dlfcn.cpp revision 5e071a18ce88d93fcffaebb9e0f62524ae504908 
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, int flags,
71                        const android_dlextinfo* extinfo, void* caller_addr) {
72  ScopedPthreadMutexLocker locker(&g_dl_mutex);
73  g_linker_logger.ResetState();
74  void* result = do_dlopen(filename, flags, extinfo, caller_addr);
75  if (result == nullptr) {
76    __bionic_format_dlerror("dlopen failed", linker_get_error_buffer());
77    return nullptr;
78  }
79  return result;
80}
81
82void* android_dlopen_ext(const char* filename, int flags, const android_dlextinfo* extinfo) {
83  void* caller_addr = __builtin_return_address(0);
84  return dlopen_ext(filename, flags, extinfo, caller_addr);
85}
86
87void* dlopen(const char* filename, int flags) {
88  void* caller_addr = __builtin_return_address(0);
89  return dlopen_ext(filename, flags, nullptr, caller_addr);
90}
91
92void* dlsym_impl(void* handle, const char* symbol, const char* version, void* caller_addr) {
93  ScopedPthreadMutexLocker locker(&g_dl_mutex);
94  g_linker_logger.ResetState();
95  void* result;
96  if (!do_dlsym(handle, symbol, version, caller_addr, &result)) {
97    __bionic_format_dlerror(linker_get_error_buffer(), nullptr);
98    return nullptr;
99  }
100
101  return result;
102}
103
104void* dlsym(void* handle, const char* symbol) {
105  void* caller_addr = __builtin_return_address(0);
106  return dlsym_impl(handle, symbol, nullptr, caller_addr);
107}
108
109void* dlvsym(void* handle, const char* symbol, const char* version) {
110  void* caller_addr = __builtin_return_address(0);
111  return dlsym_impl(handle, symbol, version, caller_addr);
112}
113
114int dladdr(const void* addr, Dl_info* info) {
115  ScopedPthreadMutexLocker locker(&g_dl_mutex);
116  return do_dladdr(addr, info);
117}
118
119int dlclose(void* handle) {
120  ScopedPthreadMutexLocker locker(&g_dl_mutex);
121  int result = do_dlclose(handle);
122  if (result != 0) {
123    __bionic_format_dlerror("dlclose failed", linker_get_error_buffer());
124  }
125  return result;
126}
127
128int dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data) {
129  ScopedPthreadMutexLocker locker(&g_dl_mutex);
130  return do_dl_iterate_phdr(cb, data);
131}
132
133void android_set_application_target_sdk_version(uint32_t target) {
134  // lock to avoid modification in the middle of dlopen.
135  ScopedPthreadMutexLocker locker(&g_dl_mutex);
136  set_application_target_sdk_version(target);
137}
138
139uint32_t android_get_application_target_sdk_version() {
140  return get_application_target_sdk_version();
141}
142
143void android_dlwarning(void* obj, void (*f)(void*, const char*)) {
144  ScopedPthreadMutexLocker locker(&g_dl_mutex);
145  get_dlwarning(obj, f);
146}
147
148bool android_init_namespaces(const char* public_ns_sonames,
149                             const char* anon_ns_library_path) {
150  ScopedPthreadMutexLocker locker(&g_dl_mutex);
151  bool success = init_namespaces(public_ns_sonames, anon_ns_library_path);
152  if (!success) {
153    __bionic_format_dlerror("android_init_namespaces failed", linker_get_error_buffer());
154  }
155
156  return success;
157}
158
159android_namespace_t* android_create_namespace(const char* name,
160                                              const char* ld_library_path,
161                                              const char* default_library_path,
162                                              uint64_t type,
163                                              const char* permitted_when_isolated_path,
164                                              android_namespace_t* parent_namespace) {
165  void* caller_addr = __builtin_return_address(0);
166  ScopedPthreadMutexLocker locker(&g_dl_mutex);
167
168  android_namespace_t* result = create_namespace(caller_addr,
169                                                 name,
170                                                 ld_library_path,
171                                                 default_library_path,
172                                                 type,
173                                                 permitted_when_isolated_path,
174                                                 parent_namespace);
175
176  if (result == nullptr) {
177    __bionic_format_dlerror("android_create_namespace failed", linker_get_error_buffer());
178  }
179
180  return result;
181}
182
183// name_offset: starting index of the name in libdl_info.strtab
184#define ELF32_SYM_INITIALIZER(name_offset, value, shndx) \
185    { name_offset, \
186      reinterpret_cast<Elf32_Addr>(value), \
187      /* st_size */ 0, \
188      ((shndx) == 0) ? 0 : (STB_GLOBAL << 4), \
189      /* st_other */ 0, \
190      shndx, \
191    }
192
193#define ELF64_SYM_INITIALIZER(name_offset, value, shndx) \
194    { name_offset, \
195      ((shndx) == 0) ? 0 : (STB_GLOBAL << 4), \
196      /* st_other */ 0, \
197      shndx, \
198      reinterpret_cast<Elf64_Addr>(value), \
199      /* st_size */ 0, \
200    }
201
202static const char ANDROID_LIBDL_STRTAB[] =
203  // 0000000 00011111 111112 22222222 2333333 3333444444444455555555556666666 6667777777777888888888899999 99999
204  // 0123456 78901234 567890 12345678 9012345 6789012345678901234567890123456 7890123456789012345678901234 56789
205    "dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0android_update_LD_LIBRARY_PATH\0android_get_LD_LIBRARY_PATH\0dl_it"
206  // 00000000001 1111111112222222222 3333333333444444444455555555556666666666777 777777788888888889999999999
207  // 01234567890 1234567890123456789 0123456789012345678901234567890123456789012 345678901234567890123456789
208    "erate_phdr\0android_dlopen_ext\0android_set_application_target_sdk_version\0android_get_application_tar"
209  // 0000000000111111 111122222222223333333333 4444444444555555555566666 6666677 777777778888888888
210  // 0123456789012345 678901234567890123456789 0123456789012345678901234 5678901 234567890123456789
211    "get_sdk_version\0android_init_namespaces\0android_create_namespace\0dlvsym\0android_dlwarning\0"
212#if defined(__arm__)
213  // 290
214    "dl_unwind_find_exidx\0"
215#endif
216    ;
217
218static ElfW(Sym) g_libdl_symtab[] = {
219  // Total length of libdl_info.strtab, including trailing 0.
