* after resolving ELF shared library symbols
*
* Copyright (C) 2004 by Joakim Tjernlund <joakim.tjernlund@lumentis.se>
- * Copyright (C) 2000-2004 by Erik Andersen <andersen@codpoet.org>
+ * Copyright (C) 2000-2006 by Erik Andersen <andersen@codepoet.org>
* Copyright (c) 1994-2000 Eric Youngdale, Peter MacDonald,
* David Engel, Hongjiu Lu and Mitch D'Souza
*
/* Various symbol table handling functions, including symbol lookup */
-
-/*
- * This is the start of the linked list that describes all of the files present
- * in the system with pointers to all of the symbol, string, and hash tables,
- * as well as all of the other good stuff in the binary.
- */
-struct elf_resolve *_dl_loaded_modules = NULL;
-
/*
* This is the list of modules that are loaded when the image is first
* started. As we add more via dlopen, they get added into other
*/
struct dyn_elf *_dl_handles = NULL;
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+/* This is the new hash function that is used by the ELF linker to generate the
+ * GNU hash table that each executable and library will have if --hash-style=[gnu,both]
+ * is passed to the linker. We need it to decode the GNU hash table. */
+static __inline__ Elf_Symndx _dl_gnu_hash (const unsigned char *name)
+{
+ unsigned long h = 5381;
+ unsigned char c;
+ for (c = *name; c != '\0'; c = *++name)
+ h = h * 33 + c;
+ return h & 0xffffffff;
+}
+#endif
/* This is the hash function that is used by the ELF linker to generate the
* hash table that each executable and library is required to have. We need
* it to decode the hash table. */
-unsigned long _dl_elf_hash(const unsigned char *name)
+static __inline__ Elf_Symndx _dl_elf_hash(const unsigned char *name)
{
- unsigned long hash = 0;
+ unsigned long hash=0;
unsigned long tmp;
while (*name) {
hash = (hash << 4) + *name++;
- if ((tmp = hash & 0xf0000000))
- hash ^= tmp >> 24;
- hash &= ~tmp;
+ tmp = hash & 0xf0000000;
+ /* The algorithm specified in the ELF ABI is as follows:
+ if (tmp != 0)
+ hash ^= tmp >> 24;
+ hash &= ~tmp;
+ But the following is equivalent and a lot
+ faster, especially on modern processors. */
+ hash ^= tmp;
+ hash ^= tmp >> 24;
}
return hash;
}
-/* Check to see if a library has already been added to the hash chain. */
-struct elf_resolve *_dl_check_hashed_files(const char *libname)
-{
- struct elf_resolve *tpnt;
- int len = _dl_strlen(libname);
-
- for (tpnt = _dl_loaded_modules; tpnt; tpnt = tpnt->next) {
- if (_dl_strncmp(tpnt->libname, libname, len) == 0 &&
- (tpnt->libname[len] == '\0' || tpnt->libname[len] == '.'))
- return tpnt;
- }
-
- return NULL;
-}
-
/*
* We call this function when we have just read an ELF library or executable.
* We add the relevant info to the symbol chain, so that we can resolve all
* externals properly.
*/
struct elf_resolve *_dl_add_elf_hash_table(const char *libname,
- char *loadaddr, unsigned long *dynamic_info, unsigned long dynamic_addr,
- unsigned long dynamic_size)
+ DL_LOADADDR_TYPE loadaddr, unsigned long *dynamic_info, unsigned long dynamic_addr,
+ attribute_unused unsigned long dynamic_size)
{
- unsigned long *hash_addr;
+ Elf_Symndx *hash_addr;
struct elf_resolve *tpnt;
int i;
- if (!_dl_loaded_modules) {
