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SHARED LIBS
- To: gdb at sourceware dot cygnus dot com
- Subject: SHARED LIBS
- From: Takis Psarogiannakopoulos <takis at XFree86 dot org>
- Date: Fri, 17 Dec 1999 15:57:18 -0800 (PST)
Hello,
I want an opinion from somebody that is familiar
with gdb shared libs code.
I apologize if this message is a bit larger than
normal.
We trying to debug mozilla M11 with gdb:
bash# ldd mozilla-bin
dynamic linker: mozilla-bin: file loaded: /dist/bin/libraptorgfx.so
dynamic linker: mozilla-bin: file loaded: /dist/bin/libmozjs.so
dynamic linker: mozilla-bin: file loaded: /dist/bin/libxpcom.so
dynamic linker: mozilla-bin: file loaded: /dist/bin/libplds3.so
dynamic linker: mozilla-bin: file loaded: /dist/bin/libplc3.so
dynamic linker: mozilla-bin: file loaded: /dist/bin/libnspr3.so
dynamic linker: mozilla-bin: file loaded: /lib/libgtk-1.2.so.0.5.0
dynamic linker: mozilla-bin: file loaded: /lib/libgdk-1.2.so.0.5.0
dynamic linker: mozilla-bin: file loaded: /usr/X11R6.3/lib/libXext.so.6.3
dynamic linker: mozilla-bin: file loaded: /usr/X11R6.3/lib/libX11.so.6.1
dynamic linker: mozilla-bin: file loaded: /usr/dglib/libsocket.so.1
dynamic linker: mozilla-bin: file loaded: /usr/dglib/libnsl.so.1
dynamic linker: mozilla-bin: file loaded: /usr/dglib/libthread.so.1
dynamic linker: mozilla-bin: file loaded: /usr/dglib/librte.so.1
dynamic linker: mozilla-bin: file loaded: /usr/dglib/libresolv.so.1
dynamic linker: mozilla-bin: file loaded: /usr/local/lib/libstdc++.so
dynamic linker: mozilla-bin: file loaded: /usr/dglib/libc.so.1
Start GDB
bash# gdb
GNU gdb 19990928 (DGUX version 4.18.3 (DG/UX 19990928))
Copyright 1998 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you
are welcome to change it and/or distribute copies of it under certain
conditions. Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for
details. This GDB was configured as "i586-dg-dguxR4.20MU05
(Build date Oct 20 1999)".
(mozilla-bin is in gstabs+ (GNU as) debug format;also all shared objects
are compiled with -fPIC , then ld -G these .o files and -gstabs+ debug.
ld is not the GNU ld for DG/UX.)
(gdb) set language c++
(gdb) file mozilla-bin
Reading symbols from mozilla-bin...done.
(gdb) info share
Cannot access memory at address 0x80081498.
(gdb) info sharedlibrary
Cannot access memory at address 0x80081498.
(gdb) break main
Breakpoint 1 at 0x804d30e: file nsAppRunner.cpp, line 653.
************************************
(gdb) sharedlibrary libraptorgfx.so
***********************************
Cannot access memory at address 0x80081498.
(gdb) run
Starting program: /dist/bin/mozilla-bin
Breakpoint 1, main (argc=1, argv=0x8047800) at nsAppRunner.cpp:653
653 if (argc == 2) {
(gdb) info sharedlibrary
From To Syms Read Shared Object Library
0x8008c000 0x800b8994 Yes /dist/bin/libraptorgfx.so
0x800ba000 0x801290a0 Yes /dist/bin/libmozjs.so
0x8012b000 0x801d5a58 Yes /dist/bin/libxpcom.so
0x801d7000 0x801dc068 Yes /dist/bin/libplds3.so
0x801de000 0x801e2ae9 Yes /dist/bin/libplc3.so
0x801e4000 0x8022a544 Yes /dist/bin/libnspr3.so
0x8022c000 0x8036d5e0 Yes /lib/libgtk-1.2.so.0.5.0
0x8036f000 0x803a53dc Yes /lib/libgdk-1.2.so.0.5.0
0x803a7000 0x803b3d64 Yes /usr/X11R6.3/lib/libXext.so.6.3
0x803b5000 0x804752a8 Yes /usr/X11R6.3/lib/libX11.so.6.1
0x80477000 0x8048065c Yes /usr/dglib/libsocket.so.1
0x80482000 0x804b5580 Yes /usr/dglib/libnsl.so.1
0x804b9000 0x804c924c Yes /usr/dglib/libthread.so.1
0x804cb000 0x804cda68 Yes /usr/dglib/librte.so.1
0x804cf000 0x804d1684 Yes /usr/dglib/libresolv.so.1
0x804d3000 0x80524a24 Yes /usr/local/lib/libstdc++.so
0x80000000 0x80086310 Yes /usr/dglib/libc.so.1
(gdb) shared libtestdynamic.so (TRY to load this shared object)
(gdb) info shared
From To Syms Read Shared Object Library
0x8008c000 0x800b8994 Yes /dist/bin/libraptorgfx.so
0x800ba000 0x801290a0 Yes /dist/bin/libmozjs.so
0x8012b000 0x801d5a58 Yes /dist/bin/libxpcom.so
0x801d7000 0x801dc068 Yes /dist/bin/libplds3.so
0x801de000 0x801e2ae9 Yes /dist/bin/libplc3.so
0x801e4000 0x8022a544 Yes /dist/bin/libnspr3.so
0x8022c000 0x8036d5e0 Yes /lib/libgtk-1.2.so.0.5.0
0x8036f000 0x803a53dc Yes /lib/libgdk-1.2.so.0.5.0
0x803a7000 0x803b3d64 Yes /usr/X11R6.3/lib/libXext.so.6.3
0x803b5000 0x804752a8 Yes /usr/X11R6.3/lib/libX11.so.6.1
0x80477000 0x8048065c Yes /usr/dglib/libsocket.so.1
0x80482000 0x804b5580 Yes /usr/dglib/libnsl.so.1
0x804b9000 0x804c924c Yes /usr/dglib/libthread.so.1
0x804cb000 0x804cda68 Yes /usr/dglib/librte.so.1
0x804cf000 0x804d1684 Yes /usr/dglib/libresolv.so.1
0x804d3000 0x80524a24 Yes /usr/local/lib/libstdc++.so
0x80000000 0x80086310 Yes /usr/dglib/libc.so.1
It didnt load the shared object requested!
(gdb) info sharedlibrary
From To Syms Read Shared Object Library
0x8008c000 0x800b8994 Yes /dist/bin/libraptorgfx.so
0x800ba000 0x801290a0 Yes /dist/bin/libmozjs.so
0x8012b000 0x801d5a58 Yes /dist/bin/libxpcom.so
0x801d7000 0x801dc068 Yes /dist/bin/libplds3.so
0x801de000 0x801e2ae9 Yes /dist/bin/libplc3.so
0x801e4000 0x8022a544 Yes /dist/bin/libnspr3.so
0x8022c000 0x8036d5e0 Yes /lib/libgtk-1.2.so.0.5.0
0x8036f000 0x803a53dc Yes /lib/libgdk-1.2.so.0.5.0
0x803a7000 0x803b3d64 Yes /usr/X11R6.3/lib/libXext.so.6.3
0x803b5000 0x804752a8 Yes /usr/X11R6.3/lib/libX11.so.6.1
0x80477000 0x8048065c Yes /usr/dglib/libsocket.so.1
0x80482000 0x804b5580 Yes /usr/dglib/libnsl.so.1
0x804b9000 0x804c924c Yes /usr/dglib/libthread.so.1
0x804cb000 0x804cda68 Yes /usr/dglib/librte.so.1
0x804cf000 0x804d1684 Yes /usr/dglib/libresolv.so.1
0x804d3000 0x80524a24 Yes /usr/local/lib/libstdc++.so
0x80000000 0x80086310 Yes /usr/dglib/libc.so.1
info sharedlibrary also doesnt show the requested shared object
loaded.
Now I have this general problem: If I have mozilla-bin (as above)
depending (say look above ldd) from libmozjs.so and I do
gdb mozilla-bin
....
