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 #include <sys/mman.h>
   9
  10 #include <arch/elf.h>
  11 #include <objtool/builtin.h>
  12 #include <objtool/cfi.h>
  13 #include <objtool/arch.h>
  14 #include <objtool/check.h>
  15 #include <objtool/special.h>
  16 #include <objtool/warn.h>
  17 #include <objtool/endianness.h>
  18
  19 #include <linux/objtool.h>
  20 #include <linux/hashtable.h>
  21 #include <linux/kernel.h>
  22 #include <linux/static_call_types.h>
  23
  24 struct alternative {
  25         struct list_head list;
  26         struct instruction *insn;
  27         bool skip_orig;
  28 };
  29
  30 static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
  31
  32 static struct cfi_init_state initial_func_cfi;
  33 static struct cfi_state init_cfi;
  34 static struct cfi_state func_cfi;
  35
  36 struct instruction *find_insn(struct objtool_file *file,
  37                               struct section *sec, unsigned long offset)
  38 {
  39         struct instruction *insn;
  40
  41         hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
  42                 if (insn->sec == sec && insn->offset == offset)
  43                         return insn;
  44         }
  45
  46         return NULL;
  47 }
  48
  49 static struct instruction *next_insn_same_sec(struct objtool_file *file,
  50                                               struct instruction *insn)
  51 {
  52         struct instruction *next = list_next_entry(insn, list);
  53
  54         if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
  55                 return NULL;
  56
  57         return next;
  58 }
  59
  60 static struct instruction *next_insn_same_func(struct objtool_file *file,
  61                                                struct instruction *insn)
  62 {
  63         struct instruction *next = list_next_entry(insn, list);
  64         struct symbol *func = insn->func;
  65
  66         if (!func)
  67                 return NULL;
  68
  69         if (&next->list != &file->insn_list && next->func == func)
  70                 return next;
  71
  72         /* Check if we're already in the subfunction: */
  73         if (func == func->cfunc)
  74                 return NULL;
  75
  76         /* Move to the subfunction: */
  77         return find_insn(file, func->cfunc->sec, func->cfunc->offset);
  78 }
  79
  80 static struct instruction *prev_insn_same_sym(struct objtool_file *file,
  81                                                struct instruction *insn)
  82 {
  83         struct instruction *prev = list_prev_entry(insn, list);
  84
  85         if (&prev->list != &file->insn_list && prev->func == insn->func)
  86                 return prev;
  87
  88         return NULL;
  89 }
  90
  91 #define func_for_each_insn(file, func, insn)                            \
  92         for (insn = find_insn(file, func->sec, func->offset);           \
  93              insn;                                                      \
  94              insn = next_insn_same_func(file, insn))
  95
  96 #define sym_for_each_insn(file, sym, insn)                              \
  97         for (insn = find_insn(file, sym->sec, sym->offset);             \
  98              insn && &insn->list != &file->insn_list &&                 \
  99                 insn->sec == sym->sec &&                                \
 100                 insn->offset < sym->offset + sym->len;                  \
 101              insn = list_next_entry(insn, list))
 102
 103 #define sym_for_each_insn_continue_reverse(file, sym, insn)             \
 104         for (insn = list_prev_entry(insn, list);                        \
 105              &insn->list != &file->insn_list &&                         \
 106                 insn->sec == sym->sec && insn->offset >= sym->offset;   \
 107              insn = list_prev_entry(insn, list))
 108
 109 #define sec_for_each_insn_from(file, insn)                              \
 110         for (; insn; insn = next_insn_same_sec(file, insn))
 111
 112 #define sec_for_each_insn_continue(file, insn)                          \
 113         for (insn = next_insn_same_sec(file, insn); insn;               \
 114              insn = next_insn_same_sec(file, insn))
 115
 116 static bool is_jump_table_jump(struct instruction *insn)
 117 {
 118         struct alt_group *alt_group = insn->alt_group;
 119
 120         if (insn->jump_table)
 121                 return true;
 122
 123         /* Retpoline alternative for a jump table? */
 124         return alt_group && alt_group->orig_group &&
 125                alt_group->orig_group->first_insn->jump_table;
 126 }
 127
 128 static bool is_sibling_call(struct instruction *insn)
 129 {
 130         /*
 131          * Assume only ELF functions can make sibling calls.  This ensures
 132          * sibling call detection consistency between vmlinux.o and individual
 133          * objects.
 134          */
 135         if (!insn->func)
 136                 return false;
 137
 138         /* An indirect jump is either a sibling call or a jump to a table. */
 139         if (insn->type == INSN_JUMP_DYNAMIC)
 140                 return !is_jump_table_jump(insn);
 141
 142         /* add_jump_destinations() sets insn->call_dest for sibling calls. */
 143         return (is_static_jump(insn) && insn->call_dest);
 144 }
 145
 146 /*
 147  * This checks to see if the given function is a "noreturn" function.
 148  *
 149  * For global functions which are outside the scope of this object file, we
 150  * have to keep a manual list of them.
 151  *
 152  * For local functions, we have to detect them manually by simply looking for
 153  * the lack of a return instruction.
 154  */
 155 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 156                                 int recursion)
 157 {
 158         int i;
 159         struct instruction *insn;
 160         bool empty = true;
 161
 162         /*
 163          * Unfortunately these have to be hard coded because the noreturn
 164          * attribute isn't provided in ELF data.
 165          */
 166         static const char * const global_noreturns[] = {
 167                 "__stack_chk_fail",
 168                 "panic",
 169                 "do_exit",
 170                 "do_task_dead",
 171                 "kthread_exit",
 172                 "make_task_dead",
 173                 "__module_put_and_kthread_exit",
 174                 "kthread_complete_and_exit",
 175                 "__reiserfs_panic",
 176                 "lbug_with_loc",
 177                 "fortify_panic",
 178                 "usercopy_abort",
 179                 "machine_real_restart",
 180                 "rewind_stack_and_make_dead",
 181                 "kunit_try_catch_throw",
 182                 "xen_start_kernel",
 183                 "cpu_bringup_and_idle",
 184                 "do_group_exit",
 185                 "stop_this_cpu",
 186                 "__invalid_creds",
 187                "cpu_startup_entry",
 188         };
 189
 190         if (!func)
 191                 return false;
 192
 193         if (func->bind == STB_WEAK)
 194                 return false;
 195
 196         if (func->bind == STB_GLOBAL)
 197                 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
 198                         if (!strcmp(func->name, global_noreturns[i]))
 199                                 return true;
 200
 201         if (!func->len)
 202                 return false;
 203
 204         insn = find_insn(file, func->sec, func->offset);
 205         if (!insn->func)
 206                 return false;
 207
 208         func_for_each_insn(file, func, insn) {
 209                 empty = false;
 210
 211                 if (insn->type == INSN_RETURN)
 212                         return false;
 213         }
 214
 215         if (empty)
 216                 return false;
 217
 218         /*
 219          * A function can have a sibling call instead of a return.  In that
 220          * case, the function's dead-end status depends on whether the target
 221          * of the sibling call returns.
 222          */
 223         func_for_each_insn(file, func, insn) {
 224                 if (is_sibling_call(insn)) {
 225                         struct instruction *dest = insn->jump_dest;
 226
 227                         if (!dest)
 228                                 /* sibling call to another file */
 229                                 return false;
 230
 231                         /* local sibling call */
 232                         if (recursion == 5) {
 233                                 /*
 234                                  * Infinite recursion: two functions have
 235                                  * sibling calls to each other.  This is a very
 236                                  * rare case.  It means they aren't dead ends.
 237                                  */
 238                                 return false;
 239                         }
 240
 241                         return __dead_end_function(file, dest->func, recursion+1);
 242                 }
 243         }
 244
 245         return true;
 246 }
 247
 248 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
 249 {
 250         return __dead_end_function(file, func, 0);
 251 }
 252
 253 static void init_cfi_state(struct cfi_state *cfi)
 254 {
 255         int i;
 256
 257         for (i = 0; i < CFI_NUM_REGS; i++) {
 258                 cfi->regs[i].base = CFI_UNDEFINED;
 259                 cfi->vals[i].base = CFI_UNDEFINED;
 260         }
 261         cfi->cfa.base = CFI_UNDEFINED;
 262         cfi->drap_reg = CFI_UNDEFINED;
 263         cfi->drap_offset = -1;
 264 }
 265
 266 static void init_insn_state(struct insn_state *state, struct section *sec)
 267 {
 268         memset(state, 0, sizeof(*state));
 269         init_cfi_state(&state->cfi);
 270
 271         /*
 272          * We need the full vmlinux for noinstr validation, otherwise we can
 273          * not correctly determine insn->call_dest->sec (external symbols do
 274          * not have a section).
 275          */
 276         if (opts.vmlinux && opts.noinstr && sec)
 277                 state->noinstr = sec->noinstr;
 278 }
 279
 280 static struct cfi_state *cfi_alloc(void)
 281 {
 282         struct cfi_state *cfi = calloc(sizeof(struct cfi_state), 1);
 283         if (!cfi) {
 284                 WARN("calloc failed");
 285                 exit(1);
 286         }
 287         nr_cfi++;
 288         return cfi;
 289 }
 290
 291 static int cfi_bits;
 292 static struct hlist_head *cfi_hash;
 293
 294 static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
 295 {
 296         return memcmp((void *)cfi1 + sizeof(cfi1->hash),
 297                       (void *)cfi2 + sizeof(cfi2->hash),
 298                       sizeof(struct cfi_state) - sizeof(struct hlist_node));
 299 }
 300
 301 static inline u32 cfi_key(struct cfi_state *cfi)
 302 {
 303         return jhash((void *)cfi + sizeof(cfi->hash),
 304                      sizeof(*cfi) - sizeof(cfi->hash), 0);
 305 }
 306
 307 static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
 308 {
 309         struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
 310         struct cfi_state *obj;
 311
 312         hlist_for_each_entry(obj, head, hash) {
 313                 if (!cficmp(cfi, obj)) {
 314                         nr_cfi_cache++;
 315                         return obj;
 316                 }
 317         }
 318
 319         obj = cfi_alloc();
 320         *obj = *cfi;
 321         hlist_add_head(&obj->hash, head);
 322
 323         return obj;
 324 }
 325
 326 static void cfi_hash_add(struct cfi_state *cfi)
 327 {
 328         struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
 329
 330         hlist_add_head(&cfi->hash, head);
 331 }
 332
 333 static void *cfi_hash_alloc(unsigned long size)
 334 {
 335         cfi_bits = max(10, ilog2(size));
 336         cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
 337                         PROT_READ|PROT_WRITE,
 338                         MAP_PRIVATE|MAP_ANON, -1, 0);
 339         if (cfi_hash == (void *)-1L) {
 340                 WARN("mmap fail cfi_hash");
 341                 cfi_hash = NULL;
 342         }  else if (opts.stats) {
 343                 printf("cfi_bits: %d\n", cfi_bits);
 344         }
 345
 346         return cfi_hash;
 347 }
 348
 349 static unsigned long nr_insns;
 350 static unsigned long nr_insns_visited;
 351
 352 /*
 353  * Call the arch-specific instruction decoder for all the instructions and add
 354  * them to the global instruction list.
 355  */
 356 static int decode_instructions(struct objtool_file *file)
 357 {
 358         struct section *sec;
 359         struct symbol *func;
 360         unsigned long offset;
 361         struct instruction *insn;
 362         int ret;
 363
 364         for_each_sec(file, sec) {
 365
 366                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
 367                         continue;
 368
 369                 if (strcmp(sec->name, ".altinstr_replacement") &&
 370                     strcmp(sec->name, ".altinstr_aux") &&
 371                     strncmp(sec->name, ".discard.", 9))
 372                         sec->text = true;
 373
 374                 if (!strcmp(sec->name, ".noinstr.text") ||
 375                     !strcmp(sec->name, ".entry.text"))
 376                         sec->noinstr = true;
 377
 378                 for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
 379                         insn = malloc(sizeof(*insn));
 380                         if (!insn) {
 381                                 WARN("malloc failed");
 382                                 return -1;
 383                         }
 384                         memset(insn, 0, sizeof(*insn));
 385                         INIT_LIST_HEAD(&insn->alts);
 386                         INIT_LIST_HEAD(&insn->stack_ops);
 387                         INIT_LIST_HEAD(&insn->call_node);
 388
 389                         insn->sec = sec;
 390                         insn->offset = offset;
 391
 392                         ret = arch_decode_instruction(file, sec, offset,
 393                                                       sec->sh.sh_size - offset,
 394                                                       &insn->len, &insn->type,
 395                                                       &insn->immediate,
 396                                                       &insn->stack_ops);
 397                         if (ret)
 398                                 goto err;
 399
 400                         /*
 401                          * By default, "ud2" is a dead end unless otherwise
 402                          * annotated, because GCC 7 inserts it for certain
 403                          * divide-by-zero cases.
 404                          */
 405                         if (insn->type == INSN_BUG)
 406                                 insn->dead_end = true;
 407
 408                         hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
 409                         list_add_tail(&insn->list, &file->insn_list);
 410                         nr_insns++;
 411                 }
 412
 413                 list_for_each_entry(func, &sec->symbol_list, list) {
 414                         if (func->type != STT_FUNC || func->alias != func)
 415                                 continue;
 416
 417                         if (!find_insn(file, sec, func->offset)) {
 418                                 WARN("%s(): can't find starting instruction",
 419                                      func->name);
 420                                 return -1;
 421                         }
 422
 423                         sym_for_each_insn(file, func, insn) {
 424                                 insn->func = func;
 425                                 if (insn->type == INSN_ENDBR && list_empty(&insn->call_node)) {
 426                                         if (insn->offset == insn->func->offset) {
 427                                                 list_add_tail(&insn->call_node, &file->endbr_list);
 428                                                 file->nr_endbr++;
 429                                         } else {
 430                                                 file->nr_endbr_int++;
 431                                         }
 432                                 }
 433                         }
 434                 }
 435         }
 436
 437         if (opts.stats)
 438                 printf("nr_insns: %lu\n", nr_insns);
 439
 440         return 0;
 441
 442 err:
 443         free(insn);
 444         return ret;
 445 }
 446
 447 /*
 448  * Read the pv_ops[] .data table to find the static initialized values.
 449  */
 450 static int add_pv_ops(struct objtool_file *file, const char *symname)
 451 {
 452         struct symbol *sym, *func;
 453         unsigned long off, end;
 454         struct reloc *rel;
 455         int idx;
 456
 457         sym = find_symbol_by_name(file->elf, symname);
 458         if (!sym)
 459                 return 0;
 460
 461         off = sym->offset;
 462         end = off + sym->len;
 463         for (;;) {
 464                 rel = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off);
 465                 if (!rel)
 466                         break;
 467
 468                 func = rel->sym;
 469                 if (func->type == STT_SECTION)
 470                         func = find_symbol_by_offset(rel->sym->sec, rel->addend);
 471
 472                 idx = (rel->offset - sym->offset) / sizeof(unsigned long);
 473
 474                 objtool_pv_add(file, idx, func);
 475
 476                 off = rel->offset + 1;
 477                 if (off > end)
 478                         break;
 479         }
 480
 481         return 0;
 482 }
 483
 484 /*
 485  * Allocate and initialize file->pv_ops[].
