1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
12 #include <objtool/builtin.h>
13 #include <objtool/cfi.h>
14 #include <objtool/arch.h>
15 #include <objtool/check.h>
16 #include <objtool/special.h>
17 #include <objtool/warn.h>
18 #include <objtool/endianness.h>
20 #include <linux/objtool_types.h>
21 #include <linux/hashtable.h>
22 #include <linux/kernel.h>
23 #include <linux/static_call_types.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;
37 struct instruction *find_insn(struct objtool_file *file,
38 struct section *sec, unsigned long offset)
40 struct instruction *insn;
42 hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
43 if (insn->sec == sec && insn->offset == offset)
50 struct instruction *next_insn_same_sec(struct objtool_file *file,
51 struct instruction *insn)
53 if (insn->idx == INSN_CHUNK_MAX)
54 return find_insn(file, insn->sec, insn->offset + insn->len);
63 static struct instruction *next_insn_same_func(struct objtool_file *file,
64 struct instruction *insn)
66 struct instruction *next = next_insn_same_sec(file, insn);
67 struct symbol *func = insn_func(insn);
72 if (next && insn_func(next) == func)
75 /* Check if we're already in the subfunction: */
76 if (func == func->cfunc)
79 /* Move to the subfunction: */
80 return find_insn(file, func->cfunc->sec, func->cfunc->offset);
83 static struct instruction *prev_insn_same_sec(struct objtool_file *file,
84 struct instruction *insn)
88 return find_insn(file, insn->sec, insn->offset - insn->prev_len);
95 static struct instruction *prev_insn_same_sym(struct objtool_file *file,
96 struct instruction *insn)
98 struct instruction *prev = prev_insn_same_sec(file, insn);
100 if (prev && insn_func(prev) == insn_func(insn))
106 #define for_each_insn(file, insn) \
107 for (struct section *__sec, *__fake = (struct section *)1; \
108 __fake; __fake = NULL) \
109 for_each_sec(file, __sec) \
110 sec_for_each_insn(file, __sec, insn)
112 #define func_for_each_insn(file, func, insn) \
113 for (insn = find_insn(file, func->sec, func->offset); \
115 insn = next_insn_same_func(file, insn))
117 #define sym_for_each_insn(file, sym, insn) \
118 for (insn = find_insn(file, sym->sec, sym->offset); \
119 insn && insn->offset < sym->offset + sym->len; \
120 insn = next_insn_same_sec(file, insn))
122 #define sym_for_each_insn_continue_reverse(file, sym, insn) \
123 for (insn = prev_insn_same_sec(file, insn); \
124 insn && insn->offset >= sym->offset; \
125 insn = prev_insn_same_sec(file, insn))
127 #define sec_for_each_insn_from(file, insn) \
128 for (; insn; insn = next_insn_same_sec(file, insn))
130 #define sec_for_each_insn_continue(file, insn) \
131 for (insn = next_insn_same_sec(file, insn); insn; \
132 insn = next_insn_same_sec(file, insn))
134 static inline struct symbol *insn_call_dest(struct instruction *insn)
136 if (insn->type == INSN_JUMP_DYNAMIC ||
137 insn->type == INSN_CALL_DYNAMIC)
140 return insn->_call_dest;
143 static inline struct reloc *insn_jump_table(struct instruction *insn)
145 if (insn->type == INSN_JUMP_DYNAMIC ||
146 insn->type == INSN_CALL_DYNAMIC)
147 return insn->_jump_table;
152 static bool is_jump_table_jump(struct instruction *insn)
154 struct alt_group *alt_group = insn->alt_group;
156 if (insn_jump_table(insn))
159 /* Retpoline alternative for a jump table? */
160 return alt_group && alt_group->orig_group &&
161 insn_jump_table(alt_group->orig_group->first_insn);
164 static bool is_sibling_call(struct instruction *insn)
167 * Assume only STT_FUNC calls have jump-tables.
169 if (insn_func(insn)) {
170 /* An indirect jump is either a sibling call or a jump to a table. */
171 if (insn->type == INSN_JUMP_DYNAMIC)
172 return !is_jump_table_jump(insn);
175 /* add_jump_destinations() sets insn_call_dest(insn) for sibling calls. */
176 return (is_static_jump(insn) && insn_call_dest(insn));
180 * This checks to see if the given function is a "noreturn" function.
182 * For global functions which are outside the scope of this object file, we
183 * have to keep a manual list of them.
185 * For local functions, we have to detect them manually by simply looking for
186 * the lack of a return instruction.
188 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
192 struct instruction *insn;
196 * Unfortunately these have to be hard coded because the noreturn
197 * attribute isn't provided in ELF data. Keep 'em sorted.
199 static const char * const global_noreturns[] = {
201 "__module_put_and_kthread_exit",
204 "__ubsan_handle_builtin_unreachable",
205 "arch_call_rest_init",
206 "arch_cpu_idle_dead",
208 "cpu_bringup_and_idle",
213 "ex_handler_msr_mce",
217 "kthread_complete_and_exit",
219 "kunit_try_catch_throw",
221 "machine_real_restart",
224 "nmi_panic_self_stop",
226 "panic_smp_self_stop",
229 "rewind_stack_and_make_dead",
235 "x86_64_start_kernel",
236 "x86_64_start_reservations",
237 "xen_cpu_bringup_again",
244 if (func->bind == STB_GLOBAL || func->bind == STB_WEAK)
245 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
246 if (!strcmp(func->name, global_noreturns[i]))
249 if (func->bind == STB_WEAK)
255 insn = find_insn(file, func->sec, func->offset);
256 if (!insn || !insn_func(insn))
259 func_for_each_insn(file, func, insn) {
262 if (insn->type == INSN_RETURN)
270 * A function can have a sibling call instead of a return. In that
271 * case, the function's dead-end status depends on whether the target
272 * of the sibling call returns.
274 func_for_each_insn(file, func, insn) {
275 if (is_sibling_call(insn)) {
276 struct instruction *dest = insn->jump_dest;
279 /* sibling call to another file */
282 /* local sibling call */
283 if (recursion == 5) {
285 * Infinite recursion: two functions have
286 * sibling calls to each other. This is a very
287 * rare case. It means they aren't dead ends.
292 return __dead_end_function(file, insn_func(dest), recursion+1);
299 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
301 return __dead_end_function(file, func, 0);
304 static void init_cfi_state(struct cfi_state *cfi)
308 for (i = 0; i < CFI_NUM_REGS; i++) {
309 cfi->regs[i].base = CFI_UNDEFINED;
310 cfi->vals[i].base = CFI_UNDEFINED;
312 cfi->cfa.base = CFI_UNDEFINED;
313 cfi->drap_reg = CFI_UNDEFINED;
314 cfi->drap_offset = -1;
317 static void init_insn_state(struct objtool_file *file, struct insn_state *state,
320 memset(state, 0, sizeof(*state));
321 init_cfi_state(&state->cfi);
324 * We need the full vmlinux for noinstr validation, otherwise we can
325 * not correctly determine insn_call_dest(insn)->sec (external symbols
326 * do not have a section).
328 if (opts.link && opts.noinstr && sec)
329 state->noinstr = sec->noinstr;
332 static struct cfi_state *cfi_alloc(void)
334 struct cfi_state *cfi = calloc(sizeof(struct cfi_state), 1);
336 WARN("calloc failed");
344 static struct hlist_head *cfi_hash;
346 static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
348 return memcmp((void *)cfi1 + sizeof(cfi1->hash),
349 (void *)cfi2 + sizeof(cfi2->hash),
350 sizeof(struct cfi_state) - sizeof(struct hlist_node));
353 static inline u32 cfi_key(struct cfi_state *cfi)
355 return jhash((void *)cfi + sizeof(cfi->hash),
356 sizeof(*cfi) - sizeof(cfi->hash), 0);
359 static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
361 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
362 struct cfi_state *obj;
364 hlist_for_each_entry(obj, head, hash) {
365 if (!cficmp(cfi, obj)) {
373 hlist_add_head(&obj->hash, head);
378 static void cfi_hash_add(struct cfi_state *cfi)
380 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
382 hlist_add_head(&cfi->hash, head);
385 static void *cfi_hash_alloc(unsigned long size)
387 cfi_bits = max(10, ilog2(size));
388 cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
389 PROT_READ|PROT_WRITE,
390 MAP_PRIVATE|MAP_ANON, -1, 0);
391 if (cfi_hash == (void *)-1L) {
392 WARN("mmap fail cfi_hash");
394 } else if (opts.stats) {
395 printf("cfi_bits: %d\n", cfi_bits);
401 static unsigned long nr_insns;
402 static unsigned long nr_insns_visited;
405 * Call the arch-specific instruction decoder for all the instructions and add
406 * them to the global instruction list.
408 static int decode_instructions(struct objtool_file *file)
412 unsigned long offset;
413 struct instruction *insn;
416 for_each_sec(file, sec) {
417 struct instruction *insns = NULL;
421 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
424 if (strcmp(sec->name, ".altinstr_replacement") &&
425 strcmp(sec->name, ".altinstr_aux") &&
426 strncmp(sec->name, ".discard.", 9))
429 if (!strcmp(sec->name, ".noinstr.text") ||
430 !strcmp(sec->name, ".entry.text") ||
431 !strcmp(sec->name, ".cpuidle.text") ||
432 !strncmp(sec->name, ".text.__x86.", 12))
436 * .init.text code is ran before userspace and thus doesn't
437 * strictly need retpolines, except for modules which are
438 * loaded late, they very much do need retpoline in their
441 if (!strcmp(sec->name, ".init.text") && !opts.module)
444 for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
445 if (!insns || idx == INSN_CHUNK_MAX) {
446 insns = calloc(sizeof(*insn), INSN_CHUNK_SIZE);
448 WARN("malloc failed");
458 INIT_LIST_HEAD(&insn->call_node);
460 insn->offset = offset;
461 insn->prev_len = prev_len;
463 ret = arch_decode_instruction(file, sec, offset,
464 sec->sh.sh_size - offset,
469 prev_len = insn->len;
472 * By default, "ud2" is a dead end unless otherwise
473 * annotated, because GCC 7 inserts it for certain
474 * divide-by-zero cases.
476 if (insn->type == INSN_BUG)
477 insn->dead_end = true;
479 hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
483 // printf("%s: last chunk used: %d\n", sec->name, (int)idx);
485 sec_for_each_sym(sec, func) {
486 if (func->type != STT_NOTYPE && func->type != STT_FUNC)
489 if (func->offset == sec->sh.sh_size) {
490 /* Heuristic: likely an "end" symbol */
491 if (func->type == STT_NOTYPE)
493 WARN("%s(): STT_FUNC at end of section",
498 if (func->return_thunk || func->alias != func)
501 if (!find_insn(file, sec, func->offset)) {
502 WARN("%s(): can't find starting instruction",
507 sym_for_each_insn(file, func, insn) {
509 if (func->type == STT_FUNC &&
510 insn->type == INSN_ENDBR &&
511 list_empty(&insn->call_node)) {
512 if (insn->offset == func->offset) {
513 list_add_tail(&insn->call_node, &file->endbr_list);
516 file->nr_endbr_int++;
524 printf("nr_insns: %lu\n", nr_insns);
530 * Read the pv_ops[] .data table to find the static initialized values.
532 static int add_pv_ops(struct objtool_file *file, const char *symname)
534 struct symbol *sym, *func;
535 unsigned long off, end;
539 sym = find_symbol_by_name(file->elf, symname);
544 end = off + sym->len;
546 rel = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off);
551 if (func->type == STT_SECTION)
552 func = find_symbol_by_offset(rel->sym->sec, rel->addend);
554 idx = (rel->offset - sym->offset) / sizeof(unsigned long);
556 objtool_pv_add(file, idx, func);
558 off = rel->offset + 1;
567 * Allocate and initialize file->pv_ops[].
569 static int init_pv_ops(struct objtool_file *file)
571 static const char *pv_ops_tables[] = {
587 sym = find_symbol_by_name(file->elf, "pv_ops");
591 nr = sym->len / sizeof(unsigned long);
592 file->pv_ops = calloc(sizeof(struct pv_state), nr);
596 for (idx = 0; idx < nr; idx++)
597 INIT_LIST_HEAD(&file->pv_ops[idx].targets);
599 for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++)
600 add_pv_ops(file, pv_ops);
605 static struct instruction *find_last_insn(struct objtool_file *file,
608 struct instruction *insn = NULL;
610 unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
612 for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
613 insn = find_insn(file, sec, offset);
619 * Mark "ud2" instructions and manually annotated dead ends.
