1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
11 #include <objtool/builtin.h>
12 #include <objtool/cfi.h>
13 #include <objtool/arch.h>
14 #include <objtool/check.h>
15 #include <objtool/special.h>
16 #include <objtool/warn.h>
17 #include <objtool/endianness.h>
19 #include <linux/objtool_types.h>
20 #include <linux/hashtable.h>
21 #include <linux/kernel.h>
22 #include <linux/static_call_types.h>
23 #include <linux/string.h>
26 struct alternative *next;
27 struct instruction *insn;
31 static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
33 static struct cfi_init_state initial_func_cfi;
34 static struct cfi_state init_cfi;
35 static struct cfi_state func_cfi;
36 static struct cfi_state force_undefined_cfi;
38 struct instruction *find_insn(struct objtool_file *file,
39 struct section *sec, unsigned long offset)
41 struct instruction *insn;
43 hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
44 if (insn->sec == sec && insn->offset == offset)
51 struct instruction *next_insn_same_sec(struct objtool_file *file,
52 struct instruction *insn)
54 if (insn->idx == INSN_CHUNK_MAX)
55 return find_insn(file, insn->sec, insn->offset + insn->len);
64 static struct instruction *next_insn_same_func(struct objtool_file *file,
65 struct instruction *insn)
67 struct instruction *next = next_insn_same_sec(file, insn);
68 struct symbol *func = insn_func(insn);
73 if (next && insn_func(next) == func)
76 /* Check if we're already in the subfunction: */
77 if (func == func->cfunc)
80 /* Move to the subfunction: */
81 return find_insn(file, func->cfunc->sec, func->cfunc->offset);
84 static struct instruction *prev_insn_same_sec(struct objtool_file *file,
85 struct instruction *insn)
89 return find_insn(file, insn->sec, insn->offset - insn->prev_len);
96 static struct instruction *prev_insn_same_sym(struct objtool_file *file,
97 struct instruction *insn)
99 struct instruction *prev = prev_insn_same_sec(file, insn);
101 if (prev && insn_func(prev) == insn_func(insn))
107 #define for_each_insn(file, insn) \
108 for (struct section *__sec, *__fake = (struct section *)1; \
109 __fake; __fake = NULL) \
110 for_each_sec(file, __sec) \
111 sec_for_each_insn(file, __sec, insn)
113 #define func_for_each_insn(file, func, insn) \
114 for (insn = find_insn(file, func->sec, func->offset); \
116 insn = next_insn_same_func(file, insn))
118 #define sym_for_each_insn(file, sym, insn) \
119 for (insn = find_insn(file, sym->sec, sym->offset); \
120 insn && insn->offset < sym->offset + sym->len; \
121 insn = next_insn_same_sec(file, insn))
123 #define sym_for_each_insn_continue_reverse(file, sym, insn) \
124 for (insn = prev_insn_same_sec(file, insn); \
125 insn && insn->offset >= sym->offset; \
126 insn = prev_insn_same_sec(file, insn))
128 #define sec_for_each_insn_from(file, insn) \
129 for (; insn; insn = next_insn_same_sec(file, insn))
131 #define sec_for_each_insn_continue(file, insn) \
132 for (insn = next_insn_same_sec(file, insn); insn; \
133 insn = next_insn_same_sec(file, insn))
135 static inline struct symbol *insn_call_dest(struct instruction *insn)
137 if (insn->type == INSN_JUMP_DYNAMIC ||
138 insn->type == INSN_CALL_DYNAMIC)
141 return insn->_call_dest;
144 static inline struct reloc *insn_jump_table(struct instruction *insn)
146 if (insn->type == INSN_JUMP_DYNAMIC ||
147 insn->type == INSN_CALL_DYNAMIC)
148 return insn->_jump_table;
153 static bool is_jump_table_jump(struct instruction *insn)
155 struct alt_group *alt_group = insn->alt_group;
157 if (insn_jump_table(insn))
160 /* Retpoline alternative for a jump table? */
161 return alt_group && alt_group->orig_group &&
162 insn_jump_table(alt_group->orig_group->first_insn);
165 static bool is_sibling_call(struct instruction *insn)
168 * Assume only STT_FUNC calls have jump-tables.
170 if (insn_func(insn)) {
171 /* An indirect jump is either a sibling call or a jump to a table. */
172 if (insn->type == INSN_JUMP_DYNAMIC)
173 return !is_jump_table_jump(insn);
176 /* add_jump_destinations() sets insn_call_dest(insn) for sibling calls. */
177 return (is_static_jump(insn) && insn_call_dest(insn));
181 * This checks to see if the given function is a "noreturn" function.
183 * For global functions which are outside the scope of this object file, we
184 * have to keep a manual list of them.
186 * For local functions, we have to detect them manually by simply looking for
187 * the lack of a return instruction.
189 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
193 struct instruction *insn;
196 #define NORETURN(func) __stringify(func),
197 static const char * const global_noreturns[] = {
198 #include "noreturns.h"
205 if (func->bind == STB_GLOBAL || func->bind == STB_WEAK)
206 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
207 if (!strcmp(func->name, global_noreturns[i]))
210 if (func->bind == STB_WEAK)
216 insn = find_insn(file, func->sec, func->offset);
217 if (!insn || !insn_func(insn))
220 func_for_each_insn(file, func, insn) {
223 if (insn->type == INSN_RETURN)
231 * A function can have a sibling call instead of a return. In that
232 * case, the function's dead-end status depends on whether the target
233 * of the sibling call returns.
235 func_for_each_insn(file, func, insn) {
236 if (is_sibling_call(insn)) {
237 struct instruction *dest = insn->jump_dest;
240 /* sibling call to another file */
243 /* local sibling call */
244 if (recursion == 5) {
246 * Infinite recursion: two functions have
247 * sibling calls to each other. This is a very
248 * rare case. It means they aren't dead ends.
253 return __dead_end_function(file, insn_func(dest), recursion+1);
260 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
262 return __dead_end_function(file, func, 0);
265 static void init_cfi_state(struct cfi_state *cfi)
269 for (i = 0; i < CFI_NUM_REGS; i++) {
270 cfi->regs[i].base = CFI_UNDEFINED;
271 cfi->vals[i].base = CFI_UNDEFINED;
273 cfi->cfa.base = CFI_UNDEFINED;
274 cfi->drap_reg = CFI_UNDEFINED;
275 cfi->drap_offset = -1;
278 static void init_insn_state(struct objtool_file *file, struct insn_state *state,
281 memset(state, 0, sizeof(*state));
282 init_cfi_state(&state->cfi);
285 * We need the full vmlinux for noinstr validation, otherwise we can
286 * not correctly determine insn_call_dest(insn)->sec (external symbols
287 * do not have a section).
289 if (opts.link && opts.noinstr && sec)
290 state->noinstr = sec->noinstr;
293 static struct cfi_state *cfi_alloc(void)
295 struct cfi_state *cfi = calloc(1, sizeof(struct cfi_state));
297 WARN("calloc failed");
305 static struct hlist_head *cfi_hash;
307 static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
309 return memcmp((void *)cfi1 + sizeof(cfi1->hash),
310 (void *)cfi2 + sizeof(cfi2->hash),
311 sizeof(struct cfi_state) - sizeof(struct hlist_node));
314 static inline u32 cfi_key(struct cfi_state *cfi)
316 return jhash((void *)cfi + sizeof(cfi->hash),
317 sizeof(*cfi) - sizeof(cfi->hash), 0);
320 static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
322 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
323 struct cfi_state *obj;
325 hlist_for_each_entry(obj, head, hash) {
326 if (!cficmp(cfi, obj)) {
334 hlist_add_head(&obj->hash, head);
339 static void cfi_hash_add(struct cfi_state *cfi)
341 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
343 hlist_add_head(&cfi->hash, head);
346 static void *cfi_hash_alloc(unsigned long size)
348 cfi_bits = max(10, ilog2(size));
349 cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
350 PROT_READ|PROT_WRITE,
351 MAP_PRIVATE|MAP_ANON, -1, 0);
352 if (cfi_hash == (void *)-1L) {
353 WARN("mmap fail cfi_hash");
355 } else if (opts.stats) {
356 printf("cfi_bits: %d\n", cfi_bits);
362 static unsigned long nr_insns;
363 static unsigned long nr_insns_visited;
366 * Call the arch-specific instruction decoder for all the instructions and add
367 * them to the global instruction list.
369 static int decode_instructions(struct objtool_file *file)
373 unsigned long offset;
374 struct instruction *insn;
377 for_each_sec(file, sec) {
378 struct instruction *insns = NULL;
382 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
385 if (strcmp(sec->name, ".altinstr_replacement") &&
386 strcmp(sec->name, ".altinstr_aux") &&
387 strncmp(sec->name, ".discard.", 9))
390 if (!strcmp(sec->name, ".noinstr.text") ||
391 !strcmp(sec->name, ".entry.text") ||
392 !strcmp(sec->name, ".cpuidle.text") ||
393 !strncmp(sec->name, ".text..__x86.", 13))
397 * .init.text code is ran before userspace and thus doesn't
398 * strictly need retpolines, except for modules which are
399 * loaded late, they very much do need retpoline in their
402 if (!strcmp(sec->name, ".init.text") && !opts.module)
405 for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
406 if (!insns || idx == INSN_CHUNK_MAX) {
407 insns = calloc(sizeof(*insn), INSN_CHUNK_SIZE);
409 WARN("malloc failed");
419 INIT_LIST_HEAD(&insn->call_node);
421 insn->offset = offset;
422 insn->prev_len = prev_len;
424 ret = arch_decode_instruction(file, sec, offset,
425 sec->sh.sh_size - offset,
430 prev_len = insn->len;
433 * By default, "ud2" is a dead end unless otherwise
434 * annotated, because GCC 7 inserts it for certain
435 * divide-by-zero cases.
437 if (insn->type == INSN_BUG)
438 insn->dead_end = true;
440 hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
444 // printf("%s: last chunk used: %d\n", sec->name, (int)idx);
446 sec_for_each_sym(sec, func) {
447 if (func->type != STT_NOTYPE && func->type != STT_FUNC)
450 if (func->offset == sec->sh.sh_size) {
451 /* Heuristic: likely an "end" symbol */
452 if (func->type == STT_NOTYPE)
454 WARN("%s(): STT_FUNC at end of section",
459 if (func->embedded_insn || func->alias != func)
462 if (!find_insn(file, sec, func->offset)) {
463 WARN("%s(): can't find starting instruction",
468 sym_for_each_insn(file, func, insn) {
470 if (func->type == STT_FUNC &&
471 insn->type == INSN_ENDBR &&
472 list_empty(&insn->call_node)) {
473 if (insn->offset == func->offset) {
474 list_add_tail(&insn->call_node, &file->endbr_list);
477 file->nr_endbr_int++;
485 printf("nr_insns: %lu\n", nr_insns);
491 * Read the pv_ops[] .data table to find the static initialized values.
493 static int add_pv_ops(struct objtool_file *file, const char *symname)
495 struct symbol *sym, *func;
496 unsigned long off, end;
500 sym = find_symbol_by_name(file->elf, symname);
505 end = off + sym->len;
507 reloc = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off);
512 if (func->type == STT_SECTION)
513 func = find_symbol_by_offset(reloc->sym->sec,
514 reloc_addend(reloc));
516 idx = (reloc_offset(reloc) - sym->offset) / sizeof(unsigned long);
518 objtool_pv_add(file, idx, func);
520 off = reloc_offset(reloc) + 1;
529 * Allocate and initialize file->pv_ops[].
531 static int init_pv_ops(struct objtool_file *file)
533 static const char *pv_ops_tables[] = {
549 sym = find_symbol_by_name(file->elf, "pv_ops");
553 nr = sym->len / sizeof(unsigned long);
554 file->pv_ops = calloc(sizeof(struct pv_state), nr);
558 for (idx = 0; idx < nr; idx++)
559 INIT_LIST_HEAD(&file->pv_ops[idx].targets);
561 for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++)
562 add_pv_ops(file, pv_ops);
567 static struct instruction *find_last_insn(struct objtool_file *file,
570 struct instruction *insn = NULL;
572 unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
574 for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
575 insn = find_insn(file, sec, offset);
581 * Mark "ud2" instructions and manually annotated dead ends.
583 static int add_dead_ends(struct objtool_file *file)
585 struct section *rsec;
587 struct instruction *insn;
588 unsigned long offset;
591 * Check for manually annotated dead ends.
