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TOMOYO Linux Cross Reference
Linux/tools/objtool/check.c

Version: ~ [ linux-4.19-rc7 ] ~ [ linux-4.18.12 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.74 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.131 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.159 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.123 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.59 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.39.4 ] ~ [ linux-2.6.38.8 ] ~ [ linux-2.6.37.6 ] ~ [ linux-2.6.36.4 ] ~ [ linux-2.6.35.14 ] ~ [ linux-2.6.34.15 ] ~ [ linux-2.6.33.20 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.31.14 ] ~ [ linux-2.6.30.10 ] ~ [ linux-2.6.29.6 ] ~ [ linux-2.6.28.10 ] ~ [ linux-2.6.27.62 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 /*
  2  * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
  3  *
  4  * This program is free software; you can redistribute it and/or
  5  * modify it under the terms of the GNU General Public License
  6  * as published by the Free Software Foundation; either version 2
  7  * of the License, or (at your option) any later version.
  8  *
  9  * This program is distributed in the hope that it will be useful,
 10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12  * GNU General Public License for more details.
 13  *
 14  * You should have received a copy of the GNU General Public License
 15  * along with this program; if not, see <http://www.gnu.org/licenses/>.
 16  */
 17 
 18 #include <string.h>
 19 #include <stdlib.h>
 20 
 21 #include "builtin.h"
 22 #include "check.h"
 23 #include "elf.h"
 24 #include "special.h"
 25 #include "arch.h"
 26 #include "warn.h"
 27 
 28 #include <linux/hashtable.h>
 29 #include <linux/kernel.h>
 30 
 31 struct alternative {
 32         struct list_head list;
 33         struct instruction *insn;
 34 };
 35 
 36 const char *objname;
 37 struct cfi_state initial_func_cfi;
 38 
 39 struct instruction *find_insn(struct objtool_file *file,
 40                               struct section *sec, unsigned long offset)
 41 {
 42         struct instruction *insn;
 43 
 44         hash_for_each_possible(file->insn_hash, insn, hash, offset)
 45                 if (insn->sec == sec && insn->offset == offset)
 46                         return insn;
 47 
 48         return NULL;
 49 }
 50 
 51 static struct instruction *next_insn_same_sec(struct objtool_file *file,
 52                                               struct instruction *insn)
 53 {
 54         struct instruction *next = list_next_entry(insn, list);
 55 
 56         if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
 57                 return NULL;
 58 
 59         return next;
 60 }
 61 
 62 static struct instruction *next_insn_same_func(struct objtool_file *file,
 63                                                struct instruction *insn)
 64 {
 65         struct instruction *next = list_next_entry(insn, list);
 66         struct symbol *func = insn->func;
 67 
 68         if (!func)
 69                 return NULL;
 70 
 71         if (&next->list != &file->insn_list && next->func == func)
 72                 return next;
 73 
 74         /* Check if we're already in the subfunction: */
 75         if (func == func->cfunc)
 76                 return NULL;
 77 
 78         /* Move to the subfunction: */
 79         return find_insn(file, func->cfunc->sec, func->cfunc->offset);
 80 }
 81 
 82 #define func_for_each_insn_all(file, func, insn)                        \
 83         for (insn = find_insn(file, func->sec, func->offset);           \
 84              insn;                                                      \
 85              insn = next_insn_same_func(file, insn))
 86 
 87 #define func_for_each_insn(file, func, insn)                            \
 88         for (insn = find_insn(file, func->sec, func->offset);           \
 89              insn && &insn->list != &file->insn_list &&                 \
 90                 insn->sec == func->sec &&                               \
 91                 insn->offset < func->offset + func->len;                \
 92              insn = list_next_entry(insn, list))
 93 
 94 #define func_for_each_insn_continue_reverse(file, func, insn)           \
 95         for (insn = list_prev_entry(insn, list);                        \
 96              &insn->list != &file->insn_list &&                         \
 97                 insn->sec == func->sec && insn->offset >= func->offset; \
 98              insn = list_prev_entry(insn, list))
 99 
100 #define sec_for_each_insn_from(file, insn)                              \
101         for (; insn; insn = next_insn_same_sec(file, insn))
102 
103 #define sec_for_each_insn_continue(file, insn)                          \
104         for (insn = next_insn_same_sec(file, insn); insn;               \
105              insn = next_insn_same_sec(file, insn))
106 
107 /*
108  * Check if the function has been manually whitelisted with the
109  * STACK_FRAME_NON_STANDARD macro, or if it should be automatically whitelisted
110  * due to its use of a context switching instruction.
111  */
112 static bool ignore_func(struct objtool_file *file, struct symbol *func)
113 {
114         struct rela *rela;
115 
116         /* check for STACK_FRAME_NON_STANDARD */
117         if (file->whitelist && file->whitelist->rela)
118                 list_for_each_entry(rela, &file->whitelist->rela->rela_list, list) {
119                         if (rela->sym->type == STT_SECTION &&
120                             rela->sym->sec == func->sec &&
121                             rela->addend == func->offset)
122                                 return true;
123                         if (rela->sym->type == STT_FUNC && rela->sym == func)
124                                 return true;
125                 }
126 
127         return false;
128 }
129 
130 /*
131  * This checks to see if the given function is a "noreturn" function.
132  *
133  * For global functions which are outside the scope of this object file, we
134  * have to keep a manual list of them.
135  *
136  * For local functions, we have to detect them manually by simply looking for
137  * the lack of a return instruction.
138  *
139  * Returns:
140  *  -1: error
141  *   0: no dead end
142  *   1: dead end
143  */
144 static int __dead_end_function(struct objtool_file *file, struct symbol *func,
145                                int recursion)
146 {
147         int i;
148         struct instruction *insn;
149         bool empty = true;
150 
151         /*
152          * Unfortunately these have to be hard coded because the noreturn
153          * attribute isn't provided in ELF data.
154          */
155         static const char * const global_noreturns[] = {
156                 "__stack_chk_fail",
157                 "panic",
158                 "do_exit",
159                 "do_task_dead",
160                 "__module_put_and_exit",
161                 "complete_and_exit",
162                 "kvm_spurious_fault",
163                 "__reiserfs_panic",
164                 "lbug_with_loc",
165                 "fortify_panic",
166                 "usercopy_abort",
167                 "machine_real_restart",
168         };
169 
170         if (func->bind == STB_WEAK)
171                 return 0;
172 
173         if (func->bind == STB_GLOBAL)
174                 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
175                         if (!strcmp(func->name, global_noreturns[i]))
176                                 return 1;
177 
178         if (!func->len)
179                 return 0;
180 
181         insn = find_insn(file, func->sec, func->offset);
182         if (!insn->func)
183                 return 0;
184 
185         func_for_each_insn_all(file, func, insn) {
186                 empty = false;
187 
188                 if (insn->type == INSN_RETURN)
189                         return 0;
190         }
191 
192         if (empty)
193                 return 0;
194 
195         /*
196          * A function can have a sibling call instead of a return.  In that
197          * case, the function's dead-end status depends on whether the target
198          * of the sibling call returns.
199          */
200         func_for_each_insn_all(file, func, insn) {
201                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
202                         struct instruction *dest = insn->jump_dest;
203 
204                         if (!dest)
205                                 /* sibling call to another file */
206                                 return 0;
207 
208                         if (dest->func && dest->func->pfunc != insn->func->pfunc) {
209 
210                                 /* local sibling call */
211                                 if (recursion == 5) {
212                                         /*
213                                          * Infinite recursion: two functions
214                                          * have sibling calls to each other.
215                                          * This is a very rare case.  It means
216                                          * they aren't dead ends.
217                                          */
218                                         return 0;
219                                 }
220 
221                                 return __dead_end_function(file, dest->func,
222                                                            recursion + 1);
223                         }
224                 }
225 
226                 if (insn->type == INSN_JUMP_DYNAMIC && list_empty(&insn->alts))
227                         /* sibling call */
228                         return 0;
229         }
230 
231         return 1;
232 }
233 
234 static int dead_end_function(struct objtool_file *file, struct symbol *func)
235 {
236         return __dead_end_function(file, func, 0);
237 }
238 
239 static void clear_insn_state(struct insn_state *state)
240 {
241         int i;
242 
243         memset(state, 0, sizeof(*state));
244         state->cfa.base = CFI_UNDEFINED;
245         for (i = 0; i < CFI_NUM_REGS; i++) {
246                 state->regs[i].base = CFI_UNDEFINED;
247                 state->vals[i].base = CFI_UNDEFINED;
248         }
249         state->drap_reg = CFI_UNDEFINED;
250         state->drap_offset = -1;
251 }
252 
253 /*
254  * Call the arch-specific instruction decoder for all the instructions and add
255  * them to the global instruction list.
