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 <inttypes.h>
   9 #include <sys/mman.h>
  10
  11 #include <arch/elf.h>
  12 #include <objtool/builtin.h>
  13 #include <objtool/cfi.h>
  14 #include <objtool/arch.h>
  15 #include <objtool/check.h>
  16 #include <objtool/special.h>
  17 #include <objtool/warn.h>
  18 #include <objtool/endianness.h>
  19
  20 #include <linux/objtool_types.h>
  21 #include <linux/hashtable.h>
  22 #include <linux/kernel.h>
  23 #include <linux/static_call_types.h>
  24
  25 struct alternative {
  26         struct alternative *next;
  27         struct instruction *insn;
  28         bool skip_orig;
  29 };
  30
  31 static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
  32
  33 static struct cfi_init_state initial_func_cfi;
  34 static struct cfi_state init_cfi;
  35 static struct cfi_state func_cfi;
  36
  37 struct instruction *find_insn(struct objtool_file *file,
  38                               struct section *sec, unsigned long offset)
  39 {
  40         struct instruction *insn;
  41
  42         hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
  43                 if (insn->sec == sec && insn->offset == offset)
  44                         return insn;
  45         }
  46
  47         return NULL;
  48 }
  49
  50 struct instruction *next_insn_same_sec(struct objtool_file *file,
  51                                        struct instruction *insn)
  52 {
  53         if (insn->idx == INSN_CHUNK_MAX)
  54                 return find_insn(file, insn->sec, insn->offset + insn->len);
  55
  56         insn++;
  57         if (!insn->len)
  58                 return NULL;
  59
  60         return insn;
  61 }
  62
  63 static struct instruction *next_insn_same_func(struct objtool_file *file,
  64                                                struct instruction *insn)
  65 {
  66         struct instruction *next = next_insn_same_sec(file, insn);
  67         struct symbol *func = insn_func(insn);
  68
  69         if (!func)
  70                 return NULL;
  71
  72         if (next && insn_func(next) == func)
  73                 return next;
  74
  75         /* Check if we're already in the subfunction: */
  76         if (func == func->cfunc)
  77                 return NULL;
  78
  79         /* Move to the subfunction: */
  80         return find_insn(file, func->cfunc->sec, func->cfunc->offset);
  81 }
  82
  83 static struct instruction *prev_insn_same_sec(struct objtool_file *file,
  84                                               struct instruction *insn)
  85 {
  86         if (insn->idx == 0) {
  87                 if (insn->prev_len)
  88                         return find_insn(file, insn->sec, insn->offset - insn->prev_len);
  89                 return NULL;
  90         }
  91
  92         return insn - 1;
  93 }
  94
  95 static struct instruction *prev_insn_same_sym(struct objtool_file *file,
  96                                               struct instruction *insn)
  97 {
  98         struct instruction *prev = prev_insn_same_sec(file, insn);
  99
 100         if (prev && insn_func(prev) == insn_func(insn))
 101                 return prev;
 102
 103         return NULL;
 104 }
 105
 106 #define for_each_insn(file, insn)                                       \
 107         for (struct section *__sec, *__fake = (struct section *)1;      \
 108              __fake; __fake = NULL)                                     \
 109                 for_each_sec(file, __sec)                               \
 110                         sec_for_each_insn(file, __sec, insn)
 111
 112 #define func_for_each_insn(file, func, insn)                            \
 113         for (insn = find_insn(file, func->sec, func->offset);           \
 114              insn;                                                      \
 115              insn = next_insn_same_func(file, insn))
 116
 117 #define sym_for_each_insn(file, sym, insn)                              \
 118         for (insn = find_insn(file, sym->sec, sym->offset);             \
 119              insn && insn->offset < sym->offset + sym->len;             \
 120              insn = next_insn_same_sec(file, insn))
 121
 122 #define sym_for_each_insn_continue_reverse(file, sym, insn)             \
 123         for (insn = prev_insn_same_sec(file, insn);                     \
 124              insn && insn->offset >= sym->offset;                       \
 125              insn = prev_insn_same_sec(file, insn))
 126
 127 #define sec_for_each_insn_from(file, insn)                              \
 128         for (; insn; insn = next_insn_same_sec(file, insn))
 129
 130 #define sec_for_each_insn_continue(file, insn)                          \
 131         for (insn = next_insn_same_sec(file, insn); insn;               \
 132              insn = next_insn_same_sec(file, insn))
 133
 134 static inline struct symbol *insn_call_dest(struct instruction *insn)
 135 {
 136         if (insn->type == INSN_JUMP_DYNAMIC ||
 137             insn->type == INSN_CALL_DYNAMIC)
 138                 return NULL;
 139
 140         return insn->_call_dest;
 141 }
 142
 143 static inline struct reloc *insn_jump_table(struct instruction *insn)
 144 {
 145         if (insn->type == INSN_JUMP_DYNAMIC ||
 146             insn->type == INSN_CALL_DYNAMIC)
 147                 return insn->_jump_table;
 148
 149         return NULL;
 150 }
 151
 152 static bool is_jump_table_jump(struct instruction *insn)
 153 {
 154         struct alt_group *alt_group = insn->alt_group;
 155
 156         if (insn_jump_table(insn))
 157                 return true;
 158
 159         /* Retpoline alternative for a jump table? */
 160         return alt_group && alt_group->orig_group &&
 161                insn_jump_table(alt_group->orig_group->first_insn);
 162 }
 163
 164 static bool is_sibling_call(struct instruction *insn)
 165 {
 166         /*
 167          * Assume only STT_FUNC calls have jump-tables.
 168          */
 169         if (insn_func(insn)) {
 170                 /* An indirect jump is either a sibling call or a jump to a table. */
 171                 if (insn->type == INSN_JUMP_DYNAMIC)
 172                         return !is_jump_table_jump(insn);
 173         }
 174
 175         /* add_jump_destinations() sets insn_call_dest(insn) for sibling calls. */
 176         return (is_static_jump(insn) && insn_call_dest(insn));
 177 }
 178
 179 /*
 180  * This checks to see if the given function is a "noreturn" function.
 181  *
 182  * For global functions which are outside the scope of this object file, we
 183  * have to keep a manual list of them.
 184  *
 185  * For local functions, we have to detect them manually by simply looking for
 186  * the lack of a return instruction.
 187  */
 188 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 189                                 int recursion)
 190 {
 191         int i;
 192         struct instruction *insn;
 193         bool empty = true;
 194
 195         /*
 196          * Unfortunately these have to be hard coded because the noreturn
 197          * attribute isn't provided in ELF data. Keep 'em sorted.
 198          */
 199         static const char * const global_noreturns[] = {
 200                 "__invalid_creds",
 201                 "__module_put_and_kthread_exit",
 202                 "__reiserfs_panic",
 203                 "__stack_chk_fail",
 204                 "__ubsan_handle_builtin_unreachable",
 205                 "arch_call_rest_init",
 206                 "arch_cpu_idle_dead",
 207                 "btrfs_assertfail",
 208                 "cpu_bringup_and_idle",
 209                 "cpu_startup_entry",
 210                 "do_exit",
 211                 "do_group_exit",
 212                 "do_task_dead",
 213                 "ex_handler_msr_mce",
 214                 "fortify_panic",
 215                 "hlt_play_dead",
 216                 "hv_ghcb_terminate",
 217                 "kthread_complete_and_exit",
 218                 "kthread_exit",
 219                 "kunit_try_catch_throw",
 220                 "lbug_with_loc",
 221                 "machine_real_restart",
 222                 "make_task_dead",
 223                 "mpt_halt_firmware",
 224                 "nmi_panic_self_stop",
 225                 "panic",
 226                 "panic_smp_self_stop",
 227                 "rest_init",
 228                 "resume_play_dead",
 229                 "rewind_stack_and_make_dead",
 230                 "sev_es_terminate",
 231                 "snp_abort",
 232                 "start_kernel",
 233                 "stop_this_cpu",
 234                 "usercopy_abort",
 235                 "x86_64_start_kernel",
 236                 "x86_64_start_reservations",
 237                 "xen_cpu_bringup_again",
 238                 "xen_start_kernel",
 239         };
 240
 241         if (!func)
 242                 return false;
 243
 244         if (func->bind == STB_GLOBAL || func->bind == STB_WEAK)
 245                 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
 246                         if (!strcmp(func->name, global_noreturns[i]))
 247                                 return true;
 248
 249         if (func->bind == STB_WEAK)
 250                 return false;
 251
 252         if (!func->len)
 253                 return false;
 254
 255         insn = find_insn(file, func->sec, func->offset);
 256         if (!insn || !insn_func(insn))
 257                 return false;
 258
 259         func_for_each_insn(file, func, insn) {
 260                 empty = false;
 261
 262                 if (insn->type == INSN_RETURN)
 263                         return false;
 264         }
 265
 266         if (empty)
 267                 return false;
 268
 269         /*
 270          * A function can have a sibling call instead of a return.  In that
 271          * case, the function's dead-end status depends on whether the target
 272          * of the sibling call returns.
 273          */
 274         func_for_each_insn(file, func, insn) {
 275                 if (is_sibling_call(insn)) {
 276                         struct instruction *dest = insn->jump_dest;
 277
 278                         if (!dest)
 279                                 /* sibling call to another file */
 280                                 return false;
 281
 282                         /* local sibling call */
 283                         if (recursion == 5) {
 284                                 /*
 285                                  * Infinite recursion: two functions have
 286                                  * sibling calls to each other.  This is a very
 287                                  * rare case.  It means they aren't dead ends.
 288                                  */
 289                                 return false;
 290                         }
 291
 292                         return __dead_end_function(file, insn_func(dest), recursion+1);
 293                 }
 294         }
 295
 296         return true;
 297 }
 298
 299 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
 300 {
 301         return __dead_end_function(file, func, 0);
 302 }
 303
 304 static void init_cfi_state(struct cfi_state *cfi)
 305 {
 306         int i;
 307
 308         for (i = 0; i < CFI_NUM_REGS; i++) {
 309                 cfi->regs[i].base = CFI_UNDEFINED;
 310                 cfi->vals[i].base = CFI_UNDEFINED;
 311         }
 312         cfi->cfa.base = CFI_UNDEFINED;
 313         cfi->drap_reg = CFI_UNDEFINED;
 314         cfi->drap_offset = -1;
 315 }
 316
 317 static void init_insn_state(struct objtool_file *file, struct insn_state *state,
 318                             struct section *sec)
 319 {
 320         memset(state, 0, sizeof(*state));
 321         init_cfi_state(&state->cfi);
 322
 323         /*
 324          * We need the full vmlinux for noinstr validation, otherwise we can
 325          * not correctly determine insn_call_dest(insn)->sec (external symbols
 326          * do not have a section).
 327          */
 328         if (opts.link && opts.noinstr && sec)
 329                 state->noinstr = sec->noinstr;
 330 }
 331
 332 static struct cfi_state *cfi_alloc(void)
 333 {
 334         struct cfi_state *cfi = calloc(sizeof(struct cfi_state), 1);
 335         if (!cfi) {
 336                 WARN("calloc failed");
 337                 exit(1);
 338         }
 339         nr_cfi++;
 340         return cfi;
 341 }
 342
 343 static int cfi_bits;
 344 static struct hlist_head *cfi_hash;
 345
 346 static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
 347 {
 348         return memcmp((void *)cfi1 + sizeof(cfi1->hash),
 349                       (void *)cfi2 + sizeof(cfi2->hash),
 350                       sizeof(struct cfi_state) - sizeof(struct hlist_node));
 351 }
 352
 353 static inline u32 cfi_key(struct cfi_state *cfi)
 354 {
 355         return jhash((void *)cfi + sizeof(cfi->hash),
 356                      sizeof(*cfi) - sizeof(cfi->hash), 0);
 357 }
 358
 359 static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
 360 {
 361         struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
 362         struct cfi_state *obj;
 363
 364         hlist_for_each_entry(obj, head, hash) {
 365                 if (!cficmp(cfi, obj)) {
 366                         nr_cfi_cache++;
 367                         return obj;
 368                 }
 369         }
 370
 371         obj = cfi_alloc();
 372         *obj = *cfi;
 373         hlist_add_head(&obj->hash, head);
 374
 375         return obj;
 376 }
 377
 378 static void cfi_hash_add(struct cfi_state *cfi)
 379 {
 380         struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
 381
 382         hlist_add_head(&cfi->hash, head);
 383 }
 384
 385 static void *cfi_hash_alloc(unsigned long size)
 386 {
 387         cfi_bits = max(10, ilog2(size));
 388         cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
 389                         PROT_READ|PROT_WRITE,
 390                         MAP_PRIVATE|MAP_ANON, -1, 0);
 391         if (cfi_hash == (void *)-1L) {
 392                 WARN("mmap fail cfi_hash");
 393                 cfi_hash = NULL;
 394         }  else if (opts.stats) {
 395                 printf("cfi_bits: %d\n", cfi_bits);
 396         }
 397
 398         return cfi_hash;
 399 }
 400
 401 static unsigned long nr_insns;
 402 static unsigned long nr_insns_visited;
 403
 404 /*
 405  * Call the arch-specific instruction decoder for all the instructions and add
 406  * them to the global instruction list.
 407  */
 408 static int decode_instructions(struct objtool_file *file)
 409 {
 410         struct section *sec;
 411         struct symbol *func;
 412         unsigned long offset;
 413         struct instruction *insn;
 414         int ret;
 415
 416         for_each_sec(file, sec) {
 417                 struct instruction *insns = NULL;
 418                 u8 prev_len = 0;
 419                 u8 idx = 0;
 420
 421                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
 422                         continue;
 423
 424                 if (strcmp(sec->name, ".altinstr_replacement") &&
 425                     strcmp(sec->name, ".altinstr_aux") &&
 426                     strncmp(sec->name, ".discard.", 9))
 427                         sec->text = true;
 428
 429                 if (!strcmp(sec->name, ".noinstr.text") ||
 430                     !strcmp(sec->name, ".entry.text") ||
 431                     !strcmp(sec->name, ".cpuidle.text") ||
 432                     !strncmp(sec->name, ".text.__x86.", 12))
 433                         sec->noinstr = true;
 434
 435                 /*
 436                  * .init.text code is ran before userspace and thus doesn't
 437                  * strictly need retpolines, except for modules which are
 438                  * loaded late, they very much do need retpoline in their
 439                  * .init.text
 440                  */
 441                 if (!strcmp(sec->name, ".init.text") && !opts.module)
 442                         sec->init = true;
 443
 444                 for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
 445                         if (!insns || idx == INSN_CHUNK_MAX) {
 446                                 insns = calloc(sizeof(*insn), INSN_CHUNK_SIZE);
 447                                 if (!insns) {
 448                                         WARN("malloc failed");
 449                                         return -1;
 450                                 }
 451                                 idx = 0;
 452                         } else {
 453                                 idx++;
 454                         }
 455                         insn = &insns[idx];
 456                         insn->idx = idx;
 457
 458                         INIT_LIST_HEAD(&insn->call_node);
 459                         insn->sec = sec;
 460                         insn->offset = offset;
 461                         insn->prev_len = prev_len;
 462
 463                         ret = arch_decode_instruction(file, sec, offset,
 464                                                       sec->sh.sh_size - offset,
 465                                                       insn);
 466                         if (ret)
 467                                 return ret;
 468
 469                         prev_len = insn->len;
 470
 471                         /*
 472                          * By default, "ud2" is a dead end unless otherwise
 473                          * annotated, because GCC 7 inserts it for certain
 474                          * divide-by-zero cases.
 475                          */
 476                         if (insn->type == INSN_BUG)
 477                                 insn->dead_end = true;
 478
 479                         hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
 480                         nr_insns++;
 481                 }
 482
 483 //              printf("%s: last chunk used: %d\n", sec->name, (int)idx);
 484
 485                 sec_for_each_sym(sec, func) {
 486                         if (func->type != STT_NOTYPE && func->type != STT_FUNC)
 487                                 continue;
 488
 489                         if (func->offset == sec->sh.sh_size) {
 490                                 /* Heuristic: likely an "end" symbol */
 491                                 if (func->type == STT_NOTYPE)
 492                                         continue;
 493                                 WARN("%s(): STT_FUNC at end of section",
 494                                      func->name);
 495                                 return -1;
 496                         }
 497
 498                         if (func->return_thunk || func->alias != func)
 499                                 continue;
 500
 501                         if (!find_insn(file, sec, func->offset)) {
 502                                 WARN("%s(): can't find starting instruction",
 503                                      func->name);
 504                                 return -1;
 505                         }
 506
 507                         sym_for_each_insn(file, func, insn) {
 508                                 insn->sym = func;
 509                                 if (func->type == STT_FUNC &&
 510                                     insn->type == INSN_ENDBR &&
 511                                     list_empty(&insn->call_node)) {
 512                                         if (insn->offset == func->offset) {
 513                                                 list_add_tail(&insn->call_node, &file->endbr_list);
 514                                                 file->nr_endbr++;
 515                                         } else {
 516                                                 file->nr_endbr_int++;
 517                                         }
 518                                 }
 519                         }
 520                 }
 521         }
 522
 523         if (opts.stats)
 524                 printf("nr_insns: %lu\n", nr_insns);
 525
 526         return 0;
 527 }
 528
 529 /*
 530  * Read the pv_ops[] .data table to find the static initialized values.
 531  */
 532 static int add_pv_ops(struct objtool_file *file, const char *symname)
 533 {
 534         struct symbol *sym, *func;
 535         unsigned long off, end;
 536         struct reloc *rel;
 537         int idx;
 538
 539         sym = find_symbol_by_name(file->elf, symname);
 540         if (!sym)
 541                 return 0;
 542
 543         off = sym->offset;
 544         end = off + sym->len;
 545         for (;;) {
 546                 rel = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off);
 547                 if (!rel)
 548                         break;
 549
 550                 func = rel->sym;
 551                 if (func->type == STT_SECTION)
 552                         func = find_symbol_by_offset(rel->sym->sec, rel->addend);
 553
 554                 idx = (rel->offset - sym->offset) / sizeof(unsigned long);
 555
 556                 objtool_pv_add(file, idx, func);
 557
 558                 off = rel->offset + 1;
 559                 if (off > end)
 560                         break;
 561         }
 562
 563         return 0;
 564 }
 565
 566 /*
 567  * Allocate and initialize file->pv_ops[].
