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 <inttypes.h>
   9 #include <sys/mman.h>
  10
  11 #include <arch/elf.h>
  12 #include <objtool/builtin.h>
  13 #include <objtool/cfi.h>
  14 #include <objtool/arch.h>
  15 #include <objtool/check.h>
  16 #include <objtool/special.h>
  17 #include <objtool/warn.h>
  18 #include <objtool/endianness.h>
  19
  20 #include <linux/objtool.h>
  21 #include <linux/hashtable.h>
  22 #include <linux/kernel.h>
  23 #include <linux/static_call_types.h>
  24
  25 struct alternative {
  26         struct list_head list;
  27         struct instruction *insn;
  28         bool skip_orig;
  29 };
  30
  31 static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
  32
  33 static struct cfi_init_state initial_func_cfi;
  34 static struct cfi_state init_cfi;
  35 static struct cfi_state func_cfi;
  36
  37 struct instruction *find_insn(struct objtool_file *file,
  38                               struct section *sec, unsigned long offset)
  39 {
  40         struct instruction *insn;
  41
  42         hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
  43                 if (insn->sec == sec && insn->offset == offset)
  44                         return insn;
  45         }
  46
  47         return NULL;
  48 }
  49
  50 static struct instruction *next_insn_same_sec(struct objtool_file *file,
  51                                               struct instruction *insn)
  52 {
  53         struct instruction *next = list_next_entry(insn, list);
  54
  55         if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
  56                 return NULL;
  57
  58         return next;
  59 }
  60
  61 static struct instruction *next_insn_same_func(struct objtool_file *file,
  62                                                struct instruction *insn)
  63 {
  64         struct instruction *next = list_next_entry(insn, list);
  65         struct symbol *func = insn->func;
  66
  67         if (!func)
  68                 return NULL;
  69
  70         if (&next->list != &file->insn_list && next->func == func)
  71                 return next;
  72
  73         /* Check if we're already in the subfunction: */
  74         if (func == func->cfunc)
  75                 return NULL;
  76
  77         /* Move to the subfunction: */
  78         return find_insn(file, func->cfunc->sec, func->cfunc->offset);
  79 }
  80
  81 static struct instruction *prev_insn_same_sym(struct objtool_file *file,
  82                                                struct instruction *insn)
  83 {
  84         struct instruction *prev = list_prev_entry(insn, list);
  85
  86         if (&prev->list != &file->insn_list && prev->func == insn->func)
  87                 return prev;
  88
  89         return NULL;
  90 }
  91
  92 #define func_for_each_insn(file, func, insn)                            \
  93         for (insn = find_insn(file, func->sec, func->offset);           \
  94              insn;                                                      \
  95              insn = next_insn_same_func(file, insn))
  96
  97 #define sym_for_each_insn(file, sym, insn)                              \
  98         for (insn = find_insn(file, sym->sec, sym->offset);             \
  99              insn && &insn->list != &file->insn_list &&                 \
 100                 insn->sec == sym->sec &&                                \
 101                 insn->offset < sym->offset + sym->len;                  \
 102              insn = list_next_entry(insn, list))
 103
 104 #define sym_for_each_insn_continue_reverse(file, sym, insn)             \
 105         for (insn = list_prev_entry(insn, list);                        \
 106              &insn->list != &file->insn_list &&                         \
 107                 insn->sec == sym->sec && insn->offset >= sym->offset;   \
 108              insn = list_prev_entry(insn, list))
 109
 110 #define sec_for_each_insn_from(file, insn)                              \
 111         for (; insn; insn = next_insn_same_sec(file, insn))
 112
 113 #define sec_for_each_insn_continue(file, insn)                          \
 114         for (insn = next_insn_same_sec(file, insn); insn;               \
 115              insn = next_insn_same_sec(file, insn))
 116
 117 static bool is_jump_table_jump(struct instruction *insn)
 118 {
 119         struct alt_group *alt_group = insn->alt_group;
 120
 121         if (insn->jump_table)
 122                 return true;
 123
 124         /* Retpoline alternative for a jump table? */
 125         return alt_group && alt_group->orig_group &&
 126                alt_group->orig_group->first_insn->jump_table;
 127 }
 128
 129 static bool is_sibling_call(struct instruction *insn)
 130 {
 131         /*
 132          * Assume only ELF functions can make sibling calls.  This ensures
 133          * sibling call detection consistency between vmlinux.o and individual
 134          * objects.
 135          */
 136         if (!insn->func)
 137                 return false;
 138
 139         /* An indirect jump is either a sibling call or a jump to a table. */
 140         if (insn->type == INSN_JUMP_DYNAMIC)
 141                 return !is_jump_table_jump(insn);
 142
 143         /* add_jump_destinations() sets insn->call_dest for sibling calls. */
 144         return (is_static_jump(insn) && insn->call_dest);
 145 }
 146
 147 /*
 148  * This checks to see if the given function is a "noreturn" function.
 149  *
 150  * For global functions which are outside the scope of this object file, we
 151  * have to keep a manual list of them.
 152  *
 153  * For local functions, we have to detect them manually by simply looking for
 154  * the lack of a return instruction.
 155  */
 156 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 157                                 int recursion)
 158 {
 159         int i;
 160         struct instruction *insn;
 161         bool empty = true;
 162
 163         /*
 164          * Unfortunately these have to be hard coded because the noreturn
 165          * attribute isn't provided in ELF data.
 166          */
 167         static const char * const global_noreturns[] = {
 168                 "__stack_chk_fail",
 169                 "panic",
 170                 "do_exit",
 171                 "do_task_dead",
 172                 "make_task_dead",
 173                 "__module_put_and_exit",
 174                 "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         };
 185
 186         if (!func)
 187                 return false;
 188
 189         if (func->bind == STB_WEAK)
 190                 return false;
 191
 192         if (func->bind == STB_GLOBAL)
 193                 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
 194                         if (!strcmp(func->name, global_noreturns[i]))
 195                                 return true;
 196
 197         if (!func->len)
 198                 return false;
 199
 200         insn = find_insn(file, func->sec, func->offset);
 201         if (!insn || !insn->func)
 202                 return false;
 203
 204         func_for_each_insn(file, func, insn) {
 205                 empty = false;
 206
 207                 if (insn->type == INSN_RETURN)
 208                         return false;
 209         }
 210
 211         if (empty)
 212                 return false;
 213
 214         /*
 215          * A function can have a sibling call instead of a return.  In that
 216          * case, the function's dead-end status depends on whether the target
 217          * of the sibling call returns.
 218          */
 219         func_for_each_insn(file, func, insn) {
 220                 if (is_sibling_call(insn)) {
 221                         struct instruction *dest = insn->jump_dest;
 222
 223                         if (!dest)
 224                                 /* sibling call to another file */
 225                                 return false;
 226
 227                         /* local sibling call */
 228                         if (recursion == 5) {
 229                                 /*
 230                                  * Infinite recursion: two functions have
 231                                  * sibling calls to each other.  This is a very
 232                                  * rare case.  It means they aren't dead ends.
 233                                  */
 234                                 return false;
 235                         }
 236
 237                         return __dead_end_function(file, dest->func, recursion+1);
 238                 }
 239         }
 240
 241         return true;
 242 }
 243
 244 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
 245 {
 246         return __dead_end_function(file, func, 0);
 247 }
 248
 249 static void init_cfi_state(struct cfi_state *cfi)
 250 {
 251         int i;
 252
 253         for (i = 0; i < CFI_NUM_REGS; i++) {
 254                 cfi->regs[i].base = CFI_UNDEFINED;
 255                 cfi->vals[i].base = CFI_UNDEFINED;
 256         }
 257         cfi->cfa.base = CFI_UNDEFINED;
 258         cfi->drap_reg = CFI_UNDEFINED;
 259         cfi->drap_offset = -1;
 260 }
 261
 262 static void init_insn_state(struct insn_state *state, struct section *sec)
 263 {
 264         memset(state, 0, sizeof(*state));
 265         init_cfi_state(&state->cfi);
 266
 267         /*
 268          * We need the full vmlinux for noinstr validation, otherwise we can
 269          * not correctly determine insn->call_dest->sec (external symbols do
 270          * not have a section).
 271          */
 272         if (vmlinux && noinstr && sec)
 273                 state->noinstr = sec->noinstr;
 274 }
 275
 276 static struct cfi_state *cfi_alloc(void)
 277 {
 278         struct cfi_state *cfi = calloc(sizeof(struct cfi_state), 1);
 279         if (!cfi) {
 280                 WARN("calloc failed");
 281                 exit(1);
 282         }
 283         nr_cfi++;
 284         return cfi;
 285 }
 286
 287 static int cfi_bits;
 288 static struct hlist_head *cfi_hash;
 289
 290 static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
 291 {
 292         return memcmp((void *)cfi1 + sizeof(cfi1->hash),
 293                       (void *)cfi2 + sizeof(cfi2->hash),
 294                       sizeof(struct cfi_state) - sizeof(struct hlist_node));
 295 }
 296
 297 static inline u32 cfi_key(struct cfi_state *cfi)
 298 {
 299         return jhash((void *)cfi + sizeof(cfi->hash),
 300                      sizeof(*cfi) - sizeof(cfi->hash), 0);
 301 }
 302
 303 static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
 304 {
 305         struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
 306         struct cfi_state *obj;
 307
 308         hlist_for_each_entry(obj, head, hash) {
 309                 if (!cficmp(cfi, obj)) {
 310                         nr_cfi_cache++;
 311                         return obj;
 312                 }
 313         }
 314
 315         obj = cfi_alloc();
 316         *obj = *cfi;
 317         hlist_add_head(&obj->hash, head);
 318
 319         return obj;
 320 }
 321
 322 static void cfi_hash_add(struct cfi_state *cfi)
 323 {
 324         struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
 325
 326         hlist_add_head(&cfi->hash, head);
 327 }
 328
 329 static void *cfi_hash_alloc(unsigned long size)
 330 {
 331         cfi_bits = max(10, ilog2(size));
 332         cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
 333                         PROT_READ|PROT_WRITE,
 334                         MAP_PRIVATE|MAP_ANON, -1, 0);
 335         if (cfi_hash == (void *)-1L) {
 336                 WARN("mmap fail cfi_hash");
 337                 cfi_hash = NULL;
 338         }  else if (stats) {
 339                 printf("cfi_bits: %d\n", cfi_bits);
 340         }
 341
 342         return cfi_hash;
 343 }
 344
 345 static unsigned long nr_insns;
 346 static unsigned long nr_insns_visited;
 347
 348 /*
 349  * Call the arch-specific instruction decoder for all the instructions and add
 350  * them to the global instruction list.
 351  */
 352 static int decode_instructions(struct objtool_file *file)
 353 {
 354         struct section *sec;
 355         struct symbol *func;
 356         unsigned long offset;
 357         struct instruction *insn;
 358         int ret;
 359
 360         for_each_sec(file, sec) {
 361
 362                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
 363                         continue;
 364
 365                 if (strcmp(sec->name, ".altinstr_replacement") &&
 366                     strcmp(sec->name, ".altinstr_aux") &&
 367                     strncmp(sec->name, ".discard.", 9))
 368                         sec->text = true;
 369
 370                 if (!strcmp(sec->name, ".noinstr.text") ||
 371                     !strcmp(sec->name, ".entry.text") ||
 372                     !strncmp(sec->name, ".text.__x86.", 12))
 373                         sec->noinstr = true;
 374
 375                 for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
 376                         insn = malloc(sizeof(*insn));
 377                         if (!insn) {
 378                                 WARN("malloc failed");
 379                                 return -1;
 380                         }
 381                         memset(insn, 0, sizeof(*insn));
 382                         INIT_LIST_HEAD(&insn->alts);
 383                         INIT_LIST_HEAD(&insn->stack_ops);
 384
 385                         insn->sec = sec;
 386                         insn->offset = offset;
 387
 388                         ret = arch_decode_instruction(file->elf, sec, offset,
 389                                                       sec->sh.sh_size - offset,
 390                                                       &insn->len, &insn->type,
 391                                                       &insn->immediate,
 392                                                       &insn->stack_ops);
 393                         if (ret)
 394                                 goto err;
 395
 396                         hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
 397                         list_add_tail(&insn->list, &file->insn_list);
 398                         nr_insns++;
 399                 }
 400
 401                 list_for_each_entry(func, &sec->symbol_list, list) {
 402                         if (func->type != STT_FUNC || func->alias != func)
 403                                 continue;
 404
 405                         if (!find_insn(file, sec, func->offset)) {
 406                                 WARN("%s(): can't find starting instruction",
 407                                      func->name);
 408                                 return -1;
 409                         }
 410
 411                         sym_for_each_insn(file, func, insn)
 412                                 insn->func = func;
 413                 }
 414         }
 415
 416         if (stats)
 417                 printf("nr_insns: %lu\n", nr_insns);
 418
 419         return 0;
 420
 421 err:
 422         free(insn);
 423         return ret;
 424 }
 425
 426 static struct instruction *find_last_insn(struct objtool_file *file,
 427                                           struct section *sec)
 428 {
 429         struct instruction *insn = NULL;
 430         unsigned int offset;
 431         unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
 432
 433         for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
 434                 insn = find_insn(file, sec, offset);
 435
 436         return insn;
 437 }
 438
 439 /*
 440  * Mark "ud2" instructions and manually annotated dead ends.
 441  */
 442 static int add_dead_ends(struct objtool_file *file)
 443 {
 444         struct section *sec;
 445         struct reloc *reloc;
 446         struct instruction *insn;
 447
 448         /*
 449          * By default, "ud2" is a dead end unless otherwise annotated, because
 450          * GCC 7 inserts it for certain divide-by-zero cases.
 451          */
 452         for_each_insn(file, insn)
 453                 if (insn->type == INSN_BUG)
 454                         insn->dead_end = true;
 455
 456         /*
 457          * Check for manually annotated dead ends.
 458          */
 459         sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
 460         if (!sec)
 461                 goto reachable;
 462
 463         list_for_each_entry(reloc, &sec->reloc_list, list) {
 464                 if (reloc->sym->type != STT_SECTION) {
 465                         WARN("unexpected relocation symbol type in %s", sec->name);
 466                         return -1;
 467                 }
 468                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 469                 if (insn)
 470                         insn = list_prev_entry(insn, list);
 471                 else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
 472                         insn = find_last_insn(file, reloc->sym->sec);
 473                         if (!insn) {
 474                                 WARN("can't find unreachable insn at %s+0x%" PRIx64,
 475                                      reloc->sym->sec->name, reloc->addend);
 476                                 return -1;
 477                         }
 478                 } else {
 479                         WARN("can't find unreachable insn at %s+0x%" PRIx64,
 480                              reloc->sym->sec->name, reloc->addend);
 481                         return -1;
 482                 }
 483
 484                 insn->dead_end = true;
 485         }
 486
 487 reachable:
 488         /*
 489          * These manually annotated reachable checks are needed for GCC 4.4,
 490          * where the Linux unreachable() macro isn't supported.  In that case
 491          * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
 492          * not a dead end.
