tools/objtool/check.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
   4  */
   5
   6 #include <string.h>
   7 #include <stdlib.h>
   8 #include <sys/mman.h>
   9
  10 #include <arch/elf.h>
  11 #include <objtool/builtin.h>
  12 #include <objtool/cfi.h>
  13 #include <objtool/arch.h>
  14 #include <objtool/check.h>
  15 #include <objtool/special.h>
  16 #include <objtool/warn.h>
  17 #include <objtool/endianness.h>
  18
  19 #include <linux/objtool.h>
  20 #include <linux/hashtable.h>
  21 #include <linux/kernel.h>
  22 #include <linux/static_call_types.h>
  23
  24 struct alternative {
  25         struct list_head list;
  26         struct instruction *insn;
  27         bool skip_orig;
  28 };
  29
  30 static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
  31
  32 static struct cfi_init_state initial_func_cfi;
  33 static struct cfi_state init_cfi;
  34 static struct cfi_state func_cfi;
  35
  36 struct instruction *find_insn(struct objtool_file *file,
  37                               struct section *sec, unsigned long offset)
  38 {
  39         struct instruction *insn;
  40
  41         hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
  42                 if (insn->sec == sec && insn->offset == offset)
  43                         return insn;
  44         }
  45
  46         return NULL;
  47 }
  48
  49 static struct instruction *next_insn_same_sec(struct objtool_file *file,
  50                                               struct instruction *insn)
  51 {
  52         struct instruction *next = list_next_entry(insn, list);
  53
  54         if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
  55                 return NULL;
  56
  57         return next;
  58 }
  59
  60 static struct instruction *next_insn_same_func(struct objtool_file *file,
  61                                                struct instruction *insn)
  62 {
  63         struct instruction *next = list_next_entry(insn, list);
  64         struct symbol *func = insn->func;
  65
  66         if (!func)
  67                 return NULL;
  68
  69         if (&next->list != &file->insn_list && next->func == func)
  70                 return next;
  71
  72         /* Check if we're already in the subfunction: */
  73         if (func == func->cfunc)
  74                 return NULL;
  75
  76         /* Move to the subfunction: */
  77         return find_insn(file, func->cfunc->sec, func->cfunc->offset);
  78 }
  79
  80 static struct instruction *prev_insn_same_sym(struct objtool_file *file,
  81                                                struct instruction *insn)
  82 {
  83         struct instruction *prev = list_prev_entry(insn, list);
  84
  85         if (&prev->list != &file->insn_list && prev->func == insn->func)
  86                 return prev;
  87
  88         return NULL;
  89 }
  90
  91 #define func_for_each_insn(file, func, insn)                            \
  92         for (insn = find_insn(file, func->sec, func->offset);           \
  93              insn;                                                      \
  94              insn = next_insn_same_func(file, insn))
  95
  96 #define sym_for_each_insn(file, sym, insn)                              \
  97         for (insn = find_insn(file, sym->sec, sym->offset);             \
  98              insn && &insn->list != &file->insn_list &&                 \
  99                 insn->sec == sym->sec &&                                \
 100                 insn->offset < sym->offset + sym->len;                  \
 101              insn = list_next_entry(insn, list))
 102
 103 #define sym_for_each_insn_continue_reverse(file, sym, insn)             \
 104         for (insn = list_prev_entry(insn, list);                        \
 105              &insn->list != &file->insn_list &&                         \
 106                 insn->sec == sym->sec && insn->offset >= sym->offset;   \
 107              insn = list_prev_entry(insn, list))
 108
 109 #define sec_for_each_insn_from(file, insn)                              \
 110         for (; insn; insn = next_insn_same_sec(file, insn))
 111
 112 #define sec_for_each_insn_continue(file, insn)                          \
 113         for (insn = next_insn_same_sec(file, insn); insn;               \
 114              insn = next_insn_same_sec(file, insn))
 115
 116 static bool is_jump_table_jump(struct instruction *insn)
 117 {
 118         struct alt_group *alt_group = insn->alt_group;
 119
 120         if (insn->jump_table)
 121                 return true;
 122
 123         /* Retpoline alternative for a jump table? */
 124         return alt_group && alt_group->orig_group &&
 125                alt_group->orig_group->first_insn->jump_table;
 126 }
 127
 128 static bool is_sibling_call(struct instruction *insn)
 129 {
 130         /*
 131          * Assume only ELF functions can make sibling calls.  This ensures
 132          * sibling call detection consistency between vmlinux.o and individual
 133          * objects.
 134          */
 135         if (!insn->func)
 136                 return false;
 137
 138         /* An indirect jump is either a sibling call or a jump to a table. */
 139         if (insn->type == INSN_JUMP_DYNAMIC)
 140                 return !is_jump_table_jump(insn);
 141
 142         /* add_jump_destinations() sets insn->call_dest for sibling calls. */
 143         return (is_static_jump(insn) && insn->call_dest);
 144 }
 145
 146 /*
 147  * This checks to see if the given function is a "noreturn" function.
 148  *
 149  * For global functions which are outside the scope of this object file, we
 150  * have to keep a manual list of them.
 151  *
 152  * For local functions, we have to detect them manually by simply looking for
 153  * the lack of a return instruction.
 154  */
 155 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 156                                 int recursion)
 157 {
 158         int i;
 159         struct instruction *insn;
 160         bool empty = true;
 161
 162         /*
 163          * Unfortunately these have to be hard coded because the noreturn
 164          * attribute isn't provided in ELF data.
 165          */
 166         static const char * const global_noreturns[] = {
 167                 "__stack_chk_fail",
 168                 "panic",
 169                 "do_exit",
 170                 "do_task_dead",
 171                 "kthread_exit",
 172                 "make_task_dead",
 173                 "__module_put_and_kthread_exit",
 174                 "kthread_complete_and_exit",
 175                 "__reiserfs_panic",
 176                 "lbug_with_loc",
 177                 "fortify_panic",
 178                 "usercopy_abort",
 179                 "machine_real_restart",
 180                 "rewind_stack_and_make_dead",
 181                 "kunit_try_catch_throw",
 182                 "xen_start_kernel",
 183                 "cpu_bringup_and_idle",
 184         };
 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->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                         sec->noinstr = true;
 373
 374                 for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
 375                         insn = malloc(sizeof(*insn));
 376                         if (!insn) {
 377                                 WARN("malloc failed");
 378                                 return -1;
 379                         }
 380                         memset(insn, 0, sizeof(*insn));
 381                         INIT_LIST_HEAD(&insn->alts);
 382                         INIT_LIST_HEAD(&insn->stack_ops);
 383
 384                         insn->sec = sec;
 385                         insn->offset = offset;
 386
 387                         ret = arch_decode_instruction(file, sec, offset,
 388                                                       sec->sh.sh_size - offset,
 389                                                       &insn->len, &insn->type,
 390                                                       &insn->immediate,
 391                                                       &insn->stack_ops);
 392                         if (ret)
 393                                 goto err;
 394
 395                         hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
 396                         list_add_tail(&insn->list, &file->insn_list);
 397                         nr_insns++;
 398                 }
 399
 400                 list_for_each_entry(func, &sec->symbol_list, list) {
 401                         if (func->type != STT_FUNC || func->alias != func)
 402                                 continue;
 403
 404                         if (!find_insn(file, sec, func->offset)) {
 405                                 WARN("%s(): can't find starting instruction",
 406                                      func->name);
 407                                 return -1;
 408                         }
 409
 410                         sym_for_each_insn(file, func, insn)
 411                                 insn->func = func;
 412                 }
 413         }
 414
 415         if (stats)
 416                 printf("nr_insns: %lu\n", nr_insns);
 417
 418         return 0;
 419
 420 err:
 421         free(insn);
 422         return ret;
 423 }
 424
 425 /*
 426  * Read the pv_ops[] .data table to find the static initialized values.
 427  */
 428 static int add_pv_ops(struct objtool_file *file, const char *symname)
 429 {
 430         struct symbol *sym, *func;
 431         unsigned long off, end;
 432         struct reloc *rel;
 433         int idx;
 434
 435         sym = find_symbol_by_name(file->elf, symname);
 436         if (!sym)
 437                 return 0;
 438
 439         off = sym->offset;
 440         end = off + sym->len;
 441         for (;;) {
 442                 rel = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off);
 443                 if (!rel)
 444                         break;
 445
 446                 func = rel->sym;
 447                 if (func->type == STT_SECTION)
 448                         func = find_symbol_by_offset(rel->sym->sec, rel->addend);
 449
 450                 idx = (rel->offset - sym->offset) / sizeof(unsigned long);
 451
 452                 objtool_pv_add(file, idx, func);
 453
 454                 off = rel->offset + 1;
 455                 if (off > end)
 456                         break;
 457         }
 458
 459         return 0;
 460 }
 461
 462 /*
 463  * Allocate and initialize file->pv_ops[].
 464  */
 465 static int init_pv_ops(struct objtool_file *file)
 466 {
 467         static const char *pv_ops_tables[] = {
 468                 "pv_ops",
 469                 "xen_cpu_ops",
 470                 "xen_irq_ops",
 471                 "xen_mmu_ops",
 472                 NULL,
 473         };
 474         const char *pv_ops;
 475         struct symbol *sym;
 476         int idx, nr;
 477
 478         if (!noinstr)
 479                 return 0;
 480
 481         file->pv_ops = NULL;
 482
 483         sym = find_symbol_by_name(file->elf, "pv_ops");
 484         if (!sym)
 485                 return 0;
 486
 487         nr = sym->len / sizeof(unsigned long);
 488         file->pv_ops = calloc(sizeof(struct pv_state), nr);
 489         if (!file->pv_ops)
 490                 return -1;
 491
 492         for (idx = 0; idx < nr; idx++)
 493                 INIT_LIST_HEAD(&file->pv_ops[idx].targets);
 494
 495         for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++)
 496                 add_pv_ops(file, pv_ops);
 497
 498         return 0;
 499 }
 500
 501 static struct instruction *find_last_insn(struct objtool_file *file,
 502                                           struct section *sec)
 503 {
 504         struct instruction *insn = NULL;
 505         unsigned int offset;
 506         unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
 507
 508         for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
 509                 insn = find_insn(file, sec, offset);
 510
 511         return insn;
 512 }
 513
 514 /*
 515  * Mark "ud2" instructions and manually annotated dead ends.
 516  */
 517 static int add_dead_ends(struct objtool_file *file)
 518 {
 519         struct section *sec;
 520         struct reloc *reloc;
 521         struct instruction *insn;
 522
 523         /*
 524          * By default, "ud2" is a dead end unless otherwise annotated, because
 525          * GCC 7 inserts it for certain divide-by-zero cases.
 526          */
 527         for_each_insn(file, insn)
 528                 if (insn->type == INSN_BUG)
 529                         insn->dead_end = true;
 530
 531         /*
 532          * Check for manually annotated dead ends.
 533          */
 534         sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
 535         if (!sec)
 536                 goto reachable;
 537
 538         list_for_each_entry(reloc, &sec->reloc_list, list) {
 539                 if (reloc->sym->type != STT_SECTION) {
 540                         WARN("unexpected relocation symbol type in %s", sec->name);
 541                         return -1;
 542                 }
 543                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 544                 if (insn)
 545                         insn = list_prev_entry(insn, list);
 546                 else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
 547                         insn = find_last_insn(file, reloc->sym->sec);
 548                         if (!insn) {
 549                                 WARN("can't find unreachable insn at %s+0x%x",
 550                                      reloc->sym->sec->name, reloc->addend);
 551                                 return -1;
 552                         }
 553                 } else {
 554                         WARN("can't find unreachable insn at %s+0x%x",
 555                              reloc->sym->sec->name, reloc->addend);
 556                         return -1;
 557                 }
 558
 559                 insn->dead_end = true;
 560         }
 561
 562 reachable:
 563         /*
 564          * These manually annotated reachable checks are needed for GCC 4.4,
 565          * where the Linux unreachable() macro isn't supported.  In that case
 566          * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
 567          * not a dead end.