593 rsec = find_section_by_name(file->elf, ".rela.discard.unreachable");
597 for_each_reloc(rsec, reloc) {
598 if (reloc->sym->type == STT_SECTION) {
599 offset = reloc_addend(reloc);
600 } else if (reloc->sym->local_label) {
601 offset = reloc->sym->offset;
603 WARN("unexpected relocation symbol type in %s", rsec->name);
607 insn = find_insn(file, reloc->sym->sec, offset);
609 insn = prev_insn_same_sec(file, insn);
610 else if (offset == reloc->sym->sec->sh.sh_size) {
611 insn = find_last_insn(file, reloc->sym->sec);
613 WARN("can't find unreachable insn at %s+0x%" PRIx64,
614 reloc->sym->sec->name, offset);
618 WARN("can't find unreachable insn at %s+0x%" PRIx64,
619 reloc->sym->sec->name, offset);
623 insn->dead_end = true;
628 * These manually annotated reachable checks are needed for GCC 4.4,
629 * where the Linux unreachable() macro isn't supported. In that case
630 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
633 rsec = find_section_by_name(file->elf, ".rela.discard.reachable");
637 for_each_reloc(rsec, reloc) {
638 if (reloc->sym->type == STT_SECTION) {
639 offset = reloc_addend(reloc);
640 } else if (reloc->sym->local_label) {
641 offset = reloc->sym->offset;
643 WARN("unexpected relocation symbol type in %s", rsec->name);
647 insn = find_insn(file, reloc->sym->sec, offset);
649 insn = prev_insn_same_sec(file, insn);
650 else if (offset == reloc->sym->sec->sh.sh_size) {
651 insn = find_last_insn(file, reloc->sym->sec);
653 WARN("can't find reachable insn at %s+0x%" PRIx64,
654 reloc->sym->sec->name, offset);
658 WARN("can't find reachable insn at %s+0x%" PRIx64,
659 reloc->sym->sec->name, offset);
663 insn->dead_end = false;
669 static int create_static_call_sections(struct objtool_file *file)
671 struct static_call_site *site;
673 struct instruction *insn;
674 struct symbol *key_sym;
675 char *key_name, *tmp;
678 sec = find_section_by_name(file->elf, ".static_call_sites");
680 INIT_LIST_HEAD(&file->static_call_list);
681 WARN("file already has .static_call_sites section, skipping");
685 if (list_empty(&file->static_call_list))
689 list_for_each_entry(insn, &file->static_call_list, call_node)
692 sec = elf_create_section_pair(file->elf, ".static_call_sites",
693 sizeof(*site), idx, idx * 2);
697 /* Allow modules to modify the low bits of static_call_site::key */
698 sec->sh.sh_flags |= SHF_WRITE;
701 list_for_each_entry(insn, &file->static_call_list, call_node) {
703 /* populate reloc for 'addr' */
704 if (!elf_init_reloc_text_sym(file->elf, sec,
705 idx * sizeof(*site), idx * 2,
706 insn->sec, insn->offset))
709 /* find key symbol */
710 key_name = strdup(insn_call_dest(insn)->name);
715 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
716 STATIC_CALL_TRAMP_PREFIX_LEN)) {
717 WARN("static_call: trampoline name malformed: %s", key_name);
721 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
722 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
724 key_sym = find_symbol_by_name(file->elf, tmp);
727 WARN("static_call: can't find static_call_key symbol: %s", tmp);
733 * For modules(), the key might not be exported, which
734 * means the module can make static calls but isn't
735 * allowed to change them.
737 * In that case we temporarily set the key to be the
738 * trampoline address. This is fixed up in
739 * static_call_add_module().
741 key_sym = insn_call_dest(insn);
745 /* populate reloc for 'key' */
746 if (!elf_init_reloc_data_sym(file->elf, sec,
747 idx * sizeof(*site) + 4,
748 (idx * 2) + 1, key_sym,
749 is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
758 static int create_retpoline_sites_sections(struct objtool_file *file)
760 struct instruction *insn;
764 sec = find_section_by_name(file->elf, ".retpoline_sites");
766 WARN("file already has .retpoline_sites, skipping");
771 list_for_each_entry(insn, &file->retpoline_call_list, call_node)
777 sec = elf_create_section_pair(file->elf, ".retpoline_sites",
778 sizeof(int), idx, idx);
783 list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
785 if (!elf_init_reloc_text_sym(file->elf, sec,
786 idx * sizeof(int), idx,
787 insn->sec, insn->offset))
796 static int create_return_sites_sections(struct objtool_file *file)
798 struct instruction *insn;
802 sec = find_section_by_name(file->elf, ".return_sites");
804 WARN("file already has .return_sites, skipping");
809 list_for_each_entry(insn, &file->return_thunk_list, call_node)
815 sec = elf_create_section_pair(file->elf, ".return_sites",
816 sizeof(int), idx, idx);
821 list_for_each_entry(insn, &file->return_thunk_list, call_node) {
823 if (!elf_init_reloc_text_sym(file->elf, sec,
824 idx * sizeof(int), idx,
825 insn->sec, insn->offset))
834 static int create_ibt_endbr_seal_sections(struct objtool_file *file)
836 struct instruction *insn;
840 sec = find_section_by_name(file->elf, ".ibt_endbr_seal");
842 WARN("file already has .ibt_endbr_seal, skipping");
847 list_for_each_entry(insn, &file->endbr_list, call_node)
851 printf("ibt: ENDBR at function start: %d\n", file->nr_endbr);
852 printf("ibt: ENDBR inside functions: %d\n", file->nr_endbr_int);
853 printf("ibt: superfluous ENDBR: %d\n", idx);
859 sec = elf_create_section_pair(file->elf, ".ibt_endbr_seal",
860 sizeof(int), idx, idx);
865 list_for_each_entry(insn, &file->endbr_list, call_node) {
867 int *site = (int *)sec->data->d_buf + idx;
868 struct symbol *sym = insn->sym;
871 if (opts.module && sym && sym->type == STT_FUNC &&
872 insn->offset == sym->offset &&
873 (!strcmp(sym->name, "init_module") ||
874 !strcmp(sym->name, "cleanup_module")))
875 WARN("%s(): not an indirect call target", sym->name);
877 if (!elf_init_reloc_text_sym(file->elf, sec,
878 idx * sizeof(int), idx,
879 insn->sec, insn->offset))
888 static int create_cfi_sections(struct objtool_file *file)
894 sec = find_section_by_name(file->elf, ".cfi_sites");
896 INIT_LIST_HEAD(&file->call_list);
897 WARN("file already has .cfi_sites section, skipping");
902 for_each_sym(file, sym) {
903 if (sym->type != STT_FUNC)
906 if (strncmp(sym->name, "__cfi_", 6))
912 sec = elf_create_section_pair(file->elf, ".cfi_sites",
913 sizeof(unsigned int), idx, idx);
918 for_each_sym(file, sym) {
919 if (sym->type != STT_FUNC)
922 if (strncmp(sym->name, "__cfi_", 6))
925 if (!elf_init_reloc_text_sym(file->elf, sec,
926 idx * sizeof(unsigned int), idx,
927 sym->sec, sym->offset))
936 static int create_mcount_loc_sections(struct objtool_file *file)
938 size_t addr_size = elf_addr_size(file->elf);
939 struct instruction *insn;
943 sec = find_section_by_name(file->elf, "__mcount_loc");
945 INIT_LIST_HEAD(&file->mcount_loc_list);
946 WARN("file already has __mcount_loc section, skipping");
950 if (list_empty(&file->mcount_loc_list))
954 list_for_each_entry(insn, &file->mcount_loc_list, call_node)
957 sec = elf_create_section_pair(file->elf, "__mcount_loc", addr_size,
962 sec->sh.sh_addralign = addr_size;
965 list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
969 reloc = elf_init_reloc_text_sym(file->elf, sec, idx * addr_size, idx,
970 insn->sec, insn->offset);
974 set_reloc_type(file->elf, reloc, addr_size == 8 ? R_ABS64 : R_ABS32);
982 static int create_direct_call_sections(struct objtool_file *file)
984 struct instruction *insn;
988 sec = find_section_by_name(file->elf, ".call_sites");
990 INIT_LIST_HEAD(&file->call_list);
991 WARN("file already has .call_sites section, skipping");
995 if (list_empty(&file->call_list))
999 list_for_each_entry(insn, &file->call_list, call_node)
1002 sec = elf_create_section_pair(file->elf, ".call_sites",
1003 sizeof(unsigned int), idx, idx);
1008 list_for_each_entry(insn, &file->call_list, call_node) {
1010 if (!elf_init_reloc_text_sym(file->elf, sec,
1011 idx * sizeof(unsigned int), idx,
1012 insn->sec, insn->offset))
1022 * Warnings shouldn't be reported for ignored functions.
1024 static void add_ignores(struct objtool_file *file)
1026 struct instruction *insn;
1027 struct section *rsec;
1028 struct symbol *func;
1029 struct reloc *reloc;
1031 rsec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
1035 for_each_reloc(rsec, reloc) {
1036 switch (reloc->sym->type) {
1042 func = find_func_by_offset(reloc->sym->sec, reloc_addend(reloc));
1048 WARN("unexpected relocation symbol type in %s: %d",
1049 rsec->name, reloc->sym->type);
1053 func_for_each_insn(file, func, insn)
1054 insn->ignore = true;
1059 * This is a whitelist of functions that is allowed to be called with AC set.
1060 * The list is meant to be minimal and only contains compiler instrumentation
1061 * ABI and a few functions used to implement *_{to,from}_user() functions.
1063 * These functions must not directly change AC, but may PUSHF/POPF.
1065 static const char *uaccess_safe_builtin[] = {
1068 "kasan_check_range",
1069 /* KASAN out-of-line */
1070 "__asan_loadN_noabort",
1071 "__asan_load1_noabort",
1072 "__asan_load2_noabort",
1073 "__asan_load4_noabort",
1074 "__asan_load8_noabort",
1075 "__asan_load16_noabort",
1076 "__asan_storeN_noabort",
1077 "__asan_store1_noabort",
1078 "__asan_store2_noabort",
1079 "__asan_store4_noabort",
1080 "__asan_store8_noabort",
1081 "__asan_store16_noabort",
1082 "__kasan_check_read",
1083 "__kasan_check_write",
1085 "__asan_report_load_n_noabort",
1086 "__asan_report_load1_noabort",
1087 "__asan_report_load2_noabort",
1088 "__asan_report_load4_noabort",
1089 "__asan_report_load8_noabort",
1090 "__asan_report_load16_noabort",
1091 "__asan_report_store_n_noabort",
1092 "__asan_report_store1_noabort",
1093 "__asan_report_store2_noabort",
1094 "__asan_report_store4_noabort",
1095 "__asan_report_store8_noabort",
1096 "__asan_report_store16_noabort",
1098 "__kcsan_check_access",
1103 "kcsan_found_watchpoint",
1104 "kcsan_setup_watchpoint",
1105 "kcsan_check_scoped_accesses",
1106 "kcsan_disable_current",
1107 "kcsan_enable_current_nowarn",
1109 "__tsan_func_entry",
1111 "__tsan_read_range",
1112 "__tsan_write_range",
1123 "__tsan_read_write1",
1124 "__tsan_read_write2",
1125 "__tsan_read_write4",
1126 "__tsan_read_write8",
1127 "__tsan_read_write16",
1128 "__tsan_volatile_read1",
1129 "__tsan_volatile_read2",
1130 "__tsan_volatile_read4",
1131 "__tsan_volatile_read8",
1132 "__tsan_volatile_read16",
1133 "__tsan_volatile_write1",
1134 "__tsan_volatile_write2",
1135 "__tsan_volatile_write4",
1136 "__tsan_volatile_write8",
1137 "__tsan_volatile_write16",
1138 "__tsan_atomic8_load",
1139 "__tsan_atomic16_load",
1140 "__tsan_atomic32_load",
1141 "__tsan_atomic64_load",
1142 "__tsan_atomic8_store",
1143 "__tsan_atomic16_store",
1144 "__tsan_atomic32_store",
1145 "__tsan_atomic64_store",
1146 "__tsan_atomic8_exchange",
1147 "__tsan_atomic16_exchange",
1148 "__tsan_atomic32_exchange",
1149 "__tsan_atomic64_exchange",
1150 "__tsan_atomic8_fetch_add",
1151 "__tsan_atomic16_fetch_add",
1152 "__tsan_atomic32_fetch_add",
1153 "__tsan_atomic64_fetch_add",
1154 "__tsan_atomic8_fetch_sub",
1155 "__tsan_atomic16_fetch_sub",
1156 "__tsan_atomic32_fetch_sub",
1157 "__tsan_atomic64_fetch_sub",
1158 "__tsan_atomic8_fetch_and",
1159 "__tsan_atomic16_fetch_and",
1160 "__tsan_atomic32_fetch_and",
1161 "__tsan_atomic64_fetch_and",
1162 "__tsan_atomic8_fetch_or",
1163 "__tsan_atomic16_fetch_or",
1164 "__tsan_atomic32_fetch_or",
1165 "__tsan_atomic64_fetch_or",
1166 "__tsan_atomic8_fetch_xor",
1167 "__tsan_atomic16_fetch_xor",
1168 "__tsan_atomic32_fetch_xor",
1169 "__tsan_atomic64_fetch_xor",
1170 "__tsan_atomic8_fetch_nand",
1171 "__tsan_atomic16_fetch_nand",
1172 "__tsan_atomic32_fetch_nand",
1173 "__tsan_atomic64_fetch_nand",
1174 "__tsan_atomic8_compare_exchange_strong",
1175 "__tsan_atomic16_compare_exchange_strong",
1176 "__tsan_atomic32_compare_exchange_strong",
1177 "__tsan_atomic64_compare_exchange_strong",
1178 "__tsan_atomic8_compare_exchange_weak",
1179 "__tsan_atomic16_compare_exchange_weak",
1180 "__tsan_atomic32_compare_exchange_weak",
1181 "__tsan_atomic64_compare_exchange_weak",
1182 "__tsan_atomic8_compare_exchange_val",
1183 "__tsan_atomic16_compare_exchange_val",
1184 "__tsan_atomic32_compare_exchange_val",
1185 "__tsan_atomic64_compare_exchange_val",
1186 "__tsan_atomic_thread_fence",
1187 "__tsan_atomic_signal_fence",
1188 "__tsan_unaligned_read16",
1189 "__tsan_unaligned_write16",
1193 "__sanitizer_cov_trace_pc",
1194 "__sanitizer_cov_trace_const_cmp1",
1195 "__sanitizer_cov_trace_const_cmp2",
1196 "__sanitizer_cov_trace_const_cmp4",
1197 "__sanitizer_cov_trace_const_cmp8",
1198 "__sanitizer_cov_trace_cmp1",
1199 "__sanitizer_cov_trace_cmp2",
1200 "__sanitizer_cov_trace_cmp4",
1201 "__sanitizer_cov_trace_cmp8",
1202 "__sanitizer_cov_trace_switch",
1204 "kmsan_copy_to_user",
1206 "kmsan_unpoison_entry_regs",
1207 "kmsan_unpoison_memory",
1208 "__msan_chain_origin",
1209 "__msan_get_context_state",
1210 "__msan_instrument_asm_store",
1211 "__msan_metadata_ptr_for_load_1",
1212 "__msan_metadata_ptr_for_load_2",
1213 "__msan_metadata_ptr_for_load_4",
1214 "__msan_metadata_ptr_for_load_8",
1215 "__msan_metadata_ptr_for_load_n",
1216 "__msan_metadata_ptr_for_store_1",
1217 "__msan_metadata_ptr_for_store_2",
1218 "__msan_metadata_ptr_for_store_4",
1219 "__msan_metadata_ptr_for_store_8",
1220 "__msan_metadata_ptr_for_store_n",
1221 "__msan_poison_alloca",
1224 "ubsan_type_mismatch_common",
1225 "__ubsan_handle_type_mismatch",
1226 "__ubsan_handle_type_mismatch_v1",
1227 "__ubsan_handle_shift_out_of_bounds",
1228 "__ubsan_handle_load_invalid_value",
1230 "stackleak_track_stack",
1232 "csum_partial_copy_generic",
1234 "copy_mc_fragile_handle_tail",
1235 "copy_mc_enhanced_fast_string",
1236 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
1237 "rep_stos_alternative",
1238 "rep_movs_alternative",
1239 "__copy_user_nocache",
1243 static void add_uaccess_safe(struct objtool_file *file)
1245 struct symbol *func;
1251 for (name = uaccess_safe_builtin; *name; name++) {
1252 func = find_symbol_by_name(file->elf, *name);
1256 func->uaccess_safe = true;
1261 * FIXME: For now, just ignore any alternatives which add retpolines. This is
1262 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
1263 * But it at least allows objtool to understand the control flow *around* the
1266 static int add_ignore_alternatives(struct objtool_file *file)
1268 struct section *rsec;
1269 struct reloc *reloc;
1270 struct instruction *insn;
1272 rsec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
1276 for_each_reloc(rsec, reloc) {
1277 if (reloc->sym->type != STT_SECTION) {
1278 WARN("unexpected relocation symbol type in %s", rsec->name);
1282 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
1284 WARN("bad .discard.ignore_alts entry");
1288 insn->ignore_alts = true;
1295 * Symbols that replace INSN_CALL_DYNAMIC, every (tail) call to such a symbol
1296 * will be added to the .retpoline_sites section.
