2 * Copyright (C) 2015 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/>.
21 * This command analyzes every .o file and ensures the validity of its stack
22 * trace metadata. It enforces a set of rules on asm code and C inline
23 * assembly code so that stack traces can be reliable.
25 * For more information, see tools/objtool/Documentation/stack-validation.txt.
30 #include <subcmd/parse-options.h>
38 #include <linux/hashtable.h>
40 #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
42 #define STATE_FP_SAVED 0x1
43 #define STATE_FP_SETUP 0x2
44 #define STATE_FENTRY 0x4
47 struct list_head list;
48 struct hlist_node hash;
51 unsigned int len, state;
53 unsigned long immediate;
54 bool alt_group, visited, dead_end;
55 struct symbol *call_dest;
56 struct instruction *jump_dest;
57 struct list_head alts;
62 struct list_head list;
63 struct instruction *insn;
68 struct list_head insn_list;
69 DECLARE_HASHTABLE(insn_hash, 16);
70 struct section *rodata, *whitelist;
71 bool ignore_unreachables, c_file;
77 static struct instruction *find_insn(struct objtool_file *file,
78 struct section *sec, unsigned long offset)
80 struct instruction *insn;
82 hash_for_each_possible(file->insn_hash, insn, hash, offset)
83 if (insn->sec == sec && insn->offset == offset)
89 static struct instruction *next_insn_same_sec(struct objtool_file *file,
90 struct instruction *insn)
92 struct instruction *next = list_next_entry(insn, list);
94 if (&next->list == &file->insn_list || next->sec != insn->sec)
100 static bool gcov_enabled(struct objtool_file *file)
105 list_for_each_entry(sec, &file->elf->sections, list)
106 list_for_each_entry(sym, &sec->symbol_list, list)
107 if (!strncmp(sym->name, "__gcov_.", 8))
113 #define for_each_insn(file, insn) \
114 list_for_each_entry(insn, &file->insn_list, list)
116 #define func_for_each_insn(file, func, insn) \
117 for (insn = find_insn(file, func->sec, func->offset); \
118 insn && &insn->list != &file->insn_list && \
119 insn->sec == func->sec && \
120 insn->offset < func->offset + func->len; \
121 insn = list_next_entry(insn, list))
123 #define func_for_each_insn_continue_reverse(file, func, insn) \
124 for (insn = list_prev_entry(insn, list); \
125 &insn->list != &file->insn_list && \
126 insn->sec == func->sec && insn->offset >= func->offset; \
127 insn = list_prev_entry(insn, list))
129 #define sec_for_each_insn_from(file, insn) \
130 for (; insn; insn = next_insn_same_sec(file, insn))
134 * Check if the function has been manually whitelisted with the
135 * STACK_FRAME_NON_STANDARD macro, or if it should be automatically whitelisted
136 * due to its use of a context switching instruction.
138 static bool ignore_func(struct objtool_file *file, struct symbol *func)
141 struct instruction *insn;
143 /* check for STACK_FRAME_NON_STANDARD */
144 if (file->whitelist && file->whitelist->rela)
145 list_for_each_entry(rela, &file->whitelist->rela->rela_list, list) {
146 if (rela->sym->type == STT_SECTION &&
147 rela->sym->sec == func->sec &&
148 rela->addend == func->offset)
150 if (rela->sym->type == STT_FUNC && rela->sym == func)
154 /* check if it has a context switching instruction */
155 func_for_each_insn(file, func, insn)
156 if (insn->type == INSN_CONTEXT_SWITCH)
163 * This checks to see if the given function is a "noreturn" function.
165 * For global functions which are outside the scope of this object file, we
166 * have to keep a manual list of them.
168 * For local functions, we have to detect them manually by simply looking for
169 * the lack of a return instruction.
176 static int __dead_end_function(struct objtool_file *file, struct symbol *func,
180 struct instruction *insn;
184 * Unfortunately these have to be hard coded because the noreturn
185 * attribute isn't provided in ELF data.
