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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
24struct alternative {
25 struct alternative *next;
26 struct instruction *insn;
27 bool skip_orig;
28};
29
30static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
31
32static struct cfi_init_state initial_func_cfi;
33static struct cfi_state init_cfi;
34static struct cfi_state func_cfi;
35static struct cfi_state force_undefined_cfi;
36
37struct instruction *find_insn(struct objtool_file *file,
38 struct section *sec, unsigned long offset)
39{
40 struct instruction *insn;
41
42 hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
43 if (insn->sec == sec && insn->offset == offset)
44 return insn;
45 }
46
47 return NULL;
48}
49
50struct instruction *next_insn_same_sec(struct objtool_file *file,
51 struct instruction *insn)
52{
53 if (insn->idx == INSN_CHUNK_MAX)
54 return find_insn(file, insn->sec, insn->offset + insn->len);
55
56 insn++;
57 if (!insn->len)
58 return NULL;
59
60 return insn;
61}
62
63static struct instruction *next_insn_same_func(struct objtool_file *file,
64 struct instruction *insn)
65{
66 struct instruction *next = next_insn_same_sec(file, insn);
67 struct symbol *func = insn_func(insn);
68
69 if (!func)
70 return NULL;
71
72 if (next && insn_func(next) == func)
73 return next;
74
75 /* Check if we're already in the subfunction: */
76 if (func == func->cfunc)
77 return NULL;
78
79 /* Move to the subfunction: */
80 return find_insn(file, func->cfunc->sec, func->cfunc->offset);
81}
82
83static struct instruction *prev_insn_same_sec(struct objtool_file *file,
84 struct instruction *insn)
85{
86 if (insn->idx == 0) {
87 if (insn->prev_len)
88 return find_insn(file, insn->sec, insn->offset - insn->prev_len);
89 return NULL;
90 }
91
92 return insn - 1;
93}
94
95static struct instruction *prev_insn_same_sym(struct objtool_file *file,
96 struct instruction *insn)
97{
98 struct instruction *prev = prev_insn_same_sec(file, insn);
99
100 if (prev && insn_func(prev) == insn_func(insn))
101 return prev;
102
103 return NULL;
104}
105
106#define for_each_insn(file, insn) \
107 for (struct section *__sec, *__fake = (struct section *)1; \
108 __fake; __fake = NULL) \
109 for_each_sec(file, __sec) \
110 sec_for_each_insn(file, __sec, insn)
111
112#define func_for_each_insn(file, func, insn) \
113 for (insn = find_insn(file, func->sec, func->offset); \
114 insn; \
115 insn = next_insn_same_func(file, insn))
116
117#define sym_for_each_insn(file, sym, insn) \
118 for (insn = find_insn(file, sym->sec, sym->offset); \
119 insn && insn->offset < sym->offset + sym->len; \
120 insn = next_insn_same_sec(file, insn))
121
122#define sym_for_each_insn_continue_reverse(file, sym, insn) \
123 for (insn = prev_insn_same_sec(file, insn); \
124 insn && insn->offset >= sym->offset; \
125 insn = prev_insn_same_sec(file, insn))
126
127#define sec_for_each_insn_from(file, insn) \
128 for (; insn; insn = next_insn_same_sec(file, insn))
129
130#define sec_for_each_insn_continue(file, insn) \
131 for (insn = next_insn_same_sec(file, insn); insn; \
132 insn = next_insn_same_sec(file, insn))
133
134static inline struct symbol *insn_call_dest(struct instruction *insn)
135{
136 if (insn->type == INSN_JUMP_DYNAMIC ||
137 insn->type == INSN_CALL_DYNAMIC)
138 return NULL;
139
140 return insn->_call_dest;
141}
142
143static inline struct reloc *insn_jump_table(struct instruction *insn)
144{
145 if (insn->type == INSN_JUMP_DYNAMIC ||
146 insn->type == INSN_CALL_DYNAMIC)
147 return insn->_jump_table;
148
149 return NULL;
150}
151
152static bool is_jump_table_jump(struct instruction *insn)
153{
154 struct alt_group *alt_group = insn->alt_group;
155
156 if (insn_jump_table(insn))
157 return true;
158
159 /* Retpoline alternative for a jump table? */
160 return alt_group && alt_group->orig_group &&
161 insn_jump_table(alt_group->orig_group->first_insn);
162}
163
164static bool is_sibling_call(struct instruction *insn)
165{
166 /*
167 * Assume only STT_FUNC calls have jump-tables.
168 */
169 if (insn_func(insn)) {
170 /* An indirect jump is either a sibling call or a jump to a table. */
171 if (insn->type == INSN_JUMP_DYNAMIC)
172 return !is_jump_table_jump(insn);
173 }
174
175 /* add_jump_destinations() sets insn_call_dest(insn) for sibling calls. */
176 return (is_static_jump(insn) && insn_call_dest(insn));
177}
178
179/*
180 * This checks to see if the given function is a "noreturn" function.
181 *
182 * For global functions which are outside the scope of this object file, we
183 * have to keep a manual list of them.
184 *
185 * For local functions, we have to detect them manually by simply looking for
186 * the lack of a return instruction.
187 */
188static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
189 int recursion)
190{
191 int i;
192 struct instruction *insn;
193 bool empty = true;
194
195#define NORETURN(func) __stringify(func),
196 static const char * const global_noreturns[] = {
197#include "noreturns.h"
198 };
199#undef NORETURN
200
201 if (!func)
202 return false;
203
204 if (func->bind == STB_GLOBAL || func->bind == STB_WEAK)
205 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
206 if (!strcmp(func->name, global_noreturns[i]))
207 return true;
208
209 if (func->bind == STB_WEAK)
210 return false;
211
212 if (!func->len)
213 return false;
214
215 insn = find_insn(file, func->sec, func->offset);
216 if (!insn || !insn_func(insn))
217 return false;
218
219 func_for_each_insn(file, func, insn) {
220 empty = false;
221
222 if (insn->type == INSN_RETURN)
223 return false;
224 }
225
226 if (empty)
227 return false;
228
229 /*
230 * A function can have a sibling call instead of a return. In that
231 * case, the function's dead-end status depends on whether the target
232 * of the sibling call returns.
233 */
234 func_for_each_insn(file, func, insn) {
235 if (is_sibling_call(insn)) {
236 struct instruction *dest = insn->jump_dest;
237
238 if (!dest)
239 /* sibling call to another file */
240 return false;
241
242 /* local sibling call */
243 if (recursion == 5) {
244 /*
245 * Infinite recursion: two functions have
246 * sibling calls to each other. This is a very
247 * rare case. It means they aren't dead ends.
248 */
249 return false;
250 }
251
252 return __dead_end_function(file, insn_func(dest), recursion+1);
253 }
254 }
255
256 return true;
257}
258
259static bool dead_end_function(struct objtool_file *file, struct symbol *func)
260{
261 return __dead_end_function(file, func, 0);
262}
263
264static void init_cfi_state(struct cfi_state *cfi)
265{
266 int i;
267
268 for (i = 0; i < CFI_NUM_REGS; i++) {
269 cfi->regs[i].base = CFI_UNDEFINED;
270 cfi->vals[i].base = CFI_UNDEFINED;
271 }
272 cfi->cfa.base = CFI_UNDEFINED;
273 cfi->drap_reg = CFI_UNDEFINED;
274 cfi->drap_offset = -1;
275}
276
277static void init_insn_state(struct objtool_file *file, struct insn_state *state,
278 struct section *sec)
279{
280 memset(state, 0, sizeof(*state));
281 init_cfi_state(&state->cfi);
282
283 /*
284 * We need the full vmlinux for noinstr validation, otherwise we can
285 * not correctly determine insn_call_dest(insn)->sec (external symbols
286 * do not have a section).
287 */
288 if (opts.link && opts.noinstr && sec)
289 state->noinstr = sec->noinstr;
290}
291
292static struct cfi_state *cfi_alloc(void)
293{
294 struct cfi_state *cfi = calloc(1, sizeof(struct cfi_state));
295 if (!cfi) {
296 WARN("calloc failed");
297 exit(1);
298 }
299 nr_cfi++;
300 return cfi;
301}
302
303static int cfi_bits;
304static struct hlist_head *cfi_hash;
305
306static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
307{
308 return memcmp((void *)cfi1 + sizeof(cfi1->hash),
309 (void *)cfi2 + sizeof(cfi2->hash),
310 sizeof(struct cfi_state) - sizeof(struct hlist_node));
311}
312
313static inline u32 cfi_key(struct cfi_state *cfi)
314{
315 return jhash((void *)cfi + sizeof(cfi->hash),
316 sizeof(*cfi) - sizeof(cfi->hash), 0);
317}
318
319static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
320{
321 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
322 struct cfi_state *obj;
323
324 hlist_for_each_entry(obj, head, hash) {
325 if (!cficmp(cfi, obj)) {
326 nr_cfi_cache++;
327 return obj;
328 }
329 }
330
331 obj = cfi_alloc();
332 *obj = *cfi;
333 hlist_add_head(&obj->hash, head);
334
335 return obj;
336}
337
338static void cfi_hash_add(struct cfi_state *cfi)
339{
340 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
341
342 hlist_add_head(&cfi->hash, head);
343}
344
345static void *cfi_hash_alloc(unsigned long size)
346{
347 cfi_bits = max(10, ilog2(size));
348 cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
349 PROT_READ|PROT_WRITE,
350 MAP_PRIVATE|MAP_ANON, -1, 0);
351 if (cfi_hash == (void *)-1L) {
352 WARN("mmap fail cfi_hash");
353 cfi_hash = NULL;
354 } else if (opts.stats) {
355 printf("cfi_bits: %d\n", cfi_bits);
356 }
357
358 return cfi_hash;
359}
360
361static unsigned long nr_insns;
362static unsigned long nr_insns_visited;
363
364/*
365 * Call the arch-specific instruction decoder for all the instructions and add
366 * them to the global instruction list.
367 */
368static int decode_instructions(struct objtool_file *file)
369{
370 struct section *sec;
371 struct symbol *func;
372 unsigned long offset;
373 struct instruction *insn;
374 int ret;
375
376 for_each_sec(file, sec) {
377 struct instruction *insns = NULL;
378 u8 prev_len = 0;
379 u8 idx = 0;
380
381 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
382 continue;
383
384 if (strcmp(sec->name, ".altinstr_replacement") &&
385 strcmp(sec->name, ".altinstr_aux") &&
386 strncmp(sec->name, ".discard.", 9))
387 sec->text = true;
388
389 if (!strcmp(sec->name, ".noinstr.text") ||
390 !strcmp(sec->name, ".entry.text") ||
391 !strcmp(sec->name, ".cpuidle.text") ||
392 !strncmp(sec->name, ".text..__x86.", 13))
393 sec->noinstr = true;
394
395 /*
396 * .init.text code is ran before userspace and thus doesn't
397 * strictly need retpolines, except for modules which are
398 * loaded late, they very much do need retpoline in their
399 * .init.text
400 */
401 if (!strcmp(sec->name, ".init.text") && !opts.module)
402 sec->init = true;
403
404 for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
405 if (!insns || idx == INSN_CHUNK_MAX) {
406 insns = calloc(sizeof(*insn), INSN_CHUNK_SIZE);
407 if (!insns) {
408 WARN("malloc failed");
409 return -1;
410 }
411 idx = 0;
412 } else {
413 idx++;
414 }
415 insn = &insns[idx];
416 insn->idx = idx;
417
418 INIT_LIST_HEAD(&insn->call_node);
419 insn->sec = sec;
420 insn->offset = offset;
421 insn->prev_len = prev_len;
422
423 ret = arch_decode_instruction(file, sec, offset,
424 sec->sh.sh_size - offset,
425 insn);
426 if (ret)
427 return ret;
428
429 prev_len = insn->len;
430
431 /*
432 * By default, "ud2" is a dead end unless otherwise
433 * annotated, because GCC 7 inserts it for certain
434 * divide-by-zero cases.
435 */
436 if (insn->type == INSN_BUG)
437 insn->dead_end = true;
438
439 hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
440 nr_insns++;
441 }
442
443// printf("%s: last chunk used: %d\n", sec->name, (int)idx);
444
445 sec_for_each_sym(sec, func) {
446 if (func->type != STT_NOTYPE && func->type != STT_FUNC)
447 continue;
448
449 if (func->offset == sec->sh.sh_size) {
450 /* Heuristic: likely an "end" symbol */
451 if (func->type == STT_NOTYPE)
452 continue;
453 WARN("%s(): STT_FUNC at end of section",
454 func->name);
455 return -1;
456 }
457
458 if (func->embedded_insn || func->alias != func)
459 continue;
460
461 if (!find_insn(file, sec, func->offset)) {
462 WARN("%s(): can't find starting instruction",
463 func->name);
464 return -1;
465 }
466
467 sym_for_each_insn(file, func, insn) {
468 insn->sym = func;
469 if (func->type == STT_FUNC &&
470 insn->type == INSN_ENDBR &&
471 list_empty(&insn->call_node)) {
472 if (insn->offset == func->offset) {
473 list_add_tail(&insn->call_node, &file->endbr_list);
474 file->nr_endbr++;
475 } else {
476 file->nr_endbr_int++;
477 }
478 }
479 }
480 }
481 }
482
483 if (opts.stats)
484 printf("nr_insns: %lu\n", nr_insns);
485
486 return 0;
487}
488
489/*
490 * Read the pv_ops[] .data table to find the static initialized values.
491 */
492static int add_pv_ops(struct objtool_file *file, const char *symname)
493{
494 struct symbol *sym, *func;
495 unsigned long off, end;
496 struct reloc *reloc;
497 int idx;
498
499 sym = find_symbol_by_name(file->elf, symname);
500 if (!sym)
501 return 0;
502
503 off = sym->offset;
504 end = off + sym->len;
505 for (;;) {
506 reloc = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off);
507 if (!reloc)
508 break;
509
510 func = reloc->sym;
511 if (func->type == STT_SECTION)
512 func = find_symbol_by_offset(reloc->sym->sec,
513 reloc_addend(reloc));
514
515 idx = (reloc_offset(reloc) - sym->offset) / sizeof(unsigned long);
516
517 objtool_pv_add(file, idx, func);
518
519 off = reloc_offset(reloc) + 1;
520 if (off > end)
521 break;
522 }
523
524 return 0;
525}
526
527/*
528 * Allocate and initialize file->pv_ops[].
529 */
530static int init_pv_ops(struct objtool_file *file)
531{
532 static const char *pv_ops_tables[] = {
533 "pv_ops",
534 "xen_cpu_ops",
535 "xen_irq_ops",
536 "xen_mmu_ops",
537 NULL,
538 };
539 const char *pv_ops;
540 struct symbol *sym;
541 int idx, nr;
542
543 if (!opts.noinstr)
544 return 0;
545
546 file->pv_ops = NULL;
547
548 sym = find_symbol_by_name(file->elf, "pv_ops");
549 if (!sym)
550 return 0;
551
552 nr = sym->len / sizeof(unsigned long);
553 file->pv_ops = calloc(sizeof(struct pv_state), nr);
554 if (!file->pv_ops)
555 return -1;
556
557 for (idx = 0; idx < nr; idx++)
558 INIT_LIST_HEAD(&file->pv_ops[idx].targets);
559
560 for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++)
561 add_pv_ops(file, pv_ops);
562
563 return 0;
564}
565
566static struct instruction *find_last_insn(struct objtool_file *file,
567 struct section *sec)
568{
569 struct instruction *insn = NULL;
570 unsigned int offset;
571 unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
572
573 for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
574 insn = find_insn(file, sec, offset);
575
576 return insn;
577}
578
579/*
580 * Mark "ud2" instructions and manually annotated dead ends.
581 */
582static int add_dead_ends(struct objtool_file *file)
583{
584 struct section *rsec;
585 struct reloc *reloc;
586 struct instruction *insn;
587 s64 addend;
588
589 /*
590 * Check for manually annotated dead ends.
591 */
592 rsec = find_section_by_name(file->elf, ".rela.discard.unreachable");
593 if (!rsec)
594 goto reachable;
595
596 for_each_reloc(rsec, reloc) {
597
598 if (reloc->sym->type != STT_SECTION) {
599 WARN("unexpected relocation symbol type in %s", rsec->name);
600 return -1;
601 }
602
603 addend = reloc_addend(reloc);
604
605 insn = find_insn(file, reloc->sym->sec, addend);
606 if (insn)
607 insn = prev_insn_same_sec(file, insn);
608 else if (addend == reloc->sym->sec->sh.sh_size) {
609 insn = find_last_insn(file, reloc->sym->sec);
610 if (!insn) {
611 WARN("can't find unreachable insn at %s+0x%" PRIx64,
612 reloc->sym->sec->name, addend);
613 return -1;
614 }
615 } else {
616 WARN("can't find unreachable insn at %s+0x%" PRIx64,
617 reloc->sym->sec->name, addend);
618 return -1;
619 }
620
621 insn->dead_end = true;
622 }
623
624reachable:
625 /*
626 * These manually annotated reachable checks are needed for GCC 4.4,
627 * where the Linux unreachable() macro isn't supported. In that case
628 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
629 * not a dead end.
