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[thirdparty/linux.git] / tools / objtool / check.c
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
4 */
5
6 #include <string.h>
7 #include <stdlib.h>
8
9 #include "builtin.h"
10 #include "check.h"
11 #include "elf.h"
12 #include "special.h"
13 #include "arch.h"
14 #include "warn.h"
15
16 #include <linux/hashtable.h>
17 #include <linux/kernel.h>
18
19 #define FAKE_JUMP_OFFSET -1
20
21 #define C_JUMP_TABLE_SECTION ".rodata..c_jump_table"
22
23 struct alternative {
24 struct list_head list;
25 struct instruction *insn;
26 bool skip_orig;
27 };
28
29 const char *objname;
30 struct cfi_state initial_func_cfi;
31
32 struct instruction *find_insn(struct objtool_file *file,
33 struct section *sec, unsigned long offset)
34 {
35 struct instruction *insn;
36
37 hash_for_each_possible(file->insn_hash, insn, hash, offset)
38 if (insn->sec == sec && insn->offset == offset)
39 return insn;
40
41 return NULL;
42 }
43
44 static struct instruction *next_insn_same_sec(struct objtool_file *file,
45 struct instruction *insn)
46 {
47 struct instruction *next = list_next_entry(insn, list);
48
49 if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
50 return NULL;
51
52 return next;
53 }
54
55 static struct instruction *next_insn_same_func(struct objtool_file *file,
56 struct instruction *insn)
57 {
58 struct instruction *next = list_next_entry(insn, list);
59 struct symbol *func = insn->func;
60
61 if (!func)
62 return NULL;
63
64 if (&next->list != &file->insn_list && next->func == func)
65 return next;
66
67 /* Check if we're already in the subfunction: */
68 if (func == func->cfunc)
69 return NULL;
70
71 /* Move to the subfunction: */
72 return find_insn(file, func->cfunc->sec, func->cfunc->offset);
73 }
74
75 #define func_for_each_insn_all(file, func, insn) \
76 for (insn = find_insn(file, func->sec, func->offset); \
77 insn; \
78 insn = next_insn_same_func(file, insn))
79
80 #define func_for_each_insn(file, func, insn) \
81 for (insn = find_insn(file, func->sec, func->offset); \
82 insn && &insn->list != &file->insn_list && \
83 insn->sec == func->sec && \
84 insn->offset < func->offset + func->len; \
85 insn = list_next_entry(insn, list))
86
87 #define func_for_each_insn_continue_reverse(file, func, insn) \
88 for (insn = list_prev_entry(insn, list); \
89 &insn->list != &file->insn_list && \
90 insn->sec == func->sec && insn->offset >= func->offset; \
91 insn = list_prev_entry(insn, list))
92
93 #define sec_for_each_insn_from(file, insn) \
94 for (; insn; insn = next_insn_same_sec(file, insn))
95
96 #define sec_for_each_insn_continue(file, insn) \
97 for (insn = next_insn_same_sec(file, insn); insn; \
98 insn = next_insn_same_sec(file, insn))
99
100 static bool is_sibling_call(struct instruction *insn)
101 {
102 /* An indirect jump is either a sibling call or a jump to a table. */
103 if (insn->type == INSN_JUMP_DYNAMIC)
104 return list_empty(&insn->alts);
105
106 if (insn->type != INSN_JUMP_CONDITIONAL &&
107 insn->type != INSN_JUMP_UNCONDITIONAL)
108 return false;
109
110 /* add_jump_destinations() sets insn->call_dest for sibling calls. */
111 return !!insn->call_dest;
112 }
113
114 /*
115 * This checks to see if the given function is a "noreturn" function.
116 *
117 * For global functions which are outside the scope of this object file, we
118 * have to keep a manual list of them.
119 *
120 * For local functions, we have to detect them manually by simply looking for
121 * the lack of a return instruction.
122 */
123 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
124 int recursion)
125 {
126 int i;
127 struct instruction *insn;
128 bool empty = true;
129
130 /*
131 * Unfortunately these have to be hard coded because the noreturn
132 * attribute isn't provided in ELF data.
133 */
134 static const char * const global_noreturns[] = {
135 "__stack_chk_fail",
136 "panic",
137 "do_exit",
138 "do_task_dead",
139 "__module_put_and_exit",
140 "complete_and_exit",
141 "kvm_spurious_fault",
142 "__reiserfs_panic",
143 "lbug_with_loc",
144 "fortify_panic",
145 "usercopy_abort",
146 "machine_real_restart",
147 "rewind_stack_do_exit",
148 };
149
150 if (!func)
151 return false;
152
153 if (func->bind == STB_WEAK)
154 return false;
155
156 if (func->bind == STB_GLOBAL)
157 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
158 if (!strcmp(func->name, global_noreturns[i]))
159 return true;
160
161 if (!func->len)
162 return false;
163
164 insn = find_insn(file, func->sec, func->offset);
165 if (!insn->func)
166 return false;
167
168 func_for_each_insn_all(file, func, insn) {
169 empty = false;
170
171 if (insn->type == INSN_RETURN)
172 return false;
173 }
174
175 if (empty)
176 return false;
177
178 /*
179 * A function can have a sibling call instead of a return. In that
180 * case, the function's dead-end status depends on whether the target
181 * of the sibling call returns.
182 */
183 func_for_each_insn_all(file, func, insn) {
184 if (is_sibling_call(insn)) {
185 struct instruction *dest = insn->jump_dest;
186
187 if (!dest)
188 /* sibling call to another file */
189 return false;
190
191 /* local sibling call */
192 if (recursion == 5) {
193 /*
194 * Infinite recursion: two functions have
195 * sibling calls to each other. This is a very
196 * rare case. It means they aren't dead ends.
197 */
198 return false;
199 }
200
201 return __dead_end_function(file, dest->func, recursion+1);
202 }
203 }
204
205 return true;
206 }
207
208 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
209 {
210 return __dead_end_function(file, func, 0);
211 }
212
213 static void clear_insn_state(struct insn_state *state)
214 {
215 int i;
216
217 memset(state, 0, sizeof(*state));
218 state->cfa.base = CFI_UNDEFINED;
219 for (i = 0; i < CFI_NUM_REGS; i++) {
220 state->regs[i].base = CFI_UNDEFINED;
221 state->vals[i].base = CFI_UNDEFINED;
222 }
223 state->drap_reg = CFI_UNDEFINED;
224 state->drap_offset = -1;
225 }
226
227 /*
228 * Call the arch-specific instruction decoder for all the instructions and add
229 * them to the global instruction list.
230 */
231 static int decode_instructions(struct objtool_file *file)
232 {
233 struct section *sec;
234 struct symbol *func;
235 unsigned long offset;
236 struct instruction *insn;
237 int ret;
238
239 for_each_sec(file, sec) {
240
241 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
242 continue;
243
244 if (strcmp(sec->name, ".altinstr_replacement") &&
245 strcmp(sec->name, ".altinstr_aux") &&
246 strncmp(sec->name, ".discard.", 9))
247 sec->text = true;
248
249 for (offset = 0; offset < sec->len; offset += insn->len) {
250 insn = malloc(sizeof(*insn));
251 if (!insn) {
252 WARN("malloc failed");
253 return -1;
254 }
255 memset(insn, 0, sizeof(*insn));
256 INIT_LIST_HEAD(&insn->alts);
257 clear_insn_state(&insn->state);
258
259 insn->sec = sec;
260 insn->offset = offset;
261
262 ret = arch_decode_instruction(file->elf, sec, offset,
263 sec->len - offset,
264 &insn->len, &insn->type,
265 &insn->immediate,
266 &insn->stack_op);
267 if (ret)
268 goto err;
269
270 hash_add(file->insn_hash, &insn->hash, insn->offset);
271 list_add_tail(&insn->list, &file->insn_list);
272 }
273
274 list_for_each_entry(func, &sec->symbol_list, list) {
275 if (func->type != STT_FUNC || func->alias != func)
276 continue;
277
278 if (!find_insn(file, sec, func->offset)) {
279 WARN("%s(): can't find starting instruction",
280 func->name);
281 return -1;
282 }
283
284 func_for_each_insn(file, func, insn)
285 insn->func = func;
286 }
287 }
288
289 return 0;
290
291 err:
292 free(insn);
293 return ret;
294 }
295
296 /*
297 * Mark "ud2" instructions and manually annotated dead ends.
298 */
299 static int add_dead_ends(struct objtool_file *file)
300 {
301 struct section *sec;
302 struct rela *rela;
303 struct instruction *insn;
304 bool found;
305
306 /*
307 * By default, "ud2" is a dead end unless otherwise annotated, because
308 * GCC 7 inserts it for certain divide-by-zero cases.
309 */
310 for_each_insn(file, insn)
311 if (insn->type == INSN_BUG)
312 insn->dead_end = true;
313
314 /*
315 * Check for manually annotated dead ends.
