/* Find debugging and symbol information for a module in libdwfl.
Copyright (C) 2005-2012, 2014, 2015 Red Hat, Inc.
This file is part of elfutils.
This file is free software; you can redistribute it and/or modify
it under the terms of either
* the GNU Lesser General Public License as published by the Free
Software Foundation; either version 3 of the License, or (at
your option) any later version
or
* the GNU General Public License as published by the Free
Software Foundation; either version 2 of the License, or (at
your option) any later version
or both in parallel, as here.
elfutils 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 copies of the GNU General Public License and
the GNU Lesser General Public License along with this program. If
not, see <http://www.gnu.org/licenses/>. */
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include "libdwflP.h"
#include <inttypes.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include "../libdw/libdwP.h" /* DWARF_E_* values are here. */
#include "../libelf/libelfP.h"
#include "system.h"
static inline Dwfl_Error
open_elf_file (Elf **elf, int *fd, char **name)
{
if (*elf == NULL)
{
/* CBFAIL uses errno if it's set, so clear it first in case we don't
set it with an open failure below. */
errno = 0;
/* If there was a pre-primed file name left that the callback left
behind, try to open that file name. */
if (*fd < 0 && *name != NULL)
*fd = TEMP_FAILURE_RETRY (open (*name, O_RDONLY));
if (*fd < 0)
return CBFAIL;
return __libdw_open_file (fd, elf, true, false);
}
else if (unlikely (elf_kind (*elf) != ELF_K_ELF))
{
elf_end (*elf);
*elf = NULL;
close (*fd);
*fd = -1;
return DWFL_E_BADELF;
}
/* Elf file already open and looks fine. */
return DWFL_E_NOERROR;
}
/* Open libelf FILE->fd and compute the load base of ELF as loaded in MOD.
When we return success, FILE->elf and FILE->vaddr are set up. */
static inline Dwfl_Error
open_elf (Dwfl_Module *mod, struct dwfl_file *file)
{
Dwfl_Error error = open_elf_file (&file->elf, &file->fd, &file->name);
if (error != DWFL_E_NOERROR)
return error;
GElf_Ehdr ehdr_mem, *ehdr = gelf_getehdr (file->elf, &ehdr_mem);
if (ehdr == NULL)
{
elf_error:
elf_end (file->elf);
file->elf = NULL;
close (file->fd);
file->fd = -1;
return DWFL_E (LIBELF, elf_errno ());
}
if (ehdr->e_type != ET_REL)
{
/* In any non-ET_REL file, we compute the "synchronization address".
We start with the address at the end of the first PT_LOAD
segment. When prelink converts REL to RELA in an ET_DYN
file, it expands the space between the beginning of the
segment and the actual code/data addresses. Since that
change wasn't made in the debug file, the distance from
p_vaddr to an address of interest (in an st_value or DWARF
data) now differs between the main and debug files. The
distance from address_sync to an address of interest remains
consistent.
If there are no section headers at all (full stripping), then
the end of the first segment is a valid synchronization address.
This cannot happen in a prelinked file, since prelink itself
relies on section headers for prelinking and for undoing it.
(If you do full stripping on a prelinked file, then you get what
you deserve--you can neither undo the prelinking, nor expect to
line it up with a debug file separated before prelinking.)
However, when prelink processes an ET_EXEC file, it can do
something different. There it juggles the "special" sections
(SHT_DYNSYM et al) to make space for the additional prelink
special sections. Sometimes it will do this by moving a special
section like .dynstr after the real program sections in the first
PT_LOAD segment--i.e. to the end. That changes the end address of
the segment, so it no longer lines up correctly and is not a valid
synchronization address to use. Because of this, we need to apply
a different prelink-savvy means to discover the synchronization
address when there is a separate debug file and a prelinked main
file. That is done in find_debuginfo, below. */
size_t phnum;
if (unlikely (elf_getphdrnum (file->elf, &phnum) != 0))
goto elf_error;
file->vaddr = file->address_sync = 0;
for (size_t i = 0; i < phnum; ++i)
{
GElf_Phdr ph_mem;
GElf_Phdr *ph = gelf_getphdr (file->elf, i, &ph_mem);
if (unlikely (ph == NULL))
goto elf_error;
if (ph->p_type == PT_LOAD)
{
file->vaddr = ph->p_vaddr & -ph->p_align;
file->address_sync = ph->p_vaddr + ph->p_memsz;
break;
}
}
}
/* We only want to set the module e_type explictly once, derived from
the main ELF file. (It might be changed for the kernel, because
that is special - see below.) open_elf is always called first for
the main ELF file, because both find_dw and find_symtab call
__libdwfl_getelf first to open the main file. So don't let debug
or aux files override the module e_type. The kernel heuristic
below could otherwise trigger for non-kernel/non-main files, since
their phdrs might not match the actual load addresses. */
if (file == &mod->main)
{
mod->e_type = ehdr->e_type;
/* Relocatable Linux kernels are ET_EXEC but act like ET_DYN. */
if (mod->e_type == ET_EXEC && file->vaddr != mod->low_addr)
mod->e_type = ET_DYN;
}
else
assert (mod->main.elf != NULL);
return DWFL_E_NOERROR;
}
/* We have an authoritative build ID for this module MOD, so don't use
a file by name that doesn't match that ID. */
static void
mod_verify_build_id (Dwfl_Module *mod)
{
assert (mod->build_id_len > 0);
switch (__builtin_expect (__libdwfl_find_build_id (mod, false,
mod->main.elf), 2))
{
case 2:
/* Build ID matches as it should. */
return;
case -1: /* ELF error. */
mod->elferr = INTUSE(dwfl_errno) ();
break;
case 0: /* File has no build ID note. */
case 1: /* FIle has a build ID that does not match. */
mod->elferr = DWFL_E_WRONG_ID_ELF;
break;
default:
abort ();
}
/* We get here when it was the right ELF file. Clear it out. */
elf_end (mod->main.elf);
mod->main.elf = NULL;
if (mod->main.fd >= 0)
{
close (mod->main.fd);
mod->main.fd = -1;
}
}
/* Find the main ELF file for this module and open libelf on it.
