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old-cross-binutils/gdb/solib-svr4.c
Jan Kratochvil 3957565a96 gdb/ 
Drop lazy lm_info reading.
	* solib-svr4.c (struct lm_info): Remove field lm.  New fields l_addr_p,
	l_addr_inferior, l_ld, l_next, l_prev and l_name.
	(lm_info_read): New function.
	(lm_addr_from_link_map, lm_dynamic_from_link_map): Remove.
	(lm_addr_check): Use l_addr_p.  No longer use lm_addr_from_link_map and
	lm_dynamic_from_link_map.
	(lm_next, lm_prev, lm_name): Remove.
	(svr4_keep_data_in_core): Use lm_info_read, drop the lm_info entries
	initialization incl. read_memory.  No longer use lm_name.
	(svr4_free_so): Drop lm_info->lm freeing.
	(svr4_default_sos): Initialize lminfo with zeroes.  Use l_addr_p.  Drop
	explicit lm_addr and lm initialization.
	(svr4_read_so_list): Use lm_info_read, drop the initailization of
	fields by hand, incl. read_memory.  No longer use lm_next, lm_prev and
	lm_name.
2011-10-14 07:58:58 +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, 2011
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
{
/* Amount by which addresses in the binary should be relocated to
match the inferior. The direct inferior value is L_ADDR_INFERIOR.
When prelinking is involved and the prelink base address changes,
we may need a different offset - the recomputed offset is in L_ADDR.
It is commonly the same value. It is cached as we want to warn about
the difference and compute it only once. L_ADDR is valid
iff L_ADDR_P. */
CORE_ADDR l_addr, l_addr_inferior;
unsigned int l_addr_p : 1;
/* The target location of lm. */
CORE_ADDR lm_addr;
/* Values read in from inferior's fields of the same name. */
CORE_ADDR l_ld, l_next, l_prev, l_name;
};
/* 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 const char * const solib_break_names[] =
{
"r_debug_state",
"_r_debug_state",
"_dl_debug_state",
"rtld_db_dlactivity",
"__dl_rtld_db_dlactivity",
"_rtld_debug_state",
NULL
};
static const char * const bkpt_names[] =
{
"_start",
"__start",
"main",
NULL
};
static const char * const 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));
}
static struct lm_info *
lm_info_read (CORE_ADDR lm_addr)
{
struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
gdb_byte *lm;
struct lm_info *lm_info;
struct cleanup *back_to;
lm = xmalloc (lmo->link_map_size);
back_to = make_cleanup (xfree, lm);
if (target_read_memory (lm_addr, lm, lmo->link_map_size) != 0)
{
warning (_("Error reading shared library list entry at %s"),
paddress (target_gdbarch, lm_addr)),
lm_info = NULL;
}
else
{
struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
lm_info = xzalloc (sizeof (*lm_info));
lm_info->lm_addr = lm_addr;
lm_info->l_addr_inferior = extract_typed_address (&lm[lmo->l_addr_offset],
ptr_type);
lm_info->l_ld = extract_typed_address (&lm[lmo->l_ld_offset], ptr_type);
lm_info->l_next = extract_typed_address (&lm[lmo->l_next_offset],
ptr_type);
lm_info->l_prev = extract_typed_address (&lm[lmo->l_prev_offset],
ptr_type);
lm_info->l_name = extract_typed_address (&lm[lmo->l_name_offset],
ptr_type);
}
do_cleanups (back_to);
return lm_info;
}
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_addr_check (struct so_list *so, bfd *abfd)
{
if (!so->lm_info->l_addr_p)
{
struct bfd_section *dyninfo_sect;
CORE_ADDR l_addr, l_dynaddr, dynaddr;
l_addr = so->lm_info->l_addr_inferior;
if (! abfd || ! has_lm_dynamic_from_link_map ())
goto set_addr;
l_dynaddr = so->lm_info->l_ld;
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. */
l_addr = l_dynaddr - dynaddr;
if ((l_addr & (minpagesize - 1)) == 0
&& (l_addr & align) == ((l_dynaddr - dynaddr) & align))
{
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
{
/* There is no way to verify the library file matches. prelink
can during prelinking of an unprelinked file (or unprelinking
of a prelinked file) shift the DYNAMIC segment by arbitrary
offset without any page size alignment. There is no way to
find out the ELF header and/or Program Headers for a limited
verification if it they match. One could do a verification
of the DYNAMIC segment. Still the found address is the best
one GDB could find. */
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;
so->lm_info->l_addr_p = 1;
}
return so->lm_info->l_addr;
}
/* 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 (const char *);
/* 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;
}
/* Locate the base address of dynamic linker structs for SVR4 elf
targets.
