2 * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
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.
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.
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/>.
28 #include <linux/hashtable.h>
29 #include <linux/kernel.h>
32 struct list_head list
;
33 struct instruction
*insn
;
37 struct cfi_state initial_func_cfi
;
39 struct instruction
*find_insn(struct objtool_file
*file
,
40 struct section
*sec
, unsigned long offset
)
42 struct instruction
*insn
;
44 hash_for_each_possible(file
->insn_hash
, insn
, hash
, offset
)
45 if (insn
->sec
== sec
&& insn
->offset
== offset
)
51 static struct instruction
*next_insn_same_sec(struct objtool_file
*file
,
52 struct instruction
*insn
)
54 struct instruction
*next
= list_next_entry(insn
, list
);
56 if (!next
|| &next
->list
== &file
->insn_list
|| next
->sec
!= insn
->sec
)
62 static struct instruction
*next_insn_same_func(struct objtool_file
*file
,
63 struct instruction
*insn
)
65 struct instruction
*next
= list_next_entry(insn
, list
);
66 struct symbol
*func
= insn
->func
;
71 if (&next
->list
!= &file
->insn_list
&& next
->func
== func
)
74 /* Check if we're already in the subfunction: */
75 if (func
== func
->cfunc
)
78 /* Move to the subfunction: */
79 return find_insn(file
, func
->cfunc
->sec
, func
->cfunc
->offset
);
82 #define func_for_each_insn_all(file, func, insn) \
83 for (insn = find_insn(file, func->sec, func->offset); \
85 insn = next_insn_same_func(file, insn))
87 #define func_for_each_insn(file, func, insn) \
88 for (insn = find_insn(file, func->sec, func->offset); \
89 insn && &insn->list != &file->insn_list && \
90 insn->sec == func->sec && \
91 insn->offset < func->offset + func->len; \
92 insn = list_next_entry(insn, list))
94 #define func_for_each_insn_continue_reverse(file, func, insn) \
95 for (insn = list_prev_entry(insn, list); \
96 &insn->list != &file->insn_list && \
97 insn->sec == func->sec && insn->offset >= func->offset; \
98 insn = list_prev_entry(insn, list))
100 #define sec_for_each_insn_from(file, insn) \
101 for (; insn; insn = next_insn_same_sec(file, insn))
103 #define sec_for_each_insn_continue(file, insn) \
104 for (insn = next_insn_same_sec(file, insn); insn; \
105 insn = next_insn_same_sec(file, insn))
108 * Check if the function has been manually whitelisted with the
109 * STACK_FRAME_NON_STANDARD macro, or if it should be automatically whitelisted
110 * due to its use of a context switching instruction.
112 static bool ignore_func(struct objtool_file
*file
, struct symbol
*func
)
116 /* check for STACK_FRAME_NON_STANDARD */
117 if (file
->whitelist
&& file
->whitelist
->rela
)
118 list_for_each_entry(rela
, &file
->whitelist
->rela
->rela_list
, list
) {
119 if (rela
->sym
->type
== STT_SECTION
&&
120 rela
->sym
->sec
== func
->sec
&&
121 rela
->addend
== func
->offset
)
123 if (rela
->sym
->type
== STT_FUNC
&& rela
->sym
== func
)
131 * This checks to see if the given function is a "noreturn" function.
133 * For global functions which are outside the scope of this object file, we
134 * have to keep a manual list of them.
136 * For local functions, we have to detect them manually by simply looking for
137 * the lack of a return instruction.
144 static int __dead_end_function(struct objtool_file
*file
, struct symbol
*func
,
148 struct instruction
*insn
;
152 * Unfortunately these have to be hard coded because the noreturn
153 * attribute isn't provided in ELF data.
155 static const char * const global_noreturns
[] = {
160 "__module_put_and_exit",
162 "kvm_spurious_fault",
167 "machine_real_restart",
170 if (func
->bind
== STB_WEAK
)
173 if (func
->bind
== STB_GLOBAL
)
174 for (i
= 0; i
< ARRAY_SIZE(global_noreturns
); i
++)
175 if (!strcmp(func
->name
, global_noreturns
[i
]))
181 insn
= find_insn(file
, func
->sec
, func
->offset
);
185 func_for_each_insn_all(file
, func
, insn
) {
188 if (insn
->type
== INSN_RETURN
)
196 * A function can have a sibling call instead of a return. In that
197 * case, the function's dead-end status depends on whether the target
198 * of the sibling call returns.
200 func_for_each_insn_all(file
, func
, insn
) {
201 if (insn
->type
== INSN_JUMP_UNCONDITIONAL
) {
202 struct instruction
*dest
= insn
->jump_dest
;
205 /* sibling call to another file */
208 if (dest
->func
&& dest
->func
->pfunc
!= insn
->func
->pfunc
) {
210 /* local sibling call */
211 if (recursion
== 5) {
213 * Infinite recursion: two functions
214 * have sibling calls to each other.
215 * This is a very rare case. It means
216 * they aren't dead ends.
221 return __dead_end_function(file
, dest
->func
,
226 if (insn
->type
== INSN_JUMP_DYNAMIC
&& list_empty(&insn
->alts
))
234 static int dead_end_function(struct objtool_file
*file
, struct symbol
*func
)
236 return __dead_end_function(file
, func
, 0);
239 static void clear_insn_state(struct insn_state
*state
)
243 memset(state
, 0, sizeof(*state
));
244 state
->cfa
.base
= CFI_UNDEFINED
;
245 for (i
= 0; i
< CFI_NUM_REGS
; i
++) {
246 state
->regs
[i
].base
= CFI_UNDEFINED
;
247 state
->vals
[i
].base
= CFI_UNDEFINED
;
249 state
->drap_reg
= CFI_UNDEFINED
;
250 state
->drap_offset
= -1;
254 * Call the arch-specific instruction decoder for all the instructions and add
255 * them to the global instruction list.
257 static int decode_instructions(struct objtool_file
*file
)
261 unsigned long offset
;
262 struct instruction
*insn
;
265 for_each_sec(file
, sec
) {
267 if (!(sec
->sh
.sh_flags
& SHF_EXECINSTR
))
270 if (strcmp(sec
->name
, ".altinstr_replacement") &&
271 strcmp(sec
->name
, ".altinstr_aux") &&
272 strncmp(sec
->name
, ".discard.", 9))
275 for (offset
= 0; offset
< sec
->len
; offset
+= insn
->len
) {
276 insn
= malloc(sizeof(*insn
));
278 WARN("malloc failed");
281 memset(insn
, 0, sizeof(*insn
));
282 INIT_LIST_HEAD(&insn
->alts
);
283 clear_insn_state(&insn
->state
);
286 insn
->offset
= offset
;
288 ret
= arch_decode_instruction(file
->elf
, sec
, offset
,
290 &insn
->len
, &insn
->type
,
296 if (!insn
->type
|| insn
->type
> INSN_LAST
) {
297 WARN_FUNC("invalid instruction type %d",
298 insn
->sec
, insn
->offset
, insn
->type
);
303 hash_add(file
->insn_hash
, &insn
->hash
, insn
->offset
);
304 list_add_tail(&insn
->list
, &file
->insn_list
);
307 list_for_each_entry(func
, &sec
->symbol_list
, list
) {
308 if (func
->type
!= STT_FUNC
)
311 if (!find_insn(file
, sec
, func
->offset
)) {
312 WARN("%s(): can't find starting instruction",
317 func_for_each_insn(file
, func
, insn
)
331 * Mark "ud2" instructions and manually annotated dead ends.