 568          */
 569         sec = find_section_by_name(file->elf, ".rela.discard.reachable");
 570         if (!sec)
 571                 return 0;
 572
 573         list_for_each_entry(reloc, &sec->reloc_list, list) {
 574                 if (reloc->sym->type != STT_SECTION) {
 575                         WARN("unexpected relocation symbol type in %s", sec->name);
 576                         return -1;
 577                 }
 578                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 579                 if (insn)
 580                         insn = list_prev_entry(insn, list);
 581                 else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
 582                         insn = find_last_insn(file, reloc->sym->sec);
 583                         if (!insn) {
 584                                 WARN("can't find reachable insn at %s+0x%x",
 585                                      reloc->sym->sec->name, reloc->addend);
 586                                 return -1;
 587                         }
 588                 } else {
 589                         WARN("can't find reachable insn at %s+0x%x",
 590                              reloc->sym->sec->name, reloc->addend);
 591                         return -1;
 592                 }
 593
 594                 insn->dead_end = false;
 595         }
 596
 597         return 0;
 598 }
 599
 600 static int create_static_call_sections(struct objtool_file *file)
 601 {
 602         struct section *sec;
 603         struct static_call_site *site;
 604         struct instruction *insn;
 605         struct symbol *key_sym;
 606         char *key_name, *tmp;
 607         int idx;
 608
 609         sec = find_section_by_name(file->elf, ".static_call_sites");
 610         if (sec) {
 611                 INIT_LIST_HEAD(&file->static_call_list);
 612                 WARN("file already has .static_call_sites section, skipping");
 613                 return 0;
 614         }
 615
 616         if (list_empty(&file->static_call_list))
 617                 return 0;
 618
 619         idx = 0;
 620         list_for_each_entry(insn, &file->static_call_list, call_node)
 621                 idx++;
 622
 623         sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE,
 624                                  sizeof(struct static_call_site), idx);
 625         if (!sec)
 626                 return -1;
 627
 628         idx = 0;
 629         list_for_each_entry(insn, &file->static_call_list, call_node) {
 630
 631                 site = (struct static_call_site *)sec->data->d_buf + idx;
 632                 memset(site, 0, sizeof(struct static_call_site));
 633
 634                 /* populate reloc for 'addr' */
 635                 if (elf_add_reloc_to_insn(file->elf, sec,
 636                                           idx * sizeof(struct static_call_site),
 637                                           R_X86_64_PC32,
 638                                           insn->sec, insn->offset))
 639                         return -1;
 640
 641                 /* find key symbol */
 642                 key_name = strdup(insn->call_dest->name);
 643                 if (!key_name) {
 644                         perror("strdup");
 645                         return -1;
 646                 }
 647                 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
 648                             STATIC_CALL_TRAMP_PREFIX_LEN)) {
 649                         WARN("static_call: trampoline name malformed: %s", key_name);
 650                         return -1;
 651                 }
 652                 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
 653                 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
 654
 655                 key_sym = find_symbol_by_name(file->elf, tmp);
 656                 if (!key_sym) {
 657                         if (!module) {
 658                                 WARN("static_call: can't find static_call_key symbol: %s", tmp);
 659                                 return -1;
 660                         }
 661
 662                         /*
 663                          * For modules(), the key might not be exported, which
 664                          * means the module can make static calls but isn't
 665                          * allowed to change them.
 666                          *
 667                          * In that case we temporarily set the key to be the
 668                          * trampoline address.  This is fixed up in
 669                          * static_call_add_module().
 670                          */
 671                         key_sym = insn->call_dest;
 672                 }
 673                 free(key_name);
 674
 675                 /* populate reloc for 'key' */
 676                 if (elf_add_reloc(file->elf, sec,
 677                                   idx * sizeof(struct static_call_site) + 4,
 678                                   R_X86_64_PC32, key_sym,
 679                                   is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
 680                         return -1;
 681
 682                 idx++;
 683         }
 684
 685         return 0;
 686 }
 687
 688 static int create_retpoline_sites_sections(struct objtool_file *file)
 689 {
 690         struct instruction *insn;
 691         struct section *sec;
 692         int idx;
 693
 694         sec = find_section_by_name(file->elf, ".retpoline_sites");
 695         if (sec) {
 696                 WARN("file already has .retpoline_sites, skipping");
 697                 return 0;
 698         }
 699
 700         idx = 0;
 701         list_for_each_entry(insn, &file->retpoline_call_list, call_node)
 702                 idx++;
 703
 704         if (!idx)
 705                 return 0;
 706
 707         sec = elf_create_section(file->elf, ".retpoline_sites", 0,
 708                                  sizeof(int), idx);
 709         if (!sec) {
 710                 WARN("elf_create_section: .retpoline_sites");
 711                 return -1;
 712         }
 713
 714         idx = 0;
 715         list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
 716
 717                 int *site = (int *)sec->data->d_buf + idx;
 718                 *site = 0;
 719
 720                 if (elf_add_reloc_to_insn(file->elf, sec,
 721                                           idx * sizeof(int),
 722                                           R_X86_64_PC32,
 723                                           insn->sec, insn->offset)) {
 724                         WARN("elf_add_reloc_to_insn: .retpoline_sites");
 725                         return -1;
 726                 }
 727
 728                 idx++;
 729         }
 730
 731         return 0;
 732 }
 733
 734 static int create_mcount_loc_sections(struct objtool_file *file)
 735 {
 736         struct section *sec;
 737         unsigned long *loc;
 738         struct instruction *insn;
 739         int idx;
 740
 741         sec = find_section_by_name(file->elf, "__mcount_loc");
 742         if (sec) {
 743                 INIT_LIST_HEAD(&file->mcount_loc_list);
 744                 WARN("file already has __mcount_loc section, skipping");
 745                 return 0;
 746         }
 747
 748         if (list_empty(&file->mcount_loc_list))
 749                 return 0;
 750
 751         idx = 0;
 752         list_for_each_entry(insn, &file->mcount_loc_list, call_node)
 753                 idx++;
 754
 755         sec = elf_create_section(file->elf, "__mcount_loc", 0, sizeof(unsigned long), idx);
 756         if (!sec)
 757                 return -1;
 758
 759         idx = 0;
 760         list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
 761
 762                 loc = (unsigned long *)sec->data->d_buf + idx;
 763                 memset(loc, 0, sizeof(unsigned long));
 764
 765                 if (elf_add_reloc_to_insn(file->elf, sec,
 766                                           idx * sizeof(unsigned long),
 767                                           R_X86_64_64,
 768                                           insn->sec, insn->offset))
 769                         return -1;
 770
 771                 idx++;
 772         }
 773
 774         return 0;
 775 }
 776
 777 /*
 778  * Warnings shouldn't be reported for ignored functions.
 779  */
 780 static void add_ignores(struct objtool_file *file)
 781 {
 782         struct instruction *insn;
 783         struct section *sec;
 784         struct symbol *func;
 785         struct reloc *reloc;
 786
 787         sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
 788         if (!sec)
 789                 return;
 790
 791         list_for_each_entry(reloc, &sec->reloc_list, list) {
 792                 switch (reloc->sym->type) {
 793                 case STT_FUNC:
 794                         func = reloc->sym;
 795                         break;
 796
 797                 case STT_SECTION:
 798                         func = find_func_by_offset(reloc->sym->sec, reloc->addend);
 799                         if (!func)
 800                                 continue;
 801                         break;
 802
 803                 default:
 804                         WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type);
 805                         continue;
 806                 }
 807
 808                 func_for_each_insn(file, func, insn)
 809                         insn->ignore = true;
 810         }
 811 }
 812
 813 /*
 814  * This is a whitelist of functions that is allowed to be called with AC set.
 815  * The list is meant to be minimal and only contains compiler instrumentation
 816  * ABI and a few functions used to implement *_{to,from}_user() functions.
 817  *
 818  * These functions must not directly change AC, but may PUSHF/POPF.
 819  */
 820 static const char *uaccess_safe_builtin[] = {
 821         /* KASAN */
 822         "kasan_report",
 823         "kasan_check_range",
 824         /* KASAN out-of-line */
 825         "__asan_loadN_noabort",
 826         "__asan_load1_noabort",
 827         "__asan_load2_noabort",
 828         "__asan_load4_noabort",
 829         "__asan_load8_noabort",
 830         "__asan_load16_noabort",
 831         "__asan_storeN_noabort",
 832         "__asan_store1_noabort",
 833         "__asan_store2_noabort",
 834         "__asan_store4_noabort",
 835         "__asan_store8_noabort",
 836         "__asan_store16_noabort",
 837         "__kasan_check_read",
 838         "__kasan_check_write",
 839         /* KASAN in-line */
 840         "__asan_report_load_n_noabort",
 841         "__asan_report_load1_noabort",
 842         "__asan_report_load2_noabort",
 843         "__asan_report_load4_noabort",
 844         "__asan_report_load8_noabort",
 845         "__asan_report_load16_noabort",
 846         "__asan_report_store_n_noabort",
 847         "__asan_report_store1_noabort",
 848         "__asan_report_store2_noabort",
 849         "__asan_report_store4_noabort",
 850         "__asan_report_store8_noabort",
 851         "__asan_report_store16_noabort",
 852         /* KCSAN */
 853         "__kcsan_check_access",
 854         "__kcsan_mb",
 855         "__kcsan_wmb",
 856         "__kcsan_rmb",
 857         "__kcsan_release",
 858         "kcsan_found_watchpoint",
 859         "kcsan_setup_watchpoint",
 860         "kcsan_check_scoped_accesses",
 861         "kcsan_disable_current",
 862         "kcsan_enable_current_nowarn",
 863         /* KCSAN/TSAN */
 864         "__tsan_func_entry",
 865         "__tsan_func_exit",
 866         "__tsan_read_range",
 867         "__tsan_write_range",
 868         "__tsan_read1",
 869         "__tsan_read2",
 870         "__tsan_read4",
 871         "__tsan_read8",
 872         "__tsan_read16",
 873         "__tsan_write1",
 874         "__tsan_write2",
 875         "__tsan_write4",
 876         "__tsan_write8",
 877         "__tsan_write16",
 878         "__tsan_read_write1",
 879         "__tsan_read_write2",
 880         "__tsan_read_write4",
 881         "__tsan_read_write8",
 882         "__tsan_read_write16",
 883         "__tsan_atomic8_load",
 884         "__tsan_atomic16_load",
 885         "__tsan_atomic32_load",
 886         "__tsan_atomic64_load",
 887         "__tsan_atomic8_store",
 888         "__tsan_atomic16_store",
 889         "__tsan_atomic32_store",
 890         "__tsan_atomic64_store",
 891         "__tsan_atomic8_exchange",
 892         "__tsan_atomic16_exchange",
 893         "__tsan_atomic32_exchange",
 894         "__tsan_atomic64_exchange",
 895         "__tsan_atomic8_fetch_add",
 896         "__tsan_atomic16_fetch_add",
 897         "__tsan_atomic32_fetch_add",
 898         "__tsan_atomic64_fetch_add",
 899         "__tsan_atomic8_fetch_sub",
 900         "__tsan_atomic16_fetch_sub",
 901         "__tsan_atomic32_fetch_sub",
 902         "__tsan_atomic64_fetch_sub",
 903         "__tsan_atomic8_fetch_and",
 904         "__tsan_atomic16_fetch_and",
 905         "__tsan_atomic32_fetch_and",
 906         "__tsan_atomic64_fetch_and",
 907         "__tsan_atomic8_fetch_or",
 908         "__tsan_atomic16_fetch_or",
 909         "__tsan_atomic32_fetch_or",
 910         "__tsan_atomic64_fetch_or",
 911         "__tsan_atomic8_fetch_xor",
 912         "__tsan_atomic16_fetch_xor",
 913         "__tsan_atomic32_fetch_xor",
 914         "__tsan_atomic64_fetch_xor",
 915         "__tsan_atomic8_fetch_nand",
 916         "__tsan_atomic16_fetch_nand",
 917         "__tsan_atomic32_fetch_nand",
 918         "__tsan_atomic64_fetch_nand",
 919         "__tsan_atomic8_compare_exchange_strong",
 920         "__tsan_atomic16_compare_exchange_strong",
 921         "__tsan_atomic32_compare_exchange_strong",
 922         "__tsan_atomic64_compare_exchange_strong",
 923         "__tsan_atomic8_compare_exchange_weak",
 924         "__tsan_atomic16_compare_exchange_weak",
 925         "__tsan_atomic32_compare_exchange_weak",
 926         "__tsan_atomic64_compare_exchange_weak",
 927         "__tsan_atomic8_compare_exchange_val",
 928         "__tsan_atomic16_compare_exchange_val",
 929         "__tsan_atomic32_compare_exchange_val",
 930         "__tsan_atomic64_compare_exchange_val",
 931         "__tsan_atomic_thread_fence",
 932         "__tsan_atomic_signal_fence",
 933         /* KCOV */
 934         "write_comp_data",
 935         "check_kcov_mode",
 936         "__sanitizer_cov_trace_pc",
 937         "__sanitizer_cov_trace_const_cmp1",
 938         "__sanitizer_cov_trace_const_cmp2",
 939         "__sanitizer_cov_trace_const_cmp4",
 940         "__sanitizer_cov_trace_const_cmp8",
 941         "__sanitizer_cov_trace_cmp1",
 942         "__sanitizer_cov_trace_cmp2",
 943         "__sanitizer_cov_trace_cmp4",
 944         "__sanitizer_cov_trace_cmp8",
 945         "__sanitizer_cov_trace_switch",
 946         /* UBSAN */
 947         "ubsan_type_mismatch_common",
 948         "__ubsan_handle_type_mismatch",
 949         "__ubsan_handle_type_mismatch_v1",
 950         "__ubsan_handle_shift_out_of_bounds",
 951         /* misc */
 952         "csum_partial_copy_generic",
 953         "copy_mc_fragile",
 954         "copy_mc_fragile_handle_tail",
 955         "copy_mc_enhanced_fast_string",
 956         "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
 957         NULL
 958 };
 959
 960 static void add_uaccess_safe(struct objtool_file *file)
 961 {
 962         struct symbol *func;
 963         const char **name;
 964
 965         if (!uaccess)
 966                 return;
 967
 968         for (name = uaccess_safe_builtin; *name; name++) {
 969                 func = find_symbol_by_name(file->elf, *name);
 970                 if (!func)
 971                         continue;
 972
 973                 func->uaccess_safe = true;
 974         }
 975 }
 976
 977 /*
 978  * FIXME: For now, just ignore any alternatives which add retpolines.  This is
 979  * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
 980  * But it at least allows objtool to understand the control flow *around* the
 981  * retpoline.
