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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#include <inttypes.h>
9#include <sys/mman.h>
10
11#include <objtool/builtin.h>
12#include <objtool/cfi.h>
13#include <objtool/arch.h>
14#include <objtool/check.h>
15#include <objtool/special.h>
16#include <objtool/warn.h>
17#include <objtool/endianness.h>
18
19#include <linux/objtool_types.h>
20#include <linux/hashtable.h>
21#include <linux/kernel.h>
22#include <linux/static_call_types.h>
23#include <linux/string.h>
24
25struct alternative {
26 struct alternative *next;
27 struct instruction *insn;
28 bool skip_orig;
29};
30
31static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
32
33static struct cfi_init_state initial_func_cfi;
34static struct cfi_state init_cfi;
35static struct cfi_state func_cfi;
36static struct cfi_state force_undefined_cfi;
37
38struct instruction *find_insn(struct objtool_file *file,
39 struct section *sec, unsigned long offset)
40{
41 struct instruction *insn;
42
43 hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
44 if (insn->sec == sec && insn->offset == offset)
45 return insn;
46 }
47
48 return NULL;
49}
50
51struct instruction *next_insn_same_sec(struct objtool_file *file,
52 struct instruction *insn)
53{
54 if (insn->idx == INSN_CHUNK_MAX)
55 return find_insn(file, insn->sec, insn->offset + insn->len);
56
57 insn++;
58 if (!insn->len)
59 return NULL;
60
61 return insn;
62}
63
64static struct instruction *next_insn_same_func(struct objtool_file *file,
65 struct instruction *insn)
66{
67 struct instruction *next = next_insn_same_sec(file, insn);
68 struct symbol *func = insn_func(insn);
69
70 if (!func)
71 return NULL;
72
73 if (next && insn_func(next) == func)
74 return next;
75
76 /* Check if we're already in the subfunction: */
77 if (func == func->cfunc)
78 return NULL;
79
80 /* Move to the subfunction: */
81 return find_insn(file, func->cfunc->sec, func->cfunc->offset);
82}
83
84static struct instruction *prev_insn_same_sec(struct objtool_file *file,
85 struct instruction *insn)
86{
87 if (insn->idx == 0) {
88 if (insn->prev_len)
89 return find_insn(file, insn->sec, insn->offset - insn->prev_len);
90 return NULL;
91 }
92
93 return insn - 1;
94}
95
96static struct instruction *prev_insn_same_sym(struct objtool_file *file,
97 struct instruction *insn)
98{
99 struct instruction *prev = prev_insn_same_sec(file, insn);
100
101 if (prev && insn_func(prev) == insn_func(insn))
102 return prev;
103
104 return NULL;
105}
106
107#define for_each_insn(file, insn) \
108 for (struct section *__sec, *__fake = (struct section *)1; \
109 __fake; __fake = NULL) \
110 for_each_sec(file, __sec) \
111 sec_for_each_insn(file, __sec, insn)
112
113#define func_for_each_insn(file, func, insn) \
114 for (insn = find_insn(file, func->sec, func->offset); \
115 insn; \
116 insn = next_insn_same_func(file, insn))
117
118#define sym_for_each_insn(file, sym, insn) \
119 for (insn = find_insn(file, sym->sec, sym->offset); \
120 insn && insn->offset < sym->offset + sym->len; \
121 insn = next_insn_same_sec(file, insn))
122
123#define sym_for_each_insn_continue_reverse(file, sym, insn) \
124 for (insn = prev_insn_same_sec(file, insn); \
125 insn && insn->offset >= sym->offset; \
126 insn = prev_insn_same_sec(file, insn))
127
128#define sec_for_each_insn_from(file, insn) \
129 for (; insn; insn = next_insn_same_sec(file, insn))
130
131#define sec_for_each_insn_continue(file, insn) \
132 for (insn = next_insn_same_sec(file, insn); insn; \
133 insn = next_insn_same_sec(file, insn))
134
135static inline struct symbol *insn_call_dest(struct instruction *insn)
136{
137 if (insn->type == INSN_JUMP_DYNAMIC ||
138 insn->type == INSN_CALL_DYNAMIC)
139 return NULL;
140
141 return insn->_call_dest;
142}
143
144static inline struct reloc *insn_jump_table(struct instruction *insn)
145{
146 if (insn->type == INSN_JUMP_DYNAMIC ||
147 insn->type == INSN_CALL_DYNAMIC)
148 return insn->_jump_table;
149
150 return NULL;
151}
152
153static bool is_jump_table_jump(struct instruction *insn)
154{
155 struct alt_group *alt_group = insn->alt_group;
156
157 if (insn_jump_table(insn))
158 return true;
159
160 /* Retpoline alternative for a jump table? */
161 return alt_group && alt_group->orig_group &&
162 insn_jump_table(alt_group->orig_group->first_insn);
163}
164
165static bool is_sibling_call(struct instruction *insn)
166{
167 /*
168 * Assume only STT_FUNC calls have jump-tables.
169 */
170 if (insn_func(insn)) {
171 /* An indirect jump is either a sibling call or a jump to a table. */
172 if (insn->type == INSN_JUMP_DYNAMIC)
173 return !is_jump_table_jump(insn);
174 }
175
176 /* add_jump_destinations() sets insn_call_dest(insn) for sibling calls. */
177 return (is_static_jump(insn) && insn_call_dest(insn));
178}
179
180/*
181 * This checks to see if the given function is a "noreturn" function.
182 *
183 * For global functions which are outside the scope of this object file, we
184 * have to keep a manual list of them.
185 *
186 * For local functions, we have to detect them manually by simply looking for
187 * the lack of a return instruction.
188 */
189static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
190 int recursion)
191{
192 int i;
193 struct instruction *insn;
194 bool empty = true;
195
196#define NORETURN(func) __stringify(func),
197 static const char * const global_noreturns[] = {
198#include "noreturns.h"
199 };
200#undef NORETURN
201
202 if (!func)
203 return false;
204
205 if (func->bind == STB_GLOBAL || func->bind == STB_WEAK)
206 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
207 if (!strcmp(func->name, global_noreturns[i]))
208 return true;
209
210 if (func->bind == STB_WEAK)
211 return false;
212
213 if (!func->len)
214 return false;
215
216 insn = find_insn(file, func->sec, func->offset);
217 if (!insn || !insn_func(insn))
218 return false;
219
220 func_for_each_insn(file, func, insn) {
221 empty = false;
222
223 if (insn->type == INSN_RETURN)
224 return false;
225 }
226
227 if (empty)
228 return false;
229
230 /*
231 * A function can have a sibling call instead of a return. In that
232 * case, the function's dead-end status depends on whether the target
233 * of the sibling call returns.
234 */
235 func_for_each_insn(file, func, insn) {
236 if (is_sibling_call(insn)) {
237 struct instruction *dest = insn->jump_dest;
238
239 if (!dest)
240 /* sibling call to another file */
241 return false;
242
243 /* local sibling call */
244 if (recursion == 5) {
245 /*
246 * Infinite recursion: two functions have
247 * sibling calls to each other. This is a very
248 * rare case. It means they aren't dead ends.
249 */
250 return false;
251 }
252
253 return __dead_end_function(file, insn_func(dest), recursion+1);
254 }
255 }
256
257 return true;
258}
259
260static bool dead_end_function(struct objtool_file *file, struct symbol *func)
261{
262 return __dead_end_function(file, func, 0);
263}
264
265static void init_cfi_state(struct cfi_state *cfi)
266{
267 int i;
268
269 for (i = 0; i < CFI_NUM_REGS; i++) {
270 cfi->regs[i].base = CFI_UNDEFINED;
271 cfi->vals[i].base = CFI_UNDEFINED;
272 }
273 cfi->cfa.base = CFI_UNDEFINED;
274 cfi->drap_reg = CFI_UNDEFINED;
275 cfi->drap_offset = -1;
276}
277
278static void init_insn_state(struct objtool_file *file, struct insn_state *state,
279 struct section *sec)
280{
281 memset(state, 0, sizeof(*state));
282 init_cfi_state(&state->cfi);
283
284 /*
285 * We need the full vmlinux for noinstr validation, otherwise we can
286 * not correctly determine insn_call_dest(insn)->sec (external symbols
287 * do not have a section).
288 */
289 if (opts.link && opts.noinstr && sec)
290 state->noinstr = sec->noinstr;
291}
292
293static struct cfi_state *cfi_alloc(void)
294{
295 struct cfi_state *cfi = calloc(1, sizeof(struct cfi_state));
296 if (!cfi) {
297 WARN("calloc failed");
298 exit(1);
299 }
300 nr_cfi++;
301 return cfi;
302}
303
304static int cfi_bits;
305static struct hlist_head *cfi_hash;
306
307static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
308{
309 return memcmp((void *)cfi1 + sizeof(cfi1->hash),
310 (void *)cfi2 + sizeof(cfi2->hash),
311 sizeof(struct cfi_state) - sizeof(struct hlist_node));
312}
313
314static inline u32 cfi_key(struct cfi_state *cfi)
315{
316 return jhash((void *)cfi + sizeof(cfi->hash),
317 sizeof(*cfi) - sizeof(cfi->hash), 0);
318}
319
320static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
321{
322 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
323 struct cfi_state *obj;
324
325 hlist_for_each_entry(obj, head, hash) {
326 if (!cficmp(cfi, obj)) {
327 nr_cfi_cache++;
328 return obj;
329 }
330 }
331
332 obj = cfi_alloc();
333 *obj = *cfi;
334 hlist_add_head(&obj->hash, head);
335
336 return obj;
337}
338
339static void cfi_hash_add(struct cfi_state *cfi)
340{
341 struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
342
343 hlist_add_head(&cfi->hash, head);
344}
345
346static void *cfi_hash_alloc(unsigned long size)
347{
348 cfi_bits = max(10, ilog2(size));
349 cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
350 PROT_READ|PROT_WRITE,
351 MAP_PRIVATE|MAP_ANON, -1, 0);
352 if (cfi_hash == (void *)-1L) {
353 WARN("mmap fail cfi_hash");
354 cfi_hash = NULL;
355 } else if (opts.stats) {
356 printf("cfi_bits: %d\n", cfi_bits);
357 }
358
359 return cfi_hash;
360}
361
362static unsigned long nr_insns;
363static unsigned long nr_insns_visited;
364
365/*
366 * Call the arch-specific instruction decoder for all the instructions and add
367 * them to the global instruction list.
368 */
369static int decode_instructions(struct objtool_file *file)
370{
371 struct section *sec;
372 struct symbol *func;
373 unsigned long offset;
374 struct instruction *insn;
375 int ret;
376
377 for_each_sec(file, sec) {
378 struct instruction *insns = NULL;
379 u8 prev_len = 0;
380 u8 idx = 0;
381
382 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
383 continue;
384
385 if (strcmp(sec->name, ".altinstr_replacement") &&
386 strcmp(sec->name, ".altinstr_aux") &&
387 strncmp(sec->name, ".discard.", 9))
388 sec->text = true;
389
390 if (!strcmp(sec->name, ".noinstr.text") ||
391 !strcmp(sec->name, ".entry.text") ||
392 !strcmp(sec->name, ".cpuidle.text") ||
393 !strncmp(sec->name, ".text..__x86.", 13))
394 sec->noinstr = true;
395
396 /*
397 * .init.text code is ran before userspace and thus doesn't
398 * strictly need retpolines, except for modules which are
399 * loaded late, they very much do need retpoline in their
400 * .init.text
401 */
402 if (!strcmp(sec->name, ".init.text") && !opts.module)
403 sec->init = true;
404
405 for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
406 if (!insns || idx == INSN_CHUNK_MAX) {
407 insns = calloc(sizeof(*insn), INSN_CHUNK_SIZE);
408 if (!insns) {
409 WARN("malloc failed");
410 return -1;
411 }
412 idx = 0;
413 } else {
414 idx++;
415 }
416 insn = &insns[idx];
417 insn->idx = idx;
418
419 INIT_LIST_HEAD(&insn->call_node);
420 insn->sec = sec;
421 insn->offset = offset;
422 insn->prev_len = prev_len;
423
424 ret = arch_decode_instruction(file, sec, offset,
425 sec->sh.sh_size - offset,
426 insn);
427 if (ret)
428 return ret;
429
430 prev_len = insn->len;
431
432 /*
433 * By default, "ud2" is a dead end unless otherwise
434 * annotated, because GCC 7 inserts it for certain
435 * divide-by-zero cases.
436 */
437 if (insn->type == INSN_BUG)
438 insn->dead_end = true;
439
440 hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
441 nr_insns++;
442 }
443
444// printf("%s: last chunk used: %d\n", sec->name, (int)idx);
445
446 sec_for_each_sym(sec, func) {
447 if (func->type != STT_NOTYPE && func->type != STT_FUNC)
448 continue;
449
450 if (func->offset == sec->sh.sh_size) {
451 /* Heuristic: likely an "end" symbol */
452 if (func->type == STT_NOTYPE)
453 continue;
454 WARN("%s(): STT_FUNC at end of section",
455 func->name);
456 return -1;
457 }
458
459 if (func->embedded_insn || func->alias != func)
460 continue;
461
462 if (!find_insn(file, sec, func->offset)) {
463 WARN("%s(): can't find starting instruction",
464 func->name);
465 return -1;
466 }
467
468 sym_for_each_insn(file, func, insn) {
469 insn->sym = func;
470 if (func->type == STT_FUNC &&
471 insn->type == INSN_ENDBR &&
472 list_empty(&insn->call_node)) {
473 if (insn->offset == func->offset) {
474 list_add_tail(&insn->call_node, &file->endbr_list);
475 file->nr_endbr++;
476 } else {
477 file->nr_endbr_int++;
478 }
479 }
480 }
481 }
482 }
483
484 if (opts.stats)
485 printf("nr_insns: %lu\n", nr_insns);
486
487 return 0;
488}
489
490/*
491 * Read the pv_ops[] .data table to find the static initialized values.
492 */
493static int add_pv_ops(struct objtool_file *file, const char *symname)
494{
495 struct symbol *sym, *func;
496 unsigned long off, end;
497 struct reloc *reloc;
498 int idx;
499
500 sym = find_symbol_by_name(file->elf, symname);
501 if (!sym)
502 return 0;
503
504 off = sym->offset;
505 end = off + sym->len;
506 for (;;) {
507 reloc = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off);
508 if (!reloc)
509 break;
510
511 func = reloc->sym;
512 if (func->type == STT_SECTION)
513 func = find_symbol_by_offset(reloc->sym->sec,
514 reloc_addend(reloc));
515
516 idx = (reloc_offset(reloc) - sym->offset) / sizeof(unsigned long);
517
518 objtool_pv_add(file, idx, func);
519
520 off = reloc_offset(reloc) + 1;
521 if (off > end)
522 break;
523 }
524
525 return 0;
526}
527
528/*
529 * Allocate and initialize file->pv_ops[].
530 */
531static int init_pv_ops(struct objtool_file *file)
532{
533 static const char *pv_ops_tables[] = {
534 "pv_ops",
535 "xen_cpu_ops",
536 "xen_irq_ops",
537 "xen_mmu_ops",
538 NULL,
539 };
540 const char *pv_ops;
541 struct symbol *sym;
542 int idx, nr;
543
544 if (!opts.noinstr)
545 return 0;
546
547 file->pv_ops = NULL;
548
549 sym = find_symbol_by_name(file->elf, "pv_ops");
550 if (!sym)
551 return 0;
552
553 nr = sym->len / sizeof(unsigned long);
554 file->pv_ops = calloc(sizeof(struct pv_state), nr);
555 if (!file->pv_ops)
556 return -1;
557
558 for (idx = 0; idx < nr; idx++)
559 INIT_LIST_HEAD(&file->pv_ops[idx].targets);
560
561 for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++)
562 add_pv_ops(file, pv_ops);
563
564 return 0;
565}
566
567static struct instruction *find_last_insn(struct objtool_file *file,
568 struct section *sec)
569{
570 struct instruction *insn = NULL;
571 unsigned int offset;
572 unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
573
574 for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
575 insn = find_insn(file, sec, offset);
576
577 return insn;
578}
579
580/*
581 * Mark "ud2" instructions and manually annotated dead ends.
582 */
583static int add_dead_ends(struct objtool_file *file)
584{
585 struct section *rsec;
586 struct reloc *reloc;
587 struct instruction *insn;
588 uint64_t offset;
589
590 /*
591 * Check for manually annotated dead ends.
592 */
593 rsec = find_section_by_name(file->elf, ".rela.discard.unreachable");
594 if (!rsec)
595 goto reachable;
596
597 for_each_reloc(rsec, reloc) {
598 if (reloc->sym->type == STT_SECTION) {
599 offset = reloc_addend(reloc);
600 } else if (reloc->sym->local_label) {
601 offset = reloc->sym->offset;
602 } else {
603 WARN("unexpected relocation symbol type in %s", rsec->name);
604 return -1;
605 }
606
607 insn = find_insn(file, reloc->sym->sec, offset);
608 if (insn)
609 insn = prev_insn_same_sec(file, insn);
610 else if (offset == reloc->sym->sec->sh.sh_size) {
611 insn = find_last_insn(file, reloc->sym->sec);
612 if (!insn) {
613 WARN("can't find unreachable insn at %s+0x%" PRIx64,
614 reloc->sym->sec->name, offset);
615 return -1;
616 }
617 } else {
618 WARN("can't find unreachable insn at %s+0x%" PRIx64,
619 reloc->sym->sec->name, offset);
620 return -1;
621 }
622
623 insn->dead_end = true;
624 }
625
626reachable:
627 /*
628 * These manually annotated reachable checks are needed for GCC 4.4,
629 * where the Linux unreachable() macro isn't supported. In that case
630 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
631 * not a dead end.
