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(sizeof(struct cfi_state), 1);
 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                  * Cross-function jump.
1615                  */
1616                 if (insn_func(insn) && insn_func(jump_dest) &&
1617                     insn_func(insn) != insn_func(jump_dest)) {
1618
1619                         /*
1620                          * For GCC 8+, create parent/child links for any cold
1621                          * subfunctions.  This is _mostly_ redundant with a
1622                          * similar initialization in read_symbols().
1623                          *
1624                          * If a function has aliases, we want the *first* such
1625                          * function in the symbol table to be the subfunction's
1626                          * parent.  In that case we overwrite the
1627                          * initialization done in read_symbols().
1628                          *
1629                          * However this code can't completely replace the
1630                          * read_symbols() code because this doesn't detect the
1631                          * case where the parent function's only reference to a
1632                          * subfunction is through a jump table.
1633                          */
1634                         if (!strstr(insn_func(insn)->name, ".cold") &&
1635                             strstr(insn_func(jump_dest)->name, ".cold")) {
1636                                 insn_func(insn)->cfunc = insn_func(jump_dest);
1637                                 insn_func(jump_dest)->pfunc = insn_func(insn);
1638                         }
1639                 }
1640
1641                 if (jump_is_sibling_call(file, insn, jump_dest)) {
1642                         /*
1643                          * Internal sibling call without reloc or with
1644                          * STT_SECTION reloc.
1645                          */
1646                         add_call_dest(file, insn, insn_func(jump_dest), true);
1647                         continue;
1648                 }
1649
1650                 insn->jump_dest = jump_dest;
1651         }
1652
1653         return 0;
1654 }
1655
1656 static struct symbol *find_call_destination(struct section *sec, unsigned long offset)
1657 {
1658         struct symbol *call_dest;
1659
1660         call_dest = find_func_by_offset(sec, offset);
1661         if (!call_dest)
1662                 call_dest = find_symbol_by_offset(sec, offset);
1663
1664         return call_dest;
1665 }
1666
1667 /*
1668  * Find the destination instructions for all calls.
1669  */
1670 static int add_call_destinations(struct objtool_file *file)
1671 {
1672         struct instruction *insn;
1673         unsigned long dest_off;
1674         struct symbol *dest;
1675         struct reloc *reloc;
1676
1677         for_each_insn(file, insn) {
1678                 if (insn->type != INSN_CALL)
1679                         continue;
1680
1681                 reloc = insn_reloc(file, insn);
1682                 if (!reloc) {
1683                         dest_off = arch_jump_destination(insn);
1684                         dest = find_call_destination(insn->sec, dest_off);
1685
1686                         add_call_dest(file, insn, dest, false);
1687
1688                         if (insn->ignore)
1689                                 continue;
1690
1691                         if (!insn_call_dest(insn)) {
1692                                 WARN_INSN(insn, "unannotated intra-function call");
1693                                 return -1;
1694                         }
1695
1696                         if (insn_func(insn) && insn_call_dest(insn)->type != STT_FUNC) {
1697                                 WARN_INSN(insn, "unsupported call to non-function");
1698                                 return -1;
1699                         }
1700
1701                 } else if (reloc->sym->type == STT_SECTION) {
1702                         dest_off = arch_dest_reloc_offset(reloc_addend(reloc));
1703                         dest = find_call_destination(reloc->sym->sec, dest_off);
1704                         if (!dest) {
1705                                 WARN_INSN(insn, "can't find call dest symbol at %s+0x%lx",
1706                                           reloc->sym->sec->name, dest_off);
1707                                 return -1;
1708                         }
1709
1710                         add_call_dest(file, insn, dest, false);
1711
1712                 } else if (reloc->sym->retpoline_thunk) {
1713                         add_retpoline_call(file, insn);
1714
1715                 } else
1716                         add_call_dest(file, insn, reloc->sym, false);
1717         }
1718
1719         return 0;
1720 }
1721
1722 /*
1723  * The .alternatives section requires some extra special care over and above
1724  * other special sections because alternatives are patched in place.
1725  */
1726 static int handle_group_alt(struct objtool_file *file,
1727                             struct special_alt *special_alt,
1728                             struct instruction *orig_insn,
1729                             struct instruction **new_insn)
1730 {
1731         struct instruction *last_new_insn = NULL, *insn, *nop = NULL;
1732         struct alt_group *orig_alt_group, *new_alt_group;
1733         unsigned long dest_off;
1734
1735         orig_alt_group = orig_insn->alt_group;
1736         if (!orig_alt_group) {
1737                 struct instruction *last_orig_insn = NULL;
1738
1739                 orig_alt_group = malloc(sizeof(*orig_alt_group));
1740                 if (!orig_alt_group) {
1741                         WARN("malloc failed");
1742                         return -1;
1743                 }
1744                 orig_alt_group->cfi = calloc(special_alt->orig_len,
1745                                              sizeof(struct cfi_state *));
1746                 if (!orig_alt_group->cfi) {
1747                         WARN("calloc failed");
1748                         return -1;
1749                 }
1750
1751                 insn = orig_insn;
1752                 sec_for_each_insn_from(file, insn) {
1753                         if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
1754                                 break;
1755
1756                         insn->alt_group = orig_alt_group;
1757                         last_orig_insn = insn;
1758                 }
1759                 orig_alt_group->orig_group = NULL;
1760                 orig_alt_group->first_insn = orig_insn;
1761                 orig_alt_group->last_insn = last_orig_insn;
1762                 orig_alt_group->nop = NULL;
1763         } else {
1764                 if (orig_alt_group->last_insn->offset + orig_alt_group->last_insn->len -
1765                     orig_alt_group->first_insn->offset != special_alt->orig_len) {
1766                         WARN_INSN(orig_insn, "weirdly overlapping alternative! %ld != %d",
1767                                   orig_alt_group->last_insn->offset +
1768                                   orig_alt_group->last_insn->len -
1769                                   orig_alt_group->first_insn->offset,
1770                                   special_alt->orig_len);
1771                         return -1;
1772                 }
1773         }
1774
1775         new_alt_group = malloc(sizeof(*new_alt_group));
1776         if (!new_alt_group) {
1777                 WARN("malloc failed");
1778                 return -1;
1779         }
1780
1781         if (special_alt->new_len < special_alt->orig_len) {
1782                 /*
1783                  * Insert a fake nop at the end to make the replacement
1784                  * alt_group the same size as the original.  This is needed to
1785                  * allow propagate_alt_cfi() to do its magic.  When the last
1786                  * instruction affects the stack, the instruction after it (the
1787                  * nop) will propagate the new state to the shared CFI array.
1788                  */
1789                 nop = malloc(sizeof(*nop));
1790                 if (!nop) {
1791                         WARN("malloc failed");
1792                         return -1;
1793                 }
1794                 memset(nop, 0, sizeof(*nop));
1795
1796                 nop->sec = special_alt->new_sec;
1797                 nop->offset = special_alt->new_off + special_alt->new_len;
1798                 nop->len = special_alt->orig_len - special_alt->new_len;
1799                 nop->type = INSN_NOP;
1800                 nop->sym = orig_insn->sym;
1801                 nop->alt_group = new_alt_group;
1802                 nop->ignore = orig_insn->ignore_alts;
1803         }
1804
1805         if (!special_alt->new_len) {
1806                 *new_insn = nop;
1807                 goto end;
1808         }
1809
1810         insn = *new_insn;
1811         sec_for_each_insn_from(file, insn) {
1812                 struct reloc *alt_reloc;
1813
1814                 if (insn->offset >= special_alt->new_off + special_alt->new_len)
1815                         break;
1816
1817                 last_new_insn = insn;
1818
1819                 insn->ignore = orig_insn->ignore_alts;
1820                 insn->sym = orig_insn->sym;
1821                 insn->alt_group = new_alt_group;
1822
1823                 /*
1824                  * Since alternative replacement code is copy/pasted by the
1825                  * kernel after applying relocations, generally such code can't
1826                  * have relative-address relocation references to outside the
1827                  * .altinstr_replacement section, unless the arch's
1828                  * alternatives code can adjust the relative offsets
1829                  * accordingly.
1830                  */
1831                 alt_reloc = insn_reloc(file, insn);
1832                 if (alt_reloc && arch_pc_relative_reloc(alt_reloc) &&
1833                     !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
1834
1835                         WARN_INSN(insn, "unsupported relocation in alternatives section");
1836                         return -1;
1837                 }
1838
1839                 if (!is_static_jump(insn))
1840                         continue;
1841
1842                 if (!insn->immediate)
1843                         continue;
1844
1845                 dest_off = arch_jump_destination(insn);
1846                 if (dest_off == special_alt->new_off + special_alt->new_len) {
1847                         insn->jump_dest = next_insn_same_sec(file, orig_alt_group->last_insn);
1848                         if (!insn->jump_dest) {
1849                                 WARN_INSN(insn, "can't find alternative jump destination");
1850                                 return -1;
1851                         }
1852                 }
1853         }
1854
1855         if (!last_new_insn) {
1856                 WARN_FUNC("can't find last new alternative instruction",
1857                           special_alt->new_sec, special_alt->new_off);
1858                 return -1;
1859         }
1860
1861 end:
1862         new_alt_group->orig_group = orig_alt_group;
1863         new_alt_group->first_insn = *new_insn;
1864         new_alt_group->last_insn = last_new_insn;
1865         new_alt_group->nop = nop;
1866         new_alt_group->cfi = orig_alt_group->cfi;
1867         return 0;
1868 }
1869
1870 /*
1871  * A jump table entry can either convert a nop to a jump or a jump to a nop.
1872  * If the original instruction is a jump, make the alt entry an effective nop
1873  * by just skipping the original instruction.
1874  */
1875 static int handle_jump_alt(struct objtool_file *file,
1876                            struct special_alt *special_alt,
1877                            struct instruction *orig_insn,
1878                            struct instruction **new_insn)
1879 {
1880         if (orig_insn->type != INSN_JUMP_UNCONDITIONAL &&
1881             orig_insn->type != INSN_NOP) {
1882
1883                 WARN_INSN(orig_insn, "unsupported instruction at jump label");
1884                 return -1;
1885         }
1886
1887         if (opts.hack_jump_label && special_alt->key_addend & 2) {
1888                 struct reloc *reloc = insn_reloc(file, orig_insn);
1889
1890                 if (reloc)
1891                         set_reloc_type(file->elf, reloc, R_NONE);
1892                 elf_write_insn(file->elf, orig_insn->sec,
1893                                orig_insn->offset, orig_insn->len,
1894                                arch_nop_insn(orig_insn->len));
1895                 orig_insn->type = INSN_NOP;
1896         }
1897
1898         if (orig_insn->type == INSN_NOP) {
1899                 if (orig_insn->len == 2)
1900                         file->jl_nop_short++;
1901                 else
1902                         file->jl_nop_long++;
1903
1904                 return 0;
1905         }
1906
1907         if (orig_insn->len == 2)
1908                 file->jl_short++;
1909         else
1910                 file->jl_long++;
1911
1912         *new_insn = next_insn_same_sec(file, orig_insn);
1913         return 0;
1914 }
1915
1916 /*
1917  * Read all the special sections which have alternate instructions which can be
1918  * patched in or redirected to at runtime.  Each instruction having alternate
1919  * instruction(s) has them added to its insn->alts list, which will be
1920  * traversed in validate_branch().
