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treewide: remove redundant IS_ERR() before error code check
[linux/fpc-iii.git] / tools / objtool / check.c
blob4768d91c6d686d26be9fc78cbdf5ac468fbb5cb7
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
4 */
5
6 #include <string.h>
7 #include <stdlib.h>
8
9 #include "builtin.h"
10 #include "check.h"
11 #include "elf.h"
12 #include "special.h"
13 #include "arch.h"
14 #include "warn.h"
15
16 #include <linux/hashtable.h>
17 #include <linux/kernel.h>
18
19 #define FAKE_JUMP_OFFSET -1
20
21 #define C_JUMP_TABLE_SECTION ".rodata..c_jump_table"
22
23 struct alternative {
24 struct list_head list;
25 struct instruction *insn;
26 bool skip_orig;
27 };
28
29 const char *objname;
30 struct cfi_state initial_func_cfi;
31
32 struct instruction *find_insn(struct objtool_file *file,
33 struct section *sec, unsigned long offset)
34 {
35 struct instruction *insn;
36
37 hash_for_each_possible(file->insn_hash, insn, hash, offset)
38 if (insn->sec == sec && insn->offset == offset)
39 return insn;
40
41 return NULL;
42 }
43
44 static struct instruction *next_insn_same_sec(struct objtool_file *file,
45 struct instruction *insn)
46 {
47 struct instruction *next = list_next_entry(insn, list);
48
49 if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
50 return NULL;
51
52 return next;
53 }
54
55 static struct instruction *next_insn_same_func(struct objtool_file *file,
56 struct instruction *insn)
57 {
58 struct instruction *next = list_next_entry(insn, list);
59 struct symbol *func = insn->func;
60
61 if (!func)
62 return NULL;
63
64 if (&next->list != &file->insn_list && next->func == func)
65 return next;
66
67 /* Check if we're already in the subfunction: */
68 if (func == func->cfunc)
69 return NULL;
70
71 /* Move to the subfunction: */
72 return find_insn(file, func->cfunc->sec, func->cfunc->offset);
73 }
74
75 #define func_for_each_insn_all(file, func, insn) \
76 for (insn = find_insn(file, func->sec, func->offset); \
77 insn; \
78 insn = next_insn_same_func(file, insn))
79
80 #define func_for_each_insn(file, func, insn) \
81 for (insn = find_insn(file, func->sec, func->offset); \
82 insn && &insn->list != &file->insn_list && \
83 insn->sec == func->sec && \
84 insn->offset < func->offset + func->len; \
85 insn = list_next_entry(insn, list))
86
87 #define func_for_each_insn_continue_reverse(file, func, insn) \
88 for (insn = list_prev_entry(insn, list); \
89 &insn->list != &file->insn_list && \
90 insn->sec == func->sec && insn->offset >= func->offset; \
91 insn = list_prev_entry(insn, list))
92
93 #define sec_for_each_insn_from(file, insn) \
94 for (; insn; insn = next_insn_same_sec(file, insn))
95
96 #define sec_for_each_insn_continue(file, insn) \
97 for (insn = next_insn_same_sec(file, insn); insn; \
98 insn = next_insn_same_sec(file, insn))
99
100 static bool is_sibling_call(struct instruction *insn)
101 {
102 /* An indirect jump is either a sibling call or a jump to a table. */
103 if (insn->type == INSN_JUMP_DYNAMIC)
104 return list_empty(&insn->alts);
105
106 if (insn->type != INSN_JUMP_CONDITIONAL &&
107 insn->type != INSN_JUMP_UNCONDITIONAL)
108 return false;
109
110 /* add_jump_destinations() sets insn->call_dest for sibling calls. */
111 return !!insn->call_dest;
112 }
113
114 /*
115 * This checks to see if the given function is a "noreturn" function.
116 *
117 * For global functions which are outside the scope of this object file, we
118 * have to keep a manual list of them.
119 *
120 * For local functions, we have to detect them manually by simply looking for
121 * the lack of a return instruction.
122 */
123 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
124 int recursion)
125 {
126 int i;
127 struct instruction *insn;
128 bool empty = true;
129
130 /*
131 * Unfortunately these have to be hard coded because the noreturn
132 * attribute isn't provided in ELF data.
133 */
134 static const char * const global_noreturns[] = {
135 "__stack_chk_fail",
136 "panic",
137 "do_exit",
138 "do_task_dead",
139 "__module_put_and_exit",
140 "complete_and_exit",
141 "__reiserfs_panic",
142 "lbug_with_loc",
143 "fortify_panic",
144 "usercopy_abort",
145 "machine_real_restart",
146 "rewind_stack_do_exit",
147 "kunit_try_catch_throw",
148 };
149
150 if (!func)
151 return false;
152
153 if (func->bind == STB_WEAK)
154 return false;
155
156 if (func->bind == STB_GLOBAL)
157 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
158 if (!strcmp(func->name, global_noreturns[i]))
159 return true;
160
161 if (!func->len)
162 return false;
163
164 insn = find_insn(file, func->sec, func->offset);
165 if (!insn->func)
166 return false;
167
168 func_for_each_insn_all(file, func, insn) {
169 empty = false;
170
171 if (insn->type == INSN_RETURN)
172 return false;
173 }
174
175 if (empty)
176 return false;
177
178 /*
179 * A function can have a sibling call instead of a return. In that
180 * case, the function's dead-end status depends on whether the target
181 * of the sibling call returns.
182 */
183 func_for_each_insn_all(file, func, insn) {
184 if (is_sibling_call(insn)) {
185 struct instruction *dest = insn->jump_dest;
186
187 if (!dest)
188 /* sibling call to another file */
189 return false;
190
191 /* local sibling call */
192 if (recursion == 5) {
193 /*
194 * Infinite recursion: two functions have
195 * sibling calls to each other. This is a very
196 * rare case. It means they aren't dead ends.
197 */
198 return false;
199 }
200
201 return __dead_end_function(file, dest->func, recursion+1);
202 }
203 }
204
205 return true;
206 }
207
208 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
209 {
210 return __dead_end_function(file, func, 0);
211 }
212
213 static void clear_insn_state(struct insn_state *state)
214 {
215 int i;
216
217 memset(state, 0, sizeof(*state));
218 state->cfa.base = CFI_UNDEFINED;
219 for (i = 0; i < CFI_NUM_REGS; i++) {
220 state->regs[i].base = CFI_UNDEFINED;
221 state->vals[i].base = CFI_UNDEFINED;
222 }
223 state->drap_reg = CFI_UNDEFINED;
224 state->drap_offset = -1;
225 }
226
227 /*
228 * Call the arch-specific instruction decoder for all the instructions and add
229 * them to the global instruction list.
230 */
231 static int decode_instructions(struct objtool_file *file)
232 {
233 struct section *sec;
234 struct symbol *func;
235 unsigned long offset;
236 struct instruction *insn;
237 int ret;
238
239 for_each_sec(file, sec) {
240
241 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
242 continue;
243
244 if (strcmp(sec->name, ".altinstr_replacement") &&
245 strcmp(sec->name, ".altinstr_aux") &&
246 strncmp(sec->name, ".discard.", 9))
247 sec->text = true;
248
249 for (offset = 0; offset < sec->len; offset += insn->len) {
250 insn = malloc(sizeof(*insn));
251 if (!insn) {
252 WARN("malloc failed");
253 return -1;
254 }
255 memset(insn, 0, sizeof(*insn));
256 INIT_LIST_HEAD(&insn->alts);
257 clear_insn_state(&insn->state);
258
259 insn->sec = sec;
260 insn->offset = offset;
261
262 ret = arch_decode_instruction(file->elf, sec, offset,
263 sec->len - offset,
264 &insn->len, &insn->type,
265 &insn->immediate,
266 &insn->stack_op);
267 if (ret)
268 goto err;
269
270 hash_add(file->insn_hash, &insn->hash, insn->offset);
271 list_add_tail(&insn->list, &file->insn_list);
272 }
273
274 list_for_each_entry(func, &sec->symbol_list, list) {
275 if (func->type != STT_FUNC || func->alias != func)
276 continue;
277
278 if (!find_insn(file, sec, func->offset)) {
279 WARN("%s(): can't find starting instruction",
280 func->name);
281 return -1;
282 }
283
284 func_for_each_insn(file, func, insn)
285 insn->func = func;
286 }
287 }
288
289 return 0;
290
291 err:
292 free(insn);
293 return ret;
294 }
295
296 /*
297 * Mark "ud2" instructions and manually annotated dead ends.
298 */
299 static int add_dead_ends(struct objtool_file *file)
300 {
301 struct section *sec;
302 struct rela *rela;
303 struct instruction *insn;
304 bool found;
305
306 /*
307 * By default, "ud2" is a dead end unless otherwise annotated, because
308 * GCC 7 inserts it for certain divide-by-zero cases.
309 */
310 for_each_insn(file, insn)
311 if (insn->type == INSN_BUG)
312 insn->dead_end = true;
313
314 /*
315 * Check for manually annotated dead ends.
