diff options
Diffstat (limited to 'elf/dl-lookup.c')
| -rw-r--r-- | elf/dl-lookup.c | 129 |
1 files changed, 129 insertions, 0 deletions
diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c new file mode 100644 index 0000000..b4600b1 --- /dev/null +++ b/elf/dl-lookup.c @@ -0,0 +1,129 @@ +/* Look up a symbol in the loaded objects. +Copyright (C) 1995 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 Library General Public License as +published by the Free Software Foundation; either version 2 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 +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. If +not, write to the Free Software Foundation, Inc., 675 Mass Ave, +Cambridge, MA 02139, USA. */ + +#include <stddef.h> +#include <libelf.h> +#include <link.h> + +/* Search loaded objects' symbol tables for a definition of + the symbol UNDEF_NAME. Don't use a PLT defn in UNDEF_MAP, since + that is the object making the reference. */ + +Elf32_Addr +_dl_lookup_symbol (const char *undef_name, const Elf32_Sym **ref, + struct link_map *symbol_scope) +{ + unsigned long int hash = elf_hash (undef_name); + struct link_map *map; + struct + { + Elf32_Addr a; + const Elf32_Sym *s; + } weak_value = { 0, NULL }; + + /* Search the relevant loaded objects for a definition. */ + for (map = symbol_scope; map; map = map->l_next) + { + const Elf32_Sym *symtab; + const char *strtab; + Elf32_Word symidx; + + symtab = ((void *) map->l_addr + map->l_info[DT_SYMTAB]->d_un.d_ptr); + strtab = ((void *) map->l_addr + map->l_info[DT_STRTAB]->d_un.d_ptr); + + /* Search the appropriate hash bucket in this object's symbol table + for a definition for the same symbol name. */ + for (symidx = map->l_buckets[hash % map->l_nbuckets]; + symidx != STN_UNDEF; + symidx = map->l_chain[symidx]) + { + const Elf32_Sym *sym = &symtab[symidx]; + + if (sym->st_value == 0) + continue; + + switch (ELF32_ST_TYPE (sym->st_info)) + { + case STT_NOTYPE: + case STT_FUNC: + case STT_OBJECT: + break; + default: + /* Not a code/data definition. */ + continue; + } + + if (sym == *ref) + /* This is the same symbol we are looking for the value for. + If it is a PLT entry, it will have a value of its own; + but that is not what we are looking for. */ + continue; + + if (strcmp (strtab + sym->st_name, undef_name)) + /* Not the symbol we are looking for. */ + continue; + + switch (ELF32_ST_BIND (sym->st_info)) + { + case STB_GLOBAL: + /* Global definition. Just what we need. */ + *ref = sym; + return map->l_addr; + case STB_WEAK: + /* Weak definition. Use this value if we don't find another. */ + if (weak_value.a == 0) + { + weak_value.s = sym; + weak_value.a = map->l_addr; + } + break; + default: + /* Local symbols are ignored. */ + break; + } + } + } + + if (weak_value.s == NULL) + { + const char msg[] = "undefined symbol: "; + char buf[sizeof msg + strlen (undef_name)]; + memcpy (buf, msg, sizeof msg - 1); + memcpy (&buf[sizeof msg - 1], undef_name, sizeof buf - sizeof msg); + _dl_signal_error (0, msg); + } + + *ref = weak_value.s; + return weak_value.a; +} + + +/* Cache the location of MAP's hash table. */ + +void +_dl_setup_hash (struct link_map *map) +{ + Elf32_Word *hash = (void *) map->l_addr + map->l_info[DT_HASH]->d_un.d_ptr; + Elf32_Word nchain; + map->l_nbuckets = *hash++; + nchain = *hash++; + map->l_buckets = hash; + hash += map->l_nbuckets; + map->l_chain = hash; +} |