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.h>
20 #include <linux/hashtable.h>
21 #include <linux/kernel.h>
22 #include <linux/static_call_types.h>
25 struct list_head list;
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;
36 struct instruction *find_insn(struct objtool_file *file,
37 struct section *sec, unsigned long offset)
39 struct instruction *insn;
41 hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
42 if (insn->sec == sec && insn->offset == offset)
49 static struct instruction *next_insn_same_sec(struct objtool_file *file,
50 struct instruction *insn)
52 struct instruction *next = list_next_entry(insn, list);
54 if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
60 static struct instruction *next_insn_same_func(struct objtool_file *file,
61 struct instruction *insn)
63 struct instruction *next = list_next_entry(insn, list);
64 struct symbol *func = insn->func;
69 if (&next->list != &file->insn_list && next->func == func)
72 /* Check if we're already in the subfunction: */
73 if (func == func->cfunc)
76 /* Move to the subfunction: */
77 return find_insn(file, func->cfunc->sec, func->cfunc->offset);
80 static struct instruction *prev_insn_same_sym(struct objtool_file *file,
81 struct instruction *insn)
83 struct instruction *prev = list_prev_entry(insn, list);
85 if (&prev->list != &file->insn_list && prev->func == insn->func)
91 #define func_for_each_insn(file, func, insn) \
92 for (insn = find_insn(file, func->sec, func->offset); \
94 insn = next_insn_same_func(file, insn))
96 #define sym_for_each_insn(file, sym, insn) \
97 for (insn = find_insn(file, sym->sec, sym->offset); \
98 insn && &insn->list != &file->insn_list && \
99 insn->sec == sym->sec && \
100 insn->offset < sym->offset + sym->len; \
101 insn = list_next_entry(insn, list))
103 #define sym_for_each_insn_continue_reverse(file, sym, insn) \
104 for (insn = list_prev_entry(insn, list); \
105 &insn->list != &file->insn_list && \
106 insn->sec == sym->sec && insn->offset >= sym->offset; \
107 insn = list_prev_entry(insn, list))
109 #define sec_for_each_insn_from(file, insn) \
110 for (; insn; insn = next_insn_same_sec(file, insn))
112 #define sec_for_each_insn_continue(file, insn) \
113 for (insn = next_insn_same_sec(file, insn); insn; \
114 insn = next_insn_same_sec(file, insn))
116 static bool is_jump_table_jump(struct instruction *insn)
118 struct alt_group *alt_group = insn->alt_group;
120 if (insn->jump_table)
123 /* Retpoline alternative for a jump table? */
124 return alt_group && alt_group->orig_group &&
125 alt_group->orig_group->first_insn->jump_table;
128 static bool is_sibling_call(struct instruction *insn)
131 * Assume only ELF functions can make sibling calls. This ensures
132 * sibling call detection consistency between vmlinux.o and individual
138 /* An indirect jump is either a sibling call or a jump to a table. */
139 if (insn->type == INSN_JUMP_DYNAMIC)
140 return !is_jump_table_jump(insn);
142 /* add_jump_destinations() sets insn->call_dest for sibling calls. */
143 return (is_static_jump(insn) && insn->call_dest);
147 * This checks to see if the given function is a "noreturn" function.
149 * For global functions which are outside the scope of this object file, we
150 * have to keep a manual list of them.
152 * For local functions, we have to detect them manually by simply looking for
153 * the lack of a return instruction.
155 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
159 struct instruction *insn;
163 * Unfortunately these have to be hard coded because the noreturn
164 * attribute isn't provided in ELF data.
166 static const char * const global_noreturns[] = {
173 "__module_put_and_kthread_exit",
174 "kthread_complete_and_exit",
179 "machine_real_restart",
180 "rewind_stack_and_make_dead",
181 "kunit_try_catch_throw",
183 "cpu_bringup_and_idle",
192 if (func->bind == STB_WEAK)
195 if (func->bind == STB_GLOBAL)
196 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
197 if (!strcmp(func->name, global_noreturns[i]))
203 insn = find_insn(file, func->sec, func->offset);
207 func_for_each_insn(file, func, insn) {
210 if (insn->type == INSN_RETURN)
218 * A function can have a sibling call instead of a return. In that
219 * case, the function's dead-end status depends on whether the target
220 * of the sibling call returns.
222 func_for_each_insn(file, func, insn) {
223 if (is_sibling_call(insn)) {
224 struct instruction *dest = insn->jump_dest;
227 /* sibling call to another file */
230 /* local sibling call */
231 if (recursion == 5) {
233 * Infinite recursion: two functions have
234 * sibling calls to each other. This is a very
235 * rare case. It means they aren't dead ends.
240 return __dead_end_function(file, dest->func, recursion+1);
247 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
249 return __dead_end_function(file, func, 0);
252 static void init_cfi_state(struct cfi_state *cfi)
256 for (i = 0; i < CFI_NUM_REGS; i++) {
257 cfi->regs[i].base = CFI_UNDEFINED;
258 cfi->vals[i].base = CFI_UNDEFINED;
260 cfi->cfa.base = CFI_UNDEFINED;
261 cfi->drap_reg = CFI_UNDEFINED;
262 cfi->drap_offset = -1;
265 static void init_insn_state(struct insn_state *state, struct section *sec)
267 memset(state, 0, sizeof(*state));
268 init_cfi_state(&state->cfi);
271 * We need the full vmlinux for noinstr validation, otherwise we can
272 * not correctly determine insn->call_dest->sec (external symbols do
273 * not have a section).
275 if (vmlinux && noinstr && sec)
276 state->noinstr = sec->noinstr;
279 static struct cfi_state *cfi_alloc(void)
281 struct cfi_state *cfi = calloc(sizeof(struct cfi_state), 1);
283 WARN("calloc failed");
291 static struct hlist_head *cfi_hash;
293 static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
295 return memcmp((void *)cfi1 + sizeof(cfi1->hash),
296 (void *)cfi2 + sizeof(cfi2->hash),
297 sizeof(struct cfi_state) - sizeof(struct hlist_node));
300 static inline u32 cfi_key(struct cfi_state *cfi)
302 return jhash((void *)cfi + sizeof(cfi->hash),
303 sizeof(*cfi) - sizeof(cfi->hash), 0);
306 static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
308 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
309 struct cfi_state *obj;
311 hlist_for_each_entry(obj, head, hash) {
312 if (!cficmp(cfi, obj)) {
320 hlist_add_head(&obj->hash, head);
325 static void cfi_hash_add(struct cfi_state *cfi)
327 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
329 hlist_add_head(&cfi->hash, head);
332 static void *cfi_hash_alloc(unsigned long size)
334 cfi_bits = max(10, ilog2(size));
335 cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
336 PROT_READ|PROT_WRITE,
337 MAP_PRIVATE|MAP_ANON, -1, 0);
338 if (cfi_hash == (void *)-1L) {
339 WARN("mmap fail cfi_hash");
342 printf("cfi_bits: %d\n", cfi_bits);
348 static unsigned long nr_insns;
349 static unsigned long nr_insns_visited;
352 * Call the arch-specific instruction decoder for all the instructions and add
353 * them to the global instruction list.
355 static int decode_instructions(struct objtool_file *file)
359 unsigned long offset;
360 struct instruction *insn;
363 for_each_sec(file, sec) {
365 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
368 if (strcmp(sec->name, ".altinstr_replacement") &&
369 strcmp(sec->name, ".altinstr_aux") &&
370 strncmp(sec->name, ".discard.", 9))
373 if (!strcmp(sec->name, ".noinstr.text") ||
374 !strcmp(sec->name, ".entry.text"))
377 for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
378 insn = malloc(sizeof(*insn));
380 WARN("malloc failed");
383 memset(insn, 0, sizeof(*insn));
384 INIT_LIST_HEAD(&insn->alts);
385 INIT_LIST_HEAD(&insn->stack_ops);
386 INIT_LIST_HEAD(&insn->call_node);
389 insn->offset = offset;
391 ret = arch_decode_instruction(file, sec, offset,
392 sec->sh.sh_size - offset,
393 &insn->len, &insn->type,
400 * By default, "ud2" is a dead end unless otherwise
401 * annotated, because GCC 7 inserts it for certain
402 * divide-by-zero cases.
404 if (insn->type == INSN_BUG)
405 insn->dead_end = true;
407 hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
408 list_add_tail(&insn->list, &file->insn_list);
412 list_for_each_entry(func, &sec->symbol_list, list) {
413 if (func->type != STT_FUNC || func->alias != func)
416 if (!find_insn(file, sec, func->offset)) {
417 WARN("%s(): can't find starting instruction",
422 sym_for_each_insn(file, func, insn) {
424 if (insn->type == INSN_ENDBR && list_empty(&insn->call_node)) {
425 if (insn->offset == insn->func->offset) {
426 list_add_tail(&insn->call_node, &file->endbr_list);
429 file->nr_endbr_int++;
437 printf("nr_insns: %lu\n", nr_insns);
447 * Read the pv_ops[] .data table to find the static initialized values.
449 static int add_pv_ops(struct objtool_file *file, const char *symname)
451 struct symbol *sym, *func;
452 unsigned long off, end;
456 sym = find_symbol_by_name(file->elf, symname);
461 end = off + sym->len;
463 rel = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off);
468 if (func->type == STT_SECTION)
469 func = find_symbol_by_offset(rel->sym->sec, rel->addend);
471 idx = (rel->offset - sym->offset) / sizeof(unsigned long);
473 objtool_pv_add(file, idx, func);
475 off = rel->offset + 1;
484 * Allocate and initialize file->pv_ops[].
486 static int init_pv_ops(struct objtool_file *file)
488 static const char *pv_ops_tables[] = {
504 sym = find_symbol_by_name(file->elf, "pv_ops");
508 nr = sym->len / sizeof(unsigned long);
509 file->pv_ops = calloc(sizeof(struct pv_state), nr);
513 for (idx = 0; idx < nr; idx++)
514 INIT_LIST_HEAD(&file->pv_ops[idx].targets);
516 for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++)
517 add_pv_ops(file, pv_ops);
522 static struct instruction *find_last_insn(struct objtool_file *file,
525 struct instruction *insn = NULL;
527 unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
529 for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
530 insn = find_insn(file, sec, offset);
536 * Mark "ud2" instructions and manually annotated dead ends.
