1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
16 #include <linux/hashtable.h>
17 #include <linux/kernel.h>
19 #define FAKE_JUMP_OFFSET -1
21 #define C_JUMP_TABLE_SECTION ".rodata..c_jump_table"
24 struct list_head list;
25 struct instruction *insn;
30 struct cfi_state initial_func_cfi;
32 struct instruction *find_insn(struct objtool_file *file,
33 struct section *sec, unsigned long offset)
35 struct instruction *insn;
37 hash_for_each_possible(file->insn_hash, insn, hash, offset)
38 if (insn->sec == sec && insn->offset == offset)
44 static struct instruction *next_insn_same_sec(struct objtool_file *file,
45 struct instruction *insn)
47 struct instruction *next = list_next_entry(insn, list);
49 if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
55 static struct instruction *next_insn_same_func(struct objtool_file *file,
56 struct instruction *insn)
58 struct instruction *next = list_next_entry(insn, list);
59 struct symbol *func = insn->func;
64 if (&next->list != &file->insn_list && next->func == func)
67 /* Check if we're already in the subfunction: */
68 if (func == func->cfunc)
71 /* Move to the subfunction: */
72 return find_insn(file, func->cfunc->sec, func->cfunc->offset);
75 #define func_for_each_insn_all(file, func, insn) \
76 for (insn = find_insn(file, func->sec, func->offset); \
78 insn = next_insn_same_func(file, insn))
80 #define func_for_each_insn(file, func, insn) \
81 for (insn = find_insn(file, func->sec, func->offset); \
82 insn && &insn->list != &file->insn_list && \
83 insn->sec == func->sec && \
84 insn->offset < func->offset + func->len; \
85 insn = list_next_entry(insn, list))
87 #define func_for_each_insn_continue_reverse(file, func, insn) \
88 for (insn = list_prev_entry(insn, list); \
89 &insn->list != &file->insn_list && \
90 insn->sec == func->sec && insn->offset >= func->offset; \
91 insn = list_prev_entry(insn, list))
93 #define sec_for_each_insn_from(file, insn) \
94 for (; insn; insn = next_insn_same_sec(file, insn))
96 #define sec_for_each_insn_continue(file, insn) \
97 for (insn = next_insn_same_sec(file, insn); insn; \
98 insn = next_insn_same_sec(file, insn))
100 static bool is_sibling_call(struct instruction *insn)
102 /* An indirect jump is either a sibling call or a jump to a table. */
103 if (insn->type == INSN_JUMP_DYNAMIC)
104 return list_empty(&insn->alts);
106 if (insn->type != INSN_JUMP_CONDITIONAL &&
107 insn->type != INSN_JUMP_UNCONDITIONAL)
110 /* add_jump_destinations() sets insn->call_dest for sibling calls. */
111 return !!insn->call_dest;
115 * This checks to see if the given function is a "noreturn" function.
117 * For global functions which are outside the scope of this object file, we
118 * have to keep a manual list of them.
120 * For local functions, we have to detect them manually by simply looking for
121 * the lack of a return instruction.
123 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
127 struct instruction *insn;
131 * Unfortunately these have to be hard coded because the noreturn
132 * attribute isn't provided in ELF data.
134 static const char * const global_noreturns[] = {
139 "__module_put_and_exit",
141 "kvm_spurious_fault",
146 "machine_real_restart",
147 "rewind_stack_do_exit",
153 if (func->bind == STB_WEAK)
156 if (func->bind == STB_GLOBAL)
157 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
158 if (!strcmp(func->name, global_noreturns[i]))
164 insn = find_insn(file, func->sec, func->offset);
168 func_for_each_insn_all(file, func, insn) {
171 if (insn->type == INSN_RETURN)
179 * A function can have a sibling call instead of a return. In that
180 * case, the function's dead-end status depends on whether the target
181 * of the sibling call returns.
183 func_for_each_insn_all(file, func, insn) {
184 if (is_sibling_call(insn)) {
185 struct instruction *dest = insn->jump_dest;
188 /* sibling call to another file */
191 /* local sibling call */
192 if (recursion == 5) {
194 * Infinite recursion: two functions have
195 * sibling calls to each other. This is a very
196 * rare case. It means they aren't dead ends.
201 return __dead_end_function(file, dest->func, recursion+1);
208 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
210 return __dead_end_function(file, func, 0);
213 static void clear_insn_state(struct insn_state *state)
217 memset(state, 0, sizeof(*state));
218 state->cfa.base = CFI_UNDEFINED;
219 for (i = 0; i < CFI_NUM_REGS; i++) {
220 state->regs[i].base = CFI_UNDEFINED;
221 state->vals[i].base = CFI_UNDEFINED;
223 state->drap_reg = CFI_UNDEFINED;
224 state->drap_offset = -1;
228 * Call the arch-specific instruction decoder for all the instructions and add
229 * them to the global instruction list.
231 static int decode_instructions(struct objtool_file *file)
235 unsigned long offset;
236 struct instruction *insn;
239 for_each_sec(file, sec) {
241 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
244 if (strcmp(sec->name, ".altinstr_replacement") &&
245 strcmp(sec->name, ".altinstr_aux") &&
246 strncmp(sec->name, ".discard.", 9))
249 for (offset = 0; offset < sec->len; offset += insn->len) {
250 insn = malloc(sizeof(*insn));
252 WARN("malloc failed");
255 memset(insn, 0, sizeof(*insn));
256 INIT_LIST_HEAD(&insn->alts);
257 clear_insn_state(&insn->state);
260 insn->offset = offset;
262 ret = arch_decode_instruction(file->elf, sec, offset,
264 &insn->len, &insn->type,
270 hash_add(file->insn_hash, &insn->hash, insn->offset);
271 list_add_tail(&insn->list, &file->insn_list);
274 list_for_each_entry(func, &sec->symbol_list, list) {
275 if (func->type != STT_FUNC || func->alias != func)
278 if (!find_insn(file, sec, func->offset)) {
279 WARN("%s(): can't find starting instruction",
284 func_for_each_insn(file, func, insn)
297 * Mark "ud2" instructions and manually annotated dead ends.
299 static int add_dead_ends(struct objtool_file *file)
303 struct instruction *insn;
307 * By default, "ud2" is a dead end unless otherwise annotated, because
308 * GCC 7 inserts it for certain divide-by-zero cases.
310 for_each_insn(file, insn)
311 if (insn->type == INSN_BUG)
312 insn->dead_end = true;
315 * Check for manually annotated dead ends.