 982  */
 983 static int add_ignore_alternatives(struct objtool_file *file)
 984 {
 985         struct section *sec;
 986         struct reloc *reloc;
 987         struct instruction *insn;
 988
 989         sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
 990         if (!sec)
 991                 return 0;
 992
 993         list_for_each_entry(reloc, &sec->reloc_list, list) {
 994                 if (reloc->sym->type != STT_SECTION) {
 995                         WARN("unexpected relocation symbol type in %s", sec->name);
 996                         return -1;
 997                 }
 998
 999                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1000                 if (!insn) {
1001                         WARN("bad .discard.ignore_alts entry");
1002                         return -1;
1003                 }
1004
1005                 insn->ignore_alts = true;
1006         }
1007
1008         return 0;
1009 }
1010
1011 __weak bool arch_is_retpoline(struct symbol *sym)
1012 {
1013         return false;
1014 }
1015
1016 #define NEGATIVE_RELOC  ((void *)-1L)
1017
1018 static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
1019 {
1020         if (insn->reloc == NEGATIVE_RELOC)
1021                 return NULL;
1022
1023         if (!insn->reloc) {
1024                 if (!file)
1025                         return NULL;
1026
1027                 insn->reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1028                                                        insn->offset, insn->len);
1029                 if (!insn->reloc) {
1030                         insn->reloc = NEGATIVE_RELOC;
1031                         return NULL;
1032                 }
1033         }
1034
1035         return insn->reloc;
1036 }
1037
1038 static void remove_insn_ops(struct instruction *insn)
1039 {
1040         struct stack_op *op, *tmp;
1041
1042         list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
1043                 list_del(&op->list);
1044                 free(op);
1045         }
1046 }
1047
1048 static void annotate_call_site(struct objtool_file *file,
1049                                struct instruction *insn, bool sibling)
1050 {
1051         struct reloc *reloc = insn_reloc(file, insn);
1052         struct symbol *sym = insn->call_dest;
1053
1054         if (!sym)
1055                 sym = reloc->sym;
1056
1057         /*
1058          * Alternative replacement code is just template code which is
1059          * sometimes copied to the original instruction. For now, don't
1060          * annotate it. (In the future we might consider annotating the
1061          * original instruction if/when it ever makes sense to do so.)
1062          */
1063         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1064                 return;
1065
1066         if (sym->static_call_tramp) {
1067                 list_add_tail(&insn->call_node, &file->static_call_list);
1068                 return;
1069         }
1070
1071         if (sym->retpoline_thunk) {
1072                 list_add_tail(&insn->call_node, &file->retpoline_call_list);
1073                 return;
1074         }
1075
1076         /*
1077          * Many compilers cannot disable KCOV or sanitizer calls with a function
1078          * attribute so they need a little help, NOP out any such calls from
1079          * noinstr text.
1080          */
1081         if (insn->sec->noinstr && sym->profiling_func) {
1082                 if (reloc) {
1083                         reloc->type = R_NONE;
1084                         elf_write_reloc(file->elf, reloc);
1085                 }
1086
1087                 elf_write_insn(file->elf, insn->sec,
1088                                insn->offset, insn->len,
1089                                sibling ? arch_ret_insn(insn->len)
1090                                        : arch_nop_insn(insn->len));
1091
1092                 insn->type = sibling ? INSN_RETURN : INSN_NOP;
1093                 return;
1094         }
1095
1096         if (mcount && sym->fentry) {
1097                 if (sibling)
1098                         WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset);
1099
1100                 if (reloc) {
1101                         reloc->type = R_NONE;
1102                         elf_write_reloc(file->elf, reloc);
1103                 }
1104
1105                 elf_write_insn(file->elf, insn->sec,
1106                                insn->offset, insn->len,
1107                                arch_nop_insn(insn->len));
1108
1109                 insn->type = INSN_NOP;
1110
1111                 list_add_tail(&insn->call_node, &file->mcount_loc_list);
1112                 return;
1113         }
1114 }
1115
1116 static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1117                           struct symbol *dest, bool sibling)
1118 {
1119         insn->call_dest = dest;
1120         if (!dest)
1121                 return;
1122
1123         /*
1124          * Whatever stack impact regular CALLs have, should be undone
1125          * by the RETURN of the called function.
1126          *
1127          * Annotated intra-function calls retain the stack_ops but
1128          * are converted to JUMP, see read_intra_function_calls().
1129          */
1130         remove_insn_ops(insn);
1131
1132         annotate_call_site(file, insn, sibling);
1133 }
1134
1135 static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1136 {
1137         /*
1138          * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1139          * so convert them accordingly.
1140          */
1141         switch (insn->type) {
1142         case INSN_CALL:
1143                 insn->type = INSN_CALL_DYNAMIC;
1144                 break;
1145         case INSN_JUMP_UNCONDITIONAL:
1146                 insn->type = INSN_JUMP_DYNAMIC;
1147                 break;
1148         case INSN_JUMP_CONDITIONAL:
1149                 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1150                 break;
1151         default:
1152                 return;
1153         }
1154
1155         insn->retpoline_safe = true;
1156
1157         /*
1158          * Whatever stack impact regular CALLs have, should be undone
1159          * by the RETURN of the called function.
1160          *
1161          * Annotated intra-function calls retain the stack_ops but
1162          * are converted to JUMP, see read_intra_function_calls().
1163          */
1164         remove_insn_ops(insn);
1165
1166         annotate_call_site(file, insn, false);
1167 }
1168 /*
1169  * Find the destination instructions for all jumps.
1170  */
1171 static int add_jump_destinations(struct objtool_file *file)
1172 {
1173         struct instruction *insn;
1174         struct reloc *reloc;
1175         struct section *dest_sec;
1176         unsigned long dest_off;
1177
1178         for_each_insn(file, insn) {
1179                 if (!is_static_jump(insn))
1180                         continue;
1181
1182                 reloc = insn_reloc(file, insn);
1183                 if (!reloc) {
1184                         dest_sec = insn->sec;
1185                         dest_off = arch_jump_destination(insn);
1186                 } else if (reloc->sym->type == STT_SECTION) {
1187                         dest_sec = reloc->sym->sec;
1188                         dest_off = arch_dest_reloc_offset(reloc->addend);
1189                 } else if (reloc->sym->retpoline_thunk) {
1190                         add_retpoline_call(file, insn);
1191                         continue;
1192                 } else if (insn->func) {
1193                         /* internal or external sibling call (with reloc) */
1194                         add_call_dest(file, insn, reloc->sym, true);
1195                         continue;
1196                 } else if (reloc->sym->sec->idx) {
1197                         dest_sec = reloc->sym->sec;
1198                         dest_off = reloc->sym->sym.st_value +
1199                                    arch_dest_reloc_offset(reloc->addend);
1200                 } else {
1201                         /* non-func asm code jumping to another file */
1202                         continue;
1203                 }
1204
1205                 insn->jump_dest = find_insn(file, dest_sec, dest_off);
1206                 if (!insn->jump_dest) {
1207
1208                         /*
1209                          * This is a special case where an alt instruction
1210                          * jumps past the end of the section.  These are
1211                          * handled later in handle_group_alt().
1212                          */
1213                         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1214                                 continue;
1215
1216                         WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
1217                                   insn->sec, insn->offset, dest_sec->name,
1218                                   dest_off);
1219                         return -1;
1220                 }
1221
1222                 /*
1223                  * Cross-function jump.
1224                  */
1225                 if (insn->func && insn->jump_dest->func &&
1226                     insn->func != insn->jump_dest->func) {
1227
1228                         /*
1229                          * For GCC 8+, create parent/child links for any cold
1230                          * subfunctions.  This is _mostly_ redundant with a
1231                          * similar initialization in read_symbols().
1232                          *
1233                          * If a function has aliases, we want the *first* such
1234                          * function in the symbol table to be the subfunction's
1235                          * parent.  In that case we overwrite the
1236                          * initialization done in read_symbols().
1237                          *
1238                          * However this code can't completely replace the
1239                          * read_symbols() code because this doesn't detect the
1240                          * case where the parent function's only reference to a
1241                          * subfunction is through a jump table.
1242                          */
1243                         if (!strstr(insn->func->name, ".cold") &&
1244                             strstr(insn->jump_dest->func->name, ".cold")) {
1245                                 insn->func->cfunc = insn->jump_dest->func;
1246                                 insn->jump_dest->func->pfunc = insn->func;
1247
1248                         } else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
1249                                    insn->jump_dest->offset == insn->jump_dest->func->offset) {
1250                                 /* internal sibling call (without reloc) */
1251                                 add_call_dest(file, insn, insn->jump_dest->func, true);
1252                         }
1253                 }
1254         }
1255
1256         return 0;
1257 }
1258
1259 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1260 {
1261         struct symbol *call_dest;
1262
1263         call_dest = find_func_by_offset(sec, offset);
1264         if (!call_dest)
1265                 call_dest = find_symbol_by_offset(sec, offset);
1266
1267         return call_dest;
1268 }
1269
1270 /*
1271  * Find the destination instructions for all calls.
1272  */
1273 static int add_call_destinations(struct objtool_file *file)
1274 {
1275         struct instruction *insn;
1276         unsigned long dest_off;
1277         struct symbol *dest;
1278         struct reloc *reloc;
1279
1280         for_each_insn(file, insn) {
1281                 if (insn->type != INSN_CALL)
1282                         continue;
1283
1284                 reloc = insn_reloc(file, insn);
1285                 if (!reloc) {
1286                         dest_off = arch_jump_destination(insn);
1287                         dest = find_call_destination(insn->sec, dest_off);
1288
1289                         add_call_dest(file, insn, dest, false);
1290
1291                         if (insn->ignore)
1292                                 continue;
1293
1294                         if (!insn->call_dest) {
1295                                 WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);
1296                                 return -1;
1297                         }
1298
1299                         if (insn->func && insn->call_dest->type != STT_FUNC) {
1300                                 WARN_FUNC("unsupported call to non-function",
1301                                           insn->sec, insn->offset);
1302                                 return -1;
1303                         }
1304
1305                 } else if (reloc->sym->type == STT_SECTION) {
1306                         dest_off = arch_dest_reloc_offset(reloc->addend);
1307                         dest = find_call_destination(reloc->sym->sec, dest_off);
1308                         if (!dest) {
1309                                 WARN_FUNC("can't find call dest symbol at %s+0x%lx",
1310                                           insn->sec, insn->offset,
1311                                           reloc->sym->sec->name,
1312                                           dest_off);
1313                                 return -1;
1314                         }
1315
1316                         add_call_dest(file, insn, dest, false);
1317
1318                 } else if (reloc->sym->retpoline_thunk) {
1319                         add_retpoline_call(file, insn);
1320
1321                 } else
1322                         add_call_dest(file, insn, reloc->sym, false);
1323         }
1324
1325         return 0;
1326 }
1327
1328 /*
1329  * The .alternatives section requires some extra special care over and above
1330  * other special sections because alternatives are patched in place.
1331  */
1332 static int handle_group_alt(struct objtool_file *file,
1333                             struct special_alt *special_alt,
1334                             struct instruction *orig_insn,
1335                             struct instruction **new_insn)
1336 {
1337         struct instruction *last_orig_insn, *last_new_insn = NULL, *insn, *nop = NULL;
1338         struct alt_group *orig_alt_group, *new_alt_group;
1339         unsigned long dest_off;
1340
1341
1342         orig_alt_group = malloc(sizeof(*orig_alt_group));
1343         if (!orig_alt_group) {
1344                 WARN("malloc failed");
1345                 return -1;
1346         }
1347         orig_alt_group->cfi = calloc(special_alt->orig_len,
1348                                      sizeof(struct cfi_state *));
1349         if (!orig_alt_group->cfi) {
1350                 WARN("calloc failed");
1351                 return -1;
1352         }
1353
1354         last_orig_insn = NULL;
1355         insn = orig_insn;
1356         sec_for_each_insn_from(file, insn) {
1357                 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1358                         break;
1359
1360                 insn->alt_group = orig_alt_group;
1361                 last_orig_insn = insn;
1362         }
1363         orig_alt_group->orig_group = NULL;
1364         orig_alt_group->first_insn = orig_insn;
1365         orig_alt_group->last_insn = last_orig_insn;
1366
1367
1368         new_alt_group = malloc(sizeof(*new_alt_group));
1369         if (!new_alt_group) {
1370                 WARN("malloc failed");
1371                 return -1;
1372         }
1373
1374         if (special_alt->new_len < special_alt->orig_len) {
1375                 /*
1376                  * Insert a fake nop at the end to make the replacement
1377                  * alt_group the same size as the original.  This is needed to
1378                  * allow propagate_alt_cfi() to do its magic.  When the last
1379                  * instruction affects the stack, the instruction after it (the
1380                  * nop) will propagate the new state to the shared CFI array.
