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 <arch/elf.h>
12 #include <objtool/builtin.h>
13 #include <objtool/cfi.h>
14 #include <objtool/arch.h>
15 #include <objtool/check.h>
16 #include <objtool/special.h>
17 #include <objtool/warn.h>
18 #include <objtool/endianness.h>
19
20 #include <linux/objtool.h>
21 #include <linux/hashtable.h>
22 #include <linux/kernel.h>
23 #include <linux/static_call_types.h>
24
25 struct alternative {
26 struct list_head list;
27 struct instruction *insn;
28 bool skip_orig;
29 };
30
31 static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
32
33 static struct cfi_init_state initial_func_cfi;
34 static struct cfi_state init_cfi;
35 static struct cfi_state func_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 static struct instruction *next_insn_same_sec(struct objtool_file *file,
51 struct instruction *insn)
52 {
53 struct instruction *next = list_next_entry(insn, list);
54
55 if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
56 return NULL;
57
58 return next;
59 }
60
next_insn_same_func(struct objtool_file * file,struct instruction * insn)61 static struct instruction *next_insn_same_func(struct objtool_file *file,
62 struct instruction *insn)
63 {
64 struct instruction *next = list_next_entry(insn, list);
65 struct symbol *func = insn->func;
66
67 if (!func)
68 return NULL;
69
70 if (&next->list != &file->insn_list && next->func == func)
71 return next;
72
73 /* Check if we're already in the subfunction: */
74 if (func == func->cfunc)
75 return NULL;
76
77 /* Move to the subfunction: */
78 return find_insn(file, func->cfunc->sec, func->cfunc->offset);
79 }
80
prev_insn_same_sym(struct objtool_file * file,struct instruction * insn)81 static struct instruction *prev_insn_same_sym(struct objtool_file *file,
82 struct instruction *insn)
83 {
84 struct instruction *prev = list_prev_entry(insn, list);
85
86 if (&prev->list != &file->insn_list && prev->func == insn->func)
87 return prev;
88
89 return NULL;
90 }
91
92 #define func_for_each_insn(file, func, insn) \
93 for (insn = find_insn(file, func->sec, func->offset); \
94 insn; \
95 insn = next_insn_same_func(file, insn))
96
97 #define sym_for_each_insn(file, sym, insn) \
98 for (insn = find_insn(file, sym->sec, sym->offset); \
99 insn && &insn->list != &file->insn_list && \
100 insn->sec == sym->sec && \
101 insn->offset < sym->offset + sym->len; \
102 insn = list_next_entry(insn, list))
103
104 #define sym_for_each_insn_continue_reverse(file, sym, insn) \
105 for (insn = list_prev_entry(insn, list); \
106 &insn->list != &file->insn_list && \
107 insn->sec == sym->sec && insn->offset >= sym->offset; \
108 insn = list_prev_entry(insn, list))
109
110 #define sec_for_each_insn_from(file, insn) \
111 for (; insn; insn = next_insn_same_sec(file, insn))
112
113 #define sec_for_each_insn_continue(file, insn) \
114 for (insn = next_insn_same_sec(file, insn); insn; \
115 insn = next_insn_same_sec(file, insn))
116
is_jump_table_jump(struct instruction * insn)117 static bool is_jump_table_jump(struct instruction *insn)
118 {
119 struct alt_group *alt_group = insn->alt_group;
120
121 if (insn->jump_table)
122 return true;
123
124 /* Retpoline alternative for a jump table? */
125 return alt_group && alt_group->orig_group &&
126 alt_group->orig_group->first_insn->jump_table;
127 }
128
is_sibling_call(struct instruction * insn)129 static bool is_sibling_call(struct instruction *insn)
130 {
131 /*
132 * Assume only ELF functions can make sibling calls. This ensures
133 * sibling call detection consistency between vmlinux.o and individual
134 * objects.
135 */
136 if (!insn->func)
137 return false;
138
139 /* An indirect jump is either a sibling call or a jump to a table. */
140 if (insn->type == INSN_JUMP_DYNAMIC)
141 return !is_jump_table_jump(insn);
142
143 /* add_jump_destinations() sets insn->call_dest for sibling calls. */
144 return (is_static_jump(insn) && insn->call_dest);
145 }
146
147 /*
148 * This checks to see if the given function is a "noreturn" function.
149 *
150 * For global functions which are outside the scope of this object file, we
151 * have to keep a manual list of them.
152 *
153 * For local functions, we have to detect them manually by simply looking for
154 * the lack of a return instruction.
155 */
__dead_end_function(struct objtool_file * file,struct symbol * func,int recursion)156 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
157 int recursion)
158 {
159 int i;
160 struct instruction *insn;
161 bool empty = true;
162
163 /*
164 * Unfortunately these have to be hard coded because the noreturn
165 * attribute isn't provided in ELF data. Keep 'em sorted.
166 */
167 static const char * const global_noreturns[] = {
168 "__invalid_creds",
169 "__module_put_and_kthread_exit",
170 "__reiserfs_panic",
171 "__stack_chk_fail",
172 "__ubsan_handle_builtin_unreachable",
173 "cpu_bringup_and_idle",
174 "cpu_startup_entry",
175 "do_exit",
176 "do_group_exit",
177 "do_task_dead",
178 "ex_handler_msr_mce",
179 "fortify_panic",
180 "kthread_complete_and_exit",
181 "kthread_exit",
182 "kunit_try_catch_throw",
183 "lbug_with_loc",
184 "machine_real_restart",
185 "make_task_dead",
186 "panic",
187 "rewind_stack_and_make_dead",
188 "sev_es_terminate",
189 "snp_abort",
190 "stop_this_cpu",
191 "usercopy_abort",
192 "xen_start_kernel",
193 };
194
195 if (!func)
196 return false;
197
198 if (func->bind == STB_WEAK)
199 return false;
200
201 if (func->bind == STB_GLOBAL)
202 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
203 if (!strcmp(func->name, global_noreturns[i]))
204 return true;
205
206 if (!func->len)
207 return false;
208
209 insn = find_insn(file, func->sec, func->offset);
210 if (!insn || !insn->func)
211 return false;
212
213 func_for_each_insn(file, func, insn) {
214 empty = false;
215
216 if (insn->type == INSN_RETURN)
217 return false;
218 }
219
220 if (empty)
221 return false;
222
223 /*
224 * A function can have a sibling call instead of a return. In that
225 * case, the function's dead-end status depends on whether the target
226 * of the sibling call returns.
227 */
228 func_for_each_insn(file, func, insn) {
229 if (is_sibling_call(insn)) {
230 struct instruction *dest = insn->jump_dest;
231
232 if (!dest)
233 /* sibling call to another file */
234 return false;
235
236 /* local sibling call */
237 if (recursion == 5) {
238 /*
239 * Infinite recursion: two functions have
240 * sibling calls to each other. This is a very
241 * rare case. It means they aren't dead ends.
242 */
243 return false;
244 }
245
246 return __dead_end_function(file, dest->func, recursion+1);
247 }
248 }
249
250 return true;
251 }
252
dead_end_function(struct objtool_file * file,struct symbol * func)253 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
254 {
255 return __dead_end_function(file, func, 0);
256 }
257
init_cfi_state(struct cfi_state * cfi)258 static void init_cfi_state(struct cfi_state *cfi)
259 {
260 int i;
261
262 for (i = 0; i < CFI_NUM_REGS; i++) {
263 cfi->regs[i].base = CFI_UNDEFINED;
264 cfi->vals[i].base = CFI_UNDEFINED;
265 }
266 cfi->cfa.base = CFI_UNDEFINED;
267 cfi->drap_reg = CFI_UNDEFINED;
268 cfi->drap_offset = -1;
269 }
270
init_insn_state(struct objtool_file * file,struct insn_state * state,struct section * sec)271 static void init_insn_state(struct objtool_file *file, struct insn_state *state,
272 struct section *sec)
273 {
274 memset(state, 0, sizeof(*state));
275 init_cfi_state(&state->cfi);
276
277 /*
278 * We need the full vmlinux for noinstr validation, otherwise we can
279 * not correctly determine insn->call_dest->sec (external symbols do
280 * not have a section).
281 */
282 if (opts.link && opts.noinstr && sec)
283 state->noinstr = sec->noinstr;
284 }
285
cfi_alloc(void)286 static struct cfi_state *cfi_alloc(void)
287 {
288 struct cfi_state *cfi = calloc(sizeof(struct cfi_state), 1);
289 if (!cfi) {
290 WARN("calloc failed");
291 exit(1);
292 }
293 nr_cfi++;
294 return cfi;
295 }
296
297 static int cfi_bits;
298 static struct hlist_head *cfi_hash;
299
cficmp(struct cfi_state * cfi1,struct cfi_state * cfi2)300 static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
301 {
302 return memcmp((void *)cfi1 + sizeof(cfi1->hash),
303 (void *)cfi2 + sizeof(cfi2->hash),
304 sizeof(struct cfi_state) - sizeof(struct hlist_node));
305 }
306
cfi_key(struct cfi_state * cfi)307 static inline u32 cfi_key(struct cfi_state *cfi)
308 {
309 return jhash((void *)cfi + sizeof(cfi->hash),
310 sizeof(*cfi) - sizeof(cfi->hash), 0);
311 }
312
cfi_hash_find_or_add(struct cfi_state * cfi)313 static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
314 {
315 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
316 struct cfi_state *obj;
317
318 hlist_for_each_entry(obj, head, hash) {
319 if (!cficmp(cfi, obj)) {
320 nr_cfi_cache++;
321 return obj;
322 }
323 }
324
325 obj = cfi_alloc();
326 *obj = *cfi;
327 hlist_add_head(&obj->hash, head);
328
329 return obj;
330 }
331
cfi_hash_add(struct cfi_state * cfi)332 static void cfi_hash_add(struct cfi_state *cfi)
333 {
334 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
335
336 hlist_add_head(&cfi->hash, head);
337 }
338
cfi_hash_alloc(unsigned long size)339 static void *cfi_hash_alloc(unsigned long size)
340 {
341 cfi_bits = max(10, ilog2(size));
342 cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
343 PROT_READ|PROT_WRITE,
344 MAP_PRIVATE|MAP_ANON, -1, 0);
345 if (cfi_hash == (void *)-1L) {
346 WARN("mmap fail cfi_hash");
347 cfi_hash = NULL;
348 } else if (opts.stats) {
349 printf("cfi_bits: %d\n", cfi_bits);
350 }
351
352 return cfi_hash;
353 }
354
355 static unsigned long nr_insns;
356 static unsigned long nr_insns_visited;
357
358 /*
359 * Call the arch-specific instruction decoder for all the instructions and add
360 * them to the global instruction list.
361 */
decode_instructions(struct objtool_file * file)362 static int decode_instructions(struct objtool_file *file)
363 {
364 struct section *sec;
365 struct symbol *func;
366 unsigned long offset;
367 struct instruction *insn;
368 int ret;
369
370 for_each_sec(file, sec) {
371
372 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
373 continue;
374
375 if (strcmp(sec->name, ".altinstr_replacement") &&
376 strcmp(sec->name, ".altinstr_aux") &&
377 strncmp(sec->name, ".discard.", 9))
378 sec->text = true;
379
380 if (!strcmp(sec->name, ".noinstr.text") ||
381 !strcmp(sec->name, ".entry.text") ||
382 !strncmp(sec->name, ".text.__x86.", 12))
383 sec->noinstr = true;
384
385 for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
386 insn = malloc(sizeof(*insn));
387 if (!insn) {
388 WARN("malloc failed");
389 return -1;
390 }
391 memset(insn, 0, sizeof(*insn));
392 INIT_LIST_HEAD(&insn->alts);
393 INIT_LIST_HEAD(&insn->stack_ops);
394 INIT_LIST_HEAD(&insn->call_node);
395
396 insn->sec = sec;
397 insn->offset = offset;
398
399 ret = arch_decode_instruction(file, sec, offset,
400 sec->sh.sh_size - offset,
401 &insn->len, &insn->type,
402 &insn->immediate,
403 &insn->stack_ops);
404 if (ret)
405 goto err;
406
407 /*
408 * By default, "ud2" is a dead end unless otherwise
409 * annotated, because GCC 7 inserts it for certain
410 * divide-by-zero cases.
411 */
412 if (insn->type == INSN_BUG)
413 insn->dead_end = true;
414
415 hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
416 list_add_tail(&insn->list, &file->insn_list);
417 nr_insns++;
418 }
419
420 list_for_each_entry(func, &sec->symbol_list, list) {
421 if (func->type != STT_FUNC || func->alias != func)
422 continue;
423
424 if (!find_insn(file, sec, func->offset)) {
425 WARN("%s(): can't find starting instruction",
426 func->name);
427 return -1;
428 }
429
430 sym_for_each_insn(file, func, insn) {
431 insn->func = func;
432 if (insn->type == INSN_ENDBR && list_empty(&insn->call_node)) {
433 if (insn->offset == insn->func->offset) {
434 list_add_tail(&insn->call_node, &file->endbr_list);
435 file->nr_endbr++;
436 } else {
437 file->nr_endbr_int++;
438 }
439 }
440 }
441 }
442 }
443
444 if (opts.stats)
445 printf("nr_insns: %lu\n", nr_insns);
446
447 return 0;
448
449 err:
450 free(insn);
451 return ret;
452 }
453
454 /*
455 * Read the pv_ops[] .data table to find the static initialized values.
456 */
add_pv_ops(struct objtool_file * file,const char * symname)457 static int add_pv_ops(struct objtool_file *file, const char *symname)
458 {
459 struct symbol *sym, *func;
460 unsigned long off, end;
461 struct reloc *rel;
462 int idx;
463
464 sym = find_symbol_by_name(file->elf, symname);
465 if (!sym)
466 return 0;
467
468 off = sym->offset;
469 end = off + sym->len;
470 for (;;) {
471 rel = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off);
472 if (!rel)
473 break;
474
475 func = rel->sym;
476 if (func->type == STT_SECTION)
477 func = find_symbol_by_offset(rel->sym->sec, rel->addend);
478
479 idx = (rel->offset - sym->offset) / sizeof(unsigned long);
480
481 objtool_pv_add(file, idx, func);
482
483 off = rel->offset + 1;
484 if (off > end)
485 break;
486 }
487
488 return 0;
489 }
490
491 /*
492 * Allocate and initialize file->pv_ops[].
493 */
init_pv_ops(struct objtool_file * file)494 static int init_pv_ops(struct objtool_file *file)
495 {
496 static const char *pv_ops_tables[] = {
497 "pv_ops",
498 "xen_cpu_ops",
499 "xen_irq_ops",
500 "xen_mmu_ops",
501 NULL,
502 };
503 const char *pv_ops;
504 struct symbol *sym;
505 int idx, nr;
506
507 if (!opts.noinstr)
508 return 0;
509
510 file->pv_ops = NULL;
511
512 sym = find_symbol_by_name(file->elf, "pv_ops");
513 if (!sym)
514 return 0;
515
516 nr = sym->len / sizeof(unsigned long);
517 file->pv_ops = calloc(sizeof(struct pv_state), nr);
518 if (!file->pv_ops)
519 return -1;
520
521 for (idx = 0; idx < nr; idx++)
522 INIT_LIST_HEAD(&file->pv_ops[idx].targets);
523
524 for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++)
525 add_pv_ops(file, pv_ops);
526
527 return 0;
528 }
529
find_last_insn(struct objtool_file * file,struct section * sec)530 static struct instruction *find_last_insn(struct objtool_file *file,
531 struct section *sec)
532 {
533 struct instruction *insn = NULL;
534 unsigned int offset;
535 unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
536
537 for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
538 insn = find_insn(file, sec, offset);
539
540 return insn;
541 }
542
543 /*
544 * Mark "ud2" instructions and manually annotated dead ends.
545 */
add_dead_ends(struct objtool_file * file)546 static int add_dead_ends(struct objtool_file *file)
547 {
548 struct section *sec;
549 struct reloc *reloc;
550 struct instruction *insn;
551
552 /*
553 * Check for manually annotated dead ends.
554 */
555 sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
556 if (!sec)
557 goto reachable;
558
559 list_for_each_entry(reloc, &sec->reloc_list, list) {
560 if (reloc->sym->type != STT_SECTION) {
561 WARN("unexpected relocation symbol type in %s", sec->name);
562 return -1;
563 }
564 insn = find_insn(file, reloc->sym->sec, reloc->addend);
565 if (insn)
566 insn = list_prev_entry(insn, list);
567 else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
568 insn = find_last_insn(file, reloc->sym->sec);
569 if (!insn) {
570 WARN("can't find unreachable insn at %s+0x%" PRIx64,
571 reloc->sym->sec->name, reloc->addend);
572 return -1;
573 }
574 } else {
575 WARN("can't find unreachable insn at %s+0x%" PRIx64,
576 reloc->sym->sec->name, reloc->addend);
577 return -1;
578 }
579
580 insn->dead_end = true;
581 }
582
583 reachable:
584 /*
585 * These manually annotated reachable checks are needed for GCC 4.4,
586 * where the Linux unreachable() macro isn't supported. In that case
587 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
588 * not a dead end.
