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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
4 */
5
6#include <string.h>
7#include <stdlib.h>
8#include <inttypes.h>
9#include <sys/mman.h>
10
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>
18
19#include <linux/objtool_types.h>
20#include <linux/hashtable.h>
21#include <linux/kernel.h>
22#include <linux/static_call_types.h>
23#include <linux/string.h>
24
25struct alternative {
26 struct alternative *next;
27 struct instruction *insn;
28 bool skip_orig;
29};
30
31static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
32
33static struct cfi_init_state initial_func_cfi;
34static struct cfi_state init_cfi;
35static struct cfi_state func_cfi;
36static struct cfi_state force_undefined_cfi;
37
38struct instruction *find_insn(struct objtool_file *file,
39 struct section *sec, unsigned long offset)
40{
41 struct instruction *insn;
42
43 hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
44 if (insn->sec == sec && insn->offset == offset)
45 return insn;
46 }
47
48 return NULL;
49}
50
51struct instruction *next_insn_same_sec(struct objtool_file *file,
52 struct instruction *insn)
53{
54 if (insn->idx == INSN_CHUNK_MAX)
55 return find_insn(file, insn->sec, insn->offset + insn->len);
56
57 insn++;
58 if (!insn->len)
59 return NULL;
60
61 return insn;
62}
63
64static struct instruction *next_insn_same_func(struct objtool_file *file,
65 struct instruction *insn)
66{
67 struct instruction *next = next_insn_same_sec(file, insn);
68 struct symbol *func = insn_func(insn);
69
70 if (!func)
71 return NULL;
72
73 if (next && insn_func(next) == func)
74 return next;
75
76 /* Check if we're already in the subfunction: */
77 if (func == func->cfunc)
78 return NULL;
79
80 /* Move to the subfunction: */
81 return find_insn(file, func->cfunc->sec, func->cfunc->offset);
82}
83
84static struct instruction *prev_insn_same_sec(struct objtool_file *file,
85 struct instruction *insn)
86{
87 if (insn->idx == 0) {
88 if (insn->prev_len)
89 return find_insn(file, insn->sec, insn->offset - insn->prev_len);
90 return NULL;
91 }
92
93 return insn - 1;
94}
95
96static struct instruction *prev_insn_same_sym(struct objtool_file *file,
97 struct instruction *insn)
98{
99 struct instruction *prev = prev_insn_same_sec(file, insn);
100
101 if (prev && insn_func(prev) == insn_func(insn))
102 return prev;
103
104 return NULL;
105}
106
107#define for_each_insn(file, insn) \
108 for (struct section *__sec, *__fake = (struct section *)1; \
109 __fake; __fake = NULL) \
110 for_each_sec(file, __sec) \
111 sec_for_each_insn(file, __sec, insn)
112
113#define func_for_each_insn(file, func, insn) \
114 for (insn = find_insn(file, func->sec, func->offset); \
115 insn; \
116 insn = next_insn_same_func(file, insn))
117
118#define sym_for_each_insn(file, sym, insn) \
119 for (insn = find_insn(file, sym->sec, sym->offset); \
120 insn && insn->offset < sym->offset + sym->len; \
121 insn = next_insn_same_sec(file, insn))
122
123#define sym_for_each_insn_continue_reverse(file, sym, insn) \
124 for (insn = prev_insn_same_sec(file, insn); \
125 insn && insn->offset >= sym->offset; \
126 insn = prev_insn_same_sec(file, insn))
127
128#define sec_for_each_insn_from(file, insn) \
129 for (; insn; insn = next_insn_same_sec(file, insn))
130
131#define sec_for_each_insn_continue(file, insn) \
132 for (insn = next_insn_same_sec(file, insn); insn; \
133 insn = next_insn_same_sec(file, insn))
134
135static inline struct symbol *insn_call_dest(struct instruction *insn)
136{
137 if (insn->type == INSN_JUMP_DYNAMIC ||
138 insn->type == INSN_CALL_DYNAMIC)
139 return NULL;
140
141 return insn->_call_dest;
142}
143
144static inline struct reloc *insn_jump_table(struct instruction *insn)
145{
146 if (insn->type == INSN_JUMP_DYNAMIC ||
147 insn->type == INSN_CALL_DYNAMIC)
148 return insn->_jump_table;
149
150 return NULL;
151}
152
153static bool is_jump_table_jump(struct instruction *insn)
154{
155 struct alt_group *alt_group = insn->alt_group;
156
157 if (insn_jump_table(insn))
158 return true;
159
160 /* Retpoline alternative for a jump table? */
161 return alt_group && alt_group->orig_group &&
162 insn_jump_table(alt_group->orig_group->first_insn);
163}
164
165static bool is_sibling_call(struct instruction *insn)
166{
167 /*
168 * Assume only STT_FUNC calls have jump-tables.
169 */
170 if (insn_func(insn)) {
171 /* An indirect jump is either a sibling call or a jump to a table. */
172 if (insn->type == INSN_JUMP_DYNAMIC)
173 return !is_jump_table_jump(insn);
174 }
175
176 /* add_jump_destinations() sets insn_call_dest(insn) for sibling calls. */
177 return (is_static_jump(insn) && insn_call_dest(insn));
178}
179
180/*
181 * Checks if a string ends with another.
182 */
183static bool str_ends_with(const char *s, const char *sub)
184{
185 const int slen = strlen(s);
186 const int sublen = strlen(sub);
187
188 if (sublen > slen)
189 return 0;
190
191 return !memcmp(s + slen - sublen, sub, sublen);
192}
193
194/*
195 * Checks if a function is a Rust "noreturn" one.
196 */
197static bool is_rust_noreturn(const struct symbol *func)
198{
199 /*
200 * If it does not start with "_R", then it is not a Rust symbol.
201 */
202 if (strncmp(func->name, "_R", 2))
203 return false;
204
205 /*
206 * These are just heuristics -- we do not control the precise symbol
207 * name, due to the crate disambiguators (which depend on the compiler)
208 * as well as changes to the source code itself between versions (since
209 * these come from the Rust standard library).
210 */
211 return str_ends_with(func->name, "_4core5sliceSp15copy_from_slice17len_mismatch_fail") ||
212 str_ends_with(func->name, "_4core6option13unwrap_failed") ||
213 str_ends_with(func->name, "_4core6result13unwrap_failed") ||
214 str_ends_with(func->name, "_4core9panicking5panic") ||
215 str_ends_with(func->name, "_4core9panicking9panic_fmt") ||
216 str_ends_with(func->name, "_4core9panicking14panic_explicit") ||
217 str_ends_with(func->name, "_4core9panicking14panic_nounwind") ||
218 str_ends_with(func->name, "_4core9panicking18panic_bounds_check") ||
219 str_ends_with(func->name, "_4core9panicking19assert_failed_inner") ||
220 str_ends_with(func->name, "_4core9panicking36panic_misaligned_pointer_dereference") ||
221 strstr(func->name, "_4core9panicking13assert_failed") ||
222 strstr(func->name, "_4core9panicking11panic_const24panic_const_") ||
223 (strstr(func->name, "_4core5slice5index24slice_") &&
224 str_ends_with(func->name, "_fail"));
225}
226
227/*
228 * This checks to see if the given function is a "noreturn" function.
229 *
230 * For global functions which are outside the scope of this object file, we
231 * have to keep a manual list of them.
232 *
233 * For local functions, we have to detect them manually by simply looking for
234 * the lack of a return instruction.
235 */
236static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
237 int recursion)
238{
239 int i;
240 struct instruction *insn;
241 bool empty = true;
242
243#define NORETURN(func) __stringify(func),
244 static const char * const global_noreturns[] = {
245#include "noreturns.h"
246 };
247#undef NORETURN
248
249 if (!func)
250 return false;
251
252 if (func->bind == STB_GLOBAL || func->bind == STB_WEAK) {
253 if (is_rust_noreturn(func))
254 return true;
255
256 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
257 if (!strcmp(func->name, global_noreturns[i]))
258 return true;
259 }
260
261 if (func->bind == STB_WEAK)
262 return false;
263
264 if (!func->len)
265 return false;
266
267 insn = find_insn(file, func->sec, func->offset);
268 if (!insn || !insn_func(insn))
269 return false;
270
271 func_for_each_insn(file, func, insn) {
272 empty = false;
273
274 if (insn->type == INSN_RETURN)
275 return false;
276 }
277
278 if (empty)
279 return false;
280
281 /*
282 * A function can have a sibling call instead of a return. In that
283 * case, the function's dead-end status depends on whether the target
284 * of the sibling call returns.
285 */
286 func_for_each_insn(file, func, insn) {
287 if (is_sibling_call(insn)) {
288 struct instruction *dest = insn->jump_dest;
289
290 if (!dest)
291 /* sibling call to another file */
292 return false;
293
294 /* local sibling call */
295 if (recursion == 5) {
296 /*
297 * Infinite recursion: two functions have
298 * sibling calls to each other. This is a very
299 * rare case. It means they aren't dead ends.
300 */
301 return false;
302 }
303
304 return __dead_end_function(file, insn_func(dest), recursion+1);
305 }
306 }
307
308 return true;
309}
310
311static bool dead_end_function(struct objtool_file *file, struct symbol *func)
312{
313 return __dead_end_function(file, func, 0);
314}
315
316static void init_cfi_state(struct cfi_state *cfi)
317{
318 int i;
319
320 for (i = 0; i < CFI_NUM_REGS; i++) {
321 cfi->regs[i].base = CFI_UNDEFINED;
322 cfi->vals[i].base = CFI_UNDEFINED;
323 }
324 cfi->cfa.base = CFI_UNDEFINED;
325 cfi->drap_reg = CFI_UNDEFINED;
326 cfi->drap_offset = -1;
327}
328
329static void init_insn_state(struct objtool_file *file, struct insn_state *state,
330 struct section *sec)
331{
332 memset(state, 0, sizeof(*state));
333 init_cfi_state(&state->cfi);
334
335 /*
336 * We need the full vmlinux for noinstr validation, otherwise we can
337 * not correctly determine insn_call_dest(insn)->sec (external symbols
338 * do not have a section).
339 */
340 if (opts.link && opts.noinstr && sec)
341 state->noinstr = sec->noinstr;
342}
343
344static struct cfi_state *cfi_alloc(void)
345{
346 struct cfi_state *cfi = calloc(1, sizeof(struct cfi_state));
347 if (!cfi) {
348 WARN("calloc failed");
349 exit(1);
350 }
351 nr_cfi++;
352 return cfi;
353}
354
355static int cfi_bits;
356static struct hlist_head *cfi_hash;
357
358static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
359{
360 return memcmp((void *)cfi1 + sizeof(cfi1->hash),
361 (void *)cfi2 + sizeof(cfi2->hash),
362 sizeof(struct cfi_state) - sizeof(struct hlist_node));
363}
364
365static inline u32 cfi_key(struct cfi_state *cfi)
366{
367 return jhash((void *)cfi + sizeof(cfi->hash),
368 sizeof(*cfi) - sizeof(cfi->hash), 0);
369}
370
371static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
372{
373 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
374 struct cfi_state *obj;
375
376 hlist_for_each_entry(obj, head, hash) {
377 if (!cficmp(cfi, obj)) {
378 nr_cfi_cache++;
379 return obj;
380 }
381 }
382
383 obj = cfi_alloc();
384 *obj = *cfi;
385 hlist_add_head(&obj->hash, head);
386
387 return obj;
388}
389
390static void cfi_hash_add(struct cfi_state *cfi)
391{
392 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
393
394 hlist_add_head(&cfi->hash, head);
395}
396
397static void *cfi_hash_alloc(unsigned long size)
398{
399 cfi_bits = max(10, ilog2(size));
400 cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
401 PROT_READ|PROT_WRITE,
402 MAP_PRIVATE|MAP_ANON, -1, 0);
403 if (cfi_hash == (void *)-1L) {
404 WARN("mmap fail cfi_hash");
405 cfi_hash = NULL;
406 } else if (opts.stats) {
407 printf("cfi_bits: %d\n", cfi_bits);
408 }
409
410 return cfi_hash;
411}
412
413static unsigned long nr_insns;
414static unsigned long nr_insns_visited;
415
416/*
417 * Call the arch-specific instruction decoder for all the instructions and add
418 * them to the global instruction list.
419 */
420static int decode_instructions(struct objtool_file *file)
421{
422 struct section *sec;
423 struct symbol *func;
424 unsigned long offset;
425 struct instruction *insn;
426 int ret;
427
428 for_each_sec(file, sec) {
429 struct instruction *insns = NULL;
430 u8 prev_len = 0;
431 u8 idx = 0;
432
433 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
434 continue;
435
436 if (strcmp(sec->name, ".altinstr_replacement") &&
437 strcmp(sec->name, ".altinstr_aux") &&
438 strncmp(sec->name, ".discard.", 9))
439 sec->text = true;
440
441 if (!strcmp(sec->name, ".noinstr.text") ||
442 !strcmp(sec->name, ".entry.text") ||
443 !strcmp(sec->name, ".cpuidle.text") ||
444 !strncmp(sec->name, ".text..__x86.", 13))
445 sec->noinstr = true;
446
447 /*
448 * .init.text code is ran before userspace and thus doesn't
449 * strictly need retpolines, except for modules which are
450 * loaded late, they very much do need retpoline in their
451 * .init.text
452 */
453 if (!strcmp(sec->name, ".init.text") && !opts.module)
454 sec->init = true;
455
456 for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
457 if (!insns || idx == INSN_CHUNK_MAX) {
458 insns = calloc(sizeof(*insn), INSN_CHUNK_SIZE);
459 if (!insns) {
460 WARN("malloc failed");
461 return -1;
462 }
463 idx = 0;
464 } else {
465 idx++;
466 }
467 insn = &insns[idx];
468 insn->idx = idx;
469
470 INIT_LIST_HEAD(&insn->call_node);
471 insn->sec = sec;
472 insn->offset = offset;
473 insn->prev_len = prev_len;
474
475 ret = arch_decode_instruction(file, sec, offset,
476 sec->sh.sh_size - offset,
477 insn);
478 if (ret)
479 return ret;
480
481 prev_len = insn->len;
482
483 /*
484 * By default, "ud2" is a dead end unless otherwise
485 * annotated, because GCC 7 inserts it for certain
486 * divide-by-zero cases.
487 */
488 if (insn->type == INSN_BUG)
489 insn->dead_end = true;
490
491 hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
492 nr_insns++;
493 }
494
495// printf("%s: last chunk used: %d\n", sec->name, (int)idx);
496
497 sec_for_each_sym(sec, func) {
498 if (func->type != STT_NOTYPE && func->type != STT_FUNC)
499 continue;
500
501 if (func->offset == sec->sh.sh_size) {
502 /* Heuristic: likely an "end" symbol */
503 if (func->type == STT_NOTYPE)
504 continue;
505 WARN("%s(): STT_FUNC at end of section",
506 func->name);
507 return -1;
508 }
509
510 if (func->embedded_insn || func->alias != func)
511 continue;
512
513 if (!find_insn(file, sec, func->offset)) {
514 WARN("%s(): can't find starting instruction",
515 func->name);
516 return -1;
517 }
518
519 sym_for_each_insn(file, func, insn) {
520 insn->sym = func;
521 if (func->type == STT_FUNC &&
522 insn->type == INSN_ENDBR &&
523 list_empty(&insn->call_node)) {
524 if (insn->offset == func->offset) {
525 list_add_tail(&insn->call_node, &file->endbr_list);
526 file->nr_endbr++;
527 } else {
528 file->nr_endbr_int++;
529 }
530 }
531 }
532 }
533 }
534
535 if (opts.stats)
536 printf("nr_insns: %lu\n", nr_insns);
537
538 return 0;
539}
540
541/*
542 * Read the pv_ops[] .data table to find the static initialized values.
543 */
544static int add_pv_ops(struct objtool_file *file, const char *symname)
545{
546 struct symbol *sym, *func;
547 unsigned long off, end;
548 struct reloc *reloc;
549 int idx;
550
551 sym = find_symbol_by_name(file->elf, symname);
552 if (!sym)
553 return 0;
554
555 off = sym->offset;
556 end = off + sym->len;
557 for (;;) {
558 reloc = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off);
559 if (!reloc)
560 break;
561
562 func = reloc->sym;
563 if (func->type == STT_SECTION)
564 func = find_symbol_by_offset(reloc->sym->sec,
565 reloc_addend(reloc));
566
567 idx = (reloc_offset(reloc) - sym->offset) / sizeof(unsigned long);
568
569 objtool_pv_add(file, idx, func);
570
571 off = reloc_offset(reloc) + 1;
572 if (off > end)
573 break;
574 }
575
576 return 0;
577}
578
579/*
580 * Allocate and initialize file->pv_ops[].
581 */
582static int init_pv_ops(struct objtool_file *file)
583{
584 static const char *pv_ops_tables[] = {
585 "pv_ops",
586 "xen_cpu_ops",
587 "xen_irq_ops",
588 "xen_mmu_ops",
589 NULL,
590 };
591 const char *pv_ops;
592 struct symbol *sym;
593 int idx, nr;
594
595 if (!opts.noinstr)
596 return 0;
597
598 file->pv_ops = NULL;
599
600 sym = find_symbol_by_name(file->elf, "pv_ops");
601 if (!sym)
602 return 0;
603
604 nr = sym->len / sizeof(unsigned long);
605 file->pv_ops = calloc(sizeof(struct pv_state), nr);
606 if (!file->pv_ops)
607 return -1;
608
609 for (idx = 0; idx < nr; idx++)
610 INIT_LIST_HEAD(&file->pv_ops[idx].targets);
611
612 for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++)
613 add_pv_ops(file, pv_ops);
614
615 return 0;
616}
617
618static struct instruction *find_last_insn(struct objtool_file *file,
619 struct section *sec)
620{
621 struct instruction *insn = NULL;
622 unsigned int offset;
623 unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
624
625 for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
626 insn = find_insn(file, sec, offset);
627
628 return insn;
629}
630
631/*
632 * Mark "ud2" instructions and manually annotated dead ends.
633 */
634static int add_dead_ends(struct objtool_file *file)
635{
636 struct section *rsec;
637 struct reloc *reloc;
638 struct instruction *insn;
639 uint64_t offset;
640
641 /*
642 * UD2 defaults to being a dead-end, allow them to be annotated for
643 * non-fatal, eg WARN.
644 */
645 rsec = find_section_by_name(file->elf, ".rela.discard.reachable");
646 if (!rsec)
647 return 0;
648
649 for_each_reloc(rsec, reloc) {
650 if (reloc->sym->type == STT_SECTION) {
651 offset = reloc_addend(reloc);
652 } else if (reloc->sym->local_label) {
653 offset = reloc->sym->offset;
654 } else {
655 WARN("unexpected relocation symbol type in %s", rsec->name);
656 return -1;
657 }
658
659 insn = find_insn(file, reloc->sym->sec, offset);
660 if (insn)
661 insn = prev_insn_same_sec(file, insn);
662 else if (offset == reloc->sym->sec->sh.sh_size) {
663 insn = find_last_insn(file, reloc->sym->sec);
664 if (!insn) {
665 WARN("can't find reachable insn at %s+0x%" PRIx64,
666 reloc->sym->sec->name, offset);
667 return -1;
668 }
669 } else {
670 WARN("can't find reachable insn at %s+0x%" PRIx64,
671 reloc->sym->sec->name, offset);
672 return -1;
673 }
674
675 insn->dead_end = false;
676 }
677
678 return 0;
679}
680
681static int create_static_call_sections(struct objtool_file *file)
682{
683 struct static_call_site *site;
684 struct section *sec;
685 struct instruction *insn;
686 struct symbol *key_sym;
687 char *key_name, *tmp;
688 int idx;
689
690 sec = find_section_by_name(file->elf, ".static_call_sites");
691 if (sec) {
692 INIT_LIST_HEAD(&file->static_call_list);
693 WARN("file already has .static_call_sites section, skipping");
694 return 0;
695 }
696
697 if (list_empty(&file->static_call_list))
698 return 0;
699
700 idx = 0;
701 list_for_each_entry(insn, &file->static_call_list, call_node)
702 idx++;
703
704 sec = elf_create_section_pair(file->elf, ".static_call_sites",
705 sizeof(*site), idx, idx * 2);
706 if (!sec)
707 return -1;
708
709 /* Allow modules to modify the low bits of static_call_site::key */
710 sec->sh.sh_flags |= SHF_WRITE;
711
712 idx = 0;
713 list_for_each_entry(insn, &file->static_call_list, call_node) {
714
715 /* populate reloc for 'addr' */
716 if (!elf_init_reloc_text_sym(file->elf, sec,
717 idx * sizeof(*site), idx * 2,
718 insn->sec, insn->offset))
719 return -1;
720
721 /* find key symbol */
722 key_name = strdup(insn_call_dest(insn)->name);
723 if (!key_name) {
724 perror("strdup");
725 return -1;
726 }
727 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
728 STATIC_CALL_TRAMP_PREFIX_LEN)) {
729 WARN("static_call: trampoline name malformed: %s", key_name);
730 free(key_name);
731 return -1;
732 }
733 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
734 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
735
736 key_sym = find_symbol_by_name(file->elf, tmp);
737 if (!key_sym) {
738 if (!opts.module) {
739 WARN("static_call: can't find static_call_key symbol: %s", tmp);
740 free(key_name);
741 return -1;
742 }
743
744 /*
745 * For modules(), the key might not be exported, which
746 * means the module can make static calls but isn't
747 * allowed to change them.
748 *
749 * In that case we temporarily set the key to be the
750 * trampoline address. This is fixed up in
751 * static_call_add_module().
752 */
753 key_sym = insn_call_dest(insn);
754 }
755 free(key_name);
756
757 /* populate reloc for 'key' */
758 if (!elf_init_reloc_data_sym(file->elf, sec,
759 idx * sizeof(*site) + 4,
760 (idx * 2) + 1, key_sym,
761 is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
762 return -1;
763
764 idx++;
765 }
766
767 return 0;
768}
769
770static int create_retpoline_sites_sections(struct objtool_file *file)
771{
772 struct instruction *insn;
773 struct section *sec;
774 int idx;
775
776 sec = find_section_by_name(file->elf, ".retpoline_sites");
777 if (sec) {
778 WARN("file already has .retpoline_sites, skipping");
779 return 0;
780 }
781
782 idx = 0;
783 list_for_each_entry(insn, &file->retpoline_call_list, call_node)
784 idx++;
785
786 if (!idx)
787 return 0;
788
789 sec = elf_create_section_pair(file->elf, ".retpoline_sites",
790 sizeof(int), idx, idx);
791 if (!sec)
792 return -1;
793
794 idx = 0;
795 list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
796
797 if (!elf_init_reloc_text_sym(file->elf, sec,
798 idx * sizeof(int), idx,
799 insn->sec, insn->offset))
800 return -1;
801
802 idx++;
803 }
804
805 return 0;
806}
807
808static int create_return_sites_sections(struct objtool_file *file)
809{
810 struct instruction *insn;
811 struct section *sec;
812 int idx;
813
814 sec = find_section_by_name(file->elf, ".return_sites");
815 if (sec) {
816 WARN("file already has .return_sites, skipping");
817 return 0;
818 }
819
820 idx = 0;
821 list_for_each_entry(insn, &file->return_thunk_list, call_node)
822 idx++;
823
824 if (!idx)
825 return 0;
826
827 sec = elf_create_section_pair(file->elf, ".return_sites",
828 sizeof(int), idx, idx);
829 if (!sec)
830 return -1;
831
832 idx = 0;
833 list_for_each_entry(insn, &file->return_thunk_list, call_node) {
834
835 if (!elf_init_reloc_text_sym(file->elf, sec,
836 idx * sizeof(int), idx,
837 insn->sec, insn->offset))
838 return -1;
839
840 idx++;
841 }
842
843 return 0;
844}
845
846static int create_ibt_endbr_seal_sections(struct objtool_file *file)
847{
848 struct instruction *insn;
849 struct section *sec;
850 int idx;
851
852 sec = find_section_by_name(file->elf, ".ibt_endbr_seal");
853 if (sec) {
854 WARN("file already has .ibt_endbr_seal, skipping");
855 return 0;
856 }
857
858 idx = 0;
859 list_for_each_entry(insn, &file->endbr_list, call_node)
860 idx++;
861
862 if (opts.stats) {
863 printf("ibt: ENDBR at function start: %d\n", file->nr_endbr);
864 printf("ibt: ENDBR inside functions: %d\n", file->nr_endbr_int);
865 printf("ibt: superfluous ENDBR: %d\n", idx);
866 }
867
868 if (!idx)
869 return 0;
870
871 sec = elf_create_section_pair(file->elf, ".ibt_endbr_seal",
872 sizeof(int), idx, idx);
873 if (!sec)
874 return -1;
875
876 idx = 0;
877 list_for_each_entry(insn, &file->endbr_list, call_node) {
878
879 int *site = (int *)sec->data->d_buf + idx;
880 struct symbol *sym = insn->sym;
881 *site = 0;
882
883 if (opts.module && sym && sym->type == STT_FUNC &&
884 insn->offset == sym->offset &&
885 (!strcmp(sym->name, "init_module") ||
886 !strcmp(sym->name, "cleanup_module")))
887 WARN("%s(): not an indirect call target", sym->name);
888
889 if (!elf_init_reloc_text_sym(file->elf, sec,
890 idx * sizeof(int), idx,
891 insn->sec, insn->offset))
892 return -1;
893
894 idx++;
895 }
896
897 return 0;
898}
899
900static int create_cfi_sections(struct objtool_file *file)
901{
902 struct section *sec;
903 struct symbol *sym;
904 int idx;
905
906 sec = find_section_by_name(file->elf, ".cfi_sites");
907 if (sec) {
908 INIT_LIST_HEAD(&file->call_list);
909 WARN("file already has .cfi_sites section, skipping");
910 return 0;
911 }
912
913 idx = 0;
914 for_each_sym(file, sym) {
915 if (sym->type != STT_FUNC)
916 continue;
917
918 if (strncmp(sym->name, "__cfi_", 6))
919 continue;
920
921 idx++;
922 }
923
924 sec = elf_create_section_pair(file->elf, ".cfi_sites",
925 sizeof(unsigned int), idx, idx);
926 if (!sec)
927 return -1;
928
929 idx = 0;
930 for_each_sym(file, sym) {
931 if (sym->type != STT_FUNC)
932 continue;
933
934 if (strncmp(sym->name, "__cfi_", 6))
935 continue;
936
937 if (!elf_init_reloc_text_sym(file->elf, sec,
938 idx * sizeof(unsigned int), idx,
939 sym->sec, sym->offset))
940 return -1;
941
942 idx++;
943 }
944
945 return 0;
946}
947
948static int create_mcount_loc_sections(struct objtool_file *file)
949{
950 size_t addr_size = elf_addr_size(file->elf);
951 struct instruction *insn;
952 struct section *sec;
953 int idx;
954
955 sec = find_section_by_name(file->elf, "__mcount_loc");
956 if (sec) {
957 INIT_LIST_HEAD(&file->mcount_loc_list);
958 WARN("file already has __mcount_loc section, skipping");
959 return 0;
960 }
961
962 if (list_empty(&file->mcount_loc_list))
963 return 0;
964
965 idx = 0;
966 list_for_each_entry(insn, &file->mcount_loc_list, call_node)
967 idx++;
968
969 sec = elf_create_section_pair(file->elf, "__mcount_loc", addr_size,
970 idx, idx);
971 if (!sec)
972 return -1;
973
974 sec->sh.sh_addralign = addr_size;
975
976 idx = 0;
977 list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
978
979 struct reloc *reloc;
980
981 reloc = elf_init_reloc_text_sym(file->elf, sec, idx * addr_size, idx,
982 insn->sec, insn->offset);
983 if (!reloc)
984 return -1;
985
986 set_reloc_type(file->elf, reloc, addr_size == 8 ? R_ABS64 : R_ABS32);
987
988 idx++;
989 }
990
991 return 0;
992}
993
994static int create_direct_call_sections(struct objtool_file *file)
995{
996 struct instruction *insn;
997 struct section *sec;
998 int idx;
999
1000 sec = find_section_by_name(file->elf, ".call_sites");
1001 if (sec) {
1002 INIT_LIST_HEAD(&file->call_list);
1003 WARN("file already has .call_sites section, skipping");
1004 return 0;
1005 }
1006
1007 if (list_empty(&file->call_list))
1008 return 0;
1009
1010 idx = 0;
1011 list_for_each_entry(insn, &file->call_list, call_node)
1012 idx++;
1013
1014 sec = elf_create_section_pair(file->elf, ".call_sites",
1015 sizeof(unsigned int), idx, idx);
1016 if (!sec)
1017 return -1;
1018
1019 idx = 0;
1020 list_for_each_entry(insn, &file->call_list, call_node) {
1021
1022 if (!elf_init_reloc_text_sym(file->elf, sec,
1023 idx * sizeof(unsigned int), idx,
1024 insn->sec, insn->offset))
1025 return -1;
1026
1027 idx++;
1028 }
1029
1030 return 0;
1031}
1032
1033/*
1034 * Warnings shouldn't be reported for ignored functions.
1035 */
1036static void add_ignores(struct objtool_file *file)
1037{
1038 struct instruction *insn;
1039 struct section *rsec;
1040 struct symbol *func;
1041 struct reloc *reloc;
1042
1043 rsec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
1044 if (!rsec)
1045 return;
1046
1047 for_each_reloc(rsec, reloc) {
1048 switch (reloc->sym->type) {
1049 case STT_FUNC:
1050 func = reloc->sym;
1051 break;
1052
1053 case STT_SECTION:
1054 func = find_func_by_offset(reloc->sym->sec, reloc_addend(reloc));
1055 if (!func)
1056 continue;
1057 break;
1058
1059 default:
1060 WARN("unexpected relocation symbol type in %s: %d",
1061 rsec->name, reloc->sym->type);
1062 continue;
1063 }
1064
1065 func_for_each_insn(file, func, insn)
1066 insn->ignore = true;
1067 }
1068}
1069
1070/*
1071 * This is a whitelist of functions that is allowed to be called with AC set.
1072 * The list is meant to be minimal and only contains compiler instrumentation
1073 * ABI and a few functions used to implement *_{to,from}_user() functions.
1074 *
1075 * These functions must not directly change AC, but may PUSHF/POPF.
1076 */
1077static const char *uaccess_safe_builtin[] = {
1078 /* KASAN */
1079 "kasan_report",
1080 "kasan_check_range",
1081 /* KASAN out-of-line */
1082 "__asan_loadN_noabort",
1083 "__asan_load1_noabort",
1084 "__asan_load2_noabort",
1085 "__asan_load4_noabort",
1086 "__asan_load8_noabort",
1087 "__asan_load16_noabort",
1088 "__asan_storeN_noabort",
1089 "__asan_store1_noabort",
1090 "__asan_store2_noabort",
1091 "__asan_store4_noabort",
1092 "__asan_store8_noabort",
1093 "__asan_store16_noabort",
1094 "__kasan_check_read",
1095 "__kasan_check_write",
1096 /* KASAN in-line */
1097 "__asan_report_load_n_noabort",
1098 "__asan_report_load1_noabort",
1099 "__asan_report_load2_noabort",
1100 "__asan_report_load4_noabort",
1101 "__asan_report_load8_noabort",
1102 "__asan_report_load16_noabort",
1103 "__asan_report_store_n_noabort",
1104 "__asan_report_store1_noabort",
1105 "__asan_report_store2_noabort",
1106 "__asan_report_store4_noabort",
1107 "__asan_report_store8_noabort",
1108 "__asan_report_store16_noabort",
1109 /* KCSAN */
1110 "__kcsan_check_access",
1111 "__kcsan_mb",
1112 "__kcsan_wmb",
1113 "__kcsan_rmb",
1114 "__kcsan_release",
1115 "kcsan_found_watchpoint",
1116 "kcsan_setup_watchpoint",
1117 "kcsan_check_scoped_accesses",
1118 "kcsan_disable_current",
1119 "kcsan_enable_current_nowarn",
1120 /* KCSAN/TSAN */
1121 "__tsan_func_entry",
1122 "__tsan_func_exit",
1123 "__tsan_read_range",
1124 "__tsan_write_range",
1125 "__tsan_read1",
1126 "__tsan_read2",
1127 "__tsan_read4",
1128 "__tsan_read8",
1129 "__tsan_read16",
1130 "__tsan_write1",
1131 "__tsan_write2",
1132 "__tsan_write4",
1133 "__tsan_write8",
1134 "__tsan_write16",
1135 "__tsan_read_write1",
1136 "__tsan_read_write2",
1137 "__tsan_read_write4",
1138 "__tsan_read_write8",
1139 "__tsan_read_write16",
1140 "__tsan_volatile_read1",
1141 "__tsan_volatile_read2",
1142 "__tsan_volatile_read4",
1143 "__tsan_volatile_read8",
1144 "__tsan_volatile_read16",
1145 "__tsan_volatile_write1",
1146 "__tsan_volatile_write2",
1147 "__tsan_volatile_write4",
1148 "__tsan_volatile_write8",
1149 "__tsan_volatile_write16",
1150 "__tsan_atomic8_load",
1151 "__tsan_atomic16_load",
1152 "__tsan_atomic32_load",
1153 "__tsan_atomic64_load",
1154 "__tsan_atomic8_store",
1155 "__tsan_atomic16_store",
1156 "__tsan_atomic32_store",
1157 "__tsan_atomic64_store",
1158 "__tsan_atomic8_exchange",
1159 "__tsan_atomic16_exchange",
1160 "__tsan_atomic32_exchange",
1161 "__tsan_atomic64_exchange",
1162 "__tsan_atomic8_fetch_add",
1163 "__tsan_atomic16_fetch_add",
1164 "__tsan_atomic32_fetch_add",
1165 "__tsan_atomic64_fetch_add",
1166 "__tsan_atomic8_fetch_sub",
1167 "__tsan_atomic16_fetch_sub",
1168 "__tsan_atomic32_fetch_sub",
1169 "__tsan_atomic64_fetch_sub",
1170 "__tsan_atomic8_fetch_and",
1171 "__tsan_atomic16_fetch_and",
1172 "__tsan_atomic32_fetch_and",
1173 "__tsan_atomic64_fetch_and",
1174 "__tsan_atomic8_fetch_or",
1175 "__tsan_atomic16_fetch_or",
1176 "__tsan_atomic32_fetch_or",
1177 "__tsan_atomic64_fetch_or",
1178 "__tsan_atomic8_fetch_xor",
1179 "__tsan_atomic16_fetch_xor",
1180 "__tsan_atomic32_fetch_xor",
1181 "__tsan_atomic64_fetch_xor",
1182 "__tsan_atomic8_fetch_nand",
1183 "__tsan_atomic16_fetch_nand",
1184 "__tsan_atomic32_fetch_nand",
1185 "__tsan_atomic64_fetch_nand",
1186 "__tsan_atomic8_compare_exchange_strong",
1187 "__tsan_atomic16_compare_exchange_strong",
1188 "__tsan_atomic32_compare_exchange_strong",
1189 "__tsan_atomic64_compare_exchange_strong",
1190 "__tsan_atomic8_compare_exchange_weak",
1191 "__tsan_atomic16_compare_exchange_weak",
1192 "__tsan_atomic32_compare_exchange_weak",
1193 "__tsan_atomic64_compare_exchange_weak",
1194 "__tsan_atomic8_compare_exchange_val",
1195 "__tsan_atomic16_compare_exchange_val",
1196 "__tsan_atomic32_compare_exchange_val",
1197 "__tsan_atomic64_compare_exchange_val",
1198 "__tsan_atomic_thread_fence",
1199 "__tsan_atomic_signal_fence",
1200 "__tsan_unaligned_read16",
1201 "__tsan_unaligned_write16",
1202 /* KCOV */
1203 "write_comp_data",
1204 "check_kcov_mode",
1205 "__sanitizer_cov_trace_pc",
1206 "__sanitizer_cov_trace_const_cmp1",
1207 "__sanitizer_cov_trace_const_cmp2",
1208 "__sanitizer_cov_trace_const_cmp4",
1209 "__sanitizer_cov_trace_const_cmp8",
1210 "__sanitizer_cov_trace_cmp1",
1211 "__sanitizer_cov_trace_cmp2",
1212 "__sanitizer_cov_trace_cmp4",
1213 "__sanitizer_cov_trace_cmp8",
1214 "__sanitizer_cov_trace_switch",
1215 /* KMSAN */
1216 "kmsan_copy_to_user",
1217 "kmsan_disable_current",
1218 "kmsan_enable_current",
1219 "kmsan_report",
1220 "kmsan_unpoison_entry_regs",
1221 "kmsan_unpoison_memory",
1222 "__msan_chain_origin",
1223 "__msan_get_context_state",
1224 "__msan_instrument_asm_store",
1225 "__msan_metadata_ptr_for_load_1",
1226 "__msan_metadata_ptr_for_load_2",
1227 "__msan_metadata_ptr_for_load_4",
1228 "__msan_metadata_ptr_for_load_8",
1229 "__msan_metadata_ptr_for_load_n",
1230 "__msan_metadata_ptr_for_store_1",
1231 "__msan_metadata_ptr_for_store_2",
1232 "__msan_metadata_ptr_for_store_4",
1233 "__msan_metadata_ptr_for_store_8",
1234 "__msan_metadata_ptr_for_store_n",
1235 "__msan_poison_alloca",
1236 "__msan_warning",
1237 /* UBSAN */
1238 "ubsan_type_mismatch_common",
1239 "__ubsan_handle_type_mismatch",
1240 "__ubsan_handle_type_mismatch_v1",
1241 "__ubsan_handle_shift_out_of_bounds",
1242 "__ubsan_handle_load_invalid_value",
1243 /* STACKLEAK */
1244 "stackleak_track_stack",
1245 /* misc */
1246 "csum_partial_copy_generic",
1247 "copy_mc_fragile",
1248 "copy_mc_fragile_handle_tail",
1249 "copy_mc_enhanced_fast_string",
1250 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
1251 "rep_stos_alternative",
1252 "rep_movs_alternative",
1253 "__copy_user_nocache",
1254 NULL
1255};
1256
1257static void add_uaccess_safe(struct objtool_file *file)
1258{
1259 struct symbol *func;
1260 const char **name;
1261
1262 if (!opts.uaccess)
1263 return;
1264
1265 for (name = uaccess_safe_builtin; *name; name++) {
1266 func = find_symbol_by_name(file->elf, *name);
1267 if (!func)
1268 continue;
1269
1270 func->uaccess_safe = true;
1271 }
1272}
1273
1274/*
1275 * FIXME: For now, just ignore any alternatives which add retpolines. This is
1276 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
1277 * But it at least allows objtool to understand the control flow *around* the
1278 * retpoline.
