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 with a function attribute
1076          * so they need a little help, NOP out any KCOV calls from noinstr
1077          * text.
1078          */
1079         if (insn->sec->noinstr && sym->kcov) {
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 static int classify_symbols(struct objtool_file *file)
1995 {
1996         struct section *sec;
1997         struct symbol *func;
1998
1999         for_each_sec(file, sec) {
2000                 list_for_each_entry(func, &sec->symbol_list, list) {
2001                         if (func->bind != STB_GLOBAL)
2002                                 continue;
2003
2004                         if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2005                                      strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2006                                 func->static_call_tramp = true;
2007
2008                         if (arch_is_retpoline(func))
2009                                 func->retpoline_thunk = true;
2010
2011                         if (!strcmp(func->name, "__fentry__"))
2012                                 func->fentry = true;
2013
2014                         if (!strncmp(func->name, "__sanitizer_cov_", 16))
2015                                 func->kcov = true;
2016                 }
2017         }
2018
2019         return 0;
2020 }
2021
2022 static void mark_rodata(struct objtool_file *file)
2023 {
2024         struct section *sec;
2025         bool found = false;
2026
2027         /*
2028          * Search for the following rodata sections, each of which can
2029          * potentially contain jump tables:
2030          *
2031          * - .rodata: can contain GCC switch tables
2032          * - .rodata.<func>: same, if -fdata-sections is being used
2033          * - .rodata..c_jump_table: contains C annotated jump tables
2034          *
2035          * .rodata.str1.* sections are ignored; they don't contain jump tables.
2036          */
2037         for_each_sec(file, sec) {
2038                 if (!strncmp(sec->name, ".rodata", 7) &&
2039                     !strstr(sec->name, ".str1.")) {
2040                         sec->rodata = true;
2041                         found = true;
2042                 }
2043         }
2044
2045         file->rodata = found;
2046 }
2047
2048 static int decode_sections(struct objtool_file *file)
2049 {
2050         int ret;
2051
2052         mark_rodata(file);
2053
2054         ret = init_pv_ops(file);
2055         if (ret)
2056                 return ret;
2057
2058         ret = decode_instructions(file);
2059         if (ret)
2060                 return ret;
2061
2062         ret = add_dead_ends(file);
2063         if (ret)
2064                 return ret;
2065
2066         add_ignores(file);
2067         add_uaccess_safe(file);
2068
2069         ret = add_ignore_alternatives(file);
2070         if (ret)
2071                 return ret;
2072
2073         /*
2074          * Must be before add_{jump_call}_destination.
2075          */
2076         ret = classify_symbols(file);
2077         if (ret)
2078                 return ret;
2079
2080         /*
2081          * Must be before add_special_section_alts() as that depends on
2082          * jump_dest being set.
2083          */
2084         ret = add_jump_destinations(file);
2085         if (ret)
2086                 return ret;
2087
2088         ret = add_special_section_alts(file);
2089         if (ret)
2090                 return ret;
2091
2092         /*
2093          * Must be before add_call_destination(); it changes INSN_CALL to
2094          * INSN_JUMP.
2095          */
2096         ret = read_intra_function_calls(file);
2097         if (ret)
2098                 return ret;
2099
2100         ret = add_call_destinations(file);
2101         if (ret)
2102                 return ret;
2103
2104         ret = add_jump_table_alts(file);
2105         if (ret)
2106                 return ret;
2107
2108         ret = read_unwind_hints(file);
2109         if (ret)
2110                 return ret;
2111
2112         ret = read_retpoline_hints(file);
2113         if (ret)
2114                 return ret;
2115
2116         ret = read_instr_hints(file);
2117         if (ret)
2118                 return ret;
2119
2120         return 0;
2121 }
2122
2123 static bool is_fentry_call(struct instruction *insn)
2124 {
2125         if (insn->type == INSN_CALL &&
2126             insn->call_dest &&
2127             insn->call_dest->fentry)
2128                 return true;
2129
2130         return false;
2131 }
2132
2133 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2134 {
2135         struct cfi_state *cfi = &state->cfi;
2136         int i;
2137
2138         if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2139                 return true;
2140
2141         if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2142                 return true;
2143
2144         if (cfi->stack_size != initial_func_cfi.cfa.offset)
2145                 return true;
2146
2147         for (i = 0; i < CFI_NUM_REGS; i++) {
2148                 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2149                     cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2150                         return true;
2151         }
2152
2153         return false;
2154 }
2155
2156 static bool check_reg_frame_pos(const struct cfi_reg *reg,
2157                                 int expected_offset)
2158 {
2159         return reg->base == CFI_CFA &&
2160                reg->offset == expected_offset;
2161 }
2162
2163 static bool has_valid_stack_frame(struct insn_state *state)
2164 {
2165         struct cfi_state *cfi = &state->cfi;
2166
2167         if (cfi->cfa.base == CFI_BP &&
2168             check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2169             check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2170                 return true;
2171
2172         if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2173                 return true;
2174
2175         return false;
2176 }
2177
2178 static int update_cfi_state_regs(struct instruction *insn,
2179                                   struct cfi_state *cfi,
2180                                   struct stack_op *op)
2181 {
2182         struct cfi_reg *cfa = &cfi->cfa;
2183
2184         if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2185                 return 0;
2186
2187         /* push */
2188         if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2189                 cfa->offset += 8;
2190
2191         /* pop */
2192         if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2193                 cfa->offset -= 8;
2194
2195         /* add immediate to sp */
2196         if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2197             op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2198                 cfa->offset -= op->src.offset;
2199
2200         return 0;
2201 }
2202
2203 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2204 {
2205         if (arch_callee_saved_reg(reg) &&
2206             cfi->regs[reg].base == CFI_UNDEFINED) {
2207                 cfi->regs[reg].base = base;
2208                 cfi->regs[reg].offset = offset;
2209         }
2210 }
2211
2212 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2213 {
2214         cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2215         cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2216 }
2217
2218 /*
2219  * A note about DRAP stack alignment:
2220  *
2221  * GCC has the concept of a DRAP register, which is used to help keep track of
2222  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
2223  * register.  The typical DRAP pattern is:
2224  *
2225  *   4c 8d 54 24 08             lea    0x8(%rsp),%r10
2226  *   48 83 e4 c0                and    $0xffffffffffffffc0,%rsp
2227  *   41 ff 72 f8                pushq  -0x8(%r10)
2228  *   55                         push   %rbp
2229  *   48 89 e5                   mov    %rsp,%rbp
2230  *                              (more pushes)
2231  *   41 52                      push   %r10
2232  *                              ...
