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
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
|
/* x86 CET initializers function.
Copyright (C) 2018-2023 Free Software Foundation, Inc.
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 <unistd.h>
#include <errno.h>
#include <libintl.h>
#include <ldsodefs.h>
#include <dl-cet.h>
/* GNU_PROPERTY_X86_FEATURE_1_IBT and GNU_PROPERTY_X86_FEATURE_1_SHSTK
are defined in <elf.h>, which are only available for C sources.
X86_FEATURE_1_IBT and X86_FEATURE_1_SHSTK are defined in <sysdep.h>
which are available for both C and asm sources. They must match. */
#if GNU_PROPERTY_X86_FEATURE_1_IBT != X86_FEATURE_1_IBT
# error GNU_PROPERTY_X86_FEATURE_1_IBT != X86_FEATURE_1_IBT
#endif
#if GNU_PROPERTY_X86_FEATURE_1_SHSTK != X86_FEATURE_1_SHSTK
# error GNU_PROPERTY_X86_FEATURE_1_SHSTK != X86_FEATURE_1_SHSTK
#endif
struct dl_cet_info
{
const char *program;
/* Check how IBT and SHSTK should be enabled. */
enum dl_x86_cet_control enable_ibt_type;
enum dl_x86_cet_control enable_shstk_type;
/* If IBT and SHSTK were previously enabled. */
unsigned int feature_1_enabled;
/* If IBT and SHSTK should be enabled. */
unsigned int enable_feature_1;
/* If there are any legacy shared object. */
unsigned int feature_1_legacy;
/* Which shared object is the first legacy shared object. */
unsigned int feature_1_legacy_ibt;
unsigned int feature_1_legacy_shstk;
};
/* Check if the object M and its dependencies are legacy object. */
static void
dl_check_legacy_object (struct link_map *m,
struct dl_cet_info *info)
{
unsigned int i;
struct link_map *l = NULL;
i = m->l_searchlist.r_nlist;
while (i-- > 0)
{
/* Check each shared object to see if IBT and SHSTK are enabled. */
l = m->l_initfini[i];
if (l->l_init_called)
continue;
#ifdef SHARED
/* Skip check for ld.so since it has the features enabled. The
features will be disabled later if they are not enabled in
executable. */
if (l == &GL(dl_rtld_map)
|| l->l_real == &GL(dl_rtld_map)
|| (info->program != NULL && l == m))
continue;
#endif
/* IBT and SHSTK set only if enabled in executable and all DSOs.
NB: cet_always_on is handled outside of the loop. */
info->enable_feature_1 &= ((l->l_x86_feature_1_and
& (GNU_PROPERTY_X86_FEATURE_1_IBT
| GNU_PROPERTY_X86_FEATURE_1_SHSTK))
| ~(GNU_PROPERTY_X86_FEATURE_1_IBT
| GNU_PROPERTY_X86_FEATURE_1_SHSTK));
if ((info->feature_1_legacy
& GNU_PROPERTY_X86_FEATURE_1_IBT) == 0
&& ((info->enable_feature_1
& GNU_PROPERTY_X86_FEATURE_1_IBT)
!= (info->feature_1_enabled
& GNU_PROPERTY_X86_FEATURE_1_IBT)))
{
info->feature_1_legacy_ibt = i;
info->feature_1_legacy |= GNU_PROPERTY_X86_FEATURE_1_IBT;
}
if ((info->feature_1_legacy
& GNU_PROPERTY_X86_FEATURE_1_SHSTK) == 0
&& ((info->enable_feature_1
& GNU_PROPERTY_X86_FEATURE_1_SHSTK)
!= (info->feature_1_enabled
& GNU_PROPERTY_X86_FEATURE_1_SHSTK)))
{
info->feature_1_legacy_shstk = i;
info->feature_1_legacy |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
}
}
/* Handle cet_always_on. */
if ((info->feature_1_enabled
& GNU_PROPERTY_X86_FEATURE_1_IBT) != 0
&& info->enable_ibt_type == cet_always_on)
{
info->feature_1_legacy &= ~GNU_PROPERTY_X86_FEATURE_1_IBT;
info->enable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_IBT;
}
if ((info->feature_1_enabled
& GNU_PROPERTY_X86_FEATURE_1_SHSTK) != 0
&& info->enable_shstk_type == cet_always_on)
{
info->feature_1_legacy &= ~GNU_PROPERTY_X86_FEATURE_1_SHSTK;
info->enable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
}
}
#ifdef SHARED
/* Enable IBT and SHSTK only if they are enabled in executable. Set
feature bits properly at the start of the program. */
static void
dl_cet_check_startup (struct link_map *m, struct dl_cet_info *info)
{
/* NB: IBT and SHSTK may be disabled by environment variable:
GLIBC_TUNABLES=glibc.cpu.hwcaps=-IBT,-SHSTK.