 568  */
 569 static int init_pv_ops(struct objtool_file *file)
 570 {
 571         static const char *pv_ops_tables[] = {
 572                 "pv_ops",
 573                 "xen_cpu_ops",
 574                 "xen_irq_ops",
 575                 "xen_mmu_ops",
 576                 NULL,
 577         };
 578         const char *pv_ops;
 579         struct symbol *sym;
 580         int idx, nr;
 581
 582         if (!opts.noinstr)
 583                 return 0;
 584
 585         file->pv_ops = NULL;
 586
 587         sym = find_symbol_by_name(file->elf, "pv_ops");
 588         if (!sym)
 589                 return 0;
 590
 591         nr = sym->len / sizeof(unsigned long);
 592         file->pv_ops = calloc(sizeof(struct pv_state), nr);
 593         if (!file->pv_ops)
 594                 return -1;
 595
 596         for (idx = 0; idx < nr; idx++)
 597                 INIT_LIST_HEAD(&file->pv_ops[idx].targets);
 598
 599         for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++)
 600                 add_pv_ops(file, pv_ops);
 601
 602         return 0;
 603 }
 604
 605 static struct instruction *find_last_insn(struct objtool_file *file,
 606                                           struct section *sec)
 607 {
 608         struct instruction *insn = NULL;
 609         unsigned int offset;
 610         unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
 611
 612         for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
 613                 insn = find_insn(file, sec, offset);
 614
 615         return insn;
 616 }
 617
 618 /*
 619  * Mark "ud2" instructions and manually annotated dead ends.
 620  */
 621 static int add_dead_ends(struct objtool_file *file)
 622 {
 623         struct section *sec;
 624         struct reloc *reloc;
 625         struct instruction *insn;
 626
 627         /*
 628          * Check for manually annotated dead ends.
 629          */
 630         sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
 631         if (!sec)
 632                 goto reachable;
 633
 634         list_for_each_entry(reloc, &sec->reloc_list, list) {
 635                 if (reloc->sym->type != STT_SECTION) {
 636                         WARN("unexpected relocation symbol type in %s", sec->name);
 637                         return -1;
 638                 }
 639                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 640                 if (insn)
 641                         insn = prev_insn_same_sec(file, insn);
 642                 else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
 643                         insn = find_last_insn(file, reloc->sym->sec);
 644                         if (!insn) {
 645                                 WARN("can't find unreachable insn at %s+0x%" PRIx64,
 646                                      reloc->sym->sec->name, reloc->addend);
 647                                 return -1;
 648                         }
 649                 } else {
 650                         WARN("can't find unreachable insn at %s+0x%" PRIx64,
 651                              reloc->sym->sec->name, reloc->addend);
 652                         return -1;
 653                 }
 654
 655                 insn->dead_end = true;
 656         }
 657
 658 reachable:
 659         /*
 660          * These manually annotated reachable checks are needed for GCC 4.4,
 661          * where the Linux unreachable() macro isn't supported.  In that case
 662          * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
 663          * not a dead end.
 664          */
 665         sec = find_section_by_name(file->elf, ".rela.discard.reachable");
 666         if (!sec)
 667                 return 0;
 668
 669         list_for_each_entry(reloc, &sec->reloc_list, list) {
 670                 if (reloc->sym->type != STT_SECTION) {
 671                         WARN("unexpected relocation symbol type in %s", sec->name);
 672                         return -1;
 673                 }
 674                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 675                 if (insn)
 676                         insn = prev_insn_same_sec(file, insn);
 677                 else if (reloc->addend == reloc->sym->sec->sh.sh_size) {
 678                         insn = find_last_insn(file, reloc->sym->sec);
 679                         if (!insn) {
 680                                 WARN("can't find reachable insn at %s+0x%" PRIx64,
 681                                      reloc->sym->sec->name, reloc->addend);
 682                                 return -1;
 683                         }
 684                 } else {
 685                         WARN("can't find reachable insn at %s+0x%" PRIx64,
 686                              reloc->sym->sec->name, reloc->addend);
 687                         return -1;
 688                 }
 689
 690                 insn->dead_end = false;
 691         }
 692
 693         return 0;
 694 }
 695
 696 static int create_static_call_sections(struct objtool_file *file)
 697 {
 698         struct section *sec;
 699         struct static_call_site *site;
 700         struct instruction *insn;
 701         struct symbol *key_sym;
 702         char *key_name, *tmp;
 703         int idx;
 704
 705         sec = find_section_by_name(file->elf, ".static_call_sites");
 706         if (sec) {
 707                 INIT_LIST_HEAD(&file->static_call_list);
 708                 WARN("file already has .static_call_sites section, skipping");
 709                 return 0;
 710         }
 711
 712         if (list_empty(&file->static_call_list))
 713                 return 0;
 714
 715         idx = 0;
 716         list_for_each_entry(insn, &file->static_call_list, call_node)
 717                 idx++;
 718
 719         sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE,
 720                                  sizeof(struct static_call_site), idx);
 721         if (!sec)
 722                 return -1;
 723
 724         idx = 0;
 725         list_for_each_entry(insn, &file->static_call_list, call_node) {
 726
 727                 site = (struct static_call_site *)sec->data->d_buf + idx;
 728                 memset(site, 0, sizeof(struct static_call_site));
 729
 730                 /* populate reloc for 'addr' */
 731                 if (elf_add_reloc_to_insn(file->elf, sec,
 732                                           idx * sizeof(struct static_call_site),
 733                                           R_X86_64_PC32,
 734                                           insn->sec, insn->offset))
 735                         return -1;
 736
 737                 /* find key symbol */
 738                 key_name = strdup(insn_call_dest(insn)->name);
 739                 if (!key_name) {
 740                         perror("strdup");
 741                         return -1;
 742                 }
 743                 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
 744                             STATIC_CALL_TRAMP_PREFIX_LEN)) {
 745                         WARN("static_call: trampoline name malformed: %s", key_name);
 746                         free(key_name);
 747                         return -1;
 748                 }
 749                 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
 750                 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
 751
 752                 key_sym = find_symbol_by_name(file->elf, tmp);
 753                 if (!key_sym) {
 754                         if (!opts.module) {
 755                                 WARN("static_call: can't find static_call_key symbol: %s", tmp);
 756                                 free(key_name);
 757                                 return -1;
 758                         }
 759
 760                         /*
 761                          * For modules(), the key might not be exported, which
 762                          * means the module can make static calls but isn't
 763                          * allowed to change them.
 764                          *
 765                          * In that case we temporarily set the key to be the
 766                          * trampoline address.  This is fixed up in
 767                          * static_call_add_module().
 768                          */
 769                         key_sym = insn_call_dest(insn);
 770                 }
 771                 free(key_name);
 772
 773                 /* populate reloc for 'key' */
 774                 if (elf_add_reloc(file->elf, sec,
 775                                   idx * sizeof(struct static_call_site) + 4,
 776                                   R_X86_64_PC32, key_sym,
 777                                   is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
 778                         return -1;
 779
 780                 idx++;
 781         }
 782
 783         return 0;
 784 }
 785
 786 static int create_retpoline_sites_sections(struct objtool_file *file)
 787 {
 788         struct instruction *insn;
 789         struct section *sec;
 790         int idx;
 791
 792         sec = find_section_by_name(file->elf, ".retpoline_sites");
 793         if (sec) {
 794                 WARN("file already has .retpoline_sites, skipping");
 795                 return 0;
 796         }
 797
 798         idx = 0;
 799         list_for_each_entry(insn, &file->retpoline_call_list, call_node)
 800                 idx++;
 801
 802         if (!idx)
 803                 return 0;
 804
 805         sec = elf_create_section(file->elf, ".retpoline_sites", 0,
 806                                  sizeof(int), idx);
 807         if (!sec) {
 808                 WARN("elf_create_section: .retpoline_sites");
 809                 return -1;
 810         }
 811
 812         idx = 0;
 813         list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
 814
 815                 int *site = (int *)sec->data->d_buf + idx;
 816                 *site = 0;
 817
 818                 if (elf_add_reloc_to_insn(file->elf, sec,
 819                                           idx * sizeof(int),
 820                                           R_X86_64_PC32,
 821                                           insn->sec, insn->offset)) {
 822                         WARN("elf_add_reloc_to_insn: .retpoline_sites");
 823                         return -1;
 824                 }
 825
 826                 idx++;
 827         }
 828
 829         return 0;
 830 }
 831
 832 static int create_return_sites_sections(struct objtool_file *file)
 833 {
 834         struct instruction *insn;
 835         struct section *sec;
 836         int idx;
 837
 838         sec = find_section_by_name(file->elf, ".return_sites");
 839         if (sec) {
 840                 WARN("file already has .return_sites, skipping");
 841                 return 0;
 842         }
 843
 844         idx = 0;
 845         list_for_each_entry(insn, &file->return_thunk_list, call_node)
 846                 idx++;
 847
 848         if (!idx)
 849                 return 0;
 850
 851         sec = elf_create_section(file->elf, ".return_sites", 0,
 852                                  sizeof(int), idx);
 853         if (!sec) {
 854                 WARN("elf_create_section: .return_sites");
 855                 return -1;
 856         }
 857
 858         idx = 0;
 859         list_for_each_entry(insn, &file->return_thunk_list, call_node) {
 860
 861                 int *site = (int *)sec->data->d_buf + idx;
 862                 *site = 0;
 863
 864                 if (elf_add_reloc_to_insn(file->elf, sec,
 865                                           idx * sizeof(int),
 866                                           R_X86_64_PC32,
 867                                           insn->sec, insn->offset)) {
 868                         WARN("elf_add_reloc_to_insn: .return_sites");
 869                         return -1;
 870                 }
 871
 872                 idx++;
 873         }
 874
 875         return 0;
 876 }
 877
 878 static int create_ibt_endbr_seal_sections(struct objtool_file *file)
 879 {
 880         struct instruction *insn;
 881         struct section *sec;
 882         int idx;
 883
 884         sec = find_section_by_name(file->elf, ".ibt_endbr_seal");
 885         if (sec) {
 886                 WARN("file already has .ibt_endbr_seal, skipping");
 887                 return 0;
 888         }
 889
 890         idx = 0;
 891         list_for_each_entry(insn, &file->endbr_list, call_node)
 892                 idx++;
 893
 894         if (opts.stats) {
 895                 printf("ibt: ENDBR at function start: %d\n", file->nr_endbr);
 896                 printf("ibt: ENDBR inside functions:  %d\n", file->nr_endbr_int);
 897                 printf("ibt: superfluous ENDBR:       %d\n", idx);
 898         }
 899
 900         if (!idx)
 901                 return 0;
 902
 903         sec = elf_create_section(file->elf, ".ibt_endbr_seal", 0,
 904                                  sizeof(int), idx);
 905         if (!sec) {
 906                 WARN("elf_create_section: .ibt_endbr_seal");
 907                 return -1;
 908         }
 909
 910         idx = 0;
 911         list_for_each_entry(insn, &file->endbr_list, call_node) {
 912
 913                 int *site = (int *)sec->data->d_buf + idx;
 914                 struct symbol *sym = insn->sym;
 915                 *site = 0;
 916
 917                 if (opts.module && sym && sym->type == STT_FUNC &&
 918                     insn->offset == sym->offset &&
 919                     (!strcmp(sym->name, "init_module") ||
 920                      !strcmp(sym->name, "cleanup_module")))
 921                         WARN("%s(): not an indirect call target", sym->name);
 922
 923                 if (elf_add_reloc_to_insn(file->elf, sec,
 924                                           idx * sizeof(int),
 925                                           R_X86_64_PC32,
 926                                           insn->sec, insn->offset)) {
 927                         WARN("elf_add_reloc_to_insn: .ibt_endbr_seal");
 928                         return -1;
 929                 }
 930
 931                 idx++;
 932         }
 933
 934         return 0;
 935 }
 936
 937 static int create_cfi_sections(struct objtool_file *file)
 938 {
 939         struct section *sec;
 940         struct symbol *sym;
 941         unsigned int *loc;
 942         int idx;
 943
 944         sec = find_section_by_name(file->elf, ".cfi_sites");
 945         if (sec) {
 946                 INIT_LIST_HEAD(&file->call_list);
 947                 WARN("file already has .cfi_sites section, skipping");
 948                 return 0;
 949         }
 950
 951         idx = 0;
 952         for_each_sym(file, sym) {
 953                 if (sym->type != STT_FUNC)
 954                         continue;
 955
 956                 if (strncmp(sym->name, "__cfi_", 6))
 957                         continue;
 958
 959                 idx++;
 960         }
 961
 962         sec = elf_create_section(file->elf, ".cfi_sites", 0, sizeof(unsigned int), idx);
 963         if (!sec)
 964                 return -1;
 965
 966         idx = 0;
 967         for_each_sym(file, sym) {
 968                 if (sym->type != STT_FUNC)
 969                         continue;
 970
 971                 if (strncmp(sym->name, "__cfi_", 6))
 972                         continue;
 973
 974                 loc = (unsigned int *)sec->data->d_buf + idx;
 975                 memset(loc, 0, sizeof(unsigned int));
 976
 977                 if (elf_add_reloc_to_insn(file->elf, sec,
 978                                           idx * sizeof(unsigned int),
 979                                           R_X86_64_PC32,
 980                                           sym->sec, sym->offset))
 981                         return -1;
 982
 983                 idx++;
 984         }
 985
 986         return 0;
 987 }
 988
 989 static int create_mcount_loc_sections(struct objtool_file *file)
 990 {
 991         int addrsize = elf_class_addrsize(file->elf);
 992         struct instruction *insn;
 993         struct section *sec;
 994         int idx;
 995
 996         sec = find_section_by_name(file->elf, "__mcount_loc");
 997         if (sec) {
 998                 INIT_LIST_HEAD(&file->mcount_loc_list);
 999                 WARN("file already has __mcount_loc section, skipping");
1000                 return 0;
1001         }
1002
1003         if (list_empty(&file->mcount_loc_list))
1004                 return 0;
1005
1006         idx = 0;
1007         list_for_each_entry(insn, &file->mcount_loc_list, call_node)
1008                 idx++;
1009
1010         sec = elf_create_section(file->elf, "__mcount_loc", 0, addrsize, idx);
1011         if (!sec)
1012                 return -1;
1013
1014         sec->sh.sh_addralign = addrsize;
1015
1016         idx = 0;
1017         list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
1018                 void *loc;
1019
1020                 loc = sec->data->d_buf + idx;
1021                 memset(loc, 0, addrsize);
1022
1023                 if (elf_add_reloc_to_insn(file->elf, sec, idx,
1024                                           addrsize == sizeof(u64) ? R_ABS64 : R_ABS32,
1025                                           insn->sec, insn->offset))
1026                         return -1;
1027
1028                 idx += addrsize;
1029         }
1030
1031         return 0;
1032 }
1033
1034 static int create_direct_call_sections(struct objtool_file *file)
1035 {
1036         struct instruction *insn;
1037         struct section *sec;
1038         unsigned int *loc;
1039         int idx;
1040
1041         sec = find_section_by_name(file->elf, ".call_sites");
1042         if (sec) {
1043                 INIT_LIST_HEAD(&file->call_list);
1044                 WARN("file already has .call_sites section, skipping");
1045                 return 0;
1046         }
1047
1048         if (list_empty(&file->call_list))
1049                 return 0;
1050
1051         idx = 0;
1052         list_for_each_entry(insn, &file->call_list, call_node)
1053                 idx++;
1054
1055         sec = elf_create_section(file->elf, ".call_sites", 0, sizeof(unsigned int), idx);
1056         if (!sec)
1057                 return -1;
1058
1059         idx = 0;
1060         list_for_each_entry(insn, &file->call_list, call_node) {
1061
1062                 loc = (unsigned int *)sec->data->d_buf + idx;
1063                 memset(loc, 0, sizeof(unsigned int));
1064
1065                 if (elf_add_reloc_to_insn(file->elf, sec,
1066                                           idx * sizeof(unsigned int),
1067                                           R_X86_64_PC32,
1068                                           insn->sec, insn->offset))
1069                         return -1;
1070
1071                 idx++;
1072         }
1073
1074         return 0;
1075 }
1076
1077 /*
1078  * Warnings shouldn't be reported for ignored functions.
1079  */
1080 static void add_ignores(struct objtool_file *file)
1081 {
1082         struct instruction *insn;
1083         struct section *sec;
1084         struct symbol *func;
1085         struct reloc *reloc;
1086
1087         sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
1088         if (!sec)
1089                 return;
1090
1091         list_for_each_entry(reloc, &sec->reloc_list, list) {
1092                 switch (reloc->sym->type) {
1093                 case STT_FUNC:
1094                         func = reloc->sym;
1095                         break;
1096
1097                 case STT_SECTION:
1098                         func = find_func_by_offset(reloc->sym->sec, reloc->addend);
1099                         if (!func)
1100                                 continue;
1101                         break;
1102
1103                 default:
1104                         WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type);
1105                         continue;
1106                 }
1107
1108                 func_for_each_insn(file, func, insn)
1109                         insn->ignore = true;
1110         }
1111 }
1112
1113 /*
1114  * This is a whitelist of functions that is allowed to be called with AC set.
1115  * The list is meant to be minimal and only contains compiler instrumentation
1116  * ABI and a few functions used to implement *_{to,from}_user() functions.
1117  *
1118  * These functions must not directly change AC, but may PUSHF/POPF.