589 */
590 sec = find_section_by_name(file->elf, ".rela.discard.reachable");
591 if (!sec)
592 return 0;
593
594 list_for_each_entry(reloc, &sec->reloc_list, list) {
595 if (reloc->sym->type != STT_SECTION) {
596 WARN("unexpected relocation symbol type in %s", sec->name);
597 return -1;
598 }
599 insn = find_insn(file, reloc->sym->sec, reloc->addend);
600 if (insn)
601 insn = list_prev_entry(insn, list);
602 else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
603 insn = find_last_insn(file, reloc->sym->sec);
604 if (!insn) {
605 WARN("can't find reachable insn at %s+0x%" PRIx64,
606 reloc->sym->sec->name, reloc->addend);
607 return -1;
608 }
609 } else {
610 WARN("can't find reachable insn at %s+0x%" PRIx64,
611 reloc->sym->sec->name, reloc->addend);
612 return -1;
613 }
614
615 insn->dead_end = false;
616 }
617
618 return 0;
619 }
620
create_static_call_sections(struct objtool_file * file)621 static int create_static_call_sections(struct objtool_file *file)
622 {
623 struct section *sec;
624 struct static_call_site *site;
625 struct instruction *insn;
626 struct symbol *key_sym;
627 char *key_name, *tmp;
628 int idx;
629
630 sec = find_section_by_name(file->elf, ".static_call_sites");
631 if (sec) {
632 INIT_LIST_HEAD(&file->static_call_list);
633 WARN("file already has .static_call_sites section, skipping");
634 return 0;
635 }
636
637 if (list_empty(&file->static_call_list))
638 return 0;
639
640 idx = 0;
641 list_for_each_entry(insn, &file->static_call_list, call_node)
642 idx++;
643
644 sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE,
645 sizeof(struct static_call_site), idx);
646 if (!sec)
647 return -1;
648
649 idx = 0;
650 list_for_each_entry(insn, &file->static_call_list, call_node) {
651
652 site = (struct static_call_site *)sec->data->d_buf + idx;
653 memset(site, 0, sizeof(struct static_call_site));
654
655 /* populate reloc for 'addr' */
656 if (elf_add_reloc_to_insn(file->elf, sec,
657 idx * sizeof(struct static_call_site),
658 R_X86_64_PC32,
659 insn->sec, insn->offset))
660 return -1;
661
662 /* find key symbol */
663 key_name = strdup(insn->call_dest->name);
664 if (!key_name) {
665 perror("strdup");
666 return -1;
667 }
668 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
669 STATIC_CALL_TRAMP_PREFIX_LEN)) {
670 WARN("static_call: trampoline name malformed: %s", key_name);
671 return -1;
672 }
673 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
674 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
675
676 key_sym = find_symbol_by_name(file->elf, tmp);
677 if (!key_sym) {
678 if (!opts.module) {
679 WARN("static_call: can't find static_call_key symbol: %s", tmp);
680 return -1;
681 }
682
683 /*
684 * For modules(), the key might not be exported, which
685 * means the module can make static calls but isn't
686 * allowed to change them.
687 *
688 * In that case we temporarily set the key to be the
689 * trampoline address. This is fixed up in
690 * static_call_add_module().
691 */
692 key_sym = insn->call_dest;
693 }
694 free(key_name);
695
696 /* populate reloc for 'key' */
697 if (elf_add_reloc(file->elf, sec,
698 idx * sizeof(struct static_call_site) + 4,
699 R_X86_64_PC32, key_sym,
700 is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
701 return -1;
702
703 idx++;
704 }
705
706 return 0;
707 }
708
create_retpoline_sites_sections(struct objtool_file * file)709 static int create_retpoline_sites_sections(struct objtool_file *file)
710 {
711 struct instruction *insn;
712 struct section *sec;
713 int idx;
714
715 sec = find_section_by_name(file->elf, ".retpoline_sites");
716 if (sec) {
717 WARN("file already has .retpoline_sites, skipping");
718 return 0;
719 }
720
721 idx = 0;
722 list_for_each_entry(insn, &file->retpoline_call_list, call_node)
723 idx++;
724
725 if (!idx)
726 return 0;
727
728 sec = elf_create_section(file->elf, ".retpoline_sites", 0,
729 sizeof(int), idx);
730 if (!sec) {
731 WARN("elf_create_section: .retpoline_sites");
732 return -1;
733 }
734
735 idx = 0;
736 list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
737
738 int *site = (int *)sec->data->d_buf + idx;
739 *site = 0;
740
741 if (elf_add_reloc_to_insn(file->elf, sec,
742 idx * sizeof(int),
743 R_X86_64_PC32,
744 insn->sec, insn->offset)) {
745 WARN("elf_add_reloc_to_insn: .retpoline_sites");
746 return -1;
747 }
748
749 idx++;
750 }
751
752 return 0;
753 }
754
create_return_sites_sections(struct objtool_file * file)755 static int create_return_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, ".return_sites");
762 if (sec) {
763 WARN("file already has .return_sites, skipping");
764 return 0;
765 }
766
767 idx = 0;
768 list_for_each_entry(insn, &file->return_thunk_list, call_node)
769 idx++;
770
771 if (!idx)
772 return 0;
773
774 sec = elf_create_section(file->elf, ".return_sites", 0,
775 sizeof(int), idx);
776 if (!sec) {
777 WARN("elf_create_section: .return_sites");
778 return -1;
779 }
780
781 idx = 0;
782 list_for_each_entry(insn, &file->return_thunk_list, call_node) {
783
784 int *site = (int *)sec->data->d_buf + idx;
785 *site = 0;
786
787 if (elf_add_reloc_to_insn(file->elf, sec,
788 idx * sizeof(int),
789 R_X86_64_PC32,
790 insn->sec, insn->offset)) {
791 WARN("elf_add_reloc_to_insn: .return_sites");
792 return -1;
793 }
794
795 idx++;
796 }
797
798 return 0;
799 }
800
create_ibt_endbr_seal_sections(struct objtool_file * file)801 static int create_ibt_endbr_seal_sections(struct objtool_file *file)
802 {
803 struct instruction *insn;
804 struct section *sec;
805 int idx;
806
807 sec = find_section_by_name(file->elf, ".ibt_endbr_seal");
808 if (sec) {
809 WARN("file already has .ibt_endbr_seal, skipping");
810 return 0;
811 }
812
813 idx = 0;
814 list_for_each_entry(insn, &file->endbr_list, call_node)
815 idx++;
816
817 if (opts.stats) {
818 printf("ibt: ENDBR at function start: %d\n", file->nr_endbr);
819 printf("ibt: ENDBR inside functions: %d\n", file->nr_endbr_int);
820 printf("ibt: superfluous ENDBR: %d\n", idx);
821 }
822
823 if (!idx)
824 return 0;
825
826 sec = elf_create_section(file->elf, ".ibt_endbr_seal", 0,
827 sizeof(int), idx);
828 if (!sec) {
829 WARN("elf_create_section: .ibt_endbr_seal");
830 return -1;
831 }
832
833 idx = 0;
834 list_for_each_entry(insn, &file->endbr_list, call_node) {
835
836 int *site = (int *)sec->data->d_buf + idx;
837 *site = 0;
838
839 if (elf_add_reloc_to_insn(file->elf, sec,
840 idx * sizeof(int),
841 R_X86_64_PC32,
842 insn->sec, insn->offset)) {
843 WARN("elf_add_reloc_to_insn: .ibt_endbr_seal");
844 return -1;
845 }
846
847 idx++;
848 }
849
850 return 0;
851 }
852
create_mcount_loc_sections(struct objtool_file * file)853 static int create_mcount_loc_sections(struct objtool_file *file)
854 {
855 struct section *sec;
856 unsigned long *loc;
857 struct instruction *insn;
858 int idx;
859
860 sec = find_section_by_name(file->elf, "__mcount_loc");
861 if (sec) {
862 INIT_LIST_HEAD(&file->mcount_loc_list);
863 WARN("file already has __mcount_loc section, skipping");
864 return 0;
865 }
866
867 if (list_empty(&file->mcount_loc_list))
868 return 0;
869
870 idx = 0;
871 list_for_each_entry(insn, &file->mcount_loc_list, call_node)
872 idx++;
873
874 sec = elf_create_section(file->elf, "__mcount_loc", 0, sizeof(unsigned long), idx);
875 if (!sec)
876 return -1;
877
878 idx = 0;
879 list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
880
881 loc = (unsigned long *)sec->data->d_buf + idx;
882 memset(loc, 0, sizeof(unsigned long));
883
884 if (elf_add_reloc_to_insn(file->elf, sec,
885 idx * sizeof(unsigned long),
886 R_X86_64_64,
887 insn->sec, insn->offset))
888 return -1;
889
890 idx++;
891 }
892
893 return 0;
894 }
895
896 /*
897 * Warnings shouldn't be reported for ignored functions.
898 */
add_ignores(struct objtool_file * file)899 static void add_ignores(struct objtool_file *file)
900 {
901 struct instruction *insn;
902 struct section *sec;
903 struct symbol *func;
904 struct reloc *reloc;
905
906 sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
907 if (!sec)
908 return;
909
910 list_for_each_entry(reloc, &sec->reloc_list, list) {
911 switch (reloc->sym->type) {
912 case STT_FUNC:
913 func = reloc->sym;
914 break;
915
916 case STT_SECTION:
917 func = find_func_by_offset(reloc->sym->sec, reloc->addend);
918 if (!func)
919 continue;
920 break;
921
922 default:
923 WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type);
924 continue;
925 }
926
927 func_for_each_insn(file, func, insn)
928 insn->ignore = true;
929 }
930 }
931
932 /*
933 * This is a whitelist of functions that is allowed to be called with AC set.
934 * The list is meant to be minimal and only contains compiler instrumentation
935 * ABI and a few functions used to implement *_{to,from}_user() functions.
936 *
937 * These functions must not directly change AC, but may PUSHF/POPF.
938 */
939 static const char *uaccess_safe_builtin[] = {
940 /* KASAN */
941 "kasan_report",
942 "kasan_check_range",
943 /* KASAN out-of-line */
944 "__asan_loadN_noabort",
945 "__asan_load1_noabort",
946 "__asan_load2_noabort",
947 "__asan_load4_noabort",
948 "__asan_load8_noabort",
949 "__asan_load16_noabort",
950 "__asan_storeN_noabort",
951 "__asan_store1_noabort",
952 "__asan_store2_noabort",
953 "__asan_store4_noabort",
954 "__asan_store8_noabort",
955 "__asan_store16_noabort",
956 "__kasan_check_read",
957 "__kasan_check_write",
958 /* KASAN in-line */
959 "__asan_report_load_n_noabort",
960 "__asan_report_load1_noabort",
961 "__asan_report_load2_noabort",
962 "__asan_report_load4_noabort",
963 "__asan_report_load8_noabort",
964 "__asan_report_load16_noabort",
965 "__asan_report_store_n_noabort",
966 "__asan_report_store1_noabort",
967 "__asan_report_store2_noabort",
968 "__asan_report_store4_noabort",
969 "__asan_report_store8_noabort",
970 "__asan_report_store16_noabort",
971 /* KCSAN */
972 "__kcsan_check_access",
973 "__kcsan_mb",
974 "__kcsan_wmb",
975 "__kcsan_rmb",
976 "__kcsan_release",
977 "kcsan_found_watchpoint",
978 "kcsan_setup_watchpoint",
979 "kcsan_check_scoped_accesses",
980 "kcsan_disable_current",
981 "kcsan_enable_current_nowarn",
982 /* KCSAN/TSAN */
983 "__tsan_func_entry",
984 "__tsan_func_exit",
985 "__tsan_read_range",
986 "__tsan_write_range",
987 "__tsan_read1",
988 "__tsan_read2",
989 "__tsan_read4",
990 "__tsan_read8",
991 "__tsan_read16",
992 "__tsan_write1",
993 "__tsan_write2",
994 "__tsan_write4",
995 "__tsan_write8",
996 "__tsan_write16",
997 "__tsan_read_write1",
998 "__tsan_read_write2",
999 "__tsan_read_write4",
1000 "__tsan_read_write8",
1001 "__tsan_read_write16",
1002 "__tsan_volatile_read1",
1003 "__tsan_volatile_read2",
1004 "__tsan_volatile_read4",
1005 "__tsan_volatile_read8",
1006 "__tsan_volatile_read16",
1007 "__tsan_volatile_write1",
1008 "__tsan_volatile_write2",
1009 "__tsan_volatile_write4",
1010 "__tsan_volatile_write8",
1011 "__tsan_volatile_write16",
1012 "__tsan_atomic8_load",
1013 "__tsan_atomic16_load",
1014 "__tsan_atomic32_load",
1015 "__tsan_atomic64_load",
1016 "__tsan_atomic8_store",
1017 "__tsan_atomic16_store",
1018 "__tsan_atomic32_store",
1019 "__tsan_atomic64_store",
1020 "__tsan_atomic8_exchange",
1021 "__tsan_atomic16_exchange",
1022 "__tsan_atomic32_exchange",
1023 "__tsan_atomic64_exchange",
1024 "__tsan_atomic8_fetch_add",
1025 "__tsan_atomic16_fetch_add",
1026 "__tsan_atomic32_fetch_add",
1027 "__tsan_atomic64_fetch_add",
1028 "__tsan_atomic8_fetch_sub",
1029 "__tsan_atomic16_fetch_sub",
1030 "__tsan_atomic32_fetch_sub",
1031 "__tsan_atomic64_fetch_sub",
1032 "__tsan_atomic8_fetch_and",
1033 "__tsan_atomic16_fetch_and",
1034 "__tsan_atomic32_fetch_and",
1035 "__tsan_atomic64_fetch_and",
1036 "__tsan_atomic8_fetch_or",
1037 "__tsan_atomic16_fetch_or",
1038 "__tsan_atomic32_fetch_or",
1039 "__tsan_atomic64_fetch_or",
1040 "__tsan_atomic8_fetch_xor",
1041 "__tsan_atomic16_fetch_xor",
1042 "__tsan_atomic32_fetch_xor",
1043 "__tsan_atomic64_fetch_xor",
1044 "__tsan_atomic8_fetch_nand",
1045 "__tsan_atomic16_fetch_nand",
1046 "__tsan_atomic32_fetch_nand",
1047 "__tsan_atomic64_fetch_nand",
1048 "__tsan_atomic8_compare_exchange_strong",
1049 "__tsan_atomic16_compare_exchange_strong",
1050 "__tsan_atomic32_compare_exchange_strong",
1051 "__tsan_atomic64_compare_exchange_strong",
1052 "__tsan_atomic8_compare_exchange_weak",
1053 "__tsan_atomic16_compare_exchange_weak",
1054 "__tsan_atomic32_compare_exchange_weak",
1055 "__tsan_atomic64_compare_exchange_weak",
1056 "__tsan_atomic8_compare_exchange_val",
1057 "__tsan_atomic16_compare_exchange_val",
1058 "__tsan_atomic32_compare_exchange_val",
1059 "__tsan_atomic64_compare_exchange_val",
1060 "__tsan_atomic_thread_fence",
1061 "__tsan_atomic_signal_fence",
1062 /* KCOV */
1063 "write_comp_data",
1064 "check_kcov_mode",
1065 "__sanitizer_cov_trace_pc",
1066 "__sanitizer_cov_trace_const_cmp1",
1067 "__sanitizer_cov_trace_const_cmp2",
1068 "__sanitizer_cov_trace_const_cmp4",
1069 "__sanitizer_cov_trace_const_cmp8",
1070 "__sanitizer_cov_trace_cmp1",
1071 "__sanitizer_cov_trace_cmp2",
1072 "__sanitizer_cov_trace_cmp4",
1073 "__sanitizer_cov_trace_cmp8",
1074 "__sanitizer_cov_trace_switch",
1075 /* KMSAN */
1076 "kmsan_copy_to_user",
1077 "kmsan_report",
1078 "kmsan_unpoison_entry_regs",
1079 "kmsan_unpoison_memory",
1080 "__msan_chain_origin",
1081 "__msan_get_context_state",
1082 "__msan_instrument_asm_store",
1083 "__msan_metadata_ptr_for_load_1",
1084 "__msan_metadata_ptr_for_load_2",
1085 "__msan_metadata_ptr_for_load_4",
1086 "__msan_metadata_ptr_for_load_8",
1087 "__msan_metadata_ptr_for_load_n",
1088 "__msan_metadata_ptr_for_store_1",
1089 "__msan_metadata_ptr_for_store_2",
1090 "__msan_metadata_ptr_for_store_4",
1091 "__msan_metadata_ptr_for_store_8",
1092 "__msan_metadata_ptr_for_store_n",
1093 "__msan_poison_alloca",
1094 "__msan_warning",
1095 /* UBSAN */
1096 "ubsan_type_mismatch_common",
1097 "__ubsan_handle_type_mismatch",
1098 "__ubsan_handle_type_mismatch_v1",
1099 "__ubsan_handle_shift_out_of_bounds",
1100 /* misc */
1101 "csum_partial_copy_generic",
1102 "copy_mc_fragile",
1103 "copy_mc_fragile_handle_tail",
1104 "copy_mc_enhanced_fast_string",
1105 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
1106 "clear_user_erms",
1107 "clear_user_rep_good",
1108 "clear_user_original",
1109 NULL
1110 };
1111
add_uaccess_safe(struct objtool_file * file)1112 static void add_uaccess_safe(struct objtool_file *file)
1113 {
1114 struct symbol *func;
1115 const char **name;
1116
1117 if (!opts.uaccess)
1118 return;
1119
1120 for (name = uaccess_safe_builtin; *name; name++) {
1121 func = find_symbol_by_name(file->elf, *name);
1122 if (!func)
1123 continue;
1124
1125 func->uaccess_safe = true;
1126 }
1127 }
1128
1129 /*
1130 * FIXME: For now, just ignore any alternatives which add retpolines. This is
1131 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
1132 * But it at least allows objtool to understand the control flow *around* the
1133 * retpoline.
