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Merge branch 'linus' into core/objtool, to pick up dependent fixes
[mirror_ubuntu-bionic-kernel.git] / tools / objtool / check.c
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 goto err;
271
272 if (!insn->type || insn->type > INSN_LAST) {
273 WARN_FUNC("invalid instruction type %d",
274 insn->sec, insn->offset, insn->type);
275 ret = -1;
276 goto err;
277 }
278
279 hash_add(file->insn_hash, &insn->hash, insn->offset);
280 list_add_tail(&insn->list, &file->insn_list);
281 }
282
283 list_for_each_entry(func, &sec->symbol_list, list) {
284 if (func->type != STT_FUNC)
285 continue;
286
287 if (!find_insn(file, sec, func->offset)) {
288 WARN("%s(): can't find starting instruction",
289 func->name);
290 return -1;
291 }
292
293 func_for_each_insn(file, func, insn)
294 if (!insn->func)
295 insn->func = func;
296 }
297 }
298
299 return 0;
300
301 err:
302 free(insn);
303 return ret;
304 }
305
306 /*
307 * Mark "ud2" instructions and manually annotated dead ends.
308 */
309 static int add_dead_ends(struct objtool_file *file)
310 {
311 struct section *sec;
312 struct rela *rela;
313 struct instruction *insn;
314 bool found;
315
316 /*
317 * By default, "ud2" is a dead end unless otherwise annotated, because
318 * GCC 7 inserts it for certain divide-by-zero cases.
319 */
320 for_each_insn(file, insn)
321 if (insn->type == INSN_BUG)
322 insn->dead_end = true;
323
324 /*
325 * Check for manually annotated dead ends.
326 */
327 sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
328 if (!sec)
329 goto reachable;
330
331 list_for_each_entry(rela, &sec->rela_list, list) {
332 if (rela->sym->type != STT_SECTION) {
333 WARN("unexpected relocation symbol type in %s", sec->name);
334 return -1;
335 }
336 insn = find_insn(file, rela->sym->sec, rela->addend);
337 if (insn)
338 insn = list_prev_entry(insn, list);
339 else if (rela->addend == rela->sym->sec->len) {
340 found = false;
341 list_for_each_entry_reverse(insn, &file->insn_list, list) {
342 if (insn->sec == rela->sym->sec) {
343 found = true;
344 break;
345 }
346 }
347
348 if (!found) {
349 WARN("can't find unreachable insn at %s+0x%x",
350 rela->sym->sec->name, rela->addend);
351 return -1;
352 }
353 } else {
354 WARN("can't find unreachable insn at %s+0x%x",
355 rela->sym->sec->name, rela->addend);
356 return -1;
357 }
358
359 insn->dead_end = true;
360 }
361
362 reachable:
363 /*
364 * These manually annotated reachable checks are needed for GCC 4.4,
365 * where the Linux unreachable() macro isn't supported. In that case
366 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
367 * not a dead end.
368 */
369 sec = find_section_by_name(file->elf, ".rela.discard.reachable");
370 if (!sec)
371 return 0;
372
373 list_for_each_entry(rela, &sec->rela_list, list) {
374 if (rela->sym->type != STT_SECTION) {
375 WARN("unexpected relocation symbol type in %s", sec->name);
376 return -1;
377 }
378 insn = find_insn(file, rela->sym->sec, rela->addend);
379 if (insn)
380 insn = list_prev_entry(insn, list);
381 else if (rela->addend == rela->sym->sec->len) {
382 found = false;
383 list_for_each_entry_reverse(insn, &file->insn_list, list) {
384 if (insn->sec == rela->sym->sec) {
385 found = true;
386 break;
387 }
388 }
389
390 if (!found) {
391 WARN("can't find reachable insn at %s+0x%x",
392 rela->sym->sec->name, rela->addend);
393 return -1;
394 }
395 } else {
396 WARN("can't find reachable insn at %s+0x%x",
397 rela->sym->sec->name, rela->addend);
398 return -1;
399 }
400
401 insn->dead_end = false;
402 }
403
404 return 0;
405 }
406
407 /*
408 * Warnings shouldn't be reported for ignored functions.
409 */
410 static void add_ignores(struct objtool_file *file)
411 {
412 struct instruction *insn;
413 struct section *sec;
414 struct symbol *func;
415
416 for_each_sec(file, sec) {
417 list_for_each_entry(func, &sec->symbol_list, list) {
418 if (func->type != STT_FUNC)
419 continue;
420
421 if (!ignore_func(file, func))
422 continue;
423
424 func_for_each_insn(file, func, insn)
425 insn->ignore = true;
426 }
427 }
428 }
429
430 /*
431 * Find the destination instructions for all jumps.
432 */
433 static int add_jump_destinations(struct objtool_file *file)
434 {
435 struct instruction *insn;
436 struct rela *rela;
437 struct section *dest_sec;
438 unsigned long dest_off;
439
440 for_each_insn(file, insn) {
441 if (insn->type != INSN_JUMP_CONDITIONAL &&
442 insn->type != INSN_JUMP_UNCONDITIONAL)
443 continue;
444
445 if (insn->ignore)
446 continue;
447
448 rela = find_rela_by_dest_range(insn->sec, insn->offset,
449 insn->len);
450 if (!rela) {
451 dest_sec = insn->sec;
452 dest_off = insn->offset + insn->len + insn->immediate;
453 } else if (rela->sym->type == STT_SECTION) {
454 dest_sec = rela->sym->sec;
455 dest_off = rela->addend + 4;
456 } else if (rela->sym->sec->idx) {
457 dest_sec = rela->sym->sec;
458 dest_off = rela->sym->sym.st_value + rela->addend + 4;
459 } else {
460 /* sibling call */
461 insn->jump_dest = 0;
462 continue;
463 }
464
465 insn->jump_dest = find_insn(file, dest_sec, dest_off);
466 if (!insn->jump_dest) {
467
468 /*
469 * This is a special case where an alt instruction
470 * jumps past the end of the section. These are
471 * handled later in handle_group_alt().
472 */
473 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
474 continue;
475
476 WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
477 insn->sec, insn->offset, dest_sec->name,
478 dest_off);
479 return -1;
480 }
481 }
482
483 return 0;
484 }
485
486 /*
487 * Find the destination instructions for all calls.
