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 <objtool/builtin.h>
  12 #include <objtool/cfi.h>
  13 #include <objtool/arch.h>
  14 #include <objtool/check.h>
  15 #include <objtool/special.h>
  16 #include <objtool/warn.h>
  17 #include <objtool/endianness.h>
  18
  19 #include <linux/objtool_types.h>
  20 #include <linux/hashtable.h>
  21 #include <linux/kernel.h>
  22 #include <linux/static_call_types.h>
  23
  24 struct alternative {
  25         struct alternative *next;
  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 static struct cfi_state force_undefined_cfi;
  36
  37 struct instruction *find_insn(struct objtool_file *file,
  38                               struct section *sec, unsigned long offset)
  39 {
  40         struct instruction *insn;
  41
  42         hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
  43                 if (insn->sec == sec && insn->offset == offset)
  44                         return insn;
  45         }
  46
  47         return NULL;
  48 }
  49
  50 struct instruction *next_insn_same_sec(struct objtool_file *file,
  51                                        struct instruction *insn)
  52 {
  53         if (insn->idx == INSN_CHUNK_MAX)
  54                 return find_insn(file, insn->sec, insn->offset + insn->len);
  55
  56         insn++;
  57         if (!insn->len)
  58                 return NULL;
  59
  60         return insn;
  61 }
  62
  63 static struct instruction *next_insn_same_func(struct objtool_file *file,
  64                                                struct instruction *insn)
  65 {
  66         struct instruction *next = next_insn_same_sec(file, insn);
  67         struct symbol *func = insn_func(insn);
  68
  69         if (!func)
  70                 return NULL;
  71
  72         if (next && insn_func(next) == func)
  73                 return next;
  74
  75         /* Check if we're already in the subfunction: */
  76         if (func == func->cfunc)
  77                 return NULL;
  78
  79         /* Move to the subfunction: */
  80         return find_insn(file, func->cfunc->sec, func->cfunc->offset);
  81 }
  82
  83 static struct instruction *prev_insn_same_sec(struct objtool_file *file,
  84                                               struct instruction *insn)
  85 {
  86         if (insn->idx == 0) {
  87                 if (insn->prev_len)
  88                         return find_insn(file, insn->sec, insn->offset - insn->prev_len);
  89                 return NULL;
  90         }
  91
  92         return insn - 1;
  93 }
  94
  95 static struct instruction *prev_insn_same_sym(struct objtool_file *file,
  96                                               struct instruction *insn)
  97 {
  98         struct instruction *prev = prev_insn_same_sec(file, insn);
  99
 100         if (prev && insn_func(prev) == insn_func(insn))
 101                 return prev;
 102
 103         return NULL;
 104 }
 105
 106 #define for_each_insn(file, insn)                                       \
 107         for (struct section *__sec, *__fake = (struct section *)1;      \
 108              __fake; __fake = NULL)                                     \
 109                 for_each_sec(file, __sec)                               \
 110                         sec_for_each_insn(file, __sec, insn)
 111
 112 #define func_for_each_insn(file, func, insn)                            \
 113         for (insn = find_insn(file, func->sec, func->offset);           \
 114              insn;                                                      \
 115              insn = next_insn_same_func(file, insn))
 116
 117 #define sym_for_each_insn(file, sym, insn)                              \
 118         for (insn = find_insn(file, sym->sec, sym->offset);             \
 119              insn && insn->offset < sym->offset + sym->len;             \
 120              insn = next_insn_same_sec(file, insn))
 121
 122 #define sym_for_each_insn_continue_reverse(file, sym, insn)             \
 123         for (insn = prev_insn_same_sec(file, insn);                     \
 124              insn && insn->offset >= sym->offset;                       \
 125              insn = prev_insn_same_sec(file, insn))
 126
 127 #define sec_for_each_insn_from(file, insn)                              \
 128         for (; insn; insn = next_insn_same_sec(file, insn))
 129
 130 #define sec_for_each_insn_continue(file, insn)                          \
 131         for (insn = next_insn_same_sec(file, insn); insn;               \
 132              insn = next_insn_same_sec(file, insn))
 133
 134 static inline struct symbol *insn_call_dest(struct instruction *insn)
 135 {
 136         if (insn->type == INSN_JUMP_DYNAMIC ||
 137             insn->type == INSN_CALL_DYNAMIC)
 138                 return NULL;
 139
 140         return insn->_call_dest;
 141 }
 142
 143 static inline struct reloc *insn_jump_table(struct instruction *insn)
 144 {
 145         if (insn->type == INSN_JUMP_DYNAMIC ||
 146             insn->type == INSN_CALL_DYNAMIC)
 147                 return insn->_jump_table;
 148
 149         return NULL;
 150 }
 151
 152 static bool is_jump_table_jump(struct instruction *insn)
 153 {
 154         struct alt_group *alt_group = insn->alt_group;
 155
 156         if (insn_jump_table(insn))
 157                 return true;
 158
 159         /* Retpoline alternative for a jump table? */
 160         return alt_group && alt_group->orig_group &&
 161                insn_jump_table(alt_group->orig_group->first_insn);
 162 }
 163
 164 static bool is_sibling_call(struct instruction *insn)
 165 {
 166         /*
 167          * Assume only STT_FUNC calls have jump-tables.
 168          */
 169         if (insn_func(insn)) {
 170                 /* An indirect jump is either a sibling call or a jump to a table. */
 171                 if (insn->type == INSN_JUMP_DYNAMIC)
 172                         return !is_jump_table_jump(insn);
 173         }
 174
 175         /* add_jump_destinations() sets insn_call_dest(insn) for sibling calls. */
 176         return (is_static_jump(insn) && insn_call_dest(insn));
 177 }
 178
 179 /*
 180  * This checks to see if the given function is a "noreturn" function.
 181  *
 182  * For global functions which are outside the scope of this object file, we
 183  * have to keep a manual list of them.
 184  *
 185  * For local functions, we have to detect them manually by simply looking for
 186  * the lack of a return instruction.
 187  */
 188 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 189                                 int recursion)
 190 {
 191         int i;
 192         struct instruction *insn;
 193         bool empty = true;
 194
 195 #define NORETURN(func) __stringify(func),
 196         static const char * const global_noreturns[] = {
 197 #include "noreturns.h"
 198         };
 199 #undef NORETURN
 200
 201         if (!func)
 202                 return false;
 203
 204         if (func->bind == STB_GLOBAL || func->bind == STB_WEAK)
 205                 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
 206                         if (!strcmp(func->name, global_noreturns[i]))
 207                                 return true;
 208
 209         if (func->bind == STB_WEAK)
 210                 return false;
 211
 212         if (!func->len)
 213                 return false;
 214
 215         insn = find_insn(file, func->sec, func->offset);
 216         if (!insn || !insn_func(insn))
 217                 return false;
 218
 219         func_for_each_insn(file, func, insn) {
 220                 empty = false;
 221
 222                 if (insn->type == INSN_RETURN)
 223                         return false;
 224         }
 225
 226         if (empty)
 227                 return false;
 228
 229         /*
 230          * A function can have a sibling call instead of a return.  In that
 231          * case, the function's dead-end status depends on whether the target
 232          * of the sibling call returns.
 233          */
 234         func_for_each_insn(file, func, insn) {
 235                 if (is_sibling_call(insn)) {
 236                         struct instruction *dest = insn->jump_dest;
 237
 238                         if (!dest)
 239                                 /* sibling call to another file */
 240                                 return false;
 241
 242                         /* local sibling call */
 243                         if (recursion == 5) {
 244                                 /*
 245                                  * Infinite recursion: two functions have
 246                                  * sibling calls to each other.  This is a very
 247                                  * rare case.  It means they aren't dead ends.
 248                                  */
 249                                 return false;
 250                         }
 251
 252                         return __dead_end_function(file, insn_func(dest), recursion+1);
 253                 }
 254         }
 255
 256         return true;
 257 }
 258
 259 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
 260 {
 261         return __dead_end_function(file, func, 0);
 262 }
 263
 264 static void init_cfi_state(struct cfi_state *cfi)
 265 {
 266         int i;
 267
 268         for (i = 0; i < CFI_NUM_REGS; i++) {
 269                 cfi->regs[i].base = CFI_UNDEFINED;
 270                 cfi->vals[i].base = CFI_UNDEFINED;
 271         }
 272         cfi->cfa.base = CFI_UNDEFINED;
 273         cfi->drap_reg = CFI_UNDEFINED;
 274         cfi->drap_offset = -1;
 275 }
 276
 277 static void init_insn_state(struct objtool_file *file, struct insn_state *state,
 278                             struct section *sec)
 279 {
 280         memset(state, 0, sizeof(*state));
 281         init_cfi_state(&state->cfi);
 282
 283         /*
 284          * We need the full vmlinux for noinstr validation, otherwise we can
 285          * not correctly determine insn_call_dest(insn)->sec (external symbols
 286          * do not have a section).
 287          */
 288         if (opts.link && opts.noinstr && sec)
 289                 state->noinstr = sec->noinstr;
 290 }
 291
 292 static struct cfi_state *cfi_alloc(void)
 293 {
 294         struct cfi_state *cfi = calloc(1, sizeof(struct cfi_state));
 295         if (!cfi) {
 296                 WARN("calloc failed");
 297                 exit(1);
 298         }
 299         nr_cfi++;
 300         return cfi;
 301 }
 302
 303 static int cfi_bits;
 304 static struct hlist_head *cfi_hash;
 305
 306 static inline bool cficmp(struct cfi_state *cfi1, struct cfi_state *cfi2)
 307 {
 308         return memcmp((void *)cfi1 + sizeof(cfi1->hash),
 309                       (void *)cfi2 + sizeof(cfi2->hash),
 310                       sizeof(struct cfi_state) - sizeof(struct hlist_node));
 311 }
 312
 313 static inline u32 cfi_key(struct cfi_state *cfi)
 314 {
 315         return jhash((void *)cfi + sizeof(cfi->hash),
 316                      sizeof(*cfi) - sizeof(cfi->hash), 0);
 317 }
 318
 319 static struct cfi_state *cfi_hash_find_or_add(struct cfi_state *cfi)
 320 {
 321         struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
 322         struct cfi_state *obj;
 323
 324         hlist_for_each_entry(obj, head, hash) {
 325                 if (!cficmp(cfi, obj)) {
 326                         nr_cfi_cache++;
 327                         return obj;
 328                 }
 329         }
 330
 331         obj = cfi_alloc();
 332         *obj = *cfi;
 333         hlist_add_head(&obj->hash, head);
 334
 335         return obj;
 336 }
 337
 338 static void cfi_hash_add(struct cfi_state *cfi)
 339 {
 340         struct hlist_head *head = &cfi_hash[hash_min(cfi_key(cfi), cfi_bits)];
 341
 342         hlist_add_head(&cfi->hash, head);
 343 }
 344
 345 static void *cfi_hash_alloc(unsigned long size)
 346 {
 347         cfi_bits = max(10, ilog2(size));
 348         cfi_hash = mmap(NULL, sizeof(struct hlist_head) << cfi_bits,
 349                         PROT_READ|PROT_WRITE,
 350                         MAP_PRIVATE|MAP_ANON, -1, 0);
 351         if (cfi_hash == (void *)-1L) {
 352                 WARN("mmap fail cfi_hash");
 353                 cfi_hash = NULL;
 354         }  else if (opts.stats) {
 355                 printf("cfi_bits: %d\n", cfi_bits);
 356         }
 357
 358         return cfi_hash;
 359 }
 360
 361 static unsigned long nr_insns;
 362 static unsigned long nr_insns_visited;
 363
 364 /*
 365  * Call the arch-specific instruction decoder for all the instructions and add
 366  * them to the global instruction list.
 367  */
 368 static int decode_instructions(struct objtool_file *file)
 369 {
 370         struct section *sec;
 371         struct symbol *func;
 372         unsigned long offset;
 373         struct instruction *insn;
 374         int ret;
 375
 376         for_each_sec(file, sec) {
 377                 struct instruction *insns = NULL;
 378                 u8 prev_len = 0;
 379                 u8 idx = 0;
 380
 381                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
 382                         continue;
 383
 384                 if (strcmp(sec->name, ".altinstr_replacement") &&
 385                     strcmp(sec->name, ".altinstr_aux") &&
 386                     strncmp(sec->name, ".discard.", 9))
 387                         sec->text = true;
 388
 389                 if (!strcmp(sec->name, ".noinstr.text") ||
 390                     !strcmp(sec->name, ".entry.text") ||
 391                     !strcmp(sec->name, ".cpuidle.text") ||
 392                     !strncmp(sec->name, ".text..__x86.", 13))
 393                         sec->noinstr = true;
 394
 395                 /*
 396                  * .init.text code is ran before userspace and thus doesn't
 397                  * strictly need retpolines, except for modules which are
 398                  * loaded late, they very much do need retpoline in their
 399                  * .init.text
 400                  */
 401                 if (!strcmp(sec->name, ".init.text") && !opts.module)
 402                         sec->init = true;
 403
 404                 for (offset = 0; offset < sec->sh.sh_size; offset += insn->len) {
 405                         if (!insns || idx == INSN_CHUNK_MAX) {
 406                                 insns = calloc(sizeof(*insn), INSN_CHUNK_SIZE);
 407                                 if (!insns) {
 408                                         WARN("malloc failed");
 409                                         return -1;
 410                                 }
 411                                 idx = 0;
 412                         } else {
 413                                 idx++;
 414                         }
 415                         insn = &insns[idx];
 416                         insn->idx = idx;
 417
 418                         INIT_LIST_HEAD(&insn->call_node);
 419                         insn->sec = sec;
 420                         insn->offset = offset;
 421                         insn->prev_len = prev_len;
 422
 423                         ret = arch_decode_instruction(file, sec, offset,
 424                                                       sec->sh.sh_size - offset,
 425                                                       insn);
 426                         if (ret)
 427                                 return ret;
 428
 429                         prev_len = insn->len;
 430
 431                         /*
 432                          * By default, "ud2" is a dead end unless otherwise
 433                          * annotated, because GCC 7 inserts it for certain
 434                          * divide-by-zero cases.
 435                          */
 436                         if (insn->type == INSN_BUG)
 437                                 insn->dead_end = true;
 438
 439                         hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
 440                         nr_insns++;
 441                 }
 442
 443 //              printf("%s: last chunk used: %d\n", sec->name, (int)idx);
 444
 445                 sec_for_each_sym(sec, func) {
 446                         if (func->type != STT_NOTYPE && func->type != STT_FUNC)
 447                                 continue;
 448
 449                         if (func->offset == sec->sh.sh_size) {
 450                                 /* Heuristic: likely an "end" symbol */
 451                                 if (func->type == STT_NOTYPE)
 452                                         continue;
 453                                 WARN("%s(): STT_FUNC at end of section",
 454                                      func->name);
 455                                 return -1;
 456                         }
 457
 458                         if (func->embedded_insn || func->alias != func)
 459                                 continue;
 460
 461                         if (!find_insn(file, sec, func->offset)) {
 462                                 WARN("%s(): can't find starting instruction",
 463                                      func->name);
 464                                 return -1;
 465                         }
 466
 467                         sym_for_each_insn(file, func, insn) {
 468                                 insn->sym = func;
 469                                 if (func->type == STT_FUNC &&
 470                                     insn->type == INSN_ENDBR &&
 471                                     list_empty(&insn->call_node)) {
 472                                         if (insn->offset == func->offset) {
 473                                                 list_add_tail(&insn->call_node, &file->endbr_list);
 474                                                 file->nr_endbr++;
 475                                         } else {
 476                                                 file->nr_endbr_int++;
 477                                         }
 478                                 }
 479                         }
 480                 }
 481         }
 482
 483         if (opts.stats)
 484                 printf("nr_insns: %lu\n", nr_insns);
 485
 486         return 0;
 487 }
 488
 489 /*
 490  * Read the pv_ops[] .data table to find the static initialized values.
 491  */
 492 static int add_pv_ops(struct objtool_file *file, const char *symname)
 493 {
 494         struct symbol *sym, *func;
 495         unsigned long off, end;
 496         struct reloc *reloc;
 497         int idx;
 498
 499         sym = find_symbol_by_name(file->elf, symname);
 500         if (!sym)
 501                 return 0;
 502
 503         off = sym->offset;
 504         end = off + sym->len;
 505         for (;;) {
 506                 reloc = find_reloc_by_dest_range(file->elf, sym->sec, off, end - off);
 507                 if (!reloc)
 508                         break;
 509
 510                 func = reloc->sym;
 511                 if (func->type == STT_SECTION)
 512                         func = find_symbol_by_offset(reloc->sym->sec,
 513                                                      reloc_addend(reloc));
 514
 515                 idx = (reloc_offset(reloc) - sym->offset) / sizeof(unsigned long);
 516
 517                 objtool_pv_add(file, idx, func);
 518
 519                 off = reloc_offset(reloc) + 1;
 520                 if (off > end)
 521                         break;
 522         }
 523
 524         return 0;
 525 }
 526
 527 /*
 528  * Allocate and initialize file->pv_ops[].
 529  */
 530 static int init_pv_ops(struct objtool_file *file)
 531 {
 532         static const char *pv_ops_tables[] = {
 533                 "pv_ops",
 534                 "xen_cpu_ops",
 535                 "xen_irq_ops",
 536                 "xen_mmu_ops",
 537                 NULL,
 538         };
 539         const char *pv_ops;
 540         struct symbol *sym;
 541         int idx, nr;
 542
 543         if (!opts.noinstr)
 544                 return 0;
 545
 546         file->pv_ops = NULL;
 547
 548         sym = find_symbol_by_name(file->elf, "pv_ops");
 549         if (!sym)
 550                 return 0;
 551
 552         nr = sym->len / sizeof(unsigned long);
 553         file->pv_ops = calloc(sizeof(struct pv_state), nr);
 554         if (!file->pv_ops)
 555                 return -1;
 556
 557         for (idx = 0; idx < nr; idx++)
 558                 INIT_LIST_HEAD(&file->pv_ops[idx].targets);
 559
 560         for (idx = 0; (pv_ops = pv_ops_tables[idx]); idx++)
 561                 add_pv_ops(file, pv_ops);
 562
 563         return 0;
 564 }
 565
 566 static struct instruction *find_last_insn(struct objtool_file *file,
 567                                           struct section *sec)
 568 {
 569         struct instruction *insn = NULL;
 570         unsigned int offset;
 571         unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
 572
 573         for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
 574                 insn = find_insn(file, sec, offset);
 575
 576         return insn;
 577 }
 578
 579 /*
 580  * Mark "ud2" instructions and manually annotated dead ends.
 581  */
 582 static int add_dead_ends(struct objtool_file *file)
 583 {
 584         struct section *rsec;
 585         struct reloc *reloc;
 586         struct instruction *insn;
 587         s64 addend;
 588
 589         /*
 590          * Check for manually annotated dead ends.
