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
   9 #include <arch/elf.h>
  10 #include <objtool/builtin.h>
  11 #include <objtool/cfi.h>
  12 #include <objtool/arch.h>
  13 #include <objtool/check.h>
  14 #include <objtool/special.h>
  15 #include <objtool/warn.h>
  16 #include <objtool/endianness.h>
  17
  18 #include <linux/objtool.h>
  19 #include <linux/hashtable.h>
  20 #include <linux/kernel.h>
  21 #include <linux/static_call_types.h>
  22
  23 struct alternative {
  24         struct list_head list;
  25         struct instruction *insn;
  26         bool skip_orig;
  27 };
  28
  29 struct cfi_init_state initial_func_cfi;
  30
  31 struct instruction *find_insn(struct objtool_file *file,
  32                               struct section *sec, unsigned long offset)
  33 {
  34         struct instruction *insn;
  35
  36         hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
  37                 if (insn->sec == sec && insn->offset == offset)
  38                         return insn;
  39         }
  40
  41         return NULL;
  42 }
  43
  44 static struct instruction *next_insn_same_sec(struct objtool_file *file,
  45                                               struct instruction *insn)
  46 {
  47         struct instruction *next = list_next_entry(insn, list);
  48
  49         if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
  50                 return NULL;
  51
  52         return next;
  53 }
  54
  55 static struct instruction *next_insn_same_func(struct objtool_file *file,
  56                                                struct instruction *insn)
  57 {
  58         struct instruction *next = list_next_entry(insn, list);
  59         struct symbol *func = insn->func;
  60
  61         if (!func)
  62                 return NULL;
  63
  64         if (&next->list != &file->insn_list && next->func == func)
  65                 return next;
  66
  67         /* Check if we're already in the subfunction: */
  68         if (func == func->cfunc)
  69                 return NULL;
  70
  71         /* Move to the subfunction: */
  72         return find_insn(file, func->cfunc->sec, func->cfunc->offset);
  73 }
  74
  75 static struct instruction *prev_insn_same_sym(struct objtool_file *file,
  76                                                struct instruction *insn)
  77 {
  78         struct instruction *prev = list_prev_entry(insn, list);
  79
  80         if (&prev->list != &file->insn_list && prev->func == insn->func)
  81                 return prev;
  82
  83         return NULL;
  84 }
  85
  86 #define func_for_each_insn(file, func, insn)                            \
  87         for (insn = find_insn(file, func->sec, func->offset);           \
  88              insn;                                                      \
  89              insn = next_insn_same_func(file, insn))
  90
  91 #define sym_for_each_insn(file, sym, insn)                              \
  92         for (insn = find_insn(file, sym->sec, sym->offset);             \
  93              insn && &insn->list != &file->insn_list &&                 \
  94                 insn->sec == sym->sec &&                                \
  95                 insn->offset < sym->offset + sym->len;                  \
  96              insn = list_next_entry(insn, list))
  97
  98 #define sym_for_each_insn_continue_reverse(file, sym, insn)             \
  99         for (insn = list_prev_entry(insn, list);                        \
 100              &insn->list != &file->insn_list &&                         \
 101                 insn->sec == sym->sec && insn->offset >= sym->offset;   \
 102              insn = list_prev_entry(insn, list))
 103
 104 #define sec_for_each_insn_from(file, insn)                              \
 105         for (; insn; insn = next_insn_same_sec(file, insn))
 106
 107 #define sec_for_each_insn_continue(file, insn)                          \
 108         for (insn = next_insn_same_sec(file, insn); insn;               \
 109              insn = next_insn_same_sec(file, insn))
 110
 111 static bool is_sibling_call(struct instruction *insn)
 112 {
 113         /*
 114          * Assume only ELF functions can make sibling calls.  This ensures
 115          * sibling call detection consistency between vmlinux.o and individual
 116          * objects.
 117          */
 118         if (!insn->func)
 119                 return false;
 120
 121         /* An indirect jump is either a sibling call or a jump to a table. */
 122         if (insn->type == INSN_JUMP_DYNAMIC)
 123                 return list_empty(&insn->alts);
 124
 125         /* add_jump_destinations() sets insn->call_dest for sibling calls. */
 126         return (is_static_jump(insn) && insn->call_dest);
 127 }
 128
 129 /*
 130  * This checks to see if the given function is a "noreturn" function.
 131  *
 132  * For global functions which are outside the scope of this object file, we
 133  * have to keep a manual list of them.
 134  *
 135  * For local functions, we have to detect them manually by simply looking for
 136  * the lack of a return instruction.
 137  */
 138 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 139                                 int recursion)
 140 {
 141         int i;
 142         struct instruction *insn;
 143         bool empty = true;
 144
 145         /*
 146          * Unfortunately these have to be hard coded because the noreturn
 147          * attribute isn't provided in ELF data.
 148          */
 149         static const char * const global_noreturns[] = {
 150                 "__stack_chk_fail",
 151                 "panic",
 152                 "do_exit",
 153                 "do_task_dead",
 154                 "__module_put_and_exit",
 155                 "complete_and_exit",
 156                 "__reiserfs_panic",
 157                 "lbug_with_loc",
 158                 "fortify_panic",
 159                 "usercopy_abort",
 160                 "machine_real_restart",
 161                 "rewind_stack_do_exit",
 162                 "kunit_try_catch_throw",
 163                 "xen_start_kernel",
 164         };
 165
 166         if (!func)
 167                 return false;
 168
 169         if (func->bind == STB_WEAK)
 170                 return false;
 171
 172         if (func->bind == STB_GLOBAL)
 173                 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
 174                         if (!strcmp(func->name, global_noreturns[i]))
 175                                 return true;
 176
 177         if (!func->len)
 178                 return false;
 179
 180         insn = find_insn(file, func->sec, func->offset);
 181         if (!insn->func)
 182                 return false;
 183
 184         func_for_each_insn(file, func, insn) {
 185                 empty = false;
 186
 187                 if (insn->type == INSN_RETURN)
 188                         return false;
 189         }
 190
 191         if (empty)
 192                 return false;
 193
 194         /*
 195          * A function can have a sibling call instead of a return.  In that
 196          * case, the function's dead-end status depends on whether the target
 197          * of the sibling call returns.
 198          */
 199         func_for_each_insn(file, func, insn) {
 200                 if (is_sibling_call(insn)) {
 201                         struct instruction *dest = insn->jump_dest;
 202
 203                         if (!dest)
 204                                 /* sibling call to another file */
 205                                 return false;
 206
 207                         /* local sibling call */
 208                         if (recursion == 5) {
 209                                 /*
 210                                  * Infinite recursion: two functions have
 211                                  * sibling calls to each other.  This is a very
 212                                  * rare case.  It means they aren't dead ends.
 213                                  */
 214                                 return false;
 215                         }
 216
 217                         return __dead_end_function(file, dest->func, recursion+1);
 218                 }
 219         }
 220
 221         return true;
 222 }
 223
 224 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
 225 {
 226         return __dead_end_function(file, func, 0);
 227 }
 228
 229 static void init_cfi_state(struct cfi_state *cfi)
 230 {
 231         int i;
 232
 233         for (i = 0; i < CFI_NUM_REGS; i++) {
 234                 cfi->regs[i].base = CFI_UNDEFINED;
 235                 cfi->vals[i].base = CFI_UNDEFINED;
 236         }
 237         cfi->cfa.base = CFI_UNDEFINED;
 238         cfi->drap_reg = CFI_UNDEFINED;
 239         cfi->drap_offset = -1;
 240 }
 241
 242 static void init_insn_state(struct insn_state *state, struct section *sec)
 243 {
 244         memset(state, 0, sizeof(*state));
 245         init_cfi_state(&state->cfi);
 246
 247         /*
 248          * We need the full vmlinux for noinstr validation, otherwise we can
 249          * not correctly determine insn->call_dest->sec (external symbols do
 250          * not have a section).
 251          */
 252         if (vmlinux && noinstr && sec)
 253                 state->noinstr = sec->noinstr;
 254 }
 255
 256 /*
 257  * Call the arch-specific instruction decoder for all the instructions and add
 258  * them to the global instruction list.
 259  */
 260 static int decode_instructions(struct objtool_file *file)
 261 {
 262         struct section *sec;
 263         struct symbol *func;
 264         unsigned long offset;
 265         struct instruction *insn;
 266         unsigned long nr_insns = 0;
 267         int ret;
 268
 269         for_each_sec(file, sec) {
 270
 271                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
 272                         continue;
 273
 274                 if (strcmp(sec->name, ".altinstr_replacement") &&
 275                     strcmp(sec->name, ".altinstr_aux") &&
 276                     strncmp(sec->name, ".discard.", 9))
 277                         sec->text = true;
 278
 279                 if (!strcmp(sec->name, ".noinstr.text") ||
 280                     !strcmp(sec->name, ".entry.text"))
 281                         sec->noinstr = true;
 282
 283                 for (offset = 0; offset < sec->len; offset += insn->len) {
 284                         insn = malloc(sizeof(*insn));
 285                         if (!insn) {
 286                                 WARN("malloc failed");
 287                                 return -1;
 288                         }
 289                         memset(insn, 0, sizeof(*insn));
 290                         INIT_LIST_HEAD(&insn->alts);
 291                         INIT_LIST_HEAD(&insn->stack_ops);
 292                         init_cfi_state(&insn->cfi);
 293
 294                         insn->sec = sec;
 295                         insn->offset = offset;
 296
 297                         ret = arch_decode_instruction(file->elf, sec, offset,
 298                                                       sec->len - offset,
 299                                                       &insn->len, &insn->type,
 300                                                       &insn->immediate,
 301                                                       &insn->stack_ops);
 302                         if (ret)
 303                                 goto err;
 304
 305                         hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
 306                         list_add_tail(&insn->list, &file->insn_list);
 307                         nr_insns++;
 308                 }
 309
 310                 list_for_each_entry(func, &sec->symbol_list, list) {
 311                         if (func->type != STT_FUNC || func->alias != func)
 312                                 continue;
 313
 314                         if (!find_insn(file, sec, func->offset)) {
 315                                 WARN("%s(): can't find starting instruction",
 316                                      func->name);
 317                                 return -1;
 318                         }
 319
 320                         sym_for_each_insn(file, func, insn)
 321                                 insn->func = func;
 322                 }
 323         }
 324
 325         if (stats)
 326                 printf("nr_insns: %lu\n", nr_insns);
 327
 328         return 0;
 329
 330 err:
 331         free(insn);
 332         return ret;
 333 }
 334
 335 static struct instruction *find_last_insn(struct objtool_file *file,
 336                                           struct section *sec)
 337 {
 338         struct instruction *insn = NULL;
 339         unsigned int offset;
 340         unsigned int end = (sec->len > 10) ? sec->len - 10 : 0;
 341
 342         for (offset = sec->len - 1; offset >= end && !insn; offset--)
 343                 insn = find_insn(file, sec, offset);
 344
 345         return insn;
 346 }
 347
 348 /*
 349  * Mark "ud2" instructions and manually annotated dead ends.
 350  */
 351 static int add_dead_ends(struct objtool_file *file)
 352 {
 353         struct section *sec;
 354         struct reloc *reloc;
 355         struct instruction *insn;
 356
 357         /*
 358          * By default, "ud2" is a dead end unless otherwise annotated, because
 359          * GCC 7 inserts it for certain divide-by-zero cases.
 360          */
 361         for_each_insn(file, insn)
 362                 if (insn->type == INSN_BUG)
 363                         insn->dead_end = true;
 364
 365         /*
 366          * Check for manually annotated dead ends.
 367          */
 368         sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
 369         if (!sec)
 370                 goto reachable;
 371
 372         list_for_each_entry(reloc, &sec->reloc_list, list) {
 373                 if (reloc->sym->type != STT_SECTION) {
 374                         WARN("unexpected relocation symbol type in %s", sec->name);
 375                         return -1;
 376                 }
 377                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 378                 if (insn)
 379                         insn = list_prev_entry(insn, list);
 380                 else if (reloc->addend == reloc->sym->sec->len) {
 381                         insn = find_last_insn(file, reloc->sym->sec);
 382                         if (!insn) {
 383                                 WARN("can't find unreachable insn at %s+0x%x",
 384                                      reloc->sym->sec->name, reloc->addend);
 385                                 return -1;
 386                         }
 387                 } else {
 388                         WARN("can't find unreachable insn at %s+0x%x",
 389                              reloc->sym->sec->name, reloc->addend);
 390                         return -1;
 391                 }
 392
 393                 insn->dead_end = true;
 394         }
 395
 396 reachable:
 397         /*
 398          * These manually annotated reachable checks are needed for GCC 4.4,
 399          * where the Linux unreachable() macro isn't supported.  In that case
 400          * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
 401          * not a dead end.
