Loading...
Note: File does not exist in v3.15.
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
23struct alternative {
24 struct list_head list;
25 struct instruction *insn;
26 bool skip_orig;
27};
28
29const char *objname;
30struct cfi_state initial_func_cfi;
31
32struct 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
44static 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
55static 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
100static 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 */
123static 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 "__reiserfs_panic",
142 "lbug_with_loc",
143 "fortify_panic",
144 "usercopy_abort",
145 "machine_real_restart",
146 "rewind_stack_do_exit",
147 };
148
149 if (!func)
150 return false;
151
152 if (func->bind == STB_WEAK)
153 return false;
154
155 if (func->bind == STB_GLOBAL)
156 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
157 if (!strcmp(func->name, global_noreturns[i]))
158 return true;
159
160 if (!func->len)
161 return false;
162
163 insn = find_insn(file, func->sec, func->offset);
164 if (!insn->func)
165 return false;
166
167 func_for_each_insn_all(file, func, insn) {
168 empty = false;
169
170 if (insn->type == INSN_RETURN)
171 return false;
172 }
173
174 if (empty)
175 return false;
176
177 /*
178 * A function can have a sibling call instead of a return. In that
179 * case, the function's dead-end status depends on whether the target
180 * of the sibling call returns.
181 */
182 func_for_each_insn_all(file, func, insn) {
183 if (is_sibling_call(insn)) {
184 struct instruction *dest = insn->jump_dest;
185
186 if (!dest)
187 /* sibling call to another file */
188 return false;
189
190 /* local sibling call */
191 if (recursion == 5) {
192 /*
193 * Infinite recursion: two functions have
194 * sibling calls to each other. This is a very
195 * rare case. It means they aren't dead ends.
196 */
197 return false;
198 }
199
200 return __dead_end_function(file, dest->func, recursion+1);
201 }
202 }
203
204 return true;
205}
206
207static bool dead_end_function(struct objtool_file *file, struct symbol *func)
208{
209 return __dead_end_function(file, func, 0);
210}
211
212static void clear_insn_state(struct insn_state *state)
213{
214 int i;
215
216 memset(state, 0, sizeof(*state));
217 state->cfa.base = CFI_UNDEFINED;
218 for (i = 0; i < CFI_NUM_REGS; i++) {
219 state->regs[i].base = CFI_UNDEFINED;
220 state->vals[i].base = CFI_UNDEFINED;
221 }
222 state->drap_reg = CFI_UNDEFINED;
223 state->drap_offset = -1;
224}
225
226/*
227 * Call the arch-specific instruction decoder for all the instructions and add
228 * them to the global instruction list.
229 */
230static int decode_instructions(struct objtool_file *file)
231{
232 struct section *sec;
233 struct symbol *func;
234 unsigned long offset;
235 struct instruction *insn;
236 int ret;
237
238 for_each_sec(file, sec) {
239
240 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
241 continue;
242
243 if (strcmp(sec->name, ".altinstr_replacement") &&
244 strcmp(sec->name, ".altinstr_aux") &&
245 strncmp(sec->name, ".discard.", 9))
246 sec->text = true;
247
248 for (offset = 0; offset < sec->len; offset += insn->len) {
249 insn = malloc(sizeof(*insn));
250 if (!insn) {
251 WARN("malloc failed");
252 return -1;
253 }
254 memset(insn, 0, sizeof(*insn));
255 INIT_LIST_HEAD(&insn->alts);
256 clear_insn_state(&insn->state);
257
258 insn->sec = sec;
259 insn->offset = offset;
260
261 ret = arch_decode_instruction(file->elf, sec, offset,
262 sec->len - offset,
263 &insn->len, &insn->type,
264 &insn->immediate,
265 &insn->stack_op);
266 if (ret)
267 goto err;
268
269 hash_add(file->insn_hash, &insn->hash, insn->offset);
270 list_add_tail(&insn->list, &file->insn_list);
271 }
272
273 list_for_each_entry(func, &sec->symbol_list, list) {
274 if (func->type != STT_FUNC || func->alias != func)
275 continue;
276
277 if (!find_insn(file, sec, func->offset)) {
278 WARN("%s(): can't find starting instruction",
279 func->name);
280 return -1;
281 }
282
283 func_for_each_insn(file, func, insn)
284 insn->func = func;
285 }
286 }
287
288 return 0;
289
290err:
291 free(insn);
292 return ret;
293}
294
295/*
296 * Mark "ud2" instructions and manually annotated dead ends.
297 */
298static int add_dead_ends(struct objtool_file *file)
299{
300 struct section *sec;
301 struct rela *rela;
302 struct instruction *insn;
303 bool found;
304
305 /*
306 * By default, "ud2" is a dead end unless otherwise annotated, because
307 * GCC 7 inserts it for certain divide-by-zero cases.
308 */
309 for_each_insn(file, insn)
310 if (insn->type == INSN_BUG)
311 insn->dead_end = true;
312
313 /*
314 * Check for manually annotated dead ends.
315 */
316 sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
317 if (!sec)
318 goto reachable;
319
320 list_for_each_entry(rela, &sec->rela_list, list) {
321 if (rela->sym->type != STT_SECTION) {
322 WARN("unexpected relocation symbol type in %s", sec->name);
323 return -1;
324 }
325 insn = find_insn(file, rela->sym->sec, rela->addend);
326 if (insn)
327 insn = list_prev_entry(insn, list);
328 else if (rela->addend == rela->sym->sec->len) {
329 found = false;
330 list_for_each_entry_reverse(insn, &file->insn_list, list) {
331 if (insn->sec == rela->sym->sec) {
332 found = true;
333 break;
334 }
335 }
336
337 if (!found) {
338 WARN("can't find unreachable insn at %s+0x%x",
339 rela->sym->sec->name, rela->addend);
340 return -1;
341 }
342 } else {
343 WARN("can't find unreachable insn at %s+0x%x",
344 rela->sym->sec->name, rela->addend);
345 return -1;
346 }
347
348 insn->dead_end = true;
349 }
350
351reachable:
352 /*
353 * These manually annotated reachable checks are needed for GCC 4.4,
354 * where the Linux unreachable() macro isn't supported. In that case
355 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
356 * not a dead end.
357 */
358 sec = find_section_by_name(file->elf, ".rela.discard.reachable");
359 if (!sec)
360 return 0;
361
362 list_for_each_entry(rela, &sec->rela_list, list) {
363 if (rela->sym->type != STT_SECTION) {
364 WARN("unexpected relocation symbol type in %s", sec->name);
365 return -1;
366 }
367 insn = find_insn(file, rela->sym->sec, rela->addend);
368 if (insn)
369 insn = list_prev_entry(insn, list);
370 else if (rela->addend == rela->sym->sec->len) {
371 found = false;
372 list_for_each_entry_reverse(insn, &file->insn_list, list) {
373 if (insn->sec == rela->sym->sec) {
374 found = true;
375 break;
376 }
377 }
378
379 if (!found) {
380 WARN("can't find reachable insn at %s+0x%x",
381 rela->sym->sec->name, rela->addend);
382 return -1;
383 }
384 } else {
385 WARN("can't find reachable insn at %s+0x%x",
386 rela->sym->sec->name, rela->addend);
387 return -1;
388 }
389
390 insn->dead_end = false;
391 }
392
393 return 0;
394}
395
396/*
397 * Warnings shouldn't be reported for ignored functions.