488 */
489 static int add_call_destinations(struct objtool_file *file)
490 {
491 struct instruction *insn;
492 unsigned long dest_off;
493 struct rela *rela;
494
495 for_each_insn(file, insn) {
496 if (insn->type != INSN_CALL)
497 continue;
498
499 rela = find_rela_by_dest_range(insn->sec, insn->offset,
500 insn->len);
501 if (!rela) {
502 dest_off = insn->offset + insn->len + insn->immediate;
503 insn->call_dest = find_symbol_by_offset(insn->sec,
504 dest_off);
505 if (!insn->call_dest) {
506 WARN_FUNC("can't find call dest symbol at offset 0x%lx",
507 insn->sec, insn->offset, dest_off);
508 return -1;
509 }
510 } else if (rela->sym->type == STT_SECTION) {
511 insn->call_dest = find_symbol_by_offset(rela->sym->sec,
512 rela->addend+4);
513 if (!insn->call_dest ||
514 insn->call_dest->type != STT_FUNC) {
515 WARN_FUNC("can't find call dest symbol at %s+0x%x",
516 insn->sec, insn->offset,
517 rela->sym->sec->name,
518 rela->addend + 4);
519 return -1;
520 }
521 } else
522 insn->call_dest = rela->sym;
523 }
524
525 return 0;
526 }
527
528 /*
529 * The .alternatives section requires some extra special care, over and above
530 * what other special sections require:
531 *
532 * 1. Because alternatives are patched in-place, we need to insert a fake jump
533 * instruction at the end so that validate_branch() skips all the original
534 * replaced instructions when validating the new instruction path.
535 *
536 * 2. An added wrinkle is that the new instruction length might be zero. In
537 * that case the old instructions are replaced with noops. We simulate that
538 * by creating a fake jump as the only new instruction.
539 *
540 * 3. In some cases, the alternative section includes an instruction which
541 * conditionally jumps to the _end_ of the entry. We have to modify these
542 * jumps' destinations to point back to .text rather than the end of the
543 * entry in .altinstr_replacement.
544 *
545 * 4. It has been requested that we don't validate the !POPCNT feature path
546 * which is a "very very small percentage of machines".
547 */
548 static int handle_group_alt(struct objtool_file *file,
549 struct special_alt *special_alt,
550 struct instruction *orig_insn,
551 struct instruction **new_insn)
552 {
553 struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump;
554 unsigned long dest_off;
555
556 last_orig_insn = NULL;
557 insn = orig_insn;
558 sec_for_each_insn_from(file, insn) {
559 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
560 break;
561
562 if (special_alt->skip_orig)
563 insn->type = INSN_NOP;
564
565 insn->alt_group = true;
566 last_orig_insn = insn;
567 }
568
569 if (!next_insn_same_sec(file, last_orig_insn)) {
570 WARN("%s: don't know how to handle alternatives at end of section",
571 special_alt->orig_sec->name);
572 return -1;
573 }
574
575 fake_jump = malloc(sizeof(*fake_jump));
576 if (!fake_jump) {
577 WARN("malloc failed");
578 return -1;
579 }
580 memset(fake_jump, 0, sizeof(*fake_jump));
581 INIT_LIST_HEAD(&fake_jump->alts);
582 clear_insn_state(&fake_jump->state);
583
584 fake_jump->sec = special_alt->new_sec;
585 fake_jump->offset = -1;
586 fake_jump->type = INSN_JUMP_UNCONDITIONAL;
587 fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
588 fake_jump->ignore = true;
589
590 if (!special_alt->new_len) {
591 *new_insn = fake_jump;
592 return 0;
593 }
594
595 last_new_insn = NULL;
596 insn = *new_insn;
597 sec_for_each_insn_from(file, insn) {
598 if (insn->offset >= special_alt->new_off + special_alt->new_len)
599 break;
600
601 last_new_insn = insn;
602
603 if (insn->type != INSN_JUMP_CONDITIONAL &&
604 insn->type != INSN_JUMP_UNCONDITIONAL)
605 continue;
606
607 if (!insn->immediate)
608 continue;
609
610 dest_off = insn->offset + insn->len + insn->immediate;
611 if (dest_off == special_alt->new_off + special_alt->new_len)
612 insn->jump_dest = fake_jump;
613
614 if (!insn->jump_dest) {
615 WARN_FUNC("can't find alternative jump destination",
616 insn->sec, insn->offset);
617 return -1;
618 }
619 }
620
621 if (!last_new_insn) {
622 WARN_FUNC("can't find last new alternative instruction",
623 special_alt->new_sec, special_alt->new_off);
624 return -1;
625 }
626
627 list_add(&fake_jump->list, &last_new_insn->list);
628
629 return 0;
630 }
631
632 /*
633 * A jump table entry can either convert a nop to a jump or a jump to a nop.
634 * If the original instruction is a jump, make the alt entry an effective nop
635 * by just skipping the original instruction.
636 */
637 static int handle_jump_alt(struct objtool_file *file,
638 struct special_alt *special_alt,
639 struct instruction *orig_insn,
640 struct instruction **new_insn)
641 {
642 if (orig_insn->type == INSN_NOP)
643 return 0;
644
645 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
646 WARN_FUNC("unsupported instruction at jump label",
647 orig_insn->sec, orig_insn->offset);
648 return -1;
649 }
650
651 *new_insn = list_next_entry(orig_insn, list);
652 return 0;
653 }
654
655 /*
656 * Read all the special sections which have alternate instructions which can be
657 * patched in or redirected to at runtime. Each instruction having alternate
658 * instruction(s) has them added to its insn->alts list, which will be
659 * traversed in validate_branch().