 402          */
 403         sec = find_section_by_name(file->elf, ".rela.discard.reachable");
 404         if (!sec)
 405                 return 0;
 406
 407         list_for_each_entry(reloc, &sec->reloc_list, list) {
 408                 if (reloc->sym->type != STT_SECTION) {
 409                         WARN("unexpected relocation symbol type in %s", sec->name);
 410                         return -1;
 411                 }
 412                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 413                 if (insn)
 414                         insn = list_prev_entry(insn, list);
 415                 else if (reloc->addend == reloc->sym->sec->len) {
 416                         insn = find_last_insn(file, reloc->sym->sec);
 417                         if (!insn) {
 418                                 WARN("can't find reachable insn at %s+0x%x",
 419                                      reloc->sym->sec->name, reloc->addend);
 420                                 return -1;
 421                         }
 422                 } else {
 423                         WARN("can't find reachable insn at %s+0x%x",
 424                              reloc->sym->sec->name, reloc->addend);
 425                         return -1;
 426                 }
 427
 428                 insn->dead_end = false;
 429         }
 430
 431         return 0;
 432 }
 433
 434 static int create_static_call_sections(struct objtool_file *file)
 435 {
 436         struct section *sec, *reloc_sec;
 437         struct reloc *reloc;
 438         struct static_call_site *site;
 439         struct instruction *insn;
 440         struct symbol *key_sym;
 441         char *key_name, *tmp;
 442         int idx;
 443
 444         sec = find_section_by_name(file->elf, ".static_call_sites");
 445         if (sec) {
 446                 INIT_LIST_HEAD(&file->static_call_list);
 447                 WARN("file already has .static_call_sites section, skipping");
 448                 return 0;
 449         }
 450
 451         if (list_empty(&file->static_call_list))
 452                 return 0;
 453
 454         idx = 0;
 455         list_for_each_entry(insn, &file->static_call_list, static_call_node)
 456                 idx++;
 457
 458         sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE,
 459                                  sizeof(struct static_call_site), idx);
 460         if (!sec)
 461                 return -1;
 462
 463         reloc_sec = elf_create_reloc_section(file->elf, sec, SHT_RELA);
 464         if (!reloc_sec)
 465                 return -1;
 466
 467         idx = 0;
 468         list_for_each_entry(insn, &file->static_call_list, static_call_node) {
 469
 470                 site = (struct static_call_site *)sec->data->d_buf + idx;
 471                 memset(site, 0, sizeof(struct static_call_site));
 472
 473                 /* populate reloc for 'addr' */
 474                 reloc = malloc(sizeof(*reloc));
 475
 476                 if (!reloc) {
 477                         perror("malloc");
 478                         return -1;
 479                 }
 480                 memset(reloc, 0, sizeof(*reloc));
 481
 482                 insn_to_reloc_sym_addend(insn->sec, insn->offset, reloc);
 483                 if (!reloc->sym) {
 484                         WARN_FUNC("static call tramp: missing containing symbol",
 485                                   insn->sec, insn->offset);
 486                         return -1;
 487                 }
 488
 489                 reloc->type = R_X86_64_PC32;
 490                 reloc->offset = idx * sizeof(struct static_call_site);
 491                 reloc->sec = reloc_sec;
 492                 elf_add_reloc(file->elf, reloc);
 493
 494                 /* find key symbol */
 495                 key_name = strdup(insn->call_dest->name);
 496                 if (!key_name) {
 497                         perror("strdup");
 498                         return -1;
 499                 }
 500                 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
 501                             STATIC_CALL_TRAMP_PREFIX_LEN)) {
 502                         WARN("static_call: trampoline name malformed: %s", key_name);
 503                         return -1;
 504                 }
 505                 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
 506                 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
 507
 508                 key_sym = find_symbol_by_name(file->elf, tmp);
 509                 if (!key_sym) {
 510                         if (!module) {
 511                                 WARN("static_call: can't find static_call_key symbol: %s", tmp);
 512                                 return -1;
 513                         }
 514
 515                         /*
 516                          * For modules(), the key might not be exported, which
 517                          * means the module can make static calls but isn't
 518                          * allowed to change them.
 519                          *
 520                          * In that case we temporarily set the key to be the
 521                          * trampoline address.  This is fixed up in
 522                          * static_call_add_module().
 523                          */
 524                         key_sym = insn->call_dest;
 525                 }
 526                 free(key_name);
 527
 528                 /* populate reloc for 'key' */
 529                 reloc = malloc(sizeof(*reloc));
 530                 if (!reloc) {
 531                         perror("malloc");
 532                         return -1;
 533                 }
 534                 memset(reloc, 0, sizeof(*reloc));
 535                 reloc->sym = key_sym;
 536                 reloc->addend = is_sibling_call(insn) ? STATIC_CALL_SITE_TAIL : 0;
 537                 reloc->type = R_X86_64_PC32;
 538                 reloc->offset = idx * sizeof(struct static_call_site) + 4;
 539                 reloc->sec = reloc_sec;
 540                 elf_add_reloc(file->elf, reloc);
 541
 542                 idx++;
 543         }
 544
 545         if (elf_rebuild_reloc_section(file->elf, reloc_sec))
 546                 return -1;
 547
 548         return 0;
 549 }
 550
 551 static int create_mcount_loc_sections(struct objtool_file *file)
 552 {
 553         struct section *sec, *reloc_sec;
 554         struct reloc *reloc;
 555         unsigned long *loc;
 556         struct instruction *insn;
 557         int idx;
 558
 559         sec = find_section_by_name(file->elf, "__mcount_loc");
 560         if (sec) {
 561                 INIT_LIST_HEAD(&file->mcount_loc_list);
 562                 WARN("file already has __mcount_loc section, skipping");
 563                 return 0;
 564         }
 565
 566         if (list_empty(&file->mcount_loc_list))
 567                 return 0;
 568
 569         idx = 0;
 570         list_for_each_entry(insn, &file->mcount_loc_list, mcount_loc_node)
 571                 idx++;
 572
 573         sec = elf_create_section(file->elf, "__mcount_loc", 0, sizeof(unsigned long), idx);
 574         if (!sec)
 575                 return -1;
 576
 577         reloc_sec = elf_create_reloc_section(file->elf, sec, SHT_RELA);
 578         if (!reloc_sec)
 579                 return -1;
 580
 581         idx = 0;
 582         list_for_each_entry(insn, &file->mcount_loc_list, mcount_loc_node) {
 583
 584                 loc = (unsigned long *)sec->data->d_buf + idx;
 585                 memset(loc, 0, sizeof(unsigned long));
 586
 587                 reloc = malloc(sizeof(*reloc));
 588                 if (!reloc) {
 589                         perror("malloc");
 590                         return -1;
 591                 }
 592                 memset(reloc, 0, sizeof(*reloc));
 593
 594                 if (insn->sec->sym) {
 595                         reloc->sym = insn->sec->sym;
 596                         reloc->addend = insn->offset;
 597                 } else {
 598                         reloc->sym = find_symbol_containing(insn->sec, insn->offset);
 599
 600                         if (!reloc->sym) {
 601                                 WARN("missing symbol for insn at offset 0x%lx\n",
 602                                      insn->offset);
 603                                 return -1;
 604                         }
 605
 606                         reloc->addend = insn->offset - reloc->sym->offset;
 607                 }
 608
 609                 reloc->type = R_X86_64_64;
 610                 reloc->offset = idx * sizeof(unsigned long);
 611                 reloc->sec = reloc_sec;
 612                 elf_add_reloc(file->elf, reloc);
 613
 614                 idx++;
 615         }
 616
 617         if (elf_rebuild_reloc_section(file->elf, reloc_sec))
 618                 return -1;
 619
 620         return 0;
 621 }
 622
 623 /*
 624  * Warnings shouldn't be reported for ignored functions.
 625  */
 626 static void add_ignores(struct objtool_file *file)
 627 {
 628         struct instruction *insn;
 629         struct section *sec;
 630         struct symbol *func;
 631         struct reloc *reloc;
 632
 633         sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
 634         if (!sec)
 635                 return;
 636
 637         list_for_each_entry(reloc, &sec->reloc_list, list) {
 638                 switch (reloc->sym->type) {
 639                 case STT_FUNC:
 640                         func = reloc->sym;
 641                         break;
 642
 643                 case STT_SECTION:
 644                         func = find_func_by_offset(reloc->sym->sec, reloc->addend);
 645                         if (!func)
 646                                 continue;
 647                         break;
 648
 649                 default:
 650                         WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type);
 651                         continue;
 652                 }
 653
 654                 func_for_each_insn(file, func, insn)
 655                         insn->ignore = true;
 656         }
 657 }
 658
 659 /*
 660  * This is a whitelist of functions that is allowed to be called with AC set.
 661  * The list is meant to be minimal and only contains compiler instrumentation
 662  * ABI and a few functions used to implement *_{to,from}_user() functions.
 663  *
 664  * These functions must not directly change AC, but may PUSHF/POPF.
 665  */
 666 static const char *uaccess_safe_builtin[] = {
 667         /* KASAN */
 668         "kasan_report",
 669         "kasan_check_range",
 670         /* KASAN out-of-line */
 671         "__asan_loadN_noabort",
 672         "__asan_load1_noabort",
 673         "__asan_load2_noabort",
 674         "__asan_load4_noabort",
 675         "__asan_load8_noabort",
 676         "__asan_load16_noabort",
 677         "__asan_storeN_noabort",
 678         "__asan_store1_noabort",
 679         "__asan_store2_noabort",
 680         "__asan_store4_noabort",
 681         "__asan_store8_noabort",
 682         "__asan_store16_noabort",
 683         "__kasan_check_read",
 684         "__kasan_check_write",
 685         /* KASAN in-line */
 686         "__asan_report_load_n_noabort",
 687         "__asan_report_load1_noabort",
 688         "__asan_report_load2_noabort",
 689         "__asan_report_load4_noabort",
 690         "__asan_report_load8_noabort",
 691         "__asan_report_load16_noabort",
 692         "__asan_report_store_n_noabort",
 693         "__asan_report_store1_noabort",
 694         "__asan_report_store2_noabort",
 695         "__asan_report_store4_noabort",
 696         "__asan_report_store8_noabort",
 697         "__asan_report_store16_noabort",
 698         /* KCSAN */
 699         "__kcsan_check_access",
 700         "kcsan_found_watchpoint",
 701         "kcsan_setup_watchpoint",
 702         "kcsan_check_scoped_accesses",
 703         "kcsan_disable_current",
 704         "kcsan_enable_current_nowarn",
 705         /* KCSAN/TSAN */
 706         "__tsan_func_entry",
 707         "__tsan_func_exit",
 708         "__tsan_read_range",
 709         "__tsan_write_range",
 710         "__tsan_read1",
 711         "__tsan_read2",
 712         "__tsan_read4",
 713         "__tsan_read8",
 714         "__tsan_read16",
 715         "__tsan_write1",
 716         "__tsan_write2",
 717         "__tsan_write4",
 718         "__tsan_write8",
 719         "__tsan_write16",
 720         "__tsan_read_write1",
 721         "__tsan_read_write2",
 722         "__tsan_read_write4",
 723         "__tsan_read_write8",
 724         "__tsan_read_write16",
 725         "__tsan_atomic8_load",
 726         "__tsan_atomic16_load",
 727         "__tsan_atomic32_load",
 728         "__tsan_atomic64_load",
 729         "__tsan_atomic8_store",
 730         "__tsan_atomic16_store",
 731         "__tsan_atomic32_store",
 732         "__tsan_atomic64_store",
 733         "__tsan_atomic8_exchange",
 734         "__tsan_atomic16_exchange",
 735         "__tsan_atomic32_exchange",
 736         "__tsan_atomic64_exchange",
 737         "__tsan_atomic8_fetch_add",
 738         "__tsan_atomic16_fetch_add",
 739         "__tsan_atomic32_fetch_add",
 740         "__tsan_atomic64_fetch_add",
 741         "__tsan_atomic8_fetch_sub",
 742         "__tsan_atomic16_fetch_sub",
 743         "__tsan_atomic32_fetch_sub",
 744         "__tsan_atomic64_fetch_sub",
 745         "__tsan_atomic8_fetch_and",
 746         "__tsan_atomic16_fetch_and",
 747         "__tsan_atomic32_fetch_and",
 748         "__tsan_atomic64_fetch_and",
 749         "__tsan_atomic8_fetch_or",
 750         "__tsan_atomic16_fetch_or",
 751         "__tsan_atomic32_fetch_or",
 752         "__tsan_atomic64_fetch_or",
 753         "__tsan_atomic8_fetch_xor",
 754         "__tsan_atomic16_fetch_xor",
 755         "__tsan_atomic32_fetch_xor",
 756         "__tsan_atomic64_fetch_xor",
 757         "__tsan_atomic8_fetch_nand",
 758         "__tsan_atomic16_fetch_nand",
 759         "__tsan_atomic32_fetch_nand",
 760         "__tsan_atomic64_fetch_nand",
 761         "__tsan_atomic8_compare_exchange_strong",
 762         "__tsan_atomic16_compare_exchange_strong",
 763         "__tsan_atomic32_compare_exchange_strong",
 764         "__tsan_atomic64_compare_exchange_strong",
 765         "__tsan_atomic8_compare_exchange_weak",
 766         "__tsan_atomic16_compare_exchange_weak",
 767         "__tsan_atomic32_compare_exchange_weak",
 768         "__tsan_atomic64_compare_exchange_weak",
 769         "__tsan_atomic8_compare_exchange_val",
 770         "__tsan_atomic16_compare_exchange_val",
 771         "__tsan_atomic32_compare_exchange_val",
 772         "__tsan_atomic64_compare_exchange_val",
 773         "__tsan_atomic_thread_fence",
 774         "__tsan_atomic_signal_fence",
 775         /* KCOV */
 776         "write_comp_data",
 777         "check_kcov_mode",
 778         "__sanitizer_cov_trace_pc",
 779         "__sanitizer_cov_trace_const_cmp1",
 780         "__sanitizer_cov_trace_const_cmp2",
 781         "__sanitizer_cov_trace_const_cmp4",
 782         "__sanitizer_cov_trace_const_cmp8",
 783         "__sanitizer_cov_trace_cmp1",
 784         "__sanitizer_cov_trace_cmp2",
 785         "__sanitizer_cov_trace_cmp4",
 786         "__sanitizer_cov_trace_cmp8",
 787         "__sanitizer_cov_trace_switch",
 788         /* UBSAN */
 789         "ubsan_type_mismatch_common",
 790         "__ubsan_handle_type_mismatch",
 791         "__ubsan_handle_type_mismatch_v1",
 792         "__ubsan_handle_shift_out_of_bounds",
 793         /* misc */
 794         "csum_partial_copy_generic",
 795         "copy_mc_fragile",
 796         "copy_mc_fragile_handle_tail",
 797         "copy_mc_enhanced_fast_string",
 798         "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
 799         NULL
 800 };
 801
 802 static void add_uaccess_safe(struct objtool_file *file)
 803 {
 804         struct symbol *func;
 805         const char **name;
 806
 807         if (!uaccess)
 808                 return;
 809
 810         for (name = uaccess_safe_builtin; *name; name++) {
 811                 func = find_symbol_by_name(file->elf, *name);
 812                 if (!func)
 813                         continue;
 814
 815                 func->uaccess_safe = true;
 816         }
 817 }
 818
 819 /*
 820  * FIXME: For now, just ignore any alternatives which add retpolines.  This is
 821  * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
 822  * But it at least allows objtool to understand the control flow *around* the
 823  * retpoline.