 591          */
 592         rsec = find_section_by_name(file->elf, ".rela.discard.unreachable");
 593         if (!rsec)
 594                 goto reachable;
 595
 596         for_each_reloc(rsec, reloc) {
 597
 598                 if (reloc->sym->type != STT_SECTION) {
 599                         WARN("unexpected relocation symbol type in %s", rsec->name);
 600                         return -1;
 601                 }
 602
 603                 addend = reloc_addend(reloc);
 604
 605                 insn = find_insn(file, reloc->sym->sec, addend);
 606                 if (insn)
 607                         insn = prev_insn_same_sec(file, insn);
 608                 else if (addend == reloc->sym->sec->sh.sh_size) {
 609                         insn = find_last_insn(file, reloc->sym->sec);
 610                         if (!insn) {
 611                                 WARN("can't find unreachable insn at %s+0x%" PRIx64,
 612                                      reloc->sym->sec->name, addend);
 613                                 return -1;
 614                         }
 615                 } else {
 616                         WARN("can't find unreachable insn at %s+0x%" PRIx64,
 617                              reloc->sym->sec->name, addend);
 618                         return -1;
 619                 }
 620
 621                 insn->dead_end = true;
 622         }
 623
 624 reachable:
 625         /*
 626          * These manually annotated reachable checks are needed for GCC 4.4,
 627          * where the Linux unreachable() macro isn't supported.  In that case
 628          * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
 629          * not a dead end.
 630          */
 631         rsec = find_section_by_name(file->elf, ".rela.discard.reachable");
 632         if (!rsec)
 633                 return 0;
 634
 635         for_each_reloc(rsec, reloc) {
 636
 637                 if (reloc->sym->type != STT_SECTION) {
 638                         WARN("unexpected relocation symbol type in %s", rsec->name);
 639                         return -1;
 640                 }
 641
 642                 addend = reloc_addend(reloc);
 643
 644                 insn = find_insn(file, reloc->sym->sec, addend);
 645                 if (insn)
 646                         insn = prev_insn_same_sec(file, insn);
 647                 else if (addend == reloc->sym->sec->sh.sh_size) {
 648                         insn = find_last_insn(file, reloc->sym->sec);
 649                         if (!insn) {
 650                                 WARN("can't find reachable insn at %s+0x%" PRIx64,
 651                                      reloc->sym->sec->name, addend);
 652                                 return -1;
 653                         }
 654                 } else {
 655                         WARN("can't find reachable insn at %s+0x%" PRIx64,
 656                              reloc->sym->sec->name, addend);
 657                         return -1;
 658                 }
 659
 660                 insn->dead_end = false;
 661         }
 662
 663         return 0;
 664 }
 665
 666 static int create_static_call_sections(struct objtool_file *file)
 667 {
 668         struct static_call_site *site;
 669         struct section *sec;
 670         struct instruction *insn;
 671         struct symbol *key_sym;
 672         char *key_name, *tmp;
 673         int idx;
 674
 675         sec = find_section_by_name(file->elf, ".static_call_sites");
 676         if (sec) {
 677                 INIT_LIST_HEAD(&file->static_call_list);
 678                 WARN("file already has .static_call_sites section, skipping");
 679                 return 0;
 680         }
 681
 682         if (list_empty(&file->static_call_list))
 683                 return 0;
 684
 685         idx = 0;
 686         list_for_each_entry(insn, &file->static_call_list, call_node)
 687                 idx++;
 688
 689         sec = elf_create_section_pair(file->elf, ".static_call_sites",
 690                                       sizeof(*site), idx, idx * 2);
 691         if (!sec)
 692                 return -1;
 693
 694         /* Allow modules to modify the low bits of static_call_site::key */
 695         sec->sh.sh_flags |= SHF_WRITE;
 696
 697         idx = 0;
 698         list_for_each_entry(insn, &file->static_call_list, call_node) {
 699
 700                 /* populate reloc for 'addr' */
 701                 if (!elf_init_reloc_text_sym(file->elf, sec,
 702                                              idx * sizeof(*site), idx * 2,
 703                                              insn->sec, insn->offset))
 704                         return -1;
 705
 706                 /* find key symbol */
 707                 key_name = strdup(insn_call_dest(insn)->name);
 708                 if (!key_name) {
 709                         perror("strdup");
 710                         return -1;
 711                 }
 712                 if (strncmp(key_name, STATIC_CALL_TRAMP_PREFIX_STR,
 713                             STATIC_CALL_TRAMP_PREFIX_LEN)) {
 714                         WARN("static_call: trampoline name malformed: %s", key_name);
 715                         free(key_name);
 716                         return -1;
 717                 }
 718                 tmp = key_name + STATIC_CALL_TRAMP_PREFIX_LEN - STATIC_CALL_KEY_PREFIX_LEN;
 719                 memcpy(tmp, STATIC_CALL_KEY_PREFIX_STR, STATIC_CALL_KEY_PREFIX_LEN);
 720
 721                 key_sym = find_symbol_by_name(file->elf, tmp);
 722                 if (!key_sym) {
 723                         if (!opts.module) {
 724                                 WARN("static_call: can't find static_call_key symbol: %s", tmp);
 725                                 free(key_name);
 726                                 return -1;
 727                         }
 728
 729                         /*
 730                          * For modules(), the key might not be exported, which
 731                          * means the module can make static calls but isn't
 732                          * allowed to change them.
 733                          *
 734                          * In that case we temporarily set the key to be the
 735                          * trampoline address.  This is fixed up in
 736                          * static_call_add_module().
 737                          */
 738                         key_sym = insn_call_dest(insn);
 739                 }
 740                 free(key_name);
 741
 742                 /* populate reloc for 'key' */
 743                 if (!elf_init_reloc_data_sym(file->elf, sec,
 744                                              idx * sizeof(*site) + 4,
 745                                              (idx * 2) + 1, key_sym,
 746                                              is_sibling_call(insn) * STATIC_CALL_SITE_TAIL))
 747                         return -1;
 748
 749                 idx++;
 750         }
 751
 752         return 0;
 753 }
 754
 755 static int create_retpoline_sites_sections(struct objtool_file *file)
 756 {
 757         struct instruction *insn;
 758         struct section *sec;
 759         int idx;
 760
 761         sec = find_section_by_name(file->elf, ".retpoline_sites");
 762         if (sec) {
 763                 WARN("file already has .retpoline_sites, skipping");
 764                 return 0;
 765         }
 766
 767         idx = 0;
 768         list_for_each_entry(insn, &file->retpoline_call_list, call_node)
 769                 idx++;
 770
 771         if (!idx)
 772                 return 0;
 773
 774         sec = elf_create_section_pair(file->elf, ".retpoline_sites",
 775                                       sizeof(int), idx, idx);
 776         if (!sec)
 777                 return -1;
 778
 779         idx = 0;
 780         list_for_each_entry(insn, &file->retpoline_call_list, call_node) {
 781
 782                 if (!elf_init_reloc_text_sym(file->elf, sec,
 783                                              idx * sizeof(int), idx,
 784                                              insn->sec, insn->offset))
 785                         return -1;
 786
 787                 idx++;
 788         }
 789
 790         return 0;
 791 }
 792
 793 static int create_return_sites_sections(struct objtool_file *file)
 794 {
 795         struct instruction *insn;
 796         struct section *sec;
 797         int idx;
 798
 799         sec = find_section_by_name(file->elf, ".return_sites");
 800         if (sec) {
 801                 WARN("file already has .return_sites, skipping");
 802                 return 0;
 803         }
 804
 805         idx = 0;
 806         list_for_each_entry(insn, &file->return_thunk_list, call_node)
 807                 idx++;
 808
 809         if (!idx)
 810                 return 0;
 811
 812         sec = elf_create_section_pair(file->elf, ".return_sites",
 813                                       sizeof(int), idx, idx);
 814         if (!sec)
 815                 return -1;
 816
 817         idx = 0;
 818         list_for_each_entry(insn, &file->return_thunk_list, call_node) {
 819
 820                 if (!elf_init_reloc_text_sym(file->elf, sec,
 821                                              idx * sizeof(int), idx,
 822                                              insn->sec, insn->offset))
 823                         return -1;
 824
 825                 idx++;
 826         }
 827
 828         return 0;
 829 }
 830
 831 static int create_ibt_endbr_seal_sections(struct objtool_file *file)
 832 {
 833         struct instruction *insn;
 834         struct section *sec;
 835         int idx;
 836
 837         sec = find_section_by_name(file->elf, ".ibt_endbr_seal");
 838         if (sec) {
 839                 WARN("file already has .ibt_endbr_seal, skipping");
 840                 return 0;
 841         }
 842
 843         idx = 0;
 844         list_for_each_entry(insn, &file->endbr_list, call_node)
 845                 idx++;
 846
 847         if (opts.stats) {
 848                 printf("ibt: ENDBR at function start: %d\n", file->nr_endbr);
 849                 printf("ibt: ENDBR inside functions:  %d\n", file->nr_endbr_int);
 850                 printf("ibt: superfluous ENDBR:       %d\n", idx);
 851         }
 852
 853         if (!idx)
 854                 return 0;
 855
 856         sec = elf_create_section_pair(file->elf, ".ibt_endbr_seal",
 857                                       sizeof(int), idx, idx);
 858         if (!sec)
 859                 return -1;
 860
 861         idx = 0;
 862         list_for_each_entry(insn, &file->endbr_list, call_node) {
 863
 864                 int *site = (int *)sec->data->d_buf + idx;
 865                 struct symbol *sym = insn->sym;
 866                 *site = 0;
 867
 868                 if (opts.module && sym && sym->type == STT_FUNC &&
 869                     insn->offset == sym->offset &&
 870                     (!strcmp(sym->name, "init_module") ||
 871                      !strcmp(sym->name, "cleanup_module")))
 872                         WARN("%s(): not an indirect call target", sym->name);
 873
 874                 if (!elf_init_reloc_text_sym(file->elf, sec,
 875                                              idx * sizeof(int), idx,
 876                                              insn->sec, insn->offset))
 877                         return -1;
 878
 879                 idx++;
 880         }
 881
 882         return 0;
 883 }
 884
 885 static int create_cfi_sections(struct objtool_file *file)
 886 {
 887         struct section *sec;
 888         struct symbol *sym;
 889         int idx;
 890
 891         sec = find_section_by_name(file->elf, ".cfi_sites");
 892         if (sec) {
 893                 INIT_LIST_HEAD(&file->call_list);
 894                 WARN("file already has .cfi_sites section, skipping");
 895                 return 0;
 896         }
 897
 898         idx = 0;
 899         for_each_sym(file, sym) {
 900                 if (sym->type != STT_FUNC)
 901                         continue;
 902
 903                 if (strncmp(sym->name, "__cfi_", 6))
 904                         continue;
 905
 906                 idx++;
 907         }
 908
 909         sec = elf_create_section_pair(file->elf, ".cfi_sites",
 910                                       sizeof(unsigned int), idx, idx);
 911         if (!sec)
 912                 return -1;
 913
 914         idx = 0;
 915         for_each_sym(file, sym) {
 916                 if (sym->type != STT_FUNC)
 917                         continue;
 918
 919                 if (strncmp(sym->name, "__cfi_", 6))
 920                         continue;
 921
 922                 if (!elf_init_reloc_text_sym(file->elf, sec,
 923                                              idx * sizeof(unsigned int), idx,
 924                                              sym->sec, sym->offset))
 925                         return -1;
 926
 927                 idx++;
 928         }
 929
 930         return 0;
 931 }
 932
 933 static int create_mcount_loc_sections(struct objtool_file *file)
 934 {
 935         size_t addr_size = elf_addr_size(file->elf);
 936         struct instruction *insn;
 937         struct section *sec;
 938         int idx;
 939
 940         sec = find_section_by_name(file->elf, "__mcount_loc");
 941         if (sec) {
 942                 INIT_LIST_HEAD(&file->mcount_loc_list);
 943                 WARN("file already has __mcount_loc section, skipping");
 944                 return 0;
 945         }
 946
 947         if (list_empty(&file->mcount_loc_list))
 948                 return 0;
 949
 950         idx = 0;
 951         list_for_each_entry(insn, &file->mcount_loc_list, call_node)
 952                 idx++;
 953
 954         sec = elf_create_section_pair(file->elf, "__mcount_loc", addr_size,
 955                                       idx, idx);
 956         if (!sec)
 957                 return -1;
 958
 959         sec->sh.sh_addralign = addr_size;
 960
 961         idx = 0;
 962         list_for_each_entry(insn, &file->mcount_loc_list, call_node) {
 963
 964                 struct reloc *reloc;
 965
 966                 reloc = elf_init_reloc_text_sym(file->elf, sec, idx * addr_size, idx,
 967                                                insn->sec, insn->offset);
 968                 if (!reloc)
 969                         return -1;
 970
 971                 set_reloc_type(file->elf, reloc, addr_size == 8 ? R_ABS64 : R_ABS32);
 972
 973                 idx++;
 974         }
 975
 976         return 0;
 977 }
 978
 979 static int create_direct_call_sections(struct objtool_file *file)
 980 {
 981         struct instruction *insn;
 982         struct section *sec;
 983         int idx;
 984
 985         sec = find_section_by_name(file->elf, ".call_sites");
 986         if (sec) {
 987                 INIT_LIST_HEAD(&file->call_list);
 988                 WARN("file already has .call_sites section, skipping");
 989                 return 0;
 990         }
 991
 992         if (list_empty(&file->call_list))
 993                 return 0;
 994
 995         idx = 0;
 996         list_for_each_entry(insn, &file->call_list, call_node)
 997                 idx++;
 998
 999         sec = elf_create_section_pair(file->elf, ".call_sites",
1000                                       sizeof(unsigned int), idx, idx);
1001         if (!sec)
1002                 return -1;
1003
1004         idx = 0;
1005         list_for_each_entry(insn, &file->call_list, call_node) {
1006
1007                 if (!elf_init_reloc_text_sym(file->elf, sec,
1008                                              idx * sizeof(unsigned int), idx,
1009                                              insn->sec, insn->offset))
1010                         return -1;
1011
1012                 idx++;
1013         }
1014
1015         return 0;
1016 }
1017
1018 /*
1019  * Warnings shouldn't be reported for ignored functions.
1020  */
1021 static void add_ignores(struct objtool_file *file)
1022 {
1023         struct instruction *insn;
1024         struct section *rsec;
1025         struct symbol *func;
1026         struct reloc *reloc;
1027
1028         rsec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
1029         if (!rsec)
1030                 return;
1031
1032         for_each_reloc(rsec, reloc) {
1033                 switch (reloc->sym->type) {
1034                 case STT_FUNC:
1035                         func = reloc->sym;
1036                         break;
1037
1038                 case STT_SECTION:
1039                         func = find_func_by_offset(reloc->sym->sec, reloc_addend(reloc));
1040                         if (!func)
1041                                 continue;
1042                         break;
1043
1044                 default:
1045                         WARN("unexpected relocation symbol type in %s: %d",
1046                              rsec->name, reloc->sym->type);
1047                         continue;
1048                 }
1049
1050                 func_for_each_insn(file, func, insn)
1051                         insn->ignore = true;
1052         }
1053 }
1054
1055 /*
1056  * This is a whitelist of functions that is allowed to be called with AC set.
1057  * The list is meant to be minimal and only contains compiler instrumentation
1058  * ABI and a few functions used to implement *_{to,from}_user() functions.
1059  *
1060  * These functions must not directly change AC, but may PUSHF/POPF.
1061  */
1062 static const char *uaccess_safe_builtin[] = {
1063         /* KASAN */
1064         "kasan_report",
1065         "kasan_check_range",
1066         /* KASAN out-of-line */
1067         "__asan_loadN_noabort",
1068         "__asan_load1_noabort",
1069         "__asan_load2_noabort",
1070         "__asan_load4_noabort",
1071         "__asan_load8_noabort",
1072         "__asan_load16_noabort",
1073         "__asan_storeN_noabort",
1074         "__asan_store1_noabort",
1075         "__asan_store2_noabort",
1076         "__asan_store4_noabort",
1077         "__asan_store8_noabort",
1078         "__asan_store16_noabort",
1079         "__kasan_check_read",
1080         "__kasan_check_write",
1081         /* KASAN in-line */
1082         "__asan_report_load_n_noabort",
1083         "__asan_report_load1_noabort",
1084         "__asan_report_load2_noabort",
1085         "__asan_report_load4_noabort",
1086         "__asan_report_load8_noabort",
1087         "__asan_report_load16_noabort",
1088         "__asan_report_store_n_noabort",
1089         "__asan_report_store1_noabort",
1090         "__asan_report_store2_noabort",
1091         "__asan_report_store4_noabort",
1092         "__asan_report_store8_noabort",
1093         "__asan_report_store16_noabort",
1094         /* KCSAN */
1095         "__kcsan_check_access",
1096         "__kcsan_mb",
1097         "__kcsan_wmb",
1098         "__kcsan_rmb",
1099         "__kcsan_release",
1100         "kcsan_found_watchpoint",
1101         "kcsan_setup_watchpoint",
1102         "kcsan_check_scoped_accesses",
1103         "kcsan_disable_current",
1104         "kcsan_enable_current_nowarn",
1105         /* KCSAN/TSAN */
1106         "__tsan_func_entry",
1107         "__tsan_func_exit",
1108         "__tsan_read_range",
1109         "__tsan_write_range",
1110         "__tsan_read1",
1111         "__tsan_read2",
1112         "__tsan_read4",
1113         "__tsan_read8",
1114         "__tsan_read16",
1115         "__tsan_write1",
1116         "__tsan_write2",
1117         "__tsan_write4",
1118         "__tsan_write8",
1119         "__tsan_write16",
1120         "__tsan_read_write1",
1121         "__tsan_read_write2",
1122         "__tsan_read_write4",
1123         "__tsan_read_write8",
1124         "__tsan_read_write16",
1125         "__tsan_volatile_read1",
1126         "__tsan_volatile_read2",
1127         "__tsan_volatile_read4",
1128         "__tsan_volatile_read8",
1129         "__tsan_volatile_read16",
1130         "__tsan_volatile_write1",
1131         "__tsan_volatile_write2",
1132         "__tsan_volatile_write4",
1133         "__tsan_volatile_write8",
1134         "__tsan_volatile_write16",
1135         "__tsan_atomic8_load",
1136         "__tsan_atomic16_load",
1137         "__tsan_atomic32_load",
1138         "__tsan_atomic64_load",
1139         "__tsan_atomic8_store",
1140         "__tsan_atomic16_store",
1141         "__tsan_atomic32_store",
1142         "__tsan_atomic64_store",
1143         "__tsan_atomic8_exchange",
1144         "__tsan_atomic16_exchange",
1145         "__tsan_atomic32_exchange",
1146         "__tsan_atomic64_exchange",
1147         "__tsan_atomic8_fetch_add",
1148         "__tsan_atomic16_fetch_add",
1149         "__tsan_atomic32_fetch_add",
1150         "__tsan_atomic64_fetch_add",
1151         "__tsan_atomic8_fetch_sub",
1152         "__tsan_atomic16_fetch_sub",
1153         "__tsan_atomic32_fetch_sub",
1154         "__tsan_atomic64_fetch_sub",
1155         "__tsan_atomic8_fetch_and",
1156         "__tsan_atomic16_fetch_and",
1157         "__tsan_atomic32_fetch_and",
1158         "__tsan_atomic64_fetch_and",
1159         "__tsan_atomic8_fetch_or",
1160         "__tsan_atomic16_fetch_or",
1161         "__tsan_atomic32_fetch_or",
1162         "__tsan_atomic64_fetch_or",
1163         "__tsan_atomic8_fetch_xor",
1164         "__tsan_atomic16_fetch_xor",
1165         "__tsan_atomic32_fetch_xor",
1166         "__tsan_atomic64_fetch_xor",
1167         "__tsan_atomic8_fetch_nand",
1168         "__tsan_atomic16_fetch_nand",
1169         "__tsan_atomic32_fetch_nand",
1170         "__tsan_atomic64_fetch_nand",
1171         "__tsan_atomic8_compare_exchange_strong",
1172         "__tsan_atomic16_compare_exchange_strong",
1173         "__tsan_atomic32_compare_exchange_strong",
1174         "__tsan_atomic64_compare_exchange_strong",
1175         "__tsan_atomic8_compare_exchange_weak",
1176         "__tsan_atomic16_compare_exchange_weak",
1177         "__tsan_atomic32_compare_exchange_weak",
1178         "__tsan_atomic64_compare_exchange_weak",
1179         "__tsan_atomic8_compare_exchange_val",
1180         "__tsan_atomic16_compare_exchange_val",
1181         "__tsan_atomic32_compare_exchange_val",
1182         "__tsan_atomic64_compare_exchange_val",
1183         "__tsan_atomic_thread_fence",
1184         "__tsan_atomic_signal_fence",
1185         "__tsan_unaligned_read16",
1186         "__tsan_unaligned_write16",
1187         /* KCOV */
1188         "write_comp_data",
1189         "check_kcov_mode",
1190         "__sanitizer_cov_trace_pc",
1191         "__sanitizer_cov_trace_const_cmp1",
1192         "__sanitizer_cov_trace_const_cmp2",
1193         "__sanitizer_cov_trace_const_cmp4",
1194         "__sanitizer_cov_trace_const_cmp8",
1195         "__sanitizer_cov_trace_cmp1",
1196         "__sanitizer_cov_trace_cmp2",
1197         "__sanitizer_cov_trace_cmp4",
1198         "__sanitizer_cov_trace_cmp8",
1199         "__sanitizer_cov_trace_switch",
1200         /* KMSAN */
1201         "kmsan_copy_to_user",
1202         "kmsan_report",
1203         "kmsan_unpoison_entry_regs",
1204         "kmsan_unpoison_memory",
1205         "__msan_chain_origin",
1206         "__msan_get_context_state",
1207         "__msan_instrument_asm_store",
1208         "__msan_metadata_ptr_for_load_1",
1209         "__msan_metadata_ptr_for_load_2",
1210         "__msan_metadata_ptr_for_load_4",
1211         "__msan_metadata_ptr_for_load_8",
1212         "__msan_metadata_ptr_for_load_n",
1213         "__msan_metadata_ptr_for_store_1",
1214         "__msan_metadata_ptr_for_store_2",
1215         "__msan_metadata_ptr_for_store_4",
1216         "__msan_metadata_ptr_for_store_8",
1217         "__msan_metadata_ptr_for_store_n",
1218         "__msan_poison_alloca",
1219         "__msan_warning",
1220         /* UBSAN */
1221         "ubsan_type_mismatch_common",
1222         "__ubsan_handle_type_mismatch",
1223         "__ubsan_handle_type_mismatch_v1",
1224         "__ubsan_handle_shift_out_of_bounds",
1225         "__ubsan_handle_load_invalid_value",
1226         /* STACKLEAK */
1227         "stackleak_track_stack",
1228         /* misc */
1229         "csum_partial_copy_generic",
1230         "copy_mc_fragile",
1231         "copy_mc_fragile_handle_tail",
1232         "copy_mc_enhanced_fast_string",
1233         "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
1234         "rep_stos_alternative",
1235         "rep_movs_alternative",
1236         "__copy_user_nocache",
1237         NULL
1238 };
1239
1240 static void add_uaccess_safe(struct objtool_file *file)
1241 {
1242         struct symbol *func;
1243         const char **name;
1244
1245         if (!opts.uaccess)
1246                 return;
1247
1248         for (name = uaccess_safe_builtin; *name; name++) {
1249                 func = find_symbol_by_name(file->elf, *name);
1250                 if (!func)
1251                         continue;
1252
1253                 func->uaccess_safe = true;
1254         }
1255 }
1256
1257 /*
1258  * FIXME: For now, just ignore any alternatives which add retpolines.  This is
1259  * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
1260  * But it at least allows objtool to understand the control flow *around* the
1261  * retpoline.