1381                  */
1382                 nop = malloc(sizeof(*nop));
1383                 if (!nop) {
1384                         WARN("malloc failed");
1385                         return -1;
1386                 }
1387                 memset(nop, 0, sizeof(*nop));
1388                 INIT_LIST_HEAD(&nop->alts);
1389                 INIT_LIST_HEAD(&nop->stack_ops);
1390
1391                 nop->sec = special_alt->new_sec;
1392                 nop->offset = special_alt->new_off + special_alt->new_len;
1393                 nop->len = special_alt->orig_len - special_alt->new_len;
1394                 nop->type = INSN_NOP;
1395                 nop->func = orig_insn->func;
1396                 nop->alt_group = new_alt_group;
1397                 nop->ignore = orig_insn->ignore_alts;
1398         }
1399
1400         if (!special_alt->new_len) {
1401                 *new_insn = nop;
1402                 goto end;
1403         }
1404
1405         insn = *new_insn;
1406         sec_for_each_insn_from(file, insn) {
1407                 struct reloc *alt_reloc;
1408
1409                 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1410                         break;
1411
1412                 last_new_insn = insn;
1413
1414                 insn->ignore = orig_insn->ignore_alts;
1415                 insn->func = orig_insn->func;
1416                 insn->alt_group = new_alt_group;
1417
1418                 /*
1419                  * Since alternative replacement code is copy/pasted by the
1420                  * kernel after applying relocations, generally such code can't
1421                  * have relative-address relocation references to outside the
1422                  * .altinstr_replacement section, unless the arch's
1423                  * alternatives code can adjust the relative offsets
1424                  * accordingly.
1425                  */
1426                 alt_reloc = insn_reloc(file, insn);
1427                 if (alt_reloc &&
1428                     !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1429
1430                         WARN_FUNC("unsupported relocation in alternatives section",
1431                                   insn->sec, insn->offset);
1432                         return -1;
1433                 }
1434
1435                 if (!is_static_jump(insn))
1436                         continue;
1437
1438                 if (!insn->immediate)
1439                         continue;
1440
1441                 dest_off = arch_jump_destination(insn);
1442                 if (dest_off == special_alt->new_off + special_alt->new_len)
1443                         insn->jump_dest = next_insn_same_sec(file, last_orig_insn);
1444
1445                 if (!insn->jump_dest) {
1446                         WARN_FUNC("can't find alternative jump destination",
1447                                   insn->sec, insn->offset);
1448                         return -1;
1449                 }
1450         }
1451
1452         if (!last_new_insn) {
1453                 WARN_FUNC("can't find last new alternative instruction",
1454                           special_alt->new_sec, special_alt->new_off);
1455                 return -1;
1456         }
1457
1458         if (nop)
1459                 list_add(&nop->list, &last_new_insn->list);
1460 end:
1461         new_alt_group->orig_group = orig_alt_group;
1462         new_alt_group->first_insn = *new_insn;
1463         new_alt_group->last_insn = nop ? : last_new_insn;
1464         new_alt_group->cfi = orig_alt_group->cfi;
1465         return 0;
1466 }
1467
1468 /*
1469  * A jump table entry can either convert a nop to a jump or a jump to a nop.
1470  * If the original instruction is a jump, make the alt entry an effective nop
1471  * by just skipping the original instruction.
1472  */
1473 static int handle_jump_alt(struct objtool_file *file,
1474                            struct special_alt *special_alt,
1475                            struct instruction *orig_insn,
1476                            struct instruction **new_insn)
1477 {
1478         if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1479             orig_insn->type != INSN_NOP) {
1480
1481                 WARN_FUNC("unsupported instruction at jump label",
1482                           orig_insn->sec, orig_insn->offset);
1483                 return -1;
1484         }
1485
1486         if (special_alt->key_addend & 2) {
1487                 struct reloc *reloc = insn_reloc(file, orig_insn);
1488
1489                 if (reloc) {
1490                         reloc->type = R_NONE;
1491                         elf_write_reloc(file->elf, reloc);
1492                 }
1493                 elf_write_insn(file->elf, orig_insn->sec,
1494                                orig_insn->offset, orig_insn->len,
1495                                arch_nop_insn(orig_insn->len));
1496                 orig_insn->type = INSN_NOP;
1497         }
1498
1499         if (orig_insn->type == INSN_NOP) {
1500                 if (orig_insn->len == 2)
1501                         file->jl_nop_short++;
1502                 else
1503                         file->jl_nop_long++;
1504
1505                 return 0;
1506         }
1507
1508         if (orig_insn->len == 2)
1509                 file->jl_short++;
1510         else
1511                 file->jl_long++;
1512
1513         *new_insn = list_next_entry(orig_insn, list);
1514         return 0;
1515 }
1516
1517 /*
1518  * Read all the special sections which have alternate instructions which can be
1519  * patched in or redirected to at runtime.  Each instruction having alternate
1520  * instruction(s) has them added to its insn->alts list, which will be
1521  * traversed in validate_branch().
1522  */
1523 static int add_special_section_alts(struct objtool_file *file)
1524 {
1525         struct list_head special_alts;
1526         struct instruction *orig_insn, *new_insn;
1527         struct special_alt *special_alt, *tmp;
1528         struct alternative *alt;
1529         int ret;
1530
1531         ret = special_get_alts(file->elf, &special_alts);
1532         if (ret)
1533                 return ret;
1534
1535         list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1536
1537                 orig_insn = find_insn(file, special_alt->orig_sec,
1538                                       special_alt->orig_off);
1539                 if (!orig_insn) {
1540                         WARN_FUNC("special: can't find orig instruction",
1541                                   special_alt->orig_sec, special_alt->orig_off);
1542                         ret = -1;
1543                         goto out;
1544                 }
1545
1546                 new_insn = NULL;
1547                 if (!special_alt->group || special_alt->new_len) {
1548                         new_insn = find_insn(file, special_alt->new_sec,
1549                                              special_alt->new_off);
1550                         if (!new_insn) {
1551                                 WARN_FUNC("special: can't find new instruction",
1552                                           special_alt->new_sec,
1553                                           special_alt->new_off);
1554                                 ret = -1;
1555                                 goto out;
1556                         }
1557                 }
1558
1559                 if (special_alt->group) {
1560                         if (!special_alt->orig_len) {
1561                                 WARN_FUNC("empty alternative entry",
1562                                           orig_insn->sec, orig_insn->offset);
1563                                 continue;
1564                         }
1565
1566                         ret = handle_group_alt(file, special_alt, orig_insn,
1567                                                &new_insn);
1568                         if (ret)
1569                                 goto out;
1570                 } else if (special_alt->jump_or_nop) {
1571                         ret = handle_jump_alt(file, special_alt, orig_insn,
1572                                               &new_insn);
1573                         if (ret)
1574                                 goto out;
1575                 }
1576
1577                 alt = malloc(sizeof(*alt));
1578                 if (!alt) {
1579                         WARN("malloc failed");
1580                         ret = -1;
1581                         goto out;
1582                 }
1583
1584                 alt->insn = new_insn;
1585                 alt->skip_orig = special_alt->skip_orig;
1586                 orig_insn->ignore_alts |= special_alt->skip_alt;
1587                 list_add_tail(&alt->list, &orig_insn->alts);
1588
1589                 list_del(&special_alt->list);
1590                 free(special_alt);
1591         }
1592
1593         if (stats) {
1594                 printf("jl\\\tNOP\tJMP\n");
1595                 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
1596                 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
1597         }
1598
1599 out:
1600         return ret;
1601 }
1602
1603 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
1604                             struct reloc *table)
1605 {
1606         struct reloc *reloc = table;
1607         struct instruction *dest_insn;
1608         struct alternative *alt;
1609         struct symbol *pfunc = insn->func->pfunc;
1610         unsigned int prev_offset = 0;
1611
1612         /*
1613          * Each @reloc is a switch table relocation which points to the target
1614          * instruction.
1615          */
1616         list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
1617
1618                 /* Check for the end of the table: */
1619                 if (reloc != table && reloc->jump_table_start)
1620                         break;
1621
1622                 /* Make sure the table entries are consecutive: */
1623                 if (prev_offset && reloc->offset != prev_offset + 8)
1624                         break;
1625
1626                 /* Detect function pointers from contiguous objects: */
1627                 if (reloc->sym->sec == pfunc->sec &&
1628                     reloc->addend == pfunc->offset)
1629                         break;
1630
1631                 dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
1632                 if (!dest_insn)
1633                         break;
1634
1635                 /* Make sure the destination is in the same function: */
1636                 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
1637                         break;
1638
1639                 alt = malloc(sizeof(*alt));
1640                 if (!alt) {
1641                         WARN("malloc failed");
1642                         return -1;
1643                 }
1644
1645                 alt->insn = dest_insn;
1646                 list_add_tail(&alt->list, &insn->alts);
1647                 prev_offset = reloc->offset;
1648         }
1649
1650         if (!prev_offset) {
1651                 WARN_FUNC("can't find switch jump table",
1652                           insn->sec, insn->offset);
1653                 return -1;
1654         }
1655
1656         return 0;
1657 }
1658
1659 /*
1660  * find_jump_table() - Given a dynamic jump, find the switch jump table
1661  * associated with it.
1662  */
1663 static struct reloc *find_jump_table(struct objtool_file *file,
1664                                       struct symbol *func,
1665                                       struct instruction *insn)
1666 {
1667         struct reloc *table_reloc;
1668         struct instruction *dest_insn, *orig_insn = insn;
1669
1670         /*
1671          * Backward search using the @first_jump_src links, these help avoid
1672          * much of the 'in between' code. Which avoids us getting confused by
1673          * it.
1674          */
1675         for (;
1676              insn && insn->func && insn->func->pfunc == func;
1677              insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
1678
1679                 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1680                         break;
1681
1682                 /* allow small jumps within the range */
1683                 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1684                     insn->jump_dest &&
1685                     (insn->jump_dest->offset <= insn->offset ||
1686                      insn->jump_dest->offset > orig_insn->offset))
1687                     break;
1688
1689                 table_reloc = arch_find_switch_table(file, insn);
1690                 if (!table_reloc)
1691                         continue;
1692                 dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
1693                 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1694                         continue;
1695
1696                 return table_reloc;
1697         }
1698
1699         return NULL;
1700 }
1701
1702 /*
1703  * First pass: Mark the head of each jump table so that in the next pass,
1704  * we know when a given jump table ends and the next one starts.
1705  */
1706 static void mark_func_jump_tables(struct objtool_file *file,
1707                                     struct symbol *func)
1708 {
1709         struct instruction *insn, *last = NULL;
1710         struct reloc *reloc;
1711
1712         func_for_each_insn(file, func, insn) {
1713                 if (!last)
1714                         last = insn;
1715
1716                 /*
1717                  * Store back-pointers for unconditional forward jumps such
1718                  * that find_jump_table() can back-track using those and
1719                  * avoid some potentially confusing code.
1720                  */
1721                 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1722                     insn->offset > last->offset &&
1723                     insn->jump_dest->offset > insn->offset &&
1724                     !insn->jump_dest->first_jump_src) {
1725
1726                         insn->jump_dest->first_jump_src = insn;
1727                         last = insn->jump_dest;
1728                 }
1729
1730                 if (insn->type != INSN_JUMP_DYNAMIC)
1731                         continue;
1732
1733                 reloc = find_jump_table(file, func, insn);
1734                 if (reloc) {
1735                         reloc->jump_table_start = true;
1736                         insn->jump_table = reloc;
1737                 }
1738         }
1739 }
1740
1741 static int add_func_jump_tables(struct objtool_file *file,
1742                                   struct symbol *func)
1743 {
1744         struct instruction *insn;
1745         int ret;
1746
1747         func_for_each_insn(file, func, insn) {
1748                 if (!insn->jump_table)
1749                         continue;
1750
1751                 ret = add_jump_table(file, insn, insn->jump_table);
1752                 if (ret)
1753                         return ret;
1754         }
1755
1756         return 0;
1757 }
1758
1759 /*
1760  * For some switch statements, gcc generates a jump table in the .rodata
1761  * section which contains a list of addresses within the function to jump to.
1762  * This finds these jump tables and adds them to the insn->alts lists.
