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
254
255
256
257
258
259
260
261
262
263
264
265
266
267
|
/* Manage TLS descriptors. i386 version.
Copyright (C) 2005-2019 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, see
<https://www.gnu.org/licenses/>. */
#include <link.h>
#include <ldsodefs.h>
#include <elf/dynamic-link.h>
#include <tls.h>
#include <dl-tlsdesc.h>
#include <dl-unmap-segments.h>
#include <tlsdeschtab.h>
/* The following 4 functions take an entry_check_offset argument.
It's computed by the caller as an offset between its entry point
and the call site, such that by adding the built-in return address
that is implicitly passed to the function with this offset, we can
easily obtain the caller's entry point to compare with the entry
point given in the TLS descriptor. If it's changed, we want to
return immediately. */
/* This function is used to lazily resolve TLS_DESC REL relocations
that reference the *ABS* segment in their own link maps. The
argument is the addend originally stored there. */
void
__attribute__ ((regparm (3))) attribute_hidden
_dl_tlsdesc_resolve_abs_plus_addend_fixup (struct tlsdesc volatile *td,
struct link_map *l,
ptrdiff_t entry_check_offset)
{
ptrdiff_t addend = (ptrdiff_t) td->arg;
if (_dl_tlsdesc_resolve_early_return_p (td, __builtin_return_address (0)
- entry_check_offset))
return;
#ifndef SHARED
CHECK_STATIC_TLS (l, l);
#else
if (!TRY_STATIC_TLS (l, l))
{
td->arg = _dl_make_tlsdesc_dynamic (l, addend);
td->entry = _dl_tlsdesc_dynamic;
}
else
#endif
{
td->arg = (void*) (addend - l->l_tls_offset);
td->entry = _dl_tlsdesc_return;
}
_dl_tlsdesc_wake_up_held_fixups ();
}
/* This function is used to lazily resolve TLS_DESC REL relocations
that originally had zero addends. The argument location, that
originally held the addend, is used to hold a pointer to the
relocation, but it has to be restored before we call the function
that applies relocations. */
void
__attribute__ ((regparm (3))) attribute_hidden
_dl_tlsdesc_resolve_rel_fixup (struct tlsdesc volatile *td,
struct link_map *l,
ptrdiff_t entry_check_offset)
{
const ElfW(Rel) *reloc = td->arg;
if (_dl_tlsdesc_resolve_early_return_p (td, __builtin_return_address (0)
- entry_check_offset))
return;
/* The code below was borrowed from _dl_fixup(),
except for checking for STB_LOCAL. */
const ElfW(Sym) *const symtab
= (const void *) D_PTR (l, l_info[DT_SYMTAB]);
const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
const ElfW(Sym) *sym = &symtab[ELFW(R_SYM) (reloc->r_info)];
lookup_t result;
/* Look up the target symbol. If the normal lookup rules are not
used don't look in the global scope. */
if (ELFW(ST_BIND) (sym->st_info) != STB_LOCAL
&& __builtin_expect (ELFW(ST_VISIBILITY) (sym->st_other), 0) == 0)
{
const struct r_found_version *version = NULL;
if (l->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
{
const ElfW(Half) *vernum =
(const void *) D_PTR (l, l_info[VERSYMIDX (DT_VERSYM)]);
ElfW(Half) ndx = vernum[ELFW(R_SYM) (reloc->r_info)] & 0x7fff;
version = &l->l_versions[ndx];
if (version->hash == 0)
version = NULL;
}
result = _dl_lookup_symbol_x (strtab + sym->st_name, l, &sym,
l->l_scope, version, ELF_RTYPE_CLASS_PLT,
DL_LOOKUP_ADD_DEPENDENCY, NULL);
}
else
{
/* We already found the symbol. The module (and therefore its load
address) is also known. */
result = l;
}
if (!sym)
{
td->arg = 0;
td->entry = _dl_tlsdesc_undefweak;
}
else
{
# ifndef SHARED
CHECK_STATIC_TLS (l, result);
# else
if (!TRY_STATIC_TLS (l, result))
{
td->arg = _dl_make_tlsdesc_dynamic (result, sym->st_value);
td->entry = _dl_tlsdesc_dynamic;
}
else
# endif
{
td->arg = (void*)(sym->st_value - result->l_tls_offset);
td->entry = _dl_tlsdesc_return;
}
}
_dl_tlsdesc_wake_up_held_fixups ();
}
/* This function is used to lazily resolve TLS_DESC RELA relocations.
