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[thirdparty/linux.git] / tools / objtool / check.c
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
4 */
5
6 #include <string.h>
7 #include <stdlib.h>
8
9 #include "builtin.h"
10 #include "check.h"
11 #include "elf.h"
12 #include "special.h"
13 #include "arch.h"
14 #include "warn.h"
15
16 #include <linux/hashtable.h>
17 #include <linux/kernel.h>
18
19 #define FAKE_JUMP_OFFSET -1
20
21 #define C_JUMP_TABLE_SECTION ".rodata..c_jump_table"
22
23 struct alternative {
24 struct list_head list;
25 struct instruction *insn;
26 bool skip_orig;
27 };
28
29 const char *objname;
30 struct cfi_state initial_func_cfi;
31
32 struct instruction *find_insn(struct objtool_file *file,
33 struct section *sec, unsigned long offset)
34 {
35 struct instruction *insn;
36
37 hash_for_each_possible(file->insn_hash, insn, hash, offset)
38 if (insn->sec == sec && insn->offset == offset)
39 return insn;
40
41 return NULL;
42 }
43
44 static struct instruction *next_insn_same_sec(struct objtool_file *file,
45 struct instruction *insn)
46 {
47 struct instruction *next = list_next_entry(insn, list);
48
49 if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
50 return NULL;
51
52 return next;
53 }
54
55 static struct instruction *next_insn_same_func(struct objtool_file *file,
56 struct instruction *insn)
57 {
58 struct instruction *next = list_next_entry(insn, list);
59 struct symbol *func = insn->func;
60
61 if (!func)
62 return NULL;
63
64 if (&next->list != &file->insn_list && next->func == func)
65 return next;
66
67 /* Check if we're already in the subfunction: */
68 if (func == func->cfunc)
69 return NULL;
70
71 /* Move to the subfunction: */
72 return find_insn(file, func->cfunc->sec, func->cfunc->offset);
73 }
74
75 #define func_for_each_insn(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 &&
1054 insn->sec == func->sec &&
1055 insn->offset >= func->offset;
1056
1057 insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
1058
1059 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1060 break;
1061
1062 /* allow small jumps within the range */
1063 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1064 insn->jump_dest &&
1065 (insn->jump_dest->offset <= insn->offset ||
1066 insn->jump_dest->offset > orig_insn->offset))
1067 break;
1068
1069 /* look for a relocation which references .rodata */
1070 text_rela = find_rela_by_dest_range(file->elf, insn->sec,
1071 insn->offset, insn->len);
1072 if (!text_rela || text_rela->sym->type != STT_SECTION ||
1073 !text_rela->sym->sec->rodata)
1074 continue;
1075
1076 table_offset = text_rela->addend;
1077 table_sec = text_rela->sym->sec;
1078
1079 if (text_rela->type == R_X86_64_PC32)
1080 table_offset += 4;
1081
1082 /*
1083 * Make sure the .rodata address isn't associated with a
1084 * symbol. GCC jump tables are anonymous data.
1085 *
1086 * Also support C jump tables which are in the same format as
1087 * switch jump tables. For objtool to recognize them, they
1088 * need to be placed in the C_JUMP_TABLE_SECTION section. They
1089 * have symbols associated with them.
1090 */
1091 if (find_symbol_containing(table_sec, table_offset) &&
1092 strcmp(table_sec->name, C_JUMP_TABLE_SECTION))
1093 continue;
1094
1095 /*
1096 * Each table entry has a rela associated with it. The rela
1097 * should reference text in the same function as the original
1098 * instruction.
1099 */
1100 table_rela = find_rela_by_dest(file->elf, table_sec, table_offset);
1101 if (!table_rela)
1102 continue;
1103 dest_insn = find_insn(file, table_rela->sym->sec, table_rela->addend);
1104 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1105 continue;
1106
1107 /*
1108 * Use of RIP-relative switch jumps is quite rare, and
1109 * indicates a rare GCC quirk/bug which can leave dead code
1110 * behind.
1111 */
1112 if (text_rela->type == R_X86_64_PC32)
1113 file->ignore_unreachables = true;
1114
1115 return table_rela;
1116 }
1117
1118 return NULL;
1119 }
1120
1121 /*
1122 * First pass: Mark the head of each jump table so that in the next pass,
1123 * we know when a given jump table ends and the next one starts.
1124 */
1125 static void mark_func_jump_tables(struct objtool_file *file,
1126 struct symbol *func)
1127 {
1128 struct instruction *insn, *last = NULL;
1129 struct rela *rela;
1130
1131 func_for_each_insn(file, func, insn) {
1132 if (!last)
1133 last = insn;
1134
1135 /*
1136 * Store back-pointers for unconditional forward jumps such
1137 * that find_jump_table() can back-track using those and
1138 * avoid some potentially confusing code.
1139 */
1140 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1141 insn->offset > last->offset &&
1142 insn->jump_dest->offset > insn->offset &&
1143 !insn->jump_dest->first_jump_src) {
1144
1145 insn->jump_dest->first_jump_src = insn;
1146 last = insn->jump_dest;
1147 }
1148
1149 if (insn->type != INSN_JUMP_DYNAMIC)
1150 continue;
1151
1152 rela = find_jump_table(file, func, insn);
1153 if (rela) {
1154 rela->jump_table_start = true;
1155 insn->jump_table = rela;
1156 }
1157 }
1158 }
1159
1160 static int add_func_jump_tables(struct objtool_file *file,
1161 struct symbol *func)
1162 {
1163 struct instruction *insn;
1164 int ret;
1165
1166 func_for_each_insn(file, func, insn) {
1167 if (!insn->jump_table)
1168 continue;
1169
1170 ret = add_jump_table(file, insn, insn->jump_table);
1171 if (ret)
1172 return ret;
1173 }
1174
1175 return 0;
1176 }
1177
1178 /*
1179 * For some switch statements, gcc generates a jump table in the .rodata
1180 * section which contains a list of addresses within the function to jump to.
