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authorJosh Poimboeuf <jpoimboe@redhat.com>2017-06-28 11:11:05 -0400
committerIngo Molnar <mingo@kernel.org>2017-06-30 04:19:19 -0400
commitdcc914f44f065ef73685b37e59877a5bb3cb7358 (patch)
tree38ec8f7dee26ae770a14dcb7cb8563cd49b81074 /tools/objtool
parent4d8a991d460d4fa4829beaffdcba45a217ca0fa7 (diff)
objtool: Move checking code to check.c
In preparation for the new 'objtool undwarf generate' command, which will rely on 'objtool check', move the checking code from builtin-check.c to check.c where it can be used by other commands. Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Reviewed-by: Jiri Slaby <jslaby@suse.cz> Cc: Andy Lutomirski <luto@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: live-patching@vger.kernel.org Link: http://lkml.kernel.org/r/294c5c695fd73c1a5000bbe5960a7c9bec4ee6b4.1498659915.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'tools/objtool')
-rw-r--r--tools/objtool/Build1
-rw-r--r--tools/objtool/builtin-check.c1281
-rw-r--r--tools/objtool/check.c1263
-rw-r--r--tools/objtool/check.h51
4 files changed, 1328 insertions, 1268 deletions
diff --git a/tools/objtool/Build b/tools/objtool/Build
index d6cdece5e58b..6f2e1987c4d9 100644
--- a/tools/objtool/Build
+++ b/tools/objtool/Build
@@ -1,5 +1,6 @@
1objtool-y += arch/$(SRCARCH)/ 1objtool-y += arch/$(SRCARCH)/
2objtool-y += builtin-check.o 2objtool-y += builtin-check.o
3objtool-y += check.o
3objtool-y += elf.o 4objtool-y += elf.o
4objtool-y += special.o 5objtool-y += special.o
5objtool-y += objtool.o 6objtool-y += objtool.o
diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index 5f66697fe1e0..365c34ecab26 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -1,5 +1,5 @@
1/* 1/*
2 * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com> 2 * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
3 * 3 *
4 * This program is free software; you can redistribute it and/or 4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License 5 * modify it under the terms of the GNU General Public License
@@ -25,1287 +25,32 @@
25 * For more information, see tools/objtool/Documentation/stack-validation.txt. 25 * For more information, see tools/objtool/Documentation/stack-validation.txt.
26 */ 26 */
27 27
28#include <string.h>
29#include <stdlib.h>
30#include <subcmd/parse-options.h> 28#include <subcmd/parse-options.h>
31
32#include "builtin.h" 29#include "builtin.h"
33#include "elf.h" 30#include "check.h"
34#include "special.h"
35#include "arch.h"
36#include "warn.h"
37
38#include <linux/hashtable.h>
39#include <linux/kernel.h>
40
41#define STATE_FP_SAVED 0x1
42#define STATE_FP_SETUP 0x2
43#define STATE_FENTRY 0x4
44
45struct instruction {
46 struct list_head list;
47 struct hlist_node hash;
48 struct section *sec;
49 unsigned long offset;
50 unsigned int len, state;
51 unsigned char type;
52 unsigned long immediate;
53 bool alt_group, visited, dead_end;
54 struct symbol *call_dest;
55 struct instruction *jump_dest;
56 struct list_head alts;
57 struct symbol *func;
58};
59
60struct alternative {
61 struct list_head list;
62 struct instruction *insn;
63};
64
65struct objtool_file {
66 struct elf *elf;
67 struct list_head insn_list;
68 DECLARE_HASHTABLE(insn_hash, 16);
69 struct section *rodata, *whitelist;
70 bool ignore_unreachables, c_file;
71};
72
73const char *objname;
74static bool nofp;
75
76static struct instruction *find_insn(struct objtool_file *file,
77 struct section *sec, unsigned long offset)
78{
79 struct instruction *insn;
80
81 hash_for_each_possible(file->insn_hash, insn, hash, offset)
82 if (insn->sec == sec && insn->offset == offset)
83 return insn;
84
85 return NULL;
86}
87
88static struct instruction *next_insn_same_sec(struct objtool_file *file,
89 struct instruction *insn)
90{
91 struct instruction *next = list_next_entry(insn, list);
92
93 if (&next->list == &file->insn_list || next->sec != insn->sec)
94 return NULL;
95
96 return next;
97}
98
99static bool gcov_enabled(struct objtool_file *file)
100{
101 struct section *sec;
102 struct symbol *sym;
103
104 list_for_each_entry(sec, &file->elf->sections, list)
105 list_for_each_entry(sym, &sec->symbol_list, list)
106 if (!strncmp(sym->name, "__gcov_.", 8))
107 return true;
108
109 return false;
110}
111
112#define for_each_insn(file, insn) \
113 list_for_each_entry(insn, &file->insn_list, list)
114
115#define func_for_each_insn(file, func, insn) \
116 for (insn = find_insn(file, func->sec, func->offset); \
117 insn && &insn->list != &file->insn_list && \
118 insn->sec == func->sec && \
119 insn->offset < func->offset + func->len; \
120 insn = list_next_entry(insn, list))
121
122#define func_for_each_insn_continue_reverse(file, func, insn) \
123 for (insn = list_prev_entry(insn, list); \
124 &insn->list != &file->insn_list && \
125 insn->sec == func->sec && insn->offset >= func->offset; \
126 insn = list_prev_entry(insn, list))
127
128#define sec_for_each_insn_from(file, insn) \
129 for (; insn; insn = next_insn_same_sec(file, insn))
130
131
132/*
133 * Check if the function has been manually whitelisted with the
134 * STACK_FRAME_NON_STANDARD macro, or if it should be automatically whitelisted
135 * due to its use of a context switching instruction.
136 */
137static bool ignore_func(struct objtool_file *file, struct symbol *func)
138{
139 struct rela *rela;
140 struct instruction *insn;
141
142 /* check for STACK_FRAME_NON_STANDARD */
143 if (file->whitelist && file->whitelist->rela)
144 list_for_each_entry(rela, &file->whitelist->rela->rela_list, list) {
145 if (rela->sym->type == STT_SECTION &&
146 rela->sym->sec == func->sec &&
147 rela->addend == func->offset)
148 return true;
149 if (rela->sym->type == STT_FUNC && rela->sym == func)
150 return true;
151 }
152
153 /* check if it has a context switching instruction */
154 func_for_each_insn(file, func, insn)
155 if (insn->type == INSN_CONTEXT_SWITCH)
156 return true;
157
158 return false;
159}
160
161/*
162 * This checks to see if the given function is a "noreturn" function.
163 *
164 * For global functions which are outside the scope of this object file, we
165 * have to keep a manual list of them.
166 *
167 * For local functions, we have to detect them manually by simply looking for
168 * the lack of a return instruction.
169 *
170 * Returns:
171 * -1: error
172 * 0: no dead end
173 * 1: dead end
174 */
175static int __dead_end_function(struct objtool_file *file, struct symbol *func,
176 int recursion)
177{
178 int i;
179 struct instruction *insn;
180 bool empty = true;
181
182 /*
183 * Unfortunately these have to be hard coded because the noreturn
184 * attribute isn't provided in ELF data.
185 */
186 static const char * const global_noreturns[] = {
187 "__stack_chk_fail",
188 "panic",
189 "do_exit",
190 "do_task_dead",
191 "__module_put_and_exit",
192 "complete_and_exit",
193 "kvm_spurious_fault",
194 "__reiserfs_panic",
195 "lbug_with_loc",
196 "fortify_panic",
197 };
198
199 if (func->bind == STB_WEAK)
200 return 0;
201
202 if (func->bind == STB_GLOBAL)
203 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
204 if (!strcmp(func->name, global_noreturns[i]))
205 return 1;
206
207 if (!func->sec)
208 return 0;
209
210 func_for_each_insn(file, func, insn) {
211 empty = false;
212
213 if (insn->type == INSN_RETURN)
214 return 0;
215 }
216
217 if (empty)
218 return 0;
219
220 /*
221 * A function can have a sibling call instead of a return. In that
222 * case, the function's dead-end status depends on whether the target
223 * of the sibling call returns.
224 */
225 func_for_each_insn(file, func, insn) {
226 if (insn->sec != func->sec ||
227 insn->offset >= func->offset + func->len)
228 break;
229
230 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
231 struct instruction *dest = insn->jump_dest;
232 struct symbol *dest_func;
233
234 if (!dest)
235 /* sibling call to another file */
236 return 0;
237
238 if (dest->sec != func->sec ||
239 dest->offset < func->offset ||
240 dest->offset >= func->offset + func->len) {
241 /* local sibling call */
242 dest_func = find_symbol_by_offset(dest->sec,
243 dest->offset);
244 if (!dest_func)
245 continue;
246
247 if (recursion == 5) {
248 WARN_FUNC("infinite recursion (objtool bug!)",
249 dest->sec, dest->offset);
250 return -1;
251 }
252
253 return __dead_end_function(file, dest_func,
254 recursion + 1);
255 }
256 }
257
258 if (insn->type == INSN_JUMP_DYNAMIC && list_empty(&insn->alts))
259 /* sibling call */
260 return 0;
261 }
262
263 return 1;
264}
265
266static int dead_end_function(struct objtool_file *file, struct symbol *func)
267{
268 return __dead_end_function(file, func, 0);
269}
270
271/*
272 * Call the arch-specific instruction decoder for all the instructions and add
273 * them to the global instruction list.