538 static int add_dead_ends(struct objtool_file *file)
542 struct instruction *insn;
545 * Check for manually annotated dead ends.
547 sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
551 list_for_each_entry(reloc, &sec->reloc_list, list) {
552 if (reloc->sym->type != STT_SECTION) {
553 WARN("unexpected relocation symbol type in %s", sec->name);
556 insn = find_insn(file, reloc->sym->sec, reloc->addend);
558 insn = list_prev_entry(insn, list);
559 else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
560 insn = find_last_insn(file, reloc->sym->sec);
562 WARN("can't find unreachable insn at %s+0x%x",
563 reloc->sym->sec->name, reloc->addend);
567 WARN("can't find unreachable insn at %s+0x%x",
568 reloc->sym->sec->name, reloc->addend);
572 insn->dead_end = true;
577 * These manually annotated reachable checks are needed for GCC 4.4,
578 * where the Linux unreachable() macro isn't supported. In that case
579 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
582 sec = find_section_by_name(file->elf, ".rela.discard.reachable");
586 list_for_each_entry(reloc, &sec->reloc_list, list) {
587 if (reloc->sym->type != STT_SECTION) {
588 WARN("unexpected relocation symbol type in %s", sec->name);
591 insn = find_insn(file, reloc->sym->sec, reloc->addend);
593 insn = list_prev_entry(insn, list);
594 else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
595 insn = find_last_insn(file, reloc->sym->sec);
597 WARN("can't find reachable insn at %s+0x%x",
598 reloc->sym->sec->name, reloc->addend);
602 WARN("can't find reachable insn at %s+0x%x",
603 reloc->sym->sec->name, reloc->addend);
607 insn->dead_end = false;
613 static int create_static_call_sections(struct objtool_file *file)
616 struct static_call_site *site;
617 struct instruction *insn;
618 struct symbol *key_sym;
619 char *key_name, *tmp;
622 sec = find_section_by_name(file->elf, ".static_call_sites");
624 INIT_LIST_HEAD(&file->static_call_list);
625 WARN("file already has .static_call_sites section, skipping");
629 if (list_empty(&file->static_call_list))
633 list_for_each_entry(insn, &file->static_call_list, call_node)
636 sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE,
637 sizeof(struct static_call_site), idx);
642 list_for_each_entry(insn, &file->static_call_list, call_node) {
644 site = (struct static_call_site *)sec->data->d_buf + idx;
645 memset(site, 0, sizeof(struct static_call_site));
647 /* populate reloc for 'addr' */
648 if (elf_add_reloc_to_insn(file->elf, sec,
649 idx * sizeof(struct static_call_site),
651 insn->sec, insn->offset))
654 /* find key symbol */
655 key_name = strdup(insn->call_dest->name);
660 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
661 STATIC_CALL_TRAMP_PREFIX_LEN)) {
662 WARN("static_call: trampoline name malformed: %s", key_name);
665 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
666 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
668 key_sym = find_symbol_by_name(file->elf, tmp);
671 WARN("static_call: can't find static_call_key symbol: %s", tmp);
676 * For modules(), the key might not be exported, which
677 * means the module can make static calls but isn't
678 * allowed to change them.
680 * In that case we temporarily set the key to be the
681 * trampoline address. This is fixed up in
682 * static_call_add_module().
684 key_sym = insn->call_dest;
688 /* populate reloc for 'key' */
689 if (elf_add_reloc(file->elf, sec,
690 idx * sizeof(struct static_call_site) + 4,
691 R_X86_64_PC32, key_sym,
692 is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
701 static int create_retpoline_sites_sections(struct objtool_file *file)
703 struct instruction *insn;
707 sec = find_section_by_name(file->elf, ".retpoline_sites");
709 WARN("file already has .retpoline_sites, skipping");
714 list_for_each_entry(insn, &file->retpoline_call_list, call_node)
720 sec = elf_create_section(file->elf, ".retpoline_sites", 0,
723 WARN("elf_create_section: .retpoline_sites");
728 list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
730 int *site = (int *)sec->data->d_buf + idx;
733 if (elf_add_reloc_to_insn(file->elf, sec,
736 insn->sec, insn->offset)) {
737 WARN("elf_add_reloc_to_insn: .retpoline_sites");
747 static int create_ibt_endbr_seal_sections(struct objtool_file *file)
749 struct instruction *insn;
753 sec = find_section_by_name(file->elf, ".ibt_endbr_seal");
755 WARN("file already has .ibt_endbr_seal, skipping");
760 list_for_each_entry(insn, &file->endbr_list, call_node)
764 printf("ibt: ENDBR at function start: %d\n", file->nr_endbr);
765 printf("ibt: ENDBR inside functions: %d\n", file->nr_endbr_int);
766 printf("ibt: superfluous ENDBR: %d\n", idx);
772 sec = elf_create_section(file->elf, ".ibt_endbr_seal", 0,
775 WARN("elf_create_section: .ibt_endbr_seal");
780 list_for_each_entry(insn, &file->endbr_list, call_node) {
782 int *site = (int *)sec->data->d_buf + idx;
785 if (elf_add_reloc_to_insn(file->elf, sec,
788 insn->sec, insn->offset)) {
789 WARN("elf_add_reloc_to_insn: .ibt_endbr_seal");
799 static int create_mcount_loc_sections(struct objtool_file *file)
803 struct instruction *insn;
806 sec = find_section_by_name(file->elf, "__mcount_loc");
808 INIT_LIST_HEAD(&file->mcount_loc_list);
809 WARN("file already has __mcount_loc section, skipping");
813 if (list_empty(&file->mcount_loc_list))
817 list_for_each_entry(insn, &file->mcount_loc_list, call_node)
820 sec = elf_create_section(file->elf, "__mcount_loc", 0, sizeof(unsigned long), idx);
825 list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
827 loc = (unsigned long *)sec->data->d_buf + idx;
828 memset(loc, 0, sizeof(unsigned long));
830 if (elf_add_reloc_to_insn(file->elf, sec,
831 idx * sizeof(unsigned long),
833 insn->sec, insn->offset))
843 * Warnings shouldn't be reported for ignored functions.
845 static void add_ignores(struct objtool_file *file)
847 struct instruction *insn;
852 sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
856 list_for_each_entry(reloc, &sec->reloc_list, list) {
857 switch (reloc->sym->type) {
863 func = find_func_by_offset(reloc->sym->sec, reloc->addend);
869 WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type);
873 func_for_each_insn(file, func, insn)
879 * This is a whitelist of functions that is allowed to be called with AC set.
880 * The list is meant to be minimal and only contains compiler instrumentation
881 * ABI and a few functions used to implement *_{to,from}_user() functions.
883 * These functions must not directly change AC, but may PUSHF/POPF.
885 static const char *uaccess_safe_builtin[] = {
889 /* KASAN out-of-line */
890 "__asan_loadN_noabort",
891 "__asan_load1_noabort",
892 "__asan_load2_noabort",
893 "__asan_load4_noabort",
894 "__asan_load8_noabort",
895 "__asan_load16_noabort",
896 "__asan_storeN_noabort",
897 "__asan_store1_noabort",
898 "__asan_store2_noabort",
899 "__asan_store4_noabort",
900 "__asan_store8_noabort",
901 "__asan_store16_noabort",
902 "__kasan_check_read",
903 "__kasan_check_write",
905 "__asan_report_load_n_noabort",
906 "__asan_report_load1_noabort",
907 "__asan_report_load2_noabort",
908 "__asan_report_load4_noabort",
909 "__asan_report_load8_noabort",
910 "__asan_report_load16_noabort",
911 "__asan_report_store_n_noabort",
912 "__asan_report_store1_noabort",
913 "__asan_report_store2_noabort",
914 "__asan_report_store4_noabort",
915 "__asan_report_store8_noabort",
916 "__asan_report_store16_noabort",
918 "__kcsan_check_access",
923 "kcsan_found_watchpoint",
924 "kcsan_setup_watchpoint",
925 "kcsan_check_scoped_accesses",
926 "kcsan_disable_current",
927 "kcsan_enable_current_nowarn",
932 "__tsan_write_range",
943 "__tsan_read_write1",
944 "__tsan_read_write2",
945 "__tsan_read_write4",
946 "__tsan_read_write8",
947 "__tsan_read_write16",
948 "__tsan_atomic8_load",
949 "__tsan_atomic16_load",
950 "__tsan_atomic32_load",
951 "__tsan_atomic64_load",
952 "__tsan_atomic8_store",
953 "__tsan_atomic16_store",
954 "__tsan_atomic32_store",
955 "__tsan_atomic64_store",
956 "__tsan_atomic8_exchange",
957 "__tsan_atomic16_exchange",
958 "__tsan_atomic32_exchange",
959 "__tsan_atomic64_exchange",
960 "__tsan_atomic8_fetch_add",
961 "__tsan_atomic16_fetch_add",
962 "__tsan_atomic32_fetch_add",
963 "__tsan_atomic64_fetch_add",
964 "__tsan_atomic8_fetch_sub",
965 "__tsan_atomic16_fetch_sub",
966 "__tsan_atomic32_fetch_sub",
967 "__tsan_atomic64_fetch_sub",
968 "__tsan_atomic8_fetch_and",
969 "__tsan_atomic16_fetch_and",
970 "__tsan_atomic32_fetch_and",
971 "__tsan_atomic64_fetch_and",
972 "__tsan_atomic8_fetch_or",
973 "__tsan_atomic16_fetch_or",
974 "__tsan_atomic32_fetch_or",
975 "__tsan_atomic64_fetch_or",
976 "__tsan_atomic8_fetch_xor",
977 "__tsan_atomic16_fetch_xor",
978 "__tsan_atomic32_fetch_xor",
979 "__tsan_atomic64_fetch_xor",
980 "__tsan_atomic8_fetch_nand",
981 "__tsan_atomic16_fetch_nand",
982 "__tsan_atomic32_fetch_nand",
983 "__tsan_atomic64_fetch_nand",
984 "__tsan_atomic8_compare_exchange_strong",
985 "__tsan_atomic16_compare_exchange_strong",
986 "__tsan_atomic32_compare_exchange_strong",
987 "__tsan_atomic64_compare_exchange_strong",
988 "__tsan_atomic8_compare_exchange_weak",
989 "__tsan_atomic16_compare_exchange_weak",
990 "__tsan_atomic32_compare_exchange_weak",
991 "__tsan_atomic64_compare_exchange_weak",
992 "__tsan_atomic8_compare_exchange_val",
993 "__tsan_atomic16_compare_exchange_val",
994 "__tsan_atomic32_compare_exchange_val",
995 "__tsan_atomic64_compare_exchange_val",
996 "__tsan_atomic_thread_fence",
997 "__tsan_atomic_signal_fence",
1001 "__sanitizer_cov_trace_pc",
1002 "__sanitizer_cov_trace_const_cmp1",
1003 "__sanitizer_cov_trace_const_cmp2",
