. This transformation uses the
output_section
field of the asymbol
’s
asection
See Sections.
coff_mangle_symbols
This routine runs though the provided symbol table and uses the offsets generated by the previous pass and the pointers generated when the symbol table was read in to create the structured hierarchy required by coff. It changes each pointer to a symbol into the index into the symbol table of the asymbol.
coff_write_symbols
This routine runs through the symbol table and patches up the symbols from their internal form into the coff way, calls the bit twiddlers, and writes out the table to the file.
coff_symbol_type
Description
The hidden information for an asymbol
is described in a
combined_entry_type
:
typedef struct coff_ptr_struct { /* Remembers the offset from the first symbol in the file for this symbol. Generated by coff_renumber_symbols. */ unsigned int offset; /* Should the value of this symbol be renumbered. Used for XCOFF C_BSTAT symbols. Set by coff_slurp_symbol_table. */ unsigned int fix_value : 1; /* Should the tag field of this symbol be renumbered. Created by coff_pointerize_aux. */ unsigned int fix_tag : 1; /* Should the endidx field of this symbol be renumbered. Created by coff_pointerize_aux. */ unsigned int fix_end : 1; /* Should the x_csect.x_scnlen field be renumbered. Created by coff_pointerize_aux. */ unsigned int fix_scnlen : 1; /* Fix up an XCOFF C_BINCL/C_EINCL symbol. The value is the index into the line number entries. Set by coff_slurp_symbol_table. */ unsigned int fix_line : 1; /* The container for the symbol structure as read and translated from the file. */ union { union internal_auxent auxent; struct internal_syment syment; } u; /* Selector for the union above. */ bool is_sym; } combined_entry_type; /* Each canonical asymbol really looks like this: */ typedef struct coff_symbol_struct { /* The actual symbol which the rest of BFD works with */ asymbol symbol; /* A pointer to the hidden information for this symbol */ combined_entry_type *native; /* A pointer to the linenumber information for this symbol */ struct lineno_cache_entry *lineno; /* Have the line numbers been relocated yet ? */ bool done_lineno; } coff_symbol_type;
bfd_coff_backend_data
/* COFF symbol classifications. */ enum coff_symbol_classification { /* Global symbol. */ COFF_SYMBOL_GLOBAL, /* Common symbol. */ COFF_SYMBOL_COMMON, /* Undefined symbol. */ COFF_SYMBOL_UNDEFINED, /* Local symbol. */ COFF_SYMBOL_LOCAL, /* PE section symbol. */ COFF_SYMBOL_PE_SECTION }; typedef asection * (*coff_gc_mark_hook_fn) (asection *, struct bfd_link_info *, struct internal_reloc *, struct coff_link_hash_entry *, struct internal_syment *);
Special entry points for gdb to swap in coff symbol table parts:
typedef struct { void (*_bfd_coff_swap_aux_in) (bfd *, void *, int, int, int, int, void *); void (*_bfd_coff_swap_sym_in) (bfd *, void *, void *); void (*_bfd_coff_swap_lineno_in) (bfd *, void *, void *); unsigned int (*_bfd_coff_swap_aux_out) (bfd *, void *, int, int, int, int, void *); unsigned int (*_bfd_coff_swap_sym_out) (bfd *, void *, void *); unsigned int (*_bfd_coff_swap_lineno_out) (bfd *, void *, void *); unsigned int (*_bfd_coff_swap_reloc_out) (bfd *, void *, void *); unsigned int (*_bfd_coff_swap_filehdr_out) (bfd *, void *, void *); unsigned int (*_bfd_coff_swap_aouthdr_out) (bfd *, void *, void *); unsigned int (*_bfd_coff_swap_scnhdr_out) (bfd *, void *, void *); unsigned int _bfd_filhsz; unsigned int _bfd_aoutsz; unsigned