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, *jump_dest;
1275         struct reloc *reloc;
1276         struct section *dest_sec;
1277         unsigned long dest_off;
1278
1279         for_each_insn(file, insn) {
1280                 if (insn->jump_dest) {
1281                         /*
1282                          * handle_group_alt() may have previously set
1283                          * 'jump_dest' for some alternatives.
1284                          */
1285                         continue;
1286                 }
1287                 if (!is_static_jump(insn))
1288                         continue;
1289
1290                 reloc = insn_reloc(file, insn);
1291                 if (!reloc) {
1292                         dest_sec = insn->sec;
1293                         dest_off = arch_jump_destination(insn);
1294                 } else if (reloc->sym->type == STT_SECTION) {
1295                         dest_sec = reloc->sym->sec;
1296                         dest_off = arch_dest_reloc_offset(reloc->addend);
1297                 } else if (reloc->sym->retpoline_thunk) {
1298                         add_retpoline_call(file, insn);
1299                         continue;
1300                 } else if (insn->func) {
1301                         /*
1302                          * External sibling call or internal sibling call with
1303                          * STT_FUNC reloc.
1304                          */
1305                         add_call_dest(file, insn, reloc->sym, true);
1306                         continue;
1307                 } else if (reloc->sym->sec->idx) {
1308                         dest_sec = reloc->sym->sec;
1309                         dest_off = reloc->sym->sym.st_value +
1310                                    arch_dest_reloc_offset(reloc->addend);
1311                 } else {
1312                         /* non-func asm code jumping to another file */
1313                         continue;
1314                 }
1315
1316                 jump_dest = find_insn(file, dest_sec, dest_off);
1317                 if (!jump_dest) {
1318                         WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
1319                                   insn->sec, insn->offset, dest_sec->name,
1320                                   dest_off);
1321                         return -1;
1322                 }
1323
1324                 /*
1325                  * Cross-function jump.
1326                  */
1327                 if (insn->func && jump_dest->func &&
1328                     insn->func != jump_dest->func) {
1329
1330                         /*
1331                          * For GCC 8+, create parent/child links for any cold
1332                          * subfunctions.  This is _mostly_ redundant with a
1333                          * similar initialization in read_symbols().
1334                          *
1335                          * If a function has aliases, we want the *first* such
1336                          * function in the symbol table to be the subfunction's
1337                          * parent.  In that case we overwrite the
1338                          * initialization done in read_symbols().
1339                          *
1340                          * However this code can't completely replace the
1341                          * read_symbols() code because this doesn't detect the
1342                          * case where the parent function's only reference to a
1343                          * subfunction is through a jump table.
1344                          */
1345                         if (!strstr(insn->func->name, ".cold") &&
1346                             strstr(jump_dest->func->name, ".cold")) {
1347                                 insn->func->cfunc = jump_dest->func;
1348                                 jump_dest->func->pfunc = insn->func;
1349
1350                         } else if (!same_function(insn, jump_dest) &&
1351                                    is_first_func_insn(file, jump_dest)) {
1352                                 /*
1353                                  * Internal sibling call without reloc or with
1354                                  * STT_SECTION reloc.
1355                                  */
1356                                 add_call_dest(file, insn, jump_dest->func, true);
1357                                 continue;
1358                         }
1359                 }
1360
1361                 insn->jump_dest = jump_dest;
1362         }
1363
1364         return 0;
1365 }
1366
1367 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1368 {
1369         struct symbol *call_dest;
1370
1371         call_dest = find_func_by_offset(sec, offset);
1372         if (!call_dest)
1373                 call_dest = find_symbol_by_offset(sec, offset);
1374
1375         return call_dest;
1376 }
1377
1378 /*
1379  * Find the destination instructions for all calls.
1380  */
1381 static int add_call_destinations(struct objtool_file *file)
1382 {
1383         struct instruction *insn;
1384         unsigned long dest_off;
1385         struct symbol *dest;
1386         struct reloc *reloc;
1387
1388         for_each_insn(file, insn) {
1389                 if (insn->type != INSN_CALL)
1390                         continue;
1391
1392                 reloc = insn_reloc(file, insn);
1393                 if (!reloc) {
1394                         dest_off = arch_jump_destination(insn);
1395                         dest = find_call_destination(insn->sec, dest_off);
1396
1397                         add_call_dest(file, insn, dest, false);
1398
1399                         if (insn->ignore)
1400                                 continue;
1401
1402                         if (!insn->call_dest) {
1403                                 WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);
1404                                 return -1;
1405                         }
1406
1407                         if (insn->func && insn->call_dest->type != STT_FUNC) {
1408                                 WARN_FUNC("unsupported call to non-function",
1409                                           insn->sec, insn->offset);
1410                                 return -1;
1411                         }
1412
1413                 } else if (reloc->sym->type == STT_SECTION) {
1414                         dest_off = arch_dest_reloc_offset(reloc->addend);
1415                         dest = find_call_destination(reloc->sym->sec, dest_off);
1416                         if (!dest) {
1417                                 WARN_FUNC("can't find call dest symbol at %s+0x%lx",
1418                                           insn->sec, insn->offset,
1419                                           reloc->sym->sec->name,
1420                                           dest_off);
1421                                 return -1;
1422                         }
1423
1424                         add_call_dest(file, insn, dest, false);
1425
1426                 } else if (reloc->sym->retpoline_thunk) {
1427                         add_retpoline_call(file, insn);
1428
1429                 } else
1430                         add_call_dest(file, insn, reloc->sym, false);
1431         }
1432
1433         return 0;
1434 }
1435
1436 /*
1437  * The .alternatives section requires some extra special care over and above
1438  * other special sections because alternatives are patched in place.
1439  */
1440 static int handle_group_alt(struct objtool_file *file,
1441                             struct special_alt *special_alt,
1442                             struct instruction *orig_insn,
1443                             struct instruction **new_insn)
1444 {
1445         struct instruction *last_orig_insn, *last_new_insn = NULL, *insn, *nop = NULL;
1446         struct alt_group *orig_alt_group, *new_alt_group;
1447         unsigned long dest_off;
1448
1449
1450         orig_alt_group = malloc(sizeof(*orig_alt_group));
1451         if (!orig_alt_group) {
1452                 WARN("malloc failed");
1453                 return -1;
1454         }
1455         orig_alt_group->cfi = calloc(special_alt->orig_len,
1456                                      sizeof(struct cfi_state *));
1457         if (!orig_alt_group->cfi) {
1458                 WARN("calloc failed");
1459                 return -1;
1460         }
1461
1462         last_orig_insn = NULL;
1463         insn = orig_insn;
1464         sec_for_each_insn_from(file, insn) {
1465                 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1466                         break;
1467
1468                 insn->alt_group = orig_alt_group;
1469                 last_orig_insn = insn;
1470         }
1471         orig_alt_group->orig_group = NULL;
1472         orig_alt_group->first_insn = orig_insn;
1473         orig_alt_group->last_insn = last_orig_insn;
1474
1475
1476         new_alt_group = malloc(sizeof(*new_alt_group));
1477         if (!new_alt_group) {
1478                 WARN("malloc failed");
1479                 return -1;
1480         }
1481
1482         if (special_alt->new_len < special_alt->orig_len) {
1483                 /*
1484                  * Insert a fake nop at the end to make the replacement
1485                  * alt_group the same size as the original.  This is needed to
1486                  * allow propagate_alt_cfi() to do its magic.  When the last
1487                  * instruction affects the stack, the instruction after it (the
1488                  * nop) will propagate the new state to the shared CFI array.
1489                  */
1490                 nop = malloc(sizeof(*nop));
1491                 if (!nop) {
1492                         WARN("malloc failed");
1493                         return -1;
1494                 }
1495                 memset(nop, 0, sizeof(*nop));
1496                 INIT_LIST_HEAD(&nop->alts);
1497                 INIT_LIST_HEAD(&nop->stack_ops);
1498
1499                 nop->sec = special_alt->new_sec;
1500                 nop->offset = special_alt->new_off + special_alt->new_len;
1501                 nop->len = special_alt->orig_len - special_alt->new_len;
1502                 nop->type = INSN_NOP;
1503                 nop->func = orig_insn->func;
1504                 nop->alt_group = new_alt_group;
1505                 nop->ignore = orig_insn->ignore_alts;
1506         }
1507
1508         if (!special_alt->new_len) {
1509                 *new_insn = nop;
1510                 goto end;
1511         }
1512
1513         insn = *new_insn;
1514         sec_for_each_insn_from(file, insn) {
1515                 struct reloc *alt_reloc;
1516
1517                 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1518                         break;
1519
1520                 last_new_insn = insn;
1521
1522                 insn->ignore = orig_insn->ignore_alts;
1523                 insn->func = orig_insn->func;
1524                 insn->alt_group = new_alt_group;
1525
1526                 /*
1527                  * Since alternative replacement code is copy/pasted by the
1528                  * kernel after applying relocations, generally such code can't
1529                  * have relative-address relocation references to outside the
1530                  * .altinstr_replacement section, unless the arch's
1531                  * alternatives code can adjust the relative offsets
1532                  * accordingly.
1533                  */
1534                 alt_reloc = insn_reloc(file, insn);
1535                 if (alt_reloc &&
1536                     !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1537
1538                         WARN_FUNC("unsupported relocation in alternatives section",
1539                                   insn->sec, insn->offset);
1540                         return -1;
1541                 }
1542
1543                 if (!is_static_jump(insn))
1544                         continue;
1545
1546                 if (!insn->immediate)
1547                         continue;
1548
1549                 dest_off = arch_jump_destination(insn);
1550                 if (dest_off == special_alt->new_off + special_alt->new_len) {
1551                         insn->jump_dest = next_insn_same_sec(file, last_orig_insn);
1552                         if (!insn->jump_dest) {
1553                                 WARN_FUNC("can't find alternative jump destination",
1554                                           insn->sec, insn->offset);
1555                                 return -1;
1556                         }
1557                 }
1558         }
1559
1560         if (!last_new_insn) {
1561                 WARN_FUNC("can't find last new alternative instruction",
1562                           special_alt->new_sec, special_alt->new_off);
1563                 return -1;
1564         }
1565
1566         if (nop)
1567                 list_add(&nop->list, &last_new_insn->list);
1568 end:
1569         new_alt_group->orig_group = orig_alt_group;
1570         new_alt_group->first_insn = *new_insn;
1571         new_alt_group->last_insn = nop ? : last_new_insn;
1572         new_alt_group->cfi = orig_alt_group->cfi;
1573         return 0;
1574 }
1575
1576 /*
1577  * A jump table entry can either convert a nop to a jump or a jump to a nop.