1279 */
1280static int add_ignore_alternatives(struct objtool_file *file)
1281{
1282 struct section *rsec;
1283 struct reloc *reloc;
1284 struct instruction *insn;
1285
1286 rsec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
1287 if (!rsec)
1288 return 0;
1289
1290 for_each_reloc(rsec, reloc) {
1291 if (reloc->sym->type != STT_SECTION) {
1292 WARN("unexpected relocation symbol type in %s", rsec->name);
1293 return -1;
1294 }
1295
1296 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
1297 if (!insn) {
1298 WARN("bad .discard.ignore_alts entry");
1299 return -1;
1300 }
1301
1302 insn->ignore_alts = true;
1303 }
1304
1305 return 0;
1306}
1307
1308/*
1309 * Symbols that replace INSN_CALL_DYNAMIC, every (tail) call to such a symbol
1310 * will be added to the .retpoline_sites section.
1311 */
1312__weak bool arch_is_retpoline(struct symbol *sym)
1313{
1314 return false;
1315}
1316
1317/*
1318 * Symbols that replace INSN_RETURN, every (tail) call to such a symbol
1319 * will be added to the .return_sites section.
1320 */
1321__weak bool arch_is_rethunk(struct symbol *sym)
1322{
1323 return false;
1324}
1325
1326/*
1327 * Symbols that are embedded inside other instructions, because sometimes crazy
1328 * code exists. These are mostly ignored for validation purposes.
1329 */
1330__weak bool arch_is_embedded_insn(struct symbol *sym)
1331{
1332 return false;
1333}
1334
1335static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
1336{
1337 struct reloc *reloc;
1338
1339 if (insn->no_reloc)
1340 return NULL;
1341
1342 if (!file)
1343 return NULL;
1344
1345 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1346 insn->offset, insn->len);
1347 if (!reloc) {
1348 insn->no_reloc = 1;
1349 return NULL;
1350 }
1351
1352 return reloc;
1353}
1354
1355static void remove_insn_ops(struct instruction *insn)
1356{
1357 struct stack_op *op, *next;
1358
1359 for (op = insn->stack_ops; op; op = next) {
1360 next = op->next;
1361 free(op);
1362 }
1363 insn->stack_ops = NULL;
1364}
1365
1366static void annotate_call_site(struct objtool_file *file,
1367 struct instruction *insn, bool sibling)
1368{
1369 struct reloc *reloc = insn_reloc(file, insn);
1370 struct symbol *sym = insn_call_dest(insn);
1371
1372 if (!sym)
1373 sym = reloc->sym;
1374
1375 /*
1376 * Alternative replacement code is just template code which is
1377 * sometimes copied to the original instruction. For now, don't
1378 * annotate it. (In the future we might consider annotating the
1379 * original instruction if/when it ever makes sense to do so.)
1380 */
1381 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1382 return;
1383
1384 if (sym->static_call_tramp) {
1385 list_add_tail(&insn->call_node, &file->static_call_list);
1386 return;
1387 }
1388
1389 if (sym->retpoline_thunk) {
1390 list_add_tail(&insn->call_node, &file->retpoline_call_list);
1391 return;
1392 }
1393
1394 /*
1395 * Many compilers cannot disable KCOV or sanitizer calls with a function
1396 * attribute so they need a little help, NOP out any such calls from
1397 * noinstr text.
1398 */
1399 if (opts.hack_noinstr && insn->sec->noinstr && sym->profiling_func) {
1400 if (reloc)
1401 set_reloc_type(file->elf, reloc, R_NONE);
1402
1403 elf_write_insn(file->elf, insn->sec,
1404 insn->offset, insn->len,
1405 sibling ? arch_ret_insn(insn->len)
1406 : arch_nop_insn(insn->len));
1407
1408 insn->type = sibling ? INSN_RETURN : INSN_NOP;
1409
1410 if (sibling) {
1411 /*
1412 * We've replaced the tail-call JMP insn by two new
1413 * insn: RET; INT3, except we only have a single struct
1414 * insn here. Mark it retpoline_safe to avoid the SLS
1415 * warning, instead of adding another insn.
1416 */
1417 insn->retpoline_safe = true;
1418 }
1419
1420 return;
1421 }
1422
1423 if (opts.mcount && sym->fentry) {
1424 if (sibling)
1425 WARN_INSN(insn, "tail call to __fentry__ !?!?");
1426 if (opts.mnop) {
1427 if (reloc)
1428 set_reloc_type(file->elf, reloc, R_NONE);
1429
1430 elf_write_insn(file->elf, insn->sec,
1431 insn->offset, insn->len,
1432 arch_nop_insn(insn->len));
1433
1434 insn->type = INSN_NOP;
1435 }
1436
1437 list_add_tail(&insn->call_node, &file->mcount_loc_list);
1438 return;
1439 }
1440
1441 if (insn->type == INSN_CALL && !insn->sec->init)
1442 list_add_tail(&insn->call_node, &file->call_list);
1443
1444 if (!sibling && dead_end_function(file, sym))
1445 insn->dead_end = true;
1446}
1447
1448static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1449 struct symbol *dest, bool sibling)
1450{
1451 insn->_call_dest = dest;
1452 if (!dest)
1453 return;
1454
1455 /*
1456 * Whatever stack impact regular CALLs have, should be undone
1457 * by the RETURN of the called function.
1458 *
1459 * Annotated intra-function calls retain the stack_ops but
1460 * are converted to JUMP, see read_intra_function_calls().
1461 */
1462 remove_insn_ops(insn);
1463
1464 annotate_call_site(file, insn, sibling);
1465}
1466
1467static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1468{
1469 /*
1470 * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1471 * so convert them accordingly.
1472 */
1473 switch (insn->type) {
1474 case INSN_CALL:
1475 insn->type = INSN_CALL_DYNAMIC;
1476 break;
1477 case INSN_JUMP_UNCONDITIONAL:
1478 insn->type = INSN_JUMP_DYNAMIC;
1479 break;
1480 case INSN_JUMP_CONDITIONAL:
1481 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1482 break;
1483 default:
1484 return;
1485 }
1486
1487 insn->retpoline_safe = true;
1488
1489 /*
1490 * Whatever stack impact regular CALLs have, should be undone
1491 * by the RETURN of the called function.
1492 *
1493 * Annotated intra-function calls retain the stack_ops but
1494 * are converted to JUMP, see read_intra_function_calls().
1495 */
1496 remove_insn_ops(insn);
1497
1498 annotate_call_site(file, insn, false);
1499}
1500
1501static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add)
1502{
1503 /*
1504 * Return thunk tail calls are really just returns in disguise,
1505 * so convert them accordingly.
1506 */
1507 insn->type = INSN_RETURN;
1508 insn->retpoline_safe = true;
1509
1510 if (add)
1511 list_add_tail(&insn->call_node, &file->return_thunk_list);
1512}
1513
1514static bool is_first_func_insn(struct objtool_file *file,
1515 struct instruction *insn, struct symbol *sym)
1516{
1517 if (insn->offset == sym->offset)
1518 return true;
1519
1520 /* Allow direct CALL/JMP past ENDBR */
1521 if (opts.ibt) {
1522 struct instruction *prev = prev_insn_same_sym(file, insn);
1523
1524 if (prev && prev->type == INSN_ENDBR &&
1525 insn->offset == sym->offset + prev->len)
1526 return true;
1527 }
1528
1529 return false;
1530}
1531
1532/*
1533 * A sibling call is a tail-call to another symbol -- to differentiate from a
1534 * recursive tail-call which is to the same symbol.
1535 */
1536static bool jump_is_sibling_call(struct objtool_file *file,
1537 struct instruction *from, struct instruction *to)
1538{
1539 struct symbol *fs = from->sym;
1540 struct symbol *ts = to->sym;
1541
1542 /* Not a sibling call if from/to a symbol hole */
1543 if (!fs || !ts)
1544 return false;
1545
1546 /* Not a sibling call if not targeting the start of a symbol. */
1547 if (!is_first_func_insn(file, to, ts))
1548 return false;
1549
1550 /* Disallow sibling calls into STT_NOTYPE */
1551 if (ts->type == STT_NOTYPE)
1552 return false;
1553
1554 /* Must not be self to be a sibling */
1555 return fs->pfunc != ts->pfunc;
1556}
1557
1558/*
1559 * Find the destination instructions for all jumps.
1560 */
1561static int add_jump_destinations(struct objtool_file *file)
1562{
1563 struct instruction *insn, *jump_dest;
1564 struct reloc *reloc;
1565 struct section *dest_sec;
1566 unsigned long dest_off;
1567
1568 for_each_insn(file, insn) {
1569 if (insn->jump_dest) {
1570 /*
1571 * handle_group_alt() may have previously set
1572 * 'jump_dest' for some alternatives.
1573 */
1574 continue;
1575 }
1576 if (!is_static_jump(insn))
1577 continue;
1578
1579 reloc = insn_reloc(file, insn);
1580 if (!reloc) {
1581 dest_sec = insn->sec;
1582 dest_off = arch_jump_destination(insn);
1583 } else if (reloc->sym->type == STT_SECTION) {
1584 dest_sec = reloc->sym->sec;
1585 dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
1586 } else if (reloc->sym->retpoline_thunk) {
1587 add_retpoline_call(file, insn);
1588 continue;
1589 } else if (reloc->sym->return_thunk) {
1590 add_return_call(file, insn, true);
1591 continue;
1592 } else if (insn_func(insn)) {
1593 /*
1594 * External sibling call or internal sibling call with
1595 * STT_FUNC reloc.
1596 */
1597 add_call_dest(file, insn, reloc->sym, true);
1598 continue;
1599 } else if (reloc->sym->sec->idx) {
1600 dest_sec = reloc->sym->sec;
1601 dest_off = reloc->sym->sym.st_value +
1602 arch_dest_reloc_offset(reloc_addend(reloc));
1603 } else {
1604 /* non-func asm code jumping to another file */
1605 continue;
1606 }
1607
1608 jump_dest = find_insn(file, dest_sec, dest_off);
1609 if (!jump_dest) {
1610 struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off);
1611
1612 /*
1613 * This is a special case for retbleed_untrain_ret().
1614 * It jumps to __x86_return_thunk(), but objtool
1615 * can't find the thunk's starting RET
1616 * instruction, because the RET is also in the
1617 * middle of another instruction. Objtool only
1618 * knows about the outer instruction.
1619 */
1620 if (sym && sym->embedded_insn) {
1621 add_return_call(file, insn, false);
1622 continue;
1623 }
1624
1625 WARN_INSN(insn, "can't find jump dest instruction at %s+0x%lx",
1626 dest_sec->name, dest_off);
1627 return -1;
1628 }
1629
1630 /*
1631 * An intra-TU jump in retpoline.o might not have a relocation
1632 * for its jump dest, in which case the above
1633 * add_{retpoline,return}_call() didn't happen.
1634 */
1635 if (jump_dest->sym && jump_dest->offset == jump_dest->sym->offset) {
1636 if (jump_dest->sym->retpoline_thunk) {
1637 add_retpoline_call(file, insn);
1638 continue;
1639 }
1640 if (jump_dest->sym->return_thunk) {
1641 add_return_call(file, insn, true);
1642 continue;
1643 }
1644 }
1645
1646 /*
1647 * Cross-function jump.
1648 */
1649 if (insn_func(insn) && insn_func(jump_dest) &&
1650 insn_func(insn) != insn_func(jump_dest)) {
1651
1652 /*
1653 * For GCC 8+, create parent/child links for any cold
1654 * subfunctions. This is _mostly_ redundant with a
1655 * similar initialization in read_symbols().
1656 *
1657 * If a function has aliases, we want the *first* such
1658 * function in the symbol table to be the subfunction's
1659 * parent. In that case we overwrite the
1660 * initialization done in read_symbols().
1661 *
1662 * However this code can't completely replace the
1663 * read_symbols() code because this doesn't detect the
1664 * case where the parent function's only reference to a
1665 * subfunction is through a jump table.
1666 */
1667 if (!strstr(insn_func(insn)->name, ".cold") &&
1668 strstr(insn_func(jump_dest)->name, ".cold")) {
1669 insn_func(insn)->cfunc = insn_func(jump_dest);
1670 insn_func(jump_dest)->pfunc = insn_func(insn);
1671 }
1672 }
1673
1674 if (jump_is_sibling_call(file, insn, jump_dest)) {
1675 /*
1676 * Internal sibling call without reloc or with
1677 * STT_SECTION reloc.
1678 */
1679 add_call_dest(file, insn, insn_func(jump_dest), true);
1680 continue;
1681 }
1682
1683 insn->jump_dest = jump_dest;
1684 }
1685
1686 return 0;
1687}
1688
1689static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1690{
1691 struct symbol *call_dest;
1692
1693 call_dest = find_func_by_offset(sec, offset);
1694 if (!call_dest)
1695 call_dest = find_symbol_by_offset(sec, offset);
1696
1697 return call_dest;
1698}
1699
1700/*
1701 * Find the destination instructions for all calls.
1702 */
1703static int add_call_destinations(struct objtool_file *file)
1704{
1705 struct instruction *insn;
1706 unsigned long dest_off;
1707 struct symbol *dest;
1708 struct reloc *reloc;
1709
1710 for_each_insn(file, insn) {
1711 if (insn->type != INSN_CALL)
1712 continue;
1713
1714 reloc = insn_reloc(file, insn);
1715 if (!reloc) {
1716 dest_off = arch_jump_destination(insn);
1717 dest = find_call_destination(insn->sec, dest_off);
1718
1719 add_call_dest(file, insn, dest, false);
1720
1721 if (insn->ignore)
1722 continue;
1723
1724 if (!insn_call_dest(insn)) {
1725 WARN_INSN(insn, "unannotated intra-function call");
1726 return -1;
1727 }
1728
1729 if (insn_func(insn) && insn_call_dest(insn)->type != STT_FUNC) {
1730 WARN_INSN(insn, "unsupported call to non-function");
1731 return -1;
1732 }
1733
1734 } else if (reloc->sym->type == STT_SECTION) {
1735 dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
1736 dest = find_call_destination(reloc->sym->sec, dest_off);
1737 if (!dest) {
1738 WARN_INSN(insn, "can't find call dest symbol at %s+0x%lx",
1739 reloc->sym->sec->name, dest_off);
1740 return -1;
1741 }
1742
1743 add_call_dest(file, insn, dest, false);
1744
1745 } else if (reloc->sym->retpoline_thunk) {
1746 add_retpoline_call(file, insn);
1747
1748 } else
1749 add_call_dest(file, insn, reloc->sym, false);
1750 }
1751
1752 return 0;
1753}
1754
1755/*
1756 * The .alternatives section requires some extra special care over and above
1757 * other special sections because alternatives are patched in place.
1758 */
1759static int handle_group_alt(struct objtool_file *file,
1760 struct special_alt *special_alt,
1761 struct instruction *orig_insn,
1762 struct instruction **new_insn)
1763{
1764 struct instruction *last_new_insn = NULL, *insn, *nop = NULL;
1765 struct alt_group *orig_alt_group, *new_alt_group;
1766 unsigned long dest_off;
1767
1768 orig_alt_group = orig_insn->alt_group;
1769 if (!orig_alt_group) {
1770 struct instruction *last_orig_insn = NULL;
1771
1772 orig_alt_group = malloc(sizeof(*orig_alt_group));
1773 if (!orig_alt_group) {
1774 WARN("malloc failed");
1775 return -1;
1776 }
1777 orig_alt_group->cfi = calloc(special_alt->orig_len,
1778 sizeof(struct cfi_state *));
1779 if (!orig_alt_group->cfi) {
1780 WARN("calloc failed");
1781 return -1;
1782 }
1783
1784 insn = orig_insn;
1785 sec_for_each_insn_from(file, insn) {
1786 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1787 break;
1788
1789 insn->alt_group = orig_alt_group;
1790 last_orig_insn = insn;
1791 }
1792 orig_alt_group->orig_group = NULL;
1793 orig_alt_group->first_insn = orig_insn;
1794 orig_alt_group->last_insn = last_orig_insn;
1795 orig_alt_group->nop = NULL;
1796 } else {
1797 if (orig_alt_group->last_insn->offset + orig_alt_group->last_insn->len -
1798 orig_alt_group->first_insn->offset != special_alt->orig_len) {
1799 WARN_INSN(orig_insn, "weirdly overlapping alternative! %ld != %d",
1800 orig_alt_group->last_insn->offset +
1801 orig_alt_group->last_insn->len -
1802 orig_alt_group->first_insn->offset,
1803 special_alt->orig_len);
1804 return -1;
1805 }
1806 }
1807
1808 new_alt_group = malloc(sizeof(*new_alt_group));
1809 if (!new_alt_group) {
1810 WARN("malloc failed");
1811 return -1;
1812 }
1813
1814 if (special_alt->new_len < special_alt->orig_len) {
1815 /*
1816 * Insert a fake nop at the end to make the replacement
1817 * alt_group the same size as the original. This is needed to
1818 * allow propagate_alt_cfi() to do its magic. When the last
1819 * instruction affects the stack, the instruction after it (the
1820 * nop) will propagate the new state to the shared CFI array.
1821 */
1822 nop = malloc(sizeof(*nop));
1823 if (!nop) {
1824 WARN("malloc failed");
1825 return -1;
1826 }
1827 memset(nop, 0, sizeof(*nop));
1828
1829 nop->sec = special_alt->new_sec;
1830 nop->offset = special_alt->new_off + special_alt->new_len;
1831 nop->len = special_alt->orig_len - special_alt->new_len;
1832 nop->type = INSN_NOP;
1833 nop->sym = orig_insn->sym;
1834 nop->alt_group = new_alt_group;
1835 nop->ignore = orig_insn->ignore_alts;
1836 }
1837
1838 if (!special_alt->new_len) {
1839 *new_insn = nop;
1840 goto end;
1841 }
1842
1843 insn = *new_insn;
1844 sec_for_each_insn_from(file, insn) {
1845 struct reloc *alt_reloc;
1846
1847 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1848 break;
1849
1850 last_new_insn = insn;
1851
1852 insn->ignore = orig_insn->ignore_alts;
1853 insn->sym = orig_insn->sym;
1854 insn->alt_group = new_alt_group;
1855
1856 /*
1857 * Since alternative replacement code is copy/pasted by the
1858 * kernel after applying relocations, generally such code can't
1859 * have relative-address relocation references to outside the
1860 * .altinstr_replacement section, unless the arch's
1861 * alternatives code can adjust the relative offsets
1862 * accordingly.
1863 */
1864 alt_reloc = insn_reloc(file, insn);
1865 if (alt_reloc && arch_pc_relative_reloc(alt_reloc) &&
1866 !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1867
1868 WARN_INSN(insn, "unsupported relocation in alternatives section");
1869 return -1;
1870 }
1871
1872 if (!is_static_jump(insn))
1873 continue;
1874
1875 if (!insn->immediate)
1876 continue;
1877
1878 dest_off = arch_jump_destination(insn);
1879 if (dest_off == special_alt->new_off + special_alt->new_len) {
1880 insn->jump_dest = next_insn_same_sec(file, orig_alt_group->last_insn);
1881 if (!insn->jump_dest) {
1882 WARN_INSN(insn, "can't find alternative jump destination");
1883 return -1;
1884 }
1885 }
1886 }
1887
1888 if (!last_new_insn) {
1889 WARN_FUNC("can't find last new alternative instruction",
1890 special_alt->new_sec, special_alt->new_off);
1891 return -1;
1892 }
1893
1894end:
1895 new_alt_group->orig_group = orig_alt_group;
1896 new_alt_group->first_insn = *new_insn;
1897 new_alt_group->last_insn = last_new_insn;
1898 new_alt_group->nop = nop;
1899 new_alt_group->cfi = orig_alt_group->cfi;
1900 return 0;
1901}
1902
1903/*
1904 * A jump table entry can either convert a nop to a jump or a jump to a nop.
1905 * If the original instruction is a jump, make the alt entry an effective nop
1906 * by just skipping the original instruction.
1907 */
1908static int handle_jump_alt(struct objtool_file *file,
1909 struct special_alt *special_alt,
1910 struct instruction *orig_insn,
1911 struct instruction **new_insn)
1912{
1913 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1914 orig_insn->type != INSN_NOP) {
1915
1916 WARN_INSN(orig_insn, "unsupported instruction at jump label");
1917 return -1;
1918 }
1919
1920 if (opts.hack_jump_label && special_alt->key_addend & 2) {
1921 struct reloc *reloc = insn_reloc(file, orig_insn);
1922
1923 if (reloc)
1924 set_reloc_type(file->elf, reloc, R_NONE);
1925 elf_write_insn(file->elf, orig_insn->sec,
1926 orig_insn->offset, orig_insn->len,
1927 arch_nop_insn(orig_insn->len));
1928 orig_insn->type = INSN_NOP;
1929 }
1930
1931 if (orig_insn->type == INSN_NOP) {
1932 if (orig_insn->len == 2)
1933 file->jl_nop_short++;
1934 else
1935 file->jl_nop_long++;
1936
1937 return 0;
1938 }
1939
1940 if (orig_insn->len == 2)
1941 file->jl_short++;
1942 else
1943 file->jl_long++;
1944
1945 *new_insn = next_insn_same_sec(file, orig_insn);
1946 return 0;
1947}
1948
1949/*
1950 * Read all the special sections which have alternate instructions which can be
1951 * patched in or redirected to at runtime. Each instruction having alternate
1952 * instruction(s) has them added to its insn->alts list, which will be
1953 * traversed in validate_branch().
1954 */
1955static int add_special_section_alts(struct objtool_file *file)
1956{
1957 struct list_head special_alts;
1958 struct instruction *orig_insn, *new_insn;
1959 struct special_alt *special_alt, *tmp;
1960 struct alternative *alt;
1961 int ret;
1962
1963 ret = special_get_alts(file->elf, &special_alts);
1964 if (ret)
1965 return ret;
1966
1967 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1968
1969 orig_insn = find_insn(file, special_alt->orig_sec,
1970 special_alt->orig_off);
1971 if (!orig_insn) {
1972 WARN_FUNC("special: can't find orig instruction",
1973 special_alt->orig_sec, special_alt->orig_off);
1974 ret = -1;
1975 goto out;
1976 }
1977
1978 new_insn = NULL;
1979 if (!special_alt->group || special_alt->new_len) {
1980 new_insn = find_insn(file, special_alt->new_sec,
1981 special_alt->new_off);
1982 if (!new_insn) {
1983 WARN_FUNC("special: can't find new instruction",
1984 special_alt->new_sec,
1985 special_alt->new_off);
1986 ret = -1;
1987 goto out;
1988 }
1989 }
1990
1991 if (special_alt->group) {
1992 if (!special_alt->orig_len) {
1993 WARN_INSN(orig_insn, "empty alternative entry");
1994 continue;
1995 }
1996
1997 ret = handle_group_alt(file, special_alt, orig_insn,
1998 &new_insn);
1999 if (ret)
2000 goto out;
2001 } else if (special_alt->jump_or_nop) {
2002 ret = handle_jump_alt(file, special_alt, orig_insn,
2003 &new_insn);
2004 if (ret)
2005 goto out;
2006 }
2007
2008 alt = malloc(sizeof(*alt));
2009 if (!alt) {
2010 WARN("malloc failed");
2011 ret = -1;
2012 goto out;
2013 }
2014
2015 alt->insn = new_insn;
2016 alt->skip_orig = special_alt->skip_orig;
2017 orig_insn->ignore_alts |= special_alt->skip_alt;
2018 alt->next = orig_insn->alts;
2019 orig_insn->alts = alt;
2020
2021 list_del(&special_alt->list);
2022 free(special_alt);
2023 }
2024
2025 if (opts.stats) {
2026 printf("jl\\\tNOP\tJMP\n");
2027 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
2028 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
2029 }
2030
2031out:
2032 return ret;
2033}
2034
2035static int add_jump_table(struct objtool_file *file, struct instruction *insn,
2036 struct reloc *next_table)
2037{
2038 struct symbol *pfunc = insn_func(insn)->pfunc;
2039 struct reloc *table = insn_jump_table(insn);
2040 struct instruction *dest_insn;
2041 unsigned int prev_offset = 0;
2042 struct reloc *reloc = table;
2043 struct alternative *alt;
2044
2045 /*
2046 * Each @reloc is a switch table relocation which points to the target
2047 * instruction.
2048 */
2049 for_each_reloc_from(table->sec, reloc) {
2050
2051 /* Check for the end of the table: */
2052 if (reloc != table && reloc == next_table)
2053 break;
2054
2055 /* Make sure the table entries are consecutive: */
2056 if (prev_offset && reloc_offset(reloc) != prev_offset + 8)
2057 break;
2058
2059 /* Detect function pointers from contiguous objects: */
2060 if (reloc->sym->sec == pfunc->sec &&
2061 reloc_addend(reloc) == pfunc->offset)
2062 break;
2063
2064 dest_insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2065 if (!dest_insn)
2066 break;
2067
2068 /* Make sure the destination is in the same function: */
2069 if (!insn_func(dest_insn) || insn_func(dest_insn)->pfunc != pfunc)
2070 break;
2071
2072 alt = malloc(sizeof(*alt));
2073 if (!alt) {
2074 WARN("malloc failed");
2075 return -1;
2076 }
2077
2078 alt->insn = dest_insn;
2079 alt->next = insn->alts;
2080 insn->alts = alt;
2081 prev_offset = reloc_offset(reloc);
2082 }
2083
2084 if (!prev_offset) {
2085 WARN_INSN(insn, "can't find switch jump table");
2086 return -1;
2087 }
2088
2089 return 0;
2090}
2091
2092/*
2093 * find_jump_table() - Given a dynamic jump, find the switch jump table
2094 * associated with it.
2095 */
2096static struct reloc *find_jump_table(struct objtool_file *file,
2097 struct symbol *func,
2098 struct instruction *insn)
2099{
2100 struct reloc *table_reloc;
2101 struct instruction *dest_insn, *orig_insn = insn;
2102
2103 /*
2104 * Backward search using the @first_jump_src links, these help avoid
2105 * much of the 'in between' code. Which avoids us getting confused by
2106 * it.
2107 */
2108 for (;
2109 insn && insn_func(insn) && insn_func(insn)->pfunc == func;
2110 insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
2111
2112 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
2113 break;
2114
2115 /* allow small jumps within the range */
2116 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
2117 insn->jump_dest &&
2118 (insn->jump_dest->offset <= insn->offset ||
2119 insn->jump_dest->offset > orig_insn->offset))
2120 break;
2121
2122 table_reloc = arch_find_switch_table(file, insn);
2123 if (!table_reloc)
2124 continue;
2125 dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
2126 if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
2127 continue;
2128
2129 return table_reloc;
2130 }
2131
2132 return NULL;
2133}
2134
2135/*
2136 * First pass: Mark the head of each jump table so that in the next pass,
2137 * we know when a given jump table ends and the next one starts.
2138 */
2139static void mark_func_jump_tables(struct objtool_file *file,
2140 struct symbol *func)
2141{
2142 struct instruction *insn, *last = NULL;
2143 struct reloc *reloc;
2144
2145 func_for_each_insn(file, func, insn) {
2146 if (!last)
2147 last = insn;
2148
2149 /*
2150 * Store back-pointers for unconditional forward jumps such
2151 * that find_jump_table() can back-track using those and
2152 * avoid some potentially confusing code.
2153 */
2154 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
2155 insn->offset > last->offset &&
2156 insn->jump_dest->offset > insn->offset &&
2157 !insn->jump_dest->first_jump_src) {
2158
2159 insn->jump_dest->first_jump_src = insn;
2160 last = insn->jump_dest;
2161 }
2162
2163 if (insn->type != INSN_JUMP_DYNAMIC)
2164 continue;
2165
2166 reloc = find_jump_table(file, func, insn);
2167 if (reloc)
2168 insn->_jump_table = reloc;
2169 }
2170}
2171
2172static int add_func_jump_tables(struct objtool_file *file,
2173 struct symbol *func)
2174{
2175 struct instruction *insn, *insn_t1 = NULL, *insn_t2;
2176 int ret = 0;
2177
2178 func_for_each_insn(file, func, insn) {
2179 if (!insn_jump_table(insn))
2180 continue;
2181
2182 if (!insn_t1) {
2183 insn_t1 = insn;
2184 continue;
2185 }
2186
2187 insn_t2 = insn;
2188
2189 ret = add_jump_table(file, insn_t1, insn_jump_table(insn_t2));
2190 if (ret)
2191 return ret;
2192
2193 insn_t1 = insn_t2;
2194 }
2195
2196 if (insn_t1)
2197 ret = add_jump_table(file, insn_t1, NULL);
2198
2199 return ret;
2200}
2201
2202/*
2203 * For some switch statements, gcc generates a jump table in the .rodata
2204 * section which contains a list of addresses within the function to jump to.
2205 * This finds these jump tables and adds them to the insn->alts lists.
2206 */
2207static int add_jump_table_alts(struct objtool_file *file)
2208{
2209 struct symbol *func;
2210 int ret;
2211
2212 if (!file->rodata)
2213 return 0;
2214
2215 for_each_sym(file, func) {
2216 if (func->type != STT_FUNC)
2217 continue;
2218
2219 mark_func_jump_tables(file, func);
2220 ret = add_func_jump_tables(file, func);
2221 if (ret)
2222 return ret;
2223 }
2224
2225 return 0;
2226}
2227
2228static void set_func_state(struct cfi_state *state)
2229{
2230 state->cfa = initial_func_cfi.cfa;
2231 memcpy(&state->regs, &initial_func_cfi.regs,
2232 CFI_NUM_REGS * sizeof(struct cfi_reg));
2233 state->stack_size = initial_func_cfi.cfa.offset;
2234 state->type = UNWIND_HINT_TYPE_CALL;
2235}
2236
2237static int read_unwind_hints(struct objtool_file *file)
2238{
2239 struct cfi_state cfi = init_cfi;
2240 struct section *sec;
2241 struct unwind_hint *hint;
2242 struct instruction *insn;
2243 struct reloc *reloc;
2244 unsigned long offset;
2245 int i;
2246
2247 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
2248 if (!sec)
2249 return 0;
2250
2251 if (!sec->rsec) {
2252 WARN("missing .rela.discard.unwind_hints section");
2253 return -1;
2254 }
2255
2256 if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
2257 WARN("struct unwind_hint size mismatch");
2258 return -1;
2259 }
2260
2261 file->hints = true;
2262
2263 for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
2264 hint = (struct unwind_hint *)sec->data->d_buf + i;
2265
2266 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
2267 if (!reloc) {
2268 WARN("can't find reloc for unwind_hints[%d]", i);
2269 return -1;
2270 }
2271
2272 if (reloc->sym->type == STT_SECTION) {
2273 offset = reloc_addend(reloc);
2274 } else if (reloc->sym->local_label) {
2275 offset = reloc->sym->offset;
2276 } else {
2277 WARN("unexpected relocation symbol type in %s", sec->rsec->name);
2278 return -1;
2279 }
2280
2281 insn = find_insn(file, reloc->sym->sec, offset);
2282 if (!insn) {
2283 WARN("can't find insn for unwind_hints[%d]", i);
2284 return -1;
2285 }
2286
2287 insn->hint = true;
2288
2289 if (hint->type == UNWIND_HINT_TYPE_UNDEFINED) {
2290 insn->cfi = &force_undefined_cfi;
2291 continue;
2292 }
2293
2294 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
2295 insn->hint = false;
2296 insn->save = true;
2297 continue;
2298 }
2299
2300 if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
2301 insn->restore = true;
2302 continue;
2303 }
2304
2305 if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
2306 struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
2307
2308 if (sym && sym->bind == STB_GLOBAL) {
2309 if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) {
2310 WARN_INSN(insn, "UNWIND_HINT_IRET_REGS without ENDBR");
2311 }
2312 }
2313 }
2314
2315 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
2316 insn->cfi = &func_cfi;
2317 continue;
2318 }
2319
2320 if (insn->cfi)
2321 cfi = *(insn->cfi);
2322
2323 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
2324 WARN_INSN(insn, "unsupported unwind_hint sp base reg %d", hint->sp_reg);
2325 return -1;
2326 }
2327
2328 cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
2329 cfi.type = hint->type;
2330 cfi.signal = hint->signal;
2331
2332 insn->cfi = cfi_hash_find_or_add(&cfi);
2333 }
2334
2335 return 0;
2336}
2337
2338static int read_noendbr_hints(struct objtool_file *file)
2339{
2340 struct instruction *insn;
2341 struct section *rsec;
2342 struct reloc *reloc;
2343
2344 rsec = find_section_by_name(file->elf, ".rela.discard.noendbr");
2345 if (!rsec)
2346 return 0;
2347
2348 for_each_reloc(rsec, reloc) {
2349 insn = find_insn(file, reloc->sym->sec,
2350 reloc->sym->offset + reloc_addend(reloc));
2351 if (!insn) {
2352 WARN("bad .discard.noendbr entry");
2353 return -1;
2354 }
2355
2356 insn->noendbr = 1;
2357 }
2358
2359 return 0;
2360}
2361
2362static int read_retpoline_hints(struct objtool_file *file)
2363{
2364 struct section *rsec;
2365 struct instruction *insn;
2366 struct reloc *reloc;
2367
2368 rsec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
2369 if (!rsec)
2370 return 0;
2371
2372 for_each_reloc(rsec, reloc) {
2373 if (reloc->sym->type != STT_SECTION) {
2374 WARN("unexpected relocation symbol type in %s", rsec->name);
2375 return -1;
2376 }
2377
2378 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2379 if (!insn) {
2380 WARN("bad .discard.retpoline_safe entry");
2381 return -1;
2382 }
2383
2384 if (insn->type != INSN_JUMP_DYNAMIC &&
2385 insn->type != INSN_CALL_DYNAMIC &&
2386 insn->type != INSN_RETURN &&
2387 insn->type != INSN_NOP) {
2388 WARN_INSN(insn, "retpoline_safe hint not an indirect jump/call/ret/nop");
2389 return -1;
2390 }
2391
2392 insn->retpoline_safe = true;
2393 }
2394
2395 return 0;
2396}
2397
2398static int read_instr_hints(struct objtool_file *file)
2399{
2400 struct section *rsec;
2401 struct instruction *insn;
2402 struct reloc *reloc;
2403
2404 rsec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2405 if (!rsec)
2406 return 0;
2407
2408 for_each_reloc(rsec, reloc) {
2409 if (reloc->sym->type != STT_SECTION) {
2410 WARN("unexpected relocation symbol type in %s", rsec->name);
2411 return -1;
2412 }
2413
2414 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2415 if (!insn) {
2416 WARN("bad .discard.instr_end entry");
2417 return -1;
2418 }
2419
2420 insn->instr--;
2421 }
2422
2423 rsec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2424 if (!rsec)
2425 return 0;
2426
2427 for_each_reloc(rsec, reloc) {
2428 if (reloc->sym->type != STT_SECTION) {
2429 WARN("unexpected relocation symbol type in %s", rsec->name);
2430 return -1;
2431 }
2432
2433 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2434 if (!insn) {
2435 WARN("bad .discard.instr_begin entry");
2436 return -1;
2437 }
2438
2439 insn->instr++;
2440 }
2441
2442 return 0;
2443}
2444
2445static int read_validate_unret_hints(struct objtool_file *file)
2446{
2447 struct section *rsec;
2448 struct instruction *insn;
2449 struct reloc *reloc;
2450
2451 rsec = find_section_by_name(file->elf, ".rela.discard.validate_unret");
2452 if (!rsec)
2453 return 0;
2454
2455 for_each_reloc(rsec, reloc) {
2456 if (reloc->sym->type != STT_SECTION) {
2457 WARN("unexpected relocation symbol type in %s", rsec->name);
2458 return -1;
2459 }
2460
2461 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2462 if (!insn) {
2463 WARN("bad .discard.instr_end entry");
2464 return -1;
2465 }
2466 insn->unret = 1;
2467 }
2468
2469 return 0;
2470}
2471
2472
2473static int read_intra_function_calls(struct objtool_file *file)
2474{
2475 struct instruction *insn;
2476 struct section *rsec;
2477 struct reloc *reloc;
2478
2479 rsec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2480 if (!rsec)
2481 return 0;
2482
2483 for_each_reloc(rsec, reloc) {
2484 unsigned long dest_off;
2485
2486 if (reloc->sym->type != STT_SECTION) {
2487 WARN("unexpected relocation symbol type in %s",
2488 rsec->name);
2489 return -1;
2490 }
2491
2492 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2493 if (!insn) {
2494 WARN("bad .discard.intra_function_call entry");
2495 return -1;
2496 }
2497
2498 if (insn->type != INSN_CALL) {
2499 WARN_INSN(insn, "intra_function_call not a direct call");
2500 return -1;
2501 }
2502
2503 /*
2504 * Treat intra-function CALLs as JMPs, but with a stack_op.
