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netlink: access nlk groups safely in netlink bind and getname
[linux/fpc-iii.git] / tools / objtool / check.c
blobf744617c9946d7eaaa293b3aba5b63dddf19278b
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
21 #include "check.h"
22 #include "elf.h"
23 #include "special.h"
24 #include "arch.h"
25 #include "warn.h"
26
27 #include <linux/hashtable.h>
28 #include <linux/kernel.h>
29
30 struct alternative {
31 struct list_head list;
32 struct instruction *insn;
33 };
34
35 const char *objname;
36 static bool no_fp;
37 struct cfi_state initial_func_cfi;
38
39 struct instruction *find_insn(struct objtool_file *file,
40 struct section *sec, unsigned long offset)
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
56 if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
57 return NULL;
58
59 return next;
60 }
61
62 #define func_for_each_insn(file, func, insn) \
63 for (insn = find_insn(file, func->sec, func->offset); \
64 insn && &insn->list != &file->insn_list && \
65 insn->sec == func->sec && \
66 insn->offset < func->offset + func->len; \
67 insn = list_next_entry(insn, list))
68
69 #define func_for_each_insn_continue_reverse(file, func, insn) \
70 for (insn = list_prev_entry(insn, list); \
71 &insn->list != &file->insn_list && \
72 insn->sec == func->sec && insn->offset >= func->offset; \
73 insn = list_prev_entry(insn, list))
74
75 #define sec_for_each_insn_from(file, insn) \
76 for (; insn; insn = next_insn_same_sec(file, insn))
77
78 #define sec_for_each_insn_continue(file, insn) \
79 for (insn = next_insn_same_sec(file, insn); insn; \
80 insn = next_insn_same_sec(file, insn))
81
82 /*
83 * Check if the function has been manually whitelisted with the
84 * STACK_FRAME_NON_STANDARD macro, or if it should be automatically whitelisted
85 * due to its use of a context switching instruction.
86 */
87 static bool ignore_func(struct objtool_file *file, struct symbol *func)
88 {
89 struct rela *rela;
90
91 /* check for STACK_FRAME_NON_STANDARD */
92 if (file->whitelist && file->whitelist->rela)
93 list_for_each_entry(rela, &file->whitelist->rela->rela_list, list) {
94 if (rela->sym->type == STT_SECTION &&
95 rela->sym->sec == func->sec &&
96 rela->addend == func->offset)
97 return true;
98 if (rela->sym->type == STT_FUNC && rela->sym == func)
99 return true;
100 }
101
102 return false;
103 }
104
105 /*
106 * This checks to see if the given function is a "noreturn" function.
107 *
108 * For global functions which are outside the scope of this object file, we
109 * have to keep a manual list of them.
110 *
111 * For local functions, we have to detect them manually by simply looking for
112 * the lack of a return instruction.
113 *
114 * Returns:
115 * -1: error
116 * 0: no dead end
117 * 1: dead end
118 */
119 static int __dead_end_function(struct objtool_file *file, struct symbol *func,
120 int recursion)
121 {
122 int i;
123 struct instruction *insn;
124 bool empty = true;
125
126 /*
127 * Unfortunately these have to be hard coded because the noreturn
128 * attribute isn't provided in ELF data.
129 */
130 static const char * const global_noreturns[] = {
131 "__stack_chk_fail",
132 "panic",
133 "do_exit",
134 "do_task_dead",
135 "__module_put_and_exit",
136 "complete_and_exit",
137 "kvm_spurious_fault",
138 "__reiserfs_panic",
139 "lbug_with_loc",
140 "fortify_panic",
141 };
142
143 if (func->bind == STB_WEAK)
144 return 0;
145
146 if (func->bind == STB_GLOBAL)
147 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
148 if (!strcmp(func->name, global_noreturns[i]))
149 return 1;
150
151 if (!func->sec)
152 return 0;
153
154 func_for_each_insn(file, func, insn) {
155 empty = false;
156
157 if (insn->type == INSN_RETURN)
158 return 0;
159 }
160
161 if (empty)
162 return 0;
163
164 /*
165 * A function can have a sibling call instead of a return. In that
166 * case, the function's dead-end status depends on whether the target
167 * of the sibling call returns.
168 */
169 func_for_each_insn(file, func, insn) {
170 if (insn->sec != func->sec ||
171 insn->offset >= func->offset + func->len)
172 break;
173
174 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
175 struct instruction *dest = insn->jump_dest;
176 struct symbol *dest_func;
177
178 if (!dest)
179 /* sibling call to another file */
180 return 0;
181
182 if (dest->sec != func->sec ||
183 dest->offset < func->offset ||
184 dest->offset >= func->offset + func->len) {
185 /* local sibling call */
186 dest_func = find_symbol_by_offset(dest->sec,
187 dest->offset);
188 if (!dest_func)
189 continue;
190
191 if (recursion == 5) {
192 WARN_FUNC("infinite recursion (objtool bug!)",
193 dest->sec, dest->offset);
194 return -1;
195 }
196
197 return __dead_end_function(file, dest_func,
198 recursion + 1);
199 }
200 }
201
202 if (insn->type == INSN_JUMP_DYNAMIC && list_empty(&insn->alts))
203 /* sibling call */
204 return 0;
205 }
206
207 return 1;
208 }
209
210 static int dead_end_function(struct objtool_file *file, struct symbol *func)
211 {
212 return __dead_end_function(file, func, 0);
213 }
214
215 static void clear_insn_state(struct insn_state *state)
216 {
217 int i;
218
219 memset(state, 0, sizeof(*state));
220 state->cfa.base = CFI_UNDEFINED;
221 for (i = 0; i < CFI_NUM_REGS; i++) {
222 state->regs[i].base = CFI_UNDEFINED;
223 state->vals[i].base = CFI_UNDEFINED;
224 }
225 state->drap_reg = CFI_UNDEFINED;
226 state->drap_offset = -1;
227 }
228
229 /*
230 * Call the arch-specific instruction decoder for all the instructions and add
231 * them to the global instruction list.
232 */
233 static int decode_instructions(struct objtool_file *file)
234 {
235 struct section *sec;
236 struct symbol *func;
237 unsigned long offset;
238 struct instruction *insn;
239 int ret;
240
241 for_each_sec(file, sec) {
242
243 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
244 continue;
245
246 if (strcmp(sec->name, ".altinstr_replacement") &&
247 strcmp(sec->name, ".altinstr_aux") &&
248 strncmp(sec->name, ".discard.", 9))
249 sec->text = true;
250
251 for (offset = 0; offset < sec->len; offset += insn->len) {
252 insn = malloc(sizeof(*insn));
253 if (!insn) {
254 WARN("malloc failed");
255 return -1;
256 }
257 memset(insn, 0, sizeof(*insn));
258 INIT_LIST_HEAD(&insn->alts);
259 clear_insn_state(&insn->state);
260
261 insn->sec = sec;
262 insn->offset = offset;
263
264 ret = arch_decode_instruction(file->elf, sec, offset,
265 sec->len - offset,
266 &insn->len, &insn->type,
267 &insn->immediate,
268 &insn->stack_op);
269 if (ret)
270 return ret;
271
272 if (!insn->type || insn->type > INSN_LAST) {
273 WARN_FUNC("invalid instruction type %d",
274 insn->sec, insn->offset, insn->type);
275 return -1;
276 }
277
278 hash_add(file->insn_hash, &insn->hash, insn->offset);
279 list_add_tail(&insn->list, &file->insn_list);
280 }
281
282 list_for_each_entry(func, &sec->symbol_list, list) {
283 if (func->type != STT_FUNC)
284 continue;
285
286 if (!find_insn(file, sec, func->offset)) {
287 WARN("%s(): can't find starting instruction",
288 func->name);
289 return -1;
290 }
291
292 func_for_each_insn(file, func, insn)
293 if (!insn->func)
294 insn->func = func;
295 }
296 }
297
298 return 0;
299 }
300
301 /*
302 * Mark "ud2" instructions and manually annotated dead ends.