1578  * If the original instruction is a jump, make the alt entry an effective nop
1579  * by just skipping the original instruction.
1580  */
1581 static int handle_jump_alt(struct objtool_file *file,
1582                            struct special_alt *special_alt,
1583                            struct instruction *orig_insn,
1584                            struct instruction **new_insn)
1585 {
1586         if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1587             orig_insn->type != INSN_NOP) {
1588
1589                 WARN_FUNC("unsupported instruction at jump label",
1590                           orig_insn->sec, orig_insn->offset);
1591                 return -1;
1592         }
1593
1594         if (special_alt->key_addend & 2) {
1595                 struct reloc *reloc = insn_reloc(file, orig_insn);
1596
1597                 if (reloc) {
1598                         reloc->type = R_NONE;
1599                         elf_write_reloc(file->elf, reloc);
1600                 }
1601                 elf_write_insn(file->elf, orig_insn->sec,
1602                                orig_insn->offset, orig_insn->len,
1603                                arch_nop_insn(orig_insn->len));
1604                 orig_insn->type = INSN_NOP;
1605         }
1606
1607         if (orig_insn->type == INSN_NOP) {
1608                 if (orig_insn->len == 2)
1609                         file->jl_nop_short++;
1610                 else
1611                         file->jl_nop_long++;
1612
1613                 return 0;
1614         }
1615
1616         if (orig_insn->len == 2)
1617                 file->jl_short++;
1618         else
1619                 file->jl_long++;
1620
1621         *new_insn = list_next_entry(orig_insn, list);
1622         return 0;
1623 }
1624
1625 /*
1626  * Read all the special sections which have alternate instructions which can be
1627  * patched in or redirected to at runtime.  Each instruction having alternate
1628  * instruction(s) has them added to its insn->alts list, which will be
1629  * traversed in validate_branch().
1630  */
1631 static int add_special_section_alts(struct objtool_file *file)
1632 {
1633         struct list_head special_alts;
1634         struct instruction *orig_insn, *new_insn;
1635         struct special_alt *special_alt, *tmp;
1636         struct alternative *alt;
1637         int ret;
1638
1639         ret = special_get_alts(file->elf, &special_alts);
1640         if (ret)
1641                 return ret;
1642
1643         list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1644
1645                 orig_insn = find_insn(file, special_alt->orig_sec,
1646                                       special_alt->orig_off);
1647                 if (!orig_insn) {
1648                         WARN_FUNC("special: can't find orig instruction",
1649                                   special_alt->orig_sec, special_alt->orig_off);
1650                         ret = -1;
1651                         goto out;
1652                 }
1653
1654                 new_insn = NULL;
1655                 if (!special_alt->group || special_alt->new_len) {
1656                         new_insn = find_insn(file, special_alt->new_sec,
1657                                              special_alt->new_off);
1658                         if (!new_insn) {
1659                                 WARN_FUNC("special: can't find new instruction",
1660                                           special_alt->new_sec,
1661                                           special_alt->new_off);
1662                                 ret = -1;
1663                                 goto out;
1664                         }
1665                 }
1666
1667                 if (special_alt->group) {
1668                         if (!special_alt->orig_len) {
1669                                 WARN_FUNC("empty alternative entry",
1670                                           orig_insn->sec, orig_insn->offset);
1671                                 continue;
1672                         }
1673
1674                         ret = handle_group_alt(file, special_alt, orig_insn,
1675                                                &new_insn);
1676                         if (ret)
1677                                 goto out;
1678                 } else if (special_alt->jump_or_nop) {
1679                         ret = handle_jump_alt(file, special_alt, orig_insn,
1680                                               &new_insn);
1681                         if (ret)
1682                                 goto out;
1683                 }
1684
1685                 alt = malloc(sizeof(*alt));
1686                 if (!alt) {
1687                         WARN("malloc failed");
1688                         ret = -1;
1689                         goto out;
1690                 }
1691
1692                 alt->insn = new_insn;
1693                 alt->skip_orig = special_alt->skip_orig;
1694                 orig_insn->ignore_alts |= special_alt->skip_alt;
1695                 list_add_tail(&alt->list, &orig_insn->alts);
1696
1697                 list_del(&special_alt->list);
1698                 free(special_alt);
1699         }
1700
1701         if (stats) {
1702                 printf("jl\\\tNOP\tJMP\n");
1703                 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
1704                 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
1705         }
1706
1707 out:
1708         return ret;
1709 }
1710
1711 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
1712                             struct reloc *table)
1713 {
1714         struct reloc *reloc = table;
1715         struct instruction *dest_insn;
1716         struct alternative *alt;
1717         struct symbol *pfunc = insn->func->pfunc;
1718         unsigned int prev_offset = 0;
1719
1720         /*
1721          * Each @reloc is a switch table relocation which points to the target
1722          * instruction.
1723          */
1724         list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
1725
1726                 /* Check for the end of the table: */
1727                 if (reloc != table && reloc->jump_table_start)
1728                         break;
1729
1730                 /* Make sure the table entries are consecutive: */
1731                 if (prev_offset && reloc->offset != prev_offset + 8)
1732                         break;
1733
1734                 /* Detect function pointers from contiguous objects: */
1735                 if (reloc->sym->sec == pfunc->sec &&
1736                     reloc->addend == pfunc->offset)
1737                         break;
1738
1739                 dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
1740                 if (!dest_insn)
1741                         break;
1742
1743                 /* Make sure the destination is in the same function: */
1744                 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
1745                         break;
1746
1747                 alt = malloc(sizeof(*alt));
1748                 if (!alt) {
1749                         WARN("malloc failed");
1750                         return -1;
1751                 }
1752
1753                 alt->insn = dest_insn;
1754                 list_add_tail(&alt->list, &insn->alts);
1755                 prev_offset = reloc->offset;
1756         }
1757
1758         if (!prev_offset) {
1759                 WARN_FUNC("can't find switch jump table",
1760                           insn->sec, insn->offset);
1761                 return -1;
1762         }
1763
1764         return 0;
1765 }
1766
1767 /*
1768  * find_jump_table() - Given a dynamic jump, find the switch jump table
1769  * associated with it.
1770  */
1771 static struct reloc *find_jump_table(struct objtool_file *file,
1772                                       struct symbol *func,
1773                                       struct instruction *insn)
1774 {
1775         struct reloc *table_reloc;
1776         struct instruction *dest_insn, *orig_insn = insn;
1777
1778         /*
1779          * Backward search using the @first_jump_src links, these help avoid
1780          * much of the 'in between' code. Which avoids us getting confused by
1781          * it.
1782          */
1783         for (;
1784              insn && insn->func && insn->func->pfunc == func;
1785              insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
1786
1787                 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1788                         break;
1789
1790                 /* allow small jumps within the range */
1791                 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1792                     insn->jump_dest &&
1793                     (insn->jump_dest->offset <= insn->offset ||
1794                      insn->jump_dest->offset > orig_insn->offset))
1795                     break;
1796
1797                 table_reloc = arch_find_switch_table(file, insn);
1798                 if (!table_reloc)
1799                         continue;
1800                 dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
1801                 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1802                         continue;
1803
1804                 return table_reloc;
1805         }
1806
1807         return NULL;
1808 }
1809
1810 /*
1811  * First pass: Mark the head of each jump table so that in the next pass,
1812  * we know when a given jump table ends and the next one starts.
1813  */
1814 static void mark_func_jump_tables(struct objtool_file *file,
1815                                     struct symbol *func)
1816 {
1817         struct instruction *insn, *last = NULL;
1818         struct reloc *reloc;
1819
1820         func_for_each_insn(file, func, insn) {
1821                 if (!last)
1822                         last = insn;
1823
1824                 /*
1825                  * Store back-pointers for unconditional forward jumps such
1826                  * that find_jump_table() can back-track using those and
1827                  * avoid some potentially confusing code.
1828                  */
1829                 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1830                     insn->offset > last->offset &&
1831                     insn->jump_dest->offset > insn->offset &&
1832                     !insn->jump_dest->first_jump_src) {
1833
1834                         insn->jump_dest->first_jump_src = insn;
1835                         last = insn->jump_dest;
1836                 }
1837
1838                 if (insn->type != INSN_JUMP_DYNAMIC)
1839                         continue;
1840
1841                 reloc = find_jump_table(file, func, insn);
1842                 if (reloc) {
1843                         reloc->jump_table_start = true;
1844                         insn->jump_table = reloc;
1845                 }
1846         }
1847 }
1848
1849 static int add_func_jump_tables(struct objtool_file *file,
1850                                   struct symbol *func)
1851 {
1852         struct instruction *insn;
1853         int ret;
1854
1855         func_for_each_insn(file, func, insn) {
1856                 if (!insn->jump_table)
1857                         continue;
1858
1859                 ret = add_jump_table(file, insn, insn->jump_table);
1860                 if (ret)
1861                         return ret;
1862         }
1863
1864         return 0;
1865 }
1866
1867 /*
1868  * For some switch statements, gcc generates a jump table in the .rodata
1869  * section which contains a list of addresses within the function to jump to.
1870  * This finds these jump tables and adds them to the insn->alts lists.
