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dcc914f4 JP |
1 | /* |
2 | * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com> | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or | |
5 | * modify it under the terms of the GNU General Public License | |
6 | * as published by the Free Software Foundation; either version 2 | |
7 | * of the License, or (at your option) any later version. | |
8 | * | |
9 | * This program 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 | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
15 | * along with this program; if not, see <http://www.gnu.org/licenses/>. | |
16 | */ | |
17 | ||
18 | #include <string.h> | |
19 | #include <stdlib.h> | |
20 | ||
43a4525f | 21 | #include "builtin.h" |
dcc914f4 JP |
22 | #include "check.h" |
23 | #include "elf.h" | |
24 | #include "special.h" | |
25 | #include "arch.h" | |
26 | #include "warn.h" | |
27 | ||
28 | #include <linux/hashtable.h> | |
29 | #include <linux/kernel.h> | |
30 | ||
dcc914f4 JP |
31 | struct alternative { |
32 | struct list_head list; | |
33 | struct instruction *insn; | |
34 | }; | |
35 | ||
36 | const char *objname; | |
baa41469 | 37 | struct cfi_state initial_func_cfi; |
dcc914f4 | 38 | |
627fce14 JP |
39 | struct instruction *find_insn(struct objtool_file *file, |
40 | struct section *sec, unsigned long offset) | |
dcc914f4 JP |
41 | { |
42 | struct instruction *insn; | |
43 | ||
44 | hash_for_each_possible(file->insn_hash, insn, hash, offset) | |
45 | if (insn->sec == sec && insn->offset == offset) | |
46 | return insn; | |
47 | ||
48 | return NULL; | |
49 | } | |
50 | ||
51 | static struct instruction *next_insn_same_sec(struct objtool_file *file, | |
52 | struct instruction *insn) | |
53 | { | |
54 | struct instruction *next = list_next_entry(insn, list); | |
55 | ||
baa41469 | 56 | if (!next || &next->list == &file->insn_list || next->sec != insn->sec) |
dcc914f4 JP |
57 | return NULL; |
58 | ||
59 | return next; | |
60 | } | |
61 | ||
13810435 JP |
62 | static struct instruction *next_insn_same_func(struct objtool_file *file, |
63 | struct instruction *insn) | |
64 | { | |
65 | struct instruction *next = list_next_entry(insn, list); | |
66 | struct symbol *func = insn->func; | |
67 | ||
68 | if (!func) | |
69 | return NULL; | |
70 | ||
71 | if (&next->list != &file->insn_list && next->func == func) | |
72 | return next; | |
73 | ||
74 | /* Check if we're already in the subfunction: */ | |
75 | if (func == func->cfunc) | |
76 | return NULL; | |
77 | ||
78 | /* Move to the subfunction: */ | |
79 | return find_insn(file, func->cfunc->sec, func->cfunc->offset); | |
80 | } | |
81 | ||
82 | #define func_for_each_insn_all(file, func, insn) \ | |
83 | for (insn = find_insn(file, func->sec, func->offset); \ | |
84 | insn; \ | |
85 | insn = next_insn_same_func(file, insn)) | |
86 | ||
dcc914f4 JP |
87 | #define func_for_each_insn(file, func, insn) \ |
88 | for (insn = find_insn(file, func->sec, func->offset); \ | |
89 | insn && &insn->list != &file->insn_list && \ | |
90 | insn->sec == func->sec && \ | |
91 | insn->offset < func->offset + func->len; \ | |
92 | insn = list_next_entry(insn, list)) | |
93 | ||
94 | #define func_for_each_insn_continue_reverse(file, func, insn) \ | |
95 | for (insn = list_prev_entry(insn, list); \ | |
96 | &insn->list != &file->insn_list && \ | |
97 | insn->sec == func->sec && insn->offset >= func->offset; \ | |
98 | insn = list_prev_entry(insn, list)) | |
99 | ||
100 | #define sec_for_each_insn_from(file, insn) \ | |
101 | for (; insn; insn = next_insn_same_sec(file, insn)) | |
102 | ||
baa41469 JP |
103 | #define sec_for_each_insn_continue(file, insn) \ |
104 | for (insn = next_insn_same_sec(file, insn); insn; \ | |
105 | insn = next_insn_same_sec(file, insn)) | |
dcc914f4 JP |
106 | |
107 | /* | |
108 | * Check if the function has been manually whitelisted with the | |
109 | * STACK_FRAME_NON_STANDARD macro, or if it should be automatically whitelisted | |
110 | * due to its use of a context switching instruction. | |
111 | */ | |
112 | static bool ignore_func(struct objtool_file *file, struct symbol *func) | |
113 | { | |
114 | struct rela *rela; | |
dcc914f4 JP |
115 | |
116 | /* check for STACK_FRAME_NON_STANDARD */ | |
117 | if (file->whitelist && file->whitelist->rela) | |
118 | list_for_each_entry(rela, &file->whitelist->rela->rela_list, list) { | |
119 | if (rela->sym->type == STT_SECTION && | |
120 | rela->sym->sec == func->sec && | |
121 | rela->addend == func->offset) | |
122 | return true; | |
123 | if (rela->sym->type == STT_FUNC && rela->sym == func) | |
124 | return true; | |
125 | } | |
126 | ||
dcc914f4 JP |
127 | return false; |
128 | } | |
129 | ||
130 | /* | |
131 | * This checks to see if the given function is a "noreturn" function. | |
132 | * | |
133 | * For global functions which are outside the scope of this object file, we | |
134 | * have to keep a manual list of them. | |
135 | * | |
136 | * For local functions, we have to detect them manually by simply looking for | |
137 | * the lack of a return instruction. | |
138 | * | |
139 | * Returns: | |
140 | * -1: error | |
141 | * 0: no dead end | |
142 | * 1: dead end | |
143 | */ | |
144 | static int __dead_end_function(struct objtool_file *file, struct symbol *func, | |
145 | int recursion) | |
146 | { | |
147 | int i; | |
148 | struct instruction *insn; | |
149 | bool empty = true; | |
150 | ||
151 | /* | |
152 | * Unfortunately these have to be hard coded because the noreturn | |
153 | * attribute isn't provided in ELF data. | |
154 | */ | |
155 | static const char * const global_noreturns[] = { | |
156 | "__stack_chk_fail", | |
157 | "panic", | |
158 | "do_exit", | |
159 | "do_task_dead", | |
160 | "__module_put_and_exit", | |
161 | "complete_and_exit", | |
162 | "kvm_spurious_fault", | |
163 | "__reiserfs_panic", | |
164 | "lbug_with_loc", | |
165 | "fortify_panic", | |
b394d468 | 166 | "usercopy_abort", |
684fb246 | 167 | "machine_real_restart", |
dcc914f4 JP |
168 | }; |
169 | ||
170 | if (func->bind == STB_WEAK) | |
171 | return 0; | |
172 | ||
173 | if (func->bind == STB_GLOBAL) | |
174 | for (i = 0; i < ARRAY_SIZE(global_noreturns); i++) | |
175 | if (!strcmp(func->name, global_noreturns[i])) | |
176 | return 1; | |
177 | ||
13810435 | 178 | if (!func->len) |
dcc914f4 JP |
179 | return 0; |
180 | ||
13810435 JP |
181 | insn = find_insn(file, func->sec, func->offset); |
182 | if (!insn->func) | |
183 | return 0; | |
184 | ||
185 | func_for_each_insn_all(file, func, insn) { | |
dcc914f4 JP |
186 | empty = false; |
187 | ||
188 | if (insn->type == INSN_RETURN) | |
189 | return 0; | |
190 | } | |
191 | ||
192 | if (empty) | |
193 | return 0; | |
194 | ||
195 | /* | |
196 | * A function can have a sibling call instead of a return. In that | |
197 | * case, the function's dead-end status depends on whether the target | |
198 | * of the sibling call returns. | |
199 | */ | |
13810435 | 200 | func_for_each_insn_all(file, func, insn) { |
dcc914f4 JP |
201 | if (insn->type == INSN_JUMP_UNCONDITIONAL) { |
202 | struct instruction *dest = insn->jump_dest; | |
dcc914f4 JP |
203 | |
204 | if (!dest) | |
205 | /* sibling call to another file */ | |
206 | return 0; | |
207 | ||
13810435 | 208 | if (dest->func && dest->func->pfunc != insn->func->pfunc) { |
dcc914f4 | 209 | |
13810435 | 210 | /* local sibling call */ |
dcc914f4 | 211 | if (recursion == 5) { |
0afd0d9e JP |
212 | /* |
213 | * Infinite recursion: two functions | |
214 | * have sibling calls to each other. | |
215 | * This is a very rare case. It means | |
216 | * they aren't dead ends. | |
217 | */ | |
218 | return 0; | |
dcc914f4 JP |
219 | } |
220 | ||
13810435 | 221 | return __dead_end_function(file, dest->func, |
dcc914f4 JP |
222 | recursion + 1); |
223 | } | |
224 | } | |
225 | ||
226 | if (insn->type == INSN_JUMP_DYNAMIC && list_empty(&insn->alts)) | |
227 | /* sibling call */ | |
228 | return 0; | |
229 | } | |
230 | ||
231 | return 1; | |
232 | } | |
233 | ||
234 | static int dead_end_function(struct objtool_file *file, struct symbol *func) | |
235 | { | |
236 | return __dead_end_function(file, func, 0); | |
237 | } | |
238 | ||
baa41469 JP |
239 | static void clear_insn_state(struct insn_state *state) |
240 | { | |
241 | int i; | |
242 | ||
243 | memset(state, 0, sizeof(*state)); | |
244 | state->cfa.base = CFI_UNDEFINED; | |
dd88a0a0 | 245 | for (i = 0; i < CFI_NUM_REGS; i++) { |
baa41469 | 246 | state->regs[i].base = CFI_UNDEFINED; |
dd88a0a0 JP |
247 | state->vals[i].base = CFI_UNDEFINED; |
248 | } | |
baa41469 | 249 | state->drap_reg = CFI_UNDEFINED; |
bf4d1a83 | 250 | state->drap_offset = -1; |
baa41469 JP |
251 | } |
252 | ||
dcc914f4 JP |
253 | /* |
254 | * Call the arch-specific instruction decoder for all the instructions and add | |
255 | * them to the global instruction list. | |
256 | */ | |
257 | static int decode_instructions(struct objtool_file *file) | |
258 | { | |
259 | struct section *sec; | |
260 | struct symbol *func; | |
261 | unsigned long offset; | |
262 | struct instruction *insn; | |
263 | int ret; | |
264 | ||
baa41469 | 265 | for_each_sec(file, sec) { |
dcc914f4 JP |
266 | |
267 | if (!(sec->sh.sh_flags & SHF_EXECINSTR)) | |
268 | continue; | |
269 | ||
627fce14 JP |
270 | if (strcmp(sec->name, ".altinstr_replacement") && |
271 | strcmp(sec->name, ".altinstr_aux") && | |
272 | strncmp(sec->name, ".discard.", 9)) | |
273 | sec->text = true; | |
274 | ||
dcc914f4 JP |
275 | for (offset = 0; offset < sec->len; offset += insn->len) { |
276 | insn = malloc(sizeof(*insn)); | |