621 static int add_dead_ends(struct objtool_file *file)
625 struct instruction *insn;
628 * Check for manually annotated dead ends.
630 sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
634 list_for_each_entry(reloc, &sec->reloc_list, list) {
635 if (reloc->sym->type != STT_SECTION) {
636 WARN("unexpected relocation symbol type in %s", sec->name);
639 insn = find_insn(file, reloc->sym->sec, reloc->addend);
641 insn = prev_insn_same_sec(file, insn);
642 else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
643 insn = find_last_insn(file, reloc->sym->sec);
645 WARN("can't find unreachable insn at %s+0x%" PRIx64,
646 reloc->sym->sec->name, reloc->addend);
650 WARN("can't find unreachable insn at %s+0x%" PRIx64,
651 reloc->sym->sec->name, reloc->addend);
655 insn->dead_end = true;
660 * These manually annotated reachable checks are needed for GCC 4.4,
661 * where the Linux unreachable() macro isn't supported. In that case
662 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
665 sec = find_section_by_name(file->elf, ".rela.discard.reachable");
669 list_for_each_entry(reloc, &sec->reloc_list, list) {
670 if (reloc->sym->type != STT_SECTION) {
671 WARN("unexpected relocation symbol type in %s", sec->name);
674 insn = find_insn(file, reloc->sym->sec, reloc->addend);
676 insn = prev_insn_same_sec(file, insn);
677 else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
678 insn = find_last_insn(file, reloc->sym->sec);
680 WARN("can't find reachable insn at %s+0x%" PRIx64,
681 reloc->sym->sec->name, reloc->addend);
685 WARN("can't find reachable insn at %s+0x%" PRIx64,
686 reloc->sym->sec->name, reloc->addend);
690 insn->dead_end = false;
696 static int create_static_call_sections(struct objtool_file *file)
699 struct static_call_site *site;
700 struct instruction *insn;
701 struct symbol *key_sym;
702 char *key_name, *tmp;
705 sec = find_section_by_name(file->elf, ".static_call_sites");
707 INIT_LIST_HEAD(&file->static_call_list);
708 WARN("file already has .static_call_sites section, skipping");
712 if (list_empty(&file->static_call_list))
716 list_for_each_entry(insn, &file->static_call_list, call_node)
719 sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE,
720 sizeof(struct static_call_site), idx);
725 list_for_each_entry(insn, &file->static_call_list, call_node) {
727 site = (struct static_call_site *)sec->data->d_buf + idx;
728 memset(site, 0, sizeof(struct static_call_site));
730 /* populate reloc for 'addr' */
731 if (elf_add_reloc_to_insn(file->elf, sec,
732 idx * sizeof(struct static_call_site),
734 insn->sec, insn->offset))
737 /* find key symbol */
738 key_name = strdup(insn_call_dest(insn)->name);
743 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
744 STATIC_CALL_TRAMP_PREFIX_LEN)) {
745 WARN("static_call: trampoline name malformed: %s", key_name);
749 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
750 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
752 key_sym = find_symbol_by_name(file->elf, tmp);
755 WARN("static_call: can't find static_call_key symbol: %s", tmp);
761 * For modules(), the key might not be exported, which
762 * means the module can make static calls but isn't
763 * allowed to change them.
765 * In that case we temporarily set the key to be the
766 * trampoline address. This is fixed up in
767 * static_call_add_module().
769 key_sym = insn_call_dest(insn);
773 /* populate reloc for 'key' */
774 if (elf_add_reloc(file->elf, sec,
775 idx * sizeof(struct static_call_site) + 4,
776 R_X86_64_PC32, key_sym,
777 is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
786 static int create_retpoline_sites_sections(struct objtool_file *file)
788 struct instruction *insn;
792 sec = find_section_by_name(file->elf, ".retpoline_sites");
794 WARN("file already has .retpoline_sites, skipping");
799 list_for_each_entry(insn, &file->retpoline_call_list, call_node)
805 sec = elf_create_section(file->elf, ".retpoline_sites", 0,
808 WARN("elf_create_section: .retpoline_sites");
813 list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
815 int *site = (int *)sec->data->d_buf + idx;
818 if (elf_add_reloc_to_insn(file->elf, sec,
821 insn->sec, insn->offset)) {
822 WARN("elf_add_reloc_to_insn: .retpoline_sites");
832 static int create_return_sites_sections(struct objtool_file *file)
834 struct instruction *insn;
838 sec = find_section_by_name(file->elf, ".return_sites");
840 WARN("file already has .return_sites, skipping");
845 list_for_each_entry(insn, &file->return_thunk_list, call_node)
851 sec = elf_create_section(file->elf, ".return_sites", 0,
854 WARN("elf_create_section: .return_sites");
859 list_for_each_entry(insn, &file->return_thunk_list, call_node) {
861 int *site = (int *)sec->data->d_buf + idx;
864 if (elf_add_reloc_to_insn(file->elf, sec,
867 insn->sec, insn->offset)) {
868 WARN("elf_add_reloc_to_insn: .return_sites");
878 static int create_ibt_endbr_seal_sections(struct objtool_file *file)
880 struct instruction *insn;
884 sec = find_section_by_name(file->elf, ".ibt_endbr_seal");
886 WARN("file already has .ibt_endbr_seal, skipping");
891 list_for_each_entry(insn, &file->endbr_list, call_node)
895 printf("ibt: ENDBR at function start: %d\n", file->nr_endbr);
896 printf("ibt: ENDBR inside functions: %d\n", file->nr_endbr_int);
897 printf("ibt: superfluous ENDBR: %d\n", idx);
903 sec = elf_create_section(file->elf, ".ibt_endbr_seal", 0,
906 WARN("elf_create_section: .ibt_endbr_seal");
911 list_for_each_entry(insn, &file->endbr_list, call_node) {
913 int *site = (int *)sec->data->d_buf + idx;
914 struct symbol *sym = insn->sym;
917 if (opts.module && sym && sym->type == STT_FUNC &&
918 insn->offset == sym->offset &&
919 (!strcmp(sym->name, "init_module") ||
920 !strcmp(sym->name, "cleanup_module")))
921 WARN("%s(): not an indirect call target", sym->name);
923 if (elf_add_reloc_to_insn(file->elf, sec,
926 insn->sec, insn->offset)) {
927 WARN("elf_add_reloc_to_insn: .ibt_endbr_seal");
937 static int create_cfi_sections(struct objtool_file *file)
944 sec = find_section_by_name(file->elf, ".cfi_sites");
946 INIT_LIST_HEAD(&file->call_list);
947 WARN("file already has .cfi_sites section, skipping");
952 for_each_sym(file, sym) {
953 if (sym->type != STT_FUNC)
956 if (strncmp(sym->name, "__cfi_", 6))
962 sec = elf_create_section(file->elf, ".cfi_sites", 0, sizeof(unsigned int), idx);
967 for_each_sym(file, sym) {
968 if (sym->type != STT_FUNC)
971 if (strncmp(sym->name, "__cfi_", 6))
974 loc = (unsigned int *)sec->data->d_buf + idx;
975 memset(loc, 0, sizeof(unsigned int));
977 if (elf_add_reloc_to_insn(file->elf, sec,
978 idx * sizeof(unsigned int),
980 sym->sec, sym->offset))
989 static int create_mcount_loc_sections(struct objtool_file *file)
991 int addrsize = elf_class_addrsize(file->elf);
992 struct instruction *insn;
996 sec = find_section_by_name(file->elf, "__mcount_loc");
998 INIT_LIST_HEAD(&file->mcount_loc_list);
999 WARN("file already has __mcount_loc section, skipping");
1003 if (list_empty(&file->mcount_loc_list))
1007 list_for_each_entry(insn, &file->mcount_loc_list, call_node)
1010 sec = elf_create_section(file->elf, "__mcount_loc", 0, addrsize, idx);
1014 sec->sh.sh_addralign = addrsize;
1017 list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
1020 loc = sec->data->d_buf + idx;
1021 memset(loc, 0, addrsize);
1023 if (elf_add_reloc_to_insn(file->elf, sec, idx,
1024 addrsize == sizeof(u64) ? R_ABS64 : R_ABS32,
1025 insn->sec, insn->offset))
1034 static int create_direct_call_sections(struct objtool_file *file)
1036 struct instruction *insn;
1037 struct section *sec;
1041 sec = find_section_by_name(file->elf, ".call_sites");
1043 INIT_LIST_HEAD(&file->call_list);
1044 WARN("file already has .call_sites section, skipping");
1048 if (list_empty(&file->call_list))
1052 list_for_each_entry(insn, &file->call_list, call_node)
1055 sec = elf_create_section(file->elf, ".call_sites", 0, sizeof(unsigned int), idx);
1060 list_for_each_entry(insn, &file->call_list, call_node) {
1062 loc = (unsigned int *)sec->data->d_buf + idx;
1063 memset(loc, 0, sizeof(unsigned int));
1065 if (elf_add_reloc_to_insn(file->elf, sec,
1066 idx * sizeof(unsigned int),
1068 insn->sec, insn->offset))
1078 * Warnings shouldn't be reported for ignored functions.
1080 static void add_ignores(struct objtool_file *file)
1082 struct instruction *insn;
1083 struct section *sec;
1084 struct symbol *func;
1085 struct reloc *reloc;
1087 sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
1091 list_for_each_entry(reloc, &sec->reloc_list, list) {
1092 switch (reloc->sym->type) {
1098 func = find_func_by_offset(reloc->sym->sec, reloc->addend);
1104 WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type);
1108 func_for_each_insn(file, func, insn)
1109 insn->ignore = true;
1114 * This is a whitelist of functions that is allowed to be called with AC set.
1115 * The list is meant to be minimal and only contains compiler instrumentation
1116 * ABI and a few functions used to implement *_{to,from}_user() functions.
1118 * These functions must not directly change AC, but may PUSHF/POPF.
