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io_uring: reset -EBUSY error when io sq thread is waken up
[thirdparty/linux.git] / tools / objtool / check.c
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
4 */
5
6 #include <string.h>
7 #include <stdlib.h>
8
9 #include "builtin.h"
10 #include "check.h"
11 #include "elf.h"
12 #include "special.h"
13 #include "arch.h"
14 #include "warn.h"
15
16 #include <linux/hashtable.h>
17 #include <linux/kernel.h>
18
19 #define FAKE_JUMP_OFFSET -1
20
21 #define C_JUMP_TABLE_SECTION ".rodata..c_jump_table"
22
23 struct alternative {
24 struct list_head list;
25 struct instruction *insn;
26 bool skip_orig;
27 };
28
29 const char *objname;
30 struct cfi_state initial_func_cfi;
31
32 struct instruction *find_insn(struct objtool_file *file,
33 struct section *sec, unsigned long offset)
34 {
35 struct instruction *insn;
36
37 hash_for_each_possible(file->insn_hash, insn, hash, offset)
38 if (insn->sec == sec && insn->offset == offset)
39 return insn;
40
41 return NULL;
42 }
43
44 static struct instruction *next_insn_same_sec(struct objtool_file *file,
45 struct instruction *insn)
46 {
47 struct instruction *next = list_next_entry(insn, list);
48
49 if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
50 return NULL;
51
52 return next;
53 }
54
55 static struct instruction *next_insn_same_func(struct objtool_file *file,
56 struct instruction *insn)
57 {
58 struct instruction *next = list_next_entry(insn, list);
59 struct symbol *func = insn->func;
60
61 if (!func)
62 return NULL;
63
64 if (&next->list != &file->insn_list && next->func == func)
65 return next;
66
67 /* Check if we're already in the subfunction: */
68 if (func == func->cfunc)
69 return NULL;
70
71 /* Move to the subfunction: */
72 return find_insn(file, func->cfunc->sec, func->cfunc->offset);
73 }
74
75 #define func_for_each_insn(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 "__sanitizer_cov_trace_switch",
492 /* UBSAN */
493 "ubsan_type_mismatch_common",
494 "__ubsan_handle_type_mismatch",
495 "__ubsan_handle_type_mismatch_v1",
496 "__ubsan_handle_shift_out_of_bounds",
497 /* misc */
498 "csum_partial_copy_generic",
499 "__memcpy_mcsafe",
500 "mcsafe_handle_tail",
501 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
502 NULL
503 };
504
505 static void add_uaccess_safe(struct objtool_file *file)
506 {
507 struct symbol *func;
508 const char **name;
509
510 if (!uaccess)
511 return;
512
513 for (name = uaccess_safe_builtin; *name; name++) {
514 func = find_symbol_by_name(file->elf, *name);
515 if (!func)
516 continue;
517
518 func->uaccess_safe = true;
519 }
520 }
521
522 /*
523 * FIXME: For now, just ignore any alternatives which add retpolines. This is
524 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
525 * But it at least allows objtool to understand the control flow *around* the
526 * retpoline.
527 */
528 static int add_ignore_alternatives(struct objtool_file *file)
529 {
530 struct section *sec;
531 struct rela *rela;
532 struct instruction *insn;
533
534 sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
535 if (!sec)
536 return 0;
537
538 list_for_each_entry(rela, &sec->rela_list, list) {
539 if (rela->sym->type != STT_SECTION) {
540 WARN("unexpected relocation symbol type in %s", sec->name);
541 return -1;
542 }
543
544 insn = find_insn(file, rela->sym->sec, rela->addend);
545 if (!insn) {
546 WARN("bad .discard.ignore_alts entry");
547 return -1;
548 }
549
550 insn->ignore_alts = true;
551 }
552
553 return 0;
554 }
555
556 /*
557 * Find the destination instructions for all jumps.
558 */
559 static int add_jump_destinations(struct objtool_file *file)
560 {
561 struct instruction *insn;
562 struct rela *rela;
563 struct section *dest_sec;
564 unsigned long dest_off;
565
566 for_each_insn(file, insn) {
567 if (!is_static_jump(insn))
568 continue;
569
570 if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET)
571 continue;
572
573 rela = find_rela_by_dest_range(file->elf, insn->sec,
574 insn->offset, insn->len);
575 if (!rela) {
576 dest_sec = insn->sec;
577 dest_off = insn->offset + insn->len + insn->immediate;
578 } else if (rela->sym->type == STT_SECTION) {
579 dest_sec = rela->sym->sec;
580 dest_off = rela->addend + 4;
581 } else if (rela->sym->sec->idx) {
582 dest_sec = rela->sym->sec;
583 dest_off = rela->sym->sym.st_value + rela->addend + 4;
584 } else if (strstr(rela->sym->name, "_indirect_thunk_")) {
585 /*
586 * Retpoline jumps are really dynamic jumps in
587 * disguise, so convert them accordingly.
588 */
589 if (insn->type == INSN_JUMP_UNCONDITIONAL)
590 insn->type = INSN_JUMP_DYNAMIC;
591 else
592 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
593
594 insn->retpoline_safe = true;
595 continue;
596 } else {
597 /* external sibling call */
598 insn->call_dest = rela->sym;
599 continue;
600 }
601
602 insn->jump_dest = find_insn(file, dest_sec, dest_off);
603 if (!insn->jump_dest) {
604
605 /*
606 * This is a special case where an alt instruction
607 * jumps past the end of the section. These are
608 * handled later in handle_group_alt().
609 */
610 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
611 continue;
612
613 WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
614 insn->sec, insn->offset, dest_sec->name,
615 dest_off);
616 return -1;
617 }
618
619 /*
620 * Cross-function jump.
621 */
622 if (insn->func && insn->jump_dest->func &&
623 insn->func != insn->jump_dest->func) {
624
625 /*
626 * For GCC 8+, create parent/child links for any cold
627 * subfunctions. This is _mostly_ redundant with a
628 * similar initialization in read_symbols().
629 *
630 * If a function has aliases, we want the *first* such
631 * function in the symbol table to be the subfunction's
632 * parent. In that case we overwrite the
633 * initialization done in read_symbols().
634 *
635 * However this code can't completely replace the
636 * read_symbols() code because this doesn't detect the
637 * case where the parent function's only reference to a
638 * subfunction is through a jump table.
639 */
640 if (!strstr(insn->func->name, ".cold.") &&
641 strstr(insn->jump_dest->func->name, ".cold.")) {
642 insn->func->cfunc = insn->jump_dest->func;
643 insn->jump_dest->func->pfunc = insn->func;
644
645 } else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
646 insn->jump_dest->offset == insn->jump_dest->func->offset) {
647
648 /* internal sibling call */
649 insn->call_dest = insn->jump_dest->func;
650 }
651 }
652 }
653
654 return 0;
655 }
656
657 /*
658 * Find the destination instructions for all calls.
659 */
660 static int add_call_destinations(struct objtool_file *file)
661 {
662 struct instruction *insn;
663 unsigned long dest_off;
664 struct rela *rela;
665
666 for_each_insn(file, insn) {
667 if (insn->type != INSN_CALL)
668 continue;
669
670 rela = find_rela_by_dest_range(file->elf, insn->sec,
671 insn->offset, insn->len);
672 if (!rela) {
673 dest_off = insn->offset + insn->len + insn->immediate;
674 insn->call_dest = find_func_by_offset(insn->sec, dest_off);
675 if (!insn->call_dest)
676 insn->call_dest = find_symbol_by_offset(insn->sec, dest_off);
677
678 if (insn->ignore)
679 continue;
680
681 if (!insn->call_dest) {
682 WARN_FUNC("unsupported intra-function call",
683 insn->sec, insn->offset);
684 if (retpoline)
685 WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");
686 return -1;
687 }
688
689 if (insn->func && insn->call_dest->type != STT_FUNC) {
690 WARN_FUNC("unsupported call to non-function",
691 insn->sec, insn->offset);
692 return -1;
693 }
694
695 } else if (rela->sym->type == STT_SECTION) {
696 insn->call_dest = find_func_by_offset(rela->sym->sec,
697 rela->addend+4);
698 if (!insn->call_dest) {
699 WARN_FUNC("can't find call dest symbol at %s+0x%x",
700 insn->sec, insn->offset,
701 rela->sym->sec->name,
702 rela->addend + 4);
703 return -1;
704 }
705 } else
706 insn->call_dest = rela->sym;
707 }
708
709 return 0;
710 }
711
712 /*
713 * The .alternatives section requires some extra special care, over and above
714 * what other special sections require:
715 *
716 * 1. Because alternatives are patched in-place, we need to insert a fake jump
717 * instruction at the end so that validate_branch() skips all the original
718 * replaced instructions when validating the new instruction path.