2505 * See add_call_destinations(), which strips stack_ops from
2506 * normal CALLs.
2507 */
2508 insn->type = INSN_JUMP_UNCONDITIONAL;
2509
2510 dest_off = arch_jump_destination(insn);
2511 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2512 if (!insn->jump_dest) {
2513 WARN_INSN(insn, "can't find call dest at %s+0x%lx",
2514 insn->sec->name, dest_off);
2515 return -1;
2516 }
2517 }
2518
2519 return 0;
2520}
2521
2522/*
2523 * Return true if name matches an instrumentation function, where calls to that
2524 * function from noinstr code can safely be removed, but compilers won't do so.
2525 */
2526static bool is_profiling_func(const char *name)
2527{
2528 /*
2529 * Many compilers cannot disable KCOV with a function attribute.
2530 */
2531 if (!strncmp(name, "__sanitizer_cov_", 16))
2532 return true;
2533
2534 /*
2535 * Some compilers currently do not remove __tsan_func_entry/exit nor
2536 * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2537 * the __no_sanitize_thread attribute, remove them. Once the kernel's
2538 * minimum Clang version is 14.0, this can be removed.
2539 */
2540 if (!strncmp(name, "__tsan_func_", 12) ||
2541 !strcmp(name, "__tsan_atomic_signal_fence"))
2542 return true;
2543
2544 return false;
2545}
2546
2547static int classify_symbols(struct objtool_file *file)
2548{
2549 struct symbol *func;
2550
2551 for_each_sym(file, func) {
2552 if (func->type == STT_NOTYPE && strstarts(func->name, ".L"))
2553 func->local_label = true;
2554
2555 if (func->bind != STB_GLOBAL)
2556 continue;
2557
2558 if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2559 strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2560 func->static_call_tramp = true;
2561
2562 if (arch_is_retpoline(func))
2563 func->retpoline_thunk = true;
2564
2565 if (arch_is_rethunk(func))
2566 func->return_thunk = true;
2567
2568 if (arch_is_embedded_insn(func))
2569 func->embedded_insn = true;
2570
2571 if (arch_ftrace_match(func->name))
2572 func->fentry = true;
2573
2574 if (is_profiling_func(func->name))
2575 func->profiling_func = true;
2576 }
2577
2578 return 0;
2579}
2580
2581static void mark_rodata(struct objtool_file *file)
2582{
2583 struct section *sec;
2584 bool found = false;
2585
2586 /*
2587 * Search for the following rodata sections, each of which can
2588 * potentially contain jump tables:
2589 *
2590 * - .rodata: can contain GCC switch tables
2591 * - .rodata.<func>: same, if -fdata-sections is being used
2592 * - .data.rel.ro.c_jump_table: contains C annotated jump tables
2593 *
2594 * .rodata.str1.* sections are ignored; they don't contain jump tables.
2595 */
2596 for_each_sec(file, sec) {
2597 if ((!strncmp(sec->name, ".rodata", 7) &&
2598 !strstr(sec->name, ".str1.")) ||
2599 !strncmp(sec->name, ".data.rel.ro", 12)) {
2600 sec->rodata = true;
2601 found = true;
2602 }
2603 }
2604
2605 file->rodata = found;
2606}
2607
2608static int decode_sections(struct objtool_file *file)
2609{
2610 int ret;
2611
2612 mark_rodata(file);
2613
2614 ret = init_pv_ops(file);
2615 if (ret)
2616 return ret;
2617
2618 /*
2619 * Must be before add_{jump_call}_destination.
2620 */
2621 ret = classify_symbols(file);
2622 if (ret)
2623 return ret;
2624
2625 ret = decode_instructions(file);
2626 if (ret)
2627 return ret;
2628
2629 add_ignores(file);
2630 add_uaccess_safe(file);
2631
2632 ret = add_ignore_alternatives(file);
2633 if (ret)
2634 return ret;
2635
2636 /*
2637 * Must be before read_unwind_hints() since that needs insn->noendbr.
2638 */
2639 ret = read_noendbr_hints(file);
2640 if (ret)
2641 return ret;
2642
2643 /*
2644 * Must be before add_jump_destinations(), which depends on 'func'
2645 * being set for alternatives, to enable proper sibling call detection.
2646 */
2647 if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) {
2648 ret = add_special_section_alts(file);
2649 if (ret)
2650 return ret;
2651 }
2652
2653 ret = add_jump_destinations(file);
2654 if (ret)
2655 return ret;
2656
2657 /*
2658 * Must be before add_call_destination(); it changes INSN_CALL to
2659 * INSN_JUMP.
2660 */
2661 ret = read_intra_function_calls(file);
2662 if (ret)
2663 return ret;
2664
2665 ret = add_call_destinations(file);
2666 if (ret)
2667 return ret;
2668
2669 /*
2670 * Must be after add_call_destinations() such that it can override
2671 * dead_end_function() marks.
2672 */
2673 ret = add_dead_ends(file);
2674 if (ret)
2675 return ret;
2676
2677 ret = add_jump_table_alts(file);
2678 if (ret)
2679 return ret;
2680
2681 ret = read_unwind_hints(file);
2682 if (ret)
2683 return ret;
2684
2685 ret = read_retpoline_hints(file);
2686 if (ret)
2687 return ret;
2688
2689 ret = read_instr_hints(file);
2690 if (ret)
2691 return ret;
2692
2693 ret = read_validate_unret_hints(file);
2694 if (ret)
2695 return ret;
2696
2697 return 0;
2698}
2699
2700static bool is_special_call(struct instruction *insn)
2701{
2702 if (insn->type == INSN_CALL) {
2703 struct symbol *dest = insn_call_dest(insn);
2704
2705 if (!dest)
2706 return false;
2707
2708 if (dest->fentry || dest->embedded_insn)
2709 return true;
2710 }
2711
2712 return false;
2713}
2714
2715static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2716{
2717 struct cfi_state *cfi = &state->cfi;
2718 int i;
2719
2720 if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2721 return true;
2722
2723 if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2724 return true;
2725
2726 if (cfi->stack_size != initial_func_cfi.cfa.offset)
2727 return true;
2728
2729 for (i = 0; i < CFI_NUM_REGS; i++) {
2730 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2731 cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2732 return true;
2733 }
2734
2735 return false;
2736}
2737
2738static bool check_reg_frame_pos(const struct cfi_reg *reg,
2739 int expected_offset)
2740{
2741 return reg->base == CFI_CFA &&
2742 reg->offset == expected_offset;
2743}
2744
2745static bool has_valid_stack_frame(struct insn_state *state)
2746{
2747 struct cfi_state *cfi = &state->cfi;
2748
2749 if (cfi->cfa.base == CFI_BP &&
2750 check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2751 check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2752 return true;
2753
2754 if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2755 return true;
2756
2757 return false;
2758}
2759
2760static int update_cfi_state_regs(struct instruction *insn,
2761 struct cfi_state *cfi,
2762 struct stack_op *op)
2763{
2764 struct cfi_reg *cfa = &cfi->cfa;
2765
2766 if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2767 return 0;
2768
2769 /* push */
2770 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2771 cfa->offset += 8;
2772
2773 /* pop */
2774 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2775 cfa->offset -= 8;
2776
2777 /* add immediate to sp */
2778 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2779 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2780 cfa->offset -= op->src.offset;
2781
2782 return 0;
2783}
2784
2785static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2786{
2787 if (arch_callee_saved_reg(reg) &&
2788 cfi->regs[reg].base == CFI_UNDEFINED) {
2789 cfi->regs[reg].base = base;
2790 cfi->regs[reg].offset = offset;
2791 }
2792}
2793
2794static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2795{
2796 cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2797 cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2798}
2799
2800/*
2801 * A note about DRAP stack alignment:
2802 *
2803 * GCC has the concept of a DRAP register, which is used to help keep track of
2804 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
2805 * register. The typical DRAP pattern is:
2806 *
2807 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
2808 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
2809 * 41 ff 72 f8 pushq -0x8(%r10)
2810 * 55 push %rbp
2811 * 48 89 e5 mov %rsp,%rbp
2812 * (more pushes)
2813 * 41 52 push %r10
2814 * ...
2815 * 41 5a pop %r10
2816 * (more pops)
2817 * 5d pop %rbp
2818 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2819 * c3 retq
2820 *
2821 * There are some variations in the epilogues, like:
2822 *
2823 * 5b pop %rbx
2824 * 41 5a pop %r10
2825 * 41 5c pop %r12
2826 * 41 5d pop %r13
2827 * 41 5e pop %r14
2828 * c9 leaveq
2829 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2830 * c3 retq
2831 *
2832 * and:
2833 *
2834 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
2835 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
2836 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
2837 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
2838 * c9 leaveq
2839 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2840 * c3 retq
2841 *
2842 * Sometimes r13 is used as the DRAP register, in which case it's saved and
2843 * restored beforehand:
2844 *
2845 * 41 55 push %r13
2846 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
2847 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
2848 * ...
2849 * 49 8d 65 f0 lea -0x10(%r13),%rsp
2850 * 41 5d pop %r13
2851 * c3 retq
2852 */
2853static int update_cfi_state(struct instruction *insn,
2854 struct instruction *next_insn,
2855 struct cfi_state *cfi, struct stack_op *op)
2856{
2857 struct cfi_reg *cfa = &cfi->cfa;
2858 struct cfi_reg *regs = cfi->regs;
2859
2860 /* ignore UNWIND_HINT_UNDEFINED regions */
2861 if (cfi->force_undefined)
2862 return 0;
2863
2864 /* stack operations don't make sense with an undefined CFA */
2865 if (cfa->base == CFI_UNDEFINED) {
2866 if (insn_func(insn)) {
2867 WARN_INSN(insn, "undefined stack state");
2868 return -1;
2869 }
2870 return 0;
2871 }
2872
2873 if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2874 cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2875 return update_cfi_state_regs(insn, cfi, op);
2876
2877 switch (op->dest.type) {
2878
2879 case OP_DEST_REG:
2880 switch (op->src.type) {
2881
2882 case OP_SRC_REG:
2883 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2884 cfa->base == CFI_SP &&
2885 check_reg_frame_pos(®s[CFI_BP], -cfa->offset)) {
2886
2887 /* mov %rsp, %rbp */
2888 cfa->base = op->dest.reg;
2889 cfi->bp_scratch = false;
2890 }
2891
2892 else if (op->src.reg == CFI_SP &&
2893 op->dest.reg == CFI_BP && cfi->drap) {
2894
2895 /* drap: mov %rsp, %rbp */
2896 regs[CFI_BP].base = CFI_BP;
2897 regs[CFI_BP].offset = -cfi->stack_size;
2898 cfi->bp_scratch = false;
2899 }
2900
2901 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2902
2903 /*
2904 * mov %rsp, %reg
2905 *
2906 * This is needed for the rare case where GCC
2907 * does:
2908 *
2909 * mov %rsp, %rax
2910 * ...
2911 * mov %rax, %rsp
2912 */
2913 cfi->vals[op->dest.reg].base = CFI_CFA;
2914 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2915 }
2916
2917 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2918 (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2919
2920 /*
2921 * mov %rbp, %rsp
2922 *
2923 * Restore the original stack pointer (Clang).
2924 */
2925 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2926 }
2927
2928 else if (op->dest.reg == cfa->base) {
2929
2930 /* mov %reg, %rsp */
2931 if (cfa->base == CFI_SP &&
2932 cfi->vals[op->src.reg].base == CFI_CFA) {
2933
2934 /*
2935 * This is needed for the rare case
2936 * where GCC does something dumb like:
2937 *
2938 * lea 0x8(%rsp), %rcx
2939 * ...
2940 * mov %rcx, %rsp
2941 */
2942 cfa->offset = -cfi->vals[op->src.reg].offset;
2943 cfi->stack_size = cfa->offset;
2944
2945 } else if (cfa->base == CFI_SP &&
2946 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2947 cfi->vals[op->src.reg].offset == cfa->offset) {
2948
2949 /*
2950 * Stack swizzle:
2951 *
2952 * 1: mov %rsp, (%[tos])
2953 * 2: mov %[tos], %rsp
2954 * ...
2955 * 3: pop %rsp
2956 *
2957 * Where:
2958 *
2959 * 1 - places a pointer to the previous
2960 * stack at the Top-of-Stack of the
2961 * new stack.
2962 *
2963 * 2 - switches to the new stack.
2964 *
2965 * 3 - pops the Top-of-Stack to restore
2966 * the original stack.
2967 *
2968 * Note: we set base to SP_INDIRECT
2969 * here and preserve offset. Therefore
2970 * when the unwinder reaches ToS it
2971 * will dereference SP and then add the
2972 * offset to find the next frame, IOW:
2973 * (%rsp) + offset.
2974 */
2975 cfa->base = CFI_SP_INDIRECT;
2976
2977 } else {
2978 cfa->base = CFI_UNDEFINED;
2979 cfa->offset = 0;
2980 }
2981 }
2982
2983 else if (op->dest.reg == CFI_SP &&
2984 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2985 cfi->vals[op->src.reg].offset == cfa->offset) {
2986
2987 /*
2988 * The same stack swizzle case 2) as above. But
2989 * because we can't change cfa->base, case 3)
2990 * will become a regular POP. Pretend we're a
2991 * PUSH so things don't go unbalanced.
2992 */
2993 cfi->stack_size += 8;
2994 }
2995
2996
2997 break;
2998
2999 case OP_SRC_ADD:
3000 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
3001
3002 /* add imm, %rsp */
3003 cfi->stack_size -= op->src.offset;
3004 if (cfa->base == CFI_SP)
3005 cfa->offset -= op->src.offset;
3006 break;
3007 }
3008
3009 if (op->dest.reg == CFI_BP && op->src.reg == CFI_SP &&
3010 insn->sym->frame_pointer) {
3011 /* addi.d fp,sp,imm on LoongArch */
3012 if (cfa->base == CFI_SP && cfa->offset == op->src.offset) {
3013 cfa->base = CFI_BP;
3014 cfa->offset = 0;
3015 }
3016 break;
3017 }
3018
3019 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
3020 /* addi.d sp,fp,imm on LoongArch */
3021 if (cfa->base == CFI_BP && cfa->offset == 0) {
3022 if (insn->sym->frame_pointer) {
3023 cfa->base = CFI_SP;
3024 cfa->offset = -op->src.offset;
3025 }
3026 } else {
3027 /* lea disp(%rbp), %rsp */
3028 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
3029 }
3030 break;
3031 }
3032
3033 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
3034
3035 /* drap: lea disp(%rsp), %drap */
3036 cfi->drap_reg = op->dest.reg;
3037
3038 /*
3039 * lea disp(%rsp), %reg
3040 *
3041 * This is needed for the rare case where GCC
3042 * does something dumb like:
3043 *
3044 * lea 0x8(%rsp), %rcx
3045 * ...
3046 * mov %rcx, %rsp
3047 */
3048 cfi->vals[op->dest.reg].base = CFI_CFA;
3049 cfi->vals[op->dest.reg].offset = \
3050 -cfi->stack_size + op->src.offset;
3051
3052 break;
3053 }
3054
3055 if (cfi->drap && op->dest.reg == CFI_SP &&
3056 op->src.reg == cfi->drap_reg) {
3057
3058 /* drap: lea disp(%drap), %rsp */
3059 cfa->base = CFI_SP;
3060 cfa->offset = cfi->stack_size = -op->src.offset;
3061 cfi->drap_reg = CFI_UNDEFINED;
3062 cfi->drap = false;
3063 break;
3064 }
3065
3066 if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
3067 WARN_INSN(insn, "unsupported stack register modification");
3068 return -1;
3069 }
3070
3071 break;
3072
3073 case OP_SRC_AND:
3074 if (op->dest.reg != CFI_SP ||
3075 (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
3076 (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
3077 WARN_INSN(insn, "unsupported stack pointer realignment");
3078 return -1;
3079 }
3080
3081 if (cfi->drap_reg != CFI_UNDEFINED) {
3082 /* drap: and imm, %rsp */
3083 cfa->base = cfi->drap_reg;
3084 cfa->offset = cfi->stack_size = 0;
3085 cfi->drap = true;
3086 }
3087
3088 /*
3089 * Older versions of GCC (4.8ish) realign the stack
3090 * without DRAP, with a frame pointer.
3091 */
3092
3093 break;
3094
3095 case OP_SRC_POP:
3096 case OP_SRC_POPF:
3097 if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
3098
3099 /* pop %rsp; # restore from a stack swizzle */
3100 cfa->base = CFI_SP;
3101 break;
3102 }
3103
3104 if (!cfi->drap && op->dest.reg == cfa->base) {
3105
3106 /* pop %rbp */
3107 cfa->base = CFI_SP;
3108 }
3109
3110 if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
3111 op->dest.reg == cfi->drap_reg &&
3112 cfi->drap_offset == -cfi->stack_size) {
3113
3114 /* drap: pop %drap */
3115 cfa->base = cfi->drap_reg;
3116 cfa->offset = 0;
3117 cfi->drap_offset = -1;
3118
3119 } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
3120
3121 /* pop %reg */
3122 restore_reg(cfi, op->dest.reg);
3123 }
3124
3125 cfi->stack_size -= 8;
3126 if (cfa->base == CFI_SP)
3127 cfa->offset -= 8;
3128
3129 break;
3130
3131 case OP_SRC_REG_INDIRECT:
3132 if (!cfi->drap && op->dest.reg == cfa->base &&
3133 op->dest.reg == CFI_BP) {
3134
3135 /* mov disp(%rsp), %rbp */
3136 cfa->base = CFI_SP;
3137 cfa->offset = cfi->stack_size;
3138 }
3139
3140 if (cfi->drap && op->src.reg == CFI_BP &&
3141 op->src.offset == cfi->drap_offset) {
3142
3143 /* drap: mov disp(%rbp), %drap */
3144 cfa->base = cfi->drap_reg;
3145 cfa->offset = 0;
3146 cfi->drap_offset = -1;
3147 }
3148
3149 if (cfi->drap && op->src.reg == CFI_BP &&
3150 op->src.offset == regs[op->dest.reg].offset) {
3151
3152 /* drap: mov disp(%rbp), %reg */
3153 restore_reg(cfi, op->dest.reg);
3154
3155 } else if (op->src.reg == cfa->base &&
3156 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
3157
3158 /* mov disp(%rbp), %reg */
3159 /* mov disp(%rsp), %reg */
3160 restore_reg(cfi, op->dest.reg);
3161
3162 } else if (op->src.reg == CFI_SP &&
3163 op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
3164
3165 /* mov disp(%rsp), %reg */
3166 restore_reg(cfi, op->dest.reg);
3167 }
3168
3169 break;
3170
3171 default:
3172 WARN_INSN(insn, "unknown stack-related instruction");
3173 return -1;
3174 }
3175
3176 break;
3177
3178 case OP_DEST_PUSH:
3179 case OP_DEST_PUSHF:
3180 cfi->stack_size += 8;
3181 if (cfa->base == CFI_SP)
3182 cfa->offset += 8;
3183
3184 if (op->src.type != OP_SRC_REG)
3185 break;
3186
3187 if (cfi->drap) {
3188 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3189
3190 /* drap: push %drap */
3191 cfa->base = CFI_BP_INDIRECT;
3192 cfa->offset = -cfi->stack_size;
3193
3194 /* save drap so we know when to restore it */
3195 cfi->drap_offset = -cfi->stack_size;
3196
3197 } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
3198
3199 /* drap: push %rbp */
3200 cfi->stack_size = 0;
3201
3202 } else {
3203
3204 /* drap: push %reg */
3205 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
3206 }
3207
3208 } else {
3209
3210 /* push %reg */
3211 save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
3212 }
3213
3214 /* detect when asm code uses rbp as a scratch register */
3215 if (opts.stackval && insn_func(insn) && op->src.reg == CFI_BP &&
3216 cfa->base != CFI_BP)
3217 cfi->bp_scratch = true;
3218 break;
3219
3220 case OP_DEST_REG_INDIRECT:
3221
3222 if (cfi->drap) {
3223 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3224
3225 /* drap: mov %drap, disp(%rbp) */
3226 cfa->base = CFI_BP_INDIRECT;
3227 cfa->offset = op->dest.offset;
3228
3229 /* save drap offset so we know when to restore it */
3230 cfi->drap_offset = op->dest.offset;
3231 } else {
3232
3233 /* drap: mov reg, disp(%rbp) */
3234 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
3235 }
3236
3237 } else if (op->dest.reg == cfa->base) {
3238
3239 /* mov reg, disp(%rbp) */
3240 /* mov reg, disp(%rsp) */
3241 save_reg(cfi, op->src.reg, CFI_CFA,
3242 op->dest.offset - cfi->cfa.offset);
3243
3244 } else if (op->dest.reg == CFI_SP) {
3245
3246 /* mov reg, disp(%rsp) */
3247 save_reg(cfi, op->src.reg, CFI_CFA,
3248 op->dest.offset - cfi->stack_size);
3249
3250 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
3251
3252 /* mov %rsp, (%reg); # setup a stack swizzle. */
3253 cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
3254 cfi->vals[op->dest.reg].offset = cfa->offset;
3255 }
3256
3257 break;
3258
3259 case OP_DEST_MEM:
3260 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
3261 WARN_INSN(insn, "unknown stack-related memory operation");
3262 return -1;
3263 }
3264
3265 /* pop mem */
3266 cfi->stack_size -= 8;
3267 if (cfa->base == CFI_SP)
3268 cfa->offset -= 8;
3269
3270 break;
3271
3272 default:
3273 WARN_INSN(insn, "unknown stack-related instruction");
3274 return -1;
3275 }
3276
3277 return 0;
3278}
3279
3280/*
3281 * The stack layouts of alternatives instructions can sometimes diverge when
3282 * they have stack modifications. That's fine as long as the potential stack
3283 * layouts don't conflict at any given potential instruction boundary.
3284 *
3285 * Flatten the CFIs of the different alternative code streams (both original
3286 * and replacement) into a single shared CFI array which can be used to detect
3287 * conflicts and nicely feed a linear array of ORC entries to the unwinder.
3288 */
3289static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
3290{
3291 struct cfi_state **alt_cfi;
3292 int group_off;
3293
3294 if (!insn->alt_group)
3295 return 0;
3296
3297 if (!insn->cfi) {
3298 WARN("CFI missing");
3299 return -1;
3300 }
3301
3302 alt_cfi = insn->alt_group->cfi;
3303 group_off = insn->offset - insn->alt_group->first_insn->offset;
3304
3305 if (!alt_cfi[group_off]) {
3306 alt_cfi[group_off] = insn->cfi;
3307 } else {
3308 if (cficmp(alt_cfi[group_off], insn->cfi)) {
3309 struct alt_group *orig_group = insn->alt_group->orig_group ?: insn->alt_group;
3310 struct instruction *orig = orig_group->first_insn;
3311 char *where = offstr(insn->sec, insn->offset);
3312 WARN_INSN(orig, "stack layout conflict in alternatives: %s", where);
3313 free(where);
3314 return -1;
3315 }
3316 }
3317
3318 return 0;
3319}
3320
3321static int handle_insn_ops(struct instruction *insn,
3322 struct instruction *next_insn,
3323 struct insn_state *state)
3324{
3325 struct stack_op *op;
3326
3327 for (op = insn->stack_ops; op; op = op->next) {
3328
3329 if (update_cfi_state(insn, next_insn, &state->cfi, op))
3330 return 1;
3331
3332 if (!insn->alt_group)
3333 continue;
3334
3335 if (op->dest.type == OP_DEST_PUSHF) {
3336 if (!state->uaccess_stack) {
3337 state->uaccess_stack = 1;
3338 } else if (state->uaccess_stack >> 31) {
3339 WARN_INSN(insn, "PUSHF stack exhausted");
3340 return 1;
3341 }
3342 state->uaccess_stack <<= 1;
3343 state->uaccess_stack |= state->uaccess;
3344 }
3345
3346 if (op->src.type == OP_SRC_POPF) {
3347 if (state->uaccess_stack) {
3348 state->uaccess = state->uaccess_stack & 1;
3349 state->uaccess_stack >>= 1;
3350 if (state->uaccess_stack == 1)
3351 state->uaccess_stack = 0;
3352 }
3353 }
3354 }
3355
3356 return 0;
3357}
3358
3359static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
3360{
3361 struct cfi_state *cfi1 = insn->cfi;
3362 int i;
3363
3364 if (!cfi1) {
3365 WARN("CFI missing");
3366 return false;
3367 }
3368
3369 if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
3370
3371 WARN_INSN(insn, "stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
3372 cfi1->cfa.base, cfi1->cfa.offset,
3373 cfi2->cfa.base, cfi2->cfa.offset);
3374
3375 } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
3376 for (i = 0; i < CFI_NUM_REGS; i++) {
3377 if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
3378 sizeof(struct cfi_reg)))
3379 continue;
3380
3381 WARN_INSN(insn, "stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
3382 i, cfi1->regs[i].base, cfi1->regs[i].offset,
3383 i, cfi2->regs[i].base, cfi2->regs[i].offset);
3384 break;
3385 }
3386
3387 } else if (cfi1->type != cfi2->type) {
3388
3389 WARN_INSN(insn, "stack state mismatch: type1=%d type2=%d",
3390 cfi1->type, cfi2->type);
3391
3392 } else if (cfi1->drap != cfi2->drap ||
3393 (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
3394 (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
3395
3396 WARN_INSN(insn, "stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
3397 cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
3398 cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
3399
3400 } else
3401 return true;
3402
3403 return false;
3404}
3405
3406static inline bool func_uaccess_safe(struct symbol *func)
3407{
3408 if (func)
3409 return func->uaccess_safe;
3410
3411 return false;
3412}
3413
3414static inline const char *call_dest_name(struct instruction *insn)
3415{
3416 static char pvname[19];
3417 struct reloc *reloc;
3418 int idx;
3419
3420 if (insn_call_dest(insn))
3421 return insn_call_dest(insn)->name;
3422
3423 reloc = insn_reloc(NULL, insn);
3424 if (reloc && !strcmp(reloc->sym->name, "pv_ops")) {
3425 idx = (reloc_addend(reloc) / sizeof(void *));
3426 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
3427 return pvname;
3428 }
3429
3430 return "{dynamic}";
3431}
3432
3433static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3434{
3435 struct symbol *target;
3436 struct reloc *reloc;
3437 int idx;
3438
3439 reloc = insn_reloc(file, insn);
3440 if (!reloc || strcmp(reloc->sym->name, "pv_ops"))
3441 return false;
3442
3443 idx = (arch_dest_reloc_offset(reloc_addend(reloc)) / sizeof(void *));
3444
3445 if (file->pv_ops[idx].clean)
3446 return true;
3447
3448 file->pv_ops[idx].clean = true;
3449
3450 list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3451 if (!target->sec->noinstr) {
3452 WARN("pv_ops[%d]: %s", idx, target->name);
3453 file->pv_ops[idx].clean = false;
3454 }
3455 }
3456
3457 return file->pv_ops[idx].clean;
3458}
3459
3460static inline bool noinstr_call_dest(struct objtool_file *file,
3461 struct instruction *insn,
3462 struct symbol *func)
3463{
3464 /*
3465 * We can't deal with indirect function calls at present;
3466 * assume they're instrumented.
3467 */
3468 if (!func) {
3469 if (file->pv_ops)
3470 return pv_call_dest(file, insn);
3471
3472 return false;
3473 }
3474
3475 /*
3476 * If the symbol is from a noinstr section; we good.
3477 */
3478 if (func->sec->noinstr)
3479 return true;
3480
3481 /*
3482 * If the symbol is a static_call trampoline, we can't tell.
3483 */
3484 if (func->static_call_tramp)
3485 return true;
3486
3487 /*
3488 * The __ubsan_handle_*() calls are like WARN(), they only happen when
3489 * something 'BAD' happened. At the risk of taking the machine down,
3490 * let them proceed to get the message out.
3491 */
3492 if (!strncmp(func->name, "__ubsan_handle_", 15))
3493 return true;
3494
3495 return false;
3496}
3497
3498static int validate_call(struct objtool_file *file,
3499 struct instruction *insn,
3500 struct insn_state *state)
3501{
3502 if (state->noinstr && state->instr <= 0 &&
3503 !noinstr_call_dest(file, insn, insn_call_dest(insn))) {
3504 WARN_INSN(insn, "call to %s() leaves .noinstr.text section", call_dest_name(insn));
3505 return 1;
3506 }
3507
3508 if (state->uaccess && !func_uaccess_safe(insn_call_dest(insn))) {
3509 WARN_INSN(insn, "call to %s() with UACCESS enabled", call_dest_name(insn));
3510 return 1;
3511 }
3512
3513 if (state->df) {
3514 WARN_INSN(insn, "call to %s() with DF set", call_dest_name(insn));
3515 return 1;
3516 }
3517
3518 return 0;
3519}
3520
3521static int validate_sibling_call(struct objtool_file *file,
3522 struct instruction *insn,
3523 struct insn_state *state)
3524{
3525 if (insn_func(insn) && has_modified_stack_frame(insn, state)) {
3526 WARN_INSN(insn, "sibling call from callable instruction with modified stack frame");
3527 return 1;
3528 }
3529
3530 return validate_call(file, insn, state);
3531}
3532
3533static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3534{
3535 if (state->noinstr && state->instr > 0) {
3536 WARN_INSN(insn, "return with instrumentation enabled");
3537 return 1;
3538 }
3539
3540 if (state->uaccess && !func_uaccess_safe(func)) {
3541 WARN_INSN(insn, "return with UACCESS enabled");
3542 return 1;
3543 }
3544
3545 if (!state->uaccess && func_uaccess_safe(func)) {
3546 WARN_INSN(insn, "return with UACCESS disabled from a UACCESS-safe function");
3547 return 1;
3548 }
3549
3550 if (state->df) {
3551 WARN_INSN(insn, "return with DF set");
3552 return 1;
3553 }
3554
3555 if (func && has_modified_stack_frame(insn, state)) {
3556 WARN_INSN(insn, "return with modified stack frame");
3557 return 1;
3558 }
3559
3560 if (state->cfi.bp_scratch) {
3561 WARN_INSN(insn, "BP used as a scratch register");
3562 return 1;
3563 }
3564
3565 return 0;
3566}
3567
3568static struct instruction *next_insn_to_validate(struct objtool_file *file,
3569 struct instruction *insn)
3570{
3571 struct alt_group *alt_group = insn->alt_group;
3572
3573 /*
3574 * Simulate the fact that alternatives are patched in-place. When the
3575 * end of a replacement alt_group is reached, redirect objtool flow to
3576 * the end of the original alt_group.
3577 *
3578 * insn->alts->insn -> alt_group->first_insn
3579 * ...
3580 * alt_group->last_insn
3581 * [alt_group->nop] -> next(orig_group->last_insn)
3582 */
3583 if (alt_group) {
3584 if (alt_group->nop) {
3585 /* ->nop implies ->orig_group */
3586 if (insn == alt_group->last_insn)
3587 return alt_group->nop;
3588 if (insn == alt_group->nop)
3589 goto next_orig;
3590 }
3591 if (insn == alt_group->last_insn && alt_group->orig_group)
3592 goto next_orig;
3593 }
3594
3595 return next_insn_same_sec(file, insn);
3596
3597next_orig:
3598 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3599}
3600
3601/*
3602 * Follow the branch starting at the given instruction, and recursively follow
3603 * any other branches (jumps). Meanwhile, track the frame pointer state at
3604 * each instruction and validate all the rules described in
3605 * tools/objtool/Documentation/objtool.txt.
