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
|
/* Look up a symbol in the loaded objects.
Copyright (C) 1995,96,97,98,99,2000,2001,2002 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#if VERSIONED
# define FCT do_lookup_versioned
# define ARG const struct r_found_version *const version
#else
# define FCT do_lookup
# define ARG int flags
#endif
/* Inner part of the lookup functions. We return a value > 0 if we
found the symbol, the value 0 if nothing is found and < 0 if
something bad happened. */
static inline int
FCT (const char *undef_name, unsigned long int hash, const ElfW(Sym) *ref,
struct sym_val *result, struct r_scope_elem *scope, size_t i, ARG,
struct link_map *skip, int type_class)
{
struct link_map **list = scope->r_list;
size_t n = scope->r_nlist;
struct link_map *map;
do
{
const ElfW(Sym) *symtab;
const char *strtab;
const ElfW(Half) *verstab;
Elf_Symndx symidx;
const ElfW(Sym) *sym;
#if ! VERSIONED
int num_versions = 0;
const ElfW(Sym) *versioned_sym = NULL;
#endif
map = list[i];
/* Here come the extra test needed for `_dl_lookup_symbol_skip'. */
if (skip != NULL && map == skip)
continue;
/* Don't search the executable when resolving a copy reloc. */
if ((type_class & ELF_RTYPE_CLASS_COPY) && map->l_type == lt_executable)
continue;
/* Print some debugging info if wanted. */
if (__builtin_expect (GL(dl_debug_mask) & DL_DEBUG_SYMBOLS, 0))
INTUSE(_dl_debug_printf) ("symbol=%s; lookup in file=%s\n",
undef_name, (map->l_name[0]
? map->l_name : rtld_progname));
symtab = (const void *) D_PTR (map, l_info[DT_SYMTAB]);
strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
verstab = map->l_versyms;
/* Search the appropriate hash bucket in this object's symbol table
for a definition for the same symbol name. */
for (symidx = map->l_buckets[hash % map->l_nbuckets];
symidx != STN_UNDEF;
symidx = map->l_chain[symidx])
{
sym = &symtab[symidx];
assert (ELF_RTYPE_CLASS_PLT == 1);
if ((sym->st_value == 0 /* No value. */
#ifdef USE_TLS
&& ELFW(ST_TYPE) (sym->st_info) != STT_TLS
#endif
)
|| (type_class & (sym->st_shndx == SHN_UNDEF)))
continue;
if (ELFW(ST_TYPE) (sym->st_info) > STT_FUNC
#ifdef USE_TLS
&& ELFW(ST_TYPE) (sym->st_info) != STT_TLS
#endif
)
/* Ignore all but STT_NOTYPE, STT_OBJECT and STT_FUNC
entries (and STT_TLS if TLS is supported) since these
are no code/data definitions. */
continue;
if (sym != ref && strcmp (strtab + sym->st_name, undef_name))
/* Not the symbol we are looking for. */
continue;
#if VERSIONED
if (__builtin_expect (verstab == NULL, 0))
{
/* We need a versioned symbol but haven't found any. If
this is the object which is referenced in the verneed
entry it is a bug in the library since a symbol must
not simply disappear.
It would also be a bug in the object since it means that
the list of required versions is incomplete and so the
tests in dl-version.c haven't found a problem.*/
assert (version->filename == NULL
|| ! _dl_name_match_p (version->filename, map));
/* Otherwise we accept the symbol. */
}
else
{
/* We can match the version information or use the
default one if it is not hidden. */
ElfW(Half) ndx = verstab[symidx] & 0x7fff;
if ((map->l_versions[ndx].hash != version->hash
|| strcmp (map->l_versions[ndx].name, version->name))
&& (version->hidden || map->l_versions[ndx].hash
|| (verstab[symidx] & 0x8000)))
/* It's not the version we want. */
continue;
}
#else
/* No specific version is selected. There are two ways we
can got here:
- a binary which does not include versioning information
is loaded
- dlsym() instead of dlvsym() is used to get a symbol which
might exist in more than one form
If the library does not provide symbol version
information there is no problem at at: we simply use the
symbol if it is defined.
These two lookups need to be handled differently if the
library defines versions. In the case of the old
unversioned application the oldest (default) version
should be used. In case of a dlsym() call the latest and
public interface should be returned. */
if (verstab != NULL)
{
if ((verstab[symidx] & 0x7fff)
>= ((flags & DL_LOOKUP_RETURN_NEWEST) ? 2 : 3))
{
/* Don't accept hidden symbols. */
if ((verstab[symidx] & 0x8000) == 0 && num_versions++ == 0)
/* No version so far. */
versioned_sym = sym;
continue;
}
}
#endif
/* There cannot be another entry for this symbol so stop here. */
goto found_it;
}
/* If we have seen exactly one versioned symbol while we are
looking for an unversioned symbol and the version is not the
default version we still accept this symbol since there are
no possible ambiguities. */
#if VERSIONED
sym = NULL;
#else
sym = num_versions == 1 ? versioned_sym : NULL;
#endif
if (sym != NULL)
{
found_it:
switch (ELFW(ST_BIND) (sym->st_info))
{
case STB_WEAK:
/* Weak definition. Use this value if we don't find another. */
if (__builtin_expect (GL(dl_dynamic_weak), 0))
{
if (! result->s)
{
result->s = sym;
result->m = map;
}
break;
}
/* FALLTHROUGH */
case STB_GLOBAL:
/* Global definition. Just what we need. */
result->s = sym;
result->m = map;
return 1;
default:
/* Local symbols are ignored. */
break;
}
}
#if VERSIONED
/* If this current map is the one mentioned in the verneed entry
and we have not found a weak entry, it is a bug. */
if (symidx == STN_UNDEF && version->filename != NULL
&& __builtin_expect (_dl_name_match_p (version->filename, map), 0))
return -1;
#endif
}
while (++i < n);
/* We have not found anything until now. */
return 0;
}
#undef FCT
#undef ARG
#undef VERSIONED
|