1298 __weak bool arch_is_retpoline(struct symbol *sym)
1304 * Symbols that replace INSN_RETURN, every (tail) call to such a symbol
1305 * will be added to the .return_sites section.
1307 __weak bool arch_is_rethunk(struct symbol *sym)
1313 * Symbols that are embedded inside other instructions, because sometimes crazy
1314 * code exists. These are mostly ignored for validation purposes.
1316 __weak bool arch_is_embedded_insn(struct symbol *sym)
1321 static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
1323 struct reloc *reloc;
1331 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1332 insn->offset, insn->len);
1341 static void remove_insn_ops(struct instruction *insn)
1343 struct stack_op *op, *next;
1345 for (op = insn->stack_ops; op; op = next) {
1349 insn->stack_ops = NULL;
1352 static void annotate_call_site(struct objtool_file *file,
1353 struct instruction *insn, bool sibling)
1355 struct reloc *reloc = insn_reloc(file, insn);
1356 struct symbol *sym = insn_call_dest(insn);
1362 * Alternative replacement code is just template code which is
1363 * sometimes copied to the original instruction. For now, don't
1364 * annotate it. (In the future we might consider annotating the
1365 * original instruction if/when it ever makes sense to do so.)
1367 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1370 if (sym->static_call_tramp) {
1371 list_add_tail(&insn->call_node, &file->static_call_list);
1375 if (sym->retpoline_thunk) {
1376 list_add_tail(&insn->call_node, &file->retpoline_call_list);
1381 * Many compilers cannot disable KCOV or sanitizer calls with a function
1382 * attribute so they need a little help, NOP out any such calls from
1385 if (opts.hack_noinstr && insn->sec->noinstr && sym->profiling_func) {
1387 set_reloc_type(file->elf, reloc, R_NONE);
1389 elf_write_insn(file->elf, insn->sec,
1390 insn->offset, insn->len,
1391 sibling ? arch_ret_insn(insn->len)
1392 : arch_nop_insn(insn->len));
1394 insn->type = sibling ? INSN_RETURN : INSN_NOP;
1398 * We've replaced the tail-call JMP insn by two new
1399 * insn: RET; INT3, except we only have a single struct
1400 * insn here. Mark it retpoline_safe to avoid the SLS
1401 * warning, instead of adding another insn.
1403 insn->retpoline_safe = true;
1409 if (opts.mcount && sym->fentry) {
1411 WARN_INSN(insn, "tail call to __fentry__ !?!?");
1414 set_reloc_type(file->elf, reloc, R_NONE);
1416 elf_write_insn(file->elf, insn->sec,
1417 insn->offset, insn->len,
1418 arch_nop_insn(insn->len));
1420 insn->type = INSN_NOP;
1423 list_add_tail(&insn->call_node, &file->mcount_loc_list);
1427 if (insn->type == INSN_CALL && !insn->sec->init)
1428 list_add_tail(&insn->call_node, &file->call_list);
1430 if (!sibling && dead_end_function(file, sym))
1431 insn->dead_end = true;
1434 static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1435 struct symbol *dest, bool sibling)
1437 insn->_call_dest = dest;
1442 * Whatever stack impact regular CALLs have, should be undone
1443 * by the RETURN of the called function.
1445 * Annotated intra-function calls retain the stack_ops but
1446 * are converted to JUMP, see read_intra_function_calls().
1448 remove_insn_ops(insn);
1450 annotate_call_site(file, insn, sibling);
1453 static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1456 * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1457 * so convert them accordingly.
1459 switch (insn->type) {
1461 insn->type = INSN_CALL_DYNAMIC;
1463 case INSN_JUMP_UNCONDITIONAL:
1464 insn->type = INSN_JUMP_DYNAMIC;
1466 case INSN_JUMP_CONDITIONAL:
1467 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1473 insn->retpoline_safe = true;
1476 * Whatever stack impact regular CALLs have, should be undone
1477 * by the RETURN of the called function.
1479 * Annotated intra-function calls retain the stack_ops but
1480 * are converted to JUMP, see read_intra_function_calls().
1482 remove_insn_ops(insn);
1484 annotate_call_site(file, insn, false);
1487 static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add)
1490 * Return thunk tail calls are really just returns in disguise,
1491 * so convert them accordingly.
1493 insn->type = INSN_RETURN;
1494 insn->retpoline_safe = true;
1497 list_add_tail(&insn->call_node, &file->return_thunk_list);
1500 static bool is_first_func_insn(struct objtool_file *file,
1501 struct instruction *insn, struct symbol *sym)
1503 if (insn->offset == sym->offset)
1506 /* Allow direct CALL/JMP past ENDBR */
1508 struct instruction *prev = prev_insn_same_sym(file, insn);
1510 if (prev && prev->type == INSN_ENDBR &&
1511 insn->offset == sym->offset + prev->len)
1519 * A sibling call is a tail-call to another symbol -- to differentiate from a
1520 * recursive tail-call which is to the same symbol.
1522 static bool jump_is_sibling_call(struct objtool_file *file,
1523 struct instruction *from, struct instruction *to)
1525 struct symbol *fs = from->sym;
1526 struct symbol *ts = to->sym;
1528 /* Not a sibling call if from/to a symbol hole */
1532 /* Not a sibling call if not targeting the start of a symbol. */
1533 if (!is_first_func_insn(file, to, ts))
1536 /* Disallow sibling calls into STT_NOTYPE */
1537 if (ts->type == STT_NOTYPE)
1540 /* Must not be self to be a sibling */
1541 return fs->pfunc != ts->pfunc;
1545 * Find the destination instructions for all jumps.
1547 static int add_jump_destinations(struct objtool_file *file)
1549 struct instruction *insn, *jump_dest;
1550 struct reloc *reloc;
1551 struct section *dest_sec;
1552 unsigned long dest_off;
1554 for_each_insn(file, insn) {
1555 if (insn->jump_dest) {
1557 * handle_group_alt() may have previously set
1558 * 'jump_dest' for some alternatives.
1562 if (!is_static_jump(insn))
1565 reloc = insn_reloc(file, insn);
1567 dest_sec = insn->sec;
1568 dest_off = arch_jump_destination(insn);
1569 } else if (reloc->sym->type == STT_SECTION) {
1570 dest_sec = reloc->sym->sec;
1571 dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
1572 } else if (reloc->sym->retpoline_thunk) {
1573 add_retpoline_call(file, insn);
1575 } else if (reloc->sym->return_thunk) {
1576 add_return_call(file, insn, true);
1578 } else if (insn_func(insn)) {
1580 * External sibling call or internal sibling call with
1583 add_call_dest(file, insn, reloc->sym, true);
1585 } else if (reloc->sym->sec->idx) {
1586 dest_sec = reloc->sym->sec;
1587 dest_off = reloc->sym->sym.st_value +
1588 arch_dest_reloc_offset(reloc_addend(reloc));
1590 /* non-func asm code jumping to another file */
1594 jump_dest = find_insn(file, dest_sec, dest_off);
1596 struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off);
1599 * This is a special case for retbleed_untrain_ret().
1600 * It jumps to __x86_return_thunk(), but objtool
1601 * can't find the thunk's starting RET
1602 * instruction, because the RET is also in the
1603 * middle of another instruction. Objtool only
1604 * knows about the outer instruction.
1606 if (sym && sym->embedded_insn) {
1607 add_return_call(file, insn, false);
1611 WARN_INSN(insn, "can't find jump dest instruction at %s+0x%lx",
1612 dest_sec->name, dest_off);
1617 * An intra-TU jump in retpoline.o might not have a relocation
1618 * for its jump dest, in which case the above
1619 * add_{retpoline,return}_call() didn't happen.
1621 if (jump_dest->sym && jump_dest->offset == jump_dest->sym->offset) {
1622 if (jump_dest->sym->retpoline_thunk) {
1623 add_retpoline_call(file, insn);
1626 if (jump_dest->sym->return_thunk) {
1627 add_return_call(file, insn, true);
1633 * Cross-function jump.
1635 if (insn_func(insn) && insn_func(jump_dest) &&
1636 insn_func(insn) != insn_func(jump_dest)) {
1639 * For GCC 8+, create parent/child links for any cold
1640 * subfunctions. This is _mostly_ redundant with a
1641 * similar initialization in read_symbols().
1643 * If a function has aliases, we want the *first* such
1644 * function in the symbol table to be the subfunction's
1645 * parent. In that case we overwrite the
1646 * initialization done in read_symbols().
1648 * However this code can't completely replace the
1649 * read_symbols() code because this doesn't detect the
1650 * case where the parent function's only reference to a
1651 * subfunction is through a jump table.
1653 if (!strstr(insn_func(insn)->name, ".cold") &&
1654 strstr(insn_func(jump_dest)->name, ".cold")) {
1655 insn_func(insn)->cfunc = insn_func(jump_dest);
1656 insn_func(jump_dest)->pfunc = insn_func(insn);
1660 if (jump_is_sibling_call(file, insn, jump_dest)) {
1662 * Internal sibling call without reloc or with
1663 * STT_SECTION reloc.
1665 add_call_dest(file, insn, insn_func(jump_dest), true);
1669 insn->jump_dest = jump_dest;
1675 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1677 struct symbol *call_dest;
1679 call_dest = find_func_by_offset(sec, offset);
1681 call_dest = find_symbol_by_offset(sec, offset);
1687 * Find the destination instructions for all calls.
