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objtool: Optimize find_rela_by_dest_range()
[mirror_ubuntu-jammy-kernel.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(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 sym_for_each_insn(file, sym, insn) \
81 for (insn = find_insn(file, sym->sec, sym->offset); \
82 insn && &insn->list != &file->insn_list && \
83 insn->sec == sym->sec && \
84 insn->offset < sym->offset + sym->len; \
85 insn = list_next_entry(insn, list))
86
87 #define sym_for_each_insn_continue_reverse(file, sym, insn) \
88 for (insn = list_prev_entry(insn, list); \
89 &insn->list != &file->insn_list && \
90 insn->sec == sym->sec && insn->offset >= sym->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_static_jump(struct instruction *insn)
101 {
102 return insn->type == INSN_JUMP_CONDITIONAL ||
103 insn->type == INSN_JUMP_UNCONDITIONAL;
104 }
105
106 static bool is_sibling_call(struct instruction *insn)
107 {
108 /* An indirect jump is either a sibling call or a jump to a table. */
109 if (insn->type == INSN_JUMP_DYNAMIC)
110 return list_empty(&insn->alts);
111
112 if (!is_static_jump(insn))
113 return false;
114
115 /* add_jump_destinations() sets insn->call_dest for sibling calls. */
116 return !!insn->call_dest;
117 }
118
119 /*
120 * This checks to see if the given function is a "noreturn" function.
121 *
122 * For global functions which are outside the scope of this object file, we
123 * have to keep a manual list of them.
124 *
125 * For local functions, we have to detect them manually by simply looking for
126 * the lack of a return instruction.
127 */
128 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
129 int recursion)
130 {
131 int i;
132 struct instruction *insn;
133 bool empty = true;
134
135 /*
136 * Unfortunately these have to be hard coded because the noreturn
137 * attribute isn't provided in ELF data.
138 */
139 static const char * const global_noreturns[] = {
140 "__stack_chk_fail",
141 "panic",
142 "do_exit",
143 "do_task_dead",
144 "__module_put_and_exit",
145 "complete_and_exit",
146 "__reiserfs_panic",
147 "lbug_with_loc",
148 "fortify_panic",
149 "usercopy_abort",
150 "machine_real_restart",
151 "rewind_stack_do_exit",
152 "kunit_try_catch_throw",
153 };
154
155 if (!func)
156 return false;
157
158 if (func->bind == STB_WEAK)
159 return false;
160
161 if (func->bind == STB_GLOBAL)
162 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
163 if (!strcmp(func->name, global_noreturns[i]))
164 return true;
165
166 if (!func->len)
167 return false;
168
169 insn = find_insn(file, func->sec, func->offset);
170 if (!insn->func)
171 return false;
172
173 func_for_each_insn(file, func, insn) {
174 empty = false;
175
176 if (insn->type == INSN_RETURN)
177 return false;
178 }
179
180 if (empty)
181 return false;
182
183 /*
184 * A function can have a sibling call instead of a return. In that
185 * case, the function's dead-end status depends on whether the target
186 * of the sibling call returns.
187 */
188 func_for_each_insn(file, func, insn) {
189 if (is_sibling_call(insn)) {
190 struct instruction *dest = insn->jump_dest;
191
192 if (!dest)
193 /* sibling call to another file */
194 return false;
195
196 /* local sibling call */
197 if (recursion == 5) {
198 /*
199 * Infinite recursion: two functions have
200 * sibling calls to each other. This is a very
201 * rare case. It means they aren't dead ends.
202 */
203 return false;
204 }
205
206 return __dead_end_function(file, dest->func, recursion+1);
207 }
208 }
209
210 return true;
211 }
212
213 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
214 {
215 return __dead_end_function(file, func, 0);
216 }
217
218 static void clear_insn_state(struct insn_state *state)
219 {
220 int i;
221
222 memset(state, 0, sizeof(*state));
223 state->cfa.base = CFI_UNDEFINED;
224 for (i = 0; i < CFI_NUM_REGS; i++) {
225 state->regs[i].base = CFI_UNDEFINED;
226 state->vals[i].base = CFI_UNDEFINED;
227 }
228 state->drap_reg = CFI_UNDEFINED;
229 state->drap_offset = -1;
230 }
231
232 /*
233 * Call the arch-specific instruction decoder for all the instructions and add
234 * them to the global instruction list.
235 */
236 static int decode_instructions(struct objtool_file *file)
237 {
238 struct section *sec;
239 struct symbol *func;
240 unsigned long offset;
241 struct instruction *insn;
242 unsigned long nr_insns = 0;
243 int ret;
244
245 for_each_sec(file, sec) {
246
247 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
248 continue;
249
250 if (strcmp(sec->name, ".altinstr_replacement") &&
251 strcmp(sec->name, ".altinstr_aux") &&
252 strncmp(sec->name, ".discard.", 9))
253 sec->text = true;
254
255 for (offset = 0; offset < sec->len; offset += insn->len) {
256 insn = malloc(sizeof(*insn));
257 if (!insn) {
258 WARN("malloc failed");
259 return -1;
260 }
261 memset(insn, 0, sizeof(*insn));
262 INIT_LIST_HEAD(&insn->alts);
263 clear_insn_state(&insn->state);
264
265 insn->sec = sec;
266 insn->offset = offset;
267
268 ret = arch_decode_instruction(file->elf, sec, offset,
269 sec->len - offset,
270 &insn->len, &insn->type,
271 &insn->immediate,
272 &insn->stack_op);
273 if (ret)
274 goto err;
275
276 hash_add(file->insn_hash, &insn->hash, insn->offset);
277 list_add_tail(&insn->list, &file->insn_list);
278 nr_insns++;
279 }
280
281 list_for_each_entry(func, &sec->symbol_list, list) {
282 if (func->type != STT_FUNC || func->alias != func)
283 continue;
284
285 if (!find_insn(file, sec, func->offset)) {
286 WARN("%s(): can't find starting instruction",
287 func->name);
288 return -1;
289 }
290
291 sym_for_each_insn(file, func, insn)
292 insn->func = func;
293 }
294 }
295
296 if (stats)
297 printf("nr_insns: %lu\n", nr_insns);
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 struct rela *rela;
416
417 sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
418 if (!sec)
419 return;
420
421 list_for_each_entry(rela, &sec->rela_list, list) {
422 switch (rela->sym->type) {
423 case STT_FUNC:
424 func = rela->sym;
425 break;
426
427 case STT_SECTION:
428 func = find_func_by_offset(rela->sym->sec, rela->addend);
429 if (!func)
430 continue;
431 break;
432
433 default:
434 WARN("unexpected relocation symbol type in %s: %d", sec->name, rela->sym->type);
435 continue;
436 }
437
438 func_for_each_insn(file, func, insn)
439 insn->ignore = true;
440 }
441 }
442
443 /*
444 * This is a whitelist of functions that is allowed to be called with AC set.
445 * The list is meant to be minimal and only contains compiler instrumentation
446 * ABI and a few functions used to implement *_{to,from}_user() functions.
447 *
448 * These functions must not directly change AC, but may PUSHF/POPF.
449 */
450 static const char *uaccess_safe_builtin[] = {
451 /* KASAN */
452 "kasan_report",
453 "check_memory_region",
454 /* KASAN out-of-line */
455 "__asan_loadN_noabort",
456 "__asan_load1_noabort",
457 "__asan_load2_noabort",
458 "__asan_load4_noabort",
459 "__asan_load8_noabort",
460 "__asan_load16_noabort",
461 "__asan_storeN_noabort",
462 "__asan_store1_noabort",
463 "__asan_store2_noabort",
464 "__asan_store4_noabort",
465 "__asan_store8_noabort",
466 "__asan_store16_noabort",
467 /* KASAN in-line */
468 "__asan_report_load_n_noabort",
469 "__asan_report_load1_noabort",
470 "__asan_report_load2_noabort",
471 "__asan_report_load4_noabort",
472 "__asan_report_load8_noabort",
473 "__asan_report_load16_noabort",
474 "__asan_report_store_n_noabort",
475 "__asan_report_store1_noabort",
476 "__asan_report_store2_noabort",
477 "__asan_report_store4_noabort",
478 "__asan_report_store8_noabort",
479 "__asan_report_store16_noabort",
480 /* KCOV */
481 "write_comp_data",
482 "__sanitizer_cov_trace_pc",
483 "__sanitizer_cov_trace_const_cmp1",
484 "__sanitizer_cov_trace_const_cmp2",
485 "__sanitizer_cov_trace_const_cmp4",
486 "__sanitizer_cov_trace_const_cmp8",
487 "__sanitizer_cov_trace_cmp1",
488 "__sanitizer_cov_trace_cmp2",
489 "__sanitizer_cov_trace_cmp4",
490 "__sanitizer_cov_trace_cmp8",
491 /* UBSAN */
492 "ubsan_type_mismatch_common",
493 "__ubsan_handle_type_mismatch",
494 "__ubsan_handle_type_mismatch_v1",
495 "__ubsan_handle_shift_out_of_bounds",
496 /* misc */
497 "csum_partial_copy_generic",
498 "__memcpy_mcsafe",
499 "mcsafe_handle_tail",
500 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
501 NULL
502 };
503
504 static void add_uaccess_safe(struct objtool_file *file)
505 {
506 struct symbol *func;
507 const char **name;
508
509 if (!uaccess)
510 return;
511
512 for (name = uaccess_safe_builtin; *name; name++) {
513 func = find_symbol_by_name(file->elf, *name);
514 if (!func)
515 continue;
516
517 func->uaccess_safe = true;
518 }
519 }
520
521 /*
522 * FIXME: For now, just ignore any alternatives which add retpolines. This is
523 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
524 * But it at least allows objtool to understand the control flow *around* the
525 * retpoline.