 824  */
 825 static int add_ignore_alternatives(struct objtool_file *file)
 826 {
 827         struct section *sec;
 828         struct reloc *reloc;
 829         struct instruction *insn;
 830
 831         sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
 832         if (!sec)
 833                 return 0;
 834
 835         list_for_each_entry(reloc, &sec->reloc_list, list) {
 836                 if (reloc->sym->type != STT_SECTION) {
 837                         WARN("unexpected relocation symbol type in %s", sec->name);
 838                         return -1;
 839                 }
 840
 841                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 842                 if (!insn) {
 843                         WARN("bad .discard.ignore_alts entry");
 844                         return -1;
 845                 }
 846
 847                 insn->ignore_alts = true;
 848         }
 849
 850         return 0;
 851 }
 852
 853 /*
 854  * Find the destination instructions for all jumps.
 855  */
 856 static int add_jump_destinations(struct objtool_file *file)
 857 {
 858         struct instruction *insn;
 859         struct reloc *reloc;
 860         struct section *dest_sec;
 861         unsigned long dest_off;
 862
 863         for_each_insn(file, insn) {
 864                 if (!is_static_jump(insn))
 865                         continue;
 866
 867                 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
 868                                                  insn->offset, insn->len);
 869                 if (!reloc) {
 870                         dest_sec = insn->sec;
 871                         dest_off = arch_jump_destination(insn);
 872                 } else if (reloc->sym->type == STT_SECTION) {
 873                         dest_sec = reloc->sym->sec;
 874                         dest_off = arch_dest_reloc_offset(reloc->addend);
 875                 } else if (!strncmp(reloc->sym->name, "__x86_indirect_thunk_", 21) ||
 876                            !strncmp(reloc->sym->name, "__x86_retpoline_", 16)) {
 877                         /*
 878                          * Retpoline jumps are really dynamic jumps in
 879                          * disguise, so convert them accordingly.
 880                          */
 881                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
 882                                 insn->type = INSN_JUMP_DYNAMIC;
 883                         else
 884                                 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
 885
 886                         insn->retpoline_safe = true;
 887                         continue;
 888                 } else if (insn->func) {
 889                         /* internal or external sibling call (with reloc) */
 890                         insn->call_dest = reloc->sym;
 891                         if (insn->call_dest->static_call_tramp) {
 892                                 list_add_tail(&insn->static_call_node,
 893                                               &file->static_call_list);
 894                         }
 895                         continue;
 896                 } else if (reloc->sym->sec->idx) {
 897                         dest_sec = reloc->sym->sec;
 898                         dest_off = reloc->sym->sym.st_value +
 899                                    arch_dest_reloc_offset(reloc->addend);
 900                 } else {
 901                         /* non-func asm code jumping to another file */
 902                         continue;
 903                 }
 904
 905                 insn->jump_dest = find_insn(file, dest_sec, dest_off);
 906                 if (!insn->jump_dest) {
 907
 908                         /*
 909                          * This is a special case where an alt instruction
 910                          * jumps past the end of the section.  These are
 911                          * handled later in handle_group_alt().
 912                          */
 913                         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
 914                                 continue;
 915
 916                         WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
 917                                   insn->sec, insn->offset, dest_sec->name,
 918                                   dest_off);
 919                         return -1;
 920                 }
 921
 922                 /*
 923                  * Cross-function jump.
 924                  */
 925                 if (insn->func && insn->jump_dest->func &&
 926                     insn->func != insn->jump_dest->func) {
 927
 928                         /*
 929                          * For GCC 8+, create parent/child links for any cold
 930                          * subfunctions.  This is _mostly_ redundant with a
 931                          * similar initialization in read_symbols().
 932                          *
 933                          * If a function has aliases, we want the *first* such
 934                          * function in the symbol table to be the subfunction's
 935                          * parent.  In that case we overwrite the
 936                          * initialization done in read_symbols().
 937                          *
 938                          * However this code can't completely replace the
 939                          * read_symbols() code because this doesn't detect the
 940                          * case where the parent function's only reference to a
 941                          * subfunction is through a jump table.
 942                          */
 943                         if (!strstr(insn->func->name, ".cold") &&
 944                             strstr(insn->jump_dest->func->name, ".cold")) {
 945                                 insn->func->cfunc = insn->jump_dest->func;
 946                                 insn->jump_dest->func->pfunc = insn->func;
 947
 948                         } else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
 949                                    insn->jump_dest->offset == insn->jump_dest->func->offset) {
 950
 951                                 /* internal sibling call (without reloc) */
 952                                 insn->call_dest = insn->jump_dest->func;
 953                                 if (insn->call_dest->static_call_tramp) {
 954                                         list_add_tail(&insn->static_call_node,
 955                                                       &file->static_call_list);
 956                                 }
 957                         }
 958                 }
 959         }
 960
 961         return 0;
 962 }
 963
 964 static void remove_insn_ops(struct instruction *insn)
 965 {
 966         struct stack_op *op, *tmp;
 967
 968         list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
 969                 list_del(&op->list);
 970                 free(op);
 971         }
 972 }
 973
 974 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
 975 {
 976         struct symbol *call_dest;
 977
 978         call_dest = find_func_by_offset(sec, offset);
 979         if (!call_dest)
 980                 call_dest = find_symbol_by_offset(sec, offset);
 981
 982         return call_dest;
 983 }
 984
 985 /*
 986  * Find the destination instructions for all calls.
 987  */
 988 static int add_call_destinations(struct objtool_file *file)
 989 {
 990         struct instruction *insn;
 991         unsigned long dest_off;
 992         struct reloc *reloc;
 993
 994         for_each_insn(file, insn) {
 995                 if (insn->type != INSN_CALL)
 996                         continue;
 997
 998                 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
 999                                                insn->offset, insn->len);
1000                 if (!reloc) {
1001                         dest_off = arch_jump_destination(insn);
1002                         insn->call_dest = find_call_destination(insn->sec, dest_off);
1003
1004                         if (insn->ignore)
1005                                 continue;
1006
1007                         if (!insn->call_dest) {
1008                                 WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);
1009                                 return -1;
1010                         }
1011
1012                         if (insn->func && insn->call_dest->type != STT_FUNC) {
1013                                 WARN_FUNC("unsupported call to non-function",
1014                                           insn->sec, insn->offset);
1015                                 return -1;
1016                         }
1017
1018                 } else if (reloc->sym->type == STT_SECTION) {
1019                         dest_off = arch_dest_reloc_offset(reloc->addend);
1020                         insn->call_dest = find_call_destination(reloc->sym->sec,
1021                                                                 dest_off);
1022                         if (!insn->call_dest) {
1023                                 WARN_FUNC("can't find call dest symbol at %s+0x%lx",
1024                                           insn->sec, insn->offset,
1025                                           reloc->sym->sec->name,
1026                                           dest_off);
1027                                 return -1;
1028                         }
1029                 } else
1030                         insn->call_dest = reloc->sym;
1031
1032                 /*
1033                  * Many compilers cannot disable KCOV with a function attribute
1034                  * so they need a little help, NOP out any KCOV calls from noinstr
1035                  * text.
1036                  */
1037                 if (insn->sec->noinstr &&
1038                     !strncmp(insn->call_dest->name, "__sanitizer_cov_", 16)) {
1039                         if (reloc) {
1040                                 reloc->type = R_NONE;
1041                                 elf_write_reloc(file->elf, reloc);
1042                         }
1043
1044                         elf_write_insn(file->elf, insn->sec,
1045                                        insn->offset, insn->len,
1046                                        arch_nop_insn(insn->len));
1047                         insn->type = INSN_NOP;
1048                 }
1049
1050                 if (mcount && !strcmp(insn->call_dest->name, "__fentry__")) {
1051                         if (reloc) {
1052                                 reloc->type = R_NONE;
1053                                 elf_write_reloc(file->elf, reloc);
1054                         }
1055
1056                         elf_write_insn(file->elf, insn->sec,
1057                                        insn->offset, insn->len,
1058                                        arch_nop_insn(insn->len));
1059
1060                         insn->type = INSN_NOP;
1061
1062                         list_add_tail(&insn->mcount_loc_node,
1063                                       &file->mcount_loc_list);
1064                 }
1065
1066                 /*
1067                  * Whatever stack impact regular CALLs have, should be undone
1068                  * by the RETURN of the called function.
1069                  *
1070                  * Annotated intra-function calls retain the stack_ops but
1071                  * are converted to JUMP, see read_intra_function_calls().
1072                  */
1073                 remove_insn_ops(insn);
1074         }
1075
1076         return 0;
1077 }
1078
1079 /*
1080  * The .alternatives section requires some extra special care over and above
1081  * other special sections because alternatives are patched in place.