1262  */
1263 static int add_ignore_alternatives(struct objtool_file *file)
1264 {
1265         struct section *rsec;
1266         struct reloc *reloc;
1267         struct instruction *insn;
1268
1269         rsec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
1270         if (!rsec)
1271                 return 0;
1272
1273         for_each_reloc(rsec, reloc) {
1274                 if (reloc->sym->type != STT_SECTION) {
1275                         WARN("unexpected relocation symbol type in %s", rsec->name);
1276                         return -1;
1277                 }
1278
1279                 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
1280                 if (!insn) {
1281                         WARN("bad .discard.ignore_alts entry");
1282                         return -1;
1283                 }
1284
1285                 insn->ignore_alts = true;
1286         }
1287
1288         return 0;
1289 }
1290
1291 /*
1292  * Symbols that replace INSN_CALL_DYNAMIC, every (tail) call to such a symbol
1293  * will be added to the .retpoline_sites section.
1294  */
1295 __weak bool arch_is_retpoline(struct symbol *sym)
1296 {
1297         return false;
1298 }
1299
1300 /*
1301  * Symbols that replace INSN_RETURN, every (tail) call to such a symbol
1302  * will be added to the .return_sites section.
1303  */
1304 __weak bool arch_is_rethunk(struct symbol *sym)
1305 {
1306         return false;
1307 }
1308
1309 /*
1310  * Symbols that are embedded inside other instructions, because sometimes crazy
1311  * code exists. These are mostly ignored for validation purposes.
1312  */
1313 __weak bool arch_is_embedded_insn(struct symbol *sym)
1314 {
1315         return false;
1316 }
1317
1318 static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
1319 {
1320         struct reloc *reloc;
1321
1322         if (insn->no_reloc)
1323                 return NULL;
1324
1325         if (!file)
1326                 return NULL;
1327
1328         reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1329                                          insn->offset, insn->len);
1330         if (!reloc) {
1331                 insn->no_reloc = 1;
1332                 return NULL;
1333         }
1334
1335         return reloc;
1336 }
1337
1338 static void remove_insn_ops(struct instruction *insn)
1339 {
1340         struct stack_op *op, *next;
1341
1342         for (op = insn->stack_ops; op; op = next) {
1343                 next = op->next;
1344                 free(op);
1345         }
1346         insn->stack_ops = NULL;
1347 }
1348
1349 static void annotate_call_site(struct objtool_file *file,
1350                                struct instruction *insn, bool sibling)
1351 {
1352         struct reloc *reloc = insn_reloc(file, insn);
1353         struct symbol *sym = insn_call_dest(insn);
1354
1355         if (!sym)
1356                 sym = reloc->sym;
1357
1358         /*
1359          * Alternative replacement code is just template code which is
1360          * sometimes copied to the original instruction. For now, don't
1361          * annotate it. (In the future we might consider annotating the
1362          * original instruction if/when it ever makes sense to do so.)
1363          */
1364         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
1365                 return;
1366
1367         if (sym->static_call_tramp) {
1368                 list_add_tail(&insn->call_node, &file->static_call_list);
1369                 return;
1370         }
1371
1372         if (sym->retpoline_thunk) {
1373                 list_add_tail(&insn->call_node, &file->retpoline_call_list);
1374                 return;
1375         }
1376
1377         /*
1378          * Many compilers cannot disable KCOV or sanitizer calls with a function
1379          * attribute so they need a little help, NOP out any such calls from
1380          * noinstr text.
1381          */
1382         if (opts.hack_noinstr && insn->sec->noinstr && sym->profiling_func) {
1383                 if (reloc)
1384                         set_reloc_type(file->elf, reloc, R_NONE);
1385
1386                 elf_write_insn(file->elf, insn->sec,
1387                                insn->offset, insn->len,
1388                                sibling ? arch_ret_insn(insn->len)
1389                                        : arch_nop_insn(insn->len));
1390
1391                 insn->type = sibling ? INSN_RETURN : INSN_NOP;
1392
1393                 if (sibling) {
1394                         /*
1395                          * We've replaced the tail-call JMP insn by two new
1396                          * insn: RET; INT3, except we only have a single struct
1397                          * insn here. Mark it retpoline_safe to avoid the SLS
1398                          * warning, instead of adding another insn.
1399                          */
1400                         insn->retpoline_safe = true;
1401                 }
1402
1403                 return;
1404         }
1405
1406         if (opts.mcount && sym->fentry) {
1407                 if (sibling)
1408                         WARN_INSN(insn, "tail call to __fentry__ !?!?");
1409                 if (opts.mnop) {
1410                         if (reloc)
1411                                 set_reloc_type(file->elf, reloc, R_NONE);
1412
1413                         elf_write_insn(file->elf, insn->sec,
1414                                        insn->offset, insn->len,
1415                                        arch_nop_insn(insn->len));
1416
1417                         insn->type = INSN_NOP;
1418                 }
1419
1420                 list_add_tail(&insn->call_node, &file->mcount_loc_list);
1421                 return;
1422         }
1423
1424         if (insn->type == INSN_CALL && !insn->sec->init)
1425                 list_add_tail(&insn->call_node, &file->call_list);
1426
1427         if (!sibling && dead_end_function(file, sym))
1428                 insn->dead_end = true;
1429 }
1430
1431 static void add_call_dest(struct objtool_file *file, struct instruction *insn,
1432                           struct symbol *dest, bool sibling)
1433 {
1434         insn->_call_dest = dest;
1435         if (!dest)
1436                 return;
1437
1438         /*
1439          * Whatever stack impact regular CALLs have, should be undone
1440          * by the RETURN of the called function.
1441          *
1442          * Annotated intra-function calls retain the stack_ops but
1443          * are converted to JUMP, see read_intra_function_calls().
1444          */
1445         remove_insn_ops(insn);
1446
1447         annotate_call_site(file, insn, sibling);
1448 }
1449
1450 static void add_retpoline_call(struct objtool_file *file, struct instruction *insn)
1451 {
1452         /*
1453          * Retpoline calls/jumps are really dynamic calls/jumps in disguise,
1454          * so convert them accordingly.
1455          */
1456         switch (insn->type) {
1457         case INSN_CALL:
1458                 insn->type = INSN_CALL_DYNAMIC;
1459                 break;
1460         case INSN_JUMP_UNCONDITIONAL:
1461                 insn->type = INSN_JUMP_DYNAMIC;
1462                 break;
1463         case INSN_JUMP_CONDITIONAL:
1464                 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
1465                 break;
1466         default:
1467                 return;
1468         }
1469
1470         insn->retpoline_safe = true;
1471
1472         /*
1473          * Whatever stack impact regular CALLs have, should be undone
1474          * by the RETURN of the called function.
1475          *
1476          * Annotated intra-function calls retain the stack_ops but
1477          * are converted to JUMP, see read_intra_function_calls().
1478          */
1479         remove_insn_ops(insn);
1480
1481         annotate_call_site(file, insn, false);
1482 }
1483
1484 static void add_return_call(struct objtool_file *file, struct instruction *insn, bool add)
1485 {
1486         /*
1487          * Return thunk tail calls are really just returns in disguise,
1488          * so convert them accordingly.
1489          */
1490         insn->type = INSN_RETURN;
1491         insn->retpoline_safe = true;
1492
1493         if (add)
1494                 list_add_tail(&insn->call_node, &file->return_thunk_list);
1495 }
1496
1497 static bool is_first_func_insn(struct objtool_file *file,
1498                                struct instruction *insn, struct symbol *sym)
1499 {
1500         if (insn->offset == sym->offset)
1501                 return true;
1502
1503         /* Allow direct CALL/JMP past ENDBR */
1504         if (opts.ibt) {
1505                 struct instruction *prev = prev_insn_same_sym(file, insn);
1506
1507                 if (prev && prev->type == INSN_ENDBR &&
1508                     insn->offset == sym->offset + prev->len)
1509                         return true;
1510         }
1511
1512         return false;
1513 }
1514
1515 /*
1516  * A sibling call is a tail-call to another symbol -- to differentiate from a
1517  * recursive tail-call which is to the same symbol.
1518  */
1519 static bool jump_is_sibling_call(struct objtool_file *file,
1520                                  struct instruction *from, struct instruction *to)
1521 {
1522         struct symbol *fs = from->sym;
1523         struct symbol *ts = to->sym;
1524
1525         /* Not a sibling call if from/to a symbol hole */
1526         if (!fs || !ts)
1527                 return false;
1528
1529         /* Not a sibling call if not targeting the start of a symbol. */
1530         if (!is_first_func_insn(file, to, ts))
1531                 return false;
1532
1533         /* Disallow sibling calls into STT_NOTYPE */
1534         if (ts->type == STT_NOTYPE)
1535                 return false;
1536
1537         /* Must not be self to be a sibling */
1538         return fs->pfunc != ts->pfunc;
1539 }
1540
1541 /*
1542  * Find the destination instructions for all jumps.
1543  */
1544 static int add_jump_destinations(struct objtool_file *file)
1545 {
1546         struct instruction *insn, *jump_dest;
1547         struct reloc *reloc;
1548         struct section *dest_sec;
1549         unsigned long dest_off;
1550
1551         for_each_insn(file, insn) {
1552                 if (insn->jump_dest) {
1553                         /*
1554                          * handle_group_alt() may have previously set
1555                          * 'jump_dest' for some alternatives.
1556                          */
1557                         continue;
1558                 }
1559                 if (!is_static_jump(insn))
1560                         continue;
1561
1562                 reloc = insn_reloc(file, insn);
1563                 if (!reloc) {
1564                         dest_sec = insn->sec;
1565                         dest_off = arch_jump_destination(insn);
1566                 } else if (reloc->sym->type == STT_SECTION) {
1567                         dest_sec = reloc->sym->sec;
1568                         dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
1569                 } else if (reloc->sym->retpoline_thunk) {
1570                         add_retpoline_call(file, insn);
1571                         continue;
1572                 } else if (reloc->sym->return_thunk) {
1573                         add_return_call(file, insn, true);
1574                         continue;
1575                 } else if (insn_func(insn)) {
1576                         /*
1577                          * External sibling call or internal sibling call with
1578                          * STT_FUNC reloc.
1579                          */
1580                         add_call_dest(file, insn, reloc->sym, true);
1581                         continue;
1582                 } else if (reloc->sym->sec->idx) {
1583                         dest_sec = reloc->sym->sec;
1584                         dest_off = reloc->sym->sym.st_value +
1585                                    arch_dest_reloc_offset(reloc_addend(reloc));
1586                 } else {
1587                         /* non-func asm code jumping to another file */
1588                         continue;
1589                 }
1590
1591                 jump_dest = find_insn(file, dest_sec, dest_off);
1592                 if (!jump_dest) {
1593                         struct symbol *sym = find_symbol_by_offset(dest_sec, dest_off);
1594
1595                         /*
1596                          * This is a special case for retbleed_untrain_ret().
1597                          * It jumps to __x86_return_thunk(), but objtool
1598                          * can't find the thunk's starting RET
1599                          * instruction, because the RET is also in the
1600                          * middle of another instruction.  Objtool only
1601                          * knows about the outer instruction.
1602                          */
1603                         if (sym && sym->embedded_insn) {
1604                                 add_return_call(file, insn, false);
1605                                 continue;
1606                         }
1607
1608                         WARN_INSN(insn, "can't find jump dest instruction at %s+0x%lx",
1609                                   dest_sec->name, dest_off);
1610                         return -1;
1611                 }
1612
1613                 /*
1614                  * An intra-TU jump in retpoline.o might not have a relocation
1615                  * for its jump dest, in which case the above
1616                  * add_{retpoline,return}_call() didn't happen.
1617                  */
1618                 if (jump_dest->sym && jump_dest->offset == jump_dest->sym->offset) {
1619                         if (jump_dest->sym->retpoline_thunk) {
1620                                 add_retpoline_call(file, insn);
1621                                 continue;
1622                         }
1623                         if (jump_dest->sym->return_thunk) {
1624                                 add_return_call(file, insn, true);
1625                                 continue;
1626                         }
1627                 }
1628
1629                 /*
1630                  * Cross-function jump.
1631                  */
1632                 if (insn_func(insn) && insn_func(jump_dest) &&
1633                     insn_func(insn) != insn_func(jump_dest)) {
1634
1635                         /*
1636                          * For GCC 8+, create parent/child links for any cold
1637                          * subfunctions.  This is _mostly_ redundant with a
1638                          * similar initialization in read_symbols().
1639                          *
1640                          * If a function has aliases, we want the *first* such
1641                          * function in the symbol table to be the subfunction's
1642                          * parent.  In that case we overwrite the
1643                          * initialization done in read_symbols().
1644                          *
1645                          * However this code can't completely replace the
1646                          * read_symbols() code because this doesn't detect the
1647                          * case where the parent function's only reference to a
1648                          * subfunction is through a jump table.
1649                          */
1650                         if (!strstr(insn_func(insn)->name, ".cold") &&
1651                             strstr(insn_func(jump_dest)->name, ".cold")) {
1652                                 insn_func(insn)->cfunc = insn_func(jump_dest);
1653                                 insn_func(jump_dest)->pfunc = insn_func(insn);
1654                         }
1655                 }
1656
1657                 if (jump_is_sibling_call(file, insn, jump_dest)) {
1658                         /*
1659                          * Internal sibling call without reloc or with
1660                          * STT_SECTION reloc.
1661                          */
1662                         add_call_dest(file, insn, insn_func(jump_dest), true);
1663                         continue;
1664                 }
1665
1666                 insn->jump_dest = jump_dest;
1667         }
1668
1669         return 0;
1670 }
1671
1672 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1673 {
1674         struct symbol *call_dest;
1675
1676         call_dest = find_func_by_offset(sec, offset);
1677         if (!call_dest)
1678                 call_dest = find_symbol_by_offset(sec, offset);
1679
1680         return call_dest;
1681 }
1682
1683 /*
1684  * Find the destination instructions for all calls.
1685  */
1686 static int add_call_destinations(struct objtool_file *file)
1687 {
1688         struct instruction *insn;
1689         unsigned long dest_off;
1690         struct symbol *dest;
1691         struct reloc *reloc;
1692
1693         for_each_insn(file, insn) {
1694                 if (insn->type != INSN_CALL)
1695                         continue;
1696
1697                 reloc = insn_reloc(file, insn);
1698                 if (!reloc) {
1699                         dest_off = arch_jump_destination(insn);
1700                         dest = find_call_destination(insn->sec, dest_off);
1701
1702                         add_call_dest(file, insn, dest, false);
1703
1704                         if (insn->ignore)
1705                                 continue;
1706
1707                         if (!insn_call_dest(insn)) {
1708                                 WARN_INSN(insn, "unannotated intra-function call");
1709                                 return -1;
1710                         }
1711
1712                         if (insn_func(insn) && insn_call_dest(insn)->type != STT_FUNC) {
1713                                 WARN_INSN(insn, "unsupported call to non-function");
1714                                 return -1;
1715                         }
1716
1717                 } else if (reloc->sym->type == STT_SECTION) {
1718                         dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
1719                         dest = find_call_destination(reloc->sym->sec, dest_off);
1720                         if (!dest) {
1721                                 WARN_INSN(insn, "can't find call dest symbol at %s+0x%lx",
1722                                           reloc->sym->sec->name, dest_off);
1723                                 return -1;
1724                         }
1725
1726                         add_call_dest(file, insn, dest, false);
1727
1728                 } else if (reloc->sym->retpoline_thunk) {
1729                         add_retpoline_call(file, insn);
1730
1731                 } else
1732                         add_call_dest(file, insn, reloc->sym, false);
1733         }
1734
1735         return 0;
1736 }
1737
1738 /*
1739  * The .alternatives section requires some extra special care over and above
1740  * other special sections because alternatives are patched in place.