2233  *   41 5a                      pop    %r10
2234  *                              (more pops)
2235  *   5d                         pop    %rbp
2236  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2237  *   c3                         retq
2238  *
2239  * There are some variations in the epilogues, like:
2240  *
2241  *   5b                         pop    %rbx
2242  *   41 5a                      pop    %r10
2243  *   41 5c                      pop    %r12
2244  *   41 5d                      pop    %r13
2245  *   41 5e                      pop    %r14
2246  *   c9                         leaveq
2247  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2248  *   c3                         retq
2249  *
2250  * and:
2251  *
2252  *   4c 8b 55 e8                mov    -0x18(%rbp),%r10
2253  *   48 8b 5d e0                mov    -0x20(%rbp),%rbx
2254  *   4c 8b 65 f0                mov    -0x10(%rbp),%r12
2255  *   4c 8b 6d f8                mov    -0x8(%rbp),%r13
2256  *   c9                         leaveq
2257  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2258  *   c3                         retq
2259  *
2260  * Sometimes r13 is used as the DRAP register, in which case it's saved and
2261  * restored beforehand:
2262  *
2263  *   41 55                      push   %r13
2264  *   4c 8d 6c 24 10             lea    0x10(%rsp),%r13
2265  *   48 83 e4 f0                and    $0xfffffffffffffff0,%rsp
2266  *                              ...
2267  *   49 8d 65 f0                lea    -0x10(%r13),%rsp
2268  *   41 5d                      pop    %r13
2269  *   c3                         retq
2270  */
2271 static int update_cfi_state(struct instruction *insn,
2272                             struct instruction *next_insn,
2273                             struct cfi_state *cfi, struct stack_op *op)
2274 {
2275         struct cfi_reg *cfa = &cfi->cfa;
2276         struct cfi_reg *regs = cfi->regs;
2277
2278         /* stack operations don't make sense with an undefined CFA */
2279         if (cfa->base == CFI_UNDEFINED) {
2280                 if (insn->func) {
2281                         WARN_FUNC("undefined stack state", insn->sec, insn->offset);
2282                         return -1;
2283                 }
2284                 return 0;
2285         }
2286
2287         if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2288             cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2289                 return update_cfi_state_regs(insn, cfi, op);
2290
2291         switch (op->dest.type) {
2292
2293         case OP_DEST_REG:
2294                 switch (op->src.type) {
2295
2296                 case OP_SRC_REG:
2297                         if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2298                             cfa->base == CFI_SP &&
2299                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset)) {
2300
2301                                 /* mov %rsp, %rbp */
2302                                 cfa->base = op->dest.reg;
2303                                 cfi->bp_scratch = false;
2304                         }
2305
2306                         else if (op->src.reg == CFI_SP &&
2307                                  op->dest.reg == CFI_BP && cfi->drap) {
2308
2309                                 /* drap: mov %rsp, %rbp */
2310                                 regs[CFI_BP].base = CFI_BP;
2311                                 regs[CFI_BP].offset = -cfi->stack_size;
2312                                 cfi->bp_scratch = false;
2313                         }
2314
2315                         else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2316
2317                                 /*
2318                                  * mov %rsp, %reg
2319                                  *
2320                                  * This is needed for the rare case where GCC
2321                                  * does:
2322                                  *
2323                                  *   mov    %rsp, %rax
2324                                  *   ...
2325                                  *   mov    %rax, %rsp
2326                                  */
2327                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2328                                 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2329                         }
2330
2331                         else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2332                                  (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2333
2334                                 /*
2335                                  * mov %rbp, %rsp
2336                                  *
2337                                  * Restore the original stack pointer (Clang).
2338                                  */
2339                                 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2340                         }
2341
2342                         else if (op->dest.reg == cfa->base) {
2343
2344                                 /* mov %reg, %rsp */
2345                                 if (cfa->base == CFI_SP &&
2346                                     cfi->vals[op->src.reg].base == CFI_CFA) {
2347
2348                                         /*
2349                                          * This is needed for the rare case
2350                                          * where GCC does something dumb like:
2351                                          *
2352                                          *   lea    0x8(%rsp), %rcx
2353                                          *   ...
2354                                          *   mov    %rcx, %rsp
2355                                          */
2356                                         cfa->offset = -cfi->vals[op->src.reg].offset;
2357                                         cfi->stack_size = cfa->offset;
2358
2359                                 } else if (cfa->base == CFI_SP &&
2360                                            cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2361                                            cfi->vals[op->src.reg].offset == cfa->offset) {
2362
2363                                         /*
2364                                          * Stack swizzle:
2365                                          *
2366                                          * 1: mov %rsp, (%[tos])
2367                                          * 2: mov %[tos], %rsp
2368                                          *    ...
2369                                          * 3: pop %rsp
2370                                          *
2371                                          * Where:
2372                                          *
2373                                          * 1 - places a pointer to the previous
2374                                          *     stack at the Top-of-Stack of the
2375                                          *     new stack.
2376                                          *
2377                                          * 2 - switches to the new stack.
2378                                          *
2379                                          * 3 - pops the Top-of-Stack to restore
2380                                          *     the original stack.
