1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
11 #include <objtool/builtin.h>
12 #include <objtool/cfi.h>
13 #include <objtool/arch.h>
14 #include <objtool/check.h>
15 #include <objtool/special.h>
16 #include <objtool/warn.h>
17 #include <objtool/endianness.h>
19 #include <linux/objtool_types.h>
20 #include <linux/hashtable.h>
21 #include <linux/kernel.h>
22 #include <linux/static_call_types.h>
25 struct alternative *next;
26 struct instruction *insn;
30 static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
32 static struct cfi_init_state initial_func_cfi;
33 static struct cfi_state init_cfi;
34 static struct cfi_state func_cfi;
35 static struct cfi_state force_undefined_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;
195 #define NORETURN(func) __stringify(func),
196 static const char * const global_noreturns[] = {
197 #include "noreturns.h"
204 if (func->bind == STB_GLOBAL || func->bind == STB_WEAK)
205 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
206 if (!strcmp(func->name, global_noreturns[i]))
209 if (func->bind == STB_WEAK)
215 insn = find_insn(file, func->sec, func->offset);
216 if (!insn || !insn_func(insn))
219 func_for_each_insn(file, func, insn) {
222 if (insn->type == INSN_RETURN)
230 * A function can have a sibling call instead of a return. In that
231 * case, the function's dead-end status depends on whether the target
232 * of the sibling call returns.
234 func_for_each_insn(file, func, insn) {
235 if (is_sibling_call(insn)) {
236 struct instruction *dest = insn->jump_dest;
239 /* sibling call to another file */
242 /* local sibling call */
243 if (recursion == 5) {
245 * Infinite recursion: two functions have
246 * sibling calls to each other. This is a very
247 * rare case. It means they aren't dead ends.
252 return __dead_end_function(file, insn_func(dest), recursion+1);
259 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
261 return __dead_end_function(file, func, 0);
264 static void init_cfi_state(struct cfi_state *cfi)
268 for (i = 0; i < CFI_NUM_REGS; i++) {
269 cfi->regs[i].base = CFI_UNDEFINED;
270 cfi->vals[i].base = CFI_UNDEFINED;
272 cfi->cfa.base = CFI_UNDEFINED;
273 cfi->drap_reg = CFI_UNDEFINED;
274 cfi->drap_offset = -1;
277 static void init_insn_state(struct objtool_file *file, struct insn_state *state,
280 memset(state, 0, sizeof(*state));
281 init_cfi_state(&state->cfi);
284 * We need the full vmlinux for noinstr validation, otherwise we can
285 * not correctly determine insn_call_dest(insn)->sec (external symbols
286 * do not have a section).
288 if (opts.link && opts.noinstr && sec)
289 state->noinstr = sec->noinstr;
292 static struct cfi_state *cfi_alloc(void)
294 struct cfi_state *cfi = calloc(sizeof(struct cfi_state), 1);
296 WARN("calloc failed");
304 static struct hlist_head *cfi_hash;
306 static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
308 return memcmp((void *)cfi1 + sizeof(cfi1->hash),
309 (void *)cfi2 + sizeof(cfi2->hash),
310 sizeof(struct cfi_state) - sizeof(struct hlist_node));
313 static inline u32 cfi_key(struct cfi_state *cfi)
315 return jhash((void *)cfi + sizeof(cfi->hash),
316 sizeof(*cfi) - sizeof(cfi->hash), 0);
319 static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
321 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
322 struct cfi_state *obj;
324 hlist_for_each_entry(obj, head, hash) {
325 if (!cficmp(cfi, obj)) {
333 hlist_add_head(&obj->hash, head);
338 static void cfi_hash_add(struct cfi_state *cfi)
340 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
342 hlist_add_head(&cfi->hash, head);
345 static void *cfi_hash_alloc(unsigned long size)
347 cfi_bits = max(10, ilog2(size));
348 cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
349 PROT_READ|PROT_WRITE,
350 MAP_PRIVATE|MAP_ANON, -1, 0);
351 if (cfi_hash == (void *)-1L) {
352 WARN("mmap fail cfi_hash");
354 } else if (opts.stats) {
355 printf("cfi_bits: %d\n", cfi_bits);
361 static unsigned long nr_insns;
362 static unsigned long nr_insns_visited;
365 * Call the arch-specific instruction decoder for all the instructions and add
366 * them to the global instruction list.
368 static int decode_instructions(struct objtool_file *file)
372 unsigned long offset;
373 struct instruction *insn;
376 for_each_sec(file, sec) {
377 struct instruction *insns = NULL;
381 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
384 if (strcmp(sec->name, ".altinstr_replacement") &&
385 strcmp(sec->name, ".altinstr_aux") &&
386 strncmp(sec->name, ".discard.", 9))
389 if (!strcmp(sec->name, ".noinstr.text") ||
390 !strcmp(sec->name, ".entry.text") ||
391 !strcmp(sec->name, ".cpuidle.text") ||
392 !strncmp(sec->name, ".text..__x86.", 13))
396 * .init.text code is ran before userspace and thus doesn't
397 * strictly need retpolines, except for modules which are
398 * loaded late, they very much do need retpoline in their
401 if (!strcmp(sec->name, ".init.text") && !opts.module)
404 for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
405 if (!insns || idx == INSN_CHUNK_MAX) {
406 insns = calloc(sizeof(*insn), INSN_CHUNK_SIZE);
408 WARN("malloc failed");
418 INIT_LIST_HEAD(&insn->call_node);
420 insn->offset = offset;
421 insn->prev_len = prev_len;
423 ret = arch_decode_instruction(file, sec, offset,
424 sec->sh.sh_size - offset,
429 prev_len = insn->len;
432 * By default, "ud2" is a dead end unless otherwise
433 * annotated, because GCC 7 inserts it for certain
434 * divide-by-zero cases.
436 if (insn->type == INSN_BUG)
437 insn->dead_end = true;
439 hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
443 // printf("%s: last chunk used: %d\n", sec->name, (int)idx);
445 sec_for_each_sym(sec, func) {
446 if (func->type != STT_NOTYPE && func->type != STT_FUNC)
449 if (func->offset == sec->sh.sh_size) {
450 /* Heuristic: likely an "end" symbol */
451 if (func->type == STT_NOTYPE)
453 WARN("%s(): STT_FUNC at end of section",
458 if (func->embedded_insn || func->alias != func)
461 if (!find_insn(file, sec, func->offset)) {
462 WARN("%s(): can't find starting instruction",
467 sym_for_each_insn(file, func, insn) {
469 if (func->type == STT_FUNC &&
470 insn->type == INSN_ENDBR &&
471 list_empty(&insn->call_node)) {
472 if (insn->offset == func->offset) {
473 list_add_tail(&insn->call_node, &file->endbr_list);
476 file->nr_endbr_int++;
484 printf("nr_insns: %lu\n", nr_insns);
490 * Read the pv_ops[] .data table to find the static initialized values.
492 static int add_pv_ops(struct objtool_file *file, const char *symname)
494 struct symbol *sym, *func;
495 unsigned long off, end;
499 sym = find_symbol_by_name(file->elf, symname);
504 end = off + sym->len;
506 reloc = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off);
511 if (func->type == STT_SECTION)
512 func = find_symbol_by_offset(reloc->sym->sec,
513 reloc_addend(reloc));
515 idx = (reloc_offset(reloc) - sym->offset) / sizeof(unsigned long);
517 objtool_pv_add(file, idx, func);
519 off = reloc_offset(reloc) + 1;
528 * Allocate and initialize file->pv_ops[].
530 static int init_pv_ops(struct objtool_file *file)
532 static const char *pv_ops_tables[] = {
548 sym = find_symbol_by_name(file->elf, "pv_ops");
552 nr = sym->len / sizeof(unsigned long);
553 file->pv_ops = calloc(sizeof(struct pv_state), nr);
557 for (idx = 0; idx < nr; idx++)
558 INIT_LIST_HEAD(&file->pv_ops[idx].targets);
560 for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++)
561 add_pv_ops(file, pv_ops);
566 static struct instruction *find_last_insn(struct objtool_file *file,
569 struct instruction *insn = NULL;
571 unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
573 for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
574 insn = find_insn(file, sec, offset);
580 * Mark "ud2" instructions and manually annotated dead ends.
582 static int add_dead_ends(struct objtool_file *file)
584 struct section *rsec;
586 struct instruction *insn;
590 * Check for manually annotated dead ends.
592 rsec = find_section_by_name(file->elf, ".rela.discard.unreachable");
596 for_each_reloc(rsec, reloc) {
598 if (reloc->sym->type != STT_SECTION) {
599 WARN("unexpected relocation symbol type in %s", rsec->name);
603 addend = reloc_addend(reloc);
605 insn = find_insn(file, reloc->sym->sec, addend);
607 insn = prev_insn_same_sec(file, insn);
608 else if (addend == reloc->sym->sec->sh.sh_size) {
609 insn = find_last_insn(file, reloc->sym->sec);
611 WARN("can't find unreachable insn at %s+0x%" PRIx64,
612 reloc->sym->sec->name, addend);
616 WARN("can't find unreachable insn at %s+0x%" PRIx64,
617 reloc->sym->sec->name, addend);
621 insn->dead_end = true;
626 * These manually annotated reachable checks are needed for GCC 4.4,
627 * where the Linux unreachable() macro isn't supported. In that case
628 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
631 rsec = find_section_by_name(file->elf, ".rela.discard.reachable");
635 for_each_reloc(rsec, reloc) {
637 if (reloc->sym->type != STT_SECTION) {
638 WARN("unexpected relocation symbol type in %s", rsec->name);
642 addend = reloc_addend(reloc);
644 insn = find_insn(file, reloc->sym->sec, addend);
646 insn = prev_insn_same_sec(file, insn);
647 else if (addend == reloc->sym->sec->sh.sh_size) {
648 insn = find_last_insn(file, reloc->sym->sec);
650 WARN("can't find reachable insn at %s+0x%" PRIx64,
651 reloc->sym->sec->name, addend);
655 WARN("can't find reachable insn at %s+0x%" PRIx64,
656 reloc->sym->sec->name, addend);
660 insn->dead_end = false;
666 static int create_static_call_sections(struct objtool_file *file)
668 struct static_call_site *site;
670 struct instruction *insn;
671 struct symbol *key_sym;
672 char *key_name, *tmp;
675 sec = find_section_by_name(file->elf, ".static_call_sites");
677 INIT_LIST_HEAD(&file->static_call_list);
678 WARN("file already has .static_call_sites section, skipping");
682 if (list_empty(&file->static_call_list))
686 list_for_each_entry(insn, &file->static_call_list, call_node)
689 sec = elf_create_section_pair(file->elf, ".static_call_sites",
690 sizeof(*site), idx, idx * 2);
694 /* Allow modules to modify the low bits of static_call_site::key */
695 sec->sh.sh_flags |= SHF_WRITE;
698 list_for_each_entry(insn, &file->static_call_list, call_node) {
700 /* populate reloc for 'addr' */
701 if (!elf_init_reloc_text_sym(file->elf, sec,
702 idx * sizeof(*site), idx * 2,
703 insn->sec, insn->offset))
706 /* find key symbol */
707 key_name = strdup(insn_call_dest(insn)->name);
712 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
713 STATIC_CALL_TRAMP_PREFIX_LEN)) {
714 WARN("static_call: trampoline name malformed: %s", key_name);
718 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
719 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
721 key_sym = find_symbol_by_name(file->elf, tmp);
724 WARN("static_call: can't find static_call_key symbol: %s", tmp);
730 * For modules(), the key might not be exported, which
731 * means the module can make static calls but isn't
732 * allowed to change them.
734 * In that case we temporarily set the key to be the
735 * trampoline address. This is fixed up in
736 * static_call_add_module().