316 */
317 sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
318 if (!sec)
319 goto reachable;
320
321 list_for_each_entry(rela, &sec->rela_list, list) {
322 if (rela->sym->type != STT_SECTION) {
323 WARN("unexpected relocation symbol type in %s", sec->name);
324 return -1;
325 }
326 insn = find_insn(file, rela->sym->sec, rela->addend);
327 if (insn)
328 insn = list_prev_entry(insn, list);
329 else if (rela->addend == rela->sym->sec->len) {
330 found = false;
331 list_for_each_entry_reverse(insn, &file->insn_list, list) {
332 if (insn->sec == rela->sym->sec) {
333 found = true;
334 break;
335 }
336 }
337
338 if (!found) {
339 WARN("can't find unreachable insn at %s+0x%x",
340 rela->sym->sec->name, rela->addend);
341 return -1;
342 }
343 } else {
344 WARN("can't find unreachable insn at %s+0x%x",
345 rela->sym->sec->name, rela->addend);
346 return -1;
347 }
348
349 insn->dead_end = true;
350 }
351
352 reachable:
353 /*
354 * These manually annotated reachable checks are needed for GCC 4.4,
355 * where the Linux unreachable() macro isn't supported. In that case
356 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
357 * not a dead end.
358 */
359 sec = find_section_by_name(file->elf, ".rela.discard.reachable");
360 if (!sec)
361 return 0;
362
363 list_for_each_entry(rela, &sec->rela_list, list) {
364 if (rela->sym->type != STT_SECTION) {
365 WARN("unexpected relocation symbol type in %s", sec->name);
366 return -1;
367 }
368 insn = find_insn(file, rela->sym->sec, rela->addend);
369 if (insn)
370 insn = list_prev_entry(insn, list);
371 else if (rela->addend == rela->sym->sec->len) {
372 found = false;
373 list_for_each_entry_reverse(insn, &file->insn_list, list) {
374 if (insn->sec == rela->sym->sec) {
375 found = true;
376 break;
377 }
378 }
379
380 if (!found) {
381 WARN("can't find reachable insn at %s+0x%x",
382 rela->sym->sec->name, rela->addend);
383 return -1;
384 }
385 } else {
386 WARN("can't find reachable insn at %s+0x%x",
387 rela->sym->sec->name, rela->addend);
388 return -1;
389 }
390
391 insn->dead_end = false;
392 }
393
394 return 0;
395 }
396
397 /*
398 * Warnings shouldn't be reported for ignored functions.
399 */
400 static void add_ignores(struct objtool_file *file)
401 {
402 struct instruction *insn;
403 struct section *sec;
404 struct symbol *func;
405 struct rela *rela;
406
407 sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
408 if (!sec)
409 return;
410
411 list_for_each_entry(rela, &sec->rela_list, list) {
412 switch (rela->sym->type) {
413 case STT_FUNC:
414 func = rela->sym;
415 break;
416
417 case STT_SECTION:
418 func = find_symbol_by_offset(rela->sym->sec, rela->addend);
419 if (!func || func->type != STT_FUNC)
420 continue;
421 break;
422
423 default:
424 WARN("unexpected relocation symbol type in %s: %d", sec->name, rela->sym->type);
425 continue;
426 }
427
428 func_for_each_insn_all(file, func, insn)
429 insn->ignore = true;
430 }
431 }
432
433 /*
434 * This is a whitelist of functions that is allowed to be called with AC set.
435 * The list is meant to be minimal and only contains compiler instrumentation
436 * ABI and a few functions used to implement *_{to,from}_user() functions.
437 *
438 * These functions must not directly change AC, but may PUSHF/POPF.
439 */
440 static const char *uaccess_safe_builtin[] = {
441 /* KASAN */
442 "kasan_report",
443 "check_memory_region",
444 /* KASAN out-of-line */
445 "__asan_loadN_noabort",
446 "__asan_load1_noabort",
447 "__asan_load2_noabort",
448 "__asan_load4_noabort",
449 "__asan_load8_noabort",
450 "__asan_load16_noabort",
451 "__asan_storeN_noabort",
452 "__asan_store1_noabort",
453 "__asan_store2_noabort",
454 "__asan_store4_noabort",
455 "__asan_store8_noabort",
456 "__asan_store16_noabort",
457 /* KASAN in-line */
458 "__asan_report_load_n_noabort",
459 "__asan_report_load1_noabort",
460 "__asan_report_load2_noabort",
461 "__asan_report_load4_noabort",
462 "__asan_report_load8_noabort",
463 "__asan_report_load16_noabort",
464 "__asan_report_store_n_noabort",
465 "__asan_report_store1_noabort",
466 "__asan_report_store2_noabort",
467 "__asan_report_store4_noabort",
468 "__asan_report_store8_noabort",
469 "__asan_report_store16_noabort",
470 /* KCOV */
471 "write_comp_data",
472 "__sanitizer_cov_trace_pc",
473 "__sanitizer_cov_trace_const_cmp1",
474 "__sanitizer_cov_trace_const_cmp2",
475 "__sanitizer_cov_trace_const_cmp4",
476 "__sanitizer_cov_trace_const_cmp8",
477 "__sanitizer_cov_trace_cmp1",
478 "__sanitizer_cov_trace_cmp2",
479 "__sanitizer_cov_trace_cmp4",
480 "__sanitizer_cov_trace_cmp8",
481 /* UBSAN */
482 "ubsan_type_mismatch_common",
483 "__ubsan_handle_type_mismatch",
484 "__ubsan_handle_type_mismatch_v1",
485 /* misc */
486 "csum_partial_copy_generic",
487 "__memcpy_mcsafe",
488 "mcsafe_handle_tail",
489 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
490 NULL
491 };
492
493 static void add_uaccess_safe(struct objtool_file *file)
494 {
495 struct symbol *func;
496 const char **name;
497
498 if (!uaccess)
499 return;
500
501 for (name = uaccess_safe_builtin; *name; name++) {
502 func = find_symbol_by_name(file->elf, *name);
503 if (!func)
504 continue;
505
506 func->uaccess_safe = true;
507 }
508 }
509
510 /*
511 * FIXME: For now, just ignore any alternatives which add retpolines. This is
512 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
513 * But it at least allows objtool to understand the control flow *around* the
514 * retpoline.
515 */
516 static int add_ignore_alternatives(struct objtool_file *file)
517 {
518 struct section *sec;
519 struct rela *rela;
520 struct instruction *insn;
521
522 sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
523 if (!sec)
524 return 0;
525
526 list_for_each_entry(rela, &sec->rela_list, list) {
527 if (rela->sym->type != STT_SECTION) {
528 WARN("unexpected relocation symbol type in %s", sec->name);
529 return -1;
530 }
531
532 insn = find_insn(file, rela->sym->sec, rela->addend);
533 if (!insn) {
534 WARN("bad .discard.ignore_alts entry");
535 return -1;
536 }
537
538 insn->ignore_alts = true;
539 }
540
541 return 0;
542 }
543
544 /*
545 * Find the destination instructions for all jumps.
546 */
547 static int add_jump_destinations(struct objtool_file *file)
548 {
549 struct instruction *insn;
550 struct rela *rela;
551 struct section *dest_sec;
552 unsigned long dest_off;
553
554 for_each_insn(file, insn) {
555 if (insn->type != INSN_JUMP_CONDITIONAL &&
556 insn->type != INSN_JUMP_UNCONDITIONAL)
557 continue;
558
559 if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET)
560 continue;
561
562 rela = find_rela_by_dest_range(insn->sec, insn->offset,
563 insn->len);
564 if (!rela) {
565 dest_sec = insn->sec;
566 dest_off = insn->offset + insn->len + insn->immediate;
567 } else if (rela->sym->type == STT_SECTION) {
568 dest_sec = rela->sym->sec;
569 dest_off = rela->addend + 4;
570 } else if (rela->sym->sec->idx) {
571 dest_sec = rela->sym->sec;
572 dest_off = rela->sym->sym.st_value + rela->addend + 4;
573 } else if (strstr(rela->sym->name, "_indirect_thunk_")) {
574 /*
575 * Retpoline jumps are really dynamic jumps in
576 * disguise, so convert them accordingly.
577 */
578 if (insn->type == INSN_JUMP_UNCONDITIONAL)
579 insn->type = INSN_JUMP_DYNAMIC;
580 else
581 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
582
583 insn->retpoline_safe = true;
584 continue;
585 } else {
586 /* external sibling call */
587 insn->call_dest = rela->sym;
588 continue;
589 }
590
591 insn->jump_dest = find_insn(file, dest_sec, dest_off);
592 if (!insn->jump_dest) {
593
594 /*
595 * This is a special case where an alt instruction
596 * jumps past the end of the section. These are
597 * handled later in handle_group_alt().
598 */
599 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
600 continue;
601
602 WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
603 insn->sec, insn->offset, dest_sec->name,
604 dest_off);
605 return -1;
606 }
607
608 /*
609 * Cross-function jump.
610 */
611 if (insn->func && insn->jump_dest->func &&
612 insn->func != insn->jump_dest->func) {
613
614 /*
615 * For GCC 8+, create parent/child links for any cold
616 * subfunctions. This is _mostly_ redundant with a
617 * similar initialization in read_symbols().
618 *
619 * If a function has aliases, we want the *first* such
620 * function in the symbol table to be the subfunction's
621 * parent. In that case we overwrite the
622 * initialization done in read_symbols().
623 *
624 * However this code can't completely replace the
625 * read_symbols() code because this doesn't detect the
626 * case where the parent function's only reference to a
627 * subfunction is through a jump table.
