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binutils-gdb/gdb/solib-svr4.c
Michael Snyder 1cd337a56b 2010-05-05 Michael Snyder <msnyder@vmware.com> 
* solib-svr4.c (find_program_interpreter): Delete unused variable.
	(svr4_solib_create_inferior_hook): Add ifdef around
	conditionally-used variable declarations.
2010-05-05 19:50:10 +00:00

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/* Handle SVR4 shared libraries for GDB, the GNU Debugger.
Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000,
2001, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
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 3 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, see <http://www.gnu.org/licenses/>. */
#include "defs.h"
#include "elf/external.h"
#include "elf/common.h"
#include "elf/mips.h"
#include "symtab.h"
#include "bfd.h"
#include "symfile.h"
#include "objfiles.h"
#include "gdbcore.h"
#include "target.h"
#include "inferior.h"
#include "regcache.h"
#include "gdbthread.h"
#include "observer.h"
#include "gdb_assert.h"
#include "solist.h"
#include "solib.h"
#include "solib-svr4.h"
#include "bfd-target.h"
#include "elf-bfd.h"
#include "exec.h"
#include "auxv.h"
#include "exceptions.h"
static struct link_map_offsets *svr4_fetch_link_map_offsets (void);
static int svr4_have_link_map_offsets (void);
static void svr4_relocate_main_executable (void);
/* Link map info to include in an allocated so_list entry */
struct lm_info
{
/* Pointer to copy of link map from inferior. The type is char *
rather than void *, so that we may use byte offsets to find the
various fields without the need for a cast. */
gdb_byte *lm;
/* Amount by which addresses in the binary should be relocated to
match the inferior. This could most often be taken directly
from lm, but when prelinking is involved and the prelink base
address changes, we may need a different offset, we want to
warn about the difference and compute it only once. */
CORE_ADDR l_addr;
/* The target location of lm. */
CORE_ADDR lm_addr;
};
/* 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. */
static char *solib_break_names[] =
{
"r_debug_state",
"_r_debug_state",
"_dl_debug_state",
"rtld_db_dlactivity",
"__dl_rtld_db_dlactivity",
"_rtld_debug_state",
NULL
};
static char *bkpt_names[] =
{
"_start",
"__start",
"main",
NULL
};
static char *main_name_list[] =
{
"main_$main",
NULL
};
/* Return non-zero if GDB_SO_NAME and INFERIOR_SO_NAME represent
the same shared library. */
static int
svr4_same_1 (const char *gdb_so_name, const char *inferior_so_name)
{
if (strcmp (gdb_so_name, inferior_so_name) == 0)
return 1;
/* On Solaris, when starting inferior we think that dynamic linker is
/usr/lib/ld.so.1, but later on, the table of loaded shared libraries
contains /lib/ld.so.1. Sometimes one file is a link to another, but
sometimes they have identical content, but are not linked to each
other. We don't restrict this check for Solaris, but the chances
of running into this situation elsewhere are very low. */
if (strcmp (gdb_so_name, "/usr/lib/ld.so.1") == 0
&& strcmp (inferior_so_name, "/lib/ld.so.1") == 0)
return 1;
/* Similarly, we observed the same issue with sparc64, but with
different locations. */
if (strcmp (gdb_so_name, "/usr/lib/sparcv9/ld.so.1") == 0
&& strcmp (inferior_so_name, "/lib/sparcv9/ld.so.1") == 0)
return 1;
return 0;
}
static int
svr4_same (struct so_list *gdb, struct so_list *inferior)
{
return (svr4_same_1 (gdb->so_original_name, inferior->so_original_name));
}
/* link map access functions */
static CORE_ADDR
LM_ADDR_FROM_LINK_MAP (struct so_list *so)
{
struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
return extract_typed_address (so->lm_info->lm + lmo->l_addr_offset,
ptr_type);
}
static int
HAS_LM_DYNAMIC_FROM_LINK_MAP (void)
{
struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
return lmo->l_ld_offset >= 0;
}
static CORE_ADDR
LM_DYNAMIC_FROM_LINK_MAP (struct so_list *so)
{
struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
return extract_typed_address (so->lm_info->lm + lmo->l_ld_offset,
ptr_type);
}
static CORE_ADDR
LM_ADDR_CHECK (struct so_list *so, bfd *abfd)
{
if (so->lm_info->l_addr == (CORE_ADDR)-1)
{
struct bfd_section *dyninfo_sect;
CORE_ADDR l_addr, l_dynaddr, dynaddr;
l_addr = LM_ADDR_FROM_LINK_MAP (so);
if (! abfd || ! HAS_LM_DYNAMIC_FROM_LINK_MAP ())
goto set_addr;
l_dynaddr = LM_DYNAMIC_FROM_LINK_MAP (so);
dyninfo_sect = bfd_get_section_by_name (abfd, ".dynamic");
if (dyninfo_sect == NULL)
goto set_addr;
dynaddr = bfd_section_vma (abfd, dyninfo_sect);
if (dynaddr + l_addr != l_dynaddr)
{
CORE_ADDR align = 0x1000;
CORE_ADDR minpagesize = align;
if (bfd_get_flavour (abfd) == bfd_target_elf_flavour)
{
Elf_Internal_Ehdr *ehdr = elf_tdata (abfd)->elf_header;
Elf_Internal_Phdr *phdr = elf_tdata (abfd)->phdr;
int i;
align = 1;
for (i = 0; i < ehdr->e_phnum; i++)
if (phdr[i].p_type == PT_LOAD && phdr[i].p_align > align)
align = phdr[i].p_align;
minpagesize = get_elf_backend_data (abfd)->minpagesize;
}
/* Turn it into a mask. */
align--;
/* If the changes match the alignment requirements, we
assume we're using a core file that was generated by the
same binary, just prelinked with a different base offset.
If it doesn't match, we may have a different binary, the
same binary with the dynamic table loaded at an unrelated
location, or anything, really. To avoid regressions,
don't adjust the base offset in the latter case, although
odds are that, if things really changed, debugging won't
quite work.
One could expect more the condition
((l_addr & align) == 0 && ((l_dynaddr - dynaddr) & align) == 0)
but the one below is relaxed for PPC. The PPC kernel supports
either 4k or 64k page sizes. To be prepared for 64k pages,
PPC ELF files are built using an alignment requirement of 64k.
However, when running on a kernel supporting 4k pages, the memory
mapping of the library may not actually happen on a 64k boundary!
(In the usual case where (l_addr & align) == 0, this check is
equivalent to the possibly expected check above.)
