tools/objtool/check.c

   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                 "rewind_stack_do_exit",
 169         };
 170
 171         if (func->bind == STB_WEAK)
 172                 return 0;
 173
 174         if (func->bind == STB_GLOBAL)
 175                 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
 176                         if (!strcmp(func->name, global_noreturns[i]))
 177                                 return 1;
 178
 179         if (!func->len)
 180                 return 0;
 181
 182         insn = find_insn(file, func->sec, func->offset);
 183         if (!insn->func)
 184                 return 0;
 185
 186         func_for_each_insn_all(file, func, insn) {
 187                 empty = false;
 188
 189                 if (insn->type == INSN_RETURN)
 190                         return 0;
 191         }
 192
 193         if (empty)
 194                 return 0;
 195
 196         /*
 197          * A function can have a sibling call instead of a return.  In that
 198          * case, the function's dead-end status depends on whether the target
 199          * of the sibling call returns.
 200          */
 201         func_for_each_insn_all(file, func, insn) {
 202                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
 203                         struct instruction *dest = insn->jump_dest;
 204
 205                         if (!dest)
 206                                 /* sibling call to another file */
 207                                 return 0;
 208
 209                         if (dest->func && dest->func->pfunc != insn->func->pfunc) {
 210
 211                                 /* local sibling call */
 212                                 if (recursion == 5) {
 213                                         /*
 214                                          * Infinite recursion: two functions
 215                                          * have sibling calls to each other.
 216                                          * This is a very rare case.  It means
 217                                          * they aren't dead ends.
 218                                          */
 219                                         return 0;
 220                                 }
 221
 222                                 return __dead_end_function(file, dest->func,
 223                                                            recursion + 1);
 224                         }
 225                 }
 226
 227                 if (insn->type == INSN_JUMP_DYNAMIC && list_empty(&insn->alts))
 228                         /* sibling call */
 229                         return 0;
 230         }
 231
 232         return 1;
 233 }
 234
 235 static int dead_end_function(struct objtool_file *file, struct symbol *func)
 236 {
 237         return __dead_end_function(file, func, 0);
 238 }
 239
 240 static void clear_insn_state(struct insn_state *state)
 241 {
 242         int i;
 243
 244         memset(state, 0, sizeof(*state));
 245         state->cfa.base = CFI_UNDEFINED;
 246         for (i = 0; i < CFI_NUM_REGS; i++) {
 247                 state->regs[i].base = CFI_UNDEFINED;
 248                 state->vals[i].base = CFI_UNDEFINED;
 249         }
 250         state->drap_reg = CFI_UNDEFINED;
 251         state->drap_offset = -1;
 252 }
 253
 254 /*
 255  * Call the arch-specific instruction decoder for all the instructions and add
 256  * them to the global instruction list.
 257  */
 258 static int decode_instructions(struct objtool_file *file)
 259 {
 260         struct section *sec;
 261         struct symbol *func;
 262         unsigned long offset;
 263         struct instruction *insn;
 264         int ret;
 265
 266         for_each_sec(file, sec) {
 267
 268                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
 269                         continue;
 270
 271                 if (strcmp(sec->name, ".altinstr_replacement") &&
 272                     strcmp(sec->name, ".altinstr_aux") &&
 273                     strncmp(sec->name, ".discard.", 9))
 274                         sec->text = true;
 275
 276                 for (offset = 0; offset < sec->len; offset += insn->len) {
 277                         insn = malloc(sizeof(*insn));
 278                         if (!insn) {
 279                                 WARN("malloc failed");
 280                                 return -1;
 281                         }
 282                         memset(insn, 0, sizeof(*insn));
 283                         INIT_LIST_HEAD(&insn->alts);
 284                         clear_insn_state(&insn->state);
 285
 286                         insn->sec = sec;
 287                         insn->offset = offset;
 288
 289                         ret = arch_decode_instruction(file->elf, sec, offset,
 290                                                       sec->len - offset,
 291                                                       &insn->len, &insn->type,
 292                                                       &insn->immediate,
 293                                                       &insn->stack_op);
 294                         if (ret)
 295                                 goto err;
 296
 297                         if (!insn->type || insn->type > INSN_LAST) {
 298                                 WARN_FUNC("invalid instruction type %d",
 299                                           insn->sec, insn->offset, insn->type);
 300                                 ret = -1;
 301                                 goto err;
 302                         }
 303
 304                         hash_add(file->insn_hash, &insn->hash, insn->offset);
 305                         list_add_tail(&insn->list, &file->insn_list);
 306                 }
 307
 308                 list_for_each_entry(func, &sec->symbol_list, list) {
 309                         if (func->type != STT_FUNC)
 310                                 continue;
 311
 312                         if (!find_insn(file, sec, func->offset)) {
 313                                 WARN("%s(): can't find starting instruction",
 314                                      func->name);
 315                                 return -1;
 316                         }
 317
 318                         func_for_each_insn(file, func, insn)
 319                                 if (!insn->func)
 320                                         insn->func = func;
 321                 }
 322         }
 323
 324         return 0;
 325
 326 err:
 327         free(insn);
 328         return ret;
 329 }
 330
 331 /*
 332  * Mark "ud2" instructions and manually annotated dead ends.
 333  */
 334 static int add_dead_ends(struct objtool_file *file)
 335 {
 336         struct section *sec;
 337         struct rela *rela;
 338         struct instruction *insn;
 339         bool found;
 340
 341         /*
 342          * By default, "ud2" is a dead end unless otherwise annotated, because
 343          * GCC 7 inserts it for certain divide-by-zero cases.
 344          */
 345         for_each_insn(file, insn)
 346                 if (insn->type == INSN_BUG)
 347                         insn->dead_end = true;
 348
 349         /*
 350          * Check for manually annotated dead ends.
 351          */
 352         sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
 353         if (!sec)
 354                 goto reachable;
 355
 356         list_for_each_entry(rela, &sec->rela_list, list) {
 357                 if (rela->sym->type != STT_SECTION) {
 358                         WARN("unexpected relocation symbol type in %s", sec->name);
 359                         return -1;
 360                 }
 361                 insn = find_insn(file, rela->sym->sec, rela->addend);
 362                 if (insn)
 363                         insn = list_prev_entry(insn, list);
 364                 else if (rela->addend == rela->sym->sec->len) {
 365                         found = false;
 366                         list_for_each_entry_reverse(insn, &file->insn_list, list) {
 367                                 if (insn->sec == rela->sym->sec) {
 368                                         found = true;
 369                                         break;
 370                                 }
 371                         }
 372
 373                         if (!found) {
 374                                 WARN("can't find unreachable insn at %s+0x%x",
 375                                      rela->sym->sec->name, rela->addend);
 376                                 return -1;
 377                         }
 378                 } else {
 379                         WARN("can't find unreachable insn at %s+0x%x",
 380                              rela->sym->sec->name, rela->addend);
 381                         return -1;
 382                 }
 383
 384                 insn->dead_end = true;
 385         }
 386
 387 reachable:
 388         /*
 389          * These manually annotated reachable checks are needed for GCC 4.4,
 390          * where the Linux unreachable() macro isn't supported.  In that case
 391          * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
 392          * not a dead end.
 393          */
 394         sec = find_section_by_name(file->elf, ".rela.discard.reachable");
 395         if (!sec)
 396                 return 0;
 397
 398         list_for_each_entry(rela, &sec->rela_list, list) {
 399                 if (rela->sym->type != STT_SECTION) {
 400                         WARN("unexpected relocation symbol type in %s", sec->name);
 401                         return -1;
 402                 }
 403                 insn = find_insn(file, rela->sym->sec, rela->addend);
 404                 if (insn)
 405                         insn = list_prev_entry(insn, list);
 406                 else if (rela->addend == rela->sym->sec->len) {
 407                         found = false;
 408                         list_for_each_entry_reverse(insn, &file->insn_list, list) {
 409                                 if (insn->sec == rela->sym->sec) {
 410                                         found = true;
 411                                         break;
 412                                 }
 413                         }
 414
 415                         if (!found) {
 416                                 WARN("can't find reachable insn at %s+0x%x",
 417                                      rela->sym->sec->name, rela->addend);
 418                                 return -1;
 419                         }
 420                 } else {
 421                         WARN("can't find reachable insn at %s+0x%x",
 422                              rela->sym->sec->name, rela->addend);
 423                         return -1;
 424                 }
 425
 426                 insn->dead_end = false;
 427         }
 428
 429         return 0;
 430 }
 431
 432 /*
 433  * Warnings shouldn't be reported for ignored functions.