317 sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
321 list_for_each_entry(rela, &sec->rela_list, list) {
322 if (rela->sym->type != STT_SECTION) {
323 WARN("unexpected relocation symbol type in %s", sec->name);
326 insn = find_insn(file, rela->sym->sec, rela->addend);
328 insn = list_prev_entry(insn, list);
329 else if (rela->addend == rela->sym->sec->len) {
331 list_for_each_entry_reverse(insn, &file->insn_list, list) {
332 if (insn->sec == rela->sym->sec) {
339 WARN("can't find unreachable insn at %s+0x%x",
340 rela->sym->sec->name, rela->addend);
344 WARN("can't find unreachable insn at %s+0x%x",
345 rela->sym->sec->name, rela->addend);
349 insn->dead_end = true;
354 * These manually annotated reachable checks are needed for GCC 4.4,
355 * where the Linux unreachable() macro isn't supported. In that case
356 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
359 sec = find_section_by_name(file->elf, ".rela.discard.reachable");
363 list_for_each_entry(rela, &sec->rela_list, list) {
364 if (rela->sym->type != STT_SECTION) {
365 WARN("unexpected relocation symbol type in %s", sec->name);
368 insn = find_insn(file, rela->sym->sec, rela->addend);
370 insn = list_prev_entry(insn, list);
371 else if (rela->addend == rela->sym->sec->len) {
373 list_for_each_entry_reverse(insn, &file->insn_list, list) {
374 if (insn->sec == rela->sym->sec) {
381 WARN("can't find reachable insn at %s+0x%x",
382 rela->sym->sec->name, rela->addend);
386 WARN("can't find reachable insn at %s+0x%x",
387 rela->sym->sec->name, rela->addend);
391 insn->dead_end = false;
398 * Warnings shouldn't be reported for ignored functions.
400 static void add_ignores(struct objtool_file *file)
402 struct instruction *insn;
407 sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
411 list_for_each_entry(rela, &sec->rela_list, list) {
412 switch (rela->sym->type) {
418 func = find_symbol_by_offset(rela->sym->sec, rela->addend);
419 if (!func || func->type != STT_FUNC)
424 WARN("unexpected relocation symbol type in %s: %d", sec->name, rela->sym->type);
428 func_for_each_insn_all(file, func, insn)
434 * This is a whitelist of functions that is allowed to be called with AC set.
435 * The list is meant to be minimal and only contains compiler instrumentation
436 * ABI and a few functions used to implement *_{to,from}_user() functions.
438 * These functions must not directly change AC, but may PUSHF/POPF.
440 static const char *uaccess_safe_builtin[] = {
443 "check_memory_region",
444 /* KASAN out-of-line */
445 "__asan_loadN_noabort",
446 "__asan_load1_noabort",
447 "__asan_load2_noabort",
448 "__asan_load4_noabort",
449 "__asan_load8_noabort",
450 "__asan_load16_noabort",
451 "__asan_storeN_noabort",
452 "__asan_store1_noabort",
453 "__asan_store2_noabort",
454 "__asan_store4_noabort",
455 "__asan_store8_noabort",
456 "__asan_store16_noabort",
458 "__asan_report_load_n_noabort",
459 "__asan_report_load1_noabort",
460 "__asan_report_load2_noabort",
461 "__asan_report_load4_noabort",
462 "__asan_report_load8_noabort",
463 "__asan_report_load16_noabort",
464 "__asan_report_store_n_noabort",
465 "__asan_report_store1_noabort",
466 "__asan_report_store2_noabort",
467 "__asan_report_store4_noabort",
468 "__asan_report_store8_noabort",
469 "__asan_report_store16_noabort",
472 "__sanitizer_cov_trace_pc",
473 "__sanitizer_cov_trace_const_cmp1",
474 "__sanitizer_cov_trace_const_cmp2",
475 "__sanitizer_cov_trace_const_cmp4",
476 "__sanitizer_cov_trace_const_cmp8",
477 "__sanitizer_cov_trace_cmp1",
478 "__sanitizer_cov_trace_cmp2",
479 "__sanitizer_cov_trace_cmp4",
480 "__sanitizer_cov_trace_cmp8",
482 "ubsan_type_mismatch_common",
483 "__ubsan_handle_type_mismatch",
484 "__ubsan_handle_type_mismatch_v1",
486 "csum_partial_copy_generic",
488 "mcsafe_handle_tail",
489 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
493 static void add_uaccess_safe(struct objtool_file *file)
501 for (name = uaccess_safe_builtin; *name; name++) {
502 func = find_symbol_by_name(file->elf, *name);
506 func->uaccess_safe = true;
511 * FIXME: For now, just ignore any alternatives which add retpolines. This is
512 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
513 * But it at least allows objtool to understand the control flow *around* the
516 static int add_ignore_alternatives(struct objtool_file *file)
520 struct instruction *insn;
522 sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
526 list_for_each_entry(rela, &sec->rela_list, list) {
527 if (rela->sym->type != STT_SECTION) {
528 WARN("unexpected relocation symbol type in %s", sec->name);
532 insn = find_insn(file, rela->sym->sec, rela->addend);
534 WARN("bad .discard.ignore_alts entry");
538 insn->ignore_alts = true;
545 * Find the destination instructions for all jumps.
547 static int add_jump_destinations(struct objtool_file *file)
549 struct instruction *insn;
551 struct section *dest_sec;
552 unsigned long dest_off;
554 for_each_insn(file, insn) {
555 if (insn->type != INSN_JUMP_CONDITIONAL &&
556 insn->type != INSN_JUMP_UNCONDITIONAL)
559 if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET)
562 rela = find_rela_by_dest_range(insn->sec, insn->offset,
565 dest_sec = insn->sec;
566 dest_off = insn->offset + insn->len + insn->immediate;
567 } else if (rela->sym->type == STT_SECTION) {
568 dest_sec = rela->sym->sec;
569 dest_off = rela->addend + 4;
570 } else if (rela->sym->sec->idx) {
571 dest_sec = rela->sym->sec;
572 dest_off = rela->sym->sym.st_value + rela->addend + 4;
573 } else if (strstr(rela->sym->name, "_indirect_thunk_")) {
575 * Retpoline jumps are really dynamic jumps in
576 * disguise, so convert them accordingly.
578 if (insn->type == INSN_JUMP_UNCONDITIONAL)
579 insn->type = INSN_JUMP_DYNAMIC;
581 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
583 insn->retpoline_safe = true;
586 /* external sibling call */
587 insn->call_dest = rela->sym;
591 insn->jump_dest = find_insn(file, dest_sec, dest_off);
592 if (!insn->jump_dest) {
595 * This is a special case where an alt instruction
596 * jumps past the end of the section. These are
597 * handled later in handle_group_alt().