316 */
317 sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
318 if (!sec)
319 goto reachable;
320
321 list_for_each_entry(rela, &sec->rela_list, list) {
322 if (rela->sym->type != STT_SECTION) {
323 WARN("unexpected relocation symbol type in %s", sec->name);
324 return -1;
325 }
326 insn = find_insn(file, rela->sym->sec, rela->addend);
327 if (insn)
328 insn = list_prev_entry(insn, list);
329 else if (rela->addend == rela->sym->sec->len) {
330 found = false;
331 list_for_each_entry_reverse(insn, &file->insn_list, list) {
332 if (insn->sec == rela->sym->sec) {
333 found = true;
334 break;
335 }
336 }
337
338 if (!found) {
339 WARN("can't find unreachable insn at %s+0x%x",
340 rela->sym->sec->name, rela->addend);
341 return -1;
342 }
343 } else {
344 WARN("can't find unreachable insn at %s+0x%x",
345 rela->sym->sec->name, rela->addend);
346 return -1;
347 }
348
349 insn->dead_end = true;
350 }
351
352 reachable:
353 /*
354 * These manually annotated reachable checks are needed for GCC 4.4,
355 * where the Linux unreachable() macro isn't supported. In that case
356 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
357 * not a dead end.
358 */
359 sec = find_section_by_name(file->elf, ".rela.discard.reachable");
360 if (!sec)
361 return 0;
362
363 list_for_each_entry(rela, &sec->rela_list, list) {
364 if (rela->sym->type != STT_SECTION) {
365 WARN("unexpected relocation symbol type in %s", sec->name);
366 return -1;
367 }
368 insn = find_insn(file, rela->sym->sec, rela->addend);
369 if (insn)
370 insn = list_prev_entry(insn, list);
371 else if (rela->addend == rela->sym->sec->len) {
372 found = false;
373 list_for_each_entry_reverse(insn, &file->insn_list, list) {
374 if (insn->sec == rela->sym->sec) {
375 found = true;
376 break;
377 }
378 }
379
380 if (!found) {
381 WARN("can't find reachable insn at %s+0x%x",
382 rela->sym->sec->name, rela->addend);
383 return -1;
384 }
385 } else {
386 WARN("can't find reachable insn at %s+0x%x",
387 rela->sym->sec->name, rela->addend);
388 return -1;
389 }
390
391 insn->dead_end = false;
392 }
393
394 return 0;
395 }
396
397 /*
398 * Warnings shouldn't be reported for ignored functions.
399 */
400 static void add_ignores(struct objtool_file *file)
401 {
402 struct instruction *insn;
403 struct section *sec;
404 struct symbol *func;
405 struct rela *rela;
406
407 sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
408 if (!sec)
409 return;
410
411 list_for_each_entry(rela, &sec->rela_list, list) {
412 switch (rela->sym->type) {
413 case STT_FUNC:
414 func = rela->sym;
415 break;
416
417 case STT_SECTION:
418 func = find_symbol_by_offset(rela->sym->sec, rela->addend);
419 if (!func || func->type != STT_FUNC)
420 continue;
421 break;
422
423 default:
424 WARN("unexpected relocation symbol type in %s: %d", sec->name, rela->sym->type);
425 continue;
426 }
427
428 func_for_each_insn_all(file, func, insn)
429 insn->ignore = true;
430 }
431 }
432
433 /*
434 * This is a whitelist of functions that is allowed to be called with AC set.
435 * The list is meant to be minimal and only contains compiler instrumentation
436 * ABI and a few functions used to implement *_{to,from}_user() functions.
437 *
438 * These functions must not directly change AC, but may PUSHF/POPF.
439 */
440 static const char *uaccess_safe_builtin[] = {
441 /* KASAN */
442 "kasan_report",
443 "check_memory_region",
444 /* KASAN out-of-line */
445 "__asan_loadN_noabort",
446 "__asan_load1_noabort",
447 "__asan_load2_noabort",
448 "__asan_load4_noabort",
449 "__asan_load8_noabort",
450 "__asan_load16_noabort",
451 "__asan_storeN_noabort",
452 "__asan_store1_noabort",
453 "__asan_store2_noabort",
454 "__asan_store4_noabort",
455 "__asan_store8_noabort",
456 "__asan_store16_noabort",
457 /* KASAN in-line */
458 "__asan_report_load_n_noabort",
459 "__asan_report_load1_noabort",
460 "__asan_report_load2_noabort",
461 "__asan_report_load4_noabort",
462 "__asan_report_load8_noabort",
463 "__asan_report_load16_noabort",
464 "__asan_report_store_n_noabort",
465 "__asan_report_store1_noabort",
466 "__asan_report_store2_noabort",
467 "__asan_report_store4_noabort",
468 "__asan_report_store8_noabort",
469 "__asan_report_store16_noabort",
470 /* KCOV */
471 "write_comp_data",
472 "__sanitizer_cov_trace_pc",
473 "__sanitizer_cov_trace_const_cmp1",
474 "__sanitizer_cov_trace_const_cmp2",
475 "__sanitizer_cov_trace_const_cmp4",
476 "__sanitizer_cov_trace_const_cmp8",
477 "__sanitizer_cov_trace_cmp1",
478 "__sanitizer_cov_trace_cmp2",
479 "__sanitizer_cov_trace_cmp4",
480 "__sanitizer_cov_trace_cmp8",
481 /* UBSAN */
482 "ubsan_type_mismatch_common",
483 "__ubsan_handle_type_mismatch",
484 "__ubsan_handle_type_mismatch_v1",
485 "__ubsan_handle_shift_out_of_bounds",
486 /* misc */
487 "csum_partial_copy_generic",
488 "__memcpy_mcsafe",
489 "mcsafe_handle_tail",
490 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
491 NULL
492 };
493
494 static void add_uaccess_safe(struct objtool_file *file)
495 {
496 struct symbol *func;
497 const char **name;
498
499 if (!uaccess)
500 return;
501
502 for (name = uaccess_safe_builtin; *name; name++) {
503 func = find_symbol_by_name(file->elf, *name);
504 if (!func)
505 continue;
506
507 func->uaccess_safe = true;
508 }
509 }
510
511 /*
512 * FIXME: For now, just ignore any alternatives which add retpolines. This is
513 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
514 * But it at least allows objtool to understand the control flow *around* the
515 * retpoline.
516 */
517 static int add_ignore_alternatives(struct objtool_file *file)
518 {
519 struct section *sec;
520 struct rela *rela;
521 struct instruction *insn;
522
523 sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
524 if (!sec)
525 return 0;
526
527 list_for_each_entry(rela, &sec->rela_list, list) {
528 if (rela->sym->type != STT_SECTION) {
529 WARN("unexpected relocation symbol type in %s", sec->name);
530 return -1;
531 }
532
533 insn = find_insn(file, rela->sym->sec, rela->addend);
534 if (!insn) {
535 WARN("bad .discard.ignore_alts entry");
536 return -1;
537 }
538
539 insn->ignore_alts = true;
540 }
541
542 return 0;
543 }
544
545 /*
546 * Find the destination instructions for all jumps.
547 */
548 static int add_jump_destinations(struct objtool_file *file)
549 {
550 struct instruction *insn;
551 struct rela *rela;
552 struct section *dest_sec;
553 unsigned long dest_off;
554
555 for_each_insn(file, insn) {
556 if (insn->type != INSN_JUMP_CONDITIONAL &&
557 insn->type != INSN_JUMP_UNCONDITIONAL)
558 continue;
559
560 if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET)
561 continue;
562
563 rela = find_rela_by_dest_range(insn->sec, insn->offset,
564 insn->len);
565 if (!rela) {
566 dest_sec = insn->sec;
567 dest_off = insn->offset + insn->len + insn->immediate;
568 } else if (rela->sym->type == STT_SECTION) {
569 dest_sec = rela->sym->sec;
570 dest_off = rela->addend + 4;
571 } else if (rela->sym->sec->idx) {
572 dest_sec = rela->sym->sec;
573 dest_off = rela->sym->sym.st_value + rela->addend + 4;
574 } else if (strstr(rela->sym->name, "_indirect_thunk_")) {
575 /*
576 * Retpoline jumps are really dynamic jumps in
577 * disguise, so convert them accordingly.
578 */
579 if (insn->type == INSN_JUMP_UNCONDITIONAL)
580 insn->type = INSN_JUMP_DYNAMIC;
581 else
582 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
583
584 insn->retpoline_safe = true;
585 continue;
586 } else {
587 /* external sibling call */
588 insn->call_dest = rela->sym;
589 continue;
590 }
591
592 insn->jump_dest = find_insn(file, dest_sec, dest_off);
593 if (!insn->jump_dest) {
594
595 /*
596 * This is a special case where an alt instruction
597 * jumps past the end of the section. These are
598 * handled later in handle_group_alt().
599 */
600 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
601 continue;
602
603 WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
604 insn->sec, insn->offset, dest_sec->name,
605 dest_off);
606 return -1;
607 }
608
609 /*
610 * Cross-function jump.
611 */
612 if (insn->func && insn->jump_dest->func &&
613 insn->func != insn->jump_dest->func) {
614
615 /*
616 * For GCC 8+, create parent/child links for any cold
617 * subfunctions. This is _mostly_ redundant with a
618 * similar initialization in read_symbols().
619 *
620 * If a function has aliases, we want the *first* such
621 * function in the symbol table to be the subfunction's
622 * parent. In that case we overwrite the
623 * initialization done in read_symbols().