 434  */
 435 static void add_ignores(struct objtool_file *file)
 436 {
 437         struct instruction *insn;
 438         struct section *sec;
 439         struct symbol *func;
 440
 441         for_each_sec(file, sec) {
 442                 list_for_each_entry(func, &sec->symbol_list, list) {
 443                         if (func->type != STT_FUNC)
 444                                 continue;
 445
 446                         if (!ignore_func(file, func))
 447                                 continue;
 448
 449                         func_for_each_insn_all(file, func, insn)
 450                                 insn->ignore = true;
 451                 }
 452         }
 453 }
 454
 455 /*
 456  * FIXME: For now, just ignore any alternatives which add retpolines.  This is
 457  * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
 458  * But it at least allows objtool to understand the control flow *around* the
 459  * retpoline.
 460  */
 461 static int add_nospec_ignores(struct objtool_file *file)
 462 {
 463         struct section *sec;
 464         struct rela *rela;
 465         struct instruction *insn;
 466
 467         sec = find_section_by_name(file->elf, ".rela.discard.nospec");
 468         if (!sec)
 469                 return 0;
 470
 471         list_for_each_entry(rela, &sec->rela_list, list) {
 472                 if (rela->sym->type != STT_SECTION) {
 473                         WARN("unexpected relocation symbol type in %s", sec->name);
 474                         return -1;
 475                 }
 476
 477                 insn = find_insn(file, rela->sym->sec, rela->addend);
 478                 if (!insn) {
 479                         WARN("bad .discard.nospec entry");
 480                         return -1;
 481                 }
 482
 483                 insn->ignore_alts = true;
 484         }
 485
 486         return 0;
 487 }
 488
 489 /*
 490  * Find the destination instructions for all jumps.
 491  */
 492 static int add_jump_destinations(struct objtool_file *file)
 493 {
 494         struct instruction *insn;
 495         struct rela *rela;
 496         struct section *dest_sec;
 497         unsigned long dest_off;
 498
 499         for_each_insn(file, insn) {
 500                 if (insn->type != INSN_JUMP_CONDITIONAL &&
 501                     insn->type != INSN_JUMP_UNCONDITIONAL)
 502                         continue;
 503
 504                 if (insn->ignore)
 505                         continue;
 506
 507                 rela = find_rela_by_dest_range(insn->sec, insn->offset,
 508                                                insn->len);
 509                 if (!rela) {
 510                         dest_sec = insn->sec;
 511                         dest_off = insn->offset + insn->len + insn->immediate;
 512                 } else if (rela->sym->type == STT_SECTION) {
 513                         dest_sec = rela->sym->sec;
 514                         dest_off = rela->addend + 4;
 515                 } else if (rela->sym->sec->idx) {
 516                         dest_sec = rela->sym->sec;
 517                         dest_off = rela->sym->sym.st_value + rela->addend + 4;
 518                 } else if (strstr(rela->sym->name, "_indirect_thunk_")) {
 519                         /*
 520                          * Retpoline jumps are really dynamic jumps in
 521                          * disguise, so convert them accordingly.
 522                          */
 523                         insn->type = INSN_JUMP_DYNAMIC;
 524                         insn->retpoline_safe = true;
 525                         continue;
 526                 } else {
 527                         /* sibling call */
 528                         insn->jump_dest = 0;
 529                         continue;
 530                 }
 531
 532                 insn->jump_dest = find_insn(file, dest_sec, dest_off);
 533                 if (!insn->jump_dest) {
 534
 535                         /*
 536                          * This is a special case where an alt instruction
 537                          * jumps past the end of the section.  These are
 538                          * handled later in handle_group_alt().
 539                          */
 540                         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
 541                                 continue;
 542
 543                         WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
 544                                   insn->sec, insn->offset, dest_sec->name,
 545                                   dest_off);
 546                         return -1;
 547                 }
 548
 549                 /*
 550                  * For GCC 8+, create parent/child links for any cold
 551                  * subfunctions.  This is _mostly_ redundant with a similar
 552                  * initialization in read_symbols().
 553                  *
 554                  * If a function has aliases, we want the *first* such function
 555                  * in the symbol table to be the subfunction's parent.  In that
 556                  * case we overwrite the initialization done in read_symbols().
 557                  *
 558                  * However this code can't completely replace the
 559                  * read_symbols() code because this doesn't detect the case
 560                  * where the parent function's only reference to a subfunction
 561                  * is through a switch table.
 562                  */
 563                 if (insn->func && insn->jump_dest->func &&
 564                     insn->func != insn->jump_dest->func &&
 565                     !strstr(insn->func->name, ".cold.") &&
 566                     strstr(insn->jump_dest->func->name, ".cold.")) {
 567                         insn->func->cfunc = insn->jump_dest->func;
 568                         insn->jump_dest->func->pfunc = insn->func;
 569                 }
 570         }
 571
 572         return 0;
 573 }
 574
 575 /*
 576  * Find the destination instructions for all calls.
 577  */
 578 static int add_call_destinations(struct objtool_file *file)
 579 {
 580         struct instruction *insn;
 581         unsigned long dest_off;
 582         struct rela *rela;
 583
 584         for_each_insn(file, insn) {
 585                 if (insn->type != INSN_CALL)
 586                         continue;
 587
 588                 rela = find_rela_by_dest_range(insn->sec, insn->offset,
 589                                                insn->len);
 590                 if (!rela) {
 591                         dest_off = insn->offset + insn->len + insn->immediate;
 592                         insn->call_dest = find_symbol_by_offset(insn->sec,
 593                                                                 dest_off);
 594
 595                         if (!insn->call_dest && !insn->ignore) {
 596                                 WARN_FUNC("unsupported intra-function call",
 597                                           insn->sec, insn->offset);
 598                                 if (retpoline)
 599                                         WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");
 600                                 return -1;
 601                         }
 602
 603                 } else if (rela->sym->type == STT_SECTION) {
 604                         insn->call_dest = find_symbol_by_offset(rela->sym->sec,
 605                                                                 rela->addend+4);
 606                         if (!insn->call_dest ||
 607                             insn->call_dest->type != STT_FUNC) {
 608                                 WARN_FUNC("can't find call dest symbol at %s+0x%x",
 609                                           insn->sec, insn->offset,
 610                                           rela->sym->sec->name,
 611                                           rela->addend + 4);
 612                                 return -1;
 613                         }
 614                 } else
 615                         insn->call_dest = rela->sym;
 616         }
 617
 618         return 0;
 619 }
 620
 621 /*
 622  * The .alternatives section requires some extra special care, over and above
 623  * what other special sections require:
 624  *
 625  * 1. Because alternatives are patched in-place, we need to insert a fake jump
 626  *    instruction at the end so that validate_branch() skips all the original
 627  *    replaced instructions when validating the new instruction path.
 628  *
 629  * 2. An added wrinkle is that the new instruction length might be zero.  In
 630  *    that case the old instructions are replaced with noops.  We simulate that
 631  *    by creating a fake jump as the only new instruction.
 632  *
 633  * 3. In some cases, the alternative section includes an instruction which
 634  *    conditionally jumps to the _end_ of the entry.  We have to modify these
 635  *    jumps' destinations to point back to .text rather than the end of the
 636  *    entry in .altinstr_replacement.
 637  *
 638  * 4. It has been requested that we don't validate the !POPCNT feature path
 639  *    which is a "very very small percentage of machines".
