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->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_atomic8_load",
1003 "__tsan_atomic16_load",
1004 "__tsan_atomic32_load",
1005 "__tsan_atomic64_load",
1006 "__tsan_atomic8_store",
1007 "__tsan_atomic16_store",
1008 "__tsan_atomic32_store",
1009 "__tsan_atomic64_store",
1010 "__tsan_atomic8_exchange",
1011 "__tsan_atomic16_exchange",
1012 "__tsan_atomic32_exchange",
1013 "__tsan_atomic64_exchange",
1014 "__tsan_atomic8_fetch_add",
1015 "__tsan_atomic16_fetch_add",
1016 "__tsan_atomic32_fetch_add",
1017 "__tsan_atomic64_fetch_add",
1018 "__tsan_atomic8_fetch_sub",
1019 "__tsan_atomic16_fetch_sub",
1020 "__tsan_atomic32_fetch_sub",
1021 "__tsan_atomic64_fetch_sub",
1022 "__tsan_atomic8_fetch_and",
1023 "__tsan_atomic16_fetch_and",
1024 "__tsan_atomic32_fetch_and",
1025 "__tsan_atomic64_fetch_and",
1026 "__tsan_atomic8_fetch_or",
1027 "__tsan_atomic16_fetch_or",
1028 "__tsan_atomic32_fetch_or",
1029 "__tsan_atomic64_fetch_or",
1030 "__tsan_atomic8_fetch_xor",
1031 "__tsan_atomic16_fetch_xor",
1032 "__tsan_atomic32_fetch_xor",
1033 "__tsan_atomic64_fetch_xor",
1034 "__tsan_atomic8_fetch_nand",
1035 "__tsan_atomic16_fetch_nand",
1036 "__tsan_atomic32_fetch_nand",
1037 "__tsan_atomic64_fetch_nand",
1038 "__tsan_atomic8_compare_exchange_strong",
1039 "__tsan_atomic16_compare_exchange_strong",
1040 "__tsan_atomic32_compare_exchange_strong",
1041 "__tsan_atomic64_compare_exchange_strong",
1042 "__tsan_atomic8_compare_exchange_weak",
1043 "__tsan_atomic16_compare_exchange_weak",
1044 "__tsan_atomic32_compare_exchange_weak",
1045 "__tsan_atomic64_compare_exchange_weak",
1046 "__tsan_atomic8_compare_exchange_val",
1047 "__tsan_atomic16_compare_exchange_val",
1048 "__tsan_atomic32_compare_exchange_val",
1049 "__tsan_atomic64_compare_exchange_val",
1050 "__tsan_atomic_thread_fence",
1051 "__tsan_atomic_signal_fence",
1052 /* KCOV */
1053 "write_comp_data",
1054 "check_kcov_mode",
1055 "__sanitizer_cov_trace_pc",
1056 "__sanitizer_cov_trace_const_cmp1",
1057 "__sanitizer_cov_trace_const_cmp2",
1058 "__sanitizer_cov_trace_const_cmp4",
1059 "__sanitizer_cov_trace_const_cmp8",
1060 "__sanitizer_cov_trace_cmp1",
1061 "__sanitizer_cov_trace_cmp2",
1062 "__sanitizer_cov_trace_cmp4",
1063 "__sanitizer_cov_trace_cmp8",
1064 "__sanitizer_cov_trace_switch",
1065 /* KMSAN */
1066 "kmsan_copy_to_user",
1067 "kmsan_report",
1068 "kmsan_unpoison_entry_regs",
1069 "kmsan_unpoison_memory",
1070 "__msan_chain_origin",
1071 "__msan_get_context_state",
1072 "__msan_instrument_asm_store",
1073 "__msan_metadata_ptr_for_load_1",
1074 "__msan_metadata_ptr_for_load_2",
1075 "__msan_metadata_ptr_for_load_4",
1076 "__msan_metadata_ptr_for_load_8",
1077 "__msan_metadata_ptr_for_load_n",
1078 "__msan_metadata_ptr_for_store_1",
1079 "__msan_metadata_ptr_for_store_2",
1080 "__msan_metadata_ptr_for_store_4",
1081 "__msan_metadata_ptr_for_store_8",
1082 "__msan_metadata_ptr_for_store_n",
1083 "__msan_poison_alloca",
1084 "__msan_warning",
1085 /* UBSAN */
1086 "ubsan_type_mismatch_common",
1087 "__ubsan_handle_type_mismatch",
1088 "__ubsan_handle_type_mismatch_v1",
1089 "__ubsan_handle_shift_out_of_bounds",
1090 /* misc */
1091 "csum_partial_copy_generic",
1092 "copy_mc_fragile",
1093 "copy_mc_fragile_handle_tail",
1094 "copy_mc_enhanced_fast_string",
1095 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
1096 "clear_user_erms",
1097 "clear_user_rep_good",
1098 "clear_user_original",
1099 NULL
1100 };
1101
add_uaccess_safe(struct objtool_file * file)1102 static void add_uaccess_safe(struct objtool_file *file)
1103 {
1104 struct symbol *func;
1105 const char **name;
1106
1107 if (!opts.uaccess)
1108 return;
1109
1110 for (name = uaccess_safe_builtin; *name; name++) {
1111 func = find_symbol_by_name(file->elf, *name);
1112 if (!func)
1113 continue;
1114
1115 func->uaccess_safe = true;
1116 }
1117 }
1118
1119 /*
1120 * FIXME: For now, just ignore any alternatives which add retpolines. This is
1121 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
1122 * But it at least allows objtool to understand the control flow *around* the
1123 * retpoline.
1124 */
add_ignore_alternatives(struct objtool_file * file)1125 static int add_ignore_alternatives(struct objtool_file *file)
1126 {
1127 struct section *sec;
1128 struct reloc *reloc;
1129 struct instruction *insn;
1130
1131 sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
1132 if (!sec)
1133 return 0;
1134
1135 list_for_each_entry(reloc, &sec->reloc_list, list) {
1136 if (reloc->sym->type != STT_SECTION) {
1137 WARN("unexpected relocation symbol type in %s", sec->name);
1138 return -1;
1139 }
1140
1141 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1142 if (!insn) {
1143 WARN("bad .discard.ignore_alts entry");
1144 return -1;
1145 }
1146
1147 insn->ignore_alts = true;
1148 }
1149
1150 return 0;
1151 }
1152
arch_is_retpoline(struct symbol * sym)1153 __weak bool arch_is_retpoline(struct symbol *sym)
1154 {
1155 return false;
1156 }
1157
arch_is_rethunk(struct symbol * sym)1158 __weak bool arch_is_rethunk(struct symbol *sym)
1159 {
1160 return false;
1161 }
1162
1163 #define NEGATIVE_RELOC ((void *)-1L)
1164
insn_reloc(struct objtool_file * file,struct instruction * insn)1165 static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
1166 {
1167 if (insn->reloc == NEGATIVE_RELOC)
1168 return NULL;
1169
1170 if (!insn->reloc) {
1171 if (!file)
1172 return NULL;
1173
1174 insn->reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1175 insn->offset, insn->len);
1176 if (!insn->reloc) {
1177 insn->reloc = NEGATIVE_RELOC;
1178 return NULL;
1179 }
1180 }
1181
1182 return insn->reloc;
1183 }
1184
remove_insn_ops(struct instruction * insn)1185 static void remove_insn_ops(struct instruction *insn)
1186 {
1187 struct stack_op *op, *tmp;
1188
1189 list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
1190 list_del(&op->list);
1191 free(op);
1192 }
1193 }
1194
annotate_call_site(struct objtool_file * file,struct instruction * insn,bool sibling)1195 static void annotate_call_site(struct objtool_file *file,
1196 struct instruction *insn, bool sibling)
1197 {
1198 struct reloc *reloc = insn_reloc(file, insn);
1199 struct symbol *sym = insn->call_dest;
1200
1201 if (!sym)
1202 sym = reloc->sym;
1203
1204 /*
1205 * Alternative replacement code is just template code which is
1206 * sometimes copied to the original instruction. For now, don't
1207 * annotate it. (In the future we might consider annotating the
1208 * original instruction if/when it ever makes sense to do so.)
1209 */
1210 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1211 return;
1212
1213 if (sym->static_call_tramp) {
1214 list_add_tail(&insn->call_node, &file->static_call_list);
1215 return;
1216 }
1217
1218 if (sym->retpoline_thunk) {
1219 list_add_tail(&insn->call_node, &file->retpoline_call_list);
1220 return;
1221 }
1222
1223 /*
1224 * Many compilers cannot disable KCOV or sanitizer calls with a function
1225 * attribute so they need a little help, NOP out any such calls from
1226 * noinstr text.
1227 */
1228 if (opts.hack_noinstr && insn->sec->noinstr && sym->profiling_func) {
1229 if (reloc) {
1230 reloc->type = R_NONE;
1231 elf_write_reloc(file->elf, reloc);
1232 }
1233
1234 elf_write_insn(file->elf, insn->sec,
1235 insn->offset, insn->len,
1236 sibling ? arch_ret_insn(insn->len)
1237 : arch_nop_insn(insn->len));
1238
1239 insn->type = sibling ? INSN_RETURN : INSN_NOP;
1240
1241 if (sibling) {
1242 /*
1243 * We've replaced the tail-call JMP insn by two new
1244 * insn: RET; INT3, except we only have a single struct
1245 * insn here. Mark it retpoline_safe to avoid the SLS
1246 * warning, instead of adding another insn.
1247 */
1248 insn->retpoline_safe = true;
1249 }
1250
1251 return;
1252 }
1253
1254 if (opts.mcount && sym->fentry) {
1255 if (sibling)
1256 WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset);
1257
1258 if (reloc) {
1259 reloc->type = R_NONE;
1260 elf_write_reloc(file->elf, reloc);
1261 }
1262
1263 elf_write_insn(file->elf, insn->sec,
1264 insn->offset, insn->len,
1265 arch_nop_insn(insn->len));
1266
1267 insn->type = INSN_NOP;
1268
1269 list_add_tail(&insn->call_node, &file->mcount_loc_list);
1270 return;
1271 }
1272
1273 if (!sibling && dead_end_function(file, sym))
1274 insn->dead_end = true;
1275 }
1276
add_call_dest(struct objtool_file * file,struct instruction * insn,struct symbol * dest,bool sibling)1277 static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1278 struct symbol *dest, bool sibling)
1279 {
1280 insn->call_dest = dest;
1281 if (!dest)
1282 return;
1283
1284 /*
1285 * Whatever stack impact regular CALLs have, should be undone
1286 * by the RETURN of the called function.
1287 *
1288 * Annotated intra-function calls retain the stack_ops but
1289 * are converted to JUMP, see read_intra_function_calls().
1290 */
1291 remove_insn_ops(insn);
1292
1293 annotate_call_site(file, insn, sibling);
1294 }
1295
add_retpoline_call(struct objtool_file * file,struct instruction * insn)1296 static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1297 {
1298 /*
1299 * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1300 * so convert them accordingly.
1301 */
1302 switch (insn->type) {
1303 case INSN_CALL:
1304 insn->type = INSN_CALL_DYNAMIC;
1305 break;
1306 case INSN_JUMP_UNCONDITIONAL:
1307 insn->type = INSN_JUMP_DYNAMIC;
1308 break;
1309 case INSN_JUMP_CONDITIONAL:
1310 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1311 break;
1312 default:
1313 return;
1314 }
1315
1316 insn->retpoline_safe = true;
1317
1318 /*
1319 * Whatever stack impact regular CALLs have, should be undone
1320 * by the RETURN of the called function.
1321 *
1322 * Annotated intra-function calls retain the stack_ops but
1323 * are converted to JUMP, see read_intra_function_calls().
1324 */
1325 remove_insn_ops(insn);
1326
1327 annotate_call_site(file, insn, false);
1328 }
1329
add_return_call(struct objtool_file * file,struct instruction * insn,bool add)1330 static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add)
1331 {
1332 /*
1333 * Return thunk tail calls are really just returns in disguise,
1334 * so convert them accordingly.
1335 */
1336 insn->type = INSN_RETURN;
1337 insn->retpoline_safe = true;
1338
1339 if (add)
1340 list_add_tail(&insn->call_node, &file->return_thunk_list);
1341 }
1342
same_function(struct instruction * insn1,struct instruction * insn2)1343 static bool same_function(struct instruction *insn1, struct instruction *insn2)
1344 {
1345 return insn1->func->pfunc == insn2->func->pfunc;
1346 }
1347
is_first_func_insn(struct objtool_file * file,struct instruction * insn)1348 static bool is_first_func_insn(struct objtool_file *file, struct instruction *insn)
1349 {
1350 if (insn->offset == insn->func->offset)
1351 return true;
1352
1353 if (opts.ibt) {
1354 struct instruction *prev = prev_insn_same_sym(file, insn);
1355
1356 if (prev && prev->type == INSN_ENDBR &&
1357 insn->offset == insn->func->offset + prev->len)
1358 return true;
1359 }
1360
1361 return false;
1362 }
1363
1364 /*
1365 * Find the destination instructions for all jumps.