When we return success, MOD->main.elf and MOD->main.bias are set up. */
void
internal_function
__libdwfl_getelf (Dwfl_Module *mod)
{
if (mod->main.elf != NULL /* Already done. */
|| mod->elferr != DWFL_E_NOERROR) /* Cached failure. */
return;
mod->main.fd = (*mod->dwfl->callbacks->find_elf) (MODCB_ARGS (mod),
&mod->main.name,
&mod->main.elf);
const bool fallback = mod->main.elf == NULL && mod->main.fd < 0;
mod->elferr = open_elf (mod, &mod->main);
if (mod->elferr != DWFL_E_NOERROR)
return;
if (!mod->main.valid)
{
/* Clear any explicitly reported build ID, just in case it was wrong.
We'll fetch it from the file when asked. */
free (mod->build_id_bits);
mod->build_id_bits = NULL;
mod->build_id_len = 0;
}
else if (fallback)
mod_verify_build_id (mod);
mod->main_bias = mod->e_type == ET_REL ? 0 : mod->low_addr - mod->main.vaddr;
}
static inline void
consider_shdr (GElf_Addr interp,
GElf_Word sh_type,
GElf_Xword sh_flags,
GElf_Addr sh_addr,
GElf_Xword sh_size,
GElf_Addr *phighest)
{
if ((sh_flags & SHF_ALLOC)
&& ((sh_type == SHT_PROGBITS && sh_addr != interp)
|| sh_type == SHT_NOBITS))
{
const GElf_Addr sh_end = sh_addr + sh_size;
if (sh_end > *phighest)
*phighest = sh_end;
}
}
/* If the main file might have been prelinked, then we need to
discover the correct synchronization address between the main and
debug files. Because of prelink's section juggling, we cannot rely
on the address_sync computed from PT_LOAD segments (see open_elf).
We will attempt to discover a synchronization address based on the
section headers instead. But finding a section address that is
safe to use requires identifying which sections are SHT_PROGBITS.
We can do that in the main file, but in the debug file all the
allocated sections have been transformed into SHT_NOBITS so we have
lost the means to match them up correctly.
The only method left to us is to decode the .gnu.prelink_undo
section in the prelinked main file. This shows what the sections
looked like before prelink juggled them--when they still had a
direct correspondence to the debug file. */
static Dwfl_Error
find_prelink_address_sync (Dwfl_Module *mod, struct dwfl_file *file)
{
/* The magic section is only identified by name. */
size_t shstrndx;
if (elf_getshdrstrndx (mod->main.elf, &shstrndx) < 0)
return DWFL_E_LIBELF;
Elf_Scn *scn = NULL;
while ((scn = elf_nextscn (mod->main.elf, scn)) != NULL)
{
GElf_Shdr shdr_mem;
GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
if (unlikely (shdr == NULL))
return DWFL_E_LIBELF;
if (shdr->sh_type == SHT_PROGBITS
&& !(shdr->sh_flags & SHF_ALLOC)
&& shdr->sh_name != 0)
{
const char *secname = elf_strptr (mod->main.elf, shstrndx,
shdr->sh_name);
if (unlikely (secname == NULL))
return DWFL_E_LIBELF;
if (!strcmp (secname, ".gnu.prelink_undo"))
break;
}
}
if (scn == NULL)
/* There was no .gnu.prelink_undo section. */
return DWFL_E_NOERROR;
Elf_Data *undodata = elf_rawdata (scn, NULL);
if (unlikely (undodata == NULL))
return DWFL_E_LIBELF;
/* Decode the section. It consists of the original ehdr, phdrs,
and shdrs (but omits section 0). */
union
{
Elf32_Ehdr e32;
Elf64_Ehdr e64;
} ehdr;
Elf_Data dst =
{
.d_buf = &ehdr,
.d_size = sizeof ehdr,
.d_type = ELF_T_EHDR,
.d_version = EV_CURRENT
};
Elf_Data src = *undodata;
src.d_size = gelf_fsize (mod->main.elf, ELF_T_EHDR, 1, EV_CURRENT);
src.d_type = ELF_T_EHDR;
if (unlikely (gelf_xlatetom (mod->main.elf, &dst, &src,
elf_getident (mod->main.elf, NULL)[EI_DATA])
== NULL))
return DWFL_E_LIBELF;
size_t shentsize = gelf_fsize (mod->main.elf, ELF_T_SHDR, 1, EV_CURRENT);
size_t phentsize = gelf_fsize (mod->main.elf, ELF_T_PHDR, 1, EV_CURRENT);
uint_fast16_t phnum;
uint_fast16_t shnum;
if (ehdr.e32.e_ident[EI_CLASS] == ELFCLASS32)
{
if (ehdr.e32.e_shentsize != shentsize
|| ehdr.e32.e_phentsize != phentsize)
return DWFL_E_BAD_PRELINK;
phnum = ehdr.e32.e_phnum;
shnum = ehdr.e32.e_shnum;
}
else
{
if (ehdr.e64.e_shentsize != shentsize
|| ehdr.e64.e_phentsize != phentsize)
return DWFL_E_BAD_PRELINK;
phnum = ehdr.e64.e_phnum;
shnum = ehdr.e64.e_shnum;
}
/* Since prelink does not store the zeroth section header in the undo
section, it cannot support SHN_XINDEX encoding. */
if (unlikely (shnum >= SHN_LORESERVE) || unlikely(shnum == 0)
|| unlikely (undodata->d_size != (src.d_size
+ phnum * phentsize
+ (shnum - 1) * shentsize)))
return DWFL_E_BAD_PRELINK;
--shnum;
/* We look at the allocated SHT_PROGBITS (or SHT_NOBITS) sections. (Most
every file will have some SHT_PROGBITS sections, but it's possible to
have one with nothing but .bss, i.e. SHT_NOBITS.) The special sections
that can be moved around have different sh_type values--except for
.interp, the section that became the PT_INTERP segment. So we exclude
the SHT_PROGBITS section whose address matches the PT_INTERP p_vaddr.