1921  */
1922 static int add_special_section_alts(struct objtool_file *file)
1923 {
1924         struct list_head special_alts;
1925         struct instruction *orig_insn, *new_insn;
1926         struct special_alt *special_alt, *tmp;
1927         struct alternative *alt;
1928         int ret;
1929
1930         ret = special_get_alts(file->elf, &special_alts);
1931         if (ret)
1932                 return ret;
1933
1934         list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
1935
1936                 orig_insn = find_insn(file, special_alt->orig_sec,
1937                                       special_alt->orig_off);
1938                 if (!orig_insn) {
1939                         WARN_FUNC("special: can't find orig instruction",
1940                                   special_alt->orig_sec, special_alt->orig_off);
1941                         ret = -1;
1942                         goto out;
1943                 }
1944
1945                 new_insn = NULL;
1946                 if (!special_alt->group || special_alt->new_len) {
1947                         new_insn = find_insn(file, special_alt->new_sec,
1948                                              special_alt->new_off);
1949                         if (!new_insn) {
1950                                 WARN_FUNC("special: can't find new instruction",
1951                                           special_alt->new_sec,
1952                                           special_alt->new_off);
1953                                 ret = -1;
1954                                 goto out;
1955                         }
1956                 }
1957
1958                 if (special_alt->group) {
1959                         if (!special_alt->orig_len) {
1960                                 WARN_INSN(orig_insn, "empty alternative entry");
1961                                 continue;
1962                         }
1963
1964                         ret = handle_group_alt(file, special_alt, orig_insn,
1965                                                &new_insn);
1966                         if (ret)
1967                                 goto out;
1968                 } else if (special_alt->jump_or_nop) {
1969                         ret = handle_jump_alt(file, special_alt, orig_insn,
1970                                               &new_insn);
1971                         if (ret)
1972                                 goto out;
1973                 }
1974
1975                 alt = malloc(sizeof(*alt));
1976                 if (!alt) {
1977                         WARN("malloc failed");
1978                         ret = -1;
1979                         goto out;
1980                 }
1981
1982                 alt->insn = new_insn;
1983                 alt->skip_orig = special_alt->skip_orig;
1984                 orig_insn->ignore_alts |= special_alt->skip_alt;
1985                 alt->next = orig_insn->alts;
1986                 orig_insn->alts = alt;
1987
1988                 list_del(&special_alt->list);
1989                 free(special_alt);
1990         }
1991
1992         if (opts.stats) {
1993                 printf("jl\\\tNOP\tJMP\n");
1994                 printf("short:\t%ld\t%ld\n", file->jl_nop_short, file->jl_short);
1995                 printf("long:\t%ld\t%ld\n", file->jl_nop_long, file->jl_long);
1996         }
1997
1998 out:
1999         return ret;
2000 }
2001
2002 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
2003                           struct reloc *next_table)
2004 {
2005         struct symbol *pfunc = insn_func(insn)->pfunc;
2006         struct reloc *table = insn_jump_table(insn);
2007         struct instruction *dest_insn;
2008         unsigned int prev_offset = 0;
2009         struct reloc *reloc = table;
2010         struct alternative *alt;
2011
2012         /*
2013          * Each @reloc is a switch table relocation which points to the target
2014          * instruction.
2015          */
2016         for_each_reloc_from(table->sec, reloc) {
2017
2018                 /* Check for the end of the table: */
2019                 if (reloc != table && reloc == next_table)
2020                         break;
2021
2022                 /* Make sure the table entries are consecutive: */
2023                 if (prev_offset && reloc_offset(reloc) != prev_offset + 8)
2024                         break;
2025
2026                 /* Detect function pointers from contiguous objects: */
2027                 if (reloc->sym->sec == pfunc->sec &&
2028                     reloc_addend(reloc) == pfunc->offset)
2029                         break;
2030
2031                 dest_insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2032                 if (!dest_insn)
2033                         break;
2034
2035                 /* Make sure the destination is in the same function: */
2036                 if (!insn_func(dest_insn) || insn_func(dest_insn)->pfunc != pfunc)
2037                         break;
2038
2039                 alt = malloc(sizeof(*alt));
2040                 if (!alt) {
2041                         WARN("malloc failed");
2042                         return -1;
2043                 }
2044
2045                 alt->insn = dest_insn;
2046                 alt->next = insn->alts;
2047                 insn->alts = alt;
2048                 prev_offset = reloc_offset(reloc);
2049         }
2050
2051         if (!prev_offset) {
2052                 WARN_INSN(insn, "can't find switch jump table");
2053                 return -1;
2054         }
2055
2056         return 0;
2057 }
2058
2059 /*
2060  * find_jump_table() - Given a dynamic jump, find the switch jump table
2061  * associated with it.
2062  */
2063 static struct reloc *find_jump_table(struct objtool_file *file,
2064                                       struct symbol *func,
2065                                       struct instruction *insn)
2066 {
2067         struct reloc *table_reloc;
2068         struct instruction *dest_insn, *orig_insn = insn;
2069
2070         /*
2071          * Backward search using the @first_jump_src links, these help avoid
2072          * much of the 'in between' code. Which avoids us getting confused by
2073          * it.
2074          */
2075         for (;
2076              insn && insn_func(insn) && insn_func(insn)->pfunc == func;
2077              insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
2078
2079                 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
2080                         break;
2081
2082                 /* allow small jumps within the range */
2083                 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
2084                     insn->jump_dest &&
2085                     (insn->jump_dest->offset <= insn->offset ||
2086                      insn->jump_dest->offset > orig_insn->offset))
2087                     break;
2088
2089                 table_reloc = arch_find_switch_table(file, insn);
2090                 if (!table_reloc)
2091                         continue;
2092                 dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
2093                 if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
2094                         continue;
2095
2096                 return table_reloc;
2097         }
2098
2099         return NULL;
2100 }
2101
2102 /*
2103  * First pass: Mark the head of each jump table so that in the next pass,
2104  * we know when a given jump table ends and the next one starts.
2105  */
2106 static void mark_func_jump_tables(struct objtool_file *file,
2107                                     struct symbol *func)
2108 {
2109         struct instruction *insn, *last = NULL;
2110         struct reloc *reloc;
2111
2112         func_for_each_insn(file, func, insn) {
2113                 if (!last)
2114                         last = insn;
2115
2116                 /*
2117                  * Store back-pointers for unconditional forward jumps such
2118                  * that find_jump_table() can back-track using those and
2119                  * avoid some potentially confusing code.
2120                  */
2121                 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
2122                     insn->offset > last->offset &&
2123                     insn->jump_dest->offset > insn->offset &&
2124                     !insn->jump_dest->first_jump_src) {
2125
2126                         insn->jump_dest->first_jump_src = insn;
2127                         last = insn->jump_dest;
2128                 }
2129
2130                 if (insn->type != INSN_JUMP_DYNAMIC)
2131                         continue;
2132
2133                 reloc = find_jump_table(file, func, insn);
2134                 if (reloc)
2135                         insn->_jump_table = reloc;
2136         }
2137 }
2138
2139 static int add_func_jump_tables(struct objtool_file *file,
2140                                   struct symbol *func)
2141 {
2142         struct instruction *insn, *insn_t1 = NULL, *insn_t2;
2143         int ret = 0;
2144
2145         func_for_each_insn(file, func, insn) {
2146                 if (!insn_jump_table(insn))
2147                         continue;
2148
2149                 if (!insn_t1) {
2150                         insn_t1 = insn;
2151                         continue;
2152                 }
2153
2154                 insn_t2 = insn;
2155
2156                 ret = add_jump_table(file, insn_t1, insn_jump_table(insn_t2));
2157                 if (ret)
2158                         return ret;
2159
2160                 insn_t1 = insn_t2;
2161         }
2162
2163         if (insn_t1)
2164                 ret = add_jump_table(file, insn_t1, NULL);
2165
2166         return ret;
2167 }
2168
2169 /*
2170  * For some switch statements, gcc generates a jump table in the .rodata
2171  * section which contains a list of addresses within the function to jump to.
2172  * This finds these jump tables and adds them to the insn->alts lists.
2173  */
2174 static int add_jump_table_alts(struct objtool_file *file)
2175 {
2176         struct symbol *func;
2177         int ret;
2178
2179         if (!file->rodata)
2180                 return 0;
2181
2182         for_each_sym(file, func) {
2183                 if (func->type != STT_FUNC)
2184                         continue;
2185
2186                 mark_func_jump_tables(file, func);
2187                 ret = add_func_jump_tables(file, func);
2188                 if (ret)
2189                         return ret;
2190         }
2191
2192         return 0;
2193 }
2194
2195 static void set_func_state(struct cfi_state *state)
2196 {
2197         state->cfa = initial_func_cfi.cfa;
2198         memcpy(&state->regs, &initial_func_cfi.regs,
2199                CFI_NUM_REGS * sizeof(struct cfi_reg));
2200         state->stack_size = initial_func_cfi.cfa.offset;
2201         state->type = UNWIND_HINT_TYPE_CALL;
2202 }
2203
2204 static int read_unwind_hints(struct objtool_file *file)
2205 {
2206         struct cfi_state cfi = init_cfi;
2207         struct section *sec;
2208         struct unwind_hint *hint;
2209         struct instruction *insn;
2210         struct reloc *reloc;
2211         int i;
2212
2213         sec = find_section_by_name(file->elf, ".discard.unwind_hints");
2214         if (!sec)
2215                 return 0;
2216
2217         if (!sec->rsec) {
2218                 WARN("missing .rela.discard.unwind_hints section");
2219                 return -1;
2220         }
2221
2222         if (sec->sh.sh_size % sizeof(struct unwind_hint)) {
2223                 WARN("struct unwind_hint size mismatch");
2224                 return -1;
2225         }
2226
2227         file->hints = true;
2228
2229         for (i = 0; i < sec->sh.sh_size / sizeof(struct unwind_hint); i++) {
2230                 hint = (struct unwind_hint *)sec->data->d_buf + i;
2231
2232                 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
2233                 if (!reloc) {
2234                         WARN("can't find reloc for unwind_hints[%d]", i);
2235                         return -1;
2236                 }
2237
2238                 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2239                 if (!insn) {
2240                         WARN("can't find insn for unwind_hints[%d]", i);
2241                         return -1;
2242                 }
2243
2244                 insn->hint = true;
2245
2246                 if (hint->type == UNWIND_HINT_TYPE_UNDEFINED) {
2247                         insn->cfi = &force_undefined_cfi;
2248                         continue;
2249                 }
2250
2251                 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
2252                         insn->hint = false;
2253                         insn->save = true;
2254                         continue;
2255                 }
2256
2257                 if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
2258                         insn->restore = true;
2259                         continue;
2260                 }
2261
2262                 if (hint->type == UNWIND_HINT_TYPE_REGS_PARTIAL) {
2263                         struct symbol *sym = find_symbol_by_offset(insn->sec, insn->offset);
2264
2265                         if (sym && sym->bind == STB_GLOBAL) {
2266                                 if (opts.ibt && insn->type != INSN_ENDBR && !insn->noendbr) {
2267                                         WARN_INSN(insn, "UNWIND_HINT_IRET_REGS without ENDBR");
2268                                 }
2269                         }
2270                 }
2271
2272                 if (hint->type == UNWIND_HINT_TYPE_FUNC) {
2273                         insn->cfi = &func_cfi;
2274                         continue;
2275                 }
2276
2277                 if (insn->cfi)
2278                         cfi = *(insn->cfi);
2279
2280                 if (arch_decode_hint_reg(hint->sp_reg, &cfi.cfa.base)) {
2281                         WARN_INSN(insn, "unsupported unwind_hint sp base reg %d", hint->sp_reg);
2282                         return -1;
2283                 }
2284
2285                 cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
2286                 cfi.type = hint->type;
2287                 cfi.signal = hint->signal;
2288
2289                 insn->cfi = cfi_hash_find_or_add(&cfi);
2290         }
2291
2292         return 0;
2293 }
2294
2295 static int read_noendbr_hints(struct objtool_file *file)
2296 {
2297         struct instruction *insn;
2298         struct section *rsec;
2299         struct reloc *reloc;
2300
2301         rsec = find_section_by_name(file->elf, ".rela.discard.noendbr");
2302         if (!rsec)
2303                 return 0;
2304
2305         for_each_reloc(rsec, reloc) {
2306                 insn = find_insn(file, reloc->sym->sec,
2307                                  reloc->sym->offset + reloc_addend(reloc));
2308                 if (!insn) {
2309                         WARN("bad .discard.noendbr entry");
2310                         return -1;
2311                 }
2312
2313                 insn->noendbr = 1;
2314         }
2315
2316         return 0;
2317 }
2318
2319 static int read_retpoline_hints(struct objtool_file *file)
2320 {
2321         struct section *rsec;
2322         struct instruction *insn;