256  */
257 static int decode_instructions(struct objtool_file *file)
258 {
259         struct section *sec;
260         struct symbol *func;
261         unsigned long offset;
262         struct instruction *insn;
263         int ret;
264 
265         for_each_sec(file, sec) {
266 
267                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
268                         continue;
269 
270                 if (strcmp(sec->name, ".altinstr_replacement") &&
271                     strcmp(sec->name, ".altinstr_aux") &&
272                     strncmp(sec->name, ".discard.", 9))
273                         sec->text = true;
274 
275                 for (offset = 0; offset < sec->len; offset += insn->len) {
276                         insn = malloc(sizeof(*insn));
277                         if (!insn) {
278                                 WARN("malloc failed");
279                                 return -1;
280                         }
281                         memset(insn, 0, sizeof(*insn));
282                         INIT_LIST_HEAD(&insn->alts);
283                         clear_insn_state(&insn->state);
284 
285                         insn->sec = sec;
286                         insn->offset = offset;
287 
288                         ret = arch_decode_instruction(file->elf, sec, offset,
289                                                       sec->len - offset,
290                                                       &insn->len, &insn->type,
291                                                       &insn->immediate,
292                                                       &insn->stack_op);
293                         if (ret)
294                                 goto err;
295 
296                         if (!insn->type || insn->type > INSN_LAST) {
297                                 WARN_FUNC("invalid instruction type %d",
298                                           insn->sec, insn->offset, insn->type);
299                                 ret = -1;
300                                 goto err;
301                         }
302 
303                         hash_add(file->insn_hash, &insn->hash, insn->offset);
304                         list_add_tail(&insn->list, &file->insn_list);
305                 }
306 
307                 list_for_each_entry(func, &sec->symbol_list, list) {
308                         if (func->type != STT_FUNC)
309                                 continue;
310 
311                         if (!find_insn(file, sec, func->offset)) {
312                                 WARN("%s(): can't find starting instruction",
313                                      func->name);
314                                 return -1;
315                         }
316 
317                         func_for_each_insn(file, func, insn)
318                                 if (!insn->func)
319                                         insn->func = func;
320                 }
321         }
322 
323         return 0;
324 
325 err:
326         free(insn);
327         return ret;
328 }
329 
330 /*
331  * Mark "ud2" instructions and manually annotated dead ends.
332  */
333 static int add_dead_ends(struct objtool_file *file)
334 {
335         struct section *sec;
336         struct rela *rela;
337         struct instruction *insn;
338         bool found;
339 
340         /*
341          * By default, "ud2" is a dead end unless otherwise annotated, because
342          * GCC 7 inserts it for certain divide-by-zero cases.
343          */
344         for_each_insn(file, insn)
345                 if (insn->type == INSN_BUG)
346                         insn->dead_end = true;
347 
348         /*
349          * Check for manually annotated dead ends.
350          */
351         sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
352         if (!sec)
353                 goto reachable;
354 
355         list_for_each_entry(rela, &sec->rela_list, list) {
356                 if (rela->sym->type != STT_SECTION) {
357                         WARN("unexpected relocation symbol type in %s", sec->name);
358                         return -1;
359                 }
360                 insn = find_insn(file, rela->sym->sec, rela->addend);
361                 if (insn)
362                         insn = list_prev_entry(insn, list);
363                 else if (rela->addend == rela->sym->sec->len) {
364                         found = false;
365                         list_for_each_entry_reverse(insn, &file->insn_list, list) {
366                                 if (insn->sec == rela->sym->sec) {
367                                         found = true;
368                                         break;
369                                 }
370                         }
371 
372                         if (!found) {
373                                 WARN("can't find unreachable insn at %s+0x%x",
374                                      rela->sym->sec->name, rela->addend);
375                                 return -1;
376                         }
377                 } else {
378                         WARN("can't find unreachable insn at %s+0x%x",
379                              rela->sym->sec->name, rela->addend);
380                         return -1;
381                 }
382 
383                 insn->dead_end = true;
384         }
385 
386 reachable:
387         /*
388          * These manually annotated reachable checks are needed for GCC 4.4,
389          * where the Linux unreachable() macro isn't supported.  In that case
390          * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
391          * not a dead end.
392          */
393         sec = find_section_by_name(file->elf, ".rela.discard.reachable");
394         if (!sec)
395                 return 0;
396 
397         list_for_each_entry(rela, &sec->rela_list, list) {
398                 if (rela->sym->type != STT_SECTION) {
399                         WARN("unexpected relocation symbol type in %s", sec->name);
400                         return -1;
401                 }
402                 insn = find_insn(file, rela->sym->sec, rela->addend);
403                 if (insn)
404                         insn = list_prev_entry(insn, list);
405                 else if (rela->addend == rela->sym->sec->len) {
406                         found = false;
407                         list_for_each_entry_reverse(insn, &file->insn_list, list) {
408                                 if (insn->sec == rela->sym->sec) {
409                                         found = true;
410                                         break;
411                                 }
412                         }
413 
414                         if (!found) {
415                                 WARN("can't find reachable insn at %s+0x%x",
416                                      rela->sym->sec->name, rela->addend);
417                                 return -1;
418                         }
419                 } else {
420                         WARN("can't find reachable insn at %s+0x%x",
421                              rela->sym->sec->name, rela->addend);
422                         return -1;
423                 }
424 
425                 insn->dead_end = false;
426         }
427 
428         return 0;
429 }
430 
431 /*
432  * Warnings shouldn't be reported for ignored functions.
433  */
434 static void add_ignores(struct objtool_file *file)
435 {
436         struct instruction *insn;
437         struct section *sec;
438         struct symbol *func;
439 
440         for_each_sec(file, sec) {
441                 list_for_each_entry(func, &sec->symbol_list, list) {
442                         if (func->type != STT_FUNC)
443                                 continue;
444 
445                         if (!ignore_func(file, func))
446                                 continue;
447 
448                         func_for_each_insn_all(file, func, insn)
449                                 insn->ignore = true;
450                 }
451         }
452 }
453 
454 /*
455  * FIXME: For now, just ignore any alternatives which add retpolines.  This is
456  * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
457  * But it at least allows objtool to understand the control flow *around* the
458  * retpoline.
459  */
460 static int add_nospec_ignores(struct objtool_file *file)
461 {
462         struct section *sec;
463         struct rela *rela;
464         struct instruction *insn;
465 
466         sec = find_section_by_name(file->elf, ".rela.discard.nospec");
467         if (!sec)
468                 return 0;
469 
470         list_for_each_entry(rela, &sec->rela_list, list) {
471                 if (rela->sym->type != STT_SECTION) {
472                         WARN("unexpected relocation symbol type in %s", sec->name);
473                         return -1;
474                 }
475 
476                 insn = find_insn(file, rela->sym->sec, rela->addend);
477                 if (!insn) {
478                         WARN("bad .discard.nospec entry");
479                         return -1;
480                 }
481 
482                 insn->ignore_alts = true;
483         }
484 
485         return 0;
486 }
487 
488 /*
489  * Find the destination instructions for all jumps.
490  */
491 static int add_jump_destinations(struct objtool_file *file)
492 {
493         struct instruction *insn;
494         struct rela *rela;
495         struct section *dest_sec;
496         unsigned long dest_off;
497 
498         for_each_insn(file, insn) {
499                 if (insn->type != INSN_JUMP_CONDITIONAL &&
500                     insn->type != INSN_JUMP_UNCONDITIONAL)
501                         continue;
502 
503                 if (insn->ignore)
504                         continue;
505 
506                 rela = find_rela_by_dest_range(insn->sec, insn->offset,
507                                                insn->len);
508                 if (!rela) {
509                         dest_sec = insn->sec;
510                         dest_off = insn->offset + insn->len + insn->immediate;
511                 } else if (rela->sym->type == STT_SECTION) {
512                         dest_sec = rela->sym->sec;
513                         dest_off = rela->addend + 4;
514                 } else if (rela->sym->sec->idx) {
515                         dest_sec = rela->sym->sec;
516                         dest_off = rela->sym->sym.st_value + rela->addend + 4;
517                 } else if (strstr(rela->sym->name, "_indirect_thunk_")) {
518                         /*
519                          * Retpoline jumps are really dynamic jumps in
520                          * disguise, so convert them accordingly.
521                          */
522                         insn->type = INSN_JUMP_DYNAMIC;
523                         insn->retpoline_safe = true;
524                         continue;
525                 } else {
526                         /* sibling call */
527                         insn->jump_dest = 0;
528                         continue;
529                 }
530 
531                 insn->jump_dest = find_insn(file, dest_sec, dest_off);
532                 if (!insn->jump_dest) {
533 
534                         /*
535                          * This is a special case where an alt instruction
536                          * jumps past the end of the section.  These are
537                          * handled later in handle_group_alt().
538                          */
539                         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
540                                 continue;
541 
542                         WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
543                                   insn->sec, insn->offset, dest_sec->name,
544                                   dest_off);
545                         return -1;
546                 }
547 
548                 /*
549                  * For GCC 8+, create parent/child links for any cold
550                  * subfunctions.  This is _mostly_ redundant with a similar
551                  * initialization in read_symbols().