1134 */
add_ignore_alternatives(struct objtool_file * file)1135 static int add_ignore_alternatives(struct objtool_file *file)
1136 {
1137 struct section *sec;
1138 struct reloc *reloc;
1139 struct instruction *insn;
1140
1141 sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
1142 if (!sec)
1143 return 0;
1144
1145 list_for_each_entry(reloc, &sec->reloc_list, list) {
1146 if (reloc->sym->type != STT_SECTION) {
1147 WARN("unexpected relocation symbol type in %s", sec->name);
1148 return -1;
1149 }
1150
1151 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1152 if (!insn) {
1153 WARN("bad .discard.ignore_alts entry");
1154 return -1;
1155 }
1156
1157 insn->ignore_alts = true;
1158 }
1159
1160 return 0;
1161 }
1162
arch_is_retpoline(struct symbol * sym)1163 __weak bool arch_is_retpoline(struct symbol *sym)
1164 {
1165 return false;
1166 }
1167
arch_is_rethunk(struct symbol * sym)1168 __weak bool arch_is_rethunk(struct symbol *sym)
1169 {
1170 return false;
1171 }
1172
1173 #define NEGATIVE_RELOC ((void *)-1L)
1174
insn_reloc(struct objtool_file * file,struct instruction * insn)1175 static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
1176 {
1177 if (insn->reloc == NEGATIVE_RELOC)
1178 return NULL;
1179
1180 if (!insn->reloc) {
1181 if (!file)
1182 return NULL;
1183
1184 insn->reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1185 insn->offset, insn->len);
1186 if (!insn->reloc) {
1187 insn->reloc = NEGATIVE_RELOC;
1188 return NULL;
1189 }
1190 }
1191
1192 return insn->reloc;
1193 }
1194
remove_insn_ops(struct instruction * insn)1195 static void remove_insn_ops(struct instruction *insn)
1196 {
1197 struct stack_op *op, *tmp;
1198
1199 list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
1200 list_del(&op->list);
1201 free(op);
1202 }
1203 }
1204
annotate_call_site(struct objtool_file * file,struct instruction * insn,bool sibling)1205 static void annotate_call_site(struct objtool_file *file,
1206 struct instruction *insn, bool sibling)
1207 {
1208 struct reloc *reloc = insn_reloc(file, insn);
1209 struct symbol *sym = insn->call_dest;
1210
1211 if (!sym)
1212 sym = reloc->sym;
1213
1214 /*
1215 * Alternative replacement code is just template code which is
1216 * sometimes copied to the original instruction. For now, don't
1217 * annotate it. (In the future we might consider annotating the
1218 * original instruction if/when it ever makes sense to do so.)
1219 */
1220 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1221 return;
1222
1223 if (sym->static_call_tramp) {
1224 list_add_tail(&insn->call_node, &file->static_call_list);
1225 return;
1226 }
1227
1228 if (sym->retpoline_thunk) {
1229 list_add_tail(&insn->call_node, &file->retpoline_call_list);
1230 return;
1231 }
1232
1233 /*
1234 * Many compilers cannot disable KCOV or sanitizer calls with a function
1235 * attribute so they need a little help, NOP out any such calls from
1236 * noinstr text.
1237 */
1238 if (opts.hack_noinstr && insn->sec->noinstr && sym->profiling_func) {
1239 if (reloc) {
1240 reloc->type = R_NONE;
1241 elf_write_reloc(file->elf, reloc);
1242 }
1243
1244 elf_write_insn(file->elf, insn->sec,
1245 insn->offset, insn->len,
1246 sibling ? arch_ret_insn(insn->len)
1247 : arch_nop_insn(insn->len));
1248
1249 insn->type = sibling ? INSN_RETURN : INSN_NOP;
1250
1251 if (sibling) {
1252 /*
1253 * We've replaced the tail-call JMP insn by two new
1254 * insn: RET; INT3, except we only have a single struct
1255 * insn here. Mark it retpoline_safe to avoid the SLS
1256 * warning, instead of adding another insn.
1257 */
1258 insn->retpoline_safe = true;
1259 }
1260
1261 return;
1262 }
1263
1264 if (opts.mcount && sym->fentry) {
1265 if (sibling)
1266 WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset);
1267
1268 if (reloc) {
1269 reloc->type = R_NONE;
1270 elf_write_reloc(file->elf, reloc);
1271 }
1272
1273 elf_write_insn(file->elf, insn->sec,
1274 insn->offset, insn->len,
1275 arch_nop_insn(insn->len));
1276
1277 insn->type = INSN_NOP;
1278
1279 list_add_tail(&insn->call_node, &file->mcount_loc_list);
1280 return;
1281 }
1282
1283 if (!sibling && dead_end_function(file, sym))
1284 insn->dead_end = true;
1285 }
1286
add_call_dest(struct objtool_file * file,struct instruction * insn,struct symbol * dest,bool sibling)1287 static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1288 struct symbol *dest, bool sibling)
1289 {
1290 insn->call_dest = dest;
1291 if (!dest)
1292 return;
1293
1294 /*
1295 * Whatever stack impact regular CALLs have, should be undone
1296 * by the RETURN of the called function.
1297 *
1298 * Annotated intra-function calls retain the stack_ops but
1299 * are converted to JUMP, see read_intra_function_calls().
1300 */
1301 remove_insn_ops(insn);
1302
1303 annotate_call_site(file, insn, sibling);
1304 }
1305
add_retpoline_call(struct objtool_file * file,struct instruction * insn)1306 static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1307 {
1308 /*
1309 * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1310 * so convert them accordingly.
1311 */
1312 switch (insn->type) {
1313 case INSN_CALL:
1314 insn->type = INSN_CALL_DYNAMIC;
1315 break;
1316 case INSN_JUMP_UNCONDITIONAL:
1317 insn->type = INSN_JUMP_DYNAMIC;
1318 break;
1319 case INSN_JUMP_CONDITIONAL:
1320 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1321 break;
1322 default:
1323 return;
1324 }
1325
1326 insn->retpoline_safe = true;
1327
1328 /*
1329 * Whatever stack impact regular CALLs have, should be undone
1330 * by the RETURN of the called function.
1331 *
1332 * Annotated intra-function calls retain the stack_ops but
1333 * are converted to JUMP, see read_intra_function_calls().
1334 */
1335 remove_insn_ops(insn);
1336
1337 annotate_call_site(file, insn, false);
1338 }
1339
add_return_call(struct objtool_file * file,struct instruction * insn,bool add)1340 static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add)
1341 {
1342 /*
1343 * Return thunk tail calls are really just returns in disguise,
1344 * so convert them accordingly.
1345 */
1346 insn->type = INSN_RETURN;
1347 insn->retpoline_safe = true;
1348
1349 if (add)
1350 list_add_tail(&insn->call_node, &file->return_thunk_list);
1351 }
1352
same_function(struct instruction * insn1,struct instruction * insn2)1353 static bool same_function(struct instruction *insn1, struct instruction *insn2)
1354 {
1355 return insn1->func->pfunc == insn2->func->pfunc;
1356 }
1357
is_first_func_insn(struct objtool_file * file,struct instruction * insn)1358 static bool is_first_func_insn(struct objtool_file *file, struct instruction *insn)
1359 {
1360 if (insn->offset == insn->func->offset)
1361 return true;
1362
1363 if (opts.ibt) {
1364 struct instruction *prev = prev_insn_same_sym(file, insn);
1365
1366 if (prev && prev->type == INSN_ENDBR &&
1367 insn->offset == insn->func->offset + prev->len)
1368 return true;
1369 }
1370
1371 return false;
1372 }
1373
1374 /*
1375 * Find the destination instructions for all jumps.
1376 */
add_jump_destinations(struct objtool_file * file)1377 static int add_jump_destinations(struct objtool_file *file)
1378 {
1379 struct instruction *insn, *jump_dest;
1380 struct reloc *reloc;
1381 struct section *dest_sec;
1382 unsigned long dest_off;
1383
1384 for_each_insn(file, insn) {
1385 if (insn->jump_dest) {
1386 /*
1387 * handle_group_alt() may have previously set
1388 * 'jump_dest' for some alternatives.
1389 */
1390 continue;
1391 }
1392 if (!is_static_jump(insn))
1393 continue;
1394
1395 reloc = insn_reloc(file, insn);
1396 if (!reloc) {
1397 dest_sec = insn->sec;
1398 dest_off = arch_jump_destination(insn);
1399 } else if (reloc->sym->type == STT_SECTION) {
1400 dest_sec = reloc->sym->sec;
1401 dest_off = arch_dest_reloc_offset(reloc->addend);
1402 } else if (reloc->sym->retpoline_thunk) {
1403 add_retpoline_call(file, insn);
1404 continue;
1405 } else if (reloc->sym->return_thunk) {
1406 add_return_call(file, insn, true);
1407 continue;
1408 } else if (insn->func) {
1409 /*
1410 * External sibling call or internal sibling call with
1411 * STT_FUNC reloc.
1412 */
1413 add_call_dest(file, insn, reloc->sym, true);
1414 continue;
1415 } else if (reloc->sym->sec->idx) {
1416 dest_sec = reloc->sym->sec;
1417 dest_off = reloc->sym->sym.st_value +
1418 arch_dest_reloc_offset(reloc->addend);
1419 } else {
1420 /* non-func asm code jumping to another file */
1421 continue;
1422 }
1423
1424 jump_dest = find_insn(file, dest_sec, dest_off);
1425 if (!jump_dest) {
1426 struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off);
1427
1428 /*
1429 * This is a special case for zen_untrain_ret().
1430 * It jumps to __x86_return_thunk(), but objtool
1431 * can't find the thunk's starting RET
1432 * instruction, because the RET is also in the
1433 * middle of another instruction. Objtool only
1434 * knows about the outer instruction.
1435 */
1436 if (sym && sym->return_thunk) {
1437 add_return_call(file, insn, false);
1438 continue;
1439 }
1440
1441 WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
1442 insn->sec, insn->offset, dest_sec->name,
1443 dest_off);
1444 return -1;
1445 }
1446
1447 /*
1448 * Cross-function jump.
1449 */
1450 if (insn->func && jump_dest->func &&
1451 insn->func != jump_dest->func) {
1452
1453 /*
1454 * For GCC 8+, create parent/child links for any cold
1455 * subfunctions. This is _mostly_ redundant with a
1456 * similar initialization in read_symbols().
1457 *
1458 * If a function has aliases, we want the *first* such
1459 * function in the symbol table to be the subfunction's
1460 * parent. In that case we overwrite the
1461 * initialization done in read_symbols().
1462 *
1463 * However this code can't completely replace the
1464 * read_symbols() code because this doesn't detect the
1465 * case where the parent function's only reference to a
1466 * subfunction is through a jump table.
1467 */
1468 if (!strstr(insn->func->name, ".cold") &&
1469 strstr(jump_dest->func->name, ".cold")) {
1470 insn->func->cfunc = jump_dest->func;
1471 jump_dest->func->pfunc = insn->func;
1472
1473 } else if (!same_function(insn, jump_dest) &&
1474 is_first_func_insn(file, jump_dest)) {
1475 /*
1476 * Internal sibling call without reloc or with
1477 * STT_SECTION reloc.
1478 */
1479 add_call_dest(file, insn, jump_dest->func, true);
1480 continue;
1481 }
1482 }
1483
1484 insn->jump_dest = jump_dest;
1485 }
1486
1487 return 0;
1488 }
1489
find_call_destination(struct section * sec,unsigned long offset)1490 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1491 {
1492 struct symbol *call_dest;
1493
1494 call_dest = find_func_by_offset(sec, offset);
1495 if (!call_dest)
1496 call_dest = find_symbol_by_offset(sec, offset);
1497
1498 return call_dest;
1499 }
1500
1501 /*
1502 * Find the destination instructions for all calls.
1503 */
add_call_destinations(struct objtool_file * file)1504 static int add_call_destinations(struct objtool_file *file)
1505 {
1506 struct instruction *insn;
1507 unsigned long dest_off;
1508 struct symbol *dest;
1509 struct reloc *reloc;
1510
1511 for_each_insn(file, insn) {
1512 if (insn->type != INSN_CALL)
1513 continue;
1514
1515 reloc = insn_reloc(file, insn);
1516 if (!reloc) {
1517 dest_off = arch_jump_destination(insn);
1518 dest = find_call_destination(insn->sec, dest_off);
1519
1520 add_call_dest(file, insn, dest, false);
1521
1522 if (insn->ignore)
1523 continue;
1524
1525 if (!insn->call_dest) {
1526 WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);
1527 return -1;
1528 }
1529
1530 if (insn->func && insn->call_dest->type != STT_FUNC) {
1531 WARN_FUNC("unsupported call to non-function",
1532 insn->sec, insn->offset);
1533 return -1;
1534 }
1535
1536 } else if (reloc->sym->type == STT_SECTION) {
1537 dest_off = arch_dest_reloc_offset(reloc->addend);
1538 dest = find_call_destination(reloc->sym->sec, dest_off);
1539 if (!dest) {
1540 WARN_FUNC("can't find call dest symbol at %s+0x%lx",
1541 insn->sec, insn->offset,
1542 reloc->sym->sec->name,
1543 dest_off);
1544 return -1;
1545 }
1546
1547 add_call_dest(file, insn, dest, false);
1548
1549 } else if (reloc->sym->retpoline_thunk) {
1550 add_retpoline_call(file, insn);
1551
1552 } else
1553 add_call_dest(file, insn, reloc->sym, false);
1554 }
1555
1556 return 0;
1557 }
1558
1559 /*
1560 * The .alternatives section requires some extra special care over and above
1561 * other special sections because alternatives are patched in place.
1562 */
handle_group_alt(struct objtool_file * file,struct special_alt * special_alt,struct instruction * orig_insn,struct instruction ** new_insn)1563 static int handle_group_alt(struct objtool_file *file,
1564 struct special_alt *special_alt,
1565 struct instruction *orig_insn,
1566 struct instruction **new_insn)
1567 {
1568 struct instruction *last_orig_insn, *last_new_insn = NULL, *insn, *nop = NULL;
1569 struct alt_group *orig_alt_group, *new_alt_group;
1570 unsigned long dest_off;
1571
1572
1573 orig_alt_group = malloc(sizeof(*orig_alt_group));
1574 if (!orig_alt_group) {
1575 WARN("malloc failed");
1576 return -1;
1577 }
1578 orig_alt_group->cfi = calloc(special_alt->orig_len,
1579 sizeof(struct cfi_state *));
1580 if (!orig_alt_group->cfi) {
1581 WARN("calloc failed");
1582 return -1;
1583 }
1584
1585 last_orig_insn = NULL;
1586 insn = orig_insn;
1587 sec_for_each_insn_from(file, insn) {
1588 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1589 break;
1590
1591 insn->alt_group = orig_alt_group;
1592 last_orig_insn = insn;
1593 }
1594 orig_alt_group->orig_group = NULL;
1595 orig_alt_group->first_insn = orig_insn;
1596 orig_alt_group->last_insn = last_orig_insn;
1597
1598
1599 new_alt_group = malloc(sizeof(*new_alt_group));
1600 if (!new_alt_group) {
1601 WARN("malloc failed");
1602 return -1;
1603 }
1604
1605 if (special_alt->new_len < special_alt->orig_len) {
1606 /*
1607 * Insert a fake nop at the end to make the replacement
1608 * alt_group the same size as the original. This is needed to
1609 * allow propagate_alt_cfi() to do its magic. When the last
1610 * instruction affects the stack, the instruction after it (the
1611 * nop) will propagate the new state to the shared CFI array.