660 */
661 static int add_special_section_alts(struct objtool_file *file)
662 {
663 struct list_head special_alts;
664 struct instruction *orig_insn, *new_insn;
665 struct special_alt *special_alt, *tmp;
666 struct alternative *alt;
667 int ret;
668
669 ret = special_get_alts(file->elf, &special_alts);
670 if (ret)
671 return ret;
672
673 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
674 alt = malloc(sizeof(*alt));
675 if (!alt) {
676 WARN("malloc failed");
677 ret = -1;
678 goto out;
679 }
680
681 orig_insn = find_insn(file, special_alt->orig_sec,
682 special_alt->orig_off);
683 if (!orig_insn) {
684 WARN_FUNC("special: can't find orig instruction",
685 special_alt->orig_sec, special_alt->orig_off);
686 ret = -1;
687 goto out;
688 }
689
690 new_insn = NULL;
691 if (!special_alt->group || special_alt->new_len) {
692 new_insn = find_insn(file, special_alt->new_sec,
693 special_alt->new_off);
694 if (!new_insn) {
695 WARN_FUNC("special: can't find new instruction",
696 special_alt->new_sec,
697 special_alt->new_off);
698 ret = -1;
699 goto out;
700 }
701 }
702
703 if (special_alt->group) {
704 ret = handle_group_alt(file, special_alt, orig_insn,
705 &new_insn);
706 if (ret)
707 goto out;
708 } else if (special_alt->jump_or_nop) {
709 ret = handle_jump_alt(file, special_alt, orig_insn,
710 &new_insn);
711 if (ret)
712 goto out;
713 }
714
715 alt->insn = new_insn;
716 list_add_tail(&alt->list, &orig_insn->alts);
717
718 list_del(&special_alt->list);
719 free(special_alt);
720 }
721
722 out:
723 return ret;
724 }
725
726 static int add_switch_table(struct objtool_file *file, struct symbol *func,
727 struct instruction *insn, struct rela *table,
728 struct rela *next_table)
729 {
730 struct rela *rela = table;
731 struct instruction *alt_insn;
732 struct alternative *alt;
733
734 list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) {
735 if (rela == next_table)
736 break;
737
738 if (rela->sym->sec != insn->sec ||
739 rela->addend <= func->offset ||
740 rela->addend >= func->offset + func->len)
741 break;
742
743 alt_insn = find_insn(file, insn->sec, rela->addend);
744 if (!alt_insn) {
745 WARN("%s: can't find instruction at %s+0x%x",
746 file->rodata->rela->name, insn->sec->name,
747 rela->addend);
748 return -1;
749 }
750
751 alt = malloc(sizeof(*alt));
752 if (!alt) {
753 WARN("malloc failed");
754 return -1;
755 }
756
757 alt->insn = alt_insn;
758 list_add_tail(&alt->list, &insn->alts);
759 }
760
761 return 0;
762 }
763
764 /*
765 * find_switch_table() - Given a dynamic jump, find the switch jump table in
766 * .rodata associated with it.
767 *
768 * There are 3 basic patterns:
769 *
770 * 1. jmpq *[rodata addr](,%reg,8)
771 *
772 * This is the most common case by far. It jumps to an address in a simple
773 * jump table which is stored in .rodata.
774 *
775 * 2. jmpq *[rodata addr](%rip)
776 *
777 * This is caused by a rare GCC quirk, currently only seen in three driver
778 * functions in the kernel, only with certain obscure non-distro configs.
779 *
780 * As part of an optimization, GCC makes a copy of an existing switch jump
781 * table, modifies it, and then hard-codes the jump (albeit with an indirect
782 * jump) to use a single entry in the table. The rest of the jump table and
783 * some of its jump targets remain as dead code.
784 *
785 * In such a case we can just crudely ignore all unreachable instruction
786 * warnings for the entire object file. Ideally we would just ignore them
787 * for the function, but that would require redesigning the code quite a
788 * bit. And honestly that's just not worth doing: unreachable instruction
789 * warnings are of questionable value anyway, and this is such a rare issue.
790 *
791 * 3. mov [rodata addr],%reg1
792 * ... some instructions ...
793 * jmpq *(%reg1,%reg2,8)
794 *
795 * This is a fairly uncommon pattern which is new for GCC 6. As of this
796 * writing, there are 11 occurrences of it in the allmodconfig kernel.
797 *
798 * TODO: Once we have DWARF CFI and smarter instruction decoding logic,
799 * ensure the same register is used in the mov and jump instructions.
800 */
801 static struct rela *find_switch_table(struct objtool_file *file,
802 struct symbol *func,
803 struct instruction *insn)
804 {
805 struct rela *text_rela, *rodata_rela;
806 struct instruction *orig_insn = insn;
807
808 text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len);
809 if (text_rela && text_rela->sym == file->rodata->sym) {
810 /* case 1 */
811 rodata_rela = find_rela_by_dest(file->rodata,
812 text_rela->addend);
813 if (rodata_rela)
814 return rodata_rela;
815
816 /* case 2 */
817 rodata_rela = find_rela_by_dest(file->rodata,
818 text_rela->addend + 4);
819 if (!rodata_rela)
820 return NULL;
821 file->ignore_unreachables = true;
822 return rodata_rela;
823 }
824
825 /* case 3 */
826 func_for_each_insn_continue_reverse(file, func, insn) {
827 if (insn->type == INSN_JUMP_DYNAMIC)
828 break;
829
830 /* allow small jumps within the range */
831 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
832 insn->jump_dest &&
833 (insn->jump_dest->offset <= insn->offset ||
834 insn->jump_dest->offset > orig_insn->offset))
835 break;
836
837 /* look for a relocation which references .rodata */
838 text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
839 insn->len);
840 if (!text_rela || text_rela->sym != file->rodata->sym)
841 continue;
842
843 /*
844 * Make sure the .rodata address isn't associated with a
845 * symbol. gcc jump tables are anonymous data.
846 */
847 if (find_symbol_containing(file->rodata, text_rela->addend))
848 continue;
849
850 return find_rela_by_dest(file->rodata, text_rela->addend);
851 }
852
853 return NULL;
854 }
855
856 static int add_func_switch_tables(struct objtool_file *file,
857 struct symbol *func)
858 {
859 struct instruction *insn, *prev_jump = NULL;
860 struct rela *rela, *prev_rela = NULL;
861 int ret;
862
863 func_for_each_insn(file, func, insn) {
864 if (insn->type != INSN_JUMP_DYNAMIC)
865 continue;
866
867 rela = find_switch_table(file, func, insn);
868 if (!rela)
869 continue;
870
871 /*
872 * We found a switch table, but we don't know yet how big it
873 * is. Don't add it until we reach the end of the function or
874 * the beginning of another switch table in the same function.
875 */
876 if (prev_jump) {
877 ret = add_switch_table(file, func, prev_jump, prev_rela,
878 rela);
879 if (ret)
880 return ret;
881 }
882
883 prev_jump = insn;
884 prev_rela = rela;
885 }
886
887 if (prev_jump) {
888 ret = add_switch_table(file, func, prev_jump, prev_rela, NULL);
889 if (ret)
890 return ret;
891 }
892
893 return 0;
894 }
895
896 /*
897 * For some switch statements, gcc generates a jump table in the .rodata
898 * section which contains a list of addresses within the function to jump to.