628 */
629 if (!strstr(insn->func->name, ".cold.") &&
630 strstr(insn->jump_dest->func->name, ".cold.")) {
631 insn->func->cfunc = insn->jump_dest->func;
632 insn->jump_dest->func->pfunc = insn->func;
633
634 } else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
635 insn->jump_dest->offset == insn->jump_dest->func->offset) {
636
637 /* internal sibling call */
638 insn->call_dest = insn->jump_dest->func;
639 }
640 }
641 }
642
643 return 0;
644 }
645
646 /*
647 * Find the destination instructions for all calls.
648 */
649 static int add_call_destinations(struct objtool_file *file)
650 {
651 struct instruction *insn;
652 unsigned long dest_off;
653 struct rela *rela;
654
655 for_each_insn(file, insn) {
656 if (insn->type != INSN_CALL)
657 continue;
658
659 rela = find_rela_by_dest_range(insn->sec, insn->offset,
660 insn->len);
661 if (!rela) {
662 dest_off = insn->offset + insn->len + insn->immediate;
663 insn->call_dest = find_symbol_by_offset(insn->sec,
664 dest_off);
665
666 if (!insn->call_dest && !insn->ignore) {
667 WARN_FUNC("unsupported intra-function call",
668 insn->sec, insn->offset);
669 if (retpoline)
670 WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");
671 return -1;
672 }
673
674 } else if (rela->sym->type == STT_SECTION) {
675 insn->call_dest = find_symbol_by_offset(rela->sym->sec,
676 rela->addend+4);
677 if (!insn->call_dest ||
678 insn->call_dest->type != STT_FUNC) {
679 WARN_FUNC("can't find call dest symbol at %s+0x%x",
680 insn->sec, insn->offset,
681 rela->sym->sec->name,
682 rela->addend + 4);
683 return -1;
684 }
685 } else
686 insn->call_dest = rela->sym;
687 }
688
689 return 0;
690 }
691
692 /*
693 * The .alternatives section requires some extra special care, over and above
694 * what other special sections require:
695 *
696 * 1. Because alternatives are patched in-place, we need to insert a fake jump
697 * instruction at the end so that validate_branch() skips all the original
698 * replaced instructions when validating the new instruction path.
699 *
700 * 2. An added wrinkle is that the new instruction length might be zero. In
701 * that case the old instructions are replaced with noops. We simulate that
702 * by creating a fake jump as the only new instruction.
703 *
704 * 3. In some cases, the alternative section includes an instruction which
705 * conditionally jumps to the _end_ of the entry. We have to modify these
706 * jumps' destinations to point back to .text rather than the end of the
707 * entry in .altinstr_replacement.
708 */
709 static int handle_group_alt(struct objtool_file *file,
710 struct special_alt *special_alt,
711 struct instruction *orig_insn,
712 struct instruction **new_insn)
713 {
714 struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
715 unsigned long dest_off;
716
717 last_orig_insn = NULL;
718 insn = orig_insn;
719 sec_for_each_insn_from(file, insn) {
720 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
721 break;
722
723 insn->alt_group = true;
724 last_orig_insn = insn;
725 }
726
727 if (next_insn_same_sec(file, last_orig_insn)) {
728 fake_jump = malloc(sizeof(*fake_jump));
729 if (!fake_jump) {
730 WARN("malloc failed");
731 return -1;
732 }
733 memset(fake_jump, 0, sizeof(*fake_jump));
734 INIT_LIST_HEAD(&fake_jump->alts);
735 clear_insn_state(&fake_jump->state);
736
737 fake_jump->sec = special_alt->new_sec;
738 fake_jump->offset = FAKE_JUMP_OFFSET;
739 fake_jump->type = INSN_JUMP_UNCONDITIONAL;
740 fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
741 fake_jump->func = orig_insn->func;
742 }
743
744 if (!special_alt->new_len) {
745 if (!fake_jump) {
746 WARN("%s: empty alternative at end of section",
747 special_alt->orig_sec->name);
748 return -1;
749 }
750
751 *new_insn = fake_jump;
752 return 0;
753 }
754
755 last_new_insn = NULL;
756 insn = *new_insn;
757 sec_for_each_insn_from(file, insn) {
758 if (insn->offset >= special_alt->new_off + special_alt->new_len)
759 break;
760
761 last_new_insn = insn;
762
763 insn->ignore = orig_insn->ignore_alts;
764 insn->func = orig_insn->func;
765
766 if (insn->type != INSN_JUMP_CONDITIONAL &&
767 insn->type != INSN_JUMP_UNCONDITIONAL)
768 continue;
769
770 if (!insn->immediate)
771 continue;
772
773 dest_off = insn->offset + insn->len + insn->immediate;
774 if (dest_off == special_alt->new_off + special_alt->new_len) {
775 if (!fake_jump) {
776 WARN("%s: alternative jump to end of section",
777 special_alt->orig_sec->name);
778 return -1;
779 }
780 insn->jump_dest = fake_jump;
781 }
782
783 if (!insn->jump_dest) {
784 WARN_FUNC("can't find alternative jump destination",
785 insn->sec, insn->offset);
786 return -1;
787 }
788 }
789
790 if (!last_new_insn) {
791 WARN_FUNC("can't find last new alternative instruction",
792 special_alt->new_sec, special_alt->new_off);
793 return -1;
794 }
795
796 if (fake_jump)
797 list_add(&fake_jump->list, &last_new_insn->list);
798
799 return 0;
800 }
801
802 /*
803 * A jump table entry can either convert a nop to a jump or a jump to a nop.
804 * If the original instruction is a jump, make the alt entry an effective nop
805 * by just skipping the original instruction.
806 */
807 static int handle_jump_alt(struct objtool_file *file,
808 struct special_alt *special_alt,
809 struct instruction *orig_insn,
810 struct instruction **new_insn)
811 {
812 if (orig_insn->type == INSN_NOP)
813 return 0;
814
815 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
816 WARN_FUNC("unsupported instruction at jump label",
817 orig_insn->sec, orig_insn->offset);
818 return -1;
819 }
820
821 *new_insn = list_next_entry(orig_insn, list);
822 return 0;
823 }
824
825 /*
826 * Read all the special sections which have alternate instructions which can be
827 * patched in or redirected to at runtime. Each instruction having alternate
828 * instruction(s) has them added to its insn->alts list, which will be
829 * traversed in validate_branch().
830 */
831 static int add_special_section_alts(struct objtool_file *file)
832 {
833 struct list_head special_alts;
834 struct instruction *orig_insn, *new_insn;
835 struct special_alt *special_alt, *tmp;
836 struct alternative *alt;
837 int ret;
838
839 ret = special_get_alts(file->elf, &special_alts);
840 if (ret)
841 return ret;
842
843 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
844
845 orig_insn = find_insn(file, special_alt->orig_sec,
846 special_alt->orig_off);
847 if (!orig_insn) {
848 WARN_FUNC("special: can't find orig instruction",
849 special_alt->orig_sec, special_alt->orig_off);
850 ret = -1;
851 goto out;
852 }
853
854 new_insn = NULL;
855 if (!special_alt->group || special_alt->new_len) {
856 new_insn = find_insn(file, special_alt->new_sec,
857 special_alt->new_off);
858 if (!new_insn) {
859 WARN_FUNC("special: can't find new instruction",
860 special_alt->new_sec,
861 special_alt->new_off);
862 ret = -1;
863 goto out;
864 }
865 }
866
867 if (special_alt->group) {
868 ret = handle_group_alt(file, special_alt, orig_insn,
869 &new_insn);
870 if (ret)
871 goto out;
872 } else if (special_alt->jump_or_nop) {
873 ret = handle_jump_alt(file, special_alt, orig_insn,
874 &new_insn);
875 if (ret)
876 goto out;
877 }
878
879 alt = malloc(sizeof(*alt));
880 if (!alt) {
881 WARN("malloc failed");
882 ret = -1;
883 goto out;
884 }
885
886 alt->insn = new_insn;
887 alt->skip_orig = special_alt->skip_orig;
888 orig_insn->ignore_alts |= special_alt->skip_alt;
889 list_add_tail(&alt->list, &orig_insn->alts);
890
891 list_del(&special_alt->list);
892 free(special_alt);
893 }
894
895 out:
896 return ret;
897 }
898
899 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
900 struct rela *table)
901 {
902 struct rela *rela = table;
903 struct instruction *dest_insn;
904 struct alternative *alt;
905 struct symbol *pfunc = insn->func->pfunc;
906 unsigned int prev_offset = 0;
907
908 /*
909 * Each @rela is a switch table relocation which points to the target
910 * instruction.