No breakpoint main, no run
and we give
gdb shared libmozjs.so
or
gdb sharedlibrary libmozjs.so
gdb answers with an error like
Cannot access memory at address 0x80081498.
However a breakpoint in main and a run will load libmozjs.so
as well all other shared objects that mozilla-bin depends
upon. I am attaching with this e-mail file the gdb/solib.c
Inside there is a small mod SVR4_SHARED_LIBS_DGUX_FLAVOR
(and we define SVR4_SHARED_LIBS_DGUX_FLAVOR 1 in the nm-dgux.h)
Can anybody with familarity on this file have a look on that mod?
I suspect that maybe the reason for not allowing me to load shared
libs manually. Any ideas what I can do alternatively in solib.c
so that I correct this functionality for the DG/UX OS?
Regards,
Takis
/* Handle SunOS and SVR4 shared libraries for GDB, the GNU Debugger.
Copyright 1990, 91, 92, 93, 94, 95, 96, 98, 1999
Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include "defs.h"
/* This file is only compilable if link.h is available. */
#ifdef HAVE_LINK_H
#include <sys/types.h>
#include <signal.h>
#include "gdb_string.h"
#include <sys/param.h>
#include <fcntl.h>
#ifndef SVR4_SHARED_LIBS
/* SunOS shared libs need the nlist structure. */
#include <a.out.h>
#else
#include "elf/external.h"
#endif
#include <link.h>
#include "symtab.h"
#include "bfd.h"
#include "symfile.h"
#include "objfiles.h"
#include "gdbcore.h"
#include "command.h"
#include "target.h"
#include "frame.h"
#include "gnu-regex.h"
#include "inferior.h"
#include "environ.h"
#include "language.h"
#include "gdbcmd.h"
#define MAX_PATH_SIZE 512 /* FIXME: Should be dynamic */
/* On SVR4 systems, a list of symbols in the dynamic linker where
GDB can try to place a breakpoint to monitor shared library
events.
If none of these symbols are found, or other errors occur, then
SVR4 systems will fall back to using a symbol as the "startup
mapping complete" breakpoint address. */
#ifdef SVR4_SHARED_LIBS
static char *solib_break_names[] =
{
"r_debug_state",
"_r_debug_state",
"_dl_debug_state",
"rtld_db_dlactivity",
NULL
};
#endif
#define BKPT_AT_SYMBOL 1
#if defined (BKPT_AT_SYMBOL) && defined (SVR4_SHARED_LIBS)
static char *bkpt_names[] =
{
#ifdef SOLIB_BKPT_NAME
SOLIB_BKPT_NAME, /* Prefer configured name if it exists. */
#endif
"_start",
"main",
NULL
};
#endif
/* Symbols which are used to locate the base of the link map structures. */
#ifndef SVR4_SHARED_LIBS
static char *debug_base_symbols[] =
{
"_DYNAMIC",
"_DYNAMIC__MGC",
NULL
};
#endif
static char *main_name_list[] =
{
"main_$main",
NULL
};
/* local data declarations */
#ifndef SVR4_SHARED_LIBS
#define LM_ADDR(so) ((so) -> lm.lm_addr)
#define LM_NEXT(so) ((so) -> lm.lm_next)
#define LM_NAME(so) ((so) -> lm.lm_name)
/* Test for first link map entry; first entry is a shared library. */
#define IGNORE_FIRST_LINK_MAP_ENTRY(x) (0)
static struct link_dynamic dynamic_copy;
static struct link_dynamic_2 ld_2_copy;
static struct ld_debug debug_copy;
static CORE_ADDR debug_addr;
static CORE_ADDR flag_addr;
#else /* SVR4_SHARED_LIBS */
#define LM_ADDR(so) ((so) -> lm.l_addr)
#define LM_NEXT(so) ((so) -> lm.l_next)
#define LM_NAME(so) ((so) -> lm.l_name)
/* Test for first link map entry; first entry is the exec-file. */
#define IGNORE_FIRST_LINK_MAP_ENTRY(x) ((x).l_prev == NULL)
static struct r_debug debug_copy;
char shadow_contents[BREAKPOINT_MAX]; /* Stash old bkpt addr contents */
#endif /* !SVR4_SHARED_LIBS */
struct so_list
{
struct so_list *next; /* next structure in linked list */
struct link_map lm; /* copy of link map from inferior */
struct link_map *lmaddr; /* addr in inferior lm was read from */
CORE_ADDR lmend; /* upper addr bound of mapped object */
char so_name[MAX_PATH_SIZE]; /* shared object lib name (FIXME) */
char symbols_loaded; /* flag: symbols read in yet? */
char from_tty; /* flag: print msgs? */
struct objfile *objfile; /* objfile for loaded lib */
struct section_table *sections;
struct section_table *sections_end;
struct section_table *textsection;
bfd *abfd;
};
static struct so_list *so_list_head; /* List of known shared objects */
static CORE_ADDR debug_base; /* Base of dynamic linker structures */
static CORE_ADDR breakpoint_addr; /* Address where end bkpt is set */
static int solib_cleanup_queued = 0; /* make_run_cleanup called */
extern int
fdmatch PARAMS ((int, int)); /* In libiberty */
/* Local function prototypes */
static void
do_clear_solib PARAMS ((PTR));
static int
match_main PARAMS ((char *));
static void
special_symbol_handling PARAMS ((struct so_list *));
static void
sharedlibrary_command PARAMS ((char *, int));
static int
enable_break PARAMS ((void));
static void
info_sharedlibrary_command PARAMS ((char *, int));
static int symbol_add_stub PARAMS ((PTR));
static struct so_list *
find_solib PARAMS ((struct so_list *));
static struct link_map *
first_link_map_member PARAMS ((void));
static CORE_ADDR
locate_base PARAMS ((void));
static int solib_map_sections PARAMS ((PTR));
#ifdef SVR4_SHARED_LIBS
static CORE_ADDR
elf_locate_base PARAMS ((void));
#else
static int
disable_break PARAMS ((void));
static void
allocate_rt_common_objfile PARAMS ((void));
static void
solib_add_common_symbols PARAMS ((struct rtc_symb *));
#endif
void _initialize_solib PARAMS ((void));
/* If non-zero, this is a prefix that will be added to the front of the name
shared libraries with an absolute filename for loading. */
static char *solib_absolute_prefix = NULL;
/* If non-empty, this is a search path for loading non-absolute shared library
symbol files. This takes precedence over the environment variables PATH
and LD_LIBRARY_PATH. */
static char *solib_search_path = NULL;
/*
LOCAL FUNCTION
solib_map_sections -- open bfd and build sections for shared lib
SYNOPSIS
static int solib_map_sections (struct so_list *so)
DESCRIPTION
Given a pointer to one of the shared objects in our list
of mapped objects, use the recorded name to open a bfd
descriptor for the object, build a section table, and then
relocate all the section addresses by the base address at
which the shared object was mapped.
FIXMES
In most (all?) cases the shared object file name recorded in the
dynamic linkage tables will be a fully qualified pathname. For
cases where it isn't, do we really mimic the systems search
mechanism correctly in the below code (particularly the tilde
expansion stuff?).