 493          */
 494         sec = find_section_by_name(file->elf, ".rela.discard.reachable");
 495         if (!sec)
 496                 return 0;
 497
 498         list_for_each_entry(reloc, &sec->reloc_list, list) {
 499                 if (reloc->sym->type != STT_SECTION) {
 500                         WARN("unexpected relocation symbol type in %s", sec->name);
 501                         return -1;
 502                 }
 503                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 504                 if (insn)
 505                         insn = list_prev_entry(insn, list);
 506                 else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
 507                         insn = find_last_insn(file, reloc->sym->sec);
 508                         if (!insn) {
 509                                 WARN("can't find reachable insn at %s+0x%" PRIx64,
 510                                      reloc->sym->sec->name, reloc->addend);
 511                                 return -1;
 512                         }
 513                 } else {
 514                         WARN("can't find reachable insn at %s+0x%" PRIx64,
 515                              reloc->sym->sec->name, reloc->addend);
 516                         return -1;
 517                 }
 518
 519                 insn->dead_end = false;
 520         }
 521
 522         return 0;
 523 }
 524
 525 static int create_static_call_sections(struct objtool_file *file)
 526 {
 527         struct section *sec;
 528         struct static_call_site *site;
 529         struct instruction *insn;
 530         struct symbol *key_sym;
 531         char *key_name, *tmp;
 532         int idx;
 533
 534         sec = find_section_by_name(file->elf, ".static_call_sites");
 535         if (sec) {
 536                 INIT_LIST_HEAD(&file->static_call_list);
 537                 WARN("file already has .static_call_sites section, skipping");
 538                 return 0;
 539         }
 540
 541         if (list_empty(&file->static_call_list))
 542                 return 0;
 543
 544         idx = 0;
 545         list_for_each_entry(insn, &file->static_call_list, call_node)
 546                 idx++;
 547
 548         sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE,
 549                                  sizeof(struct static_call_site), idx);
 550         if (!sec)
 551                 return -1;
 552
 553         idx = 0;
 554         list_for_each_entry(insn, &file->static_call_list, call_node) {
 555
 556                 site = (struct static_call_site *)sec->data->d_buf + idx;
 557                 memset(site, 0, sizeof(struct static_call_site));
 558
 559                 /* populate reloc for 'addr' */
 560                 if (elf_add_reloc_to_insn(file->elf, sec,
 561                                           idx * sizeof(struct static_call_site),
 562                                           R_X86_64_PC32,
 563                                           insn->sec, insn->offset))
 564                         return -1;
 565
 566                 /* find key symbol */
 567                 key_name = strdup(insn->call_dest->name);
 568                 if (!key_name) {
 569                         perror("strdup");
 570                         return -1;
 571                 }
 572                 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
 573                             STATIC_CALL_TRAMP_PREFIX_LEN)) {
 574                         WARN("static_call: trampoline name malformed: %s", key_name);
 575                         return -1;
 576                 }
 577                 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
 578                 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
 579
 580                 key_sym = find_symbol_by_name(file->elf, tmp);
 581                 if (!key_sym) {
 582                         if (!module) {
 583                                 WARN("static_call: can't find static_call_key symbol: %s", tmp);
 584                                 return -1;
 585                         }
 586
 587                         /*
 588                          * For modules(), the key might not be exported, which
 589                          * means the module can make static calls but isn't
 590                          * allowed to change them.
 591                          *
 592                          * In that case we temporarily set the key to be the
 593                          * trampoline address.  This is fixed up in
 594                          * static_call_add_module().
 595                          */
 596                         key_sym = insn->call_dest;
 597                 }
 598                 free(key_name);
 599
 600                 /* populate reloc for 'key' */
 601                 if (elf_add_reloc(file->elf, sec,
 602                                   idx * sizeof(struct static_call_site) + 4,
 603                                   R_X86_64_PC32, key_sym,
 604                                   is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
 605                         return -1;
 606
 607                 idx++;
 608         }
 609
 610         return 0;
 611 }
 612
 613 static int create_retpoline_sites_sections(struct objtool_file *file)
 614 {
 615         struct instruction *insn;
 616         struct section *sec;
 617         int idx;
 618
 619         sec = find_section_by_name(file->elf, ".retpoline_sites");
 620         if (sec) {
 621                 WARN("file already has .retpoline_sites, skipping");
 622                 return 0;
 623         }
 624
 625         idx = 0;
 626         list_for_each_entry(insn, &file->retpoline_call_list, call_node)
 627                 idx++;
 628
 629         if (!idx)
 630                 return 0;
 631
 632         sec = elf_create_section(file->elf, ".retpoline_sites", 0,
 633                                  sizeof(int), idx);
 634         if (!sec) {
 635                 WARN("elf_create_section: .retpoline_sites");
 636                 return -1;
 637         }
 638
 639         idx = 0;
 640         list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
 641
 642                 int *site = (int *)sec->data->d_buf + idx;
 643                 *site = 0;
 644
 645                 if (elf_add_reloc_to_insn(file->elf, sec,
 646                                           idx * sizeof(int),
 647                                           R_X86_64_PC32,
 648                                           insn->sec, insn->offset)) {
 649                         WARN("elf_add_reloc_to_insn: .retpoline_sites");
 650                         return -1;
 651                 }
 652
 653                 idx++;
 654         }
 655
 656         return 0;
 657 }
 658
 659 static int create_return_sites_sections(struct objtool_file *file)
 660 {
 661         struct instruction *insn;
 662         struct section *sec;
 663         int idx;
 664
 665         sec = find_section_by_name(file->elf, ".return_sites");
 666         if (sec) {
 667                 WARN("file already has .return_sites, skipping");
 668                 return 0;
 669         }
 670
 671         idx = 0;
 672         list_for_each_entry(insn, &file->return_thunk_list, call_node)
 673                 idx++;
 674
 675         if (!idx)
 676                 return 0;
 677
 678         sec = elf_create_section(file->elf, ".return_sites", 0,
 679                                  sizeof(int), idx);
 680         if (!sec) {
 681                 WARN("elf_create_section: .return_sites");
 682                 return -1;
 683         }
 684
 685         idx = 0;
 686         list_for_each_entry(insn, &file->return_thunk_list, call_node) {
 687
 688                 int *site = (int *)sec->data->d_buf + idx;
 689                 *site = 0;
 690
 691                 if (elf_add_reloc_to_insn(file->elf, sec,
 692                                           idx * sizeof(int),
 693                                           R_X86_64_PC32,
 694                                           insn->sec, insn->offset)) {
 695                         WARN("elf_add_reloc_to_insn: .return_sites");
 696                         return -1;
 697                 }
 698
 699                 idx++;
 700         }
 701
 702         return 0;
 703 }
 704
 705 static int create_mcount_loc_sections(struct objtool_file *file)
 706 {
 707         struct section *sec;
 708         unsigned long *loc;
 709         struct instruction *insn;
 710         int idx;
 711
 712         sec = find_section_by_name(file->elf, "__mcount_loc");
 713         if (sec) {
 714                 INIT_LIST_HEAD(&file->mcount_loc_list);
 715                 WARN("file already has __mcount_loc section, skipping");
 716                 return 0;
 717         }
 718
 719         if (list_empty(&file->mcount_loc_list))
 720                 return 0;
 721
 722         idx = 0;
 723         list_for_each_entry(insn, &file->mcount_loc_list, call_node)
 724                 idx++;
 725
 726         sec = elf_create_section(file->elf, "__mcount_loc", 0, sizeof(unsigned long), idx);
 727         if (!sec)
 728                 return -1;
 729
 730         idx = 0;
 731         list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
 732
 733                 loc = (unsigned long *)sec->data->d_buf + idx;
 734                 memset(loc, 0, sizeof(unsigned long));
 735
 736                 if (elf_add_reloc_to_insn(file->elf, sec,
 737                                           idx * sizeof(unsigned long),
 738                                           R_X86_64_64,
 739                                           insn->sec, insn->offset))
 740                         return -1;
 741
 742                 idx++;
 743         }
 744
 745         return 0;
 746 }
 747
 748 /*
 749  * Warnings shouldn't be reported for ignored functions.
 750  */
 751 static void add_ignores(struct objtool_file *file)
 752 {
 753         struct instruction *insn;
 754         struct section *sec;
 755         struct symbol *func;
 756         struct reloc *reloc;
 757
 758         sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
 759         if (!sec)
 760                 return;
 761
 762         list_for_each_entry(reloc, &sec->reloc_list, list) {
 763                 switch (reloc->sym->type) {
 764                 case STT_FUNC:
 765                         func = reloc->sym;
 766                         break;
 767
 768                 case STT_SECTION:
 769                         func = find_func_by_offset(reloc->sym->sec, reloc->addend);
 770                         if (!func)
 771                                 continue;
 772                         break;
 773
 774                 default:
 775                         WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type);
 776                         continue;
 777                 }
 778
 779                 func_for_each_insn(file, func, insn)
 780                         insn->ignore = true;
 781         }
 782 }
 783
 784 /*
 785  * This is a whitelist of functions that is allowed to be called with AC set.
 786  * The list is meant to be minimal and only contains compiler instrumentation
 787  * ABI and a few functions used to implement *_{to,from}_user() functions.
 788  *
 789  * These functions must not directly change AC, but may PUSHF/POPF.
 790  */
 791 static const char *uaccess_safe_builtin[] = {
 792         /* KASAN */
 793         "kasan_report",
 794         "kasan_check_range",
 795         /* KASAN out-of-line */
 796         "__asan_loadN_noabort",
 797         "__asan_load1_noabort",
 798         "__asan_load2_noabort",
 799         "__asan_load4_noabort",
 800         "__asan_load8_noabort",
 801         "__asan_load16_noabort",
 802         "__asan_storeN_noabort",
 803         "__asan_store1_noabort",
 804         "__asan_store2_noabort",
 805         "__asan_store4_noabort",
 806         "__asan_store8_noabort",
 807         "__asan_store16_noabort",
 808         "__kasan_check_read",
 809         "__kasan_check_write",
 810         /* KASAN in-line */
 811         "__asan_report_load_n_noabort",
 812         "__asan_report_load1_noabort",
 813         "__asan_report_load2_noabort",
 814         "__asan_report_load4_noabort",
 815         "__asan_report_load8_noabort",
 816         "__asan_report_load16_noabort",
 817         "__asan_report_store_n_noabort",
 818         "__asan_report_store1_noabort",
 819         "__asan_report_store2_noabort",
 820         "__asan_report_store4_noabort",
 821         "__asan_report_store8_noabort",
 822         "__asan_report_store16_noabort",
 823         /* KCSAN */
 824         "__kcsan_check_access",
 825         "kcsan_found_watchpoint",
 826         "kcsan_setup_watchpoint",
 827         "kcsan_check_scoped_accesses",
 828         "kcsan_disable_current",
 829         "kcsan_enable_current_nowarn",
 830         /* KCSAN/TSAN */
 831         "__tsan_func_entry",
 832         "__tsan_func_exit",
 833         "__tsan_read_range",
 834         "__tsan_write_range",
 835         "__tsan_read1",
 836         "__tsan_read2",
 837         "__tsan_read4",
 838         "__tsan_read8",
 839         "__tsan_read16",
 840         "__tsan_write1",
 841         "__tsan_write2",
 842         "__tsan_write4",
 843         "__tsan_write8",
 844         "__tsan_write16",
 845         "__tsan_read_write1",
 846         "__tsan_read_write2",
 847         "__tsan_read_write4",
 848         "__tsan_read_write8",
 849         "__tsan_read_write16",
 850         "__tsan_volatile_read1",
 851         "__tsan_volatile_read2",
 852         "__tsan_volatile_read4",
 853         "__tsan_volatile_read8",
 854         "__tsan_volatile_read16",
 855         "__tsan_volatile_write1",
 856         "__tsan_volatile_write2",
 857         "__tsan_volatile_write4",
 858         "__tsan_volatile_write8",
 859         "__tsan_volatile_write16",
 860         "__tsan_atomic8_load",
 861         "__tsan_atomic16_load",
 862         "__tsan_atomic32_load",
 863         "__tsan_atomic64_load",
 864         "__tsan_atomic8_store",
 865         "__tsan_atomic16_store",
 866         "__tsan_atomic32_store",
 867         "__tsan_atomic64_store",
 868         "__tsan_atomic8_exchange",
 869         "__tsan_atomic16_exchange",
 870         "__tsan_atomic32_exchange",
 871         "__tsan_atomic64_exchange",
 872         "__tsan_atomic8_fetch_add",
 873         "__tsan_atomic16_fetch_add",
 874         "__tsan_atomic32_fetch_add",
 875         "__tsan_atomic64_fetch_add",
 876         "__tsan_atomic8_fetch_sub",
 877         "__tsan_atomic16_fetch_sub",
 878         "__tsan_atomic32_fetch_sub",
 879         "__tsan_atomic64_fetch_sub",
 880         "__tsan_atomic8_fetch_and",
 881         "__tsan_atomic16_fetch_and",
 882         "__tsan_atomic32_fetch_and",
 883         "__tsan_atomic64_fetch_and",
 884         "__tsan_atomic8_fetch_or",
 885         "__tsan_atomic16_fetch_or",
 886         "__tsan_atomic32_fetch_or",
 887         "__tsan_atomic64_fetch_or",
 888         "__tsan_atomic8_fetch_xor",
 889         "__tsan_atomic16_fetch_xor",
 890         "__tsan_atomic32_fetch_xor",
 891         "__tsan_atomic64_fetch_xor",
 892         "__tsan_atomic8_fetch_nand",
 893         "__tsan_atomic16_fetch_nand",
 894         "__tsan_atomic32_fetch_nand",
 895         "__tsan_atomic64_fetch_nand",
 896         "__tsan_atomic8_compare_exchange_strong",
 897         "__tsan_atomic16_compare_exchange_strong",
 898         "__tsan_atomic32_compare_exchange_strong",
 899         "__tsan_atomic64_compare_exchange_strong",
 900         "__tsan_atomic8_compare_exchange_weak",
 901         "__tsan_atomic16_compare_exchange_weak",
 902         "__tsan_atomic32_compare_exchange_weak",
 903         "__tsan_atomic64_compare_exchange_weak",
 904         "__tsan_atomic8_compare_exchange_val",
 905         "__tsan_atomic16_compare_exchange_val",
 906         "__tsan_atomic32_compare_exchange_val",
 907         "__tsan_atomic64_compare_exchange_val",
 908         "__tsan_atomic_thread_fence",
 909         "__tsan_atomic_signal_fence",
 910         /* KCOV */
 911         "write_comp_data",
 912         "check_kcov_mode",
 913         "__sanitizer_cov_trace_pc",
 914         "__sanitizer_cov_trace_const_cmp1",
 915         "__sanitizer_cov_trace_const_cmp2",
 916         "__sanitizer_cov_trace_const_cmp4",
 917         "__sanitizer_cov_trace_const_cmp8",
 918         "__sanitizer_cov_trace_cmp1",
 919         "__sanitizer_cov_trace_cmp2",
 920         "__sanitizer_cov_trace_cmp4",
 921         "__sanitizer_cov_trace_cmp8",
 922         "__sanitizer_cov_trace_switch",
 923         /* UBSAN */
 924         "ubsan_type_mismatch_common",
 925         "__ubsan_handle_type_mismatch",
 926         "__ubsan_handle_type_mismatch_v1",
 927         "__ubsan_handle_shift_out_of_bounds",
 928         /* misc */
 929         "csum_partial_copy_generic",
 930         "copy_mc_fragile",
 931         "copy_mc_fragile_handle_tail",
 932         "copy_mc_enhanced_fast_string",
 933         "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
 934         NULL
 935 };
 936
 937 static void add_uaccess_safe(struct objtool_file *file)
 938 {
 939         struct symbol *func;
 940         const char **name;
 941
 942         if (!uaccess)
 943                 return;
 944
 945         for (name = uaccess_safe_builtin; *name; name++) {
 946                 func = find_symbol_by_name(file->elf, *name);
 947                 if (!func)
 948                         continue;
 949
 950                 func->uaccess_safe = true;
 951         }
 952 }
 953
 954 /*
 955  * FIXME: For now, just ignore any alternatives which add retpolines.  This is
 956  * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
 957  * But it at least allows objtool to understand the control flow *around* the
 958  * retpoline.
