xref: /linux/tools/objtool/check.c (revision fba2689ee77e63b05e203b3f26079ef915e55660)
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 <sys/mman.h>
9 
10 #include <arch/elf.h>
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.h>
20 #include <linux/hashtable.h>
21 #include <linux/kernel.h>
22 #include <linux/static_call_types.h>
23 
24 struct alternative {
25 	struct list_head list;
26 	struct instruction *insn;
27 	bool skip_orig;
28 };
29 
30 static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
31 
32 static struct cfi_init_state initial_func_cfi;
33 static struct cfi_state init_cfi;
34 static struct cfi_state func_cfi;
35 
36 struct instruction *find_insn(struct objtool_file *file,
37 			      struct section *sec, unsigned long offset)
38 {
39 	struct instruction *insn;
40 
41 	hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
42 		if (insn->sec == sec && insn->offset == offset)
43 			return insn;
44 	}
45 
46 	return NULL;
47 }
48 
49 static struct instruction *next_insn_same_sec(struct objtool_file *file,
50 					      struct instruction *insn)
51 {
52 	struct instruction *next = list_next_entry(insn, list);
53 
54 	if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
55 		return NULL;
56 
57 	return next;
58 }
59 
60 static struct instruction *next_insn_same_func(struct objtool_file *file,
61 					       struct instruction *insn)
62 {
63 	struct instruction *next = list_next_entry(insn, list);
64 	struct symbol *func = insn->func;
65 
66 	if (!func)
67 		return NULL;
68 
69 	if (&next->list != &file->insn_list && next->func == func)
70 		return next;
71 
72 	/* Check if we're already in the subfunction: */
73 	if (func == func->cfunc)
74 		return NULL;
75 
76 	/* Move to the subfunction: */
77 	return find_insn(file, func->cfunc->sec, func->cfunc->offset);
78 }
79 
80 static struct instruction *prev_insn_same_sym(struct objtool_file *file,
81 					       struct instruction *insn)
82 {
83 	struct instruction *prev = list_prev_entry(insn, list);
84 
85 	if (&prev->list != &file->insn_list && prev->func == insn->func)
86 		return prev;
87 
88 	return NULL;
89 }
90 
91 #define func_for_each_insn(file, func, insn)				\
92 	for (insn = find_insn(file, func->sec, func->offset);		\
93 	     insn;							\
94 	     insn = next_insn_same_func(file, insn))
95 
96 #define sym_for_each_insn(file, sym, insn)				\
97 	for (insn = find_insn(file, sym->sec, sym->offset);		\
98 	     insn && &insn->list != &file->insn_list &&			\
99 		insn->sec == sym->sec &&				\
100 		insn->offset < sym->offset + sym->len;			\
101 	     insn = list_next_entry(insn, list))
102 
103 #define sym_for_each_insn_continue_reverse(file, sym, insn)		\
104 	for (insn = list_prev_entry(insn, list);			\
105 	     &insn->list != &file->insn_list &&				\
106 		insn->sec == sym->sec && insn->offset >= sym->offset;	\
107 	     insn = list_prev_entry(insn, list))
108 
109 #define sec_for_each_insn_from(file, insn)				\
110 	for (; insn; insn = next_insn_same_sec(file, insn))
111 
112 #define sec_for_each_insn_continue(file, insn)				\
113 	for (insn = next_insn_same_sec(file, insn); insn;		\
114 	     insn = next_insn_same_sec(file, insn))
115 
116 static bool is_jump_table_jump(struct instruction *insn)
117 {
118 	struct alt_group *alt_group = insn->alt_group;
119 
120 	if (insn->jump_table)
121 		return true;
122 
123 	/* Retpoline alternative for a jump table? */
124 	return alt_group && alt_group->orig_group &&
125 	       alt_group->orig_group->first_insn->jump_table;
126 }
127 
128 static bool is_sibling_call(struct instruction *insn)
129 {
130 	/*
131 	 * Assume only ELF functions can make sibling calls.  This ensures
132 	 * sibling call detection consistency between vmlinux.o and individual
133 	 * objects.
134 	 */
135 	if (!insn->func)
136 		return false;
137 
138 	/* An indirect jump is either a sibling call or a jump to a table. */
139 	if (insn->type == INSN_JUMP_DYNAMIC)
140 		return !is_jump_table_jump(insn);
141 
142 	/* add_jump_destinations() sets insn->call_dest for sibling calls. */
143 	return (is_static_jump(insn) && insn->call_dest);
144 }
145 
146 /*
147  * This checks to see if the given function is a "noreturn" function.
148  *
149  * For global functions which are outside the scope of this object file, we
150  * have to keep a manual list of them.
151  *
152  * For local functions, we have to detect them manually by simply looking for
153  * the lack of a return instruction.
154  */
155 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
156 				int recursion)
157 {
158 	int i;
159 	struct instruction *insn;
160 	bool empty = true;
161 
162 	/*
163 	 * Unfortunately these have to be hard coded because the noreturn
164 	 * attribute isn't provided in ELF data.
165 	 */
166 	static const char * const global_noreturns[] = {
167 		"__stack_chk_fail",
168 		"panic",
169 		"do_exit",
170 		"do_task_dead",
171 		"kthread_exit",
172 		"make_task_dead",
173 		"__module_put_and_kthread_exit",
174 		"kthread_complete_and_exit",
175 		"__reiserfs_panic",
176 		"lbug_with_loc",
177 		"fortify_panic",
178 		"usercopy_abort",
179 		"machine_real_restart",
180 		"rewind_stack_and_make_dead",
181 		"kunit_try_catch_throw",
182 		"xen_start_kernel",
183 		"cpu_bringup_and_idle",
184 		"do_group_exit",
185 		"stop_this_cpu",
186 		"__invalid_creds",
187 	};
188 
189 	if (!func)
190 		return false;
191 
192 	if (func->bind == STB_WEAK)
193 		return false;
194 
195 	if (func->bind == STB_GLOBAL)
196 		for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
197 			if (!strcmp(func->name, global_noreturns[i]))
198 				return true;
199 
200 	if (!func->len)
201 		return false;
202 
203 	insn = find_insn(file, func->sec, func->offset);
204 	if (!insn->func)
205 		return false;
206 
207 	func_for_each_insn(file, func, insn) {
208 		empty = false;
209 
210 		if (insn->type == INSN_RETURN)
211 			return false;
212 	}
213 
214 	if (empty)
215 		return false;
216 
217 	/*
218 	 * A function can have a sibling call instead of a return.  In that
219 	 * case, the function's dead-end status depends on whether the target
220 	 * of the sibling call returns.
221 	 */
222 	func_for_each_insn(file, func, insn) {
223 		if (is_sibling_call(insn)) {
224 			struct instruction *dest = insn->jump_dest;
225 
226 			if (!dest)
227 				/* sibling call to another file */
228 				return false;
229 
230 			/* local sibling call */
231 			if (recursion == 5) {
232 				/*
233 				 * Infinite recursion: two functions have
234 				 * sibling calls to each other.  This is a very
235 				 * rare case.  It means they aren't dead ends.
236 				 */
237 				return false;
238 			}
239 
240 			return __dead_end_function(file, dest->func, recursion+1);
241 		}
242 	}
243 
244 	return true;
245 }
246 
247 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
248 {
249 	return __dead_end_function(file, func, 0);
250 }
251 
252 static void init_cfi_state(struct cfi_state *cfi)
253 {
254 	int i;
255 
256 	for (i = 0; i < CFI_NUM_REGS; i++) {
257 		cfi->regs[i].base = CFI_UNDEFINED;
258 		cfi->vals[i].base = CFI_UNDEFINED;
259 	}
260 	cfi->cfa.base = CFI_UNDEFINED;
261 	cfi->drap_reg = CFI_UNDEFINED;
262 	cfi->drap_offset = -1;
263 }
264 
265 static void init_insn_state(struct insn_state *state, struct section *sec)
266 {
267 	memset(state, 0, sizeof(*state));
268 	init_cfi_state(&state->cfi);
269 
270 	/*
271 	 * We need the full vmlinux for noinstr validation, otherwise we can
272 	 * not correctly determine insn->call_dest->sec (external symbols do
273 	 * not have a section).
274 	 */
275 	if (vmlinux && noinstr && sec)
276 		state->noinstr = sec->noinstr;
277 }
278 
279 static struct cfi_state *cfi_alloc(void)
280 {
281 	struct cfi_state *cfi = calloc(sizeof(struct cfi_state), 1);
282 	if (!cfi) {
283 		WARN("calloc failed");
284 		exit(1);
285 	}
286 	nr_cfi++;
287 	return cfi;
288 }
289 
290 static int cfi_bits;
291 static struct hlist_head *cfi_hash;
292 
293 static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
294 {
295 	return memcmp((void *)cfi1 + sizeof(cfi1->hash),
296 		      (void *)cfi2 + sizeof(cfi2->hash),
297 		      sizeof(struct cfi_state) - sizeof(struct hlist_node));
298 }
299 
300 static inline u32 cfi_key(struct cfi_state *cfi)
301 {
302 	return jhash((void *)cfi + sizeof(cfi->hash),
303 		     sizeof(*cfi) - sizeof(cfi->hash), 0);
304 }
305 
306 static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
307 {
308 	struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
309 	struct cfi_state *obj;
310 
311 	hlist_for_each_entry(obj, head, hash) {
312 		if (!cficmp(cfi, obj)) {
313 			nr_cfi_cache++;
314 			return obj;
315 		}
316 	}
317 
318 	obj = cfi_alloc();
319 	*obj = *cfi;
320 	hlist_add_head(&obj->hash, head);
321 
322 	return obj;
323 }
324 
325 static void cfi_hash_add(struct cfi_state *cfi)
326 {
327 	struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
328 
329 	hlist_add_head(&cfi->hash, head);
330 }
331 
332 static void *cfi_hash_alloc(unsigned long size)
333 {
334 	cfi_bits = max(10, ilog2(size));
335 	cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
336 			PROT_READ|PROT_WRITE,
337 			MAP_PRIVATE|MAP_ANON, -1, 0);
338 	if (cfi_hash == (void *)-1L) {
339 		WARN("mmap fail cfi_hash");
340 		cfi_hash = NULL;
341 	}  else if (stats) {
342 		printf("cfi_bits: %d\n", cfi_bits);
343 	}
344 
345 	return cfi_hash;
346 }
347 
348 static unsigned long nr_insns;
349 static unsigned long nr_insns_visited;
350 
351 /*
352  * Call the arch-specific instruction decoder for all the instructions and add
353  * them to the global instruction list.
354  */
355 static int decode_instructions(struct objtool_file *file)
356 {
357 	struct section *sec;
358 	struct symbol *func;
359 	unsigned long offset;
360 	struct instruction *insn;
361 	int ret;
362 
363 	for_each_sec(file, sec) {
364 
365 		if (!(sec->sh.sh_flags & SHF_EXECINSTR))
366 			continue;
367 
368 		if (strcmp(sec->name, ".altinstr_replacement") &&
369 		    strcmp(sec->name, ".altinstr_aux") &&
370 		    strncmp(sec->name, ".discard.", 9))
371 			sec->text = true;
372 
373 		if (!strcmp(sec->name, ".noinstr.text") ||
374 		    !strcmp(sec->name, ".entry.text"))
375 			sec->noinstr = true;
376 
377 		for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
378 			insn = malloc(sizeof(*insn));
379 			if (!insn) {
380 				WARN("malloc failed");
381 				return -1;
382 			}
383 			memset(insn, 0, sizeof(*insn));
384 			INIT_LIST_HEAD(&insn->alts);
385 			INIT_LIST_HEAD(&insn->stack_ops);
386 			INIT_LIST_HEAD(&insn->call_node);
387 
388 			insn->sec = sec;
389 			insn->offset = offset;
390 
391 			ret = arch_decode_instruction(file, sec, offset,
392 						      sec->sh.sh_size - offset,
393 						      &insn->len, &insn->type,
394 						      &insn->immediate,
395 						      &insn->stack_ops);
396 			if (ret)
397 				goto err;
398 
399 			/*
400 			 * By default, "ud2" is a dead end unless otherwise
401 			 * annotated, because GCC 7 inserts it for certain
402 			 * divide-by-zero cases.
403 			 */
404 			if (insn->type == INSN_BUG)
405 				insn->dead_end = true;
406 
407 			hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
408 			list_add_tail(&insn->list, &file->insn_list);
409 			nr_insns++;
410 		}
411 
412 		list_for_each_entry(func, &sec->symbol_list, list) {
413 			if (func->type != STT_FUNC || func->alias != func)
414 				continue;
415 
416 			if (!find_insn(file, sec, func->offset)) {
417 				WARN("%s(): can't find starting instruction",
418 				     func->name);
419 				return -1;
420 			}
421 
422 			sym_for_each_insn(file, func, insn) {
423 				insn->func = func;
424 				if (insn->type == INSN_ENDBR && list_empty(&insn->call_node)) {
425 					if (insn->offset == insn->func->offset) {
426 						list_add_tail(&insn->call_node, &file->endbr_list);
427 						file->nr_endbr++;
428 					} else {
429 						file->nr_endbr_int++;
430 					}
431 				}
432 			}
433 		}
434 	}
435 
436 	if (stats)
437 		printf("nr_insns: %lu\n", nr_insns);
438 
439 	return 0;
440 
441 err:
442 	free(insn);
443 	return ret;
444 }
445 
446 /*
447  * Read the pv_ops[] .data table to find the static initialized values.
448  */
449 static int add_pv_ops(struct objtool_file *file, const char *symname)
450 {
451 	struct symbol *sym, *func;
452 	unsigned long off, end;
453 	struct reloc *rel;
454 	int idx;
455 
456 	sym = find_symbol_by_name(file->elf, symname);
457 	if (!sym)
458 		return 0;
459 
460 	off = sym->offset;
461 	end = off + sym->len;
462 	for (;;) {
463 		rel = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off);
464 		if (!rel)
465 			break;
466 
467 		func = rel->sym;
468 		if (func->type == STT_SECTION)
469 			func = find_symbol_by_offset(rel->sym->sec, rel->addend);
470 
471 		idx = (rel->offset - sym->offset) / sizeof(unsigned long);
472 
473 		objtool_pv_add(file, idx, func);
474 
475 		off = rel->offset + 1;
476 		if (off > end)
477 			break;
478 	}
479 
480 	return 0;
481 }
482 
483 /*
484  * Allocate and initialize file->pv_ops[].
485  */
486 static int init_pv_ops(struct objtool_file *file)
487 {
488 	static const char *pv_ops_tables[] = {
489 		"pv_ops",
490 		"xen_cpu_ops",
491 		"xen_irq_ops",
492 		"xen_mmu_ops",
493 		NULL,
494 	};
495 	const char *pv_ops;
496 	struct symbol *sym;
497 	int idx, nr;
498 
499 	if (!noinstr)
500 		return 0;
501 
502 	file->pv_ops = NULL;
503 
504 	sym = find_symbol_by_name(file->elf, "pv_ops");
505 	if (!sym)
506 		return 0;
507 
508 	nr = sym->len / sizeof(unsigned long);
509 	file->pv_ops = calloc(sizeof(struct pv_state), nr);
510 	if (!file->pv_ops)
511 		return -1;
512 
513 	for (idx = 0; idx < nr; idx++)
514 		INIT_LIST_HEAD(&file->pv_ops[idx].targets);
515 
516 	for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++)
517 		add_pv_ops(file, pv_ops);
518 
519 	return 0;
520 }
521 
522 static struct instruction *find_last_insn(struct objtool_file *file,
523 					  struct section *sec)
524 {
525 	struct instruction *insn = NULL;
526 	unsigned int offset;
527 	unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
528 
529 	for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
530 		insn = find_insn(file, sec, offset);
531 
532 	return insn;
533 }
534 
535 /*
536  * Mark "ud2" instructions and manually annotated dead ends.