*/
static int
solib_map_sections (arg)
PTR arg;
{
struct so_list *so = (struct so_list *) arg; /* catch_errors bogon */
char *filename;
char *scratch_pathname;
int scratch_chan;
struct section_table *p;
struct cleanup *old_chain;
bfd *abfd;
filename = tilde_expand (so->so_name);
if (solib_absolute_prefix && ROOTED_P (filename))
/* Prefix shared libraries with absolute filenames with
SOLIB_ABSOLUTE_PREFIX. */
{
char *pfxed_fn;
int pfx_len;
pfx_len = strlen (solib_absolute_prefix);
/* Remove trailing slashes. */
while (pfx_len > 0 && SLASH_P (solib_absolute_prefix[pfx_len - 1]))
pfx_len--;
pfxed_fn = xmalloc (pfx_len + strlen (filename) + 1);
strcpy (pfxed_fn, solib_absolute_prefix);
strcat (pfxed_fn, filename);
free (filename);
filename = pfxed_fn;
}
old_chain = make_cleanup (free, filename);
scratch_chan = -1;
if (solib_search_path)
scratch_chan = openp (solib_search_path,
1, filename, O_RDONLY, 0, &scratch_pathname);
if (scratch_chan < 0)
scratch_chan = openp (get_in_environ (inferior_environ, "PATH"),
1, filename, O_RDONLY, 0, &scratch_pathname);
if (scratch_chan < 0)
{
scratch_chan = openp (get_in_environ
(inferior_environ, "LD_LIBRARY_PATH"),
1, filename, O_RDONLY, 0, &scratch_pathname);
}
if (scratch_chan < 0)
{
perror_with_name (filename);
}
/* Leave scratch_pathname allocated. abfd->name will point to it. */
abfd = bfd_fdopenr (scratch_pathname, gnutarget, scratch_chan);
if (!abfd)
{
close (scratch_chan);
error ("Could not open `%s' as an executable file: %s",
scratch_pathname, bfd_errmsg (bfd_get_error ()));
}
/* Leave bfd open, core_xfer_memory and "info files" need it. */
so->abfd = abfd;
abfd->cacheable = true;
/* copy full path name into so_name, so that later symbol_file_add can find
it */
if (strlen (scratch_pathname) >= MAX_PATH_SIZE)
error ("Full path name length of shared library exceeds MAX_PATH_SIZE in so_list structure.");
strcpy (so->so_name, scratch_pathname);
if (!bfd_check_format (abfd, bfd_object))
{
error ("\"%s\": not in executable format: %s.",
scratch_pathname, bfd_errmsg (bfd_get_error ()));
}
if (build_section_table (abfd, &so->sections, &so->sections_end))
{
error ("Can't find the file sections in `%s': %s",
bfd_get_filename (abfd), bfd_errmsg (bfd_get_error ()));
}
for (p = so->sections; p < so->sections_end; p++)
{
/* Relocate the section binding addresses as recorded in the shared
object's file by the base address to which the object was actually
mapped. */
p->addr += (CORE_ADDR) LM_ADDR (so);
p->endaddr += (CORE_ADDR) LM_ADDR (so);
so->lmend = (CORE_ADDR) max (p->endaddr, so->lmend);
if (STREQ (p->the_bfd_section->name, ".text"))
{
so->textsection = p;
}
}
/* Free the file names, close the file now. */
do_cleanups (old_chain);
return (1);
}
#ifndef SVR4_SHARED_LIBS
/* Allocate the runtime common object file. */
static void
allocate_rt_common_objfile ()
{
struct objfile *objfile;
struct objfile *last_one;
objfile = (struct objfile *) xmalloc (sizeof (struct objfile));
memset (objfile, 0, sizeof (struct objfile));
objfile->md = NULL;
obstack_specify_allocation (&objfile->psymbol_cache.cache, 0, 0,
xmalloc, free);
obstack_specify_allocation (&objfile->psymbol_obstack, 0, 0, xmalloc,
free);
obstack_specify_allocation (&objfile->symbol_obstack, 0, 0, xmalloc,
free);
obstack_specify_allocation (&objfile->type_obstack, 0, 0, xmalloc,
free);
objfile->name = mstrsave (objfile->md, "rt_common");
/* Add this file onto the tail of the linked list of other such files. */
objfile->next = NULL;
if (object_files == NULL)
object_files = objfile;
else
{
for (last_one = object_files;
last_one->next;
last_one = last_one->next);
last_one->next = objfile;
}
rt_common_objfile = objfile;
}
/* Read all dynamically loaded common symbol definitions from the inferior
and put them into the minimal symbol table for the runtime common
objfile. */
static void
solib_add_common_symbols (rtc_symp)
struct rtc_symb *rtc_symp;
{
struct rtc_symb inferior_rtc_symb;
struct nlist inferior_rtc_nlist;
int len;
char *name;
/* Remove any runtime common symbols from previous runs. */
if (rt_common_objfile != NULL && rt_common_objfile->minimal_symbol_count)
{
obstack_free (&rt_common_objfile->symbol_obstack, 0);
obstack_specify_allocation (&rt_common_objfile->symbol_obstack, 0, 0,
xmalloc, free);
rt_common_objfile->minimal_symbol_count = 0;
rt_common_objfile->msymbols = NULL;
}
init_minimal_symbol_collection ();
make_cleanup ((make_cleanup_func) discard_minimal_symbols, 0);
while (rtc_symp)
{
read_memory ((CORE_ADDR) rtc_symp,
(char *) &inferior_rtc_symb,
sizeof (inferior_rtc_symb));
read_memory ((CORE_ADDR) inferior_rtc_symb.rtc_sp,
(char *) &inferior_rtc_nlist,
sizeof (inferior_rtc_nlist));
if (inferior_rtc_nlist.n_type == N_COMM)
{
/* FIXME: The length of the symbol name is not available, but in the
current implementation the common symbol is allocated immediately
behind the name of the symbol. */
len = inferior_rtc_nlist.n_value - inferior_rtc_nlist.n_un.n_strx;
name = xmalloc (len);
read_memory ((CORE_ADDR) inferior_rtc_nlist.n_un.n_name, name, len);
/* Allocate the runtime common objfile if necessary. */
if (rt_common_objfile == NULL)
allocate_rt_common_objfile ();
prim_record_minimal_symbol (name, inferior_rtc_nlist.n_value,
mst_bss, rt_common_objfile);
free (name);
}
rtc_symp = inferior_rtc_symb.rtc_next;
}
/* Install any minimal symbols that have been collected as the current
minimal symbols for the runtime common objfile. */
install_minimal_symbols (rt_common_objfile);
}
#endif /* SVR4_SHARED_LIBS */
#ifdef SVR4_SHARED_LIBS
static CORE_ADDR
bfd_lookup_symbol PARAMS ((bfd *, char *));
/*
LOCAL FUNCTION
bfd_lookup_symbol -- lookup the value for a specific symbol
SYNOPSIS
CORE_ADDR bfd_lookup_symbol (bfd *abfd, char *symname)
DESCRIPTION
An expensive way to lookup the value of a single symbol for
bfd's that are only temporary anyway. This is used by the
shared library support to find the address of the debugger
interface structures in the shared library.
Note that 0 is specifically allowed as an error return (no
such symbol).
*/
static CORE_ADDR
bfd_lookup_symbol (abfd, symname)
bfd *abfd;
char *symname;
{
unsigned int storage_needed;
asymbol *sym;
asymbol **symbol_table;
unsigned int number_of_symbols;
unsigned int i;
struct cleanup *back_to;
CORE_ADDR symaddr = 0;
storage_needed = bfd_get_symtab_upper_bound (abfd);
if (storage_needed > 0)
{
symbol_table = (asymbol **) xmalloc (storage_needed);
back_to = make_cleanup (free, (PTR) symbol_table);
number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table);
for (i = 0; i < number_of_symbols; i++)
{
sym = *symbol_table++;
if (STREQ (sym->name, symname))
{
/* Bfd symbols are section relative. */
symaddr = sym->value + sym->section->vma;
break;
}
}
do_cleanups (back_to);
}
return (symaddr);
}
#ifdef HANDLE_SVR4_EXEC_EMULATORS
/*
Solaris BCP (the part of Solaris which allows it to run SunOS4
a.out files) throws in another wrinkle. Solaris does not fill
in the usual a.out link map structures when running BCP programs,
the only way to get at them is via groping around in the dynamic
linker.
The dynamic linker and it's structures are located in the shared
C library, which gets run as the executable's "interpreter" by
the kernel.
Note that we can assume nothing about the process state at the time
we need to find these structures. We may be stopped on the first
instruction of the interpreter (C shared library), the first
instruction of the executable itself, or somewhere else entirely
(if we attached to the process for example).
*/
static char *debug_base_symbols[] =
{
"r_debug", /* Solaris 2.3 */
"_r_debug", /* Solaris 2.1, 2.2 */
NULL
};
static int
look_for_base PARAMS ((int, CORE_ADDR));
/*
LOCAL FUNCTION
look_for_base -- examine file for each mapped address segment
SYNOPSYS
static int look_for_base (int fd, CORE_ADDR baseaddr)
DESCRIPTION
This function is passed to proc_iterate_over_mappings, which
causes it to get called once for each mapped address space, with
an open file descriptor for the file mapped to that space, and the
base address of that mapped space.
