]> git.ipfire.org Git - thirdparty/glibc.git/blame - sysdeps/x86/dl-cet.c
Update copyright dates with scripts/update-copyrights.
[thirdparty/glibc.git] / sysdeps / x86 / dl-cet.c
CommitLineData
f753fa7d 1/* x86 CET initializers function.
04277e02 2 Copyright (C) 2018-2019 Free Software Foundation, Inc.
f753fa7d
L
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <http://www.gnu.org/licenses/>. */
17
18#include <unistd.h>
19#include <errno.h>
20#include <libintl.h>
21#include <ldsodefs.h>
22#include <dl-cet.h>
23#include <cet-tunables.h>
24
25/* GNU_PROPERTY_X86_FEATURE_1_IBT and GNU_PROPERTY_X86_FEATURE_1_SHSTK
26 are defined in <elf.h>, which are only available for C sources.
27 X86_FEATURE_1_IBT and X86_FEATURE_1_SHSTK are defined in <sysdep.h>
28 which are available for both C and asm sources. They must match. */
29#if GNU_PROPERTY_X86_FEATURE_1_IBT != X86_FEATURE_1_IBT
30# error GNU_PROPERTY_X86_FEATURE_1_IBT != X86_FEATURE_1_IBT
31#endif
32#if GNU_PROPERTY_X86_FEATURE_1_SHSTK != X86_FEATURE_1_SHSTK
33# error GNU_PROPERTY_X86_FEATURE_1_SHSTK != X86_FEATURE_1_SHSTK
34#endif
35
36static int
37dl_cet_mark_legacy_region (struct link_map *l)
38{
39 /* Mark PT_LOAD segments with PF_X in legacy code page bitmap. */
40 size_t i, phnum = l->l_phnum;
41 const ElfW(Phdr) *phdr = l->l_phdr;
42#ifdef __x86_64__
43 typedef unsigned long long word_t;
44#else
45 typedef unsigned long word_t;
46#endif
47 unsigned int bits_to_set;
48 word_t mask_to_set;
49#define BITS_PER_WORD (sizeof (word_t) * 8)
50#define BITMAP_FIRST_WORD_MASK(start) \
51 (~((word_t) 0) << ((start) & (BITS_PER_WORD - 1)))
52#define BITMAP_LAST_WORD_MASK(nbits) \
53 (~((word_t) 0) >> (-(nbits) & (BITS_PER_WORD - 1)))
54
55 word_t *bitmap = (word_t *) GL(dl_x86_legacy_bitmap)[0];
56 word_t bitmap_size = GL(dl_x86_legacy_bitmap)[1];
57 word_t *p;
58 size_t page_size = GLRO(dl_pagesize);
59
60 for (i = 0; i < phnum; i++)
61 if (phdr[i].p_type == PT_LOAD && (phdr[i].p_flags & PF_X))
62 {
63 /* One bit in legacy bitmap represents a page. */
64 ElfW(Addr) start = (phdr[i].p_vaddr + l->l_addr) / page_size;
65 ElfW(Addr) len = (phdr[i].p_memsz + page_size - 1) / page_size;
66 ElfW(Addr) end = start + len;
67
68 if ((end / 8) > bitmap_size)
69 return -EINVAL;
70
71 p = bitmap + (start / BITS_PER_WORD);
72 bits_to_set = BITS_PER_WORD - (start % BITS_PER_WORD);
73 mask_to_set = BITMAP_FIRST_WORD_MASK (start);
74
75 while (len >= bits_to_set)
76 {
77 *p |= mask_to_set;
78 len -= bits_to_set;
79 bits_to_set = BITS_PER_WORD;
80 mask_to_set = ~((word_t) 0);
81 p++;
82 }
83 if (len)
84 {
85 mask_to_set &= BITMAP_LAST_WORD_MASK (end);
86 *p |= mask_to_set;
87 }
88 }
89
90 return 0;
91}
92
93/* Check if object M is compatible with CET. */
94
95static void
96dl_cet_check (struct link_map *m, const char *program)
97{
98 /* Check how IBT should be enabled. */
99 unsigned int enable_ibt_type
100 = GL(dl_x86_feature_1)[1] & ((1 << CET_MAX) - 1);
101 /* Check how SHSTK should be enabled. */
102 unsigned int enable_shstk_type
103 = ((GL(dl_x86_feature_1)[1] >> CET_MAX) & ((1 << CET_MAX) - 1));
104
105 /* No legacy object check if both IBT and SHSTK are always on. */
106 if (enable_ibt_type == CET_ALWAYS_ON
107 && enable_shstk_type == CET_ALWAYS_ON)
108 return;
109
110 /* Check if IBT is enabled by kernel. */
111 bool ibt_enabled
112 = (GL(dl_x86_feature_1)[0] & GNU_PROPERTY_X86_FEATURE_1_IBT) != 0;
113 /* Check if SHSTK is enabled by kernel. */
114 bool shstk_enabled
115 = (GL(dl_x86_feature_1)[0] & GNU_PROPERTY_X86_FEATURE_1_SHSTK) != 0;
116
117 if (ibt_enabled || shstk_enabled)
118 {
119 struct link_map *l = NULL;
120
121 /* Check if IBT and SHSTK are enabled in object. */
122 bool enable_ibt = (ibt_enabled
123 && enable_ibt_type != CET_ALWAYS_OFF);
124 bool enable_shstk = (shstk_enabled
125 && enable_shstk_type != CET_ALWAYS_OFF);
126 if (program)
127 {
128 /* Enable IBT and SHSTK only if they are enabled in executable.