537  */
538 static int add_dead_ends(struct objtool_file *file)
539 {
540 	struct section *sec;
541 	struct reloc *reloc;
542 	struct instruction *insn;
543 
544 	/*
545 	 * Check for manually annotated dead ends.
546 	 */
547 	sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
548 	if (!sec)
549 		goto reachable;
550 
551 	list_for_each_entry(reloc, &sec->reloc_list, list) {
552 		if (reloc->sym->type != STT_SECTION) {
553 			WARN("unexpected relocation symbol type in %s", sec->name);
554 			return -1;
555 		}
556 		insn = find_insn(file, reloc->sym->sec, reloc->addend);
557 		if (insn)
558 			insn = list_prev_entry(insn, list);
559 		else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
560 			insn = find_last_insn(file, reloc->sym->sec);
561 			if (!insn) {
562 				WARN("can't find unreachable insn at %s+0x%x",
563 				     reloc->sym->sec->name, reloc->addend);
564 				return -1;
565 			}
566 		} else {
567 			WARN("can't find unreachable insn at %s+0x%x",
568 			     reloc->sym->sec->name, reloc->addend);
569 			return -1;
570 		}
571 
572 		insn->dead_end = true;
573 	}
574 
575 reachable:
576 	/*
577 	 * These manually annotated reachable checks are needed for GCC 4.4,
578 	 * where the Linux unreachable() macro isn't supported.  In that case
579 	 * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
580 	 * not a dead end.
581 	 */
582 	sec = find_section_by_name(file->elf, ".rela.discard.reachable");
583 	if (!sec)
584 		return 0;
585 
586 	list_for_each_entry(reloc, &sec->reloc_list, list) {
587 		if (reloc->sym->type != STT_SECTION) {
588 			WARN("unexpected relocation symbol type in %s", sec->name);
589 			return -1;
590 		}
591 		insn = find_insn(file, reloc->sym->sec, reloc->addend);
592 		if (insn)
593 			insn = list_prev_entry(insn, list);
594 		else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
595 			insn = find_last_insn(file, reloc->sym->sec);
596 			if (!insn) {
597 				WARN("can't find reachable insn at %s+0x%x",
598 				     reloc->sym->sec->name, reloc->addend);
599 				return -1;
600 			}
601 		} else {
602 			WARN("can't find reachable insn at %s+0x%x",
603 			     reloc->sym->sec->name, reloc->addend);
604 			return -1;
605 		}
606 
607 		insn->dead_end = false;
608 	}
609 
610 	return 0;
611 }
612 
613 static int create_static_call_sections(struct objtool_file *file)
614 {
615 	struct section *sec;
616 	struct static_call_site *site;
617 	struct instruction *insn;
618 	struct symbol *key_sym;
619 	char *key_name, *tmp;
620 	int idx;
621 
622 	sec = find_section_by_name(file->elf, ".static_call_sites");
623 	if (sec) {
624 		INIT_LIST_HEAD(&file->static_call_list);
625 		WARN("file already has .static_call_sites section, skipping");
626 		return 0;
627 	}
628 
629 	if (list_empty(&file->static_call_list))
630 		return 0;
631 
632 	idx = 0;
633 	list_for_each_entry(insn, &file->static_call_list, call_node)
634 		idx++;
635 
636 	sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE,
637 				 sizeof(struct static_call_site), idx);
638 	if (!sec)
639 		return -1;
640 
641 	idx = 0;
642 	list_for_each_entry(insn, &file->static_call_list, call_node) {
643 
644 		site = (struct static_call_site *)sec->data->d_buf + idx;
645 		memset(site, 0, sizeof(struct static_call_site));
646 
647 		/* populate reloc for 'addr' */
648 		if (elf_add_reloc_to_insn(file->elf, sec,
649 					  idx * sizeof(struct static_call_site),
650 					  R_X86_64_PC32,
651 					  insn->sec, insn->offset))
652 			return -1;
653 
654 		/* find key symbol */
655 		key_name = strdup(insn->call_dest->name);
656 		if (!key_name) {
657 			perror("strdup");
658 			return -1;
659 		}
660 		if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
661 			    STATIC_CALL_TRAMP_PREFIX_LEN)) {
662 			WARN("static_call: trampoline name malformed: %s", key_name);
663 			return -1;
664 		}
665 		tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
666 		memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
667 
668 		key_sym = find_symbol_by_name(file->elf, tmp);
669 		if (!key_sym) {
670 			if (!module) {
671 				WARN("static_call: can't find static_call_key symbol: %s", tmp);
672 				return -1;
673 			}
674 
675 			/*
676 			 * For modules(), the key might not be exported, which
677 			 * means the module can make static calls but isn't
678 			 * allowed to change them.
679 			 *
680 			 * In that case we temporarily set the key to be the
681 			 * trampoline address.  This is fixed up in
682 			 * static_call_add_module().
683 			 */
684 			key_sym = insn->call_dest;
685 		}
686 		free(key_name);
687 
688 		/* populate reloc for 'key' */
689 		if (elf_add_reloc(file->elf, sec,
690 				  idx * sizeof(struct static_call_site) + 4,
691 				  R_X86_64_PC32, key_sym,
692 				  is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
693 			return -1;
694 
695 		idx++;
696 	}
697 
698 	return 0;
699 }
700 
701 static int create_retpoline_sites_sections(struct objtool_file *file)
702 {
703 	struct instruction *insn;
704 	struct section *sec;
705 	int idx;
706 
707 	sec = find_section_by_name(file->elf, ".retpoline_sites");
708 	if (sec) {
709 		WARN("file already has .retpoline_sites, skipping");
710 		return 0;
711 	}
712 
713 	idx = 0;
714 	list_for_each_entry(insn, &file->retpoline_call_list, call_node)
715 		idx++;
716 
717 	if (!idx)
718 		return 0;
719 
720 	sec = elf_create_section(file->elf, ".retpoline_sites", 0,
721 				 sizeof(int), idx);
722 	if (!sec) {
723 		WARN("elf_create_section: .retpoline_sites");
724 		return -1;
725 	}
726 
727 	idx = 0;
728 	list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
729 
730 		int *site = (int *)sec->data->d_buf + idx;
731 		*site = 0;
732 
733 		if (elf_add_reloc_to_insn(file->elf, sec,
734 					  idx * sizeof(int),
735 					  R_X86_64_PC32,
736 					  insn->sec, insn->offset)) {
737 			WARN("elf_add_reloc_to_insn: .retpoline_sites");
738 			return -1;
739 		}
740 
741 		idx++;
742 	}
743 
744 	return 0;
745 }
746 
747 static int create_ibt_endbr_seal_sections(struct objtool_file *file)
748 {
749 	struct instruction *insn;
750 	struct section *sec;
751 	int idx;
752 
753 	sec = find_section_by_name(file->elf, ".ibt_endbr_seal");
754 	if (sec) {
755 		WARN("file already has .ibt_endbr_seal, skipping");
756 		return 0;
757 	}
758 
759 	idx = 0;
760 	list_for_each_entry(insn, &file->endbr_list, call_node)
761 		idx++;
762 
763 	if (stats) {
764 		printf("ibt: ENDBR at function start: %d\n", file->nr_endbr);
765 		printf("ibt: ENDBR inside functions:  %d\n", file->nr_endbr_int);
766 		printf("ibt: superfluous ENDBR:       %d\n", idx);
767 	}
768 
769 	if (!idx)
770 		return 0;
771 
772 	sec = elf_create_section(file->elf, ".ibt_endbr_seal", 0,
773 				 sizeof(int), idx);
774 	if (!sec) {
775 		WARN("elf_create_section: .ibt_endbr_seal");
776 		return -1;
777 	}
778 
779 	idx = 0;
780 	list_for_each_entry(insn, &file->endbr_list, call_node) {
781 
782 		int *site = (int *)sec->data->d_buf + idx;
783 		*site = 0;
784 
785 		if (elf_add_reloc_to_insn(file->elf, sec,
786 					  idx * sizeof(int),
787 					  R_X86_64_PC32,
788 					  insn->sec, insn->offset)) {
789 			WARN("elf_add_reloc_to_insn: .ibt_endbr_seal");
790 			return -1;
791 		}
792 
793 		idx++;
794 	}
795 
796 	return 0;
797 }
798 
799 static int create_mcount_loc_sections(struct objtool_file *file)
800 {
801 	struct section *sec;
802 	unsigned long *loc;
803 	struct instruction *insn;
804 	int idx;
805 
806 	sec = find_section_by_name(file->elf, "__mcount_loc");
807 	if (sec) {
808 		INIT_LIST_HEAD(&file->mcount_loc_list);
809 		WARN("file already has __mcount_loc section, skipping");
810 		return 0;
811 	}
812 
813 	if (list_empty(&file->mcount_loc_list))
814 		return 0;
815 
816 	idx = 0;
817 	list_for_each_entry(insn, &file->mcount_loc_list, call_node)
818 		idx++;
819 
820 	sec = elf_create_section(file->elf, "__mcount_loc", 0, sizeof(unsigned long), idx);
821 	if (!sec)
822 		return -1;
823 
824 	idx = 0;
825 	list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
826 
827 		loc = (unsigned long *)sec->data->d_buf + idx;
828 		memset(loc, 0, sizeof(unsigned long));
829 
830 		if (elf_add_reloc_to_insn(file->elf, sec,
831 					  idx * sizeof(unsigned long),
832 					  R_X86_64_64,
833 					  insn->sec, insn->offset))
834 			return -1;
835 
836 		idx++;
837 	}
838 
839 	return 0;
840 }
841 
842 /*
843  * Warnings shouldn't be reported for ignored functions.
844  */
845 static void add_ignores(struct objtool_file *file)
846 {
847 	struct instruction *insn;
848 	struct section *sec;
849 	struct symbol *func;
850 	struct reloc *reloc;
851 
852 	sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
853 	if (!sec)
854 		return;
855 
856 	list_for_each_entry(reloc, &sec->reloc_list, list) {
857 		switch (reloc->sym->type) {
858 		case STT_FUNC:
859 			func = reloc->sym;
860 			break;
861 
862 		case STT_SECTION:
863 			func = find_func_by_offset(reloc->sym->sec, reloc->addend);
864 			if (!func)
865 				continue;
866 			break;
867 
868 		default:
869 			WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type);
870 			continue;
871 		}
872 
873 		func_for_each_insn(file, func, insn)
874 			insn->ignore = true;
875 	}
876 }
877 
878 /*
879  * This is a whitelist of functions that is allowed to be called with AC set.
880  * The list is meant to be minimal and only contains compiler instrumentation
881  * ABI and a few functions used to implement *_{to,from}_user() functions.
882  *
883  * These functions must not directly change AC, but may PUSHF/POPF.
884  */
885 static const char *uaccess_safe_builtin[] = {
886 	/* KASAN */
887 	"kasan_report",
888 	"kasan_check_range",
889 	/* KASAN out-of-line */
890 	"__asan_loadN_noabort",
891 	"__asan_load1_noabort",
892 	"__asan_load2_noabort",
893 	"__asan_load4_noabort",
894 	"__asan_load8_noabort",
895 	"__asan_load16_noabort",
896 	"__asan_storeN_noabort",
897 	"__asan_store1_noabort",
898 	"__asan_store2_noabort",
899 	"__asan_store4_noabort",
900 	"__asan_store8_noabort",
901 	"__asan_store16_noabort",
902 	"__kasan_check_read",
903 	"__kasan_check_write",
904 	/* KASAN in-line */
905 	"__asan_report_load_n_noabort",
906 	"__asan_report_load1_noabort",
907 	"__asan_report_load2_noabort",
908 	"__asan_report_load4_noabort",
909 	"__asan_report_load8_noabort",
910 	"__asan_report_load16_noabort",
911 	"__asan_report_store_n_noabort",
912 	"__asan_report_store1_noabort",
913 	"__asan_report_store2_noabort",
914 	"__asan_report_store4_noabort",
915 	"__asan_report_store8_noabort",
916 	"__asan_report_store16_noabort",
917 	/* KCSAN */
918 	"__kcsan_check_access",
919 	"__kcsan_mb",
920 	"__kcsan_wmb",
921 	"__kcsan_rmb",
922 	"__kcsan_release",
923 	"kcsan_found_watchpoint",
924 	"kcsan_setup_watchpoint",
925 	"kcsan_check_scoped_accesses",
926 	"kcsan_disable_current",
927 	"kcsan_enable_current_nowarn",
928 	/* KCSAN/TSAN */
929 	"__tsan_func_entry",
930 	"__tsan_func_exit",
931 	"__tsan_read_range",
932 	"__tsan_write_range",
933 	"__tsan_read1",
934 	"__tsan_read2",
935 	"__tsan_read4",
936 	"__tsan_read8",
937 	"__tsan_read16",
938 	"__tsan_write1",
939 	"__tsan_write2",
940 	"__tsan_write4",
941 	"__tsan_write8",
942 	"__tsan_write16",
943 	"__tsan_read_write1",
944 	"__tsan_read_write2",
945 	"__tsan_read_write4",
946 	"__tsan_read_write8",
947 	"__tsan_read_write16",
948 	"__tsan_atomic8_load",
949 	"__tsan_atomic16_load",
950 	"__tsan_atomic32_load",
951 	"__tsan_atomic64_load",
952 	"__tsan_atomic8_store",
953 	"__tsan_atomic16_store",
954 	"__tsan_atomic32_store",
955 	"__tsan_atomic64_store",
956 	"__tsan_atomic8_exchange",
957 	"__tsan_atomic16_exchange",
958 	"__tsan_atomic32_exchange",
959 	"__tsan_atomic64_exchange",
960 	"__tsan_atomic8_fetch_add",
961 	"__tsan_atomic16_fetch_add",
962 	"__tsan_atomic32_fetch_add",
963 	"__tsan_atomic64_fetch_add",
964 	"__tsan_atomic8_fetch_sub",
965 	"__tsan_atomic16_fetch_sub",
966 	"__tsan_atomic32_fetch_sub",
967 	"__tsan_atomic64_fetch_sub",
968 	"__tsan_atomic8_fetch_and",
969 	"__tsan_atomic16_fetch_and",
970 	"__tsan_atomic32_fetch_and",
971 	"__tsan_atomic64_fetch_and",
972 	"__tsan_atomic8_fetch_or",
973 	"__tsan_atomic16_fetch_or",
974 	"__tsan_atomic32_fetch_or",
975 	"__tsan_atomic64_fetch_or",
976 	"__tsan_atomic8_fetch_xor",
977 	"__tsan_atomic16_fetch_xor",
978 	"__tsan_atomic32_fetch_xor",
979 	"__tsan_atomic64_fetch_xor",
980 	"__tsan_atomic8_fetch_nand",
981 	"__tsan_atomic16_fetch_nand",
982 	"__tsan_atomic32_fetch_nand",
983 	"__tsan_atomic64_fetch_nand",
984 	"__tsan_atomic8_compare_exchange_strong",
985 	"__tsan_atomic16_compare_exchange_strong",
986 	"__tsan_atomic32_compare_exchange_strong",
987 	"__tsan_atomic64_compare_exchange_strong",
988 	"__tsan_atomic8_compare_exchange_weak",
989 	"__tsan_atomic16_compare_exchange_weak",
990 	"__tsan_atomic32_compare_exchange_weak",
991 	"__tsan_atomic64_compare_exchange_weak",
992 	"__tsan_atomic8_compare_exchange_val",
993 	"__tsan_atomic16_compare_exchange_val",
994 	"__tsan_atomic32_compare_exchange_val",
995 	"__tsan_atomic64_compare_exchange_val",
996 	"__tsan_atomic_thread_fence",
997 	"__tsan_atomic_signal_fence",
998 	/* KCOV */
999 	"write_comp_data",
1000 	"check_kcov_mode",
1001 	"__sanitizer_cov_trace_pc",
1002 	"__sanitizer_cov_trace_const_cmp1",
1003 	"__sanitizer_cov_trace_const_cmp2",
1004 	"__sanitizer_cov_trace_const_cmp4",
1005 	"__sanitizer_cov_trace_const_cmp8",
1006 	"__sanitizer_cov_trace_cmp1",
1007 	"__sanitizer_cov_trace_cmp2",
1008 	"__sanitizer_cov_trace_cmp4",
1009 	"__sanitizer_cov_trace_cmp8",
1010 	"__sanitizer_cov_trace_switch",
1011 	/* UBSAN */
1012 	"ubsan_type_mismatch_common",
1013 	"__ubsan_handle_type_mismatch",
1014 	"__ubsan_handle_type_mismatch_v1",
1015 	"__ubsan_handle_shift_out_of_bounds",
1016 	/* misc */
1017 	"csum_partial_copy_generic",
1018 	"copy_mc_fragile",
1019 	"copy_mc_fragile_handle_tail",
1020 	"copy_mc_enhanced_fast_string",
1021 	"ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
1022 	NULL
1023 };
1024 
1025 static void add_uaccess_safe(struct objtool_file *file)
1026 {
1027 	struct symbol *func;
1028 	const char **name;
1029 
1030 	if (!uaccess)
1031 		return;
1032 
1033 	for (name = uaccess_safe_builtin; *name; name++) {
1034 		func = find_symbol_by_name(file->elf, *name);
1035 		if (!func)
1036 			continue;
1037 
1038 		func->uaccess_safe = true;
1039 	}
1040 }
1041 
1042 /*
1043  * FIXME: For now, just ignore any alternatives which add retpolines.  This is
1044  * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
1045  * But it at least allows objtool to understand the control flow *around* the
1046  * retpoline.