911 */
912 list_for_each_entry_from(rela, &table->sec->rela_list, list) {
913
914 /* Check for the end of the table: */
915 if (rela != table && rela->jump_table_start)
916 break;
917
918 /* Make sure the table entries are consecutive: */
919 if (prev_offset && rela->offset != prev_offset + 8)
920 break;
921
922 /* Detect function pointers from contiguous objects: */
923 if (rela->sym->sec == pfunc->sec &&
924 rela->addend == pfunc->offset)
925 break;
926
927 dest_insn = find_insn(file, rela->sym->sec, rela->addend);
928 if (!dest_insn)
929 break;
930
931 /* Make sure the destination is in the same function: */
932 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
933 break;
934
935 alt = malloc(sizeof(*alt));
936 if (!alt) {
937 WARN("malloc failed");
938 return -1;
939 }
940
941 alt->insn = dest_insn;
942 list_add_tail(&alt->list, &insn->alts);
943 prev_offset = rela->offset;
944 }
945
946 if (!prev_offset) {
947 WARN_FUNC("can't find switch jump table",
948 insn->sec, insn->offset);
949 return -1;
950 }
951
952 return 0;
953 }
954
955 /*
956 * find_jump_table() - Given a dynamic jump, find the switch jump table in
957 * .rodata associated with it.
958 *
959 * There are 3 basic patterns:
960 *
961 * 1. jmpq *[rodata addr](,%reg,8)
962 *
963 * This is the most common case by far. It jumps to an address in a simple
964 * jump table which is stored in .rodata.
965 *
966 * 2. jmpq *[rodata addr](%rip)
967 *
968 * This is caused by a rare GCC quirk, currently only seen in three driver
969 * functions in the kernel, only with certain obscure non-distro configs.
970 *
971 * As part of an optimization, GCC makes a copy of an existing switch jump
972 * table, modifies it, and then hard-codes the jump (albeit with an indirect
973 * jump) to use a single entry in the table. The rest of the jump table and
974 * some of its jump targets remain as dead code.
975 *
976 * In such a case we can just crudely ignore all unreachable instruction
977 * warnings for the entire object file. Ideally we would just ignore them
978 * for the function, but that would require redesigning the code quite a
979 * bit. And honestly that's just not worth doing: unreachable instruction
980 * warnings are of questionable value anyway, and this is such a rare issue.
981 *
982 * 3. mov [rodata addr],%reg1
983 * ... some instructions ...
984 * jmpq *(%reg1,%reg2,8)
985 *
986 * This is a fairly uncommon pattern which is new for GCC 6. As of this
987 * writing, there are 11 occurrences of it in the allmodconfig kernel.
988 *
989 * As of GCC 7 there are quite a few more of these and the 'in between' code
990 * is significant. Esp. with KASAN enabled some of the code between the mov
991 * and jmpq uses .rodata itself, which can confuse things.
992 *
993 * TODO: Once we have DWARF CFI and smarter instruction decoding logic,
994 * ensure the same register is used in the mov and jump instructions.
995 *
996 * NOTE: RETPOLINE made it harder still to decode dynamic jumps.
997 */
998 static struct rela *find_jump_table(struct objtool_file *file,
999 struct symbol *func,
1000 struct instruction *insn)
1001 {
1002 struct rela *text_rela, *table_rela;
1003 struct instruction *orig_insn = insn;
1004 struct section *table_sec;
1005 unsigned long table_offset;
1006
1007 /*
1008 * Backward search using the @first_jump_src links, these help avoid
1009 * much of the 'in between' code. Which avoids us getting confused by
1010 * it.
1011 */
1012 for (;
1013 &insn->list != &file->insn_list &&
1014 insn->sec == func->sec &&
1015 insn->offset >= func->offset;
1016
1017 insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
1018
1019 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1020 break;
1021
1022 /* allow small jumps within the range */
1023 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1024 insn->jump_dest &&
1025 (insn->jump_dest->offset <= insn->offset ||
1026 insn->jump_dest->offset > orig_insn->offset))
1027 break;
1028
1029 /* look for a relocation which references .rodata */
1030 text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
1031 insn->len);
1032 if (!text_rela || text_rela->sym->type != STT_SECTION ||
1033 !text_rela->sym->sec->rodata)
1034 continue;
1035
1036 table_offset = text_rela->addend;
1037 table_sec = text_rela->sym->sec;
1038
1039 if (text_rela->type == R_X86_64_PC32)
1040 table_offset += 4;
1041
1042 /*
1043 * Make sure the .rodata address isn't associated with a
1044 * symbol. GCC jump tables are anonymous data.
1045 *
1046 * Also support C jump tables which are in the same format as
1047 * switch jump tables. For objtool to recognize them, they
1048 * need to be placed in the C_JUMP_TABLE_SECTION section. They
1049 * have symbols associated with them.
1050 */
1051 if (find_symbol_containing(table_sec, table_offset) &&
1052 strcmp(table_sec->name, C_JUMP_TABLE_SECTION))
1053 continue;
1054
1055 /* Each table entry has a rela associated with it. */
1056 table_rela = find_rela_by_dest(table_sec, table_offset);
1057 if (!table_rela)
1058 continue;
1059
1060 /*
1061 * Use of RIP-relative switch jumps is quite rare, and
1062 * indicates a rare GCC quirk/bug which can leave dead code
1063 * behind.
1064 */
1065 if (text_rela->type == R_X86_64_PC32)
1066 file->ignore_unreachables = true;
1067
1068 return table_rela;
1069 }
1070
1071 return NULL;
1072 }
1073
1074 /*
1075 * First pass: Mark the head of each jump table so that in the next pass,
1076 * we know when a given jump table ends and the next one starts.
1077 */
1078 static void mark_func_jump_tables(struct objtool_file *file,
1079 struct symbol *func)
1080 {
1081 struct instruction *insn, *last = NULL;
1082 struct rela *rela;
1083
1084 func_for_each_insn_all(file, func, insn) {
1085 if (!last)
1086 last = insn;
1087
1088 /*
1089 * Store back-pointers for unconditional forward jumps such
1090 * that find_jump_table() can back-track using those and
1091 * avoid some potentially confusing code.
1092 */
1093 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1094 insn->offset > last->offset &&
1095 insn->jump_dest->offset > insn->offset &&
1096 !insn->jump_dest->first_jump_src) {
1097
1098 insn->jump_dest->first_jump_src = insn;
1099 last = insn->jump_dest;
1100 }
1101
1102 if (insn->type != INSN_JUMP_DYNAMIC)
1103 continue;
1104
1105 rela = find_jump_table(file, func, insn);
1106 if (rela) {
1107 rela->jump_table_start = true;
1108 insn->jump_table = rela;
1109 }
1110 }
1111 }
1112
1113 static int add_func_jump_tables(struct objtool_file *file,
1114 struct symbol *func)
1115 {
1116 struct instruction *insn;
1117 int ret;
1118
1119 func_for_each_insn_all(file, func, insn) {
1120 if (!insn->jump_table)
1121 continue;
1122
1123 ret = add_jump_table(file, insn, insn->jump_table);
1124 if (ret)
1125 return ret;
1126 }
1127
1128 return 0;
1129 }
1130
1131 /*
1132 * For some switch statements, gcc generates a jump table in the .rodata
1133 * section which contains a list of addresses within the function to jump to.
1134 * This finds these jump tables and adds them to the insn->alts lists.