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;
}
/* Locate the base address of dynamic linker structs.
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 name_lm;
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 = lm_info_read (ldsomap);
make_cleanup (xfree, new->lm_info);
name_lm = new->lm_info ? new->lm_info->l_name : 0;
do_cleanups (old_chain);
return (name_lm >= vaddr && name_lm < vaddr + size);
}
/* Implement the "open_symbol_file_object" target_so_ops method.
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. */
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? ")))
{
do_cleanups (cleanups);
return 0;
}
/* Always locate the debug struct, in case it has moved. */
info->debug_base = 0;
if (locate_base (info) == 0)
{
do_cleanups (cleanups);
return 0; /* failed somehow... */
}
/* First link map member should be the executable. */
lm = solib_svr4_r_map (info);
if (lm == 0)
{
do_cleanups (cleanups);
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);
if (l_name == 0)
{
do_cleanups (cleanups);
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));
do_cleanups (cleanups);
return 0;
}
/* Have a pathname: read the symbol file. */
symbol_file_add_main (filename, from_tty);
do_cleanups (cleanups);
return 1;
}
/* Implementation for target_so_ops.free_so. */
static void
svr4_free_so (struct so_list *so)
{
xfree (so->lm_info);
}
/* Free so_list built so far (called via cleanup). */
static void
svr4_free_library_list (void *p_list)
{
struct so_list *list = *(struct so_list **) p_list;
while (list != NULL)
{
struct so_list *next = list->next;
svr4_free_so (list);
list = next;
}
}
/* 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 *new;
if (!info->debug_loader_offset_p)
return NULL;
new = XZALLOC (struct so_list);
new->lm_info = xzalloc (sizeof (struct lm_info));
/* Nothing will ever check the other fields if we set l_addr_p. */
new->lm_info->l_addr = info->debug_loader_offset;
new->lm_info->l_addr_p = 1;
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);
return new;
}
/* Read the whole inferior libraries chain starting at address LM. Add the
entries to the tail referenced by LINK_PTR_PTR. Ignore the first entry if
IGNORE_FIRST and set global MAIN_LM_ADDR according to it. */
static void
svr4_read_so_list (CORE_ADDR lm, struct so_list ***link_ptr_ptr,
int ignore_first)
{
CORE_ADDR prev_lm = 0, next_lm;
for (; lm != 0; prev_lm = lm, lm = next_lm)
{
struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
struct so_list *new;
struct cleanup *old_chain;
int errcode;
char *buffer;
new = XZALLOC (struct so_list);
old_chain = make_cleanup_free_so (new);
new->lm_info = lm_info_read (lm);
if (new->lm_info == NULL)
{
do_cleanups (old_chain);
break;
}
next_lm = new->lm_info->l_next;
if (new->lm_info->l_prev != prev_lm)
{
warning (_("Corrupted shared library list"));
do_cleanups (old_chain);
break;
}
/* 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 && new->lm_info->l_prev == 0)
{
struct svr4_info *info = get_svr4_info ();
info->main_lm_addr = new->lm_info->lm_addr;
do_cleanups (old_chain);
continue;
}
/* Extract this shared object's name. */
target_read_string (new->lm_info->l_name, &buffer,
SO_NAME_MAX_PATH_SIZE - 1, &errcode);
if (errcode != 0)
{
warning (_("Can't read pathname for load map: %s."),
safe_strerror (errcode));
do_cleanups (old_chain);
continue;
}
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))
{
do_cleanups (old_chain);
continue;
}
discard_cleanups (old_chain);
new->next = 0;
**link_ptr_ptr = new;
*link_ptr_ptr = &new->next;
