tools/objtool/check.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
   4  */
   5
   6 #include <string.h>
   7 #include <stdlib.h>
   8
   9 #include <arch/elf.h>
  10 #include <objtool/builtin.h>
  11 #include <objtool/cfi.h>
  12 #include <objtool/arch.h>
  13 #include <objtool/check.h>
  14 #include <objtool/special.h>
  15 #include <objtool/warn.h>
  16 #include <objtool/endianness.h>
  17
  18 #include <linux/objtool.h>
  19 #include <linux/hashtable.h>
  20 #include <linux/kernel.h>
  21 #include <linux/static_call_types.h>
  22
  23 struct alternative {
  24         struct list_head list;
  25         struct instruction *insn;
  26         bool skip_orig;
  27 };
  28
  29 struct cfi_init_state initial_func_cfi;
  30
  31 struct instruction *find_insn(struct objtool_file *file,
  32                               struct section *sec, unsigned long offset)
  33 {
  34         struct instruction *insn;
  35
  36         hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
  37                 if (insn->sec == sec && insn->offset == offset)
  38                         return insn;
  39         }
  40
  41         return NULL;
  42 }
  43
  44 static struct instruction *next_insn_same_sec(struct objtool_file *file,
  45                                               struct instruction *insn)
  46 {
  47         struct instruction *next = list_next_entry(insn, list);
  48
  49         if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
  50                 return NULL;
  51
  52         return next;
  53 }
  54
  55 static struct instruction *next_insn_same_func(struct objtool_file *file,
  56                                                struct instruction *insn)
  57 {
  58         struct instruction *next = list_next_entry(insn, list);
  59         struct symbol *func = insn->func;
  60
  61         if (!func)
  62                 return NULL;
  63
  64         if (&next->list != &file->insn_list && next->func == func)
  65                 return next;
  66
  67         /* Check if we're already in the subfunction: */
  68         if (func == func->cfunc)
  69                 return NULL;
  70
  71         /* Move to the subfunction: */
  72         return find_insn(file, func->cfunc->sec, func->cfunc->offset);
  73 }
  74
  75 static struct instruction *prev_insn_same_sym(struct objtool_file *file,
  76                                                struct instruction *insn)
  77 {
  78         struct instruction *prev = list_prev_entry(insn, list);
  79
  80         if (&prev->list != &file->insn_list && prev->func == insn->func)
  81                 return prev;
  82
  83         return NULL;
  84 }
  85
  86 #define func_for_each_insn(file, func, insn)                            \
  87         for (insn = find_insn(file, func->sec, func->offset);           \
  88              insn;                                                      \
  89              insn = next_insn_same_func(file, insn))
  90
  91 #define sym_for_each_insn(file, sym, insn)                              \
  92         for (insn = find_insn(file, sym->sec, sym->offset);             \
  93              insn && &insn->list != &file->insn_list &&                 \
  94                 insn->sec == sym->sec &&                                \
  95                 insn->offset < sym->offset + sym->len;                  \
  96              insn = list_next_entry(insn, list))
  97
  98 #define sym_for_each_insn_continue_reverse(file, sym, insn)             \
  99         for (insn = list_prev_entry(insn, list);                        \
 100              &insn->list != &file->insn_list &&                         \
 101                 insn->sec == sym->sec && insn->offset >= sym->offset;   \
 102              insn = list_prev_entry(insn, list))
 103
 104 #define sec_for_each_insn_from(file, insn)                              \
 105         for (; insn; insn = next_insn_same_sec(file, insn))
 106
 107 #define sec_for_each_insn_continue(file, insn)                          \
 108         for (insn = next_insn_same_sec(file, insn); insn;               \
 109              insn = next_insn_same_sec(file, insn))
 110
 111 static bool is_jump_table_jump(struct instruction *insn)
 112 {
 113         struct alt_group *alt_group = insn->alt_group;
 114
 115         if (insn->jump_table)
 116                 return true;
 117
 118         /* Retpoline alternative for a jump table? */
 119         return alt_group && alt_group->orig_group &&
 120                alt_group->orig_group->first_insn->jump_table;
 121 }
 122
 123 static bool is_sibling_call(struct instruction *insn)
 124 {
 125         /*
 126          * Assume only ELF functions can make sibling calls.  This ensures
 127          * sibling call detection consistency between vmlinux.o and individual
 128          * objects.
 129          */
 130         if (!insn->func)
 131                 return false;
 132
 133         /* An indirect jump is either a sibling call or a jump to a table. */
 134         if (insn->type == INSN_JUMP_DYNAMIC)
 135                 return !is_jump_table_jump(insn);
 136
 137         /* add_jump_destinations() sets insn->call_dest for sibling calls. */
 138         return (is_static_jump(insn) && insn->call_dest);
 139 }
 140
 141 /*
 142  * This checks to see if the given function is a "noreturn" function.
 143  *
 144  * For global functions which are outside the scope of this object file, we
 145  * have to keep a manual list of them.
 146  *
 147  * For local functions, we have to detect them manually by simply looking for
 148  * the lack of a return instruction.
 149  */
 150 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 151                                 int recursion)
 152 {
 153         int i;
 154         struct instruction *insn;
 155         bool empty = true;
 156
 157         /*
 158          * Unfortunately these have to be hard coded because the noreturn
 159          * attribute isn't provided in ELF data.
 160          */
 161         static const char * const global_noreturns[] = {
 162                 "__stack_chk_fail",
 163                 "panic",
 164                 "do_exit",
 165                 "do_task_dead",
 166                 "__module_put_and_exit",
 167                 "complete_and_exit",
 168                 "__reiserfs_panic",
 169                 "lbug_with_loc",
 170                 "fortify_panic",
 171                 "usercopy_abort",
 172                 "machine_real_restart",
 173                 "rewind_stack_do_exit",
 174                 "kunit_try_catch_throw",
 175                 "xen_start_kernel",
 176         };
 177
 178         if (!func)
 179                 return false;
 180
 181         if (func->bind == STB_WEAK)
 182                 return false;
 183
 184         if (func->bind == STB_GLOBAL)
 185                 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
 186                         if (!strcmp(func->name, global_noreturns[i]))
 187                                 return true;
 188
 189         if (!func->len)
 190                 return false;
 191
 192         insn = find_insn(file, func->sec, func->offset);
 193         if (!insn->func)
 194                 return false;
 195
 196         func_for_each_insn(file, func, insn) {
 197                 empty = false;
 198
 199                 if (insn->type == INSN_RETURN)
 200                         return false;
 201         }
 202
 203         if (empty)
 204                 return false;
 205
 206         /*
 207          * A function can have a sibling call instead of a return.  In that
 208          * case, the function's dead-end status depends on whether the target
 209          * of the sibling call returns.
 210          */
 211         func_for_each_insn(file, func, insn) {
 212                 if (is_sibling_call(insn)) {
 213                         struct instruction *dest = insn->jump_dest;
 214
 215                         if (!dest)
 216                                 /* sibling call to another file */
 217                                 return false;
 218
 219                         /* local sibling call */
 220                         if (recursion == 5) {
 221                                 /*
 222                                  * Infinite recursion: two functions have
 223                                  * sibling calls to each other.  This is a very
 224                                  * rare case.  It means they aren't dead ends.
 225                                  */
 226                                 return false;
 227                         }
 228
 229                         return __dead_end_function(file, dest->func, recursion+1);
 230                 }
 231         }
 232
 233         return true;
 234 }
 235
 236 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
 237 {
 238         return __dead_end_function(file, func, 0);
 239 }
 240
 241 static void init_cfi_state(struct cfi_state *cfi)
 242 {
 243         int i;
 244
 245         for (i = 0; i < CFI_NUM_REGS; i++) {
 246                 cfi->regs[i].base = CFI_UNDEFINED;
 247                 cfi->vals[i].base = CFI_UNDEFINED;
 248         }
 249         cfi->cfa.base = CFI_UNDEFINED;
 250         cfi->drap_reg = CFI_UNDEFINED;
 251         cfi->drap_offset = -1;
 252 }
 253
 254 static void init_insn_state(struct insn_state *state, struct section *sec)
 255 {
 256         memset(state, 0, sizeof(*state));
 257         init_cfi_state(&state->cfi);
 258
 259         /*
 260          * We need the full vmlinux for noinstr validation, otherwise we can
 261          * not correctly determine insn->call_dest->sec (external symbols do
 262          * not have a section).
 263          */
 264         if (vmlinux && noinstr && sec)
 265                 state->noinstr = sec->noinstr;
 266 }
 267
 268 /*
 269  * Call the arch-specific instruction decoder for all the instructions and add
 270  * them to the global instruction list.
 271  */
 272 static int decode_instructions(struct objtool_file *file)
 273 {
 274         struct section *sec;
 275         struct symbol *func;
 276         unsigned long offset;
 277         struct instruction *insn;
 278         unsigned long nr_insns = 0;
 279         int ret;
 280
 281         for_each_sec(file, sec) {
 282
 283                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
 284                         continue;
 285
 286                 if (strcmp(sec->name, ".altinstr_replacement") &&
 287                     strcmp(sec->name, ".altinstr_aux") &&
 288                     strncmp(sec->name, ".discard.", 9))
 289                         sec->text = true;
 290
 291                 if (!strcmp(sec->name, ".noinstr.text") ||
 292                     !strcmp(sec->name, ".entry.text"))
 293                         sec->noinstr = true;
 294
 295                 for (offset = 0; offset < sec->len; offset += insn->len) {
 296                         insn = malloc(sizeof(*insn));
 297                         if (!insn) {
 298                                 WARN("malloc failed");
 299                                 return -1;
 300                         }
 301                         memset(insn, 0, sizeof(*insn));
 302                         INIT_LIST_HEAD(&insn->alts);
 303                         INIT_LIST_HEAD(&insn->stack_ops);
 304                         init_cfi_state(&insn->cfi);
 305
 306                         insn->sec = sec;
 307                         insn->offset = offset;
 308
 309                         ret = arch_decode_instruction(file->elf, sec, offset,
 310                                                       sec->len - offset,
 311                                                       &insn->len, &insn->type,
 312                                                       &insn->immediate,
 313                                                       &insn->stack_ops);
 314                         if (ret)
 315                                 goto err;
 316
 317                         hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
 318                         list_add_tail(&insn->list, &file->insn_list);
 319                         nr_insns++;
 320                 }
 321
 322                 list_for_each_entry(func, &sec->symbol_list, list) {
 323                         if (func->type != STT_FUNC || func->alias != func)
 324                                 continue;
 325
 326                         if (!find_insn(file, sec, func->offset)) {
 327                                 WARN("%s(): can't find starting instruction",
 328                                      func->name);
 329                                 return -1;
 330                         }
 331
 332                         sym_for_each_insn(file, func, insn)
 333                                 insn->func = func;
 334                 }
 335         }
 336
 337         if (stats)
 338                 printf("nr_insns: %lu\n", nr_insns);
 339
 340         return 0;
 341
 342 err:
 343         free(insn);
 344         return ret;
 345 }
 346
 347 static struct instruction *find_last_insn(struct objtool_file *file,
 348                                           struct section *sec)
 349 {
 350         struct instruction *insn = NULL;
 351         unsigned int offset;
 352         unsigned int end = (sec->len > 10) ? sec->len - 10 : 0;
 353
 354         for (offset = sec->len - 1; offset >= end && !insn; offset--)
 355                 insn = find_insn(file, sec, offset);
 356
 357         return insn;
 358 }
 359
 360 /*
 361  * Mark "ud2" instructions and manually annotated dead ends.
 362  */
 363 static int add_dead_ends(struct objtool_file *file)
 364 {
 365         struct section *sec;
 366         struct reloc *reloc;
 367         struct instruction *insn;
 368
 369         /*
 370          * By default, "ud2" is a dead end unless otherwise annotated, because
 371          * GCC 7 inserts it for certain divide-by-zero cases.
 372          */
 373         for_each_insn(file, insn)
 374                 if (insn->type == INSN_BUG)
 375                         insn->dead_end = true;
 376
 377         /*
 378          * Check for manually annotated dead ends.