3606 */
3607static int validate_branch(struct objtool_file *file, struct symbol *func,
3608 struct instruction *insn, struct insn_state state)
3609{
3610 struct alternative *alt;
3611 struct instruction *next_insn, *prev_insn = NULL;
3612 struct section *sec;
3613 u8 visited;
3614 int ret;
3615
3616 sec = insn->sec;
3617
3618 while (1) {
3619 next_insn = next_insn_to_validate(file, insn);
3620
3621 if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {
3622 /* Ignore KCFI type preambles, which always fall through */
3623 if (!strncmp(func->name, "__cfi_", 6) ||
3624 !strncmp(func->name, "__pfx_", 6))
3625 return 0;
3626
3627 WARN("%s() falls through to next function %s()",
3628 func->name, insn_func(insn)->name);
3629 return 1;
3630 }
3631
3632 if (func && insn->ignore) {
3633 WARN_INSN(insn, "BUG: why am I validating an ignored function?");
3634 return 1;
3635 }
3636
3637 visited = VISITED_BRANCH << state.uaccess;
3638 if (insn->visited & VISITED_BRANCH_MASK) {
3639 if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3640 return 1;
3641
3642 if (insn->visited & visited)
3643 return 0;
3644 } else {
3645 nr_insns_visited++;
3646 }
3647
3648 if (state.noinstr)
3649 state.instr += insn->instr;
3650
3651 if (insn->hint) {
3652 if (insn->restore) {
3653 struct instruction *save_insn, *i;
3654
3655 i = insn;
3656 save_insn = NULL;
3657
3658 sym_for_each_insn_continue_reverse(file, func, i) {
3659 if (i->save) {
3660 save_insn = i;
3661 break;
3662 }
3663 }
3664
3665 if (!save_insn) {
3666 WARN_INSN(insn, "no corresponding CFI save for CFI restore");
3667 return 1;
3668 }
3669
3670 if (!save_insn->visited) {
3671 /*
3672 * If the restore hint insn is at the
3673 * beginning of a basic block and was
3674 * branched to from elsewhere, and the
3675 * save insn hasn't been visited yet,
3676 * defer following this branch for now.
3677 * It will be seen later via the
3678 * straight-line path.
3679 */
3680 if (!prev_insn)
3681 return 0;
3682
3683 WARN_INSN(insn, "objtool isn't smart enough to handle this CFI save/restore combo");
3684 return 1;
3685 }
3686
3687 insn->cfi = save_insn->cfi;
3688 nr_cfi_reused++;
3689 }
3690
3691 state.cfi = *insn->cfi;
3692 } else {
3693 /* XXX track if we actually changed state.cfi */
3694
3695 if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3696 insn->cfi = prev_insn->cfi;
3697 nr_cfi_reused++;
3698 } else {
3699 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3700 }
3701 }
3702
3703 insn->visited |= visited;
3704
3705 if (propagate_alt_cfi(file, insn))
3706 return 1;
3707
3708 if (!insn->ignore_alts && insn->alts) {
3709 bool skip_orig = false;
3710
3711 for (alt = insn->alts; alt; alt = alt->next) {
3712 if (alt->skip_orig)
3713 skip_orig = true;
3714
3715 ret = validate_branch(file, func, alt->insn, state);
3716 if (ret) {
3717 BT_INSN(insn, "(alt)");
3718 return ret;
3719 }
3720 }
3721
3722 if (skip_orig)
3723 return 0;
3724 }
3725
3726 if (handle_insn_ops(insn, next_insn, &state))
3727 return 1;
3728
3729 switch (insn->type) {
3730
3731 case INSN_RETURN:
3732 return validate_return(func, insn, &state);
3733
3734 case INSN_CALL:
3735 case INSN_CALL_DYNAMIC:
3736 ret = validate_call(file, insn, &state);
3737 if (ret)
3738 return ret;
3739
3740 if (opts.stackval && func && !is_special_call(insn) &&
3741 !has_valid_stack_frame(&state)) {
3742 WARN_INSN(insn, "call without frame pointer save/setup");
3743 return 1;
3744 }
3745
3746 if (insn->dead_end)
3747 return 0;
3748
3749 break;
3750
3751 case INSN_JUMP_CONDITIONAL:
3752 case INSN_JUMP_UNCONDITIONAL:
3753 if (is_sibling_call(insn)) {
3754 ret = validate_sibling_call(file, insn, &state);
3755 if (ret)
3756 return ret;
3757
3758 } else if (insn->jump_dest) {
3759 ret = validate_branch(file, func,
3760 insn->jump_dest, state);
3761 if (ret) {
3762 BT_INSN(insn, "(branch)");
3763 return ret;
3764 }
3765 }
3766
3767 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3768 return 0;
3769
3770 break;
3771
3772 case INSN_JUMP_DYNAMIC:
3773 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3774 if (is_sibling_call(insn)) {
3775 ret = validate_sibling_call(file, insn, &state);
3776 if (ret)
3777 return ret;
3778 }
3779
3780 if (insn->type == INSN_JUMP_DYNAMIC)
3781 return 0;
3782
3783 break;
3784
3785 case INSN_CONTEXT_SWITCH:
3786 if (func) {
3787 if (!next_insn || !next_insn->hint) {
3788 WARN_INSN(insn, "unsupported instruction in callable function");
3789 return 1;
3790 }
3791 break;
3792 }
3793 return 0;
3794
3795 case INSN_STAC:
3796 if (state.uaccess) {
3797 WARN_INSN(insn, "recursive UACCESS enable");
3798 return 1;
3799 }
3800
3801 state.uaccess = true;
3802 break;
3803
3804 case INSN_CLAC:
3805 if (!state.uaccess && func) {
3806 WARN_INSN(insn, "redundant UACCESS disable");
3807 return 1;
3808 }
3809
3810 if (func_uaccess_safe(func) && !state.uaccess_stack) {
3811 WARN_INSN(insn, "UACCESS-safe disables UACCESS");
3812 return 1;
3813 }
3814
3815 state.uaccess = false;
3816 break;
3817
3818 case INSN_STD:
3819 if (state.df) {
3820 WARN_INSN(insn, "recursive STD");
3821 return 1;
3822 }
3823
3824 state.df = true;
3825 break;
3826
3827 case INSN_CLD:
3828 if (!state.df && func) {
3829 WARN_INSN(insn, "redundant CLD");
3830 return 1;
3831 }
3832
3833 state.df = false;
3834 break;
3835
3836 default:
3837 break;
3838 }
3839
3840 if (insn->dead_end)
3841 return 0;
3842
3843 if (!next_insn) {
3844 if (state.cfi.cfa.base == CFI_UNDEFINED)
3845 return 0;
3846 WARN("%s: unexpected end of section", sec->name);
3847 return 1;
3848 }
3849
3850 prev_insn = insn;
3851 insn = next_insn;
3852 }
3853
3854 return 0;
3855}
3856
3857static int validate_unwind_hint(struct objtool_file *file,
3858 struct instruction *insn,
3859 struct insn_state *state)
3860{
3861 if (insn->hint && !insn->visited && !insn->ignore) {
3862 int ret = validate_branch(file, insn_func(insn), insn, *state);
3863 if (ret)
3864 BT_INSN(insn, "<=== (hint)");
3865 return ret;
3866 }
3867
3868 return 0;
3869}
3870
3871static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3872{
3873 struct instruction *insn;
3874 struct insn_state state;
3875 int warnings = 0;
3876
3877 if (!file->hints)
3878 return 0;
3879
3880 init_insn_state(file, &state, sec);
3881
3882 if (sec) {
3883 sec_for_each_insn(file, sec, insn)
3884 warnings += validate_unwind_hint(file, insn, &state);
3885 } else {
3886 for_each_insn(file, insn)
3887 warnings += validate_unwind_hint(file, insn, &state);
3888 }
3889
3890 return warnings;
3891}
3892
3893/*
3894 * Validate rethunk entry constraint: must untrain RET before the first RET.
3895 *
3896 * Follow every branch (intra-function) and ensure VALIDATE_UNRET_END comes
3897 * before an actual RET instruction.
3898 */
3899static int validate_unret(struct objtool_file *file, struct instruction *insn)
3900{
3901 struct instruction *next, *dest;
3902 int ret;
3903
3904 for (;;) {
3905 next = next_insn_to_validate(file, insn);
3906
3907 if (insn->visited & VISITED_UNRET)
3908 return 0;
3909
3910 insn->visited |= VISITED_UNRET;
3911
3912 if (!insn->ignore_alts && insn->alts) {
3913 struct alternative *alt;
3914 bool skip_orig = false;
3915
3916 for (alt = insn->alts; alt; alt = alt->next) {
3917 if (alt->skip_orig)
3918 skip_orig = true;
3919
3920 ret = validate_unret(file, alt->insn);
3921 if (ret) {
3922 BT_INSN(insn, "(alt)");
3923 return ret;
3924 }
3925 }
3926
3927 if (skip_orig)
3928 return 0;
3929 }
3930
3931 switch (insn->type) {
3932
3933 case INSN_CALL_DYNAMIC:
3934 case INSN_JUMP_DYNAMIC:
3935 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3936 WARN_INSN(insn, "early indirect call");
3937 return 1;
3938
3939 case INSN_JUMP_UNCONDITIONAL:
3940 case INSN_JUMP_CONDITIONAL:
3941 if (!is_sibling_call(insn)) {
3942 if (!insn->jump_dest) {
3943 WARN_INSN(insn, "unresolved jump target after linking?!?");
3944 return -1;
3945 }
3946 ret = validate_unret(file, insn->jump_dest);
3947 if (ret) {
3948 BT_INSN(insn, "(branch%s)",
3949 insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : "");
3950 return ret;
3951 }
3952
3953 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3954 return 0;
3955
3956 break;
3957 }
3958
3959 /* fallthrough */
3960 case INSN_CALL:
3961 dest = find_insn(file, insn_call_dest(insn)->sec,
3962 insn_call_dest(insn)->offset);
3963 if (!dest) {
3964 WARN("Unresolved function after linking!?: %s",
3965 insn_call_dest(insn)->name);
3966 return -1;
3967 }
3968
3969 ret = validate_unret(file, dest);
3970 if (ret) {
3971 BT_INSN(insn, "(call)");
3972 return ret;
3973 }
3974 /*
3975 * If a call returns without error, it must have seen UNTRAIN_RET.
3976 * Therefore any non-error return is a success.
3977 */
3978 return 0;
3979
3980 case INSN_RETURN:
3981 WARN_INSN(insn, "RET before UNTRAIN");
3982 return 1;
3983
3984 case INSN_NOP:
3985 if (insn->retpoline_safe)
3986 return 0;
3987 break;
3988
3989 default:
3990 break;
3991 }
3992
3993 if (!next) {
3994 WARN_INSN(insn, "teh end!");
3995 return -1;
3996 }
3997 insn = next;
3998 }
3999
4000 return 0;
4001}
4002
4003/*
4004 * Validate that all branches starting at VALIDATE_UNRET_BEGIN encounter
4005 * VALIDATE_UNRET_END before RET.
4006 */
4007static int validate_unrets(struct objtool_file *file)
4008{
4009 struct instruction *insn;
4010 int ret, warnings = 0;
4011
4012 for_each_insn(file, insn) {
4013 if (!insn->unret)
4014 continue;
4015
4016 ret = validate_unret(file, insn);
4017 if (ret < 0) {
4018 WARN_INSN(insn, "Failed UNRET validation");
4019 return ret;
4020 }
4021 warnings += ret;
4022 }
4023
4024 return warnings;
4025}
4026
4027static int validate_retpoline(struct objtool_file *file)
4028{
4029 struct instruction *insn;
4030 int warnings = 0;
4031
4032 for_each_insn(file, insn) {
4033 if (insn->type != INSN_JUMP_DYNAMIC &&
4034 insn->type != INSN_CALL_DYNAMIC &&
4035 insn->type != INSN_RETURN)
4036 continue;
4037
4038 if (insn->retpoline_safe)
4039 continue;
4040
4041 if (insn->sec->init)
4042 continue;
4043
4044 if (insn->type == INSN_RETURN) {
4045 if (opts.rethunk) {
4046 WARN_INSN(insn, "'naked' return found in MITIGATION_RETHUNK build");
4047 } else
4048 continue;
4049 } else {
4050 WARN_INSN(insn, "indirect %s found in MITIGATION_RETPOLINE build",
4051 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
4052 }
4053
4054 warnings++;
4055 }
4056
4057 return warnings;
4058}
4059
4060static bool is_kasan_insn(struct instruction *insn)
4061{
4062 return (insn->type == INSN_CALL &&
4063 !strcmp(insn_call_dest(insn)->name, "__asan_handle_no_return"));
4064}
4065
4066static bool is_ubsan_insn(struct instruction *insn)
4067{
4068 return (insn->type == INSN_CALL &&
4069 !strcmp(insn_call_dest(insn)->name,
4070 "__ubsan_handle_builtin_unreachable"));
4071}
4072
4073static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
4074{
4075 int i;
4076 struct instruction *prev_insn;
4077
4078 if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
4079 return true;
4080
4081 /*
4082 * Ignore alternative replacement instructions. This can happen
4083 * when a whitelisted function uses one of the ALTERNATIVE macros.
4084 */
4085 if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
4086 !strcmp(insn->sec->name, ".altinstr_aux"))
4087 return true;
4088
4089 /*
4090 * Whole archive runs might encounter dead code from weak symbols.
4091 * This is where the linker will have dropped the weak symbol in
4092 * favour of a regular symbol, but leaves the code in place.
4093 *
4094 * In this case we'll find a piece of code (whole function) that is not
4095 * covered by a !section symbol. Ignore them.
4096 */
4097 if (opts.link && !insn_func(insn)) {
4098 int size = find_symbol_hole_containing(insn->sec, insn->offset);
4099 unsigned long end = insn->offset + size;
4100
4101 if (!size) /* not a hole */
4102 return false;
4103
4104 if (size < 0) /* hole until the end */
4105 return true;
4106
4107 sec_for_each_insn_continue(file, insn) {
4108 /*
4109 * If we reach a visited instruction at or before the
4110 * end of the hole, ignore the unreachable.
4111 */
4112 if (insn->visited)
4113 return true;
4114
4115 if (insn->offset >= end)
4116 break;
4117
4118 /*
4119 * If this hole jumps to a .cold function, mark it ignore too.
4120 */
4121 if (insn->jump_dest && insn_func(insn->jump_dest) &&
4122 strstr(insn_func(insn->jump_dest)->name, ".cold")) {
4123 struct instruction *dest = insn->jump_dest;
4124 func_for_each_insn(file, insn_func(dest), dest)
4125 dest->ignore = true;
4126 }
4127 }
4128
4129 return false;
4130 }
4131
4132 if (!insn_func(insn))
4133 return false;
4134
4135 if (insn_func(insn)->static_call_tramp)
4136 return true;
4137
4138 /*
4139 * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
4140 * __builtin_unreachable(). The BUG() macro has an unreachable() after
4141 * the UD2, which causes GCC's undefined trap logic to emit another UD2
4142 * (or occasionally a JMP to UD2).
4143 *
4144 * It may also insert a UD2 after calling a __noreturn function.
4145 */
4146 prev_insn = prev_insn_same_sec(file, insn);
4147 if (prev_insn->dead_end &&
4148 (insn->type == INSN_BUG ||
4149 (insn->type == INSN_JUMP_UNCONDITIONAL &&
4150 insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
4151 return true;
4152
4153 /*
4154 * Check if this (or a subsequent) instruction is related to
4155 * CONFIG_UBSAN or CONFIG_KASAN.
4156 *
4157 * End the search at 5 instructions to avoid going into the weeds.
4158 */
4159 for (i = 0; i < 5; i++) {
4160
4161 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
4162 return true;
4163
4164 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
4165 if (insn->jump_dest &&
4166 insn_func(insn->jump_dest) == insn_func(insn)) {
4167 insn = insn->jump_dest;
4168 continue;
4169 }
4170
4171 break;
4172 }
4173
4174 if (insn->offset + insn->len >= insn_func(insn)->offset + insn_func(insn)->len)
4175 break;
4176
4177 insn = next_insn_same_sec(file, insn);
4178 }
4179
4180 return false;
4181}
4182
4183static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
4184{
4185 struct instruction *insn, *prev;
4186 struct cfi_state *cfi;
4187
4188 insn = find_insn(file, func->sec, func->offset);
4189 if (!insn)
4190 return -1;
4191
4192 for (prev = prev_insn_same_sec(file, insn);
4193 prev;
4194 prev = prev_insn_same_sec(file, prev)) {
4195 u64 offset;
4196
4197 if (prev->type != INSN_NOP)
4198 return -1;
4199
4200 offset = func->offset - prev->offset;
4201
4202 if (offset > opts.prefix)
4203 return -1;
4204
4205 if (offset < opts.prefix)
4206 continue;
4207
4208 elf_create_prefix_symbol(file->elf, func, opts.prefix);
4209 break;
4210 }
4211
4212 if (!prev)
4213 return -1;
4214
4215 if (!insn->cfi) {
4216 /*
4217 * This can happen if stack validation isn't enabled or the
4218 * function is annotated with STACK_FRAME_NON_STANDARD.
4219 */
4220 return 0;
4221 }
4222
4223 /* Propagate insn->cfi to the prefix code */
4224 cfi = cfi_hash_find_or_add(insn->cfi);
4225 for (; prev != insn; prev = next_insn_same_sec(file, prev))
4226 prev->cfi = cfi;
4227
4228 return 0;
4229}
4230
4231static int add_prefix_symbols(struct objtool_file *file)
4232{
4233 struct section *sec;
4234 struct symbol *func;
4235
4236 for_each_sec(file, sec) {
4237 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4238 continue;
4239
4240 sec_for_each_sym(sec, func) {
4241 if (func->type != STT_FUNC)
4242 continue;
4243
4244 add_prefix_symbol(file, func);
4245 }
4246 }
4247
4248 return 0;
4249}
4250
4251static int validate_symbol(struct objtool_file *file, struct section *sec,
4252 struct symbol *sym, struct insn_state *state)
4253{
4254 struct instruction *insn;
4255 int ret;
4256
4257 if (!sym->len) {
4258 WARN("%s() is missing an ELF size annotation", sym->name);
4259 return 1;
4260 }
4261
4262 if (sym->pfunc != sym || sym->alias != sym)
4263 return 0;
4264
4265 insn = find_insn(file, sec, sym->offset);
4266 if (!insn || insn->ignore || insn->visited)
4267 return 0;
4268
4269 state->uaccess = sym->uaccess_safe;
4270
4271 ret = validate_branch(file, insn_func(insn), insn, *state);
4272 if (ret)
4273 BT_INSN(insn, "<=== (sym)");
4274 return ret;
4275}
4276
4277static int validate_section(struct objtool_file *file, struct section *sec)
4278{
4279 struct insn_state state;
4280 struct symbol *func;
4281 int warnings = 0;
4282
4283 sec_for_each_sym(sec, func) {
4284 if (func->type != STT_FUNC)
4285 continue;
4286
4287 init_insn_state(file, &state, sec);
4288 set_func_state(&state.cfi);
4289
4290 warnings += validate_symbol(file, sec, func, &state);
4291 }
4292
4293 return warnings;
4294}
4295
4296static int validate_noinstr_sections(struct objtool_file *file)
4297{
4298 struct section *sec;
4299 int warnings = 0;
4300
4301 sec = find_section_by_name(file->elf, ".noinstr.text");
4302 if (sec) {
4303 warnings += validate_section(file, sec);
4304 warnings += validate_unwind_hints(file, sec);
4305 }
4306
4307 sec = find_section_by_name(file->elf, ".entry.text");
4308 if (sec) {
4309 warnings += validate_section(file, sec);
4310 warnings += validate_unwind_hints(file, sec);
4311 }
4312
4313 sec = find_section_by_name(file->elf, ".cpuidle.text");
4314 if (sec) {
4315 warnings += validate_section(file, sec);
4316 warnings += validate_unwind_hints(file, sec);
4317 }
4318
4319 return warnings;
4320}
4321
4322static int validate_functions(struct objtool_file *file)
4323{
4324 struct section *sec;
4325 int warnings = 0;
4326
4327 for_each_sec(file, sec) {
4328 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4329 continue;
4330
4331 warnings += validate_section(file, sec);
4332 }
4333
4334 return warnings;
4335}
4336
4337static void mark_endbr_used(struct instruction *insn)
4338{
4339 if (!list_empty(&insn->call_node))
4340 list_del_init(&insn->call_node);
4341}
4342
4343static bool noendbr_range(struct objtool_file *file, struct instruction *insn)
4344{
4345 struct symbol *sym = find_symbol_containing(insn->sec, insn->offset-1);
4346 struct instruction *first;
4347
4348 if (!sym)
4349 return false;
4350
4351 first = find_insn(file, sym->sec, sym->offset);
4352 if (!first)
4353 return false;
4354
4355 if (first->type != INSN_ENDBR && !first->noendbr)
4356 return false;
4357
4358 return insn->offset == sym->offset + sym->len;
4359}
4360
4361static int __validate_ibt_insn(struct objtool_file *file, struct instruction *insn,
4362 struct instruction *dest)
4363{
4364 if (dest->type == INSN_ENDBR) {
4365 mark_endbr_used(dest);
4366 return 0;
4367 }
4368
4369 if (insn_func(dest) && insn_func(insn) &&
4370 insn_func(dest)->pfunc == insn_func(insn)->pfunc) {
4371 /*
4372 * Anything from->to self is either _THIS_IP_ or
4373 * IRET-to-self.
4374 *
4375 * There is no sane way to annotate _THIS_IP_ since the
4376 * compiler treats the relocation as a constant and is
4377 * happy to fold in offsets, skewing any annotation we
4378 * do, leading to vast amounts of false-positives.
4379 *
4380 * There's also compiler generated _THIS_IP_ through
4381 * KCOV and such which we have no hope of annotating.
4382 *
4383 * As such, blanket accept self-references without
4384 * issue.
4385 */
4386 return 0;
4387 }
4388
4389 /*
4390 * Accept anything ANNOTATE_NOENDBR.
4391 */
4392 if (dest->noendbr)
4393 return 0;
4394
4395 /*
4396 * Accept if this is the instruction after a symbol
4397 * that is (no)endbr -- typical code-range usage.
4398 */
4399 if (noendbr_range(file, dest))
4400 return 0;
4401
4402 WARN_INSN(insn, "relocation to !ENDBR: %s", offstr(dest->sec, dest->offset));
4403 return 1;
4404}
4405
4406static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
4407{
4408 struct instruction *dest;
4409 struct reloc *reloc;
4410 unsigned long off;
4411 int warnings = 0;
4412
4413 /*
4414 * Looking for function pointer load relocations. Ignore
4415 * direct/indirect branches:
4416 */
4417 switch (insn->type) {
4418
4419 case INSN_CALL:
4420 case INSN_CALL_DYNAMIC:
4421 case INSN_JUMP_CONDITIONAL:
4422 case INSN_JUMP_UNCONDITIONAL:
4423 case INSN_JUMP_DYNAMIC:
4424 case INSN_JUMP_DYNAMIC_CONDITIONAL:
4425 case INSN_RETURN:
4426 case INSN_NOP:
4427 return 0;
4428
4429 case INSN_LEA_RIP:
4430 if (!insn_reloc(file, insn)) {
4431 /* local function pointer reference without reloc */
4432
4433 off = arch_jump_destination(insn);
4434
4435 dest = find_insn(file, insn->sec, off);
4436 if (!dest) {
4437 WARN_INSN(insn, "corrupt function pointer reference");
4438 return 1;
4439 }
4440
4441 return __validate_ibt_insn(file, insn, dest);
4442 }
4443 break;
4444
4445 default:
4446 break;
4447 }
4448
4449 for (reloc = insn_reloc(file, insn);
4450 reloc;
4451 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
4452 reloc_offset(reloc) + 1,
4453 (insn->offset + insn->len) - (reloc_offset(reloc) + 1))) {
4454
4455 off = reloc->sym->offset;
4456 if (reloc_type(reloc) == R_X86_64_PC32 ||
4457 reloc_type(reloc) == R_X86_64_PLT32)
4458 off += arch_dest_reloc_offset(reloc_addend(reloc));
4459 else
4460 off += reloc_addend(reloc);
4461
4462 dest = find_insn(file, reloc->sym->sec, off);
4463 if (!dest)
4464 continue;
4465
4466 warnings += __validate_ibt_insn(file, insn, dest);
4467 }
4468
4469 return warnings;
4470}
4471
4472static int validate_ibt_data_reloc(struct objtool_file *file,
4473 struct reloc *reloc)
4474{
4475 struct instruction *dest;
4476
4477 dest = find_insn(file, reloc->sym->sec,
4478 reloc->sym->offset + reloc_addend(reloc));
4479 if (!dest)
4480 return 0;
4481
4482 if (dest->type == INSN_ENDBR) {
4483 mark_endbr_used(dest);
4484 return 0;
4485 }
4486
4487 if (dest->noendbr)
4488 return 0;
4489
4490 WARN_FUNC("data relocation to !ENDBR: %s",
4491 reloc->sec->base, reloc_offset(reloc),
4492 offstr(dest->sec, dest->offset));
4493
4494 return 1;
4495}
4496
4497/*
4498 * Validate IBT rules and remove used ENDBR instructions from the seal list.
4499 * Unused ENDBR instructions will be annotated for sealing (i.e., replaced with
4500 * NOPs) later, in create_ibt_endbr_seal_sections().
4501 */
4502static int validate_ibt(struct objtool_file *file)
4503{
4504 struct section *sec;
4505 struct reloc *reloc;
4506 struct instruction *insn;
4507 int warnings = 0;
4508
4509 for_each_insn(file, insn)
4510 warnings += validate_ibt_insn(file, insn);
4511
4512 for_each_sec(file, sec) {
4513
4514 /* Already done by validate_ibt_insn() */
4515 if (sec->sh.sh_flags & SHF_EXECINSTR)
4516 continue;
4517
4518 if (!sec->rsec)
4519 continue;
4520
4521 /*
4522 * These sections can reference text addresses, but not with
4523 * the intent to indirect branch to them.
4524 */
4525 if ((!strncmp(sec->name, ".discard", 8) &&
4526 strcmp(sec->name, ".discard.ibt_endbr_noseal")) ||
4527 !strncmp(sec->name, ".debug", 6) ||
4528 !strcmp(sec->name, ".altinstructions") ||
4529 !strcmp(sec->name, ".ibt_endbr_seal") ||
4530 !strcmp(sec->name, ".orc_unwind_ip") ||
4531 !strcmp(sec->name, ".parainstructions") ||
4532 !strcmp(sec->name, ".retpoline_sites") ||
4533 !strcmp(sec->name, ".smp_locks") ||
4534 !strcmp(sec->name, ".static_call_sites") ||
4535 !strcmp(sec->name, "_error_injection_whitelist") ||
4536 !strcmp(sec->name, "_kprobe_blacklist") ||
4537 !strcmp(sec->name, "__bug_table") ||
4538 !strcmp(sec->name, "__ex_table") ||
4539 !strcmp(sec->name, "__jump_table") ||
4540 !strcmp(sec->name, "__mcount_loc") ||
4541 !strcmp(sec->name, ".kcfi_traps") ||
4542 !strcmp(sec->name, ".llvm.call-graph-profile") ||
4543 !strcmp(sec->name, ".llvm_bb_addr_map") ||
4544 !strcmp(sec->name, "__tracepoints") ||
4545 strstr(sec->name, "__patchable_function_entries"))
4546 continue;
4547
4548 for_each_reloc(sec->rsec, reloc)
4549 warnings += validate_ibt_data_reloc(file, reloc);
4550 }
4551
4552 return warnings;
4553}
4554
4555static int validate_sls(struct objtool_file *file)
4556{
4557 struct instruction *insn, *next_insn;
4558 int warnings = 0;
4559
4560 for_each_insn(file, insn) {
4561 next_insn = next_insn_same_sec(file, insn);
4562
4563 if (insn->retpoline_safe)
4564 continue;
4565
4566 switch (insn->type) {
4567 case INSN_RETURN:
4568 if (!next_insn || next_insn->type != INSN_TRAP) {
4569 WARN_INSN(insn, "missing int3 after ret");
4570 warnings++;
4571 }
4572
4573 break;
4574 case INSN_JUMP_DYNAMIC:
4575 if (!next_insn || next_insn->type != INSN_TRAP) {
4576 WARN_INSN(insn, "missing int3 after indirect jump");
4577 warnings++;
4578 }
4579 break;
4580 default:
4581 break;
4582 }
4583 }
4584
4585 return warnings;
4586}
4587
4588static bool ignore_noreturn_call(struct instruction *insn)
4589{
4590 struct symbol *call_dest = insn_call_dest(insn);
4591
4592 /*
4593 * FIXME: hack, we need a real noreturn solution
4594 *
4595 * Problem is, exc_double_fault() may or may not return, depending on
4596 * whether CONFIG_X86_ESPFIX64 is set. But objtool has no visibility
4597 * to the kernel config.
4598 *
4599 * Other potential ways to fix it:
4600 *
4601 * - have compiler communicate __noreturn functions somehow
4602 * - remove CONFIG_X86_ESPFIX64
4603 * - read the .config file
4604 * - add a cmdline option
4605 * - create a generic objtool annotation format (vs a bunch of custom
4606 * formats) and annotate it
4607 */
4608 if (!strcmp(call_dest->name, "exc_double_fault")) {
4609 /* prevent further unreachable warnings for the caller */
4610 insn->sym->warned = 1;
4611 return true;
4612 }
4613
4614 return false;
4615}
4616
4617static int validate_reachable_instructions(struct objtool_file *file)
4618{
4619 struct instruction *insn, *prev_insn;
4620 struct symbol *call_dest;
4621 int warnings = 0;
4622
4623 if (file->ignore_unreachables)
4624 return 0;
4625
4626 for_each_insn(file, insn) {
4627 if (insn->visited || ignore_unreachable_insn(file, insn))
4628 continue;
4629
4630 prev_insn = prev_insn_same_sec(file, insn);
4631 if (prev_insn && prev_insn->dead_end) {
4632 call_dest = insn_call_dest(prev_insn);
4633 if (call_dest && !ignore_noreturn_call(prev_insn)) {
4634 WARN_INSN(insn, "%s() is missing a __noreturn annotation",
4635 call_dest->name);
4636 warnings++;
4637 continue;
4638 }
4639 }
4640
4641 WARN_INSN(insn, "unreachable instruction");
4642 warnings++;
4643 }
4644
4645 return warnings;
4646}
4647
4648/* 'funcs' is a space-separated list of function names */
4649static int disas_funcs(const char *funcs)
4650{
4651 const char *objdump_str, *cross_compile;
4652 int size, ret;
4653 char *cmd;
4654
4655 cross_compile = getenv("CROSS_COMPILE");
4656
4657 objdump_str = "%sobjdump -wdr %s | gawk -M -v _funcs='%s' '"
4658 "BEGIN { split(_funcs, funcs); }"
4659 "/^$/ { func_match = 0; }"
4660 "/<.*>:/ { "
4661 "f = gensub(/.*<(.*)>:/, \"\\\\1\", 1);"
4662 "for (i in funcs) {"
4663 "if (funcs[i] == f) {"
4664 "func_match = 1;"
4665 "base = strtonum(\"0x\" $1);"
4666 "break;"
4667 "}"
4668 "}"
4669 "}"
4670 "{"
4671 "if (func_match) {"
4672 "addr = strtonum(\"0x\" $1);"
4673 "printf(\"%%04x \", addr - base);"
4674 "print;"
4675 "}"
4676 "}' 1>&2";
4677
4678 /* fake snprintf() to calculate the size */
4679 size = snprintf(NULL, 0, objdump_str, cross_compile, objname, funcs) + 1;
4680 if (size <= 0) {
4681 WARN("objdump string size calculation failed");
4682 return -1;
4683 }
4684
4685 cmd = malloc(size);
4686
4687 /* real snprintf() */
4688 snprintf(cmd, size, objdump_str, cross_compile, objname, funcs);
4689 ret = system(cmd);
4690 if (ret) {
4691 WARN("disassembly failed: %d", ret);
4692 return -1;
4693 }
4694
4695 return 0;
4696}
4697
4698static int disas_warned_funcs(struct objtool_file *file)
4699{
4700 struct symbol *sym;
4701 char *funcs = NULL, *tmp;
4702
4703 for_each_sym(file, sym) {
4704 if (sym->warned) {
4705 if (!funcs) {
4706 funcs = malloc(strlen(sym->name) + 1);
4707 strcpy(funcs, sym->name);
4708 } else {
4709 tmp = malloc(strlen(funcs) + strlen(sym->name) + 2);
4710 sprintf(tmp, "%s %s", funcs, sym->name);
4711 free(funcs);
4712 funcs = tmp;
4713 }
4714 }
4715 }
4716
4717 if (funcs)
4718 disas_funcs(funcs);
4719
4720 return 0;
4721}
4722
4723struct insn_chunk {
4724 void *addr;
4725 struct insn_chunk *next;
4726};
4727
4728/*
4729 * Reduce peak RSS usage by freeing insns memory before writing the ELF file,
4730 * which can trigger more allocations for .debug_* sections whose data hasn't
4731 * been read yet.
4732 */
4733static void free_insns(struct objtool_file *file)
4734{
4735 struct instruction *insn;
4736 struct insn_chunk *chunks = NULL, *chunk;
4737
4738 for_each_insn(file, insn) {
4739 if (!insn->idx) {
4740 chunk = malloc(sizeof(*chunk));
4741 chunk->addr = insn;
4742 chunk->next = chunks;
4743 chunks = chunk;
4744 }
4745 }
4746
4747 for (chunk = chunks; chunk; chunk = chunk->next)
4748 free(chunk->addr);
4749}
4750
4751int check(struct objtool_file *file)
4752{
4753 int ret, warnings = 0;
4754
4755 arch_initial_func_cfi_state(&initial_func_cfi);
4756 init_cfi_state(&init_cfi);
4757 init_cfi_state(&func_cfi);
4758 set_func_state(&func_cfi);
4759 init_cfi_state(&force_undefined_cfi);
4760 force_undefined_cfi.force_undefined = true;
4761
4762 if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
4763 goto out;
4764
4765 cfi_hash_add(&init_cfi);
4766 cfi_hash_add(&func_cfi);
4767
4768 ret = decode_sections(file);
4769 if (ret < 0)
4770 goto out;
4771
4772 warnings += ret;
4773
4774 if (!nr_insns)
4775 goto out;
4776
4777 if (opts.retpoline) {
4778 ret = validate_retpoline(file);
4779 if (ret < 0)
4780 return ret;
4781 warnings += ret;
4782 }
4783
4784 if (opts.stackval || opts.orc || opts.uaccess) {
4785 ret = validate_functions(file);
4786 if (ret < 0)
4787 goto out;
4788 warnings += ret;
4789
4790 ret = validate_unwind_hints(file, NULL);
4791 if (ret < 0)
4792 goto out;
4793 warnings += ret;
4794
4795 if (!warnings) {
4796 ret = validate_reachable_instructions(file);
4797 if (ret < 0)
4798 goto out;
4799 warnings += ret;
4800 }
4801
4802 } else if (opts.noinstr) {
4803 ret = validate_noinstr_sections(file);
4804 if (ret < 0)
4805 goto out;
4806 warnings += ret;
4807 }
4808
4809 if (opts.unret) {
4810 /*
4811 * Must be after validate_branch() and friends, it plays
4812 * further games with insn->visited.
4813 */
4814 ret = validate_unrets(file);
4815 if (ret < 0)
4816 return ret;
4817 warnings += ret;
4818 }
4819
4820 if (opts.ibt) {
4821 ret = validate_ibt(file);
4822 if (ret < 0)
4823 goto out;
4824 warnings += ret;
4825 }
4826
4827 if (opts.sls) {
4828 ret = validate_sls(file);
4829 if (ret < 0)
4830 goto out;
4831 warnings += ret;
4832 }
4833
4834 if (opts.static_call) {
4835 ret = create_static_call_sections(file);
4836 if (ret < 0)
4837 goto out;
4838 warnings += ret;
4839 }
4840
4841 if (opts.retpoline) {
4842 ret = create_retpoline_sites_sections(file);
4843 if (ret < 0)
4844 goto out;
4845 warnings += ret;
4846 }
4847
4848 if (opts.cfi) {
4849 ret = create_cfi_sections(file);
4850 if (ret < 0)
4851 goto out;
4852 warnings += ret;
4853 }
4854
4855 if (opts.rethunk) {
4856 ret = create_return_sites_sections(file);
4857 if (ret < 0)
4858 goto out;
4859 warnings += ret;
4860
4861 if (opts.hack_skylake) {
4862 ret = create_direct_call_sections(file);
4863 if (ret < 0)
4864 goto out;
4865 warnings += ret;
4866 }
4867 }
4868
4869 if (opts.mcount) {
4870 ret = create_mcount_loc_sections(file);
4871 if (ret < 0)
4872 goto out;
4873 warnings += ret;
4874 }
4875
4876 if (opts.prefix) {
4877 ret = add_prefix_symbols(file);
4878 if (ret < 0)
4879 return ret;
4880 warnings += ret;
4881 }
4882
4883 if (opts.ibt) {
4884 ret = create_ibt_endbr_seal_sections(file);
4885 if (ret < 0)
4886 goto out;
4887 warnings += ret;
4888 }
4889
4890 if (opts.orc && nr_insns) {
4891 ret = orc_create(file);
4892 if (ret < 0)
4893 goto out;
4894 warnings += ret;
4895 }
4896
4897 free_insns(file);
4898
4899 if (opts.verbose)
4900 disas_warned_funcs(file);
4901
4902 if (opts.stats) {
4903 printf("nr_insns_visited: %ld\n", nr_insns_visited);
4904 printf("nr_cfi: %ld\n", nr_cfi);
4905 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
4906 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
4907 }
4908
4909out:
4910 /*
4911 * For now, don't fail the kernel build on fatal warnings. These
4912 * errors are still fairly common due to the growing matrix of
4913 * supported toolchains and their recent pace of change.