187 static const char * const global_noreturns[] = {
192 "__module_put_and_exit",
194 "kvm_spurious_fault",
199 if (func->bind == STB_WEAK)
202 if (func->bind == STB_GLOBAL)
203 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
204 if (!strcmp(func->name, global_noreturns[i]))
210 func_for_each_insn(file, func, insn) {
213 if (insn->type == INSN_RETURN)
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.
225 func_for_each_insn(file, func, insn) {
226 if (insn->sec != func->sec ||
227 insn->offset >= func->offset + func->len)
230 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
231 struct instruction *dest = insn->jump_dest;
232 struct symbol *dest_func;
235 /* sibling call to another file */
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,
247 if (recursion == 5) {
248 WARN_FUNC("infinite recursion (objtool bug!)",
249 dest->sec, dest->offset);
253 return __dead_end_function(file, dest_func,
258 if (insn->type == INSN_JUMP_DYNAMIC && list_empty(&insn->alts))
266 static int dead_end_function(struct objtool_file *file, struct symbol *func)
268 return __dead_end_function(file, func, 0);
272 * Call the arch-specific instruction decoder for all the instructions and add
273 * them to the global instruction list.
275 static int decode_instructions(struct objtool_file *file)
279 unsigned long offset;
280 struct instruction *insn;
283 list_for_each_entry(sec, &file->elf->sections, list) {
285 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
288 for (offset = 0; offset < sec->len; offset += insn->len) {
289 insn = malloc(sizeof(*insn));
290 memset(insn, 0, sizeof(*insn));
292 INIT_LIST_HEAD(&insn->alts);
294 insn->offset = offset;
296 ret = arch_decode_instruction(file->elf, sec, offset,
298 &insn->len, &insn->type,
303 if (!insn->type || insn->type > INSN_LAST) {
304 WARN_FUNC("invalid instruction type %d",
305 insn->sec, insn->offset, insn->type);
309 hash_add(file->insn_hash, &insn->hash, insn->offset);
310 list_add_tail(&insn->list, &file->insn_list);
313 list_for_each_entry(func, &sec->symbol_list, list) {
314 if (func->type != STT_FUNC)
317 if (!find_insn(file, sec, func->offset)) {
318 WARN("%s(): can't find starting instruction",
323 func_for_each_insn(file, func, insn)
333 * Find all uses of the unreachable() macro, which are code path dead ends.
335 static int add_dead_ends(struct objtool_file *file)
339 struct instruction *insn;
342 sec = find_section_by_name(file->elf, ".rela__unreachable");
346 list_for_each_entry(rela, &sec->rela_list, list) {
347 if (rela->sym->type != STT_SECTION) {
348 WARN("unexpected relocation symbol type in .rela__unreachable");
351 insn = find_insn(file, rela->sym->sec, rela->addend);
353 insn = list_prev_entry(insn, list);
354 else if (rela->addend == rela->sym->sec->len) {
356 list_for_each_entry_reverse(insn, &file->insn_list, list) {
357 if (insn->sec == rela->sym->sec) {
364 WARN("can't find unreachable insn at %s+0x%x",
365 rela->sym->sec->name, rela->addend);
369 WARN("can't find unreachable insn at %s+0x%x",
370 rela->sym->sec->name, rela->addend);
374 insn->dead_end = true;
381 * Warnings shouldn't be reported for ignored functions.
383 static void add_ignores(struct objtool_file *file)
385 struct instruction *insn;
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)
394 if (!ignore_func(file, func))
397 func_for_each_insn(file, func, insn)
398 insn->visited = true;
404 * Find the destination instructions for all jumps.