1082  */
1083 static int handle_group_alt(struct objtool_file *file,
1084                             struct special_alt *special_alt,
1085                             struct instruction *orig_insn,
1086                             struct instruction **new_insn)
1087 {
1088         struct instruction *last_orig_insn, *last_new_insn = NULL, *insn, *nop = NULL;
1089         struct alt_group *orig_alt_group, *new_alt_group;
1090         unsigned long dest_off;
1091
1092
1093         orig_alt_group = malloc(sizeof(*orig_alt_group));
1094         if (!orig_alt_group) {
1095                 WARN("malloc failed");
1096                 return -1;
1097         }
1098         orig_alt_group->cfi = calloc(special_alt->orig_len,
1099                                      sizeof(struct cfi_state *));
1100         if (!orig_alt_group->cfi) {
1101                 WARN("calloc failed");
1102                 return -1;
1103         }
1104
1105         last_orig_insn = NULL;
1106         insn = orig_insn;
1107         sec_for_each_insn_from(file, insn) {
1108                 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1109                         break;
1110
1111                 insn->alt_group = orig_alt_group;
1112                 last_orig_insn = insn;
1113         }
1114         orig_alt_group->orig_group = NULL;
1115         orig_alt_group->first_insn = orig_insn;
1116         orig_alt_group->last_insn = last_orig_insn;
1117
1118
1119         new_alt_group = malloc(sizeof(*new_alt_group));
1120         if (!new_alt_group) {
1121                 WARN("malloc failed");
1122                 return -1;
1123         }
1124
1125         if (special_alt->new_len < special_alt->orig_len) {
1126                 /*
1127                  * Insert a fake nop at the end to make the replacement
1128                  * alt_group the same size as the original.  This is needed to
1129                  * allow propagate_alt_cfi() to do its magic.  When the last
1130                  * instruction affects the stack, the instruction after it (the
1131                  * nop) will propagate the new state to the shared CFI array.
1132                  */
1133                 nop = malloc(sizeof(*nop));
1134                 if (!nop) {
1135                         WARN("malloc failed");
1136                         return -1;
1137                 }
1138                 memset(nop, 0, sizeof(*nop));
1139                 INIT_LIST_HEAD(&nop->alts);
1140                 INIT_LIST_HEAD(&nop->stack_ops);
1141                 init_cfi_state(&nop->cfi);
1142
1143                 nop->sec = special_alt->new_sec;
1144                 nop->offset = special_alt->new_off + special_alt->new_len;
1145                 nop->len = special_alt->orig_len - special_alt->new_len;
1146                 nop->type = INSN_NOP;
1147                 nop->func = orig_insn->func;
1148                 nop->alt_group = new_alt_group;
1149                 nop->ignore = orig_insn->ignore_alts;
1150         }
1151
1152         if (!special_alt->new_len) {
1153                 *new_insn = nop;
1154                 goto end;
1155         }
1156
1157         insn = *new_insn;
1158         sec_for_each_insn_from(file, insn) {
1159                 struct reloc *alt_reloc;
1160
1161                 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1162                         break;
1163
1164                 last_new_insn = insn;
1165
1166                 insn->ignore = orig_insn->ignore_alts;
1167                 insn->func = orig_insn->func;
1168                 insn->alt_group = new_alt_group;
1169
1170                 /*
1171                  * Since alternative replacement code is copy/pasted by the
1172                  * kernel after applying relocations, generally such code can't
1173                  * have relative-address relocation references to outside the
1174                  * .altinstr_replacement section, unless the arch's
1175                  * alternatives code can adjust the relative offsets
1176                  * accordingly.
1177                  */
1178                 alt_reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1179                                                    insn->offset, insn->len);
1180                 if (alt_reloc &&
1181                     !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1182
1183                         WARN_FUNC("unsupported relocation in alternatives section",
1184                                   insn->sec, insn->offset);
1185                         return -1;
1186                 }
1187
1188                 if (!is_static_jump(insn))
1189                         continue;
1190
1191                 if (!insn->immediate)
1192                         continue;
1193
1194                 dest_off = arch_jump_destination(insn);
1195                 if (dest_off == special_alt->new_off + special_alt->new_len)
1196                         insn->jump_dest = next_insn_same_sec(file, last_orig_insn);
1197
1198                 if (!insn->jump_dest) {
1199                         WARN_FUNC("can't find alternative jump destination",
1200                                   insn->sec, insn->offset);
1201                         return -1;
1202                 }
1203         }
1204
1205         if (!last_new_insn) {
1206                 WARN_FUNC("can't find last new alternative instruction",
1207                           special_alt->new_sec, special_alt->new_off);
1208                 return -1;
1209         }
1210
1211         if (nop)
1212                 list_add(&nop->list, &last_new_insn->list);
1213 end:
1214         new_alt_group->orig_group = orig_alt_group;
1215         new_alt_group->first_insn = *new_insn;
1216         new_alt_group->last_insn = nop ? : last_new_insn;
1217         new_alt_group->cfi = orig_alt_group->cfi;
1218         return 0;
1219 }
1220
1221 /*
1222  * A jump table entry can either convert a nop to a jump or a jump to a nop.
1223  * If the original instruction is a jump, make the alt entry an effective nop
1224  * by just skipping the original instruction.
1225  */
1226 static int handle_jump_alt(struct objtool_file *file,
1227                            struct special_alt *special_alt,
1228                            struct instruction *orig_insn,
1229                            struct instruction **new_insn)
1230 {
1231         if (orig_insn->type == INSN_NOP)
1232                 return 0;
1233
1234         if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
1235                 WARN_FUNC("unsupported instruction at jump label",
1236                           orig_insn->sec, orig_insn->offset);
1237                 return -1;
1238         }
1239
1240         *new_insn = list_next_entry(orig_insn, list);
1241         return 0;
1242 }
1243
1244 /*
1245  * Read all the special sections which have alternate instructions which can be
1246  * patched in or redirected to at runtime.  Each instruction having alternate
1247  * instruction(s) has them added to its insn->alts list, which will be
1248  * traversed in validate_branch().
1249  */
1250 static int add_special_section_alts(struct objtool_file *file)
1251 {
1252         struct list_head special_alts;
1253         struct instruction *orig_insn, *new_insn;
1254         struct special_alt *special_alt, *tmp;
1255         struct alternative *alt;
1256         int ret;
1257
1258         ret = special_get_alts(file->elf, &special_alts);
1259         if (ret)
1260                 return ret;
1261
1262         list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1263
1264                 orig_insn = find_insn(file, special_alt->orig_sec,
1265                                       special_alt->orig_off);
1266                 if (!orig_insn) {
1267                         WARN_FUNC("special: can't find orig instruction",
1268                                   special_alt->orig_sec, special_alt->orig_off);
1269                         ret = -1;
1270                         goto out;
1271                 }
1272
1273                 new_insn = NULL;
1274                 if (!special_alt->group || special_alt->new_len) {
1275                         new_insn = find_insn(file, special_alt->new_sec,
1276                                              special_alt->new_off);
1277                         if (!new_insn) {
1278                                 WARN_FUNC("special: can't find new instruction",
1279                                           special_alt->new_sec,
1280                                           special_alt->new_off);
1281                                 ret = -1;
1282                                 goto out;
1283                         }
1284                 }
1285
1286                 if (special_alt->group) {
1287                         if (!special_alt->orig_len) {
1288                                 WARN_FUNC("empty alternative entry",
1289                                           orig_insn->sec, orig_insn->offset);
1290                                 continue;
1291                         }
1292
1293                         ret = handle_group_alt(file, special_alt, orig_insn,
1294                                                &new_insn);
1295                         if (ret)
1296                                 goto out;
1297                 } else if (special_alt->jump_or_nop) {
1298                         ret = handle_jump_alt(file, special_alt, orig_insn,
1299                                               &new_insn);
1300                         if (ret)
1301                                 goto out;
1302                 }
1303
1304                 alt = malloc(sizeof(*alt));
1305                 if (!alt) {
1306                         WARN("malloc failed");
1307                         ret = -1;
1308                         goto out;
1309                 }
1310
1311                 alt->insn = new_insn;
1312                 alt->skip_orig = special_alt->skip_orig;
1313                 orig_insn->ignore_alts |= special_alt->skip_alt;
1314                 list_add_tail(&alt->list, &orig_insn->alts);
1315
1316                 list_del(&special_alt->list);
1317                 free(special_alt);
1318         }
1319
1320 out:
1321         return ret;
1322 }
1323
1324 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
1325                             struct reloc *table)
1326 {
1327         struct reloc *reloc = table;
1328         struct instruction *dest_insn;
1329         struct alternative *alt;
1330         struct symbol *pfunc = insn->func->pfunc;
1331         unsigned int prev_offset = 0;
1332
1333         /*
1334          * Each @reloc is a switch table relocation which points to the target
1335          * instruction.
1336          */
1337         list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
1338
1339                 /* Check for the end of the table: */
1340                 if (reloc != table && reloc->jump_table_start)
1341                         break;
1342
1343                 /* Make sure the table entries are consecutive: */
1344                 if (prev_offset && reloc->offset != prev_offset + 8)
1345                         break;
1346
1347                 /* Detect function pointers from contiguous objects: */
1348                 if (reloc->sym->sec == pfunc->sec &&
1349                     reloc->addend == pfunc->offset)
1350                         break;
1351
1352                 dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
1353                 if (!dest_insn)
1354                         break;
1355
1356                 /* Make sure the destination is in the same function: */
1357                 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
1358                         break;
1359
1360                 alt = malloc(sizeof(*alt));
1361                 if (!alt) {
1362                         WARN("malloc failed");
1363                         return -1;
1364                 }
1365
1366                 alt->insn = dest_insn;
1367                 list_add_tail(&alt->list, &insn->alts);
1368                 prev_offset = reloc->offset;
1369         }
1370
1371         if (!prev_offset) {
1372                 WARN_FUNC("can't find switch jump table",
1373                           insn->sec, insn->offset);
1374                 return -1;
1375         }
1376
1377         return 0;
1378 }
1379
1380 /*
1381  * find_jump_table() - Given a dynamic jump, find the switch jump table
1382  * associated with it.
1383  */
1384 static struct reloc *find_jump_table(struct objtool_file *file,
1385                                       struct symbol *func,
1386                                       struct instruction *insn)
1387 {
1388         struct reloc *table_reloc;
1389         struct instruction *dest_insn, *orig_insn = insn;
1390
1391         /*
1392          * Backward search using the @first_jump_src links, these help avoid
1393          * much of the 'in between' code. Which avoids us getting confused by
1394          * it.
1395          */
1396         for (;
1397              insn && insn->func && insn->func->pfunc == func;
1398              insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
1399
1400                 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1401                         break;
1402
1403                 /* allow small jumps within the range */
1404                 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1405                     insn->jump_dest &&
1406                     (insn->jump_dest->offset <= insn->offset ||
1407                      insn->jump_dest->offset > orig_insn->offset))
1408                     break;
1409
1410                 table_reloc = arch_find_switch_table(file, insn);
1411                 if (!table_reloc)
1412                         continue;
1413                 dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
1414                 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1415                         continue;
1416
1417                 return table_reloc;
1418         }
1419
1420         return NULL;
1421 }
1422
1423 /*
1424  * First pass: Mark the head of each jump table so that in the next pass,
1425  * we know when a given jump table ends and the next one starts.
1426  */
1427 static void mark_func_jump_tables(struct objtool_file *file,
1428                                     struct symbol *func)
1429 {
1430         struct instruction *insn, *last = NULL;
1431         struct reloc *reloc;
1432
1433         func_for_each_insn(file, func, insn) {
1434                 if (!last)
1435                         last = insn;
1436
1437                 /*
1438                  * Store back-pointers for unconditional forward jumps such
1439                  * that find_jump_table() can back-track using those and
1440                  * avoid some potentially confusing code.
1441                  */
1442                 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1443                     insn->offset > last->offset &&
1444                     insn->jump_dest->offset > insn->offset &&
1445                     !insn->jump_dest->first_jump_src) {
1446
1447                         insn->jump_dest->first_jump_src = insn;
1448                         last = insn->jump_dest;
1449                 }
1450
1451                 if (insn->type != INSN_JUMP_DYNAMIC)
1452                         continue;
1453
1454                 reloc = find_jump_table(file, func, insn);
1455                 if (reloc) {
1456                         reloc->jump_table_start = true;
1457                         insn->jump_table = reloc;
1458                 }
1459         }
1460 }
1461
1462 static int add_func_jump_tables(struct objtool_file *file,
1463                                   struct symbol *func)
1464 {
1465         struct instruction *insn;
1466         int ret;
1467
1468         func_for_each_insn(file, func, insn) {
1469                 if (!insn->jump_table)
1470                         continue;
1471
1472                 ret = add_jump_table(file, insn, insn->jump_table);
1473                 if (ret)
1474                         return ret;
1475         }
1476
1477         return 0;
1478 }
1479
1480 /*
1481  * For some switch statements, gcc generates a jump table in the .rodata
1482  * section which contains a list of addresses within the function to jump to.
1483  * This finds these jump tables and adds them to the insn->alts lists.