1004 "__sanitizer_cov_trace_const_cmp4",
1005 "__sanitizer_cov_trace_const_cmp8",
1006 "__sanitizer_cov_trace_cmp1",
1007 "__sanitizer_cov_trace_cmp2",
1008 "__sanitizer_cov_trace_cmp4",
1009 "__sanitizer_cov_trace_cmp8",
1010 "__sanitizer_cov_trace_switch",
1012 "ubsan_type_mismatch_common",
1013 "__ubsan_handle_type_mismatch",
1014 "__ubsan_handle_type_mismatch_v1",
1015 "__ubsan_handle_shift_out_of_bounds",
1017 "csum_partial_copy_generic",
1019 "copy_mc_fragile_handle_tail",
1020 "copy_mc_enhanced_fast_string",
1021 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
1025 static void add_uaccess_safe(struct objtool_file *file)
1027 struct symbol *func;
1033 for (name = uaccess_safe_builtin; *name; name++) {
1034 func = find_symbol_by_name(file->elf, *name);
1038 func->uaccess_safe = true;
1043 * FIXME: For now, just ignore any alternatives which add retpolines. This is
1044 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
1045 * But it at least allows objtool to understand the control flow *around* the
1048 static int add_ignore_alternatives(struct objtool_file *file)
1050 struct section *sec;
1051 struct reloc *reloc;
1052 struct instruction *insn;
1054 sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
1058 list_for_each_entry(reloc, &sec->reloc_list, list) {
1059 if (reloc->sym->type != STT_SECTION) {
1060 WARN("unexpected relocation symbol type in %s", sec->name);
1064 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1066 WARN("bad .discard.ignore_alts entry");
1070 insn->ignore_alts = true;
1076 __weak bool arch_is_retpoline(struct symbol *sym)
1081 #define NEGATIVE_RELOC ((void *)-1L)
1083 static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
1085 if (insn->reloc == NEGATIVE_RELOC)
1092 insn->reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1093 insn->offset, insn->len);
1095 insn->reloc = NEGATIVE_RELOC;
1103 static void remove_insn_ops(struct instruction *insn)
1105 struct stack_op *op, *tmp;
1107 list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
1108 list_del(&op->list);
1113 static void annotate_call_site(struct objtool_file *file,
1114 struct instruction *insn, bool sibling)
1116 struct reloc *reloc = insn_reloc(file, insn);
1117 struct symbol *sym = insn->call_dest;
1123 * Alternative replacement code is just template code which is
1124 * sometimes copied to the original instruction. For now, don't
1125 * annotate it. (In the future we might consider annotating the
1126 * original instruction if/when it ever makes sense to do so.)
1128 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1131 if (sym->static_call_tramp) {
1132 list_add_tail(&insn->call_node, &file->static_call_list);
1136 if (sym->retpoline_thunk) {
1137 list_add_tail(&insn->call_node, &file->retpoline_call_list);
1142 * Many compilers cannot disable KCOV or sanitizer calls with a function
1143 * attribute so they need a little help, NOP out any such calls from
1146 if (insn->sec->noinstr && sym->profiling_func) {
1148 reloc->type = R_NONE;
1149 elf_write_reloc(file->elf, reloc);
1152 elf_write_insn(file->elf, insn->sec,
1153 insn->offset, insn->len,
1154 sibling ? arch_ret_insn(insn->len)
1155 : arch_nop_insn(insn->len));
1157 insn->type = sibling ? INSN_RETURN : INSN_NOP;
1161 * We've replaced the tail-call JMP insn by two new
1162 * insn: RET; INT3, except we only have a single struct
1163 * insn here. Mark it retpoline_safe to avoid the SLS
1164 * warning, instead of adding another insn.
1166 insn->retpoline_safe = true;
1172 if (mcount && sym->fentry) {
1174 WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset);
1177 reloc->type = R_NONE;
1178 elf_write_reloc(file->elf, reloc);
1181 elf_write_insn(file->elf, insn->sec,
1182 insn->offset, insn->len,
1183 arch_nop_insn(insn->len));
1185 insn->type = INSN_NOP;
1187 list_add_tail(&insn->call_node, &file->mcount_loc_list);
1191 if (!sibling && dead_end_function(file, sym))
1192 insn->dead_end = true;
1195 static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1196 struct symbol *dest, bool sibling)
1198 insn->call_dest = dest;
1203 * Whatever stack impact regular CALLs have, should be undone
1204 * by the RETURN of the called function.
1206 * Annotated intra-function calls retain the stack_ops but
1207 * are converted to JUMP, see read_intra_function_calls().
1209 remove_insn_ops(insn);
1211 annotate_call_site(file, insn, sibling);
1214 static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1217 * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1218 * so convert them accordingly.
1220 switch (insn->type) {
1222 insn->type = INSN_CALL_DYNAMIC;
1224 case INSN_JUMP_UNCONDITIONAL:
1225 insn->type = INSN_JUMP_DYNAMIC;
1227 case INSN_JUMP_CONDITIONAL:
1228 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1234 insn->retpoline_safe = true;
1237 * Whatever stack impact regular CALLs have, should be undone
1238 * by the RETURN of the called function.
1240 * Annotated intra-function calls retain the stack_ops but
1241 * are converted to JUMP, see read_intra_function_calls().
1243 remove_insn_ops(insn);
1245 annotate_call_site(file, insn, false);
1248 static bool same_function(struct instruction *insn1, struct instruction *insn2)
1250 return insn1->func->pfunc == insn2->func->pfunc;
1253 static bool is_first_func_insn(struct objtool_file *file, struct instruction *insn)
1255 if (insn->offset == insn->func->offset)
1259 struct instruction *prev = prev_insn_same_sym(file, insn);
1261 if (prev && prev->type == INSN_ENDBR &&
1262 insn->offset == insn->func->offset + prev->len)
1270 * Find the destination instructions for all jumps.
1272 static int add_jump_destinations(struct objtool_file *file)
1274 struct instruction *insn;
1275 struct reloc *reloc;
1276 struct section *dest_sec;
1277 unsigned long dest_off;
1279 for_each_insn(file, insn) {
1280 if (!is_static_jump(insn))
1283 reloc = insn_reloc(file, insn);
1285 dest_sec = insn->sec;
1286 dest_off = arch_jump_destination(insn);
1287 } else if (reloc->sym->type == STT_SECTION) {
1288 dest_sec = reloc->sym->sec;
1289 dest_off = arch_dest_reloc_offset(reloc->addend);
1290 } else if (reloc->sym->retpoline_thunk) {
1291 add_retpoline_call(file, insn);
1293 } else if (insn->func) {
1294 /* internal or external sibling call (with reloc) */
1295 add_call_dest(file, insn, reloc->sym, true);
1297 } else if (reloc->sym->sec->idx) {
1298 dest_sec = reloc->sym->sec;
1299 dest_off = reloc->sym->sym.st_value +
1300 arch_dest_reloc_offset(reloc->addend);
1302 /* non-func asm code jumping to another file */
1306 insn->jump_dest = find_insn(file, dest_sec, dest_off);
1307 if (!insn->jump_dest) {
1310 * This is a special case where an alt instruction
1311 * jumps past the end of the section. These are
1312 * handled later in handle_group_alt().
1314 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1317 WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
1318 insn->sec, insn->offset, dest_sec->name,
1324 * Cross-function jump.
1326 if (insn->func && insn->jump_dest->func &&
1327 insn->func != insn->jump_dest->func) {
1330 * For GCC 8+, create parent/child links for any cold
1331 * subfunctions. This is _mostly_ redundant with a
1332 * similar initialization in read_symbols().
1334 * If a function has aliases, we want the *first* such
1335 * function in the symbol table to be the subfunction's
1336 * parent. In that case we overwrite the
1337 * initialization done in read_symbols().
1339 * However this code can't completely replace the
1340 * read_symbols() code because this doesn't detect the
1341 * case where the parent function's only reference to a
1342 * subfunction is through a jump table.
1344 if (!strstr(insn->func->name, ".cold") &&
1345 strstr(insn->jump_dest->func->name, ".cold")) {
1346 insn->func->cfunc = insn->jump_dest->func;
1347 insn->jump_dest->func->pfunc = insn->func;
1349 } else if (!same_function(insn, insn->jump_dest) &&
1350 is_first_func_insn(file, insn->jump_dest)) {
1351 /* internal sibling call (without reloc) */
1352 add_call_dest(file, insn, insn->jump_dest->func, true);
1360 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1362 struct symbol *call_dest;
1364 call_dest = find_func_by_offset(sec, offset);
1366 call_dest = find_symbol_by_offset(sec, offset);
1372 * Find the destination instructions for all calls.
1374 static int add_call_destinations(struct objtool_file *file)
1376 struct instruction *insn;
1377 unsigned long dest_off;
1378 struct symbol *dest;
1379 struct reloc *reloc;
1381 for_each_insn(file, insn) {
1382 if (insn->type != INSN_CALL)
1385 reloc = insn_reloc(file, insn);
1387 dest_off = arch_jump_destination(insn);
1388 dest = find_call_destination(insn->sec, dest_off);
1390 add_call_dest(file, insn, dest, false);
1395 if (!insn->call_dest) {
1396 WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);
1400 if (insn->func && insn->call_dest->type != STT_FUNC) {
1401 WARN_FUNC("unsupported call to non-function",
1402 insn->sec, insn->offset);
1406 } else if (reloc->sym->type == STT_SECTION) {
1407 dest_off = arch_dest_reloc_offset(reloc->addend);
1408 dest = find_call_destination(reloc->sym->sec, dest_off);
1410 WARN_FUNC("can't find call dest symbol at %s+0x%lx",
1411 insn->sec, insn->offset,
1412 reloc->sym->sec->name,
1417 add_call_dest(file, insn, dest, false);
1419 } else if (reloc->sym->retpoline_thunk) {
1420 add_retpoline_call(file, insn);
1423 add_call_dest(file, insn, reloc->sym, false);
1430 * The .alternatives section requires some extra special care over and above
1431 * other special sections because alternatives are patched in place.