1135 */
1136 static int add_jump_table_alts(struct objtool_file *file)
1137 {
1138 struct section *sec;
1139 struct symbol *func;
1140 int ret;
1141
1142 if (!file->rodata)
1143 return 0;
1144
1145 for_each_sec(file, sec) {
1146 list_for_each_entry(func, &sec->symbol_list, list) {
1147 if (func->type != STT_FUNC)
1148 continue;
1149
1150 mark_func_jump_tables(file, func);
1151 ret = add_func_jump_tables(file, func);
1152 if (ret)
1153 return ret;
1154 }
1155 }
1156
1157 return 0;
1158 }
1159
1160 static int read_unwind_hints(struct objtool_file *file)
1161 {
1162 struct section *sec, *relasec;
1163 struct rela *rela;
1164 struct unwind_hint *hint;
1165 struct instruction *insn;
1166 struct cfi_reg *cfa;
1167 int i;
1168
1169 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1170 if (!sec)
1171 return 0;
1172
1173 relasec = sec->rela;
1174 if (!relasec) {
1175 WARN("missing .rela.discard.unwind_hints section");
1176 return -1;
1177 }
1178
1179 if (sec->len % sizeof(struct unwind_hint)) {
1180 WARN("struct unwind_hint size mismatch");
1181 return -1;
1182 }
1183
1184 file->hints = true;
1185
1186 for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
1187 hint = (struct unwind_hint *)sec->data->d_buf + i;
1188
1189 rela = find_rela_by_dest(sec, i * sizeof(*hint));
1190 if (!rela) {
1191 WARN("can't find rela for unwind_hints[%d]", i);
1192 return -1;
1193 }
1194
1195 insn = find_insn(file, rela->sym->sec, rela->addend);
1196 if (!insn) {
1197 WARN("can't find insn for unwind_hints[%d]", i);
1198 return -1;
1199 }
1200
1201 cfa = &insn->state.cfa;
1202
1203 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
1204 insn->save = true;
1205 continue;
1206
1207 } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
1208 insn->restore = true;
1209 insn->hint = true;
1210 continue;
1211 }
1212
1213 insn->hint = true;
1214
1215 switch (hint->sp_reg) {
1216 case ORC_REG_UNDEFINED:
1217 cfa->base = CFI_UNDEFINED;
1218 break;
1219 case ORC_REG_SP:
1220 cfa->base = CFI_SP;
1221 break;
1222 case ORC_REG_BP:
1223 cfa->base = CFI_BP;
1224 break;
1225 case ORC_REG_SP_INDIRECT:
1226 cfa->base = CFI_SP_INDIRECT;
1227 break;
1228 case ORC_REG_R10:
1229 cfa->base = CFI_R10;
1230 break;
1231 case ORC_REG_R13:
1232 cfa->base = CFI_R13;
1233 break;
1234 case ORC_REG_DI:
1235 cfa->base = CFI_DI;
1236 break;
1237 case ORC_REG_DX:
1238 cfa->base = CFI_DX;
1239 break;
1240 default:
1241 WARN_FUNC("unsupported unwind_hint sp base reg %d",
1242 insn->sec, insn->offset, hint->sp_reg);
1243 return -1;
1244 }
1245
1246 cfa->offset = hint->sp_offset;
1247 insn->state.type = hint->type;
1248 insn->state.end = hint->end;
1249 }
1250
1251 return 0;
1252 }
1253
1254 static int read_retpoline_hints(struct objtool_file *file)
1255 {
1256 struct section *sec;
1257 struct instruction *insn;
1258 struct rela *rela;
1259
1260 sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1261 if (!sec)
1262 return 0;
1263
1264 list_for_each_entry(rela, &sec->rela_list, list) {
1265 if (rela->sym->type != STT_SECTION) {
1266 WARN("unexpected relocation symbol type in %s", sec->name);
1267 return -1;
1268 }
1269
1270 insn = find_insn(file, rela->sym->sec, rela->addend);
1271 if (!insn) {
1272 WARN("bad .discard.retpoline_safe entry");
1273 return -1;
1274 }
1275
1276 if (insn->type != INSN_JUMP_DYNAMIC &&
1277 insn->type != INSN_CALL_DYNAMIC) {
1278 WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1279 insn->sec, insn->offset);
1280 return -1;
1281 }
1282
1283 insn->retpoline_safe = true;
1284 }
1285
1286 return 0;
1287 }
1288
1289 static void mark_rodata(struct objtool_file *file)
1290 {
1291 struct section *sec;
1292 bool found = false;
1293
1294 /*
1295 * Search for the following rodata sections, each of which can
1296 * potentially contain jump tables:
1297 *
1298 * - .rodata: can contain GCC switch tables
1299 * - .rodata.<func>: same, if -fdata-sections is being used
1300 * - .rodata..c_jump_table: contains C annotated jump tables
1301 *
1302 * .rodata.str1.* sections are ignored; they don't contain jump tables.
1303 */
1304 for_each_sec(file, sec) {
1305 if ((!strncmp(sec->name, ".rodata", 7) && !strstr(sec->name, ".str1.")) ||
1306 !strcmp(sec->name, C_JUMP_TABLE_SECTION)) {
1307 sec->rodata = true;
1308 found = true;
1309 }
1310 }
1311
1312 file->rodata = found;
1313 }
1314
1315 static int decode_sections(struct objtool_file *file)
1316 {
1317 int ret;
1318
1319 mark_rodata(file);
1320
1321 ret = decode_instructions(file);
1322 if (ret)
1323 return ret;
1324
1325 ret = add_dead_ends(file);
1326 if (ret)
1327 return ret;
1328
1329 add_ignores(file);
1330 add_uaccess_safe(file);
1331
1332 ret = add_ignore_alternatives(file);
1333 if (ret)
1334 return ret;
1335
1336 ret = add_jump_destinations(file);
1337 if (ret)
1338 return ret;
1339
1340 ret = add_special_section_alts(file);
1341 if (ret)
1342 return ret;
1343
1344 ret = add_call_destinations(file);
1345 if (ret)
1346 return ret;
1347
1348 ret = add_jump_table_alts(file);
1349 if (ret)
1350 return ret;
1351
1352 ret = read_unwind_hints(file);
1353 if (ret)
1354 return ret;
1355
1356 ret = read_retpoline_hints(file);
1357 if (ret)
1358 return ret;
1359
1360 return 0;
1361 }
1362
1363 static bool is_fentry_call(struct instruction *insn)
1364 {
1365 if (insn->type == INSN_CALL &&
1366 insn->call_dest->type == STT_NOTYPE &&
1367 !strcmp(insn->call_dest->name, "__fentry__"))
1368 return true;
1369
1370 return false;
1371 }
1372
1373 static bool has_modified_stack_frame(struct insn_state *state)
1374 {
1375 int i;
1376
1377 if (state->cfa.base != initial_func_cfi.cfa.base ||
1378 state->cfa.offset != initial_func_cfi.cfa.offset ||
1379 state->stack_size != initial_func_cfi.cfa.offset ||
1380 state->drap)
1381 return true;
1382
1383 for (i = 0; i < CFI_NUM_REGS; i++)
1384 if (state->regs[i].base != initial_func_cfi.regs[i].base ||
1385 state->regs[i].offset != initial_func_cfi.regs[i].offset)
1386 return true;
1387
1388 return false;
1389 }
1390
1391 static bool has_valid_stack_frame(struct insn_state *state)
1392 {
1393 if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
1394 state->regs[CFI_BP].offset == -16)
1395 return true;
1396
1397 if (state->drap && state->regs[CFI_BP].base == CFI_BP)
1398 return true;
1399
1400 return false;
1401 }
1402
1403 static int update_insn_state_regs(struct instruction *insn, struct insn_state *state)
1404 {
1405 struct cfi_reg *cfa = &state->cfa;
1406 struct stack_op *op = &insn->stack_op;
1407
1408 if (cfa->base != CFI_SP)
1409 return 0;
1410
1411 /* push */
1412 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
1413 cfa->offset += 8;
1414
1415 /* pop */
1416 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
1417 cfa->offset -= 8;
1418
1419 /* add immediate to sp */
1420 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1421 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1422 cfa->offset -= op->src.offset;
1423
1424 return 0;
1425 }
1426
1427 static void save_reg(struct insn_state *state, unsigned char reg, int base,
1428 int offset)
1429 {
1430 if (arch_callee_saved_reg(reg) &&
1431 state->regs[reg].base == CFI_UNDEFINED) {
1432 state->regs[reg].base = base;
1433 state->regs[reg].offset = offset;
1434 }
1435 }
1436
1437 static void restore_reg(struct insn_state *state, unsigned char reg)
1438 {
1439 state->regs[reg].base = CFI_UNDEFINED;
1440 state->regs[reg].offset = 0;
1441 }
1442
1443 /*
1444 * A note about DRAP stack alignment:
1445 *
1446 * GCC has the concept of a DRAP register, which is used to help keep track of
1447 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
1448 * register. The typical DRAP pattern is:
1449 *
1450 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
1451 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
1452 * 41 ff 72 f8 pushq -0x8(%r10)
1453 * 55 push %rbp
1454 * 48 89 e5 mov %rsp,%rbp
1455 * (more pushes)
1456 * 41 52 push %r10
1457 * ...
1458 * 41 5a pop %r10
1459 * (more pops)
1460 * 5d pop %rbp
1461 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1462 * c3 retq
1463 *
1464 * There are some variations in the epilogues, like:
1465 *
1466 * 5b pop %rbx
1467 * 41 5a pop %r10
1468 * 41 5c pop %r12
1469 * 41 5d pop %r13
1470 * 41 5e pop %r14
1471 * c9 leaveq
1472 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1473 * c3 retq
1474 *
1475 * and:
1476 *
1477 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
1478 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
1479 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
1480 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
1481 * c9 leaveq
1482 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1483 * c3 retq
1484 *
1485 * Sometimes r13 is used as the DRAP register, in which case it's saved and
1486 * restored beforehand:
1487 *
1488 * 41 55 push %r13
1489 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
1490 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
1491 * ...
1492 * 49 8d 65 f0 lea -0x10(%r13),%rsp
1493 * 41 5d pop %r13
1494 * c3 retq
1495 */
1496 static int update_insn_state(struct instruction *insn, struct insn_state *state)
1497 {
1498 struct stack_op *op = &insn->stack_op;
1499 struct cfi_reg *cfa = &state->cfa;
1500 struct cfi_reg *regs = state->regs;
1501
1502 /* stack operations don't make sense with an undefined CFA */
1503 if (cfa->base == CFI_UNDEFINED) {
1504 if (insn->func) {
1505 WARN_FUNC("undefined stack state", insn->sec, insn->offset);
1506 return -1;
1507 }
1508 return 0;
1509 }
1510
1511 if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET)
1512 return update_insn_state_regs(insn, state);
1513
1514 switch (op->dest.type) {
1515
1516 case OP_DEST_REG:
1517 switch (op->src.type) {
1518
1519 case OP_SRC_REG:
1520 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
1521 cfa->base == CFI_SP &&
1522 regs[CFI_BP].base == CFI_CFA &&
1523 regs[CFI_BP].offset == -cfa->offset) {
1524
1525 /* mov %rsp, %rbp */
1526 cfa->base = op->dest.reg;
1527 state->bp_scratch = false;
1528 }
1529
1530 else if (op->src.reg == CFI_SP &&
1531 op->dest.reg == CFI_BP && state->drap) {
1532
1533 /* drap: mov %rsp, %rbp */
1534 regs[CFI_BP].base = CFI_BP;
1535 regs[CFI_BP].offset = -state->stack_size;
1536 state->bp_scratch = false;
1537 }
1538
1539 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1540
1541 /*
1542 * mov %rsp, %reg
1543 *
1544 * This is needed for the rare case where GCC
1545 * does:
1546 *
1547 * mov %rsp, %rax
1548 * ...