 486  */
 487 static int init_pv_ops(struct objtool_file *file)
 488 {
 489         static const char *pv_ops_tables[] = {
 490                 "pv_ops",
 491                 "xen_cpu_ops",
 492                 "xen_irq_ops",
 493                 "xen_mmu_ops",
 494                 NULL,
 495         };
 496         const char *pv_ops;
 497         struct symbol *sym;
 498         int idx, nr;
 499
 500         if (!opts.noinstr)
 501                 return 0;
 502
 503         file->pv_ops = NULL;
 504
 505         sym = find_symbol_by_name(file->elf, "pv_ops");
 506         if (!sym)
 507                 return 0;
 508
 509         nr = sym->len / sizeof(unsigned long);
 510         file->pv_ops = calloc(sizeof(struct pv_state), nr);
 511         if (!file->pv_ops)
 512                 return -1;
 513
 514         for (idx = 0; idx < nr; idx++)
 515                 INIT_LIST_HEAD(&file->pv_ops[idx].targets);
 516
 517         for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++)
 518                 add_pv_ops(file, pv_ops);
 519
 520         return 0;
 521 }
 522
 523 static struct instruction *find_last_insn(struct objtool_file *file,
 524                                           struct section *sec)
 525 {
 526         struct instruction *insn = NULL;
 527         unsigned int offset;
 528         unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
 529
 530         for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
 531                 insn = find_insn(file, sec, offset);
 532
 533         return insn;
 534 }
 535
 536 /*
 537  * Mark "ud2" instructions and manually annotated dead ends.
 538  */
 539 static int add_dead_ends(struct objtool_file *file)
 540 {
 541         struct section *sec;
 542         struct reloc *reloc;
 543         struct instruction *insn;
 544
 545         /*
 546          * Check for manually annotated dead ends.
 547          */
 548         sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
 549         if (!sec)
 550                 goto reachable;
 551
 552         list_for_each_entry(reloc, &sec->reloc_list, list) {
 553                 if (reloc->sym->type != STT_SECTION) {
 554                         WARN("unexpected relocation symbol type in %s", sec->name);
 555                         return -1;
 556                 }
 557                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 558                 if (insn)
 559                         insn = list_prev_entry(insn, list);
 560                 else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
 561                         insn = find_last_insn(file, reloc->sym->sec);
 562                         if (!insn) {
 563                                 WARN("can't find unreachable insn at %s+0x%lx",
 564                                      reloc->sym->sec->name, reloc->addend);
 565                                 return -1;
 566                         }
 567                 } else {
 568                         WARN("can't find unreachable insn at %s+0x%lx",
 569                              reloc->sym->sec->name, reloc->addend);
 570                         return -1;
 571                 }
 572
 573                 insn->dead_end = true;
 574         }
 575
 576 reachable:
 577         /*
 578          * These manually annotated reachable checks are needed for GCC 4.4,
 579          * where the Linux unreachable() macro isn't supported.  In that case
 580          * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
 581          * not a dead end.
 582          */
 583         sec = find_section_by_name(file->elf, ".rela.discard.reachable");
 584         if (!sec)
 585                 return 0;
 586
 587         list_for_each_entry(reloc, &sec->reloc_list, list) {
 588                 if (reloc->sym->type != STT_SECTION) {
 589                         WARN("unexpected relocation symbol type in %s", sec->name);
 590                         return -1;
 591                 }
 592                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 593                 if (insn)
 594                         insn = list_prev_entry(insn, list);
 595                 else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
 596                         insn = find_last_insn(file, reloc->sym->sec);
 597                         if (!insn) {
 598                                 WARN("can't find reachable insn at %s+0x%lx",
 599                                      reloc->sym->sec->name, reloc->addend);
 600                                 return -1;
 601                         }
 602                 } else {
 603                         WARN("can't find reachable insn at %s+0x%lx",
 604                              reloc->sym->sec->name, reloc->addend);
 605                         return -1;
 606                 }
 607
 608                 insn->dead_end = false;
 609         }
 610
 611         return 0;
 612 }
 613
 614 static int create_static_call_sections(struct objtool_file *file)
 615 {
 616         struct section *sec;
 617         struct static_call_site *site;
 618         struct instruction *insn;
 619         struct symbol *key_sym;
 620         char *key_name, *tmp;
 621         int idx;
 622
 623         sec = find_section_by_name(file->elf, ".static_call_sites");
 624         if (sec) {
 625                 INIT_LIST_HEAD(&file->static_call_list);
 626                 WARN("file already has .static_call_sites section, skipping");
 627                 return 0;
 628         }
 629
 630         if (list_empty(&file->static_call_list))
 631                 return 0;
 632
 633         idx = 0;
 634         list_for_each_entry(insn, &file->static_call_list, call_node)
 635                 idx++;
 636
 637         sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE,
 638                                  sizeof(struct static_call_site), idx);
 639         if (!sec)
 640                 return -1;
 641
 642         idx = 0;
 643         list_for_each_entry(insn, &file->static_call_list, call_node) {
 644
 645                 site = (struct static_call_site *)sec->data->d_buf + idx;
 646                 memset(site, 0, sizeof(struct static_call_site));
 647
 648                 /* populate reloc for 'addr' */
 649                 if (elf_add_reloc_to_insn(file->elf, sec,
 650                                           idx * sizeof(struct static_call_site),
 651                                           R_X86_64_PC32,
 652                                           insn->sec, insn->offset))
 653                         return -1;
 654
 655                 /* find key symbol */
 656                 key_name = strdup(insn->call_dest->name);
 657                 if (!key_name) {
 658                         perror("strdup");
 659                         return -1;
 660                 }
 661                 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
 662                             STATIC_CALL_TRAMP_PREFIX_LEN)) {
 663                         WARN("static_call: trampoline name malformed: %s", key_name);
 664                         return -1;
 665                 }
 666                 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
 667                 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
 668
 669                 key_sym = find_symbol_by_name(file->elf, tmp);
 670                 if (!key_sym) {
 671                         if (!opts.module) {
 672                                 WARN("static_call: can't find static_call_key symbol: %s", tmp);
 673                                 return -1;
 674                         }
 675
 676                         /*
 677                          * For modules(), the key might not be exported, which
 678                          * means the module can make static calls but isn't
 679                          * allowed to change them.
 680                          *
 681                          * In that case we temporarily set the key to be the
 682                          * trampoline address.  This is fixed up in
 683                          * static_call_add_module().
 684                          */
 685                         key_sym = insn->call_dest;
 686                 }
 687                 free(key_name);
 688
 689                 /* populate reloc for 'key' */
 690                 if (elf_add_reloc(file->elf, sec,
 691                                   idx * sizeof(struct static_call_site) + 4,
 692                                   R_X86_64_PC32, key_sym,
 693                                   is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
 694                         return -1;
 695
 696                 idx++;
 697         }
 698
 699         return 0;
 700 }
 701
 702 static int create_retpoline_sites_sections(struct objtool_file *file)
 703 {
 704         struct instruction *insn;
 705         struct section *sec;
 706         int idx;
 707
 708         sec = find_section_by_name(file->elf, ".retpoline_sites");
 709         if (sec) {
 710                 WARN("file already has .retpoline_sites, skipping");
 711                 return 0;
 712         }
 713
 714         idx = 0;
 715         list_for_each_entry(insn, &file->retpoline_call_list, call_node)
 716                 idx++;
 717
 718         if (!idx)
 719                 return 0;
 720
 721         sec = elf_create_section(file->elf, ".retpoline_sites", 0,
 722                                  sizeof(int), idx);
 723         if (!sec) {
 724                 WARN("elf_create_section: .retpoline_sites");
 725                 return -1;
 726         }
 727
 728         idx = 0;
 729         list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
 730
 731                 int *site = (int *)sec->data->d_buf + idx;
 732                 *site = 0;
 733
 734                 if (elf_add_reloc_to_insn(file->elf, sec,
 735                                           idx * sizeof(int),
 736                                           R_X86_64_PC32,
 737                                           insn->sec, insn->offset)) {
 738                         WARN("elf_add_reloc_to_insn: .retpoline_sites");
 739                         return -1;
 740                 }
 741
 742                 idx++;
 743         }
 744
 745         return 0;
 746 }
 747
 748 static int create_ibt_endbr_seal_sections(struct objtool_file *file)
 749 {
 750         struct instruction *insn;
 751         struct section *sec;
 752         int idx;
 753
 754         sec = find_section_by_name(file->elf, ".ibt_endbr_seal");
 755         if (sec) {
 756                 WARN("file already has .ibt_endbr_seal, skipping");
 757                 return 0;
 758         }
 759
 760         idx = 0;
 761         list_for_each_entry(insn, &file->endbr_list, call_node)
 762                 idx++;
 763
 764         if (opts.stats) {
 765                 printf("ibt: ENDBR at function start: %d\n", file->nr_endbr);
 766                 printf("ibt: ENDBR inside functions:  %d\n", file->nr_endbr_int);
 767                 printf("ibt: superfluous ENDBR:       %d\n", idx);
 768         }
 769
 770         if (!idx)
 771                 return 0;
 772
 773         sec = elf_create_section(file->elf, ".ibt_endbr_seal", 0,
 774                                  sizeof(int), idx);
 775         if (!sec) {
 776                 WARN("elf_create_section: .ibt_endbr_seal");
 777                 return -1;
 778         }
 779
 780         idx = 0;
 781         list_for_each_entry(insn, &file->endbr_list, call_node) {
 782
 783                 int *site = (int *)sec->data->d_buf + idx;
 784                 *site = 0;
 785
 786                 if (elf_add_reloc_to_insn(file->elf, sec,
 787                                           idx * sizeof(int),
 788                                           R_X86_64_PC32,
 789                                           insn->sec, insn->offset)) {
 790                         WARN("elf_add_reloc_to_insn: .ibt_endbr_seal");
 791                         return -1;
 792                 }
 793
 794                 idx++;
 795         }
 796
 797         return 0;
 798 }
 799
 800 static int create_mcount_loc_sections(struct objtool_file *file)
 801 {
 802         struct section *sec;
 803         unsigned long *loc;
 804         struct instruction *insn;
 805         int idx;
 806
 807         sec = find_section_by_name(file->elf, "__mcount_loc");
 808         if (sec) {
 809                 INIT_LIST_HEAD(&file->mcount_loc_list);
 810                 WARN("file already has __mcount_loc section, skipping");
 811                 return 0;
 812         }
 813
 814         if (list_empty(&file->mcount_loc_list))
 815                 return 0;
 816
 817         idx = 0;
 818         list_for_each_entry(insn, &file->mcount_loc_list, call_node)
 819                 idx++;
 820
 821         sec = elf_create_section(file->elf, "__mcount_loc", 0, sizeof(unsigned long), idx);
 822         if (!sec)
 823                 return -1;
 824
 825         idx = 0;
 826         list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
 827
 828                 loc = (unsigned long *)sec->data->d_buf + idx;
 829                 memset(loc, 0, sizeof(unsigned long));
 830
 831                 if (elf_add_reloc_to_insn(file->elf, sec,
 832                                           idx * sizeof(unsigned long),
 833                                           R_X86_64_64,
 834                                           insn->sec, insn->offset))
 835                         return -1;
 836
 837                 idx++;
 838         }
 839
 840         return 0;
 841 }
 842
 843 /*
 844  * Warnings shouldn't be reported for ignored functions.
 845  */
 846 static void add_ignores(struct objtool_file *file)
 847 {
 848         struct instruction *insn;
 849         struct section *sec;
 850         struct symbol *func;
 851         struct reloc *reloc;
 852
 853         sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
 854         if (!sec)
 855                 return;
 856
 857         list_for_each_entry(reloc, &sec->reloc_list, list) {
 858                 switch (reloc->sym->type) {
 859                 case STT_FUNC:
 860                         func = reloc->sym;
 861                         break;
 862
 863                 case STT_SECTION:
 864                         func = find_func_by_offset(reloc->sym->sec, reloc->addend);
 865                         if (!func)
 866                                 continue;
 867                         break;
 868
 869                 default:
 870                         WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type);
 871                         continue;
 872                 }
 873
 874                 func_for_each_insn(file, func, insn)
 875                         insn->ignore = true;
 876         }
 877 }
 878
 879 /*
 880  * This is a whitelist of functions that is allowed to be called with AC set.
 881  * The list is meant to be minimal and only contains compiler instrumentation
 882  * ABI and a few functions used to implement *_{to,from}_user() functions.
 883  *
 884  * These functions must not directly change AC, but may PUSHF/POPF.
 885  */
 886 static const char *uaccess_safe_builtin[] = {
 887         /* KASAN */
 888         "kasan_report",
 889         "kasan_check_range",
 890         /* KASAN out-of-line */
 891         "__asan_loadN_noabort",
 892         "__asan_load1_noabort",
 893         "__asan_load2_noabort",
 894         "__asan_load4_noabort",
 895         "__asan_load8_noabort",
 896         "__asan_load16_noabort",
 897         "__asan_storeN_noabort",
 898         "__asan_store1_noabort",
 899         "__asan_store2_noabort",
 900         "__asan_store4_noabort",
 901         "__asan_store8_noabort",
 902         "__asan_store16_noabort",
 903         "__kasan_check_read",
 904         "__kasan_check_write",
 905         /* KASAN in-line */
 906         "__asan_report_load_n_noabort",
 907         "__asan_report_load1_noabort",
 908         "__asan_report_load2_noabort",
 909         "__asan_report_load4_noabort",
 910         "__asan_report_load8_noabort",
 911         "__asan_report_load16_noabort",
 912         "__asan_report_store_n_noabort",
 913         "__asan_report_store1_noabort",
 914         "__asan_report_store2_noabort",
 915         "__asan_report_store4_noabort",
 916         "__asan_report_store8_noabort",
 917         "__asan_report_store16_noabort",
 918         /* KCSAN */
 919         "__kcsan_check_access",
 920         "__kcsan_mb",
 921         "__kcsan_wmb",
 922         "__kcsan_rmb",
 923         "__kcsan_release",
 924         "kcsan_found_watchpoint",
 925         "kcsan_setup_watchpoint",
 926         "kcsan_check_scoped_accesses",
 927         "kcsan_disable_current",
 928         "kcsan_enable_current_nowarn",
 929         /* KCSAN/TSAN */
 930         "__tsan_func_entry",
 931         "__tsan_func_exit",
 932         "__tsan_read_range",
 933         "__tsan_write_range",
 934         "__tsan_read1",
 935         "__tsan_read2",
 936         "__tsan_read4",
 937         "__tsan_read8",
 938         "__tsan_read16",
 939         "__tsan_write1",
 940         "__tsan_write2",
 941         "__tsan_write4",
 942         "__tsan_write8",
 943         "__tsan_write16",
 944         "__tsan_read_write1",
 945         "__tsan_read_write2",
 946         "__tsan_read_write4",
 947         "__tsan_read_write8",
 948         "__tsan_read_write16",
 949         "__tsan_atomic8_load",
 950         "__tsan_atomic16_load",
 951         "__tsan_atomic32_load",
 952         "__tsan_atomic64_load",
 953         "__tsan_atomic8_store",
 954         "__tsan_atomic16_store",
 955         "__tsan_atomic32_store",
 956         "__tsan_atomic64_store",
 957         "__tsan_atomic8_exchange",
 958         "__tsan_atomic16_exchange",
 959         "__tsan_atomic32_exchange",
 960         "__tsan_atomic64_exchange",
 961         "__tsan_atomic8_fetch_add",
 962         "__tsan_atomic16_fetch_add",
 963         "__tsan_atomic32_fetch_add",
 964         "__tsan_atomic64_fetch_add",
 965         "__tsan_atomic8_fetch_sub",
 966         "__tsan_atomic16_fetch_sub",
 967         "__tsan_atomic32_fetch_sub",
 968         "__tsan_atomic64_fetch_sub",
 969         "__tsan_atomic8_fetch_and",
 970         "__tsan_atomic16_fetch_and",
 971         "__tsan_atomic32_fetch_and",
 972         "__tsan_atomic64_fetch_and",
 973         "__tsan_atomic8_fetch_or",
 974         "__tsan_atomic16_fetch_or",
 975         "__tsan_atomic32_fetch_or",
 976         "__tsan_atomic64_fetch_or",
 977         "__tsan_atomic8_fetch_xor",
 978         "__tsan_atomic16_fetch_xor",
 979         "__tsan_atomic32_fetch_xor",
 980         "__tsan_atomic64_fetch_xor",
 981         "__tsan_atomic8_fetch_nand",
 982         "__tsan_atomic16_fetch_nand",
 983         "__tsan_atomic32_fetch_nand",
 984         "__tsan_atomic64_fetch_nand",
 985         "__tsan_atomic8_compare_exchange_strong",
 986         "__tsan_atomic16_compare_exchange_strong",
 987         "__tsan_atomic32_compare_exchange_strong",
 988         "__tsan_atomic64_compare_exchange_strong",
 989         "__tsan_atomic8_compare_exchange_weak",
 990         "__tsan_atomic16_compare_exchange_weak",
 991         "__tsan_atomic32_compare_exchange_weak",
 992         "__tsan_atomic64_compare_exchange_weak",
 993         "__tsan_atomic8_compare_exchange_val",
 994         "__tsan_atomic16_compare_exchange_val",
 995         "__tsan_atomic32_compare_exchange_val",
 996         "__tsan_atomic64_compare_exchange_val",
 997         "__tsan_atomic_thread_fence",
 998         "__tsan_atomic_signal_fence",
 999         /* KCOV */
1000         "write_comp_data",
1001         "check_kcov_mode",
1002         "__sanitizer_cov_trace_pc",
1003         "__sanitizer_cov_trace_const_cmp1",
1004         "__sanitizer_cov_trace_const_cmp2",
1005         "__sanitizer_cov_trace_const_cmp4",
1006         "__sanitizer_cov_trace_const_cmp8",
1007         "__sanitizer_cov_trace_cmp1",
1008         "__sanitizer_cov_trace_cmp2",
1009         "__sanitizer_cov_trace_cmp4",
1010         "__sanitizer_cov_trace_cmp8",
1011         "__sanitizer_cov_trace_switch",
1012         /* UBSAN */
1013         "ubsan_type_mismatch_common",
1014         "__ubsan_handle_type_mismatch",
1015         "__ubsan_handle_type_mismatch_v1",
1016         "__ubsan_handle_shift_out_of_bounds",
1017         /* misc */
1018         "csum_partial_copy_generic",
1019         "copy_mc_fragile",
1020         "copy_mc_fragile_handle_tail",
1021         "copy_mc_enhanced_fast_string",
1022         "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
1023         NULL
1024 };
1025
1026 static void add_uaccess_safe(struct objtool_file *file)
1027 {
1028         struct symbol *func;
1029         const char **name;
1030
1031         if (!opts.uaccess)
1032                 return;
1033
1034         for (name = uaccess_safe_builtin; *name; name++) {
1035                 func = find_symbol_by_name(file->elf, *name);
1036                 if (!func)
1037                         continue;
1038
1039                 func->uaccess_safe = true;
1040         }
1041 }
1042
1043 /*
1044  * FIXME: For now, just ignore any alternatives which add retpolines.  This is
1045  * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
1046  * But it at least allows objtool to understand the control flow *around* the
1047  * retpoline.
