tools/objtool/check.c

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