int _bfd_scnhsz; unsigned int _bfd_symesz; unsigned int _bfd_auxesz; unsigned int _bfd_relsz; unsigned int _bfd_linesz; unsigned int _bfd_filnmlen; bool _bfd_coff_long_filenames; bool _bfd_coff_long_section_names; bool (*_bfd_coff_set_long_section_names) (bfd *, int); unsigned int _bfd_coff_default_section_alignment_power; bool _bfd_coff_force_symnames_in_strings; unsigned int _bfd_coff_debug_string_prefix_length; unsigned int _bfd_coff_max_nscns; void (*_bfd_coff_swap_filehdr_in) (bfd *, void *, void *); void (*_bfd_coff_swap_aouthdr_in) (bfd *, void *, void *); void (*_bfd_coff_swap_scnhdr_in) (bfd *, void *, void *); void (*_bfd_coff_swap_reloc_in) (bfd *abfd, void *, void *); bool (*_bfd_coff_bad_format_hook) (bfd *, void *); bool (*_bfd_coff_set_arch_mach_hook) (bfd *, void *); void * (*_bfd_coff_mkobject_hook) (bfd *, void *, void *); bool (*_bfd_styp_to_sec_flags_hook) (bfd *, void *, const char *, asection *, flagword *); void (*_bfd_set_alignment_hook) (bfd *, asection *, void *); bool (*_bfd_coff_slurp_symbol_table) (bfd *); bool (*_bfd_coff_symname_in_debug) (bfd *, struct internal_syment *); bool (*_bfd_coff_pointerize_aux_hook) (bfd *, combined_entry_type *, combined_entry_type *, unsigned int, combined_entry_type *); bool (*_bfd_coff_print_aux) (bfd *, FILE *, combined_entry_type *, combined_entry_type *, combined_entry_type *, unsigned int); void (*_bfd_coff_reloc16_extra_cases) (bfd *, struct bfd_link_info *, struct bfd_link_order *, arelent *, bfd_byte *, unsigned int *, unsigned int *); int (*_bfd_coff_reloc16_estimate) (bfd *, asection *, arelent *, unsigned int, struct bfd_link_info *); enum coff_symbol_classification (*_bfd_coff_classify_symbol) (bfd *, struct internal_syment *); bool (*_bfd_coff_compute_section_file_positions) (bfd *); bool (*_bfd_coff_start_final_link) (bfd *, struct bfd_link_info *); bool (*_bfd_coff_relocate_section) (bfd *, struct bfd_link_info *, bfd *, asection *, bfd_byte *, struct internal_reloc *, struct internal_syment *, asection **); reloc_howto_type *(*_bfd_coff_rtype_to_howto) (bfd *, asection *, struct internal_reloc *, struct coff_link_hash_entry *, struct internal_syment *, bfd_vma *); bool (*_bfd_coff_adjust_symndx) (bfd *, struct bfd_link_info *, bfd *, asection *, struct internal_reloc *, bool *); bool (*_bfd_coff_link_add_one_symbol) (struct bfd_link_info *, bfd *, const char *, flagword, asection *, bfd_vma, const char *, bool, bool, struct bfd_link_hash_entry **); bool (*_bfd_coff_link_output_has_begun) (bfd *, struct coff_final_link_info *); bool (*_bfd_coff_final_link_postscript) (bfd *, struct coff_final_link_info *); bool (*_bfd_coff_print_pdata) (bfd *, void *); } bfd_coff_backend_data; #define coff_backend_info(abfd) \ ((bfd_coff_backend_data *) (abfd)->xvec->backend_data) #define bfd_coff_swap_aux_in(a,e,t,c,ind,num,i) \ ((coff_backend_info (a)->_bfd_coff_swap_aux_in) (a,e,t,c,ind,num,i)) #define bfd_coff_swap_sym_in(a,e,i) \ ((coff_backend_info (a)->_bfd_coff_swap_sym_in) (a,e,i)) #define bfd_coff_swap_lineno_in(a,e,i) \ ((coff_backend_info ( a)->_bfd_coff_swap_lineno_in) (a,e,i)) #define bfd_coff_swap_reloc_out(abfd, i, o) \ ((coff_backend_info (abfd)->_bfd_coff_swap_reloc_out) (abfd, i, o)) #define bfd_coff_swap_lineno_out(abfd, i, o) \ ((coff_backend_info (abfd)->_bfd_coff_swap_lineno_out) (abfd, i, o)) #define bfd_coff_swap_aux_out(a,i,t,c,ind,num,o) \ ((coff_backend_info (a)->_bfd_coff_swap_aux_out) (a,i,t,c,ind,num,o)) #define