398 */
399static void add_ignores(struct objtool_file *file)
400{
401 struct instruction *insn;
402 struct section *sec;
403 struct symbol *func;
404 struct rela *rela;
405
406 sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
407 if (!sec)
408 return;
409
410 list_for_each_entry(rela, &sec->rela_list, list) {
411 switch (rela->sym->type) {
412 case STT_FUNC:
413 func = rela->sym;
414 break;
415
416 case STT_SECTION:
417 func = find_symbol_by_offset(rela->sym->sec, rela->addend);
418 if (!func || func->type != STT_FUNC)
419 continue;
420 break;
421
422 default:
423 WARN("unexpected relocation symbol type in %s: %d", sec->name, rela->sym->type);
424 continue;
425 }
426
427 func_for_each_insn_all(file, func, insn)
428 insn->ignore = true;
429 }
430}
431
432/*
433 * This is a whitelist of functions that is allowed to be called with AC set.
434 * The list is meant to be minimal and only contains compiler instrumentation
435 * ABI and a few functions used to implement *_{to,from}_user() functions.
436 *
437 * These functions must not directly change AC, but may PUSHF/POPF.
438 */
439static const char *uaccess_safe_builtin[] = {
440 /* KASAN */
441 "kasan_report",
442 "check_memory_region",
443 /* KASAN out-of-line */
444 "__asan_loadN_noabort",
445 "__asan_load1_noabort",
446 "__asan_load2_noabort",
447 "__asan_load4_noabort",
448 "__asan_load8_noabort",
449 "__asan_load16_noabort",
450 "__asan_storeN_noabort",
451 "__asan_store1_noabort",
452 "__asan_store2_noabort",
453 "__asan_store4_noabort",
454 "__asan_store8_noabort",
455 "__asan_store16_noabort",
456 /* KASAN in-line */
457 "__asan_report_load_n_noabort",
458 "__asan_report_load1_noabort",
459 "__asan_report_load2_noabort",
460 "__asan_report_load4_noabort",
461 "__asan_report_load8_noabort",
462 "__asan_report_load16_noabort",
463 "__asan_report_store_n_noabort",
464 "__asan_report_store1_noabort",
465 "__asan_report_store2_noabort",
466 "__asan_report_store4_noabort",
467 "__asan_report_store8_noabort",
468 "__asan_report_store16_noabort",
469 /* KCOV */
470 "write_comp_data",
471 "__sanitizer_cov_trace_pc",
472 "__sanitizer_cov_trace_const_cmp1",
473 "__sanitizer_cov_trace_const_cmp2",
474 "__sanitizer_cov_trace_const_cmp4",
475 "__sanitizer_cov_trace_const_cmp8",
476 "__sanitizer_cov_trace_cmp1",
477 "__sanitizer_cov_trace_cmp2",
478 "__sanitizer_cov_trace_cmp4",
479 "__sanitizer_cov_trace_cmp8",
480 /* UBSAN */
481 "ubsan_type_mismatch_common",
482 "__ubsan_handle_type_mismatch",
483 "__ubsan_handle_type_mismatch_v1",
484 /* misc */
485 "csum_partial_copy_generic",
486 "__memcpy_mcsafe",
487 "mcsafe_handle_tail",
488 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
489 NULL
490};
491
492static void add_uaccess_safe(struct objtool_file *file)
493{
494 struct symbol *func;
495 const char **name;
496
497 if (!uaccess)
498 return;
499
500 for (name = uaccess_safe_builtin; *name; name++) {
501 func = find_symbol_by_name(file->elf, *name);
502 if (!func)
503 continue;
504
505 func->uaccess_safe = true;
506 }
507}
508
509/*
510 * FIXME: For now, just ignore any alternatives which add retpolines. This is
511 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
512 * But it at least allows objtool to understand the control flow *around* the
513 * retpoline.
514 */
515static int add_ignore_alternatives(struct objtool_file *file)
516{
517 struct section *sec;
518 struct rela *rela;
519 struct instruction *insn;
520
521 sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
522 if (!sec)
523 return 0;
524
525 list_for_each_entry(rela, &sec->rela_list, list) {
526 if (rela->sym->type != STT_SECTION) {
527 WARN("unexpected relocation symbol type in %s", sec->name);
528 return -1;
529 }
530
531 insn = find_insn(file, rela->sym->sec, rela->addend);
532 if (!insn) {
533 WARN("bad .discard.ignore_alts entry");
534 return -1;
535 }
536
537 insn->ignore_alts = true;
538 }
539
540 return 0;
541}
542
543/*
544 * Find the destination instructions for all jumps.
545 */
546static int add_jump_destinations(struct objtool_file *file)
547{
548 struct instruction *insn;
549 struct rela *rela;
550 struct section *dest_sec;
551 unsigned long dest_off;
552
553 for_each_insn(file, insn) {
554 if (insn->type != INSN_JUMP_CONDITIONAL &&
555 insn->type != INSN_JUMP_UNCONDITIONAL)
556 continue;
557
558 if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET)
559 continue;
560
561 rela = find_rela_by_dest_range(insn->sec, insn->offset,
562 insn->len);
563 if (!rela) {
564 dest_sec = insn->sec;
565 dest_off = insn->offset + insn->len + insn->immediate;
566 } else if (rela->sym->type == STT_SECTION) {
567 dest_sec = rela->sym->sec;
568 dest_off = rela->addend + 4;
569 } else if (rela->sym->sec->idx) {
570 dest_sec = rela->sym->sec;
571 dest_off = rela->sym->sym.st_value + rela->addend + 4;
572 } else if (strstr(rela->sym->name, "_indirect_thunk_")) {
573 /*
574 * Retpoline jumps are really dynamic jumps in
575 * disguise, so convert them accordingly.
576 */
577 if (insn->type == INSN_JUMP_UNCONDITIONAL)
578 insn->type = INSN_JUMP_DYNAMIC;
579 else
580 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
581
582 insn->retpoline_safe = true;
583 continue;
584 } else {
585 /* external sibling call */
586 insn->call_dest = rela->sym;
587 continue;
588 }
589
590 insn->jump_dest = find_insn(file, dest_sec, dest_off);
591 if (!insn->jump_dest) {
592
593 /*
594 * This is a special case where an alt instruction
595 * jumps past the end of the section. These are
596 * handled later in handle_group_alt().