Our job is to find the debug base symbol in the file that this
fd is open on, if it exists, and if so, initialize the dynamic
linker structure base address debug_base.
Note that this is a computationally expensive proposition, since
we basically have to open a bfd on every call, so we specifically
avoid opening the exec file.
*/
static int
look_for_base (fd, baseaddr)
int fd;
CORE_ADDR baseaddr;
{
bfd *interp_bfd;
CORE_ADDR address = 0;
char **symbolp;
/* If the fd is -1, then there is no file that corresponds to this
mapped memory segment, so skip it. Also, if the fd corresponds
to the exec file, skip it as well. */
if (fd == -1
|| (exec_bfd != NULL
&& fdmatch (fileno ((FILE *) (exec_bfd->iostream)), fd)))
{
return (0);
}
/* Try to open whatever random file this fd corresponds to. Note that
we have no way currently to find the filename. Don't gripe about
any problems we might have, just fail. */
if ((interp_bfd = bfd_fdopenr ("unnamed", gnutarget, fd)) == NULL)
{
return (0);
}
if (!bfd_check_format (interp_bfd, bfd_object))
{
/* FIXME-leak: on failure, might not free all memory associated with
interp_bfd. */
bfd_close (interp_bfd);
return (0);
}
/* Now try to find our debug base symbol in this file, which we at
least know to be a valid ELF executable or shared library. */
for (symbolp = debug_base_symbols; *symbolp != NULL; symbolp++)
{
address = bfd_lookup_symbol (interp_bfd, *symbolp);
if (address != 0)
{
break;
}
}
if (address == 0)
{
/* FIXME-leak: on failure, might not free all memory associated with
interp_bfd. */
bfd_close (interp_bfd);
return (0);
}
/* Eureka! We found the symbol. But now we may need to relocate it
by the base address. If the symbol's value is less than the base
address of the shared library, then it hasn't yet been relocated
by the dynamic linker, and we have to do it ourself. FIXME: Note
that we make the assumption that the first segment that corresponds
to the shared library has the base address to which the library
was relocated. */
if (address < baseaddr)
{
address += baseaddr;
}
debug_base = address;
/* FIXME-leak: on failure, might not free all memory associated with
interp_bfd. */
bfd_close (interp_bfd);
return (1);
}
#endif /* HANDLE_SVR4_EXEC_EMULATORS */
/*
LOCAL FUNCTION
elf_locate_base -- locate the base address of dynamic linker structs
for SVR4 elf targets.
SYNOPSIS
CORE_ADDR elf_locate_base (void)
DESCRIPTION
For SVR4 elf targets the address of the dynamic linker's runtime
structure is contained within the dynamic info section in the
executable file. The dynamic section is also mapped into the
inferior address space. Because the runtime loader fills in the
real address before starting the inferior, we have to read in the
dynamic info section from the inferior address space.
If there are any errors while trying to find the address, we
silently return 0, otherwise the found address is returned.
*/
static CORE_ADDR
elf_locate_base ()
{
sec_ptr dyninfo_sect;
int dyninfo_sect_size;
CORE_ADDR dyninfo_addr;
char *buf;
char *bufend;
/* Find the start address of the .dynamic section. */
dyninfo_sect = bfd_get_section_by_name (exec_bfd, ".dynamic");
if (dyninfo_sect == NULL)
return 0;
dyninfo_addr = bfd_section_vma (exec_bfd, dyninfo_sect);
/* Read in .dynamic section, silently ignore errors. */
dyninfo_sect_size = bfd_section_size (exec_bfd, dyninfo_sect);
buf = alloca (dyninfo_sect_size);
if (target_read_memory (dyninfo_addr, buf, dyninfo_sect_size))
return 0;
/* Find the DT_DEBUG entry in the the .dynamic section.
For mips elf we look for DT_MIPS_RLD_MAP, mips elf apparently has
no DT_DEBUG entries. */
#ifndef TARGET_ELF64
for (bufend = buf + dyninfo_sect_size;
buf < bufend;
buf += sizeof (Elf32_External_Dyn))
{
Elf32_External_Dyn *x_dynp = (Elf32_External_Dyn *) buf;
long dyn_tag;
CORE_ADDR dyn_ptr;
dyn_tag = bfd_h_get_32 (exec_bfd, (bfd_byte *) x_dynp->d_tag);
if (dyn_tag == DT_NULL)
break;
else if (dyn_tag == DT_DEBUG)
{
dyn_ptr = bfd_h_get_32 (exec_bfd, (bfd_byte *) x_dynp->d_un.d_ptr);
return dyn_ptr;
}
#ifdef DT_MIPS_RLD_MAP
else if (dyn_tag == DT_MIPS_RLD_MAP)
{
char pbuf[TARGET_PTR_BIT / HOST_CHAR_BIT];
/* DT_MIPS_RLD_MAP contains a pointer to the address
of the dynamic link structure. */
dyn_ptr = bfd_h_get_32 (exec_bfd, (bfd_byte *) x_dynp->d_un.d_ptr);
if (target_read_memory (dyn_ptr, pbuf, sizeof (pbuf)))
return 0;
return extract_unsigned_integer (pbuf, sizeof (pbuf));
}
#endif
}
#else /* ELF64 */
for (bufend = buf + dyninfo_sect_size;
buf < bufend;
buf += sizeof (Elf64_External_Dyn))
{
Elf64_External_Dyn *x_dynp = (Elf64_External_Dyn *) buf;
long dyn_tag;
CORE_ADDR dyn_ptr;
dyn_tag = bfd_h_get_64 (exec_bfd, (bfd_byte *) x_dynp->d_tag);
if (dyn_tag == DT_NULL)
break;
else if (dyn_tag == DT_DEBUG)
{
dyn_ptr = bfd_h_get_64 (exec_bfd, (bfd_byte *) x_dynp->d_un.d_ptr);
return dyn_ptr;
}
}
#endif
/* DT_DEBUG entry not found. */
return 0;
}
#endif /* SVR4_SHARED_LIBS */
/*
LOCAL FUNCTION
locate_base -- locate the base address of dynamic linker structs
SYNOPSIS
CORE_ADDR locate_base (void)
DESCRIPTION
For both the SunOS and SVR4 shared library implementations, if the
inferior executable has been linked dynamically, there is a single
address somewhere in the inferior's data space which is the key to
locating all of the dynamic linker's runtime structures. This
address is the value of the debug base symbol. The job of this
function is to find and return that address, or to return 0 if there
is no such address (the executable is statically linked for example).
For SunOS, the job is almost trivial, since the dynamic linker and
all of it's structures are statically linked to the executable at
link time. Thus the symbol for the address we are looking for has
already been added to the minimal symbol table for the executable's
objfile at the time the symbol file's symbols were read, and all we
have to do is look it up there. Note that we explicitly do NOT want
to find the copies in the shared library.
The SVR4 version is a bit more complicated because the address
is contained somewhere in the dynamic info section. We have to go
to a lot more work to discover the address of the debug base symbol.
Because of this complexity, we cache the value we find and return that
value on subsequent invocations. Note there is no copy in the
executable symbol tables.
*/
static CORE_ADDR
locate_base ()
{
#ifndef SVR4_SHARED_LIBS
struct minimal_symbol *msymbol;
CORE_ADDR address = 0;
char **symbolp;
/* For SunOS, we want to limit the search for the debug base symbol to the
executable being debugged, since there is a duplicate named symbol in the
shared library. We don't want the shared library versions. */
for (symbolp = debug_base_symbols; *symbolp != NULL; symbolp++)
{
msymbol = lookup_minimal_symbol (*symbolp, NULL, symfile_objfile);
if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
{
address = SYMBOL_VALUE_ADDRESS (msymbol);
return (address);
}
}
return (0);
#elif defined(SVR4_SHARED_LIBS_DGUX_FLAVOR)
/* DG/ux does not have /proc so we can't use the SVR4_SHARED_LIBS
version of the code below.