1120 static const char *uaccess_safe_builtin[] = {
1123 "kasan_check_range",
1124 /* KASAN out-of-line */
1125 "__asan_loadN_noabort",
1126 "__asan_load1_noabort",
1127 "__asan_load2_noabort",
1128 "__asan_load4_noabort",
1129 "__asan_load8_noabort",
1130 "__asan_load16_noabort",
1131 "__asan_storeN_noabort",
1132 "__asan_store1_noabort",
1133 "__asan_store2_noabort",
1134 "__asan_store4_noabort",
1135 "__asan_store8_noabort",
1136 "__asan_store16_noabort",
1137 "__kasan_check_read",
1138 "__kasan_check_write",
1140 "__asan_report_load_n_noabort",
1141 "__asan_report_load1_noabort",
1142 "__asan_report_load2_noabort",
1143 "__asan_report_load4_noabort",
1144 "__asan_report_load8_noabort",
1145 "__asan_report_load16_noabort",
1146 "__asan_report_store_n_noabort",
1147 "__asan_report_store1_noabort",
1148 "__asan_report_store2_noabort",
1149 "__asan_report_store4_noabort",
1150 "__asan_report_store8_noabort",
1151 "__asan_report_store16_noabort",
1153 "__kcsan_check_access",
1158 "kcsan_found_watchpoint",
1159 "kcsan_setup_watchpoint",
1160 "kcsan_check_scoped_accesses",
1161 "kcsan_disable_current",
1162 "kcsan_enable_current_nowarn",
1164 "__tsan_func_entry",
1166 "__tsan_read_range",
1167 "__tsan_write_range",
1178 "__tsan_read_write1",
1179 "__tsan_read_write2",
1180 "__tsan_read_write4",
1181 "__tsan_read_write8",
1182 "__tsan_read_write16",
1183 "__tsan_volatile_read1",
1184 "__tsan_volatile_read2",
1185 "__tsan_volatile_read4",
1186 "__tsan_volatile_read8",
1187 "__tsan_volatile_read16",
1188 "__tsan_volatile_write1",
1189 "__tsan_volatile_write2",
1190 "__tsan_volatile_write4",
1191 "__tsan_volatile_write8",
1192 "__tsan_volatile_write16",
1193 "__tsan_atomic8_load",
1194 "__tsan_atomic16_load",
1195 "__tsan_atomic32_load",
1196 "__tsan_atomic64_load",
1197 "__tsan_atomic8_store",
1198 "__tsan_atomic16_store",
1199 "__tsan_atomic32_store",
1200 "__tsan_atomic64_store",
1201 "__tsan_atomic8_exchange",
1202 "__tsan_atomic16_exchange",
1203 "__tsan_atomic32_exchange",
1204 "__tsan_atomic64_exchange",
1205 "__tsan_atomic8_fetch_add",
1206 "__tsan_atomic16_fetch_add",
1207 "__tsan_atomic32_fetch_add",
1208 "__tsan_atomic64_fetch_add",
1209 "__tsan_atomic8_fetch_sub",
1210 "__tsan_atomic16_fetch_sub",
1211 "__tsan_atomic32_fetch_sub",
1212 "__tsan_atomic64_fetch_sub",
1213 "__tsan_atomic8_fetch_and",
1214 "__tsan_atomic16_fetch_and",
1215 "__tsan_atomic32_fetch_and",
1216 "__tsan_atomic64_fetch_and",
1217 "__tsan_atomic8_fetch_or",
1218 "__tsan_atomic16_fetch_or",
1219 "__tsan_atomic32_fetch_or",
1220 "__tsan_atomic64_fetch_or",
1221 "__tsan_atomic8_fetch_xor",
1222 "__tsan_atomic16_fetch_xor",
1223 "__tsan_atomic32_fetch_xor",
1224 "__tsan_atomic64_fetch_xor",
1225 "__tsan_atomic8_fetch_nand",
1226 "__tsan_atomic16_fetch_nand",
1227 "__tsan_atomic32_fetch_nand",
1228 "__tsan_atomic64_fetch_nand",
1229 "__tsan_atomic8_compare_exchange_strong",
1230 "__tsan_atomic16_compare_exchange_strong",
1231 "__tsan_atomic32_compare_exchange_strong",
1232 "__tsan_atomic64_compare_exchange_strong",
1233 "__tsan_atomic8_compare_exchange_weak",
1234 "__tsan_atomic16_compare_exchange_weak",
1235 "__tsan_atomic32_compare_exchange_weak",
1236 "__tsan_atomic64_compare_exchange_weak",
1237 "__tsan_atomic8_compare_exchange_val",
1238 "__tsan_atomic16_compare_exchange_val",
1239 "__tsan_atomic32_compare_exchange_val",
1240 "__tsan_atomic64_compare_exchange_val",
1241 "__tsan_atomic_thread_fence",
1242 "__tsan_atomic_signal_fence",
1243 "__tsan_unaligned_read16",
1244 "__tsan_unaligned_write16",
1248 "__sanitizer_cov_trace_pc",
1249 "__sanitizer_cov_trace_const_cmp1",
1250 "__sanitizer_cov_trace_const_cmp2",
1251 "__sanitizer_cov_trace_const_cmp4",
1252 "__sanitizer_cov_trace_const_cmp8",
1253 "__sanitizer_cov_trace_cmp1",
1254 "__sanitizer_cov_trace_cmp2",
1255 "__sanitizer_cov_trace_cmp4",
1256 "__sanitizer_cov_trace_cmp8",
1257 "__sanitizer_cov_trace_switch",
1259 "kmsan_copy_to_user",
1261 "kmsan_unpoison_entry_regs",
1262 "kmsan_unpoison_memory",
1263 "__msan_chain_origin",
1264 "__msan_get_context_state",
1265 "__msan_instrument_asm_store",
1266 "__msan_metadata_ptr_for_load_1",
1267 "__msan_metadata_ptr_for_load_2",
1268 "__msan_metadata_ptr_for_load_4",
1269 "__msan_metadata_ptr_for_load_8",
1270 "__msan_metadata_ptr_for_load_n",
1271 "__msan_metadata_ptr_for_store_1",
1272 "__msan_metadata_ptr_for_store_2",
1273 "__msan_metadata_ptr_for_store_4",
1274 "__msan_metadata_ptr_for_store_8",
1275 "__msan_metadata_ptr_for_store_n",
1276 "__msan_poison_alloca",
1279 "ubsan_type_mismatch_common",
1280 "__ubsan_handle_type_mismatch",
1281 "__ubsan_handle_type_mismatch_v1",
1282 "__ubsan_handle_shift_out_of_bounds",
1283 "__ubsan_handle_load_invalid_value",
1285 "stackleak_track_stack",
1287 "csum_partial_copy_generic",
1289 "copy_mc_fragile_handle_tail",
1290 "copy_mc_enhanced_fast_string",
1291 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
1292 "rep_stos_alternative",
1293 "rep_movs_alternative",
1294 "__copy_user_nocache",
1298 static void add_uaccess_safe(struct objtool_file *file)
1300 struct symbol *func;
1306 for (name = uaccess_safe_builtin; *name; name++) {
1307 func = find_symbol_by_name(file->elf, *name);
1311 func->uaccess_safe = true;
1316 * FIXME: For now, just ignore any alternatives which add retpolines. This is
1317 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
1318 * But it at least allows objtool to understand the control flow *around* the
1321 static int add_ignore_alternatives(struct objtool_file *file)
1323 struct section *sec;
1324 struct reloc *reloc;
1325 struct instruction *insn;
1327 sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
1331 list_for_each_entry(reloc, &sec->reloc_list, list) {
1332 if (reloc->sym->type != STT_SECTION) {
1333 WARN("unexpected relocation symbol type in %s", sec->name);
1337 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1339 WARN("bad .discard.ignore_alts entry");
1343 insn->ignore_alts = true;
1349 __weak bool arch_is_retpoline(struct symbol *sym)
1354 __weak bool arch_is_rethunk(struct symbol *sym)
1359 static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
1361 struct reloc *reloc;
1369 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1370 insn->offset, insn->len);
1379 static void remove_insn_ops(struct instruction *insn)
1381 struct stack_op *op, *next;
1383 for (op = insn->stack_ops; op; op = next) {
1387 insn->stack_ops = NULL;
1390 static void annotate_call_site(struct objtool_file *file,
1391 struct instruction *insn, bool sibling)
1393 struct reloc *reloc = insn_reloc(file, insn);
1394 struct symbol *sym = insn_call_dest(insn);
1400 * Alternative replacement code is just template code which is
1401 * sometimes copied to the original instruction. For now, don't
1402 * annotate it. (In the future we might consider annotating the
1403 * original instruction if/when it ever makes sense to do so.)
1405 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1408 if (sym->static_call_tramp) {
1409 list_add_tail(&insn->call_node, &file->static_call_list);
1413 if (sym->retpoline_thunk) {
1414 list_add_tail(&insn->call_node, &file->retpoline_call_list);
1419 * Many compilers cannot disable KCOV or sanitizer calls with a function
1420 * attribute so they need a little help, NOP out any such calls from
1423 if (opts.hack_noinstr && insn->sec->noinstr && sym->profiling_func) {
1425 reloc->type = R_NONE;
1426 elf_write_reloc(file->elf, reloc);
1429 elf_write_insn(file->elf, insn->sec,
1430 insn->offset, insn->len,
1431 sibling ? arch_ret_insn(insn->len)
1432 : arch_nop_insn(insn->len));
1434 insn->type = sibling ? INSN_RETURN : INSN_NOP;
1438 * We've replaced the tail-call JMP insn by two new
1439 * insn: RET; INT3, except we only have a single struct
1440 * insn here. Mark it retpoline_safe to avoid the SLS
1441 * warning, instead of adding another insn.
1443 insn->retpoline_safe = true;
1449 if (opts.mcount && sym->fentry) {
1451 WARN_INSN(insn, "tail call to __fentry__ !?!?");
1454 reloc->type = R_NONE;
1455 elf_write_reloc(file->elf, reloc);
1458 elf_write_insn(file->elf, insn->sec,
1459 insn->offset, insn->len,
1460 arch_nop_insn(insn->len));
1462 insn->type = INSN_NOP;
1465 list_add_tail(&insn->call_node, &file->mcount_loc_list);
1469 if (insn->type == INSN_CALL && !insn->sec->init)
1470 list_add_tail(&insn->call_node, &file->call_list);
1472 if (!sibling && dead_end_function(file, sym))
1473 insn->dead_end = true;
1476 static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1477 struct symbol *dest, bool sibling)
1479 insn->_call_dest = dest;
1484 * Whatever stack impact regular CALLs have, should be undone
1485 * by the RETURN of the called function.
1487 * Annotated intra-function calls retain the stack_ops but
1488 * are converted to JUMP, see read_intra_function_calls().
1490 remove_insn_ops(insn);
1492 annotate_call_site(file, insn, sibling);
1495 static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1498 * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1499 * so convert them accordingly.
1501 switch (insn->type) {
1503 insn->type = INSN_CALL_DYNAMIC;
1505 case INSN_JUMP_UNCONDITIONAL:
1506 insn->type = INSN_JUMP_DYNAMIC;
1508 case INSN_JUMP_CONDITIONAL:
1509 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1515 insn->retpoline_safe = true;
1518 * Whatever stack impact regular CALLs have, should be undone
1519 * by the RETURN of the called function.
1521 * Annotated intra-function calls retain the stack_ops but
1522 * are converted to JUMP, see read_intra_function_calls().
1524 remove_insn_ops(insn);
1526 annotate_call_site(file, insn, false);
1529 static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add)
1532 * Return thunk tail calls are really just returns in disguise,
1533 * so convert them accordingly.
1535 insn->type = INSN_RETURN;
1536 insn->retpoline_safe = true;
1539 list_add_tail(&insn->call_node, &file->return_thunk_list);
1542 static bool is_first_func_insn(struct objtool_file *file,
1543 struct instruction *insn, struct symbol *sym)
1545 if (insn->offset == sym->offset)
1548 /* Allow direct CALL/JMP past ENDBR */
1550 struct instruction *prev = prev_insn_same_sym(file, insn);
1552 if (prev && prev->type == INSN_ENDBR &&
1553 insn->offset == sym->offset + prev->len)
1561 * A sibling call is a tail-call to another symbol -- to differentiate from a
1562 * recursive tail-call which is to the same symbol.
1564 static bool jump_is_sibling_call(struct objtool_file *file,
1565 struct instruction *from, struct instruction *to)
1567 struct symbol *fs = from->sym;
1568 struct symbol *ts = to->sym;
1570 /* Not a sibling call if from/to a symbol hole */
1574 /* Not a sibling call if not targeting the start of a symbol. */
1575 if (!is_first_func_insn(file, to, ts))
1578 /* Disallow sibling calls into STT_NOTYPE */
1579 if (ts->type == STT_NOTYPE)
1582 /* Must not be self to be a sibling */
1583 return fs->pfunc != ts->pfunc;
1587 * Find the destination instructions for all jumps.
1589 static int add_jump_destinations(struct objtool_file *file)
1591 struct instruction *insn, *jump_dest;
1592 struct reloc *reloc;
1593 struct section *dest_sec;
1594 unsigned long dest_off;
1596 for_each_insn(file, insn) {
1597 if (insn->jump_dest) {
1599 * handle_group_alt() may have previously set
1600 * 'jump_dest' for some alternatives.
1604 if (!is_static_jump(insn))
1607 reloc = insn_reloc(file, insn);
1609 dest_sec = insn->sec;
1610 dest_off = arch_jump_destination(insn);
1611 } else if (reloc->sym->type == STT_SECTION) {
1612 dest_sec = reloc->sym->sec;
1613 dest_off = arch_dest_reloc_offset(reloc->addend);
1614 } else if (reloc->sym->retpoline_thunk) {
1615 add_retpoline_call(file, insn);
1617 } else if (reloc->sym->return_thunk) {
1618 add_return_call(file, insn, true);
1620 } else if (insn_func(insn)) {
1622 * External sibling call or internal sibling call with
1625 add_call_dest(file, insn, reloc->sym, true);
1627 } else if (reloc->sym->sec->idx) {
1628 dest_sec = reloc->sym->sec;
1629 dest_off = reloc->sym->sym.st_value +
1630 arch_dest_reloc_offset(reloc->addend);
1632 /* non-func asm code jumping to another file */
1636 jump_dest = find_insn(file, dest_sec, dest_off);
1638 struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off);
1641 * This is a special case for zen_untrain_ret().
1642 * It jumps to __x86_return_thunk(), but objtool
1643 * can't find the thunk's starting RET
1644 * instruction, because the RET is also in the
1645 * middle of another instruction. Objtool only
1646 * knows about the outer instruction.
1648 if (sym && sym->return_thunk) {
1649 add_return_call(file, insn, false);
1653 WARN_INSN(insn, "can't find jump dest instruction at %s+0x%lx",
1654 dest_sec->name, dest_off);
1659 * Cross-function jump.