129 NB: IBT and SHSTK may be disabled by environment variable:
130
dce452dc 131 GLIBC_TUNABLES=glibc.cpu.hwcaps=-IBT,-SHSTK
f753fa7d
L
132 */
133 enable_ibt &= (HAS_CPU_FEATURE (IBT)
134 && (enable_ibt_type == CET_ALWAYS_ON
135 || (m->l_cet & lc_ibt) != 0));
136 enable_shstk &= (HAS_CPU_FEATURE (SHSTK)
137 && (enable_shstk_type == CET_ALWAYS_ON
138 || (m->l_cet & lc_shstk) != 0));
139 }
140
141 /* ld.so is CET-enabled by kernel. But shared objects may not
142 support IBT nor SHSTK. */
143 if (enable_ibt || enable_shstk)
144 {
145 int res;
146 unsigned int i;
147 unsigned int first_legacy, last_legacy;
148 bool need_legacy_bitmap = false;
149
150 i = m->l_searchlist.r_nlist;
151 while (i-- > 0)
152 {
153 /* Check each shared object to see if IBT and SHSTK are
154 enabled. */
155 l = m->l_initfini[i];
156
157 if (l->l_init_called)
158 continue;
159
160#ifdef SHARED
161 /* Skip CET check for ld.so since ld.so is CET-enabled.
162 CET will be disabled later if CET isn't enabled in
163 executable. */
164 if (l == &GL(dl_rtld_map)
165 || l->l_real == &GL(dl_rtld_map)
166 || (program && l == m))
167 continue;
168#endif
169
170 if (enable_ibt
171 && enable_ibt_type != CET_ALWAYS_ON
172 && !(l->l_cet & lc_ibt))
173 {
174 /* Remember the first and last legacy objects. */
175 if (!need_legacy_bitmap)
176 last_legacy = i;
177 first_legacy = i;
178 need_legacy_bitmap = true;
179 }
180
181 /* SHSTK is enabled only if it is enabled in executable as
182 well as all shared objects. */
183 enable_shstk &= (enable_shstk_type == CET_ALWAYS_ON
184 || (l->l_cet & lc_shstk) != 0);
185 }
186
187 if (need_legacy_bitmap)
188 {
189 if (GL(dl_x86_legacy_bitmap)[0])
190 {
191 /* Change legacy bitmap to writable. */
192 if (__mprotect ((void *) GL(dl_x86_legacy_bitmap)[0],
193 GL(dl_x86_legacy_bitmap)[1],
194 PROT_READ | PROT_WRITE) < 0)
195 {
196mprotect_failure:
197 if (program)
198 _dl_fatal_printf ("%s: mprotect legacy bitmap failed\n",
199 l->l_name);
200 else
201 _dl_signal_error (EINVAL, l->l_name, "dlopen",
202 N_("mprotect legacy bitmap failed"));
203 }
204 }
205 else
206 {
207 /* Allocate legacy bitmap. */
208 int res = dl_cet_allocate_legacy_bitmap
209 (GL(dl_x86_legacy_bitmap));
210 if (res != 0)
211 {
212 if (program)
213 _dl_fatal_printf ("%s: legacy bitmap isn't available\n",
214 l->l_name);
215 else
216 _dl_signal_error (EINVAL, l->l_name, "dlopen",
217 N_("legacy bitmap isn't available"));
218 }
219 }
220
221 /* Put legacy shared objects in legacy bitmap. */
222 for (i = first_legacy; i <= last_legacy; i++)
223 {
224 l = m->l_initfini[i];
225
226 if (l->l_init_called || (l->l_cet & lc_ibt))
227 continue;
228
229#ifdef SHARED
230 if (l == &GL(dl_rtld_map)
231 || l->l_real == &GL(dl_rtld_map)
232 || (program && l == m))
233 continue;
234#endif
235
236 /* If IBT is enabled in executable and IBT isn't enabled