 640  */
 641 static int handle_group_alt(struct objtool_file *file,
 642                             struct special_alt *special_alt,
 643                             struct instruction *orig_insn,
 644                             struct instruction **new_insn)
 645 {
 646         struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
 647         unsigned long dest_off;
 648
 649         last_orig_insn = NULL;
 650         insn = orig_insn;
 651         sec_for_each_insn_from(file, insn) {
 652                 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
 653                         break;
 654
 655                 if (special_alt->skip_orig)
 656                         insn->type = INSN_NOP;
 657
 658                 insn->alt_group = true;
 659                 last_orig_insn = insn;
 660         }
 661
 662         if (next_insn_same_sec(file, last_orig_insn)) {
 663                 fake_jump = malloc(sizeof(*fake_jump));
 664                 if (!fake_jump) {
 665                         WARN("malloc failed");
 666                         return -1;
 667                 }
 668                 memset(fake_jump, 0, sizeof(*fake_jump));
 669                 INIT_LIST_HEAD(&fake_jump->alts);
 670                 clear_insn_state(&fake_jump->state);
 671
 672                 fake_jump->sec = special_alt->new_sec;
 673                 fake_jump->offset = -1;
 674                 fake_jump->type = INSN_JUMP_UNCONDITIONAL;
 675                 fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
 676                 fake_jump->ignore = true;
 677         }
 678
 679         if (!special_alt->new_len) {
 680                 if (!fake_jump) {
 681                         WARN("%s: empty alternative at end of section",
 682                              special_alt->orig_sec->name);
 683                         return -1;
 684                 }
 685
 686                 *new_insn = fake_jump;
 687                 return 0;
 688         }
 689
 690         last_new_insn = NULL;
 691         insn = *new_insn;
 692         sec_for_each_insn_from(file, insn) {
 693                 if (insn->offset >= special_alt->new_off + special_alt->new_len)
 694                         break;
 695
 696                 last_new_insn = insn;
 697
 698                 insn->ignore = orig_insn->ignore_alts;
 699
 700                 if (insn->type != INSN_JUMP_CONDITIONAL &&
 701                     insn->type != INSN_JUMP_UNCONDITIONAL)
 702                         continue;
 703
 704                 if (!insn->immediate)
 705                         continue;
 706
 707                 dest_off = insn->offset + insn->len + insn->immediate;
 708                 if (dest_off == special_alt->new_off + special_alt->new_len) {
 709                         if (!fake_jump) {
 710                                 WARN("%s: alternative jump to end of section",
 711                                      special_alt->orig_sec->name);
 712                                 return -1;
 713                         }
 714                         insn->jump_dest = fake_jump;
 715                 }
 716
 717                 if (!insn->jump_dest) {
 718                         WARN_FUNC("can't find alternative jump destination",
 719                                   insn->sec, insn->offset);
 720                         return -1;
 721                 }
 722         }
 723
 724         if (!last_new_insn) {
 725                 WARN_FUNC("can't find last new alternative instruction",
 726                           special_alt->new_sec, special_alt->new_off);
 727                 return -1;
 728         }
 729
 730         if (fake_jump)
 731                 list_add(&fake_jump->list, &last_new_insn->list);
 732
 733         return 0;
 734 }
 735
 736 /*
 737  * A jump table entry can either convert a nop to a jump or a jump to a nop.
 738  * If the original instruction is a jump, make the alt entry an effective nop
 739  * by just skipping the original instruction.
 740  */
 741 static int handle_jump_alt(struct objtool_file *file,
 742                            struct special_alt *special_alt,
 743                            struct instruction *orig_insn,
 744                            struct instruction **new_insn)
 745 {
 746         if (orig_insn->type == INSN_NOP)
 747                 return 0;
 748
 749         if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
 750                 WARN_FUNC("unsupported instruction at jump label",
 751                           orig_insn->sec, orig_insn->offset);
 752                 return -1;
 753         }
 754
 755         *new_insn = list_next_entry(orig_insn, list);
 756         return 0;
 757 }
 758
 759 /*
 760  * Read all the special sections which have alternate instructions which can be
 761  * patched in or redirected to at runtime.  Each instruction having alternate
 762  * instruction(s) has them added to its insn->alts list, which will be
 763  * traversed in validate_branch().
 764  */
 765 static int add_special_section_alts(struct objtool_file *file)
 766 {
 767         struct list_head special_alts;
 768         struct instruction *orig_insn, *new_insn;
 769         struct special_alt *special_alt, *tmp;
 770         struct alternative *alt;
 771         int ret;
 772
 773         ret = special_get_alts(file->elf, &special_alts);
 774         if (ret)
 775                 return ret;
 776
 777         list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
 778
 779                 orig_insn = find_insn(file, special_alt->orig_sec,
 780                                       special_alt->orig_off);
 781                 if (!orig_insn) {
 782                         WARN_FUNC("special: can't find orig instruction",
 783                                   special_alt->orig_sec, special_alt->orig_off);
 784                         ret = -1;
 785                         goto out;
 786                 }
 787
 788                 new_insn = NULL;
 789                 if (!special_alt->group || special_alt->new_len) {
 790                         new_insn = find_insn(file, special_alt->new_sec,
 791                                              special_alt->new_off);
 792                         if (!new_insn) {
 793                                 WARN_FUNC("special: can't find new instruction",
 794                                           special_alt->new_sec,
 795                                           special_alt->new_off);
 796                                 ret = -1;
 797                                 goto out;
 798                         }
 799                 }
 800
 801                 if (special_alt->group) {
 802                         ret = handle_group_alt(file, special_alt, orig_insn,
 803                                                &new_insn);
 804                         if (ret)
 805                                 goto out;
 806                 } else if (special_alt->jump_or_nop) {
 807                         ret = handle_jump_alt(file, special_alt, orig_insn,
 808                                               &new_insn);
 809                         if (ret)
 810                                 goto out;
 811                 }
 812
 813                 alt = malloc(sizeof(*alt));
 814                 if (!alt) {
 815                         WARN("malloc failed");
 816                         ret = -1;
 817                         goto out;
 818                 }
 819
 820                 alt->insn = new_insn;
 821                 list_add_tail(&alt->list, &orig_insn->alts);
 822
 823                 list_del(&special_alt->list);
 824                 free(special_alt);
 825         }
 826
 827 out:
 828         return ret;
 829 }
 830
 831 static int add_switch_table(struct objtool_file *file, struct instruction *insn,
 832                             struct rela *table, struct rela *next_table)
 833 {
 834         struct rela *rela = table;
 835         struct instruction *alt_insn;
 836         struct alternative *alt;
 837         struct symbol *pfunc = insn->func->pfunc;
 838         unsigned int prev_offset = 0;
 839
 840         list_for_each_entry_from(rela, &table->rela_sec->rela_list, list) {
 841                 if (rela == next_table)
 842                         break;
 843
 844                 /* Make sure the switch table entries are consecutive: */
 845                 if (prev_offset && rela->offset != prev_offset + 8)
 846                         break;
 847
 848                 /* Detect function pointers from contiguous objects: */
 849                 if (rela->sym->sec == pfunc->sec &&
 850                     rela->addend == pfunc->offset)
 851                         break;
 852
 853                 alt_insn = find_insn(file, rela->sym->sec, rela->addend);
 854                 if (!alt_insn)
 855                         break;
 856
 857                 /* Make sure the jmp dest is in the function or subfunction: */
 858                 if (alt_insn->func->pfunc != pfunc)
 859                         break;
 860
 861                 alt = malloc(sizeof(*alt));
 862                 if (!alt) {
 863                         WARN("malloc failed");
 864                         return -1;
 865                 }
 866
 867                 alt->insn = alt_insn;
 868                 list_add_tail(&alt->list, &insn->alts);
 869                 prev_offset = rela->offset;
 870         }
 871
 872         if (!prev_offset) {
 873                 WARN_FUNC("can't find switch jump table",
 874                           insn->sec, insn->offset);
 875                 return -1;
 876         }
 877
 878         return 0;
 879 }
 880
 881 /*
 882  * find_switch_table() - Given a dynamic jump, find the switch jump table in
 883  * .rodata associated with it.
 884  *
 885  * There are 3 basic patterns:
 886  *
 887  * 1. jmpq *[rodata addr](,%reg,8)
 888  *
 889  *    This is the most common case by far.  It jumps to an address in a simple
 890  *    jump table which is stored in .rodata.
 891  *
 892  * 2. jmpq *[rodata addr](%rip)
 893  *
 894  *    This is caused by a rare GCC quirk, currently only seen in three driver
 895  *    functions in the kernel, only with certain obscure non-distro configs.
 896  *
 897  *    As part of an optimization, GCC makes a copy of an existing switch jump
 898  *    table, modifies it, and then hard-codes the jump (albeit with an indirect
 899  *    jump) to use a single entry in the table.  The rest of the jump table and
 900  *    some of its jump targets remain as dead code.
 901  *
 902  *    In such a case we can just crudely ignore all unreachable instruction
 903  *    warnings for the entire object file.  Ideally we would just ignore them
 904  *    for the function, but that would require redesigning the code quite a
 905  *    bit.  And honestly that's just not worth doing: unreachable instruction
 906  *    warnings are of questionable value anyway, and this is such a rare issue.
 907  *
 908  * 3. mov [rodata addr],%reg1
 909  *    ... some instructions ...
