1 /* 2 * Copyright (C) 2007 The Android Open Source Project 3 * 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 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 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. 15 */ 16 17 #include "linker.h" 18 #include "linker_dlwarning.h" 19 20 #include <pthread.h> 21 #include <stdio.h> 22 #include <stdlib.h> 23 #include <string.h> 24 #include <android/api-level.h> 25 26 #include <bionic/pthread_internal.h> 27 #include "private/bionic_tls.h" 28 #include "private/ScopedPthreadMutexLocker.h" 29 #include "private/ThreadLocalBuffer.h" 30 31 /* This file hijacks the symbols stubbed out in libdl.so. */ 32 33 static pthread_mutex_t g_dl_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP; 34 35 static const char* __bionic_set_dlerror(char* new_value) { 36 char** dlerror_slot = &reinterpret_cast<char**>(__get_tls())[TLS_SLOT_DLERROR]; 37 38 const char* old_value = *dlerror_slot; 39 *dlerror_slot = new_value; 40 return old_value; 41 } 42 43 static void __bionic_format_dlerror(const char* msg, const char* detail) { 44 char* buffer = __get_thread()->dlerror_buffer; 45 strlcpy(buffer, msg, __BIONIC_DLERROR_BUFFER_SIZE); 46 if (detail != nullptr) { 47 strlcat(buffer, ": ", __BIONIC_DLERROR_BUFFER_SIZE); 48 strlcat(buffer, detail, __BIONIC_DLERROR_BUFFER_SIZE); 49 } 50 51 __bionic_set_dlerror(buffer); 52 } 53 54 const char* dlerror() { 55 const char* old_value = __bionic_set_dlerror(nullptr); 56 return old_value; 57 } 58 59 void android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) { 60 ScopedPthreadMutexLocker locker(&g_dl_mutex); 61 do_android_get_LD_LIBRARY_PATH(buffer, buffer_size); 62 } 63 64 void android_update_LD_LIBRARY_PATH(const char* ld_library_path) { 65 ScopedPthreadMutexLocker locker(&g_dl_mutex); 66 do_android_update_LD_LIBRARY_PATH(ld_library_path); 67 } 68 69 static void* dlopen_ext(const char* filename, int flags, 70 const android_dlextinfo* extinfo, void* caller_addr) { 71 ScopedPthreadMutexLocker locker(&g_dl_mutex); 72 void* result = do_dlopen(filename, flags, extinfo, caller_addr); 73 if (result == nullptr) { 74 __bionic_format_dlerror("dlopen failed", linker_get_error_buffer()); 75 return nullptr; 76 } 77 return result; 78 } 79 80 void* android_dlopen_ext(const char* filename, int flags, const android_dlextinfo* extinfo) { 81 void* caller_addr = __builtin_return_address(0); 82 return dlopen_ext(filename, flags, extinfo, caller_addr); 83 } 84 85 void* dlopen(const char* filename, int flags) { 86 void* caller_addr = __builtin_return_address(0); 87 return dlopen_ext(filename, flags, nullptr, caller_addr); 88 } 89 90 void* dlsym_impl(void* handle, const char* symbol, const char* version, void* caller_addr) { 91 ScopedPthreadMutexLocker locker(&g_dl_mutex); 92 void* result; 93 if (!do_dlsym(handle, symbol, version, caller_addr, &result)) { 94 __bionic_format_dlerror(linker_get_error_buffer(), nullptr); 95 return nullptr; 96 } 97 98 return result; 99 } 100 101 void* dlsym(void* handle, const char* symbol) { 102 void* caller_addr = __builtin_return_address(0); 103 return dlsym_impl(handle, symbol, nullptr, caller_addr); 104 } 105 106 void* dlvsym(void* handle, const char* symbol, const char* version) { 107 void* caller_addr = __builtin_return_address(0); 108 return dlsym_impl(handle, symbol, version, caller_addr); 109 } 110 111 int dladdr(const void* addr, Dl_info* info) { 112 ScopedPthreadMutexLocker locker(&g_dl_mutex); 113 return do_dladdr(addr, info); 114 } 115 116 int dlclose(void* handle) { 117 ScopedPthreadMutexLocker locker(&g_dl_mutex); 118 int result = do_dlclose(handle); 119 if (result != 0) { 120 __bionic_format_dlerror("dlclose failed", linker_get_error_buffer()); 121 } 122 return result; 123 } 124 125 int dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data) { 126 ScopedPthreadMutexLocker locker(&g_dl_mutex); 127 return do_dl_iterate_phdr(cb, data); 128 } 129 130 void android_set_application_target_sdk_version(uint32_t target) { 131 // lock to avoid modification in the middle of dlopen. 