632 */
633 rsec = find_section_by_name(file->elf, ".rela.discard.reachable");
634 if (!rsec)
635 return 0;
636
637 for_each_reloc(rsec, reloc) {
638 if (reloc->sym->type == STT_SECTION) {
639 offset = reloc_addend(reloc);
640 } else if (reloc->sym->local_label) {
641 offset = reloc->sym->offset;
642 } else {
643 WARN("unexpected relocation symbol type in %s", rsec->name);
644 return -1;
645 }
646
647 insn = find_insn(file, reloc->sym->sec, offset);
648 if (insn)
649 insn = prev_insn_same_sec(file, insn);
650 else if (offset == reloc->sym->sec->sh.sh_size) {
651 insn = find_last_insn(file, reloc->sym->sec);
652 if (!insn) {
653 WARN("can't find reachable insn at %s+0x%" PRIx64,
654 reloc->sym->sec->name, offset);
655 return -1;
656 }
657 } else {
658 WARN("can't find reachable insn at %s+0x%" PRIx64,
659 reloc->sym->sec->name, offset);
660 return -1;
661 }
662
663 insn->dead_end = false;
664 }
665
666 return 0;
667}
668
669static int create_static_call_sections(struct objtool_file *file)
670{
671 struct static_call_site *site;
672 struct section *sec;
673 struct instruction *insn;
674 struct symbol *key_sym;
675 char *key_name, *tmp;
676 int idx;
677
678 sec = find_section_by_name(file->elf, ".static_call_sites");
679 if (sec) {
680 INIT_LIST_HEAD(&file->static_call_list);
681 WARN("file already has .static_call_sites section, skipping");
682 return 0;
683 }
684
685 if (list_empty(&file->static_call_list))
686 return 0;
687
688 idx = 0;
689 list_for_each_entry(insn, &file->static_call_list, call_node)
690 idx++;
691
692 sec = elf_create_section_pair(file->elf, ".static_call_sites",
693 sizeof(*site), idx, idx * 2);
694 if (!sec)
695 return -1;
696
697 /* Allow modules to modify the low bits of static_call_site::key */
698 sec->sh.sh_flags |= SHF_WRITE;
699
700 idx = 0;
701 list_for_each_entry(insn, &file->static_call_list, call_node) {
702
703 /* populate reloc for 'addr' */
704 if (!elf_init_reloc_text_sym(file->elf, sec,
705 idx * sizeof(*site), idx * 2,
706 insn->sec, insn->offset))
707 return -1;
708
709 /* find key symbol */
710 key_name = strdup(insn_call_dest(insn)->name);
711 if (!key_name) {
712 perror("strdup");
713 return -1;
714 }
715 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
716 STATIC_CALL_TRAMP_PREFIX_LEN)) {
717 WARN("static_call: trampoline name malformed: %s", key_name);
718 free(key_name);
719 return -1;
720 }
721 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
722 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
723
724 key_sym = find_symbol_by_name(file->elf, tmp);
725 if (!key_sym) {
726 if (!opts.module) {
727 WARN("static_call: can't find static_call_key symbol: %s", tmp);
728 free(key_name);
729 return -1;
730 }
731
732 /*
733 * For modules(), the key might not be exported, which
734 * means the module can make static calls but isn't
735 * allowed to change them.
736 *
737 * In that case we temporarily set the key to be the
738 * trampoline address. This is fixed up in
739 * static_call_add_module().
740 */
741 key_sym = insn_call_dest(insn);
742 }
743 free(key_name);
744
745 /* populate reloc for 'key' */
746 if (!elf_init_reloc_data_sym(file->elf, sec,
747 idx * sizeof(*site) + 4,
748 (idx * 2) + 1, key_sym,
749 is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
750 return -1;
751
752 idx++;
753 }
754
755 return 0;
756}
757
758static int create_retpoline_sites_sections(struct objtool_file *file)
759{
760 struct instruction *insn;
761 struct section *sec;
762 int idx;
763
764 sec = find_section_by_name(file->elf, ".retpoline_sites");
765 if (sec) {
766 WARN("file already has .retpoline_sites, skipping");
767 return 0;
768 }
769
770 idx = 0;
771 list_for_each_entry(insn, &file->retpoline_call_list, call_node)
772 idx++;
773
774 if (!idx)
775 return 0;
776
777 sec = elf_create_section_pair(file->elf, ".retpoline_sites",
778 sizeof(int), idx, idx);
779 if (!sec)
780 return -1;
781
782 idx = 0;
783 list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
784
785 if (!elf_init_reloc_text_sym(file->elf, sec,
786 idx * sizeof(int), idx,
787 insn->sec, insn->offset))
788 return -1;
789
790 idx++;
791 }
792
793 return 0;
794}
795
796static int create_return_sites_sections(struct objtool_file *file)
797{
798 struct instruction *insn;
799 struct section *sec;
800 int idx;
801
802 sec = find_section_by_name(file->elf, ".return_sites");
803 if (sec) {
804 WARN("file already has .return_sites, skipping");
805 return 0;
806 }
807
808 idx = 0;
809 list_for_each_entry(insn, &file->return_thunk_list, call_node)
810 idx++;
811
812 if (!idx)
813 return 0;
814
815 sec = elf_create_section_pair(file->elf, ".return_sites",
816 sizeof(int), idx, idx);
817 if (!sec)
818 return -1;
819
820 idx = 0;
821 list_for_each_entry(insn, &file->return_thunk_list, call_node) {
822
823 if (!elf_init_reloc_text_sym(file->elf, sec,
824 idx * sizeof(int), idx,
825 insn->sec, insn->offset))
826 return -1;
827
828 idx++;
829 }
830
831 return 0;
832}
833
834static int create_ibt_endbr_seal_sections(struct objtool_file *file)
835{
836 struct instruction *insn;
837 struct section *sec;
838 int idx;
839
840 sec = find_section_by_name(file->elf, ".ibt_endbr_seal");
841 if (sec) {
842 WARN("file already has .ibt_endbr_seal, skipping");
843 return 0;
844 }
845
846 idx = 0;
847 list_for_each_entry(insn, &file->endbr_list, call_node)
848 idx++;
849
850 if (opts.stats) {
851 printf("ibt: ENDBR at function start: %d\n", file->nr_endbr);
852 printf("ibt: ENDBR inside functions: %d\n", file->nr_endbr_int);
853 printf("ibt: superfluous ENDBR: %d\n", idx);
854 }
855
856 if (!idx)
857 return 0;
858
859 sec = elf_create_section_pair(file->elf, ".ibt_endbr_seal",
860 sizeof(int), idx, idx);
861 if (!sec)
862 return -1;
863
864 idx = 0;
865 list_for_each_entry(insn, &file->endbr_list, call_node) {
866
867 int *site = (int *)sec->data->d_buf + idx;
868 struct symbol *sym = insn->sym;
869 *site = 0;
870
871 if (opts.module && sym && sym->type == STT_FUNC &&
872 insn->offset == sym->offset &&
873 (!strcmp(sym->name, "init_module") ||
874 !strcmp(sym->name, "cleanup_module")))
875 WARN("%s(): not an indirect call target", sym->name);
876
877 if (!elf_init_reloc_text_sym(file->elf, sec,
878 idx * sizeof(int), idx,
879 insn->sec, insn->offset))
880 return -1;
881
882 idx++;
883 }
884
885 return 0;
886}
887
888static int create_cfi_sections(struct objtool_file *file)
889{
890 struct section *sec;
891 struct symbol *sym;
892 int idx;
893
894 sec = find_section_by_name(file->elf, ".cfi_sites");
895 if (sec) {
896 INIT_LIST_HEAD(&file->call_list);
897 WARN("file already has .cfi_sites section, skipping");
898 return 0;
899 }
900
901 idx = 0;
902 for_each_sym(file, sym) {
903 if (sym->type != STT_FUNC)
904 continue;
905
906 if (strncmp(sym->name, "__cfi_", 6))
907 continue;
908
909 idx++;
910 }
911
912 sec = elf_create_section_pair(file->elf, ".cfi_sites",
913 sizeof(unsigned int), idx, idx);
914 if (!sec)
915 return -1;
916
917 idx = 0;
918 for_each_sym(file, sym) {
919 if (sym->type != STT_FUNC)
920 continue;
921
922 if (strncmp(sym->name, "__cfi_", 6))
923 continue;
924
925 if (!elf_init_reloc_text_sym(file->elf, sec,
926 idx * sizeof(unsigned int), idx,
927 sym->sec, sym->offset))
928 return -1;
929
930 idx++;
931 }
932
933 return 0;
934}
935
936static int create_mcount_loc_sections(struct objtool_file *file)
937{
938 size_t addr_size = elf_addr_size(file->elf);
939 struct instruction *insn;
940 struct section *sec;
941 int idx;
942
943 sec = find_section_by_name(file->elf, "__mcount_loc");
944 if (sec) {
945 INIT_LIST_HEAD(&file->mcount_loc_list);
946 WARN("file already has __mcount_loc section, skipping");
947 return 0;
948 }
949
950 if (list_empty(&file->mcount_loc_list))
951 return 0;
952
953 idx = 0;
954 list_for_each_entry(insn, &file->mcount_loc_list, call_node)
955 idx++;
956
957 sec = elf_create_section_pair(file->elf, "__mcount_loc", addr_size,
958 idx, idx);
959 if (!sec)
960 return -1;
961
962 sec->sh.sh_addralign = addr_size;
963
964 idx = 0;
965 list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
966
967 struct reloc *reloc;
968
969 reloc = elf_init_reloc_text_sym(file->elf, sec, idx * addr_size, idx,
970 insn->sec, insn->offset);
971 if (!reloc)
972 return -1;
973
974 set_reloc_type(file->elf, reloc, addr_size == 8 ? R_ABS64 : R_ABS32);
975
976 idx++;
977 }
978
979 return 0;
980}
981
982static int create_direct_call_sections(struct objtool_file *file)
983{
984 struct instruction *insn;
985 struct section *sec;
986 int idx;
987
988 sec = find_section_by_name(file->elf, ".call_sites");
989 if (sec) {
990 INIT_LIST_HEAD(&file->call_list);
991 WARN("file already has .call_sites section, skipping");
992 return 0;
993 }
994
995 if (list_empty(&file->call_list))
996 return 0;
997
998 idx = 0;
999 list_for_each_entry(insn, &file->call_list, call_node)
1000 idx++;
1001
1002 sec = elf_create_section_pair(file->elf, ".call_sites",
1003 sizeof(unsigned int), idx, idx);
1004 if (!sec)
1005 return -1;
1006
1007 idx = 0;
1008 list_for_each_entry(insn, &file->call_list, call_node) {
1009
1010 if (!elf_init_reloc_text_sym(file->elf, sec,
1011 idx * sizeof(unsigned int), idx,
1012 insn->sec, insn->offset))
1013 return -1;
1014
1015 idx++;
1016 }
1017
1018 return 0;
1019}
1020
1021/*
1022 * Warnings shouldn't be reported for ignored functions.
1023 */
1024static void add_ignores(struct objtool_file *file)
1025{
1026 struct instruction *insn;
1027 struct section *rsec;
1028 struct symbol *func;
1029 struct reloc *reloc;
1030
1031 rsec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
1032 if (!rsec)
1033 return;
1034
1035 for_each_reloc(rsec, reloc) {
1036 switch (reloc->sym->type) {
1037 case STT_FUNC:
1038 func = reloc->sym;
1039 break;
1040
1041 case STT_SECTION:
1042 func = find_func_by_offset(reloc->sym->sec, reloc_addend(reloc));
1043 if (!func)
1044 continue;
1045 break;
1046
1047 default:
1048 WARN("unexpected relocation symbol type in %s: %d",
1049 rsec->name, reloc->sym->type);
1050 continue;
1051 }
1052
1053 func_for_each_insn(file, func, insn)
1054 insn->ignore = true;
1055 }
1056}
1057
1058/*
1059 * This is a whitelist of functions that is allowed to be called with AC set.
1060 * The list is meant to be minimal and only contains compiler instrumentation
1061 * ABI and a few functions used to implement *_{to,from}_user() functions.
1062 *
1063 * These functions must not directly change AC, but may PUSHF/POPF.
1064 */
1065static const char *uaccess_safe_builtin[] = {
1066 /* KASAN */
1067 "kasan_report",
1068 "kasan_check_range",
1069 /* KASAN out-of-line */
1070 "__asan_loadN_noabort",
1071 "__asan_load1_noabort",
1072 "__asan_load2_noabort",
1073 "__asan_load4_noabort",
1074 "__asan_load8_noabort",
1075 "__asan_load16_noabort",
1076 "__asan_storeN_noabort",
1077 "__asan_store1_noabort",
1078 "__asan_store2_noabort",
1079 "__asan_store4_noabort",
1080 "__asan_store8_noabort",
1081 "__asan_store16_noabort",
1082 "__kasan_check_read",
1083 "__kasan_check_write",
1084 /* KASAN in-line */
1085 "__asan_report_load_n_noabort",
1086 "__asan_report_load1_noabort",
1087 "__asan_report_load2_noabort",
1088 "__asan_report_load4_noabort",
1089 "__asan_report_load8_noabort",
1090 "__asan_report_load16_noabort",
1091 "__asan_report_store_n_noabort",
1092 "__asan_report_store1_noabort",
1093 "__asan_report_store2_noabort",
1094 "__asan_report_store4_noabort",
1095 "__asan_report_store8_noabort",
1096 "__asan_report_store16_noabort",
1097 /* KCSAN */
1098 "__kcsan_check_access",
1099 "__kcsan_mb",
1100 "__kcsan_wmb",
1101 "__kcsan_rmb",
1102 "__kcsan_release",
1103 "kcsan_found_watchpoint",
1104 "kcsan_setup_watchpoint",
1105 "kcsan_check_scoped_accesses",
1106 "kcsan_disable_current",
1107 "kcsan_enable_current_nowarn",
1108 /* KCSAN/TSAN */
1109 "__tsan_func_entry",
1110 "__tsan_func_exit",
1111 "__tsan_read_range",
1112 "__tsan_write_range",
1113 "__tsan_read1",
1114 "__tsan_read2",
1115 "__tsan_read4",
1116 "__tsan_read8",
1117 "__tsan_read16",
1118 "__tsan_write1",
1119 "__tsan_write2",
1120 "__tsan_write4",
1121 "__tsan_write8",
1122 "__tsan_write16",
1123 "__tsan_read_write1",
1124 "__tsan_read_write2",
1125 "__tsan_read_write4",
1126 "__tsan_read_write8",
1127 "__tsan_read_write16",
1128 "__tsan_volatile_read1",
1129 "__tsan_volatile_read2",
1130 "__tsan_volatile_read4",
1131 "__tsan_volatile_read8",
1132 "__tsan_volatile_read16",
1133 "__tsan_volatile_write1",
1134 "__tsan_volatile_write2",
1135 "__tsan_volatile_write4",
1136 "__tsan_volatile_write8",
1137 "__tsan_volatile_write16",
1138 "__tsan_atomic8_load",
1139 "__tsan_atomic16_load",
1140 "__tsan_atomic32_load",
1141 "__tsan_atomic64_load",
1142 "__tsan_atomic8_store",
1143 "__tsan_atomic16_store",
1144 "__tsan_atomic32_store",
1145 "__tsan_atomic64_store",
1146 "__tsan_atomic8_exchange",
1147 "__tsan_atomic16_exchange",
1148 "__tsan_atomic32_exchange",
1149 "__tsan_atomic64_exchange",
1150 "__tsan_atomic8_fetch_add",
1151 "__tsan_atomic16_fetch_add",
1152 "__tsan_atomic32_fetch_add",
1153 "__tsan_atomic64_fetch_add",
1154 "__tsan_atomic8_fetch_sub",
1155 "__tsan_atomic16_fetch_sub",
1156 "__tsan_atomic32_fetch_sub",
1157 "__tsan_atomic64_fetch_sub",
1158 "__tsan_atomic8_fetch_and",
1159 "__tsan_atomic16_fetch_and",
1160 "__tsan_atomic32_fetch_and",
1161 "__tsan_atomic64_fetch_and",
1162 "__tsan_atomic8_fetch_or",
1163 "__tsan_atomic16_fetch_or",
1164 "__tsan_atomic32_fetch_or",
1165 "__tsan_atomic64_fetch_or",
1166 "__tsan_atomic8_fetch_xor",
1167 "__tsan_atomic16_fetch_xor",
1168 "__tsan_atomic32_fetch_xor",
1169 "__tsan_atomic64_fetch_xor",
1170 "__tsan_atomic8_fetch_nand",
1171 "__tsan_atomic16_fetch_nand",
1172 "__tsan_atomic32_fetch_nand",
1173 "__tsan_atomic64_fetch_nand",
1174 "__tsan_atomic8_compare_exchange_strong",
1175 "__tsan_atomic16_compare_exchange_strong",
1176 "__tsan_atomic32_compare_exchange_strong",
1177 "__tsan_atomic64_compare_exchange_strong",
1178 "__tsan_atomic8_compare_exchange_weak",
1179 "__tsan_atomic16_compare_exchange_weak",
1180 "__tsan_atomic32_compare_exchange_weak",
1181 "__tsan_atomic64_compare_exchange_weak",
1182 "__tsan_atomic8_compare_exchange_val",
1183 "__tsan_atomic16_compare_exchange_val",
1184 "__tsan_atomic32_compare_exchange_val",
1185 "__tsan_atomic64_compare_exchange_val",
1186 "__tsan_atomic_thread_fence",
1187 "__tsan_atomic_signal_fence",
1188 "__tsan_unaligned_read16",
1189 "__tsan_unaligned_write16",
1190 /* KCOV */
1191 "write_comp_data",
1192 "check_kcov_mode",
1193 "__sanitizer_cov_trace_pc",
1194 "__sanitizer_cov_trace_const_cmp1",
1195 "__sanitizer_cov_trace_const_cmp2",
1196 "__sanitizer_cov_trace_const_cmp4",
1197 "__sanitizer_cov_trace_const_cmp8",
1198 "__sanitizer_cov_trace_cmp1",
1199 "__sanitizer_cov_trace_cmp2",
1200 "__sanitizer_cov_trace_cmp4",
1201 "__sanitizer_cov_trace_cmp8",
1202 "__sanitizer_cov_trace_switch",
1203 /* KMSAN */
1204 "kmsan_copy_to_user",
1205 "kmsan_report",
1206 "kmsan_unpoison_entry_regs",
1207 "kmsan_unpoison_memory",
1208 "__msan_chain_origin",
1209 "__msan_get_context_state",
1210 "__msan_instrument_asm_store",
1211 "__msan_metadata_ptr_for_load_1",
1212 "__msan_metadata_ptr_for_load_2",
1213 "__msan_metadata_ptr_for_load_4",
1214 "__msan_metadata_ptr_for_load_8",
1215 "__msan_metadata_ptr_for_load_n",
1216 "__msan_metadata_ptr_for_store_1",
1217 "__msan_metadata_ptr_for_store_2",
1218 "__msan_metadata_ptr_for_store_4",
1219 "__msan_metadata_ptr_for_store_8",
1220 "__msan_metadata_ptr_for_store_n",
1221 "__msan_poison_alloca",
1222 "__msan_warning",
1223 /* UBSAN */
1224 "ubsan_type_mismatch_common",
1225 "__ubsan_handle_type_mismatch",
1226 "__ubsan_handle_type_mismatch_v1",
1227 "__ubsan_handle_shift_out_of_bounds",
1228 "__ubsan_handle_load_invalid_value",
1229 /* STACKLEAK */
1230 "stackleak_track_stack",
1231 /* misc */
1232 "csum_partial_copy_generic",
1233 "copy_mc_fragile",
1234 "copy_mc_fragile_handle_tail",
1235 "copy_mc_enhanced_fast_string",
1236 "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
1237 "rep_stos_alternative",
1238 "rep_movs_alternative",
1239 "__copy_user_nocache",
1240 NULL
1241};
1242
1243static void add_uaccess_safe(struct objtool_file *file)
1244{
1245 struct symbol *func;
1246 const char **name;
1247
1248 if (!opts.uaccess)
1249 return;
1250
1251 for (name = uaccess_safe_builtin; *name; name++) {
1252 func = find_symbol_by_name(file->elf, *name);
1253 if (!func)
1254 continue;
1255
1256 func->uaccess_safe = true;
1257 }
1258}
1259
1260/*
1261 * FIXME: For now, just ignore any alternatives which add retpolines. This is
1262 * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
1263 * But it at least allows objtool to understand the control flow *around* the
1264 * retpoline.