738 key_sym = insn_call_dest(insn);
742 /* populate reloc for 'key' */
743 if (!elf_init_reloc_data_sym(file->elf, sec,
744 idx * sizeof(*site) + 4,
745 (idx * 2) + 1, key_sym,
746 is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
755 static int create_retpoline_sites_sections(struct objtool_file *file)
757 struct instruction *insn;
761 sec = find_section_by_name(file->elf, ".retpoline_sites");
763 WARN("file already has .retpoline_sites, skipping");
768 list_for_each_entry(insn, &file->retpoline_call_list, call_node)
774 sec = elf_create_section_pair(file->elf, ".retpoline_sites",
775 sizeof(int), idx, idx);
780 list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
782 if (!elf_init_reloc_text_sym(file->elf, sec,
783 idx * sizeof(int), idx,
784 insn->sec, insn->offset))
793 static int create_return_sites_sections(struct objtool_file *file)
795 struct instruction *insn;
799 sec = find_section_by_name(file->elf, ".return_sites");
801 WARN("file already has .return_sites, skipping");
806 list_for_each_entry(insn, &file->return_thunk_list, call_node)
812 sec = elf_create_section_pair(file->elf, ".return_sites",
813 sizeof(int), idx, idx);
818 list_for_each_entry(insn, &file->return_thunk_list, call_node) {
820 if (!elf_init_reloc_text_sym(file->elf, sec,
821 idx * sizeof(int), idx,
822 insn->sec, insn->offset))
831 static int create_ibt_endbr_seal_sections(struct objtool_file *file)
833 struct instruction *insn;
837 sec = find_section_by_name(file->elf, ".ibt_endbr_seal");
839 WARN("file already has .ibt_endbr_seal, skipping");
844 list_for_each_entry(insn, &file->endbr_list, call_node)
848 printf("ibt: ENDBR at function start: %d\n", file->nr_endbr);
849 printf("ibt: ENDBR inside functions: %d\n", file->nr_endbr_int);
850 printf("ibt: superfluous ENDBR: %d\n", idx);
856 sec = elf_create_section_pair(file->elf, ".ibt_endbr_seal",
857 sizeof(int), idx, idx);
862 list_for_each_entry(insn, &file->endbr_list, call_node) {
864 int *site = (int *)sec->data->d_buf + idx;
865 struct symbol *sym = insn->sym;
868 if (opts.module && sym && sym->type == STT_FUNC &&
869 insn->offset == sym->offset &&
870 (!strcmp(sym->name, "init_module") ||
871 !strcmp(sym->name, "cleanup_module")))
872 WARN("%s(): not an indirect call target", sym->name);
874 if (!elf_init_reloc_text_sym(file->elf, sec,
875 idx * sizeof(int), idx,
876 insn->sec, insn->offset))
885 static int create_cfi_sections(struct objtool_file *file)
891 sec = find_section_by_name(file->elf, ".cfi_sites");
893 INIT_LIST_HEAD(&file->call_list);
894 WARN("file already has .cfi_sites section, skipping");
899 for_each_sym(file, sym) {
900 if (sym->type != STT_FUNC)
903 if (strncmp(sym->name, "__cfi_", 6))
909 sec = elf_create_section_pair(file->elf, ".cfi_sites",
910 sizeof(unsigned int), idx, idx);
915 for_each_sym(file, sym) {
916 if (sym->type != STT_FUNC)
919 if (strncmp(sym->name, "__cfi_", 6))
922 if (!elf_init_reloc_text_sym(file->elf, sec,
923 idx * sizeof(unsigned int), idx,
924 sym->sec, sym->offset))
933 static int create_mcount_loc_sections(struct objtool_file *file)
935 size_t addr_size = elf_addr_size(file->elf);
936 struct instruction *insn;
940 sec = find_section_by_name(file->elf, "__mcount_loc");
942 INIT_LIST_HEAD(&file->mcount_loc_list);
943 WARN("file already has __mcount_loc section, skipping");
947 if (list_empty(&file->mcount_loc_list))
951 list_for_each_entry(insn, &file->mcount_loc_list, call_node)
954 sec = elf_create_section_pair(file->elf, "__mcount_loc", addr_size,
959 sec->sh.sh_addralign = addr_size;
962 list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
966 reloc = elf_init_reloc_text_sym(file->elf, sec, idx * addr_size, idx,
967 insn->sec, insn->offset);
971 set_reloc_type(file->elf, reloc, addr_size == 8 ? R_ABS64 : R_ABS32);
979 static int create_direct_call_sections(struct objtool_file *file)
981 struct instruction *insn;
985 sec = find_section_by_name(file->elf, ".call_sites");
987 INIT_LIST_HEAD(&file->call_list);
988 WARN("file already has .call_sites section, skipping");
992 if (list_empty(&file->call_list))
996 list_for_each_entry(insn, &file->call_list, call_node)
999 sec = elf_create_section_pair(file->elf, ".call_sites",
1000 sizeof(unsigned int), idx, idx);
1005 list_for_each_entry(insn, &file->call_list, call_node) {
1007 if (!elf_init_reloc_text_sym(file->elf, sec,
1008 idx * sizeof(unsigned int), idx,
1009 insn->sec, insn->offset))
1019 * Warnings shouldn't be reported for ignored functions.
1021 static void add_ignores(struct objtool_file *file)
1023 struct instruction *insn;
1024 struct section *rsec;
1025 struct symbol *func;
1026 struct reloc *reloc;
1028 rsec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
1032 for_each_reloc(rsec, reloc) {
1033 switch (reloc->sym->type) {
1039 func = find_func_by_offset(reloc->sym->sec, reloc_addend(reloc));
1045 WARN("unexpected relocation symbol type in %s: %d",
1046 rsec->name, reloc->sym->type);
1050 func_for_each_insn(file, func, insn)
1051 insn->ignore = true;
1056 * This is a whitelist of functions that is allowed to be called with AC set.
1057 * The list is meant to be minimal and only contains compiler instrumentation
1058 * ABI and a few functions used to implement *_{to,from}_user() functions.
1060 * These functions must not directly change AC, but may PUSHF/POPF.
1062 static const char *uaccess_safe_builtin[] = {
1065 "kasan_check_range",
1066 /* KASAN out-of-line */
1067 "__asan_loadN_noabort",
1068 "__asan_load1_noabort",
1069 "__asan_load2_noabort",
1070 "__asan_load4_noabort",
1071 "__asan_load8_noabort",
1072 "__asan_load16_noabort",
1073 "__asan_storeN_noabort",
1074 "__asan_store1_noabort",
1075 "__asan_store2_noabort",
1076 "__asan_store4_noabort",
1077 "__asan_store8_noabort",
1078 "__asan_store16_noabort",
1079 "__kasan_check_read",
1080 "__kasan_check_write",
1082 "__asan_report_load_n_noabort",
1083 "__asan_report_load1_noabort",
1084 "__asan_report_load2_noabort",
1085 "__asan_report_load4_noabort",
1086 "__asan_report_load8_noabort",
1087 "__asan_report_load16_noabort",
1088 "__asan_report_store_n_noabort",
1089 "__asan_report_store1_noabort",
1090 "__asan_report_store2_noabort",
1091 "__asan_report_store4_noabort",
1092 "__asan_report_store8_noabort",
1093 "__asan_report_store16_noabort",
1095 "__kcsan_check_access",
1100 "kcsan_found_watchpoint",
1101 "kcsan_setup_watchpoint",
1102 "kcsan_check_scoped_accesses",
1103 "kcsan_disable_current",
1104 "kcsan_enable_current_nowarn",
1106 "__tsan_func_entry",
1108 "__tsan_read_range",
1109 "__tsan_write_range",
1120 "__tsan_read_write1",
1121 "__tsan_read_write2",
1122 "__tsan_read_write4",
1123 "__tsan_read_write8",
1124 "__tsan_read_write16",
1125 "__tsan_volatile_read1",
1126 "__tsan_volatile_read2",
1127 "__tsan_volatile_read4",
1128 "__tsan_volatile_read8",
1129 "__tsan_volatile_read16",
1130 "__tsan_volatile_write1",
1131 "__tsan_volatile_write2",
1132 "__tsan_volatile_write4",
1133 "__tsan_volatile_write8",
1134 "__tsan_volatile_write16",
1135 "__tsan_atomic8_load",
1136 "__tsan_atomic16_load",
1137 "__tsan_atomic32_load",
1138 "__tsan_atomic64_load",
1139 "__tsan_atomic8_store",
1140 "__tsan_atomic16_store",
1141 "__tsan_atomic32_store",
1142 "__tsan_atomic64_store",
1143 "__tsan_atomic8_exchange",
1144 "__tsan_atomic16_exchange",
1145 "__tsan_atomic32_exchange",
1146 "__tsan_atomic64_exchange",
1147 "__tsan_atomic8_fetch_add",
1148 "__tsan_atomic16_fetch_add",
1149 "__tsan_atomic32_fetch_add",
1150 "__tsan_atomic64_fetch_add",
1151 "__tsan_atomic8_fetch_sub",
1152 "__tsan_atomic16_fetch_sub",
1153 "__tsan_atomic32_fetch_sub",
1154 "__tsan_atomic64_fetch_sub",
1155 "__tsan_atomic8_fetch_and",
1156 "__tsan_atomic16_fetch_and",
1157 "__tsan_atomic32_fetch_and",
1158 "__tsan_atomic64_fetch_and",
1159 "__tsan_atomic8_fetch_or",
1160 "__tsan_atomic16_fetch_or",
1161 "__tsan_atomic32_fetch_or",
1162 "__tsan_atomic64_fetch_or",
1163 "__tsan_atomic8_fetch_xor",
1164 "__tsan_atomic16_fetch_xor",
1165 "__tsan_atomic32_fetch_xor",
1166 "__tsan_atomic64_fetch_xor",
1167 "__tsan_atomic8_fetch_nand",
1168 "__tsan_atomic16_fetch_nand",
1169 "__tsan_atomic32_fetch_nand",
1170 "__tsan_atomic64_fetch_nand",
1171 "__tsan_atomic8_compare_exchange_strong",
1172 "__tsan_atomic16_compare_exchange_strong",
1173 "__tsan_atomic32_compare_exchange_strong",
1174 "__tsan_atomic64_compare_exchange_strong",
1175 "__tsan_atomic8_compare_exchange_weak",
1176 "__tsan_atomic16_compare_exchange_weak",
1177 "__tsan_atomic32_compare_exchange_weak",
1178 "__tsan_atomic64_compare_exchange_weak",
1179 "__tsan_atomic8_compare_exchange_val",
1180 "__tsan_atomic16_compare_exchange_val",
1181 "__tsan_atomic32_compare_exchange_val",
1182 "__tsan_atomic64_compare_exchange_val",
1183 "__tsan_atomic_thread_fence",
1184 "__tsan_atomic_signal_fence",
1185 "__tsan_unaligned_read16",
1186 "__tsan_unaligned_write16",
1190 "__sanitizer_cov_trace_pc",
1191 "__sanitizer_cov_trace_const_cmp1",
1192 "__sanitizer_cov_trace_const_cmp2",
1193 "__sanitizer_cov_trace_const_cmp4",
1194 "__sanitizer_cov_trace_const_cmp8",
1195 "__sanitizer_cov_trace_cmp1",
1196 "__sanitizer_cov_trace_cmp2",
1197 "__sanitizer_cov_trace_cmp4",
1198 "__sanitizer_cov_trace_cmp8",
1199 "__sanitizer_cov_trace_switch",
1201 "kmsan_copy_to_user",
1203 "kmsan_unpoison_entry_regs",
1204 "kmsan_unpoison_memory",
1205 "__msan_chain_origin",
1206 "__msan_get_context_state",
1207 "__msan_instrument_asm_store",
1208 "__msan_metadata_ptr_for_load_1",
1209 "__msan_metadata_ptr_for_load_2",
1210 "__msan_metadata_ptr_for_load_4",
1211 "__msan_metadata_ptr_for_load_8",
1212 "__msan_metadata_ptr_for_load_n",
1213 "__msan_metadata_ptr_for_store_1",
1214 "__msan_metadata_ptr_for_store_2",
1215 "__msan_metadata_ptr_for_store_4",
1216 "__msan_metadata_ptr_for_store_8",
1217 "__msan_metadata_ptr_for_store_n",
1218 "__msan_poison_alloca",
1221 "ubsan_type_mismatch_common",
1222 "__ubsan_handle_type_mismatch",
1223 "__ubsan_handle_type_mismatch_v1",
1224 "__ubsan_handle_shift_out_of_bounds",
1225 "__ubsan_handle_load_invalid_value",
1227 "stackleak_track_stack",
1229 "csum_partial_copy_generic",
1231 "copy_mc_fragile_handle_tail",
1232 "copy_mc_enhanced_fast_string",
1233 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
1234 "rep_stos_alternative",
1235 "rep_movs_alternative",
1236 "__copy_user_nocache",
1240 static void add_uaccess_safe(struct objtool_file *file)
1242 struct symbol *func;
1248 for (name = uaccess_safe_builtin; *name; name++) {
1249 func = find_symbol_by_name(file->elf, *name);
1253 func->uaccess_safe = true;
1258 * FIXME: For now, just ignore any alternatives which add retpolines. This is
1259 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
1260 * But it at least allows objtool to understand the control flow *around* the
1263 static int add_ignore_alternatives(struct objtool_file *file)
1265 struct section *rsec;
1266 struct reloc *reloc;
1267 struct instruction *insn;
1269 rsec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
1273 for_each_reloc(rsec, reloc) {
1274 if (reloc->sym->type != STT_SECTION) {
1275 WARN("unexpected relocation symbol type in %s", rsec->name);
1279 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
1281 WARN("bad .discard.ignore_alts entry");
1285 insn->ignore_alts = true;
1292 * Symbols that replace INSN_CALL_DYNAMIC, every (tail) call to such a symbol
1293 * will be added to the .retpoline_sites section.