526 */
527 static int add_ignore_alternatives(struct objtool_file *file)
528 {
529 struct section *sec;
530 struct rela *rela;
531 struct instruction *insn;
532
533 sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
534 if (!sec)
535 return 0;
536
537 list_for_each_entry(rela, &sec->rela_list, list) {
538 if (rela->sym->type != STT_SECTION) {
539 WARN("unexpected relocation symbol type in %s", sec->name);
540 return -1;
541 }
542
543 insn = find_insn(file, rela->sym->sec, rela->addend);
544 if (!insn) {
545 WARN("bad .discard.ignore_alts entry");
546 return -1;
547 }
548
549 insn->ignore_alts = true;
550 }
551
552 return 0;
553 }
554
555 /*
556 * Find the destination instructions for all jumps.
557 */
558 static int add_jump_destinations(struct objtool_file *file)
559 {
560 struct instruction *insn;
561 struct rela *rela;
562 struct section *dest_sec;
563 unsigned long dest_off;
564
565 for_each_insn(file, insn) {
566 if (!is_static_jump(insn))
567 continue;
568
569 if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET)
570 continue;
571
572 rela = find_rela_by_dest_range(file->elf, insn->sec,
573 insn->offset, insn->len);
574 if (!rela) {
575 dest_sec = insn->sec;
576 dest_off = insn->offset + insn->len + insn->immediate;
577 } else if (rela->sym->type == STT_SECTION) {
578 dest_sec = rela->sym->sec;
579 dest_off = rela->addend + 4;
580 } else if (rela->sym->sec->idx) {
581 dest_sec = rela->sym->sec;
582 dest_off = rela->sym->sym.st_value + rela->addend + 4;
583 } else if (strstr(rela->sym->name, "_indirect_thunk_")) {
584 /*
585 * Retpoline jumps are really dynamic jumps in
586 * disguise, so convert them accordingly.
587 */
588 if (insn->type == INSN_JUMP_UNCONDITIONAL)
589 insn->type = INSN_JUMP_DYNAMIC;
590 else
591 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
592
593 insn->retpoline_safe = true;
594 continue;
595 } else {
596 /* external sibling call */
597 insn->call_dest = rela->sym;
598 continue;
599 }
600
601 insn->jump_dest = find_insn(file, dest_sec, dest_off);
602 if (!insn->jump_dest) {
603
604 /*
605 * This is a special case where an alt instruction
606 * jumps past the end of the section. These are
607 * handled later in handle_group_alt().
608 */
609 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
610 continue;
611
612 WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
613 insn->sec, insn->offset, dest_sec->name,
614 dest_off);
615 return -1;
616 }
617
618 /*
619 * Cross-function jump.
620 */
621 if (insn->func && insn->jump_dest->func &&
622 insn->func != insn->jump_dest->func) {
623
624 /*
625 * For GCC 8+, create parent/child links for any cold
626 * subfunctions. This is _mostly_ redundant with a
627 * similar initialization in read_symbols().
628 *
629 * If a function has aliases, we want the *first* such
630 * function in the symbol table to be the subfunction's
631 * parent. In that case we overwrite the
632 * initialization done in read_symbols().
633 *
634 * However this code can't completely replace the
635 * read_symbols() code because this doesn't detect the
636 * case where the parent function's only reference to a
637 * subfunction is through a jump table.
638 */
639 if (!strstr(insn->func->name, ".cold.") &&
640 strstr(insn->jump_dest->func->name, ".cold.")) {
641 insn->func->cfunc = insn->jump_dest->func;
642 insn->jump_dest->func->pfunc = insn->func;
643
644 } else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
645 insn->jump_dest->offset == insn->jump_dest->func->offset) {
646
647 /* internal sibling call */
648 insn->call_dest = insn->jump_dest->func;
649 }
650 }
651 }
652
653 return 0;
654 }
655
656 /*
657 * Find the destination instructions for all calls.
658 */
659 static int add_call_destinations(struct objtool_file *file)
660 {
661 struct instruction *insn;
662 unsigned long dest_off;
663 struct rela *rela;
664
665 for_each_insn(file, insn) {
666 if (insn->type != INSN_CALL)
667 continue;
668
669 rela = find_rela_by_dest_range(file->elf, insn->sec,
670 insn->offset, insn->len);
671 if (!rela) {
672 dest_off = insn->offset + insn->len + insn->immediate;
673 insn->call_dest = find_func_by_offset(insn->sec, dest_off);
674 if (!insn->call_dest)
675 insn->call_dest = find_symbol_by_offset(insn->sec, dest_off);
676
677 if (insn->ignore)
678 continue;
679
680 if (!insn->call_dest) {
681 WARN_FUNC("unsupported intra-function call",
682 insn->sec, insn->offset);
683 if (retpoline)
684 WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");
685 return -1;
686 }
687
688 if (insn->func && insn->call_dest->type != STT_FUNC) {
689 WARN_FUNC("unsupported call to non-function",
690 insn->sec, insn->offset);
691 return -1;
692 }
693
694 } else if (rela->sym->type == STT_SECTION) {
695 insn->call_dest = find_func_by_offset(rela->sym->sec,
696 rela->addend+4);
697 if (!insn->call_dest) {
698 WARN_FUNC("can't find call dest symbol at %s+0x%x",
699 insn->sec, insn->offset,
700 rela->sym->sec->name,
701 rela->addend + 4);
702 return -1;
703 }
704 } else
705 insn->call_dest = rela->sym;
706 }
707
708 return 0;
709 }
710
711 /*
712 * The .alternatives section requires some extra special care, over and above
713 * what other special sections require:
714 *
715 * 1. Because alternatives are patched in-place, we need to insert a fake jump
716 * instruction at the end so that validate_branch() skips all the original
717 * replaced instructions when validating the new instruction path.
718 *
719 * 2. An added wrinkle is that the new instruction length might be zero. In
720 * that case the old instructions are replaced with noops. We simulate that
721 * by creating a fake jump as the only new instruction.
722 *
723 * 3. In some cases, the alternative section includes an instruction which
724 * conditionally jumps to the _end_ of the entry. We have to modify these
725 * jumps' destinations to point back to .text rather than the end of the
726 * entry in .altinstr_replacement.
727 */
728 static int handle_group_alt(struct objtool_file *file,
729 struct special_alt *special_alt,
730 struct instruction *orig_insn,
731 struct instruction **new_insn)
732 {
733 struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
734 unsigned long dest_off;
735
736 last_orig_insn = NULL;
737 insn = orig_insn;
738 sec_for_each_insn_from(file, insn) {
739 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
740 break;
741
742 insn->alt_group = true;
743 last_orig_insn = insn;
744 }
745
746 if (next_insn_same_sec(file, last_orig_insn)) {
747 fake_jump = malloc(sizeof(*fake_jump));
748 if (!fake_jump) {
749 WARN("malloc failed");
750 return -1;
751 }
752 memset(fake_jump, 0, sizeof(*fake_jump));
753 INIT_LIST_HEAD(&fake_jump->alts);
754 clear_insn_state(&fake_jump->state);
755
756 fake_jump->sec = special_alt->new_sec;
757 fake_jump->offset = FAKE_JUMP_OFFSET;
758 fake_jump->type = INSN_JUMP_UNCONDITIONAL;
759 fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
760 fake_jump->func = orig_insn->func;
761 }
762
763 if (!special_alt->new_len) {
764 if (!fake_jump) {
765 WARN("%s: empty alternative at end of section",
766 special_alt->orig_sec->name);
767 return -1;
768 }
769
770 *new_insn = fake_jump;
771 return 0;
772 }
773
774 last_new_insn = NULL;
775 insn = *new_insn;
776 sec_for_each_insn_from(file, insn) {
777 if (insn->offset >= special_alt->new_off + special_alt->new_len)
778 break;
779
780 last_new_insn = insn;
781
782 insn->ignore = orig_insn->ignore_alts;
783 insn->func = orig_insn->func;
784
785 /*
786 * Since alternative replacement code is copy/pasted by the
787 * kernel after applying relocations, generally such code can't
788 * have relative-address relocation references to outside the
789 * .altinstr_replacement section, unless the arch's
790 * alternatives code can adjust the relative offsets
791 * accordingly.