2323         struct reloc *reloc;
2324
2325         rsec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
2326         if (!rsec)
2327                 return 0;
2328
2329         for_each_reloc(rsec, reloc) {
2330                 if (reloc->sym->type != STT_SECTION) {
2331                         WARN("unexpected relocation symbol type in %s", rsec->name);
2332                         return -1;
2333                 }
2334
2335                 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2336                 if (!insn) {
2337                         WARN("bad .discard.retpoline_safe entry");
2338                         return -1;
2339                 }
2340
2341                 if (insn->type != INSN_JUMP_DYNAMIC &&
2342                     insn->type != INSN_CALL_DYNAMIC &&
2343                     insn->type != INSN_RETURN &&
2344                     insn->type != INSN_NOP) {
2345                         WARN_INSN(insn, "retpoline_safe hint not an indirect jump/call/ret/nop");
2346                         return -1;
2347                 }
2348
2349                 insn->retpoline_safe = true;
2350         }
2351
2352         return 0;
2353 }
2354
2355 static int read_instr_hints(struct objtool_file *file)
2356 {
2357         struct section *rsec;
2358         struct instruction *insn;
2359         struct reloc *reloc;
2360
2361         rsec = find_section_by_name(file->elf, ".rela.discard.instr_end");
2362         if (!rsec)
2363                 return 0;
2364
2365         for_each_reloc(rsec, reloc) {
2366                 if (reloc->sym->type != STT_SECTION) {
2367                         WARN("unexpected relocation symbol type in %s", rsec->name);
2368                         return -1;
2369                 }
2370
2371                 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2372                 if (!insn) {
2373                         WARN("bad .discard.instr_end entry");
2374                         return -1;
2375                 }
2376
2377                 insn->instr--;
2378         }
2379
2380         rsec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
2381         if (!rsec)
2382                 return 0;
2383
2384         for_each_reloc(rsec, reloc) {
2385                 if (reloc->sym->type != STT_SECTION) {
2386                         WARN("unexpected relocation symbol type in %s", rsec->name);
2387                         return -1;
2388                 }
2389
2390                 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2391                 if (!insn) {
2392                         WARN("bad .discard.instr_begin entry");
2393                         return -1;
2394                 }
2395
2396                 insn->instr++;
2397         }
2398
2399         return 0;
2400 }
2401
2402 static int read_validate_unret_hints(struct objtool_file *file)
2403 {
2404         struct section *rsec;
2405         struct instruction *insn;
2406         struct reloc *reloc;
2407
2408         rsec = find_section_by_name(file->elf, ".rela.discard.validate_unret");
2409         if (!rsec)
2410                 return 0;
2411
2412         for_each_reloc(rsec, reloc) {
2413                 if (reloc->sym->type != STT_SECTION) {
2414                         WARN("unexpected relocation symbol type in %s", rsec->name);
2415                         return -1;
2416                 }
2417
2418                 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2419                 if (!insn) {
2420                         WARN("bad .discard.instr_end entry");
2421                         return -1;
2422                 }
2423                 insn->unret = 1;
2424         }
2425
2426         return 0;
2427 }
2428
2429
2430 static int read_intra_function_calls(struct objtool_file *file)
2431 {
2432         struct instruction *insn;
2433         struct section *rsec;
2434         struct reloc *reloc;
2435
2436         rsec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
2437         if (!rsec)
2438                 return 0;
2439
2440         for_each_reloc(rsec, reloc) {
2441                 unsigned long dest_off;
2442
2443                 if (reloc->sym->type != STT_SECTION) {
2444                         WARN("unexpected relocation symbol type in %s",
2445                              rsec->name);
2446                         return -1;
2447                 }
2448
2449                 insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
2450                 if (!insn) {
2451                         WARN("bad .discard.intra_function_call entry");
2452                         return -1;
2453                 }
2454
2455                 if (insn->type != INSN_CALL) {
2456                         WARN_INSN(insn, "intra_function_call not a direct call");
2457                         return -1;
2458                 }
2459
2460                 /*
2461                  * Treat intra-function CALLs as JMPs, but with a stack_op.
2462                  * See add_call_destinations(), which strips stack_ops from
2463                  * normal CALLs.
2464                  */
2465                 insn->type = INSN_JUMP_UNCONDITIONAL;
2466
2467                 dest_off = arch_jump_destination(insn);
2468                 insn->jump_dest = find_insn(file, insn->sec, dest_off);
2469                 if (!insn->jump_dest) {
2470                         WARN_INSN(insn, "can't find call dest at %s+0x%lx",
2471                                   insn->sec->name, dest_off);
2472                         return -1;
2473                 }
2474         }
2475
2476         return 0;
2477 }
2478
2479 /*
2480  * Return true if name matches an instrumentation function, where calls to that
2481  * function from noinstr code can safely be removed, but compilers won't do so.
2482  */
2483 static bool is_profiling_func(const char *name)
2484 {
2485         /*
2486          * Many compilers cannot disable KCOV with a function attribute.
2487          */
2488         if (!strncmp(name, "__sanitizer_cov_", 16))
2489                 return true;
2490
2491         /*
2492          * Some compilers currently do not remove __tsan_func_entry/exit nor
2493          * __tsan_atomic_signal_fence (used for barrier instrumentation) with
2494          * the __no_sanitize_thread attribute, remove them. Once the kernel's
2495          * minimum Clang version is 14.0, this can be removed.
2496          */
2497         if (!strncmp(name, "__tsan_func_", 12) ||
2498             !strcmp(name, "__tsan_atomic_signal_fence"))
2499                 return true;
2500
2501         return false;
2502 }
2503
2504 static int classify_symbols(struct objtool_file *file)
2505 {
2506         struct symbol *func;
2507
2508         for_each_sym(file, func) {
2509                 if (func->bind != STB_GLOBAL)
2510                         continue;
2511
2512                 if (!strncmp(func->name, STATIC_CALL_TRAMP_PREFIX_STR,
2513                              strlen(STATIC_CALL_TRAMP_PREFIX_STR)))
2514                         func->static_call_tramp = true;
2515
2516                 if (arch_is_retpoline(func))
2517                         func->retpoline_thunk = true;
2518
2519                 if (arch_is_rethunk(func))
2520                         func->return_thunk = true;
2521
2522                 if (arch_is_embedded_insn(func))
2523                         func->embedded_insn = true;
2524
2525                 if (arch_ftrace_match(func->name))
2526                         func->fentry = true;
2527
2528                 if (is_profiling_func(func->name))
2529                         func->profiling_func = true;
2530         }
2531
2532         return 0;
2533 }
2534
2535 static void mark_rodata(struct objtool_file *file)
2536 {
2537         struct section *sec;
2538         bool found = false;
2539
2540         /*
2541          * Search for the following rodata sections, each of which can
2542          * potentially contain jump tables:
2543          *
2544          * - .rodata: can contain GCC switch tables
2545          * - .rodata.<func>: same, if -fdata-sections is being used
2546          * - .rodata..c_jump_table: contains C annotated jump tables
2547          *
2548          * .rodata.str1.* sections are ignored; they don't contain jump tables.
2549          */
2550         for_each_sec(file, sec) {
2551                 if (!strncmp(sec->name, ".rodata", 7) &&
2552                     !strstr(sec->name, ".str1.")) {
2553                         sec->rodata = true;
2554                         found = true;
2555                 }
2556         }
2557
2558         file->rodata = found;
2559 }
2560
2561 static int decode_sections(struct objtool_file *file)
2562 {
2563         int ret;
2564
2565         mark_rodata(file);
2566
2567         ret = init_pv_ops(file);
2568         if (ret)
2569                 return ret;
2570
2571         /*
2572          * Must be before add_{jump_call}_destination.
2573          */
2574         ret = classify_symbols(file);
2575         if (ret)
2576                 return ret;
2577
2578         ret = decode_instructions(file);
2579         if (ret)
2580                 return ret;
2581
2582         add_ignores(file);
2583         add_uaccess_safe(file);
2584
2585         ret = add_ignore_alternatives(file);
2586         if (ret)
2587                 return ret;
2588
2589         /*
2590          * Must be before read_unwind_hints() since that needs insn->noendbr.
2591          */
2592         ret = read_noendbr_hints(file);
2593         if (ret)
2594                 return ret;
2595
2596         /*
2597          * Must be before add_jump_destinations(), which depends on 'func'
2598          * being set for alternatives, to enable proper sibling call detection.
2599          */
2600         if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) {
2601                 ret = add_special_section_alts(file);
2602                 if (ret)
2603                         return ret;
2604         }
2605
2606         ret = add_jump_destinations(file);
2607         if (ret)
2608                 return ret;
2609
2610         /*
2611          * Must be before add_call_destination(); it changes INSN_CALL to
2612          * INSN_JUMP.
2613          */
2614         ret = read_intra_function_calls(file);
2615         if (ret)
2616                 return ret;
2617
2618         ret = add_call_destinations(file);
2619         if (ret)
2620                 return ret;
2621
2622         /*
2623          * Must be after add_call_destinations() such that it can override
2624          * dead_end_function() marks.
2625          */
2626         ret = add_dead_ends(file);
2627         if (ret)
2628                 return ret;
2629
2630         ret = add_jump_table_alts(file);
2631         if (ret)
2632                 return ret;
2633
2634         ret = read_unwind_hints(file);
2635         if (ret)
2636                 return ret;
2637
2638         ret = read_retpoline_hints(file);
2639         if (ret)
2640                 return ret;
2641
2642         ret = read_instr_hints(file);
2643         if (ret)
2644                 return ret;
2645
2646         ret = read_validate_unret_hints(file);
2647         if (ret)
2648                 return ret;
2649
2650         return 0;
2651 }
2652
2653 static bool is_special_call(struct instruction *insn)
2654 {
2655         if (insn->type == INSN_CALL) {
2656                 struct symbol *dest = insn_call_dest(insn);
2657
2658                 if (!dest)
2659                         return false;
2660
2661                 if (dest->fentry || dest->embedded_insn)
2662                         return true;
2663         }
2664
2665         return false;
2666 }
2667
2668 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
2669 {
2670         struct cfi_state *cfi = &state->cfi;
2671         int i;
2672
2673         if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
2674                 return true;
2675
2676         if (cfi->cfa.offset != initial_func_cfi.cfa.offset)
2677                 return true;
2678
2679         if (cfi->stack_size != initial_func_cfi.cfa.offset)
2680                 return true;
2681
2682         for (i = 0; i < CFI_NUM_REGS; i++) {
2683                 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
2684                     cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
2685                         return true;
2686         }
2687
2688         return false;
2689 }
2690
2691 static bool check_reg_frame_pos(const struct cfi_reg *reg,
2692                                 int expected_offset)
2693 {
2694         return reg->base == CFI_CFA &&
2695                reg->offset == expected_offset;
2696 }
2697
2698 static bool has_valid_stack_frame(struct insn_state *state)
2699 {
2700         struct cfi_state *cfi = &state->cfi;
2701
2702         if (cfi->cfa.base == CFI_BP &&
2703             check_reg_frame_pos(&cfi->regs[CFI_BP], -cfi->cfa.offset) &&
2704             check_reg_frame_pos(&cfi->regs[CFI_RA], -cfi->cfa.offset + 8))
2705                 return true;
2706
2707         if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
2708                 return true;
2709
2710         return false;
2711 }
2712
2713 static int update_cfi_state_regs(struct instruction *insn,
2714                                   struct cfi_state *cfi,
2715                                   struct stack_op *op)
2716 {
2717         struct cfi_reg *cfa = &cfi->cfa;
2718
2719         if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
2720                 return 0;
2721
2722         /* push */
2723         if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
2724                 cfa->offset += 8;
2725
2726         /* pop */
2727         if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
2728                 cfa->offset -= 8;
2729
2730         /* add immediate to sp */
2731         if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
2732             op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
2733                 cfa->offset -= op->src.offset;
2734
2735         return 0;
2736 }
2737
2738 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
2739 {
2740         if (arch_callee_saved_reg(reg) &&
2741             cfi->regs[reg].base == CFI_UNDEFINED) {
2742                 cfi->regs[reg].base = base;
2743                 cfi->regs[reg].offset = offset;
2744         }
2745 }
2746
2747 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
2748 {
2749         cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
2750         cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
2751 }
2752
2753 /*
2754  * A note about DRAP stack alignment:
2755  *
2756  * GCC has the concept of a DRAP register, which is used to help keep track of
2757  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
2758  * register.  The typical DRAP pattern is:
2759  *
2760  *   4c 8d 54 24 08             lea    0x8(%rsp),%r10
2761  *   48 83 e4 c0                and    $0xffffffffffffffc0,%rsp
2762  *   41 ff 72 f8                pushq  -0x8(%r10)
2763  *   55                         push   %rbp
2764  *   48 89 e5                   mov    %rsp,%rbp
2765  *                              (more pushes)
2766  *   41 52                      push   %r10
2767  *                              ...