333 static int add_dead_ends(struct objtool_file
*file
)
337 struct instruction
*insn
;
341 * By default, "ud2" is a dead end unless otherwise annotated, because
342 * GCC 7 inserts it for certain divide-by-zero cases.
344 for_each_insn(file
, insn
)
345 if (insn
->type
== INSN_BUG
)
346 insn
->dead_end
= true;
349 * Check for manually annotated dead ends.
351 sec
= find_section_by_name(file
->elf
, ".rela.discard.unreachable");
355 list_for_each_entry(rela
, &sec
->rela_list
, list
) {
356 if (rela
->sym
->type
!= STT_SECTION
) {
357 WARN("unexpected relocation symbol type in %s", sec
->name
);
360 insn
= find_insn(file
, rela
->sym
->sec
, rela
->addend
);
362 insn
= list_prev_entry(insn
, list
);
363 else if (rela
->addend
== rela
->sym
->sec
->len
) {
365 list_for_each_entry_reverse(insn
, &file
->insn_list
, list
) {
366 if (insn
->sec
== rela
->sym
->sec
) {
373 WARN("can't find unreachable insn at %s+0x%x",
374 rela
->sym
->sec
->name
, rela
->addend
);
378 WARN("can't find unreachable insn at %s+0x%x",
379 rela
->sym
->sec
->name
, rela
->addend
);
383 insn
->dead_end
= true;
388 * These manually annotated reachable checks are needed for GCC 4.4,
389 * where the Linux unreachable() macro isn't supported. In that case
390 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
393 sec
= find_section_by_name(file
->elf
, ".rela.discard.reachable");
397 list_for_each_entry(rela
, &sec
->rela_list
, list
) {
398 if (rela
->sym
->type
!= STT_SECTION
) {
399 WARN("unexpected relocation symbol type in %s", sec
->name
);
402 insn
= find_insn(file
, rela
->sym
->sec
, rela
->addend
);
404 insn
= list_prev_entry(insn
, list
);
405 else if (rela
->addend
== rela
->sym
->sec
->len
) {
407 list_for_each_entry_reverse(insn
, &file
->insn_list
, list
) {
408 if (insn
->sec
== rela
->sym
->sec
) {
415 WARN("can't find reachable insn at %s+0x%x",
416 rela
->sym
->sec
->name
, rela
->addend
);
420 WARN("can't find reachable insn at %s+0x%x",
421 rela
->sym
->sec
->name
, rela
->addend
);
425 insn
->dead_end
= false;
432 * Warnings shouldn't be reported for ignored functions.
434 static void add_ignores(struct objtool_file
*file
)
436 struct instruction
*insn
;
440 for_each_sec(file
, sec
) {
441 list_for_each_entry(func
, &sec
->symbol_list
, list
) {
442 if (func
->type
!= STT_FUNC
)
445 if (!ignore_func(file
, func
))
448 func_for_each_insn_all(file
, func
, insn
)
455 * FIXME: For now, just ignore any alternatives which add retpolines. This is
456 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
457 * But it at least allows objtool to understand the control flow *around* the
460 static int add_nospec_ignores(struct objtool_file
*file
)
464 struct instruction
*insn
;
466 sec
= find_section_by_name(file
->elf
, ".rela.discard.nospec");
470 list_for_each_entry(rela
, &sec
->rela_list
, list
) {
471 if (rela
->sym
->type
!= STT_SECTION
) {
472 WARN("unexpected relocation symbol type in %s", sec
->name
);
476 insn
= find_insn(file
, rela
->sym
->sec
, rela
->addend
);
478 WARN("bad .discard.nospec entry");
482 insn
->ignore_alts
= true;
489 * Find the destination instructions for all jumps.
491 static int add_jump_destinations(struct objtool_file
*file
)
493 struct instruction
*insn
;
495 struct section
*dest_sec
;
496 unsigned long dest_off
;
498 for_each_insn(file
, insn
) {
499 if (insn
->type
!= INSN_JUMP_CONDITIONAL
&&
500 insn
->type
!= INSN_JUMP_UNCONDITIONAL
)
506 rela
= find_rela_by_dest_range(insn
->sec
, insn
->offset
,
509 dest_sec
= insn
->sec
;
510 dest_off
= insn
->offset
+ insn
->len
+ insn
->immediate
;
511 } else if (rela
->sym
->type
== STT_SECTION
) {
512 dest_sec
= rela
->sym
->sec
;
513 dest_off
= rela
->addend
+ 4;
514 } else if (rela
->sym
->sec
->idx
) {
515 dest_sec
= rela
->sym
->sec
;
516 dest_off
= rela
->sym
->sym
.st_value
+ rela
->addend
+ 4;
517 } else if (strstr(rela
->sym
->name
, "_indirect_thunk_")) {
519 * Retpoline jumps are really dynamic jumps in
520 * disguise, so convert them accordingly.
522 insn
->type
= INSN_JUMP_DYNAMIC
;
523 insn
->retpoline_safe
= true;
531 insn
->jump_dest
= find_insn(file
, dest_sec
, dest_off
);
532 if (!insn
->jump_dest
) {
535 * This is a special case where an alt instruction
536 * jumps past the end of the section. These are
537 * handled later in handle_group_alt().
539 if (!strcmp(insn
->sec
->name
, ".altinstr_replacement"))
542 WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
543 insn
->sec
, insn
->offset
, dest_sec
->name
,
549 * For GCC 8+, create parent/child links for any cold
550 * subfunctions. This is _mostly_ redundant with a similar
551 * initialization in read_symbols().
553 * If a function has aliases, we want the *first* such function
554 * in the symbol table to be the subfunction's parent. In that
555 * case we overwrite the initialization done in read_symbols().
557 * However this code can't completely replace the
558 * read_symbols() code because this doesn't detect the case
559 * where the parent function's only reference to a subfunction
560 * is through a switch table.
562 if (insn
->func
&& insn
->jump_dest
->func
&&
563 insn
->func
!= insn
->jump_dest
->func
&&
564 !strstr(insn
->func
->name
, ".cold.") &&
565 strstr(insn
->jump_dest
->func
->name
, ".cold.")) {
566 insn
->func
->cfunc
= insn
->jump_dest
->func
;
567 insn
->jump_dest
->func
->pfunc
= insn
->func
;
575 * Find the destination instructions for all calls.