1181 * This finds these jump tables and adds them to the insn->alts lists.
1182 */
1183 static int add_jump_table_alts(struct objtool_file *file)
1184 {
1185 struct section *sec;
1186 struct symbol *func;
1187 int ret;
1188
1189 if (!file->rodata)
1190 return 0;
1191
1192 for_each_sec(file, sec) {
1193 list_for_each_entry(func, &sec->symbol_list, list) {
1194 if (func->type != STT_FUNC)
1195 continue;
1196
1197 mark_func_jump_tables(file, func);
1198 ret = add_func_jump_tables(file, func);
1199 if (ret)
1200 return ret;
1201 }
1202 }
1203
1204 return 0;
1205 }
1206
1207 static int read_unwind_hints(struct objtool_file *file)
1208 {
1209 struct section *sec, *relasec;
1210 struct rela *rela;
1211 struct unwind_hint *hint;
1212 struct instruction *insn;
1213 struct cfi_reg *cfa;
1214 int i;
1215
1216 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1217 if (!sec)
1218 return 0;
1219
1220 relasec = sec->rela;
1221 if (!relasec) {
1222 WARN("missing .rela.discard.unwind_hints section");
1223 return -1;
1224 }
1225
1226 if (sec->len % sizeof(struct unwind_hint)) {
1227 WARN("struct unwind_hint size mismatch");
1228 return -1;
1229 }
1230
1231 file->hints = true;
1232
1233 for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
1234 hint = (struct unwind_hint *)sec->data->d_buf + i;
1235
1236 rela = find_rela_by_dest(file->elf, sec, i * sizeof(*hint));
1237 if (!rela) {
1238 WARN("can't find rela for unwind_hints[%d]", i);
1239 return -1;
1240 }
1241
1242 insn = find_insn(file, rela->sym->sec, rela->addend);
1243 if (!insn) {
1244 WARN("can't find insn for unwind_hints[%d]", i);
1245 return -1;
1246 }
1247
1248 cfa = &insn->state.cfa;
1249
1250 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
1251 insn->save = true;
1252 continue;
1253
1254 } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
1255 insn->restore = true;
1256 insn->hint = true;
1257 continue;
1258 }
1259
1260 insn->hint = true;
1261
1262 switch (hint->sp_reg) {
1263 case ORC_REG_UNDEFINED:
1264 cfa->base = CFI_UNDEFINED;
1265 break;
1266 case ORC_REG_SP:
1267 cfa->base = CFI_SP;
1268 break;
1269 case ORC_REG_BP:
1270 cfa->base = CFI_BP;
1271 break;
1272 case ORC_REG_SP_INDIRECT:
1273 cfa->base = CFI_SP_INDIRECT;
1274 break;
1275 case ORC_REG_R10:
1276 cfa->base = CFI_R10;
1277 break;
1278 case ORC_REG_R13:
1279 cfa->base = CFI_R13;
1280 break;
1281 case ORC_REG_DI:
1282 cfa->base = CFI_DI;
1283 break;
1284 case ORC_REG_DX:
1285 cfa->base = CFI_DX;
1286 break;
1287 default:
1288 WARN_FUNC("unsupported unwind_hint sp base reg %d",
1289 insn->sec, insn->offset, hint->sp_reg);
1290 return -1;
1291 }
1292
1293 cfa->offset = hint->sp_offset;
1294 insn->state.type = hint->type;
1295 insn->state.end = hint->end;
1296 }
1297
1298 return 0;
1299 }
1300
1301 static int read_retpoline_hints(struct objtool_file *file)
1302 {
1303 struct section *sec;
1304 struct instruction *insn;
1305 struct rela *rela;
1306
1307 sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1308 if (!sec)
1309 return 0;
1310
1311 list_for_each_entry(rela, &sec->rela_list, list) {
1312 if (rela->sym->type != STT_SECTION) {
1313 WARN("unexpected relocation symbol type in %s", sec->name);
1314 return -1;
1315 }
1316
1317 insn = find_insn(file, rela->sym->sec, rela->addend);
1318 if (!insn) {
1319 WARN("bad .discard.retpoline_safe entry");
1320 return -1;
1321 }
1322
1323 if (insn->type != INSN_JUMP_DYNAMIC &&
1324 insn->type != INSN_CALL_DYNAMIC) {
1325 WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1326 insn->sec, insn->offset);
1327 return -1;
1328 }
1329
1330 insn->retpoline_safe = true;
1331 }
1332
1333 return 0;
1334 }
1335
1336 static void mark_rodata(struct objtool_file *file)
1337 {
1338 struct section *sec;
1339 bool found = false;
1340
1341 /*
1342 * Search for the following rodata sections, each of which can
1343 * potentially contain jump tables:
1344 *
1345 * - .rodata: can contain GCC switch tables
1346 * - .rodata.<func>: same, if -fdata-sections is being used
1347 * - .rodata..c_jump_table: contains C annotated jump tables
1348 *
1349 * .rodata.str1.* sections are ignored; they don't contain jump tables.