132 ScopedPthreadMutexLocker locker(&g_dl_mutex); 133 set_application_target_sdk_version(target); 134 } 135 136 uint32_t android_get_application_target_sdk_version() { 137 return get_application_target_sdk_version(); 138 } 139 140 void android_dlwarning(void* obj, void (*f)(void*, const char*)) { 141 ScopedPthreadMutexLocker locker(&g_dl_mutex); 142 get_dlwarning(obj, f); 143 } 144 145 bool android_init_namespaces(const char* public_ns_sonames, 146 const char* anon_ns_library_path) { 147 ScopedPthreadMutexLocker locker(&g_dl_mutex); 148 bool success = init_namespaces(public_ns_sonames, anon_ns_library_path); 149 if (!success) { 150 __bionic_format_dlerror("android_init_namespaces failed", linker_get_error_buffer()); 151 } 152 153 return success; 154 } 155 156 android_namespace_t* android_create_namespace(const char* name, 157 const char* ld_library_path, 158 const char* default_library_path, 159 uint64_t type, 160 const char* permitted_when_isolated_path, 161 android_namespace_t* parent_namespace) { 162 void* caller_addr = __builtin_return_address(0); 163 ScopedPthreadMutexLocker locker(&g_dl_mutex); 164 165 android_namespace_t* result = create_namespace(caller_addr, 166 name, 167 ld_library_path, 168 default_library_path, 169 type, 170 permitted_when_isolated_path, 171 parent_namespace); 172 173 if (result == nullptr) { 174 __bionic_format_dlerror("android_create_namespace failed", linker_get_error_buffer()); 175 } 176 177 return result; 178 } 179 180 // name_offset: starting index of the name in libdl_info.strtab 181 #define ELF32_SYM_INITIALIZER(name_offset, value, shndx) \ 182 { name_offset, \ 183 reinterpret_cast<Elf32_Addr>(value), \ 184 /* st_size */ 0, \ 185 (shndx == 0) ? 0 : (STB_GLOBAL << 4), \ 186 /* st_other */ 0, \ 187 shndx, \ 188 } 189 190 #define ELF64_SYM_INITIALIZER(name_offset, value, shndx) \ 191 { name_offset, \ 192 (shndx == 0) ? 0 : (STB_GLOBAL << 4), \ 193 /* st_other */ 0, \ 194 shndx, \ 195 reinterpret_cast<Elf64_Addr>(value), \ 196 /* st_size */ 0, \ 197 } 198 199 static const char ANDROID_LIBDL_STRTAB[] = 200 // 0000000 00011111 111112 22222222 2333333 3333444444444455555555556666666 6667777777777888888888899999 99999 201 // 0123456 78901234 567890 12345678 9012345 6789012345678901234567890123456 7890123456789012345678901234 56789 202 "dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0android_update_LD_LIBRARY_PATH\0android_get_LD_LIBRARY_PATH\0dl_it" 203 // 00000000001 1111111112222222222 3333333333444444444455555555556666666666777 777777788888888889999999999 204 // 01234567890 1234567890123456789 0123456789012345678901234567890123456789012 345678901234567890123456789 205 "erate_phdr\0android_dlopen_ext\0android_set_application_target_sdk_version\0android_get_application_tar" 206 // 0000000000111111 111122222222223333333333 4444444444555555555566666 6666677 777777778888888888 207 // 0123456789012345 678901234567890123456789 0123456789012345678901234 5678901 234567890123456789 208 "get_sdk_version\0android_init_namespaces\0android_create_namespace\0dlvsym\0android_dlwarning\0" 209 #if defined(__arm__) 210 // 290 211 "dl_unwind_find_exidx\0" 212 #endif 213 ; 214 215 static ElfW(Sym) g_libdl_symtab[] = { 216 // Total length of libdl_info.strtab, including trailing 0. 