577 static int add_call_destinations(struct objtool_file
*file
)
579 struct instruction
*insn
;
580 unsigned long dest_off
;
583 for_each_insn(file
, insn
) {
584 if (insn
->type
!= INSN_CALL
)
587 rela
= find_rela_by_dest_range(insn
->sec
, insn
->offset
,
590 dest_off
= insn
->offset
+ insn
->len
+ insn
->immediate
;
591 insn
->call_dest
= find_symbol_by_offset(insn
->sec
,
594 if (!insn
->call_dest
&& !insn
->ignore
) {
595 WARN_FUNC("unsupported intra-function call",
596 insn
->sec
, insn
->offset
);
598 WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");
602 } else if (rela
->sym
->type
== STT_SECTION
) {
603 insn
->call_dest
= find_symbol_by_offset(rela
->sym
->sec
,
605 if (!insn
->call_dest
||
606 insn
->call_dest
->type
!= STT_FUNC
) {
607 WARN_FUNC("can't find call dest symbol at %s+0x%x",
608 insn
->sec
, insn
->offset
,
609 rela
->sym
->sec
->name
,
614 insn
->call_dest
= rela
->sym
;
621 * The .alternatives section requires some extra special care, over and above
622 * what other special sections require:
624 * 1. Because alternatives are patched in-place, we need to insert a fake jump
625 * instruction at the end so that validate_branch() skips all the original
626 * replaced instructions when validating the new instruction path.
628 * 2. An added wrinkle is that the new instruction length might be zero. In
629 * that case the old instructions are replaced with noops. We simulate that
630 * by creating a fake jump as the only new instruction.
632 * 3. In some cases, the alternative section includes an instruction which
633 * conditionally jumps to the _end_ of the entry. We have to modify these
634 * jumps' destinations to point back to .text rather than the end of the
635 * entry in .altinstr_replacement.
637 * 4. It has been requested that we don't validate the !POPCNT feature path
638 * which is a "very very small percentage of machines".
640 static int handle_group_alt(struct objtool_file
*file
,
641 struct special_alt
*special_alt
,
642 struct instruction
*orig_insn
,
643 struct instruction
**new_insn
)
645 struct instruction
*last_orig_insn
, *last_new_insn
, *insn
, *fake_jump
= NULL
;
646 unsigned long dest_off
;
648 last_orig_insn
= NULL
;
650 sec_for_each_insn_from(file
, insn
) {
651 if (insn
->offset
>= special_alt
->orig_off
+ special_alt
->orig_len
)
654 if (special_alt
->skip_orig
)
655 insn
->type
= INSN_NOP
;
657 insn
->alt_group
= true;
658 last_orig_insn
= insn
;
661 if (next_insn_same_sec(file
, last_orig_insn
)) {
662 fake_jump
= malloc(sizeof(*fake_jump
));
664 WARN("malloc failed");
667 memset(fake_jump
, 0, sizeof(*fake_jump
));
668 INIT_LIST_HEAD(&fake_jump
->alts
);
669 clear_insn_state(&fake_jump
->state
);
671 fake_jump
->sec
= special_alt
->new_sec
;
672 fake_jump
->offset
= -1;
673 fake_jump
->type
= INSN_JUMP_UNCONDITIONAL
;
674 fake_jump
->jump_dest
= list_next_entry(last_orig_insn
, list
);
675 fake_jump
->ignore
= true;
678 if (!special_alt
->new_len
) {
680 WARN("%s: empty alternative at end of section",
681 special_alt
->orig_sec
->name
);
685 *new_insn
= fake_jump
;
689 last_new_insn
= NULL
;
691 sec_for_each_insn_from(file
, insn
) {
692 if (insn
->offset
>= special_alt
->new_off
+ special_alt
->new_len
)
695 last_new_insn
= insn
;
697 insn
->ignore
= orig_insn
->ignore_alts
;
699 if (insn
->type
!= INSN_JUMP_CONDITIONAL
&&
700 insn
->type
!= INSN_JUMP_UNCONDITIONAL
)
703 if (!insn
->immediate
)
706 dest_off
= insn
->offset
+ insn
->len
+ insn
->immediate
;
707 if (dest_off
== special_alt
->new_off
+ special_alt
->new_len
) {
709 WARN("%s: alternative jump to end of section",
710 special_alt
->orig_sec
->name
);
713 insn
->jump_dest
= fake_jump
;
716 if (!insn
->jump_dest
) {
717 WARN_FUNC("can't find alternative jump destination",
718 insn
->sec
, insn
->offset
);
723 if (!last_new_insn
) {
724 WARN_FUNC("can't find last new alternative instruction",
725 special_alt
->new_sec
, special_alt
->new_off
);
730 list_add(&fake_jump
->list
, &last_new_insn
->list
);
736 * A jump table entry can either convert a nop to a jump or a jump to a nop.
737 * If the original instruction is a jump, make the alt entry an effective nop
738 * by just skipping the original instruction.
740 static int handle_jump_alt(struct objtool_file
*file
,
741 struct special_alt
*special_alt
,
742 struct instruction
*orig_insn
,
743 struct instruction
**new_insn
)
745 if (orig_insn
->type
== INSN_NOP
)
748 if (orig_insn
->type
!= INSN_JUMP_UNCONDITIONAL
) {
749 WARN_FUNC("unsupported instruction at jump label",
750 orig_insn
->sec
, orig_insn
->offset
);
754 *new_insn
= list_next_entry(orig_insn
, list
);
759 * Read all the special sections which have alternate instructions which can be
760 * patched in or redirected to at runtime. Each instruction having alternate
761 * instruction(s) has them added to its insn->alts list, which will be
762 * traversed in validate_branch().
764 static int add_special_section_alts(struct objtool_file
*file
)
766 struct list_head special_alts
;
767 struct instruction
*orig_insn
, *new_insn
;
768 struct special_alt
*special_alt
, *tmp
;
769 struct alternative
*alt
;
772 ret
= special_get_alts(file
->elf
, &special_alts
);
776 list_for_each_entry_safe(special_alt
, tmp
, &special_alts
, list
) {
778 orig_insn
= find_insn(file
, special_alt
->orig_sec
,
779 special_alt
->orig_off
);
781 WARN_FUNC("special: can't find orig instruction",
782 special_alt
->orig_sec
, special_alt
->orig_off
);
788 if (!special_alt
->group
|| special_alt
->new_len
) {
789 new_insn
= find_insn(file
, special_alt
->new_sec
,
790 special_alt
->new_off
);
792 WARN_FUNC("special: can't find new instruction",
793 special_alt
->new_sec
,
794 special_alt
->new_off
);
800 if (special_alt
->group
) {
801 ret
= handle_group_alt(file
, special_alt
, orig_insn
,
805 } else if (special_alt
->jump_or_nop
) {
806 ret
= handle_jump_alt(file
, special_alt
, orig_insn
,
812 alt
= malloc(sizeof(*alt
));
814 WARN("malloc failed");
819 alt
->insn
= new_insn
;
820 list_add_tail(&alt
->list
, &orig_insn
->alts
);
822 list_del(&special_alt
->list
);
830 static int add_switch_table(struct objtool_file
*file
, struct instruction
*insn
,
831 struct rela
*table
, struct rela
*next_table
)
833 struct rela
*rela
= table
;
834 struct instruction
*alt_insn
;
835 struct alternative
*alt
;
836 struct symbol
*pfunc
= insn
->func
->pfunc
;
837 unsigned int prev_offset
= 0;
839 list_for_each_entry_from(rela
, &table
->rela_sec
->rela_list
, list
) {
840 if (rela
== next_table
)
843 /* Make sure the switch table entries are consecutive: */
844 if (prev_offset
&& rela
->offset
!= prev_offset
+ 8)
847 /* Detect function pointers from contiguous objects: */
848 if (rela
->sym
->sec
== pfunc
->sec
&&
849 rela
->addend
== pfunc
->offset
)
852 alt_insn
= find_insn(file
, rela
->sym
->sec
, rela
->addend
);
856 /* Make sure the jmp dest is in the function or subfunction: */
857 if (alt_insn
->func
->pfunc
!= pfunc
)
860 alt
= malloc(sizeof(*alt
));
862 WARN("malloc failed");
866 alt
->insn
= alt_insn
;
867 list_add_tail(&alt
->list
, &insn
->alts
);
868 prev_offset
= rela
->offset
;
872 WARN_FUNC("can't find switch jump table",
873 insn
->sec
, insn
->offset
);
881 * find_switch_table() - Given a dynamic jump, find the switch jump table in
882 * .rodata associated with it.