274 */
275static int decode_instructions(struct objtool_file *file)
276{
277 struct section *sec;
278 struct symbol *func;
279 unsigned long offset;
280 struct instruction *insn;
281 int ret;
282
283 list_for_each_entry(sec, &file->elf->sections, list) {
284
285 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
286 continue;
287
288 for (offset = 0; offset < sec->len; offset += insn->len) {
289 insn = malloc(sizeof(*insn));
290 memset(insn, 0, sizeof(*insn));
291
292 INIT_LIST_HEAD(&insn->alts);
293 insn->sec = sec;
294 insn->offset = offset;
295
296 ret = arch_decode_instruction(file->elf, sec, offset,
297 sec->len - offset,
298 &insn->len, &insn->type,
299 &insn->immediate);
300 if (ret)
301 return ret;
302
303 if (!insn->type || insn->type > INSN_LAST) {
304 WARN_FUNC("invalid instruction type %d",
305 insn->sec, insn->offset, insn->type);
306 return -1;
307 }
308
309 hash_add(file->insn_hash, &insn->hash, insn->offset);
310 list_add_tail(&insn->list, &file->insn_list);
311 }
312
313 list_for_each_entry(func, &sec->symbol_list, list) {
314 if (func->type != STT_FUNC)
315 continue;
316
317 if (!find_insn(file, sec, func->offset)) {
318 WARN("%s(): can't find starting instruction",
319 func->name);
320 return -1;
321 }
322
323 func_for_each_insn(file, func, insn)
324 if (!insn->func)
325 insn->func = func;
326 }
327 }
328
329 return 0;
330}
331
332/*
333 * Find all uses of the unreachable() macro, which are code path dead ends.
334 */
335static int add_dead_ends(struct objtool_file *file)
336{
337 struct section *sec;
338 struct rela *rela;
339 struct instruction *insn;
340 bool found;
341
342 sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
343 if (!sec)
344 return 0;
345
346 list_for_each_entry(rela, &sec->rela_list, list) {
347 if (rela->sym->type != STT_SECTION) {
348 WARN("unexpected relocation symbol type in %s", sec->name);
349 return -1;
350 }
351 insn = find_insn(file, rela->sym->sec, rela->addend);
352 if (insn)
353 insn = list_prev_entry(insn, list);
354 else if (rela->addend == rela->sym->sec->len) {
355 found = false;
356 list_for_each_entry_reverse(insn, &file->insn_list, list) {
357 if (insn->sec == rela->sym->sec) {
358 found = true;
359 break;
360 }
361 }
362
363 if (!found) {
364 WARN("can't find unreachable insn at %s+0x%x",
365 rela->sym->sec->name, rela->addend);
366 return -1;
367 }
368 } else {
369 WARN("can't find unreachable insn at %s+0x%x",
370 rela->sym->sec->name, rela->addend);
371 return -1;
372 }
373
374 insn->dead_end = true;
375 }
376
377 return 0;
378}
379
380/*
381 * Warnings shouldn't be reported for ignored functions.
382 */
383static void add_ignores(struct objtool_file *file)
384{
385 struct instruction *insn;
386 struct section *sec;
387 struct symbol *func;
388
389 list_for_each_entry(sec, &file->elf->sections, list) {
390 list_for_each_entry(func, &sec->symbol_list, list) {
391 if (func->type != STT_FUNC)
392 continue;
393
394 if (!ignore_func(file, func))
395 continue;
396
397 func_for_each_insn(file, func, insn)
398 insn->visited = true;
399 }
400 }
401}
402
403/*
404 * Find the destination instructions for all jumps.
405 */
406static int add_jump_destinations(struct objtool_file *file)
407{
408 struct instruction *insn;
409 struct rela *rela;
410 struct section *dest_sec;
411 unsigned long dest_off;
412
413 for_each_insn(file, insn) {
414 if (insn->type != INSN_JUMP_CONDITIONAL &&
415 insn->type != INSN_JUMP_UNCONDITIONAL)
416 continue;
417
418 /* skip ignores */
419 if (insn->visited)
420 continue;
421
422 rela = find_rela_by_dest_range(insn->sec, insn->offset,
423 insn->len);
424 if (!rela) {
425 dest_sec = insn->sec;
426 dest_off = insn->offset + insn->len + insn->immediate;
427 } else if (rela->sym->type == STT_SECTION) {
428 dest_sec = rela->sym->sec;
429 dest_off = rela->addend + 4;
430 } else if (rela->sym->sec->idx) {
431 dest_sec = rela->sym->sec;
432 dest_off = rela->sym->sym.st_value + rela->addend + 4;
433 } else {
434 /* sibling call */
435 insn->jump_dest = 0;
436 continue;
437 }
438
439 insn->jump_dest = find_insn(file, dest_sec, dest_off);
440 if (!insn->jump_dest) {
441
442 /*
443 * This is a special case where an alt instruction
444 * jumps past the end of the section. These are
445 * handled later in handle_group_alt().
446 */
447 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
448 continue;
449
450 WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
451 insn->sec, insn->offset, dest_sec->name,
452 dest_off);
453 return -1;
454 }
455 }
456
457 return 0;
458}
459
460/*
461 * Find the destination instructions for all calls.
462 */
463static int add_call_destinations(struct objtool_file *file)
464{
465 struct instruction *insn;
466 unsigned long dest_off;
467 struct rela *rela;
468
469 for_each_insn(file, insn) {
470 if (insn->type != INSN_CALL)
471 continue;
472
473 rela = find_rela_by_dest_range(insn->sec, insn->offset,
474 insn->len);
475 if (!rela) {
476 dest_off = insn->offset + insn->len + insn->immediate;
477 insn->call_dest = find_symbol_by_offset(insn->sec,
478 dest_off);
479 if (!insn->call_dest) {
480 WARN_FUNC("can't find call dest symbol at offset 0x%lx",
481 insn->sec, insn->offset, dest_off);
482 return -1;
483 }
484 } else if (rela->sym->type == STT_SECTION) {
485 insn->call_dest = find_symbol_by_offset(rela->sym->sec,
486 rela->addend+4);
487 if (!insn->call_dest ||
488 insn->call_dest->type != STT_FUNC) {
489 WARN_FUNC("can't find call dest symbol at %s+0x%x",
490 insn->sec, insn->offset,
491 rela->sym->sec->name,
492 rela->addend + 4);
493 return -1;
494 }
495 } else
496 insn->call_dest = rela->sym;
497 }
498
499 return 0;
500}
501
502/*
503 * The .alternatives section requires some extra special care, over and above
504 * what other special sections require:
505 *
506 * 1. Because alternatives are patched in-place, we need to insert a fake jump
507 * instruction at the end so that validate_branch() skips all the original
508 * replaced instructions when validating the new instruction path.
509 *
510 * 2. An added wrinkle is that the new instruction length might be zero. In
511 * that case the old instructions are replaced with noops. We simulate that
512 * by creating a fake jump as the only new instruction.
513 *
514 * 3. In some cases, the alternative section includes an instruction which
515 * conditionally jumps to the _end_ of the entry. We have to modify these
516 * jumps' destinations to point back to .text rather than the end of the
517 * entry in .altinstr_replacement.
518 *
519 * 4. It has been requested that we don't validate the !POPCNT feature path
520 * which is a "very very small percentage of machines".
521 */
522static int handle_group_alt(struct objtool_file *file,
523 struct special_alt *special_alt,
524 struct instruction *orig_insn,
525 struct instruction **new_insn)
526{
527 struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump;
528 unsigned long dest_off;
529
530 last_orig_insn = NULL;
531 insn = orig_insn;
532 sec_for_each_insn_from(file, insn) {
533 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
534 break;
535
536 if (special_alt->skip_orig)
537 insn->type = INSN_NOP;
538
539 insn->alt_group = true;
540 last_orig_insn = insn;
541 }
542
543 if (!next_insn_same_sec(file, last_orig_insn)) {
544 WARN("%s: don't know how to handle alternatives at end of section",
545 special_alt->orig_sec->name);
546 return -1;
547 }
548
549 fake_jump = malloc(sizeof(*fake_jump));
550 if (!fake_jump) {
551 WARN("malloc failed");
552 return -1;
553 }
554 memset(fake_jump, 0, sizeof(*fake_jump));
555 INIT_LIST_HEAD(&fake_jump->alts);
556 fake_jump->sec = special_alt->new_sec;
557 fake_jump->offset = -1;
558 fake_jump->type = INSN_JUMP_UNCONDITIONAL;
559 fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
560
561 if (!special_alt->new_len) {
562 *new_insn = fake_jump;
563 return 0;
564 }
565
566 last_new_insn = NULL;
567 insn = *new_insn;
568 sec_for_each_insn_from(file, insn) {
569 if (insn->offset >= special_alt->new_off + special_alt->new_len)
570 break;
571
572 last_new_insn = insn;
573
574 if (insn->type != INSN_JUMP_CONDITIONAL &&
575 insn->type != INSN_JUMP_UNCONDITIONAL)
576 continue;
577
578 if (!insn->immediate)
579 continue;
580
581 dest_off = insn->offset + insn->len + insn->immediate;
582 if (dest_off == special_alt->new_off + special_alt->new_len)
583 insn->jump_dest = fake_jump;
584
585 if (!insn->jump_dest) {
586 WARN_FUNC("can't find alternative jump destination",
587 insn->sec, insn->offset);
588 return -1;
589 }
590 }
591
592 if (!last_new_insn) {
593 WARN_FUNC("can't find last new alternative instruction",
594 special_alt->new_sec, special_alt->new_off);
595 return -1;
596 }
597
598 list_add(&fake_jump->list, &last_new_insn->list);
599
600 return 0;
601}
602
603/*
604 * A jump table entry can either convert a nop to a jump or a jump to a nop.
605 * If the original instruction is a jump, make the alt entry an effective nop
606 * by just skipping the original instruction.