1612 */
1613 nop = malloc(sizeof(*nop));
1614 if (!nop) {
1615 WARN("malloc failed");
1616 return -1;
1617 }
1618 memset(nop, 0, sizeof(*nop));
1619 INIT_LIST_HEAD(&nop->alts);
1620 INIT_LIST_HEAD(&nop->stack_ops);
1621
1622 nop->sec = special_alt->new_sec;
1623 nop->offset = special_alt->new_off + special_alt->new_len;
1624 nop->len = special_alt->orig_len - special_alt->new_len;
1625 nop->type = INSN_NOP;
1626 nop->func = orig_insn->func;
1627 nop->alt_group = new_alt_group;
1628 nop->ignore = orig_insn->ignore_alts;
1629 }
1630
1631 if (!special_alt->new_len) {
1632 *new_insn = nop;
1633 goto end;
1634 }
1635
1636 insn = *new_insn;
1637 sec_for_each_insn_from(file, insn) {
1638 struct reloc *alt_reloc;
1639
1640 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1641 break;
1642
1643 last_new_insn = insn;
1644
1645 insn->ignore = orig_insn->ignore_alts;
1646 insn->func = orig_insn->func;
1647 insn->alt_group = new_alt_group;
1648
1649 /*
1650 * Since alternative replacement code is copy/pasted by the
1651 * kernel after applying relocations, generally such code can't
1652 * have relative-address relocation references to outside the
1653 * .altinstr_replacement section, unless the arch's
1654 * alternatives code can adjust the relative offsets
1655 * accordingly.
1656 */
1657 alt_reloc = insn_reloc(file, insn);
1658 if (alt_reloc &&
1659 !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1660
1661 WARN_FUNC("unsupported relocation in alternatives section",
1662 insn->sec, insn->offset);
1663 return -1;
1664 }
1665
1666 if (!is_static_jump(insn))
1667 continue;
1668
1669 if (!insn->immediate)
1670 continue;
1671
1672 dest_off = arch_jump_destination(insn);
1673 if (dest_off == special_alt->new_off + special_alt->new_len) {
1674 insn->jump_dest = next_insn_same_sec(file, last_orig_insn);
1675 if (!insn->jump_dest) {
1676 WARN_FUNC("can't find alternative jump destination",
1677 insn->sec, insn->offset);
1678 return -1;
1679 }
1680 }
1681 }
1682
1683 if (!last_new_insn) {
1684 WARN_FUNC("can't find last new alternative instruction",
1685 special_alt->new_sec, special_alt->new_off);
1686 return -1;
1687 }
1688
1689 if (nop)
1690 list_add(&nop->list, &last_new_insn->list);
1691 end:
1692 new_alt_group->orig_group = orig_alt_group;
1693 new_alt_group->first_insn = *new_insn;
1694 new_alt_group->last_insn = nop ? : last_new_insn;
1695 new_alt_group->cfi = orig_alt_group->cfi;
1696 return 0;
1697 }
1698
1699 /*
1700 * A jump table entry can either convert a nop to a jump or a jump to a nop.
1701 * If the original instruction is a jump, make the alt entry an effective nop
1702 * by just skipping the original instruction.
1703 */
handle_jump_alt(struct objtool_file * file,struct special_alt * special_alt,struct instruction * orig_insn,struct instruction ** new_insn)1704 static int handle_jump_alt(struct objtool_file *file,
1705 struct special_alt *special_alt,
1706 struct instruction *orig_insn,
1707 struct instruction **new_insn)
1708 {
1709 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1710 orig_insn->type != INSN_NOP) {
1711
1712 WARN_FUNC("unsupported instruction at jump label",
1713 orig_insn->sec, orig_insn->offset);
1714 return -1;
1715 }
1716
1717 if (opts.hack_jump_label && special_alt->key_addend & 2) {
1718 struct reloc *reloc = insn_reloc(file, orig_insn);
1719
1720 if (reloc) {
1721 reloc->type = R_NONE;
1722 elf_write_reloc(file->elf, reloc);
1723 }
1724 elf_write_insn(file->elf, orig_insn->sec,
1725 orig_insn->offset, orig_insn->len,
1726 arch_nop_insn(orig_insn->len));
1727 orig_insn->type = INSN_NOP;
1728 }
1729
1730 if (orig_insn->type == INSN_NOP) {
1731 if (orig_insn->len == 2)
1732 file->jl_nop_short++;
1733 else
1734 file->jl_nop_long++;
1735
1736 return 0;
1737 }
1738
1739 if (orig_insn->len == 2)
1740 file->jl_short++;
1741 else
1742 file->jl_long++;
1743
1744 *new_insn = list_next_entry(orig_insn, list);
1745 return 0;
1746 }
1747
1748 /*
1749 * Read all the special sections which have alternate instructions which can be
1750 * patched in or redirected to at runtime. Each instruction having alternate
1751 * instruction(s) has them added to its insn->alts list, which will be
1752 * traversed in validate_branch().
1753 */
add_special_section_alts(struct objtool_file * file)1754 static int add_special_section_alts(struct objtool_file *file)
1755 {
1756 struct list_head special_alts;
1757 struct instruction *orig_insn, *new_insn;
1758 struct special_alt *special_alt, *tmp;
1759 struct alternative *alt;
1760 int ret;
1761
1762 ret = special_get_alts(file->elf, &special_alts);
1763 if (ret)
1764 return ret;
1765
1766 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1767
1768 orig_insn = find_insn(file, special_alt->orig_sec,
1769 special_alt->orig_off);
1770 if (!orig_insn) {
1771 WARN_FUNC("special: can't find orig instruction",
1772 special_alt->orig_sec, special_alt->orig_off);
1773 ret = -1;
1774 goto out;
1775 }
1776
1777 new_insn = NULL;
1778 if (!special_alt->group || special_alt->new_len) {
1779 new_insn = find_insn(file, special_alt->new_sec,
1780 special_alt->new_off);
1781 if (!new_insn) {
1782 WARN_FUNC("special: can't find new instruction",
1783 special_alt->new_sec,
1784 special_alt->new_off);
1785 ret = -1;
1786 goto out;
1787 }
1788 }
1789
1790 if (special_alt->group) {
1791 if (!special_alt->orig_len) {
1792 WARN_FUNC("empty alternative entry",
1793 orig_insn->sec, orig_insn->offset);
1794 continue;
1795 }
1796
1797 ret = handle_group_alt(file, special_alt, orig_insn,
1798 &new_insn);
1799 if (ret)
1800 goto out;
1801 } else if (special_alt->jump_or_nop) {
1802 ret = handle_jump_alt(file, special_alt, orig_insn,
1803 &new_insn);
1804 if (ret)
1805 goto out;
1806 }
1807
1808 alt = malloc(sizeof(*alt));
1809 if (!alt) {
1810 WARN("malloc failed");
1811 ret = -1;
1812 goto out;
1813 }
1814
1815 alt->insn = new_insn;
1816 alt->skip_orig = special_alt->skip_orig;
1817 orig_insn->ignore_alts |= special_alt->skip_alt;
1818 list_add_tail(&alt->list, &orig_insn->alts);
1819
1820 list_del(&special_alt->list);
1821 free(special_alt);
1822 }
1823
1824 if (opts.stats) {
1825 printf("jl\\\tNOP\tJMP\n");
1826 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
1827 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
1828 }
1829
1830 out:
1831 return ret;
1832 }
1833
add_jump_table(struct objtool_file * file,struct instruction * insn,struct reloc * table)1834 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
1835 struct reloc *table)
1836 {
1837 struct reloc *reloc = table;
1838 struct instruction *dest_insn;
1839 struct alternative *alt;
1840 struct symbol *pfunc = insn->func->pfunc;
1841 unsigned int prev_offset = 0;
1842
1843 /*
1844 * Each @reloc is a switch table relocation which points to the target
1845 * instruction.
1846 */
1847 list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
1848
1849 /* Check for the end of the table: */
1850 if (reloc != table && reloc->jump_table_start)
1851 break;
1852
1853 /* Make sure the table entries are consecutive: */
1854 if (prev_offset && reloc->offset != prev_offset + 8)
1855 break;
1856
1857 /* Detect function pointers from contiguous objects: */
1858 if (reloc->sym->sec == pfunc->sec &&
1859 reloc->addend == pfunc->offset)
1860 break;
1861
1862 dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
1863 if (!dest_insn)
1864 break;
1865
1866 /* Make sure the destination is in the same function: */
1867 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
1868 break;
1869
1870 alt = malloc(sizeof(*alt));
1871 if (!alt) {
1872 WARN("malloc failed");
1873 return -1;
1874 }
1875
1876 alt->insn = dest_insn;
1877 list_add_tail(&alt->list, &insn->alts);
1878 prev_offset = reloc->offset;
1879 }
1880
1881 if (!prev_offset) {
1882 WARN_FUNC("can't find switch jump table",
1883 insn->sec, insn->offset);
1884 return -1;
1885 }
1886
1887 return 0;
1888 }
1889
1890 /*
1891 * find_jump_table() - Given a dynamic jump, find the switch jump table
1892 * associated with it.
1893 */
find_jump_table(struct objtool_file * file,struct symbol * func,struct instruction * insn)1894 static struct reloc *find_jump_table(struct objtool_file *file,
1895 struct symbol *func,
1896 struct instruction *insn)
1897 {
1898 struct reloc *table_reloc;
1899 struct instruction *dest_insn, *orig_insn = insn;
1900
1901 /*
1902 * Backward search using the @first_jump_src links, these help avoid
1903 * much of the 'in between' code. Which avoids us getting confused by
1904 * it.
1905 */
1906 for (;
1907 insn && insn->func && insn->func->pfunc == func;
1908 insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
1909
1910 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1911 break;
1912
1913 /* allow small jumps within the range */
1914 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1915 insn->jump_dest &&
1916 (insn->jump_dest->offset <= insn->offset ||
1917 insn->jump_dest->offset > orig_insn->offset))
1918 break;
1919
1920 table_reloc = arch_find_switch_table(file, insn);
1921 if (!table_reloc)
1922 continue;
1923 dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
1924 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1925 continue;
1926
1927 return table_reloc;
1928 }
1929
1930 return NULL;
1931 }
1932
1933 /*
1934 * First pass: Mark the head of each jump table so that in the next pass,
1935 * we know when a given jump table ends and the next one starts.
1936 */
mark_func_jump_tables(struct objtool_file * file,struct symbol * func)1937 static void mark_func_jump_tables(struct objtool_file *file,
1938 struct symbol *func)
1939 {
1940 struct instruction *insn, *last = NULL;
1941 struct reloc *reloc;
1942
1943 func_for_each_insn(file, func, insn) {
1944 if (!last)
1945 last = insn;
1946
1947 /*
1948 * Store back-pointers for unconditional forward jumps such
1949 * that find_jump_table() can back-track using those and
1950 * avoid some potentially confusing code.
1951 */
1952 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1953 insn->offset > last->offset &&
1954 insn->jump_dest->offset > insn->offset &&
1955 !insn->jump_dest->first_jump_src) {
1956
1957 insn->jump_dest->first_jump_src = insn;
1958 last = insn->jump_dest;
1959 }
1960
1961 if (insn->type != INSN_JUMP_DYNAMIC)
1962 continue;
1963
1964 reloc = find_jump_table(file, func, insn);
1965 if (reloc) {
1966 reloc->jump_table_start = true;
1967 insn->jump_table = reloc;
1968 }
1969 }
1970 }
1971
add_func_jump_tables(struct objtool_file * file,struct symbol * func)1972 static int add_func_jump_tables(struct objtool_file *file,
1973 struct symbol *func)
1974 {
1975 struct instruction *insn;
1976 int ret;
1977
1978 func_for_each_insn(file, func, insn) {
1979 if (!insn->jump_table)
1980 continue;
1981
1982 ret = add_jump_table(file, insn, insn->jump_table);
1983 if (ret)
1984 return ret;
1985 }
1986
1987 return 0;
1988 }
1989
1990 /*
1991 * For some switch statements, gcc generates a jump table in the .rodata
1992 * section which contains a list of addresses within the function to jump to.
1993 * This finds these jump tables and adds them to the insn->alts lists.