630 */
631 rsec = find_section_by_name(file->elf, ".rela.discard.reachable");
632 if (!rsec)
633 return 0;
634
635 for_each_reloc(rsec, reloc) {
636
637 if (reloc->sym->type != STT_SECTION) {
638 WARN("unexpected relocation symbol type in %s", rsec->name);
639 return -1;
640 }
641
642 addend = reloc_addend(reloc);
643
644 insn = find_insn(file, reloc->sym->sec, addend);
645 if (insn)
646 insn = prev_insn_same_sec(file, insn);
647 else if (addend == reloc->sym->sec->sh.sh_size) {
648 insn = find_last_insn(file, reloc->sym->sec);
649 if (!insn) {
650 WARN("can't find reachable insn at %s+0x%" PRIx64,
651 reloc->sym->sec->name, addend);
652 return -1;
653 }
654 } else {
655 WARN("can't find reachable insn at %s+0x%" PRIx64,
656 reloc->sym->sec->name, addend);
657 return -1;
658 }
659
660 insn->dead_end = false;
661 }
662
663 return 0;
664}
665
666static int create_static_call_sections(struct objtool_file *file)
667{
668 struct static_call_site *site;
669 struct section *sec;
670 struct instruction *insn;
671 struct symbol *key_sym;
672 char *key_name, *tmp;
673 int idx;
674
675 sec = find_section_by_name(file->elf, ".static_call_sites");
676 if (sec) {
677 INIT_LIST_HEAD(&file->static_call_list);
678 WARN("file already has .static_call_sites section, skipping");
679 return 0;
680 }
681
682 if (list_empty(&file->static_call_list))
683 return 0;
684
685 idx = 0;
686 list_for_each_entry(insn, &file->static_call_list, call_node)
687 idx++;
688
689 sec = elf_create_section_pair(file->elf, ".static_call_sites",
690 sizeof(*site), idx, idx * 2);
691 if (!sec)
692 return -1;
693
694 /* Allow modules to modify the low bits of static_call_site::key */
695 sec->sh.sh_flags |= SHF_WRITE;
696
697 idx = 0;
698 list_for_each_entry(insn, &file->static_call_list, call_node) {
699
700 /* populate reloc for 'addr' */
701 if (!elf_init_reloc_text_sym(file->elf, sec,
702 idx * sizeof(*site), idx * 2,
703 insn->sec, insn->offset))
704 return -1;
705
706 /* find key symbol */
707 key_name = strdup(insn_call_dest(insn)->name);
708 if (!key_name) {
709 perror("strdup");
710 return -1;
711 }
712 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
713 STATIC_CALL_TRAMP_PREFIX_LEN)) {
714 WARN("static_call: trampoline name malformed: %s", key_name);
715 free(key_name);
716 return -1;
717 }
718 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
719 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
720
721 key_sym = find_symbol_by_name(file->elf, tmp);
722 if (!key_sym) {
723 if (!opts.module) {
724 WARN("static_call: can't find static_call_key symbol: %s", tmp);
725 free(key_name);
726 return -1;
727 }
728
729 /*
730 * For modules(), the key might not be exported, which
731 * means the module can make static calls but isn't
732 * allowed to change them.
733 *
734 * In that case we temporarily set the key to be the
735 * trampoline address. This is fixed up in
736 * static_call_add_module().
737 */
738 key_sym = insn_call_dest(insn);
739 }
740 free(key_name);
741
742 /* populate reloc for 'key' */
743 if (!elf_init_reloc_data_sym(file->elf, sec,
744 idx * sizeof(*site) + 4,
745 (idx * 2) + 1, key_sym,
746 is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
747 return -1;
748
749 idx++;
750 }
751
752 return 0;
753}
754
755static int create_retpoline_sites_sections(struct objtool_file *file)
756{
757 struct instruction *insn;
758 struct section *sec;
759 int idx;
760
761 sec = find_section_by_name(file->elf, ".retpoline_sites");
762 if (sec) {
763 WARN("file already has .retpoline_sites, skipping");
764 return 0;
765 }
766
767 idx = 0;
768 list_for_each_entry(insn, &file->retpoline_call_list, call_node)
769 idx++;
770
771 if (!idx)
772 return 0;
773
774 sec = elf_create_section_pair(file->elf, ".retpoline_sites",
775 sizeof(int), idx, idx);
776 if (!sec)
777 return -1;
778
779 idx = 0;
780 list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
781
782 if (!elf_init_reloc_text_sym(file->elf, sec,
783 idx * sizeof(int), idx,
784 insn->sec, insn->offset))
785 return -1;
786
787 idx++;
788 }
789
790 return 0;
791}
792
793static int create_return_sites_sections(struct objtool_file *file)
794{
795 struct instruction *insn;
796 struct section *sec;
797 int idx;
798
799 sec = find_section_by_name(file->elf, ".return_sites");
800 if (sec) {
801 WARN("file already has .return_sites, skipping");
802 return 0;
803 }
804
805 idx = 0;
806 list_for_each_entry(insn, &file->return_thunk_list, call_node)
807 idx++;
808
809 if (!idx)
810 return 0;
811
812 sec = elf_create_section_pair(file->elf, ".return_sites",
813 sizeof(int), idx, idx);
814 if (!sec)
815 return -1;
816
817 idx = 0;
818 list_for_each_entry(insn, &file->return_thunk_list, call_node) {
819
820 if (!elf_init_reloc_text_sym(file->elf, sec,
821 idx * sizeof(int), idx,
822 insn->sec, insn->offset))
823 return -1;
824
825 idx++;
826 }
827
828 return 0;
829}
830
831static int create_ibt_endbr_seal_sections(struct objtool_file *file)
832{
833 struct instruction *insn;
834 struct section *sec;
835 int idx;
836
837 sec = find_section_by_name(file->elf, ".ibt_endbr_seal");
838 if (sec) {
839 WARN("file already has .ibt_endbr_seal, skipping");
840 return 0;
841 }
842
843 idx = 0;
844 list_for_each_entry(insn, &file->endbr_list, call_node)
845 idx++;
846
847 if (opts.stats) {
848 printf("ibt: ENDBR at function start: %d\n", file->nr_endbr);
849 printf("ibt: ENDBR inside functions: %d\n", file->nr_endbr_int);
850 printf("ibt: superfluous ENDBR: %d\n", idx);
851 }
852
853 if (!idx)
854 return 0;
855
856 sec = elf_create_section_pair(file->elf, ".ibt_endbr_seal",
857 sizeof(int), idx, idx);
858 if (!sec)
859 return -1;
860
861 idx = 0;
862 list_for_each_entry(insn, &file->endbr_list, call_node) {
863
864 int *site = (int *)sec->data->d_buf + idx;
865 struct symbol *sym = insn->sym;
866 *site = 0;
867
868 if (opts.module && sym && sym->type == STT_FUNC &&
869 insn->offset == sym->offset &&
870 (!strcmp(sym->name, "init_module") ||
871 !strcmp(sym->name, "cleanup_module")))
872 WARN("%s(): not an indirect call target", sym->name);
873
874 if (!elf_init_reloc_text_sym(file->elf, sec,
875 idx * sizeof(int), idx,
876 insn->sec, insn->offset))
877 return -1;
878
879 idx++;
880 }
881
882 return 0;
883}
884
885static int create_cfi_sections(struct objtool_file *file)
886{
887 struct section *sec;
888 struct symbol *sym;
889 int idx;
890
891 sec = find_section_by_name(file->elf, ".cfi_sites");
892 if (sec) {
893 INIT_LIST_HEAD(&file->call_list);
894 WARN("file already has .cfi_sites section, skipping");
895 return 0;
896 }
897
898 idx = 0;
899 for_each_sym(file, sym) {
900 if (sym->type != STT_FUNC)
901 continue;
902
903 if (strncmp(sym->name, "__cfi_", 6))
904 continue;
905
906 idx++;
907 }
908
909 sec = elf_create_section_pair(file->elf, ".cfi_sites",
910 sizeof(unsigned int), idx, idx);
911 if (!sec)
912 return -1;
913
914 idx = 0;
915 for_each_sym(file, sym) {
916 if (sym->type != STT_FUNC)
917 continue;
918
919 if (strncmp(sym->name, "__cfi_", 6))
920 continue;
921
922 if (!elf_init_reloc_text_sym(file->elf, sec,
923 idx * sizeof(unsigned int), idx,
924 sym->sec, sym->offset))
925 return -1;
926
927 idx++;
928 }
929
930 return 0;
931}
932
933static int create_mcount_loc_sections(struct objtool_file *file)
934{
935 size_t addr_size = elf_addr_size(file->elf);
936 struct instruction *insn;
937 struct section *sec;
938 int idx;
939
940 sec = find_section_by_name(file->elf, "__mcount_loc");
941 if (sec) {
942 INIT_LIST_HEAD(&file->mcount_loc_list);
943 WARN("file already has __mcount_loc section, skipping");
944 return 0;
945 }
946
947 if (list_empty(&file->mcount_loc_list))
948 return 0;
949
950 idx = 0;
951 list_for_each_entry(insn, &file->mcount_loc_list, call_node)
952 idx++;
953
954 sec = elf_create_section_pair(file->elf, "__mcount_loc", addr_size,
955 idx, idx);
956 if (!sec)
957 return -1;
958
959 sec->sh.sh_addralign = addr_size;
960
961 idx = 0;
962 list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
963
964 struct reloc *reloc;
965
966 reloc = elf_init_reloc_text_sym(file->elf, sec, idx * addr_size, idx,
967 insn->sec, insn->offset);
968 if (!reloc)
969 return -1;
970
971 set_reloc_type(file->elf, reloc, addr_size == 8 ? R_ABS64 : R_ABS32);
972
973 idx++;
974 }
975
976 return 0;
977}
978
979static int create_direct_call_sections(struct objtool_file *file)
980{
981 struct instruction *insn;
982 struct section *sec;
983 int idx;
984
985 sec = find_section_by_name(file->elf, ".call_sites");
986 if (sec) {
987 INIT_LIST_HEAD(&file->call_list);
988 WARN("file already has .call_sites section, skipping");
989 return 0;
990 }
991
992 if (list_empty(&file->call_list))
993 return 0;
994
995 idx = 0;
996 list_for_each_entry(insn, &file->call_list, call_node)
997 idx++;
998
999 sec = elf_create_section_pair(file->elf, ".call_sites",
1000 sizeof(unsigned int), idx, idx);
1001 if (!sec)
1002 return -1;
1003
1004 idx = 0;
1005 list_for_each_entry(insn, &file->call_list, call_node) {
1006
1007 if (!elf_init_reloc_text_sym(file->elf, sec,
1008 idx * sizeof(unsigned int), idx,
1009 insn->sec, insn->offset))
1010 return -1;
1011
1012 idx++;
1013 }
1014
1015 return 0;
1016}
1017
1018/*
1019 * Warnings shouldn't be reported for ignored functions.
1020 */
1021static void add_ignores(struct objtool_file *file)
1022{
1023 struct instruction *insn;
1024 struct section *rsec;
1025 struct symbol *func;
1026 struct reloc *reloc;
1027
1028 rsec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
1029 if (!rsec)
1030 return;
1031
1032 for_each_reloc(rsec, reloc) {
1033 switch (reloc->sym->type) {
1034 case STT_FUNC:
1035 func = reloc->sym;
1036 break;
1037
1038 case STT_SECTION:
1039 func = find_func_by_offset(reloc->sym->sec, reloc_addend(reloc));
1040 if (!func)
1041 continue;
1042 break;
1043
1044 default:
1045 WARN("unexpected relocation symbol type in %s: %d",
1046 rsec->name, reloc->sym->type);
1047 continue;
1048 }
1049
1050 func_for_each_insn(file, func, insn)
1051 insn->ignore = true;
1052 }
1053}
1054
1055/*
1056 * This is a whitelist of functions that is allowed to be called with AC set.
1057 * The list is meant to be minimal and only contains compiler instrumentation
1058 * ABI and a few functions used to implement *_{to,from}_user() functions.
1059 *
1060 * These functions must not directly change AC, but may PUSHF/POPF.
1061 */
1062static const char *uaccess_safe_builtin[] = {
1063 /* KASAN */
1064 "kasan_report",
1065 "kasan_check_range",
1066 /* KASAN out-of-line */
1067 "__asan_loadN_noabort",
1068 "__asan_load1_noabort",
1069 "__asan_load2_noabort",
1070 "__asan_load4_noabort",
1071 "__asan_load8_noabort",
1072 "__asan_load16_noabort",
1073 "__asan_storeN_noabort",
1074 "__asan_store1_noabort",
1075 "__asan_store2_noabort",
1076 "__asan_store4_noabort",
1077 "__asan_store8_noabort",
1078 "__asan_store16_noabort",
1079 "__kasan_check_read",
1080 "__kasan_check_write",
1081 /* KASAN in-line */
1082 "__asan_report_load_n_noabort",
1083 "__asan_report_load1_noabort",
1084 "__asan_report_load2_noabort",
1085 "__asan_report_load4_noabort",
1086 "__asan_report_load8_noabort",
1087 "__asan_report_load16_noabort",
1088 "__asan_report_store_n_noabort",
1089 "__asan_report_store1_noabort",
1090 "__asan_report_store2_noabort",
1091 "__asan_report_store4_noabort",
1092 "__asan_report_store8_noabort",
1093 "__asan_report_store16_noabort",
1094 /* KCSAN */
1095 "__kcsan_check_access",
1096 "__kcsan_mb",
1097 "__kcsan_wmb",
1098 "__kcsan_rmb",
1099 "__kcsan_release",
1100 "kcsan_found_watchpoint",
1101 "kcsan_setup_watchpoint",
1102 "kcsan_check_scoped_accesses",
1103 "kcsan_disable_current",
1104 "kcsan_enable_current_nowarn",
1105 /* KCSAN/TSAN */
1106 "__tsan_func_entry",
1107 "__tsan_func_exit",
1108 "__tsan_read_range",
1109 "__tsan_write_range",
1110 "__tsan_read1",
1111 "__tsan_read2",
1112 "__tsan_read4",
1113 "__tsan_read8",
1114 "__tsan_read16",
1115 "__tsan_write1",
1116 "__tsan_write2",
1117 "__tsan_write4",
1118 "__tsan_write8",
1119 "__tsan_write16",
1120 "__tsan_read_write1",
1121 "__tsan_read_write2",
1122 "__tsan_read_write4",
1123 "__tsan_read_write8",
1124 "__tsan_read_write16",
1125 "__tsan_volatile_read1",
1126 "__tsan_volatile_read2",
1127 "__tsan_volatile_read4",
1128 "__tsan_volatile_read8",
1129 "__tsan_volatile_read16",
1130 "__tsan_volatile_write1",
1131 "__tsan_volatile_write2",
1132 "__tsan_volatile_write4",
1133 "__tsan_volatile_write8",
1134 "__tsan_volatile_write16",
1135 "__tsan_atomic8_load",
1136 "__tsan_atomic16_load",
1137 "__tsan_atomic32_load",
1138 "__tsan_atomic64_load",
1139 "__tsan_atomic8_store",
1140 "__tsan_atomic16_store",
1141 "__tsan_atomic32_store",
1142 "__tsan_atomic64_store",
1143 "__tsan_atomic8_exchange",
1144 "__tsan_atomic16_exchange",
1145 "__tsan_atomic32_exchange",
1146 "__tsan_atomic64_exchange",
1147 "__tsan_atomic8_fetch_add",
1148 "__tsan_atomic16_fetch_add",
1149 "__tsan_atomic32_fetch_add",
1150 "__tsan_atomic64_fetch_add",
1151 "__tsan_atomic8_fetch_sub",
1152 "__tsan_atomic16_fetch_sub",
1153 "__tsan_atomic32_fetch_sub",
1154 "__tsan_atomic64_fetch_sub",
1155 "__tsan_atomic8_fetch_and",
1156 "__tsan_atomic16_fetch_and",
1157 "__tsan_atomic32_fetch_and",
1158 "__tsan_atomic64_fetch_and",
1159 "__tsan_atomic8_fetch_or",
1160 "__tsan_atomic16_fetch_or",
1161 "__tsan_atomic32_fetch_or",
1162 "__tsan_atomic64_fetch_or",
1163 "__tsan_atomic8_fetch_xor",
1164 "__tsan_atomic16_fetch_xor",
1165 "__tsan_atomic32_fetch_xor",
1166 "__tsan_atomic64_fetch_xor",
1167 "__tsan_atomic8_fetch_nand",
1168 "__tsan_atomic16_fetch_nand",
1169 "__tsan_atomic32_fetch_nand",
1170 "__tsan_atomic64_fetch_nand",
1171 "__tsan_atomic8_compare_exchange_strong",
1172 "__tsan_atomic16_compare_exchange_strong",
1173 "__tsan_atomic32_compare_exchange_strong",
1174 "__tsan_atomic64_compare_exchange_strong",
1175 "__tsan_atomic8_compare_exchange_weak",
1176 "__tsan_atomic16_compare_exchange_weak",
1177 "__tsan_atomic32_compare_exchange_weak",
1178 "__tsan_atomic64_compare_exchange_weak",
1179 "__tsan_atomic8_compare_exchange_val",
1180 "__tsan_atomic16_compare_exchange_val",
1181 "__tsan_atomic32_compare_exchange_val",
1182 "__tsan_atomic64_compare_exchange_val",
1183 "__tsan_atomic_thread_fence",
1184 "__tsan_atomic_signal_fence",
1185 "__tsan_unaligned_read16",
1186 "__tsan_unaligned_write16",
1187 /* KCOV */
1188 "write_comp_data",
1189 "check_kcov_mode",
1190 "__sanitizer_cov_trace_pc",
1191 "__sanitizer_cov_trace_const_cmp1",
1192 "__sanitizer_cov_trace_const_cmp2",
1193 "__sanitizer_cov_trace_const_cmp4",
1194 "__sanitizer_cov_trace_const_cmp8",
1195 "__sanitizer_cov_trace_cmp1",
1196 "__sanitizer_cov_trace_cmp2",
1197 "__sanitizer_cov_trace_cmp4",
1198 "__sanitizer_cov_trace_cmp8",
1199 "__sanitizer_cov_trace_switch",
1200 /* KMSAN */
1201 "kmsan_copy_to_user",
1202 "kmsan_report",
1203 "kmsan_unpoison_entry_regs",
1204 "kmsan_unpoison_memory",
1205 "__msan_chain_origin",
1206 "__msan_get_context_state",
1207 "__msan_instrument_asm_store",
1208 "__msan_metadata_ptr_for_load_1",
1209 "__msan_metadata_ptr_for_load_2",
1210 "__msan_metadata_ptr_for_load_4",
1211 "__msan_metadata_ptr_for_load_8",
1212 "__msan_metadata_ptr_for_load_n",
1213 "__msan_metadata_ptr_for_store_1",
1214 "__msan_metadata_ptr_for_store_2",
1215 "__msan_metadata_ptr_for_store_4",
1216 "__msan_metadata_ptr_for_store_8",
1217 "__msan_metadata_ptr_for_store_n",
1218 "__msan_poison_alloca",
1219 "__msan_warning",
1220 /* UBSAN */
1221 "ubsan_type_mismatch_common",
1222 "__ubsan_handle_type_mismatch",
1223 "__ubsan_handle_type_mismatch_v1",
1224 "__ubsan_handle_shift_out_of_bounds",
1225 "__ubsan_handle_load_invalid_value",
1226 /* STACKLEAK */
1227 "stackleak_track_stack",
1228 /* misc */
1229 "csum_partial_copy_generic",
1230 "copy_mc_fragile",
1231 "copy_mc_fragile_handle_tail",
1232 "copy_mc_enhanced_fast_string",
1233 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
1234 "rep_stos_alternative",
1235 "rep_movs_alternative",
1236 "__copy_user_nocache",
1237 NULL
1238};
1239
1240static void add_uaccess_safe(struct objtool_file *file)
1241{
1242 struct symbol *func;
1243 const char **name;
1244
1245 if (!opts.uaccess)
1246 return;
1247
1248 for (name = uaccess_safe_builtin; *name; name++) {
1249 func = find_symbol_by_name(file->elf, *name);
1250 if (!func)
1251 continue;
1252
1253 func->uaccess_safe = true;
1254 }
1255}
1256
1257/*
1258 * FIXME: For now, just ignore any alternatives which add retpolines. This is
1259 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
1260 * But it at least allows objtool to understand the control flow *around* the
1261 * retpoline.
