269 lines
8.6 KiB
C
269 lines
8.6 KiB
C
/* Look up a symbol in the loaded objects.
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Copyright (C) 1995-2004, 2005, 2006, 2007 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, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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/* Inner part of the lookup functions. We return a value > 0 if we
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found the symbol, the value 0 if nothing is found and < 0 if
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something bad happened. */
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static int
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__attribute_noinline__
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do_lookup_x (const char *undef_name, uint_fast32_t new_hash,
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unsigned long int *old_hash, const ElfW(Sym) *ref,
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struct sym_val *result, struct r_scope_elem *scope, size_t i,
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const struct r_found_version *const version, int flags,
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struct link_map *skip, int type_class)
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{
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size_t n = scope->r_nlist;
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/* Make sure we read the value before proceeding. Otherwise we
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might use r_list pointing to the initial scope and r_nlist being
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the value after a resize. That is the only path in dl-open.c not
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protected by GSCOPE. A read barrier here might be to expensive. */
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__asm volatile ("" : "+r" (n), "+m" (scope->r_list));
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struct link_map **list = scope->r_list;
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do
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{
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/* These variables are used in the nested function. */
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Elf_Symndx symidx;
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int num_versions = 0;
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const ElfW(Sym) *versioned_sym = NULL;
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const struct link_map *map = list[i]->l_real;
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/* Here come the extra test needed for `_dl_lookup_symbol_skip'. */
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if (map == skip)
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continue;
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/* Don't search the executable when resolving a copy reloc. */
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if ((type_class & ELF_RTYPE_CLASS_COPY) && map->l_type == lt_executable)
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continue;
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/* Do not look into objects which are going to be removed. */
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if (map->l_removed)
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continue;
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/* Print some debugging info if wanted. */
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if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_SYMBOLS, 0))
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_dl_debug_printf ("symbol=%s; lookup in file=%s [%lu]\n",
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undef_name,
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map->l_name[0] ? map->l_name : rtld_progname,
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map->l_ns);
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/* If the hash table is empty there is nothing to do here. */
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if (map->l_nbuckets == 0)
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continue;
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/* The tables for this map. */
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const ElfW(Sym) *symtab = (const void *) D_PTR (map, l_info[DT_SYMTAB]);
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const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
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/* Nested routine to check whether the symbol matches. */
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const ElfW(Sym) *
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__attribute_noinline__
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check_match (const ElfW(Sym) *sym)
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{
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assert (ELF_RTYPE_CLASS_PLT == 1);
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if (__builtin_expect ((sym->st_value == 0 /* No value. */
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&& ELFW(ST_TYPE) (sym->st_info) != STT_TLS)
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|| (type_class & (sym->st_shndx == SHN_UNDEF)),
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0))
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return NULL;
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if (__builtin_expect (ELFW(ST_TYPE) (sym->st_info) > STT_FUNC
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&& ELFW(ST_TYPE) (sym->st_info) != STT_TLS, 0))
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/* Ignore all but STT_NOTYPE, STT_OBJECT and STT_FUNC
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entries (and STT_TLS if TLS is supported) since these
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are no code/data definitions. */
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return NULL;
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if (sym != ref && strcmp (strtab + sym->st_name, undef_name))
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/* Not the symbol we are looking for. */
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return NULL;
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const ElfW(Half) *verstab = map->l_versyms;
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if (version != NULL)
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{
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if (__builtin_expect (verstab == NULL, 0))
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{
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/* We need a versioned symbol but haven't found any. If
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this is the object which is referenced in the verneed
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entry it is a bug in the library since a symbol must
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not simply disappear.
