Group identifier of a comdat group
Alan Modra
amodra@bigpond.net.au
Mon Jun 3 18:01:00 GMT 2002
I'm committing this one. Differs from the last patch in that the BFD
section for a SHT_GROUP ELF section takes it's name from the group
signature symbol. Gas makes the name of the group section the same as
the signature, but the spec says the ELF section name is irrelevant.
Also, gas now makes a group GRP_COMDAT if any component section is
named .gnu.linkonce*.
bfd/ChangeLog
* elf.c (setup_group): Set SEC_LINK_ONCE on GRP_COMDAT groups.
(bfd_section_from_shdr): Likewise. Set section name of group
sections from signature.
(group_signature): Split out from setup_group. Ensure symbol table
is available.
(bfd_elf_discard_group): New function.
(_bfd_elf_make_section_from_shdr): Don't set SEC_LINK_ONCE on
.gnu.linkonce* sections if they are members of a group.
(set_group_contents): Set GRP_COMDAT flag.
* section.c (bfd_discard_group): New function.
* bfd-in.h (bfd_elf_discard_group): Declare.
* bfd-in2.h: Regenerate.
* elf-bfd.h (struct bfd_elf_section_data): Add linkonce_p field.
(elf_linkonce_p): Define.
gas/ChangeLog
* config/obj-elf.c (obj_elf_change_section): Set and check elf
linkonce flag. Print all warnings.
(obj_elf_section): Parse ",comdat" for groups.
(elf_frob_file): Set SEC_LINK_ONCE on COMDAT groups. Check
consistency of comdat flag.
ld/ChangeLog
* ldlang.c (section_already_linked): Call bfd_discard_group. Typo fix.
Index: bfd/bfd-in.h
===================================================================
RCS file: /cvs/src/src/bfd/bfd-in.h,v
retrieving revision 1.46
diff -u -p -r1.46 bfd-in.h
--- bfd/bfd-in.h 29 May 2002 16:03:04 -0000 1.46
+++ bfd/bfd-in.h 4 Jun 2002 00:06:55 -0000
@@ -657,6 +657,8 @@ extern boolean bfd_elf32_discard_info
PARAMS ((bfd *, struct bfd_link_info *));
extern boolean bfd_elf64_discard_info
PARAMS ((bfd *, struct bfd_link_info *));
+extern void bfd_elf_discard_group
+ PARAMS ((bfd *, struct sec *));
/* Return an upper bound on the number of bytes required to store a
copy of ABFD's program header table entries. Return -1 if an error
Index: bfd/elf-bfd.h
===================================================================
RCS file: /cvs/src/src/bfd/elf-bfd.h,v
retrieving revision 1.73
diff -u -p -r1.73 elf-bfd.h
--- bfd/elf-bfd.h 31 May 2002 02:59:47 -0000 1.73
+++ bfd/elf-bfd.h 4 Jun 2002 00:07:05 -0000
@@ -926,11 +926,15 @@ struct bfd_elf_section_data
/* Nonzero if this section uses RELA relocations, rather than REL. */
unsigned int use_rela_p:1;
+
+ /* Nonzero when a group is COMDAT. */
+ unsigned int linkonce_p:1;
};
#define elf_section_data(sec) ((struct bfd_elf_section_data*)sec->used_by_bfd)
#define elf_group_name(sec) (elf_section_data(sec)->group_name)
#define elf_next_in_group(sec) (elf_section_data(sec)->next_in_group)
+#define elf_linkonce_p(sec) (elf_section_data(sec)->linkonce_p)
/* Return true if section has been discarded. */
#define elf_discarded_section(sec) \
Index: bfd/elf.c
===================================================================
RCS file: /cvs/src/src/bfd/elf.c,v
retrieving revision 1.140
diff -u -p -r1.140 elf.c
--- bfd/elf.c 31 May 2002 02:59:47 -0000 1.140
+++ bfd/elf.c 4 Jun 2002 00:07:10 -0000
@@ -50,6 +50,7 @@ static boolean prep_headers PARAMS ((bfd
static boolean swap_out_syms PARAMS ((bfd *, struct bfd_strtab_hash **, int));
static boolean copy_private_bfd_data PARAMS ((bfd *, bfd *));
static char *elf_read PARAMS ((bfd *, file_ptr, bfd_size_type));
+static const char *group_signature PARAMS ((bfd *, Elf_Internal_Shdr *));
