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
24 struct alternative {
25 struct alternative *next;
26 struct instruction *insn;
27 bool skip_orig;
28 };
29
30 static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
31
32 static struct cfi_init_state initial_func_cfi;
33 static struct cfi_state init_cfi;
34 static struct cfi_state func_cfi;
35 static struct cfi_state force_undefined_cfi;
36
find_insn(struct objtool_file * file,struct section * sec,unsigned long offset)37 struct 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
next_insn_same_sec(struct objtool_file * file,struct instruction * insn)50 struct 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
next_insn_same_func(struct objtool_file * file,struct instruction * insn)63 static 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
prev_insn_same_sec(struct objtool_file * file,struct instruction * insn)83 static 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
prev_insn_same_sym(struct objtool_file * file,struct instruction * insn)95 static 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
insn_call_dest(struct instruction * insn)134 static 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
insn_jump_table(struct instruction * insn)143 static 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
is_jump_table_jump(struct instruction * insn)152 static 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
is_sibling_call(struct instruction * insn)164 static 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 */
__dead_end_function(struct objtool_file * file,struct symbol * func,int recursion)188 static 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
dead_end_function(struct objtool_file * file,struct symbol * func)259 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
260 {
261 return __dead_end_function(file, func, 0);
262 }
263
init_cfi_state(struct cfi_state * cfi)264 static 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
init_insn_state(struct objtool_file * file,struct insn_state * state,struct section * sec)277 static 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
cfi_alloc(void)292 static struct cfi_state *cfi_alloc(void)
293 {
294 struct cfi_state *cfi = calloc(sizeof(struct cfi_state), 1);
295 if (!cfi) {
296 WARN("calloc failed");
297 exit(1);
298 }
299 nr_cfi++;
300 return cfi;
301 }
302
303 static int cfi_bits;
304 static struct hlist_head *cfi_hash;
305
cficmp(struct cfi_state * cfi1,struct cfi_state * cfi2)306 static 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
cfi_key(struct cfi_state * cfi)313 static 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
cfi_hash_find_or_add(struct cfi_state * cfi)319 static 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
cfi_hash_add(struct cfi_state * cfi)338 static 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
cfi_hash_alloc(unsigned long size)345 static 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
361 static unsigned long nr_insns;
362 static 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 */
decode_instructions(struct objtool_file * file)368 static 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 */
add_pv_ops(struct objtool_file * file,const char * symname)492 static 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 */
init_pv_ops(struct objtool_file * file)530 static 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
find_last_insn(struct objtool_file * file,struct section * sec)566 static 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 */
add_dead_ends(struct objtool_file * file)582 static 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
624 reachable:
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
create_static_call_sections(struct objtool_file * file)666 static 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
create_retpoline_sites_sections(struct objtool_file * file)755 static 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
create_return_sites_sections(struct objtool_file * file)793 static 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
create_ibt_endbr_seal_sections(struct objtool_file * file)831 static 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
create_cfi_sections(struct objtool_file * file)885 static 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
create_mcount_loc_sections(struct objtool_file * file)933 static 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
create_direct_call_sections(struct objtool_file * file)979 static 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 */
add_ignores(struct objtool_file * file)1021 static 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 */
1062 static 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
add_uaccess_safe(struct objtool_file * file)1240 static 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 */
add_ignore_alternatives(struct objtool_file * file)1263 static 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 */
arch_is_retpoline(struct symbol * sym)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 */
arch_is_rethunk(struct symbol * sym)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 */
arch_is_embedded_insn(struct symbol * sym)1313 __weak bool arch_is_embedded_insn(struct symbol *sym)
1314 {
1315 return false;
1316 }
1317
insn_reloc(struct objtool_file * file,struct instruction * insn)1318 static 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
remove_insn_ops(struct instruction * insn)1338 static 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
annotate_call_site(struct objtool_file * file,struct instruction * insn,bool sibling)1349 static 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
add_call_dest(struct objtool_file * file,struct instruction * insn,struct symbol * dest,bool sibling)1431 static 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
add_retpoline_call(struct objtool_file * file,struct instruction * insn)1450 static 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
add_return_call(struct objtool_file * file,struct instruction * insn,bool add)1484 static 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
is_first_func_insn(struct objtool_file * file,struct instruction * insn,struct symbol * sym)1497 static 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 */
jump_is_sibling_call(struct objtool_file * file,struct instruction * from,struct instruction * to)1519 static 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 */
add_jump_destinations(struct objtool_file * file)1544 static 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 * Cross-function jump.
1615 */
1616 if (insn_func(insn) && insn_func(jump_dest) &&
1617 insn_func(insn) != insn_func(jump_dest)) {
1618
1619 /*
1620 * For GCC 8+, create parent/child links for any cold
1621 * subfunctions. This is _mostly_ redundant with a
1622 * similar initialization in read_symbols().
1623 *
1624 * If a function has aliases, we want the *first* such
1625 * function in the symbol table to be the subfunction's
1626 * parent. In that case we overwrite the
1627 * initialization done in read_symbols().
1628 *
1629 * However this code can't completely replace the
1630 * read_symbols() code because this doesn't detect the
1631 * case where the parent function's only reference to a
1632 * subfunction is through a jump table.
1633 */
1634 if (!strstr(insn_func(insn)->name, ".cold") &&
1635 strstr(insn_func(jump_dest)->name, ".cold")) {
1636 insn_func(insn)->cfunc = insn_func(jump_dest);
1637 insn_func(jump_dest)->pfunc = insn_func(insn);
1638 }
1639 }
1640
1641 if (jump_is_sibling_call(file, insn, jump_dest)) {
1642 /*
1643 * Internal sibling call without reloc or with
1644 * STT_SECTION reloc.
1645 */
1646 add_call_dest(file, insn, insn_func(jump_dest), true);
1647 continue;
1648 }
1649
1650 insn->jump_dest = jump_dest;
1651 }
1652
1653 return 0;
1654 }
1655
find_call_destination(struct section * sec,unsigned long offset)1656 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1657 {
1658 struct symbol *call_dest;
1659
1660 call_dest = find_func_by_offset(sec, offset);
1661 if (!call_dest)
1662 call_dest = find_symbol_by_offset(sec, offset);
1663
1664 return call_dest;
1665 }
1666
1667 /*
1668 * Find the destination instructions for all calls.
1669 */
add_call_destinations(struct objtool_file * file)1670 static int add_call_destinations(struct objtool_file *file)
1671 {
1672 struct instruction *insn;
1673 unsigned long dest_off;
1674 struct symbol *dest;
1675 struct reloc *reloc;
1676
1677 for_each_insn(file, insn) {
1678 if (insn->type != INSN_CALL)
1679 continue;
1680
1681 reloc = insn_reloc(file, insn);
1682 if (!reloc) {
1683 dest_off = arch_jump_destination(insn);
1684 dest = find_call_destination(insn->sec, dest_off);
1685
1686 add_call_dest(file, insn, dest, false);
1687
1688 if (insn->ignore)
1689 continue;
1690
1691 if (!insn_call_dest(insn)) {
1692 WARN_INSN(insn, "unannotated intra-function call");
1693 return -1;
1694 }
1695
1696 if (insn_func(insn) && insn_call_dest(insn)->type != STT_FUNC) {
1697 WARN_INSN(insn, "unsupported call to non-function");
1698 return -1;
1699 }
1700
1701 } else if (reloc->sym->type == STT_SECTION) {
1702 dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
1703 dest = find_call_destination(reloc->sym->sec, dest_off);
1704 if (!dest) {
1705 WARN_INSN(insn, "can't find call dest symbol at %s+0x%lx",
1706 reloc->sym->sec->name, dest_off);
1707 return -1;
1708 }
1709
1710 add_call_dest(file, insn, dest, false);
1711
1712 } else if (reloc->sym->retpoline_thunk) {
1713 add_retpoline_call(file, insn);
1714
1715 } else
1716 add_call_dest(file, insn, reloc->sym, false);
1717 }
1718
1719 return 0;
1720 }
1721
1722 /*
1723 * The .alternatives section requires some extra special care over and above
1724 * other special sections because alternatives are patched in place.
1725 */
handle_group_alt(struct objtool_file * file,struct special_alt * special_alt,struct instruction * orig_insn,struct instruction ** new_insn)1726 static int handle_group_alt(struct objtool_file *file,
1727 struct special_alt *special_alt,
1728 struct instruction *orig_insn,
1729 struct instruction **new_insn)
1730 {
1731 struct instruction *last_new_insn = NULL, *insn, *nop = NULL;
1732 struct alt_group *orig_alt_group, *new_alt_group;
1733 unsigned long dest_off;
1734
1735 orig_alt_group = orig_insn->alt_group;
1736 if (!orig_alt_group) {
1737 struct instruction *last_orig_insn = NULL;
1738
1739 orig_alt_group = malloc(sizeof(*orig_alt_group));
1740 if (!orig_alt_group) {
1741 WARN("malloc failed");
1742 return -1;
1743 }
1744 orig_alt_group->cfi = calloc(special_alt->orig_len,
1745 sizeof(struct cfi_state *));
1746 if (!orig_alt_group->cfi) {
1747 WARN("calloc failed");
1748 return -1;
1749 }
1750
1751 insn = orig_insn;
1752 sec_for_each_insn_from(file, insn) {
1753 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1754 break;
1755
1756 insn->alt_group = orig_alt_group;
1757 last_orig_insn = insn;
1758 }
1759 orig_alt_group->orig_group = NULL;
1760 orig_alt_group->first_insn = orig_insn;
1761 orig_alt_group->last_insn = last_orig_insn;
1762 orig_alt_group->nop = NULL;
1763 } else {
1764 if (orig_alt_group->last_insn->offset + orig_alt_group->last_insn->len -
1765 orig_alt_group->first_insn->offset != special_alt->orig_len) {
1766 WARN_INSN(orig_insn, "weirdly overlapping alternative! %ld != %d",
1767 orig_alt_group->last_insn->offset +
1768 orig_alt_group->last_insn->len -
1769 orig_alt_group->first_insn->offset,
1770 special_alt->orig_len);
1771 return -1;
1772 }
1773 }
1774
1775 new_alt_group = malloc(sizeof(*new_alt_group));
1776 if (!new_alt_group) {
1777 WARN("malloc failed");
1778 return -1;
1779 }
1780
1781 if (special_alt->new_len < special_alt->orig_len) {
1782 /*
1783 * Insert a fake nop at the end to make the replacement
1784 * alt_group the same size as the original. This is needed to
1785 * allow propagate_alt_cfi() to do its magic. When the last
1786 * instruction affects the stack, the instruction after it (the
1787 * nop) will propagate the new state to the shared CFI array.
1788 */
1789 nop = malloc(sizeof(*nop));
1790 if (!nop) {
1791 WARN("malloc failed");
1792 return -1;
1793 }
1794 memset(nop, 0, sizeof(*nop));
1795
1796 nop->sec = special_alt->new_sec;
1797 nop->offset = special_alt->new_off + special_alt->new_len;
1798 nop->len = special_alt->orig_len - special_alt->new_len;
1799 nop->type = INSN_NOP;
1800 nop->sym = orig_insn->sym;
1801 nop->alt_group = new_alt_group;
1802 nop->ignore = orig_insn->ignore_alts;
1803 }
1804
1805 if (!special_alt->new_len) {
1806 *new_insn = nop;
1807 goto end;
1808 }
1809
1810 insn = *new_insn;
1811 sec_for_each_insn_from(file, insn) {
1812 struct reloc *alt_reloc;
1813
1814 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1815 break;
1816
1817 last_new_insn = insn;
1818
1819 insn->ignore = orig_insn->ignore_alts;
1820 insn->sym = orig_insn->sym;
1821 insn->alt_group = new_alt_group;
1822
1823 /*
1824 * Since alternative replacement code is copy/pasted by the
1825 * kernel after applying relocations, generally such code can't
1826 * have relative-address relocation references to outside the
1827 * .altinstr_replacement section, unless the arch's
1828 * alternatives code can adjust the relative offsets
1829 * accordingly.
1830 */
1831 alt_reloc = insn_reloc(file, insn);
1832 if (alt_reloc && arch_pc_relative_reloc(alt_reloc) &&
1833 !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1834
1835 WARN_INSN(insn, "unsupported relocation in alternatives section");
1836 return -1;
1837 }
1838
1839 if (!is_static_jump(insn))
1840 continue;
1841
1842 if (!insn->immediate)
1843 continue;
1844
1845 dest_off = arch_jump_destination(insn);
1846 if (dest_off == special_alt->new_off + special_alt->new_len) {
1847 insn->jump_dest = next_insn_same_sec(file, orig_alt_group->last_insn);
1848 if (!insn->jump_dest) {
1849 WARN_INSN(insn, "can't find alternative jump destination");
1850 return -1;
1851 }
1852 }
1853 }
1854
1855 if (!last_new_insn) {
1856 WARN_FUNC("can't find last new alternative instruction",
1857 special_alt->new_sec, special_alt->new_off);
1858 return -1;
1859 }
1860
1861 end:
1862 new_alt_group->orig_group = orig_alt_group;
1863 new_alt_group->first_insn = *new_insn;
1864 new_alt_group->last_insn = last_new_insn;
1865 new_alt_group->nop = nop;
1866 new_alt_group->cfi = orig_alt_group->cfi;
1867 return 0;
1868 }
1869
1870 /*
1871 * A jump table entry can either convert a nop to a jump or a jump to a nop.