406 static int add_jump_destinations(struct objtool_file *file)
408 struct instruction *insn;
410 struct section *dest_sec;
411 unsigned long dest_off;
413 for_each_insn(file, insn) {
414 if (insn->type != INSN_JUMP_CONDITIONAL &&
415 insn->type != INSN_JUMP_UNCONDITIONAL)
422 rela = find_rela_by_dest_range(insn->sec, insn->offset,
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;
439 insn->jump_dest = find_insn(file, dest_sec, dest_off);
440 if (!insn->jump_dest) {
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().
447 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
450 WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
451 insn->sec, insn->offset, dest_sec->name,
461 * Find the destination instructions for all calls.
463 static int add_call_destinations(struct objtool_file *file)
465 struct instruction *insn;
466 unsigned long dest_off;
469 for_each_insn(file, insn) {
470 if (insn->type != INSN_CALL)
473 rela = find_rela_by_dest_range(insn->sec, insn->offset,
476 dest_off = insn->offset + insn->len + insn->immediate;
477 insn->call_dest = find_symbol_by_offset(insn->sec,
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);
484 } else if (rela->sym->type == STT_SECTION) {
485 insn->call_dest = find_symbol_by_offset(rela->sym->sec,
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,
496 insn->call_dest = rela->sym;
503 * The .alternatives section requires some extra special care, over and above
504 * what other special sections require:
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.
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.
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.
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".
522 static int handle_group_alt(struct objtool_file *file,
523 struct special_alt *special_alt,
524 struct instruction *orig_insn,
525 struct instruction **new_insn)
527 struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump;
528 unsigned long dest_off;
530 last_orig_insn = NULL;
532 sec_for_each_insn_from(file, insn) {
533 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
536 if (special_alt->skip_orig)
537 insn->type = INSN_NOP;
539 insn->alt_group = true;
540 last_orig_insn = insn;
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);
549 fake_jump = malloc(sizeof(*fake_jump));
551 WARN("malloc failed");
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);
561 if (!special_alt->new_len) {
562 *new_insn = fake_jump;
566 last_new_insn = NULL;
568 sec_for_each_insn_from(file, insn) {
569 if (insn->offset >= special_alt->new_off + special_alt->new_len)
572 last_new_insn = insn;
574 if (insn->type != INSN_JUMP_CONDITIONAL &&
575 insn->type != INSN_JUMP_UNCONDITIONAL)
578 if (!insn->immediate)
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;
585 if (!insn->jump_dest) {
586 WARN_FUNC("can't find alternative jump destination",
587 insn->sec, insn->offset);
592 if (!last_new_insn) {
593 WARN_FUNC("can't find last new alternative instruction",
594 special_alt->new_sec, special_alt->new_off);
598 list_add(&fake_jump->list, &last_new_insn->list);
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.
608 static int handle_jump_alt(struct objtool_file *file,
609 struct special_alt *special_alt,
610 struct instruction *orig_insn,
611 struct instruction **new_insn)
613 if (orig_insn->type == INSN_NOP)
616 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
617 WARN_FUNC("unsupported instruction at jump label",
618 orig_insn->sec, orig_insn->offset);
622 *new_insn = list_next_entry(orig_insn, list);
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().