792 *
793 * The x86 alternatives code adjusts the offsets only when it
794 * encounters a branch instruction at the very beginning of the
795 * replacement group.
796 */
797 if ((insn->offset != special_alt->new_off ||
798 (insn->type != INSN_CALL && !is_static_jump(insn))) &&
799 find_rela_by_dest_range(file->elf, insn->sec, insn->offset, insn->len)) {
800
801 WARN_FUNC("unsupported relocation in alternatives section",
802 insn->sec, insn->offset);
803 return -1;
804 }
805
806 if (!is_static_jump(insn))
807 continue;
808
809 if (!insn->immediate)
810 continue;
811
812 dest_off = insn->offset + insn->len + insn->immediate;
813 if (dest_off == special_alt->new_off + special_alt->new_len) {
814 if (!fake_jump) {
815 WARN("%s: alternative jump to end of section",
816 special_alt->orig_sec->name);
817 return -1;
818 }
819 insn->jump_dest = fake_jump;
820 }
821
822 if (!insn->jump_dest) {
823 WARN_FUNC("can't find alternative jump destination",
824 insn->sec, insn->offset);
825 return -1;
826 }
827 }
828
829 if (!last_new_insn) {
830 WARN_FUNC("can't find last new alternative instruction",
831 special_alt->new_sec, special_alt->new_off);
832 return -1;
833 }
834
835 if (fake_jump)
836 list_add(&fake_jump->list, &last_new_insn->list);
837
838 return 0;
839 }
840
841 /*
842 * A jump table entry can either convert a nop to a jump or a jump to a nop.
843 * If the original instruction is a jump, make the alt entry an effective nop
844 * by just skipping the original instruction.
845 */
846 static int handle_jump_alt(struct objtool_file *file,
847 struct special_alt *special_alt,
848 struct instruction *orig_insn,
849 struct instruction **new_insn)
850 {
851 if (orig_insn->type == INSN_NOP)
852 return 0;
853
854 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
855 WARN_FUNC("unsupported instruction at jump label",
856 orig_insn->sec, orig_insn->offset);
857 return -1;
858 }
859
860 *new_insn = list_next_entry(orig_insn, list);
861 return 0;
862 }
863
864 /*
865 * Read all the special sections which have alternate instructions which can be
866 * patched in or redirected to at runtime. Each instruction having alternate
867 * instruction(s) has them added to its insn->alts list, which will be
868 * traversed in validate_branch().
869 */
870 static int add_special_section_alts(struct objtool_file *file)
871 {
872 struct list_head special_alts;
873 struct instruction *orig_insn, *new_insn;
874 struct special_alt *special_alt, *tmp;
875 struct alternative *alt;
876 int ret;
877
878 ret = special_get_alts(file->elf, &special_alts);
879 if (ret)
880 return ret;
881
882 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
883
884 orig_insn = find_insn(file, special_alt->orig_sec,
885 special_alt->orig_off);
886 if (!orig_insn) {
887 WARN_FUNC("special: can't find orig instruction",
888 special_alt->orig_sec, special_alt->orig_off);
889 ret = -1;
890 goto out;
891 }
892
893 new_insn = NULL;
894 if (!special_alt->group || special_alt->new_len) {
895 new_insn = find_insn(file, special_alt->new_sec,
896 special_alt->new_off);
897 if (!new_insn) {
898 WARN_FUNC("special: can't find new instruction",
899 special_alt->new_sec,
900 special_alt->new_off);
901 ret = -1;
902 goto out;
903 }
904 }
905
906 if (special_alt->group) {
907 ret = handle_group_alt(file, special_alt, orig_insn,
908 &new_insn);
909 if (ret)
910 goto out;
911 } else if (special_alt->jump_or_nop) {
912 ret = handle_jump_alt(file, special_alt, orig_insn,
913 &new_insn);
914 if (ret)
915 goto out;
916 }
917
918 alt = malloc(sizeof(*alt));
919 if (!alt) {
920 WARN("malloc failed");
921 ret = -1;
922 goto out;
923 }
924
925 alt->insn = new_insn;
926 alt->skip_orig = special_alt->skip_orig;
927 orig_insn->ignore_alts |= special_alt->skip_alt;
928 list_add_tail(&alt->list, &orig_insn->alts);
929
930 list_del(&special_alt->list);
931 free(special_alt);
932 }
933
934 out:
935 return ret;
936 }
937
938 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
939 struct rela *table)
940 {
941 struct rela *rela = table;
942 struct instruction *dest_insn;
943 struct alternative *alt;
944 struct symbol *pfunc = insn->func->pfunc;
945 unsigned int prev_offset = 0;
946
947 /*
948 * Each @rela is a switch table relocation which points to the target
949 * instruction.
950 */
951 list_for_each_entry_from(rela, &table->sec->rela_list, list) {
952
953 /* Check for the end of the table: */
954 if (rela != table && rela->jump_table_start)
955 break;
956
957 /* Make sure the table entries are consecutive: */
958 if (prev_offset && rela->offset != prev_offset + 8)
959 break;
960
961 /* Detect function pointers from contiguous objects: */
962 if (rela->sym->sec == pfunc->sec &&
963 rela->addend == pfunc->offset)
964 break;
965
966 dest_insn = find_insn(file, rela->sym->sec, rela->addend);
967 if (!dest_insn)
968 break;
969
970 /* Make sure the destination is in the same function: */
971 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
972 break;
973
974 alt = malloc(sizeof(*alt));
975 if (!alt) {
976 WARN("malloc failed");
977 return -1;
978 }
979
980 alt->insn = dest_insn;
981 list_add_tail(&alt->list, &insn->alts);
982 prev_offset = rela->offset;
983 }
984
985 if (!prev_offset) {
986 WARN_FUNC("can't find switch jump table",
987 insn->sec, insn->offset);
988 return -1;
989 }
990
991 return 0;
992 }
993
994 /*
995 * find_jump_table() - Given a dynamic jump, find the switch jump table in
996 * .rodata associated with it.
997 *
998 * There are 3 basic patterns:
999 *
1000 * 1. jmpq *[rodata addr](,%reg,8)
1001 *
1002 * This is the most common case by far. It jumps to an address in a simple
1003 * jump table which is stored in .rodata.
1004 *
1005 * 2. jmpq *[rodata addr](%rip)
1006 *
1007 * This is caused by a rare GCC quirk, currently only seen in three driver
1008 * functions in the kernel, only with certain obscure non-distro configs.
1009 *
1010 * As part of an optimization, GCC makes a copy of an existing switch jump
1011 * table, modifies it, and then hard-codes the jump (albeit with an indirect
1012 * jump) to use a single entry in the table. The rest of the jump table and
1013 * some of its jump targets remain as dead code.
1014 *
1015 * In such a case we can just crudely ignore all unreachable instruction
1016 * warnings for the entire object file. Ideally we would just ignore them
1017 * for the function, but that would require redesigning the code quite a
1018 * bit. And honestly that's just not worth doing: unreachable instruction
1019 * warnings are of questionable value anyway, and this is such a rare issue.
1020 *
1021 * 3. mov [rodata addr],%reg1
1022 * ... some instructions ...
1023 * jmpq *(%reg1,%reg2,8)
1024 *
1025 * This is a fairly uncommon pattern which is new for GCC 6. As of this
1026 * writing, there are 11 occurrences of it in the allmodconfig kernel.
1027 *
1028 * As of GCC 7 there are quite a few more of these and the 'in between' code
1029 * is significant. Esp. with KASAN enabled some of the code between the mov
1030 * and jmpq uses .rodata itself, which can confuse things.
1031 *
1032 * TODO: Once we have DWARF CFI and smarter instruction decoding logic,
1033 * ensure the same register is used in the mov and jump instructions.
1034 *
1035 * NOTE: RETPOLINE made it harder still to decode dynamic jumps.