1119  */
1120 static const char *uaccess_safe_builtin[] = {
1121         /* KASAN */
1122         "kasan_report",
1123         "kasan_check_range",
1124         /* KASAN out-of-line */
1125         "__asan_loadN_noabort",
1126         "__asan_load1_noabort",
1127         "__asan_load2_noabort",
1128         "__asan_load4_noabort",
1129         "__asan_load8_noabort",
1130         "__asan_load16_noabort",
1131         "__asan_storeN_noabort",
1132         "__asan_store1_noabort",
1133         "__asan_store2_noabort",
1134         "__asan_store4_noabort",
1135         "__asan_store8_noabort",
1136         "__asan_store16_noabort",
1137         "__kasan_check_read",
1138         "__kasan_check_write",
1139         /* KASAN in-line */
1140         "__asan_report_load_n_noabort",
1141         "__asan_report_load1_noabort",
1142         "__asan_report_load2_noabort",
1143         "__asan_report_load4_noabort",
1144         "__asan_report_load8_noabort",
1145         "__asan_report_load16_noabort",
1146         "__asan_report_store_n_noabort",
1147         "__asan_report_store1_noabort",
1148         "__asan_report_store2_noabort",
1149         "__asan_report_store4_noabort",
1150         "__asan_report_store8_noabort",
1151         "__asan_report_store16_noabort",
1152         /* KCSAN */
1153         "__kcsan_check_access",
1154         "__kcsan_mb",
1155         "__kcsan_wmb",
1156         "__kcsan_rmb",
1157         "__kcsan_release",
1158         "kcsan_found_watchpoint",
1159         "kcsan_setup_watchpoint",
1160         "kcsan_check_scoped_accesses",
1161         "kcsan_disable_current",
1162         "kcsan_enable_current_nowarn",
1163         /* KCSAN/TSAN */
1164         "__tsan_func_entry",
1165         "__tsan_func_exit",
1166         "__tsan_read_range",
1167         "__tsan_write_range",
1168         "__tsan_read1",
1169         "__tsan_read2",
1170         "__tsan_read4",
1171         "__tsan_read8",
1172         "__tsan_read16",
1173         "__tsan_write1",
1174         "__tsan_write2",
1175         "__tsan_write4",
1176         "__tsan_write8",
1177         "__tsan_write16",
1178         "__tsan_read_write1",
1179         "__tsan_read_write2",
1180         "__tsan_read_write4",
1181         "__tsan_read_write8",
1182         "__tsan_read_write16",
1183         "__tsan_volatile_read1",
1184         "__tsan_volatile_read2",
1185         "__tsan_volatile_read4",
1186         "__tsan_volatile_read8",
1187         "__tsan_volatile_read16",
1188         "__tsan_volatile_write1",
1189         "__tsan_volatile_write2",
1190         "__tsan_volatile_write4",
1191         "__tsan_volatile_write8",
1192         "__tsan_volatile_write16",
1193         "__tsan_atomic8_load",
1194         "__tsan_atomic16_load",
1195         "__tsan_atomic32_load",
1196         "__tsan_atomic64_load",
1197         "__tsan_atomic8_store",
1198         "__tsan_atomic16_store",
1199         "__tsan_atomic32_store",
1200         "__tsan_atomic64_store",
1201         "__tsan_atomic8_exchange",
1202         "__tsan_atomic16_exchange",
1203         "__tsan_atomic32_exchange",
1204         "__tsan_atomic64_exchange",
1205         "__tsan_atomic8_fetch_add",
1206         "__tsan_atomic16_fetch_add",
1207         "__tsan_atomic32_fetch_add",
1208         "__tsan_atomic64_fetch_add",
1209         "__tsan_atomic8_fetch_sub",
1210         "__tsan_atomic16_fetch_sub",
1211         "__tsan_atomic32_fetch_sub",
1212         "__tsan_atomic64_fetch_sub",
1213         "__tsan_atomic8_fetch_and",
1214         "__tsan_atomic16_fetch_and",
1215         "__tsan_atomic32_fetch_and",
1216         "__tsan_atomic64_fetch_and",
1217         "__tsan_atomic8_fetch_or",
1218         "__tsan_atomic16_fetch_or",
1219         "__tsan_atomic32_fetch_or",
1220         "__tsan_atomic64_fetch_or",
1221         "__tsan_atomic8_fetch_xor",
1222         "__tsan_atomic16_fetch_xor",
1223         "__tsan_atomic32_fetch_xor",
1224         "__tsan_atomic64_fetch_xor",
1225         "__tsan_atomic8_fetch_nand",
1226         "__tsan_atomic16_fetch_nand",
1227         "__tsan_atomic32_fetch_nand",
1228         "__tsan_atomic64_fetch_nand",
1229         "__tsan_atomic8_compare_exchange_strong",
1230         "__tsan_atomic16_compare_exchange_strong",
1231         "__tsan_atomic32_compare_exchange_strong",
1232         "__tsan_atomic64_compare_exchange_strong",
1233         "__tsan_atomic8_compare_exchange_weak",
1234         "__tsan_atomic16_compare_exchange_weak",
1235         "__tsan_atomic32_compare_exchange_weak",
1236         "__tsan_atomic64_compare_exchange_weak",
1237         "__tsan_atomic8_compare_exchange_val",
1238         "__tsan_atomic16_compare_exchange_val",
1239         "__tsan_atomic32_compare_exchange_val",
1240         "__tsan_atomic64_compare_exchange_val",
1241         "__tsan_atomic_thread_fence",
1242         "__tsan_atomic_signal_fence",
1243         "__tsan_unaligned_read16",
1244         "__tsan_unaligned_write16",
1245         /* KCOV */
1246         "write_comp_data",
1247         "check_kcov_mode",
1248         "__sanitizer_cov_trace_pc",
1249         "__sanitizer_cov_trace_const_cmp1",
1250         "__sanitizer_cov_trace_const_cmp2",
1251         "__sanitizer_cov_trace_const_cmp4",
1252         "__sanitizer_cov_trace_const_cmp8",
1253         "__sanitizer_cov_trace_cmp1",
1254         "__sanitizer_cov_trace_cmp2",
1255         "__sanitizer_cov_trace_cmp4",
1256         "__sanitizer_cov_trace_cmp8",
1257         "__sanitizer_cov_trace_switch",
1258         /* KMSAN */
1259         "kmsan_copy_to_user",
1260         "kmsan_report",
1261         "kmsan_unpoison_entry_regs",
1262         "kmsan_unpoison_memory",
1263         "__msan_chain_origin",
1264         "__msan_get_context_state",
1265         "__msan_instrument_asm_store",
1266         "__msan_metadata_ptr_for_load_1",
1267         "__msan_metadata_ptr_for_load_2",
1268         "__msan_metadata_ptr_for_load_4",
1269         "__msan_metadata_ptr_for_load_8",
1270         "__msan_metadata_ptr_for_load_n",
1271         "__msan_metadata_ptr_for_store_1",
1272         "__msan_metadata_ptr_for_store_2",
1273         "__msan_metadata_ptr_for_store_4",
1274         "__msan_metadata_ptr_for_store_8",
1275         "__msan_metadata_ptr_for_store_n",
1276         "__msan_poison_alloca",
1277         "__msan_warning",
1278         /* UBSAN */
1279         "ubsan_type_mismatch_common",
1280         "__ubsan_handle_type_mismatch",
1281         "__ubsan_handle_type_mismatch_v1",
1282         "__ubsan_handle_shift_out_of_bounds",
1283         "__ubsan_handle_load_invalid_value",
1284         /* STACKLEAK */
1285         "stackleak_track_stack",
1286         /* misc */
1287         "csum_partial_copy_generic",
1288         "copy_mc_fragile",
1289         "copy_mc_fragile_handle_tail",
1290         "copy_mc_enhanced_fast_string",
1291         "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
1292         "rep_stos_alternative",
1293         "rep_movs_alternative",
1294         "__copy_user_nocache",
1295         NULL
1296 };
1297
1298 static void add_uaccess_safe(struct objtool_file *file)
1299 {
1300         struct symbol *func;
1301         const char **name;
1302
1303         if (!opts.uaccess)
1304                 return;
1305
1306         for (name = uaccess_safe_builtin; *name; name++) {
1307                 func = find_symbol_by_name(file->elf, *name);
1308                 if (!func)
1309                         continue;
1310
1311                 func->uaccess_safe = true;
1312         }
1313 }
1314
1315 /*
1316  * FIXME: For now, just ignore any alternatives which add retpolines.  This is
1317  * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
1318  * But it at least allows objtool to understand the control flow *around* the
1319  * retpoline.
1320  */
1321 static int add_ignore_alternatives(struct objtool_file *file)
1322 {
1323         struct section *sec;
1324         struct reloc *reloc;
1325         struct instruction *insn;
1326
1327         sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
1328         if (!sec)
1329                 return 0;
1330
1331         list_for_each_entry(reloc, &sec->reloc_list, list) {
1332                 if (reloc->sym->type != STT_SECTION) {
1333                         WARN("unexpected relocation symbol type in %s", sec->name);
1334                         return -1;
1335                 }
1336
1337                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1338                 if (!insn) {
1339                         WARN("bad .discard.ignore_alts entry");
1340                         return -1;
1341                 }
1342
1343                 insn->ignore_alts = true;
1344         }
1345
1346         return 0;
1347 }
1348
1349 __weak bool arch_is_retpoline(struct symbol *sym)
1350 {
1351         return false;
1352 }
1353
1354 __weak bool arch_is_rethunk(struct symbol *sym)
1355 {
1356         return false;
1357 }
1358
1359 static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
1360 {
1361         struct reloc *reloc;
1362
1363         if (insn->no_reloc)
1364                 return NULL;
1365
1366         if (!file)
1367                 return NULL;
1368
1369         reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1370                                          insn->offset, insn->len);
1371         if (!reloc) {
1372                 insn->no_reloc = 1;
1373                 return NULL;
1374         }
1375
1376         return reloc;
1377 }
1378
1379 static void remove_insn_ops(struct instruction *insn)
1380 {
1381         struct stack_op *op, *next;
1382
1383         for (op = insn->stack_ops; op; op = next) {
1384                 next = op->next;
1385                 free(op);
1386         }
1387         insn->stack_ops = NULL;
1388 }
1389
1390 static void annotate_call_site(struct objtool_file *file,
1391                                struct instruction *insn, bool sibling)
1392 {
1393         struct reloc *reloc = insn_reloc(file, insn);
1394         struct symbol *sym = insn_call_dest(insn);
1395
1396         if (!sym)
1397                 sym = reloc->sym;
1398
1399         /*
1400          * Alternative replacement code is just template code which is
1401          * sometimes copied to the original instruction. For now, don't
1402          * annotate it. (In the future we might consider annotating the
1403          * original instruction if/when it ever makes sense to do so.)
1404          */
1405         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1406                 return;
1407
1408         if (sym->static_call_tramp) {
1409                 list_add_tail(&insn->call_node, &file->static_call_list);
1410                 return;
1411         }
1412
1413         if (sym->retpoline_thunk) {
1414                 list_add_tail(&insn->call_node, &file->retpoline_call_list);
1415                 return;
1416         }
1417
1418         /*
1419          * Many compilers cannot disable KCOV or sanitizer calls with a function
1420          * attribute so they need a little help, NOP out any such calls from
1421          * noinstr text.
1422          */
1423         if (opts.hack_noinstr && insn->sec->noinstr && sym->profiling_func) {
1424                 if (reloc) {
1425                         reloc->type = R_NONE;
1426                         elf_write_reloc(file->elf, reloc);
1427                 }
1428
1429                 elf_write_insn(file->elf, insn->sec,
1430                                insn->offset, insn->len,
1431                                sibling ? arch_ret_insn(insn->len)
1432                                        : arch_nop_insn(insn->len));
1433
1434                 insn->type = sibling ? INSN_RETURN : INSN_NOP;
1435
1436                 if (sibling) {
1437                         /*
1438                          * We've replaced the tail-call JMP insn by two new
1439                          * insn: RET; INT3, except we only have a single struct
1440                          * insn here. Mark it retpoline_safe to avoid the SLS
1441                          * warning, instead of adding another insn.
1442                          */
1443                         insn->retpoline_safe = true;
1444                 }
1445
1446                 return;
1447         }
1448
1449         if (opts.mcount && sym->fentry) {
1450                 if (sibling)
1451                         WARN_INSN(insn, "tail call to __fentry__ !?!?");
1452                 if (opts.mnop) {
1453                         if (reloc) {
1454                                 reloc->type = R_NONE;
1455                                 elf_write_reloc(file->elf, reloc);
1456                         }
1457
1458                         elf_write_insn(file->elf, insn->sec,
1459                                        insn->offset, insn->len,
1460                                        arch_nop_insn(insn->len));
1461
1462                         insn->type = INSN_NOP;
1463                 }
1464
1465                 list_add_tail(&insn->call_node, &file->mcount_loc_list);
1466                 return;
1467         }
1468
1469         if (insn->type == INSN_CALL && !insn->sec->init)
1470                 list_add_tail(&insn->call_node, &file->call_list);
1471
1472         if (!sibling && dead_end_function(file, sym))
1473                 insn->dead_end = true;
1474 }
1475
1476 static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1477                           struct symbol *dest, bool sibling)
1478 {
1479         insn->_call_dest = dest;
1480         if (!dest)
1481                 return;
1482
1483         /*
1484          * Whatever stack impact regular CALLs have, should be undone
1485          * by the RETURN of the called function.
1486          *
1487          * Annotated intra-function calls retain the stack_ops but
1488          * are converted to JUMP, see read_intra_function_calls().
1489          */
1490         remove_insn_ops(insn);
1491
1492         annotate_call_site(file, insn, sibling);
1493 }
1494
1495 static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1496 {
1497         /*
1498          * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1499          * so convert them accordingly.
1500          */
1501         switch (insn->type) {
1502         case INSN_CALL:
1503                 insn->type = INSN_CALL_DYNAMIC;
1504                 break;
1505         case INSN_JUMP_UNCONDITIONAL:
1506                 insn->type = INSN_JUMP_DYNAMIC;
1507                 break;
1508         case INSN_JUMP_CONDITIONAL:
1509                 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1510                 break;
1511         default:
1512                 return;
1513         }
1514
1515         insn->retpoline_safe = true;
1516
1517         /*
1518          * Whatever stack impact regular CALLs have, should be undone
1519          * by the RETURN of the called function.
1520          *
1521          * Annotated intra-function calls retain the stack_ops but
1522          * are converted to JUMP, see read_intra_function_calls().
1523          */
1524         remove_insn_ops(insn);
1525
1526         annotate_call_site(file, insn, false);
1527 }
1528
1529 static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add)
1530 {
1531         /*
1532          * Return thunk tail calls are really just returns in disguise,
1533          * so convert them accordingly.
1534          */
1535         insn->type = INSN_RETURN;
1536         insn->retpoline_safe = true;
1537
1538         if (add)
1539                 list_add_tail(&insn->call_node, &file->return_thunk_list);
1540 }
1541
1542 static bool is_first_func_insn(struct objtool_file *file,
1543                                struct instruction *insn, struct symbol *sym)
1544 {
1545         if (insn->offset == sym->offset)
1546                 return true;
1547
1548         /* Allow direct CALL/JMP past ENDBR */
1549         if (opts.ibt) {
1550                 struct instruction *prev = prev_insn_same_sym(file, insn);
1551
1552                 if (prev && prev->type == INSN_ENDBR &&
1553                     insn->offset == sym->offset + prev->len)
1554                         return true;
1555         }
1556
1557         return false;
1558 }
1559
1560 /*
1561  * A sibling call is a tail-call to another symbol -- to differentiate from a
1562  * recursive tail-call which is to the same symbol.
1563  */
1564 static bool jump_is_sibling_call(struct objtool_file *file,
1565                                  struct instruction *from, struct instruction *to)
1566 {
1567         struct symbol *fs = from->sym;
1568         struct symbol *ts = to->sym;
1569
1570         /* Not a sibling call if from/to a symbol hole */
1571         if (!fs || !ts)
1572                 return false;
1573
1574         /* Not a sibling call if not targeting the start of a symbol. */
1575         if (!is_first_func_insn(file, to, ts))
1576                 return false;
1577
1578         /* Disallow sibling calls into STT_NOTYPE */
1579         if (ts->type == STT_NOTYPE)
1580                 return false;
1581
1582         /* Must not be self to be a sibling */
1583         return fs->pfunc != ts->pfunc;
1584 }
1585
1586 /*
1587  * Find the destination instructions for all jumps.
1588  */
1589 static int add_jump_destinations(struct objtool_file *file)
1590 {
1591         struct instruction *insn, *jump_dest;
1592         struct reloc *reloc;
1593         struct section *dest_sec;
1594         unsigned long dest_off;
1595
1596         for_each_insn(file, insn) {
1597                 if (insn->jump_dest) {
1598                         /*
1599                          * handle_group_alt() may have previously set
1600                          * 'jump_dest' for some alternatives.
1601                          */
1602                         continue;
1603                 }
1604                 if (!is_static_jump(insn))
1605                         continue;
1606
1607                 reloc = insn_reloc(file, insn);
1608                 if (!reloc) {
1609                         dest_sec = insn->sec;
1610                         dest_off = arch_jump_destination(insn);
1611                 } else if (reloc->sym->type == STT_SECTION) {
1612                         dest_sec = reloc->sym->sec;
1613                         dest_off = arch_dest_reloc_offset(reloc->addend);
1614                 } else if (reloc->sym->retpoline_thunk) {
1615                         add_retpoline_call(file, insn);
1616                         continue;
1617                 } else if (reloc->sym->return_thunk) {
1618                         add_return_call(file, insn, true);
1619                         continue;
1620                 } else if (insn_func(insn)) {
1621                         /*
1622                          * External sibling call or internal sibling call with
1623                          * STT_FUNC reloc.
1624                          */
1625                         add_call_dest(file, insn, reloc->sym, true);
1626                         continue;
1627                 } else if (reloc->sym->sec->idx) {
1628                         dest_sec = reloc->sym->sec;
1629                         dest_off = reloc->sym->sym.st_value +
1630                                    arch_dest_reloc_offset(reloc->addend);
1631                 } else {
1632                         /* non-func asm code jumping to another file */
1633                         continue;
1634                 }
1635
1636                 jump_dest = find_insn(file, dest_sec, dest_off);
1637                 if (!jump_dest) {
1638                         struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off);
1639
1640                         /*
1641                          * This is a special case for zen_untrain_ret().
1642                          * It jumps to __x86_return_thunk(), but objtool
1643                          * can't find the thunk's starting RET
1644                          * instruction, because the RET is also in the
1645                          * middle of another instruction.  Objtool only
1646                          * knows about the outer instruction.
1647                          */
1648                         if (sym && sym->return_thunk) {
1649                                 add_return_call(file, insn, false);
1650                                 continue;
1651                         }
1652
1653                         WARN_INSN(insn, "can't find jump dest instruction at %s+0x%lx",
1654                                   dest_sec->name, dest_off);
1655                         return -1;
1656                 }
1657
1658                 /*
1659                  * Cross-function jump.
1660                  */
1661                 if (insn_func(insn) && insn_func(jump_dest) &&
1662                     insn_func(insn) != insn_func(jump_dest)) {
1663
1664                         /*
1665                          * For GCC 8+, create parent/child links for any cold
1666                          * subfunctions.  This is _mostly_ redundant with a
1667                          * similar initialization in read_symbols().
1668                          *
1669                          * If a function has aliases, we want the *first* such
1670                          * function in the symbol table to be the subfunction's
1671                          * parent.  In that case we overwrite the
1672                          * initialization done in read_symbols().
1673                          *
1674                          * However this code can't completely replace the
1675                          * read_symbols() code because this doesn't detect the
1676                          * case where the parent function's only reference to a
1677                          * subfunction is through a jump table.