 910  *    jmpq *(%reg1,%reg2,8)
 911  *
 912  *    This is a fairly uncommon pattern which is new for GCC 6.  As of this
 913  *    writing, there are 11 occurrences of it in the allmodconfig kernel.
 914  *
 915  *    As of GCC 7 there are quite a few more of these and the 'in between' code
 916  *    is significant. Esp. with KASAN enabled some of the code between the mov
 917  *    and jmpq uses .rodata itself, which can confuse things.
 918  *
 919  *    TODO: Once we have DWARF CFI and smarter instruction decoding logic,
 920  *    ensure the same register is used in the mov and jump instructions.
 921  *
 922  *    NOTE: RETPOLINE made it harder still to decode dynamic jumps.
 923  */
 924 static struct rela *find_switch_table(struct objtool_file *file,
 925                                       struct symbol *func,
 926                                       struct instruction *insn)
 927 {
 928         struct rela *text_rela, *rodata_rela;
 929         struct instruction *orig_insn = insn;
 930         struct section *rodata_sec;
 931         unsigned long table_offset;
 932
 933         /*
 934          * Backward search using the @first_jump_src links, these help avoid
 935          * much of the 'in between' code. Which avoids us getting confused by
 936          * it.
 937          */
 938         for (;
 939              &insn->list != &file->insn_list &&
 940              insn->sec == func->sec &&
 941              insn->offset >= func->offset;
 942
 943              insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
 944
 945                 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
 946                         break;
 947
 948                 /* allow small jumps within the range */
 949                 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
 950                     insn->jump_dest &&
 951                     (insn->jump_dest->offset <= insn->offset ||
 952                      insn->jump_dest->offset > orig_insn->offset))
 953                     break;
 954
 955                 /* look for a relocation which references .rodata */
 956                 text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
 957                                                     insn->len);
 958                 if (!text_rela || text_rela->sym->type != STT_SECTION ||
 959                     !text_rela->sym->sec->rodata)
 960                         continue;
 961
 962                 table_offset = text_rela->addend;
 963                 rodata_sec = text_rela->sym->sec;
 964
 965                 if (text_rela->type == R_X86_64_PC32)
 966                         table_offset += 4;
 967
 968                 /*
 969                  * Make sure the .rodata address isn't associated with a
 970                  * symbol.  gcc jump tables are anonymous data.
 971                  */
 972                 if (find_symbol_containing(rodata_sec, table_offset))
 973                         continue;
 974
 975                 rodata_rela = find_rela_by_dest(rodata_sec, table_offset);
 976                 if (rodata_rela) {
 977                         /*
 978                          * Use of RIP-relative switch jumps is quite rare, and
 979                          * indicates a rare GCC quirk/bug which can leave dead
 980                          * code behind.
 981                          */
 982                         if (text_rela->type == R_X86_64_PC32)
 983                                 file->ignore_unreachables = true;
 984
 985                         return rodata_rela;
 986                 }
 987         }
 988
 989         return NULL;
 990 }
 991
 992
 993 static int add_func_switch_tables(struct objtool_file *file,
 994                                   struct symbol *func)
 995 {
 996         struct instruction *insn, *last = NULL, *prev_jump = NULL;
 997         struct rela *rela, *prev_rela = NULL;
 998         int ret;
 999
1000         func_for_each_insn_all(file, func, insn) {
1001                 if (!last)
1002                         last = insn;
1003
1004                 /*
1005                  * Store back-pointers for unconditional forward jumps such
1006                  * that find_switch_table() can back-track using those and
1007                  * avoid some potentially confusing code.
1008                  */
1009                 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1010                     insn->offset > last->offset &&
1011                     insn->jump_dest->offset > insn->offset &&
1012                     !insn->jump_dest->first_jump_src) {
1013
1014                         insn->jump_dest->first_jump_src = insn;
1015                         last = insn->jump_dest;
1016                 }
1017
1018                 if (insn->type != INSN_JUMP_DYNAMIC)
1019                         continue;
1020
1021                 rela = find_switch_table(file, func, insn);
1022                 if (!rela)
1023                         continue;
1024
1025                 /*
1026                  * We found a switch table, but we don't know yet how big it
1027                  * is.  Don't add it until we reach the end of the function or
1028                  * the beginning of another switch table in the same function.
1029                  */
1030                 if (prev_jump) {
1031                         ret = add_switch_table(file, prev_jump, prev_rela, rela);
1032                         if (ret)
1033                                 return ret;
1034                 }
1035
1036                 prev_jump = insn;
1037                 prev_rela = rela;
1038         }
1039
1040         if (prev_jump) {
1041                 ret = add_switch_table(file, prev_jump, prev_rela, NULL);
1042                 if (ret)
1043                         return ret;
1044         }
1045
1046         return 0;
1047 }
1048
1049 /*
1050  * For some switch statements, gcc generates a jump table in the .rodata
1051  * section which contains a list of addresses within the function to jump to.
1052  * This finds these jump tables and adds them to the insn->alts lists.
1053  */
1054 static int add_switch_table_alts(struct objtool_file *file)
1055 {
1056         struct section *sec;
1057         struct symbol *func;
1058         int ret;
1059
1060         if (!file->rodata)
1061                 return 0;
1062
1063         for_each_sec(file, sec) {
1064                 list_for_each_entry(func, &sec->symbol_list, list) {
1065                         if (func->type != STT_FUNC)
1066                                 continue;
1067
1068                         ret = add_func_switch_tables(file, func);
1069                         if (ret)
1070                                 return ret;
1071                 }
1072         }
1073
1074         return 0;
1075 }
1076
1077 static int read_unwind_hints(struct objtool_file *file)
1078 {
1079         struct section *sec, *relasec;
1080         struct rela *rela;
1081         struct unwind_hint *hint;
1082         struct instruction *insn;
1083         struct cfi_reg *cfa;
1084         int i;
1085
1086         sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1087         if (!sec)
1088                 return 0;
1089
1090         relasec = sec->rela;
1091         if (!relasec) {
1092                 WARN("missing .rela.discard.unwind_hints section");
1093                 return -1;
1094         }
1095
1096         if (sec->len % sizeof(struct unwind_hint)) {
1097                 WARN("struct unwind_hint size mismatch");
1098                 return -1;
1099         }
1100
1101         file->hints = true;
1102
1103         for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
1104                 hint = (struct unwind_hint *)sec->data->d_buf + i;
1105
1106                 rela = find_rela_by_dest(sec, i * sizeof(*hint));
1107                 if (!rela) {
1108                         WARN("can't find rela for unwind_hints[%d]", i);
1109                         return -1;
1110                 }
1111
1112                 insn = find_insn(file, rela->sym->sec, rela->addend);
1113                 if (!insn) {
1114                         WARN("can't find insn for unwind_hints[%d]", i);
1115                         return -1;
1116                 }
1117
1118                 cfa = &insn->state.cfa;
1119
1120                 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
1121                         insn->save = true;
1122                         continue;
1123
1124                 } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
1125                         insn->restore = true;
1126                         insn->hint = true;
1127                         continue;
1128                 }
1129
1130                 insn->hint = true;
1131
1132                 switch (hint->sp_reg) {
1133                 case ORC_REG_UNDEFINED:
1134                         cfa->base = CFI_UNDEFINED;
1135                         break;
1136                 case ORC_REG_SP:
1137                         cfa->base = CFI_SP;
1138                         break;
1139                 case ORC_REG_BP:
1140                         cfa->base = CFI_BP;
1141                         break;
1142                 case ORC_REG_SP_INDIRECT:
1143                         cfa->base = CFI_SP_INDIRECT;
1144                         break;
1145                 case ORC_REG_R10:
1146                         cfa->base = CFI_R10;
1147                         break;
1148                 case ORC_REG_R13:
1149                         cfa->base = CFI_R13;
1150                         break;
1151                 case ORC_REG_DI:
1152                         cfa->base = CFI_DI;
1153                         break;
1154                 case ORC_REG_DX:
1155                         cfa->base = CFI_DX;
1156                         break;
1157                 default:
1158                         WARN_FUNC("unsupported unwind_hint sp base reg %d",
1159                                   insn->sec, insn->offset, hint->sp_reg);
1160                         return -1;
1161                 }
1162
1163                 cfa->offset = hint->sp_offset;
1164                 insn->state.type = hint->type;
1165                 insn->state.end = hint->end;
1166         }
1167
1168         return 0;
1169 }
1170
1171 static int read_retpoline_hints(struct objtool_file *file)
1172 {
1173         struct section *sec;
1174         struct instruction *insn;
1175         struct rela *rela;
1176
1177         sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1178         if (!sec)
1179                 return 0;
1180
1181         list_for_each_entry(rela, &sec->rela_list, list) {
1182                 if (rela->sym->type != STT_SECTION) {
1183                         WARN("unexpected relocation symbol type in %s", sec->name);
1184                         return -1;
1185                 }
1186
1187                 insn = find_insn(file, rela->sym->sec, rela->addend);
1188                 if (!insn) {
1189                         WARN("bad .discard.retpoline_safe entry");
1190                         return -1;
1191                 }
1192
1193                 if (insn->type != INSN_JUMP_DYNAMIC &&
1194                     insn->type != INSN_CALL_DYNAMIC) {
1195                         WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1196                                   insn->sec, insn->offset);
1197                         return -1;
1198                 }
1199
1200                 insn->retpoline_safe = true;
1201         }
1202
1203         return 0;
1204 }
1205
1206 static void mark_rodata(struct objtool_file *file)
1207 {
1208         struct section *sec;
1209         bool found = false;
1210
1211         /*
1212          * This searches for the .rodata section or multiple .rodata.func_name
1213          * sections if -fdata-sections is being used. The .str.1.1 and .str.1.8
1214          * rodata sections are ignored as they don't contain jump tables.