1366 */
add_jump_destinations(struct objtool_file * file)1367 static int add_jump_destinations(struct objtool_file *file)
1368 {
1369 struct instruction *insn, *jump_dest;
1370 struct reloc *reloc;
1371 struct section *dest_sec;
1372 unsigned long dest_off;
1373
1374 for_each_insn(file, insn) {
1375 if (insn->jump_dest) {
1376 /*
1377 * handle_group_alt() may have previously set
1378 * 'jump_dest' for some alternatives.
1379 */
1380 continue;
1381 }
1382 if (!is_static_jump(insn))
1383 continue;
1384
1385 reloc = insn_reloc(file, insn);
1386 if (!reloc) {
1387 dest_sec = insn->sec;
1388 dest_off = arch_jump_destination(insn);
1389 } else if (reloc->sym->type == STT_SECTION) {
1390 dest_sec = reloc->sym->sec;
1391 dest_off = arch_dest_reloc_offset(reloc->addend);
1392 } else if (reloc->sym->retpoline_thunk) {
1393 add_retpoline_call(file, insn);
1394 continue;
1395 } else if (reloc->sym->return_thunk) {
1396 add_return_call(file, insn, true);
1397 continue;
1398 } else if (insn->func) {
1399 /*
1400 * External sibling call or internal sibling call with
1401 * STT_FUNC reloc.
1402 */
1403 add_call_dest(file, insn, reloc->sym, true);
1404 continue;
1405 } else if (reloc->sym->sec->idx) {
1406 dest_sec = reloc->sym->sec;
1407 dest_off = reloc->sym->sym.st_value +
1408 arch_dest_reloc_offset(reloc->addend);
1409 } else {
1410 /* non-func asm code jumping to another file */
1411 continue;
1412 }
1413
1414 jump_dest = find_insn(file, dest_sec, dest_off);
1415 if (!jump_dest) {
1416 struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off);
1417
1418 /*
1419 * This is a special case for zen_untrain_ret().
1420 * It jumps to __x86_return_thunk(), but objtool
1421 * can't find the thunk's starting RET
1422 * instruction, because the RET is also in the
1423 * middle of another instruction. Objtool only
1424 * knows about the outer instruction.
1425 */
1426 if (sym && sym->return_thunk) {
1427 add_return_call(file, insn, false);
1428 continue;
1429 }
1430
1431 WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
1432 insn->sec, insn->offset, dest_sec->name,
1433 dest_off);
1434 return -1;
1435 }
1436
1437 /*
1438 * Cross-function jump.
1439 */
1440 if (insn->func && jump_dest->func &&
1441 insn->func != jump_dest->func) {
1442
1443 /*
1444 * For GCC 8+, create parent/child links for any cold
1445 * subfunctions. This is _mostly_ redundant with a
1446 * similar initialization in read_symbols().
1447 *
1448 * If a function has aliases, we want the *first* such
1449 * function in the symbol table to be the subfunction's
1450 * parent. In that case we overwrite the
1451 * initialization done in read_symbols().
1452 *
1453 * However this code can't completely replace the
1454 * read_symbols() code because this doesn't detect the
1455 * case where the parent function's only reference to a
1456 * subfunction is through a jump table.
1457 */
1458 if (!strstr(insn->func->name, ".cold") &&
1459 strstr(jump_dest->func->name, ".cold")) {
1460 insn->func->cfunc = jump_dest->func;
1461 jump_dest->func->pfunc = insn->func;
1462
1463 } else if (!same_function(insn, jump_dest) &&
1464 is_first_func_insn(file, jump_dest)) {
1465 /*
1466 * Internal sibling call without reloc or with
1467 * STT_SECTION reloc.
1468 */
1469 add_call_dest(file, insn, jump_dest->func, true);
1470 continue;
1471 }
1472 }
1473
1474 insn->jump_dest = jump_dest;
1475 }
1476
1477 return 0;
1478 }
1479
find_call_destination(struct section * sec,unsigned long offset)1480 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1481 {
1482 struct symbol *call_dest;
1483
1484 call_dest = find_func_by_offset(sec, offset);
1485 if (!call_dest)
1486 call_dest = find_symbol_by_offset(sec, offset);
1487
1488 return call_dest;
1489 }
1490
1491 /*
1492 * Find the destination instructions for all calls.
1493 */
add_call_destinations(struct objtool_file * file)1494 static int add_call_destinations(struct objtool_file *file)
1495 {
1496 struct instruction *insn;
1497 unsigned long dest_off;
1498 struct symbol *dest;
1499 struct reloc *reloc;
1500
1501 for_each_insn(file, insn) {
1502 if (insn->type != INSN_CALL)
1503 continue;
1504
1505 reloc = insn_reloc(file, insn);
1506 if (!reloc) {
1507 dest_off = arch_jump_destination(insn);
1508 dest = find_call_destination(insn->sec, dest_off);
1509
1510 add_call_dest(file, insn, dest, false);
1511
1512 if (insn->ignore)
1513 continue;
1514
1515 if (!insn->call_dest) {
1516 WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);
1517 return -1;
1518 }
1519
1520 if (insn->func && insn->call_dest->type != STT_FUNC) {
1521 WARN_FUNC("unsupported call to non-function",
1522 insn->sec, insn->offset);
1523 return -1;
1524 }
1525
1526 } else if (reloc->sym->type == STT_SECTION) {
1527 dest_off = arch_dest_reloc_offset(reloc->addend);
1528 dest = find_call_destination(reloc->sym->sec, dest_off);
1529 if (!dest) {
1530 WARN_FUNC("can't find call dest symbol at %s+0x%lx",
1531 insn->sec, insn->offset,
1532 reloc->sym->sec->name,
1533 dest_off);
1534 return -1;
1535 }
1536
1537 add_call_dest(file, insn, dest, false);
1538
1539 } else if (reloc->sym->retpoline_thunk) {
1540 add_retpoline_call(file, insn);
1541
1542 } else
1543 add_call_dest(file, insn, reloc->sym, false);
1544 }
1545
1546 return 0;
1547 }
1548
1549 /*
1550 * The .alternatives section requires some extra special care over and above
1551 * other special sections because alternatives are patched in place.
1552 */
handle_group_alt(struct objtool_file * file,struct special_alt * special_alt,struct instruction * orig_insn,struct instruction ** new_insn)1553 static int handle_group_alt(struct objtool_file *file,
1554 struct special_alt *special_alt,
1555 struct instruction *orig_insn,
1556 struct instruction **new_insn)
1557 {
1558 struct instruction *last_orig_insn, *last_new_insn = NULL, *insn, *nop = NULL;
1559 struct alt_group *orig_alt_group, *new_alt_group;
1560 unsigned long dest_off;
1561
1562
1563 orig_alt_group = malloc(sizeof(*orig_alt_group));
1564 if (!orig_alt_group) {
1565 WARN("malloc failed");
1566 return -1;
1567 }
1568 orig_alt_group->cfi = calloc(special_alt->orig_len,
1569 sizeof(struct cfi_state *));
1570 if (!orig_alt_group->cfi) {
1571 WARN("calloc failed");
1572 return -1;
1573 }
1574
1575 last_orig_insn = NULL;
1576 insn = orig_insn;
1577 sec_for_each_insn_from(file, insn) {
1578 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1579 break;
1580
1581 insn->alt_group = orig_alt_group;
1582 last_orig_insn = insn;
1583 }
1584 orig_alt_group->orig_group = NULL;
1585 orig_alt_group->first_insn = orig_insn;
1586 orig_alt_group->last_insn = last_orig_insn;
1587
1588
1589 new_alt_group = malloc(sizeof(*new_alt_group));
1590 if (!new_alt_group) {
1591 WARN("malloc failed");
1592 return -1;
1593 }
1594
1595 if (special_alt->new_len < special_alt->orig_len) {
1596 /*
1597 * Insert a fake nop at the end to make the replacement
1598 * alt_group the same size as the original. This is needed to
1599 * allow propagate_alt_cfi() to do its magic. When the last
1600 * instruction affects the stack, the instruction after it (the
1601 * nop) will propagate the new state to the shared CFI array.
1602 */
1603 nop = malloc(sizeof(*nop));
1604 if (!nop) {
1605 WARN("malloc failed");
1606 return -1;
1607 }
1608 memset(nop, 0, sizeof(*nop));
1609 INIT_LIST_HEAD(&nop->alts);
1610 INIT_LIST_HEAD(&nop->stack_ops);
1611
1612 nop->sec = special_alt->new_sec;
1613 nop->offset = special_alt->new_off + special_alt->new_len;
1614 nop->len = special_alt->orig_len - special_alt->new_len;
1615 nop->type = INSN_NOP;
1616 nop->func = orig_insn->func;
1617 nop->alt_group = new_alt_group;
1618 nop->ignore = orig_insn->ignore_alts;
1619 }
1620
1621 if (!special_alt->new_len) {
1622 *new_insn = nop;
1623 goto end;
1624 }
1625
1626 insn = *new_insn;
1627 sec_for_each_insn_from(file, insn) {
1628 struct reloc *alt_reloc;
1629
1630 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1631 break;
1632
1633 last_new_insn = insn;
1634
1635 insn->ignore = orig_insn->ignore_alts;
1636 insn->func = orig_insn->func;
1637 insn->alt_group = new_alt_group;
1638
1639 /*
1640 * Since alternative replacement code is copy/pasted by the
1641 * kernel after applying relocations, generally such code can't
1642 * have relative-address relocation references to outside the
1643 * .altinstr_replacement section, unless the arch's
1644 * alternatives code can adjust the relative offsets
1645 * accordingly.
1646 */
1647 alt_reloc = insn_reloc(file, insn);
1648 if (alt_reloc &&
1649 !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1650
1651 WARN_FUNC("unsupported relocation in alternatives section",
1652 insn->sec, insn->offset);
1653 return -1;
1654 }
1655
1656 if (!is_static_jump(insn))
1657 continue;
1658
1659 if (!insn->immediate)
1660 continue;
1661
1662 dest_off = arch_jump_destination(insn);
1663 if (dest_off == special_alt->new_off + special_alt->new_len) {
1664 insn->jump_dest = next_insn_same_sec(file, last_orig_insn);
1665 if (!insn->jump_dest) {
1666 WARN_FUNC("can't find alternative jump destination",
1667 insn->sec, insn->offset);
1668 return -1;
1669 }
1670 }
1671 }
1672
1673 if (!last_new_insn) {
1674 WARN_FUNC("can't find last new alternative instruction",
1675 special_alt->new_sec, special_alt->new_off);
1676 return -1;
1677 }
1678
1679 if (nop)
1680 list_add(&nop->list, &last_new_insn->list);
1681 end:
1682 new_alt_group->orig_group = orig_alt_group;
1683 new_alt_group->first_insn = *new_insn;
1684 new_alt_group->last_insn = nop ? : last_new_insn;
1685 new_alt_group->cfi = orig_alt_group->cfi;
1686 return 0;
1687 }
1688
1689 /*
1690 * A jump table entry can either convert a nop to a jump or a jump to a nop.
1691 * If the original instruction is a jump, make the alt entry an effective nop
1692 * by just skipping the original instruction.
1693 */
handle_jump_alt(struct objtool_file * file,struct special_alt * special_alt,struct instruction * orig_insn,struct instruction ** new_insn)1694 static int handle_jump_alt(struct objtool_file *file,
1695 struct special_alt *special_alt,
1696 struct instruction *orig_insn,
1697 struct instruction **new_insn)
1698 {
1699 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1700 orig_insn->type != INSN_NOP) {
1701
1702 WARN_FUNC("unsupported instruction at jump label",
1703 orig_insn->sec, orig_insn->offset);
1704 return -1;
1705 }
1706
1707 if (opts.hack_jump_label && special_alt->key_addend & 2) {
1708 struct reloc *reloc = insn_reloc(file, orig_insn);
1709
1710 if (reloc) {
1711 reloc->type = R_NONE;
1712 elf_write_reloc(file->elf, reloc);
1713 }
1714 elf_write_insn(file->elf, orig_insn->sec,
1715 orig_insn->offset, orig_insn->len,
1716 arch_nop_insn(orig_insn->len));
1717 orig_insn->type = INSN_NOP;
1718 }
1719
1720 if (orig_insn->type == INSN_NOP) {
1721 if (orig_insn->len == 2)
1722 file->jl_nop_short++;
1723 else
1724 file->jl_nop_long++;
1725
1726 return 0;
1727 }
1728
1729 if (orig_insn->len == 2)
1730 file->jl_short++;
1731 else
1732 file->jl_long++;
1733
1734 *new_insn = list_next_entry(orig_insn, list);
1735 return 0;
1736 }
1737
1738 /*
1739 * Read all the special sections which have alternate instructions which can be
1740 * patched in or redirected to at runtime. Each instruction having alternate
1741 * instruction(s) has them added to its insn->alts list, which will be
1742 * traversed in validate_branch().