- tpnt = _dl_loaded_modules = (struct elf_resolve *) _dl_malloc(sizeof(struct elf_resolve));
- _dl_memset(tpnt, 0, sizeof(struct elf_resolve));
- } else {
- tpnt = _dl_loaded_modules;
- while (tpnt->next)
- tpnt = tpnt->next;
- tpnt->next = (struct elf_resolve *) _dl_malloc(sizeof(struct elf_resolve));
- _dl_memset(tpnt->next, 0, sizeof(struct elf_resolve));
- tpnt->next->prev = tpnt;
- tpnt = tpnt->next;
- };
+ tpnt = _dl_malloc(sizeof(struct elf_resolve));
+ _dl_memset(tpnt, 0, sizeof(struct elf_resolve));
+
+ if (!_dl_loaded_modules)
+ _dl_loaded_modules = tpnt;
+ else {
+ struct elf_resolve *t = _dl_loaded_modules;
+ while (t->next)
+ t = t->next;
+ t->next = tpnt;
+ t->next->prev = t;
+ tpnt = t->next;
+ }
tpnt->next = NULL;
tpnt->init_flag = 0;
tpnt->libname = _dl_strdup(libname);
tpnt->dynamic_addr = (ElfW(Dyn) *)dynamic_addr;
- tpnt->dynamic_size = dynamic_size;
tpnt->libtype = loaded_file;
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+ if (dynamic_info[DT_GNU_HASH_IDX] != 0) {
+ Elf32_Word *hash32 = (Elf_Symndx*)dynamic_info[DT_GNU_HASH_IDX];
+
+ tpnt->nbucket = *hash32++;
+ Elf32_Word symbias = *hash32++;
+ Elf32_Word bitmask_nwords = *hash32++;
+ /* Must be a power of two. */
+ _dl_assert ((bitmask_nwords & (bitmask_nwords - 1)) == 0);
+ tpnt->l_gnu_bitmask_idxbits = bitmask_nwords - 1;
+ tpnt->l_gnu_shift = *hash32++;
+
+ tpnt->l_gnu_bitmask = (ElfW(Addr) *) hash32;
+ hash32 += __ELF_NATIVE_CLASS / 32 * bitmask_nwords;
+
+ tpnt->l_gnu_buckets = hash32;
+ hash32 += tpnt->nbucket;
+ tpnt->l_gnu_chain_zero = hash32 - symbias;
+ } else
+ /* Fall using old SysV hash table if GNU hash is not present */
+#endif
+
if (dynamic_info[DT_HASH] != 0) {
- hash_addr = (unsigned long *) (intptr_t)(dynamic_info[DT_HASH] + loadaddr);
+ hash_addr = (Elf_Symndx*)dynamic_info[DT_HASH];
tpnt->nbucket = *hash_addr++;
tpnt->nchain = *hash_addr++;
tpnt->elf_buckets = hash_addr;
hash_addr += tpnt->nbucket;
tpnt->chains = hash_addr;
}
- tpnt->loadaddr = (ElfW(Addr))loadaddr;
- for (i = 0; i < 24; i++)
+ tpnt->loadaddr = loadaddr;
+ for (i = 0; i < DYNAMIC_SIZE; i++)
tpnt->dynamic_info[i] = dynamic_info[i];
-#ifdef __mips__
- {
- Elf32_Dyn *dpnt = (Elf32_Dyn *) dynamic_addr;
-
- while(dpnt->d_tag) {
- if (dpnt->d_tag == DT_MIPS_GOTSYM)
- tpnt->mips_gotsym = dpnt->d_un.d_val;
- if (dpnt->d_tag == DT_MIPS_LOCAL_GOTNO)
- tpnt->mips_local_gotno = dpnt->d_un.d_val;
- if (dpnt->d_tag == DT_MIPS_SYMTABNO)
- tpnt->mips_symtabno = dpnt->d_un.d_val;
- dpnt++;
+ return tpnt;
+}
+
+
+/* Routine to check whether the symbol matches. */
+static __attribute_noinline__ const ElfW(Sym) *
+check_match (const ElfW(Sym) *sym, char *strtab, const char* undef_name, int type_class)
+{
+
+#if defined(USE_TLS) && USE_TLS
+ if ((sym->st_value == 0 && (ELF_ST_TYPE(sym->st_info) != STT_TLS))
+ || (type_class & (sym->st_shndx == SHN_UNDEF)))
+ /* No value or undefined symbol itself */
+ return NULL;
+
+ if (ELF_ST_TYPE(sym->st_info) > STT_FUNC
+ && ELF_ST_TYPE(sym->st_info) != STT_COMMON
+ && ELF_ST_TYPE(sym->st_info) != STT_TLS)
+ /* Ignore all but STT_NOTYPE, STT_OBJECT, STT_FUNC and STT_COMMON
+ * entries (and STT_TLS if TLS is supported) since these
+ * are no code/data definitions.
