dlfcn.cpp revision c12acef96bd80c419654e159e1dc24a69513a86d 
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_globals.h"
19#include "linker_dlwarning.h"
20
21#include <pthread.h>
22#include <stdio.h>
23#include <stdlib.h>
24#include <string.h>
25#include <android/api-level.h>
26
27#include <bionic/pthread_internal.h>
28#include "private/bionic_tls.h"
29#include "private/ScopedPthreadMutexLocker.h"
30#include "private/ThreadLocalBuffer.h"
31
32/* This file hijacks the symbols stubbed out in libdl.so. */
33
34static pthread_mutex_t g_dl_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
35
36static char* __bionic_set_dlerror(char* new_value) {
37  char** dlerror_slot = &reinterpret_cast<char**>(__get_tls())[TLS_SLOT_DLERROR];
38
39  char* old_value = *dlerror_slot;
40  *dlerror_slot = new_value;
41  return old_value;
42}
43
44static void __bionic_format_dlerror(const char* msg, const char* detail) {
45  char* buffer = __get_thread()->dlerror_buffer;
46  strlcpy(buffer, msg, __BIONIC_DLERROR_BUFFER_SIZE);
47  if (detail != nullptr) {
48    strlcat(buffer, ": ", __BIONIC_DLERROR_BUFFER_SIZE);
49    strlcat(buffer, detail, __BIONIC_DLERROR_BUFFER_SIZE);
50  }
51
52  __bionic_set_dlerror(buffer);
53}
54
55char* __dlerror() {
56  char* old_value = __bionic_set_dlerror(nullptr);
57  return old_value;
58}
59
60void __android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
61  ScopedPthreadMutexLocker locker(&g_dl_mutex);
62  do_android_get_LD_LIBRARY_PATH(buffer, buffer_size);
63}
64
65void __android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
66  ScopedPthreadMutexLocker locker(&g_dl_mutex);
67  do_android_update_LD_LIBRARY_PATH(ld_library_path);
68}
69
70static void* dlopen_ext(const char* filename,
71                        int flags,
72                        const android_dlextinfo* extinfo,
73                        const void* caller_addr) {
74  ScopedPthreadMutexLocker locker(&g_dl_mutex);
75  g_linker_logger.ResetState();
76  void* result = do_dlopen(filename, flags, extinfo, caller_addr);
77  if (result == nullptr) {
78    __bionic_format_dlerror("dlopen failed", linker_get_error_buffer());
79    return nullptr;
80  }
81  return result;
82}
83
84void* __android_dlopen_ext(const char* filename,
85                           int flags,
86                           const android_dlextinfo* extinfo,
87                           const void* caller_addr) {
88  return dlopen_ext(filename, flags, extinfo, caller_addr);
89}
90
91void* __dlopen(const char* filename, int flags, const void* caller_addr) {
92  return dlopen_ext(filename, flags, nullptr, caller_addr);
93}
94
95void* dlsym_impl(void* handle, const char* symbol, const char* version, const void* caller_addr) {
96  ScopedPthreadMutexLocker locker(&g_dl_mutex);
97  g_linker_logger.ResetState();
98  void* result;
99  if (!do_dlsym(handle, symbol, version, caller_addr, &result)) {
100    __bionic_format_dlerror(linker_get_error_buffer(), nullptr);
101    return nullptr;
102  }
103
104  return result;
105}
106
107void* __dlsym(void* handle, const char* symbol, const void* caller_addr) {
108  return dlsym_impl(handle, symbol, nullptr, caller_addr);
109}
110
111void* __dlvsym(void* handle, const char* symbol, const char* version, const void* caller_addr) {
112  return dlsym_impl(handle, symbol, version, caller_addr);
113}
114
115int __dladdr(const void* addr, Dl_info* info) {
116  ScopedPthreadMutexLocker locker(&g_dl_mutex);
117  return do_dladdr(addr, info);
118}
119
120int __dlclose(void* handle) {
121  ScopedPthreadMutexLocker locker(&g_dl_mutex);
122  int result = do_dlclose(handle);
123  if (result != 0) {
124    __bionic_format_dlerror("dlclose failed", linker_get_error_buffer());
125  }
126  return result;
127}
128
129int __dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data) {
130  ScopedPthreadMutexLocker locker(&g_dl_mutex);
131  return do_dl_iterate_phdr(cb, data);
132}
133
134#if defined(__arm__)
135_Unwind_Ptr __dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) {
136  ScopedPthreadMutexLocker locker(&g_dl_mutex);
137  return do_dl_unwind_find_exidx(pc, pcount);
138}
139#endif
140
141void __android_set_application_target_sdk_version(uint32_t target) {
142  // lock to avoid modification in the middle of dlopen.