For this reason, we must examine the phdrs first to find PT_INTERP. */
GElf_Addr main_interp = 0;
{
size_t main_phnum;
if (unlikely (elf_getphdrnum (mod->main.elf, &main_phnum)))
return DWFL_E_LIBELF;
for (size_t i = 0; i < main_phnum; ++i)
{
GElf_Phdr phdr;
if (unlikely (gelf_getphdr (mod->main.elf, i, &phdr) == NULL))
return DWFL_E_LIBELF;
if (phdr.p_type == PT_INTERP)
{
main_interp = phdr.p_vaddr;
break;
}
}
}
src.d_buf += src.d_size;
src.d_type = ELF_T_PHDR;
src.d_size = phnum * phentsize;
GElf_Addr undo_interp = 0;
bool class32 = ehdr.e32.e_ident[EI_CLASS] == ELFCLASS32;
{
size_t phdr_size = class32 ? sizeof (Elf32_Phdr) : sizeof (Elf64_Phdr);
if (unlikely (phnum > SIZE_MAX / phdr_size))
return DWFL_E_NOMEM;
const size_t phdrs_bytes = phnum * phdr_size;
void *phdrs = malloc (phdrs_bytes);
if (unlikely (phdrs == NULL))
return DWFL_E_NOMEM;
dst.d_buf = phdrs;
dst.d_size = phdrs_bytes;
if (unlikely (gelf_xlatetom (mod->main.elf, &dst, &src,
ehdr.e32.e_ident[EI_DATA]) == NULL))
{
free (phdrs);
return DWFL_E_LIBELF;
}
if (class32)
{
Elf32_Phdr (*p32)[phnum] = phdrs;
for (uint_fast16_t i = 0; i < phnum; ++i)
if ((*p32)[i].p_type == PT_INTERP)
{
undo_interp = (*p32)[i].p_vaddr;
break;
}
}
else
{
Elf64_Phdr (*p64)[phnum] = phdrs;
for (uint_fast16_t i = 0; i < phnum; ++i)
if ((*p64)[i].p_type == PT_INTERP)
{
undo_interp = (*p64)[i].p_vaddr;
break;
}
}
free (phdrs);
}
if (unlikely ((main_interp == 0) != (undo_interp == 0)))
return DWFL_E_BAD_PRELINK;
src.d_buf += src.d_size;
src.d_type = ELF_T_SHDR;
src.d_size = gelf_fsize (mod->main.elf, ELF_T_SHDR, shnum, EV_CURRENT);
size_t shdr_size = class32 ? sizeof (Elf32_Shdr) : sizeof (Elf64_Shdr);
if (unlikely (shnum > SIZE_MAX / shdr_size))
return DWFL_E_NOMEM;
const size_t shdrs_bytes = shnum * shdr_size;
void *shdrs = malloc (shdrs_bytes);
if (unlikely (shdrs == NULL))
return DWFL_E_NOMEM;
dst.d_buf = shdrs;
dst.d_size = shdrs_bytes;
if (unlikely (gelf_xlatetom (mod->main.elf, &dst, &src,
ehdr.e32.e_ident[EI_DATA]) == NULL))
{
free (shdrs);
return DWFL_E_LIBELF;
}
/* Now we can look at the original section headers of the main file
before it was prelinked. First we'll apply our method to the main
file sections as they are after prelinking, to calculate the
synchronization address of the main file. Then we'll apply that
same method to the saved section headers, to calculate the matching
synchronization address of the debug file.
The method is to consider SHF_ALLOC sections that are either
SHT_PROGBITS or SHT_NOBITS, excluding the section whose sh_addr
matches the PT_INTERP p_vaddr. The special sections that can be
moved by prelink have other types, except for .interp (which
becomes PT_INTERP). The "real" sections cannot move as such, but
.bss can be split into .dynbss and .bss, with the total memory
image remaining the same but being spread across the two sections.
So we consider the highest section end, which still matches up. */
GElf_Addr highest;
highest = 0;
scn = NULL;
while ((scn = elf_nextscn (mod->main.elf, scn)) != NULL)
{
GElf_Shdr sh_mem;
GElf_Shdr *sh = gelf_getshdr (scn, &sh_mem);
if (unlikely (sh == NULL))
{
free (shdrs);
return DWFL_E_LIBELF;
}
consider_shdr (main_interp, sh->sh_type, sh->sh_flags,
sh->sh_addr, sh->sh_size, &highest);
}
if (highest > mod->main.vaddr)
{
mod->main.address_sync = highest;
highest = 0;
if (class32)
{
Elf32_Shdr (*s32)[shnum] = shdrs;
for (size_t i = 0; i < shnum; ++i)
consider_shdr (undo_interp, (*s32)[i].sh_type,
(*s32)[i].sh_flags, (*s32)[i].sh_addr,
(*s32)[i].sh_size, &highest);
}
else
{
Elf64_Shdr (*s64)[shnum] = shdrs;
for (size_t i = 0; i < shnum; ++i)
consider_shdr (undo_interp, (*s64)[i].sh_type,
(*s64)[i].sh_flags, (*s64)[i].sh_addr,
(*s64)[i].sh_size, &highest);
}
if (highest > file->vaddr)
file->address_sync = highest;
else
{
free (shdrs);
return DWFL_E_BAD_PRELINK;
}
}
free (shdrs);
return DWFL_E_NOERROR;
}
/* Find the separate debuginfo file for this module and open libelf on it.