1994 */
add_jump_table_alts(struct objtool_file * file)1995 static int add_jump_table_alts(struct objtool_file *file)
1996 {
1997 struct section *sec;
1998 struct symbol *func;
1999 int ret;
2000
2001 if (!file->rodata)
2002 return 0;
2003
2004 for_each_sec(file, sec) {
2005 list_for_each_entry(func, &sec->symbol_list, list) {
2006 if (func->type != STT_FUNC)
2007 continue;
2008
2009 mark_func_jump_tables(file, func);
2010 ret = add_func_jump_tables(file, func);
2011 if (ret)
2012 return ret;
2013 }
2014 }
2015
2016 return 0;
2017 }
2018
set_func_state(struct cfi_state * state)2019 static void set_func_state(struct cfi_state *state)
2020 {
2021 state->cfa = initial_func_cfi.cfa;
2022 memcpy(&state->regs, &initial_func_cfi.regs,
2023 CFI_NUM_REGS * sizeof(struct cfi_reg));
2024 state->stack_size = initial_func_cfi.cfa.offset;
2025 }
2026
read_unwind_hints(struct objtool_file * file)2027 static int read_unwind_hints(struct objtool_file *file)
2028 {
2029 struct cfi_state cfi = init_cfi;
2030 struct section *sec, *relocsec;
2031 struct unwind_hint *hint;
2032 struct instruction *insn;
2033 struct reloc *reloc;
2034 int i;
2035
2036 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
2037 if (!sec)
2038 return 0;
2039
2040 relocsec = sec->reloc;
2041 if (!relocsec) {
2042 WARN("missing .rela.discard.unwind_hints section");
2043 return -1;
2044 }
2045
2046 if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
2047 WARN("struct unwind_hint size mismatch");
2048 return -1;
2049 }
2050
2051 file->hints = true;
2052
2053 for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
2054 hint = (struct unwind_hint *)sec->data->d_buf + i;
2055
2056 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
2057 if (!reloc) {
2058 WARN("can't find reloc for unwind_hints[%d]", i);
2059 return -1;
2060 }
2061
2062 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2063 if (!insn) {
2064 WARN("can't find insn for unwind_hints[%d]", i);
2065 return -1;
2066 }
2067
2068 insn->hint = true;
2069
2070 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
2071 insn->hint = false;
2072 insn->save = true;
2073 continue;
2074 }
2075
2076 if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
2077 insn->restore = true;
2078 continue;
2079 }
2080
2081 if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
2082 struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
2083
2084 if (sym && sym->bind == STB_GLOBAL) {
2085 if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) {
2086 WARN_FUNC("UNWIND_HINT_IRET_REGS without ENDBR",
2087 insn->sec, insn->offset);
2088 }
2089
2090 insn->entry = 1;
2091 }
2092 }
2093
2094 if (hint->type == UNWIND_HINT_TYPE_ENTRY) {
2095 hint->type = UNWIND_HINT_TYPE_CALL;
2096 insn->entry = 1;
2097 }
2098
2099 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
2100 insn->cfi = &func_cfi;
2101 continue;
2102 }
2103
2104 if (insn->cfi)
2105 cfi = *(insn->cfi);
2106
2107 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
2108 WARN_FUNC("unsupported unwind_hint sp base reg %d",
2109 insn->sec, insn->offset, hint->sp_reg);
2110 return -1;
2111 }
2112
2113 cfi.cfa.offset = bswap_if_needed(hint->sp_offset);
2114 cfi.type = hint->type;
2115 cfi.end = hint->end;
2116
2117 insn->cfi = cfi_hash_find_or_add(&cfi);
2118 }
2119
2120 return 0;
2121 }
2122
read_noendbr_hints(struct objtool_file * file)2123 static int read_noendbr_hints(struct objtool_file *file)
2124 {
2125 struct section *sec;
2126 struct instruction *insn;
2127 struct reloc *reloc;
2128
2129 sec = find_section_by_name(file->elf, ".rela.discard.noendbr");
2130 if (!sec)
2131 return 0;
2132
2133 list_for_each_entry(reloc, &sec->reloc_list, list) {
2134 insn = find_insn(file, reloc->sym->sec, reloc->sym->offset + reloc->addend);
2135 if (!insn) {
2136 WARN("bad .discard.noendbr entry");
2137 return -1;
2138 }
2139
2140 insn->noendbr = 1;
2141 }
2142
2143 return 0;
2144 }
2145
read_retpoline_hints(struct objtool_file * file)2146 static int read_retpoline_hints(struct objtool_file *file)
2147 {
2148 struct section *sec;
2149 struct instruction *insn;
2150 struct reloc *reloc;
2151
2152 sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
2153 if (!sec)
2154 return 0;
2155
2156 list_for_each_entry(reloc, &sec->reloc_list, list) {
2157 if (reloc->sym->type != STT_SECTION) {
2158 WARN("unexpected relocation symbol type in %s", sec->name);
2159 return -1;
2160 }
2161
2162 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2163 if (!insn) {
2164 WARN("bad .discard.retpoline_safe entry");
2165 return -1;
2166 }
2167
2168 if (insn->type != INSN_JUMP_DYNAMIC &&
2169 insn->type != INSN_CALL_DYNAMIC &&
2170 insn->type != INSN_RETURN &&
2171 insn->type != INSN_NOP) {
2172 WARN_FUNC("retpoline_safe hint not an indirect jump/call/ret/nop",
2173 insn->sec, insn->offset);
2174 return -1;
2175 }
2176
2177 insn->retpoline_safe = true;
2178 }
2179
2180 return 0;
2181 }
2182
read_instr_hints(struct objtool_file * file)2183 static int read_instr_hints(struct objtool_file *file)
2184 {
2185 struct section *sec;
2186 struct instruction *insn;
2187 struct reloc *reloc;
2188
2189 sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2190 if (!sec)
2191 return 0;
2192
2193 list_for_each_entry(reloc, &sec->reloc_list, list) {
2194 if (reloc->sym->type != STT_SECTION) {
2195 WARN("unexpected relocation symbol type in %s", sec->name);
2196 return -1;
2197 }
2198
2199 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2200 if (!insn) {
2201 WARN("bad .discard.instr_end entry");
2202 return -1;
2203 }
2204
2205 insn->instr--;
2206 }
2207
2208 sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2209 if (!sec)
2210 return 0;
2211
2212 list_for_each_entry(reloc, &sec->reloc_list, list) {
2213 if (reloc->sym->type != STT_SECTION) {
2214 WARN("unexpected relocation symbol type in %s", sec->name);
2215 return -1;
2216 }
2217
2218 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2219 if (!insn) {
2220 WARN("bad .discard.instr_begin entry");
2221 return -1;
2222 }
2223
2224 insn->instr++;
2225 }
2226
2227 return 0;
2228 }
2229
read_intra_function_calls(struct objtool_file * file)2230 static int read_intra_function_calls(struct objtool_file *file)
2231 {
2232 struct instruction *insn;
2233 struct section *sec;
2234 struct reloc *reloc;
2235
2236 sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2237 if (!sec)
2238 return 0;
2239
2240 list_for_each_entry(reloc, &sec->reloc_list, list) {
2241 unsigned long dest_off;
2242
2243 if (reloc->sym->type != STT_SECTION) {
2244 WARN("unexpected relocation symbol type in %s",
2245 sec->name);
2246 return -1;
2247 }
2248
2249 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2250 if (!insn) {
2251 WARN("bad .discard.intra_function_call entry");
2252 return -1;
2253 }
2254
2255 if (insn->type != INSN_CALL) {
2256 WARN_FUNC("intra_function_call not a direct call",
2257 insn->sec, insn->offset);
2258 return -1;
2259 }
2260
2261 /*
2262 * Treat intra-function CALLs as JMPs, but with a stack_op.
2263 * See add_call_destinations(), which strips stack_ops from
2264 * normal CALLs.
2265 */
2266 insn->type = INSN_JUMP_UNCONDITIONAL;
2267
2268 dest_off = arch_jump_destination(insn);
2269 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2270 if (!insn->jump_dest) {
2271 WARN_FUNC("can't find call dest at %s+0x%lx",
2272 insn->sec, insn->offset,
2273 insn->sec->name, dest_off);
2274 return -1;
2275 }
2276 }
2277
2278 return 0;
2279 }
2280
2281 /*
2282 * Return true if name matches an instrumentation function, where calls to that
2283 * function from noinstr code can safely be removed, but compilers won't do so.
2284 */
is_profiling_func(const char * name)2285 static bool is_profiling_func(const char *name)
2286 {
2287 /*
2288 * Many compilers cannot disable KCOV with a function attribute.
2289 */
2290 if (!strncmp(name, "__sanitizer_cov_", 16))
2291 return true;
2292
2293 /*
2294 * Some compilers currently do not remove __tsan_func_entry/exit nor
2295 * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2296 * the __no_sanitize_thread attribute, remove them. Once the kernel's
2297 * minimum Clang version is 14.0, this can be removed.
2298 */
2299 if (!strncmp(name, "__tsan_func_", 12) ||
2300 !strcmp(name, "__tsan_atomic_signal_fence"))
2301 return true;
2302
2303 return false;
2304 }
2305
classify_symbols(struct objtool_file * file)2306 static int classify_symbols(struct objtool_file *file)
2307 {
2308 struct section *sec;
2309 struct symbol *func;
2310
2311 for_each_sec(file, sec) {
2312 list_for_each_entry(func, &sec->symbol_list, list) {
2313 if (func->bind != STB_GLOBAL)
2314 continue;
2315
2316 if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2317 strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2318 func->static_call_tramp = true;
2319
2320 if (arch_is_retpoline(func))
2321 func->retpoline_thunk = true;
2322
2323 if (arch_is_rethunk(func))
2324 func->return_thunk = true;
2325
2326 if (!strcmp(func->name, "__fentry__"))
2327 func->fentry = true;
2328
2329 if (is_profiling_func(func->name))
2330 func->profiling_func = true;
2331 }
2332 }
2333
2334 return 0;
2335 }
2336
mark_rodata(struct objtool_file * file)2337 static void mark_rodata(struct objtool_file *file)
2338 {
2339 struct section *sec;
2340 bool found = false;
2341
2342 /*
2343 * Search for the following rodata sections, each of which can
2344 * potentially contain jump tables:
2345 *
2346 * - .rodata: can contain GCC switch tables
2347 * - .rodata.<func>: same, if -fdata-sections is being used
2348 * - .rodata..c_jump_table: contains C annotated jump tables
2349 *
2350 * .rodata.str1.* sections are ignored; they don't contain jump tables.
2351 */
2352 for_each_sec(file, sec) {
2353 if (!strncmp(sec->name, ".rodata", 7) &&
2354 !strstr(sec->name, ".str1.")) {
2355 sec->rodata = true;
2356 found = true;
2357 }
2358 }
2359
2360 file->rodata = found;
2361 }
2362
decode_sections(struct objtool_file * file)2363 static int decode_sections(struct objtool_file *file)
2364 {
2365 int ret;
2366
2367 mark_rodata(file);
2368
2369 ret = init_pv_ops(file);
2370 if (ret)
2371 return ret;
2372
2373 ret = decode_instructions(file);
2374 if (ret)
2375 return ret;
2376
2377 add_ignores(file);
2378 add_uaccess_safe(file);
2379
2380 ret = add_ignore_alternatives(file);
2381 if (ret)
2382 return ret;
2383
2384 /*
2385 * Must be before read_unwind_hints() since that needs insn->noendbr.
2386 */
2387 ret = read_noendbr_hints(file);
2388 if (ret)
2389 return ret;
2390
2391 /*
2392 * Must be before add_{jump_call}_destination.
2393 */
2394 ret = classify_symbols(file);
2395 if (ret)
2396 return ret;
2397
2398 /*
2399 * Must be before add_jump_destinations(), which depends on 'func'
2400 * being set for alternatives, to enable proper sibling call detection.
2401 */
2402 ret = add_special_section_alts(file);
2403 if (ret)
2404 return ret;
2405
2406 ret = add_jump_destinations(file);
2407 if (ret)
2408 return ret;
2409
2410 /*
2411 * Must be before add_call_destination(); it changes INSN_CALL to
2412 * INSN_JUMP.
2413 */
2414 ret = read_intra_function_calls(file);
2415 if (ret)
2416 return ret;
2417
2418 ret = add_call_destinations(file);
2419 if (ret)
2420 return ret;
2421
2422 /*
2423 * Must be after add_call_destinations() such that it can override
2424 * dead_end_function() marks.
2425 */
2426 ret = add_dead_ends(file);
2427 if (ret)
2428 return ret;
2429
2430 ret = add_jump_table_alts(file);
2431 if (ret)
2432 return ret;
2433
2434 ret = read_unwind_hints(file);
2435 if (ret)
2436 return ret;
2437
2438 ret = read_retpoline_hints(file);
2439 if (ret)
2440 return ret;
2441
2442 ret = read_instr_hints(file);
2443 if (ret)
2444 return ret;
2445
2446 return 0;
2447 }
2448
is_fentry_call(struct instruction * insn)2449 static bool is_fentry_call(struct instruction *insn)
2450 {
2451 if (insn->type == INSN_CALL &&
2452 insn->call_dest &&
2453 insn->call_dest->fentry)
2454 return true;
2455
2456 return false;
2457 }
2458
has_modified_stack_frame(struct instruction * insn,struct insn_state * state)2459 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2460 {
2461 struct cfi_state *cfi = &state->cfi;
2462 int i;
2463
2464 if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2465 return true;
2466
2467 if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2468 return true;
2469
2470 if (cfi->stack_size != initial_func_cfi.cfa.offset)
2471 return true;
2472
2473 for (i = 0; i < CFI_NUM_REGS; i++) {
2474 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2475 cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2476 return true;
2477 }
2478
2479 return false;
2480 }
2481
check_reg_frame_pos(const struct cfi_reg * reg,int expected_offset)2482 static bool check_reg_frame_pos(const struct cfi_reg *reg,
2483 int expected_offset)
2484 {
2485 return reg->base == CFI_CFA &&
2486 reg->offset == expected_offset;
2487 }
2488
has_valid_stack_frame(struct insn_state * state)2489 static bool has_valid_stack_frame(struct insn_state *state)
2490 {
2491 struct cfi_state *cfi = &state->cfi;
2492
2493 if (cfi->cfa.base == CFI_BP &&
2494 check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2495 check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2496 return true;
2497
2498 if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2499 return true;
2500
2501 return false;
2502 }
2503
update_cfi_state_regs(struct instruction * insn,struct cfi_state * cfi,struct stack_op * op)2504 static int update_cfi_state_regs(struct instruction *insn,
2505 struct cfi_state *cfi,
2506 struct stack_op *op)
2507 {
2508 struct cfi_reg *cfa = &cfi->cfa;
2509
2510 if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2511 return 0;
2512
2513 /* push */
2514 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2515 cfa->offset += 8;
2516
2517 /* pop */
2518 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2519 cfa->offset -= 8;
2520
2521 /* add immediate to sp */
2522 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2523 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2524 cfa->offset -= op->src.offset;
2525
2526 return 0;
2527 }
2528
save_reg(struct cfi_state * cfi,unsigned char reg,int base,int offset)2529 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2530 {
2531 if (arch_callee_saved_reg(reg) &&
2532 cfi->regs[reg].base == CFI_UNDEFINED) {
2533 cfi->regs[reg].base = base;
2534 cfi->regs[reg].offset = offset;
2535 }
2536 }
2537
restore_reg(struct cfi_state * cfi,unsigned char reg)2538 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2539 {
2540 cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2541 cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2542 }
2543
2544 /*
2545 * A note about DRAP stack alignment:
2546 *
2547 * GCC has the concept of a DRAP register, which is used to help keep track of
2548 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
2549 * register. The typical DRAP pattern is:
2550 *
2551 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
2552 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
2553 * 41 ff 72 f8 pushq -0x8(%r10)
2554 * 55 push %rbp
2555 * 48 89 e5 mov %rsp,%rbp
2556 * (more pushes)
2557 * 41 52 push %r10
2558 * ...
2559 * 41 5a pop %r10
2560 * (more pops)
2561 * 5d pop %rbp
2562 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2563 * c3 retq
2564 *
2565 * There are some variations in the epilogues, like:
2566 *
2567 * 5b pop %rbx
2568 * 41 5a pop %r10
2569 * 41 5c pop %r12
2570 * 41 5d pop %r13
2571 * 41 5e pop %r14
2572 * c9 leaveq
2573 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2574 * c3 retq
2575 *
2576 * and:
2577 *
2578 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
2579 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
2580 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
2581 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
2582 * c9 leaveq
2583 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2584 * c3 retq
2585 *
2586 * Sometimes r13 is used as the DRAP register, in which case it's saved and
2587 * restored beforehand:
2588 *
2589 * 41 55 push %r13
2590 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
2591 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
2592 * ...
2593 * 49 8d 65 f0 lea -0x10(%r13),%rsp
2594 * 41 5d pop %r13
2595 * c3 retq
2596 */
update_cfi_state(struct instruction * insn,struct instruction * next_insn,struct cfi_state * cfi,struct stack_op * op)2597 static int update_cfi_state(struct instruction *insn,
2598 struct instruction *next_insn,
2599 struct cfi_state *cfi, struct stack_op *op)
2600 {
2601 struct cfi_reg *cfa = &cfi->cfa;
2602 struct cfi_reg *regs = cfi->regs;
2603
2604 /* stack operations don't make sense with an undefined CFA */
2605 if (cfa->base == CFI_UNDEFINED) {
2606 if (insn->func) {
2607 WARN_FUNC("undefined stack state", insn->sec, insn->offset);
2608 return -1;
2609 }
2610 return 0;
2611 }
2612
2613 if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2614 cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2615 return update_cfi_state_regs(insn, cfi, op);
2616
2617 switch (op->dest.type) {
2618
2619 case OP_DEST_REG:
2620 switch (op->src.type) {
2621
2622 case OP_SRC_REG:
2623 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2624 cfa->base == CFI_SP &&
2625 check_reg_frame_pos(®s[CFI_BP], -cfa->offset)) {
2626
2627 /* mov %rsp, %rbp */
2628 cfa->base = op->dest.reg;
2629 cfi->bp_scratch = false;
2630 }
2631
2632 else if (op->src.reg == CFI_SP &&
2633 op->dest.reg == CFI_BP && cfi->drap) {
2634
2635 /* drap: mov %rsp, %rbp */
2636 regs[CFI_BP].base = CFI_BP;
2637 regs[CFI_BP].offset = -cfi->stack_size;
2638 cfi->bp_scratch = false;
2639 }
2640
2641 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2642
2643 /*
2644 * mov %rsp, %reg
2645 *
2646 * This is needed for the rare case where GCC
2647 * does:
2648 *
2649 * mov %rsp, %rax
2650 * ...
2651 * mov %rax, %rsp
2652 */
2653 cfi->vals[op->dest.reg].base = CFI_CFA;
2654 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2655 }
2656
2657 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2658 (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2659
2660 /*
2661 * mov %rbp, %rsp
2662 *
2663 * Restore the original stack pointer (Clang).
2664 */
2665 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2666 }
2667
2668 else if (op->dest.reg == cfa->base) {
2669
2670 /* mov %reg, %rsp */
2671 if (cfa->base == CFI_SP &&
2672 cfi->vals[op->src.reg].base == CFI_CFA) {
2673
2674 /*
2675 * This is needed for the rare case
2676 * where GCC does something dumb like:
2677 *
2678 * lea 0x8(%rsp), %rcx
2679 * ...
2680 * mov %rcx, %rsp
2681 */
2682 cfa->offset = -cfi->vals[op->src.reg].offset;
2683 cfi->stack_size = cfa->offset;
2684
2685 } else if (cfa->base == CFI_SP &&
2686 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2687 cfi->vals[op->src.reg].offset == cfa->offset) {
2688
2689 /*
2690 * Stack swizzle:
2691 *
2692 * 1: mov %rsp, (%[tos])
2693 * 2: mov %[tos], %rsp
2694 * ...