1036 */
1037 static struct rela *find_jump_table(struct objtool_file *file,
1038 struct symbol *func,
1039 struct instruction *insn)
1040 {
1041 struct rela *text_rela, *table_rela;
1042 struct instruction *dest_insn, *orig_insn = insn;
1043 struct section *table_sec;
1044 unsigned long table_offset;
1045
1046 /*
1047 * Backward search using the @first_jump_src links, these help avoid
1048 * much of the 'in between' code. Which avoids us getting confused by
1049 * it.
1050 */
1051 for (;
1052 &insn->list != &file->insn_list &&
1053 insn->sec == func->sec &&
1054 insn->offset >= func->offset;
1055
1056 insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
1057
1058 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1059 break;
1060
1061 /* allow small jumps within the range */
1062 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1063 insn->jump_dest &&
1064 (insn->jump_dest->offset <= insn->offset ||
1065 insn->jump_dest->offset > orig_insn->offset))
1066 break;
1067
1068 /* look for a relocation which references .rodata */
1069 text_rela = find_rela_by_dest_range(file->elf, insn->sec,
1070 insn->offset, insn->len);
1071 if (!text_rela || text_rela->sym->type != STT_SECTION ||
1072 !text_rela->sym->sec->rodata)
1073 continue;
1074
1075 table_offset = text_rela->addend;
1076 table_sec = text_rela->sym->sec;
1077
1078 if (text_rela->type == R_X86_64_PC32)
1079 table_offset += 4;
1080
1081 /*
1082 * Make sure the .rodata address isn't associated with a
1083 * symbol. GCC jump tables are anonymous data.
1084 *
1085 * Also support C jump tables which are in the same format as
1086 * switch jump tables. For objtool to recognize them, they
1087 * need to be placed in the C_JUMP_TABLE_SECTION section. They
1088 * have symbols associated with them.
1089 */
1090 if (find_symbol_containing(table_sec, table_offset) &&
1091 strcmp(table_sec->name, C_JUMP_TABLE_SECTION))
1092 continue;
1093
1094 /*
1095 * Each table entry has a rela associated with it. The rela
1096 * should reference text in the same function as the original
1097 * instruction.
1098 */
1099 table_rela = find_rela_by_dest(file->elf, table_sec, table_offset);
1100 if (!table_rela)
1101 continue;
1102 dest_insn = find_insn(file, table_rela->sym->sec, table_rela->addend);
1103 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1104 continue;
1105
1106 /*
1107 * Use of RIP-relative switch jumps is quite rare, and
1108 * indicates a rare GCC quirk/bug which can leave dead code
1109 * behind.
1110 */
1111 if (text_rela->type == R_X86_64_PC32)
1112 file->ignore_unreachables = true;
1113
1114 return table_rela;
1115 }
1116
1117 return NULL;
1118 }
1119
1120 /*
1121 * First pass: Mark the head of each jump table so that in the next pass,
1122 * we know when a given jump table ends and the next one starts.
1123 */
1124 static void mark_func_jump_tables(struct objtool_file *file,
1125 struct symbol *func)
1126 {
1127 struct instruction *insn, *last = NULL;
1128 struct rela *rela;
1129
1130 func_for_each_insn(file, func, insn) {
1131 if (!last)
1132 last = insn;
1133
1134 /*
1135 * Store back-pointers for unconditional forward jumps such
1136 * that find_jump_table() can back-track using those and
1137 * avoid some potentially confusing code.
1138 */
1139 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1140 insn->offset > last->offset &&
1141 insn->jump_dest->offset > insn->offset &&
1142 !insn->jump_dest->first_jump_src) {
1143
1144 insn->jump_dest->first_jump_src = insn;
1145 last = insn->jump_dest;
1146 }
1147
1148 if (insn->type != INSN_JUMP_DYNAMIC)
1149 continue;
1150
1151 rela = find_jump_table(file, func, insn);
1152 if (rela) {
1153 rela->jump_table_start = true;
1154 insn->jump_table = rela;
1155 }
1156 }
1157 }
1158
1159 static int add_func_jump_tables(struct objtool_file *file,
1160 struct symbol *func)
1161 {
1162 struct instruction *insn;
1163 int ret;
1164
1165 func_for_each_insn(file, func, insn) {
1166 if (!insn->jump_table)
1167 continue;
1168
1169 ret = add_jump_table(file, insn, insn->jump_table);
1170 if (ret)
1171 return ret;
1172 }
1173
1174 return 0;
1175 }
1176
1177 /*
1178 * For some switch statements, gcc generates a jump table in the .rodata
1179 * section which contains a list of addresses within the function to jump to.
1180 * This finds these jump tables and adds them to the insn->alts lists.
1181 */
1182 static int add_jump_table_alts(struct objtool_file *file)
1183 {
1184 struct section *sec;
1185 struct symbol *func;
1186 int ret;
1187
1188 if (!file->rodata)
1189 return 0;
1190
1191 for_each_sec(file, sec) {
1192 list_for_each_entry(func, &sec->symbol_list, list) {
1193 if (func->type != STT_FUNC)
1194 continue;
1195
1196 mark_func_jump_tables(file, func);
1197 ret = add_func_jump_tables(file, func);
1198 if (ret)
1199 return ret;
1200 }
1201 }
1202
1203 return 0;
1204 }
1205
1206 static int read_unwind_hints(struct objtool_file *file)
1207 {
1208 struct section *sec, *relasec;
1209 struct rela *rela;
1210 struct unwind_hint *hint;
1211 struct instruction *insn;
1212 struct cfi_reg *cfa;
1213 int i;
1214
1215 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1216 if (!sec)
1217 return 0;
1218
1219 relasec = sec->rela;
1220 if (!relasec) {
1221 WARN("missing .rela.discard.unwind_hints section");
1222 return -1;
1223 }
1224
1225 if (sec->len % sizeof(struct unwind_hint)) {
1226 WARN("struct unwind_hint size mismatch");
1227 return -1;
1228 }
1229
1230 file->hints = true;
1231
1232 for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
1233 hint = (struct unwind_hint *)sec->data->d_buf + i;
1234
1235 rela = find_rela_by_dest(file->elf, sec, i * sizeof(*hint));
1236 if (!rela) {
1237 WARN("can't find rela for unwind_hints[%d]", i);
1238 return -1;
1239 }
1240
1241 insn = find_insn(file, rela->sym->sec, rela->addend);
1242 if (!insn) {
1243 WARN("can't find insn for unwind_hints[%d]", i);
1244 return -1;
1245 }
1246
1247 cfa = &insn->state.cfa;
1248
1249 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
1250 insn->save = true;
1251 continue;
1252
1253 } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
1254 insn->restore = true;
1255 insn->hint = true;
1256 continue;
1257 }
1258
1259 insn->hint = true;
1260
1261 switch (hint->sp_reg) {
1262 case ORC_REG_UNDEFINED:
1263 cfa->base = CFI_UNDEFINED;
1264 break;
1265 case ORC_REG_SP:
1266 cfa->base = CFI_SP;
1267 break;
1268 case ORC_REG_BP:
1269 cfa->base = CFI_BP;
1270 break;
1271 case ORC_REG_SP_INDIRECT:
1272 cfa->base = CFI_SP_INDIRECT;
1273 break;
1274 case ORC_REG_R10:
1275 cfa->base = CFI_R10;
1276 break;
1277 case ORC_REG_R13:
1278 cfa->base = CFI_R13;
1279 break;
1280 case ORC_REG_DI:
1281 cfa->base = CFI_DI;
1282 break;
1283 case ORC_REG_DX:
1284 cfa->base = CFI_DX;
1285 break;
1286 default:
1287 WARN_FUNC("unsupported unwind_hint sp base reg %d",
1288 insn->sec, insn->offset, hint->sp_reg);
1289 return -1;
1290 }
1291
1292 cfa->offset = hint->sp_offset;
1293 insn->state.type = hint->type;
1294 insn->state.end = hint->end;
1295 }
1296
1297 return 0;
1298 }
1299
1300 static int read_retpoline_hints(struct objtool_file *file)
1301 {
1302 struct section *sec;
1303 struct instruction *insn;
1304 struct rela *rela;
1305
1306 sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1307 if (!sec)
1308 return 0;
1309
1310 list_for_each_entry(rela, &sec->rela_list, list) {
1311 if (rela->sym->type != STT_SECTION) {
1312 WARN("unexpected relocation symbol type in %s", sec->name);
1313 return -1;
1314 }
1315
1316 insn = find_insn(file, rela->sym->sec, rela->addend);
1317 if (!insn) {
1318 WARN("bad .discard.retpoline_safe entry");
1319 return -1;
1320 }
1321
1322 if (insn->type != INSN_JUMP_DYNAMIC &&
1323 insn->type != INSN_CALL_DYNAMIC) {
1324 WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1325 insn->sec, insn->offset);
1326 return -1;
1327 }
1328
1329 insn->retpoline_safe = true;
1330 }
1331
1332 return 0;
1333 }
1334
1335 static void mark_rodata(struct objtool_file *file)
1336 {
1337 struct section *sec;
1338 bool found = false;
1339
1340 /*
1341 * Search for the following rodata sections, each of which can
1342 * potentially contain jump tables:
1343 *
1344 * - .rodata: can contain GCC switch tables
1345 * - .rodata.<func>: same, if -fdata-sections is being used
1346 * - .rodata..c_jump_table: contains C annotated jump tables
1347 *
1348 * .rodata.str1.* sections are ignored; they don't contain jump tables.