When we return success, MOD->debug is set up. */
static Dwfl_Error
find_debuginfo (Dwfl_Module *mod)
{
if (mod->debug.elf != NULL)
return DWFL_E_NOERROR;
GElf_Word debuglink_crc = 0;
const char *debuglink_file;
debuglink_file = INTUSE(dwelf_elf_gnu_debuglink) (mod->main.elf,
&debuglink_crc);
mod->debug.fd = (*mod->dwfl->callbacks->find_debuginfo) (MODCB_ARGS (mod),
mod->main.name,
debuglink_file,
debuglink_crc,
&mod->debug.name);
Dwfl_Error result = open_elf (mod, &mod->debug);
if (result == DWFL_E_NOERROR && mod->debug.address_sync != 0)
result = find_prelink_address_sync (mod, &mod->debug);
return result;
}
/* Try to find the alternative debug link for the given DWARF and set
it if found. Only called when mod->dw is already setup but still
might need an alternative (dwz multi) debug file. filename is either
the main or debug name from which the Dwarf was created. */
static void
find_debug_altlink (Dwfl_Module *mod, const char *filename)
{
assert (mod->dw != NULL);
const char *altname;
const void *build_id;
ssize_t build_id_len = INTUSE(dwelf_dwarf_gnu_debugaltlink) (mod->dw,
&altname,
&build_id);
if (build_id_len > 0)
{
/* We could store altfile in the module, but don't really need it. */
char *altfile = NULL;
mod->alt_fd = (*mod->dwfl->callbacks->find_debuginfo) (MODCB_ARGS (mod),
filename,
altname,
0,
&altfile);
/* The (internal) callbacks might just set mod->alt_elf directly
because they open the Elf anyway for sanity checking.
Otherwise open either the given file name or use the fd
returned. */
Dwfl_Error error = open_elf_file (&mod->alt_elf, &mod->alt_fd,
&altfile);
if (error == DWFL_E_NOERROR)
{
mod->alt = INTUSE(dwarf_begin_elf) (mod->alt_elf,
DWARF_C_READ, NULL);
if (mod->alt == NULL)
{
elf_end (mod->alt_elf);
mod->alt_elf = NULL;
close (mod->alt_fd);
mod->alt_fd = -1;
}
else
dwarf_setalt (mod->dw, mod->alt);
}
free (altfile); /* See above, we don't really need it. */
}
}
/* Try to find a symbol table in FILE.
Returns DWFL_E_NOERROR if a proper one is found.
Returns DWFL_E_NO_SYMTAB if not, but still sets results for SHT_DYNSYM. */
static Dwfl_Error
load_symtab (struct dwfl_file *file, struct dwfl_file **symfile,
Elf_Scn **symscn, Elf_Scn **xndxscn,
size_t *syments, int *first_global, GElf_Word *strshndx)
{
bool symtab = false;
Elf_Scn *scn = NULL;
while ((scn = elf_nextscn (file->elf, scn)) != NULL)
{
GElf_Shdr shdr_mem, *shdr = gelf_getshdr (scn, &shdr_mem);
if (shdr != NULL)
switch (shdr->sh_type)
{
case SHT_SYMTAB:
if (shdr->sh_entsize == 0)
break;
symtab = true;
*symscn = scn;
*symfile = file;
*strshndx = shdr->sh_link;
*syments = shdr->sh_size / shdr->sh_entsize;
*first_global = shdr->sh_info;
if (*xndxscn != NULL)
return DWFL_E_NOERROR;
break;
case SHT_DYNSYM:
if (symtab)
break;
/* Use this if need be, but keep looking for SHT_SYMTAB. */
if (shdr->sh_entsize == 0)
break;
*symscn = scn;
*symfile = file;
*strshndx = shdr->sh_link;
*syments = shdr->sh_size / shdr->sh_entsize;
*first_global = shdr->sh_info;
break;
case SHT_SYMTAB_SHNDX:
*xndxscn = scn;
if (symtab)
return DWFL_E_NOERROR;
break;
default:
break;
}
}
if (symtab)
/* We found one, though no SHT_SYMTAB_SHNDX to go with it. */
return DWFL_E_NOERROR;
/* We found no SHT_SYMTAB, so any SHT_SYMTAB_SHNDX was bogus.
We might have found an SHT_DYNSYM and set *SYMSCN et al though. */
*xndxscn = NULL;
return DWFL_E_NO_SYMTAB;
}
/* Translate addresses into file offsets.
OFFS[*] start out zero and remain zero if unresolved. */
static void
find_offsets (Elf *elf, GElf_Addr main_bias, size_t phnum, size_t n,
GElf_Addr addrs[n], GElf_Off offs[n])
{
size_t unsolved = n;
for (size_t i = 0; i < phnum; ++i)
{
GElf_Phdr phdr_mem;
GElf_Phdr *phdr = gelf_getphdr (elf, i, &phdr_mem);
if (phdr != NULL && phdr->p_type == PT_LOAD && phdr->p_memsz > 0)
for (size_t j = 0; j < n; ++j)
if (offs[j] == 0
&& addrs[j] >= phdr->p_vaddr + main_bias
&& addrs[j] - (phdr->p_vaddr + main_bias) < phdr->p_filesz)
{
offs[j] = addrs[j] - (phdr->p_vaddr + main_bias) + phdr->p_offset;
if (--unsolved == 0)
break;
}
}
}
/* Various addresses we might want to pull from the dynamic segment. */
enum
{
i_symtab,
i_strtab,
i_hash,
i_gnu_hash,
i_max
};
/* Translate pointers into file offsets. ADJUST is either zero
in case the dynamic segment wasn't adjusted or mod->main_bias.
Will set mod->symfile if the translated offsets can be used as
symbol table. */
static void
translate_offs (GElf_Addr adjust,
Dwfl_Module *mod, size_t phnum,
GElf_Addr addrs[i_max], GElf_Xword strsz,
GElf_Ehdr *ehdr)
{
GElf_Off offs[i_max] = { 0, };
find_offsets (mod->main.elf, adjust, phnum, i_max, addrs, offs);
/* Figure out the size of the symbol table. */
if (offs[i_hash] != 0)
{
/* In the original format, .hash says the size of .dynsym. */
size_t entsz = SH_ENTSIZE_HASH (ehdr);
Elf_Data *data = elf_getdata_rawchunk (mod->main.elf,
offs[i_hash] + entsz, entsz,
(entsz == 4
? ELF_T_WORD : ELF_T_XWORD));
if (data != NULL)
mod->syments = (entsz == 4
? *(const GElf_Word *) data->d_buf
: *(const GElf_Xword *) data->d_buf);
}
if (offs[i_gnu_hash] != 0 && mod->syments == 0)
{
/* In the new format, we can derive it with some work. */
const struct
{
Elf32_Word nbuckets;
Elf32_Word symndx;
Elf32_Word maskwords;
Elf32_Word shift2;
} *header;
Elf_Data *data = elf_getdata_rawchunk (mod->main.elf, offs[i_gnu_hash],
sizeof *header, ELF_T_WORD);
if (data != NULL)
{
header = data->d_buf;
Elf32_Word nbuckets = header->nbuckets;
Elf32_Word symndx = header->symndx;
GElf_Off buckets_at = (offs[i_gnu_hash] + sizeof *header
+ (gelf_getclass (mod->main.elf)
* sizeof (Elf32_Word)
* header->maskwords));
// elf_getdata_rawchunk takes a size_t, make sure it
// doesn't overflow.
