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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
4 */
5
6#include <string.h>
7#include <stdlib.h>
8
9#include <arch/elf.h>
10#include <objtool/builtin.h>
11#include <objtool/cfi.h>
12#include <objtool/arch.h>
13#include <objtool/check.h>
14#include <objtool/special.h>
15#include <objtool/warn.h>
16#include <objtool/endianness.h>
17
18#include <linux/objtool.h>
19#include <linux/hashtable.h>
20#include <linux/kernel.h>
21#include <linux/static_call_types.h>
22
23struct alternative {
24 struct list_head list;
25 struct instruction *insn;
26 bool skip_orig;
27};
28
29struct cfi_init_state initial_func_cfi;
30
31struct instruction *find_insn(struct objtool_file *file,
32 struct section *sec, unsigned long offset)
33{
34 struct instruction *insn;
35
36 hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
37 if (insn->sec == sec && insn->offset == offset)
38 return insn;
39 }
40
41 return NULL;
42}
43
44static struct instruction *next_insn_same_sec(struct objtool_file *file,
45 struct instruction *insn)
46{
47 struct instruction *next = list_next_entry(insn, list);
48
49 if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
50 return NULL;
51
52 return next;
53}
54
55static struct instruction *next_insn_same_func(struct objtool_file *file,
56 struct instruction *insn)
57{
58 struct instruction *next = list_next_entry(insn, list);
59 struct symbol *func = insn->func;
60
61 if (!func)
62 return NULL;
63
64 if (&next->list != &file->insn_list && next->func == func)
65 return next;
66
67 /* Check if we're already in the subfunction: */
68 if (func == func->cfunc)
69 return NULL;
70
71 /* Move to the subfunction: */
72 return find_insn(file, func->cfunc->sec, func->cfunc->offset);
73}
74
75static struct instruction *prev_insn_same_sym(struct objtool_file *file,
76 struct instruction *insn)
77{
78 struct instruction *prev = list_prev_entry(insn, list);
79
80 if (&prev->list != &file->insn_list && prev->func == insn->func)
81 return prev;
82
83 return NULL;
84}
85
86#define func_for_each_insn(file, func, insn) \
87 for (insn = find_insn(file, func->sec, func->offset); \
88 insn; \
89 insn = next_insn_same_func(file, insn))
90
91#define sym_for_each_insn(file, sym, insn) \
92 for (insn = find_insn(file, sym->sec, sym->offset); \
93 insn && &insn->list != &file->insn_list && \
94 insn->sec == sym->sec && \
95 insn->offset < sym->offset + sym->len; \
96 insn = list_next_entry(insn, list))
97
98#define sym_for_each_insn_continue_reverse(file, sym, insn) \
99 for (insn = list_prev_entry(insn, list); \
100 &insn->list != &file->insn_list && \
101 insn->sec == sym->sec && insn->offset >= sym->offset; \
102 insn = list_prev_entry(insn, list))
103
104#define sec_for_each_insn_from(file, insn) \
105 for (; insn; insn = next_insn_same_sec(file, insn))
106
107#define sec_for_each_insn_continue(file, insn) \
108 for (insn = next_insn_same_sec(file, insn); insn; \
109 insn = next_insn_same_sec(file, insn))
110
111static bool is_jump_table_jump(struct instruction *insn)
112{
113 struct alt_group *alt_group = insn->alt_group;
114
115 if (insn->jump_table)
116 return true;
117
118 /* Retpoline alternative for a jump table? */
119 return alt_group && alt_group->orig_group &&
120 alt_group->orig_group->first_insn->jump_table;
121}
122
123static bool is_sibling_call(struct instruction *insn)
124{
125 /*
126 * Assume only ELF functions can make sibling calls. This ensures
127 * sibling call detection consistency between vmlinux.o and individual
128 * objects.
129 */
130 if (!insn->func)
131 return false;
132
133 /* An indirect jump is either a sibling call or a jump to a table. */
134 if (insn->type == INSN_JUMP_DYNAMIC)
135 return !is_jump_table_jump(insn);
136
137 /* add_jump_destinations() sets insn->call_dest for sibling calls. */
138 return (is_static_jump(insn) && insn->call_dest);
139}
140
141/*
142 * This checks to see if the given function is a "noreturn" function.
143 *
144 * For global functions which are outside the scope of this object file, we
145 * have to keep a manual list of them.
146 *
147 * For local functions, we have to detect them manually by simply looking for
148 * the lack of a return instruction.
149 */
150static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
151 int recursion)
152{
153 int i;
154 struct instruction *insn;
155 bool empty = true;
156
157 /*
158 * Unfortunately these have to be hard coded because the noreturn
159 * attribute isn't provided in ELF data.
160 */
161 static const char * const global_noreturns[] = {
162 "__stack_chk_fail",
163 "panic",
164 "do_exit",
165 "do_task_dead",
166 "__module_put_and_exit",
167 "complete_and_exit",
168 "__reiserfs_panic",
169 "lbug_with_loc",
170 "fortify_panic",
171 "usercopy_abort",
172 "machine_real_restart",
173 "rewind_stack_do_exit",
174 "kunit_try_catch_throw",
175 "xen_start_kernel",
176 };
177
178 if (!func)
179 return false;
180
181 if (func->bind == STB_WEAK)
182 return false;
183
184 if (func->bind == STB_GLOBAL)
185 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
186 if (!strcmp(func->name, global_noreturns[i]))
187 return true;
188
189 if (!func->len)
190 return false;
191
192 insn = find_insn(file, func->sec, func->offset);
193 if (!insn->func)
194 return false;
195
196 func_for_each_insn(file, func, insn) {
197 empty = false;
198
199 if (insn->type == INSN_RETURN)
200 return false;
201 }
202
203 if (empty)
204 return false;
205
206 /*
207 * A function can have a sibling call instead of a return. In that
208 * case, the function's dead-end status depends on whether the target
209 * of the sibling call returns.
210 */
211 func_for_each_insn(file, func, insn) {
212 if (is_sibling_call(insn)) {
213 struct instruction *dest = insn->jump_dest;
214
215 if (!dest)
216 /* sibling call to another file */
217 return false;
218
219 /* local sibling call */
220 if (recursion == 5) {
221 /*
222 * Infinite recursion: two functions have
223 * sibling calls to each other. This is a very
224 * rare case. It means they aren't dead ends.
225 */
226 return false;
227 }
228
229 return __dead_end_function(file, dest->func, recursion+1);
230 }
231 }
232
233 return true;
234}
235
236static bool dead_end_function(struct objtool_file *file, struct symbol *func)
237{
238 return __dead_end_function(file, func, 0);
239}
240
241static void init_cfi_state(struct cfi_state *cfi)
242{
243 int i;
244
245 for (i = 0; i < CFI_NUM_REGS; i++) {
246 cfi->regs[i].base = CFI_UNDEFINED;
247 cfi->vals[i].base = CFI_UNDEFINED;
248 }
249 cfi->cfa.base = CFI_UNDEFINED;
250 cfi->drap_reg = CFI_UNDEFINED;
251 cfi->drap_offset = -1;
252}
253
254static void init_insn_state(struct insn_state *state, struct section *sec)
255{
256 memset(state, 0, sizeof(*state));
257 init_cfi_state(&state->cfi);
258
259 /*
260 * We need the full vmlinux for noinstr validation, otherwise we can
261 * not correctly determine insn->call_dest->sec (external symbols do
262 * not have a section).
263 */
264 if (vmlinux && noinstr && sec)
265 state->noinstr = sec->noinstr;
266}
267
268/*
269 * Call the arch-specific instruction decoder for all the instructions and add
270 * them to the global instruction list.
271 */
272static int decode_instructions(struct objtool_file *file)
273{
274 struct section *sec;
275 struct symbol *func;
276 unsigned long offset;
277 struct instruction *insn;
278 unsigned long nr_insns = 0;
279 int ret;
280
281 for_each_sec(file, sec) {
282
283 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
284 continue;
285
286 if (strcmp(sec->name, ".altinstr_replacement") &&
287 strcmp(sec->name, ".altinstr_aux") &&
288 strncmp(sec->name, ".discard.", 9))
289 sec->text = true;
290
291 if (!strcmp(sec->name, ".noinstr.text") ||
292 !strcmp(sec->name, ".entry.text"))
293 sec->noinstr = true;
294
295 for (offset = 0; offset < sec->len; offset += insn->len) {
296 insn = malloc(sizeof(*insn));
297 if (!insn) {
298 WARN("malloc failed");
299 return -1;
300 }
301 memset(insn, 0, sizeof(*insn));
302 INIT_LIST_HEAD(&insn->alts);
303 INIT_LIST_HEAD(&insn->stack_ops);
304 init_cfi_state(&insn->cfi);
305
306 insn->sec = sec;
307 insn->offset = offset;
308
309 ret = arch_decode_instruction(file->elf, sec, offset,
310 sec->len - offset,
311 &insn->len, &insn->type,
312 &insn->immediate,
313 &insn->stack_ops);
314 if (ret)
315 goto err;
316
317 hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
318 list_add_tail(&insn->list, &file->insn_list);
319 nr_insns++;
320 }
321
322 list_for_each_entry(func, &sec->symbol_list, list) {
323 if (func->type != STT_FUNC || func->alias != func)
324 continue;
325
326 if (!find_insn(file, sec, func->offset)) {
327 WARN("%s(): can't find starting instruction",
328 func->name);
329 return -1;
330 }
331
332 sym_for_each_insn(file, func, insn)
333 insn->func = func;
334 }
335 }
336
337 if (stats)
338 printf("nr_insns: %lu\n", nr_insns);
339
340 return 0;
341
342err:
343 free(insn);
344 return ret;
345}
346
347static struct instruction *find_last_insn(struct objtool_file *file,
348 struct section *sec)
349{
350 struct instruction *insn = NULL;
351 unsigned int offset;
352 unsigned int end = (sec->len > 10) ? sec->len - 10 : 0;
353
354 for (offset = sec->len - 1; offset >= end && !insn; offset--)
355 insn = find_insn(file, sec, offset);
356
357 return insn;
358}
359
360/*
361 * Mark "ud2" instructions and manually annotated dead ends.
362 */
363static int add_dead_ends(struct objtool_file *file)
364{
365 struct section *sec;
366 struct reloc *reloc;
367 struct instruction *insn;
368
369 /*
370 * By default, "ud2" is a dead end unless otherwise annotated, because
371 * GCC 7 inserts it for certain divide-by-zero cases.
372 */
373 for_each_insn(file, insn)
374 if (insn->type == INSN_BUG)
375 insn->dead_end = true;
376
377 /*
378 * Check for manually annotated dead ends.
379 */
380 sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
381 if (!sec)
382 goto reachable;
383
384 list_for_each_entry(reloc, &sec->reloc_list, list) {
385 if (reloc->sym->type != STT_SECTION) {
386 WARN("unexpected relocation symbol type in %s", sec->name);
387 return -1;
388 }
389 insn = find_insn(file, reloc->sym->sec, reloc->addend);
390 if (insn)
391 insn = list_prev_entry(insn, list);
392 else if (reloc->addend == reloc->sym->sec->len) {
393 insn = find_last_insn(file, reloc->sym->sec);
394 if (!insn) {
395 WARN("can't find unreachable insn at %s+0x%x",
396 reloc->sym->sec->name, reloc->addend);
397 return -1;
398 }
399 } else {
400 WARN("can't find unreachable insn at %s+0x%x",
401 reloc->sym->sec->name, reloc->addend);
402 return -1;
403 }
404
405 insn->dead_end = true;
406 }
407
408reachable:
409 /*
410 * These manually annotated reachable checks are needed for GCC 4.4,
411 * where the Linux unreachable() macro isn't supported. In that case
412 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
413 * not a dead end.
414 */
415 sec = find_section_by_name(file->elf, ".rela.discard.reachable");
416 if (!sec)
417 return 0;
418
419 list_for_each_entry(reloc, &sec->reloc_list, list) {
420 if (reloc->sym->type != STT_SECTION) {
421 WARN("unexpected relocation symbol type in %s", sec->name);
422 return -1;
423 }
424 insn = find_insn(file, reloc->sym->sec, reloc->addend);
425 if (insn)
426 insn = list_prev_entry(insn, list);
427 else if (reloc->addend == reloc->sym->sec->len) {
428 insn = find_last_insn(file, reloc->sym->sec);
429 if (!insn) {
430 WARN("can't find reachable insn at %s+0x%x",
431 reloc->sym->sec->name, reloc->addend);
432 return -1;
433 }
434 } else {
435 WARN("can't find reachable insn at %s+0x%x",
436 reloc->sym->sec->name, reloc->addend);
437 return -1;
438 }
439
440 insn->dead_end = false;
441 }
442
443 return 0;
444}
445
446static int create_static_call_sections(struct objtool_file *file)
447{
448 struct section *sec;
449 struct static_call_site *site;
450 struct instruction *insn;
451 struct symbol *key_sym;
452 char *key_name, *tmp;
453 int idx;
454
455 sec = find_section_by_name(file->elf, ".static_call_sites");
456 if (sec) {
457 INIT_LIST_HEAD(&file->static_call_list);
458 WARN("file already has .static_call_sites section, skipping");
459 return 0;
460 }
461
462 if (list_empty(&file->static_call_list))
463 return 0;
464
465 idx = 0;
466 list_for_each_entry(insn, &file->static_call_list, call_node)
467 idx++;
468
469 sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE,
470 sizeof(struct static_call_site), idx);
471 if (!sec)
472 return -1;
473
474 idx = 0;
475 list_for_each_entry(insn, &file->static_call_list, call_node) {
476
477 site = (struct static_call_site *)sec->data->d_buf + idx;
478 memset(site, 0, sizeof(struct static_call_site));
479
480 /* populate reloc for 'addr' */
481 if (elf_add_reloc_to_insn(file->elf, sec,
482 idx * sizeof(struct static_call_site),
483 R_X86_64_PC32,
484 insn->sec, insn->offset))
485 return -1;
486
487 /* find key symbol */
488 key_name = strdup(insn->call_dest->name);
489 if (!key_name) {
490 perror("strdup");
491 return -1;
492 }
493 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
494 STATIC_CALL_TRAMP_PREFIX_LEN)) {
495 WARN("static_call: trampoline name malformed: %s", key_name);
496 return -1;
497 }
498 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
499 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
500
501 key_sym = find_symbol_by_name(file->elf, tmp);
502 if (!key_sym) {
503 if (!module) {
504 WARN("static_call: can't find static_call_key symbol: %s", tmp);
505 return -1;
506 }
507
508 /*
509 * For modules(), the key might not be exported, which
510 * means the module can make static calls but isn't
511 * allowed to change them.
512 *
513 * In that case we temporarily set the key to be the
514 * trampoline address. This is fixed up in
515 * static_call_add_module().
516 */
517 key_sym = insn->call_dest;
518 }
519 free(key_name);
520
521 /* populate reloc for 'key' */
522 if (elf_add_reloc(file->elf, sec,
523 idx * sizeof(struct static_call_site) + 4,
524 R_X86_64_PC32, key_sym,
525 is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
526 return -1;
527
528 idx++;
529 }
530
531 return 0;
532}
533
534static int create_mcount_loc_sections(struct objtool_file *file)
535{
536 struct section *sec;
537 unsigned long *loc;
538 struct instruction *insn;
539 int idx;
540
541 sec = find_section_by_name(file->elf, "__mcount_loc");
542 if (sec) {
543 INIT_LIST_HEAD(&file->mcount_loc_list);
544 WARN("file already has __mcount_loc section, skipping");
545 return 0;
546 }
547
548 if (list_empty(&file->mcount_loc_list))
549 return 0;
550
551 idx = 0;
552 list_for_each_entry(insn, &file->mcount_loc_list, mcount_loc_node)
553 idx++;
554
555 sec = elf_create_section(file->elf, "__mcount_loc", 0, sizeof(unsigned long), idx);
556 if (!sec)
557 return -1;
558
559 idx = 0;
560 list_for_each_entry(insn, &file->mcount_loc_list, mcount_loc_node) {
561
562 loc = (unsigned long *)sec->data->d_buf + idx;
563 memset(loc, 0, sizeof(unsigned long));
564
565 if (elf_add_reloc_to_insn(file->elf, sec,
566 idx * sizeof(unsigned long),
567 R_X86_64_64,
568 insn->sec, insn->offset))
569 return -1;
570
571 idx++;
572 }
573
574 return 0;
575}
576
577/*
578 * Warnings shouldn't be reported for ignored functions.
579 */
580static void add_ignores(struct objtool_file *file)
581{
582 struct instruction *insn;
583 struct section *sec;
584 struct symbol *func;
585 struct reloc *reloc;
586
587 sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
588 if (!sec)
589 return;
590
591 list_for_each_entry(reloc, &sec->reloc_list, list) {
592 switch (reloc->sym->type) {
593 case STT_FUNC:
594 func = reloc->sym;
595 break;
596
597 case STT_SECTION:
598 func = find_func_by_offset(reloc->sym->sec, reloc->addend);
599 if (!func)
600 continue;
601 break;
602
603 default:
604 WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type);
605 continue;
606 }
607
608 func_for_each_insn(file, func, insn)
609 insn->ignore = true;
610 }
611}
612
613/*
614 * This is a whitelist of functions that is allowed to be called with AC set.
615 * The list is meant to be minimal and only contains compiler instrumentation
616 * ABI and a few functions used to implement *_{to,from}_user() functions.
617 *
618 * These functions must not directly change AC, but may PUSHF/POPF.
619 */
620static const char *uaccess_safe_builtin[] = {
621 /* KASAN */
622 "kasan_report",
623 "kasan_check_range",
624 /* KASAN out-of-line */
625 "__asan_loadN_noabort",
626 "__asan_load1_noabort",
627 "__asan_load2_noabort",
628 "__asan_load4_noabort",
629 "__asan_load8_noabort",
630 "__asan_load16_noabort",
631 "__asan_storeN_noabort",
632 "__asan_store1_noabort",
633 "__asan_store2_noabort",
634 "__asan_store4_noabort",
635 "__asan_store8_noabort",
636 "__asan_store16_noabort",
637 "__kasan_check_read",
638 "__kasan_check_write",
639 /* KASAN in-line */
640 "__asan_report_load_n_noabort",
641 "__asan_report_load1_noabort",
642 "__asan_report_load2_noabort",
643 "__asan_report_load4_noabort",
644 "__asan_report_load8_noabort",
645 "__asan_report_load16_noabort",
646 "__asan_report_store_n_noabort",
647 "__asan_report_store1_noabort",
648 "__asan_report_store2_noabort",
649 "__asan_report_store4_noabort",
650 "__asan_report_store8_noabort",
651 "__asan_report_store16_noabort",
652 /* KCSAN */
653 "__kcsan_check_access",
654 "kcsan_found_watchpoint",
655 "kcsan_setup_watchpoint",
656 "kcsan_check_scoped_accesses",
657 "kcsan_disable_current",
658 "kcsan_enable_current_nowarn",
659 /* KCSAN/TSAN */
660 "__tsan_func_entry",
661 "__tsan_func_exit",
662 "__tsan_read_range",
663 "__tsan_write_range",
664 "__tsan_read1",
665 "__tsan_read2",
666 "__tsan_read4",
667 "__tsan_read8",
668 "__tsan_read16",
669 "__tsan_write1",
670 "__tsan_write2",
671 "__tsan_write4",
672 "__tsan_write8",
673 "__tsan_write16",
674 "__tsan_read_write1",
675 "__tsan_read_write2",
676 "__tsan_read_write4",
677 "__tsan_read_write8",
678 "__tsan_read_write16",
679 "__tsan_atomic8_load",
680 "__tsan_atomic16_load",
681 "__tsan_atomic32_load",
682 "__tsan_atomic64_load",
683 "__tsan_atomic8_store",
684 "__tsan_atomic16_store",
685 "__tsan_atomic32_store",
686 "__tsan_atomic64_store",
687 "__tsan_atomic8_exchange",
688 "__tsan_atomic16_exchange",
689 "__tsan_atomic32_exchange",
690 "__tsan_atomic64_exchange",
691 "__tsan_atomic8_fetch_add",
692 "__tsan_atomic16_fetch_add",
693 "__tsan_atomic32_fetch_add",
694 "__tsan_atomic64_fetch_add",
695 "__tsan_atomic8_fetch_sub",
696 "__tsan_atomic16_fetch_sub",
697 "__tsan_atomic32_fetch_sub",
698 "__tsan_atomic64_fetch_sub",
699 "__tsan_atomic8_fetch_and",
700 "__tsan_atomic16_fetch_and",
701 "__tsan_atomic32_fetch_and",
702 "__tsan_atomic64_fetch_and",
703 "__tsan_atomic8_fetch_or",
704 "__tsan_atomic16_fetch_or",
705 "__tsan_atomic32_fetch_or",
706 "__tsan_atomic64_fetch_or",
707 "__tsan_atomic8_fetch_xor",
708 "__tsan_atomic16_fetch_xor",
709 "__tsan_atomic32_fetch_xor",
710 "__tsan_atomic64_fetch_xor",
711 "__tsan_atomic8_fetch_nand",
712 "__tsan_atomic16_fetch_nand",
713 "__tsan_atomic32_fetch_nand",
714 "__tsan_atomic64_fetch_nand",
715 "__tsan_atomic8_compare_exchange_strong",
716 "__tsan_atomic16_compare_exchange_strong",
717 "__tsan_atomic32_compare_exchange_strong",
718 "__tsan_atomic64_compare_exchange_strong",
719 "__tsan_atomic8_compare_exchange_weak",
720 "__tsan_atomic16_compare_exchange_weak",
721 "__tsan_atomic32_compare_exchange_weak",
722 "__tsan_atomic64_compare_exchange_weak",
723 "__tsan_atomic8_compare_exchange_val",
724 "__tsan_atomic16_compare_exchange_val",
725 "__tsan_atomic32_compare_exchange_val",
726 "__tsan_atomic64_compare_exchange_val",
727 "__tsan_atomic_thread_fence",
728 "__tsan_atomic_signal_fence",
729 /* KCOV */
730 "write_comp_data",
731 "check_kcov_mode",
732 "__sanitizer_cov_trace_pc",
733 "__sanitizer_cov_trace_const_cmp1",
734 "__sanitizer_cov_trace_const_cmp2",
735 "__sanitizer_cov_trace_const_cmp4",
736 "__sanitizer_cov_trace_const_cmp8",
737 "__sanitizer_cov_trace_cmp1",
738 "__sanitizer_cov_trace_cmp2",
739 "__sanitizer_cov_trace_cmp4",
740 "__sanitizer_cov_trace_cmp8",
741 "__sanitizer_cov_trace_switch",
742 /* UBSAN */
743 "ubsan_type_mismatch_common",
744 "__ubsan_handle_type_mismatch",
745 "__ubsan_handle_type_mismatch_v1",
746 "__ubsan_handle_shift_out_of_bounds",
747 /* misc */
748 "csum_partial_copy_generic",
749 "copy_mc_fragile",
750 "copy_mc_fragile_handle_tail",
751 "copy_mc_enhanced_fast_string",
752 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
753 NULL
754};
755
756static void add_uaccess_safe(struct objtool_file *file)
757{
758 struct symbol *func;
759 const char **name;
760
761 if (!uaccess)
762 return;
763
764 for (name = uaccess_safe_builtin; *name; name++) {
765 func = find_symbol_by_name(file->elf, *name);
766 if (!func)
767 continue;
768
769 func->uaccess_safe = true;
770 }
771}
772
773/*
774 * FIXME: For now, just ignore any alternatives which add retpolines. This is
775 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
776 * But it at least allows objtool to understand the control flow *around* the
777 * retpoline.