4914 */
4915 return 0;
4916}
1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
4 */
5
6#include <string.h>
7#include <stdlib.h>
8#include <inttypes.h>
9#include <sys/mman.h>
10
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>
18
19#include <linux/objtool_types.h>
20#include <linux/hashtable.h>
21#include <linux/kernel.h>
22#include <linux/static_call_types.h>
23#include <linux/string.h>
24
25struct alternative {
26 struct alternative *next;
27 struct instruction *insn;
28 bool skip_orig;
29};
30
31static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
32
33static struct cfi_init_state initial_func_cfi;
34static struct cfi_state init_cfi;
35static struct cfi_state func_cfi;
36static struct cfi_state force_undefined_cfi;
37
38struct instruction *find_insn(struct objtool_file *file,
39 struct section *sec, unsigned long offset)
40{
41 struct instruction *insn;
42
43 hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
44 if (insn->sec == sec && insn->offset == offset)
45 return insn;
46 }
47
48 return NULL;
49}
50
51struct instruction *next_insn_same_sec(struct objtool_file *file,
52 struct instruction *insn)
53{
54 if (insn->idx == INSN_CHUNK_MAX)
55 return find_insn(file, insn->sec, insn->offset + insn->len);
56
57 insn++;
58 if (!insn->len)
59 return NULL;
60
61 return insn;
62}
63
64static struct instruction *next_insn_same_func(struct objtool_file *file,
65 struct instruction *insn)
66{
67 struct instruction *next = next_insn_same_sec(file, insn);
68 struct symbol *func = insn_func(insn);
69
70 if (!func)
71 return NULL;
72
73 if (next && insn_func(next) == func)
74 return next;
75
76 /* Check if we're already in the subfunction: */
77 if (func == func->cfunc)
78 return NULL;
79
80 /* Move to the subfunction: */
81 return find_insn(file, func->cfunc->sec, func->cfunc->offset);
82}
83
84static struct instruction *prev_insn_same_sec(struct objtool_file *file,
85 struct instruction *insn)
86{
87 if (insn->idx == 0) {
88 if (insn->prev_len)
89 return find_insn(file, insn->sec, insn->offset - insn->prev_len);
90 return NULL;
91 }
92
93 return insn - 1;
94}
95
96static struct instruction *prev_insn_same_sym(struct objtool_file *file,
97 struct instruction *insn)
98{
99 struct instruction *prev = prev_insn_same_sec(file, insn);
100
101 if (prev && insn_func(prev) == insn_func(insn))
102 return prev;
103
104 return NULL;
105}
106
107#define for_each_insn(file, insn) \
108 for (struct section *__sec, *__fake = (struct section *)1; \
109 __fake; __fake = NULL) \
110 for_each_sec(file, __sec) \
111 sec_for_each_insn(file, __sec, insn)
112
113#define func_for_each_insn(file, func, insn) \
114 for (insn = find_insn(file, func->sec, func->offset); \
115 insn; \
116 insn = next_insn_same_func(file, insn))
117
118#define sym_for_each_insn(file, sym, insn) \
119 for (insn = find_insn(file, sym->sec, sym->offset); \
120 insn && insn->offset < sym->offset + sym->len; \
121 insn = next_insn_same_sec(file, insn))
122
123#define sym_for_each_insn_continue_reverse(file, sym, insn) \
124 for (insn = prev_insn_same_sec(file, insn); \
125 insn && insn->offset >= sym->offset; \
126 insn = prev_insn_same_sec(file, insn))
127
128#define sec_for_each_insn_from(file, insn) \
129 for (; insn; insn = next_insn_same_sec(file, insn))
130
131#define sec_for_each_insn_continue(file, insn) \
132 for (insn = next_insn_same_sec(file, insn); insn; \
133 insn = next_insn_same_sec(file, insn))
134
135static inline struct symbol *insn_call_dest(struct instruction *insn)
136{
137 if (insn->type == INSN_JUMP_DYNAMIC ||
138 insn->type == INSN_CALL_DYNAMIC)
139 return NULL;
140
141 return insn->_call_dest;
142}
143
144static inline struct reloc *insn_jump_table(struct instruction *insn)
145{
146 if (insn->type == INSN_JUMP_DYNAMIC ||
147 insn->type == INSN_CALL_DYNAMIC)
148 return insn->_jump_table;
149
150 return NULL;
151}
152
153static bool is_jump_table_jump(struct instruction *insn)
154{
155 struct alt_group *alt_group = insn->alt_group;
156
157 if (insn_jump_table(insn))
158 return true;
159
160 /* Retpoline alternative for a jump table? */
161 return alt_group && alt_group->orig_group &&
162 insn_jump_table(alt_group->orig_group->first_insn);
163}
164
165static bool is_sibling_call(struct instruction *insn)
166{
167 /*
168 * Assume only STT_FUNC calls have jump-tables.
169 */
170 if (insn_func(insn)) {
171 /* An indirect jump is either a sibling call or a jump to a table. */
172 if (insn->type == INSN_JUMP_DYNAMIC)
173 return !is_jump_table_jump(insn);
174 }
175
176 /* add_jump_destinations() sets insn_call_dest(insn) for sibling calls. */
177 return (is_static_jump(insn) && insn_call_dest(insn));
178}
179
180/*
181 * This checks to see if the given function is a "noreturn" function.
182 *
183 * For global functions which are outside the scope of this object file, we
184 * have to keep a manual list of them.
185 *
186 * For local functions, we have to detect them manually by simply looking for
187 * the lack of a return instruction.
188 */
189static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
190 int recursion)
191{
192 int i;
193 struct instruction *insn;
194 bool empty = true;
195
196#define NORETURN(func) __stringify(func),
197 static const char * const global_noreturns[] = {
198#include "noreturns.h"
199 };
200#undef NORETURN
201
202 if (!func)
203 return false;
204
205 if (func->bind == STB_GLOBAL || func->bind == STB_WEAK)
206 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
207 if (!strcmp(func->name, global_noreturns[i]))
208 return true;
209
210 if (func->bind == STB_WEAK)
211 return false;
212
213 if (!func->len)
214 return false;
215
216 insn = find_insn(file, func->sec, func->offset);
217 if (!insn || !insn_func(insn))
218 return false;
219
220 func_for_each_insn(file, func, insn) {
221 empty = false;
222
223 if (insn->type == INSN_RETURN)
224 return false;
225 }
226
227 if (empty)
228 return false;
229
230 /*
231 * A function can have a sibling call instead of a return. In that
232 * case, the function's dead-end status depends on whether the target
233 * of the sibling call returns.
234 */
235 func_for_each_insn(file, func, insn) {
236 if (is_sibling_call(insn)) {
237 struct instruction *dest = insn->jump_dest;
238
239 if (!dest)
240 /* sibling call to another file */
241 return false;
242
243 /* local sibling call */
244 if (recursion == 5) {
245 /*
246 * Infinite recursion: two functions have
247 * sibling calls to each other. This is a very
248 * rare case. It means they aren't dead ends.
249 */
250 return false;
251 }
252
253 return __dead_end_function(file, insn_func(dest), recursion+1);
254 }
255 }
256
257 return true;
258}
259
260static bool dead_end_function(struct objtool_file *file, struct symbol *func)
261{
262 return __dead_end_function(file, func, 0);
263}
264
265static void init_cfi_state(struct cfi_state *cfi)
266{
267 int i;
268
269 for (i = 0; i < CFI_NUM_REGS; i++) {
270 cfi->regs[i].base = CFI_UNDEFINED;
271 cfi->vals[i].base = CFI_UNDEFINED;
272 }
273 cfi->cfa.base = CFI_UNDEFINED;
274 cfi->drap_reg = CFI_UNDEFINED;
275 cfi->drap_offset = -1;
276}
277
278static void init_insn_state(struct objtool_file *file, struct insn_state *state,
279 struct section *sec)
280{
281 memset(state, 0, sizeof(*state));
282 init_cfi_state(&state->cfi);
283
284 /*
285 * We need the full vmlinux for noinstr validation, otherwise we can
286 * not correctly determine insn_call_dest(insn)->sec (external symbols
287 * do not have a section).
288 */
289 if (opts.link && opts.noinstr && sec)
290 state->noinstr = sec->noinstr;
291}
292
293static struct cfi_state *cfi_alloc(void)
294{
295 struct cfi_state *cfi = calloc(1, sizeof(struct cfi_state));
296 if (!cfi) {
297 WARN("calloc failed");
298 exit(1);
299 }
300 nr_cfi++;
301 return cfi;
302}
303
304static int cfi_bits;
305static struct hlist_head *cfi_hash;
306
307static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
308{
309 return memcmp((void *)cfi1 + sizeof(cfi1->hash),
310 (void *)cfi2 + sizeof(cfi2->hash),
311 sizeof(struct cfi_state) - sizeof(struct hlist_node));
312}
313
314static inline u32 cfi_key(struct cfi_state *cfi)
315{
316 return jhash((void *)cfi + sizeof(cfi->hash),
317 sizeof(*cfi) - sizeof(cfi->hash), 0);
318}
319
320static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
321{
322 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
323 struct cfi_state *obj;
324
325 hlist_for_each_entry(obj, head, hash) {
326 if (!cficmp(cfi, obj)) {
327 nr_cfi_cache++;
328 return obj;
329 }
330 }
331
332 obj = cfi_alloc();
333 *obj = *cfi;
334 hlist_add_head(&obj->hash, head);
335
336 return obj;
337}
338
339static void cfi_hash_add(struct cfi_state *cfi)
340{
341 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
342
343 hlist_add_head(&cfi->hash, head);
344}
345
346static void *cfi_hash_alloc(unsigned long size)
347{
348 cfi_bits = max(10, ilog2(size));
349 cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
350 PROT_READ|PROT_WRITE,
351 MAP_PRIVATE|MAP_ANON, -1, 0);
352 if (cfi_hash == (void *)-1L) {
353 WARN("mmap fail cfi_hash");
354 cfi_hash = NULL;
355 } else if (opts.stats) {
356 printf("cfi_bits: %d\n", cfi_bits);
357 }
358
359 return cfi_hash;
360}
361
362static unsigned long nr_insns;
363static unsigned long nr_insns_visited;
364
365/*
366 * Call the arch-specific instruction decoder for all the instructions and add
367 * them to the global instruction list.
368 */
369static int decode_instructions(struct objtool_file *file)
370{
371 struct section *sec;
372 struct symbol *func;
373 unsigned long offset;
374 struct instruction *insn;
375 int ret;
376
377 for_each_sec(file, sec) {
378 struct instruction *insns = NULL;
379 u8 prev_len = 0;
380 u8 idx = 0;
381
382 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
383 continue;
384
385 if (strcmp(sec->name, ".altinstr_replacement") &&
386 strcmp(sec->name, ".altinstr_aux") &&
387 strncmp(sec->name, ".discard.", 9))
388 sec->text = true;
389
390 if (!strcmp(sec->name, ".noinstr.text") ||
391 !strcmp(sec->name, ".entry.text") ||
392 !strcmp(sec->name, ".cpuidle.text") ||
393 !strncmp(sec->name, ".text..__x86.", 13))
394 sec->noinstr = true;
395
396 /*
397 * .init.text code is ran before userspace and thus doesn't
398 * strictly need retpolines, except for modules which are
399 * loaded late, they very much do need retpoline in their
400 * .init.text
401 */
402 if (!strcmp(sec->name, ".init.text") && !opts.module)
403 sec->init = true;
404
405 for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
406 if (!insns || idx == INSN_CHUNK_MAX) {
407 insns = calloc(sizeof(*insn), INSN_CHUNK_SIZE);
408 if (!insns) {
409 WARN("malloc failed");
410 return -1;
411 }
412 idx = 0;
413 } else {
414 idx++;
415 }
416 insn = &insns[idx];
417 insn->idx = idx;
418
419 INIT_LIST_HEAD(&insn->call_node);
420 insn->sec = sec;
421 insn->offset = offset;
422 insn->prev_len = prev_len;
423
424 ret = arch_decode_instruction(file, sec, offset,
425 sec->sh.sh_size - offset,
426 insn);
427 if (ret)
428 return ret;
429
430 prev_len = insn->len;
431
432 /*
433 * By default, "ud2" is a dead end unless otherwise
434 * annotated, because GCC 7 inserts it for certain
435 * divide-by-zero cases.
436 */
437 if (insn->type == INSN_BUG)
438 insn->dead_end = true;
439
440 hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
441 nr_insns++;
442 }
443
444// printf("%s: last chunk used: %d\n", sec->name, (int)idx);
445
446 sec_for_each_sym(sec, func) {
447 if (func->type != STT_NOTYPE && func->type != STT_FUNC)
448 continue;
449
450 if (func->offset == sec->sh.sh_size) {
451 /* Heuristic: likely an "end" symbol */
452 if (func->type == STT_NOTYPE)
453 continue;
454 WARN("%s(): STT_FUNC at end of section",
455 func->name);
456 return -1;
457 }
458
459 if (func->embedded_insn || func->alias != func)
460 continue;
461
462 if (!find_insn(file, sec, func->offset)) {
463 WARN("%s(): can't find starting instruction",
464 func->name);
465 return -1;
466 }
467
468 sym_for_each_insn(file, func, insn) {
469 insn->sym = func;
470 if (func->type == STT_FUNC &&
471 insn->type == INSN_ENDBR &&
472 list_empty(&insn->call_node)) {
473 if (insn->offset == func->offset) {
474 list_add_tail(&insn->call_node, &file->endbr_list);
475 file->nr_endbr++;
476 } else {
477 file->nr_endbr_int++;
478 }
479 }
480 }
481 }
482 }
483
484 if (opts.stats)
485 printf("nr_insns: %lu\n", nr_insns);
486
487 return 0;
488}
489
490/*
491 * Read the pv_ops[] .data table to find the static initialized values.
492 */
493static int add_pv_ops(struct objtool_file *file, const char *symname)
494{
495 struct symbol *sym, *func;
496 unsigned long off, end;
497 struct reloc *reloc;
498 int idx;
499
500 sym = find_symbol_by_name(file->elf, symname);
501 if (!sym)
502 return 0;
503
504 off = sym->offset;
505 end = off + sym->len;
506 for (;;) {
507 reloc = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off);
508 if (!reloc)
509 break;
510
511 func = reloc->sym;
512 if (func->type == STT_SECTION)
513 func = find_symbol_by_offset(reloc->sym->sec,
514 reloc_addend(reloc));
515
516 idx = (reloc_offset(reloc) - sym->offset) / sizeof(unsigned long);
517
518 objtool_pv_add(file, idx, func);
519
520 off = reloc_offset(reloc) + 1;
521 if (off > end)
522 break;
523 }
524
525 return 0;
526}
527
528/*
529 * Allocate and initialize file->pv_ops[].
530 */
531static int init_pv_ops(struct objtool_file *file)
532{
533 static const char *pv_ops_tables[] = {
534 "pv_ops",
535 "xen_cpu_ops",
536 "xen_irq_ops",
537 "xen_mmu_ops",
538 NULL,
539 };
540 const char *pv_ops;
541 struct symbol *sym;
542 int idx, nr;
543
544 if (!opts.noinstr)
545 return 0;
546
547 file->pv_ops = NULL;
548
549 sym = find_symbol_by_name(file->elf, "pv_ops");
550 if (!sym)
551 return 0;
552
553 nr = sym->len / sizeof(unsigned long);
554 file->pv_ops = calloc(sizeof(struct pv_state), nr);
555 if (!file->pv_ops)
556 return -1;
557
558 for (idx = 0; idx < nr; idx++)
559 INIT_LIST_HEAD(&file->pv_ops[idx].targets);
560
561 for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++)
562 add_pv_ops(file, pv_ops);
563
564 return 0;
565}
566
567static struct instruction *find_last_insn(struct objtool_file *file,
568 struct section *sec)
569{
570 struct instruction *insn = NULL;
571 unsigned int offset;
572 unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
573
574 for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
575 insn = find_insn(file, sec, offset);
576
577 return insn;
578}
579
580/*
581 * Mark "ud2" instructions and manually annotated dead ends.
582 */
583static int add_dead_ends(struct objtool_file *file)
584{
585 struct section *rsec;
586 struct reloc *reloc;
587 struct instruction *insn;
588 uint64_t offset;
589
590 /*
591 * Check for manually annotated dead ends.
592 */
593 rsec = find_section_by_name(file->elf, ".rela.discard.unreachable");
594 if (!rsec)
595 goto reachable;
596
597 for_each_reloc(rsec, reloc) {
598 if (reloc->sym->type == STT_SECTION) {
599 offset = reloc_addend(reloc);
600 } else if (reloc->sym->local_label) {
601 offset = reloc->sym->offset;
602 } else {
603 WARN("unexpected relocation symbol type in %s", rsec->name);
604 return -1;
605 }
606
607 insn = find_insn(file, reloc->sym->sec, offset);
608 if (insn)
609 insn = prev_insn_same_sec(file, insn);
610 else if (offset == reloc->sym->sec->sh.sh_size) {
611 insn = find_last_insn(file, reloc->sym->sec);
612 if (!insn) {
613 WARN("can't find unreachable insn at %s+0x%" PRIx64,
614 reloc->sym->sec->name, offset);
615 return -1;
616 }
617 } else {
618 WARN("can't find unreachable insn at %s+0x%" PRIx64,
619 reloc->sym->sec->name, offset);
620 return -1;
621 }
622
623 insn->dead_end = true;
624 }
625
626reachable:
627 /*
628 * These manually annotated reachable checks are needed for GCC 4.4,
629 * where the Linux unreachable() macro isn't supported. In that case
630 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
631 * not a dead end.
632 */
633 rsec = find_section_by_name(file->elf, ".rela.discard.reachable");
634 if (!rsec)
635 return 0;
636
637 for_each_reloc(rsec, reloc) {
638 if (reloc->sym->type == STT_SECTION) {
639 offset = reloc_addend(reloc);
640 } else if (reloc->sym->local_label) {
641 offset = reloc->sym->offset;
642 } else {
643 WARN("unexpected relocation symbol type in %s", rsec->name);
644 return -1;
645 }
646
647 insn = find_insn(file, reloc->sym->sec, offset);
648 if (insn)
649 insn = prev_insn_same_sec(file, insn);
650 else if (offset == reloc->sym->sec->sh.sh_size) {
651 insn = find_last_insn(file, reloc->sym->sec);
652 if (!insn) {
653 WARN("can't find reachable insn at %s+0x%" PRIx64,
654 reloc->sym->sec->name, offset);
655 return -1;
656 }
657 } else {
658 WARN("can't find reachable insn at %s+0x%" PRIx64,
659 reloc->sym->sec->name, offset);
660 return -1;
661 }
662
663 insn->dead_end = false;
664 }
665
666 return 0;
667}
668
669static int create_static_call_sections(struct objtool_file *file)
670{
671 struct static_call_site *site;
672 struct section *sec;
673 struct instruction *insn;
674 struct symbol *key_sym;
675 char *key_name, *tmp;
676 int idx;
677
678 sec = find_section_by_name(file->elf, ".static_call_sites");
679 if (sec) {
680 INIT_LIST_HEAD(&file->static_call_list);
681 WARN("file already has .static_call_sites section, skipping");
682 return 0;
683 }
684
685 if (list_empty(&file->static_call_list))
686 return 0;
687
688 idx = 0;
689 list_for_each_entry(insn, &file->static_call_list, call_node)
690 idx++;
691
692 sec = elf_create_section_pair(file->elf, ".static_call_sites",
693 sizeof(*site), idx, idx * 2);
694 if (!sec)
695 return -1;
696
697 /* Allow modules to modify the low bits of static_call_site::key */
698 sec->sh.sh_flags |= SHF_WRITE;
699
700 idx = 0;
701 list_for_each_entry(insn, &file->static_call_list, call_node) {
702
703 /* populate reloc for 'addr' */
704 if (!elf_init_reloc_text_sym(file->elf, sec,
705 idx * sizeof(*site), idx * 2,
706 insn->sec, insn->offset))
707 return -1;
708
709 /* find key symbol */
710 key_name = strdup(insn_call_dest(insn)->name);
711 if (!key_name) {
712 perror("strdup");
713 return -1;
714 }
715 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
716 STATIC_CALL_TRAMP_PREFIX_LEN)) {
717 WARN("static_call: trampoline name malformed: %s", key_name);
718 free(key_name);
719 return -1;
720 }
721 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
722 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
723
724 key_sym = find_symbol_by_name(file->elf, tmp);
725 if (!key_sym) {
726 if (!opts.module) {
727 WARN("static_call: can't find static_call_key symbol: %s", tmp);
728 free(key_name);
729 return -1;
730 }
731
732 /*
733 * For modules(), the key might not be exported, which
734 * means the module can make static calls but isn't
735 * allowed to change them.
736 *
737 * In that case we temporarily set the key to be the
738 * trampoline address. This is fixed up in
739 * static_call_add_module().
740 */
741 key_sym = insn_call_dest(insn);
742 }
743 free(key_name);
744
745 /* populate reloc for 'key' */
746 if (!elf_init_reloc_data_sym(file->elf, sec,
747 idx * sizeof(*site) + 4,
748 (idx * 2) + 1, key_sym,
749 is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
750 return -1;
751
752 idx++;
753 }
754
755 return 0;
756}
757
758static int create_retpoline_sites_sections(struct objtool_file *file)
759{
760 struct instruction *insn;
761 struct section *sec;
762 int idx;
763
764 sec = find_section_by_name(file->elf, ".retpoline_sites");
765 if (sec) {
766 WARN("file already has .retpoline_sites, skipping");
767 return 0;
768 }
769
770 idx = 0;
771 list_for_each_entry(insn, &file->retpoline_call_list, call_node)
772 idx++;
773
774 if (!idx)
775 return 0;
776
777 sec = elf_create_section_pair(file->elf, ".retpoline_sites",
778 sizeof(int), idx, idx);
779 if (!sec)
780 return -1;
781
782 idx = 0;
783 list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
784
785 if (!elf_init_reloc_text_sym(file->elf, sec,
786 idx * sizeof(int), idx,
787 insn->sec, insn->offset))
788 return -1;
789
790 idx++;
791 }
792
793 return 0;
794}
795
796static int create_return_sites_sections(struct objtool_file *file)
797{
798 struct instruction *insn;
799 struct section *sec;
800 int idx;
801
802 sec = find_section_by_name(file->elf, ".return_sites");
803 if (sec) {
804 WARN("file already has .return_sites, skipping");
805 return 0;
806 }
807
808 idx = 0;
809 list_for_each_entry(insn, &file->return_thunk_list, call_node)
810 idx++;
811
812 if (!idx)
813 return 0;
814
815 sec = elf_create_section_pair(file->elf, ".return_sites",
816 sizeof(int), idx, idx);
817 if (!sec)
818 return -1;
819
820 idx = 0;
821 list_for_each_entry(insn, &file->return_thunk_list, call_node) {
822
823 if (!elf_init_reloc_text_sym(file->elf, sec,
824 idx * sizeof(int), idx,
825 insn->sec, insn->offset))
826 return -1;
827
828 idx++;
829 }
830
831 return 0;
832}
833
834static int create_ibt_endbr_seal_sections(struct objtool_file *file)
835{
836 struct instruction *insn;
837 struct section *sec;
838 int idx;
839
840 sec = find_section_by_name(file->elf, ".ibt_endbr_seal");
841 if (sec) {
842 WARN("file already has .ibt_endbr_seal, skipping");
843 return 0;
844 }
845
846 idx = 0;
847 list_for_each_entry(insn, &file->endbr_list, call_node)
848 idx++;
849
850 if (opts.stats) {
851 printf("ibt: ENDBR at function start: %d\n", file->nr_endbr);
852 printf("ibt: ENDBR inside functions: %d\n", file->nr_endbr_int);
853 printf("ibt: superfluous ENDBR: %d\n", idx);
854 }
855
856 if (!idx)
857 return 0;
858
859 sec = elf_create_section_pair(file->elf, ".ibt_endbr_seal",
860 sizeof(int), idx, idx);
861 if (!sec)
862 return -1;
863
864 idx = 0;
865 list_for_each_entry(insn, &file->endbr_list, call_node) {
866
867 int *site = (int *)sec->data->d_buf + idx;
868 struct symbol *sym = insn->sym;
869 *site = 0;
870
871 if (opts.module && sym && sym->type == STT_FUNC &&
872 insn->offset == sym->offset &&
873 (!strcmp(sym->name, "init_module") ||
874 !strcmp(sym->name, "cleanup_module")))
875 WARN("%s(): not an indirect call target", sym->name);
876
877 if (!elf_init_reloc_text_sym(file->elf, sec,
878 idx * sizeof(int), idx,
879 insn->sec, insn->offset))
880 return -1;
881
882 idx++;
883 }
884
885 return 0;
886}
887
888static int create_cfi_sections(struct objtool_file *file)
889{
890 struct section *sec;
891 struct symbol *sym;
892 int idx;
893
894 sec = find_section_by_name(file->elf, ".cfi_sites");
895 if (sec) {
896 INIT_LIST_HEAD(&file->call_list);
897 WARN("file already has .cfi_sites section, skipping");
898 return 0;
899 }
900
901 idx = 0;
902 for_each_sym(file, sym) {
903 if (sym->type != STT_FUNC)
904 continue;
905
906 if (strncmp(sym->name, "__cfi_", 6))
907 continue;
908
909 idx++;
910 }
911
912 sec = elf_create_section_pair(file->elf, ".cfi_sites",
913 sizeof(unsigned int), idx, idx);
914 if (!sec)
915 return -1;
916
917 idx = 0;
918 for_each_sym(file, sym) {
919 if (sym->type != STT_FUNC)
920 continue;
921
922 if (strncmp(sym->name, "__cfi_", 6))
923 continue;
924
925 if (!elf_init_reloc_text_sym(file->elf, sec,
926 idx * sizeof(unsigned int), idx,
927 sym->sec, sym->offset))
928 return -1;
929
930 idx++;
931 }
932
933 return 0;
934}
935
936static int create_mcount_loc_sections(struct objtool_file *file)
937{
938 size_t addr_size = elf_addr_size(file->elf);
939 struct instruction *insn;
940 struct section *sec;
941 int idx;
942
943 sec = find_section_by_name(file->elf, "__mcount_loc");
944 if (sec) {
945 INIT_LIST_HEAD(&file->mcount_loc_list);
946 WARN("file already has __mcount_loc section, skipping");
947 return 0;
948 }
949
950 if (list_empty(&file->mcount_loc_list))
951 return 0;
952
953 idx = 0;
954 list_for_each_entry(insn, &file->mcount_loc_list, call_node)
955 idx++;
956
957 sec = elf_create_section_pair(file->elf, "__mcount_loc", addr_size,
958 idx, idx);
959 if (!sec)
960 return -1;
961
962 sec->sh.sh_addralign = addr_size;
963
964 idx = 0;
965 list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
966
967 struct reloc *reloc;
968
969 reloc = elf_init_reloc_text_sym(file->elf, sec, idx * addr_size, idx,
970 insn->sec, insn->offset);
971 if (!reloc)
972 return -1;
973
974 set_reloc_type(file->elf, reloc, addr_size == 8 ? R_ABS64 : R_ABS32);
975
976 idx++;
977 }
978
979 return 0;
980}
981
982static int create_direct_call_sections(struct objtool_file *file)
983{
984 struct instruction *insn;
985 struct section *sec;
986 int idx;
987
988 sec = find_section_by_name(file->elf, ".call_sites");
989 if (sec) {
990 INIT_LIST_HEAD(&file->call_list);
991 WARN("file already has .call_sites section, skipping");
992 return 0;
993 }
994
995 if (list_empty(&file->call_list))
996 return 0;
997
998 idx = 0;
999 list_for_each_entry(insn, &file->call_list, call_node)
1000 idx++;
1001
1002 sec = elf_create_section_pair(file->elf, ".call_sites",
1003 sizeof(unsigned int), idx, idx);
1004 if (!sec)
1005 return -1;
1006
1007 idx = 0;
1008 list_for_each_entry(insn, &file->call_list, call_node) {
1009
1010 if (!elf_init_reloc_text_sym(file->elf, sec,
1011 idx * sizeof(unsigned int), idx,
1012 insn->sec, insn->offset))
1013 return -1;
1014
1015 idx++;
1016 }
1017
1018 return 0;
1019}
1020
1021/*
1022 * Warnings shouldn't be reported for ignored functions.
1023 */
1024static void add_ignores(struct objtool_file *file)
1025{
1026 struct instruction *insn;
1027 struct section *rsec;
1028 struct symbol *func;
1029 struct reloc *reloc;
1030
1031 rsec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
1032 if (!rsec)
1033 return;
1034
1035 for_each_reloc(rsec, reloc) {
1036 switch (reloc->sym->type) {
1037 case STT_FUNC:
1038 func = reloc->sym;
1039 break;
1040
1041 case STT_SECTION:
1042 func = find_func_by_offset(reloc->sym->sec, reloc_addend(reloc));
1043 if (!func)
1044 continue;
1045 break;
1046
1047 default:
1048 WARN("unexpected relocation symbol type in %s: %d",
1049 rsec->name, reloc->sym->type);
1050 continue;
1051 }
1052
1053 func_for_each_insn(file, func, insn)
1054 insn->ignore = true;
1055 }
1056}
1057
1058/*
1059 * This is a whitelist of functions that is allowed to be called with AC set.
1060 * The list is meant to be minimal and only contains compiler instrumentation
1061 * ABI and a few functions used to implement *_{to,from}_user() functions.
1062 *
1063 * These functions must not directly change AC, but may PUSHF/POPF.
1064 */
1065static const char *uaccess_safe_builtin[] = {
1066 /* KASAN */
1067 "kasan_report",
1068 "kasan_check_range",
1069 /* KASAN out-of-line */
1070 "__asan_loadN_noabort",
1071 "__asan_load1_noabort",
1072 "__asan_load2_noabort",
1073 "__asan_load4_noabort",
1074 "__asan_load8_noabort",
1075 "__asan_load16_noabort",
1076 "__asan_storeN_noabort",
1077 "__asan_store1_noabort",
1078 "__asan_store2_noabort",
1079 "__asan_store4_noabort",
1080 "__asan_store8_noabort",
1081 "__asan_store16_noabort",
1082 "__kasan_check_read",
1083 "__kasan_check_write",
1084 /* KASAN in-line */
1085 "__asan_report_load_n_noabort",
1086 "__asan_report_load1_noabort",
1087 "__asan_report_load2_noabort",
1088 "__asan_report_load4_noabort",
1089 "__asan_report_load8_noabort",
1090 "__asan_report_load16_noabort",
1091 "__asan_report_store_n_noabort",
1092 "__asan_report_store1_noabort",
1093 "__asan_report_store2_noabort",
1094 "__asan_report_store4_noabort",
1095 "__asan_report_store8_noabort",
1096 "__asan_report_store16_noabort",
1097 /* KCSAN */
1098 "__kcsan_check_access",
1099 "__kcsan_mb",
1100 "__kcsan_wmb",
1101 "__kcsan_rmb",
1102 "__kcsan_release",
1103 "kcsan_found_watchpoint",
1104 "kcsan_setup_watchpoint",
1105 "kcsan_check_scoped_accesses",
1106 "kcsan_disable_current",
1107 "kcsan_enable_current_nowarn",
1108 /* KCSAN/TSAN */
1109 "__tsan_func_entry",
1110 "__tsan_func_exit",
1111 "__tsan_read_range",
1112 "__tsan_write_range",
1113 "__tsan_read1",
1114 "__tsan_read2",
1115 "__tsan_read4",
1116 "__tsan_read8",
1117 "__tsan_read16",
1118 "__tsan_write1",
1119 "__tsan_write2",
1120 "__tsan_write4",
1121 "__tsan_write8",
1122 "__tsan_write16",
1123 "__tsan_read_write1",
1124 "__tsan_read_write2",
1125 "__tsan_read_write4",
1126 "__tsan_read_write8",
1127 "__tsan_read_write16",
1128 "__tsan_volatile_read1",
1129 "__tsan_volatile_read2",
1130 "__tsan_volatile_read4",
1131 "__tsan_volatile_read8",
1132 "__tsan_volatile_read16",
1133 "__tsan_volatile_write1",
1134 "__tsan_volatile_write2",
1135 "__tsan_volatile_write4",
1136 "__tsan_volatile_write8",
1137 "__tsan_volatile_write16",
1138 "__tsan_atomic8_load",
1139 "__tsan_atomic16_load",
1140 "__tsan_atomic32_load",
1141 "__tsan_atomic64_load",
1142 "__tsan_atomic8_store",
1143 "__tsan_atomic16_store",
1144 "__tsan_atomic32_store",
1145 "__tsan_atomic64_store",
1146 "__tsan_atomic8_exchange",
1147 "__tsan_atomic16_exchange",
1148 "__tsan_atomic32_exchange",
1149 "__tsan_atomic64_exchange",
1150 "__tsan_atomic8_fetch_add",
1151 "__tsan_atomic16_fetch_add",
1152 "__tsan_atomic32_fetch_add",
1153 "__tsan_atomic64_fetch_add",
1154 "__tsan_atomic8_fetch_sub",
1155 "__tsan_atomic16_fetch_sub",
1156 "__tsan_atomic32_fetch_sub",
1157 "__tsan_atomic64_fetch_sub",
1158 "__tsan_atomic8_fetch_and",
1159 "__tsan_atomic16_fetch_and",
1160 "__tsan_atomic32_fetch_and",
1161 "__tsan_atomic64_fetch_and",
1162 "__tsan_atomic8_fetch_or",
1163 "__tsan_atomic16_fetch_or",
1164 "__tsan_atomic32_fetch_or",
1165 "__tsan_atomic64_fetch_or",
1166 "__tsan_atomic8_fetch_xor",
1167 "__tsan_atomic16_fetch_xor",
1168 "__tsan_atomic32_fetch_xor",
1169 "__tsan_atomic64_fetch_xor",
1170 "__tsan_atomic8_fetch_nand",
1171 "__tsan_atomic16_fetch_nand",
1172 "__tsan_atomic32_fetch_nand",
1173 "__tsan_atomic64_fetch_nand",
1174 "__tsan_atomic8_compare_exchange_strong",
1175 "__tsan_atomic16_compare_exchange_strong",
1176 "__tsan_atomic32_compare_exchange_strong",
1177 "__tsan_atomic64_compare_exchange_strong",
1178 "__tsan_atomic8_compare_exchange_weak",
1179 "__tsan_atomic16_compare_exchange_weak",
1180 "__tsan_atomic32_compare_exchange_weak",
1181 "__tsan_atomic64_compare_exchange_weak",
1182 "__tsan_atomic8_compare_exchange_val",
1183 "__tsan_atomic16_compare_exchange_val",
1184 "__tsan_atomic32_compare_exchange_val",
1185 "__tsan_atomic64_compare_exchange_val",
1186 "__tsan_atomic_thread_fence",
1187 "__tsan_atomic_signal_fence",
1188 "__tsan_unaligned_read16",
1189 "__tsan_unaligned_write16",
1190 /* KCOV */
1191 "write_comp_data",
1192 "check_kcov_mode",
1193 "__sanitizer_cov_trace_pc",
1194 "__sanitizer_cov_trace_const_cmp1",
1195 "__sanitizer_cov_trace_const_cmp2",
1196 "__sanitizer_cov_trace_const_cmp4",
1197 "__sanitizer_cov_trace_const_cmp8",
1198 "__sanitizer_cov_trace_cmp1",
1199 "__sanitizer_cov_trace_cmp2",
1200 "__sanitizer_cov_trace_cmp4",
1201 "__sanitizer_cov_trace_cmp8",
1202 "__sanitizer_cov_trace_switch",
1203 /* KMSAN */
1204 "kmsan_copy_to_user",
1205 "kmsan_report",
1206 "kmsan_unpoison_entry_regs",
1207 "kmsan_unpoison_memory",
1208 "__msan_chain_origin",
1209 "__msan_get_context_state",
1210 "__msan_instrument_asm_store",
1211 "__msan_metadata_ptr_for_load_1",
1212 "__msan_metadata_ptr_for_load_2",
1213 "__msan_metadata_ptr_for_load_4",
1214 "__msan_metadata_ptr_for_load_8",
1215 "__msan_metadata_ptr_for_load_n",
1216 "__msan_metadata_ptr_for_store_1",
1217 "__msan_metadata_ptr_for_store_2",
1218 "__msan_metadata_ptr_for_store_4",
1219 "__msan_metadata_ptr_for_store_8",
1220 "__msan_metadata_ptr_for_store_n",
1221 "__msan_poison_alloca",
1222 "__msan_warning",
1223 /* UBSAN */
1224 "ubsan_type_mismatch_common",
1225 "__ubsan_handle_type_mismatch",
1226 "__ubsan_handle_type_mismatch_v1",
1227 "__ubsan_handle_shift_out_of_bounds",
1228 "__ubsan_handle_load_invalid_value",
1229 /* STACKLEAK */
1230 "stackleak_track_stack",
1231 /* misc */
1232 "csum_partial_copy_generic",
1233 "copy_mc_fragile",
1234 "copy_mc_fragile_handle_tail",
1235 "copy_mc_enhanced_fast_string",
1236 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
1237 "rep_stos_alternative",
1238 "rep_movs_alternative",
1239 "__copy_user_nocache",
1240 NULL
1241};
1242
1243static void add_uaccess_safe(struct objtool_file *file)
1244{
1245 struct symbol *func;
1246 const char **name;
1247
1248 if (!opts.uaccess)
1249 return;
1250
1251 for (name = uaccess_safe_builtin; *name; name++) {
1252 func = find_symbol_by_name(file->elf, *name);
1253 if (!func)
1254 continue;
1255
1256 func->uaccess_safe = true;
1257 }
1258}
1259
1260/*
1261 * FIXME: For now, just ignore any alternatives which add retpolines. This is
1262 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
1263 * But it at least allows objtool to understand the control flow *around* the
1264 * retpoline.