1484  */
1485 static int add_jump_table_alts(struct objtool_file *file)
1486 {
1487         struct section *sec;
1488         struct symbol *func;
1489         int ret;
1490
1491         if (!file->rodata)
1492                 return 0;
1493
1494         for_each_sec(file, sec) {
1495                 list_for_each_entry(func, &sec->symbol_list, list) {
1496                         if (func->type != STT_FUNC)
1497                                 continue;
1498
1499                         mark_func_jump_tables(file, func);
1500                         ret = add_func_jump_tables(file, func);
1501                         if (ret)
1502                                 return ret;
1503                 }
1504         }
1505
1506         return 0;
1507 }
1508
1509 static void set_func_state(struct cfi_state *state)
1510 {
1511         state->cfa = initial_func_cfi.cfa;
1512         memcpy(&state->regs, &initial_func_cfi.regs,
1513                CFI_NUM_REGS * sizeof(struct cfi_reg));
1514         state->stack_size = initial_func_cfi.cfa.offset;
1515 }
1516
1517 static int read_unwind_hints(struct objtool_file *file)
1518 {
1519         struct section *sec, *relocsec;
1520         struct reloc *reloc;
1521         struct unwind_hint *hint;
1522         struct instruction *insn;
1523         int i;
1524
1525         sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1526         if (!sec)
1527                 return 0;
1528
1529         relocsec = sec->reloc;
1530         if (!relocsec) {
1531                 WARN("missing .rela.discard.unwind_hints section");
1532                 return -1;
1533         }
1534
1535         if (sec->len % sizeof(struct unwind_hint)) {
1536                 WARN("struct unwind_hint size mismatch");
1537                 return -1;
1538         }
1539
1540         file->hints = true;
1541
1542         for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
1543                 hint = (struct unwind_hint *)sec->data->d_buf + i;
1544
1545                 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
1546                 if (!reloc) {
1547                         WARN("can't find reloc for unwind_hints[%d]", i);
1548                         return -1;
1549                 }
1550
1551                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1552                 if (!insn) {
1553                         WARN("can't find insn for unwind_hints[%d]", i);
1554                         return -1;
1555                 }
1556
1557                 insn->hint = true;
1558
1559                 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
1560                         set_func_state(&insn->cfi);
1561                         continue;
1562                 }
1563
1564                 if (arch_decode_hint_reg(insn, hint->sp_reg)) {
1565                         WARN_FUNC("unsupported unwind_hint sp base reg %d",
1566                                   insn->sec, insn->offset, hint->sp_reg);
1567                         return -1;
1568                 }
1569
1570                 insn->cfi.cfa.offset = bswap_if_needed(hint->sp_offset);
1571                 insn->cfi.type = hint->type;
1572                 insn->cfi.end = hint->end;
1573         }
1574
1575         return 0;
1576 }
1577
1578 static int read_retpoline_hints(struct objtool_file *file)
1579 {
1580         struct section *sec;
1581         struct instruction *insn;
1582         struct reloc *reloc;
1583
1584         sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1585         if (!sec)
1586                 return 0;
1587
1588         list_for_each_entry(reloc, &sec->reloc_list, list) {
1589                 if (reloc->sym->type != STT_SECTION) {
1590                         WARN("unexpected relocation symbol type in %s", sec->name);
1591                         return -1;
1592                 }
1593
1594                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1595                 if (!insn) {
1596                         WARN("bad .discard.retpoline_safe entry");
1597                         return -1;
1598                 }
1599
1600                 if (insn->type != INSN_JUMP_DYNAMIC &&
1601                     insn->type != INSN_CALL_DYNAMIC) {
1602                         WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1603                                   insn->sec, insn->offset);
1604                         return -1;
1605                 }
1606
1607                 insn->retpoline_safe = true;
1608         }
1609
1610         return 0;
1611 }
1612
1613 static int read_instr_hints(struct objtool_file *file)
1614 {
1615         struct section *sec;
1616         struct instruction *insn;
1617         struct reloc *reloc;
1618
1619         sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
1620         if (!sec)
1621                 return 0;
1622
1623         list_for_each_entry(reloc, &sec->reloc_list, list) {
1624                 if (reloc->sym->type != STT_SECTION) {
1625                         WARN("unexpected relocation symbol type in %s", sec->name);
1626                         return -1;
1627                 }
1628
1629                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1630                 if (!insn) {
1631                         WARN("bad .discard.instr_end entry");
1632                         return -1;
1633                 }
1634
1635                 insn->instr--;
1636         }
1637
1638         sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
1639         if (!sec)
1640                 return 0;
1641
1642         list_for_each_entry(reloc, &sec->reloc_list, list) {
1643                 if (reloc->sym->type != STT_SECTION) {
1644                         WARN("unexpected relocation symbol type in %s", sec->name);
1645                         return -1;
1646                 }
1647
1648                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1649                 if (!insn) {
1650                         WARN("bad .discard.instr_begin entry");
1651                         return -1;
1652                 }
1653
1654                 insn->instr++;
1655         }
1656
1657         return 0;
1658 }
1659
1660 static int read_intra_function_calls(struct objtool_file *file)
1661 {
1662         struct instruction *insn;
1663         struct section *sec;
1664         struct reloc *reloc;
1665
1666         sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
1667         if (!sec)
1668                 return 0;
1669
1670         list_for_each_entry(reloc, &sec->reloc_list, list) {
1671                 unsigned long dest_off;
1672
1673                 if (reloc->sym->type != STT_SECTION) {
1674                         WARN("unexpected relocation symbol type in %s",
1675                              sec->name);
1676                         return -1;
1677                 }
1678
1679                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1680                 if (!insn) {
1681                         WARN("bad .discard.intra_function_call entry");
1682                         return -1;
1683                 }
1684
1685                 if (insn->type != INSN_CALL) {
1686                         WARN_FUNC("intra_function_call not a direct call",
1687                                   insn->sec, insn->offset);
1688                         return -1;
1689                 }
1690
1691                 /*
1692                  * Treat intra-function CALLs as JMPs, but with a stack_op.
1693                  * See add_call_destinations(), which strips stack_ops from
1694                  * normal CALLs.
1695                  */
1696                 insn->type = INSN_JUMP_UNCONDITIONAL;
1697
1698                 dest_off = insn->offset + insn->len + insn->immediate;
1699                 insn->jump_dest = find_insn(file, insn->sec, dest_off);
1700                 if (!insn->jump_dest) {
1701                         WARN_FUNC("can't find call dest at %s+0x%lx",
1702                                   insn->sec, insn->offset,
1703                                   insn->sec->name, dest_off);
1704                         return -1;
1705                 }
1706         }
1707
1708         return 0;
1709 }
1710
1711 static int read_static_call_tramps(struct objtool_file *file)
1712 {
1713         struct section *sec;
1714         struct symbol *func;
1715
1716         for_each_sec(file, sec) {
1717                 list_for_each_entry(func, &sec->symbol_list, list) {
1718                         if (func->bind == STB_GLOBAL &&
1719                             !strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
1720                                      strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
1721                                 func->static_call_tramp = true;
1722                 }
1723         }
1724
1725         return 0;
1726 }
1727
1728 static void mark_rodata(struct objtool_file *file)
1729 {
1730         struct section *sec;
1731         bool found = false;
1732
1733         /*
1734          * Search for the following rodata sections, each of which can
1735          * potentially contain jump tables:
1736          *
1737          * - .rodata: can contain GCC switch tables
1738          * - .rodata.<func>: same, if -fdata-sections is being used
1739          * - .rodata..c_jump_table: contains C annotated jump tables
1740          *
1741          * .rodata.str1.* sections are ignored; they don't contain jump tables.
1742          */
1743         for_each_sec(file, sec) {
1744                 if (!strncmp(sec->name, ".rodata", 7) &&
1745                     !strstr(sec->name, ".str1.")) {
1746                         sec->rodata = true;
1747                         found = true;
1748                 }
1749         }
1750
1751         file->rodata = found;
1752 }
1753
1754 static int decode_sections(struct objtool_file *file)
1755 {
1756         int ret;
1757
1758         mark_rodata(file);
1759
1760         ret = decode_instructions(file);
1761         if (ret)
1762                 return ret;
1763
1764         ret = add_dead_ends(file);
1765         if (ret)
1766                 return ret;
1767
1768         add_ignores(file);
1769         add_uaccess_safe(file);
1770
1771         ret = add_ignore_alternatives(file);
1772         if (ret)
1773                 return ret;
1774
1775         ret = read_static_call_tramps(file);
1776         if (ret)
1777                 return ret;
1778
1779         ret = add_jump_destinations(file);
1780         if (ret)
1781                 return ret;
1782
1783         ret = add_special_section_alts(file);
1784         if (ret)
1785                 return ret;
1786
1787         ret = read_intra_function_calls(file);
1788         if (ret)
1789                 return ret;
1790
1791         ret = add_call_destinations(file);
1792         if (ret)
1793                 return ret;
1794
1795         ret = add_jump_table_alts(file);
1796         if (ret)
1797                 return ret;
1798
1799         ret = read_unwind_hints(file);
1800         if (ret)
1801                 return ret;
1802
1803         ret = read_retpoline_hints(file);
1804         if (ret)
1805                 return ret;
1806
1807         ret = read_instr_hints(file);
1808         if (ret)
1809                 return ret;
1810
1811         return 0;
1812 }
1813
1814 static bool is_fentry_call(struct instruction *insn)
1815 {
1816         if (insn->type == INSN_CALL && insn->call_dest &&
1817             insn->call_dest->type == STT_NOTYPE &&
1818             !strcmp(insn->call_dest->name, "__fentry__"))
1819                 return true;
1820
1821         return false;
1822 }
1823
1824 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
1825 {
1826         struct cfi_state *cfi = &state->cfi;
1827         int i;
1828
1829         if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
1830                 return true;
1831
1832         if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
1833                 return true;
1834
1835         if (cfi->stack_size != initial_func_cfi.cfa.offset)
1836                 return true;
1837
1838         for (i = 0; i < CFI_NUM_REGS; i++) {
1839                 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
1840                     cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
1841                         return true;
1842         }
1843
1844         return false;
1845 }
1846
1847 static bool check_reg_frame_pos(const struct cfi_reg *reg,
1848                                 int expected_offset)
1849 {
1850         return reg->base == CFI_CFA &&
1851                reg->offset == expected_offset;
1852 }
1853
1854 static bool has_valid_stack_frame(struct insn_state *state)
1855 {
1856         struct cfi_state *cfi = &state->cfi;
1857
1858         if (cfi->cfa.base == CFI_BP &&
1859             check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
1860             check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
1861                 return true;
1862
1863         if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
1864                 return true;
1865
1866         return false;
1867 }
1868
1869 static int update_cfi_state_regs(struct instruction *insn,
1870                                   struct cfi_state *cfi,
1871                                   struct stack_op *op)
1872 {
1873         struct cfi_reg *cfa = &cfi->cfa;
1874
1875         if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
1876                 return 0;
1877
1878         /* push */
1879         if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
1880                 cfa->offset += 8;
1881
1882         /* pop */
1883         if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
1884                 cfa->offset -= 8;
1885
1886         /* add immediate to sp */
1887         if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1888             op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1889                 cfa->offset -= op->src.offset;
1890
1891         return 0;
1892 }
1893
1894 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
1895 {
1896         if (arch_callee_saved_reg(reg) &&
1897             cfi->regs[reg].base == CFI_UNDEFINED) {
1898                 cfi->regs[reg].base = base;
1899                 cfi->regs[reg].offset = offset;
1900         }
1901 }
1902
1903 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
1904 {
1905         cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
1906         cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
1907 }
1908
1909 /*
1910  * A note about DRAP stack alignment:
1911  *
1912  * GCC has the concept of a DRAP register, which is used to help keep track of
1913  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
1914  * register.  The typical DRAP pattern is:
1915  *
1916  *   4c 8d 54 24 08             lea    0x8(%rsp),%r10
1917  *   48 83 e4 c0                and    $0xffffffffffffffc0,%rsp
1918  *   41 ff 72 f8                pushq  -0x8(%r10)
1919  *   55                         push   %rbp
1920  *   48 89 e5                   mov    %rsp,%rbp
1921  *                              (more pushes)
1922  *   41 52                      push   %r10
1923  *                              ...