1433 static int handle_group_alt(struct objtool_file *file,
1434 struct special_alt *special_alt,
1435 struct instruction *orig_insn,
1436 struct instruction **new_insn)
1438 struct instruction *last_orig_insn, *last_new_insn = NULL, *insn, *nop = NULL;
1439 struct alt_group *orig_alt_group, *new_alt_group;
1440 unsigned long dest_off;
1443 orig_alt_group = malloc(sizeof(*orig_alt_group));
1444 if (!orig_alt_group) {
1445 WARN("malloc failed");
1448 orig_alt_group->cfi = calloc(special_alt->orig_len,
1449 sizeof(struct cfi_state *));
1450 if (!orig_alt_group->cfi) {
1451 WARN("calloc failed");
1455 last_orig_insn = NULL;
1457 sec_for_each_insn_from(file, insn) {
1458 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1461 insn->alt_group = orig_alt_group;
1462 last_orig_insn = insn;
1464 orig_alt_group->orig_group = NULL;
1465 orig_alt_group->first_insn = orig_insn;
1466 orig_alt_group->last_insn = last_orig_insn;
1469 new_alt_group = malloc(sizeof(*new_alt_group));
1470 if (!new_alt_group) {
1471 WARN("malloc failed");
1475 if (special_alt->new_len < special_alt->orig_len) {
1477 * Insert a fake nop at the end to make the replacement
1478 * alt_group the same size as the original. This is needed to
1479 * allow propagate_alt_cfi() to do its magic. When the last
1480 * instruction affects the stack, the instruction after it (the
1481 * nop) will propagate the new state to the shared CFI array.
1483 nop = malloc(sizeof(*nop));
1485 WARN("malloc failed");
1488 memset(nop, 0, sizeof(*nop));
1489 INIT_LIST_HEAD(&nop->alts);
1490 INIT_LIST_HEAD(&nop->stack_ops);
1492 nop->sec = special_alt->new_sec;
1493 nop->offset = special_alt->new_off + special_alt->new_len;
1494 nop->len = special_alt->orig_len - special_alt->new_len;
1495 nop->type = INSN_NOP;
1496 nop->func = orig_insn->func;
1497 nop->alt_group = new_alt_group;
1498 nop->ignore = orig_insn->ignore_alts;
1501 if (!special_alt->new_len) {
1507 sec_for_each_insn_from(file, insn) {
1508 struct reloc *alt_reloc;
1510 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1513 last_new_insn = insn;
1515 insn->ignore = orig_insn->ignore_alts;
1516 insn->func = orig_insn->func;
1517 insn->alt_group = new_alt_group;
1520 * Since alternative replacement code is copy/pasted by the
1521 * kernel after applying relocations, generally such code can't
1522 * have relative-address relocation references to outside the
1523 * .altinstr_replacement section, unless the arch's
1524 * alternatives code can adjust the relative offsets
1527 alt_reloc = insn_reloc(file, insn);
1529 !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1531 WARN_FUNC("unsupported relocation in alternatives section",
1532 insn->sec, insn->offset);
1536 if (!is_static_jump(insn))
1539 if (!insn->immediate)
1542 dest_off = arch_jump_destination(insn);
1543 if (dest_off == special_alt->new_off + special_alt->new_len)
1544 insn->jump_dest = next_insn_same_sec(file, last_orig_insn);
1546 if (!insn->jump_dest) {
1547 WARN_FUNC("can't find alternative jump destination",
1548 insn->sec, insn->offset);
1553 if (!last_new_insn) {
1554 WARN_FUNC("can't find last new alternative instruction",
1555 special_alt->new_sec, special_alt->new_off);
1560 list_add(&nop->list, &last_new_insn->list);
1562 new_alt_group->orig_group = orig_alt_group;
1563 new_alt_group->first_insn = *new_insn;
1564 new_alt_group->last_insn = nop ? : last_new_insn;
1565 new_alt_group->cfi = orig_alt_group->cfi;
1570 * A jump table entry can either convert a nop to a jump or a jump to a nop.
1571 * If the original instruction is a jump, make the alt entry an effective nop
1572 * by just skipping the original instruction.
1574 static int handle_jump_alt(struct objtool_file *file,
1575 struct special_alt *special_alt,
1576 struct instruction *orig_insn,
1577 struct instruction **new_insn)
1579 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1580 orig_insn->type != INSN_NOP) {
1582 WARN_FUNC("unsupported instruction at jump label",
1583 orig_insn->sec, orig_insn->offset);
1587 if (special_alt->key_addend & 2) {
1588 struct reloc *reloc = insn_reloc(file, orig_insn);
1591 reloc->type = R_NONE;
1592 elf_write_reloc(file->elf, reloc);
1594 elf_write_insn(file->elf, orig_insn->sec,
1595 orig_insn->offset, orig_insn->len,
1596 arch_nop_insn(orig_insn->len));
1597 orig_insn->type = INSN_NOP;
1600 if (orig_insn->type == INSN_NOP) {
1601 if (orig_insn->len == 2)
1602 file->jl_nop_short++;
1604 file->jl_nop_long++;
1609 if (orig_insn->len == 2)
1614 *new_insn = list_next_entry(orig_insn, list);
1619 * Read all the special sections which have alternate instructions which can be
1620 * patched in or redirected to at runtime. Each instruction having alternate
1621 * instruction(s) has them added to its insn->alts list, which will be
1622 * traversed in validate_branch().
1624 static int add_special_section_alts(struct objtool_file *file)
1626 struct list_head special_alts;
1627 struct instruction *orig_insn, *new_insn;
1628 struct special_alt *special_alt, *tmp;
1629 struct alternative *alt;
1632 ret = special_get_alts(file->elf, &special_alts);
1636 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1638 orig_insn = find_insn(file, special_alt->orig_sec,
1639 special_alt->orig_off);
1641 WARN_FUNC("special: can't find orig instruction",
1642 special_alt->orig_sec, special_alt->orig_off);
1648 if (!special_alt->group || special_alt->new_len) {
1649 new_insn = find_insn(file, special_alt->new_sec,
1650 special_alt->new_off);
1652 WARN_FUNC("special: can't find new instruction",
1653 special_alt->new_sec,
1654 special_alt->new_off);
1660 if (special_alt->group) {
1661 if (!special_alt->orig_len) {
1662 WARN_FUNC("empty alternative entry",
1663 orig_insn->sec, orig_insn->offset);
1667 ret = handle_group_alt(file, special_alt, orig_insn,
1671 } else if (special_alt->jump_or_nop) {
1672 ret = handle_jump_alt(file, special_alt, orig_insn,
1678 alt = malloc(sizeof(*alt));
1680 WARN("malloc failed");
1685 alt->insn = new_insn;
1686 alt->skip_orig = special_alt->skip_orig;
1687 orig_insn->ignore_alts |= special_alt->skip_alt;
1688 list_add_tail(&alt->list, &orig_insn->alts);
1690 list_del(&special_alt->list);
1695 printf("jl\\\tNOP\tJMP\n");
1696 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
1697 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
1704 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
1705 struct reloc *table)
1707 struct reloc *reloc = table;
1708 struct instruction *dest_insn;
1709 struct alternative *alt;
1710 struct symbol *pfunc = insn->func->pfunc;
1711 unsigned int prev_offset = 0;
1714 * Each @reloc is a switch table relocation which points to the target
1717 list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
1719 /* Check for the end of the table: */
1720 if (reloc != table && reloc->jump_table_start)
1723 /* Make sure the table entries are consecutive: */
1724 if (prev_offset && reloc->offset != prev_offset + 8)
1727 /* Detect function pointers from contiguous objects: */
1728 if (reloc->sym->sec == pfunc->sec &&
1729 reloc->addend == pfunc->offset)
1732 dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
1736 /* Make sure the destination is in the same function: */
1737 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
1740 alt = malloc(sizeof(*alt));
1742 WARN("malloc failed");
1746 alt->insn = dest_insn;
1747 list_add_tail(&alt->list, &insn->alts);
1748 prev_offset = reloc->offset;
1752 WARN_FUNC("can't find switch jump table",
1753 insn->sec, insn->offset);
1761 * find_jump_table() - Given a dynamic jump, find the switch jump table
1762 * associated with it.
1764 static struct reloc *find_jump_table(struct objtool_file *file,
1765 struct symbol *func,
1766 struct instruction *insn)
1768 struct reloc *table_reloc;
1769 struct instruction *dest_insn, *orig_insn = insn;
1772 * Backward search using the @first_jump_src links, these help avoid
1773 * much of the 'in between' code. Which avoids us getting confused by
1777 insn && insn->func && insn->func->pfunc == func;
1778 insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
1780 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1783 /* allow small jumps within the range */
1784 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1786 (insn->jump_dest->offset <= insn->offset ||
1787 insn->jump_dest->offset > orig_insn->offset))
1790 table_reloc = arch_find_switch_table(file, insn);
1793 dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
1794 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1804 * First pass: Mark the head of each jump table so that in the next pass,
1805 * we know when a given jump table ends and the next one starts.
1807 static void mark_func_jump_tables(struct objtool_file *file,
1808 struct symbol *func)
1810 struct instruction *insn, *last = NULL;
1811 struct reloc *reloc;
1813 func_for_each_insn(file, func, insn) {
1818 * Store back-pointers for unconditional forward jumps such
1819 * that find_jump_table() can back-track using those and
1820 * avoid some potentially confusing code.
1822 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1823 insn->offset > last->offset &&
1824 insn->jump_dest->offset > insn->offset &&
1825 !insn->jump_dest->first_jump_src) {
1827 insn->jump_dest->first_jump_src = insn;
1828 last = insn->jump_dest;
1831 if (insn->type != INSN_JUMP_DYNAMIC)
1834 reloc = find_jump_table(file, func, insn);
1836 reloc->jump_table_start = true;
1837 insn->jump_table = reloc;
1842 static int add_func_jump_tables(struct objtool_file *file,
1843 struct symbol *func)
1845 struct instruction *insn;
1848 func_for_each_insn(file, func, insn) {
1849 if (!insn->jump_table)
1852 ret = add_jump_table(file, insn, insn->jump_table);
1861 * For some switch statements, gcc generates a jump table in the .rodata
1862 * section which contains a list of addresses within the function to jump to.