1047  */
1048 static int add_ignore_alternatives(struct objtool_file *file)
1049 {
1050 	struct section *sec;
1051 	struct reloc *reloc;
1052 	struct instruction *insn;
1053 
1054 	sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
1055 	if (!sec)
1056 		return 0;
1057 
1058 	list_for_each_entry(reloc, &sec->reloc_list, list) {
1059 		if (reloc->sym->type != STT_SECTION) {
1060 			WARN("unexpected relocation symbol type in %s", sec->name);
1061 			return -1;
1062 		}
1063 
1064 		insn = find_insn(file, reloc->sym->sec, reloc->addend);
1065 		if (!insn) {
1066 			WARN("bad .discard.ignore_alts entry");
1067 			return -1;
1068 		}
1069 
1070 		insn->ignore_alts = true;
1071 	}
1072 
1073 	return 0;
1074 }
1075 
1076 __weak bool arch_is_retpoline(struct symbol *sym)
1077 {
1078 	return false;
1079 }
1080 
1081 #define NEGATIVE_RELOC	((void *)-1L)
1082 
1083 static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
1084 {
1085 	if (insn->reloc == NEGATIVE_RELOC)
1086 		return NULL;
1087 
1088 	if (!insn->reloc) {
1089 		if (!file)
1090 			return NULL;
1091 
1092 		insn->reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1093 						       insn->offset, insn->len);
1094 		if (!insn->reloc) {
1095 			insn->reloc = NEGATIVE_RELOC;
1096 			return NULL;
1097 		}
1098 	}
1099 
1100 	return insn->reloc;
1101 }
1102 
1103 static void remove_insn_ops(struct instruction *insn)
1104 {
1105 	struct stack_op *op, *tmp;
1106 
1107 	list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
1108 		list_del(&op->list);
1109 		free(op);
1110 	}
1111 }
1112 
1113 static void annotate_call_site(struct objtool_file *file,
1114 			       struct instruction *insn, bool sibling)
1115 {
1116 	struct reloc *reloc = insn_reloc(file, insn);
1117 	struct symbol *sym = insn->call_dest;
1118 
1119 	if (!sym)
1120 		sym = reloc->sym;
1121 
1122 	/*
1123 	 * Alternative replacement code is just template code which is
1124 	 * sometimes copied to the original instruction. For now, don't
1125 	 * annotate it. (In the future we might consider annotating the
1126 	 * original instruction if/when it ever makes sense to do so.)
1127 	 */
1128 	if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1129 		return;
1130 
1131 	if (sym->static_call_tramp) {
1132 		list_add_tail(&insn->call_node, &file->static_call_list);
1133 		return;
1134 	}
1135 
1136 	if (sym->retpoline_thunk) {
1137 		list_add_tail(&insn->call_node, &file->retpoline_call_list);
1138 		return;
1139 	}
1140 
1141 	/*
1142 	 * Many compilers cannot disable KCOV or sanitizer calls with a function
1143 	 * attribute so they need a little help, NOP out any such calls from
1144 	 * noinstr text.
1145 	 */
1146 	if (insn->sec->noinstr && sym->profiling_func) {
1147 		if (reloc) {
1148 			reloc->type = R_NONE;
1149 			elf_write_reloc(file->elf, reloc);
1150 		}
1151 
1152 		elf_write_insn(file->elf, insn->sec,
1153 			       insn->offset, insn->len,
1154 			       sibling ? arch_ret_insn(insn->len)
1155 			               : arch_nop_insn(insn->len));
1156 
1157 		insn->type = sibling ? INSN_RETURN : INSN_NOP;
1158 		return;
1159 	}
1160 
1161 	if (mcount && sym->fentry) {
1162 		if (sibling)
1163 			WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset);
1164 
1165 		if (reloc) {
1166 			reloc->type = R_NONE;
1167 			elf_write_reloc(file->elf, reloc);
1168 		}
1169 
1170 		elf_write_insn(file->elf, insn->sec,
1171 			       insn->offset, insn->len,
1172 			       arch_nop_insn(insn->len));
1173 
1174 		insn->type = INSN_NOP;
1175 
1176 		list_add_tail(&insn->call_node, &file->mcount_loc_list);
1177 		return;
1178 	}
1179 
1180 	if (!sibling && dead_end_function(file, sym))
1181 		insn->dead_end = true;
1182 }
1183 
1184 static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1185 			  struct symbol *dest, bool sibling)
1186 {
1187 	insn->call_dest = dest;
1188 	if (!dest)
1189 		return;
1190 
1191 	/*
1192 	 * Whatever stack impact regular CALLs have, should be undone
1193 	 * by the RETURN of the called function.
1194 	 *
1195 	 * Annotated intra-function calls retain the stack_ops but
1196 	 * are converted to JUMP, see read_intra_function_calls().
1197 	 */
1198 	remove_insn_ops(insn);
1199 
1200 	annotate_call_site(file, insn, sibling);
1201 }
1202 
1203 static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1204 {
1205 	/*
1206 	 * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1207 	 * so convert them accordingly.
1208 	 */
1209 	switch (insn->type) {
1210 	case INSN_CALL:
1211 		insn->type = INSN_CALL_DYNAMIC;
1212 		break;
1213 	case INSN_JUMP_UNCONDITIONAL:
1214 		insn->type = INSN_JUMP_DYNAMIC;
1215 		break;
1216 	case INSN_JUMP_CONDITIONAL:
1217 		insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1218 		break;
1219 	default:
1220 		return;
1221 	}
1222 
1223 	insn->retpoline_safe = true;
1224 
1225 	/*
1226 	 * Whatever stack impact regular CALLs have, should be undone
1227 	 * by the RETURN of the called function.
1228 	 *
1229 	 * Annotated intra-function calls retain the stack_ops but
1230 	 * are converted to JUMP, see read_intra_function_calls().
1231 	 */
1232 	remove_insn_ops(insn);
1233 
1234 	annotate_call_site(file, insn, false);
1235 }
1236 
1237 static bool same_function(struct instruction *insn1, struct instruction *insn2)
1238 {
1239 	return insn1->func->pfunc == insn2->func->pfunc;
1240 }
1241 
1242 static bool is_first_func_insn(struct instruction *insn)
1243 {
1244 	return insn->offset == insn->func->offset ||
1245 	       (insn->type == INSN_ENDBR &&
1246 		insn->offset == insn->func->offset + insn->len);
1247 }
1248 
1249 /*
1250  * Find the destination instructions for all jumps.
1251  */
1252 static int add_jump_destinations(struct objtool_file *file)
1253 {
1254 	struct instruction *insn;
1255 	struct reloc *reloc;
1256 	struct section *dest_sec;
1257 	unsigned long dest_off;
1258 
1259 	for_each_insn(file, insn) {
1260 		if (!is_static_jump(insn))
1261 			continue;
1262 
1263 		reloc = insn_reloc(file, insn);
1264 		if (!reloc) {
1265 			dest_sec = insn->sec;
1266 			dest_off = arch_jump_destination(insn);
1267 		} else if (reloc->sym->type == STT_SECTION) {
1268 			dest_sec = reloc->sym->sec;
1269 			dest_off = arch_dest_reloc_offset(reloc->addend);
1270 		} else if (reloc->sym->retpoline_thunk) {
1271 			add_retpoline_call(file, insn);
1272 			continue;
1273 		} else if (insn->func) {
1274 			/* internal or external sibling call (with reloc) */
1275 			add_call_dest(file, insn, reloc->sym, true);
1276 			continue;
1277 		} else if (reloc->sym->sec->idx) {
1278 			dest_sec = reloc->sym->sec;
1279 			dest_off = reloc->sym->sym.st_value +
1280 				   arch_dest_reloc_offset(reloc->addend);
1281 		} else {
1282 			/* non-func asm code jumping to another file */
1283 			continue;
1284 		}
1285 
1286 		insn->jump_dest = find_insn(file, dest_sec, dest_off);
1287 		if (!insn->jump_dest) {
1288 
1289 			/*
1290 			 * This is a special case where an alt instruction
1291 			 * jumps past the end of the section.  These are
1292 			 * handled later in handle_group_alt().
1293 			 */
1294 			if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1295 				continue;
1296 
1297 			WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
1298 				  insn->sec, insn->offset, dest_sec->name,
1299 				  dest_off);
1300 			return -1;
1301 		}
1302 
1303 		/*
1304 		 * Cross-function jump.
1305 		 */
1306 		if (insn->func && insn->jump_dest->func &&
1307 		    insn->func != insn->jump_dest->func) {
1308 
1309 			/*
1310 			 * For GCC 8+, create parent/child links for any cold
1311 			 * subfunctions.  This is _mostly_ redundant with a
1312 			 * similar initialization in read_symbols().
1313 			 *
1314 			 * If a function has aliases, we want the *first* such
1315 			 * function in the symbol table to be the subfunction's
1316 			 * parent.  In that case we overwrite the
1317 			 * initialization done in read_symbols().
1318 			 *
1319 			 * However this code can't completely replace the
1320 			 * read_symbols() code because this doesn't detect the
1321 			 * case where the parent function's only reference to a
1322 			 * subfunction is through a jump table.
1323 			 */
1324 			if (!strstr(insn->func->name, ".cold") &&
1325 			    strstr(insn->jump_dest->func->name, ".cold")) {
1326 				insn->func->cfunc = insn->jump_dest->func;
1327 				insn->jump_dest->func->pfunc = insn->func;
1328 
1329 			} else if (!same_function(insn, insn->jump_dest) &&
1330 				   is_first_func_insn(insn->jump_dest)) {
1331 				/* internal sibling call (without reloc) */
1332 				add_call_dest(file, insn, insn->jump_dest->func, true);
1333 			}
1334 		}
1335 	}
1336 
1337 	return 0;
1338 }
1339 
1340 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1341 {
1342 	struct symbol *call_dest;
1343 
1344 	call_dest = find_func_by_offset(sec, offset);
1345 	if (!call_dest)
1346 		call_dest = find_symbol_by_offset(sec, offset);
1347 
1348 	return call_dest;
1349 }
1350 
1351 /*
1352  * Find the destination instructions for all calls.
1353  */
1354 static int add_call_destinations(struct objtool_file *file)
1355 {
1356 	struct instruction *insn;
1357 	unsigned long dest_off;
1358 	struct symbol *dest;
1359 	struct reloc *reloc;
1360 
1361 	for_each_insn(file, insn) {
1362 		if (insn->type != INSN_CALL)
1363 			continue;
1364 
1365 		reloc = insn_reloc(file, insn);
1366 		if (!reloc) {
1367 			dest_off = arch_jump_destination(insn);
1368 			dest = find_call_destination(insn->sec, dest_off);
1369 
1370 			add_call_dest(file, insn, dest, false);
1371 
1372 			if (insn->ignore)
1373 				continue;
1374 
1375 			if (!insn->call_dest) {
1376 				WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);
1377 				return -1;
1378 			}
1379 
1380 			if (insn->func && insn->call_dest->type != STT_FUNC) {
1381 				WARN_FUNC("unsupported call to non-function",
1382 					  insn->sec, insn->offset);
1383 				return -1;
1384 			}
1385 
1386 		} else if (reloc->sym->type == STT_SECTION) {
1387 			dest_off = arch_dest_reloc_offset(reloc->addend);
1388 			dest = find_call_destination(reloc->sym->sec, dest_off);
1389 			if (!dest) {
1390 				WARN_FUNC("can't find call dest symbol at %s+0x%lx",
1391 					  insn->sec, insn->offset,
1392 					  reloc->sym->sec->name,
1393 					  dest_off);
1394 				return -1;
1395 			}
1396 
1397 			add_call_dest(file, insn, dest, false);
1398 
1399 		} else if (reloc->sym->retpoline_thunk) {
1400 			add_retpoline_call(file, insn);
1401 
1402 		} else
1403 			add_call_dest(file, insn, reloc->sym, false);
1404 	}
1405 
1406 	return 0;
1407 }
1408 
1409 /*
1410  * The .alternatives section requires some extra special care over and above
1411  * other special sections because alternatives are patched in place.
1412  */
1413 static int handle_group_alt(struct objtool_file *file,
1414 			    struct special_alt *special_alt,
1415 			    struct instruction *orig_insn,
1416 			    struct instruction **new_insn)
1417 {
1418 	struct instruction *last_orig_insn, *last_new_insn = NULL, *insn, *nop = NULL;
1419 	struct alt_group *orig_alt_group, *new_alt_group;
1420 	unsigned long dest_off;
1421 
1422 
1423 	orig_alt_group = malloc(sizeof(*orig_alt_group));
1424 	if (!orig_alt_group) {
1425 		WARN("malloc failed");
1426 		return -1;
1427 	}
1428 	orig_alt_group->cfi = calloc(special_alt->orig_len,
1429 				     sizeof(struct cfi_state *));
1430 	if (!orig_alt_group->cfi) {
1431 		WARN("calloc failed");
1432 		return -1;
1433 	}
1434 
1435 	last_orig_insn = NULL;
1436 	insn = orig_insn;
1437 	sec_for_each_insn_from(file, insn) {
1438 		if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1439 			break;
1440 
1441 		insn->alt_group = orig_alt_group;
1442 		last_orig_insn = insn;
1443 	}
1444 	orig_alt_group->orig_group = NULL;
1445 	orig_alt_group->first_insn = orig_insn;
1446 	orig_alt_group->last_insn = last_orig_insn;
1447 
1448 
1449 	new_alt_group = malloc(sizeof(*new_alt_group));
1450 	if (!new_alt_group) {
1451 		WARN("malloc failed");
1452 		return -1;
1453 	}
1454 
1455 	if (special_alt->new_len < special_alt->orig_len) {
1456 		/*
1457 		 * Insert a fake nop at the end to make the replacement
1458 		 * alt_group the same size as the original.  This is needed to
1459 		 * allow propagate_alt_cfi() to do its magic.  When the last
1460 		 * instruction affects the stack, the instruction after it (the
1461 		 * nop) will propagate the new state to the shared CFI array.
