tools/objtool/check.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
   4  */
   5
   6 #include <string.h>
   7 #include <stdlib.h>
   8 #include <sys/mman.h>
   9
  10 #include <arch/elf.h>
  11 #include <objtool/builtin.h>
  12 #include <objtool/cfi.h>
  13 #include <objtool/arch.h>
  14 #include <objtool/check.h>
  15 #include <objtool/special.h>
  16 #include <objtool/warn.h>
  17 #include <objtool/endianness.h>
  18
  19 #include <linux/objtool.h>
  20 #include <linux/hashtable.h>
  21 #include <linux/kernel.h>
  22 #include <linux/static_call_types.h>
  23
  24 struct alternative {
  25         struct list_head list;
  26         struct instruction *insn;
  27         bool skip_orig;
  28 };
  29
  30 static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
  31
  32 static struct cfi_init_state initial_func_cfi;
  33 static struct cfi_state init_cfi;
  34 static struct cfi_state func_cfi;
  35
  36 struct instruction *find_insn(struct objtool_file *file,
  37                               struct section *sec, unsigned long offset)
  38 {
  39         struct instruction *insn;
  40
  41         hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
  42                 if (insn->sec == sec && insn->offset == offset)
  43                         return insn;
  44         }
  45
  46         return NULL;
  47 }
  48
  49 static struct instruction *next_insn_same_sec(struct objtool_file *file,
  50                                               struct instruction *insn)
  51 {
  52         struct instruction *next = list_next_entry(insn, list);
  53
  54         if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
  55                 return NULL;
  56
  57         return next;
  58 }
  59
  60 static struct instruction *next_insn_same_func(struct objtool_file *file,
  61                                                struct instruction *insn)
  62 {
  63         struct instruction *next = list_next_entry(insn, list);
  64         struct symbol *func = insn->func;
  65
  66         if (!func)
  67                 return NULL;
  68
  69         if (&next->list != &file->insn_list && next->func == func)
  70                 return next;
  71
  72         /* Check if we're already in the subfunction: */
  73         if (func == func->cfunc)
  74                 return NULL;
  75
  76         /* Move to the subfunction: */
  77         return find_insn(file, func->cfunc->sec, func->cfunc->offset);
  78 }
  79
  80 static struct instruction *prev_insn_same_sym(struct objtool_file *file,
  81                                                struct instruction *insn)
  82 {
  83         struct instruction *prev = list_prev_entry(insn, list);
  84
  85         if (&prev->list != &file->insn_list && prev->func == insn->func)
  86                 return prev;
  87
  88         return NULL;
  89 }
  90
  91 #define func_for_each_insn(file, func, insn)                            \
  92         for (insn = find_insn(file, func->sec, func->offset);           \
  93              insn;                                                      \
  94              insn = next_insn_same_func(file, insn))
  95
  96 #define sym_for_each_insn(file, sym, insn)                              \
  97         for (insn = find_insn(file, sym->sec, sym->offset);             \
  98              insn && &insn->list != &file->insn_list &&                 \
  99                 insn->sec == sym->sec &&                                \
 100                 insn->offset < sym->offset + sym->len;                  \
 101              insn = list_next_entry(insn, list))
 102
 103 #define sym_for_each_insn_continue_reverse(file, sym, insn)             \
 104         for (insn = list_prev_entry(insn, list);                        \
 105              &insn->list != &file->insn_list &&                         \
 106                 insn->sec == sym->sec && insn->offset >= sym->offset;   \
 107              insn = list_prev_entry(insn, list))
 108
 109 #define sec_for_each_insn_from(file, insn)                              \
 110         for (; insn; insn = next_insn_same_sec(file, insn))
 111
 112 #define sec_for_each_insn_continue(file, insn)                          \
 113         for (insn = next_insn_same_sec(file, insn); insn;               \
 114              insn = next_insn_same_sec(file, insn))
 115
 116 static bool is_jump_table_jump(struct instruction *insn)
 117 {
 118         struct alt_group *alt_group = insn->alt_group;
 119
 120         if (insn->jump_table)
 121                 return true;
 122
 123         /* Retpoline alternative for a jump table? */
 124         return alt_group && alt_group->orig_group &&
 125                alt_group->orig_group->first_insn->jump_table;
 126 }
 127
 128 static bool is_sibling_call(struct instruction *insn)
 129 {
 130         /*
 131          * Assume only ELF functions can make sibling calls.  This ensures
 132          * sibling call detection consistency between vmlinux.o and individual
 133          * objects.
 134          */
 135         if (!insn->func)
 136                 return false;
 137
 138         /* An indirect jump is either a sibling call or a jump to a table. */
 139         if (insn->type == INSN_JUMP_DYNAMIC)
 140                 return !is_jump_table_jump(insn);
 141
 142         /* add_jump_destinations() sets insn->call_dest for sibling calls. */
 143         return (is_static_jump(insn) && insn->call_dest);
 144 }
 145
 146 /*
 147  * This checks to see if the given function is a "noreturn" function.
 148  *
 149  * For global functions which are outside the scope of this object file, we
 150  * have to keep a manual list of them.
 151  *
 152  * For local functions, we have to detect them manually by simply looking for
 153  * the lack of a return instruction.
 154  */
 155 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 156                                 int recursion)
 157 {
 158         int i;
 159         struct instruction *insn;
 160         bool empty = true;
 161
 162         /*
 163          * Unfortunately these have to be hard coded because the noreturn
 164          * attribute isn't provided in ELF data.
 165          */
 166         static const char * const global_noreturns[] = {
 167                 "__stack_chk_fail",
 168                 "panic",
 169                 "do_exit",
 170                 "do_task_dead",
 171                 "kthread_exit",
 172                 "make_task_dead",
 173                 "__module_put_and_kthread_exit",
 174                 "kthread_complete_and_exit",
 175                 "__reiserfs_panic",
 176                 "lbug_with_loc",
 177                 "fortify_panic",
 178                 "usercopy_abort",
 179                 "machine_real_restart",
 180                 "rewind_stack_and_make_dead",
 181                 "kunit_try_catch_throw",
 182                 "xen_start_kernel",
 183                 "cpu_bringup_and_idle",
 184                 "do_group_exit",
 185                 "stop_this_cpu",
 186                 "__invalid_creds",
 187         };
 188
 189         if (!func)
 190                 return false;
 191
 192         if (func->bind == STB_WEAK)
 193                 return false;
 194
 195         if (func->bind == STB_GLOBAL)
 196                 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
 197                         if (!strcmp(func->name, global_noreturns[i]))
 198                                 return true;
 199
 200         if (!func->len)
 201                 return false;
 202
 203         insn = find_insn(file, func->sec, func->offset);
 204         if (!insn->func)
 205                 return false;
 206
 207         func_for_each_insn(file, func, insn) {
 208                 empty = false;
 209
 210                 if (insn->type == INSN_RETURN)
 211                         return false;
 212         }
 213
 214         if (empty)
 215                 return false;
 216
 217         /*
 218          * A function can have a sibling call instead of a return.  In that
 219          * case, the function's dead-end status depends on whether the target
 220          * of the sibling call returns.
 221          */
 222         func_for_each_insn(file, func, insn) {
 223                 if (is_sibling_call(insn)) {
 224                         struct instruction *dest = insn->jump_dest;
 225
 226                         if (!dest)
 227                                 /* sibling call to another file */
 228                                 return false;
 229
 230                         /* local sibling call */
 231                         if (recursion == 5) {
 232                                 /*
 233                                  * Infinite recursion: two functions have
 234                                  * sibling calls to each other.  This is a very
 235                                  * rare case.  It means they aren't dead ends.
 236                                  */
 237                                 return false;
 238                         }
 239
 240                         return __dead_end_function(file, dest->func, recursion+1);
 241                 }
 242         }
 243
 244         return true;
 245 }
 246
 247 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
 248 {
 249         return __dead_end_function(file, func, 0);
 250 }
 251
 252 static void init_cfi_state(struct cfi_state *cfi)
 253 {
 254         int i;
 255
 256         for (i = 0; i < CFI_NUM_REGS; i++) {
 257                 cfi->regs[i].base = CFI_UNDEFINED;
 258                 cfi->vals[i].base = CFI_UNDEFINED;
 259         }
 260         cfi->cfa.base = CFI_UNDEFINED;
 261         cfi->drap_reg = CFI_UNDEFINED;
 262         cfi->drap_offset = -1;
 263 }
 264
 265 static void init_insn_state(struct insn_state *state, struct section *sec)
 266 {
 267         memset(state, 0, sizeof(*state));
 268         init_cfi_state(&state->cfi);
 269
 270         /*
 271          * We need the full vmlinux for noinstr validation, otherwise we can
 272          * not correctly determine insn->call_dest->sec (external symbols do
 273          * not have a section).
 274          */
 275         if (vmlinux && noinstr && sec)
 276                 state->noinstr = sec->noinstr;
 277 }
 278
 279 static struct cfi_state *cfi_alloc(void)
 280 {
 281         struct cfi_state *cfi = calloc(sizeof(struct cfi_state), 1);
 282         if (!cfi) {
 283                 WARN("calloc failed");
 284                 exit(1);
 285         }
 286         nr_cfi++;
 287         return cfi;
 288 }
 289
 290 static int cfi_bits;
 291 static struct hlist_head *cfi_hash;
 292
 293 static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
 294 {
 295         return memcmp((void *)cfi1 + sizeof(cfi1->hash),
 296                       (void *)cfi2 + sizeof(cfi2->hash),
 297                       sizeof(struct cfi_state) - sizeof(struct hlist_node));
 298 }
 299
 300 static inline u32 cfi_key(struct cfi_state *cfi)
 301 {
 302         return jhash((void *)cfi + sizeof(cfi->hash),
 303                      sizeof(*cfi) - sizeof(cfi->hash), 0);
 304 }
 305
 306 static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
 307 {
 308         struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
 309         struct cfi_state *obj;
 310
 311         hlist_for_each_entry(obj, head, hash) {
 312                 if (!cficmp(cfi, obj)) {
 313                         nr_cfi_cache++;
 314                         return obj;
 315                 }
 316         }
 317
 318         obj = cfi_alloc();
 319         *obj = *cfi;
 320         hlist_add_head(&obj->hash, head);
 321
 322         return obj;
 323 }
 324
 325 static void cfi_hash_add(struct cfi_state *cfi)
 326 {
 327         struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
 328
 329         hlist_add_head(&cfi->hash, head);
 330 }
 331
 332 static void *cfi_hash_alloc(unsigned long size)
 333 {
 334         cfi_bits = max(10, ilog2(size));
 335         cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
 336                         PROT_READ|PROT_WRITE,
 337                         MAP_PRIVATE|MAP_ANON, -1, 0);
 338         if (cfi_hash == (void *)-1L) {
 339                 WARN("mmap fail cfi_hash");
 340                 cfi_hash = NULL;
 341         }  else if (stats) {
 342                 printf("cfi_bits: %d\n", cfi_bits);
 343         }
 344
 345         return cfi_hash;
 346 }
 347
 348 static unsigned long nr_insns;
 349 static unsigned long nr_insns_visited;
 350
 351 /*
 352  * Call the arch-specific instruction decoder for all the instructions and add
 353  * them to the global instruction list.
 354  */
 355 static int decode_instructions(struct objtool_file *file)
 356 {
 357         struct section *sec;
 358         struct symbol *func;
 359         unsigned long offset;
 360         struct instruction *insn;
 361         int ret;
 362
 363         for_each_sec(file, sec) {
 364
 365                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
 366                         continue;
 367
 368                 if (strcmp(sec->name, ".altinstr_replacement") &&
 369                     strcmp(sec->name, ".altinstr_aux") &&
 370                     strncmp(sec->name, ".discard.", 9))
 371                         sec->text = true;
 372
 373                 if (!strcmp(sec->name, ".noinstr.text") ||
 374                     !strcmp(sec->name, ".entry.text"))
 375                         sec->noinstr = true;
 376
 377                 for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
 378                         insn = malloc(sizeof(*insn));
 379                         if (!insn) {
 380                                 WARN("malloc failed");
 381                                 return -1;
 382                         }
 383                         memset(insn, 0, sizeof(*insn));
 384                         INIT_LIST_HEAD(&insn->alts);
 385                         INIT_LIST_HEAD(&insn->stack_ops);
 386                         INIT_LIST_HEAD(&insn->call_node);
 387
 388                         insn->sec = sec;
 389                         insn->offset = offset;
 390
 391                         ret = arch_decode_instruction(file, sec, offset,
 392                                                       sec->sh.sh_size - offset,
 393                                                       &insn->len, &insn->type,
 394                                                       &insn->immediate,
 395                                                       &insn->stack_ops);
 396                         if (ret)
 397                                 goto err;
 398
 399                         /*
 400                          * By default, "ud2" is a dead end unless otherwise
 401                          * annotated, because GCC 7 inserts it for certain
 402                          * divide-by-zero cases.
 403                          */
 404                         if (insn->type == INSN_BUG)
 405                                 insn->dead_end = true;
 406
 407                         hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
 408                         list_add_tail(&insn->list, &file->insn_list);
 409                         nr_insns++;
 410                 }
 411
 412                 list_for_each_entry(func, &sec->symbol_list, list) {
 413                         if (func->type != STT_FUNC || func->alias != func)
 414                                 continue;
 415
 416                         if (!find_insn(file, sec, func->offset)) {
 417                                 WARN("%s(): can't find starting instruction",
 418                                      func->name);
 419                                 return -1;
 420                         }
 421
 422                         sym_for_each_insn(file, func, insn) {
 423                                 insn->func = func;
 424                                 if (insn->type == INSN_ENDBR && list_empty(&insn->call_node)) {
 425                                         if (insn->offset == insn->func->offset) {
 426                                                 list_add_tail(&insn->call_node, &file->endbr_list);
 427                                                 file->nr_endbr++;
 428                                         } else {
 429                                                 file->nr_endbr_int++;
 430                                         }
 431                                 }
 432                         }
 433                 }
 434         }
 435
 436         if (stats)
 437                 printf("nr_insns: %lu\n", nr_insns);
 438
 439         return 0;
 440
 441 err:
 442         free(insn);
 443         return ret;
 444 }
 445
 446 /*
 447  * Read the pv_ops[] .data table to find the static initialized values.
 448  */
 449 static int add_pv_ops(struct objtool_file *file, const char *symname)
 450 {
 451         struct symbol *sym, *func;
 452         unsigned long off, end;
 453         struct reloc *rel;
 454         int idx;
 455
 456         sym = find_symbol_by_name(file->elf, symname);
 457         if (!sym)
 458                 return 0;
 459
 460         off = sym->offset;
 461         end = off + sym->len;
 462         for (;;) {
 463                 rel = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off);
 464                 if (!rel)
 465                         break;
 466
 467                 func = rel->sym;
 468                 if (func->type == STT_SECTION)
 469                         func = find_symbol_by_offset(rel->sym->sec, rel->addend);
 470
 471                 idx = (rel->offset - sym->offset) / sizeof(unsigned long);
 472
 473                 objtool_pv_add(file, idx, func);
 474
 475                 off = rel->offset + 1;
 476                 if (off > end)
 477                         break;
 478         }
 479
 480         return 0;
 481 }
 482
 483 /*
 484  * Allocate and initialize file->pv_ops[].