#if SIZE_MAX <= UINT32_MAX
if (nbuckets > SIZE_MAX / sizeof (Elf32_Word))
data = NULL;
else
#endif
data = elf_getdata_rawchunk (mod->main.elf, buckets_at,
nbuckets * sizeof (Elf32_Word),
ELF_T_WORD);
if (data != NULL && symndx < nbuckets)
{
const Elf32_Word *const buckets = data->d_buf;
Elf32_Word maxndx = symndx;
for (Elf32_Word bucket = 0; bucket < nbuckets; ++bucket)
if (buckets[bucket] > maxndx)
maxndx = buckets[bucket];
GElf_Off hasharr_at = (buckets_at
+ nbuckets * sizeof (Elf32_Word));
hasharr_at += (maxndx - symndx) * sizeof (Elf32_Word);
do
{
data = elf_getdata_rawchunk (mod->main.elf,
hasharr_at,
sizeof (Elf32_Word),
ELF_T_WORD);
if (data != NULL
&& (*(const Elf32_Word *) data->d_buf & 1u))
{
mod->syments = maxndx + 1;
break;
}
++maxndx;
hasharr_at += sizeof (Elf32_Word);
}
while (data != NULL);
}
}
}
if (offs[i_strtab] > offs[i_symtab] && mod->syments == 0)
mod->syments = ((offs[i_strtab] - offs[i_symtab])
/ gelf_fsize (mod->main.elf,
ELF_T_SYM, 1, EV_CURRENT));
if (mod->syments > 0)
{
mod->symdata = elf_getdata_rawchunk (mod->main.elf,
offs[i_symtab],
gelf_fsize (mod->main.elf,
ELF_T_SYM,
mod->syments,
EV_CURRENT),
ELF_T_SYM);
if (mod->symdata != NULL)
{
mod->symstrdata = elf_getdata_rawchunk (mod->main.elf,
offs[i_strtab],
strsz,
ELF_T_BYTE);
if (mod->symstrdata == NULL)
mod->symdata = NULL;
}
if (mod->symdata == NULL)
mod->symerr = DWFL_E (LIBELF, elf_errno ());
else
{
mod->symfile = &mod->main;
mod->symerr = DWFL_E_NOERROR;
}
}
}
/* Try to find a dynamic symbol table via phdrs. */
static void
find_dynsym (Dwfl_Module *mod)
{
GElf_Ehdr ehdr_mem;
GElf_Ehdr *ehdr = gelf_getehdr (mod->main.elf, &ehdr_mem);
size_t phnum;
if (unlikely (elf_getphdrnum (mod->main.elf, &phnum) != 0))
return;
for (size_t i = 0; i < phnum; ++i)
{
GElf_Phdr phdr_mem;
GElf_Phdr *phdr = gelf_getphdr (mod->main.elf, i, &phdr_mem);
if (phdr == NULL)
break;
if (phdr->p_type == PT_DYNAMIC)
{
/* Examine the dynamic section for the pointers we need. */
Elf_Data *data = elf_getdata_rawchunk (mod->main.elf,
phdr->p_offset, phdr->p_filesz,
ELF_T_DYN);
if (data == NULL)
continue;
GElf_Addr addrs[i_max] = { 0, };
GElf_Xword strsz = 0;
size_t n = data->d_size / gelf_fsize (mod->main.elf,
ELF_T_DYN, 1, EV_CURRENT);
for (size_t j = 0; j < n; ++j)
{
GElf_Dyn dyn_mem;
GElf_Dyn *dyn = gelf_getdyn (data, j, &dyn_mem);
if (dyn != NULL)
switch (dyn->d_tag)
{
case DT_SYMTAB:
addrs[i_symtab] = dyn->d_un.d_ptr;
continue;
case DT_HASH:
addrs[i_hash] = dyn->d_un.d_ptr;
continue;
case DT_GNU_HASH:
addrs[i_gnu_hash] = dyn->d_un.d_ptr;
continue;
case DT_STRTAB:
addrs[i_strtab] = dyn->d_un.d_ptr;
continue;
case DT_STRSZ:
strsz = dyn->d_un.d_val;
continue;
default:
continue;
case DT_NULL:
break;
}
break;
}
/* First try unadjusted, like ELF files from disk, vdso.
Then try for already adjusted dynamic section, like ELF
from remote memory. */
translate_offs (0, mod, phnum, addrs, strsz, ehdr);
if (mod->symfile == NULL)
translate_offs (mod->main_bias, mod, phnum, addrs, strsz, ehdr);
return;
}
}
}
#if USE_LZMA
/* Try to find the offset between the main file and .gnu_debugdata. */
static bool
find_aux_address_sync (Dwfl_Module *mod)
{
/* Don't trust the phdrs in the minisymtab elf file to be setup correctly.