1462 		 */
1463 		nop = malloc(sizeof(*nop));
1464 		if (!nop) {
1465 			WARN("malloc failed");
1466 			return -1;
1467 		}
1468 		memset(nop, 0, sizeof(*nop));
1469 		INIT_LIST_HEAD(&nop->alts);
1470 		INIT_LIST_HEAD(&nop->stack_ops);
1471 
1472 		nop->sec = special_alt->new_sec;
1473 		nop->offset = special_alt->new_off + special_alt->new_len;
1474 		nop->len = special_alt->orig_len - special_alt->new_len;
1475 		nop->type = INSN_NOP;
1476 		nop->func = orig_insn->func;
1477 		nop->alt_group = new_alt_group;
1478 		nop->ignore = orig_insn->ignore_alts;
1479 	}
1480 
1481 	if (!special_alt->new_len) {
1482 		*new_insn = nop;
1483 		goto end;
1484 	}
1485 
1486 	insn = *new_insn;
1487 	sec_for_each_insn_from(file, insn) {
1488 		struct reloc *alt_reloc;
1489 
1490 		if (insn->offset >= special_alt->new_off + special_alt->new_len)
1491 			break;
1492 
1493 		last_new_insn = insn;
1494 
1495 		insn->ignore = orig_insn->ignore_alts;
1496 		insn->func = orig_insn->func;
1497 		insn->alt_group = new_alt_group;
1498 
1499 		/*
1500 		 * Since alternative replacement code is copy/pasted by the
1501 		 * kernel after applying relocations, generally such code can't
1502 		 * have relative-address relocation references to outside the
1503 		 * .altinstr_replacement section, unless the arch's
1504 		 * alternatives code can adjust the relative offsets
1505 		 * accordingly.
1506 		 */
1507 		alt_reloc = insn_reloc(file, insn);
1508 		if (alt_reloc &&
1509 		    !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1510 
1511 			WARN_FUNC("unsupported relocation in alternatives section",
1512 				  insn->sec, insn->offset);
1513 			return -1;
1514 		}
1515 
1516 		if (!is_static_jump(insn))
1517 			continue;
1518 
1519 		if (!insn->immediate)
1520 			continue;
1521 
1522 		dest_off = arch_jump_destination(insn);
1523 		if (dest_off == special_alt->new_off + special_alt->new_len)
1524 			insn->jump_dest = next_insn_same_sec(file, last_orig_insn);
1525 
1526 		if (!insn->jump_dest) {
1527 			WARN_FUNC("can't find alternative jump destination",
1528 				  insn->sec, insn->offset);
1529 			return -1;
1530 		}
1531 	}
1532 
1533 	if (!last_new_insn) {
1534 		WARN_FUNC("can't find last new alternative instruction",
1535 			  special_alt->new_sec, special_alt->new_off);
1536 		return -1;
1537 	}
1538 
1539 	if (nop)
1540 		list_add(&nop->list, &last_new_insn->list);
1541 end:
1542 	new_alt_group->orig_group = orig_alt_group;
1543 	new_alt_group->first_insn = *new_insn;
1544 	new_alt_group->last_insn = nop ? : last_new_insn;
1545 	new_alt_group->cfi = orig_alt_group->cfi;
1546 	return 0;
1547 }
1548 
1549 /*
1550  * A jump table entry can either convert a nop to a jump or a jump to a nop.
1551  * If the original instruction is a jump, make the alt entry an effective nop
1552  * by just skipping the original instruction.
1553  */
1554 static int handle_jump_alt(struct objtool_file *file,
1555 			   struct special_alt *special_alt,
1556 			   struct instruction *orig_insn,
1557 			   struct instruction **new_insn)
1558 {
1559 	if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1560 	    orig_insn->type != INSN_NOP) {
1561 
1562 		WARN_FUNC("unsupported instruction at jump label",
1563 			  orig_insn->sec, orig_insn->offset);
1564 		return -1;
1565 	}
1566 
1567 	if (special_alt->key_addend & 2) {
1568 		struct reloc *reloc = insn_reloc(file, orig_insn);
1569 
1570 		if (reloc) {
1571 			reloc->type = R_NONE;
1572 			elf_write_reloc(file->elf, reloc);
1573 		}
1574 		elf_write_insn(file->elf, orig_insn->sec,
1575 			       orig_insn->offset, orig_insn->len,
1576 			       arch_nop_insn(orig_insn->len));
1577 		orig_insn->type = INSN_NOP;
1578 	}
1579 
1580 	if (orig_insn->type == INSN_NOP) {
1581 		if (orig_insn->len == 2)
1582 			file->jl_nop_short++;
1583 		else
1584 			file->jl_nop_long++;
1585 
1586 		return 0;
1587 	}
1588 
1589 	if (orig_insn->len == 2)
1590 		file->jl_short++;
1591 	else
1592 		file->jl_long++;
1593 
1594 	*new_insn = list_next_entry(orig_insn, list);
1595 	return 0;
1596 }
1597 
1598 /*
1599  * Read all the special sections which have alternate instructions which can be
1600  * patched in or redirected to at runtime.  Each instruction having alternate
1601  * instruction(s) has them added to its insn->alts list, which will be
1602  * traversed in validate_branch().
1603  */
1604 static int add_special_section_alts(struct objtool_file *file)
1605 {
1606 	struct list_head special_alts;
1607 	struct instruction *orig_insn, *new_insn;
1608 	struct special_alt *special_alt, *tmp;
1609 	struct alternative *alt;
1610 	int ret;
1611 
1612 	ret = special_get_alts(file->elf, &special_alts);
1613 	if (ret)
1614 		return ret;
1615 
1616 	list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1617 
1618 		orig_insn = find_insn(file, special_alt->orig_sec,
1619 				      special_alt->orig_off);
1620 		if (!orig_insn) {
1621 			WARN_FUNC("special: can't find orig instruction",
1622 				  special_alt->orig_sec, special_alt->orig_off);
1623 			ret = -1;
1624 			goto out;
1625 		}
1626 
1627 		new_insn = NULL;
1628 		if (!special_alt->group || special_alt->new_len) {
1629 			new_insn = find_insn(file, special_alt->new_sec,
1630 					     special_alt->new_off);
1631 			if (!new_insn) {
1632 				WARN_FUNC("special: can't find new instruction",
1633 					  special_alt->new_sec,
1634 					  special_alt->new_off);
1635 				ret = -1;
1636 				goto out;
1637 			}
1638 		}
1639 
1640 		if (special_alt->group) {
1641 			if (!special_alt->orig_len) {
1642 				WARN_FUNC("empty alternative entry",
1643 					  orig_insn->sec, orig_insn->offset);
1644 				continue;
1645 			}
1646 
1647 			ret = handle_group_alt(file, special_alt, orig_insn,
1648 					       &new_insn);
1649 			if (ret)
1650 				goto out;
1651 		} else if (special_alt->jump_or_nop) {
1652 			ret = handle_jump_alt(file, special_alt, orig_insn,
1653 					      &new_insn);
1654 			if (ret)
1655 				goto out;
1656 		}
1657 
1658 		alt = malloc(sizeof(*alt));
1659 		if (!alt) {
1660 			WARN("malloc failed");
1661 			ret = -1;
1662 			goto out;
1663 		}
1664 
1665 		alt->insn = new_insn;
1666 		alt->skip_orig = special_alt->skip_orig;
1667 		orig_insn->ignore_alts |= special_alt->skip_alt;
1668 		list_add_tail(&alt->list, &orig_insn->alts);
1669 
1670 		list_del(&special_alt->list);
1671 		free(special_alt);
1672 	}
1673 
1674 	if (stats) {
1675 		printf("jl\\\tNOP\tJMP\n");
1676 		printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
1677 		printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
1678 	}
1679 
1680 out:
1681 	return ret;
1682 }
1683 
1684 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
1685 			    struct reloc *table)
1686 {
1687 	struct reloc *reloc = table;
1688 	struct instruction *dest_insn;
1689 	struct alternative *alt;
1690 	struct symbol *pfunc = insn->func->pfunc;
1691 	unsigned int prev_offset = 0;
1692 
1693 	/*
1694 	 * Each @reloc is a switch table relocation which points to the target
1695 	 * instruction.
1696 	 */
1697 	list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
1698 
1699 		/* Check for the end of the table: */
1700 		if (reloc != table && reloc->jump_table_start)
1701 			break;
1702 
1703 		/* Make sure the table entries are consecutive: */
1704 		if (prev_offset && reloc->offset != prev_offset + 8)
1705 			break;
1706 
1707 		/* Detect function pointers from contiguous objects: */
1708 		if (reloc->sym->sec == pfunc->sec &&
1709 		    reloc->addend == pfunc->offset)
1710 			break;
1711 
1712 		dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
1713 		if (!dest_insn)
1714 			break;
1715 
1716 		/* Make sure the destination is in the same function: */
1717 		if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
1718 			break;
1719 
1720 		alt = malloc(sizeof(*alt));
1721 		if (!alt) {
1722 			WARN("malloc failed");
1723 			return -1;
1724 		}
1725 
1726 		alt->insn = dest_insn;
1727 		list_add_tail(&alt->list, &insn->alts);
1728 		prev_offset = reloc->offset;
1729 	}
1730 
1731 	if (!prev_offset) {
1732 		WARN_FUNC("can't find switch jump table",
1733 			  insn->sec, insn->offset);
1734 		return -1;
1735 	}
1736 
1737 	return 0;
1738 }
1739 
1740 /*
1741  * find_jump_table() - Given a dynamic jump, find the switch jump table
1742  * associated with it.
1743  */
1744 static struct reloc *find_jump_table(struct objtool_file *file,
1745 				      struct symbol *func,
1746 				      struct instruction *insn)
1747 {
1748 	struct reloc *table_reloc;
1749 	struct instruction *dest_insn, *orig_insn = insn;
1750 
1751 	/*
1752 	 * Backward search using the @first_jump_src links, these help avoid
1753 	 * much of the 'in between' code. Which avoids us getting confused by
1754 	 * it.
1755 	 */
1756 	for (;
1757 	     insn && insn->func && insn->func->pfunc == func;
1758 	     insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
1759 
1760 		if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1761 			break;
1762 
1763 		/* allow small jumps within the range */
1764 		if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1765 		    insn->jump_dest &&
1766 		    (insn->jump_dest->offset <= insn->offset ||
1767 		     insn->jump_dest->offset > orig_insn->offset))
1768 		    break;
1769 
1770 		table_reloc = arch_find_switch_table(file, insn);
1771 		if (!table_reloc)
1772 			continue;
1773 		dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
1774 		if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1775 			continue;
1776 
1777 		return table_reloc;
1778 	}
1779 
1780 	return NULL;
1781 }
1782 
1783 /*
1784  * First pass: Mark the head of each jump table so that in the next pass,
1785  * we know when a given jump table ends and the next one starts.
1786  */
1787 static void mark_func_jump_tables(struct objtool_file *file,
1788 				    struct symbol *func)
1789 {
1790 	struct instruction *insn, *last = NULL;
1791 	struct reloc *reloc;
1792 
1793 	func_for_each_insn(file, func, insn) {
1794 		if (!last)
1795 			last = insn;
1796 
1797 		/*
1798 		 * Store back-pointers for unconditional forward jumps such
1799 		 * that find_jump_table() can back-track using those and
1800 		 * avoid some potentially confusing code.
1801 		 */
1802 		if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1803 		    insn->offset > last->offset &&
1804 		    insn->jump_dest->offset > insn->offset &&
1805 		    !insn->jump_dest->first_jump_src) {
1806 
1807 			insn->jump_dest->first_jump_src = insn;
1808 			last = insn->jump_dest;
1809 		}
1810 
1811 		if (insn->type != INSN_JUMP_DYNAMIC)
1812 			continue;
1813 
1814 		reloc = find_jump_table(file, func, insn);
1815 		if (reloc) {
1816 			reloc->jump_table_start = true;
1817 			insn->jump_table = reloc;
1818 		}
1819 	}
1820 }
1821 
1822 static int add_func_jump_tables(struct objtool_file *file,
1823 				  struct symbol *func)
1824 {
1825 	struct instruction *insn;
1826 	int ret;
1827 
1828 	func_for_each_insn(file, func, insn) {
1829 		if (!insn->jump_table)
1830 			continue;
1831 
1832 		ret = add_jump_table(file, insn, insn->jump_table);
1833 		if (ret)
1834 			return ret;
1835 	}
1836 
1837 	return 0;
1838 }
1839 
1840 /*
1841  * For some switch statements, gcc generates a jump table in the .rodata
1842  * section which contains a list of addresses within the function to jump to.
1843  * This finds these jump tables and adds them to the insn->alts lists.