1295 __weak bool arch_is_retpoline(struct symbol *sym)
1301 * Symbols that replace INSN_RETURN, every (tail) call to such a symbol
1302 * will be added to the .return_sites section.
1304 __weak bool arch_is_rethunk(struct symbol *sym)
1310 * Symbols that are embedded inside other instructions, because sometimes crazy
1311 * code exists. These are mostly ignored for validation purposes.
1313 __weak bool arch_is_embedded_insn(struct symbol *sym)
1318 static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
1320 struct reloc *reloc;
1328 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1329 insn->offset, insn->len);
1338 static void remove_insn_ops(struct instruction *insn)
1340 struct stack_op *op, *next;
1342 for (op = insn->stack_ops; op; op = next) {
1346 insn->stack_ops = NULL;
1349 static void annotate_call_site(struct objtool_file *file,
1350 struct instruction *insn, bool sibling)
1352 struct reloc *reloc = insn_reloc(file, insn);
1353 struct symbol *sym = insn_call_dest(insn);
1359 * Alternative replacement code is just template code which is
1360 * sometimes copied to the original instruction. For now, don't
1361 * annotate it. (In the future we might consider annotating the
1362 * original instruction if/when it ever makes sense to do so.)
1364 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1367 if (sym->static_call_tramp) {
1368 list_add_tail(&insn->call_node, &file->static_call_list);
1372 if (sym->retpoline_thunk) {
1373 list_add_tail(&insn->call_node, &file->retpoline_call_list);
1378 * Many compilers cannot disable KCOV or sanitizer calls with a function
1379 * attribute so they need a little help, NOP out any such calls from
1382 if (opts.hack_noinstr && insn->sec->noinstr && sym->profiling_func) {
1384 set_reloc_type(file->elf, reloc, R_NONE);
1386 elf_write_insn(file->elf, insn->sec,
1387 insn->offset, insn->len,
1388 sibling ? arch_ret_insn(insn->len)
1389 : arch_nop_insn(insn->len));
1391 insn->type = sibling ? INSN_RETURN : INSN_NOP;
1395 * We've replaced the tail-call JMP insn by two new
1396 * insn: RET; INT3, except we only have a single struct
1397 * insn here. Mark it retpoline_safe to avoid the SLS
1398 * warning, instead of adding another insn.
1400 insn->retpoline_safe = true;
1406 if (opts.mcount && sym->fentry) {
1408 WARN_INSN(insn, "tail call to __fentry__ !?!?");
1411 set_reloc_type(file->elf, reloc, R_NONE);
1413 elf_write_insn(file->elf, insn->sec,
1414 insn->offset, insn->len,
1415 arch_nop_insn(insn->len));
1417 insn->type = INSN_NOP;
1420 list_add_tail(&insn->call_node, &file->mcount_loc_list);
1424 if (insn->type == INSN_CALL && !insn->sec->init)
1425 list_add_tail(&insn->call_node, &file->call_list);
1427 if (!sibling && dead_end_function(file, sym))
1428 insn->dead_end = true;
1431 static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1432 struct symbol *dest, bool sibling)
1434 insn->_call_dest = dest;
1439 * Whatever stack impact regular CALLs have, should be undone
1440 * by the RETURN of the called function.
1442 * Annotated intra-function calls retain the stack_ops but
1443 * are converted to JUMP, see read_intra_function_calls().
1445 remove_insn_ops(insn);
1447 annotate_call_site(file, insn, sibling);
1450 static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1453 * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1454 * so convert them accordingly.
1456 switch (insn->type) {
1458 insn->type = INSN_CALL_DYNAMIC;
1460 case INSN_JUMP_UNCONDITIONAL:
1461 insn->type = INSN_JUMP_DYNAMIC;
1463 case INSN_JUMP_CONDITIONAL:
1464 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1470 insn->retpoline_safe = true;
1473 * Whatever stack impact regular CALLs have, should be undone
1474 * by the RETURN of the called function.
1476 * Annotated intra-function calls retain the stack_ops but
1477 * are converted to JUMP, see read_intra_function_calls().
1479 remove_insn_ops(insn);
1481 annotate_call_site(file, insn, false);
1484 static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add)
1487 * Return thunk tail calls are really just returns in disguise,
1488 * so convert them accordingly.
1490 insn->type = INSN_RETURN;
1491 insn->retpoline_safe = true;
1494 list_add_tail(&insn->call_node, &file->return_thunk_list);
1497 static bool is_first_func_insn(struct objtool_file *file,
1498 struct instruction *insn, struct symbol *sym)
1500 if (insn->offset == sym->offset)
1503 /* Allow direct CALL/JMP past ENDBR */
1505 struct instruction *prev = prev_insn_same_sym(file, insn);
1507 if (prev && prev->type == INSN_ENDBR &&
1508 insn->offset == sym->offset + prev->len)
1516 * A sibling call is a tail-call to another symbol -- to differentiate from a
1517 * recursive tail-call which is to the same symbol.
1519 static bool jump_is_sibling_call(struct objtool_file *file,
1520 struct instruction *from, struct instruction *to)
1522 struct symbol *fs = from->sym;
1523 struct symbol *ts = to->sym;
1525 /* Not a sibling call if from/to a symbol hole */
1529 /* Not a sibling call if not targeting the start of a symbol. */
1530 if (!is_first_func_insn(file, to, ts))
1533 /* Disallow sibling calls into STT_NOTYPE */
1534 if (ts->type == STT_NOTYPE)
1537 /* Must not be self to be a sibling */
1538 return fs->pfunc != ts->pfunc;
1542 * Find the destination instructions for all jumps.
1544 static int add_jump_destinations(struct objtool_file *file)
1546 struct instruction *insn, *jump_dest;
1547 struct reloc *reloc;
1548 struct section *dest_sec;
1549 unsigned long dest_off;
1551 for_each_insn(file, insn) {
1552 if (insn->jump_dest) {
1554 * handle_group_alt() may have previously set
1555 * 'jump_dest' for some alternatives.
1559 if (!is_static_jump(insn))
1562 reloc = insn_reloc(file, insn);
1564 dest_sec = insn->sec;
1565 dest_off = arch_jump_destination(insn);
1566 } else if (reloc->sym->type == STT_SECTION) {
1567 dest_sec = reloc->sym->sec;
1568 dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
1569 } else if (reloc->sym->retpoline_thunk) {
1570 add_retpoline_call(file, insn);
1572 } else if (reloc->sym->return_thunk) {
1573 add_return_call(file, insn, true);
1575 } else if (insn_func(insn)) {
1577 * External sibling call or internal sibling call with
1580 add_call_dest(file, insn, reloc->sym, true);
1582 } else if (reloc->sym->sec->idx) {
1583 dest_sec = reloc->sym->sec;
1584 dest_off = reloc->sym->sym.st_value +
1585 arch_dest_reloc_offset(reloc_addend(reloc));
1587 /* non-func asm code jumping to another file */
1591 jump_dest = find_insn(file, dest_sec, dest_off);
1593 struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off);
1596 * This is a special case for retbleed_untrain_ret().
1597 * It jumps to __x86_return_thunk(), but objtool
1598 * can't find the thunk's starting RET
1599 * instruction, because the RET is also in the
1600 * middle of another instruction. Objtool only
1601 * knows about the outer instruction.
1603 if (sym && sym->embedded_insn) {
1604 add_return_call(file, insn, false);
1608 WARN_INSN(insn, "can't find jump dest instruction at %s+0x%lx",
1609 dest_sec->name, dest_off);
1614 * Cross-function jump.
1616 if (insn_func(insn) && insn_func(jump_dest) &&
1617 insn_func(insn) != insn_func(jump_dest)) {
1620 * For GCC 8+, create parent/child links for any cold
1621 * subfunctions. This is _mostly_ redundant with a
1622 * similar initialization in read_symbols().
1624 * If a function has aliases, we want the *first* such
1625 * function in the symbol table to be the subfunction's
1626 * parent. In that case we overwrite the
1627 * initialization done in read_symbols().
1629 * However this code can't completely replace the
1630 * read_symbols() code because this doesn't detect the
1631 * case where the parent function's only reference to a
1632 * subfunction is through a jump table.
1634 if (!strstr(insn_func(insn)->name, ".cold") &&
1635 strstr(insn_func(jump_dest)->name, ".cold")) {
1636 insn_func(insn)->cfunc = insn_func(jump_dest);
1637 insn_func(jump_dest)->pfunc = insn_func(insn);
1641 if (jump_is_sibling_call(file, insn, jump_dest)) {
1643 * Internal sibling call without reloc or with
1644 * STT_SECTION reloc.
1646 add_call_dest(file, insn, insn_func(jump_dest), true);
1650 insn->jump_dest = jump_dest;
1656 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1658 struct symbol *call_dest;
1660 call_dest = find_func_by_offset(sec, offset);
1662 call_dest = find_symbol_by_offset(sec, offset);
1668 * Find the destination instructions for all calls.
1670 static int add_call_destinations(struct objtool_file *file)
1672 struct instruction *insn;
1673 unsigned long dest_off;
1674 struct symbol *dest;
1675 struct reloc *reloc;
1677 for_each_insn(file, insn) {
1678 if (insn->type != INSN_CALL)
1681 reloc = insn_reloc(file, insn);
1683 dest_off = arch_jump_destination(insn);
1684 dest = find_call_destination(insn->sec, dest_off);
1686 add_call_dest(file, insn, dest, false);
1691 if (!insn_call_dest(insn)) {
1692 WARN_INSN(insn, "unannotated intra-function call");
1696 if (insn_func(insn) && insn_call_dest(insn)->type != STT_FUNC) {
1697 WARN_INSN(insn, "unsupported call to non-function");
1701 } else if (reloc->sym->type == STT_SECTION) {
1702 dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
1703 dest = find_call_destination(reloc->sym->sec, dest_off);
1705 WARN_INSN(insn, "can't find call dest symbol at %s+0x%lx",
1706 reloc->sym->sec->name, dest_off);
1710 add_call_dest(file, insn, dest, false);
1712 } else if (reloc->sym->retpoline_thunk) {
1713 add_retpoline_call(file, insn);
1716 add_call_dest(file, insn, reloc->sym, false);
1723 * The .alternatives section requires some extra special care over and above
1724 * other special sections because alternatives are patched in place.
1726 static int handle_group_alt(struct objtool_file *file,
1727 struct special_alt *special_alt,
1728 struct instruction *orig_insn,
1729 struct instruction **new_insn)
1731 struct instruction *last_new_insn = NULL, *insn, *nop = NULL;
1732 struct alt_group *orig_alt_group, *new_alt_group;
1733 unsigned long dest_off;
1735 orig_alt_group = orig_insn->alt_group;
1736 if (!orig_alt_group) {
1737 struct instruction *last_orig_insn = NULL;
1739 orig_alt_group = malloc(sizeof(*orig_alt_group));
1740 if (!orig_alt_group) {
1741 WARN("malloc failed");
1744 orig_alt_group->cfi = calloc(special_alt->orig_len,
1745 sizeof(struct cfi_state *));
1746 if (!orig_alt_group->cfi) {
1747 WARN("calloc failed");
1752 sec_for_each_insn_from(file, insn) {
1753 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1756 insn->alt_group = orig_alt_group;
1757 last_orig_insn = insn;
1759 orig_alt_group->orig_group = NULL;
1760 orig_alt_group->first_insn = orig_insn;
1761 orig_alt_group->last_insn = last_orig_insn;
1762 orig_alt_group->nop = NULL;
1764 if (orig_alt_group->last_insn->offset + orig_alt_group->last_insn->len -
1765 orig_alt_group->first_insn->offset != special_alt->orig_len) {
1766 WARN_INSN(orig_insn, "weirdly overlapping alternative! %ld != %d",
1767 orig_alt_group->last_insn->offset +
1768 orig_alt_group->last_insn->len -
1769 orig_alt_group->first_insn->offset,
1770 special_alt->orig_len);
1775 new_alt_group = malloc(sizeof(*new_alt_group));
1776 if (!new_alt_group) {
1777 WARN("malloc failed");
1781 if (special_alt->new_len < special_alt->orig_len) {
1783 * Insert a fake nop at the end to make the replacement
1784 * alt_group the same size as the original. This is needed to
1785 * allow propagate_alt_cfi() to do its magic. When the last
1786 * instruction affects the stack, the instruction after it (the
1787 * nop) will propagate the new state to the shared CFI array.