1350 */
1351 for_each_sec(file, sec) {
1352 if ((!strncmp(sec->name, ".rodata", 7) && !strstr(sec->name, ".str1.")) ||
1353 !strcmp(sec->name, C_JUMP_TABLE_SECTION)) {
1354 sec->rodata = true;
1355 found = true;
1356 }
1357 }
1358
1359 file->rodata = found;
1360 }
1361
1362 static int decode_sections(struct objtool_file *file)
1363 {
1364 int ret;
1365
1366 mark_rodata(file);
1367
1368 ret = decode_instructions(file);
1369 if (ret)
1370 return ret;
1371
1372 ret = add_dead_ends(file);
1373 if (ret)
1374 return ret;
1375
1376 add_ignores(file);
1377 add_uaccess_safe(file);
1378
1379 ret = add_ignore_alternatives(file);
1380 if (ret)
1381 return ret;
1382
1383 ret = add_jump_destinations(file);
1384 if (ret)
1385 return ret;
1386
1387 ret = add_special_section_alts(file);
1388 if (ret)
1389 return ret;
1390
1391 ret = add_call_destinations(file);
1392 if (ret)
1393 return ret;
1394
1395 ret = add_jump_table_alts(file);
1396 if (ret)
1397 return ret;
1398
1399 ret = read_unwind_hints(file);
1400 if (ret)
1401 return ret;
1402
1403 ret = read_retpoline_hints(file);
1404 if (ret)
1405 return ret;
1406
1407 return 0;
1408 }
1409
1410 static bool is_fentry_call(struct instruction *insn)
1411 {
1412 if (insn->type == INSN_CALL &&
1413 insn->call_dest->type == STT_NOTYPE &&
1414 !strcmp(insn->call_dest->name, "__fentry__"))
1415 return true;
1416
1417 return false;
1418 }
1419
1420 static bool has_modified_stack_frame(struct insn_state *state)
1421 {
1422 int i;
1423
1424 if (state->cfa.base != initial_func_cfi.cfa.base ||
1425 state->cfa.offset != initial_func_cfi.cfa.offset ||
1426 state->stack_size != initial_func_cfi.cfa.offset ||
1427 state->drap)
1428 return true;
1429
1430 for (i = 0; i < CFI_NUM_REGS; i++)
1431 if (state->regs[i].base != initial_func_cfi.regs[i].base ||
1432 state->regs[i].offset != initial_func_cfi.regs[i].offset)
1433 return true;
1434
1435 return false;
1436 }
1437
1438 static bool has_valid_stack_frame(struct insn_state *state)
1439 {
1440 if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
1441 state->regs[CFI_BP].offset == -16)
1442 return true;
1443
1444 if (state->drap && state->regs[CFI_BP].base == CFI_BP)
1445 return true;
1446
1447 return false;
1448 }
1449
1450 static int update_insn_state_regs(struct instruction *insn, struct insn_state *state)
1451 {
1452 struct cfi_reg *cfa = &state->cfa;
1453 struct stack_op *op = &insn->stack_op;
1454
1455 if (cfa->base != CFI_SP)
1456 return 0;
1457
1458 /* push */
1459 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
1460 cfa->offset += 8;
1461
1462 /* pop */
1463 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
1464 cfa->offset -= 8;
1465
1466 /* add immediate to sp */
1467 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1468 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1469 cfa->offset -= op->src.offset;
1470
1471 return 0;
1472 }
1473
1474 static void save_reg(struct insn_state *state, unsigned char reg, int base,
1475 int offset)
1476 {
1477 if (arch_callee_saved_reg(reg) &&
1478 state->regs[reg].base == CFI_UNDEFINED) {
1479 state->regs[reg].base = base;
1480 state->regs[reg].offset = offset;
1481 }
1482 }
1483
1484 static void restore_reg(struct insn_state *state, unsigned char reg)
1485 {
1486 state->regs[reg].base = CFI_UNDEFINED;
1487 state->regs[reg].offset = 0;
1488 }
1489
1490 /*
1491 * A note about DRAP stack alignment:
1492 *
1493 * GCC has the concept of a DRAP register, which is used to help keep track of
1494 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
1495 * register. The typical DRAP pattern is:
1496 *
1497 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
1498 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
1499 * 41 ff 72 f8 pushq -0x8(%r10)
1500 * 55 push %rbp
1501 * 48 89 e5 mov %rsp,%rbp
1502 * (more pushes)
1503 * 41 52 push %r10
1504 * ...
1505 * 41 5a pop %r10
1506 * (more pops)
1507 * 5d pop %rbp
1508 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1509 * c3 retq
1510 *
1511 * There are some variations in the epilogues, like:
1512 *
1513 * 5b pop %rbx
1514 * 41 5a pop %r10
1515 * 41 5c pop %r12
1516 * 41 5d pop %r13
1517 * 41 5e pop %r14
1518 * c9 leaveq
1519 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1520 * c3 retq
1521 *
1522 * and:
1523 *
1524 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
1525 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
1526 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
1527 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
1528 * c9 leaveq
1529 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1530 * c3 retq
1531 *
1532 * Sometimes r13 is used as the DRAP register, in which case it's saved and
1533 * restored beforehand:
1534 *
1535 * 41 55 push %r13
1536 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
1537 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
1538 * ...