2695 * 3: pop %rsp
2696 *
2697 * Where:
2698 *
2699 * 1 - places a pointer to the previous
2700 * stack at the Top-of-Stack of the
2701 * new stack.
2702 *
2703 * 2 - switches to the new stack.
2704 *
2705 * 3 - pops the Top-of-Stack to restore
2706 * the original stack.
2707 *
2708 * Note: we set base to SP_INDIRECT
2709 * here and preserve offset. Therefore
2710 * when the unwinder reaches ToS it
2711 * will dereference SP and then add the
2712 * offset to find the next frame, IOW:
2713 * (%rsp) + offset.
2714 */
2715 cfa->base = CFI_SP_INDIRECT;
2716
2717 } else {
2718 cfa->base = CFI_UNDEFINED;
2719 cfa->offset = 0;
2720 }
2721 }
2722
2723 else if (op->dest.reg == CFI_SP &&
2724 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2725 cfi->vals[op->src.reg].offset == cfa->offset) {
2726
2727 /*
2728 * The same stack swizzle case 2) as above. But
2729 * because we can't change cfa->base, case 3)
2730 * will become a regular POP. Pretend we're a
2731 * PUSH so things don't go unbalanced.
2732 */
2733 cfi->stack_size += 8;
2734 }
2735
2736
2737 break;
2738
2739 case OP_SRC_ADD:
2740 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2741
2742 /* add imm, %rsp */
2743 cfi->stack_size -= op->src.offset;
2744 if (cfa->base == CFI_SP)
2745 cfa->offset -= op->src.offset;
2746 break;
2747 }
2748
2749 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2750
2751 /* lea disp(%rbp), %rsp */
2752 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2753 break;
2754 }
2755
2756 if (!cfi->drap && op->src.reg == CFI_SP &&
2757 op->dest.reg == CFI_BP && cfa->base == CFI_SP &&
2758 check_reg_frame_pos(®s[CFI_BP], -cfa->offset + op->src.offset)) {
2759
2760 /* lea disp(%rsp), %rbp */
2761 cfa->base = CFI_BP;
2762 cfa->offset -= op->src.offset;
2763 cfi->bp_scratch = false;
2764 break;
2765 }
2766
2767 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2768
2769 /* drap: lea disp(%rsp), %drap */
2770 cfi->drap_reg = op->dest.reg;
2771
2772 /*
2773 * lea disp(%rsp), %reg
2774 *
2775 * This is needed for the rare case where GCC
2776 * does something dumb like:
2777 *
2778 * lea 0x8(%rsp), %rcx
2779 * ...
2780 * mov %rcx, %rsp
2781 */
2782 cfi->vals[op->dest.reg].base = CFI_CFA;
2783 cfi->vals[op->dest.reg].offset = \
2784 -cfi->stack_size + op->src.offset;
2785
2786 break;
2787 }
2788
2789 if (cfi->drap && op->dest.reg == CFI_SP &&
2790 op->src.reg == cfi->drap_reg) {
2791
2792 /* drap: lea disp(%drap), %rsp */
2793 cfa->base = CFI_SP;
2794 cfa->offset = cfi->stack_size = -op->src.offset;
2795 cfi->drap_reg = CFI_UNDEFINED;
2796 cfi->drap = false;
2797 break;
2798 }
2799
2800 if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
2801 WARN_FUNC("unsupported stack register modification",
2802 insn->sec, insn->offset);
2803 return -1;
2804 }
2805
2806 break;
2807
2808 case OP_SRC_AND:
2809 if (op->dest.reg != CFI_SP ||
2810 (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
2811 (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
2812 WARN_FUNC("unsupported stack pointer realignment",
2813 insn->sec, insn->offset);
2814 return -1;
2815 }
2816
2817 if (cfi->drap_reg != CFI_UNDEFINED) {
2818 /* drap: and imm, %rsp */
2819 cfa->base = cfi->drap_reg;
2820 cfa->offset = cfi->stack_size = 0;
2821 cfi->drap = true;
2822 }
2823
2824 /*
2825 * Older versions of GCC (4.8ish) realign the stack
2826 * without DRAP, with a frame pointer.
2827 */
2828
2829 break;
2830
2831 case OP_SRC_POP:
2832 case OP_SRC_POPF:
2833 if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
2834
2835 /* pop %rsp; # restore from a stack swizzle */
2836 cfa->base = CFI_SP;
2837 break;
2838 }
2839
2840 if (!cfi->drap && op->dest.reg == cfa->base) {
2841
2842 /* pop %rbp */
2843 cfa->base = CFI_SP;
2844 }
2845
2846 if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
2847 op->dest.reg == cfi->drap_reg &&
2848 cfi->drap_offset == -cfi->stack_size) {
2849
2850 /* drap: pop %drap */
2851 cfa->base = cfi->drap_reg;
2852 cfa->offset = 0;
2853 cfi->drap_offset = -1;
2854
2855 } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
2856
2857 /* pop %reg */
2858 restore_reg(cfi, op->dest.reg);
2859 }
2860
2861 cfi->stack_size -= 8;
2862 if (cfa->base == CFI_SP)
2863 cfa->offset -= 8;
2864
2865 break;
2866
2867 case OP_SRC_REG_INDIRECT:
2868 if (!cfi->drap && op->dest.reg == cfa->base &&
2869 op->dest.reg == CFI_BP) {
2870
2871 /* mov disp(%rsp), %rbp */
2872 cfa->base = CFI_SP;
2873 cfa->offset = cfi->stack_size;
2874 }
2875
2876 if (cfi->drap && op->src.reg == CFI_BP &&
2877 op->src.offset == cfi->drap_offset) {
2878
2879 /* drap: mov disp(%rbp), %drap */
2880 cfa->base = cfi->drap_reg;
2881 cfa->offset = 0;
2882 cfi->drap_offset = -1;
2883 }
2884
2885 if (cfi->drap && op->src.reg == CFI_BP &&
2886 op->src.offset == regs[op->dest.reg].offset) {
2887
2888 /* drap: mov disp(%rbp), %reg */
2889 restore_reg(cfi, op->dest.reg);
2890
2891 } else if (op->src.reg == cfa->base &&
2892 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
2893
2894 /* mov disp(%rbp), %reg */
2895 /* mov disp(%rsp), %reg */
2896 restore_reg(cfi, op->dest.reg);
2897
2898 } else if (op->src.reg == CFI_SP &&
2899 op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
2900
2901 /* mov disp(%rsp), %reg */
2902 restore_reg(cfi, op->dest.reg);
2903 }
2904
2905 break;
2906
2907 default:
2908 WARN_FUNC("unknown stack-related instruction",
2909 insn->sec, insn->offset);
2910 return -1;
2911 }
2912
2913 break;
2914
2915 case OP_DEST_PUSH:
2916 case OP_DEST_PUSHF:
2917 cfi->stack_size += 8;
2918 if (cfa->base == CFI_SP)
2919 cfa->offset += 8;
2920
2921 if (op->src.type != OP_SRC_REG)
2922 break;
2923
2924 if (cfi->drap) {
2925 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2926
2927 /* drap: push %drap */
2928 cfa->base = CFI_BP_INDIRECT;
2929 cfa->offset = -cfi->stack_size;
2930
2931 /* save drap so we know when to restore it */
2932 cfi->drap_offset = -cfi->stack_size;
2933
2934 } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
2935
2936 /* drap: push %rbp */
2937 cfi->stack_size = 0;
2938
2939 } else {
2940
2941 /* drap: push %reg */
2942 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
2943 }
2944
2945 } else {
2946
2947 /* push %reg */
2948 save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
2949 }
2950
2951 /* detect when asm code uses rbp as a scratch register */
2952 if (opts.stackval && insn->func && op->src.reg == CFI_BP &&
2953 cfa->base != CFI_BP)
2954 cfi->bp_scratch = true;
2955 break;
2956
2957 case OP_DEST_REG_INDIRECT:
2958
2959 if (cfi->drap) {
2960 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2961
2962 /* drap: mov %drap, disp(%rbp) */
2963 cfa->base = CFI_BP_INDIRECT;
2964 cfa->offset = op->dest.offset;
2965
2966 /* save drap offset so we know when to restore it */
2967 cfi->drap_offset = op->dest.offset;
2968 } else {
2969
2970 /* drap: mov reg, disp(%rbp) */
2971 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
2972 }
2973
2974 } else if (op->dest.reg == cfa->base) {
2975
2976 /* mov reg, disp(%rbp) */
2977 /* mov reg, disp(%rsp) */
2978 save_reg(cfi, op->src.reg, CFI_CFA,
2979 op->dest.offset - cfi->cfa.offset);
2980
2981 } else if (op->dest.reg == CFI_SP) {
2982
2983 /* mov reg, disp(%rsp) */
2984 save_reg(cfi, op->src.reg, CFI_CFA,
2985 op->dest.offset - cfi->stack_size);
2986
2987 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
2988
2989 /* mov %rsp, (%reg); # setup a stack swizzle. */
2990 cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
2991 cfi->vals[op->dest.reg].offset = cfa->offset;
2992 }
2993
2994 break;
2995
2996 case OP_DEST_MEM:
2997 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
2998 WARN_FUNC("unknown stack-related memory operation",
2999 insn->sec, insn->offset);
3000 return -1;
3001 }
3002
3003 /* pop mem */
3004 cfi->stack_size -= 8;
3005 if (cfa->base == CFI_SP)
3006 cfa->offset -= 8;
3007
3008 break;
3009
3010 default:
3011 WARN_FUNC("unknown stack-related instruction",
3012 insn->sec, insn->offset);
3013 return -1;
3014 }
3015
3016 return 0;
3017 }
3018
3019 /*
3020 * The stack layouts of alternatives instructions can sometimes diverge when
3021 * they have stack modifications. That's fine as long as the potential stack
3022 * layouts don't conflict at any given potential instruction boundary.
3023 *
3024 * Flatten the CFIs of the different alternative code streams (both original
3025 * and replacement) into a single shared CFI array which can be used to detect
3026 * conflicts and nicely feed a linear array of ORC entries to the unwinder.
3027 */
propagate_alt_cfi(struct objtool_file * file,struct instruction * insn)3028 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
3029 {
3030 struct cfi_state **alt_cfi;
3031 int group_off;
3032
3033 if (!insn->alt_group)
3034 return 0;
3035
3036 if (!insn->cfi) {
3037 WARN("CFI missing");
3038 return -1;
3039 }
3040
3041 alt_cfi = insn->alt_group->cfi;
3042 group_off = insn->offset - insn->alt_group->first_insn->offset;
3043
3044 if (!alt_cfi[group_off]) {
3045 alt_cfi[group_off] = insn->cfi;
3046 } else {
3047 if (cficmp(alt_cfi[group_off], insn->cfi)) {
3048 WARN_FUNC("stack layout conflict in alternatives",
3049 insn->sec, insn->offset);
3050 return -1;
3051 }
3052 }
3053
3054 return 0;
3055 }
3056
handle_insn_ops(struct instruction * insn,struct instruction * next_insn,struct insn_state * state)3057 static int handle_insn_ops(struct instruction *insn,
3058 struct instruction *next_insn,
3059 struct insn_state *state)
3060 {
3061 struct stack_op *op;
3062
3063 list_for_each_entry(op, &insn->stack_ops, list) {
3064
3065 if (update_cfi_state(insn, next_insn, &state->cfi, op))
3066 return 1;
3067
3068 if (!insn->alt_group)
3069 continue;
3070
3071 if (op->dest.type == OP_DEST_PUSHF) {
3072 if (!state->uaccess_stack) {
3073 state->uaccess_stack = 1;
3074 } else if (state->uaccess_stack >> 31) {
3075 WARN_FUNC("PUSHF stack exhausted",
3076 insn->sec, insn->offset);
3077 return 1;
3078 }
3079 state->uaccess_stack <<= 1;
3080 state->uaccess_stack |= state->uaccess;
3081 }
3082
3083 if (op->src.type == OP_SRC_POPF) {
3084 if (state->uaccess_stack) {
3085 state->uaccess = state->uaccess_stack & 1;
3086 state->uaccess_stack >>= 1;
3087 if (state->uaccess_stack == 1)
3088 state->uaccess_stack = 0;
3089 }
3090 }
3091 }
3092
3093 return 0;
3094 }
3095
insn_cfi_match(struct instruction * insn,struct cfi_state * cfi2)3096 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
3097 {
3098 struct cfi_state *cfi1 = insn->cfi;
3099 int i;
3100
3101 if (!cfi1) {
3102 WARN("CFI missing");
3103 return false;
3104 }
3105
3106 if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
3107
3108 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
3109 insn->sec, insn->offset,
3110 cfi1->cfa.base, cfi1->cfa.offset,
3111 cfi2->cfa.base, cfi2->cfa.offset);
3112
3113 } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
3114 for (i = 0; i < CFI_NUM_REGS; i++) {
3115 if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
3116 sizeof(struct cfi_reg)))
3117 continue;
3118
3119 WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
3120 insn->sec, insn->offset,
3121 i, cfi1->regs[i].base, cfi1->regs[i].offset,
3122 i, cfi2->regs[i].base, cfi2->regs[i].offset);
3123 break;
3124 }
3125
3126 } else if (cfi1->type != cfi2->type) {
3127
3128 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
3129 insn->sec, insn->offset, cfi1->type, cfi2->type);
3130
3131 } else if (cfi1->drap != cfi2->drap ||
3132 (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
3133 (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
3134
3135 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
3136 insn->sec, insn->offset,
3137 cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
3138 cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
3139
3140 } else
3141 return true;
3142
3143 return false;
3144 }
3145
func_uaccess_safe(struct symbol * func)3146 static inline bool func_uaccess_safe(struct symbol *func)
3147 {
3148 if (func)
3149 return func->uaccess_safe;
3150
3151 return false;
3152 }
3153
call_dest_name(struct instruction * insn)3154 static inline const char *call_dest_name(struct instruction *insn)
3155 {
3156 static char pvname[19];
3157 struct reloc *rel;
3158 int idx;
3159
3160 if (insn->call_dest)
3161 return insn->call_dest->name;
3162
3163 rel = insn_reloc(NULL, insn);
3164 if (rel && !strcmp(rel->sym->name, "pv_ops")) {
3165 idx = (rel->addend / sizeof(void *));
3166 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
3167 return pvname;
3168 }
3169
3170 return "{dynamic}";
3171 }
3172
pv_call_dest(struct objtool_file * file,struct instruction * insn)3173 static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3174 {
3175 struct symbol *target;
3176 struct reloc *rel;
3177 int idx;
3178
3179 rel = insn_reloc(file, insn);
3180 if (!rel || strcmp(rel->sym->name, "pv_ops"))
3181 return false;
3182
3183 idx = (arch_dest_reloc_offset(rel->addend) / sizeof(void *));
3184
3185 if (file->pv_ops[idx].clean)
3186 return true;
3187
3188 file->pv_ops[idx].clean = true;
3189
3190 list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3191 if (!target->sec->noinstr) {
3192 WARN("pv_ops[%d]: %s", idx, target->name);
3193 file->pv_ops[idx].clean = false;
3194 }
3195 }
3196
3197 return file->pv_ops[idx].clean;
3198 }
3199
noinstr_call_dest(struct objtool_file * file,struct instruction * insn,struct symbol * func)3200 static inline bool noinstr_call_dest(struct objtool_file *file,
3201 struct instruction *insn,
3202 struct symbol *func)
3203 {
3204 /*
3205 * We can't deal with indirect function calls at present;
3206 * assume they're instrumented.
3207 */
3208 if (!func) {
3209 if (file->pv_ops)
3210 return pv_call_dest(file, insn);
3211
3212 return false;
3213 }
3214
3215 /*
3216 * If the symbol is from a noinstr section; we good.
3217 */
3218 if (func->sec->noinstr)
3219 return true;
3220
3221 /*
3222 * The __ubsan_handle_*() calls are like WARN(), they only happen when
3223 * something 'BAD' happened. At the risk of taking the machine down,
3224 * let them proceed to get the message out.