1743 */
add_special_section_alts(struct objtool_file * file)1744 static int add_special_section_alts(struct objtool_file *file)
1745 {
1746 struct list_head special_alts;
1747 struct instruction *orig_insn, *new_insn;
1748 struct special_alt *special_alt, *tmp;
1749 struct alternative *alt;
1750 int ret;
1751
1752 ret = special_get_alts(file->elf, &special_alts);
1753 if (ret)
1754 return ret;
1755
1756 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1757
1758 orig_insn = find_insn(file, special_alt->orig_sec,
1759 special_alt->orig_off);
1760 if (!orig_insn) {
1761 WARN_FUNC("special: can't find orig instruction",
1762 special_alt->orig_sec, special_alt->orig_off);
1763 ret = -1;
1764 goto out;
1765 }
1766
1767 new_insn = NULL;
1768 if (!special_alt->group || special_alt->new_len) {
1769 new_insn = find_insn(file, special_alt->new_sec,
1770 special_alt->new_off);
1771 if (!new_insn) {
1772 WARN_FUNC("special: can't find new instruction",
1773 special_alt->new_sec,
1774 special_alt->new_off);
1775 ret = -1;
1776 goto out;
1777 }
1778 }
1779
1780 if (special_alt->group) {
1781 if (!special_alt->orig_len) {
1782 WARN_FUNC("empty alternative entry",
1783 orig_insn->sec, orig_insn->offset);
1784 continue;
1785 }
1786
1787 ret = handle_group_alt(file, special_alt, orig_insn,
1788 &new_insn);
1789 if (ret)
1790 goto out;
1791 } else if (special_alt->jump_or_nop) {
1792 ret = handle_jump_alt(file, special_alt, orig_insn,
1793 &new_insn);
1794 if (ret)
1795 goto out;
1796 }
1797
1798 alt = malloc(sizeof(*alt));
1799 if (!alt) {
1800 WARN("malloc failed");
1801 ret = -1;
1802 goto out;
1803 }
1804
1805 alt->insn = new_insn;
1806 alt->skip_orig = special_alt->skip_orig;
1807 orig_insn->ignore_alts |= special_alt->skip_alt;
1808 list_add_tail(&alt->list, &orig_insn->alts);
1809
1810 list_del(&special_alt->list);
1811 free(special_alt);
1812 }
1813
1814 if (opts.stats) {
1815 printf("jl\\\tNOP\tJMP\n");
1816 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
1817 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
1818 }
1819
1820 out:
1821 return ret;
1822 }
1823
add_jump_table(struct objtool_file * file,struct instruction * insn,struct reloc * table)1824 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
1825 struct reloc *table)
1826 {
1827 struct reloc *reloc = table;
1828 struct instruction *dest_insn;
1829 struct alternative *alt;
1830 struct symbol *pfunc = insn->func->pfunc;
1831 unsigned int prev_offset = 0;
1832
1833 /*
1834 * Each @reloc is a switch table relocation which points to the target
1835 * instruction.
1836 */
1837 list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
1838
1839 /* Check for the end of the table: */
1840 if (reloc != table && reloc->jump_table_start)
1841 break;
1842
1843 /* Make sure the table entries are consecutive: */
1844 if (prev_offset && reloc->offset != prev_offset + 8)
1845 break;
1846
1847 /* Detect function pointers from contiguous objects: */
1848 if (reloc->sym->sec == pfunc->sec &&
1849 reloc->addend == pfunc->offset)
1850 break;
1851
1852 dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
1853 if (!dest_insn)
1854 break;
1855
1856 /* Make sure the destination is in the same function: */
1857 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
1858 break;
1859
1860 alt = malloc(sizeof(*alt));
1861 if (!alt) {
1862 WARN("malloc failed");
1863 return -1;
1864 }
1865
1866 alt->insn = dest_insn;
1867 list_add_tail(&alt->list, &insn->alts);
1868 prev_offset = reloc->offset;
1869 }
1870
1871 if (!prev_offset) {
1872 WARN_FUNC("can't find switch jump table",
1873 insn->sec, insn->offset);
1874 return -1;
1875 }
1876
1877 return 0;
1878 }
1879
1880 /*
1881 * find_jump_table() - Given a dynamic jump, find the switch jump table
1882 * associated with it.
1883 */
find_jump_table(struct objtool_file * file,struct symbol * func,struct instruction * insn)1884 static struct reloc *find_jump_table(struct objtool_file *file,
1885 struct symbol *func,
1886 struct instruction *insn)
1887 {
1888 struct reloc *table_reloc;
1889 struct instruction *dest_insn, *orig_insn = insn;
1890
1891 /*
1892 * Backward search using the @first_jump_src links, these help avoid
1893 * much of the 'in between' code. Which avoids us getting confused by
1894 * it.
1895 */
1896 for (;
1897 insn && insn->func && insn->func->pfunc == func;
1898 insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
1899
1900 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1901 break;
1902
1903 /* allow small jumps within the range */
1904 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1905 insn->jump_dest &&
1906 (insn->jump_dest->offset <= insn->offset ||
1907 insn->jump_dest->offset > orig_insn->offset))
1908 break;
1909
1910 table_reloc = arch_find_switch_table(file, insn);
1911 if (!table_reloc)
1912 continue;
1913 dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
1914 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1915 continue;
1916
1917 return table_reloc;
1918 }
1919
1920 return NULL;
1921 }
1922
1923 /*
1924 * First pass: Mark the head of each jump table so that in the next pass,
1925 * we know when a given jump table ends and the next one starts.
1926 */
mark_func_jump_tables(struct objtool_file * file,struct symbol * func)1927 static void mark_func_jump_tables(struct objtool_file *file,
1928 struct symbol *func)
1929 {
1930 struct instruction *insn, *last = NULL;
1931 struct reloc *reloc;
1932
1933 func_for_each_insn(file, func, insn) {
1934 if (!last)
1935 last = insn;
1936
1937 /*
1938 * Store back-pointers for unconditional forward jumps such
1939 * that find_jump_table() can back-track using those and
1940 * avoid some potentially confusing code.
1941 */
1942 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1943 insn->offset > last->offset &&
1944 insn->jump_dest->offset > insn->offset &&
1945 !insn->jump_dest->first_jump_src) {
1946
1947 insn->jump_dest->first_jump_src = insn;
1948 last = insn->jump_dest;
1949 }
1950
1951 if (insn->type != INSN_JUMP_DYNAMIC)
1952 continue;
1953
1954 reloc = find_jump_table(file, func, insn);
1955 if (reloc) {
1956 reloc->jump_table_start = true;
1957 insn->jump_table = reloc;
1958 }
1959 }
1960 }
1961
add_func_jump_tables(struct objtool_file * file,struct symbol * func)1962 static int add_func_jump_tables(struct objtool_file *file,
1963 struct symbol *func)
1964 {
1965 struct instruction *insn;
1966 int ret;
1967
1968 func_for_each_insn(file, func, insn) {
1969 if (!insn->jump_table)
1970 continue;
1971
1972 ret = add_jump_table(file, insn, insn->jump_table);
1973 if (ret)
1974 return ret;
1975 }
1976
1977 return 0;
1978 }
1979
1980 /*
1981 * For some switch statements, gcc generates a jump table in the .rodata
1982 * section which contains a list of addresses within the function to jump to.
1983 * This finds these jump tables and adds them to the insn->alts lists.
1984 */
add_jump_table_alts(struct objtool_file * file)1985 static int add_jump_table_alts(struct objtool_file *file)
1986 {
1987 struct section *sec;
1988 struct symbol *func;
1989 int ret;
1990
1991 if (!file->rodata)
1992 return 0;
1993
1994 for_each_sec(file, sec) {
1995 list_for_each_entry(func, &sec->symbol_list, list) {
1996 if (func->type != STT_FUNC)
1997 continue;
1998
1999 mark_func_jump_tables(file, func);
2000 ret = add_func_jump_tables(file, func);
2001 if (ret)
2002 return ret;
2003 }
2004 }
2005
2006 return 0;
2007 }
2008
set_func_state(struct cfi_state * state)2009 static void set_func_state(struct cfi_state *state)
2010 {
2011 state->cfa = initial_func_cfi.cfa;
2012 memcpy(&state->regs, &initial_func_cfi.regs,
2013 CFI_NUM_REGS * sizeof(struct cfi_reg));
2014 state->stack_size = initial_func_cfi.cfa.offset;
2015 }
2016
read_unwind_hints(struct objtool_file * file)2017 static int read_unwind_hints(struct objtool_file *file)
2018 {
2019 struct cfi_state cfi = init_cfi;
2020 struct section *sec, *relocsec;
2021 struct unwind_hint *hint;
2022 struct instruction *insn;
2023 struct reloc *reloc;
2024 int i;
2025
2026 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
2027 if (!sec)
2028 return 0;
2029
2030 relocsec = sec->reloc;
2031 if (!relocsec) {
2032 WARN("missing .rela.discard.unwind_hints section");
2033 return -1;
2034 }
2035
2036 if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
2037 WARN("struct unwind_hint size mismatch");
2038 return -1;
2039 }
2040
2041 file->hints = true;
2042
2043 for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
2044 hint = (struct unwind_hint *)sec->data->d_buf + i;
2045
2046 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
2047 if (!reloc) {
2048 WARN("can't find reloc for unwind_hints[%d]", i);
2049 return -1;
2050 }
2051
2052 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2053 if (!insn) {
2054 WARN("can't find insn for unwind_hints[%d]", i);
2055 return -1;
2056 }
2057
2058 insn->hint = true;
2059
2060 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
2061 insn->hint = false;
2062 insn->save = true;
2063 continue;
2064 }
2065
2066 if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
2067 insn->restore = true;
2068 continue;
2069 }
2070
2071 if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
2072 struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
2073
2074 if (sym && sym->bind == STB_GLOBAL) {
2075 if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) {
2076 WARN_FUNC("UNWIND_HINT_IRET_REGS without ENDBR",
2077 insn->sec, insn->offset);
2078 }
2079
2080 insn->entry = 1;
2081 }
2082 }
2083
2084 if (hint->type == UNWIND_HINT_TYPE_ENTRY) {
2085 hint->type = UNWIND_HINT_TYPE_CALL;
2086 insn->entry = 1;
2087 }
2088
2089 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
2090 insn->cfi = &func_cfi;
2091 continue;
2092 }
2093
2094 if (insn->cfi)
2095 cfi = *(insn->cfi);
2096
2097 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
2098 WARN_FUNC("unsupported unwind_hint sp base reg %d",
2099 insn->sec, insn->offset, hint->sp_reg);
2100 return -1;
2101 }
2102
2103 cfi.cfa.offset = bswap_if_needed(hint->sp_offset);
2104 cfi.type = hint->type;
2105 cfi.end = hint->end;
2106
2107 insn->cfi = cfi_hash_find_or_add(&cfi);
2108 }
2109
2110 return 0;
2111 }
2112
read_noendbr_hints(struct objtool_file * file)2113 static int read_noendbr_hints(struct objtool_file *file)
2114 {
2115 struct section *sec;
2116 struct instruction *insn;
2117 struct reloc *reloc;
2118
2119 sec = find_section_by_name(file->elf, ".rela.discard.noendbr");
2120 if (!sec)
2121 return 0;
2122
2123 list_for_each_entry(reloc, &sec->reloc_list, list) {
2124 insn = find_insn(file, reloc->sym->sec, reloc->sym->offset + reloc->addend);
2125 if (!insn) {
2126 WARN("bad .discard.noendbr entry");
2127 return -1;
2128 }
2129
2130 insn->noendbr = 1;
2131 }
2132
2133 return 0;
2134 }
2135
read_retpoline_hints(struct objtool_file * file)2136 static int read_retpoline_hints(struct objtool_file *file)
2137 {
2138 struct section *sec;
2139 struct instruction *insn;
2140 struct reloc *reloc;
2141
2142 sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
2143 if (!sec)
2144 return 0;
2145
2146 list_for_each_entry(reloc, &sec->reloc_list, list) {
2147 if (reloc->sym->type != STT_SECTION) {
2148 WARN("unexpected relocation symbol type in %s", sec->name);
2149 return -1;
2150 }
2151
2152 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2153 if (!insn) {
2154 WARN("bad .discard.retpoline_safe entry");
2155 return -1;
2156 }
2157
2158 if (insn->type != INSN_JUMP_DYNAMIC &&
2159 insn->type != INSN_CALL_DYNAMIC &&
2160 insn->type != INSN_RETURN &&
2161 insn->type != INSN_NOP) {
2162 WARN_FUNC("retpoline_safe hint not an indirect jump/call/ret/nop",
2163 insn->sec, insn->offset);
2164 return -1;
2165 }
2166
2167 insn->retpoline_safe = true;
2168 }
2169
2170 return 0;
2171 }
2172
read_instr_hints(struct objtool_file * file)2173 static int read_instr_hints(struct objtool_file *file)
2174 {
2175 struct section *sec;
2176 struct instruction *insn;
2177 struct reloc *reloc;
2178
2179 sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2180 if (!sec)
2181 return 0;
2182
2183 list_for_each_entry(reloc, &sec->reloc_list, list) {
2184 if (reloc->sym->type != STT_SECTION) {
2185 WARN("unexpected relocation symbol type in %s", sec->name);
2186 return -1;
2187 }
2188
2189 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2190 if (!insn) {
2191 WARN("bad .discard.instr_end entry");
2192 return -1;
2193 }
2194
2195 insn->instr--;
2196 }
2197
2198 sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2199 if (!sec)
2200 return 0;
2201
2202 list_for_each_entry(reloc, &sec->reloc_list, list) {
2203 if (reloc->sym->type != STT_SECTION) {
2204 WARN("unexpected relocation symbol type in %s", sec->name);
2205 return -1;
2206 }
2207
2208 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2209 if (!insn) {
2210 WARN("bad .discard.instr_begin entry");
2211 return -1;
2212 }
2213
2214 insn->instr++;
2215 }
2216
2217 return 0;
2218 }
2219
read_intra_function_calls(struct objtool_file * file)2220 static int read_intra_function_calls(struct objtool_file *file)
2221 {
2222 struct instruction *insn;
2223 struct section *sec;
2224 struct reloc *reloc;
2225
2226 sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2227 if (!sec)
2228 return 0;
2229
2230 list_for_each_entry(reloc, &sec->reloc_list, list) {
2231 unsigned long dest_off;
2232
2233 if (reloc->sym->type != STT_SECTION) {
2234 WARN("unexpected relocation symbol type in %s",
2235 sec->name);
2236 return -1;
2237 }
2238
2239 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2240 if (!insn) {
2241 WARN("bad .discard.intra_function_call entry");
2242 return -1;
2243 }
2244
2245 if (insn->type != INSN_CALL) {
2246 WARN_FUNC("intra_function_call not a direct call",
2247 insn->sec, insn->offset);
2248 return -1;
2249 }
2250
2251 /*
2252 * Treat intra-function CALLs as JMPs, but with a stack_op.