217 // This is actually the STH_UNDEF entry. Technically, it's 218 // supposed to have st_name == 0, but instead, it points to an index 219 // in the strtab with a \0 to make iterating through the symtab easier. 220 ELFW(SYM_INITIALIZER)(sizeof(ANDROID_LIBDL_STRTAB) - 1, nullptr, 0), 221 ELFW(SYM_INITIALIZER)( 0, &dlopen, 1), 222 ELFW(SYM_INITIALIZER)( 7, &dlclose, 1), 223 ELFW(SYM_INITIALIZER)( 15, &dlsym, 1), 224 ELFW(SYM_INITIALIZER)( 21, &dlerror, 1), 225 ELFW(SYM_INITIALIZER)( 29, &dladdr, 1), 226 ELFW(SYM_INITIALIZER)( 36, &android_update_LD_LIBRARY_PATH, 1), 227 ELFW(SYM_INITIALIZER)( 67, &android_get_LD_LIBRARY_PATH, 1), 228 ELFW(SYM_INITIALIZER)( 95, &dl_iterate_phdr, 1), 229 ELFW(SYM_INITIALIZER)(111, &android_dlopen_ext, 1), 230 ELFW(SYM_INITIALIZER)(130, &android_set_application_target_sdk_version, 1), 231 ELFW(SYM_INITIALIZER)(173, &android_get_application_target_sdk_version, 1), 232 ELFW(SYM_INITIALIZER)(216, &android_init_namespaces, 1), 233 ELFW(SYM_INITIALIZER)(240, &android_create_namespace, 1), 234 ELFW(SYM_INITIALIZER)(265, &dlvsym, 1), 235 ELFW(SYM_INITIALIZER)(272, &android_dlwarning, 1), 236 #if defined(__arm__) 237 ELFW(SYM_INITIALIZER)(290, &dl_unwind_find_exidx, 1), 238 #endif 239 }; 240 241 // Fake out a hash table with a single bucket. 242 // 243 // A search of the hash table will look through g_libdl_symtab starting with index 1, then 244 // use g_libdl_chains to find the next index to look at. g_libdl_chains should be set up to 245 // walk through every element in g_libdl_symtab, and then end with 0 (sentinel value). 246 // 247 // That is, g_libdl_chains should look like { 0, 2, 3, ... N, 0 } where N is the number 248 // of actual symbols, or nelems(g_libdl_symtab)-1 (since the first element of g_libdl_symtab is not 249 // a real symbol). (See soinfo_elf_lookup().) 250 // 251 // Note that adding any new symbols here requires stubbing them out in libdl. 252 static unsigned g_libdl_buckets[1] = { 1 }; 253 #if defined(__arm__) 254 static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 0 }; 255 #else 256 static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0 }; 257 #endif 258 259 static uint8_t __libdl_info_buf[sizeof(soinfo)] __attribute__((aligned(8))); 260 static soinfo* __libdl_info = nullptr; 261 262 extern android_namespace_t g_default_namespace; 263 264 // This is used by the dynamic linker. Every process gets these symbols for free. 265 soinfo* get_libdl_info() { 266 if (__libdl_info == nullptr) { 267 __libdl_info = new (__libdl_info_buf) soinfo(&g_default_namespace, "libdl.so", nullptr, 0, RTLD_GLOBAL); 268 __libdl_info->flags_ |= FLAG_LINKED; 269 __libdl_info->strtab_ = ANDROID_LIBDL_STRTAB; 270 __libdl_info->symtab_ = g_libdl_symtab; 271 __libdl_info->nbucket_ = sizeof(g_libdl_buckets)/sizeof(unsigned); 272 __libdl_info->nchain_ = sizeof(g_libdl_chains)/sizeof(unsigned); 273 __libdl_info->bucket_ = g_libdl_buckets; 274 __libdl_info->chain_ = g_libdl_chains; 275 __libdl_info->ref_count_ = 1; 276 __libdl_info->strtab_size_ = sizeof(ANDROID_LIBDL_STRTAB); 277 __libdl_info->local_group_root_ = __libdl_info; 278 __libdl_info->soname_ = "libdl.so"; 279 __libdl_info->target_sdk_version_ = __ANDROID_API__; 280 __libdl_info->generate_handle(); 281 #if defined(__work_around_b_24465209__) 282 strlcpy(__libdl_info->old_name_, __libdl_info->soname_, sizeof(__libdl_info->old_name_)); 283 #endif 284 } 285 286 return __libdl_info; 287 } 288