1872 * If the original instruction is a jump, make the alt entry an effective nop
1873 * by just skipping the original instruction.
1874 */
handle_jump_alt(struct objtool_file * file,struct special_alt * special_alt,struct instruction * orig_insn,struct instruction ** new_insn)1875 static int handle_jump_alt(struct objtool_file *file,
1876 struct special_alt *special_alt,
1877 struct instruction *orig_insn,
1878 struct instruction **new_insn)
1879 {
1880 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1881 orig_insn->type != INSN_NOP) {
1882
1883 WARN_INSN(orig_insn, "unsupported instruction at jump label");
1884 return -1;
1885 }
1886
1887 if (opts.hack_jump_label && special_alt->key_addend & 2) {
1888 struct reloc *reloc = insn_reloc(file, orig_insn);
1889
1890 if (reloc)
1891 set_reloc_type(file->elf, reloc, R_NONE);
1892 elf_write_insn(file->elf, orig_insn->sec,
1893 orig_insn->offset, orig_insn->len,
1894 arch_nop_insn(orig_insn->len));
1895 orig_insn->type = INSN_NOP;
1896 }
1897
1898 if (orig_insn->type == INSN_NOP) {
1899 if (orig_insn->len == 2)
1900 file->jl_nop_short++;
1901 else
1902 file->jl_nop_long++;
1903
1904 return 0;
1905 }
1906
1907 if (orig_insn->len == 2)
1908 file->jl_short++;
1909 else
1910 file->jl_long++;
1911
1912 *new_insn = next_insn_same_sec(file, orig_insn);
1913 return 0;
1914 }
1915
1916 /*
1917 * Read all the special sections which have alternate instructions which can be
1918 * patched in or redirected to at runtime. Each instruction having alternate
1919 * instruction(s) has them added to its insn->alts list, which will be
1920 * traversed in validate_branch().
1921 */
add_special_section_alts(struct objtool_file * file)1922 static int add_special_section_alts(struct objtool_file *file)
1923 {
1924 struct list_head special_alts;
1925 struct instruction *orig_insn, *new_insn;
1926 struct special_alt *special_alt, *tmp;
1927 struct alternative *alt;
1928 int ret;
1929
1930 ret = special_get_alts(file->elf, &special_alts);
1931 if (ret)
1932 return ret;
1933
1934 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1935
1936 orig_insn = find_insn(file, special_alt->orig_sec,
1937 special_alt->orig_off);
1938 if (!orig_insn) {
1939 WARN_FUNC("special: can't find orig instruction",
1940 special_alt->orig_sec, special_alt->orig_off);
1941 ret = -1;
1942 goto out;
1943 }
1944
1945 new_insn = NULL;
1946 if (!special_alt->group || special_alt->new_len) {
1947 new_insn = find_insn(file, special_alt->new_sec,
1948 special_alt->new_off);
1949 if (!new_insn) {
1950 WARN_FUNC("special: can't find new instruction",
1951 special_alt->new_sec,
1952 special_alt->new_off);
1953 ret = -1;
1954 goto out;
1955 }
1956 }
1957
1958 if (special_alt->group) {
1959 if (!special_alt->orig_len) {
1960 WARN_INSN(orig_insn, "empty alternative entry");
1961 continue;
1962 }
1963
1964 ret = handle_group_alt(file, special_alt, orig_insn,
1965 &new_insn);
1966 if (ret)
1967 goto out;
1968 } else if (special_alt->jump_or_nop) {
1969 ret = handle_jump_alt(file, special_alt, orig_insn,
1970 &new_insn);
1971 if (ret)
1972 goto out;
1973 }
1974
1975 alt = malloc(sizeof(*alt));
1976 if (!alt) {
1977 WARN("malloc failed");
1978 ret = -1;
1979 goto out;
1980 }
1981
1982 alt->insn = new_insn;
1983 alt->skip_orig = special_alt->skip_orig;
1984 orig_insn->ignore_alts |= special_alt->skip_alt;
1985 alt->next = orig_insn->alts;
1986 orig_insn->alts = alt;
1987
1988 list_del(&special_alt->list);
1989 free(special_alt);
1990 }
1991
1992 if (opts.stats) {
1993 printf("jl\\\tNOP\tJMP\n");
1994 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
1995 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
1996 }
1997
1998 out:
1999 return ret;
2000 }
2001
add_jump_table(struct objtool_file * file,struct instruction * insn,struct reloc * next_table)2002 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
2003 struct reloc *next_table)
2004 {
2005 struct symbol *pfunc = insn_func(insn)->pfunc;
2006 struct reloc *table = insn_jump_table(insn);
2007 struct instruction *dest_insn;
2008 unsigned int prev_offset = 0;
2009 struct reloc *reloc = table;
2010 struct alternative *alt;
2011
2012 /*
2013 * Each @reloc is a switch table relocation which points to the target
2014 * instruction.
2015 */
2016 for_each_reloc_from(table->sec, reloc) {
2017
2018 /* Check for the end of the table: */
2019 if (reloc != table && reloc == next_table)
2020 break;
2021
2022 /* Make sure the table entries are consecutive: */
2023 if (prev_offset && reloc_offset(reloc) != prev_offset + 8)
2024 break;
2025
2026 /* Detect function pointers from contiguous objects: */
2027 if (reloc->sym->sec == pfunc->sec &&
2028 reloc_addend(reloc) == pfunc->offset)
2029 break;
2030
2031 dest_insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2032 if (!dest_insn)
2033 break;
2034
2035 /* Make sure the destination is in the same function: */
2036 if (!insn_func(dest_insn) || insn_func(dest_insn)->pfunc != pfunc)
2037 break;
2038
2039 alt = malloc(sizeof(*alt));
2040 if (!alt) {
2041 WARN("malloc failed");
2042 return -1;
2043 }
2044
2045 alt->insn = dest_insn;
2046 alt->next = insn->alts;
2047 insn->alts = alt;
2048 prev_offset = reloc_offset(reloc);
2049 }
2050
2051 if (!prev_offset) {
2052 WARN_INSN(insn, "can't find switch jump table");
2053 return -1;
2054 }
2055
2056 return 0;
2057 }
2058
2059 /*
2060 * find_jump_table() - Given a dynamic jump, find the switch jump table
2061 * associated with it.
2062 */
find_jump_table(struct objtool_file * file,struct symbol * func,struct instruction * insn)2063 static struct reloc *find_jump_table(struct objtool_file *file,
2064 struct symbol *func,
2065 struct instruction *insn)
2066 {
2067 struct reloc *table_reloc;
2068 struct instruction *dest_insn, *orig_insn = insn;
2069
2070 /*
2071 * Backward search using the @first_jump_src links, these help avoid
2072 * much of the 'in between' code. Which avoids us getting confused by
2073 * it.
2074 */
2075 for (;
2076 insn && insn_func(insn) && insn_func(insn)->pfunc == func;
2077 insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
2078
2079 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
2080 break;
2081
2082 /* allow small jumps within the range */
2083 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
2084 insn->jump_dest &&
2085 (insn->jump_dest->offset <= insn->offset ||
2086 insn->jump_dest->offset > orig_insn->offset))
2087 break;
2088
2089 table_reloc = arch_find_switch_table(file, insn);
2090 if (!table_reloc)
2091 continue;
2092 dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
2093 if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
2094 continue;
2095
2096 return table_reloc;
2097 }
2098
2099 return NULL;
2100 }
2101
2102 /*
2103 * First pass: Mark the head of each jump table so that in the next pass,
2104 * we know when a given jump table ends and the next one starts.
2105 */
mark_func_jump_tables(struct objtool_file * file,struct symbol * func)2106 static void mark_func_jump_tables(struct objtool_file *file,
2107 struct symbol *func)
2108 {
2109 struct instruction *insn, *last = NULL;
2110 struct reloc *reloc;
2111
2112 func_for_each_insn(file, func, insn) {
2113 if (!last)
2114 last = insn;
2115
2116 /*
2117 * Store back-pointers for unconditional forward jumps such
2118 * that find_jump_table() can back-track using those and
2119 * avoid some potentially confusing code.
2120 */
2121 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
2122 insn->offset > last->offset &&
2123 insn->jump_dest->offset > insn->offset &&
2124 !insn->jump_dest->first_jump_src) {
2125
2126 insn->jump_dest->first_jump_src = insn;
2127 last = insn->jump_dest;
2128 }
2129
2130 if (insn->type != INSN_JUMP_DYNAMIC)
2131 continue;
2132
2133 reloc = find_jump_table(file, func, insn);
2134 if (reloc)
2135 insn->_jump_table = reloc;
2136 }
2137 }
2138
add_func_jump_tables(struct objtool_file * file,struct symbol * func)2139 static int add_func_jump_tables(struct objtool_file *file,
2140 struct symbol *func)
2141 {
2142 struct instruction *insn, *insn_t1 = NULL, *insn_t2;
2143 int ret = 0;
2144
2145 func_for_each_insn(file, func, insn) {
2146 if (!insn_jump_table(insn))
2147 continue;
2148
2149 if (!insn_t1) {
2150 insn_t1 = insn;
2151 continue;
2152 }
2153
2154 insn_t2 = insn;
2155
2156 ret = add_jump_table(file, insn_t1, insn_jump_table(insn_t2));
2157 if (ret)
2158 return ret;
2159
2160 insn_t1 = insn_t2;
2161 }
2162
2163 if (insn_t1)
2164 ret = add_jump_table(file, insn_t1, NULL);
2165
2166 return ret;
2167 }
2168
2169 /*
2170 * For some switch statements, gcc generates a jump table in the .rodata
2171 * section which contains a list of addresses within the function to jump to.
2172 * This finds these jump tables and adds them to the insn->alts lists.