1048  */
1049 static int add_ignore_alternatives(struct objtool_file *file)
1050 {
1051         struct section *sec;
1052         struct reloc *reloc;
1053         struct instruction *insn;
1054
1055         sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
1056         if (!sec)
1057                 return 0;
1058
1059         list_for_each_entry(reloc, &sec->reloc_list, list) {
1060                 if (reloc->sym->type != STT_SECTION) {
1061                         WARN("unexpected relocation symbol type in %s", sec->name);
1062                         return -1;
1063                 }
1064
1065                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1066                 if (!insn) {
1067                         WARN("bad .discard.ignore_alts entry");
1068                         return -1;
1069                 }
1070
1071                 insn->ignore_alts = true;
1072         }
1073
1074         return 0;
1075 }
1076
1077 __weak bool arch_is_retpoline(struct symbol *sym)
1078 {
1079         return false;
1080 }
1081
1082 #define NEGATIVE_RELOC  ((void *)-1L)
1083
1084 static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
1085 {
1086         if (insn->reloc == NEGATIVE_RELOC)
1087                 return NULL;
1088
1089         if (!insn->reloc) {
1090                 if (!file)
1091                         return NULL;
1092
1093                 insn->reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1094                                                        insn->offset, insn->len);
1095                 if (!insn->reloc) {
1096                         insn->reloc = NEGATIVE_RELOC;
1097                         return NULL;
1098                 }
1099         }
1100
1101         return insn->reloc;
1102 }
1103
1104 static void remove_insn_ops(struct instruction *insn)
1105 {
1106         struct stack_op *op, *tmp;
1107
1108         list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
1109                 list_del(&op->list);
1110                 free(op);
1111         }
1112 }
1113
1114 static void annotate_call_site(struct objtool_file *file,
1115                                struct instruction *insn, bool sibling)
1116 {
1117         struct reloc *reloc = insn_reloc(file, insn);
1118         struct symbol *sym = insn->call_dest;
1119
1120         if (!sym)
1121                 sym = reloc->sym;
1122
1123         /*
1124          * Alternative replacement code is just template code which is
1125          * sometimes copied to the original instruction. For now, don't
1126          * annotate it. (In the future we might consider annotating the
1127          * original instruction if/when it ever makes sense to do so.)
1128          */
1129         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1130                 return;
1131
1132         if (sym->static_call_tramp) {
1133                 list_add_tail(&insn->call_node, &file->static_call_list);
1134                 return;
1135         }
1136
1137         if (sym->retpoline_thunk) {
1138                 list_add_tail(&insn->call_node, &file->retpoline_call_list);
1139                 return;
1140         }
1141
1142         /*
1143          * Many compilers cannot disable KCOV or sanitizer calls with a function
1144          * attribute so they need a little help, NOP out any such calls from
1145          * noinstr text.
1146          */
1147         if (insn->sec->noinstr && sym->profiling_func) {
1148                 if (reloc) {
1149                         reloc->type = R_NONE;
1150                         elf_write_reloc(file->elf, reloc);
1151                 }
1152
1153                 elf_write_insn(file->elf, insn->sec,
1154                                insn->offset, insn->len,
1155                                sibling ? arch_ret_insn(insn->len)
1156                                        : arch_nop_insn(insn->len));
1157
1158                 insn->type = sibling ? INSN_RETURN : INSN_NOP;
1159
1160                 if (sibling) {
1161                         /*
1162                          * We've replaced the tail-call JMP insn by two new
1163                          * insn: RET; INT3, except we only have a single struct
1164                          * insn here. Mark it retpoline_safe to avoid the SLS
1165                          * warning, instead of adding another insn.
1166                          */
1167                         insn->retpoline_safe = true;
1168                 }
1169
1170                 return;
1171         }
1172
1173         if (opts.mcount && sym->fentry) {
1174                 if (sibling)
1175                         WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset);
1176
1177                 if (reloc) {
1178                         reloc->type = R_NONE;
1179                         elf_write_reloc(file->elf, reloc);
1180                 }
1181
1182                 elf_write_insn(file->elf, insn->sec,
1183                                insn->offset, insn->len,
1184                                arch_nop_insn(insn->len));
1185
1186                 insn->type = INSN_NOP;
1187
1188                 list_add_tail(&insn->call_node, &file->mcount_loc_list);
1189                 return;
1190         }
1191
1192         if (!sibling && dead_end_function(file, sym))
1193                 insn->dead_end = true;
1194 }
1195
1196 static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1197                           struct symbol *dest, bool sibling)
1198 {
1199         insn->call_dest = dest;
1200         if (!dest)
1201                 return;
1202
1203         /*
1204          * Whatever stack impact regular CALLs have, should be undone
1205          * by the RETURN of the called function.
1206          *
1207          * Annotated intra-function calls retain the stack_ops but
1208          * are converted to JUMP, see read_intra_function_calls().
1209          */
1210         remove_insn_ops(insn);
1211
1212         annotate_call_site(file, insn, sibling);
1213 }
1214
1215 static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1216 {
1217         /*
1218          * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1219          * so convert them accordingly.
1220          */
1221         switch (insn->type) {
1222         case INSN_CALL:
1223                 insn->type = INSN_CALL_DYNAMIC;
1224                 break;
1225         case INSN_JUMP_UNCONDITIONAL:
1226                 insn->type = INSN_JUMP_DYNAMIC;
1227                 break;
1228         case INSN_JUMP_CONDITIONAL:
1229                 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1230                 break;
1231         default:
1232                 return;
1233         }
1234
1235         insn->retpoline_safe = true;
1236
1237         /*
1238          * Whatever stack impact regular CALLs have, should be undone
1239          * by the RETURN of the called function.
1240          *
1241          * Annotated intra-function calls retain the stack_ops but
1242          * are converted to JUMP, see read_intra_function_calls().
1243          */
1244         remove_insn_ops(insn);
1245
1246         annotate_call_site(file, insn, false);
1247 }
1248
1249 static bool same_function(struct instruction *insn1, struct instruction *insn2)
1250 {
1251         return insn1->func->pfunc == insn2->func->pfunc;
1252 }
1253
1254 static bool is_first_func_insn(struct objtool_file *file, struct instruction *insn)
1255 {
1256         if (insn->offset == insn->func->offset)
1257                 return true;
1258
1259         if (opts.ibt) {
1260                 struct instruction *prev = prev_insn_same_sym(file, insn);
1261
1262                 if (prev && prev->type == INSN_ENDBR &&
1263                     insn->offset == insn->func->offset + prev->len)
1264                         return true;
1265         }
1266
1267         return false;
1268 }
1269
1270 /*
1271  * Find the destination instructions for all jumps.
1272  */
1273 static int add_jump_destinations(struct objtool_file *file)
1274 {
1275         struct instruction *insn, *jump_dest;
1276         struct reloc *reloc;
1277         struct section *dest_sec;
1278         unsigned long dest_off;
1279
1280         for_each_insn(file, insn) {
1281                 if (insn->jump_dest) {
1282                         /*
1283                          * handle_group_alt() may have previously set
1284                          * 'jump_dest' for some alternatives.
1285                          */
1286                         continue;
1287                 }
1288                 if (!is_static_jump(insn))
1289                         continue;
1290
1291                 reloc = insn_reloc(file, insn);
1292                 if (!reloc) {
1293                         dest_sec = insn->sec;
1294                         dest_off = arch_jump_destination(insn);
1295                 } else if (reloc->sym->type == STT_SECTION) {
1296                         dest_sec = reloc->sym->sec;
1297                         dest_off = arch_dest_reloc_offset(reloc->addend);
1298                 } else if (reloc->sym->retpoline_thunk) {
1299                         add_retpoline_call(file, insn);
1300                         continue;
1301                 } else if (insn->func) {
1302                         /*
1303                          * External sibling call or internal sibling call with
1304                          * STT_FUNC reloc.
1305                          */
1306                         add_call_dest(file, insn, reloc->sym, true);
1307                         continue;
1308                 } else if (reloc->sym->sec->idx) {
1309                         dest_sec = reloc->sym->sec;
1310                         dest_off = reloc->sym->sym.st_value +
1311                                    arch_dest_reloc_offset(reloc->addend);
1312                 } else {
1313                         /* non-func asm code jumping to another file */
1314                         continue;
1315                 }
1316
1317                 jump_dest = find_insn(file, dest_sec, dest_off);
1318                 if (!jump_dest) {
1319                         WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
1320                                   insn->sec, insn->offset, dest_sec->name,
1321                                   dest_off);
1322                         return -1;
1323                 }
1324
1325                 /*
1326                  * Cross-function jump.
1327                  */
1328                 if (insn->func && jump_dest->func &&
1329                     insn->func != jump_dest->func) {
1330
1331                         /*
1332                          * For GCC 8+, create parent/child links for any cold
1333                          * subfunctions.  This is _mostly_ redundant with a
1334                          * similar initialization in read_symbols().
1335                          *
1336                          * If a function has aliases, we want the *first* such
1337                          * function in the symbol table to be the subfunction's
1338                          * parent.  In that case we overwrite the
1339                          * initialization done in read_symbols().
1340                          *
1341                          * However this code can't completely replace the
1342                          * read_symbols() code because this doesn't detect the
1343                          * case where the parent function's only reference to a
1344                          * subfunction is through a jump table.
1345                          */
1346                         if (!strstr(insn->func->name, ".cold") &&
1347                             strstr(jump_dest->func->name, ".cold")) {
1348                                 insn->func->cfunc = jump_dest->func;
1349                                 jump_dest->func->pfunc = insn->func;
1350
1351                         } else if (!same_function(insn, jump_dest) &&
1352                                    is_first_func_insn(file, jump_dest)) {
1353                                 /*
1354                                  * Internal sibling call without reloc or with
1355                                  * STT_SECTION reloc.
1356                                  */
1357                                 add_call_dest(file, insn, jump_dest->func, true);
1358                                 continue;
1359                         }
1360                 }
1361
1362                 insn->jump_dest = jump_dest;
1363         }
1364
1365         return 0;
1366 }
1367
1368 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1369 {
1370         struct symbol *call_dest;
1371
1372         call_dest = find_func_by_offset(sec, offset);
1373         if (!call_dest)
1374                 call_dest = find_symbol_by_offset(sec, offset);
1375
1376         return call_dest;
1377 }
1378
1379 /*
1380  * Find the destination instructions for all calls.
1381  */
1382 static int add_call_destinations(struct objtool_file *file)
1383 {
1384         struct instruction *insn;
1385         unsigned long dest_off;
1386         struct symbol *dest;
1387         struct reloc *reloc;
1388
1389         for_each_insn(file, insn) {
1390                 if (insn->type != INSN_CALL)
1391                         continue;
1392
1393                 reloc = insn_reloc(file, insn);
1394                 if (!reloc) {
1395                         dest_off = arch_jump_destination(insn);
1396                         dest = find_call_destination(insn->sec, dest_off);
1397
1398                         add_call_dest(file, insn, dest, false);
1399
1400                         if (insn->ignore)
1401                                 continue;
1402
1403                         if (!insn->call_dest) {
1404                                 WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);
1405                                 return -1;
1406                         }
1407
1408                         if (insn->func && insn->call_dest->type != STT_FUNC) {
1409                                 WARN_FUNC("unsupported call to non-function",
1410                                           insn->sec, insn->offset);
1411                                 return -1;
1412                         }
1413
1414                 } else if (reloc->sym->type == STT_SECTION) {
1415                         dest_off = arch_dest_reloc_offset(reloc->addend);
1416                         dest = find_call_destination(reloc->sym->sec, dest_off);
1417                         if (!dest) {
1418                                 WARN_FUNC("can't find call dest symbol at %s+0x%lx",
1419                                           insn->sec, insn->offset,
1420                                           reloc->sym->sec->name,
1421                                           dest_off);
1422                                 return -1;
1423                         }
1424
1425                         add_call_dest(file, insn, dest, false);
1426
1427                 } else if (reloc->sym->retpoline_thunk) {
1428                         add_retpoline_call(file, insn);
1429
1430                 } else
1431                         add_call_dest(file, insn, reloc->sym, false);
1432         }
1433
1434         return 0;
1435 }
1436
1437 /*
1438  * The .alternatives section requires some extra special care over and above
1439  * other special sections because alternatives are patched in place.