1678                          */
1679                         if (!strstr(insn_func(insn)->name, ".cold") &&
1680                             strstr(insn_func(jump_dest)->name, ".cold")) {
1681                                 insn_func(insn)->cfunc = insn_func(jump_dest);
1682                                 insn_func(jump_dest)->pfunc = insn_func(insn);
1683                         }
1684                 }
1685
1686                 if (jump_is_sibling_call(file, insn, jump_dest)) {
1687                         /*
1688                          * Internal sibling call without reloc or with
1689                          * STT_SECTION reloc.
1690                          */
1691                         add_call_dest(file, insn, insn_func(jump_dest), true);
1692                         continue;
1693                 }
1694
1695                 insn->jump_dest = jump_dest;
1696         }
1697
1698         return 0;
1699 }
1700
1701 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1702 {
1703         struct symbol *call_dest;
1704
1705         call_dest = find_func_by_offset(sec, offset);
1706         if (!call_dest)
1707                 call_dest = find_symbol_by_offset(sec, offset);
1708
1709         return call_dest;
1710 }
1711
1712 /*
1713  * Find the destination instructions for all calls.
1714  */
1715 static int add_call_destinations(struct objtool_file *file)
1716 {
1717         struct instruction *insn;
1718         unsigned long dest_off;
1719         struct symbol *dest;
1720         struct reloc *reloc;
1721
1722         for_each_insn(file, insn) {
1723                 if (insn->type != INSN_CALL)
1724                         continue;
1725
1726                 reloc = insn_reloc(file, insn);
1727                 if (!reloc) {
1728                         dest_off = arch_jump_destination(insn);
1729                         dest = find_call_destination(insn->sec, dest_off);
1730
1731                         add_call_dest(file, insn, dest, false);
1732
1733                         if (insn->ignore)
1734                                 continue;
1735
1736                         if (!insn_call_dest(insn)) {
1737                                 WARN_INSN(insn, "unannotated intra-function call");
1738                                 return -1;
1739                         }
1740
1741                         if (insn_func(insn) && insn_call_dest(insn)->type != STT_FUNC) {
1742                                 WARN_INSN(insn, "unsupported call to non-function");
1743                                 return -1;
1744                         }
1745
1746                 } else if (reloc->sym->type == STT_SECTION) {
1747                         dest_off = arch_dest_reloc_offset(reloc->addend);
1748                         dest = find_call_destination(reloc->sym->sec, dest_off);
1749                         if (!dest) {
1750                                 WARN_INSN(insn, "can't find call dest symbol at %s+0x%lx",
1751                                           reloc->sym->sec->name, dest_off);
1752                                 return -1;
1753                         }
1754
1755                         add_call_dest(file, insn, dest, false);
1756
1757                 } else if (reloc->sym->retpoline_thunk) {
1758                         add_retpoline_call(file, insn);
1759
1760                 } else
1761                         add_call_dest(file, insn, reloc->sym, false);
1762         }
1763
1764         return 0;
1765 }
1766
1767 /*
1768  * The .alternatives section requires some extra special care over and above
1769  * other special sections because alternatives are patched in place.
1770  */
1771 static int handle_group_alt(struct objtool_file *file,
1772                             struct special_alt *special_alt,
1773                             struct instruction *orig_insn,
1774                             struct instruction **new_insn)
1775 {
1776         struct instruction *last_new_insn = NULL, *insn, *nop = NULL;
1777         struct alt_group *orig_alt_group, *new_alt_group;
1778         unsigned long dest_off;
1779
1780         orig_alt_group = orig_insn->alt_group;
1781         if (!orig_alt_group) {
1782                 struct instruction *last_orig_insn = NULL;
1783
1784                 orig_alt_group = malloc(sizeof(*orig_alt_group));
1785                 if (!orig_alt_group) {
1786                         WARN("malloc failed");
1787                         return -1;
1788                 }
1789                 orig_alt_group->cfi = calloc(special_alt->orig_len,
1790                                              sizeof(struct cfi_state *));
1791                 if (!orig_alt_group->cfi) {
1792                         WARN("calloc failed");
1793                         return -1;
1794                 }
1795
1796                 insn = orig_insn;
1797                 sec_for_each_insn_from(file, insn) {
1798                         if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1799                                 break;
1800
1801                         insn->alt_group = orig_alt_group;
1802                         last_orig_insn = insn;
1803                 }
1804                 orig_alt_group->orig_group = NULL;
1805                 orig_alt_group->first_insn = orig_insn;
1806                 orig_alt_group->last_insn = last_orig_insn;
1807                 orig_alt_group->nop = NULL;
1808         } else {
1809                 if (orig_alt_group->last_insn->offset + orig_alt_group->last_insn->len -
1810                     orig_alt_group->first_insn->offset != special_alt->orig_len) {
1811                         WARN_INSN(orig_insn, "weirdly overlapping alternative! %ld != %d",
1812                                   orig_alt_group->last_insn->offset +
1813                                   orig_alt_group->last_insn->len -
1814                                   orig_alt_group->first_insn->offset,
1815                                   special_alt->orig_len);
1816                         return -1;
1817                 }
1818         }
1819
1820         new_alt_group = malloc(sizeof(*new_alt_group));
1821         if (!new_alt_group) {
1822                 WARN("malloc failed");
1823                 return -1;
1824         }
1825
1826         if (special_alt->new_len < special_alt->orig_len) {
1827                 /*
1828                  * Insert a fake nop at the end to make the replacement
1829                  * alt_group the same size as the original.  This is needed to
1830                  * allow propagate_alt_cfi() to do its magic.  When the last
1831                  * instruction affects the stack, the instruction after it (the
1832                  * nop) will propagate the new state to the shared CFI array.
1833                  */
1834                 nop = malloc(sizeof(*nop));
1835                 if (!nop) {
1836                         WARN("malloc failed");
1837                         return -1;
1838                 }
1839                 memset(nop, 0, sizeof(*nop));
1840
1841                 nop->sec = special_alt->new_sec;
1842                 nop->offset = special_alt->new_off + special_alt->new_len;
1843                 nop->len = special_alt->orig_len - special_alt->new_len;
1844                 nop->type = INSN_NOP;
1845                 nop->sym = orig_insn->sym;
1846                 nop->alt_group = new_alt_group;
1847                 nop->ignore = orig_insn->ignore_alts;
1848         }
1849
1850         if (!special_alt->new_len) {
1851                 *new_insn = nop;
1852                 goto end;
1853         }
1854
1855         insn = *new_insn;
1856         sec_for_each_insn_from(file, insn) {
1857                 struct reloc *alt_reloc;
1858
1859                 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1860                         break;
1861
1862                 last_new_insn = insn;
1863
1864                 insn->ignore = orig_insn->ignore_alts;
1865                 insn->sym = orig_insn->sym;
1866                 insn->alt_group = new_alt_group;
1867
1868                 /*
1869                  * Since alternative replacement code is copy/pasted by the
1870                  * kernel after applying relocations, generally such code can't
1871                  * have relative-address relocation references to outside the
1872                  * .altinstr_replacement section, unless the arch's
1873                  * alternatives code can adjust the relative offsets
1874                  * accordingly.
1875                  */
1876                 alt_reloc = insn_reloc(file, insn);
1877                 if (alt_reloc && arch_pc_relative_reloc(alt_reloc) &&
1878                     !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1879
1880                         WARN_INSN(insn, "unsupported relocation in alternatives section");
1881                         return -1;
1882                 }
1883
1884                 if (!is_static_jump(insn))
1885                         continue;
1886
1887                 if (!insn->immediate)
1888                         continue;
1889
1890                 dest_off = arch_jump_destination(insn);
1891                 if (dest_off == special_alt->new_off + special_alt->new_len) {
1892                         insn->jump_dest = next_insn_same_sec(file, orig_alt_group->last_insn);
1893                         if (!insn->jump_dest) {
1894                                 WARN_INSN(insn, "can't find alternative jump destination");
1895                                 return -1;
1896                         }
1897                 }
1898         }
1899
1900         if (!last_new_insn) {
1901                 WARN_FUNC("can't find last new alternative instruction",
1902                           special_alt->new_sec, special_alt->new_off);
1903                 return -1;
1904         }
1905
1906 end:
1907         new_alt_group->orig_group = orig_alt_group;
1908         new_alt_group->first_insn = *new_insn;
1909         new_alt_group->last_insn = last_new_insn;
1910         new_alt_group->nop = nop;
1911         new_alt_group->cfi = orig_alt_group->cfi;
1912         return 0;
1913 }
1914
1915 /*
1916  * A jump table entry can either convert a nop to a jump or a jump to a nop.
1917  * If the original instruction is a jump, make the alt entry an effective nop
1918  * by just skipping the original instruction.
1919  */
1920 static int handle_jump_alt(struct objtool_file *file,
1921                            struct special_alt *special_alt,
1922                            struct instruction *orig_insn,
1923                            struct instruction **new_insn)
1924 {
1925         if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1926             orig_insn->type != INSN_NOP) {
1927
1928                 WARN_INSN(orig_insn, "unsupported instruction at jump label");
1929                 return -1;
1930         }
1931
1932         if (opts.hack_jump_label && special_alt->key_addend & 2) {
1933                 struct reloc *reloc = insn_reloc(file, orig_insn);
1934
1935                 if (reloc) {
1936                         reloc->type = R_NONE;
1937                         elf_write_reloc(file->elf, reloc);
1938                 }
1939                 elf_write_insn(file->elf, orig_insn->sec,
1940                                orig_insn->offset, orig_insn->len,
1941                                arch_nop_insn(orig_insn->len));
1942                 orig_insn->type = INSN_NOP;
1943         }
1944
1945         if (orig_insn->type == INSN_NOP) {
1946                 if (orig_insn->len == 2)
1947                         file->jl_nop_short++;
1948                 else
1949                         file->jl_nop_long++;
1950
1951                 return 0;
1952         }
1953
1954         if (orig_insn->len == 2)
1955                 file->jl_short++;
1956         else
1957                 file->jl_long++;
1958
1959         *new_insn = next_insn_same_sec(file, orig_insn);
1960         return 0;
1961 }
1962
1963 /*
1964  * Read all the special sections which have alternate instructions which can be
1965  * patched in or redirected to at runtime.  Each instruction having alternate
1966  * instruction(s) has them added to its insn->alts list, which will be
1967  * traversed in validate_branch().
1968  */
1969 static int add_special_section_alts(struct objtool_file *file)
1970 {
1971         struct list_head special_alts;
1972         struct instruction *orig_insn, *new_insn;
1973         struct special_alt *special_alt, *tmp;
1974         struct alternative *alt;
1975         int ret;
1976
1977         ret = special_get_alts(file->elf, &special_alts);
1978         if (ret)
1979                 return ret;
1980
1981         list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1982
1983                 orig_insn = find_insn(file, special_alt->orig_sec,
1984                                       special_alt->orig_off);
1985                 if (!orig_insn) {
1986                         WARN_FUNC("special: can't find orig instruction",
1987                                   special_alt->orig_sec, special_alt->orig_off);
1988                         ret = -1;
1989                         goto out;
1990                 }
1991
1992                 new_insn = NULL;
1993                 if (!special_alt->group || special_alt->new_len) {
1994                         new_insn = find_insn(file, special_alt->new_sec,
1995                                              special_alt->new_off);
1996                         if (!new_insn) {
1997                                 WARN_FUNC("special: can't find new instruction",
1998                                           special_alt->new_sec,
1999                                           special_alt->new_off);
2000                                 ret = -1;
2001                                 goto out;
2002                         }
2003                 }
2004
2005                 if (special_alt->group) {
2006                         if (!special_alt->orig_len) {
2007                                 WARN_INSN(orig_insn, "empty alternative entry");
2008                                 continue;
2009                         }
2010
2011                         ret = handle_group_alt(file, special_alt, orig_insn,
2012                                                &new_insn);
2013                         if (ret)
2014                                 goto out;
2015                 } else if (special_alt->jump_or_nop) {
2016                         ret = handle_jump_alt(file, special_alt, orig_insn,
2017                                               &new_insn);
2018                         if (ret)
2019                                 goto out;
2020                 }
2021
2022                 alt = malloc(sizeof(*alt));
2023                 if (!alt) {
2024                         WARN("malloc failed");
2025                         ret = -1;
2026                         goto out;
2027                 }
2028
2029                 alt->insn = new_insn;
2030                 alt->skip_orig = special_alt->skip_orig;
2031                 orig_insn->ignore_alts |= special_alt->skip_alt;
2032                 alt->next = orig_insn->alts;
2033                 orig_insn->alts = alt;
2034
2035                 list_del(&special_alt->list);
2036                 free(special_alt);
2037         }
2038
2039         if (opts.stats) {
2040                 printf("jl\\\tNOP\tJMP\n");
2041                 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
2042                 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
2043         }
2044
2045 out:
2046         return ret;
2047 }
2048
2049 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
2050                             struct reloc *table)
2051 {
2052         struct reloc *reloc = table;
2053         struct instruction *dest_insn;
2054         struct alternative *alt;
2055         struct symbol *pfunc = insn_func(insn)->pfunc;
2056         unsigned int prev_offset = 0;
2057
2058         /*
2059          * Each @reloc is a switch table relocation which points to the target
2060          * instruction.
2061          */
2062         list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
2063
2064                 /* Check for the end of the table: */
2065                 if (reloc != table && reloc->jump_table_start)
2066                         break;
2067
2068                 /* Make sure the table entries are consecutive: */
2069                 if (prev_offset && reloc->offset != prev_offset + 8)
2070                         break;
2071
2072                 /* Detect function pointers from contiguous objects: */
2073                 if (reloc->sym->sec == pfunc->sec &&
2074                     reloc->addend == pfunc->offset)
2075                         break;
2076
2077                 dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
2078                 if (!dest_insn)
2079                         break;
2080
2081                 /* Make sure the destination is in the same function: */
2082                 if (!insn_func(dest_insn) || insn_func(dest_insn)->pfunc != pfunc)
2083                         break;
2084
2085                 alt = malloc(sizeof(*alt));
2086                 if (!alt) {
2087                         WARN("malloc failed");
2088                         return -1;
2089                 }
2090
2091                 alt->insn = dest_insn;
2092                 alt->next = insn->alts;
2093                 insn->alts = alt;
2094                 prev_offset = reloc->offset;
2095         }
2096
2097         if (!prev_offset) {
2098                 WARN_INSN(insn, "can't find switch jump table");
2099                 return -1;
2100         }
2101
2102         return 0;
2103 }
2104
2105 /*
2106  * find_jump_table() - Given a dynamic jump, find the switch jump table
2107  * associated with it.
2108  */
2109 static struct reloc *find_jump_table(struct objtool_file *file,
2110                                       struct symbol *func,
2111                                       struct instruction *insn)
2112 {
2113         struct reloc *table_reloc;
2114         struct instruction *dest_insn, *orig_insn = insn;
2115
2116         /*
2117          * Backward search using the @first_jump_src links, these help avoid
2118          * much of the 'in between' code. Which avoids us getting confused by
2119          * it.
2120          */
2121         for (;
2122              insn && insn_func(insn) && insn_func(insn)->pfunc == func;
2123              insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
2124
2125                 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
2126                         break;
2127
2128                 /* allow small jumps within the range */
2129                 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
2130                     insn->jump_dest &&
2131                     (insn->jump_dest->offset <= insn->offset ||
2132                      insn->jump_dest->offset > orig_insn->offset))
2133                     break;
2134
2135                 table_reloc = arch_find_switch_table(file, insn);
2136                 if (!table_reloc)
2137                         continue;
2138                 dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
2139                 if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
2140                         continue;
2141
2142                 return table_reloc;
2143         }
2144
2145         return NULL;
2146 }
2147
2148 /*
2149  * First pass: Mark the head of each jump table so that in the next pass,
2150  * we know when a given jump table ends and the next one starts.
2151  */
2152 static void mark_func_jump_tables(struct objtool_file *file,
2153                                     struct symbol *func)
2154 {
2155         struct instruction *insn, *last = NULL;
2156         struct reloc *reloc;
2157
2158         func_for_each_insn(file, func, insn) {
2159                 if (!last)
2160                         last = insn;
2161
2162                 /*
2163                  * Store back-pointers for unconditional forward jumps such
2164                  * that find_jump_table() can back-track using those and
2165                  * avoid some potentially confusing code.
2166                  */
2167                 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
2168                     insn->offset > last->offset &&
2169                     insn->jump_dest->offset > insn->offset &&
2170                     !insn->jump_dest->first_jump_src) {
2171
2172                         insn->jump_dest->first_jump_src = insn;
2173                         last = insn->jump_dest;
2174                 }
2175
2176                 if (insn->type != INSN_JUMP_DYNAMIC)
2177                         continue;
2178
2179                 reloc = find_jump_table(file, func, insn);
2180                 if (reloc) {
2181                         reloc->jump_table_start = true;
2182                         insn->_jump_table = reloc;
2183                 }
2184         }
2185 }
2186
2187 static int add_func_jump_tables(struct objtool_file *file,
2188                                   struct symbol *func)
2189 {
2190         struct instruction *insn;
2191         int ret;
2192
2193         func_for_each_insn(file, func, insn) {
2194                 if (!insn_jump_table(insn))
2195                         continue;
2196
2197                 ret = add_jump_table(file, insn, insn_jump_table(insn));
2198                 if (ret)
2199                         return ret;
2200         }
2201
2202         return 0;
2203 }
2204
2205 /*
2206  * For some switch statements, gcc generates a jump table in the .rodata
2207  * section which contains a list of addresses within the function to jump to.
2208  * This finds these jump tables and adds them to the insn->alts lists.