2173 */
add_jump_table_alts(struct objtool_file * file)2174 static int add_jump_table_alts(struct objtool_file *file)
2175 {
2176 struct symbol *func;
2177 int ret;
2178
2179 if (!file->rodata)
2180 return 0;
2181
2182 for_each_sym(file, func) {
2183 if (func->type != STT_FUNC)
2184 continue;
2185
2186 mark_func_jump_tables(file, func);
2187 ret = add_func_jump_tables(file, func);
2188 if (ret)
2189 return ret;
2190 }
2191
2192 return 0;
2193 }
2194
set_func_state(struct cfi_state * state)2195 static void set_func_state(struct cfi_state *state)
2196 {
2197 state->cfa = initial_func_cfi.cfa;
2198 memcpy(&state->regs, &initial_func_cfi.regs,
2199 CFI_NUM_REGS * sizeof(struct cfi_reg));
2200 state->stack_size = initial_func_cfi.cfa.offset;
2201 state->type = UNWIND_HINT_TYPE_CALL;
2202 }
2203
read_unwind_hints(struct objtool_file * file)2204 static int read_unwind_hints(struct objtool_file *file)
2205 {
2206 struct cfi_state cfi = init_cfi;
2207 struct section *sec;
2208 struct unwind_hint *hint;
2209 struct instruction *insn;
2210 struct reloc *reloc;
2211 int i;
2212
2213 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
2214 if (!sec)
2215 return 0;
2216
2217 if (!sec->rsec) {
2218 WARN("missing .rela.discard.unwind_hints section");
2219 return -1;
2220 }
2221
2222 if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
2223 WARN("struct unwind_hint size mismatch");
2224 return -1;
2225 }
2226
2227 file->hints = true;
2228
2229 for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
2230 hint = (struct unwind_hint *)sec->data->d_buf + i;
2231
2232 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
2233 if (!reloc) {
2234 WARN("can't find reloc for unwind_hints[%d]", i);
2235 return -1;
2236 }
2237
2238 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2239 if (!insn) {
2240 WARN("can't find insn for unwind_hints[%d]", i);
2241 return -1;
2242 }
2243
2244 insn->hint = true;
2245
2246 if (hint->type == UNWIND_HINT_TYPE_UNDEFINED) {
2247 insn->cfi = &force_undefined_cfi;
2248 continue;
2249 }
2250
2251 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
2252 insn->hint = false;
2253 insn->save = true;
2254 continue;
2255 }
2256
2257 if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
2258 insn->restore = true;
2259 continue;
2260 }
2261
2262 if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
2263 struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
2264
2265 if (sym && sym->bind == STB_GLOBAL) {
2266 if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) {
2267 WARN_INSN(insn, "UNWIND_HINT_IRET_REGS without ENDBR");
2268 }
2269 }
2270 }
2271
2272 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
2273 insn->cfi = &func_cfi;
2274 continue;
2275 }
2276
2277 if (insn->cfi)
2278 cfi = *(insn->cfi);
2279
2280 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
2281 WARN_INSN(insn, "unsupported unwind_hint sp base reg %d", hint->sp_reg);
2282 return -1;
2283 }
2284
2285 cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
2286 cfi.type = hint->type;
2287 cfi.signal = hint->signal;
2288
2289 insn->cfi = cfi_hash_find_or_add(&cfi);
2290 }
2291
2292 return 0;
2293 }
2294
read_noendbr_hints(struct objtool_file * file)2295 static int read_noendbr_hints(struct objtool_file *file)
2296 {
2297 struct instruction *insn;
2298 struct section *rsec;
2299 struct reloc *reloc;
2300
2301 rsec = find_section_by_name(file->elf, ".rela.discard.noendbr");
2302 if (!rsec)
2303 return 0;
2304
2305 for_each_reloc(rsec, reloc) {
2306 insn = find_insn(file, reloc->sym->sec,
2307 reloc->sym->offset + reloc_addend(reloc));
2308 if (!insn) {
2309 WARN("bad .discard.noendbr entry");
2310 return -1;
2311 }
2312
2313 insn->noendbr = 1;
2314 }
2315
2316 return 0;
2317 }
2318
read_retpoline_hints(struct objtool_file * file)2319 static int read_retpoline_hints(struct objtool_file *file)
2320 {
2321 struct section *rsec;
2322 struct instruction *insn;
2323 struct reloc *reloc;
2324
2325 rsec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
2326 if (!rsec)
2327 return 0;
2328
2329 for_each_reloc(rsec, reloc) {
2330 if (reloc->sym->type != STT_SECTION) {
2331 WARN("unexpected relocation symbol type in %s", rsec->name);
2332 return -1;
2333 }
2334
2335 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2336 if (!insn) {
2337 WARN("bad .discard.retpoline_safe entry");
2338 return -1;
2339 }
2340
2341 if (insn->type != INSN_JUMP_DYNAMIC &&
2342 insn->type != INSN_CALL_DYNAMIC &&
2343 insn->type != INSN_RETURN &&
2344 insn->type != INSN_NOP) {
2345 WARN_INSN(insn, "retpoline_safe hint not an indirect jump/call/ret/nop");
2346 return -1;
2347 }
2348
2349 insn->retpoline_safe = true;
2350 }
2351
2352 return 0;
2353 }
2354
read_instr_hints(struct objtool_file * file)2355 static int read_instr_hints(struct objtool_file *file)
2356 {
2357 struct section *rsec;
2358 struct instruction *insn;
2359 struct reloc *reloc;
2360
2361 rsec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2362 if (!rsec)
2363 return 0;
2364
2365 for_each_reloc(rsec, reloc) {
2366 if (reloc->sym->type != STT_SECTION) {
2367 WARN("unexpected relocation symbol type in %s", rsec->name);
2368 return -1;
2369 }
2370
2371 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2372 if (!insn) {
2373 WARN("bad .discard.instr_end entry");
2374 return -1;
2375 }
2376
2377 insn->instr--;
2378 }
2379
2380 rsec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2381 if (!rsec)
2382 return 0;
2383
2384 for_each_reloc(rsec, reloc) {
2385 if (reloc->sym->type != STT_SECTION) {
2386 WARN("unexpected relocation symbol type in %s", rsec->name);
2387 return -1;
2388 }
2389
2390 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2391 if (!insn) {
2392 WARN("bad .discard.instr_begin entry");
2393 return -1;
2394 }
2395
2396 insn->instr++;
2397 }
2398
2399 return 0;
2400 }
2401
read_validate_unret_hints(struct objtool_file * file)2402 static int read_validate_unret_hints(struct objtool_file *file)
2403 {
2404 struct section *rsec;
2405 struct instruction *insn;
2406 struct reloc *reloc;
2407
2408 rsec = find_section_by_name(file->elf, ".rela.discard.validate_unret");
2409 if (!rsec)
2410 return 0;
2411
2412 for_each_reloc(rsec, reloc) {
2413 if (reloc->sym->type != STT_SECTION) {
2414 WARN("unexpected relocation symbol type in %s", rsec->name);
2415 return -1;
2416 }
2417
2418 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2419 if (!insn) {
2420 WARN("bad .discard.instr_end entry");
2421 return -1;
2422 }
2423 insn->unret = 1;
2424 }
2425
2426 return 0;
2427 }
2428
2429
read_intra_function_calls(struct objtool_file * file)2430 static int read_intra_function_calls(struct objtool_file *file)
2431 {
2432 struct instruction *insn;
2433 struct section *rsec;
2434 struct reloc *reloc;
2435
2436 rsec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2437 if (!rsec)
2438 return 0;
2439
2440 for_each_reloc(rsec, reloc) {
2441 unsigned long dest_off;
2442
2443 if (reloc->sym->type != STT_SECTION) {
2444 WARN("unexpected relocation symbol type in %s",
2445 rsec->name);
2446 return -1;
2447 }
2448
2449 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2450 if (!insn) {
2451 WARN("bad .discard.intra_function_call entry");
2452 return -1;
2453 }
2454
2455 if (insn->type != INSN_CALL) {
2456 WARN_INSN(insn, "intra_function_call not a direct call");
2457 return -1;
2458 }
2459
2460 /*
2461 * Treat intra-function CALLs as JMPs, but with a stack_op.
2462 * See add_call_destinations(), which strips stack_ops from
2463 * normal CALLs.
2464 */
2465 insn->type = INSN_JUMP_UNCONDITIONAL;
2466
2467 dest_off = arch_jump_destination(insn);
2468 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2469 if (!insn->jump_dest) {
2470 WARN_INSN(insn, "can't find call dest at %s+0x%lx",
2471 insn->sec->name, dest_off);
2472 return -1;
2473 }
2474 }
2475
2476 return 0;
2477 }
2478
2479 /*
2480 * Return true if name matches an instrumentation function, where calls to that
2481 * function from noinstr code can safely be removed, but compilers won't do so.
2482 */
is_profiling_func(const char * name)2483 static bool is_profiling_func(const char *name)
2484 {
2485 /*
2486 * Many compilers cannot disable KCOV with a function attribute.
2487 */
2488 if (!strncmp(name, "__sanitizer_cov_", 16))
2489 return true;
2490
2491 /*
2492 * Some compilers currently do not remove __tsan_func_entry/exit nor
2493 * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2494 * the __no_sanitize_thread attribute, remove them. Once the kernel's
2495 * minimum Clang version is 14.0, this can be removed.
2496 */
2497 if (!strncmp(name, "__tsan_func_", 12) ||
2498 !strcmp(name, "__tsan_atomic_signal_fence"))
2499 return true;
2500
2501 return false;
2502 }
2503
classify_symbols(struct objtool_file * file)2504 static int classify_symbols(struct objtool_file *file)
2505 {
2506 struct symbol *func;
2507
2508 for_each_sym(file, func) {
2509 if (func->bind != STB_GLOBAL)
2510 continue;
2511
2512 if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2513 strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2514 func->static_call_tramp = true;
2515
2516 if (arch_is_retpoline(func))
2517 func->retpoline_thunk = true;
2518
2519 if (arch_is_rethunk(func))
2520 func->return_thunk = true;
2521
2522 if (arch_is_embedded_insn(func))
2523 func->embedded_insn = true;
2524
2525 if (arch_ftrace_match(func->name))
2526 func->fentry = true;
2527
2528 if (is_profiling_func(func->name))
2529 func->profiling_func = true;
2530 }
2531
2532 return 0;
2533 }
2534
mark_rodata(struct objtool_file * file)2535 static void mark_rodata(struct objtool_file *file)
2536 {
2537 struct section *sec;
2538 bool found = false;
2539
2540 /*
2541 * Search for the following rodata sections, each of which can
2542 * potentially contain jump tables:
2543 *
2544 * - .rodata: can contain GCC switch tables
2545 * - .rodata.<func>: same, if -fdata-sections is being used
2546 * - .rodata..c_jump_table: contains C annotated jump tables
2547 *
2548 * .rodata.str1.* sections are ignored; they don't contain jump tables.
2549 */
2550 for_each_sec(file, sec) {
2551 if (!strncmp(sec->name, ".rodata", 7) &&
2552 !strstr(sec->name, ".str1.")) {
2553 sec->rodata = true;
2554 found = true;
2555 }
2556 }
2557
2558 file->rodata = found;
2559 }
2560
decode_sections(struct objtool_file * file)2561 static int decode_sections(struct objtool_file *file)
2562 {
2563 int ret;
2564
2565 mark_rodata(file);
2566
2567 ret = init_pv_ops(file);
2568 if (ret)
2569 return ret;
2570
2571 /*
2572 * Must be before add_{jump_call}_destination.
2573 */
2574 ret = classify_symbols(file);
2575 if (ret)
2576 return ret;
2577
2578 ret = decode_instructions(file);
2579 if (ret)
2580 return ret;
2581
2582 add_ignores(file);
2583 add_uaccess_safe(file);
2584
2585 ret = add_ignore_alternatives(file);
2586 if (ret)
2587 return ret;
2588
2589 /*
2590 * Must be before read_unwind_hints() since that needs insn->noendbr.
2591 */
2592 ret = read_noendbr_hints(file);
2593 if (ret)
2594 return ret;
2595
2596 /*
2597 * Must be before add_jump_destinations(), which depends on 'func'
2598 * being set for alternatives, to enable proper sibling call detection.
2599 */
2600 if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) {
2601 ret = add_special_section_alts(file);
2602 if (ret)
2603 return ret;
2604 }
2605
2606 ret = add_jump_destinations(file);
2607 if (ret)
2608 return ret;
2609
2610 /*
2611 * Must be before add_call_destination(); it changes INSN_CALL to
2612 * INSN_JUMP.
2613 */
2614 ret = read_intra_function_calls(file);
2615 if (ret)
2616 return ret;
2617
2618 ret = add_call_destinations(file);
2619 if (ret)
2620 return ret;
2621
2622 /*
2623 * Must be after add_call_destinations() such that it can override
2624 * dead_end_function() marks.
2625 */
2626 ret = add_dead_ends(file);
2627 if (ret)
2628 return ret;
2629
2630 ret = add_jump_table_alts(file);
2631 if (ret)
2632 return ret;
2633
2634 ret = read_unwind_hints(file);
2635 if (ret)
2636 return ret;
2637
2638 ret = read_retpoline_hints(file);
2639 if (ret)
2640 return ret;
2641
2642 ret = read_instr_hints(file);
2643 if (ret)
2644 return ret;
2645
2646 ret = read_validate_unret_hints(file);
2647 if (ret)
2648 return ret;
2649
2650 return 0;
2651 }
2652
is_special_call(struct instruction * insn)2653 static bool is_special_call(struct instruction *insn)
2654 {
2655 if (insn->type == INSN_CALL) {
2656 struct symbol *dest = insn_call_dest(insn);
2657
2658 if (!dest)
2659 return false;
2660
2661 if (dest->fentry || dest->embedded_insn)
2662 return true;
2663 }
2664
2665 return false;
2666 }
2667
has_modified_stack_frame(struct instruction * insn,struct insn_state * state)2668 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2669 {
2670 struct cfi_state *cfi = &state->cfi;
2671 int i;
2672
2673 if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2674 return true;
2675
2676 if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2677 return true;
2678
2679 if (cfi->stack_size != initial_func_cfi.cfa.offset)
2680 return true;
2681
2682 for (i = 0; i < CFI_NUM_REGS; i++) {
2683 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2684 cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2685 return true;
2686 }
2687
2688 return false;
2689 }
2690
check_reg_frame_pos(const struct cfi_reg * reg,int expected_offset)2691 static bool check_reg_frame_pos(const struct cfi_reg *reg,
2692 int expected_offset)
2693 {
2694 return reg->base == CFI_CFA &&
2695 reg->offset == expected_offset;
2696 }
2697
has_valid_stack_frame(struct insn_state * state)2698 static bool has_valid_stack_frame(struct insn_state *state)
2699 {
2700 struct cfi_state *cfi = &state->cfi;
2701
2702 if (cfi->cfa.base == CFI_BP &&
2703 check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2704 check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2705 return true;
2706
2707 if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2708 return true;
2709
2710 return false;
2711 }
2712
update_cfi_state_regs(struct instruction * insn,struct cfi_state * cfi,struct stack_op * op)2713 static int update_cfi_state_regs(struct instruction *insn,
2714 struct cfi_state *cfi,
2715 struct stack_op *op)
2716 {
2717 struct cfi_reg *cfa = &cfi->cfa;
2718
2719 if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2720 return 0;
2721
2722 /* push */
2723 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2724 cfa->offset += 8;
2725
2726 /* pop */
2727 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2728 cfa->offset -= 8;
2729
2730 /* add immediate to sp */
2731 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2732 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2733 cfa->offset -= op->src.offset;
2734
2735 return 0;
2736 }
2737
save_reg(struct cfi_state * cfi,unsigned char reg,int base,int offset)2738 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2739 {
2740 if (arch_callee_saved_reg(reg) &&
2741 cfi->regs[reg].base == CFI_UNDEFINED) {
2742 cfi->regs[reg].base = base;
2743 cfi->regs[reg].offset = offset;
2744 }
2745 }
2746
restore_reg(struct cfi_state * cfi,unsigned char reg)2747 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2748 {
2749 cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2750 cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2751 }
2752
2753 /*
2754 * A note about DRAP stack alignment:
2755 *
2756 * GCC has the concept of a DRAP register, which is used to help keep track of
2757 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
2758 * register. The typical DRAP pattern is:
2759 *
2760 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
2761 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
2762 * 41 ff 72 f8 pushq -0x8(%r10)
2763 * 55 push %rbp
2764 * 48 89 e5 mov %rsp,%rbp
2765 * (more pushes)
2766 * 41 52 push %r10
2767 * ...