1661 if (insn_func(insn) && insn_func(jump_dest) &&
1662 insn_func(insn) != insn_func(jump_dest)) {
1665 * For GCC 8+, create parent/child links for any cold
1666 * subfunctions. This is _mostly_ redundant with a
1667 * similar initialization in read_symbols().
1669 * If a function has aliases, we want the *first* such
1670 * function in the symbol table to be the subfunction's
1671 * parent. In that case we overwrite the
1672 * initialization done in read_symbols().
1674 * However this code can't completely replace the
1675 * read_symbols() code because this doesn't detect the
1676 * case where the parent function's only reference to a
1677 * subfunction is through a jump table.
1679 if (!strstr(insn_func(insn)->name, ".cold") &&
1680 strstr(insn_func(jump_dest)->name, ".cold")) {
1681 insn_func(insn)->cfunc = insn_func(jump_dest);
1682 insn_func(jump_dest)->pfunc = insn_func(insn);
1686 if (jump_is_sibling_call(file, insn, jump_dest)) {
1688 * Internal sibling call without reloc or with
1689 * STT_SECTION reloc.
1691 add_call_dest(file, insn, insn_func(jump_dest), true);
1695 insn->jump_dest = jump_dest;
1701 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1703 struct symbol *call_dest;
1705 call_dest = find_func_by_offset(sec, offset);
1707 call_dest = find_symbol_by_offset(sec, offset);
1713 * Find the destination instructions for all calls.
1715 static int add_call_destinations(struct objtool_file *file)
1717 struct instruction *insn;
1718 unsigned long dest_off;
1719 struct symbol *dest;
1720 struct reloc *reloc;
1722 for_each_insn(file, insn) {
1723 if (insn->type != INSN_CALL)
1726 reloc = insn_reloc(file, insn);
1728 dest_off = arch_jump_destination(insn);
1729 dest = find_call_destination(insn->sec, dest_off);
1731 add_call_dest(file, insn, dest, false);
1736 if (!insn_call_dest(insn)) {
1737 WARN_INSN(insn, "unannotated intra-function call");
1741 if (insn_func(insn) && insn_call_dest(insn)->type != STT_FUNC) {
1742 WARN_INSN(insn, "unsupported call to non-function");
1746 } else if (reloc->sym->type == STT_SECTION) {
1747 dest_off = arch_dest_reloc_offset(reloc->addend);
1748 dest = find_call_destination(reloc->sym->sec, dest_off);
1750 WARN_INSN(insn, "can't find call dest symbol at %s+0x%lx",
1751 reloc->sym->sec->name, dest_off);
1755 add_call_dest(file, insn, dest, false);
1757 } else if (reloc->sym->retpoline_thunk) {
1758 add_retpoline_call(file, insn);
1761 add_call_dest(file, insn, reloc->sym, false);
1768 * The .alternatives section requires some extra special care over and above
1769 * other special sections because alternatives are patched in place.
1771 static int handle_group_alt(struct objtool_file *file,
1772 struct special_alt *special_alt,
1773 struct instruction *orig_insn,
1774 struct instruction **new_insn)
1776 struct instruction *last_new_insn = NULL, *insn, *nop = NULL;
1777 struct alt_group *orig_alt_group, *new_alt_group;
1778 unsigned long dest_off;
1780 orig_alt_group = orig_insn->alt_group;
1781 if (!orig_alt_group) {
1782 struct instruction *last_orig_insn = NULL;
1784 orig_alt_group = malloc(sizeof(*orig_alt_group));
1785 if (!orig_alt_group) {
1786 WARN("malloc failed");
1789 orig_alt_group->cfi = calloc(special_alt->orig_len,
1790 sizeof(struct cfi_state *));
1791 if (!orig_alt_group->cfi) {
1792 WARN("calloc failed");
1797 sec_for_each_insn_from(file, insn) {
1798 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1801 insn->alt_group = orig_alt_group;
1802 last_orig_insn = insn;
1804 orig_alt_group->orig_group = NULL;
1805 orig_alt_group->first_insn = orig_insn;
1806 orig_alt_group->last_insn = last_orig_insn;
1807 orig_alt_group->nop = NULL;
1809 if (orig_alt_group->last_insn->offset + orig_alt_group->last_insn->len -
1810 orig_alt_group->first_insn->offset != special_alt->orig_len) {
1811 WARN_INSN(orig_insn, "weirdly overlapping alternative! %ld != %d",
1812 orig_alt_group->last_insn->offset +
1813 orig_alt_group->last_insn->len -
1814 orig_alt_group->first_insn->offset,
1815 special_alt->orig_len);
1820 new_alt_group = malloc(sizeof(*new_alt_group));
1821 if (!new_alt_group) {
1822 WARN("malloc failed");
1826 if (special_alt->new_len < special_alt->orig_len) {
1828 * Insert a fake nop at the end to make the replacement
1829 * alt_group the same size as the original. This is needed to
1830 * allow propagate_alt_cfi() to do its magic. When the last
1831 * instruction affects the stack, the instruction after it (the
1832 * nop) will propagate the new state to the shared CFI array.
1834 nop = malloc(sizeof(*nop));
1836 WARN("malloc failed");
1839 memset(nop, 0, sizeof(*nop));
1841 nop->sec = special_alt->new_sec;
1842 nop->offset = special_alt->new_off + special_alt->new_len;
1843 nop->len = special_alt->orig_len - special_alt->new_len;
1844 nop->type = INSN_NOP;
1845 nop->sym = orig_insn->sym;
1846 nop->alt_group = new_alt_group;
1847 nop->ignore = orig_insn->ignore_alts;
1850 if (!special_alt->new_len) {
1856 sec_for_each_insn_from(file, insn) {
1857 struct reloc *alt_reloc;
1859 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1862 last_new_insn = insn;
1864 insn->ignore = orig_insn->ignore_alts;
1865 insn->sym = orig_insn->sym;
1866 insn->alt_group = new_alt_group;
1869 * Since alternative replacement code is copy/pasted by the
1870 * kernel after applying relocations, generally such code can't
1871 * have relative-address relocation references to outside the
1872 * .altinstr_replacement section, unless the arch's
1873 * alternatives code can adjust the relative offsets
1876 alt_reloc = insn_reloc(file, insn);
1877 if (alt_reloc && arch_pc_relative_reloc(alt_reloc) &&
1878 !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1880 WARN_INSN(insn, "unsupported relocation in alternatives section");
1884 if (!is_static_jump(insn))
1887 if (!insn->immediate)
1890 dest_off = arch_jump_destination(insn);
1891 if (dest_off == special_alt->new_off + special_alt->new_len) {
1892 insn->jump_dest = next_insn_same_sec(file, orig_alt_group->last_insn);
1893 if (!insn->jump_dest) {
1894 WARN_INSN(insn, "can't find alternative jump destination");
1900 if (!last_new_insn) {
1901 WARN_FUNC("can't find last new alternative instruction",
1902 special_alt->new_sec, special_alt->new_off);
1907 new_alt_group->orig_group = orig_alt_group;
1908 new_alt_group->first_insn = *new_insn;
1909 new_alt_group->last_insn = last_new_insn;
1910 new_alt_group->nop = nop;
1911 new_alt_group->cfi = orig_alt_group->cfi;
1916 * A jump table entry can either convert a nop to a jump or a jump to a nop.
1917 * If the original instruction is a jump, make the alt entry an effective nop
1918 * by just skipping the original instruction.
1920 static int handle_jump_alt(struct objtool_file *file,
1921 struct special_alt *special_alt,
1922 struct instruction *orig_insn,
1923 struct instruction **new_insn)
1925 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1926 orig_insn->type != INSN_NOP) {
1928 WARN_INSN(orig_insn, "unsupported instruction at jump label");
1932 if (opts.hack_jump_label && special_alt->key_addend & 2) {
1933 struct reloc *reloc = insn_reloc(file, orig_insn);
1936 reloc->type = R_NONE;
1937 elf_write_reloc(file->elf, reloc);
1939 elf_write_insn(file->elf, orig_insn->sec,
1940 orig_insn->offset, orig_insn->len,
1941 arch_nop_insn(orig_insn->len));
1942 orig_insn->type = INSN_NOP;
1945 if (orig_insn->type == INSN_NOP) {
1946 if (orig_insn->len == 2)
1947 file->jl_nop_short++;
1949 file->jl_nop_long++;
1954 if (orig_insn->len == 2)
1959 *new_insn = next_insn_same_sec(file, orig_insn);
1964 * Read all the special sections which have alternate instructions which can be
1965 * patched in or redirected to at runtime. Each instruction having alternate
1966 * instruction(s) has them added to its insn->alts list, which will be
1967 * traversed in validate_branch().
1969 static int add_special_section_alts(struct objtool_file *file)
1971 struct list_head special_alts;
1972 struct instruction *orig_insn, *new_insn;
1973 struct special_alt *special_alt, *tmp;
1974 struct alternative *alt;
1977 ret = special_get_alts(file->elf, &special_alts);
1981 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1983 orig_insn = find_insn(file, special_alt->orig_sec,
1984 special_alt->orig_off);
1986 WARN_FUNC("special: can't find orig instruction",
1987 special_alt->orig_sec, special_alt->orig_off);
1993 if (!special_alt->group || special_alt->new_len) {
1994 new_insn = find_insn(file, special_alt->new_sec,
1995 special_alt->new_off);
1997 WARN_FUNC("special: can't find new instruction",
1998 special_alt->new_sec,
1999 special_alt->new_off);
2005 if (special_alt->group) {
2006 if (!special_alt->orig_len) {
2007 WARN_INSN(orig_insn, "empty alternative entry");
2011 ret = handle_group_alt(file, special_alt, orig_insn,
2015 } else if (special_alt->jump_or_nop) {
2016 ret = handle_jump_alt(file, special_alt, orig_insn,
2022 alt = malloc(sizeof(*alt));
2024 WARN("malloc failed");
2029 alt->insn = new_insn;
2030 alt->skip_orig = special_alt->skip_orig;
2031 orig_insn->ignore_alts |= special_alt->skip_alt;
2032 alt->next = orig_insn->alts;
2033 orig_insn->alts = alt;
2035 list_del(&special_alt->list);
2040 printf("jl\\\tNOP\tJMP\n");
2041 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
2042 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
2049 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
2050 struct reloc *table)
2052 struct reloc *reloc = table;
2053 struct instruction *dest_insn;
2054 struct alternative *alt;
2055 struct symbol *pfunc = insn_func(insn)->pfunc;
2056 unsigned int prev_offset = 0;
2059 * Each @reloc is a switch table relocation which points to the target
2062 list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
2064 /* Check for the end of the table: */
2065 if (reloc != table && reloc->jump_table_start)
2068 /* Make sure the table entries are consecutive: */
2069 if (prev_offset && reloc->offset != prev_offset + 8)
2072 /* Detect function pointers from contiguous objects: */
2073 if (reloc->sym->sec == pfunc->sec &&
2074 reloc->addend == pfunc->offset)
2077 dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
2081 /* Make sure the destination is in the same function: */
2082 if (!insn_func(dest_insn) || insn_func(dest_insn)->pfunc != pfunc)
2085 alt = malloc(sizeof(*alt));
2087 WARN("malloc failed");
2091 alt->insn = dest_insn;
2092 alt->next = insn->alts;
2094 prev_offset = reloc->offset;
2098 WARN_INSN(insn, "can't find switch jump table");
2106 * find_jump_table() - Given a dynamic jump, find the switch jump table
2107 * associated with it.
2109 static struct reloc *find_jump_table(struct objtool_file *file,
2110 struct symbol *func,
2111 struct instruction *insn)
2113 struct reloc *table_reloc;
2114 struct instruction *dest_insn, *orig_insn = insn;
2117 * Backward search using the @first_jump_src links, these help avoid
2118 * much of the 'in between' code. Which avoids us getting confused by
2122 insn && insn_func(insn) && insn_func(insn)->pfunc == func;
2123 insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
2125 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
2128 /* allow small jumps within the range */
2129 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
2131 (insn->jump_dest->offset <= insn->offset ||
2132 insn->jump_dest->offset > orig_insn->offset))
2135 table_reloc = arch_find_switch_table(file, insn);
2138 dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
2139 if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
2149 * First pass: Mark the head of each jump table so that in the next pass,
2150 * we know when a given jump table ends and the next one starts.