1863 * This finds these jump tables and adds them to the insn->alts lists.
1865 static int add_jump_table_alts(struct objtool_file *file)
1867 struct section *sec;
1868 struct symbol *func;
1874 for_each_sec(file, sec) {
1875 list_for_each_entry(func, &sec->symbol_list, list) {
1876 if (func->type != STT_FUNC)
1879 mark_func_jump_tables(file, func);
1880 ret = add_func_jump_tables(file, func);
1889 static void set_func_state(struct cfi_state *state)
1891 state->cfa = initial_func_cfi.cfa;
1892 memcpy(&state->regs, &initial_func_cfi.regs,
1893 CFI_NUM_REGS * sizeof(struct cfi_reg));
1894 state->stack_size = initial_func_cfi.cfa.offset;
1897 static int read_unwind_hints(struct objtool_file *file)
1899 struct cfi_state cfi = init_cfi;
1900 struct section *sec, *relocsec;
1901 struct unwind_hint *hint;
1902 struct instruction *insn;
1903 struct reloc *reloc;
1906 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1910 relocsec = sec->reloc;
1912 WARN("missing .rela.discard.unwind_hints section");
1916 if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
1917 WARN("struct unwind_hint size mismatch");
1923 for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
1924 hint = (struct unwind_hint *)sec->data->d_buf + i;
1926 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
1928 WARN("can't find reloc for unwind_hints[%d]", i);
1932 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1934 WARN("can't find insn for unwind_hints[%d]", i);
1940 if (ibt && hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
1941 struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
1943 if (sym && sym->bind == STB_GLOBAL &&
1944 insn->type != INSN_ENDBR && !insn->noendbr) {
1945 WARN_FUNC("UNWIND_HINT_IRET_REGS without ENDBR",
1946 insn->sec, insn->offset);
1950 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
1951 insn->cfi = &func_cfi;
1958 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
1959 WARN_FUNC("unsupported unwind_hint sp base reg %d",
1960 insn->sec, insn->offset, hint->sp_reg);
1964 cfi.cfa.offset = bswap_if_needed(hint->sp_offset);
1965 cfi.type = hint->type;
1966 cfi.end = hint->end;
1968 insn->cfi = cfi_hash_find_or_add(&cfi);
1974 static int read_noendbr_hints(struct objtool_file *file)
1976 struct section *sec;
1977 struct instruction *insn;
1978 struct reloc *reloc;
1980 sec = find_section_by_name(file->elf, ".rela.discard.noendbr");
1984 list_for_each_entry(reloc, &sec->reloc_list, list) {
1985 insn = find_insn(file, reloc->sym->sec, reloc->sym->offset + reloc->addend);
1987 WARN("bad .discard.noendbr entry");
1991 if (insn->type == INSN_ENDBR)
1992 WARN_FUNC("ANNOTATE_NOENDBR on ENDBR", insn->sec, insn->offset);
2000 static int read_retpoline_hints(struct objtool_file *file)
2002 struct section *sec;
2003 struct instruction *insn;
2004 struct reloc *reloc;
2006 sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
2010 list_for_each_entry(reloc, &sec->reloc_list, list) {
2011 if (reloc->sym->type != STT_SECTION) {
2012 WARN("unexpected relocation symbol type in %s", sec->name);
2016 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2018 WARN("bad .discard.retpoline_safe entry");
2022 if (insn->type != INSN_JUMP_DYNAMIC &&
2023 insn->type != INSN_CALL_DYNAMIC) {
2024 WARN_FUNC("retpoline_safe hint not an indirect jump/call",
2025 insn->sec, insn->offset);
2029 insn->retpoline_safe = true;
2035 static int read_instr_hints(struct objtool_file *file)
2037 struct section *sec;
2038 struct instruction *insn;
2039 struct reloc *reloc;
2041 sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2045 list_for_each_entry(reloc, &sec->reloc_list, list) {
2046 if (reloc->sym->type != STT_SECTION) {
2047 WARN("unexpected relocation symbol type in %s", sec->name);
2051 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2053 WARN("bad .discard.instr_end entry");
2060 sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2064 list_for_each_entry(reloc, &sec->reloc_list, list) {
2065 if (reloc->sym->type != STT_SECTION) {
2066 WARN("unexpected relocation symbol type in %s", sec->name);
2070 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2072 WARN("bad .discard.instr_begin entry");
2082 static int read_intra_function_calls(struct objtool_file *file)
2084 struct instruction *insn;
2085 struct section *sec;
2086 struct reloc *reloc;
2088 sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2092 list_for_each_entry(reloc, &sec->reloc_list, list) {
2093 unsigned long dest_off;
2095 if (reloc->sym->type != STT_SECTION) {
2096 WARN("unexpected relocation symbol type in %s",
2101 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2103 WARN("bad .discard.intra_function_call entry");
2107 if (insn->type != INSN_CALL) {
2108 WARN_FUNC("intra_function_call not a direct call",
2109 insn->sec, insn->offset);
2114 * Treat intra-function CALLs as JMPs, but with a stack_op.
2115 * See add_call_destinations(), which strips stack_ops from
2118 insn->type = INSN_JUMP_UNCONDITIONAL;
2120 dest_off = insn->offset + insn->len + insn->immediate;
2121 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2122 if (!insn->jump_dest) {
2123 WARN_FUNC("can't find call dest at %s+0x%lx",
2124 insn->sec, insn->offset,
2125 insn->sec->name, dest_off);
2134 * Return true if name matches an instrumentation function, where calls to that
2135 * function from noinstr code can safely be removed, but compilers won't do so.
2137 static bool is_profiling_func(const char *name)
2140 * Many compilers cannot disable KCOV with a function attribute.
2142 if (!strncmp(name, "__sanitizer_cov_", 16))
2146 * Some compilers currently do not remove __tsan_func_entry/exit nor
2147 * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2148 * the __no_sanitize_thread attribute, remove them. Once the kernel's
2149 * minimum Clang version is 14.0, this can be removed.
2151 if (!strncmp(name, "__tsan_func_", 12) ||
2152 !strcmp(name, "__tsan_atomic_signal_fence"))
2158 static int classify_symbols(struct objtool_file *file)
2160 struct section *sec;
2161 struct symbol *func;
2163 for_each_sec(file, sec) {
2164 list_for_each_entry(func, &sec->symbol_list, list) {
2165 if (func->bind != STB_GLOBAL)
2168 if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2169 strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2170 func->static_call_tramp = true;
2172 if (arch_is_retpoline(func))
2173 func->retpoline_thunk = true;
2175 if (!strcmp(func->name, "__fentry__"))
2176 func->fentry = true;
2178 if (is_profiling_func(func->name))
2179 func->profiling_func = true;
2186 static void mark_rodata(struct objtool_file *file)
2188 struct section *sec;
2192 * Search for the following rodata sections, each of which can
2193 * potentially contain jump tables:
2195 * - .rodata: can contain GCC switch tables
2196 * - .rodata.<func>: same, if -fdata-sections is being used
2197 * - .rodata..c_jump_table: contains C annotated jump tables
2199 * .rodata.str1.* sections are ignored; they don't contain jump tables.
2201 for_each_sec(file, sec) {
2202 if (!strncmp(sec->name, ".rodata", 7) &&
2203 !strstr(sec->name, ".str1.")) {
2209 file->rodata = found;
2212 static int decode_sections(struct objtool_file *file)
2218 ret = init_pv_ops(file);
2222 ret = decode_instructions(file);
2227 add_uaccess_safe(file);
2229 ret = add_ignore_alternatives(file);
2234 * Must be before read_unwind_hints() since that needs insn->noendbr.
2236 ret = read_noendbr_hints(file);
2241 * Must be before add_{jump_call}_destination.
2243 ret = classify_symbols(file);
2248 * Must be before add_special_section_alts() as that depends on
2249 * jump_dest being set.
2251 ret = add_jump_destinations(file);
2255 ret = add_special_section_alts(file);
2260 * Must be before add_call_destination(); it changes INSN_CALL to
2263 ret = read_intra_function_calls(file);
2267 ret = add_call_destinations(file);
2272 * Must be after add_call_destinations() such that it can override
2273 * dead_end_function() marks.
2275 ret = add_dead_ends(file);
2279 ret = add_jump_table_alts(file);
2283 ret = read_unwind_hints(file);
2287 ret = read_retpoline_hints(file);
2291 ret = read_instr_hints(file);
2298 static bool is_fentry_call(struct instruction *insn)
2300 if (insn->type == INSN_CALL &&
2302 insn->call_dest->fentry)
2308 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2310 struct cfi_state *cfi = &state->cfi;
2313 if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2316 if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2319 if (cfi->stack_size != initial_func_cfi.cfa.offset)
2322 for (i = 0; i < CFI_NUM_REGS; i++) {
2323 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2324 cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2331 static bool check_reg_frame_pos(const struct cfi_reg *reg,
2332 int expected_offset)
2334 return reg->base == CFI_CFA &&
2335 reg->offset == expected_offset;
2338 static bool has_valid_stack_frame(struct insn_state *state)
2340 struct cfi_state *cfi = &state->cfi;
2342 if (cfi->cfa.base == CFI_BP &&
2343 check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2344 check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2347 if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2353 static int update_cfi_state_regs(struct instruction *insn,
2354 struct cfi_state *cfi,
2355 struct stack_op *op)
2357 struct cfi_reg *cfa = &cfi->cfa;
2359 if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2363 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2367 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2370 /* add immediate to sp */
2371 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2372 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2373 cfa->offset -= op->src.offset;
2378 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2380 if (arch_callee_saved_reg(reg) &&
2381 cfi->regs[reg].base == CFI_UNDEFINED) {
2382 cfi->regs[reg].base = base;
2383 cfi->regs[reg].offset = offset;
2387 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2389 cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2390 cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2394 * A note about DRAP stack alignment:
2396 * GCC has the concept of a DRAP register, which is used to help keep track of
2397 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
2398 * register. The typical DRAP pattern is:
2400 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
2401 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
2402 * 41 ff 72 f8 pushq -0x8(%r10)
2404 * 48 89 e5 mov %rsp,%rbp
2411 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2414 * There are some variations in the epilogues, like:
2422 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2427 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
2428 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
2429 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
2430 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
2432 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2435 * Sometimes r13 is used as the DRAP register, in which case it's saved and
2436 * restored beforehand:
2439 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
2440 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
2442 * 49 8d 65 f0 lea -0x10(%r13),%rsp
2446 static int update_cfi_state(struct instruction *insn,
2447 struct instruction *next_insn,
2448 struct cfi_state *cfi, struct stack_op *op)
2450 struct cfi_reg *cfa = &cfi->cfa;
2451 struct cfi_reg *regs = cfi->regs;
2453 /* stack operations don't make sense with an undefined CFA */
2454 if (cfa->base == CFI_UNDEFINED) {
2456 WARN_FUNC("undefined stack state", insn->sec, insn->offset);
2462 if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2463 cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2464 return update_cfi_state_regs(insn, cfi, op);
2466 switch (op->dest.type) {
2469 switch (op->src.type) {
2472 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2473 cfa->base == CFI_SP &&
2474 check_reg_frame_pos(®s[CFI_BP], -cfa->offset)) {
2476 /* mov %rsp, %rbp */
2477 cfa->base = op->dest.reg;
2478 cfi->bp_scratch = false;
2481 else if (op->src.reg == CFI_SP &&
2482 op->dest.reg == CFI_BP && cfi->drap) {
2484 /* drap: mov %rsp, %rbp */
2485 regs[CFI_BP].base = CFI_BP;
2486 regs[CFI_BP].offset = -cfi->stack_size;
2487 cfi->bp_scratch = false;
2490 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2495 * This is needed for the rare case where GCC
2502 cfi->vals[op->dest.reg].base = CFI_CFA;
2503 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2506 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2507 (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2512 * Restore the original stack pointer (Clang).