884 * There are 3 basic patterns:
886 * 1. jmpq *[rodata addr](,%reg,8)
888 * This is the most common case by far. It jumps to an address in a simple
889 * jump table which is stored in .rodata.
891 * 2. jmpq *[rodata addr](%rip)
893 * This is caused by a rare GCC quirk, currently only seen in three driver
894 * functions in the kernel, only with certain obscure non-distro configs.
896 * As part of an optimization, GCC makes a copy of an existing switch jump
897 * table, modifies it, and then hard-codes the jump (albeit with an indirect
898 * jump) to use a single entry in the table. The rest of the jump table and
899 * some of its jump targets remain as dead code.
901 * In such a case we can just crudely ignore all unreachable instruction
902 * warnings for the entire object file. Ideally we would just ignore them
903 * for the function, but that would require redesigning the code quite a
904 * bit. And honestly that's just not worth doing: unreachable instruction
905 * warnings are of questionable value anyway, and this is such a rare issue.
907 * 3. mov [rodata addr],%reg1
908 * ... some instructions ...
909 * jmpq *(%reg1,%reg2,8)
911 * This is a fairly uncommon pattern which is new for GCC 6. As of this
912 * writing, there are 11 occurrences of it in the allmodconfig kernel.
914 * As of GCC 7 there are quite a few more of these and the 'in between' code
915 * is significant. Esp. with KASAN enabled some of the code between the mov
916 * and jmpq uses .rodata itself, which can confuse things.
918 * TODO: Once we have DWARF CFI and smarter instruction decoding logic,
919 * ensure the same register is used in the mov and jump instructions.
921 * NOTE: RETPOLINE made it harder still to decode dynamic jumps.
923 static struct rela
*find_switch_table(struct objtool_file
*file
,
925 struct instruction
*insn
)
927 struct rela
*text_rela
, *rodata_rela
;
928 struct instruction
*orig_insn
= insn
;
929 struct section
*rodata_sec
;
930 unsigned long table_offset
;
933 * Backward search using the @first_jump_src links, these help avoid
934 * much of the 'in between' code. Which avoids us getting confused by
938 &insn
->list
!= &file
->insn_list
&&
939 insn
->sec
== func
->sec
&&
940 insn
->offset
>= func
->offset
;
942 insn
= insn
->first_jump_src
?: list_prev_entry(insn
, list
)) {
944 if (insn
!= orig_insn
&& insn
->type
== INSN_JUMP_DYNAMIC
)
947 /* allow small jumps within the range */
948 if (insn
->type
== INSN_JUMP_UNCONDITIONAL
&&
950 (insn
->jump_dest
->offset
<= insn
->offset
||
951 insn
->jump_dest
->offset
> orig_insn
->offset
))
954 /* look for a relocation which references .rodata */
955 text_rela
= find_rela_by_dest_range(insn
->sec
, insn
->offset
,
957 if (!text_rela
|| text_rela
->sym
->type
!= STT_SECTION
||
958 !text_rela
->sym
->sec
->rodata
)
961 table_offset
= text_rela
->addend
;
962 rodata_sec
= text_rela
->sym
->sec
;
964 if (text_rela
->type
== R_X86_64_PC32
)
968 * Make sure the .rodata address isn't associated with a
969 * symbol. gcc jump tables are anonymous data.
971 if (find_symbol_containing(rodata_sec
, table_offset
))
974 rodata_rela
= find_rela_by_dest(rodata_sec
, table_offset
);
977 * Use of RIP-relative switch jumps is quite rare, and
978 * indicates a rare GCC quirk/bug which can leave dead
981 if (text_rela
->type
== R_X86_64_PC32
)
982 file
->ignore_unreachables
= true;
992 static int add_func_switch_tables(struct objtool_file
*file
,
995 struct instruction
*insn
, *last
= NULL
, *prev_jump
= NULL
;
996 struct rela
*rela
, *prev_rela
= NULL
;
999 func_for_each_insn_all(file
, func
, insn
) {
1004 * Store back-pointers for unconditional forward jumps such
1005 * that find_switch_table() can back-track using those and
1006 * avoid some potentially confusing code.
1008 if (insn
->type
== INSN_JUMP_UNCONDITIONAL
&& insn
->jump_dest
&&
1009 insn
->offset
> last
->offset
&&
1010 insn
->jump_dest
->offset
> insn
->offset
&&
1011 !insn
->jump_dest
->first_jump_src
) {
1013 insn
->jump_dest
->first_jump_src
= insn
;
1014 last
= insn
->jump_dest
;
1017 if (insn
->type
!= INSN_JUMP_DYNAMIC
)
1020 rela
= find_switch_table(file
, func
, insn
);
1025 * We found a switch table, but we don't know yet how big it
1026 * is. Don't add it until we reach the end of the function or
1027 * the beginning of another switch table in the same function.
1030 ret
= add_switch_table(file
, prev_jump
, prev_rela
, rela
);
1040 ret
= add_switch_table(file
, prev_jump
, prev_rela
, NULL
);
1049 * For some switch statements, gcc generates a jump table in the .rodata
1050 * section which contains a list of addresses within the function to jump to.
1051 * This finds these jump tables and adds them to the insn->alts lists.