1440  */
1441 static int handle_group_alt(struct objtool_file *file,
1442                             struct special_alt *special_alt,
1443                             struct instruction *orig_insn,
1444                             struct instruction **new_insn)
1445 {
1446         struct instruction *last_orig_insn, *last_new_insn = NULL, *insn, *nop = NULL;
1447         struct alt_group *orig_alt_group, *new_alt_group;
1448         unsigned long dest_off;
1449
1450
1451         orig_alt_group = malloc(sizeof(*orig_alt_group));
1452         if (!orig_alt_group) {
1453                 WARN("malloc failed");
1454                 return -1;
1455         }
1456         orig_alt_group->cfi = calloc(special_alt->orig_len,
1457                                      sizeof(struct cfi_state *));
1458         if (!orig_alt_group->cfi) {
1459                 WARN("calloc failed");
1460                 return -1;
1461         }
1462
1463         last_orig_insn = NULL;
1464         insn = orig_insn;
1465         sec_for_each_insn_from(file, insn) {
1466                 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1467                         break;
1468
1469                 insn->alt_group = orig_alt_group;
1470                 last_orig_insn = insn;
1471         }
1472         orig_alt_group->orig_group = NULL;
1473         orig_alt_group->first_insn = orig_insn;
1474         orig_alt_group->last_insn = last_orig_insn;
1475
1476
1477         new_alt_group = malloc(sizeof(*new_alt_group));
1478         if (!new_alt_group) {
1479                 WARN("malloc failed");
1480                 return -1;
1481         }
1482
1483         if (special_alt->new_len < special_alt->orig_len) {
1484                 /*
1485                  * Insert a fake nop at the end to make the replacement
1486                  * alt_group the same size as the original.  This is needed to
1487                  * allow propagate_alt_cfi() to do its magic.  When the last
1488                  * instruction affects the stack, the instruction after it (the
1489                  * nop) will propagate the new state to the shared CFI array.
1490                  */
1491                 nop = malloc(sizeof(*nop));
1492                 if (!nop) {
1493                         WARN("malloc failed");
1494                         return -1;
1495                 }
1496                 memset(nop, 0, sizeof(*nop));
1497                 INIT_LIST_HEAD(&nop->alts);
1498                 INIT_LIST_HEAD(&nop->stack_ops);
1499
1500                 nop->sec = special_alt->new_sec;
1501                 nop->offset = special_alt->new_off + special_alt->new_len;
1502                 nop->len = special_alt->orig_len - special_alt->new_len;
1503                 nop->type = INSN_NOP;
1504                 nop->func = orig_insn->func;
1505                 nop->alt_group = new_alt_group;
1506                 nop->ignore = orig_insn->ignore_alts;
1507         }
1508
1509         if (!special_alt->new_len) {
1510                 *new_insn = nop;
1511                 goto end;
1512         }
1513
1514         insn = *new_insn;
1515         sec_for_each_insn_from(file, insn) {
1516                 struct reloc *alt_reloc;
1517
1518                 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1519                         break;
1520
1521                 last_new_insn = insn;
1522
1523                 insn->ignore = orig_insn->ignore_alts;
1524                 insn->func = orig_insn->func;
1525                 insn->alt_group = new_alt_group;
1526
1527                 /*
1528                  * Since alternative replacement code is copy/pasted by the
1529                  * kernel after applying relocations, generally such code can't
1530                  * have relative-address relocation references to outside the
1531                  * .altinstr_replacement section, unless the arch's
1532                  * alternatives code can adjust the relative offsets
1533                  * accordingly.
1534                  */
1535                 alt_reloc = insn_reloc(file, insn);
1536                 if (alt_reloc &&
1537                     !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1538
1539                         WARN_FUNC("unsupported relocation in alternatives section",
1540                                   insn->sec, insn->offset);
1541                         return -1;
1542                 }
1543
1544                 if (!is_static_jump(insn))
1545                         continue;
1546
1547                 if (!insn->immediate)
1548                         continue;
1549
1550                 dest_off = arch_jump_destination(insn);
1551                 if (dest_off == special_alt->new_off + special_alt->new_len) {
1552                         insn->jump_dest = next_insn_same_sec(file, last_orig_insn);
1553                         if (!insn->jump_dest) {
1554                                 WARN_FUNC("can't find alternative jump destination",
1555                                           insn->sec, insn->offset);
1556                                 return -1;
1557                         }
1558                 }
1559         }
1560
1561         if (!last_new_insn) {
1562                 WARN_FUNC("can't find last new alternative instruction",
1563                           special_alt->new_sec, special_alt->new_off);
1564                 return -1;
1565         }
1566
1567         if (nop)
1568                 list_add(&nop->list, &last_new_insn->list);
1569 end:
1570         new_alt_group->orig_group = orig_alt_group;
1571         new_alt_group->first_insn = *new_insn;
1572         new_alt_group->last_insn = nop ? : last_new_insn;
1573         new_alt_group->cfi = orig_alt_group->cfi;
1574         return 0;
1575 }
1576
1577 /*
1578  * A jump table entry can either convert a nop to a jump or a jump to a nop.
1579  * If the original instruction is a jump, make the alt entry an effective nop
1580  * by just skipping the original instruction.
1581  */
1582 static int handle_jump_alt(struct objtool_file *file,
1583                            struct special_alt *special_alt,
1584                            struct instruction *orig_insn,
1585                            struct instruction **new_insn)
1586 {
1587         if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1588             orig_insn->type != INSN_NOP) {
1589
1590                 WARN_FUNC("unsupported instruction at jump label",
1591                           orig_insn->sec, orig_insn->offset);
1592                 return -1;
1593         }
1594
1595         if (special_alt->key_addend & 2) {
1596                 struct reloc *reloc = insn_reloc(file, orig_insn);
1597
1598                 if (reloc) {
1599                         reloc->type = R_NONE;
1600                         elf_write_reloc(file->elf, reloc);
1601                 }
1602                 elf_write_insn(file->elf, orig_insn->sec,
1603                                orig_insn->offset, orig_insn->len,
1604                                arch_nop_insn(orig_insn->len));
1605                 orig_insn->type = INSN_NOP;
1606         }
1607
1608         if (orig_insn->type == INSN_NOP) {
1609                 if (orig_insn->len == 2)
1610                         file->jl_nop_short++;
1611                 else
1612                         file->jl_nop_long++;
1613
1614                 return 0;
1615         }
1616
1617         if (orig_insn->len == 2)
1618                 file->jl_short++;
1619         else
1620                 file->jl_long++;
1621
1622         *new_insn = list_next_entry(orig_insn, list);
1623         return 0;
1624 }
1625
1626 /*
1627  * Read all the special sections which have alternate instructions which can be
1628  * patched in or redirected to at runtime.  Each instruction having alternate
1629  * instruction(s) has them added to its insn->alts list, which will be
1630  * traversed in validate_branch().
1631  */
1632 static int add_special_section_alts(struct objtool_file *file)
1633 {
1634         struct list_head special_alts;
1635         struct instruction *orig_insn, *new_insn;
1636         struct special_alt *special_alt, *tmp;
1637         struct alternative *alt;
1638         int ret;
1639
1640         ret = special_get_alts(file->elf, &special_alts);
1641         if (ret)
1642                 return ret;
1643
1644         list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1645
1646                 orig_insn = find_insn(file, special_alt->orig_sec,
1647                                       special_alt->orig_off);
1648                 if (!orig_insn) {
1649                         WARN_FUNC("special: can't find orig instruction",
1650                                   special_alt->orig_sec, special_alt->orig_off);
1651                         ret = -1;
1652                         goto out;
1653                 }
1654
1655                 new_insn = NULL;
1656                 if (!special_alt->group || special_alt->new_len) {
1657                         new_insn = find_insn(file, special_alt->new_sec,
1658                                              special_alt->new_off);
1659                         if (!new_insn) {
1660                                 WARN_FUNC("special: can't find new instruction",
1661                                           special_alt->new_sec,
1662                                           special_alt->new_off);
1663                                 ret = -1;
1664                                 goto out;
1665                         }
1666                 }
1667
1668                 if (special_alt->group) {
1669                         if (!special_alt->orig_len) {
1670                                 WARN_FUNC("empty alternative entry",
1671                                           orig_insn->sec, orig_insn->offset);
1672                                 continue;
1673                         }
1674
1675                         ret = handle_group_alt(file, special_alt, orig_insn,
1676                                                &new_insn);
1677                         if (ret)
1678                                 goto out;
1679                 } else if (special_alt->jump_or_nop) {
1680                         ret = handle_jump_alt(file, special_alt, orig_insn,
1681                                               &new_insn);
1682                         if (ret)
1683                                 goto out;
1684                 }
1685
1686                 alt = malloc(sizeof(*alt));
1687                 if (!alt) {
1688                         WARN("malloc failed");
1689                         ret = -1;
1690                         goto out;
1691                 }
1692
1693                 alt->insn = new_insn;
1694                 alt->skip_orig = special_alt->skip_orig;
1695                 orig_insn->ignore_alts |= special_alt->skip_alt;
1696                 list_add_tail(&alt->list, &orig_insn->alts);
1697
1698                 list_del(&special_alt->list);
1699                 free(special_alt);
1700         }
1701
1702         if (opts.stats) {
1703                 printf("jl\\\tNOP\tJMP\n");
1704                 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
1705                 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
1706         }
1707
1708 out:
1709         return ret;
1710 }
1711
1712 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
1713                             struct reloc *table)
1714 {
1715         struct reloc *reloc = table;
1716         struct instruction *dest_insn;
1717         struct alternative *alt;
1718         struct symbol *pfunc = insn->func->pfunc;
1719         unsigned int prev_offset = 0;
1720
1721         /*
1722          * Each @reloc is a switch table relocation which points to the target
1723          * instruction.
1724          */
1725         list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
1726
1727                 /* Check for the end of the table: */
1728                 if (reloc != table && reloc->jump_table_start)
1729                         break;
1730
1731                 /* Make sure the table entries are consecutive: */
1732                 if (prev_offset && reloc->offset != prev_offset + 8)
1733                         break;
1734
1735                 /* Detect function pointers from contiguous objects: */
1736                 if (reloc->sym->sec == pfunc->sec &&
1737                     reloc->addend == pfunc->offset)
1738                         break;
1739
1740                 dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
1741                 if (!dest_insn)
1742                         break;
1743
1744                 /* Make sure the destination is in the same function: */
1745                 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
1746                         break;
1747
1748                 alt = malloc(sizeof(*alt));
1749                 if (!alt) {
1750                         WARN("malloc failed");
1751                         return -1;
1752                 }
1753
1754                 alt->insn = dest_insn;
1755                 list_add_tail(&alt->list, &insn->alts);
1756                 prev_offset = reloc->offset;
1757         }
1758
1759         if (!prev_offset) {
1760                 WARN_FUNC("can't find switch jump table",
1761                           insn->sec, insn->offset);
1762                 return -1;
1763         }
1764
1765         return 0;
1766 }
1767
1768 /*
1769  * find_jump_table() - Given a dynamic jump, find the switch jump table
1770  * associated with it.
1771  */
1772 static struct reloc *find_jump_table(struct objtool_file *file,
1773                                       struct symbol *func,
1774                                       struct instruction *insn)
1775 {
1776         struct reloc *table_reloc;
1777         struct instruction *dest_insn, *orig_insn = insn;
1778
1779         /*
1780          * Backward search using the @first_jump_src links, these help avoid
1781          * much of the 'in between' code. Which avoids us getting confused by
1782          * it.
1783          */
1784         for (;
1785              insn && insn->func && insn->func->pfunc == func;
1786              insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
1787
1788                 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1789                         break;
1790
1791                 /* allow small jumps within the range */
1792                 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1793                     insn->jump_dest &&
1794                     (insn->jump_dest->offset <= insn->offset ||
1795                      insn->jump_dest->offset > orig_insn->offset))
1796                     break;
1797
1798                 table_reloc = arch_find_switch_table(file, insn);
1799                 if (!table_reloc)
1800                         continue;
1801                 dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
1802                 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1803                         continue;
1804
1805                 return table_reloc;
1806         }
1807
1808         return NULL;
1809 }
1810
1811 /*
1812  * First pass: Mark the head of each jump table so that in the next pass,
1813  * we know when a given jump table ends and the next one starts.
1814  */
1815 static void mark_func_jump_tables(struct objtool_file *file,
1816                                     struct symbol *func)
1817 {
1818         struct instruction *insn, *last = NULL;
1819         struct reloc *reloc;
1820
1821         func_for_each_insn(file, func, insn) {
1822                 if (!last)
1823                         last = insn;
1824
1825                 /*
1826                  * Store back-pointers for unconditional forward jumps such
1827                  * that find_jump_table() can back-track using those and
1828                  * avoid some potentially confusing code.
1829                  */
1830                 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1831                     insn->offset > last->offset &&
1832                     insn->jump_dest->offset > insn->offset &&
1833                     !insn->jump_dest->first_jump_src) {
1834
1835                         insn->jump_dest->first_jump_src = insn;
1836                         last = insn->jump_dest;
1837                 }
1838
1839                 if (insn->type != INSN_JUMP_DYNAMIC)
1840                         continue;
1841
1842                 reloc = find_jump_table(file, func, insn);
1843                 if (reloc) {
1844                         reloc->jump_table_start = true;
1845                         insn->jump_table = reloc;
1846                 }
1847         }
1848 }
1849
1850 static int add_func_jump_tables(struct objtool_file *file,
1851                                   struct symbol *func)
1852 {
1853         struct instruction *insn;
1854         int ret;
1855
1856         func_for_each_insn(file, func, insn) {
1857                 if (!insn->jump_table)
1858                         continue;
1859
1860                 ret = add_jump_table(file, insn, insn->jump_table);
1861                 if (ret)
1862                         return ret;
1863         }
1864
1865         return 0;
1866 }
1867
1868 /*
1869  * For some switch statements, gcc generates a jump table in the .rodata
1870  * section which contains a list of addresses within the function to jump to.
1871  * This finds these jump tables and adds them to the insn->alts lists.