1349 */
1350 for_each_sec(file, sec) {
1351 if ((!strncmp(sec->name, ".rodata", 7) && !strstr(sec->name, ".str1.")) ||
1352 !strcmp(sec->name, C_JUMP_TABLE_SECTION)) {
1353 sec->rodata = true;
1354 found = true;
1355 }
1356 }
1357
1358 file->rodata = found;
1359 }
1360
1361 static int decode_sections(struct objtool_file *file)
1362 {
1363 int ret;
1364
1365 mark_rodata(file);
1366
1367 ret = decode_instructions(file);
1368 if (ret)
1369 return ret;
1370
1371 ret = add_dead_ends(file);
1372 if (ret)
1373 return ret;
1374
1375 add_ignores(file);
1376 add_uaccess_safe(file);
1377
1378 ret = add_ignore_alternatives(file);
1379 if (ret)
1380 return ret;
1381
1382 ret = add_jump_destinations(file);
1383 if (ret)
1384 return ret;
1385
1386 ret = add_special_section_alts(file);
1387 if (ret)
1388 return ret;
1389
1390 ret = add_call_destinations(file);
1391 if (ret)
1392 return ret;
1393
1394 ret = add_jump_table_alts(file);
1395 if (ret)
1396 return ret;
1397
1398 ret = read_unwind_hints(file);
1399 if (ret)
1400 return ret;
1401
1402 ret = read_retpoline_hints(file);
1403 if (ret)
1404 return ret;
1405
1406 return 0;
1407 }
1408
1409 static bool is_fentry_call(struct instruction *insn)
1410 {
1411 if (insn->type == INSN_CALL &&
1412 insn->call_dest->type == STT_NOTYPE &&
1413 !strcmp(insn->call_dest->name, "__fentry__"))
1414 return true;
1415
1416 return false;
1417 }
1418
1419 static bool has_modified_stack_frame(struct insn_state *state)
1420 {
1421 int i;
1422
1423 if (state->cfa.base != initial_func_cfi.cfa.base ||
1424 state->cfa.offset != initial_func_cfi.cfa.offset ||
1425 state->stack_size != initial_func_cfi.cfa.offset ||
1426 state->drap)
1427 return true;
1428
1429 for (i = 0; i < CFI_NUM_REGS; i++)
1430 if (state->regs[i].base != initial_func_cfi.regs[i].base ||
1431 state->regs[i].offset != initial_func_cfi.regs[i].offset)
1432 return true;
1433
1434 return false;
1435 }
1436
1437 static bool has_valid_stack_frame(struct insn_state *state)
1438 {
1439 if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
1440 state->regs[CFI_BP].offset == -16)
1441 return true;
1442
1443 if (state->drap && state->regs[CFI_BP].base == CFI_BP)
1444 return true;
1445
1446 return false;
1447 }
1448
1449 static int update_insn_state_regs(struct instruction *insn, struct insn_state *state)
1450 {
1451 struct cfi_reg *cfa = &state->cfa;
1452 struct stack_op *op = &insn->stack_op;
1453
1454 if (cfa->base != CFI_SP)
1455 return 0;
1456
1457 /* push */
1458 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
1459 cfa->offset += 8;
1460
1461 /* pop */
1462 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
1463 cfa->offset -= 8;
1464
1465 /* add immediate to sp */
1466 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1467 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1468 cfa->offset -= op->src.offset;
1469
1470 return 0;
1471 }
1472
1473 static void save_reg(struct insn_state *state, unsigned char reg, int base,
1474 int offset)
1475 {
1476 if (arch_callee_saved_reg(reg) &&
1477 state->regs[reg].base == CFI_UNDEFINED) {
1478 state->regs[reg].base = base;
1479 state->regs[reg].offset = offset;
1480 }
1481 }
1482
1483 static void restore_reg(struct insn_state *state, unsigned char reg)
1484 {
1485 state->regs[reg].base = CFI_UNDEFINED;
1486 state->regs[reg].offset = 0;
1487 }
1488
1489 /*
1490 * A note about DRAP stack alignment:
1491 *
1492 * GCC has the concept of a DRAP register, which is used to help keep track of
1493 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
1494 * register. The typical DRAP pattern is:
1495 *
1496 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
1497 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
1498 * 41 ff 72 f8 pushq -0x8(%r10)
1499 * 55 push %rbp
1500 * 48 89 e5 mov %rsp,%rbp
1501 * (more pushes)
1502 * 41 52 push %r10
1503 * ...
1504 * 41 5a pop %r10
1505 * (more pops)
1506 * 5d pop %rbp
1507 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1508 * c3 retq
1509 *
1510 * There are some variations in the epilogues, like:
1511 *
1512 * 5b pop %rbx
1513 * 41 5a pop %r10
1514 * 41 5c pop %r12
1515 * 41 5d pop %r13
1516 * 41 5e pop %r14
1517 * c9 leaveq
1518 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1519 * c3 retq
1520 *
1521 * and:
1522 *
1523 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
1524 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
1525 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
1526 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
1527 * c9 leaveq
1528 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1529 * c3 retq
1530 *
1531 * Sometimes r13 is used as the DRAP register, in which case it's saved and
1532 * restored beforehand:
1533 *
1534 * 41 55 push %r13
1535 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
1536 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
1537 * ...
1538 * 49 8d 65 f0 lea -0x10(%r13),%rsp
1539 * 41 5d pop %r13
1540 * c3 retq
1541 */
1542 static int update_insn_state(struct instruction *insn, struct insn_state *state)
1543 {
1544 struct stack_op *op = &insn->stack_op;
1545 struct cfi_reg *cfa = &state->cfa;
1546 struct cfi_reg *regs = state->regs;
1547
1548 /* stack operations don't make sense with an undefined CFA */
1549 if (cfa->base == CFI_UNDEFINED) {
1550 if (insn->func) {
1551 WARN_FUNC("undefined stack state", insn->sec, insn->offset);
1552 return -1;
1553 }
1554 return 0;
1555 }
1556
1557 if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET)
1558 return update_insn_state_regs(insn, state);
1559
1560 switch (op->dest.type) {
1561
1562 case OP_DEST_REG:
1563 switch (op->src.type) {
1564
1565 case OP_SRC_REG:
1566 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
1567 cfa->base == CFI_SP &&
1568 regs[CFI_BP].base == CFI_CFA &&
1569 regs[CFI_BP].offset == -cfa->offset) {
1570
1571 /* mov %rsp, %rbp */
1572 cfa->base = op->dest.reg;
1573 state->bp_scratch = false;
1574 }
1575
1576 else if (op->src.reg == CFI_SP &&
1577 op->dest.reg == CFI_BP && state->drap) {
1578
1579 /* drap: mov %rsp, %rbp */
1580 regs[CFI_BP].base = CFI_BP;
1581 regs[CFI_BP].offset = -state->stack_size;
1582 state->bp_scratch = false;
1583 }
1584
1585 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1586
1587 /*
1588 * mov %rsp, %reg
1589 *
1590 * This is needed for the rare case where GCC
1591 * does:
1592 *
1593 * mov %rsp, %rax
1594 * ...
1595 * mov %rax, %rsp
1596 */
1597 state->vals[op->dest.reg].base = CFI_CFA;
1598 state->vals[op->dest.reg].offset = -state->stack_size;
1599 }
1600
1601 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
1602 cfa->base == CFI_BP) {
1603
1604 /*
1605 * mov %rbp, %rsp
1606 *
1607 * Restore the original stack pointer (Clang).
1608 */
1609 state->stack_size = -state->regs[CFI_BP].offset;
1610 }
1611
1612 else if (op->dest.reg == cfa->base) {
1613
1614 /* mov %reg, %rsp */
1615 if (cfa->base == CFI_SP &&
1616 state->vals[op->src.reg].base == CFI_CFA) {
1617
1618 /*
1619 * This is needed for the rare case
1620 * where GCC does something dumb like:
1621 *
1622 * lea 0x8(%rsp), %rcx
1623 * ...