We need to find the dynamic linker variable _r_debug. The
dynamic linker is found by looking at the .interp section of
the executable file, then we lookup the relative address of
_r_debug in the symbol table. Finally we add in the base address
at which the dynamic linker was loaded.
All this is rather expensive, so we cache the address.
*/
static CORE_ADDR address = 0;
char * interp_name;
if (address)
{
return address;
}
if (exec_bfd != NULL)
{
interp_name = elf_interpreter (exec_bfd);
}
if (interp_name)
{
bfd * abfd;
unsigned int storage_needed;
asymbol *sym;
asymbol **symbol_table;
unsigned int number_of_symbols;
abfd = bfd_openr (interp_name, 0 );
if (!abfd)
{
return 0;
}
if (!bfd_check_format (abfd, bfd_object))
{
return 0;
}
storage_needed = bfd_get_symtab_upper_bound (abfd);
if (storage_needed > 0)
{
int i;
symbol_table = (asymbol **) xmalloc (storage_needed);
number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table);
for (i = 0; i < number_of_symbols; i++)
{
sym = symbol_table[i];
if (sym -> name == NULL || *sym -> name == '\0')
{
/* Skip names that don't exist (shouldn't happen), or names
that are null strings (may happen). */
continue;
}
if (strcmp(sym->name,"_r_debug") == 0)
{
address = 0x80000000 + sym->value + sym->section->vma;
break;
}
}
free (symbol_table);
}
bfd_close (abfd);
}
return (address);
#else /* SVR4_SHARED_LIBS */
/* Check to see if we have a currently valid address, and if so, avoid
doing all this work again and just return the cached address. If
we have no cached address, try to locate it in the dynamic info
section for ELF executables. */
if (debug_base == 0)
{
if (exec_bfd != NULL
&& bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
debug_base = elf_locate_base ();
#ifdef HANDLE_SVR4_EXEC_EMULATORS
/* Try it the hard way for emulated executables. */
else if (inferior_pid != 0 && target_has_execution)
proc_iterate_over_mappings (look_for_base);
#endif
}
return (debug_base);
#endif /* !SVR4_SHARED_LIBS */
}
/*
LOCAL FUNCTION
first_link_map_member -- locate first member in dynamic linker's map
SYNOPSIS
static struct link_map *first_link_map_member (void)
DESCRIPTION
Read in a copy of the first member in the inferior's dynamic
link map from the inferior's dynamic linker structures, and return
a pointer to the copy in our address space.
*/
static struct link_map *
first_link_map_member ()
{
struct link_map *lm = NULL;
#ifndef SVR4_SHARED_LIBS
read_memory (debug_base, (char *) &dynamic_copy, sizeof (dynamic_copy));
if (dynamic_copy.ld_version >= 2)
{
/* It is a version that we can deal with, so read in the secondary
structure and find the address of the link map list from it. */
read_memory ((CORE_ADDR) dynamic_copy.ld_un.ld_2, (char *) &ld_2_copy,
sizeof (struct link_dynamic_2));
lm = ld_2_copy.ld_loaded;
}
#else /* SVR4_SHARED_LIBS */
read_memory (debug_base, (char *) &debug_copy, sizeof (struct r_debug));
/* FIXME: Perhaps we should validate the info somehow, perhaps by
checking r_version for a known version number, or r_state for
RT_CONSISTENT. */
lm = debug_copy.r_map;
#endif /* !SVR4_SHARED_LIBS */
return (lm);
}
#ifdef SVR4_SHARED_LIBS
/*
LOCAL FUNCTION
open_exec_file_object
SYNOPSIS
void open_symbol_file_object (int from_tty)
DESCRIPTION
If no open symbol file, attempt to locate and open the main symbol
file. On SVR4 systems, this is the first link map entry. If its
name is here, we can open it. Useful when attaching to a process
without first loading its symbol file.
*/
int
open_symbol_file_object (arg)
PTR arg;
{
int from_tty = (int) arg; /* sneak past catch_errors */
struct link_map *lm, lmcopy;
char *filename;
int errcode;
if (symfile_objfile)
if (!query ("Attempt to reload symbols from process? "))
return 0;
if ((debug_base = locate_base ()) == 0)
return 0; /* failed somehow... */
/* First link map member should be the executable. */
if ((lm = first_link_map_member ()) == NULL)
return 0; /* failed somehow... */
/* Read from target memory to GDB. */
read_memory ((CORE_ADDR) lm, (void *) &lmcopy, sizeof (lmcopy));
if (lmcopy.l_name == 0)
return 0; /* no filename. */
/* Now fetch the filename from target memory. */
target_read_string ((CORE_ADDR) lmcopy.l_name, &filename,
MAX_PATH_SIZE - 1, &errcode);
if (errcode)
{
warning ("failed to read exec filename from attached file: %s",
safe_strerror (errcode));
return 0;
}
make_cleanup ((make_cleanup_func) free, (void *) filename);
/* Have a pathname: read the symbol file. */
symbol_file_command (filename, from_tty);
return 1;
}
#endif /* SVR4_SHARED_LIBS */
/*
LOCAL FUNCTION
find_solib -- step through list of shared objects
SYNOPSIS
struct so_list *find_solib (struct so_list *so_list_ptr)
DESCRIPTION
This module contains the routine which finds the names of any
loaded "images" in the current process. The argument in must be
NULL on the first call, and then the returned value must be passed
in on subsequent calls. This provides the capability to "step" down
the list of loaded objects. On the last object, a NULL value is
returned.
The arg and return value are "struct link_map" pointers, as defined
in <link.h>.
*/
static struct so_list *
find_solib (so_list_ptr)
struct so_list *so_list_ptr; /* Last lm or NULL for first one */
{
struct so_list *so_list_next = NULL;
struct link_map *lm = NULL;
struct so_list *new;
if (so_list_ptr == NULL)
{
/* We are setting up for a new scan through the loaded images. */
if ((so_list_next = so_list_head) == NULL)
{
/* We have not already read in the dynamic linking structures
from the inferior, lookup the address of the base structure. */
debug_base = locate_base ();
if (debug_base != 0)
{
/* Read the base structure in and find the address of the first
link map list member. */
lm = first_link_map_member ();
}
}
}
else
{
/* We have been called before, and are in the process of walking
the shared library list. Advance to the next shared object. */
if ((lm = LM_NEXT (so_list_ptr)) == NULL)
{
/* We have hit the end of the list, so check to see if any were
added, but be quiet if we can't read from the target any more. */
int status = target_read_memory ((CORE_ADDR) so_list_ptr->lmaddr,
(char *) &(so_list_ptr->lm),
sizeof (struct link_map));
if (status == 0)
{
lm = LM_NEXT (so_list_ptr);
}
else
{
lm = NULL;
}
}
so_list_next = so_list_ptr->next;
}
if ((so_list_next == NULL) && (lm != NULL))
{
/* Get next link map structure from inferior image and build a local
abbreviated load_map structure */
new = (struct so_list *) xmalloc (sizeof (struct so_list));
memset ((char *) new, 0, sizeof (struct so_list));
new->lmaddr = lm;
/* Add the new node as the next node in the list, or as the root
node if this is the first one. */
if (so_list_ptr != NULL)
{
so_list_ptr->next = new;
}
else
{
so_list_head = new;
if (!solib_cleanup_queued)
{
make_run_cleanup (do_clear_solib, NULL);
solib_cleanup_queued = 1;
}
}
so_list_next = new;
read_memory ((CORE_ADDR) lm, (char *) &(new->lm),
sizeof (struct link_map));
/* For SVR4 versions, the first entry in the link map is for the
inferior executable, so we must ignore it. For some versions of
SVR4, it has no name. For others (Solaris 2.3 for example), it
does have a name, so we can no longer use a missing name to
decide when to ignore it. */
if (!IGNORE_FIRST_LINK_MAP_ENTRY (new->lm))
{
int errcode;
char *buffer;
target_read_string ((CORE_ADDR) LM_NAME (new), &buffer,
MAX_PATH_SIZE - 1, &errcode);
if (errcode != 0)
{
warning ("find_solib: Can't read pathname for load map: %s\n",
safe_strerror (errcode));
return (so_list_next);
}
strncpy (new->so_name, buffer, MAX_PATH_SIZE - 1);
new->so_name[MAX_PATH_SIZE - 1] = '\0';
free (buffer);
catch_errors (solib_map_sections, new,
"Error while mapping shared library sections:\n",
RETURN_MASK_ALL);
}
}
return (so_list_next);
}
/* A small stub to get us past the arg-passing pinhole of catch_errors. */
static int
symbol_add_stub (arg)
PTR arg;
{
register struct so_list *so = (struct so_list *) arg; /* catch_errs bogon */
CORE_ADDR text_addr = 0;
if (so->textsection)
text_addr = so->textsection->addr;
else if (so->abfd != NULL)
{
asection *lowest_sect;
/* If we didn't find a mapped non zero sized .text section, set up
text_addr so that the relocation in symbol_file_add does no harm. */
lowest_sect = bfd_get_section_by_name (so->abfd, ".text");
if (lowest_sect == NULL)
bfd_map_over_sections (so->abfd, find_lowest_section,
(PTR) &lowest_sect);
if (lowest_sect)
text_addr = bfd_section_vma (so->abfd, lowest_sect)
+ (CORE_ADDR) LM_ADDR (so);
}
ALL_OBJFILES (so->objfile)
{
if (strcmp (so->objfile->name, so->so_name) == 0)
return 1;
}
so->objfile =
symbol_file_add (so->so_name, so->from_tty,
text_addr,
0, 0, 0, 0, 1);
return (1);
}
/* This function will check the so name to see if matches the main list.