1871  */
1872 static int add_jump_table_alts(struct objtool_file *file)
1873 {
1874         struct section *sec;
1875         struct symbol *func;
1876         int ret;
1877
1878         if (!file->rodata)
1879                 return 0;
1880
1881         for_each_sec(file, sec) {
1882                 list_for_each_entry(func, &sec->symbol_list, list) {
1883                         if (func->type != STT_FUNC)
1884                                 continue;
1885
1886                         mark_func_jump_tables(file, func);
1887                         ret = add_func_jump_tables(file, func);
1888                         if (ret)
1889                                 return ret;
1890                 }
1891         }
1892
1893         return 0;
1894 }
1895
1896 static void set_func_state(struct cfi_state *state)
1897 {
1898         state->cfa = initial_func_cfi.cfa;
1899         memcpy(&state->regs, &initial_func_cfi.regs,
1900                CFI_NUM_REGS * sizeof(struct cfi_reg));
1901         state->stack_size = initial_func_cfi.cfa.offset;
1902 }
1903
1904 static int read_unwind_hints(struct objtool_file *file)
1905 {
1906         struct cfi_state cfi = init_cfi;
1907         struct section *sec, *relocsec;
1908         struct unwind_hint *hint;
1909         struct instruction *insn;
1910         struct reloc *reloc;
1911         int i;
1912
1913         sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1914         if (!sec)
1915                 return 0;
1916
1917         relocsec = sec->reloc;
1918         if (!relocsec) {
1919                 WARN("missing .rela.discard.unwind_hints section");
1920                 return -1;
1921         }
1922
1923         if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
1924                 WARN("struct unwind_hint size mismatch");
1925                 return -1;
1926         }
1927
1928         file->hints = true;
1929
1930         for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
1931                 hint = (struct unwind_hint *)sec->data->d_buf + i;
1932
1933                 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
1934                 if (!reloc) {
1935                         WARN("can't find reloc for unwind_hints[%d]", i);
1936                         return -1;
1937                 }
1938
1939                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1940                 if (!insn) {
1941                         WARN("can't find insn for unwind_hints[%d]", i);
1942                         return -1;
1943                 }
1944
1945                 insn->hint = true;
1946
1947                 if (ibt && hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
1948                         struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
1949
1950                         if (sym && sym->bind == STB_GLOBAL &&
1951                             insn->type != INSN_ENDBR && !insn->noendbr) {
1952                                 WARN_FUNC("UNWIND_HINT_IRET_REGS without ENDBR",
1953                                           insn->sec, insn->offset);
1954                         }
1955                 }
1956
1957                 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
1958                         insn->cfi = &func_cfi;
1959                         continue;
1960                 }
1961
1962                 if (insn->cfi)
1963                         cfi = *(insn->cfi);
1964
1965                 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
1966                         WARN_FUNC("unsupported unwind_hint sp base reg %d",
1967                                   insn->sec, insn->offset, hint->sp_reg);
1968                         return -1;
1969                 }
1970
1971                 cfi.cfa.offset = bswap_if_needed(hint->sp_offset);
1972                 cfi.type = hint->type;
1973                 cfi.end = hint->end;
1974
1975                 insn->cfi = cfi_hash_find_or_add(&cfi);
1976         }
1977
1978         return 0;
1979 }
1980
1981 static int read_noendbr_hints(struct objtool_file *file)
1982 {
1983         struct section *sec;
1984         struct instruction *insn;
1985         struct reloc *reloc;
1986
1987         sec = find_section_by_name(file->elf, ".rela.discard.noendbr");
1988         if (!sec)
1989                 return 0;
1990
1991         list_for_each_entry(reloc, &sec->reloc_list, list) {
1992                 insn = find_insn(file, reloc->sym->sec, reloc->sym->offset + reloc->addend);
1993                 if (!insn) {
1994                         WARN("bad .discard.noendbr entry");
1995                         return -1;
1996                 }
1997
1998                 if (insn->type == INSN_ENDBR)
1999                         WARN_FUNC("ANNOTATE_NOENDBR on ENDBR", insn->sec, insn->offset);
2000
2001                 insn->noendbr = 1;
2002         }
2003
2004         return 0;
2005 }
2006
2007 static int read_retpoline_hints(struct objtool_file *file)
2008 {
2009         struct section *sec;
2010         struct instruction *insn;
2011         struct reloc *reloc;
2012
2013         sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
2014         if (!sec)
2015                 return 0;
2016
2017         list_for_each_entry(reloc, &sec->reloc_list, list) {
2018                 if (reloc->sym->type != STT_SECTION) {
2019                         WARN("unexpected relocation symbol type in %s", sec->name);
2020                         return -1;
2021                 }
2022
2023                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2024                 if (!insn) {
2025                         WARN("bad .discard.retpoline_safe entry");
2026                         return -1;
2027                 }
2028
2029                 if (insn->type != INSN_JUMP_DYNAMIC &&
2030                     insn->type != INSN_CALL_DYNAMIC) {
2031                         WARN_FUNC("retpoline_safe hint not an indirect jump/call",
2032                                   insn->sec, insn->offset);
2033                         return -1;
2034                 }
2035
2036                 insn->retpoline_safe = true;
2037         }
2038
2039         return 0;
2040 }
2041
2042 static int read_instr_hints(struct objtool_file *file)
2043 {
2044         struct section *sec;
2045         struct instruction *insn;
2046         struct reloc *reloc;
2047
2048         sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2049         if (!sec)
2050                 return 0;
2051
2052         list_for_each_entry(reloc, &sec->reloc_list, list) {
2053                 if (reloc->sym->type != STT_SECTION) {
2054                         WARN("unexpected relocation symbol type in %s", sec->name);
2055                         return -1;
2056                 }
2057
2058                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2059                 if (!insn) {
2060                         WARN("bad .discard.instr_end entry");
2061                         return -1;
2062                 }
2063
2064                 insn->instr--;
2065         }
2066
2067         sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2068         if (!sec)
2069                 return 0;
2070
2071         list_for_each_entry(reloc, &sec->reloc_list, list) {
2072                 if (reloc->sym->type != STT_SECTION) {
2073                         WARN("unexpected relocation symbol type in %s", sec->name);
2074                         return -1;
2075                 }
2076
2077                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2078                 if (!insn) {
2079                         WARN("bad .discard.instr_begin entry");
2080                         return -1;
2081                 }
2082
2083                 insn->instr++;
2084         }
2085
2086         return 0;
2087 }
2088
2089 static int read_intra_function_calls(struct objtool_file *file)
2090 {
2091         struct instruction *insn;
2092         struct section *sec;
2093         struct reloc *reloc;
2094
2095         sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2096         if (!sec)
2097                 return 0;
2098
2099         list_for_each_entry(reloc, &sec->reloc_list, list) {
2100                 unsigned long dest_off;
2101
2102                 if (reloc->sym->type != STT_SECTION) {
2103                         WARN("unexpected relocation symbol type in %s",
2104                              sec->name);
2105                         return -1;
2106                 }
2107
2108                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2109                 if (!insn) {
2110                         WARN("bad .discard.intra_function_call entry");
2111                         return -1;
2112                 }
2113
2114                 if (insn->type != INSN_CALL) {
2115                         WARN_FUNC("intra_function_call not a direct call",
2116                                   insn->sec, insn->offset);
2117                         return -1;
2118                 }
2119
2120                 /*
2121                  * Treat intra-function CALLs as JMPs, but with a stack_op.
2122                  * See add_call_destinations(), which strips stack_ops from
2123                  * normal CALLs.
2124                  */
2125                 insn->type = INSN_JUMP_UNCONDITIONAL;
2126
2127                 dest_off = insn->offset + insn->len + insn->immediate;
2128                 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2129                 if (!insn->jump_dest) {
2130                         WARN_FUNC("can't find call dest at %s+0x%lx",
2131                                   insn->sec, insn->offset,
2132                                   insn->sec->name, dest_off);
2133                         return -1;
2134                 }
2135         }
2136
2137         return 0;
2138 }
2139
2140 /*
2141  * Return true if name matches an instrumentation function, where calls to that
2142  * function from noinstr code can safely be removed, but compilers won't do so.
2143  */
2144 static bool is_profiling_func(const char *name)
2145 {
2146         /*
2147          * Many compilers cannot disable KCOV with a function attribute.
2148          */
2149         if (!strncmp(name, "__sanitizer_cov_", 16))
2150                 return true;
2151
2152         /*
2153          * Some compilers currently do not remove __tsan_func_entry/exit nor
2154          * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2155          * the __no_sanitize_thread attribute, remove them. Once the kernel's
2156          * minimum Clang version is 14.0, this can be removed.
2157          */
2158         if (!strncmp(name, "__tsan_func_", 12) ||
2159             !strcmp(name, "__tsan_atomic_signal_fence"))
2160                 return true;
2161
2162         return false;
2163 }
2164
2165 static int classify_symbols(struct objtool_file *file)
2166 {
2167         struct section *sec;
2168         struct symbol *func;
2169
2170         for_each_sec(file, sec) {
2171                 list_for_each_entry(func, &sec->symbol_list, list) {
2172                         if (func->bind != STB_GLOBAL)
2173                                 continue;
2174
2175                         if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2176                                      strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2177                                 func->static_call_tramp = true;
2178
2179                         if (arch_is_retpoline(func))
2180                                 func->retpoline_thunk = true;
2181
2182                         if (!strcmp(func->name, "__fentry__"))
2183                                 func->fentry = true;
2184
2185                         if (is_profiling_func(func->name))
2186                                 func->profiling_func = true;
2187                 }
2188         }
2189
2190         return 0;
2191 }
2192
2193 static void mark_rodata(struct objtool_file *file)
2194 {
2195         struct section *sec;
2196         bool found = false;
2197
2198         /*
2199          * Search for the following rodata sections, each of which can
2200          * potentially contain jump tables:
2201          *
2202          * - .rodata: can contain GCC switch tables
2203          * - .rodata.<func>: same, if -fdata-sections is being used
2204          * - .rodata..c_jump_table: contains C annotated jump tables
2205          *
2206          * .rodata.str1.* sections are ignored; they don't contain jump tables.
2207          */
2208         for_each_sec(file, sec) {
2209                 if (!strncmp(sec->name, ".rodata", 7) &&
2210                     !strstr(sec->name, ".str1.")) {
2211                         sec->rodata = true;
2212                         found = true;
2213                 }
2214         }
2215
2216         file->rodata = found;
2217 }
2218
2219 static int decode_sections(struct objtool_file *file)
2220 {
2221         int ret;
2222
2223         mark_rodata(file);
2224
2225         ret = init_pv_ops(file);
2226         if (ret)
2227                 return ret;
2228
2229         ret = decode_instructions(file);
2230         if (ret)
2231                 return ret;
2232
2233         add_ignores(file);
2234         add_uaccess_safe(file);
2235
2236         ret = add_ignore_alternatives(file);
2237         if (ret)
2238                 return ret;
2239
2240         /*
2241          * Must be before read_unwind_hints() since that needs insn->noendbr.
2242          */
2243         ret = read_noendbr_hints(file);
2244         if (ret)
2245                 return ret;
2246
2247         /*
2248          * Must be before add_{jump_call}_destination.
2249          */
2250         ret = classify_symbols(file);
2251         if (ret)
2252                 return ret;
2253
2254         /*
2255          * Must be before add_jump_destinations(), which depends on 'func'
2256          * being set for alternatives, to enable proper sibling call detection.
