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/* Locate the shared object symbol nearest a given address.
Copyright (C) 1996-2022 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <dlfcn.h>
#include <stddef.h>
#include <ldsodefs.h>
static inline void
__attribute ((always_inline))
determine_info (const ElfW(Addr) addr, struct link_map *match, Dl_info *info,
struct link_map **mapp, const ElfW(Sym) **symbolp)
{
/* Now we know what object the address lies in. */
info->dli_fname = match->l_name;
info->dli_fbase = (void *) match->l_map_start;
/* If this is the main program the information is incomplete. */
if (__builtin_expect (match->l_name[0], 'a') == '\0'
&& match->l_type == lt_executable)
info->dli_fname = _dl_argv[0];
const ElfW(Sym) *symtab
= (const ElfW(Sym) *) D_PTR (match, l_info[DT_SYMTAB]);
const char *strtab = (const char *) D_PTR (match, l_info[DT_STRTAB]);
ElfW(Word) strtabsize = match->l_info[DT_STRSZ]->d_un.d_val;
const ElfW(Sym) *matchsym = NULL;
if (match->l_info[ELF_MACHINE_GNU_HASH_ADDRIDX] != NULL)
{
/* We look at all symbol table entries referenced by the hash
table. */
for (Elf_Symndx bucket = 0; bucket < match->l_nbuckets; ++bucket)
{
Elf32_Word symndx = match->l_gnu_buckets[bucket];
if (symndx != 0)
{
const Elf32_Word *hasharr = &match->l_gnu_chain_zero[symndx];
do
{
/* The hash table never references local symbols so
we can omit that test here. */
symndx = ELF_MACHINE_HASH_SYMIDX (match, hasharr);
if ((symtab[symndx].st_shndx != SHN_UNDEF
|| symtab[symndx].st_value != 0)
&& symtab[symndx].st_shndx != SHN_ABS
&& ELFW(ST_TYPE) (symtab[symndx].st_info) != STT_TLS
&& DL_ADDR_SYM_MATCH (match, &symtab[symndx],
matchsym, addr)
&& symtab[symndx].st_name < strtabsize)
matchsym = (ElfW(Sym) *) &symtab[symndx];
}
while ((*hasharr++ & 1u) == 0);
}
}
}
else
{
const ElfW(Sym) *symtabend;
if (match->l_info[DT_HASH] != NULL)
symtabend = (symtab
+ ((Elf_Symndx *) D_PTR (match, l_info[DT_HASH]))[1]);
else
/* There is no direct way to determine the number of symbols in the
dynamic symbol table and no hash table is present. The ELF
binary is ill-formed but what shall we do? Use the beginning of
the string table which generally follows the symbol table. */
symtabend = (const ElfW(Sym) *) strtab;
for (; (void *) symtab < (void *) symtabend; ++symtab)
if ((ELFW(ST_BIND) (symtab->st_info) == STB_GLOBAL
|| ELFW(ST_BIND) (symtab->st_info) == STB_WEAK)
&& __glibc_likely (!dl_symbol_visibility_binds_local_p (symtab))
&& ELFW(ST_TYPE) (symtab->st_info) != STT_TLS
&& (symtab->st_shndx != SHN_UNDEF
|| symtab->st_value != 0)
&& symtab->st_shndx != SHN_ABS
&& DL_ADDR_SYM_MATCH (match, symtab, matchsym, addr)
&& symtab->st_name < strtabsize)
matchsym = (ElfW(Sym) *) symtab;
}
if (mapp)
*mapp = match;
if (symbolp)
*symbolp = matchsym;
if (matchsym)
{
/* We found a symbol close by. Fill in its name and exact
address. */
lookup_t matchl = LOOKUP_VALUE (match);
info->dli_sname = strtab + matchsym->st_name;
info->dli_saddr = DL_SYMBOL_ADDRESS (matchl, matchsym);
}
else
{
/* No symbol matches. We return only the containing object. */
info->dli_sname = NULL;
info->dli_saddr = NULL;
}
}
int
_dl_addr (const void *address, Dl_info *info,
struct link_map **mapp, const ElfW(Sym) **symbolp)
{
const ElfW(Addr) addr = DL_LOOKUP_ADDRESS (address);
int result = 0;
/* Protect against concurrent loads and unloads. */
__rtld_lock_lock_recursive (GL(dl_load_lock));
struct link_map *l = _dl_find_dso_for_object (addr);
if (l)
{
determine_info (addr, l, info, mapp, symbolp);
result = 1;
}
__rtld_lock_unlock_recursive (GL(dl_load_lock));
return result;
}
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