baa41469 JP |
277 | if (!insn) { |
278 | WARN("malloc failed"); | |
279 | return -1; | |
280 | } | |
dcc914f4 | 281 | memset(insn, 0, sizeof(*insn)); |
dcc914f4 | 282 | INIT_LIST_HEAD(&insn->alts); |
baa41469 JP |
283 | clear_insn_state(&insn->state); |
284 | ||
dcc914f4 JP |
285 | insn->sec = sec; |
286 | insn->offset = offset; | |
287 | ||
288 | ret = arch_decode_instruction(file->elf, sec, offset, | |
289 | sec->len - offset, | |
290 | &insn->len, &insn->type, | |
baa41469 JP |
291 | &insn->immediate, |
292 | &insn->stack_op); | |
dcc914f4 | 293 | if (ret) |
b7037983 | 294 | goto err; |
dcc914f4 JP |
295 | |
296 | if (!insn->type || insn->type > INSN_LAST) { | |
297 | WARN_FUNC("invalid instruction type %d", | |
298 | insn->sec, insn->offset, insn->type); | |
b7037983 KB |
299 | ret = -1; |
300 | goto err; | |
dcc914f4 JP |
301 | } |
302 | ||
303 | hash_add(file->insn_hash, &insn->hash, insn->offset); | |
304 | list_add_tail(&insn->list, &file->insn_list); | |
305 | } | |
306 | ||
307 | list_for_each_entry(func, &sec->symbol_list, list) { | |
308 | if (func->type != STT_FUNC) | |
309 | continue; | |
310 | ||
311 | if (!find_insn(file, sec, func->offset)) { | |
312 | WARN("%s(): can't find starting instruction", | |
313 | func->name); | |
314 | return -1; | |
315 | } | |
316 | ||
317 | func_for_each_insn(file, func, insn) | |
318 | if (!insn->func) | |
319 | insn->func = func; | |
320 | } | |
321 | } | |
322 | ||
323 | return 0; | |
b7037983 KB |
324 | |
325 | err: | |
326 | free(insn); | |
327 | return ret; | |
dcc914f4 JP |
328 | } |
329 | ||
330 | /* | |
649ea4d5 | 331 | * Mark "ud2" instructions and manually annotated dead ends. |
dcc914f4 JP |
332 | */ |
333 | static int add_dead_ends(struct objtool_file *file) | |
334 | { | |
335 | struct section *sec; | |
336 | struct rela *rela; | |
337 | struct instruction *insn; | |
338 | bool found; | |
339 | ||
649ea4d5 JP |
340 | /* |
341 | * By default, "ud2" is a dead end unless otherwise annotated, because | |
342 | * GCC 7 inserts it for certain divide-by-zero cases. | |
343 | */ | |
344 | for_each_insn(file, insn) | |
345 | if (insn->type == INSN_BUG) | |
346 | insn->dead_end = true; | |
347 | ||
348 | /* | |
349 | * Check for manually annotated dead ends. | |
350 | */ | |
dcc914f4 JP |
351 | sec = find_section_by_name(file->elf, ".rela.discard.unreachable"); |
352 | if (!sec) | |
649ea4d5 | 353 | goto reachable; |
dcc914f4 JP |
354 | |
355 | list_for_each_entry(rela, &sec->rela_list, list) { | |
356 | if (rela->sym->type != STT_SECTION) { | |
357 | WARN("unexpected relocation symbol type in %s", sec->name); | |
358 | return -1; | |
359 | } | |
360 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
361 | if (insn) | |
362 | insn = list_prev_entry(insn, list); | |
363 | else if (rela->addend == rela->sym->sec->len) { | |
364 | found = false; | |
365 | list_for_each_entry_reverse(insn, &file->insn_list, list) { | |
366 | if (insn->sec == rela->sym->sec) { | |
367 | found = true; | |
368 | break; | |
369 | } | |
370 | } | |
371 | ||
372 | if (!found) { | |
373 | WARN("can't find unreachable insn at %s+0x%x", | |
374 | rela->sym->sec->name, rela->addend); | |
375 | return -1; | |
376 | } | |
377 | } else { | |
378 | WARN("can't find unreachable insn at %s+0x%x", | |
379 | rela->sym->sec->name, rela->addend); | |
380 | return -1; | |
381 | } | |
382 | ||
383 | insn->dead_end = true; | |
384 | } | |
385 | ||
649ea4d5 JP |
386 | reachable: |
387 | /* | |
388 | * These manually annotated reachable checks are needed for GCC 4.4, | |
389 | * where the Linux unreachable() macro isn't supported. In that case | |
390 | * GCC doesn't know the "ud2" is fatal, so it generates code as if it's | |
391 | * not a dead end. | |
392 | */ | |
393 | sec = find_section_by_name(file->elf, ".rela.discard.reachable"); | |
394 | if (!sec) | |
395 | return 0; | |
396 | ||
397 | list_for_each_entry(rela, &sec->rela_list, list) { | |
398 | if (rela->sym->type != STT_SECTION) { | |
399 | WARN("unexpected relocation symbol type in %s", sec->name); | |
400 | return -1; | |
401 | } | |
402 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
403 | if (insn) | |
404 | insn = list_prev_entry(insn, list); | |
405 | else if (rela->addend == rela->sym->sec->len) { | |
406 | found = false; | |
407 | list_for_each_entry_reverse(insn, &file->insn_list, list) { | |
408 | if (insn->sec == rela->sym->sec) { | |
409 | found = true; | |
410 | break; | |
411 | } | |
412 | } | |
413 | ||
414 | if (!found) { | |
415 | WARN("can't find reachable insn at %s+0x%x", | |
416 | rela->sym->sec->name, rela->addend); | |
417 | return -1; | |
418 | } | |
419 | } else { | |
420 | WARN("can't find reachable insn at %s+0x%x", | |
421 | rela->sym->sec->name, rela->addend); | |
422 | return -1; | |
423 | } | |
424 | ||
425 | insn->dead_end = false; | |
426 | } | |
427 | ||
dcc914f4 JP |
428 | return 0; |
429 | } | |
430 | ||
431 | /* | |
432 | * Warnings shouldn't be reported for ignored functions. | |
433 | */ | |
434 | static void add_ignores(struct objtool_file *file) | |
435 | { | |
436 | struct instruction *insn; | |
437 | struct section *sec; | |
438 | struct symbol *func; | |
439 | ||
baa41469 | 440 | for_each_sec(file, sec) { |
dcc914f4 JP |
441 | list_for_each_entry(func, &sec->symbol_list, list) { |
442 | if (func->type != STT_FUNC) | |
443 | continue; | |
444 | ||
445 | if (!ignore_func(file, func)) | |
446 | continue; | |
447 | ||
13810435 | 448 | func_for_each_insn_all(file, func, insn) |
baa41469 | 449 | insn->ignore = true; |
dcc914f4 JP |
450 | } |
451 | } | |
452 | } | |
453 | ||
258c7605 JP |
454 | /* |
455 | * FIXME: For now, just ignore any alternatives which add retpolines. This is | |
456 | * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline. | |
457 | * But it at least allows objtool to understand the control flow *around* the | |
458 | * retpoline. | |
459 | */ | |
460 | static int add_nospec_ignores(struct objtool_file *file) | |
461 | { | |
462 | struct section *sec; | |
463 | struct rela *rela; | |
464 | struct instruction *insn; | |
465 | ||
466 | sec = find_section_by_name(file->elf, ".rela.discard.nospec"); | |
467 | if (!sec) | |
468 | return 0; | |
469 | ||
470 | list_for_each_entry(rela, &sec->rela_list, list) { | |
471 | if (rela->sym->type != STT_SECTION) { | |
472 | WARN("unexpected relocation symbol type in %s", sec->name); | |
473 | return -1; | |
474 | } | |
475 | ||
476 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
477 | if (!insn) { | |
478 | WARN("bad .discard.nospec entry"); | |
479 | return -1; | |
480 | } | |
481 | ||
482 | insn->ignore_alts = true; | |
483 | } | |
484 | ||
485 | return 0; | |
486 | } | |
487 | ||
dcc914f4 JP |
488 | /* |
489 | * Find the destination instructions for all jumps. | |
490 | */ | |
491 | static int add_jump_destinations(struct objtool_file *file) | |
492 | { | |
493 | struct instruction *insn; | |
494 | struct rela *rela; | |
495 | struct section *dest_sec; | |
496 | unsigned long dest_off; | |
497 | ||
498 | for_each_insn(file, insn) { | |
499 | if (insn->type != INSN_JUMP_CONDITIONAL && | |
500 | insn->type != INSN_JUMP_UNCONDITIONAL) | |
501 | continue; | |
502 | ||
baa41469 | 503 | if (insn->ignore) |
dcc914f4 JP |
504 | continue; |
505 | ||
506 | rela = find_rela_by_dest_range(insn->sec, insn->offset, | |
507 | insn->len); | |
508 | if (!rela) { | |
509 | dest_sec = insn->sec; | |
510 | dest_off = insn->offset + insn->len + insn->immediate; | |
511 | } else if (rela->sym->type == STT_SECTION) { | |
512 | dest_sec = rela->sym->sec; | |
513 | dest_off = rela->addend + 4; | |
514 | } else if (rela->sym->sec->idx) { | |
515 | dest_sec = rela->sym->sec; | |
516 | dest_off = rela->sym->sym.st_value + rela->addend + 4; | |
39b73533 JP |
517 | } else if (strstr(rela->sym->name, "_indirect_thunk_")) { |
518 | /* | |
519 | * Retpoline jumps are really dynamic jumps in | |
520 | * disguise, so convert them accordingly. | |
521 | */ | |
522 | insn->type = INSN_JUMP_DYNAMIC; | |
b5bc2231 | 523 | insn->retpoline_safe = true; |
39b73533 | 524 | continue; |
dcc914f4 JP |
525 | } else { |
526 | /* sibling call */ | |
527 | insn->jump_dest = 0; | |
528 | continue; | |
529 | } | |
530 | ||
531 | insn->jump_dest = find_insn(file, dest_sec, dest_off); | |
532 | if (!insn->jump_dest) { | |
533 | ||
534 | /* | |
535 | * This is a special case where an alt instruction | |
536 | * jumps past the end of the section. These are | |
537 | * handled later in handle_group_alt(). | |
538 | */ | |
539 | if (!strcmp(insn->sec->name, ".altinstr_replacement")) | |
540 | continue; | |
541 | ||
542 | WARN_FUNC("can't find jump dest instruction at %s+0x%lx", | |
543 | insn->sec, insn->offset, dest_sec->name, | |
544 | dest_off); | |
545 | return -1; | |
546 | } | |
cd77849a JP |
547 | |
548 | /* | |
549 | * For GCC 8+, create parent/child links for any cold | |
550 | * subfunctions. This is _mostly_ redundant with a similar | |
551 | * initialization in read_symbols(). | |
552 | * | |
553 | * If a function has aliases, we want the *first* such function | |
554 | * in the symbol table to be the subfunction's parent. In that | |
555 | * case we overwrite the initialization done in read_symbols(). | |
556 | * | |
557 | * However this code can't completely replace the | |
558 | * read_symbols() code because this doesn't detect the case | |
559 | * where the parent function's only reference to a subfunction | |
560 | * is through a switch table. | |
561 | */ | |
562 | if (insn->func && insn->jump_dest->func && | |