632 static int add_special_section_alts(struct objtool_file *file)
634 struct list_head special_alts;
635 struct instruction *orig_insn, *new_insn;
636 struct special_alt *special_alt, *tmp;
637 struct alternative *alt;
640 ret = special_get_alts(file->elf, &special_alts);
644 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
645 alt = malloc(sizeof(*alt));
647 WARN("malloc failed");
652 orig_insn = find_insn(file, special_alt->orig_sec,
653 special_alt->orig_off);
655 WARN_FUNC("special: can't find orig instruction",
656 special_alt->orig_sec, special_alt->orig_off);
662 if (!special_alt->group || special_alt->new_len) {
663 new_insn = find_insn(file, special_alt->new_sec,
664 special_alt->new_off);
666 WARN_FUNC("special: can't find new instruction",
667 special_alt->new_sec,
668 special_alt->new_off);
674 if (special_alt->group) {
675 ret = handle_group_alt(file, special_alt, orig_insn,
679 } else if (special_alt->jump_or_nop) {
680 ret = handle_jump_alt(file, special_alt, orig_insn,
686 alt->insn = new_insn;
687 list_add_tail(&alt->list, &orig_insn->alts);
689 list_del(&special_alt->list);
697 static int add_switch_table(struct objtool_file *file, struct symbol *func,
698 struct instruction *insn, struct rela *table,
699 struct rela *next_table)
701 struct rela *rela = table;
702 struct instruction *alt_insn;
703 struct alternative *alt;
705 list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) {
706 if (rela == next_table)
709 if (rela->sym->sec != insn->sec ||
710 rela->addend <= func->offset ||
711 rela->addend >= func->offset + func->len)
714 alt_insn = find_insn(file, insn->sec, rela->addend);
716 WARN("%s: can't find instruction at %s+0x%x",
717 file->rodata->rela->name, insn->sec->name,
722 alt = malloc(sizeof(*alt));
724 WARN("malloc failed");
728 alt->insn = alt_insn;
729 list_add_tail(&alt->list, &insn->alts);
736 * find_switch_table() - Given a dynamic jump, find the switch jump table in
737 * .rodata associated with it.
739 * There are 3 basic patterns:
741 * 1. jmpq *[rodata addr](,%reg,8)
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.
746 * 2. jmpq *[rodata addr](%rip)
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.
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.
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.
762 * 3. mov [rodata addr],%reg1
763 * ... some instructions ...
764 * jmpq *(%reg1,%reg2,8)
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.
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.
772 static struct rela *find_switch_table(struct objtool_file *file,
774 struct instruction *insn)
776 struct rela *text_rela, *rodata_rela;
777 struct instruction *orig_insn = insn;
779 text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len);
780 if (text_rela && text_rela->sym == file->rodata->sym) {
782 rodata_rela = find_rela_by_dest(file->rodata,
788 rodata_rela = find_rela_by_dest(file->rodata,
789 text_rela->addend + 4);
792 file->ignore_unreachables = true;
797 func_for_each_insn_continue_reverse(file, func, insn) {
798 if (insn->type == INSN_JUMP_DYNAMIC)
801 /* allow small jumps within the range */
802 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
804 (insn->jump_dest->offset <= insn->offset ||
805 insn->jump_dest->offset > orig_insn->offset))
808 text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
810 if (text_rela && text_rela->sym == file->rodata->sym)
811 return find_rela_by_dest(file->rodata,
818 static int add_func_switch_tables(struct objtool_file *file,
821 struct instruction *insn, *prev_jump = NULL;
822 struct rela *rela, *prev_rela = NULL;
825 func_for_each_insn(file, func, insn) {
826 if (insn->type != INSN_JUMP_DYNAMIC)
829 rela = find_switch_table(file, func, insn);
834 * We found a switch table, but we don't know yet how big it
835 * is. Don't add it until we reach the end of the function or
836 * the beginning of another switch table in the same function.
839 ret = add_switch_table(file, func, prev_jump, prev_rela,
850 ret = add_switch_table(file, func, prev_jump, prev_rela, NULL);
859 * For some switch statements, gcc generates a jump table in the .rodata
860 * section which contains a list of addresses within the function to jump to.
861 * This finds these jump tables and adds them to the insn->alts lists.