3225 */
3226 if (!strncmp(func->name, "__ubsan_handle_", 15))
3227 return true;
3228
3229 return false;
3230 }
3231
validate_call(struct objtool_file * file,struct instruction * insn,struct insn_state * state)3232 static int validate_call(struct objtool_file *file,
3233 struct instruction *insn,
3234 struct insn_state *state)
3235 {
3236 if (state->noinstr && state->instr <= 0 &&
3237 !noinstr_call_dest(file, insn, insn->call_dest)) {
3238 WARN_FUNC("call to %s() leaves .noinstr.text section",
3239 insn->sec, insn->offset, call_dest_name(insn));
3240 return 1;
3241 }
3242
3243 if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
3244 WARN_FUNC("call to %s() with UACCESS enabled",
3245 insn->sec, insn->offset, call_dest_name(insn));
3246 return 1;
3247 }
3248
3249 if (state->df) {
3250 WARN_FUNC("call to %s() with DF set",
3251 insn->sec, insn->offset, call_dest_name(insn));
3252 return 1;
3253 }
3254
3255 return 0;
3256 }
3257
validate_sibling_call(struct objtool_file * file,struct instruction * insn,struct insn_state * state)3258 static int validate_sibling_call(struct objtool_file *file,
3259 struct instruction *insn,
3260 struct insn_state *state)
3261 {
3262 if (has_modified_stack_frame(insn, state)) {
3263 WARN_FUNC("sibling call from callable instruction with modified stack frame",
3264 insn->sec, insn->offset);
3265 return 1;
3266 }
3267
3268 return validate_call(file, insn, state);
3269 }
3270
validate_return(struct symbol * func,struct instruction * insn,struct insn_state * state)3271 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3272 {
3273 if (state->noinstr && state->instr > 0) {
3274 WARN_FUNC("return with instrumentation enabled",
3275 insn->sec, insn->offset);
3276 return 1;
3277 }
3278
3279 if (state->uaccess && !func_uaccess_safe(func)) {
3280 WARN_FUNC("return with UACCESS enabled",
3281 insn->sec, insn->offset);
3282 return 1;
3283 }
3284
3285 if (!state->uaccess && func_uaccess_safe(func)) {
3286 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
3287 insn->sec, insn->offset);
3288 return 1;
3289 }
3290
3291 if (state->df) {
3292 WARN_FUNC("return with DF set",
3293 insn->sec, insn->offset);
3294 return 1;
3295 }
3296
3297 if (func && has_modified_stack_frame(insn, state)) {
3298 WARN_FUNC("return with modified stack frame",
3299 insn->sec, insn->offset);
3300 return 1;
3301 }
3302
3303 if (state->cfi.bp_scratch) {
3304 WARN_FUNC("BP used as a scratch register",
3305 insn->sec, insn->offset);
3306 return 1;
3307 }
3308
3309 return 0;
3310 }
3311
next_insn_to_validate(struct objtool_file * file,struct instruction * insn)3312 static struct instruction *next_insn_to_validate(struct objtool_file *file,
3313 struct instruction *insn)
3314 {
3315 struct alt_group *alt_group = insn->alt_group;
3316
3317 /*
3318 * Simulate the fact that alternatives are patched in-place. When the
3319 * end of a replacement alt_group is reached, redirect objtool flow to
3320 * the end of the original alt_group.
3321 */
3322 if (alt_group && insn == alt_group->last_insn && alt_group->orig_group)
3323 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3324
3325 return next_insn_same_sec(file, insn);
3326 }
3327
3328 /*
3329 * Follow the branch starting at the given instruction, and recursively follow
3330 * any other branches (jumps). Meanwhile, track the frame pointer state at
3331 * each instruction and validate all the rules described in
3332 * tools/objtool/Documentation/objtool.txt.
3333 */
validate_branch(struct objtool_file * file,struct symbol * func,struct instruction * insn,struct insn_state state)3334 static int validate_branch(struct objtool_file *file, struct symbol *func,
3335 struct instruction *insn, struct insn_state state)
3336 {
3337 struct alternative *alt;
3338 struct instruction *next_insn, *prev_insn = NULL;
3339 struct section *sec;
3340 u8 visited;
3341 int ret;
3342
3343 sec = insn->sec;
3344
3345 while (1) {
3346 next_insn = next_insn_to_validate(file, insn);
3347
3348 if (func && insn->func && func != insn->func->pfunc) {
3349 /* Ignore KCFI type preambles, which always fall through */
3350 if (!strncmp(func->name, "__cfi_", 6))
3351 return 0;
3352
3353 WARN("%s() falls through to next function %s()",
3354 func->name, insn->func->name);
3355 return 1;
3356 }
3357
3358 if (func && insn->ignore) {
3359 WARN_FUNC("BUG: why am I validating an ignored function?",
3360 sec, insn->offset);
3361 return 1;
3362 }
3363
3364 visited = VISITED_BRANCH << state.uaccess;
3365 if (insn->visited & VISITED_BRANCH_MASK) {
3366 if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3367 return 1;
3368
3369 if (insn->visited & visited)
3370 return 0;
3371 } else {
3372 nr_insns_visited++;
3373 }
3374
3375 if (state.noinstr)
3376 state.instr += insn->instr;
3377
3378 if (insn->hint) {
3379 if (insn->restore) {
3380 struct instruction *save_insn, *i;
3381
3382 i = insn;
3383 save_insn = NULL;
3384
3385 sym_for_each_insn_continue_reverse(file, func, i) {
3386 if (i->save) {
3387 save_insn = i;
3388 break;
3389 }
3390 }
3391
3392 if (!save_insn) {
3393 WARN_FUNC("no corresponding CFI save for CFI restore",
3394 sec, insn->offset);
3395 return 1;
3396 }
3397
3398 if (!save_insn->visited) {
3399 WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
3400 sec, insn->offset);
3401 return 1;
3402 }
3403
3404 insn->cfi = save_insn->cfi;
3405 nr_cfi_reused++;
3406 }
3407
3408 state.cfi = *insn->cfi;
3409 } else {
3410 /* XXX track if we actually changed state.cfi */
3411
3412 if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3413 insn->cfi = prev_insn->cfi;
3414 nr_cfi_reused++;
3415 } else {
3416 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3417 }
3418 }
3419
3420 insn->visited |= visited;
3421
3422 if (propagate_alt_cfi(file, insn))
3423 return 1;
3424
3425 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
3426 bool skip_orig = false;
3427
3428 list_for_each_entry(alt, &insn->alts, list) {
3429 if (alt->skip_orig)
3430 skip_orig = true;
3431
3432 ret = validate_branch(file, func, alt->insn, state);
3433 if (ret) {
3434 if (opts.backtrace)
3435 BT_FUNC("(alt)", insn);
3436 return ret;
3437 }
3438 }
3439
3440 if (skip_orig)
3441 return 0;
3442 }
3443
3444 if (handle_insn_ops(insn, next_insn, &state))
3445 return 1;
3446
3447 switch (insn->type) {
3448
3449 case INSN_RETURN:
3450 return validate_return(func, insn, &state);
3451
3452 case INSN_CALL:
3453 case INSN_CALL_DYNAMIC:
3454 ret = validate_call(file, insn, &state);
3455 if (ret)
3456 return ret;
3457
3458 if (opts.stackval && func && !is_fentry_call(insn) &&
3459 !has_valid_stack_frame(&state)) {
3460 WARN_FUNC("call without frame pointer save/setup",
3461 sec, insn->offset);
3462 return 1;
3463 }
3464
3465 if (insn->dead_end)
3466 return 0;
3467
3468 break;
3469
3470 case INSN_JUMP_CONDITIONAL:
3471 case INSN_JUMP_UNCONDITIONAL:
3472 if (is_sibling_call(insn)) {
3473 ret = validate_sibling_call(file, insn, &state);
3474 if (ret)
3475 return ret;
3476
3477 } else if (insn->jump_dest) {
3478 ret = validate_branch(file, func,
3479 insn->jump_dest, state);
3480 if (ret) {
3481 if (opts.backtrace)
3482 BT_FUNC("(branch)", insn);
3483 return ret;
3484 }
3485 }
3486
3487 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3488 return 0;
3489
3490 break;
3491
3492 case INSN_JUMP_DYNAMIC:
3493 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3494 if (is_sibling_call(insn)) {
3495 ret = validate_sibling_call(file, insn, &state);
3496 if (ret)
3497 return ret;
3498 }
3499
3500 if (insn->type == INSN_JUMP_DYNAMIC)
3501 return 0;
3502
3503 break;
3504
3505 case INSN_CONTEXT_SWITCH:
3506 if (func && (!next_insn || !next_insn->hint)) {
3507 WARN_FUNC("unsupported instruction in callable function",
3508 sec, insn->offset);
3509 return 1;
3510 }
3511 return 0;
3512
3513 case INSN_STAC:
3514 if (state.uaccess) {
3515 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
3516 return 1;
3517 }
3518
3519 state.uaccess = true;
3520 break;
3521
3522 case INSN_CLAC:
3523 if (!state.uaccess && func) {
3524 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
3525 return 1;
3526 }
3527
3528 if (func_uaccess_safe(func) && !state.uaccess_stack) {
3529 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
3530 return 1;
3531 }
3532
3533 state.uaccess = false;
3534 break;
3535
3536 case INSN_STD:
3537 if (state.df) {
3538 WARN_FUNC("recursive STD", sec, insn->offset);
3539 return 1;
3540 }
3541
3542 state.df = true;
3543 break;
3544
3545 case INSN_CLD:
3546 if (!state.df && func) {
3547 WARN_FUNC("redundant CLD", sec, insn->offset);
3548 return 1;
3549 }
3550
3551 state.df = false;
3552 break;
3553
3554 default:
3555 break;
3556 }
3557
3558 if (insn->dead_end)
3559 return 0;
3560
3561 if (!next_insn) {
3562 if (state.cfi.cfa.base == CFI_UNDEFINED)
3563 return 0;
3564 WARN("%s: unexpected end of section", sec->name);
3565 return 1;
3566 }
3567
3568 prev_insn = insn;
3569 insn = next_insn;
3570 }
3571
3572 return 0;
3573 }
3574
validate_unwind_hints(struct objtool_file * file,struct section * sec)3575 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3576 {
3577 struct instruction *insn;
3578 struct insn_state state;
3579 int ret, warnings = 0;
3580
3581 if (!file->hints)
3582 return 0;
3583
3584 init_insn_state(file, &state, sec);
3585
3586 if (sec) {
3587 insn = find_insn(file, sec, 0);
3588 if (!insn)
3589 return 0;
3590 } else {
3591 insn = list_first_entry(&file->insn_list, typeof(*insn), list);
3592 }
3593
3594 while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) {
3595 if (insn->hint && !insn->visited && !insn->ignore) {
3596 ret = validate_branch(file, insn->func, insn, state);
3597 if (ret && opts.backtrace)
3598 BT_FUNC("<=== (hint)", insn);
3599 warnings += ret;
3600 }
3601
3602 insn = list_next_entry(insn, list);
3603 }
3604
3605 return warnings;
3606 }
3607
3608 /*
3609 * Validate rethunk entry constraint: must untrain RET before the first RET.
3610 *
3611 * Follow every branch (intra-function) and ensure ANNOTATE_UNRET_END comes
3612 * before an actual RET instruction.
3613 */
validate_entry(struct objtool_file * file,struct instruction * insn)3614 static int validate_entry(struct objtool_file *file, struct instruction *insn)
3615 {
3616 struct instruction *next, *dest;
3617 int ret, warnings = 0;
3618
3619 for (;;) {
3620 next = next_insn_to_validate(file, insn);
3621
3622 if (insn->visited & VISITED_ENTRY)
3623 return 0;
3624
3625 insn->visited |= VISITED_ENTRY;
3626
3627 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
3628 struct alternative *alt;
3629 bool skip_orig = false;
3630
3631 list_for_each_entry(alt, &insn->alts, list) {
3632 if (alt->skip_orig)
3633 skip_orig = true;
3634
3635 ret = validate_entry(file, alt->insn);
3636 if (ret) {
3637 if (opts.backtrace)
3638 BT_FUNC("(alt)", insn);
3639 return ret;
3640 }
3641 }
3642
3643 if (skip_orig)
3644 return 0;
3645 }
3646
3647 switch (insn->type) {
3648
3649 case INSN_CALL_DYNAMIC:
3650 case INSN_JUMP_DYNAMIC:
3651 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3652 WARN_FUNC("early indirect call", insn->sec, insn->offset);
3653 return 1;
3654
3655 case INSN_JUMP_UNCONDITIONAL:
3656 case INSN_JUMP_CONDITIONAL:
3657 if (!is_sibling_call(insn)) {
3658 if (!insn->jump_dest) {
3659 WARN_FUNC("unresolved jump target after linking?!?",
3660 insn->sec, insn->offset);
3661 return -1;
3662 }
3663 ret = validate_entry(file, insn->jump_dest);
3664 if (ret) {
3665 if (opts.backtrace) {
3666 BT_FUNC("(branch%s)", insn,
3667 insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : "");
3668 }
3669 return ret;
3670 }
3671
3672 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3673 return 0;
3674
3675 break;
3676 }
3677
3678 /* fallthrough */
3679 case INSN_CALL:
3680 dest = find_insn(file, insn->call_dest->sec,
3681 insn->call_dest->offset);
3682 if (!dest) {
3683 WARN("Unresolved function after linking!?: %s",
3684 insn->call_dest->name);
3685 return -1;
3686 }
3687
3688 ret = validate_entry(file, dest);
3689 if (ret) {
3690 if (opts.backtrace)
3691 BT_FUNC("(call)", insn);
3692 return ret;
3693 }
3694 /*
3695 * If a call returns without error, it must have seen UNTRAIN_RET.
3696 * Therefore any non-error return is a success.
3697 */
3698 return 0;
3699
3700 case INSN_RETURN:
3701 WARN_FUNC("RET before UNTRAIN", insn->sec, insn->offset);
3702 return 1;
3703
3704 case INSN_NOP:
3705 if (insn->retpoline_safe)
3706 return 0;
3707 break;
3708
3709 default:
3710 break;
3711 }
3712
3713 if (!next) {
3714 WARN_FUNC("teh end!", insn->sec, insn->offset);
3715 return -1;
3716 }
3717 insn = next;
3718 }
3719
3720 return warnings;
3721 }
3722
3723 /*
3724 * Validate that all branches starting at 'insn->entry' encounter UNRET_END
3725 * before RET.
3726 */
validate_unret(struct objtool_file * file)3727 static int validate_unret(struct objtool_file *file)
3728 {
3729 struct instruction *insn;
3730 int ret, warnings = 0;
3731
3732 for_each_insn(file, insn) {
3733 if (!insn->entry)
3734 continue;
3735
3736 ret = validate_entry(file, insn);
3737 if (ret < 0) {
3738 WARN_FUNC("Failed UNRET validation", insn->sec, insn->offset);
3739 return ret;
3740 }
3741 warnings += ret;
3742 }
3743
3744 return warnings;
3745 }
3746
validate_retpoline(struct objtool_file * file)3747 static int validate_retpoline(struct objtool_file *file)
3748 {
3749 struct instruction *insn;
3750 int warnings = 0;
3751
3752 for_each_insn(file, insn) {
3753 if (insn->type != INSN_JUMP_DYNAMIC &&
3754 insn->type != INSN_CALL_DYNAMIC &&
3755 insn->type != INSN_RETURN)
3756 continue;
3757
3758 if (insn->retpoline_safe)
3759 continue;
3760
3761 /*
3762 * .init.text code is ran before userspace and thus doesn't
3763 * strictly need retpolines, except for modules which are
3764 * loaded late, they very much do need retpoline in their
3765 * .init.text
3766 */
3767 if (!strcmp(insn->sec->name, ".init.text") && !opts.module)
3768 continue;
3769
3770 if (insn->type == INSN_RETURN) {
3771 if (opts.rethunk) {
3772 WARN_FUNC("'naked' return found in RETHUNK build",
3773 insn->sec, insn->offset);
3774 } else
3775 continue;
3776 } else {
3777 WARN_FUNC("indirect %s found in RETPOLINE build",
3778 insn->sec, insn->offset,
3779 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
3780 }
3781
3782 warnings++;
3783 }
3784
3785 return warnings;
3786 }
3787
is_kasan_insn(struct instruction * insn)3788 static bool is_kasan_insn(struct instruction *insn)
3789 {
3790 return (insn->type == INSN_CALL &&
3791 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
3792 }
3793
is_ubsan_insn(struct instruction * insn)3794 static bool is_ubsan_insn(struct instruction *insn)
3795 {
3796 return (insn->type == INSN_CALL &&
3797 !strcmp(insn->call_dest->name,
3798 "__ubsan_handle_builtin_unreachable"));
3799 }
3800
ignore_unreachable_insn(struct objtool_file * file,struct instruction * insn)3801 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
3802 {
3803 int i;
3804 struct instruction *prev_insn;
3805
3806 if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
3807 return true;
3808
3809 /*
3810 * Ignore alternative replacement instructions. This can happen
3811 * when a whitelisted function uses one of the ALTERNATIVE macros.
3812 */
3813 if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
3814 !strcmp(insn->sec->name, ".altinstr_aux"))
3815 return true;
3816
3817 /*
3818 * Whole archive runs might encounter dead code from weak symbols.