The argument location is used to hold a pointer to the relocation. */
void
__attribute__ ((regparm (3))) attribute_hidden
_dl_tlsdesc_resolve_rela_fixup (struct tlsdesc volatile *td,
struct link_map *l,
ptrdiff_t entry_check_offset)
{
const ElfW(Rela) *reloc = td->arg;
if (_dl_tlsdesc_resolve_early_return_p (td, __builtin_return_address (0)
- entry_check_offset))
return;
/* The code below was borrowed from _dl_fixup(),
except for checking for STB_LOCAL. */
const ElfW(Sym) *const symtab
= (const void *) D_PTR (l, l_info[DT_SYMTAB]);
const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
const ElfW(Sym) *sym = &symtab[ELFW(R_SYM) (reloc->r_info)];
lookup_t result;
/* Look up the target symbol. If the normal lookup rules are not
used don't look in the global scope. */
if (ELFW(ST_BIND) (sym->st_info) != STB_LOCAL
&& __builtin_expect (ELFW(ST_VISIBILITY) (sym->st_other), 0) == 0)
{
const struct r_found_version *version = NULL;
if (l->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
{
const ElfW(Half) *vernum =
(const void *) D_PTR (l, l_info[VERSYMIDX (DT_VERSYM)]);
ElfW(Half) ndx = vernum[ELFW(R_SYM) (reloc->r_info)] & 0x7fff;
version = &l->l_versions[ndx];
if (version->hash == 0)
version = NULL;
}
result = _dl_lookup_symbol_x (strtab + sym->st_name, l, &sym,
l->l_scope, version, ELF_RTYPE_CLASS_PLT,
DL_LOOKUP_ADD_DEPENDENCY, NULL);
}
else
{
/* We already found the symbol. The module (and therefore its load
address) is also known. */
result = l;
}
if (!sym)
{
td->arg = (void*) reloc->r_addend;
td->entry = _dl_tlsdesc_undefweak;
}
else
{
# ifndef SHARED
CHECK_STATIC_TLS (l, result);
# else
if (!TRY_STATIC_TLS (l, result))
{
td->arg = _dl_make_tlsdesc_dynamic (result, sym->st_value
+ reloc->r_addend);
td->entry = _dl_tlsdesc_dynamic;
}
else
# endif
{
td->arg = (void*) (sym->st_value - result->l_tls_offset
+ reloc->r_addend);
td->entry = _dl_tlsdesc_return;
}
}
_dl_tlsdesc_wake_up_held_fixups ();
}
/* This function is used to avoid busy waiting for other threads to
complete the lazy relocation. Once another thread wins the race to
relocate a TLS descriptor, it sets the descriptor up such that this
function is called to wait until the resolver releases the
lock. */
void
__attribute__ ((regparm (3))) attribute_hidden
_dl_tlsdesc_resolve_hold_fixup (struct tlsdesc volatile *td,
struct link_map *l __attribute__((__unused__)),
ptrdiff_t entry_check_offset)
{
/* Maybe we're lucky and can return early. */
if (__builtin_return_address (0) - entry_check_offset != td->entry)
return;
/* Locking here will stop execution until the running resolver runs
_dl_tlsdesc_wake_up_held_fixups(), releasing the lock.
FIXME: We'd be better off waiting on a condition variable, such
that we didn't have to hold the lock throughout the relocation
processing. */
__rtld_lock_lock_recursive (GL(dl_load_lock));
__rtld_lock_unlock_recursive (GL(dl_load_lock));
}
/* Unmap the dynamic object, but also release its TLS descriptor table
if there is one. */
void
_dl_unmap (struct link_map *map)
{
_dl_unmap_segments (map);
#ifdef SHARED
if (map->l_mach.tlsdesc_table)
htab_delete (map->l_mach.tlsdesc_table);
#endif
}
|