 485  */
 486 static int init_pv_ops(struct objtool_file *file)
 487 {
 488         static const char *pv_ops_tables[] = {
 489                 "pv_ops",
 490                 "xen_cpu_ops",
 491                 "xen_irq_ops",
 492                 "xen_mmu_ops",
 493                 NULL,
 494         };
 495         const char *pv_ops;
 496         struct symbol *sym;
 497         int idx, nr;
 498
 499         if (!noinstr)
 500                 return 0;
 501
 502         file->pv_ops = NULL;
 503
 504         sym = find_symbol_by_name(file->elf, "pv_ops");
 505         if (!sym)
 506                 return 0;
 507
 508         nr = sym->len / sizeof(unsigned long);
 509         file->pv_ops = calloc(sizeof(struct pv_state), nr);
 510         if (!file->pv_ops)
 511                 return -1;
 512
 513         for (idx = 0; idx < nr; idx++)
 514                 INIT_LIST_HEAD(&file->pv_ops[idx].targets);
 515
 516         for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++)
 517                 add_pv_ops(file, pv_ops);
 518
 519         return 0;
 520 }
 521
 522 static struct instruction *find_last_insn(struct objtool_file *file,
 523                                           struct section *sec)
 524 {
 525         struct instruction *insn = NULL;
 526         unsigned int offset;
 527         unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
 528
 529         for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
 530                 insn = find_insn(file, sec, offset);
 531
 532         return insn;
 533 }
 534
 535 /*
 536  * Mark "ud2" instructions and manually annotated dead ends.
 537  */
 538 static int add_dead_ends(struct objtool_file *file)
 539 {
 540         struct section *sec;
 541         struct reloc *reloc;
 542         struct instruction *insn;
 543
 544         /*
 545          * Check for manually annotated dead ends.
 546          */
 547         sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
 548         if (!sec)
 549                 goto reachable;
 550
 551         list_for_each_entry(reloc, &sec->reloc_list, list) {
 552                 if (reloc->sym->type != STT_SECTION) {
 553                         WARN("unexpected relocation symbol type in %s", sec->name);
 554                         return -1;
 555                 }
 556                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 557                 if (insn)
 558                         insn = list_prev_entry(insn, list);
 559                 else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
 560                         insn = find_last_insn(file, reloc->sym->sec);
 561                         if (!insn) {
 562                                 WARN("can't find unreachable insn at %s+0x%x",
 563                                      reloc->sym->sec->name, reloc->addend);
 564                                 return -1;
 565                         }
 566                 } else {
 567                         WARN("can't find unreachable insn at %s+0x%x",
 568                              reloc->sym->sec->name, reloc->addend);
 569                         return -1;
 570                 }
 571
 572                 insn->dead_end = true;
 573         }
 574
 575 reachable:
 576         /*
 577          * These manually annotated reachable checks are needed for GCC 4.4,
 578          * where the Linux unreachable() macro isn't supported.  In that case
 579          * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
 580          * not a dead end.
 581          */
 582         sec = find_section_by_name(file->elf, ".rela.discard.reachable");
 583         if (!sec)
 584                 return 0;
 585
 586         list_for_each_entry(reloc, &sec->reloc_list, list) {
 587                 if (reloc->sym->type != STT_SECTION) {
 588                         WARN("unexpected relocation symbol type in %s", sec->name);
 589                         return -1;
 590                 }
 591                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 592                 if (insn)
 593                         insn = list_prev_entry(insn, list);
 594                 else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
 595                         insn = find_last_insn(file, reloc->sym->sec);
 596                         if (!insn) {
 597                                 WARN("can't find reachable insn at %s+0x%x",
 598                                      reloc->sym->sec->name, reloc->addend);
 599                                 return -1;
 600                         }
 601                 } else {
 602                         WARN("can't find reachable insn at %s+0x%x",
 603                              reloc->sym->sec->name, reloc->addend);
 604                         return -1;
 605                 }
 606
 607                 insn->dead_end = false;
 608         }
 609
 610         return 0;
 611 }
 612
 613 static int create_static_call_sections(struct objtool_file *file)
 614 {
 615         struct section *sec;
 616         struct static_call_site *site;
 617         struct instruction *insn;
 618         struct symbol *key_sym;
 619         char *key_name, *tmp;
 620         int idx;
 621
 622         sec = find_section_by_name(file->elf, ".static_call_sites");
 623         if (sec) {
 624                 INIT_LIST_HEAD(&file->static_call_list);
 625                 WARN("file already has .static_call_sites section, skipping");
 626                 return 0;
 627         }
 628
 629         if (list_empty(&file->static_call_list))
 630                 return 0;
 631
 632         idx = 0;
 633         list_for_each_entry(insn, &file->static_call_list, call_node)
 634                 idx++;
 635
 636         sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE,
 637                                  sizeof(struct static_call_site), idx);
 638         if (!sec)
 639                 return -1;
 640
 641         idx = 0;
 642         list_for_each_entry(insn, &file->static_call_list, call_node) {
 643
 644                 site = (struct static_call_site *)sec->data->d_buf + idx;
 645                 memset(site, 0, sizeof(struct static_call_site));
 646
 647                 /* populate reloc for 'addr' */
 648                 if (elf_add_reloc_to_insn(file->elf, sec,
 649                                           idx * sizeof(struct static_call_site),
 650                                           R_X86_64_PC32,
 651                                           insn->sec, insn->offset))
 652                         return -1;
 653
 654                 /* find key symbol */
 655                 key_name = strdup(insn->call_dest->name);
 656                 if (!key_name) {
 657                         perror("strdup");
 658                         return -1;
 659                 }
 660                 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
 661                             STATIC_CALL_TRAMP_PREFIX_LEN)) {
 662                         WARN("static_call: trampoline name malformed: %s", key_name);
 663                         return -1;
 664                 }
 665                 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
 666                 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
 667
 668                 key_sym = find_symbol_by_name(file->elf, tmp);
 669                 if (!key_sym) {
 670                         if (!module) {
 671                                 WARN("static_call: can't find static_call_key symbol: %s", tmp);
 672                                 return -1;
 673                         }
 674
 675                         /*
 676                          * For modules(), the key might not be exported, which
 677                          * means the module can make static calls but isn't
 678                          * allowed to change them.
 679                          *
 680                          * In that case we temporarily set the key to be the
 681                          * trampoline address.  This is fixed up in
 682                          * static_call_add_module().
 683                          */
 684                         key_sym = insn->call_dest;
 685                 }
 686                 free(key_name);
 687
 688                 /* populate reloc for 'key' */
 689                 if (elf_add_reloc(file->elf, sec,
 690                                   idx * sizeof(struct static_call_site) + 4,
 691                                   R_X86_64_PC32, key_sym,
 692                                   is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
 693                         return -1;
 694
 695                 idx++;
 696         }
 697
 698         return 0;
 699 }
 700
 701 static int create_retpoline_sites_sections(struct objtool_file *file)
 702 {
 703         struct instruction *insn;
 704         struct section *sec;
 705         int idx;
 706
 707         sec = find_section_by_name(file->elf, ".retpoline_sites");
 708         if (sec) {
 709                 WARN("file already has .retpoline_sites, skipping");
 710                 return 0;
 711         }
 712
 713         idx = 0;
 714         list_for_each_entry(insn, &file->retpoline_call_list, call_node)
 715                 idx++;
 716
 717         if (!idx)
 718                 return 0;
 719
 720         sec = elf_create_section(file->elf, ".retpoline_sites", 0,
 721                                  sizeof(int), idx);
 722         if (!sec) {
 723                 WARN("elf_create_section: .retpoline_sites");
 724                 return -1;
 725         }
 726
 727         idx = 0;
 728         list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
 729
 730                 int *site = (int *)sec->data->d_buf + idx;
 731                 *site = 0;
 732
 733                 if (elf_add_reloc_to_insn(file->elf, sec,
 734                                           idx * sizeof(int),
 735                                           R_X86_64_PC32,
 736                                           insn->sec, insn->offset)) {
 737                         WARN("elf_add_reloc_to_insn: .retpoline_sites");
 738                         return -1;
 739                 }
 740
 741                 idx++;
 742         }
 743
 744         return 0;
 745 }
 746
 747 static int create_ibt_endbr_seal_sections(struct objtool_file *file)
 748 {
 749         struct instruction *insn;
 750         struct section *sec;
 751         int idx;
 752
 753         sec = find_section_by_name(file->elf, ".ibt_endbr_seal");
 754         if (sec) {
 755                 WARN("file already has .ibt_endbr_seal, skipping");
 756                 return 0;
 757         }
 758
 759         idx = 0;
 760         list_for_each_entry(insn, &file->endbr_list, call_node)
 761                 idx++;
 762
 763         if (stats) {
 764                 printf("ibt: ENDBR at function start: %d\n", file->nr_endbr);
 765                 printf("ibt: ENDBR inside functions:  %d\n", file->nr_endbr_int);
 766                 printf("ibt: superfluous ENDBR:       %d\n", idx);
 767         }
 768
 769         if (!idx)
 770                 return 0;
 771
 772         sec = elf_create_section(file->elf, ".ibt_endbr_seal", 0,
 773                                  sizeof(int), idx);
 774         if (!sec) {
 775                 WARN("elf_create_section: .ibt_endbr_seal");
 776                 return -1;
 777         }
 778
 779         idx = 0;
 780         list_for_each_entry(insn, &file->endbr_list, call_node) {
 781
 782                 int *site = (int *)sec->data->d_buf + idx;
 783                 *site = 0;
 784
 785                 if (elf_add_reloc_to_insn(file->elf, sec,
 786                                           idx * sizeof(int),
 787                                           R_X86_64_PC32,
 788                                           insn->sec, insn->offset)) {
 789                         WARN("elf_add_reloc_to_insn: .ibt_endbr_seal");
 790                         return -1;
 791                 }
 792
 793                 idx++;
 794         }
 795
 796         return 0;
 797 }
 798
 799 static int create_mcount_loc_sections(struct objtool_file *file)
 800 {
 801         struct section *sec;
 802         unsigned long *loc;
 803         struct instruction *insn;
 804         int idx;
 805
 806         sec = find_section_by_name(file->elf, "__mcount_loc");
 807         if (sec) {
 808                 INIT_LIST_HEAD(&file->mcount_loc_list);
 809                 WARN("file already has __mcount_loc section, skipping");
 810                 return 0;
 811         }
 812
 813         if (list_empty(&file->mcount_loc_list))
 814                 return 0;
 815
 816         idx = 0;
 817         list_for_each_entry(insn, &file->mcount_loc_list, call_node)
 818                 idx++;
 819
 820         sec = elf_create_section(file->elf, "__mcount_loc", 0, sizeof(unsigned long), idx);
 821         if (!sec)
 822                 return -1;
 823
 824         idx = 0;
 825         list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
 826
 827                 loc = (unsigned long *)sec->data->d_buf + idx;
 828                 memset(loc, 0, sizeof(unsigned long));
 829
 830                 if (elf_add_reloc_to_insn(file->elf, sec,
 831                                           idx * sizeof(unsigned long),
 832                                           R_X86_64_64,
 833                                           insn->sec, insn->offset))
 834                         return -1;
 835
 836                 idx++;
 837         }
 838
 839         return 0;
 840 }
 841
 842 /*
 843  * Warnings shouldn't be reported for ignored functions.
 844  */
 845 static void add_ignores(struct objtool_file *file)
 846 {
 847         struct instruction *insn;
 848         struct section *sec;
 849         struct symbol *func;
 850         struct reloc *reloc;
 851
 852         sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
 853         if (!sec)
 854                 return;
 855
 856         list_for_each_entry(reloc, &sec->reloc_list, list) {
 857                 switch (reloc->sym->type) {
 858                 case STT_FUNC:
 859                         func = reloc->sym;
 860                         break;
 861
 862                 case STT_SECTION:
 863                         func = find_func_by_offset(reloc->sym->sec, reloc->addend);
 864                         if (!func)
 865                                 continue;
 866                         break;
 867
 868                 default:
 869                         WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type);
 870                         continue;
 871                 }
 872
 873                 func_for_each_insn(file, func, insn)
 874                         insn->ignore = true;
 875         }
 876 }
 877
 878 /*
 879  * This is a whitelist of functions that is allowed to be called with AC set.
 880  * The list is meant to be minimal and only contains compiler instrumentation
 881  * ABI and a few functions used to implement *_{to,from}_user() functions.
 882  *
 883  * These functions must not directly change AC, but may PUSHF/POPF.
