tools/objtool/check.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
   4  */
   5
   6 #include <string.h>
   7 #include <stdlib.h>
   8 #include <inttypes.h>
   9 #include <sys/mman.h>
  10
  11 #include "builtin.h"
  12 #include "cfi.h"
  13 #include "arch.h"
  14 #include "check.h"
  15 #include "special.h"
  16 #include "warn.h"
  17 #include "arch_elf.h"
  18
  19 #include <linux/objtool.h>
  20 #include <linux/hashtable.h>
  21 #include <linux/kernel.h>
  22 #include <linux/static_call_types.h>
  23
  24 struct alternative {
  25         struct list_head list;
  26         struct instruction *insn;
  27         bool skip_orig;
  28 };
  29
  30 static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
  31
  32 static struct cfi_init_state initial_func_cfi;
  33 static struct cfi_state init_cfi;
  34 static struct cfi_state func_cfi;
  35
  36 struct instruction *find_insn(struct objtool_file *file,
  37                               struct section *sec, unsigned long offset)
  38 {
  39         struct instruction *insn;
  40
  41         hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
  42                 if (insn->sec == sec && insn->offset == offset)
  43                         return insn;
  44         }
  45
  46         return NULL;
  47 }
  48
  49 static struct instruction *next_insn_same_sec(struct objtool_file *file,
  50                                               struct instruction *insn)
  51 {
  52         struct instruction *next = list_next_entry(insn, list);
  53
  54         if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
  55                 return NULL;
  56
  57         return next;
  58 }
  59
  60 static struct instruction *next_insn_same_func(struct objtool_file *file,
  61                                                struct instruction *insn)
  62 {
  63         struct instruction *next = list_next_entry(insn, list);
  64         struct symbol *func = insn->func;
  65
  66         if (!func)
  67                 return NULL;
  68
  69         if (&next->list != &file->insn_list && next->func == func)
  70                 return next;
  71
  72         /* Check if we're already in the subfunction: */
  73         if (func == func->cfunc)
  74                 return NULL;
  75
  76         /* Move to the subfunction: */
  77         return find_insn(file, func->cfunc->sec, func->cfunc->offset);
  78 }
  79
  80 static struct instruction *prev_insn_same_sym(struct objtool_file *file,
  81                                                struct instruction *insn)
  82 {
  83         struct instruction *prev = list_prev_entry(insn, list);
  84
  85         if (&prev->list != &file->insn_list && prev->func == insn->func)
  86                 return prev;
  87
  88         return NULL;
  89 }
  90
  91 #define func_for_each_insn(file, func, insn)                            \
  92         for (insn = find_insn(file, func->sec, func->offset);           \
  93              insn;                                                      \
  94              insn = next_insn_same_func(file, insn))
  95
  96 #define sym_for_each_insn(file, sym, insn)                              \
  97         for (insn = find_insn(file, sym->sec, sym->offset);             \
  98              insn && &insn->list != &file->insn_list &&                 \
  99                 insn->sec == sym->sec &&                                \
 100                 insn->offset < sym->offset + sym->len;                  \
 101              insn = list_next_entry(insn, list))
 102
 103 #define sym_for_each_insn_continue_reverse(file, sym, insn)             \
 104         for (insn = list_prev_entry(insn, list);                        \
 105              &insn->list != &file->insn_list &&                         \
 106                 insn->sec == sym->sec && insn->offset >= sym->offset;   \
 107              insn = list_prev_entry(insn, list))
 108
 109 #define sec_for_each_insn_from(file, insn)                              \
 110         for (; insn; insn = next_insn_same_sec(file, insn))
 111
 112 #define sec_for_each_insn_continue(file, insn)                          \
 113         for (insn = next_insn_same_sec(file, insn); insn;               \
 114              insn = next_insn_same_sec(file, insn))
 115
 116 static bool is_jump_table_jump(struct instruction *insn)
 117 {
 118         struct alt_group *alt_group = insn->alt_group;
 119
 120         if (insn->jump_table)
 121                 return true;
 122
 123         /* Retpoline alternative for a jump table? */
 124         return alt_group && alt_group->orig_group &&
 125                alt_group->orig_group->first_insn->jump_table;
 126 }
 127
 128 static bool is_sibling_call(struct instruction *insn)
 129 {
 130         /*
 131          * Assume only ELF functions can make sibling calls.  This ensures
 132          * sibling call detection consistency between vmlinux.o and individual
 133          * objects.
 134          */
 135         if (!insn->func)
 136                 return false;
 137
 138         /* An indirect jump is either a sibling call or a jump to a table. */
 139         if (insn->type == INSN_JUMP_DYNAMIC)
 140                 return !is_jump_table_jump(insn);
 141
 142         /* add_jump_destinations() sets insn->call_dest for sibling calls. */
 143         return (is_static_jump(insn) && insn->call_dest);
 144 }
 145
 146 /*
 147  * This checks to see if the given function is a "noreturn" function.
 148  *
 149  * For global functions which are outside the scope of this object file, we
 150  * have to keep a manual list of them.
 151  *
 152  * For local functions, we have to detect them manually by simply looking for
 153  * the lack of a return instruction.
 154  */
 155 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 156                                 int recursion)
 157 {
 158         int i;
 159         struct instruction *insn;
 160         bool empty = true;
 161
 162         /*
 163          * Unfortunately these have to be hard coded because the noreturn
 164          * attribute isn't provided in ELF data.
 165          */
 166         static const char * const global_noreturns[] = {
 167                 "__stack_chk_fail",
 168                 "panic",
 169                 "do_exit",
 170                 "do_task_dead",
 171                 "make_task_dead",
 172                 "__module_put_and_exit",
 173                 "complete_and_exit",
 174                 "__reiserfs_panic",
 175                 "lbug_with_loc",
 176                 "fortify_panic",
 177                 "usercopy_abort",
 178                 "machine_real_restart",
 179                 "rewind_stack_and_make_dead",
 180                 "kunit_try_catch_throw",
 181                 "xen_start_kernel",
 182                 "cpu_bringup_and_idle",
 183                 "stop_this_cpu",
 184         };
 185
 186         if (!func)
 187                 return false;
 188
 189         if (func->bind == STB_WEAK)
 190                 return false;
 191
 192         if (func->bind == STB_GLOBAL)
 193                 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
 194                         if (!strcmp(func->name, global_noreturns[i]))
 195                                 return true;
 196
 197         if (!func->len)
 198                 return false;
 199
 200         insn = find_insn(file, func->sec, func->offset);
 201         if (!insn || !insn->func)
 202                 return false;
 203
 204         func_for_each_insn(file, func, insn) {
 205                 empty = false;
 206
 207                 if (insn->type == INSN_RETURN)
 208                         return false;
 209         }
 210
 211         if (empty)
 212                 return false;
 213
 214         /*
 215          * A function can have a sibling call instead of a return.  In that
 216          * case, the function's dead-end status depends on whether the target
 217          * of the sibling call returns.
 218          */
 219         func_for_each_insn(file, func, insn) {
 220                 if (is_sibling_call(insn)) {
 221                         struct instruction *dest = insn->jump_dest;
 222
 223                         if (!dest)
 224                                 /* sibling call to another file */
 225                                 return false;
 226
 227                         /* local sibling call */
 228                         if (recursion == 5) {
 229                                 /*
 230                                  * Infinite recursion: two functions have
 231                                  * sibling calls to each other.  This is a very
 232                                  * rare case.  It means they aren't dead ends.
 233                                  */
 234                                 return false;
 235                         }
 236
 237                         return __dead_end_function(file, dest->func, recursion+1);
 238                 }
 239         }
 240
 241         return true;
 242 }
 243
 244 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
 245 {
 246         return __dead_end_function(file, func, 0);
 247 }
 248
 249 static void init_cfi_state(struct cfi_state *cfi)
 250 {
 251         int i;
 252
 253         for (i = 0; i < CFI_NUM_REGS; i++) {
 254                 cfi->regs[i].base = CFI_UNDEFINED;
 255                 cfi->vals[i].base = CFI_UNDEFINED;
 256         }
 257         cfi->cfa.base = CFI_UNDEFINED;
 258         cfi->drap_reg = CFI_UNDEFINED;
 259         cfi->drap_offset = -1;
 260 }
 261
 262 static void init_insn_state(struct insn_state *state, struct section *sec)
 263 {
 264         memset(state, 0, sizeof(*state));
 265         init_cfi_state(&state->cfi);
 266
 267         /*
 268          * We need the full vmlinux for noinstr validation, otherwise we can
 269          * not correctly determine insn->call_dest->sec (external symbols do
 270          * not have a section).
 271          */
 272         if (vmlinux && sec)
 273                 state->noinstr = sec->noinstr;
 274 }
 275
 276 static struct cfi_state *cfi_alloc(void)
 277 {
 278         struct cfi_state *cfi = calloc(sizeof(struct cfi_state), 1);
 279         if (!cfi) {
 280                 WARN("calloc failed");
 281                 exit(1);
 282         }
 283         nr_cfi++;
 284         return cfi;
 285 }
 286
 287 static int cfi_bits;
 288 static struct hlist_head *cfi_hash;
 289
 290 static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
 291 {
 292         return memcmp((void *)cfi1 + sizeof(cfi1->hash),
 293                       (void *)cfi2 + sizeof(cfi2->hash),
 294                       sizeof(struct cfi_state) - sizeof(struct hlist_node));
 295 }
 296
 297 static inline u32 cfi_key(struct cfi_state *cfi)
 298 {
 299         return jhash((void *)cfi + sizeof(cfi->hash),
 300                      sizeof(*cfi) - sizeof(cfi->hash), 0);
 301 }
 302
 303 static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
 304 {
 305         struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
 306         struct cfi_state *obj;
 307
 308         hlist_for_each_entry(obj, head, hash) {
 309                 if (!cficmp(cfi, obj)) {
 310                         nr_cfi_cache++;
 311                         return obj;
 312                 }
 313         }
 314
 315         obj = cfi_alloc();
 316         *obj = *cfi;
 317         hlist_add_head(&obj->hash, head);
 318
 319         return obj;
 320 }
 321
 322 static void cfi_hash_add(struct cfi_state *cfi)
 323 {
 324         struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
 325
 326         hlist_add_head(&cfi->hash, head);
 327 }
 328
 329 static void *cfi_hash_alloc(void)
 330 {
 331         cfi_bits = vmlinux ? ELF_HASH_BITS - 3 : 13;
 332         cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
 333                         PROT_READ|PROT_WRITE,
 334                         MAP_PRIVATE|MAP_ANON, -1, 0);
 335         if (cfi_hash == (void *)-1L) {
 336                 WARN("mmap fail cfi_hash");
 337                 cfi_hash = NULL;
 338         }  else if (stats) {
 339                 printf("cfi_bits: %d\n", cfi_bits);
 340         }
 341
 342         return cfi_hash;
 343 }
 344
 345 static unsigned long nr_insns;
 346 static unsigned long nr_insns_visited;
 347
 348 /*
 349  * Call the arch-specific instruction decoder for all the instructions and add
 350  * them to the global instruction list.
 351  */
 352 static int decode_instructions(struct objtool_file *file)
 353 {
 354         struct section *sec;
 355         struct symbol *func;
 356         unsigned long offset;
 357         struct instruction *insn;
 358         int ret;
 359
 360         for_each_sec(file, sec) {
 361
 362                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
 363                         continue;
 364
 365                 if (strcmp(sec->name, ".altinstr_replacement") &&
 366                     strcmp(sec->name, ".altinstr_aux") &&
 367                     strncmp(sec->name, ".discard.", 9))
 368                         sec->text = true;
 369
 370                 if (!strcmp(sec->name, ".noinstr.text") ||
 371                     !strcmp(sec->name, ".entry.text") ||
 372                     !strncmp(sec->name, ".text..__x86.", 13))
 373                         sec->noinstr = true;
 374
 375                 for (offset = 0; offset < sec->len; offset += insn->len) {
 376                         insn = malloc(sizeof(*insn));
 377                         if (!insn) {
 378                                 WARN("malloc failed");
 379                                 return -1;
 380                         }
 381                         memset(insn, 0, sizeof(*insn));
 382                         INIT_LIST_HEAD(&insn->alts);
 383                         INIT_LIST_HEAD(&insn->stack_ops);
 384
 385                         insn->sec = sec;
 386                         insn->offset = offset;
 387
 388                         ret = arch_decode_instruction(file->elf, sec, offset,
 389                                                       sec->len - offset,
 390                                                       &insn->len, &insn->type,
 391                                                       &insn->immediate,
 392                                                       &insn->stack_ops);
 393                         if (ret)
 394                                 goto err;
 395
 396                         hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
 397                         list_add_tail(&insn->list, &file->insn_list);
 398                         nr_insns++;
 399                 }
 400
 401                 list_for_each_entry(func, &sec->symbol_list, list) {
 402                         if (func->type != STT_FUNC || func->alias != func)
 403                                 continue;
 404
 405                         if (!find_insn(file, sec, func->offset)) {
 406                                 WARN("%s(): can't find starting instruction",
 407                                      func->name);
 408                                 return -1;
 409                         }
 410
 411                         sym_for_each_insn(file, func, insn)
 412                                 insn->func = func;
 413                 }
 414         }
 415
 416         if (stats)
 417                 printf("nr_insns: %lu\n", nr_insns);
 418
 419         return 0;
 420
 421 err:
 422         free(insn);
 423         return ret;
 424 }
 425
 426 static struct instruction *find_last_insn(struct objtool_file *file,
 427                                           struct section *sec)
 428 {
 429         struct instruction *insn = NULL;
 430         unsigned int offset;
 431         unsigned int end = (sec->len > 10) ? sec->len - 10 : 0;
 432
 433         for (offset = sec->len - 1; offset >= end && !insn; offset--)
 434                 insn = find_insn(file, sec, offset);
 435
 436         return insn;
 437 }
 438
 439 /*
 440  * Mark "ud2" instructions and manually annotated dead ends.