The address_sync is equal to the main file it is embedded in at first. */
mod->aux_sym.address_sync = mod->main.address_sync;
/* Adjust address_sync for the difference in entry addresses, attempting to
account for ELF relocation changes after aux was split. */
GElf_Ehdr ehdr_main, ehdr_aux;
if (unlikely (gelf_getehdr (mod->main.elf, &ehdr_main) == NULL)
|| unlikely (gelf_getehdr (mod->aux_sym.elf, &ehdr_aux) == NULL))
return false;
mod->aux_sym.address_sync += ehdr_aux.e_entry - ehdr_main.e_entry;
/* The shdrs are setup OK to make find_prelink_address_sync () do the right
thing, which is possibly more reliable, but it needs .gnu.prelink_undo. */
if (mod->aux_sym.address_sync != 0)
return find_prelink_address_sync (mod, &mod->aux_sym) == DWFL_E_NOERROR;
return true;
}
#endif
/* Try to find the auxiliary symbol table embedded in the main elf file
section .gnu_debugdata. Only matters if the symbol information comes
from the main file dynsym. No harm done if not found. */
static void
find_aux_sym (Dwfl_Module *mod __attribute__ ((unused)),
Elf_Scn **aux_symscn __attribute__ ((unused)),
Elf_Scn **aux_xndxscn __attribute__ ((unused)),
GElf_Word *aux_strshndx __attribute__ ((unused)))
{
/* Since a .gnu_debugdata section is compressed using lzma don't do
anything unless we have support for that. */
#if USE_LZMA
Elf *elf = mod->main.elf;
size_t shstrndx;
if (elf_getshdrstrndx (elf, &shstrndx) < 0)
return;
Elf_Scn *scn = NULL;
while ((scn = elf_nextscn (elf, scn)) != NULL)
{
GElf_Shdr shdr_mem;
GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
if (shdr == NULL)
return;
const char *name = elf_strptr (elf, shstrndx, shdr->sh_name);
if (name == NULL)
return;
if (!strcmp (name, ".gnu_debugdata"))
break;
}
if (scn == NULL)
return;
/* Found the .gnu_debugdata section. Uncompress the lzma image and
turn it into an ELF image. */
Elf_Data *rawdata = elf_rawdata (scn, NULL);
if (rawdata == NULL)
return;
Dwfl_Error error;
void *buffer = NULL;
size_t size = 0;
error = __libdw_unlzma (-1, 0, rawdata->d_buf, rawdata->d_size,
&buffer, &size);
if (error == DWFL_E_NOERROR)
{
if (unlikely (size == 0))
free (buffer);
else
{
mod->aux_sym.elf = elf_memory (buffer, size);
if (mod->aux_sym.elf == NULL)
free (buffer);
else
{
mod->aux_sym.fd = -1;
mod->aux_sym.elf->flags |= ELF_F_MALLOCED;
if (open_elf (mod, &mod->aux_sym) != DWFL_E_NOERROR)
return;
if (! find_aux_address_sync (mod))
{
elf_end (mod->aux_sym.elf);
mod->aux_sym.elf = NULL;
return;
}
/* So far, so good. Get minisymtab table data and cache it. */
bool minisymtab = false;
scn = NULL;
while ((scn = elf_nextscn (mod->aux_sym.elf, scn)) != NULL)
{
GElf_Shdr shdr_mem, *shdr = gelf_getshdr (scn, &shdr_mem);
if (shdr != NULL)
switch (shdr->sh_type)
{
case SHT_SYMTAB:
if (shdr->sh_entsize == 0)
return;
minisymtab = true;
*aux_symscn = scn;
*aux_strshndx = shdr->sh_link;
mod->aux_syments = shdr->sh_size / shdr->sh_entsize;
mod->aux_first_global = shdr->sh_info;
if (*aux_xndxscn != NULL)
return;
break;
case SHT_SYMTAB_SHNDX:
*aux_xndxscn = scn;
if (minisymtab)
return;
break;
default:
break;
}
}
if (minisymtab)
/* We found one, though no SHT_SYMTAB_SHNDX to go with it. */
return;
/* We found no SHT_SYMTAB, so everything else is bogus. */
*aux_xndxscn = NULL;
*aux_strshndx = 0;
mod->aux_syments = 0;
elf_end (mod->aux_sym.elf);
mod->aux_sym.elf = NULL;
return;
}
}
}
else
free (buffer);
#endif
}
/* Try to find a symbol table in either MOD->main.elf or MOD->debug.elf. */
static void
find_symtab (Dwfl_Module *mod)
{
if (mod->symdata != NULL || mod->aux_symdata != NULL /* Already done. */
|| mod->symerr != DWFL_E_NOERROR) /* Cached previous failure. */
return;
__libdwfl_getelf (mod);
mod->symerr = mod->elferr;
if (mod->symerr != DWFL_E_NOERROR)
return;
/* First see if the main ELF file has the debugging information. */
Elf_Scn *symscn = NULL, *xndxscn = NULL;
Elf_Scn *aux_symscn = NULL, *aux_xndxscn = NULL;
GElf_Word strshndx, aux_strshndx = 0;
mod->symerr = load_symtab (&mod->main, &mod->symfile, &symscn,
&xndxscn, &mod->syments, &mod->first_global,
&strshndx);
switch (mod->symerr)
{
default:
return;
case DWFL_E_NOERROR:
break;
case DWFL_E_NO_SYMTAB:
/* Now we have to look for a separate debuginfo file. */
mod->symerr = find_debuginfo (mod);
switch (mod->symerr)
{
default:
return;
case DWFL_E_NOERROR:
mod->symerr = load_symtab (&mod->debug, &mod->symfile, &symscn,
&xndxscn, &mod->syments,
&mod->first_global, &strshndx);
break;
case DWFL_E_CB: /* The find_debuginfo hook failed. */
mod->symerr = DWFL_E_NO_SYMTAB;
break;
}
switch (mod->symerr)
{
default:
return;
case DWFL_E_NOERROR:
break;
case DWFL_E_NO_SYMTAB:
/* There might be an auxiliary table. */