899 * This finds these jump tables and adds them to the insn->alts lists.
900 */
901 static int add_switch_table_alts(struct objtool_file *file)
902 {
903 struct section *sec;
904 struct symbol *func;
905 int ret;
906
907 if (!file->rodata || !file->rodata->rela)
908 return 0;
909
910 for_each_sec(file, sec) {
911 list_for_each_entry(func, &sec->symbol_list, list) {
912 if (func->type != STT_FUNC)
913 continue;
914
915 ret = add_func_switch_tables(file, func);
916 if (ret)
917 return ret;
918 }
919 }
920
921 return 0;
922 }
923
924 static int read_unwind_hints(struct objtool_file *file)
925 {
926 struct section *sec, *relasec;
927 struct rela *rela;
928 struct unwind_hint *hint;
929 struct instruction *insn;
930 struct cfi_reg *cfa;
931 int i;
932
933 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
934 if (!sec)
935 return 0;
936
937 relasec = sec->rela;
938 if (!relasec) {
939 WARN("missing .rela.discard.unwind_hints section");
940 return -1;
941 }
942
943 if (sec->len % sizeof(struct unwind_hint)) {
944 WARN("struct unwind_hint size mismatch");
945 return -1;
946 }
947
948 file->hints = true;
949
950 for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
951 hint = (struct unwind_hint *)sec->data->d_buf + i;
952
953 rela = find_rela_by_dest(sec, i * sizeof(*hint));
954 if (!rela) {
955 WARN("can't find rela for unwind_hints[%d]", i);
956 return -1;
957 }
958
959 insn = find_insn(file, rela->sym->sec, rela->addend);
960 if (!insn) {
961 WARN("can't find insn for unwind_hints[%d]", i);
962 return -1;
963 }
964
965 cfa = &insn->state.cfa;
966
967 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
968 insn->save = true;
969 continue;
970
971 } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
972 insn->restore = true;
973 insn->hint = true;
974 continue;
975 }
976
977 insn->hint = true;
978
979 switch (hint->sp_reg) {
980 case ORC_REG_UNDEFINED:
981 cfa->base = CFI_UNDEFINED;
982 break;
983 case ORC_REG_SP:
984 cfa->base = CFI_SP;
985 break;
986 case ORC_REG_BP:
987 cfa->base = CFI_BP;
988 break;
989 case ORC_REG_SP_INDIRECT:
990 cfa->base = CFI_SP_INDIRECT;
991 break;
992 case ORC_REG_R10:
993 cfa->base = CFI_R10;
994 break;
995 case ORC_REG_R13:
996 cfa->base = CFI_R13;
997 break;
998 case ORC_REG_DI:
999 cfa->base = CFI_DI;
1000 break;
1001 case ORC_REG_DX:
1002 cfa->base = CFI_DX;
1003 break;
1004 default:
1005 WARN_FUNC("unsupported unwind_hint sp base reg %d",
1006 insn->sec, insn->offset, hint->sp_reg);
1007 return -1;
1008 }
1009
1010 cfa->offset = hint->sp_offset;
1011 insn->state.type = hint->type;
1012 }
1013
1014 return 0;
1015 }
1016
1017 static int decode_sections(struct objtool_file *file)
1018 {
1019 int ret;
1020
1021 ret = decode_instructions(file);
1022 if (ret)
1023 return ret;
1024
1025 ret = add_dead_ends(file);
1026 if (ret)
1027 return ret;
1028
1029 add_ignores(file);
1030
1031 ret = add_jump_destinations(file);
1032 if (ret)
1033 return ret;
1034
1035 ret = add_call_destinations(file);
1036 if (ret)
1037 return ret;
1038
1039 ret = add_special_section_alts(file);
1040 if (ret)
1041 return ret;
1042
1043 ret = add_switch_table_alts(file);
1044 if (ret)
1045 return ret;
1046
1047 ret = read_unwind_hints(file);
1048 if (ret)
1049 return ret;
1050
1051 return 0;
1052 }
1053
1054 static bool is_fentry_call(struct instruction *insn)
1055 {
1056 if (insn->type == INSN_CALL &&
1057 insn->call_dest->type == STT_NOTYPE &&
1058 !strcmp(insn->call_dest->name, "__fentry__"))
1059 return true;
1060
1061 return false;
1062 }
1063
1064 static bool has_modified_stack_frame(struct insn_state *state)
1065 {
1066 int i;
1067
1068 if (state->cfa.base != initial_func_cfi.cfa.base ||
1069 state->cfa.offset != initial_func_cfi.cfa.offset ||
1070 state->stack_size != initial_func_cfi.cfa.offset ||
1071 state->drap)
1072 return true;
1073
1074 for (i = 0; i < CFI_NUM_REGS; i++)
1075 if (state->regs[i].base != initial_func_cfi.regs[i].base ||
1076 state->regs[i].offset != initial_func_cfi.regs[i].offset)
1077 return true;
1078
1079 return false;
1080 }
1081
1082 static bool has_valid_stack_frame(struct insn_state *state)
1083 {
1084 if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
1085 state->regs[CFI_BP].offset == -16)
1086 return true;
1087
1088 if (state->drap && state->regs[CFI_BP].base == CFI_BP)
1089 return true;
1090
1091 return false;
1092 }
1093
1094 static int update_insn_state_regs(struct instruction *insn, struct insn_state *state)
1095 {
1096 struct cfi_reg *cfa = &state->cfa;
1097 struct stack_op *op = &insn->stack_op;
1098
1099 if (cfa->base != CFI_SP)
1100 return 0;
1101
1102 /* push */
1103 if (op->dest.type == OP_DEST_PUSH)
1104 cfa->offset += 8;
1105
1106 /* pop */
1107 if (op->src.type == OP_SRC_POP)
1108 cfa->offset -= 8;
1109
1110 /* add immediate to sp */
1111 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1112 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1113 cfa->offset -= op->src.offset;
1114
1115 return 0;
1116 }
1117
1118 static void save_reg(struct insn_state *state, unsigned char reg, int base,
1119 int offset)
1120 {
1121 if (arch_callee_saved_reg(reg) &&
1122 state->regs[reg].base == CFI_UNDEFINED) {
1123 state->regs[reg].base = base;
1124 state->regs[reg].offset = offset;
1125 }
1126 }
1127
1128 static void restore_reg(struct insn_state *state, unsigned char reg)
1129 {
1130 state->regs[reg].base = CFI_UNDEFINED;
1131 state->regs[reg].offset = 0;
1132 }
1133
1134 /*
1135 * A note about DRAP stack alignment:
1136 *
1137 * GCC has the concept of a DRAP register, which is used to help keep track of
1138 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
1139 * register. The typical DRAP pattern is:
1140 *
1141 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
1142 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
1143 * 41 ff 72 f8 pushq -0x8(%r10)
1144 * 55 push %rbp
1145 * 48 89 e5 mov %rsp,%rbp
1146 * (more pushes)
1147 * 41 52 push %r10
1148 * ...