624 *
625 * However this code can't completely replace the
626 * read_symbols() code because this doesn't detect the
627 * case where the parent function's only reference to a
628 * subfunction is through a jump table.
629 */
630 if (!strstr(insn->func->name, ".cold.") &&
631 strstr(insn->jump_dest->func->name, ".cold.")) {
632 insn->func->cfunc = insn->jump_dest->func;
633 insn->jump_dest->func->pfunc = insn->func;
634
635 } else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
636 insn->jump_dest->offset == insn->jump_dest->func->offset) {
637
638 /* internal sibling call */
639 insn->call_dest = insn->jump_dest->func;
640 }
641 }
642 }
643
644 return 0;
645 }
646
647 /*
648 * Find the destination instructions for all calls.
649 */
650 static int add_call_destinations(struct objtool_file *file)
651 {
652 struct instruction *insn;
653 unsigned long dest_off;
654 struct rela *rela;
655
656 for_each_insn(file, insn) {
657 if (insn->type != INSN_CALL)
658 continue;
659
660 rela = find_rela_by_dest_range(insn->sec, insn->offset,
661 insn->len);
662 if (!rela) {
663 dest_off = insn->offset + insn->len + insn->immediate;
664 insn->call_dest = find_symbol_by_offset(insn->sec,
665 dest_off);
666
667 if (!insn->call_dest && !insn->ignore) {
668 WARN_FUNC("unsupported intra-function call",
669 insn->sec, insn->offset);
670 if (retpoline)
671 WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");
672 return -1;
673 }
674
675 } else if (rela->sym->type == STT_SECTION) {
676 insn->call_dest = find_symbol_by_offset(rela->sym->sec,
677 rela->addend+4);
678 if (!insn->call_dest ||
679 insn->call_dest->type != STT_FUNC) {
680 WARN_FUNC("can't find call dest symbol at %s+0x%x",
681 insn->sec, insn->offset,
682 rela->sym->sec->name,
683 rela->addend + 4);
684 return -1;
685 }
686 } else
687 insn->call_dest = rela->sym;
688 }
689
690 return 0;
691 }
692
693 /*
694 * The .alternatives section requires some extra special care, over and above
695 * what other special sections require:
696 *
697 * 1. Because alternatives are patched in-place, we need to insert a fake jump
698 * instruction at the end so that validate_branch() skips all the original
699 * replaced instructions when validating the new instruction path.
700 *
701 * 2. An added wrinkle is that the new instruction length might be zero. In
702 * that case the old instructions are replaced with noops. We simulate that
703 * by creating a fake jump as the only new instruction.
704 *
705 * 3. In some cases, the alternative section includes an instruction which
706 * conditionally jumps to the _end_ of the entry. We have to modify these
707 * jumps' destinations to point back to .text rather than the end of the
708 * entry in .altinstr_replacement.
709 */
710 static int handle_group_alt(struct objtool_file *file,
711 struct special_alt *special_alt,
712 struct instruction *orig_insn,
713 struct instruction **new_insn)
714 {
715 struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
716 unsigned long dest_off;
717
718 last_orig_insn = NULL;
719 insn = orig_insn;
720 sec_for_each_insn_from(file, insn) {
721 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
722 break;
723
724 insn->alt_group = true;
725 last_orig_insn = insn;
726 }
727
728 if (next_insn_same_sec(file, last_orig_insn)) {
729 fake_jump = malloc(sizeof(*fake_jump));
730 if (!fake_jump) {
731 WARN("malloc failed");
732 return -1;
733 }
734 memset(fake_jump, 0, sizeof(*fake_jump));
735 INIT_LIST_HEAD(&fake_jump->alts);
736 clear_insn_state(&fake_jump->state);
737
738 fake_jump->sec = special_alt->new_sec;
739 fake_jump->offset = FAKE_JUMP_OFFSET;
740 fake_jump->type = INSN_JUMP_UNCONDITIONAL;
741 fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
742 fake_jump->func = orig_insn->func;
743 }
744
745 if (!special_alt->new_len) {
746 if (!fake_jump) {
747 WARN("%s: empty alternative at end of section",
748 special_alt->orig_sec->name);
749 return -1;
750 }
751
752 *new_insn = fake_jump;
753 return 0;
754 }
755
756 last_new_insn = NULL;
757 insn = *new_insn;
758 sec_for_each_insn_from(file, insn) {
759 if (insn->offset >= special_alt->new_off + special_alt->new_len)
760 break;
761
762 last_new_insn = insn;
763
764 insn->ignore = orig_insn->ignore_alts;
765 insn->func = orig_insn->func;
766
767 if (insn->type != INSN_JUMP_CONDITIONAL &&
768 insn->type != INSN_JUMP_UNCONDITIONAL)
769 continue;
770
771 if (!insn->immediate)
772 continue;
773
774 dest_off = insn->offset + insn->len + insn->immediate;
775 if (dest_off == special_alt->new_off + special_alt->new_len) {
776 if (!fake_jump) {
777 WARN("%s: alternative jump to end of section",
778 special_alt->orig_sec->name);
779 return -1;
780 }
781 insn->jump_dest = fake_jump;
782 }
783
784 if (!insn->jump_dest) {
785 WARN_FUNC("can't find alternative jump destination",
786 insn->sec, insn->offset);
787 return -1;
788 }
789 }
790
791 if (!last_new_insn) {
792 WARN_FUNC("can't find last new alternative instruction",
793 special_alt->new_sec, special_alt->new_off);
794 return -1;
795 }
796
797 if (fake_jump)
798 list_add(&fake_jump->list, &last_new_insn->list);
799
800 return 0;
801 }
802
803 /*
804 * A jump table entry can either convert a nop to a jump or a jump to a nop.
805 * If the original instruction is a jump, make the alt entry an effective nop
806 * by just skipping the original instruction.
807 */
808 static int handle_jump_alt(struct objtool_file *file,
809 struct special_alt *special_alt,
810 struct instruction *orig_insn,
811 struct instruction **new_insn)
812 {
813 if (orig_insn->type == INSN_NOP)
814 return 0;
815
816 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
817 WARN_FUNC("unsupported instruction at jump label",
818 orig_insn->sec, orig_insn->offset);
819 return -1;
820 }
821
822 *new_insn = list_next_entry(orig_insn, list);
823 return 0;
824 }
825
826 /*
827 * Read all the special sections which have alternate instructions which can be
828 * patched in or redirected to at runtime. Each instruction having alternate
829 * instruction(s) has them added to its insn->alts list, which will be
830 * traversed in validate_branch().
831 */
832 static int add_special_section_alts(struct objtool_file *file)
833 {
834 struct list_head special_alts;
835 struct instruction *orig_insn, *new_insn;
836 struct special_alt *special_alt, *tmp;
837 struct alternative *alt;
838 int ret;
839
840 ret = special_get_alts(file->elf, &special_alts);
841 if (ret)
842 return ret;
843
844 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
845
846 orig_insn = find_insn(file, special_alt->orig_sec,
847 special_alt->orig_off);
848 if (!orig_insn) {
849 WARN_FUNC("special: can't find orig instruction",
850 special_alt->orig_sec, special_alt->orig_off);
851 ret = -1;
852 goto out;
853 }
854
855 new_insn = NULL;
856 if (!special_alt->group || special_alt->new_len) {
857 new_insn = find_insn(file, special_alt->new_sec,
858 special_alt->new_off);
859 if (!new_insn) {
860 WARN_FUNC("special: can't find new instruction",
861 special_alt->new_sec,
862 special_alt->new_off);
863 ret = -1;
864 goto out;
865 }
866 }
867
868 if (special_alt->group) {
869 ret = handle_group_alt(file, special_alt, orig_insn,
870 &new_insn);
871 if (ret)
872 goto out;
873 } else if (special_alt->jump_or_nop) {
874 ret = handle_jump_alt(file, special_alt, orig_insn,
875 &new_insn);
876 if (ret)
877 goto out;
878 }
879
880 alt = malloc(sizeof(*alt));
881 if (!alt) {
882 WARN("malloc failed");
883 ret = -1;
884 goto out;
885 }
886
887 alt->insn = new_insn;
888 alt->skip_orig = special_alt->skip_orig;
889 orig_insn->ignore_alts |= special_alt->skip_alt;
890 list_add_tail(&alt->list, &orig_insn->alts);
891
892 list_del(&special_alt->list);
893 free(special_alt);
894 }
895
896 out:
897 return ret;
898 }
899
900 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
901 struct rela *table)
902 {
903 struct rela *rela = table;
904 struct instruction *dest_insn;
905 struct alternative *alt;
906 struct symbol *pfunc = insn->func->pfunc;
907 unsigned int prev_offset = 0;
908
909 /*
910 * Each @rela is a switch table relocation which points to the target
911 * instruction.