1763  */
1764 static int add_jump_table_alts(struct objtool_file *file)
1765 {
1766         struct section *sec;
1767         struct symbol *func;
1768         int ret;
1769
1770         if (!file->rodata)
1771                 return 0;
1772
1773         for_each_sec(file, sec) {
1774                 list_for_each_entry(func, &sec->symbol_list, list) {
1775                         if (func->type != STT_FUNC)
1776                                 continue;
1777
1778                         mark_func_jump_tables(file, func);
1779                         ret = add_func_jump_tables(file, func);
1780                         if (ret)
1781                                 return ret;
1782                 }
1783         }
1784
1785         return 0;
1786 }
1787
1788 static void set_func_state(struct cfi_state *state)
1789 {
1790         state->cfa = initial_func_cfi.cfa;
1791         memcpy(&state->regs, &initial_func_cfi.regs,
1792                CFI_NUM_REGS * sizeof(struct cfi_reg));
1793         state->stack_size = initial_func_cfi.cfa.offset;
1794 }
1795
1796 static int read_unwind_hints(struct objtool_file *file)
1797 {
1798         struct cfi_state cfi = init_cfi;
1799         struct section *sec, *relocsec;
1800         struct unwind_hint *hint;
1801         struct instruction *insn;
1802         struct reloc *reloc;
1803         int i;
1804
1805         sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1806         if (!sec)
1807                 return 0;
1808
1809         relocsec = sec->reloc;
1810         if (!relocsec) {
1811                 WARN("missing .rela.discard.unwind_hints section");
1812                 return -1;
1813         }
1814
1815         if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
1816                 WARN("struct unwind_hint size mismatch");
1817                 return -1;
1818         }
1819
1820         file->hints = true;
1821
1822         for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
1823                 hint = (struct unwind_hint *)sec->data->d_buf + i;
1824
1825                 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
1826                 if (!reloc) {
1827                         WARN("can't find reloc for unwind_hints[%d]", i);
1828                         return -1;
1829                 }
1830
1831                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1832                 if (!insn) {
1833                         WARN("can't find insn for unwind_hints[%d]", i);
1834                         return -1;
1835                 }
1836
1837                 insn->hint = true;
1838
1839                 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
1840                         insn->cfi = &func_cfi;
1841                         continue;
1842                 }
1843
1844                 if (insn->cfi)
1845                         cfi = *(insn->cfi);
1846
1847                 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
1848                         WARN_FUNC("unsupported unwind_hint sp base reg %d",
1849                                   insn->sec, insn->offset, hint->sp_reg);
1850                         return -1;
1851                 }
1852
1853                 cfi.cfa.offset = bswap_if_needed(hint->sp_offset);
1854                 cfi.type = hint->type;
1855                 cfi.end = hint->end;
1856
1857                 insn->cfi = cfi_hash_find_or_add(&cfi);
1858         }
1859
1860         return 0;
1861 }
1862
1863 static int read_retpoline_hints(struct objtool_file *file)
1864 {
1865         struct section *sec;
1866         struct instruction *insn;
1867         struct reloc *reloc;
1868
1869         sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1870         if (!sec)
1871                 return 0;
1872
1873         list_for_each_entry(reloc, &sec->reloc_list, list) {
1874                 if (reloc->sym->type != STT_SECTION) {
1875                         WARN("unexpected relocation symbol type in %s", sec->name);
1876                         return -1;
1877                 }
1878
1879                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1880                 if (!insn) {
1881                         WARN("bad .discard.retpoline_safe entry");
1882                         return -1;
1883                 }
1884
1885                 if (insn->type != INSN_JUMP_DYNAMIC &&
1886                     insn->type != INSN_CALL_DYNAMIC) {
1887                         WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1888                                   insn->sec, insn->offset);
1889                         return -1;
1890                 }
1891
1892                 insn->retpoline_safe = true;
1893         }
1894
1895         return 0;
1896 }
1897
1898 static int read_instr_hints(struct objtool_file *file)
1899 {
1900         struct section *sec;
1901         struct instruction *insn;
1902         struct reloc *reloc;
1903
1904         sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
1905         if (!sec)
1906                 return 0;
1907
1908         list_for_each_entry(reloc, &sec->reloc_list, list) {
1909                 if (reloc->sym->type != STT_SECTION) {
1910                         WARN("unexpected relocation symbol type in %s", sec->name);
1911                         return -1;
1912                 }
1913
1914                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1915                 if (!insn) {
1916                         WARN("bad .discard.instr_end entry");
1917                         return -1;
1918                 }
1919
1920                 insn->instr--;
1921         }
1922
1923         sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
1924         if (!sec)
1925                 return 0;
1926
1927         list_for_each_entry(reloc, &sec->reloc_list, list) {
1928                 if (reloc->sym->type != STT_SECTION) {
1929                         WARN("unexpected relocation symbol type in %s", sec->name);
1930                         return -1;
1931                 }
1932
1933                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1934                 if (!insn) {
1935                         WARN("bad .discard.instr_begin entry");
1936                         return -1;
1937                 }
1938
1939                 insn->instr++;
1940         }
1941
1942         return 0;
1943 }
1944
1945 static int read_intra_function_calls(struct objtool_file *file)
1946 {
1947         struct instruction *insn;
1948         struct section *sec;
1949         struct reloc *reloc;
1950
1951         sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
1952         if (!sec)
1953                 return 0;
1954
1955         list_for_each_entry(reloc, &sec->reloc_list, list) {
1956                 unsigned long dest_off;
1957
1958                 if (reloc->sym->type != STT_SECTION) {
1959                         WARN("unexpected relocation symbol type in %s",
1960                              sec->name);
1961                         return -1;
1962                 }
1963
1964                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1965                 if (!insn) {
1966                         WARN("bad .discard.intra_function_call entry");
1967                         return -1;
1968                 }
1969
1970                 if (insn->type != INSN_CALL) {
1971                         WARN_FUNC("intra_function_call not a direct call",
1972                                   insn->sec, insn->offset);
1973                         return -1;
1974                 }
1975
1976                 /*
1977                  * Treat intra-function CALLs as JMPs, but with a stack_op.
1978                  * See add_call_destinations(), which strips stack_ops from
1979                  * normal CALLs.
1980                  */
1981                 insn->type = INSN_JUMP_UNCONDITIONAL;
1982
1983                 dest_off = insn->offset + insn->len + insn->immediate;
1984                 insn->jump_dest = find_insn(file, insn->sec, dest_off);
1985                 if (!insn->jump_dest) {
1986                         WARN_FUNC("can't find call dest at %s+0x%lx",
1987                                   insn->sec, insn->offset,
1988                                   insn->sec->name, dest_off);
1989                         return -1;
1990                 }
1991         }
1992
1993         return 0;
1994 }
1995
1996 /*
1997  * Return true if name matches an instrumentation function, where calls to that
1998  * function from noinstr code can safely be removed, but compilers won't do so.
1999  */
2000 static bool is_profiling_func(const char *name)
2001 {
2002         /*
2003          * Many compilers cannot disable KCOV with a function attribute.
2004          */
2005         if (!strncmp(name, "__sanitizer_cov_", 16))
2006                 return true;
2007
2008         /*
2009          * Some compilers currently do not remove __tsan_func_entry/exit nor
2010          * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2011          * the __no_sanitize_thread attribute, remove them. Once the kernel's
2012          * minimum Clang version is 14.0, this can be removed.
2013          */
2014         if (!strncmp(name, "__tsan_func_", 12) ||
2015             !strcmp(name, "__tsan_atomic_signal_fence"))
2016                 return true;
2017
2018         return false;
2019 }
2020
2021 static int classify_symbols(struct objtool_file *file)
2022 {
2023         struct section *sec;
2024         struct symbol *func;
2025
2026         for_each_sec(file, sec) {
2027                 list_for_each_entry(func, &sec->symbol_list, list) {
2028                         if (func->bind != STB_GLOBAL)
2029                                 continue;
2030
2031                         if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2032                                      strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2033                                 func->static_call_tramp = true;
2034
2035                         if (arch_is_retpoline(func))
2036                                 func->retpoline_thunk = true;
2037
2038                         if (!strcmp(func->name, "__fentry__"))
2039                                 func->fentry = true;
2040
2041                         if (is_profiling_func(func->name))
2042                                 func->profiling_func = true;
2043                 }
2044         }
2045
2046         return 0;
2047 }
2048
2049 static void mark_rodata(struct objtool_file *file)
2050 {
2051         struct section *sec;
2052         bool found = false;
2053
2054         /*
2055          * Search for the following rodata sections, each of which can
2056          * potentially contain jump tables:
2057          *
2058          * - .rodata: can contain GCC switch tables
2059          * - .rodata.<func>: same, if -fdata-sections is being used
2060          * - .rodata..c_jump_table: contains C annotated jump tables
2061          *
2062          * .rodata.str1.* sections are ignored; they don't contain jump tables.
2063          */
2064         for_each_sec(file, sec) {
2065                 if (!strncmp(sec->name, ".rodata", 7) &&
2066                     !strstr(sec->name, ".str1.")) {
2067                         sec->rodata = true;
2068                         found = true;
2069                 }
2070         }
2071
2072         file->rodata = found;
2073 }
2074
2075 static int decode_sections(struct objtool_file *file)
2076 {
2077         int ret;
2078
2079         mark_rodata(file);
2080
2081         ret = init_pv_ops(file);
2082         if (ret)
2083                 return ret;
2084
2085         ret = decode_instructions(file);
2086         if (ret)
2087                 return ret;
2088
2089         ret = add_dead_ends(file);
2090         if (ret)
2091                 return ret;
2092
2093         add_ignores(file);
2094         add_uaccess_safe(file);
2095
2096         ret = add_ignore_alternatives(file);
2097         if (ret)
2098                 return ret;
2099
2100         /*
2101          * Must be before add_{jump_call}_destination.
2102          */
2103         ret = classify_symbols(file);
2104         if (ret)
2105                 return ret;
2106
2107         /*
2108          * Must be before add_special_section_alts() as that depends on
2109          * jump_dest being set.
2110          */
2111         ret = add_jump_destinations(file);
2112         if (ret)
2113                 return ret;
2114
2115         ret = add_special_section_alts(file);
2116         if (ret)
2117                 return ret;
2118
2119         /*
2120          * Must be before add_call_destination(); it changes INSN_CALL to
2121          * INSN_JUMP.
2122          */
2123         ret = read_intra_function_calls(file);
2124         if (ret)
2125                 return ret;
2126
2127         ret = add_call_destinations(file);
2128         if (ret)
2129                 return ret;
2130
2131         ret = add_jump_table_alts(file);
2132         if (ret)
2133                 return ret;
2134
2135         ret = read_unwind_hints(file);
2136         if (ret)
2137                 return ret;
2138
2139         ret = read_retpoline_hints(file);
2140         if (ret)
2141                 return ret;
2142
2143         ret = read_instr_hints(file);
2144         if (ret)
2145                 return ret;
2146
2147         return 0;
2148 }
2149
2150 static bool is_fentry_call(struct instruction *insn)
2151 {
2152         if (insn->type == INSN_CALL &&
2153             insn->call_dest &&
2154             insn->call_dest->fentry)
2155                 return true;
2156
2157         return false;
2158 }
2159
2160 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2161 {
2162         struct cfi_state *cfi = &state->cfi;
2163         int i;
2164
2165         if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2166                 return true;
2167
2168         if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2169                 return true;
2170
2171         if (cfi->stack_size != initial_func_cfi.cfa.offset)
2172                 return true;
2173
2174         for (i = 0; i < CFI_NUM_REGS; i++) {
2175                 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2176                     cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2177                         return true;
2178         }
2179
2180         return false;
2181 }
2182
2183 static bool check_reg_frame_pos(const struct cfi_reg *reg,
2184                                 int expected_offset)
2185 {
2186         return reg->base == CFI_CFA &&
2187                reg->offset == expected_offset;
2188 }
2189
2190 static bool has_valid_stack_frame(struct insn_state *state)
2191 {
2192         struct cfi_state *cfi = &state->cfi;
2193
2194         if (cfi->cfa.base == CFI_BP &&
2195             check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2196             check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2197                 return true;
2198
2199         if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2200                 return true;
2201
2202         return false;
2203 }
2204
2205 static int update_cfi_state_regs(struct instruction *insn,
2206                                   struct cfi_state *cfi,
2207                                   struct stack_op *op)
2208 {
2209         struct cfi_reg *cfa = &cfi->cfa;
2210
2211         if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2212                 return 0;
2213
2214         /* push */
2215         if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2216                 cfa->offset += 8;
2217
2218         /* pop */
2219         if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2220                 cfa->offset -= 8;
2221
2222         /* add immediate to sp */
2223         if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2224             op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2225                 cfa->offset -= op->src.offset;
2226
2227         return 0;
2228 }
2229
2230 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2231 {
2232         if (arch_callee_saved_reg(reg) &&
2233             cfi->regs[reg].base == CFI_UNDEFINED) {
2234                 cfi->regs[reg].base = base;
2235                 cfi->regs[reg].offset = offset;
2236         }
2237 }
2238
2239 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2240 {
2241         cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2242         cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2243 }
2244
2245 /*
2246  * A note about DRAP stack alignment:
2247  *
2248  * GCC has the concept of a DRAP register, which is used to help keep track of
2249  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
2250  * register.  The typical DRAP pattern is:
2251  *
2252  *   4c 8d 54 24 08             lea    0x8(%rsp),%r10
2253  *   48 83 e4 c0                and    $0xffffffffffffffc0,%rsp
2254  *   41 ff 72 f8                pushq  -0x8(%r10)
2255  *   55                         push   %rbp
2256  *   48 89 e5                   mov    %rsp,%rbp
2257  *                              (more pushes)
2258  *   41 52                      push   %r10
2259  *                              ...
2260  *   41 5a                      pop    %r10
2261  *                              (more pops)
2262  *   5d                         pop    %rbp
2263  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2264  *   c3                         retq
2265  *
2266  * There are some variations in the epilogues, like:
2267  *
2268  *   5b                         pop    %rbx
2269  *   41 5a                      pop    %r10
2270  *   41 5c                      pop    %r12
2271  *   41 5d                      pop    %r13
2272  *   41 5e                      pop    %r14
2273  *   c9                         leaveq
2274  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2275  *   c3                         retq
2276  *
2277  * and:
2278  *
2279  *   4c 8b 55 e8                mov    -0x18(%rbp),%r10
2280  *   48 8b 5d e0                mov    -0x20(%rbp),%rbx
2281  *   4c 8b 65 f0                mov    -0x10(%rbp),%r12
2282  *   4c 8b 6d f8                mov    -0x8(%rbp),%r13
2283  *   c9                         leaveq
2284  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2285  *   c3                         retq
2286  *
2287  * Sometimes r13 is used as the DRAP register, in which case it's saved and
2288  * restored beforehand:
2289  *
2290  *   41 55                      push   %r13
2291  *   4c 8d 6c 24 10             lea    0x10(%rsp),%r13
2292  *   48 83 e4 f0                and    $0xfffffffffffffff0,%rsp
2293  *                              ...