Even on PPC it must be zero-aligned at least for MINPAGESIZE. */
if ((l_addr & (minpagesize - 1)) == 0
&& (l_addr & align) == ((l_dynaddr - dynaddr) & align))
{
l_addr = l_dynaddr - dynaddr;
if (info_verbose)
printf_unfiltered (_("Using PIC (Position Independent Code) "
"prelink displacement %s for \"%s\".\n"),
paddress (target_gdbarch, l_addr),
so->so_name);
}
else
warning (_(".dynamic section for \"%s\" "
"is not at the expected address "
"(wrong library or version mismatch?)"), so->so_name);
}
set_addr:
so->lm_info->l_addr = l_addr;
}
return so->lm_info->l_addr;
}
static CORE_ADDR
LM_NEXT (struct so_list *so)
{
struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
return extract_typed_address (so->lm_info->lm + lmo->l_next_offset,
ptr_type);
}
static CORE_ADDR
LM_PREV (struct so_list *so)
{
struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
return extract_typed_address (so->lm_info->lm + lmo->l_prev_offset,
ptr_type);
}
static CORE_ADDR
LM_NAME (struct so_list *so)
{
struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
return extract_typed_address (so->lm_info->lm + lmo->l_name_offset,
ptr_type);
}
static int
IGNORE_FIRST_LINK_MAP_ENTRY (struct so_list *so)
{
/* Assume that everything is a library if the dynamic loader was loaded
late by a static executable. */
if (exec_bfd && bfd_get_section_by_name (exec_bfd, ".dynamic") == NULL)
return 0;
return LM_PREV (so) == 0;
}
/* Per pspace SVR4 specific data. */
struct svr4_info
{
CORE_ADDR debug_base; /* Base of dynamic linker structures */
/* Validity flag for debug_loader_offset. */
int debug_loader_offset_p;
/* Load address for the dynamic linker, inferred. */
CORE_ADDR debug_loader_offset;
/* Name of the dynamic linker, valid if debug_loader_offset_p. */
char *debug_loader_name;
/* Load map address for the main executable. */
CORE_ADDR main_lm_addr;
CORE_ADDR interp_text_sect_low;
CORE_ADDR interp_text_sect_high;
CORE_ADDR interp_plt_sect_low;
CORE_ADDR interp_plt_sect_high;
};
/* Per-program-space data key. */
static const struct program_space_data *solib_svr4_pspace_data;
static void
svr4_pspace_data_cleanup (struct program_space *pspace, void *arg)
{
struct svr4_info *info;
info = program_space_data (pspace, solib_svr4_pspace_data);
xfree (info);
}
/* Get the current svr4 data. If none is found yet, add it now. This
function always returns a valid object. */
static struct svr4_info *
get_svr4_info (void)
{
struct svr4_info *info;
info = program_space_data (current_program_space, solib_svr4_pspace_data);
if (info != NULL)
return info;
info = XZALLOC (struct svr4_info);
set_program_space_data (current_program_space, solib_svr4_pspace_data, info);
return info;
}
/* Local function prototypes */
static int match_main (char *);
static CORE_ADDR bfd_lookup_symbol (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
notification routine in the shared library.
The returned symbol may be in a code or data section; functions
will normally be in a code section, but may be in a data section
if this architecture uses function descriptors.
Note that 0 is specifically allowed as an error return (no
such symbol).
*/
static CORE_ADDR
bfd_lookup_symbol (bfd *abfd, char *symname)
{
long 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 (xfree, symbol_table);
number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table);
for (i = 0; i < number_of_symbols; i++)
{
sym = *symbol_table++;
if (strcmp (sym->name, symname) == 0
&& (sym->section->flags & (SEC_CODE | SEC_DATA)) != 0)
{
/* BFD symbols are section relative. */
symaddr = sym->value + sym->section->vma;
break;
}
}
do_cleanups (back_to);
}
if (symaddr)
return symaddr;
/* On FreeBSD, the dynamic linker is stripped by default. So we'll
have to check the dynamic string table too. */
storage_needed = bfd_get_dynamic_symtab_upper_bound (abfd);
if (storage_needed > 0)
{
symbol_table = (asymbol **) xmalloc (storage_needed);
back_to = make_cleanup (xfree, symbol_table);
number_of_symbols = bfd_canonicalize_dynamic_symtab (abfd, symbol_table);
for (i = 0; i < number_of_symbols; i++)
{
sym = *symbol_table++;
if (strcmp (sym->name, symname) == 0
&& (sym->section->flags & (SEC_CODE | SEC_DATA)) != 0)
{
/* BFD symbols are section relative. */
symaddr = sym->value + sym->section->vma;
break;
}
}
do_cleanups (back_to);
}
return symaddr;
}
/* Read program header TYPE from inferior memory. The header is found
by scanning the OS auxillary vector.
If TYPE == -1, return the program headers instead of the contents of
one program header.
Return a pointer to allocated memory holding the program header contents,
or NULL on failure. If sucessful, and unless P_SECT_SIZE is NULL, the
size of those contents is returned to P_SECT_SIZE. Likewise, the target
architecture size (32-bit or 64-bit) is returned to P_ARCH_SIZE. */
static gdb_byte *
read_program_header (int type, int *p_sect_size, int *p_arch_size)
{
enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
CORE_ADDR at_phdr, at_phent, at_phnum;
int arch_size, sect_size;
CORE_ADDR sect_addr;
gdb_byte *buf;
/* Get required auxv elements from target. */
if (target_auxv_search (&current_target, AT_PHDR, &at_phdr) <= 0)
return 0;
if (target_auxv_search (&current_target, AT_PHENT, &at_phent) <= 0)
return 0;
if (target_auxv_search (&current_target, AT_PHNUM, &at_phnum) <= 0)
return 0;
if (!at_phdr || !at_phnum)
return 0;
/* Determine ELF architecture type. */
if (at_phent == sizeof (Elf32_External_Phdr))
arch_size = 32;
else if (at_phent == sizeof (Elf64_External_Phdr))
arch_size = 64;
else
return 0;
/* Find the requested segment. */
if (type == -1)
{
sect_addr = at_phdr;
sect_size = at_phent * at_phnum;
}
else if (arch_size == 32)
{
Elf32_External_Phdr phdr;
int i;
/* Search for requested PHDR. */
for (i = 0; i < at_phnum; i++)
{
if (target_read_memory (at_phdr + i * sizeof (phdr),
(gdb_byte *)&phdr, sizeof (phdr)))
return 0;
if (extract_unsigned_integer ((gdb_byte *)phdr.p_type,
4, byte_order) == type)
break;
}
if (i == at_phnum)
return 0;
/* Retrieve address and size. */
sect_addr = extract_unsigned_integer ((gdb_byte *)phdr.p_vaddr,
4, byte_order);
sect_size = extract_unsigned_integer ((gdb_byte *)phdr.p_memsz,
4, byte_order);
}
else
{
Elf64_External_Phdr phdr;
int i;
/* Search for requested PHDR. */
for (i = 0; i < at_phnum; i++)
{
if (target_read_memory (at_phdr + i * sizeof (phdr),
(gdb_byte *)&phdr, sizeof (phdr)))
return 0;
if (extract_unsigned_integer ((gdb_byte *)phdr.p_type,
4, byte_order) == type)
break;
}
if (i == at_phnum)
return 0;
/* Retrieve address and size. */
sect_addr = extract_unsigned_integer ((gdb_byte *)phdr.p_vaddr,
8, byte_order);
sect_size = extract_unsigned_integer ((gdb_byte *)phdr.p_memsz,