static boolean setup_group PARAMS ((bfd *, Elf_Internal_Shdr *, asection *));
static void merge_sections_remove_hook PARAMS ((bfd *, asection *));
static void elf_fake_sections PARAMS ((bfd *, asection *, PTR));
@@ -361,6 +362,35 @@ typedef union elf_internal_group {
unsigned int flags;
} Elf_Internal_Group;
+/* Return the name of the group signature symbol. Why isn't the
+ signature just a string? */
+
+static const char *
+group_signature (abfd, ghdr)
+ bfd *abfd;
+ Elf_Internal_Shdr *ghdr;
+{
+ struct elf_backend_data *bed;
+ file_ptr pos;
+ unsigned char ename[4];
+ unsigned long iname;
+
+ /* First we need to ensure the symbol table is available. */
+ if (! bfd_section_from_shdr (abfd, ghdr->sh_link))
+ return NULL;
+
+ /* Fortunately, the name index is at the same place in the external
+ symbol for both 32 and 64 bit ELF. */
+ bed = get_elf_backend_data (abfd);
+ pos = elf_tdata (abfd)->symtab_hdr.sh_offset;
+ pos += ghdr->sh_info * bed->s->sizeof_sym;
+ if (bfd_seek (abfd, pos, SEEK_SET) != 0
+ || bfd_bread (ename, (bfd_size_type) 4, abfd) != 4)
+ return NULL;
+ iname = H_GET_32 (abfd, ename);
+ return elf_string_from_elf_strtab (abfd, iname);
+}
+
/* Set next_in_group list pointer, and group name for NEWSECT. */
static boolean
@@ -440,6 +470,9 @@ setup_group (abfd, hdr, newsect)
if (src == shdr->contents)
{
dest->flags = idx;
+ if (shdr->bfd_section != NULL && (idx & GRP_COMDAT))
+ shdr->bfd_section->flags
+ |= SEC_LINK_ONCE | SEC_LINK_DUPLICATES_DISCARD;
break;
}
if (idx >= shnum)
@@ -492,32 +525,20 @@ setup_group (abfd, hdr, newsect)
}
else
{
- struct elf_backend_data *bed;
- file_ptr pos;
- unsigned char ename[4];
- unsigned long iname;
const char *gname;
- /* Humbug. Get the name from the group signature
- symbol. Why isn't the signature just a string?
- Fortunately, the name index is at the same
- place in the external symbol for both 32 and 64
- bit ELF. */
- bed = get_elf_backend_data (abfd);
- pos = elf_tdata (abfd)->symtab_hdr.sh_offset;
- pos += shdr->sh_info * bed->s->sizeof_sym;
- if (bfd_seek (abfd, pos, SEEK_SET) != 0
- || bfd_bread (ename, (bfd_size_type) 4, abfd) != 4)
+ gname = group_signature (abfd, shdr);
+ if (gname == NULL)
return false;
- iname = H_GET_32 (abfd, ename);
- gname = elf_string_from_elf_strtab (abfd, iname);
elf_group_name (newsect) = gname;
/* Start a circular list with one element. */
elf_next_in_group (newsect) = newsect;
}
+
if (shdr->bfd_section != NULL)
elf_next_in_group (shdr->bfd_section) = newsect;
+
i = num_group - 1;
break;
}
@@ -532,6 +553,24 @@ setup_group (abfd, hdr, newsect)
return true;
}
+void
+bfd_elf_discard_group (abfd, group)
+ bfd *abfd ATTRIBUTE_UNUSED;
+ asection *group;
+{
+ asection *first = elf_next_in_group (group);
+ asection *s = first;
+
+ while (s != NULL)
+ {
+ s->output_section = bfd_abs_section_ptr;
+ s = elf_next_in_group (s);
+ /* These lists are circular. */
+ if (s == first)
+ break;
+ }
+}
+
/* Make a BFD section from an ELF section. We store a pointer to the
BFD section in the bfd_section field of the header. */
@@ -620,7 +659,8 @@ _bfd_elf_make_section_from_shdr (abfd, h
The symbols will be defined as weak, so that multiple definitions
are permitted. The GNU linker extension is to actually discard
all but one of the sections. */
- if (strncmp (name, ".gnu.linkonce", sizeof ".gnu.linkonce" - 1) == 0)
+ if (strncmp (name, ".gnu.linkonce", sizeof ".gnu.linkonce" - 1) == 0
+ && elf_next_in_group (newsect) == NULL)
flags |= SEC_LINK_ONCE | SEC_LINK_DUPLICATES_DISCARD;
bed = get_elf_backend_data (abfd);