1624 * mov %rcx, %rsp
1625 */
1626 cfa->offset = -state->vals[op->src.reg].offset;
1627 state->stack_size = cfa->offset;
1628
1629 } else {
1630 cfa->base = CFI_UNDEFINED;
1631 cfa->offset = 0;
1632 }
1633 }
1634
1635 break;
1636
1637 case OP_SRC_ADD:
1638 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
1639
1640 /* add imm, %rsp */
1641 state->stack_size -= op->src.offset;
1642 if (cfa->base == CFI_SP)
1643 cfa->offset -= op->src.offset;
1644 break;
1645 }
1646
1647 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
1648
1649 /* lea disp(%rbp), %rsp */
1650 state->stack_size = -(op->src.offset + regs[CFI_BP].offset);
1651 break;
1652 }
1653
1654 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1655
1656 /* drap: lea disp(%rsp), %drap */
1657 state->drap_reg = op->dest.reg;
1658
1659 /*
1660 * lea disp(%rsp), %reg
1661 *
1662 * This is needed for the rare case where GCC
1663 * does something dumb like:
1664 *
1665 * lea 0x8(%rsp), %rcx
1666 * ...
1667 * mov %rcx, %rsp
1668 */
1669 state->vals[op->dest.reg].base = CFI_CFA;
1670 state->vals[op->dest.reg].offset = \
1671 -state->stack_size + op->src.offset;
1672
1673 break;
1674 }
1675
1676 if (state->drap && op->dest.reg == CFI_SP &&
1677 op->src.reg == state->drap_reg) {
1678
1679 /* drap: lea disp(%drap), %rsp */
1680 cfa->base = CFI_SP;
1681 cfa->offset = state->stack_size = -op->src.offset;
1682 state->drap_reg = CFI_UNDEFINED;
1683 state->drap = false;
1684 break;
1685 }
1686
1687 if (op->dest.reg == state->cfa.base) {
1688 WARN_FUNC("unsupported stack register modification",
1689 insn->sec, insn->offset);
1690 return -1;
1691 }
1692
1693 break;
1694
1695 case OP_SRC_AND:
1696 if (op->dest.reg != CFI_SP ||
1697 (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
1698 (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
1699 WARN_FUNC("unsupported stack pointer realignment",
1700 insn->sec, insn->offset);
1701 return -1;
1702 }
1703
1704 if (state->drap_reg != CFI_UNDEFINED) {
1705 /* drap: and imm, %rsp */
1706 cfa->base = state->drap_reg;
1707 cfa->offset = state->stack_size = 0;
1708 state->drap = true;
1709 }
1710
1711 /*
1712 * Older versions of GCC (4.8ish) realign the stack
1713 * without DRAP, with a frame pointer.
1714 */
1715
1716 break;
1717
1718 case OP_SRC_POP:
1719 case OP_SRC_POPF:
1720 if (!state->drap && op->dest.type == OP_DEST_REG &&
1721 op->dest.reg == cfa->base) {
1722
1723 /* pop %rbp */
1724 cfa->base = CFI_SP;
1725 }
1726
1727 if (state->drap && cfa->base == CFI_BP_INDIRECT &&
1728 op->dest.type == OP_DEST_REG &&
1729 op->dest.reg == state->drap_reg &&
1730 state->drap_offset == -state->stack_size) {
1731
1732 /* drap: pop %drap */
1733 cfa->base = state->drap_reg;
1734 cfa->offset = 0;
1735 state->drap_offset = -1;
1736
1737 } else if (regs[op->dest.reg].offset == -state->stack_size) {
1738
1739 /* pop %reg */
1740 restore_reg(state, op->dest.reg);
1741 }
1742
1743 state->stack_size -= 8;
1744 if (cfa->base == CFI_SP)
1745 cfa->offset -= 8;
1746
1747 break;
1748
1749 case OP_SRC_REG_INDIRECT:
1750 if (state->drap && op->src.reg == CFI_BP &&
1751 op->src.offset == state->drap_offset) {
1752
1753 /* drap: mov disp(%rbp), %drap */
1754 cfa->base = state->drap_reg;
1755 cfa->offset = 0;
1756 state->drap_offset = -1;
1757 }
1758
1759 if (state->drap && op->src.reg == CFI_BP &&
1760 op->src.offset == regs[op->dest.reg].offset) {
1761
1762 /* drap: mov disp(%rbp), %reg */
1763 restore_reg(state, op->dest.reg);
1764
1765 } else if (op->src.reg == cfa->base &&
1766 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
1767
1768 /* mov disp(%rbp), %reg */
1769 /* mov disp(%rsp), %reg */
1770 restore_reg(state, op->dest.reg);
1771 }
1772
1773 break;
1774
1775 default:
1776 WARN_FUNC("unknown stack-related instruction",
1777 insn->sec, insn->offset);
1778 return -1;
1779 }
1780
1781 break;
1782
1783 case OP_DEST_PUSH:
1784 case OP_DEST_PUSHF:
1785 state->stack_size += 8;
1786 if (cfa->base == CFI_SP)
1787 cfa->offset += 8;
1788
1789 if (op->src.type != OP_SRC_REG)
1790 break;
1791
1792 if (state->drap) {
1793 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1794
1795 /* drap: push %drap */
1796 cfa->base = CFI_BP_INDIRECT;
1797 cfa->offset = -state->stack_size;
1798
1799 /* save drap so we know when to restore it */
1800 state->drap_offset = -state->stack_size;
1801
1802 } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
1803
1804 /* drap: push %rbp */
1805 state->stack_size = 0;
1806
1807 } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1808
1809 /* drap: push %reg */
1810 save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
1811 }
1812
1813 } else {
1814
1815 /* push %reg */
1816 save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
1817 }
1818
1819 /* detect when asm code uses rbp as a scratch register */
1820 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
1821 cfa->base != CFI_BP)
1822 state->bp_scratch = true;
1823 break;
1824
1825 case OP_DEST_REG_INDIRECT:
1826
1827 if (state->drap) {
1828 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1829
1830 /* drap: mov %drap, disp(%rbp) */
1831 cfa->base = CFI_BP_INDIRECT;
1832 cfa->offset = op->dest.offset;
1833
1834 /* save drap offset so we know when to restore it */
1835 state->drap_offset = op->dest.offset;
1836 }
1837
1838 else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1839
1840 /* drap: mov reg, disp(%rbp) */
1841 save_reg(state, op->src.reg, CFI_BP, op->dest.offset);
1842 }
1843
1844 } else if (op->dest.reg == cfa->base) {
1845
1846 /* mov reg, disp(%rbp) */
1847 /* mov reg, disp(%rsp) */
1848 save_reg(state, op->src.reg, CFI_CFA,
1849 op->dest.offset - state->cfa.offset);
1850 }
1851
1852 break;
1853
1854 case OP_DEST_LEAVE:
1855 if ((!state->drap && cfa->base != CFI_BP) ||
1856 (state->drap && cfa->base != state->drap_reg)) {
1857 WARN_FUNC("leave instruction with modified stack frame",
1858 insn->sec, insn->offset);
1859 return -1;
1860 }
1861
1862 /* leave (mov %rbp, %rsp; pop %rbp) */
1863
1864 state->stack_size = -state->regs[CFI_BP].offset - 8;
1865 restore_reg(state, CFI_BP);
1866
1867 if (!state->drap) {
1868 cfa->base = CFI_SP;
1869 cfa->offset -= 8;
1870 }
1871
1872 break;
1873
1874 case OP_DEST_MEM:
1875 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
1876 WARN_FUNC("unknown stack-related memory operation",
1877 insn->sec, insn->offset);
1878 return -1;
1879 }
1880
1881 /* pop mem */
1882 state->stack_size -= 8;
1883 if (cfa->base == CFI_SP)
1884 cfa->offset -= 8;
1885
1886 break;
1887
1888 default:
1889 WARN_FUNC("unknown stack-related instruction",
1890 insn->sec, insn->offset);
1891 return -1;
1892 }
1893
1894 return 0;
1895 }
1896
1897 static bool insn_state_match(struct instruction *insn, struct insn_state *state)
1898 {
1899 struct insn_state *state1 = &insn->state, *state2 = state;
1900 int i;
1901
1902 if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
1903 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
1904 insn->sec, insn->offset,
1905 state1->cfa.base, state1->cfa.offset,
1906 state2->cfa.base, state2->cfa.offset);
1907
1908 } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
1909 for (i = 0; i < CFI_NUM_REGS; i++) {
1910 if (!memcmp(&state1->regs[i], &state2->regs[i],
1911 sizeof(struct cfi_reg)))
1912 continue;
1913
1914 WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
1915 insn->sec, insn->offset,
1916 i, state1->regs[i].base, state1->regs[i].offset,