1265 */
1266static int add_ignore_alternatives(struct objtool_file *file)
1267{
1268 struct section *rsec;
1269 struct reloc *reloc;
1270 struct instruction *insn;
1271
1272 rsec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
1273 if (!rsec)
1274 return 0;
1275
1276 for_each_reloc(rsec, reloc) {
1277 if (reloc->sym->type != STT_SECTION) {
1278 WARN("unexpected relocation symbol type in %s", rsec->name);
1279 return -1;
1280 }
1281
1282 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
1283 if (!insn) {
1284 WARN("bad .discard.ignore_alts entry");
1285 return -1;
1286 }
1287
1288 insn->ignore_alts = true;
1289 }
1290
1291 return 0;
1292}
1293
1294/*
1295 * Symbols that replace INSN_CALL_DYNAMIC, every (tail) call to such a symbol
1296 * will be added to the .retpoline_sites section.
1297 */
1298__weak bool arch_is_retpoline(struct symbol *sym)
1299{
1300 return false;
1301}
1302
1303/*
1304 * Symbols that replace INSN_RETURN, every (tail) call to such a symbol
1305 * will be added to the .return_sites section.
1306 */
1307__weak bool arch_is_rethunk(struct symbol *sym)
1308{
1309 return false;
1310}
1311
1312/*
1313 * Symbols that are embedded inside other instructions, because sometimes crazy
1314 * code exists. These are mostly ignored for validation purposes.
1315 */
1316__weak bool arch_is_embedded_insn(struct symbol *sym)
1317{
1318 return false;
1319}
1320
1321static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
1322{
1323 struct reloc *reloc;
1324
1325 if (insn->no_reloc)
1326 return NULL;
1327
1328 if (!file)
1329 return NULL;
1330
1331 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1332 insn->offset, insn->len);
1333 if (!reloc) {
1334 insn->no_reloc = 1;
1335 return NULL;
1336 }
1337
1338 return reloc;
1339}
1340
1341static void remove_insn_ops(struct instruction *insn)
1342{
1343 struct stack_op *op, *next;
1344
1345 for (op = insn->stack_ops; op; op = next) {
1346 next = op->next;
1347 free(op);
1348 }
1349 insn->stack_ops = NULL;
1350}
1351
1352static void annotate_call_site(struct objtool_file *file,
1353 struct instruction *insn, bool sibling)
1354{
1355 struct reloc *reloc = insn_reloc(file, insn);
1356 struct symbol *sym = insn_call_dest(insn);
1357
1358 if (!sym)
1359 sym = reloc->sym;
1360
1361 /*
1362 * Alternative replacement code is just template code which is
1363 * sometimes copied to the original instruction. For now, don't
1364 * annotate it. (In the future we might consider annotating the
1365 * original instruction if/when it ever makes sense to do so.)
1366 */
1367 if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1368 return;
1369
1370 if (sym->static_call_tramp) {
1371 list_add_tail(&insn->call_node, &file->static_call_list);
1372 return;
1373 }
1374
1375 if (sym->retpoline_thunk) {
1376 list_add_tail(&insn->call_node, &file->retpoline_call_list);
1377 return;
1378 }
1379
1380 /*
1381 * Many compilers cannot disable KCOV or sanitizer calls with a function
1382 * attribute so they need a little help, NOP out any such calls from
1383 * noinstr text.
1384 */
1385 if (opts.hack_noinstr && insn->sec->noinstr && sym->profiling_func) {
1386 if (reloc)
1387 set_reloc_type(file->elf, reloc, R_NONE);
1388
1389 elf_write_insn(file->elf, insn->sec,
1390 insn->offset, insn->len,
1391 sibling ? arch_ret_insn(insn->len)
1392 : arch_nop_insn(insn->len));
1393
1394 insn->type = sibling ? INSN_RETURN : INSN_NOP;
1395
1396 if (sibling) {
1397 /*
1398 * We've replaced the tail-call JMP insn by two new
1399 * insn: RET; INT3, except we only have a single struct
1400 * insn here. Mark it retpoline_safe to avoid the SLS
1401 * warning, instead of adding another insn.
1402 */
1403 insn->retpoline_safe = true;
1404 }
1405
1406 return;
1407 }
1408
1409 if (opts.mcount && sym->fentry) {
1410 if (sibling)
1411 WARN_INSN(insn, "tail call to __fentry__ !?!?");
1412 if (opts.mnop) {
1413 if (reloc)
1414 set_reloc_type(file->elf, reloc, R_NONE);
1415
1416 elf_write_insn(file->elf, insn->sec,
1417 insn->offset, insn->len,
1418 arch_nop_insn(insn->len));
1419
1420 insn->type = INSN_NOP;
1421 }
1422
1423 list_add_tail(&insn->call_node, &file->mcount_loc_list);
1424 return;
1425 }
1426
1427 if (insn->type == INSN_CALL && !insn->sec->init)
1428 list_add_tail(&insn->call_node, &file->call_list);
1429
1430 if (!sibling && dead_end_function(file, sym))
1431 insn->dead_end = true;
1432}
1433
1434static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1435 struct symbol *dest, bool sibling)
1436{
1437 insn->_call_dest = dest;
1438 if (!dest)
1439 return;
1440
1441 /*
1442 * Whatever stack impact regular CALLs have, should be undone
1443 * by the RETURN of the called function.
1444 *
1445 * Annotated intra-function calls retain the stack_ops but
1446 * are converted to JUMP, see read_intra_function_calls().
1447 */
1448 remove_insn_ops(insn);
1449
1450 annotate_call_site(file, insn, sibling);
1451}
1452
1453static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1454{
1455 /*
1456 * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1457 * so convert them accordingly.
1458 */
1459 switch (insn->type) {
1460 case INSN_CALL:
1461 insn->type = INSN_CALL_DYNAMIC;
1462 break;
1463 case INSN_JUMP_UNCONDITIONAL:
1464 insn->type = INSN_JUMP_DYNAMIC;
1465 break;
1466 case INSN_JUMP_CONDITIONAL:
1467 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1468 break;
1469 default:
1470 return;
1471 }
1472
1473 insn->retpoline_safe = true;
1474
1475 /*
1476 * Whatever stack impact regular CALLs have, should be undone
1477 * by the RETURN of the called function.
1478 *
1479 * Annotated intra-function calls retain the stack_ops but
1480 * are converted to JUMP, see read_intra_function_calls().
1481 */
1482 remove_insn_ops(insn);
1483
1484 annotate_call_site(file, insn, false);
1485}
1486
1487static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add)
1488{
1489 /*
1490 * Return thunk tail calls are really just returns in disguise,
1491 * so convert them accordingly.
1492 */
1493 insn->type = INSN_RETURN;
1494 insn->retpoline_safe = true;
1495
1496 if (add)
1497 list_add_tail(&insn->call_node, &file->return_thunk_list);
1498}
1499
1500static bool is_first_func_insn(struct objtool_file *file,
1501 struct instruction *insn, struct symbol *sym)
1502{
1503 if (insn->offset == sym->offset)
1504 return true;
1505
1506 /* Allow direct CALL/JMP past ENDBR */
1507 if (opts.ibt) {
1508 struct instruction *prev = prev_insn_same_sym(file, insn);
1509
1510 if (prev && prev->type == INSN_ENDBR &&
1511 insn->offset == sym->offset + prev->len)
1512 return true;
1513 }
1514
1515 return false;
1516}
1517
1518/*
1519 * A sibling call is a tail-call to another symbol -- to differentiate from a
1520 * recursive tail-call which is to the same symbol.
1521 */
1522static bool jump_is_sibling_call(struct objtool_file *file,
1523 struct instruction *from, struct instruction *to)
1524{
1525 struct symbol *fs = from->sym;
1526 struct symbol *ts = to->sym;
1527
1528 /* Not a sibling call if from/to a symbol hole */
1529 if (!fs || !ts)
1530 return false;
1531
1532 /* Not a sibling call if not targeting the start of a symbol. */
1533 if (!is_first_func_insn(file, to, ts))
1534 return false;
1535
1536 /* Disallow sibling calls into STT_NOTYPE */
1537 if (ts->type == STT_NOTYPE)
1538 return false;
1539
1540 /* Must not be self to be a sibling */
1541 return fs->pfunc != ts->pfunc;
1542}
1543
1544/*
1545 * Find the destination instructions for all jumps.
1546 */
1547static int add_jump_destinations(struct objtool_file *file)
1548{
1549 struct instruction *insn, *jump_dest;
1550 struct reloc *reloc;
1551 struct section *dest_sec;
1552 unsigned long dest_off;
1553
1554 for_each_insn(file, insn) {
1555 if (insn->jump_dest) {
1556 /*
1557 * handle_group_alt() may have previously set
1558 * 'jump_dest' for some alternatives.
1559 */
1560 continue;
1561 }
1562 if (!is_static_jump(insn))
1563 continue;
1564
1565 reloc = insn_reloc(file, insn);
1566 if (!reloc) {
1567 dest_sec = insn->sec;
1568 dest_off = arch_jump_destination(insn);
1569 } else if (reloc->sym->type == STT_SECTION) {
1570 dest_sec = reloc->sym->sec;
1571 dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
1572 } else if (reloc->sym->retpoline_thunk) {
1573 add_retpoline_call(file, insn);
1574 continue;
1575 } else if (reloc->sym->return_thunk) {
1576 add_return_call(file, insn, true);
1577 continue;
1578 } else if (insn_func(insn)) {
1579 /*
1580 * External sibling call or internal sibling call with
1581 * STT_FUNC reloc.
1582 */
1583 add_call_dest(file, insn, reloc->sym, true);
1584 continue;
1585 } else if (reloc->sym->sec->idx) {
1586 dest_sec = reloc->sym->sec;
1587 dest_off = reloc->sym->sym.st_value +
1588 arch_dest_reloc_offset(reloc_addend(reloc));
1589 } else {
1590 /* non-func asm code jumping to another file */
1591 continue;
1592 }
1593
1594 jump_dest = find_insn(file, dest_sec, dest_off);
1595 if (!jump_dest) {
1596 struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off);
1597
1598 /*
1599 * This is a special case for retbleed_untrain_ret().
1600 * It jumps to __x86_return_thunk(), but objtool
1601 * can't find the thunk's starting RET
1602 * instruction, because the RET is also in the
1603 * middle of another instruction. Objtool only
1604 * knows about the outer instruction.
1605 */
1606 if (sym && sym->embedded_insn) {
1607 add_return_call(file, insn, false);
1608 continue;
1609 }
1610
1611 WARN_INSN(insn, "can't find jump dest instruction at %s+0x%lx",
1612 dest_sec->name, dest_off);
1613 return -1;
1614 }
1615
1616 /*
1617 * An intra-TU jump in retpoline.o might not have a relocation
1618 * for its jump dest, in which case the above
1619 * add_{retpoline,return}_call() didn't happen.
1620 */
1621 if (jump_dest->sym && jump_dest->offset == jump_dest->sym->offset) {
1622 if (jump_dest->sym->retpoline_thunk) {
1623 add_retpoline_call(file, insn);
1624 continue;
1625 }
1626 if (jump_dest->sym->return_thunk) {
1627 add_return_call(file, insn, true);
1628 continue;
1629 }
1630 }
1631
1632 /*
1633 * Cross-function jump.
1634 */
1635 if (insn_func(insn) && insn_func(jump_dest) &&
1636 insn_func(insn) != insn_func(jump_dest)) {
1637
1638 /*
1639 * For GCC 8+, create parent/child links for any cold
1640 * subfunctions. This is _mostly_ redundant with a
1641 * similar initialization in read_symbols().
1642 *
1643 * If a function has aliases, we want the *first* such
1644 * function in the symbol table to be the subfunction's
1645 * parent. In that case we overwrite the
1646 * initialization done in read_symbols().
1647 *
1648 * However this code can't completely replace the
1649 * read_symbols() code because this doesn't detect the
1650 * case where the parent function's only reference to a
1651 * subfunction is through a jump table.
1652 */
1653 if (!strstr(insn_func(insn)->name, ".cold") &&
1654 strstr(insn_func(jump_dest)->name, ".cold")) {
1655 insn_func(insn)->cfunc = insn_func(jump_dest);
1656 insn_func(jump_dest)->pfunc = insn_func(insn);
1657 }
1658 }
1659
1660 if (jump_is_sibling_call(file, insn, jump_dest)) {
1661 /*
1662 * Internal sibling call without reloc or with
1663 * STT_SECTION reloc.
1664 */
1665 add_call_dest(file, insn, insn_func(jump_dest), true);
1666 continue;
1667 }
1668
1669 insn->jump_dest = jump_dest;
1670 }
1671
1672 return 0;
1673}
1674
1675static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1676{
1677 struct symbol *call_dest;
1678
1679 call_dest = find_func_by_offset(sec, offset);
1680 if (!call_dest)
1681 call_dest = find_symbol_by_offset(sec, offset);
1682
1683 return call_dest;
1684}
1685
1686/*
1687 * Find the destination instructions for all calls.
1688 */
1689static int add_call_destinations(struct objtool_file *file)
1690{
1691 struct instruction *insn;
1692 unsigned long dest_off;
1693 struct symbol *dest;
1694 struct reloc *reloc;
1695
1696 for_each_insn(file, insn) {
1697 if (insn->type != INSN_CALL)
1698 continue;
1699
1700 reloc = insn_reloc(file, insn);
1701 if (!reloc) {
1702 dest_off = arch_jump_destination(insn);
1703 dest = find_call_destination(insn->sec, dest_off);
1704
1705 add_call_dest(file, insn, dest, false);
1706
1707 if (insn->ignore)
1708 continue;
1709
1710 if (!insn_call_dest(insn)) {
1711 WARN_INSN(insn, "unannotated intra-function call");
1712 return -1;
1713 }
1714
1715 if (insn_func(insn) && insn_call_dest(insn)->type != STT_FUNC) {
1716 WARN_INSN(insn, "unsupported call to non-function");
1717 return -1;
1718 }
1719
1720 } else if (reloc->sym->type == STT_SECTION) {
1721 dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
1722 dest = find_call_destination(reloc->sym->sec, dest_off);
1723 if (!dest) {
1724 WARN_INSN(insn, "can't find call dest symbol at %s+0x%lx",
1725 reloc->sym->sec->name, dest_off);
1726 return -1;
1727 }
1728
1729 add_call_dest(file, insn, dest, false);
1730
1731 } else if (reloc->sym->retpoline_thunk) {
1732 add_retpoline_call(file, insn);
1733
1734 } else
1735 add_call_dest(file, insn, reloc->sym, false);
1736 }
1737
1738 return 0;
1739}
1740
1741/*
1742 * The .alternatives section requires some extra special care over and above
1743 * other special sections because alternatives are patched in place.