719 *
720 * 2. An added wrinkle is that the new instruction length might be zero. In
721 * that case the old instructions are replaced with noops. We simulate that
722 * by creating a fake jump as the only new instruction.
723 *
724 * 3. In some cases, the alternative section includes an instruction which
725 * conditionally jumps to the _end_ of the entry. We have to modify these
726 * jumps' destinations to point back to .text rather than the end of the
727 * entry in .altinstr_replacement.
728 */
729 static int handle_group_alt(struct objtool_file *file,
730 struct special_alt *special_alt,
731 struct instruction *orig_insn,
732 struct instruction **new_insn)
733 {
734 struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
735 unsigned long dest_off;
736
737 last_orig_insn = NULL;
738 insn = orig_insn;
739 sec_for_each_insn_from(file, insn) {
740 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
741 break;
742
743 insn->alt_group = true;
744 last_orig_insn = insn;
745 }
746
747 if (next_insn_same_sec(file, last_orig_insn)) {
748 fake_jump = malloc(sizeof(*fake_jump));
749 if (!fake_jump) {
750 WARN("malloc failed");
751 return -1;
752 }
753 memset(fake_jump, 0, sizeof(*fake_jump));
754 INIT_LIST_HEAD(&fake_jump->alts);
755 clear_insn_state(&fake_jump->state);
756
757 fake_jump->sec = special_alt->new_sec;
758 fake_jump->offset = FAKE_JUMP_OFFSET;
759 fake_jump->type = INSN_JUMP_UNCONDITIONAL;
760 fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
761 fake_jump->func = orig_insn->func;
762 }
763
764 if (!special_alt->new_len) {
765 if (!fake_jump) {
766 WARN("%s: empty alternative at end of section",
767 special_alt->orig_sec->name);
768 return -1;
769 }
770
771 *new_insn = fake_jump;
772 return 0;
773 }
774
775 last_new_insn = NULL;
776 insn = *new_insn;
777 sec_for_each_insn_from(file, insn) {
778 if (insn->offset >= special_alt->new_off + special_alt->new_len)
779 break;
780
781 last_new_insn = insn;
782
783 insn->ignore = orig_insn->ignore_alts;
784 insn->func = orig_insn->func;
785
786 /*
787 * Since alternative replacement code is copy/pasted by the
788 * kernel after applying relocations, generally such code can't
789 * have relative-address relocation references to outside the
790 * .altinstr_replacement section, unless the arch's
791 * alternatives code can adjust the relative offsets
792 * accordingly.
793 *
794 * The x86 alternatives code adjusts the offsets only when it
795 * encounters a branch instruction at the very beginning of the
796 * replacement group.
797 */
798 if ((insn->offset != special_alt->new_off ||
799 (insn->type != INSN_CALL && !is_static_jump(insn))) &&
800 find_rela_by_dest_range(file->elf, insn->sec, insn->offset, insn->len)) {
801
802 WARN_FUNC("unsupported relocation in alternatives section",
803 insn->sec, insn->offset);
804 return -1;
805 }
806
807 if (!is_static_jump(insn))
808 continue;
809
810 if (!insn->immediate)
811 continue;
812
813 dest_off = insn->offset + insn->len + insn->immediate;
814 if (dest_off == special_alt->new_off + special_alt->new_len) {
815 if (!fake_jump) {
816 WARN("%s: alternative jump to end of section",
817 special_alt->orig_sec->name);
818 return -1;
819 }
820 insn->jump_dest = fake_jump;
821 }
822
823 if (!insn->jump_dest) {
824 WARN_FUNC("can't find alternative jump destination",
825 insn->sec, insn->offset);
826 return -1;
827 }
828 }
829
830 if (!last_new_insn) {
831 WARN_FUNC("can't find last new alternative instruction",
832 special_alt->new_sec, special_alt->new_off);
833 return -1;
834 }
835
836 if (fake_jump)
837 list_add(&fake_jump->list, &last_new_insn->list);
838
839 return 0;
840 }
841
842 /*
843 * A jump table entry can either convert a nop to a jump or a jump to a nop.
844 * If the original instruction is a jump, make the alt entry an effective nop
845 * by just skipping the original instruction.
846 */
847 static int handle_jump_alt(struct objtool_file *file,
848 struct special_alt *special_alt,
849 struct instruction *orig_insn,
850 struct instruction **new_insn)
851 {
852 if (orig_insn->type == INSN_NOP)
853 return 0;
854
855 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
856 WARN_FUNC("unsupported instruction at jump label",
857 orig_insn->sec, orig_insn->offset);
858 return -1;
859 }
860
861 *new_insn = list_next_entry(orig_insn, list);
862 return 0;
863 }
864
865 /*
866 * Read all the special sections which have alternate instructions which can be
867 * patched in or redirected to at runtime. Each instruction having alternate
868 * instruction(s) has them added to its insn->alts list, which will be
869 * traversed in validate_branch().
870 */
871 static int add_special_section_alts(struct objtool_file *file)
872 {
873 struct list_head special_alts;
874 struct instruction *orig_insn, *new_insn;
875 struct special_alt *special_alt, *tmp;
876 struct alternative *alt;
877 int ret;
878
879 ret = special_get_alts(file->elf, &special_alts);
880 if (ret)
881 return ret;
882
883 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
884
885 orig_insn = find_insn(file, special_alt->orig_sec,
886 special_alt->orig_off);
887 if (!orig_insn) {
888 WARN_FUNC("special: can't find orig instruction",
889 special_alt->orig_sec, special_alt->orig_off);
890 ret = -1;
891 goto out;
892 }
893
894 new_insn = NULL;
895 if (!special_alt->group || special_alt->new_len) {
896 new_insn = find_insn(file, special_alt->new_sec,
897 special_alt->new_off);
898 if (!new_insn) {
899 WARN_FUNC("special: can't find new instruction",
900 special_alt->new_sec,
901 special_alt->new_off);
902 ret = -1;
903 goto out;
904 }
905 }
906
907 if (special_alt->group) {
908 ret = handle_group_alt(file, special_alt, orig_insn,
909 &new_insn);
910 if (ret)
911 goto out;
912 } else if (special_alt->jump_or_nop) {
913 ret = handle_jump_alt(file, special_alt, orig_insn,
914 &new_insn);
915 if (ret)
916 goto out;
917 }
918
919 alt = malloc(sizeof(*alt));
920 if (!alt) {
921 WARN("malloc failed");
922 ret = -1;
923 goto out;
924 }
925
926 alt->insn = new_insn;
927 alt->skip_orig = special_alt->skip_orig;
928 orig_insn->ignore_alts |= special_alt->skip_alt;
929 list_add_tail(&alt->list, &orig_insn->alts);
930
931 list_del(&special_alt->list);
932 free(special_alt);
933 }
934
935 out:
936 return ret;
937 }
938
939 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
940 struct rela *table)
941 {
942 struct rela *rela = table;
943 struct instruction *dest_insn;
944 struct alternative *alt;
945 struct symbol *pfunc = insn->func->pfunc;
946 unsigned int prev_offset = 0;
947
948 /*
949 * Each @rela is a switch table relocation which points to the target
950 * instruction.