2768  *   41 5a                      pop    %r10
2769  *                              (more pops)
2770  *   5d                         pop    %rbp
2771  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2772  *   c3                         retq
2773  *
2774  * There are some variations in the epilogues, like:
2775  *
2776  *   5b                         pop    %rbx
2777  *   41 5a                      pop    %r10
2778  *   41 5c                      pop    %r12
2779  *   41 5d                      pop    %r13
2780  *   41 5e                      pop    %r14
2781  *   c9                         leaveq
2782  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2783  *   c3                         retq
2784  *
2785  * and:
2786  *
2787  *   4c 8b 55 e8                mov    -0x18(%rbp),%r10
2788  *   48 8b 5d e0                mov    -0x20(%rbp),%rbx
2789  *   4c 8b 65 f0                mov    -0x10(%rbp),%r12
2790  *   4c 8b 6d f8                mov    -0x8(%rbp),%r13
2791  *   c9                         leaveq
2792  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
2793  *   c3                         retq
2794  *
2795  * Sometimes r13 is used as the DRAP register, in which case it's saved and
2796  * restored beforehand:
2797  *
2798  *   41 55                      push   %r13
2799  *   4c 8d 6c 24 10             lea    0x10(%rsp),%r13
2800  *   48 83 e4 f0                and    $0xfffffffffffffff0,%rsp
2801  *                              ...
2802  *   49 8d 65 f0                lea    -0x10(%r13),%rsp
2803  *   41 5d                      pop    %r13
2804  *   c3                         retq
2805  */
2806 static int update_cfi_state(struct instruction *insn,
2807                             struct instruction *next_insn,
2808                             struct cfi_state *cfi, struct stack_op *op)
2809 {
2810         struct cfi_reg *cfa = &cfi->cfa;
2811         struct cfi_reg *regs = cfi->regs;
2812
2813         /* ignore UNWIND_HINT_UNDEFINED regions */
2814         if (cfi->force_undefined)
2815                 return 0;
2816
2817         /* stack operations don't make sense with an undefined CFA */
2818         if (cfa->base == CFI_UNDEFINED) {
2819                 if (insn_func(insn)) {
2820                         WARN_INSN(insn, "undefined stack state");
2821                         return -1;
2822                 }
2823                 return 0;
2824         }
2825
2826         if (cfi->type == UNWIND_HINT_TYPE_REGS ||
2827             cfi->type == UNWIND_HINT_TYPE_REGS_PARTIAL)
2828                 return update_cfi_state_regs(insn, cfi, op);
2829
2830         switch (op->dest.type) {
2831
2832         case OP_DEST_REG:
2833                 switch (op->src.type) {
2834
2835                 case OP_SRC_REG:
2836                         if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
2837                             cfa->base == CFI_SP &&
2838                             check_reg_frame_pos(&regs[CFI_BP], -cfa->offset)) {
2839
2840                                 /* mov %rsp, %rbp */
2841                                 cfa->base = op->dest.reg;
2842                                 cfi->bp_scratch = false;
2843                         }
2844
2845                         else if (op->src.reg == CFI_SP &&
2846                                  op->dest.reg == CFI_BP && cfi->drap) {
2847
2848                                 /* drap: mov %rsp, %rbp */
2849                                 regs[CFI_BP].base = CFI_BP;
2850                                 regs[CFI_BP].offset = -cfi->stack_size;
2851                                 cfi->bp_scratch = false;
2852                         }
2853
2854                         else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2855
2856                                 /*
2857                                  * mov %rsp, %reg
2858                                  *
2859                                  * This is needed for the rare case where GCC
2860                                  * does:
2861                                  *
2862                                  *   mov    %rsp, %rax
2863                                  *   ...
2864                                  *   mov    %rax, %rsp
2865                                  */
2866                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2867                                 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
2868                         }
2869
2870                         else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
2871                                  (cfa->base == CFI_BP || cfa->base == cfi->drap_reg)) {
2872
2873                                 /*
2874                                  * mov %rbp, %rsp
2875                                  *
2876                                  * Restore the original stack pointer (Clang).
2877                                  */
2878                                 cfi->stack_size = -cfi->regs[CFI_BP].offset;
2879                         }
2880
2881                         else if (op->dest.reg == cfa->base) {
2882
2883                                 /* mov %reg, %rsp */
2884                                 if (cfa->base == CFI_SP &&
2885                                     cfi->vals[op->src.reg].base == CFI_CFA) {
2886
2887                                         /*
2888                                          * This is needed for the rare case
2889                                          * where GCC does something dumb like:
2890                                          *
2891                                          *   lea    0x8(%rsp), %rcx
2892                                          *   ...
2893                                          *   mov    %rcx, %rsp
2894                                          */
2895                                         cfa->offset = -cfi->vals[op->src.reg].offset;
2896                                         cfi->stack_size = cfa->offset;
2897
2898                                 } else if (cfa->base == CFI_SP &&
2899                                            cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2900                                            cfi->vals[op->src.reg].offset == cfa->offset) {
2901
2902                                         /*
2903                                          * Stack swizzle:
2904                                          *
2905                                          * 1: mov %rsp, (%[tos])
2906                                          * 2: mov %[tos], %rsp
2907                                          *    ...
2908                                          * 3: pop %rsp
2909                                          *
2910                                          * Where:
2911                                          *
2912                                          * 1 - places a pointer to the previous
2913                                          *     stack at the Top-of-Stack of the
2914                                          *     new stack.
2915                                          *
2916                                          * 2 - switches to the new stack.
2917                                          *
2918                                          * 3 - pops the Top-of-Stack to restore
2919                                          *     the original stack.
2920                                          *
2921                                          * Note: we set base to SP_INDIRECT
2922                                          * here and preserve offset. Therefore
2923                                          * when the unwinder reaches ToS it
2924                                          * will dereference SP and then add the
2925                                          * offset to find the next frame, IOW:
2926                                          * (%rsp) + offset.
2927                                          */
2928                                         cfa->base = CFI_SP_INDIRECT;
2929
2930                                 } else {
2931                                         cfa->base = CFI_UNDEFINED;
2932                                         cfa->offset = 0;
2933                                 }
2934                         }
2935
2936                         else if (op->dest.reg == CFI_SP &&
2937                                  cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
2938                                  cfi->vals[op->src.reg].offset == cfa->offset) {
2939
2940                                 /*
2941                                  * The same stack swizzle case 2) as above. But
2942                                  * because we can't change cfa->base, case 3)
2943                                  * will become a regular POP. Pretend we're a
2944                                  * PUSH so things don't go unbalanced.
2945                                  */
2946                                 cfi->stack_size += 8;
2947                         }
2948
2949
2950                         break;
2951
2952                 case OP_SRC_ADD:
2953                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
2954
2955                                 /* add imm, %rsp */
2956                                 cfi->stack_size -= op->src.offset;
2957                                 if (cfa->base == CFI_SP)
2958                                         cfa->offset -= op->src.offset;
2959                                 break;
2960                         }
2961
2962                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
2963
2964                                 /* lea disp(%rbp), %rsp */
2965                                 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
2966                                 break;
2967                         }
2968
2969                         if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
2970
2971                                 /* drap: lea disp(%rsp), %drap */
2972                                 cfi->drap_reg = op->dest.reg;
2973
2974                                 /*
2975                                  * lea disp(%rsp), %reg
2976                                  *
2977                                  * This is needed for the rare case where GCC
2978                                  * does something dumb like:
2979                                  *
2980                                  *   lea    0x8(%rsp), %rcx
2981                                  *   ...
2982                                  *   mov    %rcx, %rsp
2983                                  */
2984                                 cfi->vals[op->dest.reg].base = CFI_CFA;
2985                                 cfi->vals[op->dest.reg].offset = \
2986                                         -cfi->stack_size + op->src.offset;
2987
2988                                 break;
2989                         }
2990
2991                         if (cfi->drap && op->dest.reg == CFI_SP &&
2992                             op->src.reg == cfi->drap_reg) {
2993
2994                                  /* drap: lea disp(%drap), %rsp */
2995                                 cfa->base = CFI_SP;
2996                                 cfa->offset = cfi->stack_size = -op->src.offset;
2997                                 cfi->drap_reg = CFI_UNDEFINED;
2998                                 cfi->drap = false;
2999                                 break;
3000                         }
3001
3002                         if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) {
3003                                 WARN_INSN(insn, "unsupported stack register modification");
3004                                 return -1;
3005                         }
3006
3007                         break;
3008
3009                 case OP_SRC_AND:
3010                         if (op->dest.reg != CFI_SP ||
3011                             (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
3012                             (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
3013                                 WARN_INSN(insn, "unsupported stack pointer realignment");
3014                                 return -1;
3015                         }
3016
3017                         if (cfi->drap_reg != CFI_UNDEFINED) {
3018                                 /* drap: and imm, %rsp */
3019                                 cfa->base = cfi->drap_reg;
3020                                 cfa->offset = cfi->stack_size = 0;
3021                                 cfi->drap = true;
3022                         }
3023
3024                         /*
3025                          * Older versions of GCC (4.8ish) realign the stack
3026                          * without DRAP, with a frame pointer.