1265 */
1266static int add_ignore_alternatives(struct objtool_file *file)
1267{
1268 struct section *rsec;
1269 struct reloc *reloc;
1270 struct instruction *insn;
1271
1272 rsec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
1273 if (!rsec)
1274 return 0;
1275
1276 for_each_reloc(rsec, reloc) {
1277 if (reloc->sym->type != STT_SECTION) {
1278 WARN("unexpected relocation symbol type in %s", rsec->name);
1279 return -1;
1280 }
1281
1282 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
1283 if (!insn) {
1284 WARN("bad .discard.ignore_alts entry");
1285 return -1;
1286 }
1287
1288 insn->ignore_alts = true;
1289 }
1290
1291 return 0;
1292}
1293
1294/*
1295 * Symbols that replace INSN_CALL_DYNAMIC, every (tail) call to such a symbol
1296 * will be added to the .retpoline_sites section.
1297 */
1298__weak bool arch_is_retpoline(struct symbol *sym)
1299{
1300 return false;
1301}
1302
1303/*
1304 * Symbols that replace INSN_RETURN, every (tail) call to such a symbol
1305 * will be added to the .return_sites section.
1306 */
1307__weak bool arch_is_rethunk(struct symbol *sym)
1308{
1309 return false;
1310}
1311
1312/*
1313 * Symbols that are embedded inside other instructions, because sometimes crazy
1314 * code exists. These are mostly ignored for validation purposes.
1315 */
1316__weak bool arch_is_embedded_insn(struct symbol *sym)
1317{
1318 return false;
1319}
1320
1321static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
1322{
1323 struct reloc *reloc;
1324
1325 if (insn->no_reloc)
1326 return NULL;
1327
1328 if (!file)
1329 return NULL;
1330
1331 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1332 insn->offset, insn->len);
1333 if (!reloc) {
1334 insn->no_reloc = 1;
1335 return NULL;
1336 }
1337
1338 return reloc;
1339}
1340
1341static void remove_insn_ops(struct instruction *insn)
1342{
1343 struct stack_op *op, *next;
1344
1345 for (op = insn->stack_ops; op; op = next) {
1346 next = op->next;
1347 free(op);
1348 }
1349 insn->stack_ops = NULL;
1350}
1351
1352static void annotate_call_site(struct objtool_file *file,
1353 struct instruction *insn, bool sibling)
1354{
1355 struct reloc *reloc = insn_reloc(file, insn);
1356 struct symbol *sym = insn_call_dest(insn);
1357
1358 if (!sym)
1359 sym = reloc->sym;
1360
1361 /*
1362 * Alternative replacement code is just template code which is
1363 * sometimes copied to the original instruction. For now, don't
1364 * annotate it. (In the future we might consider annotating the
1365 * original instruction if/when it ever makes sense to do so.)
1366 */
1367 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1368 return;
1369
1370 if (sym->static_call_tramp) {
1371 list_add_tail(&insn->call_node, &file->static_call_list);
1372 return;
1373 }
1374
1375 if (sym->retpoline_thunk) {
1376 list_add_tail(&insn->call_node, &file->retpoline_call_list);
1377 return;
1378 }
1379
1380 /*
1381 * Many compilers cannot disable KCOV or sanitizer calls with a function
1382 * attribute so they need a little help, NOP out any such calls from
1383 * noinstr text.
1384 */
1385 if (opts.hack_noinstr && insn->sec->noinstr && sym->profiling_func) {
1386 if (reloc)
1387 set_reloc_type(file->elf, reloc, R_NONE);
1388
1389 elf_write_insn(file->elf, insn->sec,
1390 insn->offset, insn->len,
1391 sibling ? arch_ret_insn(insn->len)
1392 : arch_nop_insn(insn->len));
1393
1394 insn->type = sibling ? INSN_RETURN : INSN_NOP;
1395
1396 if (sibling) {
1397 /*
1398 * We've replaced the tail-call JMP insn by two new
1399 * insn: RET; INT3, except we only have a single struct
1400 * insn here. Mark it retpoline_safe to avoid the SLS
1401 * warning, instead of adding another insn.
1402 */
1403 insn->retpoline_safe = true;
1404 }
1405
1406 return;
1407 }
1408
1409 if (opts.mcount && sym->fentry) {
1410 if (sibling)
1411 WARN_INSN(insn, "tail call to __fentry__ !?!?");
1412 if (opts.mnop) {
1413 if (reloc)
1414 set_reloc_type(file->elf, reloc, R_NONE);
1415
1416 elf_write_insn(file->elf, insn->sec,
1417 insn->offset, insn->len,
1418 arch_nop_insn(insn->len));
1419
1420 insn->type = INSN_NOP;
1421 }
1422
1423 list_add_tail(&insn->call_node, &file->mcount_loc_list);
1424 return;
1425 }
1426
1427 if (insn->type == INSN_CALL && !insn->sec->init)
1428 list_add_tail(&insn->call_node, &file->call_list);
1429
1430 if (!sibling && dead_end_function(file, sym))
1431 insn->dead_end = true;
1432}
1433
1434static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1435 struct symbol *dest, bool sibling)
1436{
1437 insn->_call_dest = dest;
1438 if (!dest)
1439 return;
1440
1441 /*
1442 * Whatever stack impact regular CALLs have, should be undone
1443 * by the RETURN of the called function.
1444 *
1445 * Annotated intra-function calls retain the stack_ops but
1446 * are converted to JUMP, see read_intra_function_calls().
1447 */
1448 remove_insn_ops(insn);
1449
1450 annotate_call_site(file, insn, sibling);
1451}
1452
1453static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1454{
1455 /*
1456 * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1457 * so convert them accordingly.
1458 */
1459 switch (insn->type) {
1460 case INSN_CALL:
1461 insn->type = INSN_CALL_DYNAMIC;
1462 break;
1463 case INSN_JUMP_UNCONDITIONAL:
1464 insn->type = INSN_JUMP_DYNAMIC;
1465 break;
1466 case INSN_JUMP_CONDITIONAL:
1467 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1468 break;
1469 default:
1470 return;
1471 }
1472
1473 insn->retpoline_safe = true;
1474
1475 /*
1476 * Whatever stack impact regular CALLs have, should be undone
1477 * by the RETURN of the called function.
1478 *
1479 * Annotated intra-function calls retain the stack_ops but
1480 * are converted to JUMP, see read_intra_function_calls().
1481 */
1482 remove_insn_ops(insn);
1483
1484 annotate_call_site(file, insn, false);
1485}
1486
1487static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add)
1488{
1489 /*
1490 * Return thunk tail calls are really just returns in disguise,
1491 * so convert them accordingly.
1492 */
1493 insn->type = INSN_RETURN;
1494 insn->retpoline_safe = true;
1495
1496 if (add)
1497 list_add_tail(&insn->call_node, &file->return_thunk_list);
1498}
1499
1500static bool is_first_func_insn(struct objtool_file *file,
1501 struct instruction *insn, struct symbol *sym)
1502{
1503 if (insn->offset == sym->offset)
1504 return true;
1505
1506 /* Allow direct CALL/JMP past ENDBR */
1507 if (opts.ibt) {
1508 struct instruction *prev = prev_insn_same_sym(file, insn);
1509
1510 if (prev && prev->type == INSN_ENDBR &&
1511 insn->offset == sym->offset + prev->len)
1512 return true;
1513 }
1514
1515 return false;
1516}
1517
1518/*
1519 * A sibling call is a tail-call to another symbol -- to differentiate from a
1520 * recursive tail-call which is to the same symbol.
1521 */
1522static bool jump_is_sibling_call(struct objtool_file *file,
1523 struct instruction *from, struct instruction *to)
1524{
1525 struct symbol *fs = from->sym;
1526 struct symbol *ts = to->sym;
1527
1528 /* Not a sibling call if from/to a symbol hole */
1529 if (!fs || !ts)
1530 return false;
1531
1532 /* Not a sibling call if not targeting the start of a symbol. */
1533 if (!is_first_func_insn(file, to, ts))
1534 return false;
1535
1536 /* Disallow sibling calls into STT_NOTYPE */
1537 if (ts->type == STT_NOTYPE)
1538 return false;
1539
1540 /* Must not be self to be a sibling */
1541 return fs->pfunc != ts->pfunc;
1542}
1543
1544/*
1545 * Find the destination instructions for all jumps.
1546 */
1547static int add_jump_destinations(struct objtool_file *file)
1548{
1549 struct instruction *insn, *jump_dest;
1550 struct reloc *reloc;
1551 struct section *dest_sec;
1552 unsigned long dest_off;
1553
1554 for_each_insn(file, insn) {
1555 if (insn->jump_dest) {
1556 /*
1557 * handle_group_alt() may have previously set
1558 * 'jump_dest' for some alternatives.
1559 */
1560 continue;
1561 }
1562 if (!is_static_jump(insn))
1563 continue;
1564
1565 reloc = insn_reloc(file, insn);
1566 if (!reloc) {
1567 dest_sec = insn->sec;
1568 dest_off = arch_jump_destination(insn);
1569 } else if (reloc->sym->type == STT_SECTION) {
1570 dest_sec = reloc->sym->sec;
1571 dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
1572 } else if (reloc->sym->retpoline_thunk) {
1573 add_retpoline_call(file, insn);
1574 continue;
1575 } else if (reloc->sym->return_thunk) {
1576 add_return_call(file, insn, true);
1577 continue;
1578 } else if (insn_func(insn)) {
1579 /*
1580 * External sibling call or internal sibling call with
1581 * STT_FUNC reloc.
1582 */
1583 add_call_dest(file, insn, reloc->sym, true);
1584 continue;
1585 } else if (reloc->sym->sec->idx) {
1586 dest_sec = reloc->sym->sec;
1587 dest_off = reloc->sym->sym.st_value +
1588 arch_dest_reloc_offset(reloc_addend(reloc));
1589 } else {
1590 /* non-func asm code jumping to another file */
1591 continue;
1592 }
1593
1594 jump_dest = find_insn(file, dest_sec, dest_off);
1595 if (!jump_dest) {
1596 struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off);
1597
1598 /*
1599 * This is a special case for retbleed_untrain_ret().
1600 * It jumps to __x86_return_thunk(), but objtool
1601 * can't find the thunk's starting RET
1602 * instruction, because the RET is also in the
1603 * middle of another instruction. Objtool only
1604 * knows about the outer instruction.
1605 */
1606 if (sym && sym->embedded_insn) {
1607 add_return_call(file, insn, false);
1608 continue;
1609 }
1610
1611 WARN_INSN(insn, "can't find jump dest instruction at %s+0x%lx",
1612 dest_sec->name, dest_off);
1613 return -1;
1614 }
1615
1616 /*
1617 * An intra-TU jump in retpoline.o might not have a relocation
1618 * for its jump dest, in which case the above
1619 * add_{retpoline,return}_call() didn't happen.
1620 */
1621 if (jump_dest->sym && jump_dest->offset == jump_dest->sym->offset) {
1622 if (jump_dest->sym->retpoline_thunk) {
1623 add_retpoline_call(file, insn);
1624 continue;
1625 }
1626 if (jump_dest->sym->return_thunk) {
1627 add_return_call(file, insn, true);
1628 continue;
1629 }
1630 }
1631
1632 /*
1633 * Cross-function jump.
1634 */
1635 if (insn_func(insn) && insn_func(jump_dest) &&
1636 insn_func(insn) != insn_func(jump_dest)) {
1637
1638 /*
1639 * For GCC 8+, create parent/child links for any cold
1640 * subfunctions. This is _mostly_ redundant with a
1641 * similar initialization in read_symbols().
1642 *
1643 * If a function has aliases, we want the *first* such
1644 * function in the symbol table to be the subfunction's
1645 * parent. In that case we overwrite the
1646 * initialization done in read_symbols().
1647 *
1648 * However this code can't completely replace the
1649 * read_symbols() code because this doesn't detect the
1650 * case where the parent function's only reference to a
1651 * subfunction is through a jump table.
1652 */
1653 if (!strstr(insn_func(insn)->name, ".cold") &&
1654 strstr(insn_func(jump_dest)->name, ".cold")) {
1655 insn_func(insn)->cfunc = insn_func(jump_dest);
1656 insn_func(jump_dest)->pfunc = insn_func(insn);
1657 }
1658 }
1659
1660 if (jump_is_sibling_call(file, insn, jump_dest)) {
1661 /*
1662 * Internal sibling call without reloc or with
1663 * STT_SECTION reloc.
1664 */
1665 add_call_dest(file, insn, insn_func(jump_dest), true);
1666 continue;
1667 }
1668
1669 insn->jump_dest = jump_dest;
1670 }
1671
1672 return 0;
1673}
1674
1675static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1676{
1677 struct symbol *call_dest;
1678
1679 call_dest = find_func_by_offset(sec, offset);
1680 if (!call_dest)
1681 call_dest = find_symbol_by_offset(sec, offset);
1682
1683 return call_dest;
1684}
1685
1686/*
1687 * Find the destination instructions for all calls.
1688 */
1689static int add_call_destinations(struct objtool_file *file)
1690{
1691 struct instruction *insn;
1692 unsigned long dest_off;
1693 struct symbol *dest;
1694 struct reloc *reloc;
1695
1696 for_each_insn(file, insn) {
1697 if (insn->type != INSN_CALL)
1698 continue;
1699
1700 reloc = insn_reloc(file, insn);
1701 if (!reloc) {
1702 dest_off = arch_jump_destination(insn);
1703 dest = find_call_destination(insn->sec, dest_off);
1704
1705 add_call_dest(file, insn, dest, false);
1706
1707 if (insn->ignore)
1708 continue;
1709
1710 if (!insn_call_dest(insn)) {
1711 WARN_INSN(insn, "unannotated intra-function call");
1712 return -1;
1713 }
1714
1715 if (insn_func(insn) && insn_call_dest(insn)->type != STT_FUNC) {
1716 WARN_INSN(insn, "unsupported call to non-function");
1717 return -1;
1718 }
1719
1720 } else if (reloc->sym->type == STT_SECTION) {
1721 dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
1722 dest = find_call_destination(reloc->sym->sec, dest_off);
1723 if (!dest) {
1724 WARN_INSN(insn, "can't find call dest symbol at %s+0x%lx",
1725 reloc->sym->sec->name, dest_off);
1726 return -1;
1727 }
1728
1729 add_call_dest(file, insn, dest, false);
1730
1731 } else if (reloc->sym->retpoline_thunk) {
1732 add_retpoline_call(file, insn);
1733
1734 } else
1735 add_call_dest(file, insn, reloc->sym, false);
1736 }
1737
1738 return 0;
1739}
1740
1741/*
1742 * The .alternatives section requires some extra special care over and above
1743 * other special sections because alternatives are patched in place.
1744 */
1745static int handle_group_alt(struct objtool_file *file,
1746 struct special_alt *special_alt,
1747 struct instruction *orig_insn,
1748 struct instruction **new_insn)
1749{
1750 struct instruction *last_new_insn = NULL, *insn, *nop = NULL;
1751 struct alt_group *orig_alt_group, *new_alt_group;
1752 unsigned long dest_off;
1753
1754 orig_alt_group = orig_insn->alt_group;
1755 if (!orig_alt_group) {
1756 struct instruction *last_orig_insn = NULL;
1757
1758 orig_alt_group = malloc(sizeof(*orig_alt_group));
1759 if (!orig_alt_group) {
1760 WARN("malloc failed");
1761 return -1;
1762 }
1763 orig_alt_group->cfi = calloc(special_alt->orig_len,
1764 sizeof(struct cfi_state *));
1765 if (!orig_alt_group->cfi) {
1766 WARN("calloc failed");
1767 return -1;
1768 }
1769
1770 insn = orig_insn;
1771 sec_for_each_insn_from(file, insn) {
1772 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1773 break;
1774
1775 insn->alt_group = orig_alt_group;
1776 last_orig_insn = insn;
1777 }
1778 orig_alt_group->orig_group = NULL;
1779 orig_alt_group->first_insn = orig_insn;
1780 orig_alt_group->last_insn = last_orig_insn;
1781 orig_alt_group->nop = NULL;
1782 } else {
1783 if (orig_alt_group->last_insn->offset + orig_alt_group->last_insn->len -
1784 orig_alt_group->first_insn->offset != special_alt->orig_len) {
1785 WARN_INSN(orig_insn, "weirdly overlapping alternative! %ld != %d",
1786 orig_alt_group->last_insn->offset +
1787 orig_alt_group->last_insn->len -
1788 orig_alt_group->first_insn->offset,
1789 special_alt->orig_len);
1790 return -1;
1791 }
1792 }
1793
1794 new_alt_group = malloc(sizeof(*new_alt_group));
1795 if (!new_alt_group) {
1796 WARN("malloc failed");
1797 return -1;
1798 }
1799
1800 if (special_alt->new_len < special_alt->orig_len) {
1801 /*
1802 * Insert a fake nop at the end to make the replacement
1803 * alt_group the same size as the original. This is needed to
1804 * allow propagate_alt_cfi() to do its magic. When the last
1805 * instruction affects the stack, the instruction after it (the
1806 * nop) will propagate the new state to the shared CFI array.
1807 */
1808 nop = malloc(sizeof(*nop));
1809 if (!nop) {
1810 WARN("malloc failed");
1811 return -1;
1812 }
1813 memset(nop, 0, sizeof(*nop));
1814
1815 nop->sec = special_alt->new_sec;
1816 nop->offset = special_alt->new_off + special_alt->new_len;
1817 nop->len = special_alt->orig_len - special_alt->new_len;
1818 nop->type = INSN_NOP;
1819 nop->sym = orig_insn->sym;
1820 nop->alt_group = new_alt_group;
1821 nop->ignore = orig_insn->ignore_alts;
1822 }
1823
1824 if (!special_alt->new_len) {
1825 *new_insn = nop;
1826 goto end;
1827 }
1828
1829 insn = *new_insn;
1830 sec_for_each_insn_from(file, insn) {
1831 struct reloc *alt_reloc;
1832
1833 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1834 break;
1835
1836 last_new_insn = insn;
1837
1838 insn->ignore = orig_insn->ignore_alts;
1839 insn->sym = orig_insn->sym;
1840 insn->alt_group = new_alt_group;
1841
1842 /*
1843 * Since alternative replacement code is copy/pasted by the
1844 * kernel after applying relocations, generally such code can't
1845 * have relative-address relocation references to outside the
1846 * .altinstr_replacement section, unless the arch's
1847 * alternatives code can adjust the relative offsets
1848 * accordingly.
1849 */
1850 alt_reloc = insn_reloc(file, insn);
1851 if (alt_reloc && arch_pc_relative_reloc(alt_reloc) &&
1852 !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1853
1854 WARN_INSN(insn, "unsupported relocation in alternatives section");
1855 return -1;
1856 }
1857
1858 if (!is_static_jump(insn))
1859 continue;
1860
1861 if (!insn->immediate)
1862 continue;
1863
1864 dest_off = arch_jump_destination(insn);
1865 if (dest_off == special_alt->new_off + special_alt->new_len) {
1866 insn->jump_dest = next_insn_same_sec(file, orig_alt_group->last_insn);
1867 if (!insn->jump_dest) {
1868 WARN_INSN(insn, "can't find alternative jump destination");
1869 return -1;
1870 }
1871 }
1872 }
1873
1874 if (!last_new_insn) {
1875 WARN_FUNC("can't find last new alternative instruction",
1876 special_alt->new_sec, special_alt->new_off);
1877 return -1;
1878 }
1879
1880end:
1881 new_alt_group->orig_group = orig_alt_group;
1882 new_alt_group->first_insn = *new_insn;
1883 new_alt_group->last_insn = last_new_insn;
1884 new_alt_group->nop = nop;
1885 new_alt_group->cfi = orig_alt_group->cfi;
1886 return 0;
1887}
1888
1889/*
1890 * A jump table entry can either convert a nop to a jump or a jump to a nop.
1891 * If the original instruction is a jump, make the alt entry an effective nop
1892 * by just skipping the original instruction.
1893 */
1894static int handle_jump_alt(struct objtool_file *file,
1895 struct special_alt *special_alt,
1896 struct instruction *orig_insn,
1897 struct instruction **new_insn)
1898{
1899 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1900 orig_insn->type != INSN_NOP) {
1901
1902 WARN_INSN(orig_insn, "unsupported instruction at jump label");
1903 return -1;
1904 }
1905
1906 if (opts.hack_jump_label && special_alt->key_addend & 2) {
1907 struct reloc *reloc = insn_reloc(file, orig_insn);
1908
1909 if (reloc)
1910 set_reloc_type(file->elf, reloc, R_NONE);
1911 elf_write_insn(file->elf, orig_insn->sec,
1912 orig_insn->offset, orig_insn->len,
1913 arch_nop_insn(orig_insn->len));
1914 orig_insn->type = INSN_NOP;
1915 }
1916
1917 if (orig_insn->type == INSN_NOP) {
1918 if (orig_insn->len == 2)
1919 file->jl_nop_short++;
1920 else
1921 file->jl_nop_long++;
1922
1923 return 0;
1924 }
1925
1926 if (orig_insn->len == 2)
1927 file->jl_short++;
1928 else
1929 file->jl_long++;
1930
1931 *new_insn = next_insn_same_sec(file, orig_insn);
1932 return 0;
1933}
1934
1935/*
1936 * Read all the special sections which have alternate instructions which can be
1937 * patched in or redirected to at runtime. Each instruction having alternate
1938 * instruction(s) has them added to its insn->alts list, which will be
1939 * traversed in validate_branch().
1940 */
1941static int add_special_section_alts(struct objtool_file *file)
1942{
1943 struct list_head special_alts;
1944 struct instruction *orig_insn, *new_insn;
1945 struct special_alt *special_alt, *tmp;
1946 struct alternative *alt;
1947 int ret;
1948
1949 ret = special_get_alts(file->elf, &special_alts);
1950 if (ret)
1951 return ret;
1952
1953 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1954
1955 orig_insn = find_insn(file, special_alt->orig_sec,
1956 special_alt->orig_off);
1957 if (!orig_insn) {
1958 WARN_FUNC("special: can't find orig instruction",
1959 special_alt->orig_sec, special_alt->orig_off);
1960 ret = -1;
1961 goto out;
1962 }
1963
1964 new_insn = NULL;
1965 if (!special_alt->group || special_alt->new_len) {
1966 new_insn = find_insn(file, special_alt->new_sec,
1967 special_alt->new_off);
1968 if (!new_insn) {
1969 WARN_FUNC("special: can't find new instruction",
1970 special_alt->new_sec,
1971 special_alt->new_off);
1972 ret = -1;
1973 goto out;
1974 }
1975 }
1976
1977 if (special_alt->group) {
1978 if (!special_alt->orig_len) {
1979 WARN_INSN(orig_insn, "empty alternative entry");
1980 continue;
1981 }
1982
1983 ret = handle_group_alt(file, special_alt, orig_insn,
1984 &new_insn);
1985 if (ret)
1986 goto out;
1987 } else if (special_alt->jump_or_nop) {
1988 ret = handle_jump_alt(file, special_alt, orig_insn,
1989 &new_insn);
1990 if (ret)
1991 goto out;
1992 }
1993
1994 alt = malloc(sizeof(*alt));
1995 if (!alt) {
1996 WARN("malloc failed");
1997 ret = -1;
1998 goto out;
1999 }
2000
2001 alt->insn = new_insn;
2002 alt->skip_orig = special_alt->skip_orig;
2003 orig_insn->ignore_alts |= special_alt->skip_alt;
2004 alt->next = orig_insn->alts;
2005 orig_insn->alts = alt;
2006
2007 list_del(&special_alt->list);
2008 free(special_alt);
2009 }
2010
2011 if (opts.stats) {
2012 printf("jl\\\tNOP\tJMP\n");
2013 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
2014 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
2015 }
2016
2017out:
2018 return ret;
2019}
2020
2021static int add_jump_table(struct objtool_file *file, struct instruction *insn,
2022 struct reloc *next_table)
2023{
2024 struct symbol *pfunc = insn_func(insn)->pfunc;
2025 struct reloc *table = insn_jump_table(insn);
2026 struct instruction *dest_insn;
2027 unsigned int prev_offset = 0;
2028 struct reloc *reloc = table;
2029 struct alternative *alt;
2030
2031 /*
2032 * Each @reloc is a switch table relocation which points to the target
2033 * instruction.
2034 */
2035 for_each_reloc_from(table->sec, reloc) {
2036
2037 /* Check for the end of the table: */
2038 if (reloc != table && reloc == next_table)
2039 break;
2040
2041 /* Make sure the table entries are consecutive: */
2042 if (prev_offset && reloc_offset(reloc) != prev_offset + 8)
2043 break;
2044
2045 /* Detect function pointers from contiguous objects: */
2046 if (reloc->sym->sec == pfunc->sec &&
2047 reloc_addend(reloc) == pfunc->offset)
2048 break;
2049
2050 dest_insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2051 if (!dest_insn)
2052 break;
2053
2054 /* Make sure the destination is in the same function: */
2055 if (!insn_func(dest_insn) || insn_func(dest_insn)->pfunc != pfunc)
2056 break;
2057
2058 alt = malloc(sizeof(*alt));
2059 if (!alt) {
2060 WARN("malloc failed");
2061 return -1;
2062 }
2063
2064 alt->insn = dest_insn;
2065 alt->next = insn->alts;
2066 insn->alts = alt;
2067 prev_offset = reloc_offset(reloc);
2068 }
2069
2070 if (!prev_offset) {
2071 WARN_INSN(insn, "can't find switch jump table");
2072 return -1;
2073 }
2074
2075 return 0;
2076}
2077
2078/*
2079 * find_jump_table() - Given a dynamic jump, find the switch jump table
2080 * associated with it.
2081 */
2082static struct reloc *find_jump_table(struct objtool_file *file,
2083 struct symbol *func,
2084 struct instruction *insn)
2085{
2086 struct reloc *table_reloc;
2087 struct instruction *dest_insn, *orig_insn = insn;
2088
2089 /*
2090 * Backward search using the @first_jump_src links, these help avoid
2091 * much of the 'in between' code. Which avoids us getting confused by
2092 * it.
2093 */
2094 for (;
2095 insn && insn_func(insn) && insn_func(insn)->pfunc == func;
2096 insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
2097
2098 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
2099 break;
2100
2101 /* allow small jumps within the range */
2102 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
2103 insn->jump_dest &&
2104 (insn->jump_dest->offset <= insn->offset ||
2105 insn->jump_dest->offset > orig_insn->offset))
2106 break;
2107
2108 table_reloc = arch_find_switch_table(file, insn);
2109 if (!table_reloc)
2110 continue;
2111 dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
2112 if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
2113 continue;
2114
2115 return table_reloc;
2116 }
2117
2118 return NULL;
2119}
2120
2121/*
2122 * First pass: Mark the head of each jump table so that in the next pass,
2123 * we know when a given jump table ends and the next one starts.
2124 */
2125static void mark_func_jump_tables(struct objtool_file *file,
2126 struct symbol *func)
2127{
2128 struct instruction *insn, *last = NULL;
2129 struct reloc *reloc;
2130
2131 func_for_each_insn(file, func, insn) {
2132 if (!last)
2133 last = insn;
2134
2135 /*
2136 * Store back-pointers for unconditional forward jumps such
2137 * that find_jump_table() can back-track using those and
2138 * avoid some potentially confusing code.
2139 */
2140 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
2141 insn->offset > last->offset &&
2142 insn->jump_dest->offset > insn->offset &&
2143 !insn->jump_dest->first_jump_src) {
2144
2145 insn->jump_dest->first_jump_src = insn;
2146 last = insn->jump_dest;
2147 }
2148
2149 if (insn->type != INSN_JUMP_DYNAMIC)
2150 continue;
2151
2152 reloc = find_jump_table(file, func, insn);
2153 if (reloc)
2154 insn->_jump_table = reloc;
2155 }
2156}
2157
2158static int add_func_jump_tables(struct objtool_file *file,
2159 struct symbol *func)
2160{
2161 struct instruction *insn, *insn_t1 = NULL, *insn_t2;
2162 int ret = 0;
2163
2164 func_for_each_insn(file, func, insn) {
2165 if (!insn_jump_table(insn))
2166 continue;
2167
2168 if (!insn_t1) {
2169 insn_t1 = insn;
2170 continue;
2171 }
2172
2173 insn_t2 = insn;
2174
2175 ret = add_jump_table(file, insn_t1, insn_jump_table(insn_t2));
2176 if (ret)
2177 return ret;
2178
2179 insn_t1 = insn_t2;
2180 }
2181
2182 if (insn_t1)
2183 ret = add_jump_table(file, insn_t1, NULL);
2184
2185 return ret;
2186}
2187
2188/*
2189 * For some switch statements, gcc generates a jump table in the .rodata
2190 * section which contains a list of addresses within the function to jump to.
2191 * This finds these jump tables and adds them to the insn->alts lists.
2192 */
2193static int add_jump_table_alts(struct objtool_file *file)
2194{
2195 struct symbol *func;
2196 int ret;
2197
2198 if (!file->rodata)
2199 return 0;
2200
2201 for_each_sym(file, func) {
2202 if (func->type != STT_FUNC)
2203 continue;
2204
2205 mark_func_jump_tables(file, func);
2206 ret = add_func_jump_tables(file, func);
2207 if (ret)
2208 return ret;
2209 }
2210
2211 return 0;
2212}
2213
2214static void set_func_state(struct cfi_state *state)
2215{
2216 state->cfa = initial_func_cfi.cfa;
2217 memcpy(&state->regs, &initial_func_cfi.regs,
2218 CFI_NUM_REGS * sizeof(struct cfi_reg));
2219 state->stack_size = initial_func_cfi.cfa.offset;
2220 state->type = UNWIND_HINT_TYPE_CALL;
2221}
2222
2223static int read_unwind_hints(struct objtool_file *file)
2224{
2225 struct cfi_state cfi = init_cfi;
2226 struct section *sec;
2227 struct unwind_hint *hint;
2228 struct instruction *insn;
2229 struct reloc *reloc;
2230 unsigned long offset;
2231 int i;
2232
2233 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
2234 if (!sec)
2235 return 0;
2236
2237 if (!sec->rsec) {
2238 WARN("missing .rela.discard.unwind_hints section");
2239 return -1;
2240 }
2241
2242 if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
2243 WARN("struct unwind_hint size mismatch");
2244 return -1;
2245 }
2246
2247 file->hints = true;
2248
2249 for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
2250 hint = (struct unwind_hint *)sec->data->d_buf + i;
2251
2252 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
2253 if (!reloc) {
2254 WARN("can't find reloc for unwind_hints[%d]", i);
2255 return -1;
2256 }
2257
2258 if (reloc->sym->type == STT_SECTION) {
2259 offset = reloc_addend(reloc);
2260 } else if (reloc->sym->local_label) {
2261 offset = reloc->sym->offset;
2262 } else {
2263 WARN("unexpected relocation symbol type in %s", sec->rsec->name);
2264 return -1;
2265 }
2266
2267 insn = find_insn(file, reloc->sym->sec, offset);
2268 if (!insn) {
2269 WARN("can't find insn for unwind_hints[%d]", i);
2270 return -1;
2271 }
2272
2273 insn->hint = true;
2274
2275 if (hint->type == UNWIND_HINT_TYPE_UNDEFINED) {
2276 insn->cfi = &force_undefined_cfi;
2277 continue;
2278 }
2279
2280 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
2281 insn->hint = false;
2282 insn->save = true;
2283 continue;
2284 }
2285
2286 if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
2287 insn->restore = true;
2288 continue;
2289 }
2290
2291 if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
2292 struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
2293
2294 if (sym && sym->bind == STB_GLOBAL) {
2295 if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) {
2296 WARN_INSN(insn, "UNWIND_HINT_IRET_REGS without ENDBR");
2297 }
2298 }
2299 }
2300
2301 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
2302 insn->cfi = &func_cfi;
2303 continue;
2304 }
2305
2306 if (insn->cfi)
2307 cfi = *(insn->cfi);
2308
2309 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
2310 WARN_INSN(insn, "unsupported unwind_hint sp base reg %d", hint->sp_reg);
2311 return -1;
2312 }
2313
2314 cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
2315 cfi.type = hint->type;
2316 cfi.signal = hint->signal;
2317
2318 insn->cfi = cfi_hash_find_or_add(&cfi);
2319 }
2320
2321 return 0;
2322}
2323
2324static int read_noendbr_hints(struct objtool_file *file)
2325{
2326 struct instruction *insn;
2327 struct section *rsec;
2328 struct reloc *reloc;
2329
2330 rsec = find_section_by_name(file->elf, ".rela.discard.noendbr");
2331 if (!rsec)
2332 return 0;
2333
2334 for_each_reloc(rsec, reloc) {
2335 insn = find_insn(file, reloc->sym->sec,
2336 reloc->sym->offset + reloc_addend(reloc));
2337 if (!insn) {
2338 WARN("bad .discard.noendbr entry");
2339 return -1;
2340 }
2341
2342 insn->noendbr = 1;
2343 }
2344
2345 return 0;
2346}
2347
2348static int read_retpoline_hints(struct objtool_file *file)
2349{
2350 struct section *rsec;
2351 struct instruction *insn;
2352 struct reloc *reloc;
2353
2354 rsec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
2355 if (!rsec)
2356 return 0;
2357
2358 for_each_reloc(rsec, reloc) {
2359 if (reloc->sym->type != STT_SECTION) {
2360 WARN("unexpected relocation symbol type in %s", rsec->name);
2361 return -1;
2362 }
2363
2364 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2365 if (!insn) {
2366 WARN("bad .discard.retpoline_safe entry");
2367 return -1;
2368 }
2369
2370 if (insn->type != INSN_JUMP_DYNAMIC &&
2371 insn->type != INSN_CALL_DYNAMIC &&
2372 insn->type != INSN_RETURN &&
2373 insn->type != INSN_NOP) {
2374 WARN_INSN(insn, "retpoline_safe hint not an indirect jump/call/ret/nop");
2375 return -1;
2376 }
2377
2378 insn->retpoline_safe = true;
2379 }
2380
2381 return 0;
2382}
2383
2384static int read_instr_hints(struct objtool_file *file)
2385{
2386 struct section *rsec;
2387 struct instruction *insn;
2388 struct reloc *reloc;
2389
2390 rsec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2391 if (!rsec)
2392 return 0;
2393
2394 for_each_reloc(rsec, reloc) {
2395 if (reloc->sym->type != STT_SECTION) {
2396 WARN("unexpected relocation symbol type in %s", rsec->name);
2397 return -1;
2398 }
2399
2400 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2401 if (!insn) {
2402 WARN("bad .discard.instr_end entry");
2403 return -1;
2404 }
2405
2406 insn->instr--;
2407 }
2408
2409 rsec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2410 if (!rsec)
2411 return 0;
2412
2413 for_each_reloc(rsec, reloc) {
2414 if (reloc->sym->type != STT_SECTION) {
2415 WARN("unexpected relocation symbol type in %s", rsec->name);
2416 return -1;
2417 }
2418
2419 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2420 if (!insn) {
2421 WARN("bad .discard.instr_begin entry");
2422 return -1;
2423 }
2424
2425 insn->instr++;
2426 }
2427
2428 return 0;
2429}
2430
2431static int read_validate_unret_hints(struct objtool_file *file)
2432{
2433 struct section *rsec;
2434 struct instruction *insn;
2435 struct reloc *reloc;
2436
2437 rsec = find_section_by_name(file->elf, ".rela.discard.validate_unret");
2438 if (!rsec)
2439 return 0;
2440
2441 for_each_reloc(rsec, reloc) {
2442 if (reloc->sym->type != STT_SECTION) {
2443 WARN("unexpected relocation symbol type in %s", rsec->name);
2444 return -1;
2445 }
2446
2447 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2448 if (!insn) {
2449 WARN("bad .discard.instr_end entry");
2450 return -1;
2451 }
2452 insn->unret = 1;
2453 }
2454
2455 return 0;
2456}
2457
2458
2459static int read_intra_function_calls(struct objtool_file *file)
2460{
2461 struct instruction *insn;
2462 struct section *rsec;
2463 struct reloc *reloc;
2464
2465 rsec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2466 if (!rsec)
2467 return 0;
2468
2469 for_each_reloc(rsec, reloc) {
2470 unsigned long dest_off;
2471
2472 if (reloc->sym->type != STT_SECTION) {
2473 WARN("unexpected relocation symbol type in %s",
2474 rsec->name);
2475 return -1;
2476 }
2477
2478 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2479 if (!insn) {
2480 WARN("bad .discard.intra_function_call entry");
2481 return -1;
2482 }
2483
2484 if (insn->type != INSN_CALL) {
2485 WARN_INSN(insn, "intra_function_call not a direct call");
2486 return -1;
2487 }
2488
2489 /*
2490 * Treat intra-function CALLs as JMPs, but with a stack_op.