1872  */
1873 static int add_jump_table_alts(struct objtool_file *file)
1874 {
1875         struct section *sec;
1876         struct symbol *func;
1877         int ret;
1878
1879         if (!file->rodata)
1880                 return 0;
1881
1882         for_each_sec(file, sec) {
1883                 list_for_each_entry(func, &sec->symbol_list, list) {
1884                         if (func->type != STT_FUNC)
1885                                 continue;
1886
1887                         mark_func_jump_tables(file, func);
1888                         ret = add_func_jump_tables(file, func);
1889                         if (ret)
1890                                 return ret;
1891                 }
1892         }
1893
1894         return 0;
1895 }
1896
1897 static void set_func_state(struct cfi_state *state)
1898 {
1899         state->cfa = initial_func_cfi.cfa;
1900         memcpy(&state->regs, &initial_func_cfi.regs,
1901                CFI_NUM_REGS * sizeof(struct cfi_reg));
1902         state->stack_size = initial_func_cfi.cfa.offset;
1903 }
1904
1905 static int read_unwind_hints(struct objtool_file *file)
1906 {
1907         struct cfi_state cfi = init_cfi;
1908         struct section *sec, *relocsec;
1909         struct unwind_hint *hint;
1910         struct instruction *insn;
1911         struct reloc *reloc;
1912         int i;
1913
1914         sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1915         if (!sec)
1916                 return 0;
1917
1918         relocsec = sec->reloc;
1919         if (!relocsec) {
1920                 WARN("missing .rela.discard.unwind_hints section");
1921                 return -1;
1922         }
1923
1924         if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
1925                 WARN("struct unwind_hint size mismatch");
1926                 return -1;
1927         }
1928
1929         file->hints = true;
1930
1931         for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
1932                 hint = (struct unwind_hint *)sec->data->d_buf + i;
1933
1934                 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
1935                 if (!reloc) {
1936                         WARN("can't find reloc for unwind_hints[%d]", i);
1937                         return -1;
1938                 }
1939
1940                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1941                 if (!insn) {
1942                         WARN("can't find insn for unwind_hints[%d]", i);
1943                         return -1;
1944                 }
1945
1946                 insn->hint = true;
1947
1948                 if (opts.ibt && hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
1949                         struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
1950
1951                         if (sym && sym->bind == STB_GLOBAL &&
1952                             insn->type != INSN_ENDBR && !insn->noendbr) {
1953                                 WARN_FUNC("UNWIND_HINT_IRET_REGS without ENDBR",
1954                                           insn->sec, insn->offset);
1955                         }
1956                 }
1957
1958                 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
1959                         insn->cfi = &func_cfi;
1960                         continue;
1961                 }
1962
1963                 if (insn->cfi)
1964                         cfi = *(insn->cfi);
1965
1966                 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
1967                         WARN_FUNC("unsupported unwind_hint sp base reg %d",
1968                                   insn->sec, insn->offset, hint->sp_reg);
1969                         return -1;
1970                 }
1971
1972                 cfi.cfa.offset = bswap_if_needed(hint->sp_offset);
1973                 cfi.type = hint->type;
1974                 cfi.end = hint->end;
1975
1976                 insn->cfi = cfi_hash_find_or_add(&cfi);
1977         }
1978
1979         return 0;
1980 }
1981
1982 static int read_noendbr_hints(struct objtool_file *file)
1983 {
1984         struct section *sec;
1985         struct instruction *insn;
1986         struct reloc *reloc;
1987
1988         sec = find_section_by_name(file->elf, ".rela.discard.noendbr");
1989         if (!sec)
1990                 return 0;
1991
1992         list_for_each_entry(reloc, &sec->reloc_list, list) {
1993                 insn = find_insn(file, reloc->sym->sec, reloc->sym->offset + reloc->addend);
1994                 if (!insn) {
1995                         WARN("bad .discard.noendbr entry");
1996                         return -1;
1997                 }
1998
1999                 if (insn->type == INSN_ENDBR)
2000                         WARN_FUNC("ANNOTATE_NOENDBR on ENDBR", insn->sec, insn->offset);
2001
2002                 insn->noendbr = 1;
2003         }
2004
2005         return 0;
2006 }
2007
2008 static int read_retpoline_hints(struct objtool_file *file)
2009 {
2010         struct section *sec;
2011         struct instruction *insn;
2012         struct reloc *reloc;
2013
2014         sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
2015         if (!sec)
2016                 return 0;
2017
2018         list_for_each_entry(reloc, &sec->reloc_list, list) {
2019                 if (reloc->sym->type != STT_SECTION) {
2020                         WARN("unexpected relocation symbol type in %s", sec->name);
2021                         return -1;
2022                 }
2023
2024                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2025                 if (!insn) {
2026                         WARN("bad .discard.retpoline_safe entry");
2027                         return -1;
2028                 }
2029
2030                 if (insn->type != INSN_JUMP_DYNAMIC &&
2031                     insn->type != INSN_CALL_DYNAMIC) {
2032                         WARN_FUNC("retpoline_safe hint not an indirect jump/call",
2033                                   insn->sec, insn->offset);
2034                         return -1;
2035                 }
2036
2037                 insn->retpoline_safe = true;
2038         }
2039
2040         return 0;
2041 }
2042
2043 static int read_instr_hints(struct objtool_file *file)
2044 {
2045         struct section *sec;
2046         struct instruction *insn;
2047         struct reloc *reloc;
2048
2049         sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2050         if (!sec)
2051                 return 0;
2052
2053         list_for_each_entry(reloc, &sec->reloc_list, list) {
2054                 if (reloc->sym->type != STT_SECTION) {
2055                         WARN("unexpected relocation symbol type in %s", sec->name);
2056                         return -1;
2057                 }
2058
2059                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2060                 if (!insn) {
2061                         WARN("bad .discard.instr_end entry");
2062                         return -1;
2063                 }
2064
2065                 insn->instr--;
2066         }
2067
2068         sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2069         if (!sec)
2070                 return 0;
2071
2072         list_for_each_entry(reloc, &sec->reloc_list, list) {
2073                 if (reloc->sym->type != STT_SECTION) {
2074                         WARN("unexpected relocation symbol type in %s", sec->name);
2075                         return -1;
2076                 }
2077
2078                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2079                 if (!insn) {
2080                         WARN("bad .discard.instr_begin entry");
2081                         return -1;
2082                 }
2083
2084                 insn->instr++;
2085         }
2086
2087         return 0;
2088 }
2089
2090 static int read_intra_function_calls(struct objtool_file *file)
2091 {
2092         struct instruction *insn;
2093         struct section *sec;
2094         struct reloc *reloc;
2095
2096         sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2097         if (!sec)
2098                 return 0;
2099
2100         list_for_each_entry(reloc, &sec->reloc_list, list) {
2101                 unsigned long dest_off;
2102
2103                 if (reloc->sym->type != STT_SECTION) {
2104                         WARN("unexpected relocation symbol type in %s",
2105                              sec->name);
2106                         return -1;
2107                 }
2108
2109                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2110                 if (!insn) {
2111                         WARN("bad .discard.intra_function_call entry");
2112                         return -1;
2113                 }
2114
2115                 if (insn->type != INSN_CALL) {
2116                         WARN_FUNC("intra_function_call not a direct call",
2117                                   insn->sec, insn->offset);
2118                         return -1;
2119                 }
2120
2121                 /*
2122                  * Treat intra-function CALLs as JMPs, but with a stack_op.
2123                  * See add_call_destinations(), which strips stack_ops from
2124                  * normal CALLs.
2125                  */
2126                 insn->type = INSN_JUMP_UNCONDITIONAL;
2127
2128                 dest_off = insn->offset + insn->len + insn->immediate;
2129                 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2130                 if (!insn->jump_dest) {
2131                         WARN_FUNC("can't find call dest at %s+0x%lx",
2132                                   insn->sec, insn->offset,
2133                                   insn->sec->name, dest_off);
2134                         return -1;
2135                 }
2136         }
2137
2138         return 0;
2139 }
2140
2141 /*
2142  * Return true if name matches an instrumentation function, where calls to that
2143  * function from noinstr code can safely be removed, but compilers won't do so.
2144  */
2145 static bool is_profiling_func(const char *name)
2146 {
2147         /*
2148          * Many compilers cannot disable KCOV with a function attribute.
2149          */
2150         if (!strncmp(name, "__sanitizer_cov_", 16))
2151                 return true;
2152
2153         /*
2154          * Some compilers currently do not remove __tsan_func_entry/exit nor
2155          * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2156          * the __no_sanitize_thread attribute, remove them. Once the kernel's
2157          * minimum Clang version is 14.0, this can be removed.
2158          */
2159         if (!strncmp(name, "__tsan_func_", 12) ||
2160             !strcmp(name, "__tsan_atomic_signal_fence"))
2161                 return true;
2162
2163         return false;
2164 }
2165
2166 static int classify_symbols(struct objtool_file *file)
2167 {
2168         struct section *sec;
2169         struct symbol *func;
2170
2171         for_each_sec(file, sec) {
2172                 list_for_each_entry(func, &sec->symbol_list, list) {
2173                         if (func->bind != STB_GLOBAL)
2174                                 continue;
2175
2176                         if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2177                                      strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2178                                 func->static_call_tramp = true;
2179
2180                         if (arch_is_retpoline(func))
2181                                 func->retpoline_thunk = true;
2182
2183                         if (!strcmp(func->name, "__fentry__"))
2184                                 func->fentry = true;
2185
2186                         if (is_profiling_func(func->name))
2187                                 func->profiling_func = true;
2188                 }
2189         }
2190
2191         return 0;
2192 }
2193
2194 static void mark_rodata(struct objtool_file *file)
2195 {
2196         struct section *sec;
2197         bool found = false;
2198
2199         /*
2200          * Search for the following rodata sections, each of which can
2201          * potentially contain jump tables:
2202          *
2203          * - .rodata: can contain GCC switch tables
2204          * - .rodata.<func>: same, if -fdata-sections is being used
2205          * - .rodata..c_jump_table: contains C annotated jump tables
2206          *
2207          * .rodata.str1.* sections are ignored; they don't contain jump tables.
2208          */
2209         for_each_sec(file, sec) {
2210                 if (!strncmp(sec->name, ".rodata", 7) &&
2211                     !strstr(sec->name, ".str1.")) {
2212                         sec->rodata = true;
2213                         found = true;
2214                 }
2215         }
2216
2217         file->rodata = found;
2218 }
2219
2220 static int decode_sections(struct objtool_file *file)
2221 {
2222         int ret;
2223
2224         mark_rodata(file);
2225
2226         ret = init_pv_ops(file);
2227         if (ret)
2228                 return ret;
2229
2230         ret = decode_instructions(file);
2231         if (ret)
2232                 return ret;
2233
2234         add_ignores(file);
2235         add_uaccess_safe(file);
2236
2237         ret = add_ignore_alternatives(file);
2238         if (ret)
2239                 return ret;
2240
2241         /*
2242          * Must be before read_unwind_hints() since that needs insn->noendbr.
2243          */
2244         ret = read_noendbr_hints(file);
2245         if (ret)
2246                 return ret;
2247
2248         /*
2249          * Must be before add_{jump_call}_destination.
2250          */
2251         ret = classify_symbols(file);
2252         if (ret)
2253                 return ret;
2254
2255         /*
2256          * Must be before add_jump_destinations(), which depends on 'func'
2257          * being set for alternatives, to enable proper sibling call detection.
2258          */
2259         ret = add_special_section_alts(file);
2260         if (ret)
2261                 return ret;
2262
2263         ret = add_jump_destinations(file);
2264         if (ret)
2265                 return ret;
2266
2267         /*
2268          * Must be before add_call_destination(); it changes INSN_CALL to
2269          * INSN_JUMP.
2270          */
2271         ret = read_intra_function_calls(file);
2272         if (ret)
2273                 return ret;
2274
2275         ret = add_call_destinations(file);
2276         if (ret)
2277                 return ret;
2278
2279         /*
2280          * Must be after add_call_destinations() such that it can override
2281          * dead_end_function() marks.
2282          */
2283         ret = add_dead_ends(file);
2284         if (ret)
2285                 return ret;
2286
2287         ret = add_jump_table_alts(file);
2288         if (ret)
2289                 return ret;
2290
2291         ret = read_unwind_hints(file);
2292         if (ret)
2293                 return ret;
2294
2295         ret = read_retpoline_hints(file);
2296         if (ret)
2297                 return ret;
2298
2299         ret = read_instr_hints(file);
2300         if (ret)
2301                 return ret;
2302
2303         return 0;
2304 }
2305
2306 static bool is_fentry_call(struct instruction *insn)
2307 {
2308         if (insn->type == INSN_CALL &&
2309             insn->call_dest &&
2310             insn->call_dest->fentry)
2311                 return true;
2312
2313         return false;
2314 }
2315
2316 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2317 {
2318         struct cfi_state *cfi = &state->cfi;
2319         int i;
2320
2321         if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2322                 return true;
2323
2324         if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2325                 return true;
2326
2327         if (cfi->stack_size != initial_func_cfi.cfa.offset)
2328                 return true;
2329
2330         for (i = 0; i < CFI_NUM_REGS; i++) {
2331                 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2332                     cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2333                         return true;
2334         }
2335
2336         return false;
2337 }
2338
2339 static bool check_reg_frame_pos(const struct cfi_reg *reg,
2340                                 int expected_offset)
2341 {
2342         return reg->base == CFI_CFA &&
2343                reg->offset == expected_offset;
2344 }
2345
2346 static bool has_valid_stack_frame(struct insn_state *state)
2347 {
2348         struct cfi_state *cfi = &state->cfi;
2349
2350         if (cfi->cfa.base == CFI_BP &&
2351             check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2352             check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2353                 return true;
2354
2355         if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2356                 return true;
2357
2358         return false;
2359 }
2360
2361 static int update_cfi_state_regs(struct instruction *insn,
2362                                   struct cfi_state *cfi,
2363                                   struct stack_op *op)
2364 {
2365         struct cfi_reg *cfa = &cfi->cfa;
2366
2367         if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2368                 return 0;
2369
2370         /* push */
2371         if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2372                 cfa->offset += 8;
2373
2374         /* pop */
2375         if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2376                 cfa->offset -= 8;
2377
2378         /* add immediate to sp */
2379         if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2380             op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2381                 cfa->offset -= op->src.offset;
2382
2383         return 0;
2384 }
2385
2386 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2387 {
2388         if (arch_callee_saved_reg(reg) &&
2389             cfi->regs[reg].base == CFI_UNDEFINED) {
2390                 cfi->regs[reg].base = base;
2391                 cfi->regs[reg].offset = offset;
2392         }
2393 }
2394
2395 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2396 {
2397         cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2398         cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2399 }
2400
2401 /*
2402  * A note about DRAP stack alignment:
2403  *
2404  * GCC has the concept of a DRAP register, which is used to help keep track of
2405  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
2406  * register.  The typical DRAP pattern is:
2407  *
2408  *   4c 8d 54 24 08             lea    0x8(%rsp),%r10
2409  *   48 83 e4 c0                and    $0xffffffffffffffc0,%rsp
2410  *   41 ff 72 f8                pushq  -0x8(%r10)
2411  *   55                         push   %rbp
2412  *   48 89 e5                   mov    %rsp,%rbp
2413  *                              (more pushes)
2414  *   41 52                      push   %r10
2415  *                              ...
2416  *   41 5a                      pop    %r10
2417  *                              (more pops)
2418  *   5d                         pop    %rbp
2419  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2420  *   c3                         retq
2421  *
2422  * There are some variations in the epilogues, like:
2423  *
2424  *   5b                         pop    %rbx
2425  *   41 5a                      pop    %r10
2426  *   41 5c                      pop    %r12
2427  *   41 5d                      pop    %r13
2428  *   41 5e                      pop    %r14
2429  *   c9                         leaveq
2430  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2431  *   c3                         retq
2432  *
2433  * and:
2434  *
2435  *   4c 8b 55 e8                mov    -0x18(%rbp),%r10
2436  *   48 8b 5d e0                mov    -0x20(%rbp),%rbx
2437  *   4c 8b 65 f0                mov    -0x10(%rbp),%r12
2438  *   4c 8b 6d f8                mov    -0x8(%rbp),%r13
2439  *   c9                         leaveq
2440  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2441  *   c3                         retq
2442  *
2443  * Sometimes r13 is used as the DRAP register, in which case it's saved and
2444  * restored beforehand:
2445  *
2446  *   41 55                      push   %r13
2447  *   4c 8d 6c 24 10             lea    0x10(%rsp),%r13
2448  *   48 83 e4 f0                and    $0xfffffffffffffff0,%rsp
2449  *                              ...
2450  *   49 8d 65 f0                lea    -0x10(%r13),%rsp
2451  *   41 5d                      pop    %r13
2452  *   c3                         retq
2453  */
2454 static int update_cfi_state(struct instruction *insn,
2455                             struct instruction *next_insn,
2456                             struct cfi_state *cfi, struct stack_op *op)
2457 {
2458         struct cfi_reg *cfa = &cfi->cfa;
2459         struct cfi_reg *regs = cfi->regs;
2460
2461         /* stack operations don't make sense with an undefined CFA */
2462         if (cfa->base == CFI_UNDEFINED) {
2463                 if (insn->func) {
2464                         WARN_FUNC("undefined stack state", insn->sec, insn->offset);
2465                         return -1;
2466                 }
2467                 return 0;
2468         }
2469
2470         if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2471             cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2472                 return update_cfi_state_regs(insn, cfi, op);
2473
2474         switch (op->dest.type) {
2475
2476         case OP_DEST_REG:
2477                 switch (op->src.type) {
2478
2479                 case OP_SRC_REG:
2480                         if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2481                             cfa->base == CFI_SP &&
2482                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset)) {
2483
2484                                 /* mov %rsp, %rbp */
2485                                 cfa->base = op->dest.reg;
2486                                 cfi->bp_scratch = false;
2487                         }
2488
2489                         else if (op->src.reg == CFI_SP &&
2490                                  op->dest.reg == CFI_BP && cfi->drap) {
2491
2492                                 /* drap: mov %rsp, %rbp */
2493                                 regs[CFI_BP].base = CFI_BP;
2494                                 regs[CFI_BP].offset = -cfi->stack_size;
2495                                 cfi->bp_scratch = false;
2496                         }
2497
2498                         else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2499
2500                                 /*
2501                                  * mov %rsp, %reg
2502                                  *
2503                                  * This is needed for the rare case where GCC
2504                                  * does:
2505                                  *
2506                                  *   mov    %rsp, %rax
2507                                  *   ...