563 | insn->func != insn->jump_dest->func && | |
564 | !strstr(insn->func->name, ".cold.") && | |
565 | strstr(insn->jump_dest->func->name, ".cold.")) { | |
566 | insn->func->cfunc = insn->jump_dest->func; | |
567 | insn->jump_dest->func->pfunc = insn->func; | |
568 | } | |
dcc914f4 JP |
569 | } |
570 | ||
571 | return 0; | |
572 | } | |
573 | ||
574 | /* | |
575 | * Find the destination instructions for all calls. | |
576 | */ | |
577 | static int add_call_destinations(struct objtool_file *file) | |
578 | { | |
579 | struct instruction *insn; | |
580 | unsigned long dest_off; | |
581 | struct rela *rela; | |
582 | ||
583 | for_each_insn(file, insn) { | |
584 | if (insn->type != INSN_CALL) | |
585 | continue; | |
586 | ||
587 | rela = find_rela_by_dest_range(insn->sec, insn->offset, | |
588 | insn->len); | |
589 | if (!rela) { | |
590 | dest_off = insn->offset + insn->len + insn->immediate; | |
591 | insn->call_dest = find_symbol_by_offset(insn->sec, | |
592 | dest_off); | |
a845c7cf JP |
593 | |
594 | if (!insn->call_dest && !insn->ignore) { | |
595 | WARN_FUNC("unsupported intra-function call", | |
596 | insn->sec, insn->offset); | |
b5bc2231 PZ |
597 | if (retpoline) |
598 | WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE."); | |
dcc914f4 JP |
599 | return -1; |
600 | } | |
a845c7cf | 601 | |
dcc914f4 JP |
602 | } else if (rela->sym->type == STT_SECTION) { |
603 | insn->call_dest = find_symbol_by_offset(rela->sym->sec, | |
604 | rela->addend+4); | |
605 | if (!insn->call_dest || | |
606 | insn->call_dest->type != STT_FUNC) { | |
607 | WARN_FUNC("can't find call dest symbol at %s+0x%x", | |
608 | insn->sec, insn->offset, | |
609 | rela->sym->sec->name, | |
610 | rela->addend + 4); | |
611 | return -1; | |
612 | } | |
613 | } else | |
614 | insn->call_dest = rela->sym; | |
615 | } | |
616 | ||
617 | return 0; | |
618 | } | |
619 | ||
620 | /* | |
621 | * The .alternatives section requires some extra special care, over and above | |
622 | * what other special sections require: | |
623 | * | |
624 | * 1. Because alternatives are patched in-place, we need to insert a fake jump | |
625 | * instruction at the end so that validate_branch() skips all the original | |
626 | * replaced instructions when validating the new instruction path. | |
627 | * | |
628 | * 2. An added wrinkle is that the new instruction length might be zero. In | |
629 | * that case the old instructions are replaced with noops. We simulate that | |
630 | * by creating a fake jump as the only new instruction. | |
631 | * | |
632 | * 3. In some cases, the alternative section includes an instruction which | |
633 | * conditionally jumps to the _end_ of the entry. We have to modify these | |
634 | * jumps' destinations to point back to .text rather than the end of the | |
635 | * entry in .altinstr_replacement. | |
636 | * | |
637 | * 4. It has been requested that we don't validate the !POPCNT feature path | |
638 | * which is a "very very small percentage of machines". | |
639 | */ | |
640 | static int handle_group_alt(struct objtool_file *file, | |
641 | struct special_alt *special_alt, | |
642 | struct instruction *orig_insn, | |
643 | struct instruction **new_insn) | |
644 | { | |
17bc3391 | 645 | struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL; |
dcc914f4 JP |
646 | unsigned long dest_off; |
647 | ||
648 | last_orig_insn = NULL; | |
649 | insn = orig_insn; | |
650 | sec_for_each_insn_from(file, insn) { | |
651 | if (insn->offset >= special_alt->orig_off + special_alt->orig_len) | |
652 | break; | |
653 | ||
654 | if (special_alt->skip_orig) | |
655 | insn->type = INSN_NOP; | |
656 | ||
657 | insn->alt_group = true; | |
658 | last_orig_insn = insn; | |
659 | } | |
660 | ||
17bc3391 JP |
661 | if (next_insn_same_sec(file, last_orig_insn)) { |
662 | fake_jump = malloc(sizeof(*fake_jump)); | |
663 | if (!fake_jump) { | |
664 | WARN("malloc failed"); | |
665 | return -1; | |
666 | } | |
667 | memset(fake_jump, 0, sizeof(*fake_jump)); | |
668 | INIT_LIST_HEAD(&fake_jump->alts); | |
669 | clear_insn_state(&fake_jump->state); | |
670 | ||
671 | fake_jump->sec = special_alt->new_sec; | |
672 | fake_jump->offset = -1; | |
673 | fake_jump->type = INSN_JUMP_UNCONDITIONAL; | |
674 | fake_jump->jump_dest = list_next_entry(last_orig_insn, list); | |
675 | fake_jump->ignore = true; | |
dcc914f4 | 676 | } |
dcc914f4 JP |
677 | |
678 | if (!special_alt->new_len) { | |
17bc3391 JP |
679 | if (!fake_jump) { |
680 | WARN("%s: empty alternative at end of section", | |
681 | special_alt->orig_sec->name); | |
682 | return -1; | |
683 | } | |
684 | ||
dcc914f4 JP |
685 | *new_insn = fake_jump; |
686 | return 0; | |
687 | } | |
688 | ||
689 | last_new_insn = NULL; | |
690 | insn = *new_insn; | |
691 | sec_for_each_insn_from(file, insn) { | |
692 | if (insn->offset >= special_alt->new_off + special_alt->new_len) | |
693 | break; | |
694 | ||
695 | last_new_insn = insn; | |
696 | ||
a845c7cf JP |
697 | insn->ignore = orig_insn->ignore_alts; |
698 | ||
dcc914f4 JP |
699 | if (insn->type != INSN_JUMP_CONDITIONAL && |
700 | insn->type != INSN_JUMP_UNCONDITIONAL) | |
701 | continue; | |
702 | ||
703 | if (!insn->immediate) | |
704 | continue; | |
705 | ||
706 | dest_off = insn->offset + insn->len + insn->immediate; | |
17bc3391 JP |
707 | if (dest_off == special_alt->new_off + special_alt->new_len) { |
708 | if (!fake_jump) { | |
709 | WARN("%s: alternative jump to end of section", | |
710 | special_alt->orig_sec->name); | |
711 | return -1; | |
712 | } | |
dcc914f4 | 713 | insn->jump_dest = fake_jump; |
17bc3391 | 714 | } |
dcc914f4 JP |
715 | |
716 | if (!insn->jump_dest) { | |
717 | WARN_FUNC("can't find alternative jump destination", | |
718 | insn->sec, insn->offset); | |
719 | return -1; | |
720 | } | |
721 | } | |
722 | ||
723 | if (!last_new_insn) { | |
724 | WARN_FUNC("can't find last new alternative instruction", | |
725 | special_alt->new_sec, special_alt->new_off); | |
726 | return -1; | |
727 | } | |
728 | ||
17bc3391 JP |
729 | if (fake_jump) |
730 | list_add(&fake_jump->list, &last_new_insn->list); | |
dcc914f4 JP |
731 | |
732 | return 0; | |
733 | } | |
734 | ||
735 | /* | |
736 | * A jump table entry can either convert a nop to a jump or a jump to a nop. | |
737 | * If the original instruction is a jump, make the alt entry an effective nop | |
738 | * by just skipping the original instruction. | |
739 | */ | |
740 | static int handle_jump_alt(struct objtool_file *file, | |
741 | struct special_alt *special_alt, | |
742 | struct instruction *orig_insn, | |
743 | struct instruction **new_insn) | |
744 | { | |
745 | if (orig_insn->type == INSN_NOP) | |
746 | return 0; | |
747 | ||
748 | if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) { | |
749 | WARN_FUNC("unsupported instruction at jump label", | |
750 | orig_insn->sec, orig_insn->offset); | |
751 | return -1; | |
752 | } | |
753 | ||
754 | *new_insn = list_next_entry(orig_insn, list); | |
755 | return 0; | |
756 | } | |
757 | ||
758 | /* | |
759 | * Read all the special sections which have alternate instructions which can be | |
760 | * patched in or redirected to at runtime. Each instruction having alternate | |
761 | * instruction(s) has them added to its insn->alts list, which will be | |
762 | * traversed in validate_branch(). | |
763 | */ | |
764 | static int add_special_section_alts(struct objtool_file *file) | |
765 | { | |
766 | struct list_head special_alts; | |
767 | struct instruction *orig_insn, *new_insn; | |
768 | struct special_alt *special_alt, *tmp; | |
769 | struct alternative *alt; | |
770 | int ret; | |
771 | ||
772 | ret = special_get_alts(file->elf, &special_alts); | |
773 | if (ret) | |
774 | return ret; | |
775 | ||
776 | list_for_each_entry_safe(special_alt, tmp, &special_alts, list) { | |
dcc914f4 JP |
777 | |
778 | orig_insn = find_insn(file, special_alt->orig_sec, | |
779 | special_alt->orig_off); | |
780 | if (!orig_insn) { | |
781 | WARN_FUNC("special: can't find orig instruction", | |
782 | special_alt->orig_sec, special_alt->orig_off); | |
783 | ret = -1; | |
784 | goto out; | |
785 | } | |
786 | ||
787 | new_insn = NULL; | |
788 | if (!special_alt->group || special_alt->new_len) { | |
789 | new_insn = find_insn(file, special_alt->new_sec, | |
790 | special_alt->new_off); | |
791 | if (!new_insn) { | |
792 | WARN_FUNC("special: can't find new instruction", | |
793 | special_alt->new_sec, | |
794 | special_alt->new_off); | |
795 | ret = -1; | |
796 | goto out; | |
797 | } | |
798 | } | |
799 | ||
800 | if (special_alt->group) { | |
801 | ret = handle_group_alt(file, special_alt, orig_insn, | |
802 | &new_insn); | |
803 | if (ret) | |
804 | goto out; | |
805 | } else if (special_alt->jump_or_nop) { | |
806 | ret = handle_jump_alt(file, special_alt, orig_insn, | |
807 | &new_insn); | |
808 | if (ret) | |
809 | goto out; | |
810 | } | |
811 | ||
258c7605 JP |
812 | alt = malloc(sizeof(*alt)); |
813 | if (!alt) { | |
814 | WARN("malloc failed"); | |
815 | ret = -1; | |
816 | goto out; | |
817 | } | |
818 | ||
dcc914f4 JP |
819 | alt->insn = new_insn; |
820 | list_add_tail(&alt->list, &orig_insn->alts); | |
821 | ||
822 | list_del(&special_alt->list); | |
823 | free(special_alt); | |
824 | } | |
825 | ||
826 | out: | |
827 | return ret; | |
828 | } | |
829 | ||
13810435 JP |
830 | static int add_switch_table(struct objtool_file *file, struct instruction *insn, |
831 | struct rela *table, struct rela *next_table) | |
dcc914f4 JP |
832 | { |
833 | struct rela *rela = table; | |
834 | struct instruction *alt_insn; | |