1924  *   41 5a                      pop    %r10
1925  *                              (more pops)
1926  *   5d                         pop    %rbp
1927  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1928  *   c3                         retq
1929  *
1930  * There are some variations in the epilogues, like:
1931  *
1932  *   5b                         pop    %rbx
1933  *   41 5a                      pop    %r10
1934  *   41 5c                      pop    %r12
1935  *   41 5d                      pop    %r13
1936  *   41 5e                      pop    %r14
1937  *   c9                         leaveq
1938  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1939  *   c3                         retq
1940  *
1941  * and:
1942  *
1943  *   4c 8b 55 e8                mov    -0x18(%rbp),%r10
1944  *   48 8b 5d e0                mov    -0x20(%rbp),%rbx
1945  *   4c 8b 65 f0                mov    -0x10(%rbp),%r12
1946  *   4c 8b 6d f8                mov    -0x8(%rbp),%r13
1947  *   c9                         leaveq
1948  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1949  *   c3                         retq
1950  *
1951  * Sometimes r13 is used as the DRAP register, in which case it's saved and
1952  * restored beforehand:
1953  *
1954  *   41 55                      push   %r13
1955  *   4c 8d 6c 24 10             lea    0x10(%rsp),%r13
1956  *   48 83 e4 f0                and    $0xfffffffffffffff0,%rsp
1957  *                              ...
1958  *   49 8d 65 f0                lea    -0x10(%r13),%rsp
1959  *   41 5d                      pop    %r13
1960  *   c3                         retq
1961  */
1962 static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi,
1963                              struct stack_op *op)
1964 {
1965         struct cfi_reg *cfa = &cfi->cfa;
1966         struct cfi_reg *regs = cfi->regs;
1967
1968         /* stack operations don't make sense with an undefined CFA */
1969         if (cfa->base == CFI_UNDEFINED) {
1970                 if (insn->func) {
1971                         WARN_FUNC("undefined stack state", insn->sec, insn->offset);
1972                         return -1;
1973                 }
1974                 return 0;
1975         }
1976
1977         if (cfi->type == UNWIND_HINT_TYPE_REGS ||
1978             cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
1979                 return update_cfi_state_regs(insn, cfi, op);
1980
1981         switch (op->dest.type) {
1982
1983         case OP_DEST_REG:
1984                 switch (op->src.type) {
1985
1986                 case OP_SRC_REG:
1987                         if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
1988                             cfa->base == CFI_SP &&
1989                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset)) {
1990
1991                                 /* mov %rsp, %rbp */
1992                                 cfa->base = op->dest.reg;
1993                                 cfi->bp_scratch = false;
1994                         }
1995
1996                         else if (op->src.reg == CFI_SP &&
1997                                  op->dest.reg == CFI_BP && cfi->drap) {
1998
1999                                 /* drap: mov %rsp, %rbp */
2000                                 regs[CFI_BP].base = CFI_BP;
2001                                 regs[CFI_BP].offset = -cfi->stack_size;
2002                                 cfi->bp_scratch = false;
2003                         }
2004
2005                         else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2006
2007                                 /*
2008                                  * mov %rsp, %reg
2009                                  *
2010                                  * This is needed for the rare case where GCC
2011                                  * does:
2012                                  *
2013                                  *   mov    %rsp, %rax
2014                                  *   ...
2015                                  *   mov    %rax, %rsp
2016                                  */
2017                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2018                                 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2019                         }
2020
2021                         else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2022                                  cfa->base == CFI_BP) {
2023
2024                                 /*
2025                                  * mov %rbp, %rsp
2026                                  *
2027                                  * Restore the original stack pointer (Clang).
2028                                  */
2029                                 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2030                         }
2031
2032                         else if (op->dest.reg == cfa->base) {
2033
2034                                 /* mov %reg, %rsp */
2035                                 if (cfa->base == CFI_SP &&
2036                                     cfi->vals[op->src.reg].base == CFI_CFA) {
2037
2038                                         /*
2039                                          * This is needed for the rare case
2040                                          * where GCC does something dumb like:
2041                                          *
2042                                          *   lea    0x8(%rsp), %rcx
2043                                          *   ...
2044                                          *   mov    %rcx, %rsp
2045                                          */
2046                                         cfa->offset = -cfi->vals[op->src.reg].offset;
2047                                         cfi->stack_size = cfa->offset;
2048
2049                                 } else if (cfa->base == CFI_SP &&
2050                                            cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2051                                            cfi->vals[op->src.reg].offset == cfa->offset) {
2052
2053                                         /*
2054                                          * Stack swizzle:
2055                                          *
2056                                          * 1: mov %rsp, (%[tos])
2057                                          * 2: mov %[tos], %rsp
2058                                          *    ...
2059                                          * 3: pop %rsp
2060                                          *
2061                                          * Where:
2062                                          *
2063                                          * 1 - places a pointer to the previous
2064                                          *     stack at the Top-of-Stack of the
2065                                          *     new stack.
2066                                          *
2067                                          * 2 - switches to the new stack.
2068                                          *
2069                                          * 3 - pops the Top-of-Stack to restore
2070                                          *     the original stack.
2071                                          *
2072                                          * Note: we set base to SP_INDIRECT
2073                                          * here and preserve offset. Therefore
2074                                          * when the unwinder reaches ToS it
2075                                          * will dereference SP and then add the
2076                                          * offset to find the next frame, IOW:
2077                                          * (%rsp) + offset.
2078                                          */
2079                                         cfa->base = CFI_SP_INDIRECT;
2080
2081                                 } else {
2082                                         cfa->base = CFI_UNDEFINED;
2083                                         cfa->offset = 0;
2084                                 }
2085                         }
2086
2087                         else if (op->dest.reg == CFI_SP &&
2088                                  cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2089                                  cfi->vals[op->src.reg].offset == cfa->offset) {
2090
2091                                 /*
2092                                  * The same stack swizzle case 2) as above. But
2093                                  * because we can't change cfa->base, case 3)
2094                                  * will become a regular POP. Pretend we're a
2095                                  * PUSH so things don't go unbalanced.
2096                                  */
2097                                 cfi->stack_size += 8;
2098                         }
2099
2100
2101                         break;
2102
2103                 case OP_SRC_ADD:
2104                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2105
2106                                 /* add imm, %rsp */
2107                                 cfi->stack_size -= op->src.offset;
2108                                 if (cfa->base == CFI_SP)
2109                                         cfa->offset -= op->src.offset;
2110                                 break;
2111                         }
2112
2113                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2114
2115                                 /* lea disp(%rbp), %rsp */
2116                                 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2117                                 break;
2118                         }
2119
2120                         if (!cfi->drap && op->src.reg == CFI_SP &&
2121                             op->dest.reg == CFI_BP && cfa->base == CFI_SP &&
2122                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset + op->src.offset)) {
2123
2124                                 /* lea disp(%rsp), %rbp */
2125                                 cfa->base = CFI_BP;
2126                                 cfa->offset -= op->src.offset;
2127                                 cfi->bp_scratch = false;
2128                                 break;
2129                         }
2130
2131                         if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2132
2133                                 /* drap: lea disp(%rsp), %drap */
2134                                 cfi->drap_reg = op->dest.reg;
2135
2136                                 /*
2137                                  * lea disp(%rsp), %reg
2138                                  *
2139                                  * This is needed for the rare case where GCC
2140                                  * does something dumb like:
2141                                  *
2142                                  *   lea    0x8(%rsp), %rcx
2143                                  *   ...
2144                                  *   mov    %rcx, %rsp
2145                                  */
2146                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2147                                 cfi->vals[op->dest.reg].offset = \
2148                                         -cfi->stack_size + op->src.offset;
2149
2150                                 break;
2151                         }
2152
2153                         if (cfi->drap && op->dest.reg == CFI_SP &&
2154                             op->src.reg == cfi->drap_reg) {
2155
2156                                  /* drap: lea disp(%drap), %rsp */
2157                                 cfa->base = CFI_SP;
2158                                 cfa->offset = cfi->stack_size = -op->src.offset;
2159                                 cfi->drap_reg = CFI_UNDEFINED;
2160                                 cfi->drap = false;
2161                                 break;
2162                         }
2163
2164                         if (op->dest.reg == cfi->cfa.base) {
2165                                 WARN_FUNC("unsupported stack register modification",
2166                                           insn->sec, insn->offset);
2167                                 return -1;
2168                         }
2169
2170                         break;
2171
2172                 case OP_SRC_AND:
2173                         if (op->dest.reg != CFI_SP ||
2174                             (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
2175                             (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
2176                                 WARN_FUNC("unsupported stack pointer realignment",
2177                                           insn->sec, insn->offset);
2178                                 return -1;
2179                         }
2180
2181                         if (cfi->drap_reg != CFI_UNDEFINED) {
2182                                 /* drap: and imm, %rsp */
2183                                 cfa->base = cfi->drap_reg;
2184                                 cfa->offset = cfi->stack_size = 0;
2185                                 cfi->drap = true;
2186                         }
2187
2188                         /*
2189                          * Older versions of GCC (4.8ish) realign the stack
2190                          * without DRAP, with a frame pointer.
2191                          */
2192
2193                         break;
2194
2195                 case OP_SRC_POP:
2196                 case OP_SRC_POPF:
2197                         if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
2198
2199                                 /* pop %rsp; # restore from a stack swizzle */
2200                                 cfa->base = CFI_SP;
2201                                 break;
2202                         }
2203
2204                         if (!cfi->drap && op->dest.reg == cfa->base) {
2205
2206                                 /* pop %rbp */
2207                                 cfa->base = CFI_SP;
2208                         }
2209
2210                         if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
2211                             op->dest.reg == cfi->drap_reg &&
2212                             cfi->drap_offset == -cfi->stack_size) {
2213
2214                                 /* drap: pop %drap */
2215                                 cfa->base = cfi->drap_reg;
2216                                 cfa->offset = 0;
2217                                 cfi->drap_offset = -1;
2218
2219                         } else if (regs[op->dest.reg].offset == -cfi->stack_size) {
2220
2221                                 /* pop %reg */
2222                                 restore_reg(cfi, op->dest.reg);
2223                         }
2224
2225                         cfi->stack_size -= 8;
2226                         if (cfa->base == CFI_SP)
2227                                 cfa->offset -= 8;
2228
2229                         break;
2230
2231                 case OP_SRC_REG_INDIRECT:
2232                         if (!cfi->drap && op->dest.reg == cfa->base &&
2233                             op->dest.reg == CFI_BP) {
2234
2235                                 /* mov disp(%rsp), %rbp */
2236                                 cfa->base = CFI_SP;
2237                                 cfa->offset = cfi->stack_size;
2238                         }
2239
2240                         if (cfi->drap && op->src.reg == CFI_BP &&
2241                             op->src.offset == cfi->drap_offset) {
2242
2243                                 /* drap: mov disp(%rbp), %drap */
2244                                 cfa->base = cfi->drap_reg;
2245                                 cfa->offset = 0;
2246                                 cfi->drap_offset = -1;
2247                         }
2248
2249                         if (cfi->drap && op->src.reg == CFI_BP &&
2250                             op->src.offset == regs[op->dest.reg].offset) {
2251
2252                                 /* drap: mov disp(%rbp), %reg */
2253                                 restore_reg(cfi, op->dest.reg);
2254
2255                         } else if (op->src.reg == cfa->base &&
2256                             op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
2257
2258                                 /* mov disp(%rbp), %reg */
2259                                 /* mov disp(%rsp), %reg */
2260                                 restore_reg(cfi, op->dest.reg);
2261
2262                         } else if (op->src.reg == CFI_SP &&
2263                                    op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
2264
2265                                 /* mov disp(%rsp), %reg */
2266                                 restore_reg(cfi, op->dest.reg);
2267                         }
2268
2269                         break;
2270
2271                 default:
2272                         WARN_FUNC("unknown stack-related instruction",
2273                                   insn->sec, insn->offset);
2274                         return -1;
2275                 }
2276
2277                 break;
2278
2279         case OP_DEST_PUSH:
2280         case OP_DEST_PUSHF:
2281                 cfi->stack_size += 8;
2282                 if (cfa->base == CFI_SP)
2283                         cfa->offset += 8;
2284
2285                 if (op->src.type != OP_SRC_REG)
2286                         break;
2287
2288                 if (cfi->drap) {
2289                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2290
2291                                 /* drap: push %drap */
2292                                 cfa->base = CFI_BP_INDIRECT;
2293                                 cfa->offset = -cfi->stack_size;
2294
2295                                 /* save drap so we know when to restore it */
2296                                 cfi->drap_offset = -cfi->stack_size;
2297
2298                         } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
2299
2300                                 /* drap: push %rbp */
2301                                 cfi->stack_size = 0;
2302
2303                         } else {
2304
2305                                 /* drap: push %reg */
2306                                 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
2307                         }
2308
2309                 } else {
2310
2311                         /* push %reg */
2312                         save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
2313                 }
2314
2315                 /* detect when asm code uses rbp as a scratch register */
2316                 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
2317                     cfa->base != CFI_BP)
2318                         cfi->bp_scratch = true;
2319                 break;
2320
2321         case OP_DEST_REG_INDIRECT:
2322
2323                 if (cfi->drap) {
2324                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2325
2326                                 /* drap: mov %drap, disp(%rbp) */
2327                                 cfa->base = CFI_BP_INDIRECT;
2328                                 cfa->offset = op->dest.offset;
2329
2330                                 /* save drap offset so we know when to restore it */
2331                                 cfi->drap_offset = op->dest.offset;
2332                         } else {
2333
2334                                 /* drap: mov reg, disp(%rbp) */
2335                                 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
2336                         }
2337
2338                 } else if (op->dest.reg == cfa->base) {
2339
2340                         /* mov reg, disp(%rbp) */
2341                         /* mov reg, disp(%rsp) */
2342                         save_reg(cfi, op->src.reg, CFI_CFA,
2343                                  op->dest.offset - cfi->cfa.offset);
2344
2345                 } else if (op->dest.reg == CFI_SP) {
2346
2347                         /* mov reg, disp(%rsp) */
2348                         save_reg(cfi, op->src.reg, CFI_CFA,
2349                                  op->dest.offset - cfi->stack_size);
2350
2351                 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
2352
2353                         /* mov %rsp, (%reg); # setup a stack swizzle. */
2354                         cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
2355                         cfi->vals[op->dest.reg].offset = cfa->offset;
2356                 }
2357
2358                 break;
2359
2360         case OP_DEST_LEAVE:
2361                 if ((!cfi->drap && cfa->base != CFI_BP) ||
2362                     (cfi->drap && cfa->base != cfi->drap_reg)) {
2363                         WARN_FUNC("leave instruction with modified stack frame",
2364                                   insn->sec, insn->offset);
2365                         return -1;
2366                 }
2367
2368                 /* leave (mov %rbp, %rsp; pop %rbp) */
2369
2370                 cfi->stack_size = -cfi->regs[CFI_BP].offset - 8;
2371                 restore_reg(cfi, CFI_BP);
2372
2373                 if (!cfi->drap) {
2374                         cfa->base = CFI_SP;
2375                         cfa->offset -= 8;
2376                 }
2377
2378                 break;
2379
2380         case OP_DEST_MEM:
2381                 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
2382                         WARN_FUNC("unknown stack-related memory operation",
2383                                   insn->sec, insn->offset);
2384                         return -1;
2385                 }
2386
2387                 /* pop mem */
2388                 cfi->stack_size -= 8;
2389                 if (cfa->base == CFI_SP)
2390                         cfa->offset -= 8;
2391
2392                 break;
2393
2394         default:
2395                 WARN_FUNC("unknown stack-related instruction",
2396                           insn->sec, insn->offset);
2397                 return -1;
2398         }
2399
2400         return 0;
2401 }
2402
2403 /*
2404  * The stack layouts of alternatives instructions can sometimes diverge when
2405  * they have stack modifications.  That's fine as long as the potential stack
2406  * layouts don't conflict at any given potential instruction boundary.