1689 static int add_call_destinations(struct objtool_file *file)
1691 struct instruction *insn;
1692 unsigned long dest_off;
1693 struct symbol *dest;
1694 struct reloc *reloc;
1696 for_each_insn(file, insn) {
1697 if (insn->type != INSN_CALL)
1700 reloc = insn_reloc(file, insn);
1702 dest_off = arch_jump_destination(insn);
1703 dest = find_call_destination(insn->sec, dest_off);
1705 add_call_dest(file, insn, dest, false);
1710 if (!insn_call_dest(insn)) {
1711 WARN_INSN(insn, "unannotated intra-function call");
1715 if (insn_func(insn) && insn_call_dest(insn)->type != STT_FUNC) {
1716 WARN_INSN(insn, "unsupported call to non-function");
1720 } else if (reloc->sym->type == STT_SECTION) {
1721 dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
1722 dest = find_call_destination(reloc->sym->sec, dest_off);
1724 WARN_INSN(insn, "can't find call dest symbol at %s+0x%lx",
1725 reloc->sym->sec->name, dest_off);
1729 add_call_dest(file, insn, dest, false);
1731 } else if (reloc->sym->retpoline_thunk) {
1732 add_retpoline_call(file, insn);
1735 add_call_dest(file, insn, reloc->sym, false);
1742 * The .alternatives section requires some extra special care over and above
1743 * other special sections because alternatives are patched in place.
1745 static int handle_group_alt(struct objtool_file *file,
1746 struct special_alt *special_alt,
1747 struct instruction *orig_insn,
1748 struct instruction **new_insn)
1750 struct instruction *last_new_insn = NULL, *insn, *nop = NULL;
1751 struct alt_group *orig_alt_group, *new_alt_group;
1752 unsigned long dest_off;
1754 orig_alt_group = orig_insn->alt_group;
1755 if (!orig_alt_group) {
1756 struct instruction *last_orig_insn = NULL;
1758 orig_alt_group = malloc(sizeof(*orig_alt_group));
1759 if (!orig_alt_group) {
1760 WARN("malloc failed");
1763 orig_alt_group->cfi = calloc(special_alt->orig_len,
1764 sizeof(struct cfi_state *));
1765 if (!orig_alt_group->cfi) {
1766 WARN("calloc failed");
1771 sec_for_each_insn_from(file, insn) {
1772 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1775 insn->alt_group = orig_alt_group;
1776 last_orig_insn = insn;
1778 orig_alt_group->orig_group = NULL;
1779 orig_alt_group->first_insn = orig_insn;
1780 orig_alt_group->last_insn = last_orig_insn;
1781 orig_alt_group->nop = NULL;
1783 if (orig_alt_group->last_insn->offset + orig_alt_group->last_insn->len -
1784 orig_alt_group->first_insn->offset != special_alt->orig_len) {
1785 WARN_INSN(orig_insn, "weirdly overlapping alternative! %ld != %d",
1786 orig_alt_group->last_insn->offset +
1787 orig_alt_group->last_insn->len -
1788 orig_alt_group->first_insn->offset,
1789 special_alt->orig_len);
1794 new_alt_group = malloc(sizeof(*new_alt_group));
1795 if (!new_alt_group) {
1796 WARN("malloc failed");
1800 if (special_alt->new_len < special_alt->orig_len) {
1802 * Insert a fake nop at the end to make the replacement
1803 * alt_group the same size as the original. This is needed to
1804 * allow propagate_alt_cfi() to do its magic. When the last
1805 * instruction affects the stack, the instruction after it (the
1806 * nop) will propagate the new state to the shared CFI array.
1808 nop = malloc(sizeof(*nop));
1810 WARN("malloc failed");
1813 memset(nop, 0, sizeof(*nop));
1815 nop->sec = special_alt->new_sec;
1816 nop->offset = special_alt->new_off + special_alt->new_len;
1817 nop->len = special_alt->orig_len - special_alt->new_len;
1818 nop->type = INSN_NOP;
1819 nop->sym = orig_insn->sym;
1820 nop->alt_group = new_alt_group;
1821 nop->ignore = orig_insn->ignore_alts;
1824 if (!special_alt->new_len) {
1830 sec_for_each_insn_from(file, insn) {
1831 struct reloc *alt_reloc;
1833 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1836 last_new_insn = insn;
1838 insn->ignore = orig_insn->ignore_alts;
1839 insn->sym = orig_insn->sym;
1840 insn->alt_group = new_alt_group;
1843 * Since alternative replacement code is copy/pasted by the
1844 * kernel after applying relocations, generally such code can't
1845 * have relative-address relocation references to outside the
1846 * .altinstr_replacement section, unless the arch's
1847 * alternatives code can adjust the relative offsets
1850 alt_reloc = insn_reloc(file, insn);
1851 if (alt_reloc && arch_pc_relative_reloc(alt_reloc) &&
1852 !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1854 WARN_INSN(insn, "unsupported relocation in alternatives section");
1858 if (!is_static_jump(insn))
1861 if (!insn->immediate)
1864 dest_off = arch_jump_destination(insn);
1865 if (dest_off == special_alt->new_off + special_alt->new_len) {
1866 insn->jump_dest = next_insn_same_sec(file, orig_alt_group->last_insn);
1867 if (!insn->jump_dest) {
1868 WARN_INSN(insn, "can't find alternative jump destination");
1874 if (!last_new_insn) {
1875 WARN_FUNC("can't find last new alternative instruction",
1876 special_alt->new_sec, special_alt->new_off);
1881 new_alt_group->orig_group = orig_alt_group;
1882 new_alt_group->first_insn = *new_insn;
1883 new_alt_group->last_insn = last_new_insn;
1884 new_alt_group->nop = nop;
1885 new_alt_group->cfi = orig_alt_group->cfi;
1890 * A jump table entry can either convert a nop to a jump or a jump to a nop.
1891 * If the original instruction is a jump, make the alt entry an effective nop
1892 * by just skipping the original instruction.
1894 static int handle_jump_alt(struct objtool_file *file,
1895 struct special_alt *special_alt,
1896 struct instruction *orig_insn,
1897 struct instruction **new_insn)
1899 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1900 orig_insn->type != INSN_NOP) {
1902 WARN_INSN(orig_insn, "unsupported instruction at jump label");
1906 if (opts.hack_jump_label && special_alt->key_addend & 2) {
1907 struct reloc *reloc = insn_reloc(file, orig_insn);
1910 set_reloc_type(file->elf, reloc, R_NONE);
1911 elf_write_insn(file->elf, orig_insn->sec,
1912 orig_insn->offset, orig_insn->len,
1913 arch_nop_insn(orig_insn->len));
1914 orig_insn->type = INSN_NOP;
1917 if (orig_insn->type == INSN_NOP) {
1918 if (orig_insn->len == 2)
1919 file->jl_nop_short++;
1921 file->jl_nop_long++;
1926 if (orig_insn->len == 2)
1931 *new_insn = next_insn_same_sec(file, orig_insn);
1936 * Read all the special sections which have alternate instructions which can be
1937 * patched in or redirected to at runtime. Each instruction having alternate
1938 * instruction(s) has them added to its insn->alts list, which will be
1939 * traversed in validate_branch().
1941 static int add_special_section_alts(struct objtool_file *file)
1943 struct list_head special_alts;
1944 struct instruction *orig_insn, *new_insn;
1945 struct special_alt *special_alt, *tmp;
1946 struct alternative *alt;
1949 ret = special_get_alts(file->elf, &special_alts);
1953 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1955 orig_insn = find_insn(file, special_alt->orig_sec,
1956 special_alt->orig_off);
1958 WARN_FUNC("special: can't find orig instruction",
1959 special_alt->orig_sec, special_alt->orig_off);
1965 if (!special_alt->group || special_alt->new_len) {
1966 new_insn = find_insn(file, special_alt->new_sec,
1967 special_alt->new_off);
1969 WARN_FUNC("special: can't find new instruction",
1970 special_alt->new_sec,
1971 special_alt->new_off);
1977 if (special_alt->group) {
1978 if (!special_alt->orig_len) {
1979 WARN_INSN(orig_insn, "empty alternative entry");
1983 ret = handle_group_alt(file, special_alt, orig_insn,
1987 } else if (special_alt->jump_or_nop) {
1988 ret = handle_jump_alt(file, special_alt, orig_insn,
1994 alt = malloc(sizeof(*alt));
1996 WARN("malloc failed");
2001 alt->insn = new_insn;
2002 alt->skip_orig = special_alt->skip_orig;
2003 orig_insn->ignore_alts |= special_alt->skip_alt;
2004 alt->next = orig_insn->alts;
2005 orig_insn->alts = alt;
2007 list_del(&special_alt->list);
2012 printf("jl\\\tNOP\tJMP\n");
2013 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
2014 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
2021 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
2022 struct reloc *next_table)
2024 struct symbol *pfunc = insn_func(insn)->pfunc;
2025 struct reloc *table = insn_jump_table(insn);
2026 struct instruction *dest_insn;
2027 unsigned int prev_offset = 0;
2028 struct reloc *reloc = table;
2029 struct alternative *alt;
2032 * Each @reloc is a switch table relocation which points to the target
2035 for_each_reloc_from(table->sec, reloc) {
2037 /* Check for the end of the table: */
2038 if (reloc != table && reloc == next_table)
2041 /* Make sure the table entries are consecutive: */
2042 if (prev_offset && reloc_offset(reloc) != prev_offset + 8)
2045 /* Detect function pointers from contiguous objects: */
2046 if (reloc->sym->sec == pfunc->sec &&
2047 reloc_addend(reloc) == pfunc->offset)
2050 dest_insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2054 /* Make sure the destination is in the same function: */
2055 if (!insn_func(dest_insn) || insn_func(dest_insn)->pfunc != pfunc)
2058 alt = malloc(sizeof(*alt));
2060 WARN("malloc failed");
2064 alt->insn = dest_insn;
2065 alt->next = insn->alts;
2067 prev_offset = reloc_offset(reloc);
2071 WARN_INSN(insn, "can't find switch jump table");
2079 * find_jump_table() - Given a dynamic jump, find the switch jump table
2080 * associated with it.
2082 static struct reloc *find_jump_table(struct objtool_file *file,
2083 struct symbol *func,
2084 struct instruction *insn)
2086 struct reloc *table_reloc;
2087 struct instruction *dest_insn, *orig_insn = insn;
2090 * Backward search using the @first_jump_src links, these help avoid
2091 * much of the 'in between' code. Which avoids us getting confused by
2095 insn && insn_func(insn) && insn_func(insn)->pfunc == func;
2096 insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
2098 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
2101 /* allow small jumps within the range */
2102 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
2104 (insn->jump_dest->offset <= insn->offset ||
2105 insn->jump_dest->offset > orig_insn->offset))
2108 table_reloc = arch_find_switch_table(file, insn);
2111 dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
2112 if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
2122 * First pass: Mark the head of each jump table so that in the next pass,
2123 * we know when a given jump table ends and the next one starts.
2125 static void mark_func_jump_tables(struct objtool_file *file,
2126 struct symbol *func)
2128 struct instruction *insn, *last = NULL;
2129 struct reloc *reloc;
2131 func_for_each_insn(file, func, insn) {
2136 * Store back-pointers for unconditional forward jumps such
2137 * that find_jump_table() can back-track using those and
2138 * avoid some potentially confusing code.
2140 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
2141 insn->offset > last->offset &&
2142 insn->jump_dest->offset > insn->offset &&
2143 !insn->jump_dest->first_jump_src) {
2145 insn->jump_dest->first_jump_src = insn;
2146 last = insn->jump_dest;
2149 if (insn->type != INSN_JUMP_DYNAMIC)
2152 reloc = find_jump_table(file, func, insn);
2154 insn->_jump_table = reloc;
2158 static int add_func_jump_tables(struct objtool_file *file,
2159 struct symbol *func)
2161 struct instruction *insn, *insn_t1 = NULL, *insn_t2;
2164 func_for_each_insn(file, func, insn) {
2165 if (!insn_jump_table(insn))
2175 ret = add_jump_table(file, insn_t1, insn_jump_table(insn_t2));
2183 ret = add_jump_table(file, insn_t1, NULL);
2189 * For some switch statements, gcc generates a jump table in the .rodata
2190 * section which contains a list of addresses within the function to jump to.
2191 * This finds these jump tables and adds them to the insn->alts lists.