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It would also be a bug in the object since it means that
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the list of required versions is incomplete and so the
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tests in dl-version.c haven't found a problem.*/
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assert (version->filename == NULL
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|| ! _dl_name_match_p (version->filename, map));
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/* Otherwise we accept the symbol. */
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}
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else
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{
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/* We can match the version information or use the
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default one if it is not hidden. */
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ElfW(Half) ndx = verstab[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->name))
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&& (version->hidden || map->l_versions[ndx].hash
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|| (verstab[symidx] & 0x8000)))
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/* It's not the version we want. */
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return NULL;
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}
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}
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else
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{
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/* No specific version is selected. There are two ways we
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can got here:
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- a binary which does not include versioning information
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is loaded
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- dlsym() instead of dlvsym() is used to get a symbol which
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might exist in more than one form
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If the library does not provide symbol version information
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there is no problem at at: we simply use the symbol if it
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is defined.
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These two lookups need to be handled differently if the
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library defines versions. In the case of the old
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unversioned application the oldest (default) version
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should be used. In case of a dlsym() call the latest and
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public interface should be returned. */
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if (verstab != NULL)
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{
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if ((verstab[symidx] & 0x7fff)
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>= ((flags & DL_LOOKUP_RETURN_NEWEST) ? 2 : 3))
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{
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/* Don't accept hidden symbols. */
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if ((verstab[symidx] & 0x8000) == 0
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&& num_versions++ == 0)
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/* No version so far. */
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versioned_sym = sym;
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return NULL;
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}
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}
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}
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/* There cannot be another entry for this symbol so stop here. */
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return sym;
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}
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const ElfW(Sym) *sym;
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const ElfW(Addr) *bitmask = map->l_gnu_bitmask;
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if (__builtin_expect (bitmask != NULL, 1))
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{
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ElfW(Addr) bitmask_word
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= bitmask[(new_hash / __ELF_NATIVE_CLASS)
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& map->l_gnu_bitmask_idxbits];
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unsigned int hashbit1 = new_hash & (__ELF_NATIVE_CLASS - 1);
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unsigned int hashbit2 = ((new_hash >> map->l_gnu_shift)
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& (__ELF_NATIVE_CLASS - 1));
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if (__builtin_expect ((bitmask_word >> hashbit1)
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& (bitmask_word >> hashbit2) & 1, 0))
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{
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Elf32_Word bucket = map->l_gnu_buckets[new_hash
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% 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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symidx = hasharr - map->l_gnu_chain_zero;
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sym = check_match (&symtab[symidx]);
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if (sym != NULL)
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goto found_it;
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}
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while ((*hasharr++ & 1u) == 0);
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}
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}
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/* No symbol found. */
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symidx = SHN_UNDEF;
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}
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else
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{
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if (*old_hash == 0xffffffff)
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*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 (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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sym = check_match (&symtab[symidx]);
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if (sym != NULL)
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goto found_it;
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}
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}
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/* If we have seen exactly one versioned symbol while we are
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looking for an unversioned symbol and the version is not the
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default version we still accept this symbol since there are
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no possible ambiguities. */
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sym = num_versions == 1 ? versioned_sym : NULL;
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if (sym != NULL)
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{
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found_it:
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switch (ELFW(ST_BIND) (sym->st_info))
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{
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case STB_WEAK:
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/* Weak definition. Use this value if we don't find another. */
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if (__builtin_expect (GLRO(dl_dynamic_weak), 0))
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{
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if (! result->s)
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{
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result->s = sym;
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result->m = (struct link_map *) map;
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}
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break;
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}
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/* FALLTHROUGH */
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case STB_GLOBAL:
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/* Global definition. Just what we need. */
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result->s = sym;
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result->m = (struct link_map *) map;
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return 1;
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default:
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/* Local symbols are ignored. */
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break;
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}
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}
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/* If this current map is the one mentioned in the verneed entry
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and we have not found a weak entry, it is a bug. */
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if (symidx == STN_UNDEF && version != NULL && version->filename != NULL
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&& __builtin_expect (_dl_name_match_p (version->filename, map), 0))
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return -1;
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}
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while (++i < n);
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/* We have not found anything until now. */
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return 0;
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}
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