2253 * See add_call_destinations(), which strips stack_ops from
2254 * normal CALLs.
2255 */
2256 insn->type = INSN_JUMP_UNCONDITIONAL;
2257
2258 dest_off = arch_jump_destination(insn);
2259 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2260 if (!insn->jump_dest) {
2261 WARN_FUNC("can't find call dest at %s+0x%lx",
2262 insn->sec, insn->offset,
2263 insn->sec->name, dest_off);
2264 return -1;
2265 }
2266 }
2267
2268 return 0;
2269 }
2270
2271 /*
2272 * Return true if name matches an instrumentation function, where calls to that
2273 * function from noinstr code can safely be removed, but compilers won't do so.
2274 */
is_profiling_func(const char * name)2275 static bool is_profiling_func(const char *name)
2276 {
2277 /*
2278 * Many compilers cannot disable KCOV with a function attribute.
2279 */
2280 if (!strncmp(name, "__sanitizer_cov_", 16))
2281 return true;
2282
2283 /*
2284 * Some compilers currently do not remove __tsan_func_entry/exit nor
2285 * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2286 * the __no_sanitize_thread attribute, remove them. Once the kernel's
2287 * minimum Clang version is 14.0, this can be removed.
2288 */
2289 if (!strncmp(name, "__tsan_func_", 12) ||
2290 !strcmp(name, "__tsan_atomic_signal_fence"))
2291 return true;
2292
2293 return false;
2294 }
2295
classify_symbols(struct objtool_file * file)2296 static int classify_symbols(struct objtool_file *file)
2297 {
2298 struct section *sec;
2299 struct symbol *func;
2300
2301 for_each_sec(file, sec) {
2302 list_for_each_entry(func, &sec->symbol_list, list) {
2303 if (func->bind != STB_GLOBAL)
2304 continue;
2305
2306 if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2307 strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2308 func->static_call_tramp = true;
2309
2310 if (arch_is_retpoline(func))
2311 func->retpoline_thunk = true;
2312
2313 if (arch_is_rethunk(func))
2314 func->return_thunk = true;
2315
2316 if (!strcmp(func->name, "__fentry__"))
2317 func->fentry = true;
2318
2319 if (is_profiling_func(func->name))
2320 func->profiling_func = true;
2321 }
2322 }
2323
2324 return 0;
2325 }
2326
mark_rodata(struct objtool_file * file)2327 static void mark_rodata(struct objtool_file *file)
2328 {
2329 struct section *sec;
2330 bool found = false;
2331
2332 /*
2333 * Search for the following rodata sections, each of which can
2334 * potentially contain jump tables:
2335 *
2336 * - .rodata: can contain GCC switch tables
2337 * - .rodata.<func>: same, if -fdata-sections is being used
2338 * - .rodata..c_jump_table: contains C annotated jump tables
2339 *
2340 * .rodata.str1.* sections are ignored; they don't contain jump tables.
2341 */
2342 for_each_sec(file, sec) {
2343 if (!strncmp(sec->name, ".rodata", 7) &&
2344 !strstr(sec->name, ".str1.")) {
2345 sec->rodata = true;
2346 found = true;
2347 }
2348 }
2349
2350 file->rodata = found;
2351 }
2352
decode_sections(struct objtool_file * file)2353 static int decode_sections(struct objtool_file *file)
2354 {
2355 int ret;
2356
2357 mark_rodata(file);
2358
2359 ret = init_pv_ops(file);
2360 if (ret)
2361 return ret;
2362
2363 ret = decode_instructions(file);
2364 if (ret)
2365 return ret;
2366
2367 add_ignores(file);
2368 add_uaccess_safe(file);
2369
2370 ret = add_ignore_alternatives(file);
2371 if (ret)
2372 return ret;
2373
2374 /*
2375 * Must be before read_unwind_hints() since that needs insn->noendbr.
2376 */
2377 ret = read_noendbr_hints(file);
2378 if (ret)
2379 return ret;
2380
2381 /*
2382 * Must be before add_{jump_call}_destination.
2383 */
2384 ret = classify_symbols(file);
2385 if (ret)
2386 return ret;
2387
2388 /*
2389 * Must be before add_jump_destinations(), which depends on 'func'
2390 * being set for alternatives, to enable proper sibling call detection.
2391 */
2392 ret = add_special_section_alts(file);
2393 if (ret)
2394 return ret;
2395
2396 ret = add_jump_destinations(file);
2397 if (ret)
2398 return ret;
2399
2400 /*
2401 * Must be before add_call_destination(); it changes INSN_CALL to
2402 * INSN_JUMP.
2403 */
2404 ret = read_intra_function_calls(file);
2405 if (ret)
2406 return ret;
2407
2408 ret = add_call_destinations(file);
2409 if (ret)
2410 return ret;
2411
2412 /*
2413 * Must be after add_call_destinations() such that it can override
2414 * dead_end_function() marks.
2415 */
2416 ret = add_dead_ends(file);
2417 if (ret)
2418 return ret;
2419
2420 ret = add_jump_table_alts(file);
2421 if (ret)
2422 return ret;
2423
2424 ret = read_unwind_hints(file);
2425 if (ret)
2426 return ret;
2427
2428 ret = read_retpoline_hints(file);
2429 if (ret)
2430 return ret;
2431
2432 ret = read_instr_hints(file);
2433 if (ret)
2434 return ret;
2435
2436 return 0;
2437 }
2438
is_fentry_call(struct instruction * insn)2439 static bool is_fentry_call(struct instruction *insn)
2440 {
2441 if (insn->type == INSN_CALL &&
2442 insn->call_dest &&
2443 insn->call_dest->fentry)
2444 return true;
2445
2446 return false;
2447 }
2448
has_modified_stack_frame(struct instruction * insn,struct insn_state * state)2449 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2450 {
2451 struct cfi_state *cfi = &state->cfi;
2452 int i;
2453
2454 if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2455 return true;
2456
2457 if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2458 return true;
2459
2460 if (cfi->stack_size != initial_func_cfi.cfa.offset)
2461 return true;
2462
2463 for (i = 0; i < CFI_NUM_REGS; i++) {
2464 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2465 cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2466 return true;
2467 }
2468
2469 return false;
2470 }
2471
check_reg_frame_pos(const struct cfi_reg * reg,int expected_offset)2472 static bool check_reg_frame_pos(const struct cfi_reg *reg,
2473 int expected_offset)
2474 {
2475 return reg->base == CFI_CFA &&
2476 reg->offset == expected_offset;
2477 }
2478
has_valid_stack_frame(struct insn_state * state)2479 static bool has_valid_stack_frame(struct insn_state *state)
2480 {
2481 struct cfi_state *cfi = &state->cfi;
2482
2483 if (cfi->cfa.base == CFI_BP &&
2484 check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2485 check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2486 return true;
2487
2488 if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2489 return true;
2490
2491 return false;
2492 }
2493
update_cfi_state_regs(struct instruction * insn,struct cfi_state * cfi,struct stack_op * op)2494 static int update_cfi_state_regs(struct instruction *insn,
2495 struct cfi_state *cfi,
2496 struct stack_op *op)
2497 {
2498 struct cfi_reg *cfa = &cfi->cfa;
2499
2500 if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2501 return 0;
2502
2503 /* push */
2504 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2505 cfa->offset += 8;
2506
2507 /* pop */
2508 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2509 cfa->offset -= 8;
2510
2511 /* add immediate to sp */
2512 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2513 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2514 cfa->offset -= op->src.offset;
2515
2516 return 0;
2517 }
2518
save_reg(struct cfi_state * cfi,unsigned char reg,int base,int offset)2519 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2520 {
2521 if (arch_callee_saved_reg(reg) &&
2522 cfi->regs[reg].base == CFI_UNDEFINED) {
2523 cfi->regs[reg].base = base;
2524 cfi->regs[reg].offset = offset;
2525 }
2526 }
2527
restore_reg(struct cfi_state * cfi,unsigned char reg)2528 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2529 {
2530 cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2531 cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2532 }
2533
2534 /*
2535 * A note about DRAP stack alignment:
2536 *
2537 * GCC has the concept of a DRAP register, which is used to help keep track of
2538 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
2539 * register. The typical DRAP pattern is:
2540 *
2541 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
2542 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
2543 * 41 ff 72 f8 pushq -0x8(%r10)
2544 * 55 push %rbp
2545 * 48 89 e5 mov %rsp,%rbp
2546 * (more pushes)
2547 * 41 52 push %r10
2548 * ...
2549 * 41 5a pop %r10
2550 * (more pops)
2551 * 5d pop %rbp
2552 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2553 * c3 retq
2554 *
2555 * There are some variations in the epilogues, like:
2556 *
2557 * 5b pop %rbx
2558 * 41 5a pop %r10
2559 * 41 5c pop %r12
2560 * 41 5d pop %r13
2561 * 41 5e pop %r14
2562 * c9 leaveq
2563 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2564 * c3 retq
2565 *
2566 * and:
2567 *
2568 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
2569 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
2570 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
2571 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
2572 * c9 leaveq
2573 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2574 * c3 retq
2575 *
2576 * Sometimes r13 is used as the DRAP register, in which case it's saved and
2577 * restored beforehand:
2578 *
2579 * 41 55 push %r13
2580 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
2581 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
2582 * ...
2583 * 49 8d 65 f0 lea -0x10(%r13),%rsp
2584 * 41 5d pop %r13
2585 * c3 retq
2586 */
update_cfi_state(struct instruction * insn,struct instruction * next_insn,struct cfi_state * cfi,struct stack_op * op)2587 static int update_cfi_state(struct instruction *insn,
2588 struct instruction *next_insn,
2589 struct cfi_state *cfi, struct stack_op *op)
2590 {
2591 struct cfi_reg *cfa = &cfi->cfa;
2592 struct cfi_reg *regs = cfi->regs;
2593
2594 /* stack operations don't make sense with an undefined CFA */
2595 if (cfa->base == CFI_UNDEFINED) {
2596 if (insn->func) {
2597 WARN_FUNC("undefined stack state", insn->sec, insn->offset);
2598 return -1;
2599 }
2600 return 0;
2601 }
2602
2603 if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2604 cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2605 return update_cfi_state_regs(insn, cfi, op);
2606
2607 switch (op->dest.type) {
2608
2609 case OP_DEST_REG:
2610 switch (op->src.type) {
2611
2612 case OP_SRC_REG:
2613 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2614 cfa->base == CFI_SP &&
2615 check_reg_frame_pos(®s[CFI_BP], -cfa->offset)) {
2616
2617 /* mov %rsp, %rbp */
2618 cfa->base = op->dest.reg;
2619 cfi->bp_scratch = false;
2620 }
2621
2622 else if (op->src.reg == CFI_SP &&
2623 op->dest.reg == CFI_BP && cfi->drap) {
2624
2625 /* drap: mov %rsp, %rbp */
2626 regs[CFI_BP].base = CFI_BP;
2627 regs[CFI_BP].offset = -cfi->stack_size;
2628 cfi->bp_scratch = false;
2629 }
2630
2631 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2632
2633 /*
2634 * mov %rsp, %reg
2635 *
2636 * This is needed for the rare case where GCC
2637 * does:
2638 *
2639 * mov %rsp, %rax
2640 * ...