599 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
602 WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
603 insn->sec, insn->offset, dest_sec->name,
609 * Cross-function jump.
611 if (insn->func && insn->jump_dest->func &&
612 insn->func != insn->jump_dest->func) {
615 * For GCC 8+, create parent/child links for any cold
616 * subfunctions. This is _mostly_ redundant with a
617 * similar initialization in read_symbols().
619 * If a function has aliases, we want the *first* such
620 * function in the symbol table to be the subfunction's
621 * parent. In that case we overwrite the
622 * initialization done in read_symbols().
624 * However this code can't completely replace the
625 * read_symbols() code because this doesn't detect the
626 * case where the parent function's only reference to a
627 * subfunction is through a jump table.
629 if (!strstr(insn->func->name, ".cold.") &&
630 strstr(insn->jump_dest->func->name, ".cold.")) {
631 insn->func->cfunc = insn->jump_dest->func;
632 insn->jump_dest->func->pfunc = insn->func;
634 } else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
635 insn->jump_dest->offset == insn->jump_dest->func->offset) {
637 /* internal sibling call */
638 insn->call_dest = insn->jump_dest->func;
647 * Find the destination instructions for all calls.
649 static int add_call_destinations(struct objtool_file *file)
651 struct instruction *insn;
652 unsigned long dest_off;
655 for_each_insn(file, insn) {
656 if (insn->type != INSN_CALL)
659 rela = find_rela_by_dest_range(insn->sec, insn->offset,
662 dest_off = insn->offset + insn->len + insn->immediate;
663 insn->call_dest = find_symbol_by_offset(insn->sec,
666 if (!insn->call_dest && !insn->ignore) {
667 WARN_FUNC("unsupported intra-function call",
668 insn->sec, insn->offset);
670 WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");
674 } else if (rela->sym->type == STT_SECTION) {
675 insn->call_dest = find_symbol_by_offset(rela->sym->sec,
677 if (!insn->call_dest ||
678 insn->call_dest->type != STT_FUNC) {
679 WARN_FUNC("can't find call dest symbol at %s+0x%x",
680 insn->sec, insn->offset,
681 rela->sym->sec->name,
686 insn->call_dest = rela->sym;
693 * The .alternatives section requires some extra special care, over and above
694 * what other special sections require:
696 * 1. Because alternatives are patched in-place, we need to insert a fake jump
697 * instruction at the end so that validate_branch() skips all the original
698 * replaced instructions when validating the new instruction path.
700 * 2. An added wrinkle is that the new instruction length might be zero. In
701 * that case the old instructions are replaced with noops. We simulate that
702 * by creating a fake jump as the only new instruction.
704 * 3. In some cases, the alternative section includes an instruction which
705 * conditionally jumps to the _end_ of the entry. We have to modify these
706 * jumps' destinations to point back to .text rather than the end of the
707 * entry in .altinstr_replacement.
709 static int handle_group_alt(struct objtool_file *file,
710 struct special_alt *special_alt,
711 struct instruction *orig_insn,
712 struct instruction **new_insn)
714 struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
715 unsigned long dest_off;
717 last_orig_insn = NULL;
719 sec_for_each_insn_from(file, insn) {
720 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
723 insn->alt_group = true;
724 last_orig_insn = insn;
727 if (next_insn_same_sec(file, last_orig_insn)) {
728 fake_jump = malloc(sizeof(*fake_jump));
730 WARN("malloc failed");
733 memset(fake_jump, 0, sizeof(*fake_jump));
734 INIT_LIST_HEAD(&fake_jump->alts);
735 clear_insn_state(&fake_jump->state);
737 fake_jump->sec = special_alt->new_sec;
738 fake_jump->offset = FAKE_JUMP_OFFSET;
739 fake_jump->type = INSN_JUMP_UNCONDITIONAL;
740 fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
741 fake_jump->func = orig_insn->func;
744 if (!special_alt->new_len) {
746 WARN("%s: empty alternative at end of section",
747 special_alt->orig_sec->name);
751 *new_insn = fake_jump;
755 last_new_insn = NULL;
757 sec_for_each_insn_from(file, insn) {
758 if (insn->offset >= special_alt->new_off + special_alt->new_len)
761 last_new_insn = insn;
763 insn->ignore = orig_insn->ignore_alts;
764 insn->func = orig_insn->func;
766 if (insn->type != INSN_JUMP_CONDITIONAL &&
767 insn->type != INSN_JUMP_UNCONDITIONAL)
770 if (!insn->immediate)
773 dest_off = insn->offset + insn->len + insn->immediate;
774 if (dest_off == special_alt->new_off + special_alt->new_len) {
776 WARN("%s: alternative jump to end of section",
777 special_alt->orig_sec->name);
780 insn->jump_dest = fake_jump;
783 if (!insn->jump_dest) {
784 WARN_FUNC("can't find alternative jump destination",
785 insn->sec, insn->offset);
790 if (!last_new_insn) {
791 WARN_FUNC("can't find last new alternative instruction",
792 special_alt->new_sec, special_alt->new_off);
797 list_add(&fake_jump->list, &last_new_insn->list);
803 * A jump table entry can either convert a nop to a jump or a jump to a nop.
804 * If the original instruction is a jump, make the alt entry an effective nop
805 * by just skipping the original instruction.
807 static int handle_jump_alt(struct objtool_file *file,
808 struct special_alt *special_alt,
809 struct instruction *orig_insn,
810 struct instruction **new_insn)
812 if (orig_insn->type == INSN_NOP)
815 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
816 WARN_FUNC("unsupported instruction at jump label",
817 orig_insn->sec, orig_insn->offset);
821 *new_insn = list_next_entry(orig_insn, list);
826 * Read all the special sections which have alternate instructions which can be
827 * patched in or redirected to at runtime. Each instruction having alternate
828 * instruction(s) has them added to its insn->alts list, which will be
829 * traversed in validate_branch().