1053 static int add_switch_table_alts(struct objtool_file
*file
)
1055 struct section
*sec
;
1056 struct symbol
*func
;
1062 for_each_sec(file
, sec
) {
1063 list_for_each_entry(func
, &sec
->symbol_list
, list
) {
1064 if (func
->type
!= STT_FUNC
)
1067 ret
= add_func_switch_tables(file
, func
);
1076 static int read_unwind_hints(struct objtool_file
*file
)
1078 struct section
*sec
, *relasec
;
1080 struct unwind_hint
*hint
;
1081 struct instruction
*insn
;
1082 struct cfi_reg
*cfa
;
1085 sec
= find_section_by_name(file
->elf
, ".discard.unwind_hints");
1089 relasec
= sec
->rela
;
1091 WARN("missing .rela.discard.unwind_hints section");
1095 if (sec
->len
% sizeof(struct unwind_hint
)) {
1096 WARN("struct unwind_hint size mismatch");
1102 for (i
= 0; i
< sec
->len
/ sizeof(struct unwind_hint
); i
++) {
1103 hint
= (struct unwind_hint
*)sec
->data
->d_buf
+ i
;
1105 rela
= find_rela_by_dest(sec
, i
* sizeof(*hint
));
1107 WARN("can't find rela for unwind_hints[%d]", i
);
1111 insn
= find_insn(file
, rela
->sym
->sec
, rela
->addend
);
1113 WARN("can't find insn for unwind_hints[%d]", i
);
1117 cfa
= &insn
->state
.cfa
;
1119 if (hint
->type
== UNWIND_HINT_TYPE_SAVE
) {
1123 } else if (hint
->type
== UNWIND_HINT_TYPE_RESTORE
) {
1124 insn
->restore
= true;
1131 switch (hint
->sp_reg
) {
1132 case ORC_REG_UNDEFINED
:
1133 cfa
->base
= CFI_UNDEFINED
;
1141 case ORC_REG_SP_INDIRECT
:
1142 cfa
->base
= CFI_SP_INDIRECT
;
1145 cfa
->base
= CFI_R10
;
1148 cfa
->base
= CFI_R13
;
1157 WARN_FUNC("unsupported unwind_hint sp base reg %d",
1158 insn
->sec
, insn
->offset
, hint
->sp_reg
);
1162 cfa
->offset
= hint
->sp_offset
;
1163 insn
->state
.type
= hint
->type
;
1164 insn
->state
.end
= hint
->end
;
1170 static int read_retpoline_hints(struct objtool_file
*file
)
1172 struct section
*sec
;
1173 struct instruction
*insn
;
1176 sec
= find_section_by_name(file
->elf
, ".rela.discard.retpoline_safe");
1180 list_for_each_entry(rela
, &sec
->rela_list
, list
) {
1181 if (rela
->sym
->type
!= STT_SECTION
) {
1182 WARN("unexpected relocation symbol type in %s", sec
->name
);
1186 insn
= find_insn(file
, rela
->sym
->sec
, rela
->addend
);
1188 WARN("bad .discard.retpoline_safe entry");
1192 if (insn
->type
!= INSN_JUMP_DYNAMIC
&&
1193 insn
->type
!= INSN_CALL_DYNAMIC
) {
1194 WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1195 insn
->sec
, insn
->offset
);
1199 insn
->retpoline_safe
= true;
1205 static void mark_rodata(struct objtool_file
*file
)
1207 struct section
*sec
;
1211 * This searches for the .rodata section or multiple .rodata.func_name
1212 * sections if -fdata-sections is being used. The .str.1.1 and .str.1.8
1213 * rodata sections are ignored as they don't contain jump tables.
1215 for_each_sec(file
, sec
) {
1216 if (!strncmp(sec
->name
, ".rodata", 7) &&
1217 !strstr(sec
->name
, ".str1.")) {
1223 file
->rodata
= found
;
1226 static int decode_sections(struct objtool_file
*file
)
1232 ret
= decode_instructions(file
);
1236 ret
= add_dead_ends(file
);
1242 ret
= add_nospec_ignores(file
);
1246 ret
= add_jump_destinations(file
);
1250 ret
= add_special_section_alts(file
);
1254 ret
= add_call_destinations(file
);
1258 ret
= add_switch_table_alts(file
);
1262 ret
= read_unwind_hints(file
);
1266 ret
= read_retpoline_hints(file
);
1273 static bool is_fentry_call(struct instruction
*insn
)
1275 if (insn
->type
== INSN_CALL
&&
1276 insn
->call_dest
->type
== STT_NOTYPE
&&
1277 !strcmp(insn
->call_dest
->name
, "__fentry__"))
1283 static bool has_modified_stack_frame(struct insn_state
*state
)
1287 if (state
->cfa
.base
!= initial_func_cfi
.cfa
.base
||
1288 state
->cfa
.offset
!= initial_func_cfi
.cfa
.offset
||
1289 state
->stack_size
!= initial_func_cfi
.cfa
.offset
||
1293 for (i
= 0; i
< CFI_NUM_REGS
; i
++)
1294 if (state
->regs
[i
].base
!= initial_func_cfi
.regs
[i
].base
||
1295 state
->regs
[i
].offset
!= initial_func_cfi
.regs
[i
].offset
)
1301 static bool has_valid_stack_frame(struct insn_state
*state
)
1303 if (state
->cfa
.base
== CFI_BP
&& state
->regs
[CFI_BP
].base
== CFI_CFA
&&
1304 state
->regs
[CFI_BP
].offset
== -16)
1307 if (state
->drap
&& state
->regs
[CFI_BP
].base
== CFI_BP
)
1313 static int update_insn_state_regs(struct instruction
*insn
, struct insn_state
*state
)
1315 struct cfi_reg
*cfa
= &state
->cfa
;
1316 struct stack_op
*op
= &insn
->stack_op
;
1318 if (cfa
->base
!= CFI_SP
)
1322 if (op
->dest
.type
== OP_DEST_PUSH
)
1326 if (op
->src
.type
== OP_SRC_POP
)
1329 /* add immediate to sp */
1330 if (op
->dest
.type
== OP_DEST_REG
&& op
->src
.type
== OP_SRC_ADD
&&
1331 op
->dest
.reg
== CFI_SP
&& op
->src
.reg
== CFI_SP
)
1332 cfa
->offset
-= op
->src
.offset
;
1337 static void save_reg(struct insn_state
*state
, unsigned char reg
, int base
,
1340 if (arch_callee_saved_reg(reg
) &&
1341 state
->regs
[reg
].base
== CFI_UNDEFINED
) {
1342 state
->regs
[reg
].base
= base
;
1343 state
->regs
[reg
].offset
= offset
;
1347 static void restore_reg(struct insn_state
*state
, unsigned char reg
)
1349 state
->regs
[reg
].base
= CFI_UNDEFINED
;
1350 state
->regs
[reg
].offset
= 0;
1354 * A note about DRAP stack alignment:
1356 * GCC has the concept of a DRAP register, which is used to help keep track of
1357 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
1358 * register. The typical DRAP pattern is:
1360 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
1361 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
1362 * 41 ff 72 f8 pushq -0x8(%r10)
1364 * 48 89 e5 mov %rsp,%rbp
1371 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1374 * There are some variations in the epilogues, like:
1382 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1387 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
1388 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
1389 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
1390 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
1392 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1395 * Sometimes r13 is used as the DRAP register, in which case it's saved and
1396 * restored beforehand:
1399 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
1400 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
1402 * 49 8d 65 f0 lea -0x10(%r13),%rsp
1406 static int update_insn_state(struct instruction
*insn
, struct insn_state
*state
)
1408 struct stack_op
*op
= &insn
->stack_op
;
1409 struct cfi_reg
*cfa
= &state
->cfa
;
1410 struct cfi_reg
*regs
= state
->regs
;
1412 /* stack operations don't make sense with an undefined CFA */
1413 if (cfa
->base
== CFI_UNDEFINED
) {
1415 WARN_FUNC("undefined stack state", insn
->sec
, insn
->offset
);
1421 if (state
->type
== ORC_TYPE_REGS
|| state
->type
== ORC_TYPE_REGS_IRET
)
1422 return update_insn_state_regs(insn
, state
);
1424 switch (op
->dest
.type
) {
1427 switch (op
->src
.type
) {
1430 if (op
->src
.reg
== CFI_SP
&& op
->dest
.reg
== CFI_BP
&&
1431 cfa
->base
== CFI_SP
&&
1432 regs
[CFI_BP
].base
== CFI_CFA
&&
1433 regs
[CFI_BP
].offset
== -cfa
->offset
) {
1435 /* mov %rsp, %rbp */
1436 cfa
->base
= op
->dest
.reg
;
1437 state
->bp_scratch
= false;
1440 else if (op
->src
.reg
== CFI_SP
&&
1441 op
->dest
.reg
== CFI_BP
&& state
->drap
) {
1443 /* drap: mov %rsp, %rbp */
1444 regs
[CFI_BP
].base
= CFI_BP
;
1445 regs
[CFI_BP
].offset
= -state
->stack_size
;
1446 state
->bp_scratch
= false;
1449 else if (op
->src
.reg
== CFI_SP
&& cfa
->base
== CFI_SP
) {
1454 * This is needed for the rare case where GCC
1461 state
->vals
[op
->dest
.reg
].base
= CFI_CFA
;
1462 state
->vals
[op
->dest
.reg
].offset
= -state
->stack_size
;
1465 else if (op
->src
.reg
== CFI_BP
&& op
->dest
.reg
== CFI_SP
&&
1466 cfa
->base
== CFI_BP
) {
1471 * Restore the original stack pointer (Clang).