8, byte_order);
}
/* Read in requested program header. */
buf = xmalloc (sect_size);
if (target_read_memory (sect_addr, buf, sect_size))
{
xfree (buf);
return NULL;
}
if (p_arch_size)
*p_arch_size = arch_size;
if (p_sect_size)
*p_sect_size = sect_size;
return buf;
}
/* Return program interpreter string. */
static gdb_byte *
find_program_interpreter (void)
{
gdb_byte *buf = NULL;
/* If we have an exec_bfd, use its section table. */
if (exec_bfd
&& bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
{
struct bfd_section *interp_sect;
interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
if (interp_sect != NULL)
{
int sect_size = bfd_section_size (exec_bfd, interp_sect);
buf = xmalloc (sect_size);
bfd_get_section_contents (exec_bfd, interp_sect, buf, 0, sect_size);
}
}
/* If we didn't find it, use the target auxillary vector. */
if (!buf)
buf = read_program_header (PT_INTERP, NULL, NULL);
return buf;
}
/* Scan for DYNTAG in .dynamic section of ABFD. If DYNTAG is found 1 is
returned and the corresponding PTR is set. */
static int
scan_dyntag (int dyntag, bfd *abfd, CORE_ADDR *ptr)
{
int arch_size, step, sect_size;
long dyn_tag;
CORE_ADDR dyn_ptr, dyn_addr;
gdb_byte *bufend, *bufstart, *buf;
Elf32_External_Dyn *x_dynp_32;
Elf64_External_Dyn *x_dynp_64;
struct bfd_section *sect;
struct target_section *target_section;
if (abfd == NULL)
return 0;
if (bfd_get_flavour (abfd) != bfd_target_elf_flavour)
return 0;
arch_size = bfd_get_arch_size (abfd);
if (arch_size == -1)
return 0;
/* Find the start address of the .dynamic section. */
sect = bfd_get_section_by_name (abfd, ".dynamic");
if (sect == NULL)
return 0;
for (target_section = current_target_sections->sections;
target_section < current_target_sections->sections_end;
target_section++)
if (sect == target_section->the_bfd_section)
break;
if (target_section < current_target_sections->sections_end)
dyn_addr = target_section->addr;
else
{
/* ABFD may come from OBJFILE acting only as a symbol file without being
loaded into the target (see add_symbol_file_command). This case is
such fallback to the file VMA address without the possibility of
having the section relocated to its actual in-memory address. */
dyn_addr = bfd_section_vma (abfd, sect);
}
/* Read in .dynamic from the BFD. We will get the actual value
from memory later. */
sect_size = bfd_section_size (abfd, sect);
buf = bufstart = alloca (sect_size);
if (!bfd_get_section_contents (abfd, sect,
buf, 0, sect_size))
return 0;
/* Iterate over BUF and scan for DYNTAG. If found, set PTR and return. */
step = (arch_size == 32) ? sizeof (Elf32_External_Dyn)
: sizeof (Elf64_External_Dyn);
for (bufend = buf + sect_size;
buf < bufend;
buf += step)
{
if (arch_size == 32)
{
x_dynp_32 = (Elf32_External_Dyn *) buf;
dyn_tag = bfd_h_get_32 (abfd, (bfd_byte *) x_dynp_32->d_tag);
dyn_ptr = bfd_h_get_32 (abfd, (bfd_byte *) x_dynp_32->d_un.d_ptr);
}
else
{
x_dynp_64 = (Elf64_External_Dyn *) buf;
dyn_tag = bfd_h_get_64 (abfd, (bfd_byte *) x_dynp_64->d_tag);
dyn_ptr = bfd_h_get_64 (abfd, (bfd_byte *) x_dynp_64->d_un.d_ptr);
}
if (dyn_tag == DT_NULL)
return 0;
if (dyn_tag == dyntag)
{
/* If requested, try to read the runtime value of this .dynamic
entry. */
if (ptr)
{
struct type *ptr_type;
gdb_byte ptr_buf[8];
CORE_ADDR ptr_addr;
ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
ptr_addr = dyn_addr + (buf - bufstart) + arch_size / 8;
if (target_read_memory (ptr_addr, ptr_buf, arch_size / 8) == 0)
dyn_ptr = extract_typed_address (ptr_buf, ptr_type);
*ptr = dyn_ptr;
}
return 1;
}
}
return 0;
}
/* Scan for DYNTAG in .dynamic section of the target's main executable,
found by consulting the OS auxillary vector. If DYNTAG is found 1 is
returned and the corresponding PTR is set. */
static int
scan_dyntag_auxv (int dyntag, CORE_ADDR *ptr)
{
enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
int sect_size, arch_size, step;
long dyn_tag;
CORE_ADDR dyn_ptr;
gdb_byte *bufend, *bufstart, *buf;
/* Read in .dynamic section. */
buf = bufstart = read_program_header (PT_DYNAMIC, &sect_size, &arch_size);
if (!buf)
return 0;
/* Iterate over BUF and scan for DYNTAG. If found, set PTR and return. */
step = (arch_size == 32) ? sizeof (Elf32_External_Dyn)
: sizeof (Elf64_External_Dyn);
for (bufend = buf + sect_size;
buf < bufend;
buf += step)
{
if (arch_size == 32)
{
Elf32_External_Dyn *dynp = (Elf32_External_Dyn *) buf;
dyn_tag = extract_unsigned_integer ((gdb_byte *) dynp->d_tag,
4, byte_order);
dyn_ptr = extract_unsigned_integer ((gdb_byte *) dynp->d_un.d_ptr,
4, byte_order);
}
else
{
Elf64_External_Dyn *dynp = (Elf64_External_Dyn *) buf;
dyn_tag = extract_unsigned_integer ((gdb_byte *) dynp->d_tag,
8, byte_order);
dyn_ptr = extract_unsigned_integer ((gdb_byte *) dynp->d_un.d_ptr,
8, byte_order);
}
if (dyn_tag == DT_NULL)
break;
if (dyn_tag == dyntag)
{
if (ptr)
*ptr = dyn_ptr;
xfree (bufstart);
return 1;
}
}
xfree (bufstart);
return 0;
}
/*
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 (void)
{
struct minimal_symbol *msymbol;
CORE_ADDR dyn_ptr;
/* Look for DT_MIPS_RLD_MAP first. MIPS executables use this
instead of DT_DEBUG, although they sometimes contain an unused
DT_DEBUG. */
if (scan_dyntag (DT_MIPS_RLD_MAP, exec_bfd, &dyn_ptr)
|| scan_dyntag_auxv (DT_MIPS_RLD_MAP, &dyn_ptr))
{
struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
gdb_byte *pbuf;
int pbuf_size = TYPE_LENGTH (ptr_type);
pbuf = alloca (pbuf_size);
/* DT_MIPS_RLD_MAP contains a pointer to the address
of the dynamic link structure. */
if (target_read_memory (dyn_ptr, pbuf, pbuf_size))
return 0;
return extract_typed_address (pbuf, ptr_type);
}
/* Find DT_DEBUG. */
if (scan_dyntag (DT_DEBUG, exec_bfd, &dyn_ptr)
|| scan_dyntag_auxv (DT_DEBUG, &dyn_ptr))
return dyn_ptr;
/* This may be a static executable. Look for the symbol
conventionally named _r_debug, as a last resort. */
msymbol = lookup_minimal_symbol ("_r_debug", NULL, symfile_objfile);
if (msymbol != NULL)
return SYMBOL_VALUE_ADDRESS (msymbol);
/* DT_DEBUG entry not found. */
return 0;
}
/*
LOCAL FUNCTION
locate_base -- locate the base address of dynamic linker structs
SYNOPSIS
CORE_ADDR locate_base (struct svr4_info *)
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 (struct svr4_info *info)
{
/* 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. There's no point in doing any of this
though if we don't have some link map offsets to work with. */
if (info->debug_base == 0 && svr4_have_link_map_offsets ())
info->debug_base = elf_locate_base ();
return info->debug_base;
}
/* Find the first element in the inferior's dynamic link map, and
return its address in the inferior. Return zero if the address
could not be determined.