2209  */
2210 static int add_jump_table_alts(struct objtool_file *file)
2211 {
2212         struct symbol *func;
2213         int ret;
2214
2215         if (!file->rodata)
2216                 return 0;
2217
2218         for_each_sym(file, func) {
2219                 if (func->type != STT_FUNC)
2220                         continue;
2221
2222                 mark_func_jump_tables(file, func);
2223                 ret = add_func_jump_tables(file, func);
2224                 if (ret)
2225                         return ret;
2226         }
2227
2228         return 0;
2229 }
2230
2231 static void set_func_state(struct cfi_state *state)
2232 {
2233         state->cfa = initial_func_cfi.cfa;
2234         memcpy(&state->regs, &initial_func_cfi.regs,
2235                CFI_NUM_REGS * sizeof(struct cfi_reg));
2236         state->stack_size = initial_func_cfi.cfa.offset;
2237         state->type = UNWIND_HINT_TYPE_CALL;
2238 }
2239
2240 static int read_unwind_hints(struct objtool_file *file)
2241 {
2242         struct cfi_state cfi = init_cfi;
2243         struct section *sec, *relocsec;
2244         struct unwind_hint *hint;
2245         struct instruction *insn;
2246         struct reloc *reloc;
2247         int i;
2248
2249         sec = find_section_by_name(file->elf, ".discard.unwind_hints");
2250         if (!sec)
2251                 return 0;
2252
2253         relocsec = sec->reloc;
2254         if (!relocsec) {
2255                 WARN("missing .rela.discard.unwind_hints section");
2256                 return -1;
2257         }
2258
2259         if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
2260                 WARN("struct unwind_hint size mismatch");
2261                 return -1;
2262         }
2263
2264         file->hints = true;
2265
2266         for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
2267                 hint = (struct unwind_hint *)sec->data->d_buf + i;
2268
2269                 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
2270                 if (!reloc) {
2271                         WARN("can't find reloc for unwind_hints[%d]", i);
2272                         return -1;
2273                 }
2274
2275                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2276                 if (!insn) {
2277                         WARN("can't find insn for unwind_hints[%d]", i);
2278                         return -1;
2279                 }
2280
2281                 insn->hint = true;
2282
2283                 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
2284                         insn->hint = false;
2285                         insn->save = true;
2286                         continue;
2287                 }
2288
2289                 if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
2290                         insn->restore = true;
2291                         continue;
2292                 }
2293
2294                 if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
2295                         struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
2296
2297                         if (sym && sym->bind == STB_GLOBAL) {
2298                                 if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) {
2299                                         WARN_INSN(insn, "UNWIND_HINT_IRET_REGS without ENDBR");
2300                                 }
2301                         }
2302                 }
2303
2304                 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
2305                         insn->cfi = &func_cfi;
2306                         continue;
2307                 }
2308
2309                 if (insn->cfi)
2310                         cfi = *(insn->cfi);
2311
2312                 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
2313                         WARN_INSN(insn, "unsupported unwind_hint sp base reg %d", hint->sp_reg);
2314                         return -1;
2315                 }
2316
2317                 cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
2318                 cfi.type = hint->type;
2319                 cfi.signal = hint->signal;
2320
2321                 insn->cfi = cfi_hash_find_or_add(&cfi);
2322         }
2323
2324         return 0;
2325 }
2326
2327 static int read_noendbr_hints(struct objtool_file *file)
2328 {
2329         struct section *sec;
2330         struct instruction *insn;
2331         struct reloc *reloc;
2332
2333         sec = find_section_by_name(file->elf, ".rela.discard.noendbr");
2334         if (!sec)
2335                 return 0;
2336
2337         list_for_each_entry(reloc, &sec->reloc_list, list) {
2338                 insn = find_insn(file, reloc->sym->sec, reloc->sym->offset + reloc->addend);
2339                 if (!insn) {
2340                         WARN("bad .discard.noendbr entry");
2341                         return -1;
2342                 }
2343
2344                 insn->noendbr = 1;
2345         }
2346
2347         return 0;
2348 }
2349
2350 static int read_retpoline_hints(struct objtool_file *file)
2351 {
2352         struct section *sec;
2353         struct instruction *insn;
2354         struct reloc *reloc;
2355
2356         sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
2357         if (!sec)
2358                 return 0;
2359
2360         list_for_each_entry(reloc, &sec->reloc_list, list) {
2361                 if (reloc->sym->type != STT_SECTION) {
2362                         WARN("unexpected relocation symbol type in %s", sec->name);
2363                         return -1;
2364                 }
2365
2366                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2367                 if (!insn) {
2368                         WARN("bad .discard.retpoline_safe entry");
2369                         return -1;
2370                 }
2371
2372                 if (insn->type != INSN_JUMP_DYNAMIC &&
2373                     insn->type != INSN_CALL_DYNAMIC &&
2374                     insn->type != INSN_RETURN &&
2375                     insn->type != INSN_NOP) {
2376                         WARN_INSN(insn, "retpoline_safe hint not an indirect jump/call/ret/nop");
2377                         return -1;
2378                 }
2379
2380                 insn->retpoline_safe = true;
2381         }
2382
2383         return 0;
2384 }
2385
2386 static int read_instr_hints(struct objtool_file *file)
2387 {
2388         struct section *sec;
2389         struct instruction *insn;
2390         struct reloc *reloc;
2391
2392         sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2393         if (!sec)
2394                 return 0;
2395
2396         list_for_each_entry(reloc, &sec->reloc_list, list) {
2397                 if (reloc->sym->type != STT_SECTION) {
2398                         WARN("unexpected relocation symbol type in %s", sec->name);
2399                         return -1;
2400                 }
2401
2402                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2403                 if (!insn) {
2404                         WARN("bad .discard.instr_end entry");
2405                         return -1;
2406                 }
2407
2408                 insn->instr--;
2409         }
2410
2411         sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2412         if (!sec)
2413                 return 0;
2414
2415         list_for_each_entry(reloc, &sec->reloc_list, list) {
2416                 if (reloc->sym->type != STT_SECTION) {
2417                         WARN("unexpected relocation symbol type in %s", sec->name);
2418                         return -1;
2419                 }
2420
2421                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2422                 if (!insn) {
2423                         WARN("bad .discard.instr_begin entry");
2424                         return -1;
2425                 }
2426
2427                 insn->instr++;
2428         }
2429
2430         return 0;
2431 }
2432
2433 static int read_validate_unret_hints(struct objtool_file *file)
2434 {
2435         struct section *sec;
2436         struct instruction *insn;
2437         struct reloc *reloc;
2438
2439         sec = find_section_by_name(file->elf, ".rela.discard.validate_unret");
2440         if (!sec)
2441                 return 0;
2442
2443         list_for_each_entry(reloc, &sec->reloc_list, list) {
2444                 if (reloc->sym->type != STT_SECTION) {
2445                         WARN("unexpected relocation symbol type in %s", sec->name);
2446                         return -1;
2447                 }
2448
2449                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2450                 if (!insn) {
2451                         WARN("bad .discard.instr_end entry");
2452                         return -1;
2453                 }
2454                 insn->unret = 1;
2455         }
2456
2457         return 0;
2458 }
2459
2460
2461 static int read_intra_function_calls(struct objtool_file *file)
2462 {
2463         struct instruction *insn;
2464         struct section *sec;
2465         struct reloc *reloc;
2466
2467         sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2468         if (!sec)
2469                 return 0;
2470
2471         list_for_each_entry(reloc, &sec->reloc_list, list) {
2472                 unsigned long dest_off;
2473
2474                 if (reloc->sym->type != STT_SECTION) {
2475                         WARN("unexpected relocation symbol type in %s",
2476                              sec->name);
2477                         return -1;
2478                 }
2479
2480                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
2481                 if (!insn) {
2482                         WARN("bad .discard.intra_function_call entry");
2483                         return -1;
2484                 }
2485
2486                 if (insn->type != INSN_CALL) {
2487                         WARN_INSN(insn, "intra_function_call not a direct call");
2488                         return -1;
2489                 }
2490
2491                 /*
2492                  * Treat intra-function CALLs as JMPs, but with a stack_op.
2493                  * See add_call_destinations(), which strips stack_ops from
2494                  * normal CALLs.
2495                  */
2496                 insn->type = INSN_JUMP_UNCONDITIONAL;
2497
2498                 dest_off = arch_jump_destination(insn);
2499                 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2500                 if (!insn->jump_dest) {
2501                         WARN_INSN(insn, "can't find call dest at %s+0x%lx",
2502                                   insn->sec->name, dest_off);
2503                         return -1;
2504                 }
2505         }
2506
2507         return 0;
2508 }
2509
2510 /*
2511  * Return true if name matches an instrumentation function, where calls to that
2512  * function from noinstr code can safely be removed, but compilers won't do so.
2513  */
2514 static bool is_profiling_func(const char *name)
2515 {
2516         /*
2517          * Many compilers cannot disable KCOV with a function attribute.
2518          */
2519         if (!strncmp(name, "__sanitizer_cov_", 16))
2520                 return true;
2521
2522         /*
2523          * Some compilers currently do not remove __tsan_func_entry/exit nor
2524          * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2525          * the __no_sanitize_thread attribute, remove them. Once the kernel's
2526          * minimum Clang version is 14.0, this can be removed.
2527          */
2528         if (!strncmp(name, "__tsan_func_", 12) ||
2529             !strcmp(name, "__tsan_atomic_signal_fence"))
2530                 return true;
2531
2532         return false;
2533 }
2534
2535 static int classify_symbols(struct objtool_file *file)
2536 {
2537         struct symbol *func;
2538
2539         for_each_sym(file, func) {
2540                 if (func->bind != STB_GLOBAL)
2541                         continue;
2542
2543                 if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2544                              strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2545                         func->static_call_tramp = true;
2546
2547                 if (arch_is_retpoline(func))
2548                         func->retpoline_thunk = true;
2549
2550                 if (arch_is_rethunk(func))
2551                         func->return_thunk = true;
2552
2553                 if (arch_ftrace_match(func->name))
2554                         func->fentry = true;
2555
2556                 if (is_profiling_func(func->name))
2557                         func->profiling_func = true;
2558         }
2559
2560         return 0;
2561 }
2562
2563 static void mark_rodata(struct objtool_file *file)
2564 {
2565         struct section *sec;
2566         bool found = false;
2567
2568         /*
2569          * Search for the following rodata sections, each of which can
2570          * potentially contain jump tables:
2571          *
2572          * - .rodata: can contain GCC switch tables
2573          * - .rodata.<func>: same, if -fdata-sections is being used
2574          * - .rodata..c_jump_table: contains C annotated jump tables
2575          *
2576          * .rodata.str1.* sections are ignored; they don't contain jump tables.
2577          */
2578         for_each_sec(file, sec) {
2579                 if (!strncmp(sec->name, ".rodata", 7) &&
2580                     !strstr(sec->name, ".str1.")) {
2581                         sec->rodata = true;
2582                         found = true;
2583                 }
2584         }
2585
2586         file->rodata = found;
2587 }
2588
2589 static int decode_sections(struct objtool_file *file)
2590 {
2591         int ret;
2592
2593         mark_rodata(file);
2594
2595         ret = init_pv_ops(file);
2596         if (ret)
2597                 return ret;
2598
2599         /*
2600          * Must be before add_{jump_call}_destination.
2601          */
2602         ret = classify_symbols(file);
2603         if (ret)
2604                 return ret;
2605
2606         ret = decode_instructions(file);
2607         if (ret)
2608                 return ret;
2609
2610         add_ignores(file);
2611         add_uaccess_safe(file);
2612
2613         ret = add_ignore_alternatives(file);
2614         if (ret)
2615                 return ret;
2616
2617         /*
2618          * Must be before read_unwind_hints() since that needs insn->noendbr.
2619          */
2620         ret = read_noendbr_hints(file);
2621         if (ret)
2622                 return ret;
2623
2624         /*
2625          * Must be before add_jump_destinations(), which depends on 'func'
2626          * being set for alternatives, to enable proper sibling call detection.
2627          */
2628         if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) {
2629                 ret = add_special_section_alts(file);
2630                 if (ret)
2631                         return ret;
2632         }
2633
2634         ret = add_jump_destinations(file);
2635         if (ret)
2636                 return ret;
2637
2638         /*
2639          * Must be before add_call_destination(); it changes INSN_CALL to
2640          * INSN_JUMP.
2641          */
2642         ret = read_intra_function_calls(file);
2643         if (ret)
2644                 return ret;
2645
2646         ret = add_call_destinations(file);
2647         if (ret)
2648                 return ret;
2649
2650         /*
2651          * Must be after add_call_destinations() such that it can override
2652          * dead_end_function() marks.
2653          */
2654         ret = add_dead_ends(file);
2655         if (ret)
2656                 return ret;
2657
2658         ret = add_jump_table_alts(file);
2659         if (ret)
2660                 return ret;
2661
2662         ret = read_unwind_hints(file);
2663         if (ret)
2664                 return ret;
2665
2666         ret = read_retpoline_hints(file);
2667         if (ret)
2668                 return ret;
2669
2670         ret = read_instr_hints(file);
2671         if (ret)
2672                 return ret;
2673
2674         ret = read_validate_unret_hints(file);
2675         if (ret)
2676                 return ret;
2677
2678         return 0;
2679 }
2680
2681 static bool is_fentry_call(struct instruction *insn)
2682 {
2683         if (insn->type == INSN_CALL &&
2684             insn_call_dest(insn) &&
2685             insn_call_dest(insn)->fentry)
2686                 return true;
2687
2688         return false;
2689 }
2690
2691 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2692 {
2693         struct cfi_state *cfi = &state->cfi;
2694         int i;
2695
2696         if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2697                 return true;
2698
2699         if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2700                 return true;
2701
2702         if (cfi->stack_size != initial_func_cfi.cfa.offset)
2703                 return true;
2704
2705         for (i = 0; i < CFI_NUM_REGS; i++) {
2706                 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2707                     cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2708                         return true;
2709         }
2710
2711         return false;
2712 }
2713
2714 static bool check_reg_frame_pos(const struct cfi_reg *reg,
2715                                 int expected_offset)
2716 {
2717         return reg->base == CFI_CFA &&
2718                reg->offset == expected_offset;
2719 }
2720
2721 static bool has_valid_stack_frame(struct insn_state *state)
2722 {
2723         struct cfi_state *cfi = &state->cfi;
2724
2725         if (cfi->cfa.base == CFI_BP &&
2726             check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2727             check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2728                 return true;
2729
2730         if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2731                 return true;
2732
2733         return false;
2734 }
2735
2736 static int update_cfi_state_regs(struct instruction *insn,
2737                                   struct cfi_state *cfi,
2738                                   struct stack_op *op)
2739 {
2740         struct cfi_reg *cfa = &cfi->cfa;
2741
2742         if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2743                 return 0;
2744
2745         /* push */
2746         if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2747                 cfa->offset += 8;
2748
2749         /* pop */
2750         if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2751                 cfa->offset -= 8;
2752
2753         /* add immediate to sp */
2754         if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2755             op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2756                 cfa->offset -= op->src.offset;
2757
2758         return 0;
2759 }
2760
2761 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2762 {
2763         if (arch_callee_saved_reg(reg) &&
2764             cfi->regs[reg].base == CFI_UNDEFINED) {
2765                 cfi->regs[reg].base = base;
2766                 cfi->regs[reg].offset = offset;
2767         }
2768 }
2769
2770 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2771 {
2772         cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2773         cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2774 }
2775
2776 /*
2777  * A note about DRAP stack alignment:
2778  *
2779  * GCC has the concept of a DRAP register, which is used to help keep track of
2780  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
2781  * register.  The typical DRAP pattern is:
2782  *
2783  *   4c 8d 54 24 08             lea    0x8(%rsp),%r10
2784  *   48 83 e4 c0                and    $0xffffffffffffffc0,%rsp
2785  *   41 ff 72 f8                pushq  -0x8(%r10)
2786  *   55                         push   %rbp
2787  *   48 89 e5                   mov    %rsp,%rbp
2788  *                              (more pushes)
2789  *   41 52                      push   %r10
2790  *                              ...
2791  *   41 5a                      pop    %r10
2792  *                              (more pops)
2793  *   5d                         pop    %rbp
2794  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2795  *   c3                         retq
2796  *
2797  * There are some variations in the epilogues, like:
2798  *
2799  *   5b                         pop    %rbx
2800  *   41 5a                      pop    %r10
2801  *   41 5c                      pop    %r12
2802  *   41 5d                      pop    %r13
2803  *   41 5e                      pop    %r14
2804  *   c9                         leaveq
2805  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2806  *   c3                         retq
2807  *
2808  * and:
2809  *
2810  *   4c 8b 55 e8                mov    -0x18(%rbp),%r10
2811  *   48 8b 5d e0                mov    -0x20(%rbp),%rbx
2812  *   4c 8b 65 f0                mov    -0x10(%rbp),%r12
2813  *   4c 8b 6d f8                mov    -0x8(%rbp),%r13
2814  *   c9                         leaveq
2815  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2816  *   c3                         retq
2817  *
2818  * Sometimes r13 is used as the DRAP register, in which case it's saved and
2819  * restored beforehand:
2820  *
2821  *   41 55                      push   %r13
2822  *   4c 8d 6c 24 10             lea    0x10(%rsp),%r13
2823  *   48 83 e4 f0                and    $0xfffffffffffffff0,%rsp
2824  *                              ...
2825  *   49 8d 65 f0                lea    -0x10(%r13),%rsp
2826  *   41 5d                      pop    %r13
2827  *   c3                         retq
2828  */
2829 static int update_cfi_state(struct instruction *insn,
2830                             struct instruction *next_insn,
2831                             struct cfi_state *cfi, struct stack_op *op)
2832 {
2833         struct cfi_reg *cfa = &cfi->cfa;
2834         struct cfi_reg *regs = cfi->regs;
2835
2836         /* stack operations don't make sense with an undefined CFA */
2837         if (cfa->base == CFI_UNDEFINED) {
2838                 if (insn_func(insn)) {
2839                         WARN_INSN(insn, "undefined stack state");
2840                         return -1;
2841                 }
2842                 return 0;
2843         }
2844
2845         if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2846             cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2847                 return update_cfi_state_regs(insn, cfi, op);
2848
2849         switch (op->dest.type) {
2850
2851         case OP_DEST_REG:
2852                 switch (op->src.type) {
2853
2854                 case OP_SRC_REG:
2855                         if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2856                             cfa->base == CFI_SP &&
2857                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset)) {
2858
2859                                 /* mov %rsp, %rbp */
2860                                 cfa->base = op->dest.reg;
2861                                 cfi->bp_scratch = false;
2862                         }
2863
2864                         else if (op->src.reg == CFI_SP &&
2865                                  op->dest.reg == CFI_BP && cfi->drap) {
2866
2867                                 /* drap: mov %rsp, %rbp */
2868                                 regs[CFI_BP].base = CFI_BP;
2869                                 regs[CFI_BP].offset = -cfi->stack_size;
2870                                 cfi->bp_scratch = false;
2871                         }
2872
2873                         else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2874
2875                                 /*
2876                                  * mov %rsp, %reg
2877                                  *
2878                                  * This is needed for the rare case where GCC
2879                                  * does:
2880                                  *
2881                                  *   mov    %rsp, %rax
2882                                  *   ...
2883                                  *   mov    %rax, %rsp
2884                                  */
2885                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2886                                 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2887                         }
2888
2889                         else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2890                                  (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2891
2892                                 /*
2893                                  * mov %rbp, %rsp
2894                                  *
2895                                  * Restore the original stack pointer (Clang).