1549 * mov %rax, %rsp
1550 */
1551 state->vals[op->dest.reg].base = CFI_CFA;
1552 state->vals[op->dest.reg].offset = -state->stack_size;
1553 }
1554
1555 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
1556 cfa->base == CFI_BP) {
1557
1558 /*
1559 * mov %rbp, %rsp
1560 *
1561 * Restore the original stack pointer (Clang).
1562 */
1563 state->stack_size = -state->regs[CFI_BP].offset;
1564 }
1565
1566 else if (op->dest.reg == cfa->base) {
1567
1568 /* mov %reg, %rsp */
1569 if (cfa->base == CFI_SP &&
1570 state->vals[op->src.reg].base == CFI_CFA) {
1571
1572 /*
1573 * This is needed for the rare case
1574 * where GCC does something dumb like:
1575 *
1576 * lea 0x8(%rsp), %rcx
1577 * ...
1578 * mov %rcx, %rsp
1579 */
1580 cfa->offset = -state->vals[op->src.reg].offset;
1581 state->stack_size = cfa->offset;
1582
1583 } else {
1584 cfa->base = CFI_UNDEFINED;
1585 cfa->offset = 0;
1586 }
1587 }
1588
1589 break;
1590
1591 case OP_SRC_ADD:
1592 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
1593
1594 /* add imm, %rsp */
1595 state->stack_size -= op->src.offset;
1596 if (cfa->base == CFI_SP)
1597 cfa->offset -= op->src.offset;
1598 break;
1599 }
1600
1601 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
1602
1603 /* lea disp(%rbp), %rsp */
1604 state->stack_size = -(op->src.offset + regs[CFI_BP].offset);
1605 break;
1606 }
1607
1608 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1609
1610 /* drap: lea disp(%rsp), %drap */
1611 state->drap_reg = op->dest.reg;
1612
1613 /*
1614 * lea disp(%rsp), %reg
1615 *
1616 * This is needed for the rare case where GCC
1617 * does something dumb like:
1618 *
1619 * lea 0x8(%rsp), %rcx
1620 * ...
1621 * mov %rcx, %rsp
1622 */
1623 state->vals[op->dest.reg].base = CFI_CFA;
1624 state->vals[op->dest.reg].offset = \
1625 -state->stack_size + op->src.offset;
1626
1627 break;
1628 }
1629
1630 if (state->drap && op->dest.reg == CFI_SP &&
1631 op->src.reg == state->drap_reg) {
1632
1633 /* drap: lea disp(%drap), %rsp */
1634 cfa->base = CFI_SP;
1635 cfa->offset = state->stack_size = -op->src.offset;
1636 state->drap_reg = CFI_UNDEFINED;
1637 state->drap = false;
1638 break;
1639 }
1640
1641 if (op->dest.reg == state->cfa.base) {
1642 WARN_FUNC("unsupported stack register modification",
1643 insn->sec, insn->offset);
1644 return -1;
1645 }
1646
1647 break;
1648
1649 case OP_SRC_AND:
1650 if (op->dest.reg != CFI_SP ||
1651 (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
1652 (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
1653 WARN_FUNC("unsupported stack pointer realignment",
1654 insn->sec, insn->offset);
1655 return -1;
1656 }
1657
1658 if (state->drap_reg != CFI_UNDEFINED) {
1659 /* drap: and imm, %rsp */
1660 cfa->base = state->drap_reg;
1661 cfa->offset = state->stack_size = 0;
1662 state->drap = true;
1663 }
1664
1665 /*
1666 * Older versions of GCC (4.8ish) realign the stack
1667 * without DRAP, with a frame pointer.
1668 */
1669
1670 break;
1671
1672 case OP_SRC_POP:
1673 case OP_SRC_POPF:
1674 if (!state->drap && op->dest.type == OP_DEST_REG &&
1675 op->dest.reg == cfa->base) {
1676
1677 /* pop %rbp */
1678 cfa->base = CFI_SP;
1679 }
1680
1681 if (state->drap && cfa->base == CFI_BP_INDIRECT &&
1682 op->dest.type == OP_DEST_REG &&
1683 op->dest.reg == state->drap_reg &&
1684 state->drap_offset == -state->stack_size) {
1685
1686 /* drap: pop %drap */
1687 cfa->base = state->drap_reg;
1688 cfa->offset = 0;
1689 state->drap_offset = -1;
1690
1691 } else if (regs[op->dest.reg].offset == -state->stack_size) {
1692
1693 /* pop %reg */
1694 restore_reg(state, op->dest.reg);
1695 }
1696
1697 state->stack_size -= 8;
1698 if (cfa->base == CFI_SP)
1699 cfa->offset -= 8;
1700
1701 break;
1702
1703 case OP_SRC_REG_INDIRECT:
1704 if (state->drap && op->src.reg == CFI_BP &&
1705 op->src.offset == state->drap_offset) {
1706
1707 /* drap: mov disp(%rbp), %drap */
1708 cfa->base = state->drap_reg;
1709 cfa->offset = 0;
1710 state->drap_offset = -1;
1711 }
1712
1713 if (state->drap && op->src.reg == CFI_BP &&
1714 op->src.offset == regs[op->dest.reg].offset) {
1715
1716 /* drap: mov disp(%rbp), %reg */
1717 restore_reg(state, op->dest.reg);
1718
1719 } else if (op->src.reg == cfa->base &&
1720 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
1721
1722 /* mov disp(%rbp), %reg */
1723 /* mov disp(%rsp), %reg */
1724 restore_reg(state, op->dest.reg);
1725 }
1726
1727 break;
1728
1729 default:
1730 WARN_FUNC("unknown stack-related instruction",
1731 insn->sec, insn->offset);
1732 return -1;
1733 }
1734
1735 break;
1736
1737 case OP_DEST_PUSH:
1738 case OP_DEST_PUSHF:
1739 state->stack_size += 8;
1740 if (cfa->base == CFI_SP)
1741 cfa->offset += 8;
1742
1743 if (op->src.type != OP_SRC_REG)
1744 break;
1745
1746 if (state->drap) {
1747 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1748
1749 /* drap: push %drap */
1750 cfa->base = CFI_BP_INDIRECT;
1751 cfa->offset = -state->stack_size;
1752
1753 /* save drap so we know when to restore it */
1754 state->drap_offset = -state->stack_size;
1755
1756 } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
1757
1758 /* drap: push %rbp */
1759 state->stack_size = 0;
1760
1761 } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1762
1763 /* drap: push %reg */
1764 save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
1765 }
1766
1767 } else {
1768
1769 /* push %reg */
1770 save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
1771 }
1772
1773 /* detect when asm code uses rbp as a scratch register */
1774 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
1775 cfa->base != CFI_BP)
1776 state->bp_scratch = true;
1777 break;
1778
1779 case OP_DEST_REG_INDIRECT:
1780
1781 if (state->drap) {
1782 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1783
1784 /* drap: mov %drap, disp(%rbp) */
1785 cfa->base = CFI_BP_INDIRECT;
1786 cfa->offset = op->dest.offset;
1787
1788 /* save drap offset so we know when to restore it */
1789 state->drap_offset = op->dest.offset;
1790 }
1791
1792 else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1793
1794 /* drap: mov reg, disp(%rbp) */
1795 save_reg(state, op->src.reg, CFI_BP, op->dest.offset);
1796 }
1797
1798 } else if (op->dest.reg == cfa->base) {
1799
1800 /* mov reg, disp(%rbp) */
1801 /* mov reg, disp(%rsp) */
1802 save_reg(state, op->src.reg, CFI_CFA,
1803 op->dest.offset - state->cfa.offset);
1804 }
1805
1806 break;
1807
1808 case OP_DEST_LEAVE:
1809 if ((!state->drap && cfa->base != CFI_BP) ||
1810 (state->drap && cfa->base != state->drap_reg)) {
1811 WARN_FUNC("leave instruction with modified stack frame",
1812 insn->sec, insn->offset);
1813 return -1;
1814 }
1815
1816 /* leave (mov %rbp, %rsp; pop %rbp) */
1817
1818 state->stack_size = -state->regs[CFI_BP].offset - 8;
1819 restore_reg(state, CFI_BP);
1820
1821 if (!state->drap) {
1822 cfa->base = CFI_SP;
1823 cfa->offset -= 8;
1824 }
1825
1826 break;
1827
1828 case OP_DEST_MEM:
1829 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
1830 WARN_FUNC("unknown stack-related memory operation",
1831 insn->sec, insn->offset);
1832 return -1;
1833 }
1834
1835 /* pop mem */
1836 state->stack_size -= 8;
1837 if (cfa->base == CFI_SP)
1838 cfa->offset -= 8;
1839
1840 break;
1841
1842 default:
1843 WARN_FUNC("unknown stack-related instruction",
1844 insn->sec, insn->offset);
1845 return -1;
1846 }
1847
1848 return 0;
1849 }
1850
1851 static bool insn_state_match(struct instruction *insn, struct insn_state *state)
1852 {
1853 struct insn_state *state1 = &insn->state, *state2 = state;
1854 int i;
1855
1856 if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
1857 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
1858 insn->sec, insn->offset,
1859 state1->cfa.base, state1->cfa.offset,