1741  */
1742 static int handle_group_alt(struct objtool_file *file,
1743                             struct special_alt *special_alt,
1744                             struct instruction *orig_insn,
1745                             struct instruction **new_insn)
1746 {
1747         struct instruction *last_new_insn = NULL, *insn, *nop = NULL;
1748         struct alt_group *orig_alt_group, *new_alt_group;
1749         unsigned long dest_off;
1750
1751         orig_alt_group = orig_insn->alt_group;
1752         if (!orig_alt_group) {
1753                 struct instruction *last_orig_insn = NULL;
1754
1755                 orig_alt_group = malloc(sizeof(*orig_alt_group));
1756                 if (!orig_alt_group) {
1757                         WARN("malloc failed");
1758                         return -1;
1759                 }
1760                 orig_alt_group->cfi = calloc(special_alt->orig_len,
1761                                              sizeof(struct cfi_state *));
1762                 if (!orig_alt_group->cfi) {
1763                         WARN("calloc failed");
1764                         return -1;
1765                 }
1766
1767                 insn = orig_insn;
1768                 sec_for_each_insn_from(file, insn) {
1769                         if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1770                                 break;
1771
1772                         insn->alt_group = orig_alt_group;
1773                         last_orig_insn = insn;
1774                 }
1775                 orig_alt_group->orig_group = NULL;
1776                 orig_alt_group->first_insn = orig_insn;
1777                 orig_alt_group->last_insn = last_orig_insn;
1778                 orig_alt_group->nop = NULL;
1779         } else {
1780                 if (orig_alt_group->last_insn->offset + orig_alt_group->last_insn->len -
1781                     orig_alt_group->first_insn->offset != special_alt->orig_len) {
1782                         WARN_INSN(orig_insn, "weirdly overlapping alternative! %ld != %d",
1783                                   orig_alt_group->last_insn->offset +
1784                                   orig_alt_group->last_insn->len -
1785                                   orig_alt_group->first_insn->offset,
1786                                   special_alt->orig_len);
1787                         return -1;
1788                 }
1789         }
1790
1791         new_alt_group = malloc(sizeof(*new_alt_group));
1792         if (!new_alt_group) {
1793                 WARN("malloc failed");
1794                 return -1;
1795         }
1796
1797         if (special_alt->new_len < special_alt->orig_len) {
1798                 /*
1799                  * Insert a fake nop at the end to make the replacement
1800                  * alt_group the same size as the original.  This is needed to
1801                  * allow propagate_alt_cfi() to do its magic.  When the last
1802                  * instruction affects the stack, the instruction after it (the
1803                  * nop) will propagate the new state to the shared CFI array.
1804                  */
1805                 nop = malloc(sizeof(*nop));
1806                 if (!nop) {
1807                         WARN("malloc failed");
1808                         return -1;
1809                 }
1810                 memset(nop, 0, sizeof(*nop));
1811
1812                 nop->sec = special_alt->new_sec;
1813                 nop->offset = special_alt->new_off + special_alt->new_len;
1814                 nop->len = special_alt->orig_len - special_alt->new_len;
1815                 nop->type = INSN_NOP;
1816                 nop->sym = orig_insn->sym;
1817                 nop->alt_group = new_alt_group;
1818                 nop->ignore = orig_insn->ignore_alts;
1819         }
1820
1821         if (!special_alt->new_len) {
1822                 *new_insn = nop;
1823                 goto end;
1824         }
1825
1826         insn = *new_insn;
1827         sec_for_each_insn_from(file, insn) {
1828                 struct reloc *alt_reloc;
1829
1830                 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1831                         break;
1832
1833                 last_new_insn = insn;
1834
1835                 insn->ignore = orig_insn->ignore_alts;
1836                 insn->sym = orig_insn->sym;
1837                 insn->alt_group = new_alt_group;
1838
1839                 /*
1840                  * Since alternative replacement code is copy/pasted by the
1841                  * kernel after applying relocations, generally such code can't
1842                  * have relative-address relocation references to outside the
1843                  * .altinstr_replacement section, unless the arch's
1844                  * alternatives code can adjust the relative offsets
1845                  * accordingly.
1846                  */
1847                 alt_reloc = insn_reloc(file, insn);
1848                 if (alt_reloc && arch_pc_relative_reloc(alt_reloc) &&
1849                     !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1850
1851                         WARN_INSN(insn, "unsupported relocation in alternatives section");
1852                         return -1;
1853                 }
1854
1855                 if (!is_static_jump(insn))
1856                         continue;
1857
1858                 if (!insn->immediate)
1859                         continue;
1860
1861                 dest_off = arch_jump_destination(insn);
1862                 if (dest_off == special_alt->new_off + special_alt->new_len) {
1863                         insn->jump_dest = next_insn_same_sec(file, orig_alt_group->last_insn);
1864                         if (!insn->jump_dest) {
1865                                 WARN_INSN(insn, "can't find alternative jump destination");
1866                                 return -1;
1867                         }
1868                 }
1869         }
1870
1871         if (!last_new_insn) {
1872                 WARN_FUNC("can't find last new alternative instruction",
1873                           special_alt->new_sec, special_alt->new_off);
1874                 return -1;
1875         }
1876
1877 end:
1878         new_alt_group->orig_group = orig_alt_group;
1879         new_alt_group->first_insn = *new_insn;
1880         new_alt_group->last_insn = last_new_insn;
1881         new_alt_group->nop = nop;
1882         new_alt_group->cfi = orig_alt_group->cfi;
1883         return 0;
1884 }
1885
1886 /*
1887  * A jump table entry can either convert a nop to a jump or a jump to a nop.
1888  * If the original instruction is a jump, make the alt entry an effective nop
1889  * by just skipping the original instruction.
1890  */
1891 static int handle_jump_alt(struct objtool_file *file,
1892                            struct special_alt *special_alt,
1893                            struct instruction *orig_insn,
1894                            struct instruction **new_insn)
1895 {
1896         if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1897             orig_insn->type != INSN_NOP) {
1898
1899                 WARN_INSN(orig_insn, "unsupported instruction at jump label");
1900                 return -1;
1901         }
1902
1903         if (opts.hack_jump_label && special_alt->key_addend & 2) {
1904                 struct reloc *reloc = insn_reloc(file, orig_insn);
1905
1906                 if (reloc)
1907                         set_reloc_type(file->elf, reloc, R_NONE);
1908                 elf_write_insn(file->elf, orig_insn->sec,
1909                                orig_insn->offset, orig_insn->len,
1910                                arch_nop_insn(orig_insn->len));
1911                 orig_insn->type = INSN_NOP;
1912         }
1913
1914         if (orig_insn->type == INSN_NOP) {
1915                 if (orig_insn->len == 2)
1916                         file->jl_nop_short++;
1917                 else
1918                         file->jl_nop_long++;
1919
1920                 return 0;
1921         }
1922
1923         if (orig_insn->len == 2)
1924                 file->jl_short++;
1925         else
1926                 file->jl_long++;
1927
1928         *new_insn = next_insn_same_sec(file, orig_insn);
1929         return 0;
1930 }
1931
1932 /*
1933  * Read all the special sections which have alternate instructions which can be
1934  * patched in or redirected to at runtime.  Each instruction having alternate
1935  * instruction(s) has them added to its insn->alts list, which will be
1936  * traversed in validate_branch().
1937  */
1938 static int add_special_section_alts(struct objtool_file *file)
1939 {
1940         struct list_head special_alts;
1941         struct instruction *orig_insn, *new_insn;
1942         struct special_alt *special_alt, *tmp;
1943         struct alternative *alt;
1944         int ret;
1945
1946         ret = special_get_alts(file->elf, &special_alts);
1947         if (ret)
1948                 return ret;
1949
1950         list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1951
1952                 orig_insn = find_insn(file, special_alt->orig_sec,
1953                                       special_alt->orig_off);
1954                 if (!orig_insn) {
1955                         WARN_FUNC("special: can't find orig instruction",
1956                                   special_alt->orig_sec, special_alt->orig_off);
1957                         ret = -1;
1958                         goto out;
1959                 }
1960
1961                 new_insn = NULL;
1962                 if (!special_alt->group || special_alt->new_len) {
1963                         new_insn = find_insn(file, special_alt->new_sec,
1964                                              special_alt->new_off);
1965                         if (!new_insn) {
1966                                 WARN_FUNC("special: can't find new instruction",
1967                                           special_alt->new_sec,
1968                                           special_alt->new_off);
1969                                 ret = -1;
1970                                 goto out;
1971                         }
1972                 }
1973
1974                 if (special_alt->group) {
1975                         if (!special_alt->orig_len) {
1976                                 WARN_INSN(orig_insn, "empty alternative entry");
1977                                 continue;
1978                         }
1979
1980                         ret = handle_group_alt(file, special_alt, orig_insn,
1981                                                &new_insn);
1982                         if (ret)
1983                                 goto out;
1984                 } else if (special_alt->jump_or_nop) {
1985                         ret = handle_jump_alt(file, special_alt, orig_insn,
1986                                               &new_insn);
1987                         if (ret)
1988                                 goto out;
1989                 }
1990
1991                 alt = malloc(sizeof(*alt));
1992                 if (!alt) {
1993                         WARN("malloc failed");
1994                         ret = -1;
1995                         goto out;
1996                 }
1997
1998                 alt->insn = new_insn;
1999                 alt->skip_orig = special_alt->skip_orig;
2000                 orig_insn->ignore_alts |= special_alt->skip_alt;
2001                 alt->next = orig_insn->alts;
2002                 orig_insn->alts = alt;
2003
2004                 list_del(&special_alt->list);
2005                 free(special_alt);
2006         }
2007
2008         if (opts.stats) {
2009                 printf("jl\\\tNOP\tJMP\n");
2010                 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
2011                 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
2012         }
2013
2014 out:
2015         return ret;
2016 }
2017
2018 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
2019                           struct reloc *next_table)
2020 {
2021         struct symbol *pfunc = insn_func(insn)->pfunc;
2022         struct reloc *table = insn_jump_table(insn);
2023         struct instruction *dest_insn;
2024         unsigned int prev_offset = 0;
2025         struct reloc *reloc = table;
2026         struct alternative *alt;
2027
2028         /*
2029          * Each @reloc is a switch table relocation which points to the target
2030          * instruction.
2031          */
2032         for_each_reloc_from(table->sec, reloc) {
2033
2034                 /* Check for the end of the table: */
2035                 if (reloc != table && reloc == next_table)
2036                         break;
2037
2038                 /* Make sure the table entries are consecutive: */
2039                 if (prev_offset && reloc_offset(reloc) != prev_offset + 8)
2040                         break;
2041
2042                 /* Detect function pointers from contiguous objects: */
2043                 if (reloc->sym->sec == pfunc->sec &&
2044                     reloc_addend(reloc) == pfunc->offset)
2045                         break;
2046
2047                 dest_insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2048                 if (!dest_insn)
2049                         break;
2050
2051                 /* Make sure the destination is in the same function: */
2052                 if (!insn_func(dest_insn) || insn_func(dest_insn)->pfunc != pfunc)
2053                         break;
2054
2055                 alt = malloc(sizeof(*alt));
2056                 if (!alt) {
2057                         WARN("malloc failed");
2058                         return -1;
2059                 }
2060
2061                 alt->insn = dest_insn;
2062                 alt->next = insn->alts;
2063                 insn->alts = alt;
2064                 prev_offset = reloc_offset(reloc);
2065         }
2066
2067         if (!prev_offset) {
2068                 WARN_INSN(insn, "can't find switch jump table");
2069                 return -1;
2070         }
2071
2072         return 0;
2073 }
2074
2075 /*
2076  * find_jump_table() - Given a dynamic jump, find the switch jump table
2077  * associated with it.
2078  */
2079 static struct reloc *find_jump_table(struct objtool_file *file,
2080                                       struct symbol *func,
2081                                       struct instruction *insn)
2082 {
2083         struct reloc *table_reloc;
2084         struct instruction *dest_insn, *orig_insn = insn;
2085
2086         /*
2087          * Backward search using the @first_jump_src links, these help avoid
2088          * much of the 'in between' code. Which avoids us getting confused by
2089          * it.
2090          */
2091         for (;
2092              insn && insn_func(insn) && insn_func(insn)->pfunc == func;
2093              insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
2094
2095                 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
2096                         break;
2097
2098                 /* allow small jumps within the range */
2099                 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
2100                     insn->jump_dest &&
2101                     (insn->jump_dest->offset <= insn->offset ||
2102                      insn->jump_dest->offset > orig_insn->offset))
2103                     break;
2104
2105                 table_reloc = arch_find_switch_table(file, insn);
2106                 if (!table_reloc)
2107                         continue;
2108                 dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
2109                 if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
2110                         continue;
2111
2112                 return table_reloc;
2113         }
2114
2115         return NULL;
2116 }
2117
2118 /*
2119  * First pass: Mark the head of each jump table so that in the next pass,
2120  * we know when a given jump table ends and the next one starts.
2121  */
2122 static void mark_func_jump_tables(struct objtool_file *file,
2123                                     struct symbol *func)
2124 {
2125         struct instruction *insn, *last = NULL;
2126         struct reloc *reloc;
2127
2128         func_for_each_insn(file, func, insn) {
2129                 if (!last)
2130                         last = insn;
2131
2132                 /*
2133                  * Store back-pointers for unconditional forward jumps such
2134                  * that find_jump_table() can back-track using those and
2135                  * avoid some potentially confusing code.
2136                  */
2137                 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
2138                     insn->offset > last->offset &&
2139                     insn->jump_dest->offset > insn->offset &&
2140                     !insn->jump_dest->first_jump_src) {
2141
2142                         insn->jump_dest->first_jump_src = insn;
2143                         last = insn->jump_dest;
2144                 }
2145
2146                 if (insn->type != INSN_JUMP_DYNAMIC)
2147                         continue;
2148
2149                 reloc = find_jump_table(file, func, insn);
2150                 if (reloc)
2151                         insn->_jump_table = reloc;
2152         }
2153 }
2154
2155 static int add_func_jump_tables(struct objtool_file *file,
2156                                   struct symbol *func)
2157 {
2158         struct instruction *insn, *insn_t1 = NULL, *insn_t2;
2159         int ret = 0;
2160
2161         func_for_each_insn(file, func, insn) {
2162                 if (!insn_jump_table(insn))
2163                         continue;
2164
2165                 if (!insn_t1) {
2166                         insn_t1 = insn;
2167                         continue;
2168                 }
2169
2170                 insn_t2 = insn;
2171
2172                 ret = add_jump_table(file, insn_t1, insn_jump_table(insn_t2));
2173                 if (ret)
2174                         return ret;
2175
2176                 insn_t1 = insn_t2;
2177         }
2178
2179         if (insn_t1)
2180                 ret = add_jump_table(file, insn_t1, NULL);
2181
2182         return ret;
2183 }
2184
2185 /*
2186  * For some switch statements, gcc generates a jump table in the .rodata
2187  * section which contains a list of addresses within the function to jump to.
2188  * This finds these jump tables and adds them to the insn->alts lists.
