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 #define FAKE_JUMP_OFFSET -1
  32
  33 struct alternative {
  34         struct list_head list;
  35         struct instruction *insn;
  36 };
  37
  38 const char *objname;
  39 struct cfi_state initial_func_cfi;
  40
  41 struct instruction *find_insn(struct objtool_file *file,
  42                               struct section *sec, unsigned long offset)
  43 {
  44         struct instruction *insn;
  45
  46         hash_for_each_possible(file->insn_hash, insn, hash, offset)
  47                 if (insn->sec == sec && insn->offset == offset)
  48                         return insn;
  49
  50         return NULL;
  51 }
  52
  53 static struct instruction *next_insn_same_sec(struct objtool_file *file,
  54                                               struct instruction *insn)
  55 {
  56         struct instruction *next = list_next_entry(insn, list);
  57
  58         if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
  59                 return NULL;
  60
  61         return next;
  62 }
  63
  64 static struct instruction *next_insn_same_func(struct objtool_file *file,
  65                                                struct instruction *insn)
  66 {
  67         struct instruction *next = list_next_entry(insn, list);
  68         struct symbol *func = insn->func;
  69
  70         if (!func)
  71                 return NULL;
  72
  73         if (&next->list != &file->insn_list && next->func == func)
  74                 return next;
  75
  76         /* Check if we're already in the subfunction: */
  77         if (func == func->cfunc)
  78                 return NULL;
  79
  80         /* Move to the subfunction: */
  81         return find_insn(file, func->cfunc->sec, func->cfunc->offset);
  82 }
  83
  84 #define func_for_each_insn_all(file, func, insn)                        \
  85         for (insn = find_insn(file, func->sec, func->offset);           \
  86              insn;                                                      \
  87              insn = next_insn_same_func(file, insn))
  88
  89 #define func_for_each_insn(file, func, insn)                            \
  90         for (insn = find_insn(file, func->sec, func->offset);           \
  91              insn && &insn->list != &file->insn_list &&                 \
  92                 insn->sec == func->sec &&                               \
  93                 insn->offset < func->offset + func->len;                \
  94              insn = list_next_entry(insn, list))
  95
  96 #define func_for_each_insn_continue_reverse(file, func, insn)           \
  97         for (insn = list_prev_entry(insn, list);                        \
  98              &insn->list != &file->insn_list &&                         \
  99                 insn->sec == func->sec && insn->offset >= func->offset; \
 100              insn = list_prev_entry(insn, list))
 101
 102 #define sec_for_each_insn_from(file, insn)                              \
 103         for (; insn; insn = next_insn_same_sec(file, insn))
 104
 105 #define sec_for_each_insn_continue(file, insn)                          \
 106         for (insn = next_insn_same_sec(file, insn); insn;               \
 107              insn = next_insn_same_sec(file, insn))
 108
 109 /*
 110  * Check if the function has been manually whitelisted with the
 111  * STACK_FRAME_NON_STANDARD macro, or if it should be automatically whitelisted
 112  * due to its use of a context switching instruction.
 113  */
 114 static bool ignore_func(struct objtool_file *file, struct symbol *func)
 115 {
 116         struct rela *rela;
 117
 118         /* check for STACK_FRAME_NON_STANDARD */
 119         if (file->whitelist && file->whitelist->rela)
 120                 list_for_each_entry(rela, &file->whitelist->rela->rela_list, list) {
 121                         if (rela->sym->type == STT_SECTION &&
 122                             rela->sym->sec == func->sec &&
 123                             rela->addend == func->offset)
 124                                 return true;
 125                         if (rela->sym->type == STT_FUNC && rela->sym == func)
 126                                 return true;
 127                 }
 128
 129         return false;
 130 }
 131
 132 /*
 133  * This checks to see if the given function is a "noreturn" function.
 134  *
 135  * For global functions which are outside the scope of this object file, we
 136  * have to keep a manual list of them.
 137  *
 138  * For local functions, we have to detect them manually by simply looking for
 139  * the lack of a return instruction.
 140  *
 141  * Returns:
 142  *  -1: error
 143  *   0: no dead end
 144  *   1: dead end
 145  */
 146 static int __dead_end_function(struct objtool_file *file, struct symbol *func,
 147                                int recursion)
 148 {
 149         int i;
 150         struct instruction *insn;
 151         bool empty = true;
 152
 153         /*
 154          * Unfortunately these have to be hard coded because the noreturn
 155          * attribute isn't provided in ELF data.
 156          */
 157         static const char * const global_noreturns[] = {
 158                 "__stack_chk_fail",
 159                 "panic",
 160                 "do_exit",
 161                 "do_task_dead",
 162                 "__module_put_and_exit",
 163                 "complete_and_exit",
 164                 "kvm_spurious_fault",
 165                 "__reiserfs_panic",
 166                 "lbug_with_loc",
 167                 "fortify_panic",
 168                 "usercopy_abort",
 169                 "machine_real_restart",
 170                 "rewind_stack_do_exit",
 171         };
 172
 173         if (func->bind == STB_WEAK)
 174                 return 0;
 175
 176         if (func->bind == STB_GLOBAL)
 177                 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
 178                         if (!strcmp(func->name, global_noreturns[i]))
 179                                 return 1;
 180
 181         if (!func->len)
 182                 return 0;
 183
 184         insn = find_insn(file, func->sec, func->offset);
 185         if (!insn->func)
 186                 return 0;
 187
 188         func_for_each_insn_all(file, func, insn) {
 189                 empty = false;
 190
 191                 if (insn->type == INSN_RETURN)
 192                         return 0;
 193         }
 194
 195         if (empty)
 196                 return 0;
 197
 198         /*
 199          * A function can have a sibling call instead of a return.  In that
 200          * case, the function's dead-end status depends on whether the target
 201          * of the sibling call returns.
 202          */
 203         func_for_each_insn_all(file, func, insn) {
 204                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
 205                         struct instruction *dest = insn->jump_dest;
 206
 207                         if (!dest)
 208                                 /* sibling call to another file */
 209                                 return 0;
 210
 211                         if (dest->func && dest->func->pfunc != insn->func->pfunc) {
 212
 213                                 /* local sibling call */
 214                                 if (recursion == 5) {
 215                                         /*
 216                                          * Infinite recursion: two functions
 217                                          * have sibling calls to each other.
 218                                          * This is a very rare case.  It means
 219                                          * they aren't dead ends.
 220                                          */
 221                                         return 0;
 222                                 }
 223
 224                                 return __dead_end_function(file, dest->func,
 225                                                            recursion + 1);
 226                         }
 227                 }
 228
 229                 if (insn->type == INSN_JUMP_DYNAMIC && list_empty(&insn->alts))
 230                         /* sibling call */
 231                         return 0;
 232         }
 233
 234         return 1;
 235 }
 236
 237 static int dead_end_function(struct objtool_file *file, struct symbol *func)
 238 {
 239         return __dead_end_function(file, func, 0);
 240 }
 241
 242 static void clear_insn_state(struct insn_state *state)
 243 {
 244         int i;
 245
 246         memset(state, 0, sizeof(*state));
 247         state->cfa.base = CFI_UNDEFINED;
 248         for (i = 0; i < CFI_NUM_REGS; i++) {
 249                 state->regs[i].base = CFI_UNDEFINED;
 250                 state->vals[i].base = CFI_UNDEFINED;
 251         }
 252         state->drap_reg = CFI_UNDEFINED;
 253         state->drap_offset = -1;
 254 }
 255
 256 /*
 257  * Call the arch-specific instruction decoder for all the instructions and add
 258  * them to the global instruction list.
 259  */
 260 static int decode_instructions(struct objtool_file *file)
 261 {
 262         struct section *sec;
 263         struct symbol *func;
 264         unsigned long offset;
 265         struct instruction *insn;
 266         int ret;
 267
 268         for_each_sec(file, sec) {
 269
 270                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
 271                         continue;
 272
 273                 if (strcmp(sec->name, ".altinstr_replacement") &&
 274                     strcmp(sec->name, ".altinstr_aux") &&
 275                     strncmp(sec->name, ".discard.", 9))
 276                         sec->text = true;
 277
 278                 for (offset = 0; offset < sec->len; offset += insn->len) {
 279                         insn = malloc(sizeof(*insn));
 280                         if (!insn) {
 281                                 WARN("malloc failed");
 282                                 return -1;
 283                         }
 284                         memset(insn, 0, sizeof(*insn));
 285                         INIT_LIST_HEAD(&insn->alts);
 286                         clear_insn_state(&insn->state);
 287
 288                         insn->sec = sec;
 289                         insn->offset = offset;
 290
 291                         ret = arch_decode_instruction(file->elf, sec, offset,
 292                                                       sec->len - offset,
 293                                                       &insn->len, &insn->type,
 294                                                       &insn->immediate,
 295                                                       &insn->stack_op);
 296                         if (ret)
 297                                 goto err;
 298
 299                         if (!insn->type || insn->type > INSN_LAST) {
 300                                 WARN_FUNC("invalid instruction type %d",
 301                                           insn->sec, insn->offset, insn->type);
 302                                 ret = -1;
 303                                 goto err;
 304                         }
 305
 306                         hash_add(file->insn_hash, &insn->hash, insn->offset);
 307                         list_add_tail(&insn->list, &file->insn_list);
 308                 }
 309
 310                 list_for_each_entry(func, &sec->symbol_list, list) {
 311                         if (func->type != STT_FUNC)
 312                                 continue;
 313
 314                         if (!find_insn(file, sec, func->offset)) {
 315                                 WARN("%s(): can't find starting instruction",
 316                                      func->name);
 317                                 return -1;
 318                         }
 319
 320                         func_for_each_insn(file, func, insn)
 321                                 if (!insn->func)
 322                                         insn->func = func;
 323                 }
 324         }
 325
 326         return 0;
 327
 328 err:
 329         free(insn);
 330         return ret;
 331 }
 332
 333 /*
 334  * Mark "ud2" instructions and manually annotated dead ends.