835 | struct alternative *alt; | |
fd35c88b JP |
836 | struct symbol *pfunc = insn->func->pfunc; |
837 | unsigned int prev_offset = 0; | |
dcc914f4 | 838 | |
4a60aa05 | 839 | list_for_each_entry_from(rela, &table->rela_sec->rela_list, list) { |
dcc914f4 JP |
840 | if (rela == next_table) |
841 | break; | |
842 | ||
fd35c88b JP |
843 | /* Make sure the switch table entries are consecutive: */ |
844 | if (prev_offset && rela->offset != prev_offset + 8) | |
845 | break; | |
846 | ||
847 | /* Detect function pointers from contiguous objects: */ | |
848 | if (rela->sym->sec == pfunc->sec && | |
849 | rela->addend == pfunc->offset) | |
850 | break; | |
851 | ||
13810435 JP |
852 | alt_insn = find_insn(file, rela->sym->sec, rela->addend); |
853 | if (!alt_insn) | |
dcc914f4 JP |
854 | break; |
855 | ||
13810435 | 856 | /* Make sure the jmp dest is in the function or subfunction: */ |
fd35c88b | 857 | if (alt_insn->func->pfunc != pfunc) |
13810435 | 858 | break; |
dcc914f4 JP |
859 | |
860 | alt = malloc(sizeof(*alt)); | |
861 | if (!alt) { | |
862 | WARN("malloc failed"); | |
863 | return -1; | |
864 | } | |
865 | ||
866 | alt->insn = alt_insn; | |
867 | list_add_tail(&alt->list, &insn->alts); | |
fd35c88b JP |
868 | prev_offset = rela->offset; |
869 | } | |
870 | ||
871 | if (!prev_offset) { | |
872 | WARN_FUNC("can't find switch jump table", | |
873 | insn->sec, insn->offset); | |
874 | return -1; | |
dcc914f4 JP |
875 | } |
876 | ||
877 | return 0; | |
878 | } | |
879 | ||
880 | /* | |
881 | * find_switch_table() - Given a dynamic jump, find the switch jump table in | |
882 | * .rodata associated with it. | |
883 | * | |
884 | * There are 3 basic patterns: | |
885 | * | |
886 | * 1. jmpq *[rodata addr](,%reg,8) | |
887 | * | |
888 | * This is the most common case by far. It jumps to an address in a simple | |
889 | * jump table which is stored in .rodata. | |
890 | * | |
891 | * 2. jmpq *[rodata addr](%rip) | |
892 | * | |
893 | * This is caused by a rare GCC quirk, currently only seen in three driver | |
894 | * functions in the kernel, only with certain obscure non-distro configs. | |
895 | * | |
896 | * As part of an optimization, GCC makes a copy of an existing switch jump | |
897 | * table, modifies it, and then hard-codes the jump (albeit with an indirect | |
898 | * jump) to use a single entry in the table. The rest of the jump table and | |
899 | * some of its jump targets remain as dead code. | |
900 | * | |
901 | * In such a case we can just crudely ignore all unreachable instruction | |
902 | * warnings for the entire object file. Ideally we would just ignore them | |
903 | * for the function, but that would require redesigning the code quite a | |
904 | * bit. And honestly that's just not worth doing: unreachable instruction | |
905 | * warnings are of questionable value anyway, and this is such a rare issue. | |
906 | * | |
907 | * 3. mov [rodata addr],%reg1 | |
908 | * ... some instructions ... | |
909 | * jmpq *(%reg1,%reg2,8) | |
910 | * | |
911 | * This is a fairly uncommon pattern which is new for GCC 6. As of this | |
912 | * writing, there are 11 occurrences of it in the allmodconfig kernel. | |
913 | * | |
99ce7962 PZ |
914 | * As of GCC 7 there are quite a few more of these and the 'in between' code |
915 | * is significant. Esp. with KASAN enabled some of the code between the mov | |
916 | * and jmpq uses .rodata itself, which can confuse things. | |
917 | * | |
dcc914f4 JP |
918 | * TODO: Once we have DWARF CFI and smarter instruction decoding logic, |
919 | * ensure the same register is used in the mov and jump instructions. | |
99ce7962 PZ |
920 | * |
921 | * NOTE: RETPOLINE made it harder still to decode dynamic jumps. | |
dcc914f4 JP |
922 | */ |
923 | static struct rela *find_switch_table(struct objtool_file *file, | |
924 | struct symbol *func, | |
925 | struct instruction *insn) | |
926 | { | |
927 | struct rela *text_rela, *rodata_rela; | |
928 | struct instruction *orig_insn = insn; | |
4a60aa05 | 929 | struct section *rodata_sec; |
6f5ec299 | 930 | unsigned long table_offset; |
dcc914f4 | 931 | |
99ce7962 PZ |
932 | /* |
933 | * Backward search using the @first_jump_src links, these help avoid | |
934 | * much of the 'in between' code. Which avoids us getting confused by | |
935 | * it. | |
936 | */ | |
7dec80cc | 937 | for (; |
99ce7962 PZ |
938 | &insn->list != &file->insn_list && |
939 | insn->sec == func->sec && | |
940 | insn->offset >= func->offset; | |
941 | ||
942 | insn = insn->first_jump_src ?: list_prev_entry(insn, list)) { | |
943 | ||
7dec80cc | 944 | if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC) |
dcc914f4 JP |
945 | break; |
946 | ||
947 | /* allow small jumps within the range */ | |
948 | if (insn->type == INSN_JUMP_UNCONDITIONAL && | |
949 | insn->jump_dest && | |
950 | (insn->jump_dest->offset <= insn->offset || | |
951 | insn->jump_dest->offset > orig_insn->offset)) | |
952 | break; | |
953 | ||
954 | /* look for a relocation which references .rodata */ | |
955 | text_rela = find_rela_by_dest_range(insn->sec, insn->offset, | |
956 | insn->len); | |
4a60aa05 AX |
957 | if (!text_rela || text_rela->sym->type != STT_SECTION || |
958 | !text_rela->sym->sec->rodata) | |
dcc914f4 JP |
959 | continue; |
960 | ||
6f5ec299 | 961 | table_offset = text_rela->addend; |
4a60aa05 AX |
962 | rodata_sec = text_rela->sym->sec; |
963 | ||
6f5ec299 JP |
964 | if (text_rela->type == R_X86_64_PC32) |
965 | table_offset += 4; | |
966 | ||
dcc914f4 JP |
967 | /* |
968 | * Make sure the .rodata address isn't associated with a | |
969 | * symbol. gcc jump tables are anonymous data. | |
970 | */ | |
4a60aa05 | 971 | if (find_symbol_containing(rodata_sec, table_offset)) |
1402fd8e JP |
972 | continue; |
973 | ||
4a60aa05 | 974 | rodata_rela = find_rela_by_dest(rodata_sec, table_offset); |
7dec80cc JP |
975 | if (rodata_rela) { |
976 | /* | |
977 | * Use of RIP-relative switch jumps is quite rare, and | |
978 | * indicates a rare GCC quirk/bug which can leave dead | |
979 | * code behind. | |
980 | */ | |
981 | if (text_rela->type == R_X86_64_PC32) | |
982 | file->ignore_unreachables = true; | |
983 | ||
6f5ec299 | 984 | return rodata_rela; |
7dec80cc | 985 | } |
dcc914f4 JP |
986 | } |
987 | ||
988 | return NULL; | |
989 | } | |
990 | ||
99ce7962 | 991 | |
dcc914f4 JP |
992 | static int add_func_switch_tables(struct objtool_file *file, |
993 | struct symbol *func) | |
994 | { | |
99ce7962 | 995 | struct instruction *insn, *last = NULL, *prev_jump = NULL; |
dcc914f4 JP |
996 | struct rela *rela, *prev_rela = NULL; |
997 | int ret; | |
998 | ||
13810435 | 999 | func_for_each_insn_all(file, func, insn) { |
99ce7962 PZ |
1000 | if (!last) |
1001 | last = insn; | |
1002 | ||
1003 | /* | |
1004 | * Store back-pointers for unconditional forward jumps such | |
1005 | * that find_switch_table() can back-track using those and | |
1006 | * avoid some potentially confusing code. | |
1007 | */ | |
1008 | if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest && | |
1009 | insn->offset > last->offset && | |
1010 | insn->jump_dest->offset > insn->offset && | |
1011 | !insn->jump_dest->first_jump_src) { | |
1012 | ||
1013 | insn->jump_dest->first_jump_src = insn; | |
1014 | last = insn->jump_dest; | |
1015 | } | |
1016 | ||
dcc914f4 JP |
1017 | if (insn->type != INSN_JUMP_DYNAMIC) |
1018 | continue; | |
1019 | ||
1020 | rela = find_switch_table(file, func, insn); | |
1021 | if (!rela) | |
1022 | continue; | |
1023 | ||
1024 | /* | |
1025 | * We found a switch table, but we don't know yet how big it | |
1026 | * is. Don't add it until we reach the end of the function or | |
1027 | * the beginning of another switch table in the same function. | |
1028 | */ | |
1029 | if (prev_jump) { | |
13810435 | 1030 | ret = add_switch_table(file, prev_jump, prev_rela, rela); |
dcc914f4 JP |
1031 | if (ret) |
1032 | return ret; | |
1033 | } | |
1034 | ||
1035 | prev_jump = insn; | |
1036 | prev_rela = rela; | |
1037 | } | |
1038 | ||
1039 | if (prev_jump) { | |
13810435 | 1040 | ret = add_switch_table(file, prev_jump, prev_rela, NULL); |
dcc914f4 JP |
1041 | if (ret) |
1042 | return ret; | |
1043 | } | |
1044 | ||
1045 | return 0; | |
1046 | } | |
1047 | ||
1048 | /* | |
1049 | * For some switch statements, gcc generates a jump table in the .rodata | |
1050 | * section which contains a list of addresses within the function to jump to. | |
1051 | * This finds these jump tables and adds them to the insn->alts lists. | |
1052 | */ | |
1053 | static int add_switch_table_alts(struct objtool_file *file) | |
1054 | { | |
1055 | struct section *sec; | |
1056 | struct symbol *func; | |
1057 | int ret; | |
1058 | ||
4a60aa05 | 1059 | if (!file->rodata) |
dcc914f4 JP |
1060 | return 0; |
1061 | ||
baa41469 | 1062 | for_each_sec(file, sec) { |
dcc914f4 JP |
1063 | list_for_each_entry(func, &sec->symbol_list, list) { |
1064 | if (func->type != STT_FUNC) | |
1065 | continue; | |
1066 | ||
1067 | ret = add_func_switch_tables(file, func); | |
1068 | if (ret) | |
1069 | return ret; | |
1070 | } | |
1071 | } | |
1072 | ||
1073 | return 0; | |
1074 | } | |
1075 | ||
39358a03 JP |
1076 | static int read_unwind_hints(struct objtool_file *file) |
1077 | { | |
1078 | struct section *sec, *relasec; | |
1079 | struct rela *rela; | |
1080 | struct unwind_hint *hint; | |
1081 | struct instruction *insn; | |
1082 | struct cfi_reg *cfa; | |
1083 | int i; | |
1084 | ||
1085 | sec = find_section_by_name(file->elf, ".discard.unwind_hints"); | |
1086 | if (!sec) | |