2491 * See add_call_destinations(), which strips stack_ops from
2492 * normal CALLs.
2493 */
2494 insn->type = INSN_JUMP_UNCONDITIONAL;
2495
2496 dest_off = arch_jump_destination(insn);
2497 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2498 if (!insn->jump_dest) {
2499 WARN_INSN(insn, "can't find call dest at %s+0x%lx",
2500 insn->sec->name, dest_off);
2501 return -1;
2502 }
2503 }
2504
2505 return 0;
2506}
2507
2508/*
2509 * Return true if name matches an instrumentation function, where calls to that
2510 * function from noinstr code can safely be removed, but compilers won't do so.
2511 */
2512static bool is_profiling_func(const char *name)
2513{
2514 /*
2515 * Many compilers cannot disable KCOV with a function attribute.
2516 */
2517 if (!strncmp(name, "__sanitizer_cov_", 16))
2518 return true;
2519
2520 /*
2521 * Some compilers currently do not remove __tsan_func_entry/exit nor
2522 * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2523 * the __no_sanitize_thread attribute, remove them. Once the kernel's
2524 * minimum Clang version is 14.0, this can be removed.
2525 */
2526 if (!strncmp(name, "__tsan_func_", 12) ||
2527 !strcmp(name, "__tsan_atomic_signal_fence"))
2528 return true;
2529
2530 return false;
2531}
2532
2533static int classify_symbols(struct objtool_file *file)
2534{
2535 struct symbol *func;
2536
2537 for_each_sym(file, func) {
2538 if (func->type == STT_NOTYPE && strstarts(func->name, ".L"))
2539 func->local_label = true;
2540
2541 if (func->bind != STB_GLOBAL)
2542 continue;
2543
2544 if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2545 strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2546 func->static_call_tramp = true;
2547
2548 if (arch_is_retpoline(func))
2549 func->retpoline_thunk = true;
2550
2551 if (arch_is_rethunk(func))
2552 func->return_thunk = true;
2553
2554 if (arch_is_embedded_insn(func))
2555 func->embedded_insn = true;
2556
2557 if (arch_ftrace_match(func->name))
2558 func->fentry = true;
2559
2560 if (is_profiling_func(func->name))
2561 func->profiling_func = true;
2562 }
2563
2564 return 0;
2565}
2566
2567static void mark_rodata(struct objtool_file *file)
2568{
2569 struct section *sec;
2570 bool found = false;
2571
2572 /*
2573 * Search for the following rodata sections, each of which can
2574 * potentially contain jump tables:
2575 *
2576 * - .rodata: can contain GCC switch tables
2577 * - .rodata.<func>: same, if -fdata-sections is being used
2578 * - .rodata..c_jump_table: contains C annotated jump tables
2579 *
2580 * .rodata.str1.* sections are ignored; they don't contain jump tables.
2581 */
2582 for_each_sec(file, sec) {
2583 if (!strncmp(sec->name, ".rodata", 7) &&
2584 !strstr(sec->name, ".str1.")) {
2585 sec->rodata = true;
2586 found = true;
2587 }
2588 }
2589
2590 file->rodata = found;
2591}
2592
2593static int decode_sections(struct objtool_file *file)
2594{
2595 int ret;
2596
2597 mark_rodata(file);
2598
2599 ret = init_pv_ops(file);
2600 if (ret)
2601 return ret;
2602
2603 /*
2604 * Must be before add_{jump_call}_destination.
2605 */
2606 ret = classify_symbols(file);
2607 if (ret)
2608 return ret;
2609
2610 ret = decode_instructions(file);
2611 if (ret)
2612 return ret;
2613
2614 add_ignores(file);
2615 add_uaccess_safe(file);
2616
2617 ret = add_ignore_alternatives(file);
2618 if (ret)
2619 return ret;
2620
2621 /*
2622 * Must be before read_unwind_hints() since that needs insn->noendbr.
2623 */
2624 ret = read_noendbr_hints(file);
2625 if (ret)
2626 return ret;
2627
2628 /*
2629 * Must be before add_jump_destinations(), which depends on 'func'
2630 * being set for alternatives, to enable proper sibling call detection.
2631 */
2632 if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) {
2633 ret = add_special_section_alts(file);
2634 if (ret)
2635 return ret;
2636 }
2637
2638 ret = add_jump_destinations(file);
2639 if (ret)
2640 return ret;
2641
2642 /*
2643 * Must be before add_call_destination(); it changes INSN_CALL to
2644 * INSN_JUMP.
2645 */
2646 ret = read_intra_function_calls(file);
2647 if (ret)
2648 return ret;
2649
2650 ret = add_call_destinations(file);
2651 if (ret)
2652 return ret;
2653
2654 /*
2655 * Must be after add_call_destinations() such that it can override
2656 * dead_end_function() marks.
2657 */
2658 ret = add_dead_ends(file);
2659 if (ret)
2660 return ret;
2661
2662 ret = add_jump_table_alts(file);
2663 if (ret)
2664 return ret;
2665
2666 ret = read_unwind_hints(file);
2667 if (ret)
2668 return ret;
2669
2670 ret = read_retpoline_hints(file);
2671 if (ret)
2672 return ret;
2673
2674 ret = read_instr_hints(file);
2675 if (ret)
2676 return ret;
2677
2678 ret = read_validate_unret_hints(file);
2679 if (ret)
2680 return ret;
2681
2682 return 0;
2683}
2684
2685static bool is_special_call(struct instruction *insn)
2686{
2687 if (insn->type == INSN_CALL) {
2688 struct symbol *dest = insn_call_dest(insn);
2689
2690 if (!dest)
2691 return false;
2692
2693 if (dest->fentry || dest->embedded_insn)
2694 return true;
2695 }
2696
2697 return false;
2698}
2699
2700static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2701{
2702 struct cfi_state *cfi = &state->cfi;
2703 int i;
2704
2705 if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2706 return true;
2707
2708 if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2709 return true;
2710
2711 if (cfi->stack_size != initial_func_cfi.cfa.offset)
2712 return true;
2713
2714 for (i = 0; i < CFI_NUM_REGS; i++) {
2715 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2716 cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2717 return true;
2718 }
2719
2720 return false;
2721}
2722
2723static bool check_reg_frame_pos(const struct cfi_reg *reg,
2724 int expected_offset)
2725{
2726 return reg->base == CFI_CFA &&
2727 reg->offset == expected_offset;
2728}
2729
2730static bool has_valid_stack_frame(struct insn_state *state)
2731{
2732 struct cfi_state *cfi = &state->cfi;
2733
2734 if (cfi->cfa.base == CFI_BP &&
2735 check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2736 check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2737 return true;
2738
2739 if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2740 return true;
2741
2742 return false;
2743}
2744
2745static int update_cfi_state_regs(struct instruction *insn,
2746 struct cfi_state *cfi,
2747 struct stack_op *op)
2748{
2749 struct cfi_reg *cfa = &cfi->cfa;
2750
2751 if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2752 return 0;
2753
2754 /* push */
2755 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2756 cfa->offset += 8;
2757
2758 /* pop */
2759 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2760 cfa->offset -= 8;
2761
2762 /* add immediate to sp */
2763 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2764 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2765 cfa->offset -= op->src.offset;
2766
2767 return 0;
2768}
2769
2770static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2771{
2772 if (arch_callee_saved_reg(reg) &&
2773 cfi->regs[reg].base == CFI_UNDEFINED) {
2774 cfi->regs[reg].base = base;
2775 cfi->regs[reg].offset = offset;
2776 }
2777}
2778
2779static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2780{
2781 cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2782 cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2783}
2784
2785/*
2786 * A note about DRAP stack alignment:
2787 *
2788 * GCC has the concept of a DRAP register, which is used to help keep track of
2789 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
2790 * register. The typical DRAP pattern is:
2791 *
2792 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
2793 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
2794 * 41 ff 72 f8 pushq -0x8(%r10)
2795 * 55 push %rbp
2796 * 48 89 e5 mov %rsp,%rbp
2797 * (more pushes)
2798 * 41 52 push %r10
2799 * ...
2800 * 41 5a pop %r10
2801 * (more pops)
2802 * 5d pop %rbp
2803 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2804 * c3 retq
2805 *
2806 * There are some variations in the epilogues, like:
2807 *
2808 * 5b pop %rbx
2809 * 41 5a pop %r10
2810 * 41 5c pop %r12
2811 * 41 5d pop %r13
2812 * 41 5e pop %r14
2813 * c9 leaveq
2814 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2815 * c3 retq
2816 *
2817 * and:
2818 *
2819 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
2820 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
2821 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
2822 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
2823 * c9 leaveq
2824 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2825 * c3 retq
2826 *
2827 * Sometimes r13 is used as the DRAP register, in which case it's saved and
2828 * restored beforehand:
2829 *
2830 * 41 55 push %r13
2831 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
2832 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
2833 * ...
2834 * 49 8d 65 f0 lea -0x10(%r13),%rsp
2835 * 41 5d pop %r13
2836 * c3 retq
2837 */
2838static int update_cfi_state(struct instruction *insn,
2839 struct instruction *next_insn,
2840 struct cfi_state *cfi, struct stack_op *op)
2841{
2842 struct cfi_reg *cfa = &cfi->cfa;
2843 struct cfi_reg *regs = cfi->regs;
2844
2845 /* ignore UNWIND_HINT_UNDEFINED regions */
2846 if (cfi->force_undefined)
2847 return 0;
2848
2849 /* stack operations don't make sense with an undefined CFA */
2850 if (cfa->base == CFI_UNDEFINED) {
2851 if (insn_func(insn)) {
2852 WARN_INSN(insn, "undefined stack state");
2853 return -1;
2854 }
2855 return 0;
2856 }
2857
2858 if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2859 cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2860 return update_cfi_state_regs(insn, cfi, op);
2861
2862 switch (op->dest.type) {
2863
2864 case OP_DEST_REG:
2865 switch (op->src.type) {
2866
2867 case OP_SRC_REG:
2868 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2869 cfa->base == CFI_SP &&
2870 check_reg_frame_pos(®s[CFI_BP], -cfa->offset)) {
2871
2872 /* mov %rsp, %rbp */
2873 cfa->base = op->dest.reg;
2874 cfi->bp_scratch = false;
2875 }
2876
2877 else if (op->src.reg == CFI_SP &&
2878 op->dest.reg == CFI_BP && cfi->drap) {
2879
2880 /* drap: mov %rsp, %rbp */
2881 regs[CFI_BP].base = CFI_BP;
2882 regs[CFI_BP].offset = -cfi->stack_size;
2883 cfi->bp_scratch = false;
2884 }
2885
2886 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2887
2888 /*
2889 * mov %rsp, %reg
2890 *
2891 * This is needed for the rare case where GCC
2892 * does:
2893 *
2894 * mov %rsp, %rax
2895 * ...
2896 * mov %rax, %rsp
2897 */
2898 cfi->vals[op->dest.reg].base = CFI_CFA;
2899 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2900 }
2901
2902 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2903 (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2904
2905 /*
2906 * mov %rbp, %rsp
2907 *
2908 * Restore the original stack pointer (Clang).
2909 */
2910 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2911 }
2912
2913 else if (op->dest.reg == cfa->base) {
2914
2915 /* mov %reg, %rsp */
2916 if (cfa->base == CFI_SP &&
2917 cfi->vals[op->src.reg].base == CFI_CFA) {
2918
2919 /*
2920 * This is needed for the rare case
2921 * where GCC does something dumb like:
2922 *
2923 * lea 0x8(%rsp), %rcx
2924 * ...
2925 * mov %rcx, %rsp
2926 */
2927 cfa->offset = -cfi->vals[op->src.reg].offset;
2928 cfi->stack_size = cfa->offset;
2929
2930 } else if (cfa->base == CFI_SP &&
2931 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2932 cfi->vals[op->src.reg].offset == cfa->offset) {
2933
2934 /*
2935 * Stack swizzle:
2936 *
2937 * 1: mov %rsp, (%[tos])
2938 * 2: mov %[tos], %rsp
2939 * ...
2940 * 3: pop %rsp
2941 *
2942 * Where:
2943 *
2944 * 1 - places a pointer to the previous
2945 * stack at the Top-of-Stack of the
2946 * new stack.
2947 *
2948 * 2 - switches to the new stack.
2949 *
2950 * 3 - pops the Top-of-Stack to restore
2951 * the original stack.
2952 *
2953 * Note: we set base to SP_INDIRECT
2954 * here and preserve offset. Therefore
2955 * when the unwinder reaches ToS it
2956 * will dereference SP and then add the
2957 * offset to find the next frame, IOW:
2958 * (%rsp) + offset.
2959 */
2960 cfa->base = CFI_SP_INDIRECT;
2961
2962 } else {
2963 cfa->base = CFI_UNDEFINED;
2964 cfa->offset = 0;
2965 }
2966 }
2967
2968 else if (op->dest.reg == CFI_SP &&
2969 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2970 cfi->vals[op->src.reg].offset == cfa->offset) {
2971
2972 /*
2973 * The same stack swizzle case 2) as above. But
2974 * because we can't change cfa->base, case 3)
2975 * will become a regular POP. Pretend we're a
2976 * PUSH so things don't go unbalanced.
2977 */
2978 cfi->stack_size += 8;
2979 }
2980
2981
2982 break;
2983
2984 case OP_SRC_ADD:
2985 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2986
2987 /* add imm, %rsp */
2988 cfi->stack_size -= op->src.offset;
2989 if (cfa->base == CFI_SP)
2990 cfa->offset -= op->src.offset;
2991 break;
2992 }
2993
2994 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2995
2996 /* lea disp(%rbp), %rsp */
2997 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2998 break;
2999 }
3000
3001 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
3002
3003 /* drap: lea disp(%rsp), %drap */
3004 cfi->drap_reg = op->dest.reg;
3005
3006 /*
3007 * lea disp(%rsp), %reg
3008 *
3009 * This is needed for the rare case where GCC
3010 * does something dumb like:
3011 *
3012 * lea 0x8(%rsp), %rcx
3013 * ...
3014 * mov %rcx, %rsp
3015 */
3016 cfi->vals[op->dest.reg].base = CFI_CFA;
3017 cfi->vals[op->dest.reg].offset = \
3018 -cfi->stack_size + op->src.offset;
3019
3020 break;
3021 }
3022
3023 if (cfi->drap && op->dest.reg == CFI_SP &&
3024 op->src.reg == cfi->drap_reg) {
3025
3026 /* drap: lea disp(%drap), %rsp */
3027 cfa->base = CFI_SP;
3028 cfa->offset = cfi->stack_size = -op->src.offset;
3029 cfi->drap_reg = CFI_UNDEFINED;
3030 cfi->drap = false;
3031 break;
3032 }
3033
3034 if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
3035 WARN_INSN(insn, "unsupported stack register modification");
3036 return -1;
3037 }
3038
3039 break;
3040
3041 case OP_SRC_AND:
3042 if (op->dest.reg != CFI_SP ||
3043 (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
3044 (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
3045 WARN_INSN(insn, "unsupported stack pointer realignment");
3046 return -1;
3047 }
3048
3049 if (cfi->drap_reg != CFI_UNDEFINED) {
3050 /* drap: and imm, %rsp */
3051 cfa->base = cfi->drap_reg;
3052 cfa->offset = cfi->stack_size = 0;
3053 cfi->drap = true;
3054 }
3055
3056 /*
3057 * Older versions of GCC (4.8ish) realign the stack
3058 * without DRAP, with a frame pointer.
3059 */
3060
3061 break;
3062
3063 case OP_SRC_POP:
3064 case OP_SRC_POPF:
3065 if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
3066
3067 /* pop %rsp; # restore from a stack swizzle */
3068 cfa->base = CFI_SP;
3069 break;
3070 }
3071
3072 if (!cfi->drap && op->dest.reg == cfa->base) {
3073
3074 /* pop %rbp */
3075 cfa->base = CFI_SP;
3076 }
3077
3078 if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
3079 op->dest.reg == cfi->drap_reg &&
3080 cfi->drap_offset == -cfi->stack_size) {
3081
3082 /* drap: pop %drap */
3083 cfa->base = cfi->drap_reg;
3084 cfa->offset = 0;
3085 cfi->drap_offset = -1;
3086
3087 } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
3088
3089 /* pop %reg */
3090 restore_reg(cfi, op->dest.reg);
3091 }
3092
3093 cfi->stack_size -= 8;
3094 if (cfa->base == CFI_SP)
3095 cfa->offset -= 8;
3096
3097 break;
3098
3099 case OP_SRC_REG_INDIRECT:
3100 if (!cfi->drap && op->dest.reg == cfa->base &&
3101 op->dest.reg == CFI_BP) {
3102
3103 /* mov disp(%rsp), %rbp */
3104 cfa->base = CFI_SP;
3105 cfa->offset = cfi->stack_size;
3106 }
3107
3108 if (cfi->drap && op->src.reg == CFI_BP &&
3109 op->src.offset == cfi->drap_offset) {
3110
3111 /* drap: mov disp(%rbp), %drap */
3112 cfa->base = cfi->drap_reg;
3113 cfa->offset = 0;
3114 cfi->drap_offset = -1;
3115 }
3116
3117 if (cfi->drap && op->src.reg == CFI_BP &&
3118 op->src.offset == regs[op->dest.reg].offset) {
3119
3120 /* drap: mov disp(%rbp), %reg */
3121 restore_reg(cfi, op->dest.reg);
3122
3123 } else if (op->src.reg == cfa->base &&
3124 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
3125
3126 /* mov disp(%rbp), %reg */
3127 /* mov disp(%rsp), %reg */
3128 restore_reg(cfi, op->dest.reg);
3129
3130 } else if (op->src.reg == CFI_SP &&
3131 op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
3132
3133 /* mov disp(%rsp), %reg */
3134 restore_reg(cfi, op->dest.reg);
3135 }
3136
3137 break;
3138
3139 default:
3140 WARN_INSN(insn, "unknown stack-related instruction");
3141 return -1;
3142 }
3143
3144 break;
3145
3146 case OP_DEST_PUSH:
3147 case OP_DEST_PUSHF:
3148 cfi->stack_size += 8;
3149 if (cfa->base == CFI_SP)
3150 cfa->offset += 8;
3151
3152 if (op->src.type != OP_SRC_REG)
3153 break;
3154
3155 if (cfi->drap) {
3156 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3157
3158 /* drap: push %drap */
3159 cfa->base = CFI_BP_INDIRECT;
3160 cfa->offset = -cfi->stack_size;
3161
3162 /* save drap so we know when to restore it */
3163 cfi->drap_offset = -cfi->stack_size;
3164
3165 } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
3166
3167 /* drap: push %rbp */
3168 cfi->stack_size = 0;
3169
3170 } else {
3171
3172 /* drap: push %reg */
3173 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
3174 }
3175
3176 } else {
3177
3178 /* push %reg */
3179 save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
3180 }
3181
3182 /* detect when asm code uses rbp as a scratch register */
3183 if (opts.stackval && insn_func(insn) && op->src.reg == CFI_BP &&
3184 cfa->base != CFI_BP)
3185 cfi->bp_scratch = true;
3186 break;
3187
3188 case OP_DEST_REG_INDIRECT:
3189
3190 if (cfi->drap) {
3191 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3192
3193 /* drap: mov %drap, disp(%rbp) */
3194 cfa->base = CFI_BP_INDIRECT;
3195 cfa->offset = op->dest.offset;
3196
3197 /* save drap offset so we know when to restore it */
3198 cfi->drap_offset = op->dest.offset;
3199 } else {
3200
3201 /* drap: mov reg, disp(%rbp) */
3202 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
3203 }
3204
3205 } else if (op->dest.reg == cfa->base) {
3206
3207 /* mov reg, disp(%rbp) */
3208 /* mov reg, disp(%rsp) */
3209 save_reg(cfi, op->src.reg, CFI_CFA,
3210 op->dest.offset - cfi->cfa.offset);
3211
3212 } else if (op->dest.reg == CFI_SP) {
3213
3214 /* mov reg, disp(%rsp) */
3215 save_reg(cfi, op->src.reg, CFI_CFA,
3216 op->dest.offset - cfi->stack_size);
3217
3218 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
3219
3220 /* mov %rsp, (%reg); # setup a stack swizzle. */
3221 cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
3222 cfi->vals[op->dest.reg].offset = cfa->offset;
3223 }
3224
3225 break;
3226
3227 case OP_DEST_MEM:
3228 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
3229 WARN_INSN(insn, "unknown stack-related memory operation");
3230 return -1;
3231 }
3232
3233 /* pop mem */
3234 cfi->stack_size -= 8;
3235 if (cfa->base == CFI_SP)
3236 cfa->offset -= 8;
3237
3238 break;
3239
3240 default:
3241 WARN_INSN(insn, "unknown stack-related instruction");
3242 return -1;
3243 }
3244
3245 return 0;
3246}
3247
3248/*
3249 * The stack layouts of alternatives instructions can sometimes diverge when
3250 * they have stack modifications. That's fine as long as the potential stack
3251 * layouts don't conflict at any given potential instruction boundary.
3252 *
3253 * Flatten the CFIs of the different alternative code streams (both original
3254 * and replacement) into a single shared CFI array which can be used to detect
3255 * conflicts and nicely feed a linear array of ORC entries to the unwinder.
3256 */
3257static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
3258{
3259 struct cfi_state **alt_cfi;
3260 int group_off;
3261
3262 if (!insn->alt_group)
3263 return 0;
3264
3265 if (!insn->cfi) {
3266 WARN("CFI missing");
3267 return -1;
3268 }
3269
3270 alt_cfi = insn->alt_group->cfi;
3271 group_off = insn->offset - insn->alt_group->first_insn->offset;
3272
3273 if (!alt_cfi[group_off]) {
3274 alt_cfi[group_off] = insn->cfi;
3275 } else {
3276 if (cficmp(alt_cfi[group_off], insn->cfi)) {
3277 struct alt_group *orig_group = insn->alt_group->orig_group ?: insn->alt_group;
3278 struct instruction *orig = orig_group->first_insn;
3279 char *where = offstr(insn->sec, insn->offset);
3280 WARN_INSN(orig, "stack layout conflict in alternatives: %s", where);
3281 free(where);
3282 return -1;
3283 }
3284 }
3285
3286 return 0;
3287}
3288
3289static int handle_insn_ops(struct instruction *insn,
3290 struct instruction *next_insn,
3291 struct insn_state *state)
3292{
3293 struct stack_op *op;
3294
3295 for (op = insn->stack_ops; op; op = op->next) {
3296
3297 if (update_cfi_state(insn, next_insn, &state->cfi, op))
3298 return 1;
3299
3300 if (!insn->alt_group)
3301 continue;
3302
3303 if (op->dest.type == OP_DEST_PUSHF) {
3304 if (!state->uaccess_stack) {
3305 state->uaccess_stack = 1;
3306 } else if (state->uaccess_stack >> 31) {
3307 WARN_INSN(insn, "PUSHF stack exhausted");
3308 return 1;
3309 }
3310 state->uaccess_stack <<= 1;
3311 state->uaccess_stack |= state->uaccess;
3312 }
3313
3314 if (op->src.type == OP_SRC_POPF) {
3315 if (state->uaccess_stack) {
3316 state->uaccess = state->uaccess_stack & 1;
3317 state->uaccess_stack >>= 1;
3318 if (state->uaccess_stack == 1)
3319 state->uaccess_stack = 0;
3320 }
3321 }
3322 }
3323
3324 return 0;
3325}
3326
3327static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
3328{
3329 struct cfi_state *cfi1 = insn->cfi;
3330 int i;
3331
3332 if (!cfi1) {
3333 WARN("CFI missing");
3334 return false;
3335 }
3336
3337 if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
3338
3339 WARN_INSN(insn, "stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
3340 cfi1->cfa.base, cfi1->cfa.offset,
3341 cfi2->cfa.base, cfi2->cfa.offset);
3342
3343 } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
3344 for (i = 0; i < CFI_NUM_REGS; i++) {
3345 if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
3346 sizeof(struct cfi_reg)))
3347 continue;
3348
3349 WARN_INSN(insn, "stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
3350 i, cfi1->regs[i].base, cfi1->regs[i].offset,
3351 i, cfi2->regs[i].base, cfi2->regs[i].offset);
3352 break;
3353 }
3354
3355 } else if (cfi1->type != cfi2->type) {
3356
3357 WARN_INSN(insn, "stack state mismatch: type1=%d type2=%d",
3358 cfi1->type, cfi2->type);
3359
3360 } else if (cfi1->drap != cfi2->drap ||
3361 (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
3362 (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
3363
3364 WARN_INSN(insn, "stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
3365 cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
3366 cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
3367
3368 } else
3369 return true;
3370
3371 return false;
3372}
3373
3374static inline bool func_uaccess_safe(struct symbol *func)
3375{
3376 if (func)
3377 return func->uaccess_safe;
3378
3379 return false;
3380}
3381
3382static inline const char *call_dest_name(struct instruction *insn)
3383{
3384 static char pvname[19];
3385 struct reloc *reloc;
3386 int idx;
3387
3388 if (insn_call_dest(insn))
3389 return insn_call_dest(insn)->name;
3390
3391 reloc = insn_reloc(NULL, insn);
3392 if (reloc && !strcmp(reloc->sym->name, "pv_ops")) {
3393 idx = (reloc_addend(reloc) / sizeof(void *));
3394 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
3395 return pvname;
3396 }
3397
3398 return "{dynamic}";
3399}
3400
3401static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3402{
3403 struct symbol *target;
3404 struct reloc *reloc;
3405 int idx;
3406
3407 reloc = insn_reloc(file, insn);
3408 if (!reloc || strcmp(reloc->sym->name, "pv_ops"))
3409 return false;
3410
3411 idx = (arch_dest_reloc_offset(reloc_addend(reloc)) / sizeof(void *));
3412
3413 if (file->pv_ops[idx].clean)
3414 return true;
3415
3416 file->pv_ops[idx].clean = true;
3417
3418 list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3419 if (!target->sec->noinstr) {
3420 WARN("pv_ops[%d]: %s", idx, target->name);
3421 file->pv_ops[idx].clean = false;
3422 }
3423 }
3424
3425 return file->pv_ops[idx].clean;
3426}
3427
3428static inline bool noinstr_call_dest(struct objtool_file *file,
3429 struct instruction *insn,
3430 struct symbol *func)
3431{
3432 /*
3433 * We can't deal with indirect function calls at present;
3434 * assume they're instrumented.
3435 */
3436 if (!func) {
3437 if (file->pv_ops)
3438 return pv_call_dest(file, insn);
3439
3440 return false;
3441 }
3442
3443 /*
3444 * If the symbol is from a noinstr section; we good.
3445 */
3446 if (func->sec->noinstr)
3447 return true;
3448
3449 /*
3450 * If the symbol is a static_call trampoline, we can't tell.
3451 */
3452 if (func->static_call_tramp)
3453 return true;
3454
3455 /*
3456 * The __ubsan_handle_*() calls are like WARN(), they only happen when
3457 * something 'BAD' happened. At the risk of taking the machine down,
3458 * let them proceed to get the message out.
3459 */
3460 if (!strncmp(func->name, "__ubsan_handle_", 15))
3461 return true;
3462
3463 return false;
3464}
3465
3466static int validate_call(struct objtool_file *file,
3467 struct instruction *insn,
3468 struct insn_state *state)
3469{
3470 if (state->noinstr && state->instr <= 0 &&
3471 !noinstr_call_dest(file, insn, insn_call_dest(insn))) {
3472 WARN_INSN(insn, "call to %s() leaves .noinstr.text section", call_dest_name(insn));
3473 return 1;
3474 }
3475
3476 if (state->uaccess && !func_uaccess_safe(insn_call_dest(insn))) {
3477 WARN_INSN(insn, "call to %s() with UACCESS enabled", call_dest_name(insn));
3478 return 1;
3479 }
3480
3481 if (state->df) {
3482 WARN_INSN(insn, "call to %s() with DF set", call_dest_name(insn));
3483 return 1;
3484 }
3485
3486 return 0;
3487}
3488
3489static int validate_sibling_call(struct objtool_file *file,
3490 struct instruction *insn,
3491 struct insn_state *state)
3492{
3493 if (insn_func(insn) && has_modified_stack_frame(insn, state)) {
3494 WARN_INSN(insn, "sibling call from callable instruction with modified stack frame");
3495 return 1;
3496 }
3497
3498 return validate_call(file, insn, state);
3499}
3500
3501static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3502{
3503 if (state->noinstr && state->instr > 0) {
3504 WARN_INSN(insn, "return with instrumentation enabled");
3505 return 1;
3506 }
3507
3508 if (state->uaccess && !func_uaccess_safe(func)) {
3509 WARN_INSN(insn, "return with UACCESS enabled");
3510 return 1;
3511 }
3512
3513 if (!state->uaccess && func_uaccess_safe(func)) {
3514 WARN_INSN(insn, "return with UACCESS disabled from a UACCESS-safe function");
3515 return 1;
3516 }
3517
3518 if (state->df) {
3519 WARN_INSN(insn, "return with DF set");
3520 return 1;
3521 }
3522
3523 if (func && has_modified_stack_frame(insn, state)) {
3524 WARN_INSN(insn, "return with modified stack frame");
3525 return 1;
3526 }
3527
3528 if (state->cfi.bp_scratch) {
3529 WARN_INSN(insn, "BP used as a scratch register");
3530 return 1;
3531 }
3532
3533 return 0;
3534}
3535
3536static struct instruction *next_insn_to_validate(struct objtool_file *file,
3537 struct instruction *insn)
3538{
3539 struct alt_group *alt_group = insn->alt_group;
3540
3541 /*
3542 * Simulate the fact that alternatives are patched in-place. When the
3543 * end of a replacement alt_group is reached, redirect objtool flow to
3544 * the end of the original alt_group.
3545 *
3546 * insn->alts->insn -> alt_group->first_insn
3547 * ...
3548 * alt_group->last_insn
3549 * [alt_group->nop] -> next(orig_group->last_insn)
3550 */
3551 if (alt_group) {
3552 if (alt_group->nop) {
3553 /* ->nop implies ->orig_group */
3554 if (insn == alt_group->last_insn)
3555 return alt_group->nop;
3556 if (insn == alt_group->nop)
3557 goto next_orig;
3558 }
3559 if (insn == alt_group->last_insn && alt_group->orig_group)
3560 goto next_orig;
3561 }
3562
3563 return next_insn_same_sec(file, insn);
3564
3565next_orig:
3566 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3567}
3568
3569/*
3570 * Follow the branch starting at the given instruction, and recursively follow
3571 * any other branches (jumps). Meanwhile, track the frame pointer state at
3572 * each instruction and validate all the rules described in
3573 * tools/objtool/Documentation/objtool.txt.
3574 */
3575static int validate_branch(struct objtool_file *file, struct symbol *func,
3576 struct instruction *insn, struct insn_state state)
3577{
3578 struct alternative *alt;
3579 struct instruction *next_insn, *prev_insn = NULL;
3580 struct section *sec;
3581 u8 visited;
3582 int ret;
3583
3584 sec = insn->sec;
3585
3586 while (1) {
3587 next_insn = next_insn_to_validate(file, insn);
3588
3589 if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {
3590 /* Ignore KCFI type preambles, which always fall through */
3591 if (!strncmp(func->name, "__cfi_", 6) ||
3592 !strncmp(func->name, "__pfx_", 6))
3593 return 0;
3594
3595 WARN("%s() falls through to next function %s()",
3596 func->name, insn_func(insn)->name);
3597 return 1;
3598 }
3599
3600 if (func && insn->ignore) {
3601 WARN_INSN(insn, "BUG: why am I validating an ignored function?");
3602 return 1;
3603 }
3604
3605 visited = VISITED_BRANCH << state.uaccess;
3606 if (insn->visited & VISITED_BRANCH_MASK) {
3607 if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3608 return 1;
3609
3610 if (insn->visited & visited)
3611 return 0;
3612 } else {
3613 nr_insns_visited++;
3614 }
3615
3616 if (state.noinstr)
3617 state.instr += insn->instr;
3618
3619 if (insn->hint) {
3620 if (insn->restore) {
3621 struct instruction *save_insn, *i;
3622
3623 i = insn;
3624 save_insn = NULL;
3625
3626 sym_for_each_insn_continue_reverse(file, func, i) {
3627 if (i->save) {
3628 save_insn = i;
3629 break;
3630 }
3631 }
3632
3633 if (!save_insn) {
3634 WARN_INSN(insn, "no corresponding CFI save for CFI restore");
3635 return 1;
3636 }
3637
3638 if (!save_insn->visited) {
3639 /*
3640 * If the restore hint insn is at the
3641 * beginning of a basic block and was
3642 * branched to from elsewhere, and the
3643 * save insn hasn't been visited yet,
3644 * defer following this branch for now.