 335  */
 336 static int add_dead_ends(struct objtool_file *file)
 337 {
 338         struct section *sec;
 339         struct rela *rela;
 340         struct instruction *insn;
 341         bool found;
 342
 343         /*
 344          * By default, "ud2" is a dead end unless otherwise annotated, because
 345          * GCC 7 inserts it for certain divide-by-zero cases.
 346          */
 347         for_each_insn(file, insn)
 348                 if (insn->type == INSN_BUG)
 349                         insn->dead_end = true;
 350
 351         /*
 352          * Check for manually annotated dead ends.
 353          */
 354         sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
 355         if (!sec)
 356                 goto reachable;
 357
 358         list_for_each_entry(rela, &sec->rela_list, list) {
 359                 if (rela->sym->type != STT_SECTION) {
 360                         WARN("unexpected relocation symbol type in %s", sec->name);
 361                         return -1;
 362                 }
 363                 insn = find_insn(file, rela->sym->sec, rela->addend);
 364                 if (insn)
 365                         insn = list_prev_entry(insn, list);
 366                 else if (rela->addend == rela->sym->sec->len) {
 367                         found = false;
 368                         list_for_each_entry_reverse(insn, &file->insn_list, list) {
 369                                 if (insn->sec == rela->sym->sec) {
 370                                         found = true;
 371                                         break;
 372                                 }
 373                         }
 374
 375                         if (!found) {
 376                                 WARN("can't find unreachable insn at %s+0x%x",
 377                                      rela->sym->sec->name, rela->addend);
 378                                 return -1;
 379                         }
 380                 } else {
 381                         WARN("can't find unreachable insn at %s+0x%x",
 382                              rela->sym->sec->name, rela->addend);
 383                         return -1;
 384                 }
 385
 386                 insn->dead_end = true;
 387         }
 388
 389 reachable:
 390         /*
 391          * These manually annotated reachable checks are needed for GCC 4.4,
 392          * where the Linux unreachable() macro isn't supported.  In that case
 393          * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
 394          * not a dead end.
 395          */
 396         sec = find_section_by_name(file->elf, ".rela.discard.reachable");
 397         if (!sec)
 398                 return 0;
 399
 400         list_for_each_entry(rela, &sec->rela_list, list) {
 401                 if (rela->sym->type != STT_SECTION) {
 402                         WARN("unexpected relocation symbol type in %s", sec->name);
 403                         return -1;
 404                 }
 405                 insn = find_insn(file, rela->sym->sec, rela->addend);
 406                 if (insn)
 407                         insn = list_prev_entry(insn, list);
 408                 else if (rela->addend == rela->sym->sec->len) {
 409                         found = false;
 410                         list_for_each_entry_reverse(insn, &file->insn_list, list) {
 411                                 if (insn->sec == rela->sym->sec) {
 412                                         found = true;
 413                                         break;
 414                                 }
 415                         }
 416
 417                         if (!found) {
 418                                 WARN("can't find reachable insn at %s+0x%x",
 419                                      rela->sym->sec->name, rela->addend);
 420                                 return -1;
 421                         }
 422                 } else {
 423                         WARN("can't find reachable insn at %s+0x%x",
 424                              rela->sym->sec->name, rela->addend);
 425                         return -1;
 426                 }
 427
 428                 insn->dead_end = false;
 429         }
 430
 431         return 0;
 432 }
 433
 434 /*
 435  * Warnings shouldn't be reported for ignored functions.
 436  */
 437 static void add_ignores(struct objtool_file *file)
 438 {
 439         struct instruction *insn;
 440         struct section *sec;
 441         struct symbol *func;
 442
 443         for_each_sec(file, sec) {
 444                 list_for_each_entry(func, &sec->symbol_list, list) {
 445                         if (func->type != STT_FUNC)
 446                                 continue;
 447
 448                         if (!ignore_func(file, func))
 449                                 continue;
 450
 451                         func_for_each_insn_all(file, func, insn)
 452                                 insn->ignore = true;
 453                 }
 454         }
 455 }
 456
 457 /*
 458  * FIXME: For now, just ignore any alternatives which add retpolines.  This is
 459  * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
 460  * But it at least allows objtool to understand the control flow *around* the
 461  * retpoline.
 462  */
 463 static int add_nospec_ignores(struct objtool_file *file)
 464 {
 465         struct section *sec;
 466         struct rela *rela;
 467         struct instruction *insn;
 468
 469         sec = find_section_by_name(file->elf, ".rela.discard.nospec");
 470         if (!sec)
 471                 return 0;
 472
 473         list_for_each_entry(rela, &sec->rela_list, list) {
 474                 if (rela->sym->type != STT_SECTION) {
 475                         WARN("unexpected relocation symbol type in %s", sec->name);
 476                         return -1;
 477                 }
 478
 479                 insn = find_insn(file, rela->sym->sec, rela->addend);
 480                 if (!insn) {
 481                         WARN("bad .discard.nospec entry");
 482                         return -1;
 483                 }
 484
 485                 insn->ignore_alts = true;
 486         }
 487
 488         return 0;
 489 }
 490
 491 /*
 492  * Find the destination instructions for all jumps.
 493  */
 494 static int add_jump_destinations(struct objtool_file *file)
 495 {
 496         struct instruction *insn;
 497         struct rela *rela;
 498         struct section *dest_sec;
 499         unsigned long dest_off;
 500
 501         for_each_insn(file, insn) {
 502                 if (insn->type != INSN_JUMP_CONDITIONAL &&
 503                     insn->type != INSN_JUMP_UNCONDITIONAL)
 504                         continue;
 505
 506                 if (insn->offset == FAKE_JUMP_OFFSET)
 507                         continue;
 508
 509                 rela = find_rela_by_dest_range(insn->sec, insn->offset,
 510                                                insn->len);
 511                 if (!rela) {
 512                         dest_sec = insn->sec;
 513                         dest_off = insn->offset + insn->len + insn->immediate;
 514                 } else if (rela->sym->type == STT_SECTION) {
 515                         dest_sec = rela->sym->sec;
 516                         dest_off = rela->addend + 4;
 517                 } else if (rela->sym->sec->idx) {
 518                         dest_sec = rela->sym->sec;
 519                         dest_off = rela->sym->sym.st_value + rela->addend + 4;
 520                 } else if (strstr(rela->sym->name, "_indirect_thunk_")) {
 521                         /*
 522                          * Retpoline jumps are really dynamic jumps in
 523                          * disguise, so convert them accordingly.
 524                          */
 525                         insn->type = INSN_JUMP_DYNAMIC;
 526                         insn->retpoline_safe = true;
 527                         continue;
 528                 } else {
 529                         /* sibling call */
 530                         insn->jump_dest = 0;
 531                         continue;
 532                 }
 533
 534                 insn->jump_dest = find_insn(file, dest_sec, dest_off);
 535                 if (!insn->jump_dest) {
 536
 537                         /*
 538                          * This is a special case where an alt instruction
 539                          * jumps past the end of the section.  These are
 540                          * handled later in handle_group_alt().
 541                          */
 542                         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
 543                                 continue;
 544
 545                         WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
 546                                   insn->sec, insn->offset, dest_sec->name,
 547                                   dest_off);
 548                         return -1;
 549                 }
 550
 551                 /*
 552                  * For GCC 8+, create parent/child links for any cold
 553                  * subfunctions.  This is _mostly_ redundant with a similar
 554                  * initialization in read_symbols().
 555                  *
 556                  * If a function has aliases, we want the *first* such function
 557                  * in the symbol table to be the subfunction's parent.  In that
 558                  * case we overwrite the initialization done in read_symbols().
 559                  *
 560                  * However this code can't completely replace the
 561                  * read_symbols() code because this doesn't detect the case
 562                  * where the parent function's only reference to a subfunction
 563                  * is through a switch table.
 564                  */
 565                 if (insn->func && insn->jump_dest->func &&
 566                     insn->func != insn->jump_dest->func &&
 567                     !strstr(insn->func->name, ".cold.") &&
 568                     strstr(insn->jump_dest->func->name, ".cold.")) {
 569                         insn->func->cfunc = insn->jump_dest->func;
 570                         insn->jump_dest->func->pfunc = insn->func;
 571                 }
 572         }
 573
 574         return 0;
 575 }
 576
 577 /*
 578  * Find the destination instructions for all calls.