2768 * 41 5a pop %r10
2769 * (more pops)
2770 * 5d pop %rbp
2771 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2772 * c3 retq
2773 *
2774 * There are some variations in the epilogues, like:
2775 *
2776 * 5b pop %rbx
2777 * 41 5a pop %r10
2778 * 41 5c pop %r12
2779 * 41 5d pop %r13
2780 * 41 5e pop %r14
2781 * c9 leaveq
2782 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2783 * c3 retq
2784 *
2785 * and:
2786 *
2787 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
2788 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
2789 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
2790 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
2791 * c9 leaveq
2792 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2793 * c3 retq
2794 *
2795 * Sometimes r13 is used as the DRAP register, in which case it's saved and
2796 * restored beforehand:
2797 *
2798 * 41 55 push %r13
2799 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
2800 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
2801 * ...
2802 * 49 8d 65 f0 lea -0x10(%r13),%rsp
2803 * 41 5d pop %r13
2804 * c3 retq
2805 */
update_cfi_state(struct instruction * insn,struct instruction * next_insn,struct cfi_state * cfi,struct stack_op * op)2806 static int update_cfi_state(struct instruction *insn,
2807 struct instruction *next_insn,
2808 struct cfi_state *cfi, struct stack_op *op)
2809 {
2810 struct cfi_reg *cfa = &cfi->cfa;
2811 struct cfi_reg *regs = cfi->regs;
2812
2813 /* ignore UNWIND_HINT_UNDEFINED regions */
2814 if (cfi->force_undefined)
2815 return 0;
2816
2817 /* stack operations don't make sense with an undefined CFA */
2818 if (cfa->base == CFI_UNDEFINED) {
2819 if (insn_func(insn)) {
2820 WARN_INSN(insn, "undefined stack state");
2821 return -1;
2822 }
2823 return 0;
2824 }
2825
2826 if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2827 cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2828 return update_cfi_state_regs(insn, cfi, op);
2829
2830 switch (op->dest.type) {
2831
2832 case OP_DEST_REG:
2833 switch (op->src.type) {
2834
2835 case OP_SRC_REG:
2836 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2837 cfa->base == CFI_SP &&
2838 check_reg_frame_pos(®s[CFI_BP], -cfa->offset)) {
2839
2840 /* mov %rsp, %rbp */
2841 cfa->base = op->dest.reg;
2842 cfi->bp_scratch = false;
2843 }
2844
2845 else if (op->src.reg == CFI_SP &&
2846 op->dest.reg == CFI_BP && cfi->drap) {
2847
2848 /* drap: mov %rsp, %rbp */
2849 regs[CFI_BP].base = CFI_BP;
2850 regs[CFI_BP].offset = -cfi->stack_size;
2851 cfi->bp_scratch = false;
2852 }
2853
2854 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2855
2856 /*
2857 * mov %rsp, %reg
2858 *
2859 * This is needed for the rare case where GCC
2860 * does:
2861 *
2862 * mov %rsp, %rax
2863 * ...
2864 * mov %rax, %rsp
2865 */
2866 cfi->vals[op->dest.reg].base = CFI_CFA;
2867 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2868 }
2869
2870 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2871 (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2872
2873 /*
2874 * mov %rbp, %rsp
2875 *
2876 * Restore the original stack pointer (Clang).
2877 */
2878 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2879 }
2880
2881 else if (op->dest.reg == cfa->base) {
2882
2883 /* mov %reg, %rsp */
2884 if (cfa->base == CFI_SP &&
2885 cfi->vals[op->src.reg].base == CFI_CFA) {
2886
2887 /*
2888 * This is needed for the rare case
2889 * where GCC does something dumb like:
2890 *
2891 * lea 0x8(%rsp), %rcx
2892 * ...
2893 * mov %rcx, %rsp
2894 */
2895 cfa->offset = -cfi->vals[op->src.reg].offset;
2896 cfi->stack_size = cfa->offset;
2897
2898 } else if (cfa->base == CFI_SP &&
2899 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2900 cfi->vals[op->src.reg].offset == cfa->offset) {
2901
2902 /*
2903 * Stack swizzle:
2904 *
2905 * 1: mov %rsp, (%[tos])
2906 * 2: mov %[tos], %rsp
2907 * ...
2908 * 3: pop %rsp
2909 *
2910 * Where:
2911 *
2912 * 1 - places a pointer to the previous
2913 * stack at the Top-of-Stack of the
2914 * new stack.
2915 *
2916 * 2 - switches to the new stack.
2917 *
2918 * 3 - pops the Top-of-Stack to restore
2919 * the original stack.
2920 *
2921 * Note: we set base to SP_INDIRECT
2922 * here and preserve offset. Therefore
2923 * when the unwinder reaches ToS it
2924 * will dereference SP and then add the
2925 * offset to find the next frame, IOW:
2926 * (%rsp) + offset.
2927 */
2928 cfa->base = CFI_SP_INDIRECT;
2929
2930 } else {
2931 cfa->base = CFI_UNDEFINED;
2932 cfa->offset = 0;
2933 }
2934 }
2935
2936 else if (op->dest.reg == CFI_SP &&
2937 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2938 cfi->vals[op->src.reg].offset == cfa->offset) {
2939
2940 /*
2941 * The same stack swizzle case 2) as above. But
2942 * because we can't change cfa->base, case 3)
2943 * will become a regular POP. Pretend we're a
2944 * PUSH so things don't go unbalanced.
2945 */
2946 cfi->stack_size += 8;
2947 }
2948
2949
2950 break;
2951
2952 case OP_SRC_ADD:
2953 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2954
2955 /* add imm, %rsp */
2956 cfi->stack_size -= op->src.offset;
2957 if (cfa->base == CFI_SP)
2958 cfa->offset -= op->src.offset;
2959 break;
2960 }
2961
2962 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2963
2964 /* lea disp(%rbp), %rsp */
2965 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2966 break;
2967 }
2968
2969 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2970
2971 /* drap: lea disp(%rsp), %drap */
2972 cfi->drap_reg = op->dest.reg;
2973
2974 /*
2975 * lea disp(%rsp), %reg
2976 *
2977 * This is needed for the rare case where GCC
2978 * does something dumb like:
2979 *
2980 * lea 0x8(%rsp), %rcx
2981 * ...
2982 * mov %rcx, %rsp
2983 */
2984 cfi->vals[op->dest.reg].base = CFI_CFA;
2985 cfi->vals[op->dest.reg].offset = \
2986 -cfi->stack_size + op->src.offset;
2987
2988 break;
2989 }
2990
2991 if (cfi->drap && op->dest.reg == CFI_SP &&
2992 op->src.reg == cfi->drap_reg) {
2993
2994 /* drap: lea disp(%drap), %rsp */
2995 cfa->base = CFI_SP;
2996 cfa->offset = cfi->stack_size = -op->src.offset;
2997 cfi->drap_reg = CFI_UNDEFINED;
2998 cfi->drap = false;
2999 break;
3000 }
3001
3002 if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
3003 WARN_INSN(insn, "unsupported stack register modification");
3004 return -1;
3005 }
3006
3007 break;
3008
3009 case OP_SRC_AND:
3010 if (op->dest.reg != CFI_SP ||
3011 (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
3012 (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
3013 WARN_INSN(insn, "unsupported stack pointer realignment");
3014 return -1;
3015 }
3016
3017 if (cfi->drap_reg != CFI_UNDEFINED) {
3018 /* drap: and imm, %rsp */
3019 cfa->base = cfi->drap_reg;
3020 cfa->offset = cfi->stack_size = 0;
3021 cfi->drap = true;
3022 }
3023
3024 /*
3025 * Older versions of GCC (4.8ish) realign the stack
3026 * without DRAP, with a frame pointer.
3027 */
3028
3029 break;
3030
3031 case OP_SRC_POP:
3032 case OP_SRC_POPF:
3033 if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
3034
3035 /* pop %rsp; # restore from a stack swizzle */
3036 cfa->base = CFI_SP;
3037 break;
3038 }
3039
3040 if (!cfi->drap && op->dest.reg == cfa->base) {
3041
3042 /* pop %rbp */
3043 cfa->base = CFI_SP;
3044 }
3045
3046 if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
3047 op->dest.reg == cfi->drap_reg &&
3048 cfi->drap_offset == -cfi->stack_size) {
3049
3050 /* drap: pop %drap */
3051 cfa->base = cfi->drap_reg;
3052 cfa->offset = 0;
3053 cfi->drap_offset = -1;
3054
3055 } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
3056
3057 /* pop %reg */
3058 restore_reg(cfi, op->dest.reg);
3059 }
3060
3061 cfi->stack_size -= 8;
3062 if (cfa->base == CFI_SP)
3063 cfa->offset -= 8;
3064
3065 break;
3066
3067 case OP_SRC_REG_INDIRECT:
3068 if (!cfi->drap && op->dest.reg == cfa->base &&
3069 op->dest.reg == CFI_BP) {
3070
3071 /* mov disp(%rsp), %rbp */
3072 cfa->base = CFI_SP;
3073 cfa->offset = cfi->stack_size;
3074 }
3075
3076 if (cfi->drap && op->src.reg == CFI_BP &&
3077 op->src.offset == cfi->drap_offset) {
3078
3079 /* drap: mov disp(%rbp), %drap */
3080 cfa->base = cfi->drap_reg;
3081 cfa->offset = 0;
3082 cfi->drap_offset = -1;
3083 }
3084
3085 if (cfi->drap && op->src.reg == CFI_BP &&
3086 op->src.offset == regs[op->dest.reg].offset) {
3087
3088 /* drap: mov disp(%rbp), %reg */
3089 restore_reg(cfi, op->dest.reg);
3090
3091 } else if (op->src.reg == cfa->base &&
3092 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
3093
3094 /* mov disp(%rbp), %reg */
3095 /* mov disp(%rsp), %reg */
3096 restore_reg(cfi, op->dest.reg);
3097
3098 } else if (op->src.reg == CFI_SP &&
3099 op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
3100
3101 /* mov disp(%rsp), %reg */
3102 restore_reg(cfi, op->dest.reg);
3103 }
3104
3105 break;
3106
3107 default:
3108 WARN_INSN(insn, "unknown stack-related instruction");
3109 return -1;
3110 }
3111
3112 break;
3113
3114 case OP_DEST_PUSH:
3115 case OP_DEST_PUSHF:
3116 cfi->stack_size += 8;
3117 if (cfa->base == CFI_SP)
3118 cfa->offset += 8;
3119
3120 if (op->src.type != OP_SRC_REG)
3121 break;
3122
3123 if (cfi->drap) {
3124 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3125
3126 /* drap: push %drap */
3127 cfa->base = CFI_BP_INDIRECT;
3128 cfa->offset = -cfi->stack_size;
3129
3130 /* save drap so we know when to restore it */
3131 cfi->drap_offset = -cfi->stack_size;
3132
3133 } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
3134
3135 /* drap: push %rbp */
3136 cfi->stack_size = 0;
3137
3138 } else {
3139
3140 /* drap: push %reg */
3141 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
3142 }
3143
3144 } else {
3145
3146 /* push %reg */
3147 save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
3148 }
3149
3150 /* detect when asm code uses rbp as a scratch register */
3151 if (opts.stackval && insn_func(insn) && op->src.reg == CFI_BP &&
3152 cfa->base != CFI_BP)
3153 cfi->bp_scratch = true;
3154 break;
3155
3156 case OP_DEST_REG_INDIRECT:
3157
3158 if (cfi->drap) {
3159 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3160
3161 /* drap: mov %drap, disp(%rbp) */
3162 cfa->base = CFI_BP_INDIRECT;
3163 cfa->offset = op->dest.offset;
3164
3165 /* save drap offset so we know when to restore it */
3166 cfi->drap_offset = op->dest.offset;
3167 } else {
3168
3169 /* drap: mov reg, disp(%rbp) */
3170 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
3171 }
3172
3173 } else if (op->dest.reg == cfa->base) {
3174
3175 /* mov reg, disp(%rbp) */
3176 /* mov reg, disp(%rsp) */
3177 save_reg(cfi, op->src.reg, CFI_CFA,
3178 op->dest.offset - cfi->cfa.offset);
3179
3180 } else if (op->dest.reg == CFI_SP) {
3181
3182 /* mov reg, disp(%rsp) */
3183 save_reg(cfi, op->src.reg, CFI_CFA,
3184 op->dest.offset - cfi->stack_size);
3185
3186 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
3187
3188 /* mov %rsp, (%reg); # setup a stack swizzle. */
3189 cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
3190 cfi->vals[op->dest.reg].offset = cfa->offset;
3191 }
3192
3193 break;
3194
3195 case OP_DEST_MEM:
3196 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
3197 WARN_INSN(insn, "unknown stack-related memory operation");
3198 return -1;
3199 }
3200
3201 /* pop mem */
3202 cfi->stack_size -= 8;
3203 if (cfa->base == CFI_SP)
3204 cfa->offset -= 8;
3205
3206 break;
3207
3208 default:
3209 WARN_INSN(insn, "unknown stack-related instruction");
3210 return -1;
3211 }
3212
3213 return 0;
3214 }
3215
3216 /*
3217 * The stack layouts of alternatives instructions can sometimes diverge when
3218 * they have stack modifications. That's fine as long as the potential stack
3219 * layouts don't conflict at any given potential instruction boundary.