1539 * 49 8d 65 f0 lea -0x10(%r13),%rsp
1540 * 41 5d pop %r13
1541 * c3 retq
1542 */
1543 static int update_insn_state(struct instruction *insn, struct insn_state *state)
1544 {
1545 struct stack_op *op = &insn->stack_op;
1546 struct cfi_reg *cfa = &state->cfa;
1547 struct cfi_reg *regs = state->regs;
1548
1549 /* stack operations don't make sense with an undefined CFA */
1550 if (cfa->base == CFI_UNDEFINED) {
1551 if (insn->func) {
1552 WARN_FUNC("undefined stack state", insn->sec, insn->offset);
1553 return -1;
1554 }
1555 return 0;
1556 }
1557
1558 if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET)
1559 return update_insn_state_regs(insn, state);
1560
1561 switch (op->dest.type) {
1562
1563 case OP_DEST_REG:
1564 switch (op->src.type) {
1565
1566 case OP_SRC_REG:
1567 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
1568 cfa->base == CFI_SP &&
1569 regs[CFI_BP].base == CFI_CFA &&
1570 regs[CFI_BP].offset == -cfa->offset) {
1571
1572 /* mov %rsp, %rbp */
1573 cfa->base = op->dest.reg;
1574 state->bp_scratch = false;
1575 }
1576
1577 else if (op->src.reg == CFI_SP &&
1578 op->dest.reg == CFI_BP && state->drap) {
1579
1580 /* drap: mov %rsp, %rbp */
1581 regs[CFI_BP].base = CFI_BP;
1582 regs[CFI_BP].offset = -state->stack_size;
1583 state->bp_scratch = false;
1584 }
1585
1586 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1587
1588 /*
1589 * mov %rsp, %reg
1590 *
1591 * This is needed for the rare case where GCC
1592 * does:
1593 *
1594 * mov %rsp, %rax
1595 * ...
1596 * mov %rax, %rsp
1597 */
1598 state->vals[op->dest.reg].base = CFI_CFA;
1599 state->vals[op->dest.reg].offset = -state->stack_size;
1600 }
1601
1602 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
1603 cfa->base == CFI_BP) {
1604
1605 /*
1606 * mov %rbp, %rsp
1607 *
1608 * Restore the original stack pointer (Clang).
1609 */
1610 state->stack_size = -state->regs[CFI_BP].offset;
1611 }
1612
1613 else if (op->dest.reg == cfa->base) {
1614
1615 /* mov %reg, %rsp */
1616 if (cfa->base == CFI_SP &&
1617 state->vals[op->src.reg].base == CFI_CFA) {
1618
1619 /*
1620 * This is needed for the rare case
1621 * where GCC does something dumb like:
1622 *
1623 * lea 0x8(%rsp), %rcx
1624 * ...
1625 * mov %rcx, %rsp
1626 */
1627 cfa->offset = -state->vals[op->src.reg].offset;
1628 state->stack_size = cfa->offset;
1629
1630 } else {
1631 cfa->base = CFI_UNDEFINED;
1632 cfa->offset = 0;
1633 }
1634 }
1635
1636 break;
1637
1638 case OP_SRC_ADD:
1639 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
1640
1641 /* add imm, %rsp */
1642 state->stack_size -= op->src.offset;
1643 if (cfa->base == CFI_SP)
1644 cfa->offset -= op->src.offset;
1645 break;
1646 }
1647
1648 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
1649
1650 /* lea disp(%rbp), %rsp */
1651 state->stack_size = -(op->src.offset + regs[CFI_BP].offset);
1652 break;
1653 }
1654
1655 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1656
1657 /* drap: lea disp(%rsp), %drap */
1658 state->drap_reg = op->dest.reg;
1659
1660 /*
1661 * lea disp(%rsp), %reg
1662 *
1663 * This is needed for the rare case where GCC
1664 * does something dumb like:
1665 *
1666 * lea 0x8(%rsp), %rcx
1667 * ...
1668 * mov %rcx, %rsp
1669 */
1670 state->vals[op->dest.reg].base = CFI_CFA;
1671 state->vals[op->dest.reg].offset = \
1672 -state->stack_size + op->src.offset;
1673
1674 break;
1675 }
1676
1677 if (state->drap && op->dest.reg == CFI_SP &&
1678 op->src.reg == state->drap_reg) {
1679
1680 /* drap: lea disp(%drap), %rsp */
1681 cfa->base = CFI_SP;
1682 cfa->offset = state->stack_size = -op->src.offset;
1683 state->drap_reg = CFI_UNDEFINED;
1684 state->drap = false;
1685 break;
1686 }
1687
1688 if (op->dest.reg == state->cfa.base) {
1689 WARN_FUNC("unsupported stack register modification",
1690 insn->sec, insn->offset);
1691 return -1;
1692 }
1693
1694 break;
1695
1696 case OP_SRC_AND:
1697 if (op->dest.reg != CFI_SP ||
1698 (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
1699 (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
1700 WARN_FUNC("unsupported stack pointer realignment",
1701 insn->sec, insn->offset);
1702 return -1;
1703 }
1704
1705 if (state->drap_reg != CFI_UNDEFINED) {
1706 /* drap: and imm, %rsp */
1707 cfa->base = state->drap_reg;
1708 cfa->offset = state->stack_size = 0;
1709 state->drap = true;
1710 }
1711
1712 /*
1713 * Older versions of GCC (4.8ish) realign the stack
1714 * without DRAP, with a frame pointer.