1262 */
1263static int add_ignore_alternatives(struct objtool_file *file)
1264{
1265 struct section *rsec;
1266 struct reloc *reloc;
1267 struct instruction *insn;
1268
1269 rsec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
1270 if (!rsec)
1271 return 0;
1272
1273 for_each_reloc(rsec, reloc) {
1274 if (reloc->sym->type != STT_SECTION) {
1275 WARN("unexpected relocation symbol type in %s", rsec->name);
1276 return -1;
1277 }
1278
1279 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
1280 if (!insn) {
1281 WARN("bad .discard.ignore_alts entry");
1282 return -1;
1283 }
1284
1285 insn->ignore_alts = true;
1286 }
1287
1288 return 0;
1289}
1290
1291/*
1292 * Symbols that replace INSN_CALL_DYNAMIC, every (tail) call to such a symbol
1293 * will be added to the .retpoline_sites section.
1294 */
1295__weak bool arch_is_retpoline(struct symbol *sym)
1296{
1297 return false;
1298}
1299
1300/*
1301 * Symbols that replace INSN_RETURN, every (tail) call to such a symbol
1302 * will be added to the .return_sites section.
1303 */
1304__weak bool arch_is_rethunk(struct symbol *sym)
1305{
1306 return false;
1307}
1308
1309/*
1310 * Symbols that are embedded inside other instructions, because sometimes crazy
1311 * code exists. These are mostly ignored for validation purposes.
1312 */
1313__weak bool arch_is_embedded_insn(struct symbol *sym)
1314{
1315 return false;
1316}
1317
1318static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
1319{
1320 struct reloc *reloc;
1321
1322 if (insn->no_reloc)
1323 return NULL;
1324
1325 if (!file)
1326 return NULL;
1327
1328 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1329 insn->offset, insn->len);
1330 if (!reloc) {
1331 insn->no_reloc = 1;
1332 return NULL;
1333 }
1334
1335 return reloc;
1336}
1337
1338static void remove_insn_ops(struct instruction *insn)
1339{
1340 struct stack_op *op, *next;
1341
1342 for (op = insn->stack_ops; op; op = next) {
1343 next = op->next;
1344 free(op);
1345 }
1346 insn->stack_ops = NULL;
1347}
1348
1349static void annotate_call_site(struct objtool_file *file,
1350 struct instruction *insn, bool sibling)
1351{
1352 struct reloc *reloc = insn_reloc(file, insn);
1353 struct symbol *sym = insn_call_dest(insn);
1354
1355 if (!sym)
1356 sym = reloc->sym;
1357
1358 /*
1359 * Alternative replacement code is just template code which is
1360 * sometimes copied to the original instruction. For now, don't
1361 * annotate it. (In the future we might consider annotating the
1362 * original instruction if/when it ever makes sense to do so.)
1363 */
1364 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1365 return;
1366
1367 if (sym->static_call_tramp) {
1368 list_add_tail(&insn->call_node, &file->static_call_list);
1369 return;
1370 }
1371
1372 if (sym->retpoline_thunk) {
1373 list_add_tail(&insn->call_node, &file->retpoline_call_list);
1374 return;
1375 }
1376
1377 /*
1378 * Many compilers cannot disable KCOV or sanitizer calls with a function
1379 * attribute so they need a little help, NOP out any such calls from
1380 * noinstr text.
1381 */
1382 if (opts.hack_noinstr && insn->sec->noinstr && sym->profiling_func) {
1383 if (reloc)
1384 set_reloc_type(file->elf, reloc, R_NONE);
1385
1386 elf_write_insn(file->elf, insn->sec,
1387 insn->offset, insn->len,
1388 sibling ? arch_ret_insn(insn->len)
1389 : arch_nop_insn(insn->len));
1390
1391 insn->type = sibling ? INSN_RETURN : INSN_NOP;
1392
1393 if (sibling) {
1394 /*
1395 * We've replaced the tail-call JMP insn by two new
1396 * insn: RET; INT3, except we only have a single struct
1397 * insn here. Mark it retpoline_safe to avoid the SLS
1398 * warning, instead of adding another insn.
1399 */
1400 insn->retpoline_safe = true;
1401 }
1402
1403 return;
1404 }
1405
1406 if (opts.mcount && sym->fentry) {
1407 if (sibling)
1408 WARN_INSN(insn, "tail call to __fentry__ !?!?");
1409 if (opts.mnop) {
1410 if (reloc)
1411 set_reloc_type(file->elf, reloc, R_NONE);
1412
1413 elf_write_insn(file->elf, insn->sec,
1414 insn->offset, insn->len,
1415 arch_nop_insn(insn->len));
1416
1417 insn->type = INSN_NOP;
1418 }
1419
1420 list_add_tail(&insn->call_node, &file->mcount_loc_list);
1421 return;
1422 }
1423
1424 if (insn->type == INSN_CALL && !insn->sec->init)
1425 list_add_tail(&insn->call_node, &file->call_list);
1426
1427 if (!sibling && dead_end_function(file, sym))
1428 insn->dead_end = true;
1429}
1430
1431static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1432 struct symbol *dest, bool sibling)
1433{
1434 insn->_call_dest = dest;
1435 if (!dest)
1436 return;
1437
1438 /*
1439 * Whatever stack impact regular CALLs have, should be undone
1440 * by the RETURN of the called function.
1441 *
1442 * Annotated intra-function calls retain the stack_ops but
1443 * are converted to JUMP, see read_intra_function_calls().
1444 */
1445 remove_insn_ops(insn);
1446
1447 annotate_call_site(file, insn, sibling);
1448}
1449
1450static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1451{
1452 /*
1453 * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1454 * so convert them accordingly.
1455 */
1456 switch (insn->type) {
1457 case INSN_CALL:
1458 insn->type = INSN_CALL_DYNAMIC;
1459 break;
1460 case INSN_JUMP_UNCONDITIONAL:
1461 insn->type = INSN_JUMP_DYNAMIC;
1462 break;
1463 case INSN_JUMP_CONDITIONAL:
1464 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1465 break;
1466 default:
1467 return;
1468 }
1469
1470 insn->retpoline_safe = true;
1471
1472 /*
1473 * Whatever stack impact regular CALLs have, should be undone
1474 * by the RETURN of the called function.
1475 *
1476 * Annotated intra-function calls retain the stack_ops but
1477 * are converted to JUMP, see read_intra_function_calls().
1478 */
1479 remove_insn_ops(insn);
1480
1481 annotate_call_site(file, insn, false);
1482}
1483
1484static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add)
1485{
1486 /*
1487 * Return thunk tail calls are really just returns in disguise,
1488 * so convert them accordingly.
1489 */
1490 insn->type = INSN_RETURN;
1491 insn->retpoline_safe = true;
1492
1493 if (add)
1494 list_add_tail(&insn->call_node, &file->return_thunk_list);
1495}
1496
1497static bool is_first_func_insn(struct objtool_file *file,
1498 struct instruction *insn, struct symbol *sym)
1499{
1500 if (insn->offset == sym->offset)
1501 return true;
1502
1503 /* Allow direct CALL/JMP past ENDBR */
1504 if (opts.ibt) {
1505 struct instruction *prev = prev_insn_same_sym(file, insn);
1506
1507 if (prev && prev->type == INSN_ENDBR &&
1508 insn->offset == sym->offset + prev->len)
1509 return true;
1510 }
1511
1512 return false;
1513}
1514
1515/*
1516 * A sibling call is a tail-call to another symbol -- to differentiate from a
1517 * recursive tail-call which is to the same symbol.
1518 */
1519static bool jump_is_sibling_call(struct objtool_file *file,
1520 struct instruction *from, struct instruction *to)
1521{
1522 struct symbol *fs = from->sym;
1523 struct symbol *ts = to->sym;
1524
1525 /* Not a sibling call if from/to a symbol hole */
1526 if (!fs || !ts)
1527 return false;
1528
1529 /* Not a sibling call if not targeting the start of a symbol. */
1530 if (!is_first_func_insn(file, to, ts))
1531 return false;
1532
1533 /* Disallow sibling calls into STT_NOTYPE */
1534 if (ts->type == STT_NOTYPE)
1535 return false;
1536
1537 /* Must not be self to be a sibling */
1538 return fs->pfunc != ts->pfunc;
1539}
1540
1541/*
1542 * Find the destination instructions for all jumps.
1543 */
1544static int add_jump_destinations(struct objtool_file *file)
1545{
1546 struct instruction *insn, *jump_dest;
1547 struct reloc *reloc;
1548 struct section *dest_sec;
1549 unsigned long dest_off;
1550
1551 for_each_insn(file, insn) {
1552 if (insn->jump_dest) {
1553 /*
1554 * handle_group_alt() may have previously set
1555 * 'jump_dest' for some alternatives.
1556 */
1557 continue;
1558 }
1559 if (!is_static_jump(insn))
1560 continue;
1561
1562 reloc = insn_reloc(file, insn);
1563 if (!reloc) {
1564 dest_sec = insn->sec;
1565 dest_off = arch_jump_destination(insn);
1566 } else if (reloc->sym->type == STT_SECTION) {
1567 dest_sec = reloc->sym->sec;
1568 dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
1569 } else if (reloc->sym->retpoline_thunk) {
1570 add_retpoline_call(file, insn);
1571 continue;
1572 } else if (reloc->sym->return_thunk) {
1573 add_return_call(file, insn, true);
1574 continue;
1575 } else if (insn_func(insn)) {
1576 /*
1577 * External sibling call or internal sibling call with
1578 * STT_FUNC reloc.
1579 */
1580 add_call_dest(file, insn, reloc->sym, true);
1581 continue;
1582 } else if (reloc->sym->sec->idx) {
1583 dest_sec = reloc->sym->sec;
1584 dest_off = reloc->sym->sym.st_value +
1585 arch_dest_reloc_offset(reloc_addend(reloc));
1586 } else {
1587 /* non-func asm code jumping to another file */
1588 continue;
1589 }
1590
1591 jump_dest = find_insn(file, dest_sec, dest_off);
1592 if (!jump_dest) {
1593 struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off);
1594
1595 /*
1596 * This is a special case for retbleed_untrain_ret().
1597 * It jumps to __x86_return_thunk(), but objtool
1598 * can't find the thunk's starting RET
1599 * instruction, because the RET is also in the
1600 * middle of another instruction. Objtool only
1601 * knows about the outer instruction.
1602 */
1603 if (sym && sym->embedded_insn) {
1604 add_return_call(file, insn, false);
1605 continue;
1606 }
1607
1608 WARN_INSN(insn, "can't find jump dest instruction at %s+0x%lx",
1609 dest_sec->name, dest_off);
1610 return -1;
1611 }
1612
1613 /*
1614 * An intra-TU jump in retpoline.o might not have a relocation
1615 * for its jump dest, in which case the above
1616 * add_{retpoline,return}_call() didn't happen.
1617 */
1618 if (jump_dest->sym && jump_dest->offset == jump_dest->sym->offset) {
1619 if (jump_dest->sym->retpoline_thunk) {
1620 add_retpoline_call(file, insn);
1621 continue;
1622 }
1623 if (jump_dest->sym->return_thunk) {
1624 add_return_call(file, insn, true);
1625 continue;
1626 }
1627 }
1628
1629 /*
1630 * Cross-function jump.
1631 */
1632 if (insn_func(insn) && insn_func(jump_dest) &&
1633 insn_func(insn) != insn_func(jump_dest)) {
1634
1635 /*
1636 * For GCC 8+, create parent/child links for any cold
1637 * subfunctions. This is _mostly_ redundant with a
1638 * similar initialization in read_symbols().
1639 *
1640 * If a function has aliases, we want the *first* such
1641 * function in the symbol table to be the subfunction's
1642 * parent. In that case we overwrite the
1643 * initialization done in read_symbols().
1644 *
1645 * However this code can't completely replace the
1646 * read_symbols() code because this doesn't detect the
1647 * case where the parent function's only reference to a
1648 * subfunction is through a jump table.
1649 */
1650 if (!strstr(insn_func(insn)->name, ".cold") &&
1651 strstr(insn_func(jump_dest)->name, ".cold")) {
1652 insn_func(insn)->cfunc = insn_func(jump_dest);
1653 insn_func(jump_dest)->pfunc = insn_func(insn);
1654 }
1655 }
1656
1657 if (jump_is_sibling_call(file, insn, jump_dest)) {
1658 /*
1659 * Internal sibling call without reloc or with
1660 * STT_SECTION reloc.
1661 */
1662 add_call_dest(file, insn, insn_func(jump_dest), true);
1663 continue;
1664 }
1665
1666 insn->jump_dest = jump_dest;
1667 }
1668
1669 return 0;
1670}
1671
1672static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1673{
1674 struct symbol *call_dest;
1675
1676 call_dest = find_func_by_offset(sec, offset);
1677 if (!call_dest)
1678 call_dest = find_symbol_by_offset(sec, offset);
1679
1680 return call_dest;
1681}
1682
1683/*
1684 * Find the destination instructions for all calls.
1685 */
1686static int add_call_destinations(struct objtool_file *file)
1687{
1688 struct instruction *insn;
1689 unsigned long dest_off;
1690 struct symbol *dest;
1691 struct reloc *reloc;
1692
1693 for_each_insn(file, insn) {
1694 if (insn->type != INSN_CALL)
1695 continue;
1696
1697 reloc = insn_reloc(file, insn);
1698 if (!reloc) {
1699 dest_off = arch_jump_destination(insn);
1700 dest = find_call_destination(insn->sec, dest_off);
1701
1702 add_call_dest(file, insn, dest, false);
1703
1704 if (insn->ignore)
1705 continue;
1706
1707 if (!insn_call_dest(insn)) {
1708 WARN_INSN(insn, "unannotated intra-function call");
1709 return -1;
1710 }
1711
1712 if (insn_func(insn) && insn_call_dest(insn)->type != STT_FUNC) {
1713 WARN_INSN(insn, "unsupported call to non-function");
1714 return -1;
1715 }
1716
1717 } else if (reloc->sym->type == STT_SECTION) {
1718 dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
1719 dest = find_call_destination(reloc->sym->sec, dest_off);
1720 if (!dest) {
1721 WARN_INSN(insn, "can't find call dest symbol at %s+0x%lx",
1722 reloc->sym->sec->name, dest_off);
1723 return -1;
1724 }
1725
1726 add_call_dest(file, insn, dest, false);
1727
1728 } else if (reloc->sym->retpoline_thunk) {
1729 add_retpoline_call(file, insn);
1730
1731 } else
1732 add_call_dest(file, insn, reloc->sym, false);
1733 }
1734
1735 return 0;
1736}
1737
1738/*
1739 * The .alternatives section requires some extra special care over and above
1740 * other special sections because alternatives are patched in place.