607 */
608static int handle_jump_alt(struct objtool_file *file,
609 struct special_alt *special_alt,
610 struct instruction *orig_insn,
611 struct instruction **new_insn)
612{
613 if (orig_insn->type == INSN_NOP)
614 return 0;
615
616 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
617 WARN_FUNC("unsupported instruction at jump label",
618 orig_insn->sec, orig_insn->offset);
619 return -1;
620 }
621
622 *new_insn = list_next_entry(orig_insn, list);
623 return 0;
624}
625
626/*
627 * Read all the special sections which have alternate instructions which can be
628 * patched in or redirected to at runtime. Each instruction having alternate
629 * instruction(s) has them added to its insn->alts list, which will be
630 * traversed in validate_branch().
631 */
632static int add_special_section_alts(struct objtool_file *file)
633{
634 struct list_head special_alts;
635 struct instruction *orig_insn, *new_insn;
636 struct special_alt *special_alt, *tmp;
637 struct alternative *alt;
638 int ret;
639
640 ret = special_get_alts(file->elf, &special_alts);
641 if (ret)
642 return ret;
643
644 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
645 alt = malloc(sizeof(*alt));
646 if (!alt) {
647 WARN("malloc failed");
648 ret = -1;
649 goto out;
650 }
651
652 orig_insn = find_insn(file, special_alt->orig_sec,
653 special_alt->orig_off);
654 if (!orig_insn) {
655 WARN_FUNC("special: can't find orig instruction",
656 special_alt->orig_sec, special_alt->orig_off);
657 ret = -1;
658 goto out;
659 }
660 31
661 new_insn = NULL; 32bool nofp;
662 if (!special_alt->group || special_alt->new_len) {
663 new_insn = find_insn(file, special_alt->new_sec,
664 special_alt->new_off);
665 if (!new_insn) {
666 WARN_FUNC("special: can't find new instruction",
667 special_alt->new_sec,
668 special_alt->new_off);
669 ret = -1;
670 goto out;
671 }
672 }
673 33
674 if (special_alt->group) { 34static const char * const check_usage[] = {
675 ret = handle_group_alt(file, special_alt, orig_insn,
676 &new_insn);
677 if (ret)
678 goto out;
679 } else if (special_alt->jump_or_nop) {
680 ret = handle_jump_alt(file, special_alt, orig_insn,
681 &new_insn);
682 if (ret)
683 goto out;
684 }
685
686 alt->insn = new_insn;
687 list_add_tail(&alt->list, &orig_insn->alts);
688
689 list_del(&special_alt->list);
690 free(special_alt);
691 }
692
693out:
694 return ret;
695}
696
697static int add_switch_table(struct objtool_file *file, struct symbol *func,
698 struct instruction *insn, struct rela *table,
699 struct rela *next_table)
700{
701 struct rela *rela = table;
702 struct instruction *alt_insn;
703 struct alternative *alt;
704
705 list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) {
706 if (rela == next_table)
707 break;
708
709 if (rela->sym->sec != insn->sec ||
710 rela->addend <= func->offset ||
711 rela->addend >= func->offset + func->len)
712 break;
713
714 alt_insn = find_insn(file, insn->sec, rela->addend);
715 if (!alt_insn) {
716 WARN("%s: can't find instruction at %s+0x%x",
717 file->rodata->rela->name, insn->sec->name,
718 rela->addend);
719 return -1;
720 }
721
722 alt = malloc(sizeof(*alt));
723 if (!alt) {
724 WARN("malloc failed");
725 return -1;
726 }
727
728 alt->insn = alt_insn;
729 list_add_tail(&alt->list, &insn->alts);
730 }
731
732 return 0;
733}
734
735/*
736 * find_switch_table() - Given a dynamic jump, find the switch jump table in
737 * .rodata associated with it.
738 *
739 * There are 3 basic patterns:
740 *
741 * 1. jmpq *[rodata addr](,%reg,8)
742 *
743 * This is the most common case by far. It jumps to an address in a simple
744 * jump table which is stored in .rodata.
745 *
746 * 2. jmpq *[rodata addr](%rip)
747 *
748 * This is caused by a rare GCC quirk, currently only seen in three driver
749 * functions in the kernel, only with certain obscure non-distro configs.
750 *
751 * As part of an optimization, GCC makes a copy of an existing switch jump
752 * table, modifies it, and then hard-codes the jump (albeit with an indirect
753 * jump) to use a single entry in the table. The rest of the jump table and
754 * some of its jump targets remain as dead code.
755 *
756 * In such a case we can just crudely ignore all unreachable instruction
757 * warnings for the entire object file. Ideally we would just ignore them
758 * for the function, but that would require redesigning the code quite a
759 * bit. And honestly that's just not worth doing: unreachable instruction
760 * warnings are of questionable value anyway, and this is such a rare issue.
761 *
762 * 3. mov [rodata addr],%reg1
763 * ... some instructions ...
764 * jmpq *(%reg1,%reg2,8)
765 *
766 * This is a fairly uncommon pattern which is new for GCC 6. As of this
767 * writing, there are 11 occurrences of it in the allmodconfig kernel.
768 *
769 * TODO: Once we have DWARF CFI and smarter instruction decoding logic,
770 * ensure the same register is used in the mov and jump instructions.
771 */
772static struct rela *find_switch_table(struct objtool_file *file,
773 struct symbol *func,
774 struct instruction *insn)
775{
776 struct rela *text_rela, *rodata_rela;
777 struct instruction *orig_insn = insn;
778
779 text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len);
780 if (text_rela && text_rela->sym == file->rodata->sym) {
781 /* case 1 */
782 rodata_rela = find_rela_by_dest(file->rodata,
783 text_rela->addend);
784 if (rodata_rela)
785 return rodata_rela;
786
787 /* case 2 */
788 rodata_rela = find_rela_by_dest(file->rodata,
789 text_rela->addend + 4);
790 if (!rodata_rela)
791 return NULL;
792 file->ignore_unreachables = true;
793 return rodata_rela;
794 }
795
796 /* case 3 */
797 func_for_each_insn_continue_reverse(file, func, insn) {
798 if (insn->type == INSN_JUMP_DYNAMIC)
799 break;
800
801 /* allow small jumps within the range */
802 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
803 insn->jump_dest &&
804 (insn->jump_dest->offset <= insn->offset ||
805 insn->jump_dest->offset > orig_insn->offset))
806 break;
807
808 /* look for a relocation which references .rodata */
809 text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
810 insn->len);
811 if (!text_rela || text_rela->sym != file->rodata->sym)
812 continue;
813
814 /*
815 * Make sure the .rodata address isn't associated with a
816 * symbol. gcc jump tables are anonymous data.
817 */
818 if (find_symbol_containing(file->rodata, text_rela->addend))
819 continue;
820
821 return find_rela_by_dest(file->rodata, text_rela->addend);
822 }
823
824 return NULL;
825}
826
827static int add_func_switch_tables(struct objtool_file *file,
828 struct symbol *func)
829{
830 struct instruction *insn, *prev_jump = NULL;
831 struct rela *rela, *prev_rela = NULL;
832 int ret;
833
834 func_for_each_insn(file, func, insn) {
835 if (insn->type != INSN_JUMP_DYNAMIC)
836 continue;
837
838 rela = find_switch_table(file, func, insn);
839 if (!rela)
840 continue;
841
842 /*
843 * We found a switch table, but we don't know yet how big it
844 * is. Don't add it until we reach the end of the function or
845 * the beginning of another switch table in the same function.
846 */
847 if (prev_jump) {
848 ret = add_switch_table(file, func, prev_jump, prev_rela,
849 rela);
850 if (ret)
851 return ret;
852 }
853
854 prev_jump = insn;
855 prev_rela = rela;
856 }
857
858 if (prev_jump) {
859 ret = add_switch_table(file, func, prev_jump, prev_rela, NULL);
860 if (ret)
861 return ret;
862 }
863
864 return 0;
865}
866
867/*
868 * For some switch statements, gcc generates a jump table in the .rodata
869 * section which contains a list of addresses within the function to jump to.
870 * This finds these jump tables and adds them to the insn->alts lists.
871 */
872static int add_switch_table_alts(struct objtool_file *file)
873{
874 struct section *sec;
875 struct symbol *func;
876 int ret;
877
878 if (!file->rodata || !file->rodata->rela)
879 return 0;
880
881 list_for_each_entry(sec, &file->elf->sections, list) {
882 list_for_each_entry(func, &sec->symbol_list, list) {
883 if (func->type != STT_FUNC)
884 continue;
885
886 ret = add_func_switch_tables(file, func);
887 if (ret)
888 return ret;
889 }
890 }
891
892 return 0;
893}
894
895static int decode_sections(struct objtool_file *file)
896{
897 int ret;
898
899 ret = decode_instructions(file);
900 if (ret)
901 return ret;
902
903 ret = add_dead_ends(file);
904 if (ret)
905 return ret;
906
907 add_ignores(file);
908
909 ret = add_jump_destinations(file);
910 if (ret)
911 return ret;
912
913 ret = add_call_destinations(file);
914 if (ret)
915 return ret;
916
917 ret = add_special_section_alts(file);
918 if (ret)
919 return ret;
920
921 ret = add_switch_table_alts(file);
922 if (ret)
923 return ret;
924
925 return 0;
926}
927
928static bool is_fentry_call(struct instruction *insn)
929{
930 if (insn->type == INSN_CALL &&
931 insn->call_dest->type == STT_NOTYPE &&
932 !strcmp(insn->call_dest->name, "__fentry__"))
933 return true;
934
935 return false;
936}
937
938static bool has_modified_stack_frame(struct instruction *insn)
939{
940 return (insn->state & STATE_FP_SAVED) ||
941 (insn->state & STATE_FP_SETUP);
942}
943
944static bool has_valid_stack_frame(struct instruction *insn)
945{
946 return (insn->state & STATE_FP_SAVED) &&
947 (insn->state & STATE_FP_SETUP);
948}
949
950static unsigned int frame_state(unsigned long state)
951{
952 return (state & (STATE_FP_SAVED | STATE_FP_SETUP));
953}
954
955/*
956 * Follow the branch starting at the given instruction, and recursively follow
957 * any other branches (jumps). Meanwhile, track the frame pointer state at
958 * each instruction and validate all the rules described in
959 * tools/objtool/Documentation/stack-validation.txt.