 441  */
 442 static int add_dead_ends(struct objtool_file *file)
 443 {
 444         struct section *sec;
 445         struct reloc *reloc;
 446         struct instruction *insn;
 447
 448         /*
 449          * By default, "ud2" is a dead end unless otherwise annotated, because
 450          * GCC 7 inserts it for certain divide-by-zero cases.
 451          */
 452         for_each_insn(file, insn)
 453                 if (insn->type == INSN_BUG)
 454                         insn->dead_end = true;
 455
 456         /*
 457          * Check for manually annotated dead ends.
 458          */
 459         sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
 460         if (!sec)
 461                 goto reachable;
 462
 463         list_for_each_entry(reloc, &sec->reloc_list, list) {
 464                 if (reloc->sym->type != STT_SECTION) {
 465                         WARN("unexpected relocation symbol type in %s", sec->name);
 466                         return -1;
 467                 }
 468                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 469                 if (insn)
 470                         insn = list_prev_entry(insn, list);
 471                 else if (reloc->addend == reloc->sym->sec->len) {
 472                         insn = find_last_insn(file, reloc->sym->sec);
 473                         if (!insn) {
 474                                 WARN("can't find unreachable insn at %s+0x%" PRIx64,
 475                                      reloc->sym->sec->name, reloc->addend);
 476                                 return -1;
 477                         }
 478                 } else {
 479                         WARN("can't find unreachable insn at %s+0x%" PRIx64,
 480                              reloc->sym->sec->name, reloc->addend);
 481                         return -1;
 482                 }
 483
 484                 insn->dead_end = true;
 485         }
 486
 487 reachable:
 488         /*
 489          * These manually annotated reachable checks are needed for GCC 4.4,
 490          * where the Linux unreachable() macro isn't supported.  In that case
 491          * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
 492          * not a dead end.
 493          */
 494         sec = find_section_by_name(file->elf, ".rela.discard.reachable");
 495         if (!sec)
 496                 return 0;
 497
 498         list_for_each_entry(reloc, &sec->reloc_list, list) {
 499                 if (reloc->sym->type != STT_SECTION) {
 500                         WARN("unexpected relocation symbol type in %s", sec->name);
 501                         return -1;
 502                 }
 503                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 504                 if (insn)
 505                         insn = list_prev_entry(insn, list);
 506                 else if (reloc->addend == reloc->sym->sec->len) {
 507                         insn = find_last_insn(file, reloc->sym->sec);
 508                         if (!insn) {
 509                                 WARN("can't find reachable insn at %s+0x%" PRIx64,
 510                                      reloc->sym->sec->name, reloc->addend);
 511                                 return -1;
 512                         }
 513                 } else {
 514                         WARN("can't find reachable insn at %s+0x%" PRIx64,
 515                              reloc->sym->sec->name, reloc->addend);
 516                         return -1;
 517                 }
 518
 519                 insn->dead_end = false;
 520         }
 521
 522         return 0;
 523 }
 524
 525 static int create_static_call_sections(struct objtool_file *file)
 526 {
 527         struct section *sec;
 528         struct static_call_site *site;
 529         struct instruction *insn;
 530         struct symbol *key_sym;
 531         char *key_name, *tmp;
 532         int idx;
 533
 534         sec = find_section_by_name(file->elf, ".static_call_sites");
 535         if (sec) {
 536                 INIT_LIST_HEAD(&file->static_call_list);
 537                 WARN("file already has .static_call_sites section, skipping");
 538                 return 0;
 539         }
 540
 541         if (list_empty(&file->static_call_list))
 542                 return 0;
 543
 544         idx = 0;
 545         list_for_each_entry(insn, &file->static_call_list, call_node)
 546                 idx++;
 547
 548         sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE,
 549                                  sizeof(struct static_call_site), idx);
 550         if (!sec)
 551                 return -1;
 552
 553         idx = 0;
 554         list_for_each_entry(insn, &file->static_call_list, call_node) {
 555
 556                 site = (struct static_call_site *)sec->data->d_buf + idx;
 557                 memset(site, 0, sizeof(struct static_call_site));
 558
 559                 /* populate reloc for 'addr' */
 560                 if (elf_add_reloc_to_insn(file->elf, sec,
 561                                           idx * sizeof(struct static_call_site),
 562                                           R_X86_64_PC32,
 563                                           insn->sec, insn->offset))
 564                         return -1;
 565
 566                 /* find key symbol */
 567                 key_name = strdup(insn->call_dest->name);
 568                 if (!key_name) {
 569                         perror("strdup");
 570                         return -1;
 571                 }
 572                 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
 573                             STATIC_CALL_TRAMP_PREFIX_LEN)) {
 574                         WARN("static_call: trampoline name malformed: %s", key_name);
 575                         free(key_name);
 576                         return -1;
 577                 }
 578                 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
 579                 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
 580
 581                 key_sym = find_symbol_by_name(file->elf, tmp);
 582                 if (!key_sym) {
 583                         if (!module) {
 584                                 WARN("static_call: can't find static_call_key symbol: %s", tmp);
 585                                 free(key_name);
 586                                 return -1;
 587                         }
 588
 589                         /*
 590                          * For modules(), the key might not be exported, which
 591                          * means the module can make static calls but isn't
 592                          * allowed to change them.
 593                          *
 594                          * In that case we temporarily set the key to be the
 595                          * trampoline address.  This is fixed up in
 596                          * static_call_add_module().
 597                          */
 598                         key_sym = insn->call_dest;
 599                 }
 600                 free(key_name);
 601
 602                 /* populate reloc for 'key' */
 603                 if (elf_add_reloc(file->elf, sec,
 604                                   idx * sizeof(struct static_call_site) + 4,
 605                                   R_X86_64_PC32, key_sym,
 606                                   is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
 607                         return -1;
 608
 609                 idx++;
 610         }
 611
 612         return 0;
 613 }
 614
 615 static int create_retpoline_sites_sections(struct objtool_file *file)
 616 {
 617         struct instruction *insn;
 618         struct section *sec;
 619         int idx;
 620
 621         sec = find_section_by_name(file->elf, ".retpoline_sites");
 622         if (sec) {
 623                 WARN("file already has .retpoline_sites, skipping");
 624                 return 0;
 625         }
 626
 627         idx = 0;
 628         list_for_each_entry(insn, &file->retpoline_call_list, call_node)
 629                 idx++;
 630
 631         if (!idx)
 632                 return 0;
 633
 634         sec = elf_create_section(file->elf, ".retpoline_sites", 0,
 635                                  sizeof(int), idx);
 636         if (!sec) {
 637                 WARN("elf_create_section: .retpoline_sites");
 638                 return -1;
 639         }
 640
 641         idx = 0;
 642         list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
 643
 644                 int *site = (int *)sec->data->d_buf + idx;
 645                 *site = 0;
 646
 647                 if (elf_add_reloc_to_insn(file->elf, sec,
 648                                           idx * sizeof(int),
 649                                           R_X86_64_PC32,
 650                                           insn->sec, insn->offset)) {
 651                         WARN("elf_add_reloc_to_insn: .retpoline_sites");
 652                         return -1;
 653                 }
 654
 655                 idx++;
 656         }
 657
 658         return 0;
 659 }
 660
 661 static int create_return_sites_sections(struct objtool_file *file)
 662 {
 663         struct instruction *insn;
 664         struct section *sec;
 665         int idx;
 666
 667         sec = find_section_by_name(file->elf, ".return_sites");
 668         if (sec) {
 669                 WARN("file already has .return_sites, skipping");
 670                 return 0;
 671         }
 672
 673         idx = 0;
 674         list_for_each_entry(insn, &file->return_thunk_list, call_node)
 675                 idx++;
 676
 677         if (!idx)
 678                 return 0;
 679
 680         sec = elf_create_section(file->elf, ".return_sites", 0,
 681                                  sizeof(int), idx);
 682         if (!sec) {
 683                 WARN("elf_create_section: .return_sites");
 684                 return -1;
 685         }
 686
 687         idx = 0;
 688         list_for_each_entry(insn, &file->return_thunk_list, call_node) {
 689
 690                 int *site = (int *)sec->data->d_buf + idx;
 691                 *site = 0;
 692
 693                 if (elf_add_reloc_to_insn(file->elf, sec,
 694                                           idx * sizeof(int),
 695                                           R_X86_64_PC32,
 696                                           insn->sec, insn->offset)) {
 697                         WARN("elf_add_reloc_to_insn: .return_sites");
 698                         return -1;
 699                 }
 700
 701                 idx++;
 702         }
 703
 704         return 0;
 705 }
 706
 707 /*
 708  * Warnings shouldn't be reported for ignored functions.
 709  */
 710 static void add_ignores(struct objtool_file *file)
 711 {
 712         struct instruction *insn;
 713         struct section *sec;
 714         struct symbol *func;
 715         struct reloc *reloc;
 716
 717         sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
 718         if (!sec)
 719                 return;
 720
 721         list_for_each_entry(reloc, &sec->reloc_list, list) {
 722                 switch (reloc->sym->type) {
 723                 case STT_FUNC:
 724                         func = reloc->sym;
 725                         break;
 726
 727                 case STT_SECTION:
 728                         func = find_func_by_offset(reloc->sym->sec, reloc->addend);
 729                         if (!func)
 730                                 continue;
 731                         break;
 732
 733                 default:
 734                         WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type);
 735                         continue;
 736                 }
 737
 738                 func_for_each_insn(file, func, insn)
 739                         insn->ignore = true;
 740         }
 741 }
 742
 743 /*
 744  * This is a whitelist of functions that is allowed to be called with AC set.
 745  * The list is meant to be minimal and only contains compiler instrumentation
 746  * ABI and a few functions used to implement *_{to,from}_user() functions.
 747  *
 748  * These functions must not directly change AC, but may PUSHF/POPF.
 749  */
 750 static const char *uaccess_safe_builtin[] = {
 751         /* KASAN */
 752         "kasan_report",
 753         "check_memory_region",
 754         /* KASAN out-of-line */
 755         "__asan_loadN_noabort",
 756         "__asan_load1_noabort",
 757         "__asan_load2_noabort",
 758         "__asan_load4_noabort",
 759         "__asan_load8_noabort",
 760         "__asan_load16_noabort",
 761         "__asan_storeN_noabort",
 762         "__asan_store1_noabort",
 763         "__asan_store2_noabort",
 764         "__asan_store4_noabort",
 765         "__asan_store8_noabort",
 766         "__asan_store16_noabort",
 767         "__kasan_check_read",
 768         "__kasan_check_write",
 769         /* KASAN in-line */
 770         "__asan_report_load_n_noabort",
 771         "__asan_report_load1_noabort",
 772         "__asan_report_load2_noabort",
 773         "__asan_report_load4_noabort",
 774         "__asan_report_load8_noabort",
 775         "__asan_report_load16_noabort",
 776         "__asan_report_store_n_noabort",
 777         "__asan_report_store1_noabort",
 778         "__asan_report_store2_noabort",
 779         "__asan_report_store4_noabort",
 780         "__asan_report_store8_noabort",
 781         "__asan_report_store16_noabort",
 782         /* KCSAN */
 783         "__kcsan_check_access",
 784         "kcsan_found_watchpoint",
 785         "kcsan_setup_watchpoint",
 786         "kcsan_check_scoped_accesses",
 787         "kcsan_disable_current",
 788         "kcsan_enable_current_nowarn",
 789         /* KCSAN/TSAN */
 790         "__tsan_func_entry",
 791         "__tsan_func_exit",
 792         "__tsan_read_range",
 793         "__tsan_write_range",
 794         "__tsan_read1",
 795         "__tsan_read2",
 796         "__tsan_read4",
 797         "__tsan_read8",
 798         "__tsan_read16",
 799         "__tsan_write1",
 800         "__tsan_write2",
 801         "__tsan_write4",
 802         "__tsan_write8",
 803         "__tsan_write16",
 804         "__tsan_read_write1",
 805         "__tsan_read_write2",
 806         "__tsan_read_write4",
 807         "__tsan_read_write8",
 808         "__tsan_read_write16",
 809         "__tsan_volatile_read1",
 810         "__tsan_volatile_read2",
 811         "__tsan_volatile_read4",
 812         "__tsan_volatile_read8",
 813         "__tsan_volatile_read16",
 814         "__tsan_volatile_write1",
 815         "__tsan_volatile_write2",
 816         "__tsan_volatile_write4",
 817         "__tsan_volatile_write8",
 818         "__tsan_volatile_write16",
 819         "__tsan_atomic8_load",
 820         "__tsan_atomic16_load",
 821         "__tsan_atomic32_load",
 822         "__tsan_atomic64_load",
 823         "__tsan_atomic8_store",
 824         "__tsan_atomic16_store",
 825         "__tsan_atomic32_store",
 826         "__tsan_atomic64_store",
 827         "__tsan_atomic8_exchange",
 828         "__tsan_atomic16_exchange",
 829         "__tsan_atomic32_exchange",
 830         "__tsan_atomic64_exchange",
 831         "__tsan_atomic8_fetch_add",
 832         "__tsan_atomic16_fetch_add",
 833         "__tsan_atomic32_fetch_add",
 834         "__tsan_atomic64_fetch_add",
 835         "__tsan_atomic8_fetch_sub",
 836         "__tsan_atomic16_fetch_sub",
 837         "__tsan_atomic32_fetch_sub",
 838         "__tsan_atomic64_fetch_sub",
 839         "__tsan_atomic8_fetch_and",
 840         "__tsan_atomic16_fetch_and",
 841         "__tsan_atomic32_fetch_and",
 842         "__tsan_atomic64_fetch_and",
 843         "__tsan_atomic8_fetch_or",
 844         "__tsan_atomic16_fetch_or",
 845         "__tsan_atomic32_fetch_or",
 846         "__tsan_atomic64_fetch_or",
 847         "__tsan_atomic8_fetch_xor",
 848         "__tsan_atomic16_fetch_xor",
 849         "__tsan_atomic32_fetch_xor",
 850         "__tsan_atomic64_fetch_xor",
 851         "__tsan_atomic8_fetch_nand",
 852         "__tsan_atomic16_fetch_nand",
 853         "__tsan_atomic32_fetch_nand",
 854         "__tsan_atomic64_fetch_nand",
 855         "__tsan_atomic8_compare_exchange_strong",
 856         "__tsan_atomic16_compare_exchange_strong",
 857         "__tsan_atomic32_compare_exchange_strong",
 858         "__tsan_atomic64_compare_exchange_strong",
 859         "__tsan_atomic8_compare_exchange_weak",
 860         "__tsan_atomic16_compare_exchange_weak",
 861         "__tsan_atomic32_compare_exchange_weak",
 862         "__tsan_atomic64_compare_exchange_weak",
 863         "__tsan_atomic8_compare_exchange_val",
 864         "__tsan_atomic16_compare_exchange_val",
 865         "__tsan_atomic32_compare_exchange_val",
 866         "__tsan_atomic64_compare_exchange_val",
 867         "__tsan_atomic_thread_fence",
 868         "__tsan_atomic_signal_fence",
 869         "__tsan_unaligned_read16",
 870         "__tsan_unaligned_write16",
 871         /* KCOV */
 872         "write_comp_data",
 873         "check_kcov_mode",
 874         "__sanitizer_cov_trace_pc",
 875         "__sanitizer_cov_trace_const_cmp1",
 876         "__sanitizer_cov_trace_const_cmp2",
 877         "__sanitizer_cov_trace_const_cmp4",
 878         "__sanitizer_cov_trace_const_cmp8",
 879         "__sanitizer_cov_trace_cmp1",
 880         "__sanitizer_cov_trace_cmp2",
 881         "__sanitizer_cov_trace_cmp4",
 882         "__sanitizer_cov_trace_cmp8",
 883         "__sanitizer_cov_trace_switch",
 884         /* UBSAN */
 885         "ubsan_type_mismatch_common",
 886         "__ubsan_handle_type_mismatch",
 887         "__ubsan_handle_type_mismatch_v1",
 888         "__ubsan_handle_shift_out_of_bounds",
 889         /* misc */
 890         "csum_partial_copy_generic",
 891         "copy_mc_fragile",
 892         "copy_mc_fragile_handle_tail",
 893         "copy_mc_enhanced_fast_string",
 894         "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
 895         NULL
 896 };
 897
 898 static void add_uaccess_safe(struct objtool_file *file)
 899 {
 900         struct symbol *func;
 901         const char **name;
 902
 903         if (!uaccess)
 904                 return;
 905
 906         for (name = uaccess_safe_builtin; *name; name++) {
 907                 func = find_symbol_by_name(file->elf, *name);
 908                 if (!func)
 909                         continue;
 910
 911                 func->uaccess_safe = true;
 912         }
 913 }
 914
 915 /*
 916  * FIXME: For now, just ignore any alternatives which add retpolines.  This is
 917  * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
 918  * But it at least allows objtool to understand the control flow *around* the
 919  * retpoline.