 579  */
 580 static int add_call_destinations(struct objtool_file *file)
 581 {
 582         struct instruction *insn;
 583         unsigned long dest_off;
 584         struct rela *rela;
 585
 586         for_each_insn(file, insn) {
 587                 if (insn->type != INSN_CALL)
 588                         continue;
 589
 590                 rela = find_rela_by_dest_range(insn->sec, insn->offset,
 591                                                insn->len);
 592                 if (!rela) {
 593                         dest_off = insn->offset + insn->len + insn->immediate;
 594                         insn->call_dest = find_symbol_by_offset(insn->sec,
 595                                                                 dest_off);
 596
 597                         if (!insn->call_dest && !insn->ignore) {
 598                                 WARN_FUNC("unsupported intra-function call",
 599                                           insn->sec, insn->offset);
 600                                 if (retpoline)
 601                                         WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");
 602                                 return -1;
 603                         }
 604
 605                 } else if (rela->sym->type == STT_SECTION) {
 606                         insn->call_dest = find_symbol_by_offset(rela->sym->sec,
 607                                                                 rela->addend+4);
 608                         if (!insn->call_dest ||
 609                             insn->call_dest->type != STT_FUNC) {
 610                                 WARN_FUNC("can't find call dest symbol at %s+0x%x",
 611                                           insn->sec, insn->offset,
 612                                           rela->sym->sec->name,
 613                                           rela->addend + 4);
 614                                 return -1;
 615                         }
 616                 } else
 617                         insn->call_dest = rela->sym;
 618         }
 619
 620         return 0;
 621 }
 622
 623 /*
 624  * The .alternatives section requires some extra special care, over and above
 625  * what other special sections require:
 626  *
 627  * 1. Because alternatives are patched in-place, we need to insert a fake jump
 628  *    instruction at the end so that validate_branch() skips all the original
 629  *    replaced instructions when validating the new instruction path.
 630  *
 631  * 2. An added wrinkle is that the new instruction length might be zero.  In
 632  *    that case the old instructions are replaced with noops.  We simulate that
 633  *    by creating a fake jump as the only new instruction.
 634  *
 635  * 3. In some cases, the alternative section includes an instruction which
 636  *    conditionally jumps to the _end_ of the entry.  We have to modify these
 637  *    jumps' destinations to point back to .text rather than the end of the
 638  *    entry in .altinstr_replacement.
 639  *
 640  * 4. It has been requested that we don't validate the !POPCNT feature path
 641  *    which is a "very very small percentage of machines".
 642  */
 643 static int handle_group_alt(struct objtool_file *file,
 644                             struct special_alt *special_alt,
 645                             struct instruction *orig_insn,
 646                             struct instruction **new_insn)
 647 {
 648         struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
 649         unsigned long dest_off;
 650
 651         last_orig_insn = NULL;
 652         insn = orig_insn;
 653         sec_for_each_insn_from(file, insn) {
 654                 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
 655                         break;
 656
 657                 if (special_alt->skip_orig)
 658                         insn->type = INSN_NOP;
 659
 660                 insn->alt_group = true;
 661                 last_orig_insn = insn;
 662         }
 663
 664         if (next_insn_same_sec(file, last_orig_insn)) {
 665                 fake_jump = malloc(sizeof(*fake_jump));
 666                 if (!fake_jump) {
 667                         WARN("malloc failed");
 668                         return -1;
 669                 }
 670                 memset(fake_jump, 0, sizeof(*fake_jump));
 671                 INIT_LIST_HEAD(&fake_jump->alts);
 672                 clear_insn_state(&fake_jump->state);
 673
 674                 fake_jump->sec = special_alt->new_sec;
 675                 fake_jump->offset = FAKE_JUMP_OFFSET;
 676                 fake_jump->type = INSN_JUMP_UNCONDITIONAL;
 677                 fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
 678                 fake_jump->func = orig_insn->func;
 679         }
 680
 681         if (!special_alt->new_len) {
 682                 if (!fake_jump) {
 683                         WARN("%s: empty alternative at end of section",
 684                              special_alt->orig_sec->name);
 685                         return -1;
 686                 }
 687
 688                 *new_insn = fake_jump;
 689                 return 0;
 690         }
 691
 692         last_new_insn = NULL;
 693         insn = *new_insn;
 694         sec_for_each_insn_from(file, insn) {
 695                 if (insn->offset >= special_alt->new_off + special_alt->new_len)
 696                         break;
 697
 698                 last_new_insn = insn;
 699
 700                 insn->ignore = orig_insn->ignore_alts;
 701
 702                 if (insn->type != INSN_JUMP_CONDITIONAL &&
 703                     insn->type != INSN_JUMP_UNCONDITIONAL)
 704                         continue;
 705
 706                 if (!insn->immediate)
 707                         continue;
 708
 709                 dest_off = insn->offset + insn->len + insn->immediate;
 710                 if (dest_off == special_alt->new_off + special_alt->new_len) {
 711                         if (!fake_jump) {
 712                                 WARN("%s: alternative jump to end of section",
 713                                      special_alt->orig_sec->name);
 714                                 return -1;
 715                         }
 716                         insn->jump_dest = fake_jump;
 717                 }
 718
 719                 if (!insn->jump_dest) {
 720                         WARN_FUNC("can't find alternative jump destination",
 721                                   insn->sec, insn->offset);
 722                         return -1;
 723                 }
 724         }
 725
 726         if (!last_new_insn) {
 727                 WARN_FUNC("can't find last new alternative instruction",
 728                           special_alt->new_sec, special_alt->new_off);
 729                 return -1;
 730         }
 731
 732         if (fake_jump)
 733                 list_add(&fake_jump->list, &last_new_insn->list);
 734
 735         return 0;
 736 }
 737
 738 /*
 739  * A jump table entry can either convert a nop to a jump or a jump to a nop.
 740  * If the original instruction is a jump, make the alt entry an effective nop
 741  * by just skipping the original instruction.
 742  */
 743 static int handle_jump_alt(struct objtool_file *file,
 744                            struct special_alt *special_alt,
 745                            struct instruction *orig_insn,
 746                            struct instruction **new_insn)
 747 {
 748         if (orig_insn->type == INSN_NOP)
 749                 return 0;
 750
 751         if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
 752                 WARN_FUNC("unsupported instruction at jump label",
 753                           orig_insn->sec, orig_insn->offset);
 754                 return -1;
 755         }
 756
 757         *new_insn = list_next_entry(orig_insn, list);
 758         return 0;
 759 }
 760
 761 /*
 762  * Read all the special sections which have alternate instructions which can be
 763  * patched in or redirected to at runtime.  Each instruction having alternate
 764  * instruction(s) has them added to its insn->alts list, which will be
 765  * traversed in validate_branch().
 766  */
 767 static int add_special_section_alts(struct objtool_file *file)
 768 {
 769         struct list_head special_alts;
 770         struct instruction *orig_insn, *new_insn;
 771         struct special_alt *special_alt, *tmp;
 772         struct alternative *alt;
 773         int ret;
 774
 775         ret = special_get_alts(file->elf, &special_alts);
 776         if (ret)
 777                 return ret;
 778
 779         list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
 780
 781                 orig_insn = find_insn(file, special_alt->orig_sec,
 782                                       special_alt->orig_off);
 783                 if (!orig_insn) {
 784                         WARN_FUNC("special: can't find orig instruction",
 785                                   special_alt->orig_sec, special_alt->orig_off);
 786                         ret = -1;
 787                         goto out;
 788                 }
 789
 790                 new_insn = NULL;
 791                 if (!special_alt->group || special_alt->new_len) {
 792                         new_insn = find_insn(file, special_alt->new_sec,
 793                                              special_alt->new_off);
 794                         if (!new_insn) {
 795                                 WARN_FUNC("special: can't find new instruction",
 796                                           special_alt->new_sec,
 797                                           special_alt->new_off);
 798                                 ret = -1;
 799                                 goto out;
 800                         }
 801                 }
 802
 803                 if (special_alt->group) {
 804                         if (!special_alt->orig_len) {
 805                                 WARN_FUNC("empty alternative entry",
 806                                           orig_insn->sec, orig_insn->offset);
 807                                 continue;
 808                         }
 809
 810                         ret = handle_group_alt(file, special_alt, orig_insn,
 811                                                &new_insn);
 812                         if (ret)
 813                                 goto out;
 814                 } else if (special_alt->jump_or_nop) {
 815                         ret = handle_jump_alt(file, special_alt, orig_insn,
 816                                               &new_insn);
 817                         if (ret)
 818                                 goto out;
 819                 }
 820
 821                 alt = malloc(sizeof(*alt));
 822                 if (!alt) {
 823                         WARN("malloc failed");
 824                         ret = -1;
 825                         goto out;
 826                 }
 827
 828                 alt->insn = new_insn;
 829                 list_add_tail(&alt->list, &orig_insn->alts);
 830
 831                 list_del(&special_alt->list);
 832                 free(special_alt);
 833         }
 834
 835 out:
 836         return ret;
 837 }
 838
 839 static int add_switch_table(struct objtool_file *file, struct instruction *insn,
 840                             struct rela *table, struct rela *next_table)
 841 {
 842         struct rela *rela = table;
 843         struct instruction *alt_insn;
 844         struct alternative *alt;
 845         struct symbol *pfunc = insn->func->pfunc;
 846         unsigned int prev_offset = 0;
 847
 848         list_for_each_entry_from(rela, &table->rela_sec->rela_list, list) {
 849                 if (rela == next_table)
 850                         break;
 851
 852                 /* Make sure the switch table entries are consecutive: */
 853                 if (prev_offset && rela->offset != prev_offset + 8)
 854                         break;
 855
 856                 /* Detect function pointers from contiguous objects: */
 857                 if (rela->sym->sec == pfunc->sec &&
 858                     rela->addend == pfunc->offset)
 859                         break;
 860
 861                 alt_insn = find_insn(file, rela->sym->sec, rela->addend);
 862                 if (!alt_insn)
 863                         break;
 864
 865                 /* Make sure the jmp dest is in the function or subfunction: */
 866                 if (alt_insn->func->pfunc != pfunc)
 867                         break;
 868
 869                 alt = malloc(sizeof(*alt));
 870                 if (!alt) {
 871                         WARN("malloc failed");
 872                         return -1;
 873                 }
 874
 875                 alt->insn = alt_insn;
 876                 list_add_tail(&alt->list, &insn->alts);
 877                 prev_offset = rela->offset;
 878         }
 879
 880         if (!prev_offset) {
 881                 WARN_FUNC("can't find switch jump table",
 882                           insn->sec, insn->offset);
 883                 return -1;
 884         }
 885
 886         return 0;
 887 }
 888
 889 /*
 890  * find_switch_table() - Given a dynamic jump, find the switch jump table in
 891  * .rodata associated with it.