960 */
961static int validate_branch(struct objtool_file *file,
962 struct instruction *first, unsigned char first_state)
963{
964 struct alternative *alt;
965 struct instruction *insn;
966 struct section *sec;
967 struct symbol *func = NULL;
968 unsigned char state;
969 int ret;
970
971 insn = first;
972 sec = insn->sec;
973 state = first_state;
974
975 if (insn->alt_group && list_empty(&insn->alts)) {
976 WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
977 sec, insn->offset);
978 return 1;
979 }
980
981 while (1) {
982 if (file->c_file && insn->func) {
983 if (func && func != insn->func) {
984 WARN("%s() falls through to next function %s()",
985 func->name, insn->func->name);
986 return 1;
987 }
988
989 func = insn->func;
990 }
991
992 if (insn->visited) {
993 if (frame_state(insn->state) != frame_state(state)) {
994 WARN_FUNC("frame pointer state mismatch",
995 sec, insn->offset);
996 return 1;
997 }
998
999 return 0;
1000 }
1001
1002 insn->visited = true;
1003 insn->state = state;
1004
1005 list_for_each_entry(alt, &insn->alts, list) {
1006 ret = validate_branch(file, alt->insn, state);
1007 if (ret)
1008 return 1;
1009 }
1010
1011 switch (insn->type) {
1012
1013 case INSN_FP_SAVE:
1014 if (!nofp) {
1015 if (state & STATE_FP_SAVED) {
1016 WARN_FUNC("duplicate frame pointer save",
1017 sec, insn->offset);
1018 return 1;
1019 }
1020 state |= STATE_FP_SAVED;
1021 }
1022 break;
1023
1024 case INSN_FP_SETUP:
1025 if (!nofp) {
1026 if (state & STATE_FP_SETUP) {
1027 WARN_FUNC("duplicate frame pointer setup",
1028 sec, insn->offset);
1029 return 1;
1030 }
1031 state |= STATE_FP_SETUP;
1032 }
1033 break;
1034
1035 case INSN_FP_RESTORE:
1036 if (!nofp) {
1037 if (has_valid_stack_frame(insn))
1038 state &= ~STATE_FP_SETUP;
1039
1040 state &= ~STATE_FP_SAVED;
1041 }
1042 break;
1043
1044 case INSN_RETURN:
1045 if (!nofp && has_modified_stack_frame(insn)) {
1046 WARN_FUNC("return without frame pointer restore",
1047 sec, insn->offset);
1048 return 1;
1049 }
1050 return 0;
1051
1052 case INSN_CALL:
1053 if (is_fentry_call(insn)) {
1054 state |= STATE_FENTRY;
1055 break;
1056 }
1057
1058 ret = dead_end_function(file, insn->call_dest);
1059 if (ret == 1)
1060 return 0;
1061 if (ret == -1)
1062 return 1;
1063
1064 /* fallthrough */
1065 case INSN_CALL_DYNAMIC:
1066 if (!nofp && !has_valid_stack_frame(insn)) {
1067 WARN_FUNC("call without frame pointer save/setup",
1068 sec, insn->offset);
1069 return 1;
1070 }
1071 break;
1072
1073 case INSN_JUMP_CONDITIONAL:
1074 case INSN_JUMP_UNCONDITIONAL:
1075 if (insn->jump_dest) {
1076 ret = validate_branch(file, insn->jump_dest,
1077 state);
1078 if (ret)
1079 return 1;
1080 } else if (has_modified_stack_frame(insn)) {
1081 WARN_FUNC("sibling call from callable instruction with changed frame pointer",
1082 sec, insn->offset);
1083 return 1;
1084 } /* else it's a sibling call */
1085
1086 if (insn->type == INSN_JUMP_UNCONDITIONAL)
1087 return 0;
1088
1089 break;
1090
1091 case INSN_JUMP_DYNAMIC:
1092 if (list_empty(&insn->alts) &&
1093 has_modified_stack_frame(insn)) {
1094 WARN_FUNC("sibling call from callable instruction with changed frame pointer",
1095 sec, insn->offset);
1096 return 1;
1097 }
1098
1099 return 0;
1100
1101 default:
1102 break;
1103 }
1104
1105 if (insn->dead_end)
1106 return 0;
1107
1108 insn = next_insn_same_sec(file, insn);
1109 if (!insn) {
1110 WARN("%s: unexpected end of section", sec->name);
1111 return 1;
1112 }
1113 }
1114
1115 return 0;
1116}
1117
1118static bool is_kasan_insn(struct instruction *insn)
1119{
1120 return (insn->type == INSN_CALL &&
1121 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
1122}
1123
1124static bool is_ubsan_insn(struct instruction *insn)
1125{
1126 return (insn->type == INSN_CALL &&
1127 !strcmp(insn->call_dest->name,
1128 "__ubsan_handle_builtin_unreachable"));
1129}
1130
1131static bool ignore_unreachable_insn(struct symbol *func,
1132 struct instruction *insn)
1133{
1134 int i;
1135
1136 if (insn->type == INSN_NOP)
1137 return true;
1138
1139 /*
1140 * Check if this (or a subsequent) instruction is related to
1141 * CONFIG_UBSAN or CONFIG_KASAN.
1142 *
1143 * End the search at 5 instructions to avoid going into the weeds.
1144 */
1145 for (i = 0; i < 5; i++) {
1146
1147 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
1148 return true;
1149
1150 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest) {
1151 insn = insn->jump_dest;
1152 continue;
1153 }
1154
1155 if (insn->offset + insn->len >= func->offset + func->len)
1156 break;
1157 insn = list_next_entry(insn, list);
1158 }
1159
1160 return false;
1161}
1162
1163static int validate_functions(struct objtool_file *file)
1164{
1165 struct section *sec;
1166 struct symbol *func;
1167 struct instruction *insn;
1168 int ret, warnings = 0;
1169
1170 list_for_each_entry(sec, &file->elf->sections, list) {
1171 list_for_each_entry(func, &sec->symbol_list, list) {
1172 if (func->type != STT_FUNC)
1173 continue;
1174
1175 insn = find_insn(file, sec, func->offset);
1176 if (!insn)
1177 continue;
1178
1179 ret = validate_branch(file, insn, 0);
1180 warnings += ret;
1181 }
1182 }
1183
1184 list_for_each_entry(sec, &file->elf->sections, list) {
1185 list_for_each_entry(func, &sec->symbol_list, list) {
1186 if (func->type != STT_FUNC)
1187 continue;
1188
1189 func_for_each_insn(file, func, insn) {
1190 if (insn->visited)
1191 continue;
1192
1193 insn->visited = true;
1194
1195 if (file->ignore_unreachables || warnings ||
1196 ignore_unreachable_insn(func, insn))
1197 continue;
1198
1199 /*
1200 * gcov produces a lot of unreachable
1201 * instructions. If we get an unreachable
1202 * warning and the file has gcov enabled, just
1203 * ignore it, and all other such warnings for
1204 * the file.
1205 */
1206 if (!file->ignore_unreachables &&
1207 gcov_enabled(file)) {
1208 file->ignore_unreachables = true;
1209 continue;
1210 }
1211
1212 WARN_FUNC("function has unreachable instruction", insn->sec, insn->offset);
1213 warnings++;
1214 }
1215 }
1216 }
1217
1218 return warnings;
1219}
1220
1221static int validate_uncallable_instructions(struct objtool_file *file)
1222{
1223 struct instruction *insn;
1224 int warnings = 0;
1225
1226 for_each_insn(file, insn) {
1227 if (!insn->visited && insn->type == INSN_RETURN) {
1228 WARN_FUNC("return instruction outside of a callable function",
1229 insn->sec, insn->offset);
1230 warnings++;
1231 }
1232 }
1233
1234 return warnings;
1235}
1236
1237static void cleanup(struct objtool_file *file)
1238{
1239 struct instruction *insn, *tmpinsn;
1240 struct alternative *alt, *tmpalt;
1241
1242 list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) {
1243 list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) {
1244 list_del(&alt->list);
1245 free(alt);
1246 }
1247 list_del(&insn->list);
1248 hash_del(&insn->hash);
1249 free(insn);
1250 }
1251 elf_close(file->elf);
1252}
1253
1254const char * const check_usage[] = {
1255 "objtool check [<options>] file.o", 35 "objtool check [<options>] file.o",
1256 NULL, 36 NULL,
1257}; 37};
1258 38
39const struct option check_options[] = {
40 OPT_BOOLEAN('f', "no-fp", &nofp, "Skip frame pointer validation"),
41 OPT_END(),
42};
43
1259int cmd_check(int argc, const char **argv) 44int cmd_check(int argc, const char **argv)
1260{ 45{
1261 struct objtool_file file; 46 const char *objname;
1262 int ret, warnings = 0;
1263
1264 const struct option options[] = {
1265 OPT_BOOLEAN('f', "no-fp", &nofp, "Skip frame pointer validation"),
1266 OPT_END(),
1267 };
1268 47
1269 argc = parse_options(argc, argv, options, check_usage, 0); 48 argc = parse_options(argc, argv, check_options, check_usage, 0);
1270 49
1271 if (argc != 1) 50 if (argc != 1)
1272 usage_with_options(check_usage, options); 51 usage_with_options(check_usage, check_options);
1273 52
1274 objname = argv[0]; 53 objname = argv[0];
1275 54
1276 file.elf = elf_open(objname); 55 return check(objname, nofp);
1277 if (!file.elf) {
1278 fprintf(stderr, "error reading elf file %s\n", objname);
1279 return 1;
1280 }
1281
1282 INIT_LIST_HEAD(&file.insn_list);
1283 hash_init(file.insn_hash);
1284 file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard");
1285 file.rodata = find_section_by_name(file.elf, ".rodata");
1286 file.ignore_unreachables = false;
1287 file.c_file = find_section_by_name(file.elf, ".comment");
1288
1289 ret = decode_sections(&file);
1290 if (ret < 0)
1291 goto out;
1292 warnings += ret;
1293
1294 ret = validate_functions(&file);
1295 if (ret < 0)
1296 goto out;
1297 warnings += ret;
1298
1299 ret = validate_uncallable_instructions(&file);
1300 if (ret < 0)
1301 goto out;
1302 warnings += ret;
1303
1304out:
1305 cleanup(&file);
1306
1307 /* ignore warnings for now until we get all the code cleaned up */
1308 if (ret || warnings)
1309 return 0;
1310 return 0;
1311} 56}
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
new file mode 100644
index 000000000000..231a36053e07
--- /dev/null
+++ b/tools/objtool/check.c
@@ -0,0 +1,1263 @@
1/*
2 * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version 2
7 * of the License, or (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, see <http://www.gnu.org/licenses/>.