831 static int add_special_section_alts(struct objtool_file *file)
833 struct list_head special_alts;
834 struct instruction *orig_insn, *new_insn;
835 struct special_alt *special_alt, *tmp;
836 struct alternative *alt;
839 ret = special_get_alts(file->elf, &special_alts);
843 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
845 orig_insn = find_insn(file, special_alt->orig_sec,
846 special_alt->orig_off);
848 WARN_FUNC("special: can't find orig instruction",
849 special_alt->orig_sec, special_alt->orig_off);
855 if (!special_alt->group || special_alt->new_len) {
856 new_insn = find_insn(file, special_alt->new_sec,
857 special_alt->new_off);
859 WARN_FUNC("special: can't find new instruction",
860 special_alt->new_sec,
861 special_alt->new_off);
867 if (special_alt->group) {
868 ret = handle_group_alt(file, special_alt, orig_insn,
872 } else if (special_alt->jump_or_nop) {
873 ret = handle_jump_alt(file, special_alt, orig_insn,
879 alt = malloc(sizeof(*alt));
881 WARN("malloc failed");
886 alt->insn = new_insn;
887 alt->skip_orig = special_alt->skip_orig;
888 orig_insn->ignore_alts |= special_alt->skip_alt;
889 list_add_tail(&alt->list, &orig_insn->alts);
891 list_del(&special_alt->list);
899 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
902 struct rela *rela = table;
903 struct instruction *dest_insn;
904 struct alternative *alt;
905 struct symbol *pfunc = insn->func->pfunc;
906 unsigned int prev_offset = 0;
909 * Each @rela is a switch table relocation which points to the target
912 list_for_each_entry_from(rela, &table->sec->rela_list, list) {
914 /* Check for the end of the table: */
915 if (rela != table && rela->jump_table_start)
918 /* Make sure the table entries are consecutive: */
919 if (prev_offset && rela->offset != prev_offset + 8)
922 /* Detect function pointers from contiguous objects: */
923 if (rela->sym->sec == pfunc->sec &&
924 rela->addend == pfunc->offset)
927 dest_insn = find_insn(file, rela->sym->sec, rela->addend);
931 /* Make sure the destination is in the same function: */
932 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
935 alt = malloc(sizeof(*alt));
937 WARN("malloc failed");
941 alt->insn = dest_insn;
942 list_add_tail(&alt->list, &insn->alts);
943 prev_offset = rela->offset;
947 WARN_FUNC("can't find switch jump table",
948 insn->sec, insn->offset);
956 * find_jump_table() - Given a dynamic jump, find the switch jump table in
957 * .rodata associated with it.
959 * There are 3 basic patterns:
961 * 1. jmpq *[rodata addr](,%reg,8)
963 * This is the most common case by far. It jumps to an address in a simple
964 * jump table which is stored in .rodata.
966 * 2. jmpq *[rodata addr](%rip)
968 * This is caused by a rare GCC quirk, currently only seen in three driver
969 * functions in the kernel, only with certain obscure non-distro configs.
971 * As part of an optimization, GCC makes a copy of an existing switch jump
972 * table, modifies it, and then hard-codes the jump (albeit with an indirect
973 * jump) to use a single entry in the table. The rest of the jump table and
974 * some of its jump targets remain as dead code.
976 * In such a case we can just crudely ignore all unreachable instruction
977 * warnings for the entire object file. Ideally we would just ignore them
978 * for the function, but that would require redesigning the code quite a
979 * bit. And honestly that's just not worth doing: unreachable instruction
980 * warnings are of questionable value anyway, and this is such a rare issue.
982 * 3. mov [rodata addr],%reg1
983 * ... some instructions ...
984 * jmpq *(%reg1,%reg2,8)
986 * This is a fairly uncommon pattern which is new for GCC 6. As of this
987 * writing, there are 11 occurrences of it in the allmodconfig kernel.
989 * As of GCC 7 there are quite a few more of these and the 'in between' code
990 * is significant. Esp. with KASAN enabled some of the code between the mov
991 * and jmpq uses .rodata itself, which can confuse things.
993 * TODO: Once we have DWARF CFI and smarter instruction decoding logic,
994 * ensure the same register is used in the mov and jump instructions.
996 * NOTE: RETPOLINE made it harder still to decode dynamic jumps.
998 static struct rela *find_jump_table(struct objtool_file *file,
1000 struct instruction *insn)
1002 struct rela *text_rela, *table_rela;
1003 struct instruction *orig_insn = insn;
1004 struct section *table_sec;
1005 unsigned long table_offset;
1008 * Backward search using the @first_jump_src links, these help avoid
1009 * much of the 'in between' code. Which avoids us getting confused by
1013 &insn->list != &file->insn_list &&
1014 insn->sec == func->sec &&
1015 insn->offset >= func->offset;
1017 insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
1019 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1022 /* allow small jumps within the range */
1023 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1025 (insn->jump_dest->offset <= insn->offset ||
1026 insn->jump_dest->offset > orig_insn->offset))
1029 /* look for a relocation which references .rodata */
1030 text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
1032 if (!text_rela || text_rela->sym->type != STT_SECTION ||
1033 !text_rela->sym->sec->rodata)
1036 table_offset = text_rela->addend;
1037 table_sec = text_rela->sym->sec;
1039 if (text_rela->type == R_X86_64_PC32)
1043 * Make sure the .rodata address isn't associated with a
1044 * symbol. GCC jump tables are anonymous data.
1046 * Also support C jump tables which are in the same format as
1047 * switch jump tables. For objtool to recognize them, they
1048 * need to be placed in the C_JUMP_TABLE_SECTION section. They
1049 * have symbols associated with them.
1051 if (find_symbol_containing(table_sec, table_offset) &&
1052 strcmp(table_sec->name, C_JUMP_TABLE_SECTION))
1055 /* Each table entry has a rela associated with it. */
1056 table_rela = find_rela_by_dest(table_sec, table_offset);
1061 * Use of RIP-relative switch jumps is quite rare, and
1062 * indicates a rare GCC quirk/bug which can leave dead code
1065 if (text_rela->type == R_X86_64_PC32)
1066 file->ignore_unreachables = true;
1075 * First pass: Mark the head of each jump table so that in the next pass,
1076 * we know when a given jump table ends and the next one starts.
1078 static void mark_func_jump_tables(struct objtool_file *file,
1079 struct symbol *func)
1081 struct instruction *insn, *last = NULL;
1084 func_for_each_insn_all(file, func, insn) {
1089 * Store back-pointers for unconditional forward jumps such
1090 * that find_jump_table() can back-track using those and
1091 * avoid some potentially confusing code.
1093 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1094 insn->offset > last->offset &&
1095 insn->jump_dest->offset > insn->offset &&
1096 !insn->jump_dest->first_jump_src) {
1098 insn->jump_dest->first_jump_src = insn;
1099 last = insn->jump_dest;
1102 if (insn->type != INSN_JUMP_DYNAMIC)
1105 rela = find_jump_table(file, func, insn);
1107 rela->jump_table_start = true;
1108 insn->jump_table = rela;
1113 static int add_func_jump_tables(struct objtool_file *file,
1114 struct symbol *func)
1116 struct instruction *insn;
1119 func_for_each_insn_all(file, func, insn) {
1120 if (!insn->jump_table)
1123 ret = add_jump_table(file, insn, insn->jump_table);
1132 * For some switch statements, gcc generates a jump table in the .rodata
1133 * section which contains a list of addresses within the function to jump to.