3220 *
3221 * Flatten the CFIs of the different alternative code streams (both original
3222 * and replacement) into a single shared CFI array which can be used to detect
3223 * conflicts and nicely feed a linear array of ORC entries to the unwinder.
3224 */
propagate_alt_cfi(struct objtool_file * file,struct instruction * insn)3225 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
3226 {
3227 struct cfi_state **alt_cfi;
3228 int group_off;
3229
3230 if (!insn->alt_group)
3231 return 0;
3232
3233 if (!insn->cfi) {
3234 WARN("CFI missing");
3235 return -1;
3236 }
3237
3238 alt_cfi = insn->alt_group->cfi;
3239 group_off = insn->offset - insn->alt_group->first_insn->offset;
3240
3241 if (!alt_cfi[group_off]) {
3242 alt_cfi[group_off] = insn->cfi;
3243 } else {
3244 if (cficmp(alt_cfi[group_off], insn->cfi)) {
3245 struct alt_group *orig_group = insn->alt_group->orig_group ?: insn->alt_group;
3246 struct instruction *orig = orig_group->first_insn;
3247 char *where = offstr(insn->sec, insn->offset);
3248 WARN_INSN(orig, "stack layout conflict in alternatives: %s", where);
3249 free(where);
3250 return -1;
3251 }
3252 }
3253
3254 return 0;
3255 }
3256
handle_insn_ops(struct instruction * insn,struct instruction * next_insn,struct insn_state * state)3257 static int handle_insn_ops(struct instruction *insn,
3258 struct instruction *next_insn,
3259 struct insn_state *state)
3260 {
3261 struct stack_op *op;
3262
3263 for (op = insn->stack_ops; op; op = op->next) {
3264
3265 if (update_cfi_state(insn, next_insn, &state->cfi, op))
3266 return 1;
3267
3268 if (!insn->alt_group)
3269 continue;
3270
3271 if (op->dest.type == OP_DEST_PUSHF) {
3272 if (!state->uaccess_stack) {
3273 state->uaccess_stack = 1;
3274 } else if (state->uaccess_stack >> 31) {
3275 WARN_INSN(insn, "PUSHF stack exhausted");
3276 return 1;
3277 }
3278 state->uaccess_stack <<= 1;
3279 state->uaccess_stack |= state->uaccess;
3280 }
3281
3282 if (op->src.type == OP_SRC_POPF) {
3283 if (state->uaccess_stack) {
3284 state->uaccess = state->uaccess_stack & 1;
3285 state->uaccess_stack >>= 1;
3286 if (state->uaccess_stack == 1)
3287 state->uaccess_stack = 0;
3288 }
3289 }
3290 }
3291
3292 return 0;
3293 }
3294
insn_cfi_match(struct instruction * insn,struct cfi_state * cfi2)3295 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
3296 {
3297 struct cfi_state *cfi1 = insn->cfi;
3298 int i;
3299
3300 if (!cfi1) {
3301 WARN("CFI missing");
3302 return false;
3303 }
3304
3305 if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
3306
3307 WARN_INSN(insn, "stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
3308 cfi1->cfa.base, cfi1->cfa.offset,
3309 cfi2->cfa.base, cfi2->cfa.offset);
3310
3311 } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
3312 for (i = 0; i < CFI_NUM_REGS; i++) {
3313 if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
3314 sizeof(struct cfi_reg)))
3315 continue;
3316
3317 WARN_INSN(insn, "stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
3318 i, cfi1->regs[i].base, cfi1->regs[i].offset,
3319 i, cfi2->regs[i].base, cfi2->regs[i].offset);
3320 break;
3321 }
3322
3323 } else if (cfi1->type != cfi2->type) {
3324
3325 WARN_INSN(insn, "stack state mismatch: type1=%d type2=%d",
3326 cfi1->type, cfi2->type);
3327
3328 } else if (cfi1->drap != cfi2->drap ||
3329 (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
3330 (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
3331
3332 WARN_INSN(insn, "stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
3333 cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
3334 cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
3335
3336 } else
3337 return true;
3338
3339 return false;
3340 }
3341
func_uaccess_safe(struct symbol * func)3342 static inline bool func_uaccess_safe(struct symbol *func)
3343 {
3344 if (func)
3345 return func->uaccess_safe;
3346
3347 return false;
3348 }
3349
call_dest_name(struct instruction * insn)3350 static inline const char *call_dest_name(struct instruction *insn)
3351 {
3352 static char pvname[19];
3353 struct reloc *reloc;
3354 int idx;
3355
3356 if (insn_call_dest(insn))
3357 return insn_call_dest(insn)->name;
3358
3359 reloc = insn_reloc(NULL, insn);
3360 if (reloc && !strcmp(reloc->sym->name, "pv_ops")) {
3361 idx = (reloc_addend(reloc) / sizeof(void *));
3362 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
3363 return pvname;
3364 }
3365
3366 return "{dynamic}";
3367 }
3368
pv_call_dest(struct objtool_file * file,struct instruction * insn)3369 static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3370 {
3371 struct symbol *target;
3372 struct reloc *reloc;
3373 int idx;
3374
3375 reloc = insn_reloc(file, insn);
3376 if (!reloc || strcmp(reloc->sym->name, "pv_ops"))
3377 return false;
3378
3379 idx = (arch_dest_reloc_offset(reloc_addend(reloc)) / sizeof(void *));
3380
3381 if (file->pv_ops[idx].clean)
3382 return true;
3383
3384 file->pv_ops[idx].clean = true;
3385
3386 list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3387 if (!target->sec->noinstr) {
3388 WARN("pv_ops[%d]: %s", idx, target->name);
3389 file->pv_ops[idx].clean = false;
3390 }
3391 }
3392
3393 return file->pv_ops[idx].clean;
3394 }
3395
noinstr_call_dest(struct objtool_file * file,struct instruction * insn,struct symbol * func)3396 static inline bool noinstr_call_dest(struct objtool_file *file,
3397 struct instruction *insn,
3398 struct symbol *func)
3399 {
3400 /*
3401 * We can't deal with indirect function calls at present;
3402 * assume they're instrumented.
3403 */
3404 if (!func) {
3405 if (file->pv_ops)
3406 return pv_call_dest(file, insn);
3407
3408 return false;
3409 }
3410
3411 /*
3412 * If the symbol is from a noinstr section; we good.
3413 */
3414 if (func->sec->noinstr)
3415 return true;
3416
3417 /*
3418 * If the symbol is a static_call trampoline, we can't tell.
3419 */
3420 if (func->static_call_tramp)
3421 return true;
3422
3423 /*
3424 * The __ubsan_handle_*() calls are like WARN(), they only happen when
3425 * something 'BAD' happened. At the risk of taking the machine down,
3426 * let them proceed to get the message out.
3427 */
3428 if (!strncmp(func->name, "__ubsan_handle_", 15))
3429 return true;
3430
3431 return false;
3432 }
3433
validate_call(struct objtool_file * file,struct instruction * insn,struct insn_state * state)3434 static int validate_call(struct objtool_file *file,
3435 struct instruction *insn,
3436 struct insn_state *state)
3437 {
3438 if (state->noinstr && state->instr <= 0 &&
3439 !noinstr_call_dest(file, insn, insn_call_dest(insn))) {
3440 WARN_INSN(insn, "call to %s() leaves .noinstr.text section", call_dest_name(insn));
3441 return 1;
3442 }
3443
3444 if (state->uaccess && !func_uaccess_safe(insn_call_dest(insn))) {
3445 WARN_INSN(insn, "call to %s() with UACCESS enabled", call_dest_name(insn));
3446 return 1;
3447 }
3448
3449 if (state->df) {
3450 WARN_INSN(insn, "call to %s() with DF set", call_dest_name(insn));
3451 return 1;
3452 }
3453
3454 return 0;
3455 }
3456
validate_sibling_call(struct objtool_file * file,struct instruction * insn,struct insn_state * state)3457 static int validate_sibling_call(struct objtool_file *file,
3458 struct instruction *insn,
3459 struct insn_state *state)
3460 {
3461 if (insn_func(insn) && has_modified_stack_frame(insn, state)) {
3462 WARN_INSN(insn, "sibling call from callable instruction with modified stack frame");
3463 return 1;
3464 }
3465
3466 return validate_call(file, insn, state);
3467 }
3468
validate_return(struct symbol * func,struct instruction * insn,struct insn_state * state)3469 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3470 {
3471 if (state->noinstr && state->instr > 0) {
3472 WARN_INSN(insn, "return with instrumentation enabled");
3473 return 1;
3474 }
3475
3476 if (state->uaccess && !func_uaccess_safe(func)) {
3477 WARN_INSN(insn, "return with UACCESS enabled");
3478 return 1;
3479 }
3480
3481 if (!state->uaccess && func_uaccess_safe(func)) {
3482 WARN_INSN(insn, "return with UACCESS disabled from a UACCESS-safe function");
3483 return 1;
3484 }
3485
3486 if (state->df) {
3487 WARN_INSN(insn, "return with DF set");
3488 return 1;
3489 }
3490
3491 if (func && has_modified_stack_frame(insn, state)) {
3492 WARN_INSN(insn, "return with modified stack frame");
3493 return 1;
3494 }
3495
3496 if (state->cfi.bp_scratch) {
3497 WARN_INSN(insn, "BP used as a scratch register");
3498 return 1;
3499 }
3500
3501 return 0;
3502 }
3503
next_insn_to_validate(struct objtool_file * file,struct instruction * insn)3504 static struct instruction *next_insn_to_validate(struct objtool_file *file,
3505 struct instruction *insn)
3506 {
3507 struct alt_group *alt_group = insn->alt_group;
3508
3509 /*
3510 * Simulate the fact that alternatives are patched in-place. When the
3511 * end of a replacement alt_group is reached, redirect objtool flow to
3512 * the end of the original alt_group.
3513 *
3514 * insn->alts->insn -> alt_group->first_insn
3515 * ...
3516 * alt_group->last_insn
3517 * [alt_group->nop] -> next(orig_group->last_insn)
3518 */
3519 if (alt_group) {
3520 if (alt_group->nop) {
3521 /* ->nop implies ->orig_group */
3522 if (insn == alt_group->last_insn)
3523 return alt_group->nop;
3524 if (insn == alt_group->nop)
3525 goto next_orig;
3526 }
3527 if (insn == alt_group->last_insn && alt_group->orig_group)
3528 goto next_orig;
3529 }
3530
3531 return next_insn_same_sec(file, insn);
3532
3533 next_orig:
3534 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3535 }
3536
3537 /*
3538 * Follow the branch starting at the given instruction, and recursively follow
3539 * any other branches (jumps). Meanwhile, track the frame pointer state at
3540 * each instruction and validate all the rules described in
3541 * tools/objtool/Documentation/objtool.txt.