1860 state2->cfa.base, state2->cfa.offset);
1861
1862 } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
1863 for (i = 0; i < CFI_NUM_REGS; i++) {
1864 if (!memcmp(&state1->regs[i], &state2->regs[i],
1865 sizeof(struct cfi_reg)))
1866 continue;
1867
1868 WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
1869 insn->sec, insn->offset,
1870 i, state1->regs[i].base, state1->regs[i].offset,
1871 i, state2->regs[i].base, state2->regs[i].offset);
1872 break;
1873 }
1874
1875 } else if (state1->type != state2->type) {
1876 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
1877 insn->sec, insn->offset, state1->type, state2->type);
1878
1879 } else if (state1->drap != state2->drap ||
1880 (state1->drap && state1->drap_reg != state2->drap_reg) ||
1881 (state1->drap && state1->drap_offset != state2->drap_offset)) {
1882 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
1883 insn->sec, insn->offset,
1884 state1->drap, state1->drap_reg, state1->drap_offset,
1885 state2->drap, state2->drap_reg, state2->drap_offset);
1886
1887 } else
1888 return true;
1889
1890 return false;
1891 }
1892
1893 static inline bool func_uaccess_safe(struct symbol *func)
1894 {
1895 if (func)
1896 return func->uaccess_safe;
1897
1898 return false;
1899 }
1900
1901 static inline const char *call_dest_name(struct instruction *insn)
1902 {
1903 if (insn->call_dest)
1904 return insn->call_dest->name;
1905
1906 return "{dynamic}";
1907 }
1908
1909 static int validate_call(struct instruction *insn, struct insn_state *state)
1910 {
1911 if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
1912 WARN_FUNC("call to %s() with UACCESS enabled",
1913 insn->sec, insn->offset, call_dest_name(insn));
1914 return 1;
1915 }
1916
1917 if (state->df) {
1918 WARN_FUNC("call to %s() with DF set",
1919 insn->sec, insn->offset, call_dest_name(insn));
1920 return 1;
1921 }
1922
1923 return 0;
1924 }
1925
1926 static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
1927 {
1928 if (has_modified_stack_frame(state)) {
1929 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1930 insn->sec, insn->offset);
1931 return 1;
1932 }
1933
1934 return validate_call(insn, state);
1935 }
1936
1937 /*
1938 * Follow the branch starting at the given instruction, and recursively follow
1939 * any other branches (jumps). Meanwhile, track the frame pointer state at
1940 * each instruction and validate all the rules described in
1941 * tools/objtool/Documentation/stack-validation.txt.
1942 */
1943 static int validate_branch(struct objtool_file *file, struct symbol *func,
1944 struct instruction *first, struct insn_state state)
1945 {
1946 struct alternative *alt;
1947 struct instruction *insn, *next_insn;
1948 struct section *sec;
1949 int ret;
1950
1951 insn = first;
1952 sec = insn->sec;
1953
1954 if (insn->alt_group && list_empty(&insn->alts)) {
1955 WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
1956 sec, insn->offset);
1957 return 1;
1958 }
1959
1960 while (1) {
1961 next_insn = next_insn_same_sec(file, insn);
1962
1963 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
1964 WARN("%s() falls through to next function %s()",
1965 func->name, insn->func->name);
1966 return 1;
1967 }
1968
1969 if (func && insn->ignore) {
1970 WARN_FUNC("BUG: why am I validating an ignored function?",
1971 sec, insn->offset);
1972 return 1;
1973 }
1974
1975 if (insn->visited) {
1976 if (!insn->hint && !insn_state_match(insn, &state))
1977 return 1;
1978
1979 /* If we were here with AC=0, but now have AC=1, go again */
1980 if (insn->state.uaccess || !state.uaccess)
1981 return 0;
1982 }
1983
1984 if (insn->hint) {
1985 if (insn->restore) {
1986 struct instruction *save_insn, *i;
1987
1988 i = insn;
1989 save_insn = NULL;
1990 func_for_each_insn_continue_reverse(file, func, i) {
1991 if (i->save) {
1992 save_insn = i;
1993 break;
1994 }
1995 }
1996
1997 if (!save_insn) {
1998 WARN_FUNC("no corresponding CFI save for CFI restore",
1999 sec, insn->offset);
2000 return 1;
2001 }
2002
2003 if (!save_insn->visited) {
2004 /*
2005 * Oops, no state to copy yet.
2006 * Hopefully we can reach this
2007 * instruction from another branch
2008 * after the save insn has been
2009 * visited.
2010 */
2011 if (insn == first)
2012 return 0;
2013
2014 WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
2015 sec, insn->offset);
2016 return 1;
2017 }
2018
2019 insn->state = save_insn->state;
2020 }
2021
2022 state = insn->state;
2023
2024 } else
2025 insn->state = state;
2026
2027 insn->visited = true;
2028
2029 if (!insn->ignore_alts) {
2030 bool skip_orig = false;
2031
2032 list_for_each_entry(alt, &insn->alts, list) {
2033 if (alt->skip_orig)
2034 skip_orig = true;
2035
2036 ret = validate_branch(file, func, alt->insn, state);
2037 if (ret) {
2038 if (backtrace)
2039 BT_FUNC("(alt)", insn);
2040 return ret;
2041 }
2042 }
2043
2044 if (skip_orig)
2045 return 0;
2046 }
2047
2048 switch (insn->type) {
2049
2050 case INSN_RETURN:
2051 if (state.uaccess && !func_uaccess_safe(func)) {
2052 WARN_FUNC("return with UACCESS enabled", sec, insn->offset);
2053 return 1;
2054 }
2055
2056 if (!state.uaccess && func_uaccess_safe(func)) {
2057 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function", sec, insn->offset);
2058 return 1;
2059 }
2060
2061 if (state.df) {
2062 WARN_FUNC("return with DF set", sec, insn->offset);
2063 return 1;
2064 }
2065
2066 if (func && has_modified_stack_frame(&state)) {
2067 WARN_FUNC("return with modified stack frame",
2068 sec, insn->offset);
2069 return 1;
2070 }
2071
2072 if (state.bp_scratch) {
2073 WARN("%s uses BP as a scratch register",
2074 func->name);
2075 return 1;
2076 }
2077
2078 return 0;
2079
2080 case INSN_CALL:
2081 case INSN_CALL_DYNAMIC:
2082 ret = validate_call(insn, &state);
2083 if (ret)
2084 return ret;
2085
2086 if (!no_fp && func && !is_fentry_call(insn) &&
2087 !has_valid_stack_frame(&state)) {
2088 WARN_FUNC("call without frame pointer save/setup",
2089 sec, insn->offset);
2090 return 1;
2091 }
2092
2093 if (dead_end_function(file, insn->call_dest))
2094 return 0;
2095
2096 break;
2097
2098 case INSN_JUMP_CONDITIONAL:
2099 case INSN_JUMP_UNCONDITIONAL:
2100 if (func && is_sibling_call(insn)) {
2101 ret = validate_sibling_call(insn, &state);
2102 if (ret)
2103 return ret;
2104
2105 } else if (insn->jump_dest) {
2106 ret = validate_branch(file, func,
2107 insn->jump_dest, state);
2108 if (ret) {
2109 if (backtrace)
2110 BT_FUNC("(branch)", insn);
2111 return ret;
2112 }
2113 }
2114
2115 if (insn->type == INSN_JUMP_UNCONDITIONAL)
2116 return 0;
2117
2118 break;
2119
2120 case INSN_JUMP_DYNAMIC:
2121 case INSN_JUMP_DYNAMIC_CONDITIONAL:
2122 if (func && is_sibling_call(insn)) {
2123 ret = validate_sibling_call(insn, &state);
2124 if (ret)
2125 return ret;
2126 }
2127
2128 if (insn->type == INSN_JUMP_DYNAMIC)
2129 return 0;
2130
2131 break;
2132
2133 case INSN_CONTEXT_SWITCH:
2134 if (func && (!next_insn || !next_insn->hint)) {
2135 WARN_FUNC("unsupported instruction in callable function",
2136 sec, insn->offset);
2137 return 1;
2138 }
2139 return 0;
2140
2141 case INSN_STACK:
2142 if (update_insn_state(insn, &state))
2143 return 1;
2144
2145 if (insn->stack_op.dest.type == OP_DEST_PUSHF) {
2146 if (!state.uaccess_stack) {
2147 state.uaccess_stack = 1;
2148 } else if (state.uaccess_stack >> 31) {
2149 WARN_FUNC("PUSHF stack exhausted", sec, insn->offset);
2150 return 1;
2151 }
2152 state.uaccess_stack <<= 1;
2153 state.uaccess_stack |= state.uaccess;
2154 }
2155
2156 if (insn->stack_op.src.type == OP_SRC_POPF) {
2157 if (state.uaccess_stack) {
2158 state.uaccess = state.uaccess_stack & 1;
2159 state.uaccess_stack >>= 1;
2160 if (state.uaccess_stack == 1)
2161 state.uaccess_stack = 0;
2162 }
2163 }
2164
2165 break;
2166
2167 case INSN_STAC:
2168 if (state.uaccess) {
2169 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
2170 return 1;
2171 }
2172
2173 state.uaccess = true;
2174 break;
2175
2176 case INSN_CLAC:
2177 if (!state.uaccess && func) {
2178 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
2179 return 1;
2180 }
2181
2182 if (func_uaccess_safe(func) && !state.uaccess_stack) {
2183 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
2184 return 1;
2185 }
2186
2187 state.uaccess = false;
2188 break;
2189
2190 case INSN_STD:
2191 if (state.df)
2192 WARN_FUNC("recursive STD", sec, insn->offset);
2193
2194 state.df = true;
2195 break;
2196
2197 case INSN_CLD:
2198 if (!state.df && func)
2199 WARN_FUNC("redundant CLD", sec, insn->offset);
2200
2201 state.df = false;
2202 break;
2203
2204 default:
2205 break;
2206 }
2207
2208 if (insn->dead_end)
2209 return 0;
2210
2211 if (!next_insn) {
2212 if (state.cfa.base == CFI_UNDEFINED)
2213 return 0;
2214 WARN("%s: unexpected end of section", sec->name);
2215 return 1;
2216 }
2217
2218 insn = next_insn;
2219 }
2220
2221 return 0;
2222 }
2223
2224 static int validate_unwind_hints(struct objtool_file *file)
2225 {
2226 struct instruction *insn;
2227 int ret, warnings = 0;
2228 struct insn_state state;
2229
2230 if (!file->hints)
2231 return 0;
2232
2233 clear_insn_state(&state);
2234
2235 for_each_insn(file, insn) {
2236 if (insn->hint && !insn->visited) {
2237 ret = validate_branch(file, insn->func, insn, state);
2238 if (ret && backtrace)
2239 BT_FUNC("<=== (hint)", insn);
2240 warnings += ret;
2241 }
2242 }
2243
2244 return warnings;
2245 }
2246
2247 static int validate_retpoline(struct objtool_file *file)
2248 {
2249 struct instruction *insn;
2250 int warnings = 0;
2251
2252 for_each_insn(file, insn) {
2253 if (insn->type != INSN_JUMP_DYNAMIC &&
2254 insn->type != INSN_CALL_DYNAMIC)
2255 continue;
2256
2257 if (insn->retpoline_safe)
2258 continue;
2259
2260 /*
2261 * .init.text code is ran before userspace and thus doesn't
2262 * strictly need retpolines, except for modules which are
2263 * loaded late, they very much do need retpoline in their
2264 * .init.text
2265 */
2266 if (!strcmp(insn->sec->name, ".init.text") && !module)
2267 continue;
2268
2269 WARN_FUNC("indirect %s found in RETPOLINE build",
2270 insn->sec, insn->offset,
2271 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
2272
2273 warnings++;
2274 }
2275
2276 return warnings;
2277 }
2278
2279 static bool is_kasan_insn(struct instruction *insn)
2280 {
2281 return (insn->type == INSN_CALL &&
2282 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
2283 }
2284
2285 static bool is_ubsan_insn(struct instruction *insn)
2286 {
2287 return (insn->type == INSN_CALL &&
2288 !strcmp(insn->call_dest->name,
2289 "__ubsan_handle_builtin_unreachable"));
2290 }
2291
2292 static bool ignore_unreachable_insn(struct instruction *insn)
2293 {
2294 int i;
2295
2296 if (insn->ignore || insn->type == INSN_NOP)
2297 return true;
2298
2299 /*
2300 * Ignore any unused exceptions. This can happen when a whitelisted
2301 * function has an exception table entry.
2302 *
2303 * Also ignore alternative replacement instructions. This can happen
2304 * when a whitelisted function uses one of the ALTERNATIVE macros.
2305 */
2306 if (!strcmp(insn->sec->name, ".fixup") ||
2307 !strcmp(insn->sec->name, ".altinstr_replacement") ||
2308 !strcmp(insn->sec->name, ".altinstr_aux"))
2309 return true;
2310
2311 /*
2312 * Check if this (or a subsequent) instruction is related to
2313 * CONFIG_UBSAN or CONFIG_KASAN.
2314 *
2315 * End the search at 5 instructions to avoid going into the weeds.
2316 */
2317 if (!insn->func)
2318 return false;
2319 for (i = 0; i < 5; i++) {
2320
2321 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
2322 return true;
2323
2324 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
2325 if (insn->jump_dest &&
2326 insn->jump_dest->func == insn->func) {
2327 insn = insn->jump_dest;
2328 continue;
2329 }
2330
2331 break;
2332 }
2333
2334 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
2335 break;
2336
2337 insn = list_next_entry(insn, list);
2338 }
2339
2340 return false;
2341 }
2342
2343 static int validate_functions(struct objtool_file *file)
2344 {
2345 struct section *sec;
2346 struct symbol *func;
2347 struct instruction *insn;
2348 struct insn_state state;
2349 int ret, warnings = 0;
2350
2351 clear_insn_state(&state);
2352
2353 state.cfa = initial_func_cfi.cfa;
2354 memcpy(&state.regs, &initial_func_cfi.regs,
2355 CFI_NUM_REGS * sizeof(struct cfi_reg));
2356 state.stack_size = initial_func_cfi.cfa.offset;
2357
2358 for_each_sec(file, sec) {
2359 list_for_each_entry(func, &sec->symbol_list, list) {
2360 if (func->type != STT_FUNC)
2361 continue;
2362
2363 if (!func->len) {
2364 WARN("%s() is missing an ELF size annotation",
2365 func->name);
2366 warnings++;
2367 }
2368
2369 if (func->pfunc != func || func->alias != func)
2370 continue;
2371
2372 insn = find_insn(file, sec, func->offset);
2373 if (!insn || insn->ignore || insn->visited)
2374 continue;
2375
2376 state.uaccess = func->uaccess_safe;
2377
2378 ret = validate_branch(file, func, insn, state);
2379 if (ret && backtrace)
2380 BT_FUNC("<=== (func)", insn);
2381 warnings += ret;
2382 }
2383 }
2384
2385 return warnings;
2386 }
2387
2388 static int validate_reachable_instructions(struct objtool_file *file)
2389 {
2390 struct instruction *insn;
2391
2392 if (file->ignore_unreachables)
2393 return 0;
2394
2395 for_each_insn(file, insn) {
2396 if (insn->visited || ignore_unreachable_insn(insn))
2397 continue;
2398
2399 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
2400 return 1;
2401 }
2402
2403 return 0;
2404 }
2405
2406 static void cleanup(struct objtool_file *file)
2407 {
2408 struct instruction *insn, *tmpinsn;
2409 struct alternative *alt, *tmpalt;
2410
2411 list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) {
2412 list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) {
2413 list_del(&alt->list);
2414 free(alt);
2415 }
2416 list_del(&insn->list);
2417 hash_del(&insn->hash);
2418 free(insn);
2419 }
2420 elf_close(file->elf);
2421 }
2422
2423 static struct objtool_file file;
2424
2425 int check(const char *_objname, bool orc)
2426 {
2427 int ret, warnings = 0;
2428
2429 objname = _objname;
2430
2431 file.elf = elf_read(objname, orc ? O_RDWR : O_RDONLY);
2432 if (!file.elf)
2433 return 1;
2434
2435 INIT_LIST_HEAD(&file.insn_list);
2436 hash_init(file.insn_hash);
2437 file.c_file = find_section_by_name(file.elf, ".comment");
2438 file.ignore_unreachables = no_unreachable;
2439 file.hints = false;
2440
2441 arch_initial_func_cfi_state(&initial_func_cfi);
2442
2443 ret = decode_sections(&file);
2444 if (ret < 0)
2445 goto out;
2446 warnings += ret;
2447
2448 if (list_empty(&file.insn_list))
2449 goto out;
2450
2451 if (retpoline) {
2452 ret = validate_retpoline(&file);
2453 if (ret < 0)
2454 return ret;
2455 warnings += ret;
2456 }
2457
2458 ret = validate_functions(&file);
2459 if (ret < 0)
2460 goto out;
2461 warnings += ret;
2462
2463 ret = validate_unwind_hints(&file);
2464 if (ret < 0)
2465 goto out;
2466 warnings += ret;
2467
2468 if (!warnings) {
2469 ret = validate_reachable_instructions(&file);
2470 if (ret < 0)
2471 goto out;
2472 warnings += ret;
2473 }
2474
2475 if (orc) {
2476 ret = create_orc(&file);
2477 if (ret < 0)
2478 goto out;
2479
2480 ret = create_orc_sections(&file);
2481 if (ret < 0)
2482 goto out;
2483
2484 ret = elf_write(file.elf);
2485 if (ret < 0)
2486 goto out;
2487 }
2488
2489 out:
2490 cleanup(&file);
2491
2492 /* ignore warnings for now until we get all the code cleaned up */
2493 if (ret || warnings)
2494 return 0;
2495 return 0;
2496 }
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