In some system the main object is in the list, which we want to exclude */
static int
match_main (soname)
char *soname;
{
char **mainp;
for (mainp = main_name_list; *mainp != NULL; mainp++)
{
if (strcmp (soname, *mainp) == 0)
return (1);
}
return (0);
}
/*
GLOBAL FUNCTION
solib_add -- add a shared library file to the symtab and section list
SYNOPSIS
void solib_add (char *arg_string, int from_tty,
struct target_ops *target)
DESCRIPTION
*/
void
solib_add (arg_string, from_tty, target)
char *arg_string;
int from_tty;
struct target_ops *target;
{
register struct so_list *so = NULL; /* link map state variable */
/* Last shared library that we read. */
struct so_list *so_last = NULL;
char *re_err;
int count;
int old;
#ifdef SVR4_SHARED_LIBS
/* If we are attaching to a running process for which we
have not opened a symbol file, we may be able to get its
symbols now! */
if (attach_flag &&
symfile_objfile == NULL)
catch_errors (open_symbol_file_object, (PTR) from_tty,
"Error reading attached process's symbol file.\n",
RETURN_MASK_ALL);
#endif SVR4_SHARED_LIBS
if ((re_err = re_comp (arg_string? arg_string : ".")) != NULL)
{
error ("Invalid regexp: %s", re_err);
}
/* Add the shared library sections to the section table of the
specified target, if any. */
if (target)
{
/* Count how many new section_table entries there are. */
so = NULL;
count = 0;
while ((so = find_solib (so)) != NULL)
{
if (so->so_name[0] && !match_main (so->so_name))
{
count += so->sections_end - so->sections;
}
}
if (count)
{
/* Add these section table entries to the target's table. */
old = target_resize_to_sections (target, count);
while ((so = find_solib (so)) != NULL)
{
if (so->so_name[0])
{
count = so->sections_end - so->sections;
memcpy ((char *) (target->to_sections + old),
so->sections,
(sizeof (struct section_table)) * count);
old += count;
}
}
}
}
/* Now add the symbol files. */
while ((so = find_solib (so)) != NULL)
{
if (so->so_name[0] && re_exec (so->so_name) &&
!match_main (so->so_name))
{
so->from_tty = from_tty;
if (so->symbols_loaded)
{
if (from_tty)
{
printf_unfiltered ("Symbols already loaded for %s\n", so->so_name);
}
}
else if (catch_errors
(symbol_add_stub, so,
"Error while reading shared library symbols:\n",
RETURN_MASK_ALL))
{
so_last = so;
so->symbols_loaded = 1;
}
}
}
/* Getting new symbols may change our opinion about what is
frameless. */
if (so_last)
reinit_frame_cache ();
if (so_last)
special_symbol_handling (so_last);
}
/*
LOCAL FUNCTION
info_sharedlibrary_command -- code for "info sharedlibrary"
SYNOPSIS
static void info_sharedlibrary_command ()
DESCRIPTION
Walk through the shared library list and print information
about each attached library.
*/
static void
info_sharedlibrary_command (ignore, from_tty)
char *ignore;
int from_tty;
{
register struct so_list *so = NULL; /* link map state variable */
int header_done = 0;
int addr_width;
char *addr_fmt;
if (exec_bfd == NULL)
{
printf_unfiltered ("No exec file.\n");
return;
}
#ifndef TARGET_ELF64
addr_width = 8 + 4;
addr_fmt = "08l";
#else
addr_width = 16 + 4;
addr_fmt = "016l";
#endif
while ((so = find_solib (so)) != NULL)
{
if (so->so_name[0])
{
if (!header_done)
{
printf_unfiltered ("%-*s%-*s%-12s%s\n", addr_width, "From",
addr_width, "To", "Syms Read",
"Shared Object Library");
header_done++;
}
printf_unfiltered ("%-*s", addr_width,
local_hex_string_custom ((unsigned long) LM_ADDR (so),
addr_fmt));
printf_unfiltered ("%-*s", addr_width,
local_hex_string_custom ((unsigned long) so->lmend,
addr_fmt));
printf_unfiltered ("%-12s", so->symbols_loaded ? "Yes" : "No");
printf_unfiltered ("%s\n", so->so_name);
}
}
if (so_list_head == NULL)
{
printf_unfiltered ("No shared libraries loaded at this time.\n");
}
}
/*
GLOBAL FUNCTION
solib_address -- check to see if an address is in a shared lib
SYNOPSIS
char * solib_address (CORE_ADDR address)
DESCRIPTION
Provides a hook for other gdb routines to discover whether or
not a particular address is within the mapped address space of
a shared library. Any address between the base mapping address
and the first address beyond the end of the last mapping, is
considered to be within the shared library address space, for
our purposes.
For example, this routine is called at one point to disable
breakpoints which are in shared libraries that are not currently
mapped in.
*/
char *
solib_address (address)
CORE_ADDR address;
{
register struct so_list *so = 0; /* link map state variable */
while ((so = find_solib (so)) != NULL)
{
if (so->so_name[0])
{
if ((address >= (CORE_ADDR) LM_ADDR (so)) &&
(address < (CORE_ADDR) so->lmend))
return (so->so_name);
}
}
return (0);
}
/* Called by free_all_symtabs */
void
clear_solib ()
{
struct so_list *next;
char *bfd_filename;
/* This function is expected to handle ELF shared libraries. It is
also used on Solaris, which can run either ELF or a.out binaries
(for compatibility with SunOS 4), both of which can use shared
libraries. So we don't know whether we have an ELF executable or
an a.out executable until the user chooses an executable file.
ELF shared libraries don't get mapped into the address space
until after the program starts, so we'd better not try to insert
breakpoints in them immediately. We have to wait until the
dynamic linker has loaded them; we'll hit a bp_shlib_event
breakpoint (look for calls to create_solib_event_breakpoint) when
it's ready.
SunOS shared libraries seem to be different --- they're present
as soon as the process begins execution, so there's no need to
put off inserting breakpoints. There's also nowhere to put a
bp_shlib_event breakpoint, so if we put it off, we'll never get
around to it.