1789 nop = malloc(sizeof(*nop));
1791 WARN("malloc failed");
1794 memset(nop, 0, sizeof(*nop));
1796 nop->sec = special_alt->new_sec;
1797 nop->offset = special_alt->new_off + special_alt->new_len;
1798 nop->len = special_alt->orig_len - special_alt->new_len;
1799 nop->type = INSN_NOP;
1800 nop->sym = orig_insn->sym;
1801 nop->alt_group = new_alt_group;
1802 nop->ignore = orig_insn->ignore_alts;
1805 if (!special_alt->new_len) {
1811 sec_for_each_insn_from(file, insn) {
1812 struct reloc *alt_reloc;
1814 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1817 last_new_insn = insn;
1819 insn->ignore = orig_insn->ignore_alts;
1820 insn->sym = orig_insn->sym;
1821 insn->alt_group = new_alt_group;
1824 * Since alternative replacement code is copy/pasted by the
1825 * kernel after applying relocations, generally such code can't
1826 * have relative-address relocation references to outside the
1827 * .altinstr_replacement section, unless the arch's
1828 * alternatives code can adjust the relative offsets
1831 alt_reloc = insn_reloc(file, insn);
1832 if (alt_reloc && arch_pc_relative_reloc(alt_reloc) &&
1833 !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1835 WARN_INSN(insn, "unsupported relocation in alternatives section");
1839 if (!is_static_jump(insn))
1842 if (!insn->immediate)
1845 dest_off = arch_jump_destination(insn);
1846 if (dest_off == special_alt->new_off + special_alt->new_len) {
1847 insn->jump_dest = next_insn_same_sec(file, orig_alt_group->last_insn);
1848 if (!insn->jump_dest) {
1849 WARN_INSN(insn, "can't find alternative jump destination");
1855 if (!last_new_insn) {
1856 WARN_FUNC("can't find last new alternative instruction",
1857 special_alt->new_sec, special_alt->new_off);
1862 new_alt_group->orig_group = orig_alt_group;
1863 new_alt_group->first_insn = *new_insn;
1864 new_alt_group->last_insn = last_new_insn;
1865 new_alt_group->nop = nop;
1866 new_alt_group->cfi = orig_alt_group->cfi;
1871 * A jump table entry can either convert a nop to a jump or a jump to a nop.
1872 * If the original instruction is a jump, make the alt entry an effective nop
1873 * by just skipping the original instruction.
1875 static int handle_jump_alt(struct objtool_file *file,
1876 struct special_alt *special_alt,
1877 struct instruction *orig_insn,
1878 struct instruction **new_insn)
1880 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1881 orig_insn->type != INSN_NOP) {
1883 WARN_INSN(orig_insn, "unsupported instruction at jump label");
1887 if (opts.hack_jump_label && special_alt->key_addend & 2) {
1888 struct reloc *reloc = insn_reloc(file, orig_insn);
1891 set_reloc_type(file->elf, reloc, R_NONE);
1892 elf_write_insn(file->elf, orig_insn->sec,
1893 orig_insn->offset, orig_insn->len,
1894 arch_nop_insn(orig_insn->len));
1895 orig_insn->type = INSN_NOP;
1898 if (orig_insn->type == INSN_NOP) {
1899 if (orig_insn->len == 2)
1900 file->jl_nop_short++;
1902 file->jl_nop_long++;
1907 if (orig_insn->len == 2)
1912 *new_insn = next_insn_same_sec(file, orig_insn);
1917 * Read all the special sections which have alternate instructions which can be
1918 * patched in or redirected to at runtime. Each instruction having alternate
1919 * instruction(s) has them added to its insn->alts list, which will be
1920 * traversed in validate_branch().
1922 static int add_special_section_alts(struct objtool_file *file)
1924 struct list_head special_alts;
1925 struct instruction *orig_insn, *new_insn;
1926 struct special_alt *special_alt, *tmp;
1927 struct alternative *alt;
1930 ret = special_get_alts(file->elf, &special_alts);
1934 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1936 orig_insn = find_insn(file, special_alt->orig_sec,
1937 special_alt->orig_off);
1939 WARN_FUNC("special: can't find orig instruction",
1940 special_alt->orig_sec, special_alt->orig_off);
1946 if (!special_alt->group || special_alt->new_len) {
1947 new_insn = find_insn(file, special_alt->new_sec,
1948 special_alt->new_off);
1950 WARN_FUNC("special: can't find new instruction",
1951 special_alt->new_sec,
1952 special_alt->new_off);
1958 if (special_alt->group) {
1959 if (!special_alt->orig_len) {
1960 WARN_INSN(orig_insn, "empty alternative entry");
1964 ret = handle_group_alt(file, special_alt, orig_insn,
1968 } else if (special_alt->jump_or_nop) {
1969 ret = handle_jump_alt(file, special_alt, orig_insn,
1975 alt = malloc(sizeof(*alt));
1977 WARN("malloc failed");
1982 alt->insn = new_insn;
1983 alt->skip_orig = special_alt->skip_orig;
1984 orig_insn->ignore_alts |= special_alt->skip_alt;
1985 alt->next = orig_insn->alts;
1986 orig_insn->alts = alt;
1988 list_del(&special_alt->list);
1993 printf("jl\\\tNOP\tJMP\n");
1994 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
1995 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
2002 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
2003 struct reloc *next_table)
2005 struct symbol *pfunc = insn_func(insn)->pfunc;
2006 struct reloc *table = insn_jump_table(insn);
2007 struct instruction *dest_insn;
2008 unsigned int prev_offset = 0;
2009 struct reloc *reloc = table;
2010 struct alternative *alt;
2013 * Each @reloc is a switch table relocation which points to the target
2016 for_each_reloc_from(table->sec, reloc) {
2018 /* Check for the end of the table: */
2019 if (reloc != table && reloc == next_table)
2022 /* Make sure the table entries are consecutive: */
2023 if (prev_offset && reloc_offset(reloc) != prev_offset + 8)
2026 /* Detect function pointers from contiguous objects: */
2027 if (reloc->sym->sec == pfunc->sec &&
2028 reloc_addend(reloc) == pfunc->offset)
2031 dest_insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2035 /* Make sure the destination is in the same function: */
2036 if (!insn_func(dest_insn) || insn_func(dest_insn)->pfunc != pfunc)
2039 alt = malloc(sizeof(*alt));
2041 WARN("malloc failed");
2045 alt->insn = dest_insn;
2046 alt->next = insn->alts;
2048 prev_offset = reloc_offset(reloc);
2052 WARN_INSN(insn, "can't find switch jump table");
2060 * find_jump_table() - Given a dynamic jump, find the switch jump table
2061 * associated with it.
2063 static struct reloc *find_jump_table(struct objtool_file *file,
2064 struct symbol *func,
2065 struct instruction *insn)
2067 struct reloc *table_reloc;
2068 struct instruction *dest_insn, *orig_insn = insn;
2071 * Backward search using the @first_jump_src links, these help avoid
2072 * much of the 'in between' code. Which avoids us getting confused by
2076 insn && insn_func(insn) && insn_func(insn)->pfunc == func;
2077 insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
2079 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
2082 /* allow small jumps within the range */
2083 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
2085 (insn->jump_dest->offset <= insn->offset ||
2086 insn->jump_dest->offset > orig_insn->offset))
2089 table_reloc = arch_find_switch_table(file, insn);
2092 dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
2093 if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
2103 * First pass: Mark the head of each jump table so that in the next pass,
2104 * we know when a given jump table ends and the next one starts.
2106 static void mark_func_jump_tables(struct objtool_file *file,
2107 struct symbol *func)
2109 struct instruction *insn, *last = NULL;
2110 struct reloc *reloc;
2112 func_for_each_insn(file, func, insn) {
2117 * Store back-pointers for unconditional forward jumps such
2118 * that find_jump_table() can back-track using those and
2119 * avoid some potentially confusing code.
2121 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
2122 insn->offset > last->offset &&
2123 insn->jump_dest->offset > insn->offset &&
2124 !insn->jump_dest->first_jump_src) {
2126 insn->jump_dest->first_jump_src = insn;
2127 last = insn->jump_dest;
2130 if (insn->type != INSN_JUMP_DYNAMIC)
2133 reloc = find_jump_table(file, func, insn);
2135 insn->_jump_table = reloc;
2139 static int add_func_jump_tables(struct objtool_file *file,
2140 struct symbol *func)
2142 struct instruction *insn, *insn_t1 = NULL, *insn_t2;
2145 func_for_each_insn(file, func, insn) {
2146 if (!insn_jump_table(insn))
2156 ret = add_jump_table(file, insn_t1, insn_jump_table(insn_t2));
2164 ret = add_jump_table(file, insn_t1, NULL);
2170 * For some switch statements, gcc generates a jump table in the .rodata
2171 * section which contains a list of addresses within the function to jump to.
2172 * This finds these jump tables and adds them to the insn->alts lists.
2174 static int add_jump_table_alts(struct objtool_file *file)
2176 struct symbol *func;
2182 for_each_sym(file, func) {
2183 if (func->type != STT_FUNC)
2186 mark_func_jump_tables(file, func);
2187 ret = add_func_jump_tables(file, func);
2195 static void set_func_state(struct cfi_state *state)
2197 state->cfa = initial_func_cfi.cfa;
2198 memcpy(&state->regs, &initial_func_cfi.regs,
2199 CFI_NUM_REGS * sizeof(struct cfi_reg));
2200 state->stack_size = initial_func_cfi.cfa.offset;
2201 state->type = UNWIND_HINT_TYPE_CALL;
2204 static int read_unwind_hints(struct objtool_file *file)
2206 struct cfi_state cfi = init_cfi;
2207 struct section *sec;
2208 struct unwind_hint *hint;
2209 struct instruction *insn;
2210 struct reloc *reloc;
2213 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
2218 WARN("missing .rela.discard.unwind_hints section");
2222 if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
2223 WARN("struct unwind_hint size mismatch");
2229 for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
2230 hint = (struct unwind_hint *)sec->data->d_buf + i;
2232 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
2234 WARN("can't find reloc for unwind_hints[%d]", i);
2238 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2240 WARN("can't find insn for unwind_hints[%d]", i);
2246 if (hint->type == UNWIND_HINT_TYPE_UNDEFINED) {
2247 insn->cfi = &force_undefined_cfi;
2251 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
2257 if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
2258 insn->restore = true;
2262 if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
2263 struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
2265 if (sym && sym->bind == STB_GLOBAL) {
2266 if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) {
2267 WARN_INSN(insn, "UNWIND_HINT_IRET_REGS without ENDBR");
2272 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
2273 insn->cfi = &func_cfi;
2280 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
2281 WARN_INSN(insn, "unsupported unwind_hint sp base reg %d", hint->sp_reg);
2285 cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
2286 cfi.type = hint->type;
2287 cfi.signal = hint->signal;
2289 insn->cfi = cfi_hash_find_or_add(&cfi);
2295 static int read_noendbr_hints(struct objtool_file *file)
2297 struct instruction *insn;
2298 struct section *rsec;
2299 struct reloc *reloc;
2301 rsec = find_section_by_name(file->elf, ".rela.discard.noendbr");
2305 for_each_reloc(rsec, reloc) {
2306 insn = find_insn(file, reloc->sym->sec,
2307 reloc->sym->offset + reloc_addend(reloc));
2309 WARN("bad .discard.noendbr entry");
2319 static int read_retpoline_hints(struct objtool_file *file)
2321 struct section *rsec;
2322 struct instruction *insn;
2323 struct reloc *reloc;
2325 rsec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
2329 for_each_reloc(rsec, reloc) {
2330 if (reloc->sym->type != STT_SECTION) {
2331 WARN("unexpected relocation symbol type in %s", rsec->name);
2335 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2337 WARN("bad .discard.retpoline_safe entry");
2341 if (insn->type != INSN_JUMP_DYNAMIC &&
2342 insn->type != INSN_CALL_DYNAMIC &&
2343 insn->type != INSN_RETURN &&
2344 insn->type != INSN_NOP) {
2345 WARN_INSN(insn, "retpoline_safe hint not an indirect jump/call/ret/nop");
2349 insn->retpoline_safe = true;
2355 static int read_instr_hints(struct objtool_file *file)
2357 struct section *rsec;
2358 struct instruction *insn;
2359 struct reloc *reloc;
2361 rsec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2365 for_each_reloc(rsec, reloc) {
2366 if (reloc->sym->type != STT_SECTION) {
2367 WARN("unexpected relocation symbol type in %s", rsec->name);
2371 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2373 WARN("bad .discard.instr_end entry");
2380 rsec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2384 for_each_reloc(rsec, reloc) {
2385 if (reloc->sym->type != STT_SECTION) {
2386 WARN("unexpected relocation symbol type in %s", rsec->name);
2390 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2392 WARN("bad .discard.instr_begin entry");
2402 static int read_validate_unret_hints(struct objtool_file *file)
2404 struct section *rsec;
2405 struct instruction *insn;
2406 struct reloc *reloc;
2408 rsec = find_section_by_name(file->elf, ".rela.discard.validate_unret");
2412 for_each_reloc(rsec, reloc) {
2413 if (reloc->sym->type != STT_SECTION) {
2414 WARN("unexpected relocation symbol type in %s", rsec->name);
2418 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2420 WARN("bad .discard.instr_end entry");
2430 static int read_intra_function_calls(struct objtool_file *file)
2432 struct instruction *insn;
2433 struct section *rsec;
2434 struct reloc *reloc;
2436 rsec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2440 for_each_reloc(rsec, reloc) {
2441 unsigned long dest_off;
2443 if (reloc->sym->type != STT_SECTION) {
2444 WARN("unexpected relocation symbol type in %s",
2449 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2451 WARN("bad .discard.intra_function_call entry");
2455 if (insn->type != INSN_CALL) {
2456 WARN_INSN(insn, "intra_function_call not a direct call");
2461 * Treat intra-function CALLs as JMPs, but with a stack_op.