2189  */
2190 static int add_jump_table_alts(struct objtool_file *file)
2191 {
2192         struct symbol *func;
2193         int ret;
2194
2195         if (!file->rodata)
2196                 return 0;
2197
2198         for_each_sym(file, func) {
2199                 if (func->type != STT_FUNC)
2200                         continue;
2201
2202                 mark_func_jump_tables(file, func);
2203                 ret = add_func_jump_tables(file, func);
2204                 if (ret)
2205                         return ret;
2206         }
2207
2208         return 0;
2209 }
2210
2211 static void set_func_state(struct cfi_state *state)
2212 {
2213         state->cfa = initial_func_cfi.cfa;
2214         memcpy(&state->regs, &initial_func_cfi.regs,
2215                CFI_NUM_REGS * sizeof(struct cfi_reg));
2216         state->stack_size = initial_func_cfi.cfa.offset;
2217         state->type = UNWIND_HINT_TYPE_CALL;
2218 }
2219
2220 static int read_unwind_hints(struct objtool_file *file)
2221 {
2222         struct cfi_state cfi = init_cfi;
2223         struct section *sec;
2224         struct unwind_hint *hint;
2225         struct instruction *insn;
2226         struct reloc *reloc;
2227         int i;
2228
2229         sec = find_section_by_name(file->elf, ".discard.unwind_hints");
2230         if (!sec)
2231                 return 0;
2232
2233         if (!sec->rsec) {
2234                 WARN("missing .rela.discard.unwind_hints section");
2235                 return -1;
2236         }
2237
2238         if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
2239                 WARN("struct unwind_hint size mismatch");
2240                 return -1;
2241         }
2242
2243         file->hints = true;
2244
2245         for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
2246                 hint = (struct unwind_hint *)sec->data->d_buf + i;
2247
2248                 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
2249                 if (!reloc) {
2250                         WARN("can't find reloc for unwind_hints[%d]", i);
2251                         return -1;
2252                 }
2253
2254                 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2255                 if (!insn) {
2256                         WARN("can't find insn for unwind_hints[%d]", i);
2257                         return -1;
2258                 }
2259
2260                 insn->hint = true;
2261
2262                 if (hint->type == UNWIND_HINT_TYPE_UNDEFINED) {
2263                         insn->cfi = &force_undefined_cfi;
2264                         continue;
2265                 }
2266
2267                 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
2268                         insn->hint = false;
2269                         insn->save = true;
2270                         continue;
2271                 }
2272
2273                 if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
2274                         insn->restore = true;
2275                         continue;
2276                 }
2277
2278                 if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
2279                         struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
2280
2281                         if (sym && sym->bind == STB_GLOBAL) {
2282                                 if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) {
2283                                         WARN_INSN(insn, "UNWIND_HINT_IRET_REGS without ENDBR");
2284                                 }
2285                         }
2286                 }
2287
2288                 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
2289                         insn->cfi = &func_cfi;
2290                         continue;
2291                 }
2292
2293                 if (insn->cfi)
2294                         cfi = *(insn->cfi);
2295
2296                 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
2297                         WARN_INSN(insn, "unsupported unwind_hint sp base reg %d", hint->sp_reg);
2298                         return -1;
2299                 }
2300
2301                 cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
2302                 cfi.type = hint->type;
2303                 cfi.signal = hint->signal;
2304
2305                 insn->cfi = cfi_hash_find_or_add(&cfi);
2306         }
2307
2308         return 0;
2309 }
2310
2311 static int read_noendbr_hints(struct objtool_file *file)
2312 {
2313         struct instruction *insn;
2314         struct section *rsec;
2315         struct reloc *reloc;
2316
2317         rsec = find_section_by_name(file->elf, ".rela.discard.noendbr");
2318         if (!rsec)
2319                 return 0;
2320
2321         for_each_reloc(rsec, reloc) {
2322                 insn = find_insn(file, reloc->sym->sec,
2323                                  reloc->sym->offset + reloc_addend(reloc));
2324                 if (!insn) {
2325                         WARN("bad .discard.noendbr entry");
2326                         return -1;
2327                 }
2328
2329                 insn->noendbr = 1;
2330         }
2331
2332         return 0;
2333 }
2334
2335 static int read_retpoline_hints(struct objtool_file *file)
2336 {
2337         struct section *rsec;
2338         struct instruction *insn;
2339         struct reloc *reloc;
2340
2341         rsec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
2342         if (!rsec)
2343                 return 0;
2344
2345         for_each_reloc(rsec, reloc) {
2346                 if (reloc->sym->type != STT_SECTION) {
2347                         WARN("unexpected relocation symbol type in %s", rsec->name);
2348                         return -1;
2349                 }
2350
2351                 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2352                 if (!insn) {
2353                         WARN("bad .discard.retpoline_safe entry");
2354                         return -1;
2355                 }
2356
2357                 if (insn->type != INSN_JUMP_DYNAMIC &&
2358                     insn->type != INSN_CALL_DYNAMIC &&
2359                     insn->type != INSN_RETURN &&
2360                     insn->type != INSN_NOP) {
2361                         WARN_INSN(insn, "retpoline_safe hint not an indirect jump/call/ret/nop");
2362                         return -1;
2363                 }
2364
2365                 insn->retpoline_safe = true;
2366         }
2367
2368         return 0;
2369 }
2370
2371 static int read_instr_hints(struct objtool_file *file)
2372 {
2373         struct section *rsec;
2374         struct instruction *insn;
2375         struct reloc *reloc;
2376
2377         rsec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2378         if (!rsec)
2379                 return 0;
2380
2381         for_each_reloc(rsec, reloc) {
2382                 if (reloc->sym->type != STT_SECTION) {
2383                         WARN("unexpected relocation symbol type in %s", rsec->name);
2384                         return -1;
2385                 }
2386
2387                 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2388                 if (!insn) {
2389                         WARN("bad .discard.instr_end entry");
2390                         return -1;
2391                 }
2392
2393                 insn->instr--;
2394         }
2395
2396         rsec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2397         if (!rsec)
2398                 return 0;
2399
2400         for_each_reloc(rsec, reloc) {
2401                 if (reloc->sym->type != STT_SECTION) {
2402                         WARN("unexpected relocation symbol type in %s", rsec->name);
2403                         return -1;
2404                 }
2405
2406                 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2407                 if (!insn) {
2408                         WARN("bad .discard.instr_begin entry");
2409                         return -1;
2410                 }
2411
2412                 insn->instr++;
2413         }
2414
2415         return 0;
2416 }
2417
2418 static int read_validate_unret_hints(struct objtool_file *file)
2419 {
2420         struct section *rsec;
2421         struct instruction *insn;
2422         struct reloc *reloc;
2423
2424         rsec = find_section_by_name(file->elf, ".rela.discard.validate_unret");
2425         if (!rsec)
2426                 return 0;
2427
2428         for_each_reloc(rsec, reloc) {
2429                 if (reloc->sym->type != STT_SECTION) {
2430                         WARN("unexpected relocation symbol type in %s", rsec->name);
2431                         return -1;
2432                 }
2433
2434                 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2435                 if (!insn) {
2436                         WARN("bad .discard.instr_end entry");
2437                         return -1;
2438                 }
2439                 insn->unret = 1;
2440         }
2441
2442         return 0;
2443 }
2444
2445
2446 static int read_intra_function_calls(struct objtool_file *file)
2447 {
2448         struct instruction *insn;
2449         struct section *rsec;
2450         struct reloc *reloc;
2451
2452         rsec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2453         if (!rsec)
2454                 return 0;
2455
2456         for_each_reloc(rsec, reloc) {
2457                 unsigned long dest_off;
2458
2459                 if (reloc->sym->type != STT_SECTION) {
2460                         WARN("unexpected relocation symbol type in %s",
2461                              rsec->name);
2462                         return -1;
2463                 }
2464
2465                 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2466                 if (!insn) {
2467                         WARN("bad .discard.intra_function_call entry");
2468                         return -1;
2469                 }
2470
2471                 if (insn->type != INSN_CALL) {
2472                         WARN_INSN(insn, "intra_function_call not a direct call");
2473                         return -1;
2474                 }
2475
2476                 /*
2477                  * Treat intra-function CALLs as JMPs, but with a stack_op.
2478                  * See add_call_destinations(), which strips stack_ops from
2479                  * normal CALLs.
2480                  */
2481                 insn->type = INSN_JUMP_UNCONDITIONAL;
2482
2483                 dest_off = arch_jump_destination(insn);
2484                 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2485                 if (!insn->jump_dest) {
2486                         WARN_INSN(insn, "can't find call dest at %s+0x%lx",
2487                                   insn->sec->name, dest_off);
2488                         return -1;
2489                 }
2490         }
2491
2492         return 0;
2493 }
2494
2495 /*
2496  * Return true if name matches an instrumentation function, where calls to that
2497  * function from noinstr code can safely be removed, but compilers won't do so.
2498  */
2499 static bool is_profiling_func(const char *name)
2500 {
2501         /*
2502          * Many compilers cannot disable KCOV with a function attribute.
2503          */
2504         if (!strncmp(name, "__sanitizer_cov_", 16))
2505                 return true;
2506
2507         /*
2508          * Some compilers currently do not remove __tsan_func_entry/exit nor
2509          * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2510          * the __no_sanitize_thread attribute, remove them. Once the kernel's
2511          * minimum Clang version is 14.0, this can be removed.
2512          */
2513         if (!strncmp(name, "__tsan_func_", 12) ||
2514             !strcmp(name, "__tsan_atomic_signal_fence"))
2515                 return true;
2516
2517         return false;
2518 }
2519
2520 static int classify_symbols(struct objtool_file *file)
2521 {
2522         struct symbol *func;
2523
2524         for_each_sym(file, func) {
2525                 if (func->bind != STB_GLOBAL)
2526                         continue;
2527
2528                 if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2529                              strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2530                         func->static_call_tramp = true;
2531
2532                 if (arch_is_retpoline(func))
2533                         func->retpoline_thunk = true;
2534
2535                 if (arch_is_rethunk(func))
2536                         func->return_thunk = true;
2537
2538                 if (arch_is_embedded_insn(func))
2539                         func->embedded_insn = true;
2540
2541                 if (arch_ftrace_match(func->name))
2542                         func->fentry = true;
2543
2544                 if (is_profiling_func(func->name))
2545                         func->profiling_func = true;
2546         }
2547
2548         return 0;
2549 }
2550
2551 static void mark_rodata(struct objtool_file *file)
2552 {
2553         struct section *sec;
2554         bool found = false;
2555
2556         /*
2557          * Search for the following rodata sections, each of which can
2558          * potentially contain jump tables:
2559          *
2560          * - .rodata: can contain GCC switch tables
2561          * - .rodata.<func>: same, if -fdata-sections is being used
2562          * - .rodata..c_jump_table: contains C annotated jump tables
2563          *
2564          * .rodata.str1.* sections are ignored; they don't contain jump tables.
2565          */
2566         for_each_sec(file, sec) {
2567                 if (!strncmp(sec->name, ".rodata", 7) &&
2568                     !strstr(sec->name, ".str1.")) {
2569                         sec->rodata = true;
2570                         found = true;
2571                 }
2572         }
2573
2574         file->rodata = found;
2575 }
2576
2577 static int decode_sections(struct objtool_file *file)
2578 {
2579         int ret;
2580
2581         mark_rodata(file);
2582
2583         ret = init_pv_ops(file);
2584         if (ret)
2585                 return ret;
2586
2587         /*
2588          * Must be before add_{jump_call}_destination.
2589          */
2590         ret = classify_symbols(file);
2591         if (ret)
2592                 return ret;
2593
2594         ret = decode_instructions(file);
2595         if (ret)
2596                 return ret;
2597
2598         add_ignores(file);
2599         add_uaccess_safe(file);
2600
2601         ret = add_ignore_alternatives(file);
2602         if (ret)
2603                 return ret;
2604
2605         /*
2606          * Must be before read_unwind_hints() since that needs insn->noendbr.
2607          */
2608         ret = read_noendbr_hints(file);
2609         if (ret)
2610                 return ret;
2611
2612         /*
2613          * Must be before add_jump_destinations(), which depends on 'func'
2614          * being set for alternatives, to enable proper sibling call detection.
2615          */
2616         if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) {
2617                 ret = add_special_section_alts(file);
2618                 if (ret)
2619                         return ret;
2620         }
2621
2622         ret = add_jump_destinations(file);
2623         if (ret)
2624                 return ret;
2625
2626         /*
2627          * Must be before add_call_destination(); it changes INSN_CALL to
2628          * INSN_JUMP.
2629          */
2630         ret = read_intra_function_calls(file);
2631         if (ret)
2632                 return ret;
2633
2634         ret = add_call_destinations(file);
2635         if (ret)
2636                 return ret;
2637
2638         /*
2639          * Must be after add_call_destinations() such that it can override
2640          * dead_end_function() marks.
2641          */
2642         ret = add_dead_ends(file);
2643         if (ret)
2644                 return ret;
2645
2646         ret = add_jump_table_alts(file);
2647         if (ret)
2648                 return ret;
2649
2650         ret = read_unwind_hints(file);
2651         if (ret)
2652                 return ret;
2653
2654         ret = read_retpoline_hints(file);
2655         if (ret)
2656                 return ret;
2657
2658         ret = read_instr_hints(file);
2659         if (ret)
2660                 return ret;
2661
2662         ret = read_validate_unret_hints(file);
2663         if (ret)
2664                 return ret;
2665
2666         return 0;
2667 }
2668
2669 static bool is_special_call(struct instruction *insn)
2670 {
2671         if (insn->type == INSN_CALL) {
2672                 struct symbol *dest = insn_call_dest(insn);
2673
2674                 if (!dest)
2675                         return false;
2676
2677                 if (dest->fentry || dest->embedded_insn)
2678                         return true;
2679         }
2680
2681         return false;
2682 }
2683
2684 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2685 {
2686         struct cfi_state *cfi = &state->cfi;
2687         int i;
2688
2689         if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2690                 return true;
2691
2692         if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2693                 return true;
2694
2695         if (cfi->stack_size != initial_func_cfi.cfa.offset)
2696                 return true;
2697
2698         for (i = 0; i < CFI_NUM_REGS; i++) {
2699                 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2700                     cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2701                         return true;
2702         }
2703
2704         return false;
2705 }
2706
2707 static bool check_reg_frame_pos(const struct cfi_reg *reg,
2708                                 int expected_offset)
2709 {
2710         return reg->base == CFI_CFA &&
2711                reg->offset == expected_offset;
2712 }
2713
2714 static bool has_valid_stack_frame(struct insn_state *state)
2715 {
2716         struct cfi_state *cfi = &state->cfi;
2717
2718         if (cfi->cfa.base == CFI_BP &&
2719             check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2720             check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2721                 return true;
2722
2723         if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2724                 return true;
2725
2726         return false;
2727 }
2728
2729 static int update_cfi_state_regs(struct instruction *insn,
2730                                   struct cfi_state *cfi,
2731                                   struct stack_op *op)
2732 {
2733         struct cfi_reg *cfa = &cfi->cfa;
2734
2735         if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2736                 return 0;
2737
2738         /* push */
2739         if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2740                 cfa->offset += 8;
2741
2742         /* pop */
2743         if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2744                 cfa->offset -= 8;
2745
2746         /* add immediate to sp */
2747         if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2748             op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2749                 cfa->offset -= op->src.offset;
2750
2751         return 0;
2752 }
2753
2754 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2755 {
2756         if (arch_callee_saved_reg(reg) &&
2757             cfi->regs[reg].base == CFI_UNDEFINED) {
2758                 cfi->regs[reg].base = base;
2759                 cfi->regs[reg].offset = offset;
2760         }
2761 }
2762
2763 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2764 {
2765         cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2766         cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2767 }
2768
2769 /*
2770  * A note about DRAP stack alignment:
2771  *
2772  * GCC has the concept of a DRAP register, which is used to help keep track of
2773  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
2774  * register.  The typical DRAP pattern is:
2775  *
2776  *   4c 8d 54 24 08             lea    0x8(%rsp),%r10
2777  *   48 83 e4 c0                and    $0xffffffffffffffc0,%rsp
2778  *   41 ff 72 f8                pushq  -0x8(%r10)
2779  *   55                         push   %rbp
2780  *   48 89 e5                   mov    %rsp,%rbp
2781  *                              (more pushes)
2782  *   41 52                      push   %r10
2783  *                              ...
2784  *   41 5a                      pop    %r10
2785  *                              (more pops)
2786  *   5d                         pop    %rbp
2787  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2788  *   c3                         retq
2789  *
2790  * There are some variations in the epilogues, like:
2791  *
2792  *   5b                         pop    %rbx
2793  *   41 5a                      pop    %r10
2794  *   41 5c                      pop    %r12
2795  *   41 5d                      pop    %r13
2796  *   41 5e                      pop    %r14
2797  *   c9                         leaveq
2798  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2799  *   c3                         retq
2800  *
2801  * and:
2802  *
2803  *   4c 8b 55 e8                mov    -0x18(%rbp),%r10
2804  *   48 8b 5d e0                mov    -0x20(%rbp),%rbx
2805  *   4c 8b 65 f0                mov    -0x10(%rbp),%r12
2806  *   4c 8b 6d f8                mov    -0x8(%rbp),%r13
2807  *   c9                         leaveq
2808  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2809  *   c3                         retq
2810  *
2811  * Sometimes r13 is used as the DRAP register, in which case it's saved and
2812  * restored beforehand:
2813  *
2814  *   41 55                      push   %r13
2815  *   4c 8d 6c 24 10             lea    0x10(%rsp),%r13
2816  *   48 83 e4 f0                and    $0xfffffffffffffff0,%rsp
2817  *                              ...
2818  *   49 8d 65 f0                lea    -0x10(%r13),%rsp
2819  *   41 5d                      pop    %r13
2820  *   c3                         retq
2821  */
2822 static int update_cfi_state(struct instruction *insn,
2823                             struct instruction *next_insn,
2824                             struct cfi_state *cfi, struct stack_op *op)
2825 {
2826         struct cfi_reg *cfa = &cfi->cfa;
2827         struct cfi_reg *regs = cfi->regs;
2828
2829         /* ignore UNWIND_HINT_UNDEFINED regions */
2830         if (cfi->force_undefined)
2831                 return 0;
2832
2833         /* stack operations don't make sense with an undefined CFA */
2834         if (cfa->base == CFI_UNDEFINED) {
2835                 if (insn_func(insn)) {
2836                         WARN_INSN(insn, "undefined stack state");
2837                         return -1;
2838                 }
2839                 return 0;
2840         }
2841
2842         if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2843             cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2844                 return update_cfi_state_regs(insn, cfi, op);
2845
2846         switch (op->dest.type) {
2847
2848         case OP_DEST_REG:
2849                 switch (op->src.type) {
2850
2851                 case OP_SRC_REG:
2852                         if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2853                             cfa->base == CFI_SP &&
2854                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset)) {
2855
2856                                 /* mov %rsp, %rbp */
2857                                 cfa->base = op->dest.reg;
2858                                 cfi->bp_scratch = false;
2859                         }
2860
2861                         else if (op->src.reg == CFI_SP &&
2862                                  op->dest.reg == CFI_BP && cfi->drap) {
2863
2864                                 /* drap: mov %rsp, %rbp */
2865                                 regs[CFI_BP].base = CFI_BP;
2866                                 regs[CFI_BP].offset = -cfi->stack_size;
2867                                 cfi->bp_scratch = false;
2868                         }
2869
2870                         else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2871
2872                                 /*
2873                                  * mov %rsp, %reg
2874                                  *
2875                                  * This is needed for the rare case where GCC
2876                                  * does:
2877                                  *
2878                                  *   mov    %rsp, %rax
2879                                  *   ...
2880                                  *   mov    %rax, %rsp
2881                                  */
2882                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2883                                 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2884                         }
2885
2886                         else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2887                                  (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2888
2889                                 /*
2890                                  * mov %rbp, %rsp
2891                                  *
2892                                  * Restore the original stack pointer (Clang).
2893                                  */
2894                                 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2895                         }
2896
2897                         else if (op->dest.reg == cfa->base) {
2898
2899                                 /* mov %reg, %rsp */
2900                                 if (cfa->base == CFI_SP &&
2901                                     cfi->vals[op->src.reg].base == CFI_CFA) {
2902
2903                                         /*
2904                                          * This is needed for the rare case
2905                                          * where GCC does something dumb like:
2906                                          *
2907                                          *   lea    0x8(%rsp), %rcx
2908                                          *   ...
2909                                          *   mov    %rcx, %rsp
2910                                          */
2911                                         cfa->offset = -cfi->vals[op->src.reg].offset;
2912                                         cfi->stack_size = cfa->offset;
2913
2914                                 } else if (cfa->base == CFI_SP &&
2915                                            cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2916                                            cfi->vals[op->src.reg].offset == cfa->offset) {
2917
2918                                         /*
2919                                          * Stack swizzle:
2920                                          *
2921                                          * 1: mov %rsp, (%[tos])
2922                                          * 2: mov %[tos], %rsp
2923                                          *    ...
2924                                          * 3: pop %rsp
2925                                          *
2926                                          * Where:
2927                                          *
2928                                          * 1 - places a pointer to the previous
2929                                          *     stack at the Top-of-Stack of the
2930                                          *     new stack.
2931                                          *
2932                                          * 2 - switches to the new stack.
2933                                          *
2934                                          * 3 - pops the Top-of-Stack to restore
2935                                          *     the original stack.
2936                                          *
2937                                          * Note: we set base to SP_INDIRECT
2938                                          * here and preserve offset. Therefore
2939                                          * when the unwinder reaches ToS it
2940                                          * will dereference SP and then add the
2941                                          * offset to find the next frame, IOW:
2942                                          * (%rsp) + offset.
2943                                          */
2944                                         cfa->base = CFI_SP_INDIRECT;
2945
2946                                 } else {
2947                                         cfa->base = CFI_UNDEFINED;
2948                                         cfa->offset = 0;
2949                                 }
2950                         }
2951
2952                         else if (op->dest.reg == CFI_SP &&
2953                                  cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2954                                  cfi->vals[op->src.reg].offset == cfa->offset) {
2955
2956                                 /*
2957                                  * The same stack swizzle case 2) as above. But
2958                                  * because we can't change cfa->base, case 3)
2959                                  * will become a regular POP. Pretend we're a
2960                                  * PUSH so things don't go unbalanced.
2961                                  */
2962                                 cfi->stack_size += 8;
2963                         }
2964
2965
2966                         break;
2967
2968                 case OP_SRC_ADD:
2969                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2970
2971                                 /* add imm, %rsp */
2972                                 cfi->stack_size -= op->src.offset;
2973                                 if (cfa->base == CFI_SP)
2974                                         cfa->offset -= op->src.offset;
2975                                 break;
2976                         }
2977
2978                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2979
2980                                 /* lea disp(%rbp), %rsp */
2981                                 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2982                                 break;
2983                         }
2984
2985                         if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2986
2987                                 /* drap: lea disp(%rsp), %drap */
2988                                 cfi->drap_reg = op->dest.reg;
2989
2990                                 /*
2991                                  * lea disp(%rsp), %reg
2992                                  *
2993                                  * This is needed for the rare case where GCC
2994                                  * does something dumb like:
2995                                  *
2996                                  *   lea    0x8(%rsp), %rcx
2997                                  *   ...