2152 static void mark_func_jump_tables(struct objtool_file *file,
2153 struct symbol *func)
2155 struct instruction *insn, *last = NULL;
2156 struct reloc *reloc;
2158 func_for_each_insn(file, func, insn) {
2163 * Store back-pointers for unconditional forward jumps such
2164 * that find_jump_table() can back-track using those and
2165 * avoid some potentially confusing code.
2167 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
2168 insn->offset > last->offset &&
2169 insn->jump_dest->offset > insn->offset &&
2170 !insn->jump_dest->first_jump_src) {
2172 insn->jump_dest->first_jump_src = insn;
2173 last = insn->jump_dest;
2176 if (insn->type != INSN_JUMP_DYNAMIC)
2179 reloc = find_jump_table(file, func, insn);
2181 reloc->jump_table_start = true;
2182 insn->_jump_table = reloc;
2187 static int add_func_jump_tables(struct objtool_file *file,
2188 struct symbol *func)
2190 struct instruction *insn;
2193 func_for_each_insn(file, func, insn) {
2194 if (!insn_jump_table(insn))
2197 ret = add_jump_table(file, insn, insn_jump_table(insn));
2206 * For some switch statements, gcc generates a jump table in the .rodata
2207 * section which contains a list of addresses within the function to jump to.
2208 * This finds these jump tables and adds them to the insn->alts lists.
2210 static int add_jump_table_alts(struct objtool_file *file)
2212 struct symbol *func;
2218 for_each_sym(file, func) {
2219 if (func->type != STT_FUNC)
2222 mark_func_jump_tables(file, func);
2223 ret = add_func_jump_tables(file, func);
2231 static void set_func_state(struct cfi_state *state)
2233 state->cfa = initial_func_cfi.cfa;
2234 memcpy(&state->regs, &initial_func_cfi.regs,
2235 CFI_NUM_REGS * sizeof(struct cfi_reg));
2236 state->stack_size = initial_func_cfi.cfa.offset;
2237 state->type = UNWIND_HINT_TYPE_CALL;
2240 static int read_unwind_hints(struct objtool_file *file)
2242 struct cfi_state cfi = init_cfi;
2243 struct section *sec, *relocsec;
2244 struct unwind_hint *hint;
2245 struct instruction *insn;
2246 struct reloc *reloc;
2249 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
2253 relocsec = sec->reloc;
2255 WARN("missing .rela.discard.unwind_hints section");
2259 if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
2260 WARN("struct unwind_hint size mismatch");
2266 for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
2267 hint = (struct unwind_hint *)sec->data->d_buf + i;
2269 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
2271 WARN("can't find reloc for unwind_hints[%d]", i);
2275 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2277 WARN("can't find insn for unwind_hints[%d]", i);
2283 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
2289 if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
2290 insn->restore = true;
2294 if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
2295 struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
2297 if (sym && sym->bind == STB_GLOBAL) {
2298 if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) {
2299 WARN_INSN(insn, "UNWIND_HINT_IRET_REGS without ENDBR");
2304 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
2305 insn->cfi = &func_cfi;
2312 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
2313 WARN_INSN(insn, "unsupported unwind_hint sp base reg %d", hint->sp_reg);
2317 cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
2318 cfi.type = hint->type;
2319 cfi.signal = hint->signal;
2321 insn->cfi = cfi_hash_find_or_add(&cfi);
2327 static int read_noendbr_hints(struct objtool_file *file)
2329 struct section *sec;
2330 struct instruction *insn;
2331 struct reloc *reloc;
2333 sec = find_section_by_name(file->elf, ".rela.discard.noendbr");
2337 list_for_each_entry(reloc, &sec->reloc_list, list) {
2338 insn = find_insn(file, reloc->sym->sec, reloc->sym->offset + reloc->addend);
2340 WARN("bad .discard.noendbr entry");
2350 static int read_retpoline_hints(struct objtool_file *file)
2352 struct section *sec;
2353 struct instruction *insn;
2354 struct reloc *reloc;
2356 sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
2360 list_for_each_entry(reloc, &sec->reloc_list, list) {
2361 if (reloc->sym->type != STT_SECTION) {
2362 WARN("unexpected relocation symbol type in %s", sec->name);
2366 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2368 WARN("bad .discard.retpoline_safe entry");
2372 if (insn->type != INSN_JUMP_DYNAMIC &&
2373 insn->type != INSN_CALL_DYNAMIC &&
2374 insn->type != INSN_RETURN &&
2375 insn->type != INSN_NOP) {
2376 WARN_INSN(insn, "retpoline_safe hint not an indirect jump/call/ret/nop");
2380 insn->retpoline_safe = true;
2386 static int read_instr_hints(struct objtool_file *file)
2388 struct section *sec;
2389 struct instruction *insn;
2390 struct reloc *reloc;
2392 sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2396 list_for_each_entry(reloc, &sec->reloc_list, list) {
2397 if (reloc->sym->type != STT_SECTION) {
2398 WARN("unexpected relocation symbol type in %s", sec->name);
2402 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2404 WARN("bad .discard.instr_end entry");
2411 sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2415 list_for_each_entry(reloc, &sec->reloc_list, list) {
2416 if (reloc->sym->type != STT_SECTION) {
2417 WARN("unexpected relocation symbol type in %s", sec->name);
2421 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2423 WARN("bad .discard.instr_begin entry");
2433 static int read_validate_unret_hints(struct objtool_file *file)
2435 struct section *sec;
2436 struct instruction *insn;
2437 struct reloc *reloc;
2439 sec = find_section_by_name(file->elf, ".rela.discard.validate_unret");
2443 list_for_each_entry(reloc, &sec->reloc_list, list) {
2444 if (reloc->sym->type != STT_SECTION) {
2445 WARN("unexpected relocation symbol type in %s", sec->name);
2449 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2451 WARN("bad .discard.instr_end entry");
2461 static int read_intra_function_calls(struct objtool_file *file)
2463 struct instruction *insn;
2464 struct section *sec;
2465 struct reloc *reloc;
2467 sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2471 list_for_each_entry(reloc, &sec->reloc_list, list) {
2472 unsigned long dest_off;
2474 if (reloc->sym->type != STT_SECTION) {
2475 WARN("unexpected relocation symbol type in %s",
2480 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2482 WARN("bad .discard.intra_function_call entry");
2486 if (insn->type != INSN_CALL) {
2487 WARN_INSN(insn, "intra_function_call not a direct call");
2492 * Treat intra-function CALLs as JMPs, but with a stack_op.
2493 * See add_call_destinations(), which strips stack_ops from
2496 insn->type = INSN_JUMP_UNCONDITIONAL;
2498 dest_off = arch_jump_destination(insn);
2499 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2500 if (!insn->jump_dest) {
2501 WARN_INSN(insn, "can't find call dest at %s+0x%lx",
2502 insn->sec->name, dest_off);
2511 * Return true if name matches an instrumentation function, where calls to that
2512 * function from noinstr code can safely be removed, but compilers won't do so.
2514 static bool is_profiling_func(const char *name)
2517 * Many compilers cannot disable KCOV with a function attribute.
2519 if (!strncmp(name, "__sanitizer_cov_", 16))
2523 * Some compilers currently do not remove __tsan_func_entry/exit nor
2524 * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2525 * the __no_sanitize_thread attribute, remove them. Once the kernel's
2526 * minimum Clang version is 14.0, this can be removed.
2528 if (!strncmp(name, "__tsan_func_", 12) ||
2529 !strcmp(name, "__tsan_atomic_signal_fence"))
2535 static int classify_symbols(struct objtool_file *file)
2537 struct symbol *func;
2539 for_each_sym(file, func) {
2540 if (func->bind != STB_GLOBAL)
2543 if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2544 strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2545 func->static_call_tramp = true;
2547 if (arch_is_retpoline(func))
2548 func->retpoline_thunk = true;
2550 if (arch_is_rethunk(func))
2551 func->return_thunk = true;
2553 if (arch_ftrace_match(func->name))
2554 func->fentry = true;
2556 if (is_profiling_func(func->name))
2557 func->profiling_func = true;
2563 static void mark_rodata(struct objtool_file *file)
2565 struct section *sec;
2569 * Search for the following rodata sections, each of which can
2570 * potentially contain jump tables:
2572 * - .rodata: can contain GCC switch tables
2573 * - .rodata.<func>: same, if -fdata-sections is being used
2574 * - .rodata..c_jump_table: contains C annotated jump tables
2576 * .rodata.str1.* sections are ignored; they don't contain jump tables.
2578 for_each_sec(file, sec) {
2579 if (!strncmp(sec->name, ".rodata", 7) &&
2580 !strstr(sec->name, ".str1.")) {
2586 file->rodata = found;
2589 static int decode_sections(struct objtool_file *file)
2595 ret = init_pv_ops(file);
2600 * Must be before add_{jump_call}_destination.
2602 ret = classify_symbols(file);
2606 ret = decode_instructions(file);
2611 add_uaccess_safe(file);
2613 ret = add_ignore_alternatives(file);
2618 * Must be before read_unwind_hints() since that needs insn->noendbr.
2620 ret = read_noendbr_hints(file);
2625 * Must be before add_jump_destinations(), which depends on 'func'
2626 * being set for alternatives, to enable proper sibling call detection.
2628 if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) {
2629 ret = add_special_section_alts(file);
2634 ret = add_jump_destinations(file);
2639 * Must be before add_call_destination(); it changes INSN_CALL to
2642 ret = read_intra_function_calls(file);
2646 ret = add_call_destinations(file);
2651 * Must be after add_call_destinations() such that it can override
2652 * dead_end_function() marks.
2654 ret = add_dead_ends(file);
2658 ret = add_jump_table_alts(file);
2662 ret = read_unwind_hints(file);
2666 ret = read_retpoline_hints(file);
2670 ret = read_instr_hints(file);
2674 ret = read_validate_unret_hints(file);
2681 static bool is_fentry_call(struct instruction *insn)
2683 if (insn->type == INSN_CALL &&
2684 insn_call_dest(insn) &&
2685 insn_call_dest(insn)->fentry)
2691 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2693 struct cfi_state *cfi = &state->cfi;
2696 if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2699 if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2702 if (cfi->stack_size != initial_func_cfi.cfa.offset)
2705 for (i = 0; i < CFI_NUM_REGS; i++) {
2706 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2707 cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2714 static bool check_reg_frame_pos(const struct cfi_reg *reg,
2715 int expected_offset)
2717 return reg->base == CFI_CFA &&
2718 reg->offset == expected_offset;
2721 static bool has_valid_stack_frame(struct insn_state *state)
2723 struct cfi_state *cfi = &state->cfi;
2725 if (cfi->cfa.base == CFI_BP &&
2726 check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2727 check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2730 if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2736 static int update_cfi_state_regs(struct instruction *insn,
2737 struct cfi_state *cfi,
2738 struct stack_op *op)
2740 struct cfi_reg *cfa = &cfi->cfa;
2742 if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2746 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2750 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2753 /* add immediate to sp */
2754 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2755 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2756 cfa->offset -= op->src.offset;
2761 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2763 if (arch_callee_saved_reg(reg) &&
2764 cfi->regs[reg].base == CFI_UNDEFINED) {
2765 cfi->regs[reg].base = base;
2766 cfi->regs[reg].offset = offset;
2770 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2772 cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2773 cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2777 * A note about DRAP stack alignment:
2779 * GCC has the concept of a DRAP register, which is used to help keep track of
2780 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
2781 * register. The typical DRAP pattern is:
2783 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
2784 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
2785 * 41 ff 72 f8 pushq -0x8(%r10)
2787 * 48 89 e5 mov %rsp,%rbp
2794 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2797 * There are some variations in the epilogues, like:
2805 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2810 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
2811 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
2812 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
2813 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
2815 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2818 * Sometimes r13 is used as the DRAP register, in which case it's saved and
2819 * restored beforehand:
2822 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
2823 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
2825 * 49 8d 65 f0 lea -0x10(%r13),%rsp
2829 static int update_cfi_state(struct instruction *insn,
2830 struct instruction *next_insn,
2831 struct cfi_state *cfi, struct stack_op *op)
2833 struct cfi_reg *cfa = &cfi->cfa;
2834 struct cfi_reg *regs = cfi->regs;
2836 /* stack operations don't make sense with an undefined CFA */
2837 if (cfa->base == CFI_UNDEFINED) {
2838 if (insn_func(insn)) {
2839 WARN_INSN(insn, "undefined stack state");
2845 if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2846 cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2847 return update_cfi_state_regs(insn, cfi, op);
2849 switch (op->dest.type) {
2852 switch (op->src.type) {
2855 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2856 cfa->base == CFI_SP &&
2857 check_reg_frame_pos(®s[CFI_BP], -cfa->offset)) {
2859 /* mov %rsp, %rbp */
2860 cfa->base = op->dest.reg;
2861 cfi->bp_scratch = false;
2864 else if (op->src.reg == CFI_SP &&
2865 op->dest.reg == CFI_BP && cfi->drap) {
2867 /* drap: mov %rsp, %rbp */
2868 regs[CFI_BP].base = CFI_BP;
2869 regs[CFI_BP].offset = -cfi->stack_size;
2870 cfi->bp_scratch = false;
2873 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2878 * This is needed for the rare case where GCC
2885 cfi->vals[op->dest.reg].base = CFI_CFA;
2886 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2889 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2890 (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2895 * Restore the original stack pointer (Clang).