1473 state
->stack_size
= -state
->regs
[CFI_BP
].offset
;
1476 else if (op
->dest
.reg
== cfa
->base
) {
1478 /* mov %reg, %rsp */
1479 if (cfa
->base
== CFI_SP
&&
1480 state
->vals
[op
->src
.reg
].base
== CFI_CFA
) {
1483 * This is needed for the rare case
1484 * where GCC does something dumb like:
1486 * lea 0x8(%rsp), %rcx
1490 cfa
->offset
= -state
->vals
[op
->src
.reg
].offset
;
1491 state
->stack_size
= cfa
->offset
;
1494 cfa
->base
= CFI_UNDEFINED
;
1502 if (op
->dest
.reg
== CFI_SP
&& op
->src
.reg
== CFI_SP
) {
1505 state
->stack_size
-= op
->src
.offset
;
1506 if (cfa
->base
== CFI_SP
)
1507 cfa
->offset
-= op
->src
.offset
;
1511 if (op
->dest
.reg
== CFI_SP
&& op
->src
.reg
== CFI_BP
) {
1513 /* lea disp(%rbp), %rsp */
1514 state
->stack_size
= -(op
->src
.offset
+ regs
[CFI_BP
].offset
);
1518 if (op
->src
.reg
== CFI_SP
&& cfa
->base
== CFI_SP
) {
1520 /* drap: lea disp(%rsp), %drap */
1521 state
->drap_reg
= op
->dest
.reg
;
1524 * lea disp(%rsp), %reg
1526 * This is needed for the rare case where GCC
1527 * does something dumb like:
1529 * lea 0x8(%rsp), %rcx
1533 state
->vals
[op
->dest
.reg
].base
= CFI_CFA
;
1534 state
->vals
[op
->dest
.reg
].offset
= \
1535 -state
->stack_size
+ op
->src
.offset
;
1540 if (state
->drap
&& op
->dest
.reg
== CFI_SP
&&
1541 op
->src
.reg
== state
->drap_reg
) {
1543 /* drap: lea disp(%drap), %rsp */
1545 cfa
->offset
= state
->stack_size
= -op
->src
.offset
;
1546 state
->drap_reg
= CFI_UNDEFINED
;
1547 state
->drap
= false;
1551 if (op
->dest
.reg
== state
->cfa
.base
) {
1552 WARN_FUNC("unsupported stack register modification",
1553 insn
->sec
, insn
->offset
);
1560 if (op
->dest
.reg
!= CFI_SP
||
1561 (state
->drap_reg
!= CFI_UNDEFINED
&& cfa
->base
!= CFI_SP
) ||
1562 (state
->drap_reg
== CFI_UNDEFINED
&& cfa
->base
!= CFI_BP
)) {
1563 WARN_FUNC("unsupported stack pointer realignment",
1564 insn
->sec
, insn
->offset
);
1568 if (state
->drap_reg
!= CFI_UNDEFINED
) {
1569 /* drap: and imm, %rsp */
1570 cfa
->base
= state
->drap_reg
;
1571 cfa
->offset
= state
->stack_size
= 0;
1576 * Older versions of GCC (4.8ish) realign the stack
1577 * without DRAP, with a frame pointer.
1583 if (!state
->drap
&& op
->dest
.type
== OP_DEST_REG
&&
1584 op
->dest
.reg
== cfa
->base
) {
1590 if (state
->drap
&& cfa
->base
== CFI_BP_INDIRECT
&&
1591 op
->dest
.type
== OP_DEST_REG
&&
1592 op
->dest
.reg
== state
->drap_reg
&&
1593 state
->drap_offset
== -state
->stack_size
) {
1595 /* drap: pop %drap */
1596 cfa
->base
= state
->drap_reg
;
1598 state
->drap_offset
= -1;
1600 } else if (regs
[op
->dest
.reg
].offset
== -state
->stack_size
) {
1603 restore_reg(state
, op
->dest
.reg
);
1606 state
->stack_size
-= 8;
1607 if (cfa
->base
== CFI_SP
)
1612 case OP_SRC_REG_INDIRECT
:
1613 if (state
->drap
&& op
->src
.reg
== CFI_BP
&&
1614 op
->src
.offset
== state
->drap_offset
) {
1616 /* drap: mov disp(%rbp), %drap */
1617 cfa
->base
= state
->drap_reg
;
1619 state
->drap_offset
= -1;
1622 if (state
->drap
&& op
->src
.reg
== CFI_BP
&&
1623 op
->src
.offset
== regs
[op
->dest
.reg
].offset
) {
1625 /* drap: mov disp(%rbp), %reg */
1626 restore_reg(state
, op
->dest
.reg
);
1628 } else if (op
->src
.reg
== cfa
->base
&&
1629 op
->src
.offset
== regs
[op
->dest
.reg
].offset
+ cfa
->offset
) {
1631 /* mov disp(%rbp), %reg */
1632 /* mov disp(%rsp), %reg */
1633 restore_reg(state
, op
->dest
.reg
);
1639 WARN_FUNC("unknown stack-related instruction",
1640 insn
->sec
, insn
->offset
);
1647 state
->stack_size
+= 8;
1648 if (cfa
->base
== CFI_SP
)
1651 if (op
->src
.type
!= OP_SRC_REG
)
1655 if (op
->src
.reg
== cfa
->base
&& op
->src
.reg
== state
->drap_reg
) {
1657 /* drap: push %drap */
1658 cfa
->base
= CFI_BP_INDIRECT
;
1659 cfa
->offset
= -state
->stack_size
;
1661 /* save drap so we know when to restore it */
1662 state
->drap_offset
= -state
->stack_size
;
1664 } else if (op
->src
.reg
== CFI_BP
&& cfa
->base
== state
->drap_reg
) {
1666 /* drap: push %rbp */
1667 state
->stack_size
= 0;
1669 } else if (regs
[op
->src
.reg
].base
== CFI_UNDEFINED
) {
1671 /* drap: push %reg */
1672 save_reg(state
, op
->src
.reg
, CFI_BP
, -state
->stack_size
);
1678 save_reg(state
, op
->src
.reg
, CFI_CFA
, -state
->stack_size
);
1681 /* detect when asm code uses rbp as a scratch register */