So: disable breakpoints only if we're using ELF shared libs. */
if (exec_bfd != NULL
&& bfd_get_flavour (exec_bfd) != bfd_target_aout_flavour)
disable_breakpoints_in_shlibs (1);
while (so_list_head)
{
if (so_list_head->sections)
{
free ((PTR) so_list_head->sections);
}
if (so_list_head->abfd)
{
bfd_filename = bfd_get_filename (so_list_head->abfd);
if (!bfd_close (so_list_head->abfd))
warning ("cannot close \"%s\": %s",
bfd_filename, bfd_errmsg (bfd_get_error ()));
}
else
/* This happens for the executable on SVR4. */
bfd_filename = NULL;
next = so_list_head->next;
if (bfd_filename)
free ((PTR) bfd_filename);
free ((PTR) so_list_head);
so_list_head = next;
}
debug_base = 0;
}
static void
do_clear_solib (dummy)
PTR dummy;
{
solib_cleanup_queued = 0;
clear_solib ();
}
#ifdef SVR4_SHARED_LIBS
/* Return 1 if PC lies in the dynamic symbol resolution code of the
SVR4 run time loader. */
static CORE_ADDR interp_text_sect_low;
static CORE_ADDR interp_text_sect_high;
static CORE_ADDR interp_plt_sect_low;
static CORE_ADDR interp_plt_sect_high;
int
in_svr4_dynsym_resolve_code (pc)
CORE_ADDR pc;
{
return ((pc >= interp_text_sect_low && pc < interp_text_sect_high)
|| (pc >= interp_plt_sect_low && pc < interp_plt_sect_high)
|| in_plt_section (pc, NULL));
}
#endif
/*
LOCAL FUNCTION
disable_break -- remove the "mapping changed" breakpoint
SYNOPSIS
static int disable_break ()
DESCRIPTION
Removes the breakpoint that gets hit when the dynamic linker
completes a mapping change.
*/
#ifndef SVR4_SHARED_LIBS
static int
disable_break ()
{
int status = 1;
#ifndef SVR4_SHARED_LIBS
int in_debugger = 0;
/* Read the debugger structure from the inferior to retrieve the
address of the breakpoint and the original contents of the
breakpoint address. Remove the breakpoint by writing the original
contents back. */
read_memory (debug_addr, (char *) &debug_copy, sizeof (debug_copy));
/* Set `in_debugger' to zero now. */
write_memory (flag_addr, (char *) &in_debugger, sizeof (in_debugger));
breakpoint_addr = (CORE_ADDR) debug_copy.ldd_bp_addr;
write_memory (breakpoint_addr, (char *) &debug_copy.ldd_bp_inst,
sizeof (debug_copy.ldd_bp_inst));
#else /* SVR4_SHARED_LIBS */
/* Note that breakpoint address and original contents are in our address
space, so we just need to write the original contents back. */
if (memory_remove_breakpoint (breakpoint_addr, shadow_contents) != 0)
{
status = 0;
}
#endif /* !SVR4_SHARED_LIBS */
/* For the SVR4 version, we always know the breakpoint address. For the
SunOS version we don't know it until the above code is executed.
Grumble if we are stopped anywhere besides the breakpoint address. */
if (stop_pc != breakpoint_addr)
{
warning ("stopped at unknown breakpoint while handling shared libraries");
}
return (status);
}
#endif /* #ifdef SVR4_SHARED_LIBS */
/*
LOCAL FUNCTION
enable_break -- arrange for dynamic linker to hit breakpoint
SYNOPSIS
int enable_break (void)
DESCRIPTION
Both the SunOS and the SVR4 dynamic linkers have, as part of their
debugger interface, support for arranging for the inferior to hit
a breakpoint after mapping in the shared libraries. This function
enables that breakpoint.
For SunOS, there is a special flag location (in_debugger) which we
set to 1. When the dynamic linker sees this flag set, it will set
a breakpoint at a location known only to itself, after saving the
original contents of that place and the breakpoint address itself,
in it's own internal structures. When we resume the inferior, it
will eventually take a SIGTRAP when it runs into the breakpoint.
We handle this (in a different place) by restoring the contents of
the breakpointed location (which is only known after it stops),
chasing around to locate the shared libraries that have been
loaded, then resuming.
For SVR4, the debugger interface structure contains a member (r_brk)
which is statically initialized at the time the shared library is
built, to the offset of a function (_r_debug_state) which is guaran-
teed to be called once before mapping in a library, and again when
the mapping is complete. At the time we are examining this member,
it contains only the unrelocated offset of the function, so we have
to do our own relocation. Later, when the dynamic linker actually
runs, it relocates r_brk to be the actual address of _r_debug_state().
The debugger interface structure also contains an enumeration which
is set to either RT_ADD or RT_DELETE prior to changing the mapping,
depending upon whether or not the library is being mapped or unmapped,
and then set to RT_CONSISTENT after the library is mapped/unmapped.
*/
static int
enable_break ()
{
int success = 0;
#ifndef SVR4_SHARED_LIBS
int j;
int in_debugger;
/* Get link_dynamic structure */
j = target_read_memory (debug_base, (char *) &dynamic_copy,
sizeof (dynamic_copy));
if (j)
{
/* unreadable */
return (0);
}
/* Calc address of debugger interface structure */
debug_addr = (CORE_ADDR) dynamic_copy.ldd;
/* Calc address of `in_debugger' member of debugger interface structure */
flag_addr = debug_addr + (CORE_ADDR) ((char *) &debug_copy.ldd_in_debugger -
(char *) &debug_copy);
/* Write a value of 1 to this member. */
in_debugger = 1;
write_memory (flag_addr, (char *) &in_debugger, sizeof (in_debugger));
success = 1;
#else /* SVR4_SHARED_LIBS */
#ifdef BKPT_AT_SYMBOL
struct minimal_symbol *msymbol;
char **bkpt_namep;
asection *interp_sect;
/* First, remove all the solib event breakpoints. Their addresses
may have changed since the last time we ran the program. */
remove_solib_event_breakpoints ();
#ifdef SVR4_SHARED_LIBS
interp_text_sect_low = interp_text_sect_high = 0;
interp_plt_sect_low = interp_plt_sect_high = 0;
/* Find the .interp section; if not found, warn the user and drop
into the old breakpoint at symbol code. */
interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
if (interp_sect)
{
unsigned int interp_sect_size;
char *buf;
CORE_ADDR load_addr;
bfd *tmp_bfd;
CORE_ADDR sym_addr = 0;
/* Read the contents of the .interp section into a local buffer;
the contents specify the dynamic linker this program uses. */
interp_sect_size = bfd_section_size (exec_bfd, interp_sect);
buf = alloca (interp_sect_size);
bfd_get_section_contents (exec_bfd, interp_sect,
buf, 0, interp_sect_size);
/* Now we need to figure out where the dynamic linker was
loaded so that we can load its symbols and place a breakpoint
in the dynamic linker itself.