2257          */
2258         ret = add_special_section_alts(file);
2259         if (ret)
2260                 return ret;
2261
2262         ret = add_jump_destinations(file);
2263         if (ret)
2264                 return ret;
2265
2266         /*
2267          * Must be before add_call_destination(); it changes INSN_CALL to
2268          * INSN_JUMP.
2269          */
2270         ret = read_intra_function_calls(file);
2271         if (ret)
2272                 return ret;
2273
2274         ret = add_call_destinations(file);
2275         if (ret)
2276                 return ret;
2277
2278         /*
2279          * Must be after add_call_destinations() such that it can override
2280          * dead_end_function() marks.
2281          */
2282         ret = add_dead_ends(file);
2283         if (ret)
2284                 return ret;
2285
2286         ret = add_jump_table_alts(file);
2287         if (ret)
2288                 return ret;
2289
2290         ret = read_unwind_hints(file);
2291         if (ret)
2292                 return ret;
2293
2294         ret = read_retpoline_hints(file);
2295         if (ret)
2296                 return ret;
2297
2298         ret = read_instr_hints(file);
2299         if (ret)
2300                 return ret;
2301
2302         return 0;
2303 }
2304
2305 static bool is_fentry_call(struct instruction *insn)
2306 {
2307         if (insn->type == INSN_CALL &&
2308             insn->call_dest &&
2309             insn->call_dest->fentry)
2310                 return true;
2311
2312         return false;
2313 }
2314
2315 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2316 {
2317         struct cfi_state *cfi = &state->cfi;
2318         int i;
2319
2320         if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2321                 return true;
2322
2323         if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2324                 return true;
2325
2326         if (cfi->stack_size != initial_func_cfi.cfa.offset)
2327                 return true;
2328
2329         for (i = 0; i < CFI_NUM_REGS; i++) {
2330                 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2331                     cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2332                         return true;
2333         }
2334
2335         return false;
2336 }
2337
2338 static bool check_reg_frame_pos(const struct cfi_reg *reg,
2339                                 int expected_offset)
2340 {
2341         return reg->base == CFI_CFA &&
2342                reg->offset == expected_offset;
2343 }
2344
2345 static bool has_valid_stack_frame(struct insn_state *state)
2346 {
2347         struct cfi_state *cfi = &state->cfi;
2348
2349         if (cfi->cfa.base == CFI_BP &&
2350             check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2351             check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2352                 return true;
2353
2354         if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2355                 return true;
2356
2357         return false;
2358 }
2359
2360 static int update_cfi_state_regs(struct instruction *insn,
2361                                   struct cfi_state *cfi,
2362                                   struct stack_op *op)
2363 {
2364         struct cfi_reg *cfa = &cfi->cfa;
2365
2366         if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2367                 return 0;
2368
2369         /* push */
2370         if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2371                 cfa->offset += 8;
2372
2373         /* pop */
2374         if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2375                 cfa->offset -= 8;
2376
2377         /* add immediate to sp */
2378         if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2379             op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2380                 cfa->offset -= op->src.offset;
2381
2382         return 0;
2383 }
2384
2385 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2386 {
2387         if (arch_callee_saved_reg(reg) &&
2388             cfi->regs[reg].base == CFI_UNDEFINED) {
2389                 cfi->regs[reg].base = base;
2390                 cfi->regs[reg].offset = offset;
2391         }
2392 }
2393
2394 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2395 {
2396         cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2397         cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2398 }
2399
2400 /*
2401  * A note about DRAP stack alignment:
2402  *
2403  * GCC has the concept of a DRAP register, which is used to help keep track of
2404  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
2405  * register.  The typical DRAP pattern is:
2406  *
2407  *   4c 8d 54 24 08             lea    0x8(%rsp),%r10
2408  *   48 83 e4 c0                and    $0xffffffffffffffc0,%rsp
2409  *   41 ff 72 f8                pushq  -0x8(%r10)
2410  *   55                         push   %rbp
2411  *   48 89 e5                   mov    %rsp,%rbp
2412  *                              (more pushes)
2413  *   41 52                      push   %r10
2414  *                              ...
2415  *   41 5a                      pop    %r10
2416  *                              (more pops)
2417  *   5d                         pop    %rbp
2418  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2419  *   c3                         retq
2420  *
2421  * There are some variations in the epilogues, like:
2422  *
2423  *   5b                         pop    %rbx
2424  *   41 5a                      pop    %r10
2425  *   41 5c                      pop    %r12
2426  *   41 5d                      pop    %r13
2427  *   41 5e                      pop    %r14
2428  *   c9                         leaveq
2429  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2430  *   c3                         retq
2431  *
2432  * and:
2433  *
2434  *   4c 8b 55 e8                mov    -0x18(%rbp),%r10
2435  *   48 8b 5d e0                mov    -0x20(%rbp),%rbx
2436  *   4c 8b 65 f0                mov    -0x10(%rbp),%r12
2437  *   4c 8b 6d f8                mov    -0x8(%rbp),%r13
2438  *   c9                         leaveq
2439  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2440  *   c3                         retq
2441  *
2442  * Sometimes r13 is used as the DRAP register, in which case it's saved and
2443  * restored beforehand:
2444  *
2445  *   41 55                      push   %r13
2446  *   4c 8d 6c 24 10             lea    0x10(%rsp),%r13
2447  *   48 83 e4 f0                and    $0xfffffffffffffff0,%rsp
2448  *                              ...
2449  *   49 8d 65 f0                lea    -0x10(%r13),%rsp
2450  *   41 5d                      pop    %r13
2451  *   c3                         retq
2452  */
2453 static int update_cfi_state(struct instruction *insn,
2454                             struct instruction *next_insn,
2455                             struct cfi_state *cfi, struct stack_op *op)
2456 {
2457         struct cfi_reg *cfa = &cfi->cfa;
2458         struct cfi_reg *regs = cfi->regs;
2459
2460         /* stack operations don't make sense with an undefined CFA */
2461         if (cfa->base == CFI_UNDEFINED) {
2462                 if (insn->func) {
2463                         WARN_FUNC("undefined stack state", insn->sec, insn->offset);
2464                         return -1;
2465                 }
2466                 return 0;
2467         }
2468
2469         if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2470             cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2471                 return update_cfi_state_regs(insn, cfi, op);
2472
2473         switch (op->dest.type) {
2474
2475         case OP_DEST_REG:
2476                 switch (op->src.type) {
2477
2478                 case OP_SRC_REG:
2479                         if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2480                             cfa->base == CFI_SP &&
2481                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset)) {
2482
2483                                 /* mov %rsp, %rbp */
2484                                 cfa->base = op->dest.reg;
2485                                 cfi->bp_scratch = false;
2486                         }
2487
2488                         else if (op->src.reg == CFI_SP &&
2489                                  op->dest.reg == CFI_BP && cfi->drap) {
2490
2491                                 /* drap: mov %rsp, %rbp */
2492                                 regs[CFI_BP].base = CFI_BP;
2493                                 regs[CFI_BP].offset = -cfi->stack_size;
2494                                 cfi->bp_scratch = false;
2495                         }
2496
2497                         else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2498
2499                                 /*
2500                                  * mov %rsp, %reg
2501                                  *
2502                                  * This is needed for the rare case where GCC
2503                                  * does:
2504                                  *
2505                                  *   mov    %rsp, %rax
2506                                  *   ...
2507                                  *   mov    %rax, %rsp
2508                                  */
2509                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2510                                 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2511                         }
2512
2513                         else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2514                                  (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2515
2516                                 /*
2517                                  * mov %rbp, %rsp
2518                                  *
2519                                  * Restore the original stack pointer (Clang).
2520                                  */
2521                                 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2522                         }
2523
2524                         else if (op->dest.reg == cfa->base) {
2525
2526                                 /* mov %reg, %rsp */
2527                                 if (cfa->base == CFI_SP &&
2528                                     cfi->vals[op->src.reg].base == CFI_CFA) {
2529
2530                                         /*
2531                                          * This is needed for the rare case
2532                                          * where GCC does something dumb like:
2533                                          *
2534                                          *   lea    0x8(%rsp), %rcx
2535                                          *   ...
2536                                          *   mov    %rcx, %rsp
2537                                          */
2538                                         cfa->offset = -cfi->vals[op->src.reg].offset;
2539                                         cfi->stack_size = cfa->offset;
2540
2541                                 } else if (cfa->base == CFI_SP &&
2542                                            cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2543                                            cfi->vals[op->src.reg].offset == cfa->offset) {
2544
2545                                         /*
2546                                          * Stack swizzle:
2547                                          *
2548                                          * 1: mov %rsp, (%[tos])
2549                                          * 2: mov %[tos], %rsp
2550                                          *    ...
2551                                          * 3: pop %rsp
2552                                          *
2553                                          * Where:
2554                                          *
2555                                          * 1 - places a pointer to the previous
2556                                          *     stack at the Top-of-Stack of the
2557                                          *     new stack.
2558                                          *
2559                                          * 2 - switches to the new stack.
2560                                          *
2561                                          * 3 - pops the Top-of-Stack to restore
2562                                          *     the original stack.
2563                                          *
2564                                          * Note: we set base to SP_INDIRECT
2565                                          * here and preserve offset. Therefore
2566                                          * when the unwinder reaches ToS it
2567                                          * will dereference SP and then add the
2568                                          * offset to find the next frame, IOW:
2569                                          * (%rsp) + offset.
2570                                          */
2571                                         cfa->base = CFI_SP_INDIRECT;
2572
2573                                 } else {
2574                                         cfa->base = CFI_UNDEFINED;
2575                                         cfa->offset = 0;
2576                                 }
2577                         }
2578
2579                         else if (op->dest.reg == CFI_SP &&
2580                                  cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2581                                  cfi->vals[op->src.reg].offset == cfa->offset) {
2582
2583                                 /*
2584                                  * The same stack swizzle case 2) as above. But
2585                                  * because we can't change cfa->base, case 3)
2586                                  * will become a regular POP. Pretend we're a
2587                                  * PUSH so things don't go unbalanced.