778 */
779static int add_ignore_alternatives(struct objtool_file *file)
780{
781 struct section *sec;
782 struct reloc *reloc;
783 struct instruction *insn;
784
785 sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
786 if (!sec)
787 return 0;
788
789 list_for_each_entry(reloc, &sec->reloc_list, list) {
790 if (reloc->sym->type != STT_SECTION) {
791 WARN("unexpected relocation symbol type in %s", sec->name);
792 return -1;
793 }
794
795 insn = find_insn(file, reloc->sym->sec, reloc->addend);
796 if (!insn) {
797 WARN("bad .discard.ignore_alts entry");
798 return -1;
799 }
800
801 insn->ignore_alts = true;
802 }
803
804 return 0;
805}
806
807__weak bool arch_is_retpoline(struct symbol *sym)
808{
809 return false;
810}
811
812#define NEGATIVE_RELOC ((void *)-1L)
813
814static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
815{
816 if (insn->reloc == NEGATIVE_RELOC)
817 return NULL;
818
819 if (!insn->reloc) {
820 insn->reloc = find_reloc_by_dest_range(file->elf, insn->sec,
821 insn->offset, insn->len);
822 if (!insn->reloc) {
823 insn->reloc = NEGATIVE_RELOC;
824 return NULL;
825 }
826 }
827
828 return insn->reloc;
829}
830
831/*
832 * Find the destination instructions for all jumps.
833 */
834static int add_jump_destinations(struct objtool_file *file)
835{
836 struct instruction *insn;
837 struct reloc *reloc;
838 struct section *dest_sec;
839 unsigned long dest_off;
840
841 for_each_insn(file, insn) {
842 if (!is_static_jump(insn))
843 continue;
844
845 reloc = insn_reloc(file, insn);
846 if (!reloc) {
847 dest_sec = insn->sec;
848 dest_off = arch_jump_destination(insn);
849 } else if (reloc->sym->type == STT_SECTION) {
850 dest_sec = reloc->sym->sec;
851 dest_off = arch_dest_reloc_offset(reloc->addend);
852 } else if (arch_is_retpoline(reloc->sym)) {
853 /*
854 * Retpoline jumps are really dynamic jumps in
855 * disguise, so convert them accordingly.
856 */
857 if (insn->type == INSN_JUMP_UNCONDITIONAL)
858 insn->type = INSN_JUMP_DYNAMIC;
859 else
860 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
861
862 list_add_tail(&insn->call_node,
863 &file->retpoline_call_list);
864
865 insn->retpoline_safe = true;
866 continue;
867 } else if (insn->func) {
868 /* internal or external sibling call (with reloc) */
869 insn->call_dest = reloc->sym;
870 if (insn->call_dest->static_call_tramp) {
871 list_add_tail(&insn->call_node,
872 &file->static_call_list);
873 }
874 continue;
875 } else if (reloc->sym->sec->idx) {
876 dest_sec = reloc->sym->sec;
877 dest_off = reloc->sym->sym.st_value +
878 arch_dest_reloc_offset(reloc->addend);
879 } else {
880 /* non-func asm code jumping to another file */
881 continue;
882 }
883
884 insn->jump_dest = find_insn(file, dest_sec, dest_off);
885 if (!insn->jump_dest) {
886
887 /*
888 * This is a special case where an alt instruction
889 * jumps past the end of the section. These are
890 * handled later in handle_group_alt().
891 */
892 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
893 continue;
894
895 WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
896 insn->sec, insn->offset, dest_sec->name,
897 dest_off);
898 return -1;
899 }
900
901 /*
902 * Cross-function jump.
903 */
904 if (insn->func && insn->jump_dest->func &&
905 insn->func != insn->jump_dest->func) {
906
907 /*
908 * For GCC 8+, create parent/child links for any cold
909 * subfunctions. This is _mostly_ redundant with a
910 * similar initialization in read_symbols().
911 *
912 * If a function has aliases, we want the *first* such
913 * function in the symbol table to be the subfunction's
914 * parent. In that case we overwrite the
915 * initialization done in read_symbols().
916 *
917 * However this code can't completely replace the
918 * read_symbols() code because this doesn't detect the
919 * case where the parent function's only reference to a
920 * subfunction is through a jump table.
921 */
922 if (!strstr(insn->func->name, ".cold") &&
923 strstr(insn->jump_dest->func->name, ".cold")) {
924 insn->func->cfunc = insn->jump_dest->func;
925 insn->jump_dest->func->pfunc = insn->func;
926
927 } else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
928 insn->jump_dest->offset == insn->jump_dest->func->offset) {
929
930 /* internal sibling call (without reloc) */
931 insn->call_dest = insn->jump_dest->func;
932 if (insn->call_dest->static_call_tramp) {
933 list_add_tail(&insn->call_node,
934 &file->static_call_list);
935 }
936 }
937 }
938 }
939
940 return 0;
941}
942
943static void remove_insn_ops(struct instruction *insn)
944{
945 struct stack_op *op, *tmp;
946
947 list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
948 list_del(&op->list);
949 free(op);
950 }
951}
952
953static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
954{
955 struct symbol *call_dest;
956
957 call_dest = find_func_by_offset(sec, offset);
958 if (!call_dest)
959 call_dest = find_symbol_by_offset(sec, offset);
960
961 return call_dest;
962}
963
964/*
965 * Find the destination instructions for all calls.
966 */
967static int add_call_destinations(struct objtool_file *file)
968{
969 struct instruction *insn;
970 unsigned long dest_off;
971 struct reloc *reloc;
972
973 for_each_insn(file, insn) {
974 if (insn->type != INSN_CALL)
975 continue;
976
977 reloc = insn_reloc(file, insn);
978 if (!reloc) {
979 dest_off = arch_jump_destination(insn);
980 insn->call_dest = find_call_destination(insn->sec, dest_off);
981
982 if (insn->ignore)
983 continue;
984
985 if (!insn->call_dest) {
986 WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);
987 return -1;
988 }
989
990 if (insn->func && insn->call_dest->type != STT_FUNC) {
991 WARN_FUNC("unsupported call to non-function",
992 insn->sec, insn->offset);
993 return -1;
994 }
995
996 } else if (reloc->sym->type == STT_SECTION) {
997 dest_off = arch_dest_reloc_offset(reloc->addend);
998 insn->call_dest = find_call_destination(reloc->sym->sec,
999 dest_off);
1000 if (!insn->call_dest) {
1001 WARN_FUNC("can't find call dest symbol at %s+0x%lx",
1002 insn->sec, insn->offset,
1003 reloc->sym->sec->name,
1004 dest_off);
1005 return -1;
1006 }
1007
1008 } else if (arch_is_retpoline(reloc->sym)) {
1009 /*
1010 * Retpoline calls are really dynamic calls in
1011 * disguise, so convert them accordingly.
1012 */
1013 insn->type = INSN_CALL_DYNAMIC;
1014 insn->retpoline_safe = true;
1015
1016 list_add_tail(&insn->call_node,
1017 &file->retpoline_call_list);
1018
1019 remove_insn_ops(insn);
1020 continue;
1021
1022 } else
1023 insn->call_dest = reloc->sym;
1024
1025 if (insn->call_dest && insn->call_dest->static_call_tramp) {
1026 list_add_tail(&insn->call_node,
1027 &file->static_call_list);
1028 }
1029
1030 /*
1031 * Many compilers cannot disable KCOV with a function attribute
1032 * so they need a little help, NOP out any KCOV calls from noinstr
1033 * text.
1034 */
1035 if (insn->sec->noinstr &&
1036 !strncmp(insn->call_dest->name, "__sanitizer_cov_", 16)) {
1037 if (reloc) {
1038 reloc->type = R_NONE;
1039 elf_write_reloc(file->elf, reloc);
1040 }
1041
1042 elf_write_insn(file->elf, insn->sec,
1043 insn->offset, insn->len,
1044 arch_nop_insn(insn->len));
1045 insn->type = INSN_NOP;
1046 }
1047
1048 if (mcount && !strcmp(insn->call_dest->name, "__fentry__")) {
1049 if (reloc) {
1050 reloc->type = R_NONE;
1051 elf_write_reloc(file->elf, reloc);
1052 }
1053
1054 elf_write_insn(file->elf, insn->sec,
1055 insn->offset, insn->len,
1056 arch_nop_insn(insn->len));
1057
1058 insn->type = INSN_NOP;
1059
1060 list_add_tail(&insn->mcount_loc_node,
1061 &file->mcount_loc_list);
1062 }
1063
1064 /*
1065 * Whatever stack impact regular CALLs have, should be undone
1066 * by the RETURN of the called function.
1067 *
1068 * Annotated intra-function calls retain the stack_ops but
1069 * are converted to JUMP, see read_intra_function_calls().
1070 */
1071 remove_insn_ops(insn);
1072 }
1073
1074 return 0;
1075}
1076
1077/*
1078 * The .alternatives section requires some extra special care over and above
1079 * other special sections because alternatives are patched in place.
1080 */
1081static int handle_group_alt(struct objtool_file *file,
1082 struct special_alt *special_alt,
1083 struct instruction *orig_insn,
1084 struct instruction **new_insn)
1085{
1086 struct instruction *last_orig_insn, *last_new_insn = NULL, *insn, *nop = NULL;
1087 struct alt_group *orig_alt_group, *new_alt_group;
1088 unsigned long dest_off;
1089
1090
1091 orig_alt_group = malloc(sizeof(*orig_alt_group));
1092 if (!orig_alt_group) {
1093 WARN("malloc failed");
1094 return -1;
1095 }
1096 orig_alt_group->cfi = calloc(special_alt->orig_len,
1097 sizeof(struct cfi_state *));
1098 if (!orig_alt_group->cfi) {
1099 WARN("calloc failed");
1100 return -1;
1101 }
1102
1103 last_orig_insn = NULL;
1104 insn = orig_insn;
1105 sec_for_each_insn_from(file, insn) {
1106 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1107 break;
1108
1109 insn->alt_group = orig_alt_group;
1110 last_orig_insn = insn;
1111 }
1112 orig_alt_group->orig_group = NULL;
1113 orig_alt_group->first_insn = orig_insn;
1114 orig_alt_group->last_insn = last_orig_insn;
1115
1116
1117 new_alt_group = malloc(sizeof(*new_alt_group));
1118 if (!new_alt_group) {
1119 WARN("malloc failed");
1120 return -1;
1121 }
1122
1123 if (special_alt->new_len < special_alt->orig_len) {
1124 /*
1125 * Insert a fake nop at the end to make the replacement
1126 * alt_group the same size as the original. This is needed to
1127 * allow propagate_alt_cfi() to do its magic. When the last
1128 * instruction affects the stack, the instruction after it (the
1129 * nop) will propagate the new state to the shared CFI array.
1130 */
1131 nop = malloc(sizeof(*nop));
1132 if (!nop) {
1133 WARN("malloc failed");
1134 return -1;
1135 }
1136 memset(nop, 0, sizeof(*nop));
1137 INIT_LIST_HEAD(&nop->alts);
1138 INIT_LIST_HEAD(&nop->stack_ops);
1139 init_cfi_state(&nop->cfi);
1140
1141 nop->sec = special_alt->new_sec;
1142 nop->offset = special_alt->new_off + special_alt->new_len;
1143 nop->len = special_alt->orig_len - special_alt->new_len;
1144 nop->type = INSN_NOP;
1145 nop->func = orig_insn->func;
1146 nop->alt_group = new_alt_group;
1147 nop->ignore = orig_insn->ignore_alts;
1148 }
1149
1150 if (!special_alt->new_len) {
1151 *new_insn = nop;
1152 goto end;
1153 }
1154
1155 insn = *new_insn;
1156 sec_for_each_insn_from(file, insn) {
1157 struct reloc *alt_reloc;
1158
1159 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1160 break;
1161
1162 last_new_insn = insn;
1163
1164 insn->ignore = orig_insn->ignore_alts;
1165 insn->func = orig_insn->func;
1166 insn->alt_group = new_alt_group;
1167
1168 /*
1169 * Since alternative replacement code is copy/pasted by the
1170 * kernel after applying relocations, generally such code can't
1171 * have relative-address relocation references to outside the
1172 * .altinstr_replacement section, unless the arch's
1173 * alternatives code can adjust the relative offsets
1174 * accordingly.
1175 */
1176 alt_reloc = insn_reloc(file, insn);
1177 if (alt_reloc &&
1178 !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1179
1180 WARN_FUNC("unsupported relocation in alternatives section",
1181 insn->sec, insn->offset);
1182 return -1;
1183 }
1184
1185 if (!is_static_jump(insn))
1186 continue;
1187
1188 if (!insn->immediate)
1189 continue;
1190
1191 dest_off = arch_jump_destination(insn);
1192 if (dest_off == special_alt->new_off + special_alt->new_len)
1193 insn->jump_dest = next_insn_same_sec(file, last_orig_insn);
1194
1195 if (!insn->jump_dest) {
1196 WARN_FUNC("can't find alternative jump destination",
1197 insn->sec, insn->offset);
1198 return -1;
1199 }
1200 }
1201
1202 if (!last_new_insn) {
1203 WARN_FUNC("can't find last new alternative instruction",
1204 special_alt->new_sec, special_alt->new_off);
1205 return -1;
1206 }
1207
1208 if (nop)
1209 list_add(&nop->list, &last_new_insn->list);
1210end:
1211 new_alt_group->orig_group = orig_alt_group;
1212 new_alt_group->first_insn = *new_insn;
1213 new_alt_group->last_insn = nop ? : last_new_insn;
1214 new_alt_group->cfi = orig_alt_group->cfi;
1215 return 0;
1216}
1217
1218/*
1219 * A jump table entry can either convert a nop to a jump or a jump to a nop.
1220 * If the original instruction is a jump, make the alt entry an effective nop
1221 * by just skipping the original instruction.
1222 */
1223static int handle_jump_alt(struct objtool_file *file,
1224 struct special_alt *special_alt,
1225 struct instruction *orig_insn,
1226 struct instruction **new_insn)
1227{
1228 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1229 orig_insn->type != INSN_NOP) {
1230
1231 WARN_FUNC("unsupported instruction at jump label",
1232 orig_insn->sec, orig_insn->offset);
1233 return -1;
1234 }
1235
1236 if (special_alt->key_addend & 2) {
1237 struct reloc *reloc = insn_reloc(file, orig_insn);
1238
1239 if (reloc) {
1240 reloc->type = R_NONE;
1241 elf_write_reloc(file->elf, reloc);
1242 }
1243 elf_write_insn(file->elf, orig_insn->sec,
1244 orig_insn->offset, orig_insn->len,
1245 arch_nop_insn(orig_insn->len));
1246 orig_insn->type = INSN_NOP;
1247 }
1248
1249 if (orig_insn->type == INSN_NOP) {
1250 if (orig_insn->len == 2)
1251 file->jl_nop_short++;
1252 else
1253 file->jl_nop_long++;
1254
1255 return 0;
1256 }
1257
1258 if (orig_insn->len == 2)
1259 file->jl_short++;
1260 else
1261 file->jl_long++;
1262
1263 *new_insn = list_next_entry(orig_insn, list);
1264 return 0;
1265}
1266
1267/*
1268 * Read all the special sections which have alternate instructions which can be
1269 * patched in or redirected to at runtime. Each instruction having alternate
1270 * instruction(s) has them added to its insn->alts list, which will be
1271 * traversed in validate_branch().
1272 */
1273static int add_special_section_alts(struct objtool_file *file)
1274{
1275 struct list_head special_alts;
1276 struct instruction *orig_insn, *new_insn;
1277 struct special_alt *special_alt, *tmp;
1278 struct alternative *alt;
1279 int ret;
1280
1281 ret = special_get_alts(file->elf, &special_alts);
1282 if (ret)
1283 return ret;
1284
1285 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1286
1287 orig_insn = find_insn(file, special_alt->orig_sec,
1288 special_alt->orig_off);
1289 if (!orig_insn) {
1290 WARN_FUNC("special: can't find orig instruction",
1291 special_alt->orig_sec, special_alt->orig_off);
1292 ret = -1;
1293 goto out;
1294 }
1295
1296 new_insn = NULL;
1297 if (!special_alt->group || special_alt->new_len) {
1298 new_insn = find_insn(file, special_alt->new_sec,
1299 special_alt->new_off);
1300 if (!new_insn) {
1301 WARN_FUNC("special: can't find new instruction",
1302 special_alt->new_sec,
1303 special_alt->new_off);
1304 ret = -1;
1305 goto out;
1306 }
1307 }
1308
1309 if (special_alt->group) {
1310 if (!special_alt->orig_len) {
1311 WARN_FUNC("empty alternative entry",
1312 orig_insn->sec, orig_insn->offset);
1313 continue;
1314 }
1315
1316 ret = handle_group_alt(file, special_alt, orig_insn,
1317 &new_insn);
1318 if (ret)
1319 goto out;
1320 } else if (special_alt->jump_or_nop) {
1321 ret = handle_jump_alt(file, special_alt, orig_insn,
1322 &new_insn);
1323 if (ret)
1324 goto out;
1325 }
1326
1327 alt = malloc(sizeof(*alt));
1328 if (!alt) {
1329 WARN("malloc failed");
1330 ret = -1;
1331 goto out;
1332 }
1333
1334 alt->insn = new_insn;
1335 alt->skip_orig = special_alt->skip_orig;
1336 orig_insn->ignore_alts |= special_alt->skip_alt;
1337 list_add_tail(&alt->list, &orig_insn->alts);
1338
1339 list_del(&special_alt->list);
1340 free(special_alt);
1341 }
1342
1343 if (stats) {
1344 printf("jl\\\tNOP\tJMP\n");
1345 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
1346 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
1347 }
1348
1349out:
1350 return ret;
1351}
1352
1353static int add_jump_table(struct objtool_file *file, struct instruction *insn,
1354 struct reloc *table)
1355{
1356 struct reloc *reloc = table;
1357 struct instruction *dest_insn;
1358 struct alternative *alt;
1359 struct symbol *pfunc = insn->func->pfunc;
1360 unsigned int prev_offset = 0;
1361
1362 /*
1363 * Each @reloc is a switch table relocation which points to the target
1364 * instruction.
1365 */
1366 list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
1367
1368 /* Check for the end of the table: */
1369 if (reloc != table && reloc->jump_table_start)
1370 break;
1371
1372 /* Make sure the table entries are consecutive: */
1373 if (prev_offset && reloc->offset != prev_offset + 8)
1374 break;
1375
1376 /* Detect function pointers from contiguous objects: */
1377 if (reloc->sym->sec == pfunc->sec &&
1378 reloc->addend == pfunc->offset)
1379 break;
1380
1381 dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
1382 if (!dest_insn)
1383 break;
1384
1385 /* Make sure the destination is in the same function: */
1386 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
1387 break;
1388
1389 alt = malloc(sizeof(*alt));
1390 if (!alt) {
1391 WARN("malloc failed");
1392 return -1;
1393 }
1394
1395 alt->insn = dest_insn;
1396 list_add_tail(&alt->list, &insn->alts);
1397 prev_offset = reloc->offset;
1398 }
1399
1400 if (!prev_offset) {
1401 WARN_FUNC("can't find switch jump table",
1402 insn->sec, insn->offset);
1403 return -1;
1404 }
1405
1406 return 0;
1407}
1408
1409/*
1410 * find_jump_table() - Given a dynamic jump, find the switch jump table
1411 * associated with it.
1412 */
1413static struct reloc *find_jump_table(struct objtool_file *file,
1414 struct symbol *func,
1415 struct instruction *insn)
1416{
1417 struct reloc *table_reloc;
1418 struct instruction *dest_insn, *orig_insn = insn;
1419
1420 /*
1421 * Backward search using the @first_jump_src links, these help avoid
1422 * much of the 'in between' code. Which avoids us getting confused by
1423 * it.
1424 */
1425 for (;
1426 insn && insn->func && insn->func->pfunc == func;
1427 insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
1428
1429 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1430 break;
1431
1432 /* allow small jumps within the range */
1433 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1434 insn->jump_dest &&
1435 (insn->jump_dest->offset <= insn->offset ||
1436 insn->jump_dest->offset > orig_insn->offset))
1437 break;
1438
1439 table_reloc = arch_find_switch_table(file, insn);
1440 if (!table_reloc)
1441 continue;
1442 dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
1443 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1444 continue;
1445
1446 return table_reloc;
1447 }
1448
1449 return NULL;
1450}
1451
1452/*
1453 * First pass: Mark the head of each jump table so that in the next pass,
1454 * we know when a given jump table ends and the next one starts.