 884  */
 885 static const char *uaccess_safe_builtin[] = {
 886         /* KASAN */
 887         "kasan_report",
 888         "kasan_check_range",
 889         /* KASAN out-of-line */
 890         "__asan_loadN_noabort",
 891         "__asan_load1_noabort",
 892         "__asan_load2_noabort",
 893         "__asan_load4_noabort",
 894         "__asan_load8_noabort",
 895         "__asan_load16_noabort",
 896         "__asan_storeN_noabort",
 897         "__asan_store1_noabort",
 898         "__asan_store2_noabort",
 899         "__asan_store4_noabort",
 900         "__asan_store8_noabort",
 901         "__asan_store16_noabort",
 902         "__kasan_check_read",
 903         "__kasan_check_write",
 904         /* KASAN in-line */
 905         "__asan_report_load_n_noabort",
 906         "__asan_report_load1_noabort",
 907         "__asan_report_load2_noabort",
 908         "__asan_report_load4_noabort",
 909         "__asan_report_load8_noabort",
 910         "__asan_report_load16_noabort",
 911         "__asan_report_store_n_noabort",
 912         "__asan_report_store1_noabort",
 913         "__asan_report_store2_noabort",
 914         "__asan_report_store4_noabort",
 915         "__asan_report_store8_noabort",
 916         "__asan_report_store16_noabort",
 917         /* KCSAN */
 918         "__kcsan_check_access",
 919         "__kcsan_mb",
 920         "__kcsan_wmb",
 921         "__kcsan_rmb",
 922         "__kcsan_release",
 923         "kcsan_found_watchpoint",
 924         "kcsan_setup_watchpoint",
 925         "kcsan_check_scoped_accesses",
 926         "kcsan_disable_current",
 927         "kcsan_enable_current_nowarn",
 928         /* KCSAN/TSAN */
 929         "__tsan_func_entry",
 930         "__tsan_func_exit",
 931         "__tsan_read_range",
 932         "__tsan_write_range",
 933         "__tsan_read1",
 934         "__tsan_read2",
 935         "__tsan_read4",
 936         "__tsan_read8",
 937         "__tsan_read16",
 938         "__tsan_write1",
 939         "__tsan_write2",
 940         "__tsan_write4",
 941         "__tsan_write8",
 942         "__tsan_write16",
 943         "__tsan_read_write1",
 944         "__tsan_read_write2",
 945         "__tsan_read_write4",
 946         "__tsan_read_write8",
 947         "__tsan_read_write16",
 948         "__tsan_atomic8_load",
 949         "__tsan_atomic16_load",
 950         "__tsan_atomic32_load",
 951         "__tsan_atomic64_load",
 952         "__tsan_atomic8_store",
 953         "__tsan_atomic16_store",
 954         "__tsan_atomic32_store",
 955         "__tsan_atomic64_store",
 956         "__tsan_atomic8_exchange",
 957         "__tsan_atomic16_exchange",
 958         "__tsan_atomic32_exchange",
 959         "__tsan_atomic64_exchange",
 960         "__tsan_atomic8_fetch_add",
 961         "__tsan_atomic16_fetch_add",
 962         "__tsan_atomic32_fetch_add",
 963         "__tsan_atomic64_fetch_add",
 964         "__tsan_atomic8_fetch_sub",
 965         "__tsan_atomic16_fetch_sub",
 966         "__tsan_atomic32_fetch_sub",
 967         "__tsan_atomic64_fetch_sub",
 968         "__tsan_atomic8_fetch_and",
 969         "__tsan_atomic16_fetch_and",
 970         "__tsan_atomic32_fetch_and",
 971         "__tsan_atomic64_fetch_and",
 972         "__tsan_atomic8_fetch_or",
 973         "__tsan_atomic16_fetch_or",
 974         "__tsan_atomic32_fetch_or",
 975         "__tsan_atomic64_fetch_or",
 976         "__tsan_atomic8_fetch_xor",
 977         "__tsan_atomic16_fetch_xor",
 978         "__tsan_atomic32_fetch_xor",
 979         "__tsan_atomic64_fetch_xor",
 980         "__tsan_atomic8_fetch_nand",
 981         "__tsan_atomic16_fetch_nand",
 982         "__tsan_atomic32_fetch_nand",
 983         "__tsan_atomic64_fetch_nand",
 984         "__tsan_atomic8_compare_exchange_strong",
 985         "__tsan_atomic16_compare_exchange_strong",
 986         "__tsan_atomic32_compare_exchange_strong",
 987         "__tsan_atomic64_compare_exchange_strong",
 988         "__tsan_atomic8_compare_exchange_weak",
 989         "__tsan_atomic16_compare_exchange_weak",
 990         "__tsan_atomic32_compare_exchange_weak",
 991         "__tsan_atomic64_compare_exchange_weak",
 992         "__tsan_atomic8_compare_exchange_val",
 993         "__tsan_atomic16_compare_exchange_val",
 994         "__tsan_atomic32_compare_exchange_val",
 995         "__tsan_atomic64_compare_exchange_val",
 996         "__tsan_atomic_thread_fence",
 997         "__tsan_atomic_signal_fence",
 998         /* KCOV */
 999         "write_comp_data",
1000         "check_kcov_mode",
1001         "__sanitizer_cov_trace_pc",
1002         "__sanitizer_cov_trace_const_cmp1",
1003         "__sanitizer_cov_trace_const_cmp2",
1004         "__sanitizer_cov_trace_const_cmp4",
1005         "__sanitizer_cov_trace_const_cmp8",
1006         "__sanitizer_cov_trace_cmp1",
1007         "__sanitizer_cov_trace_cmp2",
1008         "__sanitizer_cov_trace_cmp4",
1009         "__sanitizer_cov_trace_cmp8",
1010         "__sanitizer_cov_trace_switch",
1011         /* UBSAN */
1012         "ubsan_type_mismatch_common",
1013         "__ubsan_handle_type_mismatch",
1014         "__ubsan_handle_type_mismatch_v1",
1015         "__ubsan_handle_shift_out_of_bounds",
1016         /* misc */
1017         "csum_partial_copy_generic",
1018         "copy_mc_fragile",
1019         "copy_mc_fragile_handle_tail",
1020         "copy_mc_enhanced_fast_string",
1021         "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
1022         NULL
1023 };
1024
1025 static void add_uaccess_safe(struct objtool_file *file)
1026 {
1027         struct symbol *func;
1028         const char **name;
1029
1030         if (!uaccess)
1031                 return;
1032
1033         for (name = uaccess_safe_builtin; *name; name++) {
1034                 func = find_symbol_by_name(file->elf, *name);
1035                 if (!func)
1036                         continue;
1037
1038                 func->uaccess_safe = true;
1039         }
1040 }
1041
1042 /*
1043  * FIXME: For now, just ignore any alternatives which add retpolines.  This is
1044  * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
1045  * But it at least allows objtool to understand the control flow *around* the
1046  * retpoline.
1047  */
1048 static int add_ignore_alternatives(struct objtool_file *file)
1049 {
1050         struct section *sec;
1051         struct reloc *reloc;
1052         struct instruction *insn;
1053
1054         sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
1055         if (!sec)
1056                 return 0;
1057
1058         list_for_each_entry(reloc, &sec->reloc_list, list) {
1059                 if (reloc->sym->type != STT_SECTION) {
1060                         WARN("unexpected relocation symbol type in %s", sec->name);
1061                         return -1;
1062                 }
1063
1064                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1065                 if (!insn) {
1066                         WARN("bad .discard.ignore_alts entry");
1067                         return -1;
1068                 }
1069
1070                 insn->ignore_alts = true;
1071         }
1072
1073         return 0;
1074 }
1075
1076 __weak bool arch_is_retpoline(struct symbol *sym)
1077 {
1078         return false;
1079 }
1080
1081 #define NEGATIVE_RELOC  ((void *)-1L)
1082
1083 static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
1084 {
1085         if (insn->reloc == NEGATIVE_RELOC)
1086                 return NULL;
1087
1088         if (!insn->reloc) {
1089                 if (!file)
1090                         return NULL;
1091
1092                 insn->reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1093                                                        insn->offset, insn->len);
1094                 if (!insn->reloc) {
1095                         insn->reloc = NEGATIVE_RELOC;
1096                         return NULL;
1097                 }
1098         }
1099
1100         return insn->reloc;
1101 }
1102
1103 static void remove_insn_ops(struct instruction *insn)
1104 {
1105         struct stack_op *op, *tmp;
1106
1107         list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
1108                 list_del(&op->list);
1109                 free(op);
1110         }
1111 }
1112
1113 static void annotate_call_site(struct objtool_file *file,
1114                                struct instruction *insn, bool sibling)
1115 {
1116         struct reloc *reloc = insn_reloc(file, insn);
1117         struct symbol *sym = insn->call_dest;
1118
1119         if (!sym)
1120                 sym = reloc->sym;
1121
1122         /*
1123          * Alternative replacement code is just template code which is
1124          * sometimes copied to the original instruction. For now, don't
1125          * annotate it. (In the future we might consider annotating the
1126          * original instruction if/when it ever makes sense to do so.)
1127          */
1128         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1129                 return;
1130
1131         if (sym->static_call_tramp) {
1132                 list_add_tail(&insn->call_node, &file->static_call_list);
1133                 return;
1134         }
1135
1136         if (sym->retpoline_thunk) {
1137                 list_add_tail(&insn->call_node, &file->retpoline_call_list);
1138                 return;
1139         }
1140
1141         /*
1142          * Many compilers cannot disable KCOV or sanitizer calls with a function
1143          * attribute so they need a little help, NOP out any such calls from
1144          * noinstr text.
1145          */
1146         if (insn->sec->noinstr && sym->profiling_func) {
1147                 if (reloc) {
1148                         reloc->type = R_NONE;
1149                         elf_write_reloc(file->elf, reloc);
1150                 }
1151
1152                 elf_write_insn(file->elf, insn->sec,
1153                                insn->offset, insn->len,
1154                                sibling ? arch_ret_insn(insn->len)
1155                                        : arch_nop_insn(insn->len));
1156
1157                 insn->type = sibling ? INSN_RETURN : INSN_NOP;
1158
1159                 if (sibling) {
1160                         /*
1161                          * We've replaced the tail-call JMP insn by two new
1162                          * insn: RET; INT3, except we only have a single struct
1163                          * insn here. Mark it retpoline_safe to avoid the SLS
1164                          * warning, instead of adding another insn.
1165                          */
1166                         insn->retpoline_safe = true;
1167                 }
1168
1169                 return;
1170         }
1171
1172         if (mcount && sym->fentry) {
1173                 if (sibling)
1174                         WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset);
1175
1176                 if (reloc) {
1177                         reloc->type = R_NONE;
1178                         elf_write_reloc(file->elf, reloc);
1179                 }
1180
1181                 elf_write_insn(file->elf, insn->sec,
1182                                insn->offset, insn->len,
1183                                arch_nop_insn(insn->len));
1184
1185                 insn->type = INSN_NOP;
1186
1187                 list_add_tail(&insn->call_node, &file->mcount_loc_list);
1188                 return;
1189         }
1190
1191         if (!sibling && dead_end_function(file, sym))
1192                 insn->dead_end = true;
1193 }
1194
1195 static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1196                           struct symbol *dest, bool sibling)
1197 {
1198         insn->call_dest = dest;
1199         if (!dest)
1200                 return;
1201
1202         /*
1203          * Whatever stack impact regular CALLs have, should be undone
1204          * by the RETURN of the called function.
1205          *
1206          * Annotated intra-function calls retain the stack_ops but
1207          * are converted to JUMP, see read_intra_function_calls().
1208          */
1209         remove_insn_ops(insn);
1210
1211         annotate_call_site(file, insn, sibling);
1212 }
1213
1214 static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1215 {
1216         /*
1217          * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1218          * so convert them accordingly.
1219          */
1220         switch (insn->type) {
1221         case INSN_CALL:
1222                 insn->type = INSN_CALL_DYNAMIC;
1223                 break;
1224         case INSN_JUMP_UNCONDITIONAL:
1225                 insn->type = INSN_JUMP_DYNAMIC;
1226                 break;
1227         case INSN_JUMP_CONDITIONAL:
1228                 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1229                 break;
1230         default:
1231                 return;
1232         }
1233
1234         insn->retpoline_safe = true;
1235
1236         /*
1237          * Whatever stack impact regular CALLs have, should be undone
1238          * by the RETURN of the called function.
1239          *
1240          * Annotated intra-function calls retain the stack_ops but
1241          * are converted to JUMP, see read_intra_function_calls().
1242          */
1243         remove_insn_ops(insn);
1244
1245         annotate_call_site(file, insn, false);
1246 }
1247
1248 static bool same_function(struct instruction *insn1, struct instruction *insn2)
1249 {
1250         return insn1->func->pfunc == insn2->func->pfunc;
1251 }
1252
1253 static bool is_first_func_insn(struct objtool_file *file, struct instruction *insn)
1254 {
1255         if (insn->offset == insn->func->offset)
1256                 return true;
1257
1258         if (ibt) {
1259                 struct instruction *prev = prev_insn_same_sym(file, insn);
1260
1261                 if (prev && prev->type == INSN_ENDBR &&
1262                     insn->offset == insn->func->offset + prev->len)
1263                         return true;
1264         }
1265
1266         return false;
1267 }
1268
1269 /*
1270  * Find the destination instructions for all jumps.
1271  */
1272 static int add_jump_destinations(struct objtool_file *file)
1273 {
1274         struct instruction *insn;
1275         struct reloc *reloc;
1276         struct section *dest_sec;
1277         unsigned long dest_off;
1278
1279         for_each_insn(file, insn) {
1280                 if (!is_static_jump(insn))
1281                         continue;
1282
1283                 reloc = insn_reloc(file, insn);
1284                 if (!reloc) {
1285                         dest_sec = insn->sec;
1286                         dest_off = arch_jump_destination(insn);
1287                 } else if (reloc->sym->type == STT_SECTION) {
1288                         dest_sec = reloc->sym->sec;
1289                         dest_off = arch_dest_reloc_offset(reloc->addend);
1290                 } else if (reloc->sym->retpoline_thunk) {
1291                         add_retpoline_call(file, insn);
1292                         continue;
1293                 } else if (insn->func) {
1294                         /* internal or external sibling call (with reloc) */
1295                         add_call_dest(file, insn, reloc->sym, true);
1296                         continue;
1297                 } else if (reloc->sym->sec->idx) {
1298                         dest_sec = reloc->sym->sec;
1299                         dest_off = reloc->sym->sym.st_value +
1300                                    arch_dest_reloc_offset(reloc->addend);
1301                 } else {
1302                         /* non-func asm code jumping to another file */
1303                         continue;
1304                 }
1305
1306                 insn->jump_dest = find_insn(file, dest_sec, dest_off);
1307                 if (!insn->jump_dest) {
1308
1309                         /*
1310                          * This is a special case where an alt instruction
1311                          * jumps past the end of the section.  These are
1312                          * handled later in handle_group_alt().
1313                          */
1314                         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1315                                 continue;
1316
1317                         WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
1318                                   insn->sec, insn->offset, dest_sec->name,
1319                                   dest_off);
1320                         return -1;
1321                 }
1322
1323                 /*
1324                  * Cross-function jump.
1325                  */
1326                 if (insn->func && insn->jump_dest->func &&
1327                     insn->func != insn->jump_dest->func) {
1328
1329                         /*
1330                          * For GCC 8+, create parent/child links for any cold
1331                          * subfunctions.  This is _mostly_ redundant with a
1332                          * similar initialization in read_symbols().
1333                          *
1334                          * If a function has aliases, we want the *first* such
1335                          * function in the symbol table to be the subfunction's
1336                          * parent.  In that case we overwrite the
1337                          * initialization done in read_symbols().
1338                          *
1339                          * However this code can't completely replace the
1340                          * read_symbols() code because this doesn't detect the
1341                          * case where the parent function's only reference to a
1342                          * subfunction is through a jump table.
1343                          */
1344                         if (!strstr(insn->func->name, ".cold") &&
1345                             strstr(insn->jump_dest->func->name, ".cold")) {
1346                                 insn->func->cfunc = insn->jump_dest->func;
1347                                 insn->jump_dest->func->pfunc = insn->func;
1348
1349                         } else if (!same_function(insn, insn->jump_dest) &&
1350                                    is_first_func_insn(file, insn->jump_dest)) {
1351                                 /* internal sibling call (without reloc) */
1352                                 add_call_dest(file, insn, insn->jump_dest->func, true);
1353                         }
1354                 }
1355         }
1356
1357         return 0;
1358 }
1359
1360 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1361 {
1362         struct symbol *call_dest;
1363
1364         call_dest = find_func_by_offset(sec, offset);
1365         if (!call_dest)
1366                 call_dest = find_symbol_by_offset(sec, offset);
1367
1368         return call_dest;
1369 }
1370
1371 /*
1372  * Find the destination instructions for all calls.
1373  */
1374 static int add_call_destinations(struct objtool_file *file)
1375 {
1376         struct instruction *insn;
1377         unsigned long dest_off;
1378         struct symbol *dest;
1379         struct reloc *reloc;
1380
1381         for_each_insn(file, insn) {
1382                 if (insn->type != INSN_CALL)
1383                         continue;
1384
1385                 reloc = insn_reloc(file, insn);
1386                 if (!reloc) {
1387                         dest_off = arch_jump_destination(insn);
1388                         dest = find_call_destination(insn->sec, dest_off);
1389
1390                         add_call_dest(file, insn, dest, false);
1391
1392                         if (insn->ignore)
1393                                 continue;
1394
1395                         if (!insn->call_dest) {
1396                                 WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);
1397                                 return -1;
1398                         }
1399
1400                         if (insn->func && insn->call_dest->type != STT_FUNC) {
1401                                 WARN_FUNC("unsupported call to non-function",
1402                                           insn->sec, insn->offset);
1403                                 return -1;
1404                         }
1405
1406                 } else if (reloc->sym->type == STT_SECTION) {
1407                         dest_off = arch_dest_reloc_offset(reloc->addend);
1408                         dest = find_call_destination(reloc->sym->sec, dest_off);
1409                         if (!dest) {
1410                                 WARN_FUNC("can't find call dest symbol at %s+0x%lx",
1411                                           insn->sec, insn->offset,
1412                                           reloc->sym->sec->name,
1413                                           dest_off);
1414                                 return -1;
1415                         }
1416
1417                         add_call_dest(file, insn, dest, false);
1418
1419                 } else if (reloc->sym->retpoline_thunk) {
1420                         add_retpoline_call(file, insn);
1421
1422                 } else
1423                         add_call_dest(file, insn, reloc->sym, false);
1424         }
1425
1426         return 0;
1427 }
1428
1429 /*
1430  * The .alternatives section requires some extra special care over and above
1431  * other special sections because alternatives are patched in place.