1149 * 41 5a pop %r10
1150 * (more pops)
1151 * 5d pop %rbp
1152 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1153 * c3 retq
1154 *
1155 * There are some variations in the epilogues, like:
1156 *
1157 * 5b pop %rbx
1158 * 41 5a pop %r10
1159 * 41 5c pop %r12
1160 * 41 5d pop %r13
1161 * 41 5e pop %r14
1162 * c9 leaveq
1163 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1164 * c3 retq
1165 *
1166 * and:
1167 *
1168 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
1169 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
1170 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
1171 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
1172 * c9 leaveq
1173 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1174 * c3 retq
1175 *
1176 * Sometimes r13 is used as the DRAP register, in which case it's saved and
1177 * restored beforehand:
1178 *
1179 * 41 55 push %r13
1180 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
1181 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
1182 * ...
1183 * 49 8d 65 f0 lea -0x10(%r13),%rsp
1184 * 41 5d pop %r13
1185 * c3 retq
1186 */
1187 static int update_insn_state(struct instruction *insn, struct insn_state *state)
1188 {
1189 struct stack_op *op = &insn->stack_op;
1190 struct cfi_reg *cfa = &state->cfa;
1191 struct cfi_reg *regs = state->regs;
1192
1193 /* stack operations don't make sense with an undefined CFA */
1194 if (cfa->base == CFI_UNDEFINED) {
1195 if (insn->func) {
1196 WARN_FUNC("undefined stack state", insn->sec, insn->offset);
1197 return -1;
1198 }
1199 return 0;
1200 }
1201
1202 if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET)
1203 return update_insn_state_regs(insn, state);
1204
1205 switch (op->dest.type) {
1206
1207 case OP_DEST_REG:
1208 switch (op->src.type) {
1209
1210 case OP_SRC_REG:
1211 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
1212 cfa->base == CFI_SP &&
1213 regs[CFI_BP].base == CFI_CFA &&
1214 regs[CFI_BP].offset == -cfa->offset) {
1215
1216 /* mov %rsp, %rbp */
1217 cfa->base = op->dest.reg;
1218 state->bp_scratch = false;
1219 }
1220
1221 else if (op->src.reg == CFI_SP &&
1222 op->dest.reg == CFI_BP && state->drap) {
1223
1224 /* drap: mov %rsp, %rbp */
1225 regs[CFI_BP].base = CFI_BP;
1226 regs[CFI_BP].offset = -state->stack_size;
1227 state->bp_scratch = false;
1228 }
1229
1230 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1231
1232 /*
1233 * mov %rsp, %reg
1234 *
1235 * This is needed for the rare case where GCC
1236 * does:
1237 *
1238 * mov %rsp, %rax
1239 * ...
1240 * mov %rax, %rsp
1241 */
1242 state->vals[op->dest.reg].base = CFI_CFA;
1243 state->vals[op->dest.reg].offset = -state->stack_size;
1244 }
1245
1246 else if (op->dest.reg == cfa->base) {
1247
1248 /* mov %reg, %rsp */
1249 if (cfa->base == CFI_SP &&
1250 state->vals[op->src.reg].base == CFI_CFA) {
1251
1252 /*
1253 * This is needed for the rare case
1254 * where GCC does something dumb like:
1255 *
1256 * lea 0x8(%rsp), %rcx
1257 * ...
1258 * mov %rcx, %rsp
1259 */
1260 cfa->offset = -state->vals[op->src.reg].offset;
1261 state->stack_size = cfa->offset;
1262
1263 } else {
1264 cfa->base = CFI_UNDEFINED;
1265 cfa->offset = 0;
1266 }
1267 }
1268
1269 break;
1270
1271 case OP_SRC_ADD:
1272 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
1273
1274 /* add imm, %rsp */
1275 state->stack_size -= op->src.offset;
1276 if (cfa->base == CFI_SP)
1277 cfa->offset -= op->src.offset;
1278 break;
1279 }
1280
1281 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
1282
1283 /* lea disp(%rbp), %rsp */
1284 state->stack_size = -(op->src.offset + regs[CFI_BP].offset);
1285 break;
1286 }
1287
1288 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1289
1290 /* drap: lea disp(%rsp), %drap */
1291 state->drap_reg = op->dest.reg;
1292
1293 /*
1294 * lea disp(%rsp), %reg
1295 *
1296 * This is needed for the rare case where GCC
1297 * does something dumb like:
1298 *
1299 * lea 0x8(%rsp), %rcx
1300 * ...
1301 * mov %rcx, %rsp
1302 */
1303 state->vals[op->dest.reg].base = CFI_CFA;
1304 state->vals[op->dest.reg].offset = \
1305 -state->stack_size + op->src.offset;
1306
1307 break;
1308 }
1309
1310 if (state->drap && op->dest.reg == CFI_SP &&
1311 op->src.reg == state->drap_reg) {
1312
1313 /* drap: lea disp(%drap), %rsp */
1314 cfa->base = CFI_SP;
1315 cfa->offset = state->stack_size = -op->src.offset;
1316 state->drap_reg = CFI_UNDEFINED;
1317 state->drap = false;
1318 break;
1319 }
1320
1321 if (op->dest.reg == state->cfa.base) {
1322 WARN_FUNC("unsupported stack register modification",
1323 insn->sec, insn->offset);
1324 return -1;
1325 }
1326
1327 break;
1328
1329 case OP_SRC_AND:
1330 if (op->dest.reg != CFI_SP ||
1331 (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
1332 (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
1333 WARN_FUNC("unsupported stack pointer realignment",
1334 insn->sec, insn->offset);
1335 return -1;
1336 }
1337
1338 if (state->drap_reg != CFI_UNDEFINED) {
1339 /* drap: and imm, %rsp */
1340 cfa->base = state->drap_reg;
1341 cfa->offset = state->stack_size = 0;
1342 state->drap = true;
1343 }
1344
1345 /*
1346 * Older versions of GCC (4.8ish) realign the stack
1347 * without DRAP, with a frame pointer.