 920  */
 921 static int add_ignore_alternatives(struct objtool_file *file)
 922 {
 923         struct section *sec;
 924         struct reloc *reloc;
 925         struct instruction *insn;
 926
 927         sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
 928         if (!sec)
 929                 return 0;
 930
 931         list_for_each_entry(reloc, &sec->reloc_list, list) {
 932                 if (reloc->sym->type != STT_SECTION) {
 933                         WARN("unexpected relocation symbol type in %s", sec->name);
 934                         return -1;
 935                 }
 936
 937                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 938                 if (!insn) {
 939                         WARN("bad .discard.ignore_alts entry");
 940                         return -1;
 941                 }
 942
 943                 insn->ignore_alts = true;
 944         }
 945
 946         return 0;
 947 }
 948
 949 /*
 950  * Symbols that replace INSN_CALL_DYNAMIC, every (tail) call to such a symbol
 951  * will be added to the .retpoline_sites section.
 952  */
 953 __weak bool arch_is_retpoline(struct symbol *sym)
 954 {
 955         return false;
 956 }
 957
 958 /*
 959  * Symbols that replace INSN_RETURN, every (tail) call to such a symbol
 960  * will be added to the .return_sites section.
 961  */
 962 __weak bool arch_is_rethunk(struct symbol *sym)
 963 {
 964         return false;
 965 }
 966
 967 /*
 968  * Symbols that are embedded inside other instructions, because sometimes crazy
 969  * code exists. These are mostly ignored for validation purposes.
 970  */
 971 __weak bool arch_is_embedded_insn(struct symbol *sym)
 972 {
 973         return false;
 974 }
 975
 976 #define NEGATIVE_RELOC  ((void *)-1L)
 977
 978 static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
 979 {
 980         if (insn->reloc == NEGATIVE_RELOC)
 981                 return NULL;
 982
 983         if (!insn->reloc) {
 984                 insn->reloc = find_reloc_by_dest_range(file->elf, insn->sec,
 985                                                        insn->offset, insn->len);
 986                 if (!insn->reloc) {
 987                         insn->reloc = NEGATIVE_RELOC;
 988                         return NULL;
 989                 }
 990         }
 991
 992         return insn->reloc;
 993 }
 994
 995 static void remove_insn_ops(struct instruction *insn)
 996 {
 997         struct stack_op *op, *tmp;
 998
 999         list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
1000                 list_del(&op->list);
1001                 free(op);
1002         }
1003 }
1004
1005 static void annotate_call_site(struct objtool_file *file,
1006                                struct instruction *insn, bool sibling)
1007 {
1008         struct reloc *reloc = insn_reloc(file, insn);
1009         struct symbol *sym = insn->call_dest;
1010
1011         if (!sym)
1012                 sym = reloc->sym;
1013
1014         /*
1015          * Alternative replacement code is just template code which is
1016          * sometimes copied to the original instruction. For now, don't
1017          * annotate it. (In the future we might consider annotating the
1018          * original instruction if/when it ever makes sense to do so.)
1019          */
1020         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1021                 return;
1022
1023         if (sym->static_call_tramp) {
1024                 list_add_tail(&insn->call_node, &file->static_call_list);
1025                 return;
1026         }
1027
1028         if (sym->retpoline_thunk) {
1029                 list_add_tail(&insn->call_node, &file->retpoline_call_list);
1030                 return;
1031         }
1032
1033         /*
1034          * Many compilers cannot disable KCOV with a function attribute
1035          * so they need a little help, NOP out any KCOV calls from noinstr
1036          * text.
1037          */
1038         if (insn->sec->noinstr && sym->kcov) {
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                                sibling ? arch_ret_insn(insn->len)
1047                                        : arch_nop_insn(insn->len));
1048
1049                 insn->type = sibling ? INSN_RETURN : INSN_NOP;
1050
1051                 if (sibling) {
1052                         /*
1053                          * We've replaced the tail-call JMP insn by two new
1054                          * insn: RET; INT3, except we only have a single struct
1055                          * insn here. Mark it retpoline_safe to avoid the SLS
1056                          * warning, instead of adding another insn.
1057                          */
1058                         insn->retpoline_safe = true;
1059                 }
1060
1061                 return;
1062         }
1063 }
1064
1065 static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1066                           struct symbol *dest, bool sibling)
1067 {
1068         insn->call_dest = dest;
1069         if (!dest)
1070                 return;
1071
1072         /*
1073          * Whatever stack impact regular CALLs have, should be undone
1074          * by the RETURN of the called function.
1075          *
1076          * Annotated intra-function calls retain the stack_ops but
1077          * are converted to JUMP, see read_intra_function_calls().
1078          */
1079         remove_insn_ops(insn);
1080
1081         annotate_call_site(file, insn, sibling);
1082 }
1083
1084 static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1085 {
1086         /*
1087          * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1088          * so convert them accordingly.
1089          */
1090         switch (insn->type) {
1091         case INSN_CALL:
1092                 insn->type = INSN_CALL_DYNAMIC;
1093                 break;
1094         case INSN_JUMP_UNCONDITIONAL:
1095                 insn->type = INSN_JUMP_DYNAMIC;
1096                 break;
1097         case INSN_JUMP_CONDITIONAL:
1098                 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1099                 break;
1100         default:
1101                 return;
1102         }
1103
1104         insn->retpoline_safe = true;
1105
1106         /*
1107          * Whatever stack impact regular CALLs have, should be undone
1108          * by the RETURN of the called function.
1109          *
1110          * Annotated intra-function calls retain the stack_ops but
1111          * are converted to JUMP, see read_intra_function_calls().
1112          */
1113         remove_insn_ops(insn);
1114
1115         annotate_call_site(file, insn, false);
1116 }
1117
1118 static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add)
1119 {
1120         /*
1121          * Return thunk tail calls are really just returns in disguise,
1122          * so convert them accordingly.
1123          */
1124         insn->type = INSN_RETURN;
1125         insn->retpoline_safe = true;
1126
1127         /* Skip the non-text sections, specially .discard ones */
1128         if (add && insn->sec->text)
1129                 list_add_tail(&insn->call_node, &file->return_thunk_list);
1130 }
1131
1132 /*
1133  * Find the destination instructions for all jumps.
1134  */
1135 static int add_jump_destinations(struct objtool_file *file)
1136 {
1137         struct instruction *insn;
1138         struct reloc *reloc;
1139         struct section *dest_sec;
1140         unsigned long dest_off;
1141
1142         for_each_insn(file, insn) {
1143                 if (!is_static_jump(insn))
1144                         continue;
1145
1146                 reloc = insn_reloc(file, insn);
1147                 if (!reloc) {
1148                         dest_sec = insn->sec;
1149                         dest_off = arch_jump_destination(insn);
1150                 } else if (reloc->sym->type == STT_SECTION) {
1151                         dest_sec = reloc->sym->sec;
1152                         dest_off = arch_dest_reloc_offset(reloc->addend);
1153                 } else if (reloc->sym->retpoline_thunk) {
1154                         add_retpoline_call(file, insn);
1155                         continue;
1156                 } else if (reloc->sym->return_thunk) {
1157                         add_return_call(file, insn, true);
1158                         continue;
1159                 } else if (insn->func) {
1160                         /* internal or external sibling call (with reloc) */
1161                         add_call_dest(file, insn, reloc->sym, true);
1162                         continue;
1163                 } else if (reloc->sym->sec->idx) {
1164                         dest_sec = reloc->sym->sec;
1165                         dest_off = reloc->sym->sym.st_value +
1166                                    arch_dest_reloc_offset(reloc->addend);
1167                 } else {
1168                         /* non-func asm code jumping to another file */
1169                         continue;
1170                 }
1171
1172                 insn->jump_dest = find_insn(file, dest_sec, dest_off);
1173                 if (!insn->jump_dest) {
1174                         struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off);
1175
1176                         /*
1177                          * This is a special case where an alt instruction
1178                          * jumps past the end of the section.  These are
1179                          * handled later in handle_group_alt().
1180                          */
1181                         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1182                                 continue;
1183
1184                         /*
1185                          * This is a special case for retbleed_untrain_ret().
1186                          * It jumps to __x86_return_thunk(), but objtool
1187                          * can't find the thunk's starting RET
1188                          * instruction, because the RET is also in the
1189                          * middle of another instruction.  Objtool only
1190                          * knows about the outer instruction.
1191                          */
1192                         if (sym && sym->embedded_insn) {
1193                                 add_return_call(file, insn, false);
1194                                 continue;
1195                         }
1196
1197                         WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
1198                                   insn->sec, insn->offset, dest_sec->name,
1199                                   dest_off);
1200                         return -1;
1201                 }
1202
1203                 /*
1204                  * Cross-function jump.
1205                  */
1206                 if (insn->func && insn->jump_dest->func &&
1207                     insn->func != insn->jump_dest->func) {
1208
1209                         /*
1210                          * For GCC 8+, create parent/child links for any cold
1211                          * subfunctions.  This is _mostly_ redundant with a
1212                          * similar initialization in read_symbols().
1213                          *
1214                          * If a function has aliases, we want the *first* such
1215                          * function in the symbol table to be the subfunction's
1216                          * parent.  In that case we overwrite the
1217                          * initialization done in read_symbols().
1218                          *
1219                          * However this code can't completely replace the
1220                          * read_symbols() code because this doesn't detect the
1221                          * case where the parent function's only reference to a
1222                          * subfunction is through a jump table.
1223                          */
1224                         if (!strstr(insn->func->name, ".cold") &&
1225                             strstr(insn->jump_dest->func->name, ".cold")) {
1226                                 insn->func->cfunc = insn->jump_dest->func;
1227                                 insn->jump_dest->func->pfunc = insn->func;
1228
1229                         } else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
1230                                    insn->jump_dest->offset == insn->jump_dest->func->offset) {
1231                                 /* internal sibling call (without reloc) */
1232                                 add_call_dest(file, insn, insn->jump_dest->func, true);
1233                         }
1234                 }
1235         }
1236
1237         return 0;
1238 }
1239
1240 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1241 {
1242         struct symbol *call_dest;
1243
1244         call_dest = find_func_by_offset(sec, offset);
1245         if (!call_dest)
1246                 call_dest = find_symbol_by_offset(sec, offset);
1247
1248         return call_dest;
1249 }
1250
1251 /*
1252  * Find the destination instructions for all calls.