1455 */
1456static void mark_func_jump_tables(struct objtool_file *file,
1457 struct symbol *func)
1458{
1459 struct instruction *insn, *last = NULL;
1460 struct reloc *reloc;
1461
1462 func_for_each_insn(file, func, insn) {
1463 if (!last)
1464 last = insn;
1465
1466 /*
1467 * Store back-pointers for unconditional forward jumps such
1468 * that find_jump_table() can back-track using those and
1469 * avoid some potentially confusing code.
1470 */
1471 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1472 insn->offset > last->offset &&
1473 insn->jump_dest->offset > insn->offset &&
1474 !insn->jump_dest->first_jump_src) {
1475
1476 insn->jump_dest->first_jump_src = insn;
1477 last = insn->jump_dest;
1478 }
1479
1480 if (insn->type != INSN_JUMP_DYNAMIC)
1481 continue;
1482
1483 reloc = find_jump_table(file, func, insn);
1484 if (reloc) {
1485 reloc->jump_table_start = true;
1486 insn->jump_table = reloc;
1487 }
1488 }
1489}
1490
1491static int add_func_jump_tables(struct objtool_file *file,
1492 struct symbol *func)
1493{
1494 struct instruction *insn;
1495 int ret;
1496
1497 func_for_each_insn(file, func, insn) {
1498 if (!insn->jump_table)
1499 continue;
1500
1501 ret = add_jump_table(file, insn, insn->jump_table);
1502 if (ret)
1503 return ret;
1504 }
1505
1506 return 0;
1507}
1508
1509/*
1510 * For some switch statements, gcc generates a jump table in the .rodata
1511 * section which contains a list of addresses within the function to jump to.
1512 * This finds these jump tables and adds them to the insn->alts lists.
1513 */
1514static int add_jump_table_alts(struct objtool_file *file)
1515{
1516 struct section *sec;
1517 struct symbol *func;
1518 int ret;
1519
1520 if (!file->rodata)
1521 return 0;
1522
1523 for_each_sec(file, sec) {
1524 list_for_each_entry(func, &sec->symbol_list, list) {
1525 if (func->type != STT_FUNC)
1526 continue;
1527
1528 mark_func_jump_tables(file, func);
1529 ret = add_func_jump_tables(file, func);
1530 if (ret)
1531 return ret;
1532 }
1533 }
1534
1535 return 0;
1536}
1537
1538static void set_func_state(struct cfi_state *state)
1539{
1540 state->cfa = initial_func_cfi.cfa;
1541 memcpy(&state->regs, &initial_func_cfi.regs,
1542 CFI_NUM_REGS * sizeof(struct cfi_reg));
1543 state->stack_size = initial_func_cfi.cfa.offset;
1544}
1545
1546static int read_unwind_hints(struct objtool_file *file)
1547{
1548 struct section *sec, *relocsec;
1549 struct reloc *reloc;
1550 struct unwind_hint *hint;
1551 struct instruction *insn;
1552 int i;
1553
1554 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1555 if (!sec)
1556 return 0;
1557
1558 relocsec = sec->reloc;
1559 if (!relocsec) {
1560 WARN("missing .rela.discard.unwind_hints section");
1561 return -1;
1562 }
1563
1564 if (sec->len % sizeof(struct unwind_hint)) {
1565 WARN("struct unwind_hint size mismatch");
1566 return -1;
1567 }
1568
1569 file->hints = true;
1570
1571 for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
1572 hint = (struct unwind_hint *)sec->data->d_buf + i;
1573
1574 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
1575 if (!reloc) {
1576 WARN("can't find reloc for unwind_hints[%d]", i);
1577 return -1;
1578 }
1579
1580 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1581 if (!insn) {
1582 WARN("can't find insn for unwind_hints[%d]", i);
1583 return -1;
1584 }
1585
1586 insn->hint = true;
1587
1588 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
1589 set_func_state(&insn->cfi);
1590 continue;
1591 }
1592
1593 if (arch_decode_hint_reg(insn, hint->sp_reg)) {
1594 WARN_FUNC("unsupported unwind_hint sp base reg %d",
1595 insn->sec, insn->offset, hint->sp_reg);
1596 return -1;
1597 }
1598
1599 insn->cfi.cfa.offset = bswap_if_needed(hint->sp_offset);
1600 insn->cfi.type = hint->type;
1601 insn->cfi.end = hint->end;
1602 }
1603
1604 return 0;
1605}
1606
1607static int read_retpoline_hints(struct objtool_file *file)
1608{
1609 struct section *sec;
1610 struct instruction *insn;
1611 struct reloc *reloc;
1612
1613 sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1614 if (!sec)
1615 return 0;
1616
1617 list_for_each_entry(reloc, &sec->reloc_list, list) {
1618 if (reloc->sym->type != STT_SECTION) {
1619 WARN("unexpected relocation symbol type in %s", sec->name);
1620 return -1;
1621 }
1622
1623 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1624 if (!insn) {
1625 WARN("bad .discard.retpoline_safe entry");
1626 return -1;
1627 }
1628
1629 if (insn->type != INSN_JUMP_DYNAMIC &&
1630 insn->type != INSN_CALL_DYNAMIC) {
1631 WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1632 insn->sec, insn->offset);
1633 return -1;
1634 }
1635
1636 insn->retpoline_safe = true;
1637 }
1638
1639 return 0;
1640}
1641
1642static int read_instr_hints(struct objtool_file *file)
1643{
1644 struct section *sec;
1645 struct instruction *insn;
1646 struct reloc *reloc;
1647
1648 sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
1649 if (!sec)
1650 return 0;
1651
1652 list_for_each_entry(reloc, &sec->reloc_list, list) {
1653 if (reloc->sym->type != STT_SECTION) {
1654 WARN("unexpected relocation symbol type in %s", sec->name);
1655 return -1;
1656 }
1657
1658 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1659 if (!insn) {
1660 WARN("bad .discard.instr_end entry");
1661 return -1;
1662 }
1663
1664 insn->instr--;
1665 }
1666
1667 sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
1668 if (!sec)
1669 return 0;
1670
1671 list_for_each_entry(reloc, &sec->reloc_list, list) {
1672 if (reloc->sym->type != STT_SECTION) {
1673 WARN("unexpected relocation symbol type in %s", sec->name);
1674 return -1;
1675 }
1676
1677 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1678 if (!insn) {
1679 WARN("bad .discard.instr_begin entry");
1680 return -1;
1681 }
1682
1683 insn->instr++;
1684 }
1685
1686 return 0;
1687}
1688
1689static int read_intra_function_calls(struct objtool_file *file)
1690{
1691 struct instruction *insn;
1692 struct section *sec;
1693 struct reloc *reloc;
1694
1695 sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
1696 if (!sec)
1697 return 0;
1698
1699 list_for_each_entry(reloc, &sec->reloc_list, list) {
1700 unsigned long dest_off;
1701
1702 if (reloc->sym->type != STT_SECTION) {
1703 WARN("unexpected relocation symbol type in %s",
1704 sec->name);
1705 return -1;
1706 }
1707
1708 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1709 if (!insn) {
1710 WARN("bad .discard.intra_function_call entry");
1711 return -1;
1712 }
1713
1714 if (insn->type != INSN_CALL) {
1715 WARN_FUNC("intra_function_call not a direct call",
1716 insn->sec, insn->offset);
1717 return -1;
1718 }
1719
1720 /*
1721 * Treat intra-function CALLs as JMPs, but with a stack_op.
1722 * See add_call_destinations(), which strips stack_ops from
1723 * normal CALLs.
1724 */
1725 insn->type = INSN_JUMP_UNCONDITIONAL;
1726
1727 dest_off = insn->offset + insn->len + insn->immediate;
1728 insn->jump_dest = find_insn(file, insn->sec, dest_off);
1729 if (!insn->jump_dest) {
1730 WARN_FUNC("can't find call dest at %s+0x%lx",
1731 insn->sec, insn->offset,
1732 insn->sec->name, dest_off);
1733 return -1;
1734 }
1735 }
1736
1737 return 0;
1738}
1739
1740static int read_static_call_tramps(struct objtool_file *file)
1741{
1742 struct section *sec;
1743 struct symbol *func;
1744
1745 for_each_sec(file, sec) {
1746 list_for_each_entry(func, &sec->symbol_list, list) {
1747 if (func->bind == STB_GLOBAL &&
1748 !strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
1749 strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
1750 func->static_call_tramp = true;
1751 }
1752 }
1753
1754 return 0;
1755}
1756
1757static void mark_rodata(struct objtool_file *file)
1758{
1759 struct section *sec;
1760 bool found = false;
1761
1762 /*
1763 * Search for the following rodata sections, each of which can
1764 * potentially contain jump tables:
1765 *
1766 * - .rodata: can contain GCC switch tables
1767 * - .rodata.<func>: same, if -fdata-sections is being used
1768 * - .rodata..c_jump_table: contains C annotated jump tables
1769 *
1770 * .rodata.str1.* sections are ignored; they don't contain jump tables.
1771 */
1772 for_each_sec(file, sec) {
1773 if (!strncmp(sec->name, ".rodata", 7) &&
1774 !strstr(sec->name, ".str1.")) {
1775 sec->rodata = true;
1776 found = true;
1777 }
1778 }
1779
1780 file->rodata = found;
1781}
1782
1783__weak int arch_rewrite_retpolines(struct objtool_file *file)
1784{
1785 return 0;
1786}
1787
1788static int decode_sections(struct objtool_file *file)
1789{
1790 int ret;
1791
1792 mark_rodata(file);
1793
1794 ret = decode_instructions(file);
1795 if (ret)
1796 return ret;
1797
1798 ret = add_dead_ends(file);
1799 if (ret)
1800 return ret;
1801
1802 add_ignores(file);
1803 add_uaccess_safe(file);
1804
1805 ret = add_ignore_alternatives(file);
1806 if (ret)
1807 return ret;
1808
1809 /*
1810 * Must be before add_{jump_call}_destination.
1811 */
1812 ret = read_static_call_tramps(file);
1813 if (ret)
1814 return ret;
1815
1816 /*
1817 * Must be before add_special_section_alts() as that depends on
1818 * jump_dest being set.
1819 */
1820 ret = add_jump_destinations(file);
1821 if (ret)
1822 return ret;
1823
1824 ret = add_special_section_alts(file);
1825 if (ret)
1826 return ret;
1827
1828 /*
1829 * Must be before add_call_destination(); it changes INSN_CALL to
1830 * INSN_JUMP.
1831 */
1832 ret = read_intra_function_calls(file);
1833 if (ret)
1834 return ret;
1835
1836 ret = add_call_destinations(file);
1837 if (ret)
1838 return ret;
1839
1840 ret = add_jump_table_alts(file);
1841 if (ret)
1842 return ret;
1843
1844 ret = read_unwind_hints(file);
1845 if (ret)
1846 return ret;
1847
1848 ret = read_retpoline_hints(file);
1849 if (ret)
1850 return ret;
1851
1852 ret = read_instr_hints(file);
1853 if (ret)
1854 return ret;
1855
1856 /*
1857 * Must be after add_special_section_alts(), since this will emit
1858 * alternatives. Must be after add_{jump,call}_destination(), since
1859 * those create the call insn lists.
1860 */
1861 ret = arch_rewrite_retpolines(file);
1862 if (ret)
1863 return ret;
1864
1865 return 0;
1866}
1867
1868static bool is_fentry_call(struct instruction *insn)
1869{
1870 if (insn->type == INSN_CALL && insn->call_dest &&
1871 insn->call_dest->type == STT_NOTYPE &&
1872 !strcmp(insn->call_dest->name, "__fentry__"))
1873 return true;
1874
1875 return false;
1876}
1877
1878static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
1879{
1880 struct cfi_state *cfi = &state->cfi;
1881 int i;
1882
1883 if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
1884 return true;
1885
1886 if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
1887 return true;
1888
1889 if (cfi->stack_size != initial_func_cfi.cfa.offset)
1890 return true;
1891
1892 for (i = 0; i < CFI_NUM_REGS; i++) {
1893 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
1894 cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
1895 return true;
1896 }
1897
1898 return false;
1899}
1900
1901static bool check_reg_frame_pos(const struct cfi_reg *reg,
1902 int expected_offset)
1903{
1904 return reg->base == CFI_CFA &&
1905 reg->offset == expected_offset;
1906}
1907
1908static bool has_valid_stack_frame(struct insn_state *state)
1909{
1910 struct cfi_state *cfi = &state->cfi;
1911
1912 if (cfi->cfa.base == CFI_BP &&
1913 check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
1914 check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
1915 return true;
1916
1917 if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
1918 return true;
1919
1920 return false;
1921}
1922
1923static int update_cfi_state_regs(struct instruction *insn,
1924 struct cfi_state *cfi,
1925 struct stack_op *op)
1926{
1927 struct cfi_reg *cfa = &cfi->cfa;
1928
1929 if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
1930 return 0;
1931
1932 /* push */
1933 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
1934 cfa->offset += 8;
1935
1936 /* pop */
1937 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
1938 cfa->offset -= 8;
1939
1940 /* add immediate to sp */
1941 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1942 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1943 cfa->offset -= op->src.offset;
1944
1945 return 0;
1946}
1947
1948static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
1949{
1950 if (arch_callee_saved_reg(reg) &&
1951 cfi->regs[reg].base == CFI_UNDEFINED) {
1952 cfi->regs[reg].base = base;
1953 cfi->regs[reg].offset = offset;
1954 }
1955}
1956
1957static void restore_reg(struct cfi_state *cfi, unsigned char reg)
1958{
1959 cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
1960 cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
1961}
1962
1963/*
1964 * A note about DRAP stack alignment:
1965 *
1966 * GCC has the concept of a DRAP register, which is used to help keep track of
1967 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
1968 * register. The typical DRAP pattern is:
1969 *
1970 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
1971 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
1972 * 41 ff 72 f8 pushq -0x8(%r10)
1973 * 55 push %rbp
1974 * 48 89 e5 mov %rsp,%rbp
1975 * (more pushes)
1976 * 41 52 push %r10
1977 * ...
1978 * 41 5a pop %r10
1979 * (more pops)
1980 * 5d pop %rbp
1981 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1982 * c3 retq
1983 *
1984 * There are some variations in the epilogues, like:
1985 *
1986 * 5b pop %rbx
1987 * 41 5a pop %r10
1988 * 41 5c pop %r12
1989 * 41 5d pop %r13
1990 * 41 5e pop %r14
1991 * c9 leaveq
1992 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1993 * c3 retq
1994 *
1995 * and:
1996 *
1997 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
1998 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
1999 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
2000 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
2001 * c9 leaveq
2002 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2003 * c3 retq
2004 *
2005 * Sometimes r13 is used as the DRAP register, in which case it's saved and
2006 * restored beforehand:
2007 *
2008 * 41 55 push %r13
2009 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
2010 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
2011 * ...
2012 * 49 8d 65 f0 lea -0x10(%r13),%rsp
2013 * 41 5d pop %r13
2014 * c3 retq
2015 */
2016static int update_cfi_state(struct instruction *insn,
2017 struct instruction *next_insn,
2018 struct cfi_state *cfi, struct stack_op *op)
2019{
2020 struct cfi_reg *cfa = &cfi->cfa;
2021 struct cfi_reg *regs = cfi->regs;
2022
2023 /* stack operations don't make sense with an undefined CFA */
2024 if (cfa->base == CFI_UNDEFINED) {
2025 if (insn->func) {
2026 WARN_FUNC("undefined stack state", insn->sec, insn->offset);
2027 return -1;
2028 }
2029 return 0;
2030 }
2031
2032 if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2033 cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2034 return update_cfi_state_regs(insn, cfi, op);
2035
2036 switch (op->dest.type) {
2037
2038 case OP_DEST_REG:
2039 switch (op->src.type) {
2040
2041 case OP_SRC_REG:
2042 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2043 cfa->base == CFI_SP &&
2044 check_reg_frame_pos(®s[CFI_BP], -cfa->offset)) {
2045
2046 /* mov %rsp, %rbp */
2047 cfa->base = op->dest.reg;
2048 cfi->bp_scratch = false;
2049 }
2050
2051 else if (op->src.reg == CFI_SP &&
2052 op->dest.reg == CFI_BP && cfi->drap) {
2053
2054 /* drap: mov %rsp, %rbp */
2055 regs[CFI_BP].base = CFI_BP;
2056 regs[CFI_BP].offset = -cfi->stack_size;
2057 cfi->bp_scratch = false;
2058 }
2059
2060 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2061
2062 /*
2063 * mov %rsp, %reg
2064 *
2065 * This is needed for the rare case where GCC
2066 * does:
2067 *
2068 * mov %rsp, %rax
2069 * ...
2070 * mov %rax, %rsp
2071 */
2072 cfi->vals[op->dest.reg].base = CFI_CFA;
2073 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2074 }
2075
2076 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2077 (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2078
2079 /*
2080 * mov %rbp, %rsp
2081 *
2082 * Restore the original stack pointer (Clang).
2083 */
2084 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2085 }
2086
2087 else if (op->dest.reg == cfa->base) {
2088
2089 /* mov %reg, %rsp */
2090 if (cfa->base == CFI_SP &&
2091 cfi->vals[op->src.reg].base == CFI_CFA) {
2092
2093 /*
2094 * This is needed for the rare case
2095 * where GCC does something dumb like:
2096 *
2097 * lea 0x8(%rsp), %rcx
2098 * ...
2099 * mov %rcx, %rsp
2100 */
2101 cfa->offset = -cfi->vals[op->src.reg].offset;
2102 cfi->stack_size = cfa->offset;
2103
2104 } else if (cfa->base == CFI_SP &&
2105 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2106 cfi->vals[op->src.reg].offset == cfa->offset) {
2107
2108 /*
2109 * Stack swizzle:
2110 *
2111 * 1: mov %rsp, (%[tos])
2112 * 2: mov %[tos], %rsp
2113 * ...
2114 * 3: pop %rsp
2115 *
2116 * Where:
2117 *
2118 * 1 - places a pointer to the previous
2119 * stack at the Top-of-Stack of the
2120 * new stack.
2121 *
2122 * 2 - switches to the new stack.
2123 *
2124 * 3 - pops the Top-of-Stack to restore
2125 * the original stack.
2126 *
2127 * Note: we set base to SP_INDIRECT
2128 * here and preserve offset. Therefore
2129 * when the unwinder reaches ToS it
2130 * will dereference SP and then add the
2131 * offset to find the next frame, IOW:
2132 * (%rsp) + offset.
2133 */
2134 cfa->base = CFI_SP_INDIRECT;
2135
2136 } else {
2137 cfa->base = CFI_UNDEFINED;
2138 cfa->offset = 0;
2139 }
2140 }
2141
2142 else if (op->dest.reg == CFI_SP &&
2143 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2144 cfi->vals[op->src.reg].offset == cfa->offset) {
2145
2146 /*
2147 * The same stack swizzle case 2) as above. But
2148 * because we can't change cfa->base, case 3)
2149 * will become a regular POP. Pretend we're a
2150 * PUSH so things don't go unbalanced.
2151 */
2152 cfi->stack_size += 8;
2153 }
2154
2155
2156 break;
2157
2158 case OP_SRC_ADD:
2159 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2160
2161 /* add imm, %rsp */
2162 cfi->stack_size -= op->src.offset;
2163 if (cfa->base == CFI_SP)
2164 cfa->offset -= op->src.offset;
2165 break;
2166 }
2167
2168 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2169
2170 /* lea disp(%rbp), %rsp */
2171 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2172 break;
2173 }
2174
2175 if (!cfi->drap && op->src.reg == CFI_SP &&
2176 op->dest.reg == CFI_BP && cfa->base == CFI_SP &&
2177 check_reg_frame_pos(®s[CFI_BP], -cfa->offset + op->src.offset)) {
2178
2179 /* lea disp(%rsp), %rbp */
2180 cfa->base = CFI_BP;
2181 cfa->offset -= op->src.offset;
2182 cfi->bp_scratch = false;
2183 break;
2184 }
2185
2186 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2187
2188 /* drap: lea disp(%rsp), %drap */
2189 cfi->drap_reg = op->dest.reg;
2190
2191 /*
2192 * lea disp(%rsp), %reg
2193 *
2194 * This is needed for the rare case where GCC
2195 * does something dumb like:
2196 *
2197 * lea 0x8(%rsp), %rcx
2198 * ...
2199 * mov %rcx, %rsp
2200 */
2201 cfi->vals[op->dest.reg].base = CFI_CFA;
2202 cfi->vals[op->dest.reg].offset = \
2203 -cfi->stack_size + op->src.offset;
2204
2205 break;
2206 }
2207
2208 if (cfi->drap && op->dest.reg == CFI_SP &&
2209 op->src.reg == cfi->drap_reg) {
2210
2211 /* drap: lea disp(%drap), %rsp */
2212 cfa->base = CFI_SP;
2213 cfa->offset = cfi->stack_size = -op->src.offset;
2214 cfi->drap_reg = CFI_UNDEFINED;
2215 cfi->drap = false;
2216 break;
2217 }
2218
2219 if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
2220 WARN_FUNC("unsupported stack register modification",
2221 insn->sec, insn->offset);
2222 return -1;
2223 }
2224
2225 break;
2226
2227 case OP_SRC_AND:
2228 if (op->dest.reg != CFI_SP ||
2229 (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
2230 (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
2231 WARN_FUNC("unsupported stack pointer realignment",
2232 insn->sec, insn->offset);
2233 return -1;
2234 }
2235
2236 if (cfi->drap_reg != CFI_UNDEFINED) {
2237 /* drap: and imm, %rsp */
2238 cfa->base = cfi->drap_reg;
2239 cfa->offset = cfi->stack_size = 0;
2240 cfi->drap = true;
2241 }
2242
2243 /*
2244 * Older versions of GCC (4.8ish) realign the stack
2245 * without DRAP, with a frame pointer.