1744 */
1745static int handle_group_alt(struct objtool_file *file,
1746 struct special_alt *special_alt,
1747 struct instruction *orig_insn,
1748 struct instruction **new_insn)
1749{
1750 struct instruction *last_new_insn = NULL, *insn, *nop = NULL;
1751 struct alt_group *orig_alt_group, *new_alt_group;
1752 unsigned long dest_off;
1753
1754 orig_alt_group = orig_insn->alt_group;
1755 if (!orig_alt_group) {
1756 struct instruction *last_orig_insn = NULL;
1757
1758 orig_alt_group = malloc(sizeof(*orig_alt_group));
1759 if (!orig_alt_group) {
1760 WARN("malloc failed");
1761 return -1;
1762 }
1763 orig_alt_group->cfi = calloc(special_alt->orig_len,
1764 sizeof(struct cfi_state *));
1765 if (!orig_alt_group->cfi) {
1766 WARN("calloc failed");
1767 return -1;
1768 }
1769
1770 insn = orig_insn;
1771 sec_for_each_insn_from(file, insn) {
1772 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1773 break;
1774
1775 insn->alt_group = orig_alt_group;
1776 last_orig_insn = insn;
1777 }
1778 orig_alt_group->orig_group = NULL;
1779 orig_alt_group->first_insn = orig_insn;
1780 orig_alt_group->last_insn = last_orig_insn;
1781 orig_alt_group->nop = NULL;
1782 } else {
1783 if (orig_alt_group->last_insn->offset + orig_alt_group->last_insn->len -
1784 orig_alt_group->first_insn->offset != special_alt->orig_len) {
1785 WARN_INSN(orig_insn, "weirdly overlapping alternative! %ld != %d",
1786 orig_alt_group->last_insn->offset +
1787 orig_alt_group->last_insn->len -
1788 orig_alt_group->first_insn->offset,
1789 special_alt->orig_len);
1790 return -1;
1791 }
1792 }
1793
1794 new_alt_group = malloc(sizeof(*new_alt_group));
1795 if (!new_alt_group) {
1796 WARN("malloc failed");
1797 return -1;
1798 }
1799
1800 if (special_alt->new_len < special_alt->orig_len) {
1801 /*
1802 * Insert a fake nop at the end to make the replacement
1803 * alt_group the same size as the original. This is needed to
1804 * allow propagate_alt_cfi() to do its magic. When the last
1805 * instruction affects the stack, the instruction after it (the
1806 * nop) will propagate the new state to the shared CFI array.
1807 */
1808 nop = malloc(sizeof(*nop));
1809 if (!nop) {
1810 WARN("malloc failed");
1811 return -1;
1812 }
1813 memset(nop, 0, sizeof(*nop));
1814
1815 nop->sec = special_alt->new_sec;
1816 nop->offset = special_alt->new_off + special_alt->new_len;
1817 nop->len = special_alt->orig_len - special_alt->new_len;
1818 nop->type = INSN_NOP;
1819 nop->sym = orig_insn->sym;
1820 nop->alt_group = new_alt_group;
1821 nop->ignore = orig_insn->ignore_alts;
1822 }
1823
1824 if (!special_alt->new_len) {
1825 *new_insn = nop;
1826 goto end;
1827 }
1828
1829 insn = *new_insn;
1830 sec_for_each_insn_from(file, insn) {
1831 struct reloc *alt_reloc;
1832
1833 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1834 break;
1835
1836 last_new_insn = insn;
1837
1838 insn->ignore = orig_insn->ignore_alts;
1839 insn->sym = orig_insn->sym;
1840 insn->alt_group = new_alt_group;
1841
1842 /*
1843 * Since alternative replacement code is copy/pasted by the
1844 * kernel after applying relocations, generally such code can't
1845 * have relative-address relocation references to outside the
1846 * .altinstr_replacement section, unless the arch's
1847 * alternatives code can adjust the relative offsets
1848 * accordingly.
1849 */
1850 alt_reloc = insn_reloc(file, insn);
1851 if (alt_reloc && arch_pc_relative_reloc(alt_reloc) &&
1852 !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1853
1854 WARN_INSN(insn, "unsupported relocation in alternatives section");
1855 return -1;
1856 }
1857
1858 if (!is_static_jump(insn))
1859 continue;
1860
1861 if (!insn->immediate)
1862 continue;
1863
1864 dest_off = arch_jump_destination(insn);
1865 if (dest_off == special_alt->new_off + special_alt->new_len) {
1866 insn->jump_dest = next_insn_same_sec(file, orig_alt_group->last_insn);
1867 if (!insn->jump_dest) {
1868 WARN_INSN(insn, "can't find alternative jump destination");
1869 return -1;
1870 }
1871 }
1872 }
1873
1874 if (!last_new_insn) {
1875 WARN_FUNC("can't find last new alternative instruction",
1876 special_alt->new_sec, special_alt->new_off);
1877 return -1;
1878 }
1879
1880end:
1881 new_alt_group->orig_group = orig_alt_group;
1882 new_alt_group->first_insn = *new_insn;
1883 new_alt_group->last_insn = last_new_insn;
1884 new_alt_group->nop = nop;
1885 new_alt_group->cfi = orig_alt_group->cfi;
1886 return 0;
1887}
1888
1889/*
1890 * A jump table entry can either convert a nop to a jump or a jump to a nop.
1891 * If the original instruction is a jump, make the alt entry an effective nop
1892 * by just skipping the original instruction.
1893 */
1894static int handle_jump_alt(struct objtool_file *file,
1895 struct special_alt *special_alt,
1896 struct instruction *orig_insn,
1897 struct instruction **new_insn)
1898{
1899 if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1900 orig_insn->type != INSN_NOP) {
1901
1902 WARN_INSN(orig_insn, "unsupported instruction at jump label");
1903 return -1;
1904 }
1905
1906 if (opts.hack_jump_label && special_alt->key_addend & 2) {
1907 struct reloc *reloc = insn_reloc(file, orig_insn);
1908
1909 if (reloc)
1910 set_reloc_type(file->elf, reloc, R_NONE);
1911 elf_write_insn(file->elf, orig_insn->sec,
1912 orig_insn->offset, orig_insn->len,
1913 arch_nop_insn(orig_insn->len));
1914 orig_insn->type = INSN_NOP;
1915 }
1916
1917 if (orig_insn->type == INSN_NOP) {
1918 if (orig_insn->len == 2)
1919 file->jl_nop_short++;
1920 else
1921 file->jl_nop_long++;
1922
1923 return 0;
1924 }
1925
1926 if (orig_insn->len == 2)
1927 file->jl_short++;
1928 else
1929 file->jl_long++;
1930
1931 *new_insn = next_insn_same_sec(file, orig_insn);
1932 return 0;
1933}
1934
1935/*
1936 * Read all the special sections which have alternate instructions which can be
1937 * patched in or redirected to at runtime. Each instruction having alternate
1938 * instruction(s) has them added to its insn->alts list, which will be
1939 * traversed in validate_branch().
1940 */
1941static int add_special_section_alts(struct objtool_file *file)
1942{
1943 struct list_head special_alts;
1944 struct instruction *orig_insn, *new_insn;
1945 struct special_alt *special_alt, *tmp;
1946 struct alternative *alt;
1947 int ret;
1948
1949 ret = special_get_alts(file->elf, &special_alts);
1950 if (ret)
1951 return ret;
1952
1953 list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1954
1955 orig_insn = find_insn(file, special_alt->orig_sec,
1956 special_alt->orig_off);
1957 if (!orig_insn) {
1958 WARN_FUNC("special: can't find orig instruction",
1959 special_alt->orig_sec, special_alt->orig_off);
1960 ret = -1;
1961 goto out;
1962 }
1963
1964 new_insn = NULL;
1965 if (!special_alt->group || special_alt->new_len) {
1966 new_insn = find_insn(file, special_alt->new_sec,
1967 special_alt->new_off);
1968 if (!new_insn) {
1969 WARN_FUNC("special: can't find new instruction",
1970 special_alt->new_sec,
1971 special_alt->new_off);
1972 ret = -1;
1973 goto out;
1974 }
1975 }
1976
1977 if (special_alt->group) {
1978 if (!special_alt->orig_len) {
1979 WARN_INSN(orig_insn, "empty alternative entry");
1980 continue;
1981 }
1982
1983 ret = handle_group_alt(file, special_alt, orig_insn,
1984 &new_insn);
1985 if (ret)
1986 goto out;
1987 } else if (special_alt->jump_or_nop) {
1988 ret = handle_jump_alt(file, special_alt, orig_insn,
1989 &new_insn);
1990 if (ret)
1991 goto out;
1992 }
1993
1994 alt = malloc(sizeof(*alt));
1995 if (!alt) {
1996 WARN("malloc failed");
1997 ret = -1;
1998 goto out;
1999 }
2000
2001 alt->insn = new_insn;
2002 alt->skip_orig = special_alt->skip_orig;
2003 orig_insn->ignore_alts |= special_alt->skip_alt;
2004 alt->next = orig_insn->alts;
2005 orig_insn->alts = alt;
2006
2007 list_del(&special_alt->list);
2008 free(special_alt);
2009 }
2010
2011 if (opts.stats) {
2012 printf("jl\\\tNOP\tJMP\n");
2013 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
2014 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
2015 }
2016
2017out:
2018 return ret;
2019}
2020
2021static int add_jump_table(struct objtool_file *file, struct instruction *insn,
2022 struct reloc *next_table)
2023{
2024 struct symbol *pfunc = insn_func(insn)->pfunc;
2025 struct reloc *table = insn_jump_table(insn);
2026 struct instruction *dest_insn;
2027 unsigned int prev_offset = 0;
2028 struct reloc *reloc = table;
2029 struct alternative *alt;
2030
2031 /*
2032 * Each @reloc is a switch table relocation which points to the target
2033 * instruction.
2034 */
2035 for_each_reloc_from(table->sec, reloc) {
2036
2037 /* Check for the end of the table: */
2038 if (reloc != table && reloc == next_table)
2039 break;
2040
2041 /* Make sure the table entries are consecutive: */
2042 if (prev_offset && reloc_offset(reloc) != prev_offset + 8)
2043 break;
2044
2045 /* Detect function pointers from contiguous objects: */
2046 if (reloc->sym->sec == pfunc->sec &&
2047 reloc_addend(reloc) == pfunc->offset)
2048 break;
2049
2050 dest_insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2051 if (!dest_insn)
2052 break;
2053
2054 /* Make sure the destination is in the same function: */
2055 if (!insn_func(dest_insn) || insn_func(dest_insn)->pfunc != pfunc)
2056 break;
2057
2058 alt = malloc(sizeof(*alt));
2059 if (!alt) {
2060 WARN("malloc failed");
2061 return -1;
2062 }
2063
2064 alt->insn = dest_insn;
2065 alt->next = insn->alts;
2066 insn->alts = alt;
2067 prev_offset = reloc_offset(reloc);
2068 }
2069
2070 if (!prev_offset) {
2071 WARN_INSN(insn, "can't find switch jump table");
2072 return -1;
2073 }
2074
2075 return 0;
2076}
2077
2078/*
2079 * find_jump_table() - Given a dynamic jump, find the switch jump table
2080 * associated with it.
2081 */
2082static struct reloc *find_jump_table(struct objtool_file *file,
2083 struct symbol *func,
2084 struct instruction *insn)
2085{
2086 struct reloc *table_reloc;
2087 struct instruction *dest_insn, *orig_insn = insn;
2088
2089 /*
2090 * Backward search using the @first_jump_src links, these help avoid
2091 * much of the 'in between' code. Which avoids us getting confused by
2092 * it.
2093 */
2094 for (;
2095 insn && insn_func(insn) && insn_func(insn)->pfunc == func;
2096 insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
2097
2098 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
2099 break;
2100
2101 /* allow small jumps within the range */
2102 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
2103 insn->jump_dest &&
2104 (insn->jump_dest->offset <= insn->offset ||
2105 insn->jump_dest->offset > orig_insn->offset))
2106 break;
2107
2108 table_reloc = arch_find_switch_table(file, insn);
2109 if (!table_reloc)
2110 continue;
2111 dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
2112 if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
2113 continue;
2114
2115 return table_reloc;
2116 }
2117
2118 return NULL;
2119}
2120
2121/*
2122 * First pass: Mark the head of each jump table so that in the next pass,
2123 * we know when a given jump table ends and the next one starts.
2124 */
2125static void mark_func_jump_tables(struct objtool_file *file,
2126 struct symbol *func)
2127{
2128 struct instruction *insn, *last = NULL;
2129 struct reloc *reloc;
2130
2131 func_for_each_insn(file, func, insn) {
2132 if (!last)
2133 last = insn;
2134
2135 /*
2136 * Store back-pointers for unconditional forward jumps such
2137 * that find_jump_table() can back-track using those and
2138 * avoid some potentially confusing code.
2139 */
2140 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
2141 insn->offset > last->offset &&
2142 insn->jump_dest->offset > insn->offset &&
2143 !insn->jump_dest->first_jump_src) {
2144
2145 insn->jump_dest->first_jump_src = insn;
2146 last = insn->jump_dest;
2147 }
2148
2149 if (insn->type != INSN_JUMP_DYNAMIC)
2150 continue;
2151
2152 reloc = find_jump_table(file, func, insn);
2153 if (reloc)
2154 insn->_jump_table = reloc;
2155 }
2156}
2157
2158static int add_func_jump_tables(struct objtool_file *file,
2159 struct symbol *func)
2160{
2161 struct instruction *insn, *insn_t1 = NULL, *insn_t2;
2162 int ret = 0;
2163
2164 func_for_each_insn(file, func, insn) {
2165 if (!insn_jump_table(insn))
2166 continue;
2167
2168 if (!insn_t1) {
2169 insn_t1 = insn;
2170 continue;
2171 }
2172
2173 insn_t2 = insn;
2174
2175 ret = add_jump_table(file, insn_t1, insn_jump_table(insn_t2));
2176 if (ret)
2177 return ret;
2178
2179 insn_t1 = insn_t2;
2180 }
2181
2182 if (insn_t1)
2183 ret = add_jump_table(file, insn_t1, NULL);
2184
2185 return ret;
2186}
2187
2188/*
2189 * For some switch statements, gcc generates a jump table in the .rodata
2190 * section which contains a list of addresses within the function to jump to.
2191 * This finds these jump tables and adds them to the insn->alts lists.
2192 */
2193static int add_jump_table_alts(struct objtool_file *file)
2194{
2195 struct symbol *func;
2196 int ret;
2197
2198 if (!file->rodata)
2199 return 0;
2200
2201 for_each_sym(file, func) {
2202 if (func->type != STT_FUNC)
2203 continue;
2204
2205 mark_func_jump_tables(file, func);
2206 ret = add_func_jump_tables(file, func);
2207 if (ret)
2208 return ret;
2209 }
2210
2211 return 0;
2212}
2213
2214static void set_func_state(struct cfi_state *state)
2215{
2216 state->cfa = initial_func_cfi.cfa;
2217 memcpy(&state->regs, &initial_func_cfi.regs,
2218 CFI_NUM_REGS * sizeof(struct cfi_reg));
2219 state->stack_size = initial_func_cfi.cfa.offset;
2220 state->type = UNWIND_HINT_TYPE_CALL;
2221}
2222
2223static int read_unwind_hints(struct objtool_file *file)
2224{
2225 struct cfi_state cfi = init_cfi;
2226 struct section *sec;
2227 struct unwind_hint *hint;
2228 struct instruction *insn;
2229 struct reloc *reloc;
2230 unsigned long offset;
2231 int i;
2232
2233 sec = find_section_by_name(file->elf, ".discard.unwind_hints");
2234 if (!sec)
2235 return 0;
2236
2237 if (!sec->rsec) {
2238 WARN("missing .rela.discard.unwind_hints section");
2239 return -1;
2240 }
2241
2242 if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
2243 WARN("struct unwind_hint size mismatch");
2244 return -1;
2245 }
2246
2247 file->hints = true;
2248
2249 for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
2250 hint = (struct unwind_hint *)sec->data->d_buf + i;
2251
2252 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
2253 if (!reloc) {
2254 WARN("can't find reloc for unwind_hints[%d]", i);
2255 return -1;
2256 }
2257
2258 if (reloc->sym->type == STT_SECTION) {
2259 offset = reloc_addend(reloc);
2260 } else if (reloc->sym->local_label) {
2261 offset = reloc->sym->offset;
2262 } else {
2263 WARN("unexpected relocation symbol type in %s", sec->rsec->name);
2264 return -1;
2265 }
2266
2267 insn = find_insn(file, reloc->sym->sec, offset);
2268 if (!insn) {
2269 WARN("can't find insn for unwind_hints[%d]", i);
2270 return -1;
2271 }
2272
2273 insn->hint = true;
2274
2275 if (hint->type == UNWIND_HINT_TYPE_UNDEFINED) {
2276 insn->cfi = &force_undefined_cfi;
2277 continue;
2278 }
2279
2280 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
2281 insn->hint = false;
2282 insn->save = true;
2283 continue;
2284 }
2285
2286 if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
2287 insn->restore = true;
2288 continue;
2289 }
2290
2291 if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
2292 struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
2293
2294 if (sym && sym->bind == STB_GLOBAL) {
2295 if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) {
2296 WARN_INSN(insn, "UNWIND_HINT_IRET_REGS without ENDBR");
2297 }
2298 }
2299 }
2300
2301 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
2302 insn->cfi = &func_cfi;
2303 continue;
2304 }
2305
2306 if (insn->cfi)
2307 cfi = *(insn->cfi);
2308
2309 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
2310 WARN_INSN(insn, "unsupported unwind_hint sp base reg %d", hint->sp_reg);
2311 return -1;
2312 }
2313
2314 cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
2315 cfi.type = hint->type;
2316 cfi.signal = hint->signal;
2317
2318 insn->cfi = cfi_hash_find_or_add(&cfi);
2319 }
2320
2321 return 0;
2322}
2323
2324static int read_noendbr_hints(struct objtool_file *file)
2325{
2326 struct instruction *insn;
2327 struct section *rsec;
2328 struct reloc *reloc;
2329
2330 rsec = find_section_by_name(file->elf, ".rela.discard.noendbr");
2331 if (!rsec)
2332 return 0;
2333
2334 for_each_reloc(rsec, reloc) {
2335 insn = find_insn(file, reloc->sym->sec,
2336 reloc->sym->offset + reloc_addend(reloc));
2337 if (!insn) {
2338 WARN("bad .discard.noendbr entry");
2339 return -1;
2340 }
2341
2342 insn->noendbr = 1;
2343 }
2344
2345 return 0;
2346}
2347
2348static int read_retpoline_hints(struct objtool_file *file)
2349{
2350 struct section *rsec;
2351 struct instruction *insn;
2352 struct reloc *reloc;
2353
2354 rsec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
2355 if (!rsec)
2356 return 0;
2357
2358 for_each_reloc(rsec, reloc) {
2359 if (reloc->sym->type != STT_SECTION) {
2360 WARN("unexpected relocation symbol type in %s", rsec->name);
2361 return -1;
2362 }
2363
2364 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2365 if (!insn) {
2366 WARN("bad .discard.retpoline_safe entry");
2367 return -1;
2368 }
2369
2370 if (insn->type != INSN_JUMP_DYNAMIC &&
2371 insn->type != INSN_CALL_DYNAMIC &&
2372 insn->type != INSN_RETURN &&
2373 insn->type != INSN_NOP) {
2374 WARN_INSN(insn, "retpoline_safe hint not an indirect jump/call/ret/nop");
2375 return -1;
2376 }
2377
2378 insn->retpoline_safe = true;
2379 }
2380
2381 return 0;
2382}
2383
2384static int read_instr_hints(struct objtool_file *file)
2385{
2386 struct section *rsec;
2387 struct instruction *insn;
2388 struct reloc *reloc;
2389
2390 rsec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2391 if (!rsec)
2392 return 0;
2393
2394 for_each_reloc(rsec, reloc) {
2395 if (reloc->sym->type != STT_SECTION) {
2396 WARN("unexpected relocation symbol type in %s", rsec->name);
2397 return -1;
2398 }
2399
2400 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2401 if (!insn) {
2402 WARN("bad .discard.instr_end entry");
2403 return -1;
2404 }
2405
2406 insn->instr--;
2407 }
2408
2409 rsec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2410 if (!rsec)
2411 return 0;
2412
2413 for_each_reloc(rsec, reloc) {
2414 if (reloc->sym->type != STT_SECTION) {
2415 WARN("unexpected relocation symbol type in %s", rsec->name);
2416 return -1;
2417 }
2418
2419 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2420 if (!insn) {
2421 WARN("bad .discard.instr_begin entry");
2422 return -1;
2423 }
2424
2425 insn->instr++;
2426 }
2427
2428 return 0;
2429}
2430
2431static int read_validate_unret_hints(struct objtool_file *file)
2432{
2433 struct section *rsec;
2434 struct instruction *insn;
2435 struct reloc *reloc;
2436
2437 rsec = find_section_by_name(file->elf, ".rela.discard.validate_unret");
2438 if (!rsec)
2439 return 0;
2440
2441 for_each_reloc(rsec, reloc) {
2442 if (reloc->sym->type != STT_SECTION) {
2443 WARN("unexpected relocation symbol type in %s", rsec->name);
2444 return -1;
2445 }
2446
2447 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2448 if (!insn) {
2449 WARN("bad .discard.instr_end entry");
2450 return -1;
2451 }
2452 insn->unret = 1;
2453 }
2454
2455 return 0;
2456}
2457
2458
2459static int read_intra_function_calls(struct objtool_file *file)
2460{
2461 struct instruction *insn;
2462 struct section *rsec;
2463 struct reloc *reloc;
2464
2465 rsec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2466 if (!rsec)
2467 return 0;
2468
2469 for_each_reloc(rsec, reloc) {
2470 unsigned long dest_off;
2471
2472 if (reloc->sym->type != STT_SECTION) {
2473 WARN("unexpected relocation symbol type in %s",
2474 rsec->name);
2475 return -1;
2476 }
2477
2478 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2479 if (!insn) {
2480 WARN("bad .discard.intra_function_call entry");
2481 return -1;
2482 }
2483
2484 if (insn->type != INSN_CALL) {
2485 WARN_INSN(insn, "intra_function_call not a direct call");
2486 return -1;
2487 }
2488
2489 /*
2490 * Treat intra-function CALLs as JMPs, but with a stack_op.