597 */
598 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
599 continue;
600
601 WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
602 insn->sec, insn->offset, dest_sec->name,
603 dest_off);
604 return -1;
605 }
606
607 /*
608 * Cross-function jump.
609 */
610 if (insn->func && insn->jump_dest->func &&
611 insn->func != insn->jump_dest->func) {
612
613 /*
614 * For GCC 8+, create parent/child links for any cold
615 * subfunctions. This is _mostly_ redundant with a
616 * similar initialization in read_symbols().
617 *
618 * If a function has aliases, we want the *first* such
619 * function in the symbol table to be the subfunction's
620 * parent. In that case we overwrite the
621 * initialization done in read_symbols().
622 *
623 * However this code can't completely replace the
624 * read_symbols() code because this doesn't detect the
625 * case where the parent function's only reference to a
626 * subfunction is through a jump table.
627 */
628 if (!strstr(insn->func->name, ".cold.") &&
629 strstr(insn->jump_dest->func->name, ".cold.")) {
630 insn->func->cfunc = insn->jump_dest->func;
631 insn->jump_dest->func->pfunc = insn->func;
632
633 } else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
634 insn->jump_dest->offset == insn->jump_dest->func->offset) {
635
636 /* internal sibling call */
637 insn->call_dest = insn->jump_dest->func;
638 }
639 }
640 }
641
642 return 0;
643}
644
645/*
646 * Find the destination instructions for all calls.
647 */
648static int add_call_destinations(struct objtool_file *file)
649{
650 struct instruction *insn;
651 unsigned long dest_off;
652 struct rela *rela;
653
654 for_each_insn(file, insn) {
655 if (insn->type != INSN_CALL)
656 continue;
657
658 rela = find_rela_by_dest_range(insn->sec, insn->offset,
659 insn->len);
660 if (!rela) {
661 dest_off = insn->offset + insn->len + insn->immediate;
662 insn->call_dest = find_symbol_by_offset(insn->sec,
663 dest_off);
664
665 if (!insn->call_dest && !insn->ignore) {
666 WARN_FUNC("unsupported intra-function call",
667 insn->sec, insn->offset);
668 if (retpoline)
669 WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");
670 return -1;
671 }
672
673 } else if (rela->sym->type == STT_SECTION) {
674 insn->call_dest = find_symbol_by_offset(rela->sym->sec,
675 rela->addend+4);
676 if (!insn->call_dest ||
677 insn->call_dest->type != STT_FUNC) {
678 WARN_FUNC("can't find call dest symbol at %s+0x%x",
679 insn->sec, insn->offset,
680 rela->sym->sec->name,
681 rela->addend + 4);
682 return -1;
683 }
684 } else
685 insn->call_dest = rela->sym;
686 }
687
688 return 0;
689}
690
691/*
692 * The .alternatives section requires some extra special care, over and above
693 * what other special sections require:
694 *
695 * 1. Because alternatives are patched in-place, we need to insert a fake jump
696 * instruction at the end so that validate_branch() skips all the original
697 * replaced instructions when validating the new instruction path.
698 *
699 * 2. An added wrinkle is that the new instruction length might be zero. In
700 * that case the old instructions are replaced with noops. We simulate that
701 * by creating a fake jump as the only new instruction.
702 *
703 * 3. In some cases, the alternative section includes an instruction which
704 * conditionally jumps to the _end_ of the entry. We have to modify these
705 * jumps' destinations to point back to .text rather than the end of the
706 * entry in .altinstr_replacement.
707 */
708static int handle_group_alt(struct objtool_file *file,
709 struct special_alt *special_alt,
710 struct instruction *orig_insn,
711 struct instruction **new_insn)
712{
713 struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
714 unsigned long dest_off;
715
716 last_orig_insn = NULL;
717 insn = orig_insn;
718 sec_for_each_insn_from(file, insn) {
719 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
720 break;
721
722 insn->alt_group = true;
723 last_orig_insn = insn;
724 }
725
726 if (next_insn_same_sec(file, last_orig_insn)) {
727 fake_jump = malloc(sizeof(*fake_jump));
728 if (!fake_jump) {
729 WARN("malloc failed");
730 return -1;
731 }
732 memset(fake_jump, 0, sizeof(*fake_jump));
733 INIT_LIST_HEAD(&fake_jump->alts);
734 clear_insn_state(&fake_jump->state);
735
736 fake_jump->sec = special_alt->new_sec;
737 fake_jump->offset = FAKE_JUMP_OFFSET;
738 fake_jump->type = INSN_JUMP_UNCONDITIONAL;
739 fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
740 fake_jump->func = orig_insn->func;
741 }
742
743 if (!special_alt->new_len) {
744 if (!fake_jump) {
745 WARN("%s: empty alternative at end of section",
746 special_alt->orig_sec->name);
747 return -1;
748 }
749
750 *new_insn = fake_jump;
751 return 0;
752 }
753
754 last_new_insn = NULL;
755 insn = *new_insn;
756 sec_for_each_insn_from(file, insn) {
757 if (insn->offset >= special_alt->new_off + special_alt->new_len)
758 break;
759
760 last_new_insn = insn;
761
762 insn->ignore = orig_insn->ignore_alts;
763 insn->func = orig_insn->func;
764
765 if (insn->type != INSN_JUMP_CONDITIONAL &&
766 insn->type != INSN_JUMP_UNCONDITIONAL)
767 continue;
768
769 if (!insn->immediate)
770 continue;
771
772 dest_off = insn->offset + insn->len + insn->immediate;
773 if (dest_off == special_alt->new_off + special_alt->new_len) {
774 if (!fake_jump) {
775 WARN("%s: alternative jump to end of section",
776 special_alt->orig_sec->name);
777 return -1;
778 }
779 insn->jump_dest = fake_jump;
780 }
781
782 if (!insn->jump_dest) {
783 WARN_FUNC("can't find alternative jump destination",
784 insn->sec, insn->offset);
785 return -1;
786 }
787 }
788
789 if (!last_new_insn) {
790 WARN_FUNC("can't find last new alternative instruction",
791 special_alt->new_sec, special_alt->new_off);
792 return -1;
793 }
794
795 if (fake_jump)
796 list_add(&fake_jump->list, &last_new_insn->list);
797
798 return 0;
799}
800
801/*
802 * A jump table entry can either convert a nop to a jump or a jump to a nop.
803 * If the original instruction is a jump, make the alt entry an effective nop
804 * by just skipping the original instruction.
805 */
806static int handle_jump_alt(struct objtool_file *file,
807 struct special_alt *special_alt,
808 struct instruction *orig_insn,
809 struct instruction **new_insn)
810{
811 if (orig_insn->type == INSN_NOP)
812 return 0;
813
814 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
815 WARN_FUNC("unsupported instruction at jump label",
816 orig_insn->sec, orig_insn->offset);
817 return -1;
818 }
819
820 *new_insn = list_next_entry(orig_insn, list);
821 return 0;
822}
823
824/*
825 * Read all the special sections which have alternate instructions which can be
826 * patched in or redirected to at runtime. Each instruction having alternate
827 * instruction(s) has them added to its insn->alts list, which will be
828 * traversed in validate_branch().