3542 */
validate_branch(struct objtool_file * file,struct symbol * func,struct instruction * insn,struct insn_state state)3543 static int validate_branch(struct objtool_file *file, struct symbol *func,
3544 struct instruction *insn, struct insn_state state)
3545 {
3546 struct alternative *alt;
3547 struct instruction *next_insn, *prev_insn = NULL;
3548 struct section *sec;
3549 u8 visited;
3550 int ret;
3551
3552 sec = insn->sec;
3553
3554 while (1) {
3555 next_insn = next_insn_to_validate(file, insn);
3556
3557 if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {
3558 /* Ignore KCFI type preambles, which always fall through */
3559 if (!strncmp(func->name, "__cfi_", 6) ||
3560 !strncmp(func->name, "__pfx_", 6))
3561 return 0;
3562
3563 WARN("%s() falls through to next function %s()",
3564 func->name, insn_func(insn)->name);
3565 return 1;
3566 }
3567
3568 if (func && insn->ignore) {
3569 WARN_INSN(insn, "BUG: why am I validating an ignored function?");
3570 return 1;
3571 }
3572
3573 visited = VISITED_BRANCH << state.uaccess;
3574 if (insn->visited & VISITED_BRANCH_MASK) {
3575 if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3576 return 1;
3577
3578 if (insn->visited & visited)
3579 return 0;
3580 } else {
3581 nr_insns_visited++;
3582 }
3583
3584 if (state.noinstr)
3585 state.instr += insn->instr;
3586
3587 if (insn->hint) {
3588 if (insn->restore) {
3589 struct instruction *save_insn, *i;
3590
3591 i = insn;
3592 save_insn = NULL;
3593
3594 sym_for_each_insn_continue_reverse(file, func, i) {
3595 if (i->save) {
3596 save_insn = i;
3597 break;
3598 }
3599 }
3600
3601 if (!save_insn) {
3602 WARN_INSN(insn, "no corresponding CFI save for CFI restore");
3603 return 1;
3604 }
3605
3606 if (!save_insn->visited) {
3607 WARN_INSN(insn, "objtool isn't smart enough to handle this CFI save/restore combo");
3608 return 1;
3609 }
3610
3611 insn->cfi = save_insn->cfi;
3612 nr_cfi_reused++;
3613 }
3614
3615 state.cfi = *insn->cfi;
3616 } else {
3617 /* XXX track if we actually changed state.cfi */
3618
3619 if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3620 insn->cfi = prev_insn->cfi;
3621 nr_cfi_reused++;
3622 } else {
3623 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3624 }
3625 }
3626
3627 insn->visited |= visited;
3628
3629 if (propagate_alt_cfi(file, insn))
3630 return 1;
3631
3632 if (!insn->ignore_alts && insn->alts) {
3633 bool skip_orig = false;
3634
3635 for (alt = insn->alts; alt; alt = alt->next) {
3636 if (alt->skip_orig)
3637 skip_orig = true;
3638
3639 ret = validate_branch(file, func, alt->insn, state);
3640 if (ret) {
3641 BT_INSN(insn, "(alt)");
3642 return ret;
3643 }
3644 }
3645
3646 if (skip_orig)
3647 return 0;
3648 }
3649
3650 if (handle_insn_ops(insn, next_insn, &state))
3651 return 1;
3652
3653 switch (insn->type) {
3654
3655 case INSN_RETURN:
3656 return validate_return(func, insn, &state);
3657
3658 case INSN_CALL:
3659 case INSN_CALL_DYNAMIC:
3660 ret = validate_call(file, insn, &state);
3661 if (ret)
3662 return ret;
3663
3664 if (opts.stackval && func && !is_special_call(insn) &&
3665 !has_valid_stack_frame(&state)) {
3666 WARN_INSN(insn, "call without frame pointer save/setup");
3667 return 1;
3668 }
3669
3670 if (insn->dead_end)
3671 return 0;
3672
3673 break;
3674
3675 case INSN_JUMP_CONDITIONAL:
3676 case INSN_JUMP_UNCONDITIONAL:
3677 if (is_sibling_call(insn)) {
3678 ret = validate_sibling_call(file, insn, &state);
3679 if (ret)
3680 return ret;
3681
3682 } else if (insn->jump_dest) {
3683 ret = validate_branch(file, func,
3684 insn->jump_dest, state);
3685 if (ret) {
3686 BT_INSN(insn, "(branch)");
3687 return ret;
3688 }
3689 }
3690
3691 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3692 return 0;
3693
3694 break;
3695
3696 case INSN_JUMP_DYNAMIC:
3697 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3698 if (is_sibling_call(insn)) {
3699 ret = validate_sibling_call(file, insn, &state);
3700 if (ret)
3701 return ret;
3702 }
3703
3704 if (insn->type == INSN_JUMP_DYNAMIC)
3705 return 0;
3706
3707 break;
3708
3709 case INSN_CONTEXT_SWITCH:
3710 if (func && (!next_insn || !next_insn->hint)) {
3711 WARN_INSN(insn, "unsupported instruction in callable function");
3712 return 1;
3713 }
3714 return 0;
3715
3716 case INSN_STAC:
3717 if (state.uaccess) {
3718 WARN_INSN(insn, "recursive UACCESS enable");
3719 return 1;
3720 }
3721
3722 state.uaccess = true;
3723 break;
3724
3725 case INSN_CLAC:
3726 if (!state.uaccess && func) {
3727 WARN_INSN(insn, "redundant UACCESS disable");
3728 return 1;
3729 }
3730
3731 if (func_uaccess_safe(func) && !state.uaccess_stack) {
3732 WARN_INSN(insn, "UACCESS-safe disables UACCESS");
3733 return 1;
3734 }
3735
3736 state.uaccess = false;
3737 break;
3738
3739 case INSN_STD:
3740 if (state.df) {
3741 WARN_INSN(insn, "recursive STD");
3742 return 1;
3743 }
3744
3745 state.df = true;
3746 break;
3747
3748 case INSN_CLD:
3749 if (!state.df && func) {
3750 WARN_INSN(insn, "redundant CLD");
3751 return 1;
3752 }
3753
3754 state.df = false;
3755 break;
3756
3757 default:
3758 break;
3759 }
3760
3761 if (insn->dead_end)
3762 return 0;
3763
3764 if (!next_insn) {
3765 if (state.cfi.cfa.base == CFI_UNDEFINED)
3766 return 0;
3767 WARN("%s: unexpected end of section", sec->name);
3768 return 1;
3769 }
3770
3771 prev_insn = insn;
3772 insn = next_insn;
3773 }
3774
3775 return 0;
3776 }
3777
validate_unwind_hint(struct objtool_file * file,struct instruction * insn,struct insn_state * state)3778 static int validate_unwind_hint(struct objtool_file *file,
3779 struct instruction *insn,
3780 struct insn_state *state)
3781 {
3782 if (insn->hint && !insn->visited && !insn->ignore) {
3783 int ret = validate_branch(file, insn_func(insn), insn, *state);
3784 if (ret)
3785 BT_INSN(insn, "<=== (hint)");
3786 return ret;
3787 }
3788
3789 return 0;
3790 }
3791
validate_unwind_hints(struct objtool_file * file,struct section * sec)3792 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3793 {
3794 struct instruction *insn;
3795 struct insn_state state;
3796 int warnings = 0;
3797
3798 if (!file->hints)
3799 return 0;
3800
3801 init_insn_state(file, &state, sec);
3802
3803 if (sec) {
3804 sec_for_each_insn(file, sec, insn)
3805 warnings += validate_unwind_hint(file, insn, &state);
3806 } else {
3807 for_each_insn(file, insn)
3808 warnings += validate_unwind_hint(file, insn, &state);
3809 }
3810
3811 return warnings;
3812 }
3813
3814 /*
3815 * Validate rethunk entry constraint: must untrain RET before the first RET.
3816 *
3817 * Follow every branch (intra-function) and ensure VALIDATE_UNRET_END comes
3818 * before an actual RET instruction.
3819 */
validate_unret(struct objtool_file * file,struct instruction * insn)3820 static int validate_unret(struct objtool_file *file, struct instruction *insn)
3821 {
3822 struct instruction *next, *dest;
3823 int ret;
3824
3825 for (;;) {
3826 next = next_insn_to_validate(file, insn);
3827
3828 if (insn->visited & VISITED_UNRET)
3829 return 0;
3830
3831 insn->visited |= VISITED_UNRET;
3832
3833 if (!insn->ignore_alts && insn->alts) {
3834 struct alternative *alt;
3835 bool skip_orig = false;
3836
3837 for (alt = insn->alts; alt; alt = alt->next) {
3838 if (alt->skip_orig)
3839 skip_orig = true;
3840
3841 ret = validate_unret(file, alt->insn);
3842 if (ret) {
3843 BT_INSN(insn, "(alt)");
3844 return ret;
3845 }
3846 }
3847
3848 if (skip_orig)
3849 return 0;
3850 }
3851
3852 switch (insn->type) {
3853
3854 case INSN_CALL_DYNAMIC:
3855 case INSN_JUMP_DYNAMIC:
3856 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3857 WARN_INSN(insn, "early indirect call");
3858 return 1;
3859
3860 case INSN_JUMP_UNCONDITIONAL:
3861 case INSN_JUMP_CONDITIONAL:
3862 if (!is_sibling_call(insn)) {
3863 if (!insn->jump_dest) {
3864 WARN_INSN(insn, "unresolved jump target after linking?!?");
3865 return -1;
3866 }
3867 ret = validate_unret(file, insn->jump_dest);
3868 if (ret) {
3869 BT_INSN(insn, "(branch%s)",
3870 insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : "");
3871 return ret;
3872 }
3873
3874 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3875 return 0;
3876
3877 break;
3878 }
3879
3880 /* fallthrough */
3881 case INSN_CALL:
3882 dest = find_insn(file, insn_call_dest(insn)->sec,
3883 insn_call_dest(insn)->offset);
3884 if (!dest) {
3885 WARN("Unresolved function after linking!?: %s",
3886 insn_call_dest(insn)->name);
3887 return -1;
3888 }
3889
3890 ret = validate_unret(file, dest);
3891 if (ret) {
3892 BT_INSN(insn, "(call)");
3893 return ret;
3894 }
3895 /*
3896 * If a call returns without error, it must have seen UNTRAIN_RET.
3897 * Therefore any non-error return is a success.
3898 */
3899 return 0;
3900
3901 case INSN_RETURN:
3902 WARN_INSN(insn, "RET before UNTRAIN");
3903 return 1;
3904
3905 case INSN_NOP:
3906 if (insn->retpoline_safe)
3907 return 0;
3908 break;
3909
3910 default:
3911 break;
3912 }
3913
3914 if (!next) {
3915 WARN_INSN(insn, "teh end!");
3916 return -1;
3917 }
3918 insn = next;
3919 }
3920
3921 return 0;
3922 }
3923
3924 /*
3925 * Validate that all branches starting at VALIDATE_UNRET_BEGIN encounter
3926 * VALIDATE_UNRET_END before RET.
3927 */
validate_unrets(struct objtool_file * file)3928 static int validate_unrets(struct objtool_file *file)
3929 {
3930 struct instruction *insn;
3931 int ret, warnings = 0;
3932
3933 for_each_insn(file, insn) {
3934 if (!insn->unret)
3935 continue;
3936
3937 ret = validate_unret(file, insn);
3938 if (ret < 0) {
3939 WARN_INSN(insn, "Failed UNRET validation");
3940 return ret;
3941 }
3942 warnings += ret;
3943 }
3944
3945 return warnings;
3946 }
3947
validate_retpoline(struct objtool_file * file)3948 static int validate_retpoline(struct objtool_file *file)
3949 {
3950 struct instruction *insn;
3951 int warnings = 0;
3952
3953 for_each_insn(file, insn) {
3954 if (insn->type != INSN_JUMP_DYNAMIC &&
3955 insn->type != INSN_CALL_DYNAMIC &&
3956 insn->type != INSN_RETURN)
3957 continue;
3958
3959 if (insn->retpoline_safe)
3960 continue;
3961
3962 if (insn->sec->init)
3963 continue;
3964
3965 if (insn->type == INSN_RETURN) {
3966 if (opts.rethunk) {
3967 WARN_INSN(insn, "'naked' return found in RETHUNK build");
3968 } else
3969 continue;
3970 } else {
3971 WARN_INSN(insn, "indirect %s found in RETPOLINE build",
3972 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
3973 }
3974
3975 warnings++;
3976 }
3977
3978 return warnings;
3979 }
3980
is_kasan_insn(struct instruction * insn)3981 static bool is_kasan_insn(struct instruction *insn)
3982 {
3983 return (insn->type == INSN_CALL &&
3984 !strcmp(insn_call_dest(insn)->name, "__asan_handle_no_return"));
3985 }
3986
is_ubsan_insn(struct instruction * insn)3987 static bool is_ubsan_insn(struct instruction *insn)
3988 {
3989 return (insn->type == INSN_CALL &&
3990 !strcmp(insn_call_dest(insn)->name,
3991 "__ubsan_handle_builtin_unreachable"));
3992 }
3993
ignore_unreachable_insn(struct objtool_file * file,struct instruction * insn)3994 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
3995 {
3996 int i;
3997 struct instruction *prev_insn;
3998
3999 if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
4000 return true;
4001
4002 /*
4003 * Ignore alternative replacement instructions. This can happen
4004 * when a whitelisted function uses one of the ALTERNATIVE macros.
