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