3027                          */
3028
3029                         break;
3030
3031                 case OP_SRC_POP:
3032                 case OP_SRC_POPF:
3033                         if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
3034
3035                                 /* pop %rsp; # restore from a stack swizzle */
3036                                 cfa->base = CFI_SP;
3037                                 break;
3038                         }
3039
3040                         if (!cfi->drap && op->dest.reg == cfa->base) {
3041
3042                                 /* pop %rbp */
3043                                 cfa->base = CFI_SP;
3044                         }
3045
3046                         if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
3047                             op->dest.reg == cfi->drap_reg &&
3048                             cfi->drap_offset == -cfi->stack_size) {
3049
3050                                 /* drap: pop %drap */
3051                                 cfa->base = cfi->drap_reg;
3052                                 cfa->offset = 0;
3053                                 cfi->drap_offset = -1;
3054
3055                         } else if (cfi->stack_size == -regs[op->dest.reg].offset) {
3056
3057                                 /* pop %reg */
3058                                 restore_reg(cfi, op->dest.reg);
3059                         }
3060
3061                         cfi->stack_size -= 8;
3062                         if (cfa->base == CFI_SP)
3063                                 cfa->offset -= 8;
3064
3065                         break;
3066
3067                 case OP_SRC_REG_INDIRECT:
3068                         if (!cfi->drap && op->dest.reg == cfa->base &&
3069                             op->dest.reg == CFI_BP) {
3070
3071                                 /* mov disp(%rsp), %rbp */
3072                                 cfa->base = CFI_SP;
3073                                 cfa->offset = cfi->stack_size;
3074                         }
3075
3076                         if (cfi->drap && op->src.reg == CFI_BP &&
3077                             op->src.offset == cfi->drap_offset) {
3078
3079                                 /* drap: mov disp(%rbp), %drap */
3080                                 cfa->base = cfi->drap_reg;
3081                                 cfa->offset = 0;
3082                                 cfi->drap_offset = -1;
3083                         }
3084
3085                         if (cfi->drap && op->src.reg == CFI_BP &&
3086                             op->src.offset == regs[op->dest.reg].offset) {
3087
3088                                 /* drap: mov disp(%rbp), %reg */
3089                                 restore_reg(cfi, op->dest.reg);
3090
3091                         } else if (op->src.reg == cfa->base &&
3092                             op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
3093
3094                                 /* mov disp(%rbp), %reg */
3095                                 /* mov disp(%rsp), %reg */
3096                                 restore_reg(cfi, op->dest.reg);
3097
3098                         } else if (op->src.reg == CFI_SP &&
3099                                    op->src.offset == regs[op->dest.reg].offset + cfi->stack_size) {
3100
3101                                 /* mov disp(%rsp), %reg */
3102                                 restore_reg(cfi, op->dest.reg);
3103                         }
3104
3105                         break;
3106
3107                 default:
3108                         WARN_INSN(insn, "unknown stack-related instruction");
3109                         return -1;
3110                 }
3111
3112                 break;
3113
3114         case OP_DEST_PUSH:
3115         case OP_DEST_PUSHF:
3116                 cfi->stack_size += 8;
3117                 if (cfa->base == CFI_SP)
3118                         cfa->offset += 8;
3119
3120                 if (op->src.type != OP_SRC_REG)
3121                         break;
3122
3123                 if (cfi->drap) {
3124                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3125
3126                                 /* drap: push %drap */
3127                                 cfa->base = CFI_BP_INDIRECT;
3128                                 cfa->offset = -cfi->stack_size;
3129
3130                                 /* save drap so we know when to restore it */
3131                                 cfi->drap_offset = -cfi->stack_size;
3132
3133                         } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
3134
3135                                 /* drap: push %rbp */
3136                                 cfi->stack_size = 0;
3137
3138                         } else {
3139
3140                                 /* drap: push %reg */
3141                                 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
3142                         }
3143
3144                 } else {
3145
3146                         /* push %reg */
3147                         save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
3148                 }
3149
3150                 /* detect when asm code uses rbp as a scratch register */
3151                 if (opts.stackval && insn_func(insn) && op->src.reg == CFI_BP &&
3152                     cfa->base != CFI_BP)
3153                         cfi->bp_scratch = true;
3154                 break;
3155
3156         case OP_DEST_REG_INDIRECT:
3157
3158                 if (cfi->drap) {
3159                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
3160
3161                                 /* drap: mov %drap, disp(%rbp) */
3162                                 cfa->base = CFI_BP_INDIRECT;
3163                                 cfa->offset = op->dest.offset;
3164
3165                                 /* save drap offset so we know when to restore it */
3166                                 cfi->drap_offset = op->dest.offset;
3167                         } else {
3168
3169                                 /* drap: mov reg, disp(%rbp) */
3170                                 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
3171                         }
3172
3173                 } else if (op->dest.reg == cfa->base) {
3174
3175                         /* mov reg, disp(%rbp) */
3176                         /* mov reg, disp(%rsp) */
3177                         save_reg(cfi, op->src.reg, CFI_CFA,
3178                                  op->dest.offset - cfi->cfa.offset);
3179
3180                 } else if (op->dest.reg == CFI_SP) {
3181
3182                         /* mov reg, disp(%rsp) */
3183                         save_reg(cfi, op->src.reg, CFI_CFA,
3184                                  op->dest.offset - cfi->stack_size);
3185
3186                 } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
3187
3188                         /* mov %rsp, (%reg); # setup a stack swizzle. */
3189                         cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
3190                         cfi->vals[op->dest.reg].offset = cfa->offset;
3191                 }
3192
3193                 break;
3194
3195         case OP_DEST_MEM:
3196                 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
3197                         WARN_INSN(insn, "unknown stack-related memory operation");
3198                         return -1;
3199                 }
3200
3201                 /* pop mem */
3202                 cfi->stack_size -= 8;
3203                 if (cfa->base == CFI_SP)
3204                         cfa->offset -= 8;
3205
3206                 break;
3207
3208         default:
3209                 WARN_INSN(insn, "unknown stack-related instruction");
3210                 return -1;
3211         }
3212
3213         return 0;
3214 }
3215
3216 /*
3217  * The stack layouts of alternatives instructions can sometimes diverge when
3218  * they have stack modifications.  That's fine as long as the potential stack
3219  * layouts don't conflict at any given potential instruction boundary.
3220  *
3221  * Flatten the CFIs of the different alternative code streams (both original
3222  * and replacement) into a single shared CFI array which can be used to detect
3223  * conflicts and nicely feed a linear array of ORC entries to the unwinder.
3224  */
3225 static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn)
3226 {
3227         struct cfi_state **alt_cfi;
3228         int group_off;
3229
3230         if (!insn->alt_group)
3231                 return 0;
3232
3233         if (!insn->cfi) {
3234                 WARN("CFI missing");
3235                 return -1;
3236         }
3237
3238         alt_cfi = insn->alt_group->cfi;
3239         group_off = insn->offset - insn->alt_group->first_insn->offset;
3240
3241         if (!alt_cfi[group_off]) {
3242                 alt_cfi[group_off] = insn->cfi;
3243         } else {
3244                 if (cficmp(alt_cfi[group_off], insn->cfi)) {
3245                         struct alt_group *orig_group = insn->alt_group->orig_group ?: insn->alt_group;
3246                         struct instruction *orig = orig_group->first_insn;
3247                         char *where = offstr(insn->sec, insn->offset);
3248                         WARN_INSN(orig, "stack layout conflict in alternatives: %s", where);
3249                         free(where);
3250                         return -1;
3251                 }
3252         }
3253
3254         return 0;
3255 }
3256
3257 static int handle_insn_ops(struct instruction *insn,
3258                            struct instruction *next_insn,
3259                            struct insn_state *state)
3260 {
3261         struct stack_op *op;
3262
3263         for (op = insn->stack_ops; op; op = op->next) {
3264
3265                 if (update_cfi_state(insn, next_insn, &state->cfi, op))
3266                         return 1;
3267
3268                 if (!insn->alt_group)
3269                         continue;
3270
3271                 if (op->dest.type == OP_DEST_PUSHF) {
3272                         if (!state->uaccess_stack) {
3273                                 state->uaccess_stack = 1;
3274                         } else if (state->uaccess_stack >> 31) {
3275                                 WARN_INSN(insn, "PUSHF stack exhausted");
3276                                 return 1;
3277                         }
3278                         state->uaccess_stack <<= 1;
3279                         state->uaccess_stack  |= state->uaccess;
3280                 }
3281
3282                 if (op->src.type == OP_SRC_POPF) {
3283                         if (state->uaccess_stack) {
3284                                 state->uaccess = state->uaccess_stack & 1;
3285                                 state->uaccess_stack >>= 1;
3286                                 if (state->uaccess_stack == 1)
3287                                         state->uaccess_stack = 0;
3288                         }
3289                 }
3290         }
3291
3292         return 0;
3293 }
3294
3295 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
3296 {
3297         struct cfi_state *cfi1 = insn->cfi;
3298         int i;
3299
3300         if (!cfi1) {
3301                 WARN("CFI missing");
3302                 return false;
3303         }
3304
3305         if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
3306
3307                 WARN_INSN(insn, "stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
3308                           cfi1->cfa.base, cfi1->cfa.offset,
3309                           cfi2->cfa.base, cfi2->cfa.offset);
3310
3311         } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
3312                 for (i = 0; i < CFI_NUM_REGS; i++) {
3313                         if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
3314                                     sizeof(struct cfi_reg)))
3315                                 continue;
3316
3317                         WARN_INSN(insn, "stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
3318                                   i, cfi1->regs[i].base, cfi1->regs[i].offset,
3319                                   i, cfi2->regs[i].base, cfi2->regs[i].offset);
3320                         break;
3321                 }
3322
3323         } else if (cfi1->type != cfi2->type) {
3324
3325                 WARN_INSN(insn, "stack state mismatch: type1=%d type2=%d",
3326                           cfi1->type, cfi2->type);
3327
3328         } else if (cfi1->drap != cfi2->drap ||
3329                    (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
3330                    (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
3331
3332                 WARN_INSN(insn, "stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
3333                           cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
3334                           cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
3335
3336         } else
3337                 return true;
3338
3339         return false;
3340 }
3341
3342 static inline bool func_uaccess_safe(struct symbol *func)
3343 {
3344         if (func)
3345                 return func->uaccess_safe;
3346
3347         return false;
3348 }
3349
3350 static inline const char *call_dest_name(struct instruction *insn)
3351 {
3352         static char pvname[19];
3353         struct reloc *reloc;
3354         int idx;
3355
3356         if (insn_call_dest(insn))
3357                 return insn_call_dest(insn)->name;
3358
3359         reloc = insn_reloc(NULL, insn);
3360         if (reloc && !strcmp(reloc->sym->name, "pv_ops")) {
3361                 idx = (reloc_addend(reloc) / sizeof(void *));
3362                 snprintf(pvname, sizeof(pvname), "pv_ops[%d]", idx);
3363                 return pvname;
3364         }
3365
3366         return "{dynamic}";
3367 }
3368
3369 static bool pv_call_dest(struct objtool_file *file, struct instruction *insn)
3370 {
3371         struct symbol *target;
3372         struct reloc *reloc;
3373         int idx;
3374
3375         reloc = insn_reloc(file, insn);
3376         if (!reloc || strcmp(reloc->sym->name, "pv_ops"))
3377                 return false;
3378
3379         idx = (arch_dest_reloc_offset(reloc_addend(reloc)) / sizeof(void *));
3380
3381         if (file->pv_ops[idx].clean)
3382                 return true;
3383
3384         file->pv_ops[idx].clean = true;
3385
3386         list_for_each_entry(target, &file->pv_ops[idx].targets, pv_target) {
3387                 if (!target->sec->noinstr) {
3388                         WARN("pv_ops[%d]: %s", idx, target->name);
3389                         file->pv_ops[idx].clean = false;
3390                 }
3391         }
3392
3393         return file->pv_ops[idx].clean;
3394 }
3395
3396 static inline bool noinstr_call_dest(struct objtool_file *file,
3397                                      struct instruction *insn,
3398                                      struct symbol *func)
3399 {
3400         /*
3401          * We can't deal with indirect function calls at present;
3402          * assume they're instrumented.
3403          */
3404         if (!func) {
3405                 if (file->pv_ops)
3406                         return pv_call_dest(file, insn);
3407
3408                 return false;
3409         }
3410
3411         /*
3412          * If the symbol is from a noinstr section; we good.
3413          */
3414         if (func->sec->noinstr)
3415                 return true;
3416
3417         /*
3418          * If the symbol is a static_call trampoline, we can't tell.
3419          */
3420         if (func->static_call_tramp)
3421                 return true;
3422
3423         /*
3424          * The __ubsan_handle_*() calls are like WARN(), they only happen when
3425          * something 'BAD' happened. At the risk of taking the machine down,
3426          * let them proceed to get the message out.