2508                                  *   mov    %rax, %rsp
2509                                  */
2510                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2511                                 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2512                         }
2513
2514                         else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2515                                  (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2516
2517                                 /*
2518                                  * mov %rbp, %rsp
2519                                  *
2520                                  * Restore the original stack pointer (Clang).
2521                                  */
2522                                 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2523                         }
2524
2525                         else if (op->dest.reg == cfa->base) {
2526
2527                                 /* mov %reg, %rsp */
2528                                 if (cfa->base == CFI_SP &&
2529                                     cfi->vals[op->src.reg].base == CFI_CFA) {
2530
2531                                         /*
2532                                          * This is needed for the rare case
2533                                          * where GCC does something dumb like:
2534                                          *
2535                                          *   lea    0x8(%rsp), %rcx
2536                                          *   ...
2537                                          *   mov    %rcx, %rsp
2538                                          */
2539                                         cfa->offset = -cfi->vals[op->src.reg].offset;
2540                                         cfi->stack_size = cfa->offset;
2541
2542                                 } else if (cfa->base == CFI_SP &&
2543                                            cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2544                                            cfi->vals[op->src.reg].offset == cfa->offset) {
2545
2546                                         /*
2547                                          * Stack swizzle:
2548                                          *
2549                                          * 1: mov %rsp, (%[tos])
2550                                          * 2: mov %[tos], %rsp
2551                                          *    ...
2552                                          * 3: pop %rsp
2553                                          *
2554                                          * Where:
2555                                          *
2556                                          * 1 - places a pointer to the previous
2557                                          *     stack at the Top-of-Stack of the
2558                                          *     new stack.
2559                                          *
2560                                          * 2 - switches to the new stack.
2561                                          *
2562                                          * 3 - pops the Top-of-Stack to restore
2563                                          *     the original stack.
2564                                          *
2565                                          * Note: we set base to SP_INDIRECT
2566                                          * here and preserve offset. Therefore
2567                                          * when the unwinder reaches ToS it
2568                                          * will dereference SP and then add the
2569                                          * offset to find the next frame, IOW:
2570                                          * (%rsp) + offset.
2571                                          */
2572                                         cfa->base = CFI_SP_INDIRECT;
2573
2574                                 } else {
2575                                         cfa->base = CFI_UNDEFINED;
2576                                         cfa->offset = 0;
2577                                 }
2578                         }
2579
2580                         else if (op->dest.reg == CFI_SP &&
2581                                  cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2582                                  cfi->vals[op->src.reg].offset == cfa->offset) {
2583
2584                                 /*
2585                                  * The same stack swizzle case 2) as above. But
2586                                  * because we can't change cfa->base, case 3)
2587                                  * will become a regular POP. Pretend we're a
2588                                  * PUSH so things don't go unbalanced.
2589                                  */
2590                                 cfi->stack_size += 8;
2591                         }
2592
2593
2594                         break;
2595
2596                 case OP_SRC_ADD:
2597                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2598
2599                                 /* add imm, %rsp */
2600                                 cfi->stack_size -= op->src.offset;
2601                                 if (cfa->base == CFI_SP)
2602                                         cfa->offset -= op->src.offset;
2603                                 break;
2604                         }
2605
2606                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2607
2608                                 /* lea disp(%rbp), %rsp */
2609                                 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2610                                 break;
2611                         }
2612
2613                         if (!cfi->drap && op->src.reg == CFI_SP &&
2614                             op->dest.reg == CFI_BP && cfa->base == CFI_SP &&
2615                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset + op->src.offset)) {
2616
2617                                 /* lea disp(%rsp), %rbp */
2618                                 cfa->base = CFI_BP;
2619                                 cfa->offset -= op->src.offset;
2620                                 cfi->bp_scratch = false;
2621                                 break;
2622                         }
2623
2624                         if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2625
2626                                 /* drap: lea disp(%rsp), %drap */
2627                                 cfi->drap_reg = op->dest.reg;
2628
2629                                 /*
2630                                  * lea disp(%rsp), %reg
2631                                  *
2632                                  * This is needed for the rare case where GCC
2633                                  * does something dumb like:
2634                                  *
2635                                  *   lea    0x8(%rsp), %rcx
2636                                  *   ...
2637                                  *   mov    %rcx, %rsp
2638                                  */
2639                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2640                                 cfi->vals[op->dest.reg].offset = \
2641                                         -cfi->stack_size + op->src.offset;
2642
2643                                 break;
2644                         }
2645
2646                         if (cfi->drap && op->dest.reg == CFI_SP &&
2647                             op->src.reg == cfi->drap_reg) {
2648
2649                                  /* drap: lea disp(%drap), %rsp */
2650                                 cfa->base = CFI_SP;
2651                                 cfa->offset = cfi->stack_size = -op->src.offset;
2652                                 cfi->drap_reg = CFI_UNDEFINED;
2653                                 cfi->drap = false;
2654                                 break;
2655                         }
2656
2657                         if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
2658                                 WARN_FUNC("unsupported stack register modification",
2659                                           insn->sec, insn->offset);
2660                                 return -1;
2661                         }
2662
2663                         break;
2664
2665                 case OP_SRC_AND:
2666                         if (op->dest.reg != CFI_SP ||
2667                             (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
2668                             (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
2669                                 WARN_FUNC("unsupported stack pointer realignment",
2670                                           insn->sec, insn->offset);
2671                                 return -1;
2672                         }
2673
2674                         if (cfi->drap_reg != CFI_UNDEFINED) {
2675                                 /* drap: and imm, %rsp */
2676                                 cfa->base = cfi->drap_reg;
2677                                 cfa->offset = cfi->stack_size = 0;
2678                                 cfi->drap = true;
2679                         }
2680
2681                         /*
2682                          * Older versions of GCC (4.8ish) realign the stack
2683                          * without DRAP, with a frame pointer.
2684                          */
2685
2686                         break;
2687
2688                 case OP_SRC_POP:
2689                 case OP_SRC_POPF:
2690                         if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
2691
2692                                 /* pop %rsp; # restore from a stack swizzle */
2693                                 cfa->base = CFI_SP;
2694                                 break;
2695                         }
2696
2697                         if (!cfi->drap && op->dest.reg == cfa->base) {
2698
2699                                 /* pop %rbp */
2700                                 cfa->base = CFI_SP;
2701                         }
2702
2703                         if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
2704                             op->dest.reg == cfi->drap_reg &&
2705                             cfi->drap_offset == -cfi->stack_size) {
2706
2707                                 /* drap: pop %drap */
2708                                 cfa->base = cfi->drap_reg;
2709                                 cfa->offset = 0;
2710                                 cfi->drap_offset = -1;
2711
2712                         } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
2713
2714                                 /* pop %reg */
2715                                 restore_reg(cfi, op->dest.reg);
2716                         }
2717
2718                         cfi->stack_size -= 8;
2719                         if (cfa->base == CFI_SP)
2720                                 cfa->offset -= 8;
2721
2722                         break;
2723
2724                 case OP_SRC_REG_INDIRECT:
2725                         if (!cfi->drap && op->dest.reg == cfa->base &&
2726                             op->dest.reg == CFI_BP) {
2727
2728                                 /* mov disp(%rsp), %rbp */
2729                                 cfa->base = CFI_SP;
2730                                 cfa->offset = cfi->stack_size;
2731                         }
2732
2733                         if (cfi->drap && op->src.reg == CFI_BP &&
2734                             op->src.offset == cfi->drap_offset) {
2735
2736                                 /* drap: mov disp(%rbp), %drap */
2737                                 cfa->base = cfi->drap_reg;
2738                                 cfa->offset = 0;
2739                                 cfi->drap_offset = -1;
2740                         }
2741
2742                         if (cfi->drap && op->src.reg == CFI_BP &&
2743                             op->src.offset == regs[op->dest.reg].offset) {
2744
2745                                 /* drap: mov disp(%rbp), %reg */
2746                                 restore_reg(cfi, op->dest.reg);
2747
2748                         } else if (op->src.reg == cfa->base &&
2749                             op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
2750
2751                                 /* mov disp(%rbp), %reg */
2752                                 /* mov disp(%rsp), %reg */
2753                                 restore_reg(cfi, op->dest.reg);
2754
2755                         } else if (op->src.reg == CFI_SP &&
2756                                    op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
2757
2758                                 /* mov disp(%rsp), %reg */
2759                                 restore_reg(cfi, op->dest.reg);
2760                         }
2761
2762                         break;
2763
2764                 default:
2765                         WARN_FUNC("unknown stack-related instruction",
2766                                   insn->sec, insn->offset);
2767                         return -1;
2768                 }
2769
2770                 break;
2771
2772         case OP_DEST_PUSH:
2773         case OP_DEST_PUSHF:
2774                 cfi->stack_size += 8;
2775                 if (cfa->base == CFI_SP)
2776                         cfa->offset += 8;
2777
2778                 if (op->src.type != OP_SRC_REG)
2779                         break;
2780
2781                 if (cfi->drap) {
2782                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2783
2784                                 /* drap: push %drap */
2785                                 cfa->base = CFI_BP_INDIRECT;
2786                                 cfa->offset = -cfi->stack_size;
2787
2788                                 /* save drap so we know when to restore it */
2789                                 cfi->drap_offset = -cfi->stack_size;
2790
2791                         } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
2792
2793                                 /* drap: push %rbp */
2794                                 cfi->stack_size = 0;
2795
2796                         } else {
2797
2798                                 /* drap: push %reg */
2799                                 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
2800                         }
2801
2802                 } else {
2803
2804                         /* push %reg */
2805                         save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
2806                 }
2807
2808                 /* detect when asm code uses rbp as a scratch register */
2809                 if (!opts.no_fp && insn->func && op->src.reg == CFI_BP &&
2810                     cfa->base != CFI_BP)
2811                         cfi->bp_scratch = true;
2812                 break;
2813
2814         case OP_DEST_REG_INDIRECT:
2815
2816                 if (cfi->drap) {
2817                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2818
2819                                 /* drap: mov %drap, disp(%rbp) */
2820                                 cfa->base = CFI_BP_INDIRECT;
2821                                 cfa->offset = op->dest.offset;
2822
2823                                 /* save drap offset so we know when to restore it */
2824                                 cfi->drap_offset = op->dest.offset;
2825                         } else {
2826
2827                                 /* drap: mov reg, disp(%rbp) */
2828                                 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
2829                         }
2830
2831                 } else if (op->dest.reg == cfa->base) {
2832
2833                         /* mov reg, disp(%rbp) */
2834                         /* mov reg, disp(%rsp) */
2835                         save_reg(cfi, op->src.reg, CFI_CFA,
2836                                  op->dest.offset - cfi->cfa.offset);
2837
2838                 } else if (op->dest.reg == CFI_SP) {
2839
2840                         /* mov reg, disp(%rsp) */
2841                         save_reg(cfi, op->src.reg, CFI_CFA,
2842                                  op->dest.offset - cfi->stack_size);
2843
2844                 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
2845
2846                         /* mov %rsp, (%reg); # setup a stack swizzle. */
2847                         cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
2848                         cfi->vals[op->dest.reg].offset = cfa->offset;
2849                 }
2850
2851                 break;
2852
2853         case OP_DEST_MEM:
2854                 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
2855                         WARN_FUNC("unknown stack-related memory operation",
2856                                   insn->sec, insn->offset);
2857                         return -1;
2858                 }
2859
2860                 /* pop mem */
2861                 cfi->stack_size -= 8;
2862                 if (cfa->base == CFI_SP)
2863                         cfa->offset -= 8;
2864
2865                 break;
2866
2867         default:
2868                 WARN_FUNC("unknown stack-related instruction",
2869                           insn->sec, insn->offset);
2870                 return -1;
2871         }
2872
2873         return 0;
2874 }
2875
2876 /*
2877  * The stack layouts of alternatives instructions can sometimes diverge when
2878  * they have stack modifications.  That's fine as long as the potential stack
2879  * layouts don't conflict at any given potential instruction boundary.
2880  *
2881  * Flatten the CFIs of the different alternative code streams (both original
2882  * and replacement) into a single shared CFI array which can be used to detect
2883  * conflicts and nicely feed a linear array of ORC entries to the unwinder.
2884  */
2885 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
2886 {
2887         struct cfi_state **alt_cfi;
2888         int group_off;
2889
2890         if (!insn->alt_group)
2891                 return 0;
2892
2893         if (!insn->cfi) {
2894                 WARN("CFI missing");
2895                 return -1;
2896         }
2897
2898         alt_cfi = insn->alt_group->cfi;
2899         group_off = insn->offset - insn->alt_group->first_insn->offset;
2900
2901         if (!alt_cfi[group_off]) {
2902                 alt_cfi[group_off] = insn->cfi;
2903         } else {
2904                 if (cficmp(alt_cfi[group_off], insn->cfi)) {
2905                         WARN_FUNC("stack layout conflict in alternatives",
2906                                   insn->sec, insn->offset);
2907                         return -1;
2908                 }
2909         }
2910
2911         return 0;
2912 }
2913
2914 static int handle_insn_ops(struct instruction *insn,
2915                            struct instruction *next_insn,
2916                            struct insn_state *state)
2917 {
2918         struct stack_op *op;
2919
2920         list_for_each_entry(op, &insn->stack_ops, list) {
2921
2922                 if (update_cfi_state(insn, next_insn, &state->cfi, op))
2923                         return 1;
2924
2925                 if (!insn->alt_group)
2926                         continue;
2927
2928                 if (op->dest.type == OP_DEST_PUSHF) {
2929                         if (!state->uaccess_stack) {
2930                                 state->uaccess_stack = 1;
2931                         } else if (state->uaccess_stack >> 31) {
2932                                 WARN_FUNC("PUSHF stack exhausted",
2933                                           insn->sec, insn->offset);
2934                                 return 1;
2935                         }
2936                         state->uaccess_stack <<= 1;
2937                         state->uaccess_stack  |= state->uaccess;
2938                 }
2939
2940                 if (op->src.type == OP_SRC_POPF) {
2941                         if (state->uaccess_stack) {
2942                                 state->uaccess = state->uaccess_stack & 1;
2943                                 state->uaccess_stack >>= 1;
2944                                 if (state->uaccess_stack == 1)
2945                                         state->uaccess_stack = 0;
2946                         }
2947                 }
2948         }
2949
2950         return 0;
2951 }
2952
2953 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
2954 {
2955         struct cfi_state *cfi1 = insn->cfi;
2956         int i;
2957
2958         if (!cfi1) {
2959                 WARN("CFI missing");
2960                 return false;
2961         }
2962
2963         if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
2964
2965                 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
2966                           insn->sec, insn->offset,
2967                           cfi1->cfa.base, cfi1->cfa.offset,
2968                           cfi2->cfa.base, cfi2->cfa.offset);
2969
2970         } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
2971                 for (i = 0; i < CFI_NUM_REGS; i++) {
2972                         if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
2973                                     sizeof(struct cfi_reg)))
2974                                 continue;
2975
2976                         WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
2977                                   insn->sec, insn->offset,
2978                                   i, cfi1->regs[i].base, cfi1->regs[i].offset,
2979                                   i, cfi2->regs[i].base, cfi2->regs[i].offset);
2980                         break;
2981                 }
2982
2983         } else if (cfi1->type != cfi2->type) {
2984
2985                 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
2986                           insn->sec, insn->offset, cfi1->type, cfi2->type);
2987
2988         } else if (cfi1->drap != cfi2->drap ||
2989                    (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
2990                    (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
2991
2992                 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
2993                           insn->sec, insn->offset,
2994                           cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
2995                           cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
2996
2997         } else
2998                 return true;
2999
3000         return false;
3001 }
3002
3003 static inline bool func_uaccess_safe(struct symbol *func)
3004 {
3005         if (func)
3006                 return func->uaccess_safe;
3007
3008         return false;
3009 }
3010
3011 static inline const char *call_dest_name(struct instruction *insn)
3012 {
3013         static char pvname[19];
3014         struct reloc *rel;
3015         int idx;
3016
3017         if (insn->call_dest)
3018                 return insn->call_dest->name;
3019
3020         rel = insn_reloc(NULL, insn);
3021         if (rel && !strcmp(rel->sym->name, "pv_ops")) {
3022                 idx = (rel->addend / sizeof(void *));
3023                 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
3024                 return pvname;
3025         }
3026
3027         return "{dynamic}";
3028 }
3029
3030 static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3031 {
3032         struct symbol *target;
3033         struct reloc *rel;
3034         int idx;
3035
3036         rel = insn_reloc(file, insn);
3037         if (!rel || strcmp(rel->sym->name, "pv_ops"))
3038                 return false;
3039
3040         idx = (arch_dest_reloc_offset(rel->addend) / sizeof(void *));
3041
3042         if (file->pv_ops[idx].clean)
3043                 return true;
3044
3045         file->pv_ops[idx].clean = true;
3046
3047         list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3048                 if (!target->sec->noinstr) {
3049                         WARN("pv_ops[%d]: %s", idx, target->name);
3050                         file->pv_ops[idx].clean = false;
3051                 }
3052         }
3053
3054         return file->pv_ops[idx].clean;
3055 }
3056
3057 static inline bool noinstr_call_dest(struct objtool_file *file,
3058                                      struct instruction *insn,
3059                                      struct symbol *func)
3060 {
3061         /*
3062          * We can't deal with indirect function calls at present;
3063          * assume they're instrumented.