2462 * See add_call_destinations(), which strips stack_ops from
2465 insn->type = INSN_JUMP_UNCONDITIONAL;
2467 dest_off = arch_jump_destination(insn);
2468 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2469 if (!insn->jump_dest) {
2470 WARN_INSN(insn, "can't find call dest at %s+0x%lx",
2471 insn->sec->name, dest_off);
2480 * Return true if name matches an instrumentation function, where calls to that
2481 * function from noinstr code can safely be removed, but compilers won't do so.
2483 static bool is_profiling_func(const char *name)
2486 * Many compilers cannot disable KCOV with a function attribute.
2488 if (!strncmp(name, "__sanitizer_cov_", 16))
2492 * Some compilers currently do not remove __tsan_func_entry/exit nor
2493 * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2494 * the __no_sanitize_thread attribute, remove them. Once the kernel's
2495 * minimum Clang version is 14.0, this can be removed.
2497 if (!strncmp(name, "__tsan_func_", 12) ||
2498 !strcmp(name, "__tsan_atomic_signal_fence"))
2504 static int classify_symbols(struct objtool_file *file)
2506 struct symbol *func;
2508 for_each_sym(file, func) {
2509 if (func->bind != STB_GLOBAL)
2512 if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2513 strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2514 func->static_call_tramp = true;
2516 if (arch_is_retpoline(func))
2517 func->retpoline_thunk = true;
2519 if (arch_is_rethunk(func))
2520 func->return_thunk = true;
2522 if (arch_is_embedded_insn(func))
2523 func->embedded_insn = true;
2525 if (arch_ftrace_match(func->name))
2526 func->fentry = true;
2528 if (is_profiling_func(func->name))
2529 func->profiling_func = true;
2535 static void mark_rodata(struct objtool_file *file)
2537 struct section *sec;
2541 * Search for the following rodata sections, each of which can
2542 * potentially contain jump tables:
2544 * - .rodata: can contain GCC switch tables
2545 * - .rodata.<func>: same, if -fdata-sections is being used
2546 * - .rodata..c_jump_table: contains C annotated jump tables
2548 * .rodata.str1.* sections are ignored; they don't contain jump tables.
2550 for_each_sec(file, sec) {
2551 if (!strncmp(sec->name, ".rodata", 7) &&
2552 !strstr(sec->name, ".str1.")) {
2558 file->rodata = found;
2561 static int decode_sections(struct objtool_file *file)
2567 ret = init_pv_ops(file);
2572 * Must be before add_{jump_call}_destination.
2574 ret = classify_symbols(file);
2578 ret = decode_instructions(file);
2583 add_uaccess_safe(file);
2585 ret = add_ignore_alternatives(file);
2590 * Must be before read_unwind_hints() since that needs insn->noendbr.
2592 ret = read_noendbr_hints(file);
2597 * Must be before add_jump_destinations(), which depends on 'func'
2598 * being set for alternatives, to enable proper sibling call detection.
2600 if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) {
2601 ret = add_special_section_alts(file);
2606 ret = add_jump_destinations(file);
2611 * Must be before add_call_destination(); it changes INSN_CALL to
2614 ret = read_intra_function_calls(file);
2618 ret = add_call_destinations(file);
2623 * Must be after add_call_destinations() such that it can override
2624 * dead_end_function() marks.
2626 ret = add_dead_ends(file);
2630 ret = add_jump_table_alts(file);
2634 ret = read_unwind_hints(file);
2638 ret = read_retpoline_hints(file);
2642 ret = read_instr_hints(file);
2646 ret = read_validate_unret_hints(file);
2653 static bool is_special_call(struct instruction *insn)
2655 if (insn->type == INSN_CALL) {
2656 struct symbol *dest = insn_call_dest(insn);
2661 if (dest->fentry || dest->embedded_insn)
2668 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2670 struct cfi_state *cfi = &state->cfi;
2673 if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2676 if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2679 if (cfi->stack_size != initial_func_cfi.cfa.offset)
2682 for (i = 0; i < CFI_NUM_REGS; i++) {
2683 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2684 cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2691 static bool check_reg_frame_pos(const struct cfi_reg *reg,
2692 int expected_offset)
2694 return reg->base == CFI_CFA &&
2695 reg->offset == expected_offset;
2698 static bool has_valid_stack_frame(struct insn_state *state)
2700 struct cfi_state *cfi = &state->cfi;
2702 if (cfi->cfa.base == CFI_BP &&
2703 check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2704 check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2707 if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2713 static int update_cfi_state_regs(struct instruction *insn,
2714 struct cfi_state *cfi,
2715 struct stack_op *op)
2717 struct cfi_reg *cfa = &cfi->cfa;
2719 if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2723 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2727 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2730 /* add immediate to sp */
2731 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2732 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2733 cfa->offset -= op->src.offset;
2738 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2740 if (arch_callee_saved_reg(reg) &&
2741 cfi->regs[reg].base == CFI_UNDEFINED) {
2742 cfi->regs[reg].base = base;
2743 cfi->regs[reg].offset = offset;
2747 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2749 cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2750 cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2754 * A note about DRAP stack alignment:
2756 * GCC has the concept of a DRAP register, which is used to help keep track of
2757 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
2758 * register. The typical DRAP pattern is:
2760 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
2761 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
2762 * 41 ff 72 f8 pushq -0x8(%r10)
2764 * 48 89 e5 mov %rsp,%rbp
2771 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2774 * There are some variations in the epilogues, like:
2782 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2787 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
2788 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
2789 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
2790 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
2792 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2795 * Sometimes r13 is used as the DRAP register, in which case it's saved and
2796 * restored beforehand:
2799 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
2800 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
2802 * 49 8d 65 f0 lea -0x10(%r13),%rsp
2806 static int update_cfi_state(struct instruction *insn,
2807 struct instruction *next_insn,
2808 struct cfi_state *cfi, struct stack_op *op)
2810 struct cfi_reg *cfa = &cfi->cfa;
2811 struct cfi_reg *regs = cfi->regs;
2813 /* ignore UNWIND_HINT_UNDEFINED regions */
2814 if (cfi->force_undefined)
2817 /* stack operations don't make sense with an undefined CFA */
2818 if (cfa->base == CFI_UNDEFINED) {
2819 if (insn_func(insn)) {
2820 WARN_INSN(insn, "undefined stack state");
2826 if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2827 cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2828 return update_cfi_state_regs(insn, cfi, op);
2830 switch (op->dest.type) {
2833 switch (op->src.type) {
2836 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2837 cfa->base == CFI_SP &&
2838 check_reg_frame_pos(®s[CFI_BP], -cfa->offset)) {
2840 /* mov %rsp, %rbp */
2841 cfa->base = op->dest.reg;
2842 cfi->bp_scratch = false;
2845 else if (op->src.reg == CFI_SP &&
2846 op->dest.reg == CFI_BP && cfi->drap) {
2848 /* drap: mov %rsp, %rbp */
2849 regs[CFI_BP].base = CFI_BP;
2850 regs[CFI_BP].offset = -cfi->stack_size;
2851 cfi->bp_scratch = false;
2854 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2859 * This is needed for the rare case where GCC
2866 cfi->vals[op->dest.reg].base = CFI_CFA;
2867 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2870 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2871 (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2876 * Restore the original stack pointer (Clang).
2878 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2881 else if (op->dest.reg == cfa->base) {
2883 /* mov %reg, %rsp */
2884 if (cfa->base == CFI_SP &&
2885 cfi->vals[op->src.reg].base == CFI_CFA) {
2888 * This is needed for the rare case
2889 * where GCC does something dumb like:
2891 * lea 0x8(%rsp), %rcx
2895 cfa->offset = -cfi->vals[op->src.reg].offset;
2896 cfi->stack_size = cfa->offset;
2898 } else if (cfa->base == CFI_SP &&
2899 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2900 cfi->vals[op->src.reg].offset == cfa->offset) {
2905 * 1: mov %rsp, (%[tos])
2906 * 2: mov %[tos], %rsp
2912 * 1 - places a pointer to the previous
2913 * stack at the Top-of-Stack of the
2916 * 2 - switches to the new stack.
2918 * 3 - pops the Top-of-Stack to restore
2919 * the original stack.
2921 * Note: we set base to SP_INDIRECT
2922 * here and preserve offset. Therefore
2923 * when the unwinder reaches ToS it
2924 * will dereference SP and then add the
2925 * offset to find the next frame, IOW:
2928 cfa->base = CFI_SP_INDIRECT;
2931 cfa->base = CFI_UNDEFINED;
2936 else if (op->dest.reg == CFI_SP &&
2937 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2938 cfi->vals[op->src.reg].offset == cfa->offset) {
2941 * The same stack swizzle case 2) as above. But
2942 * because we can't change cfa->base, case 3)
2943 * will become a regular POP. Pretend we're a
2944 * PUSH so things don't go unbalanced.
2946 cfi->stack_size += 8;
2953 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2956 cfi->stack_size -= op->src.offset;
2957 if (cfa->base == CFI_SP)
2958 cfa->offset -= op->src.offset;
2962 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2964 /* lea disp(%rbp), %rsp */
2965 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2969 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2971 /* drap: lea disp(%rsp), %drap */
2972 cfi->drap_reg = op->dest.reg;
2975 * lea disp(%rsp), %reg
2977 * This is needed for the rare case where GCC
2978 * does something dumb like:
2980 * lea 0x8(%rsp), %rcx
2984 cfi->vals[op->dest.reg].base = CFI_CFA;
2985 cfi->vals[op->dest.reg].offset = \
2986 -cfi->stack_size + op->src.offset;
2991 if (cfi->drap && op->dest.reg == CFI_SP &&
2992 op->src.reg == cfi->drap_reg) {
2994 /* drap: lea disp(%drap), %rsp */
2996 cfa->offset = cfi->stack_size = -op->src.offset;
2997 cfi->drap_reg = CFI_UNDEFINED;
3002 if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
3003 WARN_INSN(insn, "unsupported stack register modification");
3010 if (op->dest.reg != CFI_SP ||
3011 (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
3012 (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
3013 WARN_INSN(insn, "unsupported stack pointer realignment");
3017 if (cfi->drap_reg != CFI_UNDEFINED) {
3018 /* drap: and imm, %rsp */
3019 cfa->base = cfi->drap_reg;
3020 cfa->offset = cfi->stack_size = 0;
3025 * Older versions of GCC (4.8ish) realign the stack
3026 * without DRAP, with a frame pointer.