2641 * mov %rax, %rsp
2642 */
2643 cfi->vals[op->dest.reg].base = CFI_CFA;
2644 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2645 }
2646
2647 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2648 (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2649
2650 /*
2651 * mov %rbp, %rsp
2652 *
2653 * Restore the original stack pointer (Clang).
2654 */
2655 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2656 }
2657
2658 else if (op->dest.reg == cfa->base) {
2659
2660 /* mov %reg, %rsp */
2661 if (cfa->base == CFI_SP &&
2662 cfi->vals[op->src.reg].base == CFI_CFA) {
2663
2664 /*
2665 * This is needed for the rare case
2666 * where GCC does something dumb like:
2667 *
2668 * lea 0x8(%rsp), %rcx
2669 * ...
2670 * mov %rcx, %rsp
2671 */
2672 cfa->offset = -cfi->vals[op->src.reg].offset;
2673 cfi->stack_size = cfa->offset;
2674
2675 } else if (cfa->base == CFI_SP &&
2676 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2677 cfi->vals[op->src.reg].offset == cfa->offset) {
2678
2679 /*
2680 * Stack swizzle:
2681 *
2682 * 1: mov %rsp, (%[tos])
2683 * 2: mov %[tos], %rsp
2684 * ...
2685 * 3: pop %rsp
2686 *
2687 * Where:
2688 *
2689 * 1 - places a pointer to the previous
2690 * stack at the Top-of-Stack of the
2691 * new stack.
2692 *
2693 * 2 - switches to the new stack.
2694 *
2695 * 3 - pops the Top-of-Stack to restore
2696 * the original stack.
2697 *
2698 * Note: we set base to SP_INDIRECT
2699 * here and preserve offset. Therefore
2700 * when the unwinder reaches ToS it
2701 * will dereference SP and then add the
2702 * offset to find the next frame, IOW:
2703 * (%rsp) + offset.
2704 */
2705 cfa->base = CFI_SP_INDIRECT;
2706
2707 } else {
2708 cfa->base = CFI_UNDEFINED;
2709 cfa->offset = 0;
2710 }
2711 }
2712
2713 else if (op->dest.reg == CFI_SP &&
2714 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2715 cfi->vals[op->src.reg].offset == cfa->offset) {
2716
2717 /*
2718 * The same stack swizzle case 2) as above. But
2719 * because we can't change cfa->base, case 3)
2720 * will become a regular POP. Pretend we're a
2721 * PUSH so things don't go unbalanced.
2722 */
2723 cfi->stack_size += 8;
2724 }
2725
2726
2727 break;
2728
2729 case OP_SRC_ADD:
2730 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2731
2732 /* add imm, %rsp */
2733 cfi->stack_size -= op->src.offset;
2734 if (cfa->base == CFI_SP)
2735 cfa->offset -= op->src.offset;
2736 break;
2737 }
2738
2739 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2740
2741 /* lea disp(%rbp), %rsp */
2742 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2743 break;
2744 }
2745
2746 if (!cfi->drap && op->src.reg == CFI_SP &&
2747 op->dest.reg == CFI_BP && cfa->base == CFI_SP &&
2748 check_reg_frame_pos(®s[CFI_BP], -cfa->offset + op->src.offset)) {
2749
2750 /* lea disp(%rsp), %rbp */
2751 cfa->base = CFI_BP;
2752 cfa->offset -= op->src.offset;
2753 cfi->bp_scratch = false;
2754 break;
2755 }
2756
2757 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2758
2759 /* drap: lea disp(%rsp), %drap */
2760 cfi->drap_reg = op->dest.reg;
2761
2762 /*
2763 * lea disp(%rsp), %reg
2764 *
2765 * This is needed for the rare case where GCC
2766 * does something dumb like:
2767 *
2768 * lea 0x8(%rsp), %rcx
2769 * ...
2770 * mov %rcx, %rsp
2771 */
2772 cfi->vals[op->dest.reg].base = CFI_CFA;
2773 cfi->vals[op->dest.reg].offset = \
2774 -cfi->stack_size + op->src.offset;
2775
2776 break;
2777 }
2778
2779 if (cfi->drap && op->dest.reg == CFI_SP &&
2780 op->src.reg == cfi->drap_reg) {
2781
2782 /* drap: lea disp(%drap), %rsp */
2783 cfa->base = CFI_SP;
2784 cfa->offset = cfi->stack_size = -op->src.offset;
2785 cfi->drap_reg = CFI_UNDEFINED;
2786 cfi->drap = false;
2787 break;
2788 }
2789
2790 if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
2791 WARN_FUNC("unsupported stack register modification",
2792 insn->sec, insn->offset);
2793 return -1;
2794 }
2795
2796 break;
2797
2798 case OP_SRC_AND:
2799 if (op->dest.reg != CFI_SP ||
2800 (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
2801 (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
2802 WARN_FUNC("unsupported stack pointer realignment",
2803 insn->sec, insn->offset);
2804 return -1;
2805 }
2806
2807 if (cfi->drap_reg != CFI_UNDEFINED) {
2808 /* drap: and imm, %rsp */
2809 cfa->base = cfi->drap_reg;
2810 cfa->offset = cfi->stack_size = 0;
2811 cfi->drap = true;
2812 }
2813
2814 /*
2815 * Older versions of GCC (4.8ish) realign the stack
2816 * without DRAP, with a frame pointer.
2817 */
2818
2819 break;
2820
2821 case OP_SRC_POP:
2822 case OP_SRC_POPF:
2823 if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
2824
2825 /* pop %rsp; # restore from a stack swizzle */
2826 cfa->base = CFI_SP;
2827 break;
2828 }
2829
2830 if (!cfi->drap && op->dest.reg == cfa->base) {
2831
2832 /* pop %rbp */
2833 cfa->base = CFI_SP;
2834 }
2835
2836 if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
2837 op->dest.reg == cfi->drap_reg &&
2838 cfi->drap_offset == -cfi->stack_size) {
2839
2840 /* drap: pop %drap */
2841 cfa->base = cfi->drap_reg;
2842 cfa->offset = 0;
2843 cfi->drap_offset = -1;
2844
2845 } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
2846
2847 /* pop %reg */
2848 restore_reg(cfi, op->dest.reg);
2849 }
2850
2851 cfi->stack_size -= 8;
2852 if (cfa->base == CFI_SP)
2853 cfa->offset -= 8;
2854
2855 break;
2856
2857 case OP_SRC_REG_INDIRECT:
2858 if (!cfi->drap && op->dest.reg == cfa->base &&
2859 op->dest.reg == CFI_BP) {
2860
2861 /* mov disp(%rsp), %rbp */
2862 cfa->base = CFI_SP;
2863 cfa->offset = cfi->stack_size;
2864 }
2865
2866 if (cfi->drap && op->src.reg == CFI_BP &&
2867 op->src.offset == cfi->drap_offset) {
2868
2869 /* drap: mov disp(%rbp), %drap */
2870 cfa->base = cfi->drap_reg;
2871 cfa->offset = 0;
2872 cfi->drap_offset = -1;
2873 }
2874
2875 if (cfi->drap && op->src.reg == CFI_BP &&
2876 op->src.offset == regs[op->dest.reg].offset) {
2877
2878 /* drap: mov disp(%rbp), %reg */
2879 restore_reg(cfi, op->dest.reg);
2880
2881 } else if (op->src.reg == cfa->base &&
2882 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
2883
2884 /* mov disp(%rbp), %reg */
2885 /* mov disp(%rsp), %reg */
2886 restore_reg(cfi, op->dest.reg);
2887
2888 } else if (op->src.reg == CFI_SP &&
2889 op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
2890
2891 /* mov disp(%rsp), %reg */
2892 restore_reg(cfi, op->dest.reg);
2893 }
2894
2895 break;
2896
2897 default:
2898 WARN_FUNC("unknown stack-related instruction",
2899 insn->sec, insn->offset);
2900 return -1;
2901 }
2902
2903 break;
2904
2905 case OP_DEST_PUSH:
2906 case OP_DEST_PUSHF:
2907 cfi->stack_size += 8;
2908 if (cfa->base == CFI_SP)
2909 cfa->offset += 8;
2910
2911 if (op->src.type != OP_SRC_REG)
2912 break;
2913
2914 if (cfi->drap) {
2915 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2916
2917 /* drap: push %drap */
2918 cfa->base = CFI_BP_INDIRECT;
2919 cfa->offset = -cfi->stack_size;
2920
2921 /* save drap so we know when to restore it */
2922 cfi->drap_offset = -cfi->stack_size;
2923
2924 } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
2925
2926 /* drap: push %rbp */
2927 cfi->stack_size = 0;
2928
2929 } else {
2930
2931 /* drap: push %reg */
2932 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
2933 }
2934
2935 } else {
2936
2937 /* push %reg */
2938 save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
2939 }
2940
2941 /* detect when asm code uses rbp as a scratch register */
2942 if (opts.stackval && insn->func && op->src.reg == CFI_BP &&
2943 cfa->base != CFI_BP)
2944 cfi->bp_scratch = true;
2945 break;
2946
2947 case OP_DEST_REG_INDIRECT:
2948
2949 if (cfi->drap) {
2950 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2951
2952 /* drap: mov %drap, disp(%rbp) */
2953 cfa->base = CFI_BP_INDIRECT;
2954 cfa->offset = op->dest.offset;
2955
2956 /* save drap offset so we know when to restore it */
2957 cfi->drap_offset = op->dest.offset;
2958 } else {
2959
2960 /* drap: mov reg, disp(%rbp) */
2961 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
2962 }
2963
2964 } else if (op->dest.reg == cfa->base) {
2965
2966 /* mov reg, disp(%rbp) */
2967 /* mov reg, disp(%rsp) */
2968 save_reg(cfi, op->src.reg, CFI_CFA,
2969 op->dest.offset - cfi->cfa.offset);
2970
2971 } else if (op->dest.reg == CFI_SP) {
2972
2973 /* mov reg, disp(%rsp) */
2974 save_reg(cfi, op->src.reg, CFI_CFA,
2975 op->dest.offset - cfi->stack_size);
2976
2977 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
2978
2979 /* mov %rsp, (%reg); # setup a stack swizzle. */
2980 cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
2981 cfi->vals[op->dest.reg].offset = cfa->offset;
2982 }
2983
2984 break;
2985
2986 case OP_DEST_MEM:
2987 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
2988 WARN_FUNC("unknown stack-related memory operation",
2989 insn->sec, insn->offset);
2990 return -1;
2991 }
2992
2993 /* pop mem */
2994 cfi->stack_size -= 8;
2995 if (cfa->base == CFI_SP)
2996 cfa->offset -= 8;
2997
2998 break;
2999
3000 default:
3001 WARN_FUNC("unknown stack-related instruction",
3002 insn->sec, insn->offset);
3003 return -1;
3004 }
3005
3006 return 0;
3007 }
3008
3009 /*
3010 * The stack layouts of alternatives instructions can sometimes diverge when
3011 * they have stack modifications. That's fine as long as the potential stack
3012 * layouts don't conflict at any given potential instruction boundary.
3013 *
3014 * Flatten the CFIs of the different alternative code streams (both original
3015 * and replacement) into a single shared CFI array which can be used to detect
3016 * conflicts and nicely feed a linear array of ORC entries to the unwinder.