1253  */
1254 static int add_call_destinations(struct objtool_file *file)
1255 {
1256         struct instruction *insn;
1257         unsigned long dest_off;
1258         struct symbol *dest;
1259         struct reloc *reloc;
1260
1261         for_each_insn(file, insn) {
1262                 if (insn->type != INSN_CALL)
1263                         continue;
1264
1265                 reloc = insn_reloc(file, insn);
1266                 if (!reloc) {
1267                         dest_off = arch_jump_destination(insn);
1268                         dest = find_call_destination(insn->sec, dest_off);
1269
1270                         add_call_dest(file, insn, dest, false);
1271
1272                         if (insn->ignore)
1273                                 continue;
1274
1275                         if (!insn->call_dest) {
1276                                 WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);
1277                                 return -1;
1278                         }
1279
1280                         if (insn->func && insn->call_dest->type != STT_FUNC) {
1281                                 WARN_FUNC("unsupported call to non-function",
1282                                           insn->sec, insn->offset);
1283                                 return -1;
1284                         }
1285
1286                 } else if (reloc->sym->type == STT_SECTION) {
1287                         dest_off = arch_dest_reloc_offset(reloc->addend);
1288                         dest = find_call_destination(reloc->sym->sec, dest_off);
1289                         if (!dest) {
1290                                 WARN_FUNC("can't find call dest symbol at %s+0x%lx",
1291                                           insn->sec, insn->offset,
1292                                           reloc->sym->sec->name,
1293                                           dest_off);
1294                                 return -1;
1295                         }
1296
1297                         add_call_dest(file, insn, dest, false);
1298
1299                 } else if (reloc->sym->retpoline_thunk) {
1300                         add_retpoline_call(file, insn);
1301
1302                 } else
1303                         add_call_dest(file, insn, reloc->sym, false);
1304         }
1305
1306         return 0;
1307 }
1308
1309 /*
1310  * The .alternatives section requires some extra special care over and above
1311  * other special sections because alternatives are patched in place.
1312  */
1313 static int handle_group_alt(struct objtool_file *file,
1314                             struct special_alt *special_alt,
1315                             struct instruction *orig_insn,
1316                             struct instruction **new_insn)
1317 {
1318         struct instruction *last_orig_insn, *last_new_insn = NULL, *insn, *nop = NULL;
1319         struct alt_group *orig_alt_group, *new_alt_group;
1320         unsigned long dest_off;
1321
1322
1323         orig_alt_group = malloc(sizeof(*orig_alt_group));
1324         if (!orig_alt_group) {
1325                 WARN("malloc failed");
1326                 return -1;
1327         }
1328         orig_alt_group->cfi = calloc(special_alt->orig_len,
1329                                      sizeof(struct cfi_state *));
1330         if (!orig_alt_group->cfi) {
1331                 WARN("calloc failed");
1332                 return -1;
1333         }
1334
1335         last_orig_insn = NULL;
1336         insn = orig_insn;
1337         sec_for_each_insn_from(file, insn) {
1338                 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1339                         break;
1340
1341                 insn->alt_group = orig_alt_group;
1342                 last_orig_insn = insn;
1343         }
1344         orig_alt_group->orig_group = NULL;
1345         orig_alt_group->first_insn = orig_insn;
1346         orig_alt_group->last_insn = last_orig_insn;
1347
1348
1349         new_alt_group = malloc(sizeof(*new_alt_group));
1350         if (!new_alt_group) {
1351                 WARN("malloc failed");
1352                 return -1;
1353         }
1354
1355         if (special_alt->new_len < special_alt->orig_len) {
1356                 /*
1357                  * Insert a fake nop at the end to make the replacement
1358                  * alt_group the same size as the original.  This is needed to
1359                  * allow propagate_alt_cfi() to do its magic.  When the last
1360                  * instruction affects the stack, the instruction after it (the
1361                  * nop) will propagate the new state to the shared CFI array.
1362                  */
1363                 nop = malloc(sizeof(*nop));
1364                 if (!nop) {
1365                         WARN("malloc failed");
1366                         return -1;
1367                 }
1368                 memset(nop, 0, sizeof(*nop));
1369                 INIT_LIST_HEAD(&nop->alts);
1370                 INIT_LIST_HEAD(&nop->stack_ops);
1371
1372                 nop->sec = special_alt->new_sec;
1373                 nop->offset = special_alt->new_off + special_alt->new_len;
1374                 nop->len = special_alt->orig_len - special_alt->new_len;
1375                 nop->type = INSN_NOP;
1376                 nop->func = orig_insn->func;
1377                 nop->alt_group = new_alt_group;
1378                 nop->ignore = orig_insn->ignore_alts;
1379         }
1380
1381         if (!special_alt->new_len) {
1382                 *new_insn = nop;
1383                 goto end;
1384         }
1385
1386         insn = *new_insn;
1387         sec_for_each_insn_from(file, insn) {
1388                 struct reloc *alt_reloc;
1389
1390                 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1391                         break;
1392
1393                 last_new_insn = insn;
1394
1395                 insn->ignore = orig_insn->ignore_alts;
1396                 insn->func = orig_insn->func;
1397                 insn->alt_group = new_alt_group;
1398
1399                 /*
1400                  * Since alternative replacement code is copy/pasted by the
1401                  * kernel after applying relocations, generally such code can't
1402                  * have relative-address relocation references to outside the
1403                  * .altinstr_replacement section, unless the arch's
1404                  * alternatives code can adjust the relative offsets
1405                  * accordingly.
1406                  */
1407                 alt_reloc = insn_reloc(file, insn);
1408                 if (alt_reloc &&
1409                     !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1410
1411                         WARN_FUNC("unsupported relocation in alternatives section",
1412                                   insn->sec, insn->offset);
1413                         return -1;
1414                 }
1415
1416                 if (!is_static_jump(insn))
1417                         continue;
1418
1419                 if (!insn->immediate)
1420                         continue;
1421
1422                 dest_off = arch_jump_destination(insn);
1423                 if (dest_off == special_alt->new_off + special_alt->new_len)
1424                         insn->jump_dest = next_insn_same_sec(file, last_orig_insn);
1425
1426                 if (!insn->jump_dest) {
1427                         WARN_FUNC("can't find alternative jump destination",
1428                                   insn->sec, insn->offset);
1429                         return -1;
1430                 }
1431         }
1432
1433         if (!last_new_insn) {
1434                 WARN_FUNC("can't find last new alternative instruction",
1435                           special_alt->new_sec, special_alt->new_off);
1436                 return -1;
1437         }
1438
1439         if (nop)
1440                 list_add(&nop->list, &last_new_insn->list);
1441 end:
1442         new_alt_group->orig_group = orig_alt_group;
1443         new_alt_group->first_insn = *new_insn;
1444         new_alt_group->last_insn = nop ? : last_new_insn;
1445         new_alt_group->cfi = orig_alt_group->cfi;
1446         return 0;
1447 }
1448
1449 /*
1450  * A jump table entry can either convert a nop to a jump or a jump to a nop.
1451  * If the original instruction is a jump, make the alt entry an effective nop
1452  * by just skipping the original instruction.
1453  */
1454 static int handle_jump_alt(struct objtool_file *file,
1455                            struct special_alt *special_alt,
1456                            struct instruction *orig_insn,
1457                            struct instruction **new_insn)
1458 {
1459         if (orig_insn->type == INSN_NOP)
1460                 return 0;
1461
1462         if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
1463                 WARN_FUNC("unsupported instruction at jump label",
1464                           orig_insn->sec, orig_insn->offset);
1465                 return -1;
1466         }
1467
1468         *new_insn = list_next_entry(orig_insn, list);
1469         return 0;
1470 }
1471
1472 /*
1473  * Read all the special sections which have alternate instructions which can be
1474  * patched in or redirected to at runtime.  Each instruction having alternate
1475  * instruction(s) has them added to its insn->alts list, which will be
1476  * traversed in validate_branch().
1477  */
1478 static int add_special_section_alts(struct objtool_file *file)
1479 {
1480         struct list_head special_alts;
1481         struct instruction *orig_insn, *new_insn;
1482         struct special_alt *special_alt, *tmp;
1483         struct alternative *alt;
1484         int ret;
1485
1486         ret = special_get_alts(file->elf, &special_alts);
1487         if (ret)
1488                 return ret;
1489
1490         list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1491
1492                 orig_insn = find_insn(file, special_alt->orig_sec,
1493                                       special_alt->orig_off);
1494                 if (!orig_insn) {
1495                         WARN_FUNC("special: can't find orig instruction",
1496                                   special_alt->orig_sec, special_alt->orig_off);
1497                         ret = -1;
1498                         goto out;
1499                 }
1500
1501                 new_insn = NULL;
1502                 if (!special_alt->group || special_alt->new_len) {
1503                         new_insn = find_insn(file, special_alt->new_sec,
1504                                              special_alt->new_off);
1505                         if (!new_insn) {
1506                                 WARN_FUNC("special: can't find new instruction",
1507                                           special_alt->new_sec,
1508                                           special_alt->new_off);
1509                                 ret = -1;
1510                                 goto out;
1511                         }
1512                 }
1513
1514                 if (special_alt->group) {
1515                         if (!special_alt->orig_len) {
1516                                 WARN_FUNC("empty alternative entry",
1517                                           orig_insn->sec, orig_insn->offset);
1518                                 continue;
1519                         }
1520
1521                         ret = handle_group_alt(file, special_alt, orig_insn,
1522                                                &new_insn);
1523                         if (ret)
1524                                 goto out;
1525                 } else if (special_alt->jump_or_nop) {
1526                         ret = handle_jump_alt(file, special_alt, orig_insn,
1527                                               &new_insn);
1528                         if (ret)
1529                                 goto out;
1530                 }
1531
1532                 alt = malloc(sizeof(*alt));
1533                 if (!alt) {
1534                         WARN("malloc failed");
1535                         ret = -1;
1536                         goto out;
1537                 }
1538
1539                 alt->insn = new_insn;
1540                 alt->skip_orig = special_alt->skip_orig;
1541                 orig_insn->ignore_alts |= special_alt->skip_alt;
1542                 list_add_tail(&alt->list, &orig_insn->alts);
1543
1544                 list_del(&special_alt->list);
1545                 free(special_alt);
1546         }
1547
1548 out:
1549         return ret;
1550 }
1551
1552 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
1553                             struct reloc *table)
1554 {
1555         struct reloc *reloc = table;
1556         struct instruction *dest_insn;
1557         struct alternative *alt;
1558         struct symbol *pfunc = insn->func->pfunc;
1559         unsigned int prev_offset = 0;
1560
1561         /*
1562          * Each @reloc is a switch table relocation which points to the target
1563          * instruction.
1564          */
1565         list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
1566
1567                 /* Check for the end of the table: */
1568                 if (reloc != table && reloc->jump_table_start)
1569                         break;
1570
1571                 /* Make sure the table entries are consecutive: */
1572                 if (prev_offset && reloc->offset != prev_offset + 8)
1573                         break;
1574
1575                 /* Detect function pointers from contiguous objects: */
1576                 if (reloc->sym->sec == pfunc->sec &&
1577                     reloc->addend == pfunc->offset)
1578                         break;
1579
1580                 dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
1581                 if (!dest_insn)
1582                         break;
1583
1584                 /* Make sure the destination is in the same function: */
1585                 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
1586                         break;
1587
1588                 alt = malloc(sizeof(*alt));
1589                 if (!alt) {
1590                         WARN("malloc failed");
1591                         return -1;
1592                 }
1593
1594                 alt->insn = dest_insn;
1595                 list_add_tail(&alt->list, &insn->alts);
1596                 prev_offset = reloc->offset;
1597         }
1598
1599         if (!prev_offset) {
1600                 WARN_FUNC("can't find switch jump table",
1601                           insn->sec, insn->offset);
1602                 return -1;
1603         }
1604
1605         return 0;
1606 }
1607
1608 /*
1609  * find_jump_table() - Given a dynamic jump, find the switch jump table
1610  * associated with it.
1611  */
1612 static struct reloc *find_jump_table(struct objtool_file *file,
1613                                       struct symbol *func,
1614                                       struct instruction *insn)
1615 {
1616         struct reloc *table_reloc;
1617         struct instruction *dest_insn, *orig_insn = insn;
1618
1619         /*
1620          * Backward search using the @first_jump_src links, these help avoid
1621          * much of the 'in between' code. Which avoids us getting confused by
1622          * it.
1623          */
1624         for (;
1625              insn && insn->func && insn->func->pfunc == func;
1626              insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
1627
1628                 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1629                         break;
1630
1631                 /* allow small jumps within the range */
1632                 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1633                     insn->jump_dest &&
1634                     (insn->jump_dest->offset <= insn->offset ||
1635                      insn->jump_dest->offset > orig_insn->offset))
1636                     break;
1637
1638                 table_reloc = arch_find_switch_table(file, insn);
1639                 if (!table_reloc)
1640                         continue;
1641                 dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
1642                 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1643                         continue;
1644
1645                 return table_reloc;
1646         }
1647
1648         return NULL;
1649 }
1650
1651 /*
1652  * First pass: Mark the head of each jump table so that in the next pass,
1653  * we know when a given jump table ends and the next one starts.
1654  */
1655 static void mark_func_jump_tables(struct objtool_file *file,
1656                                     struct symbol *func)
1657 {
1658         struct instruction *insn, *last = NULL;
1659         struct reloc *reloc;
1660
1661         func_for_each_insn(file, func, insn) {
1662                 if (!last)
1663                         last = insn;
1664
1665                 /*
1666                  * Store back-pointers for unconditional forward jumps such
1667                  * that find_jump_table() can back-track using those and
1668                  * avoid some potentially confusing code.
1669                  */
1670                 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1671                     insn->offset > last->offset &&
1672                     insn->jump_dest->offset > insn->offset &&
1673                     !insn->jump_dest->first_jump_src) {
1674
1675                         insn->jump_dest->first_jump_src = insn;
1676                         last = insn->jump_dest;
1677                 }
1678
1679                 if (insn->type != INSN_JUMP_DYNAMIC)
1680                         continue;
1681
1682                 reloc = find_jump_table(file, func, insn);
1683                 if (reloc) {
1684                         reloc->jump_table_start = true;
1685                         insn->jump_table = reloc;
1686                 }
1687         }
1688 }
1689
1690 static int add_func_jump_tables(struct objtool_file *file,
1691                                   struct symbol *func)
1692 {
1693         struct instruction *insn;
1694         int ret;
1695
1696         func_for_each_insn(file, func, insn) {
1697                 if (!insn->jump_table)
1698                         continue;
1699
1700                 ret = add_jump_table(file, insn, insn->jump_table);
1701                 if (ret)
1702                         return ret;
1703         }
1704
1705         return 0;
1706 }
1707
1708 /*
1709  * For some switch statements, gcc generates a jump table in the .rodata
1710  * section which contains a list of addresses within the function to jump to.
1711  * This finds these jump tables and adds them to the insn->alts lists.
