diff options
Diffstat (limited to 'elf/dl-lookup.c')
| -rw-r--r-- | elf/dl-lookup.c | 367 |
1 files changed, 365 insertions, 2 deletions
diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c index 2ba885a639..fd0d624430 100644 --- a/elf/dl-lookup.c +++ b/elf/dl-lookup.c @@ -69,8 +69,371 @@ struct sym_val #endif -/* The actual lookup code. */ -#include "do-lookup.h" +/* 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); + if (__builtin_expect ((sym->st_value == 0 /* No value. */ + && stt != STT_TLS) + || (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 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 ^ new_hash) >> 1) == 0) + { + symidx = hasharr - map->l_gnu_chain_zero; + sym = check_match (&symtab[symidx]); + if (sym != NULL) + goto found_it; + } + while ((*hasharr++ & 1u) == 0); + } + } + /* No symbol found. */ + symidx = SHN_UNDEF; + } + 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 (__builtin_expect (ELFW(ST_BIND) (sym->st_info), STB_GLOBAL)) + { + 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: + success: + /* Global definition. Just what we need. */ + result->s = sym; + result->m = (struct link_map *) map; + return 1; + + case STB_GNU_UNIQUE:; + /* We have to determine whether we already found a + symbol with this name before. If not then we have to + add it to the search table. If we already found a + definition we have to use it. */ + void enter (struct unique_sym *table, size_t size, + unsigned int hash, const char *name, + const ElfW(Sym) *sym, const struct link_map *map) + { + size_t idx = hash % size; + size_t hash2 = 1 + hash % (size - 2); + while (1) + { + if (table[idx].hashval == 0) + { + table[idx].hashval = hash; + table[idx].name = strtab + sym->st_name; + if ((type_class & ELF_RTYPE_CLASS_COPY) != 0) + { + table[idx].sym = ref; + table[idx].map = undef_map; + } + else + { + table[idx].sym = sym; + table[idx].map = map; + } + return; + } + + idx += hash2; + if (idx >= size) + idx -= size; + } + } + + struct unique_sym_table *tab + = &GL(dl_ns)[map->l_ns]._ns_unique_sym_table; + + __rtld_lock_lock_recursive (tab->lock); + + struct unique_sym *entries = tab->entries; + size_t size = tab->size; + if (entries != NULL) + { + size_t idx = new_hash % size; + size_t hash2 = 1 + new_hash % (size - 2); + while (1) + { + if (entries[idx].hashval == new_hash + && strcmp (entries[idx].name, undef_name) == 0) + { + result->s = entries[idx].sym; + result->m = (struct link_map *) entries[idx].map; + __rtld_lock_unlock_recursive (tab->lock); + return 1; + } + + if (entries[idx].hashval == 0 + && entries[idx].name == NULL) + break; + + idx += hash2; + if (idx >= size) + idx -= size; + } + + if (size * 3 <= tab->n_elements) + { + /* Expand the table. */ + size_t newsize = _dl_higher_prime_number (size); + struct unique_sym *newentries + = calloc (sizeof (struct unique_sym), newsize); + if (newentries == NULL) + { + nomem: + __rtld_lock_unlock_recursive (tab->lock); + _dl_fatal_printf ("out of memory\n"); + } + + for (idx = 0; idx < size; ++idx) + if (entries[idx].hashval != 0) + enter (newentries, newsize, entries[idx].hashval, + entries[idx].name, entries[idx].sym, + entries[idx].map); + + tab->free (entries); + tab->size = newsize; + entries = tab->entries = newentries; + tab->free = free; + } + } + else + { +#define INITIAL_NUNIQUE_SYM_TABLE 31 + size = INITIAL_NUNIQUE_SYM_TABLE; + entries = calloc (sizeof (struct unique_sym), size); + if (entries == NULL) + goto nomem; + + tab->entries = entries; + tab->size = size; + tab->free = free; + } + + enter (entries, size, new_hash, strtab + sym->st_name, sym, map); + ++tab->n_elements; + + __rtld_lock_unlock_recursive (tab->lock); + + goto success; + + 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; +} static uint_fast32_t |