1087 | return 0; | |
1088 | ||
1089 | relasec = sec->rela; | |
1090 | if (!relasec) { | |
1091 | WARN("missing .rela.discard.unwind_hints section"); | |
1092 | return -1; | |
1093 | } | |
1094 | ||
1095 | if (sec->len % sizeof(struct unwind_hint)) { | |
1096 | WARN("struct unwind_hint size mismatch"); | |
1097 | return -1; | |
1098 | } | |
1099 | ||
1100 | file->hints = true; | |
1101 | ||
1102 | for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) { | |
1103 | hint = (struct unwind_hint *)sec->data->d_buf + i; | |
1104 | ||
1105 | rela = find_rela_by_dest(sec, i * sizeof(*hint)); | |
1106 | if (!rela) { | |
1107 | WARN("can't find rela for unwind_hints[%d]", i); | |
1108 | return -1; | |
1109 | } | |
1110 | ||
1111 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
1112 | if (!insn) { | |
1113 | WARN("can't find insn for unwind_hints[%d]", i); | |
1114 | return -1; | |
1115 | } | |
1116 | ||
1117 | cfa = &insn->state.cfa; | |
1118 | ||
1119 | if (hint->type == UNWIND_HINT_TYPE_SAVE) { | |
1120 | insn->save = true; | |
1121 | continue; | |
1122 | ||
1123 | } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) { | |
1124 | insn->restore = true; | |
1125 | insn->hint = true; | |
1126 | continue; | |
1127 | } | |
1128 | ||
1129 | insn->hint = true; | |
1130 | ||
1131 | switch (hint->sp_reg) { | |
1132 | case ORC_REG_UNDEFINED: | |
1133 | cfa->base = CFI_UNDEFINED; | |
1134 | break; | |
1135 | case ORC_REG_SP: | |
1136 | cfa->base = CFI_SP; | |
1137 | break; | |
1138 | case ORC_REG_BP: | |
1139 | cfa->base = CFI_BP; | |
1140 | break; | |
1141 | case ORC_REG_SP_INDIRECT: | |
1142 | cfa->base = CFI_SP_INDIRECT; | |
1143 | break; | |
1144 | case ORC_REG_R10: | |
1145 | cfa->base = CFI_R10; | |
1146 | break; | |
1147 | case ORC_REG_R13: | |
1148 | cfa->base = CFI_R13; | |
1149 | break; | |
1150 | case ORC_REG_DI: | |
1151 | cfa->base = CFI_DI; | |
1152 | break; | |
1153 | case ORC_REG_DX: | |
1154 | cfa->base = CFI_DX; | |
1155 | break; | |
1156 | default: | |
1157 | WARN_FUNC("unsupported unwind_hint sp base reg %d", | |
1158 | insn->sec, insn->offset, hint->sp_reg); | |
1159 | return -1; | |
1160 | } | |
1161 | ||
1162 | cfa->offset = hint->sp_offset; | |
1163 | insn->state.type = hint->type; | |
d31a5802 | 1164 | insn->state.end = hint->end; |
39358a03 JP |
1165 | } |
1166 | ||
1167 | return 0; | |
1168 | } | |
1169 | ||
b5bc2231 PZ |
1170 | static int read_retpoline_hints(struct objtool_file *file) |
1171 | { | |
63474dc4 | 1172 | struct section *sec; |
b5bc2231 PZ |
1173 | struct instruction *insn; |
1174 | struct rela *rela; | |
b5bc2231 | 1175 | |
63474dc4 | 1176 | sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe"); |
b5bc2231 PZ |
1177 | if (!sec) |
1178 | return 0; | |
1179 | ||
63474dc4 JP |
1180 | list_for_each_entry(rela, &sec->rela_list, list) { |
1181 | if (rela->sym->type != STT_SECTION) { | |
1182 | WARN("unexpected relocation symbol type in %s", sec->name); | |
b5bc2231 PZ |
1183 | return -1; |
1184 | } | |
1185 | ||
1186 | insn = find_insn(file, rela->sym->sec, rela->addend); | |
1187 | if (!insn) { | |
63474dc4 | 1188 | WARN("bad .discard.retpoline_safe entry"); |
b5bc2231 PZ |
1189 | return -1; |
1190 | } | |
1191 | ||
1192 | if (insn->type != INSN_JUMP_DYNAMIC && | |
1193 | insn->type != INSN_CALL_DYNAMIC) { | |
63474dc4 | 1194 | WARN_FUNC("retpoline_safe hint not an indirect jump/call", |
b5bc2231 PZ |
1195 | insn->sec, insn->offset); |
1196 | return -1; | |
1197 | } | |
1198 | ||
1199 | insn->retpoline_safe = true; | |
1200 | } | |
1201 | ||
1202 | return 0; | |
1203 | } | |
1204 | ||
4a60aa05 AX |
1205 | static void mark_rodata(struct objtool_file *file) |
1206 | { | |
1207 | struct section *sec; | |
1208 | bool found = false; | |
1209 | ||
1210 | /* | |
1211 | * This searches for the .rodata section or multiple .rodata.func_name | |
1212 | * sections if -fdata-sections is being used. The .str.1.1 and .str.1.8 | |
1213 | * rodata sections are ignored as they don't contain jump tables. | |
1214 | */ | |
1215 | for_each_sec(file, sec) { | |
1216 | if (!strncmp(sec->name, ".rodata", 7) && | |
1217 | !strstr(sec->name, ".str1.")) { | |
1218 | sec->rodata = true; | |
1219 | found = true; | |
1220 | } | |
1221 | } | |
1222 | ||
1223 | file->rodata = found; | |
1224 | } | |
1225 | ||
dcc914f4 JP |
1226 | static int decode_sections(struct objtool_file *file) |
1227 | { | |
1228 | int ret; | |
1229 | ||
4a60aa05 AX |
1230 | mark_rodata(file); |
1231 | ||
dcc914f4 JP |
1232 | ret = decode_instructions(file); |
1233 | if (ret) | |
1234 | return ret; | |
1235 | ||
1236 | ret = add_dead_ends(file); | |
1237 | if (ret) | |
1238 | return ret; | |
1239 | ||
1240 | add_ignores(file); | |
1241 | ||
258c7605 JP |
1242 | ret = add_nospec_ignores(file); |
1243 | if (ret) | |
1244 | return ret; | |
1245 | ||
dcc914f4 JP |
1246 | ret = add_jump_destinations(file); |
1247 | if (ret) | |
1248 | return ret; | |
1249 | ||
a845c7cf | 1250 | ret = add_special_section_alts(file); |
dcc914f4 JP |
1251 | if (ret) |
1252 | return ret; | |
1253 | ||
a845c7cf | 1254 | ret = add_call_destinations(file); |
dcc914f4 JP |
1255 | if (ret) |
1256 | return ret; | |
1257 | ||
1258 | ret = add_switch_table_alts(file); | |
1259 | if (ret) | |
1260 | return ret; | |
1261 | ||
39358a03 JP |
1262 | ret = read_unwind_hints(file); |
1263 | if (ret) | |
1264 | return ret; | |
1265 | ||
b5bc2231 PZ |
1266 | ret = read_retpoline_hints(file); |
1267 | if (ret) | |
1268 | return ret; | |
1269 | ||
dcc914f4 JP |
1270 | return 0; |
1271 | } | |
1272 | ||
1273 | static bool is_fentry_call(struct instruction *insn) | |
1274 | { | |
1275 | if (insn->type == INSN_CALL && | |
1276 | insn->call_dest->type == STT_NOTYPE && | |
1277 | !strcmp(insn->call_dest->name, "__fentry__")) | |
1278 | return true; | |
1279 | ||
1280 | return false; | |
1281 | } | |
1282 | ||
baa41469 | 1283 | static bool has_modified_stack_frame(struct insn_state *state) |
dcc914f4 | 1284 | { |
baa41469 JP |
1285 | int i; |
1286 | ||
1287 | if (state->cfa.base != initial_func_cfi.cfa.base || | |
1288 | state->cfa.offset != initial_func_cfi.cfa.offset || | |
1289 | state->stack_size != initial_func_cfi.cfa.offset || | |
1290 | state->drap) | |
1291 | return true; | |
1292 | ||
1293 | for (i = 0; i < CFI_NUM_REGS; i++) | |
1294 | if (state->regs[i].base != initial_func_cfi.regs[i].base || | |
1295 | state->regs[i].offset != initial_func_cfi.regs[i].offset) | |
1296 | return true; | |
1297 | ||
1298 | return false; | |
1299 | } | |
1300 | ||
1301 | static bool has_valid_stack_frame(struct insn_state *state) | |
1302 | { | |
1303 | if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA && | |
1304 | state->regs[CFI_BP].offset == -16) | |
1305 | return true; | |
1306 | ||
1307 | if (state->drap && state->regs[CFI_BP].base == CFI_BP) | |
1308 | return true; | |
1309 | ||
1310 | return false; | |
dcc914f4 JP |
1311 | } |
1312 | ||
627fce14 JP |
1313 | static int update_insn_state_regs(struct instruction *insn, struct insn_state *state) |
1314 | { | |
1315 | struct cfi_reg *cfa = &state->cfa; | |
1316 | struct stack_op *op = &insn->stack_op; | |
1317 | ||
1318 | if (cfa->base != CFI_SP) | |
1319 | return 0; | |
1320 | ||
1321 | /* push */ | |
1322 | if (op->dest.type == OP_DEST_PUSH) | |
1323 | cfa->offset += 8; | |
1324 | ||
1325 | /* pop */ | |
1326 | if (op->src.type == OP_SRC_POP) | |
1327 | cfa->offset -= 8; | |
1328 | ||
1329 | /* add immediate to sp */ | |
1330 | if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD && | |
1331 | op->dest.reg == CFI_SP && op->src.reg == CFI_SP) | |
1332 | cfa->offset -= op->src.offset; | |
1333 | ||
1334 | return 0; | |
1335 | } | |
1336 | ||
baa41469 JP |
1337 | static void save_reg(struct insn_state *state, unsigned char reg, int base, |
1338 | int offset) | |
dcc914f4 | 1339 | { |
bf4d1a83 | 1340 | if (arch_callee_saved_reg(reg) && |
baa41469 JP |
1341 | state->regs[reg].base == CFI_UNDEFINED) { |
1342 | state->regs[reg].base = base; | |
1343 | state->regs[reg].offset = offset; | |
1344 | } | |
dcc914f4 JP |
1345 | } |
1346 | ||
baa41469 | 1347 | static void restore_reg(struct insn_state *state, unsigned char reg) |
dcc914f4 | 1348 | { |
baa41469 JP |
1349 | state->regs[reg].base = CFI_UNDEFINED; |
1350 | state->regs[reg].offset = 0; | |
1351 | } | |
1352 | ||
1353 | /* | |
1354 | * A note about DRAP stack alignment: | |
1355 | * | |
1356 | * GCC has the concept of a DRAP register, which is used to help keep track of | |
1357 | * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP | |
1358 | * register. The typical DRAP pattern is: | |
1359 | * | |
1360 | * 4c 8d 54 24 08 lea 0x8(%rsp),%r10 | |
1361 | * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp | |
1362 | * 41 ff 72 f8 pushq -0x8(%r10) | |
1363 | * 55 push %rbp | |
1364 | * 48 89 e5 mov %rsp,%rbp | |
1365 | * (more pushes) | |
1366 | * 41 52 push %r10 | |
1367 | * ... | |
1368 | * 41 5a pop %r10 | |
1369 | * (more pops) | |
1370 | * 5d pop %rbp | |
1371 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1372 | * c3 retq | |
1373 | * | |
1374 | * There are some variations in the epilogues, like: | |
1375 | * | |
1376 | * 5b pop %rbx | |
1377 | * 41 5a pop %r10 | |
1378 | * 41 5c pop %r12 | |
1379 | * 41 5d pop %r13 | |
1380 | * 41 5e pop %r14 | |
1381 | * c9 leaveq | |
1382 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1383 | * c3 retq | |
1384 | * | |
1385 | * and: | |
1386 | * | |
1387 | * 4c 8b 55 e8 mov -0x18(%rbp),%r10 | |
1388 | * 48 8b 5d e0 mov -0x20(%rbp),%rbx | |
1389 | * 4c 8b 65 f0 mov -0x10(%rbp),%r12 | |