3017 */
propagate_alt_cfi(struct objtool_file * file,struct instruction * insn)3018 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
3019 {
3020 struct cfi_state **alt_cfi;
3021 int group_off;
3022
3023 if (!insn->alt_group)
3024 return 0;
3025
3026 if (!insn->cfi) {
3027 WARN("CFI missing");
3028 return -1;
3029 }
3030
3031 alt_cfi = insn->alt_group->cfi;
3032 group_off = insn->offset - insn->alt_group->first_insn->offset;
3033
3034 if (!alt_cfi[group_off]) {
3035 alt_cfi[group_off] = insn->cfi;
3036 } else {
3037 if (cficmp(alt_cfi[group_off], insn->cfi)) {
3038 WARN_FUNC("stack layout conflict in alternatives",
3039 insn->sec, insn->offset);
3040 return -1;
3041 }
3042 }
3043
3044 return 0;
3045 }
3046
handle_insn_ops(struct instruction * insn,struct instruction * next_insn,struct insn_state * state)3047 static int handle_insn_ops(struct instruction *insn,
3048 struct instruction *next_insn,
3049 struct insn_state *state)
3050 {
3051 struct stack_op *op;
3052
3053 list_for_each_entry(op, &insn->stack_ops, list) {
3054
3055 if (update_cfi_state(insn, next_insn, &state->cfi, op))
3056 return 1;
3057
3058 if (!insn->alt_group)
3059 continue;
3060
3061 if (op->dest.type == OP_DEST_PUSHF) {
3062 if (!state->uaccess_stack) {
3063 state->uaccess_stack = 1;
3064 } else if (state->uaccess_stack >> 31) {
3065 WARN_FUNC("PUSHF stack exhausted",
3066 insn->sec, insn->offset);
3067 return 1;
3068 }
3069 state->uaccess_stack <<= 1;
3070 state->uaccess_stack |= state->uaccess;
3071 }
3072
3073 if (op->src.type == OP_SRC_POPF) {
3074 if (state->uaccess_stack) {
3075 state->uaccess = state->uaccess_stack & 1;
3076 state->uaccess_stack >>= 1;
3077 if (state->uaccess_stack == 1)
3078 state->uaccess_stack = 0;
3079 }
3080 }
3081 }
3082
3083 return 0;
3084 }
3085
insn_cfi_match(struct instruction * insn,struct cfi_state * cfi2)3086 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
3087 {
3088 struct cfi_state *cfi1 = insn->cfi;
3089 int i;
3090
3091 if (!cfi1) {
3092 WARN("CFI missing");
3093 return false;
3094 }
3095
3096 if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
3097
3098 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
3099 insn->sec, insn->offset,
3100 cfi1->cfa.base, cfi1->cfa.offset,
3101 cfi2->cfa.base, cfi2->cfa.offset);
3102
3103 } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
3104 for (i = 0; i < CFI_NUM_REGS; i++) {
3105 if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
3106 sizeof(struct cfi_reg)))
3107 continue;
3108
3109 WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
3110 insn->sec, insn->offset,
3111 i, cfi1->regs[i].base, cfi1->regs[i].offset,
3112 i, cfi2->regs[i].base, cfi2->regs[i].offset);
3113 break;
3114 }
3115
3116 } else if (cfi1->type != cfi2->type) {
3117
3118 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
3119 insn->sec, insn->offset, cfi1->type, cfi2->type);
3120
3121 } else if (cfi1->drap != cfi2->drap ||
3122 (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
3123 (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
3124
3125 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
3126 insn->sec, insn->offset,
3127 cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
3128 cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
3129
3130 } else
3131 return true;
3132
3133 return false;
3134 }
3135
func_uaccess_safe(struct symbol * func)3136 static inline bool func_uaccess_safe(struct symbol *func)
3137 {
3138 if (func)
3139 return func->uaccess_safe;
3140
3141 return false;
3142 }
3143
call_dest_name(struct instruction * insn)3144 static inline const char *call_dest_name(struct instruction *insn)
3145 {
3146 static char pvname[19];
3147 struct reloc *rel;
3148 int idx;
3149
3150 if (insn->call_dest)
3151 return insn->call_dest->name;
3152
3153 rel = insn_reloc(NULL, insn);
3154 if (rel && !strcmp(rel->sym->name, "pv_ops")) {
3155 idx = (rel->addend / sizeof(void *));
3156 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
3157 return pvname;
3158 }
3159
3160 return "{dynamic}";
3161 }
3162
pv_call_dest(struct objtool_file * file,struct instruction * insn)3163 static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3164 {
3165 struct symbol *target;
3166 struct reloc *rel;
3167 int idx;
3168
3169 rel = insn_reloc(file, insn);
3170 if (!rel || strcmp(rel->sym->name, "pv_ops"))
3171 return false;
3172
3173 idx = (arch_dest_reloc_offset(rel->addend) / sizeof(void *));
3174
3175 if (file->pv_ops[idx].clean)
3176 return true;
3177
3178 file->pv_ops[idx].clean = true;
3179
3180 list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3181 if (!target->sec->noinstr) {
3182 WARN("pv_ops[%d]: %s", idx, target->name);
3183 file->pv_ops[idx].clean = false;
3184 }
3185 }
3186
3187 return file->pv_ops[idx].clean;
3188 }
3189
noinstr_call_dest(struct objtool_file * file,struct instruction * insn,struct symbol * func)3190 static inline bool noinstr_call_dest(struct objtool_file *file,
3191 struct instruction *insn,
3192 struct symbol *func)
3193 {
3194 /*
3195 * We can't deal with indirect function calls at present;
3196 * assume they're instrumented.
3197 */
3198 if (!func) {
3199 if (file->pv_ops)
3200 return pv_call_dest(file, insn);
3201
3202 return false;
3203 }
3204
3205 /*
3206 * If the symbol is from a noinstr section; we good.
3207 */
3208 if (func->sec->noinstr)
3209 return true;
3210
3211 /*
3212 * The __ubsan_handle_*() calls are like WARN(), they only happen when
3213 * something 'BAD' happened. At the risk of taking the machine down,
3214 * let them proceed to get the message out.
3215 */
3216 if (!strncmp(func->name, "__ubsan_handle_", 15))
3217 return true;
3218
3219 return false;
3220 }
3221
validate_call(struct objtool_file * file,struct instruction * insn,struct insn_state * state)3222 static int validate_call(struct objtool_file *file,
3223 struct instruction *insn,
3224 struct insn_state *state)
3225 {
3226 if (state->noinstr && state->instr <= 0 &&
3227 !noinstr_call_dest(file, insn, insn->call_dest)) {
3228 WARN_FUNC("call to %s() leaves .noinstr.text section",
3229 insn->sec, insn->offset, call_dest_name(insn));
3230 return 1;
3231 }
3232
3233 if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
3234 WARN_FUNC("call to %s() with UACCESS enabled",
3235 insn->sec, insn->offset, call_dest_name(insn));
3236 return 1;
3237 }
3238
3239 if (state->df) {
3240 WARN_FUNC("call to %s() with DF set",
3241 insn->sec, insn->offset, call_dest_name(insn));
3242 return 1;
3243 }
3244
3245 return 0;
3246 }
3247
validate_sibling_call(struct objtool_file * file,struct instruction * insn,struct insn_state * state)3248 static int validate_sibling_call(struct objtool_file *file,
3249 struct instruction *insn,
3250 struct insn_state *state)
3251 {
3252 if (has_modified_stack_frame(insn, state)) {
3253 WARN_FUNC("sibling call from callable instruction with modified stack frame",
3254 insn->sec, insn->offset);
3255 return 1;
3256 }
3257
3258 return validate_call(file, insn, state);
3259 }
3260
validate_return(struct symbol * func,struct instruction * insn,struct insn_state * state)3261 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3262 {
3263 if (state->noinstr && state->instr > 0) {
3264 WARN_FUNC("return with instrumentation enabled",
3265 insn->sec, insn->offset);
3266 return 1;
3267 }
3268
3269 if (state->uaccess && !func_uaccess_safe(func)) {
3270 WARN_FUNC("return with UACCESS enabled",
3271 insn->sec, insn->offset);
3272 return 1;
3273 }
3274
3275 if (!state->uaccess && func_uaccess_safe(func)) {
3276 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
3277 insn->sec, insn->offset);
3278 return 1;
3279 }
3280
3281 if (state->df) {
3282 WARN_FUNC("return with DF set",
3283 insn->sec, insn->offset);
3284 return 1;
3285 }
3286
3287 if (func && has_modified_stack_frame(insn, state)) {
3288 WARN_FUNC("return with modified stack frame",
3289 insn->sec, insn->offset);
3290 return 1;
3291 }
3292
3293 if (state->cfi.bp_scratch) {
3294 WARN_FUNC("BP used as a scratch register",
3295 insn->sec, insn->offset);
3296 return 1;
3297 }
3298
3299 return 0;
3300 }
3301
next_insn_to_validate(struct objtool_file * file,struct instruction * insn)3302 static struct instruction *next_insn_to_validate(struct objtool_file *file,
3303 struct instruction *insn)
3304 {
3305 struct alt_group *alt_group = insn->alt_group;
3306
3307 /*
3308 * Simulate the fact that alternatives are patched in-place. When the
3309 * end of a replacement alt_group is reached, redirect objtool flow to
3310 * the end of the original alt_group.
3311 */
3312 if (alt_group && insn == alt_group->last_insn && alt_group->orig_group)
3313 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3314
3315 return next_insn_same_sec(file, insn);
3316 }
3317
3318 /*
3319 * Follow the branch starting at the given instruction, and recursively follow
3320 * any other branches (jumps). Meanwhile, track the frame pointer state at
3321 * each instruction and validate all the rules described in
3322 * tools/objtool/Documentation/objtool.txt.
3323 */
validate_branch(struct objtool_file * file,struct symbol * func,struct instruction * insn,struct insn_state state)3324 static int validate_branch(struct objtool_file *file, struct symbol *func,
3325 struct instruction *insn, struct insn_state state)
3326 {
3327 struct alternative *alt;
3328 struct instruction *next_insn, *prev_insn = NULL;
3329 struct section *sec;
3330 u8 visited;
3331 int ret;
3332
3333 sec = insn->sec;
3334
3335 while (1) {
3336 next_insn = next_insn_to_validate(file, insn);
3337
3338 if (func && insn->func && func != insn->func->pfunc) {
3339 /* Ignore KCFI type preambles, which always fall through */
3340 if (!strncmp(func->name, "__cfi_", 6))
3341 return 0;
3342
3343 WARN("%s() falls through to next function %s()",
3344 func->name, insn->func->name);
3345 return 1;
3346 }
3347
3348 if (func && insn->ignore) {
3349 WARN_FUNC("BUG: why am I validating an ignored function?",
3350 sec, insn->offset);
3351 return 1;
3352 }
3353
3354 visited = VISITED_BRANCH << state.uaccess;
3355 if (insn->visited & VISITED_BRANCH_MASK) {
3356 if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3357 return 1;
3358
3359 if (insn->visited & visited)
3360 return 0;
3361 } else {
3362 nr_insns_visited++;
3363 }
3364
3365 if (state.noinstr)
3366 state.instr += insn->instr;
3367
3368 if (insn->hint) {
3369 if (insn->restore) {
3370 struct instruction *save_insn, *i;
3371
3372 i = insn;
3373 save_insn = NULL;
3374
3375 sym_for_each_insn_continue_reverse(file, func, i) {
3376 if (i->save) {
3377 save_insn = i;
3378 break;
3379 }
3380 }
3381
3382 if (!save_insn) {
3383 WARN_FUNC("no corresponding CFI save for CFI restore",
3384 sec, insn->offset);
3385 return 1;
3386 }
3387
3388 if (!save_insn->visited) {
3389 WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
3390 sec, insn->offset);
3391 return 1;
3392 }
3393
3394 insn->cfi = save_insn->cfi;
3395 nr_cfi_reused++;
3396 }
3397
3398 state.cfi = *insn->cfi;
3399 } else {
3400 /* XXX track if we actually changed state.cfi */
3401
3402 if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3403 insn->cfi = prev_insn->cfi;
3404 nr_cfi_reused++;
3405 } else {
3406 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3407 }
3408 }
3409
3410 insn->visited |= visited;
3411
3412 if (propagate_alt_cfi(file, insn))
3413 return 1;
3414
3415 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
3416 bool skip_orig = false;
3417
3418 list_for_each_entry(alt, &insn->alts, list) {
3419 if (alt->skip_orig)
3420 skip_orig = true;
3421
3422 ret = validate_branch(file, func, alt->insn, state);
3423 if (ret) {
3424 if (opts.backtrace)
3425 BT_FUNC("(alt)", insn);
3426 return ret;
3427 }
3428 }
3429
3430 if (skip_orig)
3431 return 0;
3432 }
3433
3434 if (handle_insn_ops(insn, next_insn, &state))
3435 return 1;
3436
3437 switch (insn->type) {
3438
3439 case INSN_RETURN:
3440 return validate_return(func, insn, &state);
3441
3442 case INSN_CALL:
3443 case INSN_CALL_DYNAMIC:
3444 ret = validate_call(file, insn, &state);
3445 if (ret)
3446 return ret;
3447
3448 if (opts.stackval && func && !is_fentry_call(insn) &&
3449 !has_valid_stack_frame(&state)) {
3450 WARN_FUNC("call without frame pointer save/setup",
3451 sec, insn->offset);
3452 return 1;
3453 }
3454
3455 if (insn->dead_end)
3456 return 0;
3457
3458 break;
3459
3460 case INSN_JUMP_CONDITIONAL:
3461 case INSN_JUMP_UNCONDITIONAL:
3462 if (is_sibling_call(insn)) {
3463 ret = validate_sibling_call(file, insn, &state);
3464 if (ret)
3465 return ret;
3466
3467 } else if (insn->jump_dest) {
3468 ret = validate_branch(file, func,
3469 insn->jump_dest, state);
3470 if (ret) {
3471 if (opts.backtrace)
3472 BT_FUNC("(branch)", insn);
3473 return ret;
3474 }
3475 }
3476
3477 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3478 return 0;
3479
3480 break;
3481
3482 case INSN_JUMP_DYNAMIC:
3483 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3484 if (is_sibling_call(insn)) {
3485 ret = validate_sibling_call(file, insn, &state);
3486 if (ret)
3487 return ret;
3488 }
3489
3490 if (insn->type == INSN_JUMP_DYNAMIC)
3491 return 0;
3492
3493 break;
3494
3495 case INSN_CONTEXT_SWITCH:
3496 if (func && (!next_insn || !next_insn->hint)) {
3497 WARN_FUNC("unsupported instruction in callable function",
3498 sec, insn->offset);
3499 return 1;
3500 }
3501 return 0;
3502
3503 case INSN_STAC:
3504 if (state.uaccess) {
3505 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
3506 return 1;
3507 }
3508
3509 state.uaccess = true;
3510 break;
3511
3512 case INSN_CLAC:
3513 if (!state.uaccess && func) {
3514 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
3515 return 1;
3516 }
3517
3518 if (func_uaccess_safe(func) && !state.uaccess_stack) {
3519 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
3520 return 1;
3521 }
3522
3523 state.uaccess = false;
3524 break;
3525
3526 case INSN_STD:
3527 if (state.df) {
3528 WARN_FUNC("recursive STD", sec, insn->offset);
3529 return 1;
3530 }
3531
3532 state.df = true;
3533 break;
3534
3535 case INSN_CLD:
3536 if (!state.df && func) {
3537 WARN_FUNC("redundant CLD", sec, insn->offset);
3538 return 1;
3539 }
3540
3541 state.df = false;
3542 break;
3543
3544 default:
3545 break;
3546 }
3547
3548 if (insn->dead_end)
3549 return 0;
3550
3551 if (!next_insn) {
3552 if (state.cfi.cfa.base == CFI_UNDEFINED)
3553 return 0;
3554 WARN("%s: unexpected end of section", sec->name);
3555 return 1;
3556 }
3557
3558 prev_insn = insn;
3559 insn = next_insn;
3560 }
3561
3562 return 0;
3563 }
3564
validate_unwind_hints(struct objtool_file * file,struct section * sec)3565 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3566 {
3567 struct instruction *insn;
3568 struct insn_state state;
3569 int ret, warnings = 0;
3570
3571 if (!file->hints)
3572 return 0;
3573
3574 init_insn_state(file, &state, sec);
3575
3576 if (sec) {
3577 insn = find_insn(file, sec, 0);
3578 if (!insn)
3579 return 0;
3580 } else {
3581 insn = list_first_entry(&file->insn_list, typeof(*insn), list);
3582 }
3583
3584 while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) {
3585 if (insn->hint && !insn->visited && !insn->ignore) {
3586 ret = validate_branch(file, insn->func, insn, state);
3587 if (ret && opts.backtrace)
3588 BT_FUNC("<=== (hint)", insn);
3589 warnings += ret;
3590 }
3591
3592 insn = list_next_entry(insn, list);
3593 }
3594
3595 return warnings;
3596 }
3597
3598 /*
3599 * Validate rethunk entry constraint: must untrain RET before the first RET.