829 */
830static int add_special_section_alts(struct objtool_file *file)
831{
832 struct list_head special_alts;
833 struct instruction *orig_insn, *new_insn;
834 struct special_alt *special_alt, *tmp;
835 struct alternative *alt;
836 int ret;
837
838 ret = special_get_alts(file->elf, &special_alts);
839 if (ret)
840 return ret;
841
842 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
843
844 orig_insn = find_insn(file, special_alt->orig_sec,
845 special_alt->orig_off);
846 if (!orig_insn) {
847 WARN_FUNC("special: can't find orig instruction",
848 special_alt->orig_sec, special_alt->orig_off);
849 ret = -1;
850 goto out;
851 }
852
853 new_insn = NULL;
854 if (!special_alt->group || special_alt->new_len) {
855 new_insn = find_insn(file, special_alt->new_sec,
856 special_alt->new_off);
857 if (!new_insn) {
858 WARN_FUNC("special: can't find new instruction",
859 special_alt->new_sec,
860 special_alt->new_off);
861 ret = -1;
862 goto out;
863 }
864 }
865
866 if (special_alt->group) {
867 ret = handle_group_alt(file, special_alt, orig_insn,
868 &new_insn);
869 if (ret)
870 goto out;
871 } else if (special_alt->jump_or_nop) {
872 ret = handle_jump_alt(file, special_alt, orig_insn,
873 &new_insn);
874 if (ret)
875 goto out;
876 }
877
878 alt = malloc(sizeof(*alt));
879 if (!alt) {
880 WARN("malloc failed");
881 ret = -1;
882 goto out;
883 }
884
885 alt->insn = new_insn;
886 alt->skip_orig = special_alt->skip_orig;
887 orig_insn->ignore_alts |= special_alt->skip_alt;
888 list_add_tail(&alt->list, &orig_insn->alts);
889
890 list_del(&special_alt->list);
891 free(special_alt);
892 }
893
894out:
895 return ret;
896}
897
898static int add_jump_table(struct objtool_file *file, struct instruction *insn,
899 struct rela *table)
900{
901 struct rela *rela = table;
902 struct instruction *dest_insn;
903 struct alternative *alt;
904 struct symbol *pfunc = insn->func->pfunc;
905 unsigned int prev_offset = 0;
906
907 /*
908 * Each @rela is a switch table relocation which points to the target
909 * instruction.
910 */
911 list_for_each_entry_from(rela, &table->sec->rela_list, list) {
912
913 /* Check for the end of the table: */
914 if (rela != table && rela->jump_table_start)
915 break;
916
917 /* Make sure the table entries are consecutive: */
918 if (prev_offset && rela->offset != prev_offset + 8)
919 break;
920
921 /* Detect function pointers from contiguous objects: */
922 if (rela->sym->sec == pfunc->sec &&
923 rela->addend == pfunc->offset)
924 break;
925
926 dest_insn = find_insn(file, rela->sym->sec, rela->addend);
927 if (!dest_insn)
928 break;
929
930 /* Make sure the destination is in the same function: */
931 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
932 break;
933
934 alt = malloc(sizeof(*alt));
935 if (!alt) {
936 WARN("malloc failed");
937 return -1;
938 }
939
940 alt->insn = dest_insn;
941 list_add_tail(&alt->list, &insn->alts);
942 prev_offset = rela->offset;
943 }
944
945 if (!prev_offset) {
946 WARN_FUNC("can't find switch jump table",
947 insn->sec, insn->offset);
948 return -1;
949 }
950
951 return 0;
952}
953
954/*
955 * find_jump_table() - Given a dynamic jump, find the switch jump table in
956 * .rodata associated with it.
957 *
958 * There are 3 basic patterns:
959 *
960 * 1. jmpq *[rodata addr](,%reg,8)
961 *
962 * This is the most common case by far. It jumps to an address in a simple
963 * jump table which is stored in .rodata.
964 *
965 * 2. jmpq *[rodata addr](%rip)
966 *
967 * This is caused by a rare GCC quirk, currently only seen in three driver
968 * functions in the kernel, only with certain obscure non-distro configs.
969 *
970 * As part of an optimization, GCC makes a copy of an existing switch jump
971 * table, modifies it, and then hard-codes the jump (albeit with an indirect
972 * jump) to use a single entry in the table. The rest of the jump table and
973 * some of its jump targets remain as dead code.
974 *
975 * In such a case we can just crudely ignore all unreachable instruction
976 * warnings for the entire object file. Ideally we would just ignore them
977 * for the function, but that would require redesigning the code quite a
978 * bit. And honestly that's just not worth doing: unreachable instruction
979 * warnings are of questionable value anyway, and this is such a rare issue.
980 *
981 * 3. mov [rodata addr],%reg1
982 * ... some instructions ...
983 * jmpq *(%reg1,%reg2,8)
984 *
985 * This is a fairly uncommon pattern which is new for GCC 6. As of this
986 * writing, there are 11 occurrences of it in the allmodconfig kernel.
987 *
988 * As of GCC 7 there are quite a few more of these and the 'in between' code
989 * is significant. Esp. with KASAN enabled some of the code between the mov
990 * and jmpq uses .rodata itself, which can confuse things.
991 *
992 * TODO: Once we have DWARF CFI and smarter instruction decoding logic,
993 * ensure the same register is used in the mov and jump instructions.
994 *
995 * NOTE: RETPOLINE made it harder still to decode dynamic jumps.
996 */
997static struct rela *find_jump_table(struct objtool_file *file,
998 struct symbol *func,
999 struct instruction *insn)
1000{
1001 struct rela *text_rela, *table_rela;
1002 struct instruction *orig_insn = insn;
1003 struct section *table_sec;
1004 unsigned long table_offset;
1005
1006 /*
1007 * Backward search using the @first_jump_src links, these help avoid
1008 * much of the 'in between' code. Which avoids us getting confused by
1009 * it.
1010 */
1011 for (;
1012 &insn->list != &file->insn_list &&
1013 insn->sec == func->sec &&
1014 insn->offset >= func->offset;
1015
1016 insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
1017
1018 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1019 break;
1020
1021 /* allow small jumps within the range */
1022 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1023 insn->jump_dest &&
1024 (insn->jump_dest->offset <= insn->offset ||
1025 insn->jump_dest->offset > orig_insn->offset))
1026 break;
1027
1028 /* look for a relocation which references .rodata */
1029 text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
1030 insn->len);
1031 if (!text_rela || text_rela->sym->type != STT_SECTION ||
1032 !text_rela->sym->sec->rodata)
1033 continue;
1034
1035 table_offset = text_rela->addend;
1036 table_sec = text_rela->sym->sec;
1037
1038 if (text_rela->type == R_X86_64_PC32)
1039 table_offset += 4;
1040
1041 /*
1042 * Make sure the .rodata address isn't associated with a
1043 * symbol. GCC jump tables are anonymous data.