2381                                          *
2382                                          * Note: we set base to SP_INDIRECT
2383                                          * here and preserve offset. Therefore
2384                                          * when the unwinder reaches ToS it
2385                                          * will dereference SP and then add the
2386                                          * offset to find the next frame, IOW:
2387                                          * (%rsp) + offset.
2388                                          */
2389                                         cfa->base = CFI_SP_INDIRECT;
2390
2391                                 } else {
2392                                         cfa->base = CFI_UNDEFINED;
2393                                         cfa->offset = 0;
2394                                 }
2395                         }
2396
2397                         else if (op->dest.reg == CFI_SP &&
2398                                  cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2399                                  cfi->vals[op->src.reg].offset == cfa->offset) {
2400
2401                                 /*
2402                                  * The same stack swizzle case 2) as above. But
2403                                  * because we can't change cfa->base, case 3)
2404                                  * will become a regular POP. Pretend we're a
2405                                  * PUSH so things don't go unbalanced.
2406                                  */
2407                                 cfi->stack_size += 8;
2408                         }
2409
2410
2411                         break;
2412
2413                 case OP_SRC_ADD:
2414                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2415
2416                                 /* add imm, %rsp */
2417                                 cfi->stack_size -= op->src.offset;
2418                                 if (cfa->base == CFI_SP)
2419                                         cfa->offset -= op->src.offset;
2420                                 break;
2421                         }
2422
2423                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2424
2425                                 /* lea disp(%rbp), %rsp */
2426                                 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2427                                 break;
2428                         }
2429
2430                         if (!cfi->drap && op->src.reg == CFI_SP &&
2431                             op->dest.reg == CFI_BP && cfa->base == CFI_SP &&
2432                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset + op->src.offset)) {
2433
2434                                 /* lea disp(%rsp), %rbp */
2435                                 cfa->base = CFI_BP;
2436                                 cfa->offset -= op->src.offset;
2437                                 cfi->bp_scratch = false;
2438                                 break;
2439                         }
2440
2441                         if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2442
2443                                 /* drap: lea disp(%rsp), %drap */
2444                                 cfi->drap_reg = op->dest.reg;
2445
2446                                 /*
2447                                  * lea disp(%rsp), %reg
2448                                  *
2449                                  * This is needed for the rare case where GCC
2450                                  * does something dumb like:
2451                                  *
2452                                  *   lea    0x8(%rsp), %rcx
2453                                  *   ...
2454                                  *   mov    %rcx, %rsp
2455                                  */
2456                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2457                                 cfi->vals[op->dest.reg].offset = \
2458                                         -cfi->stack_size + op->src.offset;
2459
2460                                 break;
2461                         }
2462
2463                         if (cfi->drap && op->dest.reg == CFI_SP &&
2464                             op->src.reg == cfi->drap_reg) {
2465
2466                                  /* drap: lea disp(%drap), %rsp */
2467                                 cfa->base = CFI_SP;
2468                                 cfa->offset = cfi->stack_size = -op->src.offset;
2469                                 cfi->drap_reg = CFI_UNDEFINED;
2470                                 cfi->drap = false;
2471                                 break;
2472                         }
2473
2474                         if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
2475                                 WARN_FUNC("unsupported stack register modification",
2476                                           insn->sec, insn->offset);
2477                                 return -1;
2478                         }
2479
2480                         break;
2481
2482                 case OP_SRC_AND:
2483                         if (op->dest.reg != CFI_SP ||
2484                             (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
2485                             (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
2486                                 WARN_FUNC("unsupported stack pointer realignment",
2487                                           insn->sec, insn->offset);
2488                                 return -1;
2489                         }
2490
2491                         if (cfi->drap_reg != CFI_UNDEFINED) {
2492                                 /* drap: and imm, %rsp */
2493                                 cfa->base = cfi->drap_reg;
2494                                 cfa->offset = cfi->stack_size = 0;
2495                                 cfi->drap = true;
2496                         }
2497
2498                         /*
2499                          * Older versions of GCC (4.8ish) realign the stack
2500                          * without DRAP, with a frame pointer.
2501                          */
2502
2503                         break;
2504
2505                 case OP_SRC_POP:
2506                 case OP_SRC_POPF:
2507                         if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
2508
2509                                 /* pop %rsp; # restore from a stack swizzle */
2510                                 cfa->base = CFI_SP;
2511                                 break;
2512                         }
2513
2514                         if (!cfi->drap && op->dest.reg == cfa->base) {
2515
2516                                 /* pop %rbp */
2517                                 cfa->base = CFI_SP;
2518                         }
2519
2520                         if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
2521                             op->dest.reg == cfi->drap_reg &&
2522                             cfi->drap_offset == -cfi->stack_size) {
2523
2524                                 /* drap: pop %drap */
2525                                 cfa->base = cfi->drap_reg;
2526                                 cfa->offset = 0;
2527                                 cfi->drap_offset = -1;
2528