3064          */
3065         if (!func) {
3066                 if (file->pv_ops)
3067                         return pv_call_dest(file, insn);
3068
3069                 return false;
3070         }
3071
3072         /*
3073          * If the symbol is from a noinstr section; we good.
3074          */
3075         if (func->sec->noinstr)
3076                 return true;
3077
3078         /*
3079          * The __ubsan_handle_*() calls are like WARN(), they only happen when
3080          * something 'BAD' happened. At the risk of taking the machine down,
3081          * let them proceed to get the message out.
3082          */
3083         if (!strncmp(func->name, "__ubsan_handle_", 15))
3084                 return true;
3085
3086         return false;
3087 }
3088
3089 static int validate_call(struct objtool_file *file,
3090                          struct instruction *insn,
3091                          struct insn_state *state)
3092 {
3093         if (state->noinstr && state->instr <= 0 &&
3094             !noinstr_call_dest(file, insn, insn->call_dest)) {
3095                 WARN_FUNC("call to %s() leaves .noinstr.text section",
3096                                 insn->sec, insn->offset, call_dest_name(insn));
3097                 return 1;
3098         }
3099
3100         if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
3101                 WARN_FUNC("call to %s() with UACCESS enabled",
3102                                 insn->sec, insn->offset, call_dest_name(insn));
3103                 return 1;
3104         }
3105
3106         if (state->df) {
3107                 WARN_FUNC("call to %s() with DF set",
3108                                 insn->sec, insn->offset, call_dest_name(insn));
3109                 return 1;
3110         }
3111
3112         return 0;
3113 }
3114
3115 static int validate_sibling_call(struct objtool_file *file,
3116                                  struct instruction *insn,
3117                                  struct insn_state *state)
3118 {
3119         if (has_modified_stack_frame(insn, state)) {
3120                 WARN_FUNC("sibling call from callable instruction with modified stack frame",
3121                                 insn->sec, insn->offset);
3122                 return 1;
3123         }
3124
3125         return validate_call(file, insn, state);
3126 }
3127
3128 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3129 {
3130         if (state->noinstr && state->instr > 0) {
3131                 WARN_FUNC("return with instrumentation enabled",
3132                           insn->sec, insn->offset);
3133                 return 1;
3134         }
3135
3136         if (state->uaccess && !func_uaccess_safe(func)) {
3137                 WARN_FUNC("return with UACCESS enabled",
3138                           insn->sec, insn->offset);
3139                 return 1;
3140         }
3141
3142         if (!state->uaccess && func_uaccess_safe(func)) {
3143                 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
3144                           insn->sec, insn->offset);
3145                 return 1;
3146         }
3147
3148         if (state->df) {
3149                 WARN_FUNC("return with DF set",
3150                           insn->sec, insn->offset);
3151                 return 1;
3152         }
3153
3154         if (func && has_modified_stack_frame(insn, state)) {
3155                 WARN_FUNC("return with modified stack frame",
3156                           insn->sec, insn->offset);
3157                 return 1;
3158         }
3159
3160         if (state->cfi.bp_scratch) {
3161                 WARN_FUNC("BP used as a scratch register",
3162                           insn->sec, insn->offset);
3163                 return 1;
3164         }
3165
3166         return 0;
3167 }
3168
3169 static struct instruction *next_insn_to_validate(struct objtool_file *file,
3170                                                  struct instruction *insn)
3171 {
3172         struct alt_group *alt_group = insn->alt_group;
3173
3174         /*
3175          * Simulate the fact that alternatives are patched in-place.  When the
3176          * end of a replacement alt_group is reached, redirect objtool flow to
3177          * the end of the original alt_group.
3178          */
3179         if (alt_group && insn == alt_group->last_insn && alt_group->orig_group)
3180                 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3181
3182         return next_insn_same_sec(file, insn);
3183 }
3184
3185 /*
3186  * Follow the branch starting at the given instruction, and recursively follow
3187  * any other branches (jumps).  Meanwhile, track the frame pointer state at
3188  * each instruction and validate all the rules described in
3189  * tools/objtool/Documentation/stack-validation.txt.
3190  */
3191 static int validate_branch(struct objtool_file *file, struct symbol *func,
3192                            struct instruction *insn, struct insn_state state)
3193 {
3194         struct alternative *alt;
3195         struct instruction *next_insn, *prev_insn = NULL;
3196         struct section *sec;
3197         u8 visited;
3198         int ret;
3199
3200         sec = insn->sec;
3201
3202         while (1) {
3203                 next_insn = next_insn_to_validate(file, insn);
3204
3205                 if (func && insn->func && func != insn->func->pfunc) {
3206                         WARN("%s() falls through to next function %s()",
3207                              func->name, insn->func->name);
3208                         return 1;
3209                 }
3210
3211                 if (func && insn->ignore) {
3212                         WARN_FUNC("BUG: why am I validating an ignored function?",
3213                                   sec, insn->offset);
3214                         return 1;
3215                 }
3216
3217                 visited = 1 << state.uaccess;
3218                 if (insn->visited) {
3219                         if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3220                                 return 1;
3221
3222                         if (insn->visited & visited)
3223                                 return 0;
3224                 } else {
3225                         nr_insns_visited++;
3226                 }
3227
3228                 if (state.noinstr)
3229                         state.instr += insn->instr;
3230
3231                 if (insn->hint) {
3232                         state.cfi = *insn->cfi;
3233                 } else {
3234                         /* XXX track if we actually changed state.cfi */
3235
3236                         if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3237                                 insn->cfi = prev_insn->cfi;
3238                                 nr_cfi_reused++;
3239                         } else {
3240                                 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3241                         }
3242                 }
3243
3244                 insn->visited |= visited;
3245
3246                 if (propagate_alt_cfi(file, insn))
3247                         return 1;
3248
3249                 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
3250                         bool skip_orig = false;
3251
3252                         list_for_each_entry(alt, &insn->alts, list) {
3253                                 if (alt->skip_orig)
3254                                         skip_orig = true;
3255
3256                                 ret = validate_branch(file, func, alt->insn, state);
3257                                 if (ret) {
3258                                         if (opts.backtrace)
3259                                                 BT_FUNC("(alt)", insn);
3260                                         return ret;
3261                                 }
3262                         }
3263
3264                         if (skip_orig)
3265                                 return 0;
3266                 }
3267
3268                 if (handle_insn_ops(insn, next_insn, &state))
3269                         return 1;
3270
3271                 switch (insn->type) {
3272
3273                 case INSN_RETURN:
3274                         return validate_return(func, insn, &state);
3275
3276                 case INSN_CALL:
3277                 case INSN_CALL_DYNAMIC:
3278                         ret = validate_call(file, insn, &state);
3279                         if (ret)
3280                                 return ret;
3281
3282                         if (!opts.no_fp && func && !is_fentry_call(insn) &&
3283                             !has_valid_stack_frame(&state)) {
3284                                 WARN_FUNC("call without frame pointer save/setup",
3285                                           sec, insn->offset);
3286                                 return 1;
3287                         }
3288
3289                         if (insn->dead_end)
3290                                 return 0;
3291
3292                         break;
3293
3294                 case INSN_JUMP_CONDITIONAL:
3295                 case INSN_JUMP_UNCONDITIONAL:
3296                         if (is_sibling_call(insn)) {
3297                                 ret = validate_sibling_call(file, insn, &state);
3298                                 if (ret)
3299                                         return ret;
3300
3301                         } else if (insn->jump_dest) {
3302                                 ret = validate_branch(file, func,
3303                                                       insn->jump_dest, state);
3304                                 if (ret) {
3305                                         if (opts.backtrace)
3306                                                 BT_FUNC("(branch)", insn);
3307                                         return ret;
3308                                 }
3309                         }
3310
3311                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
3312                                 return 0;
3313
3314                         break;
3315
3316                 case INSN_JUMP_DYNAMIC:
3317                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3318                         if (is_sibling_call(insn)) {
3319                                 ret = validate_sibling_call(file, insn, &state);
3320                                 if (ret)
3321                                         return ret;
3322                         }
3323
3324                         if (insn->type == INSN_JUMP_DYNAMIC)
3325                                 return 0;
3326
3327                         break;
3328
3329                 case INSN_CONTEXT_SWITCH:
3330                         if (func && (!next_insn || !next_insn->hint)) {
3331                                 WARN_FUNC("unsupported instruction in callable function",
3332                                           sec, insn->offset);
3333                                 return 1;
3334                         }
3335                         return 0;
3336
3337                 case INSN_STAC:
3338                         if (state.uaccess) {
3339                                 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
3340                                 return 1;
3341                         }
3342
3343                         state.uaccess = true;
3344                         break;
3345
3346                 case INSN_CLAC:
3347                         if (!state.uaccess && func) {
3348                                 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
3349                                 return 1;
3350                         }
3351
3352                         if (func_uaccess_safe(func) && !state.uaccess_stack) {
3353                                 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
3354                                 return 1;
3355                         }
3356
3357                         state.uaccess = false;
3358                         break;
3359
3360                 case INSN_STD:
3361                         if (state.df) {
3362                                 WARN_FUNC("recursive STD", sec, insn->offset);
3363                                 return 1;
3364                         }
3365
3366                         state.df = true;
3367                         break;
3368
3369                 case INSN_CLD:
3370                         if (!state.df && func) {
3371                                 WARN_FUNC("redundant CLD", sec, insn->offset);
3372                                 return 1;
3373                         }
3374
3375                         state.df = false;
3376                         break;
3377
3378                 default:
3379                         break;
3380                 }
3381
3382                 if (insn->dead_end)
3383                         return 0;
3384
3385                 if (!next_insn) {
3386                         if (state.cfi.cfa.base == CFI_UNDEFINED)
3387                                 return 0;
3388                         WARN("%s: unexpected end of section", sec->name);
3389                         return 1;
3390                 }
3391
3392                 prev_insn = insn;
3393                 insn = next_insn;
3394         }
3395
3396         return 0;
3397 }
3398
3399 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3400 {
3401         struct instruction *insn;
3402         struct insn_state state;
3403         int ret, warnings = 0;
3404
3405         if (!file->hints)
3406                 return 0;
3407
3408         init_insn_state(&state, sec);
3409
3410         if (sec) {
3411                 insn = find_insn(file, sec, 0);
3412                 if (!insn)
3413                         return 0;
3414         } else {
3415                 insn = list_first_entry(&file->insn_list, typeof(*insn), list);
3416         }
3417
3418         while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) {
3419                 if (insn->hint && !insn->visited && !insn->ignore) {
3420                         ret = validate_branch(file, insn->func, insn, state);
3421                         if (ret && opts.backtrace)
3422                                 BT_FUNC("<=== (hint)", insn);
3423                         warnings += ret;
3424                 }
3425
3426                 insn = list_next_entry(insn, list);
3427         }
3428
3429         return warnings;
3430 }
3431
3432 static int validate_retpoline(struct objtool_file *file)
3433 {
3434         struct instruction *insn;
3435         int warnings = 0;
3436
3437         for_each_insn(file, insn) {
3438                 if (insn->type != INSN_JUMP_DYNAMIC &&
3439                     insn->type != INSN_CALL_DYNAMIC)
3440                         continue;
3441
3442                 if (insn->retpoline_safe)
3443                         continue;
3444
3445                 /*
3446                  * .init.text code is ran before userspace and thus doesn't
3447                  * strictly need retpolines, except for modules which are
3448                  * loaded late, they very much do need retpoline in their
3449                  * .init.text
3450                  */
3451                 if (!strcmp(insn->sec->name, ".init.text") && !opts.module)
3452                         continue;
3453
3454                 WARN_FUNC("indirect %s found in RETPOLINE build",
3455                           insn->sec, insn->offset,
3456                           insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
3457
3458                 warnings++;
3459         }
3460
3461         return warnings;
3462 }
3463
3464 static bool is_kasan_insn(struct instruction *insn)
3465 {
3466         return (insn->type == INSN_CALL &&
3467                 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
3468 }
3469
3470 static bool is_ubsan_insn(struct instruction *insn)
3471 {
3472         return (insn->type == INSN_CALL &&
3473                 !strcmp(insn->call_dest->name,
3474                         "__ubsan_handle_builtin_unreachable"));
3475 }
3476
3477 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
3478 {
3479         int i;
3480         struct instruction *prev_insn;
3481
3482         if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
3483                 return true;
3484
3485         /*
3486          * Ignore alternative replacement instructions.  This can happen
3487          * when a whitelisted function uses one of the ALTERNATIVE macros.
3488          */
3489         if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
3490             !strcmp(insn->sec->name, ".altinstr_aux"))
3491                 return true;
3492
3493         /*
3494          * Whole archive runs might encounder dead code from weak symbols.
3495          * This is where the linker will have dropped the weak symbol in
3496          * favour of a regular symbol, but leaves the code in place.
3497          *
3498          * In this case we'll find a piece of code (whole function) that is not
3499          * covered by a !section symbol. Ignore them.
3500          */
3501         if (!insn->func && opts.lto) {
3502                 int size = find_symbol_hole_containing(insn->sec, insn->offset);
3503                 unsigned long end = insn->offset + size;
3504
3505                 if (!size) /* not a hole */
3506                         return false;
3507
3508                 if (size < 0) /* hole until the end */
3509                         return true;
3510
3511                 sec_for_each_insn_continue(file, insn) {
3512                         /*
3513                          * If we reach a visited instruction at or before the
3514                          * end of the hole, ignore the unreachable.