1844  */
1845 static int add_jump_table_alts(struct objtool_file *file)
1846 {
1847 	struct section *sec;
1848 	struct symbol *func;
1849 	int ret;
1850 
1851 	if (!file->rodata)
1852 		return 0;
1853 
1854 	for_each_sec(file, sec) {
1855 		list_for_each_entry(func, &sec->symbol_list, list) {
1856 			if (func->type != STT_FUNC)
1857 				continue;
1858 
1859 			mark_func_jump_tables(file, func);
1860 			ret = add_func_jump_tables(file, func);
1861 			if (ret)
1862 				return ret;
1863 		}
1864 	}
1865 
1866 	return 0;
1867 }
1868 
1869 static void set_func_state(struct cfi_state *state)
1870 {
1871 	state->cfa = initial_func_cfi.cfa;
1872 	memcpy(&state->regs, &initial_func_cfi.regs,
1873 	       CFI_NUM_REGS * sizeof(struct cfi_reg));
1874 	state->stack_size = initial_func_cfi.cfa.offset;
1875 }
1876 
1877 static int read_unwind_hints(struct objtool_file *file)
1878 {
1879 	struct cfi_state cfi = init_cfi;
1880 	struct section *sec, *relocsec;
1881 	struct unwind_hint *hint;
1882 	struct instruction *insn;
1883 	struct reloc *reloc;
1884 	int i;
1885 
1886 	sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1887 	if (!sec)
1888 		return 0;
1889 
1890 	relocsec = sec->reloc;
1891 	if (!relocsec) {
1892 		WARN("missing .rela.discard.unwind_hints section");
1893 		return -1;
1894 	}
1895 
1896 	if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
1897 		WARN("struct unwind_hint size mismatch");
1898 		return -1;
1899 	}
1900 
1901 	file->hints = true;
1902 
1903 	for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
1904 		hint = (struct unwind_hint *)sec->data->d_buf + i;
1905 
1906 		reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
1907 		if (!reloc) {
1908 			WARN("can't find reloc for unwind_hints[%d]", i);
1909 			return -1;
1910 		}
1911 
1912 		insn = find_insn(file, reloc->sym->sec, reloc->addend);
1913 		if (!insn) {
1914 			WARN("can't find insn for unwind_hints[%d]", i);
1915 			return -1;
1916 		}
1917 
1918 		insn->hint = true;
1919 
1920 		if (ibt && hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
1921 			struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
1922 
1923 			if (sym && sym->bind == STB_GLOBAL &&
1924 			    insn->type != INSN_ENDBR && !insn->noendbr) {
1925 				WARN_FUNC("UNWIND_HINT_IRET_REGS without ENDBR",
1926 					  insn->sec, insn->offset);
1927 			}
1928 		}
1929 
1930 		if (hint->type == UNWIND_HINT_TYPE_FUNC) {
1931 			insn->cfi = &func_cfi;
1932 			continue;
1933 		}
1934 
1935 		if (insn->cfi)
1936 			cfi = *(insn->cfi);
1937 
1938 		if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
1939 			WARN_FUNC("unsupported unwind_hint sp base reg %d",
1940 				  insn->sec, insn->offset, hint->sp_reg);
1941 			return -1;
1942 		}
1943 
1944 		cfi.cfa.offset = bswap_if_needed(hint->sp_offset);
1945 		cfi.type = hint->type;
1946 		cfi.end = hint->end;
1947 
1948 		insn->cfi = cfi_hash_find_or_add(&cfi);
1949 	}
1950 
1951 	return 0;
1952 }
1953 
1954 static int read_noendbr_hints(struct objtool_file *file)
1955 {
1956 	struct section *sec;
1957 	struct instruction *insn;
1958 	struct reloc *reloc;
1959 
1960 	sec = find_section_by_name(file->elf, ".rela.discard.noendbr");
1961 	if (!sec)
1962 		return 0;
1963 
1964 	list_for_each_entry(reloc, &sec->reloc_list, list) {
1965 		insn = find_insn(file, reloc->sym->sec, reloc->sym->offset + reloc->addend);
1966 		if (!insn) {
1967 			WARN("bad .discard.noendbr entry");
1968 			return -1;
1969 		}
1970 
1971 		if (insn->type == INSN_ENDBR)
1972 			WARN_FUNC("ANNOTATE_NOENDBR on ENDBR", insn->sec, insn->offset);
1973 
1974 		insn->noendbr = 1;
1975 	}
1976 
1977 	return 0;
1978 }
1979 
1980 static int read_retpoline_hints(struct objtool_file *file)
1981 {
1982 	struct section *sec;
1983 	struct instruction *insn;
1984 	struct reloc *reloc;
1985 
1986 	sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1987 	if (!sec)
1988 		return 0;
1989 
1990 	list_for_each_entry(reloc, &sec->reloc_list, list) {
1991 		if (reloc->sym->type != STT_SECTION) {
1992 			WARN("unexpected relocation symbol type in %s", sec->name);
1993 			return -1;
1994 		}
1995 
1996 		insn = find_insn(file, reloc->sym->sec, reloc->addend);
1997 		if (!insn) {
1998 			WARN("bad .discard.retpoline_safe entry");
1999 			return -1;
2000 		}
2001 
2002 		if (insn->type != INSN_JUMP_DYNAMIC &&
2003 		    insn->type != INSN_CALL_DYNAMIC) {
2004 			WARN_FUNC("retpoline_safe hint not an indirect jump/call",
2005 				  insn->sec, insn->offset);
2006 			return -1;
2007 		}
2008 
2009 		insn->retpoline_safe = true;
2010 	}
2011 
2012 	return 0;
2013 }
2014 
2015 static int read_instr_hints(struct objtool_file *file)
2016 {
2017 	struct section *sec;
2018 	struct instruction *insn;
2019 	struct reloc *reloc;
2020 
2021 	sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2022 	if (!sec)
2023 		return 0;
2024 
2025 	list_for_each_entry(reloc, &sec->reloc_list, list) {
2026 		if (reloc->sym->type != STT_SECTION) {
2027 			WARN("unexpected relocation symbol type in %s", sec->name);
2028 			return -1;
2029 		}
2030 
2031 		insn = find_insn(file, reloc->sym->sec, reloc->addend);
2032 		if (!insn) {
2033 			WARN("bad .discard.instr_end entry");
2034 			return -1;
2035 		}
2036 
2037 		insn->instr--;
2038 	}
2039 
2040 	sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2041 	if (!sec)
2042 		return 0;
2043 
2044 	list_for_each_entry(reloc, &sec->reloc_list, list) {
2045 		if (reloc->sym->type != STT_SECTION) {
2046 			WARN("unexpected relocation symbol type in %s", sec->name);
2047 			return -1;
2048 		}
2049 
2050 		insn = find_insn(file, reloc->sym->sec, reloc->addend);
2051 		if (!insn) {
2052 			WARN("bad .discard.instr_begin entry");
2053 			return -1;
2054 		}
2055 
2056 		insn->instr++;
2057 	}
2058 
2059 	return 0;
2060 }
2061 
2062 static int read_intra_function_calls(struct objtool_file *file)
2063 {
2064 	struct instruction *insn;
2065 	struct section *sec;
2066 	struct reloc *reloc;
2067 
2068 	sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2069 	if (!sec)
2070 		return 0;
2071 
2072 	list_for_each_entry(reloc, &sec->reloc_list, list) {
2073 		unsigned long dest_off;
2074 
2075 		if (reloc->sym->type != STT_SECTION) {
2076 			WARN("unexpected relocation symbol type in %s",
2077 			     sec->name);
2078 			return -1;
2079 		}
2080 
2081 		insn = find_insn(file, reloc->sym->sec, reloc->addend);
2082 		if (!insn) {
2083 			WARN("bad .discard.intra_function_call entry");
2084 			return -1;
2085 		}
2086 
2087 		if (insn->type != INSN_CALL) {
2088 			WARN_FUNC("intra_function_call not a direct call",
2089 				  insn->sec, insn->offset);
2090 			return -1;
2091 		}
2092 
2093 		/*
2094 		 * Treat intra-function CALLs as JMPs, but with a stack_op.
2095 		 * See add_call_destinations(), which strips stack_ops from
2096 		 * normal CALLs.
2097 		 */
2098 		insn->type = INSN_JUMP_UNCONDITIONAL;
2099 
2100 		dest_off = insn->offset + insn->len + insn->immediate;
2101 		insn->jump_dest = find_insn(file, insn->sec, dest_off);
2102 		if (!insn->jump_dest) {
2103 			WARN_FUNC("can't find call dest at %s+0x%lx",
2104 				  insn->sec, insn->offset,
2105 				  insn->sec->name, dest_off);
2106 			return -1;
2107 		}
2108 	}
2109 
2110 	return 0;
2111 }
2112 
2113 /*
2114  * Return true if name matches an instrumentation function, where calls to that
2115  * function from noinstr code can safely be removed, but compilers won't do so.
2116  */
2117 static bool is_profiling_func(const char *name)
2118 {
2119 	/*
2120 	 * Many compilers cannot disable KCOV with a function attribute.
2121 	 */
2122 	if (!strncmp(name, "__sanitizer_cov_", 16))
2123 		return true;
2124 
2125 	/*
2126 	 * Some compilers currently do not remove __tsan_func_entry/exit nor
2127 	 * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2128 	 * the __no_sanitize_thread attribute, remove them. Once the kernel's
2129 	 * minimum Clang version is 14.0, this can be removed.
2130 	 */
2131 	if (!strncmp(name, "__tsan_func_", 12) ||
2132 	    !strcmp(name, "__tsan_atomic_signal_fence"))
2133 		return true;
2134 
2135 	return false;
2136 }
2137 
2138 static int classify_symbols(struct objtool_file *file)
2139 {
2140 	struct section *sec;
2141 	struct symbol *func;
2142 
2143 	for_each_sec(file, sec) {
2144 		list_for_each_entry(func, &sec->symbol_list, list) {
2145 			if (func->bind != STB_GLOBAL)
2146 				continue;
2147 
2148 			if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2149 				     strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2150 				func->static_call_tramp = true;
2151 
2152 			if (arch_is_retpoline(func))
2153 				func->retpoline_thunk = true;
2154 
2155 			if (!strcmp(func->name, "__fentry__"))
2156 				func->fentry = true;
2157 
2158 			if (is_profiling_func(func->name))
2159 				func->profiling_func = true;
2160 		}
2161 	}
2162 
2163 	return 0;
2164 }
2165 
2166 static void mark_rodata(struct objtool_file *file)
2167 {
2168 	struct section *sec;
2169 	bool found = false;
2170 
2171 	/*
2172 	 * Search for the following rodata sections, each of which can
2173 	 * potentially contain jump tables:
2174 	 *
2175 	 * - .rodata: can contain GCC switch tables
2176 	 * - .rodata.<func>: same, if -fdata-sections is being used
2177 	 * - .rodata..c_jump_table: contains C annotated jump tables
2178 	 *
2179 	 * .rodata.str1.* sections are ignored; they don't contain jump tables.
2180 	 */
2181 	for_each_sec(file, sec) {
2182 		if (!strncmp(sec->name, ".rodata", 7) &&
2183 		    !strstr(sec->name, ".str1.")) {
2184 			sec->rodata = true;
2185 			found = true;
2186 		}
2187 	}
2188 
2189 	file->rodata = found;
2190 }
2191 
2192 static int decode_sections(struct objtool_file *file)
2193 {
2194 	int ret;
2195 
2196 	mark_rodata(file);
2197 
2198 	ret = init_pv_ops(file);
2199 	if (ret)
2200 		return ret;
2201 
2202 	ret = decode_instructions(file);
2203 	if (ret)
2204 		return ret;
2205 
2206 	add_ignores(file);
2207 	add_uaccess_safe(file);
2208 
2209 	ret = add_ignore_alternatives(file);
2210 	if (ret)
2211 		return ret;
2212 
2213 	/*
2214 	 * Must be before read_unwind_hints() since that needs insn->noendbr.
2215 	 */
2216 	ret = read_noendbr_hints(file);
2217 	if (ret)
2218 		return ret;
2219 
2220 	/*
2221 	 * Must be before add_{jump_call}_destination.
2222 	 */
2223 	ret = classify_symbols(file);
2224 	if (ret)
2225 		return ret;
2226 
2227 	/*
2228 	 * Must be before add_special_section_alts() as that depends on
2229 	 * jump_dest being set.
2230 	 */
2231 	ret = add_jump_destinations(file);
2232 	if (ret)
2233 		return ret;
2234 
2235 	ret = add_special_section_alts(file);
2236 	if (ret)
2237 		return ret;
2238 
2239 	/*
2240 	 * Must be before add_call_destination(); it changes INSN_CALL to
2241 	 * INSN_JUMP.
2242 	 */
2243 	ret = read_intra_function_calls(file);
2244 	if (ret)
2245 		return ret;
2246 
2247 	ret = add_call_destinations(file);
2248 	if (ret)
2249 		return ret;
2250 
2251 	/*
2252 	 * Must be after add_call_destinations() such that it can override
2253 	 * dead_end_function() marks.
2254 	 */
2255 	ret = add_dead_ends(file);
2256 	if (ret)
2257 		return ret;
2258 
2259 	ret = add_jump_table_alts(file);
2260 	if (ret)
2261 		return ret;
2262 
2263 	ret = read_unwind_hints(file);
2264 	if (ret)
2265 		return ret;
2266 
2267 	ret = read_retpoline_hints(file);
2268 	if (ret)
2269 		return ret;
2270 
2271 	ret = read_instr_hints(file);
2272 	if (ret)
2273 		return ret;
2274 
2275 	return 0;
2276 }
2277 
2278 static bool is_fentry_call(struct instruction *insn)
2279 {
2280 	if (insn->type == INSN_CALL &&
2281 	    insn->call_dest &&
2282 	    insn->call_dest->fentry)
2283 		return true;
2284 
2285 	return false;
2286 }
2287 
2288 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2289 {
2290 	struct cfi_state *cfi = &state->cfi;
2291 	int i;
2292 
2293 	if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2294 		return true;
2295 
2296 	if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2297 		return true;
2298 
2299 	if (cfi->stack_size != initial_func_cfi.cfa.offset)
2300 		return true;
2301 
2302 	for (i = 0; i < CFI_NUM_REGS; i++) {
2303 		if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2304 		    cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2305 			return true;
2306 	}
2307 
2308 	return false;
2309 }
2310 
2311 static bool check_reg_frame_pos(const struct cfi_reg *reg,
2312 				int expected_offset)
2313 {
2314 	return reg->base == CFI_CFA &&
2315 	       reg->offset == expected_offset;
2316 }
2317 
2318 static bool has_valid_stack_frame(struct insn_state *state)
2319 {
2320 	struct cfi_state *cfi = &state->cfi;
2321 
2322 	if (cfi->cfa.base == CFI_BP &&
2323 	    check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2324 	    check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2325 		return true;
2326 
2327 	if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2328 		return true;
2329 
2330 	return false;
2331 }
2332 
2333 static int update_cfi_state_regs(struct instruction *insn,
2334 				  struct cfi_state *cfi,
2335 				  struct stack_op *op)
2336 {
2337 	struct cfi_reg *cfa = &cfi->cfa;
2338 
2339 	if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2340 		return 0;
2341 
2342 	/* push */
2343 	if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2344 		cfa->offset += 8;
2345 
2346 	/* pop */
2347 	if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2348 		cfa->offset -= 8;
2349 
2350 	/* add immediate to sp */
2351 	if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2352 	    op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2353 		cfa->offset -= op->src.offset;
2354 
2355 	return 0;
2356 }
2357 
2358 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2359 {
2360 	if (arch_callee_saved_reg(reg) &&
2361 	    cfi->regs[reg].base == CFI_UNDEFINED) {
2362 		cfi->regs[reg].base = base;
2363 		cfi->regs[reg].offset = offset;
2364 	}
2365 }
2366 
2367 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2368 {
2369 	cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2370 	cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2371 }
2372 
2373 /*
2374  * A note about DRAP stack alignment:
2375  *
2376  * GCC has the concept of a DRAP register, which is used to help keep track of
2377  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
2378  * register.  The typical DRAP pattern is:
2379  *
2380  *   4c 8d 54 24 08		lea    0x8(%rsp),%r10
2381  *   48 83 e4 c0		and    $0xffffffffffffffc0,%rsp
2382  *   41 ff 72 f8		pushq  -0x8(%r10)
2383  *   55				push   %rbp
2384  *   48 89 e5			mov    %rsp,%rbp
2385  *				(more pushes)
2386  *   41 52			push   %r10
2387  *				...
2388  *   41 5a			pop    %r10
2389  *				(more pops)
2390  *   5d				pop    %rbp
2391  *   49 8d 62 f8		lea    -0x8(%r10),%rsp
2392  *   c3				retq
2393  *
2394  * There are some variations in the epilogues, like:
2395  *
2396  *   5b				pop    %rbx
2397  *   41 5a			pop    %r10
2398  *   41 5c			pop    %r12
2399  *   41 5d			pop    %r13
2400  *   41 5e			pop    %r14
2401  *   c9				leaveq
2402  *   49 8d 62 f8		lea    -0x8(%r10),%rsp
2403  *   c3				retq
2404  *
2405  * and:
2406  *
2407  *   4c 8b 55 e8		mov    -0x18(%rbp),%r10
2408  *   48 8b 5d e0		mov    -0x20(%rbp),%rbx
2409  *   4c 8b 65 f0		mov    -0x10(%rbp),%r12
2410  *   4c 8b 6d f8		mov    -0x8(%rbp),%r13
2411  *   c9				leaveq
2412  *   49 8d 62 f8		lea    -0x8(%r10),%rsp
2413  *   c3				retq
2414  *
2415  * Sometimes r13 is used as the DRAP register, in which case it's saved and
2416  * restored beforehand:
2417  *
2418  *   41 55			push   %r13
2419  *   4c 8d 6c 24 10		lea    0x10(%rsp),%r13
2420  *   48 83 e4 f0		and    $0xfffffffffffffff0,%rsp
2421  *				...
2422  *   49 8d 65 f0		lea    -0x10(%r13),%rsp
2423  *   41 5d			pop    %r13
2424  *   c3				retq
2425  */
2426 static int update_cfi_state(struct instruction *insn,
2427 			    struct instruction *next_insn,
2428 			    struct cfi_state *cfi, struct stack_op *op)
2429 {
2430 	struct cfi_reg *cfa = &cfi->cfa;
2431 	struct cfi_reg *regs = cfi->regs;
2432 
2433 	/* stack operations don't make sense with an undefined CFA */
2434 	if (cfa->base == CFI_UNDEFINED) {
2435 		if (insn->func) {
2436 			WARN_FUNC("undefined stack state", insn->sec, insn->offset);
2437 			return -1;
2438 		}
2439 		return 0;
2440 	}
2441 
2442 	if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2443 	    cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2444 		return update_cfi_state_regs(insn, cfi, op);
2445 
2446 	switch (op->dest.type) {
2447 
2448 	case OP_DEST_REG:
2449 		switch (op->src.type) {
2450 
2451 		case OP_SRC_REG:
2452 			if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2453 			    cfa->base == CFI_SP &&
2454 			    check_reg_frame_pos(&regs[CFI_BP], -cfa->offset)) {
2455 
2456 				/* mov %rsp, %rbp */
2457 				cfa->base = op->dest.reg;
2458 				cfi->bp_scratch = false;
2459 			}
2460 
2461 			else if (op->src.reg == CFI_SP &&
2462 				 op->dest.reg == CFI_BP && cfi->drap) {
2463 
2464 				/* drap: mov %rsp, %rbp */
2465 				regs[CFI_BP].base = CFI_BP;
2466 				regs[CFI_BP].offset = -cfi->stack_size;
2467 				cfi->bp_scratch = false;
2468 			}
2469 
2470 			else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2471 
2472 				/*
2473 				 * mov %rsp, %reg
2474 				 *
2475 				 * This is needed for the rare case where GCC
2476 				 * does:
2477 				 *
2478 				 *   mov    %rsp, %rax
2479 				 *   ...