912 */
913 list_for_each_entry_from(rela, &table->sec->rela_list, list) {
914
915 /* Check for the end of the table: */
916 if (rela != table && rela->jump_table_start)
917 break;
918
919 /* Make sure the table entries are consecutive: */
920 if (prev_offset && rela->offset != prev_offset + 8)
921 break;
922
923 /* Detect function pointers from contiguous objects: */
924 if (rela->sym->sec == pfunc->sec &&
925 rela->addend == pfunc->offset)
926 break;
927
928 dest_insn = find_insn(file, rela->sym->sec, rela->addend);
929 if (!dest_insn)
930 break;
931
932 /* Make sure the destination is in the same function: */
933 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
934 break;
935
936 alt = malloc(sizeof(*alt));
937 if (!alt) {
938 WARN("malloc failed");
939 return -1;
940 }
941
942 alt->insn = dest_insn;
943 list_add_tail(&alt->list, &insn->alts);
944 prev_offset = rela->offset;
945 }
946
947 if (!prev_offset) {
948 WARN_FUNC("can't find switch jump table",
949 insn->sec, insn->offset);
950 return -1;
951 }
952
953 return 0;
954 }
955
956 /*
957 * find_jump_table() - Given a dynamic jump, find the switch jump table in
958 * .rodata associated with it.
959 *
960 * There are 3 basic patterns:
961 *
962 * 1. jmpq *[rodata addr](,%reg,8)
963 *
964 * This is the most common case by far. It jumps to an address in a simple
965 * jump table which is stored in .rodata.
966 *
967 * 2. jmpq *[rodata addr](%rip)
968 *
969 * This is caused by a rare GCC quirk, currently only seen in three driver
970 * functions in the kernel, only with certain obscure non-distro configs.
971 *
972 * As part of an optimization, GCC makes a copy of an existing switch jump
973 * table, modifies it, and then hard-codes the jump (albeit with an indirect
974 * jump) to use a single entry in the table. The rest of the jump table and
975 * some of its jump targets remain as dead code.
976 *
977 * In such a case we can just crudely ignore all unreachable instruction
978 * warnings for the entire object file. Ideally we would just ignore them
979 * for the function, but that would require redesigning the code quite a
980 * bit. And honestly that's just not worth doing: unreachable instruction
981 * warnings are of questionable value anyway, and this is such a rare issue.
982 *
983 * 3. mov [rodata addr],%reg1
984 * ... some instructions ...
985 * jmpq *(%reg1,%reg2,8)
986 *
987 * This is a fairly uncommon pattern which is new for GCC 6. As of this
988 * writing, there are 11 occurrences of it in the allmodconfig kernel.
989 *
990 * As of GCC 7 there are quite a few more of these and the 'in between' code
991 * is significant. Esp. with KASAN enabled some of the code between the mov
992 * and jmpq uses .rodata itself, which can confuse things.
993 *
994 * TODO: Once we have DWARF CFI and smarter instruction decoding logic,
995 * ensure the same register is used in the mov and jump instructions.
996 *
997 * NOTE: RETPOLINE made it harder still to decode dynamic jumps.
998 */
999 static struct rela *find_jump_table(struct objtool_file *file,
1000 struct symbol *func,
1001 struct instruction *insn)
1002 {
1003 struct rela *text_rela, *table_rela;
1004 struct instruction *orig_insn = insn;
1005 struct section *table_sec;
1006 unsigned long table_offset;
1007
1008 /*
1009 * Backward search using the @first_jump_src links, these help avoid
1010 * much of the 'in between' code. Which avoids us getting confused by
1011 * it.
1012 */
1013 for (;
1014 &insn->list != &file->insn_list &&
1015 insn->sec == func->sec &&
1016 insn->offset >= func->offset;
1017
1018 insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
1019
1020 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1021 break;
1022
1023 /* allow small jumps within the range */
1024 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1025 insn->jump_dest &&
1026 (insn->jump_dest->offset <= insn->offset ||
1027 insn->jump_dest->offset > orig_insn->offset))
1028 break;
1029
1030 /* look for a relocation which references .rodata */
1031 text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
1032 insn->len);
1033 if (!text_rela || text_rela->sym->type != STT_SECTION ||
1034 !text_rela->sym->sec->rodata)
1035 continue;
1036
1037 table_offset = text_rela->addend;
1038 table_sec = text_rela->sym->sec;
1039
1040 if (text_rela->type == R_X86_64_PC32)
1041 table_offset += 4;
1042
1043 /*
1044 * Make sure the .rodata address isn't associated with a
1045 * symbol. GCC jump tables are anonymous data.
1046 *
1047 * Also support C jump tables which are in the same format as
1048 * switch jump tables. For objtool to recognize them, they
1049 * need to be placed in the C_JUMP_TABLE_SECTION section. They
1050 * have symbols associated with them.
1051 */
1052 if (find_symbol_containing(table_sec, table_offset) &&
1053 strcmp(table_sec->name, C_JUMP_TABLE_SECTION))
1054 continue;
1055
1056 /* Each table entry has a rela associated with it. */
1057 table_rela = find_rela_by_dest(table_sec, table_offset);
1058 if (!table_rela)
1059 continue;
1060
1061 /*
1062 * Use of RIP-relative switch jumps is quite rare, and
1063 * indicates a rare GCC quirk/bug which can leave dead code
1064 * behind.
1065 */
1066 if (text_rela->type == R_X86_64_PC32)
1067 file->ignore_unreachables = true;
1068
1069 return table_rela;
1070 }
1071
1072 return NULL;
1073 }
1074
1075 /*
1076 * First pass: Mark the head of each jump table so that in the next pass,
1077 * we know when a given jump table ends and the next one starts.
1078 */
1079 static void mark_func_jump_tables(struct objtool_file *file,
1080 struct symbol *func)
1081 {
1082 struct instruction *insn, *last = NULL;
1083 struct rela *rela;
1084
1085 func_for_each_insn_all(file, func, insn) {
1086 if (!last)
1087 last = insn;
1088
1089 /*
1090 * Store back-pointers for unconditional forward jumps such
1091 * that find_jump_table() can back-track using those and
1092 * avoid some potentially confusing code.
1093 */
1094 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1095 insn->offset > last->offset &&
1096 insn->jump_dest->offset > insn->offset &&
1097 !insn->jump_dest->first_jump_src) {
1098
1099 insn->jump_dest->first_jump_src = insn;
1100 last = insn->jump_dest;
1101 }
1102
1103 if (insn->type != INSN_JUMP_DYNAMIC)
1104 continue;
1105
1106 rela = find_jump_table(file, func, insn);
1107 if (rela) {
1108 rela->jump_table_start = true;
1109 insn->jump_table = rela;
1110 }
1111 }
1112 }
1113
1114 static int add_func_jump_tables(struct objtool_file *file,
1115 struct symbol *func)
1116 {
1117 struct instruction *insn;
1118 int ret;
1119
1120 func_for_each_insn_all(file, func, insn) {
1121 if (!insn->jump_table)
1122 continue;
1123
1124 ret = add_jump_table(file, insn, insn->jump_table);
1125 if (ret)
1126 return ret;
1127 }
1128
1129 return 0;
1130 }
1131
1132 /*
1133 * For some switch statements, gcc generates a jump table in the .rodata
1134 * section which contains a list of addresses within the function to jump to.
1135 * This finds these jump tables and adds them to the insn->alts lists.