2407  *
2408  * Flatten the CFIs of the different alternative code streams (both original
2409  * and replacement) into a single shared CFI array which can be used to detect
2410  * conflicts and nicely feed a linear array of ORC entries to the unwinder.
2411  */
2412 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
2413 {
2414         struct cfi_state **alt_cfi;
2415         int group_off;
2416
2417         if (!insn->alt_group)
2418                 return 0;
2419
2420         alt_cfi = insn->alt_group->cfi;
2421         group_off = insn->offset - insn->alt_group->first_insn->offset;
2422
2423         if (!alt_cfi[group_off]) {
2424                 alt_cfi[group_off] = &insn->cfi;
2425         } else {
2426                 if (memcmp(alt_cfi[group_off], &insn->cfi, sizeof(struct cfi_state))) {
2427                         WARN_FUNC("stack layout conflict in alternatives",
2428                                   insn->sec, insn->offset);
2429                         return -1;
2430                 }
2431         }
2432
2433         return 0;
2434 }
2435
2436 static int handle_insn_ops(struct instruction *insn, struct insn_state *state)
2437 {
2438         struct stack_op *op;
2439
2440         list_for_each_entry(op, &insn->stack_ops, list) {
2441
2442                 if (update_cfi_state(insn, &state->cfi, op))
2443                         return 1;
2444
2445                 if (op->dest.type == OP_DEST_PUSHF) {
2446                         if (!state->uaccess_stack) {
2447                                 state->uaccess_stack = 1;
2448                         } else if (state->uaccess_stack >> 31) {
2449                                 WARN_FUNC("PUSHF stack exhausted",
2450                                           insn->sec, insn->offset);
2451                                 return 1;
2452                         }
2453                         state->uaccess_stack <<= 1;
2454                         state->uaccess_stack  |= state->uaccess;
2455                 }
2456
2457                 if (op->src.type == OP_SRC_POPF) {
2458                         if (state->uaccess_stack) {
2459                                 state->uaccess = state->uaccess_stack & 1;
2460                                 state->uaccess_stack >>= 1;
2461                                 if (state->uaccess_stack == 1)
2462                                         state->uaccess_stack = 0;
2463                         }
2464                 }
2465         }
2466
2467         return 0;
2468 }
2469
2470 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
2471 {
2472         struct cfi_state *cfi1 = &insn->cfi;
2473         int i;
2474
2475         if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
2476
2477                 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
2478                           insn->sec, insn->offset,
2479                           cfi1->cfa.base, cfi1->cfa.offset,
2480                           cfi2->cfa.base, cfi2->cfa.offset);
2481
2482         } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
2483                 for (i = 0; i < CFI_NUM_REGS; i++) {
2484                         if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
2485                                     sizeof(struct cfi_reg)))
2486                                 continue;
2487
2488                         WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
2489                                   insn->sec, insn->offset,
2490                                   i, cfi1->regs[i].base, cfi1->regs[i].offset,
2491                                   i, cfi2->regs[i].base, cfi2->regs[i].offset);
2492                         break;
2493                 }
2494
2495         } else if (cfi1->type != cfi2->type) {
2496
2497                 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
2498                           insn->sec, insn->offset, cfi1->type, cfi2->type);
2499
2500         } else if (cfi1->drap != cfi2->drap ||
2501                    (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
2502                    (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
2503
2504                 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
2505                           insn->sec, insn->offset,
2506                           cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
2507                           cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
2508
2509         } else
2510                 return true;
2511
2512         return false;
2513 }
2514
2515 static inline bool func_uaccess_safe(struct symbol *func)
2516 {
2517         if (func)
2518                 return func->uaccess_safe;
2519
2520         return false;
2521 }
2522
2523 static inline const char *call_dest_name(struct instruction *insn)
2524 {
2525         if (insn->call_dest)
2526                 return insn->call_dest->name;
2527
2528         return "{dynamic}";
2529 }
2530
2531 static inline bool noinstr_call_dest(struct symbol *func)
2532 {
2533         /*
2534          * We can't deal with indirect function calls at present;
2535          * assume they're instrumented.
2536          */
2537         if (!func)
2538                 return false;
2539
2540         /*
2541          * If the symbol is from a noinstr section; we good.
2542          */
2543         if (func->sec->noinstr)
2544                 return true;
2545
2546         /*
2547          * The __ubsan_handle_*() calls are like WARN(), they only happen when
2548          * something 'BAD' happened. At the risk of taking the machine down,
2549          * let them proceed to get the message out.
2550          */
2551         if (!strncmp(func->name, "__ubsan_handle_", 15))
2552                 return true;
2553
2554         return false;
2555 }
2556
2557 static int validate_call(struct instruction *insn, struct insn_state *state)
2558 {
2559         if (state->noinstr && state->instr <= 0 &&
2560             !noinstr_call_dest(insn->call_dest)) {
2561                 WARN_FUNC("call to %s() leaves .noinstr.text section",
2562                                 insn->sec, insn->offset, call_dest_name(insn));
2563                 return 1;
2564         }
2565
2566         if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
2567                 WARN_FUNC("call to %s() with UACCESS enabled",
2568                                 insn->sec, insn->offset, call_dest_name(insn));
2569                 return 1;
2570         }
2571
2572         if (state->df) {
2573                 WARN_FUNC("call to %s() with DF set",
2574                                 insn->sec, insn->offset, call_dest_name(insn));
2575                 return 1;
2576         }
2577
2578         return 0;
2579 }
2580
2581 static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
2582 {
2583         if (has_modified_stack_frame(insn, state)) {
2584                 WARN_FUNC("sibling call from callable instruction with modified stack frame",
2585                                 insn->sec, insn->offset);
2586                 return 1;
2587         }
2588
2589         return validate_call(insn, state);
2590 }
2591
2592 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
2593 {
2594         if (state->noinstr && state->instr > 0) {
2595                 WARN_FUNC("return with instrumentation enabled",
2596                           insn->sec, insn->offset);
2597                 return 1;
2598         }
2599
2600         if (state->uaccess && !func_uaccess_safe(func)) {
2601                 WARN_FUNC("return with UACCESS enabled",
2602                           insn->sec, insn->offset);
2603                 return 1;
2604         }
2605
2606         if (!state->uaccess && func_uaccess_safe(func)) {
2607                 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
2608                           insn->sec, insn->offset);
2609                 return 1;
2610         }
2611
2612         if (state->df) {
2613                 WARN_FUNC("return with DF set",
2614                           insn->sec, insn->offset);
2615                 return 1;
2616         }
2617
2618         if (func && has_modified_stack_frame(insn, state)) {
2619                 WARN_FUNC("return with modified stack frame",
2620                           insn->sec, insn->offset);
2621                 return 1;
2622         }
2623
2624         if (state->cfi.bp_scratch) {
2625                 WARN_FUNC("BP used as a scratch register",
2626                           insn->sec, insn->offset);
2627                 return 1;
2628         }
2629
2630         return 0;
2631 }
2632
2633 static struct instruction *next_insn_to_validate(struct objtool_file *file,
2634                                                  struct instruction *insn)
2635 {
2636         struct alt_group *alt_group = insn->alt_group;
2637
2638         /*
2639          * Simulate the fact that alternatives are patched in-place.  When the
2640          * end of a replacement alt_group is reached, redirect objtool flow to
2641          * the end of the original alt_group.
2642          */
2643         if (alt_group && insn == alt_group->last_insn && alt_group->orig_group)
2644                 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
2645
2646         return next_insn_same_sec(file, insn);
2647 }
2648
2649 /*
2650  * Follow the branch starting at the given instruction, and recursively follow
2651  * any other branches (jumps).  Meanwhile, track the frame pointer state at
2652  * each instruction and validate all the rules described in
2653  * tools/objtool/Documentation/stack-validation.txt.