1215          */
1216         for_each_sec(file, sec) {
1217                 if (!strncmp(sec->name, ".rodata", 7) &&
1218                     !strstr(sec->name, ".str1.")) {
1219                         sec->rodata = true;
1220                         found = true;
1221                 }
1222         }
1223
1224         file->rodata = found;
1225 }
1226
1227 static int decode_sections(struct objtool_file *file)
1228 {
1229         int ret;
1230
1231         mark_rodata(file);
1232
1233         ret = decode_instructions(file);
1234         if (ret)
1235                 return ret;
1236
1237         ret = add_dead_ends(file);
1238         if (ret)
1239                 return ret;
1240
1241         add_ignores(file);
1242
1243         ret = add_nospec_ignores(file);
1244         if (ret)
1245                 return ret;
1246
1247         ret = add_jump_destinations(file);
1248         if (ret)
1249                 return ret;
1250
1251         ret = add_special_section_alts(file);
1252         if (ret)
1253                 return ret;
1254
1255         ret = add_call_destinations(file);
1256         if (ret)
1257                 return ret;
1258
1259         ret = add_switch_table_alts(file);
1260         if (ret)
1261                 return ret;
1262
1263         ret = read_unwind_hints(file);
1264         if (ret)
1265                 return ret;
1266
1267         ret = read_retpoline_hints(file);
1268         if (ret)
1269                 return ret;
1270
1271         return 0;
1272 }
1273
1274 static bool is_fentry_call(struct instruction *insn)
1275 {
1276         if (insn->type == INSN_CALL &&
1277             insn->call_dest->type == STT_NOTYPE &&
1278             !strcmp(insn->call_dest->name, "__fentry__"))
1279                 return true;
1280
1281         return false;
1282 }
1283
1284 static bool has_modified_stack_frame(struct insn_state *state)
1285 {
1286         int i;
1287
1288         if (state->cfa.base != initial_func_cfi.cfa.base ||
1289             state->cfa.offset != initial_func_cfi.cfa.offset ||
1290             state->stack_size != initial_func_cfi.cfa.offset ||
1291             state->drap)
1292                 return true;
1293
1294         for (i = 0; i < CFI_NUM_REGS; i++)
1295                 if (state->regs[i].base != initial_func_cfi.regs[i].base ||
1296                     state->regs[i].offset != initial_func_cfi.regs[i].offset)
1297                         return true;
1298
1299         return false;
1300 }
1301
1302 static bool has_valid_stack_frame(struct insn_state *state)
1303 {
1304         if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
1305             state->regs[CFI_BP].offset == -16)
1306                 return true;
1307
1308         if (state->drap && state->regs[CFI_BP].base == CFI_BP)
1309                 return true;
1310
1311         return false;
1312 }
1313
1314 static int update_insn_state_regs(struct instruction *insn, struct insn_state *state)
1315 {
1316         struct cfi_reg *cfa = &state->cfa;
1317         struct stack_op *op = &insn->stack_op;
1318
1319         if (cfa->base != CFI_SP)
1320                 return 0;
1321
1322         /* push */
1323         if (op->dest.type == OP_DEST_PUSH)
1324                 cfa->offset += 8;
1325
1326         /* pop */
1327         if (op->src.type == OP_SRC_POP)
1328                 cfa->offset -= 8;
1329
1330         /* add immediate to sp */
1331         if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1332             op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1333                 cfa->offset -= op->src.offset;
1334
1335         return 0;
1336 }
1337
1338 static void save_reg(struct insn_state *state, unsigned char reg, int base,
1339                      int offset)
1340 {
1341         if (arch_callee_saved_reg(reg) &&
1342             state->regs[reg].base == CFI_UNDEFINED) {
1343                 state->regs[reg].base = base;
1344                 state->regs[reg].offset = offset;
1345         }
1346 }
1347
1348 static void restore_reg(struct insn_state *state, unsigned char reg)
1349 {
1350         state->regs[reg].base = CFI_UNDEFINED;
1351         state->regs[reg].offset = 0;
1352 }
1353
1354 /*
1355  * A note about DRAP stack alignment:
1356  *
1357  * GCC has the concept of a DRAP register, which is used to help keep track of
1358  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
1359  * register.  The typical DRAP pattern is:
1360  *
1361  *   4c 8d 54 24 08             lea    0x8(%rsp),%r10
1362  *   48 83 e4 c0                and    $0xffffffffffffffc0,%rsp
1363  *   41 ff 72 f8                pushq  -0x8(%r10)
1364  *   55                         push   %rbp
1365  *   48 89 e5                   mov    %rsp,%rbp
1366  *                              (more pushes)
1367  *   41 52                      push   %r10
1368  *                              ...
1369  *   41 5a                      pop    %r10
1370  *                              (more pops)
1371  *   5d                         pop    %rbp
1372  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1373  *   c3                         retq
1374  *
1375  * There are some variations in the epilogues, like:
1376  *
1377  *   5b                         pop    %rbx
1378  *   41 5a                      pop    %r10
1379  *   41 5c                      pop    %r12
1380  *   41 5d                      pop    %r13
1381  *   41 5e                      pop    %r14
1382  *   c9                         leaveq
1383  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1384  *   c3                         retq
1385  *
1386  * and:
1387  *
1388  *   4c 8b 55 e8                mov    -0x18(%rbp),%r10
1389  *   48 8b 5d e0                mov    -0x20(%rbp),%rbx
1390  *   4c 8b 65 f0                mov    -0x10(%rbp),%r12
1391  *   4c 8b 6d f8                mov    -0x8(%rbp),%r13
1392  *   c9                         leaveq
1393  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1394  *   c3                         retq
1395  *
1396  * Sometimes r13 is used as the DRAP register, in which case it's saved and
1397  * restored beforehand:
1398  *
1399  *   41 55                      push   %r13
1400  *   4c 8d 6c 24 10             lea    0x10(%rsp),%r13
1401  *   48 83 e4 f0                and    $0xfffffffffffffff0,%rsp
1402  *                              ...
1403  *   49 8d 65 f0                lea    -0x10(%r13),%rsp
1404  *   41 5d                      pop    %r13
1405  *   c3                         retq
1406  */
1407 static int update_insn_state(struct instruction *insn, struct insn_state *state)
1408 {
1409         struct stack_op *op = &insn->stack_op;
1410         struct cfi_reg *cfa = &state->cfa;
1411         struct cfi_reg *regs = state->regs;
1412
1413         /* stack operations don't make sense with an undefined CFA */
1414         if (cfa->base == CFI_UNDEFINED) {
1415                 if (insn->func) {
1416                         WARN_FUNC("undefined stack state", insn->sec, insn->offset);
1417                         return -1;
1418                 }
1419                 return 0;
1420         }
1421
1422         if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET)
1423                 return update_insn_state_regs(insn, state);
1424
1425         switch (op->dest.type) {
1426
1427         case OP_DEST_REG:
1428                 switch (op->src.type) {
1429
1430                 case OP_SRC_REG:
1431                         if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
1432                             cfa->base == CFI_SP &&
1433                             regs[CFI_BP].base == CFI_CFA &&
1434                             regs[CFI_BP].offset == -cfa->offset) {
1435
1436                                 /* mov %rsp, %rbp */
1437                                 cfa->base = op->dest.reg;
1438                                 state->bp_scratch = false;
1439                         }
1440
1441                         else if (op->src.reg == CFI_SP &&
1442                                  op->dest.reg == CFI_BP && state->drap) {
1443
1444                                 /* drap: mov %rsp, %rbp */
1445                                 regs[CFI_BP].base = CFI_BP;
1446                                 regs[CFI_BP].offset = -state->stack_size;
1447                                 state->bp_scratch = false;
1448                         }
1449
1450                         else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1451
1452                                 /*
1453                                  * mov %rsp, %reg
1454                                  *
1455                                  * This is needed for the rare case where GCC
1456                                  * does:
1457                                  *
1458                                  *   mov    %rsp, %rax
1459                                  *   ...