FIXME: Perhaps we should validate the info somehow, perhaps by
checking r_version for a known version number, or r_state for
RT_CONSISTENT. */
static CORE_ADDR
solib_svr4_r_map (struct svr4_info *info)
{
struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
CORE_ADDR addr = 0;
volatile struct gdb_exception ex;
TRY_CATCH (ex, RETURN_MASK_ERROR)
{
addr = read_memory_typed_address (info->debug_base + lmo->r_map_offset,
ptr_type);
}
exception_print (gdb_stderr, ex);
return addr;
}
/* Find r_brk from the inferior's debug base. */
static CORE_ADDR
solib_svr4_r_brk (struct svr4_info *info)
{
struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
return read_memory_typed_address (info->debug_base + lmo->r_brk_offset,
ptr_type);
}
/* Find the link map for the dynamic linker (if it is not in the
normal list of loaded shared objects). */
static CORE_ADDR
solib_svr4_r_ldsomap (struct svr4_info *info)
{
struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
ULONGEST version;
/* Check version, and return zero if `struct r_debug' doesn't have
the r_ldsomap member. */
version
= read_memory_unsigned_integer (info->debug_base + lmo->r_version_offset,
lmo->r_version_size, byte_order);
if (version < 2 || lmo->r_ldsomap_offset == -1)
return 0;
return read_memory_typed_address (info->debug_base + lmo->r_ldsomap_offset,
ptr_type);
}
/* On Solaris systems with some versions of the dynamic linker,
ld.so's l_name pointer points to the SONAME in the string table
rather than into writable memory. So that GDB can find shared
libraries when loading a core file generated by gcore, ensure that
memory areas containing the l_name string are saved in the core
file. */
static int
svr4_keep_data_in_core (CORE_ADDR vaddr, unsigned long size)
{
struct svr4_info *info;
CORE_ADDR ldsomap;
struct so_list *new;
struct cleanup *old_chain;
struct link_map_offsets *lmo;
CORE_ADDR lm_name;
info = get_svr4_info ();
info->debug_base = 0;
locate_base (info);
if (!info->debug_base)
return 0;
ldsomap = solib_svr4_r_ldsomap (info);
if (!ldsomap)
return 0;
lmo = svr4_fetch_link_map_offsets ();
new = XZALLOC (struct so_list);
old_chain = make_cleanup (xfree, new);
new->lm_info = xmalloc (sizeof (struct lm_info));
make_cleanup (xfree, new->lm_info);
new->lm_info->l_addr = (CORE_ADDR)-1;
new->lm_info->lm_addr = ldsomap;
new->lm_info->lm = xzalloc (lmo->link_map_size);
make_cleanup (xfree, new->lm_info->lm);
read_memory (ldsomap, new->lm_info->lm, lmo->link_map_size);
lm_name = LM_NAME (new);
do_cleanups (old_chain);
return (lm_name >= vaddr && lm_name < vaddr + size);
}
/*
LOCAL FUNCTION
open_symbol_file_object
SYNOPSIS
void open_symbol_file_object (void *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.
If FROM_TTYP dereferences to a non-zero integer, allow messages to
be printed. This parameter is a pointer rather than an int because
open_symbol_file_object() is called via catch_errors() and
catch_errors() requires a pointer argument. */
static int
open_symbol_file_object (void *from_ttyp)
{
CORE_ADDR lm, l_name;
char *filename;
int errcode;
int from_tty = *(int *)from_ttyp;
struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
int l_name_size = TYPE_LENGTH (ptr_type);
gdb_byte *l_name_buf = xmalloc (l_name_size);
struct cleanup *cleanups = make_cleanup (xfree, l_name_buf);
struct svr4_info *info = get_svr4_info ();
if (symfile_objfile)
if (!query (_("Attempt to reload symbols from process? ")))
return 0;
/* Always locate the debug struct, in case it has moved. */
info->debug_base = 0;
if (locate_base (info) == 0)
return 0; /* failed somehow... */
/* First link map member should be the executable. */
lm = solib_svr4_r_map (info);
if (lm == 0)
return 0; /* failed somehow... */
/* Read address of name from target memory to GDB. */
read_memory (lm + lmo->l_name_offset, l_name_buf, l_name_size);
/* Convert the address to host format. */
l_name = extract_typed_address (l_name_buf, ptr_type);
/* Free l_name_buf. */
do_cleanups (cleanups);
if (l_name == 0)
return 0; /* No filename. */
/* Now fetch the filename from target memory. */
target_read_string (l_name, &filename, SO_NAME_MAX_PATH_SIZE - 1, &errcode);
make_cleanup (xfree, filename);
if (errcode)
{
warning (_("failed to read exec filename from attached file: %s"),
safe_strerror (errcode));
return 0;
}
/* Have a pathname: read the symbol file. */
symbol_file_add_main (filename, from_tty);
return 1;
}
/* If no shared library information is available from the dynamic
linker, build a fallback list from other sources. */
static struct so_list *
svr4_default_sos (void)
{
struct svr4_info *info = get_svr4_info ();
struct so_list *head = NULL;
struct so_list **link_ptr = &head;
if (info->debug_loader_offset_p)
{
struct so_list *new = XZALLOC (struct so_list);
new->lm_info = xmalloc (sizeof (struct lm_info));
/* Nothing will ever check the cached copy of the link
map if we set l_addr. */
new->lm_info->l_addr = info->debug_loader_offset;
new->lm_info->lm_addr = 0;
new->lm_info->lm = NULL;
strncpy (new->so_name, info->debug_loader_name,
SO_NAME_MAX_PATH_SIZE - 1);
new->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
strcpy (new->so_original_name, new->so_name);
*link_ptr = new;
link_ptr = &new->next;
}
return head;
}
/* LOCAL FUNCTION
current_sos -- build a list of currently loaded shared objects
SYNOPSIS
struct so_list *current_sos ()
DESCRIPTION
Build a list of `struct so_list' objects describing the shared
objects currently loaded in the inferior. This list does not
include an entry for the main executable file.