3033 if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
3035 /* pop %rsp; # restore from a stack swizzle */
3040 if (!cfi->drap && op->dest.reg == cfa->base) {
3046 if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
3047 op->dest.reg == cfi->drap_reg &&
3048 cfi->drap_offset == -cfi->stack_size) {
3050 /* drap: pop %drap */
3051 cfa->base = cfi->drap_reg;
3053 cfi->drap_offset = -1;
3055 } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
3058 restore_reg(cfi, op->dest.reg);
3061 cfi->stack_size -= 8;
3062 if (cfa->base == CFI_SP)
3067 case OP_SRC_REG_INDIRECT:
3068 if (!cfi->drap && op->dest.reg == cfa->base &&
3069 op->dest.reg == CFI_BP) {
3071 /* mov disp(%rsp), %rbp */
3073 cfa->offset = cfi->stack_size;
3076 if (cfi->drap && op->src.reg == CFI_BP &&
3077 op->src.offset == cfi->drap_offset) {
3079 /* drap: mov disp(%rbp), %drap */
3080 cfa->base = cfi->drap_reg;
3082 cfi->drap_offset = -1;
3085 if (cfi->drap && op->src.reg == CFI_BP &&
3086 op->src.offset == regs[op->dest.reg].offset) {
3088 /* drap: mov disp(%rbp), %reg */
3089 restore_reg(cfi, op->dest.reg);
3091 } else if (op->src.reg == cfa->base &&
3092 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
3094 /* mov disp(%rbp), %reg */
3095 /* mov disp(%rsp), %reg */
3096 restore_reg(cfi, op->dest.reg);
3098 } else if (op->src.reg == CFI_SP &&
3099 op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
3101 /* mov disp(%rsp), %reg */
3102 restore_reg(cfi, op->dest.reg);
3108 WARN_INSN(insn, "unknown stack-related instruction");
3116 cfi->stack_size += 8;
3117 if (cfa->base == CFI_SP)
3120 if (op->src.type != OP_SRC_REG)
3124 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3126 /* drap: push %drap */
3127 cfa->base = CFI_BP_INDIRECT;
3128 cfa->offset = -cfi->stack_size;
3130 /* save drap so we know when to restore it */
3131 cfi->drap_offset = -cfi->stack_size;
3133 } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
3135 /* drap: push %rbp */
3136 cfi->stack_size = 0;
3140 /* drap: push %reg */
3141 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
3147 save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
3150 /* detect when asm code uses rbp as a scratch register */
3151 if (opts.stackval && insn_func(insn) && op->src.reg == CFI_BP &&
3152 cfa->base != CFI_BP)
3153 cfi->bp_scratch = true;
3156 case OP_DEST_REG_INDIRECT:
3159 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3161 /* drap: mov %drap, disp(%rbp) */
3162 cfa->base = CFI_BP_INDIRECT;
3163 cfa->offset = op->dest.offset;
3165 /* save drap offset so we know when to restore it */
3166 cfi->drap_offset = op->dest.offset;
3169 /* drap: mov reg, disp(%rbp) */
3170 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
3173 } else if (op->dest.reg == cfa->base) {
3175 /* mov reg, disp(%rbp) */
3176 /* mov reg, disp(%rsp) */
3177 save_reg(cfi, op->src.reg, CFI_CFA,
3178 op->dest.offset - cfi->cfa.offset);
3180 } else if (op->dest.reg == CFI_SP) {
3182 /* mov reg, disp(%rsp) */
3183 save_reg(cfi, op->src.reg, CFI_CFA,
3184 op->dest.offset - cfi->stack_size);
3186 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
3188 /* mov %rsp, (%reg); # setup a stack swizzle. */
3189 cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
3190 cfi->vals[op->dest.reg].offset = cfa->offset;
3196 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
3197 WARN_INSN(insn, "unknown stack-related memory operation");
3202 cfi->stack_size -= 8;
3203 if (cfa->base == CFI_SP)
3209 WARN_INSN(insn, "unknown stack-related instruction");
3217 * The stack layouts of alternatives instructions can sometimes diverge when
3218 * they have stack modifications. That's fine as long as the potential stack
3219 * layouts don't conflict at any given potential instruction boundary.
3221 * Flatten the CFIs of the different alternative code streams (both original
3222 * and replacement) into a single shared CFI array which can be used to detect
3223 * conflicts and nicely feed a linear array of ORC entries to the unwinder.
3225 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
3227 struct cfi_state **alt_cfi;
3230 if (!insn->alt_group)
3234 WARN("CFI missing");
3238 alt_cfi = insn->alt_group->cfi;
3239 group_off = insn->offset - insn->alt_group->first_insn->offset;
3241 if (!alt_cfi[group_off]) {
3242 alt_cfi[group_off] = insn->cfi;
3244 if (cficmp(alt_cfi[group_off], insn->cfi)) {
3245 struct alt_group *orig_group = insn->alt_group->orig_group ?: insn->alt_group;
3246 struct instruction *orig = orig_group->first_insn;
3247 char *where = offstr(insn->sec, insn->offset);
3248 WARN_INSN(orig, "stack layout conflict in alternatives: %s", where);
3257 static int handle_insn_ops(struct instruction *insn,
3258 struct instruction *next_insn,
3259 struct insn_state *state)
3261 struct stack_op *op;
3263 for (op = insn->stack_ops; op; op = op->next) {
3265 if (update_cfi_state(insn, next_insn, &state->cfi, op))
3268 if (!insn->alt_group)
3271 if (op->dest.type == OP_DEST_PUSHF) {
3272 if (!state->uaccess_stack) {
3273 state->uaccess_stack = 1;
3274 } else if (state->uaccess_stack >> 31) {
3275 WARN_INSN(insn, "PUSHF stack exhausted");
3278 state->uaccess_stack <<= 1;
3279 state->uaccess_stack |= state->uaccess;
3282 if (op->src.type == OP_SRC_POPF) {
3283 if (state->uaccess_stack) {
3284 state->uaccess = state->uaccess_stack & 1;
3285 state->uaccess_stack >>= 1;
3286 if (state->uaccess_stack == 1)
3287 state->uaccess_stack = 0;
3295 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
3297 struct cfi_state *cfi1 = insn->cfi;
3301 WARN("CFI missing");
3305 if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
3307 WARN_INSN(insn, "stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
3308 cfi1->cfa.base, cfi1->cfa.offset,
3309 cfi2->cfa.base, cfi2->cfa.offset);
3311 } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
3312 for (i = 0; i < CFI_NUM_REGS; i++) {
3313 if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
3314 sizeof(struct cfi_reg)))
3317 WARN_INSN(insn, "stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
3318 i, cfi1->regs[i].base, cfi1->regs[i].offset,
3319 i, cfi2->regs[i].base, cfi2->regs[i].offset);
3323 } else if (cfi1->type != cfi2->type) {
3325 WARN_INSN(insn, "stack state mismatch: type1=%d type2=%d",
3326 cfi1->type, cfi2->type);
3328 } else if (cfi1->drap != cfi2->drap ||
3329 (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
3330 (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
3332 WARN_INSN(insn, "stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
3333 cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
3334 cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
3342 static inline bool func_uaccess_safe(struct symbol *func)
3345 return func->uaccess_safe;
3350 static inline const char *call_dest_name(struct instruction *insn)
3352 static char pvname[19];
3353 struct reloc *reloc;
3356 if (insn_call_dest(insn))
3357 return insn_call_dest(insn)->name;
3359 reloc = insn_reloc(NULL, insn);
3360 if (reloc && !strcmp(reloc->sym->name, "pv_ops")) {
3361 idx = (reloc_addend(reloc) / sizeof(void *));
3362 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
3369 static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3371 struct symbol *target;
3372 struct reloc *reloc;
3375 reloc = insn_reloc(file, insn);
3376 if (!reloc || strcmp(reloc->sym->name, "pv_ops"))
3379 idx = (arch_dest_reloc_offset(reloc_addend(reloc)) / sizeof(void *));
3381 if (file->pv_ops[idx].clean)
3384 file->pv_ops[idx].clean = true;
3386 list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3387 if (!target->sec->noinstr) {
3388 WARN("pv_ops[%d]: %s", idx, target->name);
3389 file->pv_ops[idx].clean = false;
3393 return file->pv_ops[idx].clean;
3396 static inline bool noinstr_call_dest(struct objtool_file *file,
3397 struct instruction *insn,
3398 struct symbol *func)
3401 * We can't deal with indirect function calls at present;
3402 * assume they're instrumented.
3406 return pv_call_dest(file, insn);
3412 * If the symbol is from a noinstr section; we good.
3414 if (func->sec->noinstr)
3418 * If the symbol is a static_call trampoline, we can't tell.
3420 if (func->static_call_tramp)
3424 * The __ubsan_handle_*() calls are like WARN(), they only happen when
3425 * something 'BAD' happened. At the risk of taking the machine down,
3426 * let them proceed to get the message out.
3428 if (!strncmp(func->name, "__ubsan_handle_", 15))
3434 static int validate_call(struct objtool_file *file,
3435 struct instruction *insn,
3436 struct insn_state *state)
3438 if (state->noinstr && state->instr <= 0 &&
3439 !noinstr_call_dest(file, insn, insn_call_dest(insn))) {
3440 WARN_INSN(insn, "call to %s() leaves .noinstr.text section", call_dest_name(insn));
3444 if (state->uaccess && !func_uaccess_safe(insn_call_dest(insn))) {
3445 WARN_INSN(insn, "call to %s() with UACCESS enabled", call_dest_name(insn));
3450 WARN_INSN(insn, "call to %s() with DF set", call_dest_name(insn));
3457 static int validate_sibling_call(struct objtool_file *file,
3458 struct instruction *insn,
3459 struct insn_state *state)
3461 if (insn_func(insn) && has_modified_stack_frame(insn, state)) {
3462 WARN_INSN(insn, "sibling call from callable instruction with modified stack frame");
3466 return validate_call(file, insn, state);
3469 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3471 if (state->noinstr && state->instr > 0) {
3472 WARN_INSN(insn, "return with instrumentation enabled");
3476 if (state->uaccess && !func_uaccess_safe(func)) {
3477 WARN_INSN(insn, "return with UACCESS enabled");
3481 if (!state->uaccess && func_uaccess_safe(func)) {
3482 WARN_INSN(insn, "return with UACCESS disabled from a UACCESS-safe function");
3487 WARN_INSN(insn, "return with DF set");
3491 if (func && has_modified_stack_frame(insn, state)) {
3492 WARN_INSN(insn, "return with modified stack frame");
3496 if (state->cfi.bp_scratch) {
3497 WARN_INSN(insn, "BP used as a scratch register");
3504 static struct instruction *next_insn_to_validate(struct objtool_file *file,
3505 struct instruction *insn)
3507 struct alt_group *alt_group = insn->alt_group;
3510 * Simulate the fact that alternatives are patched in-place. When the
3511 * end of a replacement alt_group is reached, redirect objtool flow to
3512 * the end of the original alt_group.
3514 * insn->alts->insn -> alt_group->first_insn
3516 * alt_group->last_insn
3517 * [alt_group->nop] -> next(orig_group->last_insn)
3520 if (alt_group->nop) {
3521 /* ->nop implies ->orig_group */
3522 if (insn == alt_group->last_insn)
3523 return alt_group->nop;
3524 if (insn == alt_group->nop)
3527 if (insn == alt_group->last_insn && alt_group->orig_group)
3531 return next_insn_same_sec(file, insn);
3534 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3538 * Follow the branch starting at the given instruction, and recursively follow
3539 * any other branches (jumps). Meanwhile, track the frame pointer state at
3540 * each instruction and validate all the rules described in
3541 * tools/objtool/Documentation/objtool.txt.
