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
__bionic_set_dlerror(char * new_value)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
__bionic_format_dlerror(const char * msg,const char * detail)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
dlerror()54 const char* dlerror() {
55 const char* old_value = __bionic_set_dlerror(nullptr);
56 return old_value;
57 }
58
android_get_LD_LIBRARY_PATH(char * buffer,size_t buffer_size)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
android_update_LD_LIBRARY_PATH(const char * ld_library_path)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
dlopen_ext(const char * filename,int flags,const android_dlextinfo * extinfo,void * caller_addr)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
android_dlopen_ext(const char * filename,int flags,const android_dlextinfo * extinfo)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
dlopen(const char * filename,int flags)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
dlsym_impl(void * handle,const char * symbol,const char * version,void * caller_addr)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
dlsym(void * handle,const char * symbol)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
dlvsym(void * handle,const char * symbol,const char * version)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
dladdr(const void * addr,Dl_info * info)111 int dladdr(const void* addr, Dl_info* info) {
112 ScopedPthreadMutexLocker locker(&g_dl_mutex);
113 return do_dladdr(addr, info);
114 }
115
dlclose(void * handle)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
dl_iterate_phdr(int (* cb)(dl_phdr_info * info,size_t size,void * data),void * data)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
android_set_application_target_sdk_version(uint32_t target)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
android_get_application_target_sdk_version()136 uint32_t android_get_application_target_sdk_version() {
137 return get_application_target_sdk_version();
138 }
139
android_dlwarning(void * obj,void (* f)(void *,const char *))140 void android_dlwarning(void* obj, void (*f)(void*, const char*)) {
141 ScopedPthreadMutexLocker locker(&g_dl_mutex);
142 get_dlwarning(obj, f);
143 }
144
android_init_namespaces(const char * public_ns_sonames,const char * anon_ns_library_path)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
android_create_namespace(const char * name,const char * ld_library_path,const char * default_library_path,uint64_t type,const char * permitted_when_isolated_path,android_namespace_t * parent_namespace)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.
get_libdl_info()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