552                  *
553                  * If a function has aliases, we want the *first* such function
554                  * in the symbol table to be the subfunction's parent.  In that
555                  * case we overwrite the initialization done in read_symbols().
556                  *
557                  * However this code can't completely replace the
558                  * read_symbols() code because this doesn't detect the case
559                  * where the parent function's only reference to a subfunction
560                  * is through a switch table.
561                  */
562                 if (insn->func && insn->jump_dest->func &&
563                     insn->func != insn->jump_dest->func &&
564                     !strstr(insn->func->name, ".cold.") &&
565                     strstr(insn->jump_dest->func->name, ".cold.")) {
566                         insn->func->cfunc = insn->jump_dest->func;
567                         insn->jump_dest->func->pfunc = insn->func;
568                 }
569         }
570 
571         return 0;
572 }
573 
574 /*
575  * Find the destination instructions for all calls.
576  */
577 static int add_call_destinations(struct objtool_file *file)
578 {
579         struct instruction *insn;
580         unsigned long dest_off;
581         struct rela *rela;
582 
583         for_each_insn(file, insn) {
584                 if (insn->type != INSN_CALL)
585                         continue;
586 
587                 rela = find_rela_by_dest_range(insn->sec, insn->offset,
588                                                insn->len);
589                 if (!rela) {
590                         dest_off = insn->offset + insn->len + insn->immediate;
591                         insn->call_dest = find_symbol_by_offset(insn->sec,
592                                                                 dest_off);
593 
594                         if (!insn->call_dest && !insn->ignore) {
595                                 WARN_FUNC("unsupported intra-function call",
596                                           insn->sec, insn->offset);
597                                 if (retpoline)
598                                         WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");
599                                 return -1;
600                         }
601 
602                 } else if (rela->sym->type == STT_SECTION) {
603                         insn->call_dest = find_symbol_by_offset(rela->sym->sec,
604                                                                 rela->addend+4);
605                         if (!insn->call_dest ||
606                             insn->call_dest->type != STT_FUNC) {
607                                 WARN_FUNC("can't find call dest symbol at %s+0x%x",
608                                           insn->sec, insn->offset,
609                                           rela->sym->sec->name,
610                                           rela->addend + 4);
611                                 return -1;
612                         }
613                 } else
614                         insn->call_dest = rela->sym;
615         }
616 
617         return 0;
618 }
619 
620 /*
621  * The .alternatives section requires some extra special care, over and above
622  * what other special sections require:
623  *
624  * 1. Because alternatives are patched in-place, we need to insert a fake jump
625  *    instruction at the end so that validate_branch() skips all the original
626  *    replaced instructions when validating the new instruction path.
627  *
628  * 2. An added wrinkle is that the new instruction length might be zero.  In
629  *    that case the old instructions are replaced with noops.  We simulate that
630  *    by creating a fake jump as the only new instruction.
631  *
632  * 3. In some cases, the alternative section includes an instruction which
633  *    conditionally jumps to the _end_ of the entry.  We have to modify these
634  *    jumps' destinations to point back to .text rather than the end of the
635  *    entry in .altinstr_replacement.
636  *
637  * 4. It has been requested that we don't validate the !POPCNT feature path
638  *    which is a "very very small percentage of machines".
639  */
640 static int handle_group_alt(struct objtool_file *file,
641                             struct special_alt *special_alt,
642                             struct instruction *orig_insn,
643                             struct instruction **new_insn)
644 {
645         struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
646         unsigned long dest_off;
647 
648         last_orig_insn = NULL;
649         insn = orig_insn;
650         sec_for_each_insn_from(file, insn) {
651                 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
652                         break;
653 
654                 if (special_alt->skip_orig)
655                         insn->type = INSN_NOP;
656 
657                 insn->alt_group = true;
658                 last_orig_insn = insn;
659         }
660 
661         if (next_insn_same_sec(file, last_orig_insn)) {
662                 fake_jump = malloc(sizeof(*fake_jump));
663                 if (!fake_jump) {
664                         WARN("malloc failed");
665                         return -1;
666                 }
667                 memset(fake_jump, 0, sizeof(*fake_jump));
668                 INIT_LIST_HEAD(&fake_jump->alts);
669                 clear_insn_state(&fake_jump->state);
670 
671                 fake_jump->sec = special_alt->new_sec;
672                 fake_jump->offset = -1;
673                 fake_jump->type = INSN_JUMP_UNCONDITIONAL;
674                 fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
675                 fake_jump->ignore = true;
676         }
677 
678         if (!special_alt->new_len) {
679                 if (!fake_jump) {
680                         WARN("%s: empty alternative at end of section",
681                              special_alt->orig_sec->name);
682                         return -1;
683                 }
684 
685                 *new_insn = fake_jump;
686                 return 0;
687         }
688 
689         last_new_insn = NULL;
690         insn = *new_insn;
691         sec_for_each_insn_from(file, insn) {
692                 if (insn->offset >= special_alt->new_off + special_alt->new_len)
693                         break;
694 
695                 last_new_insn = insn;
696 
697                 insn->ignore = orig_insn->ignore_alts;
698 
699                 if (insn->type != INSN_JUMP_CONDITIONAL &&
700                     insn->type != INSN_JUMP_UNCONDITIONAL)
701                         continue;
702 
703                 if (!insn->immediate)
704                         continue;
705 
706                 dest_off = insn->offset + insn->len + insn->immediate;
707                 if (dest_off == special_alt->new_off + special_alt->new_len) {
708                         if (!fake_jump) {
709                                 WARN("%s: alternative jump to end of section",
710                                      special_alt->orig_sec->name);
711                                 return -1;
712                         }
713                         insn->jump_dest = fake_jump;
714                 }
715 
716                 if (!insn->jump_dest) {
717                         WARN_FUNC("can't find alternative jump destination",
718                                   insn->sec, insn->offset);
719                         return -1;
720                 }
721         }
722 
723         if (!last_new_insn) {
724                 WARN_FUNC("can't find last new alternative instruction",
725                           special_alt->new_sec, special_alt->new_off);
726                 return -1;
727         }
728 
729         if (fake_jump)
730                 list_add(&fake_jump->list, &last_new_insn->list);
731 
732         return 0;
733 }
734 
735 /*
736  * A jump table entry can either convert a nop to a jump or a jump to a nop.
737  * If the original instruction is a jump, make the alt entry an effective nop
738  * by just skipping the original instruction.
739  */
740 static int handle_jump_alt(struct objtool_file *file,
741                            struct special_alt *special_alt,
742                            struct instruction *orig_insn,
743                            struct instruction **new_insn)
744 {
745         if (orig_insn->type == INSN_NOP)
746                 return 0;
747 
748         if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
749                 WARN_FUNC("unsupported instruction at jump label",
750                           orig_insn->sec, orig_insn->offset);
751                 return -1;
752         }
753 
754         *new_insn = list_next_entry(orig_insn, list);
755         return 0;
756 }
757 
758 /*
759  * Read all the special sections which have alternate instructions which can be
760  * patched in or redirected to at runtime.  Each instruction having alternate
761  * instruction(s) has them added to its insn->alts list, which will be
762  * traversed in validate_branch().
763  */
764 static int add_special_section_alts(struct objtool_file *file)
765 {
766         struct list_head special_alts;
767         struct instruction *orig_insn, *new_insn;
768         struct special_alt *special_alt, *tmp;
769         struct alternative *alt;
770         int ret;
771 
772         ret = special_get_alts(file->elf, &special_alts);
773         if (ret)
774                 return ret;
775 
776         list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
777 
778                 orig_insn = find_insn(file, special_alt->orig_sec,
779                                       special_alt->orig_off);
780                 if (!orig_insn) {
781                         WARN_FUNC("special: can't find orig instruction",
782                                   special_alt->orig_sec, special_alt->orig_off);
783                         ret = -1;
784                         goto out;
785                 }
786 
787                 new_insn = NULL;
788                 if (!special_alt->group || special_alt->new_len) {
789                         new_insn = find_insn(file, special_alt->new_sec,
790                                              special_alt->new_off);
791                         if (!new_insn) {
792                                 WARN_FUNC("special: can't find new instruction",
793                                           special_alt->new_sec,
794                                           special_alt->new_off);
795                                 ret = -1;
796                                 goto out;
797                         }
798                 }
799 
800                 if (special_alt->group) {
801                         ret = handle_group_alt(file, special_alt, orig_insn,
802                                                &new_insn);
803                         if (ret)
804                                 goto out;
805                 } else if (special_alt->jump_or_nop) {
806                         ret = handle_jump_alt(file, special_alt, orig_insn,
807                                               &new_insn);
808                         if (ret)
809                                 goto out;
810                 }
811 
812                 alt = malloc(sizeof(*alt));
813                 if (!alt) {
814                         WARN("malloc failed");
815                         ret = -1;
816                         goto out;
817                 }
818 
819                 alt->insn = new_insn;
820                 list_add_tail(&alt->list, &orig_insn->alts);
821 
822                 list_del(&special_alt->list);
823                 free(special_alt);
824         }
825 
826 out:
827         return ret;
828 }
829 
830 static int add_switch_table(struct objtool_file *file, struct instruction *insn,
831                             struct rela *table, struct rela *next_table)
832 {
833         struct rela *rela = table;
834         struct instruction *alt_insn;
835         struct alternative *alt;
836         struct symbol *pfunc = insn->func->pfunc;
837         unsigned int prev_offset = 0;
838 
839         list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) {
840                 if (rela == next_table)
841                         break;
842 
843                 /* Make sure the switch table entries are consecutive: */
844                 if (prev_offset && rela->offset != prev_offset + 8)
845                         break;
846 
847                 /* Detect function pointers from contiguous objects: */
848                 if (rela->sym->sec == pfunc->sec &&
849                     rela->addend == pfunc->offset)
850                         break;
851 
852                 alt_insn = find_insn(file, rela->sym->sec, rela->addend);
853                 if (!alt_insn)
854                         break;
855 
856                 /* Make sure the jmp dest is in the function or subfunction: */
857                 if (alt_insn->func->pfunc != pfunc)
858                         break;
859 
860                 alt = malloc(sizeof(*alt));
861                 if (!alt) {
862                         WARN("malloc failed");
863                         return -1;
864                 }
865 
866                 alt->insn = alt_insn;
867                 list_add_tail(&alt->list, &insn->alts);
868                 prev_offset = rela->offset;
869         }
870 
871         if (!prev_offset) {
872                 WARN_FUNC("can't find switch jump table",
873                           insn->sec, insn->offset);
874                 return -1;
875         }
876 
877         return 0;
878 }
879 
880 /*
881  * find_switch_table() - Given a dynamic jump, find the switch jump table in
882  * .rodata associated with it.