2193 static int add_jump_table_alts(struct objtool_file *file)
2195 struct symbol *func;
2201 for_each_sym(file, func) {
2202 if (func->type != STT_FUNC)
2205 mark_func_jump_tables(file, func);
2206 ret = add_func_jump_tables(file, func);
2214 static void set_func_state(struct cfi_state *state)
2216 state->cfa = initial_func_cfi.cfa;
2217 memcpy(&state->regs, &initial_func_cfi.regs,
2218 CFI_NUM_REGS * sizeof(struct cfi_reg));
2219 state->stack_size = initial_func_cfi.cfa.offset;
2220 state->type = UNWIND_HINT_TYPE_CALL;
2223 static int read_unwind_hints(struct objtool_file *file)
2225 struct cfi_state cfi = init_cfi;
2226 struct section *sec;
2227 struct unwind_hint *hint;
2228 struct instruction *insn;
2229 struct reloc *reloc;
2230 unsigned long offset;
2233 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
2238 WARN("missing .rela.discard.unwind_hints section");
2242 if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
2243 WARN("struct unwind_hint size mismatch");
2249 for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
2250 hint = (struct unwind_hint *)sec->data->d_buf + i;
2252 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
2254 WARN("can't find reloc for unwind_hints[%d]", i);
2258 if (reloc->sym->type == STT_SECTION) {
2259 offset = reloc_addend(reloc);
2260 } else if (reloc->sym->local_label) {
2261 offset = reloc->sym->offset;
2263 WARN("unexpected relocation symbol type in %s", sec->rsec->name);
2267 insn = find_insn(file, reloc->sym->sec, offset);
2269 WARN("can't find insn for unwind_hints[%d]", i);
2275 if (hint->type == UNWIND_HINT_TYPE_UNDEFINED) {
2276 insn->cfi = &force_undefined_cfi;
2280 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
2286 if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
2287 insn->restore = true;
2291 if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
2292 struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
2294 if (sym && sym->bind == STB_GLOBAL) {
2295 if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) {
2296 WARN_INSN(insn, "UNWIND_HINT_IRET_REGS without ENDBR");
2301 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
2302 insn->cfi = &func_cfi;
2309 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
2310 WARN_INSN(insn, "unsupported unwind_hint sp base reg %d", hint->sp_reg);
2314 cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
2315 cfi.type = hint->type;
2316 cfi.signal = hint->signal;
2318 insn->cfi = cfi_hash_find_or_add(&cfi);
2324 static int read_noendbr_hints(struct objtool_file *file)
2326 struct instruction *insn;
2327 struct section *rsec;
2328 struct reloc *reloc;
2330 rsec = find_section_by_name(file->elf, ".rela.discard.noendbr");
2334 for_each_reloc(rsec, reloc) {
2335 insn = find_insn(file, reloc->sym->sec,
2336 reloc->sym->offset + reloc_addend(reloc));
2338 WARN("bad .discard.noendbr entry");
2348 static int read_retpoline_hints(struct objtool_file *file)
2350 struct section *rsec;
2351 struct instruction *insn;
2352 struct reloc *reloc;
2354 rsec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
2358 for_each_reloc(rsec, reloc) {
2359 if (reloc->sym->type != STT_SECTION) {
2360 WARN("unexpected relocation symbol type in %s", rsec->name);
2364 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2366 WARN("bad .discard.retpoline_safe entry");
2370 if (insn->type != INSN_JUMP_DYNAMIC &&
2371 insn->type != INSN_CALL_DYNAMIC &&
2372 insn->type != INSN_RETURN &&
2373 insn->type != INSN_NOP) {
2374 WARN_INSN(insn, "retpoline_safe hint not an indirect jump/call/ret/nop");
2378 insn->retpoline_safe = true;
2384 static int read_instr_hints(struct objtool_file *file)
2386 struct section *rsec;
2387 struct instruction *insn;
2388 struct reloc *reloc;
2390 rsec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2394 for_each_reloc(rsec, reloc) {
2395 if (reloc->sym->type != STT_SECTION) {
2396 WARN("unexpected relocation symbol type in %s", rsec->name);
2400 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2402 WARN("bad .discard.instr_end entry");
2409 rsec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2413 for_each_reloc(rsec, reloc) {
2414 if (reloc->sym->type != STT_SECTION) {
2415 WARN("unexpected relocation symbol type in %s", rsec->name);
2419 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2421 WARN("bad .discard.instr_begin entry");
2431 static int read_validate_unret_hints(struct objtool_file *file)
2433 struct section *rsec;
2434 struct instruction *insn;
2435 struct reloc *reloc;
2437 rsec = find_section_by_name(file->elf, ".rela.discard.validate_unret");
2441 for_each_reloc(rsec, reloc) {
2442 if (reloc->sym->type != STT_SECTION) {
2443 WARN("unexpected relocation symbol type in %s", rsec->name);
2447 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2449 WARN("bad .discard.instr_end entry");
2459 static int read_intra_function_calls(struct objtool_file *file)
2461 struct instruction *insn;
2462 struct section *rsec;
2463 struct reloc *reloc;
2465 rsec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2469 for_each_reloc(rsec, reloc) {
2470 unsigned long dest_off;
2472 if (reloc->sym->type != STT_SECTION) {
2473 WARN("unexpected relocation symbol type in %s",
2478 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2480 WARN("bad .discard.intra_function_call entry");
2484 if (insn->type != INSN_CALL) {
2485 WARN_INSN(insn, "intra_function_call not a direct call");
2490 * Treat intra-function CALLs as JMPs, but with a stack_op.
2491 * See add_call_destinations(), which strips stack_ops from
2494 insn->type = INSN_JUMP_UNCONDITIONAL;
2496 dest_off = arch_jump_destination(insn);
2497 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2498 if (!insn->jump_dest) {
2499 WARN_INSN(insn, "can't find call dest at %s+0x%lx",
2500 insn->sec->name, dest_off);
2509 * Return true if name matches an instrumentation function, where calls to that
2510 * function from noinstr code can safely be removed, but compilers won't do so.
2512 static bool is_profiling_func(const char *name)
2515 * Many compilers cannot disable KCOV with a function attribute.
2517 if (!strncmp(name, "__sanitizer_cov_", 16))
2521 * Some compilers currently do not remove __tsan_func_entry/exit nor
2522 * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2523 * the __no_sanitize_thread attribute, remove them. Once the kernel's
2524 * minimum Clang version is 14.0, this can be removed.
2526 if (!strncmp(name, "__tsan_func_", 12) ||
2527 !strcmp(name, "__tsan_atomic_signal_fence"))
2533 static int classify_symbols(struct objtool_file *file)
2535 struct symbol *func;
2537 for_each_sym(file, func) {
2538 if (func->type == STT_NOTYPE && strstarts(func->name, ".L"))
2539 func->local_label = true;
2541 if (func->bind != STB_GLOBAL)
2544 if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2545 strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2546 func->static_call_tramp = true;
2548 if (arch_is_retpoline(func))
2549 func->retpoline_thunk = true;
2551 if (arch_is_rethunk(func))
2552 func->return_thunk = true;
2554 if (arch_is_embedded_insn(func))
2555 func->embedded_insn = true;
2557 if (arch_ftrace_match(func->name))
2558 func->fentry = true;
2560 if (is_profiling_func(func->name))
2561 func->profiling_func = true;
2567 static void mark_rodata(struct objtool_file *file)
2569 struct section *sec;
2573 * Search for the following rodata sections, each of which can
2574 * potentially contain jump tables:
2576 * - .rodata: can contain GCC switch tables
2577 * - .rodata.<func>: same, if -fdata-sections is being used
2578 * - .rodata..c_jump_table: contains C annotated jump tables
2580 * .rodata.str1.* sections are ignored; they don't contain jump tables.
2582 for_each_sec(file, sec) {
2583 if (!strncmp(sec->name, ".rodata", 7) &&
2584 !strstr(sec->name, ".str1.")) {
2590 file->rodata = found;
2593 static int decode_sections(struct objtool_file *file)
2599 ret = init_pv_ops(file);
2604 * Must be before add_{jump_call}_destination.
2606 ret = classify_symbols(file);
2610 ret = decode_instructions(file);
2615 add_uaccess_safe(file);
2617 ret = add_ignore_alternatives(file);
2622 * Must be before read_unwind_hints() since that needs insn->noendbr.
2624 ret = read_noendbr_hints(file);
2629 * Must be before add_jump_destinations(), which depends on 'func'
2630 * being set for alternatives, to enable proper sibling call detection.
2632 if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) {
2633 ret = add_special_section_alts(file);
2638 ret = add_jump_destinations(file);
2643 * Must be before add_call_destination(); it changes INSN_CALL to
2646 ret = read_intra_function_calls(file);
2650 ret = add_call_destinations(file);
2655 * Must be after add_call_destinations() such that it can override
2656 * dead_end_function() marks.
2658 ret = add_dead_ends(file);
2662 ret = add_jump_table_alts(file);
2666 ret = read_unwind_hints(file);
2670 ret = read_retpoline_hints(file);
2674 ret = read_instr_hints(file);
2678 ret = read_validate_unret_hints(file);
2685 static bool is_special_call(struct instruction *insn)
2687 if (insn->type == INSN_CALL) {
2688 struct symbol *dest = insn_call_dest(insn);
2693 if (dest->fentry || dest->embedded_insn)
2700 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2702 struct cfi_state *cfi = &state->cfi;
2705 if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2708 if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2711 if (cfi->stack_size != initial_func_cfi.cfa.offset)
2714 for (i = 0; i < CFI_NUM_REGS; i++) {
2715 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2716 cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2723 static bool check_reg_frame_pos(const struct cfi_reg *reg,
2724 int expected_offset)
2726 return reg->base == CFI_CFA &&
2727 reg->offset == expected_offset;
2730 static bool has_valid_stack_frame(struct insn_state *state)
2732 struct cfi_state *cfi = &state->cfi;
2734 if (cfi->cfa.base == CFI_BP &&
2735 check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2736 check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2739 if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2745 static int update_cfi_state_regs(struct instruction *insn,
2746 struct cfi_state *cfi,
2747 struct stack_op *op)
2749 struct cfi_reg *cfa = &cfi->cfa;
2751 if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2755 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2759 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2762 /* add immediate to sp */
2763 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2764 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2765 cfa->offset -= op->src.offset;
2770 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2772 if (arch_callee_saved_reg(reg) &&
2773 cfi->regs[reg].base == CFI_UNDEFINED) {
2774 cfi->regs[reg].base = base;
2775 cfi->regs[reg].offset = offset;
2779 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2781 cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2782 cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2786 * A note about DRAP stack alignment:
2788 * GCC has the concept of a DRAP register, which is used to help keep track of
2789 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
2790 * register. The typical DRAP pattern is:
2792 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
2793 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
2794 * 41 ff 72 f8 pushq -0x8(%r10)
2796 * 48 89 e5 mov %rsp,%rbp
2803 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2806 * There are some variations in the epilogues, like:
2814 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2819 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
2820 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
2821 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
2822 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
2824 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2827 * Sometimes r13 is used as the DRAP register, in which case it's saved and
2828 * restored beforehand:
2831 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
2832 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
2834 * 49 8d 65 f0 lea -0x10(%r13),%rsp
2838 static int update_cfi_state(struct instruction *insn,
2839 struct instruction *next_insn,
2840 struct cfi_state *cfi, struct stack_op *op)
2842 struct cfi_reg *cfa = &cfi->cfa;
2843 struct cfi_reg *regs = cfi->regs;
2845 /* ignore UNWIND_HINT_UNDEFINED regions */
2846 if (cfi->force_undefined)
2849 /* stack operations don't make sense with an undefined CFA */
2850 if (cfa->base == CFI_UNDEFINED) {
2851 if (insn_func(insn)) {
2852 WARN_INSN(insn, "undefined stack state");
2858 if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2859 cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2860 return update_cfi_state_regs(insn, cfi, op);
2862 switch (op->dest.type) {
2865 switch (op->src.type) {
2868 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2869 cfa->base == CFI_SP &&
2870 check_reg_frame_pos(®s[CFI_BP], -cfa->offset)) {
2872 /* mov %rsp, %rbp */
2873 cfa->base = op->dest.reg;
2874 cfi->bp_scratch = false;
2877 else if (op->src.reg == CFI_SP &&
2878 op->dest.reg == CFI_BP && cfi->drap) {
2880 /* drap: mov %rsp, %rbp */
2881 regs[CFI_BP].base = CFI_BP;
2882 regs[CFI_BP].offset = -cfi->stack_size;
2883 cfi->bp_scratch = false;
2886 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2891 * This is needed for the rare case where GCC
2898 cfi->vals[op->dest.reg].base = CFI_CFA;
2899 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2902 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2903 (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2908 * Restore the original stack pointer (Clang).
2910 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2913 else if (op->dest.reg == cfa->base) {
2915 /* mov %reg, %rsp */
2916 if (cfa->base == CFI_SP &&
2917 cfi->vals[op->src.reg].base == CFI_CFA) {
2920 * This is needed for the rare case
2921 * where GCC does something dumb like:
2923 * lea 0x8(%rsp), %rcx
2927 cfa->offset = -cfi->vals[op->src.reg].offset;
2928 cfi->stack_size = cfa->offset;
2930 } else if (cfa->base == CFI_SP &&
2931 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2932 cfi->vals[op->src.reg].offset == cfa->offset) {
2937 * 1: mov %rsp, (%[tos])
2938 * 2: mov %[tos], %rsp
2944 * 1 - places a pointer to the previous
2945 * stack at the Top-of-Stack of the
2948 * 2 - switches to the new stack.
2950 * 3 - pops the Top-of-Stack to restore
2951 * the original stack.