303 */
304 static int add_dead_ends(struct objtool_file *file)
305 {
306 struct section *sec;
307 struct rela *rela;
308 struct instruction *insn;
309 bool found;
310
311 /*
312 * By default, "ud2" is a dead end unless otherwise annotated, because
313 * GCC 7 inserts it for certain divide-by-zero cases.
314 */
315 for_each_insn(file, insn)
316 if (insn->type == INSN_BUG)
317 insn->dead_end = true;
318
319 /*
320 * Check for manually annotated dead ends.
321 */
322 sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
323 if (!sec)
324 goto reachable;
325
326 list_for_each_entry(rela, &sec->rela_list, list) {
327 if (rela->sym->type != STT_SECTION) {
328 WARN("unexpected relocation symbol type in %s", sec->name);
329 return -1;
330 }
331 insn = find_insn(file, rela->sym->sec, rela->addend);
332 if (insn)
333 insn = list_prev_entry(insn, list);
334 else if (rela->addend == rela->sym->sec->len) {
335 found = false;
336 list_for_each_entry_reverse(insn, &file->insn_list, list) {
337 if (insn->sec == rela->sym->sec) {
338 found = true;
339 break;
340 }
341 }
342
343 if (!found) {
344 WARN("can't find unreachable insn at %s+0x%x",
345 rela->sym->sec->name, rela->addend);
346 return -1;
347 }
348 } else {
349 WARN("can't find unreachable insn at %s+0x%x",
350 rela->sym->sec->name, rela->addend);
351 return -1;
352 }
353
354 insn->dead_end = true;
355 }
356
357 reachable:
358 /*
359 * These manually annotated reachable checks are needed for GCC 4.4,
360 * where the Linux unreachable() macro isn't supported. In that case
361 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
362 * not a dead end.
363 */
364 sec = find_section_by_name(file->elf, ".rela.discard.reachable");
365 if (!sec)
366 return 0;
367
368 list_for_each_entry(rela, &sec->rela_list, list) {
369 if (rela->sym->type != STT_SECTION) {
370 WARN("unexpected relocation symbol type in %s", sec->name);
371 return -1;
372 }
373 insn = find_insn(file, rela->sym->sec, rela->addend);
374 if (insn)
375 insn = list_prev_entry(insn, list);
376 else if (rela->addend == rela->sym->sec->len) {
377 found = false;
378 list_for_each_entry_reverse(insn, &file->insn_list, list) {
379 if (insn->sec == rela->sym->sec) {
380 found = true;
381 break;
382 }
383 }
384
385 if (!found) {
386 WARN("can't find reachable insn at %s+0x%x",
387 rela->sym->sec->name, rela->addend);
388 return -1;
389 }
390 } else {
391 WARN("can't find reachable insn at %s+0x%x",
392 rela->sym->sec->name, rela->addend);
393 return -1;
394 }
395
396 insn->dead_end = false;
397 }
398
399 return 0;
400 }
401
402 /*
403 * Warnings shouldn't be reported for ignored functions.
404 */
405 static void add_ignores(struct objtool_file *file)
406 {
407 struct instruction *insn;
408 struct section *sec;
409 struct symbol *func;
410
411 for_each_sec(file, sec) {
412 list_for_each_entry(func, &sec->symbol_list, list) {
413 if (func->type != STT_FUNC)
414 continue;
415
416 if (!ignore_func(file, func))
417 continue;
418
419 func_for_each_insn(file, func, insn)
420 insn->ignore = true;
421 }
422 }
423 }
424
425 /*
426 * Find the destination instructions for all jumps.
427 */
428 static int add_jump_destinations(struct objtool_file *file)
429 {
430 struct instruction *insn;
431 struct rela *rela;
432 struct section *dest_sec;
433 unsigned long dest_off;
434
435 for_each_insn(file, insn) {
436 if (insn->type != INSN_JUMP_CONDITIONAL &&
437 insn->type != INSN_JUMP_UNCONDITIONAL)
438 continue;
439
440 if (insn->ignore)
441 continue;
442
443 rela = find_rela_by_dest_range(insn->sec, insn->offset,
444 insn->len);
445 if (!rela) {
446 dest_sec = insn->sec;
447 dest_off = insn->offset + insn->len + insn->immediate;
448 } else if (rela->sym->type == STT_SECTION) {
449 dest_sec = rela->sym->sec;
450 dest_off = rela->addend + 4;
451 } else if (rela->sym->sec->idx) {
452 dest_sec = rela->sym->sec;
453 dest_off = rela->sym->sym.st_value + rela->addend + 4;
454 } else {
455 /* sibling call */
456 insn->jump_dest = 0;
457 continue;
458 }
459
460 insn->jump_dest = find_insn(file, dest_sec, dest_off);
461 if (!insn->jump_dest) {
462
463 /*
464 * This is a special case where an alt instruction
465 * jumps past the end of the section. These are
466 * handled later in handle_group_alt().
467 */
468 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
469 continue;
470
471 WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
472 insn->sec, insn->offset, dest_sec->name,
473 dest_off);
474 return -1;
475 }
476 }
477
478 return 0;
479 }
480
481 /*
482 * Find the destination instructions for all calls.
483 */
484 static int add_call_destinations(struct objtool_file *file)
485 {
486 struct instruction *insn;
487 unsigned long dest_off;
488 struct rela *rela;
489
490 for_each_insn(file, insn) {
491 if (insn->type != INSN_CALL)
492 continue;
493
494 rela = find_rela_by_dest_range(insn->sec, insn->offset,
495 insn->len);
496 if (!rela) {
497 dest_off = insn->offset + insn->len + insn->immediate;
498 insn->call_dest = find_symbol_by_offset(insn->sec,
499 dest_off);
500 if (!insn->call_dest) {
501 WARN_FUNC("can't find call dest symbol at offset 0x%lx",
502 insn->sec, insn->offset, dest_off);
503 return -1;
504 }
505 } else if (rela->sym->type == STT_SECTION) {
506 insn->call_dest = find_symbol_by_offset(rela->sym->sec,
507 rela->addend+4);
508 if (!insn->call_dest ||
509 insn->call_dest->type != STT_FUNC) {
510 WARN_FUNC("can't find call dest symbol at %s+0x%x",
511 insn->sec, insn->offset,
512 rela->sym->sec->name,
513 rela->addend + 4);
514 return -1;
515 }
516 } else
517 insn->call_dest = rela->sym;
518 }
519
520 return 0;
521 }
522
523 /*
524 * The .alternatives section requires some extra special care, over and above
525 * what other special sections require:
526 *
527 * 1. Because alternatives are patched in-place, we need to insert a fake jump
528 * instruction at the end so that validate_branch() skips all the original
529 * replaced instructions when validating the new instruction path.