2588                                  */
2589                                 cfi->stack_size += 8;
2590                         }
2591
2592
2593                         break;
2594
2595                 case OP_SRC_ADD:
2596                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2597
2598                                 /* add imm, %rsp */
2599                                 cfi->stack_size -= op->src.offset;
2600                                 if (cfa->base == CFI_SP)
2601                                         cfa->offset -= op->src.offset;
2602                                 break;
2603                         }
2604
2605                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2606
2607                                 /* lea disp(%rbp), %rsp */
2608                                 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2609                                 break;
2610                         }
2611
2612                         if (!cfi->drap && op->src.reg == CFI_SP &&
2613                             op->dest.reg == CFI_BP && cfa->base == CFI_SP &&
2614                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset + op->src.offset)) {
2615
2616                                 /* lea disp(%rsp), %rbp */
2617                                 cfa->base = CFI_BP;
2618                                 cfa->offset -= op->src.offset;
2619                                 cfi->bp_scratch = false;
2620                                 break;
2621                         }
2622
2623                         if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2624
2625                                 /* drap: lea disp(%rsp), %drap */
2626                                 cfi->drap_reg = op->dest.reg;
2627
2628                                 /*
2629                                  * lea disp(%rsp), %reg
2630                                  *
2631                                  * This is needed for the rare case where GCC
2632                                  * does something dumb like:
2633                                  *
2634                                  *   lea    0x8(%rsp), %rcx
2635                                  *   ...
2636                                  *   mov    %rcx, %rsp
2637                                  */
2638                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2639                                 cfi->vals[op->dest.reg].offset = \
2640                                         -cfi->stack_size + op->src.offset;
2641
2642                                 break;
2643                         }
2644
2645                         if (cfi->drap && op->dest.reg == CFI_SP &&
2646                             op->src.reg == cfi->drap_reg) {
2647
2648                                  /* drap: lea disp(%drap), %rsp */
2649                                 cfa->base = CFI_SP;
2650                                 cfa->offset = cfi->stack_size = -op->src.offset;
2651                                 cfi->drap_reg = CFI_UNDEFINED;
2652                                 cfi->drap = false;
2653                                 break;
2654                         }
2655
2656                         if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
2657                                 WARN_FUNC("unsupported stack register modification",
2658                                           insn->sec, insn->offset);
2659                                 return -1;
2660                         }
2661
2662                         break;
2663
2664                 case OP_SRC_AND:
2665                         if (op->dest.reg != CFI_SP ||
2666                             (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
2667                             (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
2668                                 WARN_FUNC("unsupported stack pointer realignment",
2669                                           insn->sec, insn->offset);
2670                                 return -1;
2671                         }
2672
2673                         if (cfi->drap_reg != CFI_UNDEFINED) {
2674                                 /* drap: and imm, %rsp */
2675                                 cfa->base = cfi->drap_reg;
2676                                 cfa->offset = cfi->stack_size = 0;
2677                                 cfi->drap = true;
2678                         }
2679
2680                         /*
2681                          * Older versions of GCC (4.8ish) realign the stack
2682                          * without DRAP, with a frame pointer.
2683                          */
2684
2685                         break;
2686
2687                 case OP_SRC_POP:
2688                 case OP_SRC_POPF:
2689                         if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
2690
2691                                 /* pop %rsp; # restore from a stack swizzle */
2692                                 cfa->base = CFI_SP;
2693                                 break;
2694                         }
2695
2696                         if (!cfi->drap && op->dest.reg == cfa->base) {
2697
2698                                 /* pop %rbp */
2699                                 cfa->base = CFI_SP;
2700                         }
2701
2702                         if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
2703                             op->dest.reg == cfi->drap_reg &&
2704                             cfi->drap_offset == -cfi->stack_size) {
2705
2706                                 /* drap: pop %drap */
2707                                 cfa->base = cfi->drap_reg;
2708                                 cfa->offset = 0;
2709                                 cfi->drap_offset = -1;
2710
2711                         } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
2712
2713                                 /* pop %reg */
2714                                 restore_reg(cfi, op->dest.reg);
2715                         }
2716
2717                         cfi->stack_size -= 8;
2718                         if (cfa->base == CFI_SP)
2719                                 cfa->offset -= 8;
2720
2721                         break;
2722
2723                 case OP_SRC_REG_INDIRECT:
2724                         if (!cfi->drap && op->dest.reg == cfa->base &&
2725                             op->dest.reg == CFI_BP) {
2726
2727                                 /* mov disp(%rsp), %rbp */
2728                                 cfa->base = CFI_SP;
2729                                 cfa->offset = cfi->stack_size;
2730                         }
2731
2732                         if (cfi->drap && op->src.reg == CFI_BP &&
2733                             op->src.offset == cfi->drap_offset) {
2734
2735                                 /* drap: mov disp(%rbp), %drap */
2736                                 cfa->base = cfi->drap_reg;
2737                                 cfa->offset = 0;
2738                                 cfi->drap_offset = -1;
2739                         }
2740
2741                         if (cfi->drap && op->src.reg == CFI_BP &&
2742                             op->src.offset == regs[op->dest.reg].offset) {
2743
2744                                 /* drap: mov disp(%rbp), %reg */
2745                                 restore_reg(cfi, op->dest.reg);
2746
2747                         } else if (op->src.reg == cfa->base &&
2748                             op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
2749
2750                                 /* mov disp(%rbp), %reg */
2751                                 /* mov disp(%rsp), %reg */
2752                                 restore_reg(cfi, op->dest.reg);
2753
2754                         } else if (op->src.reg == CFI_SP &&
2755                                    op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
2756
2757                                 /* mov disp(%rsp), %reg */
2758                                 restore_reg(cfi, op->dest.reg);
2759                         }
2760
2761                         break;
2762
2763                 default:
2764                         WARN_FUNC("unknown stack-related instruction",
2765                                   insn->sec, insn->offset);
2766                         return -1;
2767                 }
2768
2769                 break;
2770
2771         case OP_DEST_PUSH:
2772         case OP_DEST_PUSHF:
2773                 cfi->stack_size += 8;
2774                 if (cfa->base == CFI_SP)
2775                         cfa->offset += 8;
2776
2777                 if (op->src.type != OP_SRC_REG)
2778                         break;
2779
2780                 if (cfi->drap) {
2781                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2782
2783                                 /* drap: push %drap */
2784                                 cfa->base = CFI_BP_INDIRECT;
2785                                 cfa->offset = -cfi->stack_size;
2786
2787                                 /* save drap so we know when to restore it */
2788                                 cfi->drap_offset = -cfi->stack_size;
2789
2790                         } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
2791
2792                                 /* drap: push %rbp */
2793                                 cfi->stack_size = 0;
2794
2795                         } else {
2796
2797                                 /* drap: push %reg */
2798                                 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
2799                         }
2800
2801                 } else {
2802
2803                         /* push %reg */
2804                         save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
2805                 }
2806
2807                 /* detect when asm code uses rbp as a scratch register */
2808                 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
2809                     cfa->base != CFI_BP)
2810                         cfi->bp_scratch = true;
2811                 break;
2812
2813         case OP_DEST_REG_INDIRECT:
2814
2815                 if (cfi->drap) {
2816                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2817
2818                                 /* drap: mov %drap, disp(%rbp) */
2819                                 cfa->base = CFI_BP_INDIRECT;
2820                                 cfa->offset = op->dest.offset;
2821
2822                                 /* save drap offset so we know when to restore it */
2823                                 cfi->drap_offset = op->dest.offset;
2824                         } else {
2825
2826                                 /* drap: mov reg, disp(%rbp) */
2827                                 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
2828                         }
2829
2830                 } else if (op->dest.reg == cfa->base) {
2831
2832                         /* mov reg, disp(%rbp) */
2833                         /* mov reg, disp(%rsp) */
2834                         save_reg(cfi, op->src.reg, CFI_CFA,
2835                                  op->dest.offset - cfi->cfa.offset);
2836
2837                 } else if (op->dest.reg == CFI_SP) {
2838
2839                         /* mov reg, disp(%rsp) */
2840                         save_reg(cfi, op->src.reg, CFI_CFA,
2841                                  op->dest.offset - cfi->stack_size);
2842
2843                 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
2844
2845                         /* mov %rsp, (%reg); # setup a stack swizzle. */
2846                         cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
2847                         cfi->vals[op->dest.reg].offset = cfa->offset;
2848                 }
2849
2850                 break;
2851
2852         case OP_DEST_MEM:
2853                 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
2854                         WARN_FUNC("unknown stack-related memory operation",
2855                                   insn->sec, insn->offset);
2856                         return -1;
2857                 }
2858
2859                 /* pop mem */
2860                 cfi->stack_size -= 8;
2861                 if (cfa->base == CFI_SP)
2862                         cfa->offset -= 8;
2863
2864                 break;
2865
2866         default:
2867                 WARN_FUNC("unknown stack-related instruction",
2868                           insn->sec, insn->offset);
2869                 return -1;
2870         }
2871
2872         return 0;
2873 }
2874
2875 /*
2876  * The stack layouts of alternatives instructions can sometimes diverge when
2877  * they have stack modifications.  That's fine as long as the potential stack
2878  * layouts don't conflict at any given potential instruction boundary.
2879  *
2880  * Flatten the CFIs of the different alternative code streams (both original
2881  * and replacement) into a single shared CFI array which can be used to detect
2882  * conflicts and nicely feed a linear array of ORC entries to the unwinder.