2897 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2900 else if (op->dest.reg == cfa->base) {
2902 /* mov %reg, %rsp */
2903 if (cfa->base == CFI_SP &&
2904 cfi->vals[op->src.reg].base == CFI_CFA) {
2907 * This is needed for the rare case
2908 * where GCC does something dumb like:
2910 * lea 0x8(%rsp), %rcx
2914 cfa->offset = -cfi->vals[op->src.reg].offset;
2915 cfi->stack_size = cfa->offset;
2917 } else if (cfa->base == CFI_SP &&
2918 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2919 cfi->vals[op->src.reg].offset == cfa->offset) {
2924 * 1: mov %rsp, (%[tos])
2925 * 2: mov %[tos], %rsp
2931 * 1 - places a pointer to the previous
2932 * stack at the Top-of-Stack of the
2935 * 2 - switches to the new stack.
2937 * 3 - pops the Top-of-Stack to restore
2938 * the original stack.
2940 * Note: we set base to SP_INDIRECT
2941 * here and preserve offset. Therefore
2942 * when the unwinder reaches ToS it
2943 * will dereference SP and then add the
2944 * offset to find the next frame, IOW:
2947 cfa->base = CFI_SP_INDIRECT;
2950 cfa->base = CFI_UNDEFINED;
2955 else if (op->dest.reg == CFI_SP &&
2956 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2957 cfi->vals[op->src.reg].offset == cfa->offset) {
2960 * The same stack swizzle case 2) as above. But
2961 * because we can't change cfa->base, case 3)
2962 * will become a regular POP. Pretend we're a
2963 * PUSH so things don't go unbalanced.
2965 cfi->stack_size += 8;
2972 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2975 cfi->stack_size -= op->src.offset;
2976 if (cfa->base == CFI_SP)
2977 cfa->offset -= op->src.offset;
2981 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2983 /* lea disp(%rbp), %rsp */
2984 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2988 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2990 /* drap: lea disp(%rsp), %drap */
2991 cfi->drap_reg = op->dest.reg;
2994 * lea disp(%rsp), %reg
2996 * This is needed for the rare case where GCC
2997 * does something dumb like:
2999 * lea 0x8(%rsp), %rcx
3003 cfi->vals[op->dest.reg].base = CFI_CFA;
3004 cfi->vals[op->dest.reg].offset = \
3005 -cfi->stack_size + op->src.offset;
3010 if (cfi->drap && op->dest.reg == CFI_SP &&
3011 op->src.reg == cfi->drap_reg) {
3013 /* drap: lea disp(%drap), %rsp */
3015 cfa->offset = cfi->stack_size = -op->src.offset;
3016 cfi->drap_reg = CFI_UNDEFINED;
3021 if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
3022 WARN_INSN(insn, "unsupported stack register modification");
3029 if (op->dest.reg != CFI_SP ||
3030 (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
3031 (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
3032 WARN_INSN(insn, "unsupported stack pointer realignment");
3036 if (cfi->drap_reg != CFI_UNDEFINED) {
3037 /* drap: and imm, %rsp */
3038 cfa->base = cfi->drap_reg;
3039 cfa->offset = cfi->stack_size = 0;
3044 * Older versions of GCC (4.8ish) realign the stack
3045 * without DRAP, with a frame pointer.
3052 if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
3054 /* pop %rsp; # restore from a stack swizzle */
3059 if (!cfi->drap && op->dest.reg == cfa->base) {
3065 if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
3066 op->dest.reg == cfi->drap_reg &&
3067 cfi->drap_offset == -cfi->stack_size) {
3069 /* drap: pop %drap */
3070 cfa->base = cfi->drap_reg;
3072 cfi->drap_offset = -1;
3074 } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
3077 restore_reg(cfi, op->dest.reg);
3080 cfi->stack_size -= 8;
3081 if (cfa->base == CFI_SP)
3086 case OP_SRC_REG_INDIRECT:
3087 if (!cfi->drap && op->dest.reg == cfa->base &&
3088 op->dest.reg == CFI_BP) {
3090 /* mov disp(%rsp), %rbp */
3092 cfa->offset = cfi->stack_size;
3095 if (cfi->drap && op->src.reg == CFI_BP &&
3096 op->src.offset == cfi->drap_offset) {
3098 /* drap: mov disp(%rbp), %drap */
3099 cfa->base = cfi->drap_reg;
3101 cfi->drap_offset = -1;
3104 if (cfi->drap && op->src.reg == CFI_BP &&
3105 op->src.offset == regs[op->dest.reg].offset) {
3107 /* drap: mov disp(%rbp), %reg */
3108 restore_reg(cfi, op->dest.reg);
3110 } else if (op->src.reg == cfa->base &&
3111 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
3113 /* mov disp(%rbp), %reg */
3114 /* mov disp(%rsp), %reg */
3115 restore_reg(cfi, op->dest.reg);
3117 } else if (op->src.reg == CFI_SP &&
3118 op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
3120 /* mov disp(%rsp), %reg */
3121 restore_reg(cfi, op->dest.reg);
3127 WARN_INSN(insn, "unknown stack-related instruction");
3135 cfi->stack_size += 8;
3136 if (cfa->base == CFI_SP)
3139 if (op->src.type != OP_SRC_REG)
3143 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3145 /* drap: push %drap */
3146 cfa->base = CFI_BP_INDIRECT;
3147 cfa->offset = -cfi->stack_size;
3149 /* save drap so we know when to restore it */
3150 cfi->drap_offset = -cfi->stack_size;
3152 } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
3154 /* drap: push %rbp */
3155 cfi->stack_size = 0;
3159 /* drap: push %reg */
3160 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
3166 save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
3169 /* detect when asm code uses rbp as a scratch register */
3170 if (opts.stackval && insn_func(insn) && op->src.reg == CFI_BP &&
3171 cfa->base != CFI_BP)
3172 cfi->bp_scratch = true;
3175 case OP_DEST_REG_INDIRECT:
3178 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3180 /* drap: mov %drap, disp(%rbp) */
3181 cfa->base = CFI_BP_INDIRECT;
3182 cfa->offset = op->dest.offset;
3184 /* save drap offset so we know when to restore it */
3185 cfi->drap_offset = op->dest.offset;
3188 /* drap: mov reg, disp(%rbp) */
3189 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
3192 } else if (op->dest.reg == cfa->base) {
3194 /* mov reg, disp(%rbp) */
3195 /* mov reg, disp(%rsp) */
3196 save_reg(cfi, op->src.reg, CFI_CFA,
3197 op->dest.offset - cfi->cfa.offset);
3199 } else if (op->dest.reg == CFI_SP) {
3201 /* mov reg, disp(%rsp) */
3202 save_reg(cfi, op->src.reg, CFI_CFA,
3203 op->dest.offset - cfi->stack_size);
3205 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
3207 /* mov %rsp, (%reg); # setup a stack swizzle. */
3208 cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
3209 cfi->vals[op->dest.reg].offset = cfa->offset;
3215 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
3216 WARN_INSN(insn, "unknown stack-related memory operation");
3221 cfi->stack_size -= 8;
3222 if (cfa->base == CFI_SP)
3228 WARN_INSN(insn, "unknown stack-related instruction");
3236 * The stack layouts of alternatives instructions can sometimes diverge when
3237 * they have stack modifications. That's fine as long as the potential stack
3238 * layouts don't conflict at any given potential instruction boundary.
3240 * Flatten the CFIs of the different alternative code streams (both original
3241 * and replacement) into a single shared CFI array which can be used to detect
3242 * conflicts and nicely feed a linear array of ORC entries to the unwinder.
3244 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
3246 struct cfi_state **alt_cfi;
3249 if (!insn->alt_group)
3253 WARN("CFI missing");
3257 alt_cfi = insn->alt_group->cfi;
3258 group_off = insn->offset - insn->alt_group->first_insn->offset;
3260 if (!alt_cfi[group_off]) {
3261 alt_cfi[group_off] = insn->cfi;
3263 if (cficmp(alt_cfi[group_off], insn->cfi)) {
3264 struct alt_group *orig_group = insn->alt_group->orig_group ?: insn->alt_group;
3265 struct instruction *orig = orig_group->first_insn;
3266 char *where = offstr(insn->sec, insn->offset);
3267 WARN_INSN(orig, "stack layout conflict in alternatives: %s", where);
3276 static int handle_insn_ops(struct instruction *insn,
3277 struct instruction *next_insn,
3278 struct insn_state *state)
3280 struct stack_op *op;
3282 for (op = insn->stack_ops; op; op = op->next) {
3284 if (update_cfi_state(insn, next_insn, &state->cfi, op))
3287 if (!insn->alt_group)
3290 if (op->dest.type == OP_DEST_PUSHF) {
3291 if (!state->uaccess_stack) {
3292 state->uaccess_stack = 1;
3293 } else if (state->uaccess_stack >> 31) {
3294 WARN_INSN(insn, "PUSHF stack exhausted");
3297 state->uaccess_stack <<= 1;
3298 state->uaccess_stack |= state->uaccess;
3301 if (op->src.type == OP_SRC_POPF) {
3302 if (state->uaccess_stack) {
3303 state->uaccess = state->uaccess_stack & 1;
3304 state->uaccess_stack >>= 1;
3305 if (state->uaccess_stack == 1)
3306 state->uaccess_stack = 0;
3314 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
3316 struct cfi_state *cfi1 = insn->cfi;
3320 WARN("CFI missing");
3324 if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
3326 WARN_INSN(insn, "stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
3327 cfi1->cfa.base, cfi1->cfa.offset,
3328 cfi2->cfa.base, cfi2->cfa.offset);
3330 } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
3331 for (i = 0; i < CFI_NUM_REGS; i++) {
3332 if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
3333 sizeof(struct cfi_reg)))
3336 WARN_INSN(insn, "stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
3337 i, cfi1->regs[i].base, cfi1->regs[i].offset,
3338 i, cfi2->regs[i].base, cfi2->regs[i].offset);
3342 } else if (cfi1->type != cfi2->type) {
3344 WARN_INSN(insn, "stack state mismatch: type1=%d type2=%d",
3345 cfi1->type, cfi2->type);
3347 } else if (cfi1->drap != cfi2->drap ||
3348 (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
3349 (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
3351 WARN_INSN(insn, "stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
3352 cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
3353 cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
3361 static inline bool func_uaccess_safe(struct symbol *func)
3364 return func->uaccess_safe;
3369 static inline const char *call_dest_name(struct instruction *insn)
3371 static char pvname[19];
3375 if (insn_call_dest(insn))
3376 return insn_call_dest(insn)->name;
3378 rel = insn_reloc(NULL, insn);
3379 if (rel && !strcmp(rel->sym->name, "pv_ops")) {
3380 idx = (rel->addend / sizeof(void *));
3381 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
3388 static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3390 struct symbol *target;
3394 rel = insn_reloc(file, insn);
3395 if (!rel || strcmp(rel->sym->name, "pv_ops"))
3398 idx = (arch_dest_reloc_offset(rel->addend) / sizeof(void *));
3400 if (file->pv_ops[idx].clean)
3403 file->pv_ops[idx].clean = true;
3405 list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3406 if (!target->sec->noinstr) {
3407 WARN("pv_ops[%d]: %s", idx, target->name);
3408 file->pv_ops[idx].clean = false;
3412 return file->pv_ops[idx].clean;
3415 static inline bool noinstr_call_dest(struct objtool_file *file,
3416 struct instruction *insn,
3417 struct symbol *func)
3420 * We can't deal with indirect function calls at present;
3421 * assume they're instrumented.