2246 */
2247
2248 break;
2249
2250 case OP_SRC_POP:
2251 case OP_SRC_POPF:
2252 if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
2253
2254 /* pop %rsp; # restore from a stack swizzle */
2255 cfa->base = CFI_SP;
2256 break;
2257 }
2258
2259 if (!cfi->drap && op->dest.reg == cfa->base) {
2260
2261 /* pop %rbp */
2262 cfa->base = CFI_SP;
2263 }
2264
2265 if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
2266 op->dest.reg == cfi->drap_reg &&
2267 cfi->drap_offset == -cfi->stack_size) {
2268
2269 /* drap: pop %drap */
2270 cfa->base = cfi->drap_reg;
2271 cfa->offset = 0;
2272 cfi->drap_offset = -1;
2273
2274 } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
2275
2276 /* pop %reg */
2277 restore_reg(cfi, op->dest.reg);
2278 }
2279
2280 cfi->stack_size -= 8;
2281 if (cfa->base == CFI_SP)
2282 cfa->offset -= 8;
2283
2284 break;
2285
2286 case OP_SRC_REG_INDIRECT:
2287 if (!cfi->drap && op->dest.reg == cfa->base &&
2288 op->dest.reg == CFI_BP) {
2289
2290 /* mov disp(%rsp), %rbp */
2291 cfa->base = CFI_SP;
2292 cfa->offset = cfi->stack_size;
2293 }
2294
2295 if (cfi->drap && op->src.reg == CFI_BP &&
2296 op->src.offset == cfi->drap_offset) {
2297
2298 /* drap: mov disp(%rbp), %drap */
2299 cfa->base = cfi->drap_reg;
2300 cfa->offset = 0;
2301 cfi->drap_offset = -1;
2302 }
2303
2304 if (cfi->drap && op->src.reg == CFI_BP &&
2305 op->src.offset == regs[op->dest.reg].offset) {
2306
2307 /* drap: mov disp(%rbp), %reg */
2308 restore_reg(cfi, op->dest.reg);
2309
2310 } else if (op->src.reg == cfa->base &&
2311 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
2312
2313 /* mov disp(%rbp), %reg */
2314 /* mov disp(%rsp), %reg */
2315 restore_reg(cfi, op->dest.reg);
2316
2317 } else if (op->src.reg == CFI_SP &&
2318 op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
2319
2320 /* mov disp(%rsp), %reg */
2321 restore_reg(cfi, op->dest.reg);
2322 }
2323
2324 break;
2325
2326 default:
2327 WARN_FUNC("unknown stack-related instruction",
2328 insn->sec, insn->offset);
2329 return -1;
2330 }
2331
2332 break;
2333
2334 case OP_DEST_PUSH:
2335 case OP_DEST_PUSHF:
2336 cfi->stack_size += 8;
2337 if (cfa->base == CFI_SP)
2338 cfa->offset += 8;
2339
2340 if (op->src.type != OP_SRC_REG)
2341 break;
2342
2343 if (cfi->drap) {
2344 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2345
2346 /* drap: push %drap */
2347 cfa->base = CFI_BP_INDIRECT;
2348 cfa->offset = -cfi->stack_size;
2349
2350 /* save drap so we know when to restore it */
2351 cfi->drap_offset = -cfi->stack_size;
2352
2353 } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
2354
2355 /* drap: push %rbp */
2356 cfi->stack_size = 0;
2357
2358 } else {
2359
2360 /* drap: push %reg */
2361 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
2362 }
2363
2364 } else {
2365
2366 /* push %reg */
2367 save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
2368 }
2369
2370 /* detect when asm code uses rbp as a scratch register */
2371 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
2372 cfa->base != CFI_BP)
2373 cfi->bp_scratch = true;
2374 break;
2375
2376 case OP_DEST_REG_INDIRECT:
2377
2378 if (cfi->drap) {
2379 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2380
2381 /* drap: mov %drap, disp(%rbp) */
2382 cfa->base = CFI_BP_INDIRECT;
2383 cfa->offset = op->dest.offset;
2384
2385 /* save drap offset so we know when to restore it */
2386 cfi->drap_offset = op->dest.offset;
2387 } else {
2388
2389 /* drap: mov reg, disp(%rbp) */
2390 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
2391 }
2392
2393 } else if (op->dest.reg == cfa->base) {
2394
2395 /* mov reg, disp(%rbp) */
2396 /* mov reg, disp(%rsp) */
2397 save_reg(cfi, op->src.reg, CFI_CFA,
2398 op->dest.offset - cfi->cfa.offset);
2399
2400 } else if (op->dest.reg == CFI_SP) {
2401
2402 /* mov reg, disp(%rsp) */
2403 save_reg(cfi, op->src.reg, CFI_CFA,
2404 op->dest.offset - cfi->stack_size);
2405
2406 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
2407
2408 /* mov %rsp, (%reg); # setup a stack swizzle. */
2409 cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
2410 cfi->vals[op->dest.reg].offset = cfa->offset;
2411 }
2412
2413 break;
2414
2415 case OP_DEST_MEM:
2416 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
2417 WARN_FUNC("unknown stack-related memory operation",
2418 insn->sec, insn->offset);
2419 return -1;
2420 }
2421
2422 /* pop mem */
2423 cfi->stack_size -= 8;
2424 if (cfa->base == CFI_SP)
2425 cfa->offset -= 8;
2426
2427 break;
2428
2429 default:
2430 WARN_FUNC("unknown stack-related instruction",
2431 insn->sec, insn->offset);
2432 return -1;
2433 }
2434
2435 return 0;
2436}
2437
2438/*
2439 * The stack layouts of alternatives instructions can sometimes diverge when
2440 * they have stack modifications. That's fine as long as the potential stack
2441 * layouts don't conflict at any given potential instruction boundary.
2442 *
2443 * Flatten the CFIs of the different alternative code streams (both original
2444 * and replacement) into a single shared CFI array which can be used to detect
2445 * conflicts and nicely feed a linear array of ORC entries to the unwinder.
2446 */
2447static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
2448{
2449 struct cfi_state **alt_cfi;
2450 int group_off;
2451
2452 if (!insn->alt_group)
2453 return 0;
2454
2455 alt_cfi = insn->alt_group->cfi;
2456 group_off = insn->offset - insn->alt_group->first_insn->offset;
2457
2458 if (!alt_cfi[group_off]) {
2459 alt_cfi[group_off] = &insn->cfi;
2460 } else {
2461 if (memcmp(alt_cfi[group_off], &insn->cfi, sizeof(struct cfi_state))) {
2462 WARN_FUNC("stack layout conflict in alternatives",
2463 insn->sec, insn->offset);
2464 return -1;
2465 }
2466 }
2467
2468 return 0;
2469}
2470
2471static int handle_insn_ops(struct instruction *insn,
2472 struct instruction *next_insn,
2473 struct insn_state *state)
2474{
2475 struct stack_op *op;
2476
2477 list_for_each_entry(op, &insn->stack_ops, list) {
2478
2479 if (update_cfi_state(insn, next_insn, &state->cfi, op))
2480 return 1;
2481
2482 if (!insn->alt_group)
2483 continue;
2484
2485 if (op->dest.type == OP_DEST_PUSHF) {
2486 if (!state->uaccess_stack) {
2487 state->uaccess_stack = 1;
2488 } else if (state->uaccess_stack >> 31) {
2489 WARN_FUNC("PUSHF stack exhausted",
2490 insn->sec, insn->offset);
2491 return 1;
2492 }
2493 state->uaccess_stack <<= 1;
2494 state->uaccess_stack |= state->uaccess;
2495 }
2496
2497 if (op->src.type == OP_SRC_POPF) {
2498 if (state->uaccess_stack) {
2499 state->uaccess = state->uaccess_stack & 1;
2500 state->uaccess_stack >>= 1;
2501 if (state->uaccess_stack == 1)
2502 state->uaccess_stack = 0;
2503 }
2504 }
2505 }
2506
2507 return 0;
2508}
2509
2510static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
2511{
2512 struct cfi_state *cfi1 = &insn->cfi;
2513 int i;
2514
2515 if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
2516
2517 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
2518 insn->sec, insn->offset,
2519 cfi1->cfa.base, cfi1->cfa.offset,
2520 cfi2->cfa.base, cfi2->cfa.offset);
2521
2522 } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
2523 for (i = 0; i < CFI_NUM_REGS; i++) {
2524 if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
2525 sizeof(struct cfi_reg)))
2526 continue;
2527
2528 WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
2529 insn->sec, insn->offset,
2530 i, cfi1->regs[i].base, cfi1->regs[i].offset,
2531 i, cfi2->regs[i].base, cfi2->regs[i].offset);
2532 break;
2533 }
2534
2535 } else if (cfi1->type != cfi2->type) {
2536
2537 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
2538 insn->sec, insn->offset, cfi1->type, cfi2->type);
2539
2540 } else if (cfi1->drap != cfi2->drap ||
2541 (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
2542 (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
2543
2544 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
2545 insn->sec, insn->offset,
2546 cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
2547 cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
2548
2549 } else
2550 return true;
2551
2552 return false;
2553}
2554
2555static inline bool func_uaccess_safe(struct symbol *func)
2556{
2557 if (func)
2558 return func->uaccess_safe;
2559
2560 return false;
2561}
2562
2563static inline const char *call_dest_name(struct instruction *insn)
2564{
2565 if (insn->call_dest)
2566 return insn->call_dest->name;
2567
2568 return "{dynamic}";
2569}
2570
2571static inline bool noinstr_call_dest(struct symbol *func)
2572{
2573 /*
2574 * We can't deal with indirect function calls at present;
2575 * assume they're instrumented.
2576 */
2577 if (!func)
2578 return false;
2579
2580 /*
2581 * If the symbol is from a noinstr section; we good.
2582 */
2583 if (func->sec->noinstr)
2584 return true;
2585
2586 /*
2587 * The __ubsan_handle_*() calls are like WARN(), they only happen when
2588 * something 'BAD' happened. At the risk of taking the machine down,
2589 * let them proceed to get the message out.
2590 */
2591 if (!strncmp(func->name, "__ubsan_handle_", 15))
2592 return true;
2593
2594 return false;
2595}
2596
2597static int validate_call(struct instruction *insn, struct insn_state *state)
2598{
2599 if (state->noinstr && state->instr <= 0 &&
2600 !noinstr_call_dest(insn->call_dest)) {
2601 WARN_FUNC("call to %s() leaves .noinstr.text section",
2602 insn->sec, insn->offset, call_dest_name(insn));
2603 return 1;
2604 }
2605
2606 if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
2607 WARN_FUNC("call to %s() with UACCESS enabled",
2608 insn->sec, insn->offset, call_dest_name(insn));
2609 return 1;
2610 }
2611
2612 if (state->df) {
2613 WARN_FUNC("call to %s() with DF set",
2614 insn->sec, insn->offset, call_dest_name(insn));
2615 return 1;
2616 }
2617
2618 return 0;
2619}
2620
2621static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
2622{
2623 if (has_modified_stack_frame(insn, state)) {
2624 WARN_FUNC("sibling call from callable instruction with modified stack frame",
2625 insn->sec, insn->offset);
2626 return 1;
2627 }
2628
2629 return validate_call(insn, state);
2630}
2631
2632static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
2633{
2634 if (state->noinstr && state->instr > 0) {
2635 WARN_FUNC("return with instrumentation enabled",
2636 insn->sec, insn->offset);
2637 return 1;
2638 }
2639
2640 if (state->uaccess && !func_uaccess_safe(func)) {
2641 WARN_FUNC("return with UACCESS enabled",
2642 insn->sec, insn->offset);
2643 return 1;
2644 }
2645
2646 if (!state->uaccess && func_uaccess_safe(func)) {
2647 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
2648 insn->sec, insn->offset);
2649 return 1;
2650 }
2651
2652 if (state->df) {
2653 WARN_FUNC("return with DF set",
2654 insn->sec, insn->offset);
2655 return 1;
2656 }
2657
2658 if (func && has_modified_stack_frame(insn, state)) {
2659 WARN_FUNC("return with modified stack frame",
2660 insn->sec, insn->offset);
2661 return 1;
2662 }
2663
2664 if (state->cfi.bp_scratch) {
2665 WARN_FUNC("BP used as a scratch register",
2666 insn->sec, insn->offset);
2667 return 1;
2668 }
2669
2670 return 0;
2671}
2672
2673static struct instruction *next_insn_to_validate(struct objtool_file *file,
2674 struct instruction *insn)
2675{
2676 struct alt_group *alt_group = insn->alt_group;
2677
2678 /*
2679 * Simulate the fact that alternatives are patched in-place. When the
2680 * end of a replacement alt_group is reached, redirect objtool flow to
2681 * the end of the original alt_group.
2682 */
2683 if (alt_group && insn == alt_group->last_insn && alt_group->orig_group)
2684 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
2685
2686 return next_insn_same_sec(file, insn);
2687}
2688
2689/*
2690 * Follow the branch starting at the given instruction, and recursively follow
2691 * any other branches (jumps). Meanwhile, track the frame pointer state at
2692 * each instruction and validate all the rules described in
2693 * tools/objtool/Documentation/stack-validation.txt.
2694 */
2695static int validate_branch(struct objtool_file *file, struct symbol *func,
2696 struct instruction *insn, struct insn_state state)
2697{
2698 struct alternative *alt;
2699 struct instruction *next_insn;
2700 struct section *sec;
2701 u8 visited;
2702 int ret;
2703
2704 sec = insn->sec;
2705
2706 while (1) {
2707 next_insn = next_insn_to_validate(file, insn);
2708
2709 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
2710 WARN("%s() falls through to next function %s()",
2711 func->name, insn->func->name);
2712 return 1;
2713 }
2714
2715 if (func && insn->ignore) {
2716 WARN_FUNC("BUG: why am I validating an ignored function?",
2717 sec, insn->offset);
2718 return 1;
2719 }
2720
2721 visited = 1 << state.uaccess;
2722 if (insn->visited) {
2723 if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
2724 return 1;
2725
2726 if (insn->visited & visited)
2727 return 0;
2728 }
2729
2730 if (state.noinstr)
2731 state.instr += insn->instr;
2732
2733 if (insn->hint)
2734 state.cfi = insn->cfi;
2735 else
2736 insn->cfi = state.cfi;
2737
2738 insn->visited |= visited;
2739
2740 if (propagate_alt_cfi(file, insn))
2741 return 1;
2742
2743 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
2744 bool skip_orig = false;
2745
2746 list_for_each_entry(alt, &insn->alts, list) {
2747 if (alt->skip_orig)
2748 skip_orig = true;
2749
2750 ret = validate_branch(file, func, alt->insn, state);
2751 if (ret) {
2752 if (backtrace)
2753 BT_FUNC("(alt)", insn);
2754 return ret;
2755 }
2756 }
2757
2758 if (skip_orig)
2759 return 0;
2760 }
2761
2762 if (handle_insn_ops(insn, next_insn, &state))
2763 return 1;
2764
2765 switch (insn->type) {
2766
2767 case INSN_RETURN:
2768 return validate_return(func, insn, &state);
2769
2770 case INSN_CALL:
2771 case INSN_CALL_DYNAMIC:
2772 ret = validate_call(insn, &state);
2773 if (ret)
2774 return ret;
2775
2776 if (!no_fp && func && !is_fentry_call(insn) &&
2777 !has_valid_stack_frame(&state)) {
2778 WARN_FUNC("call without frame pointer save/setup",
2779 sec, insn->offset);
2780 return 1;
2781 }
2782
2783 if (dead_end_function(file, insn->call_dest))
2784 return 0;
2785
2786 break;
2787
2788 case INSN_JUMP_CONDITIONAL:
2789 case INSN_JUMP_UNCONDITIONAL:
2790 if (is_sibling_call(insn)) {
2791 ret = validate_sibling_call(insn, &state);
2792 if (ret)
2793 return ret;
2794
2795 } else if (insn->jump_dest) {
2796 ret = validate_branch(file, func,
2797 insn->jump_dest, state);
2798 if (ret) {
2799 if (backtrace)
2800 BT_FUNC("(branch)", insn);
2801 return ret;
2802 }
2803 }
2804
2805 if (insn->type == INSN_JUMP_UNCONDITIONAL)
2806 return 0;
2807
2808 break;
2809
2810 case INSN_JUMP_DYNAMIC:
2811 case INSN_JUMP_DYNAMIC_CONDITIONAL:
2812 if (is_sibling_call(insn)) {
2813 ret = validate_sibling_call(insn, &state);
2814 if (ret)
2815 return ret;
2816 }
2817
2818 if (insn->type == INSN_JUMP_DYNAMIC)
2819 return 0;
2820
2821 break;
2822
2823 case INSN_CONTEXT_SWITCH:
2824 if (func && (!next_insn || !next_insn->hint)) {
2825 WARN_FUNC("unsupported instruction in callable function",
2826 sec, insn->offset);
2827 return 1;
2828 }
2829 return 0;
2830
2831 case INSN_STAC:
2832 if (state.uaccess) {
2833 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
2834 return 1;
2835 }
2836
2837 state.uaccess = true;
2838 break;
2839
2840 case INSN_CLAC:
2841 if (!state.uaccess && func) {
2842 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
2843 return 1;
2844 }
2845
2846 if (func_uaccess_safe(func) && !state.uaccess_stack) {
2847 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
2848 return 1;
2849 }
2850
2851 state.uaccess = false;
2852 break;
2853
2854 case INSN_STD:
2855 if (state.df) {
2856 WARN_FUNC("recursive STD", sec, insn->offset);
2857 return 1;
2858 }
2859
2860 state.df = true;
2861 break;
2862
2863 case INSN_CLD:
2864 if (!state.df && func) {
2865 WARN_FUNC("redundant CLD", sec, insn->offset);
2866 return 1;
2867 }
2868
2869 state.df = false;
2870 break;
2871
2872 default:
2873 break;
2874 }
2875
2876 if (insn->dead_end)
2877 return 0;
2878
2879 if (!next_insn) {
2880 if (state.cfi.cfa.base == CFI_UNDEFINED)
2881 return 0;
2882 WARN("%s: unexpected end of section", sec->name);
2883 return 1;
2884 }
2885
2886 insn = next_insn;
2887 }
2888
2889 return 0;
2890}
2891
2892static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
2893{
2894 struct instruction *insn;
2895 struct insn_state state;
2896 int ret, warnings = 0;
2897
2898 if (!file->hints)
2899 return 0;
2900
2901 init_insn_state(&state, sec);
2902
2903 if (sec) {
2904 insn = find_insn(file, sec, 0);
2905 if (!insn)
2906 return 0;
2907 } else {
2908 insn = list_first_entry(&file->insn_list, typeof(*insn), list);
2909 }
2910
2911 while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) {
2912 if (insn->hint && !insn->visited) {
2913 ret = validate_branch(file, insn->func, insn, state);
2914 if (ret && backtrace)
2915 BT_FUNC("<=== (hint)", insn);
2916 warnings += ret;
2917 }
2918
2919 insn = list_next_entry(insn, list);
2920 }
2921
2922 return warnings;
2923}
2924
2925static int validate_retpoline(struct objtool_file *file)
2926{
2927 struct instruction *insn;
2928 int warnings = 0;
2929
2930 for_each_insn(file, insn) {
2931 if (insn->type != INSN_JUMP_DYNAMIC &&
2932 insn->type != INSN_CALL_DYNAMIC)
2933 continue;
2934
2935 if (insn->retpoline_safe)
2936 continue;
2937
2938 /*
2939 * .init.text code is ran before userspace and thus doesn't
2940 * strictly need retpolines, except for modules which are
2941 * loaded late, they very much do need retpoline in their
2942 * .init.text
2943 */
2944 if (!strcmp(insn->sec->name, ".init.text") && !module)
2945 continue;
2946
2947 WARN_FUNC("indirect %s found in RETPOLINE build",
2948 insn->sec, insn->offset,
2949 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
2950
2951 warnings++;
2952 }
2953
2954 return warnings;
2955}
2956
2957static bool is_kasan_insn(struct instruction *insn)
2958{
2959 return (insn->type == INSN_CALL &&
2960 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
2961}
2962
2963static bool is_ubsan_insn(struct instruction *insn)
2964{
2965 return (insn->type == INSN_CALL &&
2966 !strcmp(insn->call_dest->name,
2967 "__ubsan_handle_builtin_unreachable"));
2968}
2969
2970static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
2971{
2972 int i;
2973 struct instruction *prev_insn;
2974
2975 if (insn->ignore || insn->type == INSN_NOP)
2976 return true;
2977
2978 /*
2979 * Ignore any unused exceptions. This can happen when a whitelisted
2980 * function has an exception table entry.
2981 *
2982 * Also ignore alternative replacement instructions. This can happen
2983 * when a whitelisted function uses one of the ALTERNATIVE macros.
2984 */
2985 if (!strcmp(insn->sec->name, ".fixup") ||
2986 !strcmp(insn->sec->name, ".altinstr_replacement") ||
2987 !strcmp(insn->sec->name, ".altinstr_aux"))
2988 return true;
2989
2990 if (!insn->func)
2991 return false;
2992
2993 /*
2994 * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
2995 * __builtin_unreachable(). The BUG() macro has an unreachable() after
2996 * the UD2, which causes GCC's undefined trap logic to emit another UD2
2997 * (or occasionally a JMP to UD2).
2998 *
2999 * It may also insert a UD2 after calling a __noreturn function.
3000 */
3001 prev_insn = list_prev_entry(insn, list);
3002 if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) &&
3003 (insn->type == INSN_BUG ||
3004 (insn->type == INSN_JUMP_UNCONDITIONAL &&
3005 insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
3006 return true;
3007
3008 /*
3009 * Check if this (or a subsequent) instruction is related to
3010 * CONFIG_UBSAN or CONFIG_KASAN.
3011 *
3012 * End the search at 5 instructions to avoid going into the weeds.