 379          */
 380         sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
 381         if (!sec)
 382                 goto reachable;
 383
 384         list_for_each_entry(reloc, &sec->reloc_list, list) {
 385                 if (reloc->sym->type != STT_SECTION) {
 386                         WARN("unexpected relocation symbol type in %s", sec->name);
 387                         return -1;
 388                 }
 389                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 390                 if (insn)
 391                         insn = list_prev_entry(insn, list);
 392                 else if (reloc->addend == reloc->sym->sec->len) {
 393                         insn = find_last_insn(file, reloc->sym->sec);
 394                         if (!insn) {
 395                                 WARN("can't find unreachable insn at %s+0x%x",
 396                                      reloc->sym->sec->name, reloc->addend);
 397                                 return -1;
 398                         }
 399                 } else {
 400                         WARN("can't find unreachable insn at %s+0x%x",
 401                              reloc->sym->sec->name, reloc->addend);
 402                         return -1;
 403                 }
 404
 405                 insn->dead_end = true;
 406         }
 407
 408 reachable:
 409         /*
 410          * These manually annotated reachable checks are needed for GCC 4.4,
 411          * where the Linux unreachable() macro isn't supported.  In that case
 412          * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
 413          * not a dead end.
 414          */
 415         sec = find_section_by_name(file->elf, ".rela.discard.reachable");
 416         if (!sec)
 417                 return 0;
 418
 419         list_for_each_entry(reloc, &sec->reloc_list, list) {
 420                 if (reloc->sym->type != STT_SECTION) {
 421                         WARN("unexpected relocation symbol type in %s", sec->name);
 422                         return -1;
 423                 }
 424                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 425                 if (insn)
 426                         insn = list_prev_entry(insn, list);
 427                 else if (reloc->addend == reloc->sym->sec->len) {
 428                         insn = find_last_insn(file, reloc->sym->sec);
 429                         if (!insn) {
 430                                 WARN("can't find reachable insn at %s+0x%x",
 431                                      reloc->sym->sec->name, reloc->addend);
 432                                 return -1;
 433                         }
 434                 } else {
 435                         WARN("can't find reachable insn at %s+0x%x",
 436                              reloc->sym->sec->name, reloc->addend);
 437                         return -1;
 438                 }
 439
 440                 insn->dead_end = false;
 441         }
 442
 443         return 0;
 444 }
 445
 446 static int create_static_call_sections(struct objtool_file *file)
 447 {
 448         struct section *sec;
 449         struct static_call_site *site;
 450         struct instruction *insn;
 451         struct symbol *key_sym;
 452         char *key_name, *tmp;
 453         int idx;
 454
 455         sec = find_section_by_name(file->elf, ".static_call_sites");
 456         if (sec) {
 457                 INIT_LIST_HEAD(&file->static_call_list);
 458                 WARN("file already has .static_call_sites section, skipping");
 459                 return 0;
 460         }
 461
 462         if (list_empty(&file->static_call_list))
 463                 return 0;
 464
 465         idx = 0;
 466         list_for_each_entry(insn, &file->static_call_list, call_node)
 467                 idx++;
 468
 469         sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE,
 470                                  sizeof(struct static_call_site), idx);
 471         if (!sec)
 472                 return -1;
 473
 474         idx = 0;
 475         list_for_each_entry(insn, &file->static_call_list, call_node) {
 476
 477                 site = (struct static_call_site *)sec->data->d_buf + idx;
 478                 memset(site, 0, sizeof(struct static_call_site));
 479
 480                 /* populate reloc for 'addr' */
 481                 if (elf_add_reloc_to_insn(file->elf, sec,
 482                                           idx * sizeof(struct static_call_site),
 483                                           R_X86_64_PC32,
 484                                           insn->sec, insn->offset))
 485                         return -1;
 486
 487                 /* find key symbol */
 488                 key_name = strdup(insn->call_dest->name);
 489                 if (!key_name) {
 490                         perror("strdup");
 491                         return -1;
 492                 }
 493                 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
 494                             STATIC_CALL_TRAMP_PREFIX_LEN)) {
 495                         WARN("static_call: trampoline name malformed: %s", key_name);
 496                         return -1;
 497                 }
 498                 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
 499                 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
 500
 501                 key_sym = find_symbol_by_name(file->elf, tmp);
 502                 if (!key_sym) {
 503                         if (!module) {
 504                                 WARN("static_call: can't find static_call_key symbol: %s", tmp);
 505                                 return -1;
 506                         }
 507
 508                         /*
 509                          * For modules(), the key might not be exported, which
 510                          * means the module can make static calls but isn't
 511                          * allowed to change them.
 512                          *
 513                          * In that case we temporarily set the key to be the
 514                          * trampoline address.  This is fixed up in
 515                          * static_call_add_module().
 516                          */
 517                         key_sym = insn->call_dest;
 518                 }
 519                 free(key_name);
 520
 521                 /* populate reloc for 'key' */
 522                 if (elf_add_reloc(file->elf, sec,
 523                                   idx * sizeof(struct static_call_site) + 4,
 524                                   R_X86_64_PC32, key_sym,
 525                                   is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
 526                         return -1;
 527
 528                 idx++;
 529         }
 530
 531         return 0;
 532 }
 533
 534 static int create_mcount_loc_sections(struct objtool_file *file)
 535 {
 536         struct section *sec;
 537         unsigned long *loc;
 538         struct instruction *insn;
 539         int idx;
 540
 541         sec = find_section_by_name(file->elf, "__mcount_loc");
 542         if (sec) {
 543                 INIT_LIST_HEAD(&file->mcount_loc_list);
 544                 WARN("file already has __mcount_loc section, skipping");
 545                 return 0;
 546         }
 547
 548         if (list_empty(&file->mcount_loc_list))
 549                 return 0;
 550
 551         idx = 0;
 552         list_for_each_entry(insn, &file->mcount_loc_list, mcount_loc_node)
 553                 idx++;
 554
 555         sec = elf_create_section(file->elf, "__mcount_loc", 0, sizeof(unsigned long), idx);
 556         if (!sec)
 557                 return -1;
 558
 559         idx = 0;
 560         list_for_each_entry(insn, &file->mcount_loc_list, mcount_loc_node) {
 561
 562                 loc = (unsigned long *)sec->data->d_buf + idx;
 563                 memset(loc, 0, sizeof(unsigned long));
 564
 565                 if (elf_add_reloc_to_insn(file->elf, sec,
 566                                           idx * sizeof(unsigned long),
 567                                           R_X86_64_64,
 568                                           insn->sec, insn->offset))
 569                         return -1;
 570
 571                 idx++;
 572         }
 573
 574         return 0;
 575 }
 576
 577 /*
 578  * Warnings shouldn't be reported for ignored functions.
 579  */
 580 static void add_ignores(struct objtool_file *file)
 581 {
 582         struct instruction *insn;
 583         struct section *sec;
 584         struct symbol *func;
 585         struct reloc *reloc;
 586
 587         sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
 588         if (!sec)
 589                 return;
 590
 591         list_for_each_entry(reloc, &sec->reloc_list, list) {
 592                 switch (reloc->sym->type) {
 593                 case STT_FUNC:
 594                         func = reloc->sym;
 595                         break;
 596
 597                 case STT_SECTION:
 598                         func = find_func_by_offset(reloc->sym->sec, reloc->addend);
 599                         if (!func)
 600                                 continue;
 601                         break;
 602
 603                 default:
 604                         WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type);
 605                         continue;
 606                 }
 607
 608                 func_for_each_insn(file, func, insn)
 609                         insn->ignore = true;
 610         }
 611 }
 612
 613 /*
 614  * This is a whitelist of functions that is allowed to be called with AC set.
 615  * The list is meant to be minimal and only contains compiler instrumentation
 616  * ABI and a few functions used to implement *_{to,from}_user() functions.
 617  *
 618  * These functions must not directly change AC, but may PUSHF/POPF.
 619  */
 620 static const char *uaccess_safe_builtin[] = {
 621         /* KASAN */
 622         "kasan_report",
 623         "kasan_check_range",
 624         /* KASAN out-of-line */
 625         "__asan_loadN_noabort",
 626         "__asan_load1_noabort",
 627         "__asan_load2_noabort",
 628         "__asan_load4_noabort",
 629         "__asan_load8_noabort",
 630         "__asan_load16_noabort",
 631         "__asan_storeN_noabort",
 632         "__asan_store1_noabort",
 633         "__asan_store2_noabort",
 634         "__asan_store4_noabort",
 635         "__asan_store8_noabort",
 636         "__asan_store16_noabort",
 637         "__kasan_check_read",
 638         "__kasan_check_write",
 639         /* KASAN in-line */
 640         "__asan_report_load_n_noabort",
 641         "__asan_report_load1_noabort",
 642         "__asan_report_load2_noabort",
 643         "__asan_report_load4_noabort",
 644         "__asan_report_load8_noabort",
 645         "__asan_report_load16_noabort",
 646         "__asan_report_store_n_noabort",
 647         "__asan_report_store1_noabort",
 648         "__asan_report_store2_noabort",
 649         "__asan_report_store4_noabort",
 650         "__asan_report_store8_noabort",
 651         "__asan_report_store16_noabort",
 652         /* KCSAN */
 653         "__kcsan_check_access",
 654         "kcsan_found_watchpoint",
 655         "kcsan_setup_watchpoint",
 656         "kcsan_check_scoped_accesses",
 657         "kcsan_disable_current",
 658         "kcsan_enable_current_nowarn",
 659         /* KCSAN/TSAN */
 660         "__tsan_func_entry",
 661         "__tsan_func_exit",
 662         "__tsan_read_range",
 663         "__tsan_write_range",
 664         "__tsan_read1",
 665         "__tsan_read2",
 666         "__tsan_read4",
 667         "__tsan_read8",
 668         "__tsan_read16",
 669         "__tsan_write1",
 670         "__tsan_write2",
 671         "__tsan_write4",
 672         "__tsan_write8",
 673         "__tsan_write16",
 674         "__tsan_read_write1",
 675         "__tsan_read_write2",
 676         "__tsan_read_write4",
 677         "__tsan_read_write8",
 678         "__tsan_read_write16",
 679         "__tsan_atomic8_load",
 680         "__tsan_atomic16_load",
 681         "__tsan_atomic32_load",
 682         "__tsan_atomic64_load",
 683         "__tsan_atomic8_store",
 684         "__tsan_atomic16_store",
 685         "__tsan_atomic32_store",
 686         "__tsan_atomic64_store",
 687         "__tsan_atomic8_exchange",
 688         "__tsan_atomic16_exchange",
 689         "__tsan_atomic32_exchange",
 690         "__tsan_atomic64_exchange",
 691         "__tsan_atomic8_fetch_add",
 692         "__tsan_atomic16_fetch_add",
 693         "__tsan_atomic32_fetch_add",
 694         "__tsan_atomic64_fetch_add",
 695         "__tsan_atomic8_fetch_sub",
 696         "__tsan_atomic16_fetch_sub",
 697         "__tsan_atomic32_fetch_sub",
 698         "__tsan_atomic64_fetch_sub",
 699         "__tsan_atomic8_fetch_and",
 700         "__tsan_atomic16_fetch_and",
 701         "__tsan_atomic32_fetch_and",
 702         "__tsan_atomic64_fetch_and",
 703         "__tsan_atomic8_fetch_or",
 704         "__tsan_atomic16_fetch_or",
 705         "__tsan_atomic32_fetch_or",
 706         "__tsan_atomic64_fetch_or",
 707         "__tsan_atomic8_fetch_xor",
 708         "__tsan_atomic16_fetch_xor",
 709         "__tsan_atomic32_fetch_xor",
 710         "__tsan_atomic64_fetch_xor",
 711         "__tsan_atomic8_fetch_nand",
 712         "__tsan_atomic16_fetch_nand",
 713         "__tsan_atomic32_fetch_nand",
 714         "__tsan_atomic64_fetch_nand",
 715         "__tsan_atomic8_compare_exchange_strong",
 716         "__tsan_atomic16_compare_exchange_strong",
 717         "__tsan_atomic32_compare_exchange_strong",
 718         "__tsan_atomic64_compare_exchange_strong",
 719         "__tsan_atomic8_compare_exchange_weak",
 720         "__tsan_atomic16_compare_exchange_weak",
 721         "__tsan_atomic32_compare_exchange_weak",
 722         "__tsan_atomic64_compare_exchange_weak",
 723         "__tsan_atomic8_compare_exchange_val",
 724         "__tsan_atomic16_compare_exchange_val",
 725         "__tsan_atomic32_compare_exchange_val",
 726         "__tsan_atomic64_compare_exchange_val",
 727         "__tsan_atomic_thread_fence",
 728         "__tsan_atomic_signal_fence",
 729         /* KCOV */
 730         "write_comp_data",
 731         "check_kcov_mode",
 732         "__sanitizer_cov_trace_pc",
 733         "__sanitizer_cov_trace_const_cmp1",
 734         "__sanitizer_cov_trace_const_cmp2",
 735         "__sanitizer_cov_trace_const_cmp4",
 736         "__sanitizer_cov_trace_const_cmp8",
 737         "__sanitizer_cov_trace_cmp1",
 738         "__sanitizer_cov_trace_cmp2",
 739         "__sanitizer_cov_trace_cmp4",
 740         "__sanitizer_cov_trace_cmp8",
 741         "__sanitizer_cov_trace_switch",
 742         /* UBSAN */
 743         "ubsan_type_mismatch_common",
 744         "__ubsan_handle_type_mismatch",
 745         "__ubsan_handle_type_mismatch_v1",
 746         "__ubsan_handle_shift_out_of_bounds",
 747         /* misc */
 748         "csum_partial_copy_generic",
 749         "copy_mc_fragile",
 750         "copy_mc_fragile_handle_tail",
 751         "copy_mc_enhanced_fast_string",
 752         "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
 753         NULL
 754 };
 755
 756 static void add_uaccess_safe(struct objtool_file *file)
 757 {
 758         struct symbol *func;
 759         const char **name;
 760
 761         if (!uaccess)
 762                 return;
 763
 764         for (name = uaccess_safe_builtin; *name; name++) {
 765                 func = find_symbol_by_name(file->elf, *name);
 766                 if (!func)
 767                         continue;
 768
 769                 func->uaccess_safe = true;
 770         }
 771 }
 772
 773 /*
 774  * FIXME: For now, just ignore any alternatives which add retpolines.  This is
 775  * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
 776  * But it at least allows objtool to understand the control flow *around* the
 777  * retpoline.