 892  *
 893  * There are 3 basic patterns:
 894  *
 895  * 1. jmpq *[rodata addr](,%reg,8)
 896  *
 897  *    This is the most common case by far.  It jumps to an address in a simple
 898  *    jump table which is stored in .rodata.
 899  *
 900  * 2. jmpq *[rodata addr](%rip)
 901  *
 902  *    This is caused by a rare GCC quirk, currently only seen in three driver
 903  *    functions in the kernel, only with certain obscure non-distro configs.
 904  *
 905  *    As part of an optimization, GCC makes a copy of an existing switch jump
 906  *    table, modifies it, and then hard-codes the jump (albeit with an indirect
 907  *    jump) to use a single entry in the table.  The rest of the jump table and
 908  *    some of its jump targets remain as dead code.
 909  *
 910  *    In such a case we can just crudely ignore all unreachable instruction
 911  *    warnings for the entire object file.  Ideally we would just ignore them
 912  *    for the function, but that would require redesigning the code quite a
 913  *    bit.  And honestly that's just not worth doing: unreachable instruction
 914  *    warnings are of questionable value anyway, and this is such a rare issue.
 915  *
 916  * 3. mov [rodata addr],%reg1
 917  *    ... some instructions ...
 918  *    jmpq *(%reg1,%reg2,8)
 919  *
 920  *    This is a fairly uncommon pattern which is new for GCC 6.  As of this
 921  *    writing, there are 11 occurrences of it in the allmodconfig kernel.
 922  *
 923  *    As of GCC 7 there are quite a few more of these and the 'in between' code
 924  *    is significant. Esp. with KASAN enabled some of the code between the mov
 925  *    and jmpq uses .rodata itself, which can confuse things.
 926  *
 927  *    TODO: Once we have DWARF CFI and smarter instruction decoding logic,
 928  *    ensure the same register is used in the mov and jump instructions.
 929  *
 930  *    NOTE: RETPOLINE made it harder still to decode dynamic jumps.
 931  */
 932 static struct rela *find_switch_table(struct objtool_file *file,
 933                                       struct symbol *func,
 934                                       struct instruction *insn)
 935 {
 936         struct rela *text_rela, *rodata_rela;
 937         struct instruction *orig_insn = insn;
 938         struct section *rodata_sec;
 939         unsigned long table_offset;
 940
 941         /*
 942          * Backward search using the @first_jump_src links, these help avoid
 943          * much of the 'in between' code. Which avoids us getting confused by
 944          * it.
 945          */
 946         for (;
 947              &insn->list != &file->insn_list && insn->func && insn->func->pfunc == func;
 948              insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
 949
 950                 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
 951                         break;
 952
 953                 /* allow small jumps within the range */
 954                 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
 955                     insn->jump_dest &&
 956                     (insn->jump_dest->offset <= insn->offset ||
 957                      insn->jump_dest->offset > orig_insn->offset))
 958                     break;
 959
 960                 /* look for a relocation which references .rodata */
 961                 text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
 962                                                     insn->len);
 963                 if (!text_rela || text_rela->sym->type != STT_SECTION ||
 964                     !text_rela->sym->sec->rodata)
 965                         continue;
 966
 967                 table_offset = text_rela->addend;
 968                 rodata_sec = text_rela->sym->sec;
 969
 970                 if (text_rela->type == R_X86_64_PC32)
 971                         table_offset += 4;
 972
 973                 /*
 974                  * Make sure the .rodata address isn't associated with a
 975                  * symbol.  gcc jump tables are anonymous data.
 976                  */
 977                 if (find_symbol_containing(rodata_sec, table_offset))
 978                         continue;
 979
 980                 rodata_rela = find_rela_by_dest(rodata_sec, table_offset);
 981                 if (rodata_rela) {
 982                         /*
 983                          * Use of RIP-relative switch jumps is quite rare, and
 984                          * indicates a rare GCC quirk/bug which can leave dead
 985                          * code behind.
 986                          */
 987                         if (text_rela->type == R_X86_64_PC32)
 988                                 file->ignore_unreachables = true;
 989
 990                         return rodata_rela;
 991                 }
 992         }
 993
 994         return NULL;
 995 }
 996
 997
 998 static int add_func_switch_tables(struct objtool_file *file,
 999                                   struct symbol *func)
1000 {
1001         struct instruction *insn, *last = NULL, *prev_jump = NULL;
1002         struct rela *rela, *prev_rela = NULL;
1003         int ret;
1004
1005         func_for_each_insn_all(file, func, insn) {
1006                 if (!last)
1007                         last = insn;
1008
1009                 /*
1010                  * Store back-pointers for unconditional forward jumps such
1011                  * that find_switch_table() can back-track using those and
1012                  * avoid some potentially confusing code.
1013                  */
1014                 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1015                     insn->offset > last->offset &&
1016                     insn->jump_dest->offset > insn->offset &&
1017                     !insn->jump_dest->first_jump_src) {
1018
1019                         insn->jump_dest->first_jump_src = insn;
1020                         last = insn->jump_dest;
1021                 }
1022
1023                 if (insn->type != INSN_JUMP_DYNAMIC)
1024                         continue;
1025
1026                 rela = find_switch_table(file, func, insn);
1027                 if (!rela)
1028                         continue;
1029
1030                 /*
1031                  * We found a switch table, but we don't know yet how big it
1032                  * is.  Don't add it until we reach the end of the function or
1033                  * the beginning of another switch table in the same function.
1034                  */
1035                 if (prev_jump) {
1036                         ret = add_switch_table(file, prev_jump, prev_rela, rela);
1037                         if (ret)
1038                                 return ret;
1039                 }
1040
1041                 prev_jump = insn;
1042                 prev_rela = rela;
1043         }
1044
1045         if (prev_jump) {
1046                 ret = add_switch_table(file, prev_jump, prev_rela, NULL);
1047                 if (ret)
1048                         return ret;
1049         }
1050
1051         return 0;
1052 }
1053
1054 /*
1055  * For some switch statements, gcc generates a jump table in the .rodata
1056  * section which contains a list of addresses within the function to jump to.
1057  * This finds these jump tables and adds them to the insn->alts lists.