1460                                  *   mov    %rax, %rsp
1461                                  */
1462                                 state->vals[op->dest.reg].base = CFI_CFA;
1463                                 state->vals[op->dest.reg].offset = -state->stack_size;
1464                         }
1465
1466                         else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
1467                                  cfa->base == CFI_BP) {
1468
1469                                 /*
1470                                  * mov %rbp, %rsp
1471                                  *
1472                                  * Restore the original stack pointer (Clang).
1473                                  */
1474                                 state->stack_size = -state->regs[CFI_BP].offset;
1475                         }
1476
1477                         else if (op->dest.reg == cfa->base) {
1478
1479                                 /* mov %reg, %rsp */
1480                                 if (cfa->base == CFI_SP &&
1481                                     state->vals[op->src.reg].base == CFI_CFA) {
1482
1483                                         /*
1484                                          * This is needed for the rare case
1485                                          * where GCC does something dumb like:
1486                                          *
1487                                          *   lea    0x8(%rsp), %rcx
1488                                          *   ...
1489                                          *   mov    %rcx, %rsp
1490                                          */
1491                                         cfa->offset = -state->vals[op->src.reg].offset;
1492                                         state->stack_size = cfa->offset;
1493
1494                                 } else {
1495                                         cfa->base = CFI_UNDEFINED;
1496                                         cfa->offset = 0;
1497                                 }
1498                         }
1499
1500                         break;
1501
1502                 case OP_SRC_ADD:
1503                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
1504
1505                                 /* add imm, %rsp */
1506                                 state->stack_size -= op->src.offset;
1507                                 if (cfa->base == CFI_SP)
1508                                         cfa->offset -= op->src.offset;
1509                                 break;
1510                         }
1511
1512                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
1513
1514                                 /* lea disp(%rbp), %rsp */
1515                                 state->stack_size = -(op->src.offset + regs[CFI_BP].offset);
1516                                 break;
1517                         }
1518
1519                         if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1520
1521                                 /* drap: lea disp(%rsp), %drap */
1522                                 state->drap_reg = op->dest.reg;
1523
1524                                 /*
1525                                  * lea disp(%rsp), %reg
1526                                  *
1527                                  * This is needed for the rare case where GCC
1528                                  * does something dumb like:
1529                                  *
1530                                  *   lea    0x8(%rsp), %rcx
1531                                  *   ...
1532                                  *   mov    %rcx, %rsp
1533                                  */
1534                                 state->vals[op->dest.reg].base = CFI_CFA;
1535                                 state->vals[op->dest.reg].offset = \
1536                                         -state->stack_size + op->src.offset;
1537
1538                                 break;
1539                         }
1540
1541                         if (state->drap && op->dest.reg == CFI_SP &&
1542                             op->src.reg == state->drap_reg) {
1543
1544                                  /* drap: lea disp(%drap), %rsp */
1545                                 cfa->base = CFI_SP;
1546                                 cfa->offset = state->stack_size = -op->src.offset;
1547                                 state->drap_reg = CFI_UNDEFINED;
1548                                 state->drap = false;
1549                                 break;
1550                         }
1551
1552                         if (op->dest.reg == state->cfa.base) {
1553                                 WARN_FUNC("unsupported stack register modification",
1554                                           insn->sec, insn->offset);
1555                                 return -1;
1556                         }
1557
1558                         break;
1559
1560                 case OP_SRC_AND:
1561                         if (op->dest.reg != CFI_SP ||
1562                             (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
1563                             (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
1564                                 WARN_FUNC("unsupported stack pointer realignment",
1565                                           insn->sec, insn->offset);
1566                                 return -1;
1567                         }
1568
1569                         if (state->drap_reg != CFI_UNDEFINED) {
1570                                 /* drap: and imm, %rsp */
1571                                 cfa->base = state->drap_reg;
1572                                 cfa->offset = state->stack_size = 0;
1573                                 state->drap = true;
1574                         }
1575
1576                         /*
1577                          * Older versions of GCC (4.8ish) realign the stack
1578                          * without DRAP, with a frame pointer.
1579                          */
1580
1581                         break;
1582
1583                 case OP_SRC_POP:
1584                         if (!state->drap && op->dest.type == OP_DEST_REG &&
1585                             op->dest.reg == cfa->base) {
1586
1587                                 /* pop %rbp */
1588                                 cfa->base = CFI_SP;
1589                         }
1590
1591                         if (state->drap && cfa->base == CFI_BP_INDIRECT &&
1592                             op->dest.type == OP_DEST_REG &&
1593                             op->dest.reg == state->drap_reg &&
1594                             state->drap_offset == -state->stack_size) {
1595
1596                                 /* drap: pop %drap */
1597                                 cfa->base = state->drap_reg;
1598                                 cfa->offset = 0;
1599                                 state->drap_offset = -1;
1600
1601                         } else if (regs[op->dest.reg].offset == -state->stack_size) {
1602
1603                                 /* pop %reg */
1604                                 restore_reg(state, op->dest.reg);
1605                         }
1606
1607                         state->stack_size -= 8;
1608                         if (cfa->base == CFI_SP)
1609                                 cfa->offset -= 8;
1610
1611                         break;
1612
1613                 case OP_SRC_REG_INDIRECT:
1614                         if (state->drap && op->src.reg == CFI_BP &&
1615                             op->src.offset == state->drap_offset) {
1616
1617                                 /* drap: mov disp(%rbp), %drap */
1618                                 cfa->base = state->drap_reg;
1619                                 cfa->offset = 0;
1620                                 state->drap_offset = -1;
1621                         }
1622
1623                         if (state->drap && op->src.reg == CFI_BP &&
1624                             op->src.offset == regs[op->dest.reg].offset) {
1625
1626                                 /* drap: mov disp(%rbp), %reg */
1627                                 restore_reg(state, op->dest.reg);
1628
1629                         } else if (op->src.reg == cfa->base &&
1630                             op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
1631
1632                                 /* mov disp(%rbp), %reg */
1633                                 /* mov disp(%rsp), %reg */
1634                                 restore_reg(state, op->dest.reg);
1635                         }
1636
1637                         break;
1638
1639                 default:
1640                         WARN_FUNC("unknown stack-related instruction",
1641                                   insn->sec, insn->offset);
1642                         return -1;
1643                 }
1644
1645                 break;
1646
1647         case OP_DEST_PUSH:
1648                 state->stack_size += 8;
1649                 if (cfa->base == CFI_SP)
1650                         cfa->offset += 8;
1651
1652                 if (op->src.type != OP_SRC_REG)
1653                         break;
1654
1655                 if (state->drap) {
1656                         if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1657
1658                                 /* drap: push %drap */
1659                                 cfa->base = CFI_BP_INDIRECT;
1660                                 cfa->offset = -state->stack_size;
1661
1662                                 /* save drap so we know when to restore it */
1663                                 state->drap_offset = -state->stack_size;
1664
1665                         } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
1666
1667                                 /* drap: push %rbp */
1668                                 state->stack_size = 0;
1669
1670                         } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1671
1672                                 /* drap: push %reg */
1673                                 save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
1674                         }
1675
1676                 } else {
1677
1678                         /* push %reg */
1679                         save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
1680                 }
1681
1682                 /* detect when asm code uses rbp as a scratch register */
1683                 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
1684                     cfa->base != CFI_BP)
1685                         state->bp_scratch = true;
1686                 break;
1687
1688         case OP_DEST_REG_INDIRECT:
1689
1690                 if (state->drap) {
1691                         if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1692
1693                                 /* drap: mov %drap, disp(%rbp) */
1694                                 cfa->base = CFI_BP_INDIRECT;