1432  */
1433 static int handle_group_alt(struct objtool_file *file,
1434                             struct special_alt *special_alt,
1435                             struct instruction *orig_insn,
1436                             struct instruction **new_insn)
1437 {
1438         struct instruction *last_orig_insn, *last_new_insn = NULL, *insn, *nop = NULL;
1439         struct alt_group *orig_alt_group, *new_alt_group;
1440         unsigned long dest_off;
1441
1442
1443         orig_alt_group = malloc(sizeof(*orig_alt_group));
1444         if (!orig_alt_group) {
1445                 WARN("malloc failed");
1446                 return -1;
1447         }
1448         orig_alt_group->cfi = calloc(special_alt->orig_len,
1449                                      sizeof(struct cfi_state *));
1450         if (!orig_alt_group->cfi) {
1451                 WARN("calloc failed");
1452                 return -1;
1453         }
1454
1455         last_orig_insn = NULL;
1456         insn = orig_insn;
1457         sec_for_each_insn_from(file, insn) {
1458                 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1459                         break;
1460
1461                 insn->alt_group = orig_alt_group;
1462                 last_orig_insn = insn;
1463         }
1464         orig_alt_group->orig_group = NULL;
1465         orig_alt_group->first_insn = orig_insn;
1466         orig_alt_group->last_insn = last_orig_insn;
1467
1468
1469         new_alt_group = malloc(sizeof(*new_alt_group));
1470         if (!new_alt_group) {
1471                 WARN("malloc failed");
1472                 return -1;
1473         }
1474
1475         if (special_alt->new_len < special_alt->orig_len) {
1476                 /*
1477                  * Insert a fake nop at the end to make the replacement
1478                  * alt_group the same size as the original.  This is needed to
1479                  * allow propagate_alt_cfi() to do its magic.  When the last
1480                  * instruction affects the stack, the instruction after it (the
1481                  * nop) will propagate the new state to the shared CFI array.
1482                  */
1483                 nop = malloc(sizeof(*nop));
1484                 if (!nop) {
1485                         WARN("malloc failed");
1486                         return -1;
1487                 }
1488                 memset(nop, 0, sizeof(*nop));
1489                 INIT_LIST_HEAD(&nop->alts);
1490                 INIT_LIST_HEAD(&nop->stack_ops);
1491
1492                 nop->sec = special_alt->new_sec;
1493                 nop->offset = special_alt->new_off + special_alt->new_len;
1494                 nop->len = special_alt->orig_len - special_alt->new_len;
1495                 nop->type = INSN_NOP;
1496                 nop->func = orig_insn->func;
1497                 nop->alt_group = new_alt_group;
1498                 nop->ignore = orig_insn->ignore_alts;
1499         }
1500
1501         if (!special_alt->new_len) {
1502                 *new_insn = nop;
1503                 goto end;
1504         }
1505
1506         insn = *new_insn;
1507         sec_for_each_insn_from(file, insn) {
1508                 struct reloc *alt_reloc;
1509
1510                 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1511                         break;
1512
1513                 last_new_insn = insn;
1514
1515                 insn->ignore = orig_insn->ignore_alts;
1516                 insn->func = orig_insn->func;
1517                 insn->alt_group = new_alt_group;
1518
1519                 /*
1520                  * Since alternative replacement code is copy/pasted by the
1521                  * kernel after applying relocations, generally such code can't
1522                  * have relative-address relocation references to outside the
1523                  * .altinstr_replacement section, unless the arch's
1524                  * alternatives code can adjust the relative offsets
1525                  * accordingly.
1526                  */
1527                 alt_reloc = insn_reloc(file, insn);
1528                 if (alt_reloc &&
1529                     !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1530
1531                         WARN_FUNC("unsupported relocation in alternatives section",
1532                                   insn->sec, insn->offset);
1533                         return -1;
1534                 }
1535
1536                 if (!is_static_jump(insn))
1537                         continue;
1538
1539                 if (!insn->immediate)
1540                         continue;
1541
1542                 dest_off = arch_jump_destination(insn);
1543                 if (dest_off == special_alt->new_off + special_alt->new_len)
1544                         insn->jump_dest = next_insn_same_sec(file, last_orig_insn);
1545
1546                 if (!insn->jump_dest) {
1547                         WARN_FUNC("can't find alternative jump destination",
1548                                   insn->sec, insn->offset);
1549                         return -1;
1550                 }
1551         }
1552
1553         if (!last_new_insn) {
1554                 WARN_FUNC("can't find last new alternative instruction",
1555                           special_alt->new_sec, special_alt->new_off);
1556                 return -1;
1557         }
1558
1559         if (nop)
1560                 list_add(&nop->list, &last_new_insn->list);
1561 end:
1562         new_alt_group->orig_group = orig_alt_group;
1563         new_alt_group->first_insn = *new_insn;
1564         new_alt_group->last_insn = nop ? : last_new_insn;
1565         new_alt_group->cfi = orig_alt_group->cfi;
1566         return 0;
1567 }
1568
1569 /*
1570  * A jump table entry can either convert a nop to a jump or a jump to a nop.
1571  * If the original instruction is a jump, make the alt entry an effective nop
1572  * by just skipping the original instruction.
1573  */
1574 static int handle_jump_alt(struct objtool_file *file,
1575                            struct special_alt *special_alt,
1576                            struct instruction *orig_insn,
1577                            struct instruction **new_insn)
1578 {
1579         if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1580             orig_insn->type != INSN_NOP) {
1581
1582                 WARN_FUNC("unsupported instruction at jump label",
1583                           orig_insn->sec, orig_insn->offset);
1584                 return -1;
1585         }
1586
1587         if (special_alt->key_addend & 2) {
1588                 struct reloc *reloc = insn_reloc(file, orig_insn);
1589
1590                 if (reloc) {
1591                         reloc->type = R_NONE;
1592                         elf_write_reloc(file->elf, reloc);
1593                 }
1594                 elf_write_insn(file->elf, orig_insn->sec,
1595                                orig_insn->offset, orig_insn->len,
1596                                arch_nop_insn(orig_insn->len));
1597                 orig_insn->type = INSN_NOP;
1598         }
1599
1600         if (orig_insn->type == INSN_NOP) {
1601                 if (orig_insn->len == 2)
1602                         file->jl_nop_short++;
1603                 else
1604                         file->jl_nop_long++;
1605
1606                 return 0;
1607         }
1608
1609         if (orig_insn->len == 2)
1610                 file->jl_short++;
1611         else
1612                 file->jl_long++;
1613
1614         *new_insn = list_next_entry(orig_insn, list);
1615         return 0;
1616 }
1617
1618 /*
1619  * Read all the special sections which have alternate instructions which can be
1620  * patched in or redirected to at runtime.  Each instruction having alternate
1621  * instruction(s) has them added to its insn->alts list, which will be
1622  * traversed in validate_branch().
1623  */
1624 static int add_special_section_alts(struct objtool_file *file)
1625 {
1626         struct list_head special_alts;
1627         struct instruction *orig_insn, *new_insn;
1628         struct special_alt *special_alt, *tmp;
1629         struct alternative *alt;
1630         int ret;
1631
1632         ret = special_get_alts(file->elf, &special_alts);
1633         if (ret)
1634                 return ret;
1635
1636         list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1637
1638                 orig_insn = find_insn(file, special_alt->orig_sec,
1639                                       special_alt->orig_off);
1640                 if (!orig_insn) {
1641                         WARN_FUNC("special: can't find orig instruction",
1642                                   special_alt->orig_sec, special_alt->orig_off);
1643                         ret = -1;
1644                         goto out;
1645                 }
1646
1647                 new_insn = NULL;
1648                 if (!special_alt->group || special_alt->new_len) {
1649                         new_insn = find_insn(file, special_alt->new_sec,
1650                                              special_alt->new_off);
1651                         if (!new_insn) {
1652                                 WARN_FUNC("special: can't find new instruction",
1653                                           special_alt->new_sec,
1654                                           special_alt->new_off);
1655                                 ret = -1;
1656                                 goto out;
1657                         }
1658                 }
1659
1660                 if (special_alt->group) {
1661                         if (!special_alt->orig_len) {
1662                                 WARN_FUNC("empty alternative entry",
1663                                           orig_insn->sec, orig_insn->offset);
1664                                 continue;
1665                         }
1666
1667                         ret = handle_group_alt(file, special_alt, orig_insn,
1668                                                &new_insn);
1669                         if (ret)
1670                                 goto out;
1671                 } else if (special_alt->jump_or_nop) {
1672                         ret = handle_jump_alt(file, special_alt, orig_insn,
1673                                               &new_insn);
1674                         if (ret)
1675                                 goto out;
1676                 }
1677
1678                 alt = malloc(sizeof(*alt));
1679                 if (!alt) {
1680                         WARN("malloc failed");
1681                         ret = -1;
1682                         goto out;
1683                 }
1684
1685                 alt->insn = new_insn;
1686                 alt->skip_orig = special_alt->skip_orig;
1687                 orig_insn->ignore_alts |= special_alt->skip_alt;
1688                 list_add_tail(&alt->list, &orig_insn->alts);
1689
1690                 list_del(&special_alt->list);
1691                 free(special_alt);
1692         }
1693
1694         if (stats) {
1695                 printf("jl\\\tNOP\tJMP\n");
1696                 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
1697                 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
1698         }
1699
1700 out:
1701         return ret;
1702 }
1703
1704 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
1705                             struct reloc *table)
1706 {
1707         struct reloc *reloc = table;
1708         struct instruction *dest_insn;
1709         struct alternative *alt;
1710         struct symbol *pfunc = insn->func->pfunc;
1711         unsigned int prev_offset = 0;
1712
1713         /*
1714          * Each @reloc is a switch table relocation which points to the target
1715          * instruction.
1716          */
1717         list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
1718
1719                 /* Check for the end of the table: */
1720                 if (reloc != table && reloc->jump_table_start)
1721                         break;
1722
1723                 /* Make sure the table entries are consecutive: */
1724                 if (prev_offset && reloc->offset != prev_offset + 8)
1725                         break;
1726
1727                 /* Detect function pointers from contiguous objects: */
1728                 if (reloc->sym->sec == pfunc->sec &&
1729                     reloc->addend == pfunc->offset)
1730                         break;
1731
1732                 dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
1733                 if (!dest_insn)
1734                         break;
1735
1736                 /* Make sure the destination is in the same function: */
1737                 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
1738                         break;
1739
1740                 alt = malloc(sizeof(*alt));
1741                 if (!alt) {
1742                         WARN("malloc failed");
1743                         return -1;
1744                 }
1745
1746                 alt->insn = dest_insn;
1747                 list_add_tail(&alt->list, &insn->alts);
1748                 prev_offset = reloc->offset;
1749         }
1750
1751         if (!prev_offset) {
1752                 WARN_FUNC("can't find switch jump table",
1753                           insn->sec, insn->offset);
1754                 return -1;
1755         }
1756
1757         return 0;
1758 }
1759
1760 /*
1761  * find_jump_table() - Given a dynamic jump, find the switch jump table
1762  * associated with it.
1763  */
1764 static struct reloc *find_jump_table(struct objtool_file *file,
1765                                       struct symbol *func,
1766                                       struct instruction *insn)
1767 {
1768         struct reloc *table_reloc;
1769         struct instruction *dest_insn, *orig_insn = insn;
1770
1771         /*
1772          * Backward search using the @first_jump_src links, these help avoid
1773          * much of the 'in between' code. Which avoids us getting confused by
1774          * it.
1775          */
1776         for (;
1777              insn && insn->func && insn->func->pfunc == func;
1778              insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
1779
1780                 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1781                         break;
1782
1783                 /* allow small jumps within the range */
1784                 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1785                     insn->jump_dest &&
1786                     (insn->jump_dest->offset <= insn->offset ||
1787                      insn->jump_dest->offset > orig_insn->offset))
1788                     break;
1789
1790                 table_reloc = arch_find_switch_table(file, insn);
1791                 if (!table_reloc)
1792                         continue;
1793                 dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
1794                 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1795                         continue;
1796
1797                 return table_reloc;
1798         }
1799
1800         return NULL;
1801 }
1802
1803 /*
1804  * First pass: Mark the head of each jump table so that in the next pass,
1805  * we know when a given jump table ends and the next one starts.
1806  */
1807 static void mark_func_jump_tables(struct objtool_file *file,
1808                                     struct symbol *func)
1809 {
1810         struct instruction *insn, *last = NULL;
1811         struct reloc *reloc;
1812
1813         func_for_each_insn(file, func, insn) {
1814                 if (!last)
1815                         last = insn;
1816
1817                 /*
1818                  * Store back-pointers for unconditional forward jumps such
1819                  * that find_jump_table() can back-track using those and
1820                  * avoid some potentially confusing code.
1821                  */
1822                 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1823                     insn->offset > last->offset &&
1824                     insn->jump_dest->offset > insn->offset &&
1825                     !insn->jump_dest->first_jump_src) {
1826
1827                         insn->jump_dest->first_jump_src = insn;
1828                         last = insn->jump_dest;
1829                 }
1830
1831                 if (insn->type != INSN_JUMP_DYNAMIC)
1832                         continue;
1833
1834                 reloc = find_jump_table(file, func, insn);
1835                 if (reloc) {
1836                         reloc->jump_table_start = true;
1837                         insn->jump_table = reloc;
1838                 }
1839         }
1840 }
1841
1842 static int add_func_jump_tables(struct objtool_file *file,
1843                                   struct symbol *func)
1844 {
1845         struct instruction *insn;
1846         int ret;
1847
1848         func_for_each_insn(file, func, insn) {
1849                 if (!insn->jump_table)
1850                         continue;
1851
1852                 ret = add_jump_table(file, insn, insn->jump_table);
1853                 if (ret)
1854                         return ret;
1855         }
1856
1857         return 0;
1858 }
1859
1860 /*
1861  * For some switch statements, gcc generates a jump table in the .rodata
1862  * section which contains a list of addresses within the function to jump to.
1863  * This finds these jump tables and adds them to the insn->alts lists.