 959  */
 960 static int add_ignore_alternatives(struct objtool_file *file)
 961 {
 962         struct section *sec;
 963         struct reloc *reloc;
 964         struct instruction *insn;
 965
 966         sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
 967         if (!sec)
 968                 return 0;
 969
 970         list_for_each_entry(reloc, &sec->reloc_list, list) {
 971                 if (reloc->sym->type != STT_SECTION) {
 972                         WARN("unexpected relocation symbol type in %s", sec->name);
 973                         return -1;
 974                 }
 975
 976                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 977                 if (!insn) {
 978                         WARN("bad .discard.ignore_alts entry");
 979                         return -1;
 980                 }
 981
 982                 insn->ignore_alts = true;
 983         }
 984
 985         return 0;
 986 }
 987
 988 __weak bool arch_is_retpoline(struct symbol *sym)
 989 {
 990         return false;
 991 }
 992
 993 __weak bool arch_is_rethunk(struct symbol *sym)
 994 {
 995         return false;
 996 }
 997
 998 #define NEGATIVE_RELOC  ((void *)-1L)
 999
1000 static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
1001 {
1002         if (insn->reloc == NEGATIVE_RELOC)
1003                 return NULL;
1004
1005         if (!insn->reloc) {
1006                 insn->reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1007                                                        insn->offset, insn->len);
1008                 if (!insn->reloc) {
1009                         insn->reloc = NEGATIVE_RELOC;
1010                         return NULL;
1011                 }
1012         }
1013
1014         return insn->reloc;
1015 }
1016
1017 static void remove_insn_ops(struct instruction *insn)
1018 {
1019         struct stack_op *op, *tmp;
1020
1021         list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
1022                 list_del(&op->list);
1023                 free(op);
1024         }
1025 }
1026
1027 static void annotate_call_site(struct objtool_file *file,
1028                                struct instruction *insn, bool sibling)
1029 {
1030         struct reloc *reloc = insn_reloc(file, insn);
1031         struct symbol *sym = insn->call_dest;
1032
1033         if (!sym)
1034                 sym = reloc->sym;
1035
1036         /*
1037          * Alternative replacement code is just template code which is
1038          * sometimes copied to the original instruction. For now, don't
1039          * annotate it. (In the future we might consider annotating the
1040          * original instruction if/when it ever makes sense to do so.)
1041          */
1042         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1043                 return;
1044
1045         if (sym->static_call_tramp) {
1046                 list_add_tail(&insn->call_node, &file->static_call_list);
1047                 return;
1048         }
1049
1050         if (sym->retpoline_thunk) {
1051                 list_add_tail(&insn->call_node, &file->retpoline_call_list);
1052                 return;
1053         }
1054
1055         /*
1056          * Many compilers cannot disable KCOV with a function attribute
1057          * so they need a little help, NOP out any KCOV calls from noinstr
1058          * text.
1059          */
1060         if (insn->sec->noinstr && sym->kcov) {
1061                 if (reloc) {
1062                         reloc->type = R_NONE;
1063                         elf_write_reloc(file->elf, reloc);
1064                 }
1065
1066                 elf_write_insn(file->elf, insn->sec,
1067                                insn->offset, insn->len,
1068                                sibling ? arch_ret_insn(insn->len)
1069                                        : arch_nop_insn(insn->len));
1070
1071                 insn->type = sibling ? INSN_RETURN : INSN_NOP;
1072
1073                 if (sibling) {
1074                         /*
1075                          * We've replaced the tail-call JMP insn by two new
1076                          * insn: RET; INT3, except we only have a single struct
1077                          * insn here. Mark it retpoline_safe to avoid the SLS
1078                          * warning, instead of adding another insn.
1079                          */
1080                         insn->retpoline_safe = true;
1081                 }
1082
1083                 return;
1084         }
1085
1086         if (mcount && sym->fentry) {
1087                 if (sibling)
1088                         WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset);
1089
1090                 if (reloc) {
1091                         reloc->type = R_NONE;
1092                         elf_write_reloc(file->elf, reloc);
1093                 }
1094
1095                 elf_write_insn(file->elf, insn->sec,
1096                                insn->offset, insn->len,
1097                                arch_nop_insn(insn->len));
1098
1099                 insn->type = INSN_NOP;
1100
1101                 list_add_tail(&insn->call_node, &file->mcount_loc_list);
1102                 return;
1103         }
1104 }
1105
1106 static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1107                           struct symbol *dest, bool sibling)
1108 {
1109         insn->call_dest = dest;
1110         if (!dest)
1111                 return;
1112
1113         /*
1114          * Whatever stack impact regular CALLs have, should be undone
1115          * by the RETURN of the called function.
1116          *
1117          * Annotated intra-function calls retain the stack_ops but
1118          * are converted to JUMP, see read_intra_function_calls().
1119          */
1120         remove_insn_ops(insn);
1121
1122         annotate_call_site(file, insn, sibling);
1123 }
1124
1125 static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1126 {
1127         /*
1128          * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1129          * so convert them accordingly.
1130          */
1131         switch (insn->type) {
1132         case INSN_CALL:
1133                 insn->type = INSN_CALL_DYNAMIC;
1134                 break;
1135         case INSN_JUMP_UNCONDITIONAL:
1136                 insn->type = INSN_JUMP_DYNAMIC;
1137                 break;
1138         case INSN_JUMP_CONDITIONAL:
1139                 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1140                 break;
1141         default:
1142                 return;
1143         }
1144
1145         insn->retpoline_safe = true;
1146
1147         /*
1148          * Whatever stack impact regular CALLs have, should be undone
1149          * by the RETURN of the called function.
1150          *
1151          * Annotated intra-function calls retain the stack_ops but
1152          * are converted to JUMP, see read_intra_function_calls().
1153          */
1154         remove_insn_ops(insn);
1155
1156         annotate_call_site(file, insn, false);
1157 }
1158
1159 static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add)
1160 {
1161         /*
1162          * Return thunk tail calls are really just returns in disguise,
1163          * so convert them accordingly.
1164          */
1165         insn->type = INSN_RETURN;
1166         insn->retpoline_safe = true;
1167
1168         /* Skip the non-text sections, specially .discard ones */
1169         if (add && insn->sec->text)
1170                 list_add_tail(&insn->call_node, &file->return_thunk_list);
1171 }
1172
1173 /*
1174  * Find the destination instructions for all jumps.
1175  */
1176 static int add_jump_destinations(struct objtool_file *file)
1177 {
1178         struct instruction *insn;
1179         struct reloc *reloc;
1180         struct section *dest_sec;
1181         unsigned long dest_off;
1182
1183         for_each_insn(file, insn) {
1184                 if (!is_static_jump(insn))
1185                         continue;
1186
1187                 reloc = insn_reloc(file, insn);
1188                 if (!reloc) {
1189                         dest_sec = insn->sec;
1190                         dest_off = arch_jump_destination(insn);
1191                 } else if (reloc->sym->type == STT_SECTION) {
1192                         dest_sec = reloc->sym->sec;
1193                         dest_off = arch_dest_reloc_offset(reloc->addend);
1194                 } else if (reloc->sym->retpoline_thunk) {
1195                         add_retpoline_call(file, insn);
1196                         continue;
1197                 } else if (reloc->sym->return_thunk) {
1198                         add_return_call(file, insn, true);
1199                         continue;
1200                 } else if (insn->func) {
1201                         /* internal or external sibling call (with reloc) */
1202                         add_call_dest(file, insn, reloc->sym, true);
1203                         continue;
1204                 } else if (reloc->sym->sec->idx) {
1205                         dest_sec = reloc->sym->sec;
1206                         dest_off = reloc->sym->sym.st_value +
1207                                    arch_dest_reloc_offset(reloc->addend);
1208                 } else {
1209                         /* non-func asm code jumping to another file */
1210                         continue;
1211                 }
1212
1213                 insn->jump_dest = find_insn(file, dest_sec, dest_off);
1214                 if (!insn->jump_dest) {
1215                         struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off);
1216
1217                         /*
1218                          * This is a special case where an alt instruction
1219                          * jumps past the end of the section.  These are
1220                          * handled later in handle_group_alt().
1221                          */
1222                         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1223                                 continue;
1224
1225                         /*
1226                          * This is a special case for zen_untrain_ret().
1227                          * It jumps to __x86_return_thunk(), but objtool
1228                          * can't find the thunk's starting RET
1229                          * instruction, because the RET is also in the
1230                          * middle of another instruction.  Objtool only
1231                          * knows about the outer instruction.
1232                          */
1233                         if (sym && sym->return_thunk) {
1234                                 add_return_call(file, insn, false);
1235                                 continue;
1236                         }
1237
1238                         WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
1239                                   insn->sec, insn->offset, dest_sec->name,
1240                                   dest_off);
1241                         return -1;
1242                 }
1243
1244                 /*
1245                  * Cross-function jump.
1246                  */
1247                 if (insn->func && insn->jump_dest->func &&
1248                     insn->func != insn->jump_dest->func) {
1249
1250                         /*
1251                          * For GCC 8+, create parent/child links for any cold
1252                          * subfunctions.  This is _mostly_ redundant with a
1253                          * similar initialization in read_symbols().
1254                          *
1255                          * If a function has aliases, we want the *first* such
1256                          * function in the symbol table to be the subfunction's
1257                          * parent.  In that case we overwrite the
1258                          * initialization done in read_symbols().
1259                          *
1260                          * However this code can't completely replace the
1261                          * read_symbols() code because this doesn't detect the
1262                          * case where the parent function's only reference to a
1263                          * subfunction is through a jump table.
1264                          */
1265                         if (!strstr(insn->func->name, ".cold") &&
1266                             strstr(insn->jump_dest->func->name, ".cold")) {
1267                                 insn->func->cfunc = insn->jump_dest->func;
1268                                 insn->jump_dest->func->pfunc = insn->func;
1269
1270                         } else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
1271                                    insn->jump_dest->offset == insn->jump_dest->func->offset) {
1272                                 /* internal sibling call (without reloc) */
1273                                 add_call_dest(file, insn, insn->jump_dest->func, true);
1274                         }
1275                 }
1276         }
1277
1278         return 0;
1279 }
1280
1281 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1282 {
1283         struct symbol *call_dest;
1284
1285         call_dest = find_func_by_offset(sec, offset);
1286         if (!call_dest)
1287                 call_dest = find_symbol_by_offset(sec, offset);
1288
1289         return call_dest;
1290 }
1291
1292 /*
1293  * Find the destination instructions for all calls.
1294  */
1295 static int add_call_destinations(struct objtool_file *file)
1296 {
1297         struct instruction *insn;
1298         unsigned long dest_off;
1299         struct symbol *dest;
1300         struct reloc *reloc;
1301
1302         for_each_insn(file, insn) {
1303                 if (insn->type != INSN_CALL)
1304                         continue;
1305
1306                 reloc = insn_reloc(file, insn);
1307                 if (!reloc) {
1308                         dest_off = arch_jump_destination(insn);
1309                         dest = find_call_destination(insn->sec, dest_off);
1310
1311                         add_call_dest(file, insn, dest, false);
1312
1313                         if (insn->ignore)
1314                                 continue;
1315
1316                         if (!insn->call_dest) {
1317                                 WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);
1318                                 return -1;
1319                         }
1320
1321                         if (insn->func && insn->call_dest->type != STT_FUNC) {
1322                                 WARN_FUNC("unsupported call to non-function",
1323                                           insn->sec, insn->offset);
1324                                 return -1;
1325                         }
1326
1327                 } else if (reloc->sym->type == STT_SECTION) {
1328                         dest_off = arch_dest_reloc_offset(reloc->addend);
1329                         dest = find_call_destination(reloc->sym->sec, dest_off);
1330                         if (!dest) {
1331                                 WARN_FUNC("can't find call dest symbol at %s+0x%lx",
1332                                           insn->sec, insn->offset,
1333                                           reloc->sym->sec->name,
1334                                           dest_off);
1335                                 return -1;
1336                         }
1337
1338                         add_call_dest(file, insn, dest, false);
1339
1340                 } else if (reloc->sym->retpoline_thunk) {
1341                         add_retpoline_call(file, insn);
1342
1343                 } else
1344                         add_call_dest(file, insn, reloc->sym, false);
1345         }
1346
1347         return 0;
1348 }
1349
1350 /*
1351  * The .alternatives section requires some extra special care over and above
1352  * other special sections because alternatives are patched in place.