Note that we only gather information directly available from the
inferior --- we don't examine any of the shared library files
themselves. The declaration of `struct so_list' says which fields
we provide values for. */
static struct so_list *
svr4_current_sos (void)
{
CORE_ADDR lm, prev_lm;
struct so_list *head = 0;
struct so_list **link_ptr = &head;
CORE_ADDR ldsomap = 0;
struct svr4_info *info;
info = get_svr4_info ();
/* Always locate the debug struct, in case it has moved. */
info->debug_base = 0;
locate_base (info);
/* If we can't find the dynamic linker's base structure, this
must not be a dynamically linked executable. Hmm. */
if (! info->debug_base)
return svr4_default_sos ();
/* Walk the inferior's link map list, and build our list of
`struct so_list' nodes. */
prev_lm = 0;
lm = solib_svr4_r_map (info);
while (lm)
{
struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
struct so_list *new = XZALLOC (struct so_list);
struct cleanup *old_chain = make_cleanup (xfree, new);
CORE_ADDR next_lm;
new->lm_info = xmalloc (sizeof (struct lm_info));
make_cleanup (xfree, new->lm_info);
new->lm_info->l_addr = (CORE_ADDR)-1;
new->lm_info->lm_addr = lm;
new->lm_info->lm = xzalloc (lmo->link_map_size);
make_cleanup (xfree, new->lm_info->lm);
read_memory (lm, new->lm_info->lm, lmo->link_map_size);
next_lm = LM_NEXT (new);
if (LM_PREV (new) != prev_lm)
{
warning (_("Corrupted shared library list"));
free_so (new);
next_lm = 0;
}
/* 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. */
else if (IGNORE_FIRST_LINK_MAP_ENTRY (new) && ldsomap == 0)
{
info->main_lm_addr = new->lm_info->lm_addr;
free_so (new);
}
else
{
int errcode;
char *buffer;
/* Extract this shared object's name. */
target_read_string (LM_NAME (new), &buffer,
SO_NAME_MAX_PATH_SIZE - 1, &errcode);
if (errcode != 0)
warning (_("Can't read pathname for load map: %s."),
safe_strerror (errcode));
else
{
strncpy (new->so_name, buffer, SO_NAME_MAX_PATH_SIZE - 1);
new->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
strcpy (new->so_original_name, new->so_name);
}
xfree (buffer);
/* If this entry has no name, or its name matches the name
for the main executable, don't include it in the list. */
if (! new->so_name[0]
|| match_main (new->so_name))
free_so (new);
else
{
new->next = 0;
*link_ptr = new;
link_ptr = &new->next;
}
}
prev_lm = lm;
lm = next_lm;
/* On Solaris, the dynamic linker is not in the normal list of
shared objects, so make sure we pick it up too. Having
symbol information for the dynamic linker is quite crucial
for skipping dynamic linker resolver code. */
if (lm == 0 && ldsomap == 0)
{
lm = ldsomap = solib_svr4_r_ldsomap (info);
prev_lm = 0;
}
discard_cleanups (old_chain);
}
if (head == NULL)
return svr4_default_sos ();
return head;
}
/* Get the address of the link_map for a given OBJFILE. */
CORE_ADDR
svr4_fetch_objfile_link_map (struct objfile *objfile)
{
struct so_list *so;
struct svr4_info *info = get_svr4_info ();
/* Cause svr4_current_sos() to be run if it hasn't been already. */
if (info->main_lm_addr == 0)
solib_add (NULL, 0, &current_target, auto_solib_add);
/* svr4_current_sos() will set main_lm_addr for the main executable. */
if (objfile == symfile_objfile)
return info->main_lm_addr;
/* The other link map addresses may be found by examining the list
of shared libraries. */
for (so = master_so_list (); so; so = so->next)
if (so->objfile == objfile)
return so->lm_info->lm_addr;
/* Not found! */
return 0;
}
/* On some systems, the only way to recognize the link map entry for
the main executable file is by looking at its name. Return
non-zero iff SONAME matches one of the known main executable names. */
static int
match_main (char *soname)
{
char **mainp;
for (mainp = main_name_list; *mainp != NULL; mainp++)
{
if (strcmp (soname, *mainp) == 0)
return (1);
}
return (0);
}
/* Return 1 if PC lies in the dynamic symbol resolution code of the
SVR4 run time loader. */
int
svr4_in_dynsym_resolve_code (CORE_ADDR pc)
{
struct svr4_info *info = get_svr4_info ();
return ((pc >= info->interp_text_sect_low
&& pc < info->interp_text_sect_high)
|| (pc >= info->interp_plt_sect_low
&& pc < info->interp_plt_sect_high)
|| in_plt_section (pc, NULL));
}
/* Given an executable's ABFD and target, compute the entry-point
address. */
static CORE_ADDR
exec_entry_point (struct bfd *abfd, struct target_ops *targ)
{
/* KevinB wrote ... for most targets, the address returned by
bfd_get_start_address() is the entry point for the start
function. But, for some targets, bfd_get_start_address() returns
the address of a function descriptor from which the entry point
address may be extracted. This address is extracted by
gdbarch_convert_from_func_ptr_addr(). The method
gdbarch_convert_from_func_ptr_addr() is the merely the identify
function for targets which don't use function descriptors. */
return gdbarch_convert_from_func_ptr_addr (target_gdbarch,
bfd_get_start_address (abfd),
targ);
}
/*
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 (struct svr4_info *info, int from_tty)
{
struct minimal_symbol *msymbol;
char **bkpt_namep;
asection *interp_sect;
gdb_byte *interp_name;
CORE_ADDR sym_addr;
info->interp_text_sect_low = info->interp_text_sect_high = 0;
info->interp_plt_sect_low = info->interp_plt_sect_high = 0;
/* If we already have a shared library list in the target, and
r_debug contains r_brk, set the breakpoint there - this should
mean r_brk has already been relocated. Assume the dynamic linker
is the object containing r_brk. */
solib_add (NULL, from_tty, &current_target, auto_solib_add);
sym_addr = 0;
if (info->debug_base && solib_svr4_r_map (info) != 0)
sym_addr = solib_svr4_r_brk (info);
if (sym_addr != 0)
{
struct obj_section *os;
sym_addr = gdbarch_addr_bits_remove
(target_gdbarch, gdbarch_convert_from_func_ptr_addr (target_gdbarch,
sym_addr,
&current_target));
/* On at least some versions of Solaris there's a dynamic relocation
on _r_debug.r_brk and SYM_ADDR may not be relocated yet, e.g., if
we get control before the dynamic linker has self-relocated.
Check if SYM_ADDR is in a known section, if it is assume we can
trust its value. This is just a heuristic though, it could go away
or be replaced if it's getting in the way.
On ARM we need to know whether the ISA of rtld_db_dlactivity (or
however it's spelled in your particular system) is ARM or Thumb.