530 *
531 * 2. An added wrinkle is that the new instruction length might be zero. In
532 * that case the old instructions are replaced with noops. We simulate that
533 * by creating a fake jump as the only new instruction.
534 *
535 * 3. In some cases, the alternative section includes an instruction which
536 * conditionally jumps to the _end_ of the entry. We have to modify these
537 * jumps' destinations to point back to .text rather than the end of the
538 * entry in .altinstr_replacement.
539 *
540 * 4. It has been requested that we don't validate the !POPCNT feature path
541 * which is a "very very small percentage of machines".
542 */
543 static int handle_group_alt(struct objtool_file *file,
544 struct special_alt *special_alt,
545 struct instruction *orig_insn,
546 struct instruction **new_insn)
547 {
548 struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump;
549 unsigned long dest_off;
550
551 last_orig_insn = NULL;
552 insn = orig_insn;
553 sec_for_each_insn_from(file, insn) {
554 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
555 break;
556
557 if (special_alt->skip_orig)
558 insn->type = INSN_NOP;
559
560 insn->alt_group = true;
561 last_orig_insn = insn;
562 }
563
564 if (!next_insn_same_sec(file, last_orig_insn)) {
565 WARN("%s: don't know how to handle alternatives at end of section",
566 special_alt->orig_sec->name);
567 return -1;
568 }
569
570 fake_jump = malloc(sizeof(*fake_jump));
571 if (!fake_jump) {
572 WARN("malloc failed");
573 return -1;
574 }
575 memset(fake_jump, 0, sizeof(*fake_jump));
576 INIT_LIST_HEAD(&fake_jump->alts);
577 clear_insn_state(&fake_jump->state);
578
579 fake_jump->sec = special_alt->new_sec;
580 fake_jump->offset = -1;
581 fake_jump->type = INSN_JUMP_UNCONDITIONAL;
582 fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
583 fake_jump->ignore = true;
584
585 if (!special_alt->new_len) {
586 *new_insn = fake_jump;
587 return 0;
588 }
589
590 last_new_insn = NULL;
591 insn = *new_insn;
592 sec_for_each_insn_from(file, insn) {
593 if (insn->offset >= special_alt->new_off + special_alt->new_len)
594 break;
595
596 last_new_insn = insn;
597
598 if (insn->type != INSN_JUMP_CONDITIONAL &&
599 insn->type != INSN_JUMP_UNCONDITIONAL)
600 continue;
601
602 if (!insn->immediate)
603 continue;
604
605 dest_off = insn->offset + insn->len + insn->immediate;
606 if (dest_off == special_alt->new_off + special_alt->new_len)
607 insn->jump_dest = fake_jump;
608
609 if (!insn->jump_dest) {
610 WARN_FUNC("can't find alternative jump destination",
611 insn->sec, insn->offset);
612 return -1;
613 }
614 }
615
616 if (!last_new_insn) {
617 WARN_FUNC("can't find last new alternative instruction",
618 special_alt->new_sec, special_alt->new_off);
619 return -1;
620 }
621
622 list_add(&fake_jump->list, &last_new_insn->list);
623
624 return 0;
625 }
626
627 /*
628 * A jump table entry can either convert a nop to a jump or a jump to a nop.
629 * If the original instruction is a jump, make the alt entry an effective nop
630 * by just skipping the original instruction.
631 */
632 static int handle_jump_alt(struct objtool_file *file,
633 struct special_alt *special_alt,
634 struct instruction *orig_insn,
635 struct instruction **new_insn)
636 {
637 if (orig_insn->type == INSN_NOP)
638 return 0;
639
640 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
641 WARN_FUNC("unsupported instruction at jump label",
642 orig_insn->sec, orig_insn->offset);
643 return -1;
644 }
645
646 *new_insn = list_next_entry(orig_insn, list);
647 return 0;
648 }
649
650 /*
651 * Read all the special sections which have alternate instructions which can be
652 * patched in or redirected to at runtime. Each instruction having alternate
653 * instruction(s) has them added to its insn->alts list, which will be
654 * traversed in validate_branch().
655 */
656 static int add_special_section_alts(struct objtool_file *file)
657 {
658 struct list_head special_alts;
659 struct instruction *orig_insn, *new_insn;
660 struct special_alt *special_alt, *tmp;
661 struct alternative *alt;
662 int ret;
663
664 ret = special_get_alts(file->elf, &special_alts);
665 if (ret)
666 return ret;
667
668 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
669 alt = malloc(sizeof(*alt));
670 if (!alt) {
671 WARN("malloc failed");
672 ret = -1;
673 goto out;
674 }
675
676 orig_insn = find_insn(file, special_alt->orig_sec,
677 special_alt->orig_off);
678 if (!orig_insn) {
679 WARN_FUNC("special: can't find orig instruction",
680 special_alt->orig_sec, special_alt->orig_off);
681 ret = -1;
682 goto out;
683 }
684
685 new_insn = NULL;
686 if (!special_alt->group || special_alt->new_len) {
687 new_insn = find_insn(file, special_alt->new_sec,
688 special_alt->new_off);
689 if (!new_insn) {
690 WARN_FUNC("special: can't find new instruction",
691 special_alt->new_sec,
692 special_alt->new_off);
693 ret = -1;
694 goto out;
695 }
696 }
697
698 if (special_alt->group) {
699 ret = handle_group_alt(file, special_alt, orig_insn,
700 &new_insn);
701 if (ret)
702 goto out;
703 } else if (special_alt->jump_or_nop) {
704 ret = handle_jump_alt(file, special_alt, orig_insn,
705 &new_insn);
706 if (ret)
707 goto out;
708 }
709
710 alt->insn = new_insn;
711 list_add_tail(&alt->list, &orig_insn->alts);
712
713 list_del(&special_alt->list);
714 free(special_alt);
715 }
716
717 out:
718 return ret;
719 }
720
721 static int add_switch_table(struct objtool_file *file, struct symbol *func,
722 struct instruction *insn, struct rela *table,
723 struct rela *next_table)
724 {
725 struct rela *rela = table;
726 struct instruction *alt_insn;
727 struct alternative *alt;
728
729 list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) {
730 if (rela == next_table)
731 break;
732
733 if (rela->sym->sec != insn->sec ||
734 rela->addend <= func->offset ||
735 rela->addend >= func->offset + func->len)
736 break;
737
738 alt_insn = find_insn(file, insn->sec, rela->addend);
739 if (!alt_insn) {
740 WARN("%s: can't find instruction at %s+0x%x",
741 file->rodata->rela->name, insn->sec->name,
742 rela->addend);
743 return -1;
744 }
745
746 alt = malloc(sizeof(*alt));
747 if (!alt) {
748 WARN("malloc failed");
749 return -1;
750 }
751
752 alt->insn = alt_insn;
753 list_add_tail(&alt->list, &insn->alts);
754 }
755
756 return 0;
757 }
758
759 /*
760 * find_switch_table() - Given a dynamic jump, find the switch jump table in
761 * .rodata associated with it.