+ */
+ return NULL;
+#else
+ if (type_class & (sym->st_shndx == SHN_UNDEF))
+ /* undefined symbol itself */
+ return NULL;
+
+ if (sym->st_value == 0)
+ /* No value */
+ return NULL;
+
+ if (ELF_ST_TYPE(sym->st_info) > STT_FUNC
+ && ELF_ST_TYPE(sym->st_info) != STT_COMMON)
+ /* Ignore all but STT_NOTYPE, STT_OBJECT, STT_FUNC
+ * and STT_COMMON entries since these are no
+ * code/data definitions
+ */
+ return NULL;
+#endif
+ if (_dl_strcmp(strtab + sym->st_name, undef_name) != 0)
+ return NULL;
+
+ /* This is the matching symbol */
+ return sym;
+}
+
+
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+
+static __always_inline const ElfW(Sym) *
+_dl_lookup_gnu_hash(struct elf_resolve *tpnt, ElfW(Sym) *symtab, unsigned long hash,
+ const char* undef_name, int type_class)
+{
+ Elf_Symndx symidx;
+ const ElfW(Sym) *sym;
+ char *strtab;
+
+ const ElfW(Addr) *bitmask = tpnt->l_gnu_bitmask;
+
+ ElfW(Addr) bitmask_word = bitmask[(hash / __ELF_NATIVE_CLASS) & tpnt->l_gnu_bitmask_idxbits];
+
+ unsigned int hashbit1 = hash & (__ELF_NATIVE_CLASS - 1);
+ unsigned int hashbit2 = ((hash >> tpnt->l_gnu_shift) & (__ELF_NATIVE_CLASS - 1));
+ _dl_assert (bitmask != NULL);
+
+ if (unlikely((bitmask_word >> hashbit1) & (bitmask_word >> hashbit2) & 1)) {
+ unsigned long rem;
+ Elf32_Word bucket;
+
+ do_rem (rem, hash, tpnt->nbucket);
+ bucket = tpnt->l_gnu_buckets[rem];
+
+ if (bucket != 0) {
+ const Elf32_Word *hasharr = &tpnt->l_gnu_chain_zero[bucket];
+ do {
+ if (((*hasharr ^ hash) >> 1) == 0) {
+ symidx = hasharr - tpnt->l_gnu_chain_zero;
+ strtab = (char *) (tpnt->dynamic_info[DT_STRTAB]);
+ sym = check_match (&symtab[symidx], strtab, undef_name, type_class);
+ if (sym != NULL)
+ return sym;
+ }
+ } while ((*hasharr++ & 1u) == 0);
}
}
-#endif
- return tpnt;
+ /* No symbol found. */
+ return NULL;
}
+#endif
+
+static __always_inline const ElfW(Sym) *
+_dl_lookup_sysv_hash(struct elf_resolve *tpnt, ElfW(Sym) *symtab, unsigned long hash, const char* undef_name, int type_class)
+{
+ unsigned long hn;
+ char *strtab;
+ const ElfW(Sym) *sym;
+ Elf_Symndx symidx;
+ /* Avoid calling .urem here. */
+ do_rem(hn, hash, tpnt->nbucket);
+ strtab = (char *) (tpnt->dynamic_info[DT_STRTAB]);
+
+ _dl_assert(tpnt->elf_buckets != NULL);
+
+ for (symidx = tpnt->elf_buckets[hn]; symidx != STN_UNDEF; symidx = tpnt->chains[symidx]) {
+ sym = check_match (&symtab[symidx], strtab, undef_name, type_class);
+ if (sym != NULL)
+ /* At this point the symbol is that we are looking for */
+ return sym;
+ }
+ /* No symbol found into the current module*/
+ return NULL;
+}
/*
* This function resolves externals, and this is either called when we process
* relocations or when we call an entry in the PLT table for the first time.
*/
-char *_dl_find_hash(const char *name, struct dyn_elf *rpnt, int type_class)
+char *_dl_lookup_hash(const char *name, struct r_scope_elem *scope, struct elf_resolve *mytpnt,
+ struct sym_val *symbol, int type_class, struct elf_resolve **tpntp)
{
- struct elf_resolve *tpnt;
- int si;
- char *strtab;
- Elf32_Sym *symtab;
- unsigned long elf_hash_number, hn;
- const ElfW(Sym) *sym;
- char *weak_result = NULL;
+ struct elf_resolve *tpnt = NULL;
+ ElfW(Sym) *symtab;
+ int i = 0;
- elf_hash_number = _dl_elf_hash(name);
+ unsigned long elf_hash_number = 0xffffffff;
+ const ElfW(Sym) *sym = NULL;
- /*
- NOTE! RTLD_LOCAL handling for dlopen not implemented yet.
- Everything is treated as RTLD_GLOBAL.
