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