2 * Copyright (C) 2007 The Android Open Source Project
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
8 * http://www.apache.org/licenses/LICENSE-2.0
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.
23 #include "linker_format.h"
25 /* This file hijacks the symbols stubbed out in libdl.so. */
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
34 static char dl_err_buf
[1024];
35 static const char *dl_err_str
;
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",
45 #define likely(expr) __builtin_expect (expr, 1)
46 #define unlikely(expr) __builtin_expect (expr, 0)
48 pthread_mutex_t dl_lock
= PTHREAD_MUTEX_INITIALIZER
;
50 static void set_dlerror(int err
)
52 format_buffer(dl_err_buf
, sizeof(dl_err_buf
), "%s: %s", dl_errors
[err
],
54 dl_err_str
= (const char *)&dl_err_buf
[0];
57 void *android_dlopen(const char *filename
, int flag
)
61 pthread_mutex_lock(&dl_lock
);
62 ret
= find_library(filename
);
63 if (unlikely(ret
== NULL
)) {
64 set_dlerror(DL_ERR_CANNOT_LOAD_LIBRARY
);
66 call_constructors_recursive(ret
);
69 pthread_mutex_unlock(&dl_lock
);
73 const char *android_dlerror(void)
75 const char *tmp
= dl_err_str
;
77 return (const char *)tmp
;
80 void *android_dlsym(void *handle
, const char *symbol
)
86 pthread_mutex_lock(&dl_lock
);
88 if(unlikely(handle
== 0)) {
89 set_dlerror(DL_ERR_INVALID_LIBRARY_HANDLE
);
92 if(unlikely(symbol
== 0)) {
93 set_dlerror(DL_ERR_BAD_SYMBOL_NAME
);
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
);
105 sym
= lookup(symbol
, &found
, si
->next
);
108 found
= (soinfo
*)handle
;
109 sym
= lookup_in_library(found
, symbol
);
112 if(likely(sym
!= 0)) {
113 bind
= ELF32_ST_BIND(sym
->st_info
);
115 if(likely((bind
== STB_GLOBAL
) && (sym
->st_shndx
!= 0))) {
116 unsigned ret
= sym
->st_value
+ found
->base
;
117 pthread_mutex_unlock(&dl_lock
);
121 set_dlerror(DL_ERR_SYMBOL_NOT_GLOBAL
);
124 set_dlerror(DL_ERR_SYMBOL_NOT_FOUND
);
127 pthread_mutex_unlock(&dl_lock
);
131 int android_dladdr(const void *addr
, Dl_info
*info
)
135 pthread_mutex_lock(&dl_lock
);
137 /* Determine if this address can be found in any library currently mapped */
138 soinfo
*si
= find_containing_library(addr
);
141 memset(info
, 0, sizeof(Dl_info
));
143 info
->dli_fname
= si
->name
;
144 info
->dli_fbase
= (void*)si
->base
;
146 /* Determine if any symbol in the library contains the specified address */
147 Elf32_Sym
*sym
= find_containing_symbol(addr
, si
);
150 info
->dli_sname
= si
->strtab
+ sym
->st_name
;
151 info
->dli_saddr
= (void*)(si
->base
+ sym
->st_value
);
157 pthread_mutex_unlock(&dl_lock
);
162 int android_dlclose(void *handle
)
164 pthread_mutex_lock(&dl_lock
);
165 (void)unload_library((soinfo
*)handle
);
166 pthread_mutex_unlock(&dl_lock
);
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"
177 _Unwind_Ptr
android_dl_unwind_find_exidx(_Unwind_Ptr pc
, int *pcount
);
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"
185 android_dl_iterate_phdr(int (*cb
)(struct dl_phdr_info
*info
, size_t size
, void *data
),
189 #error Unsupported architecture. Only ARM and x86 are presently supported.
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,
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,
206 st_value
: (Elf32_Addr
) &android_dlclose
,
207 st_info
: STB_GLOBAL
<< 4,
211 st_value
: (Elf32_Addr
) &android_dlsym
,
212 st_info
: STB_GLOBAL
<< 4,
216 st_value
: (Elf32_Addr
) &android_dlerror
,
217 st_info
: STB_GLOBAL
<< 4,
221 st_value
: (Elf32_Addr
) &android_dladdr
,
222 st_info
: STB_GLOBAL
<< 4,
225 #ifdef ANDROID_ARM_LINKER
227 st_value
: (Elf32_Addr
) &android_dl_unwind_find_exidx
,
228 st_info
: STB_GLOBAL
<< 4,
231 #elif defined(ANDROID_X86_LINKER)
233 st_value
: (Elf32_Addr
) &android_dl_iterate_phdr
,
234 st_info
: STB_GLOBAL
<< 4,
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).
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
254 * (see _elf_lookup())
256 * Note that adding any new symbols here requires
257 * stubbing them out in libdl.
259 static unsigned libdl_buckets
[1] = { 1 };
260 static unsigned libdl_chains
[7] = { 0, 2, 3, 4, 5, 6, 0 };
262 soinfo libdl_info
= {
266 strtab
: ANDROID_LIBDL_STRTAB
,
267 symtab
: libdl_symtab
,
271 bucket
: libdl_buckets
,