- */
-
- for (; rpnt; rpnt = rpnt->next) {
- tpnt = rpnt->dyn;
+ char *weak_result = NULL;
+ struct r_scope_elem *loop_scope;
- if (!(tpnt->rtld_flags & RTLD_GLOBAL))
- continue;
- /* Don't search the executable when resolving a copy reloc. */
- if ((type_class & ELF_RTYPE_CLASS_COPY) && tpnt->libtype == elf_executable)
- continue;
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+ unsigned long gnu_hash_number = _dl_gnu_hash((const unsigned char *)name);
+#endif
- /* Avoid calling .urem here. */
- do_rem(hn, elf_hash_number, tpnt->nbucket);
- symtab = (Elf32_Sym *) (intptr_t) (tpnt->dynamic_info[DT_SYMTAB] + tpnt->loadaddr);
- strtab = (char *) (tpnt->dynamic_info[DT_STRTAB] + tpnt->loadaddr);
+ for (loop_scope = scope; loop_scope && !sym; loop_scope = loop_scope->next) {
+ for (i = 0; i < loop_scope->r_nlist; i++) {
+ tpnt = loop_scope->r_list[i];
- for (si = tpnt->elf_buckets[hn]; si != STN_UNDEF; si = tpnt->chains[si]) {
- sym = &symtab[si];
+ if (!(tpnt->rtld_flags & RTLD_GLOBAL) && mytpnt) {
+ if (mytpnt == tpnt)
+ ;
+ else {
+ struct init_fini_list *tmp;
- if (type_class & (sym->st_shndx == SHN_UNDEF))
- continue;
- if (_dl_strcmp(strtab + sym->st_name, name) != 0)
- continue;
- if (sym->st_value == 0)
+ for (tmp = mytpnt->rtld_local; tmp; tmp = tmp->next) {
+ if (tmp->tpnt == tpnt)
+ break;
+ }
+ if (!tmp)
+ continue;
+ }
+ }
+ /* Don't search the executable when resolving a copy reloc. */
+ if ((type_class & ELF_RTYPE_CLASS_COPY) && tpnt->libtype == elf_executable)
continue;
- if (ELF32_ST_TYPE(sym->st_info) > STT_FUNC)
+
+ /* If the hash table is empty there is nothing to do here. */
+ if (tpnt->nbucket == 0)
continue;
- switch (ELF32_ST_BIND(sym->st_info)) {
+ symtab = (ElfW(Sym) *) (intptr_t) (tpnt->dynamic_info[DT_SYMTAB]);
+
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+ /* Prefer GNU hash style, if any */
+ if (tpnt->l_gnu_bitmask) {
+ sym = _dl_lookup_gnu_hash(tpnt, symtab, gnu_hash_number, name, type_class);
+ if (sym != NULL)
+ /* If sym has been found, do not search further */
+ break;
+ } else {
+#endif
+ /* Use the old SysV-style hash table */
+
+ /* Calculate the old sysv hash number only once */
+ if (elf_hash_number == 0xffffffff)
+ elf_hash_number = _dl_elf_hash((const unsigned char *)name);
+
+ sym = _dl_lookup_sysv_hash(tpnt, symtab, elf_hash_number, name, type_class);
+ if (sym != NULL)
+ /* If sym has been found, do not search further */
+ break;
+#ifdef __LDSO_GNU_HASH_SUPPORT__
+ }
+#endif
+ } /* End of inner for */
+ }
+
+ if (sym) {
+ if (symbol) {
+ symbol->s = sym;
+ symbol->m = tpnt;
+ }
+ /* At this point we have found the requested symbol, do binding */
+#if defined(USE_TLS) && USE_TLS
+ if (ELF_ST_TYPE(sym->st_info) == STT_TLS) {
+ _dl_assert(tpntp != NULL);
+ *tpntp = tpnt;
+
+ return (char *)sym->st_value;
+ }
+#endif
+
+ switch (ELF_ST_BIND(sym->st_info)) {
case STB_WEAK:
#if 0
-/* Perhaps we should support old style weak symbol handling
- * per what glibc does when you export LD_DYNAMIC_WEAK */
+ /* Perhaps we should support old style weak symbol handling
+ * per what glibc does when you export LD_DYNAMIC_WEAK */
if (!weak_result)
- weak_result = (char *)tpnt->loadaddr + sym->st_value;
+ weak_result = (char *)DL_FIND_HASH_VALUE(tpnt, type_class, sym);
break;
#endif
case STB_GLOBAL:
- return (char*)tpnt->loadaddr + sym->st_value;
+#ifdef __FDPIC__
+ if (tpntp)
+ *tpntp = tpnt;
+#endif
+ return (char *)DL_FIND_HASH_VALUE(tpnt, type_class, sym);
default: /* Local symbols not handled here */
break;
- }
}
}
+#ifdef __FDPIC__
+ if (tpntp)
+ *tpntp = tpnt;
+#endif
return weak_result;
}
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