3425 return pv_call_dest(file, insn);
3431 * If the symbol is from a noinstr section; we good.
3433 if (func->sec->noinstr)
3437 * If the symbol is a static_call trampoline, we can't tell.
3439 if (func->static_call_tramp)
3443 * The __ubsan_handle_*() calls are like WARN(), they only happen when
3444 * something 'BAD' happened. At the risk of taking the machine down,
3445 * let them proceed to get the message out.
3447 if (!strncmp(func->name, "__ubsan_handle_", 15))
3453 static int validate_call(struct objtool_file *file,
3454 struct instruction *insn,
3455 struct insn_state *state)
3457 if (state->noinstr && state->instr <= 0 &&
3458 !noinstr_call_dest(file, insn, insn_call_dest(insn))) {
3459 WARN_INSN(insn, "call to %s() leaves .noinstr.text section", call_dest_name(insn));
3463 if (state->uaccess && !func_uaccess_safe(insn_call_dest(insn))) {
3464 WARN_INSN(insn, "call to %s() with UACCESS enabled", call_dest_name(insn));
3469 WARN_INSN(insn, "call to %s() with DF set", call_dest_name(insn));
3476 static int validate_sibling_call(struct objtool_file *file,
3477 struct instruction *insn,
3478 struct insn_state *state)
3480 if (insn_func(insn) && has_modified_stack_frame(insn, state)) {
3481 WARN_INSN(insn, "sibling call from callable instruction with modified stack frame");
3485 return validate_call(file, insn, state);
3488 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3490 if (state->noinstr && state->instr > 0) {
3491 WARN_INSN(insn, "return with instrumentation enabled");
3495 if (state->uaccess && !func_uaccess_safe(func)) {
3496 WARN_INSN(insn, "return with UACCESS enabled");
3500 if (!state->uaccess && func_uaccess_safe(func)) {
3501 WARN_INSN(insn, "return with UACCESS disabled from a UACCESS-safe function");
3506 WARN_INSN(insn, "return with DF set");
3510 if (func && has_modified_stack_frame(insn, state)) {
3511 WARN_INSN(insn, "return with modified stack frame");
3515 if (state->cfi.bp_scratch) {
3516 WARN_INSN(insn, "BP used as a scratch register");
3523 static struct instruction *next_insn_to_validate(struct objtool_file *file,
3524 struct instruction *insn)
3526 struct alt_group *alt_group = insn->alt_group;
3529 * Simulate the fact that alternatives are patched in-place. When the
3530 * end of a replacement alt_group is reached, redirect objtool flow to
3531 * the end of the original alt_group.
3533 * insn->alts->insn -> alt_group->first_insn
3535 * alt_group->last_insn
3536 * [alt_group->nop] -> next(orig_group->last_insn)
3539 if (alt_group->nop) {
3540 /* ->nop implies ->orig_group */
3541 if (insn == alt_group->last_insn)
3542 return alt_group->nop;
3543 if (insn == alt_group->nop)
3546 if (insn == alt_group->last_insn && alt_group->orig_group)
3550 return next_insn_same_sec(file, insn);
3553 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3557 * Follow the branch starting at the given instruction, and recursively follow
3558 * any other branches (jumps). Meanwhile, track the frame pointer state at
3559 * each instruction and validate all the rules described in
3560 * tools/objtool/Documentation/objtool.txt.
3562 static int validate_branch(struct objtool_file *file, struct symbol *func,
3563 struct instruction *insn, struct insn_state state)
3565 struct alternative *alt;
3566 struct instruction *next_insn, *prev_insn = NULL;
3567 struct section *sec;
3574 next_insn = next_insn_to_validate(file, insn);
3576 if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {
3577 /* Ignore KCFI type preambles, which always fall through */
3578 if (!strncmp(func->name, "__cfi_", 6) ||
3579 !strncmp(func->name, "__pfx_", 6))
3582 WARN("%s() falls through to next function %s()",
3583 func->name, insn_func(insn)->name);
3587 if (func && insn->ignore) {
3588 WARN_INSN(insn, "BUG: why am I validating an ignored function?");
3592 visited = VISITED_BRANCH << state.uaccess;
3593 if (insn->visited & VISITED_BRANCH_MASK) {
3594 if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3597 if (insn->visited & visited)
3604 state.instr += insn->instr;
3607 if (insn->restore) {
3608 struct instruction *save_insn, *i;
3613 sym_for_each_insn_continue_reverse(file, func, i) {
3621 WARN_INSN(insn, "no corresponding CFI save for CFI restore");
3625 if (!save_insn->visited) {
3626 WARN_INSN(insn, "objtool isn't smart enough to handle this CFI save/restore combo");
3630 insn->cfi = save_insn->cfi;
3634 state.cfi = *insn->cfi;
3636 /* XXX track if we actually changed state.cfi */
3638 if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3639 insn->cfi = prev_insn->cfi;
3642 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3646 insn->visited |= visited;
3648 if (propagate_alt_cfi(file, insn))
3651 if (!insn->ignore_alts && insn->alts) {
3652 bool skip_orig = false;
3654 for (alt = insn->alts; alt; alt = alt->next) {
3658 ret = validate_branch(file, func, alt->insn, state);
3661 BT_FUNC("(alt)", insn);
3670 if (handle_insn_ops(insn, next_insn, &state))
3673 switch (insn->type) {
3676 return validate_return(func, insn, &state);
3679 case INSN_CALL_DYNAMIC:
3680 ret = validate_call(file, insn, &state);
3684 if (opts.stackval && func && !is_fentry_call(insn) &&
3685 !has_valid_stack_frame(&state)) {
3686 WARN_INSN(insn, "call without frame pointer save/setup");
3695 case INSN_JUMP_CONDITIONAL:
3696 case INSN_JUMP_UNCONDITIONAL:
3697 if (is_sibling_call(insn)) {
3698 ret = validate_sibling_call(file, insn, &state);
3702 } else if (insn->jump_dest) {
3703 ret = validate_branch(file, func,
3704 insn->jump_dest, state);
3707 BT_FUNC("(branch)", insn);
3712 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3717 case INSN_JUMP_DYNAMIC:
3718 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3719 if (is_sibling_call(insn)) {
3720 ret = validate_sibling_call(file, insn, &state);
3725 if (insn->type == INSN_JUMP_DYNAMIC)
3730 case INSN_CONTEXT_SWITCH:
3731 if (func && (!next_insn || !next_insn->hint)) {
3732 WARN_INSN(insn, "unsupported instruction in callable function");
3738 if (state.uaccess) {
3739 WARN_INSN(insn, "recursive UACCESS enable");
3743 state.uaccess = true;
3747 if (!state.uaccess && func) {
3748 WARN_INSN(insn, "redundant UACCESS disable");
3752 if (func_uaccess_safe(func) && !state.uaccess_stack) {
3753 WARN_INSN(insn, "UACCESS-safe disables UACCESS");
3757 state.uaccess = false;
3762 WARN_INSN(insn, "recursive STD");
3770 if (!state.df && func) {
3771 WARN_INSN(insn, "redundant CLD");
3786 if (state.cfi.cfa.base == CFI_UNDEFINED)
3788 WARN("%s: unexpected end of section", sec->name);
3799 static int validate_unwind_hint(struct objtool_file *file,
3800 struct instruction *insn,
3801 struct insn_state *state)
3803 if (insn->hint && !insn->visited && !insn->ignore) {
3804 int ret = validate_branch(file, insn_func(insn), insn, *state);
3805 if (ret && opts.backtrace)
3806 BT_FUNC("<=== (hint)", insn);
3813 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3815 struct instruction *insn;
3816 struct insn_state state;
3822 init_insn_state(file, &state, sec);
3825 sec_for_each_insn(file, sec, insn)
3826 warnings += validate_unwind_hint(file, insn, &state);
3828 for_each_insn(file, insn)
3829 warnings += validate_unwind_hint(file, insn, &state);
3836 * Validate rethunk entry constraint: must untrain RET before the first RET.
3838 * Follow every branch (intra-function) and ensure VALIDATE_UNRET_END comes
3839 * before an actual RET instruction.
3841 static int validate_unret(struct objtool_file *file, struct instruction *insn)
3843 struct instruction *next, *dest;
3844 int ret, warnings = 0;
3847 next = next_insn_to_validate(file, insn);
3849 if (insn->visited & VISITED_UNRET)
3852 insn->visited |= VISITED_UNRET;
3854 if (!insn->ignore_alts && insn->alts) {
3855 struct alternative *alt;
3856 bool skip_orig = false;
3858 for (alt = insn->alts; alt; alt = alt->next) {
3862 ret = validate_unret(file, alt->insn);
3865 BT_FUNC("(alt)", insn);
3874 switch (insn->type) {
3876 case INSN_CALL_DYNAMIC:
3877 case INSN_JUMP_DYNAMIC:
3878 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3879 WARN_INSN(insn, "early indirect call");
3882 case INSN_JUMP_UNCONDITIONAL:
3883 case INSN_JUMP_CONDITIONAL:
3884 if (!is_sibling_call(insn)) {
3885 if (!insn->jump_dest) {
3886 WARN_INSN(insn, "unresolved jump target after linking?!?");
3889 ret = validate_unret(file, insn->jump_dest);
3891 if (opts.backtrace) {
3892 BT_FUNC("(branch%s)", insn,
3893 insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : "");
3898 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3906 dest = find_insn(file, insn_call_dest(insn)->sec,
3907 insn_call_dest(insn)->offset);
3909 WARN("Unresolved function after linking!?: %s",
3910 insn_call_dest(insn)->name);
3914 ret = validate_unret(file, dest);
3917 BT_FUNC("(call)", insn);
3921 * If a call returns without error, it must have seen UNTRAIN_RET.
3922 * Therefore any non-error return is a success.
3927 WARN_INSN(insn, "RET before UNTRAIN");
3931 if (insn->retpoline_safe)
3940 WARN_INSN(insn, "teh end!");
3950 * Validate that all branches starting at VALIDATE_UNRET_BEGIN encounter
3951 * VALIDATE_UNRET_END before RET.
3953 static int validate_unrets(struct objtool_file *file)
3955 struct instruction *insn;
3956 int ret, warnings = 0;
3958 for_each_insn(file, insn) {
3962 ret = validate_unret(file, insn);
3964 WARN_INSN(insn, "Failed UNRET validation");
3973 static int validate_retpoline(struct objtool_file *file)
3975 struct instruction *insn;
3978 for_each_insn(file, insn) {
3979 if (insn->type != INSN_JUMP_DYNAMIC &&
3980 insn->type != INSN_CALL_DYNAMIC &&
3981 insn->type != INSN_RETURN)
3984 if (insn->retpoline_safe)
3987 if (insn->sec->init)
3990 if (insn->type == INSN_RETURN) {
3992 WARN_INSN(insn, "'naked' return found in RETHUNK build");
3996 WARN_INSN(insn, "indirect %s found in RETPOLINE build",
3997 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
4006 static bool is_kasan_insn(struct instruction *insn)
4008 return (insn->type == INSN_CALL &&
4009 !strcmp(insn_call_dest(insn)->name, "__asan_handle_no_return"));
4012 static bool is_ubsan_insn(struct instruction *insn)
4014 return (insn->type == INSN_CALL &&
4015 !strcmp(insn_call_dest(insn)->name,
4016 "__ubsan_handle_builtin_unreachable"));
4019 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
4022 struct instruction *prev_insn;
4024 if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
4028 * Ignore alternative replacement instructions. This can happen
4029 * when a whitelisted function uses one of the ALTERNATIVE macros.
4031 if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
4032 !strcmp(insn->sec->name, ".altinstr_aux"))
4036 * Whole archive runs might encounter dead code from weak symbols.
4037 * This is where the linker will have dropped the weak symbol in
4038 * favour of a regular symbol, but leaves the code in place.
4040 * In this case we'll find a piece of code (whole function) that is not
4041 * covered by a !section symbol. Ignore them.
4043 if (opts.link && !insn_func(insn)) {
4044 int size = find_symbol_hole_containing(insn->sec, insn->offset);
4045 unsigned long end = insn->offset + size;
4047 if (!size) /* not a hole */
4050 if (size < 0) /* hole until the end */
4053 sec_for_each_insn_continue(file, insn) {
4055 * If we reach a visited instruction at or before the
4056 * end of the hole, ignore the unreachable.
4061 if (insn->offset >= end)
4065 * If this hole jumps to a .cold function, mark it ignore too.