762 *
763 * There are 3 basic patterns:
764 *
765 * 1. jmpq *[rodata addr](,%reg,8)
766 *
767 * This is the most common case by far. It jumps to an address in a simple
768 * jump table which is stored in .rodata.
769 *
770 * 2. jmpq *[rodata addr](%rip)
771 *
772 * This is caused by a rare GCC quirk, currently only seen in three driver
773 * functions in the kernel, only with certain obscure non-distro configs.
774 *
775 * As part of an optimization, GCC makes a copy of an existing switch jump
776 * table, modifies it, and then hard-codes the jump (albeit with an indirect
777 * jump) to use a single entry in the table. The rest of the jump table and
778 * some of its jump targets remain as dead code.
779 *
780 * In such a case we can just crudely ignore all unreachable instruction
781 * warnings for the entire object file. Ideally we would just ignore them
782 * for the function, but that would require redesigning the code quite a
783 * bit. And honestly that's just not worth doing: unreachable instruction
784 * warnings are of questionable value anyway, and this is such a rare issue.
785 *
786 * 3. mov [rodata addr],%reg1
787 * ... some instructions ...
788 * jmpq *(%reg1,%reg2,8)
789 *
790 * This is a fairly uncommon pattern which is new for GCC 6. As of this
791 * writing, there are 11 occurrences of it in the allmodconfig kernel.
792 *
793 * TODO: Once we have DWARF CFI and smarter instruction decoding logic,
794 * ensure the same register is used in the mov and jump instructions.
795 */
796 static struct rela *find_switch_table(struct objtool_file *file,
797 struct symbol *func,
798 struct instruction *insn)
799 {
800 struct rela *text_rela, *rodata_rela;
801 struct instruction *orig_insn = insn;
802
803 text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len);
804 if (text_rela && text_rela->sym == file->rodata->sym) {
805 /* case 1 */
806 rodata_rela = find_rela_by_dest(file->rodata,
807 text_rela->addend);
808 if (rodata_rela)
809 return rodata_rela;
810
811 /* case 2 */
812 rodata_rela = find_rela_by_dest(file->rodata,
813 text_rela->addend + 4);
814 if (!rodata_rela)
815 return NULL;
816 file->ignore_unreachables = true;
817 return rodata_rela;
818 }
819
820 /* case 3 */
821 func_for_each_insn_continue_reverse(file, func, insn) {
822 if (insn->type == INSN_JUMP_DYNAMIC)
823 break;
824
825 /* allow small jumps within the range */
826 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
827 insn->jump_dest &&
828 (insn->jump_dest->offset <= insn->offset ||
829 insn->jump_dest->offset > orig_insn->offset))
830 break;
831
832 /* look for a relocation which references .rodata */
833 text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
834 insn->len);
835 if (!text_rela || text_rela->sym != file->rodata->sym)
836 continue;
837
838 /*
839 * Make sure the .rodata address isn't associated with a
840 * symbol. gcc jump tables are anonymous data.
841 */
842 if (find_symbol_containing(file->rodata, text_rela->addend))
843 continue;
844
845 return find_rela_by_dest(file->rodata, text_rela->addend);
846 }
847
848 return NULL;
849 }
850
851 static int add_func_switch_tables(struct objtool_file *file,
852 struct symbol *func)
853 {
854 struct instruction *insn, *prev_jump = NULL;
855 struct rela *rela, *prev_rela = NULL;
856 int ret;
857
858 func_for_each_insn(file, func, insn) {
859 if (insn->type != INSN_JUMP_DYNAMIC)
860 continue;
861
862 rela = find_switch_table(file, func, insn);
863 if (!rela)
864 continue;
865
866 /*
867 * We found a switch table, but we don't know yet how big it
868 * is. Don't add it until we reach the end of the function or
869 * the beginning of another switch table in the same function.
870 */
871 if (prev_jump) {
872 ret = add_switch_table(file, func, prev_jump, prev_rela,
873 rela);
874 if (ret)
875 return ret;
876 }
877
878 prev_jump = insn;
879 prev_rela = rela;
880 }
881
882 if (prev_jump) {
883 ret = add_switch_table(file, func, prev_jump, prev_rela, NULL);
884 if (ret)
885 return ret;
886 }
887
888 return 0;
889 }
890
891 /*
892 * For some switch statements, gcc generates a jump table in the .rodata
893 * section which contains a list of addresses within the function to jump to.
894 * This finds these jump tables and adds them to the insn->alts lists.
895 */
896 static int add_switch_table_alts(struct objtool_file *file)
897 {
898 struct section *sec;
899 struct symbol *func;
900 int ret;
901
902 if (!file->rodata || !file->rodata->rela)
903 return 0;
904
905 for_each_sec(file, sec) {
906 list_for_each_entry(func, &sec->symbol_list, list) {
907 if (func->type != STT_FUNC)
908 continue;
909
910 ret = add_func_switch_tables(file, func);
911 if (ret)
912 return ret;
913 }
914 }
915
916 return 0;
917 }
918
919 static int read_unwind_hints(struct objtool_file *file)
920 {
921 struct section *sec, *relasec;
922 struct rela *rela;
923 struct unwind_hint *hint;
924 struct instruction *insn;
925 struct cfi_reg *cfa;
926 int i;
927
928 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
929 if (!sec)
930 return 0;
931
932 relasec = sec->rela;
933 if (!relasec) {
934 WARN("missing .rela.discard.unwind_hints section");
935 return -1;
936 }
937
938 if (sec->len % sizeof(struct unwind_hint)) {
939 WARN("struct unwind_hint size mismatch");
940 return -1;
941 }
942
943 file->hints = true;
944
945 for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
946 hint = (struct unwind_hint *)sec->data->d_buf + i;
947
948 rela = find_rela_by_dest(sec, i * sizeof(*hint));
949 if (!rela) {
950 WARN("can't find rela for unwind_hints[%d]", i);
951 return -1;
952 }
953
954 insn = find_insn(file, rela->sym->sec, rela->addend);
955 if (!insn) {
956 WARN("can't find insn for unwind_hints[%d]", i);
957 return -1;
958 }
959
960 cfa = &insn->state.cfa;
961
962 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
963 insn->save = true;
964 continue;
965
966 } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
967 insn->restore = true;
968 insn->hint = true;
969 continue;
970 }
971
972 insn->hint = true;
973
974 switch (hint->sp_reg) {
975 case ORC_REG_UNDEFINED:
976 cfa->base = CFI_UNDEFINED;
977 break;
978 case ORC_REG_SP:
979 cfa->base = CFI_SP;
980 break;
981 case ORC_REG_BP:
982 cfa->base = CFI_BP;
983 break;
984 case ORC_REG_SP_INDIRECT:
985 cfa->base = CFI_SP_INDIRECT;
986 break;
987 case ORC_REG_R10:
988 cfa->base = CFI_R10;