1390 | * 4c 8b 6d f8 mov -0x8(%rbp),%r13 | |
1391 | * c9 leaveq | |
1392 | * 49 8d 62 f8 lea -0x8(%r10),%rsp | |
1393 | * c3 retq | |
1394 | * | |
1395 | * Sometimes r13 is used as the DRAP register, in which case it's saved and | |
1396 | * restored beforehand: | |
1397 | * | |
1398 | * 41 55 push %r13 | |
1399 | * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13 | |
1400 | * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp | |
1401 | * ... | |
1402 | * 49 8d 65 f0 lea -0x10(%r13),%rsp | |
1403 | * 41 5d pop %r13 | |
1404 | * c3 retq | |
1405 | */ | |
1406 | static int update_insn_state(struct instruction *insn, struct insn_state *state) | |
1407 | { | |
1408 | struct stack_op *op = &insn->stack_op; | |
1409 | struct cfi_reg *cfa = &state->cfa; | |
1410 | struct cfi_reg *regs = state->regs; | |
1411 | ||
1412 | /* stack operations don't make sense with an undefined CFA */ | |
1413 | if (cfa->base == CFI_UNDEFINED) { | |
1414 | if (insn->func) { | |
1415 | WARN_FUNC("undefined stack state", insn->sec, insn->offset); | |
1416 | return -1; | |
1417 | } | |
1418 | return 0; | |
1419 | } | |
1420 | ||
627fce14 JP |
1421 | if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET) |
1422 | return update_insn_state_regs(insn, state); | |
1423 | ||
baa41469 JP |
1424 | switch (op->dest.type) { |
1425 | ||
1426 | case OP_DEST_REG: | |
1427 | switch (op->src.type) { | |
1428 | ||
1429 | case OP_SRC_REG: | |
0d0970ee JP |
1430 | if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP && |
1431 | cfa->base == CFI_SP && | |
1432 | regs[CFI_BP].base == CFI_CFA && | |
1433 | regs[CFI_BP].offset == -cfa->offset) { | |
1434 | ||
1435 | /* mov %rsp, %rbp */ | |
1436 | cfa->base = op->dest.reg; | |
1437 | state->bp_scratch = false; | |
1438 | } | |
dd88a0a0 | 1439 | |
0d0970ee JP |
1440 | else if (op->src.reg == CFI_SP && |
1441 | op->dest.reg == CFI_BP && state->drap) { | |
dd88a0a0 | 1442 | |
0d0970ee JP |
1443 | /* drap: mov %rsp, %rbp */ |
1444 | regs[CFI_BP].base = CFI_BP; | |
1445 | regs[CFI_BP].offset = -state->stack_size; | |
1446 | state->bp_scratch = false; | |
1447 | } | |
dd88a0a0 | 1448 | |
0d0970ee JP |
1449 | else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { |
1450 | ||
1451 | /* | |
1452 | * mov %rsp, %reg | |
1453 | * | |
1454 | * This is needed for the rare case where GCC | |
1455 | * does: | |
1456 | * | |
1457 | * mov %rsp, %rax | |
1458 | * ... | |
1459 | * mov %rax, %rsp | |
1460 | */ | |
1461 | state->vals[op->dest.reg].base = CFI_CFA; | |
1462 | state->vals[op->dest.reg].offset = -state->stack_size; | |
dd88a0a0 JP |
1463 | } |
1464 | ||
3c1f0583 JP |
1465 | else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP && |
1466 | cfa->base == CFI_BP) { | |
1467 | ||
1468 | /* | |
1469 | * mov %rbp, %rsp | |
1470 | * | |
1471 | * Restore the original stack pointer (Clang). | |
1472 | */ | |
1473 | state->stack_size = -state->regs[CFI_BP].offset; | |
1474 | } | |
1475 | ||
dd88a0a0 JP |
1476 | else if (op->dest.reg == cfa->base) { |
1477 | ||
1478 | /* mov %reg, %rsp */ | |
1479 | if (cfa->base == CFI_SP && | |
1480 | state->vals[op->src.reg].base == CFI_CFA) { | |
1481 | ||
1482 | /* | |
1483 | * This is needed for the rare case | |
1484 | * where GCC does something dumb like: | |
1485 | * | |
1486 | * lea 0x8(%rsp), %rcx | |
1487 | * ... | |
1488 | * mov %rcx, %rsp | |
1489 | */ | |
1490 | cfa->offset = -state->vals[op->src.reg].offset; | |
1491 | state->stack_size = cfa->offset; | |
1492 | ||
1493 | } else { | |
1494 | cfa->base = CFI_UNDEFINED; | |
1495 | cfa->offset = 0; | |
1496 | } | |
baa41469 JP |
1497 | } |
1498 | ||
1499 | break; | |
1500 | ||
1501 | case OP_SRC_ADD: | |
1502 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) { | |
1503 | ||
1504 | /* add imm, %rsp */ | |
1505 | state->stack_size -= op->src.offset; | |
1506 | if (cfa->base == CFI_SP) | |
1507 | cfa->offset -= op->src.offset; | |
1508 | break; | |
1509 | } | |
1510 | ||
1511 | if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) { | |
1512 | ||
1513 | /* lea disp(%rbp), %rsp */ | |
1514 | state->stack_size = -(op->src.offset + regs[CFI_BP].offset); | |
1515 | break; | |
1516 | } | |
1517 | ||
dd88a0a0 | 1518 | if (op->src.reg == CFI_SP && cfa->base == CFI_SP) { |
baa41469 JP |
1519 | |
1520 | /* drap: lea disp(%rsp), %drap */ | |
1521 | state->drap_reg = op->dest.reg; | |
dd88a0a0 JP |
1522 | |
1523 | /* | |
1524 | * lea disp(%rsp), %reg | |
1525 | * | |
1526 | * This is needed for the rare case where GCC | |
1527 | * does something dumb like: | |
1528 | * | |
1529 | * lea 0x8(%rsp), %rcx | |
1530 | * ... | |
1531 | * mov %rcx, %rsp | |
1532 | */ | |
1533 | state->vals[op->dest.reg].base = CFI_CFA; | |
1534 | state->vals[op->dest.reg].offset = \ | |
1535 | -state->stack_size + op->src.offset; | |
1536 | ||
baa41469 JP |
1537 | break; |
1538 | } | |
1539 | ||
1540 | if (state->drap && op->dest.reg == CFI_SP && | |
1541 | op->src.reg == state->drap_reg) { | |
1542 | ||
1543 | /* drap: lea disp(%drap), %rsp */ | |
1544 | cfa->base = CFI_SP; | |
1545 | cfa->offset = state->stack_size = -op->src.offset; | |
1546 | state->drap_reg = CFI_UNDEFINED; | |
1547 | state->drap = false; | |
1548 | break; | |
1549 | } | |
1550 | ||
1551 | if (op->dest.reg == state->cfa.base) { | |
1552 | WARN_FUNC("unsupported stack register modification", | |
1553 | insn->sec, insn->offset); | |
1554 | return -1; | |
1555 | } | |
1556 | ||
1557 | break; | |
1558 | ||
1559 | case OP_SRC_AND: | |
1560 | if (op->dest.reg != CFI_SP || | |
1561 | (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) || | |
1562 | (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) { | |
1563 | WARN_FUNC("unsupported stack pointer realignment", | |
1564 | insn->sec, insn->offset); | |
1565 | return -1; | |
1566 | } | |
1567 | ||
1568 | if (state->drap_reg != CFI_UNDEFINED) { | |
1569 | /* drap: and imm, %rsp */ | |
1570 | cfa->base = state->drap_reg; | |
1571 | cfa->offset = state->stack_size = 0; | |
1572 | state->drap = true; | |
baa41469 JP |
1573 | } |
1574 | ||
1575 | /* | |
1576 | * Older versions of GCC (4.8ish) realign the stack | |
1577 | * without DRAP, with a frame pointer. | |
1578 | */ | |
1579 | ||
1580 | break; | |
1581 | ||
1582 | case OP_SRC_POP: | |
1583 | if (!state->drap && op->dest.type == OP_DEST_REG && | |
1584 | op->dest.reg == cfa->base) { | |
1585 | ||
1586 | /* pop %rbp */ | |
1587 | cfa->base = CFI_SP; | |
1588 | } | |
1589 | ||
bf4d1a83 JP |
1590 | if (state->drap && cfa->base == CFI_BP_INDIRECT && |
1591 | op->dest.type == OP_DEST_REG && | |
1592 | op->dest.reg == state->drap_reg && | |
1593 | state->drap_offset == -state->stack_size) { | |
baa41469 | 1594 | |
bf4d1a83 JP |
1595 | /* drap: pop %drap */ |
1596 | cfa->base = state->drap_reg; | |
1597 | cfa->offset = 0; | |
1598 | state->drap_offset = -1; | |
baa41469 | 1599 | |
bf4d1a83 | 1600 | } else if (regs[op->dest.reg].offset == -state->stack_size) { |
baa41469 | 1601 | |
bf4d1a83 | 1602 | /* pop %reg */ |
baa41469 JP |
1603 | restore_reg(state, op->dest.reg); |
1604 | } | |
1605 | ||
1606 | state->stack_size -= 8; | |
1607 | if (cfa->base == CFI_SP) | |
1608 | cfa->offset -= 8; | |
1609 | ||
1610 | break; | |
1611 | ||
1612 | case OP_SRC_REG_INDIRECT: | |
bf4d1a83 JP |
1613 | if (state->drap && op->src.reg == CFI_BP && |
1614 | op->src.offset == state->drap_offset) { | |
1615 | ||
1616 | /* drap: mov disp(%rbp), %drap */ | |
1617 | cfa->base = state->drap_reg; | |
1618 | cfa->offset = 0; | |
1619 | state->drap_offset = -1; | |
1620 | } | |
1621 | ||
baa41469 JP |
1622 | if (state->drap && op->src.reg == CFI_BP && |
1623 | op->src.offset == regs[op->dest.reg].offset) { | |
1624 | ||
1625 | /* drap: mov disp(%rbp), %reg */ | |
baa41469 JP |
1626 | restore_reg(state, op->dest.reg); |
1627 | ||
1628 | } else if (op->src.reg == cfa->base && | |
1629 | op->src.offset == regs[op->dest.reg].offset + cfa->offset) { | |
1630 | ||
1631 | /* mov disp(%rbp), %reg */ | |
1632 | /* mov disp(%rsp), %reg */ | |
1633 | restore_reg(state, op->dest.reg); | |
1634 | } | |
1635 | ||
1636 | break; | |
1637 | ||
1638 | default: | |
1639 | WARN_FUNC("unknown stack-related instruction", | |
1640 | insn->sec, insn->offset); | |
1641 | return -1; | |
1642 | } | |
1643 | ||
1644 | break; | |
1645 | ||
1646 | case OP_DEST_PUSH: | |
1647 | state->stack_size += 8; | |
1648 | if (cfa->base == CFI_SP) | |
1649 | cfa->offset += 8; | |
1650 | ||
1651 | if (op->src.type != OP_SRC_REG) | |
1652 | break; | |
1653 | ||
1654 | if (state->drap) { | |
1655 | if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) { | |
1656 | ||
1657 | /* drap: push %drap */ | |
1658 | cfa->base = CFI_BP_INDIRECT; | |
1659 | cfa->offset = -state->stack_size; | |
1660 | ||
bf4d1a83 JP |
1661 | /* save drap so we know when to restore it */ |
1662 | state->drap_offset = -state->stack_size; | |
baa41469 JP |
1663 | |
1664 | } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) { | |
1665 | ||
1666 | /* drap: push %rbp */ | |
1667 | state->stack_size = 0; | |
1668 | ||
1669 | } else if (regs[op->src.reg].base == CFI_UNDEFINED) { | |
1670 | ||
1671 | /* drap: push %reg */ | |
1672 | save_reg(state, op->src.reg, CFI_BP, -state->stack_size); | |
1673 | } | |
1674 | ||
1675 | } else { | |
1676 | ||
1677 | /* push %reg */ | |
1678 | save_reg(state, op->src.reg, CFI_CFA, -state->stack_size); | |
1679 | } | |
1680 | ||
1681 | /* detect when asm code uses rbp as a scratch register */ | |
867ac9d7 | 1682 | if (!no_fp && insn->func && op->src.reg == CFI_BP && |
baa41469 JP |