883  *
884  * There are 3 basic patterns:
885  *
886  * 1. jmpq *[rodata addr](,%reg,8)
887  *
888  *    This is the most common case by far.  It jumps to an address in a simple
889  *    jump table which is stored in .rodata.
890  *
891  * 2. jmpq *[rodata addr](%rip)
892  *
893  *    This is caused by a rare GCC quirk, currently only seen in three driver
894  *    functions in the kernel, only with certain obscure non-distro configs.
895  *
896  *    As part of an optimization, GCC makes a copy of an existing switch jump
897  *    table, modifies it, and then hard-codes the jump (albeit with an indirect
898  *    jump) to use a single entry in the table.  The rest of the jump table and
899  *    some of its jump targets remain as dead code.
900  *
901  *    In such a case we can just crudely ignore all unreachable instruction
902  *    warnings for the entire object file.  Ideally we would just ignore them
903  *    for the function, but that would require redesigning the code quite a
904  *    bit.  And honestly that's just not worth doing: unreachable instruction
905  *    warnings are of questionable value anyway, and this is such a rare issue.
906  *
907  * 3. mov [rodata addr],%reg1
908  *    ... some instructions ...
909  *    jmpq *(%reg1,%reg2,8)
910  *
911  *    This is a fairly uncommon pattern which is new for GCC 6.  As of this
912  *    writing, there are 11 occurrences of it in the allmodconfig kernel.
913  *
914  *    As of GCC 7 there are quite a few more of these and the 'in between' code
915  *    is significant. Esp. with KASAN enabled some of the code between the mov
916  *    and jmpq uses .rodata itself, which can confuse things.
917  *
918  *    TODO: Once we have DWARF CFI and smarter instruction decoding logic,
919  *    ensure the same register is used in the mov and jump instructions.
920  *
921  *    NOTE: RETPOLINE made it harder still to decode dynamic jumps.
922  */
923 static struct rela *find_switch_table(struct objtool_file *file,
924                                       struct symbol *func,
925                                       struct instruction *insn)
926 {
927         struct rela *text_rela, *rodata_rela;
928         struct instruction *orig_insn = insn;
929         unsigned long table_offset;
930 
931         /*
932          * Backward search using the @first_jump_src links, these help avoid
933          * much of the 'in between' code. Which avoids us getting confused by
934          * it.
935          */
936         for (;
937              &insn->list != &file->insn_list &&
938              insn->sec == func->sec &&
939              insn->offset >= func->offset;
940 
941              insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
942 
943                 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
944                         break;
945 
946                 /* allow small jumps within the range */
947                 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
948                     insn->jump_dest &&
949                     (insn->jump_dest->offset <= insn->offset ||
950                      insn->jump_dest->offset > orig_insn->offset))
951                     break;
952 
953                 /* look for a relocation which references .rodata */
954                 text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
955                                                     insn->len);
956                 if (!text_rela || text_rela->sym != file->rodata->sym)
957                         continue;
958 
959                 table_offset = text_rela->addend;
960                 if (text_rela->type == R_X86_64_PC32)
961                         table_offset += 4;
962 
963                 /*
964                  * Make sure the .rodata address isn't associated with a
965                  * symbol.  gcc jump tables are anonymous data.
966                  */
967                 if (find_symbol_containing(file->rodata, table_offset))
968                         continue;
969 
970                 rodata_rela = find_rela_by_dest(file->rodata, table_offset);
971                 if (rodata_rela) {
972                         /*
973                          * Use of RIP-relative switch jumps is quite rare, and
974                          * indicates a rare GCC quirk/bug which can leave dead
975                          * code behind.
976                          */
977                         if (text_rela->type == R_X86_64_PC32)
978                                 file->ignore_unreachables = true;
979 
980                         return rodata_rela;
981                 }
982         }
983 
984         return NULL;
985 }
986 
987 
988 static int add_func_switch_tables(struct objtool_file *file,
989                                   struct symbol *func)
990 {
991         struct instruction *insn, *last = NULL, *prev_jump = NULL;
992         struct rela *rela, *prev_rela = NULL;
993         int ret;
994 
995         func_for_each_insn_all(file, func, insn) {
996                 if (!last)
997                         last = insn;
998 
999                 /*
1000                  * Store back-pointers for unconditional forward jumps such
1001                  * that find_switch_table() can back-track using those and
1002                  * avoid some potentially confusing code.
1003                  */
1004                 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1005                     insn->offset > last->offset &&
1006                     insn->jump_dest->offset > insn->offset &&
1007                     !insn->jump_dest->first_jump_src) {
1008 
1009                         insn->jump_dest->first_jump_src = insn;
1010                         last = insn->jump_dest;
1011                 }
1012 
1013                 if (insn->type != INSN_JUMP_DYNAMIC)
1014                         continue;
1015 
1016                 rela = find_switch_table(file, func, insn);
1017                 if (!rela)
1018                         continue;
1019 
1020                 /*
1021                  * We found a switch table, but we don't know yet how big it
1022                  * is.  Don't add it until we reach the end of the function or
1023                  * the beginning of another switch table in the same function.
1024                  */
1025                 if (prev_jump) {
1026                         ret = add_switch_table(file, prev_jump, prev_rela, rela);
1027                         if (ret)
1028                                 return ret;
1029                 }
1030 
1031                 prev_jump = insn;
1032                 prev_rela = rela;
1033         }
1034 
1035         if (prev_jump) {
1036                 ret = add_switch_table(file, prev_jump, prev_rela, NULL);
1037                 if (ret)
1038                         return ret;
1039         }
1040 
1041         return 0;
1042 }
1043 
1044 /*
1045  * For some switch statements, gcc generates a jump table in the .rodata
1046  * section which contains a list of addresses within the function to jump to.
1047  * This finds these jump tables and adds them to the insn->alts lists.
