glibc-ports-2.14.1.tar.gz

/* Look up a symbol in the loaded objects. MIPS/Linux version - special handling of non-PIC undefined symbol rules. Copyright (C) 1995-2007, 2009, 2010, 2011 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. */ #include <alloca.h> #include <libintl.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <ldsodefs.h> #include <dl-hash.h> #include <dl-machine.h> #include <sysdep-cancel.h> #include <bits/libc-lock.h> #include <tls.h> #include <assert.h> #define VERSTAG(tag) (DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGIDX (tag)) /* We need this string more than once. */ static const char undefined_msg[] = "undefined symbol: "; struct sym_val { const ElfW(Sym) *s; struct link_map *m; }; #define make_string(string, rest...) \ ({ \ const char *all[] = { string, ## rest }; \ size_t len, cnt; \ char *result, *cp; \ \ len = 1; \ for (cnt = 0; cnt < sizeof (all) / sizeof (all[0]); ++cnt) \ len += strlen (all[cnt]); \ \ cp = result = alloca (len); \ for (cnt = 0; cnt < sizeof (all) / sizeof (all[0]); ++cnt) \ cp = __stpcpy (cp, all[cnt]); \ \ result; \ }) /* Statistics function. */ #ifdef SHARED # define bump_num_relocations() ++GL(dl_num_relocations) #else # define bump_num_relocations() ((void) 0) #endif /* 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 *undef_map) { size_t n = scope->r_nlist; /* Make sure we read the value before proceeding. Otherwise we might use r_list pointing to the initial scope and r_nlist being the value after a resize. That is the only path in dl-open.c not protected by GSCOPE. A read barrier here might be to expensive. */ __asm volatile ("" : "+r" (n), "+m" (scope->r_list)); struct link_map **list = scope->r_list; 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) { unsigned int stt = ELFW(ST_TYPE) (sym->st_info); assert (ELF_RTYPE_CLASS_PLT == 1); /* The semantics of zero/non-zero values of undefined symbols differs depending on whether the non-PIC ABI is in use. Under the non-PIC ABI, a non-zero value indicates that there is an address reference to the symbol and thus it must always be resolved (except when resolving a jump slot relocation) to the PLT entry whose address is provided as the symbol's value; a zero value indicates that this canonical-address behaviour is not required. Yet under the classic MIPS psABI, a zero value indicates that there is an address reference to the function and the dynamic linker must resolve the symbol immediately upon loading. To avoid conflict, symbols for which the dynamic linker must assume the non-PIC ABI semantics are marked with the STO_MIPS_PLT flag. */ if (__builtin_expect ((sym->st_value == 0 /* No value. */ && stt != STT_TLS) || (sym->st_shndx == SHN_UNDEF && !(sym->st_other & STO_MIPS_PLT)) || (type_class & (sym->st_shndx == SHN_UNDEF)), 0)) return NULL; /* Ignore all but STT_NOTYPE, STT_OBJECT, STT_FUNC, STT_COMMON, STT_TLS, and STT_GNU_IFUNC since these are no code/data definitions. */ #define ALLOWED_STT \ ((1 << STT_NOTYPE) | (1 << STT_OBJECT) | (1 << STT_FUNC) \ | (1 << STT_COMMON) | (1 << STT_TLS) | (1 << STT_GNU_IFUNC)) if (__builtin_expect (((1 << stt) & ALLOWED_STT) == 0, 0)) 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 all: 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. */