1695                                 cfa->offset = op->dest.offset;
1696
1697                                 /* save drap offset so we know when to restore it */
1698                                 state->drap_offset = op->dest.offset;
1699                         }
1700
1701                         else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1702
1703                                 /* drap: mov reg, disp(%rbp) */
1704                                 save_reg(state, op->src.reg, CFI_BP, op->dest.offset);
1705                         }
1706
1707                 } else if (op->dest.reg == cfa->base) {
1708
1709                         /* mov reg, disp(%rbp) */
1710                         /* mov reg, disp(%rsp) */
1711                         save_reg(state, op->src.reg, CFI_CFA,
1712                                  op->dest.offset - state->cfa.offset);
1713                 }
1714
1715                 break;
1716
1717         case OP_DEST_LEAVE:
1718                 if ((!state->drap && cfa->base != CFI_BP) ||
1719                     (state->drap && cfa->base != state->drap_reg)) {
1720                         WARN_FUNC("leave instruction with modified stack frame",
1721                                   insn->sec, insn->offset);
1722                         return -1;
1723                 }
1724
1725                 /* leave (mov %rbp, %rsp; pop %rbp) */
1726
1727                 state->stack_size = -state->regs[CFI_BP].offset - 8;
1728                 restore_reg(state, CFI_BP);
1729
1730                 if (!state->drap) {
1731                         cfa->base = CFI_SP;
1732                         cfa->offset -= 8;
1733                 }
1734
1735                 break;
1736
1737         case OP_DEST_MEM:
1738                 if (op->src.type != OP_SRC_POP) {
1739                         WARN_FUNC("unknown stack-related memory operation",
1740                                   insn->sec, insn->offset);
1741                         return -1;
1742                 }
1743
1744                 /* pop mem */
1745                 state->stack_size -= 8;
1746                 if (cfa->base == CFI_SP)
1747                         cfa->offset -= 8;
1748
1749                 break;
1750
1751         default:
1752                 WARN_FUNC("unknown stack-related instruction",
1753                           insn->sec, insn->offset);
1754                 return -1;
1755         }
1756
1757         return 0;
1758 }
1759
1760 static bool insn_state_match(struct instruction *insn, struct insn_state *state)
1761 {
1762         struct insn_state *state1 = &insn->state, *state2 = state;
1763         int i;
1764
1765         if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
1766                 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
1767                           insn->sec, insn->offset,
1768                           state1->cfa.base, state1->cfa.offset,
1769                           state2->cfa.base, state2->cfa.offset);
1770
1771         } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
1772                 for (i = 0; i < CFI_NUM_REGS; i++) {
1773                         if (!memcmp(&state1->regs[i], &state2->regs[i],
1774                                     sizeof(struct cfi_reg)))
1775                                 continue;
1776
1777                         WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
1778                                   insn->sec, insn->offset,
1779                                   i, state1->regs[i].base, state1->regs[i].offset,
1780                                   i, state2->regs[i].base, state2->regs[i].offset);
1781                         break;
1782                 }
1783
1784         } else if (state1->type != state2->type) {
1785                 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
1786                           insn->sec, insn->offset, state1->type, state2->type);
1787
1788         } else if (state1->drap != state2->drap ||
1789                  (state1->drap && state1->drap_reg != state2->drap_reg) ||
1790                  (state1->drap && state1->drap_offset != state2->drap_offset)) {
1791                 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
1792                           insn->sec, insn->offset,
1793                           state1->drap, state1->drap_reg, state1->drap_offset,
1794                           state2->drap, state2->drap_reg, state2->drap_offset);
1795
1796         } else
1797                 return true;
1798
1799         return false;
1800 }
1801
1802 /*
1803  * Follow the branch starting at the given instruction, and recursively follow
1804  * any other branches (jumps).  Meanwhile, track the frame pointer state at
1805  * each instruction and validate all the rules described in
1806  * tools/objtool/Documentation/stack-validation.txt.
1807  */
1808 static int validate_branch(struct objtool_file *file, struct instruction *first,
1809                            struct insn_state state)
1810 {
1811         struct alternative *alt;
1812         struct instruction *insn, *next_insn;
1813         struct section *sec;
1814         struct symbol *func = NULL;
1815         int ret;
1816
1817         insn = first;
1818         sec = insn->sec;
1819
1820         if (insn->alt_group && list_empty(&insn->alts)) {
1821                 WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
1822                           sec, insn->offset);
1823                 return 1;
1824         }
1825
1826         while (1) {
1827                 next_insn = next_insn_same_sec(file, insn);
1828
1829                 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
1830                         WARN("%s() falls through to next function %s()",
1831                              func->name, insn->func->name);
1832                         return 1;
1833                 }
1834
1835                 func = insn->func ? insn->func->pfunc : NULL;
1836
1837                 if (func && insn->ignore) {
1838                         WARN_FUNC("BUG: why am I validating an ignored function?",
1839                                   sec, insn->offset);
1840                         return 1;
1841                 }
1842
1843                 if (insn->visited) {
1844                         if (!insn->hint && !insn_state_match(insn, &state))
1845                                 return 1;
1846
1847                         return 0;
1848                 }
1849
1850                 if (insn->hint) {
1851                         if (insn->restore) {
1852                                 struct instruction *save_insn, *i;
1853
1854                                 i = insn;
1855                                 save_insn = NULL;
1856                                 func_for_each_insn_continue_reverse(file, insn->func, i) {
1857                                         if (i->save) {
1858                                                 save_insn = i;
1859                                                 break;
1860                                         }
1861                                 }
1862
1863                                 if (!save_insn) {
1864                                         WARN_FUNC("no corresponding CFI save for CFI restore",
1865                                                   sec, insn->offset);
1866                                         return 1;
1867                                 }
1868
1869                                 if (!save_insn->visited) {
1870                                         /*
1871                                          * Oops, no state to copy yet.
1872                                          * Hopefully we can reach this
1873                                          * instruction from another branch
1874                                          * after the save insn has been
1875                                          * visited.
1876                                          */
1877                                         if (insn == first)
1878                                                 return 0;
1879
1880                                         WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
1881                                                   sec, insn->offset);
1882                                         return 1;
1883                                 }
1884
1885                                 insn->state = save_insn->state;
1886                         }
1887
1888                         state = insn->state;
1889
1890                 } else
1891                         insn->state = state;
1892
1893                 insn->visited = true;
1894
1895                 if (!insn->ignore_alts) {
1896                         list_for_each_entry(alt, &insn->alts, list) {
1897                                 ret = validate_branch(file, alt->insn, state);
1898                                 if (ret)
1899                                         return 1;
1900                         }
1901                 }
1902
1903                 switch (insn->type) {
1904
1905                 case INSN_RETURN:
1906                         if (func && has_modified_stack_frame(&state)) {
1907                                 WARN_FUNC("return with modified stack frame",
1908                                           sec, insn->offset);
1909                                 return 1;
1910                         }
1911
1912                         if (state.bp_scratch) {
1913                                 WARN("%s uses BP as a scratch register",
1914                                      insn->func->name);
1915                                 return 1;
1916                         }
1917
1918                         return 0;
1919
1920                 case INSN_CALL:
1921                         if (is_fentry_call(insn))
1922                                 break;
1923
1924                         ret = dead_end_function(file, insn->call_dest);
1925                         if (ret == 1)
1926                                 return 0;
1927                         if (ret == -1)
1928                                 return 1;
1929
1930                         /* fallthrough */
1931                 case INSN_CALL_DYNAMIC:
1932                         if (!no_fp && func && !has_valid_stack_frame(&state)) {
1933                                 WARN_FUNC("call without frame pointer save/setup",
1934                                           sec, insn->offset);
1935                                 return 1;
1936                         }
1937                         break;
1938
1939                 case INSN_JUMP_CONDITIONAL:
1940                 case INSN_JUMP_UNCONDITIONAL:
1941                         if (insn->jump_dest &&
1942                             (!func || !insn->jump_dest->func ||
1943                              insn->jump_dest->func->pfunc == func)) {
1944                                 ret = validate_branch(file, insn->jump_dest,