2654  */
2655 static int validate_branch(struct objtool_file *file, struct symbol *func,
2656                            struct instruction *insn, struct insn_state state)
2657 {
2658         struct alternative *alt;
2659         struct instruction *next_insn;
2660         struct section *sec;
2661         u8 visited;
2662         int ret;
2663
2664         sec = insn->sec;
2665
2666         while (1) {
2667                 next_insn = next_insn_to_validate(file, insn);
2668
2669                 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
2670                         WARN("%s() falls through to next function %s()",
2671                              func->name, insn->func->name);
2672                         return 1;
2673                 }
2674
2675                 if (func && insn->ignore) {
2676                         WARN_FUNC("BUG: why am I validating an ignored function?",
2677                                   sec, insn->offset);
2678                         return 1;
2679                 }
2680
2681                 visited = 1 << state.uaccess;
2682                 if (insn->visited) {
2683                         if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
2684                                 return 1;
2685
2686                         if (insn->visited & visited)
2687                                 return 0;
2688                 }
2689
2690                 if (state.noinstr)
2691                         state.instr += insn->instr;
2692
2693                 if (insn->hint)
2694                         state.cfi = insn->cfi;
2695                 else
2696                         insn->cfi = state.cfi;
2697
2698                 insn->visited |= visited;
2699
2700                 if (propagate_alt_cfi(file, insn))
2701                         return 1;
2702
2703                 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
2704                         bool skip_orig = false;
2705
2706                         list_for_each_entry(alt, &insn->alts, list) {
2707                                 if (alt->skip_orig)
2708                                         skip_orig = true;
2709
2710                                 ret = validate_branch(file, func, alt->insn, state);
2711                                 if (ret) {
2712                                         if (backtrace)
2713                                                 BT_FUNC("(alt)", insn);
2714                                         return ret;
2715                                 }
2716                         }
2717
2718                         if (skip_orig)
2719                                 return 0;
2720                 }
2721
2722                 if (handle_insn_ops(insn, &state))
2723                         return 1;
2724
2725                 switch (insn->type) {
2726
2727                 case INSN_RETURN:
2728                         return validate_return(func, insn, &state);
2729
2730                 case INSN_CALL:
2731                 case INSN_CALL_DYNAMIC:
2732                         ret = validate_call(insn, &state);
2733                         if (ret)
2734                                 return ret;
2735
2736                         if (!no_fp && func && !is_fentry_call(insn) &&
2737                             !has_valid_stack_frame(&state)) {
2738                                 WARN_FUNC("call without frame pointer save/setup",
2739                                           sec, insn->offset);
2740                                 return 1;
2741                         }
2742
2743                         if (dead_end_function(file, insn->call_dest))
2744                                 return 0;
2745
2746                         if (insn->type == INSN_CALL && insn->call_dest->static_call_tramp) {
2747                                 list_add_tail(&insn->static_call_node,
2748                                               &file->static_call_list);
2749                         }
2750
2751                         break;
2752
2753                 case INSN_JUMP_CONDITIONAL:
2754                 case INSN_JUMP_UNCONDITIONAL:
2755                         if (is_sibling_call(insn)) {
2756                                 ret = validate_sibling_call(insn, &state);
2757                                 if (ret)
2758                                         return ret;
2759
2760                         } else if (insn->jump_dest) {
2761                                 ret = validate_branch(file, func,
2762                                                       insn->jump_dest, state);
2763                                 if (ret) {
2764                                         if (backtrace)
2765                                                 BT_FUNC("(branch)", insn);
2766                                         return ret;
2767                                 }
2768                         }
2769
2770                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
2771                                 return 0;
2772
2773                         break;
2774
2775                 case INSN_JUMP_DYNAMIC:
2776                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
2777                         if (is_sibling_call(insn)) {
2778                                 ret = validate_sibling_call(insn, &state);
2779                                 if (ret)
2780                                         return ret;
2781                         }
2782
2783                         if (insn->type == INSN_JUMP_DYNAMIC)
2784                                 return 0;
2785
2786                         break;
2787
2788                 case INSN_CONTEXT_SWITCH:
2789                         if (func && (!next_insn || !next_insn->hint)) {
2790                                 WARN_FUNC("unsupported instruction in callable function",
2791                                           sec, insn->offset);
2792                                 return 1;
2793                         }
2794                         return 0;
2795
2796                 case INSN_STAC:
2797                         if (state.uaccess) {
2798                                 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
2799                                 return 1;
2800                         }
2801
2802                         state.uaccess = true;
2803                         break;
2804
2805                 case INSN_CLAC:
2806                         if (!state.uaccess && func) {
2807                                 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
2808                                 return 1;
2809                         }
2810
2811                         if (func_uaccess_safe(func) && !state.uaccess_stack) {
2812                                 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
2813                                 return 1;
2814                         }
2815
2816                         state.uaccess = false;
2817                         break;
2818
2819                 case INSN_STD:
2820                         if (state.df) {
2821                                 WARN_FUNC("recursive STD", sec, insn->offset);
2822                                 return 1;
2823                         }
2824
2825                         state.df = true;
2826                         break;
2827
2828                 case INSN_CLD:
2829                         if (!state.df && func) {
2830                                 WARN_FUNC("redundant CLD", sec, insn->offset);
2831                                 return 1;
2832                         }
2833
2834                         state.df = false;
2835                         break;
2836
2837                 default:
2838                         break;
2839                 }
2840
2841                 if (insn->dead_end)
2842                         return 0;
2843
2844                 if (!next_insn) {
2845                         if (state.cfi.cfa.base == CFI_UNDEFINED)
2846                                 return 0;
2847                         WARN("%s: unexpected end of section", sec->name);
2848                         return 1;
2849                 }
2850
2851                 insn = next_insn;
2852         }
2853
2854         return 0;
2855 }
2856
2857 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
2858 {
2859         struct instruction *insn;
2860         struct insn_state state;
2861         int ret, warnings = 0;
2862
2863         if (!file->hints)
2864                 return 0;
2865
2866         init_insn_state(&state, sec);
2867
2868         if (sec) {
2869                 insn = find_insn(file, sec, 0);
2870                 if (!insn)
2871                         return 0;
2872         } else {
2873                 insn = list_first_entry(&file->insn_list, typeof(*insn), list);
2874         }
2875
2876         while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) {
2877                 if (insn->hint && !insn->visited) {
2878                         ret = validate_branch(file, insn->func, insn, state);
2879                         if (ret && backtrace)
2880                                 BT_FUNC("<=== (hint)", insn);
2881                         warnings += ret;
2882                 }
2883
2884                 insn = list_next_entry(insn, list);
2885         }
2886
2887         return warnings;
2888 }
2889
2890 static int validate_retpoline(struct objtool_file *file)
2891 {
2892         struct instruction *insn;
2893         int warnings = 0;
2894
2895         for_each_insn(file, insn) {
2896                 if (insn->type != INSN_JUMP_DYNAMIC &&
2897                     insn->type != INSN_CALL_DYNAMIC)
2898                         continue;
2899
2900                 if (insn->retpoline_safe)
2901                         continue;
2902
2903                 /*
2904                  * .init.text code is ran before userspace and thus doesn't
2905                  * strictly need retpolines, except for modules which are
2906                  * loaded late, they very much do need retpoline in their
2907                  * .init.text
2908                  */
2909                 if (!strcmp(insn->sec->name, ".init.text") && !module)
2910                         continue;
2911
2912                 WARN_FUNC("indirect %s found in RETPOLINE build",
2913                           insn->sec, insn->offset,
2914                           insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
2915
2916                 warnings++;
2917         }
2918
2919         return warnings;
2920 }
2921
2922 static bool is_kasan_insn(struct instruction *insn)
2923 {
2924         return (insn->type == INSN_CALL &&
2925                 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
2926 }
2927
2928 static bool is_ubsan_insn(struct instruction *insn)
2929 {
2930         return (insn->type == INSN_CALL &&
2931                 !strcmp(insn->call_dest->name,
2932                         "__ubsan_handle_builtin_unreachable"));
2933 }
2934
2935 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
2936 {
2937         int i;
2938         struct instruction *prev_insn;
2939
2940         if (insn->ignore || insn->type == INSN_NOP)
2941                 return true;
2942
2943         /*
2944          * Ignore any unused exceptions.  This can happen when a whitelisted
2945          * function has an exception table entry.
2946          *
2947          * Also ignore alternative replacement instructions.  This can happen
2948          * when a whitelisted function uses one of the ALTERNATIVE macros.
2949          */
2950         if (!strcmp(insn->sec->name, ".fixup") ||
2951             !strcmp(insn->sec->name, ".altinstr_replacement") ||
2952             !strcmp(insn->sec->name, ".altinstr_aux"))
2953                 return true;
2954
2955         if (!insn->func)
2956                 return false;
2957
2958         /*
2959          * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
2960          * __builtin_unreachable().  The BUG() macro has an unreachable() after
2961          * the UD2, which causes GCC's undefined trap logic to emit another UD2
2962          * (or occasionally a JMP to UD2).
2963          *
2964          * It may also insert a UD2 after calling a __noreturn function.
2965          */
2966         prev_insn = list_prev_entry(insn, list);
2967         if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) &&
2968             (insn->type == INSN_BUG ||
2969              (insn->type == INSN_JUMP_UNCONDITIONAL &&
2970               insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
2971                 return true;
2972
2973         /*
2974          * Check if this (or a subsequent) instruction is related to
2975          * CONFIG_UBSAN or CONFIG_KASAN.
2976          *
2977          * End the search at 5 instructions to avoid going into the weeds.
2978          */
2979         for (i = 0; i < 5; i++) {
2980
2981                 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
2982                         return true;
2983
2984                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
2985                         if (insn->jump_dest &&
2986                             insn->jump_dest->func == insn->func) {
2987                                 insn = insn->jump_dest;
2988                                 continue;
2989                         }
2990
2991                         break;
2992                 }
2993
2994                 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
2995                         break;
2996
2997                 insn = list_next_entry(insn, list);
2998         }
2999
3000         return false;
3001 }
3002
3003 static int validate_symbol(struct objtool_file *file, struct section *sec,
3004                            struct symbol *sym, struct insn_state *state)
3005 {
3006         struct instruction *insn;
3007         int ret;
3008
3009         if (!sym->len) {
3010                 WARN("%s() is missing an ELF size annotation", sym->name);
3011                 return 1;
3012         }
3013
3014         if (sym->pfunc != sym || sym->alias != sym)
3015                 return 0;
3016
3017         insn = find_insn(file, sec, sym->offset);
3018         if (!insn || insn->ignore || insn->visited)
3019                 return 0;
3020
3021         state->uaccess = sym->uaccess_safe;
3022
3023         ret = validate_branch(file, insn->func, insn, *state);
3024         if (ret && backtrace)
3025                 BT_FUNC("<=== (sym)", insn);
3026         return ret;
3027 }
3028
3029 static int validate_section(struct objtool_file *file, struct section *sec)
3030 {
3031         struct insn_state state;
3032         struct symbol *func;
3033         int warnings = 0;
3034
3035         list_for_each_entry(func, &sec->symbol_list, list) {
3036                 if (func->type != STT_FUNC)
3037                         continue;
3038
3039                 init_insn_state(&state, sec);
3040                 set_func_state(&state.cfi);
3041
3042                 warnings += validate_symbol(file, sec, func, &state);
3043         }
3044
3045         return warnings;
3046 }
3047
3048 static int validate_vmlinux_functions(struct objtool_file *file)
3049 {
3050         struct section *sec;
3051         int warnings = 0;
3052
3053         sec = find_section_by_name(file->elf, ".noinstr.text");
3054         if (sec) {
3055                 warnings += validate_section(file, sec);
3056                 warnings += validate_unwind_hints(file, sec);
3057         }
3058
3059         sec = find_section_by_name(file->elf, ".entry.text");
3060         if (sec) {
3061                 warnings += validate_section(file, sec);
3062                 warnings += validate_unwind_hints(file, sec);
3063         }
3064
3065         return warnings;
3066 }
3067
3068 static int validate_functions(struct objtool_file *file)
3069 {
3070         struct section *sec;
3071         int warnings = 0;
3072
3073         for_each_sec(file, sec) {
3074                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
3075                         continue;
3076
3077                 warnings += validate_section(file, sec);
3078         }
3079
3080         return warnings;
3081 }
3082
3083 static int validate_reachable_instructions(struct objtool_file *file)
3084 {
3085         struct instruction *insn;
3086
3087         if (file->ignore_unreachables)
3088                 return 0;
3089
3090         for_each_insn(file, insn) {
3091                 if (insn->visited || ignore_unreachable_insn(file, insn))
3092                         continue;
3093
3094                 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
3095                 return 1;
3096         }
3097
3098         return 0;
3099 }
3100
3101 int check(struct objtool_file *file)
3102 {
3103         int ret, warnings = 0;
3104
3105         arch_initial_func_cfi_state(&initial_func_cfi);
3106
3107         ret = decode_sections(file);
3108         if (ret < 0)
3109                 goto out;
3110         warnings += ret;
3111
3112         if (list_empty(&file->insn_list))
3113                 goto out;
3114
3115         if (vmlinux && !validate_dup) {
3116                 ret = validate_vmlinux_functions(file);
3117                 if (ret < 0)
3118                         goto out;
3119
3120                 warnings += ret;
3121                 goto out;
3122         }
3123
3124         if (retpoline) {
3125                 ret = validate_retpoline(file);
3126                 if (ret < 0)
3127                         return ret;
3128                 warnings += ret;
3129         }
3130
3131         ret = validate_functions(file);
3132         if (ret < 0)
3133                 goto out;
3134         warnings += ret;
3135
3136         ret = validate_unwind_hints(file, NULL);
3137         if (ret < 0)
3138                 goto out;
3139         warnings += ret;
3140
3141         if (!warnings) {
3142                 ret = validate_reachable_instructions(file);
3143                 if (ret < 0)
3144                         goto out;
3145                 warnings += ret;
3146         }
3147
3148         ret = create_static_call_sections(file);
3149         if (ret < 0)
3150                 goto out;
3151         warnings += ret;
3152
3153         if (mcount) {
3154                 ret = create_mcount_loc_sections(file);
3155                 if (ret < 0)
3156                         goto out;
3157                 warnings += ret;
3158         }
3159
3160 out:
3161         /*
3162          *  For now, don't fail the kernel build on fatal warnings.  These
3163          *  errors are still fairly common due to the growing matrix of
3164          *  supported toolchains and their recent pace of change.
3165          */
3166         return 0;
3167 }