1741 */
1742static int handle_group_alt(struct objtool_file *file,
1743 struct special_alt *special_alt,
1744 struct instruction *orig_insn,
1745 struct instruction **new_insn)
1746{
1747 struct instruction *last_new_insn = NULL, *insn, *nop = NULL;
1748 struct alt_group *orig_alt_group, *new_alt_group;
1749 unsigned long dest_off;
1750
1751 orig_alt_group = orig_insn->alt_group;
1752 if (!orig_alt_group) {
1753 struct instruction *last_orig_insn = NULL;
1754
1755 orig_alt_group = malloc(sizeof(*orig_alt_group));
1756 if (!orig_alt_group) {
1757 WARN("malloc failed");
1758 return -1;
1759 }
1760 orig_alt_group->cfi = calloc(special_alt->orig_len,
1761 sizeof(struct cfi_state *));
1762 if (!orig_alt_group->cfi) {
1763 WARN("calloc failed");
1764 return -1;
1765 }
1766
1767 insn = orig_insn;
1768 sec_for_each_insn_from(file, insn) {
1769 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1770 break;
1771
1772 insn->alt_group = orig_alt_group;
1773 last_orig_insn = insn;
1774 }
1775 orig_alt_group->orig_group = NULL;
1776 orig_alt_group->first_insn = orig_insn;
1777 orig_alt_group->last_insn = last_orig_insn;
1778 orig_alt_group->nop = NULL;
1779 } else {
1780 if (orig_alt_group->last_insn->offset + orig_alt_group->last_insn->len -
1781 orig_alt_group->first_insn->offset != special_alt->orig_len) {
1782 WARN_INSN(orig_insn, "weirdly overlapping alternative! %ld != %d",
1783 orig_alt_group->last_insn->offset +
1784 orig_alt_group->last_insn->len -
1785 orig_alt_group->first_insn->offset,
1786 special_alt->orig_len);
1787 return -1;
1788 }
1789 }
1790
1791 new_alt_group = malloc(sizeof(*new_alt_group));
1792 if (!new_alt_group) {
1793 WARN("malloc failed");
1794 return -1;
1795 }
1796
1797 if (special_alt->new_len < special_alt->orig_len) {
1798 /*
1799 * Insert a fake nop at the end to make the replacement
1800 * alt_group the same size as the original. This is needed to
1801 * allow propagate_alt_cfi() to do its magic. When the last
1802 * instruction affects the stack, the instruction after it (the
1803 * nop) will propagate the new state to the shared CFI array.
1804 */
1805 nop = malloc(sizeof(*nop));
1806 if (!nop) {
1807 WARN("malloc failed");
1808 return -1;
1809 }
1810 memset(nop, 0, sizeof(*nop));
1811
1812 nop->sec = special_alt->new_sec;
1813 nop->offset = special_alt->new_off + special_alt->new_len;
1814 nop->len = special_alt->orig_len - special_alt->new_len;
1815 nop->type = INSN_NOP;
1816 nop->sym = orig_insn->sym;
1817 nop->alt_group = new_alt_group;
1818 nop->ignore = orig_insn->ignore_alts;
1819 }
1820
1821 if (!special_alt->new_len) {
1822 *new_insn = nop;
1823 goto end;
1824 }
1825
1826 insn = *new_insn;
1827 sec_for_each_insn_from(file, insn) {
1828 struct reloc *alt_reloc;
1829
1830 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1831 break;
1832
1833 last_new_insn = insn;
1834
1835 insn->ignore = orig_insn->ignore_alts;
1836 insn->sym = orig_insn->sym;
1837 insn->alt_group = new_alt_group;
1838
1839 /*
1840 * Since alternative replacement code is copy/pasted by the
1841 * kernel after applying relocations, generally such code can't
1842 * have relative-address relocation references to outside the
1843 * .altinstr_replacement section, unless the arch's
1844 * alternatives code can adjust the relative offsets
1845 * accordingly.
1846 */
1847 alt_reloc = insn_reloc(file, insn);
1848 if (alt_reloc && arch_pc_relative_reloc(alt_reloc) &&
1849 !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1850
1851 WARN_INSN(insn, "unsupported relocation in alternatives section");
1852 return -1;
1853 }
1854
1855 if (!is_static_jump(insn))
1856 continue;
1857
1858 if (!insn->immediate)
1859 continue;
1860
1861 dest_off = arch_jump_destination(insn);
1862 if (dest_off == special_alt->new_off + special_alt->new_len) {
1863 insn->jump_dest = next_insn_same_sec(file, orig_alt_group->last_insn);
1864 if (!insn->jump_dest) {
1865 WARN_INSN(insn, "can't find alternative jump destination");
1866 return -1;
1867 }
1868 }
1869 }
1870
1871 if (!last_new_insn) {
1872 WARN_FUNC("can't find last new alternative instruction",
1873 special_alt->new_sec, special_alt->new_off);
1874 return -1;
1875 }
1876
1877end:
1878 new_alt_group->orig_group = orig_alt_group;
1879 new_alt_group->first_insn = *new_insn;
1880 new_alt_group->last_insn = last_new_insn;
1881 new_alt_group->nop = nop;
1882 new_alt_group->cfi = orig_alt_group->cfi;
1883 return 0;
1884}
1885
1886/*
1887 * A jump table entry can either convert a nop to a jump or a jump to a nop.
1888 * If the original instruction is a jump, make the alt entry an effective nop
1889 * by just skipping the original instruction.
1890 */
1891static int handle_jump_alt(struct objtool_file *file,
1892 struct special_alt *special_alt,
1893 struct instruction *orig_insn,
1894 struct instruction **new_insn)
1895{
1896 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1897 orig_insn->type != INSN_NOP) {
1898
1899 WARN_INSN(orig_insn, "unsupported instruction at jump label");
1900 return -1;
1901 }
1902
1903 if (opts.hack_jump_label && special_alt->key_addend & 2) {
1904 struct reloc *reloc = insn_reloc(file, orig_insn);
1905
1906 if (reloc)
1907 set_reloc_type(file->elf, reloc, R_NONE);
1908 elf_write_insn(file->elf, orig_insn->sec,
1909 orig_insn->offset, orig_insn->len,
1910 arch_nop_insn(orig_insn->len));
1911 orig_insn->type = INSN_NOP;
1912 }
1913
1914 if (orig_insn->type == INSN_NOP) {
1915 if (orig_insn->len == 2)
1916 file->jl_nop_short++;
1917 else
1918 file->jl_nop_long++;
1919
1920 return 0;
1921 }
1922
1923 if (orig_insn->len == 2)
1924 file->jl_short++;
1925 else
1926 file->jl_long++;
1927
1928 *new_insn = next_insn_same_sec(file, orig_insn);
1929 return 0;
1930}
1931
1932/*
1933 * Read all the special sections which have alternate instructions which can be
1934 * patched in or redirected to at runtime. Each instruction having alternate
1935 * instruction(s) has them added to its insn->alts list, which will be
1936 * traversed in validate_branch().
1937 */
1938static int add_special_section_alts(struct objtool_file *file)
1939{
1940 struct list_head special_alts;
1941 struct instruction *orig_insn, *new_insn;
1942 struct special_alt *special_alt, *tmp;
1943 struct alternative *alt;
1944 int ret;
1945
1946 ret = special_get_alts(file->elf, &special_alts);
1947 if (ret)
1948 return ret;
1949
1950 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1951
1952 orig_insn = find_insn(file, special_alt->orig_sec,
1953 special_alt->orig_off);
1954 if (!orig_insn) {
1955 WARN_FUNC("special: can't find orig instruction",
1956 special_alt->orig_sec, special_alt->orig_off);
1957 ret = -1;
1958 goto out;
1959 }
1960
1961 new_insn = NULL;
1962 if (!special_alt->group || special_alt->new_len) {
1963 new_insn = find_insn(file, special_alt->new_sec,
1964 special_alt->new_off);
1965 if (!new_insn) {
1966 WARN_FUNC("special: can't find new instruction",
1967 special_alt->new_sec,
1968 special_alt->new_off);
1969 ret = -1;
1970 goto out;
1971 }
1972 }
1973
1974 if (special_alt->group) {
1975 if (!special_alt->orig_len) {
1976 WARN_INSN(orig_insn, "empty alternative entry");
1977 continue;
1978 }
1979
1980 ret = handle_group_alt(file, special_alt, orig_insn,
1981 &new_insn);
1982 if (ret)
1983 goto out;
1984 } else if (special_alt->jump_or_nop) {
1985 ret = handle_jump_alt(file, special_alt, orig_insn,
1986 &new_insn);
1987 if (ret)
1988 goto out;
1989 }
1990
1991 alt = malloc(sizeof(*alt));
1992 if (!alt) {
1993 WARN("malloc failed");
1994 ret = -1;
1995 goto out;
1996 }
1997
1998 alt->insn = new_insn;
1999 alt->skip_orig = special_alt->skip_orig;
2000 orig_insn->ignore_alts |= special_alt->skip_alt;
2001 alt->next = orig_insn->alts;
2002 orig_insn->alts = alt;
2003
2004 list_del(&special_alt->list);
2005 free(special_alt);
2006 }
2007
2008 if (opts.stats) {
2009 printf("jl\\\tNOP\tJMP\n");
2010 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
2011 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
2012 }
2013
2014out:
2015 return ret;
2016}
2017
2018static int add_jump_table(struct objtool_file *file, struct instruction *insn,
2019 struct reloc *next_table)
2020{
2021 struct symbol *pfunc = insn_func(insn)->pfunc;
2022 struct reloc *table = insn_jump_table(insn);
2023 struct instruction *dest_insn;
2024 unsigned int prev_offset = 0;
2025 struct reloc *reloc = table;
2026 struct alternative *alt;
2027
2028 /*
2029 * Each @reloc is a switch table relocation which points to the target
2030 * instruction.
2031 */
2032 for_each_reloc_from(table->sec, reloc) {
2033
2034 /* Check for the end of the table: */
2035 if (reloc != table && reloc == next_table)
2036 break;
2037
2038 /* Make sure the table entries are consecutive: */
2039 if (prev_offset && reloc_offset(reloc) != prev_offset + 8)
2040 break;
2041
2042 /* Detect function pointers from contiguous objects: */
2043 if (reloc->sym->sec == pfunc->sec &&
2044 reloc_addend(reloc) == pfunc->offset)
2045 break;
2046
2047 dest_insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2048 if (!dest_insn)
2049 break;
2050
2051 /* Make sure the destination is in the same function: */
2052 if (!insn_func(dest_insn) || insn_func(dest_insn)->pfunc != pfunc)
2053 break;
2054
2055 alt = malloc(sizeof(*alt));
2056 if (!alt) {
2057 WARN("malloc failed");
2058 return -1;
2059 }
2060
2061 alt->insn = dest_insn;
2062 alt->next = insn->alts;
2063 insn->alts = alt;
2064 prev_offset = reloc_offset(reloc);
2065 }
2066
2067 if (!prev_offset) {
2068 WARN_INSN(insn, "can't find switch jump table");
2069 return -1;
2070 }
2071
2072 return 0;
2073}
2074
2075/*
2076 * find_jump_table() - Given a dynamic jump, find the switch jump table
2077 * associated with it.
2078 */
2079static struct reloc *find_jump_table(struct objtool_file *file,
2080 struct symbol *func,
2081 struct instruction *insn)
2082{
2083 struct reloc *table_reloc;
2084 struct instruction *dest_insn, *orig_insn = insn;
2085
2086 /*
2087 * Backward search using the @first_jump_src links, these help avoid
2088 * much of the 'in between' code. Which avoids us getting confused by
2089 * it.
2090 */
2091 for (;
2092 insn && insn_func(insn) && insn_func(insn)->pfunc == func;
2093 insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
2094
2095 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
2096 break;
2097
2098 /* allow small jumps within the range */
2099 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
2100 insn->jump_dest &&
2101 (insn->jump_dest->offset <= insn->offset ||
2102 insn->jump_dest->offset > orig_insn->offset))
2103 break;
2104
2105 table_reloc = arch_find_switch_table(file, insn);
2106 if (!table_reloc)
2107 continue;
2108 dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
2109 if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
2110 continue;
2111
2112 return table_reloc;
2113 }
2114
2115 return NULL;
2116}
2117
2118/*
2119 * First pass: Mark the head of each jump table so that in the next pass,
2120 * we know when a given jump table ends and the next one starts.
2121 */
2122static void mark_func_jump_tables(struct objtool_file *file,
2123 struct symbol *func)
2124{
2125 struct instruction *insn, *last = NULL;
2126 struct reloc *reloc;
2127
2128 func_for_each_insn(file, func, insn) {
2129 if (!last)
2130 last = insn;
2131
2132 /*
2133 * Store back-pointers for unconditional forward jumps such
2134 * that find_jump_table() can back-track using those and
2135 * avoid some potentially confusing code.
2136 */
2137 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
2138 insn->offset > last->offset &&
2139 insn->jump_dest->offset > insn->offset &&
2140 !insn->jump_dest->first_jump_src) {
2141
2142 insn->jump_dest->first_jump_src = insn;
2143 last = insn->jump_dest;
2144 }
2145
2146 if (insn->type != INSN_JUMP_DYNAMIC)
2147 continue;
2148
2149 reloc = find_jump_table(file, func, insn);
2150 if (reloc)
2151 insn->_jump_table = reloc;
2152 }
2153}
2154
2155static int add_func_jump_tables(struct objtool_file *file,
2156 struct symbol *func)
2157{
2158 struct instruction *insn, *insn_t1 = NULL, *insn_t2;
2159 int ret = 0;
2160
2161 func_for_each_insn(file, func, insn) {
2162 if (!insn_jump_table(insn))
2163 continue;
2164
2165 if (!insn_t1) {
2166 insn_t1 = insn;
2167 continue;
2168 }
2169
2170 insn_t2 = insn;
2171
2172 ret = add_jump_table(file, insn_t1, insn_jump_table(insn_t2));
2173 if (ret)
2174 return ret;
2175
2176 insn_t1 = insn_t2;
2177 }
2178
2179 if (insn_t1)
2180 ret = add_jump_table(file, insn_t1, NULL);
2181
2182 return ret;
2183}
2184
2185/*
2186 * For some switch statements, gcc generates a jump table in the .rodata
2187 * section which contains a list of addresses within the function to jump to.
2188 * This finds these jump tables and adds them to the insn->alts lists.
2189 */
2190static int add_jump_table_alts(struct objtool_file *file)
2191{
2192 struct symbol *func;
2193 int ret;
2194
2195 if (!file->rodata)
2196 return 0;
2197
2198 for_each_sym(file, func) {
2199 if (func->type != STT_FUNC)
2200 continue;
2201
2202 mark_func_jump_tables(file, func);
2203 ret = add_func_jump_tables(file, func);
2204 if (ret)
2205 return ret;
2206 }
2207
2208 return 0;
2209}
2210
2211static void set_func_state(struct cfi_state *state)
2212{
2213 state->cfa = initial_func_cfi.cfa;
2214 memcpy(&state->regs, &initial_func_cfi.regs,
2215 CFI_NUM_REGS * sizeof(struct cfi_reg));
2216 state->stack_size = initial_func_cfi.cfa.offset;
2217 state->type = UNWIND_HINT_TYPE_CALL;
2218}
2219
2220static int read_unwind_hints(struct objtool_file *file)
2221{
2222 struct cfi_state cfi = init_cfi;
2223 struct section *sec;
2224 struct unwind_hint *hint;
2225 struct instruction *insn;
2226 struct reloc *reloc;
2227 int i;
2228
2229 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
2230 if (!sec)
2231 return 0;
2232
2233 if (!sec->rsec) {
2234 WARN("missing .rela.discard.unwind_hints section");
2235 return -1;
2236 }
2237
2238 if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
2239 WARN("struct unwind_hint size mismatch");
2240 return -1;
2241 }
2242
2243 file->hints = true;
2244
2245 for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
2246 hint = (struct unwind_hint *)sec->data->d_buf + i;
2247
2248 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
2249 if (!reloc) {
2250 WARN("can't find reloc for unwind_hints[%d]", i);
2251 return -1;
2252 }
2253
2254 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2255 if (!insn) {
2256 WARN("can't find insn for unwind_hints[%d]", i);
2257 return -1;
2258 }
2259
2260 insn->hint = true;
2261
2262 if (hint->type == UNWIND_HINT_TYPE_UNDEFINED) {
2263 insn->cfi = &force_undefined_cfi;
2264 continue;
2265 }
2266
2267 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
2268 insn->hint = false;
2269 insn->save = true;
2270 continue;
2271 }
2272
2273 if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
2274 insn->restore = true;
2275 continue;
2276 }
2277
2278 if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
2279 struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
2280
2281 if (sym && sym->bind == STB_GLOBAL) {
2282 if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) {
2283 WARN_INSN(insn, "UNWIND_HINT_IRET_REGS without ENDBR");
2284 }
2285 }
2286 }
2287
2288 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
2289 insn->cfi = &func_cfi;
2290 continue;
2291 }
2292
2293 if (insn->cfi)
2294 cfi = *(insn->cfi);
2295
2296 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
2297 WARN_INSN(insn, "unsupported unwind_hint sp base reg %d", hint->sp_reg);
2298 return -1;
2299 }
2300
2301 cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
2302 cfi.type = hint->type;
2303 cfi.signal = hint->signal;
2304
2305 insn->cfi = cfi_hash_find_or_add(&cfi);
2306 }
2307
2308 return 0;
2309}
2310
2311static int read_noendbr_hints(struct objtool_file *file)
2312{
2313 struct instruction *insn;
2314 struct section *rsec;
2315 struct reloc *reloc;
2316
2317 rsec = find_section_by_name(file->elf, ".rela.discard.noendbr");
2318 if (!rsec)
2319 return 0;
2320
2321 for_each_reloc(rsec, reloc) {
2322 insn = find_insn(file, reloc->sym->sec,
2323 reloc->sym->offset + reloc_addend(reloc));
2324 if (!insn) {
2325 WARN("bad .discard.noendbr entry");
2326 return -1;
2327 }
2328
2329 insn->noendbr = 1;
2330 }
2331
2332 return 0;
2333}
2334
2335static int read_retpoline_hints(struct objtool_file *file)
2336{
2337 struct section *rsec;
2338 struct instruction *insn;
2339 struct reloc *reloc;
2340
2341 rsec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
2342 if (!rsec)
2343 return 0;
2344
2345 for_each_reloc(rsec, reloc) {
2346 if (reloc->sym->type != STT_SECTION) {
2347 WARN("unexpected relocation symbol type in %s", rsec->name);
2348 return -1;
2349 }
2350
2351 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2352 if (!insn) {
2353 WARN("bad .discard.retpoline_safe entry");
2354 return -1;
2355 }
2356
2357 if (insn->type != INSN_JUMP_DYNAMIC &&
2358 insn->type != INSN_CALL_DYNAMIC &&
2359 insn->type != INSN_RETURN &&
2360 insn->type != INSN_NOP) {
2361 WARN_INSN(insn, "retpoline_safe hint not an indirect jump/call/ret/nop");
2362 return -1;
2363 }
2364
2365 insn->retpoline_safe = true;
2366 }
2367
2368 return 0;
2369}
2370
2371static int read_instr_hints(struct objtool_file *file)
2372{
2373 struct section *rsec;
2374 struct instruction *insn;
2375 struct reloc *reloc;
2376
2377 rsec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2378 if (!rsec)
2379 return 0;
2380
2381 for_each_reloc(rsec, reloc) {
2382 if (reloc->sym->type != STT_SECTION) {
2383 WARN("unexpected relocation symbol type in %s", rsec->name);
2384 return -1;
2385 }
2386
2387 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2388 if (!insn) {
2389 WARN("bad .discard.instr_end entry");
2390 return -1;
2391 }
2392
2393 insn->instr--;
2394 }
2395
2396 rsec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2397 if (!rsec)
2398 return 0;
2399
2400 for_each_reloc(rsec, reloc) {
2401 if (reloc->sym->type != STT_SECTION) {
2402 WARN("unexpected relocation symbol type in %s", rsec->name);
2403 return -1;
2404 }
2405
2406 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2407 if (!insn) {
2408 WARN("bad .discard.instr_begin entry");
2409 return -1;
2410 }
2411
2412 insn->instr++;
2413 }
2414
2415 return 0;
2416}
2417
2418static int read_validate_unret_hints(struct objtool_file *file)
2419{
2420 struct section *rsec;
2421 struct instruction *insn;
2422 struct reloc *reloc;
2423
2424 rsec = find_section_by_name(file->elf, ".rela.discard.validate_unret");
2425 if (!rsec)
2426 return 0;
2427
2428 for_each_reloc(rsec, reloc) {
2429 if (reloc->sym->type != STT_SECTION) {
2430 WARN("unexpected relocation symbol type in %s", rsec->name);
2431 return -1;
2432 }
2433
2434 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2435 if (!insn) {
2436 WARN("bad .discard.instr_end entry");
2437 return -1;
2438 }
2439 insn->unret = 1;
2440 }
2441
2442 return 0;
2443}
2444
2445
2446static int read_intra_function_calls(struct objtool_file *file)
2447{
2448 struct instruction *insn;
2449 struct section *rsec;
2450 struct reloc *reloc;
2451
2452 rsec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2453 if (!rsec)
2454 return 0;
2455
2456 for_each_reloc(rsec, reloc) {
2457 unsigned long dest_off;
2458
2459 if (reloc->sym->type != STT_SECTION) {
2460 WARN("unexpected relocation symbol type in %s",
2461 rsec->name);
2462 return -1;
2463 }
2464
2465 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2466 if (!insn) {
2467 WARN("bad .discard.intra_function_call entry");
2468 return -1;
2469 }
2470
2471 if (insn->type != INSN_CALL) {
2472 WARN_INSN(insn, "intra_function_call not a direct call");
2473 return -1;
2474 }
2475
2476 /*
2477 * Treat intra-function CALLs as JMPs, but with a stack_op.