4067 if (insn->jump_dest && insn_func(insn->jump_dest) &&
4068 strstr(insn_func(insn->jump_dest)->name, ".cold")) {
4069 struct instruction *dest = insn->jump_dest;
4070 func_for_each_insn(file, insn_func(dest), dest)
4071 dest->ignore = true;
4078 if (!insn_func(insn))
4081 if (insn_func(insn)->static_call_tramp)
4085 * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
4086 * __builtin_unreachable(). The BUG() macro has an unreachable() after
4087 * the UD2, which causes GCC's undefined trap logic to emit another UD2
4088 * (or occasionally a JMP to UD2).
4090 * It may also insert a UD2 after calling a __noreturn function.
4092 prev_insn = prev_insn_same_sec(file, insn);
4093 if (prev_insn->dead_end &&
4094 (insn->type == INSN_BUG ||
4095 (insn->type == INSN_JUMP_UNCONDITIONAL &&
4096 insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
4100 * Check if this (or a subsequent) instruction is related to
4101 * CONFIG_UBSAN or CONFIG_KASAN.
4103 * End the search at 5 instructions to avoid going into the weeds.
4105 for (i = 0; i < 5; i++) {
4107 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
4110 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
4111 if (insn->jump_dest &&
4112 insn_func(insn->jump_dest) == insn_func(insn)) {
4113 insn = insn->jump_dest;
4120 if (insn->offset + insn->len >= insn_func(insn)->offset + insn_func(insn)->len)
4123 insn = next_insn_same_sec(file, insn);
4129 static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
4131 struct instruction *insn, *prev;
4132 struct cfi_state *cfi;
4134 insn = find_insn(file, func->sec, func->offset);
4138 for (prev = prev_insn_same_sec(file, insn);
4140 prev = prev_insn_same_sec(file, prev)) {
4143 if (prev->type != INSN_NOP)
4146 offset = func->offset - prev->offset;
4148 if (offset > opts.prefix)
4151 if (offset < opts.prefix)
4154 elf_create_prefix_symbol(file->elf, func, opts.prefix);
4163 * This can happen if stack validation isn't enabled or the
4164 * function is annotated with STACK_FRAME_NON_STANDARD.
4169 /* Propagate insn->cfi to the prefix code */
4170 cfi = cfi_hash_find_or_add(insn->cfi);
4171 for (; prev != insn; prev = next_insn_same_sec(file, prev))
4177 static int add_prefix_symbols(struct objtool_file *file)
4179 struct section *sec;
4180 struct symbol *func;
4183 for_each_sec(file, sec) {
4184 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4187 sec_for_each_sym(sec, func) {
4188 if (func->type != STT_FUNC)
4191 add_prefix_symbol(file, func);
4198 static int validate_symbol(struct objtool_file *file, struct section *sec,
4199 struct symbol *sym, struct insn_state *state)
4201 struct instruction *insn;
4205 WARN("%s() is missing an ELF size annotation", sym->name);
4209 if (sym->pfunc != sym || sym->alias != sym)
4212 insn = find_insn(file, sec, sym->offset);
4213 if (!insn || insn->ignore || insn->visited)
4216 state->uaccess = sym->uaccess_safe;
4218 ret = validate_branch(file, insn_func(insn), insn, *state);
4219 if (ret && opts.backtrace)
4220 BT_FUNC("<=== (sym)", insn);
4224 static int validate_section(struct objtool_file *file, struct section *sec)
4226 struct insn_state state;
4227 struct symbol *func;
4230 sec_for_each_sym(sec, func) {
4231 if (func->type != STT_FUNC)
4234 init_insn_state(file, &state, sec);
4235 set_func_state(&state.cfi);
4237 warnings += validate_symbol(file, sec, func, &state);
4243 static int validate_noinstr_sections(struct objtool_file *file)
4245 struct section *sec;
4248 sec = find_section_by_name(file->elf, ".noinstr.text");
4250 warnings += validate_section(file, sec);
4251 warnings += validate_unwind_hints(file, sec);
4254 sec = find_section_by_name(file->elf, ".entry.text");
4256 warnings += validate_section(file, sec);
4257 warnings += validate_unwind_hints(file, sec);
4260 sec = find_section_by_name(file->elf, ".cpuidle.text");
4262 warnings += validate_section(file, sec);
4263 warnings += validate_unwind_hints(file, sec);
4269 static int validate_functions(struct objtool_file *file)
4271 struct section *sec;
4274 for_each_sec(file, sec) {
4275 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4278 warnings += validate_section(file, sec);
4284 static void mark_endbr_used(struct instruction *insn)
4286 if (!list_empty(&insn->call_node))
4287 list_del_init(&insn->call_node);
4290 static bool noendbr_range(struct objtool_file *file, struct instruction *insn)
4292 struct symbol *sym = find_symbol_containing(insn->sec, insn->offset-1);
4293 struct instruction *first;
4298 first = find_insn(file, sym->sec, sym->offset);
4302 if (first->type != INSN_ENDBR && !first->noendbr)
4305 return insn->offset == sym->offset + sym->len;
4308 static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
4310 struct instruction *dest;
4311 struct reloc *reloc;
4316 * Looking for function pointer load relocations. Ignore
4317 * direct/indirect branches:
4319 switch (insn->type) {
4321 case INSN_CALL_DYNAMIC:
4322 case INSN_JUMP_CONDITIONAL:
4323 case INSN_JUMP_UNCONDITIONAL:
4324 case INSN_JUMP_DYNAMIC:
4325 case INSN_JUMP_DYNAMIC_CONDITIONAL:
4333 for (reloc = insn_reloc(file, insn);
4335 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
4337 (insn->offset + insn->len) - (reloc->offset + 1))) {
4340 * static_call_update() references the trampoline, which
4341 * doesn't have (or need) ENDBR. Skip warning in that case.
4343 if (reloc->sym->static_call_tramp)
4346 off = reloc->sym->offset;
4347 if (reloc->type == R_X86_64_PC32 || reloc->type == R_X86_64_PLT32)
4348 off += arch_dest_reloc_offset(reloc->addend);
4350 off += reloc->addend;
4352 dest = find_insn(file, reloc->sym->sec, off);
4356 if (dest->type == INSN_ENDBR) {
4357 mark_endbr_used(dest);
4361 if (insn_func(dest) && insn_func(dest) == insn_func(insn)) {
4363 * Anything from->to self is either _THIS_IP_ or
4366 * There is no sane way to annotate _THIS_IP_ since the
4367 * compiler treats the relocation as a constant and is
4368 * happy to fold in offsets, skewing any annotation we
4369 * do, leading to vast amounts of false-positives.
4371 * There's also compiler generated _THIS_IP_ through
4372 * KCOV and such which we have no hope of annotating.
4374 * As such, blanket accept self-references without
4381 * Accept anything ANNOTATE_NOENDBR.
4387 * Accept if this is the instruction after a symbol
4388 * that is (no)endbr -- typical code-range usage.
4390 if (noendbr_range(file, dest))
4393 WARN_INSN(insn, "relocation to !ENDBR: %s", offstr(dest->sec, dest->offset));
4401 static int validate_ibt_data_reloc(struct objtool_file *file,
4402 struct reloc *reloc)
4404 struct instruction *dest;
4406 dest = find_insn(file, reloc->sym->sec,
4407 reloc->sym->offset + reloc->addend);
4411 if (dest->type == INSN_ENDBR) {
4412 mark_endbr_used(dest);
4419 WARN_FUNC("data relocation to !ENDBR: %s",
4420 reloc->sec->base, reloc->offset,
4421 offstr(dest->sec, dest->offset));
4427 * Validate IBT rules and remove used ENDBR instructions from the seal list.
4428 * Unused ENDBR instructions will be annotated for sealing (i.e., replaced with
4429 * NOPs) later, in create_ibt_endbr_seal_sections().
4431 static int validate_ibt(struct objtool_file *file)
4433 struct section *sec;
4434 struct reloc *reloc;
4435 struct instruction *insn;
4438 for_each_insn(file, insn)
4439 warnings += validate_ibt_insn(file, insn);
4441 for_each_sec(file, sec) {
4443 /* Already done by validate_ibt_insn() */
4444 if (sec->sh.sh_flags & SHF_EXECINSTR)
4451 * These sections can reference text addresses, but not with
4452 * the intent to indirect branch to them.
4454 if ((!strncmp(sec->name, ".discard", 8) &&
4455 strcmp(sec->name, ".discard.ibt_endbr_noseal")) ||
4456 !strncmp(sec->name, ".debug", 6) ||
4457 !strcmp(sec->name, ".altinstructions") ||
4458 !strcmp(sec->name, ".ibt_endbr_seal") ||
4459 !strcmp(sec->name, ".orc_unwind_ip") ||
4460 !strcmp(sec->name, ".parainstructions") ||
4461 !strcmp(sec->name, ".retpoline_sites") ||
4462 !strcmp(sec->name, ".smp_locks") ||
4463 !strcmp(sec->name, ".static_call_sites") ||
4464 !strcmp(sec->name, "_error_injection_whitelist") ||
4465 !strcmp(sec->name, "_kprobe_blacklist") ||
4466 !strcmp(sec->name, "__bug_table") ||
4467 !strcmp(sec->name, "__ex_table") ||
4468 !strcmp(sec->name, "__jump_table") ||
4469 !strcmp(sec->name, "__mcount_loc") ||
4470 !strcmp(sec->name, ".kcfi_traps") ||
4471 strstr(sec->name, "__patchable_function_entries"))
4474 list_for_each_entry(reloc, &sec->reloc->reloc_list, list)
4475 warnings += validate_ibt_data_reloc(file, reloc);
4481 static int validate_sls(struct objtool_file *file)
4483 struct instruction *insn, *next_insn;
4486 for_each_insn(file, insn) {
4487 next_insn = next_insn_same_sec(file, insn);
4489 if (insn->retpoline_safe)
4492 switch (insn->type) {
4494 if (!next_insn || next_insn->type != INSN_TRAP) {
4495 WARN_INSN(insn, "missing int3 after ret");
4500 case INSN_JUMP_DYNAMIC:
4501 if (!next_insn || next_insn->type != INSN_TRAP) {
4502 WARN_INSN(insn, "missing int3 after indirect jump");
4514 static int validate_reachable_instructions(struct objtool_file *file)
4516 struct instruction *insn;
4518 if (file->ignore_unreachables)
4521 for_each_insn(file, insn) {
4522 if (insn->visited || ignore_unreachable_insn(file, insn))
4525 WARN_INSN(insn, "unreachable instruction");
4532 int check(struct objtool_file *file)
4534 int ret, warnings = 0;
4536 arch_initial_func_cfi_state(&initial_func_cfi);
4537 init_cfi_state(&init_cfi);
4538 init_cfi_state(&func_cfi);
4539 set_func_state(&func_cfi);
4541 if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
4544 cfi_hash_add(&init_cfi);
4545 cfi_hash_add(&func_cfi);
4547 ret = decode_sections(file);
4556 if (opts.retpoline) {
4557 ret = validate_retpoline(file);
4563 if (opts.stackval || opts.orc || opts.uaccess) {
4564 ret = validate_functions(file);
4569 ret = validate_unwind_hints(file, NULL);
4575 ret = validate_reachable_instructions(file);
4581 } else if (opts.noinstr) {
4582 ret = validate_noinstr_sections(file);
4590 * Must be after validate_branch() and friends, it plays
4591 * further games with insn->visited.
4593 ret = validate_unrets(file);
4600 ret = validate_ibt(file);
4607 ret = validate_sls(file);
4613 if (opts.static_call) {
4614 ret = create_static_call_sections(file);
4620 if (opts.retpoline) {
4621 ret = create_retpoline_sites_sections(file);
4628 ret = create_cfi_sections(file);
4635 ret = create_return_sites_sections(file);
4640 if (opts.hack_skylake) {
4641 ret = create_direct_call_sections(file);
4649 ret = create_mcount_loc_sections(file);
4656 ret = add_prefix_symbols(file);
4663 ret = create_ibt_endbr_seal_sections(file);
4669 if (opts.orc && nr_insns) {
4670 ret = orc_create(file);
4678 printf("nr_insns_visited: %ld\n", nr_insns_visited);
4679 printf("nr_cfi: %ld\n", nr_cfi);
4680 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
4681 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
4686 * For now, don't fail the kernel build on fatal warnings. These
4687 * errors are still fairly common due to the growing matrix of
4688 * supported toolchains and their recent pace of change.