1682 if (!no_fp
&& insn
->func
&& op
->src
.reg
== CFI_BP
&&
1683 cfa
->base
!= CFI_BP
)
1684 state
->bp_scratch
= true;
1687 case OP_DEST_REG_INDIRECT
:
1690 if (op
->src
.reg
== cfa
->base
&& op
->src
.reg
== state
->drap_reg
) {
1692 /* drap: mov %drap, disp(%rbp) */
1693 cfa
->base
= CFI_BP_INDIRECT
;
1694 cfa
->offset
= op
->dest
.offset
;
1696 /* save drap offset so we know when to restore it */
1697 state
->drap_offset
= op
->dest
.offset
;
1700 else if (regs
[op
->src
.reg
].base
== CFI_UNDEFINED
) {
1702 /* drap: mov reg, disp(%rbp) */
1703 save_reg(state
, op
->src
.reg
, CFI_BP
, op
->dest
.offset
);
1706 } else if (op
->dest
.reg
== cfa
->base
) {
1708 /* mov reg, disp(%rbp) */
1709 /* mov reg, disp(%rsp) */
1710 save_reg(state
, op
->src
.reg
, CFI_CFA
,
1711 op
->dest
.offset
- state
->cfa
.offset
);
1717 if ((!state
->drap
&& cfa
->base
!= CFI_BP
) ||
1718 (state
->drap
&& cfa
->base
!= state
->drap_reg
)) {
1719 WARN_FUNC("leave instruction with modified stack frame",
1720 insn
->sec
, insn
->offset
);
1724 /* leave (mov %rbp, %rsp; pop %rbp) */
1726 state
->stack_size
= -state
->regs
[CFI_BP
].offset
- 8;
1727 restore_reg(state
, CFI_BP
);
1737 if (op
->src
.type
!= OP_SRC_POP
) {
1738 WARN_FUNC("unknown stack-related memory operation",
1739 insn
->sec
, insn
->offset
);
1744 state
->stack_size
-= 8;
1745 if (cfa
->base
== CFI_SP
)
1751 WARN_FUNC("unknown stack-related instruction",
1752 insn
->sec
, insn
->offset
);
1759 static bool insn_state_match(struct instruction
*insn
, struct insn_state
*state
)
1761 struct insn_state
*state1
= &insn
->state
, *state2
= state
;
1764 if (memcmp(&state1
->cfa
, &state2
->cfa
, sizeof(state1
->cfa
))) {
1765 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
1766 insn
->sec
, insn
->offset
,
1767 state1
->cfa
.base
, state1
->cfa
.offset
,
1768 state2
->cfa
.base
, state2
->cfa
.offset
);
1770 } else if (memcmp(&state1
->regs
, &state2
->regs
, sizeof(state1
->regs
))) {
1771 for (i
= 0; i
< CFI_NUM_REGS
; i
++) {
1772 if (!memcmp(&state1
->regs
[i
], &state2
->regs
[i
],
1773 sizeof(struct cfi_reg
)))
1776 WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
1777 insn
->sec
, insn
->offset
,
1778 i
, state1
->regs
[i
].base
, state1
->regs
[i
].offset
,
1779 i
, state2
->regs
[i
].base
, state2
->regs
[i
].offset
);
1783 } else if (state1
->type
!= state2
->type
) {
1784 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
1785 insn
->sec
, insn
->offset
, state1
->type
, state2
->type
);
1787 } else if (state1
->drap
!= state2
->drap
||
1788 (state1
->drap
&& state1
->drap_reg
!= state2
->drap_reg
) ||
1789 (state1
->drap
&& state1
->drap_offset
!= state2
->drap_offset
)) {
1790 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
1791 insn
->sec
, insn
->offset
,
1792 state1
->drap
, state1
->drap_reg
, state1
->drap_offset
,
1793 state2
->drap
, state2
->drap_reg
, state2
->drap_offset
);
1802 * Follow the branch starting at the given instruction, and recursively follow
1803 * any other branches (jumps). Meanwhile, track the frame pointer state at
1804 * each instruction and validate all the rules described in
1805 * tools/objtool/Documentation/stack-validation.txt.
1807 static int validate_branch(struct objtool_file
*file
, struct instruction
*first
,
1808 struct insn_state state
)
1810 struct alternative
*alt
;
1811 struct instruction
*insn
, *next_insn
;
1812 struct section
*sec
;
1813 struct symbol
*func
= NULL
;
1819 if (insn
->alt_group
&& list_empty(&insn
->alts
)) {
1820 WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
1826 next_insn
= next_insn_same_sec(file
, insn
);
1828 if (file
->c_file
&& func
&& insn
->func
&& func
!= insn
->func
->pfunc
) {
1829 WARN("%s() falls through to next function %s()",
1830 func
->name
, insn
->func
->name
);
1834 func
= insn
->func
? insn
->func
->pfunc
: NULL
;
1836 if (func
&& insn
->ignore
) {
1837 WARN_FUNC("BUG: why am I validating an ignored function?",
1842 if (insn
->visited
) {
1843 if (!insn
->hint
&& !insn_state_match(insn
, &state
))
1850 if (insn
->restore
) {
1851 struct instruction
*save_insn
, *i
;
1855 func_for_each_insn_continue_reverse(file
, insn
->func
, i
) {
1863 WARN_FUNC("no corresponding CFI save for CFI restore",
1868 if (!save_insn
->visited
) {
1870 * Oops, no state to copy yet.