find_aux_sym (mod, &aux_symscn, &aux_xndxscn, &aux_strshndx);
if (symscn != NULL)
{
/* We still have the dynamic symbol table. */
mod->symerr = DWFL_E_NOERROR;
break;
}
if (aux_symscn != NULL)
{
/* We still have the auxiliary symbol table. */
mod->symerr = DWFL_E_NOERROR;
goto aux_cache;
}
/* Last ditch, look for dynamic symbols without section headers. */
find_dynsym (mod);
return;
}
break;
}
/* This does some sanity checks on the string table section. */
if (elf_strptr (mod->symfile->elf, strshndx, 0) == NULL)
{
elferr:
mod->symdata = NULL;
mod->syments = 0;
mod->first_global = 0;
mod->symerr = DWFL_E (LIBELF, elf_errno ());
goto aux_cleanup; /* This cleans up some more and tries find_dynsym. */
}
/* Cache the data; MOD->syments and MOD->first_global were set
above. If any of the sections is compressed, uncompress it
first. Only the string data setion could theoretically be
compressed GNU style (as .zdebug_str). Everything else only ELF
gabi style (SHF_COMPRESSED). */
Elf_Scn *symstrscn = elf_getscn (mod->symfile->elf, strshndx);
if (symstrscn == NULL)
goto elferr;
GElf_Shdr shdr_mem;
GElf_Shdr *shdr = gelf_getshdr (symstrscn, &shdr_mem);
if (shdr == NULL)
goto elferr;
size_t shstrndx;
if (elf_getshdrstrndx (mod->symfile->elf, &shstrndx) < 0)
goto elferr;
const char *sname = elf_strptr (mod->symfile->elf, shstrndx, shdr->sh_name);
if (sname == NULL)
goto elferr;
if (strncmp (sname, ".zdebug", strlen (".zdebug")) == 0)
/* Try to uncompress, but it might already have been, an error
might just indicate, already uncompressed. */
elf_compress_gnu (symstrscn, 0, 0);
if ((shdr->sh_flags & SHF_COMPRESSED) != 0)
if (elf_compress (symstrscn, 0, 0) < 0)
goto elferr;
mod->symstrdata = elf_getdata (symstrscn, NULL);
if (mod->symstrdata == NULL || mod->symstrdata->d_buf == NULL)
goto elferr;
if (xndxscn == NULL)
mod->symxndxdata = NULL;
else
{
shdr = gelf_getshdr (xndxscn, &shdr_mem);
if (shdr == NULL)
goto elferr;
if ((shdr->sh_flags & SHF_COMPRESSED) != 0)
if (elf_compress (xndxscn, 0, 0) < 0)
goto elferr;
mod->symxndxdata = elf_getdata (xndxscn, NULL);
if (mod->symxndxdata == NULL || mod->symxndxdata->d_buf == NULL)
goto elferr;
}
shdr = gelf_getshdr (symscn, &shdr_mem);
if (shdr == NULL)
goto elferr;
if ((shdr->sh_flags & SHF_COMPRESSED) != 0)
if (elf_compress (symscn, 0, 0) < 0)
goto elferr;
mod->symdata = elf_getdata (symscn, NULL);
if (mod->symdata == NULL || mod->symdata->d_buf == NULL)
goto elferr;
// Sanity check number of symbols.
shdr = gelf_getshdr (symscn, &shdr_mem);
if (shdr == NULL || shdr->sh_entsize == 0
|| mod->syments > mod->symdata->d_size / shdr->sh_entsize
|| (size_t) mod->first_global > mod->syments)
goto elferr;
/* Cache any auxiliary symbol info, when it fails, just ignore aux_sym. */
if (aux_symscn != NULL)
{
aux_cache:
/* This does some sanity checks on the string table section. */
if (elf_strptr (mod->aux_sym.elf, aux_strshndx, 0) == NULL)
{
aux_cleanup:
mod->aux_syments = 0;
elf_end (mod->aux_sym.elf);
mod->aux_sym.elf = NULL;
/* We thought we had something through shdrs, but it failed...
Last ditch, look for dynamic symbols without section headers. */
find_dynsym (mod);
return;
}
Elf_Scn *aux_strscn = elf_getscn (mod->aux_sym.elf, aux_strshndx);
if (aux_strscn == NULL)
goto elferr;
shdr = gelf_getshdr (aux_strscn, &shdr_mem);
if (shdr == NULL)
goto elferr;
size_t aux_shstrndx;
if (elf_getshdrstrndx (mod->aux_sym.elf, &aux_shstrndx) < 0)
goto elferr;
sname = elf_strptr (mod->aux_sym.elf, aux_shstrndx,
shdr->sh_name);
if (sname == NULL)
goto elferr;
if (strncmp (sname, ".zdebug", strlen (".zdebug")) == 0)
/* Try to uncompress, but it might already have been, an error
might just indicate, already uncompressed. */
elf_compress_gnu (aux_strscn, 0, 0);
if ((shdr->sh_flags & SHF_COMPRESSED) != 0)
if (elf_compress (aux_strscn, 0, 0) < 0)
goto elferr;
mod->aux_symstrdata = elf_getdata (aux_strscn, NULL);
if (mod->aux_symstrdata == NULL || mod->aux_symstrdata->d_buf == NULL)
goto aux_cleanup;
if (aux_xndxscn == NULL)
mod->aux_symxndxdata = NULL;
else
{
shdr = gelf_getshdr (aux_xndxscn, &shdr_mem);
if (shdr == NULL)
goto elferr;
if ((shdr->sh_flags & SHF_COMPRESSED) != 0)
if (elf_compress (aux_xndxscn, 0, 0) < 0)
goto elferr;
mod->aux_symxndxdata = elf_getdata (aux_xndxscn, NULL);
if (mod->aux_symxndxdata == NULL
|| mod->aux_symxndxdata->d_buf == NULL)
goto aux_cleanup;
}
shdr = gelf_getshdr (aux_symscn, &shdr_mem);
if (shdr == NULL)
goto elferr;
if ((shdr->sh_flags & SHF_COMPRESSED) != 0)
if (elf_compress (aux_symscn, 0, 0) < 0)
goto elferr;
mod->aux_symdata = elf_getdata (aux_symscn, NULL);
if (mod->aux_symdata == NULL || mod->aux_symdata->d_buf == NULL)
goto aux_cleanup;
// Sanity check number of aux symbols.
