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