3543 static int validate_branch(struct objtool_file *file, struct symbol *func,
3544 struct instruction *insn, struct insn_state state)
3546 struct alternative *alt;
3547 struct instruction *next_insn, *prev_insn = NULL;
3548 struct section *sec;
3555 next_insn = next_insn_to_validate(file, insn);
3557 if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {
3558 /* Ignore KCFI type preambles, which always fall through */
3559 if (!strncmp(func->name, "__cfi_", 6) ||
3560 !strncmp(func->name, "__pfx_", 6))
3563 WARN("%s() falls through to next function %s()",
3564 func->name, insn_func(insn)->name);
3568 if (func && insn->ignore) {
3569 WARN_INSN(insn, "BUG: why am I validating an ignored function?");
3573 visited = VISITED_BRANCH << state.uaccess;
3574 if (insn->visited & VISITED_BRANCH_MASK) {
3575 if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3578 if (insn->visited & visited)
3585 state.instr += insn->instr;
3588 if (insn->restore) {
3589 struct instruction *save_insn, *i;
3594 sym_for_each_insn_continue_reverse(file, func, i) {
3602 WARN_INSN(insn, "no corresponding CFI save for CFI restore");
3606 if (!save_insn->visited) {
3607 WARN_INSN(insn, "objtool isn't smart enough to handle this CFI save/restore combo");
3611 insn->cfi = save_insn->cfi;
3615 state.cfi = *insn->cfi;
3617 /* XXX track if we actually changed state.cfi */
3619 if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3620 insn->cfi = prev_insn->cfi;
3623 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3627 insn->visited |= visited;
3629 if (propagate_alt_cfi(file, insn))
3632 if (!insn->ignore_alts && insn->alts) {
3633 bool skip_orig = false;
3635 for (alt = insn->alts; alt; alt = alt->next) {
3639 ret = validate_branch(file, func, alt->insn, state);
3641 BT_INSN(insn, "(alt)");
3650 if (handle_insn_ops(insn, next_insn, &state))
3653 switch (insn->type) {
3656 return validate_return(func, insn, &state);
3659 case INSN_CALL_DYNAMIC:
3660 ret = validate_call(file, insn, &state);
3664 if (opts.stackval && func && !is_special_call(insn) &&
3665 !has_valid_stack_frame(&state)) {
3666 WARN_INSN(insn, "call without frame pointer save/setup");
3675 case INSN_JUMP_CONDITIONAL:
3676 case INSN_JUMP_UNCONDITIONAL:
3677 if (is_sibling_call(insn)) {
3678 ret = validate_sibling_call(file, insn, &state);
3682 } else if (insn->jump_dest) {
3683 ret = validate_branch(file, func,
3684 insn->jump_dest, state);
3686 BT_INSN(insn, "(branch)");
3691 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3696 case INSN_JUMP_DYNAMIC:
3697 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3698 if (is_sibling_call(insn)) {
3699 ret = validate_sibling_call(file, insn, &state);
3704 if (insn->type == INSN_JUMP_DYNAMIC)
3709 case INSN_CONTEXT_SWITCH:
3710 if (func && (!next_insn || !next_insn->hint)) {
3711 WARN_INSN(insn, "unsupported instruction in callable function");
3717 if (state.uaccess) {
3718 WARN_INSN(insn, "recursive UACCESS enable");
3722 state.uaccess = true;
3726 if (!state.uaccess && func) {
3727 WARN_INSN(insn, "redundant UACCESS disable");
3731 if (func_uaccess_safe(func) && !state.uaccess_stack) {
3732 WARN_INSN(insn, "UACCESS-safe disables UACCESS");
3736 state.uaccess = false;
3741 WARN_INSN(insn, "recursive STD");
3749 if (!state.df && func) {
3750 WARN_INSN(insn, "redundant CLD");
3765 if (state.cfi.cfa.base == CFI_UNDEFINED)
3767 WARN("%s: unexpected end of section", sec->name);
3778 static int validate_unwind_hint(struct objtool_file *file,
3779 struct instruction *insn,
3780 struct insn_state *state)
3782 if (insn->hint && !insn->visited && !insn->ignore) {
3783 int ret = validate_branch(file, insn_func(insn), insn, *state);
3785 BT_INSN(insn, "<=== (hint)");
3792 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3794 struct instruction *insn;
3795 struct insn_state state;
3801 init_insn_state(file, &state, sec);
3804 sec_for_each_insn(file, sec, insn)
3805 warnings += validate_unwind_hint(file, insn, &state);
3807 for_each_insn(file, insn)
3808 warnings += validate_unwind_hint(file, insn, &state);
3815 * Validate rethunk entry constraint: must untrain RET before the first RET.
3817 * Follow every branch (intra-function) and ensure VALIDATE_UNRET_END comes
3818 * before an actual RET instruction.
3820 static int validate_unret(struct objtool_file *file, struct instruction *insn)
3822 struct instruction *next, *dest;
3826 next = next_insn_to_validate(file, insn);
3828 if (insn->visited & VISITED_UNRET)
3831 insn->visited |= VISITED_UNRET;
3833 if (!insn->ignore_alts && insn->alts) {
3834 struct alternative *alt;
3835 bool skip_orig = false;
3837 for (alt = insn->alts; alt; alt = alt->next) {
3841 ret = validate_unret(file, alt->insn);
3843 BT_INSN(insn, "(alt)");
3852 switch (insn->type) {
3854 case INSN_CALL_DYNAMIC:
3855 case INSN_JUMP_DYNAMIC:
3856 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3857 WARN_INSN(insn, "early indirect call");
3860 case INSN_JUMP_UNCONDITIONAL:
3861 case INSN_JUMP_CONDITIONAL:
3862 if (!is_sibling_call(insn)) {
3863 if (!insn->jump_dest) {
3864 WARN_INSN(insn, "unresolved jump target after linking?!?");
3867 ret = validate_unret(file, insn->jump_dest);
3869 BT_INSN(insn, "(branch%s)",
3870 insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : "");
3874 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3882 dest = find_insn(file, insn_call_dest(insn)->sec,
3883 insn_call_dest(insn)->offset);
3885 WARN("Unresolved function after linking!?: %s",
3886 insn_call_dest(insn)->name);
3890 ret = validate_unret(file, dest);
3892 BT_INSN(insn, "(call)");
3896 * If a call returns without error, it must have seen UNTRAIN_RET.
3897 * Therefore any non-error return is a success.
3902 WARN_INSN(insn, "RET before UNTRAIN");
3906 if (insn->retpoline_safe)
3915 WARN_INSN(insn, "teh end!");
3925 * Validate that all branches starting at VALIDATE_UNRET_BEGIN encounter
3926 * VALIDATE_UNRET_END before RET.
3928 static int validate_unrets(struct objtool_file *file)
3930 struct instruction *insn;
3931 int ret, warnings = 0;
3933 for_each_insn(file, insn) {
3937 ret = validate_unret(file, insn);
3939 WARN_INSN(insn, "Failed UNRET validation");
3948 static int validate_retpoline(struct objtool_file *file)
3950 struct instruction *insn;
3953 for_each_insn(file, insn) {
3954 if (insn->type != INSN_JUMP_DYNAMIC &&
3955 insn->type != INSN_CALL_DYNAMIC &&
3956 insn->type != INSN_RETURN)
3959 if (insn->retpoline_safe)
3962 if (insn->sec->init)
3965 if (insn->type == INSN_RETURN) {
3967 WARN_INSN(insn, "'naked' return found in RETHUNK build");
3971 WARN_INSN(insn, "indirect %s found in RETPOLINE build",
3972 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
3981 static bool is_kasan_insn(struct instruction *insn)
3983 return (insn->type == INSN_CALL &&
3984 !strcmp(insn_call_dest(insn)->name, "__asan_handle_no_return"));
3987 static bool is_ubsan_insn(struct instruction *insn)
3989 return (insn->type == INSN_CALL &&
3990 !strcmp(insn_call_dest(insn)->name,
3991 "__ubsan_handle_builtin_unreachable"));
3994 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
3997 struct instruction *prev_insn;
3999 if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
4003 * Ignore alternative replacement instructions. This can happen
4004 * when a whitelisted function uses one of the ALTERNATIVE macros.
4006 if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
4007 !strcmp(insn->sec->name, ".altinstr_aux"))
4011 * Whole archive runs might encounter dead code from weak symbols.
4012 * This is where the linker will have dropped the weak symbol in
4013 * favour of a regular symbol, but leaves the code in place.
4015 * In this case we'll find a piece of code (whole function) that is not
4016 * covered by a !section symbol. Ignore them.
4018 if (opts.link && !insn_func(insn)) {
4019 int size = find_symbol_hole_containing(insn->sec, insn->offset);
4020 unsigned long end = insn->offset + size;
4022 if (!size) /* not a hole */
4025 if (size < 0) /* hole until the end */
4028 sec_for_each_insn_continue(file, insn) {
4030 * If we reach a visited instruction at or before the
4031 * end of the hole, ignore the unreachable.
4036 if (insn->offset >= end)
4040 * If this hole jumps to a .cold function, mark it ignore too.
4042 if (insn->jump_dest && insn_func(insn->jump_dest) &&
4043 strstr(insn_func(insn->jump_dest)->name, ".cold")) {
4044 struct instruction *dest = insn->jump_dest;
4045 func_for_each_insn(file, insn_func(dest), dest)
4046 dest->ignore = true;
4053 if (!insn_func(insn))
4056 if (insn_func(insn)->static_call_tramp)
4060 * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
4061 * __builtin_unreachable(). The BUG() macro has an unreachable() after
4062 * the UD2, which causes GCC's undefined trap logic to emit another UD2
4063 * (or occasionally a JMP to UD2).
4065 * It may also insert a UD2 after calling a __noreturn function.
4067 prev_insn = prev_insn_same_sec(file, insn);
4068 if (prev_insn->dead_end &&
4069 (insn->type == INSN_BUG ||
4070 (insn->type == INSN_JUMP_UNCONDITIONAL &&
4071 insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
4075 * Check if this (or a subsequent) instruction is related to
4076 * CONFIG_UBSAN or CONFIG_KASAN.
4078 * End the search at 5 instructions to avoid going into the weeds.
4080 for (i = 0; i < 5; i++) {
4082 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
4085 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
4086 if (insn->jump_dest &&
4087 insn_func(insn->jump_dest) == insn_func(insn)) {
4088 insn = insn->jump_dest;
4095 if (insn->offset + insn->len >= insn_func(insn)->offset + insn_func(insn)->len)
4098 insn = next_insn_same_sec(file, insn);
4104 static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
4106 struct instruction *insn, *prev;
4107 struct cfi_state *cfi;
4109 insn = find_insn(file, func->sec, func->offset);
4113 for (prev = prev_insn_same_sec(file, insn);
4115 prev = prev_insn_same_sec(file, prev)) {
4118 if (prev->type != INSN_NOP)
4121 offset = func->offset - prev->offset;
4123 if (offset > opts.prefix)
4126 if (offset < opts.prefix)
4129 elf_create_prefix_symbol(file->elf, func, opts.prefix);
4138 * This can happen if stack validation isn't enabled or the
4139 * function is annotated with STACK_FRAME_NON_STANDARD.