3600 *
3601 * Follow every branch (intra-function) and ensure ANNOTATE_UNRET_END comes
3602 * before an actual RET instruction.
3603 */
validate_entry(struct objtool_file * file,struct instruction * insn)3604 static int validate_entry(struct objtool_file *file, struct instruction *insn)
3605 {
3606 struct instruction *next, *dest;
3607 int ret, warnings = 0;
3608
3609 for (;;) {
3610 next = next_insn_to_validate(file, insn);
3611
3612 if (insn->visited & VISITED_ENTRY)
3613 return 0;
3614
3615 insn->visited |= VISITED_ENTRY;
3616
3617 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
3618 struct alternative *alt;
3619 bool skip_orig = false;
3620
3621 list_for_each_entry(alt, &insn->alts, list) {
3622 if (alt->skip_orig)
3623 skip_orig = true;
3624
3625 ret = validate_entry(file, alt->insn);
3626 if (ret) {
3627 if (opts.backtrace)
3628 BT_FUNC("(alt)", insn);
3629 return ret;
3630 }
3631 }
3632
3633 if (skip_orig)
3634 return 0;
3635 }
3636
3637 switch (insn->type) {
3638
3639 case INSN_CALL_DYNAMIC:
3640 case INSN_JUMP_DYNAMIC:
3641 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3642 WARN_FUNC("early indirect call", insn->sec, insn->offset);
3643 return 1;
3644
3645 case INSN_JUMP_UNCONDITIONAL:
3646 case INSN_JUMP_CONDITIONAL:
3647 if (!is_sibling_call(insn)) {
3648 if (!insn->jump_dest) {
3649 WARN_FUNC("unresolved jump target after linking?!?",
3650 insn->sec, insn->offset);
3651 return -1;
3652 }
3653 ret = validate_entry(file, insn->jump_dest);
3654 if (ret) {
3655 if (opts.backtrace) {
3656 BT_FUNC("(branch%s)", insn,
3657 insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : "");
3658 }
3659 return ret;
3660 }
3661
3662 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3663 return 0;
3664
3665 break;
3666 }
3667
3668 /* fallthrough */
3669 case INSN_CALL:
3670 dest = find_insn(file, insn->call_dest->sec,
3671 insn->call_dest->offset);
3672 if (!dest) {
3673 WARN("Unresolved function after linking!?: %s",
3674 insn->call_dest->name);
3675 return -1;
3676 }
3677
3678 ret = validate_entry(file, dest);
3679 if (ret) {
3680 if (opts.backtrace)
3681 BT_FUNC("(call)", insn);
3682 return ret;
3683 }
3684 /*
3685 * If a call returns without error, it must have seen UNTRAIN_RET.
3686 * Therefore any non-error return is a success.
3687 */
3688 return 0;
3689
3690 case INSN_RETURN:
3691 WARN_FUNC("RET before UNTRAIN", insn->sec, insn->offset);
3692 return 1;
3693
3694 case INSN_NOP:
3695 if (insn->retpoline_safe)
3696 return 0;
3697 break;
3698
3699 default:
3700 break;
3701 }
3702
3703 if (!next) {
3704 WARN_FUNC("teh end!", insn->sec, insn->offset);
3705 return -1;
3706 }
3707 insn = next;
3708 }
3709
3710 return warnings;
3711 }
3712
3713 /*
3714 * Validate that all branches starting at 'insn->entry' encounter UNRET_END
3715 * before RET.
3716 */
validate_unret(struct objtool_file * file)3717 static int validate_unret(struct objtool_file *file)
3718 {
3719 struct instruction *insn;
3720 int ret, warnings = 0;
3721
3722 for_each_insn(file, insn) {
3723 if (!insn->entry)
3724 continue;
3725
3726 ret = validate_entry(file, insn);
3727 if (ret < 0) {
3728 WARN_FUNC("Failed UNRET validation", insn->sec, insn->offset);
3729 return ret;
3730 }
3731 warnings += ret;
3732 }
3733
3734 return warnings;
3735 }
3736
validate_retpoline(struct objtool_file * file)3737 static int validate_retpoline(struct objtool_file *file)
3738 {
3739 struct instruction *insn;
3740 int warnings = 0;
3741
3742 for_each_insn(file, insn) {
3743 if (insn->type != INSN_JUMP_DYNAMIC &&
3744 insn->type != INSN_CALL_DYNAMIC &&
3745 insn->type != INSN_RETURN)
3746 continue;
3747
3748 if (insn->retpoline_safe)
3749 continue;
3750
3751 /*
3752 * .init.text code is ran before userspace and thus doesn't
3753 * strictly need retpolines, except for modules which are
3754 * loaded late, they very much do need retpoline in their
3755 * .init.text
3756 */
3757 if (!strcmp(insn->sec->name, ".init.text") && !opts.module)
3758 continue;
3759
3760 if (insn->type == INSN_RETURN) {
3761 if (opts.rethunk) {
3762 WARN_FUNC("'naked' return found in RETHUNK build",
3763 insn->sec, insn->offset);
3764 } else
3765 continue;
3766 } else {
3767 WARN_FUNC("indirect %s found in RETPOLINE build",
3768 insn->sec, insn->offset,
3769 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
3770 }
3771
3772 warnings++;
3773 }
3774
3775 return warnings;
3776 }
3777
is_kasan_insn(struct instruction * insn)3778 static bool is_kasan_insn(struct instruction *insn)
3779 {
3780 return (insn->type == INSN_CALL &&
3781 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
3782 }
3783
is_ubsan_insn(struct instruction * insn)3784 static bool is_ubsan_insn(struct instruction *insn)
3785 {
3786 return (insn->type == INSN_CALL &&
3787 !strcmp(insn->call_dest->name,
3788 "__ubsan_handle_builtin_unreachable"));
3789 }
3790
ignore_unreachable_insn(struct objtool_file * file,struct instruction * insn)3791 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
3792 {
3793 int i;
3794 struct instruction *prev_insn;
3795
3796 if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
3797 return true;
3798
3799 /*
3800 * Ignore alternative replacement instructions. This can happen
3801 * when a whitelisted function uses one of the ALTERNATIVE macros.
3802 */
3803 if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
3804 !strcmp(insn->sec->name, ".altinstr_aux"))
3805 return true;
3806
3807 /*
3808 * Whole archive runs might encounter dead code from weak symbols.
3809 * This is where the linker will have dropped the weak symbol in
3810 * favour of a regular symbol, but leaves the code in place.
3811 *
3812 * In this case we'll find a piece of code (whole function) that is not
3813 * covered by a !section symbol. Ignore them.
3814 */
3815 if (opts.link && !insn->func) {
3816 int size = find_symbol_hole_containing(insn->sec, insn->offset);
3817 unsigned long end = insn->offset + size;
3818
3819 if (!size) /* not a hole */
3820 return false;
3821
3822 if (size < 0) /* hole until the end */
3823 return true;
3824
3825 sec_for_each_insn_continue(file, insn) {
3826 /*
3827 * If we reach a visited instruction at or before the
3828 * end of the hole, ignore the unreachable.
3829 */
3830 if (insn->visited)
3831 return true;
3832
3833 if (insn->offset >= end)
3834 break;
3835
3836 /*
3837 * If this hole jumps to a .cold function, mark it ignore too.
3838 */
3839 if (insn->jump_dest && insn->jump_dest->func &&
3840 strstr(insn->jump_dest->func->name, ".cold")) {
3841 struct instruction *dest = insn->jump_dest;
3842 func_for_each_insn(file, dest->func, dest)
3843 dest->ignore = true;
3844 }
3845 }
3846
3847 return false;
3848 }
3849
3850 if (!insn->func)
3851 return false;
3852
3853 if (insn->func->static_call_tramp)
3854 return true;
3855
3856 /*
3857 * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
3858 * __builtin_unreachable(). The BUG() macro has an unreachable() after
3859 * the UD2, which causes GCC's undefined trap logic to emit another UD2
3860 * (or occasionally a JMP to UD2).
3861 *
3862 * It may also insert a UD2 after calling a __noreturn function.
3863 */
3864 prev_insn = list_prev_entry(insn, list);
3865 if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) &&
3866 (insn->type == INSN_BUG ||
3867 (insn->type == INSN_JUMP_UNCONDITIONAL &&
3868 insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
3869 return true;
3870
3871 /*
3872 * Check if this (or a subsequent) instruction is related to
3873 * CONFIG_UBSAN or CONFIG_KASAN.
3874 *
3875 * End the search at 5 instructions to avoid going into the weeds.