2480 				 *   mov    %rax, %rsp
2481 				 */
2482 				cfi->vals[op->dest.reg].base = CFI_CFA;
2483 				cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2484 			}
2485 
2486 			else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2487 				 (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2488 
2489 				/*
2490 				 * mov %rbp, %rsp
2491 				 *
2492 				 * Restore the original stack pointer (Clang).
2493 				 */
2494 				cfi->stack_size = -cfi->regs[CFI_BP].offset;
2495 			}
2496 
2497 			else if (op->dest.reg == cfa->base) {
2498 
2499 				/* mov %reg, %rsp */
2500 				if (cfa->base == CFI_SP &&
2501 				    cfi->vals[op->src.reg].base == CFI_CFA) {
2502 
2503 					/*
2504 					 * This is needed for the rare case
2505 					 * where GCC does something dumb like:
2506 					 *
2507 					 *   lea    0x8(%rsp), %rcx
2508 					 *   ...
2509 					 *   mov    %rcx, %rsp
2510 					 */
2511 					cfa->offset = -cfi->vals[op->src.reg].offset;
2512 					cfi->stack_size = cfa->offset;
2513 
2514 				} else if (cfa->base == CFI_SP &&
2515 					   cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2516 					   cfi->vals[op->src.reg].offset == cfa->offset) {
2517 
2518 					/*
2519 					 * Stack swizzle:
2520 					 *
2521 					 * 1: mov %rsp, (%[tos])
2522 					 * 2: mov %[tos], %rsp
2523 					 *    ...
2524 					 * 3: pop %rsp
2525 					 *
2526 					 * Where:
2527 					 *
2528 					 * 1 - places a pointer to the previous
2529 					 *     stack at the Top-of-Stack of the
2530 					 *     new stack.
2531 					 *
2532 					 * 2 - switches to the new stack.
2533 					 *
2534 					 * 3 - pops the Top-of-Stack to restore
2535 					 *     the original stack.
2536 					 *
2537 					 * Note: we set base to SP_INDIRECT
2538 					 * here and preserve offset. Therefore
2539 					 * when the unwinder reaches ToS it
2540 					 * will dereference SP and then add the
2541 					 * offset to find the next frame, IOW:
2542 					 * (%rsp) + offset.
2543 					 */
2544 					cfa->base = CFI_SP_INDIRECT;
2545 
2546 				} else {
2547 					cfa->base = CFI_UNDEFINED;
2548 					cfa->offset = 0;
2549 				}
2550 			}
2551 
2552 			else if (op->dest.reg == CFI_SP &&
2553 				 cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2554 				 cfi->vals[op->src.reg].offset == cfa->offset) {
2555 
2556 				/*
2557 				 * The same stack swizzle case 2) as above. But
2558 				 * because we can't change cfa->base, case 3)
2559 				 * will become a regular POP. Pretend we're a
2560 				 * PUSH so things don't go unbalanced.
2561 				 */
2562 				cfi->stack_size += 8;
2563 			}
2564 
2565 
2566 			break;
2567 
2568 		case OP_SRC_ADD:
2569 			if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2570 
2571 				/* add imm, %rsp */
2572 				cfi->stack_size -= op->src.offset;
2573 				if (cfa->base == CFI_SP)
2574 					cfa->offset -= op->src.offset;
2575 				break;
2576 			}
2577 
2578 			if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2579 
2580 				/* lea disp(%rbp), %rsp */
2581 				cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2582 				break;
2583 			}
2584 
2585 			if (!cfi->drap && op->src.reg == CFI_SP &&
2586 			    op->dest.reg == CFI_BP && cfa->base == CFI_SP &&
2587 			    check_reg_frame_pos(&regs[CFI_BP], -cfa->offset + op->src.offset)) {
2588 
2589 				/* lea disp(%rsp), %rbp */
2590 				cfa->base = CFI_BP;
2591 				cfa->offset -= op->src.offset;
2592 				cfi->bp_scratch = false;
2593 				break;
2594 			}
2595 
2596 			if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2597 
2598 				/* drap: lea disp(%rsp), %drap */
2599 				cfi->drap_reg = op->dest.reg;
2600 
2601 				/*
2602 				 * lea disp(%rsp), %reg
2603 				 *
2604 				 * This is needed for the rare case where GCC
2605 				 * does something dumb like:
2606 				 *
2607 				 *   lea    0x8(%rsp), %rcx
2608 				 *   ...
2609 				 *   mov    %rcx, %rsp
2610 				 */
2611 				cfi->vals[op->dest.reg].base = CFI_CFA;
2612 				cfi->vals[op->dest.reg].offset = \
2613 					-cfi->stack_size + op->src.offset;
2614 
2615 				break;
2616 			}
2617 
2618 			if (cfi->drap && op->dest.reg == CFI_SP &&
2619 			    op->src.reg == cfi->drap_reg) {
2620 
2621 				 /* drap: lea disp(%drap), %rsp */
2622 				cfa->base = CFI_SP;
2623 				cfa->offset = cfi->stack_size = -op->src.offset;
2624 				cfi->drap_reg = CFI_UNDEFINED;
2625 				cfi->drap = false;
2626 				break;
2627 			}
2628 
2629 			if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
2630 				WARN_FUNC("unsupported stack register modification",
2631 					  insn->sec, insn->offset);
2632 				return -1;
2633 			}
2634 
2635 			break;
2636 
2637 		case OP_SRC_AND:
2638 			if (op->dest.reg != CFI_SP ||
2639 			    (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
2640 			    (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
2641 				WARN_FUNC("unsupported stack pointer realignment",
2642 					  insn->sec, insn->offset);
2643 				return -1;
2644 			}
2645 
2646 			if (cfi->drap_reg != CFI_UNDEFINED) {
2647 				/* drap: and imm, %rsp */
2648 				cfa->base = cfi->drap_reg;
2649 				cfa->offset = cfi->stack_size = 0;
2650 				cfi->drap = true;
2651 			}
2652 
2653 			/*
2654 			 * Older versions of GCC (4.8ish) realign the stack
2655 			 * without DRAP, with a frame pointer.
2656 			 */
2657 
2658 			break;
2659 
2660 		case OP_SRC_POP:
2661 		case OP_SRC_POPF:
2662 			if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
2663 
2664 				/* pop %rsp; # restore from a stack swizzle */
2665 				cfa->base = CFI_SP;
2666 				break;
2667 			}
2668 
2669 			if (!cfi->drap && op->dest.reg == cfa->base) {
2670 
2671 				/* pop %rbp */
2672 				cfa->base = CFI_SP;
2673 			}
2674 
2675 			if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
2676 			    op->dest.reg == cfi->drap_reg &&
2677 			    cfi->drap_offset == -cfi->stack_size) {
2678 
2679 				/* drap: pop %drap */
2680 				cfa->base = cfi->drap_reg;
2681 				cfa->offset = 0;
2682 				cfi->drap_offset = -1;
2683 
2684 			} else if (cfi->stack_size == -regs[op->dest.reg].offset) {
2685 
2686 				/* pop %reg */
2687 				restore_reg(cfi, op->dest.reg);
2688 			}
2689 
2690 			cfi->stack_size -= 8;
2691 			if (cfa->base == CFI_SP)
2692 				cfa->offset -= 8;
2693 
2694 			break;
2695 
2696 		case OP_SRC_REG_INDIRECT:
2697 			if (!cfi->drap && op->dest.reg == cfa->base &&
2698 			    op->dest.reg == CFI_BP) {
2699 
2700 				/* mov disp(%rsp), %rbp */
2701 				cfa->base = CFI_SP;
2702 				cfa->offset = cfi->stack_size;
2703 			}
2704 
2705 			if (cfi->drap && op->src.reg == CFI_BP &&
2706 			    op->src.offset == cfi->drap_offset) {
2707 
2708 				/* drap: mov disp(%rbp), %drap */
2709 				cfa->base = cfi->drap_reg;
2710 				cfa->offset = 0;
2711 				cfi->drap_offset = -1;
2712 			}
2713 
2714 			if (cfi->drap && op->src.reg == CFI_BP &&
2715 			    op->src.offset == regs[op->dest.reg].offset) {
2716 
2717 				/* drap: mov disp(%rbp), %reg */
2718 				restore_reg(cfi, op->dest.reg);
2719 
2720 			} else if (op->src.reg == cfa->base &&
2721 			    op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
2722 
2723 				/* mov disp(%rbp), %reg */
2724 				/* mov disp(%rsp), %reg */
2725 				restore_reg(cfi, op->dest.reg);
2726 
2727 			} else if (op->src.reg == CFI_SP &&
2728 				   op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
2729 
2730 				/* mov disp(%rsp), %reg */
2731 				restore_reg(cfi, op->dest.reg);
2732 			}
2733 
2734 			break;
2735 
2736 		default:
2737 			WARN_FUNC("unknown stack-related instruction",
2738 				  insn->sec, insn->offset);
2739 			return -1;
2740 		}
2741 
2742 		break;
2743 
2744 	case OP_DEST_PUSH:
2745 	case OP_DEST_PUSHF:
2746 		cfi->stack_size += 8;
2747 		if (cfa->base == CFI_SP)
2748 			cfa->offset += 8;
2749 
2750 		if (op->src.type != OP_SRC_REG)
2751 			break;
2752 
2753 		if (cfi->drap) {
2754 			if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2755 
2756 				/* drap: push %drap */
2757 				cfa->base = CFI_BP_INDIRECT;
2758 				cfa->offset = -cfi->stack_size;
2759 
2760 				/* save drap so we know when to restore it */
2761 				cfi->drap_offset = -cfi->stack_size;
2762 
2763 			} else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
2764 
2765 				/* drap: push %rbp */
2766 				cfi->stack_size = 0;
2767 
2768 			} else {
2769 
2770 				/* drap: push %reg */
2771 				save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
2772 			}
2773 
2774 		} else {
2775 
2776 			/* push %reg */
2777 			save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
2778 		}
2779 
2780 		/* detect when asm code uses rbp as a scratch register */
2781 		if (!no_fp && insn->func && op->src.reg == CFI_BP &&
2782 		    cfa->base != CFI_BP)
2783 			cfi->bp_scratch = true;
2784 		break;
2785 
2786 	case OP_DEST_REG_INDIRECT:
2787 
2788 		if (cfi->drap) {
2789 			if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2790 
2791 				/* drap: mov %drap, disp(%rbp) */
2792 				cfa->base = CFI_BP_INDIRECT;
2793 				cfa->offset = op->dest.offset;
2794 
2795 				/* save drap offset so we know when to restore it */
2796 				cfi->drap_offset = op->dest.offset;
2797 			} else {
2798 
2799 				/* drap: mov reg, disp(%rbp) */
2800 				save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
2801 			}
2802 
2803 		} else if (op->dest.reg == cfa->base) {
2804 
2805 			/* mov reg, disp(%rbp) */
2806 			/* mov reg, disp(%rsp) */
2807 			save_reg(cfi, op->src.reg, CFI_CFA,
2808 				 op->dest.offset - cfi->cfa.offset);
2809 
2810 		} else if (op->dest.reg == CFI_SP) {
2811 
2812 			/* mov reg, disp(%rsp) */
2813 			save_reg(cfi, op->src.reg, CFI_CFA,
2814 				 op->dest.offset - cfi->stack_size);
2815 
2816 		} else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
2817 
2818 			/* mov %rsp, (%reg); # setup a stack swizzle. */
2819 			cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
2820 			cfi->vals[op->dest.reg].offset = cfa->offset;
2821 		}
2822 
2823 		break;
2824 
2825 	case OP_DEST_MEM:
2826 		if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
2827 			WARN_FUNC("unknown stack-related memory operation",
2828 				  insn->sec, insn->offset);
2829 			return -1;
2830 		}
2831 
2832 		/* pop mem */
2833 		cfi->stack_size -= 8;
2834 		if (cfa->base == CFI_SP)
2835 			cfa->offset -= 8;
2836 
2837 		break;
2838 
2839 	default:
2840 		WARN_FUNC("unknown stack-related instruction",
2841 			  insn->sec, insn->offset);
2842 		return -1;
2843 	}
2844 
2845 	return 0;
2846 }
2847 
2848 /*
2849  * The stack layouts of alternatives instructions can sometimes diverge when
2850  * they have stack modifications.  That's fine as long as the potential stack
2851  * layouts don't conflict at any given potential instruction boundary.
2852  *
2853  * Flatten the CFIs of the different alternative code streams (both original
2854  * and replacement) into a single shared CFI array which can be used to detect
2855  * conflicts and nicely feed a linear array of ORC entries to the unwinder.