2529                         } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
2530
2531                                 /* pop %reg */
2532                                 restore_reg(cfi, op->dest.reg);
2533                         }
2534
2535                         cfi->stack_size -= 8;
2536                         if (cfa->base == CFI_SP)
2537                                 cfa->offset -= 8;
2538
2539                         break;
2540
2541                 case OP_SRC_REG_INDIRECT:
2542                         if (!cfi->drap && op->dest.reg == cfa->base &&
2543                             op->dest.reg == CFI_BP) {
2544
2545                                 /* mov disp(%rsp), %rbp */
2546                                 cfa->base = CFI_SP;
2547                                 cfa->offset = cfi->stack_size;
2548                         }
2549
2550                         if (cfi->drap && op->src.reg == CFI_BP &&
2551                             op->src.offset == cfi->drap_offset) {
2552
2553                                 /* drap: mov disp(%rbp), %drap */
2554                                 cfa->base = cfi->drap_reg;
2555                                 cfa->offset = 0;
2556                                 cfi->drap_offset = -1;
2557                         }
2558
2559                         if (cfi->drap && op->src.reg == CFI_BP &&
2560                             op->src.offset == regs[op->dest.reg].offset) {
2561
2562                                 /* drap: mov disp(%rbp), %reg */
2563                                 restore_reg(cfi, op->dest.reg);
2564
2565                         } else if (op->src.reg == cfa->base &&
2566                             op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
2567
2568                                 /* mov disp(%rbp), %reg */
2569                                 /* mov disp(%rsp), %reg */
2570                                 restore_reg(cfi, op->dest.reg);
2571
2572                         } else if (op->src.reg == CFI_SP &&
2573                                    op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
2574
2575                                 /* mov disp(%rsp), %reg */
2576                                 restore_reg(cfi, op->dest.reg);
2577                         }
2578
2579                         break;
2580
2581                 default:
2582                         WARN_FUNC("unknown stack-related instruction",
2583                                   insn->sec, insn->offset);
2584                         return -1;
2585                 }
2586
2587                 break;
2588
2589         case OP_DEST_PUSH:
2590         case OP_DEST_PUSHF:
2591                 cfi->stack_size += 8;
2592                 if (cfa->base == CFI_SP)
2593                         cfa->offset += 8;
2594
2595                 if (op->src.type != OP_SRC_REG)
2596                         break;
2597
2598                 if (cfi->drap) {
2599                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2600
2601                                 /* drap: push %drap */
2602                                 cfa->base = CFI_BP_INDIRECT;
2603                                 cfa->offset = -cfi->stack_size;
2604
2605                                 /* save drap so we know when to restore it */
2606                                 cfi->drap_offset = -cfi->stack_size;
2607
2608                         } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
2609
2610                                 /* drap: push %rbp */
2611                                 cfi->stack_size = 0;
2612
2613                         } else {
2614
2615                                 /* drap: push %reg */
2616                                 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
2617                         }
2618
2619                 } else {
2620
2621                         /* push %reg */
2622                         save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
2623                 }
2624
2625                 /* detect when asm code uses rbp as a scratch register */
2626                 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
2627                     cfa->base != CFI_BP)
2628                         cfi->bp_scratch = true;
2629                 break;
2630
2631         case OP_DEST_REG_INDIRECT:
2632
2633                 if (cfi->drap) {
2634                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2635
2636                                 /* drap: mov %drap, disp(%rbp) */
2637                                 cfa->base = CFI_BP_INDIRECT;
2638                                 cfa->offset = op->dest.offset;
2639
2640                                 /* save drap offset so we know when to restore it */
2641                                 cfi->drap_offset = op->dest.offset;
2642                         } else {
2643
2644                                 /* drap: mov reg, disp(%rbp) */
2645                                 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
2646                         }
2647
2648                 } else if (op->dest.reg == cfa->base) {
2649
2650                         /* mov reg, disp(%rbp) */
2651                         /* mov reg, disp(%rsp) */
2652                         save_reg(cfi, op->src.reg, CFI_CFA,
2653                                  op->dest.offset - cfi->cfa.offset);
2654
2655                 } else if (op->dest.reg == CFI_SP) {
2656
2657                         /* mov reg, disp(%rsp) */
2658                         save_reg(cfi, op->src.reg, CFI_CFA,
2659                                  op->dest.offset - cfi->stack_size);
2660
2661                 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
2662
2663                         /* mov %rsp, (%reg); # setup a stack swizzle. */
2664                         cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
2665                         cfi->vals[op->dest.reg].offset = cfa->offset;
2666                 }
2667
2668                 break;
2669
2670         case OP_DEST_MEM:
2671                 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
2672                         WARN_FUNC("unknown stack-related memory operation",
2673                                   insn->sec, insn->offset);
2674                         return -1;
2675                 }
2676
2677                 /* pop mem */
2678                 cfi->stack_size -= 8;
2679                 if (cfa->base == CFI_SP)
2680                         cfa->offset -= 8;
2681
2682                 break;
2683
2684         default:
2685                 WARN_FUNC("unknown stack-related instruction",
2686                           insn->sec, insn->offset);
2687                 return -1;
2688         }
2689
2690         return 0;
2691 }
2692
2693 /*
2694  * The stack layouts of alternatives instructions can sometimes diverge when
2695  * they have stack modifications.  That's fine as long as the potential stack
2696  * layouts don't conflict at any given potential instruction boundary.
2697  *
2698  * Flatten the CFIs of the different alternative code streams (both original
2699  * and replacement) into a single shared CFI array which can be used to detect
2700  * conflicts and nicely feed a linear array of ORC entries to the unwinder.