1348 */
1349
1350 break;
1351
1352 case OP_SRC_POP:
1353 if (!state->drap && op->dest.type == OP_DEST_REG &&
1354 op->dest.reg == cfa->base) {
1355
1356 /* pop %rbp */
1357 cfa->base = CFI_SP;
1358 }
1359
1360 if (state->drap && cfa->base == CFI_BP_INDIRECT &&
1361 op->dest.type == OP_DEST_REG &&
1362 op->dest.reg == state->drap_reg &&
1363 state->drap_offset == -state->stack_size) {
1364
1365 /* drap: pop %drap */
1366 cfa->base = state->drap_reg;
1367 cfa->offset = 0;
1368 state->drap_offset = -1;
1369
1370 } else if (regs[op->dest.reg].offset == -state->stack_size) {
1371
1372 /* pop %reg */
1373 restore_reg(state, op->dest.reg);
1374 }
1375
1376 state->stack_size -= 8;
1377 if (cfa->base == CFI_SP)
1378 cfa->offset -= 8;
1379
1380 break;
1381
1382 case OP_SRC_REG_INDIRECT:
1383 if (state->drap && op->src.reg == CFI_BP &&
1384 op->src.offset == state->drap_offset) {
1385
1386 /* drap: mov disp(%rbp), %drap */
1387 cfa->base = state->drap_reg;
1388 cfa->offset = 0;
1389 state->drap_offset = -1;
1390 }
1391
1392 if (state->drap && op->src.reg == CFI_BP &&
1393 op->src.offset == regs[op->dest.reg].offset) {
1394
1395 /* drap: mov disp(%rbp), %reg */
1396 restore_reg(state, op->dest.reg);
1397
1398 } else if (op->src.reg == cfa->base &&
1399 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
1400
1401 /* mov disp(%rbp), %reg */
1402 /* mov disp(%rsp), %reg */
1403 restore_reg(state, op->dest.reg);
1404 }
1405
1406 break;
1407
1408 default:
1409 WARN_FUNC("unknown stack-related instruction",
1410 insn->sec, insn->offset);
1411 return -1;
1412 }
1413
1414 break;
1415
1416 case OP_DEST_PUSH:
1417 state->stack_size += 8;
1418 if (cfa->base == CFI_SP)
1419 cfa->offset += 8;
1420
1421 if (op->src.type != OP_SRC_REG)
1422 break;
1423
1424 if (state->drap) {
1425 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1426
1427 /* drap: push %drap */
1428 cfa->base = CFI_BP_INDIRECT;
1429 cfa->offset = -state->stack_size;
1430
1431 /* save drap so we know when to restore it */
1432 state->drap_offset = -state->stack_size;
1433
1434 } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
1435
1436 /* drap: push %rbp */
1437 state->stack_size = 0;
1438
1439 } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1440
1441 /* drap: push %reg */
1442 save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
1443 }
1444
1445 } else {
1446
1447 /* push %reg */
1448 save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
1449 }
1450
1451 /* detect when asm code uses rbp as a scratch register */
1452 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
1453 cfa->base != CFI_BP)
1454 state->bp_scratch = true;
1455 break;
1456
1457 case OP_DEST_REG_INDIRECT:
1458
1459 if (state->drap) {
1460 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1461
1462 /* drap: mov %drap, disp(%rbp) */
1463 cfa->base = CFI_BP_INDIRECT;
1464 cfa->offset = op->dest.offset;
1465
1466 /* save drap offset so we know when to restore it */
1467 state->drap_offset = op->dest.offset;
1468 }
1469
1470 else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1471
1472 /* drap: mov reg, disp(%rbp) */
1473 save_reg(state, op->src.reg, CFI_BP, op->dest.offset);
1474 }
1475
1476 } else if (op->dest.reg == cfa->base) {
1477
1478 /* mov reg, disp(%rbp) */
1479 /* mov reg, disp(%rsp) */
1480 save_reg(state, op->src.reg, CFI_CFA,
1481 op->dest.offset - state->cfa.offset);
1482 }
1483
1484 break;
1485
1486 case OP_DEST_LEAVE:
1487 if ((!state->drap && cfa->base != CFI_BP) ||
1488 (state->drap && cfa->base != state->drap_reg)) {
1489 WARN_FUNC("leave instruction with modified stack frame",
1490 insn->sec, insn->offset);
1491 return -1;
1492 }
1493
1494 /* leave (mov %rbp, %rsp; pop %rbp) */
1495
1496 state->stack_size = -state->regs[CFI_BP].offset - 8;
1497 restore_reg(state, CFI_BP);
1498
1499 if (!state->drap) {
1500 cfa->base = CFI_SP;
1501 cfa->offset -= 8;
1502 }
1503
1504 break;
1505
1506 case OP_DEST_MEM:
1507 if (op->src.type != OP_SRC_POP) {
1508 WARN_FUNC("unknown stack-related memory operation",
1509 insn->sec, insn->offset);
1510 return -1;
1511 }
1512
1513 /* pop mem */
1514 state->stack_size -= 8;
1515 if (cfa->base == CFI_SP)
1516 cfa->offset -= 8;
1517
1518 break;
1519
1520 default:
1521 WARN_FUNC("unknown stack-related instruction",
1522 insn->sec, insn->offset);
1523 return -1;
1524 }
1525
1526 return 0;
1527 }
1528
1529 static bool insn_state_match(struct instruction *insn, struct insn_state *state)
1530 {
1531 struct insn_state *state1 = &insn->state, *state2 = state;
1532 int i;
1533
1534 if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
1535 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
1536 insn->sec, insn->offset,
1537 state1->cfa.base, state1->cfa.offset,
1538 state2->cfa.base, state2->cfa.offset);
1539
1540 } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
1541 for (i = 0; i < CFI_NUM_REGS; i++) {
1542 if (!memcmp(&state1->regs[i], &state2->regs[i],
1543 sizeof(struct cfi_reg)))
1544 continue;
1545
1546 WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
1547 insn->sec, insn->offset,
1548 i, state1->regs[i].base, state1->regs[i].offset,
1549 i, state2->regs[i].base, state2->regs[i].offset);
1550 break;
1551 }
1552
1553 } else if (state1->type != state2->type) {
1554 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
1555 insn->sec, insn->offset, state1->type, state2->type);
1556
1557 } else if (state1->drap != state2->drap ||
1558 (state1->drap && state1->drap_reg != state2->drap_reg) ||
1559 (state1->drap && state1->drap_offset != state2->drap_offset)) {
1560 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
1561 insn->sec, insn->offset,
1562 state1->drap, state1->drap_reg, state1->drap_offset,
1563 state2->drap, state2->drap_reg, state2->drap_offset);
1564
1565 } else
1566 return true;
1567
1568 return false;
1569 }
1570
1571 /*
1572 * Follow the branch starting at the given instruction, and recursively follow
1573 * any other branches (jumps). Meanwhile, track the frame pointer state at
1574 * each instruction and validate all the rules described in
1575 * tools/objtool/Documentation/stack-validation.txt.