16 */
17
18#include <string.h>
19#include <stdlib.h>
20
21#include "check.h"
22#include "elf.h"
23#include "special.h"
24#include "arch.h"
25#include "warn.h"
26
27#include <linux/hashtable.h>
28#include <linux/kernel.h>
29
30#define STATE_FP_SAVED 0x1
31#define STATE_FP_SETUP 0x2
32#define STATE_FENTRY 0x4
33
34struct alternative {
35 struct list_head list;
36 struct instruction *insn;
37};
38
39const char *objname;
40static bool nofp;
41
42static struct instruction *find_insn(struct objtool_file *file,
43 struct section *sec, unsigned long offset)
44{
45 struct instruction *insn;
46
47 hash_for_each_possible(file->insn_hash, insn, hash, offset)
48 if (insn->sec == sec && insn->offset == offset)
49 return insn;
50
51 return NULL;
52}
53
54static struct instruction *next_insn_same_sec(struct objtool_file *file,
55 struct instruction *insn)
56{
57 struct instruction *next = list_next_entry(insn, list);
58
59 if (&next->list == &file->insn_list || next->sec != insn->sec)
60 return NULL;
61
62 return next;
63}
64
65static bool gcov_enabled(struct objtool_file *file)
66{
67 struct section *sec;
68 struct symbol *sym;
69
70 list_for_each_entry(sec, &file->elf->sections, list)
71 list_for_each_entry(sym, &sec->symbol_list, list)
72 if (!strncmp(sym->name, "__gcov_.", 8))
73 return true;
74
75 return false;
76}
77
78#define for_each_insn(file, insn) \
79 list_for_each_entry(insn, &file->insn_list, list)
80
81#define func_for_each_insn(file, func, insn) \
82 for (insn = find_insn(file, func->sec, func->offset); \
83 insn && &insn->list != &file->insn_list && \
84 insn->sec == func->sec && \
85 insn->offset < func->offset + func->len; \
86 insn = list_next_entry(insn, list))
87
88#define func_for_each_insn_continue_reverse(file, func, insn) \
89 for (insn = list_prev_entry(insn, list); \
90 &insn->list != &file->insn_list && \
91 insn->sec == func->sec && insn->offset >= func->offset; \
92 insn = list_prev_entry(insn, list))
93
94#define sec_for_each_insn_from(file, insn) \
95 for (; insn; insn = next_insn_same_sec(file, insn))
96
97
98/*
99 * Check if the function has been manually whitelisted with the
100 * STACK_FRAME_NON_STANDARD macro, or if it should be automatically whitelisted
101 * due to its use of a context switching instruction.
102 */
103static bool ignore_func(struct objtool_file *file, struct symbol *func)
104{
105 struct rela *rela;
106 struct instruction *insn;
107
108 /* check for STACK_FRAME_NON_STANDARD */
109 if (file->whitelist && file->whitelist->rela)
110 list_for_each_entry(rela, &file->whitelist->rela->rela_list, list) {
111 if (rela->sym->type == STT_SECTION &&
112 rela->sym->sec == func->sec &&
113 rela->addend == func->offset)
114 return true;
115 if (rela->sym->type == STT_FUNC && rela->sym == func)
116 return true;
117 }
118
119 /* check if it has a context switching instruction */
120 func_for_each_insn(file, func, insn)
121 if (insn->type == INSN_CONTEXT_SWITCH)
122 return true;
123
124 return false;
125}
126
127/*
128 * This checks to see if the given function is a "noreturn" function.
129 *
130 * For global functions which are outside the scope of this object file, we
131 * have to keep a manual list of them.
132 *
133 * For local functions, we have to detect them manually by simply looking for
134 * the lack of a return instruction.
135 *
136 * Returns:
137 * -1: error
138 * 0: no dead end
139 * 1: dead end
140 */
141static int __dead_end_function(struct objtool_file *file, struct symbol *func,
142 int recursion)
143{
144 int i;
145 struct instruction *insn;
146 bool empty = true;
147
148 /*
149 * Unfortunately these have to be hard coded because the noreturn
150 * attribute isn't provided in ELF data.
151 */
152 static const char * const global_noreturns[] = {
153 "__stack_chk_fail",
154 "panic",
155 "do_exit",
156 "do_task_dead",
157 "__module_put_and_exit",
158 "complete_and_exit",
159 "kvm_spurious_fault",
160 "__reiserfs_panic",
161 "lbug_with_loc",
162 "fortify_panic",
163 };
164
165 if (func->bind == STB_WEAK)
166 return 0;
167
168 if (func->bind == STB_GLOBAL)
169 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
170 if (!strcmp(func->name, global_noreturns[i]))
171 return 1;
172
173 if (!func->sec)
174 return 0;
175
176 func_for_each_insn(file, func, insn) {
177 empty = false;
178
179 if (insn->type == INSN_RETURN)
180 return 0;
181 }
182
183 if (empty)
184 return 0;
185
186 /*
187 * A function can have a sibling call instead of a return. In that
188 * case, the function's dead-end status depends on whether the target
189 * of the sibling call returns.
190 */
191 func_for_each_insn(file, func, insn) {
192 if (insn->sec != func->sec ||
193 insn->offset >= func->offset + func->len)
194 break;
195
196 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
197 struct instruction *dest = insn->jump_dest;
198 struct symbol *dest_func;
199
200 if (!dest)
201 /* sibling call to another file */
202 return 0;
203
204 if (dest->sec != func->sec ||
205 dest->offset < func->offset ||
206 dest->offset >= func->offset + func->len) {
207 /* local sibling call */
208 dest_func = find_symbol_by_offset(dest->sec,
209 dest->offset);
210 if (!dest_func)
211 continue;
212
213 if (recursion == 5) {
214 WARN_FUNC("infinite recursion (objtool bug!)",
215 dest->sec, dest->offset);
216 return -1;
217 }
218
219 return __dead_end_function(file, dest_func,
220 recursion + 1);
221 }
222 }
223
224 if (insn->type == INSN_JUMP_DYNAMIC && list_empty(&insn->alts))
225 /* sibling call */
226 return 0;
227 }
228
229 return 1;
230}
231
232static int dead_end_function(struct objtool_file *file, struct symbol *func)
233{
234 return __dead_end_function(file, func, 0);
235}
236
237/*
238 * Call the arch-specific instruction decoder for all the instructions and add
239 * them to the global instruction list.
240 */
241static int decode_instructions(struct objtool_file *file)
242{
243 struct section *sec;
244 struct symbol *func;
245 unsigned long offset;
246 struct instruction *insn;
247 int ret;
248
249 list_for_each_entry(sec, &file->elf->sections, list) {
250
251 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
252 continue;
253
254 for (offset = 0; offset < sec->len; offset += insn->len) {
255 insn = malloc(sizeof(*insn));
256 memset(insn, 0, sizeof(*insn));
257
258 INIT_LIST_HEAD(&insn->alts);
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 if (ret)
267 return ret;
268
269 if (!insn->type || insn->type > INSN_LAST) {
270 WARN_FUNC("invalid instruction type %d",
271 insn->sec, insn->offset, insn->type);
272 return -1;
273 }
274
275 hash_add(file->insn_hash, &insn->hash, insn->offset);
276 list_add_tail(&insn->list, &file->insn_list);
277 }
278
279 list_for_each_entry(func, &sec->symbol_list, list) {
280 if (func->type != STT_FUNC)
281 continue;
282
283 if (!find_insn(file, sec, func->offset)) {
284 WARN("%s(): can't find starting instruction",
285 func->name);
286 return -1;
287 }
288
289 func_for_each_insn(file, func, insn)
290 if (!insn->func)
291 insn->func = func;
292 }
293 }
294
295 return 0;
296}
297
298/*
299 * Find all uses of the unreachable() macro, which are code path dead ends.