shdr = gelf_getshdr (aux_symscn, &shdr_mem);
if (mod->aux_syments > mod->aux_symdata->d_size / shdr->sh_entsize
|| (size_t) mod->aux_first_global > mod->aux_syments)
goto aux_cleanup;
}
}
/* Try to open a libebl backend for MOD. */
Dwfl_Error
internal_function
__libdwfl_module_getebl (Dwfl_Module *mod)
{
if (mod->ebl == NULL)
{
__libdwfl_getelf (mod);
if (mod->elferr != DWFL_E_NOERROR)
return mod->elferr;
mod->ebl = ebl_openbackend (mod->main.elf);
if (mod->ebl == NULL)
return DWFL_E_LIBEBL;
}
return DWFL_E_NOERROR;
}
/* Try to start up libdw on DEBUGFILE. */
static Dwfl_Error
load_dw (Dwfl_Module *mod, struct dwfl_file *debugfile)
{
if (mod->e_type == ET_REL && !debugfile->relocated)
{
const Dwfl_Callbacks *const cb = mod->dwfl->callbacks;
/* The debugging sections have to be relocated. */
if (cb->section_address == NULL)
return DWFL_E_NOREL;
Dwfl_Error error = __libdwfl_module_getebl (mod);
if (error != DWFL_E_NOERROR)
return error;
find_symtab (mod);
Dwfl_Error result = mod->symerr;
if (result == DWFL_E_NOERROR)
result = __libdwfl_relocate (mod, debugfile->elf, true);
if (result != DWFL_E_NOERROR)
return result;
}
mod->dw = INTUSE(dwarf_begin_elf) (debugfile->elf, DWARF_C_READ, NULL);
if (mod->dw == NULL)
{
int err = INTUSE(dwarf_errno) ();
return err == DWARF_E_NO_DWARF ? DWFL_E_NO_DWARF : DWFL_E (LIBDW, err);
}
/* Do this after dwarf_begin_elf has a chance to process the fd. */
if (mod->e_type == ET_REL && !debugfile->relocated)
{
/* Don't keep the file descriptors around. */
if (mod->main.fd != -1 && elf_cntl (mod->main.elf, ELF_C_FDREAD) == 0)
{
close (mod->main.fd);
mod->main.fd = -1;
}
if (debugfile->fd != -1 && elf_cntl (debugfile->elf, ELF_C_FDREAD) == 0)
{
close (debugfile->fd);
debugfile->fd = -1;
}
}
/* We might have already closed the fd when we asked dwarf_begin_elf to
create an Dwarf. Help out a little in case we need to find an alt or
dwo file later. */
if (mod->dw->debugdir == NULL && mod->elfdir != NULL
&& debugfile == &mod->main)
mod->dw->debugdir = strdup (mod->elfdir);
/* Until we have iterated through all CU's, we might do lazy lookups. */
mod->lazycu = 1;
return DWFL_E_NOERROR;
}
/* Try to start up libdw on either the main file or the debuginfo file. */
static void
find_dw (Dwfl_Module *mod)
{
if (mod->dw != NULL /* Already done. */
|| mod->dwerr != DWFL_E_NOERROR) /* Cached previous failure. */
return;
__libdwfl_getelf (mod);
mod->dwerr = mod->elferr;
if (mod->dwerr != DWFL_E_NOERROR)
return;
/* First see if the main ELF file has the debugging information. */
mod->dwerr = load_dw (mod, &mod->main);
switch (mod->dwerr)
{
case DWFL_E_NOERROR:
mod->debug.elf = mod->main.elf;
mod->debug.address_sync = mod->main.address_sync;
/* The Dwarf might need an alt debug file, find that now after
everything about the debug file has been setup (the
find_debuginfo callback might need it). */
find_debug_altlink (mod, mod->main.name);
return;
case DWFL_E_NO_DWARF:
break;
default:
goto canonicalize;
}
/* Now we have to look for a separate debuginfo file. */
mod->dwerr = find_debuginfo (mod);
switch (mod->dwerr)
{
case DWFL_E_NOERROR:
mod->dwerr = load_dw (mod, &mod->debug);
if (mod->dwerr == DWFL_E_NOERROR)
{
/* The Dwarf might need an alt debug file, find that now after
everything about the debug file has been setup (the
find_debuginfo callback might need it). */
find_debug_altlink (mod, mod->debug.name);
return;
}
break;
case DWFL_E_CB: /* The find_debuginfo hook failed. */
mod->dwerr = DWFL_E_NO_DWARF;
return;
default:
break;
}
canonicalize:
mod->dwerr = __libdwfl_canon_error (mod->dwerr);
}
Dwarf *
dwfl_module_getdwarf (Dwfl_Module *mod, Dwarf_Addr *bias)
{
if (mod == NULL)
return NULL;
find_dw (mod);
if (mod->dwerr == DWFL_E_NOERROR)
{
/* If dwfl_module_getelf was used previously, then partial apply
relocation to miscellaneous sections in the debug file too. */
if (mod->e_type == ET_REL
&& mod->main.relocated && ! mod->debug.relocated)
{
mod->debug.relocated = true;
if (mod->debug.elf != mod->main.elf)
(void) __libdwfl_relocate (mod, mod->debug.elf, false);
}
*bias = dwfl_adjusted_dwarf_addr (mod, 0);
return mod->dw;
}
__libdwfl_seterrno (mod->dwerr);
return NULL;
}
INTDEF (dwfl_module_getdwarf)
int
dwfl_module_getsymtab (Dwfl_Module *mod)
{
if (mod == NULL)
return -1;
find_symtab (mod);
if (mod->symerr == DWFL_E_NOERROR)
/* We will skip the auxiliary zero entry if there is another one. */
return (mod->syments + mod->aux_syments
- (mod->syments > 0 && mod->aux_syments > 0 ? 1 : 0));
__libdwfl_seterrno (mod->symerr);
return -1;
}
INTDEF (dwfl_module_getsymtab)
int
dwfl_module_getsymtab_first_global (Dwfl_Module *mod)
{
if (mod == NULL)
return -1;
find_symtab (mod);
if (mod->symerr == DWFL_E_NOERROR)
{
/* All local symbols should come before all global symbols. If
we have an auxiliary table make sure all the main locals come
first, then all aux locals, then all main globals and finally all
aux globals. And skip the auxiliary table zero undefined
entry. */
int skip_aux_zero = (mod->syments > 0 && mod->aux_syments > 0) ? 1 : 0;
return mod->first_global + mod->aux_first_global - skip_aux_zero;
}
__libdwfl_seterrno (mod->symerr);
return -1;
}
INTDEF (dwfl_module_getsymtab_first_global)