1136 */
1137 static int add_jump_table_alts(struct objtool_file *file)
1138 {
1139 struct section *sec;
1140 struct symbol *func;
1141 int ret;
1142
1143 if (!file->rodata)
1144 return 0;
1145
1146 for_each_sec(file, sec) {
1147 list_for_each_entry(func, &sec->symbol_list, list) {
1148 if (func->type != STT_FUNC)
1149 continue;
1150
1151 mark_func_jump_tables(file, func);
1152 ret = add_func_jump_tables(file, func);
1153 if (ret)
1154 return ret;
1155 }
1156 }
1157
1158 return 0;
1159 }
1160
1161 static int read_unwind_hints(struct objtool_file *file)
1162 {
1163 struct section *sec, *relasec;
1164 struct rela *rela;
1165 struct unwind_hint *hint;
1166 struct instruction *insn;
1167 struct cfi_reg *cfa;
1168 int i;
1169
1170 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1171 if (!sec)
1172 return 0;
1173
1174 relasec = sec->rela;
1175 if (!relasec) {
1176 WARN("missing .rela.discard.unwind_hints section");
1177 return -1;
1178 }
1179
1180 if (sec->len % sizeof(struct unwind_hint)) {
1181 WARN("struct unwind_hint size mismatch");
1182 return -1;
1183 }
1184
1185 file->hints = true;
1186
1187 for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
1188 hint = (struct unwind_hint *)sec->data->d_buf + i;
1189
1190 rela = find_rela_by_dest(sec, i * sizeof(*hint));
1191 if (!rela) {
1192 WARN("can't find rela for unwind_hints[%d]", i);
1193 return -1;
1194 }
1195
1196 insn = find_insn(file, rela->sym->sec, rela->addend);
1197 if (!insn) {
1198 WARN("can't find insn for unwind_hints[%d]", i);
1199 return -1;
1200 }
1201
1202 cfa = &insn->state.cfa;
1203
1204 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
1205 insn->save = true;
1206 continue;
1207
1208 } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
1209 insn->restore = true;
1210 insn->hint = true;
1211 continue;
1212 }
1213
1214 insn->hint = true;
1215
1216 switch (hint->sp_reg) {
1217 case ORC_REG_UNDEFINED:
1218 cfa->base = CFI_UNDEFINED;
1219 break;
1220 case ORC_REG_SP:
1221 cfa->base = CFI_SP;
1222 break;
1223 case ORC_REG_BP:
1224 cfa->base = CFI_BP;
1225 break;
1226 case ORC_REG_SP_INDIRECT:
1227 cfa->base = CFI_SP_INDIRECT;
1228 break;
1229 case ORC_REG_R10:
1230 cfa->base = CFI_R10;
1231 break;
1232 case ORC_REG_R13:
1233 cfa->base = CFI_R13;
1234 break;
1235 case ORC_REG_DI:
1236 cfa->base = CFI_DI;
1237 break;
1238 case ORC_REG_DX:
1239 cfa->base = CFI_DX;
1240 break;
1241 default:
1242 WARN_FUNC("unsupported unwind_hint sp base reg %d",
1243 insn->sec, insn->offset, hint->sp_reg);
1244 return -1;
1245 }
1246
1247 cfa->offset = hint->sp_offset;
1248 insn->state.type = hint->type;
1249 insn->state.end = hint->end;
1250 }
1251
1252 return 0;
1253 }
1254
1255 static int read_retpoline_hints(struct objtool_file *file)
1256 {
1257 struct section *sec;
1258 struct instruction *insn;
1259 struct rela *rela;
1260
1261 sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1262 if (!sec)
1263 return 0;
1264
1265 list_for_each_entry(rela, &sec->rela_list, list) {
1266 if (rela->sym->type != STT_SECTION) {
1267 WARN("unexpected relocation symbol type in %s", sec->name);
1268 return -1;
1269 }
1270
1271 insn = find_insn(file, rela->sym->sec, rela->addend);
1272 if (!insn) {
1273 WARN("bad .discard.retpoline_safe entry");
1274 return -1;
1275 }
1276
1277 if (insn->type != INSN_JUMP_DYNAMIC &&
1278 insn->type != INSN_CALL_DYNAMIC) {
1279 WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1280 insn->sec, insn->offset);
1281 return -1;
1282 }
1283
1284 insn->retpoline_safe = true;
1285 }
1286
1287 return 0;
1288 }
1289
1290 static void mark_rodata(struct objtool_file *file)
1291 {
1292 struct section *sec;
1293 bool found = false;
1294
1295 /*
1296 * Search for the following rodata sections, each of which can
1297 * potentially contain jump tables:
1298 *
1299 * - .rodata: can contain GCC switch tables
1300 * - .rodata.<func>: same, if -fdata-sections is being used
1301 * - .rodata..c_jump_table: contains C annotated jump tables
1302 *
1303 * .rodata.str1.* sections are ignored; they don't contain jump tables.
1304 */
1305 for_each_sec(file, sec) {
1306 if ((!strncmp(sec->name, ".rodata", 7) && !strstr(sec->name, ".str1.")) ||
1307 !strcmp(sec->name, C_JUMP_TABLE_SECTION)) {
1308 sec->rodata = true;
1309 found = true;
1310 }
1311 }
1312
1313 file->rodata = found;
1314 }
1315
1316 static int decode_sections(struct objtool_file *file)
1317 {
1318 int ret;
1319
1320 mark_rodata(file);
1321
1322 ret = decode_instructions(file);
1323 if (ret)
1324 return ret;
1325
1326 ret = add_dead_ends(file);
1327 if (ret)
1328 return ret;
1329
1330 add_ignores(file);
1331 add_uaccess_safe(file);
1332
1333 ret = add_ignore_alternatives(file);
1334 if (ret)
1335 return ret;
1336
1337 ret = add_jump_destinations(file);
1338 if (ret)
1339 return ret;
1340
1341 ret = add_special_section_alts(file);
1342 if (ret)
1343 return ret;
1344
1345 ret = add_call_destinations(file);
1346 if (ret)
1347 return ret;
1348
1349 ret = add_jump_table_alts(file);
1350 if (ret)
1351 return ret;
1352
1353 ret = read_unwind_hints(file);
1354 if (ret)
1355 return ret;
1356
1357 ret = read_retpoline_hints(file);
1358 if (ret)
1359 return ret;
1360
1361 return 0;
1362 }
1363
1364 static bool is_fentry_call(struct instruction *insn)
1365 {
1366 if (insn->type == INSN_CALL &&
1367 insn->call_dest->type == STT_NOTYPE &&
1368 !strcmp(insn->call_dest->name, "__fentry__"))
1369 return true;
1370
1371 return false;
1372 }
1373
1374 static bool has_modified_stack_frame(struct insn_state *state)
1375 {
1376 int i;
1377
1378 if (state->cfa.base != initial_func_cfi.cfa.base ||
1379 state->cfa.offset != initial_func_cfi.cfa.offset ||
1380 state->stack_size != initial_func_cfi.cfa.offset ||
1381 state->drap)
1382 return true;
1383
1384 for (i = 0; i < CFI_NUM_REGS; i++)
1385 if (state->regs[i].base != initial_func_cfi.regs[i].base ||
1386 state->regs[i].offset != initial_func_cfi.regs[i].offset)
1387 return true;
1388
1389 return false;
1390 }
1391
1392 static bool has_valid_stack_frame(struct insn_state *state)
1393 {
1394 if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
1395 state->regs[CFI_BP].offset == -16)
1396 return true;
1397
1398 if (state->drap && state->regs[CFI_BP].base == CFI_BP)
1399 return true;
1400
1401 return false;
1402 }
1403
1404 static int update_insn_state_regs(struct instruction *insn, struct insn_state *state)
1405 {
1406 struct cfi_reg *cfa = &state->cfa;
1407 struct stack_op *op = &insn->stack_op;
1408
1409 if (cfa->base != CFI_SP)
1410 return 0;
1411
1412 /* push */
1413 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
1414 cfa->offset += 8;
1415
1416 /* pop */
1417 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
1418 cfa->offset -= 8;
1419
1420 /* add immediate to sp */
1421 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1422 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1423 cfa->offset -= op->src.offset;
1424
1425 return 0;
1426 }
1427
1428 static void save_reg(struct insn_state *state, unsigned char reg, int base,
1429 int offset)
1430 {
1431 if (arch_callee_saved_reg(reg) &&
1432 state->regs[reg].base == CFI_UNDEFINED) {
1433 state->regs[reg].base = base;
1434 state->regs[reg].offset = offset;
1435 }
1436 }
1437
1438 static void restore_reg(struct insn_state *state, unsigned char reg)
1439 {
1440 state->regs[reg].base = CFI_UNDEFINED;
1441 state->regs[reg].offset = 0;
1442 }
1443
1444 /*
1445 * A note about DRAP stack alignment:
1446 *
1447 * GCC has the concept of a DRAP register, which is used to help keep track of
1448 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
1449 * register. The typical DRAP pattern is:
1450 *
1451 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
1452 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
1453 * 41 ff 72 f8 pushq -0x8(%r10)
1454 * 55 push %rbp
1455 * 48 89 e5 mov %rsp,%rbp
1456 * (more pushes)
1457 * 41 52 push %r10
1458 * ...
1459 * 41 5a pop %r10
1460 * (more pops)
1461 * 5d pop %rbp
1462 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1463 * c3 retq
1464 *
1465 * There are some variations in the epilogues, like:
1466 *
1467 * 5b pop %rbx
1468 * 41 5a pop %r10
1469 * 41 5c pop %r12
1470 * 41 5d pop %r13
1471 * 41 5e pop %r14
1472 * c9 leaveq
1473 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1474 * c3 retq
1475 *
1476 * and:
1477 *
1478 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
1479 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
1480 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
1481 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
1482 * c9 leaveq
1483 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1484 * c3 retq
1485 *
1486 * Sometimes r13 is used as the DRAP register, in which case it's saved and
1487 * restored beforehand:
1488 *
1489 * 41 55 push %r13
1490 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
1491 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
1492 * ...
1493 * 49 8d 65 f0 lea -0x10(%r13),%rsp
1494 * 41 5d pop %r13
1495 * c3 retq
1496 */
1497 static int update_insn_state(struct instruction *insn, struct insn_state *state)
1498 {
1499 struct stack_op *op = &insn->stack_op;
1500 struct cfi_reg *cfa = &state->cfa;
1501 struct cfi_reg *regs = state->regs;
1502
1503 /* stack operations don't make sense with an undefined CFA */
1504 if (cfa->base == CFI_UNDEFINED) {
1505 if (insn->func) {
1506 WARN_FUNC("undefined stack state", insn->sec, insn->offset);
1507 return -1;
1508 }
1509 return 0;
1510 }
1511
1512 if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET)
1513 return update_insn_state_regs(insn, state);
1514
1515 switch (op->dest.type) {
1516
1517 case OP_DEST_REG:
1518 switch (op->src.type) {
1519
1520 case OP_SRC_REG:
1521 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
1522 cfa->base == CFI_SP &&
1523 regs[CFI_BP].base == CFI_CFA &&
1524 regs[CFI_BP].offset == -cfa->offset) {
1525
1526 /* mov %rsp, %rbp */
1527 cfa->base = op->dest.reg;
1528 state->bp_scratch = false;
1529 }
1530
1531 else if (op->src.reg == CFI_SP &&
1532 op->dest.reg == CFI_BP && state->drap) {
1533
1534 /* drap: mov %rsp, %rbp */
1535 regs[CFI_BP].base = CFI_BP;
1536 regs[CFI_BP].offset = -state->stack_size;
1537 state->bp_scratch = false;
1538 }
1539
1540 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1541
1542 /*
1543 * mov %rsp, %reg
1544 *
1545 * This is needed for the rare case where GCC
1546 * does:
1547 *
1548 * mov %rsp, %rax
1549 * ...