1715 */
1716
1717 break;
1718
1719 case OP_SRC_POP:
1720 case OP_SRC_POPF:
1721 if (!state->drap && op->dest.type == OP_DEST_REG &&
1722 op->dest.reg == cfa->base) {
1723
1724 /* pop %rbp */
1725 cfa->base = CFI_SP;
1726 }
1727
1728 if (state->drap && cfa->base == CFI_BP_INDIRECT &&
1729 op->dest.type == OP_DEST_REG &&
1730 op->dest.reg == state->drap_reg &&
1731 state->drap_offset == -state->stack_size) {
1732
1733 /* drap: pop %drap */
1734 cfa->base = state->drap_reg;
1735 cfa->offset = 0;
1736 state->drap_offset = -1;
1737
1738 } else if (regs[op->dest.reg].offset == -state->stack_size) {
1739
1740 /* pop %reg */
1741 restore_reg(state, op->dest.reg);
1742 }
1743
1744 state->stack_size -= 8;
1745 if (cfa->base == CFI_SP)
1746 cfa->offset -= 8;
1747
1748 break;
1749
1750 case OP_SRC_REG_INDIRECT:
1751 if (state->drap && op->src.reg == CFI_BP &&
1752 op->src.offset == state->drap_offset) {
1753
1754 /* drap: mov disp(%rbp), %drap */
1755 cfa->base = state->drap_reg;
1756 cfa->offset = 0;
1757 state->drap_offset = -1;
1758 }
1759
1760 if (state->drap && op->src.reg == CFI_BP &&
1761 op->src.offset == regs[op->dest.reg].offset) {
1762
1763 /* drap: mov disp(%rbp), %reg */
1764 restore_reg(state, op->dest.reg);
1765
1766 } else if (op->src.reg == cfa->base &&
1767 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
1768
1769 /* mov disp(%rbp), %reg */
1770 /* mov disp(%rsp), %reg */
1771 restore_reg(state, op->dest.reg);
1772 }
1773
1774 break;
1775
1776 default:
1777 WARN_FUNC("unknown stack-related instruction",
1778 insn->sec, insn->offset);
1779 return -1;
1780 }
1781
1782 break;
1783
1784 case OP_DEST_PUSH:
1785 case OP_DEST_PUSHF:
1786 state->stack_size += 8;
1787 if (cfa->base == CFI_SP)
1788 cfa->offset += 8;
1789
1790 if (op->src.type != OP_SRC_REG)
1791 break;
1792
1793 if (state->drap) {
1794 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1795
1796 /* drap: push %drap */
1797 cfa->base = CFI_BP_INDIRECT;
1798 cfa->offset = -state->stack_size;
1799
1800 /* save drap so we know when to restore it */
1801 state->drap_offset = -state->stack_size;
1802
1803 } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
1804
1805 /* drap: push %rbp */
1806 state->stack_size = 0;
1807
1808 } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1809
1810 /* drap: push %reg */
1811 save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
1812 }
1813
1814 } else {
1815
1816 /* push %reg */
1817 save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
1818 }
1819
1820 /* detect when asm code uses rbp as a scratch register */
1821 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
1822 cfa->base != CFI_BP)
1823 state->bp_scratch = true;
1824 break;
1825
1826 case OP_DEST_REG_INDIRECT:
1827
1828 if (state->drap) {
1829 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1830
1831 /* drap: mov %drap, disp(%rbp) */
1832 cfa->base = CFI_BP_INDIRECT;
1833 cfa->offset = op->dest.offset;
1834
1835 /* save drap offset so we know when to restore it */
1836 state->drap_offset = op->dest.offset;
1837 }
1838
1839 else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1840
1841 /* drap: mov reg, disp(%rbp) */
1842 save_reg(state, op->src.reg, CFI_BP, op->dest.offset);
1843 }
1844
1845 } else if (op->dest.reg == cfa->base) {
1846
1847 /* mov reg, disp(%rbp) */
1848 /* mov reg, disp(%rsp) */
1849 save_reg(state, op->src.reg, CFI_CFA,
1850 op->dest.offset - state->cfa.offset);
1851 }
1852
1853 break;
1854
1855 case OP_DEST_LEAVE:
1856 if ((!state->drap && cfa->base != CFI_BP) ||
1857 (state->drap && cfa->base != state->drap_reg)) {
1858 WARN_FUNC("leave instruction with modified stack frame",
1859 insn->sec, insn->offset);
1860 return -1;
1861 }
1862
1863 /* leave (mov %rbp, %rsp; pop %rbp) */
1864
1865 state->stack_size = -state->regs[CFI_BP].offset - 8;
1866 restore_reg(state, CFI_BP);
1867
1868 if (!state->drap) {
1869 cfa->base = CFI_SP;
1870 cfa->offset -= 8;
1871 }
1872
1873 break;
1874
1875 case OP_DEST_MEM:
1876 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
1877 WARN_FUNC("unknown stack-related memory operation",
1878 insn->sec, insn->offset);
1879 return -1;
1880 }
1881
1882 /* pop mem */
1883 state->stack_size -= 8;
1884 if (cfa->base == CFI_SP)
1885 cfa->offset -= 8;
1886
1887 break;
1888
1889 default:
1890 WARN_FUNC("unknown stack-related instruction",
1891 insn->sec, insn->offset);
1892 return -1;
1893 }
1894
1895 return 0;
1896 }
1897
1898 static bool insn_state_match(struct instruction *insn, struct insn_state *state)
1899 {
1900 struct insn_state *state1 = &insn->state, *state2 = state;
1901 int i;
1902
1903 if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
1904 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
1905 insn->sec, insn->offset,
1906 state1->cfa.base, state1->cfa.offset,
1907 state2->cfa.base, state2->cfa.offset);
1908
1909 } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