2514 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2517 else if (op->dest.reg == cfa->base) {
2519 /* mov %reg, %rsp */
2520 if (cfa->base == CFI_SP &&
2521 cfi->vals[op->src.reg].base == CFI_CFA) {
2524 * This is needed for the rare case
2525 * where GCC does something dumb like:
2527 * lea 0x8(%rsp), %rcx
2531 cfa->offset = -cfi->vals[op->src.reg].offset;
2532 cfi->stack_size = cfa->offset;
2534 } else if (cfa->base == CFI_SP &&
2535 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2536 cfi->vals[op->src.reg].offset == cfa->offset) {
2541 * 1: mov %rsp, (%[tos])
2542 * 2: mov %[tos], %rsp
2548 * 1 - places a pointer to the previous
2549 * stack at the Top-of-Stack of the
2552 * 2 - switches to the new stack.
2554 * 3 - pops the Top-of-Stack to restore
2555 * the original stack.
2557 * Note: we set base to SP_INDIRECT
2558 * here and preserve offset. Therefore
2559 * when the unwinder reaches ToS it
2560 * will dereference SP and then add the
2561 * offset to find the next frame, IOW:
2564 cfa->base = CFI_SP_INDIRECT;
2567 cfa->base = CFI_UNDEFINED;
2572 else if (op->dest.reg == CFI_SP &&
2573 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2574 cfi->vals[op->src.reg].offset == cfa->offset) {
2577 * The same stack swizzle case 2) as above. But
2578 * because we can't change cfa->base, case 3)
2579 * will become a regular POP. Pretend we're a
2580 * PUSH so things don't go unbalanced.
2582 cfi->stack_size += 8;
2589 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2592 cfi->stack_size -= op->src.offset;
2593 if (cfa->base == CFI_SP)
2594 cfa->offset -= op->src.offset;
2598 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2600 /* lea disp(%rbp), %rsp */
2601 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2605 if (!cfi->drap && op->src.reg == CFI_SP &&
2606 op->dest.reg == CFI_BP && cfa->base == CFI_SP &&
2607 check_reg_frame_pos(®s[CFI_BP], -cfa->offset + op->src.offset)) {
2609 /* lea disp(%rsp), %rbp */
2611 cfa->offset -= op->src.offset;
2612 cfi->bp_scratch = false;
2616 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2618 /* drap: lea disp(%rsp), %drap */
2619 cfi->drap_reg = op->dest.reg;
2622 * lea disp(%rsp), %reg
2624 * This is needed for the rare case where GCC
2625 * does something dumb like:
2627 * lea 0x8(%rsp), %rcx
2631 cfi->vals[op->dest.reg].base = CFI_CFA;
2632 cfi->vals[op->dest.reg].offset = \
2633 -cfi->stack_size + op->src.offset;
2638 if (cfi->drap && op->dest.reg == CFI_SP &&
2639 op->src.reg == cfi->drap_reg) {
2641 /* drap: lea disp(%drap), %rsp */
2643 cfa->offset = cfi->stack_size = -op->src.offset;
2644 cfi->drap_reg = CFI_UNDEFINED;
2649 if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
2650 WARN_FUNC("unsupported stack register modification",
2651 insn->sec, insn->offset);
2658 if (op->dest.reg != CFI_SP ||
2659 (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
2660 (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
2661 WARN_FUNC("unsupported stack pointer realignment",
2662 insn->sec, insn->offset);
2666 if (cfi->drap_reg != CFI_UNDEFINED) {
2667 /* drap: and imm, %rsp */
2668 cfa->base = cfi->drap_reg;
2669 cfa->offset = cfi->stack_size = 0;
2674 * Older versions of GCC (4.8ish) realign the stack
2675 * without DRAP, with a frame pointer.
2682 if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
2684 /* pop %rsp; # restore from a stack swizzle */
2689 if (!cfi->drap && op->dest.reg == cfa->base) {
2695 if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
2696 op->dest.reg == cfi->drap_reg &&
2697 cfi->drap_offset == -cfi->stack_size) {
2699 /* drap: pop %drap */
2700 cfa->base = cfi->drap_reg;
2702 cfi->drap_offset = -1;
2704 } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
2707 restore_reg(cfi, op->dest.reg);
2710 cfi->stack_size -= 8;
2711 if (cfa->base == CFI_SP)
2716 case OP_SRC_REG_INDIRECT:
2717 if (!cfi->drap && op->dest.reg == cfa->base &&
2718 op->dest.reg == CFI_BP) {
2720 /* mov disp(%rsp), %rbp */
2722 cfa->offset = cfi->stack_size;
2725 if (cfi->drap && op->src.reg == CFI_BP &&
2726 op->src.offset == cfi->drap_offset) {
2728 /* drap: mov disp(%rbp), %drap */
2729 cfa->base = cfi->drap_reg;
2731 cfi->drap_offset = -1;
2734 if (cfi->drap && op->src.reg == CFI_BP &&
2735 op->src.offset == regs[op->dest.reg].offset) {
2737 /* drap: mov disp(%rbp), %reg */
2738 restore_reg(cfi, op->dest.reg);
2740 } else if (op->src.reg == cfa->base &&
2741 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
2743 /* mov disp(%rbp), %reg */
2744 /* mov disp(%rsp), %reg */
2745 restore_reg(cfi, op->dest.reg);
2747 } else if (op->src.reg == CFI_SP &&
2748 op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
2750 /* mov disp(%rsp), %reg */
2751 restore_reg(cfi, op->dest.reg);
2757 WARN_FUNC("unknown stack-related instruction",
2758 insn->sec, insn->offset);
2766 cfi->stack_size += 8;
2767 if (cfa->base == CFI_SP)
2770 if (op->src.type != OP_SRC_REG)
2774 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2776 /* drap: push %drap */
2777 cfa->base = CFI_BP_INDIRECT;
2778 cfa->offset = -cfi->stack_size;
2780 /* save drap so we know when to restore it */
2781 cfi->drap_offset = -cfi->stack_size;
2783 } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
2785 /* drap: push %rbp */
2786 cfi->stack_size = 0;
2790 /* drap: push %reg */
2791 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
2797 save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
2800 /* detect when asm code uses rbp as a scratch register */
2801 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
2802 cfa->base != CFI_BP)
2803 cfi->bp_scratch = true;
2806 case OP_DEST_REG_INDIRECT:
2809 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2811 /* drap: mov %drap, disp(%rbp) */
2812 cfa->base = CFI_BP_INDIRECT;
2813 cfa->offset = op->dest.offset;
2815 /* save drap offset so we know when to restore it */
2816 cfi->drap_offset = op->dest.offset;
2819 /* drap: mov reg, disp(%rbp) */
2820 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
2823 } else if (op->dest.reg == cfa->base) {
2825 /* mov reg, disp(%rbp) */
2826 /* mov reg, disp(%rsp) */
2827 save_reg(cfi, op->src.reg, CFI_CFA,
2828 op->dest.offset - cfi->cfa.offset);
2830 } else if (op->dest.reg == CFI_SP) {
2832 /* mov reg, disp(%rsp) */
2833 save_reg(cfi, op->src.reg, CFI_CFA,
2834 op->dest.offset - cfi->stack_size);
2836 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
2838 /* mov %rsp, (%reg); # setup a stack swizzle. */
2839 cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
2840 cfi->vals[op->dest.reg].offset = cfa->offset;
2846 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
2847 WARN_FUNC("unknown stack-related memory operation",
2848 insn->sec, insn->offset);
2853 cfi->stack_size -= 8;
2854 if (cfa->base == CFI_SP)
2860 WARN_FUNC("unknown stack-related instruction",
2861 insn->sec, insn->offset);
2869 * The stack layouts of alternatives instructions can sometimes diverge when
2870 * they have stack modifications. That's fine as long as the potential stack
2871 * layouts don't conflict at any given potential instruction boundary.
2873 * Flatten the CFIs of the different alternative code streams (both original
2874 * and replacement) into a single shared CFI array which can be used to detect
2875 * conflicts and nicely feed a linear array of ORC entries to the unwinder.