bfd_coff_swap_sym_out(abfd, i,o) \ ((coff_backend_info (abfd)->_bfd_coff_swap_sym_out) (abfd, i, o)) #define bfd_coff_swap_scnhdr_out(abfd, i,o) \ ((coff_backend_info (abfd)->_bfd_coff_swap_scnhdr_out) (abfd, i, o)) #define bfd_coff_swap_filehdr_out(abfd, i,o) \ ((coff_backend_info (abfd)->_bfd_coff_swap_filehdr_out) (abfd, i, o)) #define bfd_coff_swap_aouthdr_out(abfd, i,o) \ ((coff_backend_info (abfd)->_bfd_coff_swap_aouthdr_out) (abfd, i, o)) #define bfd_coff_filhsz(abfd) (coff_backend_info (abfd)->_bfd_filhsz) #define bfd_coff_aoutsz(abfd) (coff_backend_info (abfd)->_bfd_aoutsz) #define bfd_coff_scnhsz(abfd) (coff_backend_info (abfd)->_bfd_scnhsz) #define bfd_coff_symesz(abfd) (coff_backend_info (abfd)->_bfd_symesz) #define bfd_coff_auxesz(abfd) (coff_backend_info (abfd)->_bfd_auxesz) #define bfd_coff_relsz(abfd) (coff_backend_info (abfd)->_bfd_relsz) #define bfd_coff_linesz(abfd) (coff_backend_info (abfd)->_bfd_linesz) #define bfd_coff_filnmlen(abfd) (coff_backend_info (abfd)->_bfd_filnmlen) #define bfd_coff_long_filenames(abfd) \ (coff_backend_info (abfd)->_bfd_coff_long_filenames) #define bfd_coff_long_section_names(abfd) \ (coff_backend_info (abfd)->_bfd_coff_long_section_names) #define bfd_coff_set_long_section_names(abfd, enable) \ ((coff_backend_info (abfd)->_bfd_coff_set_long_section_names) (abfd, enable)) #define bfd_coff_default_section_alignment_power(abfd) \ (coff_backend_info (abfd)->_bfd_coff_default_section_alignment_power) #define bfd_coff_max_nscns(abfd) \ (coff_backend_info (abfd)->_bfd_coff_max_nscns) #define bfd_coff_swap_filehdr_in(abfd, i,o) \ ((coff_backend_info (abfd)->_bfd_coff_swap_filehdr_in) (abfd, i, o)) #define bfd_coff_swap_aouthdr_in(abfd, i,o) \ ((coff_backend_info (abfd)->_bfd_coff_swap_aouthdr_in) (abfd, i, o)) #define bfd_coff_swap_scnhdr_in(abfd, i,o) \ ((coff_backend_info (abfd)->_bfd_coff_swap_scnhdr_in) (abfd, i, o)) #define bfd_coff_swap_reloc_in(abfd, i, o) \ ((coff_backend_info (abfd)->_bfd_coff_swap_reloc_in) (abfd, i, o)) #define bfd_coff_bad_format_hook(abfd, filehdr) \ ((coff_backend_info (abfd)->_bfd_coff_bad_format_hook) (abfd, filehdr)) #define bfd_coff_set_arch_mach_hook(abfd, filehdr)\ ((coff_backend_info (abfd)->_bfd_coff_set_arch_mach_hook) (abfd, filehdr)) #define bfd_coff_mkobject_hook(abfd, filehdr, aouthdr)\ ((coff_backend_info (abfd)->_bfd_coff_mkobject_hook)\ (abfd, filehdr, aouthdr)) #define bfd_coff_styp_to_sec_flags_hook(abfd, scnhdr, name, section, flags_ptr)\ ((coff_backend_info (abfd)->_bfd_styp_to_sec_flags_hook)\ (abfd, scnhdr, name, section, flags_ptr)) #define bfd_coff_set_alignment_hook(abfd, sec, scnhdr)\ ((coff_backend_info (abfd)->_bfd_set_alignment_hook) (abfd, sec, scnhdr)) #define bfd_coff_slurp_symbol_table(abfd)\ ((coff_backend_info (abfd)->_bfd_coff_slurp_symbol_table) (abfd)) #define bfd_coff_symname_in_debug(abfd, sym)\ ((coff_backend_info (abfd)->_bfd_coff_symname_in_debug) (abfd, sym)) #define bfd_coff_force_symnames_in_strings(abfd)\ (coff_backend_info (abfd)->_bfd_coff_force_symnames_in_strings) #define bfd_coff_debug_string_prefix_length(abfd)\ (coff_backend_info (abfd)->_bfd_coff_debug_string_prefix_length) #define bfd_coff_print_aux(abfd, file, base, symbol, aux, indaux)\ ((coff_backend_info (abfd)->_bfd_coff_print_aux)\ (abfd, file, base, symbol, aux, indaux)) #define bfd_coff_reloc16_extra_cases(abfd, link_info, link_order,\ reloc, data, src_ptr, dst_ptr)\ ((coff_backend_info (abfd)->_bfd_coff_reloc16_extra_cases)\ (abfd, link_info, link_order, reloc, data, src_ptr, dst_ptr)) #define bfd_coff_reloc16_estimate(abfd, section, reloc, shrink, link_info)\ ((coff_backend_info (abfd)->_bfd_coff_reloc16_estimate)\ (abfd, section, reloc, shrink, link_info)) #define bfd_coff_classify_symbol(abfd, sym)\ ((coff_backend_info (abfd)->_bfd_coff_classify_symbol)\ (abfd, sym)) #define bfd_coff_compute_section_file_positions(abfd)\ ((coff_backend_info (abfd)->_bfd_coff_compute_section_file_positions)\ (abfd)) #define bfd_coff_start_final_link(obfd, info)\ ((coff_backend_info (obfd)->_bfd_coff_start_final_link)\ (obfd, info)) #define bfd_coff_relocate_section(obfd,info,ibfd,o,con,rel,isyms,secs)\ ((coff_backend_info (ibfd)->_bfd_coff_relocate_section)\ (obfd, info, ibfd, o, con, rel, isyms, secs)) #define bfd_coff_rtype_to_howto(abfd, sec, rel, h, sym, addendp)\ ((coff_backend_info (abfd)->_bfd_coff_rtype_to_howto)\ (abfd, sec, rel, h, sym, addendp)) #define bfd_coff_adjust_symndx(obfd, info, ibfd, sec, rel, adjustedp)\ ((coff_backend_info (abfd)->_bfd_coff_adjust_symndx)\ (obfd, info, ibfd, sec, rel, adjustedp)) #define bfd_coff_link_add_one_symbol(info, abfd, name, flags, section,\ value, string, cp, coll, hashp)\ ((coff_backend_info (abfd)->_bfd_coff_link_add_one_symbol)\ (info, abfd, name, flags, section, value, string, cp, coll, hashp)) #define bfd_coff_link_output_has_begun(a,p) \ ((coff_backend_info (a)->_bfd_coff_link_output_has_begun) (a, p)) #define bfd_coff_final_link_postscript(a,p) \ ((coff_backend_info (a)->_bfd_coff_final_link_postscript) (a, p)) #define bfd_coff_have_print_pdata(a) \ (coff_backend_info (a)->_bfd_coff_print_pdata) #define bfd_coff_print_pdata(a,p) \ ((coff_backend_info (a)->_bfd_coff_print_pdata) (a, p)) /* Macro: Returns true if the bfd is a PE executable as opposed to a PE object file. */ #define bfd_pei_p(abfd) \ (startswith ((abfd)->xvec->name, "pei-"))
To write relocations, the back end steps though the
canonical relocation table and create an
internal_reloc
. The symbol index to use is removed from
the offset
field in the symbol table supplied. The
address comes directly from the sum of the section base
address and the relocation offset; the type is dug directly
from the howto field. Then the internal_reloc
is
swapped into the shape of an external_reloc
and written
out to disk.
Creating the linenumber table is done by reading in the entire coff linenumber table, and creating another table for internal use.
A coff linenumber table is structured so that each function is marked as having a line number of 0. Each line within the function is an offset from the first line in the function. The base of the line number information for the table is stored in the symbol associated with the function.
Note: The PE format uses line number 0 for a flag indicating a new source file.
The information is copied from the external to the internal table, and each symbol which marks a function is marked by pointing its...
How does this work ?
Coff relocations are easily transformed into the internal BFD form
(arelent
).
Reading a coff relocation table is done in the following stages:
bfd_canonicalize_symtab
. The back end will call that
routine and save the result if a canonicalization hasn’t been done.
r_type
to directly produce an index
into a howto table vector.
Next: mmo, Previous: coff, Up: BFD back ends [Contents][Index]
BFD support for ELF formats is being worked on. Currently, the best supported back ends are for sparc and i386 (running svr4 or Solaris 2).