1134 * This finds these jump tables and adds them to the insn->alts lists.
1136 static int add_jump_table_alts(struct objtool_file *file)
1138 struct section *sec;
1139 struct symbol *func;
1145 for_each_sec(file, sec) {
1146 list_for_each_entry(func, &sec->symbol_list, list) {
1147 if (func->type != STT_FUNC)
1150 mark_func_jump_tables(file, func);
1151 ret = add_func_jump_tables(file, func);
1160 static int read_unwind_hints(struct objtool_file *file)
1162 struct section *sec, *relasec;
1164 struct unwind_hint *hint;
1165 struct instruction *insn;
1166 struct cfi_reg *cfa;
1169 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1173 relasec = sec->rela;
1175 WARN("missing .rela.discard.unwind_hints section");
1179 if (sec->len % sizeof(struct unwind_hint)) {
1180 WARN("struct unwind_hint size mismatch");
1186 for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
1187 hint = (struct unwind_hint *)sec->data->d_buf + i;
1189 rela = find_rela_by_dest(sec, i * sizeof(*hint));
1191 WARN("can't find rela for unwind_hints[%d]", i);
1195 insn = find_insn(file, rela->sym->sec, rela->addend);
1197 WARN("can't find insn for unwind_hints[%d]", i);
1201 cfa = &insn->state.cfa;
1203 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
1207 } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
1208 insn->restore = true;
1215 switch (hint->sp_reg) {
1216 case ORC_REG_UNDEFINED:
1217 cfa->base = CFI_UNDEFINED;
1225 case ORC_REG_SP_INDIRECT:
1226 cfa->base = CFI_SP_INDIRECT;
1229 cfa->base = CFI_R10;
1232 cfa->base = CFI_R13;
1241 WARN_FUNC("unsupported unwind_hint sp base reg %d",
1242 insn->sec, insn->offset, hint->sp_reg);
1246 cfa->offset = hint->sp_offset;
1247 insn->state.type = hint->type;
1248 insn->state.end = hint->end;
1254 static int read_retpoline_hints(struct objtool_file *file)
1256 struct section *sec;
1257 struct instruction *insn;
1260 sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1264 list_for_each_entry(rela, &sec->rela_list, list) {
1265 if (rela->sym->type != STT_SECTION) {
1266 WARN("unexpected relocation symbol type in %s", sec->name);
1270 insn = find_insn(file, rela->sym->sec, rela->addend);
1272 WARN("bad .discard.retpoline_safe entry");
1276 if (insn->type != INSN_JUMP_DYNAMIC &&
1277 insn->type != INSN_CALL_DYNAMIC) {
1278 WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1279 insn->sec, insn->offset);
1283 insn->retpoline_safe = true;
1289 static void mark_rodata(struct objtool_file *file)
1291 struct section *sec;
1295 * Search for the following rodata sections, each of which can
1296 * potentially contain jump tables:
1298 * - .rodata: can contain GCC switch tables
1299 * - .rodata.<func>: same, if -fdata-sections is being used
1300 * - .rodata..c_jump_table: contains C annotated jump tables
1302 * .rodata.str1.* sections are ignored; they don't contain jump tables.
1304 for_each_sec(file, sec) {
1305 if ((!strncmp(sec->name, ".rodata", 7) && !strstr(sec->name, ".str1.")) ||
1306 !strcmp(sec->name, C_JUMP_TABLE_SECTION)) {
1312 file->rodata = found;
1315 static int decode_sections(struct objtool_file *file)
1321 ret = decode_instructions(file);
1325 ret = add_dead_ends(file);
1330 add_uaccess_safe(file);
1332 ret = add_ignore_alternatives(file);
1336 ret = add_jump_destinations(file);
1340 ret = add_special_section_alts(file);
1344 ret = add_call_destinations(file);
1348 ret = add_jump_table_alts(file);
1352 ret = read_unwind_hints(file);
1356 ret = read_retpoline_hints(file);
1363 static bool is_fentry_call(struct instruction *insn)
1365 if (insn->type == INSN_CALL &&
1366 insn->call_dest->type == STT_NOTYPE &&
1367 !strcmp(insn->call_dest->name, "__fentry__"))
1373 static bool has_modified_stack_frame(struct insn_state *state)
1377 if (state->cfa.base != initial_func_cfi.cfa.base ||
1378 state->cfa.offset != initial_func_cfi.cfa.offset ||
1379 state->stack_size != initial_func_cfi.cfa.offset ||
1383 for (i = 0; i < CFI_NUM_REGS; i++)
1384 if (state->regs[i].base != initial_func_cfi.regs[i].base ||
1385 state->regs[i].offset != initial_func_cfi.regs[i].offset)
1391 static bool has_valid_stack_frame(struct insn_state *state)
1393 if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
1394 state->regs[CFI_BP].offset == -16)
1397 if (state->drap && state->regs[CFI_BP].base == CFI_BP)
1403 static int update_insn_state_regs(struct instruction *insn, struct insn_state *state)
1405 struct cfi_reg *cfa = &state->cfa;
1406 struct stack_op *op = &insn->stack_op;
1408 if (cfa->base != CFI_SP)
1412 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
1416 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
1419 /* add immediate to sp */
1420 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1421 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1422 cfa->offset -= op->src.offset;
1427 static void save_reg(struct insn_state *state, unsigned char reg, int base,
1430 if (arch_callee_saved_reg(reg) &&
1431 state->regs[reg].base == CFI_UNDEFINED) {
1432 state->regs[reg].base = base;
1433 state->regs[reg].offset = offset;
1437 static void restore_reg(struct insn_state *state, unsigned char reg)
1439 state->regs[reg].base = CFI_UNDEFINED;
1440 state->regs[reg].offset = 0;
1444 * A note about DRAP stack alignment:
1446 * GCC has the concept of a DRAP register, which is used to help keep track of
1447 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
1448 * register. The typical DRAP pattern is:
1450 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
1451 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
1452 * 41 ff 72 f8 pushq -0x8(%r10)
1454 * 48 89 e5 mov %rsp,%rbp
1461 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1464 * There are some variations in the epilogues, like:
1472 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1477 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
1478 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
1479 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
1480 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
1482 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1485 * Sometimes r13 is used as the DRAP register, in which case it's saved and
1486 * restored beforehand:
1489 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
1490 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
1492 * 49 8d 65 f0 lea -0x10(%r13),%rsp
1496 static int update_insn_state(struct instruction *insn, struct insn_state *state)
1498 struct stack_op *op = &insn->stack_op;
1499 struct cfi_reg *cfa = &state->cfa;
1500 struct cfi_reg *regs = state->regs;
1502 /* stack operations don't make sense with an undefined CFA */
1503 if (cfa->base == CFI_UNDEFINED) {
1505 WARN_FUNC("undefined stack state", insn->sec, insn->offset);
1511 if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET)
1512 return update_insn_state_regs(insn, state);
1514 switch (op->dest.type) {
1517 switch (op->src.type) {
1520 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
1521 cfa->base == CFI_SP &&
1522 regs[CFI_BP].base == CFI_CFA &&
1523 regs[CFI_BP].offset == -cfa->offset) {
1525 /* mov %rsp, %rbp */
1526 cfa->base = op->dest.reg;
1527 state->bp_scratch = false;
1530 else if (op->src.reg == CFI_SP &&
1531 op->dest.reg == CFI_BP && state->drap) {
1533 /* drap: mov %rsp, %rbp */
1534 regs[CFI_BP].base = CFI_BP;
1535 regs[CFI_BP].offset = -state->stack_size;
1536 state->bp_scratch = false;
1539 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1544 * This is needed for the rare case where GCC
1551 state->vals[op->dest.reg].base = CFI_CFA;
1552 state->vals[op->dest.reg].offset = -state->stack_size;
1555 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
1556 cfa->base == CFI_BP) {
1561 * Restore the original stack pointer (Clang).