989 break;
990 case ORC_REG_R13:
991 cfa->base = CFI_R13;
992 break;
993 case ORC_REG_DI:
994 cfa->base = CFI_DI;
995 break;
996 case ORC_REG_DX:
997 cfa->base = CFI_DX;
998 break;
999 default:
1000 WARN_FUNC("unsupported unwind_hint sp base reg %d",
1001 insn->sec, insn->offset, hint->sp_reg);
1002 return -1;
1003 }
1004
1005 cfa->offset = hint->sp_offset;
1006 insn->state.type = hint->type;
1007 }
1008
1009 return 0;
1010 }
1011
1012 static int decode_sections(struct objtool_file *file)
1013 {
1014 int ret;
1015
1016 ret = decode_instructions(file);
1017 if (ret)
1018 return ret;
1019
1020 ret = add_dead_ends(file);
1021 if (ret)
1022 return ret;
1023
1024 add_ignores(file);
1025
1026 ret = add_jump_destinations(file);
1027 if (ret)
1028 return ret;
1029
1030 ret = add_call_destinations(file);
1031 if (ret)
1032 return ret;
1033
1034 ret = add_special_section_alts(file);
1035 if (ret)
1036 return ret;
1037
1038 ret = add_switch_table_alts(file);
1039 if (ret)
1040 return ret;
1041
1042 ret = read_unwind_hints(file);
1043 if (ret)
1044 return ret;
1045
1046 return 0;
1047 }
1048
1049 static bool is_fentry_call(struct instruction *insn)
1050 {
1051 if (insn->type == INSN_CALL &&
1052 insn->call_dest->type == STT_NOTYPE &&
1053 !strcmp(insn->call_dest->name, "__fentry__"))
1054 return true;
1055
1056 return false;
1057 }
1058
1059 static bool has_modified_stack_frame(struct insn_state *state)
1060 {
1061 int i;
1062
1063 if (state->cfa.base != initial_func_cfi.cfa.base ||
1064 state->cfa.offset != initial_func_cfi.cfa.offset ||
1065 state->stack_size != initial_func_cfi.cfa.offset ||
1066 state->drap)
1067 return true;
1068
1069 for (i = 0; i < CFI_NUM_REGS; i++)
1070 if (state->regs[i].base != initial_func_cfi.regs[i].base ||
1071 state->regs[i].offset != initial_func_cfi.regs[i].offset)
1072 return true;
1073
1074 return false;
1075 }
1076
1077 static bool has_valid_stack_frame(struct insn_state *state)
1078 {
1079 if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
1080 state->regs[CFI_BP].offset == -16)
1081 return true;
1082
1083 if (state->drap && state->regs[CFI_BP].base == CFI_BP)
1084 return true;
1085
1086 return false;
1087 }
1088
1089 static int update_insn_state_regs(struct instruction *insn, struct insn_state *state)
1090 {
1091 struct cfi_reg *cfa = &state->cfa;
1092 struct stack_op *op = &insn->stack_op;
1093
1094 if (cfa->base != CFI_SP)
1095 return 0;
1096
1097 /* push */
1098 if (op->dest.type == OP_DEST_PUSH)
1099 cfa->offset += 8;
1100
1101 /* pop */
1102 if (op->src.type == OP_SRC_POP)
1103 cfa->offset -= 8;
1104
1105 /* add immediate to sp */
1106 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1107 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1108 cfa->offset -= op->src.offset;
1109
1110 return 0;
1111 }
1112
1113 static void save_reg(struct insn_state *state, unsigned char reg, int base,
1114 int offset)
1115 {
1116 if (arch_callee_saved_reg(reg) &&
1117 state->regs[reg].base == CFI_UNDEFINED) {
1118 state->regs[reg].base = base;
1119 state->regs[reg].offset = offset;
1120 }
1121 }
1122
1123 static void restore_reg(struct insn_state *state, unsigned char reg)
1124 {
1125 state->regs[reg].base = CFI_UNDEFINED;
1126 state->regs[reg].offset = 0;
1127 }
1128
1129 /*
1130 * A note about DRAP stack alignment:
1131 *
1132 * GCC has the concept of a DRAP register, which is used to help keep track of
1133 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
1134 * register. The typical DRAP pattern is:
1135 *
1136 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
1137 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
1138 * 41 ff 72 f8 pushq -0x8(%r10)
1139 * 55 push %rbp
1140 * 48 89 e5 mov %rsp,%rbp
1141 * (more pushes)
1142 * 41 52 push %r10
1143 * ...
1144 * 41 5a pop %r10
1145 * (more pops)
1146 * 5d pop %rbp
1147 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1148 * c3 retq
1149 *
1150 * There are some variations in the epilogues, like:
1151 *
1152 * 5b pop %rbx
1153 * 41 5a pop %r10
1154 * 41 5c pop %r12
1155 * 41 5d pop %r13
1156 * 41 5e pop %r14
1157 * c9 leaveq
1158 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1159 * c3 retq
1160 *
1161 * and:
1162 *
1163 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
1164 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
1165 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
1166 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
1167 * c9 leaveq
1168 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1169 * c3 retq
1170 *
1171 * Sometimes r13 is used as the DRAP register, in which case it's saved and
1172 * restored beforehand:
1173 *
1174 * 41 55 push %r13
1175 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
1176 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
1177 * ...
1178 * 49 8d 65 f0 lea -0x10(%r13),%rsp
1179 * 41 5d pop %r13
1180 * c3 retq
1181 */
1182 static int update_insn_state(struct instruction *insn, struct insn_state *state)
1183 {
1184 struct stack_op *op = &insn->stack_op;
1185 struct cfi_reg *cfa = &state->cfa;
1186 struct cfi_reg *regs = state->regs;
1187
1188 /* stack operations don't make sense with an undefined CFA */
1189 if (cfa->base == CFI_UNDEFINED) {
1190 if (insn->func) {
1191 WARN_FUNC("undefined stack state", insn->sec, insn->offset);
1192 return -1;
1193 }
1194 return 0;
1195 }
1196
1197 if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET)
1198 return update_insn_state_regs(insn, state);
1199
1200 switch (op->dest.type) {
1201
1202 case OP_DEST_REG:
1203 switch (op->src.type) {
1204
1205 case OP_SRC_REG:
1206 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP) {
1207
1208 if (cfa->base == CFI_SP &&
1209 regs[CFI_BP].base == CFI_CFA &&
1210 regs[CFI_BP].offset == -cfa->offset) {
1211
1212 /* mov %rsp, %rbp */
1213 cfa->base = op->dest.reg;
1214 state->bp_scratch = false;
1215 }
1216
1217 else if (state->drap) {
1218
1219 /* drap: mov %rsp, %rbp */
1220 regs[CFI_BP].base = CFI_BP;
1221 regs[CFI_BP].offset = -state->stack_size;
1222 state->bp_scratch = false;
1223 }
1224 }
1225
1226 else if (op->dest.reg == cfa->base) {
1227
1228 /* mov %reg, %rsp */
1229 if (cfa->base == CFI_SP &&
1230 state->vals[op->src.reg].base == CFI_CFA) {
1231
1232 /*
1233 * This is needed for the rare case
1234 * where GCC does something dumb like:
1235 *
1236 * lea 0x8(%rsp), %rcx
1237 * ...
