2 * Copyright (C) 2007 The Android Open Source Project
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
23 #include <android/dlext.h>
25 #include <bionic/pthread_internal.h>
26 #include "private/bionic_tls.h"
27 #include "private/ScopedPthreadMutexLocker.h"
28 #include "private/ThreadLocalBuffer.h"
30 /* This file hijacks the symbols stubbed out in libdl.so. */
32 static pthread_mutex_t g_dl_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER;
34 static const char* __bionic_set_dlerror(char* new_value) {
35 char** dlerror_slot = &reinterpret_cast<char**>(__get_tls())[TLS_SLOT_DLERROR];
37 const char* old_value = *dlerror_slot;
38 *dlerror_slot = new_value;
42 static void __bionic_format_dlerror(const char* msg, const char* detail) {
43 char* buffer = __get_thread()->dlerror_buffer;
44 strlcpy(buffer, msg, __BIONIC_DLERROR_BUFFER_SIZE);
45 if (detail != nullptr) {
46 strlcat(buffer, ": ", __BIONIC_DLERROR_BUFFER_SIZE);
47 strlcat(buffer, detail, __BIONIC_DLERROR_BUFFER_SIZE);
50 __bionic_set_dlerror(buffer);
53 const char* dlerror() {
54 const char* old_value = __bionic_set_dlerror(nullptr);
58 void android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
59 ScopedPthreadMutexLocker locker(&g_dl_mutex);
60 do_android_get_LD_LIBRARY_PATH(buffer, buffer_size);
63 void android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
64 ScopedPthreadMutexLocker locker(&g_dl_mutex);
65 do_android_update_LD_LIBRARY_PATH(ld_library_path);
68 static void* dlopen_ext(const char* filename, int flags, const android_dlextinfo* extinfo) {
69 ScopedPthreadMutexLocker locker(&g_dl_mutex);
70 soinfo* result = do_dlopen(filename, flags, extinfo);
71 if (result == nullptr) {
72 __bionic_format_dlerror("dlopen failed", linker_get_error_buffer());
78 void* android_dlopen_ext(const char* filename, int flags, const android_dlextinfo* extinfo) {
79 return dlopen_ext(filename, flags, extinfo);
82 void* dlopen(const char* filename, int flags) {
83 return dlopen_ext(filename, flags, nullptr);
86 void* dlsym(void* handle, const char* symbol) {
87 ScopedPthreadMutexLocker locker(&g_dl_mutex);
89 #if !defined(__LP64__)
90 if (handle == nullptr) {
91 __bionic_format_dlerror("dlsym library handle is null", nullptr);
96 if (symbol == nullptr) {
97 __bionic_format_dlerror("dlsym symbol name is null", nullptr);
101 soinfo* found = nullptr;
102 ElfW(Sym)* sym = nullptr;
103 if (handle == RTLD_DEFAULT) {
104 sym = dlsym_linear_lookup(symbol, &found, nullptr);
105 } else if (handle == RTLD_NEXT) {
106 void* caller_addr = __builtin_return_address(0);
107 soinfo* si = find_containing_library(caller_addr);
110 if (si && si->next) {
111 sym = dlsym_linear_lookup(symbol, &found, si->next);
114 sym = dlsym_handle_lookup(reinterpret_cast<soinfo*>(handle), &found, symbol);
117 if (sym != nullptr) {
118 unsigned bind = ELF_ST_BIND(sym->st_info);
120 if ((bind == STB_GLOBAL || bind == STB_WEAK) && sym->st_shndx != 0) {
121 return reinterpret_cast<void*>(found->resolve_symbol_address(sym));
124 __bionic_format_dlerror("symbol found but not global", symbol);
127 __bionic_format_dlerror("undefined symbol", symbol);
132 int dladdr(const void* addr, Dl_info* info) {
133 ScopedPthreadMutexLocker locker(&g_dl_mutex);
135 // Determine if this address can be found in any library currently mapped.
136 soinfo* si = find_containing_library(addr);
141 memset(info, 0, sizeof(Dl_info));
143 info->dli_fname = si->name;
144 // Address at which the shared object is loaded.
145 info->dli_fbase = reinterpret_cast<void*>(si->base);
147 // Determine if any symbol in the library contains the specified address.
148 ElfW(Sym)* sym = dladdr_find_symbol(si, addr);
149 if (sym != nullptr) {
150 info->dli_sname = si->get_string(sym->st_name);
151 info->dli_saddr = reinterpret_cast<void*>(si->resolve_symbol_address(sym));
157 int dlclose(void* handle) {
158 ScopedPthreadMutexLocker locker(&g_dl_mutex);
159 do_dlclose(reinterpret_cast<soinfo*>(handle));
160 // dlclose has no defined errors.