1563 state->stack_size = -state->regs[CFI_BP].offset;
1566 else if (op->dest.reg == cfa->base) {
1568 /* mov %reg, %rsp */
1569 if (cfa->base == CFI_SP &&
1570 state->vals[op->src.reg].base == CFI_CFA) {
1573 * This is needed for the rare case
1574 * where GCC does something dumb like:
1576 * lea 0x8(%rsp), %rcx
1580 cfa->offset = -state->vals[op->src.reg].offset;
1581 state->stack_size = cfa->offset;
1584 cfa->base = CFI_UNDEFINED;
1592 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
1595 state->stack_size -= op->src.offset;
1596 if (cfa->base == CFI_SP)
1597 cfa->offset -= op->src.offset;
1601 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
1603 /* lea disp(%rbp), %rsp */
1604 state->stack_size = -(op->src.offset + regs[CFI_BP].offset);
1608 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1610 /* drap: lea disp(%rsp), %drap */
1611 state->drap_reg = op->dest.reg;
1614 * lea disp(%rsp), %reg
1616 * This is needed for the rare case where GCC
1617 * does something dumb like:
1619 * lea 0x8(%rsp), %rcx
1623 state->vals[op->dest.reg].base = CFI_CFA;
1624 state->vals[op->dest.reg].offset = \
1625 -state->stack_size + op->src.offset;
1630 if (state->drap && op->dest.reg == CFI_SP &&
1631 op->src.reg == state->drap_reg) {
1633 /* drap: lea disp(%drap), %rsp */
1635 cfa->offset = state->stack_size = -op->src.offset;
1636 state->drap_reg = CFI_UNDEFINED;
1637 state->drap = false;
1641 if (op->dest.reg == state->cfa.base) {
1642 WARN_FUNC("unsupported stack register modification",
1643 insn->sec, insn->offset);
1650 if (op->dest.reg != CFI_SP ||
1651 (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
1652 (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
1653 WARN_FUNC("unsupported stack pointer realignment",
1654 insn->sec, insn->offset);
1658 if (state->drap_reg != CFI_UNDEFINED) {
1659 /* drap: and imm, %rsp */
1660 cfa->base = state->drap_reg;
1661 cfa->offset = state->stack_size = 0;
1666 * Older versions of GCC (4.8ish) realign the stack
1667 * without DRAP, with a frame pointer.
1674 if (!state->drap && op->dest.type == OP_DEST_REG &&
1675 op->dest.reg == cfa->base) {
1681 if (state->drap && cfa->base == CFI_BP_INDIRECT &&
1682 op->dest.type == OP_DEST_REG &&
1683 op->dest.reg == state->drap_reg &&
1684 state->drap_offset == -state->stack_size) {
1686 /* drap: pop %drap */
1687 cfa->base = state->drap_reg;
1689 state->drap_offset = -1;
1691 } else if (regs[op->dest.reg].offset == -state->stack_size) {
1694 restore_reg(state, op->dest.reg);
1697 state->stack_size -= 8;
1698 if (cfa->base == CFI_SP)
1703 case OP_SRC_REG_INDIRECT:
1704 if (state->drap && op->src.reg == CFI_BP &&
1705 op->src.offset == state->drap_offset) {
1707 /* drap: mov disp(%rbp), %drap */
1708 cfa->base = state->drap_reg;
1710 state->drap_offset = -1;
1713 if (state->drap && op->src.reg == CFI_BP &&
1714 op->src.offset == regs[op->dest.reg].offset) {
1716 /* drap: mov disp(%rbp), %reg */
1717 restore_reg(state, op->dest.reg);
1719 } else if (op->src.reg == cfa->base &&
1720 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
1722 /* mov disp(%rbp), %reg */
1723 /* mov disp(%rsp), %reg */
1724 restore_reg(state, op->dest.reg);
1730 WARN_FUNC("unknown stack-related instruction",
1731 insn->sec, insn->offset);
1739 state->stack_size += 8;
1740 if (cfa->base == CFI_SP)
1743 if (op->src.type != OP_SRC_REG)
1747 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1749 /* drap: push %drap */
1750 cfa->base = CFI_BP_INDIRECT;
1751 cfa->offset = -state->stack_size;
1753 /* save drap so we know when to restore it */
1754 state->drap_offset = -state->stack_size;
1756 } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
1758 /* drap: push %rbp */
1759 state->stack_size = 0;
1761 } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1763 /* drap: push %reg */
1764 save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
1770 save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
1773 /* detect when asm code uses rbp as a scratch register */
1774 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
1775 cfa->base != CFI_BP)
1776 state->bp_scratch = true;
1779 case OP_DEST_REG_INDIRECT:
1782 if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1784 /* drap: mov %drap, disp(%rbp) */
1785 cfa->base = CFI_BP_INDIRECT;
1786 cfa->offset = op->dest.offset;
1788 /* save drap offset so we know when to restore it */
1789 state->drap_offset = op->dest.offset;
1792 else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1794 /* drap: mov reg, disp(%rbp) */
1795 save_reg(state, op->src.reg, CFI_BP, op->dest.offset);
1798 } else if (op->dest.reg == cfa->base) {
1800 /* mov reg, disp(%rbp) */
1801 /* mov reg, disp(%rsp) */
1802 save_reg(state, op->src.reg, CFI_CFA,
1803 op->dest.offset - state->cfa.offset);
1809 if ((!state->drap && cfa->base != CFI_BP) ||
1810 (state->drap && cfa->base != state->drap_reg)) {
1811 WARN_FUNC("leave instruction with modified stack frame",
1812 insn->sec, insn->offset);
1816 /* leave (mov %rbp, %rsp; pop %rbp) */
1818 state->stack_size = -state->regs[CFI_BP].offset - 8;
1819 restore_reg(state, CFI_BP);
1829 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
1830 WARN_FUNC("unknown stack-related memory operation",
1831 insn->sec, insn->offset);
1836 state->stack_size -= 8;
1837 if (cfa->base == CFI_SP)
1843 WARN_FUNC("unknown stack-related instruction",
1844 insn->sec, insn->offset);
1851 static bool insn_state_match(struct instruction *insn, struct insn_state *state)
1853 struct insn_state *state1 = &insn->state, *state2 = state;
1856 if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