2998                                  *   mov    %rcx, %rsp
2999                                  */
3000                                 cfi->vals[op->dest.reg].base = CFI_CFA;
3001                                 cfi->vals[op->dest.reg].offset = \
3002                                         -cfi->stack_size + op->src.offset;
3003
3004                                 break;
3005                         }
3006
3007                         if (cfi->drap && op->dest.reg == CFI_SP &&
3008                             op->src.reg == cfi->drap_reg) {
3009
3010                                  /* drap: lea disp(%drap), %rsp */
3011                                 cfa->base = CFI_SP;
3012                                 cfa->offset = cfi->stack_size = -op->src.offset;
3013                                 cfi->drap_reg = CFI_UNDEFINED;
3014                                 cfi->drap = false;
3015                                 break;
3016                         }
3017
3018                         if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
3019                                 WARN_INSN(insn, "unsupported stack register modification");
3020                                 return -1;
3021                         }
3022
3023                         break;
3024
3025                 case OP_SRC_AND:
3026                         if (op->dest.reg != CFI_SP ||
3027                             (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
3028                             (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
3029                                 WARN_INSN(insn, "unsupported stack pointer realignment");
3030                                 return -1;
3031                         }
3032
3033                         if (cfi->drap_reg != CFI_UNDEFINED) {
3034                                 /* drap: and imm, %rsp */
3035                                 cfa->base = cfi->drap_reg;
3036                                 cfa->offset = cfi->stack_size = 0;
3037                                 cfi->drap = true;
3038                         }
3039
3040                         /*
3041                          * Older versions of GCC (4.8ish) realign the stack
3042                          * without DRAP, with a frame pointer.
3043                          */
3044
3045                         break;
3046
3047                 case OP_SRC_POP:
3048                 case OP_SRC_POPF:
3049                         if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
3050
3051                                 /* pop %rsp; # restore from a stack swizzle */
3052                                 cfa->base = CFI_SP;
3053                                 break;
3054                         }
3055
3056                         if (!cfi->drap && op->dest.reg == cfa->base) {
3057
3058                                 /* pop %rbp */
3059                                 cfa->base = CFI_SP;
3060                         }
3061
3062                         if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
3063                             op->dest.reg == cfi->drap_reg &&
3064                             cfi->drap_offset == -cfi->stack_size) {
3065
3066                                 /* drap: pop %drap */
3067                                 cfa->base = cfi->drap_reg;
3068                                 cfa->offset = 0;
3069                                 cfi->drap_offset = -1;
3070
3071                         } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
3072
3073                                 /* pop %reg */
3074                                 restore_reg(cfi, op->dest.reg);
3075                         }
3076
3077                         cfi->stack_size -= 8;
3078                         if (cfa->base == CFI_SP)
3079                                 cfa->offset -= 8;
3080
3081                         break;
3082
3083                 case OP_SRC_REG_INDIRECT:
3084                         if (!cfi->drap && op->dest.reg == cfa->base &&
3085                             op->dest.reg == CFI_BP) {
3086
3087                                 /* mov disp(%rsp), %rbp */
3088                                 cfa->base = CFI_SP;
3089                                 cfa->offset = cfi->stack_size;
3090                         }
3091
3092                         if (cfi->drap && op->src.reg == CFI_BP &&
3093                             op->src.offset == cfi->drap_offset) {
3094
3095                                 /* drap: mov disp(%rbp), %drap */
3096                                 cfa->base = cfi->drap_reg;
3097                                 cfa->offset = 0;
3098                                 cfi->drap_offset = -1;
3099                         }
3100
3101                         if (cfi->drap && op->src.reg == CFI_BP &&
3102                             op->src.offset == regs[op->dest.reg].offset) {
3103
3104                                 /* drap: mov disp(%rbp), %reg */
3105                                 restore_reg(cfi, op->dest.reg);
3106
3107                         } else if (op->src.reg == cfa->base &&
3108                             op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
3109
3110                                 /* mov disp(%rbp), %reg */
3111                                 /* mov disp(%rsp), %reg */
3112                                 restore_reg(cfi, op->dest.reg);
3113
3114                         } else if (op->src.reg == CFI_SP &&
3115                                    op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
3116
3117                                 /* mov disp(%rsp), %reg */
3118                                 restore_reg(cfi, op->dest.reg);
3119                         }
3120
3121                         break;
3122
3123                 default:
3124                         WARN_INSN(insn, "unknown stack-related instruction");
3125                         return -1;
3126                 }
3127
3128                 break;
3129
3130         case OP_DEST_PUSH:
3131         case OP_DEST_PUSHF:
3132                 cfi->stack_size += 8;
3133                 if (cfa->base == CFI_SP)
3134                         cfa->offset += 8;
3135
3136                 if (op->src.type != OP_SRC_REG)
3137                         break;
3138
3139                 if (cfi->drap) {
3140                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3141
3142                                 /* drap: push %drap */
3143                                 cfa->base = CFI_BP_INDIRECT;
3144                                 cfa->offset = -cfi->stack_size;
3145
3146                                 /* save drap so we know when to restore it */
3147                                 cfi->drap_offset = -cfi->stack_size;
3148
3149                         } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
3150
3151                                 /* drap: push %rbp */
3152                                 cfi->stack_size = 0;
3153
3154                         } else {
3155
3156                                 /* drap: push %reg */
3157                                 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
3158                         }
3159
3160                 } else {
3161
3162                         /* push %reg */
3163                         save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
3164                 }
3165
3166                 /* detect when asm code uses rbp as a scratch register */
3167                 if (opts.stackval && insn_func(insn) && op->src.reg == CFI_BP &&
3168                     cfa->base != CFI_BP)
3169                         cfi->bp_scratch = true;
3170                 break;
3171
3172         case OP_DEST_REG_INDIRECT:
3173
3174                 if (cfi->drap) {
3175                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3176
3177                                 /* drap: mov %drap, disp(%rbp) */
3178                                 cfa->base = CFI_BP_INDIRECT;
3179                                 cfa->offset = op->dest.offset;
3180
3181                                 /* save drap offset so we know when to restore it */
3182                                 cfi->drap_offset = op->dest.offset;
3183                         } else {
3184
3185                                 /* drap: mov reg, disp(%rbp) */
3186                                 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
3187                         }
3188
3189                 } else if (op->dest.reg == cfa->base) {
3190
3191                         /* mov reg, disp(%rbp) */
3192                         /* mov reg, disp(%rsp) */
3193                         save_reg(cfi, op->src.reg, CFI_CFA,
3194                                  op->dest.offset - cfi->cfa.offset);
3195
3196                 } else if (op->dest.reg == CFI_SP) {
3197
3198                         /* mov reg, disp(%rsp) */
3199                         save_reg(cfi, op->src.reg, CFI_CFA,
3200                                  op->dest.offset - cfi->stack_size);
3201
3202                 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
3203
3204                         /* mov %rsp, (%reg); # setup a stack swizzle. */
3205                         cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
3206                         cfi->vals[op->dest.reg].offset = cfa->offset;
3207                 }
3208
3209                 break;
3210
3211         case OP_DEST_MEM:
3212                 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
3213                         WARN_INSN(insn, "unknown stack-related memory operation");
3214                         return -1;
3215                 }
3216
3217                 /* pop mem */
3218                 cfi->stack_size -= 8;
3219                 if (cfa->base == CFI_SP)
3220                         cfa->offset -= 8;
3221
3222                 break;
3223
3224         default:
3225                 WARN_INSN(insn, "unknown stack-related instruction");
3226                 return -1;
3227         }
3228
3229         return 0;
3230 }
3231
3232 /*
3233  * The stack layouts of alternatives instructions can sometimes diverge when
3234  * they have stack modifications.  That's fine as long as the potential stack
3235  * layouts don't conflict at any given potential instruction boundary.
3236  *
3237  * Flatten the CFIs of the different alternative code streams (both original
3238  * and replacement) into a single shared CFI array which can be used to detect
3239  * conflicts and nicely feed a linear array of ORC entries to the unwinder.
3240  */
3241 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
3242 {
3243         struct cfi_state **alt_cfi;
3244         int group_off;
3245
3246         if (!insn->alt_group)
3247                 return 0;
3248
3249         if (!insn->cfi) {
3250                 WARN("CFI missing");
3251                 return -1;
3252         }
3253
3254         alt_cfi = insn->alt_group->cfi;
3255         group_off = insn->offset - insn->alt_group->first_insn->offset;
3256
3257         if (!alt_cfi[group_off]) {
3258                 alt_cfi[group_off] = insn->cfi;
3259         } else {
3260                 if (cficmp(alt_cfi[group_off], insn->cfi)) {
3261                         struct alt_group *orig_group = insn->alt_group->orig_group ?: insn->alt_group;
3262                         struct instruction *orig = orig_group->first_insn;
3263                         char *where = offstr(insn->sec, insn->offset);
3264                         WARN_INSN(orig, "stack layout conflict in alternatives: %s", where);
3265                         free(where);
3266                         return -1;
3267                 }
3268         }
3269
3270         return 0;
3271 }
3272
3273 static int handle_insn_ops(struct instruction *insn,
3274                            struct instruction *next_insn,
3275                            struct insn_state *state)
3276 {
3277         struct stack_op *op;
3278
3279         for (op = insn->stack_ops; op; op = op->next) {
3280
3281                 if (update_cfi_state(insn, next_insn, &state->cfi, op))
3282                         return 1;
3283
3284                 if (!insn->alt_group)
3285                         continue;
3286
3287                 if (op->dest.type == OP_DEST_PUSHF) {
3288                         if (!state->uaccess_stack) {
3289                                 state->uaccess_stack = 1;
3290                         } else if (state->uaccess_stack >> 31) {
3291                                 WARN_INSN(insn, "PUSHF stack exhausted");
3292                                 return 1;
3293                         }
3294                         state->uaccess_stack <<= 1;
3295                         state->uaccess_stack  |= state->uaccess;
3296                 }
3297
3298                 if (op->src.type == OP_SRC_POPF) {
3299                         if (state->uaccess_stack) {
3300                                 state->uaccess = state->uaccess_stack & 1;
3301                                 state->uaccess_stack >>= 1;
3302                                 if (state->uaccess_stack == 1)
3303                                         state->uaccess_stack = 0;
3304                         }
3305                 }
3306         }
3307
3308         return 0;
3309 }
3310
3311 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
3312 {
3313         struct cfi_state *cfi1 = insn->cfi;
3314         int i;
3315
3316         if (!cfi1) {
3317                 WARN("CFI missing");
3318                 return false;
3319         }
3320
3321         if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
3322
3323                 WARN_INSN(insn, "stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
3324                           cfi1->cfa.base, cfi1->cfa.offset,
3325                           cfi2->cfa.base, cfi2->cfa.offset);
3326
3327         } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
3328                 for (i = 0; i < CFI_NUM_REGS; i++) {
3329                         if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
3330                                     sizeof(struct cfi_reg)))
3331                                 continue;
3332
3333                         WARN_INSN(insn, "stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
3334                                   i, cfi1->regs[i].base, cfi1->regs[i].offset,
3335                                   i, cfi2->regs[i].base, cfi2->regs[i].offset);
3336                         break;
3337                 }
3338
3339         } else if (cfi1->type != cfi2->type) {
3340
3341                 WARN_INSN(insn, "stack state mismatch: type1=%d type2=%d",
3342                           cfi1->type, cfi2->type);
3343
3344         } else if (cfi1->drap != cfi2->drap ||
3345                    (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
3346                    (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
3347
3348                 WARN_INSN(insn, "stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
3349                           cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
3350                           cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
3351
3352         } else
3353                 return true;
3354
3355         return false;
3356 }
3357
3358 static inline bool func_uaccess_safe(struct symbol *func)
3359 {
3360         if (func)
3361                 return func->uaccess_safe;
3362
3363         return false;
3364 }
3365
3366 static inline const char *call_dest_name(struct instruction *insn)
3367 {
3368         static char pvname[19];
3369         struct reloc *reloc;
3370         int idx;
3371
3372         if (insn_call_dest(insn))
3373                 return insn_call_dest(insn)->name;
3374
3375         reloc = insn_reloc(NULL, insn);
3376         if (reloc && !strcmp(reloc->sym->name, "pv_ops")) {
3377                 idx = (reloc_addend(reloc) / sizeof(void *));
3378                 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
3379                 return pvname;
3380         }
3381
3382         return "{dynamic}";
3383 }
3384
3385 static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3386 {
3387         struct symbol *target;
3388         struct reloc *reloc;
3389         int idx;
3390
3391         reloc = insn_reloc(file, insn);
3392         if (!reloc || strcmp(reloc->sym->name, "pv_ops"))
3393                 return false;
3394
3395         idx = (arch_dest_reloc_offset(reloc_addend(reloc)) / sizeof(void *));
3396
3397         if (file->pv_ops[idx].clean)
3398                 return true;
3399
3400         file->pv_ops[idx].clean = true;
3401
3402         list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3403                 if (!target->sec->noinstr) {
3404                         WARN("pv_ops[%d]: %s", idx, target->name);
3405                         file->pv_ops[idx].clean = false;
3406                 }
3407         }
3408
3409         return file->pv_ops[idx].clean;
3410 }
3411
3412 static inline bool noinstr_call_dest(struct objtool_file *file,
3413                                      struct instruction *insn,
3414                                      struct symbol *func)
3415 {
3416         /*
3417          * We can't deal with indirect function calls at present;
3418          * assume they're instrumented.
3419          */
3420         if (!func) {
3421                 if (file->pv_ops)
3422                         return pv_call_dest(file, insn);
3423
3424                 return false;
3425         }
3426
3427         /*
3428          * If the symbol is from a noinstr section; we good.
3429          */
3430         if (func->sec->noinstr)
3431                 return true;
3432
3433         /*
3434          * If the symbol is a static_call trampoline, we can't tell.
3435          */
3436         if (func->static_call_tramp)
3437                 return true;
3438
3439         /*
3440          * The __ubsan_handle_*() calls are like WARN(), they only happen when
3441          * something 'BAD' happened. At the risk of taking the machine down,
3442          * let them proceed to get the message out.
3443          */
3444         if (!strncmp(func->name, "__ubsan_handle_", 15))
3445                 return true;
3446
3447         return false;
3448 }
3449
3450 static int validate_call(struct objtool_file *file,
3451                          struct instruction *insn,
3452                          struct insn_state *state)
3453 {
3454         if (state->noinstr && state->instr <= 0 &&
3455             !noinstr_call_dest(file, insn, insn_call_dest(insn))) {
3456                 WARN_INSN(insn, "call to %s() leaves .noinstr.text section", call_dest_name(insn));
3457                 return 1;
3458         }
3459
3460         if (state->uaccess && !func_uaccess_safe(insn_call_dest(insn))) {
3461                 WARN_INSN(insn, "call to %s() with UACCESS enabled", call_dest_name(insn));
3462                 return 1;
3463         }
3464
3465         if (state->df) {
3466                 WARN_INSN(insn, "call to %s() with DF set", call_dest_name(insn));
3467                 return 1;
3468         }
3469
3470         return 0;
3471 }
3472
3473 static int validate_sibling_call(struct objtool_file *file,
3474                                  struct instruction *insn,
3475                                  struct insn_state *state)
3476 {
3477         if (insn_func(insn) && has_modified_stack_frame(insn, state)) {
3478                 WARN_INSN(insn, "sibling call from callable instruction with modified stack frame");
3479                 return 1;
3480         }
3481
3482         return validate_call(file, insn, state);
3483 }
3484
3485 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3486 {
3487         if (state->noinstr && state->instr > 0) {
3488                 WARN_INSN(insn, "return with instrumentation enabled");
3489                 return 1;
3490         }
3491
3492         if (state->uaccess && !func_uaccess_safe(func)) {
3493                 WARN_INSN(insn, "return with UACCESS enabled");
3494                 return 1;
3495         }
3496
3497         if (!state->uaccess && func_uaccess_safe(func)) {
3498                 WARN_INSN(insn, "return with UACCESS disabled from a UACCESS-safe function");
3499                 return 1;
3500         }
3501
3502         if (state->df) {
3503                 WARN_INSN(insn, "return with DF set");
3504                 return 1;
3505         }
3506
3507         if (func && has_modified_stack_frame(insn, state)) {
3508                 WARN_INSN(insn, "return with modified stack frame");
3509                 return 1;
3510         }
3511
3512         if (state->cfi.bp_scratch) {
3513                 WARN_INSN(insn, "BP used as a scratch register");
3514                 return 1;
3515         }
3516
3517         return 0;
3518 }
3519
3520 static struct instruction *next_insn_to_validate(struct objtool_file *file,
3521                                                  struct instruction *insn)
3522 {
3523         struct alt_group *alt_group = insn->alt_group;
3524
3525         /*
3526          * Simulate the fact that alternatives are patched in-place.  When the
3527          * end of a replacement alt_group is reached, redirect objtool flow to
3528          * the end of the original alt_group.
3529          *
3530          * insn->alts->insn -> alt_group->first_insn
3531          *                     ...
3532          *                     alt_group->last_insn
3533          *                     [alt_group->nop]      -> next(orig_group->last_insn)
3534          */
3535         if (alt_group) {
3536                 if (alt_group->nop) {
3537                         /* ->nop implies ->orig_group */
3538                         if (insn == alt_group->last_insn)
3539                                 return alt_group->nop;
3540                         if (insn == alt_group->nop)
3541                                 goto next_orig;
3542                 }
3543                 if (insn == alt_group->last_insn && alt_group->orig_group)
3544                         goto next_orig;
3545         }
3546
3547         return next_insn_same_sec(file, insn);
3548
3549 next_orig:
3550         return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3551 }
3552
3553 /*
3554  * Follow the branch starting at the given instruction, and recursively follow
3555  * any other branches (jumps).  Meanwhile, track the frame pointer state at
3556  * each instruction and validate all the rules described in
3557  * tools/objtool/Documentation/objtool.txt.
3558  */
3559 static int validate_branch(struct objtool_file *file, struct symbol *func,
3560                            struct instruction *insn, struct insn_state state)
3561 {
3562         struct alternative *alt;
3563         struct instruction *next_insn, *prev_insn = NULL;
3564         struct section *sec;
3565         u8 visited;
3566         int ret;
3567
3568         sec = insn->sec;
3569
3570         while (1) {
3571                 next_insn = next_insn_to_validate(file, insn);
3572
3573                 if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {
3574                         /* Ignore KCFI type preambles, which always fall through */
3575                         if (!strncmp(func->name, "__cfi_", 6) ||
3576                             !strncmp(func->name, "__pfx_", 6))
3577                                 return 0;
3578
3579                         WARN("%s() falls through to next function %s()",
3580                              func->name, insn_func(insn)->name);
3581                         return 1;
3582                 }
3583
3584                 if (func && insn->ignore) {
3585                         WARN_INSN(insn, "BUG: why am I validating an ignored function?");
3586                         return 1;
3587                 }
3588
3589                 visited = VISITED_BRANCH << state.uaccess;
3590                 if (insn->visited & VISITED_BRANCH_MASK) {
3591                         if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3592                                 return 1;
3593
3594                         if (insn->visited & visited)
3595                                 return 0;
3596                 } else {
3597                         nr_insns_visited++;
3598                 }
3599
3600                 if (state.noinstr)
3601                         state.instr += insn->instr;
3602
3603                 if (insn->hint) {
3604                         if (insn->restore) {
3605                                 struct instruction *save_insn, *i;
3606
3607                                 i = insn;
3608                                 save_insn = NULL;
3609
3610                                 sym_for_each_insn_continue_reverse(file, func, i) {
3611                                         if (i->save) {
3612                                                 save_insn = i;
3613                                                 break;
3614                                         }
3615                                 }
3616
3617                                 if (!save_insn) {
3618                                         WARN_INSN(insn, "no corresponding CFI save for CFI restore");
3619                                         return 1;
3620                                 }
3621
3622                                 if (!save_insn->visited) {
3623                                         /*
3624                                          * If the restore hint insn is at the
3625                                          * beginning of a basic block and was
3626                                          * branched to from elsewhere, and the
3627                                          * save insn hasn't been visited yet,
3628                                          * defer following this branch for now.