1910 for (i = 0; i < CFI_NUM_REGS; i++) {
1911 if (!memcmp(&state1->regs[i], &state2->regs[i],
1912 sizeof(struct cfi_reg)))
1913 continue;
1914
1915 WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
1916 insn->sec, insn->offset,
1917 i, state1->regs[i].base, state1->regs[i].offset,
1918 i, state2->regs[i].base, state2->regs[i].offset);
1919 break;
1920 }
1921
1922 } else if (state1->type != state2->type) {
1923 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
1924 insn->sec, insn->offset, state1->type, state2->type);
1925
1926 } else if (state1->drap != state2->drap ||
1927 (state1->drap && state1->drap_reg != state2->drap_reg) ||
1928 (state1->drap && state1->drap_offset != state2->drap_offset)) {
1929 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
1930 insn->sec, insn->offset,
1931 state1->drap, state1->drap_reg, state1->drap_offset,
1932 state2->drap, state2->drap_reg, state2->drap_offset);
1933
1934 } else
1935 return true;
1936
1937 return false;
1938 }
1939
1940 static inline bool func_uaccess_safe(struct symbol *func)
1941 {
1942 if (func)
1943 return func->uaccess_safe;
1944
1945 return false;
1946 }
1947
1948 static inline const char *call_dest_name(struct instruction *insn)
1949 {
1950 if (insn->call_dest)
1951 return insn->call_dest->name;
1952
1953 return "{dynamic}";
1954 }
1955
1956 static int validate_call(struct instruction *insn, struct insn_state *state)
1957 {
1958 if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
1959 WARN_FUNC("call to %s() with UACCESS enabled",
1960 insn->sec, insn->offset, call_dest_name(insn));
1961 return 1;
1962 }
1963
1964 if (state->df) {
1965 WARN_FUNC("call to %s() with DF set",
1966 insn->sec, insn->offset, call_dest_name(insn));
1967 return 1;
1968 }
1969
1970 return 0;
1971 }
1972
1973 static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
1974 {
1975 if (has_modified_stack_frame(state)) {
1976 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1977 insn->sec, insn->offset);
1978 return 1;
1979 }
1980
1981 return validate_call(insn, state);
1982 }
1983
1984 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
1985 {
1986 if (state->uaccess && !func_uaccess_safe(func)) {
1987 WARN_FUNC("return with UACCESS enabled",
1988 insn->sec, insn->offset);
1989 return 1;
1990 }
1991
1992 if (!state->uaccess && func_uaccess_safe(func)) {
1993 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
1994 insn->sec, insn->offset);
1995 return 1;
1996 }
1997
1998 if (state->df) {
1999 WARN_FUNC("return with DF set",
2000 insn->sec, insn->offset);
2001 return 1;
2002 }
2003
2004 if (func && has_modified_stack_frame(state)) {
2005 WARN_FUNC("return with modified stack frame",
2006 insn->sec, insn->offset);
2007 return 1;
2008 }
2009
2010 if (state->bp_scratch) {
2011 WARN("%s uses BP as a scratch register",
2012 func->name);
2013 return 1;
2014 }
2015
2016 return 0;
2017 }
2018
2019 /*
2020 * Follow the branch starting at the given instruction, and recursively follow
2021 * any other branches (jumps). Meanwhile, track the frame pointer state at
2022 * each instruction and validate all the rules described in
2023 * tools/objtool/Documentation/stack-validation.txt.
2024 */
2025 static int validate_branch(struct objtool_file *file, struct symbol *func,
2026 struct instruction *first, struct insn_state state)
2027 {
2028 struct alternative *alt;
2029 struct instruction *insn, *next_insn;
2030 struct section *sec;
2031 u8 visited;
2032 int ret;
2033
2034 insn = first;
2035 sec = insn->sec;
2036
2037 if (insn->alt_group && list_empty(&insn->alts)) {
2038 WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
2039 sec, insn->offset);
2040 return 1;
2041 }
2042
2043 while (1) {
2044 next_insn = next_insn_same_sec(file, insn);
2045
2046 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
2047 WARN("%s() falls through to next function %s()",
2048 func->name, insn->func->name);
2049 return 1;
2050 }
2051
2052 if (func && insn->ignore) {
2053 WARN_FUNC("BUG: why am I validating an ignored function?",
2054 sec, insn->offset);
2055 return 1;
2056 }
2057
2058 visited = 1 << state.uaccess;
2059 if (insn->visited) {
2060 if (!insn->hint && !insn_state_match(insn, &state))
2061 return 1;
2062
2063 if (insn->visited & visited)
2064 return 0;
2065 }
2066
2067 if (insn->hint) {
2068 if (insn->restore) {
2069 struct instruction *save_insn, *i;
2070
2071 i = insn;
2072 save_insn = NULL;
2073 sym_for_each_insn_continue_reverse(file, func, i) {
2074 if (i->save) {
2075 save_insn = i;
2076 break;
2077 }
2078 }
2079
2080 if (!save_insn) {
2081 WARN_FUNC("no corresponding CFI save for CFI restore",
2082 sec, insn->offset);
2083 return 1;
2084 }
2085
2086 if (!save_insn->visited) {
2087 /*
2088 * Oops, no state to copy yet.
2089 * Hopefully we can reach this
2090 * instruction from another branch
2091 * after the save insn has been
2092 * visited.