1857 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
1858 insn->sec, insn->offset,
1859 state1->cfa.base, state1->cfa.offset,
1860 state2->cfa.base, state2->cfa.offset);
1862 } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
1863 for (i = 0; i < CFI_NUM_REGS; i++) {
1864 if (!memcmp(&state1->regs[i], &state2->regs[i],
1865 sizeof(struct cfi_reg)))
1868 WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
1869 insn->sec, insn->offset,
1870 i, state1->regs[i].base, state1->regs[i].offset,
1871 i, state2->regs[i].base, state2->regs[i].offset);
1875 } else if (state1->type != state2->type) {
1876 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
1877 insn->sec, insn->offset, state1->type, state2->type);
1879 } else if (state1->drap != state2->drap ||
1880 (state1->drap && state1->drap_reg != state2->drap_reg) ||
1881 (state1->drap && state1->drap_offset != state2->drap_offset)) {
1882 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
1883 insn->sec, insn->offset,
1884 state1->drap, state1->drap_reg, state1->drap_offset,
1885 state2->drap, state2->drap_reg, state2->drap_offset);
1893 static inline bool func_uaccess_safe(struct symbol *func)
1896 return func->uaccess_safe;
1901 static inline const char *call_dest_name(struct instruction *insn)
1903 if (insn->call_dest)
1904 return insn->call_dest->name;
1909 static int validate_call(struct instruction *insn, struct insn_state *state)
1911 if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
1912 WARN_FUNC("call to %s() with UACCESS enabled",
1913 insn->sec, insn->offset, call_dest_name(insn));
1918 WARN_FUNC("call to %s() with DF set",
1919 insn->sec, insn->offset, call_dest_name(insn));
1926 static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
1928 if (has_modified_stack_frame(state)) {
1929 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1930 insn->sec, insn->offset);
1934 return validate_call(insn, state);
1938 * Follow the branch starting at the given instruction, and recursively follow
1939 * any other branches (jumps). Meanwhile, track the frame pointer state at
1940 * each instruction and validate all the rules described in
1941 * tools/objtool/Documentation/stack-validation.txt.
1943 static int validate_branch(struct objtool_file *file, struct symbol *func,
1944 struct instruction *first, struct insn_state state)
1946 struct alternative *alt;
1947 struct instruction *insn, *next_insn;
1948 struct section *sec;
1955 if (insn->alt_group && list_empty(&insn->alts)) {
1956 WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
1962 next_insn = next_insn_same_sec(file, insn);
1964 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
1965 WARN("%s() falls through to next function %s()",
1966 func->name, insn->func->name);
1970 if (func && insn->ignore) {
1971 WARN_FUNC("BUG: why am I validating an ignored function?",
1976 visited = 1 << state.uaccess;
1977 if (insn->visited) {
1978 if (!insn->hint && !insn_state_match(insn, &state))
1981 if (insn->visited & visited)
1986 if (insn->restore) {
1987 struct instruction *save_insn, *i;
1991 func_for_each_insn_continue_reverse(file, func, i) {
1999 WARN_FUNC("no corresponding CFI save for CFI restore",
2004 if (!save_insn->visited) {
2006 * Oops, no state to copy yet.
2007 * Hopefully we can reach this
2008 * instruction from another branch
2009 * after the save insn has been
2015 WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
2020 insn->state = save_insn->state;
2023 state = insn->state;
2026 insn->state = state;
2028 insn->visited |= visited;
2030 if (!insn->ignore_alts) {
2031 bool skip_orig = false;
2033 list_for_each_entry(alt, &insn->alts, list) {
2037 ret = validate_branch(file, func, alt->insn, state);
2040 BT_FUNC("(alt)", insn);
2049 switch (insn->type) {
2052 if (state.uaccess && !func_uaccess_safe(func)) {
2053 WARN_FUNC("return with UACCESS enabled", sec, insn->offset);
2057 if (!state.uaccess && func_uaccess_safe(func)) {
2058 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function", sec, insn->offset);
2063 WARN_FUNC("return with DF set", sec, insn->offset);
2067 if (func && has_modified_stack_frame(&state)) {
2068 WARN_FUNC("return with modified stack frame",
2073 if (state.bp_scratch) {
2074 WARN("%s uses BP as a scratch register",
2082 case INSN_CALL_DYNAMIC:
2083 ret = validate_call(insn, &state);
2087 if (!no_fp && func && !is_fentry_call(insn) &&
2088 !has_valid_stack_frame(&state)) {
2089 WARN_FUNC("call without frame pointer save/setup",
2094 if (dead_end_function(file, insn->call_dest))
2099 case INSN_JUMP_CONDITIONAL:
2100 case INSN_JUMP_UNCONDITIONAL:
2101 if (func && is_sibling_call(insn)) {
2102 ret = validate_sibling_call(insn, &state);
2106 } else if (insn->jump_dest) {
2107 ret = validate_branch(file, func,
2108 insn->jump_dest, state);
2111 BT_FUNC("(branch)", insn);
2116 if (insn->type == INSN_JUMP_UNCONDITIONAL)
2121 case INSN_JUMP_DYNAMIC:
2122 case INSN_JUMP_DYNAMIC_CONDITIONAL:
2123 if (func && is_sibling_call(insn)) {
2124 ret = validate_sibling_call(insn, &state);
2129 if (insn->type == INSN_JUMP_DYNAMIC)
2134 case INSN_CONTEXT_SWITCH:
2135 if (func && (!next_insn || !next_insn->hint)) {
2136 WARN_FUNC("unsupported instruction in callable function",
2143 if (update_insn_state(insn, &state))
2146 if (insn->stack_op.dest.type == OP_DEST_PUSHF) {
2147 if (!state.uaccess_stack) {
2148 state.uaccess_stack = 1;
2149 } else if (state.uaccess_stack >> 31) {
2150 WARN_FUNC("PUSHF stack exhausted", sec, insn->offset);
2153 state.uaccess_stack <<= 1;
2154 state.uaccess_stack |= state.uaccess;