951 */
952 list_for_each_entry_from(rela, &table->sec->rela_list, list) {
953
954 /* Check for the end of the table: */
955 if (rela != table && rela->jump_table_start)
956 break;
957
958 /* Make sure the table entries are consecutive: */
959 if (prev_offset && rela->offset != prev_offset + 8)
960 break;
961
962 /* Detect function pointers from contiguous objects: */
963 if (rela->sym->sec == pfunc->sec &&
964 rela->addend == pfunc->offset)
965 break;
966
967 dest_insn = find_insn(file, rela->sym->sec, rela->addend);
968 if (!dest_insn)
969 break;
970
971 /* Make sure the destination is in the same function: */
972 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
973 break;
974
975 alt = malloc(sizeof(*alt));
976 if (!alt) {
977 WARN("malloc failed");
978 return -1;
979 }
980
981 alt->insn = dest_insn;
982 list_add_tail(&alt->list, &insn->alts);
983 prev_offset = rela->offset;
984 }
985
986 if (!prev_offset) {
987 WARN_FUNC("can't find switch jump table",
988 insn->sec, insn->offset);
989 return -1;
990 }
991
992 return 0;
993 }
994
995 /*
996 * find_jump_table() - Given a dynamic jump, find the switch jump table in
997 * .rodata associated with it.
998 *
999 * There are 3 basic patterns:
1000 *
1001 * 1. jmpq *[rodata addr](,%reg,8)
1002 *
1003 * This is the most common case by far. It jumps to an address in a simple
1004 * jump table which is stored in .rodata.
1005 *
1006 * 2. jmpq *[rodata addr](%rip)
1007 *
1008 * This is caused by a rare GCC quirk, currently only seen in three driver
1009 * functions in the kernel, only with certain obscure non-distro configs.
1010 *
1011 * As part of an optimization, GCC makes a copy of an existing switch jump
1012 * table, modifies it, and then hard-codes the jump (albeit with an indirect
1013 * jump) to use a single entry in the table. The rest of the jump table and
1014 * some of its jump targets remain as dead code.
1015 *
1016 * In such a case we can just crudely ignore all unreachable instruction
1017 * warnings for the entire object file. Ideally we would just ignore them
1018 * for the function, but that would require redesigning the code quite a
1019 * bit. And honestly that's just not worth doing: unreachable instruction
1020 * warnings are of questionable value anyway, and this is such a rare issue.
1021 *
1022 * 3. mov [rodata addr],%reg1
1023 * ... some instructions ...
1024 * jmpq *(%reg1,%reg2,8)
1025 *
1026 * This is a fairly uncommon pattern which is new for GCC 6. As of this
1027 * writing, there are 11 occurrences of it in the allmodconfig kernel.
1028 *
1029 * As of GCC 7 there are quite a few more of these and the 'in between' code
1030 * is significant. Esp. with KASAN enabled some of the code between the mov
1031 * and jmpq uses .rodata itself, which can confuse things.
1032 *
1033 * TODO: Once we have DWARF CFI and smarter instruction decoding logic,
1034 * ensure the same register is used in the mov and jump instructions.
1035 *
1036 * NOTE: RETPOLINE made it harder still to decode dynamic jumps.
1037 */
1038 static struct rela *find_jump_table(struct objtool_file *file,
1039 struct symbol *func,
1040 struct instruction *insn)
1041 {
1042 struct rela *text_rela, *table_rela;
1043 struct instruction *dest_insn, *orig_insn = insn;
1044 struct section *table_sec;
1045 unsigned long table_offset;
1046
1047 /*
1048 * Backward search using the @first_jump_src links, these help avoid
1049 * much of the 'in between' code. Which avoids us getting confused by
1050 * it.
1051 */
1052 for (;
1053 &insn->list != &file->insn_list && insn->func && insn->func->pfunc == func;
1054 insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
1055
1056 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1057 break;
1058
1059 /* allow small jumps within the range */
1060 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1061 insn->jump_dest &&
1062 (insn->jump_dest->offset <= insn->offset ||
1063 insn->jump_dest->offset > orig_insn->offset))
1064 break;
1065
1066 /* look for a relocation which references .rodata */
1067 text_rela = find_rela_by_dest_range(file->elf, insn->sec,
1068 insn->offset, insn->len);
1069 if (!text_rela || text_rela->sym->type != STT_SECTION ||
1070 !text_rela->sym->sec->rodata)
1071 continue;
1072
1073 table_offset = text_rela->addend;
1074 table_sec = text_rela->sym->sec;
1075
1076 if (text_rela->type == R_X86_64_PC32)
1077 table_offset += 4;
1078
1079 /*
1080 * Make sure the .rodata address isn't associated with a
1081 * symbol. GCC jump tables are anonymous data.
1082 *
1083 * Also support C jump tables which are in the same format as
1084 * switch jump tables. For objtool to recognize them, they
1085 * need to be placed in the C_JUMP_TABLE_SECTION section. They
1086 * have symbols associated with them.
1087 */
1088 if (find_symbol_containing(table_sec, table_offset) &&
1089 strcmp(table_sec->name, C_JUMP_TABLE_SECTION))
1090 continue;
1091
1092 /*
1093 * Each table entry has a rela associated with it. The rela
1094 * should reference text in the same function as the original
1095 * instruction.
1096 */
1097 table_rela = find_rela_by_dest(file->elf, table_sec, table_offset);
1098 if (!table_rela)
1099 continue;
1100 dest_insn = find_insn(file, table_rela->sym->sec, table_rela->addend);
1101 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1102 continue;
1103
1104 /*
1105 * Use of RIP-relative switch jumps is quite rare, and
1106 * indicates a rare GCC quirk/bug which can leave dead code
1107 * behind.
1108 */
1109 if (text_rela->type == R_X86_64_PC32)
1110 file->ignore_unreachables = true;
1111
1112 return table_rela;
1113 }
1114
1115 return NULL;
1116 }
1117
1118 /*
1119 * First pass: Mark the head of each jump table so that in the next pass,
1120 * we know when a given jump table ends and the next one starts.
1121 */
1122 static void mark_func_jump_tables(struct objtool_file *file,
1123 struct symbol *func)
1124 {
1125 struct instruction *insn, *last = NULL;
1126 struct rela *rela;
1127
1128 func_for_each_insn(file, func, insn) {
1129 if (!last)
1130 last = insn;
1131
1132 /*
1133 * Store back-pointers for unconditional forward jumps such
1134 * that find_jump_table() can back-track using those and
1135 * avoid some potentially confusing code.
1136 */
1137 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1138 insn->offset > last->offset &&
1139 insn->jump_dest->offset > insn->offset &&
1140 !insn->jump_dest->first_jump_src) {
1141
1142 insn->jump_dest->first_jump_src = insn;
1143 last = insn->jump_dest;
1144 }
1145
1146 if (insn->type != INSN_JUMP_DYNAMIC)
1147 continue;
1148
1149 rela = find_jump_table(file, func, insn);
1150 if (rela) {
1151 rela->jump_table_start = true;
1152 insn->jump_table = rela;
1153 }
1154 }
1155 }
1156
1157 static int add_func_jump_tables(struct objtool_file *file,
1158 struct symbol *func)
1159 {
1160 struct instruction *insn;
1161 int ret;
1162
1163 func_for_each_insn(file, func, insn) {
1164 if (!insn->jump_table)
1165 continue;
1166
1167 ret = add_jump_table(file, insn, insn->jump_table);
1168 if (ret)
1169 return ret;
1170 }
1171
1172 return 0;
1173 }
1174
1175 /*
1176 * For some switch statements, gcc generates a jump table in the .rodata
1177 * section which contains a list of addresses within the function to jump to.
1178 * This finds these jump tables and adds them to the insn->alts lists.