2478 * See add_call_destinations(), which strips stack_ops from
2479 * normal CALLs.
2480 */
2481 insn->type = INSN_JUMP_UNCONDITIONAL;
2482
2483 dest_off = arch_jump_destination(insn);
2484 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2485 if (!insn->jump_dest) {
2486 WARN_INSN(insn, "can't find call dest at %s+0x%lx",
2487 insn->sec->name, dest_off);
2488 return -1;
2489 }
2490 }
2491
2492 return 0;
2493}
2494
2495/*
2496 * Return true if name matches an instrumentation function, where calls to that
2497 * function from noinstr code can safely be removed, but compilers won't do so.
2498 */
2499static bool is_profiling_func(const char *name)
2500{
2501 /*
2502 * Many compilers cannot disable KCOV with a function attribute.
2503 */
2504 if (!strncmp(name, "__sanitizer_cov_", 16))
2505 return true;
2506
2507 /*
2508 * Some compilers currently do not remove __tsan_func_entry/exit nor
2509 * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2510 * the __no_sanitize_thread attribute, remove them. Once the kernel's
2511 * minimum Clang version is 14.0, this can be removed.
2512 */
2513 if (!strncmp(name, "__tsan_func_", 12) ||
2514 !strcmp(name, "__tsan_atomic_signal_fence"))
2515 return true;
2516
2517 return false;
2518}
2519
2520static int classify_symbols(struct objtool_file *file)
2521{
2522 struct symbol *func;
2523
2524 for_each_sym(file, func) {
2525 if (func->bind != STB_GLOBAL)
2526 continue;
2527
2528 if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2529 strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2530 func->static_call_tramp = true;
2531
2532 if (arch_is_retpoline(func))
2533 func->retpoline_thunk = true;
2534
2535 if (arch_is_rethunk(func))
2536 func->return_thunk = true;
2537
2538 if (arch_is_embedded_insn(func))
2539 func->embedded_insn = true;
2540
2541 if (arch_ftrace_match(func->name))
2542 func->fentry = true;
2543
2544 if (is_profiling_func(func->name))
2545 func->profiling_func = true;
2546 }
2547
2548 return 0;
2549}
2550
2551static void mark_rodata(struct objtool_file *file)
2552{
2553 struct section *sec;
2554 bool found = false;
2555
2556 /*
2557 * Search for the following rodata sections, each of which can
2558 * potentially contain jump tables:
2559 *
2560 * - .rodata: can contain GCC switch tables
2561 * - .rodata.<func>: same, if -fdata-sections is being used
2562 * - .rodata..c_jump_table: contains C annotated jump tables
2563 *
2564 * .rodata.str1.* sections are ignored; they don't contain jump tables.
2565 */
2566 for_each_sec(file, sec) {
2567 if (!strncmp(sec->name, ".rodata", 7) &&
2568 !strstr(sec->name, ".str1.")) {
2569 sec->rodata = true;
2570 found = true;
2571 }
2572 }
2573
2574 file->rodata = found;
2575}
2576
2577static int decode_sections(struct objtool_file *file)
2578{
2579 int ret;
2580
2581 mark_rodata(file);
2582
2583 ret = init_pv_ops(file);
2584 if (ret)
2585 return ret;
2586
2587 /*
2588 * Must be before add_{jump_call}_destination.
2589 */
2590 ret = classify_symbols(file);
2591 if (ret)
2592 return ret;
2593
2594 ret = decode_instructions(file);
2595 if (ret)
2596 return ret;
2597
2598 add_ignores(file);
2599 add_uaccess_safe(file);
2600
2601 ret = add_ignore_alternatives(file);
2602 if (ret)
2603 return ret;
2604
2605 /*
2606 * Must be before read_unwind_hints() since that needs insn->noendbr.
2607 */
2608 ret = read_noendbr_hints(file);
2609 if (ret)
2610 return ret;
2611
2612 /*
2613 * Must be before add_jump_destinations(), which depends on 'func'
2614 * being set for alternatives, to enable proper sibling call detection.
2615 */
2616 if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) {
2617 ret = add_special_section_alts(file);
2618 if (ret)
2619 return ret;
2620 }
2621
2622 ret = add_jump_destinations(file);
2623 if (ret)
2624 return ret;
2625
2626 /*
2627 * Must be before add_call_destination(); it changes INSN_CALL to
2628 * INSN_JUMP.
2629 */
2630 ret = read_intra_function_calls(file);
2631 if (ret)
2632 return ret;
2633
2634 ret = add_call_destinations(file);
2635 if (ret)
2636 return ret;
2637
2638 /*
2639 * Must be after add_call_destinations() such that it can override
2640 * dead_end_function() marks.
2641 */
2642 ret = add_dead_ends(file);
2643 if (ret)
2644 return ret;
2645
2646 ret = add_jump_table_alts(file);
2647 if (ret)
2648 return ret;
2649
2650 ret = read_unwind_hints(file);
2651 if (ret)
2652 return ret;
2653
2654 ret = read_retpoline_hints(file);
2655 if (ret)
2656 return ret;
2657
2658 ret = read_instr_hints(file);
2659 if (ret)
2660 return ret;
2661
2662 ret = read_validate_unret_hints(file);
2663 if (ret)
2664 return ret;
2665
2666 return 0;
2667}
2668
2669static bool is_special_call(struct instruction *insn)
2670{
2671 if (insn->type == INSN_CALL) {
2672 struct symbol *dest = insn_call_dest(insn);
2673
2674 if (!dest)
2675 return false;
2676
2677 if (dest->fentry || dest->embedded_insn)
2678 return true;
2679 }
2680
2681 return false;
2682}
2683
2684static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2685{
2686 struct cfi_state *cfi = &state->cfi;
2687 int i;
2688
2689 if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2690 return true;
2691
2692 if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2693 return true;
2694
2695 if (cfi->stack_size != initial_func_cfi.cfa.offset)
2696 return true;
2697
2698 for (i = 0; i < CFI_NUM_REGS; i++) {
2699 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2700 cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2701 return true;
2702 }
2703
2704 return false;
2705}
2706
2707static bool check_reg_frame_pos(const struct cfi_reg *reg,
2708 int expected_offset)
2709{
2710 return reg->base == CFI_CFA &&
2711 reg->offset == expected_offset;
2712}
2713
2714static bool has_valid_stack_frame(struct insn_state *state)
2715{
2716 struct cfi_state *cfi = &state->cfi;
2717
2718 if (cfi->cfa.base == CFI_BP &&
2719 check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2720 check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2721 return true;
2722
2723 if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2724 return true;
2725
2726 return false;
2727}
2728
2729static int update_cfi_state_regs(struct instruction *insn,
2730 struct cfi_state *cfi,
2731 struct stack_op *op)
2732{
2733 struct cfi_reg *cfa = &cfi->cfa;
2734
2735 if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2736 return 0;
2737
2738 /* push */
2739 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2740 cfa->offset += 8;
2741
2742 /* pop */
2743 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2744 cfa->offset -= 8;
2745
2746 /* add immediate to sp */
2747 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2748 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2749 cfa->offset -= op->src.offset;
2750
2751 return 0;
2752}
2753
2754static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2755{
2756 if (arch_callee_saved_reg(reg) &&
2757 cfi->regs[reg].base == CFI_UNDEFINED) {
2758 cfi->regs[reg].base = base;
2759 cfi->regs[reg].offset = offset;
2760 }
2761}
2762
2763static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2764{
2765 cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2766 cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2767}
2768
2769/*
2770 * A note about DRAP stack alignment:
2771 *
2772 * GCC has the concept of a DRAP register, which is used to help keep track of
2773 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
2774 * register. The typical DRAP pattern is:
2775 *
2776 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
2777 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
2778 * 41 ff 72 f8 pushq -0x8(%r10)
2779 * 55 push %rbp
2780 * 48 89 e5 mov %rsp,%rbp
2781 * (more pushes)
2782 * 41 52 push %r10
2783 * ...
2784 * 41 5a pop %r10
2785 * (more pops)
2786 * 5d pop %rbp
2787 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2788 * c3 retq
2789 *
2790 * There are some variations in the epilogues, like:
2791 *
2792 * 5b pop %rbx
2793 * 41 5a pop %r10
2794 * 41 5c pop %r12
2795 * 41 5d pop %r13
2796 * 41 5e pop %r14
2797 * c9 leaveq
2798 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2799 * c3 retq
2800 *
2801 * and:
2802 *
2803 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
2804 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
2805 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
2806 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
2807 * c9 leaveq
2808 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2809 * c3 retq
2810 *
2811 * Sometimes r13 is used as the DRAP register, in which case it's saved and
2812 * restored beforehand:
2813 *
2814 * 41 55 push %r13
2815 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
2816 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
2817 * ...
2818 * 49 8d 65 f0 lea -0x10(%r13),%rsp
2819 * 41 5d pop %r13
2820 * c3 retq
2821 */
2822static int update_cfi_state(struct instruction *insn,
2823 struct instruction *next_insn,
2824 struct cfi_state *cfi, struct stack_op *op)
2825{
2826 struct cfi_reg *cfa = &cfi->cfa;
2827 struct cfi_reg *regs = cfi->regs;
2828
2829 /* ignore UNWIND_HINT_UNDEFINED regions */
2830 if (cfi->force_undefined)
2831 return 0;
2832
2833 /* stack operations don't make sense with an undefined CFA */
2834 if (cfa->base == CFI_UNDEFINED) {
2835 if (insn_func(insn)) {
2836 WARN_INSN(insn, "undefined stack state");
2837 return -1;
2838 }
2839 return 0;
2840 }
2841
2842 if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2843 cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2844 return update_cfi_state_regs(insn, cfi, op);
2845
2846 switch (op->dest.type) {
2847
2848 case OP_DEST_REG:
2849 switch (op->src.type) {
2850
2851 case OP_SRC_REG:
2852 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2853 cfa->base == CFI_SP &&
2854 check_reg_frame_pos(®s[CFI_BP], -cfa->offset)) {
2855
2856 /* mov %rsp, %rbp */
2857 cfa->base = op->dest.reg;
2858 cfi->bp_scratch = false;
2859 }
2860
2861 else if (op->src.reg == CFI_SP &&
2862 op->dest.reg == CFI_BP && cfi->drap) {
2863
2864 /* drap: mov %rsp, %rbp */
2865 regs[CFI_BP].base = CFI_BP;
2866 regs[CFI_BP].offset = -cfi->stack_size;
2867 cfi->bp_scratch = false;
2868 }
2869
2870 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2871
2872 /*
2873 * mov %rsp, %reg
2874 *
2875 * This is needed for the rare case where GCC
2876 * does:
2877 *
2878 * mov %rsp, %rax
2879 * ...
2880 * mov %rax, %rsp
2881 */
2882 cfi->vals[op->dest.reg].base = CFI_CFA;
2883 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2884 }
2885
2886 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2887 (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2888
2889 /*
2890 * mov %rbp, %rsp
2891 *
2892 * Restore the original stack pointer (Clang).
2893 */
2894 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2895 }
2896
2897 else if (op->dest.reg == cfa->base) {
2898
2899 /* mov %reg, %rsp */
2900 if (cfa->base == CFI_SP &&
2901 cfi->vals[op->src.reg].base == CFI_CFA) {
2902
2903 /*
2904 * This is needed for the rare case
2905 * where GCC does something dumb like:
2906 *
2907 * lea 0x8(%rsp), %rcx
2908 * ...
2909 * mov %rcx, %rsp
2910 */
2911 cfa->offset = -cfi->vals[op->src.reg].offset;
2912 cfi->stack_size = cfa->offset;
2913
2914 } else if (cfa->base == CFI_SP &&
2915 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2916 cfi->vals[op->src.reg].offset == cfa->offset) {
2917
2918 /*
2919 * Stack swizzle:
2920 *
2921 * 1: mov %rsp, (%[tos])
2922 * 2: mov %[tos], %rsp
2923 * ...
2924 * 3: pop %rsp
2925 *
2926 * Where:
2927 *
2928 * 1 - places a pointer to the previous
2929 * stack at the Top-of-Stack of the
2930 * new stack.
2931 *
2932 * 2 - switches to the new stack.
2933 *
2934 * 3 - pops the Top-of-Stack to restore
2935 * the original stack.
2936 *
2937 * Note: we set base to SP_INDIRECT
2938 * here and preserve offset. Therefore
2939 * when the unwinder reaches ToS it
2940 * will dereference SP and then add the
2941 * offset to find the next frame, IOW:
2942 * (%rsp) + offset.
2943 */
2944 cfa->base = CFI_SP_INDIRECT;
2945
2946 } else {
2947 cfa->base = CFI_UNDEFINED;
2948 cfa->offset = 0;
2949 }
2950 }
2951
2952 else if (op->dest.reg == CFI_SP &&
2953 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2954 cfi->vals[op->src.reg].offset == cfa->offset) {
2955
2956 /*
2957 * The same stack swizzle case 2) as above. But
2958 * because we can't change cfa->base, case 3)
2959 * will become a regular POP. Pretend we're a
2960 * PUSH so things don't go unbalanced.
2961 */
2962 cfi->stack_size += 8;
2963 }
2964
2965
2966 break;
2967
2968 case OP_SRC_ADD:
2969 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2970
2971 /* add imm, %rsp */
2972 cfi->stack_size -= op->src.offset;
2973 if (cfa->base == CFI_SP)
2974 cfa->offset -= op->src.offset;
2975 break;
2976 }
2977
2978 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2979
2980 /* lea disp(%rbp), %rsp */
2981 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2982 break;
2983 }
2984
2985 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2986
2987 /* drap: lea disp(%rsp), %drap */
2988 cfi->drap_reg = op->dest.reg;
2989
2990 /*
2991 * lea disp(%rsp), %reg
2992 *
2993 * This is needed for the rare case where GCC
2994 * does something dumb like:
2995 *
2996 * lea 0x8(%rsp), %rcx
2997 * ...
2998 * mov %rcx, %rsp
2999 */
3000 cfi->vals[op->dest.reg].base = CFI_CFA;
3001 cfi->vals[op->dest.reg].offset = \
3002 -cfi->stack_size + op->src.offset;
3003
3004 break;
3005 }
3006
3007 if (cfi->drap && op->dest.reg == CFI_SP &&
3008 op->src.reg == cfi->drap_reg) {
3009
3010 /* drap: lea disp(%drap), %rsp */
3011 cfa->base = CFI_SP;
3012 cfa->offset = cfi->stack_size = -op->src.offset;
3013 cfi->drap_reg = CFI_UNDEFINED;
3014 cfi->drap = false;
3015 break;
3016 }
3017
3018 if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
3019 WARN_INSN(insn, "unsupported stack register modification");
3020 return -1;
3021 }
3022
3023 break;
3024
3025 case OP_SRC_AND:
3026 if (op->dest.reg != CFI_SP ||
3027 (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
3028 (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
3029 WARN_INSN(insn, "unsupported stack pointer realignment");
3030 return -1;
3031 }
3032
3033 if (cfi->drap_reg != CFI_UNDEFINED) {
3034 /* drap: and imm, %rsp */
3035 cfa->base = cfi->drap_reg;
3036 cfa->offset = cfi->stack_size = 0;
3037 cfi->drap = true;
3038 }
3039
3040 /*
3041 * Older versions of GCC (4.8ish) realign the stack
3042 * without DRAP, with a frame pointer.