 778  */
 779 static int add_ignore_alternatives(struct objtool_file *file)
 780 {
 781         struct section *sec;
 782         struct reloc *reloc;
 783         struct instruction *insn;
 784
 785         sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
 786         if (!sec)
 787                 return 0;
 788
 789         list_for_each_entry(reloc, &sec->reloc_list, list) {
 790                 if (reloc->sym->type != STT_SECTION) {
 791                         WARN("unexpected relocation symbol type in %s", sec->name);
 792                         return -1;
 793                 }
 794
 795                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 796                 if (!insn) {
 797                         WARN("bad .discard.ignore_alts entry");
 798                         return -1;
 799                 }
 800
 801                 insn->ignore_alts = true;
 802         }
 803
 804         return 0;
 805 }
 806
 807 __weak bool arch_is_retpoline(struct symbol *sym)
 808 {
 809         return false;
 810 }
 811
 812 #define NEGATIVE_RELOC  ((void *)-1L)
 813
 814 static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
 815 {
 816         if (insn->reloc == NEGATIVE_RELOC)
 817                 return NULL;
 818
 819         if (!insn->reloc) {
 820                 insn->reloc = find_reloc_by_dest_range(file->elf, insn->sec,
 821                                                        insn->offset, insn->len);
 822                 if (!insn->reloc) {
 823                         insn->reloc = NEGATIVE_RELOC;
 824                         return NULL;
 825                 }
 826         }
 827
 828         return insn->reloc;
 829 }
 830
 831 /*
 832  * Find the destination instructions for all jumps.
 833  */
 834 static int add_jump_destinations(struct objtool_file *file)
 835 {
 836         struct instruction *insn;
 837         struct reloc *reloc;
 838         struct section *dest_sec;
 839         unsigned long dest_off;
 840
 841         for_each_insn(file, insn) {
 842                 if (!is_static_jump(insn))
 843                         continue;
 844
 845                 reloc = insn_reloc(file, insn);
 846                 if (!reloc) {
 847                         dest_sec = insn->sec;
 848                         dest_off = arch_jump_destination(insn);
 849                 } else if (reloc->sym->type == STT_SECTION) {
 850                         dest_sec = reloc->sym->sec;
 851                         dest_off = arch_dest_reloc_offset(reloc->addend);
 852                 } else if (arch_is_retpoline(reloc->sym)) {
 853                         /*
 854                          * Retpoline jumps are really dynamic jumps in
 855                          * disguise, so convert them accordingly.
 856                          */
 857                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
 858                                 insn->type = INSN_JUMP_DYNAMIC;
 859                         else
 860                                 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
 861
 862                         list_add_tail(&insn->call_node,
 863                                       &file->retpoline_call_list);
 864
 865                         insn->retpoline_safe = true;
 866                         continue;
 867                 } else if (insn->func) {
 868                         /* internal or external sibling call (with reloc) */
 869                         insn->call_dest = reloc->sym;
 870                         if (insn->call_dest->static_call_tramp) {
 871                                 list_add_tail(&insn->call_node,
 872                                               &file->static_call_list);
 873                         }
 874                         continue;
 875                 } else if (reloc->sym->sec->idx) {
 876                         dest_sec = reloc->sym->sec;
 877                         dest_off = reloc->sym->sym.st_value +
 878                                    arch_dest_reloc_offset(reloc->addend);
 879                 } else {
 880                         /* non-func asm code jumping to another file */
 881                         continue;
 882                 }
 883
 884                 insn->jump_dest = find_insn(file, dest_sec, dest_off);
 885                 if (!insn->jump_dest) {
 886
 887                         /*
 888                          * This is a special case where an alt instruction
 889                          * jumps past the end of the section.  These are
 890                          * handled later in handle_group_alt().
 891                          */
 892                         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
 893                                 continue;
 894
 895                         WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
 896                                   insn->sec, insn->offset, dest_sec->name,
 897                                   dest_off);
 898                         return -1;
 899                 }
 900
 901                 /*
 902                  * Cross-function jump.
 903                  */
 904                 if (insn->func && insn->jump_dest->func &&
 905                     insn->func != insn->jump_dest->func) {
 906
 907                         /*
 908                          * For GCC 8+, create parent/child links for any cold
 909                          * subfunctions.  This is _mostly_ redundant with a
 910                          * similar initialization in read_symbols().
 911                          *
 912                          * If a function has aliases, we want the *first* such
 913                          * function in the symbol table to be the subfunction's
 914                          * parent.  In that case we overwrite the
 915                          * initialization done in read_symbols().
 916                          *
 917                          * However this code can't completely replace the
 918                          * read_symbols() code because this doesn't detect the
 919                          * case where the parent function's only reference to a
 920                          * subfunction is through a jump table.
 921                          */
 922                         if (!strstr(insn->func->name, ".cold") &&
 923                             strstr(insn->jump_dest->func->name, ".cold")) {
 924                                 insn->func->cfunc = insn->jump_dest->func;
 925                                 insn->jump_dest->func->pfunc = insn->func;
 926
 927                         } else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
 928                                    insn->jump_dest->offset == insn->jump_dest->func->offset) {
 929
 930                                 /* internal sibling call (without reloc) */
 931                                 insn->call_dest = insn->jump_dest->func;
 932                                 if (insn->call_dest->static_call_tramp) {
 933                                         list_add_tail(&insn->call_node,
 934                                                       &file->static_call_list);
 935                                 }
 936                         }
 937                 }
 938         }
 939
 940         return 0;
 941 }
 942
 943 static void remove_insn_ops(struct instruction *insn)
 944 {
 945         struct stack_op *op, *tmp;
 946
 947         list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
 948                 list_del(&op->list);
 949                 free(op);
 950         }
 951 }
 952
 953 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
 954 {
 955         struct symbol *call_dest;
 956
 957         call_dest = find_func_by_offset(sec, offset);
 958         if (!call_dest)
 959                 call_dest = find_symbol_by_offset(sec, offset);
 960
 961         return call_dest;
 962 }
 963
 964 /*
 965  * Find the destination instructions for all calls.
 966  */
 967 static int add_call_destinations(struct objtool_file *file)
 968 {
 969         struct instruction *insn;
 970         unsigned long dest_off;
 971         struct reloc *reloc;
 972
 973         for_each_insn(file, insn) {
 974                 if (insn->type != INSN_CALL)
 975                         continue;
 976
 977                 reloc = insn_reloc(file, insn);
 978                 if (!reloc) {
 979                         dest_off = arch_jump_destination(insn);
 980                         insn->call_dest = find_call_destination(insn->sec, dest_off);
 981
 982                         if (insn->ignore)
 983                                 continue;
 984
 985                         if (!insn->call_dest) {
 986                                 WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);
 987                                 return -1;
 988                         }
 989
 990                         if (insn->func && insn->call_dest->type != STT_FUNC) {
 991                                 WARN_FUNC("unsupported call to non-function",
 992                                           insn->sec, insn->offset);
 993                                 return -1;
 994                         }
 995
 996                 } else if (reloc->sym->type == STT_SECTION) {
 997                         dest_off = arch_dest_reloc_offset(reloc->addend);
 998                         insn->call_dest = find_call_destination(reloc->sym->sec,
 999                                                                 dest_off);
1000                         if (!insn->call_dest) {
1001                                 WARN_FUNC("can't find call dest symbol at %s+0x%lx",
1002                                           insn->sec, insn->offset,
1003                                           reloc->sym->sec->name,
1004                                           dest_off);
1005                                 return -1;
1006                         }
1007
1008                 } else if (arch_is_retpoline(reloc->sym)) {
1009                         /*
1010                          * Retpoline calls are really dynamic calls in
1011                          * disguise, so convert them accordingly.
1012                          */
1013                         insn->type = INSN_CALL_DYNAMIC;
1014                         insn->retpoline_safe = true;
1015
1016                         list_add_tail(&insn->call_node,
1017                                       &file->retpoline_call_list);
1018
1019                         remove_insn_ops(insn);
1020                         continue;
1021
1022                 } else
1023                         insn->call_dest = reloc->sym;
1024
1025                 if (insn->call_dest && insn->call_dest->static_call_tramp) {
1026                         list_add_tail(&insn->call_node,
1027                                       &file->static_call_list);
1028                 }
1029
1030                 /*
1031                  * Many compilers cannot disable KCOV with a function attribute
1032                  * so they need a little help, NOP out any KCOV calls from noinstr
1033                  * text.
1034                  */
1035                 if (insn->sec->noinstr &&
1036                     !strncmp(insn->call_dest->name, "__sanitizer_cov_", 16)) {
1037                         if (reloc) {
1038                                 reloc->type = R_NONE;
1039                                 elf_write_reloc(file->elf, reloc);
1040                         }
1041
1042                         elf_write_insn(file->elf, insn->sec,
1043                                        insn->offset, insn->len,
1044                                        arch_nop_insn(insn->len));
1045                         insn->type = INSN_NOP;
1046                 }
1047
1048                 if (mcount && !strcmp(insn->call_dest->name, "__fentry__")) {
1049                         if (reloc) {
1050                                 reloc->type = R_NONE;
1051                                 elf_write_reloc(file->elf, reloc);
1052                         }
1053
1054                         elf_write_insn(file->elf, insn->sec,
1055                                        insn->offset, insn->len,
1056                                        arch_nop_insn(insn->len));
1057
1058                         insn->type = INSN_NOP;
1059
1060                         list_add_tail(&insn->mcount_loc_node,
1061                                       &file->mcount_loc_list);
1062                 }
1063
1064                 /*
1065                  * Whatever stack impact regular CALLs have, should be undone
1066                  * by the RETURN of the called function.
1067                  *
1068                  * Annotated intra-function calls retain the stack_ops but
1069                  * are converted to JUMP, see read_intra_function_calls().
1070                  */
1071                 remove_insn_ops(insn);
1072         }
1073
1074         return 0;
1075 }
1076
1077 /*
1078  * The .alternatives section requires some extra special care over and above
1079  * other special sections because alternatives are patched in place.
1080  */
1081 static int handle_group_alt(struct objtool_file *file,
1082                             struct special_alt *special_alt,
1083                             struct instruction *orig_insn,
1084                             struct instruction **new_insn)
1085 {
1086         struct instruction *last_orig_insn, *last_new_insn = NULL, *insn, *nop = NULL;
1087         struct alt_group *orig_alt_group, *new_alt_group;
1088         unsigned long dest_off;
1089
1090
1091         orig_alt_group = malloc(sizeof(*orig_alt_group));
1092         if (!orig_alt_group) {
1093                 WARN("malloc failed");
1094                 return -1;
1095         }
1096         orig_alt_group->cfi = calloc(special_alt->orig_len,
1097                                      sizeof(struct cfi_state *));
1098         if (!orig_alt_group->cfi) {
1099                 WARN("calloc failed");
1100                 return -1;
1101         }
1102
1103         last_orig_insn = NULL;
1104         insn = orig_insn;
1105         sec_for_each_insn_from(file, insn) {
1106                 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1107                         break;
1108
1109                 insn->alt_group = orig_alt_group;
1110                 last_orig_insn = insn;
1111         }
1112         orig_alt_group->orig_group = NULL;
1113         orig_alt_group->first_insn = orig_insn;
1114         orig_alt_group->last_insn = last_orig_insn;
1115
1116
1117         new_alt_group = malloc(sizeof(*new_alt_group));
1118         if (!new_alt_group) {
1119                 WARN("malloc failed");
1120                 return -1;
1121         }
1122
1123         if (special_alt->new_len < special_alt->orig_len) {
1124                 /*
1125                  * Insert a fake nop at the end to make the replacement
1126                  * alt_group the same size as the original.  This is needed to
1127                  * allow propagate_alt_cfi() to do its magic.  When the last
1128                  * instruction affects the stack, the instruction after it (the
1129                  * nop) will propagate the new state to the shared CFI array.