This address is stored on the stack. However, I've been unable
to find any magic formula to find it for Solaris (appears to
be trivial on GNU/Linux). Therefore, we have to try an alternate
mechanism to find the dynamic linker's base address. */
tmp_bfd = bfd_openr (buf, gnutarget);
if (tmp_bfd == NULL)
goto bkpt_at_symbol;
/* Make sure the dynamic linker's really a useful object. */
if (!bfd_check_format (tmp_bfd, bfd_object))
{
warning ("Unable to grok dynamic linker %s as an object file", buf);
bfd_close (tmp_bfd);
goto bkpt_at_symbol;
}
/* We find the dynamic linker's base address by examining the
current pc (which point at the entry point for the dynamic
linker) and subtracting the offset of the entry point. */
load_addr = read_pc () - tmp_bfd->start_address;
/* Record the relocated start and end address of the dynamic linker
text and plt section for in_svr4_dynsym_resolve_code. */
interp_sect = bfd_get_section_by_name (tmp_bfd, ".text");
if (interp_sect)
{
interp_text_sect_low =
bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
interp_text_sect_high =
interp_text_sect_low + bfd_section_size (tmp_bfd, interp_sect);
}
interp_sect = bfd_get_section_by_name (tmp_bfd, ".plt");
if (interp_sect)
{
interp_plt_sect_low =
bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
interp_plt_sect_high =
interp_plt_sect_low + bfd_section_size (tmp_bfd, interp_sect);
}
/* Now try to set a breakpoint in the dynamic linker. */
for (bkpt_namep = solib_break_names; *bkpt_namep != NULL; bkpt_namep++)
{
sym_addr = bfd_lookup_symbol (tmp_bfd, *bkpt_namep);
if (sym_addr != 0)
break;
}
/* We're done with the temporary bfd. */
bfd_close (tmp_bfd);
if (sym_addr != 0)
{
create_solib_event_breakpoint (load_addr + sym_addr);
return 1;
}
/* For whatever reason we couldn't set a breakpoint in the dynamic
linker. Warn and drop into the old code. */
bkpt_at_symbol:
warning ("Unable to find dynamic linker breakpoint function.\nGDB will be unable to debug shared library initializers\nand track explicitly loaded dynamic code.");
}
#endif
/* Scan through the list of symbols, trying to look up the symbol and
set a breakpoint there. Terminate loop when we/if we succeed. */
breakpoint_addr = 0;
for (bkpt_namep = bkpt_names; *bkpt_namep != NULL; bkpt_namep++)
{
msymbol = lookup_minimal_symbol (*bkpt_namep, NULL, symfile_objfile);
if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
{
create_solib_event_breakpoint (SYMBOL_VALUE_ADDRESS (msymbol));
return 1;
}
}
/* Nothing good happened. */
success = 0;
#endif /* BKPT_AT_SYMBOL */
#endif /* !SVR4_SHARED_LIBS */
return (success);
}
/*
GLOBAL FUNCTION
solib_create_inferior_hook -- shared library startup support
SYNOPSIS
void solib_create_inferior_hook()
DESCRIPTION
When gdb starts up the inferior, it nurses it along (through the
shell) until it is ready to execute it's first instruction. At this
point, this function gets called via expansion of the macro
SOLIB_CREATE_INFERIOR_HOOK.
For SunOS executables, this first instruction is typically the
one at "_start", or a similar text label, regardless of whether
the executable is statically or dynamically linked. The runtime
startup code takes care of dynamically linking in any shared
libraries, once gdb allows the inferior to continue.
For SVR4 executables, this first instruction is either the first
instruction in the dynamic linker (for dynamically linked
executables) or the instruction at "start" for statically linked
executables. For dynamically linked executables, the system
first exec's /lib/libc.so.N, which contains the dynamic linker,
and starts it running. The dynamic linker maps in any needed
shared libraries, maps in the actual user executable, and then
jumps to "start" in the user executable.
For both SunOS shared libraries, and SVR4 shared libraries, we
can arrange to cooperate with the dynamic linker to discover the
names of shared libraries that are dynamically linked, and the
base addresses to which they are linked.
This function is responsible for discovering those names and
addresses, and saving sufficient information about them to allow
their symbols to be read at a later time.
FIXME
Between enable_break() and disable_break(), this code does not
properly handle hitting breakpoints which the user might have
set in the startup code or in the dynamic linker itself. Proper
handling will probably have to wait until the implementation is
changed to use the "breakpoint handler function" method.
Also, what if child has exit()ed? Must exit loop somehow.
*/
void
solib_create_inferior_hook ()
{
/* If we are using the BKPT_AT_SYMBOL code, then we don't need the base
yet. In fact, in the case of a SunOS4 executable being run on
Solaris, we can't get it yet. find_solib will get it when it needs
it. */
#if !(defined (SVR4_SHARED_LIBS) && defined (BKPT_AT_SYMBOL))
if ((debug_base = locate_base ()) == 0)
{
/* Can't find the symbol or the executable is statically linked. */
return;
}
#endif
if (!enable_break ())
{
warning ("shared library handler failed to enable breakpoint");
return;
}
#if !defined(SVR4_SHARED_LIBS) || defined(_SCO_DS)
/* SCO and SunOS need the loop below, other systems should be using the
special shared library breakpoints and the shared library breakpoint
service routine.
Now run the target. It will eventually hit the breakpoint, at
which point all of the libraries will have been mapped in and we
can go groveling around in the dynamic linker structures to find
out what we need to know about them. */
clear_proceed_status ();
stop_soon_quietly = 1;
stop_signal = TARGET_SIGNAL_0;
do
{
target_resume (-1, 0, stop_signal);
wait_for_inferior ();
}
while (stop_signal != TARGET_SIGNAL_TRAP);
stop_soon_quietly = 0;
#if !defined(_SCO_DS)
/* We are now either at the "mapping complete" breakpoint (or somewhere
else, a condition we aren't prepared to deal with anyway), so adjust
the PC as necessary after a breakpoint, disable the breakpoint, and
add any shared libraries that were mapped in. */
if (DECR_PC_AFTER_BREAK)
{
stop_pc -= DECR_PC_AFTER_BREAK;
write_register (PC_REGNUM, stop_pc);
}
if (!disable_break ())
{
warning ("shared library handler failed to disable breakpoint");
}
if (auto_solib_add)
solib_add ((char *) 0, 0, (struct target_ops *) 0);
#endif /* ! _SCO_DS */
#endif
}
/*
LOCAL FUNCTION
special_symbol_handling -- additional shared library symbol handling
SYNOPSIS
void special_symbol_handling (struct so_list *so)
DESCRIPTION
Once the symbols from a shared object have been loaded in the usual
way, we are called to do any system specific symbol handling that
is needed.
For SunOS4, this consists of grunging around in the dynamic
linkers structures to find symbol definitions for "common" symbols
and adding them to the minimal symbol table for the runtime common
objfile.
*/
static void
special_symbol_handling (so)
struct so_list *so;
{
#ifndef SVR4_SHARED_LIBS
int j;
if (debug_addr == 0)
{
/* Get link_dynamic structure */
j = target_read_memory (debug_base, (char *) &dynamic_copy,
sizeof (dynamic_copy));
if (j)
{
/* unreadable */
return;
}
/* Calc address of debugger interface structure */
/* FIXME, this needs work for cross-debugging of core files
(byteorder, size, alignment, etc). */
debug_addr = (CORE_ADDR) dynamic_copy.ldd;
}
/* Read the debugger structure from the inferior, just to make sure
we have a current copy. */
j = target_read_memory (debug_addr, (char *) &debug_copy,
sizeof (debug_copy));
if (j)
return; /* unreadable */
/* Get common symbol definitions for the loaded object. */
if (debug_copy.ldd_cp)
{
solib_add_common_symbols (debug_copy.ldd_cp);
}
#endif /* !SVR4_SHARED_LIBS */
}
/*
LOCAL FUNCTION
sharedlibrary_command -- handle command to explicitly add library
SYNOPSIS
static void sharedlibrary_command (char *args, int from_tty)
DESCRIPTION
*/
static void
sharedlibrary_command (args, from_tty)
char *args;
int from_tty;
{
dont_repeat ();
solib_add (args, from_tty, (struct target_ops *) 0);
}
#endif /* HAVE_LINK_H */
void
_initialize_solib ()
{
#ifdef HAVE_LINK_H
add_com ("sharedlibrary", class_files, sharedlibrary_command,
"Load shared object library symbols for files matching REGEXP.");
add_info ("sharedlibrary", info_sharedlibrary_command,
"Status of loaded shared object libraries.");
add_show_from_set
(add_set_cmd ("auto-solib-add", class_support, var_zinteger,
(char *) &auto_solib_add,
"Set autoloading of shared library symbols.\n\
If nonzero, symbols from all shared object libraries will be loaded\n\
automatically when the inferior begins execution or when the dynamic linker\n\
informs gdb that a new library has been loaded. Otherwise, symbols\n\
must be loaded manually, using `sharedlibrary'.",
&setlist),
&showlist);
add_show_from_set
(add_set_cmd ("solib-absolute-prefix", class_support, var_filename,
(char *) &solib_absolute_prefix,
"Set prefix for loading absolute shared library symbol files.\n\
For other (relative) files, you can add values using `set solib-search-path'.",
&setlist),
&showlist);
add_show_from_set
(add_set_cmd ("solib-search-path", class_support, var_string,
(char *) &solib_search_path,
"Set the search path for loading non-absolute shared library symbol files.\n\
This takes precedence over the environment variables PATH and LD_LIBRARY_PATH.",
&setlist),
&showlist);
#endif /* HAVE_LINK_H */
}