2856  */
2857 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
2858 {
2859 	struct cfi_state **alt_cfi;
2860 	int group_off;
2861 
2862 	if (!insn->alt_group)
2863 		return 0;
2864 
2865 	if (!insn->cfi) {
2866 		WARN("CFI missing");
2867 		return -1;
2868 	}
2869 
2870 	alt_cfi = insn->alt_group->cfi;
2871 	group_off = insn->offset - insn->alt_group->first_insn->offset;
2872 
2873 	if (!alt_cfi[group_off]) {
2874 		alt_cfi[group_off] = insn->cfi;
2875 	} else {
2876 		if (cficmp(alt_cfi[group_off], insn->cfi)) {
2877 			WARN_FUNC("stack layout conflict in alternatives",
2878 				  insn->sec, insn->offset);
2879 			return -1;
2880 		}
2881 	}
2882 
2883 	return 0;
2884 }
2885 
2886 static int handle_insn_ops(struct instruction *insn,
2887 			   struct instruction *next_insn,
2888 			   struct insn_state *state)
2889 {
2890 	struct stack_op *op;
2891 
2892 	list_for_each_entry(op, &insn->stack_ops, list) {
2893 
2894 		if (update_cfi_state(insn, next_insn, &state->cfi, op))
2895 			return 1;
2896 
2897 		if (!insn->alt_group)
2898 			continue;
2899 
2900 		if (op->dest.type == OP_DEST_PUSHF) {
2901 			if (!state->uaccess_stack) {
2902 				state->uaccess_stack = 1;
2903 			} else if (state->uaccess_stack >> 31) {
2904 				WARN_FUNC("PUSHF stack exhausted",
2905 					  insn->sec, insn->offset);
2906 				return 1;
2907 			}
2908 			state->uaccess_stack <<= 1;
2909 			state->uaccess_stack  |= state->uaccess;
2910 		}
2911 
2912 		if (op->src.type == OP_SRC_POPF) {
2913 			if (state->uaccess_stack) {
2914 				state->uaccess = state->uaccess_stack & 1;
2915 				state->uaccess_stack >>= 1;
2916 				if (state->uaccess_stack == 1)
2917 					state->uaccess_stack = 0;
2918 			}
2919 		}
2920 	}
2921 
2922 	return 0;
2923 }
2924 
2925 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
2926 {
2927 	struct cfi_state *cfi1 = insn->cfi;
2928 	int i;
2929 
2930 	if (!cfi1) {
2931 		WARN("CFI missing");
2932 		return false;
2933 	}
2934 
2935 	if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
2936 
2937 		WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
2938 			  insn->sec, insn->offset,
2939 			  cfi1->cfa.base, cfi1->cfa.offset,
2940 			  cfi2->cfa.base, cfi2->cfa.offset);
2941 
2942 	} else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
2943 		for (i = 0; i < CFI_NUM_REGS; i++) {
2944 			if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
2945 				    sizeof(struct cfi_reg)))
2946 				continue;
2947 
2948 			WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
2949 				  insn->sec, insn->offset,
2950 				  i, cfi1->regs[i].base, cfi1->regs[i].offset,
2951 				  i, cfi2->regs[i].base, cfi2->regs[i].offset);
2952 			break;
2953 		}
2954 
2955 	} else if (cfi1->type != cfi2->type) {
2956 
2957 		WARN_FUNC("stack state mismatch: type1=%d type2=%d",
2958 			  insn->sec, insn->offset, cfi1->type, cfi2->type);
2959 
2960 	} else if (cfi1->drap != cfi2->drap ||
2961 		   (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
2962 		   (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
2963 
2964 		WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
2965 			  insn->sec, insn->offset,
2966 			  cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
2967 			  cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
2968 
2969 	} else
2970 		return true;
2971 
2972 	return false;
2973 }
2974 
2975 static inline bool func_uaccess_safe(struct symbol *func)
2976 {
2977 	if (func)
2978 		return func->uaccess_safe;
2979 
2980 	return false;
2981 }
2982 
2983 static inline const char *call_dest_name(struct instruction *insn)
2984 {
2985 	static char pvname[19];
2986 	struct reloc *rel;
2987 	int idx;
2988 
2989 	if (insn->call_dest)
2990 		return insn->call_dest->name;
2991 
2992 	rel = insn_reloc(NULL, insn);
2993 	if (rel && !strcmp(rel->sym->name, "pv_ops")) {
2994 		idx = (rel->addend / sizeof(void *));
2995 		snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
2996 		return pvname;
2997 	}
2998 
2999 	return "{dynamic}";
3000 }
3001 
3002 static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3003 {
3004 	struct symbol *target;
3005 	struct reloc *rel;
3006 	int idx;
3007 
3008 	rel = insn_reloc(file, insn);
3009 	if (!rel || strcmp(rel->sym->name, "pv_ops"))
3010 		return false;
3011 
3012 	idx = (arch_dest_reloc_offset(rel->addend) / sizeof(void *));
3013 
3014 	if (file->pv_ops[idx].clean)
3015 		return true;
3016 
3017 	file->pv_ops[idx].clean = true;
3018 
3019 	list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3020 		if (!target->sec->noinstr) {
3021 			WARN("pv_ops[%d]: %s", idx, target->name);
3022 			file->pv_ops[idx].clean = false;
3023 		}
3024 	}
3025 
3026 	return file->pv_ops[idx].clean;
3027 }
3028 
3029 static inline bool noinstr_call_dest(struct objtool_file *file,
3030 				     struct instruction *insn,
3031 				     struct symbol *func)
3032 {
3033 	/*
3034 	 * We can't deal with indirect function calls at present;
3035 	 * assume they're instrumented.
3036 	 */
3037 	if (!func) {
3038 		if (file->pv_ops)
3039 			return pv_call_dest(file, insn);
3040 
3041 		return false;
3042 	}
3043 
3044 	/*
3045 	 * If the symbol is from a noinstr section; we good.
3046 	 */
3047 	if (func->sec->noinstr)
3048 		return true;
3049 
3050 	/*
3051 	 * The __ubsan_handle_*() calls are like WARN(), they only happen when
3052 	 * something 'BAD' happened. At the risk of taking the machine down,
3053 	 * let them proceed to get the message out.
3054 	 */
3055 	if (!strncmp(func->name, "__ubsan_handle_", 15))
3056 		return true;
3057 
3058 	return false;
3059 }
3060 
3061 static int validate_call(struct objtool_file *file,
3062 			 struct instruction *insn,
3063 			 struct insn_state *state)
3064 {
3065 	if (state->noinstr && state->instr <= 0 &&
3066 	    !noinstr_call_dest(file, insn, insn->call_dest)) {
3067 		WARN_FUNC("call to %s() leaves .noinstr.text section",
3068 				insn->sec, insn->offset, call_dest_name(insn));
3069 		return 1;
3070 	}
3071 
3072 	if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
3073 		WARN_FUNC("call to %s() with UACCESS enabled",
3074 				insn->sec, insn->offset, call_dest_name(insn));
3075 		return 1;
3076 	}
3077 
3078 	if (state->df) {
3079 		WARN_FUNC("call to %s() with DF set",
3080 				insn->sec, insn->offset, call_dest_name(insn));
3081 		return 1;
3082 	}
3083 
3084 	return 0;
3085 }
3086 
3087 static int validate_sibling_call(struct objtool_file *file,
3088 				 struct instruction *insn,
3089 				 struct insn_state *state)
3090 {
3091 	if (has_modified_stack_frame(insn, state)) {
3092 		WARN_FUNC("sibling call from callable instruction with modified stack frame",
3093 				insn->sec, insn->offset);
3094 		return 1;
3095 	}
3096 
3097 	return validate_call(file, insn, state);
3098 }
3099 
3100 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3101 {
3102 	if (state->noinstr && state->instr > 0) {
3103 		WARN_FUNC("return with instrumentation enabled",
3104 			  insn->sec, insn->offset);
3105 		return 1;
3106 	}
3107 
3108 	if (state->uaccess && !func_uaccess_safe(func)) {
3109 		WARN_FUNC("return with UACCESS enabled",
3110 			  insn->sec, insn->offset);
3111 		return 1;
3112 	}
3113 
3114 	if (!state->uaccess && func_uaccess_safe(func)) {
3115 		WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
3116 			  insn->sec, insn->offset);
3117 		return 1;
3118 	}
3119 
3120 	if (state->df) {
3121 		WARN_FUNC("return with DF set",
3122 			  insn->sec, insn->offset);
3123 		return 1;
3124 	}
3125 
3126 	if (func && has_modified_stack_frame(insn, state)) {
3127 		WARN_FUNC("return with modified stack frame",
3128 			  insn->sec, insn->offset);
3129 		return 1;
3130 	}
3131 
3132 	if (state->cfi.bp_scratch) {
3133 		WARN_FUNC("BP used as a scratch register",
3134 			  insn->sec, insn->offset);
3135 		return 1;
3136 	}
3137 
3138 	return 0;
3139 }
3140 
3141 static struct instruction *next_insn_to_validate(struct objtool_file *file,
3142 						 struct instruction *insn)
3143 {
3144 	struct alt_group *alt_group = insn->alt_group;
3145 
3146 	/*
3147 	 * Simulate the fact that alternatives are patched in-place.  When the
3148 	 * end of a replacement alt_group is reached, redirect objtool flow to
3149 	 * the end of the original alt_group.
3150 	 */
3151 	if (alt_group && insn == alt_group->last_insn && alt_group->orig_group)
3152 		return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3153 
3154 	return next_insn_same_sec(file, insn);
3155 }
3156 
3157 static struct instruction *
3158 validate_ibt_reloc(struct objtool_file *file, struct reloc *reloc)
3159 {
3160 	struct instruction *dest;
3161 	struct section *sec;
3162 	unsigned long off;
3163 
3164 	sec = reloc->sym->sec;
3165 	off = reloc->sym->offset;
3166 
3167 	if ((reloc->sec->base->sh.sh_flags & SHF_EXECINSTR) &&
3168 	    (reloc->type == R_X86_64_PC32 || reloc->type == R_X86_64_PLT32))
3169 		off += arch_dest_reloc_offset(reloc->addend);
3170 	else
3171 		off += reloc->addend;
3172 
3173 	dest = find_insn(file, sec, off);
3174 	if (!dest)
3175 		return NULL;
3176 
3177 	if (dest->type == INSN_ENDBR) {
3178 		if (!list_empty(&dest->call_node))
3179 			list_del_init(&dest->call_node);
3180 
3181 		return NULL;
3182 	}
3183 
3184 	if (reloc->sym->static_call_tramp)
3185 		return NULL;
3186 
3187 	return dest;
3188 }
3189 
3190 static void warn_noendbr(const char *msg, struct section *sec, unsigned long offset,
3191 			 struct instruction *dest)
3192 {
3193 	WARN_FUNC("%srelocation to !ENDBR: %s+0x%lx", sec, offset, msg,
3194 		  dest->func ? dest->func->name : dest->sec->name,
3195 		  dest->func ? dest->offset - dest->func->offset : dest->offset);
3196 }
3197 
3198 static void validate_ibt_dest(struct objtool_file *file, struct instruction *insn,
3199 			      struct instruction *dest)
3200 {
3201 	if (dest->func && dest->func == insn->func) {
3202 		/*
3203 		 * Anything from->to self is either _THIS_IP_ or IRET-to-self.
3204 		 *
3205 		 * There is no sane way to annotate _THIS_IP_ since the compiler treats the
3206 		 * relocation as a constant and is happy to fold in offsets, skewing any
3207 		 * annotation we do, leading to vast amounts of false-positives.
3208 		 *
3209 		 * There's also compiler generated _THIS_IP_ through KCOV and
3210 		 * such which we have no hope of annotating.
3211 		 *
3212 		 * As such, blanket accept self-references without issue.
3213 		 */
3214 		return;
3215 	}
3216 
3217 	if (dest->noendbr)
3218 		return;
3219 
3220 	warn_noendbr("", insn->sec, insn->offset, dest);
3221 }
3222 
3223 static void validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
3224 {
3225 	struct instruction *dest;
3226 	struct reloc *reloc;
3227 
3228 	switch (insn->type) {
3229 	case INSN_CALL:
3230 	case INSN_CALL_DYNAMIC:
3231 	case INSN_JUMP_CONDITIONAL:
3232 	case INSN_JUMP_UNCONDITIONAL:
3233 	case INSN_JUMP_DYNAMIC:
3234 	case INSN_JUMP_DYNAMIC_CONDITIONAL:
3235 	case INSN_RETURN:
3236 		/*
3237 		 * We're looking for code references setting up indirect code
3238 		 * flow. As such, ignore direct code flow and the actual
3239 		 * dynamic branches.
3240 		 */
3241 		return;
3242 
3243 	case INSN_NOP:
3244 		/*
3245 		 * handle_group_alt() will create INSN_NOP instruction that
3246 		 * don't belong to any section, ignore all NOP since they won't
3247 		 * carry a (useful) relocation anyway.
3248 		 */
3249 		return;
3250 
3251 	default:
3252 		break;
3253 	}
3254 
3255 	for (reloc = insn_reloc(file, insn);
3256 	     reloc;
3257 	     reloc = find_reloc_by_dest_range(file->elf, insn->sec,
3258 					      reloc->offset + 1,
3259 					      (insn->offset + insn->len) - (reloc->offset + 1))) {
3260 		dest = validate_ibt_reloc(file, reloc);
3261 		if (dest)
3262 			validate_ibt_dest(file, insn, dest);
3263 	}
3264 }
3265 
3266 /*
3267  * Follow the branch starting at the given instruction, and recursively follow
3268  * any other branches (jumps).  Meanwhile, track the frame pointer state at
3269  * each instruction and validate all the rules described in
3270  * tools/objtool/Documentation/stack-validation.txt.
3271  */
3272 static int validate_branch(struct objtool_file *file, struct symbol *func,
3273 			   struct instruction *insn, struct insn_state state)
3274 {
3275 	struct alternative *alt;
3276 	struct instruction *next_insn, *prev_insn = NULL;
3277 	struct section *sec;
3278 	u8 visited;
3279 	int ret;
3280 
3281 	sec = insn->sec;
3282 
3283 	while (1) {
3284 		next_insn = next_insn_to_validate(file, insn);
3285 
3286 		if (file->c_file && func && insn->func && func != insn->func->pfunc) {
3287 			WARN("%s() falls through to next function %s()",
3288 			     func->name, insn->func->name);
3289 			return 1;
3290 		}
3291 
3292 		if (func && insn->ignore) {
3293 			WARN_FUNC("BUG: why am I validating an ignored function?",
3294 				  sec, insn->offset);
3295 			return 1;
3296 		}
3297 
3298 		visited = 1 << state.uaccess;
3299 		if (insn->visited) {
3300 			if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3301 				return 1;
3302 
3303 			if (insn->visited & visited)
3304 				return 0;
3305 		} else {
3306 			nr_insns_visited++;
3307 		}
3308 
3309 		if (state.noinstr)
3310 			state.instr += insn->instr;
3311 
3312 		if (insn->hint) {
3313 			state.cfi = *insn->cfi;
3314 		} else {
3315 			/* XXX track if we actually changed state.cfi */
3316 
3317 			if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3318 				insn->cfi = prev_insn->cfi;
3319 				nr_cfi_reused++;
3320 			} else {
3321 				insn->cfi = cfi_hash_find_or_add(&state.cfi);
3322 			}
3323 		}
3324 
3325 		insn->visited |= visited;
3326 
3327 		if (propagate_alt_cfi(file, insn))
3328 			return 1;
3329 
3330 		if (!insn->ignore_alts && !list_empty(&insn->alts)) {
3331 			bool skip_orig = false;
3332 
3333 			list_for_each_entry(alt, &insn->alts, list) {
3334 				if (alt->skip_orig)
3335 					skip_orig = true;
3336 
3337 				ret = validate_branch(file, func, alt->insn, state);
3338 				if (ret) {
3339 					if (backtrace)
3340 						BT_FUNC("(alt)", insn);
3341 					return ret;
3342 				}
3343 			}
3344 
3345 			if (skip_orig)
3346 				return 0;
3347 		}
3348 
3349 		if (handle_insn_ops(insn, next_insn, &state))
3350 			return 1;
3351 
3352 		switch (insn->type) {
3353 
3354 		case INSN_RETURN:
3355 			if (sls && !insn->retpoline_safe &&
3356 			    next_insn && next_insn->type != INSN_TRAP) {
3357 				WARN_FUNC("missing int3 after ret",
3358 					  insn->sec, insn->offset);
3359 			}
3360 			return validate_return(func, insn, &state);
3361 
3362 		case INSN_CALL:
3363 		case INSN_CALL_DYNAMIC:
3364 			ret = validate_call(file, insn, &state);
3365 			if (ret)
3366 				return ret;
3367 
3368 			if (!no_fp && func && !is_fentry_call(insn) &&
3369 			    !has_valid_stack_frame(&state)) {
3370 				WARN_FUNC("call without frame pointer save/setup",
3371 					  sec, insn->offset);
3372 				return 1;
3373 			}
3374 
3375 			if (insn->dead_end)
3376 				return 0;
3377 
3378 			break;
3379 
3380 		case INSN_JUMP_CONDITIONAL:
3381 		case INSN_JUMP_UNCONDITIONAL:
3382 			if (is_sibling_call(insn)) {
3383 				ret = validate_sibling_call(file, insn, &state);
3384 				if (ret)
3385 					return ret;
3386 
3387 			} else if (insn->jump_dest) {
3388 				ret = validate_branch(file, func,
3389 						      insn->jump_dest, state);
3390 				if (ret) {
3391 					if (backtrace)
3392 						BT_FUNC("(branch)", insn);
3393 					return ret;
3394 				}
3395 			}
3396 
3397 			if (insn->type == INSN_JUMP_UNCONDITIONAL)
3398 				return 0;
3399 
3400 			break;
3401 
3402 		case INSN_JUMP_DYNAMIC:
3403 			if (sls && !insn->retpoline_safe &&
3404 			    next_insn && next_insn->type != INSN_TRAP) {
3405 				WARN_FUNC("missing int3 after indirect jump",
3406 					  insn->sec, insn->offset);
3407 			}
3408 
3409 			/* fallthrough */
3410 		case INSN_JUMP_DYNAMIC_CONDITIONAL:
3411 			if (is_sibling_call(insn)) {
3412 				ret = validate_sibling_call(file, insn, &state);
3413 				if (ret)
3414 					return ret;
3415 			}
3416 
3417 			if (insn->type == INSN_JUMP_DYNAMIC)
3418 				return 0;
3419 
3420 			break;
3421 
3422 		case INSN_CONTEXT_SWITCH:
3423 			if (func && (!next_insn || !next_insn->hint)) {
3424 				WARN_FUNC("unsupported instruction in callable function",
3425 					  sec, insn->offset);
3426 				return 1;
3427 			}
3428 			return 0;
3429 
3430 		case INSN_STAC:
3431 			if (state.uaccess) {
3432 				WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
3433 				return 1;
3434 			}
3435 
3436 			state.uaccess = true;
3437 			break;
3438 
3439 		case INSN_CLAC:
3440 			if (!state.uaccess && func) {
3441 				WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
3442 				return 1;
3443 			}
3444 
3445 			if (func_uaccess_safe(func) && !state.uaccess_stack) {
3446 				WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
3447 				return 1;
3448 			}
3449 
3450 			state.uaccess = false;
3451 			break;
3452 
3453 		case INSN_STD:
3454 			if (state.df) {
3455 				WARN_FUNC("recursive STD", sec, insn->offset);
3456 				return 1;
3457 			}
3458 
3459 			state.df = true;
3460 			break;
3461 
3462 		case INSN_CLD:
3463 			if (!state.df && func) {
3464 				WARN_FUNC("redundant CLD", sec, insn->offset);
3465 				return 1;
3466 			}
3467 
3468 			state.df = false;
3469 			break;
3470 
3471 		default:
3472 			break;
3473 		}
3474 
3475 		if (ibt)
3476 			validate_ibt_insn(file, insn);
3477 
3478 		if (insn->dead_end)
3479 			return 0;
3480 
3481 		if (!next_insn) {
3482 			if (state.cfi.cfa.base == CFI_UNDEFINED)
3483 				return 0;
3484 			WARN("%s: unexpected end of section", sec->name);
3485 			return 1;
3486 		}
3487 
3488 		prev_insn = insn;
3489 		insn = next_insn;
3490 	}
3491 
3492 	return 0;
3493 }
3494 
3495 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3496 {
3497 	struct instruction *insn;
3498 	struct insn_state state;
3499 	int ret, warnings = 0;
3500 
3501 	if (!file->hints)
3502 		return 0;
3503 
3504 	init_insn_state(&state, sec);
3505 
3506 	if (sec) {
3507 		insn = find_insn(file, sec, 0);
3508 		if (!insn)
3509 			return 0;
3510 	} else {
3511 		insn = list_first_entry(&file->insn_list, typeof(*insn), list);
3512 	}
3513 
3514 	while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) {
3515 		if (insn->hint && !insn->visited && !insn->ignore) {
3516 			ret = validate_branch(file, insn->func, insn, state);
3517 			if (ret && backtrace)
3518 				BT_FUNC("<=== (hint)", insn);
3519 			warnings += ret;
3520 		}
3521 
3522 		insn = list_next_entry(insn, list);
3523 	}
3524 
3525 	return warnings;
3526 }
3527 
3528 static int validate_retpoline(struct objtool_file *file)
3529 {
3530 	struct instruction *insn;
3531 	int warnings = 0;
3532 
3533 	for_each_insn(file, insn) {
3534 		if (insn->type != INSN_JUMP_DYNAMIC &&
3535 		    insn->type != INSN_CALL_DYNAMIC)
3536 			continue;
3537 
3538 		if (insn->retpoline_safe)
3539 			continue;
3540 
3541 		/*
3542 		 * .init.text code is ran before userspace and thus doesn't
3543 		 * strictly need retpolines, except for modules which are
3544 		 * loaded late, they very much do need retpoline in their
3545 		 * .init.text
3546 		 */
3547 		if (!strcmp(insn->sec->name, ".init.text") && !module)
3548 			continue;
3549 
3550 		WARN_FUNC("indirect %s found in RETPOLINE build",
3551 			  insn->sec, insn->offset,
3552 			  insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
3553 
3554 		warnings++;
3555 	}
3556 
3557 	return warnings;
3558 }
3559 
3560 static bool is_kasan_insn(struct instruction *insn)
3561 {
3562 	return (insn->type == INSN_CALL &&
3563 		!strcmp(insn->call_dest->name, "__asan_handle_no_return"));
3564 }
3565 
3566 static bool is_ubsan_insn(struct instruction *insn)
3567 {
3568 	return (insn->type == INSN_CALL &&
3569 		!strcmp(insn->call_dest->name,
3570 			"__ubsan_handle_builtin_unreachable"));
3571 }
3572 
3573 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
3574 {
3575 	int i;
3576 	struct instruction *prev_insn;
3577 
3578 	if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
3579 		return true;
3580 
3581 	/*
3582 	 * Ignore alternative replacement instructions.  This can happen
3583 	 * when a whitelisted function uses one of the ALTERNATIVE macros.