300 */
301static int add_dead_ends(struct objtool_file *file)
302{
303 struct section *sec;
304 struct rela *rela;
305 struct instruction *insn;
306 bool found;
307
308 sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
309 if (!sec)
310 return 0;
311
312 list_for_each_entry(rela, &sec->rela_list, list) {
313 if (rela->sym->type != STT_SECTION) {
314 WARN("unexpected relocation symbol type in %s", sec->name);
315 return -1;
316 }
317 insn = find_insn(file, rela->sym->sec, rela->addend);
318 if (insn)
319 insn = list_prev_entry(insn, list);
320 else if (rela->addend == rela->sym->sec->len) {
321 found = false;
322 list_for_each_entry_reverse(insn, &file->insn_list, list) {
323 if (insn->sec == rela->sym->sec) {
324 found = true;
325 break;
326 }
327 }
328
329 if (!found) {
330 WARN("can't find unreachable insn at %s+0x%x",
331 rela->sym->sec->name, rela->addend);
332 return -1;
333 }
334 } else {
335 WARN("can't find unreachable insn at %s+0x%x",
336 rela->sym->sec->name, rela->addend);
337 return -1;
338 }
339
340 insn->dead_end = true;
341 }
342
343 return 0;
344}
345
346/*
347 * Warnings shouldn't be reported for ignored functions.
348 */
349static void add_ignores(struct objtool_file *file)
350{
351 struct instruction *insn;
352 struct section *sec;
353 struct symbol *func;
354
355 list_for_each_entry(sec, &file->elf->sections, list) {
356 list_for_each_entry(func, &sec->symbol_list, list) {
357 if (func->type != STT_FUNC)
358 continue;
359
360 if (!ignore_func(file, func))
361 continue;
362
363 func_for_each_insn(file, func, insn)
364 insn->visited = true;
365 }
366 }
367}
368
369/*
370 * Find the destination instructions for all jumps.
371 */
372static int add_jump_destinations(struct objtool_file *file)
373{
374 struct instruction *insn;
375 struct rela *rela;
376 struct section *dest_sec;
377 unsigned long dest_off;
378
379 for_each_insn(file, insn) {
380 if (insn->type != INSN_JUMP_CONDITIONAL &&
381 insn->type != INSN_JUMP_UNCONDITIONAL)
382 continue;
383
384 /* skip ignores */
385 if (insn->visited)
386 continue;
387
388 rela = find_rela_by_dest_range(insn->sec, insn->offset,
389 insn->len);
390 if (!rela) {
391 dest_sec = insn->sec;
392 dest_off = insn->offset + insn->len + insn->immediate;
393 } else if (rela->sym->type == STT_SECTION) {
394 dest_sec = rela->sym->sec;
395 dest_off = rela->addend + 4;
396 } else if (rela->sym->sec->idx) {
397 dest_sec = rela->sym->sec;
398 dest_off = rela->sym->sym.st_value + rela->addend + 4;
399 } else {
400 /* sibling call */
401 insn->jump_dest = 0;
402 continue;
403 }
404
405 insn->jump_dest = find_insn(file, dest_sec, dest_off);
406 if (!insn->jump_dest) {
407
408 /*
409 * This is a special case where an alt instruction
410 * jumps past the end of the section. These are
411 * handled later in handle_group_alt().
412 */
413 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
414 continue;
415
416 WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
417 insn->sec, insn->offset, dest_sec->name,
418 dest_off);
419 return -1;
420 }
421 }
422
423 return 0;
424}
425
426/*
427 * Find the destination instructions for all calls.
428 */
429static int add_call_destinations(struct objtool_file *file)
430{
431 struct instruction *insn;
432 unsigned long dest_off;
433 struct rela *rela;
434
435 for_each_insn(file, insn) {
436 if (insn->type != INSN_CALL)
437 continue;
438
439 rela = find_rela_by_dest_range(insn->sec, insn->offset,
440 insn->len);
441 if (!rela) {
442 dest_off = insn->offset + insn->len + insn->immediate;
443 insn->call_dest = find_symbol_by_offset(insn->sec,
444 dest_off);
445 if (!insn->call_dest) {
446 WARN_FUNC("can't find call dest symbol at offset 0x%lx",
447 insn->sec, insn->offset, dest_off);
448 return -1;
449 }
450 } else if (rela->sym->type == STT_SECTION) {
451 insn->call_dest = find_symbol_by_offset(rela->sym->sec,
452 rela->addend+4);
453 if (!insn->call_dest ||
454 insn->call_dest->type != STT_FUNC) {
455 WARN_FUNC("can't find call dest symbol at %s+0x%x",
456 insn->sec, insn->offset,
457 rela->sym->sec->name,
458 rela->addend + 4);
459 return -1;
460 }
461 } else
462 insn->call_dest = rela->sym;
463 }
464
465 return 0;
466}
467
468/*
469 * The .alternatives section requires some extra special care, over and above
470 * what other special sections require:
471 *
472 * 1. Because alternatives are patched in-place, we need to insert a fake jump
473 * instruction at the end so that validate_branch() skips all the original
474 * replaced instructions when validating the new instruction path.
475 *
476 * 2. An added wrinkle is that the new instruction length might be zero. In
477 * that case the old instructions are replaced with noops. We simulate that
478 * by creating a fake jump as the only new instruction.
479 *
480 * 3. In some cases, the alternative section includes an instruction which
481 * conditionally jumps to the _end_ of the entry. We have to modify these
482 * jumps' destinations to point back to .text rather than the end of the
483 * entry in .altinstr_replacement.
484 *
485 * 4. It has been requested that we don't validate the !POPCNT feature path
486 * which is a "very very small percentage of machines".
487 */
488static int handle_group_alt(struct objtool_file *file,
489 struct special_alt *special_alt,
490 struct instruction *orig_insn,
491 struct instruction **new_insn)
492{
493 struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump;
494 unsigned long dest_off;
495
496 last_orig_insn = NULL;
497 insn = orig_insn;
498 sec_for_each_insn_from(file, insn) {
499 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
500 break;
501
502 if (special_alt->skip_orig)
503 insn->type = INSN_NOP;
504
505 insn->alt_group = true;
506 last_orig_insn = insn;
507 }
508
509 if (!next_insn_same_sec(file, last_orig_insn)) {
510 WARN("%s: don't know how to handle alternatives at end of section",
511 special_alt->orig_sec->name);
512 return -1;
513 }
514
515 fake_jump = malloc(sizeof(*fake_jump));
516 if (!fake_jump) {
517 WARN("malloc failed");
518 return -1;
519 }
520 memset(fake_jump, 0, sizeof(*fake_jump));
521 INIT_LIST_HEAD(&fake_jump->alts);
522 fake_jump->sec = special_alt->new_sec;
523 fake_jump->offset = -1;
524 fake_jump->type = INSN_JUMP_UNCONDITIONAL;
525 fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
526
527 if (!special_alt->new_len) {
528 *new_insn = fake_jump;
529 return 0;
530 }
531
532 last_new_insn = NULL;
533 insn = *new_insn;
534 sec_for_each_insn_from(file, insn) {
535 if (insn->offset >= special_alt->new_off + special_alt->new_len)
536 break;
537
538 last_new_insn = insn;
539
540 if (insn->type != INSN_JUMP_CONDITIONAL &&
541 insn->type != INSN_JUMP_UNCONDITIONAL)
542 continue;
543
544 if (!insn->immediate)
545 continue;
546
547 dest_off = insn->offset + insn->len + insn->immediate;
548 if (dest_off == special_alt->new_off + special_alt->new_len)
549 insn->jump_dest = fake_jump;
550
551 if (!insn->jump_dest) {
552 WARN_FUNC("can't find alternative jump destination",
553 insn->sec, insn->offset);
554 return -1;
555 }
556 }
557
558 if (!last_new_insn) {
559 WARN_FUNC("can't find last new alternative instruction",
560 special_alt->new_sec, special_alt->new_off);
561 return -1;
562 }
563
564 list_add(&fake_jump->list, &last_new_insn->list);
565
566 return 0;
567}
568
569/*
570 * A jump table entry can either convert a nop to a jump or a jump to a nop.
571 * If the original instruction is a jump, make the alt entry an effective nop
572 * by just skipping the original instruction.
573 */
574static int handle_jump_alt(struct objtool_file *file,
575 struct special_alt *special_alt,
576 struct instruction *orig_insn,
577 struct instruction **new_insn)
578{
579 if (orig_insn->type == INSN_NOP)
580 return 0;
581
582 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
583 WARN_FUNC("unsupported instruction at jump label",
584 orig_insn->sec, orig_insn->offset);
585 return -1;
586 }
587
588 *new_insn = list_next_entry(orig_insn, list);
589 return 0;
590}
591
592/*
593 * Read all the special sections which have alternate instructions which can be
594 * patched in or redirected to at runtime. Each instruction having alternate
595 * instruction(s) has them added to its insn->alts list, which will be
596 * traversed in validate_branch().