1048  */
1049 static int add_switch_table_alts(struct objtool_file *file)
1050 {
1051         struct section *sec;
1052         struct symbol *func;
1053         int ret;
1054 
1055         if (!file->rodata || !file->rodata->rela)
1056                 return 0;
1057 
1058         for_each_sec(file, sec) {
1059                 list_for_each_entry(func, &sec->symbol_list, list) {
1060                         if (func->type != STT_FUNC)
1061                                 continue;
1062 
1063                         ret = add_func_switch_tables(file, func);
1064                         if (ret)
1065                                 return ret;
1066                 }
1067         }
1068 
1069         return 0;
1070 }
1071 
1072 static int read_unwind_hints(struct objtool_file *file)
1073 {
1074         struct section *sec, *relasec;
1075         struct rela *rela;
1076         struct unwind_hint *hint;
1077         struct instruction *insn;
1078         struct cfi_reg *cfa;
1079         int i;
1080 
1081         sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1082         if (!sec)
1083                 return 0;
1084 
1085         relasec = sec->rela;
1086         if (!relasec) {
1087                 WARN("missing .rela.discard.unwind_hints section");
1088                 return -1;
1089         }
1090 
1091         if (sec->len % sizeof(struct unwind_hint)) {
1092                 WARN("struct unwind_hint size mismatch");
1093                 return -1;
1094         }
1095 
1096         file->hints = true;
1097 
1098         for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
1099                 hint = (struct unwind_hint *)sec->data->d_buf + i;
1100 
1101                 rela = find_rela_by_dest(sec, i * sizeof(*hint));
1102                 if (!rela) {
1103                         WARN("can't find rela for unwind_hints[%d]", i);
1104                         return -1;
1105                 }
1106 
1107                 insn = find_insn(file, rela->sym->sec, rela->addend);
1108                 if (!insn) {
1109                         WARN("can't find insn for unwind_hints[%d]", i);
1110                         return -1;
1111                 }
1112 
1113                 cfa = &insn->state.cfa;
1114 
1115                 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
1116                         insn->save = true;
1117                         continue;
1118 
1119                 } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
1120                         insn->restore = true;
1121                         insn->hint = true;
1122                         continue;
1123                 }
1124 
1125                 insn->hint = true;
1126 
1127                 switch (hint->sp_reg) {
1128                 case ORC_REG_UNDEFINED:
1129                         cfa->base = CFI_UNDEFINED;
1130                         break;
1131                 case ORC_REG_SP:
1132                         cfa->base = CFI_SP;
1133                         break;
1134                 case ORC_REG_BP:
1135                         cfa->base = CFI_BP;
1136                         break;
1137                 case ORC_REG_SP_INDIRECT:
1138                         cfa->base = CFI_SP_INDIRECT;
1139                         break;
1140                 case ORC_REG_R10:
1141                         cfa->base = CFI_R10;
1142                         break;
1143                 case ORC_REG_R13:
1144                         cfa->base = CFI_R13;
1145                         break;
1146                 case ORC_REG_DI:
1147                         cfa->base = CFI_DI;
1148                         break;
1149                 case ORC_REG_DX:
1150                         cfa->base = CFI_DX;
1151                         break;
1152                 default:
1153                         WARN_FUNC("unsupported unwind_hint sp base reg %d",
1154                                   insn->sec, insn->offset, hint->sp_reg);
1155                         return -1;
1156                 }
1157 
1158                 cfa->offset = hint->sp_offset;
1159                 insn->state.type = hint->type;
1160                 insn->state.end = hint->end;
1161         }
1162 
1163         return 0;
1164 }
1165 
1166 static int read_retpoline_hints(struct objtool_file *file)
1167 {
1168         struct section *sec;
1169         struct instruction *insn;
1170         struct rela *rela;
1171 
1172         sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1173         if (!sec)
1174                 return 0;
1175 
1176         list_for_each_entry(rela, &sec->rela_list, list) {
1177                 if (rela->sym->type != STT_SECTION) {
1178                         WARN("unexpected relocation symbol type in %s", sec->name);
1179                         return -1;
1180                 }
1181 
1182                 insn = find_insn(file, rela->sym->sec, rela->addend);
1183                 if (!insn) {
1184                         WARN("bad .discard.retpoline_safe entry");
1185                         return -1;
1186                 }
1187 
1188                 if (insn->type != INSN_JUMP_DYNAMIC &&
1189                     insn->type != INSN_CALL_DYNAMIC) {
1190                         WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1191                                   insn->sec, insn->offset);
1192                         return -1;
1193                 }
1194 
1195                 insn->retpoline_safe = true;
1196         }
1197 
1198         return 0;
1199 }
1200 
1201 static int decode_sections(struct objtool_file *file)
1202 {
1203         int ret;
1204 
1205         ret = decode_instructions(file);
1206         if (ret)
1207                 return ret;
1208 
1209         ret = add_dead_ends(file);
1210         if (ret)
1211                 return ret;
1212 
1213         add_ignores(file);
1214 
1215         ret = add_nospec_ignores(file);
1216         if (ret)
1217                 return ret;
1218 
1219         ret = add_jump_destinations(file);
1220         if (ret)
1221                 return ret;
1222 
1223         ret = add_special_section_alts(file);
1224         if (ret)
1225                 return ret;
1226 
1227         ret = add_call_destinations(file);
1228         if (ret)
1229                 return ret;
1230 
1231         ret = add_switch_table_alts(file);
1232         if (ret)
1233                 return ret;
1234 
1235         ret = read_unwind_hints(file);
1236         if (ret)
1237                 return ret;
1238 
1239         ret = read_retpoline_hints(file);
1240         if (ret)
1241                 return ret;
1242 
1243         return 0;
1244 }
1245 
1246 static bool is_fentry_call(struct instruction *insn)
1247 {
1248         if (insn->type == INSN_CALL &&
1249             insn->call_dest->type == STT_NOTYPE &&
1250             !strcmp(insn->call_dest->name, "__fentry__"))
1251                 return true;
1252 
1253         return false;
1254 }
1255 
1256 static bool has_modified_stack_frame(struct insn_state *state)
1257 {
1258         int i;
1259 
1260         if (state->cfa.base != initial_func_cfi.cfa.base ||
1261             state->cfa.offset != initial_func_cfi.cfa.offset ||
1262             state->stack_size != initial_func_cfi.cfa.offset ||
1263             state->drap)
1264                 return true;
1265 
1266         for (i = 0; i < CFI_NUM_REGS; i++)
1267                 if (state->regs[i].base != initial_func_cfi.regs[i].base ||
1268                     state->regs[i].offset != initial_func_cfi.regs[i].offset)
1269                         return true;
1270 
1271         return false;
1272 }
1273 
1274 static bool has_valid_stack_frame(struct insn_state *state)
1275 {
1276         if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
1277             state->regs[CFI_BP].offset == -16)
1278                 return true;
1279 
1280         if (state->drap && state->regs[CFI_BP].base == CFI_BP)
1281                 return true;
1282 
1283         return false;
1284 }
1285 
1286 static int update_insn_state_regs(struct instruction *insn, struct insn_state *state)
1287 {
1288         struct cfi_reg *cfa = &state->cfa;
1289         struct stack_op *op = &insn->stack_op;
1290 
1291         if (cfa->base != CFI_SP)
1292                 return 0;
1293 
1294         /* push */
1295         if (op->dest.type == OP_DEST_PUSH)
1296                 cfa->offset += 8;
1297 
1298         /* pop */
1299         if (op->src.type == OP_SRC_POP)
1300                 cfa->offset -= 8;
1301 
1302         /* add immediate to sp */
1303         if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1304             op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1305                 cfa->offset -= op->src.offset;
1306 
1307         return 0;
1308 }
1309 
1310 static void save_reg(struct insn_state *state, unsigned char reg, int base,
1311                      int offset)
1312 {
1313         if (arch_callee_saved_reg(reg) &&
1314             state->regs[reg].base == CFI_UNDEFINED) {
1315                 state->regs[reg].base = base;
1316                 state->regs[reg].offset = offset;
1317         }
1318 }
1319 
1320 static void restore_reg(struct insn_state *state, unsigned char reg)
1321 {
1322         state->regs[reg].base = CFI_UNDEFINED;
1323         state->regs[reg].offset = 0;
1324 }
1325 
1326 /*
1327  * A note about DRAP stack alignment:
1328  *
1329  * GCC has the concept of a DRAP register, which is used to help keep track of
1330  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
1331  * register.  The typical DRAP pattern is:
1332  *
1333  *   4c 8d 54 24 08             lea    0x8(%rsp),%r10
1334  *   48 83 e4 c0                and    $0xffffffffffffffc0,%rsp
1335  *   41 ff 72 f8                pushq  -0x8(%r10)
1336  *   55                         push   %rbp
1337  *   48 89 e5                   mov    %rsp,%rbp
1338  *                              (more pushes)
1339  *   41 52                      push   %r10
1340  *                              ...
1341  *   41 5a                      pop    %r10
1342  *                              (more pops)
1343  *   5d                         pop    %rbp
1344  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1345  *   c3                         retq
1346  *
1347  * There are some variations in the epilogues, like:
1348  *
1349  *   5b                         pop    %rbx
1350  *   41 5a                      pop    %r10
1351  *   41 5c                      pop    %r12
1352  *   41 5d                      pop    %r13
1353  *   41 5e                      pop    %r14
1354  *   c9                         leaveq
1355  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1356  *   c3                         retq
1357  *
1358  * and:
1359  *
1360  *   4c 8b 55 e8                mov    -0x18(%rbp),%r10
1361  *   48 8b 5d e0                mov    -0x20(%rbp),%rbx
1362  *   4c 8b 65 f0                mov    -0x10(%rbp),%r12
1363  *   4c 8b 6d f8                mov    -0x8(%rbp),%r13
1364  *   c9                         leaveq
1365  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1366  *   c3                         retq
1367  *
1368  * Sometimes r13 is used as the DRAP register, in which case it's saved and
1369  * restored beforehand:
1370  *
1371  *   41 55                      push   %r13
1372  *   4c 8d 6c 24 10             lea    0x10(%rsp),%r13
1373  *   48 83 e4 f0                and    $0xfffffffffffffff0,%rsp
1374  *                              ...