1130                  */
1131                 nop = malloc(sizeof(*nop));
1132                 if (!nop) {
1133                         WARN("malloc failed");
1134                         return -1;
1135                 }
1136                 memset(nop, 0, sizeof(*nop));
1137                 INIT_LIST_HEAD(&nop->alts);
1138                 INIT_LIST_HEAD(&nop->stack_ops);
1139                 init_cfi_state(&nop->cfi);
1140
1141                 nop->sec = special_alt->new_sec;
1142                 nop->offset = special_alt->new_off + special_alt->new_len;
1143                 nop->len = special_alt->orig_len - special_alt->new_len;
1144                 nop->type = INSN_NOP;
1145                 nop->func = orig_insn->func;
1146                 nop->alt_group = new_alt_group;
1147                 nop->ignore = orig_insn->ignore_alts;
1148         }
1149
1150         if (!special_alt->new_len) {
1151                 *new_insn = nop;
1152                 goto end;
1153         }
1154
1155         insn = *new_insn;
1156         sec_for_each_insn_from(file, insn) {
1157                 struct reloc *alt_reloc;
1158
1159                 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1160                         break;
1161
1162                 last_new_insn = insn;
1163
1164                 insn->ignore = orig_insn->ignore_alts;
1165                 insn->func = orig_insn->func;
1166                 insn->alt_group = new_alt_group;
1167
1168                 /*
1169                  * Since alternative replacement code is copy/pasted by the
1170                  * kernel after applying relocations, generally such code can't
1171                  * have relative-address relocation references to outside the
1172                  * .altinstr_replacement section, unless the arch's
1173                  * alternatives code can adjust the relative offsets
1174                  * accordingly.
1175                  */
1176                 alt_reloc = insn_reloc(file, insn);
1177                 if (alt_reloc &&
1178                     !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1179
1180                         WARN_FUNC("unsupported relocation in alternatives section",
1181                                   insn->sec, insn->offset);
1182                         return -1;
1183                 }
1184
1185                 if (!is_static_jump(insn))
1186                         continue;
1187
1188                 if (!insn->immediate)
1189                         continue;
1190
1191                 dest_off = arch_jump_destination(insn);
1192                 if (dest_off == special_alt->new_off + special_alt->new_len)
1193                         insn->jump_dest = next_insn_same_sec(file, last_orig_insn);
1194
1195                 if (!insn->jump_dest) {
1196                         WARN_FUNC("can't find alternative jump destination",
1197                                   insn->sec, insn->offset);
1198                         return -1;
1199                 }
1200         }
1201
1202         if (!last_new_insn) {
1203                 WARN_FUNC("can't find last new alternative instruction",
1204                           special_alt->new_sec, special_alt->new_off);
1205                 return -1;
1206         }
1207
1208         if (nop)
1209                 list_add(&nop->list, &last_new_insn->list);
1210 end:
1211         new_alt_group->orig_group = orig_alt_group;
1212         new_alt_group->first_insn = *new_insn;
1213         new_alt_group->last_insn = nop ? : last_new_insn;
1214         new_alt_group->cfi = orig_alt_group->cfi;
1215         return 0;
1216 }
1217
1218 /*
1219  * A jump table entry can either convert a nop to a jump or a jump to a nop.
1220  * If the original instruction is a jump, make the alt entry an effective nop
1221  * by just skipping the original instruction.
1222  */
1223 static int handle_jump_alt(struct objtool_file *file,
1224                            struct special_alt *special_alt,
1225                            struct instruction *orig_insn,
1226                            struct instruction **new_insn)
1227 {
1228         if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1229             orig_insn->type != INSN_NOP) {
1230
1231                 WARN_FUNC("unsupported instruction at jump label",
1232                           orig_insn->sec, orig_insn->offset);
1233                 return -1;
1234         }
1235
1236         if (special_alt->key_addend & 2) {
1237                 struct reloc *reloc = insn_reloc(file, orig_insn);
1238
1239                 if (reloc) {
1240                         reloc->type = R_NONE;
1241                         elf_write_reloc(file->elf, reloc);
1242                 }
1243                 elf_write_insn(file->elf, orig_insn->sec,
1244                                orig_insn->offset, orig_insn->len,
1245                                arch_nop_insn(orig_insn->len));
1246                 orig_insn->type = INSN_NOP;
1247         }
1248
1249         if (orig_insn->type == INSN_NOP) {
1250                 if (orig_insn->len == 2)
1251                         file->jl_nop_short++;
1252                 else
1253                         file->jl_nop_long++;
1254
1255                 return 0;
1256         }
1257
1258         if (orig_insn->len == 2)
1259                 file->jl_short++;
1260         else
1261                 file->jl_long++;
1262
1263         *new_insn = list_next_entry(orig_insn, list);
1264         return 0;
1265 }
1266
1267 /*
1268  * Read all the special sections which have alternate instructions which can be
1269  * patched in or redirected to at runtime.  Each instruction having alternate
1270  * instruction(s) has them added to its insn->alts list, which will be
1271  * traversed in validate_branch().
1272  */
1273 static int add_special_section_alts(struct objtool_file *file)
1274 {
1275         struct list_head special_alts;
1276         struct instruction *orig_insn, *new_insn;
1277         struct special_alt *special_alt, *tmp;
1278         struct alternative *alt;
1279         int ret;
1280
1281         ret = special_get_alts(file->elf, &special_alts);
1282         if (ret)
1283                 return ret;
1284
1285         list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1286
1287                 orig_insn = find_insn(file, special_alt->orig_sec,
1288                                       special_alt->orig_off);
1289                 if (!orig_insn) {
1290                         WARN_FUNC("special: can't find orig instruction",
1291                                   special_alt->orig_sec, special_alt->orig_off);
1292                         ret = -1;
1293                         goto out;
1294                 }
1295
1296                 new_insn = NULL;
1297                 if (!special_alt->group || special_alt->new_len) {
1298                         new_insn = find_insn(file, special_alt->new_sec,
1299                                              special_alt->new_off);
1300                         if (!new_insn) {
1301                                 WARN_FUNC("special: can't find new instruction",
1302                                           special_alt->new_sec,
1303                                           special_alt->new_off);
1304                                 ret = -1;
1305                                 goto out;
1306                         }
1307                 }
1308
1309                 if (special_alt->group) {
1310                         if (!special_alt->orig_len) {
1311                                 WARN_FUNC("empty alternative entry",
1312                                           orig_insn->sec, orig_insn->offset);
1313                                 continue;
1314                         }
1315
1316                         ret = handle_group_alt(file, special_alt, orig_insn,
1317                                                &new_insn);
1318                         if (ret)
1319                                 goto out;
1320                 } else if (special_alt->jump_or_nop) {
1321                         ret = handle_jump_alt(file, special_alt, orig_insn,
1322                                               &new_insn);
1323                         if (ret)
1324                                 goto out;
1325                 }
1326
1327                 alt = malloc(sizeof(*alt));
1328                 if (!alt) {
1329                         WARN("malloc failed");
1330                         ret = -1;
1331                         goto out;
1332                 }
1333
1334                 alt->insn = new_insn;
1335                 alt->skip_orig = special_alt->skip_orig;
1336                 orig_insn->ignore_alts |= special_alt->skip_alt;
1337                 list_add_tail(&alt->list, &orig_insn->alts);
1338
1339                 list_del(&special_alt->list);
1340                 free(special_alt);
1341         }
1342
1343         if (stats) {
1344                 printf("jl\\\tNOP\tJMP\n");
1345                 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
1346                 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
1347         }
1348
1349 out:
1350         return ret;
1351 }
1352
1353 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
1354                             struct reloc *table)
1355 {
1356         struct reloc *reloc = table;
1357         struct instruction *dest_insn;
1358         struct alternative *alt;
1359         struct symbol *pfunc = insn->func->pfunc;
1360         unsigned int prev_offset = 0;
1361
1362         /*
1363          * Each @reloc is a switch table relocation which points to the target
1364          * instruction.
1365          */
1366         list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
1367
1368                 /* Check for the end of the table: */
1369                 if (reloc != table && reloc->jump_table_start)
1370                         break;
1371
1372                 /* Make sure the table entries are consecutive: */
1373                 if (prev_offset && reloc->offset != prev_offset + 8)
1374                         break;
1375
1376                 /* Detect function pointers from contiguous objects: */
1377                 if (reloc->sym->sec == pfunc->sec &&
1378                     reloc->addend == pfunc->offset)
1379                         break;
1380
1381                 dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
1382                 if (!dest_insn)
1383                         break;
1384
1385                 /* Make sure the destination is in the same function: */
1386                 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
1387                         break;
1388
1389                 alt = malloc(sizeof(*alt));
1390                 if (!alt) {
1391                         WARN("malloc failed");
1392                         return -1;
1393                 }
1394
1395                 alt->insn = dest_insn;
1396                 list_add_tail(&alt->list, &insn->alts);
1397                 prev_offset = reloc->offset;
1398         }
1399
1400         if (!prev_offset) {
1401                 WARN_FUNC("can't find switch jump table",
1402                           insn->sec, insn->offset);
1403                 return -1;
1404         }
1405
1406         return 0;
1407 }
1408
1409 /*
1410  * find_jump_table() - Given a dynamic jump, find the switch jump table
1411  * associated with it.
1412  */
1413 static struct reloc *find_jump_table(struct objtool_file *file,
1414                                       struct symbol *func,
1415                                       struct instruction *insn)
1416 {
1417         struct reloc *table_reloc;
1418         struct instruction *dest_insn, *orig_insn = insn;
1419
1420         /*
1421          * Backward search using the @first_jump_src links, these help avoid
1422          * much of the 'in between' code. Which avoids us getting confused by
1423          * it.
1424          */
1425         for (;
1426              insn && insn->func && insn->func->pfunc == func;
1427              insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
1428
1429                 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1430                         break;
1431
1432                 /* allow small jumps within the range */
1433                 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1434                     insn->jump_dest &&
1435                     (insn->jump_dest->offset <= insn->offset ||
1436                      insn->jump_dest->offset > orig_insn->offset))
1437                     break;
1438
1439                 table_reloc = arch_find_switch_table(file, insn);
1440                 if (!table_reloc)
1441                         continue;
1442                 dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
1443                 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1444                         continue;
1445
1446                 return table_reloc;
1447         }
1448
1449         return NULL;
1450 }
1451
1452 /*
1453  * First pass: Mark the head of each jump table so that in the next pass,
1454  * we know when a given jump table ends and the next one starts.
1455  */
1456 static void mark_func_jump_tables(struct objtool_file *file,
1457                                     struct symbol *func)
1458 {
1459         struct instruction *insn, *last = NULL;
1460         struct reloc *reloc;
1461
1462         func_for_each_insn(file, func, insn) {
1463                 if (!last)
1464                         last = insn;
1465
1466                 /*
1467                  * Store back-pointers for unconditional forward jumps such
1468                  * that find_jump_table() can back-track using those and
1469                  * avoid some potentially confusing code.
1470                  */
1471                 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1472                     insn->offset > last->offset &&
1473                     insn->jump_dest->offset > insn->offset &&
1474                     !insn->jump_dest->first_jump_src) {
1475
1476                         insn->jump_dest->first_jump_src = insn;
1477                         last = insn->jump_dest;
1478                 }
1479
1480                 if (insn->type != INSN_JUMP_DYNAMIC)
1481                         continue;
1482
1483                 reloc = find_jump_table(file, func, insn);
1484                 if (reloc) {
1485                         reloc->jump_table_start = true;
1486                         insn->jump_table = reloc;
1487                 }
1488         }
1489 }
1490
1491 static int add_func_jump_tables(struct objtool_file *file,
1492                                   struct symbol *func)
1493 {
1494         struct instruction *insn;
1495         int ret;
1496
1497         func_for_each_insn(file, func, insn) {
1498                 if (!insn->jump_table)
1499                         continue;
1500
1501                 ret = add_jump_table(file, insn, insn->jump_table);
1502                 if (ret)
1503                         return ret;
1504         }
1505
1506         return 0;
1507 }
1508
1509 /*
1510  * For some switch statements, gcc generates a jump table in the .rodata
1511  * section which contains a list of addresses within the function to jump to.