3584 	 */
3585 	if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
3586 	    !strcmp(insn->sec->name, ".altinstr_aux"))
3587 		return true;
3588 
3589 	/*
3590 	 * Whole archive runs might encounder dead code from weak symbols.
3591 	 * This is where the linker will have dropped the weak symbol in
3592 	 * favour of a regular symbol, but leaves the code in place.
3593 	 *
3594 	 * In this case we'll find a piece of code (whole function) that is not
3595 	 * covered by a !section symbol. Ignore them.
3596 	 */
3597 	if (!insn->func && lto) {
3598 		int size = find_symbol_hole_containing(insn->sec, insn->offset);
3599 		unsigned long end = insn->offset + size;
3600 
3601 		if (!size) /* not a hole */
3602 			return false;
3603 
3604 		if (size < 0) /* hole until the end */
3605 			return true;
3606 
3607 		sec_for_each_insn_continue(file, insn) {
3608 			/*
3609 			 * If we reach a visited instruction at or before the
3610 			 * end of the hole, ignore the unreachable.
3611 			 */
3612 			if (insn->visited)
3613 				return true;
3614 
3615 			if (insn->offset >= end)
3616 				break;
3617 
3618 			/*
3619 			 * If this hole jumps to a .cold function, mark it ignore too.
3620 			 */
3621 			if (insn->jump_dest && insn->jump_dest->func &&
3622 			    strstr(insn->jump_dest->func->name, ".cold")) {
3623 				struct instruction *dest = insn->jump_dest;
3624 				func_for_each_insn(file, dest->func, dest)
3625 					dest->ignore = true;
3626 			}
3627 		}
3628 
3629 		return false;
3630 	}
3631 
3632 	if (!insn->func)
3633 		return false;
3634 
3635 	if (insn->func->static_call_tramp)
3636 		return true;
3637 
3638 	/*
3639 	 * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
3640 	 * __builtin_unreachable().  The BUG() macro has an unreachable() after
3641 	 * the UD2, which causes GCC's undefined trap logic to emit another UD2
3642 	 * (or occasionally a JMP to UD2).
3643 	 *
3644 	 * It may also insert a UD2 after calling a __noreturn function.
3645 	 */
3646 	prev_insn = list_prev_entry(insn, list);
3647 	if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) &&
3648 	    (insn->type == INSN_BUG ||
3649 	     (insn->type == INSN_JUMP_UNCONDITIONAL &&
3650 	      insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
3651 		return true;
3652 
3653 	/*
3654 	 * Check if this (or a subsequent) instruction is related to
3655 	 * CONFIG_UBSAN or CONFIG_KASAN.
3656 	 *
3657 	 * End the search at 5 instructions to avoid going into the weeds.
3658 	 */
3659 	for (i = 0; i < 5; i++) {
3660 
3661 		if (is_kasan_insn(insn) || is_ubsan_insn(insn))
3662 			return true;
3663 
3664 		if (insn->type == INSN_JUMP_UNCONDITIONAL) {
3665 			if (insn->jump_dest &&
3666 			    insn->jump_dest->func == insn->func) {
3667 				insn = insn->jump_dest;
3668 				continue;
3669 			}
3670 
3671 			break;
3672 		}
3673 
3674 		if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
3675 			break;
3676 
3677 		insn = list_next_entry(insn, list);
3678 	}
3679 
3680 	return false;
3681 }
3682 
3683 static int validate_symbol(struct objtool_file *file, struct section *sec,
3684 			   struct symbol *sym, struct insn_state *state)
3685 {
3686 	struct instruction *insn;
3687 	int ret;
3688 
3689 	if (!sym->len) {
3690 		WARN("%s() is missing an ELF size annotation", sym->name);
3691 		return 1;
3692 	}
3693 
3694 	if (sym->pfunc != sym || sym->alias != sym)
3695 		return 0;
3696 
3697 	insn = find_insn(file, sec, sym->offset);
3698 	if (!insn || insn->ignore || insn->visited)
3699 		return 0;
3700 
3701 	state->uaccess = sym->uaccess_safe;
3702 
3703 	ret = validate_branch(file, insn->func, insn, *state);
3704 	if (ret && backtrace)
3705 		BT_FUNC("<=== (sym)", insn);
3706 	return ret;
3707 }
3708 
3709 static int validate_section(struct objtool_file *file, struct section *sec)
3710 {
3711 	struct insn_state state;
3712 	struct symbol *func;
3713 	int warnings = 0;
3714 
3715 	list_for_each_entry(func, &sec->symbol_list, list) {
3716 		if (func->type != STT_FUNC)
3717 			continue;
3718 
3719 		init_insn_state(&state, sec);
3720 		set_func_state(&state.cfi);
3721 
3722 		warnings += validate_symbol(file, sec, func, &state);
3723 	}
3724 
3725 	return warnings;
3726 }
3727 
3728 static int validate_vmlinux_functions(struct objtool_file *file)
3729 {
3730 	struct section *sec;
3731 	int warnings = 0;
3732 
3733 	sec = find_section_by_name(file->elf, ".noinstr.text");
3734 	if (sec) {
3735 		warnings += validate_section(file, sec);
3736 		warnings += validate_unwind_hints(file, sec);
3737 	}
3738 
3739 	sec = find_section_by_name(file->elf, ".entry.text");
3740 	if (sec) {
3741 		warnings += validate_section(file, sec);
3742 		warnings += validate_unwind_hints(file, sec);
3743 	}
3744 
3745 	return warnings;
3746 }
3747 
3748 static int validate_functions(struct objtool_file *file)
3749 {
3750 	struct section *sec;
3751 	int warnings = 0;
3752 
3753 	for_each_sec(file, sec) {
3754 		if (!(sec->sh.sh_flags & SHF_EXECINSTR))
3755 			continue;
3756 
3757 		warnings += validate_section(file, sec);
3758 	}
3759 
3760 	return warnings;
3761 }
3762 
3763 static int validate_ibt(struct objtool_file *file)
3764 {
3765 	struct section *sec;
3766 	struct reloc *reloc;
3767 
3768 	for_each_sec(file, sec) {
3769 		bool is_data;
3770 
3771 		/* already done in validate_branch() */
3772 		if (sec->sh.sh_flags & SHF_EXECINSTR)
3773 			continue;
3774 
3775 		if (!sec->reloc)
3776 			continue;
3777 
3778 		if (!strncmp(sec->name, ".orc", 4))
3779 			continue;
3780 
3781 		if (!strncmp(sec->name, ".discard", 8))
3782 			continue;
3783 
3784 		if (!strncmp(sec->name, ".debug", 6))
3785 			continue;
3786 
3787 		if (!strcmp(sec->name, "_error_injection_whitelist"))
3788 			continue;
3789 
3790 		if (!strcmp(sec->name, "_kprobe_blacklist"))
3791 			continue;
3792 
3793 		is_data = strstr(sec->name, ".data") || strstr(sec->name, ".rodata");
3794 
3795 		list_for_each_entry(reloc, &sec->reloc->reloc_list, list) {
3796 			struct instruction *dest;
3797 
3798 			dest = validate_ibt_reloc(file, reloc);
3799 			if (is_data && dest && !dest->noendbr) {
3800 				warn_noendbr("data ", reloc->sym->sec,
3801 					     reloc->sym->offset + reloc->addend,
3802 					     dest);
3803 			}
3804 		}
3805 	}
3806 
3807 	return 0;
3808 }
3809 
3810 static int validate_reachable_instructions(struct objtool_file *file)
3811 {
3812 	struct instruction *insn;
3813 
3814 	if (file->ignore_unreachables)
3815 		return 0;
3816 
3817 	for_each_insn(file, insn) {
3818 		if (insn->visited || ignore_unreachable_insn(file, insn))
3819 			continue;
3820 
3821 		WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
3822 		return 1;
3823 	}
3824 
3825 	return 0;
3826 }
3827 
3828 int check(struct objtool_file *file)
3829 {
3830 	int ret, warnings = 0;
3831 
3832 	if (lto && !(vmlinux || module)) {
3833 		fprintf(stderr, "--lto requires: --vmlinux or --module\n");
3834 		return 1;
3835 	}
3836 
3837 	if (ibt && !lto) {
3838 		fprintf(stderr, "--ibt requires: --lto\n");
3839 		return 1;
3840 	}
3841 
3842 	arch_initial_func_cfi_state(&initial_func_cfi);
3843 	init_cfi_state(&init_cfi);
3844 	init_cfi_state(&func_cfi);
3845 	set_func_state(&func_cfi);
3846 
3847 	if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
3848 		goto out;
3849 
3850 	cfi_hash_add(&init_cfi);
3851 	cfi_hash_add(&func_cfi);
3852 
3853 	ret = decode_sections(file);
3854 	if (ret < 0)
3855 		goto out;
3856 
3857 	warnings += ret;
3858 
3859 	if (list_empty(&file->insn_list))
3860 		goto out;
3861 
3862 	if (vmlinux && !lto) {
3863 		ret = validate_vmlinux_functions(file);
3864 		if (ret < 0)
3865 			goto out;
3866 
3867 		warnings += ret;
3868 		goto out;
3869 	}
3870 
3871 	if (retpoline) {
3872 		ret = validate_retpoline(file);
3873 		if (ret < 0)
3874 			return ret;
3875 		warnings += ret;
3876 	}
3877 
3878 	ret = validate_functions(file);
3879 	if (ret < 0)
3880 		goto out;
3881 	warnings += ret;
3882 
3883 	ret = validate_unwind_hints(file, NULL);
3884 	if (ret < 0)
3885 		goto out;
3886 	warnings += ret;
3887 
3888 	if (ibt) {
3889 		ret = validate_ibt(file);
3890 		if (ret < 0)
3891 			goto out;
3892 		warnings += ret;
3893 	}
3894 
3895 	if (!warnings) {
3896 		ret = validate_reachable_instructions(file);
3897 		if (ret < 0)
3898 			goto out;
3899 		warnings += ret;
3900 	}
3901 
3902 	ret = create_static_call_sections(file);
3903 	if (ret < 0)
3904 		goto out;
3905 	warnings += ret;
3906 
3907 	if (retpoline) {
3908 		ret = create_retpoline_sites_sections(file);
3909 		if (ret < 0)
3910 			goto out;
3911 		warnings += ret;
3912 	}
3913 
3914 	if (mcount) {
3915 		ret = create_mcount_loc_sections(file);
3916 		if (ret < 0)
3917 			goto out;
3918 		warnings += ret;
3919 	}
3920 
3921 	if (ibt) {
3922 		ret = create_ibt_endbr_seal_sections(file);
3923 		if (ret < 0)
3924 			goto out;
3925 		warnings += ret;
3926 	}
3927 
3928 	if (stats) {
3929 		printf("nr_insns_visited: %ld\n", nr_insns_visited);
3930 		printf("nr_cfi: %ld\n", nr_cfi);
3931 		printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
3932 		printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
3933 	}
3934 
3935 out:
3936 	/*
3937 	 *  For now, don't fail the kernel build on fatal warnings.  These
3938 	 *  errors are still fairly common due to the growing matrix of
3939 	 *  supported toolchains and their recent pace of change.
3940 	 */
3941 	return 0;
3942 }
3943