2701  */
2702 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
2703 {
2704         struct cfi_state **alt_cfi;
2705         int group_off;
2706
2707         if (!insn->alt_group)
2708                 return 0;
2709
2710         if (!insn->cfi) {
2711                 WARN("CFI missing");
2712                 return -1;
2713         }
2714
2715         alt_cfi = insn->alt_group->cfi;
2716         group_off = insn->offset - insn->alt_group->first_insn->offset;
2717
2718         if (!alt_cfi[group_off]) {
2719                 alt_cfi[group_off] = insn->cfi;
2720         } else {
2721                 if (cficmp(alt_cfi[group_off], insn->cfi)) {
2722                         WARN_FUNC("stack layout conflict in alternatives",
2723                                   insn->sec, insn->offset);
2724                         return -1;
2725                 }
2726         }
2727
2728         return 0;
2729 }
2730
2731 static int handle_insn_ops(struct instruction *insn,
2732                            struct instruction *next_insn,
2733                            struct insn_state *state)
2734 {
2735         struct stack_op *op;
2736
2737         list_for_each_entry(op, &insn->stack_ops, list) {
2738
2739                 if (update_cfi_state(insn, next_insn, &state->cfi, op))
2740                         return 1;
2741
2742                 if (!insn->alt_group)
2743                         continue;
2744
2745                 if (op->dest.type == OP_DEST_PUSHF) {
2746                         if (!state->uaccess_stack) {
2747                                 state->uaccess_stack = 1;
2748                         } else if (state->uaccess_stack >> 31) {
2749                                 WARN_FUNC("PUSHF stack exhausted",
2750                                           insn->sec, insn->offset);
2751                                 return 1;
2752                         }
2753                         state->uaccess_stack <<= 1;
2754                         state->uaccess_stack  |= state->uaccess;
2755                 }
2756
2757                 if (op->src.type == OP_SRC_POPF) {
2758                         if (state->uaccess_stack) {
2759                                 state->uaccess = state->uaccess_stack & 1;
2760                                 state->uaccess_stack >>= 1;
2761                                 if (state->uaccess_stack == 1)
2762                                         state->uaccess_stack = 0;
2763                         }
2764                 }
2765         }
2766
2767         return 0;
2768 }
2769
2770 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
2771 {
2772         struct cfi_state *cfi1 = insn->cfi;
2773         int i;
2774
2775         if (!cfi1) {
2776                 WARN("CFI missing");
2777                 return false;
2778         }
2779
2780         if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
2781
2782                 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
2783                           insn->sec, insn->offset,
2784                           cfi1->cfa.base, cfi1->cfa.offset,
2785                           cfi2->cfa.base, cfi2->cfa.offset);
2786
2787         } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
2788                 for (i = 0; i < CFI_NUM_REGS; i++) {
2789                         if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
2790                                     sizeof(struct cfi_reg)))
2791                                 continue;
2792
2793                         WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
2794                                   insn->sec, insn->offset,
2795                                   i, cfi1->regs[i].base, cfi1->regs[i].offset,
2796                                   i, cfi2->regs[i].base, cfi2->regs[i].offset);
2797                         break;
2798                 }
2799
2800         } else if (cfi1->type != cfi2->type) {
2801
2802                 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
2803                           insn->sec, insn->offset, cfi1->type, cfi2->type);
2804
2805         } else if (cfi1->drap != cfi2->drap ||
2806                    (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
2807                    (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
2808
2809                 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
2810                           insn->sec, insn->offset,
2811                           cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
2812                           cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
2813
2814         } else
2815                 return true;
2816
2817         return false;
2818 }
2819
2820 static inline bool func_uaccess_safe(struct symbol *func)
2821 {
2822         if (func)
2823                 return func->uaccess_safe;
2824
2825         return false;
2826 }
2827
2828 static inline const char *call_dest_name(struct instruction *insn)
2829 {
2830         static char pvname[16];
2831         struct reloc *rel;
2832         int idx;
2833
2834         if (insn->call_dest)
2835                 return insn->call_dest->name;
2836
2837         rel = insn_reloc(NULL, insn);
2838         if (rel && !strcmp(rel->sym->name, "pv_ops")) {
2839                 idx = (rel->addend / sizeof(void *));
2840                 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
2841                 return pvname;
2842         }
2843
2844         return "{dynamic}";
2845 }
2846
2847 static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
2848 {
2849         struct symbol *target;
2850         struct reloc *rel;
2851         int idx;
2852
2853         rel = insn_reloc(file, insn);
2854         if (!rel || strcmp(rel->sym->name, "pv_ops"))
2855                 return false;
2856
2857         idx = (arch_dest_reloc_offset(rel->addend) / sizeof(void *));
2858
2859         if (file->pv_ops[idx].clean)
2860                 return true;
2861
2862         file->pv_ops[idx].clean = true;
2863
2864         list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
2865                 if (!target->sec->noinstr) {
2866                         WARN("pv_ops[%d]: %s", idx, target->name);
2867                         file->pv_ops[idx].clean = false;
2868                 }
2869         }
2870
2871         return file->pv_ops[idx].clean;
2872 }
2873
2874 static inline bool noinstr_call_dest(struct objtool_file *file,
2875                                      struct instruction *insn,
2876                                      struct symbol *func)
2877 {
2878         /*
2879          * We can't deal with indirect function calls at present;
2880          * assume they're instrumented.
2881          */
2882         if (!func) {
2883                 if (file->pv_ops)
2884                         return pv_call_dest(file, insn);
2885
2886                 return false;
2887         }
2888
2889         /*
2890          * If the symbol is from a noinstr section; we good.
2891          */
2892         if (func->sec->noinstr)
2893                 return true;
2894
2895         /*
2896          * The __ubsan_handle_*() calls are like WARN(), they only happen when
2897          * something 'BAD' happened. At the risk of taking the machine down,
2898          * let them proceed to get the message out.