3043 */
3044
3045 break;
3046
3047 case OP_SRC_POP:
3048 case OP_SRC_POPF:
3049 if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
3050
3051 /* pop %rsp; # restore from a stack swizzle */
3052 cfa->base = CFI_SP;
3053 break;
3054 }
3055
3056 if (!cfi->drap && op->dest.reg == cfa->base) {
3057
3058 /* pop %rbp */
3059 cfa->base = CFI_SP;
3060 }
3061
3062 if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
3063 op->dest.reg == cfi->drap_reg &&
3064 cfi->drap_offset == -cfi->stack_size) {
3065
3066 /* drap: pop %drap */
3067 cfa->base = cfi->drap_reg;
3068 cfa->offset = 0;
3069 cfi->drap_offset = -1;
3070
3071 } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
3072
3073 /* pop %reg */
3074 restore_reg(cfi, op->dest.reg);
3075 }
3076
3077 cfi->stack_size -= 8;
3078 if (cfa->base == CFI_SP)
3079 cfa->offset -= 8;
3080
3081 break;
3082
3083 case OP_SRC_REG_INDIRECT:
3084 if (!cfi->drap && op->dest.reg == cfa->base &&
3085 op->dest.reg == CFI_BP) {
3086
3087 /* mov disp(%rsp), %rbp */
3088 cfa->base = CFI_SP;
3089 cfa->offset = cfi->stack_size;
3090 }
3091
3092 if (cfi->drap && op->src.reg == CFI_BP &&
3093 op->src.offset == cfi->drap_offset) {
3094
3095 /* drap: mov disp(%rbp), %drap */
3096 cfa->base = cfi->drap_reg;
3097 cfa->offset = 0;
3098 cfi->drap_offset = -1;
3099 }
3100
3101 if (cfi->drap && op->src.reg == CFI_BP &&
3102 op->src.offset == regs[op->dest.reg].offset) {
3103
3104 /* drap: mov disp(%rbp), %reg */
3105 restore_reg(cfi, op->dest.reg);
3106
3107 } else if (op->src.reg == cfa->base &&
3108 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
3109
3110 /* mov disp(%rbp), %reg */
3111 /* mov disp(%rsp), %reg */
3112 restore_reg(cfi, op->dest.reg);
3113
3114 } else if (op->src.reg == CFI_SP &&
3115 op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
3116
3117 /* mov disp(%rsp), %reg */
3118 restore_reg(cfi, op->dest.reg);
3119 }
3120
3121 break;
3122
3123 default:
3124 WARN_INSN(insn, "unknown stack-related instruction");
3125 return -1;
3126 }
3127
3128 break;
3129
3130 case OP_DEST_PUSH:
3131 case OP_DEST_PUSHF:
3132 cfi->stack_size += 8;
3133 if (cfa->base == CFI_SP)
3134 cfa->offset += 8;
3135
3136 if (op->src.type != OP_SRC_REG)
3137 break;
3138
3139 if (cfi->drap) {
3140 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3141
3142 /* drap: push %drap */
3143 cfa->base = CFI_BP_INDIRECT;
3144 cfa->offset = -cfi->stack_size;
3145
3146 /* save drap so we know when to restore it */
3147 cfi->drap_offset = -cfi->stack_size;
3148
3149 } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
3150
3151 /* drap: push %rbp */
3152 cfi->stack_size = 0;
3153
3154 } else {
3155
3156 /* drap: push %reg */
3157 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
3158 }
3159
3160 } else {
3161
3162 /* push %reg */
3163 save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
3164 }
3165
3166 /* detect when asm code uses rbp as a scratch register */
3167 if (opts.stackval && insn_func(insn) && op->src.reg == CFI_BP &&
3168 cfa->base != CFI_BP)
3169 cfi->bp_scratch = true;
3170 break;
3171
3172 case OP_DEST_REG_INDIRECT:
3173
3174 if (cfi->drap) {
3175 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3176
3177 /* drap: mov %drap, disp(%rbp) */
3178 cfa->base = CFI_BP_INDIRECT;
3179 cfa->offset = op->dest.offset;
3180
3181 /* save drap offset so we know when to restore it */
3182 cfi->drap_offset = op->dest.offset;
3183 } else {
3184
3185 /* drap: mov reg, disp(%rbp) */
3186 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
3187 }
3188
3189 } else if (op->dest.reg == cfa->base) {
3190
3191 /* mov reg, disp(%rbp) */
3192 /* mov reg, disp(%rsp) */
3193 save_reg(cfi, op->src.reg, CFI_CFA,
3194 op->dest.offset - cfi->cfa.offset);
3195
3196 } else if (op->dest.reg == CFI_SP) {
3197
3198 /* mov reg, disp(%rsp) */
3199 save_reg(cfi, op->src.reg, CFI_CFA,
3200 op->dest.offset - cfi->stack_size);
3201
3202 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
3203
3204 /* mov %rsp, (%reg); # setup a stack swizzle. */
3205 cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
3206 cfi->vals[op->dest.reg].offset = cfa->offset;
3207 }
3208
3209 break;
3210
3211 case OP_DEST_MEM:
3212 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
3213 WARN_INSN(insn, "unknown stack-related memory operation");
3214 return -1;
3215 }
3216
3217 /* pop mem */
3218 cfi->stack_size -= 8;
3219 if (cfa->base == CFI_SP)
3220 cfa->offset -= 8;
3221
3222 break;
3223
3224 default:
3225 WARN_INSN(insn, "unknown stack-related instruction");
3226 return -1;
3227 }
3228
3229 return 0;
3230}
3231
3232/*
3233 * The stack layouts of alternatives instructions can sometimes diverge when
3234 * they have stack modifications. That's fine as long as the potential stack
3235 * layouts don't conflict at any given potential instruction boundary.
3236 *
3237 * Flatten the CFIs of the different alternative code streams (both original
3238 * and replacement) into a single shared CFI array which can be used to detect
3239 * conflicts and nicely feed a linear array of ORC entries to the unwinder.
3240 */
3241static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
3242{
3243 struct cfi_state **alt_cfi;
3244 int group_off;
3245
3246 if (!insn->alt_group)
3247 return 0;
3248
3249 if (!insn->cfi) {
3250 WARN("CFI missing");
3251 return -1;
3252 }
3253
3254 alt_cfi = insn->alt_group->cfi;
3255 group_off = insn->offset - insn->alt_group->first_insn->offset;
3256
3257 if (!alt_cfi[group_off]) {
3258 alt_cfi[group_off] = insn->cfi;
3259 } else {
3260 if (cficmp(alt_cfi[group_off], insn->cfi)) {
3261 struct alt_group *orig_group = insn->alt_group->orig_group ?: insn->alt_group;
3262 struct instruction *orig = orig_group->first_insn;
3263 char *where = offstr(insn->sec, insn->offset);
3264 WARN_INSN(orig, "stack layout conflict in alternatives: %s", where);
3265 free(where);
3266 return -1;
3267 }
3268 }
3269
3270 return 0;
3271}
3272
3273static int handle_insn_ops(struct instruction *insn,
3274 struct instruction *next_insn,
3275 struct insn_state *state)
3276{
3277 struct stack_op *op;
3278
3279 for (op = insn->stack_ops; op; op = op->next) {
3280
3281 if (update_cfi_state(insn, next_insn, &state->cfi, op))
3282 return 1;
3283
3284 if (!insn->alt_group)
3285 continue;
3286
3287 if (op->dest.type == OP_DEST_PUSHF) {
3288 if (!state->uaccess_stack) {
3289 state->uaccess_stack = 1;
3290 } else if (state->uaccess_stack >> 31) {
3291 WARN_INSN(insn, "PUSHF stack exhausted");
3292 return 1;
3293 }
3294 state->uaccess_stack <<= 1;
3295 state->uaccess_stack |= state->uaccess;
3296 }
3297
3298 if (op->src.type == OP_SRC_POPF) {
3299 if (state->uaccess_stack) {
3300 state->uaccess = state->uaccess_stack & 1;
3301 state->uaccess_stack >>= 1;
3302 if (state->uaccess_stack == 1)
3303 state->uaccess_stack = 0;
3304 }
3305 }
3306 }
3307
3308 return 0;
3309}
3310
3311static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
3312{
3313 struct cfi_state *cfi1 = insn->cfi;
3314 int i;
3315
3316 if (!cfi1) {
3317 WARN("CFI missing");
3318 return false;
3319 }
3320
3321 if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
3322
3323 WARN_INSN(insn, "stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
3324 cfi1->cfa.base, cfi1->cfa.offset,
3325 cfi2->cfa.base, cfi2->cfa.offset);
3326
3327 } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
3328 for (i = 0; i < CFI_NUM_REGS; i++) {
3329 if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
3330 sizeof(struct cfi_reg)))
3331 continue;
3332
3333 WARN_INSN(insn, "stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
3334 i, cfi1->regs[i].base, cfi1->regs[i].offset,
3335 i, cfi2->regs[i].base, cfi2->regs[i].offset);
3336 break;
3337 }
3338
3339 } else if (cfi1->type != cfi2->type) {
3340
3341 WARN_INSN(insn, "stack state mismatch: type1=%d type2=%d",
3342 cfi1->type, cfi2->type);
3343
3344 } else if (cfi1->drap != cfi2->drap ||
3345 (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
3346 (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
3347
3348 WARN_INSN(insn, "stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
3349 cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
3350 cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
3351
3352 } else
3353 return true;
3354
3355 return false;
3356}
3357
3358static inline bool func_uaccess_safe(struct symbol *func)
3359{
3360 if (func)
3361 return func->uaccess_safe;
3362
3363 return false;
3364}
3365
3366static inline const char *call_dest_name(struct instruction *insn)
3367{
3368 static char pvname[19];
3369 struct reloc *reloc;
3370 int idx;
3371
3372 if (insn_call_dest(insn))
3373 return insn_call_dest(insn)->name;
3374
3375 reloc = insn_reloc(NULL, insn);
3376 if (reloc && !strcmp(reloc->sym->name, "pv_ops")) {
3377 idx = (reloc_addend(reloc) / sizeof(void *));
3378 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
3379 return pvname;
3380 }
3381
3382 return "{dynamic}";
3383}
3384
3385static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3386{
3387 struct symbol *target;
3388 struct reloc *reloc;
3389 int idx;
3390
3391 reloc = insn_reloc(file, insn);
3392 if (!reloc || strcmp(reloc->sym->name, "pv_ops"))
3393 return false;
3394
3395 idx = (arch_dest_reloc_offset(reloc_addend(reloc)) / sizeof(void *));
3396
3397 if (file->pv_ops[idx].clean)
3398 return true;
3399
3400 file->pv_ops[idx].clean = true;
3401
3402 list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3403 if (!target->sec->noinstr) {
3404 WARN("pv_ops[%d]: %s", idx, target->name);
3405 file->pv_ops[idx].clean = false;
3406 }
3407 }
3408
3409 return file->pv_ops[idx].clean;
3410}
3411
3412static inline bool noinstr_call_dest(struct objtool_file *file,
3413 struct instruction *insn,
3414 struct symbol *func)
3415{
3416 /*
3417 * We can't deal with indirect function calls at present;
3418 * assume they're instrumented.
3419 */
3420 if (!func) {
3421 if (file->pv_ops)
3422 return pv_call_dest(file, insn);
3423
3424 return false;
3425 }
3426
3427 /*
3428 * If the symbol is from a noinstr section; we good.
3429 */
3430 if (func->sec->noinstr)
3431 return true;
3432
3433 /*
3434 * If the symbol is a static_call trampoline, we can't tell.
3435 */
3436 if (func->static_call_tramp)
3437 return true;
3438
3439 /*
3440 * The __ubsan_handle_*() calls are like WARN(), they only happen when
3441 * something 'BAD' happened. At the risk of taking the machine down,
3442 * let them proceed to get the message out.
3443 */
3444 if (!strncmp(func->name, "__ubsan_handle_", 15))
3445 return true;
3446
3447 return false;
3448}
3449
3450static int validate_call(struct objtool_file *file,
3451 struct instruction *insn,
3452 struct insn_state *state)
3453{
3454 if (state->noinstr && state->instr <= 0 &&
3455 !noinstr_call_dest(file, insn, insn_call_dest(insn))) {
3456 WARN_INSN(insn, "call to %s() leaves .noinstr.text section", call_dest_name(insn));
3457 return 1;
3458 }
3459
3460 if (state->uaccess && !func_uaccess_safe(insn_call_dest(insn))) {
3461 WARN_INSN(insn, "call to %s() with UACCESS enabled", call_dest_name(insn));
3462 return 1;
3463 }
3464
3465 if (state->df) {
3466 WARN_INSN(insn, "call to %s() with DF set", call_dest_name(insn));
3467 return 1;
3468 }
3469
3470 return 0;
3471}
3472
3473static int validate_sibling_call(struct objtool_file *file,
3474 struct instruction *insn,
3475 struct insn_state *state)
3476{
3477 if (insn_func(insn) && has_modified_stack_frame(insn, state)) {
3478 WARN_INSN(insn, "sibling call from callable instruction with modified stack frame");
3479 return 1;
3480 }
3481
3482 return validate_call(file, insn, state);
3483}
3484
3485static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3486{
3487 if (state->noinstr && state->instr > 0) {
3488 WARN_INSN(insn, "return with instrumentation enabled");
3489 return 1;
3490 }
3491
3492 if (state->uaccess && !func_uaccess_safe(func)) {
3493 WARN_INSN(insn, "return with UACCESS enabled");
3494 return 1;
3495 }
3496
3497 if (!state->uaccess && func_uaccess_safe(func)) {
3498 WARN_INSN(insn, "return with UACCESS disabled from a UACCESS-safe function");
3499 return 1;
3500 }
3501
3502 if (state->df) {
3503 WARN_INSN(insn, "return with DF set");
3504 return 1;
3505 }
3506
3507 if (func && has_modified_stack_frame(insn, state)) {
3508 WARN_INSN(insn, "return with modified stack frame");
3509 return 1;
3510 }
3511
3512 if (state->cfi.bp_scratch) {
3513 WARN_INSN(insn, "BP used as a scratch register");
3514 return 1;
3515 }
3516
3517 return 0;
3518}
3519
3520static struct instruction *next_insn_to_validate(struct objtool_file *file,
3521 struct instruction *insn)
3522{
3523 struct alt_group *alt_group = insn->alt_group;
3524
3525 /*
3526 * Simulate the fact that alternatives are patched in-place. When the
3527 * end of a replacement alt_group is reached, redirect objtool flow to
3528 * the end of the original alt_group.
3529 *
3530 * insn->alts->insn -> alt_group->first_insn
3531 * ...
3532 * alt_group->last_insn
3533 * [alt_group->nop] -> next(orig_group->last_insn)
3534 */
3535 if (alt_group) {
3536 if (alt_group->nop) {
3537 /* ->nop implies ->orig_group */
3538 if (insn == alt_group->last_insn)
3539 return alt_group->nop;
3540 if (insn == alt_group->nop)
3541 goto next_orig;
3542 }
3543 if (insn == alt_group->last_insn && alt_group->orig_group)
3544 goto next_orig;
3545 }
3546
3547 return next_insn_same_sec(file, insn);
3548
3549next_orig:
3550 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3551}
3552
3553/*
3554 * Follow the branch starting at the given instruction, and recursively follow
3555 * any other branches (jumps). Meanwhile, track the frame pointer state at
3556 * each instruction and validate all the rules described in
3557 * tools/objtool/Documentation/objtool.txt.