3819 * This is where the linker will have dropped the weak symbol in
3820 * favour of a regular symbol, but leaves the code in place.
3821 *
3822 * In this case we'll find a piece of code (whole function) that is not
3823 * covered by a !section symbol. Ignore them.
3824 */
3825 if (opts.link && !insn->func) {
3826 int size = find_symbol_hole_containing(insn->sec, insn->offset);
3827 unsigned long end = insn->offset + size;
3828
3829 if (!size) /* not a hole */
3830 return false;
3831
3832 if (size < 0) /* hole until the end */
3833 return true;
3834
3835 sec_for_each_insn_continue(file, insn) {
3836 /*
3837 * If we reach a visited instruction at or before the
3838 * end of the hole, ignore the unreachable.
3839 */
3840 if (insn->visited)
3841 return true;
3842
3843 if (insn->offset >= end)
3844 break;
3845
3846 /*
3847 * If this hole jumps to a .cold function, mark it ignore too.
3848 */
3849 if (insn->jump_dest && insn->jump_dest->func &&
3850 strstr(insn->jump_dest->func->name, ".cold")) {
3851 struct instruction *dest = insn->jump_dest;
3852 func_for_each_insn(file, dest->func, dest)
3853 dest->ignore = true;
3854 }
3855 }
3856
3857 return false;
3858 }
3859
3860 if (!insn->func)
3861 return false;
3862
3863 if (insn->func->static_call_tramp)
3864 return true;
3865
3866 /*
3867 * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
3868 * __builtin_unreachable(). The BUG() macro has an unreachable() after
3869 * the UD2, which causes GCC's undefined trap logic to emit another UD2
3870 * (or occasionally a JMP to UD2).
3871 *
3872 * It may also insert a UD2 after calling a __noreturn function.
3873 */
3874 prev_insn = list_prev_entry(insn, list);
3875 if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) &&
3876 (insn->type == INSN_BUG ||
3877 (insn->type == INSN_JUMP_UNCONDITIONAL &&
3878 insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
3879 return true;
3880
3881 /*
3882 * Check if this (or a subsequent) instruction is related to
3883 * CONFIG_UBSAN or CONFIG_KASAN.
3884 *
3885 * End the search at 5 instructions to avoid going into the weeds.
3886 */
3887 for (i = 0; i < 5; i++) {
3888
3889 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
3890 return true;
3891
3892 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
3893 if (insn->jump_dest &&
3894 insn->jump_dest->func == insn->func) {
3895 insn = insn->jump_dest;
3896 continue;
3897 }
3898
3899 break;
3900 }
3901
3902 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
3903 break;
3904
3905 insn = list_next_entry(insn, list);
3906 }
3907
3908 return false;
3909 }
3910
validate_symbol(struct objtool_file * file,struct section * sec,struct symbol * sym,struct insn_state * state)3911 static int validate_symbol(struct objtool_file *file, struct section *sec,
3912 struct symbol *sym, struct insn_state *state)
3913 {
3914 struct instruction *insn;
3915 int ret;
3916
3917 if (!sym->len) {
3918 WARN("%s() is missing an ELF size annotation", sym->name);
3919 return 1;
3920 }
3921
3922 if (sym->pfunc != sym || sym->alias != sym)
3923 return 0;
3924
3925 insn = find_insn(file, sec, sym->offset);
3926 if (!insn || insn->ignore || insn->visited)
3927 return 0;
3928
3929 state->uaccess = sym->uaccess_safe;
3930
3931 ret = validate_branch(file, insn->func, insn, *state);
3932 if (ret && opts.backtrace)
3933 BT_FUNC("<=== (sym)", insn);
3934 return ret;
3935 }
3936
validate_section(struct objtool_file * file,struct section * sec)3937 static int validate_section(struct objtool_file *file, struct section *sec)
3938 {
3939 struct insn_state state;
3940 struct symbol *func;
3941 int warnings = 0;
3942
3943 list_for_each_entry(func, &sec->symbol_list, list) {
3944 if (func->type != STT_FUNC)
3945 continue;
3946
3947 init_insn_state(file, &state, sec);
3948 set_func_state(&state.cfi);
3949
3950 warnings += validate_symbol(file, sec, func, &state);
3951 }
3952
3953 return warnings;
3954 }
3955
validate_noinstr_sections(struct objtool_file * file)3956 static int validate_noinstr_sections(struct objtool_file *file)
3957 {
3958 struct section *sec;
3959 int warnings = 0;
3960
3961 sec = find_section_by_name(file->elf, ".noinstr.text");
3962 if (sec) {
3963 warnings += validate_section(file, sec);
3964 warnings += validate_unwind_hints(file, sec);
3965 }
3966
3967 sec = find_section_by_name(file->elf, ".entry.text");
3968 if (sec) {
3969 warnings += validate_section(file, sec);
3970 warnings += validate_unwind_hints(file, sec);
3971 }
3972
3973 return warnings;
3974 }
3975
validate_functions(struct objtool_file * file)3976 static int validate_functions(struct objtool_file *file)
3977 {
3978 struct section *sec;
3979 int warnings = 0;
3980
3981 for_each_sec(file, sec) {
3982 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
3983 continue;
3984
3985 warnings += validate_section(file, sec);
3986 }
3987
3988 return warnings;
3989 }
3990
mark_endbr_used(struct instruction * insn)3991 static void mark_endbr_used(struct instruction *insn)
3992 {
3993 if (!list_empty(&insn->call_node))
3994 list_del_init(&insn->call_node);
3995 }
3996
validate_ibt_insn(struct objtool_file * file,struct instruction * insn)3997 static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
3998 {
3999 struct instruction *dest;
4000 struct reloc *reloc;
4001 unsigned long off;
4002 int warnings = 0;
4003
4004 /*
4005 * Looking for function pointer load relocations. Ignore
4006 * direct/indirect branches:
4007 */
4008 switch (insn->type) {
4009 case INSN_CALL:
4010 case INSN_CALL_DYNAMIC:
4011 case INSN_JUMP_CONDITIONAL:
4012 case INSN_JUMP_UNCONDITIONAL:
4013 case INSN_JUMP_DYNAMIC:
4014 case INSN_JUMP_DYNAMIC_CONDITIONAL:
4015 case INSN_RETURN:
4016 case INSN_NOP:
4017 return 0;
4018 default:
4019 break;
4020 }
4021
4022 for (reloc = insn_reloc(file, insn);
4023 reloc;
4024 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
4025 reloc->offset + 1,
4026 (insn->offset + insn->len) - (reloc->offset + 1))) {
4027
4028 /*
4029 * static_call_update() references the trampoline, which
4030 * doesn't have (or need) ENDBR. Skip warning in that case.
4031 */
4032 if (reloc->sym->static_call_tramp)
4033 continue;
4034
4035 off = reloc->sym->offset;
4036 if (reloc->type == R_X86_64_PC32 || reloc->type == R_X86_64_PLT32)
4037 off += arch_dest_reloc_offset(reloc->addend);
4038 else
4039 off += reloc->addend;
4040
4041 dest = find_insn(file, reloc->sym->sec, off);
4042 if (!dest)
4043 continue;
4044
4045 if (dest->type == INSN_ENDBR) {
4046 mark_endbr_used(dest);
4047 continue;
4048 }
4049
4050 if (dest->func && dest->func == insn->func) {
4051 /*
4052 * Anything from->to self is either _THIS_IP_ or
4053 * IRET-to-self.
4054 *
4055 * There is no sane way to annotate _THIS_IP_ since the
4056 * compiler treats the relocation as a constant and is
4057 * happy to fold in offsets, skewing any annotation we
4058 * do, leading to vast amounts of false-positives.
4059 *
4060 * There's also compiler generated _THIS_IP_ through
4061 * KCOV and such which we have no hope of annotating.
4062 *
4063 * As such, blanket accept self-references without
4064 * issue.
4065 */
4066 continue;
4067 }
4068
4069 if (dest->noendbr)
4070 continue;
4071
4072 WARN_FUNC("relocation to !ENDBR: %s",
4073 insn->sec, insn->offset,
4074 offstr(dest->sec, dest->offset));
4075
4076 warnings++;
4077 }
4078
4079 return warnings;
4080 }
4081
validate_ibt_data_reloc(struct objtool_file * file,struct reloc * reloc)4082 static int validate_ibt_data_reloc(struct objtool_file *file,
4083 struct reloc *reloc)
4084 {
4085 struct instruction *dest;
4086
4087 dest = find_insn(file, reloc->sym->sec,
4088 reloc->sym->offset + reloc->addend);
4089 if (!dest)
4090 return 0;
4091
4092 if (dest->type == INSN_ENDBR) {
4093 mark_endbr_used(dest);
4094 return 0;
4095 }
4096
4097 if (dest->noendbr)
4098 return 0;
4099
4100 WARN_FUNC("data relocation to !ENDBR: %s",
4101 reloc->sec->base, reloc->offset,
4102 offstr(dest->sec, dest->offset));
4103
4104 return 1;
4105 }
4106
4107 /*
4108 * Validate IBT rules and remove used ENDBR instructions from the seal list.
4109 * Unused ENDBR instructions will be annotated for sealing (i.e., replaced with
4110 * NOPs) later, in create_ibt_endbr_seal_sections().
4111 */
validate_ibt(struct objtool_file * file)4112 static int validate_ibt(struct objtool_file *file)
4113 {
4114 struct section *sec;
4115 struct reloc *reloc;
4116 struct instruction *insn;
4117 int warnings = 0;
4118
4119 for_each_insn(file, insn)
4120 warnings += validate_ibt_insn(file, insn);
4121
4122 for_each_sec(file, sec) {
4123
4124 /* Already done by validate_ibt_insn() */
4125 if (sec->sh.sh_flags & SHF_EXECINSTR)
4126 continue;
4127
4128 if (!sec->reloc)
4129 continue;
4130
4131 /*
4132 * These sections can reference text addresses, but not with
4133 * the intent to indirect branch to them.
4134 */
4135 if ((!strncmp(sec->name, ".discard", 8) &&
4136 strcmp(sec->name, ".discard.ibt_endbr_noseal")) ||
4137 !strncmp(sec->name, ".debug", 6) ||
4138 !strcmp(sec->name, ".altinstructions") ||
4139 !strcmp(sec->name, ".ibt_endbr_seal") ||
4140 !strcmp(sec->name, ".orc_unwind_ip") ||
4141 !strcmp(sec->name, ".parainstructions") ||
4142 !strcmp(sec->name, ".retpoline_sites") ||
4143 !strcmp(sec->name, ".smp_locks") ||
4144 !strcmp(sec->name, ".static_call_sites") ||
4145 !strcmp(sec->name, "_error_injection_whitelist") ||
4146 !strcmp(sec->name, "_kprobe_blacklist") ||
4147 !strcmp(sec->name, "__bug_table") ||
4148 !strcmp(sec->name, "__ex_table") ||
4149 !strcmp(sec->name, "__jump_table") ||
4150 !strcmp(sec->name, "__mcount_loc") ||
4151 !strcmp(sec->name, ".kcfi_traps") ||
4152 strstr(sec->name, "__patchable_function_entries"))
4153 continue;
4154
4155 list_for_each_entry(reloc, &sec->reloc->reloc_list, list)
4156 warnings += validate_ibt_data_reloc(file, reloc);
4157 }
4158
4159 return warnings;
4160 }
4161
validate_sls(struct objtool_file * file)4162 static int validate_sls(struct objtool_file *file)
4163 {
4164 struct instruction *insn, *next_insn;
4165 int warnings = 0;
4166
4167 for_each_insn(file, insn) {
4168 next_insn = next_insn_same_sec(file, insn);
4169
4170 if (insn->retpoline_safe)
4171 continue;
4172
4173 switch (insn->type) {
4174 case INSN_RETURN:
4175 if (!next_insn || next_insn->type != INSN_TRAP) {
4176 WARN_FUNC("missing int3 after ret",
4177 insn->sec, insn->offset);
4178 warnings++;
4179 }
4180
4181 break;
4182 case INSN_JUMP_DYNAMIC:
4183 if (!next_insn || next_insn->type != INSN_TRAP) {
4184 WARN_FUNC("missing int3 after indirect jump",
4185 insn->sec, insn->offset);
4186 warnings++;
4187 }
4188 break;
4189 default:
4190 break;
4191 }
4192 }
4193
4194 return warnings;
4195 }
4196
validate_reachable_instructions(struct objtool_file * file)4197 static int validate_reachable_instructions(struct objtool_file *file)
4198 {
4199 struct instruction *insn;
4200
4201 if (file->ignore_unreachables)
4202 return 0;
4203
4204 for_each_insn(file, insn) {
4205 if (insn->visited || ignore_unreachable_insn(file, insn))
4206 continue;
4207
4208 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
4209 return 1;
4210 }
4211
4212 return 0;
4213 }
4214
check(struct objtool_file * file)4215 int check(struct objtool_file *file)
4216 {
4217 int ret, warnings = 0;
4218
4219 arch_initial_func_cfi_state(&initial_func_cfi);
4220 init_cfi_state(&init_cfi);
4221 init_cfi_state(&func_cfi);
4222 set_func_state(&func_cfi);
4223
4224 if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
4225 goto out;
4226
4227 cfi_hash_add(&init_cfi);
4228 cfi_hash_add(&func_cfi);
4229
4230 ret = decode_sections(file);
4231 if (ret < 0)
4232 goto out;
4233
4234 warnings += ret;
4235
4236 if (list_empty(&file->insn_list))
4237 goto out;
4238
4239 if (opts.retpoline) {
4240 ret = validate_retpoline(file);
4241 if (ret < 0)
4242 return ret;
4243 warnings += ret;
4244 }
4245
4246 if (opts.stackval || opts.orc || opts.uaccess) {
4247 ret = validate_functions(file);
4248 if (ret < 0)
4249 goto out;
4250 warnings += ret;
4251
4252 ret = validate_unwind_hints(file, NULL);
4253 if (ret < 0)
4254 goto out;
4255 warnings += ret;
4256
4257 if (!warnings) {
4258 ret = validate_reachable_instructions(file);
4259 if (ret < 0)
4260 goto out;
4261 warnings += ret;
4262 }
4263
4264 } else if (opts.noinstr) {
4265 ret = validate_noinstr_sections(file);
4266 if (ret < 0)
4267 goto out;
4268 warnings += ret;
4269 }
4270
4271 if (opts.unret) {
4272 /*
4273 * Must be after validate_branch() and friends, it plays
4274 * further games with insn->visited.
4275 */
4276 ret = validate_unret(file);
4277 if (ret < 0)
4278 return ret;
4279 warnings += ret;
4280 }
4281
4282 if (opts.ibt) {
4283 ret = validate_ibt(file);
4284 if (ret < 0)
4285 goto out;
4286 warnings += ret;
4287 }
4288
4289 if (opts.sls) {
4290 ret = validate_sls(file);
4291 if (ret < 0)
4292 goto out;
4293 warnings += ret;
4294 }
4295
4296 if (opts.static_call) {
4297 ret = create_static_call_sections(file);
4298 if (ret < 0)
4299 goto out;
4300 warnings += ret;
4301 }
4302
4303 if (opts.retpoline) {
4304 ret = create_retpoline_sites_sections(file);
4305 if (ret < 0)
4306 goto out;
4307 warnings += ret;
4308 }
4309
4310 if (opts.rethunk) {
4311 ret = create_return_sites_sections(file);
4312 if (ret < 0)
4313 goto out;
4314 warnings += ret;
4315 }
4316
4317 if (opts.mcount) {
4318 ret = create_mcount_loc_sections(file);
4319 if (ret < 0)
4320 goto out;
4321 warnings += ret;
4322 }
4323
4324 if (opts.ibt) {
4325 ret = create_ibt_endbr_seal_sections(file);
4326 if (ret < 0)
4327 goto out;
4328 warnings += ret;
4329 }
4330
4331 if (opts.orc && !list_empty(&file->insn_list)) {
4332 ret = orc_create(file);
4333 if (ret < 0)
4334 goto out;
4335 warnings += ret;
4336 }
4337
4338
4339 if (opts.stats) {
4340 printf("nr_insns_visited: %ld\n", nr_insns_visited);
4341 printf("nr_cfi: %ld\n", nr_cfi);
4342 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
4343 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
4344 }
4345
4346 out:
4347 /*
4348 * For now, don't fail the kernel build on fatal warnings. These
4349 * errors are still fairly common due to the growing matrix of
4350 * supported toolchains and their recent pace of change.
4351 */
4352 return 0;
4353 }
4354