Documentation of the internals of the support code still needs to be written. The code is changing quickly enough that we haven’t bothered yet.
Previous: elf, Up: BFD back ends [Contents][Index]
The mmo object format is used exclusively together with Professor
Donald E. Knuth’s educational 64-bit processor MMIX. The simulator
mmix
which is available at
http://mmix.cs.hm.edu/src/index.html
understands this format. That package also includes a combined
assembler and linker called mmixal
. The mmo format has
no advantages feature-wise compared to e.g. ELF. It is a simple
non-relocatable object format with no support for archives or
debugging information, except for symbol value information and
line numbers (which is not yet implemented in BFD). See
http://mmix.cs.hm.edu/ for more
information about MMIX. The ELF format is used for intermediate
object files in the BFD implementation.
• File layout | ||
• Symbol-table | ||
• mmo section mapping |
Next: Symbol-table, Previous: mmo, Up: mmo [Contents][Index]
The mmo file contents is not partitioned into named sections as with e.g. ELF. Memory areas is formed by specifying the location of the data that follows. Only the memory area ‘0x0000…00’ to ‘0x01ff…ff’ is executable, so it is used for code (and constants) and the area ‘0x2000…00’ to ‘0x20ff…ff’ is used for writable data. See mmo section mapping.
There is provision for specifying “special data” of 65536
different types. We use type 80 (decimal), arbitrarily chosen the
same as the ELF e_machine
number for MMIX, filling it with
section information normally found in ELF objects. See mmo section mapping.
Contents is entered as 32-bit words, xor:ed over previous contents, always zero-initialized. A word that starts with the byte ‘0x98’ forms a command called a ‘lopcode’, where the next byte distinguished between the thirteen lopcodes. The two remaining bytes, called the ‘Y’ and ‘Z’ fields, or the ‘YZ’ field (a 16-bit big-endian number), are used for various purposes different for each lopcode. As documented in http://mmix.cs.hm.edu/doc/mmixal.pdf, the lopcodes are:
lop_quote
0x98000001. The next word is contents, regardless of whether it starts with 0x98 or not.
lop_loc
0x9801YYZZ, where ‘Z’ is 1 or 2. This is a location directive, setting the location for the next data to the next 32-bit word (for Z = 1) or 64-bit word (for Z = 2), plus Y * 2^56. Normally ‘Y’ is 0 for the text segment and 2 for the data segment. Beware that the low bits of non- tetrabyte-aligned values are silently discarded when being automatically incremented and when storing contents (in contrast to e.g. its use as current location when followed by lop_fixo et al before the next possibly-quoted tetrabyte contents).
lop_skip
0x9802YYZZ. Increase the current location by ‘YZ’ bytes.
lop_fixo
0x9803YYZZ, where ‘Z’ is 1 or 2. Store the current location as 64 bits into the location pointed to by the next 32-bit (Z = 1) or 64-bit (Z = 2) word, plus Y * 2^56.
lop_fixr
0x9804YYZZ. ‘YZ’ is stored into the current location plus 2 - 4 * YZ.
lop_fixrx
0x980500ZZ. ‘Z’ is 16 or 24. A value ‘L’ derived from the following 32-bit word are used in a manner similar to ‘YZ’ in lop_fixr: it is xor:ed into the current location minus 4 * L. The first byte of the word is 0 or 1. If it is 1, then L = (lowest 24 bits of word) - 2^Z, if 0, then L = (lowest 24 bits of word).
lop_file
0x9806YYZZ. ‘Y’ is the file number, ‘Z’ is count of 32-bit words. Set the file number to ‘Y’ and the line counter to 0. The next Z * 4 bytes contain the file name, padded with zeros if the count is not a multiple of four. The same ‘Y’ may occur multiple times, but ‘Z’ must be 0 for all but the first occurrence.
lop_line
0x9807YYZZ. ‘YZ’ is the line number. Together with lop_file, it forms the source location for the next 32-bit word. Note that for each non-lopcode 32-bit word, line numbers are assumed incremented by one.
lop_spec
0x9808YYZZ. ‘YZ’ is the type number. Data until the next lopcode other than lop_quote forms special data of type ‘YZ’. See mmo section mapping.