1179 */
1180 static int add_jump_table_alts(struct objtool_file *file)
1181 {
1182 struct section *sec;
1183 struct symbol *func;
1184 int ret;
1185
1186 if (!file->rodata)
1187 return 0;
1188
1189 for_each_sec(file, sec) {
1190 list_for_each_entry(func, &sec->symbol_list, list) {
1191 if (func->type != STT_FUNC)
1192 continue;
1193
1194 mark_func_jump_tables(file, func);
1195 ret = add_func_jump_tables(file, func);
1196 if (ret)
1197 return ret;
1198 }
1199 }
1200
1201 return 0;
1202 }
1203
1204 static int read_unwind_hints(struct objtool_file *file)
1205 {
1206 struct section *sec, *relasec;
1207 struct rela *rela;
1208 struct unwind_hint *hint;
1209 struct instruction *insn;
1210 struct cfi_reg *cfa;
1211 int i;
1212
1213 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1214 if (!sec)
1215 return 0;
1216
1217 relasec = sec->rela;
1218 if (!relasec) {
1219 WARN("missing .rela.discard.unwind_hints section");
1220 return -1;
1221 }
1222
1223 if (sec->len % sizeof(struct unwind_hint)) {
1224 WARN("struct unwind_hint size mismatch");
1225 return -1;
1226 }
1227
1228 file->hints = true;
1229
1230 for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
1231 hint = (struct unwind_hint *)sec->data->d_buf + i;
1232
1233 rela = find_rela_by_dest(file->elf, sec, i * sizeof(*hint));
1234 if (!rela) {
1235 WARN("can't find rela for unwind_hints[%d]", i);
1236 return -1;
1237 }
1238
1239 insn = find_insn(file, rela->sym->sec, rela->addend);
1240 if (!insn) {
1241 WARN("can't find insn for unwind_hints[%d]", i);
1242 return -1;
1243 }
1244
1245 cfa = &insn->state.cfa;
1246
1247 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
1248 insn->save = true;
1249 continue;
1250
1251 } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
1252 insn->restore = true;
1253 insn->hint = true;
1254 continue;
1255 }
1256
1257 insn->hint = true;
1258
1259 switch (hint->sp_reg) {
1260 case ORC_REG_UNDEFINED:
1261 cfa->base = CFI_UNDEFINED;
1262 break;
1263 case ORC_REG_SP:
1264 cfa->base = CFI_SP;
1265 break;
1266 case ORC_REG_BP:
1267 cfa->base = CFI_BP;
1268 break;
1269 case ORC_REG_SP_INDIRECT:
1270 cfa->base = CFI_SP_INDIRECT;
1271 break;
1272 case ORC_REG_R10:
1273 cfa->base = CFI_R10;
1274 break;
1275 case ORC_REG_R13:
1276 cfa->base = CFI_R13;
1277 break;
1278 case ORC_REG_DI:
1279 cfa->base = CFI_DI;
1280 break;
1281 case ORC_REG_DX:
1282 cfa->base = CFI_DX;
1283 break;
1284 default:
1285 WARN_FUNC("unsupported unwind_hint sp base reg %d",
1286 insn->sec, insn->offset, hint->sp_reg);
1287 return -1;
1288 }
1289
1290 cfa->offset = hint->sp_offset;
1291 insn->state.type = hint->type;
1292 insn->state.end = hint->end;
1293 }
1294
1295 return 0;
1296 }
1297
1298 static int read_retpoline_hints(struct objtool_file *file)
1299 {
1300 struct section *sec;
1301 struct instruction *insn;
1302 struct rela *rela;
1303
1304 sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1305 if (!sec)
1306 return 0;
1307
1308 list_for_each_entry(rela, &sec->rela_list, list) {
1309 if (rela->sym->type != STT_SECTION) {
1310 WARN("unexpected relocation symbol type in %s", sec->name);
1311 return -1;
1312 }
1313
1314 insn = find_insn(file, rela->sym->sec, rela->addend);
1315 if (!insn) {
1316 WARN("bad .discard.retpoline_safe entry");
1317 return -1;
1318 }
1319
1320 if (insn->type != INSN_JUMP_DYNAMIC &&
1321 insn->type != INSN_CALL_DYNAMIC) {
1322 WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1323 insn->sec, insn->offset);
1324 return -1;
1325 }
1326
1327 insn->retpoline_safe = true;
1328 }
1329
1330 return 0;
1331 }
1332
1333 static void mark_rodata(struct objtool_file *file)
1334 {
1335 struct section *sec;
1336 bool found = false;
1337
1338 /*
1339 * Search for the following rodata sections, each of which can
1340 * potentially contain jump tables:
1341 *
1342 * - .rodata: can contain GCC switch tables
1343 * - .rodata.<func>: same, if -fdata-sections is being used
1344 * - .rodata..c_jump_table: contains C annotated jump tables
1345 *
1346 * .rodata.str1.* sections are ignored; they don't contain jump tables.
1347 */
1348 for_each_sec(file, sec) {
1349 if ((!strncmp(sec->name, ".rodata", 7) && !strstr(sec->name, ".str1.")) ||
1350 !strcmp(sec->name, C_JUMP_TABLE_SECTION)) {
1351 sec->rodata = true;
1352 found = true;
1353 }
1354 }
1355
1356 file->rodata = found;
1357 }
1358
1359 static int decode_sections(struct objtool_file *file)
1360 {
1361 int ret;
1362
1363 mark_rodata(file);
1364
1365 ret = decode_instructions(file);
1366 if (ret)
1367 return ret;
1368
1369 ret = add_dead_ends(file);
1370 if (ret)
1371 return ret;
1372
1373 add_ignores(file);
1374 add_uaccess_safe(file);
1375
1376 ret = add_ignore_alternatives(file);
1377 if (ret)
1378 return ret;
1379
1380 ret = add_jump_destinations(file);
1381 if (ret)
1382 return ret;
1383
1384 ret = add_special_section_alts(file);
1385 if (ret)
1386 return ret;
1387
1388 ret = add_call_destinations(file);
1389 if (ret)
1390 return ret;
1391
1392 ret = add_jump_table_alts(file);
1393 if (ret)
1394 return ret;
1395
1396 ret = read_unwind_hints(file);
1397 if (ret)
1398 return ret;
1399
1400 ret = read_retpoline_hints(file);
1401 if (ret)
1402 return ret;
1403
1404 return 0;
1405 }
1406
1407 static bool is_fentry_call(struct instruction *insn)
1408 {
1409 if (insn->type == INSN_CALL &&
1410 insn->call_dest->type == STT_NOTYPE &&
1411 !strcmp(insn->call_dest->name, "__fentry__"))
1412 return true;
1413
1414 return false;
1415 }
1416
1417 static bool has_modified_stack_frame(struct insn_state *state)
1418 {
1419 int i;
1420
1421 if (state->cfa.base != initial_func_cfi.cfa.base ||
1422 state->cfa.offset != initial_func_cfi.cfa.offset ||
1423 state->stack_size != initial_func_cfi.cfa.offset ||
1424 state->drap)
1425 return true;
1426
1427 for (i = 0; i < CFI_NUM_REGS; i++)
1428 if (state->regs[i].base != initial_func_cfi.regs[i].base ||
1429 state->regs[i].offset != initial_func_cfi.regs[i].offset)
1430 return true;
1431
1432 return false;
1433 }
1434
1435 static bool has_valid_stack_frame(struct insn_state *state)
1436 {
1437 if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
1438 state->regs[CFI_BP].offset == -16)
1439 return true;
1440
1441 if (state->drap && state->regs[CFI_BP].base == CFI_BP)
1442 return true;
1443
1444 return false;
1445 }
1446
1447 static int update_insn_state_regs(struct instruction *insn, struct insn_state *state)
1448 {
1449 struct cfi_reg *cfa = &state->cfa;
1450 struct stack_op *op = &insn->stack_op;
1451
1452 if (cfa->base != CFI_SP)
1453 return 0;
1454
1455 /* push */
1456 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
1457 cfa->offset += 8;
1458
1459 /* pop */
1460 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
1461 cfa->offset -= 8;
1462
1463 /* add immediate to sp */
1464 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1465 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1466 cfa->offset -= op->src.offset;
1467
1468 return 0;
1469 }
1470
1471 static void save_reg(struct insn_state *state, unsigned char reg, int base,
1472 int offset)
1473 {
1474 if (arch_callee_saved_reg(reg) &&
1475 state->regs[reg].base == CFI_UNDEFINED) {
1476 state->regs[reg].base = base;
1477 state->regs[reg].offset = offset;
1478 }
1479 }
1480
1481 static void restore_reg(struct insn_state *state, unsigned char reg)
1482 {
1483 state->regs[reg].base = CFI_UNDEFINED;
1484 state->regs[reg].offset = 0;
1485 }
1486
1487 /*
1488 * A note about DRAP stack alignment:
1489 *
1490 * GCC has the concept of a DRAP register, which is used to help keep track of
1491 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
1492 * register. The typical DRAP pattern is:
1493 *
1494 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
1495 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
1496 * 41 ff 72 f8 pushq -0x8(%r10)
1497 * 55 push %rbp
1498 * 48 89 e5 mov %rsp,%rbp
1499 * (more pushes)
1500 * 41 52 push %r10
1501 * ...