1945                                                       state);
1946                                 if (ret)
1947                                         return 1;
1948
1949                         } else if (func && has_modified_stack_frame(&state)) {
1950                                 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1951                                           sec, insn->offset);
1952                                 return 1;
1953                         }
1954
1955                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
1956                                 return 0;
1957
1958                         break;
1959
1960                 case INSN_JUMP_DYNAMIC:
1961                         if (func && list_empty(&insn->alts) &&
1962                             has_modified_stack_frame(&state)) {
1963                                 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1964                                           sec, insn->offset);
1965                                 return 1;
1966                         }
1967
1968                         return 0;
1969
1970                 case INSN_CONTEXT_SWITCH:
1971                         if (func && (!next_insn || !next_insn->hint)) {
1972                                 WARN_FUNC("unsupported instruction in callable function",
1973                                           sec, insn->offset);
1974                                 return 1;
1975                         }
1976                         return 0;
1977
1978                 case INSN_STACK:
1979                         if (update_insn_state(insn, &state))
1980                                 return 1;
1981
1982                         break;
1983
1984                 default:
1985                         break;
1986                 }
1987
1988                 if (insn->dead_end)
1989                         return 0;
1990
1991                 if (!next_insn) {
1992                         if (state.cfa.base == CFI_UNDEFINED)
1993                                 return 0;
1994                         WARN("%s: unexpected end of section", sec->name);
1995                         return 1;
1996                 }
1997
1998                 insn = next_insn;
1999         }
2000
2001         return 0;
2002 }
2003
2004 static int validate_unwind_hints(struct objtool_file *file)
2005 {
2006         struct instruction *insn;
2007         int ret, warnings = 0;
2008         struct insn_state state;
2009
2010         if (!file->hints)
2011                 return 0;
2012
2013         clear_insn_state(&state);
2014
2015         for_each_insn(file, insn) {
2016                 if (insn->hint && !insn->visited) {
2017                         ret = validate_branch(file, insn, state);
2018                         warnings += ret;
2019                 }
2020         }
2021
2022         return warnings;
2023 }
2024
2025 static int validate_retpoline(struct objtool_file *file)
2026 {
2027         struct instruction *insn;
2028         int warnings = 0;
2029
2030         for_each_insn(file, insn) {
2031                 if (insn->type != INSN_JUMP_DYNAMIC &&
2032                     insn->type != INSN_CALL_DYNAMIC)
2033                         continue;
2034
2035                 if (insn->retpoline_safe)
2036                         continue;
2037
2038                 /*
2039                  * .init.text code is ran before userspace and thus doesn't
2040                  * strictly need retpolines, except for modules which are
2041                  * loaded late, they very much do need retpoline in their
2042                  * .init.text
2043                  */
2044                 if (!strcmp(insn->sec->name, ".init.text") && !module)
2045                         continue;
2046
2047                 WARN_FUNC("indirect %s found in RETPOLINE build",
2048                           insn->sec, insn->offset,
2049                           insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
2050
2051                 warnings++;
2052         }
2053
2054         return warnings;
2055 }
2056
2057 static bool is_kasan_insn(struct instruction *insn)
2058 {
2059         return (insn->type == INSN_CALL &&
2060                 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
2061 }
2062
2063 static bool is_ubsan_insn(struct instruction *insn)
2064 {
2065         return (insn->type == INSN_CALL &&
2066                 !strcmp(insn->call_dest->name,
2067                         "__ubsan_handle_builtin_unreachable"));
2068 }
2069
2070 static bool ignore_unreachable_insn(struct instruction *insn)
2071 {
2072         int i;
2073
2074         if (insn->ignore || insn->type == INSN_NOP)
2075                 return true;
2076
2077         /*
2078          * Ignore any unused exceptions.  This can happen when a whitelisted
2079          * function has an exception table entry.
2080          *
2081          * Also ignore alternative replacement instructions.  This can happen
2082          * when a whitelisted function uses one of the ALTERNATIVE macros.
2083          */
2084         if (!strcmp(insn->sec->name, ".fixup") ||
2085             !strcmp(insn->sec->name, ".altinstr_replacement") ||
2086             !strcmp(insn->sec->name, ".altinstr_aux"))
2087                 return true;
2088
2089         /*
2090          * Check if this (or a subsequent) instruction is related to
2091          * CONFIG_UBSAN or CONFIG_KASAN.
2092          *
2093          * End the search at 5 instructions to avoid going into the weeds.
2094          */
2095         if (!insn->func)
2096                 return false;
2097         for (i = 0; i < 5; i++) {
2098
2099                 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
2100                         return true;
2101
2102                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
2103                         if (insn->jump_dest &&
2104                             insn->jump_dest->func == insn->func) {
2105                                 insn = insn->jump_dest;
2106                                 continue;
2107                         }
2108
2109                         break;
2110                 }
2111
2112                 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
2113                         break;
2114
2115                 insn = list_next_entry(insn, list);
2116         }
2117
2118         return false;
2119 }
2120
2121 static int validate_functions(struct objtool_file *file)
2122 {
2123         struct section *sec;
2124         struct symbol *func;
2125         struct instruction *insn;
2126         struct insn_state state;
2127         int ret, warnings = 0;
2128
2129         clear_insn_state(&state);
2130
2131         state.cfa = initial_func_cfi.cfa;
2132         memcpy(&state.regs, &initial_func_cfi.regs,
2133                CFI_NUM_REGS * sizeof(struct cfi_reg));
2134         state.stack_size = initial_func_cfi.cfa.offset;
2135
2136         for_each_sec(file, sec) {
2137                 list_for_each_entry(func, &sec->symbol_list, list) {
2138                         if (func->type != STT_FUNC || func->pfunc != func)
2139                                 continue;
2140
2141                         insn = find_insn(file, sec, func->offset);
2142                         if (!insn || insn->ignore)
2143                                 continue;
2144
2145                         ret = validate_branch(file, insn, state);
2146                         warnings += ret;
2147                 }
2148         }
2149
2150         return warnings;
2151 }
2152
2153 static int validate_reachable_instructions(struct objtool_file *file)
2154 {
2155         struct instruction *insn;
2156
2157         if (file->ignore_unreachables)
2158                 return 0;
2159
2160         for_each_insn(file, insn) {
2161                 if (insn->visited || ignore_unreachable_insn(insn))
2162                         continue;
2163
2164                 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
2165                 return 1;
2166         }
2167
2168         return 0;
2169 }
2170
2171 static void cleanup(struct objtool_file *file)
2172 {
2173         struct instruction *insn, *tmpinsn;
2174         struct alternative *alt, *tmpalt;
2175
2176         list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) {
2177                 list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) {
2178                         list_del(&alt->list);
2179                         free(alt);
2180                 }
2181                 list_del(&insn->list);
2182                 hash_del(&insn->hash);
2183                 free(insn);
2184         }
2185         elf_close(file->elf);
2186 }
2187
2188 static struct objtool_file file;
2189
2190 int check(const char *_objname, bool orc)
2191 {
2192         int ret, warnings = 0;
2193
2194         objname = _objname;
2195
2196         file.elf = elf_open(objname, orc ? O_RDWR : O_RDONLY);
2197         if (!file.elf)
2198                 return 1;
2199
2200         INIT_LIST_HEAD(&file.insn_list);
2201         hash_init(file.insn_hash);
2202         file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard");
2203         file.c_file = find_section_by_name(file.elf, ".comment");
2204         file.ignore_unreachables = no_unreachable;
2205         file.hints = false;
2206
2207         arch_initial_func_cfi_state(&initial_func_cfi);
2208
2209         ret = decode_sections(&file);
2210         if (ret < 0)
2211                 goto out;
2212         warnings += ret;
2213
2214         if (list_empty(&file.insn_list))
2215                 goto out;
2216
2217         if (retpoline) {
2218                 ret = validate_retpoline(&file);
2219                 if (ret < 0)
2220                         return ret;
2221                 warnings += ret;
2222         }
2223
2224         ret = validate_functions(&file);
2225         if (ret < 0)
2226                 goto out;
2227         warnings += ret;
2228
2229         ret = validate_unwind_hints(&file);
2230         if (ret < 0)
2231                 goto out;
2232         warnings += ret;
2233
2234         if (!warnings) {
2235                 ret = validate_reachable_instructions(&file);
2236                 if (ret < 0)
2237                         goto out;
2238                 warnings += ret;
2239         }
2240
2241         if (orc) {
2242                 ret = create_orc(&file);
2243                 if (ret < 0)
2244                         goto out;
2245
2246                 ret = create_orc_sections(&file);
2247                 if (ret < 0)
2248                         goto out;
2249
2250                 ret = elf_write(file.elf);
2251                 if (ret < 0)
2252                         goto out;
2253         }
2254
2255 out:
2256         cleanup(&file);
2257
2258         /* ignore warnings for now until we get all the code cleaned up */
2259         if (ret || warnings)
2260                 return 0;
2261         return 0;
2262 }