597 */
598static int add_special_section_alts(struct objtool_file *file)
599{
600 struct list_head special_alts;
601 struct instruction *orig_insn, *new_insn;
602 struct special_alt *special_alt, *tmp;
603 struct alternative *alt;
604 int ret;
605
606 ret = special_get_alts(file->elf, &special_alts);
607 if (ret)
608 return ret;
609
610 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
611 alt = malloc(sizeof(*alt));
612 if (!alt) {
613 WARN("malloc failed");
614 ret = -1;
615 goto out;
616 }
617
618 orig_insn = find_insn(file, special_alt->orig_sec,
619 special_alt->orig_off);
620 if (!orig_insn) {
621 WARN_FUNC("special: can't find orig instruction",
622 special_alt->orig_sec, special_alt->orig_off);
623 ret = -1;
624 goto out;
625 }
626
627 new_insn = NULL;
628 if (!special_alt->group || special_alt->new_len) {
629 new_insn = find_insn(file, special_alt->new_sec,
630 special_alt->new_off);
631 if (!new_insn) {
632 WARN_FUNC("special: can't find new instruction",
633 special_alt->new_sec,
634 special_alt->new_off);
635 ret = -1;
636 goto out;
637 }
638 }
639
640 if (special_alt->group) {
641 ret = handle_group_alt(file, special_alt, orig_insn,
642 &new_insn);
643 if (ret)
644 goto out;
645 } else if (special_alt->jump_or_nop) {
646 ret = handle_jump_alt(file, special_alt, orig_insn,
647 &new_insn);
648 if (ret)
649 goto out;
650 }
651
652 alt->insn = new_insn;
653 list_add_tail(&alt->list, &orig_insn->alts);
654
655 list_del(&special_alt->list);
656 free(special_alt);
657 }
658
659out:
660 return ret;
661}
662
663static int add_switch_table(struct objtool_file *file, struct symbol *func,
664 struct instruction *insn, struct rela *table,
665 struct rela *next_table)
666{
667 struct rela *rela = table;
668 struct instruction *alt_insn;
669 struct alternative *alt;
670
671 list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) {
672 if (rela == next_table)
673 break;
674
675 if (rela->sym->sec != insn->sec ||
676 rela->addend <= func->offset ||
677 rela->addend >= func->offset + func->len)
678 break;
679
680 alt_insn = find_insn(file, insn->sec, rela->addend);
681 if (!alt_insn) {
682 WARN("%s: can't find instruction at %s+0x%x",
683 file->rodata->rela->name, insn->sec->name,
684 rela->addend);
685 return -1;
686 }
687
688 alt = malloc(sizeof(*alt));
689 if (!alt) {
690 WARN("malloc failed");
691 return -1;
692 }
693
694 alt->insn = alt_insn;
695 list_add_tail(&alt->list, &insn->alts);
696 }
697
698 return 0;
699}
700
701/*
702 * find_switch_table() - Given a dynamic jump, find the switch jump table in
703 * .rodata associated with it.
704 *
705 * There are 3 basic patterns:
706 *
707 * 1. jmpq *[rodata addr](,%reg,8)
708 *
709 * This is the most common case by far. It jumps to an address in a simple
710 * jump table which is stored in .rodata.
711 *
712 * 2. jmpq *[rodata addr](%rip)
713 *
714 * This is caused by a rare GCC quirk, currently only seen in three driver
715 * functions in the kernel, only with certain obscure non-distro configs.
716 *
717 * As part of an optimization, GCC makes a copy of an existing switch jump
718 * table, modifies it, and then hard-codes the jump (albeit with an indirect
719 * jump) to use a single entry in the table. The rest of the jump table and
720 * some of its jump targets remain as dead code.
721 *
722 * In such a case we can just crudely ignore all unreachable instruction
723 * warnings for the entire object file. Ideally we would just ignore them
724 * for the function, but that would require redesigning the code quite a
725 * bit. And honestly that's just not worth doing: unreachable instruction
726 * warnings are of questionable value anyway, and this is such a rare issue.
727 *
728 * 3. mov [rodata addr],%reg1
729 * ... some instructions ...
730 * jmpq *(%reg1,%reg2,8)
731 *
732 * This is a fairly uncommon pattern which is new for GCC 6. As of this
733 * writing, there are 11 occurrences of it in the allmodconfig kernel.
734 *
735 * TODO: Once we have DWARF CFI and smarter instruction decoding logic,
736 * ensure the same register is used in the mov and jump instructions.
737 */
738static struct rela *find_switch_table(struct objtool_file *file,
739 struct symbol *func,
740 struct instruction *insn)
741{
742 struct rela *text_rela, *rodata_rela;
743 struct instruction *orig_insn = insn;
744
745 text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len);
746 if (text_rela && text_rela->sym == file->rodata->sym) {
747 /* case 1 */
748 rodata_rela = find_rela_by_dest(file->rodata,
749 text_rela->addend);
750 if (rodata_rela)
751 return rodata_rela;
752
753 /* case 2 */
754 rodata_rela = find_rela_by_dest(file->rodata,
755 text_rela->addend + 4);
756 if (!rodata_rela)
757 return NULL;
758 file->ignore_unreachables = true;
759 return rodata_rela;
760 }
761
762 /* case 3 */
763 func_for_each_insn_continue_reverse(file, func, insn) {
764 if (insn->type == INSN_JUMP_DYNAMIC)
765 break;
766
767 /* allow small jumps within the range */
768 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
769 insn->jump_dest &&
770 (insn->jump_dest->offset <= insn->offset ||
771 insn->jump_dest->offset > orig_insn->offset))
772 break;
773
774 /* look for a relocation which references .rodata */
775 text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
776 insn->len);
777 if (!text_rela || text_rela->sym != file->rodata->sym)
778 continue;
779
780 /*
781 * Make sure the .rodata address isn't associated with a
782 * symbol. gcc jump tables are anonymous data.
783 */
784 if (find_symbol_containing(file->rodata, text_rela->addend))
785 continue;
786
787 return find_rela_by_dest(file->rodata, text_rela->addend);
788 }
789
790 return NULL;
791}
792
793static int add_func_switch_tables(struct objtool_file *file,
794 struct symbol *func)
795{
796 struct instruction *insn, *prev_jump = NULL;
797 struct rela *rela, *prev_rela = NULL;
798 int ret;
799
800 func_for_each_insn(file, func, insn) {
801 if (insn->type != INSN_JUMP_DYNAMIC)
802 continue;
803
804 rela = find_switch_table(file, func, insn);
805 if (!rela)
806 continue;
807
808 /*
809 * We found a switch table, but we don't know yet how big it
810 * is. Don't add it until we reach the end of the function or
811 * the beginning of another switch table in the same function.
812 */
813 if (prev_jump) {
814 ret = add_switch_table(file, func, prev_jump, prev_rela,
815 rela);
816 if (ret)
817 return ret;
818 }
819
820 prev_jump = insn;
821 prev_rela = rela;
822 }
823
824 if (prev_jump) {
825 ret = add_switch_table(file, func, prev_jump, prev_rela, NULL);
826 if (ret)
827 return ret;
828 }
829
830 return 0;
831}
832
833/*
834 * For some switch statements, gcc generates a jump table in the .rodata
835 * section which contains a list of addresses within the function to jump to.
836 * This finds these jump tables and adds them to the insn->alts lists.
837 */
838static int add_switch_table_alts(struct objtool_file *file)
839{
840 struct section *sec;
841 struct symbol *func;
842 int ret;
843
844 if (!file->rodata || !file->rodata->rela)
845 return 0;
846
847 list_for_each_entry(sec, &file->elf->sections, list) {
848 list_for_each_entry(func, &sec->symbol_list, list) {
849 if (func->type != STT_FUNC)
850 continue;
851
852 ret = add_func_switch_tables(file, func);
853 if (ret)
854 return ret;
855 }
856 }
857
858 return 0;
859}
860
861static int decode_sections(struct objtool_file *file)
862{
863 int ret;
864
865 ret = decode_instructions(file);
866 if (ret)
867 return ret;
868
869 ret = add_dead_ends(file);
870 if (ret)
871 return ret;
872
873 add_ignores(file);
874
875 ret = add_jump_destinations(file);
876 if (ret)
877 return ret;
878
879 ret = add_call_destinations(file);
880 if (ret)
881 return ret;
882
883 ret = add_special_section_alts(file);
884 if (ret)
885 return ret;
886
887 ret = add_switch_table_alts(file);
888 if (ret)
889 return ret;
890
891 return 0;
892}
893
894static bool is_fentry_call(struct instruction *insn)
895{
896 if (insn->type == INSN_CALL &&
897 insn->call_dest->type == STT_NOTYPE &&
898 !strcmp(insn->call_dest->name, "__fentry__"))
899 return true;
900
901 return false;
902}
903
904static bool has_modified_stack_frame(struct instruction *insn)
905{
906 return (insn->state & STATE_FP_SAVED) ||
907 (insn->state & STATE_FP_SETUP);
908}
909
910static bool has_valid_stack_frame(struct instruction *insn)
911{
912 return (insn->state & STATE_FP_SAVED) &&
913 (insn->state & STATE_FP_SETUP);
914}
915
916static unsigned int frame_state(unsigned long state)
917{
918 return (state & (STATE_FP_SAVED | STATE_FP_SETUP));
919}
920
921/*
922 * Follow the branch starting at the given instruction, and recursively follow
923 * any other branches (jumps). Meanwhile, track the frame pointer state at
924 * each instruction and validate all the rules described in
925 * tools/objtool/Documentation/stack-validation.txt.
