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d42e7319 JB |
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 | #define _GNU_SOURCE | |
17 | #include <dlfcn.h> | |
18 | #include <pthread.h> | |
19 | #include <time.h> | |
20 | #include <stdio.h> | |
21 | #include <string.h> | |
22 | #include "linker.h" | |
23 | #include "linker_format.h" | |
24 | ||
25 | /* This file hijacks the symbols stubbed out in libdl.so. */ | |
26 | ||
27 | #define DL_SUCCESS 0 | |
28 | #define DL_ERR_CANNOT_LOAD_LIBRARY 1 | |
29 | #define DL_ERR_INVALID_LIBRARY_HANDLE 2 | |
30 | #define DL_ERR_BAD_SYMBOL_NAME 3 | |
31 | #define DL_ERR_SYMBOL_NOT_FOUND 4 | |
32 | #define DL_ERR_SYMBOL_NOT_GLOBAL 5 | |
33 | ||
34 | static char dl_err_buf[1024]; | |
35 | static const char *dl_err_str; | |
36 | ||
37 | static const char *dl_errors[] = { | |
38 | [DL_ERR_CANNOT_LOAD_LIBRARY] = "Cannot load library", | |
39 | [DL_ERR_INVALID_LIBRARY_HANDLE] = "Invalid library handle", | |
40 | [DL_ERR_BAD_SYMBOL_NAME] = "Invalid symbol name", | |
41 | [DL_ERR_SYMBOL_NOT_FOUND] = "Symbol not found", | |
42 | [DL_ERR_SYMBOL_NOT_GLOBAL] = "Symbol is not global", | |
43 | }; | |
44 | ||
45 | #define likely(expr) __builtin_expect (expr, 1) | |
46 | #define unlikely(expr) __builtin_expect (expr, 0) | |
47 | ||
48 | pthread_mutex_t dl_lock = PTHREAD_MUTEX_INITIALIZER; | |
49 | ||
50 | static void set_dlerror(int err) | |
51 | { | |
52 | format_buffer(dl_err_buf, sizeof(dl_err_buf), "%s: %s", dl_errors[err], | |
53 | linker_get_error()); | |
54 | dl_err_str = (const char *)&dl_err_buf[0]; | |
55 | }; | |
56 | ||
57 | void *android_dlopen(const char *filename, int flag) | |
58 | { | |
59 | soinfo *ret; | |
60 | ||
61 | pthread_mutex_lock(&dl_lock); | |
62 | ret = find_library(filename); | |
63 | if (unlikely(ret == NULL)) { | |
64 | set_dlerror(DL_ERR_CANNOT_LOAD_LIBRARY); | |
65 | } else { | |
66 | call_constructors_recursive(ret); | |
67 | ret->refcount++; | |
68 | } | |
69 | pthread_mutex_unlock(&dl_lock); | |
70 | return ret; | |
71 | } | |
72 | ||
73 | const char *android_dlerror(void) | |
74 | { | |
75 | const char *tmp = dl_err_str; | |
76 | dl_err_str = NULL; | |
77 | return (const char *)tmp; | |
78 | } | |
79 | ||
80 | void *android_dlsym(void *handle, const char *symbol) | |
81 | { | |
82 | soinfo *found; | |
83 | Elf32_Sym *sym; | |
84 | unsigned bind; | |
85 | ||
86 | pthread_mutex_lock(&dl_lock); | |
87 | ||
88 | if(unlikely(handle == 0)) { | |
89 | set_dlerror(DL_ERR_INVALID_LIBRARY_HANDLE); | |
90 | goto err; | |
91 | } | |
92 | if(unlikely(symbol == 0)) { | |
93 | set_dlerror(DL_ERR_BAD_SYMBOL_NAME); | |
94 | goto err; | |
95 | } | |
96 | ||
97 | if(handle == RTLD_DEFAULT) { | |
98 | sym = lookup(symbol, &found, NULL); | |
99 | } else if(handle == RTLD_NEXT) { | |
100 | void *ret_addr = __builtin_return_address(0); | |
101 | soinfo *si = find_containing_library(ret_addr); | |
102 | ||