863 static int add_switch_table_alts(struct objtool_file *file)
869 if (!file->rodata || !file->rodata->rela)
872 list_for_each_entry(sec, &file->elf->sections, list) {
873 list_for_each_entry(func, &sec->symbol_list, list) {
874 if (func->type != STT_FUNC)
877 ret = add_func_switch_tables(file, func);
886 static int decode_sections(struct objtool_file *file)
890 ret = decode_instructions(file);
894 ret = add_dead_ends(file);
900 ret = add_jump_destinations(file);
904 ret = add_call_destinations(file);
908 ret = add_special_section_alts(file);
912 ret = add_switch_table_alts(file);
919 static bool is_fentry_call(struct instruction *insn)
921 if (insn->type == INSN_CALL &&
922 insn->call_dest->type == STT_NOTYPE &&
923 !strcmp(insn->call_dest->name, "__fentry__"))
929 static bool has_modified_stack_frame(struct instruction *insn)
931 return (insn->state & STATE_FP_SAVED) ||
932 (insn->state & STATE_FP_SETUP);
935 static bool has_valid_stack_frame(struct instruction *insn)
937 return (insn->state & STATE_FP_SAVED) &&
938 (insn->state & STATE_FP_SETUP);
941 static unsigned int frame_state(unsigned long state)
943 return (state & (STATE_FP_SAVED | STATE_FP_SETUP));
947 * Follow the branch starting at the given instruction, and recursively follow
948 * any other branches (jumps). Meanwhile, track the frame pointer state at
949 * each instruction and validate all the rules described in
950 * tools/objtool/Documentation/stack-validation.txt.
952 static int validate_branch(struct objtool_file *file,
953 struct instruction *first, unsigned char first_state)
955 struct alternative *alt;
956 struct instruction *insn;
958 struct symbol *func = NULL;
966 if (insn->alt_group && list_empty(&insn->alts)) {
967 WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
973 if (file->c_file && insn->func) {
974 if (func && func != insn->func) {
975 WARN("%s() falls through to next function %s()",
976 func->name, insn->func->name);
984 if (frame_state(insn->state) != frame_state(state)) {
985 WARN_FUNC("frame pointer state mismatch",
993 insn->visited = true;
996 list_for_each_entry(alt, &insn->alts, list) {
997 ret = validate_branch(file, alt->insn, state);
1002 switch (insn->type) {
1006 if (state & STATE_FP_SAVED) {
1007 WARN_FUNC("duplicate frame pointer save",
1011 state |= STATE_FP_SAVED;
1017 if (state & STATE_FP_SETUP) {
1018 WARN_FUNC("duplicate frame pointer setup",
1022 state |= STATE_FP_SETUP;
1026 case INSN_FP_RESTORE:
1028 if (has_valid_stack_frame(insn))
1029 state &= ~STATE_FP_SETUP;
1031 state &= ~STATE_FP_SAVED;
1036 if (!nofp && has_modified_stack_frame(insn)) {
1037 WARN_FUNC("return without frame pointer restore",
1044 if (is_fentry_call(insn)) {
1045 state |= STATE_FENTRY;
1049 ret = dead_end_function(file, insn->call_dest);
1056 case INSN_CALL_DYNAMIC:
1057 if (!nofp && !has_valid_stack_frame(insn)) {
1058 WARN_FUNC("call without frame pointer save/setup",
1064 case INSN_JUMP_CONDITIONAL:
1065 case INSN_JUMP_UNCONDITIONAL:
1066 if (insn->jump_dest) {
1067 ret = validate_branch(file, insn->jump_dest,
1071 } else if (has_modified_stack_frame(insn)) {
1072 WARN_FUNC("sibling call from callable instruction with changed frame pointer",
1075 } /* else it's a sibling call */
1077 if (insn->type == INSN_JUMP_UNCONDITIONAL)
1082 case INSN_JUMP_DYNAMIC:
1083 if (list_empty(&insn->alts) &&
1084 has_modified_stack_frame(insn)) {
1085 WARN_FUNC("sibling call from callable instruction with changed frame pointer",
1099 insn = next_insn_same_sec(file, insn);
1101 WARN("%s: unexpected end of section", sec->name);
1109 static bool is_kasan_insn(struct instruction *insn)
1111 return (insn->type == INSN_CALL &&
1112 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
1115 static bool is_ubsan_insn(struct instruction *insn)
1117 return (insn->type == INSN_CALL &&
1118 !strcmp(insn->call_dest->name,
1119 "__ubsan_handle_builtin_unreachable"));
1122 static bool ignore_unreachable_insn(struct symbol *func,
1123 struct instruction *insn)
1127 if (insn->type == INSN_NOP)
1131 * Check if this (or a subsequent) instruction is related to
1132 * CONFIG_UBSAN or CONFIG_KASAN.