1058  */
1059 static int add_switch_table_alts(struct objtool_file *file)
1060 {
1061         struct section *sec;
1062         struct symbol *func;
1063         int ret;
1064
1065         if (!file->rodata)
1066                 return 0;
1067
1068         for_each_sec(file, sec) {
1069                 list_for_each_entry(func, &sec->symbol_list, list) {
1070                         if (func->type != STT_FUNC)
1071                                 continue;
1072
1073                         ret = add_func_switch_tables(file, func);
1074                         if (ret)
1075                                 return ret;
1076                 }
1077         }
1078
1079         return 0;
1080 }
1081
1082 static int read_unwind_hints(struct objtool_file *file)
1083 {
1084         struct section *sec, *relasec;
1085         struct rela *rela;
1086         struct unwind_hint *hint;
1087         struct instruction *insn;
1088         struct cfi_reg *cfa;
1089         int i;
1090
1091         sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1092         if (!sec)
1093                 return 0;
1094
1095         relasec = sec->rela;
1096         if (!relasec) {
1097                 WARN("missing .rela.discard.unwind_hints section");
1098                 return -1;
1099         }
1100
1101         if (sec->len % sizeof(struct unwind_hint)) {
1102                 WARN("struct unwind_hint size mismatch");
1103                 return -1;
1104         }
1105
1106         file->hints = true;
1107
1108         for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
1109                 hint = (struct unwind_hint *)sec->data->d_buf + i;
1110
1111                 rela = find_rela_by_dest(sec, i * sizeof(*hint));
1112                 if (!rela) {
1113                         WARN("can't find rela for unwind_hints[%d]", i);
1114                         return -1;
1115                 }
1116
1117                 insn = find_insn(file, rela->sym->sec, rela->addend);
1118                 if (!insn) {
1119                         WARN("can't find insn for unwind_hints[%d]", i);
1120                         return -1;
1121                 }
1122
1123                 cfa = &insn->state.cfa;
1124
1125                 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
1126                         insn->save = true;
1127                         continue;
1128
1129                 } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
1130                         insn->restore = true;
1131                         insn->hint = true;
1132                         continue;
1133                 }
1134
1135                 insn->hint = true;
1136
1137                 switch (hint->sp_reg) {
1138                 case ORC_REG_UNDEFINED:
1139                         cfa->base = CFI_UNDEFINED;
1140                         break;
1141                 case ORC_REG_SP:
1142                         cfa->base = CFI_SP;
1143                         break;
1144                 case ORC_REG_BP:
1145                         cfa->base = CFI_BP;
1146                         break;
1147                 case ORC_REG_SP_INDIRECT:
1148                         cfa->base = CFI_SP_INDIRECT;
1149                         break;
1150                 case ORC_REG_R10:
1151                         cfa->base = CFI_R10;
1152                         break;
1153                 case ORC_REG_R13:
1154                         cfa->base = CFI_R13;
1155                         break;
1156                 case ORC_REG_DI:
1157                         cfa->base = CFI_DI;
1158                         break;
1159                 case ORC_REG_DX:
1160                         cfa->base = CFI_DX;
1161                         break;
1162                 default:
1163                         WARN_FUNC("unsupported unwind_hint sp base reg %d",
1164                                   insn->sec, insn->offset, hint->sp_reg);
1165                         return -1;
1166                 }
1167
1168                 cfa->offset = hint->sp_offset;
1169                 insn->state.type = hint->type;
1170                 insn->state.end = hint->end;
1171         }
1172
1173         return 0;
1174 }
1175
1176 static int read_retpoline_hints(struct objtool_file *file)
1177 {
1178         struct section *sec;
1179         struct instruction *insn;
1180         struct rela *rela;
1181
1182         sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1183         if (!sec)
1184                 return 0;
1185
1186         list_for_each_entry(rela, &sec->rela_list, list) {
1187                 if (rela->sym->type != STT_SECTION) {
1188                         WARN("unexpected relocation symbol type in %s", sec->name);
1189                         return -1;
1190                 }
1191
1192                 insn = find_insn(file, rela->sym->sec, rela->addend);
1193                 if (!insn) {
1194                         WARN("bad .discard.retpoline_safe entry");
1195                         return -1;
1196                 }
1197
1198                 if (insn->type != INSN_JUMP_DYNAMIC &&
1199                     insn->type != INSN_CALL_DYNAMIC) {
1200                         WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1201                                   insn->sec, insn->offset);
1202                         return -1;
1203                 }
1204
1205                 insn->retpoline_safe = true;
1206         }
1207
1208         return 0;
1209 }
1210
1211 static void mark_rodata(struct objtool_file *file)
1212 {
1213         struct section *sec;
1214         bool found = false;
1215
1216         /*
1217          * This searches for the .rodata section or multiple .rodata.func_name
1218          * sections if -fdata-sections is being used. The .str.1.1 and .str.1.8
1219          * rodata sections are ignored as they don't contain jump tables.
1220          */
1221         for_each_sec(file, sec) {
1222                 if (!strncmp(sec->name, ".rodata", 7) &&
1223                     !strstr(sec->name, ".str1.")) {
1224                         sec->rodata = true;
1225                         found = true;
1226                 }
1227         }
1228
1229         file->rodata = found;
1230 }
1231
1232 static int decode_sections(struct objtool_file *file)
1233 {
1234         int ret;
1235
1236         mark_rodata(file);
1237
1238         ret = decode_instructions(file);
1239         if (ret)
1240                 return ret;
1241
1242         ret = add_dead_ends(file);
1243         if (ret)
1244                 return ret;
1245
1246         add_ignores(file);
1247
1248         ret = add_nospec_ignores(file);
1249         if (ret)
1250                 return ret;
1251
1252         ret = add_jump_destinations(file);
1253         if (ret)
1254                 return ret;
1255
1256         ret = add_special_section_alts(file);
1257         if (ret)
1258                 return ret;
1259
1260         ret = add_call_destinations(file);
1261         if (ret)
1262                 return ret;
1263
1264         ret = add_switch_table_alts(file);
1265         if (ret)
1266                 return ret;
1267
1268         ret = read_unwind_hints(file);
1269         if (ret)
1270                 return ret;
1271
1272         ret = read_retpoline_hints(file);
1273         if (ret)
1274                 return ret;
1275
1276         return 0;
1277 }
1278
1279 static bool is_fentry_call(struct instruction *insn)
1280 {
1281         if (insn->type == INSN_CALL &&
1282             insn->call_dest->type == STT_NOTYPE &&
1283             !strcmp(insn->call_dest->name, "__fentry__"))
1284                 return true;
1285
1286         return false;
1287 }
1288
1289 static bool has_modified_stack_frame(struct insn_state *state)
1290 {
1291         int i;
1292
1293         if (state->cfa.base != initial_func_cfi.cfa.base ||
1294             state->cfa.offset != initial_func_cfi.cfa.offset ||
1295             state->stack_size != initial_func_cfi.cfa.offset ||
1296             state->drap)
1297                 return true;
1298
1299         for (i = 0; i < CFI_NUM_REGS; i++)
1300                 if (state->regs[i].base != initial_func_cfi.regs[i].base ||
1301                     state->regs[i].offset != initial_func_cfi.regs[i].offset)
1302                         return true;
1303
1304         return false;
1305 }
1306
1307 static bool has_valid_stack_frame(struct insn_state *state)
1308 {
1309         if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
1310             state->regs[CFI_BP].offset == -16)
1311                 return true;
1312
1313         if (state->drap && state->regs[CFI_BP].base == CFI_BP)
1314                 return true;
1315
1316         return false;
1317 }
1318
1319 static int update_insn_state_regs(struct instruction *insn, struct insn_state *state)
1320 {
1321         struct cfi_reg *cfa = &state->cfa;
1322         struct stack_op *op = &insn->stack_op;
1323
1324         if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
1325                 return 0;
1326
1327         /* push */
1328         if (op->dest.type == OP_DEST_PUSH)
1329                 cfa->offset += 8;
1330
1331         /* pop */
1332         if (op->src.type == OP_SRC_POP)
1333                 cfa->offset -= 8;
1334
1335         /* add immediate to sp */
1336         if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1337             op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1338                 cfa->offset -= op->src.offset;
1339
1340         return 0;
1341 }
1342
1343 static void save_reg(struct insn_state *state, unsigned char reg, int base,
1344                      int offset)
1345 {
1346         if (arch_callee_saved_reg(reg) &&
1347             state->regs[reg].base == CFI_UNDEFINED) {
1348                 state->regs[reg].base = base;
1349                 state->regs[reg].offset = offset;
1350         }
1351 }
1352
1353 static void restore_reg(struct insn_state *state, unsigned char reg)
1354 {
1355         state->regs[reg].base = CFI_UNDEFINED;
1356         state->regs[reg].offset = 0;
1357 }
1358
1359 /*
1360  * A note about DRAP stack alignment:
1361  *
1362  * GCC has the concept of a DRAP register, which is used to help keep track of
1363  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
1364  * register.  The typical DRAP pattern is:
1365  *
1366  *   4c 8d 54 24 08             lea    0x8(%rsp),%r10
1367  *   48 83 e4 c0                and    $0xffffffffffffffc0,%rsp
1368  *   41 ff 72 f8                pushq  -0x8(%r10)
1369  *   55                         push   %rbp
1370  *   48 89 e5                   mov    %rsp,%rbp
1371  *                              (more pushes)
1372  *   41 52                      push   %r10
1373  *                              ...
1374  *   41 5a                      pop    %r10
1375  *                              (more pops)
1376  *   5d                         pop    %rbp
1377  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1378  *   c3                         retq
1379  *
1380  * There are some variations in the epilogues, like:
1381  *
1382  *   5b                         pop    %rbx
1383  *   41 5a                      pop    %r10
1384  *   41 5c                      pop    %r12
1385  *   41 5d                      pop    %r13
1386  *   41 5e                      pop    %r14
1387  *   c9                         leaveq
1388  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1389  *   c3                         retq
1390  *
1391  * and:
1392  *
1393  *   4c 8b 55 e8                mov    -0x18(%rbp),%r10
1394  *   48 8b 5d e0                mov    -0x20(%rbp),%rbx
1395  *   4c 8b 65 f0                mov    -0x10(%rbp),%r12
1396  *   4c 8b 6d f8                mov    -0x8(%rbp),%r13
1397  *   c9                         leaveq
1398  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1399  *   c3                         retq
1400  *
1401  * Sometimes r13 is used as the DRAP register, in which case it's saved and
1402  * restored beforehand:
1403  *
1404  *   41 55                      push   %r13
1405  *   4c 8d 6c 24 10             lea    0x10(%rsp),%r13
1406  *   48 83 e4 f0                and    $0xfffffffffffffff0,%rsp
1407  *                              ...