2953 * Note: we set base to SP_INDIRECT
2954 * here and preserve offset. Therefore
2955 * when the unwinder reaches ToS it
2956 * will dereference SP and then add the
2957 * offset to find the next frame, IOW:
2960 cfa->base = CFI_SP_INDIRECT;
2963 cfa->base = CFI_UNDEFINED;
2968 else if (op->dest.reg == CFI_SP &&
2969 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2970 cfi->vals[op->src.reg].offset == cfa->offset) {
2973 * The same stack swizzle case 2) as above. But
2974 * because we can't change cfa->base, case 3)
2975 * will become a regular POP. Pretend we're a
2976 * PUSH so things don't go unbalanced.
2978 cfi->stack_size += 8;
2985 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2988 cfi->stack_size -= op->src.offset;
2989 if (cfa->base == CFI_SP)
2990 cfa->offset -= op->src.offset;
2994 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2996 /* lea disp(%rbp), %rsp */
2997 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
3001 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
3003 /* drap: lea disp(%rsp), %drap */
3004 cfi->drap_reg = op->dest.reg;
3007 * lea disp(%rsp), %reg
3009 * This is needed for the rare case where GCC
3010 * does something dumb like:
3012 * lea 0x8(%rsp), %rcx
3016 cfi->vals[op->dest.reg].base = CFI_CFA;
3017 cfi->vals[op->dest.reg].offset = \
3018 -cfi->stack_size + op->src.offset;
3023 if (cfi->drap && op->dest.reg == CFI_SP &&
3024 op->src.reg == cfi->drap_reg) {
3026 /* drap: lea disp(%drap), %rsp */
3028 cfa->offset = cfi->stack_size = -op->src.offset;
3029 cfi->drap_reg = CFI_UNDEFINED;
3034 if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
3035 WARN_INSN(insn, "unsupported stack register modification");
3042 if (op->dest.reg != CFI_SP ||
3043 (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
3044 (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
3045 WARN_INSN(insn, "unsupported stack pointer realignment");
3049 if (cfi->drap_reg != CFI_UNDEFINED) {
3050 /* drap: and imm, %rsp */
3051 cfa->base = cfi->drap_reg;
3052 cfa->offset = cfi->stack_size = 0;
3057 * Older versions of GCC (4.8ish) realign the stack
3058 * without DRAP, with a frame pointer.
3065 if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
3067 /* pop %rsp; # restore from a stack swizzle */
3072 if (!cfi->drap && op->dest.reg == cfa->base) {
3078 if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
3079 op->dest.reg == cfi->drap_reg &&
3080 cfi->drap_offset == -cfi->stack_size) {
3082 /* drap: pop %drap */
3083 cfa->base = cfi->drap_reg;
3085 cfi->drap_offset = -1;
3087 } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
3090 restore_reg(cfi, op->dest.reg);
3093 cfi->stack_size -= 8;
3094 if (cfa->base == CFI_SP)
3099 case OP_SRC_REG_INDIRECT:
3100 if (!cfi->drap && op->dest.reg == cfa->base &&
3101 op->dest.reg == CFI_BP) {
3103 /* mov disp(%rsp), %rbp */
3105 cfa->offset = cfi->stack_size;
3108 if (cfi->drap && op->src.reg == CFI_BP &&
3109 op->src.offset == cfi->drap_offset) {
3111 /* drap: mov disp(%rbp), %drap */
3112 cfa->base = cfi->drap_reg;
3114 cfi->drap_offset = -1;
3117 if (cfi->drap && op->src.reg == CFI_BP &&
3118 op->src.offset == regs[op->dest.reg].offset) {
3120 /* drap: mov disp(%rbp), %reg */
3121 restore_reg(cfi, op->dest.reg);
3123 } else if (op->src.reg == cfa->base &&
3124 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
3126 /* mov disp(%rbp), %reg */
3127 /* mov disp(%rsp), %reg */
3128 restore_reg(cfi, op->dest.reg);
3130 } else if (op->src.reg == CFI_SP &&
3131 op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
3133 /* mov disp(%rsp), %reg */
3134 restore_reg(cfi, op->dest.reg);
3140 WARN_INSN(insn, "unknown stack-related instruction");
3148 cfi->stack_size += 8;
3149 if (cfa->base == CFI_SP)
3152 if (op->src.type != OP_SRC_REG)
3156 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3158 /* drap: push %drap */
3159 cfa->base = CFI_BP_INDIRECT;
3160 cfa->offset = -cfi->stack_size;
3162 /* save drap so we know when to restore it */
3163 cfi->drap_offset = -cfi->stack_size;
3165 } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
3167 /* drap: push %rbp */
3168 cfi->stack_size = 0;
3172 /* drap: push %reg */
3173 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
3179 save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
3182 /* detect when asm code uses rbp as a scratch register */
3183 if (opts.stackval && insn_func(insn) && op->src.reg == CFI_BP &&
3184 cfa->base != CFI_BP)
3185 cfi->bp_scratch = true;
3188 case OP_DEST_REG_INDIRECT:
3191 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3193 /* drap: mov %drap, disp(%rbp) */
3194 cfa->base = CFI_BP_INDIRECT;
3195 cfa->offset = op->dest.offset;
3197 /* save drap offset so we know when to restore it */
3198 cfi->drap_offset = op->dest.offset;
3201 /* drap: mov reg, disp(%rbp) */
3202 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
3205 } else if (op->dest.reg == cfa->base) {
3207 /* mov reg, disp(%rbp) */
3208 /* mov reg, disp(%rsp) */
3209 save_reg(cfi, op->src.reg, CFI_CFA,
3210 op->dest.offset - cfi->cfa.offset);
3212 } else if (op->dest.reg == CFI_SP) {
3214 /* mov reg, disp(%rsp) */
3215 save_reg(cfi, op->src.reg, CFI_CFA,
3216 op->dest.offset - cfi->stack_size);
3218 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
3220 /* mov %rsp, (%reg); # setup a stack swizzle. */
3221 cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
3222 cfi->vals[op->dest.reg].offset = cfa->offset;
3228 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
3229 WARN_INSN(insn, "unknown stack-related memory operation");
3234 cfi->stack_size -= 8;
3235 if (cfa->base == CFI_SP)
3241 WARN_INSN(insn, "unknown stack-related instruction");
3249 * The stack layouts of alternatives instructions can sometimes diverge when
3250 * they have stack modifications. That's fine as long as the potential stack
3251 * layouts don't conflict at any given potential instruction boundary.
3253 * Flatten the CFIs of the different alternative code streams (both original
3254 * and replacement) into a single shared CFI array which can be used to detect
3255 * conflicts and nicely feed a linear array of ORC entries to the unwinder.
3257 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
3259 struct cfi_state **alt_cfi;
3262 if (!insn->alt_group)
3266 WARN("CFI missing");
3270 alt_cfi = insn->alt_group->cfi;
3271 group_off = insn->offset - insn->alt_group->first_insn->offset;
3273 if (!alt_cfi[group_off]) {
3274 alt_cfi[group_off] = insn->cfi;
3276 if (cficmp(alt_cfi[group_off], insn->cfi)) {
3277 struct alt_group *orig_group = insn->alt_group->orig_group ?: insn->alt_group;
3278 struct instruction *orig = orig_group->first_insn;
3279 char *where = offstr(insn->sec, insn->offset);
3280 WARN_INSN(orig, "stack layout conflict in alternatives: %s", where);
3289 static int handle_insn_ops(struct instruction *insn,
3290 struct instruction *next_insn,
3291 struct insn_state *state)
3293 struct stack_op *op;
3295 for (op = insn->stack_ops; op; op = op->next) {
3297 if (update_cfi_state(insn, next_insn, &state->cfi, op))
3300 if (!insn->alt_group)
3303 if (op->dest.type == OP_DEST_PUSHF) {
3304 if (!state->uaccess_stack) {
3305 state->uaccess_stack = 1;
3306 } else if (state->uaccess_stack >> 31) {
3307 WARN_INSN(insn, "PUSHF stack exhausted");
3310 state->uaccess_stack <<= 1;
3311 state->uaccess_stack |= state->uaccess;
3314 if (op->src.type == OP_SRC_POPF) {
3315 if (state->uaccess_stack) {
3316 state->uaccess = state->uaccess_stack & 1;
3317 state->uaccess_stack >>= 1;
3318 if (state->uaccess_stack == 1)
3319 state->uaccess_stack = 0;
3327 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
3329 struct cfi_state *cfi1 = insn->cfi;
3333 WARN("CFI missing");
3337 if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
3339 WARN_INSN(insn, "stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
3340 cfi1->cfa.base, cfi1->cfa.offset,
3341 cfi2->cfa.base, cfi2->cfa.offset);
3343 } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
3344 for (i = 0; i < CFI_NUM_REGS; i++) {
3345 if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
3346 sizeof(struct cfi_reg)))
3349 WARN_INSN(insn, "stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
3350 i, cfi1->regs[i].base, cfi1->regs[i].offset,
3351 i, cfi2->regs[i].base, cfi2->regs[i].offset);
3355 } else if (cfi1->type != cfi2->type) {
3357 WARN_INSN(insn, "stack state mismatch: type1=%d type2=%d",
3358 cfi1->type, cfi2->type);
3360 } else if (cfi1->drap != cfi2->drap ||
3361 (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
3362 (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
3364 WARN_INSN(insn, "stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
3365 cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
3366 cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
3374 static inline bool func_uaccess_safe(struct symbol *func)
3377 return func->uaccess_safe;
3382 static inline const char *call_dest_name(struct instruction *insn)
3384 static char pvname[19];
3385 struct reloc *reloc;
3388 if (insn_call_dest(insn))
3389 return insn_call_dest(insn)->name;
3391 reloc = insn_reloc(NULL, insn);
3392 if (reloc && !strcmp(reloc->sym->name, "pv_ops")) {
3393 idx = (reloc_addend(reloc) / sizeof(void *));
3394 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
3401 static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3403 struct symbol *target;
3404 struct reloc *reloc;
3407 reloc = insn_reloc(file, insn);
3408 if (!reloc || strcmp(reloc->sym->name, "pv_ops"))
3411 idx = (arch_dest_reloc_offset(reloc_addend(reloc)) / sizeof(void *));
3413 if (file->pv_ops[idx].clean)
3416 file->pv_ops[idx].clean = true;
3418 list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3419 if (!target->sec->noinstr) {
3420 WARN("pv_ops[%d]: %s", idx, target->name);
3421 file->pv_ops[idx].clean = false;
3425 return file->pv_ops[idx].clean;
3428 static inline bool noinstr_call_dest(struct objtool_file *file,
3429 struct instruction *insn,
3430 struct symbol *func)
3433 * We can't deal with indirect function calls at present;
3434 * assume they're instrumented.
3438 return pv_call_dest(file, insn);
3444 * If the symbol is from a noinstr section; we good.
3446 if (func->sec->noinstr)
3450 * If the symbol is a static_call trampoline, we can't tell.
3452 if (func->static_call_tramp)
3456 * The __ubsan_handle_*() calls are like WARN(), they only happen when
3457 * something 'BAD' happened. At the risk of taking the machine down,
3458 * let them proceed to get the message out.
3460 if (!strncmp(func->name, "__ubsan_handle_", 15))
3466 static int validate_call(struct objtool_file *file,
3467 struct instruction *insn,
3468 struct insn_state *state)
3470 if (state->noinstr && state->instr <= 0 &&
3471 !noinstr_call_dest(file, insn, insn_call_dest(insn))) {
3472 WARN_INSN(insn, "call to %s() leaves .noinstr.text section", call_dest_name(insn));
3476 if (state->uaccess && !func_uaccess_safe(insn_call_dest(insn))) {
3477 WARN_INSN(insn, "call to %s() with UACCESS enabled", call_dest_name(insn));
3482 WARN_INSN(insn, "call to %s() with DF set", call_dest_name(insn));
3489 static int validate_sibling_call(struct objtool_file *file,
3490 struct instruction *insn,
3491 struct insn_state *state)
3493 if (insn_func(insn) && has_modified_stack_frame(insn, state)) {
3494 WARN_INSN(insn, "sibling call from callable instruction with modified stack frame");
3498 return validate_call(file, insn, state);
3501 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3503 if (state->noinstr && state->instr > 0) {
3504 WARN_INSN(insn, "return with instrumentation enabled");
3508 if (state->uaccess && !func_uaccess_safe(func)) {
3509 WARN_INSN(insn, "return with UACCESS enabled");
3513 if (!state->uaccess && func_uaccess_safe(func)) {
3514 WARN_INSN(insn, "return with UACCESS disabled from a UACCESS-safe function");
3519 WARN_INSN(insn, "return with DF set");
3523 if (func && has_modified_stack_frame(insn, state)) {
3524 WARN_INSN(insn, "return with modified stack frame");
3528 if (state->cfi.bp_scratch) {
3529 WARN_INSN(insn, "BP used as a scratch register");
3536 static struct instruction *next_insn_to_validate(struct objtool_file *file,
3537 struct instruction *insn)
3539 struct alt_group *alt_group = insn->alt_group;
3542 * Simulate the fact that alternatives are patched in-place. When the
3543 * end of a replacement alt_group is reached, redirect objtool flow to
3544 * the end of the original alt_group.