1502 * 41 5a pop %r10
1503 * (more pops)
1504 * 5d pop %rbp
1505 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1506 * c3 retq
1507 *
1508 * There are some variations in the epilogues, like:
1509 *
1510 * 5b pop %rbx
1511 * 41 5a pop %r10
1512 * 41 5c pop %r12
1513 * 41 5d pop %r13
1514 * 41 5e pop %r14
1515 * c9 leaveq
1516 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1517 * c3 retq
1518 *
1519 * and:
1520 *
1521 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
1522 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
1523 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
1524 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
1525 * c9 leaveq
1526 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1527 * c3 retq
1528 *
1529 * Sometimes r13 is used as the DRAP register, in which case it's saved and
1530 * restored beforehand:
1531 *
1532 * 41 55 push %r13
1533 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
1534 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
1535 * ...
1536 * 49 8d 65 f0 lea -0x10(%r13),%rsp
1537 * 41 5d pop %r13
1538 * c3 retq
1539 */
1540 static int update_insn_state(struct instruction *insn, struct insn_state *state)
1541 {
1542 struct stack_op *op = &insn->stack_op;
1543 struct cfi_reg *cfa = &state->cfa;
1544 struct cfi_reg *regs = state->regs;
1545
1546 /* stack operations don't make sense with an undefined CFA */
1547 if (cfa->base == CFI_UNDEFINED) {
1548 if (insn->func) {
1549 WARN_FUNC("undefined stack state", insn->sec, insn->offset);
1550 return -1;
1551 }
1552 return 0;
1553 }
1554
1555 if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET)
1556 return update_insn_state_regs(insn, state);
1557
1558 switch (op->dest.type) {
1559
1560 case OP_DEST_REG:
1561 switch (op->src.type) {
1562
1563 case OP_SRC_REG:
1564 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
1565 cfa->base == CFI_SP &&
1566 regs[CFI_BP].base == CFI_CFA &&
1567 regs[CFI_BP].offset == -cfa->offset) {
1568
1569 /* mov %rsp, %rbp */
1570 cfa->base = op->dest.reg;
1571 state->bp_scratch = false;
1572 }
1573
1574 else if (op->src.reg == CFI_SP &&
1575 op->dest.reg == CFI_BP && state->drap) {
1576
1577 /* drap: mov %rsp, %rbp */
1578 regs[CFI_BP].base = CFI_BP;
1579 regs[CFI_BP].offset = -state->stack_size;
1580 state->bp_scratch = false;
1581 }
1582
1583 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1584
1585 /*
1586 * mov %rsp, %reg
1587 *
1588 * This is needed for the rare case where GCC
1589 * does:
1590 *
1591 * mov %rsp, %rax
1592 * ...
1593 * mov %rax, %rsp
1594 */
1595 state->vals[op->dest.reg].base = CFI_CFA;
1596 state->vals[op->dest.reg].offset = -state->stack_size;
1597 }
1598
1599 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
1600 cfa->base == CFI_BP) {
1601
1602 /*
1603 * mov %rbp, %rsp
1604 *
1605 * Restore the original stack pointer (Clang).
1606 */
1607 state->stack_size = -state->regs[CFI_BP].offset;
1608 }
1609
1610 else if (op->dest.reg == cfa->base) {
1611
1612 /* mov %reg, %rsp */
1613 if (cfa->base == CFI_SP &&
1614 state->vals[op->src.reg].base == CFI_CFA) {
1615
1616 /*
1617 * This is needed for the rare case
1618 * where GCC does something dumb like:
1619 *
1620 * lea 0x8(%rsp), %rcx
1621 * ...
1622 * mov %rcx, %rsp
1623 */
1624 cfa->offset = -state->vals[op->src.reg].offset;
1625 state->stack_size = cfa->offset;
1626
1627 } else {
1628 cfa->base = CFI_UNDEFINED;
1629 cfa->offset = 0;
1630 }
1631 }
1632
1633 break;
1634
1635 case OP_SRC_ADD:
1636 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
1637
1638 /* add imm, %rsp */
1639 state->stack_size -= op->src.offset;
1640 if (cfa->base == CFI_SP)
1641 cfa->offset -= op->src.offset;
1642 break;
1643 }
1644
1645 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
1646
1647 /* lea disp(%rbp), %rsp */
1648 state->stack_size = -(op->src.offset + regs[CFI_BP].offset);
1649 break;
1650 }
1651
1652 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1653
1654 /* drap: lea disp(%rsp), %drap */
1655 state->drap_reg = op->dest.reg;
1656
1657 /*
1658 * lea disp(%rsp), %reg
1659 *
1660 * This is needed for the rare case where GCC
1661 * does something dumb like:
1662 *
1663 * lea 0x8(%rsp), %rcx
1664 * ...
1665 * mov %rcx, %rsp
1666 */
1667 state->vals[op->dest.reg].base = CFI_CFA;
1668 state->vals[op->dest.reg].offset = \
1669 -state->stack_size + op->src.offset;
1670
1671 break;
1672 }
1673
1674 if (state->drap && op->dest.reg == CFI_SP &&
1675 op->src.reg == state->drap_reg) {
1676
1677 /* drap: lea disp(%drap), %rsp */
1678 cfa->base = CFI_SP;
1679 cfa->offset = state->stack_size = -op->src.offset;
1680 state->drap_reg = CFI_UNDEFINED;
1681 state->drap = false;
1682 break;
1683 }
1684
1685 if (op->dest.reg == state->cfa.base) {
1686 WARN_FUNC("unsupported stack register modification",
1687 insn->sec, insn->offset);
1688 return -1;
1689 }
1690
1691 break;
1692
1693 case OP_SRC_AND:
1694 if (op->dest.reg != CFI_SP ||
1695 (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
1696 (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
1697 WARN_FUNC("unsupported stack pointer realignment",
1698 insn->sec, insn->offset);
1699 return -1;
1700 }
1701
1702 if (state->drap_reg != CFI_UNDEFINED) {
1703 /* drap: and imm, %rsp */
1704 cfa->base = state->drap_reg;
1705 cfa->offset = state->stack_size = 0;
1706 state->drap = true;
1707 }
1708
1709 /*
1710 * Older versions of GCC (4.8ish) realign the stack
1711 * without DRAP, with a frame pointer.