1712  */
1713 static int add_jump_table_alts(struct objtool_file *file)
1714 {
1715         struct section *sec;
1716         struct symbol *func;
1717         int ret;
1718
1719         if (!file->rodata)
1720                 return 0;
1721
1722         for_each_sec(file, sec) {
1723                 list_for_each_entry(func, &sec->symbol_list, list) {
1724                         if (func->type != STT_FUNC)
1725                                 continue;
1726
1727                         mark_func_jump_tables(file, func);
1728                         ret = add_func_jump_tables(file, func);
1729                         if (ret)
1730                                 return ret;
1731                 }
1732         }
1733
1734         return 0;
1735 }
1736
1737 static void set_func_state(struct cfi_state *state)
1738 {
1739         state->cfa = initial_func_cfi.cfa;
1740         memcpy(&state->regs, &initial_func_cfi.regs,
1741                CFI_NUM_REGS * sizeof(struct cfi_reg));
1742         state->stack_size = initial_func_cfi.cfa.offset;
1743 }
1744
1745 static int read_unwind_hints(struct objtool_file *file)
1746 {
1747         struct cfi_state cfi = init_cfi;
1748         struct section *sec, *relocsec;
1749         struct unwind_hint *hint;
1750         struct instruction *insn;
1751         struct reloc *reloc;
1752         int i;
1753
1754         sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1755         if (!sec)
1756                 return 0;
1757
1758         relocsec = sec->reloc;
1759         if (!relocsec) {
1760                 WARN("missing .rela.discard.unwind_hints section");
1761                 return -1;
1762         }
1763
1764         if (sec->len % sizeof(struct unwind_hint)) {
1765                 WARN("struct unwind_hint size mismatch");
1766                 return -1;
1767         }
1768
1769         file->hints = true;
1770
1771         for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
1772                 hint = (struct unwind_hint *)sec->data->d_buf + i;
1773
1774                 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
1775                 if (!reloc) {
1776                         WARN("can't find reloc for unwind_hints[%d]", i);
1777                         return -1;
1778                 }
1779
1780                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1781                 if (!insn) {
1782                         WARN("can't find insn for unwind_hints[%d]", i);
1783                         return -1;
1784                 }
1785
1786                 insn->hint = true;
1787
1788                 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
1789                         insn->hint = false;
1790                         insn->save = true;
1791                         continue;
1792                 }
1793
1794                 if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
1795                         insn->restore = true;
1796                         continue;
1797                 }
1798
1799                 if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
1800                         struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
1801
1802                         if (sym && sym->bind == STB_GLOBAL) {
1803                                 insn->entry = 1;
1804                         }
1805                 }
1806
1807                 if (hint->type == UNWIND_HINT_TYPE_ENTRY) {
1808                         hint->type = UNWIND_HINT_TYPE_CALL;
1809                         insn->entry = 1;
1810                 }
1811
1812                 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
1813                         insn->cfi = &func_cfi;
1814                         continue;
1815                 }
1816
1817                 if (insn->cfi)
1818                         cfi = *(insn->cfi);
1819
1820                 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
1821                         WARN_FUNC("unsupported unwind_hint sp base reg %d",
1822                                   insn->sec, insn->offset, hint->sp_reg);
1823                         return -1;
1824                 }
1825
1826                 cfi.cfa.offset = hint->sp_offset;
1827                 cfi.type = hint->type;
1828                 cfi.end = hint->end;
1829
1830                 insn->cfi = cfi_hash_find_or_add(&cfi);
1831         }
1832
1833         return 0;
1834 }
1835
1836 static int read_retpoline_hints(struct objtool_file *file)
1837 {
1838         struct section *sec;
1839         struct instruction *insn;
1840         struct reloc *reloc;
1841
1842         sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1843         if (!sec)
1844                 return 0;
1845
1846         list_for_each_entry(reloc, &sec->reloc_list, list) {
1847                 if (reloc->sym->type != STT_SECTION) {
1848                         WARN("unexpected relocation symbol type in %s", sec->name);
1849                         return -1;
1850                 }
1851
1852                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1853                 if (!insn) {
1854                         WARN("bad .discard.retpoline_safe entry");
1855                         return -1;
1856                 }
1857
1858                 if (insn->type != INSN_JUMP_DYNAMIC &&
1859                     insn->type != INSN_CALL_DYNAMIC &&
1860                     insn->type != INSN_RETURN &&
1861                     insn->type != INSN_NOP) {
1862                         WARN_FUNC("retpoline_safe hint not an indirect jump/call/ret/nop",
1863                                   insn->sec, insn->offset);
1864                         return -1;
1865                 }
1866
1867                 insn->retpoline_safe = true;
1868         }
1869
1870         return 0;
1871 }
1872
1873 static int read_instr_hints(struct objtool_file *file)
1874 {
1875         struct section *sec;
1876         struct instruction *insn;
1877         struct reloc *reloc;
1878
1879         sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
1880         if (!sec)
1881                 return 0;
1882
1883         list_for_each_entry(reloc, &sec->reloc_list, list) {
1884                 if (reloc->sym->type != STT_SECTION) {
1885                         WARN("unexpected relocation symbol type in %s", sec->name);
1886                         return -1;
1887                 }
1888
1889                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1890                 if (!insn) {
1891                         WARN("bad .discard.instr_end entry");
1892                         return -1;
1893                 }
1894
1895                 insn->instr--;
1896         }
1897
1898         sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
1899         if (!sec)
1900                 return 0;
1901
1902         list_for_each_entry(reloc, &sec->reloc_list, list) {
1903                 if (reloc->sym->type != STT_SECTION) {
1904                         WARN("unexpected relocation symbol type in %s", sec->name);
1905                         return -1;
1906                 }
1907
1908                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1909                 if (!insn) {
1910                         WARN("bad .discard.instr_begin entry");
1911                         return -1;
1912                 }
1913
1914                 insn->instr++;
1915         }
1916
1917         return 0;
1918 }
1919
1920 static int read_intra_function_calls(struct objtool_file *file)
1921 {
1922         struct instruction *insn;
1923         struct section *sec;
1924         struct reloc *reloc;
1925
1926         sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
1927         if (!sec)
1928                 return 0;
1929
1930         list_for_each_entry(reloc, &sec->reloc_list, list) {
1931                 unsigned long dest_off;
1932
1933                 if (reloc->sym->type != STT_SECTION) {
1934                         WARN("unexpected relocation symbol type in %s",
1935                              sec->name);
1936                         return -1;
1937                 }
1938
1939                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1940                 if (!insn) {
1941                         WARN("bad .discard.intra_function_call entry");
1942                         return -1;
1943                 }
1944
1945                 if (insn->type != INSN_CALL) {
1946                         WARN_FUNC("intra_function_call not a direct call",
1947                                   insn->sec, insn->offset);
1948                         return -1;
1949                 }
1950
1951                 /*
1952                  * Treat intra-function CALLs as JMPs, but with a stack_op.
1953                  * See add_call_destinations(), which strips stack_ops from
1954                  * normal CALLs.
1955                  */
1956                 insn->type = INSN_JUMP_UNCONDITIONAL;
1957
1958                 dest_off = insn->offset + insn->len + insn->immediate;
1959                 insn->jump_dest = find_insn(file, insn->sec, dest_off);
1960                 if (!insn->jump_dest) {
1961                         WARN_FUNC("can't find call dest at %s+0x%lx",
1962                                   insn->sec, insn->offset,
1963                                   insn->sec->name, dest_off);
1964                         return -1;
1965                 }
1966         }
1967
1968         return 0;
1969 }
1970
1971 static int classify_symbols(struct objtool_file *file)
1972 {
1973         struct section *sec;
1974         struct symbol *func;
1975
1976         for_each_sec(file, sec) {
1977                 list_for_each_entry(func, &sec->symbol_list, list) {
1978                         if (func->bind != STB_GLOBAL)
1979                                 continue;
1980
1981                         if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
1982                                      strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
1983                                 func->static_call_tramp = true;
1984
1985                         if (arch_is_retpoline(func))
1986                                 func->retpoline_thunk = true;
1987
1988                         if (arch_is_rethunk(func))
1989                                 func->return_thunk = true;
1990
1991                         if (arch_is_embedded_insn(func))
1992                                 func->embedded_insn = true;
1993
1994                         if (!strcmp(func->name, "__fentry__"))
1995                                 func->fentry = true;
1996
1997                         if (!strncmp(func->name, "__sanitizer_cov_", 16))
1998                                 func->kcov = true;
1999                 }
2000         }
2001
2002         return 0;
2003 }
2004
2005 static void mark_rodata(struct objtool_file *file)
2006 {
2007         struct section *sec;
2008         bool found = false;
2009
2010         /*
2011          * Search for the following rodata sections, each of which can
2012          * potentially contain jump tables:
2013          *
2014          * - .rodata: can contain GCC switch tables
2015          * - .rodata.<func>: same, if -fdata-sections is being used
2016          * - .rodata..c_jump_table: contains C annotated jump tables
2017          *
2018          * .rodata.str1.* sections are ignored; they don't contain jump tables.
2019          */
2020         for_each_sec(file, sec) {
2021                 if (!strncmp(sec->name, ".rodata", 7) &&
2022                     !strstr(sec->name, ".str1.")) {
2023                         sec->rodata = true;
2024                         found = true;
2025                 }
2026         }
2027
2028         file->rodata = found;
2029 }
2030
2031 static int decode_sections(struct objtool_file *file)
2032 {
2033         int ret;
2034
2035         mark_rodata(file);
2036
2037         ret = decode_instructions(file);
2038         if (ret)
2039                 return ret;
2040
2041         ret = add_dead_ends(file);
2042         if (ret)
2043                 return ret;
2044
2045         add_ignores(file);
2046         add_uaccess_safe(file);
2047
2048         ret = add_ignore_alternatives(file);
2049         if (ret)
2050                 return ret;
2051
2052         /*
2053          * Must be before add_{jump_call}_destination.
2054          */
2055         ret = classify_symbols(file);
2056         if (ret)
2057                 return ret;
2058
2059         /*
2060          * Must be before add_special_section_alts() as that depends on
2061          * jump_dest being set.
2062          */
2063         ret = add_jump_destinations(file);
2064         if (ret)
2065                 return ret;
2066
2067         ret = add_special_section_alts(file);
2068         if (ret)
2069                 return ret;
2070
2071         /*
2072          * Must be before add_call_destination(); it changes INSN_CALL to
2073          * INSN_JUMP.
2074          */
2075         ret = read_intra_function_calls(file);
2076         if (ret)
2077                 return ret;
2078
2079         ret = add_call_destinations(file);
2080         if (ret)
2081                 return ret;
2082
2083         ret = add_jump_table_alts(file);
2084         if (ret)
2085                 return ret;
2086
2087         ret = read_unwind_hints(file);
2088         if (ret)
2089                 return ret;
2090
2091         ret = read_retpoline_hints(file);
2092         if (ret)
2093                 return ret;
2094
2095         ret = read_instr_hints(file);
2096         if (ret)
2097                 return ret;
2098
2099         return 0;
2100 }
2101
2102 static bool is_special_call(struct instruction *insn)
2103 {
2104         if (insn->type == INSN_CALL) {
2105                 struct symbol *dest = insn->call_dest;
2106
2107                 if (!dest)
2108                         return false;
2109
2110                 if (dest->fentry || dest->embedded_insn)
2111                         return true;
2112         }
2113
2114         return false;
2115 }
2116
2117 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2118 {
2119         struct cfi_state *cfi = &state->cfi;
2120         int i;
2121
2122         if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2123                 return true;
2124
2125         if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2126                 return true;
2127
2128         if (cfi->stack_size != initial_func_cfi.cfa.offset)
2129                 return true;
2130
2131         for (i = 0; i < CFI_NUM_REGS; i++) {
2132                 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2133                     cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2134                         return true;
2135         }
2136
2137         return false;
2138 }
2139
2140 static bool has_valid_stack_frame(struct insn_state *state)
2141 {
2142         struct cfi_state *cfi = &state->cfi;
2143
2144         if (cfi->cfa.base == CFI_BP && cfi->regs[CFI_BP].base == CFI_CFA &&
2145             cfi->regs[CFI_BP].offset == -16)
2146                 return true;
2147
2148         if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2149                 return true;
2150
2151         return false;
2152 }
2153
2154 static int update_cfi_state_regs(struct instruction *insn,
2155                                   struct cfi_state *cfi,
2156                                   struct stack_op *op)
2157 {
2158         struct cfi_reg *cfa = &cfi->cfa;
2159
2160         if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2161                 return 0;
2162
2163         /* push */
2164         if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2165                 cfa->offset += 8;
2166
2167         /* pop */
2168         if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2169                 cfa->offset -= 8;
2170
2171         /* add immediate to sp */
2172         if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2173             op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2174                 cfa->offset -= op->src.offset;
2175
2176         return 0;
2177 }
2178
2179 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2180 {
2181         if (arch_callee_saved_reg(reg) &&
2182             cfi->regs[reg].base == CFI_UNDEFINED) {
2183                 cfi->regs[reg].base = base;
2184                 cfi->regs[reg].offset = offset;
2185         }
2186 }
2187
2188 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2189 {
2190         cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2191         cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2192 }
2193
2194 /*
2195  * A note about DRAP stack alignment:
2196  *
2197  * GCC has the concept of a DRAP register, which is used to help keep track of
2198  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
2199  * register.  The typical DRAP pattern is:
2200  *
2201  *   4c 8d 54 24 08             lea    0x8(%rsp),%r10
2202  *   48 83 e4 c0                and    $0xffffffffffffffc0,%rsp
2203  *   41 ff 72 f8                pushq  -0x8(%r10)
2204  *   55                         push   %rbp
2205  *   48 89 e5                   mov    %rsp,%rbp
2206  *                              (more pushes)
2207  *   41 52                      push   %r10
2208  *                              ...