164 // name_offset: starting index of the name in libdl_info.strtab
165 #define ELF32_SYM_INITIALIZER(name_offset, value, shndx) \
167 reinterpret_cast<Elf32_Addr>(value), \
169 (shndx == 0) ? 0 : (STB_GLOBAL << 4), \
174 #define ELF64_SYM_INITIALIZER(name_offset, value, shndx) \
176 (shndx == 0) ? 0 : (STB_GLOBAL << 4), \
179 reinterpret_cast<Elf64_Addr>(value), \
184 // 0000000 00011111 111112 22222222 2333333 3333444444444455555555556666666 6667777777777888888888899999 9999900000000001 1111111112222222222 333333333344444444445
185 // 0123456 78901234 567890 12345678 9012345 6789012345678901234567890123456 7890123456789012345678901234 5678901234567890 1234567890123456789 012345678901234567890
186 # define ANDROID_LIBDL_STRTAB \
187 "dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0android_update_LD_LIBRARY_PATH\0android_get_LD_LIBRARY_PATH\0dl_iterate_phdr\0android_dlopen_ext\0dl_unwind_find_exidx\0"
188 #elif defined(__aarch64__) || defined(__i386__) || defined(__mips__) || defined(__x86_64__)
189 // 0000000 00011111 111112 22222222 2333333 3333444444444455555555556666666 6667777777777888888888899999 9999900000000001 1111111112222222222
190 // 0123456 78901234 567890 12345678 9012345 6789012345678901234567890123456 7890123456789012345678901234 5678901234567890 1234567890123456789
191 # define ANDROID_LIBDL_STRTAB \
192 "dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0android_update_LD_LIBRARY_PATH\0android_get_LD_LIBRARY_PATH\0dl_iterate_phdr\0android_dlopen_ext\0"
194 # error Unsupported architecture. Only arm, arm64, mips, mips64, x86 and x86_64 are presently supported.
197 static ElfW(Sym) g_libdl_symtab[] = {
198 // Total length of libdl_info.strtab, including trailing 0.
199 // This is actually the STH_UNDEF entry. Technically, it's
200 // supposed to have st_name == 0, but instead, it points to an index
201 // in the strtab with a \0 to make iterating through the symtab easier.
202 ELFW(SYM_INITIALIZER)(sizeof(ANDROID_LIBDL_STRTAB) - 1, nullptr, 0),
203 ELFW(SYM_INITIALIZER)( 0, &dlopen, 1),
204 ELFW(SYM_INITIALIZER)( 7, &dlclose, 1),
205 ELFW(SYM_INITIALIZER)( 15, &dlsym, 1),
206 ELFW(SYM_INITIALIZER)( 21, &dlerror, 1),
207 ELFW(SYM_INITIALIZER)( 29, &dladdr, 1),
208 ELFW(SYM_INITIALIZER)( 36, &android_update_LD_LIBRARY_PATH, 1),
209 ELFW(SYM_INITIALIZER)( 67, &android_get_LD_LIBRARY_PATH, 1),
210 ELFW(SYM_INITIALIZER)( 95, &dl_iterate_phdr, 1),
211 ELFW(SYM_INITIALIZER)(111, &android_dlopen_ext, 1),
213 ELFW(SYM_INITIALIZER)(130, &dl_unwind_find_exidx, 1),
217 // Fake out a hash table with a single bucket.
219 // A search of the hash table will look through g_libdl_symtab starting with index 1, then
220 // use g_libdl_chains to find the next index to look at. g_libdl_chains should be set up to
221 // walk through every element in g_libdl_symtab, and then end with 0 (sentinel value).
223 // That is, g_libdl_chains should look like { 0, 2, 3, ... N, 0 } where N is the number
224 // of actual symbols, or nelems(g_libdl_symtab)-1 (since the first element of g_libdl_symtab is not
225 // a real symbol). (See soinfo_elf_lookup().)
227 // Note that adding any new symbols here requires stubbing them out in libdl.
228 static unsigned g_libdl_buckets[1] = { 1 };
230 static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 0 };
232 static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 0 };
235 static soinfo __libdl_info("libdl.so", nullptr, 0, RTLD_GLOBAL);
237 // This is used by the dynamic linker. Every process gets these symbols for free.
238 soinfo* get_libdl_info() {
239 if ((__libdl_info.flags & FLAG_LINKED) == 0) {
240 __libdl_info.flags |= FLAG_LINKED;
241 __libdl_info.strtab = ANDROID_LIBDL_STRTAB;
242 __libdl_info.symtab = g_libdl_symtab;
243 __libdl_info.nbucket = sizeof(g_libdl_buckets)/sizeof(unsigned);
244 __libdl_info.nchain = sizeof(g_libdl_chains)/sizeof(unsigned);
245 __libdl_info.bucket = g_libdl_buckets;
246 __libdl_info.chain = g_libdl_chains;
247 __libdl_info.ref_count = 1;
248 __libdl_info.strtab_size = sizeof(ANDROID_LIBDL_STRTAB);
251 return &__libdl_info;