1712 */
1713
1714 break;
1715
1716 case OP_SRC_POP:
1717 case OP_SRC_POPF:
1718 if (!state->drap && op->dest.type == OP_DEST_REG &&
1719 op->dest.reg == cfa->base) {
1720
1721 /* pop %rbp */
1722 cfa->base = CFI_SP;
1723 }
1724
1725 if (state->drap && cfa->base == CFI_BP_INDIRECT &&
1726 op->dest.type == OP_DEST_REG &&
1727 op->dest.reg == state->drap_reg &&
1728 state->drap_offset == -state->stack_size) {
1729
1730 /* drap: pop %drap */
1731 cfa->base = state->drap_reg;
1732 cfa->offset = 0;
1733 state->drap_offset = -1;
1734
1735 } else if (regs[op->dest.reg].offset == -state->stack_size) {
1736
1737 /* pop %reg */
1738 restore_reg(state, op->dest.reg);
1739 }
1740
1741 state->stack_size -= 8;
1742 if (cfa->base == CFI_SP)
1743 cfa->offset -= 8;
1744
1745 break;
1746
1747 case OP_SRC_REG_INDIRECT:
1748 if (state->drap && op->src.reg == CFI_BP &&
1749 op->src.offset == state->drap_offset) {
1750
1751 /* drap: mov disp(%rbp), %drap */
1752 cfa->base = state->drap_reg;
1753 cfa->offset = 0;
1754 state->drap_offset = -1;
1755 }
1756
1757 if (state->drap && op->src.reg == CFI_BP &&
1758 op->src.offset == regs[op->dest.reg].offset) {
1759
1760 /* drap: mov disp(%rbp), %reg */
1761 restore_reg(state, op->dest.reg);
1762
1763 } else if (op->src.reg == cfa->base &&
1764 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
1765
1766 /* mov disp(%rbp), %reg */
1767 /* mov disp(%rsp), %reg */
1768 restore_reg(state, op->dest.reg);
1769 }
1770
1771 break;
1772
1773 default:
1774 WARN_FUNC("unknown stack-related instruction",
1775 insn->sec, insn->offset);
1776 return -1;
1777 }
1778
1779 break;
1780
1781 case OP_DEST_PUSH:
1782 case OP_DEST_PUSHF:
1783 state->stack_size += 8;
1784 if (cfa->base == CFI_SP)
1785 cfa->offset += 8;
1786
1787 if (op->src.type != OP_SRC_REG)
1788 break;
1789
1790 if (state->drap) {
1791 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1792
1793 /* drap: push %drap */
1794 cfa->base = CFI_BP_INDIRECT;
1795 cfa->offset = -state->stack_size;
1796
1797 /* save drap so we know when to restore it */
1798 state->drap_offset = -state->stack_size;
1799
1800 } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
1801
1802 /* drap: push %rbp */
1803 state->stack_size = 0;
1804
1805 } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1806
1807 /* drap: push %reg */
1808 save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
1809 }
1810
1811 } else {
1812
1813 /* push %reg */
1814 save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
1815 }
1816
1817 /* detect when asm code uses rbp as a scratch register */
1818 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
1819 cfa->base != CFI_BP)
1820 state->bp_scratch = true;
1821 break;
1822
1823 case OP_DEST_REG_INDIRECT:
1824
1825 if (state->drap) {
1826 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1827
1828 /* drap: mov %drap, disp(%rbp) */
1829 cfa->base = CFI_BP_INDIRECT;
1830 cfa->offset = op->dest.offset;
1831
1832 /* save drap offset so we know when to restore it */
1833 state->drap_offset = op->dest.offset;
1834 }
1835
1836 else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1837
1838 /* drap: mov reg, disp(%rbp) */
1839 save_reg(state, op->src.reg, CFI_BP, op->dest.offset);
1840 }
1841
1842 } else if (op->dest.reg == cfa->base) {
1843
1844 /* mov reg, disp(%rbp) */
1845 /* mov reg, disp(%rsp) */
1846 save_reg(state, op->src.reg, CFI_CFA,
1847 op->dest.offset - state->cfa.offset);
1848 }
1849
1850 break;
1851
1852 case OP_DEST_LEAVE:
1853 if ((!state->drap && cfa->base != CFI_BP) ||
1854 (state->drap && cfa->base != state->drap_reg)) {
1855 WARN_FUNC("leave instruction with modified stack frame",
1856 insn->sec, insn->offset);
1857 return -1;
1858 }
1859
1860 /* leave (mov %rbp, %rsp; pop %rbp) */
1861
1862 state->stack_size = -state->regs[CFI_BP].offset - 8;
1863 restore_reg(state, CFI_BP);
1864
1865 if (!state->drap) {
1866 cfa->base = CFI_SP;
1867 cfa->offset -= 8;
1868 }
1869
1870 break;
1871
1872 case OP_DEST_MEM:
1873 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
1874 WARN_FUNC("unknown stack-related memory operation",
1875 insn->sec, insn->offset);
1876 return -1;
1877 }
1878
1879 /* pop mem */
1880 state->stack_size -= 8;
1881 if (cfa->base == CFI_SP)
1882 cfa->offset -= 8;
1883
1884 break;
1885
1886 default:
1887 WARN_FUNC("unknown stack-related instruction",
1888 insn->sec, insn->offset);
1889 return -1;
1890 }
1891
1892 return 0;
1893 }
1894
1895 static bool insn_state_match(struct instruction *insn, struct insn_state *state)
1896 {
1897 struct insn_state *state1 = &insn->state, *state2 = state;
1898 int i;
1899
1900 if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
1901 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
1902 insn->sec, insn->offset,
1903 state1->cfa.base, state1->cfa.offset,
1904 state2->cfa.base, state2->cfa.offset);
1905
1906 } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
1907 for (i = 0; i < CFI_NUM_REGS; i++) {
1908 if (!memcmp(&state1->regs[i], &state2->regs[i],
1909 sizeof(struct cfi_reg)))
1910 continue;
1911
1912 WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
1913 insn->sec, insn->offset,
1914 i, state1->regs[i].base, state1->regs[i].offset,
1915 i, state2->regs[i].base, state2->regs[i].offset);
1916 break;
1917 }
1918
1919 } else if (state1->type != state2->type) {
1920 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
1921 insn->sec, insn->offset, state1->type, state2->type);
1922
1923 } else if (state1->drap != state2->drap ||
1924 (state1->drap && state1->drap_reg != state2->drap_reg) ||
1925 (state1->drap && state1->drap_offset != state2->drap_offset)) {
1926 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
1927 insn->sec, insn->offset,
1928 state1->drap, state1->drap_reg, state1->drap_offset,
1929 state2->drap, state2->drap_reg, state2->drap_offset);
1930
1931 } else
1932 return true;
1933
1934 return false;
1935 }
1936
1937 static inline bool func_uaccess_safe(struct symbol *func)
1938 {
1939 if (func)
1940 return func->uaccess_safe;
1941
1942 return false;
1943 }
1944
1945 static inline const char *call_dest_name(struct instruction *insn)
1946 {
1947 if (insn->call_dest)
1948 return insn->call_dest->name;
1949
1950 return "{dynamic}";
1951 }
1952
1953 static int validate_call(struct instruction *insn, struct insn_state *state)
1954 {
1955 if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
1956 WARN_FUNC("call to %s() with UACCESS enabled",
1957 insn->sec, insn->offset, call_dest_name(insn));
1958 return 1;
1959 }
1960
1961 if (state->df) {
1962 WARN_FUNC("call to %s() with DF set",
1963 insn->sec, insn->offset, call_dest_name(insn));
1964 return 1;
1965 }
1966
1967 return 0;
1968 }
1969
1970 static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
1971 {
1972 if (has_modified_stack_frame(state)) {
1973 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1974 insn->sec, insn->offset);
1975 return 1;
1976 }
1977
1978 return validate_call(insn, state);
1979 }
1980
1981 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
1982 {
1983 if (state->uaccess && !func_uaccess_safe(func)) {
1984 WARN_FUNC("return with UACCESS enabled",
1985 insn->sec, insn->offset);
1986 return 1;
1987 }
1988
1989 if (!state->uaccess && func_uaccess_safe(func)) {
1990 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
1991 insn->sec, insn->offset);
1992 return 1;
1993 }
1994
1995 if (state->df) {
1996 WARN_FUNC("return with DF set",
1997 insn->sec, insn->offset);
1998 return 1;
1999 }
2000
2001 if (func && has_modified_stack_frame(state)) {
2002 WARN_FUNC("return with modified stack frame",
2003 insn->sec, insn->offset);
2004 return 1;
2005 }
2006
2007 if (state->bp_scratch) {
2008 WARN_FUNC("BP used as a scratch register",
2009 insn->sec, insn->offset);
2010 return 1;
2011 }
2012
2013 return 0;
2014 }
2015
2016 /*
2017 * Follow the branch starting at the given instruction, and recursively follow
2018 * any other branches (jumps). Meanwhile, track the frame pointer state at
2019 * each instruction and validate all the rules described in
2020 * tools/objtool/Documentation/stack-validation.txt.