103 | sym = NULL; | |
104 | if(si && si->next) { | |
105 | sym = lookup(symbol, &found, si->next); | |
106 | } | |
107 | } else { | |
108 | found = (soinfo*)handle; | |
109 | sym = lookup_in_library(found, symbol); | |
110 | } | |
111 | ||
112 | if(likely(sym != 0)) { | |
113 | bind = ELF32_ST_BIND(sym->st_info); | |
114 | ||
115 | if(likely((bind == STB_GLOBAL) && (sym->st_shndx != 0))) { | |
116 | unsigned ret = sym->st_value + found->base; | |
117 | pthread_mutex_unlock(&dl_lock); | |
118 | return (void*)ret; | |
119 | } | |
120 | ||
121 | set_dlerror(DL_ERR_SYMBOL_NOT_GLOBAL); | |
122 | } | |
123 | else | |
124 | set_dlerror(DL_ERR_SYMBOL_NOT_FOUND); | |
125 | ||
126 | err: | |
127 | pthread_mutex_unlock(&dl_lock); | |
128 | return 0; | |
129 | } | |
130 | ||
131 | int android_dladdr(const void *addr, Dl_info *info) | |
132 | { | |
133 | int ret = 0; | |
134 | ||
135 | pthread_mutex_lock(&dl_lock); | |
136 | ||
137 | /* Determine if this address can be found in any library currently mapped */ | |
138 | soinfo *si = find_containing_library(addr); | |
139 | ||
140 | if(si) { | |
141 | memset(info, 0, sizeof(Dl_info)); | |
142 | ||
143 | info->dli_fname = si->name; | |
144 | info->dli_fbase = (void*)si->base; | |
145 | ||
146 | /* Determine if any symbol in the library contains the specified address */ | |
147 | Elf32_Sym *sym = find_containing_symbol(addr, si); | |
148 | ||
149 | if(sym != NULL) { | |
150 | info->dli_sname = si->strtab + sym->st_name; | |
151 | info->dli_saddr = (void*)(si->base + sym->st_value); | |
152 | } | |
153 | ||
154 | ret = 1; | |
155 | } | |
156 | ||
157 | pthread_mutex_unlock(&dl_lock); | |
158 | ||
159 | return ret; | |
160 | } | |
161 | ||
162 | int android_dlclose(void *handle) | |
163 | { | |
164 | pthread_mutex_lock(&dl_lock); | |
165 | (void)unload_library((soinfo*)handle); | |
166 | pthread_mutex_unlock(&dl_lock); | |
167 | return 0; | |
168 | } | |
169 | ||
170 | ||
171 | #if defined(ANDROID_ARM_LINKER) | |
172 | // 0000000 00011111 111112 22222222 2333333 333344444444445555555 | |
173 | // 0123456 78901234 567890 12345678 9012345 678901234567890123456 | |
174 | #define ANDROID_LIBDL_STRTAB \ | |
175 | "dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0dl_unwind_find_exidx\0" | |
176 | ||
177 | _Unwind_Ptr android_dl_unwind_find_exidx(_Unwind_Ptr pc, int *pcount); | |
178 | ||
179 | #elif defined(ANDROID_X86_LINKER) | |
180 | // 0000000 00011111 111112 22222222 2333333 3333444444444455 | |
181 | // 0123456 78901234 567890 12345678 9012345 6789012345678901 | |
182 | #define ANDROID_LIBDL_STRTAB \ | |
183 | "dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0dl_iterate_phdr\0" | |
184 | int | |
185 | android_dl_iterate_phdr(int (*cb)(struct dl_phdr_info *info, size_t size, void *data), | |
186 | void *data); | |
187 | ||
188 | #else | |
189 | #error Unsupported architecture. Only ARM and x86 are presently supported. | |