2491 * See add_call_destinations(), which strips stack_ops from
2492 * normal CALLs.
2493 */
2494 insn->type = INSN_JUMP_UNCONDITIONAL;
2495
2496 dest_off = arch_jump_destination(insn);
2497 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2498 if (!insn->jump_dest) {
2499 WARN_INSN(insn, "can't find call dest at %s+0x%lx",
2500 insn->sec->name, dest_off);
2501 return -1;
2502 }
2503 }
2504
2505 return 0;
2506}
2507
2508/*
2509 * Return true if name matches an instrumentation function, where calls to that
2510 * function from noinstr code can safely be removed, but compilers won't do so.
2511 */
2512static bool is_profiling_func(const char *name)
2513{
2514 /*
2515 * Many compilers cannot disable KCOV with a function attribute.
2516 */
2517 if (!strncmp(name, "__sanitizer_cov_", 16))
2518 return true;
2519
2520 /*
2521 * Some compilers currently do not remove __tsan_func_entry/exit nor
2522 * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2523 * the __no_sanitize_thread attribute, remove them. Once the kernel's
2524 * minimum Clang version is 14.0, this can be removed.
2525 */
2526 if (!strncmp(name, "__tsan_func_", 12) ||
2527 !strcmp(name, "__tsan_atomic_signal_fence"))
2528 return true;
2529
2530 return false;
2531}
2532
2533static int classify_symbols(struct objtool_file *file)
2534{
2535 struct symbol *func;
2536
2537 for_each_sym(file, func) {
2538 if (func->type == STT_NOTYPE && strstarts(func->name, ".L"))
2539 func->local_label = true;
2540
2541 if (func->bind != STB_GLOBAL)
2542 continue;
2543
2544 if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2545 strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2546 func->static_call_tramp = true;
2547
2548 if (arch_is_retpoline(func))
2549 func->retpoline_thunk = true;
2550
2551 if (arch_is_rethunk(func))
2552 func->return_thunk = true;
2553
2554 if (arch_is_embedded_insn(func))
2555 func->embedded_insn = true;
2556
2557 if (arch_ftrace_match(func->name))
2558 func->fentry = true;
2559
2560 if (is_profiling_func(func->name))
2561 func->profiling_func = true;
2562 }
2563
2564 return 0;
2565}
2566
2567static void mark_rodata(struct objtool_file *file)
2568{
2569 struct section *sec;
2570 bool found = false;
2571
2572 /*
2573 * Search for the following rodata sections, each of which can
2574 * potentially contain jump tables:
2575 *
2576 * - .rodata: can contain GCC switch tables
2577 * - .rodata.<func>: same, if -fdata-sections is being used
2578 * - .rodata..c_jump_table: contains C annotated jump tables
2579 *
2580 * .rodata.str1.* sections are ignored; they don't contain jump tables.
2581 */
2582 for_each_sec(file, sec) {
2583 if (!strncmp(sec->name, ".rodata", 7) &&
2584 !strstr(sec->name, ".str1.")) {
2585 sec->rodata = true;
2586 found = true;
2587 }
2588 }
2589
2590 file->rodata = found;
2591}
2592
2593static int decode_sections(struct objtool_file *file)
2594{
2595 int ret;
2596
2597 mark_rodata(file);
2598
2599 ret = init_pv_ops(file);
2600 if (ret)
2601 return ret;
2602
2603 /*
2604 * Must be before add_{jump_call}_destination.
2605 */
2606 ret = classify_symbols(file);
2607 if (ret)
2608 return ret;
2609
2610 ret = decode_instructions(file);
2611 if (ret)
2612 return ret;
2613
2614 add_ignores(file);
2615 add_uaccess_safe(file);
2616
2617 ret = add_ignore_alternatives(file);
2618 if (ret)
2619 return ret;
2620
2621 /*
2622 * Must be before read_unwind_hints() since that needs insn->noendbr.
2623 */
2624 ret = read_noendbr_hints(file);
2625 if (ret)
2626 return ret;
2627
2628 /*
2629 * Must be before add_jump_destinations(), which depends on 'func'
2630 * being set for alternatives, to enable proper sibling call detection.
2631 */
2632 if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) {
2633 ret = add_special_section_alts(file);
2634 if (ret)
2635 return ret;
2636 }
2637
2638 ret = add_jump_destinations(file);
2639 if (ret)
2640 return ret;
2641
2642 /*
2643 * Must be before add_call_destination(); it changes INSN_CALL to
2644 * INSN_JUMP.
2645 */
2646 ret = read_intra_function_calls(file);
2647 if (ret)
2648 return ret;
2649
2650 ret = add_call_destinations(file);
2651 if (ret)
2652 return ret;
2653
2654 /*
2655 * Must be after add_call_destinations() such that it can override
2656 * dead_end_function() marks.
2657 */
2658 ret = add_dead_ends(file);
2659 if (ret)
2660 return ret;
2661
2662 ret = add_jump_table_alts(file);
2663 if (ret)
2664 return ret;
2665
2666 ret = read_unwind_hints(file);
2667 if (ret)
2668 return ret;
2669
2670 ret = read_retpoline_hints(file);
2671 if (ret)
2672 return ret;
2673
2674 ret = read_instr_hints(file);
2675 if (ret)
2676 return ret;
2677
2678 ret = read_validate_unret_hints(file);
2679 if (ret)
2680 return ret;
2681
2682 return 0;
2683}
2684
2685static bool is_special_call(struct instruction *insn)
2686{
2687 if (insn->type == INSN_CALL) {
2688 struct symbol *dest = insn_call_dest(insn);
2689
2690 if (!dest)
2691 return false;
2692
2693 if (dest->fentry || dest->embedded_insn)
2694 return true;
2695 }
2696
2697 return false;
2698}
2699
2700static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2701{
2702 struct cfi_state *cfi = &state->cfi;
2703 int i;
2704
2705 if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2706 return true;
2707
2708 if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2709 return true;
2710
2711 if (cfi->stack_size != initial_func_cfi.cfa.offset)
2712 return true;
2713
2714 for (i = 0; i < CFI_NUM_REGS; i++) {
2715 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2716 cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2717 return true;
2718 }
2719
2720 return false;
2721}
2722
2723static bool check_reg_frame_pos(const struct cfi_reg *reg,
2724 int expected_offset)
2725{
2726 return reg->base == CFI_CFA &&
2727 reg->offset == expected_offset;
2728}
2729
2730static bool has_valid_stack_frame(struct insn_state *state)
2731{
2732 struct cfi_state *cfi = &state->cfi;
2733
2734 if (cfi->cfa.base == CFI_BP &&
2735 check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2736 check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2737 return true;
2738
2739 if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2740 return true;
2741
2742 return false;
2743}
2744
2745static int update_cfi_state_regs(struct instruction *insn,
2746 struct cfi_state *cfi,
2747 struct stack_op *op)
2748{
2749 struct cfi_reg *cfa = &cfi->cfa;
2750
2751 if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2752 return 0;
2753
2754 /* push */
2755 if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2756 cfa->offset += 8;
2757
2758 /* pop */
2759 if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2760 cfa->offset -= 8;
2761
2762 /* add immediate to sp */
2763 if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2764 op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2765 cfa->offset -= op->src.offset;
2766
2767 return 0;
2768}
2769
2770static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2771{
2772 if (arch_callee_saved_reg(reg) &&
2773 cfi->regs[reg].base == CFI_UNDEFINED) {
2774 cfi->regs[reg].base = base;
2775 cfi->regs[reg].offset = offset;
2776 }
2777}
2778
2779static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2780{
2781 cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2782 cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2783}
2784
2785/*
2786 * A note about DRAP stack alignment:
2787 *
2788 * GCC has the concept of a DRAP register, which is used to help keep track of
2789 * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
2790 * register. The typical DRAP pattern is:
2791 *
2792 * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
2793 * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
2794 * 41 ff 72 f8 pushq -0x8(%r10)
2795 * 55 push %rbp
2796 * 48 89 e5 mov %rsp,%rbp
2797 * (more pushes)
2798 * 41 52 push %r10
2799 * ...
2800 * 41 5a pop %r10
2801 * (more pops)
2802 * 5d pop %rbp
2803 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2804 * c3 retq
2805 *
2806 * There are some variations in the epilogues, like:
2807 *
2808 * 5b pop %rbx
2809 * 41 5a pop %r10
2810 * 41 5c pop %r12
2811 * 41 5d pop %r13
2812 * 41 5e pop %r14
2813 * c9 leaveq
2814 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2815 * c3 retq
2816 *
2817 * and:
2818 *
2819 * 4c 8b 55 e8 mov -0x18(%rbp),%r10
2820 * 48 8b 5d e0 mov -0x20(%rbp),%rbx
2821 * 4c 8b 65 f0 mov -0x10(%rbp),%r12
2822 * 4c 8b 6d f8 mov -0x8(%rbp),%r13
2823 * c9 leaveq
2824 * 49 8d 62 f8 lea -0x8(%r10),%rsp
2825 * c3 retq
2826 *
2827 * Sometimes r13 is used as the DRAP register, in which case it's saved and
2828 * restored beforehand:
2829 *
2830 * 41 55 push %r13
2831 * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
2832 * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
2833 * ...
2834 * 49 8d 65 f0 lea -0x10(%r13),%rsp
2835 * 41 5d pop %r13
2836 * c3 retq
2837 */
2838static int update_cfi_state(struct instruction *insn,
2839 struct instruction *next_insn,
2840 struct cfi_state *cfi, struct stack_op *op)
2841{
2842 struct cfi_reg *cfa = &cfi->cfa;
2843 struct cfi_reg *regs = cfi->regs;
2844
2845 /* ignore UNWIND_HINT_UNDEFINED regions */
2846 if (cfi->force_undefined)
2847 return 0;
2848
2849 /* stack operations don't make sense with an undefined CFA */
2850 if (cfa->base == CFI_UNDEFINED) {
2851 if (insn_func(insn)) {
2852 WARN_INSN(insn, "undefined stack state");
2853 return -1;
2854 }
2855 return 0;
2856 }
2857
2858 if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2859 cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2860 return update_cfi_state_regs(insn, cfi, op);
2861
2862 switch (op->dest.type) {
2863
2864 case OP_DEST_REG:
2865 switch (op->src.type) {
2866
2867 case OP_SRC_REG:
2868 if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2869 cfa->base == CFI_SP &&
2870 check_reg_frame_pos(®s[CFI_BP], -cfa->offset)) {
2871
2872 /* mov %rsp, %rbp */
2873 cfa->base = op->dest.reg;
2874 cfi->bp_scratch = false;
2875 }
2876
2877 else if (op->src.reg == CFI_SP &&
2878 op->dest.reg == CFI_BP && cfi->drap) {
2879
2880 /* drap: mov %rsp, %rbp */
2881 regs[CFI_BP].base = CFI_BP;
2882 regs[CFI_BP].offset = -cfi->stack_size;
2883 cfi->bp_scratch = false;
2884 }
2885
2886 else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2887
2888 /*
2889 * mov %rsp, %reg
2890 *
2891 * This is needed for the rare case where GCC
2892 * does:
2893 *
2894 * mov %rsp, %rax
2895 * ...
2896 * mov %rax, %rsp
2897 */
2898 cfi->vals[op->dest.reg].base = CFI_CFA;
2899 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2900 }
2901
2902 else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2903 (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2904
2905 /*
2906 * mov %rbp, %rsp
2907 *
2908 * Restore the original stack pointer (Clang).
2909 */
2910 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2911 }
2912
2913 else if (op->dest.reg == cfa->base) {
2914
2915 /* mov %reg, %rsp */
2916 if (cfa->base == CFI_SP &&
2917 cfi->vals[op->src.reg].base == CFI_CFA) {
2918
2919 /*
2920 * This is needed for the rare case
2921 * where GCC does something dumb like:
2922 *
2923 * lea 0x8(%rsp), %rcx
2924 * ...
2925 * mov %rcx, %rsp
2926 */
2927 cfa->offset = -cfi->vals[op->src.reg].offset;
2928 cfi->stack_size = cfa->offset;
2929
2930 } else if (cfa->base == CFI_SP &&
2931 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2932 cfi->vals[op->src.reg].offset == cfa->offset) {
2933
2934 /*
2935 * Stack swizzle:
2936 *
2937 * 1: mov %rsp, (%[tos])
2938 * 2: mov %[tos], %rsp
2939 * ...
2940 * 3: pop %rsp
2941 *
2942 * Where:
2943 *
2944 * 1 - places a pointer to the previous
2945 * stack at the Top-of-Stack of the
2946 * new stack.
2947 *
2948 * 2 - switches to the new stack.
2949 *
2950 * 3 - pops the Top-of-Stack to restore
2951 * the original stack.
2952 *
2953 * Note: we set base to SP_INDIRECT
2954 * here and preserve offset. Therefore
2955 * when the unwinder reaches ToS it
2956 * will dereference SP and then add the
2957 * offset to find the next frame, IOW:
2958 * (%rsp) + offset.
2959 */
2960 cfa->base = CFI_SP_INDIRECT;
2961
2962 } else {
2963 cfa->base = CFI_UNDEFINED;
2964 cfa->offset = 0;
2965 }
2966 }
2967
2968 else if (op->dest.reg == CFI_SP &&
2969 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2970 cfi->vals[op->src.reg].offset == cfa->offset) {
2971
2972 /*
2973 * The same stack swizzle case 2) as above. But
2974 * because we can't change cfa->base, case 3)
2975 * will become a regular POP. Pretend we're a
2976 * PUSH so things don't go unbalanced.
2977 */
2978 cfi->stack_size += 8;
2979 }
2980
2981
2982 break;
2983
2984 case OP_SRC_ADD:
2985 if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2986
2987 /* add imm, %rsp */
2988 cfi->stack_size -= op->src.offset;
2989 if (cfa->base == CFI_SP)
2990 cfa->offset -= op->src.offset;
2991 break;
2992 }
2993
2994 if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2995
2996 /* lea disp(%rbp), %rsp */
2997 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2998 break;
2999 }
3000
3001 if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
3002
3003 /* drap: lea disp(%rsp), %drap */
3004 cfi->drap_reg = op->dest.reg;
3005
3006 /*
3007 * lea disp(%rsp), %reg
3008 *
3009 * This is needed for the rare case where GCC
3010 * does something dumb like:
3011 *
3012 * lea 0x8(%rsp), %rcx
3013 * ...