*/
if (CPU_FEATURE_USABLE (IBT))
{
if (info->enable_ibt_type == cet_always_on)
info->enable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_IBT;
else
info->enable_feature_1 &= ((m->l_x86_feature_1_and
& GNU_PROPERTY_X86_FEATURE_1_IBT)
| ~GNU_PROPERTY_X86_FEATURE_1_IBT);
}
else
info->enable_feature_1 &= ~GNU_PROPERTY_X86_FEATURE_1_IBT;
if (CPU_FEATURE_USABLE (SHSTK))
{
if (info->enable_shstk_type == cet_always_on)
info->enable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
else
info->enable_feature_1 &= ((m->l_x86_feature_1_and
& GNU_PROPERTY_X86_FEATURE_1_SHSTK)
| ~GNU_PROPERTY_X86_FEATURE_1_SHSTK);
}
else
info->enable_feature_1 &= ~GNU_PROPERTY_X86_FEATURE_1_SHSTK;
if (info->enable_feature_1 != 0)
dl_check_legacy_object (m, info);
unsigned int disable_feature_1
= info->enable_feature_1 ^ info->feature_1_enabled;
if (disable_feature_1 != 0)
{
/* Disable features in the kernel because of legacy objects or
cet_always_off. */
if (dl_cet_disable_cet (disable_feature_1) != 0)
_dl_fatal_printf ("%s: can't disable x86 Features\n",
info->program);
/* Clear the disabled bits. Sync dl_x86_feature_1 and
info->feature_1_enabled with info->enable_feature_1. */
info->feature_1_enabled = info->enable_feature_1;
GL(dl_x86_feature_1) = info->enable_feature_1;
}
if (HAS_CPU_FEATURE (IBT) || HAS_CPU_FEATURE (SHSTK))
{
/* Lock CET features only if IBT or SHSTK are enabled and are not
enabled permissively. */
unsigned int feature_1_lock = 0;
if (((info->feature_1_enabled & GNU_PROPERTY_X86_FEATURE_1_IBT)
!= 0)
&& info->enable_ibt_type != cet_permissive)
feature_1_lock |= GNU_PROPERTY_X86_FEATURE_1_IBT;
if (((info->feature_1_enabled & GNU_PROPERTY_X86_FEATURE_1_SHSTK)
!= 0)
&& info->enable_shstk_type != cet_permissive)
feature_1_lock |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
if (feature_1_lock != 0
&& dl_cet_lock_cet () != 0)
_dl_fatal_printf ("%s: can't lock CET\n", info->program);
}
THREAD_SETMEM (THREAD_SELF, header.feature_1, GL(dl_x86_feature_1));
}
#endif
/* Check feature bits when dlopening the shared object M. */
static void
dl_cet_check_dlopen (struct link_map *m, struct dl_cet_info *info)
{
/* Check if there are any legacy objects loaded. */
if (info->enable_feature_1 != 0)
{
dl_check_legacy_object (m, info);
/* Skip if there are no legacy shared objects loaded. */
if (info->feature_1_legacy == 0)
return;
}
unsigned int disable_feature_1 = 0;
unsigned int legacy_obj = 0;
const char *msg = NULL;
if ((info->feature_1_enabled
& GNU_PROPERTY_X86_FEATURE_1_IBT) != 0
&& (info->feature_1_legacy
& GNU_PROPERTY_X86_FEATURE_1_IBT) != 0)
{
if (info->enable_ibt_type != cet_permissive)
{
legacy_obj = info->feature_1_legacy_ibt;
msg = N_("rebuild shared object with IBT support enabled");
}