4144 /* Propagate insn->cfi to the prefix code */
4145 cfi = cfi_hash_find_or_add(insn->cfi);
4146 for (; prev != insn; prev = next_insn_same_sec(file, prev))
4152 static int add_prefix_symbols(struct objtool_file *file)
4154 struct section *sec;
4155 struct symbol *func;
4157 for_each_sec(file, sec) {
4158 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4161 sec_for_each_sym(sec, func) {
4162 if (func->type != STT_FUNC)
4165 add_prefix_symbol(file, func);
4172 static int validate_symbol(struct objtool_file *file, struct section *sec,
4173 struct symbol *sym, struct insn_state *state)
4175 struct instruction *insn;
4179 WARN("%s() is missing an ELF size annotation", sym->name);
4183 if (sym->pfunc != sym || sym->alias != sym)
4186 insn = find_insn(file, sec, sym->offset);
4187 if (!insn || insn->ignore || insn->visited)
4190 state->uaccess = sym->uaccess_safe;
4192 ret = validate_branch(file, insn_func(insn), insn, *state);
4194 BT_INSN(insn, "<=== (sym)");
4198 static int validate_section(struct objtool_file *file, struct section *sec)
4200 struct insn_state state;
4201 struct symbol *func;
4204 sec_for_each_sym(sec, func) {
4205 if (func->type != STT_FUNC)
4208 init_insn_state(file, &state, sec);
4209 set_func_state(&state.cfi);
4211 warnings += validate_symbol(file, sec, func, &state);
4217 static int validate_noinstr_sections(struct objtool_file *file)
4219 struct section *sec;
4222 sec = find_section_by_name(file->elf, ".noinstr.text");
4224 warnings += validate_section(file, sec);
4225 warnings += validate_unwind_hints(file, sec);
4228 sec = find_section_by_name(file->elf, ".entry.text");
4230 warnings += validate_section(file, sec);
4231 warnings += validate_unwind_hints(file, sec);
4234 sec = find_section_by_name(file->elf, ".cpuidle.text");
4236 warnings += validate_section(file, sec);
4237 warnings += validate_unwind_hints(file, sec);
4243 static int validate_functions(struct objtool_file *file)
4245 struct section *sec;
4248 for_each_sec(file, sec) {
4249 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4252 warnings += validate_section(file, sec);
4258 static void mark_endbr_used(struct instruction *insn)
4260 if (!list_empty(&insn->call_node))
4261 list_del_init(&insn->call_node);
4264 static bool noendbr_range(struct objtool_file *file, struct instruction *insn)
4266 struct symbol *sym = find_symbol_containing(insn->sec, insn->offset-1);
4267 struct instruction *first;
4272 first = find_insn(file, sym->sec, sym->offset);
4276 if (first->type != INSN_ENDBR && !first->noendbr)
4279 return insn->offset == sym->offset + sym->len;
4282 static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
4284 struct instruction *dest;
4285 struct reloc *reloc;
4290 * Looking for function pointer load relocations. Ignore
4291 * direct/indirect branches:
4293 switch (insn->type) {
4295 case INSN_CALL_DYNAMIC:
4296 case INSN_JUMP_CONDITIONAL:
4297 case INSN_JUMP_UNCONDITIONAL:
4298 case INSN_JUMP_DYNAMIC:
4299 case INSN_JUMP_DYNAMIC_CONDITIONAL:
4307 for (reloc = insn_reloc(file, insn);
4309 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
4310 reloc_offset(reloc) + 1,
4311 (insn->offset + insn->len) - (reloc_offset(reloc) + 1))) {
4314 * static_call_update() references the trampoline, which
4315 * doesn't have (or need) ENDBR. Skip warning in that case.
4317 if (reloc->sym->static_call_tramp)
4320 off = reloc->sym->offset;
4321 if (reloc_type(reloc) == R_X86_64_PC32 ||
4322 reloc_type(reloc) == R_X86_64_PLT32)
4323 off += arch_dest_reloc_offset(reloc_addend(reloc));
4325 off += reloc_addend(reloc);
4327 dest = find_insn(file, reloc->sym->sec, off);
4331 if (dest->type == INSN_ENDBR) {
4332 mark_endbr_used(dest);
4336 if (insn_func(dest) && insn_func(insn) &&
4337 insn_func(dest)->pfunc == insn_func(insn)->pfunc) {
4339 * Anything from->to self is either _THIS_IP_ or
4342 * There is no sane way to annotate _THIS_IP_ since the
4343 * compiler treats the relocation as a constant and is
4344 * happy to fold in offsets, skewing any annotation we
4345 * do, leading to vast amounts of false-positives.
4347 * There's also compiler generated _THIS_IP_ through
4348 * KCOV and such which we have no hope of annotating.
4350 * As such, blanket accept self-references without
4357 * Accept anything ANNOTATE_NOENDBR.
4363 * Accept if this is the instruction after a symbol
4364 * that is (no)endbr -- typical code-range usage.
4366 if (noendbr_range(file, dest))
4369 WARN_INSN(insn, "relocation to !ENDBR: %s", offstr(dest->sec, dest->offset));
4377 static int validate_ibt_data_reloc(struct objtool_file *file,
4378 struct reloc *reloc)
4380 struct instruction *dest;
4382 dest = find_insn(file, reloc->sym->sec,
4383 reloc->sym->offset + reloc_addend(reloc));
4387 if (dest->type == INSN_ENDBR) {
4388 mark_endbr_used(dest);
4395 WARN_FUNC("data relocation to !ENDBR: %s",
4396 reloc->sec->base, reloc_offset(reloc),
4397 offstr(dest->sec, dest->offset));
4403 * Validate IBT rules and remove used ENDBR instructions from the seal list.
4404 * Unused ENDBR instructions will be annotated for sealing (i.e., replaced with
4405 * NOPs) later, in create_ibt_endbr_seal_sections().
4407 static int validate_ibt(struct objtool_file *file)
4409 struct section *sec;
4410 struct reloc *reloc;
4411 struct instruction *insn;
4414 for_each_insn(file, insn)
4415 warnings += validate_ibt_insn(file, insn);
4417 for_each_sec(file, sec) {
4419 /* Already done by validate_ibt_insn() */
4420 if (sec->sh.sh_flags & SHF_EXECINSTR)
4427 * These sections can reference text addresses, but not with
4428 * the intent to indirect branch to them.
4430 if ((!strncmp(sec->name, ".discard", 8) &&
4431 strcmp(sec->name, ".discard.ibt_endbr_noseal")) ||
4432 !strncmp(sec->name, ".debug", 6) ||
4433 !strcmp(sec->name, ".altinstructions") ||
4434 !strcmp(sec->name, ".ibt_endbr_seal") ||
4435 !strcmp(sec->name, ".orc_unwind_ip") ||
4436 !strcmp(sec->name, ".parainstructions") ||
4437 !strcmp(sec->name, ".retpoline_sites") ||
4438 !strcmp(sec->name, ".smp_locks") ||
4439 !strcmp(sec->name, ".static_call_sites") ||
4440 !strcmp(sec->name, "_error_injection_whitelist") ||
4441 !strcmp(sec->name, "_kprobe_blacklist") ||
4442 !strcmp(sec->name, "__bug_table") ||
4443 !strcmp(sec->name, "__ex_table") ||
4444 !strcmp(sec->name, "__jump_table") ||
4445 !strcmp(sec->name, "__mcount_loc") ||
4446 !strcmp(sec->name, ".kcfi_traps") ||
4447 strstr(sec->name, "__patchable_function_entries"))
4450 for_each_reloc(sec->rsec, reloc)
4451 warnings += validate_ibt_data_reloc(file, reloc);
4457 static int validate_sls(struct objtool_file *file)
4459 struct instruction *insn, *next_insn;
4462 for_each_insn(file, insn) {
4463 next_insn = next_insn_same_sec(file, insn);
4465 if (insn->retpoline_safe)
4468 switch (insn->type) {
4470 if (!next_insn || next_insn->type != INSN_TRAP) {
4471 WARN_INSN(insn, "missing int3 after ret");
4476 case INSN_JUMP_DYNAMIC:
4477 if (!next_insn || next_insn->type != INSN_TRAP) {
4478 WARN_INSN(insn, "missing int3 after indirect jump");
4490 static bool ignore_noreturn_call(struct instruction *insn)
4492 struct symbol *call_dest = insn_call_dest(insn);
4495 * FIXME: hack, we need a real noreturn solution
4497 * Problem is, exc_double_fault() may or may not return, depending on
4498 * whether CONFIG_X86_ESPFIX64 is set. But objtool has no visibility
4499 * to the kernel config.
4501 * Other potential ways to fix it:
4503 * - have compiler communicate __noreturn functions somehow
4504 * - remove CONFIG_X86_ESPFIX64
4505 * - read the .config file
4506 * - add a cmdline option
4507 * - create a generic objtool annotation format (vs a bunch of custom
4508 * formats) and annotate it
4510 if (!strcmp(call_dest->name, "exc_double_fault")) {
4511 /* prevent further unreachable warnings for the caller */
4512 insn->sym->warned = 1;
4519 static int validate_reachable_instructions(struct objtool_file *file)
4521 struct instruction *insn, *prev_insn;
4522 struct symbol *call_dest;
4525 if (file->ignore_unreachables)
4528 for_each_insn(file, insn) {
4529 if (insn->visited || ignore_unreachable_insn(file, insn))
4532 prev_insn = prev_insn_same_sec(file, insn);
4533 if (prev_insn && prev_insn->dead_end) {
4534 call_dest = insn_call_dest(prev_insn);
4535 if (call_dest && !ignore_noreturn_call(prev_insn)) {
4536 WARN_INSN(insn, "%s() is missing a __noreturn annotation",
4543 WARN_INSN(insn, "unreachable instruction");
4550 /* 'funcs' is a space-separated list of function names */
4551 static int disas_funcs(const char *funcs)
4553 const char *objdump_str, *cross_compile;
4557 cross_compile = getenv("CROSS_COMPILE");
4559 objdump_str = "%sobjdump -wdr %s | gawk -M -v _funcs='%s' '"
4560 "BEGIN { split(_funcs, funcs); }"
4561 "/^$/ { func_match = 0; }"
4563 "f = gensub(/.*<(.*)>:/, \"\\\\1\", 1);"
4564 "for (i in funcs) {"
4565 "if (funcs[i] == f) {"
4567 "base = strtonum(\"0x\" $1);"
4574 "addr = strtonum(\"0x\" $1);"
4575 "printf(\"%%04x \", addr - base);"
4580 /* fake snprintf() to calculate the size */
4581 size = snprintf(NULL, 0, objdump_str, cross_compile, objname, funcs) + 1;
4583 WARN("objdump string size calculation failed");
4589 /* real snprintf() */
4590 snprintf(cmd, size, objdump_str, cross_compile, objname, funcs);
4593 WARN("disassembly failed: %d", ret);
4600 static int disas_warned_funcs(struct objtool_file *file)
4603 char *funcs = NULL, *tmp;
4605 for_each_sym(file, sym) {
4608 funcs = malloc(strlen(sym->name) + 1);
4609 strcpy(funcs, sym->name);
4611 tmp = malloc(strlen(funcs) + strlen(sym->name) + 2);
4612 sprintf(tmp, "%s %s", funcs, sym->name);
4627 struct insn_chunk *next;
4631 * Reduce peak RSS usage by freeing insns memory before writing the ELF file,
4632 * which can trigger more allocations for .debug_* sections whose data hasn't
4635 static void free_insns(struct objtool_file *file)
4637 struct instruction *insn;
4638 struct insn_chunk *chunks = NULL, *chunk;
4640 for_each_insn(file, insn) {
4642 chunk = malloc(sizeof(*chunk));
4644 chunk->next = chunks;
4649 for (chunk = chunks; chunk; chunk = chunk->next)
4653 int check(struct objtool_file *file)
4655 int ret, warnings = 0;
4657 arch_initial_func_cfi_state(&initial_func_cfi);
4658 init_cfi_state(&init_cfi);
4659 init_cfi_state(&func_cfi);
4660 set_func_state(&func_cfi);
4661 init_cfi_state(&force_undefined_cfi);
4662 force_undefined_cfi.force_undefined = true;
4664 if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
4667 cfi_hash_add(&init_cfi);
4668 cfi_hash_add(&func_cfi);
4670 ret = decode_sections(file);
4679 if (opts.retpoline) {
4680 ret = validate_retpoline(file);
4686 if (opts.stackval || opts.orc || opts.uaccess) {
4687 ret = validate_functions(file);
4692 ret = validate_unwind_hints(file, NULL);
4698 ret = validate_reachable_instructions(file);
4704 } else if (opts.noinstr) {
4705 ret = validate_noinstr_sections(file);
4713 * Must be after validate_branch() and friends, it plays
4714 * further games with insn->visited.
4716 ret = validate_unrets(file);
4723 ret = validate_ibt(file);
4730 ret = validate_sls(file);
4736 if (opts.static_call) {
4737 ret = create_static_call_sections(file);
4743 if (opts.retpoline) {
4744 ret = create_retpoline_sites_sections(file);
4751 ret = create_cfi_sections(file);
4758 ret = create_return_sites_sections(file);
4763 if (opts.hack_skylake) {
4764 ret = create_direct_call_sections(file);
4772 ret = create_mcount_loc_sections(file);
4779 ret = add_prefix_symbols(file);
4786 ret = create_ibt_endbr_seal_sections(file);
4792 if (opts.orc && nr_insns) {
4793 ret = orc_create(file);
4802 disas_warned_funcs(file);
4805 printf("nr_insns_visited: %ld\n", nr_insns_visited);
4806 printf("nr_cfi: %ld\n", nr_cfi);
4807 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
4808 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
4813 * For now, don't fail the kernel build on fatal warnings. These
4814 * errors are still fairly common due to the growing matrix of
4815 * supported toolchains and their recent pace of change.