1512  * This finds these jump tables and adds them to the insn->alts lists.
1513  */
1514 static int add_jump_table_alts(struct objtool_file *file)
1515 {
1516         struct section *sec;
1517         struct symbol *func;
1518         int ret;
1519
1520         if (!file->rodata)
1521                 return 0;
1522
1523         for_each_sec(file, sec) {
1524                 list_for_each_entry(func, &sec->symbol_list, list) {
1525                         if (func->type != STT_FUNC)
1526                                 continue;
1527
1528                         mark_func_jump_tables(file, func);
1529                         ret = add_func_jump_tables(file, func);
1530                         if (ret)
1531                                 return ret;
1532                 }
1533         }
1534
1535         return 0;
1536 }
1537
1538 static void set_func_state(struct cfi_state *state)
1539 {
1540         state->cfa = initial_func_cfi.cfa;
1541         memcpy(&state->regs, &initial_func_cfi.regs,
1542                CFI_NUM_REGS * sizeof(struct cfi_reg));
1543         state->stack_size = initial_func_cfi.cfa.offset;
1544 }
1545
1546 static int read_unwind_hints(struct objtool_file *file)
1547 {
1548         struct section *sec, *relocsec;
1549         struct reloc *reloc;
1550         struct unwind_hint *hint;
1551         struct instruction *insn;
1552         int i;
1553
1554         sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1555         if (!sec)
1556                 return 0;
1557
1558         relocsec = sec->reloc;
1559         if (!relocsec) {
1560                 WARN("missing .rela.discard.unwind_hints section");
1561                 return -1;
1562         }
1563
1564         if (sec->len % sizeof(struct unwind_hint)) {
1565                 WARN("struct unwind_hint size mismatch");
1566                 return -1;
1567         }
1568
1569         file->hints = true;
1570
1571         for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
1572                 hint = (struct unwind_hint *)sec->data->d_buf + i;
1573
1574                 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
1575                 if (!reloc) {
1576                         WARN("can't find reloc for unwind_hints[%d]", i);
1577                         return -1;
1578                 }
1579
1580                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1581                 if (!insn) {
1582                         WARN("can't find insn for unwind_hints[%d]", i);
1583                         return -1;
1584                 }
1585
1586                 insn->hint = true;
1587
1588                 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
1589                         set_func_state(&insn->cfi);
1590                         continue;
1591                 }
1592
1593                 if (arch_decode_hint_reg(insn, hint->sp_reg)) {
1594                         WARN_FUNC("unsupported unwind_hint sp base reg %d",
1595                                   insn->sec, insn->offset, hint->sp_reg);
1596                         return -1;
1597                 }
1598
1599                 insn->cfi.cfa.offset = bswap_if_needed(hint->sp_offset);
1600                 insn->cfi.type = hint->type;
1601                 insn->cfi.end = hint->end;
1602         }
1603
1604         return 0;
1605 }
1606
1607 static int read_retpoline_hints(struct objtool_file *file)
1608 {
1609         struct section *sec;
1610         struct instruction *insn;
1611         struct reloc *reloc;
1612
1613         sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1614         if (!sec)
1615                 return 0;
1616
1617         list_for_each_entry(reloc, &sec->reloc_list, list) {
1618                 if (reloc->sym->type != STT_SECTION) {
1619                         WARN("unexpected relocation symbol type in %s", sec->name);
1620                         return -1;
1621                 }
1622
1623                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1624                 if (!insn) {
1625                         WARN("bad .discard.retpoline_safe entry");
1626                         return -1;
1627                 }
1628
1629                 if (insn->type != INSN_JUMP_DYNAMIC &&
1630                     insn->type != INSN_CALL_DYNAMIC) {
1631                         WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1632                                   insn->sec, insn->offset);
1633                         return -1;
1634                 }
1635
1636                 insn->retpoline_safe = true;
1637         }
1638
1639         return 0;
1640 }
1641
1642 static int read_instr_hints(struct objtool_file *file)
1643 {
1644         struct section *sec;
1645         struct instruction *insn;
1646         struct reloc *reloc;
1647
1648         sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
1649         if (!sec)
1650                 return 0;
1651
1652         list_for_each_entry(reloc, &sec->reloc_list, list) {
1653                 if (reloc->sym->type != STT_SECTION) {
1654                         WARN("unexpected relocation symbol type in %s", sec->name);
1655                         return -1;
1656                 }
1657
1658                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1659                 if (!insn) {
1660                         WARN("bad .discard.instr_end entry");
1661                         return -1;
1662                 }
1663
1664                 insn->instr--;
1665         }
1666
1667         sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
1668         if (!sec)
1669                 return 0;
1670
1671         list_for_each_entry(reloc, &sec->reloc_list, list) {
1672                 if (reloc->sym->type != STT_SECTION) {
1673                         WARN("unexpected relocation symbol type in %s", sec->name);
1674                         return -1;
1675                 }
1676
1677                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1678                 if (!insn) {
1679                         WARN("bad .discard.instr_begin entry");
1680                         return -1;
1681                 }
1682
1683                 insn->instr++;
1684         }
1685
1686         return 0;
1687 }
1688
1689 static int read_intra_function_calls(struct objtool_file *file)
1690 {
1691         struct instruction *insn;
1692         struct section *sec;
1693         struct reloc *reloc;
1694
1695         sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
1696         if (!sec)
1697                 return 0;
1698
1699         list_for_each_entry(reloc, &sec->reloc_list, list) {
1700                 unsigned long dest_off;
1701
1702                 if (reloc->sym->type != STT_SECTION) {
1703                         WARN("unexpected relocation symbol type in %s",
1704                              sec->name);
1705                         return -1;
1706                 }
1707
1708                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1709                 if (!insn) {
1710                         WARN("bad .discard.intra_function_call entry");
1711                         return -1;
1712                 }
1713
1714                 if (insn->type != INSN_CALL) {
1715                         WARN_FUNC("intra_function_call not a direct call",
1716                                   insn->sec, insn->offset);
1717                         return -1;
1718                 }
1719
1720                 /*
1721                  * Treat intra-function CALLs as JMPs, but with a stack_op.
1722                  * See add_call_destinations(), which strips stack_ops from
1723                  * normal CALLs.
1724                  */
1725                 insn->type = INSN_JUMP_UNCONDITIONAL;
1726
1727                 dest_off = insn->offset + insn->len + insn->immediate;
1728                 insn->jump_dest = find_insn(file, insn->sec, dest_off);
1729                 if (!insn->jump_dest) {
1730                         WARN_FUNC("can't find call dest at %s+0x%lx",
1731                                   insn->sec, insn->offset,
1732                                   insn->sec->name, dest_off);
1733                         return -1;
1734                 }
1735         }
1736
1737         return 0;
1738 }
1739
1740 static int read_static_call_tramps(struct objtool_file *file)
1741 {
1742         struct section *sec;
1743         struct symbol *func;
1744
1745         for_each_sec(file, sec) {
1746                 list_for_each_entry(func, &sec->symbol_list, list) {
1747                         if (func->bind == STB_GLOBAL &&
1748                             !strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
1749                                      strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
1750                                 func->static_call_tramp = true;
1751                 }
1752         }
1753
1754         return 0;
1755 }
1756
1757 static void mark_rodata(struct objtool_file *file)
1758 {
1759         struct section *sec;
1760         bool found = false;
1761
1762         /*
1763          * Search for the following rodata sections, each of which can
1764          * potentially contain jump tables:
1765          *
1766          * - .rodata: can contain GCC switch tables
1767          * - .rodata.<func>: same, if -fdata-sections is being used
1768          * - .rodata..c_jump_table: contains C annotated jump tables
1769          *
1770          * .rodata.str1.* sections are ignored; they don't contain jump tables.
1771          */
1772         for_each_sec(file, sec) {
1773                 if (!strncmp(sec->name, ".rodata", 7) &&
1774                     !strstr(sec->name, ".str1.")) {
1775                         sec->rodata = true;
1776                         found = true;
1777                 }
1778         }
1779
1780         file->rodata = found;
1781 }
1782
1783 __weak int arch_rewrite_retpolines(struct objtool_file *file)
1784 {
1785         return 0;
1786 }
1787
1788 static int decode_sections(struct objtool_file *file)
1789 {
1790         int ret;
1791
1792         mark_rodata(file);
1793
1794         ret = decode_instructions(file);
1795         if (ret)
1796                 return ret;
1797
1798         ret = add_dead_ends(file);
1799         if (ret)
1800                 return ret;
1801
1802         add_ignores(file);
1803         add_uaccess_safe(file);
1804
1805         ret = add_ignore_alternatives(file);
1806         if (ret)
1807                 return ret;
1808
1809         /*
1810          * Must be before add_{jump_call}_destination.
1811          */
1812         ret = read_static_call_tramps(file);
1813         if (ret)
1814                 return ret;
1815
1816         /*
1817          * Must be before add_special_section_alts() as that depends on
1818          * jump_dest being set.
1819          */
1820         ret = add_jump_destinations(file);
1821         if (ret)
1822                 return ret;
1823
1824         ret = add_special_section_alts(file);
1825         if (ret)
1826                 return ret;
1827
1828         /*
1829          * Must be before add_call_destination(); it changes INSN_CALL to
1830          * INSN_JUMP.
1831          */
1832         ret = read_intra_function_calls(file);
1833         if (ret)
1834                 return ret;
1835
1836         ret = add_call_destinations(file);
1837         if (ret)
1838                 return ret;
1839
1840         ret = add_jump_table_alts(file);
1841         if (ret)
1842                 return ret;
1843
1844         ret = read_unwind_hints(file);
1845         if (ret)
1846                 return ret;
1847
1848         ret = read_retpoline_hints(file);
1849         if (ret)
1850                 return ret;
1851
1852         ret = read_instr_hints(file);
1853         if (ret)
1854                 return ret;
1855
1856         /*
1857          * Must be after add_special_section_alts(), since this will emit
1858          * alternatives. Must be after add_{jump,call}_destination(), since
1859          * those create the call insn lists.
1860          */
1861         ret = arch_rewrite_retpolines(file);
1862         if (ret)
1863                 return ret;
1864
1865         return 0;
1866 }
1867
1868 static bool is_fentry_call(struct instruction *insn)
1869 {
1870         if (insn->type == INSN_CALL && insn->call_dest &&
1871             insn->call_dest->type == STT_NOTYPE &&
1872             !strcmp(insn->call_dest->name, "__fentry__"))
1873                 return true;
1874
1875         return false;
1876 }
1877
1878 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
1879 {
1880         struct cfi_state *cfi = &state->cfi;
1881         int i;
1882
1883         if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
1884                 return true;
1885
1886         if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
1887                 return true;
1888
1889         if (cfi->stack_size != initial_func_cfi.cfa.offset)
1890                 return true;
1891
1892         for (i = 0; i < CFI_NUM_REGS; i++) {
1893                 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
1894                     cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
1895                         return true;
1896         }
1897
1898         return false;
1899 }
1900
1901 static bool check_reg_frame_pos(const struct cfi_reg *reg,
1902                                 int expected_offset)
1903 {
1904         return reg->base == CFI_CFA &&
1905                reg->offset == expected_offset;
1906 }
1907
1908 static bool has_valid_stack_frame(struct insn_state *state)
1909 {
1910         struct cfi_state *cfi = &state->cfi;
1911
1912         if (cfi->cfa.base == CFI_BP &&
1913             check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
1914             check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
1915                 return true;
1916
1917         if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
1918                 return true;
1919
1920         return false;
1921 }
1922
1923 static int update_cfi_state_regs(struct instruction *insn,
1924                                   struct cfi_state *cfi,
1925                                   struct stack_op *op)
1926 {
1927         struct cfi_reg *cfa = &cfi->cfa;
1928
1929         if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
1930                 return 0;
1931
1932         /* push */
1933         if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
1934                 cfa->offset += 8;
1935
1936         /* pop */
1937         if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
1938                 cfa->offset -= 8;
1939
1940         /* add immediate to sp */
1941         if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1942             op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1943                 cfa->offset -= op->src.offset;
1944
1945         return 0;
1946 }
1947
1948 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
1949 {
1950         if (arch_callee_saved_reg(reg) &&
1951             cfi->regs[reg].base == CFI_UNDEFINED) {
1952                 cfi->regs[reg].base = base;
1953                 cfi->regs[reg].offset = offset;
1954         }
1955 }
1956
1957 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
1958 {
1959         cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
1960         cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
1961 }
1962
1963 /*
1964  * A note about DRAP stack alignment:
1965  *
1966  * GCC has the concept of a DRAP register, which is used to help keep track of
1967  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
1968  * register.  The typical DRAP pattern is:
1969  *
1970  *   4c 8d 54 24 08             lea    0x8(%rsp),%r10
1971  *   48 83 e4 c0                and    $0xffffffffffffffc0,%rsp
1972  *   41 ff 72 f8                pushq  -0x8(%r10)
1973  *   55                         push   %rbp
1974  *   48 89 e5                   mov    %rsp,%rbp
1975  *                              (more pushes)
1976  *   41 52                      push   %r10
1977  *                              ...