220  // This is actually the STH_UNDEF entry. Technically, it's
221  // supposed to have st_name == 0, but instead, it points to an index
222  // in the strtab with a \0 to make iterating through the symtab easier.
223  ELFW(SYM_INITIALIZER)(sizeof(ANDROID_LIBDL_STRTAB) - 1, nullptr, 0),
224  ELFW(SYM_INITIALIZER)(  0, &dlopen, 1),
225  ELFW(SYM_INITIALIZER)(  7, &dlclose, 1),
226  ELFW(SYM_INITIALIZER)( 15, &dlsym, 1),
227  ELFW(SYM_INITIALIZER)( 21, &dlerror, 1),
228  ELFW(SYM_INITIALIZER)( 29, &dladdr, 1),
229  ELFW(SYM_INITIALIZER)( 36, &android_update_LD_LIBRARY_PATH, 1),
230  ELFW(SYM_INITIALIZER)( 67, &android_get_LD_LIBRARY_PATH, 1),
231  ELFW(SYM_INITIALIZER)( 95, &dl_iterate_phdr, 1),
232  ELFW(SYM_INITIALIZER)(111, &android_dlopen_ext, 1),
233  ELFW(SYM_INITIALIZER)(130, &android_set_application_target_sdk_version, 1),
234  ELFW(SYM_INITIALIZER)(173, &android_get_application_target_sdk_version, 1),
235  ELFW(SYM_INITIALIZER)(216, &android_init_namespaces, 1),
236  ELFW(SYM_INITIALIZER)(240, &android_create_namespace, 1),
237  ELFW(SYM_INITIALIZER)(265, &dlvsym, 1),
238  ELFW(SYM_INITIALIZER)(272, &android_dlwarning, 1),
239#if defined(__arm__)
240  ELFW(SYM_INITIALIZER)(290, &dl_unwind_find_exidx, 1),
241#endif
242};
243
244// Fake out a hash table with a single bucket.
245//
246// A search of the hash table will look through g_libdl_symtab starting with index 1, then
247// use g_libdl_chains to find the next index to look at. g_libdl_chains should be set up to
248// walk through every element in g_libdl_symtab, and then end with 0 (sentinel value).
249//
250// That is, g_libdl_chains should look like { 0, 2, 3, ... N, 0 } where N is the number
251// of actual symbols, or nelems(g_libdl_symtab)-1 (since the first element of g_libdl_symtab is not
252// a real symbol). (See soinfo_elf_lookup().)
253//
254// Note that adding any new symbols here requires stubbing them out in libdl.
255static unsigned g_libdl_buckets[1] = { 1 };
256#if defined(__arm__)
257static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 0 };
258#else
259static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0 };
260#endif
261
262static uint8_t __libdl_info_buf[sizeof(soinfo)] __attribute__((aligned(8)));
263static soinfo* __libdl_info = nullptr;
264
265// This is used by the dynamic linker. Every process gets these symbols for free.
266soinfo* get_libdl_info() {
267  if (__libdl_info == nullptr) {
268    __libdl_info = new (__libdl_info_buf) soinfo(&g_default_namespace, "libdl.so", nullptr, 0, RTLD_GLOBAL);
269    __libdl_info->flags_ |= FLAG_LINKED;
270    __libdl_info->strtab_ = ANDROID_LIBDL_STRTAB;
271    __libdl_info->symtab_ = g_libdl_symtab;
272    __libdl_info->nbucket_ = sizeof(g_libdl_buckets)/sizeof(unsigned);
273    __libdl_info->nchain_ = sizeof(g_libdl_chains)/sizeof(unsigned);
274    __libdl_info->bucket_ = g_libdl_buckets;
275    __libdl_info->chain_ = g_libdl_chains;
276    __libdl_info->ref_count_ = 1;
277    __libdl_info->strtab_size_ = sizeof(ANDROID_LIBDL_STRTAB);
278    __libdl_info->local_group_root_ = __libdl_info;
279    __libdl_info->soname_ = "libdl.so";
280    __libdl_info->target_sdk_version_ = __ANDROID_API__;
281    __libdl_info->generate_handle();
282#if defined(__work_around_b_24465209__)
283    strlcpy(__libdl_info->old_name_, __libdl_info->soname_, sizeof(__libdl_info->old_name_));
284#endif
285  }
286
287  return __libdl_info;
288}
289