1683 | cfa->base != CFI_BP) |
1684 | state->bp_scratch = true; | |
1685 | break; | |
1686 | ||
1687 | case OP_DEST_REG_INDIRECT: | |
1688 | ||
1689 | if (state->drap) { | |
1690 | if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) { | |
1691 | ||
1692 | /* drap: mov %drap, disp(%rbp) */ | |
1693 | cfa->base = CFI_BP_INDIRECT; | |
1694 | cfa->offset = op->dest.offset; | |
1695 | ||
bf4d1a83 JP |
1696 | /* save drap offset so we know when to restore it */ |
1697 | state->drap_offset = op->dest.offset; | |
baa41469 JP |
1698 | } |
1699 | ||
1700 | else if (regs[op->src.reg].base == CFI_UNDEFINED) { | |
1701 | ||
1702 | /* drap: mov reg, disp(%rbp) */ | |
1703 | save_reg(state, op->src.reg, CFI_BP, op->dest.offset); | |
1704 | } | |
1705 | ||
1706 | } else if (op->dest.reg == cfa->base) { | |
1707 | ||
1708 | /* mov reg, disp(%rbp) */ | |
1709 | /* mov reg, disp(%rsp) */ | |
1710 | save_reg(state, op->src.reg, CFI_CFA, | |
1711 | op->dest.offset - state->cfa.offset); | |
1712 | } | |
1713 | ||
1714 | break; | |
1715 | ||
1716 | case OP_DEST_LEAVE: | |
1717 | if ((!state->drap && cfa->base != CFI_BP) || | |
1718 | (state->drap && cfa->base != state->drap_reg)) { | |
1719 | WARN_FUNC("leave instruction with modified stack frame", | |
1720 | insn->sec, insn->offset); | |
1721 | return -1; | |
1722 | } | |
1723 | ||
1724 | /* leave (mov %rbp, %rsp; pop %rbp) */ | |
1725 | ||
1726 | state->stack_size = -state->regs[CFI_BP].offset - 8; | |
1727 | restore_reg(state, CFI_BP); | |
1728 | ||
1729 | if (!state->drap) { | |
1730 | cfa->base = CFI_SP; | |
1731 | cfa->offset -= 8; | |
1732 | } | |
1733 | ||
1734 | break; | |
1735 | ||
1736 | case OP_DEST_MEM: | |
1737 | if (op->src.type != OP_SRC_POP) { | |
1738 | WARN_FUNC("unknown stack-related memory operation", | |
1739 | insn->sec, insn->offset); | |
1740 | return -1; | |
1741 | } | |
1742 | ||
1743 | /* pop mem */ | |
1744 | state->stack_size -= 8; | |
1745 | if (cfa->base == CFI_SP) | |
1746 | cfa->offset -= 8; | |
1747 | ||
1748 | break; | |
1749 | ||
1750 | default: | |
1751 | WARN_FUNC("unknown stack-related instruction", | |
1752 | insn->sec, insn->offset); | |
1753 | return -1; | |
1754 | } | |
1755 | ||
1756 | return 0; | |
1757 | } | |
1758 | ||
1759 | static bool insn_state_match(struct instruction *insn, struct insn_state *state) | |
1760 | { | |
1761 | struct insn_state *state1 = &insn->state, *state2 = state; | |
1762 | int i; | |
1763 | ||
1764 | if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) { | |
1765 | WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d", | |
1766 | insn->sec, insn->offset, | |
1767 | state1->cfa.base, state1->cfa.offset, | |
1768 | state2->cfa.base, state2->cfa.offset); | |
1769 | ||
1770 | } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) { | |
1771 | for (i = 0; i < CFI_NUM_REGS; i++) { | |
1772 | if (!memcmp(&state1->regs[i], &state2->regs[i], | |
1773 | sizeof(struct cfi_reg))) | |
1774 | continue; | |
1775 | ||
1776 | WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d", | |
1777 | insn->sec, insn->offset, | |
1778 | i, state1->regs[i].base, state1->regs[i].offset, | |
1779 | i, state2->regs[i].base, state2->regs[i].offset); | |
1780 | break; | |
1781 | } | |
1782 | ||
627fce14 JP |
1783 | } else if (state1->type != state2->type) { |
1784 | WARN_FUNC("stack state mismatch: type1=%d type2=%d", | |
1785 | insn->sec, insn->offset, state1->type, state2->type); | |
1786 | ||
baa41469 | 1787 | } else if (state1->drap != state2->drap || |
bf4d1a83 JP |
1788 | (state1->drap && state1->drap_reg != state2->drap_reg) || |
1789 | (state1->drap && state1->drap_offset != state2->drap_offset)) { | |
1790 | WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)", | |
baa41469 | 1791 | insn->sec, insn->offset, |
bf4d1a83 JP |
1792 | state1->drap, state1->drap_reg, state1->drap_offset, |
1793 | state2->drap, state2->drap_reg, state2->drap_offset); | |
baa41469 JP |
1794 | |
1795 | } else | |
1796 | return true; | |
1797 | ||
1798 | return false; | |
dcc914f4 JP |
1799 | } |
1800 | ||
1801 | /* | |
1802 | * Follow the branch starting at the given instruction, and recursively follow | |
1803 | * any other branches (jumps). Meanwhile, track the frame pointer state at | |
1804 | * each instruction and validate all the rules described in | |
1805 | * tools/objtool/Documentation/stack-validation.txt. | |
1806 | */ | |
baa41469 JP |
1807 | static int validate_branch(struct objtool_file *file, struct instruction *first, |
1808 | struct insn_state state) | |
dcc914f4 JP |
1809 | { |
1810 | struct alternative *alt; | |
39358a03 | 1811 | struct instruction *insn, *next_insn; |
dcc914f4 JP |
1812 | struct section *sec; |
1813 | struct symbol *func = NULL; | |
dcc914f4 JP |
1814 | int ret; |
1815 | ||
1816 | insn = first; | |
1817 | sec = insn->sec; | |
dcc914f4 JP |
1818 | |
1819 | if (insn->alt_group && list_empty(&insn->alts)) { | |
1820 | WARN_FUNC("don't know how to handle branch to middle of alternative instruction group", | |
1821 | sec, insn->offset); | |
12b25729 | 1822 | return 1; |
dcc914f4 JP |
1823 | } |
1824 | ||
1825 | while (1) { | |
39358a03 JP |
1826 | next_insn = next_insn_same_sec(file, insn); |
1827 | ||
13810435 | 1828 | if (file->c_file && func && insn->func && func != insn->func->pfunc) { |
ee97638b JP |
1829 | WARN("%s() falls through to next function %s()", |
1830 | func->name, insn->func->name); | |
1831 | return 1; | |
dcc914f4 JP |
1832 | } |
1833 | ||
13810435 | 1834 | func = insn->func ? insn->func->pfunc : NULL; |
baa41469 | 1835 | |
4855022a JP |
1836 | if (func && insn->ignore) { |
1837 | WARN_FUNC("BUG: why am I validating an ignored function?", | |
1838 | sec, insn->offset); | |
12b25729 | 1839 | return 1; |
4855022a JP |
1840 | } |
1841 | ||
dcc914f4 | 1842 | if (insn->visited) { |
39358a03 | 1843 | if (!insn->hint && !insn_state_match(insn, &state)) |
dcc914f4 | 1844 | return 1; |
dcc914f4 JP |
1845 | |
1846 | return 0; | |
1847 | } | |
1848 | ||
39358a03 JP |
1849 | if (insn->hint) { |
1850 | if (insn->restore) { | |
1851 | struct instruction *save_insn, *i; | |
1852 | ||
1853 | i = insn; | |
1854 | save_insn = NULL; | |
13810435 | 1855 | func_for_each_insn_continue_reverse(file, insn->func, i) { |
39358a03 JP |
1856 | if (i->save) { |
1857 | save_insn = i; | |
1858 | break; | |
1859 | } | |
1860 | } | |
1861 | ||
1862 | if (!save_insn) { | |
1863 | WARN_FUNC("no corresponding CFI save for CFI restore", | |
1864 | sec, insn->offset); | |
1865 | return 1; | |
1866 | } | |
1867 | ||
1868 | if (!save_insn->visited) { | |
1869 | /* | |
1870 | * Oops, no state to copy yet. | |
1871 | * Hopefully we can reach this | |
1872 | * instruction from another branch | |
1873 | * after the save insn has been | |
1874 | * visited. | |
1875 | */ | |
1876 | if (insn == first) | |
1877 | return 0; | |
1878 | ||
1879 | WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo", | |
1880 | sec, insn->offset); | |
1881 | return 1; | |
1882 | } | |
1883 | ||
1884 | insn->state = save_insn->state; | |
1885 | } | |
1886 | ||
1887 | state = insn->state; | |
1888 | ||
1889 | } else | |
1890 | insn->state = state; | |
dcc914f4 | 1891 | |
baa41469 JP |
1892 | insn->visited = true; |
1893 | ||
a845c7cf JP |
1894 | if (!insn->ignore_alts) { |
1895 | list_for_each_entry(alt, &insn->alts, list) { | |
1896 | ret = validate_branch(file, alt->insn, state); | |
1897 | if (ret) | |
1898 | return 1; | |
1899 | } | |
dcc914f4 JP |
1900 | } |
1901 | ||
1902 | switch (insn->type) { | |
1903 | ||
dcc914f4 | 1904 | case INSN_RETURN: |
baa41469 JP |
1905 | if (func && has_modified_stack_frame(&state)) { |
1906 | WARN_FUNC("return with modified stack frame", | |
dcc914f4 JP |
1907 | sec, insn->offset); |
1908 | return 1; | |
1909 | } | |
baa41469 JP |
1910 | |
1911 | if (state.bp_scratch) { | |
1912 | WARN("%s uses BP as a scratch register", | |
1913 | insn->func->name); | |
1914 | return 1; | |
1915 | } | |
1916 | ||
dcc914f4 JP |
1917 | return 0; |
1918 | ||
1919 | case INSN_CALL: | |
baa41469 | 1920 | if (is_fentry_call(insn)) |
dcc914f4 | 1921 | break; |
dcc914f4 JP |
1922 | |
1923 | ret = dead_end_function(file, insn->call_dest); | |
1924 | if (ret == 1) | |
1925 | return 0; | |
1926 | if (ret == -1) | |
1927 | return 1; | |
1928 | ||
1929 | /* fallthrough */ | |
1930 | case INSN_CALL_DYNAMIC: | |
867ac9d7 | 1931 | if (!no_fp && func && !has_valid_stack_frame(&state)) { |
dcc914f4 JP |
1932 | WARN_FUNC("call without frame pointer save/setup", |
1933 | sec, insn->offset); | |
1934 | return 1; | |
1935 | } | |
1936 | break; | |
1937 | ||
1938 | case INSN_JUMP_CONDITIONAL: | |
1939 | case INSN_JUMP_UNCONDITIONAL: | |
4855022a JP |
1940 | if (insn->jump_dest && |
1941 | (!func || !insn->jump_dest->func || | |
13810435 | 1942 | insn->jump_dest->func->pfunc == func)) { |
dcc914f4 JP |
1943 | ret = validate_branch(file, insn->jump_dest, |
1944 | state); | |
1945 | if (ret) | |
1946 | return 1; | |
4855022a | 1947 | |
baa41469 JP |
1948 | } else if (func && has_modified_stack_frame(&state)) { |
1949 | WARN_FUNC("sibling call from callable instruction with modified stack frame", | |
dcc914f4 JP |
1950 | sec, insn->offset); |
1951 | return 1; | |
4855022a | 1952 | } |
dcc914f4 JP |
1953 | |
1954 | if (insn->type == INSN_JUMP_UNCONDITIONAL) | |
1955 | return 0; | |
1956 | ||
1957 | break; | |
1958 | ||
1959 | case INSN_JUMP_DYNAMIC: | |
baa41469 JP |
1960 | if (func && list_empty(&insn->alts) && |
1961 | has_modified_stack_frame(&state)) { | |
1962 | WARN_FUNC("sibling call from callable instruction with modified stack frame", | |