1550 * mov %rax, %rsp
1551 */
1552 state->vals[op->dest.reg].base = CFI_CFA;
1553 state->vals[op->dest.reg].offset = -state->stack_size;
1554 }
1555
1556 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
1557 cfa->base == CFI_BP) {
1558
1559 /*
1560 * mov %rbp, %rsp
1561 *
1562 * Restore the original stack pointer (Clang).
1563 */
1564 state->stack_size = -state->regs[CFI_BP].offset;
1565 }
1566
1567 else if (op->dest.reg == cfa->base) {
1568
1569 /* mov %reg, %rsp */
1570 if (cfa->base == CFI_SP &&
1571 state->vals[op->src.reg].base == CFI_CFA) {
1572
1573 /*
1574 * This is needed for the rare case
1575 * where GCC does something dumb like:
1576 *
1577 * lea 0x8(%rsp), %rcx
1578 * ...
1579 * mov %rcx, %rsp
1580 */
1581 cfa->offset = -state->vals[op->src.reg].offset;
1582 state->stack_size = cfa->offset;
1583
1584 } else {
1585 cfa->base = CFI_UNDEFINED;
1586 cfa->offset = 0;
1587 }
1588 }
1589
1590 break;
1591
1592 case OP_SRC_ADD:
1593 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
1594
1595 /* add imm, %rsp */
1596 state->stack_size -= op->src.offset;
1597 if (cfa->base == CFI_SP)
1598 cfa->offset -= op->src.offset;
1599 break;
1600 }
1601
1602 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
1603
1604 /* lea disp(%rbp), %rsp */
1605 state->stack_size = -(op->src.offset + regs[CFI_BP].offset);
1606 break;
1607 }
1608
1609 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1610
1611 /* drap: lea disp(%rsp), %drap */
1612 state->drap_reg = op->dest.reg;
1613
1614 /*
1615 * lea disp(%rsp), %reg
1616 *
1617 * This is needed for the rare case where GCC
1618 * does something dumb like:
1619 *
1620 * lea 0x8(%rsp), %rcx
1621 * ...
1622 * mov %rcx, %rsp
1623 */
1624 state->vals[op->dest.reg].base = CFI_CFA;
1625 state->vals[op->dest.reg].offset = \
1626 -state->stack_size + op->src.offset;
1627
1628 break;
1629 }
1630
1631 if (state->drap && op->dest.reg == CFI_SP &&
1632 op->src.reg == state->drap_reg) {
1633
1634 /* drap: lea disp(%drap), %rsp */
1635 cfa->base = CFI_SP;
1636 cfa->offset = state->stack_size = -op->src.offset;
1637 state->drap_reg = CFI_UNDEFINED;
1638 state->drap = false;
1639 break;
1640 }
1641
1642 if (op->dest.reg == state->cfa.base) {
1643 WARN_FUNC("unsupported stack register modification",
1644 insn->sec, insn->offset);
1645 return -1;
1646 }
1647
1648 break;
1649
1650 case OP_SRC_AND:
1651 if (op->dest.reg != CFI_SP ||
1652 (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
1653 (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
1654 WARN_FUNC("unsupported stack pointer realignment",
1655 insn->sec, insn->offset);
1656 return -1;
1657 }
1658
1659 if (state->drap_reg != CFI_UNDEFINED) {
1660 /* drap: and imm, %rsp */
1661 cfa->base = state->drap_reg;
1662 cfa->offset = state->stack_size = 0;
1663 state->drap = true;
1664 }
1665
1666 /*
1667 * Older versions of GCC (4.8ish) realign the stack
1668 * without DRAP, with a frame pointer.
1669 */
1670
1671 break;
1672
1673 case OP_SRC_POP:
1674 case OP_SRC_POPF:
1675 if (!state->drap && op->dest.type == OP_DEST_REG &&
1676 op->dest.reg == cfa->base) {
1677
1678 /* pop %rbp */
1679 cfa->base = CFI_SP;
1680 }
1681
1682 if (state->drap && cfa->base == CFI_BP_INDIRECT &&
1683 op->dest.type == OP_DEST_REG &&
1684 op->dest.reg == state->drap_reg &&
1685 state->drap_offset == -state->stack_size) {
1686
1687 /* drap: pop %drap */
1688 cfa->base = state->drap_reg;
1689 cfa->offset = 0;
1690 state->drap_offset = -1;
1691
1692 } else if (regs[op->dest.reg].offset == -state->stack_size) {
1693
1694 /* pop %reg */
1695 restore_reg(state, op->dest.reg);
1696 }
1697
1698 state->stack_size -= 8;
1699 if (cfa->base == CFI_SP)
1700 cfa->offset -= 8;
1701
1702 break;
1703
1704 case OP_SRC_REG_INDIRECT:
1705 if (state->drap && op->src.reg == CFI_BP &&
1706 op->src.offset == state->drap_offset) {
1707
1708 /* drap: mov disp(%rbp), %drap */
1709 cfa->base = state->drap_reg;
1710 cfa->offset = 0;
1711 state->drap_offset = -1;
1712 }
1713
1714 if (state->drap && op->src.reg == CFI_BP &&
1715 op->src.offset == regs[op->dest.reg].offset) {
1716
1717 /* drap: mov disp(%rbp), %reg */
1718 restore_reg(state, op->dest.reg);
1719
1720 } else if (op->src.reg == cfa->base &&
1721 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
1722
1723 /* mov disp(%rbp), %reg */
1724 /* mov disp(%rsp), %reg */
1725 restore_reg(state, op->dest.reg);
1726 }
1727
1728 break;
1729
1730 default:
1731 WARN_FUNC("unknown stack-related instruction",
1732 insn->sec, insn->offset);
1733 return -1;
1734 }
1735
1736 break;
1737
1738 case OP_DEST_PUSH:
1739 case OP_DEST_PUSHF:
1740 state->stack_size += 8;
1741 if (cfa->base == CFI_SP)
1742 cfa->offset += 8;
1743
1744 if (op->src.type != OP_SRC_REG)
1745 break;
1746
1747 if (state->drap) {
1748 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1749
1750 /* drap: push %drap */
1751 cfa->base = CFI_BP_INDIRECT;
1752 cfa->offset = -state->stack_size;
1753
1754 /* save drap so we know when to restore it */
1755 state->drap_offset = -state->stack_size;
1756
1757 } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
1758
1759 /* drap: push %rbp */
1760 state->stack_size = 0;
1761
1762 } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1763
1764 /* drap: push %reg */
1765 save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
1766 }
1767
1768 } else {
1769
1770 /* push %reg */
1771 save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
1772 }
1773
1774 /* detect when asm code uses rbp as a scratch register */
1775 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
1776 cfa->base != CFI_BP)
1777 state->bp_scratch = true;
1778 break;
1779
1780 case OP_DEST_REG_INDIRECT:
1781
1782 if (state->drap) {
1783 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1784
1785 /* drap: mov %drap, disp(%rbp) */
1786 cfa->base = CFI_BP_INDIRECT;
1787 cfa->offset = op->dest.offset;
1788
1789 /* save drap offset so we know when to restore it */
1790 state->drap_offset = op->dest.offset;
1791 }
1792
1793 else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1794
1795 /* drap: mov reg, disp(%rbp) */
1796 save_reg(state, op->src.reg, CFI_BP, op->dest.offset);
1797 }
1798
1799 } else if (op->dest.reg == cfa->base) {
1800
1801 /* mov reg, disp(%rbp) */
1802 /* mov reg, disp(%rsp) */
1803 save_reg(state, op->src.reg, CFI_CFA,
1804 op->dest.offset - state->cfa.offset);
1805 }
1806
1807 break;
1808
1809 case OP_DEST_LEAVE:
1810 if ((!state->drap && cfa->base != CFI_BP) ||
1811 (state->drap && cfa->base != state->drap_reg)) {
1812 WARN_FUNC("leave instruction with modified stack frame",
1813 insn->sec, insn->offset);
1814 return -1;
1815 }
1816
1817 /* leave (mov %rbp, %rsp; pop %rbp) */
1818
1819 state->stack_size = -state->regs[CFI_BP].offset - 8;
1820 restore_reg(state, CFI_BP);
1821
1822 if (!state->drap) {
1823 cfa->base = CFI_SP;
1824 cfa->offset -= 8;
1825 }
1826
1827 break;
1828
1829 case OP_DEST_MEM:
1830 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
1831 WARN_FUNC("unknown stack-related memory operation",
1832 insn->sec, insn->offset);
1833 return -1;
1834 }
1835
1836 /* pop mem */
1837 state->stack_size -= 8;
1838 if (cfa->base == CFI_SP)
1839 cfa->offset -= 8;
1840
1841 break;
1842
1843 default:
1844 WARN_FUNC("unknown stack-related instruction",
1845 insn->sec, insn->offset);
1846 return -1;
1847 }
1848
1849 return 0;
1850 }
1851
1852 static bool insn_state_match(struct instruction *insn, struct insn_state *state)
1853 {
1854 struct insn_state *state1 = &insn->state, *state2 = state;
1855 int i;
1856
1857 if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
1858 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
1859 insn->sec, insn->offset,
1860 state1->cfa.base, state1->cfa.offset,