That knowledge is encoded in the address, if it's Thumb the low bit
is 1. However, we've stripped that info above and it's not clear
what all the consequences are of passing a non-addr_bits_remove'd
address to create_solib_event_breakpoint. The call to
find_pc_section verifies we know about the address and have some
hope of computing the right kind of breakpoint to use (via
symbol info). It does mean that GDB needs to be pointed at a
non-stripped version of the dynamic linker in order to obtain
information it already knows about. Sigh. */
os = find_pc_section (sym_addr);
if (os != NULL)
{
/* Record the relocated start and end address of the dynamic linker
text and plt section for svr4_in_dynsym_resolve_code. */
bfd *tmp_bfd;
CORE_ADDR load_addr;
tmp_bfd = os->objfile->obfd;
load_addr = ANOFFSET (os->objfile->section_offsets,
os->objfile->sect_index_text);
interp_sect = bfd_get_section_by_name (tmp_bfd, ".text");
if (interp_sect)
{
info->interp_text_sect_low =
bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
info->interp_text_sect_high =
info->interp_text_sect_low
+ bfd_section_size (tmp_bfd, interp_sect);
}
interp_sect = bfd_get_section_by_name (tmp_bfd, ".plt");
if (interp_sect)
{
info->interp_plt_sect_low =
bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
info->interp_plt_sect_high =
info->interp_plt_sect_low
+ bfd_section_size (tmp_bfd, interp_sect);
}
create_solib_event_breakpoint (target_gdbarch, sym_addr);
return 1;
}
}
/* Find the program interpreter; if not found, warn the user and drop
into the old breakpoint at symbol code. */
interp_name = find_program_interpreter ();
if (interp_name)
{
CORE_ADDR load_addr = 0;
int load_addr_found = 0;
int loader_found_in_list = 0;
struct so_list *so;
bfd *tmp_bfd = NULL;
struct target_ops *tmp_bfd_target;
volatile struct gdb_exception ex;
sym_addr = 0;
/* 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. */
TRY_CATCH (ex, RETURN_MASK_ALL)
{
tmp_bfd = solib_bfd_open (interp_name);
}
if (tmp_bfd == NULL)
goto bkpt_at_symbol;
/* Now convert the TMP_BFD into a target. That way target, as
well as BFD operations can be used. Note that closing the
target will also close the underlying bfd. */
tmp_bfd_target = target_bfd_reopen (tmp_bfd);
/* On a running target, we can get the dynamic linker's base
address from the shared library table. */
so = master_so_list ();
while (so)
{
if (svr4_same_1 (interp_name, so->so_original_name))
{
load_addr_found = 1;
loader_found_in_list = 1;
load_addr = LM_ADDR_CHECK (so, tmp_bfd);
break;
}
so = so->next;
}
/* If we were not able to find the base address of the loader
from our so_list, then try using the AT_BASE auxilliary entry. */
if (!load_addr_found)
if (target_auxv_search (&current_target, AT_BASE, &load_addr) > 0)
{
int addr_bit = gdbarch_addr_bit (target_gdbarch);
/* Ensure LOAD_ADDR has proper sign in its possible upper bits so
that `+ load_addr' will overflow CORE_ADDR width not creating
invalid addresses like 0x101234567 for 32bit inferiors on 64bit
GDB. */
if (addr_bit < (sizeof (CORE_ADDR) * HOST_CHAR_BIT))
{
CORE_ADDR space_size = (CORE_ADDR) 1 << addr_bit;
CORE_ADDR tmp_entry_point = exec_entry_point (tmp_bfd,
tmp_bfd_target);
gdb_assert (load_addr < space_size);
/* TMP_ENTRY_POINT exceeding SPACE_SIZE would be for prelinked
64bit ld.so with 32bit executable, it should not happen. */
if (tmp_entry_point < space_size
&& tmp_entry_point + load_addr >= space_size)
load_addr -= space_size;
}
load_addr_found = 1;
}
/* Otherwise we find the dynamic linker's base address by examining
the current pc (which should point at the entry point for the
dynamic linker) and subtracting the offset of the entry point.
This is more fragile than the previous approaches, but is a good
fallback method because it has actually been working well in
most cases. */
if (!load_addr_found)
{
struct regcache *regcache
= get_thread_arch_regcache (inferior_ptid, target_gdbarch);
load_addr = (regcache_read_pc (regcache)
- exec_entry_point (tmp_bfd, tmp_bfd_target));
}
if (!loader_found_in_list)
{
info->debug_loader_name = xstrdup (interp_name);
info->debug_loader_offset_p = 1;
info->debug_loader_offset = load_addr;
solib_add (NULL, from_tty, &current_target, auto_solib_add);
}
/* Record the relocated start and end address of the dynamic linker
text and plt section for svr4_in_dynsym_resolve_code. */
interp_sect = bfd_get_section_by_name (tmp_bfd, ".text");
if (interp_sect)
{
info->interp_text_sect_low =
bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
info->interp_text_sect_high =
info->interp_text_sect_low
+ bfd_section_size (tmp_bfd, interp_sect);
}
interp_sect = bfd_get_section_by_name (tmp_bfd, ".plt");
if (interp_sect)
{
info->interp_plt_sect_low =
bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
info->interp_plt_sect_high =
info->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;
}
if (sym_addr != 0)
/* Convert 'sym_addr' from a function pointer to an address.
Because we pass tmp_bfd_target instead of the current
target, this will always produce an unrelocated value. */
sym_addr = gdbarch_convert_from_func_ptr_addr (target_gdbarch,
sym_addr,
tmp_bfd_target);
/* We're done with both the temporary bfd and target. Remember,
closing the target closes the underlying bfd. */
target_close (tmp_bfd_target, 0);
if (sym_addr != 0)
{
create_solib_event_breakpoint (target_gdbarch, load_addr + sym_addr);
xfree (interp_name);
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:
xfree (interp_name);
warning (_("Unable to find dynamic linker breakpoint function.\n"
"GDB will be unable to debug shared library initializers\n"
"and track explicitly loaded dynamic code."));
}
/* Scan through the lists of symbols, trying to look up the symbol and
set a breakpoint there. Terminate loop when we/if we succeed. */
for (bkpt_namep = solib_break_names; *bkpt_namep != NULL; bkpt_namep++)
{
msymbol = lookup_minimal_symbol (*bkpt_namep, NULL, symfile_objfile);
if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
{
sym_addr = SYMBOL_VALUE_ADDRESS (msymbol);
sym_addr = gdbarch_convert_from_func_ptr_addr (target_gdbarch,
sym_addr,
&current_target);
create_solib_event_breakpoint (target_gdbarch, sym_addr);
return 1;
}
}
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))
{
sym_addr = SYMBOL_VALUE_ADDRESS (msymbol);
sym_addr = gdbarch_convert_from_func_ptr_addr (target_gdbarch,
sym_addr,
&current_target);
create_solib_event_breakpoint (target_gdbarch, sym_addr);
return 1;
}
}
return 0;
}
/*
LOCAL FUNCTION
special_symbol_handling -- additional shared library symbol handling
SYNOPSIS
void special_symbol_handling ()
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 consisted 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.
However, for SVR4, there's nothing to do.
*/
static void
svr4_special_symbol_handling (void)
{
svr4_relocate_main_executable ();
}
/* Read the ELF program headers from ABFD. Return the contents and
set *PHDRS_SIZE to the size of the program headers. */
static gdb_byte *
read_program_headers_from_bfd (bfd *abfd, int *phdrs_size)
{
Elf_Internal_Ehdr *ehdr;
gdb_byte *buf;
ehdr = elf_elfheader (abfd);
*phdrs_size = ehdr->e_phnum * ehdr->e_phentsize;
if (*phdrs_size == 0)
return NULL;
buf = xmalloc (*phdrs_size);
if (bfd_seek (abfd, ehdr->e_phoff, SEEK_SET) != 0
|| bfd_bread (buf, *phdrs_size, abfd) != *phdrs_size)
{
xfree (buf);
return NULL;
}
return buf;
}
/* Return 1 and fill *DISPLACEMENTP with detected PIE offset of inferior
exec_bfd. Otherwise return 0.