3876 */
3877 for (i = 0; i < 5; i++) {
3878
3879 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
3880 return true;
3881
3882 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
3883 if (insn->jump_dest &&
3884 insn->jump_dest->func == insn->func) {
3885 insn = insn->jump_dest;
3886 continue;
3887 }
3888
3889 break;
3890 }
3891
3892 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
3893 break;
3894
3895 insn = list_next_entry(insn, list);
3896 }
3897
3898 return false;
3899 }
3900
validate_symbol(struct objtool_file * file,struct section * sec,struct symbol * sym,struct insn_state * state)3901 static int validate_symbol(struct objtool_file *file, struct section *sec,
3902 struct symbol *sym, struct insn_state *state)
3903 {
3904 struct instruction *insn;
3905 int ret;
3906
3907 if (!sym->len) {
3908 WARN("%s() is missing an ELF size annotation", sym->name);
3909 return 1;
3910 }
3911
3912 if (sym->pfunc != sym || sym->alias != sym)
3913 return 0;
3914
3915 insn = find_insn(file, sec, sym->offset);
3916 if (!insn || insn->ignore || insn->visited)
3917 return 0;
3918
3919 state->uaccess = sym->uaccess_safe;
3920
3921 ret = validate_branch(file, insn->func, insn, *state);
3922 if (ret && opts.backtrace)
3923 BT_FUNC("<=== (sym)", insn);
3924 return ret;
3925 }
3926
validate_section(struct objtool_file * file,struct section * sec)3927 static int validate_section(struct objtool_file *file, struct section *sec)
3928 {
3929 struct insn_state state;
3930 struct symbol *func;
3931 int warnings = 0;
3932
3933 list_for_each_entry(func, &sec->symbol_list, list) {
3934 if (func->type != STT_FUNC)
3935 continue;
3936
3937 init_insn_state(file, &state, sec);
3938 set_func_state(&state.cfi);
3939
3940 warnings += validate_symbol(file, sec, func, &state);
3941 }
3942
3943 return warnings;
3944 }
3945
validate_noinstr_sections(struct objtool_file * file)3946 static int validate_noinstr_sections(struct objtool_file *file)
3947 {
3948 struct section *sec;
3949 int warnings = 0;
3950
3951 sec = find_section_by_name(file->elf, ".noinstr.text");
3952 if (sec) {
3953 warnings += validate_section(file, sec);
3954 warnings += validate_unwind_hints(file, sec);
3955 }
3956
3957 sec = find_section_by_name(file->elf, ".entry.text");
3958 if (sec) {
3959 warnings += validate_section(file, sec);
3960 warnings += validate_unwind_hints(file, sec);
3961 }
3962
3963 return warnings;
3964 }
3965
validate_functions(struct objtool_file * file)3966 static int validate_functions(struct objtool_file *file)
3967 {
3968 struct section *sec;
3969 int warnings = 0;
3970
3971 for_each_sec(file, sec) {
3972 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
3973 continue;
3974
3975 warnings += validate_section(file, sec);
3976 }
3977
3978 return warnings;
3979 }
3980
mark_endbr_used(struct instruction * insn)3981 static void mark_endbr_used(struct instruction *insn)
3982 {
3983 if (!list_empty(&insn->call_node))
3984 list_del_init(&insn->call_node);
3985 }
3986
validate_ibt_insn(struct objtool_file * file,struct instruction * insn)3987 static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
3988 {
3989 struct instruction *dest;
3990 struct reloc *reloc;
3991 unsigned long off;
3992 int warnings = 0;
3993
3994 /*
3995 * Looking for function pointer load relocations. Ignore
3996 * direct/indirect branches:
3997 */
3998 switch (insn->type) {
3999 case INSN_CALL:
4000 case INSN_CALL_DYNAMIC:
4001 case INSN_JUMP_CONDITIONAL:
4002 case INSN_JUMP_UNCONDITIONAL:
4003 case INSN_JUMP_DYNAMIC:
4004 case INSN_JUMP_DYNAMIC_CONDITIONAL:
4005 case INSN_RETURN:
4006 case INSN_NOP:
4007 return 0;
4008 default:
4009 break;
4010 }
4011
4012 for (reloc = insn_reloc(file, insn);
4013 reloc;
4014 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
4015 reloc->offset + 1,
4016 (insn->offset + insn->len) - (reloc->offset + 1))) {
4017
4018 /*
4019 * static_call_update() references the trampoline, which
4020 * doesn't have (or need) ENDBR. Skip warning in that case.
4021 */
4022 if (reloc->sym->static_call_tramp)
4023 continue;
4024
4025 off = reloc->sym->offset;
4026 if (reloc->type == R_X86_64_PC32 || reloc->type == R_X86_64_PLT32)
4027 off += arch_dest_reloc_offset(reloc->addend);
4028 else
4029 off += reloc->addend;
4030
4031 dest = find_insn(file, reloc->sym->sec, off);
4032 if (!dest)
4033 continue;
4034
4035 if (dest->type == INSN_ENDBR) {
4036 mark_endbr_used(dest);
4037 continue;
4038 }
4039
4040 if (dest->func && dest->func == insn->func) {
4041 /*
4042 * Anything from->to self is either _THIS_IP_ or
4043 * IRET-to-self.
4044 *
4045 * There is no sane way to annotate _THIS_IP_ since the
4046 * compiler treats the relocation as a constant and is
4047 * happy to fold in offsets, skewing any annotation we
4048 * do, leading to vast amounts of false-positives.
4049 *
4050 * There's also compiler generated _THIS_IP_ through
4051 * KCOV and such which we have no hope of annotating.
4052 *
4053 * As such, blanket accept self-references without
4054 * issue.
4055 */
4056 continue;
4057 }
4058
4059 if (dest->noendbr)
4060 continue;
4061
4062 WARN_FUNC("relocation to !ENDBR: %s",
4063 insn->sec, insn->offset,
4064 offstr(dest->sec, dest->offset));
4065
4066 warnings++;
4067 }
4068
4069 return warnings;
4070 }
4071
validate_ibt_data_reloc(struct objtool_file * file,struct reloc * reloc)4072 static int validate_ibt_data_reloc(struct objtool_file *file,
4073 struct reloc *reloc)
4074 {
4075 struct instruction *dest;
4076
4077 dest = find_insn(file, reloc->sym->sec,
4078 reloc->sym->offset + reloc->addend);
4079 if (!dest)
4080 return 0;
4081
4082 if (dest->type == INSN_ENDBR) {
4083 mark_endbr_used(dest);
4084 return 0;
4085 }
4086
4087 if (dest->noendbr)
4088 return 0;
4089
4090 WARN_FUNC("data relocation to !ENDBR: %s",
4091 reloc->sec->base, reloc->offset,
4092 offstr(dest->sec, dest->offset));
4093
4094 return 1;
4095 }
4096
4097 /*
4098 * Validate IBT rules and remove used ENDBR instructions from the seal list.
4099 * Unused ENDBR instructions will be annotated for sealing (i.e., replaced with
4100 * NOPs) later, in create_ibt_endbr_seal_sections().
4101 */
validate_ibt(struct objtool_file * file)4102 static int validate_ibt(struct objtool_file *file)
4103 {
4104 struct section *sec;
4105 struct reloc *reloc;
4106 struct instruction *insn;
4107 int warnings = 0;
4108
4109 for_each_insn(file, insn)
4110 warnings += validate_ibt_insn(file, insn);
4111
4112 for_each_sec(file, sec) {
4113
4114 /* Already done by validate_ibt_insn() */
4115 if (sec->sh.sh_flags & SHF_EXECINSTR)
4116 continue;
4117
4118 if (!sec->reloc)
4119 continue;
4120
4121 /*
4122 * These sections can reference text addresses, but not with
4123 * the intent to indirect branch to them.
4124 */
4125 if ((!strncmp(sec->name, ".discard", 8) &&
4126 strcmp(sec->name, ".discard.ibt_endbr_noseal")) ||
4127 !strncmp(sec->name, ".debug", 6) ||
4128 !strcmp(sec->name, ".altinstructions") ||
4129 !strcmp(sec->name, ".ibt_endbr_seal") ||
4130 !strcmp(sec->name, ".orc_unwind_ip") ||
4131 !strcmp(sec->name, ".parainstructions") ||
4132 !strcmp(sec->name, ".retpoline_sites") ||
4133 !strcmp(sec->name, ".smp_locks") ||
4134 !strcmp(sec->name, ".static_call_sites") ||
4135 !strcmp(sec->name, "_error_injection_whitelist") ||
4136 !strcmp(sec->name, "_kprobe_blacklist") ||
4137 !strcmp(sec->name, "__bug_table") ||
4138 !strcmp(sec->name, "__ex_table") ||
4139 !strcmp(sec->name, "__jump_table") ||
4140 !strcmp(sec->name, "__mcount_loc") ||
4141 !strcmp(sec->name, ".kcfi_traps") ||
4142 strstr(sec->name, "__patchable_function_entries"))
4143 continue;
4144
4145 list_for_each_entry(reloc, &sec->reloc->reloc_list, list)
4146 warnings += validate_ibt_data_reloc(file, reloc);
4147 }
4148
4149 return warnings;
4150 }
4151
validate_sls(struct objtool_file * file)4152 static int validate_sls(struct objtool_file *file)
4153 {
4154 struct instruction *insn, *next_insn;
4155 int warnings = 0;
4156
4157 for_each_insn(file, insn) {
4158 next_insn = next_insn_same_sec(file, insn);
4159
4160 if (insn->retpoline_safe)
4161 continue;
4162
4163 switch (insn->type) {
4164 case INSN_RETURN:
4165 if (!next_insn || next_insn->type != INSN_TRAP) {
4166 WARN_FUNC("missing int3 after ret",
4167 insn->sec, insn->offset);
4168 warnings++;
4169 }
4170
4171 break;
4172 case INSN_JUMP_DYNAMIC:
4173 if (!next_insn || next_insn->type != INSN_TRAP) {
4174 WARN_FUNC("missing int3 after indirect jump",
4175 insn->sec, insn->offset);
4176 warnings++;
4177 }
4178 break;
4179 default:
4180 break;
4181 }
4182 }
4183
4184 return warnings;
4185 }
4186
validate_reachable_instructions(struct objtool_file * file)4187 static int validate_reachable_instructions(struct objtool_file *file)
4188 {
4189 struct instruction *insn;
4190
4191 if (file->ignore_unreachables)
4192 return 0;
4193
4194 for_each_insn(file, insn) {
4195 if (insn->visited || ignore_unreachable_insn(file, insn))
4196 continue;
4197
4198 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
4199 return 1;
4200 }
4201
4202 return 0;
4203 }
4204
check(struct objtool_file * file)4205 int check(struct objtool_file *file)
4206 {
4207 int ret, warnings = 0;
4208
4209 arch_initial_func_cfi_state(&initial_func_cfi);
4210 init_cfi_state(&init_cfi);
4211 init_cfi_state(&func_cfi);
4212 set_func_state(&func_cfi);
4213
4214 if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
4215 goto out;
4216
4217 cfi_hash_add(&init_cfi);
4218 cfi_hash_add(&func_cfi);
4219
4220 ret = decode_sections(file);
4221 if (ret < 0)
4222 goto out;
4223
4224 warnings += ret;
4225
4226 if (list_empty(&file->insn_list))
4227 goto out;
4228
4229 if (opts.retpoline) {
4230 ret = validate_retpoline(file);
4231 if (ret < 0)
4232 return ret;
4233 warnings += ret;
4234 }
4235
4236 if (opts.stackval || opts.orc || opts.uaccess) {
4237 ret = validate_functions(file);
4238 if (ret < 0)
4239 goto out;
4240 warnings += ret;
4241
4242 ret = validate_unwind_hints(file, NULL);
4243 if (ret < 0)
4244 goto out;
4245 warnings += ret;
4246
4247 if (!warnings) {
4248 ret = validate_reachable_instructions(file);
4249 if (ret < 0)
4250 goto out;
4251 warnings += ret;
4252 }
4253
4254 } else if (opts.noinstr) {
4255 ret = validate_noinstr_sections(file);
4256 if (ret < 0)
4257 goto out;
4258 warnings += ret;
4259 }
4260
4261 if (opts.unret) {
4262 /*
4263 * Must be after validate_branch() and friends, it plays
4264 * further games with insn->visited.
4265 */
4266 ret = validate_unret(file);
4267 if (ret < 0)
4268 return ret;
4269 warnings += ret;
4270 }
4271
4272 if (opts.ibt) {
4273 ret = validate_ibt(file);
4274 if (ret < 0)
4275 goto out;
4276 warnings += ret;
4277 }
4278
4279 if (opts.sls) {
4280 ret = validate_sls(file);
4281 if (ret < 0)
4282 goto out;
4283 warnings += ret;
4284 }
4285
4286 if (opts.static_call) {
4287 ret = create_static_call_sections(file);
4288 if (ret < 0)
4289 goto out;
4290 warnings += ret;
4291 }
4292
4293 if (opts.retpoline) {
4294 ret = create_retpoline_sites_sections(file);
4295 if (ret < 0)
4296 goto out;
4297 warnings += ret;
4298 }
4299
4300 if (opts.rethunk) {
4301 ret = create_return_sites_sections(file);
4302 if (ret < 0)
4303 goto out;
4304 warnings += ret;
4305 }
4306
4307 if (opts.mcount) {
4308 ret = create_mcount_loc_sections(file);
4309 if (ret < 0)
4310 goto out;
4311 warnings += ret;
4312 }
4313
4314 if (opts.ibt) {
4315 ret = create_ibt_endbr_seal_sections(file);
4316 if (ret < 0)
4317 goto out;
4318 warnings += ret;
4319 }
4320
4321 if (opts.orc && !list_empty(&file->insn_list)) {
4322 ret = orc_create(file);
4323 if (ret < 0)
4324 goto out;
4325 warnings += ret;
4326 }
4327
4328
4329 if (opts.stats) {
4330 printf("nr_insns_visited: %ld\n", nr_insns_visited);
4331 printf("nr_cfi: %ld\n", nr_cfi);
4332 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
4333 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
4334 }
4335
4336 out:
4337 /*
4338 * For now, don't fail the kernel build on fatal warnings. These
4339 * errors are still fairly common due to the growing matrix of
4340 * supported toolchains and their recent pace of change.
4341 */
4342 return 0;
4343 }
4344