}
}
/* Implement the "current_sos" target_so_ops method. */
static struct so_list *
svr4_current_sos (void)
{
CORE_ADDR lm;
struct so_list *head = NULL;
struct so_list **link_ptr = &head;
struct svr4_info *info;
struct cleanup *back_to;
int ignore_first;
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 ();
/* 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)
ignore_first = 0;
else
ignore_first = 1;
back_to = make_cleanup (svr4_free_library_list, &head);
/* Walk the inferior's link map list, and build our list of
`struct so_list' nodes. */
lm = solib_svr4_r_map (info);
if (lm)
svr4_read_so_list (lm, &link_ptr, ignore_first);
/* 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. */
lm = solib_svr4_r_ldsomap (info);
if (lm)
svr4_read_so_list (lm, &link_ptr, 0);
discard_cleanups (back_to);
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 (const char *soname)
{
const char * const *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)
|| in_gnu_ifunc_stub (pc));
}
/* 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);
}
/* Helper function for gdb_bfd_lookup_symbol. */
static int
cmp_name_and_sec_flags (asymbol *sym, void *data)
{
return (strcmp (sym->name, (const char *) data) == 0
&& (sym->section->flags & (SEC_CODE | SEC_DATA)) != 0);
}
/* Arrange for dynamic linker to hit breakpoint.
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;
const char * const *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 = gdb_bfd_lookup_symbol (tmp_bfd, cmp_name_and_sec_flags,
(void *) *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;
}
}
if (!current_inferior ()->attach_flag)
{
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;
}
/* Implement the "special_symbol_handling" target_so_ops method. */
static void
svr4_special_symbol_handling (void)
{
/* Nothing to do. */
}
/* 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;
int arch_size;
buf = read_program_header (-1, &phdrs_size, &arch_size);
buf2 = read_program_headers_from_bfd (exec_bfd, &phdrs2_size);
if (buf != NULL && buf2 != NULL)
{
enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
/* We are dealing with three different addresses. EXEC_BFD
represents current address in on-disk file. target memory content
may be different from EXEC_BFD as the file may have been prelinked
to a different address after the executable has been loaded.
Moreover the address of placement in target memory can be
different from what the program headers in target memory say -
this is the goal of PIE.
Detected DISPLACEMENT covers both the offsets of PIE placement and
possible new prelink performed after start of the program. Here
relocate BUF and BUF2 just by the EXEC_BFD vs. target memory
content offset for the verification purpose. */
if (phdrs_size != phdrs2_size
|| bfd_get_arch_size (exec_bfd) != arch_size)
ok = 0;
else if (arch_size == 32
&& phdrs_size >= sizeof (Elf32_External_Phdr)
&& phdrs_size % sizeof (Elf32_External_Phdr) == 0)
{
Elf_Internal_Ehdr *ehdr2 = elf_tdata (exec_bfd)->elf_header;
Elf_Internal_Phdr *phdr2 = elf_tdata (exec_bfd)->phdr;
CORE_ADDR displacement = 0;
int i;
/* DISPLACEMENT could be found more easily by the difference of
ehdr2->e_entry. But we haven't read the ehdr yet, and we
already have enough information to compute that displacement
with what we've read. */
for (i = 0; i < ehdr2->e_phnum; i++)
if (phdr2[i].p_type == PT_LOAD)
{
Elf32_External_Phdr *phdrp;
gdb_byte *buf_vaddr_p, *buf_paddr_p;
CORE_ADDR vaddr, paddr;
CORE_ADDR displacement_vaddr = 0;
CORE_ADDR displacement_paddr = 0;