3515                          */
3516                         if (insn->visited)
3517                                 return true;
3518
3519                         if (insn->offset >= end)
3520                                 break;
3521
3522                         /*
3523                          * If this hole jumps to a .cold function, mark it ignore too.
3524                          */
3525                         if (insn->jump_dest && insn->jump_dest->func &&
3526                             strstr(insn->jump_dest->func->name, ".cold")) {
3527                                 struct instruction *dest = insn->jump_dest;
3528                                 func_for_each_insn(file, dest->func, dest)
3529                                         dest->ignore = true;
3530                         }
3531                 }
3532
3533                 return false;
3534         }
3535
3536         if (!insn->func)
3537                 return false;
3538
3539         if (insn->func->static_call_tramp)
3540                 return true;
3541
3542         /*
3543          * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
3544          * __builtin_unreachable().  The BUG() macro has an unreachable() after
3545          * the UD2, which causes GCC's undefined trap logic to emit another UD2
3546          * (or occasionally a JMP to UD2).
3547          *
3548          * It may also insert a UD2 after calling a __noreturn function.
3549          */
3550         prev_insn = list_prev_entry(insn, list);
3551         if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) &&
3552             (insn->type == INSN_BUG ||
3553              (insn->type == INSN_JUMP_UNCONDITIONAL &&
3554               insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
3555                 return true;
3556
3557         /*
3558          * Check if this (or a subsequent) instruction is related to
3559          * CONFIG_UBSAN or CONFIG_KASAN.
3560          *
3561          * End the search at 5 instructions to avoid going into the weeds.
3562          */
3563         for (i = 0; i < 5; i++) {
3564
3565                 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
3566                         return true;
3567
3568                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
3569                         if (insn->jump_dest &&
3570                             insn->jump_dest->func == insn->func) {
3571                                 insn = insn->jump_dest;
3572                                 continue;
3573                         }
3574
3575                         break;
3576                 }
3577
3578                 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
3579                         break;
3580
3581                 insn = list_next_entry(insn, list);
3582         }
3583
3584         return false;
3585 }
3586
3587 static int validate_symbol(struct objtool_file *file, struct section *sec,
3588                            struct symbol *sym, struct insn_state *state)
3589 {
3590         struct instruction *insn;
3591         int ret;
3592
3593         if (!sym->len) {
3594                 WARN("%s() is missing an ELF size annotation", sym->name);
3595                 return 1;
3596         }
3597
3598         if (sym->pfunc != sym || sym->alias != sym)
3599                 return 0;
3600
3601         insn = find_insn(file, sec, sym->offset);
3602         if (!insn || insn->ignore || insn->visited)
3603                 return 0;
3604
3605         state->uaccess = sym->uaccess_safe;
3606
3607         ret = validate_branch(file, insn->func, insn, *state);
3608         if (ret && opts.backtrace)
3609                 BT_FUNC("<=== (sym)", insn);
3610         return ret;
3611 }
3612
3613 static int validate_section(struct objtool_file *file, struct section *sec)
3614 {
3615         struct insn_state state;
3616         struct symbol *func;
3617         int warnings = 0;
3618
3619         list_for_each_entry(func, &sec->symbol_list, list) {
3620                 if (func->type != STT_FUNC)
3621                         continue;
3622
3623                 init_insn_state(&state, sec);
3624                 set_func_state(&state.cfi);
3625
3626                 warnings += validate_symbol(file, sec, func, &state);
3627         }
3628
3629         return warnings;
3630 }
3631
3632 static int validate_vmlinux_functions(struct objtool_file *file)
3633 {
3634         struct section *sec;
3635         int warnings = 0;
3636
3637         sec = find_section_by_name(file->elf, ".noinstr.text");
3638         if (sec) {
3639                 warnings += validate_section(file, sec);
3640                 warnings += validate_unwind_hints(file, sec);
3641         }
3642
3643         sec = find_section_by_name(file->elf, ".entry.text");
3644         if (sec) {
3645                 warnings += validate_section(file, sec);
3646                 warnings += validate_unwind_hints(file, sec);
3647         }
3648
3649         return warnings;
3650 }
3651
3652 static int validate_functions(struct objtool_file *file)
3653 {
3654         struct section *sec;
3655         int warnings = 0;
3656
3657         for_each_sec(file, sec) {
3658                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
3659                         continue;
3660
3661                 warnings += validate_section(file, sec);
3662         }
3663
3664         return warnings;
3665 }
3666
3667 static void mark_endbr_used(struct instruction *insn)
3668 {
3669         if (!list_empty(&insn->call_node))
3670                 list_del_init(&insn->call_node);
3671 }
3672
3673 static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
3674 {
3675         struct instruction *dest;
3676         struct reloc *reloc;
3677         unsigned long off;
3678         int warnings = 0;
3679
3680         /*
3681          * Looking for function pointer load relocations.  Ignore
3682          * direct/indirect branches:
3683          */
3684         switch (insn->type) {
3685         case INSN_CALL:
3686         case INSN_CALL_DYNAMIC:
3687         case INSN_JUMP_CONDITIONAL:
3688         case INSN_JUMP_UNCONDITIONAL:
3689         case INSN_JUMP_DYNAMIC:
3690         case INSN_JUMP_DYNAMIC_CONDITIONAL:
3691         case INSN_RETURN:
3692         case INSN_NOP:
3693                 return 0;
3694         default:
3695                 break;
3696         }
3697
3698         for (reloc = insn_reloc(file, insn);
3699              reloc;
3700              reloc = find_reloc_by_dest_range(file->elf, insn->sec,
3701                                               reloc->offset + 1,
3702                                               (insn->offset + insn->len) - (reloc->offset + 1))) {
3703
3704                 /*
3705                  * static_call_update() references the trampoline, which
3706                  * doesn't have (or need) ENDBR.  Skip warning in that case.
3707                  */
3708                 if (reloc->sym->static_call_tramp)
3709                         continue;
3710
3711                 off = reloc->sym->offset;
3712                 if (reloc->type == R_X86_64_PC32 || reloc->type == R_X86_64_PLT32)
3713                         off += arch_dest_reloc_offset(reloc->addend);
3714                 else
3715                         off += reloc->addend;
3716
3717                 dest = find_insn(file, reloc->sym->sec, off);
3718                 if (!dest)
3719                         continue;
3720
3721                 if (dest->type == INSN_ENDBR) {
3722                         mark_endbr_used(dest);
3723                         continue;
3724                 }
3725
3726                 if (dest->func && dest->func == insn->func) {
3727                         /*
3728                          * Anything from->to self is either _THIS_IP_ or
3729                          * IRET-to-self.
3730                          *
3731                          * There is no sane way to annotate _THIS_IP_ since the
3732                          * compiler treats the relocation as a constant and is
3733                          * happy to fold in offsets, skewing any annotation we
3734                          * do, leading to vast amounts of false-positives.
3735                          *
3736                          * There's also compiler generated _THIS_IP_ through
3737                          * KCOV and such which we have no hope of annotating.
3738                          *
3739                          * As such, blanket accept self-references without
3740                          * issue.
3741                          */
3742                         continue;
3743                 }
3744
3745                 if (dest->noendbr)
3746                         continue;
3747
3748                 WARN_FUNC("relocation to !ENDBR: %s",
3749                           insn->sec, insn->offset,
3750                           offstr(dest->sec, dest->offset));
3751
3752                 warnings++;
3753         }
3754
3755         return warnings;
3756 }
3757
3758 static int validate_ibt_data_reloc(struct objtool_file *file,
3759                                    struct reloc *reloc)
3760 {
3761         struct instruction *dest;
3762
3763         dest = find_insn(file, reloc->sym->sec,
3764                          reloc->sym->offset + reloc->addend);
3765         if (!dest)
3766                 return 0;
3767
3768         if (dest->type == INSN_ENDBR) {
3769                 mark_endbr_used(dest);
3770                 return 0;
3771         }
3772
3773         if (dest->noendbr)
3774                 return 0;
3775
3776         WARN_FUNC("data relocation to !ENDBR: %s",
3777                   reloc->sec->base, reloc->offset,
3778                   offstr(dest->sec, dest->offset));
3779
3780         return 1;
3781 }
3782
3783 /*
3784  * Validate IBT rules and remove used ENDBR instructions from the seal list.
3785  * Unused ENDBR instructions will be annotated for sealing (i.e., replaced with
3786  * NOPs) later, in create_ibt_endbr_seal_sections().
3787  */
3788 static int validate_ibt(struct objtool_file *file)
3789 {
3790         struct section *sec;
3791         struct reloc *reloc;
3792         struct instruction *insn;
3793         int warnings = 0;
3794
3795         for_each_insn(file, insn)
3796                 warnings += validate_ibt_insn(file, insn);
3797
3798         for_each_sec(file, sec) {
3799
3800                 /* Already done by validate_ibt_insn() */
3801                 if (sec->sh.sh_flags & SHF_EXECINSTR)
3802                         continue;
3803
3804                 if (!sec->reloc)
3805                         continue;
3806
3807                 /*
3808                  * These sections can reference text addresses, but not with
3809                  * the intent to indirect branch to them.
3810                  */
3811                 if (!strncmp(sec->name, ".discard", 8)                  ||
3812                     !strncmp(sec->name, ".debug", 6)                    ||
3813                     !strcmp(sec->name, ".altinstructions")              ||
3814                     !strcmp(sec->name, ".ibt_endbr_seal")               ||
3815                     !strcmp(sec->name, ".orc_unwind_ip")                ||
3816                     !strcmp(sec->name, ".parainstructions")             ||
3817                     !strcmp(sec->name, ".retpoline_sites")              ||
3818                     !strcmp(sec->name, ".smp_locks")                    ||
3819                     !strcmp(sec->name, ".static_call_sites")            ||
3820                     !strcmp(sec->name, "_error_injection_whitelist")    ||
3821                     !strcmp(sec->name, "_kprobe_blacklist")             ||
3822                     !strcmp(sec->name, "__bug_table")                   ||
3823                     !strcmp(sec->name, "__ex_table")                    ||
3824                     !strcmp(sec->name, "__jump_table")                  ||
3825                     !strcmp(sec->name, "__mcount_loc")                  ||
3826                     !strcmp(sec->name, "__tracepoints"))
3827                         continue;
3828
3829                 list_for_each_entry(reloc, &sec->reloc->reloc_list, list)
3830                         warnings += validate_ibt_data_reloc(file, reloc);
3831         }
3832
3833         return warnings;
3834 }
3835
3836 static int validate_sls(struct objtool_file *file)
3837 {
3838         struct instruction *insn, *next_insn;
3839         int warnings = 0;
3840
3841         for_each_insn(file, insn) {
3842                 next_insn = next_insn_same_sec(file, insn);
3843
3844                 if (insn->retpoline_safe)
3845                         continue;
3846
3847                 switch (insn->type) {
3848                 case INSN_RETURN:
3849                         if (!next_insn || next_insn->type != INSN_TRAP) {
3850                                 WARN_FUNC("missing int3 after ret",
3851                                           insn->sec, insn->offset);
3852                                 warnings++;
3853                         }
3854
3855                         break;
3856                 case INSN_JUMP_DYNAMIC:
3857                         if (!next_insn || next_insn->type != INSN_TRAP) {
3858                                 WARN_FUNC("missing int3 after indirect jump",
3859                                           insn->sec, insn->offset);
3860                                 warnings++;
3861                         }
3862                         break;
3863                 default:
3864                         break;
3865                 }
3866         }
3867
3868         return warnings;
3869 }
3870
3871 static int validate_reachable_instructions(struct objtool_file *file)
3872 {
3873         struct instruction *insn;
3874
3875         if (file->ignore_unreachables)
3876                 return 0;
3877
3878         for_each_insn(file, insn) {
3879                 if (insn->visited || ignore_unreachable_insn(file, insn))
3880                         continue;
3881
3882                 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
3883                 return 1;
3884         }
3885
3886         return 0;
3887 }
3888
3889 int check(struct objtool_file *file)
3890 {
3891         int ret, warnings = 0;
3892
3893         if (opts.lto && !(opts.vmlinux || opts.module)) {
3894                 fprintf(stderr, "--lto requires: --vmlinux or --module\n");
3895                 return 1;
3896         }
3897
3898         if (opts.ibt && !opts.lto) {
3899                 fprintf(stderr, "--ibt requires: --lto\n");
3900                 return 1;
3901         }
3902
3903         arch_initial_func_cfi_state(&initial_func_cfi);
3904         init_cfi_state(&init_cfi);
3905         init_cfi_state(&func_cfi);
3906         set_func_state(&func_cfi);
3907
3908         if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
3909                 goto out;
3910
3911         cfi_hash_add(&init_cfi);
3912         cfi_hash_add(&func_cfi);
3913
3914         ret = decode_sections(file);
3915         if (ret < 0)
3916                 goto out;
3917
3918         warnings += ret;
3919
3920         if (list_empty(&file->insn_list))
3921                 goto out;
3922
3923         if (opts.vmlinux && !opts.lto) {
3924                 ret = validate_vmlinux_functions(file);
3925                 if (ret < 0)
3926                         goto out;
3927
3928                 warnings += ret;
3929                 goto out;
3930         }
3931
3932         if (opts.retpoline) {
3933                 ret = validate_retpoline(file);
3934                 if (ret < 0)
3935                         return ret;
3936                 warnings += ret;
3937         }
3938
3939         if (opts.stackval || opts.orc || opts.uaccess) {
3940                 ret = validate_functions(file);
3941                 if (ret < 0)
3942                         goto out;
3943                 warnings += ret;
3944
3945                 ret = validate_unwind_hints(file, NULL);
3946                 if (ret < 0)
3947                         goto out;
3948                 warnings += ret;
3949
3950                 if (!warnings) {
3951                         ret = validate_reachable_instructions(file);
3952                         if (ret < 0)
3953                                 goto out;
3954                         warnings += ret;
3955                 }
3956         }
3957
3958         if (opts.ibt) {
3959                 ret = validate_ibt(file);
3960                 if (ret < 0)
3961                         goto out;
3962                 warnings += ret;
3963         }
3964
3965         if (opts.sls) {
3966                 ret = validate_sls(file);
3967                 if (ret < 0)
3968                         goto out;
3969                 warnings += ret;
3970         }
3971
3972         ret = create_static_call_sections(file);
3973         if (ret < 0)
3974                 goto out;
3975         warnings += ret;
3976
3977         if (opts.retpoline) {
3978                 ret = create_retpoline_sites_sections(file);
3979                 if (ret < 0)
3980                         goto out;
3981                 warnings += ret;
3982         }
3983
3984         if (opts.mcount) {
3985                 ret = create_mcount_loc_sections(file);
3986                 if (ret < 0)
3987                         goto out;
3988                 warnings += ret;
3989         }
3990
3991         if (opts.ibt) {
3992                 ret = create_ibt_endbr_seal_sections(file);
3993                 if (ret < 0)
3994                         goto out;
3995                 warnings += ret;
3996         }
3997
3998         if (opts.orc && !list_empty(&file->insn_list)) {
3999                 ret = orc_create(file);
4000                 if (ret < 0)
4001                         goto out;
4002                 warnings += ret;
4003         }
4004
4005
4006         if (opts.stats) {
4007                 printf("nr_insns_visited: %ld\n", nr_insns_visited);
4008                 printf("nr_cfi: %ld\n", nr_cfi);
4009                 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
4010                 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
4011         }
4012
4013 out:
4014         /*
4015          *  For now, don't fail the kernel build on fatal warnings.  These
4016          *  errors are still fairly common due to the growing matrix of
4017          *  supported toolchains and their recent pace of change.
4018          */
4019         return 0;
4020 }