1044 *
1045 * Also support C jump tables which are in the same format as
1046 * switch jump tables. For objtool to recognize them, they
1047 * need to be placed in the C_JUMP_TABLE_SECTION section. They
1048 * have symbols associated with them.
1049 */
1050 if (find_symbol_containing(table_sec, table_offset) &&
1051 strcmp(table_sec->name, C_JUMP_TABLE_SECTION))
1052 continue;
1053
1054 /* Each table entry has a rela associated with it. */
1055 table_rela = find_rela_by_dest(table_sec, table_offset);
1056 if (!table_rela)
1057 continue;
1058
1059 /*
1060 * Use of RIP-relative switch jumps is quite rare, and
1061 * indicates a rare GCC quirk/bug which can leave dead code
1062 * behind.
1063 */
1064 if (text_rela->type == R_X86_64_PC32)
1065 file->ignore_unreachables = true;
1066
1067 return table_rela;
1068 }
1069
1070 return NULL;
1071}
1072
1073/*
1074 * First pass: Mark the head of each jump table so that in the next pass,
1075 * we know when a given jump table ends and the next one starts.
1076 */
1077static void mark_func_jump_tables(struct objtool_file *file,
1078 struct symbol *func)
1079{
1080 struct instruction *insn, *last = NULL;
1081 struct rela *rela;
1082
1083 func_for_each_insn_all(file, func, insn) {
1084 if (!last)
1085 last = insn;
1086
1087 /*
1088 * Store back-pointers for unconditional forward jumps such
1089 * that find_jump_table() can back-track using those and
1090 * avoid some potentially confusing code.
1091 */
1092 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1093 insn->offset > last->offset &&
1094 insn->jump_dest->offset > insn->offset &&
1095 !insn->jump_dest->first_jump_src) {
1096
1097 insn->jump_dest->first_jump_src = insn;
1098 last = insn->jump_dest;
1099 }
1100
1101 if (insn->type != INSN_JUMP_DYNAMIC)
1102 continue;
1103
1104 rela = find_jump_table(file, func, insn);
1105 if (rela) {
1106 rela->jump_table_start = true;
1107 insn->jump_table = rela;
1108 }
1109 }
1110}
1111
1112static int add_func_jump_tables(struct objtool_file *file,
1113 struct symbol *func)
1114{
1115 struct instruction *insn;
1116 int ret;
1117
1118 func_for_each_insn_all(file, func, insn) {
1119 if (!insn->jump_table)
1120 continue;
1121
1122 ret = add_jump_table(file, insn, insn->jump_table);
1123 if (ret)
1124 return ret;
1125 }
1126
1127 return 0;
1128}
1129
1130/*
1131 * For some switch statements, gcc generates a jump table in the .rodata
1132 * section which contains a list of addresses within the function to jump to.
1133 * This finds these jump tables and adds them to the insn->alts lists.
1134 */
1135static int add_jump_table_alts(struct objtool_file *file)
1136{
1137 struct section *sec;
1138 struct symbol *func;
1139 int ret;
1140
1141 if (!file->rodata)
1142 return 0;
1143
1144 for_each_sec(file, sec) {
1145 list_for_each_entry(func, &sec->symbol_list, list) {
1146 if (func->type != STT_FUNC)
1147 continue;
1148
1149 mark_func_jump_tables(file, func);
1150 ret = add_func_jump_tables(file, func);
1151 if (ret)
1152 return ret;
1153 }
1154 }
1155
1156 return 0;
1157}
1158
1159static int read_unwind_hints(struct objtool_file *file)
1160{
1161 struct section *sec, *relasec;
1162 struct rela *rela;
1163 struct unwind_hint *hint;
1164 struct instruction *insn;
1165 struct cfi_reg *cfa;
1166 int i;
1167
1168 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1169 if (!sec)
1170 return 0;
1171
1172 relasec = sec->rela;
1173 if (!relasec) {
1174 WARN("missing .rela.discard.unwind_hints section");
1175 return -1;
1176 }
1177
1178 if (sec->len % sizeof(struct unwind_hint)) {
1179 WARN("struct unwind_hint size mismatch");
1180 return -1;
1181 }
1182
1183 file->hints = true;
1184
1185 for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
1186 hint = (struct unwind_hint *)sec->data->d_buf + i;
1187
1188 rela = find_rela_by_dest(sec, i * sizeof(*hint));
1189 if (!rela) {
1190 WARN("can't find rela for unwind_hints[%d]", i);
1191 return -1;
1192 }
1193
1194 insn = find_insn(file, rela->sym->sec, rela->addend);
1195 if (!insn) {
1196 WARN("can't find insn for unwind_hints[%d]", i);
1197 return -1;
1198 }
1199
1200 cfa = &insn->state.cfa;
1201
1202 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
1203 insn->save = true;
1204 continue;
1205
1206 } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
1207 insn->restore = true;
1208 insn->hint = true;
1209 continue;
1210 }
1211
1212 insn->hint = true;
1213
1214 switch (hint->sp_reg) {
1215 case ORC_REG_UNDEFINED:
1216 cfa->base = CFI_UNDEFINED;
1217 break;
1218 case ORC_REG_SP:
1219 cfa->base = CFI_SP;
1220 break;
1221 case ORC_REG_BP:
1222 cfa->base = CFI_BP;
1223 break;
1224 case ORC_REG_SP_INDIRECT:
1225 cfa->base = CFI_SP_INDIRECT;
1226 break;
1227 case ORC_REG_R10:
1228 cfa->base = CFI_R10;
1229 break;
1230 case ORC_REG_R13:
1231 cfa->base = CFI_R13;
1232 break;
1233 case ORC_REG_DI:
1234 cfa->base = CFI_DI;
1235 break;
1236 case ORC_REG_DX:
1237 cfa->base = CFI_DX;
1238 break;
1239 default:
1240 WARN_FUNC("unsupported unwind_hint sp base reg %d",
1241 insn->sec, insn->offset, hint->sp_reg);
1242 return -1;
1243 }
1244
1245 cfa->offset = hint->sp_offset;
1246 insn->state.type = hint->type;
1247 insn->state.end = hint->end;
1248 }
1249
1250 return 0;
1251}
1252
1253static int read_retpoline_hints(struct objtool_file *file)
1254{
1255 struct section *sec;
1256 struct instruction *insn;
1257 struct rela *rela;
1258
1259 sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1260 if (!sec)
1261 return 0;
1262
1263 list_for_each_entry(rela, &sec->rela_list, list) {
1264 if (rela->sym->type != STT_SECTION) {
1265 WARN("unexpected relocation symbol type in %s", sec->name);
1266 return -1;
1267 }
1268
1269 insn = find_insn(file, rela->sym->sec, rela->addend);
1270 if (!insn) {
1271 WARN("bad .discard.retpoline_safe entry");
1272 return -1;
1273 }
1274
1275 if (insn->type != INSN_JUMP_DYNAMIC &&
1276 insn->type != INSN_CALL_DYNAMIC) {
1277 WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1278 insn->sec, insn->offset);
1279 return -1;
1280 }
1281
1282 insn->retpoline_safe = true;
1283 }
1284
1285 return 0;
1286}
1287
1288static void mark_rodata(struct objtool_file *file)
1289{
1290 struct section *sec;
1291 bool found = false;
1292
1293 /*
1294 * Search for the following rodata sections, each of which can
1295 * potentially contain jump tables:
1296 *
1297 * - .rodata: can contain GCC switch tables
1298 * - .rodata.<func>: same, if -fdata-sections is being used
1299 * - .rodata..c_jump_table: contains C annotated jump tables
1300 *
1301 * .rodata.str1.* sections are ignored; they don't contain jump tables.