2021 */
2022 static int validate_branch(struct objtool_file *file, struct symbol *func,
2023 struct instruction *first, struct insn_state state)
2024 {
2025 struct alternative *alt;
2026 struct instruction *insn, *next_insn;
2027 struct section *sec;
2028 u8 visited;
2029 int ret;
2030
2031 insn = first;
2032 sec = insn->sec;
2033
2034 if (insn->alt_group && list_empty(&insn->alts)) {
2035 WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
2036 sec, insn->offset);
2037 return 1;
2038 }
2039
2040 while (1) {
2041 next_insn = next_insn_same_sec(file, insn);
2042
2043 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
2044 WARN("%s() falls through to next function %s()",
2045 func->name, insn->func->name);
2046 return 1;
2047 }
2048
2049 if (func && insn->ignore) {
2050 WARN_FUNC("BUG: why am I validating an ignored function?",
2051 sec, insn->offset);
2052 return 1;
2053 }
2054
2055 visited = 1 << state.uaccess;
2056 if (insn->visited) {
2057 if (!insn->hint && !insn_state_match(insn, &state))
2058 return 1;
2059
2060 if (insn->visited & visited)
2061 return 0;
2062 }
2063
2064 if (insn->hint) {
2065 if (insn->restore) {
2066 struct instruction *save_insn, *i;
2067
2068 i = insn;
2069 save_insn = NULL;
2070 sym_for_each_insn_continue_reverse(file, func, i) {
2071 if (i->save) {
2072 save_insn = i;
2073 break;
2074 }
2075 }
2076
2077 if (!save_insn) {
2078 WARN_FUNC("no corresponding CFI save for CFI restore",
2079 sec, insn->offset);
2080 return 1;
2081 }
2082
2083 if (!save_insn->visited) {
2084 /*
2085 * Oops, no state to copy yet.
2086 * Hopefully we can reach this
2087 * instruction from another branch
2088 * after the save insn has been
2089 * visited.
2090 */
2091 if (insn == first)
2092 return 0;
2093
2094 WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
2095 sec, insn->offset);
2096 return 1;
2097 }
2098
2099 insn->state = save_insn->state;
2100 }
2101
2102 state = insn->state;
2103
2104 } else
2105 insn->state = state;
2106
2107 insn->visited |= visited;
2108
2109 if (!insn->ignore_alts) {
2110 bool skip_orig = false;
2111
2112 list_for_each_entry(alt, &insn->alts, list) {
2113 if (alt->skip_orig)
2114 skip_orig = true;
2115
2116 ret = validate_branch(file, func, alt->insn, state);
2117 if (ret) {
2118 if (backtrace)
2119 BT_FUNC("(alt)", insn);
2120 return ret;
2121 }
2122 }
2123
2124 if (skip_orig)
2125 return 0;
2126 }
2127
2128 switch (insn->type) {
2129
2130 case INSN_RETURN:
2131 return validate_return(func, insn, &state);
2132
2133 case INSN_CALL:
2134 case INSN_CALL_DYNAMIC:
2135 ret = validate_call(insn, &state);
2136 if (ret)
2137 return ret;
2138
2139 if (!no_fp && func && !is_fentry_call(insn) &&
2140 !has_valid_stack_frame(&state)) {
2141 WARN_FUNC("call without frame pointer save/setup",
2142 sec, insn->offset);
2143 return 1;
2144 }
2145
2146 if (dead_end_function(file, insn->call_dest))
2147 return 0;
2148
2149 break;
2150
2151 case INSN_JUMP_CONDITIONAL:
2152 case INSN_JUMP_UNCONDITIONAL:
2153 if (func && is_sibling_call(insn)) {
2154 ret = validate_sibling_call(insn, &state);
2155 if (ret)
2156 return ret;
2157
2158 } else if (insn->jump_dest) {
2159 ret = validate_branch(file, func,
2160 insn->jump_dest, state);
2161 if (ret) {
2162 if (backtrace)
2163 BT_FUNC("(branch)", insn);
2164 return ret;
2165 }
2166 }
2167
2168 if (insn->type == INSN_JUMP_UNCONDITIONAL)
2169 return 0;
2170
2171 break;
2172
2173 case INSN_JUMP_DYNAMIC:
2174 case INSN_JUMP_DYNAMIC_CONDITIONAL:
2175 if (func && is_sibling_call(insn)) {
2176 ret = validate_sibling_call(insn, &state);
2177 if (ret)
2178 return ret;
2179 }
2180
2181 if (insn->type == INSN_JUMP_DYNAMIC)
2182 return 0;
2183
2184 break;
2185
2186 case INSN_CONTEXT_SWITCH:
2187 if (func && (!next_insn || !next_insn->hint)) {
2188 WARN_FUNC("unsupported instruction in callable function",
2189 sec, insn->offset);
2190 return 1;
2191 }
2192 return 0;
2193
2194 case INSN_STACK:
2195 if (update_insn_state(insn, &state))
2196 return 1;
2197
2198 if (insn->stack_op.dest.type == OP_DEST_PUSHF) {
2199 if (!state.uaccess_stack) {
2200 state.uaccess_stack = 1;
2201 } else if (state.uaccess_stack >> 31) {
2202 WARN_FUNC("PUSHF stack exhausted", sec, insn->offset);
2203 return 1;
2204 }
2205 state.uaccess_stack <<= 1;
2206 state.uaccess_stack |= state.uaccess;
2207 }
2208
2209 if (insn->stack_op.src.type == OP_SRC_POPF) {
2210 if (state.uaccess_stack) {
2211 state.uaccess = state.uaccess_stack & 1;
2212 state.uaccess_stack >>= 1;
2213 if (state.uaccess_stack == 1)
2214 state.uaccess_stack = 0;
2215 }
2216 }
2217
2218 break;
2219
2220 case INSN_STAC:
2221 if (state.uaccess) {
2222 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
2223 return 1;
2224 }
2225
2226 state.uaccess = true;
2227 break;
2228
2229 case INSN_CLAC:
2230 if (!state.uaccess && func) {
2231 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
2232 return 1;
2233 }
2234
2235 if (func_uaccess_safe(func) && !state.uaccess_stack) {
2236 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
2237 return 1;
2238 }
2239
2240 state.uaccess = false;
2241 break;
2242
2243 case INSN_STD:
2244 if (state.df)
2245 WARN_FUNC("recursive STD", sec, insn->offset);
2246
2247 state.df = true;
2248 break;
2249
2250 case INSN_CLD:
2251 if (!state.df && func)
2252 WARN_FUNC("redundant CLD", sec, insn->offset);
2253
2254 state.df = false;
2255 break;
2256
2257 default:
2258 break;
2259 }
2260
2261 if (insn->dead_end)
2262 return 0;
2263
2264 if (!next_insn) {
2265 if (state.cfa.base == CFI_UNDEFINED)
2266 return 0;
2267 WARN("%s: unexpected end of section", sec->name);
2268 return 1;
2269 }
2270
2271 insn = next_insn;
2272 }
2273
2274 return 0;
2275 }
2276
2277 static int validate_unwind_hints(struct objtool_file *file)
2278 {
2279 struct instruction *insn;
2280 int ret, warnings = 0;
2281 struct insn_state state;
2282
2283 if (!file->hints)
2284 return 0;
2285
2286 clear_insn_state(&state);
2287
2288 for_each_insn(file, insn) {
2289 if (insn->hint && !insn->visited) {
2290 ret = validate_branch(file, insn->func, insn, state);
2291 if (ret && backtrace)
2292 BT_FUNC("<=== (hint)", insn);
2293 warnings += ret;
2294 }
2295 }
2296
2297 return warnings;
2298 }
2299
2300 static int validate_retpoline(struct objtool_file *file)
2301 {
2302 struct instruction *insn;
2303 int warnings = 0;
2304
2305 for_each_insn(file, insn) {
2306 if (insn->type != INSN_JUMP_DYNAMIC &&
2307 insn->type != INSN_CALL_DYNAMIC)
2308 continue;
2309
2310 if (insn->retpoline_safe)
2311 continue;
2312
2313 /*
2314 * .init.text code is ran before userspace and thus doesn't
2315 * strictly need retpolines, except for modules which are
2316 * loaded late, they very much do need retpoline in their
2317 * .init.text
2318 */
2319 if (!strcmp(insn->sec->name, ".init.text") && !module)
2320 continue;
2321
2322 WARN_FUNC("indirect %s found in RETPOLINE build",
2323 insn->sec, insn->offset,
2324 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
2325
2326 warnings++;
2327 }
2328
2329 return warnings;
2330 }
2331
2332 static bool is_kasan_insn(struct instruction *insn)
2333 {
2334 return (insn->type == INSN_CALL &&
2335 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
2336 }
2337
2338 static bool is_ubsan_insn(struct instruction *insn)
2339 {
2340 return (insn->type == INSN_CALL &&
2341 !strcmp(insn->call_dest->name,
2342 "__ubsan_handle_builtin_unreachable"));
2343 }
2344
2345 static bool ignore_unreachable_insn(struct instruction *insn)
2346 {
2347 int i;
2348
2349 if (insn->ignore || insn->type == INSN_NOP)
2350 return true;
2351
2352 /*
2353 * Ignore any unused exceptions. This can happen when a whitelisted
2354 * function has an exception table entry.