1978  *   41 5a                      pop    %r10
1979  *                              (more pops)
1980  *   5d                         pop    %rbp
1981  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1982  *   c3                         retq
1983  *
1984  * There are some variations in the epilogues, like:
1985  *
1986  *   5b                         pop    %rbx
1987  *   41 5a                      pop    %r10
1988  *   41 5c                      pop    %r12
1989  *   41 5d                      pop    %r13
1990  *   41 5e                      pop    %r14
1991  *   c9                         leaveq
1992  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1993  *   c3                         retq
1994  *
1995  * and:
1996  *
1997  *   4c 8b 55 e8                mov    -0x18(%rbp),%r10
1998  *   48 8b 5d e0                mov    -0x20(%rbp),%rbx
1999  *   4c 8b 65 f0                mov    -0x10(%rbp),%r12
2000  *   4c 8b 6d f8                mov    -0x8(%rbp),%r13
2001  *   c9                         leaveq
2002  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2003  *   c3                         retq
2004  *
2005  * Sometimes r13 is used as the DRAP register, in which case it's saved and
2006  * restored beforehand:
2007  *
2008  *   41 55                      push   %r13
2009  *   4c 8d 6c 24 10             lea    0x10(%rsp),%r13
2010  *   48 83 e4 f0                and    $0xfffffffffffffff0,%rsp
2011  *                              ...
2012  *   49 8d 65 f0                lea    -0x10(%r13),%rsp
2013  *   41 5d                      pop    %r13
2014  *   c3                         retq
2015  */
2016 static int update_cfi_state(struct instruction *insn,
2017                             struct instruction *next_insn,
2018                             struct cfi_state *cfi, struct stack_op *op)
2019 {
2020         struct cfi_reg *cfa = &cfi->cfa;
2021         struct cfi_reg *regs = cfi->regs;
2022
2023         /* stack operations don't make sense with an undefined CFA */
2024         if (cfa->base == CFI_UNDEFINED) {
2025                 if (insn->func) {
2026                         WARN_FUNC("undefined stack state", insn->sec, insn->offset);
2027                         return -1;
2028                 }
2029                 return 0;
2030         }
2031
2032         if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2033             cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2034                 return update_cfi_state_regs(insn, cfi, op);
2035
2036         switch (op->dest.type) {
2037
2038         case OP_DEST_REG:
2039                 switch (op->src.type) {
2040
2041                 case OP_SRC_REG:
2042                         if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2043                             cfa->base == CFI_SP &&
2044                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset)) {
2045
2046                                 /* mov %rsp, %rbp */
2047                                 cfa->base = op->dest.reg;
2048                                 cfi->bp_scratch = false;
2049                         }
2050
2051                         else if (op->src.reg == CFI_SP &&
2052                                  op->dest.reg == CFI_BP && cfi->drap) {
2053
2054                                 /* drap: mov %rsp, %rbp */
2055                                 regs[CFI_BP].base = CFI_BP;
2056                                 regs[CFI_BP].offset = -cfi->stack_size;
2057                                 cfi->bp_scratch = false;
2058                         }
2059
2060                         else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2061
2062                                 /*
2063                                  * mov %rsp, %reg
2064                                  *
2065                                  * This is needed for the rare case where GCC
2066                                  * does:
2067                                  *
2068                                  *   mov    %rsp, %rax
2069                                  *   ...
2070                                  *   mov    %rax, %rsp
2071                                  */
2072                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2073                                 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2074                         }
2075
2076                         else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2077                                  (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2078
2079                                 /*
2080                                  * mov %rbp, %rsp
2081                                  *
2082                                  * Restore the original stack pointer (Clang).
2083                                  */
2084                                 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2085                         }
2086
2087                         else if (op->dest.reg == cfa->base) {
2088
2089                                 /* mov %reg, %rsp */
2090                                 if (cfa->base == CFI_SP &&
2091                                     cfi->vals[op->src.reg].base == CFI_CFA) {
2092
2093                                         /*
2094                                          * This is needed for the rare case
2095                                          * where GCC does something dumb like:
2096                                          *
2097                                          *   lea    0x8(%rsp), %rcx
2098                                          *   ...
2099                                          *   mov    %rcx, %rsp
2100                                          */
2101                                         cfa->offset = -cfi->vals[op->src.reg].offset;
2102                                         cfi->stack_size = cfa->offset;
2103
2104                                 } else if (cfa->base == CFI_SP &&
2105                                            cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2106                                            cfi->vals[op->src.reg].offset == cfa->offset) {
2107
2108                                         /*
2109                                          * Stack swizzle:
2110                                          *
2111                                          * 1: mov %rsp, (%[tos])
2112                                          * 2: mov %[tos], %rsp
2113                                          *    ...
2114                                          * 3: pop %rsp
2115                                          *
2116                                          * Where:
2117                                          *
2118                                          * 1 - places a pointer to the previous
2119                                          *     stack at the Top-of-Stack of the
2120                                          *     new stack.
2121                                          *
2122                                          * 2 - switches to the new stack.
2123                                          *
2124                                          * 3 - pops the Top-of-Stack to restore
2125                                          *     the original stack.
2126                                          *
2127                                          * Note: we set base to SP_INDIRECT
2128                                          * here and preserve offset. Therefore
2129                                          * when the unwinder reaches ToS it
2130                                          * will dereference SP and then add the
2131                                          * offset to find the next frame, IOW:
2132                                          * (%rsp) + offset.
2133                                          */
2134                                         cfa->base = CFI_SP_INDIRECT;
2135
2136                                 } else {
2137                                         cfa->base = CFI_UNDEFINED;
2138                                         cfa->offset = 0;
2139                                 }
2140                         }
2141
2142                         else if (op->dest.reg == CFI_SP &&
2143                                  cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2144                                  cfi->vals[op->src.reg].offset == cfa->offset) {
2145
2146                                 /*
2147                                  * The same stack swizzle case 2) as above. But
2148                                  * because we can't change cfa->base, case 3)
2149                                  * will become a regular POP. Pretend we're a
2150                                  * PUSH so things don't go unbalanced.
2151                                  */
2152                                 cfi->stack_size += 8;
2153                         }
2154
2155
2156                         break;
2157
2158                 case OP_SRC_ADD:
2159                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2160
2161                                 /* add imm, %rsp */
2162                                 cfi->stack_size -= op->src.offset;
2163                                 if (cfa->base == CFI_SP)
2164                                         cfa->offset -= op->src.offset;
2165                                 break;
2166                         }
2167
2168                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2169
2170                                 /* lea disp(%rbp), %rsp */
2171                                 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2172                                 break;
2173                         }
2174
2175                         if (!cfi->drap && op->src.reg == CFI_SP &&
2176                             op->dest.reg == CFI_BP && cfa->base == CFI_SP &&
2177                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset + op->src.offset)) {
2178
2179                                 /* lea disp(%rsp), %rbp */
2180                                 cfa->base = CFI_BP;
2181                                 cfa->offset -= op->src.offset;
2182                                 cfi->bp_scratch = false;
2183                                 break;
2184                         }
2185
2186                         if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2187
2188                                 /* drap: lea disp(%rsp), %drap */
2189                                 cfi->drap_reg = op->dest.reg;
2190
2191                                 /*
2192                                  * lea disp(%rsp), %reg
2193                                  *
2194                                  * This is needed for the rare case where GCC
2195                                  * does something dumb like:
2196                                  *
2197                                  *   lea    0x8(%rsp), %rcx
2198                                  *   ...
2199                                  *   mov    %rcx, %rsp
2200                                  */
2201                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2202                                 cfi->vals[op->dest.reg].offset = \
2203                                         -cfi->stack_size + op->src.offset;
2204
2205                                 break;
2206                         }
2207
2208                         if (cfi->drap && op->dest.reg == CFI_SP &&
2209                             op->src.reg == cfi->drap_reg) {
2210
2211                                  /* drap: lea disp(%drap), %rsp */
2212                                 cfa->base = CFI_SP;
2213                                 cfa->offset = cfi->stack_size = -op->src.offset;
2214                                 cfi->drap_reg = CFI_UNDEFINED;
2215                                 cfi->drap = false;
2216                                 break;
2217                         }
2218
2219                         if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
2220                                 WARN_FUNC("unsupported stack register modification",
2221                                           insn->sec, insn->offset);
2222                                 return -1;
2223                         }
2224
2225                         break;
2226
2227                 case OP_SRC_AND:
2228                         if (op->dest.reg != CFI_SP ||
2229                             (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
2230                             (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
2231                                 WARN_FUNC("unsupported stack pointer realignment",
2232                                           insn->sec, insn->offset);
2233                                 return -1;
2234                         }
2235
2236                         if (cfi->drap_reg != CFI_UNDEFINED) {
2237                                 /* drap: and imm, %rsp */
2238                                 cfa->base = cfi->drap_reg;
2239                                 cfa->offset = cfi->stack_size = 0;
2240                                 cfi->drap = true;
2241                         }
2242
2243                         /*
2244                          * Older versions of GCC (4.8ish) realign the stack
2245                          * without DRAP, with a frame pointer.
2246                          */
2247
2248                         break;
2249
2250                 case OP_SRC_POP:
2251                 case OP_SRC_POPF:
2252                         if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
2253
2254                                 /* pop %rsp; # restore from a stack swizzle */
2255                                 cfa->base = CFI_SP;
2256                                 break;
2257                         }
2258
2259                         if (!cfi->drap && op->dest.reg == cfa->base) {
2260
2261                                 /* pop %rbp */
2262                                 cfa->base = CFI_SP;
2263                         }
2264
2265                         if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
2266                             op->dest.reg == cfi->drap_reg &&
2267                             cfi->drap_offset == -cfi->stack_size) {
2268
2269                                 /* drap: pop %drap */
2270                                 cfa->base = cfi->drap_reg;
2271                                 cfa->offset = 0;
2272                                 cfi->drap_offset = -1;
2273
2274                         } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
2275
2276                                 /* pop %reg */
2277                                 restore_reg(cfi, op->dest.reg);
2278                         }
2279
2280                         cfi->stack_size -= 8;
2281                         if (cfa->base == CFI_SP)
2282                                 cfa->offset -= 8;
2283
2284                         break;
2285
2286                 case OP_SRC_REG_INDIRECT:
2287                         if (!cfi->drap && op->dest.reg == cfa->base &&
2288                             op->dest.reg == CFI_BP) {
2289
2290                                 /* mov disp(%rsp), %rbp */
2291                                 cfa->base = CFI_SP;
2292                                 cfa->offset = cfi->stack_size;
2293                         }
2294
2295                         if (cfi->drap && op->src.reg == CFI_BP &&
2296                             op->src.offset == cfi->drap_offset) {
2297
2298                                 /* drap: mov disp(%rbp), %drap */
2299                                 cfa->base = cfi->drap_reg;
2300                                 cfa->offset = 0;
2301                                 cfi->drap_offset = -1;
2302                         }
2303
2304                         if (cfi->drap && op->src.reg == CFI_BP &&
2305                             op->src.offset == regs[op->dest.reg].offset) {
2306
2307                                 /* drap: mov disp(%rbp), %reg */
2308                                 restore_reg(cfi, op->dest.reg);
2309
2310                         } else if (op->src.reg == cfa->base &&
2311                             op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
2312
2313                                 /* mov disp(%rbp), %reg */
2314                                 /* mov disp(%rsp), %reg */
2315                                 restore_reg(cfi, op->dest.reg);
2316
2317                         } else if (op->src.reg == CFI_SP &&
2318                                    op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
2319
2320                                 /* mov disp(%rsp), %reg */
2321                                 restore_reg(cfi, op->dest.reg);
2322                         }
2323
2324                         break;
2325
2326                 default:
2327                         WARN_FUNC("unknown stack-related instruction",
2328                                   insn->sec, insn->offset);
2329                         return -1;
2330                 }
2331
2332                 break;
2333
2334         case OP_DEST_PUSH:
2335         case OP_DEST_PUSHF:
2336                 cfi->stack_size += 8;
2337                 if (cfa->base == CFI_SP)
2338                         cfa->offset += 8;
2339
2340                 if (op->src.type != OP_SRC_REG)
2341                         break;
2342
2343                 if (cfi->drap) {
2344                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2345
2346                                 /* drap: push %drap */
2347                                 cfa->base = CFI_BP_INDIRECT;
2348                                 cfa->offset = -cfi->stack_size;
2349
2350                                 /* save drap so we know when to restore it */
2351                                 cfi->drap_offset = -cfi->stack_size;
2352
2353                         } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
2354
2355                                 /* drap: push %rbp */
2356                                 cfi->stack_size = 0;
2357
2358                         } else {
2359
2360                                 /* drap: push %reg */
2361                                 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
2362                         }
2363
2364                 } else {
2365
2366                         /* push %reg */
2367                         save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
2368                 }
2369
2370                 /* detect when asm code uses rbp as a scratch register */
2371                 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
2372                     cfa->base != CFI_BP)
2373                         cfi->bp_scratch = true;
2374                 break;
2375
2376         case OP_DEST_REG_INDIRECT:
2377
2378                 if (cfi->drap) {
2379                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2380
2381                                 /* drap: mov %drap, disp(%rbp) */
2382                                 cfa->base = CFI_BP_INDIRECT;
2383                                 cfa->offset = op->dest.offset;
2384
2385                                 /* save drap offset so we know when to restore it */
2386                                 cfi->drap_offset = op->dest.offset;
2387                         } else {
2388
2389                                 /* drap: mov reg, disp(%rbp) */
2390                                 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
2391                         }
2392
2393                 } else if (op->dest.reg == cfa->base) {
2394
2395                         /* mov reg, disp(%rbp) */
2396                         /* mov reg, disp(%rsp) */
2397                         save_reg(cfi, op->src.reg, CFI_CFA,
2398                                  op->dest.offset - cfi->cfa.offset);
2399
2400                 } else if (op->dest.reg == CFI_SP) {
2401
2402                         /* mov reg, disp(%rsp) */
2403                         save_reg(cfi, op->src.reg, CFI_CFA,
2404                                  op->dest.offset - cfi->stack_size);
2405
2406                 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
2407
2408                         /* mov %rsp, (%reg); # setup a stack swizzle. */
2409                         cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
2410                         cfi->vals[op->dest.reg].offset = cfa->offset;
2411                 }
2412
2413                 break;
2414
2415         case OP_DEST_MEM:
2416                 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
2417                         WARN_FUNC("unknown stack-related memory operation",
2418                                   insn->sec, insn->offset);
2419                         return -1;
2420                 }
2421
2422                 /* pop mem */
2423                 cfi->stack_size -= 8;
2424                 if (cfa->base == CFI_SP)
2425                         cfa->offset -= 8;
2426
2427                 break;
2428
2429         default:
2430                 WARN_FUNC("unknown stack-related instruction",
2431                           insn->sec, insn->offset);
2432                 return -1;
2433         }
2434
2435         return 0;
2436 }
2437
2438 /*
2439  * The stack layouts of alternatives instructions can sometimes diverge when
2440  * they have stack modifications.  That's fine as long as the potential stack
2441  * layouts don't conflict at any given potential instruction boundary.