1353  */
1354 static int handle_group_alt(struct objtool_file *file,
1355                             struct special_alt *special_alt,
1356                             struct instruction *orig_insn,
1357                             struct instruction **new_insn)
1358 {
1359         struct instruction *last_orig_insn, *last_new_insn = NULL, *insn, *nop = NULL;
1360         struct alt_group *orig_alt_group, *new_alt_group;
1361         unsigned long dest_off;
1362
1363
1364         orig_alt_group = malloc(sizeof(*orig_alt_group));
1365         if (!orig_alt_group) {
1366                 WARN("malloc failed");
1367                 return -1;
1368         }
1369         orig_alt_group->cfi = calloc(special_alt->orig_len,
1370                                      sizeof(struct cfi_state *));
1371         if (!orig_alt_group->cfi) {
1372                 WARN("calloc failed");
1373                 return -1;
1374         }
1375
1376         last_orig_insn = NULL;
1377         insn = orig_insn;
1378         sec_for_each_insn_from(file, insn) {
1379                 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1380                         break;
1381
1382                 insn->alt_group = orig_alt_group;
1383                 last_orig_insn = insn;
1384         }
1385         orig_alt_group->orig_group = NULL;
1386         orig_alt_group->first_insn = orig_insn;
1387         orig_alt_group->last_insn = last_orig_insn;
1388
1389
1390         new_alt_group = malloc(sizeof(*new_alt_group));
1391         if (!new_alt_group) {
1392                 WARN("malloc failed");
1393                 return -1;
1394         }
1395
1396         if (special_alt->new_len < special_alt->orig_len) {
1397                 /*
1398                  * Insert a fake nop at the end to make the replacement
1399                  * alt_group the same size as the original.  This is needed to
1400                  * allow propagate_alt_cfi() to do its magic.  When the last
1401                  * instruction affects the stack, the instruction after it (the
1402                  * nop) will propagate the new state to the shared CFI array.
1403                  */
1404                 nop = malloc(sizeof(*nop));
1405                 if (!nop) {
1406                         WARN("malloc failed");
1407                         return -1;
1408                 }
1409                 memset(nop, 0, sizeof(*nop));
1410                 INIT_LIST_HEAD(&nop->alts);
1411                 INIT_LIST_HEAD(&nop->stack_ops);
1412
1413                 nop->sec = special_alt->new_sec;
1414                 nop->offset = special_alt->new_off + special_alt->new_len;
1415                 nop->len = special_alt->orig_len - special_alt->new_len;
1416                 nop->type = INSN_NOP;
1417                 nop->func = orig_insn->func;
1418                 nop->alt_group = new_alt_group;
1419                 nop->ignore = orig_insn->ignore_alts;
1420         }
1421
1422         if (!special_alt->new_len) {
1423                 *new_insn = nop;
1424                 goto end;
1425         }
1426
1427         insn = *new_insn;
1428         sec_for_each_insn_from(file, insn) {
1429                 struct reloc *alt_reloc;
1430
1431                 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1432                         break;
1433
1434                 last_new_insn = insn;
1435
1436                 insn->ignore = orig_insn->ignore_alts;
1437                 insn->func = orig_insn->func;
1438                 insn->alt_group = new_alt_group;
1439
1440                 /*
1441                  * Since alternative replacement code is copy/pasted by the
1442                  * kernel after applying relocations, generally such code can't
1443                  * have relative-address relocation references to outside the
1444                  * .altinstr_replacement section, unless the arch's
1445                  * alternatives code can adjust the relative offsets
1446                  * accordingly.
1447                  */
1448                 alt_reloc = insn_reloc(file, insn);
1449                 if (alt_reloc &&
1450                     !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1451
1452                         WARN_FUNC("unsupported relocation in alternatives section",
1453                                   insn->sec, insn->offset);
1454                         return -1;
1455                 }
1456
1457                 if (!is_static_jump(insn))
1458                         continue;
1459
1460                 if (!insn->immediate)
1461                         continue;
1462
1463                 dest_off = arch_jump_destination(insn);
1464                 if (dest_off == special_alt->new_off + special_alt->new_len)
1465                         insn->jump_dest = next_insn_same_sec(file, last_orig_insn);
1466
1467                 if (!insn->jump_dest) {
1468                         WARN_FUNC("can't find alternative jump destination",
1469                                   insn->sec, insn->offset);
1470                         return -1;
1471                 }
1472         }
1473
1474         if (!last_new_insn) {
1475                 WARN_FUNC("can't find last new alternative instruction",
1476                           special_alt->new_sec, special_alt->new_off);
1477                 return -1;
1478         }
1479
1480         if (nop)
1481                 list_add(&nop->list, &last_new_insn->list);
1482 end:
1483         new_alt_group->orig_group = orig_alt_group;
1484         new_alt_group->first_insn = *new_insn;
1485         new_alt_group->last_insn = nop ? : last_new_insn;
1486         new_alt_group->cfi = orig_alt_group->cfi;
1487         return 0;
1488 }
1489
1490 /*
1491  * A jump table entry can either convert a nop to a jump or a jump to a nop.
1492  * If the original instruction is a jump, make the alt entry an effective nop
1493  * by just skipping the original instruction.
1494  */
1495 static int handle_jump_alt(struct objtool_file *file,
1496                            struct special_alt *special_alt,
1497                            struct instruction *orig_insn,
1498                            struct instruction **new_insn)
1499 {
1500         if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1501             orig_insn->type != INSN_NOP) {
1502
1503                 WARN_FUNC("unsupported instruction at jump label",
1504                           orig_insn->sec, orig_insn->offset);
1505                 return -1;
1506         }
1507
1508         if (special_alt->key_addend & 2) {
1509                 struct reloc *reloc = insn_reloc(file, orig_insn);
1510
1511                 if (reloc) {
1512                         reloc->type = R_NONE;
1513                         elf_write_reloc(file->elf, reloc);
1514                 }
1515                 elf_write_insn(file->elf, orig_insn->sec,
1516                                orig_insn->offset, orig_insn->len,
1517                                arch_nop_insn(orig_insn->len));
1518                 orig_insn->type = INSN_NOP;
1519         }
1520
1521         if (orig_insn->type == INSN_NOP) {
1522                 if (orig_insn->len == 2)
1523                         file->jl_nop_short++;
1524                 else
1525                         file->jl_nop_long++;
1526
1527                 return 0;
1528         }
1529
1530         if (orig_insn->len == 2)
1531                 file->jl_short++;
1532         else
1533                 file->jl_long++;
1534
1535         *new_insn = list_next_entry(orig_insn, list);
1536         return 0;
1537 }
1538
1539 /*
1540  * Read all the special sections which have alternate instructions which can be
1541  * patched in or redirected to at runtime.  Each instruction having alternate
1542  * instruction(s) has them added to its insn->alts list, which will be
1543  * traversed in validate_branch().
1544  */
1545 static int add_special_section_alts(struct objtool_file *file)
1546 {
1547         struct list_head special_alts;
1548         struct instruction *orig_insn, *new_insn;
1549         struct special_alt *special_alt, *tmp;
1550         struct alternative *alt;
1551         int ret;
1552
1553         ret = special_get_alts(file->elf, &special_alts);
1554         if (ret)
1555                 return ret;
1556
1557         list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1558
1559                 orig_insn = find_insn(file, special_alt->orig_sec,
1560                                       special_alt->orig_off);
1561                 if (!orig_insn) {
1562                         WARN_FUNC("special: can't find orig instruction",
1563                                   special_alt->orig_sec, special_alt->orig_off);
1564                         ret = -1;
1565                         goto out;
1566                 }
1567
1568                 new_insn = NULL;
1569                 if (!special_alt->group || special_alt->new_len) {
1570                         new_insn = find_insn(file, special_alt->new_sec,
1571                                              special_alt->new_off);
1572                         if (!new_insn) {
1573                                 WARN_FUNC("special: can't find new instruction",
1574                                           special_alt->new_sec,
1575                                           special_alt->new_off);
1576                                 ret = -1;
1577                                 goto out;
1578                         }
1579                 }
1580
1581                 if (special_alt->group) {
1582                         if (!special_alt->orig_len) {
1583                                 WARN_FUNC("empty alternative entry",
1584                                           orig_insn->sec, orig_insn->offset);
1585                                 continue;
1586                         }
1587
1588                         ret = handle_group_alt(file, special_alt, orig_insn,
1589                                                &new_insn);
1590                         if (ret)
1591                                 goto out;
1592                 } else if (special_alt->jump_or_nop) {
1593                         ret = handle_jump_alt(file, special_alt, orig_insn,
1594                                               &new_insn);
1595                         if (ret)
1596                                 goto out;
1597                 }
1598
1599                 alt = malloc(sizeof(*alt));
1600                 if (!alt) {
1601                         WARN("malloc failed");
1602                         ret = -1;
1603                         goto out;
1604                 }
1605
1606                 alt->insn = new_insn;
1607                 alt->skip_orig = special_alt->skip_orig;
1608                 orig_insn->ignore_alts |= special_alt->skip_alt;
1609                 list_add_tail(&alt->list, &orig_insn->alts);
1610
1611                 list_del(&special_alt->list);
1612                 free(special_alt);
1613         }
1614
1615         if (stats) {
1616                 printf("jl\\\tNOP\tJMP\n");
1617                 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
1618                 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
1619         }
1620
1621 out:
1622         return ret;
1623 }
1624
1625 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
1626                             struct reloc *table)
1627 {
1628         struct reloc *reloc = table;
1629         struct instruction *dest_insn;
1630         struct alternative *alt;
1631         struct symbol *pfunc = insn->func->pfunc;
1632         unsigned int prev_offset = 0;
1633
1634         /*
1635          * Each @reloc is a switch table relocation which points to the target
1636          * instruction.
1637          */
1638         list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
1639
1640                 /* Check for the end of the table: */
1641                 if (reloc != table && reloc->jump_table_start)
1642                         break;
1643
1644                 /* Make sure the table entries are consecutive: */
1645                 if (prev_offset && reloc->offset != prev_offset + 8)
1646                         break;
1647
1648                 /* Detect function pointers from contiguous objects: */
1649                 if (reloc->sym->sec == pfunc->sec &&
1650                     reloc->addend == pfunc->offset)
1651                         break;
1652
1653                 dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
1654                 if (!dest_insn)
1655                         break;
1656
1657                 /* Make sure the destination is in the same function: */
1658                 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
1659                         break;
1660
1661                 alt = malloc(sizeof(*alt));
1662                 if (!alt) {
1663                         WARN("malloc failed");
1664                         return -1;
1665                 }
1666
1667                 alt->insn = dest_insn;
1668                 list_add_tail(&alt->list, &insn->alts);
1669                 prev_offset = reloc->offset;
1670         }
1671
1672         if (!prev_offset) {
1673                 WARN_FUNC("can't find switch jump table",
1674                           insn->sec, insn->offset);
1675                 return -1;
1676         }
1677
1678         return 0;
1679 }
1680
1681 /*
1682  * find_jump_table() - Given a dynamic jump, find the switch jump table
1683  * associated with it.
1684  */
1685 static struct reloc *find_jump_table(struct objtool_file *file,
1686                                       struct symbol *func,
1687                                       struct instruction *insn)
1688 {
1689         struct reloc *table_reloc;
1690         struct instruction *dest_insn, *orig_insn = insn;
1691
1692         /*
1693          * Backward search using the @first_jump_src links, these help avoid
1694          * much of the 'in between' code. Which avoids us getting confused by
1695          * it.
1696          */
1697         for (;
1698              insn && insn->func && insn->func->pfunc == func;
1699              insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
1700
1701                 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1702                         break;
1703
1704                 /* allow small jumps within the range */
1705                 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1706                     insn->jump_dest &&
1707                     (insn->jump_dest->offset <= insn->offset ||
1708                      insn->jump_dest->offset > orig_insn->offset))
1709                     break;
1710
1711                 table_reloc = arch_find_switch_table(file, insn);
1712                 if (!table_reloc)
1713                         continue;
1714                 dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
1715                 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1716                         continue;
1717
1718                 return table_reloc;
1719         }
1720
1721         return NULL;
1722 }
1723
1724 /*
1725  * First pass: Mark the head of each jump table so that in the next pass,
1726  * we know when a given jump table ends and the next one starts.
1727  */
1728 static void mark_func_jump_tables(struct objtool_file *file,
1729                                     struct symbol *func)
1730 {
1731         struct instruction *insn, *last = NULL;
1732         struct reloc *reloc;
1733
1734         func_for_each_insn(file, func, insn) {
1735                 if (!last)
1736                         last = insn;
1737
1738                 /*
1739                  * Store back-pointers for unconditional forward jumps such
1740                  * that find_jump_table() can back-track using those and
1741                  * avoid some potentially confusing code.
1742                  */
1743                 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1744                     insn->offset > last->offset &&
1745                     insn->jump_dest->offset > insn->offset &&
1746                     !insn->jump_dest->first_jump_src) {
1747
1748                         insn->jump_dest->first_jump_src = insn;
1749                         last = insn->jump_dest;
1750                 }
1751
1752                 if (insn->type != INSN_JUMP_DYNAMIC)
1753                         continue;
1754
1755                 reloc = find_jump_table(file, func, insn);
1756                 if (reloc) {
1757                         reloc->jump_table_start = true;
1758                         insn->jump_table = reloc;
1759                 }
1760         }
1761 }
1762
1763 static int add_func_jump_tables(struct objtool_file *file,
1764                                   struct symbol *func)
1765 {
1766         struct instruction *insn;
1767         int ret;
1768
1769         func_for_each_insn(file, func, insn) {
1770                 if (!insn->jump_table)
1771                         continue;
1772
1773                 ret = add_jump_table(file, insn, insn->jump_table);
1774                 if (ret)
1775                         return ret;
1776         }
1777
1778         return 0;
1779 }
1780
1781 /*
1782  * For some switch statements, gcc generates a jump table in the .rodata
1783  * section which contains a list of addresses within the function to jump to.
1784  * This finds these jump tables and adds them to the insn->alts lists.