3013 */
3014 for (i = 0; i < 5; i++) {
3015
3016 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
3017 return true;
3018
3019 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
3020 if (insn->jump_dest &&
3021 insn->jump_dest->func == insn->func) {
3022 insn = insn->jump_dest;
3023 continue;
3024 }
3025
3026 break;
3027 }
3028
3029 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
3030 break;
3031
3032 insn = list_next_entry(insn, list);
3033 }
3034
3035 return false;
3036}
3037
3038static int validate_symbol(struct objtool_file *file, struct section *sec,
3039 struct symbol *sym, struct insn_state *state)
3040{
3041 struct instruction *insn;
3042 int ret;
3043
3044 if (!sym->len) {
3045 WARN("%s() is missing an ELF size annotation", sym->name);
3046 return 1;
3047 }
3048
3049 if (sym->pfunc != sym || sym->alias != sym)
3050 return 0;
3051
3052 insn = find_insn(file, sec, sym->offset);
3053 if (!insn || insn->ignore || insn->visited)
3054 return 0;
3055
3056 state->uaccess = sym->uaccess_safe;
3057
3058 ret = validate_branch(file, insn->func, insn, *state);
3059 if (ret && backtrace)
3060 BT_FUNC("<=== (sym)", insn);
3061 return ret;
3062}
3063
3064static int validate_section(struct objtool_file *file, struct section *sec)
3065{
3066 struct insn_state state;
3067 struct symbol *func;
3068 int warnings = 0;
3069
3070 list_for_each_entry(func, &sec->symbol_list, list) {
3071 if (func->type != STT_FUNC)
3072 continue;
3073
3074 init_insn_state(&state, sec);
3075 set_func_state(&state.cfi);
3076
3077 warnings += validate_symbol(file, sec, func, &state);
3078 }
3079
3080 return warnings;
3081}
3082
3083static int validate_vmlinux_functions(struct objtool_file *file)
3084{
3085 struct section *sec;
3086 int warnings = 0;
3087
3088 sec = find_section_by_name(file->elf, ".noinstr.text");
3089 if (sec) {
3090 warnings += validate_section(file, sec);
3091 warnings += validate_unwind_hints(file, sec);
3092 }
3093
3094 sec = find_section_by_name(file->elf, ".entry.text");
3095 if (sec) {
3096 warnings += validate_section(file, sec);
3097 warnings += validate_unwind_hints(file, sec);
3098 }
3099
3100 return warnings;
3101}
3102
3103static int validate_functions(struct objtool_file *file)
3104{
3105 struct section *sec;
3106 int warnings = 0;
3107
3108 for_each_sec(file, sec) {
3109 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
3110 continue;
3111
3112 warnings += validate_section(file, sec);
3113 }
3114
3115 return warnings;
3116}
3117
3118static int validate_reachable_instructions(struct objtool_file *file)
3119{
3120 struct instruction *insn;
3121
3122 if (file->ignore_unreachables)
3123 return 0;
3124
3125 for_each_insn(file, insn) {
3126 if (insn->visited || ignore_unreachable_insn(file, insn))
3127 continue;
3128
3129 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
3130 return 1;
3131 }
3132
3133 return 0;
3134}
3135
3136int check(struct objtool_file *file)
3137{
3138 int ret, warnings = 0;
3139
3140 arch_initial_func_cfi_state(&initial_func_cfi);
3141
3142 ret = decode_sections(file);
3143 if (ret < 0)
3144 goto out;
3145 warnings += ret;
3146
3147 if (list_empty(&file->insn_list))
3148 goto out;
3149
3150 if (vmlinux && !validate_dup) {
3151 ret = validate_vmlinux_functions(file);
3152 if (ret < 0)
3153 goto out;
3154
3155 warnings += ret;
3156 goto out;
3157 }
3158
3159 if (retpoline) {
3160 ret = validate_retpoline(file);
3161 if (ret < 0)
3162 return ret;
3163 warnings += ret;
3164 }
3165
3166 ret = validate_functions(file);
3167 if (ret < 0)
3168 goto out;
3169 warnings += ret;
3170
3171 ret = validate_unwind_hints(file, NULL);
3172 if (ret < 0)
3173 goto out;
3174 warnings += ret;
3175
3176 if (!warnings) {
3177 ret = validate_reachable_instructions(file);
3178 if (ret < 0)
3179 goto out;
3180 warnings += ret;
3181 }
3182
3183 ret = create_static_call_sections(file);
3184 if (ret < 0)
3185 goto out;
3186 warnings += ret;
3187
3188 if (mcount) {
3189 ret = create_mcount_loc_sections(file);
3190 if (ret < 0)
3191 goto out;
3192 warnings += ret;
3193 }
3194
3195out:
3196 /*
3197 * For now, don't fail the kernel build on fatal warnings. These
3198 * errors are still fairly common due to the growing matrix of
3199 * supported toolchains and their recent pace of change.
3200 */
3201 return 0;
3202}
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
9#include "builtin.h"
10#include "cfi.h"
11#include "arch.h"
12#include "check.h"
13#include "special.h"
14#include "warn.h"
15#include "arch_elf.h"
16
17#include <linux/hashtable.h>
18#include <linux/kernel.h>
19
20#define FAKE_JUMP_OFFSET -1
21
22#define C_JUMP_TABLE_SECTION ".rodata..c_jump_table"
23
24struct alternative {
25 struct list_head list;
26 struct instruction *insn;
27 bool skip_orig;
28};
29
30const char *objname;
31struct cfi_init_state initial_func_cfi;
32
33struct instruction *find_insn(struct objtool_file *file,
34 struct section *sec, unsigned long offset)
35{
36 struct instruction *insn;
37
38 hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
39 if (insn->sec == sec && insn->offset == offset)
40 return insn;
41 }
42
43 return NULL;
44}
45
46static struct instruction *next_insn_same_sec(struct objtool_file *file,
47 struct instruction *insn)
48{
49 struct instruction *next = list_next_entry(insn, list);
50
51 if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
52 return NULL;
53
54 return next;
55}
56
57static struct instruction *next_insn_same_func(struct objtool_file *file,
58 struct instruction *insn)
59{
60 struct instruction *next = list_next_entry(insn, list);
61 struct symbol *func = insn->func;
62
63 if (!func)
64 return NULL;
65
66 if (&next->list != &file->insn_list && next->func == func)
67 return next;
68
69 /* Check if we're already in the subfunction: */
70 if (func == func->cfunc)
71 return NULL;
72
73 /* Move to the subfunction: */
74 return find_insn(file, func->cfunc->sec, func->cfunc->offset);
75}
76
77static struct instruction *prev_insn_same_sym(struct objtool_file *file,
78 struct instruction *insn)
79{
80 struct instruction *prev = list_prev_entry(insn, list);
81
82 if (&prev->list != &file->insn_list && prev->func == insn->func)
83 return prev;
84
85 return NULL;
86}
87
88#define func_for_each_insn(file, func, insn) \
89 for (insn = find_insn(file, func->sec, func->offset); \
90 insn; \
91 insn = next_insn_same_func(file, insn))
92
93#define sym_for_each_insn(file, sym, insn) \
94 for (insn = find_insn(file, sym->sec, sym->offset); \
95 insn && &insn->list != &file->insn_list && \
96 insn->sec == sym->sec && \
97 insn->offset < sym->offset + sym->len; \
98 insn = list_next_entry(insn, list))
99
100#define sym_for_each_insn_continue_reverse(file, sym, insn) \
101 for (insn = list_prev_entry(insn, list); \
102 &insn->list != &file->insn_list && \
103 insn->sec == sym->sec && insn->offset >= sym->offset; \
104 insn = list_prev_entry(insn, list))
105
106#define sec_for_each_insn_from(file, insn) \
107 for (; insn; insn = next_insn_same_sec(file, insn))
108
109#define sec_for_each_insn_continue(file, insn) \
110 for (insn = next_insn_same_sec(file, insn); insn; \
111 insn = next_insn_same_sec(file, insn))
112
113static bool is_static_jump(struct instruction *insn)
114{
115 return insn->type == INSN_JUMP_CONDITIONAL ||
116 insn->type == INSN_JUMP_UNCONDITIONAL;
117}
118
119static bool is_sibling_call(struct instruction *insn)
120{
121 /* An indirect jump is either a sibling call or a jump to a table. */
122 if (insn->type == INSN_JUMP_DYNAMIC)
123 return list_empty(&insn->alts);
124
125 if (!is_static_jump(insn))
126 return false;
127
128 /* add_jump_destinations() sets insn->call_dest for sibling calls. */
129 return !!insn->call_dest;
130}
131
132/*
133 * This checks to see if the given function is a "noreturn" function.
134 *
135 * For global functions which are outside the scope of this object file, we
136 * have to keep a manual list of them.
137 *
138 * For local functions, we have to detect them manually by simply looking for
139 * the lack of a return instruction.
140 */
141static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
142 int recursion)
143{
144 int i;
145 struct instruction *insn;
146 bool empty = true;
147
148 /*
149 * Unfortunately these have to be hard coded because the noreturn
150 * attribute isn't provided in ELF data.
151 */
152 static const char * const global_noreturns[] = {
153 "__stack_chk_fail",
154 "panic",
155 "do_exit",
156 "do_task_dead",
157 "__module_put_and_exit",
158 "complete_and_exit",
159 "__reiserfs_panic",
160 "lbug_with_loc",
161 "fortify_panic",
162 "usercopy_abort",
163 "machine_real_restart",
164 "rewind_stack_do_exit",
165 "kunit_try_catch_throw",
166 };
167
168 if (!func)
169 return false;
170
171 if (func->bind == STB_WEAK)
172 return false;
173
174 if (func->bind == STB_GLOBAL)
175 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
176 if (!strcmp(func->name, global_noreturns[i]))
177 return true;
178
179 if (!func->len)
180 return false;
181
182 insn = find_insn(file, func->sec, func->offset);
183 if (!insn->func)
184 return false;
185
186 func_for_each_insn(file, func, insn) {
187 empty = false;
188
189 if (insn->type == INSN_RETURN)
190 return false;
191 }
192
193 if (empty)
194 return false;
195
196 /*
197 * A function can have a sibling call instead of a return. In that
198 * case, the function's dead-end status depends on whether the target
199 * of the sibling call returns.
200 */
201 func_for_each_insn(file, func, insn) {
202 if (is_sibling_call(insn)) {
203 struct instruction *dest = insn->jump_dest;
204
205 if (!dest)
206 /* sibling call to another file */
207 return false;
208
209 /* local sibling call */
210 if (recursion == 5) {
211 /*
212 * Infinite recursion: two functions have
213 * sibling calls to each other. This is a very
214 * rare case. It means they aren't dead ends.
215 */
216 return false;
217 }
218
219 return __dead_end_function(file, dest->func, recursion+1);
220 }
221 }
222
223 return true;
224}
225
226static bool dead_end_function(struct objtool_file *file, struct symbol *func)
227{
228 return __dead_end_function(file, func, 0);
229}
230
231static void init_cfi_state(struct cfi_state *cfi)
232{
233 int i;
234
235 for (i = 0; i < CFI_NUM_REGS; i++) {
236 cfi->regs[i].base = CFI_UNDEFINED;
237 cfi->vals[i].base = CFI_UNDEFINED;
238 }
239 cfi->cfa.base = CFI_UNDEFINED;
240 cfi->drap_reg = CFI_UNDEFINED;
241 cfi->drap_offset = -1;
242}
243
244static void init_insn_state(struct insn_state *state, struct section *sec)
245{
246 memset(state, 0, sizeof(*state));
247 init_cfi_state(&state->cfi);
248
249 /*
250 * We need the full vmlinux for noinstr validation, otherwise we can
251 * not correctly determine insn->call_dest->sec (external symbols do
252 * not have a section).
253 */
254 if (vmlinux && sec)
255 state->noinstr = sec->noinstr;
256}
257
258/*
259 * Call the arch-specific instruction decoder for all the instructions and add
260 * them to the global instruction list.
261 */
262static int decode_instructions(struct objtool_file *file)
263{
264 struct section *sec;
265 struct symbol *func;
266 unsigned long offset;
267 struct instruction *insn;
268 unsigned long nr_insns = 0;
269 int ret;
270
271 for_each_sec(file, sec) {
272
273 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
274 continue;
275
276 if (strcmp(sec->name, ".altinstr_replacement") &&
277 strcmp(sec->name, ".altinstr_aux") &&
278 strncmp(sec->name, ".discard.", 9))
279 sec->text = true;
280
281 if (!strcmp(sec->name, ".noinstr.text") ||
282 !strcmp(sec->name, ".entry.text"))
283 sec->noinstr = true;
284
285 for (offset = 0; offset < sec->len; offset += insn->len) {
286 insn = malloc(sizeof(*insn));
287 if (!insn) {
288 WARN("malloc failed");
289 return -1;
290 }
291 memset(insn, 0, sizeof(*insn));
292 INIT_LIST_HEAD(&insn->alts);
293 INIT_LIST_HEAD(&insn->stack_ops);
294 init_cfi_state(&insn->cfi);
295
296 insn->sec = sec;
297 insn->offset = offset;
298
299 ret = arch_decode_instruction(file->elf, sec, offset,
300 sec->len - offset,
301 &insn->len, &insn->type,
302 &insn->immediate,
303 &insn->stack_ops);
304 if (ret)
305 goto err;
306
307 hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
308 list_add_tail(&insn->list, &file->insn_list);
309 nr_insns++;
310 }
311
312 list_for_each_entry(func, &sec->symbol_list, list) {
313 if (func->type != STT_FUNC || func->alias != func)
314 continue;
315
316 if (!find_insn(file, sec, func->offset)) {
317 WARN("%s(): can't find starting instruction",
318 func->name);
319 return -1;
320 }
321
322 sym_for_each_insn(file, func, insn)
323 insn->func = func;
324 }
325 }
326
327 if (stats)
328 printf("nr_insns: %lu\n", nr_insns);
329
330 return 0;
331
332err:
333 free(insn);
334 return ret;
335}
336
337static struct instruction *find_last_insn(struct objtool_file *file,
338 struct section *sec)
339{
340 struct instruction *insn = NULL;
341 unsigned int offset;
342 unsigned int end = (sec->len > 10) ? sec->len - 10 : 0;
343
344 for (offset = sec->len - 1; offset >= end && !insn; offset--)
345 insn = find_insn(file, sec, offset);
346
347 return insn;
348}
349
350/*
351 * Mark "ud2" instructions and manually annotated dead ends.
352 */
353static int add_dead_ends(struct objtool_file *file)
354{
355 struct section *sec;
356 struct reloc *reloc;
357 struct instruction *insn;
358
359 /*
360 * By default, "ud2" is a dead end unless otherwise annotated, because
361 * GCC 7 inserts it for certain divide-by-zero cases.
362 */
363 for_each_insn(file, insn)
364 if (insn->type == INSN_BUG)
365 insn->dead_end = true;
366
367 /*
368 * Check for manually annotated dead ends.
369 */
370 sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
371 if (!sec)
372 goto reachable;
373
374 list_for_each_entry(reloc, &sec->reloc_list, list) {
375 if (reloc->sym->type != STT_SECTION) {
376 WARN("unexpected relocation symbol type in %s", sec->name);
377 return -1;
378 }
379 insn = find_insn(file, reloc->sym->sec, reloc->addend);
380 if (insn)
381 insn = list_prev_entry(insn, list);
382 else if (reloc->addend == reloc->sym->sec->len) {
383 insn = find_last_insn(file, reloc->sym->sec);
384 if (!insn) {
385 WARN("can't find unreachable insn at %s+0x%x",
386 reloc->sym->sec->name, reloc->addend);
387 return -1;
388 }
389 } else {
390 WARN("can't find unreachable insn at %s+0x%x",
391 reloc->sym->sec->name, reloc->addend);
392 return -1;
393 }
394
395 insn->dead_end = true;
396 }
397
398reachable:
399 /*
400 * These manually annotated reachable checks are needed for GCC 4.4,
401 * where the Linux unreachable() macro isn't supported. In that case
402 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
403 * not a dead end.
404 */
405 sec = find_section_by_name(file->elf, ".rela.discard.reachable");
406 if (!sec)
407 return 0;
408
409 list_for_each_entry(reloc, &sec->reloc_list, list) {
410 if (reloc->sym->type != STT_SECTION) {
411 WARN("unexpected relocation symbol type in %s", sec->name);
412 return -1;
413 }
414 insn = find_insn(file, reloc->sym->sec, reloc->addend);
415 if (insn)
416 insn = list_prev_entry(insn, list);
417 else if (reloc->addend == reloc->sym->sec->len) {
418 insn = find_last_insn(file, reloc->sym->sec);
419 if (!insn) {
420 WARN("can't find reachable insn at %s+0x%x",
421 reloc->sym->sec->name, reloc->addend);
422 return -1;
423 }
424 } else {
425 WARN("can't find reachable insn at %s+0x%x",
426 reloc->sym->sec->name, reloc->addend);
427 return -1;
428 }
429
430 insn->dead_end = false;
431 }
432
433 return 0;
434}
435
436/*
437 * Warnings shouldn't be reported for ignored functions.
438 */
439static void add_ignores(struct objtool_file *file)
440{
441 struct instruction *insn;
442 struct section *sec;
443 struct symbol *func;
444 struct reloc *reloc;
445
446 sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
447 if (!sec)
448 return;
449
450 list_for_each_entry(reloc, &sec->reloc_list, list) {
451 switch (reloc->sym->type) {
452 case STT_FUNC:
453 func = reloc->sym;
454 break;
455
456 case STT_SECTION:
457 func = find_func_by_offset(reloc->sym->sec, reloc->addend);
458 if (!func)
459 continue;
460 break;
461
462 default:
463 WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type);
464 continue;
465 }
466
467 func_for_each_insn(file, func, insn)
468 insn->ignore = true;
469 }
470}
471
472/*
473 * This is a whitelist of functions that is allowed to be called with AC set.
474 * The list is meant to be minimal and only contains compiler instrumentation
475 * ABI and a few functions used to implement *_{to,from}_user() functions.
476 *
477 * These functions must not directly change AC, but may PUSHF/POPF.
478 */
479static const char *uaccess_safe_builtin[] = {
480 /* KASAN */
481 "kasan_report",
482 "check_memory_region",
483 /* KASAN out-of-line */
484 "__asan_loadN_noabort",
485 "__asan_load1_noabort",
486 "__asan_load2_noabort",
487 "__asan_load4_noabort",
488 "__asan_load8_noabort",
489 "__asan_load16_noabort",
490 "__asan_storeN_noabort",
491 "__asan_store1_noabort",
492 "__asan_store2_noabort",
493 "__asan_store4_noabort",
494 "__asan_store8_noabort",
495 "__asan_store16_noabort",
496 /* KASAN in-line */
497 "__asan_report_load_n_noabort",
498 "__asan_report_load1_noabort",
499 "__asan_report_load2_noabort",
500 "__asan_report_load4_noabort",
501 "__asan_report_load8_noabort",
502 "__asan_report_load16_noabort",
503 "__asan_report_store_n_noabort",
504 "__asan_report_store1_noabort",
505 "__asan_report_store2_noabort",
506 "__asan_report_store4_noabort",
507 "__asan_report_store8_noabort",
508 "__asan_report_store16_noabort",
509 /* KCSAN */
510 "__kcsan_check_access",
511 "kcsan_found_watchpoint",
512 "kcsan_setup_watchpoint",
513 "kcsan_check_scoped_accesses",
514 "kcsan_disable_current",
515 "kcsan_enable_current_nowarn",
516 /* KCSAN/TSAN */
517 "__tsan_func_entry",
518 "__tsan_func_exit",
519 "__tsan_read_range",
520 "__tsan_write_range",
521 "__tsan_read1",
522 "__tsan_read2",
523 "__tsan_read4",
524 "__tsan_read8",
525 "__tsan_read16",
526 "__tsan_write1",
527 "__tsan_write2",
528 "__tsan_write4",
529 "__tsan_write8",
530 "__tsan_write16",
531 /* KCOV */
532 "write_comp_data",
533 "check_kcov_mode",
534 "__sanitizer_cov_trace_pc",
535 "__sanitizer_cov_trace_const_cmp1",
536 "__sanitizer_cov_trace_const_cmp2",
537 "__sanitizer_cov_trace_const_cmp4",
538 "__sanitizer_cov_trace_const_cmp8",
539 "__sanitizer_cov_trace_cmp1",
540 "__sanitizer_cov_trace_cmp2",
541 "__sanitizer_cov_trace_cmp4",
542 "__sanitizer_cov_trace_cmp8",
543 "__sanitizer_cov_trace_switch",
544 /* UBSAN */
545 "ubsan_type_mismatch_common",
546 "__ubsan_handle_type_mismatch",
547 "__ubsan_handle_type_mismatch_v1",
548 "__ubsan_handle_shift_out_of_bounds",
549 /* misc */
550 "csum_partial_copy_generic",
551 "__memcpy_mcsafe",
552 "mcsafe_handle_tail",
553 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
554 NULL
555};
556
557static void add_uaccess_safe(struct objtool_file *file)
558{
559 struct symbol *func;
560 const char **name;
561
562 if (!uaccess)
563 return;
564
565 for (name = uaccess_safe_builtin; *name; name++) {
566 func = find_symbol_by_name(file->elf, *name);
567 if (!func)
568 continue;
569
570 func->uaccess_safe = true;
571 }
572}
573
574/*
575 * FIXME: For now, just ignore any alternatives which add retpolines. This is
576 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
577 * But it at least allows objtool to understand the control flow *around* the
578 * retpoline.
579 */
580static int add_ignore_alternatives(struct objtool_file *file)
581{
582 struct section *sec;
583 struct reloc *reloc;
584 struct instruction *insn;
585
586 sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
587 if (!sec)
588 return 0;
589
590 list_for_each_entry(reloc, &sec->reloc_list, list) {
591 if (reloc->sym->type != STT_SECTION) {
592 WARN("unexpected relocation symbol type in %s", sec->name);
593 return -1;
594 }
595
596 insn = find_insn(file, reloc->sym->sec, reloc->addend);
597 if (!insn) {
598 WARN("bad .discard.ignore_alts entry");
599 return -1;
600 }
601
602 insn->ignore_alts = true;
603 }
604
605 return 0;
606}
607
608/*
609 * Find the destination instructions for all jumps.