2883  */
2884 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
2885 {
2886         struct cfi_state **alt_cfi;
2887         int group_off;
2888
2889         if (!insn->alt_group)
2890                 return 0;
2891
2892         if (!insn->cfi) {
2893                 WARN("CFI missing");
2894                 return -1;
2895         }
2896
2897         alt_cfi = insn->alt_group->cfi;
2898         group_off = insn->offset - insn->alt_group->first_insn->offset;
2899
2900         if (!alt_cfi[group_off]) {
2901                 alt_cfi[group_off] = insn->cfi;
2902         } else {
2903                 if (cficmp(alt_cfi[group_off], insn->cfi)) {
2904                         WARN_FUNC("stack layout conflict in alternatives",
2905                                   insn->sec, insn->offset);
2906                         return -1;
2907                 }
2908         }
2909
2910         return 0;
2911 }
2912
2913 static int handle_insn_ops(struct instruction *insn,
2914                            struct instruction *next_insn,
2915                            struct insn_state *state)
2916 {
2917         struct stack_op *op;
2918
2919         list_for_each_entry(op, &insn->stack_ops, list) {
2920
2921                 if (update_cfi_state(insn, next_insn, &state->cfi, op))
2922                         return 1;
2923
2924                 if (!insn->alt_group)
2925                         continue;
2926
2927                 if (op->dest.type == OP_DEST_PUSHF) {
2928                         if (!state->uaccess_stack) {
2929                                 state->uaccess_stack = 1;
2930                         } else if (state->uaccess_stack >> 31) {
2931                                 WARN_FUNC("PUSHF stack exhausted",
2932                                           insn->sec, insn->offset);
2933                                 return 1;
2934                         }
2935                         state->uaccess_stack <<= 1;
2936                         state->uaccess_stack  |= state->uaccess;
2937                 }
2938
2939                 if (op->src.type == OP_SRC_POPF) {
2940                         if (state->uaccess_stack) {
2941                                 state->uaccess = state->uaccess_stack & 1;
2942                                 state->uaccess_stack >>= 1;
2943                                 if (state->uaccess_stack == 1)
2944                                         state->uaccess_stack = 0;
2945                         }
2946                 }
2947         }
2948
2949         return 0;
2950 }
2951
2952 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
2953 {
2954         struct cfi_state *cfi1 = insn->cfi;
2955         int i;
2956
2957         if (!cfi1) {
2958                 WARN("CFI missing");
2959                 return false;
2960         }
2961
2962         if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
2963
2964                 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
2965                           insn->sec, insn->offset,
2966                           cfi1->cfa.base, cfi1->cfa.offset,
2967                           cfi2->cfa.base, cfi2->cfa.offset);
2968
2969         } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
2970                 for (i = 0; i < CFI_NUM_REGS; i++) {
2971                         if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
2972                                     sizeof(struct cfi_reg)))
2973                                 continue;
2974
2975                         WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
2976                                   insn->sec, insn->offset,
2977                                   i, cfi1->regs[i].base, cfi1->regs[i].offset,
2978                                   i, cfi2->regs[i].base, cfi2->regs[i].offset);
2979                         break;
2980                 }
2981
2982         } else if (cfi1->type != cfi2->type) {
2983
2984                 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
2985                           insn->sec, insn->offset, cfi1->type, cfi2->type);
2986
2987         } else if (cfi1->drap != cfi2->drap ||
2988                    (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
2989                    (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
2990
2991                 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
2992                           insn->sec, insn->offset,
2993                           cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
2994                           cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
2995
2996         } else
2997                 return true;
2998
2999         return false;
3000 }
3001
3002 static inline bool func_uaccess_safe(struct symbol *func)
3003 {
3004         if (func)
3005                 return func->uaccess_safe;
3006
3007         return false;
3008 }
3009
3010 static inline const char *call_dest_name(struct instruction *insn)
3011 {
3012         static char pvname[19];
3013         struct reloc *rel;
3014         int idx;
3015
3016         if (insn->call_dest)
3017                 return insn->call_dest->name;
3018
3019         rel = insn_reloc(NULL, insn);
3020         if (rel && !strcmp(rel->sym->name, "pv_ops")) {
3021                 idx = (rel->addend / sizeof(void *));
3022                 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
3023                 return pvname;
3024         }
3025
3026         return "{dynamic}";
3027 }
3028
3029 static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3030 {
3031         struct symbol *target;
3032         struct reloc *rel;
3033         int idx;
3034
3035         rel = insn_reloc(file, insn);
3036         if (!rel || strcmp(rel->sym->name, "pv_ops"))
3037                 return false;
3038
3039         idx = (arch_dest_reloc_offset(rel->addend) / sizeof(void *));
3040
3041         if (file->pv_ops[idx].clean)
3042                 return true;
3043
3044         file->pv_ops[idx].clean = true;
3045
3046         list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3047                 if (!target->sec->noinstr) {
3048                         WARN("pv_ops[%d]: %s", idx, target->name);
3049                         file->pv_ops[idx].clean = false;
3050                 }
3051         }
3052
3053         return file->pv_ops[idx].clean;
3054 }
3055
3056 static inline bool noinstr_call_dest(struct objtool_file *file,
3057                                      struct instruction *insn,
3058                                      struct symbol *func)
3059 {
3060         /*
3061          * We can't deal with indirect function calls at present;
3062          * assume they're instrumented.
3063          */
3064         if (!func) {
3065                 if (file->pv_ops)
3066                         return pv_call_dest(file, insn);
3067
3068                 return false;
3069         }
3070
3071         /*
3072          * If the symbol is from a noinstr section; we good.
3073          */
3074         if (func->sec->noinstr)
3075                 return true;
3076
3077         /*
3078          * The __ubsan_handle_*() calls are like WARN(), they only happen when
3079          * something 'BAD' happened. At the risk of taking the machine down,
3080          * let them proceed to get the message out.
3081          */
3082         if (!strncmp(func->name, "__ubsan_handle_", 15))
3083                 return true;
3084
3085         return false;
3086 }
3087
3088 static int validate_call(struct objtool_file *file,
3089                          struct instruction *insn,
3090                          struct insn_state *state)
3091 {
3092         if (state->noinstr && state->instr <= 0 &&
3093             !noinstr_call_dest(file, insn, insn->call_dest)) {
3094                 WARN_FUNC("call to %s() leaves .noinstr.text section",
3095                                 insn->sec, insn->offset, call_dest_name(insn));
3096                 return 1;
3097         }
3098
3099         if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
3100                 WARN_FUNC("call to %s() with UACCESS enabled",
3101                                 insn->sec, insn->offset, call_dest_name(insn));
3102                 return 1;
3103         }
3104
3105         if (state->df) {
3106                 WARN_FUNC("call to %s() with DF set",
3107                                 insn->sec, insn->offset, call_dest_name(insn));
3108                 return 1;
3109         }
3110
3111         return 0;
3112 }
3113
3114 static int validate_sibling_call(struct objtool_file *file,
3115                                  struct instruction *insn,
3116                                  struct insn_state *state)
3117 {
3118         if (has_modified_stack_frame(insn, state)) {
3119                 WARN_FUNC("sibling call from callable instruction with modified stack frame",
3120                                 insn->sec, insn->offset);
3121                 return 1;
3122         }
3123
3124         return validate_call(file, insn, state);
3125 }
3126
3127 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3128 {
3129         if (state->noinstr && state->instr > 0) {
3130                 WARN_FUNC("return with instrumentation enabled",
3131                           insn->sec, insn->offset);
3132                 return 1;
3133         }
3134
3135         if (state->uaccess && !func_uaccess_safe(func)) {
3136                 WARN_FUNC("return with UACCESS enabled",
3137                           insn->sec, insn->offset);
3138                 return 1;
3139         }
3140
3141         if (!state->uaccess && func_uaccess_safe(func)) {
3142                 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
3143                           insn->sec, insn->offset);
3144                 return 1;
3145         }
3146
3147         if (state->df) {
3148                 WARN_FUNC("return with DF set",
3149                           insn->sec, insn->offset);
3150                 return 1;
3151         }
3152
3153         if (func && has_modified_stack_frame(insn, state)) {
3154                 WARN_FUNC("return with modified stack frame",
3155                           insn->sec, insn->offset);
3156                 return 1;
3157         }
3158
3159         if (state->cfi.bp_scratch) {
3160                 WARN_FUNC("BP used as a scratch register",
3161                           insn->sec, insn->offset);
3162                 return 1;
3163         }
3164
3165         return 0;
3166 }
3167
3168 static struct instruction *next_insn_to_validate(struct objtool_file *file,
3169                                                  struct instruction *insn)
3170 {
3171         struct alt_group *alt_group = insn->alt_group;
3172
3173         /*
3174          * Simulate the fact that alternatives are patched in-place.  When the
3175          * end of a replacement alt_group is reached, redirect objtool flow to
3176          * the end of the original alt_group.
3177          */
3178         if (alt_group && insn == alt_group->last_insn && alt_group->orig_group)
3179                 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3180
3181         return next_insn_same_sec(file, insn);
3182 }
3183
3184 static struct instruction *
3185 validate_ibt_reloc(struct objtool_file *file, struct reloc *reloc)
3186 {
3187         struct instruction *dest;
3188         struct section *sec;
3189         unsigned long off;
3190
3191         sec = reloc->sym->sec;
3192         off = reloc->sym->offset;
3193
3194         if ((reloc->sec->base->sh.sh_flags & SHF_EXECINSTR) &&
3195             (reloc->type == R_X86_64_PC32 || reloc->type == R_X86_64_PLT32))
3196                 off += arch_dest_reloc_offset(reloc->addend);
3197         else
3198                 off += reloc->addend;
3199
3200         dest = find_insn(file, sec, off);
3201         if (!dest)
3202                 return NULL;
3203
3204         if (dest->type == INSN_ENDBR) {
3205                 if (!list_empty(&dest->call_node))
3206                         list_del_init(&dest->call_node);
3207
3208                 return NULL;
3209         }
3210
3211         if (reloc->sym->static_call_tramp)
3212                 return NULL;
3213
3214         return dest;
3215 }
3216
3217 static void warn_noendbr(const char *msg, struct section *sec, unsigned long offset,
3218                          struct instruction *dest)
3219 {
3220         WARN_FUNC("%srelocation to !ENDBR: %s+0x%lx", sec, offset, msg,
3221                   dest->func ? dest->func->name : dest->sec->name,
3222                   dest->func ? dest->offset - dest->func->offset : dest->offset);
3223 }
3224
3225 static void validate_ibt_dest(struct objtool_file *file, struct instruction *insn,
3226                               struct instruction *dest)
3227 {
3228         if (dest->func && dest->func == insn->func) {
3229                 /*
3230                  * Anything from->to self is either _THIS_IP_ or IRET-to-self.
3231                  *
3232                  * There is no sane way to annotate _THIS_IP_ since the compiler treats the
3233                  * relocation as a constant and is happy to fold in offsets, skewing any
3234                  * annotation we do, leading to vast amounts of false-positives.
3235                  *
3236                  * There's also compiler generated _THIS_IP_ through KCOV and
3237                  * such which we have no hope of annotating.
3238                  *
3239                  * As such, blanket accept self-references without issue.
3240                  */
3241                 return;
3242         }
3243
3244         if (dest->noendbr)
3245                 return;
3246
3247         warn_noendbr("", insn->sec, insn->offset, dest);
3248 }
3249
3250 static void validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
3251 {
3252         struct instruction *dest;
3253         struct reloc *reloc;
3254
3255         switch (insn->type) {
3256         case INSN_CALL:
3257         case INSN_CALL_DYNAMIC:
3258         case INSN_JUMP_CONDITIONAL:
3259         case INSN_JUMP_UNCONDITIONAL:
3260         case INSN_JUMP_DYNAMIC:
3261         case INSN_JUMP_DYNAMIC_CONDITIONAL:
3262         case INSN_RETURN:
3263                 /*
3264                  * We're looking for code references setting up indirect code
3265                  * flow. As such, ignore direct code flow and the actual
3266                  * dynamic branches.