1238 * mov %rcx, %rsp
1239 */
1240 cfa->offset = -state->vals[op->src.reg].offset;
1241 state->stack_size = cfa->offset;
1242
1243 } else {
1244 cfa->base = CFI_UNDEFINED;
1245 cfa->offset = 0;
1246 }
1247 }
1248
1249 break;
1250
1251 case OP_SRC_ADD:
1252 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
1253
1254 /* add imm, %rsp */
1255 state->stack_size -= op->src.offset;
1256 if (cfa->base == CFI_SP)
1257 cfa->offset -= op->src.offset;
1258 break;
1259 }
1260
1261 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
1262
1263 /* lea disp(%rbp), %rsp */
1264 state->stack_size = -(op->src.offset + regs[CFI_BP].offset);
1265 break;
1266 }
1267
1268 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1269
1270 /* drap: lea disp(%rsp), %drap */
1271 state->drap_reg = op->dest.reg;
1272
1273 /*
1274 * lea disp(%rsp), %reg
1275 *
1276 * This is needed for the rare case where GCC
1277 * does something dumb like:
1278 *
1279 * lea 0x8(%rsp), %rcx
1280 * ...
1281 * mov %rcx, %rsp
1282 */
1283 state->vals[op->dest.reg].base = CFI_CFA;
1284 state->vals[op->dest.reg].offset = \
1285 -state->stack_size + op->src.offset;
1286
1287 break;
1288 }
1289
1290 if (state->drap && op->dest.reg == CFI_SP &&
1291 op->src.reg == state->drap_reg) {
1292
1293 /* drap: lea disp(%drap), %rsp */
1294 cfa->base = CFI_SP;
1295 cfa->offset = state->stack_size = -op->src.offset;
1296 state->drap_reg = CFI_UNDEFINED;
1297 state->drap = false;
1298 break;
1299 }
1300
1301 if (op->dest.reg == state->cfa.base) {
1302 WARN_FUNC("unsupported stack register modification",
1303 insn->sec, insn->offset);
1304 return -1;
1305 }
1306
1307 break;
1308
1309 case OP_SRC_AND:
1310 if (op->dest.reg != CFI_SP ||
1311 (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
1312 (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
1313 WARN_FUNC("unsupported stack pointer realignment",
1314 insn->sec, insn->offset);
1315 return -1;
1316 }
1317
1318 if (state->drap_reg != CFI_UNDEFINED) {
1319 /* drap: and imm, %rsp */
1320 cfa->base = state->drap_reg;
1321 cfa->offset = state->stack_size = 0;
1322 state->drap = true;
1323 }
1324
1325 /*
1326 * Older versions of GCC (4.8ish) realign the stack
1327 * without DRAP, with a frame pointer.
1328 */
1329
1330 break;
1331
1332 case OP_SRC_POP:
1333 if (!state->drap && op->dest.type == OP_DEST_REG &&
1334 op->dest.reg == cfa->base) {
1335
1336 /* pop %rbp */
1337 cfa->base = CFI_SP;
1338 }
1339
1340 if (state->drap && cfa->base == CFI_BP_INDIRECT &&
1341 op->dest.type == OP_DEST_REG &&
1342 op->dest.reg == state->drap_reg &&
1343 state->drap_offset == -state->stack_size) {
1344
1345 /* drap: pop %drap */
1346 cfa->base = state->drap_reg;
1347 cfa->offset = 0;
1348 state->drap_offset = -1;
1349
1350 } else if (regs[op->dest.reg].offset == -state->stack_size) {
1351
1352 /* pop %reg */
1353 restore_reg(state, op->dest.reg);
1354 }
1355
1356 state->stack_size -= 8;
1357 if (cfa->base == CFI_SP)
1358 cfa->offset -= 8;
1359
1360 break;
1361
1362 case OP_SRC_REG_INDIRECT:
1363 if (state->drap && op->src.reg == CFI_BP &&
1364 op->src.offset == state->drap_offset) {
1365
1366 /* drap: mov disp(%rbp), %drap */
1367 cfa->base = state->drap_reg;
1368 cfa->offset = 0;
1369 state->drap_offset = -1;
1370 }
1371
1372 if (state->drap && op->src.reg == CFI_BP &&
1373 op->src.offset == regs[op->dest.reg].offset) {
1374
1375 /* drap: mov disp(%rbp), %reg */
1376 restore_reg(state, op->dest.reg);
1377
1378 } else if (op->src.reg == cfa->base &&
1379 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
1380
1381 /* mov disp(%rbp), %reg */
1382 /* mov disp(%rsp), %reg */
1383 restore_reg(state, op->dest.reg);
1384 }
1385
1386 break;
1387
1388 default:
1389 WARN_FUNC("unknown stack-related instruction",
1390 insn->sec, insn->offset);
1391 return -1;
1392 }
1393
1394 break;
1395
1396 case OP_DEST_PUSH:
1397 state->stack_size += 8;
1398 if (cfa->base == CFI_SP)
1399 cfa->offset += 8;
1400
1401 if (op->src.type != OP_SRC_REG)
1402 break;
1403
1404 if (state->drap) {
1405 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1406
1407 /* drap: push %drap */
1408 cfa->base = CFI_BP_INDIRECT;
1409 cfa->offset = -state->stack_size;
1410
1411 /* save drap so we know when to restore it */
1412 state->drap_offset = -state->stack_size;
1413
1414 } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
1415
1416 /* drap: push %rbp */
1417 state->stack_size = 0;
1418
1419 } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1420
1421 /* drap: push %reg */
1422 save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
1423 }
1424
1425 } else {
1426
1427 /* push %reg */
1428 save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
1429 }
1430
1431 /* detect when asm code uses rbp as a scratch register */
1432 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
1433 cfa->base != CFI_BP)
1434 state->bp_scratch = true;
1435 break;
1436
1437 case OP_DEST_REG_INDIRECT:
1438
1439 if (state->drap) {
1440 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1441
1442 /* drap: mov %drap, disp(%rbp) */
1443 cfa->base = CFI_BP_INDIRECT;
1444 cfa->offset = op->dest.offset;
1445
1446 /* save drap offset so we know when to restore it */
1447 state->drap_offset = op->dest.offset;
1448 }
1449
1450 else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1451
1452 /* drap: mov reg, disp(%rbp) */
1453 save_reg(state, op->src.reg, CFI_BP, op->dest.offset);
1454 }
1455
1456 } else if (op->dest.reg == cfa->base) {
1457
1458 /* mov reg, disp(%rbp) */
1459 /* mov reg, disp(%rsp) */
1460 save_reg(state, op->src.reg, CFI_CFA,
1461 op->dest.offset - state->cfa.offset);
1462 }
1463
1464 break;
1465
1466 case OP_DEST_LEAVE:
1467 if ((!state->drap && cfa->base != CFI_BP) ||
1468 (state->drap && cfa->base != state->drap_reg)) {
1469 WARN_FUNC("leave instruction with modified stack frame",
1470 insn->sec, insn->offset);
1471 return -1;
1472 }
1473
1474 /* leave (mov %rbp, %rsp; pop %rbp) */
1475
1476 state->stack_size = -state->regs[CFI_BP].offset - 8;
