117 lines
4.2 KiB
C
117 lines
4.2 KiB
C
/* Look up a symbol in a single specified object.
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Copyright (C) 1995-2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <ldsodefs.h>
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#include <string.h>
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#include <elf_machine_sym_no_match.h>
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#include <dl-hash.h>
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/* This function corresponds to do_lookup_x in elf/dl-lookup.c. The
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variant here is simplified because it requires symbol
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versioning. */
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static const ElfW(Sym) *
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check_match (const struct link_map *const map, const char *const undef_name,
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const char *version, uint32_t version_hash,
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const Elf_Symndx symidx)
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{
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const ElfW(Sym) *symtab = (const void *) D_PTR (map, l_info[DT_SYMTAB]);
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const ElfW(Sym) *sym = &symtab[symidx];
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unsigned int stt = ELFW(ST_TYPE) (sym->st_info);
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if (__glibc_unlikely ((sym->st_value == 0 /* No value. */
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&& sym->st_shndx != SHN_ABS
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&& stt != STT_TLS)
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|| elf_machine_sym_no_match (sym)))
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return NULL;
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/* Ignore all but STT_NOTYPE, STT_OBJECT, STT_FUNC,
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STT_COMMON, STT_TLS, and STT_GNU_IFUNC since these are no
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code/data definitions. */
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#define ALLOWED_STT \
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((1 << STT_NOTYPE) | (1 << STT_OBJECT) | (1 << STT_FUNC) \
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| (1 << STT_COMMON) | (1 << STT_TLS) | (1 << STT_GNU_IFUNC))
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if (__glibc_unlikely (((1 << stt) & ALLOWED_STT) == 0))
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return NULL;
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const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
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if (strcmp (strtab + sym->st_name, undef_name) != 0)
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/* Not the symbol we are looking for. */
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return NULL;
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ElfW(Half) ndx = map->l_versyms[symidx] & 0x7fff;
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if (map->l_versions[ndx].hash != version_hash
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|| strcmp (map->l_versions[ndx].name, version) != 0)
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/* It's not the version we want. */
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return NULL;
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return sym;
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}
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/* This function corresponds to do_lookup_x in elf/dl-lookup.c. The
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variant here is simplified because it does not search object
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dependencies. It is optimized for a successful lookup. */
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const ElfW(Sym) *
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_dl_lookup_direct (struct link_map *map,
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const char *undef_name, uint32_t new_hash,
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const char *version, uint32_t version_hash)
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{
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const ElfW(Addr) *bitmask = map->l_gnu_bitmask;
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if (__glibc_likely (bitmask != NULL))
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{
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Elf32_Word bucket = map->l_gnu_buckets[new_hash % map->l_nbuckets];
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if (bucket != 0)
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{
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const Elf32_Word *hasharr = &map->l_gnu_chain_zero[bucket];
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do
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if (((*hasharr ^ new_hash) >> 1) == 0)
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{
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Elf_Symndx symidx = ELF_MACHINE_HASH_SYMIDX (map, hasharr);
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const ElfW(Sym) *sym = check_match (map, undef_name,
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version, version_hash,
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symidx);
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if (sym != NULL)
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return sym;
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}
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while ((*hasharr++ & 1u) == 0);
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}
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}
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else
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{
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/* Fallback code for lack of GNU_HASH support. */
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uint32_t old_hash = _dl_elf_hash (undef_name);
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/* Use the old SysV-style hash table. Search the appropriate
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hash bucket in this object's symbol table for a definition
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for the same symbol name. */
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for (Elf_Symndx symidx = map->l_buckets[old_hash % map->l_nbuckets];
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symidx != STN_UNDEF;
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symidx = map->l_chain[symidx])
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{
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const ElfW(Sym) *sym = check_match (map, undef_name,
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version, version_hash, symidx);
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if (sym != NULL)
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return sym;
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}
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}
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return NULL;
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}
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