1134 * End the search at 5 instructions to avoid going into the weeds.
1136 for (i = 0; i < 5; i++) {
1138 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
1141 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest) {
1142 insn = insn->jump_dest;
1146 if (insn->offset + insn->len >= func->offset + func->len)
1148 insn = list_next_entry(insn, list);
1154 static int validate_functions(struct objtool_file *file)
1156 struct section *sec;
1157 struct symbol *func;
1158 struct instruction *insn;
1159 int ret, warnings = 0;
1161 list_for_each_entry(sec, &file->elf->sections, list) {
1162 list_for_each_entry(func, &sec->symbol_list, list) {
1163 if (func->type != STT_FUNC)
1166 insn = find_insn(file, sec, func->offset);
1170 ret = validate_branch(file, insn, 0);
1175 list_for_each_entry(sec, &file->elf->sections, list) {
1176 list_for_each_entry(func, &sec->symbol_list, list) {
1177 if (func->type != STT_FUNC)
1180 func_for_each_insn(file, func, insn) {
1184 insn->visited = true;
1186 if (file->ignore_unreachables || warnings ||
1187 ignore_unreachable_insn(func, insn))
1191 * gcov produces a lot of unreachable
1192 * instructions. If we get an unreachable
1193 * warning and the file has gcov enabled, just
1194 * ignore it, and all other such warnings for
1197 if (!file->ignore_unreachables &&
1198 gcov_enabled(file)) {
1199 file->ignore_unreachables = true;
1203 WARN_FUNC("function has unreachable instruction", insn->sec, insn->offset);
1212 static int validate_uncallable_instructions(struct objtool_file *file)
1214 struct instruction *insn;
1217 for_each_insn(file, insn) {
1218 if (!insn->visited && insn->type == INSN_RETURN) {
1219 WARN_FUNC("return instruction outside of a callable function",
1220 insn->sec, insn->offset);
1228 static void cleanup(struct objtool_file *file)
1230 struct instruction *insn, *tmpinsn;
1231 struct alternative *alt, *tmpalt;
1233 list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) {
1234 list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) {
1235 list_del(&alt->list);
1238 list_del(&insn->list);
1239 hash_del(&insn->hash);
1242 elf_close(file->elf);
1245 const char * const check_usage[] = {
1246 "objtool check [<options>] file.o",
1250 int cmd_check(int argc, const char **argv)
1252 struct objtool_file file;
1253 int ret, warnings = 0;
1255 const struct option options[] = {
1256 OPT_BOOLEAN('f', "no-fp", &nofp, "Skip frame pointer validation"),
1260 argc = parse_options(argc, argv, options, check_usage, 0);
1263 usage_with_options(check_usage, options);
1267 file.elf = elf_open(objname);
1269 fprintf(stderr, "error reading elf file %s\n", objname);
1273 INIT_LIST_HEAD(&file.insn_list);
1274 hash_init(file.insn_hash);
1275 file.whitelist = find_section_by_name(file.elf, "__func_stack_frame_non_standard");
1276 file.rodata = find_section_by_name(file.elf, ".rodata");
1277 file.ignore_unreachables = false;
1278 file.c_file = find_section_by_name(file.elf, ".comment");
1280 ret = decode_sections(&file);
1285 ret = validate_functions(&file);
1290 ret = validate_uncallable_instructions(&file);
1298 /* ignore warnings for now until we get all the code cleaned up */
1299 if (ret || warnings)