/* Look up a symbol in the loaded objects. Copyright (C) 1995-2004, 2005, 2006 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, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. */ /* Inner part of the lookup functions. We return a value > 0 if we found the symbol, the value 0 if nothing is found and < 0 if something bad happened. */ static int __attribute_noinline__ do_lookup_x (const char *undef_name, uint_fast32_t new_hash, unsigned long int *old_hash, const ElfW(Sym) *ref, struct sym_val *result, struct r_scope_elem *scope, size_t i, const struct r_found_version *const version, int flags, struct link_map *skip, int type_class) { struct link_map **list = scope->r_list; size_t n = scope->r_nlist; do { /* These variables are used in the nested function. */ Elf_Symndx symidx; int num_versions = 0; const ElfW(Sym) *versioned_sym = NULL; const struct link_map *map = list[i]->l_real; /* Here come the extra test needed for `_dl_lookup_symbol_skip'. */ if (map == skip) continue; /* Don't search the executable when resolving a copy reloc. */ if ((type_class & ELF_RTYPE_CLASS_COPY) && map->l_type == lt_executable) continue; /* Do not look into objects which are going to be removed. */ if (map->l_removed) continue; /* Print some debugging info if wanted. */ if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_SYMBOLS, 0)) _dl_debug_printf ("symbol=%s; lookup in file=%s [%lu]\n", undef_name, map->l_name[0] ? map->l_name : rtld_progname, map->l_ns); /* If the hash table is empty there is nothing to do here. */ if (map->l_nbuckets == 0) continue; /* The tables for this map. */ const ElfW(Sym) *symtab = (const void *) D_PTR (map, l_info[DT_SYMTAB]); const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]); /* Nested routine to check whether the symbol matches. */ const ElfW(Sym) * __attribute_noinline__ check_match (const ElfW(Sym) *sym) { assert (ELF_RTYPE_CLASS_PLT == 1); if (__builtin_expect ((sym->st_value == 0 /* No value. */ && ELFW(ST_TYPE) (sym->st_info) != STT_TLS) || (type_class & (sym->st_shndx == SHN_UNDEF)), 0)) return NULL; if (__builtin_expect (ELFW(ST_TYPE) (sym->st_info) > STT_FUNC && ELFW(ST_TYPE) (sym->st_info) != STT_TLS, 0)) /* Ignore all but STT_NOTYPE, STT_OBJECT and STT_FUNC entries (and STT_TLS if TLS is supported) since these are no code/data definitions. */ return NULL; if (sym != ref && strcmp (strtab + sym->st_name, undef_name)) /* Not the symbol we are looking for. */ return NULL; const ElfW(Half) *verstab = map->l_versyms; if (version != NULL) { if (__builtin_expect (verstab == NULL, 0)) { /* We need a versioned symbol but haven't found any. If this is the object which is referenced in the verneed entry it is a bug in the library since a symbol must not simply disappear. It would also be a bug in the object since it means that the list of required versions is incomplete and so the tests in dl-version.c haven't found a problem.*/ assert (version->filename == NULL || ! _dl_name_match_p (version->filename, map)); /* Otherwise we accept the symbol. */ } else { /* We can match the version information or use the default one if it is not hidden. */ ElfW(Half) ndx = verstab[symidx] & 0x7fff; if ((map->l_versions[ndx].hash != version->hash || strcmp (map->l_versions[ndx].name, version->name)) && (version->hidden || map->l_versions[ndx].hash || (verstab[symidx] & 0x8000))) /* It's not the version we want. */ return NULL; } } else { /* No specific version is selected. There are two ways we can got here: - a binary which does not include versioning information is loaded - dlsym() instead of dlvsym() is used to get a symbol which might exist in more than one form If the library does not provide symbol version information there is no problem at at: we simply use the symbol if it is defined. These two lookups need to be handled differently if the library defines versions. In the case of the old unversioned application the oldest (default) version should be used. In case of a dlsym() call the latest and public interface should be returned. */ if (verstab != NULL) { if ((verstab[symidx] & 0x7fff) >= ((flags & DL_LOOKUP_RETURN_NEWEST) ? 2 : 3)) { /* Don't accept hidden symbols. */ if ((verstab[symidx] & 0x8000) == 0 && num_versions++ == 0) /* No version so far. */ versioned_sym = sym; return NULL; } } } /* There cannot be another entry for this symbol so stop here. */ return sym; } const ElfW(Sym) *sym; const ElfW(Addr) *bitmask = map->l_gnu_bitmask; if (__builtin_expect (bitmask != NULL, 1)) { ElfW(Addr) bitmask_word = bitmask[(new_hash / __ELF_NATIVE_CLASS) & map->l_gnu_bitmask_idxbits]; unsigned int hashbit1 = new_hash & (__ELF_NATIVE_CLASS - 1); unsigned int hashbit2 = ((new_hash >> map->l_gnu_shift) & (__ELF_NATIVE_CLASS - 1)); if (__builtin_expect ((bitmask_word >> hashbit1) & (bitmask_word >> hashbit2) & 1, 0)) { Elf32_Word bucket = map->l_gnu_buckets[new_hash % map->l_nbuckets]; if (bucket != 0) { const Elf32_Word *hasharr = &map->l_gnu_chain_zero[bucket]; do if ((*hasharr & ~1u) == (new_hash & ~1u)) { symidx = hasharr - map->l_gnu_chain_zero; sym = check_match (&symtab[symidx]); if (sym != NULL) goto found_it; } while ((*hasharr++ & 1u) == 0); } } } else { if (*old_hash == 0xffffffff) *old_hash = _dl_elf_hash (undef_name); /* Use the old SysV-style hash table. Search the appropriate hash bucket in this object's symbol table for a definition for the same symbol name. */ for (symidx = map->l_buckets[*old_hash % map->l_nbuckets]; symidx != STN_UNDEF; symidx = map->l_chain[symidx]) { sym = check_match (&symtab[symidx]); if (sym != NULL) goto found_it; } } /* If we have seen exactly one versioned symbol while we are looking for an unversioned symbol and the version is not the default version we still accept this symbol since there are no possible ambiguities. */ sym = num_versions == 1 ? versioned_sym : NULL; if (sym != NULL) { found_it: switch (ELFW(ST_BIND) (sym->st_info)) { case STB_WEAK: /* Weak definition. Use this value if we don't find another. */ if (__builtin_expect (GLRO(dl_dynamic_weak), 0)) { if (! result->s) { result->s = sym; result->m = (struct link_map *) map; } break; } /* FALLTHROUGH */ case STB_GLOBAL: /* Global definition. Just what we need. */ result->s = sym; result->m = (struct link_map *) map; return 1; default: /* Local symbols are ignored. */ break; } } /* If this current map is the one mentioned in the verneed entry and we have not found a weak entry, it is a bug. */ if (symidx == STN_UNDEF && version != NULL && version->filename != NULL && __builtin_expect (_dl_name_match_p (version->filename, map), 0)) return -1; } while (++i < n); /* We have not found anything until now. */ return 0; }