143  ScopedPthreadMutexLocker locker(&g_dl_mutex);
144  set_application_target_sdk_version(target);
145}
146
147uint32_t __android_get_application_target_sdk_version() {
148  return get_application_target_sdk_version();
149}
150
151void __android_dlwarning(void* obj, void (*f)(void*, const char*)) {
152  ScopedPthreadMutexLocker locker(&g_dl_mutex);
153  get_dlwarning(obj, f);
154}
155
156bool __android_init_namespaces(const char* public_ns_sonames,
157                             const char* anon_ns_library_path) {
158  ScopedPthreadMutexLocker locker(&g_dl_mutex);
159  bool success = init_namespaces(public_ns_sonames, anon_ns_library_path);
160  if (!success) {
161    __bionic_format_dlerror("android_init_namespaces failed", linker_get_error_buffer());
162  }
163
164  return success;
165}
166
167android_namespace_t* __android_create_namespace(const char* name,
168                                                const char* ld_library_path,
169                                                const char* default_library_path,
170                                                uint64_t type,
171                                                const char* permitted_when_isolated_path,
172                                                android_namespace_t* parent_namespace,
173                                                const void* caller_addr) {
174  ScopedPthreadMutexLocker locker(&g_dl_mutex);
175
176  android_namespace_t* result = create_namespace(caller_addr,
177                                                 name,
178                                                 ld_library_path,
179                                                 default_library_path,
180                                                 type,
181                                                 permitted_when_isolated_path,
182                                                 parent_namespace);
183
184  if (result == nullptr) {
185    __bionic_format_dlerror("android_create_namespace failed", linker_get_error_buffer());
186  }
187
188  return result;
189}
190
191// name_offset: starting index of the name in libdl_info.strtab
192#define ELF32_SYM_INITIALIZER(name_offset, value, shndx) \
193    { name_offset, \
194      reinterpret_cast<Elf32_Addr>(value), \
195      /* st_size */ 0, \
196      ((shndx) == 0) ? 0 : (STB_GLOBAL << 4), \
197      /* st_other */ 0, \
198      shndx, \
199    }
200
201#define ELF64_SYM_INITIALIZER(name_offset, value, shndx) \
202    { name_offset, \
203      ((shndx) == 0) ? 0 : (STB_GLOBAL << 4), \
204      /* st_other */ 0, \
205      shndx, \
206      reinterpret_cast<Elf64_Addr>(value), \
207      /* st_size */ 0, \
208    }
209
210static const char ANDROID_LIBDL_STRTAB[] =
211  // 0000000000111111 11112222222222333 333333344444444 44555555555566666 6666677777777778 8888888889999999999
212  // 0123456789012345 67890123456789012 345678901234567 89012345678901234 5678901234567890 1234567890123456789
213    "__loader_dlopen\0__loader_dlclose\0__loader_dlsym\0__loader_dlerror\0__loader_dladdr\0__loader_android_up"
214  // 1*
215  // 000000000011111111112 2222222223333333333444444444455555555 5566666666667777777777888 88888889999999999
216  // 012345678901234567890 1234567890123456789012345678901234567 8901234567890123456789012 34567890123456789
217    "date_LD_LIBRARY_PATH\0__loader_android_get_LD_LIBRARY_PATH\0__loader_dl_iterate_phdr\0__loader_android_"
218  // 2*
219  // 00000000001 1111111112222222222333333333344444444445555555555666 6666666777777777788888888889999999999
220  // 01234567890 1234567890123456789012345678901234567890123456789012 3456789012345678901234567890123456789
221    "dlopen_ext\0__loader_android_set_application_target_sdk_version\0__loader_android_get_application_targ"
222  // 3*
223  // 000000000011111 111112222222222333333333344444444 4455555555556666666666777777777788 888888889999999 999
224  // 012345678901234 567890123456789012345678901234567 8901234567890123456789012345678901 234567890123456 789
225    "et_sdk_version\0__loader_android_init_namespaces\0__loader_android_create_namespace\0__loader_dlvsym\0__"
226  // 4*
227  // 0000000000111111111122222 2222233333333334444444 4445555555555666666666677777777778 8888888889999999 999
228  // 0123456789012345678901234 5678901234567890123456 7890123456789012345678901234567890 1234567890123456 789
229    "loader_android_dlwarning\0"
230#if defined(__arm__)
231  // 425
232    "__loader_dl_unwind_find_exidx\0"
233#endif
234    ;
235
236static ElfW(Sym) g_libdl_symtab[] = {
237  // Total length of libdl_info.strtab, including trailing 0.