2896                                  */
2897                                 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2898                         }
2899
2900                         else if (op->dest.reg == cfa->base) {
2901
2902                                 /* mov %reg, %rsp */
2903                                 if (cfa->base == CFI_SP &&
2904                                     cfi->vals[op->src.reg].base == CFI_CFA) {
2905
2906                                         /*
2907                                          * This is needed for the rare case
2908                                          * where GCC does something dumb like:
2909                                          *
2910                                          *   lea    0x8(%rsp), %rcx
2911                                          *   ...
2912                                          *   mov    %rcx, %rsp
2913                                          */
2914                                         cfa->offset = -cfi->vals[op->src.reg].offset;
2915                                         cfi->stack_size = cfa->offset;
2916
2917                                 } else if (cfa->base == CFI_SP &&
2918                                            cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2919                                            cfi->vals[op->src.reg].offset == cfa->offset) {
2920
2921                                         /*
2922                                          * Stack swizzle:
2923                                          *
2924                                          * 1: mov %rsp, (%[tos])
2925                                          * 2: mov %[tos], %rsp
2926                                          *    ...
2927                                          * 3: pop %rsp
2928                                          *
2929                                          * Where:
2930                                          *
2931                                          * 1 - places a pointer to the previous
2932                                          *     stack at the Top-of-Stack of the
2933                                          *     new stack.
2934                                          *
2935                                          * 2 - switches to the new stack.
2936                                          *
2937                                          * 3 - pops the Top-of-Stack to restore
2938                                          *     the original stack.
2939                                          *
2940                                          * Note: we set base to SP_INDIRECT
2941                                          * here and preserve offset. Therefore
2942                                          * when the unwinder reaches ToS it
2943                                          * will dereference SP and then add the
2944                                          * offset to find the next frame, IOW:
2945                                          * (%rsp) + offset.
2946                                          */
2947                                         cfa->base = CFI_SP_INDIRECT;
2948
2949                                 } else {
2950                                         cfa->base = CFI_UNDEFINED;
2951                                         cfa->offset = 0;
2952                                 }
2953                         }
2954
2955                         else if (op->dest.reg == CFI_SP &&
2956                                  cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2957                                  cfi->vals[op->src.reg].offset == cfa->offset) {
2958
2959                                 /*
2960                                  * The same stack swizzle case 2) as above. But
2961                                  * because we can't change cfa->base, case 3)
2962                                  * will become a regular POP. Pretend we're a
2963                                  * PUSH so things don't go unbalanced.
2964                                  */
2965                                 cfi->stack_size += 8;
2966                         }
2967
2968
2969                         break;
2970
2971                 case OP_SRC_ADD:
2972                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2973
2974                                 /* add imm, %rsp */
2975                                 cfi->stack_size -= op->src.offset;
2976                                 if (cfa->base == CFI_SP)
2977                                         cfa->offset -= op->src.offset;
2978                                 break;
2979                         }
2980
2981                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2982
2983                                 /* lea disp(%rbp), %rsp */
2984                                 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2985                                 break;
2986                         }
2987
2988                         if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2989
2990                                 /* drap: lea disp(%rsp), %drap */
2991                                 cfi->drap_reg = op->dest.reg;
2992
2993                                 /*
2994                                  * lea disp(%rsp), %reg
2995                                  *
2996                                  * This is needed for the rare case where GCC
2997                                  * does something dumb like:
2998                                  *
2999                                  *   lea    0x8(%rsp), %rcx
3000                                  *   ...
3001                                  *   mov    %rcx, %rsp
3002                                  */
3003                                 cfi->vals[op->dest.reg].base = CFI_CFA;
3004                                 cfi->vals[op->dest.reg].offset = \
3005                                         -cfi->stack_size + op->src.offset;
3006
3007                                 break;
3008                         }
3009
3010                         if (cfi->drap && op->dest.reg == CFI_SP &&
3011                             op->src.reg == cfi->drap_reg) {
3012
3013                                  /* drap: lea disp(%drap), %rsp */
3014                                 cfa->base = CFI_SP;
3015                                 cfa->offset = cfi->stack_size = -op->src.offset;
3016                                 cfi->drap_reg = CFI_UNDEFINED;
3017                                 cfi->drap = false;
3018                                 break;
3019                         }
3020
3021                         if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
3022                                 WARN_INSN(insn, "unsupported stack register modification");
3023                                 return -1;
3024                         }
3025
3026                         break;
3027
3028                 case OP_SRC_AND:
3029                         if (op->dest.reg != CFI_SP ||
3030                             (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
3031                             (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
3032                                 WARN_INSN(insn, "unsupported stack pointer realignment");
3033                                 return -1;
3034                         }
3035
3036                         if (cfi->drap_reg != CFI_UNDEFINED) {
3037                                 /* drap: and imm, %rsp */
3038                                 cfa->base = cfi->drap_reg;
3039                                 cfa->offset = cfi->stack_size = 0;
3040                                 cfi->drap = true;
3041                         }
3042
3043                         /*
3044                          * Older versions of GCC (4.8ish) realign the stack
3045                          * without DRAP, with a frame pointer.
3046                          */
3047
3048                         break;
3049
3050                 case OP_SRC_POP:
3051                 case OP_SRC_POPF:
3052                         if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
3053
3054                                 /* pop %rsp; # restore from a stack swizzle */
3055                                 cfa->base = CFI_SP;
3056                                 break;
3057                         }
3058
3059                         if (!cfi->drap && op->dest.reg == cfa->base) {
3060
3061                                 /* pop %rbp */
3062                                 cfa->base = CFI_SP;
3063                         }
3064
3065                         if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
3066                             op->dest.reg == cfi->drap_reg &&
3067                             cfi->drap_offset == -cfi->stack_size) {
3068
3069                                 /* drap: pop %drap */
3070                                 cfa->base = cfi->drap_reg;
3071                                 cfa->offset = 0;
3072                                 cfi->drap_offset = -1;
3073
3074                         } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
3075
3076                                 /* pop %reg */
3077                                 restore_reg(cfi, op->dest.reg);
3078                         }
3079
3080                         cfi->stack_size -= 8;
3081                         if (cfa->base == CFI_SP)
3082                                 cfa->offset -= 8;
3083
3084                         break;
3085
3086                 case OP_SRC_REG_INDIRECT:
3087                         if (!cfi->drap && op->dest.reg == cfa->base &&
3088                             op->dest.reg == CFI_BP) {
3089
3090                                 /* mov disp(%rsp), %rbp */
3091                                 cfa->base = CFI_SP;
3092                                 cfa->offset = cfi->stack_size;
3093                         }
3094
3095                         if (cfi->drap && op->src.reg == CFI_BP &&
3096                             op->src.offset == cfi->drap_offset) {
3097
3098                                 /* drap: mov disp(%rbp), %drap */
3099                                 cfa->base = cfi->drap_reg;
3100                                 cfa->offset = 0;
3101                                 cfi->drap_offset = -1;
3102                         }
3103
3104                         if (cfi->drap && op->src.reg == CFI_BP &&
3105                             op->src.offset == regs[op->dest.reg].offset) {
3106
3107                                 /* drap: mov disp(%rbp), %reg */
3108                                 restore_reg(cfi, op->dest.reg);
3109
3110                         } else if (op->src.reg == cfa->base &&
3111                             op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
3112
3113                                 /* mov disp(%rbp), %reg */
3114                                 /* mov disp(%rsp), %reg */
3115                                 restore_reg(cfi, op->dest.reg);
3116
3117                         } else if (op->src.reg == CFI_SP &&
3118                                    op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
3119
3120                                 /* mov disp(%rsp), %reg */
3121                                 restore_reg(cfi, op->dest.reg);
3122                         }
3123
3124                         break;
3125
3126                 default:
3127                         WARN_INSN(insn, "unknown stack-related instruction");
3128                         return -1;
3129                 }
3130
3131                 break;
3132
3133         case OP_DEST_PUSH:
3134         case OP_DEST_PUSHF:
3135                 cfi->stack_size += 8;
3136                 if (cfa->base == CFI_SP)
3137                         cfa->offset += 8;
3138
3139                 if (op->src.type != OP_SRC_REG)
3140                         break;
3141
3142                 if (cfi->drap) {
3143                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3144
3145                                 /* drap: push %drap */
3146                                 cfa->base = CFI_BP_INDIRECT;
3147                                 cfa->offset = -cfi->stack_size;
3148
3149                                 /* save drap so we know when to restore it */
3150                                 cfi->drap_offset = -cfi->stack_size;
3151
3152                         } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
3153
3154                                 /* drap: push %rbp */
3155                                 cfi->stack_size = 0;
3156
3157                         } else {
3158
3159                                 /* drap: push %reg */
3160                                 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
3161                         }
3162
3163                 } else {
3164
3165                         /* push %reg */
3166                         save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
3167                 }
3168
3169                 /* detect when asm code uses rbp as a scratch register */
3170                 if (opts.stackval && insn_func(insn) && op->src.reg == CFI_BP &&
3171                     cfa->base != CFI_BP)
3172                         cfi->bp_scratch = true;
3173                 break;
3174
3175         case OP_DEST_REG_INDIRECT:
3176
3177                 if (cfi->drap) {
3178                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3179
3180                                 /* drap: mov %drap, disp(%rbp) */
3181                                 cfa->base = CFI_BP_INDIRECT;
3182                                 cfa->offset = op->dest.offset;
3183
3184                                 /* save drap offset so we know when to restore it */
3185                                 cfi->drap_offset = op->dest.offset;
3186                         } else {
3187
3188                                 /* drap: mov reg, disp(%rbp) */
3189                                 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
3190                         }
3191
3192                 } else if (op->dest.reg == cfa->base) {
3193
3194                         /* mov reg, disp(%rbp) */
3195                         /* mov reg, disp(%rsp) */
3196                         save_reg(cfi, op->src.reg, CFI_CFA,
3197                                  op->dest.offset - cfi->cfa.offset);
3198
3199                 } else if (op->dest.reg == CFI_SP) {
3200
3201                         /* mov reg, disp(%rsp) */
3202                         save_reg(cfi, op->src.reg, CFI_CFA,
3203                                  op->dest.offset - cfi->stack_size);
3204
3205                 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
3206
3207                         /* mov %rsp, (%reg); # setup a stack swizzle. */
3208                         cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
3209                         cfi->vals[op->dest.reg].offset = cfa->offset;
3210                 }
3211
3212                 break;
3213
3214         case OP_DEST_MEM:
3215                 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
3216                         WARN_INSN(insn, "unknown stack-related memory operation");
3217                         return -1;
3218                 }
3219
3220                 /* pop mem */
3221                 cfi->stack_size -= 8;
3222                 if (cfa->base == CFI_SP)
3223                         cfa->offset -= 8;
3224
3225                 break;
3226
3227         default:
3228                 WARN_INSN(insn, "unknown stack-related instruction");
3229                 return -1;
3230         }
3231
3232         return 0;
3233 }
3234
3235 /*
3236  * The stack layouts of alternatives instructions can sometimes diverge when
3237  * they have stack modifications.  That's fine as long as the potential stack
3238  * layouts don't conflict at any given potential instruction boundary.
3239  *
3240  * Flatten the CFIs of the different alternative code streams (both original
3241  * and replacement) into a single shared CFI array which can be used to detect
3242  * conflicts and nicely feed a linear array of ORC entries to the unwinder.
3243  */
3244 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
3245 {
3246         struct cfi_state **alt_cfi;
3247         int group_off;
3248
3249         if (!insn->alt_group)
3250                 return 0;
3251
3252         if (!insn->cfi) {
3253                 WARN("CFI missing");
3254                 return -1;
3255         }
3256
3257         alt_cfi = insn->alt_group->cfi;
3258         group_off = insn->offset - insn->alt_group->first_insn->offset;
3259
3260         if (!alt_cfi[group_off]) {
3261                 alt_cfi[group_off] = insn->cfi;
3262         } else {
3263                 if (cficmp(alt_cfi[group_off], insn->cfi)) {
3264                         struct alt_group *orig_group = insn->alt_group->orig_group ?: insn->alt_group;
3265                         struct instruction *orig = orig_group->first_insn;
3266                         char *where = offstr(insn->sec, insn->offset);
3267                         WARN_INSN(orig, "stack layout conflict in alternatives: %s", where);
3268                         free(where);
3269                         return -1;
3270                 }
3271         }
3272
3273         return 0;
3274 }
3275
3276 static int handle_insn_ops(struct instruction *insn,
3277                            struct instruction *next_insn,
3278                            struct insn_state *state)
3279 {
3280         struct stack_op *op;
3281
3282         for (op = insn->stack_ops; op; op = op->next) {
3283
3284                 if (update_cfi_state(insn, next_insn, &state->cfi, op))
3285                         return 1;
3286
3287                 if (!insn->alt_group)
3288                         continue;
3289
3290                 if (op->dest.type == OP_DEST_PUSHF) {
3291                         if (!state->uaccess_stack) {
3292                                 state->uaccess_stack = 1;
3293                         } else if (state->uaccess_stack >> 31) {
3294                                 WARN_INSN(insn, "PUSHF stack exhausted");
3295                                 return 1;
3296                         }
3297                         state->uaccess_stack <<= 1;
3298                         state->uaccess_stack  |= state->uaccess;
3299                 }
3300
3301                 if (op->src.type == OP_SRC_POPF) {
3302                         if (state->uaccess_stack) {
3303                                 state->uaccess = state->uaccess_stack & 1;
3304                                 state->uaccess_stack >>= 1;
3305                                 if (state->uaccess_stack == 1)
3306                                         state->uaccess_stack = 0;
3307                         }
3308                 }
3309         }
3310
3311         return 0;
3312 }
3313
3314 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
3315 {
3316         struct cfi_state *cfi1 = insn->cfi;
3317         int i;
3318
3319         if (!cfi1) {
3320                 WARN("CFI missing");
3321                 return false;
3322         }
3323
3324         if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
3325
3326                 WARN_INSN(insn, "stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
3327                           cfi1->cfa.base, cfi1->cfa.offset,
3328                           cfi2->cfa.base, cfi2->cfa.offset);
3329
3330         } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
3331                 for (i = 0; i < CFI_NUM_REGS; i++) {
3332                         if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
3333                                     sizeof(struct cfi_reg)))
3334                                 continue;
3335
3336                         WARN_INSN(insn, "stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
3337                                   i, cfi1->regs[i].base, cfi1->regs[i].offset,
3338                                   i, cfi2->regs[i].base, cfi2->regs[i].offset);
3339                         break;
3340                 }
3341
3342         } else if (cfi1->type != cfi2->type) {
3343
3344                 WARN_INSN(insn, "stack state mismatch: type1=%d type2=%d",
3345                           cfi1->type, cfi2->type);
3346
3347         } else if (cfi1->drap != cfi2->drap ||
3348                    (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
3349                    (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
3350
3351                 WARN_INSN(insn, "stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
3352                           cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
3353                           cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
3354
3355         } else
3356                 return true;
3357
3358         return false;
3359 }
3360
3361 static inline bool func_uaccess_safe(struct symbol *func)
3362 {
3363         if (func)
3364                 return func->uaccess_safe;
3365
3366         return false;
3367 }
3368
3369 static inline const char *call_dest_name(struct instruction *insn)
3370 {
3371         static char pvname[19];
3372         struct reloc *rel;
3373         int idx;
3374
3375         if (insn_call_dest(insn))
3376                 return insn_call_dest(insn)->name;
3377
3378         rel = insn_reloc(NULL, insn);
3379         if (rel && !strcmp(rel->sym->name, "pv_ops")) {
3380                 idx = (rel->addend / sizeof(void *));
3381                 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
3382                 return pvname;
3383         }
3384
3385         return "{dynamic}";
3386 }
3387
3388 static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3389 {
3390         struct symbol *target;
3391         struct reloc *rel;
3392         int idx;
3393
3394         rel = insn_reloc(file, insn);
3395         if (!rel || strcmp(rel->sym->name, "pv_ops"))
3396                 return false;
3397
3398         idx = (arch_dest_reloc_offset(rel->addend) / sizeof(void *));
3399
3400         if (file->pv_ops[idx].clean)
3401                 return true;
3402
3403         file->pv_ops[idx].clean = true;
3404
3405         list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3406                 if (!target->sec->noinstr) {
3407                         WARN("pv_ops[%d]: %s", idx, target->name);
3408                         file->pv_ops[idx].clean = false;
3409                 }
3410         }
3411
3412         return file->pv_ops[idx].clean;
3413 }
3414
3415 static inline bool noinstr_call_dest(struct objtool_file *file,
3416                                      struct instruction *insn,
3417                                      struct symbol *func)
3418 {
3419         /*
3420          * We can't deal with indirect function calls at present;
3421          * assume they're instrumented.
3422          */
3423         if (!func) {
3424                 if (file->pv_ops)
3425                         return pv_call_dest(file, insn);
3426
3427                 return false;
3428         }
3429
3430         /*
3431          * If the symbol is from a noinstr section; we good.
3432          */
3433         if (func->sec->noinstr)
3434                 return true;
3435
3436         /*
3437          * If the symbol is a static_call trampoline, we can't tell.
3438          */
3439         if (func->static_call_tramp)
3440                 return true;
3441
3442         /*
3443          * The __ubsan_handle_*() calls are like WARN(), they only happen when
3444          * something 'BAD' happened. At the risk of taking the machine down,
3445          * let them proceed to get the message out.