1864  */
1865 static int add_jump_table_alts(struct objtool_file *file)
1866 {
1867         struct section *sec;
1868         struct symbol *func;
1869         int ret;
1870
1871         if (!file->rodata)
1872                 return 0;
1873
1874         for_each_sec(file, sec) {
1875                 list_for_each_entry(func, &sec->symbol_list, list) {
1876                         if (func->type != STT_FUNC)
1877                                 continue;
1878
1879                         mark_func_jump_tables(file, func);
1880                         ret = add_func_jump_tables(file, func);
1881                         if (ret)
1882                                 return ret;
1883                 }
1884         }
1885
1886         return 0;
1887 }
1888
1889 static void set_func_state(struct cfi_state *state)
1890 {
1891         state->cfa = initial_func_cfi.cfa;
1892         memcpy(&state->regs, &initial_func_cfi.regs,
1893                CFI_NUM_REGS * sizeof(struct cfi_reg));
1894         state->stack_size = initial_func_cfi.cfa.offset;
1895 }
1896
1897 static int read_unwind_hints(struct objtool_file *file)
1898 {
1899         struct cfi_state cfi = init_cfi;
1900         struct section *sec, *relocsec;
1901         struct unwind_hint *hint;
1902         struct instruction *insn;
1903         struct reloc *reloc;
1904         int i;
1905
1906         sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1907         if (!sec)
1908                 return 0;
1909
1910         relocsec = sec->reloc;
1911         if (!relocsec) {
1912                 WARN("missing .rela.discard.unwind_hints section");
1913                 return -1;
1914         }
1915
1916         if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
1917                 WARN("struct unwind_hint size mismatch");
1918                 return -1;
1919         }
1920
1921         file->hints = true;
1922
1923         for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
1924                 hint = (struct unwind_hint *)sec->data->d_buf + i;
1925
1926                 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
1927                 if (!reloc) {
1928                         WARN("can't find reloc for unwind_hints[%d]", i);
1929                         return -1;
1930                 }
1931
1932                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1933                 if (!insn) {
1934                         WARN("can't find insn for unwind_hints[%d]", i);
1935                         return -1;
1936                 }
1937
1938                 insn->hint = true;
1939
1940                 if (ibt && hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
1941                         struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
1942
1943                         if (sym && sym->bind == STB_GLOBAL &&
1944                             insn->type != INSN_ENDBR && !insn->noendbr) {
1945                                 WARN_FUNC("UNWIND_HINT_IRET_REGS without ENDBR",
1946                                           insn->sec, insn->offset);
1947                         }
1948                 }
1949
1950                 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
1951                         insn->cfi = &func_cfi;
1952                         continue;
1953                 }
1954
1955                 if (insn->cfi)
1956                         cfi = *(insn->cfi);
1957
1958                 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
1959                         WARN_FUNC("unsupported unwind_hint sp base reg %d",
1960                                   insn->sec, insn->offset, hint->sp_reg);
1961                         return -1;
1962                 }
1963
1964                 cfi.cfa.offset = bswap_if_needed(hint->sp_offset);
1965                 cfi.type = hint->type;
1966                 cfi.end = hint->end;
1967
1968                 insn->cfi = cfi_hash_find_or_add(&cfi);
1969         }
1970
1971         return 0;
1972 }
1973
1974 static int read_noendbr_hints(struct objtool_file *file)
1975 {
1976         struct section *sec;
1977         struct instruction *insn;
1978         struct reloc *reloc;
1979
1980         sec = find_section_by_name(file->elf, ".rela.discard.noendbr");
1981         if (!sec)
1982                 return 0;
1983
1984         list_for_each_entry(reloc, &sec->reloc_list, list) {
1985                 insn = find_insn(file, reloc->sym->sec, reloc->sym->offset + reloc->addend);
1986                 if (!insn) {
1987                         WARN("bad .discard.noendbr entry");
1988                         return -1;
1989                 }
1990
1991                 if (insn->type == INSN_ENDBR)
1992                         WARN_FUNC("ANNOTATE_NOENDBR on ENDBR", insn->sec, insn->offset);
1993
1994                 insn->noendbr = 1;
1995         }
1996
1997         return 0;
1998 }
1999
2000 static int read_retpoline_hints(struct objtool_file *file)
2001 {
2002         struct section *sec;
2003         struct instruction *insn;
2004         struct reloc *reloc;
2005
2006         sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
2007         if (!sec)
2008                 return 0;
2009
2010         list_for_each_entry(reloc, &sec->reloc_list, list) {
2011                 if (reloc->sym->type != STT_SECTION) {
2012                         WARN("unexpected relocation symbol type in %s", sec->name);
2013                         return -1;
2014                 }
2015
2016                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2017                 if (!insn) {
2018                         WARN("bad .discard.retpoline_safe entry");
2019                         return -1;
2020                 }
2021
2022                 if (insn->type != INSN_JUMP_DYNAMIC &&
2023                     insn->type != INSN_CALL_DYNAMIC) {
2024                         WARN_FUNC("retpoline_safe hint not an indirect jump/call",
2025                                   insn->sec, insn->offset);
2026                         return -1;
2027                 }
2028
2029                 insn->retpoline_safe = true;
2030         }
2031
2032         return 0;
2033 }
2034
2035 static int read_instr_hints(struct objtool_file *file)
2036 {
2037         struct section *sec;
2038         struct instruction *insn;
2039         struct reloc *reloc;
2040
2041         sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2042         if (!sec)
2043                 return 0;
2044
2045         list_for_each_entry(reloc, &sec->reloc_list, list) {
2046                 if (reloc->sym->type != STT_SECTION) {
2047                         WARN("unexpected relocation symbol type in %s", sec->name);
2048                         return -1;
2049                 }
2050
2051                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2052                 if (!insn) {
2053                         WARN("bad .discard.instr_end entry");
2054                         return -1;
2055                 }
2056
2057                 insn->instr--;
2058         }
2059
2060         sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2061         if (!sec)
2062                 return 0;
2063
2064         list_for_each_entry(reloc, &sec->reloc_list, list) {
2065                 if (reloc->sym->type != STT_SECTION) {
2066                         WARN("unexpected relocation symbol type in %s", sec->name);
2067                         return -1;
2068                 }
2069
2070                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2071                 if (!insn) {
2072                         WARN("bad .discard.instr_begin entry");
2073                         return -1;
2074                 }
2075
2076                 insn->instr++;
2077         }
2078
2079         return 0;
2080 }
2081
2082 static int read_intra_function_calls(struct objtool_file *file)
2083 {
2084         struct instruction *insn;
2085         struct section *sec;
2086         struct reloc *reloc;
2087
2088         sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2089         if (!sec)
2090                 return 0;
2091
2092         list_for_each_entry(reloc, &sec->reloc_list, list) {
2093                 unsigned long dest_off;
2094
2095                 if (reloc->sym->type != STT_SECTION) {
2096                         WARN("unexpected relocation symbol type in %s",
2097                              sec->name);
2098                         return -1;
2099                 }
2100
2101                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2102                 if (!insn) {
2103                         WARN("bad .discard.intra_function_call entry");
2104                         return -1;
2105                 }
2106
2107                 if (insn->type != INSN_CALL) {
2108                         WARN_FUNC("intra_function_call not a direct call",
2109                                   insn->sec, insn->offset);
2110                         return -1;
2111                 }
2112
2113                 /*
2114                  * Treat intra-function CALLs as JMPs, but with a stack_op.
2115                  * See add_call_destinations(), which strips stack_ops from
2116                  * normal CALLs.
2117                  */
2118                 insn->type = INSN_JUMP_UNCONDITIONAL;
2119
2120                 dest_off = insn->offset + insn->len + insn->immediate;
2121                 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2122                 if (!insn->jump_dest) {
2123                         WARN_FUNC("can't find call dest at %s+0x%lx",
2124                                   insn->sec, insn->offset,
2125                                   insn->sec->name, dest_off);
2126                         return -1;
2127                 }
2128         }
2129
2130         return 0;
2131 }
2132
2133 /*
2134  * Return true if name matches an instrumentation function, where calls to that
2135  * function from noinstr code can safely be removed, but compilers won't do so.
2136  */
2137 static bool is_profiling_func(const char *name)
2138 {
2139         /*
2140          * Many compilers cannot disable KCOV with a function attribute.
2141          */
2142         if (!strncmp(name, "__sanitizer_cov_", 16))
2143                 return true;
2144
2145         /*
2146          * Some compilers currently do not remove __tsan_func_entry/exit nor
2147          * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2148          * the __no_sanitize_thread attribute, remove them. Once the kernel's
2149          * minimum Clang version is 14.0, this can be removed.
2150          */
2151         if (!strncmp(name, "__tsan_func_", 12) ||
2152             !strcmp(name, "__tsan_atomic_signal_fence"))
2153                 return true;
2154
2155         return false;
2156 }
2157
2158 static int classify_symbols(struct objtool_file *file)
2159 {
2160         struct section *sec;
2161         struct symbol *func;
2162
2163         for_each_sec(file, sec) {
2164                 list_for_each_entry(func, &sec->symbol_list, list) {
2165                         if (func->bind != STB_GLOBAL)
2166                                 continue;
2167
2168                         if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2169                                      strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2170                                 func->static_call_tramp = true;
2171
2172                         if (arch_is_retpoline(func))
2173                                 func->retpoline_thunk = true;
2174
2175                         if (!strcmp(func->name, "__fentry__"))
2176                                 func->fentry = true;
2177
2178                         if (is_profiling_func(func->name))
2179                                 func->profiling_func = true;
2180                 }
2181         }
2182
2183         return 0;
2184 }
2185
2186 static void mark_rodata(struct objtool_file *file)
2187 {
2188         struct section *sec;
2189         bool found = false;
2190
2191         /*
2192          * Search for the following rodata sections, each of which can
2193          * potentially contain jump tables:
2194          *
2195          * - .rodata: can contain GCC switch tables
2196          * - .rodata.<func>: same, if -fdata-sections is being used
2197          * - .rodata..c_jump_table: contains C annotated jump tables
2198          *
2199          * .rodata.str1.* sections are ignored; they don't contain jump tables.
2200          */
2201         for_each_sec(file, sec) {
2202                 if (!strncmp(sec->name, ".rodata", 7) &&
2203                     !strstr(sec->name, ".str1.")) {
2204                         sec->rodata = true;
2205                         found = true;
2206                 }
2207         }
2208
2209         file->rodata = found;
2210 }
2211
2212 static int decode_sections(struct objtool_file *file)
2213 {
2214         int ret;
2215
2216         mark_rodata(file);
2217
2218         ret = init_pv_ops(file);
2219         if (ret)
2220                 return ret;
2221
2222         ret = decode_instructions(file);
2223         if (ret)
2224                 return ret;
2225
2226         add_ignores(file);
2227         add_uaccess_safe(file);
2228
2229         ret = add_ignore_alternatives(file);
2230         if (ret)
2231                 return ret;
2232
2233         /*
2234          * Must be before read_unwind_hints() since that needs insn->noendbr.
2235          */
2236         ret = read_noendbr_hints(file);
2237         if (ret)
2238                 return ret;
2239
2240         /*
2241          * Must be before add_{jump_call}_destination.
2242          */
2243         ret = classify_symbols(file);
2244         if (ret)
2245                 return ret;
2246
2247         /*
2248          * Must be before add_special_section_alts() as that depends on
2249          * jump_dest being set.
2250          */
2251         ret = add_jump_destinations(file);
2252         if (ret)
2253                 return ret;
2254
2255         ret = add_special_section_alts(file);
2256         if (ret)
2257                 return ret;
2258
2259         /*
2260          * Must be before add_call_destination(); it changes INSN_CALL to
2261          * INSN_JUMP.
2262          */
2263         ret = read_intra_function_calls(file);
2264         if (ret)
2265                 return ret;
2266
2267         ret = add_call_destinations(file);
2268         if (ret)
2269                 return ret;
2270
2271         /*
2272          * Must be after add_call_destinations() such that it can override
2273          * dead_end_function() marks.
2274          */
2275         ret = add_dead_ends(file);
2276         if (ret)
2277                 return ret;
2278
2279         ret = add_jump_table_alts(file);
2280         if (ret)
2281                 return ret;
2282
2283         ret = read_unwind_hints(file);
2284         if (ret)
2285                 return ret;
2286
2287         ret = read_retpoline_hints(file);
2288         if (ret)
2289                 return ret;
2290
2291         ret = read_instr_hints(file);
2292         if (ret)
2293                 return ret;
2294
2295         return 0;
2296 }
2297
2298 static bool is_fentry_call(struct instruction *insn)
2299 {
2300         if (insn->type == INSN_CALL &&
2301             insn->call_dest &&
2302             insn->call_dest->fentry)
2303                 return true;
2304
2305         return false;
2306 }
2307
2308 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2309 {
2310         struct cfi_state *cfi = &state->cfi;
2311         int i;
2312
2313         if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2314                 return true;
2315
2316         if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2317                 return true;
2318
2319         if (cfi->stack_size != initial_func_cfi.cfa.offset)
2320                 return true;
2321
2322         for (i = 0; i < CFI_NUM_REGS; i++) {
2323                 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2324                     cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2325                         return true;
2326         }
2327
2328         return false;
2329 }
2330
2331 static bool check_reg_frame_pos(const struct cfi_reg *reg,
2332                                 int expected_offset)
2333 {
2334         return reg->base == CFI_CFA &&
2335                reg->offset == expected_offset;
2336 }
2337
2338 static bool has_valid_stack_frame(struct insn_state *state)
2339 {
2340         struct cfi_state *cfi = &state->cfi;
2341
2342         if (cfi->cfa.base == CFI_BP &&
2343             check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2344             check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2345                 return true;
2346
2347         if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2348                 return true;
2349
2350         return false;
2351 }
2352
2353 static int update_cfi_state_regs(struct instruction *insn,
2354                                   struct cfi_state *cfi,
2355                                   struct stack_op *op)
2356 {
2357         struct cfi_reg *cfa = &cfi->cfa;
2358
2359         if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2360                 return 0;
2361
2362         /* push */
2363         if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2364                 cfa->offset += 8;
2365
2366         /* pop */
2367         if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2368                 cfa->offset -= 8;
2369
2370         /* add immediate to sp */
2371         if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2372             op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2373                 cfa->offset -= op->src.offset;
2374
2375         return 0;
2376 }
2377
2378 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2379 {
2380         if (arch_callee_saved_reg(reg) &&
2381             cfi->regs[reg].base == CFI_UNDEFINED) {
2382                 cfi->regs[reg].base = base;
2383                 cfi->regs[reg].offset = offset;
2384         }
2385 }
2386
2387 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2388 {
2389         cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2390         cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2391 }
2392
2393 /*
2394  * A note about DRAP stack alignment:
2395  *
2396  * GCC has the concept of a DRAP register, which is used to help keep track of
2397  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
2398  * register.  The typical DRAP pattern is:
2399  *
2400  *   4c 8d 54 24 08             lea    0x8(%rsp),%r10
2401  *   48 83 e4 c0                and    $0xffffffffffffffc0,%rsp
2402  *   41 ff 72 f8                pushq  -0x8(%r10)
2403  *   55                         push   %rbp
2404  *   48 89 e5                   mov    %rsp,%rbp
2405  *                              (more pushes)
2406  *   41 52                      push   %r10
2407  *                              ...
2408  *   41 5a                      pop    %r10
2409  *                              (more pops)
2410  *   5d                         pop    %rbp
2411  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2412  *   c3                         retq
2413  *
2414  * There are some variations in the epilogues, like:
2415  *
2416  *   5b                         pop    %rbx
2417  *   41 5a                      pop    %r10
2418  *   41 5c                      pop    %r12
2419  *   41 5d                      pop    %r13
2420  *   41 5e                      pop    %r14
2421  *   c9                         leaveq
2422  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2423  *   c3                         retq
2424  *
2425  * and:
2426  *
2427  *   4c 8b 55 e8                mov    -0x18(%rbp),%r10
2428  *   48 8b 5d e0                mov    -0x20(%rbp),%rbx
2429  *   4c 8b 65 f0                mov    -0x10(%rbp),%r12
2430  *   4c 8b 6d f8                mov    -0x8(%rbp),%r13
2431  *   c9                         leaveq
2432  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2433  *   c3                         retq
2434  *
2435  * Sometimes r13 is used as the DRAP register, in which case it's saved and
2436  * restored beforehand:
2437  *
2438  *   41 55                      push   %r13
2439  *   4c 8d 6c 24 10             lea    0x10(%rsp),%r13
2440  *   48 83 e4 f0                and    $0xfffffffffffffff0,%rsp
2441  *                              ...