1861 state2->cfa.base, state2->cfa.offset);
1862
1863 } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
1864 for (i = 0; i < CFI_NUM_REGS; i++) {
1865 if (!memcmp(&state1->regs[i], &state2->regs[i],
1866 sizeof(struct cfi_reg)))
1867 continue;
1868
1869 WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
1870 insn->sec, insn->offset,
1871 i, state1->regs[i].base, state1->regs[i].offset,
1872 i, state2->regs[i].base, state2->regs[i].offset);
1873 break;
1874 }
1875
1876 } else if (state1->type != state2->type) {
1877 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
1878 insn->sec, insn->offset, state1->type, state2->type);
1879
1880 } else if (state1->drap != state2->drap ||
1881 (state1->drap && state1->drap_reg != state2->drap_reg) ||
1882 (state1->drap && state1->drap_offset != state2->drap_offset)) {
1883 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
1884 insn->sec, insn->offset,
1885 state1->drap, state1->drap_reg, state1->drap_offset,
1886 state2->drap, state2->drap_reg, state2->drap_offset);
1887
1888 } else
1889 return true;
1890
1891 return false;
1892 }
1893
1894 static inline bool func_uaccess_safe(struct symbol *func)
1895 {
1896 if (func)
1897 return func->uaccess_safe;
1898
1899 return false;
1900 }
1901
1902 static inline const char *call_dest_name(struct instruction *insn)
1903 {
1904 if (insn->call_dest)
1905 return insn->call_dest->name;
1906
1907 return "{dynamic}";
1908 }
1909
1910 static int validate_call(struct instruction *insn, struct insn_state *state)
1911 {
1912 if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
1913 WARN_FUNC("call to %s() with UACCESS enabled",
1914 insn->sec, insn->offset, call_dest_name(insn));
1915 return 1;
1916 }
1917
1918 if (state->df) {
1919 WARN_FUNC("call to %s() with DF set",
1920 insn->sec, insn->offset, call_dest_name(insn));
1921 return 1;
1922 }
1923
1924 return 0;
1925 }
1926
1927 static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
1928 {
1929 if (has_modified_stack_frame(state)) {
1930 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1931 insn->sec, insn->offset);
1932 return 1;
1933 }
1934
1935 return validate_call(insn, state);
1936 }
1937
1938 /*
1939 * Follow the branch starting at the given instruction, and recursively follow
1940 * any other branches (jumps). Meanwhile, track the frame pointer state at
1941 * each instruction and validate all the rules described in
1942 * tools/objtool/Documentation/stack-validation.txt.
1943 */
1944 static int validate_branch(struct objtool_file *file, struct symbol *func,
1945 struct instruction *first, struct insn_state state)
1946 {
1947 struct alternative *alt;
1948 struct instruction *insn, *next_insn;
1949 struct section *sec;
1950 u8 visited;
1951 int ret;
1952
1953 insn = first;
1954 sec = insn->sec;
1955
1956 if (insn->alt_group && list_empty(&insn->alts)) {
1957 WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
1958 sec, insn->offset);
1959 return 1;
1960 }
1961
1962 while (1) {
1963 next_insn = next_insn_same_sec(file, insn);
1964
1965 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
1966 WARN("%s() falls through to next function %s()",
1967 func->name, insn->func->name);
1968 return 1;
1969 }
1970
1971 if (func && insn->ignore) {
1972 WARN_FUNC("BUG: why am I validating an ignored function?",
1973 sec, insn->offset);
1974 return 1;
1975 }
1976
1977 visited = 1 << state.uaccess;
1978 if (insn->visited) {
1979 if (!insn->hint && !insn_state_match(insn, &state))
1980 return 1;
1981
1982 if (insn->visited & visited)
1983 return 0;
1984 }
1985
1986 if (insn->hint) {
1987 if (insn->restore) {
1988 struct instruction *save_insn, *i;
1989
1990 i = insn;
1991 save_insn = NULL;
1992 func_for_each_insn_continue_reverse(file, func, i) {
1993 if (i->save) {
1994 save_insn = i;
1995 break;
1996 }
1997 }
1998
1999 if (!save_insn) {
2000 WARN_FUNC("no corresponding CFI save for CFI restore",
2001 sec, insn->offset);
2002 return 1;
2003 }
2004
2005 if (!save_insn->visited) {
2006 /*
2007 * Oops, no state to copy yet.
2008 * Hopefully we can reach this
2009 * instruction from another branch
2010 * after the save insn has been
2011 * visited.
2012 */
2013 if (insn == first)
2014 return 0;
2015
2016 WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
2017 sec, insn->offset);
2018 return 1;
2019 }
2020
2021 insn->state = save_insn->state;
2022 }
2023
2024 state = insn->state;
2025
2026 } else
2027 insn->state = state;
2028
2029 insn->visited |= visited;
2030
2031 if (!insn->ignore_alts) {
2032 bool skip_orig = false;
2033
2034 list_for_each_entry(alt, &insn->alts, list) {
2035 if (alt->skip_orig)
2036 skip_orig = true;
2037
2038 ret = validate_branch(file, func, alt->insn, state);
2039 if (ret) {
2040 if (backtrace)
2041 BT_FUNC("(alt)", insn);
2042 return ret;
2043 }
2044 }
2045
2046 if (skip_orig)
2047 return 0;
2048 }
2049
2050 switch (insn->type) {
2051
2052 case INSN_RETURN:
2053 if (state.uaccess && !func_uaccess_safe(func)) {
2054 WARN_FUNC("return with UACCESS enabled", sec, insn->offset);
2055 return 1;
2056 }
2057
2058 if (!state.uaccess && func_uaccess_safe(func)) {
2059 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function", sec, insn->offset);
2060 return 1;
2061 }
2062
2063 if (state.df) {
2064 WARN_FUNC("return with DF set", sec, insn->offset);
2065 return 1;
2066 }
2067
2068 if (func && has_modified_stack_frame(&state)) {
2069 WARN_FUNC("return with modified stack frame",
2070 sec, insn->offset);
2071 return 1;
2072 }
2073
2074 if (state.bp_scratch) {
2075 WARN("%s uses BP as a scratch register",
2076 func->name);
2077 return 1;
2078 }
2079
2080 return 0;
2081
2082 case INSN_CALL:
2083 case INSN_CALL_DYNAMIC:
2084 ret = validate_call(insn, &state);
2085 if (ret)
2086 return ret;
2087
2088 if (!no_fp && func && !is_fentry_call(insn) &&
2089 !has_valid_stack_frame(&state)) {
2090 WARN_FUNC("call without frame pointer save/setup",
2091 sec, insn->offset);
2092 return 1;
2093 }
2094
2095 if (dead_end_function(file, insn->call_dest))
2096 return 0;
2097
2098 break;
2099
2100 case INSN_JUMP_CONDITIONAL:
2101 case INSN_JUMP_UNCONDITIONAL:
2102 if (func && is_sibling_call(insn)) {
2103 ret = validate_sibling_call(insn, &state);
2104 if (ret)
2105 return ret;
2106
2107 } else if (insn->jump_dest) {
2108 ret = validate_branch(file, func,
2109 insn->jump_dest, state);
2110 if (ret) {
2111 if (backtrace)
2112 BT_FUNC("(branch)", insn);
2113 return ret;
2114 }
2115 }
2116
2117 if (insn->type == INSN_JUMP_UNCONDITIONAL)
2118 return 0;
2119
2120 break;
2121
2122 case INSN_JUMP_DYNAMIC:
2123 case INSN_JUMP_DYNAMIC_CONDITIONAL:
2124 if (func && is_sibling_call(insn)) {
2125 ret = validate_sibling_call(insn, &state);
2126 if (ret)
2127 return ret;
2128 }
2129
2130 if (insn->type == INSN_JUMP_DYNAMIC)
2131 return 0;
2132
2133 break;
2134
2135 case INSN_CONTEXT_SWITCH:
2136 if (func && (!next_insn || !next_insn->hint)) {
2137 WARN_FUNC("unsupported instruction in callable function",
2138 sec, insn->offset);
2139 return 1;
2140 }
2141 return 0;
2142
2143 case INSN_STACK:
2144 if (update_insn_state(insn, &state))
2145 return 1;
2146
2147 if (insn->stack_op.dest.type == OP_DEST_PUSHF) {
2148 if (!state.uaccess_stack) {
2149 state.uaccess_stack = 1;
2150 } else if (state.uaccess_stack >> 31) {
2151 WARN_FUNC("PUSHF stack exhausted", sec, insn->offset);
2152 return 1;
2153 }
2154 state.uaccess_stack <<= 1;
2155 state.uaccess_stack |= state.uaccess;
2156 }
2157
2158 if (insn->stack_op.src.type == OP_SRC_POPF) {
2159 if (state.uaccess_stack) {
2160 state.uaccess = state.uaccess_stack & 1;
2161 state.uaccess_stack >>= 1;
2162 if (state.uaccess_stack == 1)
2163 state.uaccess_stack = 0;
2164 }
2165 }
2166
2167 break;
2168