2442  *
2443  * Flatten the CFIs of the different alternative code streams (both original
2444  * and replacement) into a single shared CFI array which can be used to detect
2445  * conflicts and nicely feed a linear array of ORC entries to the unwinder.
2446  */
2447 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
2448 {
2449         struct cfi_state **alt_cfi;
2450         int group_off;
2451
2452         if (!insn->alt_group)
2453                 return 0;
2454
2455         alt_cfi = insn->alt_group->cfi;
2456         group_off = insn->offset - insn->alt_group->first_insn->offset;
2457
2458         if (!alt_cfi[group_off]) {
2459                 alt_cfi[group_off] = &insn->cfi;
2460         } else {
2461                 if (memcmp(alt_cfi[group_off], &insn->cfi, sizeof(struct cfi_state))) {
2462                         WARN_FUNC("stack layout conflict in alternatives",
2463                                   insn->sec, insn->offset);
2464                         return -1;
2465                 }
2466         }
2467
2468         return 0;
2469 }
2470
2471 static int handle_insn_ops(struct instruction *insn,
2472                            struct instruction *next_insn,
2473                            struct insn_state *state)
2474 {
2475         struct stack_op *op;
2476
2477         list_for_each_entry(op, &insn->stack_ops, list) {
2478
2479                 if (update_cfi_state(insn, next_insn, &state->cfi, op))
2480                         return 1;
2481
2482                 if (!insn->alt_group)
2483                         continue;
2484
2485                 if (op->dest.type == OP_DEST_PUSHF) {
2486                         if (!state->uaccess_stack) {
2487                                 state->uaccess_stack = 1;
2488                         } else if (state->uaccess_stack >> 31) {
2489                                 WARN_FUNC("PUSHF stack exhausted",
2490                                           insn->sec, insn->offset);
2491                                 return 1;
2492                         }
2493                         state->uaccess_stack <<= 1;
2494                         state->uaccess_stack  |= state->uaccess;
2495                 }
2496
2497                 if (op->src.type == OP_SRC_POPF) {
2498                         if (state->uaccess_stack) {
2499                                 state->uaccess = state->uaccess_stack & 1;
2500                                 state->uaccess_stack >>= 1;
2501                                 if (state->uaccess_stack == 1)
2502                                         state->uaccess_stack = 0;
2503                         }
2504                 }
2505         }
2506
2507         return 0;
2508 }
2509
2510 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
2511 {
2512         struct cfi_state *cfi1 = &insn->cfi;
2513         int i;
2514
2515         if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
2516
2517                 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
2518                           insn->sec, insn->offset,
2519                           cfi1->cfa.base, cfi1->cfa.offset,
2520                           cfi2->cfa.base, cfi2->cfa.offset);
2521
2522         } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
2523                 for (i = 0; i < CFI_NUM_REGS; i++) {
2524                         if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
2525                                     sizeof(struct cfi_reg)))
2526                                 continue;
2527
2528                         WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
2529                                   insn->sec, insn->offset,
2530                                   i, cfi1->regs[i].base, cfi1->regs[i].offset,
2531                                   i, cfi2->regs[i].base, cfi2->regs[i].offset);
2532                         break;
2533                 }
2534
2535         } else if (cfi1->type != cfi2->type) {
2536
2537                 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
2538                           insn->sec, insn->offset, cfi1->type, cfi2->type);
2539
2540         } else if (cfi1->drap != cfi2->drap ||
2541                    (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
2542                    (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
2543
2544                 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
2545                           insn->sec, insn->offset,
2546                           cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
2547                           cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
2548
2549         } else
2550                 return true;
2551
2552         return false;
2553 }
2554
2555 static inline bool func_uaccess_safe(struct symbol *func)
2556 {
2557         if (func)
2558                 return func->uaccess_safe;
2559
2560         return false;
2561 }
2562
2563 static inline const char *call_dest_name(struct instruction *insn)
2564 {
2565         if (insn->call_dest)
2566                 return insn->call_dest->name;
2567
2568         return "{dynamic}";
2569 }
2570
2571 static inline bool noinstr_call_dest(struct symbol *func)
2572 {
2573         /*
2574          * We can't deal with indirect function calls at present;
2575          * assume they're instrumented.
2576          */
2577         if (!func)
2578                 return false;
2579
2580         /*
2581          * If the symbol is from a noinstr section; we good.
2582          */
2583         if (func->sec->noinstr)
2584                 return true;
2585
2586         /*
2587          * The __ubsan_handle_*() calls are like WARN(), they only happen when
2588          * something 'BAD' happened. At the risk of taking the machine down,
2589          * let them proceed to get the message out.
2590          */
2591         if (!strncmp(func->name, "__ubsan_handle_", 15))
2592                 return true;
2593
2594         return false;
2595 }
2596
2597 static int validate_call(struct instruction *insn, struct insn_state *state)
2598 {
2599         if (state->noinstr && state->instr <= 0 &&
2600             !noinstr_call_dest(insn->call_dest)) {
2601                 WARN_FUNC("call to %s() leaves .noinstr.text section",
2602                                 insn->sec, insn->offset, call_dest_name(insn));
2603                 return 1;
2604         }
2605
2606         if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
2607                 WARN_FUNC("call to %s() with UACCESS enabled",
2608                                 insn->sec, insn->offset, call_dest_name(insn));
2609                 return 1;
2610         }
2611
2612         if (state->df) {
2613                 WARN_FUNC("call to %s() with DF set",
2614                                 insn->sec, insn->offset, call_dest_name(insn));
2615                 return 1;
2616         }
2617
2618         return 0;
2619 }
2620
2621 static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
2622 {
2623         if (has_modified_stack_frame(insn, state)) {
2624                 WARN_FUNC("sibling call from callable instruction with modified stack frame",
2625                                 insn->sec, insn->offset);
2626                 return 1;
2627         }
2628
2629         return validate_call(insn, state);
2630 }
2631
2632 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
2633 {
2634         if (state->noinstr && state->instr > 0) {
2635                 WARN_FUNC("return with instrumentation enabled",
2636                           insn->sec, insn->offset);
2637                 return 1;
2638         }
2639
2640         if (state->uaccess && !func_uaccess_safe(func)) {
2641                 WARN_FUNC("return with UACCESS enabled",
2642                           insn->sec, insn->offset);
2643                 return 1;
2644         }
2645
2646         if (!state->uaccess && func_uaccess_safe(func)) {
2647                 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
2648                           insn->sec, insn->offset);
2649                 return 1;
2650         }
2651
2652         if (state->df) {
2653                 WARN_FUNC("return with DF set",
2654                           insn->sec, insn->offset);
2655                 return 1;
2656         }
2657
2658         if (func && has_modified_stack_frame(insn, state)) {
2659                 WARN_FUNC("return with modified stack frame",
2660                           insn->sec, insn->offset);
2661                 return 1;
2662         }
2663
2664         if (state->cfi.bp_scratch) {
2665                 WARN_FUNC("BP used as a scratch register",
2666                           insn->sec, insn->offset);
2667                 return 1;
2668         }
2669
2670         return 0;
2671 }
2672
2673 static struct instruction *next_insn_to_validate(struct objtool_file *file,
2674                                                  struct instruction *insn)
2675 {
2676         struct alt_group *alt_group = insn->alt_group;
2677
2678         /*
2679          * Simulate the fact that alternatives are patched in-place.  When the
2680          * end of a replacement alt_group is reached, redirect objtool flow to
2681          * the end of the original alt_group.
2682          */
2683         if (alt_group && insn == alt_group->last_insn && alt_group->orig_group)
2684                 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
2685
2686         return next_insn_same_sec(file, insn);
2687 }
2688
2689 /*
2690  * Follow the branch starting at the given instruction, and recursively follow
2691  * any other branches (jumps).  Meanwhile, track the frame pointer state at
2692  * each instruction and validate all the rules described in
2693  * tools/objtool/Documentation/stack-validation.txt.