1375  *   49 8d 65 f0                lea    -0x10(%r13),%rsp
1376  *   41 5d                      pop    %r13
1377  *   c3                         retq
1378  */
1379 static int update_insn_state(struct instruction *insn, struct insn_state *state)
1380 {
1381         struct stack_op *op = &insn->stack_op;
1382         struct cfi_reg *cfa = &state->cfa;
1383         struct cfi_reg *regs = state->regs;
1384 
1385         /* stack operations don't make sense with an undefined CFA */
1386         if (cfa->base == CFI_UNDEFINED) {
1387                 if (insn->func) {
1388                         WARN_FUNC("undefined stack state", insn->sec, insn->offset);
1389                         return -1;
1390                 }
1391                 return 0;
1392         }
1393 
1394         if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET)
1395                 return update_insn_state_regs(insn, state);
1396 
1397         switch (op->dest.type) {
1398 
1399         case OP_DEST_REG:
1400                 switch (op->src.type) {
1401 
1402                 case OP_SRC_REG:
1403                         if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
1404                             cfa->base == CFI_SP &&
1405                             regs[CFI_BP].base == CFI_CFA &&
1406                             regs[CFI_BP].offset == -cfa->offset) {
1407 
1408                                 /* mov %rsp, %rbp */
1409                                 cfa->base = op->dest.reg;
1410                                 state->bp_scratch = false;
1411                         }
1412 
1413                         else if (op->src.reg == CFI_SP &&
1414                                  op->dest.reg == CFI_BP && state->drap) {
1415 
1416                                 /* drap: mov %rsp, %rbp */
1417                                 regs[CFI_BP].base = CFI_BP;
1418                                 regs[CFI_BP].offset = -state->stack_size;
1419                                 state->bp_scratch = false;
1420                         }
1421 
1422                         else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1423 
1424                                 /*
1425                                  * mov %rsp, %reg
1426                                  *
1427                                  * This is needed for the rare case where GCC
1428                                  * does:
1429                                  *
1430                                  *   mov    %rsp, %rax
1431                                  *   ...
1432                                  *   mov    %rax, %rsp
1433                                  */
1434                                 state->vals[op->dest.reg].base = CFI_CFA;
1435                                 state->vals[op->dest.reg].offset = -state->stack_size;
1436                         }
1437 
1438                         else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
1439                                  cfa->base == CFI_BP) {
1440 
1441                                 /*
1442                                  * mov %rbp, %rsp
1443                                  *
1444                                  * Restore the original stack pointer (Clang).
1445                                  */
1446                                 state->stack_size = -state->regs[CFI_BP].offset;
1447                         }
1448 
1449                         else if (op->dest.reg == cfa->base) {
1450 
1451                                 /* mov %reg, %rsp */
1452                                 if (cfa->base == CFI_SP &&
1453                                     state->vals[op->src.reg].base == CFI_CFA) {
1454 
1455                                         /*
1456                                          * This is needed for the rare case
1457                                          * where GCC does something dumb like:
1458                                          *
1459                                          *   lea    0x8(%rsp), %rcx
1460                                          *   ...
1461                                          *   mov    %rcx, %rsp
1462                                          */
1463                                         cfa->offset = -state->vals[op->src.reg].offset;
1464                                         state->stack_size = cfa->offset;
1465 
1466                                 } else {
1467                                         cfa->base = CFI_UNDEFINED;
1468                                         cfa->offset = 0;
1469                                 }
1470                         }
1471 
1472                         break;
1473 
1474                 case OP_SRC_ADD:
1475                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
1476 
1477                                 /* add imm, %rsp */
1478                                 state->stack_size -= op->src.offset;
1479                                 if (cfa->base == CFI_SP)
1480                                         cfa->offset -= op->src.offset;
1481                                 break;
1482                         }
1483 
1484                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
1485 
1486                                 /* lea disp(%rbp), %rsp */
1487                                 state->stack_size = -(op->src.offset + regs[CFI_BP].offset);
1488                                 break;
1489                         }
1490 
1491                         if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1492 
1493                                 /* drap: lea disp(%rsp), %drap */
1494                                 state->drap_reg = op->dest.reg;
1495 
1496                                 /*
1497                                  * lea disp(%rsp), %reg
1498                                  *
1499                                  * This is needed for the rare case where GCC
1500                                  * does something dumb like:
1501                                  *
1502                                  *   lea    0x8(%rsp), %rcx
1503                                  *   ...
1504                                  *   mov    %rcx, %rsp
1505                                  */
1506                                 state->vals[op->dest.reg].base = CFI_CFA;
1507                                 state->vals[op->dest.reg].offset = \
1508                                         -state->stack_size + op->src.offset;
1509 
1510                                 break;
1511                         }
1512 
1513                         if (state->drap && op->dest.reg == CFI_SP &&
1514                             op->src.reg == state->drap_reg) {
1515 
1516                                  /* drap: lea disp(%drap), %rsp */
1517                                 cfa->base = CFI_SP;
1518                                 cfa->offset = state->stack_size = -op->src.offset;
1519                                 state->drap_reg = CFI_UNDEFINED;
1520                                 state->drap = false;
1521                                 break;
1522                         }
1523 
1524                         if (op->dest.reg == state->cfa.base) {
1525                                 WARN_FUNC("unsupported stack register modification",
1526                                           insn->sec, insn->offset);
1527                                 return -1;
1528                         }
1529 
1530                         break;
1531 
1532                 case OP_SRC_AND:
1533                         if (op->dest.reg != CFI_SP ||
1534                             (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
1535                             (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
1536                                 WARN_FUNC("unsupported stack pointer realignment",
1537                                           insn->sec, insn->offset);
1538                                 return -1;
1539                         }
1540 
1541                         if (state->drap_reg != CFI_UNDEFINED) {
1542                                 /* drap: and imm, %rsp */
1543                                 cfa->base = state->drap_reg;
1544                                 cfa->offset = state->stack_size = 0;
1545                                 state->drap = true;
1546                         }
1547 
1548                         /*
1549                          * Older versions of GCC (4.8ish) realign the stack
1550                          * without DRAP, with a frame pointer.
1551                          */
1552 
1553                         break;
1554 
1555                 case OP_SRC_POP:
1556                         if (!state->drap && op->dest.type == OP_DEST_REG &&
1557                             op->dest.reg == cfa->base) {
1558 
1559                                 /* pop %rbp */
1560                                 cfa->base = CFI_SP;
1561                         }
1562 
1563                         if (state->drap && cfa->base == CFI_BP_INDIRECT &&
1564                             op->dest.type == OP_DEST_REG &&
1565                             op->dest.reg == state->drap_reg &&
1566                             state->drap_offset == -state->stack_size) {
1567 
1568                                 /* drap: pop %drap */
1569                                 cfa->base = state->drap_reg;
1570                                 cfa->offset = 0;
1571                                 state->drap_offset = -1;
1572 
1573                         } else if (regs[op->dest.reg].offset == -state->stack_size) {
1574 
1575                                 /* pop %reg */
1576                                 restore_reg(state, op->dest.reg);
1577                         }
1578 
1579                         state->stack_size -= 8;
1580                         if (cfa->base == CFI_SP)
1581                                 cfa->offset -= 8;
1582 
1583                         break;
1584 
1585                 case OP_SRC_REG_INDIRECT:
1586                         if (state->drap && op->src.reg == CFI_BP &&
1587                             op->src.offset == state->drap_offset) {
1588 
1589                                 /* drap: mov disp(%rbp), %drap */
1590                                 cfa->base = state->drap_reg;
1591                                 cfa->offset = 0;
1592                                 state->drap_offset = -1;
1593                         }
1594 
1595                         if (state->drap && op->src.reg == CFI_BP &&
1596                             op->src.offset == regs[op->dest.reg].offset) {
1597 
1598                                 /* drap: mov disp(%rbp), %reg */
1599                                 restore_reg(state, op->dest.reg);