2294  *   49 8d 65 f0                lea    -0x10(%r13),%rsp
2295  *   41 5d                      pop    %r13
2296  *   c3                         retq
2297  */
2298 static int update_cfi_state(struct instruction *insn,
2299                             struct instruction *next_insn,
2300                             struct cfi_state *cfi, struct stack_op *op)
2301 {
2302         struct cfi_reg *cfa = &cfi->cfa;
2303         struct cfi_reg *regs = cfi->regs;
2304
2305         /* stack operations don't make sense with an undefined CFA */
2306         if (cfa->base == CFI_UNDEFINED) {
2307                 if (insn->func) {
2308                         WARN_FUNC("undefined stack state", insn->sec, insn->offset);
2309                         return -1;
2310                 }
2311                 return 0;
2312         }
2313
2314         if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2315             cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2316                 return update_cfi_state_regs(insn, cfi, op);
2317
2318         switch (op->dest.type) {
2319
2320         case OP_DEST_REG:
2321                 switch (op->src.type) {
2322
2323                 case OP_SRC_REG:
2324                         if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2325                             cfa->base == CFI_SP &&
2326                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset)) {
2327
2328                                 /* mov %rsp, %rbp */
2329                                 cfa->base = op->dest.reg;
2330                                 cfi->bp_scratch = false;
2331                         }
2332
2333                         else if (op->src.reg == CFI_SP &&
2334                                  op->dest.reg == CFI_BP && cfi->drap) {
2335
2336                                 /* drap: mov %rsp, %rbp */
2337                                 regs[CFI_BP].base = CFI_BP;
2338                                 regs[CFI_BP].offset = -cfi->stack_size;
2339                                 cfi->bp_scratch = false;
2340                         }
2341
2342                         else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2343
2344                                 /*
2345                                  * mov %rsp, %reg
2346                                  *
2347                                  * This is needed for the rare case where GCC
2348                                  * does:
2349                                  *
2350                                  *   mov    %rsp, %rax
2351                                  *   ...
2352                                  *   mov    %rax, %rsp
2353                                  */
2354                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2355                                 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2356                         }
2357
2358                         else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2359                                  (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2360
2361                                 /*
2362                                  * mov %rbp, %rsp
2363                                  *
2364                                  * Restore the original stack pointer (Clang).
2365                                  */
2366                                 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2367                         }
2368
2369                         else if (op->dest.reg == cfa->base) {
2370
2371                                 /* mov %reg, %rsp */
2372                                 if (cfa->base == CFI_SP &&
2373                                     cfi->vals[op->src.reg].base == CFI_CFA) {
2374
2375                                         /*
2376                                          * This is needed for the rare case
2377                                          * where GCC does something dumb like:
2378                                          *
2379                                          *   lea    0x8(%rsp), %rcx
2380                                          *   ...
2381                                          *   mov    %rcx, %rsp
2382                                          */
2383                                         cfa->offset = -cfi->vals[op->src.reg].offset;
2384                                         cfi->stack_size = cfa->offset;
2385
2386                                 } else if (cfa->base == CFI_SP &&
2387                                            cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2388                                            cfi->vals[op->src.reg].offset == cfa->offset) {
2389
2390                                         /*
2391                                          * Stack swizzle:
2392                                          *
2393                                          * 1: mov %rsp, (%[tos])
2394                                          * 2: mov %[tos], %rsp
2395                                          *    ...
2396                                          * 3: pop %rsp
2397                                          *
2398                                          * Where:
2399                                          *
2400                                          * 1 - places a pointer to the previous
2401                                          *     stack at the Top-of-Stack of the
2402                                          *     new stack.
2403                                          *
2404                                          * 2 - switches to the new stack.
2405                                          *
2406                                          * 3 - pops the Top-of-Stack to restore
2407                                          *     the original stack.
2408                                          *
2409                                          * Note: we set base to SP_INDIRECT
2410                                          * here and preserve offset. Therefore
2411                                          * when the unwinder reaches ToS it
2412                                          * will dereference SP and then add the
2413                                          * offset to find the next frame, IOW:
2414                                          * (%rsp) + offset.
2415                                          */
2416                                         cfa->base = CFI_SP_INDIRECT;
2417
2418                                 } else {
2419                                         cfa->base = CFI_UNDEFINED;
2420                                         cfa->offset = 0;
2421                                 }
2422                         }
2423
2424                         else if (op->dest.reg == CFI_SP &&
2425                                  cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2426                                  cfi->vals[op->src.reg].offset == cfa->offset) {
2427
2428                                 /*
2429                                  * The same stack swizzle case 2) as above. But
2430                                  * because we can't change cfa->base, case 3)
2431                                  * will become a regular POP. Pretend we're a
2432                                  * PUSH so things don't go unbalanced.
2433                                  */
2434                                 cfi->stack_size += 8;
2435                         }
2436
2437
2438                         break;
2439
2440                 case OP_SRC_ADD:
2441                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2442
2443                                 /* add imm, %rsp */
2444                                 cfi->stack_size -= op->src.offset;
2445                                 if (cfa->base == CFI_SP)
2446                                         cfa->offset -= op->src.offset;
2447                                 break;
2448                         }
2449
2450                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2451
2452                                 /* lea disp(%rbp), %rsp */
2453                                 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2454                                 break;
2455                         }
2456
2457                         if (!cfi->drap && op->src.reg == CFI_SP &&
2458                             op->dest.reg == CFI_BP && cfa->base == CFI_SP &&
2459                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset + op->src.offset)) {
2460
2461                                 /* lea disp(%rsp), %rbp */
2462                                 cfa->base = CFI_BP;
2463                                 cfa->offset -= op->src.offset;
2464                                 cfi->bp_scratch = false;
2465                                 break;
2466                         }
2467
2468                         if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2469
2470                                 /* drap: lea disp(%rsp), %drap */
2471                                 cfi->drap_reg = op->dest.reg;
2472
2473                                 /*
2474                                  * lea disp(%rsp), %reg
2475                                  *
2476                                  * This is needed for the rare case where GCC
2477                                  * does something dumb like:
2478                                  *
2479                                  *   lea    0x8(%rsp), %rcx
2480                                  *   ...
2481                                  *   mov    %rcx, %rsp
2482                                  */
2483                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2484                                 cfi->vals[op->dest.reg].offset = \
2485                                         -cfi->stack_size + op->src.offset;
2486
2487                                 break;
2488                         }
2489
2490                         if (cfi->drap && op->dest.reg == CFI_SP &&
2491                             op->src.reg == cfi->drap_reg) {
2492
2493                                  /* drap: lea disp(%drap), %rsp */
2494                                 cfa->base = CFI_SP;
2495                                 cfa->offset = cfi->stack_size = -op->src.offset;
2496                                 cfi->drap_reg = CFI_UNDEFINED;
2497                                 cfi->drap = false;
2498                                 break;
2499                         }
2500
2501                         if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
2502                                 WARN_FUNC("unsupported stack register modification",
2503                                           insn->sec, insn->offset);
2504                                 return -1;
2505                         }
2506
2507                         break;
2508
2509                 case OP_SRC_AND:
2510                         if (op->dest.reg != CFI_SP ||
2511                             (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
2512                             (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
2513                                 WARN_FUNC("unsupported stack pointer realignment",
2514                                           insn->sec, insn->offset);
2515                                 return -1;
2516                         }
2517
2518                         if (cfi->drap_reg != CFI_UNDEFINED) {
2519                                 /* drap: and imm, %rsp */
2520                                 cfa->base = cfi->drap_reg;
2521                                 cfa->offset = cfi->stack_size = 0;
2522                                 cfi->drap = true;
2523                         }
2524
2525                         /*
2526                          * Older versions of GCC (4.8ish) realign the stack
2527                          * without DRAP, with a frame pointer.
2528                          */
2529
2530                         break;
2531
2532                 case OP_SRC_POP:
2533                 case OP_SRC_POPF:
2534                         if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
2535
2536                                 /* pop %rsp; # restore from a stack swizzle */
2537                                 cfa->base = CFI_SP;
2538                                 break;
2539                         }
2540
2541                         if (!cfi->drap && op->dest.reg == cfa->base) {
2542
2543                                 /* pop %rbp */
2544                                 cfa->base = CFI_SP;
2545                         }
2546
2547                         if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
2548                             op->dest.reg == cfi->drap_reg &&
2549                             cfi->drap_offset == -cfi->stack_size) {
2550
2551                                 /* drap: pop %drap */
2552                                 cfa->base = cfi->drap_reg;
2553                                 cfa->offset = 0;
2554                                 cfi->drap_offset = -1;
2555
2556                         } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
2557
2558                                 /* pop %reg */
2559                                 restore_reg(cfi, op->dest.reg);
2560                         }
2561
2562                         cfi->stack_size -= 8;
2563                         if (cfa->base == CFI_SP)
2564                                 cfa->offset -= 8;
2565
2566                         break;
2567
2568                 case OP_SRC_REG_INDIRECT:
2569                         if (!cfi->drap && op->dest.reg == cfa->base &&
2570                             op->dest.reg == CFI_BP) {
2571
2572                                 /* mov disp(%rsp), %rbp */
2573                                 cfa->base = CFI_SP;
2574                                 cfa->offset = cfi->stack_size;
2575                         }
2576
2577                         if (cfi->drap && op->src.reg == CFI_BP &&
2578                             op->src.offset == cfi->drap_offset) {
2579
2580                                 /* drap: mov disp(%rbp), %drap */
2581                                 cfa->base = cfi->drap_reg;
2582                                 cfa->offset = 0;
2583                                 cfi->drap_offset = -1;
2584                         }
2585
2586                         if (cfi->drap && op->src.reg == CFI_BP &&
2587                             op->src.offset == regs[op->dest.reg].offset) {
2588
2589                                 /* drap: mov disp(%rbp), %reg */
2590                                 restore_reg(cfi, op->dest.reg);
2591
2592                         } else if (op->src.reg == cfa->base &&
2593                             op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
2594
2595                                 /* mov disp(%rbp), %reg */
2596                                 /* mov disp(%rsp), %reg */
2597                                 restore_reg(cfi, op->dest.reg);
2598
2599                         } else if (op->src.reg == CFI_SP &&
2600                                    op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
2601
2602                                 /* mov disp(%rsp), %reg */
2603                                 restore_reg(cfi, op->dest.reg);
2604                         }
2605
2606                         break;
2607
2608                 default:
2609                         WARN_FUNC("unknown stack-related instruction",
2610                                   insn->sec, insn->offset);
2611                         return -1;
2612                 }
2613
2614                 break;
2615
2616         case OP_DEST_PUSH:
2617         case OP_DEST_PUSHF:
2618                 cfi->stack_size += 8;
2619                 if (cfa->base == CFI_SP)
2620                         cfa->offset += 8;
2621
2622                 if (op->src.type != OP_SRC_REG)
2623                         break;
2624
2625                 if (cfi->drap) {
2626                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2627
2628                                 /* drap: push %drap */
2629                                 cfa->base = CFI_BP_INDIRECT;
2630                                 cfa->offset = -cfi->stack_size;
2631
2632                                 /* save drap so we know when to restore it */
2633                                 cfi->drap_offset = -cfi->stack_size;
2634
2635                         } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
2636
2637                                 /* drap: push %rbp */
2638                                 cfi->stack_size = 0;
2639
2640                         } else {
2641
2642                                 /* drap: push %reg */
2643                                 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
2644                         }
2645
2646                 } else {
2647
2648                         /* push %reg */
2649                         save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
2650                 }
2651
2652                 /* detect when asm code uses rbp as a scratch register */
2653                 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
2654                     cfa->base != CFI_BP)
2655                         cfi->bp_scratch = true;
2656                 break;
2657
2658         case OP_DEST_REG_INDIRECT:
2659
2660                 if (cfi->drap) {
2661                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2662
2663                                 /* drap: mov %drap, disp(%rbp) */
2664                                 cfa->base = CFI_BP_INDIRECT;
2665                                 cfa->offset = op->dest.offset;
2666
2667                                 /* save drap offset so we know when to restore it */
2668                                 cfi->drap_offset = op->dest.offset;
2669                         } else {
2670
2671                                 /* drap: mov reg, disp(%rbp) */
2672                                 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
2673                         }
2674
2675                 } else if (op->dest.reg == cfa->base) {
2676
2677                         /* mov reg, disp(%rbp) */
2678                         /* mov reg, disp(%rsp) */
2679                         save_reg(cfi, op->src.reg, CFI_CFA,
2680                                  op->dest.offset - cfi->cfa.offset);
2681
2682                 } else if (op->dest.reg == CFI_SP) {
2683
2684                         /* mov reg, disp(%rsp) */
2685                         save_reg(cfi, op->src.reg, CFI_CFA,
2686                                  op->dest.offset - cfi->stack_size);
2687
2688                 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
2689
2690                         /* mov %rsp, (%reg); # setup a stack swizzle. */
2691                         cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
2692                         cfi->vals[op->dest.reg].offset = cfa->offset;
2693                 }
2694
2695                 break;
2696
2697         case OP_DEST_MEM:
2698                 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
2699                         WARN_FUNC("unknown stack-related memory operation",
2700                                   insn->sec, insn->offset);
2701                         return -1;
2702                 }
2703
2704                 /* pop mem */
2705                 cfi->stack_size -= 8;
2706                 if (cfa->base == CFI_SP)
2707                         cfa->offset -= 8;
2708
2709                 break;
2710
2711         default:
2712                 WARN_FUNC("unknown stack-related instruction",
2713                           insn->sec, insn->offset);
2714                 return -1;
2715         }
2716
2717         return 0;
2718 }
2719
2720 /*
2721  * The stack layouts of alternatives instructions can sometimes diverge when
2722  * they have stack modifications.  That's fine as long as the potential stack
2723  * layouts don't conflict at any given potential instruction boundary.