1302 */
1303 for_each_sec(file, sec) {
1304 if ((!strncmp(sec->name, ".rodata", 7) && !strstr(sec->name, ".str1.")) ||
1305 !strcmp(sec->name, C_JUMP_TABLE_SECTION)) {
1306 sec->rodata = true;
1307 found = true;
1308 }
1309 }
1310
1311 file->rodata = found;
1312}
1313
1314static int decode_sections(struct objtool_file *file)
1315{
1316 int ret;
1317
1318 mark_rodata(file);
1319
1320 ret = decode_instructions(file);
1321 if (ret)
1322 return ret;
1323
1324 ret = add_dead_ends(file);
1325 if (ret)
1326 return ret;
1327
1328 add_ignores(file);
1329 add_uaccess_safe(file);
1330
1331 ret = add_ignore_alternatives(file);
1332 if (ret)
1333 return ret;
1334
1335 ret = add_jump_destinations(file);
1336 if (ret)
1337 return ret;
1338
1339 ret = add_special_section_alts(file);
1340 if (ret)
1341 return ret;
1342
1343 ret = add_call_destinations(file);
1344 if (ret)
1345 return ret;
1346
1347 ret = add_jump_table_alts(file);
1348 if (ret)
1349 return ret;
1350
1351 ret = read_unwind_hints(file);
1352 if (ret)
1353 return ret;
1354
1355 ret = read_retpoline_hints(file);
1356 if (ret)
1357 return ret;
1358
1359 return 0;
1360}
1361
1362static bool is_fentry_call(struct instruction *insn)
1363{
1364 if (insn->type == INSN_CALL &&
1365 insn->call_dest->type == STT_NOTYPE &&
1366 !strcmp(insn->call_dest->name, "__fentry__"))
1367 return true;
1368
1369 return false;
1370}
1371
1372static bool has_modified_stack_frame(struct insn_state *state)
1373{
1374 int i;
1375
1376 if (state->cfa.base != initial_func_cfi.cfa.base ||
1377 state->cfa.offset != initial_func_cfi.cfa.offset ||
1378 state->stack_size != initial_func_cfi.cfa.offset ||
1379 state->drap)
1380 return true;
1381
1382 for (i = 0; i < CFI_NUM_REGS; i++)
1383 if (state->regs[i].base != initial_func_cfi.regs[i].base ||
1384 state->regs[i].offset != initial_func_cfi.regs[i].offset)
1385 return true;
1386
1387 return false;
1388}
1389
1390static bool has_valid_stack_frame(struct insn_state *state)
1391{
1392 if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
1393 state->regs[CFI_BP].offset == -16)
1394 return true;
1395
1396 if (state->drap && state->regs[CFI_BP].base == CFI_BP)
1397 return true;
1398
1399 return false;
1400}
1401
1402static int update_insn_state_regs(struct instruction *insn, struct insn_state *state)
1403{
1404 struct cfi_reg *cfa = &state->cfa;
1405 struct stack_op *op = &insn->stack_op;
1406
1407 if (cfa->base != CFI_SP)
1408 return 0;
1409
1410 /* push */
1411 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
1412 cfa->offset += 8;
1413
1414 /* pop */
1415 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
1416 cfa->offset -= 8;
1417
1418 /* add immediate to sp */
1419 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1420 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1421 cfa->offset -= op->src.offset;
1422
1423 return 0;
1424}
1425
1426static void save_reg(struct insn_state *state, unsigned char reg, int base,
1427 int offset)
1428{
1429 if (arch_callee_saved_reg(reg) &&
1430 state->regs[reg].base == CFI_UNDEFINED) {
1431 state->regs[reg].base = base;
1432 state->regs[reg].offset = offset;
1433 }
1434}
1435
1436static void restore_reg(struct insn_state *state, unsigned char reg)
1437{
1438 state->regs[reg].base = CFI_UNDEFINED;
1439 state->regs[reg].offset = 0;
1440}
1441
1442/*
1443 * A note about DRAP stack alignment:
1444 *
1445 * GCC has the concept of a DRAP register, which is used to help keep track of
1446 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
1447 * register. The typical DRAP pattern is:
1448 *
1449 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
1450 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
1451 * 41 ff 72 f8 pushq -0x8(%r10)
1452 * 55 push %rbp
1453 * 48 89 e5 mov %rsp,%rbp
1454 * (more pushes)
1455 * 41 52 push %r10
1456 * ...
1457 * 41 5a pop %r10
1458 * (more pops)
1459 * 5d pop %rbp
1460 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1461 * c3 retq
1462 *
1463 * There are some variations in the epilogues, like:
1464 *
1465 * 5b pop %rbx
1466 * 41 5a pop %r10
1467 * 41 5c pop %r12
1468 * 41 5d pop %r13
1469 * 41 5e pop %r14
1470 * c9 leaveq
1471 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1472 * c3 retq
1473 *
1474 * and:
1475 *
1476 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
1477 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
1478 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
1479 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
1480 * c9 leaveq
1481 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1482 * c3 retq
1483 *
1484 * Sometimes r13 is used as the DRAP register, in which case it's saved and
1485 * restored beforehand:
1486 *
1487 * 41 55 push %r13
1488 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
1489 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
1490 * ...