1600 
1601                         } else if (op->src.reg == cfa->base &&
1602                             op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
1603 
1604                                 /* mov disp(%rbp), %reg */
1605                                 /* mov disp(%rsp), %reg */
1606                                 restore_reg(state, op->dest.reg);
1607                         }
1608 
1609                         break;
1610 
1611                 default:
1612                         WARN_FUNC("unknown stack-related instruction",
1613                                   insn->sec, insn->offset);
1614                         return -1;
1615                 }
1616 
1617                 break;
1618 
1619         case OP_DEST_PUSH:
1620                 state->stack_size += 8;
1621                 if (cfa->base == CFI_SP)
1622                         cfa->offset += 8;
1623 
1624                 if (op->src.type != OP_SRC_REG)
1625                         break;
1626 
1627                 if (state->drap) {
1628                         if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1629 
1630                                 /* drap: push %drap */
1631                                 cfa->base = CFI_BP_INDIRECT;
1632                                 cfa->offset = -state->stack_size;
1633 
1634                                 /* save drap so we know when to restore it */
1635                                 state->drap_offset = -state->stack_size;
1636 
1637                         } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
1638 
1639                                 /* drap: push %rbp */
1640                                 state->stack_size = 0;
1641 
1642                         } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1643 
1644                                 /* drap: push %reg */
1645                                 save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
1646                         }
1647 
1648                 } else {
1649 
1650                         /* push %reg */
1651                         save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
1652                 }
1653 
1654                 /* detect when asm code uses rbp as a scratch register */
1655                 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
1656                     cfa->base != CFI_BP)
1657                         state->bp_scratch = true;
1658                 break;
1659 
1660         case OP_DEST_REG_INDIRECT:
1661 
1662                 if (state->drap) {
1663                         if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1664 
1665                                 /* drap: mov %drap, disp(%rbp) */
1666                                 cfa->base = CFI_BP_INDIRECT;
1667                                 cfa->offset = op->dest.offset;
1668 
1669                                 /* save drap offset so we know when to restore it */
1670                                 state->drap_offset = op->dest.offset;
1671                         }
1672 
1673                         else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1674 
1675                                 /* drap: mov reg, disp(%rbp) */
1676                                 save_reg(state, op->src.reg, CFI_BP, op->dest.offset);
1677                         }
1678 
1679                 } else if (op->dest.reg == cfa->base) {
1680 
1681                         /* mov reg, disp(%rbp) */
1682                         /* mov reg, disp(%rsp) */
1683                         save_reg(state, op->src.reg, CFI_CFA,
1684                                  op->dest.offset - state->cfa.offset);
1685                 }
1686 
1687                 break;
1688 
1689         case OP_DEST_LEAVE:
1690                 if ((!state->drap && cfa->base != CFI_BP) ||
1691                     (state->drap && cfa->base != state->drap_reg)) {
1692                         WARN_FUNC("leave instruction with modified stack frame",
1693                                   insn->sec, insn->offset);
1694                         return -1;
1695                 }
1696 
1697                 /* leave (mov %rbp, %rsp; pop %rbp) */
1698 
1699                 state->stack_size = -state->regs[CFI_BP].offset - 8;
1700                 restore_reg(state, CFI_BP);
1701 
1702                 if (!state->drap) {
1703                         cfa->base = CFI_SP;
1704                         cfa->offset -= 8;
1705                 }
1706 
1707                 break;
1708 
1709         case OP_DEST_MEM:
1710                 if (op->src.type != OP_SRC_POP) {
1711                         WARN_FUNC("unknown stack-related memory operation",
1712                                   insn->sec, insn->offset);
1713                         return -1;
1714                 }
1715 
1716                 /* pop mem */
1717                 state->stack_size -= 8;
1718                 if (cfa->base == CFI_SP)
1719                         cfa->offset -= 8;
1720 
1721                 break;
1722 
1723         default:
1724                 WARN_FUNC("unknown stack-related instruction",
1725                           insn->sec, insn->offset);
1726                 return -1;
1727         }
1728 
1729         return 0;
1730 }
1731 
1732 static bool insn_state_match(struct instruction *insn, struct insn_state *state)
1733 {
1734         struct insn_state *state1 = &insn->state, *state2 = state;
1735         int i;
1736 
1737         if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
1738                 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
1739                           insn->sec, insn->offset,
1740                           state1->cfa.base, state1->cfa.offset,
1741                           state2->cfa.base, state2->cfa.offset);
1742 
1743         } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
1744                 for (i = 0; i < CFI_NUM_REGS; i++) {
1745                         if (!memcmp(&state1->regs[i], &state2->regs[i],
1746                                     sizeof(struct cfi_reg)))
1747                                 continue;
1748 
1749                         WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
1750                                   insn->sec, insn->offset,
1751                                   i, state1->regs[i].base, state1->regs[i].offset,
1752                                   i, state2->regs[i].base, state2->regs[i].offset);
1753                         break;
1754                 }
1755 
1756         } else if (state1->type != state2->type) {
1757                 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
1758                           insn->sec, insn->offset, state1->type, state2->type);
1759 
1760         } else if (state1->drap != state2->drap ||
1761                  (state1->drap && state1->drap_reg != state2->drap_reg) ||
1762                  (state1->drap && state1->drap_offset != state2->drap_offset)) {
1763                 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
1764                           insn->sec, insn->offset,
1765                           state1->drap, state1->drap_reg, state1->drap_offset,
1766                           state2->drap, state2->drap_reg, state2->drap_offset);
1767 
1768         } else
1769                 return true;
1770 
1771         return false;
1772 }
1773 
1774 /*
1775  * Follow the branch starting at the given instruction, and recursively follow
1776  * any other branches (jumps).  Meanwhile, track the frame pointer state at
1777  * each instruction and validate all the rules described in
1778  * tools/objtool/Documentation/stack-validation.txt.
1779  */
1780 static int validate_branch(struct objtool_file *file, struct instruction *first,
1781                            struct insn_state state)
1782 {
1783         struct alternative *alt;
1784         struct instruction *insn, *next_insn;
1785         struct section *sec;
1786         struct symbol *func = NULL;
1787         int ret;
1788 
1789         insn = first;
1790         sec = insn->sec;
1791 
1792         if (insn->alt_group && list_empty(&insn->alts)) {
1793                 WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
1794                           sec, insn->offset);
1795                 return 1;
1796         }
1797 
1798         while (1) {
1799                 next_insn = next_insn_same_sec(file, insn);
1800 
1801                 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
1802                         WARN("%s() falls through to next function %s()",
1803                              func->name, insn->func->name);
1804                         return 1;
1805                 }
1806 
1807                 func = insn->func ? insn->func->pfunc : NULL;
1808 
1809                 if (func && insn->ignore) {
1810                         WARN_FUNC("BUG: why am I validating an ignored function?",
1811                                   sec, insn->offset);
1812                         return 1;
1813                 }
1814 
1815                 if (insn->visited) {
1816                         if (!insn->hint && !insn_state_match(insn, &state))
1817                                 return 1;
1818 
1819                         return 0;
1820                 }
1821 
1822                 if (insn->hint) {
1823                         if (insn->restore) {
1824                                 struct instruction *save_insn, *i;
1825 
1826                                 i = insn;
1827                                 save_insn = NULL;
1828                                 func_for_each_insn_continue_reverse(file, insn->func, i) {
1829                                         if (i->save) {
1830                                                 save_insn = i;
1831                                                 break;
1832                                         }
1833                                 }
1834 
1835                                 if (!save_insn) {
1836                                         WARN_FUNC("no corresponding CFI save for CFI restore",
1837                                                   sec, insn->offset);
1838                                         return 1;
1839                                 }
1840 
1841                                 if (!save_insn->visited) {
1842                                         /*
1843                                          * Oops, no state to copy yet.
1844                                          * Hopefully we can reach this
1845                                          * instruction from another branch
1846                                          * after the save insn has been
1847                                          * visited.