2899          */
2900         if (!strncmp(func->name, "__ubsan_handle_", 15))
2901                 return true;
2902
2903         return false;
2904 }
2905
2906 static int validate_call(struct objtool_file *file,
2907                          struct instruction *insn,
2908                          struct insn_state *state)
2909 {
2910         if (state->noinstr && state->instr <= 0 &&
2911             !noinstr_call_dest(file, insn, insn->call_dest)) {
2912                 WARN_FUNC("call to %s() leaves .noinstr.text section",
2913                                 insn->sec, insn->offset, call_dest_name(insn));
2914                 return 1;
2915         }
2916
2917         if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
2918                 WARN_FUNC("call to %s() with UACCESS enabled",
2919                                 insn->sec, insn->offset, call_dest_name(insn));
2920                 return 1;
2921         }
2922
2923         if (state->df) {
2924                 WARN_FUNC("call to %s() with DF set",
2925                                 insn->sec, insn->offset, call_dest_name(insn));
2926                 return 1;
2927         }
2928
2929         return 0;
2930 }
2931
2932 static int validate_sibling_call(struct objtool_file *file,
2933                                  struct instruction *insn,
2934                                  struct insn_state *state)
2935 {
2936         if (has_modified_stack_frame(insn, state)) {
2937                 WARN_FUNC("sibling call from callable instruction with modified stack frame",
2938                                 insn->sec, insn->offset);
2939                 return 1;
2940         }
2941
2942         return validate_call(file, insn, state);
2943 }
2944
2945 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
2946 {
2947         if (state->noinstr && state->instr > 0) {
2948                 WARN_FUNC("return with instrumentation enabled",
2949                           insn->sec, insn->offset);
2950                 return 1;
2951         }
2952
2953         if (state->uaccess && !func_uaccess_safe(func)) {
2954                 WARN_FUNC("return with UACCESS enabled",
2955                           insn->sec, insn->offset);
2956                 return 1;
2957         }
2958
2959         if (!state->uaccess && func_uaccess_safe(func)) {
2960                 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
2961                           insn->sec, insn->offset);
2962                 return 1;
2963         }
2964
2965         if (state->df) {
2966                 WARN_FUNC("return with DF set",
2967                           insn->sec, insn->offset);
2968                 return 1;
2969         }
2970
2971         if (func && has_modified_stack_frame(insn, state)) {
2972                 WARN_FUNC("return with modified stack frame",
2973                           insn->sec, insn->offset);
2974                 return 1;
2975         }
2976
2977         if (state->cfi.bp_scratch) {
2978                 WARN_FUNC("BP used as a scratch register",
2979                           insn->sec, insn->offset);
2980                 return 1;
2981         }
2982
2983         return 0;
2984 }
2985
2986 static struct instruction *next_insn_to_validate(struct objtool_file *file,
2987                                                  struct instruction *insn)
2988 {
2989         struct alt_group *alt_group = insn->alt_group;
2990
2991         /*
2992          * Simulate the fact that alternatives are patched in-place.  When the
2993          * end of a replacement alt_group is reached, redirect objtool flow to
2994          * the end of the original alt_group.
2995          */
2996         if (alt_group && insn == alt_group->last_insn && alt_group->orig_group)
2997                 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
2998
2999         return next_insn_same_sec(file, insn);
3000 }
3001
3002 /*
3003  * Follow the branch starting at the given instruction, and recursively follow
3004  * any other branches (jumps).  Meanwhile, track the frame pointer state at
3005  * each instruction and validate all the rules described in
3006  * tools/objtool/Documentation/stack-validation.txt.
3007  */
3008 static int validate_branch(struct objtool_file *file, struct symbol *func,
3009                            struct instruction *insn, struct insn_state state)
3010 {
3011         struct alternative *alt;
3012         struct instruction *next_insn, *prev_insn = NULL;
3013         struct section *sec;
3014         u8 visited;
3015         int ret;
3016
3017         sec = insn->sec;
3018
3019         while (1) {
3020                 next_insn = next_insn_to_validate(file, insn);
3021
3022                 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
3023                         WARN("%s() falls through to next function %s()",
3024                              func->name, insn->func->name);
3025                         return 1;
3026                 }
3027
3028                 if (func && insn->ignore) {
3029                         WARN_FUNC("BUG: why am I validating an ignored function?",
3030                                   sec, insn->offset);
3031                         return 1;
3032                 }
3033
3034                 visited = 1 << state.uaccess;
3035                 if (insn->visited) {
3036                         if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3037                                 return 1;
3038
3039                         if (insn->visited & visited)
3040                                 return 0;
3041                 } else {
3042                         nr_insns_visited++;
3043                 }
3044
3045                 if (state.noinstr)
3046                         state.instr += insn->instr;
3047
3048                 if (insn->hint) {
3049                         state.cfi = *insn->cfi;
3050                 } else {
3051                         /* XXX track if we actually changed state.cfi */
3052
3053                         if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3054                                 insn->cfi = prev_insn->cfi;
3055                                 nr_cfi_reused++;
3056                         } else {
3057                                 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3058                         }
3059                 }
3060
3061                 insn->visited |= visited;
3062
3063                 if (propagate_alt_cfi(file, insn))
3064                         return 1;
3065
3066                 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
3067                         bool skip_orig = false;
3068
3069                         list_for_each_entry(alt, &insn->alts, list) {
3070                                 if (alt->skip_orig)
3071                                         skip_orig = true;
3072
3073                                 ret = validate_branch(file, func, alt->insn, state);
3074                                 if (ret) {
3075                                         if (backtrace)
3076                                                 BT_FUNC("(alt)", insn);
3077                                         return ret;
3078                                 }
3079                         }
3080
3081                         if (skip_orig)
3082                                 return 0;
3083                 }
3084
3085                 if (handle_insn_ops(insn, next_insn, &state))
3086                         return 1;
3087
3088                 switch (insn->type) {
3089
3090                 case INSN_RETURN:
3091                         return validate_return(func, insn, &state);
3092
3093                 case INSN_CALL:
3094                 case INSN_CALL_DYNAMIC:
3095                         ret = validate_call(file, insn, &state);
3096                         if (ret)
3097                                 return ret;
3098
3099                         if (!no_fp && func && !is_fentry_call(insn) &&
3100                             !has_valid_stack_frame(&state)) {
3101                                 WARN_FUNC("call without frame pointer save/setup",
3102                                           sec, insn->offset);
3103                                 return 1;
3104                         }
3105
3106                         if (dead_end_function(file, insn->call_dest))
3107                                 return 0;
3108
3109                         break;
3110
3111                 case INSN_JUMP_CONDITIONAL:
3112                 case INSN_JUMP_UNCONDITIONAL:
3113                         if (is_sibling_call(insn)) {
3114                                 ret = validate_sibling_call(file, insn, &state);