We relocate all of the sections by the same amount. This
behavior is mandated by recent editions of the System V ABI.
According to the System V Application Binary Interface,
Edition 4.1, page 5-5:
... Though the system chooses virtual addresses for
individual processes, it maintains the segments' relative
positions. Because position-independent code uses relative
addressesing between segments, the difference between
virtual addresses in memory must match the difference
between virtual addresses in the file. The difference
between the virtual address of any segment in memory and
the corresponding virtual address in the file is thus a
single constant value for any one executable or shared
object in a given process. This difference is the base
address. One use of the base address is to relocate the
memory image of the program during dynamic linking.
The same language also appears in Edition 4.0 of the System V
ABI and is left unspecified in some of the earlier editions.
Decide if the objfile needs to be relocated. As indicated above, we will
only be here when execution is stopped. But during attachment PC can be at
arbitrary address therefore regcache_read_pc can be misleading (contrary to
the auxv AT_ENTRY value). Moreover for executable with interpreter section
regcache_read_pc would point to the interpreter and not the main executable.
So, to summarize, relocations are necessary when the start address obtained
from the executable is different from the address in auxv AT_ENTRY entry.
[ The astute reader will note that we also test to make sure that
the executable in question has the DYNAMIC flag set. It is my
opinion that this test is unnecessary (undesirable even). It
was added to avoid inadvertent relocation of an executable
whose e_type member in the ELF header is not ET_DYN. There may
be a time in the future when it is desirable to do relocations
on other types of files as well in which case this condition
should either be removed or modified to accomodate the new file
type. - Kevin, Nov 2000. ] */
static int
svr4_exec_displacement (CORE_ADDR *displacementp)
{
/* ENTRY_POINT is a possible function descriptor - before
a call to gdbarch_convert_from_func_ptr_addr. */
CORE_ADDR entry_point, displacement;
if (exec_bfd == NULL)
return 0;
/* Therefore for ELF it is ET_EXEC and not ET_DYN. Both shared libraries
being executed themselves and PIE (Position Independent Executable)
executables are ET_DYN. */
if ((bfd_get_file_flags (exec_bfd) & DYNAMIC) == 0)
return 0;
if (target_auxv_search (&current_target, AT_ENTRY, &entry_point) <= 0)
return 0;
displacement = entry_point - bfd_get_start_address (exec_bfd);
/* Verify the DISPLACEMENT candidate complies with the required page
alignment. It is cheaper than the program headers comparison below. */
if (bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
{
const struct elf_backend_data *elf = get_elf_backend_data (exec_bfd);
/* p_align of PT_LOAD segments does not specify any alignment but
only congruency of addresses:
p_offset % p_align == p_vaddr % p_align
Kernel is free to load the executable with lower alignment. */
if ((displacement & (elf->minpagesize - 1)) != 0)
return 0;
}
/* Verify that the auxilliary vector describes the same file as exec_bfd, by
comparing their program headers. If the program headers in the auxilliary
vector do not match the program headers in the executable, then we are
looking at a different file than the one used by the kernel - for
instance, "gdb program" connected to "gdbserver :PORT ld.so program". */
if (bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
{
/* Be optimistic and clear OK only if GDB was able to verify the headers
really do not match. */
int phdrs_size, phdrs2_size, ok = 1;
gdb_byte *buf, *buf2;
buf = read_program_header (-1, &phdrs_size, NULL);
buf2 = read_program_headers_from_bfd (exec_bfd, &phdrs2_size);
if (buf != NULL && buf2 != NULL
&& (phdrs_size != phdrs2_size
|| memcmp (buf, buf2, phdrs_size) != 0))
ok = 0;
xfree (buf);
xfree (buf2);
if (!ok)
return 0;
}
if (info_verbose)
{
/* It can be printed repeatedly as there is no easy way to check
the executable symbols/file has been already relocated to
displacement. */
printf_unfiltered (_("Using PIE (Position Independent Executable) "
"displacement %s for \"%s\".\n"),
paddress (target_gdbarch, displacement),
bfd_get_filename (exec_bfd));
}
*displacementp = displacement;
return 1;
}
/* Relocate the main executable. This function should be called upon
stopping the inferior process at the entry point to the program.
The entry point from BFD is compared to the AT_ENTRY of AUXV and if they are
different, the main executable is relocated by the proper amount. */
static void
svr4_relocate_main_executable (void)
{
CORE_ADDR displacement;
if (symfile_objfile)
{
int i;
/* Remote target may have already set specific offsets by `qOffsets'
which should be preferred. */
for (i = 0; i < symfile_objfile->num_sections; i++)
if (ANOFFSET (symfile_objfile->section_offsets, i) != 0)
return;
}
if (! svr4_exec_displacement (&displacement))
return;
/* Even DISPLACEMENT 0 is a valid new difference of in-memory vs. in-file
addresses. */
if (symfile_objfile)
{
struct section_offsets *new_offsets;
int i;
new_offsets = alloca (symfile_objfile->num_sections
* sizeof (*new_offsets));
for (i = 0; i < symfile_objfile->num_sections; i++)
new_offsets->offsets[i] = displacement;
objfile_relocate (symfile_objfile, new_offsets);
}
else if (exec_bfd)
{
asection *asect;
for (asect = exec_bfd->sections; asect != NULL; asect = asect->next)
exec_set_section_address (bfd_get_filename (exec_bfd), asect->index,
(bfd_section_vma (exec_bfd, asect)
+ displacement));
}
}
/*
GLOBAL FUNCTION
svr4_solib_create_inferior_hook -- shared library startup support
SYNOPSIS
void svr4_solib_create_inferior_hook (int from_tty)
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.
*/
static void
svr4_solib_create_inferior_hook (int from_tty)
{
#if defined(_SCO_DS)
struct inferior *inf;
struct thread_info *tp;
#endif /* defined(_SCO_DS) */
struct svr4_info *info;
info = get_svr4_info ();
/* Relocate the main executable if necessary. */
if (current_inferior ()->attach_flag == 0)
svr4_relocate_main_executable ();
if (!svr4_have_link_map_offsets ())
return;
if (!enable_break (info, from_tty))
return;
#if defined(_SCO_DS)
/* SCO needs 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. */
inf = current_inferior ();
tp = inferior_thread ();
clear_proceed_status ();
inf->stop_soon = STOP_QUIETLY;
tp->stop_signal = TARGET_SIGNAL_0;
do
{
target_resume (pid_to_ptid (-1), 0, tp->stop_signal);
wait_for_inferior (0);
}
while (tp->stop_signal != TARGET_SIGNAL_TRAP);
inf->stop_soon = NO_STOP_QUIETLY;
#endif /* defined(_SCO_DS) */
}
static void
svr4_clear_solib (void)
{
struct svr4_info *info;
info = get_svr4_info ();
info->debug_base = 0;
info->debug_loader_offset_p = 0;
info->debug_loader_offset = 0;
xfree (info->debug_loader_name);
info->debug_loader_name = NULL;
}
static void
svr4_free_so (struct so_list *so)
{
xfree (so->lm_info->lm);
xfree (so->lm_info);
}
/* Clear any bits of ADDR that wouldn't fit in a target-format
data pointer. "Data pointer" here refers to whatever sort of
address the dynamic linker uses to manage its sections. At the
moment, we don't support shared libraries on any processors where
code and data pointers are different sizes.