610 */
611static int add_jump_destinations(struct objtool_file *file)
612{
613 struct instruction *insn;
614 struct reloc *reloc;
615 struct section *dest_sec;
616 unsigned long dest_off;
617
618 for_each_insn(file, insn) {
619 if (!is_static_jump(insn))
620 continue;
621
622 if (insn->offset == FAKE_JUMP_OFFSET)
623 continue;
624
625 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
626 insn->offset, insn->len);
627 if (!reloc) {
628 dest_sec = insn->sec;
629 dest_off = arch_jump_destination(insn);
630 } else if (reloc->sym->type == STT_SECTION) {
631 dest_sec = reloc->sym->sec;
632 dest_off = arch_dest_reloc_offset(reloc->addend);
633 } else if (reloc->sym->sec->idx) {
634 dest_sec = reloc->sym->sec;
635 dest_off = reloc->sym->sym.st_value +
636 arch_dest_reloc_offset(reloc->addend);
637 } else if (strstr(reloc->sym->name, "_indirect_thunk_")) {
638 /*
639 * Retpoline jumps are really dynamic jumps in
640 * disguise, so convert them accordingly.
641 */
642 if (insn->type == INSN_JUMP_UNCONDITIONAL)
643 insn->type = INSN_JUMP_DYNAMIC;
644 else
645 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
646
647 insn->retpoline_safe = true;
648 continue;
649 } else {
650 /* external sibling call */
651 insn->call_dest = reloc->sym;
652 continue;
653 }
654
655 insn->jump_dest = find_insn(file, dest_sec, dest_off);
656 if (!insn->jump_dest) {
657
658 /*
659 * This is a special case where an alt instruction
660 * jumps past the end of the section. These are
661 * handled later in handle_group_alt().
662 */
663 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
664 continue;
665
666 WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
667 insn->sec, insn->offset, dest_sec->name,
668 dest_off);
669 return -1;
670 }
671
672 /*
673 * Cross-function jump.
674 */
675 if (insn->func && insn->jump_dest->func &&
676 insn->func != insn->jump_dest->func) {
677
678 /*
679 * For GCC 8+, create parent/child links for any cold
680 * subfunctions. This is _mostly_ redundant with a
681 * similar initialization in read_symbols().
682 *
683 * If a function has aliases, we want the *first* such
684 * function in the symbol table to be the subfunction's
685 * parent. In that case we overwrite the
686 * initialization done in read_symbols().
687 *
688 * However this code can't completely replace the
689 * read_symbols() code because this doesn't detect the
690 * case where the parent function's only reference to a
691 * subfunction is through a jump table.
692 */
693 if (!strstr(insn->func->name, ".cold.") &&
694 strstr(insn->jump_dest->func->name, ".cold.")) {
695 insn->func->cfunc = insn->jump_dest->func;
696 insn->jump_dest->func->pfunc = insn->func;
697
698 } else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
699 insn->jump_dest->offset == insn->jump_dest->func->offset) {
700
701 /* internal sibling call */
702 insn->call_dest = insn->jump_dest->func;
703 }
704 }
705 }
706
707 return 0;
708}
709
710static void remove_insn_ops(struct instruction *insn)
711{
712 struct stack_op *op, *tmp;
713
714 list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
715 list_del(&op->list);
716 free(op);
717 }
718}
719
720/*
721 * Find the destination instructions for all calls.
722 */
723static int add_call_destinations(struct objtool_file *file)
724{
725 struct instruction *insn;
726 unsigned long dest_off;
727 struct reloc *reloc;
728
729 for_each_insn(file, insn) {
730 if (insn->type != INSN_CALL)
731 continue;
732
733 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
734 insn->offset, insn->len);
735 if (!reloc) {
736 dest_off = arch_jump_destination(insn);
737 insn->call_dest = find_func_by_offset(insn->sec, dest_off);
738 if (!insn->call_dest)
739 insn->call_dest = find_symbol_by_offset(insn->sec, dest_off);
740
741 if (insn->ignore)
742 continue;
743
744 if (!insn->call_dest) {
745 WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);
746 return -1;
747 }
748
749 if (insn->func && insn->call_dest->type != STT_FUNC) {
750 WARN_FUNC("unsupported call to non-function",
751 insn->sec, insn->offset);
752 return -1;
753 }
754
755 } else if (reloc->sym->type == STT_SECTION) {
756 dest_off = arch_dest_reloc_offset(reloc->addend);
757 insn->call_dest = find_func_by_offset(reloc->sym->sec,
758 dest_off);
759 if (!insn->call_dest) {
760 WARN_FUNC("can't find call dest symbol at %s+0x%lx",
761 insn->sec, insn->offset,
762 reloc->sym->sec->name,
763 dest_off);
764 return -1;
765 }
766 } else
767 insn->call_dest = reloc->sym;
768
769 /*
770 * Many compilers cannot disable KCOV with a function attribute
771 * so they need a little help, NOP out any KCOV calls from noinstr
772 * text.
773 */
774 if (insn->sec->noinstr &&
775 !strncmp(insn->call_dest->name, "__sanitizer_cov_", 16)) {
776 if (reloc) {
777 reloc->type = R_NONE;
778 elf_write_reloc(file->elf, reloc);
779 }
780
781 elf_write_insn(file->elf, insn->sec,
782 insn->offset, insn->len,
783 arch_nop_insn(insn->len));
784 insn->type = INSN_NOP;
785 }
786
787 /*
788 * Whatever stack impact regular CALLs have, should be undone
789 * by the RETURN of the called function.
790 *
791 * Annotated intra-function calls retain the stack_ops but
792 * are converted to JUMP, see read_intra_function_calls().
793 */
794 remove_insn_ops(insn);
795 }
796
797 return 0;
798}
799
800/*
801 * The .alternatives section requires some extra special care, over and above
802 * what other special sections require:
803 *
804 * 1. Because alternatives are patched in-place, we need to insert a fake jump
805 * instruction at the end so that validate_branch() skips all the original
806 * replaced instructions when validating the new instruction path.
807 *
808 * 2. An added wrinkle is that the new instruction length might be zero. In
809 * that case the old instructions are replaced with noops. We simulate that
810 * by creating a fake jump as the only new instruction.
811 *
812 * 3. In some cases, the alternative section includes an instruction which
813 * conditionally jumps to the _end_ of the entry. We have to modify these
814 * jumps' destinations to point back to .text rather than the end of the
815 * entry in .altinstr_replacement.
816 */
817static int handle_group_alt(struct objtool_file *file,
818 struct special_alt *special_alt,
819 struct instruction *orig_insn,
820 struct instruction **new_insn)
821{
822 static unsigned int alt_group_next_index = 1;
823 struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
824 unsigned int alt_group = alt_group_next_index++;
825 unsigned long dest_off;
826
827 last_orig_insn = NULL;
828 insn = orig_insn;
829 sec_for_each_insn_from(file, insn) {
830 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
831 break;
832
833 insn->alt_group = alt_group;
834 last_orig_insn = insn;
835 }
836
837 if (next_insn_same_sec(file, last_orig_insn)) {
838 fake_jump = malloc(sizeof(*fake_jump));
839 if (!fake_jump) {
840 WARN("malloc failed");
841 return -1;
842 }
843 memset(fake_jump, 0, sizeof(*fake_jump));
844 INIT_LIST_HEAD(&fake_jump->alts);
845 INIT_LIST_HEAD(&fake_jump->stack_ops);
846 init_cfi_state(&fake_jump->cfi);
847
848 fake_jump->sec = special_alt->new_sec;
849 fake_jump->offset = FAKE_JUMP_OFFSET;
850 fake_jump->type = INSN_JUMP_UNCONDITIONAL;
851 fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
852 fake_jump->func = orig_insn->func;
853 }
854
855 if (!special_alt->new_len) {
856 if (!fake_jump) {
857 WARN("%s: empty alternative at end of section",
858 special_alt->orig_sec->name);
859 return -1;
860 }
861
862 *new_insn = fake_jump;
863 return 0;
864 }
865
866 last_new_insn = NULL;
867 alt_group = alt_group_next_index++;
868 insn = *new_insn;
869 sec_for_each_insn_from(file, insn) {
870 if (insn->offset >= special_alt->new_off + special_alt->new_len)
871 break;
872
873 last_new_insn = insn;
874
875 insn->ignore = orig_insn->ignore_alts;
876 insn->func = orig_insn->func;
877 insn->alt_group = alt_group;
878
879 /*
880 * Since alternative replacement code is copy/pasted by the
881 * kernel after applying relocations, generally such code can't
882 * have relative-address relocation references to outside the
883 * .altinstr_replacement section, unless the arch's
884 * alternatives code can adjust the relative offsets
885 * accordingly.
886 *
887 * The x86 alternatives code adjusts the offsets only when it
888 * encounters a branch instruction at the very beginning of the
889 * replacement group.
890 */
891 if ((insn->offset != special_alt->new_off ||
892 (insn->type != INSN_CALL && !is_static_jump(insn))) &&
893 find_reloc_by_dest_range(file->elf, insn->sec, insn->offset, insn->len)) {
894
895 WARN_FUNC("unsupported relocation in alternatives section",
896 insn->sec, insn->offset);
897 return -1;
898 }
899
900 if (!is_static_jump(insn))
901 continue;
902
903 if (!insn->immediate)
904 continue;
905
906 dest_off = arch_jump_destination(insn);
907 if (dest_off == special_alt->new_off + special_alt->new_len) {
908 if (!fake_jump) {
909 WARN("%s: alternative jump to end of section",
910 special_alt->orig_sec->name);
911 return -1;
912 }
913 insn->jump_dest = fake_jump;
914 }
915
916 if (!insn->jump_dest) {
917 WARN_FUNC("can't find alternative jump destination",
918 insn->sec, insn->offset);
919 return -1;
920 }
921 }
922
923 if (!last_new_insn) {
924 WARN_FUNC("can't find last new alternative instruction",
925 special_alt->new_sec, special_alt->new_off);
926 return -1;
927 }
928
929 if (fake_jump)
930 list_add(&fake_jump->list, &last_new_insn->list);
931
932 return 0;
933}
934
935/*
936 * A jump table entry can either convert a nop to a jump or a jump to a nop.
937 * If the original instruction is a jump, make the alt entry an effective nop
938 * by just skipping the original instruction.
939 */
940static int handle_jump_alt(struct objtool_file *file,
941 struct special_alt *special_alt,
942 struct instruction *orig_insn,
943 struct instruction **new_insn)
944{
945 if (orig_insn->type == INSN_NOP)
946 return 0;
947
948 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
949 WARN_FUNC("unsupported instruction at jump label",
950 orig_insn->sec, orig_insn->offset);
951 return -1;
952 }
953
954 *new_insn = list_next_entry(orig_insn, list);
955 return 0;
956}
957
958/*
959 * Read all the special sections which have alternate instructions which can be
960 * patched in or redirected to at runtime. Each instruction having alternate
961 * instruction(s) has them added to its insn->alts list, which will be
962 * traversed in validate_branch().
963 */
964static int add_special_section_alts(struct objtool_file *file)
965{
966 struct list_head special_alts;
967 struct instruction *orig_insn, *new_insn;
968 struct special_alt *special_alt, *tmp;
969 struct alternative *alt;
970 int ret;
971
972 ret = special_get_alts(file->elf, &special_alts);
973 if (ret)
974 return ret;
975
976 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
977
978 orig_insn = find_insn(file, special_alt->orig_sec,
979 special_alt->orig_off);
980 if (!orig_insn) {
981 WARN_FUNC("special: can't find orig instruction",
982 special_alt->orig_sec, special_alt->orig_off);
983 ret = -1;
984 goto out;
985 }
986
987 new_insn = NULL;
988 if (!special_alt->group || special_alt->new_len) {
989 new_insn = find_insn(file, special_alt->new_sec,
990 special_alt->new_off);
991 if (!new_insn) {
992 WARN_FUNC("special: can't find new instruction",
993 special_alt->new_sec,
994 special_alt->new_off);
995 ret = -1;
996 goto out;
997 }
998 }
999
1000 if (special_alt->group) {
1001 if (!special_alt->orig_len) {
1002 WARN_FUNC("empty alternative entry",
1003 orig_insn->sec, orig_insn->offset);
1004 continue;
1005 }
1006
1007 ret = handle_group_alt(file, special_alt, orig_insn,
1008 &new_insn);
1009 if (ret)
1010 goto out;
1011 } else if (special_alt->jump_or_nop) {
1012 ret = handle_jump_alt(file, special_alt, orig_insn,
1013 &new_insn);
1014 if (ret)
1015 goto out;
1016 }
1017
1018 alt = malloc(sizeof(*alt));
1019 if (!alt) {
1020 WARN("malloc failed");
1021 ret = -1;
1022 goto out;
1023 }
1024
1025 alt->insn = new_insn;
1026 alt->skip_orig = special_alt->skip_orig;
1027 orig_insn->ignore_alts |= special_alt->skip_alt;
1028 list_add_tail(&alt->list, &orig_insn->alts);
1029
1030 list_del(&special_alt->list);
1031 free(special_alt);
1032 }
1033
1034out:
1035 return ret;
1036}
1037
1038static int add_jump_table(struct objtool_file *file, struct instruction *insn,
1039 struct reloc *table)
1040{
1041 struct reloc *reloc = table;
1042 struct instruction *dest_insn;
1043 struct alternative *alt;
1044 struct symbol *pfunc = insn->func->pfunc;
1045 unsigned int prev_offset = 0;
1046
1047 /*
1048 * Each @reloc is a switch table relocation which points to the target
1049 * instruction.
1050 */
1051 list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
1052
1053 /* Check for the end of the table: */
1054 if (reloc != table && reloc->jump_table_start)
1055 break;
1056
1057 /* Make sure the table entries are consecutive: */
1058 if (prev_offset && reloc->offset != prev_offset + 8)
1059 break;
1060
1061 /* Detect function pointers from contiguous objects: */
1062 if (reloc->sym->sec == pfunc->sec &&
1063 reloc->addend == pfunc->offset)
1064 break;
1065
1066 dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
1067 if (!dest_insn)
1068 break;
1069
1070 /* Make sure the destination is in the same function: */
1071 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
1072 break;
1073
1074 alt = malloc(sizeof(*alt));
1075 if (!alt) {
1076 WARN("malloc failed");
1077 return -1;
1078 }
1079
1080 alt->insn = dest_insn;
1081 list_add_tail(&alt->list, &insn->alts);
1082 prev_offset = reloc->offset;
1083 }
1084
1085 if (!prev_offset) {
1086 WARN_FUNC("can't find switch jump table",
1087 insn->sec, insn->offset);
1088 return -1;
1089 }
1090
1091 return 0;
1092}
1093
1094/*
1095 * find_jump_table() - Given a dynamic jump, find the switch jump table in
1096 * .rodata associated with it.
1097 *
1098 * There are 3 basic patterns:
1099 *
1100 * 1. jmpq *[rodata addr](,%reg,8)
1101 *
1102 * This is the most common case by far. It jumps to an address in a simple
1103 * jump table which is stored in .rodata.
1104 *
1105 * 2. jmpq *[rodata addr](%rip)
1106 *
1107 * This is caused by a rare GCC quirk, currently only seen in three driver
1108 * functions in the kernel, only with certain obscure non-distro configs.
1109 *
1110 * As part of an optimization, GCC makes a copy of an existing switch jump
1111 * table, modifies it, and then hard-codes the jump (albeit with an indirect
1112 * jump) to use a single entry in the table. The rest of the jump table and
1113 * some of its jump targets remain as dead code.
1114 *
1115 * In such a case we can just crudely ignore all unreachable instruction
1116 * warnings for the entire object file. Ideally we would just ignore them
1117 * for the function, but that would require redesigning the code quite a
1118 * bit. And honestly that's just not worth doing: unreachable instruction
1119 * warnings are of questionable value anyway, and this is such a rare issue.
1120 *
1121 * 3. mov [rodata addr],%reg1
1122 * ... some instructions ...
1123 * jmpq *(%reg1,%reg2,8)
1124 *
1125 * This is a fairly uncommon pattern which is new for GCC 6. As of this
1126 * writing, there are 11 occurrences of it in the allmodconfig kernel.
1127 *
1128 * As of GCC 7 there are quite a few more of these and the 'in between' code
1129 * is significant. Esp. with KASAN enabled some of the code between the mov
1130 * and jmpq uses .rodata itself, which can confuse things.
1131 *
1132 * TODO: Once we have DWARF CFI and smarter instruction decoding logic,
1133 * ensure the same register is used in the mov and jump instructions.
1134 *
1135 * NOTE: RETPOLINE made it harder still to decode dynamic jumps.
1136 */
1137static struct reloc *find_jump_table(struct objtool_file *file,
1138 struct symbol *func,
1139 struct instruction *insn)
1140{
1141 struct reloc *text_reloc, *table_reloc;
1142 struct instruction *dest_insn, *orig_insn = insn;
1143 struct section *table_sec;
1144 unsigned long table_offset;
1145
1146 /*
1147 * Backward search using the @first_jump_src links, these help avoid
1148 * much of the 'in between' code. Which avoids us getting confused by
1149 * it.
1150 */
1151 for (;
1152 insn && insn->func && insn->func->pfunc == func;
1153 insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
1154
1155 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1156 break;
1157
1158 /* allow small jumps within the range */
1159 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1160 insn->jump_dest &&
1161 (insn->jump_dest->offset <= insn->offset ||
1162 insn->jump_dest->offset > orig_insn->offset))
1163 break;
1164
1165 /* look for a relocation which references .rodata */
1166 text_reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1167 insn->offset, insn->len);
1168 if (!text_reloc || text_reloc->sym->type != STT_SECTION ||
1169 !text_reloc->sym->sec->rodata)
1170 continue;
1171
1172 table_offset = text_reloc->addend;
1173 table_sec = text_reloc->sym->sec;
1174
1175 if (text_reloc->type == R_X86_64_PC32)
1176 table_offset += 4;
1177
1178 /*
1179 * Make sure the .rodata address isn't associated with a
1180 * symbol. GCC jump tables are anonymous data.
1181 *
1182 * Also support C jump tables which are in the same format as
1183 * switch jump tables. For objtool to recognize them, they
1184 * need to be placed in the C_JUMP_TABLE_SECTION section. They
1185 * have symbols associated with them.
1186 */
1187 if (find_symbol_containing(table_sec, table_offset) &&
1188 strcmp(table_sec->name, C_JUMP_TABLE_SECTION))
1189 continue;
1190
1191 /*
1192 * Each table entry has a reloc associated with it. The reloc
1193 * should reference text in the same function as the original
1194 * instruction.
1195 */
1196 table_reloc = find_reloc_by_dest(file->elf, table_sec, table_offset);
1197 if (!table_reloc)
1198 continue;
1199 dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
1200 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1201 continue;
1202
1203 /*
1204 * Use of RIP-relative switch jumps is quite rare, and
1205 * indicates a rare GCC quirk/bug which can leave dead code
1206 * behind.
1207 */
1208 if (text_reloc->type == R_X86_64_PC32)
1209 file->ignore_unreachables = true;
1210
1211 return table_reloc;
1212 }
1213
1214 return NULL;
1215}
1216
1217/*
1218 * First pass: Mark the head of each jump table so that in the next pass,
1219 * we know when a given jump table ends and the next one starts.
1220 */
1221static void mark_func_jump_tables(struct objtool_file *file,
1222 struct symbol *func)
1223{
1224 struct instruction *insn, *last = NULL;
1225 struct reloc *reloc;
1226
1227 func_for_each_insn(file, func, insn) {
1228 if (!last)
1229 last = insn;
1230
1231 /*
1232 * Store back-pointers for unconditional forward jumps such
1233 * that find_jump_table() can back-track using those and
1234 * avoid some potentially confusing code.
1235 */
1236 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1237 insn->offset > last->offset &&
1238 insn->jump_dest->offset > insn->offset &&
1239 !insn->jump_dest->first_jump_src) {
1240
1241 insn->jump_dest->first_jump_src = insn;
1242 last = insn->jump_dest;
1243 }
1244
1245 if (insn->type != INSN_JUMP_DYNAMIC)
1246 continue;
1247
1248 reloc = find_jump_table(file, func, insn);
1249 if (reloc) {
1250 reloc->jump_table_start = true;
1251 insn->jump_table = reloc;
1252 }
1253 }
1254}
1255
1256static int add_func_jump_tables(struct objtool_file *file,
1257 struct symbol *func)
1258{
1259 struct instruction *insn;
1260 int ret;
1261
1262 func_for_each_insn(file, func, insn) {
1263 if (!insn->jump_table)
1264 continue;
1265
1266 ret = add_jump_table(file, insn, insn->jump_table);
1267 if (ret)
1268 return ret;
1269 }
1270
1271 return 0;
1272}
1273
1274/*
1275 * For some switch statements, gcc generates a jump table in the .rodata
1276 * section which contains a list of addresses within the function to jump to.
1277 * This finds these jump tables and adds them to the insn->alts lists.
