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