1408  *   49 8d 65 f0                lea    -0x10(%r13),%rsp
1409  *   41 5d                      pop    %r13
1410  *   c3                         retq
1411  */
1412 static int update_insn_state(struct instruction *insn, struct insn_state *state)
1413 {
1414         struct stack_op *op = &insn->stack_op;
1415         struct cfi_reg *cfa = &state->cfa;
1416         struct cfi_reg *regs = state->regs;
1417
1418         /* stack operations don't make sense with an undefined CFA */
1419         if (cfa->base == CFI_UNDEFINED) {
1420                 if (insn->func) {
1421                         WARN_FUNC("undefined stack state", insn->sec, insn->offset);
1422                         return -1;
1423                 }
1424                 return 0;
1425         }
1426
1427         if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET)
1428                 return update_insn_state_regs(insn, state);
1429
1430         switch (op->dest.type) {
1431
1432         case OP_DEST_REG:
1433                 switch (op->src.type) {
1434
1435                 case OP_SRC_REG:
1436                         if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
1437                             cfa->base == CFI_SP &&
1438                             regs[CFI_BP].base == CFI_CFA &&
1439                             regs[CFI_BP].offset == -cfa->offset) {
1440
1441                                 /* mov %rsp, %rbp */
1442                                 cfa->base = op->dest.reg;
1443                                 state->bp_scratch = false;
1444                         }
1445
1446                         else if (op->src.reg == CFI_SP &&
1447                                  op->dest.reg == CFI_BP && state->drap) {
1448
1449                                 /* drap: mov %rsp, %rbp */
1450                                 regs[CFI_BP].base = CFI_BP;
1451                                 regs[CFI_BP].offset = -state->stack_size;
1452                                 state->bp_scratch = false;
1453                         }
1454
1455                         else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1456
1457                                 /*
1458                                  * mov %rsp, %reg
1459                                  *
1460                                  * This is needed for the rare case where GCC
1461                                  * does:
1462                                  *
1463                                  *   mov    %rsp, %rax
1464                                  *   ...
1465                                  *   mov    %rax, %rsp
1466                                  */
1467                                 state->vals[op->dest.reg].base = CFI_CFA;
1468                                 state->vals[op->dest.reg].offset = -state->stack_size;
1469                         }
1470
1471                         else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
1472                                  cfa->base == CFI_BP) {
1473
1474                                 /*
1475                                  * mov %rbp, %rsp
1476                                  *
1477                                  * Restore the original stack pointer (Clang).
1478                                  */
1479                                 state->stack_size = -state->regs[CFI_BP].offset;
1480                         }
1481
1482                         else if (op->dest.reg == cfa->base) {
1483
1484                                 /* mov %reg, %rsp */
1485                                 if (cfa->base == CFI_SP &&
1486                                     state->vals[op->src.reg].base == CFI_CFA) {
1487
1488                                         /*
1489                                          * This is needed for the rare case
1490                                          * where GCC does something dumb like:
1491                                          *
1492                                          *   lea    0x8(%rsp), %rcx
1493                                          *   ...
1494                                          *   mov    %rcx, %rsp
1495                                          */
1496                                         cfa->offset = -state->vals[op->src.reg].offset;
1497                                         state->stack_size = cfa->offset;
1498
1499                                 } else {
1500                                         cfa->base = CFI_UNDEFINED;
1501                                         cfa->offset = 0;
1502                                 }
1503                         }
1504
1505                         break;
1506
1507                 case OP_SRC_ADD:
1508                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
1509
1510                                 /* add imm, %rsp */
1511                                 state->stack_size -= op->src.offset;
1512                                 if (cfa->base == CFI_SP)
1513                                         cfa->offset -= op->src.offset;
1514                                 break;
1515                         }
1516
1517                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
1518
1519                                 /* lea disp(%rbp), %rsp */
1520                                 state->stack_size = -(op->src.offset + regs[CFI_BP].offset);
1521                                 break;
1522                         }
1523
1524                         if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1525
1526                                 /* drap: lea disp(%rsp), %drap */
1527                                 state->drap_reg = op->dest.reg;
1528
1529                                 /*
1530                                  * lea disp(%rsp), %reg
1531                                  *
1532                                  * This is needed for the rare case where GCC
1533                                  * does something dumb like:
1534                                  *
1535                                  *   lea    0x8(%rsp), %rcx
1536                                  *   ...
1537                                  *   mov    %rcx, %rsp
1538                                  */
1539                                 state->vals[op->dest.reg].base = CFI_CFA;
1540                                 state->vals[op->dest.reg].offset = \
1541                                         -state->stack_size + op->src.offset;
1542
1543                                 break;
1544                         }
1545
1546                         if (state->drap && op->dest.reg == CFI_SP &&
1547                             op->src.reg == state->drap_reg) {
1548
1549                                  /* drap: lea disp(%drap), %rsp */
1550                                 cfa->base = CFI_SP;
1551                                 cfa->offset = state->stack_size = -op->src.offset;
1552                                 state->drap_reg = CFI_UNDEFINED;
1553                                 state->drap = false;
1554                                 break;
1555                         }
1556
1557                         if (op->dest.reg == state->cfa.base) {
1558                                 WARN_FUNC("unsupported stack register modification",
1559                                           insn->sec, insn->offset);
1560                                 return -1;
1561                         }
1562
1563                         break;
1564
1565                 case OP_SRC_AND:
1566                         if (op->dest.reg != CFI_SP ||
1567                             (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
1568                             (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
1569                                 WARN_FUNC("unsupported stack pointer realignment",
1570                                           insn->sec, insn->offset);
1571                                 return -1;
1572                         }
1573
1574                         if (state->drap_reg != CFI_UNDEFINED) {
1575                                 /* drap: and imm, %rsp */
1576                                 cfa->base = state->drap_reg;
1577                                 cfa->offset = state->stack_size = 0;
1578                                 state->drap = true;
1579                         }
1580
1581                         /*
1582                          * Older versions of GCC (4.8ish) realign the stack
1583                          * without DRAP, with a frame pointer.
1584                          */
1585
1586                         break;
1587
1588                 case OP_SRC_POP:
1589                         if (!state->drap && op->dest.type == OP_DEST_REG &&
1590                             op->dest.reg == cfa->base) {
1591
1592                                 /* pop %rbp */
1593                                 cfa->base = CFI_SP;
1594                         }
1595
1596                         if (state->drap && cfa->base == CFI_BP_INDIRECT &&
1597                             op->dest.type == OP_DEST_REG &&
1598                             op->dest.reg == state->drap_reg &&
1599                             state->drap_offset == -state->stack_size) {
1600
1601                                 /* drap: pop %drap */
1602                                 cfa->base = state->drap_reg;
1603                                 cfa->offset = 0;
1604                                 state->drap_offset = -1;
1605
1606                         } else if (regs[op->dest.reg].offset == -state->stack_size) {
1607
1608                                 /* pop %reg */
1609                                 restore_reg(state, op->dest.reg);
1610                         }
1611
1612                         state->stack_size -= 8;
1613                         if (cfa->base == CFI_SP)
1614                                 cfa->offset -= 8;
1615
1616                         break;
1617
1618                 case OP_SRC_REG_INDIRECT:
1619                         if (state->drap && op->src.reg == CFI_BP &&
1620                             op->src.offset == state->drap_offset) {
1621
1622                                 /* drap: mov disp(%rbp), %drap */
1623                                 cfa->base = state->drap_reg;
1624                                 cfa->offset = 0;
1625                                 state->drap_offset = -1;
1626                         }
1627
1628                         if (state->drap && op->src.reg == CFI_BP &&
1629                             op->src.offset == regs[op->dest.reg].offset) {
1630
1631                                 /* drap: mov disp(%rbp), %reg */
1632                                 restore_reg(state, op->dest.reg);