1278 */
1279static int add_jump_table_alts(struct objtool_file *file)
1280{
1281 struct section *sec;
1282 struct symbol *func;
1283 int ret;
1284
1285 if (!file->rodata)
1286 return 0;
1287
1288 for_each_sec(file, sec) {
1289 list_for_each_entry(func, &sec->symbol_list, list) {
1290 if (func->type != STT_FUNC)
1291 continue;
1292
1293 mark_func_jump_tables(file, func);
1294 ret = add_func_jump_tables(file, func);
1295 if (ret)
1296 return ret;
1297 }
1298 }
1299
1300 return 0;
1301}
1302
1303static int read_unwind_hints(struct objtool_file *file)
1304{
1305 struct section *sec, *relocsec;
1306 struct reloc *reloc;
1307 struct unwind_hint *hint;
1308 struct instruction *insn;
1309 struct cfi_reg *cfa;
1310 int i;
1311
1312 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1313 if (!sec)
1314 return 0;
1315
1316 relocsec = sec->reloc;
1317 if (!relocsec) {
1318 WARN("missing .rela.discard.unwind_hints section");
1319 return -1;
1320 }
1321
1322 if (sec->len % sizeof(struct unwind_hint)) {
1323 WARN("struct unwind_hint size mismatch");
1324 return -1;
1325 }
1326
1327 file->hints = true;
1328
1329 for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
1330 hint = (struct unwind_hint *)sec->data->d_buf + i;
1331
1332 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
1333 if (!reloc) {
1334 WARN("can't find reloc for unwind_hints[%d]", i);
1335 return -1;
1336 }
1337
1338 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1339 if (!insn) {
1340 WARN("can't find insn for unwind_hints[%d]", i);
1341 return -1;
1342 }
1343
1344 cfa = &insn->cfi.cfa;
1345
1346 if (hint->type == UNWIND_HINT_TYPE_RET_OFFSET) {
1347 insn->ret_offset = hint->sp_offset;
1348 continue;
1349 }
1350
1351 insn->hint = true;
1352
1353 switch (hint->sp_reg) {
1354 case ORC_REG_UNDEFINED:
1355 cfa->base = CFI_UNDEFINED;
1356 break;
1357 case ORC_REG_SP:
1358 cfa->base = CFI_SP;
1359 break;
1360 case ORC_REG_BP:
1361 cfa->base = CFI_BP;
1362 break;
1363 case ORC_REG_SP_INDIRECT:
1364 cfa->base = CFI_SP_INDIRECT;
1365 break;
1366 case ORC_REG_R10:
1367 cfa->base = CFI_R10;
1368 break;
1369 case ORC_REG_R13:
1370 cfa->base = CFI_R13;
1371 break;
1372 case ORC_REG_DI:
1373 cfa->base = CFI_DI;
1374 break;
1375 case ORC_REG_DX:
1376 cfa->base = CFI_DX;
1377 break;
1378 default:
1379 WARN_FUNC("unsupported unwind_hint sp base reg %d",
1380 insn->sec, insn->offset, hint->sp_reg);
1381 return -1;
1382 }
1383
1384 cfa->offset = hint->sp_offset;
1385 insn->cfi.type = hint->type;
1386 insn->cfi.end = hint->end;
1387 }
1388
1389 return 0;
1390}
1391
1392static int read_retpoline_hints(struct objtool_file *file)
1393{
1394 struct section *sec;
1395 struct instruction *insn;
1396 struct reloc *reloc;
1397
1398 sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1399 if (!sec)
1400 return 0;
1401
1402 list_for_each_entry(reloc, &sec->reloc_list, list) {
1403 if (reloc->sym->type != STT_SECTION) {
1404 WARN("unexpected relocation symbol type in %s", sec->name);
1405 return -1;
1406 }
1407
1408 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1409 if (!insn) {
1410 WARN("bad .discard.retpoline_safe entry");
1411 return -1;
1412 }
1413
1414 if (insn->type != INSN_JUMP_DYNAMIC &&
1415 insn->type != INSN_CALL_DYNAMIC) {
1416 WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1417 insn->sec, insn->offset);
1418 return -1;
1419 }
1420
1421 insn->retpoline_safe = true;
1422 }
1423
1424 return 0;
1425}
1426
1427static int read_instr_hints(struct objtool_file *file)
1428{
1429 struct section *sec;
1430 struct instruction *insn;
1431 struct reloc *reloc;
1432
1433 sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
1434 if (!sec)
1435 return 0;
1436
1437 list_for_each_entry(reloc, &sec->reloc_list, list) {
1438 if (reloc->sym->type != STT_SECTION) {
1439 WARN("unexpected relocation symbol type in %s", sec->name);
1440 return -1;
1441 }
1442
1443 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1444 if (!insn) {
1445 WARN("bad .discard.instr_end entry");
1446 return -1;
1447 }
1448
1449 insn->instr--;
1450 }
1451
1452 sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
1453 if (!sec)
1454 return 0;
1455
1456 list_for_each_entry(reloc, &sec->reloc_list, list) {
1457 if (reloc->sym->type != STT_SECTION) {
1458 WARN("unexpected relocation symbol type in %s", sec->name);
1459 return -1;
1460 }
1461
1462 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1463 if (!insn) {
1464 WARN("bad .discard.instr_begin entry");
1465 return -1;
1466 }
1467
1468 insn->instr++;
1469 }
1470
1471 return 0;
1472}
1473
1474static int read_intra_function_calls(struct objtool_file *file)
1475{
1476 struct instruction *insn;
1477 struct section *sec;
1478 struct reloc *reloc;
1479
1480 sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
1481 if (!sec)
1482 return 0;
1483
1484 list_for_each_entry(reloc, &sec->reloc_list, list) {
1485 unsigned long dest_off;
1486
1487 if (reloc->sym->type != STT_SECTION) {
1488 WARN("unexpected relocation symbol type in %s",
1489 sec->name);
1490 return -1;
1491 }
1492
1493 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1494 if (!insn) {
1495 WARN("bad .discard.intra_function_call entry");
1496 return -1;
1497 }
1498
1499 if (insn->type != INSN_CALL) {
1500 WARN_FUNC("intra_function_call not a direct call",
1501 insn->sec, insn->offset);
1502 return -1;
1503 }
1504
1505 /*
1506 * Treat intra-function CALLs as JMPs, but with a stack_op.
1507 * See add_call_destinations(), which strips stack_ops from
1508 * normal CALLs.
1509 */
1510 insn->type = INSN_JUMP_UNCONDITIONAL;
1511
1512 dest_off = insn->offset + insn->len + insn->immediate;
1513 insn->jump_dest = find_insn(file, insn->sec, dest_off);
1514 if (!insn->jump_dest) {
1515 WARN_FUNC("can't find call dest at %s+0x%lx",
1516 insn->sec, insn->offset,
1517 insn->sec->name, dest_off);
1518 return -1;
1519 }
1520 }
1521
1522 return 0;
1523}
1524
1525static void mark_rodata(struct objtool_file *file)
1526{
1527 struct section *sec;
1528 bool found = false;
1529
1530 /*
1531 * Search for the following rodata sections, each of which can
1532 * potentially contain jump tables:
1533 *
1534 * - .rodata: can contain GCC switch tables
1535 * - .rodata.<func>: same, if -fdata-sections is being used
1536 * - .rodata..c_jump_table: contains C annotated jump tables
1537 *
1538 * .rodata.str1.* sections are ignored; they don't contain jump tables.
1539 */
1540 for_each_sec(file, sec) {
1541 if (!strncmp(sec->name, ".rodata", 7) &&
1542 !strstr(sec->name, ".str1.")) {
1543 sec->rodata = true;
1544 found = true;
1545 }
1546 }
1547
1548 file->rodata = found;
1549}
1550
1551static int decode_sections(struct objtool_file *file)
1552{
1553 int ret;
1554
1555 mark_rodata(file);
1556
1557 ret = decode_instructions(file);
1558 if (ret)
1559 return ret;
1560
1561 ret = add_dead_ends(file);
1562 if (ret)
1563 return ret;
1564
1565 add_ignores(file);
1566 add_uaccess_safe(file);
1567
1568 ret = add_ignore_alternatives(file);
1569 if (ret)
1570 return ret;
1571
1572 ret = add_jump_destinations(file);
1573 if (ret)
1574 return ret;
1575
1576 ret = add_special_section_alts(file);
1577 if (ret)
1578 return ret;
1579
1580 ret = read_intra_function_calls(file);
1581 if (ret)
1582 return ret;
1583
1584 ret = add_call_destinations(file);
1585 if (ret)
1586 return ret;
1587
1588 ret = add_jump_table_alts(file);
1589 if (ret)
1590 return ret;
1591
1592 ret = read_unwind_hints(file);
1593 if (ret)
1594 return ret;
1595
1596 ret = read_retpoline_hints(file);
1597 if (ret)
1598 return ret;
1599
1600 ret = read_instr_hints(file);
1601 if (ret)
1602 return ret;
1603
1604 return 0;
1605}
1606
1607static bool is_fentry_call(struct instruction *insn)
1608{
1609 if (insn->type == INSN_CALL && insn->call_dest &&
1610 insn->call_dest->type == STT_NOTYPE &&
1611 !strcmp(insn->call_dest->name, "__fentry__"))
1612 return true;
1613
1614 return false;
1615}
1616
1617static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
1618{
1619 u8 ret_offset = insn->ret_offset;
1620 struct cfi_state *cfi = &state->cfi;
1621 int i;
1622
1623 if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
1624 return true;
1625
1626 if (cfi->cfa.offset != initial_func_cfi.cfa.offset + ret_offset)
1627 return true;
1628
1629 if (cfi->stack_size != initial_func_cfi.cfa.offset + ret_offset)
1630 return true;
1631
1632 /*
1633 * If there is a ret offset hint then don't check registers
1634 * because a callee-saved register might have been pushed on
1635 * the stack.
1636 */
1637 if (ret_offset)
1638 return false;
1639
1640 for (i = 0; i < CFI_NUM_REGS; i++) {
1641 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
1642 cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
1643 return true;
1644 }
1645
1646 return false;
1647}
1648
1649static bool has_valid_stack_frame(struct insn_state *state)
1650{
1651 struct cfi_state *cfi = &state->cfi;
1652
1653 if (cfi->cfa.base == CFI_BP && cfi->regs[CFI_BP].base == CFI_CFA &&
1654 cfi->regs[CFI_BP].offset == -16)
1655 return true;
1656
1657 if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
1658 return true;
1659
1660 return false;
1661}
1662
1663static int update_cfi_state_regs(struct instruction *insn,
1664 struct cfi_state *cfi,
1665 struct stack_op *op)
1666{
1667 struct cfi_reg *cfa = &cfi->cfa;
1668
1669 if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
1670 return 0;
1671
1672 /* push */
1673 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
1674 cfa->offset += 8;
1675
1676 /* pop */
1677 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
1678 cfa->offset -= 8;
1679
1680 /* add immediate to sp */
1681 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1682 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1683 cfa->offset -= op->src.offset;
1684
1685 return 0;
1686}
1687
1688static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
1689{
1690 if (arch_callee_saved_reg(reg) &&
1691 cfi->regs[reg].base == CFI_UNDEFINED) {
1692 cfi->regs[reg].base = base;
1693 cfi->regs[reg].offset = offset;
1694 }
1695}
1696
1697static void restore_reg(struct cfi_state *cfi, unsigned char reg)
1698{
1699 cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
1700 cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
1701}
1702
1703/*
1704 * A note about DRAP stack alignment:
1705 *
1706 * GCC has the concept of a DRAP register, which is used to help keep track of
1707 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
1708 * register. The typical DRAP pattern is:
1709 *
1710 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
1711 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
1712 * 41 ff 72 f8 pushq -0x8(%r10)
1713 * 55 push %rbp
1714 * 48 89 e5 mov %rsp,%rbp
1715 * (more pushes)
1716 * 41 52 push %r10
1717 * ...
1718 * 41 5a pop %r10
1719 * (more pops)
1720 * 5d pop %rbp
1721 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1722 * c3 retq
1723 *
1724 * There are some variations in the epilogues, like:
1725 *
1726 * 5b pop %rbx
1727 * 41 5a pop %r10
1728 * 41 5c pop %r12
1729 * 41 5d pop %r13
1730 * 41 5e pop %r14
1731 * c9 leaveq
1732 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1733 * c3 retq
1734 *
1735 * and:
1736 *
1737 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
1738 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
1739 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
1740 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
1741 * c9 leaveq
1742 * 49 8d 62 f8 lea -0x8(%r10),%rsp
1743 * c3 retq
1744 *
1745 * Sometimes r13 is used as the DRAP register, in which case it's saved and
1746 * restored beforehand:
1747 *
1748 * 41 55 push %r13
1749 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
1750 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
1751 * ...
1752 * 49 8d 65 f0 lea -0x10(%r13),%rsp
1753 * 41 5d pop %r13
1754 * c3 retq
1755 */
1756static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi,
1757 struct stack_op *op)
1758{
1759 struct cfi_reg *cfa = &cfi->cfa;
1760 struct cfi_reg *regs = cfi->regs;
1761
1762 /* stack operations don't make sense with an undefined CFA */
1763 if (cfa->base == CFI_UNDEFINED) {
1764 if (insn->func) {
1765 WARN_FUNC("undefined stack state", insn->sec, insn->offset);
1766 return -1;
1767 }
1768 return 0;
1769 }
1770
1771 if (cfi->type == ORC_TYPE_REGS || cfi->type == ORC_TYPE_REGS_IRET)
1772 return update_cfi_state_regs(insn, cfi, op);
1773
1774 switch (op->dest.type) {
1775
1776 case OP_DEST_REG:
1777 switch (op->src.type) {
1778
1779 case OP_SRC_REG:
1780 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
1781 cfa->base == CFI_SP &&
1782 regs[CFI_BP].base == CFI_CFA &&
1783 regs[CFI_BP].offset == -cfa->offset) {
1784
1785 /* mov %rsp, %rbp */
1786 cfa->base = op->dest.reg;
1787 cfi->bp_scratch = false;
1788 }
1789
1790 else if (op->src.reg == CFI_SP &&
1791 op->dest.reg == CFI_BP && cfi->drap) {
1792
1793 /* drap: mov %rsp, %rbp */
1794 regs[CFI_BP].base = CFI_BP;
1795 regs[CFI_BP].offset = -cfi->stack_size;
1796 cfi->bp_scratch = false;
1797 }
1798
1799 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1800
1801 /*
1802 * mov %rsp, %reg
1803 *
1804 * This is needed for the rare case where GCC
1805 * does:
1806 *
1807 * mov %rsp, %rax
1808 * ...
1809 * mov %rax, %rsp
1810 */
1811 cfi->vals[op->dest.reg].base = CFI_CFA;
1812 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
1813 }
1814
1815 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
1816 cfa->base == CFI_BP) {
1817
1818 /*
1819 * mov %rbp, %rsp
1820 *
1821 * Restore the original stack pointer (Clang).
1822 */
1823 cfi->stack_size = -cfi->regs[CFI_BP].offset;
1824 }
1825
1826 else if (op->dest.reg == cfa->base) {
1827
1828 /* mov %reg, %rsp */
1829 if (cfa->base == CFI_SP &&
1830 cfi->vals[op->src.reg].base == CFI_CFA) {
1831
1832 /*
1833 * This is needed for the rare case
1834 * where GCC does something dumb like:
1835 *
1836 * lea 0x8(%rsp), %rcx
1837 * ...
1838 * mov %rcx, %rsp
1839 */
1840 cfa->offset = -cfi->vals[op->src.reg].offset;
1841 cfi->stack_size = cfa->offset;
1842
1843 } else {
1844 cfa->base = CFI_UNDEFINED;
1845 cfa->offset = 0;
1846 }
1847 }
1848
1849 break;
1850
1851 case OP_SRC_ADD:
1852 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
1853
1854 /* add imm, %rsp */
1855 cfi->stack_size -= op->src.offset;
1856 if (cfa->base == CFI_SP)
1857 cfa->offset -= op->src.offset;
1858 break;
1859 }
1860
1861 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
1862
1863 /* lea disp(%rbp), %rsp */
1864 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
1865 break;
1866 }
1867
1868 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1869
1870 /* drap: lea disp(%rsp), %drap */
1871 cfi->drap_reg = op->dest.reg;
1872
1873 /*
1874 * lea disp(%rsp), %reg
1875 *
1876 * This is needed for the rare case where GCC
1877 * does something dumb like:
1878 *
1879 * lea 0x8(%rsp), %rcx
1880 * ...
1881 * mov %rcx, %rsp
1882 */
1883 cfi->vals[op->dest.reg].base = CFI_CFA;
1884 cfi->vals[op->dest.reg].offset = \
1885 -cfi->stack_size + op->src.offset;
1886
1887 break;
1888 }
1889
1890 if (cfi->drap && op->dest.reg == CFI_SP &&
1891 op->src.reg == cfi->drap_reg) {
1892
1893 /* drap: lea disp(%drap), %rsp */
1894 cfa->base = CFI_SP;
1895 cfa->offset = cfi->stack_size = -op->src.offset;
1896 cfi->drap_reg = CFI_UNDEFINED;
1897 cfi->drap = false;
1898 break;
1899 }
1900
1901 if (op->dest.reg == cfi->cfa.base) {
1902 WARN_FUNC("unsupported stack register modification",
1903 insn->sec, insn->offset);
1904 return -1;
1905 }
1906
1907 break;
1908
1909 case OP_SRC_AND:
1910 if (op->dest.reg != CFI_SP ||
1911 (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
1912 (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
1913 WARN_FUNC("unsupported stack pointer realignment",
1914 insn->sec, insn->offset);
1915 return -1;
1916 }
1917
1918 if (cfi->drap_reg != CFI_UNDEFINED) {
1919 /* drap: and imm, %rsp */
1920 cfa->base = cfi->drap_reg;
1921 cfa->offset = cfi->stack_size = 0;
1922 cfi->drap = true;
1923 }
1924
1925 /*
1926 * Older versions of GCC (4.8ish) realign the stack
1927 * without DRAP, with a frame pointer.
1928 */
1929
1930 break;
1931
1932 case OP_SRC_POP:
1933 case OP_SRC_POPF:
1934 if (!cfi->drap && op->dest.reg == cfa->base) {
1935
1936 /* pop %rbp */
1937 cfa->base = CFI_SP;
1938 }
1939
1940 if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
1941 op->dest.reg == cfi->drap_reg &&
1942 cfi->drap_offset == -cfi->stack_size) {
1943
1944 /* drap: pop %drap */
1945 cfa->base = cfi->drap_reg;
1946 cfa->offset = 0;
1947 cfi->drap_offset = -1;
1948
1949 } else if (regs[op->dest.reg].offset == -cfi->stack_size) {
1950
1951 /* pop %reg */
1952 restore_reg(cfi, op->dest.reg);
1953 }
1954
1955 cfi->stack_size -= 8;
1956 if (cfa->base == CFI_SP)
1957 cfa->offset -= 8;
1958
1959 break;
1960
1961 case OP_SRC_REG_INDIRECT:
1962 if (cfi->drap && op->src.reg == CFI_BP &&
1963 op->src.offset == cfi->drap_offset) {
1964
1965 /* drap: mov disp(%rbp), %drap */
1966 cfa->base = cfi->drap_reg;
1967 cfa->offset = 0;
1968 cfi->drap_offset = -1;
1969 }
1970
1971 if (cfi->drap && op->src.reg == CFI_BP &&
1972 op->src.offset == regs[op->dest.reg].offset) {
1973
1974 /* drap: mov disp(%rbp), %reg */
1975 restore_reg(cfi, op->dest.reg);
1976
1977 } else if (op->src.reg == cfa->base &&
1978 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
1979
1980 /* mov disp(%rbp), %reg */
1981 /* mov disp(%rsp), %reg */
1982 restore_reg(cfi, op->dest.reg);
1983 }
1984
1985 break;
1986
1987 default:
1988 WARN_FUNC("unknown stack-related instruction",
1989 insn->sec, insn->offset);
1990 return -1;
1991 }
1992
1993 break;
1994
1995 case OP_DEST_PUSH:
1996 case OP_DEST_PUSHF:
1997 cfi->stack_size += 8;
1998 if (cfa->base == CFI_SP)
1999 cfa->offset += 8;
2000
2001 if (op->src.type != OP_SRC_REG)
2002 break;
2003
2004 if (cfi->drap) {
2005 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2006
2007 /* drap: push %drap */
2008 cfa->base = CFI_BP_INDIRECT;
2009 cfa->offset = -cfi->stack_size;
2010
2011 /* save drap so we know when to restore it */
2012 cfi->drap_offset = -cfi->stack_size;
2013
2014 } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
2015
2016 /* drap: push %rbp */
2017 cfi->stack_size = 0;
2018
2019 } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
2020
2021 /* drap: push %reg */
2022 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
2023 }
2024
2025 } else {
2026
2027 /* push %reg */
2028 save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
2029 }
2030
2031 /* detect when asm code uses rbp as a scratch register */
2032 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
2033 cfa->base != CFI_BP)
2034 cfi->bp_scratch = true;
2035 break;
2036
2037 case OP_DEST_REG_INDIRECT:
2038
2039 if (cfi->drap) {
2040 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2041
2042 /* drap: mov %drap, disp(%rbp) */
2043 cfa->base = CFI_BP_INDIRECT;
2044 cfa->offset = op->dest.offset;
2045
2046 /* save drap offset so we know when to restore it */
2047 cfi->drap_offset = op->dest.offset;
2048 }
2049
2050 else if (regs[op->src.reg].base == CFI_UNDEFINED) {
2051
2052 /* drap: mov reg, disp(%rbp) */
2053 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
2054 }
2055
2056 } else if (op->dest.reg == cfa->base) {
2057
2058 /* mov reg, disp(%rbp) */
2059 /* mov reg, disp(%rsp) */
2060 save_reg(cfi, op->src.reg, CFI_CFA,
2061 op->dest.offset - cfi->cfa.offset);
2062 }
2063
2064 break;
2065
2066 case OP_DEST_LEAVE:
2067 if ((!cfi->drap && cfa->base != CFI_BP) ||
2068 (cfi->drap && cfa->base != cfi->drap_reg)) {
2069 WARN_FUNC("leave instruction with modified stack frame",
2070 insn->sec, insn->offset);
2071 return -1;
2072 }
2073
2074 /* leave (mov %rbp, %rsp; pop %rbp) */
2075
2076 cfi->stack_size = -cfi->regs[CFI_BP].offset - 8;
2077 restore_reg(cfi, CFI_BP);
2078
2079 if (!cfi->drap) {
2080 cfa->base = CFI_SP;
2081 cfa->offset -= 8;
2082 }
2083
2084 break;
2085
2086 case OP_DEST_MEM:
2087 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
2088 WARN_FUNC("unknown stack-related memory operation",
2089 insn->sec, insn->offset);
2090 return -1;
2091 }
2092
2093 /* pop mem */
2094 cfi->stack_size -= 8;
2095 if (cfa->base == CFI_SP)
2096 cfa->offset -= 8;
2097
2098 break;
2099
2100 default:
2101 WARN_FUNC("unknown stack-related instruction",
2102 insn->sec, insn->offset);
2103 return -1;
2104 }
2105
2106 return 0;
2107}
2108
2109static int handle_insn_ops(struct instruction *insn, struct insn_state *state)
2110{
2111 struct stack_op *op;
2112
2113 list_for_each_entry(op, &insn->stack_ops, list) {
2114 struct cfi_state old_cfi = state->cfi;
2115 int res;
2116
2117 res = update_cfi_state(insn, &state->cfi, op);
2118 if (res)
2119 return res;
2120
2121 if (insn->alt_group && memcmp(&state->cfi, &old_cfi, sizeof(struct cfi_state))) {
2122 WARN_FUNC("alternative modifies stack", insn->sec, insn->offset);
2123 return -1;
2124 }
2125
2126 if (op->dest.type == OP_DEST_PUSHF) {
2127 if (!state->uaccess_stack) {
2128 state->uaccess_stack = 1;
2129 } else if (state->uaccess_stack >> 31) {
2130 WARN_FUNC("PUSHF stack exhausted",
2131 insn->sec, insn->offset);
2132 return 1;
2133 }
2134 state->uaccess_stack <<= 1;
2135 state->uaccess_stack |= state->uaccess;
2136 }
2137
2138 if (op->src.type == OP_SRC_POPF) {
2139 if (state->uaccess_stack) {
2140 state->uaccess = state->uaccess_stack & 1;
2141 state->uaccess_stack >>= 1;
2142 if (state->uaccess_stack == 1)
2143 state->uaccess_stack = 0;
2144 }
2145 }
2146 }
2147
2148 return 0;
2149}
2150
2151static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
2152{
2153 struct cfi_state *cfi1 = &insn->cfi;
2154 int i;
2155
2156 if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
2157
2158 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
2159 insn->sec, insn->offset,
2160 cfi1->cfa.base, cfi1->cfa.offset,
2161 cfi2->cfa.base, cfi2->cfa.offset);
2162
2163 } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
2164 for (i = 0; i < CFI_NUM_REGS; i++) {
2165 if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
2166 sizeof(struct cfi_reg)))
2167 continue;
2168
2169 WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
2170 insn->sec, insn->offset,
2171 i, cfi1->regs[i].base, cfi1->regs[i].offset,
2172 i, cfi2->regs[i].base, cfi2->regs[i].offset);
2173 break;
2174 }
2175
2176 } else if (cfi1->type != cfi2->type) {
2177
2178 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
2179 insn->sec, insn->offset, cfi1->type, cfi2->type);
2180
2181 } else if (cfi1->drap != cfi2->drap ||
2182 (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
2183 (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
2184
2185 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
2186 insn->sec, insn->offset,
2187 cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
2188 cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
2189
2190 } else
2191 return true;
2192
2193 return false;
2194}
2195
2196static inline bool func_uaccess_safe(struct symbol *func)
2197{
2198 if (func)
2199 return func->uaccess_safe;
2200
2201 return false;
2202}
2203
2204static inline const char *call_dest_name(struct instruction *insn)
2205{
2206 if (insn->call_dest)
2207 return insn->call_dest->name;
2208
2209 return "{dynamic}";
2210}
2211
2212static inline bool noinstr_call_dest(struct symbol *func)
2213{
2214 /*
2215 * We can't deal with indirect function calls at present;
2216 * assume they're instrumented.