1785  */
1786 static int add_jump_table_alts(struct objtool_file *file)
1787 {
1788         struct section *sec;
1789         struct symbol *func;
1790         int ret;
1791
1792         if (!file->rodata)
1793                 return 0;
1794
1795         for_each_sec(file, sec) {
1796                 list_for_each_entry(func, &sec->symbol_list, list) {
1797                         if (func->type != STT_FUNC)
1798                                 continue;
1799
1800                         mark_func_jump_tables(file, func);
1801                         ret = add_func_jump_tables(file, func);
1802                         if (ret)
1803                                 return ret;
1804                 }
1805         }
1806
1807         return 0;
1808 }
1809
1810 static void set_func_state(struct cfi_state *state)
1811 {
1812         state->cfa = initial_func_cfi.cfa;
1813         memcpy(&state->regs, &initial_func_cfi.regs,
1814                CFI_NUM_REGS * sizeof(struct cfi_reg));
1815         state->stack_size = initial_func_cfi.cfa.offset;
1816 }
1817
1818 static int read_unwind_hints(struct objtool_file *file)
1819 {
1820         struct cfi_state cfi = init_cfi;
1821         struct section *sec, *relocsec;
1822         struct unwind_hint *hint;
1823         struct instruction *insn;
1824         struct reloc *reloc;
1825         int i;
1826
1827         sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1828         if (!sec)
1829                 return 0;
1830
1831         relocsec = sec->reloc;
1832         if (!relocsec) {
1833                 WARN("missing .rela.discard.unwind_hints section");
1834                 return -1;
1835         }
1836
1837         if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
1838                 WARN("struct unwind_hint size mismatch");
1839                 return -1;
1840         }
1841
1842         file->hints = true;
1843
1844         for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
1845                 hint = (struct unwind_hint *)sec->data->d_buf + i;
1846
1847                 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
1848                 if (!reloc) {
1849                         WARN("can't find reloc for unwind_hints[%d]", i);
1850                         return -1;
1851                 }
1852
1853                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1854                 if (!insn) {
1855                         WARN("can't find insn for unwind_hints[%d]", i);
1856                         return -1;
1857                 }
1858
1859                 insn->hint = true;
1860
1861                 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
1862                         insn->hint = false;
1863                         insn->save = true;
1864                         continue;
1865                 }
1866
1867                 if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
1868                         insn->restore = true;
1869                         continue;
1870                 }
1871
1872                 if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
1873                         struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
1874
1875                         if (sym && sym->bind == STB_GLOBAL) {
1876                                 insn->entry = 1;
1877                         }
1878                 }
1879
1880                 if (hint->type == UNWIND_HINT_TYPE_ENTRY) {
1881                         hint->type = UNWIND_HINT_TYPE_CALL;
1882                         insn->entry = 1;
1883                 }
1884
1885                 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
1886                         insn->cfi = &func_cfi;
1887                         continue;
1888                 }
1889
1890                 if (insn->cfi)
1891                         cfi = *(insn->cfi);
1892
1893                 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
1894                         WARN_FUNC("unsupported unwind_hint sp base reg %d",
1895                                   insn->sec, insn->offset, hint->sp_reg);
1896                         return -1;
1897                 }
1898
1899                 cfi.cfa.offset = bswap_if_needed(hint->sp_offset);
1900                 cfi.type = hint->type;
1901                 cfi.end = hint->end;
1902
1903                 insn->cfi = cfi_hash_find_or_add(&cfi);
1904         }
1905
1906         return 0;
1907 }
1908
1909 static int read_retpoline_hints(struct objtool_file *file)
1910 {
1911         struct section *sec;
1912         struct instruction *insn;
1913         struct reloc *reloc;
1914
1915         sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1916         if (!sec)
1917                 return 0;
1918
1919         list_for_each_entry(reloc, &sec->reloc_list, list) {
1920                 if (reloc->sym->type != STT_SECTION) {
1921                         WARN("unexpected relocation symbol type in %s", sec->name);
1922                         return -1;
1923                 }
1924
1925                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1926                 if (!insn) {
1927                         WARN("bad .discard.retpoline_safe entry");
1928                         return -1;
1929                 }
1930
1931                 if (insn->type != INSN_JUMP_DYNAMIC &&
1932                     insn->type != INSN_CALL_DYNAMIC &&
1933                     insn->type != INSN_RETURN &&
1934                     insn->type != INSN_NOP) {
1935                         WARN_FUNC("retpoline_safe hint not an indirect jump/call/ret/nop",
1936                                   insn->sec, insn->offset);
1937                         return -1;
1938                 }
1939
1940                 insn->retpoline_safe = true;
1941         }
1942
1943         return 0;
1944 }
1945
1946 static int read_instr_hints(struct objtool_file *file)
1947 {
1948         struct section *sec;
1949         struct instruction *insn;
1950         struct reloc *reloc;
1951
1952         sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
1953         if (!sec)
1954                 return 0;
1955
1956         list_for_each_entry(reloc, &sec->reloc_list, list) {
1957                 if (reloc->sym->type != STT_SECTION) {
1958                         WARN("unexpected relocation symbol type in %s", sec->name);
1959                         return -1;
1960                 }
1961
1962                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1963                 if (!insn) {
1964                         WARN("bad .discard.instr_end entry");
1965                         return -1;
1966                 }
1967
1968                 insn->instr--;
1969         }
1970
1971         sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
1972         if (!sec)
1973                 return 0;
1974
1975         list_for_each_entry(reloc, &sec->reloc_list, list) {
1976                 if (reloc->sym->type != STT_SECTION) {
1977                         WARN("unexpected relocation symbol type in %s", sec->name);
1978                         return -1;
1979                 }
1980
1981                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1982                 if (!insn) {
1983                         WARN("bad .discard.instr_begin entry");
1984                         return -1;
1985                 }
1986
1987                 insn->instr++;
1988         }
1989
1990         return 0;
1991 }
1992
1993 static int read_intra_function_calls(struct objtool_file *file)
1994 {
1995         struct instruction *insn;
1996         struct section *sec;
1997         struct reloc *reloc;
1998
1999         sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2000         if (!sec)
2001                 return 0;
2002
2003         list_for_each_entry(reloc, &sec->reloc_list, list) {
2004                 unsigned long dest_off;
2005
2006                 if (reloc->sym->type != STT_SECTION) {
2007                         WARN("unexpected relocation symbol type in %s",
2008                              sec->name);
2009                         return -1;
2010                 }
2011
2012                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2013                 if (!insn) {
2014                         WARN("bad .discard.intra_function_call entry");
2015                         return -1;
2016                 }
2017
2018                 if (insn->type != INSN_CALL) {
2019                         WARN_FUNC("intra_function_call not a direct call",
2020                                   insn->sec, insn->offset);
2021                         return -1;
2022                 }
2023
2024                 /*
2025                  * Treat intra-function CALLs as JMPs, but with a stack_op.
2026                  * See add_call_destinations(), which strips stack_ops from
2027                  * normal CALLs.
2028                  */
2029                 insn->type = INSN_JUMP_UNCONDITIONAL;
2030
2031                 dest_off = insn->offset + insn->len + insn->immediate;
2032                 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2033                 if (!insn->jump_dest) {
2034                         WARN_FUNC("can't find call dest at %s+0x%lx",
2035                                   insn->sec, insn->offset,
2036                                   insn->sec->name, dest_off);
2037                         return -1;
2038                 }
2039         }
2040
2041         return 0;
2042 }
2043
2044 static int classify_symbols(struct objtool_file *file)
2045 {
2046         struct section *sec;
2047         struct symbol *func;
2048
2049         for_each_sec(file, sec) {
2050                 list_for_each_entry(func, &sec->symbol_list, list) {
2051                         if (func->bind != STB_GLOBAL)
2052                                 continue;
2053
2054                         if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2055                                      strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2056                                 func->static_call_tramp = true;
2057
2058                         if (arch_is_retpoline(func))
2059                                 func->retpoline_thunk = true;
2060
2061                         if (arch_is_rethunk(func))
2062                                 func->return_thunk = true;
2063
2064                         if (!strcmp(func->name, "__fentry__"))
2065                                 func->fentry = true;
2066
2067                         if (!strncmp(func->name, "__sanitizer_cov_", 16))
2068                                 func->kcov = true;
2069                 }
2070         }
2071
2072         return 0;
2073 }
2074
2075 static void mark_rodata(struct objtool_file *file)
2076 {
2077         struct section *sec;
2078         bool found = false;
2079
2080         /*
2081          * Search for the following rodata sections, each of which can
2082          * potentially contain jump tables:
2083          *
2084          * - .rodata: can contain GCC switch tables
2085          * - .rodata.<func>: same, if -fdata-sections is being used
2086          * - .rodata..c_jump_table: contains C annotated jump tables
2087          *
2088          * .rodata.str1.* sections are ignored; they don't contain jump tables.
2089          */
2090         for_each_sec(file, sec) {
2091                 if (!strncmp(sec->name, ".rodata", 7) &&
2092                     !strstr(sec->name, ".str1.")) {
2093                         sec->rodata = true;
2094                         found = true;
2095                 }
2096         }
2097
2098         file->rodata = found;
2099 }
2100
2101 static int decode_sections(struct objtool_file *file)
2102 {
2103         int ret;
2104
2105         mark_rodata(file);
2106
2107         ret = decode_instructions(file);
2108         if (ret)
2109                 return ret;
2110
2111         ret = add_dead_ends(file);
2112         if (ret)
2113                 return ret;
2114
2115         add_ignores(file);
2116         add_uaccess_safe(file);
2117
2118         ret = add_ignore_alternatives(file);
2119         if (ret)
2120                 return ret;
2121
2122         /*
2123          * Must be before add_{jump_call}_destination.
2124          */
2125         ret = classify_symbols(file);
2126         if (ret)
2127                 return ret;
2128
2129         /*
2130          * Must be before add_special_section_alts() as that depends on
2131          * jump_dest being set.
2132          */
2133         ret = add_jump_destinations(file);
2134         if (ret)
2135                 return ret;
2136
2137         ret = add_special_section_alts(file);
2138         if (ret)
2139                 return ret;
2140
2141         /*
2142          * Must be before add_call_destination(); it changes INSN_CALL to
2143          * INSN_JUMP.
2144          */
2145         ret = read_intra_function_calls(file);
2146         if (ret)
2147                 return ret;
2148
2149         ret = add_call_destinations(file);
2150         if (ret)
2151                 return ret;
2152
2153         ret = add_jump_table_alts(file);
2154         if (ret)
2155                 return ret;
2156
2157         ret = read_unwind_hints(file);
2158         if (ret)
2159                 return ret;
2160
2161         ret = read_retpoline_hints(file);
2162         if (ret)
2163                 return ret;
2164
2165         ret = read_instr_hints(file);
2166         if (ret)
2167                 return ret;
2168
2169         return 0;
2170 }
2171
2172 static bool is_fentry_call(struct instruction *insn)
2173 {
2174         if (insn->type == INSN_CALL &&
2175             insn->call_dest &&
2176             insn->call_dest->fentry)
2177                 return true;
2178
2179         return false;
2180 }
2181
2182 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2183 {
2184         struct cfi_state *cfi = &state->cfi;
2185         int i;
2186
2187         if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2188                 return true;
2189
2190         if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2191                 return true;
2192
2193         if (cfi->stack_size != initial_func_cfi.cfa.offset)
2194                 return true;
2195
2196         for (i = 0; i < CFI_NUM_REGS; i++) {
2197                 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2198                     cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2199                         return true;
2200         }
2201
2202         return false;
2203 }
2204
2205 static bool check_reg_frame_pos(const struct cfi_reg *reg,
2206                                 int expected_offset)
2207 {
2208         return reg->base == CFI_CFA &&
2209                reg->offset == expected_offset;
2210 }
2211
2212 static bool has_valid_stack_frame(struct insn_state *state)
2213 {
2214         struct cfi_state *cfi = &state->cfi;
2215
2216         if (cfi->cfa.base == CFI_BP &&
2217             check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2218             check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2219                 return true;
2220
2221         if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2222                 return true;
2223
2224         return false;
2225 }
2226
2227 static int update_cfi_state_regs(struct instruction *insn,
2228                                   struct cfi_state *cfi,
2229                                   struct stack_op *op)
2230 {
2231         struct cfi_reg *cfa = &cfi->cfa;
2232
2233         if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2234                 return 0;
2235
2236         /* push */
2237         if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2238                 cfa->offset += 8;
2239
2240         /* pop */
2241         if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2242                 cfa->offset -= 8;
2243
2244         /* add immediate to sp */
2245         if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2246             op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2247                 cfa->offset -= op->src.offset;
2248
2249         return 0;
2250 }
2251
2252 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2253 {
2254         if (arch_callee_saved_reg(reg) &&
2255             cfi->regs[reg].base == CFI_UNDEFINED) {
2256                 cfi->regs[reg].base = base;
2257                 cfi->regs[reg].offset = offset;
2258         }
2259 }
2260
2261 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2262 {
2263         cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2264         cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2265 }
2266
2267 /*
2268  * A note about DRAP stack alignment:
2269  *
2270  * GCC has the concept of a DRAP register, which is used to help keep track of
2271  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
2272  * register.  The typical DRAP pattern is:
2273  *
2274  *   4c 8d 54 24 08             lea    0x8(%rsp),%r10
2275  *   48 83 e4 c0                and    $0xffffffffffffffc0,%rsp
2276  *   41 ff 72 f8                pushq  -0x8(%r10)
2277  *   55                         push   %rbp
2278  *   48 89 e5                   mov    %rsp,%rbp
2279  *                              (more pushes)
2280  *   41 52                      push   %r10
2281  *                              ...
2282  *   41 5a                      pop    %r10
2283  *                              (more pops)
2284  *   5d                         pop    %rbp
2285  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2286  *   c3                         retq
2287  *
2288  * There are some variations in the epilogues, like:
2289  *
2290  *   5b                         pop    %rbx
2291  *   41 5a                      pop    %r10
2292  *   41 5c                      pop    %r12
2293  *   41 5d                      pop    %r13
2294  *   41 5e                      pop    %r14
2295  *   c9                         leaveq
2296  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2297  *   c3                         retq
2298  *
2299  * and:
2300  *
2301  *   4c 8b 55 e8                mov    -0x18(%rbp),%r10
2302  *   48 8b 5d e0                mov    -0x20(%rbp),%rbx
2303  *   4c 8b 65 f0                mov    -0x10(%rbp),%r12
2304  *   4c 8b 6d f8                mov    -0x8(%rbp),%r13
2305  *   c9                         leaveq
2306  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2307  *   c3                         retq
2308  *
2309  * Sometimes r13 is used as the DRAP register, in which case it's saved and
2310  * restored beforehand:
2311  *
2312  *   41 55                      push   %r13
2313  *   4c 8d 6c 24 10             lea    0x10(%rsp),%r13
2314  *   48 83 e4 f0                and    $0xfffffffffffffff0,%rsp
2315  *                              ...