3115                                 if (ret)
3116                                         return ret;
3117
3118                         } else if (insn->jump_dest) {
3119                                 ret = validate_branch(file, func,
3120                                                       insn->jump_dest, state);
3121                                 if (ret) {
3122                                         if (backtrace)
3123                                                 BT_FUNC("(branch)", insn);
3124                                         return ret;
3125                                 }
3126                         }
3127
3128                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
3129                                 return 0;
3130
3131                         break;
3132
3133                 case INSN_JUMP_DYNAMIC:
3134                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3135                         if (is_sibling_call(insn)) {
3136                                 ret = validate_sibling_call(file, insn, &state);
3137                                 if (ret)
3138                                         return ret;
3139                         }
3140
3141                         if (insn->type == INSN_JUMP_DYNAMIC)
3142                                 return 0;
3143
3144                         break;
3145
3146                 case INSN_CONTEXT_SWITCH:
3147                         if (func && (!next_insn || !next_insn->hint)) {
3148                                 WARN_FUNC("unsupported instruction in callable function",
3149                                           sec, insn->offset);
3150                                 return 1;
3151                         }
3152                         return 0;
3153
3154                 case INSN_STAC:
3155                         if (state.uaccess) {
3156                                 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
3157                                 return 1;
3158                         }
3159
3160                         state.uaccess = true;
3161                         break;
3162
3163                 case INSN_CLAC:
3164                         if (!state.uaccess && func) {
3165                                 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
3166                                 return 1;
3167                         }
3168
3169                         if (func_uaccess_safe(func) && !state.uaccess_stack) {
3170                                 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
3171                                 return 1;
3172                         }
3173
3174                         state.uaccess = false;
3175                         break;
3176
3177                 case INSN_STD:
3178                         if (state.df) {
3179                                 WARN_FUNC("recursive STD", sec, insn->offset);
3180                                 return 1;
3181                         }
3182
3183                         state.df = true;
3184                         break;
3185
3186                 case INSN_CLD:
3187                         if (!state.df && func) {
3188                                 WARN_FUNC("redundant CLD", sec, insn->offset);
3189                                 return 1;
3190                         }
3191
3192                         state.df = false;
3193                         break;
3194
3195                 default:
3196                         break;
3197                 }
3198
3199                 if (insn->dead_end)
3200                         return 0;
3201
3202                 if (!next_insn) {
3203                         if (state.cfi.cfa.base == CFI_UNDEFINED)
3204                                 return 0;
3205                         WARN("%s: unexpected end of section", sec->name);
3206                         return 1;
3207                 }
3208
3209                 prev_insn = insn;
3210                 insn = next_insn;
3211         }
3212
3213         return 0;
3214 }
3215
3216 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3217 {
3218         struct instruction *insn;
3219         struct insn_state state;
3220         int ret, warnings = 0;
3221
3222         if (!file->hints)
3223                 return 0;
3224
3225         init_insn_state(&state, sec);
3226
3227         if (sec) {
3228                 insn = find_insn(file, sec, 0);
3229                 if (!insn)
3230                         return 0;
3231         } else {
3232                 insn = list_first_entry(&file->insn_list, typeof(*insn), list);
3233         }
3234
3235         while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) {
3236                 if (insn->hint && !insn->visited && !insn->ignore) {
3237                         ret = validate_branch(file, insn->func, insn, state);
3238                         if (ret && backtrace)
3239                                 BT_FUNC("<=== (hint)", insn);
3240                         warnings += ret;
3241                 }
3242
3243                 insn = list_next_entry(insn, list);
3244         }
3245
3246         return warnings;
3247 }
3248
3249 static int validate_retpoline(struct objtool_file *file)
3250 {
3251         struct instruction *insn;
3252         int warnings = 0;
3253
3254         for_each_insn(file, insn) {
3255                 if (insn->type != INSN_JUMP_DYNAMIC &&
3256                     insn->type != INSN_CALL_DYNAMIC)
3257                         continue;
3258
3259                 if (insn->retpoline_safe)
3260                         continue;
3261
3262                 /*
3263                  * .init.text code is ran before userspace and thus doesn't
3264                  * strictly need retpolines, except for modules which are
3265                  * loaded late, they very much do need retpoline in their
3266                  * .init.text
3267                  */
3268                 if (!strcmp(insn->sec->name, ".init.text") && !module)
3269                         continue;
3270
3271                 WARN_FUNC("indirect %s found in RETPOLINE build",
3272                           insn->sec, insn->offset,
3273                           insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
3274
3275                 warnings++;
3276         }
3277
3278         return warnings;
3279 }
3280
3281 static bool is_kasan_insn(struct instruction *insn)
3282 {
3283         return (insn->type == INSN_CALL &&
3284                 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
3285 }
3286
3287 static bool is_ubsan_insn(struct instruction *insn)
3288 {
3289         return (insn->type == INSN_CALL &&
3290                 !strcmp(insn->call_dest->name,
3291                         "__ubsan_handle_builtin_unreachable"));
3292 }
3293
3294 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
3295 {
3296         int i;
3297         struct instruction *prev_insn;
3298
3299         if (insn->ignore || insn->type == INSN_NOP)
3300                 return true;
3301
3302         /*
3303          * Ignore any unused exceptions.  This can happen when a whitelisted
3304          * function has an exception table entry.
3305          *
3306          * Also ignore alternative replacement instructions.  This can happen
3307          * when a whitelisted function uses one of the ALTERNATIVE macros.
3308          */
3309         if (!strcmp(insn->sec->name, ".fixup") ||
3310             !strcmp(insn->sec->name, ".altinstr_replacement") ||
3311             !strcmp(insn->sec->name, ".altinstr_aux"))
3312                 return true;
3313
3314         if (!insn->func)
3315                 return false;
3316
3317         if (insn->func->static_call_tramp)
3318                 return true;
3319
3320         /*
3321          * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
3322          * __builtin_unreachable().  The BUG() macro has an unreachable() after
3323          * the UD2, which causes GCC's undefined trap logic to emit another UD2
3324          * (or occasionally a JMP to UD2).
3325          *
3326          * It may also insert a UD2 after calling a __noreturn function.
3327          */
3328         prev_insn = list_prev_entry(insn, list);
3329         if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) &&
3330             (insn->type == INSN_BUG ||
3331              (insn->type == INSN_JUMP_UNCONDITIONAL &&
3332               insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
3333                 return true;
3334
3335         /*
3336          * Check if this (or a subsequent) instruction is related to
3337          * CONFIG_UBSAN or CONFIG_KASAN.