else
disable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_IBT;
}
/* Check the next feature only if there is no error. */
if (msg == NULL
&& (info->feature_1_enabled
& GNU_PROPERTY_X86_FEATURE_1_SHSTK) != 0
&& (info->feature_1_legacy
& GNU_PROPERTY_X86_FEATURE_1_SHSTK) != 0)
{
if (info->enable_shstk_type != cet_permissive)
{
legacy_obj = info->feature_1_legacy_shstk;
msg = N_("rebuild shared object with SHSTK support enabled");
}
else
disable_feature_1 |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
}
/* If there is an error, long jump back to the caller. */
if (msg != NULL)
_dl_signal_error (0, m->l_initfini[legacy_obj]->l_name, "dlopen",
msg);
if (disable_feature_1 != 0)
{
int res = dl_cet_disable_cet (disable_feature_1);
if (res)
{
if ((disable_feature_1
& GNU_PROPERTY_X86_FEATURE_1_IBT) != 0)
msg = N_("can't disable IBT");
else
msg = N_("can't disable SHSTK");
/* Long jump back to the caller on error. */
_dl_signal_error (-res, m->l_initfini[legacy_obj]->l_name,
"dlopen", msg);
}
/* Clear the disabled bits in dl_x86_feature_1. */
GL(dl_x86_feature_1) &= ~disable_feature_1;
THREAD_SETMEM (THREAD_SELF, header.feature_1,
GL(dl_x86_feature_1));
}
}
static void
dl_cet_check (struct link_map *m, const char *program)
{
struct dl_cet_info info;
/* Check how IBT and SHSTK should be enabled. */
info.enable_ibt_type = GL(dl_x86_feature_control).ibt;
info.enable_shstk_type = GL(dl_x86_feature_control).shstk;
info.feature_1_enabled = GL(dl_x86_feature_1);
/* No legacy object check if IBT and SHSTK are always on. */
if (info.enable_ibt_type == cet_always_on
&& info.enable_shstk_type == cet_always_on)
{
#ifdef SHARED
/* Set it only during startup. */
if (program != NULL)
THREAD_SETMEM (THREAD_SELF, header.feature_1,
info.feature_1_enabled);
#endif
return;
}
/* Check if IBT and SHSTK were enabled by kernel. */
if (info.feature_1_enabled == 0)
return;
info.program = program;
/* Check which features should be enabled. */
info.enable_feature_1 = 0;
if (info.enable_ibt_type != cet_always_off)
info.enable_feature_1 |= (info.feature_1_enabled
& GNU_PROPERTY_X86_FEATURE_1_IBT);
if (info.enable_shstk_type != cet_always_off)
info.enable_feature_1 |= (info.feature_1_enabled
& GNU_PROPERTY_X86_FEATURE_1_SHSTK);
/* Start with no legacy objects. */
info.feature_1_legacy = 0;
info.feature_1_legacy_ibt = 0;
info.feature_1_legacy_shstk = 0;
#ifdef SHARED
if (program)
dl_cet_check_startup (m, &info);
else
#endif
dl_cet_check_dlopen (m, &info);
}
void
_dl_cet_open_check (struct link_map *l)
{
dl_cet_check (l, NULL);
}
#ifdef SHARED
# ifndef LINKAGE
# define LINKAGE
# endif
LINKAGE
void
_dl_cet_check (struct link_map *main_map, const char *program)
{
dl_cet_check (main_map, program);
}
#endif /* SHARED */
|