2157 if (insn->stack_op.src.type == OP_SRC_POPF) {
2158 if (state.uaccess_stack) {
2159 state.uaccess = state.uaccess_stack & 1;
2160 state.uaccess_stack >>= 1;
2161 if (state.uaccess_stack == 1)
2162 state.uaccess_stack = 0;
2169 if (state.uaccess) {
2170 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
2174 state.uaccess = true;
2178 if (!state.uaccess && func) {
2179 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
2183 if (func_uaccess_safe(func) && !state.uaccess_stack) {
2184 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
2188 state.uaccess = false;
2193 WARN_FUNC("recursive STD", sec, insn->offset);
2199 if (!state.df && func)
2200 WARN_FUNC("redundant CLD", sec, insn->offset);
2213 if (state.cfa.base == CFI_UNDEFINED)
2215 WARN("%s: unexpected end of section", sec->name);
2225 static int validate_unwind_hints(struct objtool_file *file)
2227 struct instruction *insn;
2228 int ret, warnings = 0;
2229 struct insn_state state;
2234 clear_insn_state(&state);
2236 for_each_insn(file, insn) {
2237 if (insn->hint && !insn->visited) {
2238 ret = validate_branch(file, insn->func, insn, state);
2239 if (ret && backtrace)
2240 BT_FUNC("<=== (hint)", insn);
2248 static int validate_retpoline(struct objtool_file *file)
2250 struct instruction *insn;
2253 for_each_insn(file, insn) {
2254 if (insn->type != INSN_JUMP_DYNAMIC &&
2255 insn->type != INSN_CALL_DYNAMIC)
2258 if (insn->retpoline_safe)
2262 * .init.text code is ran before userspace and thus doesn't
2263 * strictly need retpolines, except for modules which are
2264 * loaded late, they very much do need retpoline in their
2267 if (!strcmp(insn->sec->name, ".init.text") && !module)
2270 WARN_FUNC("indirect %s found in RETPOLINE build",
2271 insn->sec, insn->offset,
2272 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
2280 static bool is_kasan_insn(struct instruction *insn)
2282 return (insn->type == INSN_CALL &&
2283 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
2286 static bool is_ubsan_insn(struct instruction *insn)
2288 return (insn->type == INSN_CALL &&
2289 !strcmp(insn->call_dest->name,
2290 "__ubsan_handle_builtin_unreachable"));
2293 static bool ignore_unreachable_insn(struct instruction *insn)
2297 if (insn->ignore || insn->type == INSN_NOP)
2301 * Ignore any unused exceptions. This can happen when a whitelisted
2302 * function has an exception table entry.
2304 * Also ignore alternative replacement instructions. This can happen
2305 * when a whitelisted function uses one of the ALTERNATIVE macros.
2307 if (!strcmp(insn->sec->name, ".fixup") ||
2308 !strcmp(insn->sec->name, ".altinstr_replacement") ||
2309 !strcmp(insn->sec->name, ".altinstr_aux"))
2313 * Check if this (or a subsequent) instruction is related to
2314 * CONFIG_UBSAN or CONFIG_KASAN.
2316 * End the search at 5 instructions to avoid going into the weeds.
2320 for (i = 0; i < 5; i++) {
2322 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
2325 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
2326 if (insn->jump_dest &&
2327 insn->jump_dest->func == insn->func) {
2328 insn = insn->jump_dest;
2335 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
2338 insn = list_next_entry(insn, list);
2344 static int validate_functions(struct objtool_file *file)
2346 struct section *sec;
2347 struct symbol *func;
2348 struct instruction *insn;
2349 struct insn_state state;
2350 int ret, warnings = 0;
2352 clear_insn_state(&state);
2354 state.cfa = initial_func_cfi.cfa;
2355 memcpy(&state.regs, &initial_func_cfi.regs,
2356 CFI_NUM_REGS * sizeof(struct cfi_reg));
2357 state.stack_size = initial_func_cfi.cfa.offset;
2359 for_each_sec(file, sec) {
2360 list_for_each_entry(func, &sec->symbol_list, list) {
2361 if (func->type != STT_FUNC)
2365 WARN("%s() is missing an ELF size annotation",
2370 if (func->pfunc != func || func->alias != func)
2373 insn = find_insn(file, sec, func->offset);
2374 if (!insn || insn->ignore || insn->visited)
2377 state.uaccess = func->uaccess_safe;
2379 ret = validate_branch(file, func, insn, state);
2380 if (ret && backtrace)
2381 BT_FUNC("<=== (func)", insn);
2389 static int validate_reachable_instructions(struct objtool_file *file)
2391 struct instruction *insn;
2393 if (file->ignore_unreachables)
2396 for_each_insn(file, insn) {
2397 if (insn->visited || ignore_unreachable_insn(insn))
2400 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
2407 static void cleanup(struct objtool_file *file)
2409 struct instruction *insn, *tmpinsn;
2410 struct alternative *alt, *tmpalt;
2412 list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) {
2413 list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) {
2414 list_del(&alt->list);
2417 list_del(&insn->list);
2418 hash_del(&insn->hash);
2421 elf_close(file->elf);
2424 static struct objtool_file file;
2426 int check(const char *_objname, bool orc)
2428 int ret, warnings = 0;
2432 file.elf = elf_read(objname, orc ? O_RDWR : O_RDONLY);
2436 INIT_LIST_HEAD(&file.insn_list);
2437 hash_init(file.insn_hash);
2438 file.c_file = find_section_by_name(file.elf, ".comment");
2439 file.ignore_unreachables = no_unreachable;
2442 arch_initial_func_cfi_state(&initial_func_cfi);
2444 ret = decode_sections(&file);
2449 if (list_empty(&file.insn_list))
2453 ret = validate_retpoline(&file);
2459 ret = validate_functions(&file);
2464 ret = validate_unwind_hints(&file);
2470 ret = validate_reachable_instructions(&file);
2477 ret = create_orc(&file);
2481 ret = create_orc_sections(&file);
2485 ret = elf_write(file.elf);
2493 /* ignore warnings for now until we get all the code cleaned up */
2494 if (ret || warnings)