2316  *   49 8d 65 f0                lea    -0x10(%r13),%rsp
2317  *   41 5d                      pop    %r13
2318  *   c3                         retq
2319  */
2320 static int update_cfi_state(struct instruction *insn,
2321                             struct instruction *next_insn,
2322                             struct cfi_state *cfi, struct stack_op *op)
2323 {
2324         struct cfi_reg *cfa = &cfi->cfa;
2325         struct cfi_reg *regs = cfi->regs;
2326
2327         /* stack operations don't make sense with an undefined CFA */
2328         if (cfa->base == CFI_UNDEFINED) {
2329                 if (insn->func) {
2330                         WARN_FUNC("undefined stack state", insn->sec, insn->offset);
2331                         return -1;
2332                 }
2333                 return 0;
2334         }
2335
2336         if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2337             cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2338                 return update_cfi_state_regs(insn, cfi, op);
2339
2340         switch (op->dest.type) {
2341
2342         case OP_DEST_REG:
2343                 switch (op->src.type) {
2344
2345                 case OP_SRC_REG:
2346                         if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2347                             cfa->base == CFI_SP &&
2348                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset)) {
2349
2350                                 /* mov %rsp, %rbp */
2351                                 cfa->base = op->dest.reg;
2352                                 cfi->bp_scratch = false;
2353                         }
2354
2355                         else if (op->src.reg == CFI_SP &&
2356                                  op->dest.reg == CFI_BP && cfi->drap) {
2357
2358                                 /* drap: mov %rsp, %rbp */
2359                                 regs[CFI_BP].base = CFI_BP;
2360                                 regs[CFI_BP].offset = -cfi->stack_size;
2361                                 cfi->bp_scratch = false;
2362                         }
2363
2364                         else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2365
2366                                 /*
2367                                  * mov %rsp, %reg
2368                                  *
2369                                  * This is needed for the rare case where GCC
2370                                  * does:
2371                                  *
2372                                  *   mov    %rsp, %rax
2373                                  *   ...
2374                                  *   mov    %rax, %rsp
2375                                  */
2376                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2377                                 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2378                         }
2379
2380                         else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2381                                  (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2382
2383                                 /*
2384                                  * mov %rbp, %rsp
2385                                  *
2386                                  * Restore the original stack pointer (Clang).
2387                                  */
2388                                 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2389                         }
2390
2391                         else if (op->dest.reg == cfa->base) {
2392
2393                                 /* mov %reg, %rsp */
2394                                 if (cfa->base == CFI_SP &&
2395                                     cfi->vals[op->src.reg].base == CFI_CFA) {
2396
2397                                         /*
2398                                          * This is needed for the rare case
2399                                          * where GCC does something dumb like:
2400                                          *
2401                                          *   lea    0x8(%rsp), %rcx
2402                                          *   ...
2403                                          *   mov    %rcx, %rsp
2404                                          */
2405                                         cfa->offset = -cfi->vals[op->src.reg].offset;
2406                                         cfi->stack_size = cfa->offset;
2407
2408                                 } else if (cfa->base == CFI_SP &&
2409                                            cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2410                                            cfi->vals[op->src.reg].offset == cfa->offset) {
2411
2412                                         /*
2413                                          * Stack swizzle:
2414                                          *
2415                                          * 1: mov %rsp, (%[tos])
2416                                          * 2: mov %[tos], %rsp
2417                                          *    ...
2418                                          * 3: pop %rsp
2419                                          *
2420                                          * Where:
2421                                          *
2422                                          * 1 - places a pointer to the previous
2423                                          *     stack at the Top-of-Stack of the
2424                                          *     new stack.
2425                                          *
2426                                          * 2 - switches to the new stack.
2427                                          *
2428                                          * 3 - pops the Top-of-Stack to restore
2429                                          *     the original stack.
2430                                          *
2431                                          * Note: we set base to SP_INDIRECT
2432                                          * here and preserve offset. Therefore
2433                                          * when the unwinder reaches ToS it
2434                                          * will dereference SP and then add the
2435                                          * offset to find the next frame, IOW:
2436                                          * (%rsp) + offset.
2437                                          */
2438                                         cfa->base = CFI_SP_INDIRECT;
2439
2440                                 } else {
2441                                         cfa->base = CFI_UNDEFINED;
2442                                         cfa->offset = 0;
2443                                 }
2444                         }
2445
2446                         else if (op->dest.reg == CFI_SP &&
2447                                  cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2448                                  cfi->vals[op->src.reg].offset == cfa->offset) {
2449
2450                                 /*
2451                                  * The same stack swizzle case 2) as above. But
2452                                  * because we can't change cfa->base, case 3)
2453                                  * will become a regular POP. Pretend we're a
2454                                  * PUSH so things don't go unbalanced.
2455                                  */
2456                                 cfi->stack_size += 8;
2457                         }
2458
2459
2460                         break;
2461
2462                 case OP_SRC_ADD:
2463                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2464
2465                                 /* add imm, %rsp */
2466                                 cfi->stack_size -= op->src.offset;
2467                                 if (cfa->base == CFI_SP)
2468                                         cfa->offset -= op->src.offset;
2469                                 break;
2470                         }
2471
2472                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2473
2474                                 /* lea disp(%rbp), %rsp */
2475                                 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2476                                 break;
2477                         }
2478
2479                         if (!cfi->drap && op->src.reg == CFI_SP &&
2480                             op->dest.reg == CFI_BP && cfa->base == CFI_SP &&
2481                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset + op->src.offset)) {
2482
2483                                 /* lea disp(%rsp), %rbp */
2484                                 cfa->base = CFI_BP;
2485                                 cfa->offset -= op->src.offset;
2486                                 cfi->bp_scratch = false;
2487                                 break;
2488                         }
2489
2490                         if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2491
2492                                 /* drap: lea disp(%rsp), %drap */
2493                                 cfi->drap_reg = op->dest.reg;
2494
2495                                 /*
2496                                  * lea disp(%rsp), %reg
2497                                  *
2498                                  * This is needed for the rare case where GCC
2499                                  * does something dumb like:
2500                                  *
2501                                  *   lea    0x8(%rsp), %rcx
2502                                  *   ...
2503                                  *   mov    %rcx, %rsp
2504                                  */
2505                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2506                                 cfi->vals[op->dest.reg].offset = \
2507                                         -cfi->stack_size + op->src.offset;
2508
2509                                 break;
2510                         }
2511
2512                         if (cfi->drap && op->dest.reg == CFI_SP &&
2513                             op->src.reg == cfi->drap_reg) {
2514
2515                                  /* drap: lea disp(%drap), %rsp */
2516                                 cfa->base = CFI_SP;
2517                                 cfa->offset = cfi->stack_size = -op->src.offset;
2518                                 cfi->drap_reg = CFI_UNDEFINED;
2519                                 cfi->drap = false;
2520                                 break;
2521                         }
2522
2523                         if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
2524                                 WARN_FUNC("unsupported stack register modification",
2525                                           insn->sec, insn->offset);
2526                                 return -1;
2527                         }
2528
2529                         break;
2530
2531                 case OP_SRC_AND:
2532                         if (op->dest.reg != CFI_SP ||
2533                             (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
2534                             (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
2535                                 WARN_FUNC("unsupported stack pointer realignment",
2536                                           insn->sec, insn->offset);
2537                                 return -1;
2538                         }
2539
2540                         if (cfi->drap_reg != CFI_UNDEFINED) {
2541                                 /* drap: and imm, %rsp */
2542                                 cfa->base = cfi->drap_reg;
2543                                 cfa->offset = cfi->stack_size = 0;
2544                                 cfi->drap = true;
2545                         }
2546
2547                         /*
2548                          * Older versions of GCC (4.8ish) realign the stack
2549                          * without DRAP, with a frame pointer.
2550                          */
2551
2552                         break;
2553
2554                 case OP_SRC_POP:
2555                 case OP_SRC_POPF:
2556                         if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
2557
2558                                 /* pop %rsp; # restore from a stack swizzle */
2559                                 cfa->base = CFI_SP;
2560                                 break;
2561                         }
2562
2563                         if (!cfi->drap && op->dest.reg == cfa->base) {
2564
2565                                 /* pop %rbp */
2566                                 cfa->base = CFI_SP;
2567                         }
2568
2569                         if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
2570                             op->dest.reg == cfi->drap_reg &&
2571                             cfi->drap_offset == -cfi->stack_size) {
2572
2573                                 /* drap: pop %drap */
2574                                 cfa->base = cfi->drap_reg;
2575                                 cfa->offset = 0;
2576                                 cfi->drap_offset = -1;
2577
2578                         } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
2579
2580                                 /* pop %reg */
2581                                 restore_reg(cfi, op->dest.reg);
2582                         }
2583
2584                         cfi->stack_size -= 8;
2585                         if (cfa->base == CFI_SP)
2586                                 cfa->offset -= 8;
2587
2588                         break;
2589
2590                 case OP_SRC_REG_INDIRECT:
2591                         if (!cfi->drap && op->dest.reg == cfa->base &&
2592                             op->dest.reg == CFI_BP) {
2593
2594                                 /* mov disp(%rsp), %rbp */
2595                                 cfa->base = CFI_SP;
2596                                 cfa->offset = cfi->stack_size;
2597                         }
2598
2599                         if (cfi->drap && op->src.reg == CFI_BP &&
2600                             op->src.offset == cfi->drap_offset) {
2601
2602                                 /* drap: mov disp(%rbp), %drap */
2603                                 cfa->base = cfi->drap_reg;
2604                                 cfa->offset = 0;
2605                                 cfi->drap_offset = -1;
2606                         }
2607
2608                         if (cfi->drap && op->src.reg == CFI_BP &&
2609                             op->src.offset == regs[op->dest.reg].offset) {
2610
2611                                 /* drap: mov disp(%rbp), %reg */
2612                                 restore_reg(cfi, op->dest.reg);
2613
2614                         } else if (op->src.reg == cfa->base &&
2615                             op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
2616
2617                                 /* mov disp(%rbp), %reg */
2618                                 /* mov disp(%rsp), %reg */
2619                                 restore_reg(cfi, op->dest.reg);
2620
2621                         } else if (op->src.reg == CFI_SP &&
2622                                    op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
2623
2624                                 /* mov disp(%rsp), %reg */
2625                                 restore_reg(cfi, op->dest.reg);
2626                         }
2627
2628                         break;
2629
2630                 default:
2631                         WARN_FUNC("unknown stack-related instruction",
2632                                   insn->sec, insn->offset);
2633                         return -1;
2634                 }
2635
2636                 break;
2637
2638         case OP_DEST_PUSH:
2639         case OP_DEST_PUSHF:
2640                 cfi->stack_size += 8;
2641                 if (cfa->base == CFI_SP)
2642                         cfa->offset += 8;
2643
2644                 if (op->src.type != OP_SRC_REG)
2645                         break;
2646
2647                 if (cfi->drap) {
2648                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2649
2650                                 /* drap: push %drap */
2651                                 cfa->base = CFI_BP_INDIRECT;
2652                                 cfa->offset = -cfi->stack_size;
2653
2654                                 /* save drap so we know when to restore it */
2655                                 cfi->drap_offset = -cfi->stack_size;
2656
2657                         } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
2658
2659                                 /* drap: push %rbp */
2660                                 cfi->stack_size = 0;
2661
2662                         } else {
2663
2664                                 /* drap: push %reg */
2665                                 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
2666                         }
2667
2668                 } else {
2669
2670                         /* push %reg */
2671                         save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
2672                 }
2673
2674                 /* detect when asm code uses rbp as a scratch register */
2675                 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
2676                     cfa->base != CFI_BP)
2677                         cfi->bp_scratch = true;
2678                 break;
2679
2680         case OP_DEST_REG_INDIRECT:
2681
2682                 if (cfi->drap) {
2683                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2684
2685                                 /* drap: mov %drap, disp(%rbp) */
2686                                 cfa->base = CFI_BP_INDIRECT;
2687                                 cfa->offset = op->dest.offset;
2688
2689                                 /* save drap offset so we know when to restore it */
2690                                 cfi->drap_offset = op->dest.offset;
2691                         } else {
2692
2693                                 /* drap: mov reg, disp(%rbp) */
2694                                 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
2695                         }
2696
2697                 } else if (op->dest.reg == cfa->base) {
2698
2699                         /* mov reg, disp(%rbp) */
2700                         /* mov reg, disp(%rsp) */
2701                         save_reg(cfi, op->src.reg, CFI_CFA,
2702                                  op->dest.offset - cfi->cfa.offset);
2703
2704                 } else if (op->dest.reg == CFI_SP) {
2705
2706                         /* mov reg, disp(%rsp) */
2707                         save_reg(cfi, op->src.reg, CFI_CFA,
2708                                  op->dest.offset - cfi->stack_size);
2709
2710                 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
2711
2712                         /* mov %rsp, (%reg); # setup a stack swizzle. */
2713                         cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
2714                         cfi->vals[op->dest.reg].offset = cfa->offset;
2715                 }
2716
2717                 break;
2718
2719         case OP_DEST_MEM:
2720                 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
2721                         WARN_FUNC("unknown stack-related memory operation",
2722                                   insn->sec, insn->offset);
2723                         return -1;
2724                 }
2725
2726                 /* pop mem */
2727                 cfi->stack_size -= 8;
2728                 if (cfa->base == CFI_SP)
2729                         cfa->offset -= 8;
2730
2731                 break;
2732
2733         default:
2734                 WARN_FUNC("unknown stack-related instruction",
2735                           insn->sec, insn->offset);
2736                 return -1;
2737         }
2738
2739         return 0;
2740 }
2741
2742 /*
2743  * The stack layouts of alternatives instructions can sometimes diverge when
2744  * they have stack modifications.  That's fine as long as the potential stack
2745  * layouts don't conflict at any given potential instruction boundary.
2746  *
2747  * Flatten the CFIs of the different alternative code streams (both original
2748  * and replacement) into a single shared CFI array which can be used to detect
2749  * conflicts and nicely feed a linear array of ORC entries to the unwinder.