3267                  */
3268                 return;
3269
3270         case INSN_NOP:
3271                 /*
3272                  * handle_group_alt() will create INSN_NOP instruction that
3273                  * don't belong to any section, ignore all NOP since they won't
3274                  * carry a (useful) relocation anyway.
3275                  */
3276                 return;
3277
3278         default:
3279                 break;
3280         }
3281
3282         for (reloc = insn_reloc(file, insn);
3283              reloc;
3284              reloc = find_reloc_by_dest_range(file->elf, insn->sec,
3285                                               reloc->offset + 1,
3286                                               (insn->offset + insn->len) - (reloc->offset + 1))) {
3287                 dest = validate_ibt_reloc(file, reloc);
3288                 if (dest)
3289                         validate_ibt_dest(file, insn, dest);
3290         }
3291 }
3292
3293 /*
3294  * Follow the branch starting at the given instruction, and recursively follow
3295  * any other branches (jumps).  Meanwhile, track the frame pointer state at
3296  * each instruction and validate all the rules described in
3297  * tools/objtool/Documentation/stack-validation.txt.
3298  */
3299 static int validate_branch(struct objtool_file *file, struct symbol *func,
3300                            struct instruction *insn, struct insn_state state)
3301 {
3302         struct alternative *alt;
3303         struct instruction *next_insn, *prev_insn = NULL;
3304         struct section *sec;
3305         u8 visited;
3306         int ret;
3307
3308         sec = insn->sec;
3309
3310         while (1) {
3311                 next_insn = next_insn_to_validate(file, insn);
3312
3313                 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
3314                         WARN("%s() falls through to next function %s()",
3315                              func->name, insn->func->name);
3316                         return 1;
3317                 }
3318
3319                 if (func && insn->ignore) {
3320                         WARN_FUNC("BUG: why am I validating an ignored function?",
3321                                   sec, insn->offset);
3322                         return 1;
3323                 }
3324
3325                 visited = 1 << state.uaccess;
3326                 if (insn->visited) {
3327                         if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3328                                 return 1;
3329
3330                         if (insn->visited & visited)
3331                                 return 0;
3332                 } else {
3333                         nr_insns_visited++;
3334                 }
3335
3336                 if (state.noinstr)
3337                         state.instr += insn->instr;
3338
3339                 if (insn->hint) {
3340                         state.cfi = *insn->cfi;
3341                 } else {
3342                         /* XXX track if we actually changed state.cfi */
3343
3344                         if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3345                                 insn->cfi = prev_insn->cfi;
3346                                 nr_cfi_reused++;
3347                         } else {
3348                                 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3349                         }
3350                 }
3351
3352                 insn->visited |= visited;
3353
3354                 if (propagate_alt_cfi(file, insn))
3355                         return 1;
3356
3357                 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
3358                         bool skip_orig = false;
3359
3360                         list_for_each_entry(alt, &insn->alts, list) {
3361                                 if (alt->skip_orig)
3362                                         skip_orig = true;
3363
3364                                 ret = validate_branch(file, func, alt->insn, state);
3365                                 if (ret) {
3366                                         if (backtrace)
3367                                                 BT_FUNC("(alt)", insn);
3368                                         return ret;
3369                                 }
3370                         }
3371
3372                         if (skip_orig)
3373                                 return 0;
3374                 }
3375
3376                 if (handle_insn_ops(insn, next_insn, &state))
3377                         return 1;
3378
3379                 switch (insn->type) {
3380
3381                 case INSN_RETURN:
3382                         if (sls && !insn->retpoline_safe &&
3383                             next_insn && next_insn->type != INSN_TRAP) {
3384                                 WARN_FUNC("missing int3 after ret",
3385                                           insn->sec, insn->offset);
3386                         }
3387                         return validate_return(func, insn, &state);
3388
3389                 case INSN_CALL:
3390                 case INSN_CALL_DYNAMIC:
3391                         ret = validate_call(file, insn, &state);
3392                         if (ret)
3393                                 return ret;
3394
3395                         if (!no_fp && func && !is_fentry_call(insn) &&
3396                             !has_valid_stack_frame(&state)) {
3397                                 WARN_FUNC("call without frame pointer save/setup",
3398                                           sec, insn->offset);
3399                                 return 1;
3400                         }
3401
3402                         if (insn->dead_end)
3403                                 return 0;
3404
3405                         break;
3406
3407                 case INSN_JUMP_CONDITIONAL:
3408                 case INSN_JUMP_UNCONDITIONAL:
3409                         if (is_sibling_call(insn)) {
3410                                 ret = validate_sibling_call(file, insn, &state);
3411                                 if (ret)
3412                                         return ret;
3413
3414                         } else if (insn->jump_dest) {
3415                                 ret = validate_branch(file, func,
3416                                                       insn->jump_dest, state);
3417                                 if (ret) {
3418                                         if (backtrace)
3419                                                 BT_FUNC("(branch)", insn);
3420                                         return ret;
3421                                 }
3422                         }
3423
3424                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
3425                                 return 0;
3426
3427                         break;
3428
3429                 case INSN_JUMP_DYNAMIC:
3430                         if (sls && !insn->retpoline_safe &&
3431                             next_insn && next_insn->type != INSN_TRAP) {
3432                                 WARN_FUNC("missing int3 after indirect jump",
3433                                           insn->sec, insn->offset);
3434                         }
3435
3436                         /* fallthrough */
3437                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3438                         if (is_sibling_call(insn)) {
3439                                 ret = validate_sibling_call(file, insn, &state);
3440                                 if (ret)
3441                                         return ret;
3442                         }
3443
3444                         if (insn->type == INSN_JUMP_DYNAMIC)
3445                                 return 0;
3446
3447                         break;
3448
3449                 case INSN_CONTEXT_SWITCH:
3450                         if (func && (!next_insn || !next_insn->hint)) {
3451                                 WARN_FUNC("unsupported instruction in callable function",
3452                                           sec, insn->offset);
3453                                 return 1;
3454                         }
3455                         return 0;
3456
3457                 case INSN_STAC:
3458                         if (state.uaccess) {
3459                                 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
3460                                 return 1;
3461                         }
3462
3463                         state.uaccess = true;
3464                         break;
3465
3466                 case INSN_CLAC:
3467                         if (!state.uaccess && func) {
3468                                 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
3469                                 return 1;
3470                         }
3471
3472                         if (func_uaccess_safe(func) && !state.uaccess_stack) {
3473                                 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
3474                                 return 1;
3475                         }
3476
3477                         state.uaccess = false;
3478                         break;
3479
3480                 case INSN_STD:
3481                         if (state.df) {
3482                                 WARN_FUNC("recursive STD", sec, insn->offset);
3483                                 return 1;
3484                         }
3485
3486                         state.df = true;
3487                         break;
3488
3489                 case INSN_CLD:
3490                         if (!state.df && func) {
3491                                 WARN_FUNC("redundant CLD", sec, insn->offset);
3492                                 return 1;
3493                         }
3494
3495                         state.df = false;
3496                         break;
3497
3498                 default:
3499                         break;
3500                 }
3501
3502                 if (ibt)
3503                         validate_ibt_insn(file, insn);
3504
3505                 if (insn->dead_end)
3506                         return 0;
3507
3508                 if (!next_insn) {
3509                         if (state.cfi.cfa.base == CFI_UNDEFINED)
3510                                 return 0;
3511                         WARN("%s: unexpected end of section", sec->name);
3512                         return 1;
3513                 }
3514
3515                 prev_insn = insn;
3516                 insn = next_insn;
3517         }
3518
3519         return 0;
3520 }
3521
3522 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3523 {
3524         struct instruction *insn;
3525         struct insn_state state;
3526         int ret, warnings = 0;
3527
3528         if (!file->hints)
3529                 return 0;
3530
3531         init_insn_state(&state, sec);
3532
3533         if (sec) {
3534                 insn = find_insn(file, sec, 0);
3535                 if (!insn)
3536                         return 0;
3537         } else {
3538                 insn = list_first_entry(&file->insn_list, typeof(*insn), list);
3539         }
3540
3541         while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) {
3542                 if (insn->hint && !insn->visited && !insn->ignore) {
3543                         ret = validate_branch(file, insn->func, insn, state);
3544                         if (ret && backtrace)
3545                                 BT_FUNC("<=== (hint)", insn);
3546                         warnings += ret;
3547                 }
3548
3549                 insn = list_next_entry(insn, list);
3550         }
3551
3552         return warnings;
3553 }
3554
3555 static int validate_retpoline(struct objtool_file *file)
3556 {
3557         struct instruction *insn;
3558         int warnings = 0;
3559
3560         for_each_insn(file, insn) {
3561                 if (insn->type != INSN_JUMP_DYNAMIC &&
3562                     insn->type != INSN_CALL_DYNAMIC)
3563                         continue;
3564
3565                 if (insn->retpoline_safe)
3566                         continue;
3567
3568                 /*
3569                  * .init.text code is ran before userspace and thus doesn't
3570                  * strictly need retpolines, except for modules which are
3571                  * loaded late, they very much do need retpoline in their
3572                  * .init.text
3573                  */
3574                 if (!strcmp(insn->sec->name, ".init.text") && !module)
3575                         continue;
3576
3577                 WARN_FUNC("indirect %s found in RETPOLINE build",
3578                           insn->sec, insn->offset,
3579                           insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
3580
3581                 warnings++;
3582         }
3583
3584         return warnings;
3585 }
3586
3587 static bool is_kasan_insn(struct instruction *insn)
3588 {
3589         return (insn->type == INSN_CALL &&
3590                 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
3591 }
3592
3593 static bool is_ubsan_insn(struct instruction *insn)
3594 {
3595         return (insn->type == INSN_CALL &&
3596                 !strcmp(insn->call_dest->name,
3597                         "__ubsan_handle_builtin_unreachable"));
3598 }
3599
3600 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
3601 {
3602         int i;
3603         struct instruction *prev_insn;
3604
3605         if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
3606                 return true;
3607
3608         /*
3609          * Ignore alternative replacement instructions.  This can happen
3610          * when a whitelisted function uses one of the ALTERNATIVE macros.