Other types than 80, (or type 80 with a content that does not
parse) is stored in sections named .MMIX.spec_data.n
where n is the ‘YZ’-type. The flags for such a
sections say not to allocate or load the data. The vma is 0.
Contents of multiple occurrences of special data n is
concatenated to the data of the previous lop_spec ns. The
location in data or code at which the lop_spec occurred is lost.
lop_pre
0x980901ZZ. The first lopcode in a file. The ‘Z’ field forms the length of header information in 32-bit words, where the first word tells the time in seconds since ‘00:00:00 GMT Jan 1 1970’.
lop_post
0x980a00ZZ. Z > 32. This lopcode follows after all content-generating lopcodes in a program. The ‘Z’ field denotes the value of ‘rG’ at the beginning of the program. The following 256 - Z big-endian 64-bit words are loaded into global registers ‘$G’ … ‘$255’.
lop_stab
0x980b0000. The next-to-last lopcode in a program. Must follow immediately after the lop_post lopcode and its data. After this lopcode follows all symbols in a compressed format (see Symbol-table).
lop_end
0x980cYYZZ. The last lopcode in a program. It must follow the lop_stab lopcode and its data. The ‘YZ’ field contains the number of 32-bit words of symbol table information after the preceding lop_stab lopcode.
Note that the lopcode "fixups"; lop_fixr
, lop_fixrx
and
lop_fixo
are not generated by BFD, but are handled. They are
generated by mmixal
.
This trivial one-label, one-instruction file:
:Main TRAP 1,2,3
can be represented this way in mmo:
0x98090101 - lop_pre, one 32-bit word with timestamp. <timestamp> 0x98010002 - lop_loc, text segment, using a 64-bit address. Note that mmixal does not emit this for the file above. 0x00000000 - Address, high 32 bits. 0x00000000 - Address, low 32 bits. 0x98060002 - lop_file, 2 32-bit words for file-name. 0x74657374 - "test" 0x2e730000 - ".s\0\0" 0x98070001 - lop_line, line 1. 0x00010203 - TRAP 1,2,3 0x980a00ff - lop_post, setting $255 to 0. 0x00000000 0x00000000 0x980b0000 - lop_stab for ":Main" = 0, serial 1. 0x203a4040 See Symbol-table. 0x10404020 0x4d206120 0x69016e00 0x81000000 0x980c0005 - lop_end; symbol table contained five 32-bit words.
Next: mmo section mapping, Previous: File layout, Up: mmo [Contents][Index]
From mmixal.w (or really, the generated mmixal.tex) in the
MMIXware package which also contains the mmix
simulator:
“Symbols are stored and retrieved by means of a ‘ternary
search trie’, following ideas of Bentley and Sedgewick. (See
ACM–SIAM Symp. on Discrete Algorithms ‘8’ (1997), 360–369;
R.Sedgewick, ‘Algorithms in C’ (Reading, Mass.
Addison–Wesley, 1998), ‘15.4’.) Each trie node stores a
character, and there are branches to subtries for the cases where
a given character is less than, equal to, or greater than the
character in the trie. There also is a pointer to a symbol table
entry if a symbol ends at the current node.”
So it’s a tree encoded as a stream of bytes. The stream of bytes acts on a single virtual global symbol, adding and removing characters and signalling complete symbol points. Here, we read the stream and create symbols at the completion points.
First, there’s a control byte m
. If any of the listed bits
in m
is nonzero, we execute what stands at the right, in
the listed order:
(MMO3_LEFT)
0x40 - Traverse left trie.
(Read a new command byte and recurse.)
(MMO3_SYMBITS)
0x2f - Read the next byte as a character and store it in the
current character position; increment character position.
Test the bits of m
:
(MMO3_WCHAR)
0x80 - The character is 16-bit (so read another byte,
merge into current character.
(MMO3_TYPEBITS)
0xf - We have a complete symbol; parse the type, value
and serial number and do what should be done
with a symbol. The type and length information
is in j = (m & 0xf).
(MMO3_REGQUAL_BITS)
j == 0xf: A register variable. The following
byte tells which register.
j <= 8: An absolute symbol. Read j bytes as the
big-endian number the symbol equals.
A j = 2 with two zero bytes denotes an
unknown symbol.
j > 8: As with j <= 8, but add (0x20 << 56)
to the value in the following j - 8
bytes.