3338          *
3339          * End the search at 5 instructions to avoid going into the weeds.
3340          */
3341         for (i = 0; i < 5; i++) {
3342
3343                 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
3344                         return true;
3345
3346                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
3347                         if (insn->jump_dest &&
3348                             insn->jump_dest->func == insn->func) {
3349                                 insn = insn->jump_dest;
3350                                 continue;
3351                         }
3352
3353                         break;
3354                 }
3355
3356                 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
3357                         break;
3358
3359                 insn = list_next_entry(insn, list);
3360         }
3361
3362         return false;
3363 }
3364
3365 static int validate_symbol(struct objtool_file *file, struct section *sec,
3366                            struct symbol *sym, struct insn_state *state)
3367 {
3368         struct instruction *insn;
3369         int ret;
3370
3371         if (!sym->len) {
3372                 WARN("%s() is missing an ELF size annotation", sym->name);
3373                 return 1;
3374         }
3375
3376         if (sym->pfunc != sym || sym->alias != sym)
3377                 return 0;
3378
3379         insn = find_insn(file, sec, sym->offset);
3380         if (!insn || insn->ignore || insn->visited)
3381                 return 0;
3382
3383         state->uaccess = sym->uaccess_safe;
3384
3385         ret = validate_branch(file, insn->func, insn, *state);
3386         if (ret && backtrace)
3387                 BT_FUNC("<=== (sym)", insn);
3388         return ret;
3389 }
3390
3391 static int validate_section(struct objtool_file *file, struct section *sec)
3392 {
3393         struct insn_state state;
3394         struct symbol *func;
3395         int warnings = 0;
3396
3397         list_for_each_entry(func, &sec->symbol_list, list) {
3398                 if (func->type != STT_FUNC)
3399                         continue;
3400
3401                 init_insn_state(&state, sec);
3402                 set_func_state(&state.cfi);
3403
3404                 warnings += validate_symbol(file, sec, func, &state);
3405         }
3406
3407         return warnings;
3408 }
3409
3410 static int validate_vmlinux_functions(struct objtool_file *file)
3411 {
3412         struct section *sec;
3413         int warnings = 0;
3414
3415         sec = find_section_by_name(file->elf, ".noinstr.text");
3416         if (sec) {
3417                 warnings += validate_section(file, sec);
3418                 warnings += validate_unwind_hints(file, sec);
3419         }
3420
3421         sec = find_section_by_name(file->elf, ".entry.text");
3422         if (sec) {
3423                 warnings += validate_section(file, sec);
3424                 warnings += validate_unwind_hints(file, sec);
3425         }
3426
3427         return warnings;
3428 }
3429
3430 static int validate_functions(struct objtool_file *file)
3431 {
3432         struct section *sec;
3433         int warnings = 0;
3434
3435         for_each_sec(file, sec) {
3436                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
3437                         continue;
3438
3439                 warnings += validate_section(file, sec);
3440         }
3441
3442         return warnings;
3443 }
3444
3445 static int validate_reachable_instructions(struct objtool_file *file)
3446 {
3447         struct instruction *insn;
3448
3449         if (file->ignore_unreachables)
3450                 return 0;
3451
3452         for_each_insn(file, insn) {
3453                 if (insn->visited || ignore_unreachable_insn(file, insn))
3454                         continue;
3455
3456                 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
3457                 return 1;
3458         }
3459
3460         return 0;
3461 }
3462
3463 int check(struct objtool_file *file)
3464 {
3465         int ret, warnings = 0;
3466
3467         arch_initial_func_cfi_state(&initial_func_cfi);
3468         init_cfi_state(&init_cfi);
3469         init_cfi_state(&func_cfi);
3470         set_func_state(&func_cfi);
3471
3472         if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
3473                 goto out;
3474
3475         cfi_hash_add(&init_cfi);
3476         cfi_hash_add(&func_cfi);
3477
3478         ret = decode_sections(file);
3479         if (ret < 0)
3480                 goto out;
3481
3482         warnings += ret;
3483
3484         if (list_empty(&file->insn_list))
3485                 goto out;
3486
3487         if (vmlinux && !validate_dup) {
3488                 ret = validate_vmlinux_functions(file);
3489                 if (ret < 0)
3490                         goto out;
3491
3492                 warnings += ret;
3493                 goto out;
3494         }
3495
3496         if (retpoline) {
3497                 ret = validate_retpoline(file);
3498                 if (ret < 0)
3499                         return ret;
3500                 warnings += ret;
3501         }
3502
3503         ret = validate_functions(file);
3504         if (ret < 0)
3505                 goto out;
3506         warnings += ret;
3507
3508         ret = validate_unwind_hints(file, NULL);
3509         if (ret < 0)
3510                 goto out;
3511         warnings += ret;
3512
3513         if (!warnings) {
3514                 ret = validate_reachable_instructions(file);
3515                 if (ret < 0)
3516                         goto out;
3517                 warnings += ret;
3518         }
3519
3520         ret = create_static_call_sections(file);
3521         if (ret < 0)
3522                 goto out;
3523         warnings += ret;
3524
3525         if (retpoline) {
3526                 ret = create_retpoline_sites_sections(file);
3527                 if (ret < 0)
3528                         goto out;
3529                 warnings += ret;
3530         }
3531
3532         if (mcount) {
3533                 ret = create_mcount_loc_sections(file);
3534                 if (ret < 0)
3535                         goto out;
3536                 warnings += ret;
3537         }
3538
3539         if (stats) {
3540                 printf("nr_insns_visited: %ld\n", nr_insns_visited);
3541                 printf("nr_cfi: %ld\n", nr_cfi);
3542                 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
3543                 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
3544         }
3545
3546 out:
3547         /*
3548          *  For now, don't fail the kernel build on fatal warnings.  These
3549          *  errors are still fairly common due to the growing matrix of
3550          *  supported toolchains and their recent pace of change.
3551          */
3552         return 0;
3553 }