This isn't really the right solution. What we really need here is
a way to do arithmetic on CORE_ADDR values that respects the
natural pointer/address correspondence. (For example, on the MIPS,
converting a 32-bit pointer to a 64-bit CORE_ADDR requires you to
sign-extend the value. There, simply truncating the bits above
gdbarch_ptr_bit, as we do below, is no good.) This should probably
be a new gdbarch method or something. */
static CORE_ADDR
svr4_truncate_ptr (CORE_ADDR addr)
{
if (gdbarch_ptr_bit (target_gdbarch) == sizeof (CORE_ADDR) * 8)
/* We don't need to truncate anything, and the bit twiddling below
will fail due to overflow problems. */
return addr;
else
return addr & (((CORE_ADDR) 1 << gdbarch_ptr_bit (target_gdbarch)) - 1);
}
static void
svr4_relocate_section_addresses (struct so_list *so,
struct target_section *sec)
{
sec->addr = svr4_truncate_ptr (sec->addr + LM_ADDR_CHECK (so,
sec->bfd));
sec->endaddr = svr4_truncate_ptr (sec->endaddr + LM_ADDR_CHECK (so,
sec->bfd));
}
/* Architecture-specific operations. */
/* Per-architecture data key. */
static struct gdbarch_data *solib_svr4_data;
struct solib_svr4_ops
{
/* Return a description of the layout of `struct link_map'. */
struct link_map_offsets *(*fetch_link_map_offsets)(void);
};
/* Return a default for the architecture-specific operations. */
static void *
solib_svr4_init (struct obstack *obstack)
{
struct solib_svr4_ops *ops;
ops = OBSTACK_ZALLOC (obstack, struct solib_svr4_ops);
ops->fetch_link_map_offsets = NULL;
return ops;
}
/* Set the architecture-specific `struct link_map_offsets' fetcher for
GDBARCH to FLMO. Also, install SVR4 solib_ops into GDBARCH. */
void
set_solib_svr4_fetch_link_map_offsets (struct gdbarch *gdbarch,
struct link_map_offsets *(*flmo) (void))
{
struct solib_svr4_ops *ops = gdbarch_data (gdbarch, solib_svr4_data);
ops->fetch_link_map_offsets = flmo;
set_solib_ops (gdbarch, &svr4_so_ops);
}
/* Fetch a link_map_offsets structure using the architecture-specific
`struct link_map_offsets' fetcher. */
static struct link_map_offsets *
svr4_fetch_link_map_offsets (void)
{
struct solib_svr4_ops *ops = gdbarch_data (target_gdbarch, solib_svr4_data);
gdb_assert (ops->fetch_link_map_offsets);
return ops->fetch_link_map_offsets ();
}
/* Return 1 if a link map offset fetcher has been defined, 0 otherwise. */
static int
svr4_have_link_map_offsets (void)
{
struct solib_svr4_ops *ops = gdbarch_data (target_gdbarch, solib_svr4_data);
return (ops->fetch_link_map_offsets != NULL);
}
/* Most OS'es that have SVR4-style ELF dynamic libraries define a
`struct r_debug' and a `struct link_map' that are binary compatible
with the origional SVR4 implementation. */
/* Fetch (and possibly build) an appropriate `struct link_map_offsets'
for an ILP32 SVR4 system. */
struct link_map_offsets *
svr4_ilp32_fetch_link_map_offsets (void)
{
static struct link_map_offsets lmo;
static struct link_map_offsets *lmp = NULL;
if (lmp == NULL)
{
lmp = &lmo;
lmo.r_version_offset = 0;
lmo.r_version_size = 4;
lmo.r_map_offset = 4;
lmo.r_brk_offset = 8;
lmo.r_ldsomap_offset = 20;
/* Everything we need is in the first 20 bytes. */
lmo.link_map_size = 20;
lmo.l_addr_offset = 0;
lmo.l_name_offset = 4;
lmo.l_ld_offset = 8;
lmo.l_next_offset = 12;
lmo.l_prev_offset = 16;
}
return lmp;
}
/* Fetch (and possibly build) an appropriate `struct link_map_offsets'
for an LP64 SVR4 system. */
struct link_map_offsets *
svr4_lp64_fetch_link_map_offsets (void)
{
static struct link_map_offsets lmo;
static struct link_map_offsets *lmp = NULL;
if (lmp == NULL)
{
lmp = &lmo;
lmo.r_version_offset = 0;
lmo.r_version_size = 4;
lmo.r_map_offset = 8;
lmo.r_brk_offset = 16;
lmo.r_ldsomap_offset = 40;
/* Everything we need is in the first 40 bytes. */
lmo.link_map_size = 40;
lmo.l_addr_offset = 0;
lmo.l_name_offset = 8;
lmo.l_ld_offset = 16;
lmo.l_next_offset = 24;
lmo.l_prev_offset = 32;
}
return lmp;
}
struct target_so_ops svr4_so_ops;
/* Lookup global symbol for ELF DSOs linked with -Bsymbolic. Those DSOs have a
different rule for symbol lookup. The lookup begins here in the DSO, not in
the main executable. */
static struct symbol *
elf_lookup_lib_symbol (const struct objfile *objfile,
const char *name,
const domain_enum domain)
{
bfd *abfd;
if (objfile == symfile_objfile)
abfd = exec_bfd;
else
{
/* OBJFILE should have been passed as the non-debug one. */
gdb_assert (objfile->separate_debug_objfile_backlink == NULL);
abfd = objfile->obfd;
}
if (abfd == NULL || scan_dyntag (DT_SYMBOLIC, abfd, NULL) != 1)
return NULL;
return lookup_global_symbol_from_objfile (objfile, name, domain);
}
extern initialize_file_ftype _initialize_svr4_solib; /* -Wmissing-prototypes */
void
_initialize_svr4_solib (void)
{
solib_svr4_data = gdbarch_data_register_pre_init (solib_svr4_init);
solib_svr4_pspace_data
= register_program_space_data_with_cleanup (svr4_pspace_data_cleanup);
svr4_so_ops.relocate_section_addresses = svr4_relocate_section_addresses;
svr4_so_ops.free_so = svr4_free_so;
svr4_so_ops.clear_solib = svr4_clear_solib;
svr4_so_ops.solib_create_inferior_hook = svr4_solib_create_inferior_hook;
svr4_so_ops.special_symbol_handling = svr4_special_symbol_handling;
svr4_so_ops.current_sos = svr4_current_sos;
svr4_so_ops.open_symbol_file_object = open_symbol_file_object;
svr4_so_ops.in_dynsym_resolve_code = svr4_in_dynsym_resolve_code;
svr4_so_ops.bfd_open = solib_bfd_open;
svr4_so_ops.lookup_lib_global_symbol = elf_lookup_lib_symbol;
svr4_so_ops.same = svr4_same;
svr4_so_ops.keep_data_in_core = svr4_keep_data_in_core;
}
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