190 | #endif | |
191 | ||
192 | ||
193 | static Elf32_Sym libdl_symtab[] = { | |
194 | // total length of libdl_info.strtab, including trailing 0 | |
195 | // This is actually the the STH_UNDEF entry. Technically, it's | |
196 | // supposed to have st_name == 0, but instead, it points to an index | |
197 | // in the strtab with a \0 to make iterating through the symtab easier. | |
198 | { st_name: sizeof(ANDROID_LIBDL_STRTAB) - 1, | |
199 | }, | |
200 | { st_name: 0, // starting index of the name in libdl_info.strtab | |
201 | st_value: (Elf32_Addr) &android_dlopen, | |
202 | st_info: STB_GLOBAL << 4, | |
203 | st_shndx: 1, | |
204 | }, | |
205 | { st_name: 7, | |
206 | st_value: (Elf32_Addr) &android_dlclose, | |
207 | st_info: STB_GLOBAL << 4, | |
208 | st_shndx: 1, | |
209 | }, | |
210 | { st_name: 15, | |
211 | st_value: (Elf32_Addr) &android_dlsym, | |
212 | st_info: STB_GLOBAL << 4, | |
213 | st_shndx: 1, | |
214 | }, | |
215 | { st_name: 21, | |
216 | st_value: (Elf32_Addr) &android_dlerror, | |
217 | st_info: STB_GLOBAL << 4, | |
218 | st_shndx: 1, | |
219 | }, | |
220 | { st_name: 29, | |
221 | st_value: (Elf32_Addr) &android_dladdr, | |
222 | st_info: STB_GLOBAL << 4, | |
223 | st_shndx: 1, | |
224 | }, | |
225 | #ifdef ANDROID_ARM_LINKER | |
226 | { st_name: 36, | |
227 | st_value: (Elf32_Addr) &android_dl_unwind_find_exidx, | |
228 | st_info: STB_GLOBAL << 4, | |
229 | st_shndx: 1, | |
230 | }, | |
231 | #elif defined(ANDROID_X86_LINKER) | |
232 | { st_name: 36, | |
233 | st_value: (Elf32_Addr) &android_dl_iterate_phdr, | |
234 | st_info: STB_GLOBAL << 4, | |
235 | st_shndx: 1, | |
236 | }, | |
237 | #endif | |
238 | }; | |
239 | ||
240 | /* Fake out a hash table with a single bucket. | |
241 | * A search of the hash table will look through | |
242 | * libdl_symtab starting with index [1], then | |
243 | * use libdl_chains to find the next index to | |
244 | * look at. libdl_chains should be set up to | |
245 | * walk through every element in libdl_symtab, | |
246 | * and then end with 0 (sentinel value). | |
247 | * | |
248 | * I.e., libdl_chains should look like | |
249 | * { 0, 2, 3, ... N, 0 } where N is the number | |
250 | * of actual symbols, or nelems(libdl_symtab)-1 | |
251 | * (since the first element of libdl_symtab is not | |
252 | * a real symbol). | |
253 | * | |
254 | * (see _elf_lookup()) | |
255 | * | |
256 | * Note that adding any new symbols here requires | |
257 | * stubbing them out in libdl. | |
258 | */ | |
259 | static unsigned libdl_buckets[1] = { 1 }; | |
260 | static unsigned libdl_chains[7] = { 0, 2, 3, 4, 5, 6, 0 }; | |
261 | ||
262 | soinfo libdl_info = { | |
263 | name: "libdl.so", | |
264 | flags: FLAG_LINKED, | |
265 | ||
266 | strtab: ANDROID_LIBDL_STRTAB, | |
267 | symtab: libdl_symtab, | |
268 | ||
269 | nbucket: 1, | |
270 | nchain: 7, | |
271 | bucket: libdl_buckets, | |
272 | chain: libdl_chains, | |
273 | }; | |
274 |