1917 i, state2->regs[i].base, state2->regs[i].offset);
1918 break;
1919 }
1920
1921 } else if (state1->type != state2->type) {
1922 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
1923 insn->sec, insn->offset, state1->type, state2->type);
1924
1925 } else if (state1->drap != state2->drap ||
1926 (state1->drap && state1->drap_reg != state2->drap_reg) ||
1927 (state1->drap && state1->drap_offset != state2->drap_offset)) {
1928 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
1929 insn->sec, insn->offset,
1930 state1->drap, state1->drap_reg, state1->drap_offset,
1931 state2->drap, state2->drap_reg, state2->drap_offset);
1932
1933 } else
1934 return true;
1935
1936 return false;
1937 }
1938
1939 static inline bool func_uaccess_safe(struct symbol *func)
1940 {
1941 if (func)
1942 return func->uaccess_safe;
1943
1944 return false;
1945 }
1946
1947 static inline const char *call_dest_name(struct instruction *insn)
1948 {
1949 if (insn->call_dest)
1950 return insn->call_dest->name;
1951
1952 return "{dynamic}";
1953 }
1954
1955 static int validate_call(struct instruction *insn, struct insn_state *state)
1956 {
1957 if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
1958 WARN_FUNC("call to %s() with UACCESS enabled",
1959 insn->sec, insn->offset, call_dest_name(insn));
1960 return 1;
1961 }
1962
1963 if (state->df) {
1964 WARN_FUNC("call to %s() with DF set",
1965 insn->sec, insn->offset, call_dest_name(insn));
1966 return 1;
1967 }
1968
1969 return 0;
1970 }
1971
1972 static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
1973 {
1974 if (has_modified_stack_frame(state)) {
1975 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1976 insn->sec, insn->offset);
1977 return 1;
1978 }
1979
1980 return validate_call(insn, state);
1981 }
1982
1983 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
1984 {
1985 if (state->uaccess && !func_uaccess_safe(func)) {
1986 WARN_FUNC("return with UACCESS enabled",
1987 insn->sec, insn->offset);
1988 return 1;
1989 }
1990
1991 if (!state->uaccess && func_uaccess_safe(func)) {
1992 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
1993 insn->sec, insn->offset);
1994 return 1;
1995 }
1996
1997 if (state->df) {
1998 WARN_FUNC("return with DF set",
1999 insn->sec, insn->offset);
2000 return 1;
2001 }
2002
2003 if (func && has_modified_stack_frame(state)) {
2004 WARN_FUNC("return with modified stack frame",
2005 insn->sec, insn->offset);
2006 return 1;
2007 }
2008
2009 if (state->bp_scratch) {
2010 WARN("%s uses BP as a scratch register",
2011 func->name);
2012 return 1;
2013 }
2014
2015 return 0;
2016 }
2017
2018 /*
2019 * Follow the branch starting at the given instruction, and recursively follow
2020 * any other branches (jumps). Meanwhile, track the frame pointer state at
2021 * each instruction and validate all the rules described in
2022 * tools/objtool/Documentation/stack-validation.txt.
2023 */
2024 static int validate_branch(struct objtool_file *file, struct symbol *func,
2025 struct instruction *first, struct insn_state state)
2026 {
2027 struct alternative *alt;
2028 struct instruction *insn, *next_insn;
2029 struct section *sec;
2030 u8 visited;
2031 int ret;
2032
2033 insn = first;
2034 sec = insn->sec;
2035
2036 if (insn->alt_group && list_empty(&insn->alts)) {
2037 WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
2038 sec, insn->offset);
2039 return 1;
2040 }
2041
2042 while (1) {
2043 next_insn = next_insn_same_sec(file, insn);
2044
2045 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
2046 WARN("%s() falls through to next function %s()",
2047 func->name, insn->func->name);
2048 return 1;
2049 }
2050
2051 if (func && insn->ignore) {
2052 WARN_FUNC("BUG: why am I validating an ignored function?",
2053 sec, insn->offset);
2054 return 1;
2055 }
2056
2057 visited = 1 << state.uaccess;
2058 if (insn->visited) {
2059 if (!insn->hint && !insn_state_match(insn, &state))
2060 return 1;
2061
2062 if (insn->visited & visited)
2063 return 0;
2064 }
2065
2066 if (insn->hint) {
2067 if (insn->restore) {
2068 struct instruction *save_insn, *i;
2069
2070 i = insn;
2071 save_insn = NULL;
2072 sym_for_each_insn_continue_reverse(file, func, i) {
2073 if (i->save) {
2074 save_insn = i;
2075 break;
2076 }
2077 }
2078
2079 if (!save_insn) {
2080 WARN_FUNC("no corresponding CFI save for CFI restore",
2081 sec, insn->offset);
2082 return 1;
2083 }
2084
2085 if (!save_insn->visited) {
2086 /*
2087 * Oops, no state to copy yet.
2088 * Hopefully we can reach this
2089 * instruction from another branch
2090 * after the save insn has been
2091 * visited.
2092 */
2093 if (insn == first)
2094 return 0;
2095
2096 WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
2097 sec, insn->offset);
2098 return 1;
2099 }
2100
2101 insn->state = save_insn->state;
2102 }
2103
2104 state = insn->state;
2105
2106 } else
2107 insn->state = state;
2108
2109 insn->visited |= visited;
2110
2111 if (!insn->ignore_alts) {
2112 bool skip_orig = false;
2113
2114 list_for_each_entry(alt, &insn->alts, list) {
2115 if (alt->skip_orig)
2116 skip_orig = true;
2117
2118 ret = validate_branch(file, func, alt->insn, state);
2119 if (ret) {
2120 if (backtrace)
2121 BT_FUNC("(alt)", insn);
2122 return ret;
2123 }
2124 }
2125
2126 if (skip_orig)
2127 return 0;
2128 }
2129
2130 switch (insn->type) {
2131
2132 case INSN_RETURN:
2133 return validate_return(func, insn, &state);
2134
2135 case INSN_CALL:
2136 case INSN_CALL_DYNAMIC:
2137 ret = validate_call(insn, &state);
2138 if (ret)
2139 return ret;
2140
2141 if (!no_fp && func && !is_fentry_call(insn) &&
2142 !has_valid_stack_frame(&state)) {
2143 WARN_FUNC("call without frame pointer save/setup",
2144 sec, insn->offset);
2145 return 1;
2146 }
2147
2148 if (dead_end_function(file, insn->call_dest))
2149 return 0;
2150
2151 break;
2152
2153 case INSN_JUMP_CONDITIONAL:
2154 case INSN_JUMP_UNCONDITIONAL:
2155 if (func && is_sibling_call(insn)) {
2156 ret = validate_sibling_call(insn, &state);
2157 if (ret)
2158 return ret;
2159
2160 } else if (insn->jump_dest) {
2161 ret = validate_branch(file, func,
2162 insn->jump_dest, state);
2163 if (ret) {
2164 if (backtrace)
2165 BT_FUNC("(branch)", insn);
2166 return ret;
2167 }
2168 }
2169
2170 if (insn->type == INSN_JUMP_UNCONDITIONAL)
2171 return 0;
2172
2173 break;
2174
2175 case INSN_JUMP_DYNAMIC:
2176 case INSN_JUMP_DYNAMIC_CONDITIONAL:
2177 if (func && is_sibling_call(insn)) {
2178 ret = validate_sibling_call(insn, &state);
2179 if (ret)
2180 return ret;
2181 }
2182
2183 if (insn->type == INSN_JUMP_DYNAMIC)
2184 return 0;
2185
2186 break;
2187
2188 case INSN_CONTEXT_SWITCH:
2189 if (func && (!next_insn || !next_insn->hint)) {
2190 WARN_FUNC("unsupported instruction in callable function",
2191 sec, insn->offset);
2192 return 1;
2193 }
2194 return 0;
2195
2196 case INSN_STACK:
2197 if (update_insn_state(insn, &state))
2198 return 1;
2199
2200 if (insn->stack_op.dest.type == OP_DEST_PUSHF) {
2201 if (!state.uaccess_stack) {
2202 state.uaccess_stack = 1;
2203 } else if (state.uaccess_stack >> 31) {
2204 WARN_FUNC("PUSHF stack exhausted", sec, insn->offset);
2205 return 1;
2206 }
2207 state.uaccess_stack <<= 1;
2208 state.uaccess_stack |= state.uaccess;
2209 }
2210
2211 if (insn->stack_op.src.type == OP_SRC_POPF) {
2212 if (state.uaccess_stack) {
2213 state.uaccess = state.uaccess_stack & 1;
2214 state.uaccess_stack >>= 1;
2215 if (state.uaccess_stack == 1)
2216 state.uaccess_stack = 0;