Then comes the serial number, as a variant of
uleb128, but better named ubeb128:
Read bytes and shift the previous value left 7
(multiply by 128). Add in the new byte, repeat
until a byte has bit 7 set. The serial number
is the computed value minus 128.
(MMO3_MIDDLE)
0x20 - Traverse middle trie. (Read a new command byte
and recurse.) Decrement character position.
(MMO3_RIGHT)
0x10 - Traverse right trie. (Read a new command byte and
recurse.)
Let’s look again at the lop_stab
for the trivial file
(see File layout).
0x980b0000 - lop_stab for ":Main" = 0, serial 1. 0x203a4040 0x10404020 0x4d206120 0x69016e00 0x81000000
This forms the trivial trie (note that the path between “:” and “M” is redundant):
203a ":" 40 / 40 / 10 \ 40 / 40 / 204d "M" 2061 "a" 2069 "i" 016e "n" is the last character in a full symbol, and with a value represented in one byte. 00 The value is 0. 81 The serial number is 1.
Previous: Symbol-table, Up: mmo [Contents][Index]
The implementation in BFD uses special data type 80 (decimal) to encapsulate and describe named sections, containing e.g. debug information. If needed, any datum in the encapsulation will be quoted using lop_quote. First comes a 32-bit word holding the number of 32-bit words containing the zero-terminated zero-padded segment name. After the name there’s a 32-bit word holding flags describing the section type. Then comes a 64-bit big-endian word with the section length (in bytes), then another with the section start address. Depending on the type of section, the contents might follow, zero-padded to 32-bit boundary. For a loadable section (such as data or code), the contents might follow at some later point, not necessarily immediately, as a lop_loc with the same start address as in the section description, followed by the contents. This in effect forms a descriptor that must be emitted before the actual contents. Sections described this way must not overlap.
For areas that don’t have such descriptors, synthetic sections are
formed by BFD. Consecutive contents in the two memory areas
‘0x0000…00’ to ‘0x01ff…ff’ and
‘0x2000…00’ to ‘0x20ff…ff’ are entered in
sections named .text
and .data
respectively. If an area
is not otherwise described, but would together with a neighboring
lower area be less than ‘0x40000000’ bytes long, it is joined
with the lower area and the gap is zero-filled. For other cases,
a new section is formed, named .MMIX.sec.n
. Here,
n is a number, a running count through the mmo file,
starting at 0.
A loadable section specified as:
.section secname,"ax" TETRA 1,2,3,4,-1,-2009 BYTE 80
and linked to address ‘0x4’, is represented by the sequence:
0x98080050 - lop_spec 80 0x00000002 - two 32-bit words for the section name 0x7365636e - "secn" 0x616d6500 - "ame\0" 0x00000033 - flags CODE, READONLY, LOAD, ALLOC 0x00000000 - high 32 bits of section length 0x0000001c - section length is 28 bytes; 6 * 4 + 1 + alignment to 32 bits 0x00000000 - high 32 bits of section address 0x00000004 - section address is 4 0x98010002 - 64 bits with address of following data 0x00000000 - high 32 bits of address 0x00000004 - low 32 bits: data starts at address 4 0x00000001 - 1 0x00000002 - 2 0x00000003 - 3 0x00000004 - 4 0xffffffff - -1 0xfffff827 - -2009 0x50000000 - 80 as a byte, padded with zeros.
Note that the lop_spec wrapping does not include the section contents. Compare this to a non-loaded section specified as:
.section thirdsec TETRA 200001,100002 BYTE 38,40
This, when linked to address ‘0x200000000000001c’, is represented by:
0x98080050 - lop_spec 80 0x00000002 - two 32-bit words for the section name 0x7365636e - "thir" 0x616d6500 - "dsec" 0x00000010 - flag READONLY 0x00000000 - high 32 bits of section length 0x0000000c - section length is 12 bytes; 2 * 4 + 2 + alignment to 32 bits 0x20000000 - high 32 bits of address 0x0000001c - low 32 bits of address 0x200000000000001c 0x00030d41 - 200001 0x000186a2 - 100002 0x26280000 - 38, 40 as bytes, padded with zeros
For the latter example, the section contents must not be loaded in memory, and is therefore specified as part of the special data. The address is usually unimportant but might provide information for e.g. the DWARF 2 debugging format.
Next: BFD Index, Previous: BFD back ends, Up: Top [Contents][Index]
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