2093 */
2094 if (insn == first)
2095 return 0;
2096
2097 WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
2098 sec, insn->offset);
2099 return 1;
2100 }
2101
2102 insn->state = save_insn->state;
2103 }
2104
2105 state = insn->state;
2106
2107 } else
2108 insn->state = state;
2109
2110 insn->visited |= visited;
2111
2112 if (!insn->ignore_alts) {
2113 bool skip_orig = false;
2114
2115 list_for_each_entry(alt, &insn->alts, list) {
2116 if (alt->skip_orig)
2117 skip_orig = true;
2118
2119 ret = validate_branch(file, func, alt->insn, state);
2120 if (ret) {
2121 if (backtrace)
2122 BT_FUNC("(alt)", insn);
2123 return ret;
2124 }
2125 }
2126
2127 if (skip_orig)
2128 return 0;
2129 }
2130
2131 switch (insn->type) {
2132
2133 case INSN_RETURN:
2134 return validate_return(func, insn, &state);
2135
2136 case INSN_CALL:
2137 case INSN_CALL_DYNAMIC:
2138 ret = validate_call(insn, &state);
2139 if (ret)
2140 return ret;
2141
2142 if (!no_fp && func && !is_fentry_call(insn) &&
2143 !has_valid_stack_frame(&state)) {
2144 WARN_FUNC("call without frame pointer save/setup",
2145 sec, insn->offset);
2146 return 1;
2147 }
2148
2149 if (dead_end_function(file, insn->call_dest))
2150 return 0;
2151
2152 break;
2153
2154 case INSN_JUMP_CONDITIONAL:
2155 case INSN_JUMP_UNCONDITIONAL:
2156 if (func && is_sibling_call(insn)) {
2157 ret = validate_sibling_call(insn, &state);
2158 if (ret)
2159 return ret;
2160
2161 } else if (insn->jump_dest) {
2162 ret = validate_branch(file, func,
2163 insn->jump_dest, state);
2164 if (ret) {
2165 if (backtrace)
2166 BT_FUNC("(branch)", insn);
2167 return ret;
2168 }
2169 }
2170
2171 if (insn->type == INSN_JUMP_UNCONDITIONAL)
2172 return 0;
2173
2174 break;
2175
2176 case INSN_JUMP_DYNAMIC:
2177 case INSN_JUMP_DYNAMIC_CONDITIONAL:
2178 if (func && is_sibling_call(insn)) {
2179 ret = validate_sibling_call(insn, &state);
2180 if (ret)
2181 return ret;
2182 }
2183
2184 if (insn->type == INSN_JUMP_DYNAMIC)
2185 return 0;
2186
2187 break;
2188
2189 case INSN_CONTEXT_SWITCH:
2190 if (func && (!next_insn || !next_insn->hint)) {
2191 WARN_FUNC("unsupported instruction in callable function",
2192 sec, insn->offset);
2193 return 1;
2194 }
2195 return 0;
2196
2197 case INSN_STACK:
2198 if (update_insn_state(insn, &state))
2199 return 1;
2200
2201 if (insn->stack_op.dest.type == OP_DEST_PUSHF) {
2202 if (!state.uaccess_stack) {
2203 state.uaccess_stack = 1;
2204 } else if (state.uaccess_stack >> 31) {
2205 WARN_FUNC("PUSHF stack exhausted", sec, insn->offset);
2206 return 1;
2207 }
2208 state.uaccess_stack <<= 1;
2209 state.uaccess_stack |= state.uaccess;
2210 }
2211
2212 if (insn->stack_op.src.type == OP_SRC_POPF) {
2213 if (state.uaccess_stack) {
2214 state.uaccess = state.uaccess_stack & 1;
2215 state.uaccess_stack >>= 1;
2216 if (state.uaccess_stack == 1)
2217 state.uaccess_stack = 0;
2218 }
2219 }
2220
2221 break;
2222
2223 case INSN_STAC:
2224 if (state.uaccess) {
2225 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
2226 return 1;
2227 }
2228
2229 state.uaccess = true;
2230 break;
2231
2232 case INSN_CLAC:
2233 if (!state.uaccess && func) {
2234 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
2235 return 1;
2236 }
2237
2238 if (func_uaccess_safe(func) && !state.uaccess_stack) {
2239 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
2240 return 1;
2241 }
2242
2243 state.uaccess = false;
2244 break;
2245
2246 case INSN_STD:
2247 if (state.df)
2248 WARN_FUNC("recursive STD", sec, insn->offset);
2249
2250 state.df = true;
2251 break;
2252
2253 case INSN_CLD:
2254 if (!state.df && func)
2255 WARN_FUNC("redundant CLD", sec, insn->offset);
2256
2257 state.df = false;
2258 break;
2259
2260 default:
2261 break;
2262 }
2263
2264 if (insn->dead_end)
2265 return 0;
2266
2267 if (!next_insn) {
2268 if (state.cfa.base == CFI_UNDEFINED)
2269 return 0;
2270 WARN("%s: unexpected end of section", sec->name);
2271 return 1;
2272 }
2273
2274 insn = next_insn;
2275 }
2276
2277 return 0;
2278 }
2279
2280 static int validate_unwind_hints(struct objtool_file *file)
2281 {
2282 struct instruction *insn;
2283 int ret, warnings = 0;
2284 struct insn_state state;
2285
2286 if (!file->hints)
2287 return 0;
2288
2289 clear_insn_state(&state);
2290
2291 for_each_insn(file, insn) {
2292 if (insn->hint && !insn->visited) {
2293 ret = validate_branch(file, insn->func, insn, state);
2294 if (ret && backtrace)
2295 BT_FUNC("<=== (hint)", insn);
2296 warnings += ret;
2297 }
2298 }
2299
2300 return warnings;
2301 }
2302
2303 static int validate_retpoline(struct objtool_file *file)
2304 {
2305 struct instruction *insn;
2306 int warnings = 0;
2307
2308 for_each_insn(file, insn) {
2309 if (insn->type != INSN_JUMP_DYNAMIC &&
2310 insn->type != INSN_CALL_DYNAMIC)
2311 continue;
2312
2313 if (insn->retpoline_safe)
2314 continue;
2315
2316 /*
2317 * .init.text code is ran before userspace and thus doesn't
2318 * strictly need retpolines, except for modules which are
2319 * loaded late, they very much do need retpoline in their
2320 * .init.text
2321 */
2322 if (!strcmp(insn->sec->name, ".init.text") && !module)
2323 continue;
2324
2325 WARN_FUNC("indirect %s found in RETPOLINE build",
2326 insn->sec, insn->offset,
2327 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
2328
2329 warnings++;
2330 }
2331
2332 return warnings;
2333 }
2334
2335 static bool is_kasan_insn(struct instruction *insn)
2336 {
2337 return (insn->type == INSN_CALL &&
2338 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
2339 }
2340
2341 static bool is_ubsan_insn(struct instruction *insn)
2342 {
2343 return (insn->type == INSN_CALL &&
2344 !strcmp(insn->call_dest->name,
2345 "__ubsan_handle_builtin_unreachable"));
2346 }
2347
2348 static bool ignore_unreachable_insn(struct instruction *insn)
2349 {
2350 int i;
2351
2352 if (insn->ignore || insn->type == INSN_NOP)
2353 return true;
2354
2355 /*
2356 * Ignore any unused exceptions. This can happen when a whitelisted
2357 * function has an exception table entry.