3629                                          * It will be seen later via the
3630                                          * straight-line path.
3631                                          */
3632                                         if (!prev_insn)
3633                                                 return 0;
3634
3635                                         WARN_INSN(insn, "objtool isn't smart enough to handle this CFI save/restore combo");
3636                                         return 1;
3637                                 }
3638
3639                                 insn->cfi = save_insn->cfi;
3640                                 nr_cfi_reused++;
3641                         }
3642
3643                         state.cfi = *insn->cfi;
3644                 } else {
3645                         /* XXX track if we actually changed state.cfi */
3646
3647                         if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3648                                 insn->cfi = prev_insn->cfi;
3649                                 nr_cfi_reused++;
3650                         } else {
3651                                 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3652                         }
3653                 }
3654
3655                 insn->visited |= visited;
3656
3657                 if (propagate_alt_cfi(file, insn))
3658                         return 1;
3659
3660                 if (!insn->ignore_alts && insn->alts) {
3661                         bool skip_orig = false;
3662
3663                         for (alt = insn->alts; alt; alt = alt->next) {
3664                                 if (alt->skip_orig)
3665                                         skip_orig = true;
3666
3667                                 ret = validate_branch(file, func, alt->insn, state);
3668                                 if (ret) {
3669                                         BT_INSN(insn, "(alt)");
3670                                         return ret;
3671                                 }
3672                         }
3673
3674                         if (skip_orig)
3675                                 return 0;
3676                 }
3677
3678                 if (handle_insn_ops(insn, next_insn, &state))
3679                         return 1;
3680
3681                 switch (insn->type) {
3682
3683                 case INSN_RETURN:
3684                         return validate_return(func, insn, &state);
3685
3686                 case INSN_CALL:
3687                 case INSN_CALL_DYNAMIC:
3688                         ret = validate_call(file, insn, &state);
3689                         if (ret)
3690                                 return ret;
3691
3692                         if (opts.stackval && func && !is_special_call(insn) &&
3693                             !has_valid_stack_frame(&state)) {
3694                                 WARN_INSN(insn, "call without frame pointer save/setup");
3695                                 return 1;
3696                         }
3697
3698                         if (insn->dead_end)
3699                                 return 0;
3700
3701                         break;
3702
3703                 case INSN_JUMP_CONDITIONAL:
3704                 case INSN_JUMP_UNCONDITIONAL:
3705                         if (is_sibling_call(insn)) {
3706                                 ret = validate_sibling_call(file, insn, &state);
3707                                 if (ret)
3708                                         return ret;
3709
3710                         } else if (insn->jump_dest) {
3711                                 ret = validate_branch(file, func,
3712                                                       insn->jump_dest, state);
3713                                 if (ret) {
3714                                         BT_INSN(insn, "(branch)");
3715                                         return ret;
3716                                 }
3717                         }
3718
3719                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
3720                                 return 0;
3721
3722                         break;
3723
3724                 case INSN_JUMP_DYNAMIC:
3725                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3726                         if (is_sibling_call(insn)) {
3727                                 ret = validate_sibling_call(file, insn, &state);
3728                                 if (ret)
3729                                         return ret;
3730                         }
3731
3732                         if (insn->type == INSN_JUMP_DYNAMIC)
3733                                 return 0;
3734
3735                         break;
3736
3737                 case INSN_CONTEXT_SWITCH:
3738                         if (func && (!next_insn || !next_insn->hint)) {
3739                                 WARN_INSN(insn, "unsupported instruction in callable function");
3740                                 return 1;
3741                         }
3742                         return 0;
3743
3744                 case INSN_STAC:
3745                         if (state.uaccess) {
3746                                 WARN_INSN(insn, "recursive UACCESS enable");
3747                                 return 1;
3748                         }
3749
3750                         state.uaccess = true;
3751                         break;
3752
3753                 case INSN_CLAC:
3754                         if (!state.uaccess && func) {
3755                                 WARN_INSN(insn, "redundant UACCESS disable");
3756                                 return 1;
3757                         }
3758
3759                         if (func_uaccess_safe(func) && !state.uaccess_stack) {
3760                                 WARN_INSN(insn, "UACCESS-safe disables UACCESS");
3761                                 return 1;
3762                         }
3763
3764                         state.uaccess = false;
3765                         break;
3766
3767                 case INSN_STD:
3768                         if (state.df) {
3769                                 WARN_INSN(insn, "recursive STD");
3770                                 return 1;
3771                         }
3772
3773                         state.df = true;
3774                         break;
3775
3776                 case INSN_CLD:
3777                         if (!state.df && func) {
3778                                 WARN_INSN(insn, "redundant CLD");
3779                                 return 1;
3780                         }
3781
3782                         state.df = false;
3783                         break;
3784
3785                 default:
3786                         break;
3787                 }
3788
3789                 if (insn->dead_end)
3790                         return 0;
3791
3792                 if (!next_insn) {
3793                         if (state.cfi.cfa.base == CFI_UNDEFINED)
3794                                 return 0;
3795                         WARN("%s: unexpected end of section", sec->name);
3796                         return 1;
3797                 }
3798
3799                 prev_insn = insn;
3800                 insn = next_insn;
3801         }
3802
3803         return 0;
3804 }
3805
3806 static int validate_unwind_hint(struct objtool_file *file,
3807                                   struct instruction *insn,
3808                                   struct insn_state *state)
3809 {
3810         if (insn->hint && !insn->visited && !insn->ignore) {
3811                 int ret = validate_branch(file, insn_func(insn), insn, *state);
3812                 if (ret)
3813                         BT_INSN(insn, "<=== (hint)");
3814                 return ret;
3815         }
3816
3817         return 0;
3818 }
3819
3820 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3821 {
3822         struct instruction *insn;
3823         struct insn_state state;
3824         int warnings = 0;
3825
3826         if (!file->hints)
3827                 return 0;
3828
3829         init_insn_state(file, &state, sec);
3830
3831         if (sec) {
3832                 sec_for_each_insn(file, sec, insn)
3833                         warnings += validate_unwind_hint(file, insn, &state);
3834         } else {
3835                 for_each_insn(file, insn)
3836                         warnings += validate_unwind_hint(file, insn, &state);
3837         }
3838
3839         return warnings;
3840 }
3841
3842 /*
3843  * Validate rethunk entry constraint: must untrain RET before the first RET.
3844  *
3845  * Follow every branch (intra-function) and ensure VALIDATE_UNRET_END comes
3846  * before an actual RET instruction.
3847  */
3848 static int validate_unret(struct objtool_file *file, struct instruction *insn)
3849 {
3850         struct instruction *next, *dest;
3851         int ret;
3852
3853         for (;;) {
3854                 next = next_insn_to_validate(file, insn);
3855
3856                 if (insn->visited & VISITED_UNRET)
3857                         return 0;
3858
3859                 insn->visited |= VISITED_UNRET;
3860
3861                 if (!insn->ignore_alts && insn->alts) {
3862                         struct alternative *alt;
3863                         bool skip_orig = false;
3864
3865                         for (alt = insn->alts; alt; alt = alt->next) {
3866                                 if (alt->skip_orig)
3867                                         skip_orig = true;
3868
3869                                 ret = validate_unret(file, alt->insn);
3870                                 if (ret) {
3871                                         BT_INSN(insn, "(alt)");
3872                                         return ret;
3873                                 }
3874                         }
3875
3876                         if (skip_orig)
3877                                 return 0;
3878                 }
3879
3880                 switch (insn->type) {
3881
3882                 case INSN_CALL_DYNAMIC:
3883                 case INSN_JUMP_DYNAMIC:
3884                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3885                         WARN_INSN(insn, "early indirect call");
3886                         return 1;
3887
3888                 case INSN_JUMP_UNCONDITIONAL:
3889                 case INSN_JUMP_CONDITIONAL:
3890                         if (!is_sibling_call(insn)) {
3891                                 if (!insn->jump_dest) {
3892                                         WARN_INSN(insn, "unresolved jump target after linking?!?");
3893                                         return -1;
3894                                 }
3895                                 ret = validate_unret(file, insn->jump_dest);
3896                                 if (ret) {
3897                                         BT_INSN(insn, "(branch%s)",
3898                                                 insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : "");
3899                                         return ret;
3900                                 }
3901
3902                                 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3903                                         return 0;
3904
3905                                 break;
3906                         }
3907
3908                         /* fallthrough */
3909                 case INSN_CALL:
3910                         dest = find_insn(file, insn_call_dest(insn)->sec,
3911                                          insn_call_dest(insn)->offset);
3912                         if (!dest) {
3913                                 WARN("Unresolved function after linking!?: %s",
3914                                      insn_call_dest(insn)->name);
3915                                 return -1;
3916                         }
3917
3918                         ret = validate_unret(file, dest);
3919                         if (ret) {
3920                                 BT_INSN(insn, "(call)");
3921                                 return ret;
3922                         }
3923                         /*
3924                          * If a call returns without error, it must have seen UNTRAIN_RET.
3925                          * Therefore any non-error return is a success.
3926                          */
3927                         return 0;
3928
3929                 case INSN_RETURN:
3930                         WARN_INSN(insn, "RET before UNTRAIN");
3931                         return 1;
3932
3933                 case INSN_NOP:
3934                         if (insn->retpoline_safe)
3935                                 return 0;
3936                         break;
3937
3938                 default:
3939                         break;
3940                 }
3941
3942                 if (!next) {
3943                         WARN_INSN(insn, "teh end!");
3944                         return -1;
3945                 }
3946                 insn = next;
3947         }
3948
3949         return 0;
3950 }
3951
3952 /*
3953  * Validate that all branches starting at VALIDATE_UNRET_BEGIN encounter
3954  * VALIDATE_UNRET_END before RET.
3955  */
3956 static int validate_unrets(struct objtool_file *file)
3957 {
3958         struct instruction *insn;
3959         int ret, warnings = 0;
3960
3961         for_each_insn(file, insn) {
3962                 if (!insn->unret)
3963                         continue;
3964
3965                 ret = validate_unret(file, insn);
3966                 if (ret < 0) {
3967                         WARN_INSN(insn, "Failed UNRET validation");
3968                         return ret;
3969                 }
3970                 warnings += ret;
3971         }
3972
3973         return warnings;
3974 }
3975
3976 static int validate_retpoline(struct objtool_file *file)
3977 {
3978         struct instruction *insn;
3979         int warnings = 0;
3980
3981         for_each_insn(file, insn) {
3982                 if (insn->type != INSN_JUMP_DYNAMIC &&
3983                     insn->type != INSN_CALL_DYNAMIC &&
3984                     insn->type != INSN_RETURN)
3985                         continue;
3986
3987                 if (insn->retpoline_safe)
3988                         continue;
3989
3990                 if (insn->sec->init)
3991                         continue;
3992
3993                 if (insn->type == INSN_RETURN) {
3994                         if (opts.rethunk) {
3995                                 WARN_INSN(insn, "'naked' return found in RETHUNK build");
3996                         } else
3997                                 continue;
3998                 } else {
3999                         WARN_INSN(insn, "indirect %s found in RETPOLINE build",
4000                                   insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
4001                 }
4002
4003                 warnings++;
4004         }
4005
4006         return warnings;
4007 }
4008
4009 static bool is_kasan_insn(struct instruction *insn)
4010 {
4011         return (insn->type == INSN_CALL &&
4012                 !strcmp(insn_call_dest(insn)->name, "__asan_handle_no_return"));
4013 }
4014
4015 static bool is_ubsan_insn(struct instruction *insn)
4016 {
4017         return (insn->type == INSN_CALL &&
4018                 !strcmp(insn_call_dest(insn)->name,
4019                         "__ubsan_handle_builtin_unreachable"));
4020 }
4021
4022 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
4023 {
4024         int i;
4025         struct instruction *prev_insn;
4026
4027         if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
4028                 return true;
4029
4030         /*
4031          * Ignore alternative replacement instructions.  This can happen
4032          * when a whitelisted function uses one of the ALTERNATIVE macros.
4033          */
4034         if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
4035             !strcmp(insn->sec->name, ".altinstr_aux"))
4036                 return true;
4037
4038         /*
4039          * Whole archive runs might encounter dead code from weak symbols.
4040          * This is where the linker will have dropped the weak symbol in
4041          * favour of a regular symbol, but leaves the code in place.
4042          *
4043          * In this case we'll find a piece of code (whole function) that is not
4044          * covered by a !section symbol. Ignore them.
4045          */
4046         if (opts.link && !insn_func(insn)) {
4047                 int size = find_symbol_hole_containing(insn->sec, insn->offset);
4048                 unsigned long end = insn->offset + size;
4049
4050                 if (!size) /* not a hole */
4051                         return false;
4052
4053                 if (size < 0) /* hole until the end */
4054                         return true;
4055
4056                 sec_for_each_insn_continue(file, insn) {
4057                         /*
4058                          * If we reach a visited instruction at or before the
4059                          * end of the hole, ignore the unreachable.
4060                          */
4061                         if (insn->visited)
4062                                 return true;
4063
4064                         if (insn->offset >= end)
4065                                 break;
4066
4067                         /*
4068                          * If this hole jumps to a .cold function, mark it ignore too.
4069                          */
4070                         if (insn->jump_dest && insn_func(insn->jump_dest) &&
4071                             strstr(insn_func(insn->jump_dest)->name, ".cold")) {
4072                                 struct instruction *dest = insn->jump_dest;
4073                                 func_for_each_insn(file, insn_func(dest), dest)
4074                                         dest->ignore = true;
4075                         }
4076                 }
4077
4078                 return false;
4079         }
4080
4081         if (!insn_func(insn))
4082                 return false;
4083
4084         if (insn_func(insn)->static_call_tramp)
4085                 return true;
4086
4087         /*
4088          * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
4089          * __builtin_unreachable().  The BUG() macro has an unreachable() after
4090          * the UD2, which causes GCC's undefined trap logic to emit another UD2
4091          * (or occasionally a JMP to UD2).
4092          *
4093          * It may also insert a UD2 after calling a __noreturn function.
4094          */
4095         prev_insn = prev_insn_same_sec(file, insn);
4096         if (prev_insn->dead_end &&
4097             (insn->type == INSN_BUG ||
4098              (insn->type == INSN_JUMP_UNCONDITIONAL &&
4099               insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
4100                 return true;
4101
4102         /*
4103          * Check if this (or a subsequent) instruction is related to
4104          * CONFIG_UBSAN or CONFIG_KASAN.
4105          *
4106          * End the search at 5 instructions to avoid going into the weeds.
4107          */
4108         for (i = 0; i < 5; i++) {
4109
4110                 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
4111                         return true;
4112
4113                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
4114                         if (insn->jump_dest &&
4115                             insn_func(insn->jump_dest) == insn_func(insn)) {
4116                                 insn = insn->jump_dest;
4117                                 continue;
4118                         }
4119
4120                         break;
4121                 }
4122
4123                 if (insn->offset + insn->len >= insn_func(insn)->offset + insn_func(insn)->len)
4124                         break;
4125
4126                 insn = next_insn_same_sec(file, insn);
4127         }
4128
4129         return false;
4130 }
4131
4132 static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
4133 {
4134         struct instruction *insn, *prev;
4135         struct cfi_state *cfi;
4136
4137         insn = find_insn(file, func->sec, func->offset);
4138         if (!insn)
4139                 return -1;
4140
4141         for (prev = prev_insn_same_sec(file, insn);
4142              prev;
4143              prev = prev_insn_same_sec(file, prev)) {
4144                 u64 offset;
4145
4146                 if (prev->type != INSN_NOP)
4147                         return -1;
4148
4149                 offset = func->offset - prev->offset;
4150
4151                 if (offset > opts.prefix)
4152                         return -1;
4153
4154                 if (offset < opts.prefix)
4155                         continue;
4156
4157                 elf_create_prefix_symbol(file->elf, func, opts.prefix);
4158                 break;
4159         }
4160
4161         if (!prev)
4162                 return -1;
4163
4164         if (!insn->cfi) {
4165                 /*
4166                  * This can happen if stack validation isn't enabled or the
4167                  * function is annotated with STACK_FRAME_NON_STANDARD.