3446          */
3447         if (!strncmp(func->name, "__ubsan_handle_", 15))
3448                 return true;
3449
3450         return false;
3451 }
3452
3453 static int validate_call(struct objtool_file *file,
3454                          struct instruction *insn,
3455                          struct insn_state *state)
3456 {
3457         if (state->noinstr && state->instr <= 0 &&
3458             !noinstr_call_dest(file, insn, insn_call_dest(insn))) {
3459                 WARN_INSN(insn, "call to %s() leaves .noinstr.text section", call_dest_name(insn));
3460                 return 1;
3461         }
3462
3463         if (state->uaccess && !func_uaccess_safe(insn_call_dest(insn))) {
3464                 WARN_INSN(insn, "call to %s() with UACCESS enabled", call_dest_name(insn));
3465                 return 1;
3466         }
3467
3468         if (state->df) {
3469                 WARN_INSN(insn, "call to %s() with DF set", call_dest_name(insn));
3470                 return 1;
3471         }
3472
3473         return 0;
3474 }
3475
3476 static int validate_sibling_call(struct objtool_file *file,
3477                                  struct instruction *insn,
3478                                  struct insn_state *state)
3479 {
3480         if (insn_func(insn) && has_modified_stack_frame(insn, state)) {
3481                 WARN_INSN(insn, "sibling call from callable instruction with modified stack frame");
3482                 return 1;
3483         }
3484
3485         return validate_call(file, insn, state);
3486 }
3487
3488 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3489 {
3490         if (state->noinstr && state->instr > 0) {
3491                 WARN_INSN(insn, "return with instrumentation enabled");
3492                 return 1;
3493         }
3494
3495         if (state->uaccess && !func_uaccess_safe(func)) {
3496                 WARN_INSN(insn, "return with UACCESS enabled");
3497                 return 1;
3498         }
3499
3500         if (!state->uaccess && func_uaccess_safe(func)) {
3501                 WARN_INSN(insn, "return with UACCESS disabled from a UACCESS-safe function");
3502                 return 1;
3503         }
3504
3505         if (state->df) {
3506                 WARN_INSN(insn, "return with DF set");
3507                 return 1;
3508         }
3509
3510         if (func && has_modified_stack_frame(insn, state)) {
3511                 WARN_INSN(insn, "return with modified stack frame");
3512                 return 1;
3513         }
3514
3515         if (state->cfi.bp_scratch) {
3516                 WARN_INSN(insn, "BP used as a scratch register");
3517                 return 1;
3518         }
3519
3520         return 0;
3521 }
3522
3523 static struct instruction *next_insn_to_validate(struct objtool_file *file,
3524                                                  struct instruction *insn)
3525 {
3526         struct alt_group *alt_group = insn->alt_group;
3527
3528         /*
3529          * Simulate the fact that alternatives are patched in-place.  When the
3530          * end of a replacement alt_group is reached, redirect objtool flow to
3531          * the end of the original alt_group.
3532          *
3533          * insn->alts->insn -> alt_group->first_insn
3534          *                     ...
3535          *                     alt_group->last_insn
3536          *                     [alt_group->nop]      -> next(orig_group->last_insn)
3537          */
3538         if (alt_group) {
3539                 if (alt_group->nop) {
3540                         /* ->nop implies ->orig_group */
3541                         if (insn == alt_group->last_insn)
3542                                 return alt_group->nop;
3543                         if (insn == alt_group->nop)
3544                                 goto next_orig;
3545                 }
3546                 if (insn == alt_group->last_insn && alt_group->orig_group)
3547                         goto next_orig;
3548         }
3549
3550         return next_insn_same_sec(file, insn);
3551
3552 next_orig:
3553         return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3554 }
3555
3556 /*
3557  * Follow the branch starting at the given instruction, and recursively follow
3558  * any other branches (jumps).  Meanwhile, track the frame pointer state at
3559  * each instruction and validate all the rules described in
3560  * tools/objtool/Documentation/objtool.txt.
3561  */
3562 static int validate_branch(struct objtool_file *file, struct symbol *func,
3563                            struct instruction *insn, struct insn_state state)
3564 {
3565         struct alternative *alt;
3566         struct instruction *next_insn, *prev_insn = NULL;
3567         struct section *sec;
3568         u8 visited;
3569         int ret;
3570
3571         sec = insn->sec;
3572
3573         while (1) {
3574                 next_insn = next_insn_to_validate(file, insn);
3575
3576                 if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {
3577                         /* Ignore KCFI type preambles, which always fall through */
3578                         if (!strncmp(func->name, "__cfi_", 6) ||
3579                             !strncmp(func->name, "__pfx_", 6))
3580                                 return 0;
3581
3582                         WARN("%s() falls through to next function %s()",
3583                              func->name, insn_func(insn)->name);
3584                         return 1;
3585                 }
3586
3587                 if (func && insn->ignore) {
3588                         WARN_INSN(insn, "BUG: why am I validating an ignored function?");
3589                         return 1;
3590                 }
3591
3592                 visited = VISITED_BRANCH << state.uaccess;
3593                 if (insn->visited & VISITED_BRANCH_MASK) {
3594                         if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3595                                 return 1;
3596
3597                         if (insn->visited & visited)
3598                                 return 0;
3599                 } else {
3600                         nr_insns_visited++;
3601                 }
3602
3603                 if (state.noinstr)
3604                         state.instr += insn->instr;
3605
3606                 if (insn->hint) {
3607                         if (insn->restore) {
3608                                 struct instruction *save_insn, *i;
3609
3610                                 i = insn;
3611                                 save_insn = NULL;
3612
3613                                 sym_for_each_insn_continue_reverse(file, func, i) {
3614                                         if (i->save) {
3615                                                 save_insn = i;
3616                                                 break;
3617                                         }
3618                                 }
3619
3620                                 if (!save_insn) {
3621                                         WARN_INSN(insn, "no corresponding CFI save for CFI restore");
3622                                         return 1;
3623                                 }
3624
3625                                 if (!save_insn->visited) {
3626                                         WARN_INSN(insn, "objtool isn't smart enough to handle this CFI save/restore combo");
3627                                         return 1;
3628                                 }
3629
3630                                 insn->cfi = save_insn->cfi;
3631                                 nr_cfi_reused++;
3632                         }
3633
3634                         state.cfi = *insn->cfi;
3635                 } else {
3636                         /* XXX track if we actually changed state.cfi */
3637
3638                         if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3639                                 insn->cfi = prev_insn->cfi;
3640                                 nr_cfi_reused++;
3641                         } else {
3642                                 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3643                         }
3644                 }
3645
3646                 insn->visited |= visited;
3647
3648                 if (propagate_alt_cfi(file, insn))
3649                         return 1;
3650
3651                 if (!insn->ignore_alts && insn->alts) {
3652                         bool skip_orig = false;
3653
3654                         for (alt = insn->alts; alt; alt = alt->next) {
3655                                 if (alt->skip_orig)
3656                                         skip_orig = true;
3657
3658                                 ret = validate_branch(file, func, alt->insn, state);
3659                                 if (ret) {
3660                                         if (opts.backtrace)
3661                                                 BT_FUNC("(alt)", insn);
3662                                         return ret;
3663                                 }
3664                         }
3665
3666                         if (skip_orig)
3667                                 return 0;
3668                 }
3669
3670                 if (handle_insn_ops(insn, next_insn, &state))
3671                         return 1;
3672
3673                 switch (insn->type) {
3674
3675                 case INSN_RETURN:
3676                         return validate_return(func, insn, &state);
3677
3678                 case INSN_CALL:
3679                 case INSN_CALL_DYNAMIC:
3680                         ret = validate_call(file, insn, &state);
3681                         if (ret)
3682                                 return ret;
3683
3684                         if (opts.stackval && func && !is_fentry_call(insn) &&
3685                             !has_valid_stack_frame(&state)) {
3686                                 WARN_INSN(insn, "call without frame pointer save/setup");
3687                                 return 1;
3688                         }
3689
3690                         if (insn->dead_end)
3691                                 return 0;
3692
3693                         break;
3694
3695                 case INSN_JUMP_CONDITIONAL:
3696                 case INSN_JUMP_UNCONDITIONAL:
3697                         if (is_sibling_call(insn)) {
3698                                 ret = validate_sibling_call(file, insn, &state);
3699                                 if (ret)
3700                                         return ret;
3701
3702                         } else if (insn->jump_dest) {
3703                                 ret = validate_branch(file, func,
3704                                                       insn->jump_dest, state);
3705                                 if (ret) {
3706                                         if (opts.backtrace)
3707                                                 BT_FUNC("(branch)", insn);
3708                                         return ret;
3709                                 }
3710                         }
3711
3712                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
3713                                 return 0;
3714
3715                         break;
3716
3717                 case INSN_JUMP_DYNAMIC:
3718                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3719                         if (is_sibling_call(insn)) {
3720                                 ret = validate_sibling_call(file, insn, &state);
3721                                 if (ret)
3722                                         return ret;
3723                         }
3724
3725                         if (insn->type == INSN_JUMP_DYNAMIC)
3726                                 return 0;
3727
3728                         break;
3729
3730                 case INSN_CONTEXT_SWITCH:
3731                         if (func && (!next_insn || !next_insn->hint)) {
3732                                 WARN_INSN(insn, "unsupported instruction in callable function");
3733                                 return 1;
3734                         }
3735                         return 0;
3736
3737                 case INSN_STAC:
3738                         if (state.uaccess) {
3739                                 WARN_INSN(insn, "recursive UACCESS enable");
3740                                 return 1;
3741                         }
3742
3743                         state.uaccess = true;
3744                         break;
3745
3746                 case INSN_CLAC:
3747                         if (!state.uaccess && func) {
3748                                 WARN_INSN(insn, "redundant UACCESS disable");
3749                                 return 1;
3750                         }
3751
3752                         if (func_uaccess_safe(func) && !state.uaccess_stack) {
3753                                 WARN_INSN(insn, "UACCESS-safe disables UACCESS");
3754                                 return 1;
3755                         }
3756
3757                         state.uaccess = false;
3758                         break;
3759
3760                 case INSN_STD:
3761                         if (state.df) {
3762                                 WARN_INSN(insn, "recursive STD");
3763                                 return 1;
3764                         }
3765
3766                         state.df = true;
3767                         break;
3768
3769                 case INSN_CLD:
3770                         if (!state.df && func) {
3771                                 WARN_INSN(insn, "redundant CLD");
3772                                 return 1;
3773                         }
3774
3775                         state.df = false;
3776                         break;
3777
3778                 default:
3779                         break;
3780                 }
3781
3782                 if (insn->dead_end)
3783                         return 0;
3784
3785                 if (!next_insn) {
3786                         if (state.cfi.cfa.base == CFI_UNDEFINED)
3787                                 return 0;
3788                         WARN("%s: unexpected end of section", sec->name);
3789                         return 1;
3790                 }
3791
3792                 prev_insn = insn;
3793                 insn = next_insn;
3794         }
3795
3796         return 0;
3797 }
3798
3799 static int validate_unwind_hint(struct objtool_file *file,
3800                                   struct instruction *insn,
3801                                   struct insn_state *state)
3802 {
3803         if (insn->hint && !insn->visited && !insn->ignore) {
3804                 int ret = validate_branch(file, insn_func(insn), insn, *state);
3805                 if (ret && opts.backtrace)
3806                         BT_FUNC("<=== (hint)", insn);
3807                 return ret;
3808         }
3809
3810         return 0;
3811 }
3812
3813 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3814 {
3815         struct instruction *insn;
3816         struct insn_state state;
3817         int warnings = 0;
3818
3819         if (!file->hints)
3820                 return 0;
3821
3822         init_insn_state(file, &state, sec);
3823
3824         if (sec) {
3825                 sec_for_each_insn(file, sec, insn)
3826                         warnings += validate_unwind_hint(file, insn, &state);
3827         } else {
3828                 for_each_insn(file, insn)
3829                         warnings += validate_unwind_hint(file, insn, &state);
3830         }
3831
3832         return warnings;
3833 }
3834
3835 /*
3836  * Validate rethunk entry constraint: must untrain RET before the first RET.
3837  *
3838  * Follow every branch (intra-function) and ensure VALIDATE_UNRET_END comes
3839  * before an actual RET instruction.
3840  */
3841 static int validate_unret(struct objtool_file *file, struct instruction *insn)
3842 {
3843         struct instruction *next, *dest;
3844         int ret, warnings = 0;
3845
3846         for (;;) {
3847                 next = next_insn_to_validate(file, insn);
3848
3849                 if (insn->visited & VISITED_UNRET)
3850                         return 0;
3851
3852                 insn->visited |= VISITED_UNRET;
3853
3854                 if (!insn->ignore_alts && insn->alts) {
3855                         struct alternative *alt;
3856                         bool skip_orig = false;
3857
3858                         for (alt = insn->alts; alt; alt = alt->next) {
3859                                 if (alt->skip_orig)
3860                                         skip_orig = true;
3861
3862                                 ret = validate_unret(file, alt->insn);
3863                                 if (ret) {
3864                                         if (opts.backtrace)
3865                                                 BT_FUNC("(alt)", insn);
3866                                         return ret;
3867                                 }
3868                         }
3869
3870                         if (skip_orig)
3871                                 return 0;
3872                 }
3873
3874                 switch (insn->type) {
3875
3876                 case INSN_CALL_DYNAMIC:
3877                 case INSN_JUMP_DYNAMIC:
3878                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3879                         WARN_INSN(insn, "early indirect call");
3880                         return 1;
3881
3882                 case INSN_JUMP_UNCONDITIONAL:
3883                 case INSN_JUMP_CONDITIONAL:
3884                         if (!is_sibling_call(insn)) {
3885                                 if (!insn->jump_dest) {
3886                                         WARN_INSN(insn, "unresolved jump target after linking?!?");
3887                                         return -1;
3888                                 }
3889                                 ret = validate_unret(file, insn->jump_dest);
3890                                 if (ret) {
3891                                         if (opts.backtrace) {
3892                                                 BT_FUNC("(branch%s)", insn,
3893                                                         insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : "");
3894                                         }
3895                                         return ret;
3896                                 }
3897
3898                                 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3899                                         return 0;
3900
3901                                 break;
3902                         }
3903
3904                         /* fallthrough */
3905                 case INSN_CALL:
3906                         dest = find_insn(file, insn_call_dest(insn)->sec,
3907                                          insn_call_dest(insn)->offset);
3908                         if (!dest) {
3909                                 WARN("Unresolved function after linking!?: %s",
3910                                      insn_call_dest(insn)->name);
3911                                 return -1;
3912                         }
3913
3914                         ret = validate_unret(file, dest);
3915                         if (ret) {
3916                                 if (opts.backtrace)
3917                                         BT_FUNC("(call)", insn);
3918                                 return ret;
3919                         }
3920                         /*
3921                          * If a call returns without error, it must have seen UNTRAIN_RET.
3922                          * Therefore any non-error return is a success.
3923                          */
3924                         return 0;
3925
3926                 case INSN_RETURN:
3927                         WARN_INSN(insn, "RET before UNTRAIN");
3928                         return 1;
3929
3930                 case INSN_NOP:
3931                         if (insn->retpoline_safe)
3932                                 return 0;
3933                         break;
3934
3935                 default:
3936                         break;
3937                 }
3938
3939                 if (!next) {
3940                         WARN_INSN(insn, "teh end!");
3941                         return -1;
3942                 }
3943                 insn = next;
3944         }
3945
3946         return warnings;
3947 }
3948
3949 /*
3950  * Validate that all branches starting at VALIDATE_UNRET_BEGIN encounter
3951  * VALIDATE_UNRET_END before RET.
3952  */
3953 static int validate_unrets(struct objtool_file *file)
3954 {
3955         struct instruction *insn;
3956         int ret, warnings = 0;
3957
3958         for_each_insn(file, insn) {
3959                 if (!insn->unret)
3960                         continue;
3961
3962                 ret = validate_unret(file, insn);
3963                 if (ret < 0) {
3964                         WARN_INSN(insn, "Failed UNRET validation");
3965                         return ret;
3966                 }
3967                 warnings += ret;
3968         }
3969
3970         return warnings;
3971 }
3972
3973 static int validate_retpoline(struct objtool_file *file)
3974 {
3975         struct instruction *insn;
3976         int warnings = 0;
3977
3978         for_each_insn(file, insn) {
3979                 if (insn->type != INSN_JUMP_DYNAMIC &&
3980                     insn->type != INSN_CALL_DYNAMIC &&
3981                     insn->type != INSN_RETURN)
3982                         continue;
3983
3984                 if (insn->retpoline_safe)
3985                         continue;
3986
3987                 if (insn->sec->init)
3988                         continue;
3989
3990                 if (insn->type == INSN_RETURN) {
3991                         if (opts.rethunk) {
3992                                 WARN_INSN(insn, "'naked' return found in RETHUNK build");
3993                         } else
3994                                 continue;
3995                 } else {
3996                         WARN_INSN(insn, "indirect %s found in RETPOLINE build",
3997                                   insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
3998                 }
3999
4000                 warnings++;
4001         }
4002
4003         return warnings;
4004 }
4005
4006 static bool is_kasan_insn(struct instruction *insn)
4007 {
4008         return (insn->type == INSN_CALL &&
4009                 !strcmp(insn_call_dest(insn)->name, "__asan_handle_no_return"));
4010 }
4011
4012 static bool is_ubsan_insn(struct instruction *insn)
4013 {
4014         return (insn->type == INSN_CALL &&
4015                 !strcmp(insn_call_dest(insn)->name,
4016                         "__ubsan_handle_builtin_unreachable"));
4017 }
4018
4019 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
4020 {
4021         int i;
4022         struct instruction *prev_insn;
4023
4024         if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
4025                 return true;
4026
4027         /*
4028          * Ignore alternative replacement instructions.  This can happen
4029          * when a whitelisted function uses one of the ALTERNATIVE macros.
4030          */
4031         if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
4032             !strcmp(insn->sec->name, ".altinstr_aux"))
4033                 return true;
4034
4035         /*
4036          * Whole archive runs might encounter dead code from weak symbols.
4037          * This is where the linker will have dropped the weak symbol in
4038          * favour of a regular symbol, but leaves the code in place.
4039          *
4040          * In this case we'll find a piece of code (whole function) that is not
4041          * covered by a !section symbol. Ignore them.
4042          */
4043         if (opts.link && !insn_func(insn)) {
4044                 int size = find_symbol_hole_containing(insn->sec, insn->offset);
4045                 unsigned long end = insn->offset + size;
4046
4047                 if (!size) /* not a hole */
4048                         return false;
4049
4050                 if (size < 0) /* hole until the end */
4051                         return true;
4052
4053                 sec_for_each_insn_continue(file, insn) {
4054                         /*
4055                          * If we reach a visited instruction at or before the
4056                          * end of the hole, ignore the unreachable.
4057                          */
4058                         if (insn->visited)
4059                                 return true;
4060
4061                         if (insn->offset >= end)
4062                                 break;
4063
4064                         /*
4065                          * If this hole jumps to a .cold function, mark it ignore too.
4066                          */
4067                         if (insn->jump_dest && insn_func(insn->jump_dest) &&
4068                             strstr(insn_func(insn->jump_dest)->name, ".cold")) {
4069                                 struct instruction *dest = insn->jump_dest;
4070                                 func_for_each_insn(file, insn_func(dest), dest)
4071                                         dest->ignore = true;
4072                         }
4073                 }
4074
4075                 return false;
4076         }
4077
4078         if (!insn_func(insn))
4079                 return false;
4080
4081         if (insn_func(insn)->static_call_tramp)
4082                 return true;
4083
4084         /*
4085          * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
4086          * __builtin_unreachable().  The BUG() macro has an unreachable() after
4087          * the UD2, which causes GCC's undefined trap logic to emit another UD2
4088          * (or occasionally a JMP to UD2).