2169 case INSN_STAC:
2170 if (state.uaccess) {
2171 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
2172 return 1;
2173 }
2174
2175 state.uaccess = true;
2176 break;
2177
2178 case INSN_CLAC:
2179 if (!state.uaccess && func) {
2180 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
2181 return 1;
2182 }
2183
2184 if (func_uaccess_safe(func) && !state.uaccess_stack) {
2185 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
2186 return 1;
2187 }
2188
2189 state.uaccess = false;
2190 break;
2191
2192 case INSN_STD:
2193 if (state.df)
2194 WARN_FUNC("recursive STD", sec, insn->offset);
2195
2196 state.df = true;
2197 break;
2198
2199 case INSN_CLD:
2200 if (!state.df && func)
2201 WARN_FUNC("redundant CLD", sec, insn->offset);
2202
2203 state.df = false;
2204 break;
2205
2206 default:
2207 break;
2208 }
2209
2210 if (insn->dead_end)
2211 return 0;
2212
2213 if (!next_insn) {
2214 if (state.cfa.base == CFI_UNDEFINED)
2215 return 0;
2216 WARN("%s: unexpected end of section", sec->name);
2217 return 1;
2218 }
2219
2220 insn = next_insn;
2221 }
2222
2223 return 0;
2224 }
2225
2226 static int validate_unwind_hints(struct objtool_file *file)
2227 {
2228 struct instruction *insn;
2229 int ret, warnings = 0;
2230 struct insn_state state;
2231
2232 if (!file->hints)
2233 return 0;
2234
2235 clear_insn_state(&state);
2236
2237 for_each_insn(file, insn) {
2238 if (insn->hint && !insn->visited) {
2239 ret = validate_branch(file, insn->func, insn, state);
2240 if (ret && backtrace)
2241 BT_FUNC("<=== (hint)", insn);
2242 warnings += ret;
2243 }
2244 }
2245
2246 return warnings;
2247 }
2248
2249 static int validate_retpoline(struct objtool_file *file)
2250 {
2251 struct instruction *insn;
2252 int warnings = 0;
2253
2254 for_each_insn(file, insn) {
2255 if (insn->type != INSN_JUMP_DYNAMIC &&
2256 insn->type != INSN_CALL_DYNAMIC)
2257 continue;
2258
2259 if (insn->retpoline_safe)
2260 continue;
2261
2262 /*
2263 * .init.text code is ran before userspace and thus doesn't
2264 * strictly need retpolines, except for modules which are
2265 * loaded late, they very much do need retpoline in their
2266 * .init.text
2267 */
2268 if (!strcmp(insn->sec->name, ".init.text") && !module)
2269 continue;
2270
2271 WARN_FUNC("indirect %s found in RETPOLINE build",
2272 insn->sec, insn->offset,
2273 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
2274
2275 warnings++;
2276 }
2277
2278 return warnings;
2279 }
2280
2281 static bool is_kasan_insn(struct instruction *insn)
2282 {
2283 return (insn->type == INSN_CALL &&
2284 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
2285 }
2286
2287 static bool is_ubsan_insn(struct instruction *insn)
2288 {
2289 return (insn->type == INSN_CALL &&
2290 !strcmp(insn->call_dest->name,
2291 "__ubsan_handle_builtin_unreachable"));
2292 }
2293
2294 static bool ignore_unreachable_insn(struct instruction *insn)
2295 {
2296 int i;
2297
2298 if (insn->ignore || insn->type == INSN_NOP)
2299 return true;
2300
2301 /*
2302 * Ignore any unused exceptions. This can happen when a whitelisted
2303 * function has an exception table entry.
2304 *
2305 * Also ignore alternative replacement instructions. This can happen
2306 * when a whitelisted function uses one of the ALTERNATIVE macros.
2307 */
2308 if (!strcmp(insn->sec->name, ".fixup") ||
2309 !strcmp(insn->sec->name, ".altinstr_replacement") ||
2310 !strcmp(insn->sec->name, ".altinstr_aux"))
2311 return true;
2312
2313 /*
2314 * Check if this (or a subsequent) instruction is related to
2315 * CONFIG_UBSAN or CONFIG_KASAN.
2316 *
2317 * End the search at 5 instructions to avoid going into the weeds.
2318 */
2319 if (!insn->func)
2320 return false;
2321 for (i = 0; i < 5; i++) {
2322
2323 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
2324 return true;
2325
2326 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
2327 if (insn->jump_dest &&
2328 insn->jump_dest->func == insn->func) {
2329 insn = insn->jump_dest;
2330 continue;
2331 }
2332
2333 break;
2334 }
2335
2336 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
2337 break;
2338
2339 insn = list_next_entry(insn, list);
2340 }
2341
2342 return false;
2343 }
2344
2345 static int validate_functions(struct objtool_file *file)
2346 {
2347 struct section *sec;
2348 struct symbol *func;
2349 struct instruction *insn;
2350 struct insn_state state;
2351 int ret, warnings = 0;
2352
2353 clear_insn_state(&state);
2354
2355 state.cfa = initial_func_cfi.cfa;
2356 memcpy(&state.regs, &initial_func_cfi.regs,
2357 CFI_NUM_REGS * sizeof(struct cfi_reg));
2358 state.stack_size = initial_func_cfi.cfa.offset;
2359
2360 for_each_sec(file, sec) {
2361 list_for_each_entry(func, &sec->symbol_list, list) {
2362 if (func->type != STT_FUNC)
2363 continue;
2364
2365 if (!func->len) {
2366 WARN("%s() is missing an ELF size annotation",
2367 func->name);
2368 warnings++;
2369 }
2370
2371 if (func->pfunc != func || func->alias != func)
2372 continue;
2373
2374 insn = find_insn(file, sec, func->offset);
2375 if (!insn || insn->ignore || insn->visited)
2376 continue;
2377
2378 state.uaccess = func->uaccess_safe;
2379
2380 ret = validate_branch(file, func, insn, state);
2381 if (ret && backtrace)
2382 BT_FUNC("<=== (func)", insn);
2383 warnings += ret;
2384 }
2385 }
2386
2387 return warnings;
2388 }
2389
2390 static int validate_reachable_instructions(struct objtool_file *file)
2391 {
2392 struct instruction *insn;
2393
2394 if (file->ignore_unreachables)
2395 return 0;
2396
2397 for_each_insn(file, insn) {
2398 if (insn->visited || ignore_unreachable_insn(insn))
2399 continue;
2400
2401 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
2402 return 1;
2403 }
2404
2405 return 0;
2406 }
2407
2408 static void cleanup(struct objtool_file *file)
2409 {
2410 struct instruction *insn, *tmpinsn;
2411 struct alternative *alt, *tmpalt;
2412
2413 list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) {
2414 list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) {
2415 list_del(&alt->list);
2416 free(alt);
2417 }
2418 list_del(&insn->list);
2419 hash_del(&insn->hash);
2420 free(insn);
2421 }
2422 elf_close(file->elf);
2423 }
2424
2425 static struct objtool_file file;
2426
2427 int check(const char *_objname, bool orc)
2428 {
2429 int ret, warnings = 0;
2430
2431 objname = _objname;
2432
2433 file.elf = elf_read(objname, orc ? O_RDWR : O_RDONLY);
2434 if (!file.elf)
2435 return 1;
2436
2437 INIT_LIST_HEAD(&file.insn_list);
2438 hash_init(file.insn_hash);
2439 file.c_file = find_section_by_name(file.elf, ".comment");
2440 file.ignore_unreachables = no_unreachable;
2441 file.hints = false;
2442
2443 arch_initial_func_cfi_state(&initial_func_cfi);
2444
2445 ret = decode_sections(&file);
2446 if (ret < 0)
2447 goto out;
2448 warnings += ret;
2449
2450 if (list_empty(&file.insn_list))
2451 goto out;
2452
2453 if (retpoline) {
2454 ret = validate_retpoline(&file);
2455 if (ret < 0)
2456 return ret;
2457 warnings += ret;
2458 }
2459
2460 ret = validate_functions(&file);
2461 if (ret < 0)
2462 goto out;
2463 warnings += ret;
2464
2465 ret = validate_unwind_hints(&file);
2466 if (ret < 0)
2467 goto out;
2468 warnings += ret;
2469
2470 if (!warnings) {
2471 ret = validate_reachable_instructions(&file);
2472 if (ret < 0)
2473 goto out;
2474 warnings += ret;
2475 }
2476
2477 if (orc) {
2478 ret = create_orc(&file);
2479 if (ret < 0)
2480 goto out;
2481
2482 ret = create_orc_sections(&file);
2483 if (ret < 0)
2484 goto out;
2485
2486 ret = elf_write(file.elf);
2487 if (ret < 0)
2488 goto out;
2489 }
2490
2491 out:
2492 cleanup(&file);
2493
2494 /* ignore warnings for now until we get all the code cleaned up */
2495 if (ret || warnings)
2496 return 0;
2497 return 0;
2498 }
Linux with added FPC-III support