3427          */
3428         if (!strncmp(func->name, "__ubsan_handle_", 15))
3429                 return true;
3430
3431         return false;
3432 }
3433
3434 static int validate_call(struct objtool_file *file,
3435                          struct instruction *insn,
3436                          struct insn_state *state)
3437 {
3438         if (state->noinstr && state->instr <= 0 &&
3439             !noinstr_call_dest(file, insn, insn_call_dest(insn))) {
3440                 WARN_INSN(insn, "call to %s() leaves .noinstr.text section", call_dest_name(insn));
3441                 return 1;
3442         }
3443
3444         if (state->uaccess && !func_uaccess_safe(insn_call_dest(insn))) {
3445                 WARN_INSN(insn, "call to %s() with UACCESS enabled", call_dest_name(insn));
3446                 return 1;
3447         }
3448
3449         if (state->df) {
3450                 WARN_INSN(insn, "call to %s() with DF set", call_dest_name(insn));
3451                 return 1;
3452         }
3453
3454         return 0;
3455 }
3456
3457 static int validate_sibling_call(struct objtool_file *file,
3458                                  struct instruction *insn,
3459                                  struct insn_state *state)
3460 {
3461         if (insn_func(insn) && has_modified_stack_frame(insn, state)) {
3462                 WARN_INSN(insn, "sibling call from callable instruction with modified stack frame");
3463                 return 1;
3464         }
3465
3466         return validate_call(file, insn, state);
3467 }
3468
3469 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
3470 {
3471         if (state->noinstr && state->instr > 0) {
3472                 WARN_INSN(insn, "return with instrumentation enabled");
3473                 return 1;
3474         }
3475
3476         if (state->uaccess && !func_uaccess_safe(func)) {
3477                 WARN_INSN(insn, "return with UACCESS enabled");
3478                 return 1;
3479         }
3480
3481         if (!state->uaccess && func_uaccess_safe(func)) {
3482                 WARN_INSN(insn, "return with UACCESS disabled from a UACCESS-safe function");
3483                 return 1;
3484         }
3485
3486         if (state->df) {
3487                 WARN_INSN(insn, "return with DF set");
3488                 return 1;
3489         }
3490
3491         if (func && has_modified_stack_frame(insn, state)) {
3492                 WARN_INSN(insn, "return with modified stack frame");
3493                 return 1;
3494         }
3495
3496         if (state->cfi.bp_scratch) {
3497                 WARN_INSN(insn, "BP used as a scratch register");
3498                 return 1;
3499         }
3500
3501         return 0;
3502 }
3503
3504 static struct instruction *next_insn_to_validate(struct objtool_file *file,
3505                                                  struct instruction *insn)
3506 {
3507         struct alt_group *alt_group = insn->alt_group;
3508
3509         /*
3510          * Simulate the fact that alternatives are patched in-place.  When the
3511          * end of a replacement alt_group is reached, redirect objtool flow to
3512          * the end of the original alt_group.
3513          *
3514          * insn->alts->insn -> alt_group->first_insn
3515          *                     ...
3516          *                     alt_group->last_insn
3517          *                     [alt_group->nop]      -> next(orig_group->last_insn)
3518          */
3519         if (alt_group) {
3520                 if (alt_group->nop) {
3521                         /* ->nop implies ->orig_group */
3522                         if (insn == alt_group->last_insn)
3523                                 return alt_group->nop;
3524                         if (insn == alt_group->nop)
3525                                 goto next_orig;
3526                 }
3527                 if (insn == alt_group->last_insn && alt_group->orig_group)
3528                         goto next_orig;
3529         }
3530
3531         return next_insn_same_sec(file, insn);
3532
3533 next_orig:
3534         return next_insn_same_sec(file, alt_group->orig_group->last_insn);
3535 }
3536
3537 /*
3538  * Follow the branch starting at the given instruction, and recursively follow
3539  * any other branches (jumps).  Meanwhile, track the frame pointer state at
3540  * each instruction and validate all the rules described in
3541  * tools/objtool/Documentation/objtool.txt.
3542  */
3543 static int validate_branch(struct objtool_file *file, struct symbol *func,
3544                            struct instruction *insn, struct insn_state state)
3545 {
3546         struct alternative *alt;
3547         struct instruction *next_insn, *prev_insn = NULL;
3548         struct section *sec;
3549         u8 visited;
3550         int ret;
3551
3552         sec = insn->sec;
3553
3554         while (1) {
3555                 next_insn = next_insn_to_validate(file, insn);
3556
3557                 if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {
3558                         /* Ignore KCFI type preambles, which always fall through */
3559                         if (!strncmp(func->name, "__cfi_", 6) ||
3560                             !strncmp(func->name, "__pfx_", 6))
3561                                 return 0;
3562
3563                         WARN("%s() falls through to next function %s()",
3564                              func->name, insn_func(insn)->name);
3565                         return 1;
3566                 }
3567
3568                 if (func && insn->ignore) {
3569                         WARN_INSN(insn, "BUG: why am I validating an ignored function?");
3570                         return 1;
3571                 }
3572
3573                 visited = VISITED_BRANCH << state.uaccess;
3574                 if (insn->visited & VISITED_BRANCH_MASK) {
3575                         if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
3576                                 return 1;
3577
3578                         if (insn->visited & visited)
3579                                 return 0;
3580                 } else {
3581                         nr_insns_visited++;
3582                 }
3583
3584                 if (state.noinstr)
3585                         state.instr += insn->instr;
3586
3587                 if (insn->hint) {
3588                         if (insn->restore) {
3589                                 struct instruction *save_insn, *i;
3590
3591                                 i = insn;
3592                                 save_insn = NULL;
3593
3594                                 sym_for_each_insn_continue_reverse(file, func, i) {
3595                                         if (i->save) {
3596                                                 save_insn = i;
3597                                                 break;
3598                                         }
3599                                 }
3600
3601                                 if (!save_insn) {
3602                                         WARN_INSN(insn, "no corresponding CFI save for CFI restore");
3603                                         return 1;
3604                                 }
3605
3606                                 if (!save_insn->visited) {
3607                                         WARN_INSN(insn, "objtool isn't smart enough to handle this CFI save/restore combo");
3608                                         return 1;
3609                                 }
3610
3611                                 insn->cfi = save_insn->cfi;
3612                                 nr_cfi_reused++;
3613                         }
3614
3615                         state.cfi = *insn->cfi;
3616                 } else {
3617                         /* XXX track if we actually changed state.cfi */
3618
3619                         if (prev_insn && !cficmp(prev_insn->cfi, &state.cfi)) {
3620                                 insn->cfi = prev_insn->cfi;
3621                                 nr_cfi_reused++;
3622                         } else {
3623                                 insn->cfi = cfi_hash_find_or_add(&state.cfi);
3624                         }
3625                 }
3626
3627                 insn->visited |= visited;
3628
3629                 if (propagate_alt_cfi(file, insn))
3630                         return 1;
3631
3632                 if (!insn->ignore_alts && insn->alts) {
3633                         bool skip_orig = false;
3634
3635                         for (alt = insn->alts; alt; alt = alt->next) {
3636                                 if (alt->skip_orig)
3637                                         skip_orig = true;
3638
3639                                 ret = validate_branch(file, func, alt->insn, state);
3640                                 if (ret) {
3641                                         BT_INSN(insn, "(alt)");
3642                                         return ret;
3643                                 }
3644                         }
3645
3646                         if (skip_orig)
3647                                 return 0;
3648                 }
3649
3650                 if (handle_insn_ops(insn, next_insn, &state))
3651                         return 1;
3652
3653                 switch (insn->type) {
3654
3655                 case INSN_RETURN:
3656                         return validate_return(func, insn, &state);
3657
3658                 case INSN_CALL:
3659                 case INSN_CALL_DYNAMIC:
3660                         ret = validate_call(file, insn, &state);
3661                         if (ret)
3662                                 return ret;
3663
3664                         if (opts.stackval && func && !is_special_call(insn) &&
3665                             !has_valid_stack_frame(&state)) {
3666                                 WARN_INSN(insn, "call without frame pointer save/setup");
3667                                 return 1;
3668                         }
3669
3670                         if (insn->dead_end)
3671                                 return 0;
3672
3673                         break;
3674
3675                 case INSN_JUMP_CONDITIONAL:
3676                 case INSN_JUMP_UNCONDITIONAL:
3677                         if (is_sibling_call(insn)) {
3678                                 ret = validate_sibling_call(file, insn, &state);
3679                                 if (ret)
3680                                         return ret;
3681
3682                         } else if (insn->jump_dest) {
3683                                 ret = validate_branch(file, func,
3684                                                       insn->jump_dest, state);
3685                                 if (ret) {
3686                                         BT_INSN(insn, "(branch)");
3687                                         return ret;
3688                                 }
3689                         }
3690
3691                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
3692                                 return 0;
3693
3694                         break;
3695
3696                 case INSN_JUMP_DYNAMIC:
3697                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3698                         if (is_sibling_call(insn)) {
3699                                 ret = validate_sibling_call(file, insn, &state);
3700                                 if (ret)
3701                                         return ret;
3702                         }
3703
3704                         if (insn->type == INSN_JUMP_DYNAMIC)
3705                                 return 0;
3706
3707                         break;
3708
3709                 case INSN_CONTEXT_SWITCH:
3710                         if (func && (!next_insn || !next_insn->hint)) {
3711                                 WARN_INSN(insn, "unsupported instruction in callable function");
3712                                 return 1;
3713                         }
3714                         return 0;
3715
3716                 case INSN_STAC:
3717                         if (state.uaccess) {
3718                                 WARN_INSN(insn, "recursive UACCESS enable");
3719                                 return 1;
3720                         }
3721
3722                         state.uaccess = true;
3723                         break;
3724
3725                 case INSN_CLAC:
3726                         if (!state.uaccess && func) {
3727                                 WARN_INSN(insn, "redundant UACCESS disable");
3728                                 return 1;
3729                         }
3730
3731                         if (func_uaccess_safe(func) && !state.uaccess_stack) {
3732                                 WARN_INSN(insn, "UACCESS-safe disables UACCESS");
3733                                 return 1;
3734                         }
3735
3736                         state.uaccess = false;
3737                         break;
3738
3739                 case INSN_STD:
3740                         if (state.df) {
3741                                 WARN_INSN(insn, "recursive STD");
3742                                 return 1;
3743                         }
3744
3745                         state.df = true;
3746                         break;
3747
3748                 case INSN_CLD:
3749                         if (!state.df && func) {
3750                                 WARN_INSN(insn, "redundant CLD");
3751                                 return 1;
3752                         }
3753
3754                         state.df = false;
3755                         break;
3756
3757                 default:
3758                         break;
3759                 }
3760
3761                 if (insn->dead_end)
3762                         return 0;
3763
3764                 if (!next_insn) {
3765                         if (state.cfi.cfa.base == CFI_UNDEFINED)
3766                                 return 0;
3767                         WARN("%s: unexpected end of section", sec->name);
3768                         return 1;
3769                 }
3770
3771                 prev_insn = insn;
3772                 insn = next_insn;
3773         }
3774
3775         return 0;
3776 }
3777
3778 static int validate_unwind_hint(struct objtool_file *file,
3779                                   struct instruction *insn,
3780                                   struct insn_state *state)
3781 {
3782         if (insn->hint && !insn->visited && !insn->ignore) {
3783                 int ret = validate_branch(file, insn_func(insn), insn, *state);
3784                 if (ret)
3785                         BT_INSN(insn, "<=== (hint)");
3786                 return ret;
3787         }
3788
3789         return 0;
3790 }
3791
3792 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
3793 {
3794         struct instruction *insn;
3795         struct insn_state state;
3796         int warnings = 0;
3797
3798         if (!file->hints)
3799                 return 0;
3800
3801         init_insn_state(file, &state, sec);
3802
3803         if (sec) {
3804                 sec_for_each_insn(file, sec, insn)
3805                         warnings += validate_unwind_hint(file, insn, &state);
3806         } else {
3807                 for_each_insn(file, insn)
3808                         warnings += validate_unwind_hint(file, insn, &state);
3809         }
3810
3811         return warnings;
3812 }
3813
3814 /*
3815  * Validate rethunk entry constraint: must untrain RET before the first RET.
3816  *
3817  * Follow every branch (intra-function) and ensure VALIDATE_UNRET_END comes
3818  * before an actual RET instruction.