237 in this shard object, mark PT_LOAD segments with PF_X
238 in legacy code page bitmap. */
239 res = dl_cet_mark_legacy_region (l);
240 if (res != 0)
241 {
242 if (program)
243 _dl_fatal_printf ("%s: failed to mark legacy code region\n",
244 l->l_name);
245 else
246 _dl_signal_error (-res, l->l_name, "dlopen",
247 N_("failed to mark legacy code region"));
248 }
249 }
250
251 /* Change legacy bitmap to read-only. */
252 if (__mprotect ((void *) GL(dl_x86_legacy_bitmap)[0],
253 GL(dl_x86_legacy_bitmap)[1], PROT_READ) < 0)
254 goto mprotect_failure;
255 }
256 }
257
258 bool cet_feature_changed = false;
259
260 if (enable_ibt != ibt_enabled || enable_shstk != shstk_enabled)
261 {
262 if (!program
263 && enable_shstk_type != CET_PERMISSIVE)
264 {
265 /* When SHSTK is enabled, we can't dlopening a shared
266 object without SHSTK. */
267 if (enable_shstk != shstk_enabled)
268 _dl_signal_error (EINVAL, l->l_name, "dlopen",
269 N_("shadow stack isn't enabled"));
270 return;
271 }
272
273 /* Disable IBT and/or SHSTK if they are enabled by kernel, but
274 disabled in executable or shared objects. */
275 unsigned int cet_feature = 0;
276
277 /* Disable IBT only during program startup. */
278 if (program && !enable_ibt)
279 cet_feature |= GNU_PROPERTY_X86_FEATURE_1_IBT;
280 if (!enable_shstk)
281 cet_feature |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
282
283 int res = dl_cet_disable_cet (cet_feature);
284 if (res != 0)
285 {
286 if (program)
287 _dl_fatal_printf ("%s: can't disable CET\n", program);
288 else
289 _dl_signal_error (-res, l->l_name, "dlopen",
290 N_("can't disable CET"));
291 }
292
293 /* Clear the disabled bits in dl_x86_feature_1. */
294 GL(dl_x86_feature_1)[0] &= ~cet_feature;
295
296 cet_feature_changed = true;
297 }
298
299#ifdef SHARED
300 if (program
301 && (!shstk_enabled
302 || enable_shstk_type != CET_PERMISSIVE)
303 && (ibt_enabled || shstk_enabled))
304 {
305 /* Lock CET if IBT or SHSTK is enabled in executable. Don't
306 lock CET if SHSTK is enabled permissively. */
307 int res = dl_cet_lock_cet ();
308 if (res != 0)
309 _dl_fatal_printf ("%s: can't lock CET\n", program);
310
311 cet_feature_changed = true;
312 }
313#endif
314
315 if (cet_feature_changed)
316 {
317 unsigned int feature_1 = 0;
318 if (enable_ibt)
319 feature_1 |= GNU_PROPERTY_X86_FEATURE_1_IBT;
320 if (enable_shstk)
321 feature_1 |= GNU_PROPERTY_X86_FEATURE_1_SHSTK;
322 struct pthread *self = THREAD_SELF;
323 THREAD_SETMEM (self, header.feature_1, feature_1);
324 }
325 }
326}
327
328void
329_dl_cet_open_check (struct link_map *l)
330{
331 dl_cet_check (l, NULL);
332}
333
334#ifdef SHARED
335
336# ifndef LINKAGE
337# define LINKAGE
338# endif
339
340LINKAGE
341void
342_dl_cet_check (struct link_map *main_map, const char *program)
343{
344 dl_cet_check (main_map, program);
345}
346#endif /* SHARED */