3558 */
3559static int validate_branch(struct objtool_file *file, struct symbol *func,
3560 struct instruction *insn, struct insn_state state)
3561{
3562 struct alternative *alt;
3563 struct instruction *next_insn, *prev_insn = NULL;
3564 struct section *sec;
3565 u8 visited;
3566 int ret;
3567
3568 sec = insn->sec;
3569
3570 while (1) {
3571 next_insn = next_insn_to_validate(file, insn);
3572
3573 if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {
3574 /* Ignore KCFI type preambles, which always fall through */
3575 if (!strncmp(func->name, "__cfi_", 6) ||
3576 !strncmp(func->name, "__pfx_", 6))
3577 return 0;
3578
3579 WARN("%s() falls through to next function %s()",
3580 func->name, insn_func(insn)->name);
3581 return 1;
3582 }
3583
3584 if (func && insn->ignore) {
3585 WARN_INSN(insn, "BUG: why am I validating an ignored function?");
3586 return 1;
3587 }
3588
3589 visited = VISITED_BRANCH << state.uaccess;
3590 if (insn->visited & VISITED_BRANCH_MASK) {
3591 if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3592 return 1;
3593
3594 if (insn->visited & visited)
3595 return 0;
3596 } else {
3597 nr_insns_visited++;
3598 }
3599
3600 if (state.noinstr)
3601 state.instr += insn->instr;
3602
3603 if (insn->hint) {
3604 if (insn->restore) {
3605 struct instruction *save_insn, *i;
3606
3607 i = insn;
3608 save_insn = NULL;
3609
3610 sym_for_each_insn_continue_reverse(file, func, i) {
3611 if (i->save) {
3612 save_insn = i;
3613 break;
3614 }
3615 }
3616
3617 if (!save_insn) {
3618 WARN_INSN(insn, "no corresponding CFI save for CFI restore");
3619 return 1;
3620 }
3621
3622 if (!save_insn->visited) {
3623 WARN_INSN(insn, "objtool isn't smart enough to handle this CFI save/restore combo");
3624 return 1;
3625 }
3626
3627 insn->cfi = save_insn->cfi;
3628 nr_cfi_reused++;
3629 }
3630
3631 state.cfi = *insn->cfi;
3632 } else {
3633 /* XXX track if we actually changed state.cfi */
3634
3635 if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3636 insn->cfi = prev_insn->cfi;
3637 nr_cfi_reused++;
3638 } else {
3639 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3640 }
3641 }
3642
3643 insn->visited |= visited;
3644
3645 if (propagate_alt_cfi(file, insn))
3646 return 1;
3647
3648 if (!insn->ignore_alts && insn->alts) {
3649 bool skip_orig = false;
3650
3651 for (alt = insn->alts; alt; alt = alt->next) {
3652 if (alt->skip_orig)
3653 skip_orig = true;
3654
3655 ret = validate_branch(file, func, alt->insn, state);
3656 if (ret) {
3657 BT_INSN(insn, "(alt)");
3658 return ret;
3659 }
3660 }
3661
3662 if (skip_orig)
3663 return 0;
3664 }
3665
3666 if (handle_insn_ops(insn, next_insn, &state))
3667 return 1;
3668
3669 switch (insn->type) {
3670
3671 case INSN_RETURN:
3672 return validate_return(func, insn, &state);
3673
3674 case INSN_CALL:
3675 case INSN_CALL_DYNAMIC:
3676 ret = validate_call(file, insn, &state);
3677 if (ret)
3678 return ret;
3679
3680 if (opts.stackval && func && !is_special_call(insn) &&
3681 !has_valid_stack_frame(&state)) {
3682 WARN_INSN(insn, "call without frame pointer save/setup");
3683 return 1;
3684 }
3685
3686 if (insn->dead_end)
3687 return 0;
3688
3689 break;
3690
3691 case INSN_JUMP_CONDITIONAL:
3692 case INSN_JUMP_UNCONDITIONAL:
3693 if (is_sibling_call(insn)) {
3694 ret = validate_sibling_call(file, insn, &state);
3695 if (ret)
3696 return ret;
3697
3698 } else if (insn->jump_dest) {
3699 ret = validate_branch(file, func,
3700 insn->jump_dest, state);
3701 if (ret) {
3702 BT_INSN(insn, "(branch)");
3703 return ret;
3704 }
3705 }
3706
3707 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3708 return 0;
3709
3710 break;
3711
3712 case INSN_JUMP_DYNAMIC:
3713 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3714 if (is_sibling_call(insn)) {
3715 ret = validate_sibling_call(file, insn, &state);
3716 if (ret)
3717 return ret;
3718 }
3719
3720 if (insn->type == INSN_JUMP_DYNAMIC)
3721 return 0;
3722
3723 break;
3724
3725 case INSN_CONTEXT_SWITCH:
3726 if (func && (!next_insn || !next_insn->hint)) {
3727 WARN_INSN(insn, "unsupported instruction in callable function");
3728 return 1;
3729 }
3730 return 0;
3731
3732 case INSN_STAC:
3733 if (state.uaccess) {
3734 WARN_INSN(insn, "recursive UACCESS enable");
3735 return 1;
3736 }
3737
3738 state.uaccess = true;
3739 break;
3740
3741 case INSN_CLAC:
3742 if (!state.uaccess && func) {
3743 WARN_INSN(insn, "redundant UACCESS disable");
3744 return 1;
3745 }
3746
3747 if (func_uaccess_safe(func) && !state.uaccess_stack) {
3748 WARN_INSN(insn, "UACCESS-safe disables UACCESS");
3749 return 1;
3750 }
3751
3752 state.uaccess = false;
3753 break;
3754
3755 case INSN_STD:
3756 if (state.df) {
3757 WARN_INSN(insn, "recursive STD");
3758 return 1;
3759 }
3760
3761 state.df = true;
3762 break;
3763
3764 case INSN_CLD:
3765 if (!state.df && func) {
3766 WARN_INSN(insn, "redundant CLD");
3767 return 1;
3768 }
3769
3770 state.df = false;
3771 break;
3772
3773 default:
3774 break;
3775 }
3776
3777 if (insn->dead_end)
3778 return 0;
3779
3780 if (!next_insn) {
3781 if (state.cfi.cfa.base == CFI_UNDEFINED)
3782 return 0;
3783 WARN("%s: unexpected end of section", sec->name);
3784 return 1;
3785 }
3786
3787 prev_insn = insn;
3788 insn = next_insn;
3789 }
3790
3791 return 0;
3792}
3793
3794static int validate_unwind_hint(struct objtool_file *file,
3795 struct instruction *insn,
3796 struct insn_state *state)
3797{
3798 if (insn->hint && !insn->visited && !insn->ignore) {
3799 int ret = validate_branch(file, insn_func(insn), insn, *state);
3800 if (ret)
3801 BT_INSN(insn, "<=== (hint)");
3802 return ret;
3803 }
3804
3805 return 0;
3806}
3807
3808static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3809{
3810 struct instruction *insn;
3811 struct insn_state state;
3812 int warnings = 0;
3813
3814 if (!file->hints)
3815 return 0;
3816
3817 init_insn_state(file, &state, sec);
3818
3819 if (sec) {
3820 sec_for_each_insn(file, sec, insn)
3821 warnings += validate_unwind_hint(file, insn, &state);
3822 } else {
3823 for_each_insn(file, insn)
3824 warnings += validate_unwind_hint(file, insn, &state);
3825 }
3826
3827 return warnings;
3828}
3829
3830/*
3831 * Validate rethunk entry constraint: must untrain RET before the first RET.
3832 *
3833 * Follow every branch (intra-function) and ensure VALIDATE_UNRET_END comes
3834 * before an actual RET instruction.
3835 */
3836static int validate_unret(struct objtool_file *file, struct instruction *insn)
3837{
3838 struct instruction *next, *dest;
3839 int ret;
3840
3841 for (;;) {
3842 next = next_insn_to_validate(file, insn);
3843
3844 if (insn->visited & VISITED_UNRET)
3845 return 0;
3846
3847 insn->visited |= VISITED_UNRET;
3848
3849 if (!insn->ignore_alts && insn->alts) {
3850 struct alternative *alt;
3851 bool skip_orig = false;
3852
3853 for (alt = insn->alts; alt; alt = alt->next) {
3854 if (alt->skip_orig)
3855 skip_orig = true;
3856
3857 ret = validate_unret(file, alt->insn);
3858 if (ret) {
3859 BT_INSN(insn, "(alt)");
3860 return ret;
3861 }
3862 }
3863
3864 if (skip_orig)
3865 return 0;
3866 }
3867
3868 switch (insn->type) {
3869
3870 case INSN_CALL_DYNAMIC:
3871 case INSN_JUMP_DYNAMIC:
3872 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3873 WARN_INSN(insn, "early indirect call");
3874 return 1;
3875
3876 case INSN_JUMP_UNCONDITIONAL:
3877 case INSN_JUMP_CONDITIONAL:
3878 if (!is_sibling_call(insn)) {
3879 if (!insn->jump_dest) {
3880 WARN_INSN(insn, "unresolved jump target after linking?!?");
3881 return -1;
3882 }
3883 ret = validate_unret(file, insn->jump_dest);
3884 if (ret) {
3885 BT_INSN(insn, "(branch%s)",
3886 insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : "");
3887 return ret;
3888 }
3889
3890 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3891 return 0;
3892
3893 break;
3894 }
3895
3896 /* fallthrough */
3897 case INSN_CALL:
3898 dest = find_insn(file, insn_call_dest(insn)->sec,
3899 insn_call_dest(insn)->offset);
3900 if (!dest) {
3901 WARN("Unresolved function after linking!?: %s",
3902 insn_call_dest(insn)->name);
3903 return -1;
3904 }
3905
3906 ret = validate_unret(file, dest);
3907 if (ret) {
3908 BT_INSN(insn, "(call)");
3909 return ret;
3910 }
3911 /*
3912 * If a call returns without error, it must have seen UNTRAIN_RET.
3913 * Therefore any non-error return is a success.
3914 */
3915 return 0;
3916
3917 case INSN_RETURN:
3918 WARN_INSN(insn, "RET before UNTRAIN");
3919 return 1;
3920
3921 case INSN_NOP:
3922 if (insn->retpoline_safe)
3923 return 0;
3924 break;
3925
3926 default:
3927 break;
3928 }
3929
3930 if (!next) {
3931 WARN_INSN(insn, "teh end!");
3932 return -1;
3933 }
3934 insn = next;
3935 }
3936
3937 return 0;
3938}
3939
3940/*
3941 * Validate that all branches starting at VALIDATE_UNRET_BEGIN encounter
3942 * VALIDATE_UNRET_END before RET.
3943 */
3944static int validate_unrets(struct objtool_file *file)
3945{
3946 struct instruction *insn;
3947 int ret, warnings = 0;
3948
3949 for_each_insn(file, insn) {
3950 if (!insn->unret)
3951 continue;
3952
3953 ret = validate_unret(file, insn);
3954 if (ret < 0) {
3955 WARN_INSN(insn, "Failed UNRET validation");
3956 return ret;
3957 }
3958 warnings += ret;
3959 }
3960
3961 return warnings;
3962}
3963
3964static int validate_retpoline(struct objtool_file *file)
3965{
3966 struct instruction *insn;
3967 int warnings = 0;
3968
3969 for_each_insn(file, insn) {
3970 if (insn->type != INSN_JUMP_DYNAMIC &&
3971 insn->type != INSN_CALL_DYNAMIC &&
3972 insn->type != INSN_RETURN)
3973 continue;
3974
3975 if (insn->retpoline_safe)
3976 continue;
3977
3978 if (insn->sec->init)
3979 continue;
3980
3981 if (insn->type == INSN_RETURN) {
3982 if (opts.rethunk) {
3983 WARN_INSN(insn, "'naked' return found in RETHUNK build");
3984 } else
3985 continue;
3986 } else {
3987 WARN_INSN(insn, "indirect %s found in RETPOLINE build",
3988 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
3989 }
3990
3991 warnings++;
3992 }
3993
3994 return warnings;
3995}
3996
3997static bool is_kasan_insn(struct instruction *insn)
3998{
3999 return (insn->type == INSN_CALL &&
4000 !strcmp(insn_call_dest(insn)->name, "__asan_handle_no_return"));
4001}
4002
4003static bool is_ubsan_insn(struct instruction *insn)
4004{
4005 return (insn->type == INSN_CALL &&
4006 !strcmp(insn_call_dest(insn)->name,
4007 "__ubsan_handle_builtin_unreachable"));
4008}
4009
4010static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
4011{
4012 int i;
4013 struct instruction *prev_insn;
4014
4015 if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
4016 return true;
4017
4018 /*
4019 * Ignore alternative replacement instructions. This can happen
4020 * when a whitelisted function uses one of the ALTERNATIVE macros.
4021 */
4022 if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
4023 !strcmp(insn->sec->name, ".altinstr_aux"))
4024 return true;
4025
4026 /*
4027 * Whole archive runs might encounter dead code from weak symbols.
4028 * This is where the linker will have dropped the weak symbol in
4029 * favour of a regular symbol, but leaves the code in place.
4030 *
4031 * In this case we'll find a piece of code (whole function) that is not
4032 * covered by a !section symbol. Ignore them.
4033 */
4034 if (opts.link && !insn_func(insn)) {
4035 int size = find_symbol_hole_containing(insn->sec, insn->offset);
4036 unsigned long end = insn->offset + size;
4037
4038 if (!size) /* not a hole */
4039 return false;
4040
4041 if (size < 0) /* hole until the end */
4042 return true;
4043
4044 sec_for_each_insn_continue(file, insn) {
4045 /*
4046 * If we reach a visited instruction at or before the
4047 * end of the hole, ignore the unreachable.
4048 */
4049 if (insn->visited)
4050 return true;
4051
4052 if (insn->offset >= end)
4053 break;
4054
4055 /*
4056 * If this hole jumps to a .cold function, mark it ignore too.
4057 */
4058 if (insn->jump_dest && insn_func(insn->jump_dest) &&
4059 strstr(insn_func(insn->jump_dest)->name, ".cold")) {
4060 struct instruction *dest = insn->jump_dest;
4061 func_for_each_insn(file, insn_func(dest), dest)
4062 dest->ignore = true;
4063 }
4064 }
4065
4066 return false;
4067 }
4068
4069 if (!insn_func(insn))
4070 return false;
4071
4072 if (insn_func(insn)->static_call_tramp)
4073 return true;
4074
4075 /*
4076 * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
4077 * __builtin_unreachable(). The BUG() macro has an unreachable() after
4078 * the UD2, which causes GCC's undefined trap logic to emit another UD2
4079 * (or occasionally a JMP to UD2).
4080 *
4081 * It may also insert a UD2 after calling a __noreturn function.
4082 */
4083 prev_insn = prev_insn_same_sec(file, insn);
4084 if (prev_insn->dead_end &&
4085 (insn->type == INSN_BUG ||
4086 (insn->type == INSN_JUMP_UNCONDITIONAL &&
4087 insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
4088 return true;
4089
4090 /*
4091 * Check if this (or a subsequent) instruction is related to
4092 * CONFIG_UBSAN or CONFIG_KASAN.
4093 *
4094 * End the search at 5 instructions to avoid going into the weeds.
4095 */
4096 for (i = 0; i < 5; i++) {
4097
4098 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
4099 return true;
4100
4101 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
4102 if (insn->jump_dest &&
4103 insn_func(insn->jump_dest) == insn_func(insn)) {
4104 insn = insn->jump_dest;
4105 continue;
4106 }
4107
4108 break;
4109 }
4110
4111 if (insn->offset + insn->len >= insn_func(insn)->offset + insn_func(insn)->len)
4112 break;
4113
4114 insn = next_insn_same_sec(file, insn);
4115 }
4116
4117 return false;
4118}
4119
4120static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
4121{
4122 struct instruction *insn, *prev;
4123 struct cfi_state *cfi;
4124
4125 insn = find_insn(file, func->sec, func->offset);
4126 if (!insn)
4127 return -1;
4128
4129 for (prev = prev_insn_same_sec(file, insn);
4130 prev;
4131 prev = prev_insn_same_sec(file, prev)) {
4132 u64 offset;
4133
4134 if (prev->type != INSN_NOP)
4135 return -1;
4136
4137 offset = func->offset - prev->offset;
4138
4139 if (offset > opts.prefix)
4140 return -1;
4141
4142 if (offset < opts.prefix)
4143 continue;
4144
4145 elf_create_prefix_symbol(file->elf, func, opts.prefix);
4146 break;
4147 }
4148
4149 if (!prev)
4150 return -1;
4151
4152 if (!insn->cfi) {
4153 /*
4154 * This can happen if stack validation isn't enabled or the
4155 * function is annotated with STACK_FRAME_NON_STANDARD.
4156 */
4157 return 0;
4158 }
4159
4160 /* Propagate insn->cfi to the prefix code */
4161 cfi = cfi_hash_find_or_add(insn->cfi);
4162 for (; prev != insn; prev = next_insn_same_sec(file, prev))
4163 prev->cfi = cfi;
4164
4165 return 0;
4166}
4167
4168static int add_prefix_symbols(struct objtool_file *file)
4169{
4170 struct section *sec;
4171 struct symbol *func;
4172
4173 for_each_sec(file, sec) {
4174 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4175 continue;
4176
4177 sec_for_each_sym(sec, func) {
4178 if (func->type != STT_FUNC)
4179 continue;
4180
4181 add_prefix_symbol(file, func);
4182 }
4183 }
4184
4185 return 0;
4186}
4187
4188static int validate_symbol(struct objtool_file *file, struct section *sec,
4189 struct symbol *sym, struct insn_state *state)
4190{
4191 struct instruction *insn;
4192 int ret;
4193
4194 if (!sym->len) {
4195 WARN("%s() is missing an ELF size annotation", sym->name);
4196 return 1;
4197 }
4198
4199 if (sym->pfunc != sym || sym->alias != sym)
4200 return 0;
4201
4202 insn = find_insn(file, sec, sym->offset);
4203 if (!insn || insn->ignore || insn->visited)
4204 return 0;
4205
4206 state->uaccess = sym->uaccess_safe;
4207
4208 ret = validate_branch(file, insn_func(insn), insn, *state);
4209 if (ret)
4210 BT_INSN(insn, "<=== (sym)");
4211 return ret;
4212}
4213
4214static int validate_section(struct objtool_file *file, struct section *sec)
4215{
4216 struct insn_state state;
4217 struct symbol *func;
4218 int warnings = 0;
4219
4220 sec_for_each_sym(sec, func) {
4221 if (func->type != STT_FUNC)
4222 continue;
4223
4224 init_insn_state(file, &state, sec);
4225 set_func_state(&state.cfi);
4226
4227 warnings += validate_symbol(file, sec, func, &state);
4228 }
4229
4230 return warnings;
4231}
4232
4233static int validate_noinstr_sections(struct objtool_file *file)
4234{
4235 struct section *sec;
4236 int warnings = 0;
4237
4238 sec = find_section_by_name(file->elf, ".noinstr.text");
4239 if (sec) {
4240 warnings += validate_section(file, sec);
4241 warnings += validate_unwind_hints(file, sec);
4242 }
4243
4244 sec = find_section_by_name(file->elf, ".entry.text");
4245 if (sec) {
4246 warnings += validate_section(file, sec);
4247 warnings += validate_unwind_hints(file, sec);
4248 }
4249
4250 sec = find_section_by_name(file->elf, ".cpuidle.text");
4251 if (sec) {
4252 warnings += validate_section(file, sec);
4253 warnings += validate_unwind_hints(file, sec);
4254 }
4255
4256 return warnings;
4257}
4258
4259static int validate_functions(struct objtool_file *file)
4260{
4261 struct section *sec;
4262 int warnings = 0;
4263
4264 for_each_sec(file, sec) {
4265 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4266 continue;
4267
4268 warnings += validate_section(file, sec);
4269 }
4270
4271 return warnings;
4272}
4273
4274static void mark_endbr_used(struct instruction *insn)
4275{
4276 if (!list_empty(&insn->call_node))
4277 list_del_init(&insn->call_node);
4278}
4279
4280static bool noendbr_range(struct objtool_file *file, struct instruction *insn)
4281{
4282 struct symbol *sym = find_symbol_containing(insn->sec, insn->offset-1);
4283 struct instruction *first;
4284
4285 if (!sym)
4286 return false;
4287
4288 first = find_insn(file, sym->sec, sym->offset);
4289 if (!first)
4290 return false;
4291
4292 if (first->type != INSN_ENDBR && !first->noendbr)
4293 return false;
4294
4295 return insn->offset == sym->offset + sym->len;
4296}
4297
4298static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
4299{
4300 struct instruction *dest;
4301 struct reloc *reloc;
4302 unsigned long off;
4303 int warnings = 0;
4304
4305 /*
4306 * Looking for function pointer load relocations. Ignore
4307 * direct/indirect branches:
4308 */
4309 switch (insn->type) {
4310 case INSN_CALL:
4311 case INSN_CALL_DYNAMIC:
4312 case INSN_JUMP_CONDITIONAL:
4313 case INSN_JUMP_UNCONDITIONAL:
4314 case INSN_JUMP_DYNAMIC:
4315 case INSN_JUMP_DYNAMIC_CONDITIONAL:
4316 case INSN_RETURN:
4317 case INSN_NOP:
4318 return 0;
4319 default:
4320 break;
4321 }
4322
4323 for (reloc = insn_reloc(file, insn);
4324 reloc;
4325 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
4326 reloc_offset(reloc) + 1,
4327 (insn->offset + insn->len) - (reloc_offset(reloc) + 1))) {
4328
4329 /*
4330 * static_call_update() references the trampoline, which
4331 * doesn't have (or need) ENDBR. Skip warning in that case.
