1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
|
/* vi: set sw=4 ts=4: */
/*
* Program to load an ELF binary on a linux system, and run it
* after resolving ELF shared library symbols
*
* Copyright (C) 2004 by Joakim Tjernlund <joakim.tjernlund@lumentis.se>
* Copyright (C) 2000-2004 by Erik Andersen <andersen@codpoet.org>
* Copyright (c) 1994-2000 Eric Youngdale, Peter MacDonald,
* David Engel, Hongjiu Lu and Mitch D'Souza
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. The name of the above contributors may not be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/* Various symbol table handling functions, including symbol lookup */
/*
* This is the start of the linked list that describes all of the files present
* in the system with pointers to all of the symbol, string, and hash tables,
* as well as all of the other good stuff in the binary.
*/
struct elf_resolve *_dl_loaded_modules = NULL;
/*
* This is the list of modules that are loaded when the image is first
* started. As we add more via dlopen, they get added into other
* chains.
*/
struct dyn_elf *_dl_symbol_tables = NULL;
/*
* This is the list of modules that are loaded via dlopen. We may need
* to search these for RTLD_GLOBAL files.
*/
struct dyn_elf *_dl_handles = NULL;
/* This is the hash function that is used by the ELF linker to generate the
* hash table that each executable and library is required to have. We need
* it to decode the hash table. */
unsigned long _dl_elf_hash(const unsigned char *name)
{
unsigned long hash = 0;
unsigned long tmp;
while (*name) {
hash = (hash << 4) + *name++;
if ((tmp = hash & 0xf0000000))
hash ^= tmp >> 24;
hash &= ~tmp;
}
return hash;
}
/* Check to see if a library has already been added to the hash chain. */
struct elf_resolve *_dl_check_hashed_files(const char *libname)
{
struct elf_resolve *tpnt;
int len = _dl_strlen(libname);
for (tpnt = _dl_loaded_modules; tpnt; tpnt = tpnt->next) {
if (_dl_strncmp(tpnt->libname, libname, len) == 0 &&
(tpnt->libname[len] == '\0' || tpnt->libname[len] == '.'))
return tpnt;
}
return NULL;
}
/*
* We call this function when we have just read an ELF library or executable.
* We add the relevant info to the symbol chain, so that we can resolve all
* externals properly.
*/
struct elf_resolve *_dl_add_elf_hash_table(const char *libname,
char *loadaddr, unsigned long *dynamic_info, unsigned long dynamic_addr,
unsigned long dynamic_size)
{
unsigned long *hash_addr;
struct elf_resolve *tpnt;
int i;
if (!_dl_loaded_modules) {
tpnt = _dl_loaded_modules = (struct elf_resolve *) _dl_malloc(sizeof(struct elf_resolve));
_dl_memset(tpnt, 0, sizeof(struct elf_resolve));
} else {
tpnt = _dl_loaded_modules;
while (tpnt->next)
tpnt = tpnt->next;
tpnt->next = (struct elf_resolve *) _dl_malloc(sizeof(struct elf_resolve));
_dl_memset(tpnt->next, 0, sizeof(struct elf_resolve));
tpnt->next->prev = tpnt;
tpnt = tpnt->next;
};
tpnt->next = NULL;
tpnt->init_flag = 0;
tpnt->libname = _dl_strdup(libname);
tpnt->dynamic_addr = (ElfW(Dyn) *)dynamic_addr;
tpnt->dynamic_size = dynamic_size;
tpnt->libtype = loaded_file;
if (dynamic_info[DT_HASH] != 0) {
hash_addr = (unsigned long *) (intptr_t)(dynamic_info[DT_HASH] + loadaddr);
tpnt->nbucket = *hash_addr++;
tpnt->nchain = *hash_addr++;
tpnt->elf_buckets = hash_addr;
hash_addr += tpnt->nbucket;
tpnt->chains = hash_addr;
}
tpnt->loadaddr = (ElfW(Addr))loadaddr;
for (i = 0; i < 24; i++)
tpnt->dynamic_info[i] = dynamic_info[i];
#ifdef __mips__
{
Elf32_Dyn *dpnt = (Elf32_Dyn *) dynamic_addr;
while(dpnt->d_tag) {
if (dpnt->d_tag == DT_MIPS_GOTSYM)
tpnt->mips_gotsym = dpnt->d_un.d_val;
if (dpnt->d_tag == DT_MIPS_LOCAL_GOTNO)
tpnt->mips_local_gotno = dpnt->d_un.d_val;
if (dpnt->d_tag == DT_MIPS_SYMTABNO)
tpnt->mips_symtabno = dpnt->d_un.d_val;
dpnt++;
}
}
#endif
return tpnt;
}
/*
* This function resolves externals, and this is either called when we process
* relocations or when we call an entry in the PLT table for the first time.