1633
1634                         } else if (op->src.reg == cfa->base &&
1635                             op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
1636
1637                                 /* mov disp(%rbp), %reg */
1638                                 /* mov disp(%rsp), %reg */
1639                                 restore_reg(state, op->dest.reg);
1640                         }
1641
1642                         break;
1643
1644                 default:
1645                         WARN_FUNC("unknown stack-related instruction",
1646                                   insn->sec, insn->offset);
1647                         return -1;
1648                 }
1649
1650                 break;
1651
1652         case OP_DEST_PUSH:
1653                 state->stack_size += 8;
1654                 if (cfa->base == CFI_SP)
1655                         cfa->offset += 8;
1656
1657                 if (op->src.type != OP_SRC_REG)
1658                         break;
1659
1660                 if (state->drap) {
1661                         if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1662
1663                                 /* drap: push %drap */
1664                                 cfa->base = CFI_BP_INDIRECT;
1665                                 cfa->offset = -state->stack_size;
1666
1667                                 /* save drap so we know when to restore it */
1668                                 state->drap_offset = -state->stack_size;
1669
1670                         } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
1671
1672                                 /* drap: push %rbp */
1673                                 state->stack_size = 0;
1674
1675                         } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1676
1677                                 /* drap: push %reg */
1678                                 save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
1679                         }
1680
1681                 } else {
1682
1683                         /* push %reg */
1684                         save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
1685                 }
1686
1687                 /* detect when asm code uses rbp as a scratch register */
1688                 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
1689                     cfa->base != CFI_BP)
1690                         state->bp_scratch = true;
1691                 break;
1692
1693         case OP_DEST_REG_INDIRECT:
1694
1695                 if (state->drap) {
1696                         if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1697
1698                                 /* drap: mov %drap, disp(%rbp) */
1699                                 cfa->base = CFI_BP_INDIRECT;
1700                                 cfa->offset = op->dest.offset;
1701
1702                                 /* save drap offset so we know when to restore it */
1703                                 state->drap_offset = op->dest.offset;
1704                         }
1705
1706                         else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1707
1708                                 /* drap: mov reg, disp(%rbp) */
1709                                 save_reg(state, op->src.reg, CFI_BP, op->dest.offset);
1710                         }
1711
1712                 } else if (op->dest.reg == cfa->base) {
1713
1714                         /* mov reg, disp(%rbp) */
1715                         /* mov reg, disp(%rsp) */
1716                         save_reg(state, op->src.reg, CFI_CFA,
1717                                  op->dest.offset - state->cfa.offset);
1718                 }
1719
1720                 break;
1721
1722         case OP_DEST_LEAVE:
1723                 if ((!state->drap && cfa->base != CFI_BP) ||
1724                     (state->drap && cfa->base != state->drap_reg)) {
1725                         WARN_FUNC("leave instruction with modified stack frame",
1726                                   insn->sec, insn->offset);
1727                         return -1;
1728                 }
1729
1730                 /* leave (mov %rbp, %rsp; pop %rbp) */
1731
1732                 state->stack_size = -state->regs[CFI_BP].offset - 8;
1733                 restore_reg(state, CFI_BP);
1734
1735                 if (!state->drap) {
1736                         cfa->base = CFI_SP;
1737                         cfa->offset -= 8;
1738                 }
1739
1740                 break;
1741
1742         case OP_DEST_MEM:
1743                 if (op->src.type != OP_SRC_POP) {
1744                         WARN_FUNC("unknown stack-related memory operation",
1745                                   insn->sec, insn->offset);
1746                         return -1;
1747                 }
1748
1749                 /* pop mem */
1750                 state->stack_size -= 8;
1751                 if (cfa->base == CFI_SP)
1752                         cfa->offset -= 8;
1753
1754                 break;
1755
1756         default:
1757                 WARN_FUNC("unknown stack-related instruction",
1758                           insn->sec, insn->offset);
1759                 return -1;
1760         }
1761
1762         return 0;
1763 }
1764
1765 static bool insn_state_match(struct instruction *insn, struct insn_state *state)
1766 {
1767         struct insn_state *state1 = &insn->state, *state2 = state;
1768         int i;
1769
1770         if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
1771                 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
1772                           insn->sec, insn->offset,
1773                           state1->cfa.base, state1->cfa.offset,
1774                           state2->cfa.base, state2->cfa.offset);
1775
1776         } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
1777                 for (i = 0; i < CFI_NUM_REGS; i++) {
1778                         if (!memcmp(&state1->regs[i], &state2->regs[i],
1779                                     sizeof(struct cfi_reg)))
1780                                 continue;
1781
1782                         WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
1783                                   insn->sec, insn->offset,
1784                                   i, state1->regs[i].base, state1->regs[i].offset,
1785                                   i, state2->regs[i].base, state2->regs[i].offset);
1786                         break;
1787                 }
1788
1789         } else if (state1->type != state2->type) {
1790                 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
1791                           insn->sec, insn->offset, state1->type, state2->type);
1792
1793         } else if (state1->drap != state2->drap ||
1794                  (state1->drap && state1->drap_reg != state2->drap_reg) ||
1795                  (state1->drap && state1->drap_offset != state2->drap_offset)) {
1796                 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
1797                           insn->sec, insn->offset,
1798                           state1->drap, state1->drap_reg, state1->drap_offset,
1799                           state2->drap, state2->drap_reg, state2->drap_offset);
1800
1801         } else
1802                 return true;
1803
1804         return false;
1805 }
1806
1807 /*
1808  * Follow the branch starting at the given instruction, and recursively follow
1809  * any other branches (jumps).  Meanwhile, track the frame pointer state at
1810  * each instruction and validate all the rules described in
1811  * tools/objtool/Documentation/stack-validation.txt.
1812  */
1813 static int validate_branch(struct objtool_file *file, struct instruction *first,
1814                            struct insn_state state)
1815 {
1816         struct alternative *alt;
1817         struct instruction *insn, *next_insn;
1818         struct section *sec;
1819         struct symbol *func = NULL;
1820         int ret;
1821
1822         insn = first;
1823         sec = insn->sec;
1824
1825         if (insn->alt_group && list_empty(&insn->alts)) {
1826                 WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
1827                           sec, insn->offset);
1828                 return 1;
1829         }
1830
1831         while (1) {
1832                 next_insn = next_insn_same_sec(file, insn);
1833
1834                 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
1835                         WARN("%s() falls through to next function %s()",
1836                              func->name, insn->func->name);
1837                         return 1;
1838                 }
1839
1840                 if (insn->func)
1841                         func = insn->func->pfunc;
1842
1843                 if (func && insn->ignore) {
1844                         WARN_FUNC("BUG: why am I validating an ignored function?",
1845                                   sec, insn->offset);
1846                         return 1;
1847                 }
1848
1849                 if (insn->visited) {
1850                         if (!insn->hint && !insn_state_match(insn, &state))
1851                                 return 1;
1852
1853                         return 0;
1854                 }
1855
1856                 if (insn->hint) {
1857                         if (insn->restore) {
1858                                 struct instruction *save_insn, *i;
1859
1860                                 i = insn;
1861                                 save_insn = NULL;
1862                                 func_for_each_insn_continue_reverse(file, insn->func, i) {
1863                                         if (i->save) {
1864                                                 save_insn = i;
1865                                                 break;
1866                                         }
1867                                 }
1868
1869                                 if (!save_insn) {
1870                                         WARN_FUNC("no corresponding CFI save for CFI restore",
1871                                                   sec, insn->offset);
1872                                         return 1;
1873                                 }
1874
1875                                 if (!save_insn->visited) {
1876                                         /*
1877                                          * Oops, no state to copy yet.
1878                                          * Hopefully we can reach this
1879                                          * instruction from another branch
1880                                          * after the save insn has been
1881                                          * visited.