@@ -1576,7 +1616,7 @@ bfd_section_from_shdr (abfd, shindex)
Elf_Internal_Shdr *hdr = elf_elfsections (abfd)[shindex];
Elf_Internal_Ehdr *ehdr = elf_elfheader (abfd);
struct elf_backend_data *bed = get_elf_backend_data (abfd);
- char *name;
+ const char *name;
name = elf_string_from_elf_strtab (abfd, hdr->sh_name);
@@ -1820,7 +1860,12 @@ bfd_section_from_shdr (abfd, shindex)
return true;
case SHT_GROUP:
- /* Make a section for objcopy and relocatable links. */
+ /* We need a BFD section for objcopy and relocatable linking,
+ and it's handy to have the signature available as the section
+ name. */
+ name = group_signature (abfd, hdr);
+ if (name == NULL)
+ return false;
if (!_bfd_elf_make_section_from_shdr (abfd, hdr, name))
return false;
if (hdr->contents != NULL)
@@ -1829,6 +1874,10 @@ bfd_section_from_shdr (abfd, shindex)
unsigned int n_elt = hdr->sh_size / 4;
asection *s;
+ if (idx->flags & GRP_COMDAT)
+ hdr->bfd_section->flags
+ |= SEC_LINK_ONCE | SEC_LINK_DUPLICATES_DISCARD;
+
while (--n_elt != 0)
if ((s = (++idx)->shdr->bfd_section) != NULL
&& elf_next_in_group (s) != NULL)
@@ -2369,7 +2418,7 @@ set_group_contents (abfd, sec, failedptr
while (elt != elf_next_in_group (l->u.indirect.section));
loc -= 4;
- H_PUT_32 (abfd, 0, loc);
+ H_PUT_32 (abfd, sec->flags & SEC_LINK_ONCE ? GRP_COMDAT : 0, loc);
BFD_ASSERT (loc == sec->contents);
}
Index: bfd/section.c
===================================================================
RCS file: /cvs/src/src/bfd/section.c,v
retrieving revision 1.45
diff -u -p -r1.45 section.c
--- bfd/section.c 23 May 2002 13:12:46 -0000 1.45
+++ bfd/section.c 4 Jun 2002 00:07:49 -0000
@@ -1375,3 +1375,24 @@ _bfd_strip_section_from_output (info, s)
s->flags |= SEC_EXCLUDE;
}
+
+/*
+FUNCTION
+ bfd_discard_group
+
+SYNOPSIS
+ void bfd_discard_group (bfd *abfd, asection *group);
+
+DESCRIPTION
+ Remove all members of @var{group} from the output.
+*/
+
+void
+bfd_discard_group (abfd, group)
+ bfd *abfd;
+ asection *group;
+{
+ if ((group->flags & SEC_GROUP) != 0
+ && abfd->xvec->flavour == bfd_target_elf_flavour)
+ bfd_elf_discard_group (abfd, group);
+}
Index: gas/config/obj-elf.c
===================================================================
RCS file: /cvs/src/src/gas/config/obj-elf.c,v
retrieving revision 1.50
diff -u -p -r1.50 obj-elf.c
--- gas/config/obj-elf.c 23 May 2002 13:12:47 -0000 1.50
+++ gas/config/obj-elf.c 3 Jun 2002 23:53:29 -0000
@@ -77,7 +77,7 @@ static void obj_elf_weak PARAMS ((int));
static void obj_elf_local PARAMS ((int));
static void obj_elf_visibility PARAMS ((int));
static void obj_elf_change_section
- PARAMS ((const char *, int, int, int, const char *, int));
+ PARAMS ((const char *, int, int, int, const char *, int, int));
static int obj_elf_parse_section_letters PARAMS ((char *, size_t));
static int obj_elf_section_word PARAMS ((char *, size_t));
static char *obj_elf_section_name PARAMS ((void));
@@ -664,12 +664,13 @@ static struct special_section const spec
};
static void
-obj_elf_change_section (name, type, attr, entsize, group_name, push)
+obj_elf_change_section (name, type, attr, entsize, group_name, linkonce, push)
const char *name;
int type;
int attr;
int entsize;
const char *group_name;
+ int linkonce;
int push;
{
asection *old_sec;
@@ -758,6 +759,7 @@ obj_elf_change_section (name, type, attr
if (flags & SEC_MERGE)
sec->entsize = entsize;
elf_group_name (sec) = group_name;
+ elf_linkonce_p (sec) = linkonce;
/* Add a symbol for this section to the symbol table. */
secsym = symbol_find (name);
@@ -771,15 +773,16 @@ obj_elf_change_section (name, type, attr