2750  */
2751 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
2752 {
2753         struct cfi_state **alt_cfi;
2754         int group_off;
2755
2756         if (!insn->alt_group)
2757                 return 0;
2758
2759         if (!insn->cfi) {
2760                 WARN("CFI missing");
2761                 return -1;
2762         }
2763
2764         alt_cfi = insn->alt_group->cfi;
2765         group_off = insn->offset - insn->alt_group->first_insn->offset;
2766
2767         if (!alt_cfi[group_off]) {
2768                 alt_cfi[group_off] = insn->cfi;
2769         } else {
2770                 if (cficmp(alt_cfi[group_off], insn->cfi)) {
2771                         WARN_FUNC("stack layout conflict in alternatives",
2772                                   insn->sec, insn->offset);
2773                         return -1;
2774                 }
2775         }
2776
2777         return 0;
2778 }
2779
2780 static int handle_insn_ops(struct instruction *insn,
2781                            struct instruction *next_insn,
2782                            struct insn_state *state)
2783 {
2784         struct stack_op *op;
2785
2786         list_for_each_entry(op, &insn->stack_ops, list) {
2787
2788                 if (update_cfi_state(insn, next_insn, &state->cfi, op))
2789                         return 1;
2790
2791                 if (!insn->alt_group)
2792                         continue;
2793
2794                 if (op->dest.type == OP_DEST_PUSHF) {
2795                         if (!state->uaccess_stack) {
2796                                 state->uaccess_stack = 1;
2797                         } else if (state->uaccess_stack >> 31) {
2798                                 WARN_FUNC("PUSHF stack exhausted",
2799                                           insn->sec, insn->offset);
2800                                 return 1;
2801                         }
2802                         state->uaccess_stack <<= 1;
2803                         state->uaccess_stack  |= state->uaccess;
2804                 }
2805
2806                 if (op->src.type == OP_SRC_POPF) {
2807                         if (state->uaccess_stack) {
2808                                 state->uaccess = state->uaccess_stack & 1;
2809                                 state->uaccess_stack >>= 1;
2810                                 if (state->uaccess_stack == 1)
2811                                         state->uaccess_stack = 0;
2812                         }
2813                 }
2814         }
2815
2816         return 0;
2817 }
2818
2819 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
2820 {
2821         struct cfi_state *cfi1 = insn->cfi;
2822         int i;
2823
2824         if (!cfi1) {
2825                 WARN("CFI missing");
2826                 return false;
2827         }
2828
2829         if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
2830
2831                 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
2832                           insn->sec, insn->offset,
2833                           cfi1->cfa.base, cfi1->cfa.offset,
2834                           cfi2->cfa.base, cfi2->cfa.offset);
2835
2836         } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
2837                 for (i = 0; i < CFI_NUM_REGS; i++) {
2838                         if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
2839                                     sizeof(struct cfi_reg)))
2840                                 continue;
2841
2842                         WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
2843                                   insn->sec, insn->offset,
2844                                   i, cfi1->regs[i].base, cfi1->regs[i].offset,
2845                                   i, cfi2->regs[i].base, cfi2->regs[i].offset);
2846                         break;
2847                 }
2848
2849         } else if (cfi1->type != cfi2->type) {
2850
2851                 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
2852                           insn->sec, insn->offset, cfi1->type, cfi2->type);
2853
2854         } else if (cfi1->drap != cfi2->drap ||
2855                    (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
2856                    (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
2857
2858                 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
2859                           insn->sec, insn->offset,
2860                           cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
2861                           cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
2862
2863         } else
2864                 return true;
2865
2866         return false;
2867 }
2868
2869 static inline bool func_uaccess_safe(struct symbol *func)
2870 {
2871         if (func)
2872                 return func->uaccess_safe;
2873
2874         return false;
2875 }
2876
2877 static inline const char *call_dest_name(struct instruction *insn)
2878 {
2879         if (insn->call_dest)
2880                 return insn->call_dest->name;
2881
2882         return "{dynamic}";
2883 }
2884
2885 static inline bool noinstr_call_dest(struct symbol *func)
2886 {
2887         /*
2888          * We can't deal with indirect function calls at present;
2889          * assume they're instrumented.
2890          */
2891         if (!func)
2892                 return false;
2893
2894         /*
2895          * If the symbol is from a noinstr section; we good.
2896          */
2897         if (func->sec->noinstr)
2898                 return true;
2899
2900         /*
2901          * The __ubsan_handle_*() calls are like WARN(), they only happen when
2902          * something 'BAD' happened. At the risk of taking the machine down,
2903          * let them proceed to get the message out.
2904          */
2905         if (!strncmp(func->name, "__ubsan_handle_", 15))
2906                 return true;
2907
2908         return false;
2909 }
2910
2911 static int validate_call(struct instruction *insn, struct insn_state *state)
2912 {
2913         if (state->noinstr && state->instr <= 0 &&
2914             !noinstr_call_dest(insn->call_dest)) {
2915                 WARN_FUNC("call to %s() leaves .noinstr.text section",
2916                                 insn->sec, insn->offset, call_dest_name(insn));
2917                 return 1;
2918         }
2919
2920         if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
2921                 WARN_FUNC("call to %s() with UACCESS enabled",
2922                                 insn->sec, insn->offset, call_dest_name(insn));
2923                 return 1;
2924         }
2925
2926         if (state->df) {
2927                 WARN_FUNC("call to %s() with DF set",
2928                                 insn->sec, insn->offset, call_dest_name(insn));
2929                 return 1;
2930         }
2931
2932         return 0;
2933 }
2934
2935 static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
2936 {
2937         if (has_modified_stack_frame(insn, state)) {
2938                 WARN_FUNC("sibling call from callable instruction with modified stack frame",
2939                                 insn->sec, insn->offset);
2940                 return 1;
2941         }
2942
2943         return validate_call(insn, state);
2944 }
2945
2946 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
2947 {
2948         if (state->noinstr && state->instr > 0) {
2949                 WARN_FUNC("return with instrumentation enabled",
2950                           insn->sec, insn->offset);
2951                 return 1;
2952         }
2953
2954         if (state->uaccess && !func_uaccess_safe(func)) {
2955                 WARN_FUNC("return with UACCESS enabled",
2956                           insn->sec, insn->offset);
2957                 return 1;
2958         }
2959
2960         if (!state->uaccess && func_uaccess_safe(func)) {
2961                 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
2962                           insn->sec, insn->offset);
2963                 return 1;
2964         }
2965
2966         if (state->df) {
2967                 WARN_FUNC("return with DF set",
2968                           insn->sec, insn->offset);
2969                 return 1;
2970         }
2971
2972         if (func && has_modified_stack_frame(insn, state)) {
2973                 WARN_FUNC("return with modified stack frame",
2974                           insn->sec, insn->offset);
2975                 return 1;
2976         }
2977
2978         if (state->cfi.bp_scratch) {
2979                 WARN_FUNC("BP used as a scratch register",
2980                           insn->sec, insn->offset);
2981                 return 1;
2982         }
2983
2984         return 0;
2985 }
2986
2987 static struct instruction *next_insn_to_validate(struct objtool_file *file,
2988                                                  struct instruction *insn)
2989 {
2990         struct alt_group *alt_group = insn->alt_group;
2991
2992         /*
2993          * Simulate the fact that alternatives are patched in-place.  When the
2994          * end of a replacement alt_group is reached, redirect objtool flow to
2995          * the end of the original alt_group.
2996          */
2997         if (alt_group && insn == alt_group->last_insn && alt_group->orig_group)
2998                 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
2999
3000         return next_insn_same_sec(file, insn);
3001 }
3002
3003 /*
3004  * Follow the branch starting at the given instruction, and recursively follow
3005  * any other branches (jumps).  Meanwhile, track the frame pointer state at
3006  * each instruction and validate all the rules described in
3007  * tools/objtool/Documentation/stack-validation.txt.
3008  */
3009 static int validate_branch(struct objtool_file *file, struct symbol *func,
3010                            struct instruction *insn, struct insn_state state)
3011 {
3012         struct alternative *alt;
3013         struct instruction *next_insn, *prev_insn = NULL;
3014         struct section *sec;
3015         u8 visited;
3016         int ret;
3017
3018         sec = insn->sec;
3019
3020         while (1) {
3021                 next_insn = next_insn_to_validate(file, insn);
3022
3023                 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
3024                         WARN("%s() falls through to next function %s()",
3025                              func->name, insn->func->name);
3026                         return 1;
3027                 }
3028
3029                 if (func && insn->ignore) {
3030                         WARN_FUNC("BUG: why am I validating an ignored function?",
3031                                   sec, insn->offset);
3032                         return 1;
3033                 }
3034
3035                 visited = VISITED_BRANCH << state.uaccess;
3036                 if (insn->visited & VISITED_BRANCH_MASK) {
3037                         if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3038                                 return 1;
3039
3040                         if (insn->visited & visited)
3041                                 return 0;
3042                 } else {
3043                         nr_insns_visited++;
3044                 }
3045
3046                 if (state.noinstr)
3047                         state.instr += insn->instr;
3048
3049                 if (insn->hint) {
3050                         if (insn->restore) {
3051                                 struct instruction *save_insn, *i;
3052
3053                                 i = insn;
3054                                 save_insn = NULL;
3055
3056                                 sym_for_each_insn_continue_reverse(file, func, i) {
3057                                         if (i->save) {
3058                                                 save_insn = i;
3059                                                 break;
3060                                         }
3061                                 }
3062
3063                                 if (!save_insn) {
3064                                         WARN_FUNC("no corresponding CFI save for CFI restore",
3065                                                   sec, insn->offset);
3066                                         return 1;
3067                                 }
3068
3069                                 if (!save_insn->visited) {
3070                                         WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
3071                                                   sec, insn->offset);
3072                                         return 1;
3073                                 }
3074
3075                                 insn->cfi = save_insn->cfi;
3076                                 nr_cfi_reused++;
3077                         }
3078
3079                         state.cfi = *insn->cfi;
3080                 } else {
3081                         /* XXX track if we actually changed state.cfi */
3082
3083                         if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3084                                 insn->cfi = prev_insn->cfi;
3085                                 nr_cfi_reused++;
3086                         } else {
3087                                 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3088                         }
3089                 }
3090
3091                 insn->visited |= visited;
3092
3093                 if (propagate_alt_cfi(file, insn))
3094                         return 1;
3095
3096                 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
3097                         bool skip_orig = false;
3098
3099                         list_for_each_entry(alt, &insn->alts, list) {
3100                                 if (alt->skip_orig)
3101                                         skip_orig = true;
3102
3103                                 ret = validate_branch(file, func, alt->insn, state);
3104                                 if (ret) {
3105                                         if (backtrace)
3106                                                 BT_FUNC("(alt)", insn);
3107                                         return ret;
3108                                 }
3109                         }
3110
3111                         if (skip_orig)
3112                                 return 0;
3113                 }
3114
3115                 if (handle_insn_ops(insn, next_insn, &state))
3116                         return 1;
3117
3118                 switch (insn->type) {
3119
3120                 case INSN_RETURN:
3121                         if (sls && !insn->retpoline_safe &&
3122                             next_insn && next_insn->type != INSN_TRAP) {
3123                                 WARN_FUNC("missing int3 after ret",
3124                                           insn->sec, insn->offset);
3125                         }
3126                         return validate_return(func, insn, &state);
3127
3128                 case INSN_CALL:
3129                 case INSN_CALL_DYNAMIC:
3130                         ret = validate_call(insn, &state);
3131                         if (ret)
3132                                 return ret;
3133
3134                         if (!no_fp && func && !is_fentry_call(insn) &&
3135                             !has_valid_stack_frame(&state)) {
3136                                 WARN_FUNC("call without frame pointer save/setup",
3137                                           sec, insn->offset);
3138                                 return 1;
3139                         }
3140
3141                         if (dead_end_function(file, insn->call_dest))
3142                                 return 0;
3143
3144                         break;
3145
3146                 case INSN_JUMP_CONDITIONAL:
3147                 case INSN_JUMP_UNCONDITIONAL:
3148                         if (is_sibling_call(insn)) {
3149                                 ret = validate_sibling_call(insn, &state);
3150                                 if (ret)
3151                                         return ret;
3152
3153                         } else if (insn->jump_dest) {
3154                                 ret = validate_branch(file, func,
3155                                                       insn->jump_dest, state);
3156                                 if (ret) {
3157                                         if (backtrace)
3158                                                 BT_FUNC("(branch)", insn);
3159                                         return ret;
3160                                 }
3161                         }
3162
3163                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
3164                                 return 0;
3165
3166                         break;
3167
3168                 case INSN_JUMP_DYNAMIC:
3169                         if (sls && !insn->retpoline_safe &&
3170                             next_insn && next_insn->type != INSN_TRAP) {
3171                                 WARN_FUNC("missing int3 after indirect jump",
3172                                           insn->sec, insn->offset);
3173                         }
3174
3175                         /* fallthrough */
3176                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3177                         if (is_sibling_call(insn)) {
3178                                 ret = validate_sibling_call(insn, &state);
3179                                 if (ret)
3180                                         return ret;
3181                         }
3182
3183                         if (insn->type == INSN_JUMP_DYNAMIC)
3184                                 return 0;
3185
3186                         break;
3187
3188                 case INSN_CONTEXT_SWITCH:
3189                         if (func && (!next_insn || !next_insn->hint)) {
3190                                 WARN_FUNC("unsupported instruction in callable function",
3191                                           sec, insn->offset);
3192                                 return 1;
3193                         }
3194                         return 0;
3195
3196                 case INSN_STAC:
3197                         if (state.uaccess) {
3198                                 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
3199                                 return 1;
3200                         }
3201
3202                         state.uaccess = true;
3203                         break;
3204
3205                 case INSN_CLAC:
3206                         if (!state.uaccess && func) {
3207                                 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
3208                                 return 1;
3209                         }
3210
3211                         if (func_uaccess_safe(func) && !state.uaccess_stack) {
3212                                 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
3213                                 return 1;
3214                         }
3215
3216                         state.uaccess = false;
3217                         break;
3218
3219                 case INSN_STD:
3220                         if (state.df) {
3221                                 WARN_FUNC("recursive STD", sec, insn->offset);
3222                                 return 1;
3223                         }
3224
3225                         state.df = true;
3226                         break;
3227
3228                 case INSN_CLD:
3229                         if (!state.df && func) {
3230                                 WARN_FUNC("redundant CLD", sec, insn->offset);
3231                                 return 1;
3232                         }
3233
3234                         state.df = false;
3235                         break;
3236
3237                 default:
3238                         break;
3239                 }
3240
3241                 if (insn->dead_end)
3242                         return 0;
3243
3244                 if (!next_insn) {
3245                         if (state.cfi.cfa.base == CFI_UNDEFINED)
3246                                 return 0;
3247                         WARN("%s: unexpected end of section", sec->name);
3248                         return 1;
3249                 }
3250
3251                 prev_insn = insn;
3252                 insn = next_insn;
3253         }
3254
3255         return 0;
3256 }
3257
3258 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3259 {
3260         struct instruction *insn;
3261         struct insn_state state;
3262         int ret, warnings = 0;
3263
3264         if (!file->hints)
3265                 return 0;
3266
3267         init_insn_state(&state, sec);
3268
3269         if (sec) {
3270                 insn = find_insn(file, sec, 0);
3271                 if (!insn)
3272                         return 0;
3273         } else {
3274                 insn = list_first_entry(&file->insn_list, typeof(*insn), list);
3275         }
3276
3277         while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) {
3278                 if (insn->hint && !insn->visited) {
3279                         ret = validate_branch(file, insn->func, insn, state);
3280                         if (ret && backtrace)
3281                                 BT_FUNC("<=== (hint)", insn);
3282                         warnings += ret;
3283                 }
3284
3285                 insn = list_next_entry(insn, list);
3286         }
3287
3288         return warnings;
3289 }
3290
3291 /*
3292  * Validate rethunk entry constraint: must untrain RET before the first RET.