2724  *
2725  * Flatten the CFIs of the different alternative code streams (both original
2726  * and replacement) into a single shared CFI array which can be used to detect
2727  * conflicts and nicely feed a linear array of ORC entries to the unwinder.
2728  */
2729 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
2730 {
2731         struct cfi_state **alt_cfi;
2732         int group_off;
2733
2734         if (!insn->alt_group)
2735                 return 0;
2736
2737         if (!insn->cfi) {
2738                 WARN("CFI missing");
2739                 return -1;
2740         }
2741
2742         alt_cfi = insn->alt_group->cfi;
2743         group_off = insn->offset - insn->alt_group->first_insn->offset;
2744
2745         if (!alt_cfi[group_off]) {
2746                 alt_cfi[group_off] = insn->cfi;
2747         } else {
2748                 if (cficmp(alt_cfi[group_off], insn->cfi)) {
2749                         WARN_FUNC("stack layout conflict in alternatives",
2750                                   insn->sec, insn->offset);
2751                         return -1;
2752                 }
2753         }
2754
2755         return 0;
2756 }
2757
2758 static int handle_insn_ops(struct instruction *insn,
2759                            struct instruction *next_insn,
2760                            struct insn_state *state)
2761 {
2762         struct stack_op *op;
2763
2764         list_for_each_entry(op, &insn->stack_ops, list) {
2765
2766                 if (update_cfi_state(insn, next_insn, &state->cfi, op))
2767                         return 1;
2768
2769                 if (!insn->alt_group)
2770                         continue;
2771
2772                 if (op->dest.type == OP_DEST_PUSHF) {
2773                         if (!state->uaccess_stack) {
2774                                 state->uaccess_stack = 1;
2775                         } else if (state->uaccess_stack >> 31) {
2776                                 WARN_FUNC("PUSHF stack exhausted",
2777                                           insn->sec, insn->offset);
2778                                 return 1;
2779                         }
2780                         state->uaccess_stack <<= 1;
2781                         state->uaccess_stack  |= state->uaccess;
2782                 }
2783
2784                 if (op->src.type == OP_SRC_POPF) {
2785                         if (state->uaccess_stack) {
2786                                 state->uaccess = state->uaccess_stack & 1;
2787                                 state->uaccess_stack >>= 1;
2788                                 if (state->uaccess_stack == 1)
2789                                         state->uaccess_stack = 0;
2790                         }
2791                 }
2792         }
2793
2794         return 0;
2795 }
2796
2797 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
2798 {
2799         struct cfi_state *cfi1 = insn->cfi;
2800         int i;
2801
2802         if (!cfi1) {
2803                 WARN("CFI missing");
2804                 return false;
2805         }
2806
2807         if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
2808
2809                 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
2810                           insn->sec, insn->offset,
2811                           cfi1->cfa.base, cfi1->cfa.offset,
2812                           cfi2->cfa.base, cfi2->cfa.offset);
2813
2814         } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
2815                 for (i = 0; i < CFI_NUM_REGS; i++) {
2816                         if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
2817                                     sizeof(struct cfi_reg)))
2818                                 continue;
2819
2820                         WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
2821                                   insn->sec, insn->offset,
2822                                   i, cfi1->regs[i].base, cfi1->regs[i].offset,
2823                                   i, cfi2->regs[i].base, cfi2->regs[i].offset);
2824                         break;
2825                 }
2826
2827         } else if (cfi1->type != cfi2->type) {
2828
2829                 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
2830                           insn->sec, insn->offset, cfi1->type, cfi2->type);
2831
2832         } else if (cfi1->drap != cfi2->drap ||
2833                    (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
2834                    (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
2835
2836                 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
2837                           insn->sec, insn->offset,
2838                           cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
2839                           cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
2840
2841         } else
2842                 return true;
2843
2844         return false;
2845 }
2846
2847 static inline bool func_uaccess_safe(struct symbol *func)
2848 {
2849         if (func)
2850                 return func->uaccess_safe;
2851
2852         return false;
2853 }
2854
2855 static inline const char *call_dest_name(struct instruction *insn)
2856 {
2857         static char pvname[16];
2858         struct reloc *rel;
2859         int idx;
2860
2861         if (insn->call_dest)
2862                 return insn->call_dest->name;
2863
2864         rel = insn_reloc(NULL, insn);
2865         if (rel && !strcmp(rel->sym->name, "pv_ops")) {
2866                 idx = (rel->addend / sizeof(void *));
2867                 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
2868                 return pvname;
2869         }
2870
2871         return "{dynamic}";
2872 }
2873
2874 static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
2875 {
2876         struct symbol *target;
2877         struct reloc *rel;
2878         int idx;
2879
2880         rel = insn_reloc(file, insn);
2881         if (!rel || strcmp(rel->sym->name, "pv_ops"))
2882                 return false;
2883
2884         idx = (arch_dest_reloc_offset(rel->addend) / sizeof(void *));
2885
2886         if (file->pv_ops[idx].clean)
2887                 return true;
2888
2889         file->pv_ops[idx].clean = true;
2890
2891         list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
2892                 if (!target->sec->noinstr) {
2893                         WARN("pv_ops[%d]: %s", idx, target->name);
2894                         file->pv_ops[idx].clean = false;
2895                 }
2896         }
2897
2898         return file->pv_ops[idx].clean;
2899 }
2900
2901 static inline bool noinstr_call_dest(struct objtool_file *file,
2902                                      struct instruction *insn,
2903                                      struct symbol *func)
2904 {
2905         /*
2906          * We can't deal with indirect function calls at present;
2907          * assume they're instrumented.
2908          */
2909         if (!func) {
2910                 if (file->pv_ops)
2911                         return pv_call_dest(file, insn);
2912
2913                 return false;
2914         }
2915
2916         /*
2917          * If the symbol is from a noinstr section; we good.
2918          */
2919         if (func->sec->noinstr)
2920                 return true;
2921
2922         /*
2923          * The __ubsan_handle_*() calls are like WARN(), they only happen when
2924          * something 'BAD' happened. At the risk of taking the machine down,
2925          * let them proceed to get the message out.
2926          */
2927         if (!strncmp(func->name, "__ubsan_handle_", 15))
2928                 return true;
2929
2930         return false;
2931 }
2932
2933 static int validate_call(struct objtool_file *file,
2934                          struct instruction *insn,
2935                          struct insn_state *state)
2936 {
2937         if (state->noinstr && state->instr <= 0 &&
2938             !noinstr_call_dest(file, insn, insn->call_dest)) {
2939                 WARN_FUNC("call to %s() leaves .noinstr.text section",
2940                                 insn->sec, insn->offset, call_dest_name(insn));
2941                 return 1;
2942         }
2943
2944         if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
2945                 WARN_FUNC("call to %s() with UACCESS enabled",
2946                                 insn->sec, insn->offset, call_dest_name(insn));
2947                 return 1;
2948         }
2949
2950         if (state->df) {
2951                 WARN_FUNC("call to %s() with DF set",
2952                                 insn->sec, insn->offset, call_dest_name(insn));
2953                 return 1;
2954         }
2955
2956         return 0;
2957 }
2958
2959 static int validate_sibling_call(struct objtool_file *file,
2960                                  struct instruction *insn,
2961                                  struct insn_state *state)
2962 {
2963         if (has_modified_stack_frame(insn, state)) {
2964                 WARN_FUNC("sibling call from callable instruction with modified stack frame",
2965                                 insn->sec, insn->offset);
2966                 return 1;
2967         }
2968
2969         return validate_call(file, insn, state);
2970 }
2971
2972 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
2973 {
2974         if (state->noinstr && state->instr > 0) {
2975                 WARN_FUNC("return with instrumentation enabled",
2976                           insn->sec, insn->offset);
2977                 return 1;
2978         }
2979
2980         if (state->uaccess && !func_uaccess_safe(func)) {
2981                 WARN_FUNC("return with UACCESS enabled",
2982                           insn->sec, insn->offset);
2983                 return 1;
2984         }
2985
2986         if (!state->uaccess && func_uaccess_safe(func)) {
2987                 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
2988                           insn->sec, insn->offset);
2989                 return 1;
2990         }
2991
2992         if (state->df) {
2993                 WARN_FUNC("return with DF set",
2994                           insn->sec, insn->offset);
2995                 return 1;
2996         }
2997
2998         if (func && has_modified_stack_frame(insn, state)) {
2999                 WARN_FUNC("return with modified stack frame",
3000                           insn->sec, insn->offset);
3001                 return 1;
3002         }
3003
3004         if (state->cfi.bp_scratch) {
3005                 WARN_FUNC("BP used as a scratch register",
3006                           insn->sec, insn->offset);
3007                 return 1;
3008         }
3009
3010         return 0;
3011 }
3012
3013 static struct instruction *next_insn_to_validate(struct objtool_file *file,
3014                                                  struct instruction *insn)
3015 {
3016         struct alt_group *alt_group = insn->alt_group;
3017
3018         /*
3019          * Simulate the fact that alternatives are patched in-place.  When the
3020          * end of a replacement alt_group is reached, redirect objtool flow to
3021          * the end of the original alt_group.
3022          */
3023         if (alt_group && insn == alt_group->last_insn && alt_group->orig_group)
3024                 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3025
3026         return next_insn_same_sec(file, insn);
3027 }
3028
3029 /*
3030  * Follow the branch starting at the given instruction, and recursively follow
3031  * any other branches (jumps).  Meanwhile, track the frame pointer state at
3032  * each instruction and validate all the rules described in
3033  * tools/objtool/Documentation/stack-validation.txt.