phdrp = &((Elf32_External_Phdr *) buf)[i];
buf_vaddr_p = (gdb_byte *) &phdrp->p_vaddr;
buf_paddr_p = (gdb_byte *) &phdrp->p_paddr;
vaddr = extract_unsigned_integer (buf_vaddr_p, 4,
byte_order);
displacement_vaddr = vaddr - phdr2[i].p_vaddr;
paddr = extract_unsigned_integer (buf_paddr_p, 4,
byte_order);
displacement_paddr = paddr - phdr2[i].p_paddr;
if (displacement_vaddr == displacement_paddr)
displacement = displacement_vaddr;
break;
}
/* Now compare BUF and BUF2 with optional DISPLACEMENT. */
for (i = 0; i < phdrs_size / sizeof (Elf32_External_Phdr); i++)
{
Elf32_External_Phdr *phdrp;
Elf32_External_Phdr *phdr2p;
gdb_byte *buf_vaddr_p, *buf_paddr_p;
CORE_ADDR vaddr, paddr;
asection *plt2_asect;
phdrp = &((Elf32_External_Phdr *) buf)[i];
buf_vaddr_p = (gdb_byte *) &phdrp->p_vaddr;
buf_paddr_p = (gdb_byte *) &phdrp->p_paddr;
phdr2p = &((Elf32_External_Phdr *) buf2)[i];
/* PT_GNU_STACK is an exception by being never relocated by
prelink as its addresses are always zero. */
if (memcmp (phdrp, phdr2p, sizeof (*phdrp)) == 0)
continue;
/* Check also other adjustment combinations - PR 11786. */
vaddr = extract_unsigned_integer (buf_vaddr_p, 4,
byte_order);
vaddr -= displacement;
store_unsigned_integer (buf_vaddr_p, 4, byte_order, vaddr);
paddr = extract_unsigned_integer (buf_paddr_p, 4,
byte_order);
paddr -= displacement;
store_unsigned_integer (buf_paddr_p, 4, byte_order, paddr);
if (memcmp (phdrp, phdr2p, sizeof (*phdrp)) == 0)
continue;
/* prelink can convert .plt SHT_NOBITS to SHT_PROGBITS. */
plt2_asect = bfd_get_section_by_name (exec_bfd, ".plt");
if (plt2_asect)
{
int content2;
gdb_byte *buf_filesz_p = (gdb_byte *) &phdrp->p_filesz;
CORE_ADDR filesz;
content2 = (bfd_get_section_flags (exec_bfd, plt2_asect)
& SEC_HAS_CONTENTS) != 0;
filesz = extract_unsigned_integer (buf_filesz_p, 4,
byte_order);
/* PLT2_ASECT is from on-disk file (exec_bfd) while
FILESZ is from the in-memory image. */
if (content2)
filesz += bfd_get_section_size (plt2_asect);
else
filesz -= bfd_get_section_size (plt2_asect);
store_unsigned_integer (buf_filesz_p, 4, byte_order,
filesz);
if (memcmp (phdrp, phdr2p, sizeof (*phdrp)) == 0)
continue;
}
ok = 0;
break;
}
}
else if (arch_size == 64
&& phdrs_size >= sizeof (Elf64_External_Phdr)
&& phdrs_size % sizeof (Elf64_External_Phdr) == 0)
{
Elf_Internal_Ehdr *ehdr2 = elf_tdata (exec_bfd)->elf_header;
Elf_Internal_Phdr *phdr2 = elf_tdata (exec_bfd)->phdr;
CORE_ADDR displacement = 0;
int i;
/* DISPLACEMENT could be found more easily by the difference of
ehdr2->e_entry. But we haven't read the ehdr yet, and we
already have enough information to compute that displacement
with what we've read. */
for (i = 0; i < ehdr2->e_phnum; i++)
if (phdr2[i].p_type == PT_LOAD)
{
Elf64_External_Phdr *phdrp;
gdb_byte *buf_vaddr_p, *buf_paddr_p;
CORE_ADDR vaddr, paddr;
CORE_ADDR displacement_vaddr = 0;
CORE_ADDR displacement_paddr = 0;
phdrp = &((Elf64_External_Phdr *) buf)[i];
buf_vaddr_p = (gdb_byte *) &phdrp->p_vaddr;
buf_paddr_p = (gdb_byte *) &phdrp->p_paddr;
vaddr = extract_unsigned_integer (buf_vaddr_p, 8,
byte_order);
displacement_vaddr = vaddr - phdr2[i].p_vaddr;
paddr = extract_unsigned_integer (buf_paddr_p, 8,
byte_order);
displacement_paddr = paddr - phdr2[i].p_paddr;
if (displacement_vaddr == displacement_paddr)
displacement = displacement_vaddr;
break;
}
/* Now compare BUF and BUF2 with optional DISPLACEMENT. */
for (i = 0; i < phdrs_size / sizeof (Elf64_External_Phdr); i++)
{
Elf64_External_Phdr *phdrp;
Elf64_External_Phdr *phdr2p;
gdb_byte *buf_vaddr_p, *buf_paddr_p;