1576 */
1577 static int validate_branch(struct objtool_file *file, struct instruction *first,
1578 struct insn_state state)
1579 {
1580 struct alternative *alt;
1581 struct instruction *insn, *next_insn;
1582 struct section *sec;
1583 struct symbol *func = NULL;
1584 int ret;
1585
1586 insn = first;
1587 sec = insn->sec;
1588
1589 if (insn->alt_group && list_empty(&insn->alts)) {
1590 WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
1591 sec, insn->offset);
1592 return 1;
1593 }
1594
1595 while (1) {
1596 next_insn = next_insn_same_sec(file, insn);
1597
1598
1599 if (file->c_file && func && insn->func && func != insn->func) {
1600 WARN("%s() falls through to next function %s()",
1601 func->name, insn->func->name);
1602 return 1;
1603 }
1604
1605 if (insn->func)
1606 func = insn->func;
1607
1608 if (func && insn->ignore) {
1609 WARN_FUNC("BUG: why am I validating an ignored function?",
1610 sec, insn->offset);
1611 return 1;
1612 }
1613
1614 if (insn->visited) {
1615 if (!insn->hint && !insn_state_match(insn, &state))
1616 return 1;
1617
1618 return 0;
1619 }
1620
1621 if (insn->hint) {
1622 if (insn->restore) {
1623 struct instruction *save_insn, *i;
1624
1625 i = insn;
1626 save_insn = NULL;
1627 func_for_each_insn_continue_reverse(file, func, i) {
1628 if (i->save) {
1629 save_insn = i;
1630 break;
1631 }
1632 }
1633
1634 if (!save_insn) {
1635 WARN_FUNC("no corresponding CFI save for CFI restore",
1636 sec, insn->offset);
1637 return 1;
1638 }
1639
1640 if (!save_insn->visited) {
1641 /*
1642 * Oops, no state to copy yet.
1643 * Hopefully we can reach this
1644 * instruction from another branch
1645 * after the save insn has been
1646 * visited.
1647 */
1648 if (insn == first)
1649 return 0;
1650
1651 WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
1652 sec, insn->offset);
1653 return 1;
1654 }
1655
1656 insn->state = save_insn->state;
1657 }
1658
1659 state = insn->state;
1660
1661 } else
1662 insn->state = state;
1663
1664 insn->visited = true;
1665
1666 list_for_each_entry(alt, &insn->alts, list) {
1667 ret = validate_branch(file, alt->insn, state);
1668 if (ret)
1669 return 1;
1670 }
1671
1672 switch (insn->type) {
1673
1674 case INSN_RETURN:
1675 if (func && has_modified_stack_frame(&state)) {
1676 WARN_FUNC("return with modified stack frame",
1677 sec, insn->offset);
1678 return 1;
1679 }
1680
1681 if (state.bp_scratch) {
1682 WARN("%s uses BP as a scratch register",
1683 insn->func->name);
1684 return 1;
1685 }
1686
1687 return 0;
1688
1689 case INSN_CALL:
1690 if (is_fentry_call(insn))
1691 break;
1692
1693 ret = dead_end_function(file, insn->call_dest);
1694 if (ret == 1)
1695 return 0;
1696 if (ret == -1)
1697 return 1;
1698
1699 /* fallthrough */
1700 case INSN_CALL_DYNAMIC:
1701 if (!no_fp && func && !has_valid_stack_frame(&state)) {
1702 WARN_FUNC("call without frame pointer save/setup",
1703 sec, insn->offset);
1704 return 1;
1705 }
1706 break;
1707
1708 case INSN_JUMP_CONDITIONAL:
1709 case INSN_JUMP_UNCONDITIONAL:
1710 if (insn->jump_dest &&
1711 (!func || !insn->jump_dest->func ||
1712 func == insn->jump_dest->func)) {
1713 ret = validate_branch(file, insn->jump_dest,
1714 state);
1715 if (ret)
1716 return 1;
1717
1718 } else if (func && has_modified_stack_frame(&state)) {
1719 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1720 sec, insn->offset);
1721 return 1;
1722 }
1723
1724 if (insn->type == INSN_JUMP_UNCONDITIONAL)
1725 return 0;
1726
1727 break;
1728
1729 case INSN_JUMP_DYNAMIC:
1730 if (func && list_empty(&insn->alts) &&
1731 has_modified_stack_frame(&state)) {
1732 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1733 sec, insn->offset);
1734 return 1;
1735 }
1736
1737 return 0;
1738
1739 case INSN_CONTEXT_SWITCH:
1740 if (func && (!next_insn || !next_insn->hint)) {
1741 WARN_FUNC("unsupported instruction in callable function",
1742 sec, insn->offset);
1743 return 1;
1744 }
1745 return 0;
1746
1747 case INSN_STACK:
1748 if (update_insn_state(insn, &state))
1749 return 1;
1750
1751 break;
1752
1753 default:
1754 break;
1755 }
1756
1757 if (insn->dead_end)
1758 return 0;
1759
1760 if (!next_insn) {
1761 if (state.cfa.base == CFI_UNDEFINED)
1762 return 0;
1763 WARN("%s: unexpected end of section", sec->name);
1764 return 1;
1765 }
1766
1767 insn = next_insn;
1768 }
1769
1770 return 0;
1771 }
1772
1773 static int validate_unwind_hints(struct objtool_file *file)
1774 {
1775 struct instruction *insn;
1776 int ret, warnings = 0;
1777 struct insn_state state;
1778
1779 if (!file->hints)
1780 return 0;
1781
1782 clear_insn_state(&state);
1783
1784 for_each_insn(file, insn) {
1785 if (insn->hint && !insn->visited) {
1786 ret = validate_branch(file, insn, state);
1787 warnings += ret;
1788 }
1789 }
1790
1791 return warnings;
1792 }
1793
1794 static bool is_kasan_insn(struct instruction *insn)
1795 {
1796 return (insn->type == INSN_CALL &&
1797 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
1798 }
1799
1800 static bool is_ubsan_insn(struct instruction *insn)
1801 {
1802 return (insn->type == INSN_CALL &&
1803 !strcmp(insn->call_dest->name,
1804 "__ubsan_handle_builtin_unreachable"));
1805 }
1806
1807 static bool ignore_unreachable_insn(struct instruction *insn)
1808 {
1809 int i;
1810
1811 if (insn->ignore || insn->type == INSN_NOP)
1812 return true;
1813
1814 /*
1815 * Ignore any unused exceptions. This can happen when a whitelisted
1816 * function has an exception table entry.