2877 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
2879 struct cfi_state **alt_cfi;
2882 if (!insn->alt_group)
2886 WARN("CFI missing");
2890 alt_cfi = insn->alt_group->cfi;
2891 group_off = insn->offset - insn->alt_group->first_insn->offset;
2893 if (!alt_cfi[group_off]) {
2894 alt_cfi[group_off] = insn->cfi;
2896 if (cficmp(alt_cfi[group_off], insn->cfi)) {
2897 WARN_FUNC("stack layout conflict in alternatives",
2898 insn->sec, insn->offset);
2906 static int handle_insn_ops(struct instruction *insn,
2907 struct instruction *next_insn,
2908 struct insn_state *state)
2910 struct stack_op *op;
2912 list_for_each_entry(op, &insn->stack_ops, list) {
2914 if (update_cfi_state(insn, next_insn, &state->cfi, op))
2917 if (!insn->alt_group)
2920 if (op->dest.type == OP_DEST_PUSHF) {
2921 if (!state->uaccess_stack) {
2922 state->uaccess_stack = 1;
2923 } else if (state->uaccess_stack >> 31) {
2924 WARN_FUNC("PUSHF stack exhausted",
2925 insn->sec, insn->offset);
2928 state->uaccess_stack <<= 1;
2929 state->uaccess_stack |= state->uaccess;
2932 if (op->src.type == OP_SRC_POPF) {
2933 if (state->uaccess_stack) {
2934 state->uaccess = state->uaccess_stack & 1;
2935 state->uaccess_stack >>= 1;
2936 if (state->uaccess_stack == 1)
2937 state->uaccess_stack = 0;
2945 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
2947 struct cfi_state *cfi1 = insn->cfi;
2951 WARN("CFI missing");
2955 if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
2957 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
2958 insn->sec, insn->offset,
2959 cfi1->cfa.base, cfi1->cfa.offset,
2960 cfi2->cfa.base, cfi2->cfa.offset);
2962 } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
2963 for (i = 0; i < CFI_NUM_REGS; i++) {
2964 if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
2965 sizeof(struct cfi_reg)))
2968 WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
2969 insn->sec, insn->offset,
2970 i, cfi1->regs[i].base, cfi1->regs[i].offset,
2971 i, cfi2->regs[i].base, cfi2->regs[i].offset);
2975 } else if (cfi1->type != cfi2->type) {
2977 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
2978 insn->sec, insn->offset, cfi1->type, cfi2->type);
2980 } else if (cfi1->drap != cfi2->drap ||
2981 (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
2982 (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
2984 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
2985 insn->sec, insn->offset,
2986 cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
2987 cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
2995 static inline bool func_uaccess_safe(struct symbol *func)
2998 return func->uaccess_safe;
3003 static inline const char *call_dest_name(struct instruction *insn)
3005 static char pvname[19];
3009 if (insn->call_dest)
3010 return insn->call_dest->name;
3012 rel = insn_reloc(NULL, insn);
3013 if (rel && !strcmp(rel->sym->name, "pv_ops")) {
3014 idx = (rel->addend / sizeof(void *));
3015 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
3022 static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3024 struct symbol *target;
3028 rel = insn_reloc(file, insn);
3029 if (!rel || strcmp(rel->sym->name, "pv_ops"))
3032 idx = (arch_dest_reloc_offset(rel->addend) / sizeof(void *));
3034 if (file->pv_ops[idx].clean)
3037 file->pv_ops[idx].clean = true;
3039 list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3040 if (!target->sec->noinstr) {
3041 WARN("pv_ops[%d]: %s", idx, target->name);
3042 file->pv_ops[idx].clean = false;
3046 return file->pv_ops[idx].clean;
3049 static inline bool noinstr_call_dest(struct objtool_file *file,
3050 struct instruction *insn,
3051 struct symbol *func)
3054 * We can't deal with indirect function calls at present;
3055 * assume they're instrumented.
3059 return pv_call_dest(file, insn);
3065 * If the symbol is from a noinstr section; we good.
3067 if (func->sec->noinstr)
3071 * The __ubsan_handle_*() calls are like WARN(), they only happen when
3072 * something 'BAD' happened. At the risk of taking the machine down,
3073 * let them proceed to get the message out.
3075 if (!strncmp(func->name, "__ubsan_handle_", 15))
3081 static int validate_call(struct objtool_file *file,
3082 struct instruction *insn,
3083 struct insn_state *state)
3085 if (state->noinstr && state->instr <= 0 &&
3086 !noinstr_call_dest(file, insn, insn->call_dest)) {
3087 WARN_FUNC("call to %s() leaves .noinstr.text section",
3088 insn->sec, insn->offset, call_dest_name(insn));
3092 if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
3093 WARN_FUNC("call to %s() with UACCESS enabled",
3094 insn->sec, insn->offset, call_dest_name(insn));
3099 WARN_FUNC("call to %s() with DF set",
3100 insn->sec, insn->offset, call_dest_name(insn));
3107 static int validate_sibling_call(struct objtool_file *file,
3108 struct instruction *insn,
3109 struct insn_state *state)
3111 if (has_modified_stack_frame(insn, state)) {
3112 WARN_FUNC("sibling call from callable instruction with modified stack frame",
3113 insn->sec, insn->offset);
3117 return validate_call(file, insn, state);
3120 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3122 if (state->noinstr && state->instr > 0) {
3123 WARN_FUNC("return with instrumentation enabled",
3124 insn->sec, insn->offset);
3128 if (state->uaccess && !func_uaccess_safe(func)) {
3129 WARN_FUNC("return with UACCESS enabled",
3130 insn->sec, insn->offset);
3134 if (!state->uaccess && func_uaccess_safe(func)) {
3135 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
3136 insn->sec, insn->offset);
3141 WARN_FUNC("return with DF set",
3142 insn->sec, insn->offset);
3146 if (func && has_modified_stack_frame(insn, state)) {
3147 WARN_FUNC("return with modified stack frame",
3148 insn->sec, insn->offset);
3152 if (state->cfi.bp_scratch) {
3153 WARN_FUNC("BP used as a scratch register",
3154 insn->sec, insn->offset);
3161 static struct instruction *next_insn_to_validate(struct objtool_file *file,
3162 struct instruction *insn)
3164 struct alt_group *alt_group = insn->alt_group;
3167 * Simulate the fact that alternatives are patched in-place. When the
3168 * end of a replacement alt_group is reached, redirect objtool flow to
3169 * the end of the original alt_group.
3171 if (alt_group && insn == alt_group->last_insn && alt_group->orig_group)
3172 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3174 return next_insn_same_sec(file, insn);
3177 static struct instruction *
3178 validate_ibt_reloc(struct objtool_file *file, struct reloc *reloc)
3180 struct instruction *dest;
3181 struct section *sec;
3184 sec = reloc->sym->sec;
3185 off = reloc->sym->offset;
3187 if ((reloc->sec->base->sh.sh_flags & SHF_EXECINSTR) &&
3188 (reloc->type == R_X86_64_PC32 || reloc->type == R_X86_64_PLT32))
3189 off += arch_dest_reloc_offset(reloc->addend);
3191 off += reloc->addend;
3193 dest = find_insn(file, sec, off);
3197 if (dest->type == INSN_ENDBR) {
3198 if (!list_empty(&dest->call_node))
3199 list_del_init(&dest->call_node);
3204 if (reloc->sym->static_call_tramp)
3210 static void warn_noendbr(const char *msg, struct section *sec, unsigned long offset,
3211 struct instruction *dest)
3213 WARN_FUNC("%srelocation to !ENDBR: %s+0x%lx", sec, offset, msg,
3214 dest->func ? dest->func->name : dest->sec->name,
3215 dest->func ? dest->offset - dest->func->offset : dest->offset);
3218 static void validate_ibt_dest(struct objtool_file *file, struct instruction *insn,
3219 struct instruction *dest)
3221 if (dest->func && dest->func == insn->func) {
3223 * Anything from->to self is either _THIS_IP_ or IRET-to-self.
3225 * There is no sane way to annotate _THIS_IP_ since the compiler treats the
3226 * relocation as a constant and is happy to fold in offsets, skewing any
3227 * annotation we do, leading to vast amounts of false-positives.
3229 * There's also compiler generated _THIS_IP_ through KCOV and
3230 * such which we have no hope of annotating.
3232 * As such, blanket accept self-references without issue.
3240 warn_noendbr("", insn->sec, insn->offset, dest);
3243 static void validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
3245 struct instruction *dest;
3246 struct reloc *reloc;
3248 switch (insn->type) {
3250 case INSN_CALL_DYNAMIC:
3251 case INSN_JUMP_CONDITIONAL:
3252 case INSN_JUMP_UNCONDITIONAL:
3253 case INSN_JUMP_DYNAMIC:
3254 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3257 * We're looking for code references setting up indirect code
3258 * flow. As such, ignore direct code flow and the actual
3265 * handle_group_alt() will create INSN_NOP instruction that
3266 * don't belong to any section, ignore all NOP since they won't
3267 * carry a (useful) relocation anyway.
3275 for (reloc = insn_reloc(file, insn);
3277 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
3279 (insn->offset + insn->len) - (reloc->offset + 1))) {
3280 dest = validate_ibt_reloc(file, reloc);
3282 validate_ibt_dest(file, insn, dest);
3287 * Follow the branch starting at the given instruction, and recursively follow
3288 * any other branches (jumps). Meanwhile, track the frame pointer state at
3289 * each instruction and validate all the rules described in
3290 * tools/objtool/Documentation/stack-validation.txt.