2442  *   49 8d 65 f0                lea    -0x10(%r13),%rsp
2443  *   41 5d                      pop    %r13
2444  *   c3                         retq
2445  */
2446 static int update_cfi_state(struct instruction *insn,
2447                             struct instruction *next_insn,
2448                             struct cfi_state *cfi, struct stack_op *op)
2449 {
2450         struct cfi_reg *cfa = &cfi->cfa;
2451         struct cfi_reg *regs = cfi->regs;
2452
2453         /* stack operations don't make sense with an undefined CFA */
2454         if (cfa->base == CFI_UNDEFINED) {
2455                 if (insn->func) {
2456                         WARN_FUNC("undefined stack state", insn->sec, insn->offset);
2457                         return -1;
2458                 }
2459                 return 0;
2460         }
2461
2462         if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2463             cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2464                 return update_cfi_state_regs(insn, cfi, op);
2465
2466         switch (op->dest.type) {
2467
2468         case OP_DEST_REG:
2469                 switch (op->src.type) {
2470
2471                 case OP_SRC_REG:
2472                         if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2473                             cfa->base == CFI_SP &&
2474                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset)) {
2475
2476                                 /* mov %rsp, %rbp */
2477                                 cfa->base = op->dest.reg;
2478                                 cfi->bp_scratch = false;
2479                         }
2480
2481                         else if (op->src.reg == CFI_SP &&
2482                                  op->dest.reg == CFI_BP && cfi->drap) {
2483
2484                                 /* drap: mov %rsp, %rbp */
2485                                 regs[CFI_BP].base = CFI_BP;
2486                                 regs[CFI_BP].offset = -cfi->stack_size;
2487                                 cfi->bp_scratch = false;
2488                         }
2489
2490                         else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2491
2492                                 /*
2493                                  * mov %rsp, %reg
2494                                  *
2495                                  * This is needed for the rare case where GCC
2496                                  * does:
2497                                  *
2498                                  *   mov    %rsp, %rax
2499                                  *   ...
2500                                  *   mov    %rax, %rsp
2501                                  */
2502                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2503                                 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2504                         }
2505
2506                         else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2507                                  (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2508
2509                                 /*
2510                                  * mov %rbp, %rsp
2511                                  *
2512                                  * Restore the original stack pointer (Clang).
2513                                  */
2514                                 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2515                         }
2516
2517                         else if (op->dest.reg == cfa->base) {
2518
2519                                 /* mov %reg, %rsp */
2520                                 if (cfa->base == CFI_SP &&
2521                                     cfi->vals[op->src.reg].base == CFI_CFA) {
2522
2523                                         /*
2524                                          * This is needed for the rare case
2525                                          * where GCC does something dumb like:
2526                                          *
2527                                          *   lea    0x8(%rsp), %rcx
2528                                          *   ...
2529                                          *   mov    %rcx, %rsp
2530                                          */
2531                                         cfa->offset = -cfi->vals[op->src.reg].offset;
2532                                         cfi->stack_size = cfa->offset;
2533
2534                                 } else if (cfa->base == CFI_SP &&
2535                                            cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2536                                            cfi->vals[op->src.reg].offset == cfa->offset) {
2537
2538                                         /*
2539                                          * Stack swizzle:
2540                                          *
2541                                          * 1: mov %rsp, (%[tos])
2542                                          * 2: mov %[tos], %rsp
2543                                          *    ...
2544                                          * 3: pop %rsp
2545                                          *
2546                                          * Where:
2547                                          *
2548                                          * 1 - places a pointer to the previous
2549                                          *     stack at the Top-of-Stack of the
2550                                          *     new stack.
2551                                          *
2552                                          * 2 - switches to the new stack.
2553                                          *
2554                                          * 3 - pops the Top-of-Stack to restore
2555                                          *     the original stack.
2556                                          *
2557                                          * Note: we set base to SP_INDIRECT
2558                                          * here and preserve offset. Therefore
2559                                          * when the unwinder reaches ToS it
2560                                          * will dereference SP and then add the
2561                                          * offset to find the next frame, IOW:
2562                                          * (%rsp) + offset.
2563                                          */
2564                                         cfa->base = CFI_SP_INDIRECT;
2565
2566                                 } else {
2567                                         cfa->base = CFI_UNDEFINED;
2568                                         cfa->offset = 0;
2569                                 }
2570                         }
2571
2572                         else if (op->dest.reg == CFI_SP &&
2573                                  cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2574                                  cfi->vals[op->src.reg].offset == cfa->offset) {
2575
2576                                 /*
2577                                  * The same stack swizzle case 2) as above. But
2578                                  * because we can't change cfa->base, case 3)
2579                                  * will become a regular POP. Pretend we're a
2580                                  * PUSH so things don't go unbalanced.
2581                                  */
2582                                 cfi->stack_size += 8;
2583                         }
2584
2585
2586                         break;
2587
2588                 case OP_SRC_ADD:
2589                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2590
2591                                 /* add imm, %rsp */
2592                                 cfi->stack_size -= op->src.offset;
2593                                 if (cfa->base == CFI_SP)
2594                                         cfa->offset -= op->src.offset;
2595                                 break;
2596                         }
2597
2598                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2599
2600                                 /* lea disp(%rbp), %rsp */
2601                                 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2602                                 break;
2603                         }
2604
2605                         if (!cfi->drap && op->src.reg == CFI_SP &&
2606                             op->dest.reg == CFI_BP && cfa->base == CFI_SP &&
2607                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset + op->src.offset)) {
2608
2609                                 /* lea disp(%rsp), %rbp */
2610                                 cfa->base = CFI_BP;
2611                                 cfa->offset -= op->src.offset;
2612                                 cfi->bp_scratch = false;
2613                                 break;
2614                         }
2615
2616                         if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2617
2618                                 /* drap: lea disp(%rsp), %drap */
2619                                 cfi->drap_reg = op->dest.reg;
2620
2621                                 /*
2622                                  * lea disp(%rsp), %reg
2623                                  *
2624                                  * This is needed for the rare case where GCC
2625                                  * does something dumb like:
2626                                  *
2627                                  *   lea    0x8(%rsp), %rcx
2628                                  *   ...
2629                                  *   mov    %rcx, %rsp
2630                                  */
2631                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2632                                 cfi->vals[op->dest.reg].offset = \
2633                                         -cfi->stack_size + op->src.offset;
2634
2635                                 break;
2636                         }
2637
2638                         if (cfi->drap && op->dest.reg == CFI_SP &&
2639                             op->src.reg == cfi->drap_reg) {
2640
2641                                  /* drap: lea disp(%drap), %rsp */
2642                                 cfa->base = CFI_SP;
2643                                 cfa->offset = cfi->stack_size = -op->src.offset;
2644                                 cfi->drap_reg = CFI_UNDEFINED;
2645                                 cfi->drap = false;
2646                                 break;
2647                         }
2648
2649                         if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
2650                                 WARN_FUNC("unsupported stack register modification",
2651                                           insn->sec, insn->offset);
2652                                 return -1;
2653                         }
2654
2655                         break;
2656
2657                 case OP_SRC_AND:
2658                         if (op->dest.reg != CFI_SP ||
2659                             (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
2660                             (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
2661                                 WARN_FUNC("unsupported stack pointer realignment",
2662                                           insn->sec, insn->offset);
2663                                 return -1;
2664                         }
2665
2666                         if (cfi->drap_reg != CFI_UNDEFINED) {
2667                                 /* drap: and imm, %rsp */
2668                                 cfa->base = cfi->drap_reg;
2669                                 cfa->offset = cfi->stack_size = 0;
2670                                 cfi->drap = true;
2671                         }
2672
2673                         /*
2674                          * Older versions of GCC (4.8ish) realign the stack
2675                          * without DRAP, with a frame pointer.
2676                          */
2677
2678                         break;
2679
2680                 case OP_SRC_POP:
2681                 case OP_SRC_POPF:
2682                         if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
2683
2684                                 /* pop %rsp; # restore from a stack swizzle */
2685                                 cfa->base = CFI_SP;
2686                                 break;
2687                         }
2688
2689                         if (!cfi->drap && op->dest.reg == cfa->base) {
2690
2691                                 /* pop %rbp */
2692                                 cfa->base = CFI_SP;
2693                         }
2694
2695                         if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
2696                             op->dest.reg == cfi->drap_reg &&
2697                             cfi->drap_offset == -cfi->stack_size) {
2698
2699                                 /* drap: pop %drap */
2700                                 cfa->base = cfi->drap_reg;
2701                                 cfa->offset = 0;
2702                                 cfi->drap_offset = -1;
2703
2704                         } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
2705
2706                                 /* pop %reg */
2707                                 restore_reg(cfi, op->dest.reg);
2708                         }
2709
2710                         cfi->stack_size -= 8;
2711                         if (cfa->base == CFI_SP)
2712                                 cfa->offset -= 8;
2713
2714                         break;
2715
2716                 case OP_SRC_REG_INDIRECT:
2717                         if (!cfi->drap && op->dest.reg == cfa->base &&
2718                             op->dest.reg == CFI_BP) {
2719
2720                                 /* mov disp(%rsp), %rbp */
2721                                 cfa->base = CFI_SP;
2722                                 cfa->offset = cfi->stack_size;
2723                         }
2724
2725                         if (cfi->drap && op->src.reg == CFI_BP &&
2726                             op->src.offset == cfi->drap_offset) {
2727
2728                                 /* drap: mov disp(%rbp), %drap */
2729                                 cfa->base = cfi->drap_reg;
2730                                 cfa->offset = 0;
2731                                 cfi->drap_offset = -1;
2732                         }
2733
2734                         if (cfi->drap && op->src.reg == CFI_BP &&
2735                             op->src.offset == regs[op->dest.reg].offset) {
2736
2737                                 /* drap: mov disp(%rbp), %reg */
2738                                 restore_reg(cfi, op->dest.reg);
2739
2740                         } else if (op->src.reg == cfa->base &&
2741                             op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
2742
2743                                 /* mov disp(%rbp), %reg */
2744                                 /* mov disp(%rsp), %reg */
2745                                 restore_reg(cfi, op->dest.reg);
2746
2747                         } else if (op->src.reg == CFI_SP &&
2748                                    op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
2749
2750                                 /* mov disp(%rsp), %reg */
2751                                 restore_reg(cfi, op->dest.reg);
2752                         }
2753
2754                         break;
2755
2756                 default:
2757                         WARN_FUNC("unknown stack-related instruction",
2758                                   insn->sec, insn->offset);
2759                         return -1;
2760                 }
2761
2762                 break;
2763
2764         case OP_DEST_PUSH:
2765         case OP_DEST_PUSHF:
2766                 cfi->stack_size += 8;
2767                 if (cfa->base == CFI_SP)
2768                         cfa->offset += 8;
2769
2770                 if (op->src.type != OP_SRC_REG)
2771                         break;
2772
2773                 if (cfi->drap) {
2774                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2775
2776                                 /* drap: push %drap */
2777                                 cfa->base = CFI_BP_INDIRECT;
2778                                 cfa->offset = -cfi->stack_size;
2779
2780                                 /* save drap so we know when to restore it */
2781                                 cfi->drap_offset = -cfi->stack_size;
2782
2783                         } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
2784
2785                                 /* drap: push %rbp */
2786                                 cfi->stack_size = 0;
2787
2788                         } else {
2789
2790                                 /* drap: push %reg */
2791                                 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
2792                         }
2793
2794                 } else {
2795
2796                         /* push %reg */
2797                         save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
2798                 }
2799
2800                 /* detect when asm code uses rbp as a scratch register */
2801                 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
2802                     cfa->base != CFI_BP)
2803                         cfi->bp_scratch = true;
2804                 break;
2805
2806         case OP_DEST_REG_INDIRECT:
2807
2808                 if (cfi->drap) {
2809                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2810
2811                                 /* drap: mov %drap, disp(%rbp) */
2812                                 cfa->base = CFI_BP_INDIRECT;
2813                                 cfa->offset = op->dest.offset;
2814
2815                                 /* save drap offset so we know when to restore it */
2816                                 cfi->drap_offset = op->dest.offset;
2817                         } else {
2818
2819                                 /* drap: mov reg, disp(%rbp) */
2820                                 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
2821                         }
2822
2823                 } else if (op->dest.reg == cfa->base) {
2824
2825                         /* mov reg, disp(%rbp) */
2826                         /* mov reg, disp(%rsp) */
2827                         save_reg(cfi, op->src.reg, CFI_CFA,
2828                                  op->dest.offset - cfi->cfa.offset);
2829
2830                 } else if (op->dest.reg == CFI_SP) {
2831
2832                         /* mov reg, disp(%rsp) */
2833                         save_reg(cfi, op->src.reg, CFI_CFA,
2834                                  op->dest.offset - cfi->stack_size);
2835
2836                 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
2837
2838                         /* mov %rsp, (%reg); # setup a stack swizzle. */
2839                         cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
2840                         cfi->vals[op->dest.reg].offset = cfa->offset;
2841                 }
2842
2843                 break;
2844
2845         case OP_DEST_MEM:
2846                 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
2847                         WARN_FUNC("unknown stack-related memory operation",
2848                                   insn->sec, insn->offset);
2849                         return -1;
2850                 }
2851
2852                 /* pop mem */
2853                 cfi->stack_size -= 8;
2854                 if (cfa->base == CFI_SP)
2855                         cfa->offset -= 8;
2856
2857                 break;
2858
2859         default:
2860                 WARN_FUNC("unknown stack-related instruction",
2861                           insn->sec, insn->offset);
2862                 return -1;
2863         }
2864
2865         return 0;
2866 }
2867
2868 /*
2869  * The stack layouts of alternatives instructions can sometimes diverge when
2870  * they have stack modifications.  That's fine as long as the potential stack
2871  * layouts don't conflict at any given potential instruction boundary.
2872  *
2873  * Flatten the CFIs of the different alternative code streams (both original
2874  * and replacement) into a single shared CFI array which can be used to detect
2875  * conflicts and nicely feed a linear array of ORC entries to the unwinder.