926 */
927static int validate_branch(struct objtool_file *file,
928 struct instruction *first, unsigned char first_state)
929{
930 struct alternative *alt;
931 struct instruction *insn;
932 struct section *sec;
933 struct symbol *func = NULL;
934 unsigned char state;
935 int ret;
936
937 insn = first;
938 sec = insn->sec;
939 state = first_state;
940
941 if (insn->alt_group && list_empty(&insn->alts)) {
942 WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
943 sec, insn->offset);
944 return 1;
945 }
946
947 while (1) {
948 if (file->c_file && insn->func) {
949 if (func && func != insn->func) {
950 WARN("%s() falls through to next function %s()",
951 func->name, insn->func->name);
952 return 1;
953 }
954
955 func = insn->func;
956 }
957
958 if (insn->visited) {
959 if (frame_state(insn->state) != frame_state(state)) {
960 WARN_FUNC("frame pointer state mismatch",
961 sec, insn->offset);
962 return 1;
963 }
964
965 return 0;
966 }
967
968 insn->visited = true;
969 insn->state = state;
970
971 list_for_each_entry(alt, &insn->alts, list) {
972 ret = validate_branch(file, alt->insn, state);
973 if (ret)
974 return 1;
975 }
976
977 switch (insn->type) {
978
979 case INSN_FP_SAVE:
980 if (!nofp) {
981 if (state & STATE_FP_SAVED) {
982 WARN_FUNC("duplicate frame pointer save",
983 sec, insn->offset);
984 return 1;
985 }
986 state |= STATE_FP_SAVED;
987 }
988 break;
989
990 case INSN_FP_SETUP:
991 if (!nofp) {
992 if (state & STATE_FP_SETUP) {
993 WARN_FUNC("duplicate frame pointer setup",
994 sec, insn->offset);
995 return 1;
996 }
997 state |= STATE_FP_SETUP;
998 }
999 break;
1000
1001 case INSN_FP_RESTORE:
1002 if (!nofp) {
1003 if (has_valid_stack_frame(insn))
1004 state &= ~STATE_FP_SETUP;
1005
1006 state &= ~STATE_FP_SAVED;
1007 }
1008 break;
1009
1010 case INSN_RETURN:
1011 if (!nofp && has_modified_stack_frame(insn)) {
1012 WARN_FUNC("return without frame pointer restore",
1013 sec, insn->offset);
1014 return 1;
1015 }
1016 return 0;
1017
1018 case INSN_CALL:
1019 if (is_fentry_call(insn)) {
1020 state |= STATE_FENTRY;
1021 break;
1022 }
1023
1024 ret = dead_end_function(file, insn->call_dest);
1025 if (ret == 1)
1026 return 0;
1027 if (ret == -1)
1028 return 1;
1029
1030 /* fallthrough */
1031 case INSN_CALL_DYNAMIC:
1032 if (!nofp && !has_valid_stack_frame(insn)) {
1033 WARN_FUNC("call without frame pointer save/setup",
1034 sec, insn->offset);
1035 return 1;
1036 }
1037 break;
1038
1039 case INSN_JUMP_CONDITIONAL:
1040 case INSN_JUMP_UNCONDITIONAL:
1041 if (insn->jump_dest) {
1042 ret = validate_branch(file, insn->jump_dest,
1043 state);
1044 if (ret)
1045 return 1;
1046 } else if (has_modified_stack_frame(insn)) {
1047 WARN_FUNC("sibling call from callable instruction with changed frame pointer",
1048 sec, insn->offset);
1049 return 1;
1050 } /* else it's a sibling call */
1051
1052 if (insn->type == INSN_JUMP_UNCONDITIONAL)
1053 return 0;
1054
1055 break;
1056
1057 case INSN_JUMP_DYNAMIC:
1058 if (list_empty(&insn->alts) &&
1059 has_modified_stack_frame(insn)) {
1060 WARN_FUNC("sibling call from callable instruction with changed frame pointer",
1061 sec, insn->offset);
1062 return 1;
1063 }
1064
1065 return 0;
1066
1067 default:
1068 break;
1069 }
1070
1071 if (insn->dead_end)
1072 return 0;
1073
1074 insn = next_insn_same_sec(file, insn);
1075 if (!insn) {
1076 WARN("%s: unexpected end of section", sec->name);
1077 return 1;
1078 }
1079 }
1080
1081 return 0;
1082}
1083
1084static bool is_kasan_insn(struct instruction *insn)
1085{
1086 return (insn->type == INSN_CALL &&
1087 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
1088}
1089
1090static bool is_ubsan_insn(struct instruction *insn)
1091{
1092 return (insn->type == INSN_CALL &&
1093 !strcmp(insn->call_dest->name,
1094 "__ubsan_handle_builtin_unreachable"));
1095}
1096
1097static bool ignore_unreachable_insn(struct symbol *func,
1098 struct instruction *insn)
1099{
1100 int i;
1101
1102 if (insn->type == INSN_NOP)
1103 return true;
1104
1105 /*
1106 * Check if this (or a subsequent) instruction is related to
1107 * CONFIG_UBSAN or CONFIG_KASAN.
1108 *
1109 * End the search at 5 instructions to avoid going into the weeds.
1110 */
1111 for (i = 0; i < 5; i++) {
1112
1113 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
1114 return true;
1115
1116 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest) {
1117 insn = insn->jump_dest;
1118 continue;
1119 }
1120
1121 if (insn->offset + insn->len >= func->offset + func->len)
1122 break;
1123 insn = list_next_entry(insn, list);
1124 }
1125
1126 return false;
1127}
1128
1129static int validate_functions(struct objtool_file *file)
1130{
1131 struct section *sec;
1132 struct symbol *func;
1133 struct instruction *insn;
1134 int ret, warnings = 0;
1135
1136 list_for_each_entry(sec, &file->elf->sections, list) {
1137 list_for_each_entry(func, &sec->symbol_list, list) {
1138 if (func->type != STT_FUNC)
1139 continue;
1140
1141 insn = find_insn(file, sec, func->offset);
1142 if (!insn)
1143 continue;
1144
1145 ret = validate_branch(file, insn, 0);
1146 warnings += ret;
1147 }
1148 }
1149
1150 list_for_each_entry(sec, &file->elf->sections, list) {
1151 list_for_each_entry(func, &sec->symbol_list, list) {
1152 if (func->type != STT_FUNC)
1153 continue;
1154
1155 func_for_each_insn(file, func, insn) {
1156 if (insn->visited)
1157 continue;
1158
1159 insn->visited = true;
1160
1161 if (file->ignore_unreachables || warnings ||
1162 ignore_unreachable_insn(func, insn))
1163 continue;
1164
1165 /*
1166 * gcov produces a lot of unreachable
1167 * instructions. If we get an unreachable
1168 * warning and the file has gcov enabled, just
1169 * ignore it, and all other such warnings for
1170 * the file.
1171 */
1172 if (!file->ignore_unreachables &&
1173 gcov_enabled(file)) {
1174 file->ignore_unreachables = true;
1175 continue;
1176 }
1177
1178 WARN_FUNC("function has unreachable instruction", insn->sec, insn->offset);
1179 warnings++;
1180 }
1181 }
1182 }
1183
1184 return warnings;
1185}
1186
1187static int validate_uncallable_instructions(struct objtool_file *file)
1188{
1189 struct instruction *insn;
1190 int warnings = 0;
1191
1192 for_each_insn(file, insn) {
1193 if (!insn->visited && insn->type == INSN_RETURN) {
1194 WARN_FUNC("return instruction outside of a callable function",
1195 insn->sec, insn->offset);
1196 warnings++;
1197 }
1198 }
1199
1200 return warnings;
1201}
1202
1203static void cleanup(struct objtool_file *file)
1204{
1205 struct instruction *insn, *tmpinsn;
1206 struct alternative *alt, *tmpalt;
1207
1208 list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) {
1209 list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) {
1210 list_del(&alt->list);
1211 free(alt);
1212 }
1213 list_del(&insn->list);
1214 hash_del(&insn->hash);
1215 free(insn);
1216 }
1217 elf_close(file->elf);
1218}
1219
1220int check(const char *_objname, bool _nofp)
1221{
1222 struct objtool_file file;
1223 int ret, warnings = 0;
1224
1225 objname = _objname;
1226 nofp = _nofp;
1227
1228 file.elf = elf_open(objname);
1229 if (!file.elf) {
1230 fprintf(stderr, "error reading elf file %s\n", objname);
1231 return 1;
1232 }
1233
1234 INIT_LIST_HEAD(&file.insn_list);
1235 hash_init(file.insn_hash);
1236 file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard");
1237 file.rodata = find_section_by_name(file.elf, ".rodata");
1238 file.ignore_unreachables = false;
1239 file.c_file = find_section_by_name(file.elf, ".comment");
1240
1241 ret = decode_sections(&file);
1242 if (ret < 0)
1243 goto out;
1244 warnings += ret;
1245
1246 ret = validate_functions(&file);
1247 if (ret < 0)
1248 goto out;
1249 warnings += ret;
1250
1251 ret = validate_uncallable_instructions(&file);
1252 if (ret < 0)
1253 goto out;
1254 warnings += ret;
1255
1256out:
1257 cleanup(&file);
1258
1259 /* ignore warnings for now until we get all the code cleaned up */
1260 if (ret || warnings)
1261 return 0;
1262 return 0;
1263}
diff --git a/tools/objtool/check.h b/tools/objtool/check.h
new file mode 100644
index 000000000000..c0d2fde6b4ea
--- /dev/null
+++ b/tools/objtool/check.h
@@ -0,0 +1,51 @@
1/*
2 * Copyright (C) 2017 Josh Poimboeuf <jpoimboe@redhat.com>
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version 2
7 * of the License, or (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, see <http://www.gnu.org/licenses/>.
16 */
17
18#ifndef _CHECK_H
19#define _CHECK_H
20
21#include <stdbool.h>
22#include "elf.h"
23#include "arch.h"
24#include <linux/hashtable.h>
25
26struct instruction {
27 struct list_head list;
28 struct hlist_node hash;
29 struct section *sec;
30 unsigned long offset;
31 unsigned int len, state;
32 unsigned char type;
33 unsigned long immediate;
34 bool alt_group, visited, dead_end;
35 struct symbol *call_dest;
36 struct instruction *jump_dest;
37 struct list_head alts;
38 struct symbol *func;
39};
40
41struct objtool_file {
42 struct elf *elf;
43 struct list_head insn_list;
44 DECLARE_HASHTABLE(insn_hash, 16);
45 struct section *rodata, *whitelist;
46 bool ignore_unreachables, c_file;
47};
48
49int check(const char *objname, bool nofp);
50
51#endif /* _CHECK_H */
generated by cgit v1.2.2 (git 2.25.0) at 2026-03-10 20:13:28 -0400