CORE_ADDR vaddr, paddr;
asection *plt2_asect;
phdrp = &((Elf64_External_Phdr *) buf)[i];
buf_vaddr_p = (gdb_byte *) &phdrp->p_vaddr;
buf_paddr_p = (gdb_byte *) &phdrp->p_paddr;
phdr2p = &((Elf64_External_Phdr *) buf2)[i];
/* PT_GNU_STACK is an exception by being never relocated by
prelink as its addresses are always zero. */
if (memcmp (phdrp, phdr2p, sizeof (*phdrp)) == 0)
continue;
/* Check also other adjustment combinations - PR 11786. */
vaddr = extract_unsigned_integer (buf_vaddr_p, 8,
byte_order);
vaddr -= displacement;
store_unsigned_integer (buf_vaddr_p, 8, byte_order, vaddr);
paddr = extract_unsigned_integer (buf_paddr_p, 8,
byte_order);
paddr -= displacement;
store_unsigned_integer (buf_paddr_p, 8, byte_order, paddr);
if (memcmp (phdrp, phdr2p, sizeof (*phdrp)) == 0)
continue;
/* prelink can convert .plt SHT_NOBITS to SHT_PROGBITS. */
plt2_asect = bfd_get_section_by_name (exec_bfd, ".plt");
if (plt2_asect)
{
int content2;
gdb_byte *buf_filesz_p = (gdb_byte *) &phdrp->p_filesz;
CORE_ADDR filesz;
content2 = (bfd_get_section_flags (exec_bfd, plt2_asect)
& SEC_HAS_CONTENTS) != 0;
filesz = extract_unsigned_integer (buf_filesz_p, 8,
byte_order);
/* PLT2_ASECT is from on-disk file (exec_bfd) while
FILESZ is from the in-memory image. */
if (content2)
filesz += bfd_get_section_size (plt2_asect);
else
filesz -= bfd_get_section_size (plt2_asect);
store_unsigned_integer (buf_filesz_p, 8, byte_order,
filesz);
if (memcmp (phdrp, phdr2p, sizeof (*phdrp)) == 0)
continue;
}
ok = 0;
break;
}
}
else
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 we are re-running this executable, SYMFILE_OBJFILE->SECTION_OFFSETS
probably contains the offsets computed using the PIE displacement
from the previous run, which of course are irrelevant for this run.
So we need to determine the new PIE displacement and recompute the
section offsets accordingly, even if SYMFILE_OBJFILE->SECTION_OFFSETS
already contains pre-computed offsets.
If we cannot compute the PIE displacement, either:
- The executable is not PIE.
- SYMFILE_OBJFILE does not match the executable started in the target.
This can happen for main executable symbols loaded at the host while
`ld.so --ld-args main-executable' is loaded in the target.
Then we leave the section offsets untouched and use them as is for
this run. Either:
- These section offsets were properly reset earlier, and thus
already contain the correct values. This can happen for instance
when reconnecting via the remote protocol to a target that supports
the `qOffsets' packet.
- The section offsets were not reset earlier, and the best we can
hope is that the old offsets are still applicable to the new run. */
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));
}
}
/* Implement the "create_inferior_hook" target_solib_ops method.
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.
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. */
svr4_relocate_main_executable ();
/* No point setting a breakpoint in the dynamic linker if we can't
hit it (e.g., a core file, or a trace file). */
if (!target_has_execution)
return;
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->control.stop_soon = STOP_QUIETLY;
tp->suspend.stop_signal = TARGET_SIGNAL_0;
do
{
target_resume (pid_to_ptid (-1), 0, tp->suspend.stop_signal);
wait_for_inferior ();
}
while (tp->suspend.stop_signal != TARGET_SIGNAL_TRAP);
inf->control.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;
}
/* 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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