1848                                          */
1849                                         if (insn == first)
1850                                                 return 0;
1851 
1852                                         WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
1853                                                   sec, insn->offset);
1854                                         return 1;
1855                                 }
1856 
1857                                 insn->state = save_insn->state;
1858                         }
1859 
1860                         state = insn->state;
1861 
1862                 } else
1863                         insn->state = state;
1864 
1865                 insn->visited = true;
1866 
1867                 if (!insn->ignore_alts) {
1868                         list_for_each_entry(alt, &insn->alts, list) {
1869                                 ret = validate_branch(file, alt->insn, state);
1870                                 if (ret)
1871                                         return 1;
1872                         }
1873                 }
1874 
1875                 switch (insn->type) {
1876 
1877                 case INSN_RETURN:
1878                         if (func && has_modified_stack_frame(&state)) {
1879                                 WARN_FUNC("return with modified stack frame",
1880                                           sec, insn->offset);
1881                                 return 1;
1882                         }
1883 
1884                         if (state.bp_scratch) {
1885                                 WARN("%s uses BP as a scratch register",
1886                                      insn->func->name);
1887                                 return 1;
1888                         }
1889 
1890                         return 0;
1891 
1892                 case INSN_CALL:
1893                         if (is_fentry_call(insn))
1894                                 break;
1895 
1896                         ret = dead_end_function(file, insn->call_dest);
1897                         if (ret == 1)
1898                                 return 0;
1899                         if (ret == -1)
1900                                 return 1;
1901 
1902                         /* fallthrough */
1903                 case INSN_CALL_DYNAMIC:
1904                         if (!no_fp && func && !has_valid_stack_frame(&state)) {
1905                                 WARN_FUNC("call without frame pointer save/setup",
1906                                           sec, insn->offset);
1907                                 return 1;
1908                         }
1909                         break;
1910 
1911                 case INSN_JUMP_CONDITIONAL:
1912                 case INSN_JUMP_UNCONDITIONAL:
1913                         if (insn->jump_dest &&
1914                             (!func || !insn->jump_dest->func ||
1915                              insn->jump_dest->func->pfunc == func)) {
1916                                 ret = validate_branch(file, insn->jump_dest,
1917                                                       state);
1918                                 if (ret)
1919                                         return 1;
1920 
1921                         } else if (func && has_modified_stack_frame(&state)) {
1922                                 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1923                                           sec, insn->offset);
1924                                 return 1;
1925                         }
1926 
1927                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
1928                                 return 0;
1929 
1930                         break;
1931 
1932                 case INSN_JUMP_DYNAMIC:
1933                         if (func && list_empty(&insn->alts) &&
1934                             has_modified_stack_frame(&state)) {
1935                                 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1936                                           sec, insn->offset);
1937                                 return 1;
1938                         }
1939 
1940                         return 0;
1941 
1942                 case INSN_CONTEXT_SWITCH:
1943                         if (func && (!next_insn || !next_insn->hint)) {
1944                                 WARN_FUNC("unsupported instruction in callable function",
1945                                           sec, insn->offset);
1946                                 return 1;
1947                         }
1948                         return 0;
1949 
1950                 case INSN_STACK:
1951                         if (update_insn_state(insn, &state))
1952                                 return 1;
1953 
1954                         break;
1955 
1956                 default:
1957                         break;
1958                 }
1959 
1960                 if (insn->dead_end)
1961                         return 0;
1962 
1963                 if (!next_insn) {
1964                         if (state.cfa.base == CFI_UNDEFINED)
1965                                 return 0;
1966                         WARN("%s: unexpected end of section", sec->name);
1967                         return 1;
1968                 }
1969 
1970                 insn = next_insn;
1971         }
1972 
1973         return 0;
1974 }
1975 
1976 static int validate_unwind_hints(struct objtool_file *file)
1977 {
1978         struct instruction *insn;
1979         int ret, warnings = 0;
1980         struct insn_state state;
1981 
1982         if (!file->hints)
1983                 return 0;
1984 
1985         clear_insn_state(&state);
1986 
1987         for_each_insn(file, insn) {
1988                 if (insn->hint && !insn->visited) {
1989                         ret = validate_branch(file, insn, state);
1990                         warnings += ret;
1991                 }
1992         }
1993 
1994         return warnings;
1995 }
1996 
1997 static int validate_retpoline(struct objtool_file *file)
1998 {
1999         struct instruction *insn;
2000         int warnings = 0;
2001 
2002         for_each_insn(file, insn) {
2003                 if (insn->type != INSN_JUMP_DYNAMIC &&
2004                     insn->type != INSN_CALL_DYNAMIC)
2005                         continue;
2006 
2007                 if (insn->retpoline_safe)
2008                         continue;
2009 
2010                 /*
2011                  * .init.text code is ran before userspace and thus doesn't
2012                  * strictly need retpolines, except for modules which are
2013                  * loaded late, they very much do need retpoline in their
2014                  * .init.text
2015                  */
2016                 if (!strcmp(insn->sec->name, ".init.text") && !module)
2017                         continue;
2018 
2019                 WARN_FUNC("indirect %s found in RETPOLINE build",
2020                           insn->sec, insn->offset,
2021                           insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
2022 
2023                 warnings++;
2024         }
2025 
2026         return warnings;
2027 }
2028 
2029 static bool is_kasan_insn(struct instruction *insn)
2030 {
2031         return (insn->type == INSN_CALL &&
2032                 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
2033 }
2034 
2035 static bool is_ubsan_insn(struct instruction *insn)
2036 {
2037         return (insn->type == INSN_CALL &&
2038                 !strcmp(insn->call_dest->name,
2039                         "__ubsan_handle_builtin_unreachable"));
2040 }
2041 
2042 static bool ignore_unreachable_insn(struct instruction *insn)
2043 {
2044         int i;
2045 
2046         if (insn->ignore || insn->type == INSN_NOP)
2047                 return true;
2048 
2049         /*
2050          * Ignore any unused exceptions.  This can happen when a whitelisted
2051          * function has an exception table entry.
2052          *
2053          * Also ignore alternative replacement instructions.  This can happen
2054          * when a whitelisted function uses one of the ALTERNATIVE macros.
2055          */
2056         if (!strcmp(insn->sec->name, ".fixup") ||
2057             !strcmp(insn->sec->name, ".altinstr_replacement") ||
2058             !strcmp(insn->sec->name, ".altinstr_aux"))
2059                 return true;
2060 
2061         /*
2062          * Check if this (or a subsequent) instruction is related to
2063          * CONFIG_UBSAN or CONFIG_KASAN.
2064          *
2065          * End the search at 5 instructions to avoid going into the weeds.
2066          */
2067         if (!insn->func)
2068                 return false;
2069         for (i = 0; i < 5; i++) {
2070 
2071                 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
2072                         return true;
2073 
2074                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
2075                         if (insn->jump_dest &&
2076                             insn->jump_dest->func == insn->func) {
2077                                 insn = insn->jump_dest;
2078                                 continue;
2079                         }
2080 
2081                         break;
2082                 }
2083 
2084                 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
2085                         break;
2086 
2087                 insn = list_next_entry(insn, list);
2088         }
2089 
2090         return false;
2091 }
2092 
2093 static int validate_functions(struct objtool_file *file)
2094 {
2095         struct section *sec;
2096         struct symbol *func;
2097         struct instruction *insn;
2098         struct insn_state state;
2099         int ret, warnings = 0;
2100 
2101         clear_insn_state(&state);
2102 
2103         state.cfa = initial_func_cfi.cfa;
2104         memcpy(&state.regs, &initial_func_cfi.regs,
2105                CFI_NUM_REGS * sizeof(struct cfi_reg));
2106         state.stack_size = initial_func_cfi.cfa.offset;
2107 
2108         for_each_sec(file, sec) {
2109                 list_for_each_entry(func, &sec->symbol_list, list) {
2110                         if (func->type != STT_FUNC || func->pfunc != func)
2111                                 continue;
2112 
2113                         insn = find_insn(file, sec, func->offset);
2114                         if (!insn || insn->ignore)
2115                                 continue;
2116 
2117                         ret = validate_branch(file, insn, state);
2118                         warnings += ret;
2119                 }
2120         }
2121 
2122         return warnings;
2123 }
2124 
2125 static int validate_reachable_instructions(struct objtool_file *file)
2126 {
2127         struct instruction *insn;
2128 
2129         if (file->ignore_unreachables)
2130                 return 0;
2131 
2132         for_each_insn(file, insn) {
2133                 if (insn->visited || ignore_unreachable_insn(insn))
2134                         continue;
2135 
2136                 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
2137                 return 1;
2138         }
2139 
2140         return 0;
2141 }
2142 
2143 static void cleanup(struct objtool_file *file)
2144 {
2145         struct instruction *insn, *tmpinsn;
2146         struct alternative *alt, *tmpalt;
2147 
2148         list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) {
2149                 list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) {
2150                         list_del(&alt->list);
2151                         free(alt);
2152                 }
2153                 list_del(&insn->list);
2154                 hash_del(&insn->hash);
2155                 free(insn);
2156         }
2157         elf_close(file->elf);
2158 }
2159 
2160 int check(const char *_objname, bool orc)
2161 {
2162         struct objtool_file file;
2163         int ret, warnings = 0;
2164 
2165         objname = _objname;
2166 
2167         file.elf = elf_open(objname, orc ? O_RDWR : O_RDONLY);
2168         if (!file.elf)
2169                 return 1;
2170 
2171         INIT_LIST_HEAD(&file.insn_list);
2172         hash_init(file.insn_hash);
2173         file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard");
2174         file.rodata = find_section_by_name(file.elf, ".rodata");
2175         file.c_file = find_section_by_name(file.elf, ".comment");
2176         file.ignore_unreachables = no_unreachable;
2177         file.hints = false;
2178 
2179         arch_initial_func_cfi_state(&initial_func_cfi);
2180 
2181         ret = decode_sections(&file);
2182         if (ret < 0)
2183                 goto out;
2184         warnings += ret;
2185 
2186         if (list_empty(&file.insn_list))
2187                 goto out;
2188 
2189         if (retpoline) {
2190                 ret = validate_retpoline(&file);
2191                 if (ret < 0)
2192                         return ret;
2193                 warnings += ret;
2194         }
2195 
2196         ret = validate_functions(&file);
2197         if (ret < 0)
2198                 goto out;
2199         warnings += ret;
2200 
2201         ret = validate_unwind_hints(&file);
2202         if (ret < 0)
2203                 goto out;
2204         warnings += ret;
2205 
2206         if (!warnings) {
2207                 ret = validate_reachable_instructions(&file);
2208                 if (ret < 0)
2209                         goto out;
2210                 warnings += ret;
2211         }
2212 
2213         if (orc) {
2214                 ret = create_orc(&file);
2215                 if (ret < 0)
2216                         goto out;
2217 
2218                 ret = create_orc_sections(&file);
2219                 if (ret < 0)
2220                         goto out;
2221 
2222                 ret = elf_write(file.elf);
2223                 if (ret < 0)
2224                         goto out;
2225         }
2226 
2227 out:
2228         cleanup(&file);
2229 
2230         /* ignore warnings for now until we get all the code cleaned up */
2231         if (ret || warnings)
2232                 return 0;
2233         return 0;
2234 }
2235 

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