2217 */
2218 if (!func)
2219 return false;
2220
2221 /*
2222 * If the symbol is from a noinstr section; we good.
2223 */
2224 if (func->sec->noinstr)
2225 return true;
2226
2227 /*
2228 * The __ubsan_handle_*() calls are like WARN(), they only happen when
2229 * something 'BAD' happened. At the risk of taking the machine down,
2230 * let them proceed to get the message out.
2231 */
2232 if (!strncmp(func->name, "__ubsan_handle_", 15))
2233 return true;
2234
2235 return false;
2236}
2237
2238static int validate_call(struct instruction *insn, struct insn_state *state)
2239{
2240 if (state->noinstr && state->instr <= 0 &&
2241 !noinstr_call_dest(insn->call_dest)) {
2242 WARN_FUNC("call to %s() leaves .noinstr.text section",
2243 insn->sec, insn->offset, call_dest_name(insn));
2244 return 1;
2245 }
2246
2247 if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
2248 WARN_FUNC("call to %s() with UACCESS enabled",
2249 insn->sec, insn->offset, call_dest_name(insn));
2250 return 1;
2251 }
2252
2253 if (state->df) {
2254 WARN_FUNC("call to %s() with DF set",
2255 insn->sec, insn->offset, call_dest_name(insn));
2256 return 1;
2257 }
2258
2259 return 0;
2260}
2261
2262static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
2263{
2264 if (has_modified_stack_frame(insn, state)) {
2265 WARN_FUNC("sibling call from callable instruction with modified stack frame",
2266 insn->sec, insn->offset);
2267 return 1;
2268 }
2269
2270 return validate_call(insn, state);
2271}
2272
2273static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
2274{
2275 if (state->noinstr && state->instr > 0) {
2276 WARN_FUNC("return with instrumentation enabled",
2277 insn->sec, insn->offset);
2278 return 1;
2279 }
2280
2281 if (state->uaccess && !func_uaccess_safe(func)) {
2282 WARN_FUNC("return with UACCESS enabled",
2283 insn->sec, insn->offset);
2284 return 1;
2285 }
2286
2287 if (!state->uaccess && func_uaccess_safe(func)) {
2288 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
2289 insn->sec, insn->offset);
2290 return 1;
2291 }
2292
2293 if (state->df) {
2294 WARN_FUNC("return with DF set",
2295 insn->sec, insn->offset);
2296 return 1;
2297 }
2298
2299 if (func && has_modified_stack_frame(insn, state)) {
2300 WARN_FUNC("return with modified stack frame",
2301 insn->sec, insn->offset);
2302 return 1;
2303 }
2304
2305 if (state->cfi.bp_scratch) {
2306 WARN_FUNC("BP used as a scratch register",
2307 insn->sec, insn->offset);
2308 return 1;
2309 }
2310
2311 return 0;
2312}
2313
2314/*
2315 * Alternatives should not contain any ORC entries, this in turn means they
2316 * should not contain any CFI ops, which implies all instructions should have
2317 * the same same CFI state.
2318 *
2319 * It is possible to constuct alternatives that have unreachable holes that go
2320 * unreported (because they're NOPs), such holes would result in CFI_UNDEFINED
2321 * states which then results in ORC entries, which we just said we didn't want.
2322 *
2323 * Avoid them by copying the CFI entry of the first instruction into the whole
2324 * alternative.
2325 */
2326static void fill_alternative_cfi(struct objtool_file *file, struct instruction *insn)
2327{
2328 struct instruction *first_insn = insn;
2329 int alt_group = insn->alt_group;
2330
2331 sec_for_each_insn_continue(file, insn) {
2332 if (insn->alt_group != alt_group)
2333 break;
2334 insn->cfi = first_insn->cfi;
2335 }
2336}
2337
2338/*
2339 * Follow the branch starting at the given instruction, and recursively follow
2340 * any other branches (jumps). Meanwhile, track the frame pointer state at
2341 * each instruction and validate all the rules described in
2342 * tools/objtool/Documentation/stack-validation.txt.
2343 */
2344static int validate_branch(struct objtool_file *file, struct symbol *func,
2345 struct instruction *insn, struct insn_state state)
2346{
2347 struct alternative *alt;
2348 struct instruction *next_insn;
2349 struct section *sec;
2350 u8 visited;
2351 int ret;
2352
2353 sec = insn->sec;
2354
2355 while (1) {
2356 next_insn = next_insn_same_sec(file, insn);
2357
2358 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
2359 WARN("%s() falls through to next function %s()",
2360 func->name, insn->func->name);
2361 return 1;
2362 }
2363
2364 if (func && insn->ignore) {
2365 WARN_FUNC("BUG: why am I validating an ignored function?",
2366 sec, insn->offset);
2367 return 1;
2368 }
2369
2370 visited = 1 << state.uaccess;
2371 if (insn->visited) {
2372 if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
2373 return 1;
2374
2375 if (insn->visited & visited)
2376 return 0;
2377 }
2378
2379 if (state.noinstr)
2380 state.instr += insn->instr;
2381
2382 if (insn->hint)
2383 state.cfi = insn->cfi;
2384 else
2385 insn->cfi = state.cfi;
2386
2387 insn->visited |= visited;
2388
2389 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
2390 bool skip_orig = false;
2391
2392 list_for_each_entry(alt, &insn->alts, list) {
2393 if (alt->skip_orig)
2394 skip_orig = true;
2395
2396 ret = validate_branch(file, func, alt->insn, state);
2397 if (ret) {
2398 if (backtrace)
2399 BT_FUNC("(alt)", insn);
2400 return ret;
2401 }
2402 }
2403
2404 if (insn->alt_group)
2405 fill_alternative_cfi(file, insn);
2406
2407 if (skip_orig)
2408 return 0;
2409 }
2410
2411 if (handle_insn_ops(insn, &state))
2412 return 1;
2413
2414 switch (insn->type) {
2415
2416 case INSN_RETURN:
2417 return validate_return(func, insn, &state);
2418
2419 case INSN_CALL:
2420 case INSN_CALL_DYNAMIC:
2421 ret = validate_call(insn, &state);
2422 if (ret)
2423 return ret;
2424
2425 if (!no_fp && func && !is_fentry_call(insn) &&
2426 !has_valid_stack_frame(&state)) {
2427 WARN_FUNC("call without frame pointer save/setup",
2428 sec, insn->offset);
2429 return 1;
2430 }
2431
2432 if (dead_end_function(file, insn->call_dest))
2433 return 0;
2434
2435 break;
2436
2437 case INSN_JUMP_CONDITIONAL:
2438 case INSN_JUMP_UNCONDITIONAL:
2439 if (func && is_sibling_call(insn)) {
2440 ret = validate_sibling_call(insn, &state);
2441 if (ret)
2442 return ret;
2443
2444 } else if (insn->jump_dest) {
2445 ret = validate_branch(file, func,
2446 insn->jump_dest, state);
2447 if (ret) {
2448 if (backtrace)
2449 BT_FUNC("(branch)", insn);
2450 return ret;
2451 }
2452 }
2453
2454 if (insn->type == INSN_JUMP_UNCONDITIONAL)
2455 return 0;
2456
2457 break;
2458
2459 case INSN_JUMP_DYNAMIC:
2460 case INSN_JUMP_DYNAMIC_CONDITIONAL:
2461 if (func && is_sibling_call(insn)) {
2462 ret = validate_sibling_call(insn, &state);
2463 if (ret)
2464 return ret;
2465 }
2466
2467 if (insn->type == INSN_JUMP_DYNAMIC)
2468 return 0;
2469
2470 break;
2471
2472 case INSN_CONTEXT_SWITCH:
2473 if (func && (!next_insn || !next_insn->hint)) {
2474 WARN_FUNC("unsupported instruction in callable function",
2475 sec, insn->offset);
2476 return 1;
2477 }
2478 return 0;
2479
2480 case INSN_STAC:
2481 if (state.uaccess) {
2482 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
2483 return 1;
2484 }
2485
2486 state.uaccess = true;
2487 break;
2488
2489 case INSN_CLAC:
2490 if (!state.uaccess && func) {
2491 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
2492 return 1;
2493 }
2494
2495 if (func_uaccess_safe(func) && !state.uaccess_stack) {
2496 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
2497 return 1;
2498 }
2499
2500 state.uaccess = false;
2501 break;
2502
2503 case INSN_STD:
2504 if (state.df)
2505 WARN_FUNC("recursive STD", sec, insn->offset);
2506
2507 state.df = true;
2508 break;
2509
2510 case INSN_CLD:
2511 if (!state.df && func)
2512 WARN_FUNC("redundant CLD", sec, insn->offset);
2513
2514 state.df = false;
2515 break;
2516
2517 default:
2518 break;
2519 }
2520
2521 if (insn->dead_end)
2522 return 0;
2523
2524 if (!next_insn) {
2525 if (state.cfi.cfa.base == CFI_UNDEFINED)
2526 return 0;
2527 WARN("%s: unexpected end of section", sec->name);
2528 return 1;
2529 }
2530
2531 insn = next_insn;
2532 }
2533
2534 return 0;
2535}
2536
2537static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
2538{
2539 struct instruction *insn;
2540 struct insn_state state;
2541 int ret, warnings = 0;
2542
2543 if (!file->hints)
2544 return 0;
2545
2546 init_insn_state(&state, sec);
2547
2548 if (sec) {
2549 insn = find_insn(file, sec, 0);
2550 if (!insn)
2551 return 0;
2552 } else {
2553 insn = list_first_entry(&file->insn_list, typeof(*insn), list);
2554 }
2555
2556 while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) {
2557 if (insn->hint && !insn->visited) {
2558 ret = validate_branch(file, insn->func, insn, state);
2559 if (ret && backtrace)
2560 BT_FUNC("<=== (hint)", insn);
2561 warnings += ret;
2562 }
2563
2564 insn = list_next_entry(insn, list);
2565 }
2566
2567 return warnings;
2568}
2569
2570static int validate_retpoline(struct objtool_file *file)
2571{
2572 struct instruction *insn;
2573 int warnings = 0;
2574
2575 for_each_insn(file, insn) {
2576 if (insn->type != INSN_JUMP_DYNAMIC &&
2577 insn->type != INSN_CALL_DYNAMIC)
2578 continue;
2579
2580 if (insn->retpoline_safe)
2581 continue;
2582
2583 /*
2584 * .init.text code is ran before userspace and thus doesn't
2585 * strictly need retpolines, except for modules which are
2586 * loaded late, they very much do need retpoline in their
2587 * .init.text
2588 */
2589 if (!strcmp(insn->sec->name, ".init.text") && !module)
2590 continue;
2591
2592 WARN_FUNC("indirect %s found in RETPOLINE build",
2593 insn->sec, insn->offset,
2594 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
2595
2596 warnings++;
2597 }
2598
2599 return warnings;
2600}
2601
2602static bool is_kasan_insn(struct instruction *insn)
2603{
2604 return (insn->type == INSN_CALL &&
2605 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
2606}
2607
2608static bool is_ubsan_insn(struct instruction *insn)
2609{
2610 return (insn->type == INSN_CALL &&
2611 !strcmp(insn->call_dest->name,
2612 "__ubsan_handle_builtin_unreachable"));
2613}
2614
2615static bool ignore_unreachable_insn(struct instruction *insn)
2616{
2617 int i;
2618
2619 if (insn->ignore || insn->type == INSN_NOP)
2620 return true;
2621
2622 /*
2623 * Ignore any unused exceptions. This can happen when a whitelisted
2624 * function has an exception table entry.
2625 *
2626 * Also ignore alternative replacement instructions. This can happen
2627 * when a whitelisted function uses one of the ALTERNATIVE macros.
2628 */
2629 if (!strcmp(insn->sec->name, ".fixup") ||
2630 !strcmp(insn->sec->name, ".altinstr_replacement") ||
2631 !strcmp(insn->sec->name, ".altinstr_aux"))
2632 return true;
2633
2634 if (!insn->func)
2635 return false;
2636
2637 /*
2638 * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
2639 * __builtin_unreachable(). The BUG() macro has an unreachable() after
2640 * the UD2, which causes GCC's undefined trap logic to emit another UD2
2641 * (or occasionally a JMP to UD2).
2642 */
2643 if (list_prev_entry(insn, list)->dead_end &&
2644 (insn->type == INSN_BUG ||
2645 (insn->type == INSN_JUMP_UNCONDITIONAL &&
2646 insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
2647 return true;
2648
2649 /*
2650 * Check if this (or a subsequent) instruction is related to
2651 * CONFIG_UBSAN or CONFIG_KASAN.
2652 *
2653 * End the search at 5 instructions to avoid going into the weeds.
2654 */
2655 for (i = 0; i < 5; i++) {
2656
2657 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
2658 return true;
2659
2660 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
2661 if (insn->jump_dest &&
2662 insn->jump_dest->func == insn->func) {
2663 insn = insn->jump_dest;
2664 continue;
2665 }
2666
2667 break;
2668 }
2669
2670 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
2671 break;
2672
2673 insn = list_next_entry(insn, list);
2674 }
2675
2676 return false;
2677}
2678
2679static int validate_symbol(struct objtool_file *file, struct section *sec,
2680 struct symbol *sym, struct insn_state *state)
2681{
2682 struct instruction *insn;
2683 int ret;
2684
2685 if (!sym->len) {
2686 WARN("%s() is missing an ELF size annotation", sym->name);
2687 return 1;
2688 }
2689
2690 if (sym->pfunc != sym || sym->alias != sym)
2691 return 0;
2692
2693 insn = find_insn(file, sec, sym->offset);
2694 if (!insn || insn->ignore || insn->visited)
2695 return 0;
2696
2697 state->uaccess = sym->uaccess_safe;
2698
2699 ret = validate_branch(file, insn->func, insn, *state);
2700 if (ret && backtrace)
2701 BT_FUNC("<=== (sym)", insn);
2702 return ret;
2703}
2704
2705static int validate_section(struct objtool_file *file, struct section *sec)
2706{
2707 struct insn_state state;
2708 struct symbol *func;
2709 int warnings = 0;
2710
2711 list_for_each_entry(func, &sec->symbol_list, list) {
2712 if (func->type != STT_FUNC)
2713 continue;
2714
2715 init_insn_state(&state, sec);
2716 state.cfi.cfa = initial_func_cfi.cfa;
2717 memcpy(&state.cfi.regs, &initial_func_cfi.regs,
2718 CFI_NUM_REGS * sizeof(struct cfi_reg));
2719 state.cfi.stack_size = initial_func_cfi.cfa.offset;
2720
2721 warnings += validate_symbol(file, sec, func, &state);
2722 }
2723
2724 return warnings;
2725}
2726
2727static int validate_vmlinux_functions(struct objtool_file *file)
2728{
2729 struct section *sec;
2730 int warnings = 0;
2731
2732 sec = find_section_by_name(file->elf, ".noinstr.text");
2733 if (sec) {
2734 warnings += validate_section(file, sec);
2735 warnings += validate_unwind_hints(file, sec);
2736 }
2737
2738 sec = find_section_by_name(file->elf, ".entry.text");
2739 if (sec) {
2740 warnings += validate_section(file, sec);
2741 warnings += validate_unwind_hints(file, sec);
2742 }
2743
2744 return warnings;
2745}
2746
2747static int validate_functions(struct objtool_file *file)
2748{
2749 struct section *sec;
2750 int warnings = 0;
2751
2752 for_each_sec(file, sec) {
2753 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
2754 continue;
2755
2756 warnings += validate_section(file, sec);
2757 }
2758
2759 return warnings;
2760}
2761
2762static int validate_reachable_instructions(struct objtool_file *file)
2763{
2764 struct instruction *insn;
2765
2766 if (file->ignore_unreachables)
2767 return 0;
2768
2769 for_each_insn(file, insn) {
2770 if (insn->visited || ignore_unreachable_insn(insn))
2771 continue;
2772
2773 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
2774 return 1;
2775 }
2776
2777 return 0;
2778}
2779
2780static struct objtool_file file;
2781
2782int check(const char *_objname, bool orc)
2783{
2784 int ret, warnings = 0;
2785
2786 objname = _objname;
2787
2788 file.elf = elf_open_read(objname, O_RDWR);
2789 if (!file.elf)
2790 return 1;
2791
2792 INIT_LIST_HEAD(&file.insn_list);
2793 hash_init(file.insn_hash);
2794 file.c_file = !vmlinux && find_section_by_name(file.elf, ".comment");
2795 file.ignore_unreachables = no_unreachable;
2796 file.hints = false;
2797
2798 arch_initial_func_cfi_state(&initial_func_cfi);
2799
2800 ret = decode_sections(&file);
2801 if (ret < 0)
2802 goto out;
2803 warnings += ret;
2804
2805 if (list_empty(&file.insn_list))
2806 goto out;
2807
2808 if (vmlinux && !validate_dup) {
2809 ret = validate_vmlinux_functions(&file);
2810 if (ret < 0)
2811 goto out;
2812
2813 warnings += ret;
2814 goto out;
2815 }
2816
2817 if (retpoline) {
2818 ret = validate_retpoline(&file);
2819 if (ret < 0)
2820 return ret;
2821 warnings += ret;
2822 }
2823
2824 ret = validate_functions(&file);
2825 if (ret < 0)
2826 goto out;
2827 warnings += ret;
2828
2829 ret = validate_unwind_hints(&file, NULL);
2830 if (ret < 0)
2831 goto out;
2832 warnings += ret;
2833
2834 if (!warnings) {
2835 ret = validate_reachable_instructions(&file);
2836 if (ret < 0)
2837 goto out;
2838 warnings += ret;
2839 }
2840
2841 if (orc) {
2842 ret = create_orc(&file);
2843 if (ret < 0)
2844 goto out;
2845
2846 ret = create_orc_sections(&file);
2847 if (ret < 0)
2848 goto out;
2849 }
2850
2851 if (file.elf->changed) {
2852 ret = elf_write(file.elf);
2853 if (ret < 0)
2854 goto out;
2855 }
2856
2857out:
2858 if (ret < 0) {
2859 /*
2860 * Fatal error. The binary is corrupt or otherwise broken in
2861 * some way, or objtool itself is broken. Fail the kernel
2862 * build.
2863 */
2864 return ret;
2865 }
2866
2867 return 0;
2868}