3292 static int validate_branch(struct objtool_file *file, struct symbol *func,
3293 struct instruction *insn, struct insn_state state)
3295 struct alternative *alt;
3296 struct instruction *next_insn, *prev_insn = NULL;
3297 struct section *sec;
3304 next_insn = next_insn_to_validate(file, insn);
3306 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
3307 WARN("%s() falls through to next function %s()",
3308 func->name, insn->func->name);
3312 if (func && insn->ignore) {
3313 WARN_FUNC("BUG: why am I validating an ignored function?",
3318 visited = 1 << state.uaccess;
3319 if (insn->visited) {
3320 if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3323 if (insn->visited & visited)
3330 state.instr += insn->instr;
3333 state.cfi = *insn->cfi;
3335 /* XXX track if we actually changed state.cfi */
3337 if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3338 insn->cfi = prev_insn->cfi;
3341 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3345 insn->visited |= visited;
3347 if (propagate_alt_cfi(file, insn))
3350 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
3351 bool skip_orig = false;
3353 list_for_each_entry(alt, &insn->alts, list) {
3357 ret = validate_branch(file, func, alt->insn, state);
3360 BT_FUNC("(alt)", insn);
3369 if (handle_insn_ops(insn, next_insn, &state))
3372 switch (insn->type) {
3375 if (sls && !insn->retpoline_safe &&
3376 next_insn && next_insn->type != INSN_TRAP) {
3377 WARN_FUNC("missing int3 after ret",
3378 insn->sec, insn->offset);
3380 return validate_return(func, insn, &state);
3383 case INSN_CALL_DYNAMIC:
3384 ret = validate_call(file, insn, &state);
3388 if (!no_fp && func && !is_fentry_call(insn) &&
3389 !has_valid_stack_frame(&state)) {
3390 WARN_FUNC("call without frame pointer save/setup",
3400 case INSN_JUMP_CONDITIONAL:
3401 case INSN_JUMP_UNCONDITIONAL:
3402 if (is_sibling_call(insn)) {
3403 ret = validate_sibling_call(file, insn, &state);
3407 } else if (insn->jump_dest) {
3408 ret = validate_branch(file, func,
3409 insn->jump_dest, state);
3412 BT_FUNC("(branch)", insn);
3417 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3422 case INSN_JUMP_DYNAMIC:
3423 if (sls && !insn->retpoline_safe &&
3424 next_insn && next_insn->type != INSN_TRAP) {
3425 WARN_FUNC("missing int3 after indirect jump",
3426 insn->sec, insn->offset);
3430 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3431 if (is_sibling_call(insn)) {
3432 ret = validate_sibling_call(file, insn, &state);
3437 if (insn->type == INSN_JUMP_DYNAMIC)
3442 case INSN_CONTEXT_SWITCH:
3443 if (func && (!next_insn || !next_insn->hint)) {
3444 WARN_FUNC("unsupported instruction in callable function",
3451 if (state.uaccess) {
3452 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
3456 state.uaccess = true;
3460 if (!state.uaccess && func) {
3461 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
3465 if (func_uaccess_safe(func) && !state.uaccess_stack) {
3466 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
3470 state.uaccess = false;
3475 WARN_FUNC("recursive STD", sec, insn->offset);
3483 if (!state.df && func) {
3484 WARN_FUNC("redundant CLD", sec, insn->offset);
3496 validate_ibt_insn(file, insn);
3502 if (state.cfi.cfa.base == CFI_UNDEFINED)
3504 WARN("%s: unexpected end of section", sec->name);
3515 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3517 struct instruction *insn;
3518 struct insn_state state;
3519 int ret, warnings = 0;
3524 init_insn_state(&state, sec);
3527 insn = find_insn(file, sec, 0);
3531 insn = list_first_entry(&file->insn_list, typeof(*insn), list);
3534 while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) {
3535 if (insn->hint && !insn->visited && !insn->ignore) {
3536 ret = validate_branch(file, insn->func, insn, state);
3537 if (ret && backtrace)
3538 BT_FUNC("<=== (hint)", insn);
3542 insn = list_next_entry(insn, list);
3548 static int validate_retpoline(struct objtool_file *file)
3550 struct instruction *insn;
3553 for_each_insn(file, insn) {
3554 if (insn->type != INSN_JUMP_DYNAMIC &&
3555 insn->type != INSN_CALL_DYNAMIC)
3558 if (insn->retpoline_safe)
3562 * .init.text code is ran before userspace and thus doesn't
3563 * strictly need retpolines, except for modules which are
3564 * loaded late, they very much do need retpoline in their
3567 if (!strcmp(insn->sec->name, ".init.text") && !module)
3570 WARN_FUNC("indirect %s found in RETPOLINE build",
3571 insn->sec, insn->offset,
3572 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
3580 static bool is_kasan_insn(struct instruction *insn)
3582 return (insn->type == INSN_CALL &&
3583 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
3586 static bool is_ubsan_insn(struct instruction *insn)
3588 return (insn->type == INSN_CALL &&
3589 !strcmp(insn->call_dest->name,
3590 "__ubsan_handle_builtin_unreachable"));
3593 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
3596 struct instruction *prev_insn;
3598 if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
3602 * Ignore alternative replacement instructions. This can happen
3603 * when a whitelisted function uses one of the ALTERNATIVE macros.
3605 if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
3606 !strcmp(insn->sec->name, ".altinstr_aux"))
3610 * Whole archive runs might encounder dead code from weak symbols.
3611 * This is where the linker will have dropped the weak symbol in
3612 * favour of a regular symbol, but leaves the code in place.
3614 * In this case we'll find a piece of code (whole function) that is not
3615 * covered by a !section symbol. Ignore them.
3617 if (!insn->func && lto) {
3618 int size = find_symbol_hole_containing(insn->sec, insn->offset);
3619 unsigned long end = insn->offset + size;
3621 if (!size) /* not a hole */
3624 if (size < 0) /* hole until the end */
3627 sec_for_each_insn_continue(file, insn) {
3629 * If we reach a visited instruction at or before the
3630 * end of the hole, ignore the unreachable.
3635 if (insn->offset >= end)
3639 * If this hole jumps to a .cold function, mark it ignore too.
3641 if (insn->jump_dest && insn->jump_dest->func &&
3642 strstr(insn->jump_dest->func->name, ".cold")) {
3643 struct instruction *dest = insn->jump_dest;
3644 func_for_each_insn(file, dest->func, dest)
3645 dest->ignore = true;
3655 if (insn->func->static_call_tramp)
3659 * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
3660 * __builtin_unreachable(). The BUG() macro has an unreachable() after
3661 * the UD2, which causes GCC's undefined trap logic to emit another UD2
3662 * (or occasionally a JMP to UD2).
3664 * It may also insert a UD2 after calling a __noreturn function.
3666 prev_insn = list_prev_entry(insn, list);
3667 if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) &&
3668 (insn->type == INSN_BUG ||
3669 (insn->type == INSN_JUMP_UNCONDITIONAL &&
3670 insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
3674 * Check if this (or a subsequent) instruction is related to
3675 * CONFIG_UBSAN or CONFIG_KASAN.
3677 * End the search at 5 instructions to avoid going into the weeds.
3679 for (i = 0; i < 5; i++) {
3681 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
3684 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
3685 if (insn->jump_dest &&
3686 insn->jump_dest->func == insn->func) {
3687 insn = insn->jump_dest;
3694 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
3697 insn = list_next_entry(insn, list);
3703 static int validate_symbol(struct objtool_file *file, struct section *sec,
3704 struct symbol *sym, struct insn_state *state)
3706 struct instruction *insn;
3710 WARN("%s() is missing an ELF size annotation", sym->name);
3714 if (sym->pfunc != sym || sym->alias != sym)
3717 insn = find_insn(file, sec, sym->offset);
3718 if (!insn || insn->ignore || insn->visited)
3721 state->uaccess = sym->uaccess_safe;
3723 ret = validate_branch(file, insn->func, insn, *state);
3724 if (ret && backtrace)
3725 BT_FUNC("<=== (sym)", insn);
3729 static int validate_section(struct objtool_file *file, struct section *sec)
3731 struct insn_state state;
3732 struct symbol *func;
3735 list_for_each_entry(func, &sec->symbol_list, list) {
3736 if (func->type != STT_FUNC)
3739 init_insn_state(&state, sec);
3740 set_func_state(&state.cfi);
3742 warnings += validate_symbol(file, sec, func, &state);
3748 static int validate_vmlinux_functions(struct objtool_file *file)
3750 struct section *sec;
3753 sec = find_section_by_name(file->elf, ".noinstr.text");
3755 warnings += validate_section(file, sec);
3756 warnings += validate_unwind_hints(file, sec);
3759 sec = find_section_by_name(file->elf, ".entry.text");
3761 warnings += validate_section(file, sec);
3762 warnings += validate_unwind_hints(file, sec);
3768 static int validate_functions(struct objtool_file *file)
3770 struct section *sec;
3773 for_each_sec(file, sec) {
3774 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
3777 warnings += validate_section(file, sec);
3783 static int validate_ibt(struct objtool_file *file)
3785 struct section *sec;
3786 struct reloc *reloc;
3788 for_each_sec(file, sec) {
3791 /* already done in validate_branch() */
3792 if (sec->sh.sh_flags & SHF_EXECINSTR)
3798 if (!strncmp(sec->name, ".orc", 4))
3801 if (!strncmp(sec->name, ".discard", 8))
3804 if (!strncmp(sec->name, ".debug", 6))
3807 if (!strcmp(sec->name, "_error_injection_whitelist"))
3810 if (!strcmp(sec->name, "_kprobe_blacklist"))
3813 is_data = strstr(sec->name, ".data") || strstr(sec->name, ".rodata");
3815 list_for_each_entry(reloc, &sec->reloc->reloc_list, list) {
3816 struct instruction *dest;
3818 dest = validate_ibt_reloc(file, reloc);
3819 if (is_data && dest && !dest->noendbr) {
3820 warn_noendbr("data ", reloc->sym->sec,
3821 reloc->sym->offset + reloc->addend,
3830 static int validate_reachable_instructions(struct objtool_file *file)
3832 struct instruction *insn;
3834 if (file->ignore_unreachables)
3837 for_each_insn(file, insn) {
3838 if (insn->visited || ignore_unreachable_insn(file, insn))
3841 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
3848 int check(struct objtool_file *file)
3850 int ret, warnings = 0;
3852 if (lto && !(vmlinux || module)) {
3853 fprintf(stderr, "--lto requires: --vmlinux or --module\n");
3858 fprintf(stderr, "--ibt requires: --lto\n");
3862 arch_initial_func_cfi_state(&initial_func_cfi);
3863 init_cfi_state(&init_cfi);
3864 init_cfi_state(&func_cfi);
3865 set_func_state(&func_cfi);
3867 if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
3870 cfi_hash_add(&init_cfi);
3871 cfi_hash_add(&func_cfi);
3873 ret = decode_sections(file);
3879 if (list_empty(&file->insn_list))
3882 if (vmlinux && !lto) {
3883 ret = validate_vmlinux_functions(file);
3892 ret = validate_retpoline(file);
3898 ret = validate_functions(file);
3903 ret = validate_unwind_hints(file, NULL);
3909 ret = validate_ibt(file);
3916 ret = validate_reachable_instructions(file);
3922 ret = create_static_call_sections(file);
3928 ret = create_retpoline_sites_sections(file);
3935 ret = create_mcount_loc_sections(file);
3942 ret = create_ibt_endbr_seal_sections(file);
3949 printf("nr_insns_visited: %ld\n", nr_insns_visited);
3950 printf("nr_cfi: %ld\n", nr_cfi);
3951 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
3952 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
3957 * For now, don't fail the kernel build on fatal warnings. These
3958 * errors are still fairly common due to the growing matrix of
3959 * supported toolchains and their recent pace of change.