1871 * Hopefully we can reach this
1872 * instruction from another branch
1873 * after the save insn has been
1879 WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
1884 insn
->state
= save_insn
->state
;
1887 state
= insn
->state
;
1890 insn
->state
= state
;
1892 insn
->visited
= true;
1894 if (!insn
->ignore_alts
) {
1895 list_for_each_entry(alt
, &insn
->alts
, list
) {
1896 ret
= validate_branch(file
, alt
->insn
, state
);
1902 switch (insn
->type
) {
1905 if (func
&& has_modified_stack_frame(&state
)) {
1906 WARN_FUNC("return with modified stack frame",
1911 if (state
.bp_scratch
) {
1912 WARN("%s uses BP as a scratch register",
1920 if (is_fentry_call(insn
))
1923 ret
= dead_end_function(file
, insn
->call_dest
);
1930 case INSN_CALL_DYNAMIC
:
1931 if (!no_fp
&& func
&& !has_valid_stack_frame(&state
)) {
1932 WARN_FUNC("call without frame pointer save/setup",
1938 case INSN_JUMP_CONDITIONAL
:
1939 case INSN_JUMP_UNCONDITIONAL
:
1940 if (insn
->jump_dest
&&
1941 (!func
|| !insn
->jump_dest
->func
||
1942 insn
->jump_dest
->func
->pfunc
== func
)) {
1943 ret
= validate_branch(file
, insn
->jump_dest
,
1948 } else if (func
&& has_modified_stack_frame(&state
)) {
1949 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1954 if (insn
->type
== INSN_JUMP_UNCONDITIONAL
)
1959 case INSN_JUMP_DYNAMIC
:
1960 if (func
&& list_empty(&insn
->alts
) &&
1961 has_modified_stack_frame(&state
)) {
1962 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1969 case INSN_CONTEXT_SWITCH
:
1970 if (func
&& (!next_insn
|| !next_insn
->hint
)) {
1971 WARN_FUNC("unsupported instruction in callable function",
1978 if (update_insn_state(insn
, &state
))
1991 if (state
.cfa
.base
== CFI_UNDEFINED
)
1993 WARN("%s: unexpected end of section", sec
->name
);
2003 static int validate_unwind_hints(struct objtool_file
*file
)
2005 struct instruction
*insn
;
2006 int ret
, warnings
= 0;
2007 struct insn_state state
;
2012 clear_insn_state(&state
);
2014 for_each_insn(file
, insn
) {
2015 if (insn
->hint
&& !insn
->visited
) {
2016 ret
= validate_branch(file
, insn
, state
);
2024 static int validate_retpoline(struct objtool_file
*file
)
2026 struct instruction
*insn
;
2029 for_each_insn(file
, insn
) {
2030 if (insn
->type
!= INSN_JUMP_DYNAMIC
&&
2031 insn
->type
!= INSN_CALL_DYNAMIC
)
2034 if (insn
->retpoline_safe
)
2038 * .init.text code is ran before userspace and thus doesn't
2039 * strictly need retpolines, except for modules which are
2040 * loaded late, they very much do need retpoline in their
2043 if (!strcmp(insn
->sec
->name
, ".init.text") && !module
)
2046 WARN_FUNC("indirect %s found in RETPOLINE build",
2047 insn
->sec
, insn
->offset
,
2048 insn
->type
== INSN_JUMP_DYNAMIC
? "jump" : "call");
2056 static bool is_kasan_insn(struct instruction
*insn
)
2058 return (insn
->type
== INSN_CALL
&&
2059 !strcmp(insn
->call_dest
->name
, "__asan_handle_no_return"));
2062 static bool is_ubsan_insn(struct instruction
*insn
)
2064 return (insn
->type
== INSN_CALL
&&
2065 !strcmp(insn
->call_dest
->name
,
2066 "__ubsan_handle_builtin_unreachable"));
2069 static bool ignore_unreachable_insn(struct instruction
*insn
)
2073 if (insn
->ignore
|| insn
->type
== INSN_NOP
)
2077 * Ignore any unused exceptions. This can happen when a whitelisted
2078 * function has an exception table entry.
2080 * Also ignore alternative replacement instructions. This can happen
2081 * when a whitelisted function uses one of the ALTERNATIVE macros.
2083 if (!strcmp(insn
->sec
->name
, ".fixup") ||
2084 !strcmp(insn
->sec
->name
, ".altinstr_replacement") ||
2085 !strcmp(insn
->sec
->name
, ".altinstr_aux"))
2089 * Check if this (or a subsequent) instruction is related to
2090 * CONFIG_UBSAN or CONFIG_KASAN.
2092 * End the search at 5 instructions to avoid going into the weeds.
2096 for (i
= 0; i
< 5; i
++) {
2098 if (is_kasan_insn(insn
) || is_ubsan_insn(insn
))
2101 if (insn
->type
== INSN_JUMP_UNCONDITIONAL
) {
2102 if (insn
->jump_dest
&&
2103 insn
->jump_dest
->func
== insn
->func
) {
2104 insn
= insn
->jump_dest
;
2111 if (insn
->offset
+ insn
->len
>= insn
->func
->offset
+ insn
->func
->len
)
2114 insn
= list_next_entry(insn
, list
);
2120 static int validate_functions(struct objtool_file
*file
)
2122 struct section
*sec
;
2123 struct symbol
*func
;
2124 struct instruction
*insn
;
2125 struct insn_state state
;
2126 int ret
, warnings
= 0;
2128 clear_insn_state(&state
);
2130 state
.cfa
= initial_func_cfi
.cfa
;
2131 memcpy(&state
.regs
, &initial_func_cfi
.regs
,
2132 CFI_NUM_REGS
* sizeof(struct cfi_reg
));
2133 state
.stack_size
= initial_func_cfi
.cfa
.offset
;
2135 for_each_sec(file
, sec
) {
2136 list_for_each_entry(func
, &sec
->symbol_list
, list
) {
2137 if (func
->type
!= STT_FUNC
|| func
->pfunc
!= func
)
2140 insn
= find_insn(file
, sec
, func
->offset
);
2141 if (!insn
|| insn
->ignore
)
2144 ret
= validate_branch(file
, insn
, state
);
2152 static int validate_reachable_instructions(struct objtool_file
*file
)
2154 struct instruction
*insn
;
2156 if (file
->ignore_unreachables
)
2159 for_each_insn(file
, insn
) {
2160 if (insn
->visited
|| ignore_unreachable_insn(insn
))
2163 WARN_FUNC("unreachable instruction", insn
->sec
, insn
->offset
);
2170 static void cleanup(struct objtool_file
*file
)
2172 struct instruction
*insn
, *tmpinsn
;
2173 struct alternative
*alt
, *tmpalt
;
2175 list_for_each_entry_safe(insn
, tmpinsn
, &file
->insn_list
, list
) {
2176 list_for_each_entry_safe(alt
, tmpalt
, &insn
->alts
, list
) {
2177 list_del(&alt
->list
);
2180 list_del(&insn
->list
);
2181 hash_del(&insn
->hash
);
2184 elf_close(file
->elf
);
2187 int check(const char *_objname
, bool orc
)
2189 struct objtool_file file
;
2190 int ret
, warnings
= 0;
2194 file
.elf
= elf_open(objname
, orc
? O_RDWR
: O_RDONLY
);
2198 INIT_LIST_HEAD(&file
.insn_list
);
2199 hash_init(file
.insn_hash
);
2200 file
.whitelist
= find_section_by_name(file
.elf
, ".discard.func_stack_frame_non_standard");
2201 file
.c_file
= find_section_by_name(file
.elf
, ".comment");
2202 file
.ignore_unreachables
= no_unreachable
;
2205 arch_initial_func_cfi_state(&initial_func_cfi
);
2207 ret
= decode_sections(&file
);
2212 if (list_empty(&file
.insn_list
))
2216 ret
= validate_retpoline(&file
);
2222 ret
= validate_functions(&file
);
2227 ret
= validate_unwind_hints(&file
);
2233 ret
= validate_reachable_instructions(&file
);
2240 ret
= create_orc(&file
);
2244 ret
= create_orc_sections(&file
);
2248 ret
= elf_write(file
.elf
);
2256 /* ignore warnings for now until we get all the code cleaned up */
2257 if (ret
|| warnings
)