3014 * mov %rcx, %rsp
3015 */
3016 cfi->vals[op->dest.reg].base = CFI_CFA;
3017 cfi->vals[op->dest.reg].offset = \
3018 -cfi->stack_size + op->src.offset;
3019
3020 break;
3021 }
3022
3023 if (cfi->drap && op->dest.reg == CFI_SP &&
3024 op->src.reg == cfi->drap_reg) {
3025
3026 /* drap: lea disp(%drap), %rsp */
3027 cfa->base = CFI_SP;
3028 cfa->offset = cfi->stack_size = -op->src.offset;
3029 cfi->drap_reg = CFI_UNDEFINED;
3030 cfi->drap = false;
3031 break;
3032 }
3033
3034 if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
3035 WARN_INSN(insn, "unsupported stack register modification");
3036 return -1;
3037 }
3038
3039 break;
3040
3041 case OP_SRC_AND:
3042 if (op->dest.reg != CFI_SP ||
3043 (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
3044 (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
3045 WARN_INSN(insn, "unsupported stack pointer realignment");
3046 return -1;
3047 }
3048
3049 if (cfi->drap_reg != CFI_UNDEFINED) {
3050 /* drap: and imm, %rsp */
3051 cfa->base = cfi->drap_reg;
3052 cfa->offset = cfi->stack_size = 0;
3053 cfi->drap = true;
3054 }
3055
3056 /*
3057 * Older versions of GCC (4.8ish) realign the stack
3058 * without DRAP, with a frame pointer.
3059 */
3060
3061 break;
3062
3063 case OP_SRC_POP:
3064 case OP_SRC_POPF:
3065 if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
3066
3067 /* pop %rsp; # restore from a stack swizzle */
3068 cfa->base = CFI_SP;
3069 break;
3070 }
3071
3072 if (!cfi->drap && op->dest.reg == cfa->base) {
3073
3074 /* pop %rbp */
3075 cfa->base = CFI_SP;
3076 }
3077
3078 if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
3079 op->dest.reg == cfi->drap_reg &&
3080 cfi->drap_offset == -cfi->stack_size) {
3081
3082 /* drap: pop %drap */
3083 cfa->base = cfi->drap_reg;
3084 cfa->offset = 0;
3085 cfi->drap_offset = -1;
3086
3087 } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
3088
3089 /* pop %reg */
3090 restore_reg(cfi, op->dest.reg);
3091 }
3092
3093 cfi->stack_size -= 8;
3094 if (cfa->base == CFI_SP)
3095 cfa->offset -= 8;
3096
3097 break;
3098
3099 case OP_SRC_REG_INDIRECT:
3100 if (!cfi->drap && op->dest.reg == cfa->base &&
3101 op->dest.reg == CFI_BP) {
3102
3103 /* mov disp(%rsp), %rbp */
3104 cfa->base = CFI_SP;
3105 cfa->offset = cfi->stack_size;
3106 }
3107
3108 if (cfi->drap && op->src.reg == CFI_BP &&
3109 op->src.offset == cfi->drap_offset) {
3110
3111 /* drap: mov disp(%rbp), %drap */
3112 cfa->base = cfi->drap_reg;
3113 cfa->offset = 0;
3114 cfi->drap_offset = -1;
3115 }
3116
3117 if (cfi->drap && op->src.reg == CFI_BP &&
3118 op->src.offset == regs[op->dest.reg].offset) {
3119
3120 /* drap: mov disp(%rbp), %reg */
3121 restore_reg(cfi, op->dest.reg);
3122
3123 } else if (op->src.reg == cfa->base &&
3124 op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
3125
3126 /* mov disp(%rbp), %reg */
3127 /* mov disp(%rsp), %reg */
3128 restore_reg(cfi, op->dest.reg);
3129
3130 } else if (op->src.reg == CFI_SP &&
3131 op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
3132
3133 /* mov disp(%rsp), %reg */
3134 restore_reg(cfi, op->dest.reg);
3135 }
3136
3137 break;
3138
3139 default:
3140 WARN_INSN(insn, "unknown stack-related instruction");
3141 return -1;
3142 }
3143
3144 break;
3145
3146 case OP_DEST_PUSH:
3147 case OP_DEST_PUSHF:
3148 cfi->stack_size += 8;
3149 if (cfa->base == CFI_SP)
3150 cfa->offset += 8;
3151
3152 if (op->src.type != OP_SRC_REG)
3153 break;
3154
3155 if (cfi->drap) {
3156 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3157
3158 /* drap: push %drap */
3159 cfa->base = CFI_BP_INDIRECT;
3160 cfa->offset = -cfi->stack_size;
3161
3162 /* save drap so we know when to restore it */
3163 cfi->drap_offset = -cfi->stack_size;
3164
3165 } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
3166
3167 /* drap: push %rbp */
3168 cfi->stack_size = 0;
3169
3170 } else {
3171
3172 /* drap: push %reg */
3173 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
3174 }
3175
3176 } else {
3177
3178 /* push %reg */
3179 save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
3180 }
3181
3182 /* detect when asm code uses rbp as a scratch register */
3183 if (opts.stackval && insn_func(insn) && op->src.reg == CFI_BP &&
3184 cfa->base != CFI_BP)
3185 cfi->bp_scratch = true;
3186 break;
3187
3188 case OP_DEST_REG_INDIRECT:
3189
3190 if (cfi->drap) {
3191 if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3192
3193 /* drap: mov %drap, disp(%rbp) */
3194 cfa->base = CFI_BP_INDIRECT;
3195 cfa->offset = op->dest.offset;
3196
3197 /* save drap offset so we know when to restore it */
3198 cfi->drap_offset = op->dest.offset;
3199 } else {
3200
3201 /* drap: mov reg, disp(%rbp) */
3202 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
3203 }
3204
3205 } else if (op->dest.reg == cfa->base) {
3206
3207 /* mov reg, disp(%rbp) */
3208 /* mov reg, disp(%rsp) */
3209 save_reg(cfi, op->src.reg, CFI_CFA,
3210 op->dest.offset - cfi->cfa.offset);
3211
3212 } else if (op->dest.reg == CFI_SP) {
3213
3214 /* mov reg, disp(%rsp) */
3215 save_reg(cfi, op->src.reg, CFI_CFA,
3216 op->dest.offset - cfi->stack_size);
3217
3218 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
3219
3220 /* mov %rsp, (%reg); # setup a stack swizzle. */
3221 cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
3222 cfi->vals[op->dest.reg].offset = cfa->offset;
3223 }
3224
3225 break;
3226
3227 case OP_DEST_MEM:
3228 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
3229 WARN_INSN(insn, "unknown stack-related memory operation");
3230 return -1;
3231 }
3232
3233 /* pop mem */
3234 cfi->stack_size -= 8;
3235 if (cfa->base == CFI_SP)
3236 cfa->offset -= 8;
3237
3238 break;
3239
3240 default:
3241 WARN_INSN(insn, "unknown stack-related instruction");
3242 return -1;
3243 }
3244
3245 return 0;
3246}
3247
3248/*
3249 * The stack layouts of alternatives instructions can sometimes diverge when
3250 * they have stack modifications. That's fine as long as the potential stack
3251 * layouts don't conflict at any given potential instruction boundary.
3252 *
3253 * Flatten the CFIs of the different alternative code streams (both original
3254 * and replacement) into a single shared CFI array which can be used to detect
3255 * conflicts and nicely feed a linear array of ORC entries to the unwinder.
3256 */
3257static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
3258{
3259 struct cfi_state **alt_cfi;
3260 int group_off;
3261
3262 if (!insn->alt_group)
3263 return 0;
3264
3265 if (!insn->cfi) {
3266 WARN("CFI missing");
3267 return -1;
3268 }
3269
3270 alt_cfi = insn->alt_group->cfi;
3271 group_off = insn->offset - insn->alt_group->first_insn->offset;
3272
3273 if (!alt_cfi[group_off]) {
3274 alt_cfi[group_off] = insn->cfi;
3275 } else {
3276 if (cficmp(alt_cfi[group_off], insn->cfi)) {
3277 struct alt_group *orig_group = insn->alt_group->orig_group ?: insn->alt_group;
3278 struct instruction *orig = orig_group->first_insn;
3279 char *where = offstr(insn->sec, insn->offset);
3280 WARN_INSN(orig, "stack layout conflict in alternatives: %s", where);
3281 free(where);
3282 return -1;
3283 }
3284 }
3285
3286 return 0;
3287}
3288
3289static int handle_insn_ops(struct instruction *insn,
3290 struct instruction *next_insn,
3291 struct insn_state *state)
3292{
3293 struct stack_op *op;
3294
3295 for (op = insn->stack_ops; op; op = op->next) {
3296
3297 if (update_cfi_state(insn, next_insn, &state->cfi, op))
3298 return 1;
3299
3300 if (!insn->alt_group)
3301 continue;
3302
3303 if (op->dest.type == OP_DEST_PUSHF) {
3304 if (!state->uaccess_stack) {
3305 state->uaccess_stack = 1;
3306 } else if (state->uaccess_stack >> 31) {
3307 WARN_INSN(insn, "PUSHF stack exhausted");
3308 return 1;
3309 }
3310 state->uaccess_stack <<= 1;
3311 state->uaccess_stack |= state->uaccess;
3312 }
3313
3314 if (op->src.type == OP_SRC_POPF) {
3315 if (state->uaccess_stack) {
3316 state->uaccess = state->uaccess_stack & 1;
3317 state->uaccess_stack >>= 1;
3318 if (state->uaccess_stack == 1)
3319 state->uaccess_stack = 0;
3320 }
3321 }
3322 }
3323
3324 return 0;
3325}
3326
3327static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
3328{
3329 struct cfi_state *cfi1 = insn->cfi;
3330 int i;
3331
3332 if (!cfi1) {
3333 WARN("CFI missing");
3334 return false;
3335 }
3336
3337 if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
3338
3339 WARN_INSN(insn, "stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
3340 cfi1->cfa.base, cfi1->cfa.offset,
3341 cfi2->cfa.base, cfi2->cfa.offset);
3342
3343 } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
3344 for (i = 0; i < CFI_NUM_REGS; i++) {
3345 if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
3346 sizeof(struct cfi_reg)))
3347 continue;
3348
3349 WARN_INSN(insn, "stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
3350 i, cfi1->regs[i].base, cfi1->regs[i].offset,
3351 i, cfi2->regs[i].base, cfi2->regs[i].offset);
3352 break;
3353 }
3354
3355 } else if (cfi1->type != cfi2->type) {
3356
3357 WARN_INSN(insn, "stack state mismatch: type1=%d type2=%d",
3358 cfi1->type, cfi2->type);
3359
3360 } else if (cfi1->drap != cfi2->drap ||
3361 (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
3362 (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
3363
3364 WARN_INSN(insn, "stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
3365 cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
3366 cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
3367
3368 } else
3369 return true;
3370
3371 return false;
3372}
3373
3374static inline bool func_uaccess_safe(struct symbol *func)
3375{
3376 if (func)
3377 return func->uaccess_safe;
3378
3379 return false;
3380}
3381
3382static inline const char *call_dest_name(struct instruction *insn)
3383{
3384 static char pvname[19];
3385 struct reloc *reloc;
3386 int idx;
3387
3388 if (insn_call_dest(insn))
3389 return insn_call_dest(insn)->name;
3390
3391 reloc = insn_reloc(NULL, insn);
3392 if (reloc && !strcmp(reloc->sym->name, "pv_ops")) {
3393 idx = (reloc_addend(reloc) / sizeof(void *));
3394 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
3395 return pvname;
3396 }
3397
3398 return "{dynamic}";
3399}
3400
3401static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3402{
3403 struct symbol *target;
3404 struct reloc *reloc;
3405 int idx;
3406
3407 reloc = insn_reloc(file, insn);
3408 if (!reloc || strcmp(reloc->sym->name, "pv_ops"))
3409 return false;
3410
3411 idx = (arch_dest_reloc_offset(reloc_addend(reloc)) / sizeof(void *));
3412
3413 if (file->pv_ops[idx].clean)
3414 return true;
3415
3416 file->pv_ops[idx].clean = true;
3417
3418 list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3419 if (!target->sec->noinstr) {
3420 WARN("pv_ops[%d]: %s", idx, target->name);
3421 file->pv_ops[idx].clean = false;
3422 }
3423 }
3424
3425 return file->pv_ops[idx].clean;
3426}
3427
3428static inline bool noinstr_call_dest(struct objtool_file *file,
3429 struct instruction *insn,
3430 struct symbol *func)
3431{
3432 /*
3433 * We can't deal with indirect function calls at present;
3434 * assume they're instrumented.
3435 */
3436 if (!func) {
3437 if (file->pv_ops)
3438 return pv_call_dest(file, insn);
3439
3440 return false;
3441 }
3442
3443 /*
3444 * If the symbol is from a noinstr section; we good.
3445 */
3446 if (func->sec->noinstr)
3447 return true;
3448
3449 /*
3450 * If the symbol is a static_call trampoline, we can't tell.
3451 */
3452 if (func->static_call_tramp)
3453 return true;
3454
3455 /*
3456 * The __ubsan_handle_*() calls are like WARN(), they only happen when
3457 * something 'BAD' happened. At the risk of taking the machine down,
3458 * let them proceed to get the message out.
3459 */
3460 if (!strncmp(func->name, "__ubsan_handle_", 15))
3461 return true;
3462
3463 return false;
3464}
3465
3466static int validate_call(struct objtool_file *file,
3467 struct instruction *insn,
3468 struct insn_state *state)
3469{
3470 if (state->noinstr && state->instr <= 0 &&
3471 !noinstr_call_dest(file, insn, insn_call_dest(insn))) {
3472 WARN_INSN(insn, "call to %s() leaves .noinstr.text section", call_dest_name(insn));
3473 return 1;
3474 }
3475
3476 if (state->uaccess && !func_uaccess_safe(insn_call_dest(insn))) {
3477 WARN_INSN(insn, "call to %s() with UACCESS enabled", call_dest_name(insn));
3478 return 1;
3479 }
3480
3481 if (state->df) {
3482 WARN_INSN(insn, "call to %s() with DF set", call_dest_name(insn));
3483 return 1;
3484 }
3485
3486 return 0;
3487}
3488
3489static int validate_sibling_call(struct objtool_file *file,
3490 struct instruction *insn,
3491 struct insn_state *state)
3492{
3493 if (insn_func(insn) && has_modified_stack_frame(insn, state)) {
3494 WARN_INSN(insn, "sibling call from callable instruction with modified stack frame");
3495 return 1;
3496 }
3497
3498 return validate_call(file, insn, state);
3499}
3500
3501static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3502{
3503 if (state->noinstr && state->instr > 0) {
3504 WARN_INSN(insn, "return with instrumentation enabled");
3505 return 1;
3506 }
3507
3508 if (state->uaccess && !func_uaccess_safe(func)) {
3509 WARN_INSN(insn, "return with UACCESS enabled");
3510 return 1;
3511 }
3512
3513 if (!state->uaccess && func_uaccess_safe(func)) {
3514 WARN_INSN(insn, "return with UACCESS disabled from a UACCESS-safe function");
3515 return 1;
3516 }
3517
3518 if (state->df) {
3519 WARN_INSN(insn, "return with DF set");
3520 return 1;
3521 }
3522
3523 if (func && has_modified_stack_frame(insn, state)) {
3524 WARN_INSN(insn, "return with modified stack frame");
3525 return 1;
3526 }
3527
3528 if (state->cfi.bp_scratch) {
3529 WARN_INSN(insn, "BP used as a scratch register");
3530 return 1;
3531 }
3532
3533 return 0;
3534}
3535
3536static struct instruction *next_insn_to_validate(struct objtool_file *file,
3537 struct instruction *insn)
3538{
3539 struct alt_group *alt_group = insn->alt_group;
3540
3541 /*
3542 * Simulate the fact that alternatives are patched in-place. When the
3543 * end of a replacement alt_group is reached, redirect objtool flow to
3544 * the end of the original alt_group.
3545 *
3546 * insn->alts->insn -> alt_group->first_insn
3547 * ...
3548 * alt_group->last_insn
3549 * [alt_group->nop] -> next(orig_group->last_insn)
3550 */
3551 if (alt_group) {
3552 if (alt_group->nop) {
3553 /* ->nop implies ->orig_group */
3554 if (insn == alt_group->last_insn)
3555 return alt_group->nop;
3556 if (insn == alt_group->nop)
3557 goto next_orig;
3558 }
3559 if (insn == alt_group->last_insn && alt_group->orig_group)
3560 goto next_orig;
3561 }
3562
3563 return next_insn_same_sec(file, insn);
3564
3565next_orig:
3566 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3567}
3568
3569/*
3570 * Follow the branch starting at the given instruction, and recursively follow
3571 * any other branches (jumps). Meanwhile, track the frame pointer state at
3572 * each instruction and validate all the rules described in
3573 * tools/objtool/Documentation/objtool.txt.
3574 */
3575static int validate_branch(struct objtool_file *file, struct symbol *func,
3576 struct instruction *insn, struct insn_state state)
3577{
3578 struct alternative *alt;
3579 struct instruction *next_insn, *prev_insn = NULL;
3580 struct section *sec;
3581 u8 visited;
3582 int ret;
3583
3584 sec = insn->sec;
3585
3586 while (1) {
3587 next_insn = next_insn_to_validate(file, insn);
3588
3589 if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {
3590 /* Ignore KCFI type preambles, which always fall through */
3591 if (!strncmp(func->name, "__cfi_", 6) ||
3592 !strncmp(func->name, "__pfx_", 6))
3593 return 0;
3594
3595 WARN("%s() falls through to next function %s()",
3596 func->name, insn_func(insn)->name);
3597 return 1;
3598 }
3599
3600 if (func && insn->ignore) {
3601 WARN_INSN(insn, "BUG: why am I validating an ignored function?");
3602 return 1;
3603 }
3604
3605 visited = VISITED_BRANCH << state.uaccess;
3606 if (insn->visited & VISITED_BRANCH_MASK) {
3607 if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3608 return 1;
3609
3610 if (insn->visited & visited)
3611 return 0;
3612 } else {
3613 nr_insns_visited++;
3614 }
3615
3616 if (state.noinstr)
3617 state.instr += insn->instr;
3618
3619 if (insn->hint) {
3620 if (insn->restore) {
3621 struct instruction *save_insn, *i;
3622
3623 i = insn;
3624 save_insn = NULL;
3625
3626 sym_for_each_insn_continue_reverse(file, func, i) {
3627 if (i->save) {
3628 save_insn = i;
3629 break;
3630 }
3631 }
3632
3633 if (!save_insn) {
3634 WARN_INSN(insn, "no corresponding CFI save for CFI restore");
3635 return 1;
3636 }
3637
3638 if (!save_insn->visited) {
3639 /*
3640 * If the restore hint insn is at the
3641 * beginning of a basic block and was
3642 * branched to from elsewhere, and the
3643 * save insn hasn't been visited yet,
3644 * defer following this branch for now.