2876  */
2877 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
2878 {
2879         struct cfi_state **alt_cfi;
2880         int group_off;
2881
2882         if (!insn->alt_group)
2883                 return 0;
2884
2885         if (!insn->cfi) {
2886                 WARN("CFI missing");
2887                 return -1;
2888         }
2889
2890         alt_cfi = insn->alt_group->cfi;
2891         group_off = insn->offset - insn->alt_group->first_insn->offset;
2892
2893         if (!alt_cfi[group_off]) {
2894                 alt_cfi[group_off] = insn->cfi;
2895         } else {
2896                 if (cficmp(alt_cfi[group_off], insn->cfi)) {
2897                         WARN_FUNC("stack layout conflict in alternatives",
2898                                   insn->sec, insn->offset);
2899                         return -1;
2900                 }
2901         }
2902
2903         return 0;
2904 }
2905
2906 static int handle_insn_ops(struct instruction *insn,
2907                            struct instruction *next_insn,
2908                            struct insn_state *state)
2909 {
2910         struct stack_op *op;
2911
2912         list_for_each_entry(op, &insn->stack_ops, list) {
2913
2914                 if (update_cfi_state(insn, next_insn, &state->cfi, op))
2915                         return 1;
2916
2917                 if (!insn->alt_group)
2918                         continue;
2919
2920                 if (op->dest.type == OP_DEST_PUSHF) {
2921                         if (!state->uaccess_stack) {
2922                                 state->uaccess_stack = 1;
2923                         } else if (state->uaccess_stack >> 31) {
2924                                 WARN_FUNC("PUSHF stack exhausted",
2925                                           insn->sec, insn->offset);
2926                                 return 1;
2927                         }
2928                         state->uaccess_stack <<= 1;
2929                         state->uaccess_stack  |= state->uaccess;
2930                 }
2931
2932                 if (op->src.type == OP_SRC_POPF) {
2933                         if (state->uaccess_stack) {
2934                                 state->uaccess = state->uaccess_stack & 1;
2935                                 state->uaccess_stack >>= 1;
2936                                 if (state->uaccess_stack == 1)
2937                                         state->uaccess_stack = 0;
2938                         }
2939                 }
2940         }
2941
2942         return 0;
2943 }
2944
2945 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
2946 {
2947         struct cfi_state *cfi1 = insn->cfi;
2948         int i;
2949
2950         if (!cfi1) {
2951                 WARN("CFI missing");
2952                 return false;
2953         }
2954
2955         if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
2956
2957                 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
2958                           insn->sec, insn->offset,
2959                           cfi1->cfa.base, cfi1->cfa.offset,
2960                           cfi2->cfa.base, cfi2->cfa.offset);
2961
2962         } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
2963                 for (i = 0; i < CFI_NUM_REGS; i++) {
2964                         if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
2965                                     sizeof(struct cfi_reg)))
2966                                 continue;
2967
2968                         WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
2969                                   insn->sec, insn->offset,
2970                                   i, cfi1->regs[i].base, cfi1->regs[i].offset,
2971                                   i, cfi2->regs[i].base, cfi2->regs[i].offset);
2972                         break;
2973                 }
2974
2975         } else if (cfi1->type != cfi2->type) {
2976
2977                 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
2978                           insn->sec, insn->offset, cfi1->type, cfi2->type);
2979
2980         } else if (cfi1->drap != cfi2->drap ||
2981                    (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
2982                    (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
2983
2984                 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
2985                           insn->sec, insn->offset,
2986                           cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
2987                           cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
2988
2989         } else
2990                 return true;
2991
2992         return false;
2993 }
2994
2995 static inline bool func_uaccess_safe(struct symbol *func)
2996 {
2997         if (func)
2998                 return func->uaccess_safe;
2999
3000         return false;
3001 }
3002
3003 static inline const char *call_dest_name(struct instruction *insn)
3004 {
3005         static char pvname[19];
3006         struct reloc *rel;
3007         int idx;
3008
3009         if (insn->call_dest)
3010                 return insn->call_dest->name;
3011
3012         rel = insn_reloc(NULL, insn);
3013         if (rel && !strcmp(rel->sym->name, "pv_ops")) {
3014                 idx = (rel->addend / sizeof(void *));
3015                 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
3016                 return pvname;
3017         }
3018
3019         return "{dynamic}";
3020 }
3021
3022 static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3023 {
3024         struct symbol *target;
3025         struct reloc *rel;
3026         int idx;
3027
3028         rel = insn_reloc(file, insn);
3029         if (!rel || strcmp(rel->sym->name, "pv_ops"))
3030                 return false;
3031
3032         idx = (arch_dest_reloc_offset(rel->addend) / sizeof(void *));
3033
3034         if (file->pv_ops[idx].clean)
3035                 return true;
3036
3037         file->pv_ops[idx].clean = true;
3038
3039         list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3040                 if (!target->sec->noinstr) {
3041                         WARN("pv_ops[%d]: %s", idx, target->name);
3042                         file->pv_ops[idx].clean = false;
3043                 }
3044         }
3045
3046         return file->pv_ops[idx].clean;
3047 }
3048
3049 static inline bool noinstr_call_dest(struct objtool_file *file,
3050                                      struct instruction *insn,
3051                                      struct symbol *func)
3052 {
3053         /*
3054          * We can't deal with indirect function calls at present;
3055          * assume they're instrumented.
3056          */
3057         if (!func) {
3058                 if (file->pv_ops)
3059                         return pv_call_dest(file, insn);
3060
3061                 return false;
3062         }
3063
3064         /*
3065          * If the symbol is from a noinstr section; we good.
3066          */
3067         if (func->sec->noinstr)
3068                 return true;
3069
3070         /*
3071          * The __ubsan_handle_*() calls are like WARN(), they only happen when
3072          * something 'BAD' happened. At the risk of taking the machine down,
3073          * let them proceed to get the message out.
3074          */
3075         if (!strncmp(func->name, "__ubsan_handle_", 15))
3076                 return true;
3077
3078         return false;
3079 }
3080
3081 static int validate_call(struct objtool_file *file,
3082                          struct instruction *insn,
3083                          struct insn_state *state)
3084 {
3085         if (state->noinstr && state->instr <= 0 &&
3086             !noinstr_call_dest(file, insn, insn->call_dest)) {
3087                 WARN_FUNC("call to %s() leaves .noinstr.text section",
3088                                 insn->sec, insn->offset, call_dest_name(insn));
3089                 return 1;
3090         }
3091
3092         if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
3093                 WARN_FUNC("call to %s() with UACCESS enabled",
3094                                 insn->sec, insn->offset, call_dest_name(insn));
3095                 return 1;
3096         }
3097
3098         if (state->df) {
3099                 WARN_FUNC("call to %s() with DF set",
3100                                 insn->sec, insn->offset, call_dest_name(insn));
3101                 return 1;
3102         }
3103
3104         return 0;
3105 }
3106
3107 static int validate_sibling_call(struct objtool_file *file,
3108                                  struct instruction *insn,
3109                                  struct insn_state *state)
3110 {
3111         if (has_modified_stack_frame(insn, state)) {
3112                 WARN_FUNC("sibling call from callable instruction with modified stack frame",
3113                                 insn->sec, insn->offset);
3114                 return 1;
3115         }
3116
3117         return validate_call(file, insn, state);
3118 }
3119
3120 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3121 {
3122         if (state->noinstr && state->instr > 0) {
3123                 WARN_FUNC("return with instrumentation enabled",
3124                           insn->sec, insn->offset);
3125                 return 1;
3126         }
3127
3128         if (state->uaccess && !func_uaccess_safe(func)) {
3129                 WARN_FUNC("return with UACCESS enabled",
3130                           insn->sec, insn->offset);
3131                 return 1;
3132         }
3133
3134         if (!state->uaccess && func_uaccess_safe(func)) {
3135                 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
3136                           insn->sec, insn->offset);
3137                 return 1;
3138         }
3139
3140         if (state->df) {
3141                 WARN_FUNC("return with DF set",
3142                           insn->sec, insn->offset);
3143                 return 1;
3144         }
3145
3146         if (func && has_modified_stack_frame(insn, state)) {
3147                 WARN_FUNC("return with modified stack frame",
3148                           insn->sec, insn->offset);
3149                 return 1;
3150         }
3151
3152         if (state->cfi.bp_scratch) {
3153                 WARN_FUNC("BP used as a scratch register",
3154                           insn->sec, insn->offset);
3155                 return 1;
3156         }
3157
3158         return 0;
3159 }
3160
3161 static struct instruction *next_insn_to_validate(struct objtool_file *file,
3162                                                  struct instruction *insn)
3163 {
3164         struct alt_group *alt_group = insn->alt_group;
3165
3166         /*
3167          * Simulate the fact that alternatives are patched in-place.  When the
3168          * end of a replacement alt_group is reached, redirect objtool flow to
3169          * the end of the original alt_group.
3170          */
3171         if (alt_group && insn == alt_group->last_insn && alt_group->orig_group)
3172                 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3173
3174         return next_insn_same_sec(file, insn);
3175 }
3176
3177 static struct instruction *
3178 validate_ibt_reloc(struct objtool_file *file, struct reloc *reloc)
3179 {
3180         struct instruction *dest;
3181         struct section *sec;
3182         unsigned long off;
3183
3184         sec = reloc->sym->sec;
3185         off = reloc->sym->offset;
3186
3187         if ((reloc->sec->base->sh.sh_flags & SHF_EXECINSTR) &&
3188             (reloc->type == R_X86_64_PC32 || reloc->type == R_X86_64_PLT32))
3189                 off += arch_dest_reloc_offset(reloc->addend);
3190         else
3191                 off += reloc->addend;
3192
3193         dest = find_insn(file, sec, off);
3194         if (!dest)
3195                 return NULL;
3196
3197         if (dest->type == INSN_ENDBR) {
3198                 if (!list_empty(&dest->call_node))
3199                         list_del_init(&dest->call_node);
3200
3201                 return NULL;
3202         }
3203
3204         if (reloc->sym->static_call_tramp)
3205                 return NULL;
3206
3207         return dest;
3208 }
3209
3210 static void warn_noendbr(const char *msg, struct section *sec, unsigned long offset,
3211                          struct instruction *dest)
3212 {
3213         WARN_FUNC("%srelocation to !ENDBR: %s+0x%lx", sec, offset, msg,
3214                   dest->func ? dest->func->name : dest->sec->name,
3215                   dest->func ? dest->offset - dest->func->offset : dest->offset);
3216 }
3217
3218 static void validate_ibt_dest(struct objtool_file *file, struct instruction *insn,
3219                               struct instruction *dest)
3220 {
3221         if (dest->func && dest->func == insn->func) {
3222                 /*
3223                  * Anything from->to self is either _THIS_IP_ or IRET-to-self.
3224                  *
3225                  * There is no sane way to annotate _THIS_IP_ since the compiler treats the
3226                  * relocation as a constant and is happy to fold in offsets, skewing any
3227                  * annotation we do, leading to vast amounts of false-positives.
3228                  *
3229                  * There's also compiler generated _THIS_IP_ through KCOV and
3230                  * such which we have no hope of annotating.
3231                  *
3232                  * As such, blanket accept self-references without issue.
3233                  */
3234                 return;
3235         }
3236
3237         if (dest->noendbr)
3238                 return;
3239
3240         warn_noendbr("", insn->sec, insn->offset, dest);
3241 }
3242
3243 static void validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
3244 {
3245         struct instruction *dest;
3246         struct reloc *reloc;
3247
3248         switch (insn->type) {
3249         case INSN_CALL:
3250         case INSN_CALL_DYNAMIC:
3251         case INSN_JUMP_CONDITIONAL:
3252         case INSN_JUMP_UNCONDITIONAL:
3253         case INSN_JUMP_DYNAMIC:
3254         case INSN_JUMP_DYNAMIC_CONDITIONAL:
3255         case INSN_RETURN:
3256                 /*
3257                  * We're looking for code references setting up indirect code
3258                  * flow. As such, ignore direct code flow and the actual
3259                  * dynamic branches.
3260                  */
3261                 return;
3262
3263         case INSN_NOP:
3264                 /*
3265                  * handle_group_alt() will create INSN_NOP instruction that
3266                  * don't belong to any section, ignore all NOP since they won't
3267                  * carry a (useful) relocation anyway.
3268                  */
3269                 return;
3270
3271         default:
3272                 break;
3273         }
3274
3275         for (reloc = insn_reloc(file, insn);
3276              reloc;
3277              reloc = find_reloc_by_dest_range(file->elf, insn->sec,
3278                                               reloc->offset + 1,
3279                                               (insn->offset + insn->len) - (reloc->offset + 1))) {
3280                 dest = validate_ibt_reloc(file, reloc);
3281                 if (dest)
3282                         validate_ibt_dest(file, insn, dest);
3283         }
3284 }
3285
3286 /*
3287  * Follow the branch starting at the given instruction, and recursively follow
3288  * any other branches (jumps).  Meanwhile, track the frame pointer state at
3289  * each instruction and validate all the rules described in
3290  * tools/objtool/Documentation/stack-validation.txt.