2355 *
2356 * Also ignore alternative replacement instructions. This can happen
2357 * when a whitelisted function uses one of the ALTERNATIVE macros.
2358 */
2359 if (!strcmp(insn->sec->name, ".fixup") ||
2360 !strcmp(insn->sec->name, ".altinstr_replacement") ||
2361 !strcmp(insn->sec->name, ".altinstr_aux"))
2362 return true;
2363
2364 if (!insn->func)
2365 return false;
2366
2367 /*
2368 * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
2369 * __builtin_unreachable(). The BUG() macro has an unreachable() after
2370 * the UD2, which causes GCC's undefined trap logic to emit another UD2
2371 * (or occasionally a JMP to UD2).
2372 */
2373 if (list_prev_entry(insn, list)->dead_end &&
2374 (insn->type == INSN_BUG ||
2375 (insn->type == INSN_JUMP_UNCONDITIONAL &&
2376 insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
2377 return true;
2378
2379 /*
2380 * Check if this (or a subsequent) instruction is related to
2381 * CONFIG_UBSAN or CONFIG_KASAN.
2382 *
2383 * End the search at 5 instructions to avoid going into the weeds.
2384 */
2385 for (i = 0; i < 5; i++) {
2386
2387 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
2388 return true;
2389
2390 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
2391 if (insn->jump_dest &&
2392 insn->jump_dest->func == insn->func) {
2393 insn = insn->jump_dest;
2394 continue;
2395 }
2396
2397 break;
2398 }
2399
2400 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
2401 break;
2402
2403 insn = list_next_entry(insn, list);
2404 }
2405
2406 return false;
2407 }
2408
2409 static int validate_section(struct objtool_file *file, struct section *sec)
2410 {
2411 struct symbol *func;
2412 struct instruction *insn;
2413 struct insn_state state;
2414 int ret, warnings = 0;
2415
2416 clear_insn_state(&state);
2417
2418 state.cfa = initial_func_cfi.cfa;
2419 memcpy(&state.regs, &initial_func_cfi.regs,
2420 CFI_NUM_REGS * sizeof(struct cfi_reg));
2421 state.stack_size = initial_func_cfi.cfa.offset;
2422
2423 list_for_each_entry(func, &sec->symbol_list, list) {
2424 if (func->type != STT_FUNC)
2425 continue;
2426
2427 if (!func->len) {
2428 WARN("%s() is missing an ELF size annotation",
2429 func->name);
2430 warnings++;
2431 }
2432
2433 if (func->pfunc != func || func->alias != func)
2434 continue;
2435
2436 insn = find_insn(file, sec, func->offset);
2437 if (!insn || insn->ignore || insn->visited)
2438 continue;
2439
2440 state.uaccess = func->uaccess_safe;
2441
2442 ret = validate_branch(file, func, insn, state);
2443 if (ret && backtrace)
2444 BT_FUNC("<=== (func)", insn);
2445 warnings += ret;
2446 }
2447
2448 return warnings;
2449 }
2450
2451 static int validate_functions(struct objtool_file *file)
2452 {
2453 struct section *sec;
2454 int warnings = 0;
2455
2456 for_each_sec(file, sec)
2457 warnings += validate_section(file, sec);
2458
2459 return warnings;
2460 }
2461
2462 static int validate_reachable_instructions(struct objtool_file *file)
2463 {
2464 struct instruction *insn;
2465
2466 if (file->ignore_unreachables)
2467 return 0;
2468
2469 for_each_insn(file, insn) {
2470 if (insn->visited || ignore_unreachable_insn(insn))
2471 continue;
2472
2473 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
2474 return 1;
2475 }
2476
2477 return 0;
2478 }
2479
2480 static struct objtool_file file;
2481
2482 int check(const char *_objname, bool orc)
2483 {
2484 int ret, warnings = 0;
2485
2486 objname = _objname;
2487
2488 file.elf = elf_read(objname, orc ? O_RDWR : O_RDONLY);
2489 if (!file.elf)
2490 return 1;
2491
2492 INIT_LIST_HEAD(&file.insn_list);
2493 hash_init(file.insn_hash);
2494 file.c_file = find_section_by_name(file.elf, ".comment");
2495 file.ignore_unreachables = no_unreachable;
2496 file.hints = false;
2497
2498 arch_initial_func_cfi_state(&initial_func_cfi);
2499
2500 ret = decode_sections(&file);
2501 if (ret < 0)
2502 goto out;
2503 warnings += ret;
2504
2505 if (list_empty(&file.insn_list))
2506 goto out;
2507
2508 if (retpoline) {
2509 ret = validate_retpoline(&file);
2510 if (ret < 0)
2511 return ret;
2512 warnings += ret;
2513 }
2514
2515 ret = validate_functions(&file);
2516 if (ret < 0)
2517 goto out;
2518 warnings += ret;
2519
2520 ret = validate_unwind_hints(&file);
2521 if (ret < 0)
2522 goto out;
2523 warnings += ret;
2524
2525 if (!warnings) {
2526 ret = validate_reachable_instructions(&file);
2527 if (ret < 0)
2528 goto out;
2529 warnings += ret;
2530 }
2531
2532 if (orc) {
2533 ret = create_orc(&file);
2534 if (ret < 0)
2535 goto out;
2536
2537 ret = create_orc_sections(&file);
2538 if (ret < 0)
2539 goto out;
2540
2541 ret = elf_write(file.elf);
2542 if (ret < 0)
2543 goto out;
2544 }
2545
2546 out:
2547 if (ret < 0) {
2548 /*
2549 * Fatal error. The binary is corrupt or otherwise broken in
2550 * some way, or objtool itself is broken. Fail the kernel
2551 * build.
2552 */
2553 return ret;
2554 }
2555
2556 return 0;
2557 }
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