4168                  */
4169                 return 0;
4170         }
4171
4172         /* Propagate insn->cfi to the prefix code */
4173         cfi = cfi_hash_find_or_add(insn->cfi);
4174         for (; prev != insn; prev = next_insn_same_sec(file, prev))
4175                 prev->cfi = cfi;
4176
4177         return 0;
4178 }
4179
4180 static int add_prefix_symbols(struct objtool_file *file)
4181 {
4182         struct section *sec;
4183         struct symbol *func;
4184
4185         for_each_sec(file, sec) {
4186                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4187                         continue;
4188
4189                 sec_for_each_sym(sec, func) {
4190                         if (func->type != STT_FUNC)
4191                                 continue;
4192
4193                         add_prefix_symbol(file, func);
4194                 }
4195         }
4196
4197         return 0;
4198 }
4199
4200 static int validate_symbol(struct objtool_file *file, struct section *sec,
4201                            struct symbol *sym, struct insn_state *state)
4202 {
4203         struct instruction *insn;
4204         int ret;
4205
4206         if (!sym->len) {
4207                 WARN("%s() is missing an ELF size annotation", sym->name);
4208                 return 1;
4209         }
4210
4211         if (sym->pfunc != sym || sym->alias != sym)
4212                 return 0;
4213
4214         insn = find_insn(file, sec, sym->offset);
4215         if (!insn || insn->ignore || insn->visited)
4216                 return 0;
4217
4218         state->uaccess = sym->uaccess_safe;
4219
4220         ret = validate_branch(file, insn_func(insn), insn, *state);
4221         if (ret)
4222                 BT_INSN(insn, "<=== (sym)");
4223         return ret;
4224 }
4225
4226 static int validate_section(struct objtool_file *file, struct section *sec)
4227 {
4228         struct insn_state state;
4229         struct symbol *func;
4230         int warnings = 0;
4231
4232         sec_for_each_sym(sec, func) {
4233                 if (func->type != STT_FUNC)
4234                         continue;
4235
4236                 init_insn_state(file, &state, sec);
4237                 set_func_state(&state.cfi);
4238
4239                 warnings += validate_symbol(file, sec, func, &state);
4240         }
4241
4242         return warnings;
4243 }
4244
4245 static int validate_noinstr_sections(struct objtool_file *file)
4246 {
4247         struct section *sec;
4248         int warnings = 0;
4249
4250         sec = find_section_by_name(file->elf, ".noinstr.text");
4251         if (sec) {
4252                 warnings += validate_section(file, sec);
4253                 warnings += validate_unwind_hints(file, sec);
4254         }
4255
4256         sec = find_section_by_name(file->elf, ".entry.text");
4257         if (sec) {
4258                 warnings += validate_section(file, sec);
4259                 warnings += validate_unwind_hints(file, sec);
4260         }
4261
4262         sec = find_section_by_name(file->elf, ".cpuidle.text");
4263         if (sec) {
4264                 warnings += validate_section(file, sec);
4265                 warnings += validate_unwind_hints(file, sec);
4266         }
4267
4268         return warnings;
4269 }
4270
4271 static int validate_functions(struct objtool_file *file)
4272 {
4273         struct section *sec;
4274         int warnings = 0;
4275
4276         for_each_sec(file, sec) {
4277                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4278                         continue;
4279
4280                 warnings += validate_section(file, sec);
4281         }
4282
4283         return warnings;
4284 }
4285
4286 static void mark_endbr_used(struct instruction *insn)
4287 {
4288         if (!list_empty(&insn->call_node))
4289                 list_del_init(&insn->call_node);
4290 }
4291
4292 static bool noendbr_range(struct objtool_file *file, struct instruction *insn)
4293 {
4294         struct symbol *sym = find_symbol_containing(insn->sec, insn->offset-1);
4295         struct instruction *first;
4296
4297         if (!sym)
4298                 return false;
4299
4300         first = find_insn(file, sym->sec, sym->offset);
4301         if (!first)
4302                 return false;
4303
4304         if (first->type != INSN_ENDBR && !first->noendbr)
4305                 return false;
4306
4307         return insn->offset == sym->offset + sym->len;
4308 }
4309
4310 static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
4311 {
4312         struct instruction *dest;
4313         struct reloc *reloc;
4314         unsigned long off;
4315         int warnings = 0;
4316
4317         /*
4318          * Looking for function pointer load relocations.  Ignore
4319          * direct/indirect branches:
4320          */
4321         switch (insn->type) {
4322         case INSN_CALL:
4323         case INSN_CALL_DYNAMIC:
4324         case INSN_JUMP_CONDITIONAL:
4325         case INSN_JUMP_UNCONDITIONAL:
4326         case INSN_JUMP_DYNAMIC:
4327         case INSN_JUMP_DYNAMIC_CONDITIONAL:
4328         case INSN_RETURN:
4329         case INSN_NOP:
4330                 return 0;
4331         default:
4332                 break;
4333         }
4334
4335         for (reloc = insn_reloc(file, insn);
4336              reloc;
4337              reloc = find_reloc_by_dest_range(file->elf, insn->sec,
4338                                               reloc_offset(reloc) + 1,
4339                                               (insn->offset + insn->len) - (reloc_offset(reloc) + 1))) {
4340
4341                 /*
4342                  * static_call_update() references the trampoline, which
4343                  * doesn't have (or need) ENDBR.  Skip warning in that case.
4344                  */
4345                 if (reloc->sym->static_call_tramp)
4346                         continue;
4347
4348                 off = reloc->sym->offset;
4349                 if (reloc_type(reloc) == R_X86_64_PC32 ||
4350                     reloc_type(reloc) == R_X86_64_PLT32)
4351                         off += arch_dest_reloc_offset(reloc_addend(reloc));
4352                 else
4353                         off += reloc_addend(reloc);
4354
4355                 dest = find_insn(file, reloc->sym->sec, off);
4356                 if (!dest)
4357                         continue;
4358
4359                 if (dest->type == INSN_ENDBR) {
4360                         mark_endbr_used(dest);
4361                         continue;
4362                 }
4363
4364                 if (insn_func(dest) && insn_func(insn) &&
4365                     insn_func(dest)->pfunc == insn_func(insn)->pfunc) {
4366                         /*
4367                          * Anything from->to self is either _THIS_IP_ or
4368                          * IRET-to-self.
4369                          *
4370                          * There is no sane way to annotate _THIS_IP_ since the
4371                          * compiler treats the relocation as a constant and is
4372                          * happy to fold in offsets, skewing any annotation we
4373                          * do, leading to vast amounts of false-positives.
4374                          *
4375                          * There's also compiler generated _THIS_IP_ through
4376                          * KCOV and such which we have no hope of annotating.
4377                          *
4378                          * As such, blanket accept self-references without
4379                          * issue.
4380                          */
4381                         continue;
4382                 }
4383
4384                 /*
4385                  * Accept anything ANNOTATE_NOENDBR.
4386                  */
4387                 if (dest->noendbr)
4388                         continue;
4389
4390                 /*
4391                  * Accept if this is the instruction after a symbol
4392                  * that is (no)endbr -- typical code-range usage.
4393                  */
4394                 if (noendbr_range(file, dest))
4395                         continue;
4396
4397                 WARN_INSN(insn, "relocation to !ENDBR: %s", offstr(dest->sec, dest->offset));
4398
4399                 warnings++;
4400         }
4401
4402         return warnings;
4403 }
4404
4405 static int validate_ibt_data_reloc(struct objtool_file *file,
4406                                    struct reloc *reloc)
4407 {
4408         struct instruction *dest;
4409
4410         dest = find_insn(file, reloc->sym->sec,
4411                          reloc->sym->offset + reloc_addend(reloc));
4412         if (!dest)
4413                 return 0;
4414
4415         if (dest->type == INSN_ENDBR) {
4416                 mark_endbr_used(dest);
4417                 return 0;
4418         }
4419
4420         if (dest->noendbr)
4421                 return 0;
4422
4423         WARN_FUNC("data relocation to !ENDBR: %s",
4424                   reloc->sec->base, reloc_offset(reloc),
4425                   offstr(dest->sec, dest->offset));
4426
4427         return 1;
4428 }
4429
4430 /*
4431  * Validate IBT rules and remove used ENDBR instructions from the seal list.
4432  * Unused ENDBR instructions will be annotated for sealing (i.e., replaced with
4433  * NOPs) later, in create_ibt_endbr_seal_sections().
4434  */
4435 static int validate_ibt(struct objtool_file *file)
4436 {
4437         struct section *sec;
4438         struct reloc *reloc;
4439         struct instruction *insn;
4440         int warnings = 0;
4441
4442         for_each_insn(file, insn)
4443                 warnings += validate_ibt_insn(file, insn);
4444
4445         for_each_sec(file, sec) {
4446
4447                 /* Already done by validate_ibt_insn() */
4448                 if (sec->sh.sh_flags & SHF_EXECINSTR)
4449                         continue;
4450
4451                 if (!sec->rsec)
4452                         continue;
4453
4454                 /*
4455                  * These sections can reference text addresses, but not with
4456                  * the intent to indirect branch to them.
4457                  */
4458                 if ((!strncmp(sec->name, ".discard", 8) &&
4459                      strcmp(sec->name, ".discard.ibt_endbr_noseal"))    ||
4460                     !strncmp(sec->name, ".debug", 6)                    ||
4461                     !strcmp(sec->name, ".altinstructions")              ||
4462                     !strcmp(sec->name, ".ibt_endbr_seal")               ||
4463                     !strcmp(sec->name, ".orc_unwind_ip")                ||
4464                     !strcmp(sec->name, ".parainstructions")             ||
4465                     !strcmp(sec->name, ".retpoline_sites")              ||
4466                     !strcmp(sec->name, ".smp_locks")                    ||
4467                     !strcmp(sec->name, ".static_call_sites")            ||
4468                     !strcmp(sec->name, "_error_injection_whitelist")    ||
4469                     !strcmp(sec->name, "_kprobe_blacklist")             ||
4470                     !strcmp(sec->name, "__bug_table")                   ||
4471                     !strcmp(sec->name, "__ex_table")                    ||
4472                     !strcmp(sec->name, "__jump_table")                  ||
4473                     !strcmp(sec->name, "__mcount_loc")                  ||
4474                     !strcmp(sec->name, ".kcfi_traps")                   ||
4475                     strstr(sec->name, "__patchable_function_entries"))
4476                         continue;
4477
4478                 for_each_reloc(sec->rsec, reloc)
4479                         warnings += validate_ibt_data_reloc(file, reloc);
4480         }
4481
4482         return warnings;
4483 }
4484
4485 static int validate_sls(struct objtool_file *file)
4486 {
4487         struct instruction *insn, *next_insn;
4488         int warnings = 0;
4489
4490         for_each_insn(file, insn) {
4491                 next_insn = next_insn_same_sec(file, insn);
4492
4493                 if (insn->retpoline_safe)
4494                         continue;
4495
4496                 switch (insn->type) {
4497                 case INSN_RETURN:
4498                         if (!next_insn || next_insn->type != INSN_TRAP) {
4499                                 WARN_INSN(insn, "missing int3 after ret");
4500                                 warnings++;
4501                         }
4502
4503                         break;
4504                 case INSN_JUMP_DYNAMIC:
4505                         if (!next_insn || next_insn->type != INSN_TRAP) {
4506                                 WARN_INSN(insn, "missing int3 after indirect jump");
4507                                 warnings++;
4508                         }
4509                         break;
4510                 default:
4511                         break;
4512                 }
4513         }
4514
4515         return warnings;
4516 }
4517
4518 static bool ignore_noreturn_call(struct instruction *insn)
4519 {
4520         struct symbol *call_dest = insn_call_dest(insn);
4521
4522         /*
4523          * FIXME: hack, we need a real noreturn solution
4524          *
4525          * Problem is, exc_double_fault() may or may not return, depending on
4526          * whether CONFIG_X86_ESPFIX64 is set.  But objtool has no visibility
4527          * to the kernel config.
4528          *
4529          * Other potential ways to fix it:
4530          *
4531          *   - have compiler communicate __noreturn functions somehow
4532          *   - remove CONFIG_X86_ESPFIX64
4533          *   - read the .config file
4534          *   - add a cmdline option
4535          *   - create a generic objtool annotation format (vs a bunch of custom
4536          *     formats) and annotate it
4537          */
4538         if (!strcmp(call_dest->name, "exc_double_fault")) {
4539                 /* prevent further unreachable warnings for the caller */
4540                 insn->sym->warned = 1;
4541                 return true;
4542         }
4543
4544         return false;
4545 }
4546
4547 static int validate_reachable_instructions(struct objtool_file *file)
4548 {
4549         struct instruction *insn, *prev_insn;
4550         struct symbol *call_dest;
4551         int warnings = 0;
4552
4553         if (file->ignore_unreachables)
4554                 return 0;
4555
4556         for_each_insn(file, insn) {
4557                 if (insn->visited || ignore_unreachable_insn(file, insn))
4558                         continue;
4559
4560                 prev_insn = prev_insn_same_sec(file, insn);
4561                 if (prev_insn && prev_insn->dead_end) {
4562                         call_dest = insn_call_dest(prev_insn);
4563                         if (call_dest && !ignore_noreturn_call(prev_insn)) {
4564                                 WARN_INSN(insn, "%s() is missing a __noreturn annotation",
4565                                           call_dest->name);
4566                                 warnings++;
4567                                 continue;
4568                         }
4569                 }
4570
4571                 WARN_INSN(insn, "unreachable instruction");
4572                 warnings++;
4573         }
4574
4575         return warnings;
4576 }
4577
4578 /* 'funcs' is a space-separated list of function names */
4579 static int disas_funcs(const char *funcs)
4580 {
4581         const char *objdump_str, *cross_compile;
4582         int size, ret;
4583         char *cmd;
4584
4585         cross_compile = getenv("CROSS_COMPILE");
4586
4587         objdump_str = "%sobjdump -wdr %s | gawk -M -v _funcs='%s' '"
4588                         "BEGIN { split(_funcs, funcs); }"
4589                         "/^$/ { func_match = 0; }"
4590                         "/<.*>:/ { "
4591                                 "f = gensub(/.*<(.*)>:/, \"\\\\1\", 1);"
4592                                 "for (i in funcs) {"
4593                                         "if (funcs[i] == f) {"
4594                                                 "func_match = 1;"
4595                                                 "base = strtonum(\"0x\" $1);"
4596                                                 "break;"
4597                                         "}"
4598                                 "}"
4599                         "}"
4600                         "{"
4601                                 "if (func_match) {"
4602                                         "addr = strtonum(\"0x\" $1);"
4603                                         "printf(\"%%04x \", addr - base);"
4604                                         "print;"
4605                                 "}"
4606                         "}' 1>&2";
4607
4608         /* fake snprintf() to calculate the size */
4609         size = snprintf(NULL, 0, objdump_str, cross_compile, objname, funcs) + 1;
4610         if (size <= 0) {
4611                 WARN("objdump string size calculation failed");
4612                 return -1;
4613         }
4614
4615         cmd = malloc(size);
4616
4617         /* real snprintf() */
4618         snprintf(cmd, size, objdump_str, cross_compile, objname, funcs);
4619         ret = system(cmd);
4620         if (ret) {
4621                 WARN("disassembly failed: %d", ret);
4622                 return -1;
4623         }
4624
4625         return 0;
4626 }
4627
4628 static int disas_warned_funcs(struct objtool_file *file)
4629 {
4630         struct symbol *sym;
4631         char *funcs = NULL, *tmp;
4632
4633         for_each_sym(file, sym) {
4634                 if (sym->warned) {
4635                         if (!funcs) {
4636                                 funcs = malloc(strlen(sym->name) + 1);
4637                                 strcpy(funcs, sym->name);
4638                         } else {
4639                                 tmp = malloc(strlen(funcs) + strlen(sym->name) + 2);
4640                                 sprintf(tmp, "%s %s", funcs, sym->name);
4641                                 free(funcs);
4642                                 funcs = tmp;
4643                         }
4644                 }
4645         }
4646
4647         if (funcs)
4648                 disas_funcs(funcs);
4649
4650         return 0;
4651 }
4652
4653 struct insn_chunk {
4654         void *addr;
4655         struct insn_chunk *next;
4656 };
4657
4658 /*
4659  * Reduce peak RSS usage by freeing insns memory before writing the ELF file,
4660  * which can trigger more allocations for .debug_* sections whose data hasn't
4661  * been read yet.
4662  */
4663 static void free_insns(struct objtool_file *file)
4664 {
4665         struct instruction *insn;
4666         struct insn_chunk *chunks = NULL, *chunk;
4667
4668         for_each_insn(file, insn) {
4669                 if (!insn->idx) {
4670                         chunk = malloc(sizeof(*chunk));
4671                         chunk->addr = insn;
4672                         chunk->next = chunks;
4673                         chunks = chunk;
4674                 }
4675         }
4676
4677         for (chunk = chunks; chunk; chunk = chunk->next)
4678                 free(chunk->addr);
4679 }
4680
4681 int check(struct objtool_file *file)
4682 {
4683         int ret, warnings = 0;
4684
4685         arch_initial_func_cfi_state(&initial_func_cfi);
4686         init_cfi_state(&init_cfi);
4687         init_cfi_state(&func_cfi);
4688         set_func_state(&func_cfi);
4689         init_cfi_state(&force_undefined_cfi);
4690         force_undefined_cfi.force_undefined = true;
4691
4692         if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
4693                 goto out;
4694
4695         cfi_hash_add(&init_cfi);
4696         cfi_hash_add(&func_cfi);
4697
4698         ret = decode_sections(file);
4699         if (ret < 0)
4700                 goto out;
4701
4702         warnings += ret;
4703
4704         if (!nr_insns)
4705                 goto out;
4706
4707         if (opts.retpoline) {
4708                 ret = validate_retpoline(file);
4709                 if (ret < 0)
4710                         return ret;
4711                 warnings += ret;
4712         }
4713
4714         if (opts.stackval || opts.orc || opts.uaccess) {
4715                 ret = validate_functions(file);
4716                 if (ret < 0)
4717                         goto out;
4718                 warnings += ret;
4719
4720                 ret = validate_unwind_hints(file, NULL);
4721                 if (ret < 0)
4722                         goto out;
4723                 warnings += ret;
4724
4725                 if (!warnings) {
4726                         ret = validate_reachable_instructions(file);
4727                         if (ret < 0)
4728                                 goto out;
4729                         warnings += ret;
4730                 }
4731
4732         } else if (opts.noinstr) {
4733                 ret = validate_noinstr_sections(file);
4734                 if (ret < 0)
4735                         goto out;
4736                 warnings += ret;
4737         }
4738
4739         if (opts.unret) {
4740                 /*
4741                  * Must be after validate_branch() and friends, it plays
4742                  * further games with insn->visited.
4743                  */
4744                 ret = validate_unrets(file);
4745                 if (ret < 0)
4746                         return ret;
4747                 warnings += ret;
4748         }
4749
4750         if (opts.ibt) {
4751                 ret = validate_ibt(file);
4752                 if (ret < 0)
4753                         goto out;
4754                 warnings += ret;
4755         }
4756
4757         if (opts.sls) {
4758                 ret = validate_sls(file);
4759                 if (ret < 0)
4760                         goto out;
4761                 warnings += ret;
4762         }
4763
4764         if (opts.static_call) {
4765                 ret = create_static_call_sections(file);
4766                 if (ret < 0)
4767                         goto out;
4768                 warnings += ret;
4769         }
4770
4771         if (opts.retpoline) {
4772                 ret = create_retpoline_sites_sections(file);
4773                 if (ret < 0)
4774                         goto out;
4775                 warnings += ret;
4776         }
4777
4778         if (opts.cfi) {
4779                 ret = create_cfi_sections(file);
4780                 if (ret < 0)
4781                         goto out;
4782                 warnings += ret;
4783         }
4784
4785         if (opts.rethunk) {
4786                 ret = create_return_sites_sections(file);
4787                 if (ret < 0)
4788                         goto out;
4789                 warnings += ret;
4790
4791                 if (opts.hack_skylake) {
4792                         ret = create_direct_call_sections(file);
4793                         if (ret < 0)
4794                                 goto out;
4795                         warnings += ret;
4796                 }
4797         }
4798
4799         if (opts.mcount) {
4800                 ret = create_mcount_loc_sections(file);
4801                 if (ret < 0)
4802                         goto out;
4803                 warnings += ret;
4804         }
4805
4806         if (opts.prefix) {
4807                 ret = add_prefix_symbols(file);
4808                 if (ret < 0)
4809                         return ret;
4810                 warnings += ret;
4811         }
4812
4813         if (opts.ibt) {
4814                 ret = create_ibt_endbr_seal_sections(file);
4815                 if (ret < 0)
4816                         goto out;
4817                 warnings += ret;
4818         }
4819
4820         if (opts.orc && nr_insns) {
4821                 ret = orc_create(file);
4822                 if (ret < 0)
4823                         goto out;
4824                 warnings += ret;
4825         }
4826
4827         free_insns(file);
4828
4829         if (opts.verbose)
4830                 disas_warned_funcs(file);
4831
4832         if (opts.stats) {
4833                 printf("nr_insns_visited: %ld\n", nr_insns_visited);
4834                 printf("nr_cfi: %ld\n", nr_cfi);
4835                 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
4836                 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
4837         }
4838
4839 out:
4840         /*
4841          *  For now, don't fail the kernel build on fatal warnings.  These
4842          *  errors are still fairly common due to the growing matrix of
4843          *  supported toolchains and their recent pace of change.
4844          */
4845         return 0;
4846 }