2217 }
2218 }
2219
2220 break;
2221
2222 case INSN_STAC:
2223 if (state.uaccess) {
2224 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
2225 return 1;
2226 }
2227
2228 state.uaccess = true;
2229 break;
2230
2231 case INSN_CLAC:
2232 if (!state.uaccess && func) {
2233 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
2234 return 1;
2235 }
2236
2237 if (func_uaccess_safe(func) && !state.uaccess_stack) {
2238 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
2239 return 1;
2240 }
2241
2242 state.uaccess = false;
2243 break;
2244
2245 case INSN_STD:
2246 if (state.df)
2247 WARN_FUNC("recursive STD", sec, insn->offset);
2248
2249 state.df = true;
2250 break;
2251
2252 case INSN_CLD:
2253 if (!state.df && func)
2254 WARN_FUNC("redundant CLD", sec, insn->offset);
2255
2256 state.df = false;
2257 break;
2258
2259 default:
2260 break;
2261 }
2262
2263 if (insn->dead_end)
2264 return 0;
2265
2266 if (!next_insn) {
2267 if (state.cfa.base == CFI_UNDEFINED)
2268 return 0;
2269 WARN("%s: unexpected end of section", sec->name);
2270 return 1;
2271 }
2272
2273 insn = next_insn;
2274 }
2275
2276 return 0;
2277 }
2278
2279 static int validate_unwind_hints(struct objtool_file *file)
2280 {
2281 struct instruction *insn;
2282 int ret, warnings = 0;
2283 struct insn_state state;
2284
2285 if (!file->hints)
2286 return 0;
2287
2288 clear_insn_state(&state);
2289
2290 for_each_insn(file, insn) {
2291 if (insn->hint && !insn->visited) {
2292 ret = validate_branch(file, insn->func, insn, state);
2293 if (ret && backtrace)
2294 BT_FUNC("<=== (hint)", insn);
2295 warnings += ret;
2296 }
2297 }
2298
2299 return warnings;
2300 }
2301
2302 static int validate_retpoline(struct objtool_file *file)
2303 {
2304 struct instruction *insn;
2305 int warnings = 0;
2306
2307 for_each_insn(file, insn) {
2308 if (insn->type != INSN_JUMP_DYNAMIC &&
2309 insn->type != INSN_CALL_DYNAMIC)
2310 continue;
2311
2312 if (insn->retpoline_safe)
2313 continue;
2314
2315 /*
2316 * .init.text code is ran before userspace and thus doesn't
2317 * strictly need retpolines, except for modules which are
2318 * loaded late, they very much do need retpoline in their
2319 * .init.text
2320 */
2321 if (!strcmp(insn->sec->name, ".init.text") && !module)
2322 continue;
2323
2324 WARN_FUNC("indirect %s found in RETPOLINE build",
2325 insn->sec, insn->offset,
2326 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
2327
2328 warnings++;
2329 }
2330
2331 return warnings;
2332 }
2333
2334 static bool is_kasan_insn(struct instruction *insn)
2335 {
2336 return (insn->type == INSN_CALL &&
2337 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
2338 }
2339
2340 static bool is_ubsan_insn(struct instruction *insn)
2341 {
2342 return (insn->type == INSN_CALL &&
2343 !strcmp(insn->call_dest->name,
2344 "__ubsan_handle_builtin_unreachable"));
2345 }
2346
2347 static bool ignore_unreachable_insn(struct instruction *insn)
2348 {
2349 int i;
2350
2351 if (insn->ignore || insn->type == INSN_NOP)
2352 return true;
2353
2354 /*
2355 * Ignore any unused exceptions. This can happen when a whitelisted
2356 * function has an exception table entry.
2357 *
2358 * Also ignore alternative replacement instructions. This can happen
2359 * when a whitelisted function uses one of the ALTERNATIVE macros.
2360 */
2361 if (!strcmp(insn->sec->name, ".fixup") ||
2362 !strcmp(insn->sec->name, ".altinstr_replacement") ||
2363 !strcmp(insn->sec->name, ".altinstr_aux"))
2364 return true;
2365
2366 /*
2367 * Check if this (or a subsequent) instruction is related to
2368 * CONFIG_UBSAN or CONFIG_KASAN.
2369 *
2370 * End the search at 5 instructions to avoid going into the weeds.
2371 */
2372 if (!insn->func)
2373 return false;
2374 for (i = 0; i < 5; i++) {
2375
2376 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
2377 return true;
2378
2379 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
2380 if (insn->jump_dest &&
2381 insn->jump_dest->func == insn->func) {
2382 insn = insn->jump_dest;
2383 continue;
2384 }
2385
2386 break;
2387 }
2388
2389 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
2390 break;
2391
2392 insn = list_next_entry(insn, list);
2393 }
2394
2395 return false;
2396 }
2397
2398 static int validate_functions(struct objtool_file *file)
2399 {
2400 struct section *sec;
2401 struct symbol *func;
2402 struct instruction *insn;
2403 struct insn_state state;
2404 int ret, warnings = 0;
2405
2406 clear_insn_state(&state);
2407
2408 state.cfa = initial_func_cfi.cfa;
2409 memcpy(&state.regs, &initial_func_cfi.regs,
2410 CFI_NUM_REGS * sizeof(struct cfi_reg));
2411 state.stack_size = initial_func_cfi.cfa.offset;
2412
2413 for_each_sec(file, sec) {
2414 list_for_each_entry(func, &sec->symbol_list, list) {
2415 if (func->type != STT_FUNC)
2416 continue;
2417
2418 if (!func->len) {
2419 WARN("%s() is missing an ELF size annotation",
2420 func->name);
2421 warnings++;
2422 }
2423
2424 if (func->pfunc != func || func->alias != func)
2425 continue;
2426
2427 insn = find_insn(file, sec, func->offset);
2428 if (!insn || insn->ignore || insn->visited)
2429 continue;
2430
2431 state.uaccess = func->uaccess_safe;
2432
2433 ret = validate_branch(file, func, insn, state);
2434 if (ret && backtrace)
2435 BT_FUNC("<=== (func)", insn);
2436 warnings += ret;
2437 }
2438 }
2439
2440 return warnings;
2441 }
2442
2443 static int validate_reachable_instructions(struct objtool_file *file)
2444 {
2445 struct instruction *insn;
2446
2447 if (file->ignore_unreachables)
2448 return 0;
2449
2450 for_each_insn(file, insn) {
2451 if (insn->visited || ignore_unreachable_insn(insn))
2452 continue;
2453
2454 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
2455 return 1;
2456 }
2457
2458 return 0;
2459 }
2460
2461 static struct objtool_file file;
2462
2463 int check(const char *_objname, bool orc)
2464 {
2465 int ret, warnings = 0;
2466
2467 objname = _objname;
2468
2469 file.elf = elf_read(objname, orc ? O_RDWR : O_RDONLY);
2470 if (!file.elf)
2471 return 1;
2472
2473 INIT_LIST_HEAD(&file.insn_list);
2474 hash_init(file.insn_hash);
2475 file.c_file = find_section_by_name(file.elf, ".comment");
2476 file.ignore_unreachables = no_unreachable;
2477 file.hints = false;
2478
2479 arch_initial_func_cfi_state(&initial_func_cfi);
2480
2481 ret = decode_sections(&file);
2482 if (ret < 0)
2483 goto out;
2484 warnings += ret;
2485
2486 if (list_empty(&file.insn_list))
2487 goto out;
2488
2489 if (retpoline) {
2490 ret = validate_retpoline(&file);
2491 if (ret < 0)
2492 return ret;
2493 warnings += ret;
2494 }
2495
2496 ret = validate_functions(&file);
2497 if (ret < 0)
2498 goto out;
2499 warnings += ret;
2500
2501 ret = validate_unwind_hints(&file);
2502 if (ret < 0)
2503 goto out;
2504 warnings += ret;
2505
2506 if (!warnings) {
2507 ret = validate_reachable_instructions(&file);
2508 if (ret < 0)
2509 goto out;
2510 warnings += ret;
2511 }
2512
2513 if (orc) {
2514 ret = create_orc(&file);
2515 if (ret < 0)
2516 goto out;
2517
2518 ret = create_orc_sections(&file);
2519 if (ret < 0)
2520 goto out;
2521
2522 ret = elf_write(file.elf);
2523 if (ret < 0)
2524 goto out;
2525 }
2526
2527 out:
2528 if (ret < 0) {
2529 /*
2530 * Fatal error. The binary is corrupt or otherwise broken in
2531 * some way, or objtool itself is broken. Fail the kernel
2532 * build.
2533 */
2534 return ret;
2535 }
2536
2537 return 0;
2538 }
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