1491 * 49 8d 65 f0 lea -0x10(%r13),%rsp
1492 * 41 5d pop %r13
1493 * c3 retq
1494 */
1495static int update_insn_state(struct instruction *insn, struct insn_state *state)
1496{
1497 struct stack_op *op = &insn->stack_op;
1498 struct cfi_reg *cfa = &state->cfa;
1499 struct cfi_reg *regs = state->regs;
1500
1501 /* stack operations don't make sense with an undefined CFA */
1502 if (cfa->base == CFI_UNDEFINED) {
1503 if (insn->func) {
1504 WARN_FUNC("undefined stack state", insn->sec, insn->offset);
1505 return -1;
1506 }
1507 return 0;
1508 }
1509
1510 if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET)
1511 return update_insn_state_regs(insn, state);
1512
1513 switch (op->dest.type) {
1514
1515 case OP_DEST_REG:
1516 switch (op->src.type) {
1517
1518 case OP_SRC_REG:
1519 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
1520 cfa->base == CFI_SP &&
1521 regs[CFI_BP].base == CFI_CFA &&
1522 regs[CFI_BP].offset == -cfa->offset) {
1523
1524 /* mov %rsp, %rbp */
1525 cfa->base = op->dest.reg;
1526 state->bp_scratch = false;
1527 }
1528
1529 else if (op->src.reg == CFI_SP &&
1530 op->dest.reg == CFI_BP && state->drap) {
1531
1532 /* drap: mov %rsp, %rbp */
1533 regs[CFI_BP].base = CFI_BP;
1534 regs[CFI_BP].offset = -state->stack_size;
1535 state->bp_scratch = false;
1536 }
1537
1538 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1539
1540 /*
1541 * mov %rsp, %reg
1542 *
1543 * This is needed for the rare case where GCC
1544 * does:
1545 *
1546 * mov %rsp, %rax
1547 * ...
1548 * mov %rax, %rsp
1549 */
1550 state->vals[op->dest.reg].base = CFI_CFA;
1551 state->vals[op->dest.reg].offset = -state->stack_size;
1552 }
1553
1554 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
1555 cfa->base == CFI_BP) {
1556
1557 /*
1558 * mov %rbp, %rsp
1559 *
1560 * Restore the original stack pointer (Clang).
1561 */
1562 state->stack_size = -state->regs[CFI_BP].offset;
1563 }
1564
1565 else if (op->dest.reg == cfa->base) {
1566
1567 /* mov %reg, %rsp */
1568 if (cfa->base == CFI_SP &&
1569 state->vals[op->src.reg].base == CFI_CFA) {
1570
1571 /*
1572 * This is needed for the rare case
1573 * where GCC does something dumb like:
1574 *
1575 * lea 0x8(%rsp), %rcx
1576 * ...
1577 * mov %rcx, %rsp
1578 */
1579 cfa->offset = -state->vals[op->src.reg].offset;
1580 state->stack_size = cfa->offset;
1581
1582 } else {
1583 cfa->base = CFI_UNDEFINED;
1584 cfa->offset = 0;
1585 }
1586 }
1587
1588 break;
1589
1590 case OP_SRC_ADD:
1591 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
1592
1593 /* add imm, %rsp */
1594 state->stack_size -= op->src.offset;
1595 if (cfa->base == CFI_SP)
1596 cfa->offset -= op->src.offset;
1597 break;
1598 }
1599
1600 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
1601
1602 /* lea disp(%rbp), %rsp */
1603 state->stack_size = -(op->src.offset + regs[CFI_BP].offset);
1604 break;
1605 }
1606
1607 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1608
1609 /* drap: lea disp(%rsp), %drap */
1610 state->drap_reg = op->dest.reg;
1611
1612 /*
1613 * lea disp(%rsp), %reg
1614 *
1615 * This is needed for the rare case where GCC
1616 * does something dumb like:
1617 *
1618 * lea 0x8(%rsp), %rcx
1619 * ...
1620 * mov %rcx, %rsp
1621 */
1622 state->vals[op->dest.reg].base = CFI_CFA;
1623 state->vals[op->dest.reg].offset = \
1624 -state->stack_size + op->src.offset;
1625
1626 break;
1627 }
1628
1629 if (state->drap && op->dest.reg == CFI_SP &&
1630 op->src.reg == state->drap_reg) {
1631
1632 /* drap: lea disp(%drap), %rsp */
1633 cfa->base = CFI_SP;
1634 cfa->offset = state->stack_size = -op->src.offset;
1635 state->drap_reg = CFI_UNDEFINED;
1636 state->drap = false;
1637 break;
1638 }
1639
1640 if (op->dest.reg == state->cfa.base) {
1641 WARN_FUNC("unsupported stack register modification",
1642 insn->sec, insn->offset);
1643 return -1;
1644 }
1645
1646 break;
1647
1648 case OP_SRC_AND:
1649 if (op->dest.reg != CFI_SP ||
1650 (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
1651 (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
1652 WARN_FUNC("unsupported stack pointer realignment",
1653 insn->sec, insn->offset);
1654 return -1;
1655 }
1656
1657 if (state->drap_reg != CFI_UNDEFINED) {
1658 /* drap: and imm, %rsp */
1659 cfa->base = state->drap_reg;
1660 cfa->offset = state->stack_size = 0;
1661 state->drap = true;
1662 }
1663
1664 /*
1665 * Older versions of GCC (4.8ish) realign the stack
1666 * without DRAP, with a frame pointer.