4332 */
4333 if (reloc->sym->static_call_tramp)
4334 continue;
4335
4336 off = reloc->sym->offset;
4337 if (reloc_type(reloc) == R_X86_64_PC32 ||
4338 reloc_type(reloc) == R_X86_64_PLT32)
4339 off += arch_dest_reloc_offset(reloc_addend(reloc));
4340 else
4341 off += reloc_addend(reloc);
4342
4343 dest = find_insn(file, reloc->sym->sec, off);
4344 if (!dest)
4345 continue;
4346
4347 if (dest->type == INSN_ENDBR) {
4348 mark_endbr_used(dest);
4349 continue;
4350 }
4351
4352 if (insn_func(dest) && insn_func(insn) &&
4353 insn_func(dest)->pfunc == insn_func(insn)->pfunc) {
4354 /*
4355 * Anything from->to self is either _THIS_IP_ or
4356 * IRET-to-self.
4357 *
4358 * There is no sane way to annotate _THIS_IP_ since the
4359 * compiler treats the relocation as a constant and is
4360 * happy to fold in offsets, skewing any annotation we
4361 * do, leading to vast amounts of false-positives.
4362 *
4363 * There's also compiler generated _THIS_IP_ through
4364 * KCOV and such which we have no hope of annotating.
4365 *
4366 * As such, blanket accept self-references without
4367 * issue.
4368 */
4369 continue;
4370 }
4371
4372 /*
4373 * Accept anything ANNOTATE_NOENDBR.
4374 */
4375 if (dest->noendbr)
4376 continue;
4377
4378 /*
4379 * Accept if this is the instruction after a symbol
4380 * that is (no)endbr -- typical code-range usage.
4381 */
4382 if (noendbr_range(file, dest))
4383 continue;
4384
4385 WARN_INSN(insn, "relocation to !ENDBR: %s", offstr(dest->sec, dest->offset));
4386
4387 warnings++;
4388 }
4389
4390 return warnings;
4391}
4392
4393static int validate_ibt_data_reloc(struct objtool_file *file,
4394 struct reloc *reloc)
4395{
4396 struct instruction *dest;
4397
4398 dest = find_insn(file, reloc->sym->sec,
4399 reloc->sym->offset + reloc_addend(reloc));
4400 if (!dest)
4401 return 0;
4402
4403 if (dest->type == INSN_ENDBR) {
4404 mark_endbr_used(dest);
4405 return 0;
4406 }
4407
4408 if (dest->noendbr)
4409 return 0;
4410
4411 WARN_FUNC("data relocation to !ENDBR: %s",
4412 reloc->sec->base, reloc_offset(reloc),
4413 offstr(dest->sec, dest->offset));
4414
4415 return 1;
4416}
4417
4418/*
4419 * Validate IBT rules and remove used ENDBR instructions from the seal list.
4420 * Unused ENDBR instructions will be annotated for sealing (i.e., replaced with
4421 * NOPs) later, in create_ibt_endbr_seal_sections().
4422 */
4423static int validate_ibt(struct objtool_file *file)
4424{
4425 struct section *sec;
4426 struct reloc *reloc;
4427 struct instruction *insn;
4428 int warnings = 0;
4429
4430 for_each_insn(file, insn)
4431 warnings += validate_ibt_insn(file, insn);
4432
4433 for_each_sec(file, sec) {
4434
4435 /* Already done by validate_ibt_insn() */
4436 if (sec->sh.sh_flags & SHF_EXECINSTR)
4437 continue;
4438
4439 if (!sec->rsec)
4440 continue;
4441
4442 /*
4443 * These sections can reference text addresses, but not with
4444 * the intent to indirect branch to them.
4445 */
4446 if ((!strncmp(sec->name, ".discard", 8) &&
4447 strcmp(sec->name, ".discard.ibt_endbr_noseal")) ||
4448 !strncmp(sec->name, ".debug", 6) ||
4449 !strcmp(sec->name, ".altinstructions") ||
4450 !strcmp(sec->name, ".ibt_endbr_seal") ||
4451 !strcmp(sec->name, ".orc_unwind_ip") ||
4452 !strcmp(sec->name, ".parainstructions") ||
4453 !strcmp(sec->name, ".retpoline_sites") ||
4454 !strcmp(sec->name, ".smp_locks") ||
4455 !strcmp(sec->name, ".static_call_sites") ||
4456 !strcmp(sec->name, "_error_injection_whitelist") ||
4457 !strcmp(sec->name, "_kprobe_blacklist") ||
4458 !strcmp(sec->name, "__bug_table") ||
4459 !strcmp(sec->name, "__ex_table") ||
4460 !strcmp(sec->name, "__jump_table") ||
4461 !strcmp(sec->name, "__mcount_loc") ||
4462 !strcmp(sec->name, ".kcfi_traps") ||
4463 strstr(sec->name, "__patchable_function_entries"))
4464 continue;
4465
4466 for_each_reloc(sec->rsec, reloc)
4467 warnings += validate_ibt_data_reloc(file, reloc);
4468 }
4469
4470 return warnings;
4471}
4472
4473static int validate_sls(struct objtool_file *file)
4474{
4475 struct instruction *insn, *next_insn;
4476 int warnings = 0;
4477
4478 for_each_insn(file, insn) {
4479 next_insn = next_insn_same_sec(file, insn);
4480
4481 if (insn->retpoline_safe)
4482 continue;
4483
4484 switch (insn->type) {
4485 case INSN_RETURN:
4486 if (!next_insn || next_insn->type != INSN_TRAP) {
4487 WARN_INSN(insn, "missing int3 after ret");
4488 warnings++;
4489 }
4490
4491 break;
4492 case INSN_JUMP_DYNAMIC:
4493 if (!next_insn || next_insn->type != INSN_TRAP) {
4494 WARN_INSN(insn, "missing int3 after indirect jump");
4495 warnings++;
4496 }
4497 break;
4498 default:
4499 break;
4500 }
4501 }
4502
4503 return warnings;
4504}
4505
4506static bool ignore_noreturn_call(struct instruction *insn)
4507{
4508 struct symbol *call_dest = insn_call_dest(insn);
4509
4510 /*
4511 * FIXME: hack, we need a real noreturn solution
4512 *
4513 * Problem is, exc_double_fault() may or may not return, depending on
4514 * whether CONFIG_X86_ESPFIX64 is set. But objtool has no visibility
4515 * to the kernel config.
4516 *
4517 * Other potential ways to fix it:
4518 *
4519 * - have compiler communicate __noreturn functions somehow
4520 * - remove CONFIG_X86_ESPFIX64
4521 * - read the .config file
4522 * - add a cmdline option
4523 * - create a generic objtool annotation format (vs a bunch of custom
4524 * formats) and annotate it
4525 */
4526 if (!strcmp(call_dest->name, "exc_double_fault")) {
4527 /* prevent further unreachable warnings for the caller */
4528 insn->sym->warned = 1;
4529 return true;
4530 }
4531
4532 return false;
4533}
4534
4535static int validate_reachable_instructions(struct objtool_file *file)
4536{
4537 struct instruction *insn, *prev_insn;
4538 struct symbol *call_dest;
4539 int warnings = 0;
4540
4541 if (file->ignore_unreachables)
4542 return 0;
4543
4544 for_each_insn(file, insn) {
4545 if (insn->visited || ignore_unreachable_insn(file, insn))
4546 continue;
4547
4548 prev_insn = prev_insn_same_sec(file, insn);
4549 if (prev_insn && prev_insn->dead_end) {
4550 call_dest = insn_call_dest(prev_insn);
4551 if (call_dest && !ignore_noreturn_call(prev_insn)) {
4552 WARN_INSN(insn, "%s() is missing a __noreturn annotation",
4553 call_dest->name);
4554 warnings++;
4555 continue;
4556 }
4557 }
4558
4559 WARN_INSN(insn, "unreachable instruction");
4560 warnings++;
4561 }
4562
4563 return warnings;
4564}
4565
4566/* 'funcs' is a space-separated list of function names */
4567static int disas_funcs(const char *funcs)
4568{
4569 const char *objdump_str, *cross_compile;
4570 int size, ret;
4571 char *cmd;
4572
4573 cross_compile = getenv("CROSS_COMPILE");
4574
4575 objdump_str = "%sobjdump -wdr %s | gawk -M -v _funcs='%s' '"
4576 "BEGIN { split(_funcs, funcs); }"
4577 "/^$/ { func_match = 0; }"
4578 "/<.*>:/ { "
4579 "f = gensub(/.*<(.*)>:/, \"\\\\1\", 1);"
4580 "for (i in funcs) {"
4581 "if (funcs[i] == f) {"
4582 "func_match = 1;"
4583 "base = strtonum(\"0x\" $1);"
4584 "break;"
4585 "}"
4586 "}"
4587 "}"
4588 "{"
4589 "if (func_match) {"
4590 "addr = strtonum(\"0x\" $1);"
4591 "printf(\"%%04x \", addr - base);"
4592 "print;"
4593 "}"
4594 "}' 1>&2";
4595
4596 /* fake snprintf() to calculate the size */
4597 size = snprintf(NULL, 0, objdump_str, cross_compile, objname, funcs) + 1;
4598 if (size <= 0) {
4599 WARN("objdump string size calculation failed");
4600 return -1;
4601 }
4602
4603 cmd = malloc(size);
4604
4605 /* real snprintf() */
4606 snprintf(cmd, size, objdump_str, cross_compile, objname, funcs);
4607 ret = system(cmd);
4608 if (ret) {
4609 WARN("disassembly failed: %d", ret);
4610 return -1;
4611 }
4612
4613 return 0;
4614}
4615
4616static int disas_warned_funcs(struct objtool_file *file)
4617{
4618 struct symbol *sym;
4619 char *funcs = NULL, *tmp;
4620
4621 for_each_sym(file, sym) {
4622 if (sym->warned) {
4623 if (!funcs) {
4624 funcs = malloc(strlen(sym->name) + 1);
4625 strcpy(funcs, sym->name);
4626 } else {
4627 tmp = malloc(strlen(funcs) + strlen(sym->name) + 2);
4628 sprintf(tmp, "%s %s", funcs, sym->name);
4629 free(funcs);
4630 funcs = tmp;
4631 }
4632 }
4633 }
4634
4635 if (funcs)
4636 disas_funcs(funcs);
4637
4638 return 0;
4639}
4640
4641struct insn_chunk {
4642 void *addr;
4643 struct insn_chunk *next;
4644};
4645
4646/*
4647 * Reduce peak RSS usage by freeing insns memory before writing the ELF file,
4648 * which can trigger more allocations for .debug_* sections whose data hasn't
4649 * been read yet.
4650 */
4651static void free_insns(struct objtool_file *file)
4652{
4653 struct instruction *insn;
4654 struct insn_chunk *chunks = NULL, *chunk;
4655
4656 for_each_insn(file, insn) {
4657 if (!insn->idx) {
4658 chunk = malloc(sizeof(*chunk));
4659 chunk->addr = insn;
4660 chunk->next = chunks;
4661 chunks = chunk;
4662 }
4663 }
4664
4665 for (chunk = chunks; chunk; chunk = chunk->next)
4666 free(chunk->addr);
4667}
4668
4669int check(struct objtool_file *file)
4670{
4671 int ret, warnings = 0;
4672
4673 arch_initial_func_cfi_state(&initial_func_cfi);
4674 init_cfi_state(&init_cfi);
4675 init_cfi_state(&func_cfi);
4676 set_func_state(&func_cfi);
4677 init_cfi_state(&force_undefined_cfi);
4678 force_undefined_cfi.force_undefined = true;
4679
4680 if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
4681 goto out;
4682
4683 cfi_hash_add(&init_cfi);
4684 cfi_hash_add(&func_cfi);
4685
4686 ret = decode_sections(file);
4687 if (ret < 0)
4688 goto out;
4689
4690 warnings += ret;
4691
4692 if (!nr_insns)
4693 goto out;
4694
4695 if (opts.retpoline) {
4696 ret = validate_retpoline(file);
4697 if (ret < 0)
4698 return ret;
4699 warnings += ret;
4700 }
4701
4702 if (opts.stackval || opts.orc || opts.uaccess) {
4703 ret = validate_functions(file);
4704 if (ret < 0)
4705 goto out;
4706 warnings += ret;
4707
4708 ret = validate_unwind_hints(file, NULL);
4709 if (ret < 0)
4710 goto out;
4711 warnings += ret;
4712
4713 if (!warnings) {
4714 ret = validate_reachable_instructions(file);
4715 if (ret < 0)
4716 goto out;
4717 warnings += ret;
4718 }
4719
4720 } else if (opts.noinstr) {
4721 ret = validate_noinstr_sections(file);
4722 if (ret < 0)
4723 goto out;
4724 warnings += ret;
4725 }
4726
4727 if (opts.unret) {
4728 /*
4729 * Must be after validate_branch() and friends, it plays
4730 * further games with insn->visited.
4731 */
4732 ret = validate_unrets(file);
4733 if (ret < 0)
4734 return ret;
4735 warnings += ret;
4736 }
4737
4738 if (opts.ibt) {
4739 ret = validate_ibt(file);
4740 if (ret < 0)
4741 goto out;
4742 warnings += ret;
4743 }
4744
4745 if (opts.sls) {
4746 ret = validate_sls(file);
4747 if (ret < 0)
4748 goto out;
4749 warnings += ret;
4750 }
4751
4752 if (opts.static_call) {
4753 ret = create_static_call_sections(file);
4754 if (ret < 0)
4755 goto out;
4756 warnings += ret;
4757 }
4758
4759 if (opts.retpoline) {
4760 ret = create_retpoline_sites_sections(file);
4761 if (ret < 0)
4762 goto out;
4763 warnings += ret;
4764 }
4765
4766 if (opts.cfi) {
4767 ret = create_cfi_sections(file);
4768 if (ret < 0)
4769 goto out;
4770 warnings += ret;
4771 }
4772
4773 if (opts.rethunk) {
4774 ret = create_return_sites_sections(file);
4775 if (ret < 0)
4776 goto out;
4777 warnings += ret;
4778
4779 if (opts.hack_skylake) {
4780 ret = create_direct_call_sections(file);
4781 if (ret < 0)
4782 goto out;
4783 warnings += ret;
4784 }
4785 }
4786
4787 if (opts.mcount) {
4788 ret = create_mcount_loc_sections(file);
4789 if (ret < 0)
4790 goto out;
4791 warnings += ret;
4792 }
4793
4794 if (opts.prefix) {
4795 ret = add_prefix_symbols(file);
4796 if (ret < 0)
4797 return ret;
4798 warnings += ret;
4799 }
4800
4801 if (opts.ibt) {
4802 ret = create_ibt_endbr_seal_sections(file);
4803 if (ret < 0)
4804 goto out;
4805 warnings += ret;
4806 }
4807
4808 if (opts.orc && nr_insns) {
4809 ret = orc_create(file);
4810 if (ret < 0)
4811 goto out;
4812 warnings += ret;
4813 }
4814
4815 free_insns(file);
4816
4817 if (opts.verbose)
4818 disas_warned_funcs(file);
4819
4820 if (opts.stats) {
4821 printf("nr_insns_visited: %ld\n", nr_insns_visited);
4822 printf("nr_cfi: %ld\n", nr_cfi);
4823 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
4824 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
4825 }
4826
4827out:
4828 /*
4829 * For now, don't fail the kernel build on fatal warnings. These
4830 * errors are still fairly common due to the growing matrix of
4831 * supported toolchains and their recent pace of change.
4832 */
4833 return 0;
4834}