1817 *
1818 * Also ignore alternative replacement instructions. This can happen
1819 * when a whitelisted function uses one of the ALTERNATIVE macros.
1820 */
1821 if (!strcmp(insn->sec->name, ".fixup") ||
1822 !strcmp(insn->sec->name, ".altinstr_replacement") ||
1823 !strcmp(insn->sec->name, ".altinstr_aux"))
1824 return true;
1825
1826 /*
1827 * Check if this (or a subsequent) instruction is related to
1828 * CONFIG_UBSAN or CONFIG_KASAN.
1829 *
1830 * End the search at 5 instructions to avoid going into the weeds.
1831 */
1832 if (!insn->func)
1833 return false;
1834 for (i = 0; i < 5; i++) {
1835
1836 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
1837 return true;
1838
1839 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest) {
1840 insn = insn->jump_dest;
1841 continue;
1842 }
1843
1844 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
1845 break;
1846 insn = list_next_entry(insn, list);
1847 }
1848
1849 return false;
1850 }
1851
1852 static int validate_functions(struct objtool_file *file)
1853 {
1854 struct section *sec;
1855 struct symbol *func;
1856 struct instruction *insn;
1857 struct insn_state state;
1858 int ret, warnings = 0;
1859
1860 clear_insn_state(&state);
1861
1862 state.cfa = initial_func_cfi.cfa;
1863 memcpy(&state.regs, &initial_func_cfi.regs,
1864 CFI_NUM_REGS * sizeof(struct cfi_reg));
1865 state.stack_size = initial_func_cfi.cfa.offset;
1866
1867 for_each_sec(file, sec) {
1868 list_for_each_entry(func, &sec->symbol_list, list) {
1869 if (func->type != STT_FUNC)
1870 continue;
1871
1872 insn = find_insn(file, sec, func->offset);
1873 if (!insn || insn->ignore)
1874 continue;
1875
1876 ret = validate_branch(file, insn, state);
1877 warnings += ret;
1878 }
1879 }
1880
1881 return warnings;
1882 }
1883
1884 static int validate_reachable_instructions(struct objtool_file *file)
1885 {
1886 struct instruction *insn;
1887
1888 if (file->ignore_unreachables)
1889 return 0;
1890
1891 for_each_insn(file, insn) {
1892 if (insn->visited || ignore_unreachable_insn(insn))
1893 continue;
1894
1895 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
1896 return 1;
1897 }
1898
1899 return 0;
1900 }
1901
1902 static void cleanup(struct objtool_file *file)
1903 {
1904 struct instruction *insn, *tmpinsn;
1905 struct alternative *alt, *tmpalt;
1906
1907 list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) {
1908 list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) {
1909 list_del(&alt->list);
1910 free(alt);
1911 }
1912 list_del(&insn->list);
1913 hash_del(&insn->hash);
1914 free(insn);
1915 }
1916 elf_close(file->elf);
1917 }
1918
1919 int check(const char *_objname, bool _no_fp, bool no_unreachable, bool orc)
1920 {
1921 struct objtool_file file;
1922 int ret, warnings = 0;
1923
1924 objname = _objname;
1925 no_fp = _no_fp;
1926
1927 file.elf = elf_open(objname, orc ? O_RDWR : O_RDONLY);
1928 if (!file.elf)
1929 return 1;
1930
1931 INIT_LIST_HEAD(&file.insn_list);
1932 hash_init(file.insn_hash);
1933 file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard");
1934 file.rodata = find_section_by_name(file.elf, ".rodata");
1935 file.c_file = find_section_by_name(file.elf, ".comment");
1936 file.ignore_unreachables = no_unreachable;
1937 file.hints = false;
1938
1939 arch_initial_func_cfi_state(&initial_func_cfi);
1940
1941 ret = decode_sections(&file);
1942 if (ret < 0)
1943 goto out;
1944 warnings += ret;
1945
1946 if (list_empty(&file.insn_list))
1947 goto out;
1948
1949 ret = validate_functions(&file);
1950 if (ret < 0)
1951 goto out;
1952 warnings += ret;
1953
1954 ret = validate_unwind_hints(&file);
1955 if (ret < 0)
1956 goto out;
1957 warnings += ret;
1958
1959 if (!warnings) {
1960 ret = validate_reachable_instructions(&file);
1961 if (ret < 0)
1962 goto out;
1963 warnings += ret;
1964 }
1965
1966 if (orc) {
1967 ret = create_orc(&file);
1968 if (ret < 0)
1969 goto out;
1970
1971 ret = create_orc_sections(&file);
1972 if (ret < 0)
1973 goto out;
1974
1975 ret = elf_write(file.elf);
1976 if (ret < 0)
1977 goto out;
1978 }
1979
1980 out:
1981 cleanup(&file);
1982
1983 /* ignore warnings for now until we get all the code cleaned up */
1984 if (ret || warnings)
1985 return 0;
1986 return 0;
1987 }
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