3291  */
3292 static int validate_branch(struct objtool_file *file, struct symbol *func,
3293                            struct instruction *insn, struct insn_state state)
3294 {
3295         struct alternative *alt;
3296         struct instruction *next_insn, *prev_insn = NULL;
3297         struct section *sec;
3298         u8 visited;
3299         int ret;
3300
3301         sec = insn->sec;
3302
3303         while (1) {
3304                 next_insn = next_insn_to_validate(file, insn);
3305
3306                 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
3307                         WARN("%s() falls through to next function %s()",
3308                              func->name, insn->func->name);
3309                         return 1;
3310                 }
3311
3312                 if (func && insn->ignore) {
3313                         WARN_FUNC("BUG: why am I validating an ignored function?",
3314                                   sec, insn->offset);
3315                         return 1;
3316                 }
3317
3318                 visited = 1 << state.uaccess;
3319                 if (insn->visited) {
3320                         if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3321                                 return 1;
3322
3323                         if (insn->visited & visited)
3324                                 return 0;
3325                 } else {
3326                         nr_insns_visited++;
3327                 }
3328
3329                 if (state.noinstr)
3330                         state.instr += insn->instr;
3331
3332                 if (insn->hint) {
3333                         state.cfi = *insn->cfi;
3334                 } else {
3335                         /* XXX track if we actually changed state.cfi */
3336
3337                         if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3338                                 insn->cfi = prev_insn->cfi;
3339                                 nr_cfi_reused++;
3340                         } else {
3341                                 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3342                         }
3343                 }
3344
3345                 insn->visited |= visited;
3346
3347                 if (propagate_alt_cfi(file, insn))
3348                         return 1;
3349
3350                 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
3351                         bool skip_orig = false;
3352
3353                         list_for_each_entry(alt, &insn->alts, list) {
3354                                 if (alt->skip_orig)
3355                                         skip_orig = true;
3356
3357                                 ret = validate_branch(file, func, alt->insn, state);
3358                                 if (ret) {
3359                                         if (backtrace)
3360                                                 BT_FUNC("(alt)", insn);
3361                                         return ret;
3362                                 }
3363                         }
3364
3365                         if (skip_orig)
3366                                 return 0;
3367                 }
3368
3369                 if (handle_insn_ops(insn, next_insn, &state))
3370                         return 1;
3371
3372                 switch (insn->type) {
3373
3374                 case INSN_RETURN:
3375                         if (sls && !insn->retpoline_safe &&
3376                             next_insn && next_insn->type != INSN_TRAP) {
3377                                 WARN_FUNC("missing int3 after ret",
3378                                           insn->sec, insn->offset);
3379                         }
3380                         return validate_return(func, insn, &state);
3381
3382                 case INSN_CALL:
3383                 case INSN_CALL_DYNAMIC:
3384                         ret = validate_call(file, insn, &state);
3385                         if (ret)
3386                                 return ret;
3387
3388                         if (!no_fp && func && !is_fentry_call(insn) &&
3389                             !has_valid_stack_frame(&state)) {
3390                                 WARN_FUNC("call without frame pointer save/setup",
3391                                           sec, insn->offset);
3392                                 return 1;
3393                         }
3394
3395                         if (insn->dead_end)
3396                                 return 0;
3397
3398                         break;
3399
3400                 case INSN_JUMP_CONDITIONAL:
3401                 case INSN_JUMP_UNCONDITIONAL:
3402                         if (is_sibling_call(insn)) {
3403                                 ret = validate_sibling_call(file, insn, &state);
3404                                 if (ret)
3405                                         return ret;
3406
3407                         } else if (insn->jump_dest) {
3408                                 ret = validate_branch(file, func,
3409                                                       insn->jump_dest, state);
3410                                 if (ret) {
3411                                         if (backtrace)
3412                                                 BT_FUNC("(branch)", insn);
3413                                         return ret;
3414                                 }
3415                         }
3416
3417                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
3418                                 return 0;
3419
3420                         break;
3421
3422                 case INSN_JUMP_DYNAMIC:
3423                         if (sls && !insn->retpoline_safe &&
3424                             next_insn && next_insn->type != INSN_TRAP) {
3425                                 WARN_FUNC("missing int3 after indirect jump",
3426                                           insn->sec, insn->offset);
3427                         }
3428
3429                         /* fallthrough */
3430                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3431                         if (is_sibling_call(insn)) {
3432                                 ret = validate_sibling_call(file, insn, &state);
3433                                 if (ret)
3434                                         return ret;
3435                         }
3436
3437                         if (insn->type == INSN_JUMP_DYNAMIC)
3438                                 return 0;
3439
3440                         break;
3441
3442                 case INSN_CONTEXT_SWITCH:
3443                         if (func && (!next_insn || !next_insn->hint)) {
3444                                 WARN_FUNC("unsupported instruction in callable function",
3445                                           sec, insn->offset);
3446                                 return 1;
3447                         }
3448                         return 0;
3449
3450                 case INSN_STAC:
3451                         if (state.uaccess) {
3452                                 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
3453                                 return 1;
3454                         }
3455
3456                         state.uaccess = true;
3457                         break;
3458
3459                 case INSN_CLAC:
3460                         if (!state.uaccess && func) {
3461                                 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
3462                                 return 1;
3463                         }
3464
3465                         if (func_uaccess_safe(func) && !state.uaccess_stack) {
3466                                 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
3467                                 return 1;
3468                         }
3469
3470                         state.uaccess = false;
3471                         break;
3472
3473                 case INSN_STD:
3474                         if (state.df) {
3475                                 WARN_FUNC("recursive STD", sec, insn->offset);
3476                                 return 1;
3477                         }
3478
3479                         state.df = true;
3480                         break;
3481
3482                 case INSN_CLD:
3483                         if (!state.df && func) {
3484                                 WARN_FUNC("redundant CLD", sec, insn->offset);
3485                                 return 1;
3486                         }
3487
3488                         state.df = false;
3489                         break;
3490
3491                 default:
3492                         break;
3493                 }
3494
3495                 if (ibt)
3496                         validate_ibt_insn(file, insn);
3497
3498                 if (insn->dead_end)
3499                         return 0;
3500
3501                 if (!next_insn) {
3502                         if (state.cfi.cfa.base == CFI_UNDEFINED)
3503                                 return 0;
3504                         WARN("%s: unexpected end of section", sec->name);
3505                         return 1;
3506                 }
3507
3508                 prev_insn = insn;
3509                 insn = next_insn;
3510         }
3511
3512         return 0;
3513 }
3514
3515 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3516 {
3517         struct instruction *insn;
3518         struct insn_state state;
3519         int ret, warnings = 0;
3520
3521         if (!file->hints)
3522                 return 0;
3523
3524         init_insn_state(&state, sec);
3525
3526         if (sec) {
3527                 insn = find_insn(file, sec, 0);
3528                 if (!insn)
3529                         return 0;
3530         } else {
3531                 insn = list_first_entry(&file->insn_list, typeof(*insn), list);
3532         }
3533
3534         while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) {
3535                 if (insn->hint && !insn->visited && !insn->ignore) {
3536                         ret = validate_branch(file, insn->func, insn, state);
3537                         if (ret && backtrace)
3538                                 BT_FUNC("<=== (hint)", insn);
3539                         warnings += ret;
3540                 }
3541
3542                 insn = list_next_entry(insn, list);
3543         }
3544
3545         return warnings;
3546 }
3547
3548 static int validate_retpoline(struct objtool_file *file)
3549 {
3550         struct instruction *insn;
3551         int warnings = 0;
3552
3553         for_each_insn(file, insn) {
3554                 if (insn->type != INSN_JUMP_DYNAMIC &&
3555                     insn->type != INSN_CALL_DYNAMIC)
3556                         continue;
3557
3558                 if (insn->retpoline_safe)
3559                         continue;
3560
3561                 /*
3562                  * .init.text code is ran before userspace and thus doesn't
3563                  * strictly need retpolines, except for modules which are
3564                  * loaded late, they very much do need retpoline in their
3565                  * .init.text
3566                  */
3567                 if (!strcmp(insn->sec->name, ".init.text") && !module)
3568                         continue;
3569
3570                 WARN_FUNC("indirect %s found in RETPOLINE build",
3571                           insn->sec, insn->offset,
3572                           insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
3573
3574                 warnings++;
3575         }
3576
3577         return warnings;
3578 }
3579
3580 static bool is_kasan_insn(struct instruction *insn)
3581 {
3582         return (insn->type == INSN_CALL &&
3583                 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
3584 }
3585
3586 static bool is_ubsan_insn(struct instruction *insn)
3587 {
3588         return (insn->type == INSN_CALL &&
3589                 !strcmp(insn->call_dest->name,
3590                         "__ubsan_handle_builtin_unreachable"));
3591 }
3592
3593 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
3594 {
3595         int i;
3596         struct instruction *prev_insn;
3597
3598         if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
3599                 return true;
3600
3601         /*
3602          * Ignore alternative replacement instructions.  This can happen
3603          * when a whitelisted function uses one of the ALTERNATIVE macros.
3604          */
3605         if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
3606             !strcmp(insn->sec->name, ".altinstr_aux"))
3607                 return true;
3608
3609         /*
3610          * Whole archive runs might encounder dead code from weak symbols.
3611          * This is where the linker will have dropped the weak symbol in
3612          * favour of a regular symbol, but leaves the code in place.
3613          *
3614          * In this case we'll find a piece of code (whole function) that is not
3615          * covered by a !section symbol. Ignore them.
3616          */
3617         if (!insn->func && lto) {
3618                 int size = find_symbol_hole_containing(insn->sec, insn->offset);
3619                 unsigned long end = insn->offset + size;
3620
3621                 if (!size) /* not a hole */
3622                         return false;
3623
3624                 if (size < 0) /* hole until the end */
3625                         return true;
3626
3627                 sec_for_each_insn_continue(file, insn) {
3628                         /*
3629                          * If we reach a visited instruction at or before the
3630                          * end of the hole, ignore the unreachable.
3631                          */
3632                         if (insn->visited)
3633                                 return true;
3634
3635                         if (insn->offset >= end)
3636                                 break;
3637
3638                         /*
3639                          * If this hole jumps to a .cold function, mark it ignore too.
3640                          */
3641                         if (insn->jump_dest && insn->jump_dest->func &&
3642                             strstr(insn->jump_dest->func->name, ".cold")) {
3643                                 struct instruction *dest = insn->jump_dest;
3644                                 func_for_each_insn(file, dest->func, dest)
3645                                         dest->ignore = true;
3646                         }
3647                 }
3648
3649                 return false;
3650         }
3651
3652         if (!insn->func)
3653                 return false;
3654
3655         if (insn->func->static_call_tramp)
3656                 return true;
3657
3658         /*
3659          * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
3660          * __builtin_unreachable().  The BUG() macro has an unreachable() after
3661          * the UD2, which causes GCC's undefined trap logic to emit another UD2
3662          * (or occasionally a JMP to UD2).
3663          *
3664          * It may also insert a UD2 after calling a __noreturn function.
3665          */
3666         prev_insn = list_prev_entry(insn, list);
3667         if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) &&
3668             (insn->type == INSN_BUG ||
3669              (insn->type == INSN_JUMP_UNCONDITIONAL &&
3670               insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
3671                 return true;
3672
3673         /*
3674          * Check if this (or a subsequent) instruction is related to
3675          * CONFIG_UBSAN or CONFIG_KASAN.
3676          *
3677          * End the search at 5 instructions to avoid going into the weeds.
3678          */
3679         for (i = 0; i < 5; i++) {
3680
3681                 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
3682                         return true;
3683
3684                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
3685                         if (insn->jump_dest &&
3686                             insn->jump_dest->func == insn->func) {
3687                                 insn = insn->jump_dest;
3688                                 continue;
3689                         }
3690
3691                         break;
3692                 }
3693
3694                 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
3695                         break;
3696
3697                 insn = list_next_entry(insn, list);
3698         }
3699
3700         return false;
3701 }
3702
3703 static int validate_symbol(struct objtool_file *file, struct section *sec,
3704                            struct symbol *sym, struct insn_state *state)
3705 {
3706         struct instruction *insn;
3707         int ret;
3708
3709         if (!sym->len) {
3710                 WARN("%s() is missing an ELF size annotation", sym->name);
3711                 return 1;
3712         }
3713
3714         if (sym->pfunc != sym || sym->alias != sym)
3715                 return 0;
3716
3717         insn = find_insn(file, sec, sym->offset);
3718         if (!insn || insn->ignore || insn->visited)
3719                 return 0;
3720
3721         state->uaccess = sym->uaccess_safe;
3722
3723         ret = validate_branch(file, insn->func, insn, *state);
3724         if (ret && backtrace)
3725                 BT_FUNC("<=== (sym)", insn);
3726         return ret;
3727 }
3728
3729 static int validate_section(struct objtool_file *file, struct section *sec)
3730 {
3731         struct insn_state state;
3732         struct symbol *func;
3733         int warnings = 0;
3734
3735         list_for_each_entry(func, &sec->symbol_list, list) {
3736                 if (func->type != STT_FUNC)
3737                         continue;
3738
3739                 init_insn_state(&state, sec);
3740                 set_func_state(&state.cfi);
3741
3742                 warnings += validate_symbol(file, sec, func, &state);
3743         }
3744
3745         return warnings;
3746 }
3747
3748 static int validate_vmlinux_functions(struct objtool_file *file)
3749 {
3750         struct section *sec;
3751         int warnings = 0;
3752
3753         sec = find_section_by_name(file->elf, ".noinstr.text");
3754         if (sec) {
3755                 warnings += validate_section(file, sec);
3756                 warnings += validate_unwind_hints(file, sec);
3757         }
3758
3759         sec = find_section_by_name(file->elf, ".entry.text");
3760         if (sec) {
3761                 warnings += validate_section(file, sec);
3762                 warnings += validate_unwind_hints(file, sec);
3763         }
3764
3765         return warnings;
3766 }
3767
3768 static int validate_functions(struct objtool_file *file)
3769 {
3770         struct section *sec;
3771         int warnings = 0;
3772
3773         for_each_sec(file, sec) {
3774                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
3775                         continue;
3776
3777                 warnings += validate_section(file, sec);
3778         }
3779
3780         return warnings;
3781 }
3782
3783 static int validate_ibt(struct objtool_file *file)
3784 {
3785         struct section *sec;
3786         struct reloc *reloc;
3787
3788         for_each_sec(file, sec) {
3789                 bool is_data;
3790
3791                 /* already done in validate_branch() */
3792                 if (sec->sh.sh_flags & SHF_EXECINSTR)
3793                         continue;
3794
3795                 if (!sec->reloc)
3796                         continue;
3797
3798                 if (!strncmp(sec->name, ".orc", 4))
3799                         continue;
3800
3801                 if (!strncmp(sec->name, ".discard", 8))
3802                         continue;
3803
3804                 if (!strncmp(sec->name, ".debug", 6))
3805                         continue;
3806
3807                 if (!strcmp(sec->name, "_error_injection_whitelist"))
3808                         continue;
3809
3810                 if (!strcmp(sec->name, "_kprobe_blacklist"))
3811                         continue;
3812
3813                 is_data = strstr(sec->name, ".data") || strstr(sec->name, ".rodata");
3814
3815                 list_for_each_entry(reloc, &sec->reloc->reloc_list, list) {
3816                         struct instruction *dest;
3817
3818                         dest = validate_ibt_reloc(file, reloc);
3819                         if (is_data && dest && !dest->noendbr) {
3820                                 warn_noendbr("data ", reloc->sym->sec,
3821                                              reloc->sym->offset + reloc->addend,
3822                                              dest);
3823                         }
3824                 }
3825         }
3826
3827         return 0;
3828 }
3829
3830 static int validate_reachable_instructions(struct objtool_file *file)
3831 {
3832         struct instruction *insn;
3833
3834         if (file->ignore_unreachables)
3835                 return 0;
3836
3837         for_each_insn(file, insn) {
3838                 if (insn->visited || ignore_unreachable_insn(file, insn))
3839                         continue;
3840
3841                 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
3842                 return 1;
3843         }
3844
3845         return 0;
3846 }
3847
3848 int check(struct objtool_file *file)
3849 {
3850         int ret, warnings = 0;
3851
3852         if (lto && !(vmlinux || module)) {
3853                 fprintf(stderr, "--lto requires: --vmlinux or --module\n");
3854                 return 1;
3855         }
3856
3857         if (ibt && !lto) {
3858                 fprintf(stderr, "--ibt requires: --lto\n");
3859                 return 1;
3860         }
3861
3862         arch_initial_func_cfi_state(&initial_func_cfi);
3863         init_cfi_state(&init_cfi);
3864         init_cfi_state(&func_cfi);
3865         set_func_state(&func_cfi);
3866
3867         if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
3868                 goto out;
3869
3870         cfi_hash_add(&init_cfi);
3871         cfi_hash_add(&func_cfi);
3872
3873         ret = decode_sections(file);
3874         if (ret < 0)
3875                 goto out;
3876
3877         warnings += ret;
3878
3879         if (list_empty(&file->insn_list))
3880                 goto out;
3881
3882         if (vmlinux && !lto) {
3883                 ret = validate_vmlinux_functions(file);
3884                 if (ret < 0)
3885                         goto out;
3886
3887                 warnings += ret;
3888                 goto out;
3889         }
3890
3891         if (retpoline) {
3892                 ret = validate_retpoline(file);
3893                 if (ret < 0)
3894                         return ret;
3895                 warnings += ret;
3896         }
3897
3898         ret = validate_functions(file);
3899         if (ret < 0)
3900                 goto out;
3901         warnings += ret;
3902
3903         ret = validate_unwind_hints(file, NULL);
3904         if (ret < 0)
3905                 goto out;
3906         warnings += ret;
3907
3908         if (ibt) {
3909                 ret = validate_ibt(file);
3910                 if (ret < 0)
3911                         goto out;
3912                 warnings += ret;
3913         }
3914
3915         if (!warnings) {
3916                 ret = validate_reachable_instructions(file);
3917                 if (ret < 0)
3918                         goto out;
3919                 warnings += ret;
3920         }
3921
3922         ret = create_static_call_sections(file);
3923         if (ret < 0)
3924                 goto out;
3925         warnings += ret;
3926
3927         if (retpoline) {
3928                 ret = create_retpoline_sites_sections(file);
3929                 if (ret < 0)
3930                         goto out;
3931                 warnings += ret;
3932         }
3933
3934         if (mcount) {
3935                 ret = create_mcount_loc_sections(file);
3936                 if (ret < 0)
3937                         goto out;
3938                 warnings += ret;
3939         }
3940
3941         if (ibt) {
3942                 ret = create_ibt_endbr_seal_sections(file);
3943                 if (ret < 0)
3944                         goto out;
3945                 warnings += ret;
3946         }
3947
3948         if (stats) {
3949                 printf("nr_insns_visited: %ld\n", nr_insns_visited);
3950                 printf("nr_cfi: %ld\n", nr_cfi);
3951                 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
3952                 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
3953         }
3954
3955 out:
3956         /*
3957          *  For now, don't fail the kernel build on fatal warnings.  These
3958          *  errors are still fairly common due to the growing matrix of
3959          *  supported toolchains and their recent pace of change.
3960          */
3961         return 0;
3962 }