3546 * insn->alts->insn -> alt_group->first_insn
3548 * alt_group->last_insn
3549 * [alt_group->nop] -> next(orig_group->last_insn)
3552 if (alt_group->nop) {
3553 /* ->nop implies ->orig_group */
3554 if (insn == alt_group->last_insn)
3555 return alt_group->nop;
3556 if (insn == alt_group->nop)
3559 if (insn == alt_group->last_insn && alt_group->orig_group)
3563 return next_insn_same_sec(file, insn);
3566 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3570 * Follow the branch starting at the given instruction, and recursively follow
3571 * any other branches (jumps). Meanwhile, track the frame pointer state at
3572 * each instruction and validate all the rules described in
3573 * tools/objtool/Documentation/objtool.txt.
3575 static int validate_branch(struct objtool_file *file, struct symbol *func,
3576 struct instruction *insn, struct insn_state state)
3578 struct alternative *alt;
3579 struct instruction *next_insn, *prev_insn = NULL;
3580 struct section *sec;
3587 next_insn = next_insn_to_validate(file, insn);
3589 if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {
3590 /* Ignore KCFI type preambles, which always fall through */
3591 if (!strncmp(func->name, "__cfi_", 6) ||
3592 !strncmp(func->name, "__pfx_", 6))
3595 WARN("%s() falls through to next function %s()",
3596 func->name, insn_func(insn)->name);
3600 if (func && insn->ignore) {
3601 WARN_INSN(insn, "BUG: why am I validating an ignored function?");
3605 visited = VISITED_BRANCH << state.uaccess;
3606 if (insn->visited & VISITED_BRANCH_MASK) {
3607 if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3610 if (insn->visited & visited)
3617 state.instr += insn->instr;
3620 if (insn->restore) {
3621 struct instruction *save_insn, *i;
3626 sym_for_each_insn_continue_reverse(file, func, i) {
3634 WARN_INSN(insn, "no corresponding CFI save for CFI restore");
3638 if (!save_insn->visited) {
3640 * If the restore hint insn is at the
3641 * beginning of a basic block and was
3642 * branched to from elsewhere, and the
3643 * save insn hasn't been visited yet,
3644 * defer following this branch for now.
3645 * It will be seen later via the
3646 * straight-line path.
3651 WARN_INSN(insn, "objtool isn't smart enough to handle this CFI save/restore combo");
3655 insn->cfi = save_insn->cfi;
3659 state.cfi = *insn->cfi;
3661 /* XXX track if we actually changed state.cfi */
3663 if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3664 insn->cfi = prev_insn->cfi;
3667 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3671 insn->visited |= visited;
3673 if (propagate_alt_cfi(file, insn))
3676 if (!insn->ignore_alts && insn->alts) {
3677 bool skip_orig = false;
3679 for (alt = insn->alts; alt; alt = alt->next) {
3683 ret = validate_branch(file, func, alt->insn, state);
3685 BT_INSN(insn, "(alt)");
3694 if (handle_insn_ops(insn, next_insn, &state))
3697 switch (insn->type) {
3700 return validate_return(func, insn, &state);
3703 case INSN_CALL_DYNAMIC:
3704 ret = validate_call(file, insn, &state);
3708 if (opts.stackval && func && !is_special_call(insn) &&
3709 !has_valid_stack_frame(&state)) {
3710 WARN_INSN(insn, "call without frame pointer save/setup");
3719 case INSN_JUMP_CONDITIONAL:
3720 case INSN_JUMP_UNCONDITIONAL:
3721 if (is_sibling_call(insn)) {
3722 ret = validate_sibling_call(file, insn, &state);
3726 } else if (insn->jump_dest) {
3727 ret = validate_branch(file, func,
3728 insn->jump_dest, state);
3730 BT_INSN(insn, "(branch)");
3735 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3740 case INSN_JUMP_DYNAMIC:
3741 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3742 if (is_sibling_call(insn)) {
3743 ret = validate_sibling_call(file, insn, &state);
3748 if (insn->type == INSN_JUMP_DYNAMIC)
3753 case INSN_CONTEXT_SWITCH:
3754 if (func && (!next_insn || !next_insn->hint)) {
3755 WARN_INSN(insn, "unsupported instruction in callable function");
3761 if (state.uaccess) {
3762 WARN_INSN(insn, "recursive UACCESS enable");
3766 state.uaccess = true;
3770 if (!state.uaccess && func) {
3771 WARN_INSN(insn, "redundant UACCESS disable");
3775 if (func_uaccess_safe(func) && !state.uaccess_stack) {
3776 WARN_INSN(insn, "UACCESS-safe disables UACCESS");
3780 state.uaccess = false;
3785 WARN_INSN(insn, "recursive STD");
3793 if (!state.df && func) {
3794 WARN_INSN(insn, "redundant CLD");
3809 if (state.cfi.cfa.base == CFI_UNDEFINED)
3811 WARN("%s: unexpected end of section", sec->name);
3822 static int validate_unwind_hint(struct objtool_file *file,
3823 struct instruction *insn,
3824 struct insn_state *state)
3826 if (insn->hint && !insn->visited && !insn->ignore) {
3827 int ret = validate_branch(file, insn_func(insn), insn, *state);
3829 BT_INSN(insn, "<=== (hint)");
3836 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3838 struct instruction *insn;
3839 struct insn_state state;
3845 init_insn_state(file, &state, sec);
3848 sec_for_each_insn(file, sec, insn)
3849 warnings += validate_unwind_hint(file, insn, &state);
3851 for_each_insn(file, insn)
3852 warnings += validate_unwind_hint(file, insn, &state);
3859 * Validate rethunk entry constraint: must untrain RET before the first RET.
3861 * Follow every branch (intra-function) and ensure VALIDATE_UNRET_END comes
3862 * before an actual RET instruction.
3864 static int validate_unret(struct objtool_file *file, struct instruction *insn)
3866 struct instruction *next, *dest;
3870 next = next_insn_to_validate(file, insn);
3872 if (insn->visited & VISITED_UNRET)
3875 insn->visited |= VISITED_UNRET;
3877 if (!insn->ignore_alts && insn->alts) {
3878 struct alternative *alt;
3879 bool skip_orig = false;
3881 for (alt = insn->alts; alt; alt = alt->next) {
3885 ret = validate_unret(file, alt->insn);
3887 BT_INSN(insn, "(alt)");
3896 switch (insn->type) {
3898 case INSN_CALL_DYNAMIC:
3899 case INSN_JUMP_DYNAMIC:
3900 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3901 WARN_INSN(insn, "early indirect call");
3904 case INSN_JUMP_UNCONDITIONAL:
3905 case INSN_JUMP_CONDITIONAL:
3906 if (!is_sibling_call(insn)) {
3907 if (!insn->jump_dest) {
3908 WARN_INSN(insn, "unresolved jump target after linking?!?");
3911 ret = validate_unret(file, insn->jump_dest);
3913 BT_INSN(insn, "(branch%s)",
3914 insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : "");
3918 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3926 dest = find_insn(file, insn_call_dest(insn)->sec,
3927 insn_call_dest(insn)->offset);
3929 WARN("Unresolved function after linking!?: %s",
3930 insn_call_dest(insn)->name);
3934 ret = validate_unret(file, dest);
3936 BT_INSN(insn, "(call)");
3940 * If a call returns without error, it must have seen UNTRAIN_RET.
3941 * Therefore any non-error return is a success.
3946 WARN_INSN(insn, "RET before UNTRAIN");
3950 if (insn->retpoline_safe)
3959 WARN_INSN(insn, "teh end!");
3969 * Validate that all branches starting at VALIDATE_UNRET_BEGIN encounter
3970 * VALIDATE_UNRET_END before RET.
3972 static int validate_unrets(struct objtool_file *file)
3974 struct instruction *insn;
3975 int ret, warnings = 0;
3977 for_each_insn(file, insn) {
3981 ret = validate_unret(file, insn);
3983 WARN_INSN(insn, "Failed UNRET validation");
3992 static int validate_retpoline(struct objtool_file *file)
3994 struct instruction *insn;
3997 for_each_insn(file, insn) {
3998 if (insn->type != INSN_JUMP_DYNAMIC &&
3999 insn->type != INSN_CALL_DYNAMIC &&
4000 insn->type != INSN_RETURN)
4003 if (insn->retpoline_safe)
4006 if (insn->sec->init)
4009 if (insn->type == INSN_RETURN) {
4011 WARN_INSN(insn, "'naked' return found in MITIGATION_RETHUNK build");
4015 WARN_INSN(insn, "indirect %s found in MITIGATION_RETPOLINE build",
4016 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
4025 static bool is_kasan_insn(struct instruction *insn)
4027 return (insn->type == INSN_CALL &&
4028 !strcmp(insn_call_dest(insn)->name, "__asan_handle_no_return"));
4031 static bool is_ubsan_insn(struct instruction *insn)
4033 return (insn->type == INSN_CALL &&
4034 !strcmp(insn_call_dest(insn)->name,
4035 "__ubsan_handle_builtin_unreachable"));
4038 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
4041 struct instruction *prev_insn;
4043 if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
4047 * Ignore alternative replacement instructions. This can happen
4048 * when a whitelisted function uses one of the ALTERNATIVE macros.
4050 if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
4051 !strcmp(insn->sec->name, ".altinstr_aux"))
4055 * Whole archive runs might encounter dead code from weak symbols.
4056 * This is where the linker will have dropped the weak symbol in
4057 * favour of a regular symbol, but leaves the code in place.
4059 * In this case we'll find a piece of code (whole function) that is not
4060 * covered by a !section symbol. Ignore them.
4062 if (opts.link && !insn_func(insn)) {
4063 int size = find_symbol_hole_containing(insn->sec, insn->offset);
4064 unsigned long end = insn->offset + size;
4066 if (!size) /* not a hole */
4069 if (size < 0) /* hole until the end */
4072 sec_for_each_insn_continue(file, insn) {
4074 * If we reach a visited instruction at or before the
4075 * end of the hole, ignore the unreachable.
4080 if (insn->offset >= end)
4084 * If this hole jumps to a .cold function, mark it ignore too.
4086 if (insn->jump_dest && insn_func(insn->jump_dest) &&
4087 strstr(insn_func(insn->jump_dest)->name, ".cold")) {
4088 struct instruction *dest = insn->jump_dest;
4089 func_for_each_insn(file, insn_func(dest), dest)
4090 dest->ignore = true;
4097 if (!insn_func(insn))
4100 if (insn_func(insn)->static_call_tramp)
4104 * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
4105 * __builtin_unreachable(). The BUG() macro has an unreachable() after
4106 * the UD2, which causes GCC's undefined trap logic to emit another UD2
4107 * (or occasionally a JMP to UD2).
4109 * It may also insert a UD2 after calling a __noreturn function.
4111 prev_insn = prev_insn_same_sec(file, insn);
4112 if (prev_insn->dead_end &&
4113 (insn->type == INSN_BUG ||
4114 (insn->type == INSN_JUMP_UNCONDITIONAL &&
4115 insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
4119 * Check if this (or a subsequent) instruction is related to
4120 * CONFIG_UBSAN or CONFIG_KASAN.
4122 * End the search at 5 instructions to avoid going into the weeds.
4124 for (i = 0; i < 5; i++) {
4126 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
4129 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
4130 if (insn->jump_dest &&
4131 insn_func(insn->jump_dest) == insn_func(insn)) {
4132 insn = insn->jump_dest;
4139 if (insn->offset + insn->len >= insn_func(insn)->offset + insn_func(insn)->len)
4142 insn = next_insn_same_sec(file, insn);
4148 static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
4150 struct instruction *insn, *prev;
4151 struct cfi_state *cfi;
4153 insn = find_insn(file, func->sec, func->offset);
4157 for (prev = prev_insn_same_sec(file, insn);
4159 prev = prev_insn_same_sec(file, prev)) {
4162 if (prev->type != INSN_NOP)
4165 offset = func->offset - prev->offset;
4167 if (offset > opts.prefix)
4170 if (offset < opts.prefix)
4173 elf_create_prefix_symbol(file->elf, func, opts.prefix);
4182 * This can happen if stack validation isn't enabled or the
4183 * function is annotated with STACK_FRAME_NON_STANDARD.