3645 * It will be seen later via the
3646 * straight-line path.
3647 */
3648 if (!prev_insn)
3649 return 0;
3650
3651 WARN_INSN(insn, "objtool isn't smart enough to handle this CFI save/restore combo");
3652 return 1;
3653 }
3654
3655 insn->cfi = save_insn->cfi;
3656 nr_cfi_reused++;
3657 }
3658
3659 state.cfi = *insn->cfi;
3660 } else {
3661 /* XXX track if we actually changed state.cfi */
3662
3663 if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3664 insn->cfi = prev_insn->cfi;
3665 nr_cfi_reused++;
3666 } else {
3667 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3668 }
3669 }
3670
3671 insn->visited |= visited;
3672
3673 if (propagate_alt_cfi(file, insn))
3674 return 1;
3675
3676 if (!insn->ignore_alts && insn->alts) {
3677 bool skip_orig = false;
3678
3679 for (alt = insn->alts; alt; alt = alt->next) {
3680 if (alt->skip_orig)
3681 skip_orig = true;
3682
3683 ret = validate_branch(file, func, alt->insn, state);
3684 if (ret) {
3685 BT_INSN(insn, "(alt)");
3686 return ret;
3687 }
3688 }
3689
3690 if (skip_orig)
3691 return 0;
3692 }
3693
3694 if (handle_insn_ops(insn, next_insn, &state))
3695 return 1;
3696
3697 switch (insn->type) {
3698
3699 case INSN_RETURN:
3700 return validate_return(func, insn, &state);
3701
3702 case INSN_CALL:
3703 case INSN_CALL_DYNAMIC:
3704 ret = validate_call(file, insn, &state);
3705 if (ret)
3706 return ret;
3707
3708 if (opts.stackval && func && !is_special_call(insn) &&
3709 !has_valid_stack_frame(&state)) {
3710 WARN_INSN(insn, "call without frame pointer save/setup");
3711 return 1;
3712 }
3713
3714 if (insn->dead_end)
3715 return 0;
3716
3717 break;
3718
3719 case INSN_JUMP_CONDITIONAL:
3720 case INSN_JUMP_UNCONDITIONAL:
3721 if (is_sibling_call(insn)) {
3722 ret = validate_sibling_call(file, insn, &state);
3723 if (ret)
3724 return ret;
3725
3726 } else if (insn->jump_dest) {
3727 ret = validate_branch(file, func,
3728 insn->jump_dest, state);
3729 if (ret) {
3730 BT_INSN(insn, "(branch)");
3731 return ret;
3732 }
3733 }
3734
3735 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3736 return 0;
3737
3738 break;
3739
3740 case INSN_JUMP_DYNAMIC:
3741 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3742 if (is_sibling_call(insn)) {
3743 ret = validate_sibling_call(file, insn, &state);
3744 if (ret)
3745 return ret;
3746 }
3747
3748 if (insn->type == INSN_JUMP_DYNAMIC)
3749 return 0;
3750
3751 break;
3752
3753 case INSN_CONTEXT_SWITCH:
3754 if (func && (!next_insn || !next_insn->hint)) {
3755 WARN_INSN(insn, "unsupported instruction in callable function");
3756 return 1;
3757 }
3758 return 0;
3759
3760 case INSN_STAC:
3761 if (state.uaccess) {
3762 WARN_INSN(insn, "recursive UACCESS enable");
3763 return 1;
3764 }
3765
3766 state.uaccess = true;
3767 break;
3768
3769 case INSN_CLAC:
3770 if (!state.uaccess && func) {
3771 WARN_INSN(insn, "redundant UACCESS disable");
3772 return 1;
3773 }
3774
3775 if (func_uaccess_safe(func) && !state.uaccess_stack) {
3776 WARN_INSN(insn, "UACCESS-safe disables UACCESS");
3777 return 1;
3778 }
3779
3780 state.uaccess = false;
3781 break;
3782
3783 case INSN_STD:
3784 if (state.df) {
3785 WARN_INSN(insn, "recursive STD");
3786 return 1;
3787 }
3788
3789 state.df = true;
3790 break;
3791
3792 case INSN_CLD:
3793 if (!state.df && func) {
3794 WARN_INSN(insn, "redundant CLD");
3795 return 1;
3796 }
3797
3798 state.df = false;
3799 break;
3800
3801 default:
3802 break;
3803 }
3804
3805 if (insn->dead_end)
3806 return 0;
3807
3808 if (!next_insn) {
3809 if (state.cfi.cfa.base == CFI_UNDEFINED)
3810 return 0;
3811 WARN("%s: unexpected end of section", sec->name);
3812 return 1;
3813 }
3814
3815 prev_insn = insn;
3816 insn = next_insn;
3817 }
3818
3819 return 0;
3820}
3821
3822static int validate_unwind_hint(struct objtool_file *file,
3823 struct instruction *insn,
3824 struct insn_state *state)
3825{
3826 if (insn->hint && !insn->visited && !insn->ignore) {
3827 int ret = validate_branch(file, insn_func(insn), insn, *state);
3828 if (ret)
3829 BT_INSN(insn, "<=== (hint)");
3830 return ret;
3831 }
3832
3833 return 0;
3834}
3835
3836static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3837{
3838 struct instruction *insn;
3839 struct insn_state state;
3840 int warnings = 0;
3841
3842 if (!file->hints)
3843 return 0;
3844
3845 init_insn_state(file, &state, sec);
3846
3847 if (sec) {
3848 sec_for_each_insn(file, sec, insn)
3849 warnings += validate_unwind_hint(file, insn, &state);
3850 } else {
3851 for_each_insn(file, insn)
3852 warnings += validate_unwind_hint(file, insn, &state);
3853 }
3854
3855 return warnings;
3856}
3857
3858/*
3859 * Validate rethunk entry constraint: must untrain RET before the first RET.
3860 *
3861 * Follow every branch (intra-function) and ensure VALIDATE_UNRET_END comes
3862 * before an actual RET instruction.
3863 */
3864static int validate_unret(struct objtool_file *file, struct instruction *insn)
3865{
3866 struct instruction *next, *dest;
3867 int ret;
3868
3869 for (;;) {
3870 next = next_insn_to_validate(file, insn);
3871
3872 if (insn->visited & VISITED_UNRET)
3873 return 0;
3874
3875 insn->visited |= VISITED_UNRET;
3876
3877 if (!insn->ignore_alts && insn->alts) {
3878 struct alternative *alt;
3879 bool skip_orig = false;
3880
3881 for (alt = insn->alts; alt; alt = alt->next) {
3882 if (alt->skip_orig)
3883 skip_orig = true;
3884
3885 ret = validate_unret(file, alt->insn);
3886 if (ret) {
3887 BT_INSN(insn, "(alt)");
3888 return ret;
3889 }
3890 }
3891
3892 if (skip_orig)
3893 return 0;
3894 }
3895
3896 switch (insn->type) {
3897
3898 case INSN_CALL_DYNAMIC:
3899 case INSN_JUMP_DYNAMIC:
3900 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3901 WARN_INSN(insn, "early indirect call");
3902 return 1;
3903
3904 case INSN_JUMP_UNCONDITIONAL:
3905 case INSN_JUMP_CONDITIONAL:
3906 if (!is_sibling_call(insn)) {
3907 if (!insn->jump_dest) {
3908 WARN_INSN(insn, "unresolved jump target after linking?!?");
3909 return -1;
3910 }
3911 ret = validate_unret(file, insn->jump_dest);
3912 if (ret) {
3913 BT_INSN(insn, "(branch%s)",
3914 insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : "");
3915 return ret;
3916 }
3917
3918 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3919 return 0;
3920
3921 break;
3922 }
3923
3924 /* fallthrough */
3925 case INSN_CALL:
3926 dest = find_insn(file, insn_call_dest(insn)->sec,
3927 insn_call_dest(insn)->offset);
3928 if (!dest) {
3929 WARN("Unresolved function after linking!?: %s",
3930 insn_call_dest(insn)->name);
3931 return -1;
3932 }
3933
3934 ret = validate_unret(file, dest);
3935 if (ret) {
3936 BT_INSN(insn, "(call)");
3937 return ret;
3938 }
3939 /*
3940 * If a call returns without error, it must have seen UNTRAIN_RET.
3941 * Therefore any non-error return is a success.
3942 */
3943 return 0;
3944
3945 case INSN_RETURN:
3946 WARN_INSN(insn, "RET before UNTRAIN");
3947 return 1;
3948
3949 case INSN_NOP:
3950 if (insn->retpoline_safe)
3951 return 0;
3952 break;
3953
3954 default:
3955 break;
3956 }
3957
3958 if (!next) {
3959 WARN_INSN(insn, "teh end!");
3960 return -1;
3961 }
3962 insn = next;
3963 }
3964
3965 return 0;
3966}
3967
3968/*
3969 * Validate that all branches starting at VALIDATE_UNRET_BEGIN encounter
3970 * VALIDATE_UNRET_END before RET.
3971 */
3972static int validate_unrets(struct objtool_file *file)
3973{
3974 struct instruction *insn;
3975 int ret, warnings = 0;
3976
3977 for_each_insn(file, insn) {
3978 if (!insn->unret)
3979 continue;
3980
3981 ret = validate_unret(file, insn);
3982 if (ret < 0) {
3983 WARN_INSN(insn, "Failed UNRET validation");
3984 return ret;
3985 }
3986 warnings += ret;
3987 }
3988
3989 return warnings;
3990}
3991
3992static int validate_retpoline(struct objtool_file *file)
3993{
3994 struct instruction *insn;
3995 int warnings = 0;
3996
3997 for_each_insn(file, insn) {
3998 if (insn->type != INSN_JUMP_DYNAMIC &&
3999 insn->type != INSN_CALL_DYNAMIC &&
4000 insn->type != INSN_RETURN)
4001 continue;
4002
4003 if (insn->retpoline_safe)
4004 continue;
4005
4006 if (insn->sec->init)
4007 continue;
4008
4009 if (insn->type == INSN_RETURN) {
4010 if (opts.rethunk) {
4011 WARN_INSN(insn, "'naked' return found in MITIGATION_RETHUNK build");
4012 } else
4013 continue;
4014 } else {
4015 WARN_INSN(insn, "indirect %s found in MITIGATION_RETPOLINE build",
4016 insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
4017 }
4018
4019 warnings++;
4020 }
4021
4022 return warnings;
4023}
4024
4025static bool is_kasan_insn(struct instruction *insn)
4026{
4027 return (insn->type == INSN_CALL &&
4028 !strcmp(insn_call_dest(insn)->name, "__asan_handle_no_return"));
4029}
4030
4031static bool is_ubsan_insn(struct instruction *insn)
4032{
4033 return (insn->type == INSN_CALL &&
4034 !strcmp(insn_call_dest(insn)->name,
4035 "__ubsan_handle_builtin_unreachable"));
4036}
4037
4038static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
4039{
4040 int i;
4041 struct instruction *prev_insn;
4042
4043 if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
4044 return true;
4045
4046 /*
4047 * Ignore alternative replacement instructions. This can happen
4048 * when a whitelisted function uses one of the ALTERNATIVE macros.
4049 */
4050 if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
4051 !strcmp(insn->sec->name, ".altinstr_aux"))
4052 return true;
4053
4054 /*
4055 * Whole archive runs might encounter dead code from weak symbols.
4056 * This is where the linker will have dropped the weak symbol in
4057 * favour of a regular symbol, but leaves the code in place.
4058 *
4059 * In this case we'll find a piece of code (whole function) that is not
4060 * covered by a !section symbol. Ignore them.
4061 */
4062 if (opts.link && !insn_func(insn)) {
4063 int size = find_symbol_hole_containing(insn->sec, insn->offset);
4064 unsigned long end = insn->offset + size;
4065
4066 if (!size) /* not a hole */
4067 return false;
4068
4069 if (size < 0) /* hole until the end */
4070 return true;
4071
4072 sec_for_each_insn_continue(file, insn) {
4073 /*
4074 * If we reach a visited instruction at or before the
4075 * end of the hole, ignore the unreachable.
4076 */
4077 if (insn->visited)
4078 return true;
4079
4080 if (insn->offset >= end)
4081 break;
4082
4083 /*
4084 * If this hole jumps to a .cold function, mark it ignore too.
4085 */
4086 if (insn->jump_dest && insn_func(insn->jump_dest) &&
4087 strstr(insn_func(insn->jump_dest)->name, ".cold")) {
4088 struct instruction *dest = insn->jump_dest;
4089 func_for_each_insn(file, insn_func(dest), dest)
4090 dest->ignore = true;
4091 }
4092 }
4093
4094 return false;
4095 }
4096
4097 if (!insn_func(insn))
4098 return false;
4099
4100 if (insn_func(insn)->static_call_tramp)
4101 return true;
4102
4103 /*
4104 * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
4105 * __builtin_unreachable(). The BUG() macro has an unreachable() after
4106 * the UD2, which causes GCC's undefined trap logic to emit another UD2
4107 * (or occasionally a JMP to UD2).
4108 *
4109 * It may also insert a UD2 after calling a __noreturn function.
4110 */
4111 prev_insn = prev_insn_same_sec(file, insn);
4112 if (prev_insn->dead_end &&
4113 (insn->type == INSN_BUG ||
4114 (insn->type == INSN_JUMP_UNCONDITIONAL &&
4115 insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
4116 return true;
4117
4118 /*
4119 * Check if this (or a subsequent) instruction is related to
4120 * CONFIG_UBSAN or CONFIG_KASAN.
4121 *
4122 * End the search at 5 instructions to avoid going into the weeds.
4123 */
4124 for (i = 0; i < 5; i++) {
4125
4126 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
4127 return true;
4128
4129 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
4130 if (insn->jump_dest &&
4131 insn_func(insn->jump_dest) == insn_func(insn)) {
4132 insn = insn->jump_dest;
4133 continue;
4134 }
4135
4136 break;
4137 }
4138
4139 if (insn->offset + insn->len >= insn_func(insn)->offset + insn_func(insn)->len)
4140 break;
4141
4142 insn = next_insn_same_sec(file, insn);
4143 }
4144
4145 return false;
4146}
4147
4148static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
4149{
4150 struct instruction *insn, *prev;
4151 struct cfi_state *cfi;
4152
4153 insn = find_insn(file, func->sec, func->offset);
4154 if (!insn)
4155 return -1;
4156
4157 for (prev = prev_insn_same_sec(file, insn);
4158 prev;
4159 prev = prev_insn_same_sec(file, prev)) {
4160 u64 offset;
4161
4162 if (prev->type != INSN_NOP)
4163 return -1;
4164
4165 offset = func->offset - prev->offset;
4166
4167 if (offset > opts.prefix)
4168 return -1;
4169
4170 if (offset < opts.prefix)
4171 continue;
4172
4173 elf_create_prefix_symbol(file->elf, func, opts.prefix);
4174 break;
4175 }
4176
4177 if (!prev)
4178 return -1;
4179
4180 if (!insn->cfi) {
4181 /*
4182 * This can happen if stack validation isn't enabled or the
4183 * function is annotated with STACK_FRAME_NON_STANDARD.