3645 * It will be seen later via the
3646 * straight-line path.
3647 */
3648 if (!prev_insn)
3649 return 0;
3650
3651 WARN_INSN(insn, "objtool isn't smart enough to handle this CFI save/restore combo");
3652 return 1;
3653 }
3654
3655 insn->cfi = save_insn->cfi;
3656 nr_cfi_reused++;
3657 }
3658
3659 state.cfi = *insn->cfi;
3660 } else {
3661 /* XXX track if we actually changed state.cfi */
3662
3663 if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3664 insn->cfi = prev_insn->cfi;
3665 nr_cfi_reused++;
3666 } else {
3667 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3668 }
3669 }
3670
3671 insn->visited |= visited;
3672
3673 if (propagate_alt_cfi(file, insn))
3674 return 1;
3675
3676 if (!insn->ignore_alts && insn->alts) {
3677 bool skip_orig = false;
3678
3679 for (alt = insn->alts; alt; alt = alt->next) {
3680 if (alt->skip_orig)
3681 skip_orig = true;
3682
3683 ret = validate_branch(file, func, alt->insn, state);
3684 if (ret) {
3685 BT_INSN(insn, "(alt)");
3686 return ret;
3687 }
3688 }
3689
3690 if (skip_orig)
3691 return 0;
3692 }
3693
3694 if (handle_insn_ops(insn, next_insn, &state))
3695 return 1;
3696
3697 switch (insn->type) {
3698
3699 case INSN_RETURN:
3700 return validate_return(func, insn, &state);
3701
3702 case INSN_CALL:
3703 case INSN_CALL_DYNAMIC:
3704 ret = validate_call(file, insn, &state);
3705 if (ret)
3706 return ret;
3707
3708 if (opts.stackval && func && !is_special_call(insn) &&
3709 !has_valid_stack_frame(&state)) {
3710 WARN_INSN(insn, "call without frame pointer save/setup");
3711 return 1;
3712 }
3713
3714 if (insn->dead_end)
3715 return 0;
3716
3717 break;
3718
3719 case INSN_JUMP_CONDITIONAL:
3720 case INSN_JUMP_UNCONDITIONAL:
3721 if (is_sibling_call(insn)) {
3722 ret = validate_sibling_call(file, insn, &state);
3723 if (ret)
3724 return ret;
3725
3726 } else if (insn->jump_dest) {
3727 ret = validate_branch(file, func,
3728 insn->jump_dest, state);
3729 if (ret) {
3730 BT_INSN(insn, "(branch)");
3731 return ret;
3732 }
3733 }
3734
3735 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3736 return 0;
3737
3738 break;
3739
3740 case INSN_JUMP_DYNAMIC:
3741 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3742 if (is_sibling_call(insn)) {
3743 ret = validate_sibling_call(file, insn, &state);
3744 if (ret)
3745 return ret;
3746 }
3747
3748 if (insn->type == INSN_JUMP_DYNAMIC)
3749 return 0;
3750
3751 break;
3752
3753 case INSN_CONTEXT_SWITCH:
3754 if (func && (!next_insn || !next_insn->hint)) {
3755 WARN_INSN(insn, "unsupported instruction in callable function");
3756 return 1;
3757 }
3758 return 0;
3759
3760 case INSN_STAC:
3761 if (state.uaccess) {
3762 WARN_INSN(insn, "recursive UACCESS enable");
3763 return 1;
3764 }
3765
3766 state.uaccess = true;
3767 break;
3768
3769 case INSN_CLAC:
3770 if (!state.uaccess && func) {
3771 WARN_INSN(insn, "redundant UACCESS disable");
3772 return 1;
3773 }
3774
3775 if (func_uaccess_safe(func) && !state.uaccess_stack) {
3776 WARN_INSN(insn, "UACCESS-safe disables UACCESS");
3777 return 1;
3778 }
3779
3780 state.uaccess = false;
3781 break;
3782
3783 case INSN_STD:
3784 if (state.df) {
3785 WARN_INSN(insn, "recursive STD");
3786 return 1;
3787 }
3788
3789 state.df = true;
3790 break;
3791
3792 case INSN_CLD:
3793 if (!state.df && func) {
3794 WARN_INSN(insn, "redundant CLD");
3795 return 1;
3796 }
3797
3798 state.df = false;
3799 break;
3800
3801 default:
3802 break;
3803 }
3804
3805 if (insn->dead_end)
3806 return 0;
3807
3808 if (!next_insn) {
3809 if (state.cfi.cfa.base == CFI_UNDEFINED)
3810 return 0;
3811 WARN("%s: unexpected end of section", sec->name);
3812 return 1;
3813 }
3814
3815 prev_insn = insn;
3816 insn = next_insn;
3817 }
3818
3819 return 0;
3820}
3821
3822static int validate_unwind_hint(struct objtool_file *file,
3823 struct instruction *insn,
3824 struct insn_state *state)
3825{
3826 if (insn->hint && !insn->visited && !insn->ignore) {
3827 int ret = validate_branch(file, insn_func(insn), insn, *state);
3828 if (ret)
3829 BT_INSN(insn, "<=== (hint)");
3830 return ret;
3831 }
3832
3833 return 0;
3834}
3835
3836static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3837{
3838 struct instruction *insn;
3839 struct insn_state state;
3840 int warnings = 0;
3841
3842 if (!file->hints)
3843 return 0;
3844
3845 init_insn_state(file, &state, sec);
3846
3847 if (sec) {
3848 sec_for_each_insn(file, sec, insn)
3849 warnings += validate_unwind_hint(file, insn, &state);
3850 } else {
3851 for_each_insn(file, insn)
3852 warnings += validate_unwind_hint(file, insn, &state);
3853 }
3854
3855 return warnings;
3856}
3857
3858/*
3859 * Validate rethunk entry constraint: must untrain RET before the first RET.
3860 *
3861 * Follow every branch (intra-function) and ensure VALIDATE_UNRET_END comes
3862 * before an actual RET instruction.
3863 */
3864static int validate_unret(struct objtool_file *file, struct instruction *insn)
3865{
3866 struct instruction *next, *dest;
3867 int ret;
3868
3869 for (;;) {
3870 next = next_insn_to_validate(file, insn);
3871
3872 if (insn->visited & VISITED_UNRET)
3873 return 0;
3874
3875 insn->visited |= VISITED_UNRET;
3876
3877 if (!insn->ignore_alts && insn->alts) {
3878 struct alternative *alt;
3879 bool skip_orig = false;
3880
3881 for (alt = insn->alts; alt; alt = alt->next) {
3882 if (alt->skip_orig)
3883 skip_orig = true;
3884
3885 ret = validate_unret(file, alt->insn);
3886 if (ret) {
3887 BT_INSN(insn, "(alt)");
3888 return ret;
3889 }
3890 }
3891
3892 if (skip_orig)
3893 return 0;
3894 }
3895
3896 switch (insn->type) {
3897
3898 case INSN_CALL_DYNAMIC:
3899 case INSN_JUMP_DYNAMIC:
3900 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3901 WARN_INSN(insn, "early indirect call");
3902 return 1;
3903
3904 case INSN_JUMP_UNCONDITIONAL:
3905 case INSN_JUMP_CONDITIONAL:
3906 if (!is_sibling_call(insn)) {
3907 if (!insn->jump_dest) {
3908 WARN_INSN(insn, "unresolved jump target after linking?!?");
3909 return -1;
3910 }
3911 ret = validate_unret(file, insn->jump_dest);
3912 if (ret) {
3913 BT_INSN(insn, "(branch%s)",
3914 insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : "");
3915 return ret;
3916 }
3917
3918 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3919 return 0;
3920
3921 break;
3922 }
3923
3924 /* fallthrough */
3925 case INSN_CALL:
3926 dest = find_insn(file, insn_call_dest(insn)->sec,
3927 insn_call_dest(insn)->offset);
3928 if (!dest) {
3929 WARN("Unresolved function after linking!?: %s",
3930 insn_call_dest(insn)->name);
3931 return -1;
3932 }
3933
3934 ret = validate_unret(file, dest);
3935 if (ret) {
3936 BT_INSN(insn, "(call)");
3937 return ret;
3938 }
3939 /*
3940 * If a call returns without error, it must have seen UNTRAIN_RET.
3941 * Therefore any non-error return is a success.
3942 */
3943 return 0;
3944
3945 case INSN_RETURN:
3946 WARN_INSN(insn, "RET before UNTRAIN");
3947 return 1;
3948
3949 case INSN_NOP:
3950 if (insn->retpoline_safe)
3951 return 0;
3952 break;
3953
3954 default:
3955 break;
3956 }
3957
3958 if (!next) {
3959 WARN_INSN(insn, "teh end!");
3960 return -1;
3961 }
3962 insn = next;
3963 }
3964
3965 return 0;
3966}
3967
3968/*
3969 * Validate that all branches starting at VALIDATE_UNRET_BEGIN encounter
3970 * VALIDATE_UNRET_END before RET.
3971 */
3972static int validate_unrets(struct objtool_file *file)
3973{
3974 struct instruction *insn;
3975 int ret, warnings = 0;
3976
3977 for_each_insn(file, insn) {
3978 if (!insn->unret)
3979 continue;
3980
3981 ret = validate_unret(file, insn);
3982 if (ret < 0) {
3983 WARN_INSN(insn, "Failed UNRET validation");
3984 return ret;
3985 }
3986 warnings += ret;
3987 }
3988
3989 return warnings;
3990}
3991
3992static int validate_retpoline(struct objtool_file *file)
3993{
3994 struct instruction *insn;
3995 int warnings = 0;
3996
3997 for_each_insn(file, insn) {
3998 if (insn->type != INSN_JUMP_DYNAMIC &&
3999 insn->type != INSN_CALL_DYNAMIC &&
4000 insn->type != INSN_RETURN)
4001 continue;
4002
4003 if (insn->retpoline_safe)
4004 continue;
4005
4006 if (insn->sec->init)
4007 continue;
4008
4009 if (insn->type == INSN_RETURN) {
4010 if (opts.rethunk) {
4011 WARN_INSN(insn, "'naked' return found in MITIGATION_RETHUNK build");
4012 } else
4013 continue;
4014 } else {
4015 WARN_INSN(insn, "indirect %s found in MITIGATION_RETPOLINE build",
4016 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
4017 }
4018
4019 warnings++;
4020 }
4021
4022 return warnings;
4023}
4024
4025static bool is_kasan_insn(struct instruction *insn)
4026{
4027 return (insn->type == INSN_CALL &&
4028 !strcmp(insn_call_dest(insn)->name, "__asan_handle_no_return"));
4029}
4030
4031static bool is_ubsan_insn(struct instruction *insn)
4032{
4033 return (insn->type == INSN_CALL &&
4034 !strcmp(insn_call_dest(insn)->name,
4035 "__ubsan_handle_builtin_unreachable"));
4036}
4037
4038static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
4039{
4040 int i;
4041 struct instruction *prev_insn;
4042
4043 if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
4044 return true;
4045
4046 /*
4047 * Ignore alternative replacement instructions. This can happen
4048 * when a whitelisted function uses one of the ALTERNATIVE macros.
4049 */
4050 if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
4051 !strcmp(insn->sec->name, ".altinstr_aux"))
4052 return true;
4053
4054 /*
4055 * Whole archive runs might encounter dead code from weak symbols.
4056 * This is where the linker will have dropped the weak symbol in
4057 * favour of a regular symbol, but leaves the code in place.
4058 *
4059 * In this case we'll find a piece of code (whole function) that is not
4060 * covered by a !section symbol. Ignore them.
4061 */
4062 if (opts.link && !insn_func(insn)) {
4063 int size = find_symbol_hole_containing(insn->sec, insn->offset);
4064 unsigned long end = insn->offset + size;
4065
4066 if (!size) /* not a hole */
4067 return false;
4068
4069 if (size < 0) /* hole until the end */
4070 return true;
4071
4072 sec_for_each_insn_continue(file, insn) {
4073 /*
4074 * If we reach a visited instruction at or before the
4075 * end of the hole, ignore the unreachable.
4076 */
4077 if (insn->visited)
4078 return true;
4079
4080 if (insn->offset >= end)
4081 break;
4082
4083 /*
4084 * If this hole jumps to a .cold function, mark it ignore too.
4085 */
4086 if (insn->jump_dest && insn_func(insn->jump_dest) &&
4087 strstr(insn_func(insn->jump_dest)->name, ".cold")) {
4088 struct instruction *dest = insn->jump_dest;
4089 func_for_each_insn(file, insn_func(dest), dest)
4090 dest->ignore = true;
4091 }
4092 }
4093
4094 return false;
4095 }
4096
4097 if (!insn_func(insn))
4098 return false;
4099
4100 if (insn_func(insn)->static_call_tramp)
4101 return true;
4102
4103 /*
4104 * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
4105 * __builtin_unreachable(). The BUG() macro has an unreachable() after
4106 * the UD2, which causes GCC's undefined trap logic to emit another UD2
4107 * (or occasionally a JMP to UD2).
4108 *
4109 * It may also insert a UD2 after calling a __noreturn function.
4110 */
4111 prev_insn = prev_insn_same_sec(file, insn);
4112 if (prev_insn->dead_end &&
4113 (insn->type == INSN_BUG ||
4114 (insn->type == INSN_JUMP_UNCONDITIONAL &&
4115 insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
4116 return true;
4117
4118 /*
4119 * Check if this (or a subsequent) instruction is related to
4120 * CONFIG_UBSAN or CONFIG_KASAN.
4121 *
4122 * End the search at 5 instructions to avoid going into the weeds.
4123 */
4124 for (i = 0; i < 5; i++) {
4125
4126 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
4127 return true;
4128
4129 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
4130 if (insn->jump_dest &&
4131 insn_func(insn->jump_dest) == insn_func(insn)) {
4132 insn = insn->jump_dest;
4133 continue;
4134 }
4135
4136 break;
4137 }
4138
4139 if (insn->offset + insn->len >= insn_func(insn)->offset + insn_func(insn)->len)
4140 break;
4141
4142 insn = next_insn_same_sec(file, insn);
4143 }
4144
4145 return false;
4146}
4147
4148static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
4149{
4150 struct instruction *insn, *prev;
4151 struct cfi_state *cfi;
4152
4153 insn = find_insn(file, func->sec, func->offset);
4154 if (!insn)
4155 return -1;
4156
4157 for (prev = prev_insn_same_sec(file, insn);
4158 prev;
4159 prev = prev_insn_same_sec(file, prev)) {
4160 u64 offset;
4161
4162 if (prev->type != INSN_NOP)
4163 return -1;
4164
4165 offset = func->offset - prev->offset;
4166
4167 if (offset > opts.prefix)
4168 return -1;
4169
4170 if (offset < opts.prefix)
4171 continue;
4172
4173 elf_create_prefix_symbol(file->elf, func, opts.prefix);
4174 break;
4175 }
4176
4177 if (!prev)
4178 return -1;
4179
4180 if (!insn->cfi) {
4181 /*
4182 * This can happen if stack validation isn't enabled or the
4183 * function is annotated with STACK_FRAME_NON_STANDARD.
4184 */
4185 return 0;
4186 }
4187
4188 /* Propagate insn->cfi to the prefix code */
4189 cfi = cfi_hash_find_or_add(insn->cfi);
4190 for (; prev != insn; prev = next_insn_same_sec(file, prev))
4191 prev->cfi = cfi;
4192
4193 return 0;
4194}
4195
4196static int add_prefix_symbols(struct objtool_file *file)
4197{
4198 struct section *sec;
4199 struct symbol *func;
4200
4201 for_each_sec(file, sec) {
4202 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4203 continue;
4204
4205 sec_for_each_sym(sec, func) {
4206 if (func->type != STT_FUNC)
4207 continue;
4208
4209 add_prefix_symbol(file, func);
4210 }
4211 }
4212
4213 return 0;
4214}
4215
4216static int validate_symbol(struct objtool_file *file, struct section *sec,
4217 struct symbol *sym, struct insn_state *state)
4218{
4219 struct instruction *insn;
4220 int ret;
4221
4222 if (!sym->len) {
4223 WARN("%s() is missing an ELF size annotation", sym->name);
4224 return 1;
4225 }
4226
4227 if (sym->pfunc != sym || sym->alias != sym)
4228 return 0;
4229
4230 insn = find_insn(file, sec, sym->offset);
4231 if (!insn || insn->ignore || insn->visited)
4232 return 0;
4233
4234 state->uaccess = sym->uaccess_safe;
4235
4236 ret = validate_branch(file, insn_func(insn), insn, *state);
4237 if (ret)
4238 BT_INSN(insn, "<=== (sym)");
4239 return ret;
4240}
4241
4242static int validate_section(struct objtool_file *file, struct section *sec)
4243{
4244 struct insn_state state;
4245 struct symbol *func;
4246 int warnings = 0;
4247
4248 sec_for_each_sym(sec, func) {
4249 if (func->type != STT_FUNC)
4250 continue;
4251
4252 init_insn_state(file, &state, sec);
4253 set_func_state(&state.cfi);
4254
4255 warnings += validate_symbol(file, sec, func, &state);
4256 }
4257
4258 return warnings;
4259}
4260
4261static int validate_noinstr_sections(struct objtool_file *file)
4262{
4263 struct section *sec;
4264 int warnings = 0;
4265
4266 sec = find_section_by_name(file->elf, ".noinstr.text");
4267 if (sec) {
4268 warnings += validate_section(file, sec);
4269 warnings += validate_unwind_hints(file, sec);
4270 }
4271
4272 sec = find_section_by_name(file->elf, ".entry.text");
4273 if (sec) {
4274 warnings += validate_section(file, sec);
4275 warnings += validate_unwind_hints(file, sec);
4276 }
4277
4278 sec = find_section_by_name(file->elf, ".cpuidle.text");
4279 if (sec) {
4280 warnings += validate_section(file, sec);
4281 warnings += validate_unwind_hints(file, sec);
4282 }
4283
4284 return warnings;
4285}
4286
4287static int validate_functions(struct objtool_file *file)
4288{
4289 struct section *sec;
4290 int warnings = 0;
4291
4292 for_each_sec(file, sec) {
4293 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4294 continue;
4295
4296 warnings += validate_section(file, sec);
4297 }
4298
4299 return warnings;
4300}
4301
4302static void mark_endbr_used(struct instruction *insn)
4303{
4304 if (!list_empty(&insn->call_node))
4305 list_del_init(&insn->call_node);
4306}
4307
4308static bool noendbr_range(struct objtool_file *file, struct instruction *insn)
4309{
4310 struct symbol *sym = find_symbol_containing(insn->sec, insn->offset-1);
4311 struct instruction *first;
4312
4313 if (!sym)
4314 return false;
4315
4316 first = find_insn(file, sym->sec, sym->offset);
4317 if (!first)
4318 return false;
4319
4320 if (first->type != INSN_ENDBR && !first->noendbr)
4321 return false;
4322
4323 return insn->offset == sym->offset + sym->len;
4324}
4325
4326static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
4327{
4328 struct instruction *dest;
4329 struct reloc *reloc;
4330 unsigned long off;
4331 int warnings = 0;
4332
4333 /*
4334 * Looking for function pointer load relocations. Ignore
4335 * direct/indirect branches:
4336 */
4337 switch (insn->type) {
4338 case INSN_CALL:
4339 case INSN_CALL_DYNAMIC:
4340 case INSN_JUMP_CONDITIONAL:
4341 case INSN_JUMP_UNCONDITIONAL:
4342 case INSN_JUMP_DYNAMIC:
4343 case INSN_JUMP_DYNAMIC_CONDITIONAL:
4344 case INSN_RETURN:
4345 case INSN_NOP:
4346 return 0;
4347 default:
4348 break;
4349 }
4350
4351 for (reloc = insn_reloc(file, insn);
4352 reloc;
4353 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
4354 reloc_offset(reloc) + 1,
4355 (insn->offset + insn->len) - (reloc_offset(reloc) + 1))) {
4356
4357 /*
4358 * static_call_update() references the trampoline, which
4359 * doesn't have (or need) ENDBR. Skip warning in that case.
4360 */
4361 if (reloc->sym->static_call_tramp)
4362 continue;
4363
4364 off = reloc->sym->offset;
4365 if (reloc_type(reloc) == R_X86_64_PC32 ||
4366 reloc_type(reloc) == R_X86_64_PLT32)
4367 off += arch_dest_reloc_offset(reloc_addend(reloc));
4368 else
4369 off += reloc_addend(reloc);
4370
4371 dest = find_insn(file, reloc->sym->sec, off);
4372 if (!dest)
4373 continue;
4374
4375 if (dest->type == INSN_ENDBR) {
4376 mark_endbr_used(dest);
4377 continue;
4378 }
4379
4380 if (insn_func(dest) && insn_func(insn) &&
4381 insn_func(dest)->pfunc == insn_func(insn)->pfunc) {
4382 /*
4383 * Anything from->to self is either _THIS_IP_ or
4384 * IRET-to-self.
4385 *
4386 * There is no sane way to annotate _THIS_IP_ since the
4387 * compiler treats the relocation as a constant and is
4388 * happy to fold in offsets, skewing any annotation we
4389 * do, leading to vast amounts of false-positives.
4390 *
4391 * There's also compiler generated _THIS_IP_ through
4392 * KCOV and such which we have no hope of annotating.
4393 *
4394 * As such, blanket accept self-references without
4395 * issue.
4396 */
4397 continue;
4398 }
4399
4400 /*
4401 * Accept anything ANNOTATE_NOENDBR.
4402 */
4403 if (dest->noendbr)
4404 continue;
4405
4406 /*
4407 * Accept if this is the instruction after a symbol
4408 * that is (no)endbr -- typical code-range usage.
4409 */
4410 if (noendbr_range(file, dest))
4411 continue;
4412
4413 WARN_INSN(insn, "relocation to !ENDBR: %s", offstr(dest->sec, dest->offset));
4414
4415 warnings++;
4416 }
4417
4418 return warnings;
4419}
4420
4421static int validate_ibt_data_reloc(struct objtool_file *file,
4422 struct reloc *reloc)
4423{
4424 struct instruction *dest;
4425
4426 dest = find_insn(file, reloc->sym->sec,
4427 reloc->sym->offset + reloc_addend(reloc));
4428 if (!dest)
4429 return 0;
4430
4431 if (dest->type == INSN_ENDBR) {
4432 mark_endbr_used(dest);
4433 return 0;
4434 }
4435
4436 if (dest->noendbr)
4437 return 0;
4438
4439 WARN_FUNC("data relocation to !ENDBR: %s",
4440 reloc->sec->base, reloc_offset(reloc),
4441 offstr(dest->sec, dest->offset));
4442
4443 return 1;
4444}
4445
4446/*
4447 * Validate IBT rules and remove used ENDBR instructions from the seal list.
4448 * Unused ENDBR instructions will be annotated for sealing (i.e., replaced with
4449 * NOPs) later, in create_ibt_endbr_seal_sections().
4450 */
4451static int validate_ibt(struct objtool_file *file)
4452{
4453 struct section *sec;
4454 struct reloc *reloc;
4455 struct instruction *insn;
4456 int warnings = 0;
4457
4458 for_each_insn(file, insn)
4459 warnings += validate_ibt_insn(file, insn);
4460
4461 for_each_sec(file, sec) {
4462
4463 /* Already done by validate_ibt_insn() */
4464 if (sec->sh.sh_flags & SHF_EXECINSTR)
4465 continue;
4466
4467 if (!sec->rsec)
4468 continue;
4469
4470 /*
4471 * These sections can reference text addresses, but not with
4472 * the intent to indirect branch to them.
4473 */
4474 if ((!strncmp(sec->name, ".discard", 8) &&
4475 strcmp(sec->name, ".discard.ibt_endbr_noseal")) ||
4476 !strncmp(sec->name, ".debug", 6) ||
4477 !strcmp(sec->name, ".altinstructions") ||
4478 !strcmp(sec->name, ".ibt_endbr_seal") ||
4479 !strcmp(sec->name, ".orc_unwind_ip") ||
4480 !strcmp(sec->name, ".parainstructions") ||
4481 !strcmp(sec->name, ".retpoline_sites") ||
4482 !strcmp(sec->name, ".smp_locks") ||
4483 !strcmp(sec->name, ".static_call_sites") ||
4484 !strcmp(sec->name, "_error_injection_whitelist") ||
4485 !strcmp(sec->name, "_kprobe_blacklist") ||
4486 !strcmp(sec->name, "__bug_table") ||
4487 !strcmp(sec->name, "__ex_table") ||
4488 !strcmp(sec->name, "__jump_table") ||
4489 !strcmp(sec->name, "__mcount_loc") ||
4490 !strcmp(sec->name, ".kcfi_traps") ||
4491 strstr(sec->name, "__patchable_function_entries"))
4492 continue;
4493
4494 for_each_reloc(sec->rsec, reloc)
4495 warnings += validate_ibt_data_reloc(file, reloc);
4496 }
4497
4498 return warnings;
4499}
4500
4501static int validate_sls(struct objtool_file *file)
4502{
4503 struct instruction *insn, *next_insn;
4504 int warnings = 0;
4505
4506 for_each_insn(file, insn) {
4507 next_insn = next_insn_same_sec(file, insn);
4508
4509 if (insn->retpoline_safe)
4510 continue;
4511
4512 switch (insn->type) {
4513 case INSN_RETURN:
4514 if (!next_insn || next_insn->type != INSN_TRAP) {
4515 WARN_INSN(insn, "missing int3 after ret");
4516 warnings++;
4517 }
4518
4519 break;
4520 case INSN_JUMP_DYNAMIC:
4521 if (!next_insn || next_insn->type != INSN_TRAP) {
4522 WARN_INSN(insn, "missing int3 after indirect jump");
4523 warnings++;
4524 }
4525 break;
4526 default:
4527 break;
4528 }
4529 }
4530
4531 return warnings;
4532}
4533
4534static bool ignore_noreturn_call(struct instruction *insn)
4535{
4536 struct symbol *call_dest = insn_call_dest(insn);
4537
4538 /*
4539 * FIXME: hack, we need a real noreturn solution
4540 *
4541 * Problem is, exc_double_fault() may or may not return, depending on
4542 * whether CONFIG_X86_ESPFIX64 is set. But objtool has no visibility
4543 * to the kernel config.
4544 *
4545 * Other potential ways to fix it:
4546 *
4547 * - have compiler communicate __noreturn functions somehow
4548 * - remove CONFIG_X86_ESPFIX64
4549 * - read the .config file
4550 * - add a cmdline option
4551 * - create a generic objtool annotation format (vs a bunch of custom
4552 * formats) and annotate it
4553 */
4554 if (!strcmp(call_dest->name, "exc_double_fault")) {
4555 /* prevent further unreachable warnings for the caller */
4556 insn->sym->warned = 1;
4557 return true;
4558 }
4559
4560 return false;
4561}
4562
4563static int validate_reachable_instructions(struct objtool_file *file)
4564{
4565 struct instruction *insn, *prev_insn;
4566 struct symbol *call_dest;
4567 int warnings = 0;
4568
4569 if (file->ignore_unreachables)
4570 return 0;
4571
4572 for_each_insn(file, insn) {
4573 if (insn->visited || ignore_unreachable_insn(file, insn))
4574 continue;
4575
4576 prev_insn = prev_insn_same_sec(file, insn);
4577 if (prev_insn && prev_insn->dead_end) {
4578 call_dest = insn_call_dest(prev_insn);
4579 if (call_dest && !ignore_noreturn_call(prev_insn)) {
4580 WARN_INSN(insn, "%s() is missing a __noreturn annotation",
4581 call_dest->name);
4582 warnings++;
4583 continue;
4584 }
4585 }
4586
4587 WARN_INSN(insn, "unreachable instruction");
4588 warnings++;
4589 }
4590
4591 return warnings;
4592}
4593
4594/* 'funcs' is a space-separated list of function names */
4595static int disas_funcs(const char *funcs)
4596{
4597 const char *objdump_str, *cross_compile;
4598 int size, ret;
4599 char *cmd;
4600
4601 cross_compile = getenv("CROSS_COMPILE");
4602
4603 objdump_str = "%sobjdump -wdr %s | gawk -M -v _funcs='%s' '"
4604 "BEGIN { split(_funcs, funcs); }"
4605 "/^$/ { func_match = 0; }"
4606 "/<.*>:/ { "
4607 "f = gensub(/.*<(.*)>:/, \"\\\\1\", 1);"
4608 "for (i in funcs) {"
4609 "if (funcs[i] == f) {"
4610 "func_match = 1;"
4611 "base = strtonum(\"0x\" $1);"
4612 "break;"
4613 "}"
4614 "}"
4615 "}"
4616 "{"
4617 "if (func_match) {"
4618 "addr = strtonum(\"0x\" $1);"
4619 "printf(\"%%04x \", addr - base);"
4620 "print;"
4621 "}"
4622 "}' 1>&2";
4623
4624 /* fake snprintf() to calculate the size */
4625 size = snprintf(NULL, 0, objdump_str, cross_compile, objname, funcs) + 1;
4626 if (size <= 0) {
4627 WARN("objdump string size calculation failed");
4628 return -1;
4629 }
4630
4631 cmd = malloc(size);
4632
4633 /* real snprintf() */
4634 snprintf(cmd, size, objdump_str, cross_compile, objname, funcs);
4635 ret = system(cmd);
4636 if (ret) {
4637 WARN("disassembly failed: %d", ret);
4638 return -1;
4639 }
4640
4641 return 0;
4642}
4643
4644static int disas_warned_funcs(struct objtool_file *file)
4645{
4646 struct symbol *sym;
4647 char *funcs = NULL, *tmp;
4648
4649 for_each_sym(file, sym) {
4650 if (sym->warned) {
4651 if (!funcs) {
4652 funcs = malloc(strlen(sym->name) + 1);
4653 strcpy(funcs, sym->name);
4654 } else {
4655 tmp = malloc(strlen(funcs) + strlen(sym->name) + 2);
4656 sprintf(tmp, "%s %s", funcs, sym->name);
4657 free(funcs);
4658 funcs = tmp;
4659 }
4660 }
4661 }
4662
4663 if (funcs)
4664 disas_funcs(funcs);
4665
4666 return 0;
4667}
4668
4669struct insn_chunk {
4670 void *addr;
4671 struct insn_chunk *next;
4672};
4673
4674/*
4675 * Reduce peak RSS usage by freeing insns memory before writing the ELF file,
4676 * which can trigger more allocations for .debug_* sections whose data hasn't
4677 * been read yet.
4678 */
4679static void free_insns(struct objtool_file *file)
4680{
4681 struct instruction *insn;
4682 struct insn_chunk *chunks = NULL, *chunk;
4683
4684 for_each_insn(file, insn) {
4685 if (!insn->idx) {
4686 chunk = malloc(sizeof(*chunk));
4687 chunk->addr = insn;
4688 chunk->next = chunks;
4689 chunks = chunk;
4690 }
4691 }
4692
4693 for (chunk = chunks; chunk; chunk = chunk->next)
4694 free(chunk->addr);
4695}
4696
4697int check(struct objtool_file *file)
4698{
4699 int ret, warnings = 0;
4700
4701 arch_initial_func_cfi_state(&initial_func_cfi);
4702 init_cfi_state(&init_cfi);
4703 init_cfi_state(&func_cfi);
4704 set_func_state(&func_cfi);
4705 init_cfi_state(&force_undefined_cfi);
4706 force_undefined_cfi.force_undefined = true;
4707
4708 if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
4709 goto out;
4710
4711 cfi_hash_add(&init_cfi);
4712 cfi_hash_add(&func_cfi);
4713
4714 ret = decode_sections(file);
4715 if (ret < 0)
4716 goto out;
4717
4718 warnings += ret;
4719
4720 if (!nr_insns)
4721 goto out;
4722
4723 if (opts.retpoline) {
4724 ret = validate_retpoline(file);
4725 if (ret < 0)
4726 return ret;
4727 warnings += ret;
4728 }
4729
4730 if (opts.stackval || opts.orc || opts.uaccess) {
4731 ret = validate_functions(file);
4732 if (ret < 0)
4733 goto out;
4734 warnings += ret;
4735
4736 ret = validate_unwind_hints(file, NULL);
4737 if (ret < 0)
4738 goto out;
4739 warnings += ret;
4740
4741 if (!warnings) {
4742 ret = validate_reachable_instructions(file);
4743 if (ret < 0)
4744 goto out;
4745 warnings += ret;
4746 }
4747
4748 } else if (opts.noinstr) {
4749 ret = validate_noinstr_sections(file);
4750 if (ret < 0)
4751 goto out;
4752 warnings += ret;
4753 }
4754
4755 if (opts.unret) {
4756 /*
4757 * Must be after validate_branch() and friends, it plays
4758 * further games with insn->visited.
4759 */
4760 ret = validate_unrets(file);
4761 if (ret < 0)
4762 return ret;
4763 warnings += ret;
4764 }
4765
4766 if (opts.ibt) {
4767 ret = validate_ibt(file);
4768 if (ret < 0)
4769 goto out;
4770 warnings += ret;
4771 }
4772
4773 if (opts.sls) {
4774 ret = validate_sls(file);
4775 if (ret < 0)
4776 goto out;
4777 warnings += ret;
4778 }
4779
4780 if (opts.static_call) {
4781 ret = create_static_call_sections(file);
4782 if (ret < 0)
4783 goto out;
4784 warnings += ret;
4785 }
4786
4787 if (opts.retpoline) {
4788 ret = create_retpoline_sites_sections(file);
4789 if (ret < 0)
4790 goto out;
4791 warnings += ret;
4792 }
4793
4794 if (opts.cfi) {
4795 ret = create_cfi_sections(file);
4796 if (ret < 0)
4797 goto out;
4798 warnings += ret;
4799 }
4800
4801 if (opts.rethunk) {
4802 ret = create_return_sites_sections(file);
4803 if (ret < 0)
4804 goto out;
4805 warnings += ret;
4806
4807 if (opts.hack_skylake) {
4808 ret = create_direct_call_sections(file);
4809 if (ret < 0)
4810 goto out;
4811 warnings += ret;
4812 }
4813 }
4814
4815 if (opts.mcount) {
4816 ret = create_mcount_loc_sections(file);
4817 if (ret < 0)
4818 goto out;
4819 warnings += ret;
4820 }
4821
4822 if (opts.prefix) {
4823 ret = add_prefix_symbols(file);
4824 if (ret < 0)
4825 return ret;
4826 warnings += ret;
4827 }
4828
4829 if (opts.ibt) {
4830 ret = create_ibt_endbr_seal_sections(file);
4831 if (ret < 0)
4832 goto out;
4833 warnings += ret;
4834 }
4835
4836 if (opts.orc && nr_insns) {
4837 ret = orc_create(file);
4838 if (ret < 0)
4839 goto out;
4840 warnings += ret;
4841 }
4842
4843 free_insns(file);
4844
4845 if (opts.verbose)
4846 disas_warned_funcs(file);
4847
4848 if (opts.stats) {
4849 printf("nr_insns_visited: %ld\n", nr_insns_visited);
4850 printf("nr_cfi: %ld\n", nr_cfi);
4851 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
4852 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
4853 }
4854
4855out:
4856 /*
4857 * For now, don't fail the kernel build on fatal warnings. These
4858 * errors are still fairly common due to the growing matrix of
4859 * supported toolchains and their recent pace of change.
4860 */
4861 return 0;
4862}