1882                                          */
1883                                         if (insn == first)
1884                                                 return 0;
1885
1886                                         WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
1887                                                   sec, insn->offset);
1888                                         return 1;
1889                                 }
1890
1891                                 insn->state = save_insn->state;
1892                         }
1893
1894                         state = insn->state;
1895
1896                 } else
1897                         insn->state = state;
1898
1899                 insn->visited = true;
1900
1901                 if (!insn->ignore_alts) {
1902                         list_for_each_entry(alt, &insn->alts, list) {
1903                                 ret = validate_branch(file, alt->insn, state);
1904                                 if (ret)
1905                                         return 1;
1906                         }
1907                 }
1908
1909                 switch (insn->type) {
1910
1911                 case INSN_RETURN:
1912                         if (func && has_modified_stack_frame(&state)) {
1913                                 WARN_FUNC("return with modified stack frame",
1914                                           sec, insn->offset);
1915                                 return 1;
1916                         }
1917
1918                         if (state.bp_scratch) {
1919                                 WARN("%s uses BP as a scratch register",
1920                                      insn->func->name);
1921                                 return 1;
1922                         }
1923
1924                         return 0;
1925
1926                 case INSN_CALL:
1927                         if (is_fentry_call(insn))
1928                                 break;
1929
1930                         ret = dead_end_function(file, insn->call_dest);
1931                         if (ret == 1)
1932                                 return 0;
1933                         if (ret == -1)
1934                                 return 1;
1935
1936                         /* fallthrough */
1937                 case INSN_CALL_DYNAMIC:
1938                         if (!no_fp && func && !has_valid_stack_frame(&state)) {
1939                                 WARN_FUNC("call without frame pointer save/setup",
1940                                           sec, insn->offset);
1941                                 return 1;
1942                         }
1943                         break;
1944
1945                 case INSN_JUMP_CONDITIONAL:
1946                 case INSN_JUMP_UNCONDITIONAL:
1947                         if (insn->jump_dest &&
1948                             (!func || !insn->jump_dest->func ||
1949                              insn->jump_dest->func->pfunc == func)) {
1950                                 ret = validate_branch(file, insn->jump_dest,
1951                                                       state);
1952                                 if (ret)
1953                                         return 1;
1954
1955                         } else if (func && has_modified_stack_frame(&state)) {
1956                                 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1957                                           sec, insn->offset);
1958                                 return 1;
1959                         }
1960
1961                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
1962                                 return 0;
1963
1964                         break;
1965
1966                 case INSN_JUMP_DYNAMIC:
1967                         if (func && list_empty(&insn->alts) &&
1968                             has_modified_stack_frame(&state)) {
1969                                 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1970                                           sec, insn->offset);
1971                                 return 1;
1972                         }
1973
1974                         return 0;
1975
1976                 case INSN_CONTEXT_SWITCH:
1977                         if (func && (!next_insn || !next_insn->hint)) {
1978                                 WARN_FUNC("unsupported instruction in callable function",
1979                                           sec, insn->offset);
1980                                 return 1;
1981                         }
1982                         return 0;
1983
1984                 case INSN_STACK:
1985                         if (update_insn_state(insn, &state))
1986                                 return 1;
1987
1988                         break;
1989
1990                 default:
1991                         break;
1992                 }
1993
1994                 if (insn->dead_end)
1995                         return 0;
1996
1997                 if (!next_insn) {
1998                         if (state.cfa.base == CFI_UNDEFINED)
1999                                 return 0;
2000                         WARN("%s: unexpected end of section", sec->name);
2001                         return 1;
2002                 }
2003
2004                 insn = next_insn;
2005         }
2006
2007         return 0;
2008 }
2009
2010 static int validate_unwind_hints(struct objtool_file *file)
2011 {
2012         struct instruction *insn;
2013         int ret, warnings = 0;
2014         struct insn_state state;
2015
2016         if (!file->hints)
2017                 return 0;
2018
2019         clear_insn_state(&state);
2020
2021         for_each_insn(file, insn) {
2022                 if (insn->hint && !insn->visited) {
2023                         ret = validate_branch(file, insn, state);
2024                         warnings += ret;
2025                 }
2026         }
2027
2028         return warnings;
2029 }
2030
2031 static int validate_retpoline(struct objtool_file *file)
2032 {
2033         struct instruction *insn;
2034         int warnings = 0;
2035
2036         for_each_insn(file, insn) {
2037                 if (insn->type != INSN_JUMP_DYNAMIC &&
2038                     insn->type != INSN_CALL_DYNAMIC)
2039                         continue;
2040
2041                 if (insn->retpoline_safe)
2042                         continue;
2043
2044                 /*
2045                  * .init.text code is ran before userspace and thus doesn't
2046                  * strictly need retpolines, except for modules which are
2047                  * loaded late, they very much do need retpoline in their
2048                  * .init.text
2049                  */
2050                 if (!strcmp(insn->sec->name, ".init.text") && !module)
2051                         continue;
2052
2053                 WARN_FUNC("indirect %s found in RETPOLINE build",
2054                           insn->sec, insn->offset,
2055                           insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
2056
2057                 warnings++;
2058         }
2059
2060         return warnings;
2061 }
2062
2063 static bool is_kasan_insn(struct instruction *insn)
2064 {
2065         return (insn->type == INSN_CALL &&
2066                 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
2067 }
2068
2069 static bool is_ubsan_insn(struct instruction *insn)
2070 {
2071         return (insn->type == INSN_CALL &&
2072                 !strcmp(insn->call_dest->name,
2073                         "__ubsan_handle_builtin_unreachable"));
2074 }
2075
2076 static bool ignore_unreachable_insn(struct instruction *insn)
2077 {
2078         int i;
2079
2080         if (insn->ignore || insn->type == INSN_NOP)
2081                 return true;
2082
2083         /*
2084          * Ignore any unused exceptions.  This can happen when a whitelisted
2085          * function has an exception table entry.
2086          *
2087          * Also ignore alternative replacement instructions.  This can happen
2088          * when a whitelisted function uses one of the ALTERNATIVE macros.
2089          */
2090         if (!strcmp(insn->sec->name, ".fixup") ||
2091             !strcmp(insn->sec->name, ".altinstr_replacement") ||
2092             !strcmp(insn->sec->name, ".altinstr_aux"))
2093                 return true;
2094
2095         if (!insn->func)
2096                 return false;
2097
2098         /*
2099          * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
2100          * __builtin_unreachable().  The BUG() macro has an unreachable() after
2101          * the UD2, which causes GCC's undefined trap logic to emit another UD2
2102          * (or occasionally a JMP to UD2).
2103          */
2104         if (list_prev_entry(insn, list)->dead_end &&
2105             (insn->type == INSN_BUG ||
2106              (insn->type == INSN_JUMP_UNCONDITIONAL &&
2107               insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
2108                 return true;
2109
2110         /*
2111          * Check if this (or a subsequent) instruction is related to
2112          * CONFIG_UBSAN or CONFIG_KASAN.
2113          *
2114          * End the search at 5 instructions to avoid going into the weeds.
2115          */
2116         for (i = 0; i < 5; i++) {
2117
2118                 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
2119                         return true;
2120
2121                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
2122                         if (insn->jump_dest &&
2123                             insn->jump_dest->func == insn->func) {
2124                                 insn = insn->jump_dest;
2125                                 continue;
2126                         }
2127
2128                         break;
2129                 }
2130
2131                 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
2132                         break;
2133
2134                 insn = list_next_entry(insn, list);
2135         }
2136
2137         return false;
2138 }
2139
2140 static int validate_functions(struct objtool_file *file)
2141 {
2142         struct section *sec;
2143         struct symbol *func;
2144         struct instruction *insn;
2145         struct insn_state state;
2146         int ret, warnings = 0;
2147
2148         clear_insn_state(&state);
2149
2150         state.cfa = initial_func_cfi.cfa;
2151         memcpy(&state.regs, &initial_func_cfi.regs,
2152                CFI_NUM_REGS * sizeof(struct cfi_reg));
2153         state.stack_size = initial_func_cfi.cfa.offset;
2154
2155         for_each_sec(file, sec) {
2156                 list_for_each_entry(func, &sec->symbol_list, list) {
2157                         if (func->type != STT_FUNC || func->pfunc != func)
2158                                 continue;
2159
2160                         insn = find_insn(file, sec, func->offset);
2161                         if (!insn || insn->ignore)
2162                                 continue;
2163
2164                         ret = validate_branch(file, insn, state);
2165                         warnings += ret;
2166                 }
2167         }
2168
2169         return warnings;
2170 }
2171
2172 static int validate_reachable_instructions(struct objtool_file *file)
2173 {
2174         struct instruction *insn;
2175
2176         if (file->ignore_unreachables)
2177                 return 0;
2178
2179         for_each_insn(file, insn) {
2180                 if (insn->visited || ignore_unreachable_insn(insn))
2181                         continue;
2182
2183                 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
2184                 return 1;
2185         }
2186
2187         return 0;
2188 }
2189
2190 static void cleanup(struct objtool_file *file)
2191 {
2192         struct instruction *insn, *tmpinsn;
2193         struct alternative *alt, *tmpalt;
2194
2195         list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) {
2196                 list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) {
2197                         list_del(&alt->list);
2198                         free(alt);
2199                 }
2200                 list_del(&insn->list);
2201                 hash_del(&insn->hash);
2202                 free(insn);
2203         }
2204         elf_close(file->elf);
2205 }
2206
2207 static struct objtool_file file;
2208
2209 int check(const char *_objname, bool orc)
2210 {
2211         int ret, warnings = 0;
2212
2213         objname = _objname;
2214
2215         file.elf = elf_open(objname, orc ? O_RDWR : O_RDONLY);
2216         if (!file.elf)
2217                 return 1;
2218
2219         INIT_LIST_HEAD(&file.insn_list);
2220         hash_init(file.insn_hash);
2221         file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard");
2222         file.c_file = find_section_by_name(file.elf, ".comment");
2223         file.ignore_unreachables = no_unreachable;
2224         file.hints = false;
2225
2226         arch_initial_func_cfi_state(&initial_func_cfi);
2227
2228         ret = decode_sections(&file);
2229         if (ret < 0)
2230                 goto out;
2231         warnings += ret;
2232
2233         if (list_empty(&file.insn_list))
2234                 goto out;
2235
2236         if (retpoline) {
2237                 ret = validate_retpoline(&file);
2238                 if (ret < 0)
2239                         return ret;
2240                 warnings += ret;
2241         }
2242
2243         ret = validate_functions(&file);
2244         if (ret < 0)
2245                 goto out;
2246         warnings += ret;
2247
2248         ret = validate_unwind_hints(&file);
2249         if (ret < 0)
2250                 goto out;
2251         warnings += ret;
2252
2253         if (!warnings) {
2254                 ret = validate_reachable_instructions(&file);
2255                 if (ret < 0)
2256                         goto out;
2257                 warnings += ret;
2258         }
2259
2260         if (orc) {
2261                 ret = create_orc(&file);
2262                 if (ret < 0)
2263                         goto out;
2264
2265                 ret = create_orc_sections(&file);
2266                 if (ret < 0)
2267                         goto out;
2268
2269                 ret = elf_write(file.elf);
2270                 if (ret < 0)
2271                         goto out;
2272         }
2273
2274 out:
2275         cleanup(&file);
2276
2277         /* ignore warnings for now until we get all the code cleaned up */
2278         if (ret || warnings)
2279                 return 0;
2280         return 0;
2281 }