2209  *   41 5a                      pop    %r10
2210  *                              (more pops)
2211  *   5d                         pop    %rbp
2212  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2213  *   c3                         retq
2214  *
2215  * There are some variations in the epilogues, like:
2216  *
2217  *   5b                         pop    %rbx
2218  *   41 5a                      pop    %r10
2219  *   41 5c                      pop    %r12
2220  *   41 5d                      pop    %r13
2221  *   41 5e                      pop    %r14
2222  *   c9                         leaveq
2223  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2224  *   c3                         retq
2225  *
2226  * and:
2227  *
2228  *   4c 8b 55 e8                mov    -0x18(%rbp),%r10
2229  *   48 8b 5d e0                mov    -0x20(%rbp),%rbx
2230  *   4c 8b 65 f0                mov    -0x10(%rbp),%r12
2231  *   4c 8b 6d f8                mov    -0x8(%rbp),%r13
2232  *   c9                         leaveq
2233  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2234  *   c3                         retq
2235  *
2236  * Sometimes r13 is used as the DRAP register, in which case it's saved and
2237  * restored beforehand:
2238  *
2239  *   41 55                      push   %r13
2240  *   4c 8d 6c 24 10             lea    0x10(%rsp),%r13
2241  *   48 83 e4 f0                and    $0xfffffffffffffff0,%rsp
2242  *                              ...
2243  *   49 8d 65 f0                lea    -0x10(%r13),%rsp
2244  *   41 5d                      pop    %r13
2245  *   c3                         retq
2246  */
2247 static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi,
2248                              struct stack_op *op)
2249 {
2250         struct cfi_reg *cfa = &cfi->cfa;
2251         struct cfi_reg *regs = cfi->regs;
2252
2253         /* stack operations don't make sense with an undefined CFA */
2254         if (cfa->base == CFI_UNDEFINED) {
2255                 if (insn->func) {
2256                         WARN_FUNC("undefined stack state", insn->sec, insn->offset);
2257                         return -1;
2258                 }
2259                 return 0;
2260         }
2261
2262         if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2263             cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2264                 return update_cfi_state_regs(insn, cfi, op);
2265
2266         switch (op->dest.type) {
2267
2268         case OP_DEST_REG:
2269                 switch (op->src.type) {
2270
2271                 case OP_SRC_REG:
2272                         if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2273                             cfa->base == CFI_SP &&
2274                             regs[CFI_BP].base == CFI_CFA &&
2275                             regs[CFI_BP].offset == -cfa->offset) {
2276
2277                                 /* mov %rsp, %rbp */
2278                                 cfa->base = op->dest.reg;
2279                                 cfi->bp_scratch = false;
2280                         }
2281
2282                         else if (op->src.reg == CFI_SP &&
2283                                  op->dest.reg == CFI_BP && cfi->drap) {
2284
2285                                 /* drap: mov %rsp, %rbp */
2286                                 regs[CFI_BP].base = CFI_BP;
2287                                 regs[CFI_BP].offset = -cfi->stack_size;
2288                                 cfi->bp_scratch = false;
2289                         }
2290
2291                         else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2292
2293                                 /*
2294                                  * mov %rsp, %reg
2295                                  *
2296                                  * This is needed for the rare case where GCC
2297                                  * does:
2298                                  *
2299                                  *   mov    %rsp, %rax
2300                                  *   ...
2301                                  *   mov    %rax, %rsp
2302                                  */
2303                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2304                                 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2305                         }
2306
2307                         else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2308                                  cfa->base == CFI_BP) {
2309
2310                                 /*
2311                                  * mov %rbp, %rsp
2312                                  *
2313                                  * Restore the original stack pointer (Clang).
2314                                  */
2315                                 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2316                         }
2317
2318                         else if (op->dest.reg == cfa->base) {
2319
2320                                 /* mov %reg, %rsp */
2321                                 if (cfa->base == CFI_SP &&
2322                                     cfi->vals[op->src.reg].base == CFI_CFA) {
2323
2324                                         /*
2325                                          * This is needed for the rare case
2326                                          * where GCC does something dumb like:
2327                                          *
2328                                          *   lea    0x8(%rsp), %rcx
2329                                          *   ...
2330                                          *   mov    %rcx, %rsp
2331                                          */
2332                                         cfa->offset = -cfi->vals[op->src.reg].offset;
2333                                         cfi->stack_size = cfa->offset;
2334
2335                                 } else {
2336                                         cfa->base = CFI_UNDEFINED;
2337                                         cfa->offset = 0;
2338                                 }
2339                         }
2340
2341                         break;
2342
2343                 case OP_SRC_ADD:
2344                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2345
2346                                 /* add imm, %rsp */
2347                                 cfi->stack_size -= op->src.offset;
2348                                 if (cfa->base == CFI_SP)
2349                                         cfa->offset -= op->src.offset;
2350                                 break;
2351                         }
2352
2353                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2354
2355                                 /* lea disp(%rbp), %rsp */
2356                                 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2357                                 break;
2358                         }
2359
2360                         if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2361
2362                                 /* drap: lea disp(%rsp), %drap */
2363                                 cfi->drap_reg = op->dest.reg;
2364
2365                                 /*
2366                                  * lea disp(%rsp), %reg
2367                                  *
2368                                  * This is needed for the rare case where GCC
2369                                  * does something dumb like:
2370                                  *
2371                                  *   lea    0x8(%rsp), %rcx
2372                                  *   ...
2373                                  *   mov    %rcx, %rsp
2374                                  */
2375                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2376                                 cfi->vals[op->dest.reg].offset = \
2377                                         -cfi->stack_size + op->src.offset;
2378
2379                                 break;
2380                         }
2381
2382                         if (cfi->drap && op->dest.reg == CFI_SP &&
2383                             op->src.reg == cfi->drap_reg) {
2384
2385                                  /* drap: lea disp(%drap), %rsp */
2386                                 cfa->base = CFI_SP;
2387                                 cfa->offset = cfi->stack_size = -op->src.offset;
2388                                 cfi->drap_reg = CFI_UNDEFINED;
2389                                 cfi->drap = false;
2390                                 break;
2391                         }
2392
2393                         if (op->dest.reg == cfi->cfa.base) {
2394                                 WARN_FUNC("unsupported stack register modification",
2395                                           insn->sec, insn->offset);
2396                                 return -1;
2397                         }
2398
2399                         break;
2400
2401                 case OP_SRC_AND:
2402                         if (op->dest.reg != CFI_SP ||
2403                             (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
2404                             (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
2405                                 WARN_FUNC("unsupported stack pointer realignment",
2406                                           insn->sec, insn->offset);
2407                                 return -1;
2408                         }
2409
2410                         if (cfi->drap_reg != CFI_UNDEFINED) {
2411                                 /* drap: and imm, %rsp */
2412                                 cfa->base = cfi->drap_reg;
2413                                 cfa->offset = cfi->stack_size = 0;
2414                                 cfi->drap = true;
2415                         }
2416
2417                         /*
2418                          * Older versions of GCC (4.8ish) realign the stack
2419                          * without DRAP, with a frame pointer.
2420                          */
2421
2422                         break;
2423
2424                 case OP_SRC_POP:
2425                 case OP_SRC_POPF:
2426                         if (!cfi->drap && op->dest.reg == cfa->base) {
2427
2428                                 /* pop %rbp */
2429                                 cfa->base = CFI_SP;
2430                         }
2431
2432                         if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
2433                             op->dest.reg == cfi->drap_reg &&
2434                             cfi->drap_offset == -cfi->stack_size) {
2435
2436                                 /* drap: pop %drap */
2437                                 cfa->base = cfi->drap_reg;
2438                                 cfa->offset = 0;
2439                                 cfi->drap_offset = -1;
2440
2441                         } else if (regs[op->dest.reg].offset == -cfi->stack_size) {
2442
2443                                 /* pop %reg */
2444                                 restore_reg(cfi, op->dest.reg);
2445                         }
2446
2447                         cfi->stack_size -= 8;
2448                         if (cfa->base == CFI_SP)
2449                                 cfa->offset -= 8;
2450
2451                         break;
2452
2453                 case OP_SRC_REG_INDIRECT:
2454                         if (cfi->drap && op->src.reg == CFI_BP &&
2455                             op->src.offset == cfi->drap_offset) {
2456
2457                                 /* drap: mov disp(%rbp), %drap */
2458                                 cfa->base = cfi->drap_reg;
2459                                 cfa->offset = 0;
2460                                 cfi->drap_offset = -1;
2461                         }
2462
2463                         if (cfi->drap && op->src.reg == CFI_BP &&
2464                             op->src.offset == regs[op->dest.reg].offset) {
2465
2466                                 /* drap: mov disp(%rbp), %reg */
2467                                 restore_reg(cfi, op->dest.reg);
2468
2469                         } else if (op->src.reg == cfa->base &&
2470                             op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
2471
2472                                 /* mov disp(%rbp), %reg */
2473                                 /* mov disp(%rsp), %reg */
2474                                 restore_reg(cfi, op->dest.reg);
2475                         }
2476
2477                         break;
2478
2479                 default:
2480                         WARN_FUNC("unknown stack-related instruction",
2481                                   insn->sec, insn->offset);
2482                         return -1;
2483                 }
2484
2485                 break;
2486
2487         case OP_DEST_PUSH:
2488         case OP_DEST_PUSHF:
2489                 cfi->stack_size += 8;
2490                 if (cfa->base == CFI_SP)
2491                         cfa->offset += 8;
2492
2493                 if (op->src.type != OP_SRC_REG)
2494                         break;
2495
2496                 if (cfi->drap) {
2497                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2498
2499                                 /* drap: push %drap */
2500                                 cfa->base = CFI_BP_INDIRECT;
2501                                 cfa->offset = -cfi->stack_size;
2502
2503                                 /* save drap so we know when to restore it */
2504                                 cfi->drap_offset = -cfi->stack_size;
2505
2506                         } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
2507
2508                                 /* drap: push %rbp */
2509                                 cfi->stack_size = 0;
2510
2511                         } else {
2512
2513                                 /* drap: push %reg */
2514                                 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
2515                         }
2516
2517                 } else {
2518
2519                         /* push %reg */
2520                         save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
2521                 }
2522
2523                 /* detect when asm code uses rbp as a scratch register */
2524                 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
2525                     cfa->base != CFI_BP)
2526                         cfi->bp_scratch = true;
2527                 break;
2528
2529         case OP_DEST_REG_INDIRECT:
2530
2531                 if (cfi->drap) {
2532                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2533
2534                                 /* drap: mov %drap, disp(%rbp) */
2535                                 cfa->base = CFI_BP_INDIRECT;
2536                                 cfa->offset = op->dest.offset;
2537
2538                                 /* save drap offset so we know when to restore it */
2539                                 cfi->drap_offset = op->dest.offset;
2540                         } else {
2541
2542                                 /* drap: mov reg, disp(%rbp) */
2543                                 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
2544                         }
2545
2546                 } else if (op->dest.reg == cfa->base) {
2547
2548                         /* mov reg, disp(%rbp) */
2549                         /* mov reg, disp(%rsp) */
2550                         save_reg(cfi, op->src.reg, CFI_CFA,
2551                                  op->dest.offset - cfi->cfa.offset);
2552                 }
2553
2554                 break;
2555
2556         case OP_DEST_LEAVE:
2557                 if ((!cfi->drap && cfa->base != CFI_BP) ||
2558                     (cfi->drap && cfa->base != cfi->drap_reg)) {
2559                         WARN_FUNC("leave instruction with modified stack frame",
2560                                   insn->sec, insn->offset);
2561                         return -1;
2562                 }
2563
2564                 /* leave (mov %rbp, %rsp; pop %rbp) */
2565
2566                 cfi->stack_size = -cfi->regs[CFI_BP].offset - 8;
2567                 restore_reg(cfi, CFI_BP);
2568
2569                 if (!cfi->drap) {
2570                         cfa->base = CFI_SP;
2571                         cfa->offset -= 8;
2572                 }
2573
2574                 break;
2575
2576         case OP_DEST_MEM:
2577                 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
2578                         WARN_FUNC("unknown stack-related memory operation",
2579                                   insn->sec, insn->offset);
2580                         return -1;
2581                 }
2582
2583                 /* pop mem */
2584                 cfi->stack_size -= 8;
2585                 if (cfa->base == CFI_SP)
2586                         cfa->offset -= 8;
2587
2588                 break;
2589
2590         default:
2591                 WARN_FUNC("unknown stack-related instruction",
2592                           insn->sec, insn->offset);
2593                 return -1;
2594         }
2595
2596         return 0;
2597 }
2598
2599 /*
2600  * The stack layouts of alternatives instructions can sometimes diverge when
2601  * they have stack modifications.  That's fine as long as the potential stack
2602  * layouts don't conflict at any given potential instruction boundary.
2603  *
2604  * Flatten the CFIs of the different alternative code streams (both original
2605  * and replacement) into a single shared CFI array which can be used to detect
2606  * conflicts and nicely feed a linear array of ORC entries to the unwinder.