1477 restore_reg(state, CFI_BP);
1478
1479 if (!state->drap) {
1480 cfa->base = CFI_SP;
1481 cfa->offset -= 8;
1482 }
1483
1484 break;
1485
1486 case OP_DEST_MEM:
1487 if (op->src.type != OP_SRC_POP) {
1488 WARN_FUNC("unknown stack-related memory operation",
1489 insn->sec, insn->offset);
1490 return -1;
1491 }
1492
1493 /* pop mem */
1494 state->stack_size -= 8;
1495 if (cfa->base == CFI_SP)
1496 cfa->offset -= 8;
1497
1498 break;
1499
1500 default:
1501 WARN_FUNC("unknown stack-related instruction",
1502 insn->sec, insn->offset);
1503 return -1;
1504 }
1505
1506 return 0;
1507 }
1508
1509 static bool insn_state_match(struct instruction *insn, struct insn_state *state)
1510 {
1511 struct insn_state *state1 = &insn->state, *state2 = state;
1512 int i;
1513
1514 if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
1515 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
1516 insn->sec, insn->offset,
1517 state1->cfa.base, state1->cfa.offset,
1518 state2->cfa.base, state2->cfa.offset);
1519
1520 } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
1521 for (i = 0; i < CFI_NUM_REGS; i++) {
1522 if (!memcmp(&state1->regs[i], &state2->regs[i],
1523 sizeof(struct cfi_reg)))
1524 continue;
1525
1526 WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
1527 insn->sec, insn->offset,
1528 i, state1->regs[i].base, state1->regs[i].offset,
1529 i, state2->regs[i].base, state2->regs[i].offset);
1530 break;
1531 }
1532
1533 } else if (state1->type != state2->type) {
1534 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
1535 insn->sec, insn->offset, state1->type, state2->type);
1536
1537 } else if (state1->drap != state2->drap ||
1538 (state1->drap && state1->drap_reg != state2->drap_reg) ||
1539 (state1->drap && state1->drap_offset != state2->drap_offset)) {
1540 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
1541 insn->sec, insn->offset,
1542 state1->drap, state1->drap_reg, state1->drap_offset,
1543 state2->drap, state2->drap_reg, state2->drap_offset);
1544
1545 } else
1546 return true;
1547
1548 return false;
1549 }
1550
1551 /*
1552 * Follow the branch starting at the given instruction, and recursively follow
1553 * any other branches (jumps). Meanwhile, track the frame pointer state at
1554 * each instruction and validate all the rules described in
1555 * tools/objtool/Documentation/stack-validation.txt.
1556 */
1557 static int validate_branch(struct objtool_file *file, struct instruction *first,
1558 struct insn_state state)
1559 {
1560 struct alternative *alt;
1561 struct instruction *insn, *next_insn;
1562 struct section *sec;
1563 struct symbol *func = NULL;
1564 int ret;
1565
1566 insn = first;
1567 sec = insn->sec;
1568
1569 if (insn->alt_group && list_empty(&insn->alts)) {
1570 WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
1571 sec, insn->offset);
1572 return 1;
1573 }
1574
1575 while (1) {
1576 next_insn = next_insn_same_sec(file, insn);
1577
1578
1579 if (file->c_file && func && insn->func && func != insn->func) {
1580 WARN("%s() falls through to next function %s()",
1581 func->name, insn->func->name);
1582 return 1;
1583 }
1584
1585 if (insn->func)
1586 func = insn->func;
1587
1588 if (func && insn->ignore) {
1589 WARN_FUNC("BUG: why am I validating an ignored function?",
1590 sec, insn->offset);
1591 return 1;
1592 }
1593
1594 if (insn->visited) {
1595 if (!insn->hint && !insn_state_match(insn, &state))
1596 return 1;
1597
1598 return 0;
1599 }
1600
1601 if (insn->hint) {
1602 if (insn->restore) {
1603 struct instruction *save_insn, *i;
1604
1605 i = insn;
1606 save_insn = NULL;
1607 func_for_each_insn_continue_reverse(file, func, i) {
1608 if (i->save) {
1609 save_insn = i;
1610 break;
1611 }
1612 }
1613
1614 if (!save_insn) {
1615 WARN_FUNC("no corresponding CFI save for CFI restore",
1616 sec, insn->offset);
1617 return 1;
1618 }
1619
1620 if (!save_insn->visited) {
1621 /*
1622 * Oops, no state to copy yet.
1623 * Hopefully we can reach this
1624 * instruction from another branch
1625 * after the save insn has been
1626 * visited.
1627 */
1628 if (insn == first)
1629 return 0;
1630
1631 WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
1632 sec, insn->offset);
1633 return 1;
1634 }
1635
1636 insn->state = save_insn->state;
1637 }
1638
1639 state = insn->state;
1640
1641 } else
1642 insn->state = state;
1643
1644 insn->visited = true;
1645
1646 list_for_each_entry(alt, &insn->alts, list) {
1647 ret = validate_branch(file, alt->insn, state);
1648 if (ret)
1649 return 1;
1650 }
1651
1652 switch (insn->type) {
1653
1654 case INSN_RETURN:
1655 if (func && has_modified_stack_frame(&state)) {
1656 WARN_FUNC("return with modified stack frame",
1657 sec, insn->offset);
1658 return 1;
1659 }
1660
1661 if (state.bp_scratch) {
1662 WARN("%s uses BP as a scratch register",
1663 insn->func->name);
1664 return 1;
1665 }
1666
1667 return 0;
1668
1669 case INSN_CALL:
1670 if (is_fentry_call(insn))
1671 break;
1672
1673 ret = dead_end_function(file, insn->call_dest);
1674 if (ret == 1)
1675 return 0;
1676 if (ret == -1)
1677 return 1;
1678
1679 /* fallthrough */
1680 case INSN_CALL_DYNAMIC:
1681 if (!no_fp && func && !has_valid_stack_frame(&state)) {
1682 WARN_FUNC("call without frame pointer save/setup",
1683 sec, insn->offset);
1684 return 1;
1685 }
1686 break;
1687
1688 case INSN_JUMP_CONDITIONAL:
1689 case INSN_JUMP_UNCONDITIONAL:
1690 if (insn->jump_dest &&
1691 (!func || !insn->jump_dest->func ||
1692 func == insn->jump_dest->func)) {
1693 ret = validate_branch(file, insn->jump_dest,
1694 state);
1695 if (ret)
1696 return 1;
1697
1698 } else if (func && has_modified_stack_frame(&state)) {
1699 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1700 sec, insn->offset);
1701 return 1;
1702 }
1703
1704 if (insn->type == INSN_JUMP_UNCONDITIONAL)
1705 return 0;
1706
1707 break;
1708
1709 case INSN_JUMP_DYNAMIC:
1710 if (func && list_empty(&insn->alts) &&
1711 has_modified_stack_frame(&state)) {
1712 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1713 sec, insn->offset);