dcc914f4 JP |
1963 | sec, insn->offset); |
1964 | return 1; | |
1965 | } | |
1966 | ||
1967 | return 0; | |
1968 | ||
39358a03 JP |
1969 | case INSN_CONTEXT_SWITCH: |
1970 | if (func && (!next_insn || !next_insn->hint)) { | |
1971 | WARN_FUNC("unsupported instruction in callable function", | |
1972 | sec, insn->offset); | |
1973 | return 1; | |
1974 | } | |
1975 | return 0; | |
1976 | ||
baa41469 JP |
1977 | case INSN_STACK: |
1978 | if (update_insn_state(insn, &state)) | |
12b25729 | 1979 | return 1; |
baa41469 JP |
1980 | |
1981 | break; | |
1982 | ||
dcc914f4 JP |
1983 | default: |
1984 | break; | |
1985 | } | |
1986 | ||
1987 | if (insn->dead_end) | |
1988 | return 0; | |
1989 | ||
00d96180 JP |
1990 | if (!next_insn) { |
1991 | if (state.cfa.base == CFI_UNDEFINED) | |
1992 | return 0; | |
dcc914f4 JP |
1993 | WARN("%s: unexpected end of section", sec->name); |
1994 | return 1; | |
1995 | } | |
00d96180 JP |
1996 | |
1997 | insn = next_insn; | |
dcc914f4 JP |
1998 | } |
1999 | ||
2000 | return 0; | |
2001 | } | |
2002 | ||
39358a03 JP |
2003 | static int validate_unwind_hints(struct objtool_file *file) |
2004 | { | |
2005 | struct instruction *insn; | |
2006 | int ret, warnings = 0; | |
2007 | struct insn_state state; | |
2008 | ||
2009 | if (!file->hints) | |
2010 | return 0; | |
2011 | ||
2012 | clear_insn_state(&state); | |
2013 | ||
2014 | for_each_insn(file, insn) { | |
2015 | if (insn->hint && !insn->visited) { | |
2016 | ret = validate_branch(file, insn, state); | |
2017 | warnings += ret; | |
2018 | } | |
2019 | } | |
2020 | ||
2021 | return warnings; | |
2022 | } | |
2023 | ||
b5bc2231 PZ |
2024 | static int validate_retpoline(struct objtool_file *file) |
2025 | { | |
2026 | struct instruction *insn; | |
2027 | int warnings = 0; | |
2028 | ||
2029 | for_each_insn(file, insn) { | |
2030 | if (insn->type != INSN_JUMP_DYNAMIC && | |
2031 | insn->type != INSN_CALL_DYNAMIC) | |
2032 | continue; | |
2033 | ||
2034 | if (insn->retpoline_safe) | |
2035 | continue; | |
2036 | ||
ca41b97e PZ |
2037 | /* |
2038 | * .init.text code is ran before userspace and thus doesn't | |
2039 | * strictly need retpolines, except for modules which are | |
2040 | * loaded late, they very much do need retpoline in their | |
2041 | * .init.text | |
2042 | */ | |
2043 | if (!strcmp(insn->sec->name, ".init.text") && !module) | |
2044 | continue; | |
2045 | ||
b5bc2231 PZ |
2046 | WARN_FUNC("indirect %s found in RETPOLINE build", |
2047 | insn->sec, insn->offset, | |
2048 | insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call"); | |
2049 | ||
2050 | warnings++; | |
2051 | } | |
2052 | ||
2053 | return warnings; | |
2054 | } | |
2055 | ||
dcc914f4 JP |
2056 | static bool is_kasan_insn(struct instruction *insn) |
2057 | { | |
2058 | return (insn->type == INSN_CALL && | |
2059 | !strcmp(insn->call_dest->name, "__asan_handle_no_return")); | |
2060 | } | |
2061 | ||
2062 | static bool is_ubsan_insn(struct instruction *insn) | |
2063 | { | |
2064 | return (insn->type == INSN_CALL && | |
2065 | !strcmp(insn->call_dest->name, | |
2066 | "__ubsan_handle_builtin_unreachable")); | |
2067 | } | |
2068 | ||
baa41469 | 2069 | static bool ignore_unreachable_insn(struct instruction *insn) |
dcc914f4 JP |
2070 | { |
2071 | int i; | |
2072 | ||
baa41469 JP |
2073 | if (insn->ignore || insn->type == INSN_NOP) |
2074 | return true; | |
2075 | ||
2076 | /* | |
2077 | * Ignore any unused exceptions. This can happen when a whitelisted | |
2078 | * function has an exception table entry. | |
0e2bb2bc JP |
2079 | * |
2080 | * Also ignore alternative replacement instructions. This can happen | |
2081 | * when a whitelisted function uses one of the ALTERNATIVE macros. | |
baa41469 | 2082 | */ |
0e2bb2bc JP |
2083 | if (!strcmp(insn->sec->name, ".fixup") || |
2084 | !strcmp(insn->sec->name, ".altinstr_replacement") || | |
2085 | !strcmp(insn->sec->name, ".altinstr_aux")) | |
dcc914f4 JP |
2086 | return true; |
2087 | ||
2088 | /* | |
2089 | * Check if this (or a subsequent) instruction is related to | |
2090 | * CONFIG_UBSAN or CONFIG_KASAN. | |
2091 | * | |
2092 | * End the search at 5 instructions to avoid going into the weeds. | |
2093 | */ | |
baa41469 JP |
2094 | if (!insn->func) |
2095 | return false; | |
dcc914f4 JP |
2096 | for (i = 0; i < 5; i++) { |
2097 | ||
2098 | if (is_kasan_insn(insn) || is_ubsan_insn(insn)) | |
2099 | return true; | |
2100 | ||
fe24e271 JP |
2101 | if (insn->type == INSN_JUMP_UNCONDITIONAL) { |
2102 | if (insn->jump_dest && | |
2103 | insn->jump_dest->func == insn->func) { | |
2104 | insn = insn->jump_dest; | |
2105 | continue; | |
2106 | } | |
2107 | ||
2108 | break; | |
dcc914f4 JP |
2109 | } |
2110 | ||
baa41469 | 2111 | if (insn->offset + insn->len >= insn->func->offset + insn->func->len) |
dcc914f4 | 2112 | break; |
fe24e271 | 2113 | |
dcc914f4 JP |
2114 | insn = list_next_entry(insn, list); |
2115 | } | |
2116 | ||
2117 | return false; | |
2118 | } | |
2119 | ||
2120 | static int validate_functions(struct objtool_file *file) | |
2121 | { | |
2122 | struct section *sec; | |
2123 | struct symbol *func; | |
2124 | struct instruction *insn; | |
baa41469 | 2125 | struct insn_state state; |
dcc914f4 JP |
2126 | int ret, warnings = 0; |
2127 | ||
baa41469 JP |
2128 | clear_insn_state(&state); |
2129 | ||
2130 | state.cfa = initial_func_cfi.cfa; | |
2131 | memcpy(&state.regs, &initial_func_cfi.regs, | |
2132 | CFI_NUM_REGS * sizeof(struct cfi_reg)); | |
2133 | state.stack_size = initial_func_cfi.cfa.offset; | |
2134 | ||
2135 | for_each_sec(file, sec) { | |
dcc914f4 | 2136 | list_for_each_entry(func, &sec->symbol_list, list) { |
13810435 | 2137 | if (func->type != STT_FUNC || func->pfunc != func) |
dcc914f4 JP |
2138 | continue; |
2139 | ||
2140 | insn = find_insn(file, sec, func->offset); | |
baa41469 | 2141 | if (!insn || insn->ignore) |
dcc914f4 JP |
2142 | continue; |
2143 | ||
baa41469 | 2144 | ret = validate_branch(file, insn, state); |
dcc914f4 JP |
2145 | warnings += ret; |
2146 | } | |
2147 | } | |
2148 | ||
dcc914f4 JP |
2149 | return warnings; |
2150 | } | |
2151 | ||
baa41469 | 2152 | static int validate_reachable_instructions(struct objtool_file *file) |
dcc914f4 JP |
2153 | { |
2154 | struct instruction *insn; | |
baa41469 JP |
2155 | |
2156 | if (file->ignore_unreachables) | |
2157 | return 0; | |
dcc914f4 JP |
2158 | |
2159 | for_each_insn(file, insn) { | |
baa41469 JP |
2160 | if (insn->visited || ignore_unreachable_insn(insn)) |
2161 | continue; | |
2162 | ||
baa41469 JP |
2163 | WARN_FUNC("unreachable instruction", insn->sec, insn->offset); |
2164 | return 1; | |
dcc914f4 JP |
2165 | } |
2166 | ||
baa41469 | 2167 | return 0; |
dcc914f4 JP |
2168 | } |
2169 | ||
2170 | static void cleanup(struct objtool_file *file) | |
2171 | { | |
2172 | struct instruction *insn, *tmpinsn; | |
2173 | struct alternative *alt, *tmpalt; | |
2174 | ||
2175 | list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) { | |
2176 | list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) { | |
2177 | list_del(&alt->list); | |
2178 | free(alt); | |
2179 | } | |
2180 | list_del(&insn->list); | |
2181 | hash_del(&insn->hash); | |
2182 | free(insn); | |
2183 | } | |
2184 | elf_close(file->elf); | |
2185 | } | |
2186 | ||
43a4525f | 2187 | int check(const char *_objname, bool orc) |
dcc914f4 JP |
2188 | { |
2189 | struct objtool_file file; | |
2190 | int ret, warnings = 0; | |
2191 | ||
2192 | objname = _objname; | |
dcc914f4 | 2193 | |
627fce14 | 2194 | file.elf = elf_open(objname, orc ? O_RDWR : O_RDONLY); |
baa41469 | 2195 | if (!file.elf) |
dcc914f4 | 2196 | return 1; |
dcc914f4 JP |
2197 | |
2198 | INIT_LIST_HEAD(&file.insn_list); | |
2199 | hash_init(file.insn_hash); | |
2200 | file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard"); | |
dcc914f4 | 2201 | file.c_file = find_section_by_name(file.elf, ".comment"); |
867ac9d7 | 2202 | file.ignore_unreachables = no_unreachable; |
39358a03 | 2203 | file.hints = false; |
dcc914f4 | 2204 | |
baa41469 JP |
2205 | arch_initial_func_cfi_state(&initial_func_cfi); |
2206 | ||
dcc914f4 JP |
2207 | ret = decode_sections(&file); |
2208 | if (ret < 0) | |
2209 | goto out; | |
2210 | warnings += ret; | |
2211 | ||
baa41469 | 2212 | if (list_empty(&file.insn_list)) |
dcc914f4 | 2213 | goto out; |
dcc914f4 | 2214 | |
b5bc2231 PZ |
2215 | if (retpoline) { |
2216 | ret = validate_retpoline(&file); | |
2217 | if (ret < 0) | |
2218 | return ret; | |
2219 | warnings += ret; | |
2220 | } | |
2221 | ||
baa41469 | 2222 | ret = validate_functions(&file); |
dcc914f4 JP |
2223 | if (ret < 0) |
2224 | goto out; | |
2225 | warnings += ret; | |
2226 | ||
39358a03 JP |
2227 | ret = validate_unwind_hints(&file); |
2228 | if (ret < 0) | |
2229 | goto out; | |
2230 | warnings += ret; | |
2231 | ||
baa41469 JP |
2232 | if (!warnings) { |
2233 | ret = validate_reachable_instructions(&file); | |
2234 | if (ret < 0) | |
2235 | goto out; | |
2236 | warnings += ret; | |
2237 | } | |
2238 | ||
627fce14 JP |
2239 | if (orc) { |
2240 | ret = create_orc(&file); | |
2241 | if (ret < 0) | |
2242 | goto out; | |
2243 | ||
2244 | ret = create_orc_sections(&file); | |
2245 | if (ret < 0) | |
2246 | goto out; | |
2247 | ||
2248 | ret = elf_write(file.elf); | |
2249 | if (ret < 0) | |
2250 | goto out; | |
2251 | } | |
2252 | ||
dcc914f4 JP |
2253 | out: |
2254 | cleanup(&file); | |
2255 | ||
2256 | /* ignore warnings for now until we get all the code cleaned up */ | |
2257 | if (ret || warnings) | |
2258 | return 0; | |
2259 | return 0; | |
2260 | } |