3293  *
3294  * Follow every branch (intra-function) and ensure ANNOTATE_UNRET_END comes
3295  * before an actual RET instruction.
3296  */
3297 static int validate_entry(struct objtool_file *file, struct instruction *insn)
3298 {
3299         struct instruction *next, *dest;
3300         int ret, warnings = 0;
3301
3302         for (;;) {
3303                 next = next_insn_to_validate(file, insn);
3304
3305                 if (insn->visited & VISITED_ENTRY)
3306                         return 0;
3307
3308                 insn->visited |= VISITED_ENTRY;
3309
3310                 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
3311                         struct alternative *alt;
3312                         bool skip_orig = false;
3313
3314                         list_for_each_entry(alt, &insn->alts, list) {
3315                                 if (alt->skip_orig)
3316                                         skip_orig = true;
3317
3318                                 ret = validate_entry(file, alt->insn);
3319                                 if (ret) {
3320                                         if (backtrace)
3321                                                 BT_FUNC("(alt)", insn);
3322                                         return ret;
3323                                 }
3324                         }
3325
3326                         if (skip_orig)
3327                                 return 0;
3328                 }
3329
3330                 switch (insn->type) {
3331
3332                 case INSN_CALL_DYNAMIC:
3333                 case INSN_JUMP_DYNAMIC:
3334                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3335                         WARN_FUNC("early indirect call", insn->sec, insn->offset);
3336                         return 1;
3337
3338                 case INSN_JUMP_UNCONDITIONAL:
3339                 case INSN_JUMP_CONDITIONAL:
3340                         if (!is_sibling_call(insn)) {
3341                                 if (!insn->jump_dest) {
3342                                         WARN_FUNC("unresolved jump target after linking?!?",
3343                                                   insn->sec, insn->offset);
3344                                         return -1;
3345                                 }
3346                                 ret = validate_entry(file, insn->jump_dest);
3347                                 if (ret) {
3348                                         if (backtrace) {
3349                                                 BT_FUNC("(branch%s)", insn,
3350                                                         insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : "");
3351                                         }
3352                                         return ret;
3353                                 }
3354
3355                                 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3356                                         return 0;
3357
3358                                 break;
3359                         }
3360
3361                         /* fallthrough */
3362                 case INSN_CALL:
3363                         dest = find_insn(file, insn->call_dest->sec,
3364                                          insn->call_dest->offset);
3365                         if (!dest) {
3366                                 WARN("Unresolved function after linking!?: %s",
3367                                      insn->call_dest->name);
3368                                 return -1;
3369                         }
3370
3371                         ret = validate_entry(file, dest);
3372                         if (ret) {
3373                                 if (backtrace)
3374                                         BT_FUNC("(call)", insn);
3375                                 return ret;
3376                         }
3377                         /*
3378                          * If a call returns without error, it must have seen UNTRAIN_RET.
3379                          * Therefore any non-error return is a success.
3380                          */
3381                         return 0;
3382
3383                 case INSN_RETURN:
3384                         WARN_FUNC("RET before UNTRAIN", insn->sec, insn->offset);
3385                         return 1;
3386
3387                 case INSN_NOP:
3388                         if (insn->retpoline_safe)
3389                                 return 0;
3390                         break;
3391
3392                 default:
3393                         break;
3394                 }
3395
3396                 if (!next) {
3397                         WARN_FUNC("teh end!", insn->sec, insn->offset);
3398                         return -1;
3399                 }
3400                 insn = next;
3401         }
3402
3403         return warnings;
3404 }
3405
3406 /*
3407  * Validate that all branches starting at 'insn->entry' encounter UNRET_END
3408  * before RET.
3409  */
3410 static int validate_unret(struct objtool_file *file)
3411 {
3412         struct instruction *insn;
3413         int ret, warnings = 0;
3414
3415         for_each_insn(file, insn) {
3416                 if (!insn->entry)
3417                         continue;
3418
3419                 ret = validate_entry(file, insn);
3420                 if (ret < 0) {
3421                         WARN_FUNC("Failed UNRET validation", insn->sec, insn->offset);
3422                         return ret;
3423                 }
3424                 warnings += ret;
3425         }
3426
3427         return warnings;
3428 }
3429
3430 static int validate_retpoline(struct objtool_file *file)
3431 {
3432         struct instruction *insn;
3433         int warnings = 0;
3434
3435         for_each_insn(file, insn) {
3436                 if (insn->type != INSN_JUMP_DYNAMIC &&
3437                     insn->type != INSN_CALL_DYNAMIC &&
3438                     insn->type != INSN_RETURN)
3439                         continue;
3440
3441                 if (insn->retpoline_safe)
3442                         continue;
3443
3444                 /*
3445                  * .init.text code is ran before userspace and thus doesn't
3446                  * strictly need retpolines, except for modules which are
3447                  * loaded late, they very much do need retpoline in their
3448                  * .init.text
3449                  */
3450                 if (!strcmp(insn->sec->name, ".init.text") && !module)
3451                         continue;
3452
3453                 if (insn->type == INSN_RETURN) {
3454                         if (rethunk) {
3455                                 WARN_FUNC("'naked' return found in RETHUNK build",
3456                                           insn->sec, insn->offset);
3457                         } else
3458                                 continue;
3459                 } else {
3460                         WARN_FUNC("indirect %s found in RETPOLINE build",
3461                                   insn->sec, insn->offset,
3462                                   insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
3463                 }
3464
3465                 warnings++;
3466         }
3467
3468         return warnings;
3469 }
3470
3471 static bool is_kasan_insn(struct instruction *insn)
3472 {
3473         return (insn->type == INSN_CALL &&
3474                 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
3475 }
3476
3477 static bool is_ubsan_insn(struct instruction *insn)
3478 {
3479         return (insn->type == INSN_CALL &&
3480                 !strcmp(insn->call_dest->name,
3481                         "__ubsan_handle_builtin_unreachable"));
3482 }
3483
3484 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
3485 {
3486         int i;
3487         struct instruction *prev_insn;
3488
3489         if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
3490                 return true;
3491
3492         /*
3493          * Ignore any unused exceptions.  This can happen when a whitelisted
3494          * function has an exception table entry.
3495          *
3496          * Also ignore alternative replacement instructions.  This can happen
3497          * when a whitelisted function uses one of the ALTERNATIVE macros.
3498          */
3499         if (!strcmp(insn->sec->name, ".fixup") ||
3500             !strcmp(insn->sec->name, ".altinstr_replacement") ||
3501             !strcmp(insn->sec->name, ".altinstr_aux"))
3502                 return true;
3503
3504         if (!insn->func)
3505                 return false;
3506
3507         /*
3508          * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
3509          * __builtin_unreachable().  The BUG() macro has an unreachable() after
3510          * the UD2, which causes GCC's undefined trap logic to emit another UD2
3511          * (or occasionally a JMP to UD2).
3512          *
3513          * It may also insert a UD2 after calling a __noreturn function.
3514          */
3515         prev_insn = list_prev_entry(insn, list);
3516         if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) &&
3517             (insn->type == INSN_BUG ||
3518              (insn->type == INSN_JUMP_UNCONDITIONAL &&
3519               insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
3520                 return true;
3521
3522         /*
3523          * Check if this (or a subsequent) instruction is related to
3524          * CONFIG_UBSAN or CONFIG_KASAN.
3525          *
3526          * End the search at 5 instructions to avoid going into the weeds.
3527          */
3528         for (i = 0; i < 5; i++) {
3529
3530                 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
3531                         return true;
3532
3533                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
3534                         if (insn->jump_dest &&
3535                             insn->jump_dest->func == insn->func) {
3536                                 insn = insn->jump_dest;
3537                                 continue;
3538                         }
3539
3540                         break;
3541                 }
3542
3543                 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
3544                         break;
3545
3546                 insn = list_next_entry(insn, list);
3547         }
3548
3549         return false;
3550 }
3551
3552 static int validate_symbol(struct objtool_file *file, struct section *sec,
3553                            struct symbol *sym, struct insn_state *state)
3554 {
3555         struct instruction *insn;
3556         int ret;
3557
3558         if (!sym->len) {
3559                 WARN("%s() is missing an ELF size annotation", sym->name);
3560                 return 1;
3561         }
3562
3563         if (sym->pfunc != sym || sym->alias != sym)
3564                 return 0;
3565
3566         insn = find_insn(file, sec, sym->offset);
3567         if (!insn || insn->ignore || insn->visited)
3568                 return 0;
3569
3570         state->uaccess = sym->uaccess_safe;
3571
3572         ret = validate_branch(file, insn->func, insn, *state);
3573         if (ret && backtrace)
3574                 BT_FUNC("<=== (sym)", insn);
3575         return ret;
3576 }
3577
3578 static int validate_section(struct objtool_file *file, struct section *sec)
3579 {
3580         struct insn_state state;
3581         struct symbol *func;
3582         int warnings = 0;
3583
3584         list_for_each_entry(func, &sec->symbol_list, list) {
3585                 if (func->type != STT_FUNC)
3586                         continue;
3587
3588                 init_insn_state(&state, sec);
3589                 set_func_state(&state.cfi);
3590
3591                 warnings += validate_symbol(file, sec, func, &state);
3592         }
3593
3594         return warnings;
3595 }
3596
3597 static int validate_vmlinux_functions(struct objtool_file *file)
3598 {
3599         struct section *sec;
3600         int warnings = 0;
3601
3602         sec = find_section_by_name(file->elf, ".noinstr.text");
3603         if (sec) {
3604                 warnings += validate_section(file, sec);
3605                 warnings += validate_unwind_hints(file, sec);
3606         }
3607
3608         sec = find_section_by_name(file->elf, ".entry.text");
3609         if (sec) {
3610                 warnings += validate_section(file, sec);
3611                 warnings += validate_unwind_hints(file, sec);
3612         }
3613
3614         return warnings;
3615 }
3616
3617 static int validate_functions(struct objtool_file *file)
3618 {
3619         struct section *sec;
3620         int warnings = 0;
3621
3622         for_each_sec(file, sec) {
3623                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
3624                         continue;
3625
3626                 warnings += validate_section(file, sec);
3627         }
3628
3629         return warnings;
3630 }
3631
3632 static int validate_reachable_instructions(struct objtool_file *file)
3633 {
3634         struct instruction *insn;
3635
3636         if (file->ignore_unreachables)
3637                 return 0;
3638
3639         for_each_insn(file, insn) {
3640                 if (insn->visited || ignore_unreachable_insn(file, insn))
3641                         continue;
3642
3643                 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
3644                 return 1;
3645         }
3646
3647         return 0;
3648 }
3649
3650 int check(struct objtool_file *file)
3651 {
3652         int ret, warnings = 0;
3653
3654         arch_initial_func_cfi_state(&initial_func_cfi);
3655         init_cfi_state(&init_cfi);
3656         init_cfi_state(&func_cfi);
3657         set_func_state(&func_cfi);
3658
3659         if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
3660                 goto out;
3661
3662         cfi_hash_add(&init_cfi);
3663         cfi_hash_add(&func_cfi);
3664
3665         ret = decode_sections(file);
3666         if (ret < 0)
3667                 goto out;
3668
3669         warnings += ret;
3670
3671         if (list_empty(&file->insn_list))
3672                 goto out;
3673
3674         if (vmlinux && !validate_dup) {
3675                 ret = validate_vmlinux_functions(file);
3676                 if (ret < 0)
3677                         goto out;
3678
3679                 warnings += ret;
3680                 goto out;
3681         }
3682
3683         if (retpoline) {
3684                 ret = validate_retpoline(file);
3685                 if (ret < 0)
3686                         return ret;
3687                 warnings += ret;
3688         }
3689
3690         ret = validate_functions(file);
3691         if (ret < 0)
3692                 goto out;
3693         warnings += ret;
3694
3695         ret = validate_unwind_hints(file, NULL);
3696         if (ret < 0)
3697                 goto out;
3698         warnings += ret;
3699
3700         if (unret) {
3701                 /*
3702                  * Must be after validate_branch() and friends, it plays
3703                  * further games with insn->visited.
3704                  */
3705                 ret = validate_unret(file);
3706                 if (ret < 0)
3707                         return ret;
3708                 warnings += ret;
3709         }
3710
3711         if (!warnings) {
3712                 ret = validate_reachable_instructions(file);
3713                 if (ret < 0)
3714                         goto out;
3715                 warnings += ret;
3716         }
3717
3718         ret = create_static_call_sections(file);
3719         if (ret < 0)
3720                 goto out;
3721         warnings += ret;
3722
3723         if (retpoline) {
3724                 ret = create_retpoline_sites_sections(file);
3725                 if (ret < 0)
3726                         goto out;
3727                 warnings += ret;
3728         }
3729
3730         if (rethunk) {
3731                 ret = create_return_sites_sections(file);
3732                 if (ret < 0)
3733                         goto out;
3734                 warnings += ret;
3735         }
3736
3737         if (mcount) {
3738                 ret = create_mcount_loc_sections(file);
3739                 if (ret < 0)
3740                         goto out;
3741                 warnings += ret;
3742         }
3743
3744         if (stats) {
3745                 printf("nr_insns_visited: %ld\n", nr_insns_visited);
3746                 printf("nr_cfi: %ld\n", nr_cfi);
3747                 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
3748                 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
3749         }
3750
3751 out:
3752         /*
3753          *  For now, don't fail the kernel build on fatal warnings.  These
3754          *  errors are still fairly common due to the growing matrix of
3755          *  supported toolchains and their recent pace of change.
3756          */
3757         return 0;
3758 }