3611          */
3612         if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
3613             !strcmp(insn->sec->name, ".altinstr_aux"))
3614                 return true;
3615
3616         /*
3617          * Whole archive runs might encounder dead code from weak symbols.
3618          * This is where the linker will have dropped the weak symbol in
3619          * favour of a regular symbol, but leaves the code in place.
3620          *
3621          * In this case we'll find a piece of code (whole function) that is not
3622          * covered by a !section symbol. Ignore them.
3623          */
3624         if (!insn->func && lto) {
3625                 int size = find_symbol_hole_containing(insn->sec, insn->offset);
3626                 unsigned long end = insn->offset + size;
3627
3628                 if (!size) /* not a hole */
3629                         return false;
3630
3631                 if (size < 0) /* hole until the end */
3632                         return true;
3633
3634                 sec_for_each_insn_continue(file, insn) {
3635                         /*
3636                          * If we reach a visited instruction at or before the
3637                          * end of the hole, ignore the unreachable.
3638                          */
3639                         if (insn->visited)
3640                                 return true;
3641
3642                         if (insn->offset >= end)
3643                                 break;
3644
3645                         /*
3646                          * If this hole jumps to a .cold function, mark it ignore too.
3647                          */
3648                         if (insn->jump_dest && insn->jump_dest->func &&
3649                             strstr(insn->jump_dest->func->name, ".cold")) {
3650                                 struct instruction *dest = insn->jump_dest;
3651                                 func_for_each_insn(file, dest->func, dest)
3652                                         dest->ignore = true;
3653                         }
3654                 }
3655
3656                 return false;
3657         }
3658
3659         if (!insn->func)
3660                 return false;
3661
3662         if (insn->func->static_call_tramp)
3663                 return true;
3664
3665         /*
3666          * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
3667          * __builtin_unreachable().  The BUG() macro has an unreachable() after
3668          * the UD2, which causes GCC's undefined trap logic to emit another UD2
3669          * (or occasionally a JMP to UD2).
3670          *
3671          * It may also insert a UD2 after calling a __noreturn function.
3672          */
3673         prev_insn = list_prev_entry(insn, list);
3674         if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) &&
3675             (insn->type == INSN_BUG ||
3676              (insn->type == INSN_JUMP_UNCONDITIONAL &&
3677               insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
3678                 return true;
3679
3680         /*
3681          * Check if this (or a subsequent) instruction is related to
3682          * CONFIG_UBSAN or CONFIG_KASAN.
3683          *
3684          * End the search at 5 instructions to avoid going into the weeds.
3685          */
3686         for (i = 0; i < 5; i++) {
3687
3688                 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
3689                         return true;
3690
3691                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
3692                         if (insn->jump_dest &&
3693                             insn->jump_dest->func == insn->func) {
3694                                 insn = insn->jump_dest;
3695                                 continue;
3696                         }
3697
3698                         break;
3699                 }
3700
3701                 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
3702                         break;
3703
3704                 insn = list_next_entry(insn, list);
3705         }
3706
3707         return false;
3708 }
3709
3710 static int validate_symbol(struct objtool_file *file, struct section *sec,
3711                            struct symbol *sym, struct insn_state *state)
3712 {
3713         struct instruction *insn;
3714         int ret;
3715
3716         if (!sym->len) {
3717                 WARN("%s() is missing an ELF size annotation", sym->name);
3718                 return 1;
3719         }
3720
3721         if (sym->pfunc != sym || sym->alias != sym)
3722                 return 0;
3723
3724         insn = find_insn(file, sec, sym->offset);
3725         if (!insn || insn->ignore || insn->visited)
3726                 return 0;
3727
3728         state->uaccess = sym->uaccess_safe;
3729
3730         ret = validate_branch(file, insn->func, insn, *state);
3731         if (ret && backtrace)
3732                 BT_FUNC("<=== (sym)", insn);
3733         return ret;
3734 }
3735
3736 static int validate_section(struct objtool_file *file, struct section *sec)
3737 {
3738         struct insn_state state;
3739         struct symbol *func;
3740         int warnings = 0;
3741
3742         list_for_each_entry(func, &sec->symbol_list, list) {
3743                 if (func->type != STT_FUNC)
3744                         continue;
3745
3746                 init_insn_state(&state, sec);
3747                 set_func_state(&state.cfi);
3748
3749                 warnings += validate_symbol(file, sec, func, &state);
3750         }
3751
3752         return warnings;
3753 }
3754
3755 static int validate_vmlinux_functions(struct objtool_file *file)
3756 {
3757         struct section *sec;
3758         int warnings = 0;
3759
3760         sec = find_section_by_name(file->elf, ".noinstr.text");
3761         if (sec) {
3762                 warnings += validate_section(file, sec);
3763                 warnings += validate_unwind_hints(file, sec);
3764         }
3765
3766         sec = find_section_by_name(file->elf, ".entry.text");
3767         if (sec) {
3768                 warnings += validate_section(file, sec);
3769                 warnings += validate_unwind_hints(file, sec);
3770         }
3771
3772         return warnings;
3773 }
3774
3775 static int validate_functions(struct objtool_file *file)
3776 {
3777         struct section *sec;
3778         int warnings = 0;
3779
3780         for_each_sec(file, sec) {
3781                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
3782                         continue;
3783
3784                 warnings += validate_section(file, sec);
3785         }
3786
3787         return warnings;
3788 }
3789
3790 static int validate_ibt(struct objtool_file *file)
3791 {
3792         struct section *sec;
3793         struct reloc *reloc;
3794
3795         for_each_sec(file, sec) {
3796                 bool is_data;
3797
3798                 /* already done in validate_branch() */
3799                 if (sec->sh.sh_flags & SHF_EXECINSTR)
3800                         continue;
3801
3802                 if (!sec->reloc)
3803                         continue;
3804
3805                 if (!strncmp(sec->name, ".orc", 4))
3806                         continue;
3807
3808                 if (!strncmp(sec->name, ".discard", 8))
3809                         continue;
3810
3811                 if (!strncmp(sec->name, ".debug", 6))
3812                         continue;
3813
3814                 if (!strcmp(sec->name, "_error_injection_whitelist"))
3815                         continue;
3816
3817                 if (!strcmp(sec->name, "_kprobe_blacklist"))
3818                         continue;
3819
3820                 is_data = strstr(sec->name, ".data") || strstr(sec->name, ".rodata");
3821
3822                 list_for_each_entry(reloc, &sec->reloc->reloc_list, list) {
3823                         struct instruction *dest;
3824
3825                         dest = validate_ibt_reloc(file, reloc);
3826                         if (is_data && dest && !dest->noendbr) {
3827                                 warn_noendbr("data ", reloc->sym->sec,
3828                                              reloc->sym->offset + reloc->addend,
3829                                              dest);
3830                         }
3831                 }
3832         }
3833
3834         return 0;
3835 }
3836
3837 static int validate_reachable_instructions(struct objtool_file *file)
3838 {
3839         struct instruction *insn;
3840
3841         if (file->ignore_unreachables)
3842                 return 0;
3843
3844         for_each_insn(file, insn) {
3845                 if (insn->visited || ignore_unreachable_insn(file, insn))
3846                         continue;
3847
3848                 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
3849                 return 1;
3850         }
3851
3852         return 0;
3853 }
3854
3855 int check(struct objtool_file *file)
3856 {
3857         int ret, warnings = 0;
3858
3859         if (lto && !(vmlinux || module)) {
3860                 fprintf(stderr, "--lto requires: --vmlinux or --module\n");
3861                 return 1;
3862         }
3863
3864         if (ibt && !lto) {
3865                 fprintf(stderr, "--ibt requires: --lto\n");
3866                 return 1;
3867         }
3868
3869         arch_initial_func_cfi_state(&initial_func_cfi);
3870         init_cfi_state(&init_cfi);
3871         init_cfi_state(&func_cfi);
3872         set_func_state(&func_cfi);
3873
3874         if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
3875                 goto out;
3876
3877         cfi_hash_add(&init_cfi);
3878         cfi_hash_add(&func_cfi);
3879
3880         ret = decode_sections(file);
3881         if (ret < 0)
3882                 goto out;
3883
3884         warnings += ret;
3885
3886         if (list_empty(&file->insn_list))
3887                 goto out;
3888
3889         if (vmlinux && !lto) {
3890                 ret = validate_vmlinux_functions(file);
3891                 if (ret < 0)
3892                         goto out;
3893
3894                 warnings += ret;
3895                 goto out;
3896         }
3897
3898         if (retpoline) {
3899                 ret = validate_retpoline(file);
3900                 if (ret < 0)
3901                         return ret;
3902                 warnings += ret;
3903         }
3904
3905         ret = validate_functions(file);
3906         if (ret < 0)
3907                 goto out;
3908         warnings += ret;
3909
3910         ret = validate_unwind_hints(file, NULL);
3911         if (ret < 0)
3912                 goto out;
3913         warnings += ret;
3914
3915         if (ibt) {
3916                 ret = validate_ibt(file);
3917                 if (ret < 0)
3918                         goto out;
3919                 warnings += ret;
3920         }
3921
3922         if (!warnings) {
3923                 ret = validate_reachable_instructions(file);
3924                 if (ret < 0)
3925                         goto out;
3926                 warnings += ret;
3927         }
3928
3929         ret = create_static_call_sections(file);
3930         if (ret < 0)
3931                 goto out;
3932         warnings += ret;
3933
3934         if (retpoline) {
3935                 ret = create_retpoline_sites_sections(file);
3936                 if (ret < 0)
3937                         goto out;
3938                 warnings += ret;
3939         }
3940
3941         if (mcount) {
3942                 ret = create_mcount_loc_sections(file);
3943                 if (ret < 0)
3944                         goto out;
3945                 warnings += ret;
3946         }
3947
3948         if (ibt) {
3949                 ret = create_ibt_endbr_seal_sections(file);
3950                 if (ret < 0)
3951                         goto out;
3952                 warnings += ret;
3953         }
3954
3955         if (stats) {
3956                 printf("nr_insns_visited: %ld\n", nr_insns_visited);
3957                 printf("nr_cfi: %ld\n", nr_cfi);
3958                 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
3959                 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
3960         }
3961
3962 out:
3963         /*
3964          *  For now, don't fail the kernel build on fatal warnings.  These
3965          *  errors are still fairly common due to the growing matrix of
3966          *  supported toolchains and their recent pace of change.
3967          */
3968         return 0;
3969 }