4089          *
4090          * It may also insert a UD2 after calling a __noreturn function.
4091          */
4092         prev_insn = prev_insn_same_sec(file, insn);
4093         if (prev_insn->dead_end &&
4094             (insn->type == INSN_BUG ||
4095              (insn->type == INSN_JUMP_UNCONDITIONAL &&
4096               insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
4097                 return true;
4098
4099         /*
4100          * Check if this (or a subsequent) instruction is related to
4101          * CONFIG_UBSAN or CONFIG_KASAN.
4102          *
4103          * End the search at 5 instructions to avoid going into the weeds.
4104          */
4105         for (i = 0; i < 5; i++) {
4106
4107                 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
4108                         return true;
4109
4110                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
4111                         if (insn->jump_dest &&
4112                             insn_func(insn->jump_dest) == insn_func(insn)) {
4113                                 insn = insn->jump_dest;
4114                                 continue;
4115                         }
4116
4117                         break;
4118                 }
4119
4120                 if (insn->offset + insn->len >= insn_func(insn)->offset + insn_func(insn)->len)
4121                         break;
4122
4123                 insn = next_insn_same_sec(file, insn);
4124         }
4125
4126         return false;
4127 }
4128
4129 static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
4130 {
4131         struct instruction *insn, *prev;
4132         struct cfi_state *cfi;
4133
4134         insn = find_insn(file, func->sec, func->offset);
4135         if (!insn)
4136                 return -1;
4137
4138         for (prev = prev_insn_same_sec(file, insn);
4139              prev;
4140              prev = prev_insn_same_sec(file, prev)) {
4141                 u64 offset;
4142
4143                 if (prev->type != INSN_NOP)
4144                         return -1;
4145
4146                 offset = func->offset - prev->offset;
4147
4148                 if (offset > opts.prefix)
4149                         return -1;
4150
4151                 if (offset < opts.prefix)
4152                         continue;
4153
4154                 elf_create_prefix_symbol(file->elf, func, opts.prefix);
4155                 break;
4156         }
4157
4158         if (!prev)
4159                 return -1;
4160
4161         if (!insn->cfi) {
4162                 /*
4163                  * This can happen if stack validation isn't enabled or the
4164                  * function is annotated with STACK_FRAME_NON_STANDARD.
4165                  */
4166                 return 0;
4167         }
4168
4169         /* Propagate insn->cfi to the prefix code */
4170         cfi = cfi_hash_find_or_add(insn->cfi);
4171         for (; prev != insn; prev = next_insn_same_sec(file, prev))
4172                 prev->cfi = cfi;
4173
4174         return 0;
4175 }
4176
4177 static int add_prefix_symbols(struct objtool_file *file)
4178 {
4179         struct section *sec;
4180         struct symbol *func;
4181         int warnings = 0;
4182
4183         for_each_sec(file, sec) {
4184                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4185                         continue;
4186
4187                 sec_for_each_sym(sec, func) {
4188                         if (func->type != STT_FUNC)
4189                                 continue;
4190
4191                         add_prefix_symbol(file, func);
4192                 }
4193         }
4194
4195         return warnings;
4196 }
4197
4198 static int validate_symbol(struct objtool_file *file, struct section *sec,
4199                            struct symbol *sym, struct insn_state *state)
4200 {
4201         struct instruction *insn;
4202         int ret;
4203
4204         if (!sym->len) {
4205                 WARN("%s() is missing an ELF size annotation", sym->name);
4206                 return 1;
4207         }
4208
4209         if (sym->pfunc != sym || sym->alias != sym)
4210                 return 0;
4211
4212         insn = find_insn(file, sec, sym->offset);
4213         if (!insn || insn->ignore || insn->visited)
4214                 return 0;
4215
4216         state->uaccess = sym->uaccess_safe;
4217
4218         ret = validate_branch(file, insn_func(insn), insn, *state);
4219         if (ret && opts.backtrace)
4220                 BT_FUNC("<=== (sym)", insn);
4221         return ret;
4222 }
4223
4224 static int validate_section(struct objtool_file *file, struct section *sec)
4225 {
4226         struct insn_state state;
4227         struct symbol *func;
4228         int warnings = 0;
4229
4230         sec_for_each_sym(sec, func) {
4231                 if (func->type != STT_FUNC)
4232                         continue;
4233
4234                 init_insn_state(file, &state, sec);
4235                 set_func_state(&state.cfi);
4236
4237                 warnings += validate_symbol(file, sec, func, &state);
4238         }
4239
4240         return warnings;
4241 }
4242
4243 static int validate_noinstr_sections(struct objtool_file *file)
4244 {
4245         struct section *sec;
4246         int warnings = 0;
4247
4248         sec = find_section_by_name(file->elf, ".noinstr.text");
4249         if (sec) {
4250                 warnings += validate_section(file, sec);
4251                 warnings += validate_unwind_hints(file, sec);
4252         }
4253
4254         sec = find_section_by_name(file->elf, ".entry.text");
4255         if (sec) {
4256                 warnings += validate_section(file, sec);
4257                 warnings += validate_unwind_hints(file, sec);
4258         }
4259
4260         sec = find_section_by_name(file->elf, ".cpuidle.text");
4261         if (sec) {
4262                 warnings += validate_section(file, sec);
4263                 warnings += validate_unwind_hints(file, sec);
4264         }
4265
4266         return warnings;
4267 }
4268
4269 static int validate_functions(struct objtool_file *file)
4270 {
4271         struct section *sec;
4272         int warnings = 0;
4273
4274         for_each_sec(file, sec) {
4275                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4276                         continue;
4277
4278                 warnings += validate_section(file, sec);
4279         }
4280
4281         return warnings;
4282 }
4283
4284 static void mark_endbr_used(struct instruction *insn)
4285 {
4286         if (!list_empty(&insn->call_node))
4287                 list_del_init(&insn->call_node);
4288 }
4289
4290 static bool noendbr_range(struct objtool_file *file, struct instruction *insn)
4291 {
4292         struct symbol *sym = find_symbol_containing(insn->sec, insn->offset-1);
4293         struct instruction *first;
4294
4295         if (!sym)
4296                 return false;
4297
4298         first = find_insn(file, sym->sec, sym->offset);
4299         if (!first)
4300                 return false;
4301
4302         if (first->type != INSN_ENDBR && !first->noendbr)
4303                 return false;
4304
4305         return insn->offset == sym->offset + sym->len;
4306 }
4307
4308 static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
4309 {
4310         struct instruction *dest;
4311         struct reloc *reloc;
4312         unsigned long off;
4313         int warnings = 0;
4314
4315         /*
4316          * Looking for function pointer load relocations.  Ignore
4317          * direct/indirect branches:
4318          */
4319         switch (insn->type) {
4320         case INSN_CALL:
4321         case INSN_CALL_DYNAMIC:
4322         case INSN_JUMP_CONDITIONAL:
4323         case INSN_JUMP_UNCONDITIONAL:
4324         case INSN_JUMP_DYNAMIC:
4325         case INSN_JUMP_DYNAMIC_CONDITIONAL:
4326         case INSN_RETURN:
4327         case INSN_NOP:
4328                 return 0;
4329         default:
4330                 break;
4331         }
4332
4333         for (reloc = insn_reloc(file, insn);
4334              reloc;
4335              reloc = find_reloc_by_dest_range(file->elf, insn->sec,
4336                                               reloc->offset + 1,
4337                                               (insn->offset + insn->len) - (reloc->offset + 1))) {
4338
4339                 /*
4340                  * static_call_update() references the trampoline, which
4341                  * doesn't have (or need) ENDBR.  Skip warning in that case.
4342                  */
4343                 if (reloc->sym->static_call_tramp)
4344                         continue;
4345
4346                 off = reloc->sym->offset;
4347                 if (reloc->type == R_X86_64_PC32 || reloc->type == R_X86_64_PLT32)
4348                         off += arch_dest_reloc_offset(reloc->addend);
4349                 else
4350                         off += reloc->addend;
4351
4352                 dest = find_insn(file, reloc->sym->sec, off);
4353                 if (!dest)
4354                         continue;
4355
4356                 if (dest->type == INSN_ENDBR) {
4357                         mark_endbr_used(dest);
4358                         continue;
4359                 }
4360
4361                 if (insn_func(dest) && insn_func(dest) == insn_func(insn)) {
4362                         /*
4363                          * Anything from->to self is either _THIS_IP_ or
4364                          * IRET-to-self.
4365                          *
4366                          * There is no sane way to annotate _THIS_IP_ since the
4367                          * compiler treats the relocation as a constant and is
4368                          * happy to fold in offsets, skewing any annotation we
4369                          * do, leading to vast amounts of false-positives.
4370                          *
4371                          * There's also compiler generated _THIS_IP_ through
4372                          * KCOV and such which we have no hope of annotating.
4373                          *
4374                          * As such, blanket accept self-references without
4375                          * issue.
4376                          */
4377                         continue;
4378                 }
4379
4380                 /*
4381                  * Accept anything ANNOTATE_NOENDBR.
4382                  */
4383                 if (dest->noendbr)
4384                         continue;
4385
4386                 /*
4387                  * Accept if this is the instruction after a symbol
4388                  * that is (no)endbr -- typical code-range usage.
4389                  */
4390                 if (noendbr_range(file, dest))
4391                         continue;
4392
4393                 WARN_INSN(insn, "relocation to !ENDBR: %s", offstr(dest->sec, dest->offset));
4394
4395                 warnings++;
4396         }
4397
4398         return warnings;
4399 }
4400
4401 static int validate_ibt_data_reloc(struct objtool_file *file,
4402                                    struct reloc *reloc)
4403 {
4404         struct instruction *dest;
4405
4406         dest = find_insn(file, reloc->sym->sec,
4407                          reloc->sym->offset + reloc->addend);
4408         if (!dest)
4409                 return 0;
4410
4411         if (dest->type == INSN_ENDBR) {
4412                 mark_endbr_used(dest);
4413                 return 0;
4414         }
4415
4416         if (dest->noendbr)
4417                 return 0;
4418
4419         WARN_FUNC("data relocation to !ENDBR: %s",
4420                   reloc->sec->base, reloc->offset,
4421                   offstr(dest->sec, dest->offset));
4422
4423         return 1;
4424 }
4425
4426 /*
4427  * Validate IBT rules and remove used ENDBR instructions from the seal list.
4428  * Unused ENDBR instructions will be annotated for sealing (i.e., replaced with
4429  * NOPs) later, in create_ibt_endbr_seal_sections().
4430  */
4431 static int validate_ibt(struct objtool_file *file)
4432 {
4433         struct section *sec;
4434         struct reloc *reloc;
4435         struct instruction *insn;
4436         int warnings = 0;
4437
4438         for_each_insn(file, insn)
4439                 warnings += validate_ibt_insn(file, insn);
4440
4441         for_each_sec(file, sec) {
4442
4443                 /* Already done by validate_ibt_insn() */
4444                 if (sec->sh.sh_flags & SHF_EXECINSTR)
4445                         continue;
4446
4447                 if (!sec->reloc)
4448                         continue;
4449
4450                 /*
4451                  * These sections can reference text addresses, but not with
4452                  * the intent to indirect branch to them.
4453                  */
4454                 if ((!strncmp(sec->name, ".discard", 8) &&
4455                      strcmp(sec->name, ".discard.ibt_endbr_noseal"))    ||
4456                     !strncmp(sec->name, ".debug", 6)                    ||
4457                     !strcmp(sec->name, ".altinstructions")              ||
4458                     !strcmp(sec->name, ".ibt_endbr_seal")               ||
4459                     !strcmp(sec->name, ".orc_unwind_ip")                ||
4460                     !strcmp(sec->name, ".parainstructions")             ||
4461                     !strcmp(sec->name, ".retpoline_sites")              ||
4462                     !strcmp(sec->name, ".smp_locks")                    ||
4463                     !strcmp(sec->name, ".static_call_sites")            ||
4464                     !strcmp(sec->name, "_error_injection_whitelist")    ||
4465                     !strcmp(sec->name, "_kprobe_blacklist")             ||
4466                     !strcmp(sec->name, "__bug_table")                   ||
4467                     !strcmp(sec->name, "__ex_table")                    ||
4468                     !strcmp(sec->name, "__jump_table")                  ||
4469                     !strcmp(sec->name, "__mcount_loc")                  ||
4470                     !strcmp(sec->name, ".kcfi_traps")                   ||
4471                     strstr(sec->name, "__patchable_function_entries"))
4472                         continue;
4473
4474                 list_for_each_entry(reloc, &sec->reloc->reloc_list, list)
4475                         warnings += validate_ibt_data_reloc(file, reloc);
4476         }
4477
4478         return warnings;
4479 }
4480
4481 static int validate_sls(struct objtool_file *file)
4482 {
4483         struct instruction *insn, *next_insn;
4484         int warnings = 0;
4485
4486         for_each_insn(file, insn) {
4487                 next_insn = next_insn_same_sec(file, insn);
4488
4489                 if (insn->retpoline_safe)
4490                         continue;
4491
4492                 switch (insn->type) {
4493                 case INSN_RETURN:
4494                         if (!next_insn || next_insn->type != INSN_TRAP) {
4495                                 WARN_INSN(insn, "missing int3 after ret");
4496                                 warnings++;
4497                         }
4498
4499                         break;
4500                 case INSN_JUMP_DYNAMIC:
4501                         if (!next_insn || next_insn->type != INSN_TRAP) {
4502                                 WARN_INSN(insn, "missing int3 after indirect jump");
4503                                 warnings++;
4504                         }
4505                         break;
4506                 default:
4507                         break;
4508                 }
4509         }
4510
4511         return warnings;
4512 }
4513
4514 static int validate_reachable_instructions(struct objtool_file *file)
4515 {
4516         struct instruction *insn;
4517
4518         if (file->ignore_unreachables)
4519                 return 0;
4520
4521         for_each_insn(file, insn) {
4522                 if (insn->visited || ignore_unreachable_insn(file, insn))
4523                         continue;
4524
4525                 WARN_INSN(insn, "unreachable instruction");
4526                 return 1;
4527         }
4528
4529         return 0;
4530 }
4531
4532 int check(struct objtool_file *file)
4533 {
4534         int ret, warnings = 0;
4535
4536         arch_initial_func_cfi_state(&initial_func_cfi);
4537         init_cfi_state(&init_cfi);
4538         init_cfi_state(&func_cfi);
4539         set_func_state(&func_cfi);
4540
4541         if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
4542                 goto out;
4543
4544         cfi_hash_add(&init_cfi);
4545         cfi_hash_add(&func_cfi);
4546
4547         ret = decode_sections(file);
4548         if (ret < 0)
4549                 goto out;
4550
4551         warnings += ret;
4552
4553         if (!nr_insns)
4554                 goto out;
4555
4556         if (opts.retpoline) {
4557                 ret = validate_retpoline(file);
4558                 if (ret < 0)
4559                         return ret;
4560                 warnings += ret;
4561         }
4562
4563         if (opts.stackval || opts.orc || opts.uaccess) {
4564                 ret = validate_functions(file);
4565                 if (ret < 0)
4566                         goto out;
4567                 warnings += ret;
4568
4569                 ret = validate_unwind_hints(file, NULL);
4570                 if (ret < 0)
4571                         goto out;
4572                 warnings += ret;
4573
4574                 if (!warnings) {
4575                         ret = validate_reachable_instructions(file);
4576                         if (ret < 0)
4577                                 goto out;
4578                         warnings += ret;
4579                 }
4580
4581         } else if (opts.noinstr) {
4582                 ret = validate_noinstr_sections(file);
4583                 if (ret < 0)
4584                         goto out;
4585                 warnings += ret;
4586         }
4587
4588         if (opts.unret) {
4589                 /*
4590                  * Must be after validate_branch() and friends, it plays
4591                  * further games with insn->visited.
4592                  */
4593                 ret = validate_unrets(file);
4594                 if (ret < 0)
4595                         return ret;
4596                 warnings += ret;
4597         }
4598
4599         if (opts.ibt) {
4600                 ret = validate_ibt(file);
4601                 if (ret < 0)
4602                         goto out;
4603                 warnings += ret;
4604         }
4605
4606         if (opts.sls) {
4607                 ret = validate_sls(file);
4608                 if (ret < 0)
4609                         goto out;
4610                 warnings += ret;
4611         }
4612
4613         if (opts.static_call) {
4614                 ret = create_static_call_sections(file);
4615                 if (ret < 0)
4616                         goto out;
4617                 warnings += ret;
4618         }
4619
4620         if (opts.retpoline) {
4621                 ret = create_retpoline_sites_sections(file);
4622                 if (ret < 0)
4623                         goto out;
4624                 warnings += ret;
4625         }
4626
4627         if (opts.cfi) {
4628                 ret = create_cfi_sections(file);
4629                 if (ret < 0)
4630                         goto out;
4631                 warnings += ret;
4632         }
4633
4634         if (opts.rethunk) {
4635                 ret = create_return_sites_sections(file);
4636                 if (ret < 0)
4637                         goto out;
4638                 warnings += ret;
4639
4640                 if (opts.hack_skylake) {
4641                         ret = create_direct_call_sections(file);
4642                         if (ret < 0)
4643                                 goto out;
4644                         warnings += ret;
4645                 }
4646         }
4647
4648         if (opts.mcount) {
4649                 ret = create_mcount_loc_sections(file);
4650                 if (ret < 0)
4651                         goto out;
4652                 warnings += ret;
4653         }
4654
4655         if (opts.prefix) {
4656                 ret = add_prefix_symbols(file);
4657                 if (ret < 0)
4658                         return ret;
4659                 warnings += ret;
4660         }
4661
4662         if (opts.ibt) {
4663                 ret = create_ibt_endbr_seal_sections(file);
4664                 if (ret < 0)
4665                         goto out;
4666                 warnings += ret;
4667         }
4668
4669         if (opts.orc && nr_insns) {
4670                 ret = orc_create(file);
4671                 if (ret < 0)
4672                         goto out;
4673                 warnings += ret;
4674         }
4675
4676
4677         if (opts.stats) {
4678                 printf("nr_insns_visited: %ld\n", nr_insns_visited);
4679                 printf("nr_cfi: %ld\n", nr_cfi);
4680                 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
4681                 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
4682         }
4683
4684 out:
4685         /*
4686          *  For now, don't fail the kernel build on fatal warnings.  These
4687          *  errors are still fairly common due to the growing matrix of
4688          *  supported toolchains and their recent pace of change.
4689          */
4690         return 0;
4691 }