3819  */
3820 static int validate_unret(struct objtool_file *file, struct instruction *insn)
3821 {
3822         struct instruction *next, *dest;
3823         int ret;
3824
3825         for (;;) {
3826                 next = next_insn_to_validate(file, insn);
3827
3828                 if (insn->visited & VISITED_UNRET)
3829                         return 0;
3830
3831                 insn->visited |= VISITED_UNRET;
3832
3833                 if (!insn->ignore_alts && insn->alts) {
3834                         struct alternative *alt;
3835                         bool skip_orig = false;
3836
3837                         for (alt = insn->alts; alt; alt = alt->next) {
3838                                 if (alt->skip_orig)
3839                                         skip_orig = true;
3840
3841                                 ret = validate_unret(file, alt->insn);
3842                                 if (ret) {
3843                                         BT_INSN(insn, "(alt)");
3844                                         return ret;
3845                                 }
3846                         }
3847
3848                         if (skip_orig)
3849                                 return 0;
3850                 }
3851
3852                 switch (insn->type) {
3853
3854                 case INSN_CALL_DYNAMIC:
3855                 case INSN_JUMP_DYNAMIC:
3856                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
3857                         WARN_INSN(insn, "early indirect call");
3858                         return 1;
3859
3860                 case INSN_JUMP_UNCONDITIONAL:
3861                 case INSN_JUMP_CONDITIONAL:
3862                         if (!is_sibling_call(insn)) {
3863                                 if (!insn->jump_dest) {
3864                                         WARN_INSN(insn, "unresolved jump target after linking?!?");
3865                                         return -1;
3866                                 }
3867                                 ret = validate_unret(file, insn->jump_dest);
3868                                 if (ret) {
3869                                         BT_INSN(insn, "(branch%s)",
3870                                                 insn->type == INSN_JUMP_CONDITIONAL ? "-cond" : "");
3871                                         return ret;
3872                                 }
3873
3874                                 if (insn->type == INSN_JUMP_UNCONDITIONAL)
3875                                         return 0;
3876
3877                                 break;
3878                         }
3879
3880                         /* fallthrough */
3881                 case INSN_CALL:
3882                         dest = find_insn(file, insn_call_dest(insn)->sec,
3883                                          insn_call_dest(insn)->offset);
3884                         if (!dest) {
3885                                 WARN("Unresolved function after linking!?: %s",
3886                                      insn_call_dest(insn)->name);
3887                                 return -1;
3888                         }
3889
3890                         ret = validate_unret(file, dest);
3891                         if (ret) {
3892                                 BT_INSN(insn, "(call)");
3893                                 return ret;
3894                         }
3895                         /*
3896                          * If a call returns without error, it must have seen UNTRAIN_RET.
3897                          * Therefore any non-error return is a success.
3898                          */
3899                         return 0;
3900
3901                 case INSN_RETURN:
3902                         WARN_INSN(insn, "RET before UNTRAIN");
3903                         return 1;
3904
3905                 case INSN_NOP:
3906                         if (insn->retpoline_safe)
3907                                 return 0;
3908                         break;
3909
3910                 default:
3911                         break;
3912                 }
3913
3914                 if (!next) {
3915                         WARN_INSN(insn, "teh end!");
3916                         return -1;
3917                 }
3918                 insn = next;
3919         }
3920
3921         return 0;
3922 }
3923
3924 /*
3925  * Validate that all branches starting at VALIDATE_UNRET_BEGIN encounter
3926  * VALIDATE_UNRET_END before RET.
3927  */
3928 static int validate_unrets(struct objtool_file *file)
3929 {
3930         struct instruction *insn;
3931         int ret, warnings = 0;
3932
3933         for_each_insn(file, insn) {
3934                 if (!insn->unret)
3935                         continue;
3936
3937                 ret = validate_unret(file, insn);
3938                 if (ret < 0) {
3939                         WARN_INSN(insn, "Failed UNRET validation");
3940                         return ret;
3941                 }
3942                 warnings += ret;
3943         }
3944
3945         return warnings;
3946 }
3947
3948 static int validate_retpoline(struct objtool_file *file)
3949 {
3950         struct instruction *insn;
3951         int warnings = 0;
3952
3953         for_each_insn(file, insn) {
3954                 if (insn->type != INSN_JUMP_DYNAMIC &&
3955                     insn->type != INSN_CALL_DYNAMIC &&
3956                     insn->type != INSN_RETURN)
3957                         continue;
3958
3959                 if (insn->retpoline_safe)
3960                         continue;
3961
3962                 if (insn->sec->init)
3963                         continue;
3964
3965                 if (insn->type == INSN_RETURN) {
3966                         if (opts.rethunk) {
3967                                 WARN_INSN(insn, "'naked' return found in RETHUNK build");
3968                         } else
3969                                 continue;
3970                 } else {
3971                         WARN_INSN(insn, "indirect %s found in RETPOLINE build",
3972                                   insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
3973                 }
3974
3975                 warnings++;
3976         }
3977
3978         return warnings;
3979 }
3980
3981 static bool is_kasan_insn(struct instruction *insn)
3982 {
3983         return (insn->type == INSN_CALL &&
3984                 !strcmp(insn_call_dest(insn)->name, "__asan_handle_no_return"));
3985 }
3986
3987 static bool is_ubsan_insn(struct instruction *insn)
3988 {
3989         return (insn->type == INSN_CALL &&
3990                 !strcmp(insn_call_dest(insn)->name,
3991                         "__ubsan_handle_builtin_unreachable"));
3992 }
3993
3994 static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
3995 {
3996         int i;
3997         struct instruction *prev_insn;
3998
3999         if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
4000                 return true;
4001
4002         /*
4003          * Ignore alternative replacement instructions.  This can happen
4004          * when a whitelisted function uses one of the ALTERNATIVE macros.
4005          */
4006         if (!strcmp(insn->sec->name, ".altinstr_replacement") ||
4007             !strcmp(insn->sec->name, ".altinstr_aux"))
4008                 return true;
4009
4010         /*
4011          * Whole archive runs might encounter dead code from weak symbols.
4012          * This is where the linker will have dropped the weak symbol in
4013          * favour of a regular symbol, but leaves the code in place.
4014          *
4015          * In this case we'll find a piece of code (whole function) that is not
4016          * covered by a !section symbol. Ignore them.
4017          */
4018         if (opts.link && !insn_func(insn)) {
4019                 int size = find_symbol_hole_containing(insn->sec, insn->offset);
4020                 unsigned long end = insn->offset + size;
4021
4022                 if (!size) /* not a hole */
4023                         return false;
4024
4025                 if (size < 0) /* hole until the end */
4026                         return true;
4027
4028                 sec_for_each_insn_continue(file, insn) {
4029                         /*
4030                          * If we reach a visited instruction at or before the
4031                          * end of the hole, ignore the unreachable.
4032                          */
4033                         if (insn->visited)
4034                                 return true;
4035
4036                         if (insn->offset >= end)
4037                                 break;
4038
4039                         /*
4040                          * If this hole jumps to a .cold function, mark it ignore too.
4041                          */
4042                         if (insn->jump_dest && insn_func(insn->jump_dest) &&
4043                             strstr(insn_func(insn->jump_dest)->name, ".cold")) {
4044                                 struct instruction *dest = insn->jump_dest;
4045                                 func_for_each_insn(file, insn_func(dest), dest)
4046                                         dest->ignore = true;
4047                         }
4048                 }
4049
4050                 return false;
4051         }
4052
4053         if (!insn_func(insn))
4054                 return false;
4055
4056         if (insn_func(insn)->static_call_tramp)
4057                 return true;
4058
4059         /*
4060          * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
4061          * __builtin_unreachable().  The BUG() macro has an unreachable() after
4062          * the UD2, which causes GCC's undefined trap logic to emit another UD2
4063          * (or occasionally a JMP to UD2).
4064          *
4065          * It may also insert a UD2 after calling a __noreturn function.
4066          */
4067         prev_insn = prev_insn_same_sec(file, insn);
4068         if (prev_insn->dead_end &&
4069             (insn->type == INSN_BUG ||
4070              (insn->type == INSN_JUMP_UNCONDITIONAL &&
4071               insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
4072                 return true;
4073
4074         /*
4075          * Check if this (or a subsequent) instruction is related to
4076          * CONFIG_UBSAN or CONFIG_KASAN.
4077          *
4078          * End the search at 5 instructions to avoid going into the weeds.
4079          */
4080         for (i = 0; i < 5; i++) {
4081
4082                 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
4083                         return true;
4084
4085                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
4086                         if (insn->jump_dest &&
4087                             insn_func(insn->jump_dest) == insn_func(insn)) {
4088                                 insn = insn->jump_dest;
4089                                 continue;
4090                         }
4091
4092                         break;
4093                 }
4094
4095                 if (insn->offset + insn->len >= insn_func(insn)->offset + insn_func(insn)->len)
4096                         break;
4097
4098                 insn = next_insn_same_sec(file, insn);
4099         }
4100
4101         return false;
4102 }
4103
4104 static int add_prefix_symbol(struct objtool_file *file, struct symbol *func)
4105 {
4106         struct instruction *insn, *prev;
4107         struct cfi_state *cfi;
4108
4109         insn = find_insn(file, func->sec, func->offset);
4110         if (!insn)
4111                 return -1;
4112
4113         for (prev = prev_insn_same_sec(file, insn);
4114              prev;
4115              prev = prev_insn_same_sec(file, prev)) {
4116                 u64 offset;
4117
4118                 if (prev->type != INSN_NOP)
4119                         return -1;
4120
4121                 offset = func->offset - prev->offset;
4122
4123                 if (offset > opts.prefix)
4124                         return -1;
4125
4126                 if (offset < opts.prefix)
4127                         continue;
4128
4129                 elf_create_prefix_symbol(file->elf, func, opts.prefix);
4130                 break;
4131         }
4132
4133         if (!prev)
4134                 return -1;
4135
4136         if (!insn->cfi) {
4137                 /*
4138                  * This can happen if stack validation isn't enabled or the
4139                  * function is annotated with STACK_FRAME_NON_STANDARD.
4140                  */
4141                 return 0;
4142         }
4143
4144         /* Propagate insn->cfi to the prefix code */
4145         cfi = cfi_hash_find_or_add(insn->cfi);
4146         for (; prev != insn; prev = next_insn_same_sec(file, prev))
4147                 prev->cfi = cfi;
4148
4149         return 0;
4150 }
4151
4152 static int add_prefix_symbols(struct objtool_file *file)
4153 {
4154         struct section *sec;
4155         struct symbol *func;
4156
4157         for_each_sec(file, sec) {
4158                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4159                         continue;
4160
4161                 sec_for_each_sym(sec, func) {
4162                         if (func->type != STT_FUNC)
4163                                 continue;
4164
4165                         add_prefix_symbol(file, func);
4166                 }
4167         }
4168
4169         return 0;
4170 }
4171
4172 static int validate_symbol(struct objtool_file *file, struct section *sec,
4173                            struct symbol *sym, struct insn_state *state)
4174 {
4175         struct instruction *insn;
4176         int ret;
4177
4178         if (!sym->len) {
4179                 WARN("%s() is missing an ELF size annotation", sym->name);
4180                 return 1;
4181         }
4182
4183         if (sym->pfunc != sym || sym->alias != sym)
4184                 return 0;
4185
4186         insn = find_insn(file, sec, sym->offset);
4187         if (!insn || insn->ignore || insn->visited)
4188                 return 0;
4189
4190         state->uaccess = sym->uaccess_safe;
4191
4192         ret = validate_branch(file, insn_func(insn), insn, *state);
4193         if (ret)
4194                 BT_INSN(insn, "<=== (sym)");
4195         return ret;
4196 }
4197
4198 static int validate_section(struct objtool_file *file, struct section *sec)
4199 {
4200         struct insn_state state;
4201         struct symbol *func;
4202         int warnings = 0;
4203
4204         sec_for_each_sym(sec, func) {
4205                 if (func->type != STT_FUNC)
4206                         continue;
4207
4208                 init_insn_state(file, &state, sec);
4209                 set_func_state(&state.cfi);
4210
4211                 warnings += validate_symbol(file, sec, func, &state);
4212         }
4213
4214         return warnings;
4215 }
4216
4217 static int validate_noinstr_sections(struct objtool_file *file)
4218 {
4219         struct section *sec;
4220         int warnings = 0;
4221
4222         sec = find_section_by_name(file->elf, ".noinstr.text");
4223         if (sec) {
4224                 warnings += validate_section(file, sec);
4225                 warnings += validate_unwind_hints(file, sec);
4226         }
4227
4228         sec = find_section_by_name(file->elf, ".entry.text");
4229         if (sec) {
4230                 warnings += validate_section(file, sec);
4231                 warnings += validate_unwind_hints(file, sec);
4232         }
4233
4234         sec = find_section_by_name(file->elf, ".cpuidle.text");
4235         if (sec) {
4236                 warnings += validate_section(file, sec);
4237                 warnings += validate_unwind_hints(file, sec);
4238         }
4239
4240         return warnings;
4241 }
4242
4243 static int validate_functions(struct objtool_file *file)
4244 {
4245         struct section *sec;
4246         int warnings = 0;
4247
4248         for_each_sec(file, sec) {
4249                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
4250                         continue;
4251
4252                 warnings += validate_section(file, sec);
4253         }
4254
4255         return warnings;
4256 }
4257
4258 static void mark_endbr_used(struct instruction *insn)
4259 {
4260         if (!list_empty(&insn->call_node))
4261                 list_del_init(&insn->call_node);
4262 }
4263
4264 static bool noendbr_range(struct objtool_file *file, struct instruction *insn)
4265 {
4266         struct symbol *sym = find_symbol_containing(insn->sec, insn->offset-1);
4267         struct instruction *first;
4268
4269         if (!sym)
4270                 return false;
4271
4272         first = find_insn(file, sym->sec, sym->offset);
4273         if (!first)
4274                 return false;
4275
4276         if (first->type != INSN_ENDBR && !first->noendbr)
4277                 return false;
4278
4279         return insn->offset == sym->offset + sym->len;
4280 }
4281
4282 static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn)
4283 {
4284         struct instruction *dest;
4285         struct reloc *reloc;
4286         unsigned long off;
4287         int warnings = 0;
4288
4289         /*
4290          * Looking for function pointer load relocations.  Ignore
4291          * direct/indirect branches:
4292          */
4293         switch (insn->type) {
4294         case INSN_CALL:
4295         case INSN_CALL_DYNAMIC:
4296         case INSN_JUMP_CONDITIONAL:
4297         case INSN_JUMP_UNCONDITIONAL:
4298         case INSN_JUMP_DYNAMIC:
4299         case INSN_JUMP_DYNAMIC_CONDITIONAL:
4300         case INSN_RETURN:
4301         case INSN_NOP:
4302                 return 0;
4303         default:
4304                 break;
4305         }
4306
4307         for (reloc = insn_reloc(file, insn);
4308              reloc;
4309              reloc = find_reloc_by_dest_range(file->elf, insn->sec,
4310                                               reloc_offset(reloc) + 1,
4311                                               (insn->offset + insn->len) - (reloc_offset(reloc) + 1))) {
4312
4313                 /*
4314                  * static_call_update() references the trampoline, which
4315                  * doesn't have (or need) ENDBR.  Skip warning in that case.