1714 return 1;
1715 }
1716
1717 return 0;
1718
1719 case INSN_CONTEXT_SWITCH:
1720 if (func && (!next_insn || !next_insn->hint)) {
1721 WARN_FUNC("unsupported instruction in callable function",
1722 sec, insn->offset);
1723 return 1;
1724 }
1725 return 0;
1726
1727 case INSN_STACK:
1728 if (update_insn_state(insn, &state))
1729 return 1;
1730
1731 break;
1732
1733 default:
1734 break;
1735 }
1736
1737 if (insn->dead_end)
1738 return 0;
1739
1740 insn = next_insn;
1741 if (!insn) {
1742 WARN("%s: unexpected end of section", sec->name);
1743 return 1;
1744 }
1745 }
1746
1747 return 0;
1748 }
1749
1750 static int validate_unwind_hints(struct objtool_file *file)
1751 {
1752 struct instruction *insn;
1753 int ret, warnings = 0;
1754 struct insn_state state;
1755
1756 if (!file->hints)
1757 return 0;
1758
1759 clear_insn_state(&state);
1760
1761 for_each_insn(file, insn) {
1762 if (insn->hint && !insn->visited) {
1763 ret = validate_branch(file, insn, state);
1764 warnings += ret;
1765 }
1766 }
1767
1768 return warnings;
1769 }
1770
1771 static bool is_kasan_insn(struct instruction *insn)
1772 {
1773 return (insn->type == INSN_CALL &&
1774 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
1775 }
1776
1777 static bool is_ubsan_insn(struct instruction *insn)
1778 {
1779 return (insn->type == INSN_CALL &&
1780 !strcmp(insn->call_dest->name,
1781 "__ubsan_handle_builtin_unreachable"));
1782 }
1783
1784 static bool ignore_unreachable_insn(struct instruction *insn)
1785 {
1786 int i;
1787
1788 if (insn->ignore || insn->type == INSN_NOP)
1789 return true;
1790
1791 /*
1792 * Ignore any unused exceptions. This can happen when a whitelisted
1793 * function has an exception table entry.
1794 *
1795 * Also ignore alternative replacement instructions. This can happen
1796 * when a whitelisted function uses one of the ALTERNATIVE macros.
1797 */
1798 if (!strcmp(insn->sec->name, ".fixup") ||
1799 !strcmp(insn->sec->name, ".altinstr_replacement") ||
1800 !strcmp(insn->sec->name, ".altinstr_aux"))
1801 return true;
1802
1803 /*
1804 * Check if this (or a subsequent) instruction is related to
1805 * CONFIG_UBSAN or CONFIG_KASAN.
1806 *
1807 * End the search at 5 instructions to avoid going into the weeds.
1808 */
1809 if (!insn->func)
1810 return false;
1811 for (i = 0; i < 5; i++) {
1812
1813 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
1814 return true;
1815
1816 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest) {
1817 insn = insn->jump_dest;
1818 continue;
1819 }
1820
1821 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
1822 break;
1823 insn = list_next_entry(insn, list);
1824 }
1825
1826 return false;
1827 }
1828
1829 static int validate_functions(struct objtool_file *file)
1830 {
1831 struct section *sec;
1832 struct symbol *func;
1833 struct instruction *insn;
1834 struct insn_state state;
1835 int ret, warnings = 0;
1836
1837 clear_insn_state(&state);
1838
1839 state.cfa = initial_func_cfi.cfa;
1840 memcpy(&state.regs, &initial_func_cfi.regs,
1841 CFI_NUM_REGS * sizeof(struct cfi_reg));
1842 state.stack_size = initial_func_cfi.cfa.offset;
1843
1844 for_each_sec(file, sec) {
1845 list_for_each_entry(func, &sec->symbol_list, list) {
1846 if (func->type != STT_FUNC)
1847 continue;
1848
1849 insn = find_insn(file, sec, func->offset);
1850 if (!insn || insn->ignore)
1851 continue;
1852
1853 ret = validate_branch(file, insn, state);
1854 warnings += ret;
1855 }
1856 }
1857
1858 return warnings;
1859 }
1860
1861 static int validate_reachable_instructions(struct objtool_file *file)
1862 {
1863 struct instruction *insn;
1864
1865 if (file->ignore_unreachables)
1866 return 0;
1867
1868 for_each_insn(file, insn) {
1869 if (insn->visited || ignore_unreachable_insn(insn))
1870 continue;
1871
1872 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
1873 return 1;
1874 }
1875
1876 return 0;
1877 }
1878
1879 static void cleanup(struct objtool_file *file)
1880 {
1881 struct instruction *insn, *tmpinsn;
1882 struct alternative *alt, *tmpalt;
1883
1884 list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) {
1885 list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) {
1886 list_del(&alt->list);
1887 free(alt);
1888 }
1889 list_del(&insn->list);
1890 hash_del(&insn->hash);
1891 free(insn);
1892 }
1893 elf_close(file->elf);
1894 }
1895
1896 int check(const char *_objname, bool _no_fp, bool no_unreachable, bool orc)
1897 {
1898 struct objtool_file file;
1899 int ret, warnings = 0;
1900
1901 objname = _objname;
1902 no_fp = _no_fp;
1903
1904 file.elf = elf_open(objname, orc ? O_RDWR : O_RDONLY);
1905 if (!file.elf)
1906 return 1;
1907
1908 INIT_LIST_HEAD(&file.insn_list);
1909 hash_init(file.insn_hash);
1910 file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard");
1911 file.rodata = find_section_by_name(file.elf, ".rodata");
1912 file.c_file = find_section_by_name(file.elf, ".comment");
1913 file.ignore_unreachables = no_unreachable;
1914 file.hints = false;
1915
1916 arch_initial_func_cfi_state(&initial_func_cfi);
1917
1918 ret = decode_sections(&file);
1919 if (ret < 0)
1920 goto out;
1921 warnings += ret;
1922
1923 if (list_empty(&file.insn_list))
1924 goto out;
1925
1926 ret = validate_functions(&file);
1927 if (ret < 0)
1928 goto out;
1929 warnings += ret;
1930
1931 ret = validate_unwind_hints(&file);
1932 if (ret < 0)
1933 goto out;
1934 warnings += ret;
1935
1936 if (!warnings) {
1937 ret = validate_reachable_instructions(&file);
1938 if (ret < 0)
1939 goto out;
1940 warnings += ret;
1941 }
1942
1943 if (orc) {
1944 ret = create_orc(&file);
1945 if (ret < 0)
1946 goto out;
1947
1948 ret = create_orc_sections(&file);
1949 if (ret < 0)
1950 goto out;
1951
1952 ret = elf_write(file.elf);
1953 if (ret < 0)
1954 goto out;
1955 }
1956
1957 out:
1958 cleanup(&file);
1959
1960 /* ignore warnings for now until we get all the code cleaned up */
1961 if (ret || warnings)
1962 return 0;
1963 return 0;
1964 }
Linux with added FPC-III support