3034  */
3035 static int validate_branch(struct objtool_file *file, struct symbol *func,
3036                            struct instruction *insn, struct insn_state state)
3037 {
3038         struct alternative *alt;
3039         struct instruction *next_insn, *prev_insn = NULL;
3040         struct section *sec;
3041         u8 visited;
3042         int ret;
3043
3044         sec = insn->sec;
3045
3046         while (1) {
3047                 next_insn = next_insn_to_validate(file, insn);
3048
3049                 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
3050                         WARN("%s() falls through to next function %s()",
3051                              func->name, insn->func->name);
3052                         return 1;
3053                 }
3054
3055                 if (func && insn->ignore) {
3056                         WARN_FUNC("BUG: why am I validating an ignored function?",
3057                                   sec, insn->offset);
3058                         return 1;
3059                 }
3060
3061                 visited = 1 << state.uaccess;
3062                 if (insn->visited) {
3063                         if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3064                                 return 1;
3065
3066                         if (insn->visited & visited)
3067                                 return 0;
3068                 } else {
3069                         nr_insns_visited++;
3070                 }
3071
3072                 if (state.noinstr)
3073                         state.instr += insn->instr;
3074
3075                 if (insn->hint) {
3076                         state.cfi = *insn->cfi;
3077                 } else {
3078                         /* XXX track if we actually changed state.cfi */
3079
3080                         if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3081                                 insn->cfi = prev_insn->cfi;
3082                                 nr_cfi_reused++;
3083                         } else {
3084                                 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3085                         }
3086                 }
3087
3088                 insn->visited |= visited;
3089
3090                 if (propagate_alt_cfi(file, insn))
3091                         return 1;
3092
3093                 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
3094                         bool skip_orig = false;
3095
3096                         list_for_each_entry(alt, &insn->alts, list) {
3097                                 if (alt->skip_orig)
3098                                         skip_orig = true;
3099
3100                                 ret = validate_branch(file, func, alt->insn, state);
3101                                 if (ret) {
3102                                         if (backtrace)
3103                                                 BT_FUNC("(alt)", insn);
3104                                         return ret;
3105                                 }
3106                         }
3107
3108                         if (skip_orig)
3109                                 return 0;
3110                 }
3111
3112                 if (handle_insn_ops(insn, next_insn, &state))
3113                         return 1;
3114
3115                 switch (insn->type) {
3116
3117                 case INSN_RETURN:
3118                         if (next_insn && next_insn->type == INSN_TRAP) {
3119                                 next_insn->ignore = true;
3120                         } else if (sls && !insn->retpoline_safe) {
3121                                 WARN_FUNC("missing int3 after ret",
3122                                           insn->sec, insn->offset);
3123                         }
3124                         return validate_return(func, insn, &state);
3125
3126                 case INSN_CALL:
3127                 case INSN_CALL_DYNAMIC:
3128                         ret = validate_call(file, insn, &state);
3129                         if (ret)
3130                                 return ret;
3131
3132                         if (!no_fp && func && !is_fentry_call(insn) &&
3133                             !has_valid_stack_frame(&state)) {
3134                                 WARN_FUNC("call without frame pointer save/setup",
3135                                           sec, insn->offset);
3136                                 return 1;
3137                         }
3138
3139                         if (dead_end_function(file, insn->call_dest))
3140                                 return 0;
3141
3142                         break;
3143
3144                 case INSN_JUMP_CONDITIONAL:
3145                 case INSN_JUMP_UNCONDITIONAL:
3146                         if (is_sibling_call(insn)) {
3147                                 ret = validate_sibling_call(file, insn, &state);
3148                                 if (ret)
3149                                         return ret;
3150
3151                         } else if (insn->jump_dest) {
3152                                 ret = validate_branch(file, func,
3153                                                       insn->jump_dest, state);
3154                                 if (ret) {
3155                                         if (backtrace)
3156                                                 BT_FUNC("(branch)", insn);
3157                                         return ret;
3158                                 }
3159                         }
3160
3161                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
3162                                 return 0;
3163
3164                         break;
3165
3166                 case INSN_JUMP_DYNAMIC:
3167                         if (next_insn && next_insn->type == INSN_TRAP) {
3168                                 next_insn->ignore = true;
3169                         } else if (sls && !insn->retpoline_safe) {
3170                                 WARN_FUNC("missing int3 after indirect jump",
3171                                           insn->sec, insn->offset);
3172                         }
3173
3174                         /* fallthrough */
3175                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3176                         if (is_sibling_call(insn)) {
3177                                 ret = validate_sibling_call(file, insn, &state);
3178                                 if (ret)
3179                                         return ret;
3180                         }
3181
3182                         if (insn->type == INSN_JUMP_DYNAMIC)
3183                                 return 0;
3184
3185                         break;
3186
3187                 case INSN_CONTEXT_SWITCH:
3188                         if (func && (!next_insn || !next_insn->hint)) {
3189                                 WARN_FUNC("unsupported instruction in callable function",
3190                                           sec, insn->offset);
3191                                 return 1;
3192                         }
3193                         return 0;
3194
3195                 case INSN_STAC:
3196                         if (state.uaccess) {
3197                                 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
3198                                 return 1;
3199                         }
3200
3201                         state.uaccess = true;
3202                         break;
3203
3204                 case INSN_CLAC:
3205                         if (!state.uaccess && func) {
3206                                 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
3207                                 return 1;
3208                         }
3209
3210                         if (func_uaccess_safe(func) && !state.uaccess_stack) {
3211                                 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
3212                                 return 1;
3213                         }
3214
3215                         state.uaccess = false;
3216                         break;
3217
3218                 case INSN_STD:
3219                         if (state.df) {
3220                                 WARN_FUNC("recursive STD", sec, insn->offset);
3221                                 return 1;
3222                         }
3223
3224                         state.df = true;
3225                         break;
3226
3227                 case INSN_CLD:
3228                         if (!state.df && func) {
3229                                 WARN_FUNC("redundant CLD", sec, insn->offset);
3230                                 return 1;
3231                         }
3232
3233                         state.df = false;
3234                         break;
3235
3236                 default:
3237                         break;
3238                 }
3239
3240                 if (insn->dead_end)
3241                         return 0;
3242
3243                 if (!next_insn) {
3244                         if (state.cfi.cfa.base == CFI_UNDEFINED)
3245                                 return 0;
3246                         WARN("%s: unexpected end of section", sec->name);
3247                         return 1;
3248                 }
3249
3250                 prev_insn = insn;
3251                 insn = next_insn;
3252         }
3253
3254         return 0;
3255 }
3256
3257 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3258 {
3259         struct instruction *insn;
3260         struct insn_state state;
3261         int ret, warnings = 0;
3262
3263         if (!file->hints)
3264                 return 0;
3265
3266         init_insn_state(&state, sec);
3267
3268         if (sec) {
3269                 insn = find_insn(file, sec, 0);
3270                 if (!insn)
3271                         return 0;
3272         } else {
3273                 insn = list_first_entry(&file->insn_list, typeof(*insn), list);
3274         }
3275
3276         while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) {
3277                 if (insn->hint && !insn->visited && !insn->ignore) {
3278                         ret = validate_branch(file, insn->func, insn, state);
3279                         if (ret && backtrace)
3280                                 BT_FUNC("<=== (hint)", insn);
3281                         warnings += ret;
3282                 }
3283
3284                 insn = list_next_entry(insn, list);
3285         }
3286
3287         return warnings;
3288 }
3289
3290 static int validate_retpoline(struct objtool_file *file)
3291 {
3292         struct instruction *insn;
3293         int warnings = 0;
3294
3295         for_each_insn(file, insn) {
3296                 if (insn->type != INSN_JUMP_DYNAMIC &&
3297                     insn->type != INSN_CALL_DYNAMIC)
3298                         continue;
3299
3300                 if (insn->retpoline_safe)
3301                         continue;
3302
3303                 /*
3304                  * .init.text code is ran before userspace and thus doesn't
3305                  * strictly need retpolines, except for modules which are
3306                  * loaded late, they very much do need retpoline in their
3307                  * .init.text
3308                  */
3309                 if (!strcmp(insn->sec->name, ".init.text") && !module)
3310                         continue;
3311
3312                 WARN_FUNC("indirect %s found in RETPOLINE build",
3313                           insn->sec, insn->offset,
3314                           insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
3315
3316                 warnings++;
3317         }
3318
3319         return warnings;
3320 }
3321
3322 static bool is_kasan_insn(struct instruction *insn)
3323 {
3324         return (insn->type == INSN_CALL &&
3325                 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
3326 }
3327
3328 static bool is_ubsan_insn(struct instruction *insn)
3329 {
3330         return (insn->type == INSN_CALL &&
3331                 !strcmp(insn->call_dest->name,
3332                         "__ubsan_handle_builtin_unreachable"));
3333 }
3334
3335 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
3336 {
3337         int i;
3338         struct instruction *prev_insn;
3339
3340         if (insn->ignore || insn->type == INSN_NOP)
3341                 return true;
3342
3343         /*
3344          * Ignore alternative replacement instructions.  This can happen
3345          * when a whitelisted function uses one of the ALTERNATIVE macros.
3346          */
3347         if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
3348             !strcmp(insn->sec->name, ".altinstr_aux"))
3349                 return true;
3350
3351         if (!insn->func)
3352                 return false;
3353
3354         if (insn->func->static_call_tramp)
3355                 return true;
3356
3357         /*
3358          * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
3359          * __builtin_unreachable().  The BUG() macro has an unreachable() after
3360          * the UD2, which causes GCC's undefined trap logic to emit another UD2
3361          * (or occasionally a JMP to UD2).
3362          *
3363          * It may also insert a UD2 after calling a __noreturn function.
3364          */
3365         prev_insn = list_prev_entry(insn, list);
3366         if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) &&
3367             (insn->type == INSN_BUG ||
3368              (insn->type == INSN_JUMP_UNCONDITIONAL &&
3369               insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
3370                 return true;
3371
3372         /*
3373          * Check if this (or a subsequent) instruction is related to
3374          * CONFIG_UBSAN or CONFIG_KASAN.
3375          *
3376          * End the search at 5 instructions to avoid going into the weeds.
3377          */
3378         for (i = 0; i < 5; i++) {
3379
3380                 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
3381                         return true;
3382
3383                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
3384                         if (insn->jump_dest &&
3385                             insn->jump_dest->func == insn->func) {
3386                                 insn = insn->jump_dest;
3387                                 continue;
3388                         }
3389
3390                         break;
3391                 }
3392
3393                 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
3394                         break;
3395
3396                 insn = list_next_entry(insn, list);
3397         }
3398
3399         return false;
3400 }
3401
3402 static int validate_symbol(struct objtool_file *file, struct section *sec,
3403                            struct symbol *sym, struct insn_state *state)
3404 {
3405         struct instruction *insn;
3406         int ret;
3407
3408         if (!sym->len) {
3409                 WARN("%s() is missing an ELF size annotation", sym->name);
3410                 return 1;
3411         }
3412
3413         if (sym->pfunc != sym || sym->alias != sym)
3414                 return 0;
3415
3416         insn = find_insn(file, sec, sym->offset);
3417         if (!insn || insn->ignore || insn->visited)
3418                 return 0;
3419
3420         state->uaccess = sym->uaccess_safe;
3421
3422         ret = validate_branch(file, insn->func, insn, *state);
3423         if (ret && backtrace)
3424                 BT_FUNC("<=== (sym)", insn);
3425         return ret;
3426 }
3427
3428 static int validate_section(struct objtool_file *file, struct section *sec)
3429 {
3430         struct insn_state state;
3431         struct symbol *func;
3432         int warnings = 0;
3433
3434         list_for_each_entry(func, &sec->symbol_list, list) {
3435                 if (func->type != STT_FUNC)
3436                         continue;
3437
3438                 init_insn_state(&state, sec);
3439                 set_func_state(&state.cfi);
3440
3441                 warnings += validate_symbol(file, sec, func, &state);
3442         }
3443
3444         return warnings;
3445 }
3446
3447 static int validate_vmlinux_functions(struct objtool_file *file)
3448 {
3449         struct section *sec;
3450         int warnings = 0;
3451
3452         sec = find_section_by_name(file->elf, ".noinstr.text");
3453         if (sec) {
3454                 warnings += validate_section(file, sec);
3455                 warnings += validate_unwind_hints(file, sec);
3456         }
3457
3458         sec = find_section_by_name(file->elf, ".entry.text");
3459         if (sec) {
3460                 warnings += validate_section(file, sec);
3461                 warnings += validate_unwind_hints(file, sec);
3462         }
3463
3464         return warnings;
3465 }
3466
3467 static int validate_functions(struct objtool_file *file)
3468 {
3469         struct section *sec;
3470         int warnings = 0;
3471
3472         for_each_sec(file, sec) {
3473                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
3474                         continue;
3475
3476                 warnings += validate_section(file, sec);
3477         }
3478
3479         return warnings;
3480 }
3481
3482 static int validate_reachable_instructions(struct objtool_file *file)
3483 {
3484         struct instruction *insn;
3485
3486         if (file->ignore_unreachables)
3487                 return 0;
3488
3489         for_each_insn(file, insn) {
3490                 if (insn->visited || ignore_unreachable_insn(file, insn))
3491                         continue;
3492
3493                 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
3494                 return 1;
3495         }
3496
3497         return 0;
3498 }
3499
3500 int check(struct objtool_file *file)
3501 {
3502         int ret, warnings = 0;
3503
3504         arch_initial_func_cfi_state(&initial_func_cfi);
3505         init_cfi_state(&init_cfi);
3506         init_cfi_state(&func_cfi);
3507         set_func_state(&func_cfi);
3508
3509         if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
3510                 goto out;
3511
3512         cfi_hash_add(&init_cfi);
3513         cfi_hash_add(&func_cfi);
3514
3515         ret = decode_sections(file);
3516         if (ret < 0)
3517                 goto out;
3518
3519         warnings += ret;
3520
3521         if (list_empty(&file->insn_list))
3522                 goto out;
3523
3524         if (vmlinux && !validate_dup) {
3525                 ret = validate_vmlinux_functions(file);
3526                 if (ret < 0)
3527                         goto out;
3528
3529                 warnings += ret;
3530                 goto out;
3531         }
3532
3533         if (retpoline) {
3534                 ret = validate_retpoline(file);
3535                 if (ret < 0)
3536                         return ret;
3537                 warnings += ret;
3538         }
3539
3540         ret = validate_functions(file);
3541         if (ret < 0)
3542                 goto out;
3543         warnings += ret;
3544
3545         ret = validate_unwind_hints(file, NULL);
3546         if (ret < 0)
3547                 goto out;
3548         warnings += ret;
3549
3550         if (!warnings) {
3551                 ret = validate_reachable_instructions(file);
3552                 if (ret < 0)
3553                         goto out;
3554                 warnings += ret;
3555         }
3556
3557         ret = create_static_call_sections(file);
3558         if (ret < 0)
3559                 goto out;
3560         warnings += ret;
3561
3562         if (retpoline) {
3563                 ret = create_retpoline_sites_sections(file);
3564                 if (ret < 0)
3565                         goto out;
3566                 warnings += ret;
3567         }
3568
3569         if (mcount) {
3570                 ret = create_mcount_loc_sections(file);
3571                 if (ret < 0)
3572                         goto out;
3573                 warnings += ret;
3574         }
3575
3576         if (stats) {
3577                 printf("nr_insns_visited: %ld\n", nr_insns_visited);
3578                 printf("nr_cfi: %ld\n", nr_cfi);
3579                 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
3580                 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
3581         }
3582
3583 out:
3584         /*
3585          *  For now, don't fail the kernel build on fatal warnings.  These
3586          *  errors are still fairly common due to the growing matrix of
3587          *  supported toolchains and their recent pace of change.
3588          */
3589         return 0;
3590 }