4005 */
4006 if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
4007 !strcmp(insn->sec->name, ".altinstr_aux"))
4008 return true;
4009
4010 /*
4011 * Whole archive runs might encounter dead code from weak symbols.
4012 * This is where the linker will have dropped the weak symbol in
4013 * favour of a regular symbol, but leaves the code in place.
4014 *
4015 * In this case we'll find a piece of code (whole function) that is not
4016 * covered by a !section symbol. Ignore them.
4017 */
4018 if (opts.link && !insn_func(insn)) {
4019 int size = find_symbol_hole_containing(insn->sec, insn->offset);
4020 unsigned long end = insn->offset + size;
4021
4022 if (!size) /* not a hole */
4023 return false;
4024
4025 if (size < 0) /* hole until the end */
4026 return true;
4027
4028 sec_for_each_insn_continue(file, insn) {
4029 /*
4030 * If we reach a visited instruction at or before the
4031 * end of the hole, ignore the unreachable.
4032 */
4033 if (insn->visited)
4034 return true;
4035
4036 if (insn->offset >= end)
4037 break;
4038
4039 /*
4040 * If this hole jumps to a .cold function, mark it ignore too.
4041 */
4042 if (insn->jump_dest && insn_func(insn->jump_dest) &&
4043 strstr(insn_func(insn->jump_dest)->name, ".cold")) {
4044 struct instruction *dest = insn->jump_dest;
4045 func_for_each_insn(file, insn_func(dest), dest)
4046 dest->ignore = true;
4047 }
4048 }
4049
4050 return false;
4051 }
4052
4053 if (!insn_func(insn))
4054 return false;
4055
4056 if (insn_func(insn)->static_call_tramp)
4057 return true;
4058
4059 /*
4060 * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
4061 * __builtin_unreachable(). The BUG() macro has an unreachable() after
4062 * the UD2, which causes GCC's undefined trap logic to emit another UD2
4063 * (or occasionally a JMP to UD2).
4064 *
4065 * It may also insert a UD2 after calling a __noreturn function.
4066 */
4067 prev_insn = prev_insn_same_sec(file, insn);
4068 if (prev_insn->dead_end &&
4069 (insn->type == INSN_BUG ||
4070 (insn->type == INSN_JUMP_UNCONDITIONAL &&
4071 insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
4072 return true;
4073
4074 /*
4075 * Check if this (or a subsequent) instruction is related to
4076 * CONFIG_UBSAN or CONFIG_KASAN.
4077 *
4078 * End the search at 5 instructions to avoid going into the weeds.
4079 */
4080 for (i = 0; i < 5; i++) {
4081
4082 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
4083 return true;
4084
4085 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
4086 if (insn->jump_dest &&
4087 insn_func(insn->jump_dest) == insn_func(insn)) {
4088 insn = insn->jump_dest;
4089 continue;
4090 }
4091
4092 break;
4093 }
4094
4095 if (insn->offset + insn->len >= insn_func(insn)->offset + insn_func(insn)->len)
4096 break;
4097
4098 insn = next_insn_same_sec(file, insn);
4099 }
4100
4101 return false;
4102 }
4103
add_prefix_symbol(struct objtool_file * file,struct symbol * func)4104 static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
4105 {
4106 struct instruction *insn, *prev;
4107 struct cfi_state *cfi;
4108
4109 insn = find_insn(file, func->sec, func->offset);
4110 if (!insn)
4111 return -1;
4112
4113 for (prev = prev_insn_same_sec(file, insn);
4114 prev;
4115 prev = prev_insn_same_sec(file, prev)) {
4116 u64 offset;
4117
4118 if (prev->type != INSN_NOP)
4119 return -1;
4120
4121 offset = func->offset - prev->offset;
4122
4123 if (offset > opts.prefix)
4124 return -1;
4125
4126 if (offset < opts.prefix)
4127 continue;
4128
4129 elf_create_prefix_symbol(file->elf, func, opts.prefix);
4130 break;
4131 }
4132
4133 if (!prev)
4134 return -1;
4135
4136 if (!insn->cfi) {
4137 /*
4138 * This can happen if stack validation isn't enabled or the
4139 * function is annotated with STACK_FRAME_NON_STANDARD.
4140 */
4141 return 0;
4142 }
4143
4144 /* Propagate insn->cfi to the prefix code */
4145 cfi = cfi_hash_find_or_add(insn->cfi);
4146 for (; prev != insn; prev = next_insn_same_sec(file, prev))
4147 prev->cfi = cfi;
4148
4149 return 0;
4150 }
4151
add_prefix_symbols(struct objtool_file * file)4152 static int add_prefix_symbols(struct objtool_file *file)
4153 {
4154 struct section *sec;
4155 struct symbol *func;
4156
4157 for_each_sec(file, sec) {
4158 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4159 continue;
4160
4161 sec_for_each_sym(sec, func) {
4162 if (func->type != STT_FUNC)
4163 continue;
4164
4165 add_prefix_symbol(file, func);
4166 }
4167 }
4168
4169 return 0;
4170 }
4171
validate_symbol(struct objtool_file * file,struct section * sec,struct symbol * sym,struct insn_state * state)4172 static int validate_symbol(struct objtool_file *file, struct section *sec,
4173 struct symbol *sym, struct insn_state *state)
4174 {
4175 struct instruction *insn;
4176 int ret;
4177
4178 if (!sym->len) {
4179 WARN("%s() is missing an ELF size annotation", sym->name);
4180 return 1;
4181 }
4182
4183 if (sym->pfunc != sym || sym->alias != sym)
4184 return 0;
4185
4186 insn = find_insn(file, sec, sym->offset);
4187 if (!insn || insn->ignore || insn->visited)
4188 return 0;
4189
4190 state->uaccess = sym->uaccess_safe;
4191
4192 ret = validate_branch(file, insn_func(insn), insn, *state);
4193 if (ret)
4194 BT_INSN(insn, "<=== (sym)");
4195 return ret;
4196 }
4197
validate_section(struct objtool_file * file,struct section * sec)4198 static int validate_section(struct objtool_file *file, struct section *sec)
4199 {
4200 struct insn_state state;
4201 struct symbol *func;
4202 int warnings = 0;
4203
4204 sec_for_each_sym(sec, func) {
4205 if (func->type != STT_FUNC)
4206 continue;
4207
4208 init_insn_state(file, &state, sec);
4209 set_func_state(&state.cfi);
4210
4211 warnings += validate_symbol(file, sec, func, &state);
4212 }
4213
4214 return warnings;
4215 }
4216
validate_noinstr_sections(struct objtool_file * file)4217 static int validate_noinstr_sections(struct objtool_file *file)
4218 {
4219 struct section *sec;
4220 int warnings = 0;
4221
4222 sec = find_section_by_name(file->elf, ".noinstr.text");
4223 if (sec) {
4224 warnings += validate_section(file, sec);
4225 warnings += validate_unwind_hints(file, sec);
4226 }
4227
4228 sec = find_section_by_name(file->elf, ".entry.text");
4229 if (sec) {
4230 warnings += validate_section(file, sec);
4231 warnings += validate_unwind_hints(file, sec);
4232 }
4233
4234 sec = find_section_by_name(file->elf, ".cpuidle.text");
4235 if (sec) {
4236 warnings += validate_section(file, sec);
4237 warnings += validate_unwind_hints(file, sec);
4238 }
4239
4240 return warnings;
4241 }
4242
validate_functions(struct objtool_file * file)4243 static int validate_functions(struct objtool_file *file)
4244 {
4245 struct section *sec;
4246 int warnings = 0;
4247
4248 for_each_sec(file, sec) {
4249 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4250 continue;
4251
4252 warnings += validate_section(file, sec);
4253 }
4254
4255 return warnings;
4256 }
4257
mark_endbr_used(struct instruction * insn)4258 static void mark_endbr_used(struct instruction *insn)
4259 {
4260 if (!list_empty(&insn->call_node))
4261 list_del_init(&insn->call_node);
4262 }
4263
noendbr_range(struct objtool_file * file,struct instruction * insn)4264 static bool noendbr_range(struct objtool_file *file, struct instruction *insn)
4265 {
4266 struct symbol *sym = find_symbol_containing(insn->sec, insn->offset-1);
4267 struct instruction *first;
4268
4269 if (!sym)
4270 return false;
4271
4272 first = find_insn(file, sym->sec, sym->offset);
4273 if (!first)
4274 return false;
4275
4276 if (first->type != INSN_ENDBR && !first->noendbr)
4277 return false;
4278
4279 return insn->offset == sym->offset + sym->len;
4280 }
4281
validate_ibt_insn(struct objtool_file * file,struct instruction * insn)4282 static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
4283 {
4284 struct instruction *dest;
4285 struct reloc *reloc;
4286 unsigned long off;
4287 int warnings = 0;
4288
4289 /*
4290 * Looking for function pointer load relocations. Ignore
4291 * direct/indirect branches:
4292 */
4293 switch (insn->type) {
4294 case INSN_CALL:
4295 case INSN_CALL_DYNAMIC:
4296 case INSN_JUMP_CONDITIONAL:
4297 case INSN_JUMP_UNCONDITIONAL:
4298 case INSN_JUMP_DYNAMIC:
4299 case INSN_JUMP_DYNAMIC_CONDITIONAL:
4300 case INSN_RETURN:
4301 case INSN_NOP:
4302 return 0;
4303 default:
4304 break;
4305 }
4306
4307 for (reloc = insn_reloc(file, insn);
4308 reloc;
4309 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
4310 reloc_offset(reloc) + 1,
4311 (insn->offset + insn->len) - (reloc_offset(reloc) + 1))) {
4312
4313 /*
4314 * static_call_update() references the trampoline, which
4315 * doesn't have (or need) ENDBR. Skip warning in that case.
4316 */
4317 if (reloc->sym->static_call_tramp)
4318 continue;
4319
4320 off = reloc->sym->offset;
4321 if (reloc_type(reloc) == R_X86_64_PC32 ||
4322 reloc_type(reloc) == R_X86_64_PLT32)
4323 off += arch_dest_reloc_offset(reloc_addend(reloc));
4324 else
4325 off += reloc_addend(reloc);
4326
4327 dest = find_insn(file, reloc->sym->sec, off);
4328 if (!dest)
4329 continue;
4330
4331 if (dest->type == INSN_ENDBR) {
4332 mark_endbr_used(dest);
4333 continue;
4334 }
4335
4336 if (insn_func(dest) && insn_func(insn) &&
4337 insn_func(dest)->pfunc == insn_func(insn)->pfunc) {
4338 /*
4339 * Anything from->to self is either _THIS_IP_ or
4340 * IRET-to-self.
4341 *
4342 * There is no sane way to annotate _THIS_IP_ since the
4343 * compiler treats the relocation as a constant and is
4344 * happy to fold in offsets, skewing any annotation we
4345 * do, leading to vast amounts of false-positives.
4346 *
4347 * There's also compiler generated _THIS_IP_ through
4348 * KCOV and such which we have no hope of annotating.
4349 *
4350 * As such, blanket accept self-references without
4351 * issue.
4352 */
4353 continue;
4354 }
4355
4356 /*
4357 * Accept anything ANNOTATE_NOENDBR.
4358 */
4359 if (dest->noendbr)
4360 continue;
4361
4362 /*
4363 * Accept if this is the instruction after a symbol
4364 * that is (no)endbr -- typical code-range usage.
4365 */
4366 if (noendbr_range(file, dest))
4367 continue;
4368
4369 WARN_INSN(insn, "relocation to !ENDBR: %s", offstr(dest->sec, dest->offset));
4370
4371 warnings++;
4372 }
4373
4374 return warnings;
4375 }
4376
validate_ibt_data_reloc(struct objtool_file * file,struct reloc * reloc)4377 static int validate_ibt_data_reloc(struct objtool_file *file,
4378 struct reloc *reloc)
4379 {
4380 struct instruction *dest;
4381
4382 dest = find_insn(file, reloc->sym->sec,
4383 reloc->sym->offset + reloc_addend(reloc));
4384 if (!dest)
4385 return 0;
4386
4387 if (dest->type == INSN_ENDBR) {
4388 mark_endbr_used(dest);
4389 return 0;
4390 }
4391
4392 if (dest->noendbr)
4393 return 0;
4394
4395 WARN_FUNC("data relocation to !ENDBR: %s",
4396 reloc->sec->base, reloc_offset(reloc),
4397 offstr(dest->sec, dest->offset));
4398
4399 return 1;
4400 }
4401
4402 /*
4403 * Validate IBT rules and remove used ENDBR instructions from the seal list.
4404 * Unused ENDBR instructions will be annotated for sealing (i.e., replaced with
4405 * NOPs) later, in create_ibt_endbr_seal_sections().