*/
char *_dl_find_hash(const char *name, struct dyn_elf *rpnt1,
int type_class)
{
struct elf_resolve *tpnt;
int si;
int pass;
char *strtab;
Elf32_Sym *symtab;
unsigned long elf_hash_number, hn;
char *weak_result;
struct dyn_elf *rpnt;
const ElfW(Sym) *sym;
weak_result = 0;
elf_hash_number = _dl_elf_hash(name);
/*
* The passes are so that we can first search the regular symbols
* for whatever module was specified, and then search anything
* loaded with RTLD_GLOBAL. When pass is 1, it means we are just
* starting the first dlopened module, and anything above that
* is just the next one in the chain.
*/
if (rpnt1 == NULL)
rpnt1 = _dl_symbol_tables;
for (pass = 0; (1 == 1); pass++) {
/*
* If we are just starting to search for RTLD_GLOBAL, setup
* the pointer for the start of the search.
*/
if (pass == 1)
rpnt1 = _dl_handles;
/*
* Anything after this, we need to skip to the next module.
*/
else if (pass >= 2)
rpnt1 = rpnt1->next_handle;
/*
* Make sure we still have a module.
*/
if (rpnt1 == NULL)
break;
for (rpnt = rpnt1; rpnt; rpnt = rpnt->next) {
tpnt = rpnt->dyn;
/* Don't search the executable when resolving a copy reloc. */
if ((type_class & ELF_RTYPE_CLASS_COPY) && tpnt->libtype == elf_executable)
continue;
/*
* Avoid calling .urem here.
*/
do_rem(hn, elf_hash_number, tpnt->nbucket);
symtab = (Elf32_Sym *) (intptr_t) (tpnt->dynamic_info[DT_SYMTAB] + tpnt->loadaddr);
strtab = (char *) (tpnt->dynamic_info[DT_STRTAB] + tpnt->loadaddr);
for (si = tpnt->elf_buckets[hn]; si != STN_UNDEF; si = tpnt->chains[si]) {
sym = &symtab[si];
if (sym->st_value == 0)
continue;
if (ELF32_ST_TYPE(sym->st_info) > STT_FUNC)
continue;
if (type_class & (sym->st_shndx == SHN_UNDEF))
continue;
if (_dl_strcmp(strtab + sym->st_name, name) != 0)
continue;
switch (ELF32_ST_BIND(sym->st_info)) {
case STB_WEAK:
#ifndef __LIBDL_SHARED__
/*
Due to a special hack in libdl.c, one must handle the _dl_ symbols
according to the OLD weak symbol scheme. This stuff can be deleted
once that hack has been fixed.
*/
if(_dl_symbol((char *)name)) {
if (!weak_result)
weak_result = (char *)tpnt->loadaddr + sym->st_value;
break;
}
#endif
case STB_GLOBAL:
return (char*)tpnt->loadaddr + sym->st_value;
default: /* Local symbols not handled here */
break;
}
}
}
}
return weak_result;
}
|