2694  */
2695 static int validate_branch(struct objtool_file *file, struct symbol *func,
2696                            struct instruction *insn, struct insn_state state)
2697 {
2698         struct alternative *alt;
2699         struct instruction *next_insn;
2700         struct section *sec;
2701         u8 visited;
2702         int ret;
2703
2704         sec = insn->sec;
2705
2706         while (1) {
2707                 next_insn = next_insn_to_validate(file, insn);
2708
2709                 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
2710                         WARN("%s() falls through to next function %s()",
2711                              func->name, insn->func->name);
2712                         return 1;
2713                 }
2714
2715                 if (func && insn->ignore) {
2716                         WARN_FUNC("BUG: why am I validating an ignored function?",
2717                                   sec, insn->offset);
2718                         return 1;
2719                 }
2720
2721                 visited = 1 << state.uaccess;
2722                 if (insn->visited) {
2723                         if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
2724                                 return 1;
2725
2726                         if (insn->visited & visited)
2727                                 return 0;
2728                 }
2729
2730                 if (state.noinstr)
2731                         state.instr += insn->instr;
2732
2733                 if (insn->hint)
2734                         state.cfi = insn->cfi;
2735                 else
2736                         insn->cfi = state.cfi;
2737
2738                 insn->visited |= visited;
2739
2740                 if (propagate_alt_cfi(file, insn))
2741                         return 1;
2742
2743                 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
2744                         bool skip_orig = false;
2745
2746                         list_for_each_entry(alt, &insn->alts, list) {
2747                                 if (alt->skip_orig)
2748                                         skip_orig = true;
2749
2750                                 ret = validate_branch(file, func, alt->insn, state);
2751                                 if (ret) {
2752                                         if (backtrace)
2753                                                 BT_FUNC("(alt)", insn);
2754                                         return ret;
2755                                 }
2756                         }
2757
2758                         if (skip_orig)
2759                                 return 0;
2760                 }
2761
2762                 if (handle_insn_ops(insn, next_insn, &state))
2763                         return 1;
2764
2765                 switch (insn->type) {
2766
2767                 case INSN_RETURN:
2768                         return validate_return(func, insn, &state);
2769
2770                 case INSN_CALL:
2771                 case INSN_CALL_DYNAMIC:
2772                         ret = validate_call(insn, &state);
2773                         if (ret)
2774                                 return ret;
2775
2776                         if (!no_fp && func && !is_fentry_call(insn) &&
2777                             !has_valid_stack_frame(&state)) {
2778                                 WARN_FUNC("call without frame pointer save/setup",
2779                                           sec, insn->offset);
2780                                 return 1;
2781                         }
2782
2783                         if (dead_end_function(file, insn->call_dest))
2784                                 return 0;
2785
2786                         break;
2787
2788                 case INSN_JUMP_CONDITIONAL:
2789                 case INSN_JUMP_UNCONDITIONAL:
2790                         if (is_sibling_call(insn)) {
2791                                 ret = validate_sibling_call(insn, &state);
2792                                 if (ret)
2793                                         return ret;
2794
2795                         } else if (insn->jump_dest) {
2796                                 ret = validate_branch(file, func,
2797                                                       insn->jump_dest, state);
2798                                 if (ret) {
2799                                         if (backtrace)
2800                                                 BT_FUNC("(branch)", insn);
2801                                         return ret;
2802                                 }
2803                         }
2804
2805                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
2806                                 return 0;
2807
2808                         break;
2809
2810                 case INSN_JUMP_DYNAMIC:
2811                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
2812                         if (is_sibling_call(insn)) {
2813                                 ret = validate_sibling_call(insn, &state);
2814                                 if (ret)
2815                                         return ret;
2816                         }
2817
2818                         if (insn->type == INSN_JUMP_DYNAMIC)
2819                                 return 0;
2820
2821                         break;
2822
2823                 case INSN_CONTEXT_SWITCH:
2824                         if (func && (!next_insn || !next_insn->hint)) {
2825                                 WARN_FUNC("unsupported instruction in callable function",
2826                                           sec, insn->offset);
2827                                 return 1;
2828                         }
2829                         return 0;
2830
2831                 case INSN_STAC:
2832                         if (state.uaccess) {
2833                                 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
2834                                 return 1;
2835                         }
2836
2837                         state.uaccess = true;
2838                         break;
2839
2840                 case INSN_CLAC:
2841                         if (!state.uaccess && func) {
2842                                 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
2843                                 return 1;
2844                         }
2845
2846                         if (func_uaccess_safe(func) && !state.uaccess_stack) {
2847                                 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
2848                                 return 1;
2849                         }
2850
2851                         state.uaccess = false;
2852                         break;
2853
2854                 case INSN_STD:
2855                         if (state.df) {
2856                                 WARN_FUNC("recursive STD", sec, insn->offset);
2857                                 return 1;
2858                         }
2859
2860                         state.df = true;
2861                         break;
2862
2863                 case INSN_CLD:
2864                         if (!state.df && func) {
2865                                 WARN_FUNC("redundant CLD", sec, insn->offset);
2866                                 return 1;
2867                         }
2868
2869                         state.df = false;
2870                         break;
2871
2872                 default:
2873                         break;
2874                 }
2875
2876                 if (insn->dead_end)
2877                         return 0;
2878
2879                 if (!next_insn) {
2880                         if (state.cfi.cfa.base == CFI_UNDEFINED)
2881                                 return 0;
2882                         WARN("%s: unexpected end of section", sec->name);
2883                         return 1;
2884                 }
2885
2886                 insn = next_insn;
2887         }
2888
2889         return 0;
2890 }
2891
2892 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
2893 {
2894         struct instruction *insn;
2895         struct insn_state state;
2896         int ret, warnings = 0;
2897
2898         if (!file->hints)
2899                 return 0;
2900
2901         init_insn_state(&state, sec);
2902
2903         if (sec) {
2904                 insn = find_insn(file, sec, 0);
2905                 if (!insn)
2906                         return 0;
2907         } else {
2908                 insn = list_first_entry(&file->insn_list, typeof(*insn), list);
2909         }
2910
2911         while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) {
2912                 if (insn->hint && !insn->visited && !insn->ignore) {
2913                         ret = validate_branch(file, insn->func, insn, state);
2914                         if (ret && backtrace)
2915                                 BT_FUNC("<=== (hint)", insn);
2916                         warnings += ret;
2917                 }
2918
2919                 insn = list_next_entry(insn, list);
2920         }
2921
2922         return warnings;
2923 }
2924
2925 static int validate_retpoline(struct objtool_file *file)
2926 {
2927         struct instruction *insn;
2928         int warnings = 0;
2929
2930         for_each_insn(file, insn) {
2931                 if (insn->type != INSN_JUMP_DYNAMIC &&
2932                     insn->type != INSN_CALL_DYNAMIC)
2933                         continue;
2934
2935                 if (insn->retpoline_safe)
2936                         continue;
2937
2938                 /*
2939                  * .init.text code is ran before userspace and thus doesn't
2940                  * strictly need retpolines, except for modules which are
2941                  * loaded late, they very much do need retpoline in their
2942                  * .init.text
2943                  */
2944                 if (!strcmp(insn->sec->name, ".init.text") && !module)
2945                         continue;
2946
2947                 WARN_FUNC("indirect %s found in RETPOLINE build",
2948                           insn->sec, insn->offset,
2949                           insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
2950
2951                 warnings++;
2952         }
2953
2954         return warnings;
2955 }
2956
2957 static bool is_kasan_insn(struct instruction *insn)
2958 {
2959         return (insn->type == INSN_CALL &&
2960                 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
2961 }
2962
2963 static bool is_ubsan_insn(struct instruction *insn)
2964 {
2965         return (insn->type == INSN_CALL &&
2966                 !strcmp(insn->call_dest->name,
2967                         "__ubsan_handle_builtin_unreachable"));
2968 }
2969
2970 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
2971 {
2972         int i;
2973         struct instruction *prev_insn;
2974
2975         if (insn->ignore || insn->type == INSN_NOP)
2976                 return true;
2977
2978         /*
2979          * Ignore any unused exceptions.  This can happen when a whitelisted
2980          * function has an exception table entry.
2981          *
2982          * Also ignore alternative replacement instructions.  This can happen
2983          * when a whitelisted function uses one of the ALTERNATIVE macros.
2984          */
2985         if (!strcmp(insn->sec->name, ".fixup") ||
2986             !strcmp(insn->sec->name, ".altinstr_replacement") ||
2987             !strcmp(insn->sec->name, ".altinstr_aux"))
2988                 return true;
2989
2990         if (!insn->func)
2991                 return false;
2992
2993         /*
2994          * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
2995          * __builtin_unreachable().  The BUG() macro has an unreachable() after
2996          * the UD2, which causes GCC's undefined trap logic to emit another UD2
2997          * (or occasionally a JMP to UD2).
2998          *
2999          * It may also insert a UD2 after calling a __noreturn function.
3000          */
3001         prev_insn = list_prev_entry(insn, list);
3002         if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) &&
3003             (insn->type == INSN_BUG ||
3004              (insn->type == INSN_JUMP_UNCONDITIONAL &&
3005               insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
3006                 return true;
3007
3008         /*
3009          * Check if this (or a subsequent) instruction is related to
3010          * CONFIG_UBSAN or CONFIG_KASAN.
3011          *
3012          * End the search at 5 instructions to avoid going into the weeds.
3013          */
3014         for (i = 0; i < 5; i++) {
3015
3016                 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
3017                         return true;
3018
3019                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
3020                         if (insn->jump_dest &&
3021                             insn->jump_dest->func == insn->func) {
3022                                 insn = insn->jump_dest;
3023                                 continue;
3024                         }
3025
3026                         break;
3027                 }
3028
3029                 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
3030                         break;
3031
3032                 insn = list_next_entry(insn, list);
3033         }
3034
3035         return false;
3036 }
3037
3038 static int validate_symbol(struct objtool_file *file, struct section *sec,
3039                            struct symbol *sym, struct insn_state *state)
3040 {
3041         struct instruction *insn;
3042         int ret;
3043
3044         if (!sym->len) {
3045                 WARN("%s() is missing an ELF size annotation", sym->name);
3046                 return 1;
3047         }
3048
3049         if (sym->pfunc != sym || sym->alias != sym)
3050                 return 0;
3051
3052         insn = find_insn(file, sec, sym->offset);
3053         if (!insn || insn->ignore || insn->visited)
3054                 return 0;
3055
3056         state->uaccess = sym->uaccess_safe;
3057
3058         ret = validate_branch(file, insn->func, insn, *state);
3059         if (ret && backtrace)
3060                 BT_FUNC("<=== (sym)", insn);
3061         return ret;
3062 }
3063
3064 static int validate_section(struct objtool_file *file, struct section *sec)
3065 {
3066         struct insn_state state;
3067         struct symbol *func;
3068         int warnings = 0;
3069
3070         list_for_each_entry(func, &sec->symbol_list, list) {
3071                 if (func->type != STT_FUNC)
3072                         continue;
3073
3074                 init_insn_state(&state, sec);
3075                 set_func_state(&state.cfi);
3076
3077                 warnings += validate_symbol(file, sec, func, &state);
3078         }
3079
3080         return warnings;
3081 }
3082
3083 static int validate_vmlinux_functions(struct objtool_file *file)
3084 {
3085         struct section *sec;
3086         int warnings = 0;
3087
3088         sec = find_section_by_name(file->elf, ".noinstr.text");
3089         if (sec) {
3090                 warnings += validate_section(file, sec);
3091                 warnings += validate_unwind_hints(file, sec);
3092         }
3093
3094         sec = find_section_by_name(file->elf, ".entry.text");
3095         if (sec) {
3096                 warnings += validate_section(file, sec);
3097                 warnings += validate_unwind_hints(file, sec);
3098         }
3099
3100         return warnings;
3101 }
3102
3103 static int validate_functions(struct objtool_file *file)
3104 {
3105         struct section *sec;
3106         int warnings = 0;
3107
3108         for_each_sec(file, sec) {
3109                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
3110                         continue;
3111
3112                 warnings += validate_section(file, sec);
3113         }
3114
3115         return warnings;
3116 }
3117
3118 static int validate_reachable_instructions(struct objtool_file *file)
3119 {
3120         struct instruction *insn;
3121
3122         if (file->ignore_unreachables)
3123                 return 0;
3124
3125         for_each_insn(file, insn) {
3126                 if (insn->visited || ignore_unreachable_insn(file, insn))
3127                         continue;
3128
3129                 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
3130                 return 1;
3131         }
3132
3133         return 0;
3134 }
3135
3136 int check(struct objtool_file *file)
3137 {
3138         int ret, warnings = 0;
3139
3140         arch_initial_func_cfi_state(&initial_func_cfi);
3141
3142         ret = decode_sections(file);
3143         if (ret < 0)
3144                 goto out;
3145         warnings += ret;
3146
3147         if (list_empty(&file->insn_list))
3148                 goto out;
3149
3150         if (vmlinux && !validate_dup) {
3151                 ret = validate_vmlinux_functions(file);
3152                 if (ret < 0)
3153                         goto out;
3154
3155                 warnings += ret;
3156                 goto out;
3157         }
3158
3159         if (retpoline) {
3160                 ret = validate_retpoline(file);
3161                 if (ret < 0)
3162                         return ret;
3163                 warnings += ret;
3164         }
3165
3166         ret = validate_functions(file);
3167         if (ret < 0)
3168                 goto out;
3169         warnings += ret;
3170
3171         ret = validate_unwind_hints(file, NULL);
3172         if (ret < 0)
3173                 goto out;
3174         warnings += ret;
3175
3176         if (!warnings) {
3177                 ret = validate_reachable_instructions(file);
3178                 if (ret < 0)
3179                         goto out;
3180                 warnings += ret;
3181         }
3182
3183         ret = create_static_call_sections(file);
3184         if (ret < 0)
3185                 goto out;
3186         warnings += ret;
3187
3188         if (mcount) {
3189                 ret = create_mcount_loc_sections(file);
3190                 if (ret < 0)
3191                         goto out;
3192                 warnings += ret;
3193         }
3194
3195 out:
3196         /*
3197          *  For now, don't fail the kernel build on fatal warnings.  These
3198          *  errors are still fairly common due to the growing matrix of
3199          *  supported toolchains and their recent pace of change.
3200          */
3201         return 0;
3202 }