2607  */
2608 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
2609 {
2610         struct cfi_state **alt_cfi;
2611         int group_off;
2612
2613         if (!insn->alt_group)
2614                 return 0;
2615
2616         if (!insn->cfi) {
2617                 WARN("CFI missing");
2618                 return -1;
2619         }
2620
2621         alt_cfi = insn->alt_group->cfi;
2622         group_off = insn->offset - insn->alt_group->first_insn->offset;
2623
2624         if (!alt_cfi[group_off]) {
2625                 alt_cfi[group_off] = insn->cfi;
2626         } else {
2627                 if (cficmp(alt_cfi[group_off], insn->cfi)) {
2628                         WARN_FUNC("stack layout conflict in alternatives",
2629                                   insn->sec, insn->offset);
2630                         return -1;
2631                 }
2632         }
2633
2634         return 0;
2635 }
2636
2637 static int handle_insn_ops(struct instruction *insn, struct insn_state *state)
2638 {
2639         struct stack_op *op;
2640
2641         list_for_each_entry(op, &insn->stack_ops, list) {
2642
2643                 if (update_cfi_state(insn, &state->cfi, op))
2644                         return 1;
2645
2646                 if (op->dest.type == OP_DEST_PUSHF) {
2647                         if (!state->uaccess_stack) {
2648                                 state->uaccess_stack = 1;
2649                         } else if (state->uaccess_stack >> 31) {
2650                                 WARN_FUNC("PUSHF stack exhausted",
2651                                           insn->sec, insn->offset);
2652                                 return 1;
2653                         }
2654                         state->uaccess_stack <<= 1;
2655                         state->uaccess_stack  |= state->uaccess;
2656                 }
2657
2658                 if (op->src.type == OP_SRC_POPF) {
2659                         if (state->uaccess_stack) {
2660                                 state->uaccess = state->uaccess_stack & 1;
2661                                 state->uaccess_stack >>= 1;
2662                                 if (state->uaccess_stack == 1)
2663                                         state->uaccess_stack = 0;
2664                         }
2665                 }
2666         }
2667
2668         return 0;
2669 }
2670
2671 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
2672 {
2673         struct cfi_state *cfi1 = insn->cfi;
2674         int i;
2675
2676         if (!cfi1) {
2677                 WARN("CFI missing");
2678                 return false;
2679         }
2680
2681         if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
2682
2683                 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
2684                           insn->sec, insn->offset,
2685                           cfi1->cfa.base, cfi1->cfa.offset,
2686                           cfi2->cfa.base, cfi2->cfa.offset);
2687
2688         } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
2689                 for (i = 0; i < CFI_NUM_REGS; i++) {
2690                         if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
2691                                     sizeof(struct cfi_reg)))
2692                                 continue;
2693
2694                         WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
2695                                   insn->sec, insn->offset,
2696                                   i, cfi1->regs[i].base, cfi1->regs[i].offset,
2697                                   i, cfi2->regs[i].base, cfi2->regs[i].offset);
2698                         break;
2699                 }
2700
2701         } else if (cfi1->type != cfi2->type) {
2702
2703                 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
2704                           insn->sec, insn->offset, cfi1->type, cfi2->type);
2705
2706         } else if (cfi1->drap != cfi2->drap ||
2707                    (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
2708                    (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
2709
2710                 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
2711                           insn->sec, insn->offset,
2712                           cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
2713                           cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
2714
2715         } else
2716                 return true;
2717
2718         return false;
2719 }
2720
2721 static inline bool func_uaccess_safe(struct symbol *func)
2722 {
2723         if (func)
2724                 return func->uaccess_safe;
2725
2726         return false;
2727 }
2728
2729 static inline const char *call_dest_name(struct instruction *insn)
2730 {
2731         if (insn->call_dest)
2732                 return insn->call_dest->name;
2733
2734         return "{dynamic}";
2735 }
2736
2737 static inline bool noinstr_call_dest(struct symbol *func)
2738 {
2739         /*
2740          * We can't deal with indirect function calls at present;
2741          * assume they're instrumented.
2742          */
2743         if (!func)
2744                 return false;
2745
2746         /*
2747          * If the symbol is from a noinstr section; we good.
2748          */
2749         if (func->sec->noinstr)
2750                 return true;
2751
2752         /*
2753          * The __ubsan_handle_*() calls are like WARN(), they only happen when
2754          * something 'BAD' happened. At the risk of taking the machine down,
2755          * let them proceed to get the message out.
2756          */
2757         if (!strncmp(func->name, "__ubsan_handle_", 15))
2758                 return true;
2759
2760         return false;
2761 }
2762
2763 static int validate_call(struct instruction *insn, struct insn_state *state)
2764 {
2765         if (state->noinstr && state->instr <= 0 &&
2766             !noinstr_call_dest(insn->call_dest)) {
2767                 WARN_FUNC("call to %s() leaves .noinstr.text section",
2768                                 insn->sec, insn->offset, call_dest_name(insn));
2769                 return 1;
2770         }
2771
2772         if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
2773                 WARN_FUNC("call to %s() with UACCESS enabled",
2774                                 insn->sec, insn->offset, call_dest_name(insn));
2775                 return 1;
2776         }
2777
2778         if (state->df) {
2779                 WARN_FUNC("call to %s() with DF set",
2780                                 insn->sec, insn->offset, call_dest_name(insn));
2781                 return 1;
2782         }
2783
2784         return 0;
2785 }
2786
2787 static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
2788 {
2789         if (has_modified_stack_frame(insn, state)) {
2790                 WARN_FUNC("sibling call from callable instruction with modified stack frame",
2791                                 insn->sec, insn->offset);
2792                 return 1;
2793         }
2794
2795         return validate_call(insn, state);
2796 }
2797
2798 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
2799 {
2800         if (state->noinstr && state->instr > 0) {
2801                 WARN_FUNC("return with instrumentation enabled",
2802                           insn->sec, insn->offset);
2803                 return 1;
2804         }
2805
2806         if (state->uaccess && !func_uaccess_safe(func)) {
2807                 WARN_FUNC("return with UACCESS enabled",
2808                           insn->sec, insn->offset);
2809                 return 1;
2810         }
2811
2812         if (!state->uaccess && func_uaccess_safe(func)) {
2813                 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
2814                           insn->sec, insn->offset);
2815                 return 1;
2816         }
2817
2818         if (state->df) {
2819                 WARN_FUNC("return with DF set",
2820                           insn->sec, insn->offset);
2821                 return 1;
2822         }
2823
2824         if (func && has_modified_stack_frame(insn, state)) {
2825                 WARN_FUNC("return with modified stack frame",
2826                           insn->sec, insn->offset);
2827                 return 1;
2828         }
2829
2830         if (state->cfi.bp_scratch) {
2831                 WARN_FUNC("BP used as a scratch register",
2832                           insn->sec, insn->offset);
2833                 return 1;
2834         }
2835
2836         return 0;
2837 }
2838
2839 static struct instruction *next_insn_to_validate(struct objtool_file *file,
2840                                                  struct instruction *insn)
2841 {
2842         struct alt_group *alt_group = insn->alt_group;
2843
2844         /*
2845          * Simulate the fact that alternatives are patched in-place.  When the
2846          * end of a replacement alt_group is reached, redirect objtool flow to
2847          * the end of the original alt_group.
2848          */
2849         if (alt_group && insn == alt_group->last_insn && alt_group->orig_group)
2850                 return next_insn_same_sec(file, alt_group->orig_group->last_insn);
2851
2852         return next_insn_same_sec(file, insn);
2853 }
2854
2855 /*
2856  * Follow the branch starting at the given instruction, and recursively follow
2857  * any other branches (jumps).  Meanwhile, track the frame pointer state at
2858  * each instruction and validate all the rules described in
2859  * tools/objtool/Documentation/stack-validation.txt.
2860  */
2861 static int validate_branch(struct objtool_file *file, struct symbol *func,
2862                            struct instruction *insn, struct insn_state state)
2863 {
2864         struct alternative *alt;
2865         struct instruction *next_insn, *prev_insn = NULL;
2866         struct section *sec;
2867         u8 visited;
2868         int ret;
2869
2870         sec = insn->sec;
2871
2872         while (1) {
2873                 next_insn = next_insn_to_validate(file, insn);
2874
2875                 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
2876                         WARN("%s() falls through to next function %s()",
2877                              func->name, insn->func->name);
2878                         return 1;
2879                 }
2880
2881                 if (func && insn->ignore) {
2882                         WARN_FUNC("BUG: why am I validating an ignored function?",
2883                                   sec, insn->offset);
2884                         return 1;
2885                 }
2886
2887                 visited = VISITED_BRANCH << state.uaccess;
2888                 if (insn->visited & VISITED_BRANCH_MASK) {
2889                         if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
2890                                 return 1;
2891
2892                         if (insn->visited & visited)
2893                                 return 0;
2894                 } else {
2895                         nr_insns_visited++;
2896                 }
2897
2898                 if (state.noinstr)
2899                         state.instr += insn->instr;
2900
2901                 if (insn->hint) {
2902                         if (insn->restore) {
2903                                 struct instruction *save_insn, *i;
2904
2905                                 i = insn;
2906                                 save_insn = NULL;
2907
2908                                 sym_for_each_insn_continue_reverse(file, func, i) {
2909                                         if (i->save) {
2910                                                 save_insn = i;
2911                                                 break;
2912                                         }
2913                                 }
2914
2915                                 if (!save_insn) {
2916                                         WARN_FUNC("no corresponding CFI save for CFI restore",
2917                                                   sec, insn->offset);
2918                                         return 1;
2919                                 }
2920
2921                                 if (!save_insn->visited) {
2922                                         WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
2923                                                   sec, insn->offset);
2924                                         return 1;
2925                                 }
2926
2927                                 insn->cfi = save_insn->cfi;
2928                                 nr_cfi_reused++;
2929                         }
2930
2931                         state.cfi = *insn->cfi;
2932                 } else {
2933                         /* XXX track if we actually changed state.cfi */
2934
2935                         if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
2936                                 insn->cfi = prev_insn->cfi;
2937                                 nr_cfi_reused++;
2938                         } else {
2939                                 insn->cfi = cfi_hash_find_or_add(&state.cfi);
2940                         }
2941                 }
2942
2943                 insn->visited |= visited;
2944
2945                 if (propagate_alt_cfi(file, insn))
2946                         return 1;
2947
2948                 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
2949                         bool skip_orig = false;
2950
2951                         list_for_each_entry(alt, &insn->alts, list) {
2952                                 if (alt->skip_orig)
2953                                         skip_orig = true;
2954
2955                                 ret = validate_branch(file, func, alt->insn, state);
2956                                 if (ret) {
2957                                         if (backtrace)
2958                                                 BT_FUNC("(alt)", insn);
2959                                         return ret;
2960                                 }
2961                         }
2962
2963                         if (skip_orig)
2964                                 return 0;
2965                 }
2966
2967                 if (handle_insn_ops(insn, &state))
2968                         return 1;
2969
2970                 switch (insn->type) {
2971
2972                 case INSN_RETURN:
2973                         if (sls && !insn->retpoline_safe &&
2974                             next_insn && next_insn->type != INSN_TRAP) {
2975                                 WARN_FUNC("missing int3 after ret",
2976                                           insn->sec, insn->offset);
2977                         }
2978                         return validate_return(func, insn, &state);
2979
2980                 case INSN_CALL:
2981                 case INSN_CALL_DYNAMIC:
2982                         ret = validate_call(insn, &state);
2983                         if (ret)
2984                                 return ret;
2985
2986                         if (!no_fp && func && !is_special_call(insn) &&
2987                             !has_valid_stack_frame(&state)) {
2988                                 WARN_FUNC("call without frame pointer save/setup",
2989                                           sec, insn->offset);
2990                                 return 1;
2991                         }
2992
2993                         if (dead_end_function(file, insn->call_dest))
2994                                 return 0;
2995
2996                         break;
2997
2998                 case INSN_JUMP_CONDITIONAL:
2999                 case INSN_JUMP_UNCONDITIONAL:
3000                         if (is_sibling_call(insn)) {
3001                                 ret = validate_sibling_call(insn, &state);
3002                                 if (ret)
3003                                         return ret;
3004
3005                         } else if (insn->jump_dest) {
3006                                 ret = validate_branch(file, func,
3007                                                       insn->jump_dest, state);
3008                                 if (ret) {
3009                                         if (backtrace)
3010                                                 BT_FUNC("(branch)", insn);
3011                                         return ret;
3012                                 }
3013                         }
3014
3015                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
3016                                 return 0;
3017
3018                         break;
3019
3020                 case INSN_JUMP_DYNAMIC:
3021                         if (sls && !insn->retpoline_safe &&
3022                             next_insn && next_insn->type != INSN_TRAP) {
3023                                 WARN_FUNC("missing int3 after indirect jump",
3024                                           insn->sec, insn->offset);
3025                         }
3026
3027                         /* fallthrough */
3028                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3029                         if (is_sibling_call(insn)) {
3030                                 ret = validate_sibling_call(insn, &state);
3031                                 if (ret)
3032                                         return ret;
3033                         }
3034
3035                         if (insn->type == INSN_JUMP_DYNAMIC)
3036                                 return 0;
3037
3038                         break;
3039
3040                 case INSN_CONTEXT_SWITCH:
3041                         if (func && (!next_insn || !next_insn->hint)) {
3042                                 WARN_FUNC("unsupported instruction in callable function",
3043                                           sec, insn->offset);
3044                                 return 1;
3045                         }
3046                         return 0;
3047
3048                 case INSN_STAC:
3049                         if (state.uaccess) {
3050                                 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
3051                                 return 1;
3052                         }
3053
3054                         state.uaccess = true;
3055                         break;
3056
3057                 case INSN_CLAC:
3058                         if (!state.uaccess && func) {
3059                                 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
3060                                 return 1;
3061                         }
3062
3063                         if (func_uaccess_safe(func) && !state.uaccess_stack) {
3064                                 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
3065                                 return 1;
3066                         }
3067
3068                         state.uaccess = false;
3069                         break;
3070
3071                 case INSN_STD:
3072                         if (state.df) {
3073                                 WARN_FUNC("recursive STD", sec, insn->offset);
3074                                 return 1;
3075                         }
3076
3077                         state.df = true;
3078                         break;
3079
3080                 case INSN_CLD:
3081                         if (!state.df && func) {
3082                                 WARN_FUNC("redundant CLD", sec, insn->offset);
3083                                 return 1;
3084                         }
3085
3086                         state.df = false;
3087                         break;
3088
3089                 default:
3090                         break;
3091                 }
3092
3093                 if (insn->dead_end)
3094                         return 0;
3095
3096                 if (!next_insn) {
3097                         if (state.cfi.cfa.base == CFI_UNDEFINED)
3098                                 return 0;
3099                         WARN("%s: unexpected end of section", sec->name);
3100                         return 1;
3101                 }
3102
3103                 prev_insn = insn;
3104                 insn = next_insn;
3105         }
3106
3107         return 0;
3108 }
3109
3110 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3111 {
3112         struct instruction *insn;
3113         struct insn_state state;
3114         int ret, warnings = 0;
3115
3116         if (!file->hints)
3117                 return 0;
3118
3119         init_insn_state(&state, sec);
3120
3121         if (sec) {
3122                 insn = find_insn(file, sec, 0);
3123                 if (!insn)
3124                         return 0;
3125         } else {
3126                 insn = list_first_entry(&file->insn_list, typeof(*insn), list);
3127         }
3128
3129         while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) {
3130                 if (insn->hint && !insn->visited) {
3131                         ret = validate_branch(file, insn->func, insn, state);
3132                         if (ret && backtrace)
3133                                 BT_FUNC("<=== (hint)", insn);
3134                         warnings += ret;
3135                 }
3136
3137                 insn = list_next_entry(insn, list);
3138         }
3139
3140         return warnings;
3141 }
3142
3143 /*
3144  * Validate rethunk entry constraint: must untrain RET before the first RET.