4406 */
validate_ibt(struct objtool_file * file)4407 static int validate_ibt(struct objtool_file *file)
4408 {
4409 struct section *sec;
4410 struct reloc *reloc;
4411 struct instruction *insn;
4412 int warnings = 0;
4413
4414 for_each_insn(file, insn)
4415 warnings += validate_ibt_insn(file, insn);
4416
4417 for_each_sec(file, sec) {
4418
4419 /* Already done by validate_ibt_insn() */
4420 if (sec->sh.sh_flags & SHF_EXECINSTR)
4421 continue;
4422
4423 if (!sec->rsec)
4424 continue;
4425
4426 /*
4427 * These sections can reference text addresses, but not with
4428 * the intent to indirect branch to them.
4429 */
4430 if ((!strncmp(sec->name, ".discard", 8) &&
4431 strcmp(sec->name, ".discard.ibt_endbr_noseal")) ||
4432 !strncmp(sec->name, ".debug", 6) ||
4433 !strcmp(sec->name, ".altinstructions") ||
4434 !strcmp(sec->name, ".ibt_endbr_seal") ||
4435 !strcmp(sec->name, ".orc_unwind_ip") ||
4436 !strcmp(sec->name, ".parainstructions") ||
4437 !strcmp(sec->name, ".retpoline_sites") ||
4438 !strcmp(sec->name, ".smp_locks") ||
4439 !strcmp(sec->name, ".static_call_sites") ||
4440 !strcmp(sec->name, "_error_injection_whitelist") ||
4441 !strcmp(sec->name, "_kprobe_blacklist") ||
4442 !strcmp(sec->name, "__bug_table") ||
4443 !strcmp(sec->name, "__ex_table") ||
4444 !strcmp(sec->name, "__jump_table") ||
4445 !strcmp(sec->name, "__mcount_loc") ||
4446 !strcmp(sec->name, ".kcfi_traps") ||
4447 strstr(sec->name, "__patchable_function_entries"))
4448 continue;
4449
4450 for_each_reloc(sec->rsec, reloc)
4451 warnings += validate_ibt_data_reloc(file, reloc);
4452 }
4453
4454 return warnings;
4455 }
4456
validate_sls(struct objtool_file * file)4457 static int validate_sls(struct objtool_file *file)
4458 {
4459 struct instruction *insn, *next_insn;
4460 int warnings = 0;
4461
4462 for_each_insn(file, insn) {
4463 next_insn = next_insn_same_sec(file, insn);
4464
4465 if (insn->retpoline_safe)
4466 continue;
4467
4468 switch (insn->type) {
4469 case INSN_RETURN:
4470 if (!next_insn || next_insn->type != INSN_TRAP) {
4471 WARN_INSN(insn, "missing int3 after ret");
4472 warnings++;
4473 }
4474
4475 break;
4476 case INSN_JUMP_DYNAMIC:
4477 if (!next_insn || next_insn->type != INSN_TRAP) {
4478 WARN_INSN(insn, "missing int3 after indirect jump");
4479 warnings++;
4480 }
4481 break;
4482 default:
4483 break;
4484 }
4485 }
4486
4487 return warnings;
4488 }
4489
ignore_noreturn_call(struct instruction * insn)4490 static bool ignore_noreturn_call(struct instruction *insn)
4491 {
4492 struct symbol *call_dest = insn_call_dest(insn);
4493
4494 /*
4495 * FIXME: hack, we need a real noreturn solution
4496 *
4497 * Problem is, exc_double_fault() may or may not return, depending on
4498 * whether CONFIG_X86_ESPFIX64 is set. But objtool has no visibility
4499 * to the kernel config.
4500 *
4501 * Other potential ways to fix it:
4502 *
4503 * - have compiler communicate __noreturn functions somehow
4504 * - remove CONFIG_X86_ESPFIX64
4505 * - read the .config file
4506 * - add a cmdline option
4507 * - create a generic objtool annotation format (vs a bunch of custom
4508 * formats) and annotate it
4509 */
4510 if (!strcmp(call_dest->name, "exc_double_fault")) {
4511 /* prevent further unreachable warnings for the caller */
4512 insn->sym->warned = 1;
4513 return true;
4514 }
4515
4516 return false;
4517 }
4518
validate_reachable_instructions(struct objtool_file * file)4519 static int validate_reachable_instructions(struct objtool_file *file)
4520 {
4521 struct instruction *insn, *prev_insn;
4522 struct symbol *call_dest;
4523 int warnings = 0;
4524
4525 if (file->ignore_unreachables)
4526 return 0;
4527
4528 for_each_insn(file, insn) {
4529 if (insn->visited || ignore_unreachable_insn(file, insn))
4530 continue;
4531
4532 prev_insn = prev_insn_same_sec(file, insn);
4533 if (prev_insn && prev_insn->dead_end) {
4534 call_dest = insn_call_dest(prev_insn);
4535 if (call_dest && !ignore_noreturn_call(prev_insn)) {
4536 WARN_INSN(insn, "%s() is missing a __noreturn annotation",
4537 call_dest->name);
4538 warnings++;
4539 continue;
4540 }
4541 }
4542
4543 WARN_INSN(insn, "unreachable instruction");
4544 warnings++;
4545 }
4546
4547 return warnings;
4548 }
4549
4550 /* 'funcs' is a space-separated list of function names */
disas_funcs(const char * funcs)4551 static int disas_funcs(const char *funcs)
4552 {
4553 const char *objdump_str, *cross_compile;
4554 int size, ret;
4555 char *cmd;
4556
4557 cross_compile = getenv("CROSS_COMPILE");
4558
4559 objdump_str = "%sobjdump -wdr %s | gawk -M -v _funcs='%s' '"
4560 "BEGIN { split(_funcs, funcs); }"
4561 "/^$/ { func_match = 0; }"
4562 "/<.*>:/ { "
4563 "f = gensub(/.*<(.*)>:/, \"\\\\1\", 1);"
4564 "for (i in funcs) {"
4565 "if (funcs[i] == f) {"
4566 "func_match = 1;"
4567 "base = strtonum(\"0x\" $1);"
4568 "break;"
4569 "}"
4570 "}"
4571 "}"
4572 "{"
4573 "if (func_match) {"
4574 "addr = strtonum(\"0x\" $1);"
4575 "printf(\"%%04x \", addr - base);"
4576 "print;"
4577 "}"
4578 "}' 1>&2";
4579
4580 /* fake snprintf() to calculate the size */
4581 size = snprintf(NULL, 0, objdump_str, cross_compile, objname, funcs) + 1;
4582 if (size <= 0) {
4583 WARN("objdump string size calculation failed");
4584 return -1;
4585 }
4586
4587 cmd = malloc(size);
4588
4589 /* real snprintf() */
4590 snprintf(cmd, size, objdump_str, cross_compile, objname, funcs);
4591 ret = system(cmd);
4592 if (ret) {
4593 WARN("disassembly failed: %d", ret);
4594 return -1;
4595 }
4596
4597 return 0;
4598 }
4599
disas_warned_funcs(struct objtool_file * file)4600 static int disas_warned_funcs(struct objtool_file *file)
4601 {
4602 struct symbol *sym;
4603 char *funcs = NULL, *tmp;
4604
4605 for_each_sym(file, sym) {
4606 if (sym->warned) {
4607 if (!funcs) {
4608 funcs = malloc(strlen(sym->name) + 1);
4609 strcpy(funcs, sym->name);
4610 } else {
4611 tmp = malloc(strlen(funcs) + strlen(sym->name) + 2);
4612 sprintf(tmp, "%s %s", funcs, sym->name);
4613 free(funcs);
4614 funcs = tmp;
4615 }
4616 }
4617 }
4618
4619 if (funcs)
4620 disas_funcs(funcs);
4621
4622 return 0;
4623 }
4624
4625 struct insn_chunk {
4626 void *addr;
4627 struct insn_chunk *next;
4628 };
4629
4630 /*
4631 * Reduce peak RSS usage by freeing insns memory before writing the ELF file,
4632 * which can trigger more allocations for .debug_* sections whose data hasn't
4633 * been read yet.
4634 */
free_insns(struct objtool_file * file)4635 static void free_insns(struct objtool_file *file)
4636 {
4637 struct instruction *insn;
4638 struct insn_chunk *chunks = NULL, *chunk;
4639
4640 for_each_insn(file, insn) {
4641 if (!insn->idx) {
4642 chunk = malloc(sizeof(*chunk));
4643 chunk->addr = insn;
4644 chunk->next = chunks;
4645 chunks = chunk;
4646 }
4647 }
4648
4649 for (chunk = chunks; chunk; chunk = chunk->next)
4650 free(chunk->addr);
4651 }
4652
check(struct objtool_file * file)4653 int check(struct objtool_file *file)
4654 {
4655 int ret, warnings = 0;
4656
4657 arch_initial_func_cfi_state(&initial_func_cfi);
4658 init_cfi_state(&init_cfi);
4659 init_cfi_state(&func_cfi);
4660 set_func_state(&func_cfi);
4661 init_cfi_state(&force_undefined_cfi);
4662 force_undefined_cfi.force_undefined = true;
4663
4664 if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
4665 goto out;
4666
4667 cfi_hash_add(&init_cfi);
4668 cfi_hash_add(&func_cfi);
4669
4670 ret = decode_sections(file);
4671 if (ret < 0)
4672 goto out;
4673
4674 warnings += ret;
4675
4676 if (!nr_insns)
4677 goto out;
4678
4679 if (opts.retpoline) {
4680 ret = validate_retpoline(file);
4681 if (ret < 0)
4682 return ret;
4683 warnings += ret;
4684 }
4685
4686 if (opts.stackval || opts.orc || opts.uaccess) {
4687 ret = validate_functions(file);
4688 if (ret < 0)
4689 goto out;
4690 warnings += ret;
4691
4692 ret = validate_unwind_hints(file, NULL);
4693 if (ret < 0)
4694 goto out;
4695 warnings += ret;
4696
4697 if (!warnings) {
4698 ret = validate_reachable_instructions(file);
4699 if (ret < 0)
4700 goto out;
4701 warnings += ret;
4702 }
4703
4704 } else if (opts.noinstr) {
4705 ret = validate_noinstr_sections(file);
4706 if (ret < 0)
4707 goto out;
4708 warnings += ret;
4709 }
4710
4711 if (opts.unret) {
4712 /*
4713 * Must be after validate_branch() and friends, it plays
4714 * further games with insn->visited.
4715 */
4716 ret = validate_unrets(file);
4717 if (ret < 0)
4718 return ret;
4719 warnings += ret;
4720 }
4721
4722 if (opts.ibt) {
4723 ret = validate_ibt(file);
4724 if (ret < 0)
4725 goto out;
4726 warnings += ret;
4727 }
4728
4729 if (opts.sls) {
4730 ret = validate_sls(file);
4731 if (ret < 0)
4732 goto out;
4733 warnings += ret;
4734 }
4735
4736 if (opts.static_call) {
4737 ret = create_static_call_sections(file);
4738 if (ret < 0)
4739 goto out;
4740 warnings += ret;
4741 }
4742
4743 if (opts.retpoline) {
4744 ret = create_retpoline_sites_sections(file);
4745 if (ret < 0)
4746 goto out;
4747 warnings += ret;
4748 }
4749
4750 if (opts.cfi) {
4751 ret = create_cfi_sections(file);
4752 if (ret < 0)
4753 goto out;
4754 warnings += ret;
4755 }
4756
4757 if (opts.rethunk) {
4758 ret = create_return_sites_sections(file);
4759 if (ret < 0)
4760 goto out;
4761 warnings += ret;
4762
4763 if (opts.hack_skylake) {
4764 ret = create_direct_call_sections(file);
4765 if (ret < 0)
4766 goto out;
4767 warnings += ret;
4768 }
4769 }
4770
4771 if (opts.mcount) {
4772 ret = create_mcount_loc_sections(file);
4773 if (ret < 0)
4774 goto out;
4775 warnings += ret;
4776 }
4777
4778 if (opts.prefix) {
4779 ret = add_prefix_symbols(file);
4780 if (ret < 0)
4781 return ret;
4782 warnings += ret;
4783 }
4784
4785 if (opts.ibt) {
4786 ret = create_ibt_endbr_seal_sections(file);
4787 if (ret < 0)
4788 goto out;
4789 warnings += ret;
4790 }
4791
4792 if (opts.orc && nr_insns) {
4793 ret = orc_create(file);
4794 if (ret < 0)
4795 goto out;
4796 warnings += ret;
4797 }
4798
4799 free_insns(file);
4800
4801 if (opts.verbose)
4802 disas_warned_funcs(file);
4803
4804 if (opts.stats) {
4805 printf("nr_insns_visited: %ld\n", nr_insns_visited);
4806 printf("nr_cfi: %ld\n", nr_cfi);
4807 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
4808 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
4809 }
4810
4811 out:
4812 /*
4813 * For now, don't fail the kernel build on fatal warnings. These
4814 * errors are still fairly common due to the growing matrix of
4815 * supported toolchains and their recent pace of change.
4816 */
4817 return 0;
4818 }
4819