1667 */
1668
1669 break;
1670
1671 case OP_SRC_POP:
1672 case OP_SRC_POPF:
1673 if (!state->drap && op->dest.type == OP_DEST_REG &&
1674 op->dest.reg == cfa->base) {
1675
1676 /* pop %rbp */
1677 cfa->base = CFI_SP;
1678 }
1679
1680 if (state->drap && cfa->base == CFI_BP_INDIRECT &&
1681 op->dest.type == OP_DEST_REG &&
1682 op->dest.reg == state->drap_reg &&
1683 state->drap_offset == -state->stack_size) {
1684
1685 /* drap: pop %drap */
1686 cfa->base = state->drap_reg;
1687 cfa->offset = 0;
1688 state->drap_offset = -1;
1689
1690 } else if (regs[op->dest.reg].offset == -state->stack_size) {
1691
1692 /* pop %reg */
1693 restore_reg(state, op->dest.reg);
1694 }
1695
1696 state->stack_size -= 8;
1697 if (cfa->base == CFI_SP)
1698 cfa->offset -= 8;
1699
1700 break;
1701
1702 case OP_SRC_REG_INDIRECT:
1703 if (state->drap && op->src.reg == CFI_BP &&
1704 op->src.offset == state->drap_offset) {
1705
1706 /* drap: mov disp(%rbp), %drap */
1707 cfa->base = state->drap_reg;
1708 cfa->offset = 0;
1709 state->drap_offset = -1;
1710 }
1711
1712 if (state->drap && op->src.reg == CFI_BP &&
1713 op->src.offset == regs[op->dest.reg].offset) {
1714
1715 /* drap: mov disp(%rbp), %reg */
1716 restore_reg(state, op->dest.reg);
1717
1718 } else if (op->src.reg == cfa->base &&
1719 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
1720
1721 /* mov disp(%rbp), %reg */
1722 /* mov disp(%rsp), %reg */
1723 restore_reg(state, op->dest.reg);
1724 }
1725
1726 break;
1727
1728 default:
1729 WARN_FUNC("unknown stack-related instruction",
1730 insn->sec, insn->offset);
1731 return -1;
1732 }
1733
1734 break;
1735
1736 case OP_DEST_PUSH:
1737 case OP_DEST_PUSHF:
1738 state->stack_size += 8;
1739 if (cfa->base == CFI_SP)
1740 cfa->offset += 8;
1741
1742 if (op->src.type != OP_SRC_REG)
1743 break;
1744
1745 if (state->drap) {
1746 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1747
1748 /* drap: push %drap */
1749 cfa->base = CFI_BP_INDIRECT;
1750 cfa->offset = -state->stack_size;
1751
1752 /* save drap so we know when to restore it */
1753 state->drap_offset = -state->stack_size;
1754
1755 } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
1756
1757 /* drap: push %rbp */
1758 state->stack_size = 0;
1759
1760 } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1761
1762 /* drap: push %reg */
1763 save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
1764 }
1765
1766 } else {
1767
1768 /* push %reg */
1769 save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
1770 }
1771
1772 /* detect when asm code uses rbp as a scratch register */
1773 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
1774 cfa->base != CFI_BP)
1775 state->bp_scratch = true;
1776 break;
1777
1778 case OP_DEST_REG_INDIRECT:
1779
1780 if (state->drap) {
1781 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1782
1783 /* drap: mov %drap, disp(%rbp) */
1784 cfa->base = CFI_BP_INDIRECT;
1785 cfa->offset = op->dest.offset;
1786
1787 /* save drap offset so we know when to restore it */
1788 state->drap_offset = op->dest.offset;
1789 }
1790
1791 else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1792
1793 /* drap: mov reg, disp(%rbp) */
1794 save_reg(state, op->src.reg, CFI_BP, op->dest.offset);
1795 }
1796
1797 } else if (op->dest.reg == cfa->base) {
1798
1799 /* mov reg, disp(%rbp) */
1800 /* mov reg, disp(%rsp) */
1801 save_reg(state, op->src.reg, CFI_CFA,
1802 op->dest.offset - state->cfa.offset);
1803 }
1804
1805 break;
1806
1807 case OP_DEST_LEAVE:
1808 if ((!state->drap && cfa->base != CFI_BP) ||
1809 (state->drap && cfa->base != state->drap_reg)) {
1810 WARN_FUNC("leave instruction with modified stack frame",
1811 insn->sec, insn->offset);
1812 return -1;
1813 }
1814
1815 /* leave (mov %rbp, %rsp; pop %rbp) */
1816
1817 state->stack_size = -state->regs[CFI_BP].offset - 8;
1818 restore_reg(state, CFI_BP);
1819
1820 if (!state->drap) {
1821 cfa->base = CFI_SP;
1822 cfa->offset -= 8;
1823 }
1824
1825 break;
1826
1827 case OP_DEST_MEM:
1828 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
1829 WARN_FUNC("unknown stack-related memory operation",
1830 insn->sec, insn->offset);
1831 return -1;
1832 }
1833
1834 /* pop mem */
1835 state->stack_size -= 8;
1836 if (cfa->base == CFI_SP)
1837 cfa->offset -= 8;
1838
1839 break;
1840
1841 default:
1842 WARN_FUNC("unknown stack-related instruction",
1843 insn->sec, insn->offset);
1844 return -1;
1845 }
1846
1847 return 0;
1848}
1849
1850static bool insn_state_match(struct instruction *insn, struct insn_state *state)
1851{
1852 struct insn_state *state1 = &insn->state, *state2 = state;
1853 int i;
1854
1855 if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
1856 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
1857 insn->sec, insn->offset,
1858 state1->cfa.base, state1->cfa.offset,
1859 state2->cfa.base, state2->cfa.offset);
1860
1861 } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
1862 for (i = 0; i < CFI_NUM_REGS; i++) {
1863 if (!memcmp(&state1->regs[i], &state2->regs[i],
1864 sizeof(struct cfi_reg)))
1865 continue;
1866
1867 WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
1868 insn->sec, insn->offset,
1869 i, state1->regs[i].base, state1->regs[i].offset,
1870 i, state2->regs[i].base, state2->regs[i].offset);
1871 break;
1872 }
1873
1874 } else if (state1->type != state2->type) {
1875 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
1876 insn->sec, insn->offset, state1->type, state2->type);
1877
1878 } else if (state1->drap != state2->drap ||
1879 (state1->drap && state1->drap_reg != state2->drap_reg) ||
1880 (state1->drap && state1->drap_offset != state2->drap_offset)) {
1881 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
1882 insn->sec, insn->offset,
1883 state1->drap, state1->drap_reg, state1->drap_offset,
1884 state2->drap, state2->drap_reg, state2->drap_offset);
1885
1886 } else
1887 return true;
1888
1889 return false;
1890}
1891
1892static inline bool func_uaccess_safe(struct symbol *func)
1893{
1894 if (func)
1895 return func->uaccess_safe;
1896
1897 return false;
1898}
1899
1900static inline const char *call_dest_name(struct instruction *insn)
1901{
1902 if (insn->call_dest)
1903 return insn->call_dest->name;
1904
1905 return "{dynamic}";
1906}
1907
1908static int validate_call(struct instruction *insn, struct insn_state *state)
1909{
1910 if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
1911 WARN_FUNC("call to %s() with UACCESS enabled",
1912 insn->sec, insn->offset, call_dest_name(insn));
1913 return 1;
1914 }
1915
1916 if (state->df) {
1917 WARN_FUNC("call to %s() with DF set",
1918 insn->sec, insn->offset, call_dest_name(insn));
1919 return 1;
1920 }
1921
1922 return 0;
1923}
1924
1925static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
1926{
1927 if (has_modified_stack_frame(state)) {
1928 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1929 insn->sec, insn->offset);
1930 return 1;
1931 }
1932
1933 return validate_call(insn, state);
1934}
1935
1936/*
1937 * Follow the branch starting at the given instruction, and recursively follow
1938 * any other branches (jumps). Meanwhile, track the frame pointer state at
1939 * each instruction and validate all the rules described in
1940 * tools/objtool/Documentation/stack-validation.txt.
1941 */
1942static int validate_branch(struct objtool_file *file, struct symbol *func,
1943 struct instruction *first, struct insn_state state)
1944{
1945 struct alternative *alt;
1946 struct instruction *insn, *next_insn;
1947 struct section *sec;
1948 u8 visited;
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 visited = 1 << state.uaccess;
1976 if (insn->visited) {
1977 if (!insn->hint && !insn_state_match(insn, &state))
1978 return 1;
1979
1980 if (insn->visited & visited)
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 |= visited;
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
2224static 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
2247static 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
2279static 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
2285static 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
2292static 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
2343static 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
2388static 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
2406static 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
2423static struct objtool_file file;
2424
2425int 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
2489out:
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}