/* If section attributes are specified the second time we see a
particular section, then check that they are the same as we
saw the first time. */
- if ((old_sec->flags ^ flags)
- & (SEC_ALLOC | SEC_LOAD | SEC_READONLY | SEC_CODE
- | SEC_EXCLUDE | SEC_SORT_ENTRIES | SEC_MERGE | SEC_STRINGS
- | SEC_THREAD_LOCAL))
+ if (((old_sec->flags ^ flags)
+ & (SEC_ALLOC | SEC_LOAD | SEC_READONLY | SEC_CODE
+ | SEC_EXCLUDE | SEC_SORT_ENTRIES | SEC_MERGE | SEC_STRINGS
+ | SEC_THREAD_LOCAL))
+ || linkonce != elf_linkonce_p (sec))
as_warn (_("ignoring changed section attributes for %s"), name);
- else if ((flags & SEC_MERGE) && old_sec->entsize != (unsigned) entsize)
+ if ((flags & SEC_MERGE) && old_sec->entsize != (unsigned) entsize)
as_warn (_("ignoring changed section entity size for %s"), name);
- else if ((attr & SHF_GROUP) != 0
- && strcmp (elf_group_name (old_sec), group_name) != 0)
+ if ((attr & SHF_GROUP) != 0
+ && strcmp (elf_group_name (old_sec), group_name) != 0)
as_warn (_("ignoring new section group for %s"), name);
}
@@ -947,6 +950,7 @@ obj_elf_section (push)
char *name, *group_name, *beg;
int type, attr, dummy;
int entsize;
+ int linkonce;
#ifndef TC_I370
if (flag_mri)
@@ -977,6 +981,7 @@ obj_elf_section (push)
attr = 0;
group_name = NULL;
entsize = 0;
+ linkonce = 0;
if (*input_line_pointer == ',')
{
@@ -1050,6 +1055,13 @@ obj_elf_section (push)
group_name = obj_elf_section_name ();
if (group_name == NULL)
attr &= ~SHF_GROUP;
+ else if (strncmp (input_line_pointer, ",comdat", 7) == 0)
+ {
+ input_line_pointer += 7;
+ linkonce = 1;
+ }
+ else if (strncmp (name, ".gnu.linkonce", 13) == 0)
+ linkonce = 1;
}
else if ((attr & SHF_GROUP) != 0)
{
@@ -1085,7 +1097,7 @@ obj_elf_section (push)
demand_empty_rest_of_line ();
- obj_elf_change_section (name, type, attr, entsize, group_name, push);
+ obj_elf_change_section (name, type, attr, entsize, group_name, linkonce, push);
}
/* Change to the .data section. */
@@ -2015,8 +2027,20 @@ elf_frob_file ()
asection *s;
flagword flags;
- s = subseg_force_new (group_name, 0);
flags = SEC_READONLY | SEC_HAS_CONTENTS | SEC_IN_MEMORY | SEC_GROUP;
+ for (s = list.head[i]; s != NULL; s = elf_next_in_group (s))
+ if (elf_linkonce_p (s) != ((flags & SEC_LINK_ONCE) != 0))
+ {
+ flags |= SEC_LINK_ONCE | SEC_LINK_DUPLICATES_DISCARD;
+ if (s != list.head[i])
+ {
+ as_warn (_("assuming all members of group `%s' are COMDAT"),
+ group_name);
+ break;
+ }
+ }
+
+ s = subseg_force_new (group_name, 0);
if (s == NULL
|| !bfd_set_section_flags (stdoutput, s, flags)
|| !bfd_set_section_alignment (stdoutput, s, 2))
Index: ld/ldlang.c
===================================================================
RCS file: /cvs/src/src/ld/ldlang.c,v
retrieving revision 1.88
diff -u -p -r1.88 ldlang.c
--- ld/ldlang.c 27 May 2002 08:22:07 -0000 1.88
+++ ld/ldlang.c 3 Jun 2002 23:54:02 -0000
@@ -985,7 +985,7 @@ section_already_linked (abfd, sec, data)
of having link once sections in the first place.
Also, not merging link once sections in a relocatable link
- causes trouble for MIPS ELF, which relies in link once semantics
+ causes trouble for MIPS ELF, which relies on link once semantics
to handle the .reginfo section correctly. */
name = bfd_get_section_name (abfd, sec);
@@ -1038,6 +1038,9 @@ section_already_linked (abfd, sec, data)
does not create a lang_input_section structure for this
section. */
sec->output_section = bfd_abs_section_ptr;
+
+ if (flags & SEC_GROUP)
+ bfd_discard_group (abfd, sec);
return;
}
--
Alan Modra
IBM OzLabs - Linux Technology Centre
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