2358 *
2359 * Also ignore alternative replacement instructions. This can happen
2360 * when a whitelisted function uses one of the ALTERNATIVE macros.
2361 */
2362 if (!strcmp(insn->sec->name, ".fixup") ||
2363 !strcmp(insn->sec->name, ".altinstr_replacement") ||
2364 !strcmp(insn->sec->name, ".altinstr_aux"))
2365 return true;
2366
2367 /*
2368 * Check if this (or a subsequent) instruction is related to
2369 * CONFIG_UBSAN or CONFIG_KASAN.
2370 *
2371 * End the search at 5 instructions to avoid going into the weeds.
2372 */
2373 if (!insn->func)
2374 return false;
2375 for (i = 0; i < 5; i++) {
2376
2377 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
2378 return true;
2379
2380 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
2381 if (insn->jump_dest &&
2382 insn->jump_dest->func == insn->func) {
2383 insn = insn->jump_dest;
2384 continue;
2385 }
2386
2387 break;
2388 }
2389
2390 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
2391 break;
2392
2393 insn = list_next_entry(insn, list);
2394 }
2395
2396 return false;
2397 }
2398
2399 static int validate_section(struct objtool_file *file, struct section *sec)
2400 {
2401 struct symbol *func;
2402 struct instruction *insn;
2403 struct insn_state state;
2404 int ret, warnings = 0;
2405
2406 clear_insn_state(&state);
2407
2408 state.cfa = initial_func_cfi.cfa;
2409 memcpy(&state.regs, &initial_func_cfi.regs,
2410 CFI_NUM_REGS * sizeof(struct cfi_reg));
2411 state.stack_size = initial_func_cfi.cfa.offset;
2412
2413 list_for_each_entry(func, &sec->symbol_list, list) {
2414 if (func->type != STT_FUNC)
2415 continue;
2416
2417 if (!func->len) {
2418 WARN("%s() is missing an ELF size annotation",
2419 func->name);
2420 warnings++;
2421 }
2422
2423 if (func->pfunc != func || func->alias != func)
2424 continue;
2425
2426 insn = find_insn(file, sec, func->offset);
2427 if (!insn || insn->ignore || insn->visited)
2428 continue;
2429
2430 state.uaccess = func->uaccess_safe;
2431
2432 ret = validate_branch(file, func, insn, state);
2433 if (ret && backtrace)
2434 BT_FUNC("<=== (func)", insn);
2435 warnings += ret;
2436 }
2437
2438 return warnings;
2439 }
2440
2441 static int validate_functions(struct objtool_file *file)
2442 {
2443 struct section *sec;
2444 int warnings = 0;
2445
2446 for_each_sec(file, sec)
2447 warnings += validate_section(file, sec);
2448
2449 return warnings;
2450 }
2451
2452 static int validate_reachable_instructions(struct objtool_file *file)
2453 {
2454 struct instruction *insn;
2455
2456 if (file->ignore_unreachables)
2457 return 0;
2458
2459 for_each_insn(file, insn) {
2460 if (insn->visited || ignore_unreachable_insn(insn))
2461 continue;
2462
2463 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
2464 return 1;
2465 }
2466
2467 return 0;
2468 }
2469
2470 static struct objtool_file file;
2471
2472 int check(const char *_objname, bool orc)
2473 {
2474 int ret, warnings = 0;
2475
2476 objname = _objname;
2477
2478 file.elf = elf_read(objname, orc ? O_RDWR : O_RDONLY);
2479 if (!file.elf)
2480 return 1;
2481
2482 INIT_LIST_HEAD(&file.insn_list);
2483 hash_init(file.insn_hash);
2484 file.c_file = find_section_by_name(file.elf, ".comment");
2485 file.ignore_unreachables = no_unreachable;
2486 file.hints = false;
2487
2488 arch_initial_func_cfi_state(&initial_func_cfi);
2489
2490 ret = decode_sections(&file);
2491 if (ret < 0)
2492 goto out;
2493 warnings += ret;
2494
2495 if (list_empty(&file.insn_list))
2496 goto out;
2497
2498 if (retpoline) {
2499 ret = validate_retpoline(&file);
2500 if (ret < 0)
2501 return ret;
2502 warnings += ret;
2503 }
2504
2505 ret = validate_functions(&file);
2506 if (ret < 0)
2507 goto out;
2508 warnings += ret;
2509
2510 ret = validate_unwind_hints(&file);
2511 if (ret < 0)
2512 goto out;
2513 warnings += ret;
2514
2515 if (!warnings) {
2516 ret = validate_reachable_instructions(&file);
2517 if (ret < 0)
2518 goto out;
2519 warnings += ret;
2520 }
2521
2522 if (orc) {
2523 ret = create_orc(&file);
2524 if (ret < 0)
2525 goto out;
2526
2527 ret = create_orc_sections(&file);
2528 if (ret < 0)
2529 goto out;
2530
2531 ret = elf_write(file.elf);
2532 if (ret < 0)
2533 goto out;
2534 }
2535
2536 out:
2537 if (ret < 0) {
2538 /*
2539 * Fatal error. The binary is corrupt or otherwise broken in
2540 * some way, or objtool itself is broken. Fail the kernel
2541 * build.
2542 */
2543 return ret;
2544 }
2545
2546 return 0;
2547 }
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