238  // This is actually the STH_UNDEF entry. Technically, it's
239  // supposed to have st_name == 0, but instead, it points to an index
240  // in the strtab with a \0 to make iterating through the symtab easier.
241  ELFW(SYM_INITIALIZER)(sizeof(ANDROID_LIBDL_STRTAB) - 1, nullptr, 0),
242  ELFW(SYM_INITIALIZER)(  0, &__dlopen, 1),
243  ELFW(SYM_INITIALIZER)( 16, &__dlclose, 1),
244  ELFW(SYM_INITIALIZER)( 33, &__dlsym, 1),
245  ELFW(SYM_INITIALIZER)( 48, &__dlerror, 1),
246  ELFW(SYM_INITIALIZER)( 65, &__dladdr, 1),
247  ELFW(SYM_INITIALIZER)( 81, &__android_update_LD_LIBRARY_PATH, 1),
248  ELFW(SYM_INITIALIZER)(121, &__android_get_LD_LIBRARY_PATH, 1),
249  ELFW(SYM_INITIALIZER)(158, &__dl_iterate_phdr, 1),
250  ELFW(SYM_INITIALIZER)(183, &__android_dlopen_ext, 1),
251  ELFW(SYM_INITIALIZER)(211, &__android_set_application_target_sdk_version, 1),
252  ELFW(SYM_INITIALIZER)(263, &__android_get_application_target_sdk_version, 1),
253  ELFW(SYM_INITIALIZER)(315, &__android_init_namespaces, 1),
254  ELFW(SYM_INITIALIZER)(348, &__android_create_namespace, 1),
255  ELFW(SYM_INITIALIZER)(382, &__dlvsym, 1),
256  ELFW(SYM_INITIALIZER)(397, &__android_dlwarning, 1),
257#if defined(__arm__)
258  ELFW(SYM_INITIALIZER)(425, &__dl_unwind_find_exidx, 1),
259#endif
260};
261
262// Fake out a hash table with a single bucket.
263//
264// A search of the hash table will look through g_libdl_symtab starting with index 1, then
265// use g_libdl_chains to find the next index to look at. g_libdl_chains should be set up to
266// walk through every element in g_libdl_symtab, and then end with 0 (sentinel value).
267//
268// That is, g_libdl_chains should look like { 0, 2, 3, ... N, 0 } where N is the number
269// of actual symbols, or nelems(g_libdl_symtab)-1 (since the first element of g_libdl_symtab is not
270// a real symbol). (See soinfo_elf_lookup().)
271//
272// Note that adding any new symbols here requires stubbing them out in libdl.
273static unsigned g_libdl_buckets[1] = { 1 };
274#if defined(__arm__)
275static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 0 };
276#else
277static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0 };
278#endif
279
280static uint8_t __libdl_info_buf[sizeof(soinfo)] __attribute__((aligned(8)));
281static soinfo* __libdl_info = nullptr;
282
283// This is used by the dynamic linker. Every process gets these symbols for free.
284soinfo* get_libdl_info(const char* linker_path) {
285  if (__libdl_info == nullptr) {
286    __libdl_info = new (__libdl_info_buf) soinfo(&g_default_namespace, linker_path, nullptr, 0, 0);
287    __libdl_info->flags_ |= FLAG_LINKED;
288    __libdl_info->strtab_ = ANDROID_LIBDL_STRTAB;
289    __libdl_info->symtab_ = g_libdl_symtab;
290    __libdl_info->nbucket_ = sizeof(g_libdl_buckets)/sizeof(unsigned);
291    __libdl_info->nchain_ = sizeof(g_libdl_chains)/sizeof(unsigned);
292    __libdl_info->bucket_ = g_libdl_buckets;
293    __libdl_info->chain_ = g_libdl_chains;
294    __libdl_info->ref_count_ = 1;
295    __libdl_info->strtab_size_ = sizeof(ANDROID_LIBDL_STRTAB);
296    __libdl_info->local_group_root_ = __libdl_info;
297    __libdl_info->soname_ = "ld-android.so";
298    __libdl_info->target_sdk_version_ = __ANDROID_API__;
299    __libdl_info->generate_handle();
300#if defined(__work_around_b_24465209__)
301    strlcpy(__libdl_info->old_name_, __libdl_info->soname_, sizeof(__libdl_info->old_name_));
302#endif
303  }
304
305  return __libdl_info;
306}
307