3145  *
3146  * Follow every branch (intra-function) and ensure ANNOTATE_UNRET_END comes
3147  * before an actual RET instruction.
3148  */
3149 static int validate_entry(struct objtool_file *file, struct instruction *insn)
3150 {
3151         struct instruction *next, *dest;
3152         int ret, warnings = 0;
3153
3154         for (;;) {
3155                 next = next_insn_to_validate(file, insn);
3156
3157                 if (insn->visited & VISITED_ENTRY)
3158                         return 0;
3159
3160                 insn->visited |= VISITED_ENTRY;
3161
3162                 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
3163                         struct alternative *alt;
3164                         bool skip_orig = false;
3165
3166                         list_for_each_entry(alt, &insn->alts, list) {
3167                                 if (alt->skip_orig)
3168                                         skip_orig = true;
3169
3170                                 ret = validate_entry(file, alt->insn);
3171                                 if (ret) {
3172                                         if (backtrace)
3173                                                 BT_FUNC("(alt)", insn);
3174                                         return ret;
3175                                 }
3176                         }
3177
3178                         if (skip_orig)
3179                                 return 0;
3180                 }
3181
3182                 switch (insn->type) {
3183
3184                 case INSN_CALL_DYNAMIC:
3185                 case INSN_JUMP_DYNAMIC:
3186                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3187                         WARN_FUNC("early indirect call", insn->sec, insn->offset);
3188                         return 1;
3189
3190                 case INSN_JUMP_UNCONDITIONAL:
3191                 case INSN_JUMP_CONDITIONAL:
3192                         if (!is_sibling_call(insn)) {
3193                                 if (!insn->jump_dest) {
3194                                         WARN_FUNC("unresolved jump target after linking?!?",
3195                                                   insn->sec, insn->offset);
3196                                         return -1;
3197                                 }
3198                                 ret = validate_entry(file, insn->jump_dest);
3199                                 if (ret) {
3200                                         if (backtrace) {
3201                                                 BT_FUNC("(branch%s)", insn,
3202                                                         insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : "");
3203                                         }
3204                                         return ret;
3205                                 }
3206
3207                                 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3208                                         return 0;
3209
3210                                 break;
3211                         }
3212
3213                         /* fallthrough */
3214                 case INSN_CALL:
3215                         dest = find_insn(file, insn->call_dest->sec,
3216                                          insn->call_dest->offset);
3217                         if (!dest) {
3218                                 WARN("Unresolved function after linking!?: %s",
3219                                      insn->call_dest->name);
3220                                 return -1;
3221                         }
3222
3223                         ret = validate_entry(file, dest);
3224                         if (ret) {
3225                                 if (backtrace)
3226                                         BT_FUNC("(call)", insn);
3227                                 return ret;
3228                         }
3229                         /*
3230                          * If a call returns without error, it must have seen UNTRAIN_RET.
3231                          * Therefore any non-error return is a success.
3232                          */
3233                         return 0;
3234
3235                 case INSN_RETURN:
3236                         WARN_FUNC("RET before UNTRAIN", insn->sec, insn->offset);
3237                         return 1;
3238
3239                 case INSN_NOP:
3240                         if (insn->retpoline_safe)
3241                                 return 0;
3242                         break;
3243
3244                 default:
3245                         break;
3246                 }
3247
3248                 if (!next) {
3249                         WARN_FUNC("teh end!", insn->sec, insn->offset);
3250                         return -1;
3251                 }
3252                 insn = next;
3253         }
3254
3255         return warnings;
3256 }
3257
3258 /*
3259  * Validate that all branches starting at 'insn->entry' encounter UNRET_END
3260  * before RET.
3261  */
3262 static int validate_unret(struct objtool_file *file)
3263 {
3264         struct instruction *insn;
3265         int ret, warnings = 0;
3266
3267         for_each_insn(file, insn) {
3268                 if (!insn->entry)
3269                         continue;
3270
3271                 ret = validate_entry(file, insn);
3272                 if (ret < 0) {
3273                         WARN_FUNC("Failed UNRET validation", insn->sec, insn->offset);
3274                         return ret;
3275                 }
3276                 warnings += ret;
3277         }
3278
3279         return warnings;
3280 }
3281
3282 static int validate_retpoline(struct objtool_file *file)
3283 {
3284         struct instruction *insn;
3285         int warnings = 0;
3286
3287         for_each_insn(file, insn) {
3288                 if (insn->type != INSN_JUMP_DYNAMIC &&
3289                     insn->type != INSN_CALL_DYNAMIC &&
3290                     insn->type != INSN_RETURN)
3291                         continue;
3292
3293                 if (insn->retpoline_safe)
3294                         continue;
3295
3296                 /*
3297                  * .init.text code is ran before userspace and thus doesn't
3298                  * strictly need retpolines, except for modules which are
3299                  * loaded late, they very much do need retpoline in their
3300                  * .init.text
3301                  */
3302                 if (!strcmp(insn->sec->name, ".init.text") && !module)
3303                         continue;
3304
3305                 if (insn->type == INSN_RETURN) {
3306                         if (rethunk) {
3307                                 WARN_FUNC("'naked' return found in RETHUNK build",
3308                                           insn->sec, insn->offset);
3309                         } else
3310                                 continue;
3311                 } else {
3312                         WARN_FUNC("indirect %s found in RETPOLINE build",
3313                                   insn->sec, insn->offset,
3314                                   insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
3315                 }
3316
3317                 warnings++;
3318         }
3319
3320         return warnings;
3321 }
3322
3323 static bool is_kasan_insn(struct instruction *insn)
3324 {
3325         return (insn->type == INSN_CALL &&
3326                 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
3327 }
3328
3329 static bool is_ubsan_insn(struct instruction *insn)
3330 {
3331         return (insn->type == INSN_CALL &&
3332                 !strcmp(insn->call_dest->name,
3333                         "__ubsan_handle_builtin_unreachable"));
3334 }
3335
3336 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
3337 {
3338         int i;
3339         struct instruction *prev_insn;
3340
3341         if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
3342                 return true;
3343
3344         /*
3345          * Ignore any unused exceptions.  This can happen when a whitelisted
3346          * function has an exception table entry.
3347          *
3348          * Also ignore alternative replacement instructions.  This can happen
3349          * when a whitelisted function uses one of the ALTERNATIVE macros.
3350          */
3351         if (!strcmp(insn->sec->name, ".fixup") ||
3352             !strcmp(insn->sec->name, ".altinstr_replacement") ||
3353             !strcmp(insn->sec->name, ".altinstr_aux"))
3354                 return true;
3355
3356         if (!insn->func)
3357                 return false;
3358
3359         /*
3360          * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
3361          * __builtin_unreachable().  The BUG() macro has an unreachable() after
3362          * the UD2, which causes GCC's undefined trap logic to emit another UD2
3363          * (or occasionally a JMP to UD2).
3364          *
3365          * It may also insert a UD2 after calling a __noreturn function.
3366          */
3367         prev_insn = list_prev_entry(insn, list);
3368         if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) &&
3369             (insn->type == INSN_BUG ||
3370              (insn->type == INSN_JUMP_UNCONDITIONAL &&
3371               insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
3372                 return true;
3373
3374         /*
3375          * Check if this (or a subsequent) instruction is related to
3376          * CONFIG_UBSAN or CONFIG_KASAN.
3377          *
3378          * End the search at 5 instructions to avoid going into the weeds.
3379          */
3380         for (i = 0; i < 5; i++) {
3381
3382                 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
3383                         return true;
3384
3385                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
3386                         if (insn->jump_dest &&
3387                             insn->jump_dest->func == insn->func) {
3388                                 insn = insn->jump_dest;
3389                                 continue;
3390                         }
3391
3392                         break;
3393                 }
3394
3395                 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
3396                         break;
3397
3398                 insn = list_next_entry(insn, list);
3399         }
3400
3401         return false;
3402 }
3403
3404 static int validate_symbol(struct objtool_file *file, struct section *sec,
3405                            struct symbol *sym, struct insn_state *state)
3406 {
3407         struct instruction *insn;
3408         int ret;
3409
3410         if (!sym->len) {
3411                 WARN("%s() is missing an ELF size annotation", sym->name);
3412                 return 1;
3413         }
3414
3415         if (sym->pfunc != sym || sym->alias != sym)
3416                 return 0;
3417
3418         insn = find_insn(file, sec, sym->offset);
3419         if (!insn || insn->ignore || insn->visited)
3420                 return 0;
3421
3422         state->uaccess = sym->uaccess_safe;
3423
3424         ret = validate_branch(file, insn->func, insn, *state);
3425         if (ret && backtrace)
3426                 BT_FUNC("<=== (sym)", insn);
3427         return ret;
3428 }
3429
3430 static int validate_section(struct objtool_file *file, struct section *sec)
3431 {
3432         struct insn_state state;
3433         struct symbol *func;
3434         int warnings = 0;
3435
3436         list_for_each_entry(func, &sec->symbol_list, list) {
3437                 if (func->type != STT_FUNC)
3438                         continue;
3439
3440                 init_insn_state(&state, sec);
3441                 set_func_state(&state.cfi);
3442
3443                 warnings += validate_symbol(file, sec, func, &state);
3444         }
3445
3446         return warnings;
3447 }
3448
3449 static int validate_vmlinux_functions(struct objtool_file *file)
3450 {
3451         struct section *sec;
3452         int warnings = 0;
3453
3454         sec = find_section_by_name(file->elf, ".noinstr.text");
3455         if (sec) {
3456                 warnings += validate_section(file, sec);
3457                 warnings += validate_unwind_hints(file, sec);
3458         }
3459
3460         sec = find_section_by_name(file->elf, ".entry.text");
3461         if (sec) {
3462                 warnings += validate_section(file, sec);
3463                 warnings += validate_unwind_hints(file, sec);
3464         }
3465
3466         return warnings;
3467 }
3468
3469 static int validate_functions(struct objtool_file *file)
3470 {
3471         struct section *sec;
3472         int warnings = 0;
3473
3474         for_each_sec(file, sec) {
3475                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
3476                         continue;
3477
3478                 warnings += validate_section(file, sec);
3479         }
3480
3481         return warnings;
3482 }
3483
3484 static int validate_reachable_instructions(struct objtool_file *file)
3485 {
3486         struct instruction *insn;
3487
3488         if (file->ignore_unreachables)
3489                 return 0;
3490
3491         for_each_insn(file, insn) {
3492                 if (insn->visited || ignore_unreachable_insn(file, insn))
3493                         continue;
3494
3495                 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
3496                 return 1;
3497         }
3498
3499         return 0;
3500 }
3501
3502 int check(struct objtool_file *file)
3503 {
3504         int ret, warnings = 0;
3505
3506         arch_initial_func_cfi_state(&initial_func_cfi);
3507         init_cfi_state(&init_cfi);
3508         init_cfi_state(&func_cfi);
3509         set_func_state(&func_cfi);
3510
3511         if (!cfi_hash_alloc())
3512                 goto out;
3513
3514         cfi_hash_add(&init_cfi);
3515         cfi_hash_add(&func_cfi);
3516
3517         ret = decode_sections(file);
3518         if (ret < 0)
3519                 goto out;
3520
3521         warnings += ret;
3522
3523         if (list_empty(&file->insn_list))
3524                 goto out;
3525
3526         if (vmlinux && !validate_dup) {
3527                 ret = validate_vmlinux_functions(file);
3528                 if (ret < 0)
3529                         goto out;
3530
3531                 warnings += ret;
3532                 goto out;
3533         }
3534
3535         if (retpoline) {
3536                 ret = validate_retpoline(file);
3537                 if (ret < 0)
3538                         return ret;
3539                 warnings += ret;
3540         }
3541
3542         ret = validate_functions(file);
3543         if (ret < 0)
3544                 goto out;
3545         warnings += ret;
3546
3547         ret = validate_unwind_hints(file, NULL);
3548         if (ret < 0)
3549                 goto out;
3550         warnings += ret;
3551
3552         if (unret) {
3553                 /*
3554                  * Must be after validate_branch() and friends, it plays
3555                  * further games with insn->visited.
3556                  */
3557                 ret = validate_unret(file);
3558                 if (ret < 0)
3559                         return ret;
3560                 warnings += ret;
3561         }
3562
3563         if (!warnings) {
3564                 ret = validate_reachable_instructions(file);
3565                 if (ret < 0)
3566                         goto out;
3567                 warnings += ret;
3568         }
3569
3570         ret = create_static_call_sections(file);
3571         if (ret < 0)
3572                 goto out;
3573         warnings += ret;
3574
3575         if (retpoline) {
3576                 ret = create_retpoline_sites_sections(file);
3577                 if (ret < 0)
3578                         goto out;
3579                 warnings += ret;
3580         }
3581
3582         if (rethunk) {
3583                 ret = create_return_sites_sections(file);
3584                 if (ret < 0)
3585                         goto out;
3586                 warnings += ret;
3587         }
3588
3589         if (stats) {
3590                 printf("nr_insns_visited: %ld\n", nr_insns_visited);
3591                 printf("nr_cfi: %ld\n", nr_cfi);
3592                 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
3593                 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
3594         }
3595
3596 out:
3597         /*
3598          *  For now, don't fail the kernel build on fatal warnings.  These
3599          *  errors are still fairly common due to the growing matrix of
3600          *  supported toolchains and their recent pace of change.
3601          */
3602         return 0;
3603 }