4188 /* Propagate insn->cfi to the prefix code */
4189 cfi = cfi_hash_find_or_add(insn->cfi);
4190 for (; prev != insn; prev = next_insn_same_sec(file, prev))
4196 static int add_prefix_symbols(struct objtool_file *file)
4198 struct section *sec;
4199 struct symbol *func;
4201 for_each_sec(file, sec) {
4202 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4205 sec_for_each_sym(sec, func) {
4206 if (func->type != STT_FUNC)
4209 add_prefix_symbol(file, func);
4216 static int validate_symbol(struct objtool_file *file, struct section *sec,
4217 struct symbol *sym, struct insn_state *state)
4219 struct instruction *insn;
4223 WARN("%s() is missing an ELF size annotation", sym->name);
4227 if (sym->pfunc != sym || sym->alias != sym)
4230 insn = find_insn(file, sec, sym->offset);
4231 if (!insn || insn->ignore || insn->visited)
4234 state->uaccess = sym->uaccess_safe;
4236 ret = validate_branch(file, insn_func(insn), insn, *state);
4238 BT_INSN(insn, "<=== (sym)");
4242 static int validate_section(struct objtool_file *file, struct section *sec)
4244 struct insn_state state;
4245 struct symbol *func;
4248 sec_for_each_sym(sec, func) {
4249 if (func->type != STT_FUNC)
4252 init_insn_state(file, &state, sec);
4253 set_func_state(&state.cfi);
4255 warnings += validate_symbol(file, sec, func, &state);
4261 static int validate_noinstr_sections(struct objtool_file *file)
4263 struct section *sec;
4266 sec = find_section_by_name(file->elf, ".noinstr.text");
4268 warnings += validate_section(file, sec);
4269 warnings += validate_unwind_hints(file, sec);
4272 sec = find_section_by_name(file->elf, ".entry.text");
4274 warnings += validate_section(file, sec);
4275 warnings += validate_unwind_hints(file, sec);
4278 sec = find_section_by_name(file->elf, ".cpuidle.text");
4280 warnings += validate_section(file, sec);
4281 warnings += validate_unwind_hints(file, sec);
4287 static int validate_functions(struct objtool_file *file)
4289 struct section *sec;
4292 for_each_sec(file, sec) {
4293 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4296 warnings += validate_section(file, sec);
4302 static void mark_endbr_used(struct instruction *insn)
4304 if (!list_empty(&insn->call_node))
4305 list_del_init(&insn->call_node);
4308 static bool noendbr_range(struct objtool_file *file, struct instruction *insn)
4310 struct symbol *sym = find_symbol_containing(insn->sec, insn->offset-1);
4311 struct instruction *first;
4316 first = find_insn(file, sym->sec, sym->offset);
4320 if (first->type != INSN_ENDBR && !first->noendbr)
4323 return insn->offset == sym->offset + sym->len;
4326 static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
4328 struct instruction *dest;
4329 struct reloc *reloc;
4334 * Looking for function pointer load relocations. Ignore
4335 * direct/indirect branches:
4337 switch (insn->type) {
4339 case INSN_CALL_DYNAMIC:
4340 case INSN_JUMP_CONDITIONAL:
4341 case INSN_JUMP_UNCONDITIONAL:
4342 case INSN_JUMP_DYNAMIC:
4343 case INSN_JUMP_DYNAMIC_CONDITIONAL:
4351 for (reloc = insn_reloc(file, insn);
4353 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
4354 reloc_offset(reloc) + 1,
4355 (insn->offset + insn->len) - (reloc_offset(reloc) + 1))) {
4358 * static_call_update() references the trampoline, which
4359 * doesn't have (or need) ENDBR. Skip warning in that case.
4361 if (reloc->sym->static_call_tramp)
4364 off = reloc->sym->offset;
4365 if (reloc_type(reloc) == R_X86_64_PC32 ||
4366 reloc_type(reloc) == R_X86_64_PLT32)
4367 off += arch_dest_reloc_offset(reloc_addend(reloc));
4369 off += reloc_addend(reloc);
4371 dest = find_insn(file, reloc->sym->sec, off);
4375 if (dest->type == INSN_ENDBR) {
4376 mark_endbr_used(dest);
4380 if (insn_func(dest) && insn_func(insn) &&
4381 insn_func(dest)->pfunc == insn_func(insn)->pfunc) {
4383 * Anything from->to self is either _THIS_IP_ or
4386 * There is no sane way to annotate _THIS_IP_ since the
4387 * compiler treats the relocation as a constant and is
4388 * happy to fold in offsets, skewing any annotation we
4389 * do, leading to vast amounts of false-positives.
4391 * There's also compiler generated _THIS_IP_ through
4392 * KCOV and such which we have no hope of annotating.
4394 * As such, blanket accept self-references without
4401 * Accept anything ANNOTATE_NOENDBR.
4407 * Accept if this is the instruction after a symbol
4408 * that is (no)endbr -- typical code-range usage.
4410 if (noendbr_range(file, dest))
4413 WARN_INSN(insn, "relocation to !ENDBR: %s", offstr(dest->sec, dest->offset));
4421 static int validate_ibt_data_reloc(struct objtool_file *file,
4422 struct reloc *reloc)
4424 struct instruction *dest;
4426 dest = find_insn(file, reloc->sym->sec,
4427 reloc->sym->offset + reloc_addend(reloc));
4431 if (dest->type == INSN_ENDBR) {
4432 mark_endbr_used(dest);
4439 WARN_FUNC("data relocation to !ENDBR: %s",
4440 reloc->sec->base, reloc_offset(reloc),
4441 offstr(dest->sec, dest->offset));
4447 * Validate IBT rules and remove used ENDBR instructions from the seal list.
4448 * Unused ENDBR instructions will be annotated for sealing (i.e., replaced with
4449 * NOPs) later, in create_ibt_endbr_seal_sections().
4451 static int validate_ibt(struct objtool_file *file)
4453 struct section *sec;
4454 struct reloc *reloc;
4455 struct instruction *insn;
4458 for_each_insn(file, insn)
4459 warnings += validate_ibt_insn(file, insn);
4461 for_each_sec(file, sec) {
4463 /* Already done by validate_ibt_insn() */
4464 if (sec->sh.sh_flags & SHF_EXECINSTR)
4471 * These sections can reference text addresses, but not with
4472 * the intent to indirect branch to them.
4474 if ((!strncmp(sec->name, ".discard", 8) &&
4475 strcmp(sec->name, ".discard.ibt_endbr_noseal")) ||
4476 !strncmp(sec->name, ".debug", 6) ||
4477 !strcmp(sec->name, ".altinstructions") ||
4478 !strcmp(sec->name, ".ibt_endbr_seal") ||
4479 !strcmp(sec->name, ".orc_unwind_ip") ||
4480 !strcmp(sec->name, ".parainstructions") ||
4481 !strcmp(sec->name, ".retpoline_sites") ||
4482 !strcmp(sec->name, ".smp_locks") ||
4483 !strcmp(sec->name, ".static_call_sites") ||
4484 !strcmp(sec->name, "_error_injection_whitelist") ||
4485 !strcmp(sec->name, "_kprobe_blacklist") ||
4486 !strcmp(sec->name, "__bug_table") ||
4487 !strcmp(sec->name, "__ex_table") ||
4488 !strcmp(sec->name, "__jump_table") ||
4489 !strcmp(sec->name, "__mcount_loc") ||
4490 !strcmp(sec->name, ".kcfi_traps") ||
4491 strstr(sec->name, "__patchable_function_entries"))
4494 for_each_reloc(sec->rsec, reloc)
4495 warnings += validate_ibt_data_reloc(file, reloc);
4501 static int validate_sls(struct objtool_file *file)
4503 struct instruction *insn, *next_insn;
4506 for_each_insn(file, insn) {
4507 next_insn = next_insn_same_sec(file, insn);
4509 if (insn->retpoline_safe)
4512 switch (insn->type) {
4514 if (!next_insn || next_insn->type != INSN_TRAP) {
4515 WARN_INSN(insn, "missing int3 after ret");
4520 case INSN_JUMP_DYNAMIC:
4521 if (!next_insn || next_insn->type != INSN_TRAP) {
4522 WARN_INSN(insn, "missing int3 after indirect jump");
4534 static bool ignore_noreturn_call(struct instruction *insn)
4536 struct symbol *call_dest = insn_call_dest(insn);
4539 * FIXME: hack, we need a real noreturn solution
4541 * Problem is, exc_double_fault() may or may not return, depending on
4542 * whether CONFIG_X86_ESPFIX64 is set. But objtool has no visibility
4543 * to the kernel config.
4545 * Other potential ways to fix it:
4547 * - have compiler communicate __noreturn functions somehow
4548 * - remove CONFIG_X86_ESPFIX64
4549 * - read the .config file
4550 * - add a cmdline option
4551 * - create a generic objtool annotation format (vs a bunch of custom
4552 * formats) and annotate it
4554 if (!strcmp(call_dest->name, "exc_double_fault")) {
4555 /* prevent further unreachable warnings for the caller */
4556 insn->sym->warned = 1;
4563 static int validate_reachable_instructions(struct objtool_file *file)
4565 struct instruction *insn, *prev_insn;
4566 struct symbol *call_dest;
4569 if (file->ignore_unreachables)
4572 for_each_insn(file, insn) {
4573 if (insn->visited || ignore_unreachable_insn(file, insn))
4576 prev_insn = prev_insn_same_sec(file, insn);
4577 if (prev_insn && prev_insn->dead_end) {
4578 call_dest = insn_call_dest(prev_insn);
4579 if (call_dest && !ignore_noreturn_call(prev_insn)) {
4580 WARN_INSN(insn, "%s() is missing a __noreturn annotation",
4587 WARN_INSN(insn, "unreachable instruction");
4594 /* 'funcs' is a space-separated list of function names */
4595 static int disas_funcs(const char *funcs)
4597 const char *objdump_str, *cross_compile;
4601 cross_compile = getenv("CROSS_COMPILE");
4603 objdump_str = "%sobjdump -wdr %s | gawk -M -v _funcs='%s' '"
4604 "BEGIN { split(_funcs, funcs); }"
4605 "/^$/ { func_match = 0; }"
4607 "f = gensub(/.*<(.*)>:/, \"\\\\1\", 1);"
4608 "for (i in funcs) {"
4609 "if (funcs[i] == f) {"
4611 "base = strtonum(\"0x\" $1);"
4618 "addr = strtonum(\"0x\" $1);"
4619 "printf(\"%%04x \", addr - base);"
4624 /* fake snprintf() to calculate the size */
4625 size = snprintf(NULL, 0, objdump_str, cross_compile, objname, funcs) + 1;
4627 WARN("objdump string size calculation failed");
4633 /* real snprintf() */
4634 snprintf(cmd, size, objdump_str, cross_compile, objname, funcs);
4637 WARN("disassembly failed: %d", ret);
4644 static int disas_warned_funcs(struct objtool_file *file)
4647 char *funcs = NULL, *tmp;
4649 for_each_sym(file, sym) {
4652 funcs = malloc(strlen(sym->name) + 1);
4653 strcpy(funcs, sym->name);
4655 tmp = malloc(strlen(funcs) + strlen(sym->name) + 2);
4656 sprintf(tmp, "%s %s", funcs, sym->name);
4671 struct insn_chunk *next;
4675 * Reduce peak RSS usage by freeing insns memory before writing the ELF file,
4676 * which can trigger more allocations for .debug_* sections whose data hasn't
4679 static void free_insns(struct objtool_file *file)
4681 struct instruction *insn;
4682 struct insn_chunk *chunks = NULL, *chunk;
4684 for_each_insn(file, insn) {
4686 chunk = malloc(sizeof(*chunk));
4688 chunk->next = chunks;
4693 for (chunk = chunks; chunk; chunk = chunk->next)
4697 int check(struct objtool_file *file)
4699 int ret, warnings = 0;
4701 arch_initial_func_cfi_state(&initial_func_cfi);
4702 init_cfi_state(&init_cfi);
4703 init_cfi_state(&func_cfi);
4704 set_func_state(&func_cfi);
4705 init_cfi_state(&force_undefined_cfi);
4706 force_undefined_cfi.force_undefined = true;
4708 if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
4711 cfi_hash_add(&init_cfi);
4712 cfi_hash_add(&func_cfi);
4714 ret = decode_sections(file);
4723 if (opts.retpoline) {
4724 ret = validate_retpoline(file);
4730 if (opts.stackval || opts.orc || opts.uaccess) {
4731 ret = validate_functions(file);
4736 ret = validate_unwind_hints(file, NULL);
4742 ret = validate_reachable_instructions(file);
4748 } else if (opts.noinstr) {
4749 ret = validate_noinstr_sections(file);
4757 * Must be after validate_branch() and friends, it plays
4758 * further games with insn->visited.
4760 ret = validate_unrets(file);
4767 ret = validate_ibt(file);
4774 ret = validate_sls(file);
4780 if (opts.static_call) {
4781 ret = create_static_call_sections(file);
4787 if (opts.retpoline) {
4788 ret = create_retpoline_sites_sections(file);
4795 ret = create_cfi_sections(file);
4802 ret = create_return_sites_sections(file);
4807 if (opts.hack_skylake) {
4808 ret = create_direct_call_sections(file);
4816 ret = create_mcount_loc_sections(file);
4823 ret = add_prefix_symbols(file);
4830 ret = create_ibt_endbr_seal_sections(file);
4836 if (opts.orc && nr_insns) {
4837 ret = orc_create(file);
4846 disas_warned_funcs(file);
4849 printf("nr_insns_visited: %ld\n", nr_insns_visited);
4850 printf("nr_cfi: %ld\n", nr_cfi);
4851 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
4852 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
4857 * For now, don't fail the kernel build on fatal warnings. These
4858 * errors are still fairly common due to the growing matrix of
4859 * supported toolchains and their recent pace of change.