4184 */
4185 return 0;
4186 }
4187
4188 /* Propagate insn->cfi to the prefix code */
4189 cfi = cfi_hash_find_or_add(insn->cfi);
4190 for (; prev != insn; prev = next_insn_same_sec(file, prev))
4191 prev->cfi = cfi;
4192
4193 return 0;
4194}
4195
4196static int add_prefix_symbols(struct objtool_file *file)
4197{
4198 struct section *sec;
4199 struct symbol *func;
4200
4201 for_each_sec(file, sec) {
4202 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4203 continue;
4204
4205 sec_for_each_sym(sec, func) {
4206 if (func->type != STT_FUNC)
4207 continue;
4208
4209 add_prefix_symbol(file, func);
4210 }
4211 }
4212
4213 return 0;
4214}
4215
4216static int validate_symbol(struct objtool_file *file, struct section *sec,
4217 struct symbol *sym, struct insn_state *state)
4218{
4219 struct instruction *insn;
4220 int ret;
4221
4222 if (!sym->len) {
4223 WARN("%s() is missing an ELF size annotation", sym->name);
4224 return 1;
4225 }
4226
4227 if (sym->pfunc != sym || sym->alias != sym)
4228 return 0;
4229
4230 insn = find_insn(file, sec, sym->offset);
4231 if (!insn || insn->ignore || insn->visited)
4232 return 0;
4233
4234 state->uaccess = sym->uaccess_safe;
4235
4236 ret = validate_branch(file, insn_func(insn), insn, *state);
4237 if (ret)
4238 BT_INSN(insn, "<=== (sym)");
4239 return ret;
4240}
4241
4242static int validate_section(struct objtool_file *file, struct section *sec)
4243{
4244 struct insn_state state;
4245 struct symbol *func;
4246 int warnings = 0;
4247
4248 sec_for_each_sym(sec, func) {
4249 if (func->type != STT_FUNC)
4250 continue;
4251
4252 init_insn_state(file, &state, sec);
4253 set_func_state(&state.cfi);
4254
4255 warnings += validate_symbol(file, sec, func, &state);
4256 }
4257
4258 return warnings;
4259}
4260
4261static int validate_noinstr_sections(struct objtool_file *file)
4262{
4263 struct section *sec;
4264 int warnings = 0;
4265
4266 sec = find_section_by_name(file->elf, ".noinstr.text");
4267 if (sec) {
4268 warnings += validate_section(file, sec);
4269 warnings += validate_unwind_hints(file, sec);
4270 }
4271
4272 sec = find_section_by_name(file->elf, ".entry.text");
4273 if (sec) {
4274 warnings += validate_section(file, sec);
4275 warnings += validate_unwind_hints(file, sec);
4276 }
4277
4278 sec = find_section_by_name(file->elf, ".cpuidle.text");
4279 if (sec) {
4280 warnings += validate_section(file, sec);
4281 warnings += validate_unwind_hints(file, sec);
4282 }
4283
4284 return warnings;
4285}
4286
4287static int validate_functions(struct objtool_file *file)
4288{
4289 struct section *sec;
4290 int warnings = 0;
4291
4292 for_each_sec(file, sec) {
4293 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4294 continue;
4295
4296 warnings += validate_section(file, sec);
4297 }
4298
4299 return warnings;
4300}
4301
4302static void mark_endbr_used(struct instruction *insn)
4303{
4304 if (!list_empty(&insn->call_node))
4305 list_del_init(&insn->call_node);
4306}
4307
4308static bool noendbr_range(struct objtool_file *file, struct instruction *insn)
4309{
4310 struct symbol *sym = find_symbol_containing(insn->sec, insn->offset-1);
4311 struct instruction *first;
4312
4313 if (!sym)
4314 return false;
4315
4316 first = find_insn(file, sym->sec, sym->offset);
4317 if (!first)
4318 return false;
4319
4320 if (first->type != INSN_ENDBR && !first->noendbr)
4321 return false;
4322
4323 return insn->offset == sym->offset + sym->len;
4324}
4325
4326static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
4327{
4328 struct instruction *dest;
4329 struct reloc *reloc;
4330 unsigned long off;
4331 int warnings = 0;
4332
4333 /*
4334 * Looking for function pointer load relocations. Ignore
4335 * direct/indirect branches:
4336 */
4337 switch (insn->type) {
4338 case INSN_CALL:
4339 case INSN_CALL_DYNAMIC:
4340 case INSN_JUMP_CONDITIONAL:
4341 case INSN_JUMP_UNCONDITIONAL:
4342 case INSN_JUMP_DYNAMIC:
4343 case INSN_JUMP_DYNAMIC_CONDITIONAL:
4344 case INSN_RETURN:
4345 case INSN_NOP:
4346 return 0;
4347 default:
4348 break;
4349 }
4350
4351 for (reloc = insn_reloc(file, insn);
4352 reloc;
4353 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
4354 reloc_offset(reloc) + 1,
4355 (insn->offset + insn->len) - (reloc_offset(reloc) + 1))) {
4356
4357 /*
4358 * static_call_update() references the trampoline, which
4359 * doesn't have (or need) ENDBR. Skip warning in that case.
4360 */
4361 if (reloc->sym->static_call_tramp)
4362 continue;
4363
4364 off = reloc->sym->offset;
4365 if (reloc_type(reloc) == R_X86_64_PC32 ||
4366 reloc_type(reloc) == R_X86_64_PLT32)
4367 off += arch_dest_reloc_offset(reloc_addend(reloc));
4368 else
4369 off += reloc_addend(reloc);
4370
4371 dest = find_insn(file, reloc->sym->sec, off);
4372 if (!dest)
4373 continue;
4374
4375 if (dest->type == INSN_ENDBR) {
4376 mark_endbr_used(dest);
4377 continue;
4378 }
4379
4380 if (insn_func(dest) && insn_func(insn) &&
4381 insn_func(dest)->pfunc == insn_func(insn)->pfunc) {
4382 /*
4383 * Anything from->to self is either _THIS_IP_ or
4384 * IRET-to-self.
4385 *
4386 * There is no sane way to annotate _THIS_IP_ since the
4387 * compiler treats the relocation as a constant and is
4388 * happy to fold in offsets, skewing any annotation we
4389 * do, leading to vast amounts of false-positives.
4390 *
4391 * There's also compiler generated _THIS_IP_ through
4392 * KCOV and such which we have no hope of annotating.
4393 *
4394 * As such, blanket accept self-references without
4395 * issue.
4396 */
4397 continue;
4398 }
4399
4400 /*
4401 * Accept anything ANNOTATE_NOENDBR.
4402 */
4403 if (dest->noendbr)
4404 continue;
4405
4406 /*
4407 * Accept if this is the instruction after a symbol
4408 * that is (no)endbr -- typical code-range usage.
4409 */
4410 if (noendbr_range(file, dest))
4411 continue;
4412
4413 WARN_INSN(insn, "relocation to !ENDBR: %s", offstr(dest->sec, dest->offset));
4414
4415 warnings++;
4416 }
4417
4418 return warnings;
4419}
4420
4421static int validate_ibt_data_reloc(struct objtool_file *file,
4422 struct reloc *reloc)
4423{
4424 struct instruction *dest;
4425
4426 dest = find_insn(file, reloc->sym->sec,
4427 reloc->sym->offset + reloc_addend(reloc));
4428 if (!dest)
4429 return 0;
4430
4431 if (dest->type == INSN_ENDBR) {
4432 mark_endbr_used(dest);
4433 return 0;
4434 }
4435
4436 if (dest->noendbr)
4437 return 0;
4438
4439 WARN_FUNC("data relocation to !ENDBR: %s",
4440 reloc->sec->base, reloc_offset(reloc),
4441 offstr(dest->sec, dest->offset));
4442
4443 return 1;
4444}
4445
4446/*
4447 * Validate IBT rules and remove used ENDBR instructions from the seal list.
4448 * Unused ENDBR instructions will be annotated for sealing (i.e., replaced with
4449 * NOPs) later, in create_ibt_endbr_seal_sections().
4450 */
4451static int validate_ibt(struct objtool_file *file)
4452{
4453 struct section *sec;
4454 struct reloc *reloc;
4455 struct instruction *insn;
4456 int warnings = 0;
4457
4458 for_each_insn(file, insn)
4459 warnings += validate_ibt_insn(file, insn);
4460
4461 for_each_sec(file, sec) {
4462
4463 /* Already done by validate_ibt_insn() */
4464 if (sec->sh.sh_flags & SHF_EXECINSTR)
4465 continue;
4466
4467 if (!sec->rsec)
4468 continue;
4469
4470 /*
4471 * These sections can reference text addresses, but not with
4472 * the intent to indirect branch to them.
4473 */
4474 if ((!strncmp(sec->name, ".discard", 8) &&
4475 strcmp(sec->name, ".discard.ibt_endbr_noseal")) ||
4476 !strncmp(sec->name, ".debug", 6) ||
4477 !strcmp(sec->name, ".altinstructions") ||
4478 !strcmp(sec->name, ".ibt_endbr_seal") ||
4479 !strcmp(sec->name, ".orc_unwind_ip") ||
4480 !strcmp(sec->name, ".parainstructions") ||
4481 !strcmp(sec->name, ".retpoline_sites") ||
4482 !strcmp(sec->name, ".smp_locks") ||
4483 !strcmp(sec->name, ".static_call_sites") ||
4484 !strcmp(sec->name, "_error_injection_whitelist") ||
4485 !strcmp(sec->name, "_kprobe_blacklist") ||
4486 !strcmp(sec->name, "__bug_table") ||
4487 !strcmp(sec->name, "__ex_table") ||
4488 !strcmp(sec->name, "__jump_table") ||
4489 !strcmp(sec->name, "__mcount_loc") ||
4490 !strcmp(sec->name, ".kcfi_traps") ||
4491 strstr(sec->name, "__patchable_function_entries"))
4492 continue;
4493
4494 for_each_reloc(sec->rsec, reloc)
4495 warnings += validate_ibt_data_reloc(file, reloc);
4496 }
4497
4498 return warnings;
4499}
4500
4501static int validate_sls(struct objtool_file *file)
4502{
4503 struct instruction *insn, *next_insn;
4504 int warnings = 0;
4505
4506 for_each_insn(file, insn) {
4507 next_insn = next_insn_same_sec(file, insn);
4508
4509 if (insn->retpoline_safe)
4510 continue;
4511
4512 switch (insn->type) {
4513 case INSN_RETURN:
4514 if (!next_insn || next_insn->type != INSN_TRAP) {
4515 WARN_INSN(insn, "missing int3 after ret");
4516 warnings++;
4517 }
4518
4519 break;
4520 case INSN_JUMP_DYNAMIC:
4521 if (!next_insn || next_insn->type != INSN_TRAP) {
4522 WARN_INSN(insn, "missing int3 after indirect jump");
4523 warnings++;
4524 }
4525 break;
4526 default:
4527 break;
4528 }
4529 }
4530
4531 return warnings;
4532}
4533
4534static bool ignore_noreturn_call(struct instruction *insn)
4535{
4536 struct symbol *call_dest = insn_call_dest(insn);
4537
4538 /*
4539 * FIXME: hack, we need a real noreturn solution
4540 *
4541 * Problem is, exc_double_fault() may or may not return, depending on
4542 * whether CONFIG_X86_ESPFIX64 is set. But objtool has no visibility
4543 * to the kernel config.
4544 *
4545 * Other potential ways to fix it:
4546 *
4547 * - have compiler communicate __noreturn functions somehow
4548 * - remove CONFIG_X86_ESPFIX64
4549 * - read the .config file
4550 * - add a cmdline option
4551 * - create a generic objtool annotation format (vs a bunch of custom
4552 * formats) and annotate it
4553 */
4554 if (!strcmp(call_dest->name, "exc_double_fault")) {
4555 /* prevent further unreachable warnings for the caller */
4556 insn->sym->warned = 1;
4557 return true;
4558 }
4559
4560 return false;
4561}
4562
4563static int validate_reachable_instructions(struct objtool_file *file)
4564{
4565 struct instruction *insn, *prev_insn;
4566 struct symbol *call_dest;
4567 int warnings = 0;
4568
4569 if (file->ignore_unreachables)
4570 return 0;
4571
4572 for_each_insn(file, insn) {
4573 if (insn->visited || ignore_unreachable_insn(file, insn))
4574 continue;
4575
4576 prev_insn = prev_insn_same_sec(file, insn);
4577 if (prev_insn && prev_insn->dead_end) {
4578 call_dest = insn_call_dest(prev_insn);
4579 if (call_dest && !ignore_noreturn_call(prev_insn)) {
4580 WARN_INSN(insn, "%s() is missing a __noreturn annotation",
4581 call_dest->name);
4582 warnings++;
4583 continue;
4584 }
4585 }
4586
4587 WARN_INSN(insn, "unreachable instruction");
4588 warnings++;
4589 }
4590
4591 return warnings;
4592}
4593
4594/* 'funcs' is a space-separated list of function names */
4595static int disas_funcs(const char *funcs)
4596{
4597 const char *objdump_str, *cross_compile;
4598 int size, ret;
4599 char *cmd;
4600
4601 cross_compile = getenv("CROSS_COMPILE");
4602
4603 objdump_str = "%sobjdump -wdr %s | gawk -M -v _funcs='%s' '"
4604 "BEGIN { split(_funcs, funcs); }"
4605 "/^$/ { func_match = 0; }"
4606 "/<.*>:/ { "
4607 "f = gensub(/.*<(.*)>:/, \"\\\\1\", 1);"
4608 "for (i in funcs) {"
4609 "if (funcs[i] == f) {"
4610 "func_match = 1;"
4611 "base = strtonum(\"0x\" $1);"
4612 "break;"
4613 "}"
4614 "}"
4615 "}"
4616 "{"
4617 "if (func_match) {"
4618 "addr = strtonum(\"0x\" $1);"
4619 "printf(\"%%04x \", addr - base);"
4620 "print;"
4621 "}"
4622 "}' 1>&2";
4623
4624 /* fake snprintf() to calculate the size */
4625 size = snprintf(NULL, 0, objdump_str, cross_compile, objname, funcs) + 1;
4626 if (size <= 0) {
4627 WARN("objdump string size calculation failed");
4628 return -1;
4629 }
4630
4631 cmd = malloc(size);
4632
4633 /* real snprintf() */
4634 snprintf(cmd, size, objdump_str, cross_compile, objname, funcs);
4635 ret = system(cmd);
4636 if (ret) {
4637 WARN("disassembly failed: %d", ret);
4638 return -1;
4639 }
4640
4641 return 0;
4642}
4643
4644static int disas_warned_funcs(struct objtool_file *file)
4645{
4646 struct symbol *sym;
4647 char *funcs = NULL, *tmp;
4648
4649 for_each_sym(file, sym) {
4650 if (sym->warned) {
4651 if (!funcs) {
4652 funcs = malloc(strlen(sym->name) + 1);
4653 strcpy(funcs, sym->name);
4654 } else {
4655 tmp = malloc(strlen(funcs) + strlen(sym->name) + 2);
4656 sprintf(tmp, "%s %s", funcs, sym->name);
4657 free(funcs);
4658 funcs = tmp;
4659 }
4660 }
4661 }
4662
4663 if (funcs)
4664 disas_funcs(funcs);
4665
4666 return 0;
4667}
4668
4669struct insn_chunk {
4670 void *addr;
4671 struct insn_chunk *next;
4672};
4673
4674/*
4675 * Reduce peak RSS usage by freeing insns memory before writing the ELF file,
4676 * which can trigger more allocations for .debug_* sections whose data hasn't
4677 * been read yet.
4678 */
4679static void free_insns(struct objtool_file *file)
4680{
4681 struct instruction *insn;
4682 struct insn_chunk *chunks = NULL, *chunk;
4683
4684 for_each_insn(file, insn) {
4685 if (!insn->idx) {
4686 chunk = malloc(sizeof(*chunk));
4687 chunk->addr = insn;
4688 chunk->next = chunks;
4689 chunks = chunk;
4690 }
4691 }
4692
4693 for (chunk = chunks; chunk; chunk = chunk->next)
4694 free(chunk->addr);
4695}
4696
4697int check(struct objtool_file *file)
4698{
4699 int ret, warnings = 0;
4700
4701 arch_initial_func_cfi_state(&initial_func_cfi);
4702 init_cfi_state(&init_cfi);
4703 init_cfi_state(&func_cfi);
4704 set_func_state(&func_cfi);
4705 init_cfi_state(&force_undefined_cfi);
4706 force_undefined_cfi.force_undefined = true;
4707
4708 if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
4709 goto out;
4710
4711 cfi_hash_add(&init_cfi);
4712 cfi_hash_add(&func_cfi);
4713
4714 ret = decode_sections(file);
4715 if (ret < 0)
4716 goto out;
4717
4718 warnings += ret;
4719
4720 if (!nr_insns)
4721 goto out;
4722
4723 if (opts.retpoline) {
4724 ret = validate_retpoline(file);
4725 if (ret < 0)
4726 return ret;
4727 warnings += ret;
4728 }
4729
4730 if (opts.stackval || opts.orc || opts.uaccess) {
4731 ret = validate_functions(file);
4732 if (ret < 0)
4733 goto out;
4734 warnings += ret;
4735
4736 ret = validate_unwind_hints(file, NULL);
4737 if (ret < 0)
4738 goto out;
4739 warnings += ret;
4740
4741 if (!warnings) {
4742 ret = validate_reachable_instructions(file);
4743 if (ret < 0)
4744 goto out;
4745 warnings += ret;
4746 }
4747
4748 } else if (opts.noinstr) {
4749 ret = validate_noinstr_sections(file);
4750 if (ret < 0)
4751 goto out;
4752 warnings += ret;
4753 }
4754
4755 if (opts.unret) {
4756 /*
4757 * Must be after validate_branch() and friends, it plays
4758 * further games with insn->visited.
4759 */
4760 ret = validate_unrets(file);
4761 if (ret < 0)
4762 return ret;
4763 warnings += ret;
4764 }
4765
4766 if (opts.ibt) {
4767 ret = validate_ibt(file);
4768 if (ret < 0)
4769 goto out;
4770 warnings += ret;
4771 }
4772
4773 if (opts.sls) {
4774 ret = validate_sls(file);
4775 if (ret < 0)
4776 goto out;
4777 warnings += ret;
4778 }
4779
4780 if (opts.static_call) {
4781 ret = create_static_call_sections(file);
4782 if (ret < 0)
4783 goto out;
4784 warnings += ret;
4785 }
4786
4787 if (opts.retpoline) {
4788 ret = create_retpoline_sites_sections(file);
4789 if (ret < 0)
4790 goto out;
4791 warnings += ret;
4792 }
4793
4794 if (opts.cfi) {
4795 ret = create_cfi_sections(file);
4796 if (ret < 0)
4797 goto out;
4798 warnings += ret;
4799 }
4800
4801 if (opts.rethunk) {
4802 ret = create_return_sites_sections(file);
4803 if (ret < 0)
4804 goto out;
4805 warnings += ret;
4806
4807 if (opts.hack_skylake) {
4808 ret = create_direct_call_sections(file);
4809 if (ret < 0)
4810 goto out;
4811 warnings += ret;
4812 }
4813 }
4814
4815 if (opts.mcount) {
4816 ret = create_mcount_loc_sections(file);
4817 if (ret < 0)
4818 goto out;
4819 warnings += ret;
4820 }
4821
4822 if (opts.prefix) {
4823 ret = add_prefix_symbols(file);
4824 if (ret < 0)
4825 return ret;
4826 warnings += ret;
4827 }
4828
4829 if (opts.ibt) {
4830 ret = create_ibt_endbr_seal_sections(file);
4831 if (ret < 0)
4832 goto out;
4833 warnings += ret;
4834 }
4835
4836 if (opts.orc && nr_insns) {
4837 ret = orc_create(file);
4838 if (ret < 0)
4839 goto out;
4840 warnings += ret;
4841 }
4842
4843 free_insns(file);
4844
4845 if (opts.verbose)
4846 disas_warned_funcs(file);
4847
4848 if (opts.stats) {
4849 printf("nr_insns_visited: %ld\n", nr_insns_visited);
4850 printf("nr_cfi: %ld\n", nr_cfi);
4851 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
4852 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
4853 }
4854
4855out:
4856 /*
4857 * For now, don't fail the kernel build on fatal warnings. These
4858 * errors are still fairly common due to the growing matrix of
4859 * supported toolchains and their recent pace of change.
4860 */
4861 return 0;
4862}