4316                  */
4317                 if (reloc->sym->static_call_tramp)
4318                         continue;
4319
4320                 off = reloc->sym->offset;
4321                 if (reloc_type(reloc) == R_X86_64_PC32 ||
4322                     reloc_type(reloc) == R_X86_64_PLT32)
4323                         off += arch_dest_reloc_offset(reloc_addend(reloc));
4324                 else
4325                         off += reloc_addend(reloc);
4326
4327                 dest = find_insn(file, reloc->sym->sec, off);
4328                 if (!dest)
4329                         continue;
4330
4331                 if (dest->type == INSN_ENDBR) {
4332                         mark_endbr_used(dest);
4333                         continue;
4334                 }
4335
4336                 if (insn_func(dest) && insn_func(insn) &&
4337                     insn_func(dest)->pfunc == insn_func(insn)->pfunc) {
4338                         /*
4339                          * Anything from->to self is either _THIS_IP_ or
4340                          * IRET-to-self.
4341                          *
4342                          * There is no sane way to annotate _THIS_IP_ since the
4343                          * compiler treats the relocation as a constant and is
4344                          * happy to fold in offsets, skewing any annotation we
4345                          * do, leading to vast amounts of false-positives.
4346                          *
4347                          * There's also compiler generated _THIS_IP_ through
4348                          * KCOV and such which we have no hope of annotating.
4349                          *
4350                          * As such, blanket accept self-references without
4351                          * issue.
4352                          */
4353                         continue;
4354                 }
4355
4356                 /*
4357                  * Accept anything ANNOTATE_NOENDBR.
4358                  */
4359                 if (dest->noendbr)
4360                         continue;
4361
4362                 /*
4363                  * Accept if this is the instruction after a symbol
4364                  * that is (no)endbr -- typical code-range usage.
4365                  */
4366                 if (noendbr_range(file, dest))
4367                         continue;
4368
4369                 WARN_INSN(insn, "relocation to !ENDBR: %s", offstr(dest->sec, dest->offset));
4370
4371                 warnings++;
4372         }
4373
4374         return warnings;
4375 }
4376
4377 static int validate_ibt_data_reloc(struct objtool_file *file,
4378                                    struct reloc *reloc)
4379 {
4380         struct instruction *dest;
4381
4382         dest = find_insn(file, reloc->sym->sec,
4383                          reloc->sym->offset + reloc_addend(reloc));
4384         if (!dest)
4385                 return 0;
4386
4387         if (dest->type == INSN_ENDBR) {
4388                 mark_endbr_used(dest);
4389                 return 0;
4390         }
4391
4392         if (dest->noendbr)
4393                 return 0;
4394
4395         WARN_FUNC("data relocation to !ENDBR: %s",
4396                   reloc->sec->base, reloc_offset(reloc),
4397                   offstr(dest->sec, dest->offset));
4398
4399         return 1;
4400 }
4401
4402 /*
4403  * Validate IBT rules and remove used ENDBR instructions from the seal list.
4404  * Unused ENDBR instructions will be annotated for sealing (i.e., replaced with
4405  * NOPs) later, in create_ibt_endbr_seal_sections().
4406  */
4407 static int validate_ibt(struct objtool_file *file)
4408 {
4409         struct section *sec;
4410         struct reloc *reloc;
4411         struct instruction *insn;
4412         int warnings = 0;
4413
4414         for_each_insn(file, insn)
4415                 warnings += validate_ibt_insn(file, insn);
4416
4417         for_each_sec(file, sec) {
4418
4419                 /* Already done by validate_ibt_insn() */
4420                 if (sec->sh.sh_flags & SHF_EXECINSTR)
4421                         continue;
4422
4423                 if (!sec->rsec)
4424                         continue;
4425
4426                 /*
4427                  * These sections can reference text addresses, but not with
4428                  * the intent to indirect branch to them.
4429                  */
4430                 if ((!strncmp(sec->name, ".discard", 8) &&
4431                      strcmp(sec->name, ".discard.ibt_endbr_noseal"))    ||
4432                     !strncmp(sec->name, ".debug", 6)                    ||
4433                     !strcmp(sec->name, ".altinstructions")              ||
4434                     !strcmp(sec->name, ".ibt_endbr_seal")               ||
4435                     !strcmp(sec->name, ".orc_unwind_ip")                ||
4436                     !strcmp(sec->name, ".parainstructions")             ||
4437                     !strcmp(sec->name, ".retpoline_sites")              ||
4438                     !strcmp(sec->name, ".smp_locks")                    ||
4439                     !strcmp(sec->name, ".static_call_sites")            ||
4440                     !strcmp(sec->name, "_error_injection_whitelist")    ||
4441                     !strcmp(sec->name, "_kprobe_blacklist")             ||
4442                     !strcmp(sec->name, "__bug_table")                   ||
4443                     !strcmp(sec->name, "__ex_table")                    ||
4444                     !strcmp(sec->name, "__jump_table")                  ||
4445                     !strcmp(sec->name, "__mcount_loc")                  ||
4446                     !strcmp(sec->name, ".kcfi_traps")                   ||
4447                     strstr(sec->name, "__patchable_function_entries"))
4448                         continue;
4449
4450                 for_each_reloc(sec->rsec, reloc)
4451                         warnings += validate_ibt_data_reloc(file, reloc);
4452         }
4453
4454         return warnings;
4455 }
4456
4457 static int validate_sls(struct objtool_file *file)
4458 {
4459         struct instruction *insn, *next_insn;
4460         int warnings = 0;
4461
4462         for_each_insn(file, insn) {
4463                 next_insn = next_insn_same_sec(file, insn);
4464
4465                 if (insn->retpoline_safe)
4466                         continue;
4467
4468                 switch (insn->type) {
4469                 case INSN_RETURN:
4470                         if (!next_insn || next_insn->type != INSN_TRAP) {
4471                                 WARN_INSN(insn, "missing int3 after ret");
4472                                 warnings++;
4473                         }
4474
4475                         break;
4476                 case INSN_JUMP_DYNAMIC:
4477                         if (!next_insn || next_insn->type != INSN_TRAP) {
4478                                 WARN_INSN(insn, "missing int3 after indirect jump");
4479                                 warnings++;
4480                         }
4481                         break;
4482                 default:
4483                         break;
4484                 }
4485         }
4486
4487         return warnings;
4488 }
4489
4490 static bool ignore_noreturn_call(struct instruction *insn)
4491 {
4492         struct symbol *call_dest = insn_call_dest(insn);
4493
4494         /*
4495          * FIXME: hack, we need a real noreturn solution
4496          *
4497          * Problem is, exc_double_fault() may or may not return, depending on
4498          * whether CONFIG_X86_ESPFIX64 is set.  But objtool has no visibility
4499          * to the kernel config.
4500          *
4501          * Other potential ways to fix it:
4502          *
4503          *   - have compiler communicate __noreturn functions somehow
4504          *   - remove CONFIG_X86_ESPFIX64
4505          *   - read the .config file
4506          *   - add a cmdline option
4507          *   - create a generic objtool annotation format (vs a bunch of custom
4508          *     formats) and annotate it
4509          */
4510         if (!strcmp(call_dest->name, "exc_double_fault")) {
4511                 /* prevent further unreachable warnings for the caller */
4512                 insn->sym->warned = 1;
4513                 return true;
4514         }
4515
4516         return false;
4517 }
4518
4519 static int validate_reachable_instructions(struct objtool_file *file)
4520 {
4521         struct instruction *insn, *prev_insn;
4522         struct symbol *call_dest;
4523         int warnings = 0;
4524
4525         if (file->ignore_unreachables)
4526                 return 0;
4527
4528         for_each_insn(file, insn) {
4529                 if (insn->visited || ignore_unreachable_insn(file, insn))
4530                         continue;
4531
4532                 prev_insn = prev_insn_same_sec(file, insn);
4533                 if (prev_insn && prev_insn->dead_end) {
4534                         call_dest = insn_call_dest(prev_insn);
4535                         if (call_dest && !ignore_noreturn_call(prev_insn)) {
4536                                 WARN_INSN(insn, "%s() is missing a __noreturn annotation",
4537                                           call_dest->name);
4538                                 warnings++;
4539                                 continue;
4540                         }
4541                 }
4542
4543                 WARN_INSN(insn, "unreachable instruction");
4544                 warnings++;
4545         }
4546
4547         return warnings;
4548 }
4549
4550 /* 'funcs' is a space-separated list of function names */
4551 static int disas_funcs(const char *funcs)
4552 {
4553         const char *objdump_str, *cross_compile;
4554         int size, ret;
4555         char *cmd;
4556
4557         cross_compile = getenv("CROSS_COMPILE");
4558
4559         objdump_str = "%sobjdump -wdr %s | gawk -M -v _funcs='%s' '"
4560                         "BEGIN { split(_funcs, funcs); }"
4561                         "/^$/ { func_match = 0; }"
4562                         "/<.*>:/ { "
4563                                 "f = gensub(/.*<(.*)>:/, \"\\\\1\", 1);"
4564                                 "for (i in funcs) {"
4565                                         "if (funcs[i] == f) {"
4566                                                 "func_match = 1;"
4567                                                 "base = strtonum(\"0x\" $1);"
4568                                                 "break;"
4569                                         "}"
4570                                 "}"
4571                         "}"
4572                         "{"
4573                                 "if (func_match) {"
4574                                         "addr = strtonum(\"0x\" $1);"
4575                                         "printf(\"%%04x \", addr - base);"
4576                                         "print;"
4577                                 "}"
4578                         "}' 1>&2";
4579
4580         /* fake snprintf() to calculate the size */
4581         size = snprintf(NULL, 0, objdump_str, cross_compile, objname, funcs) + 1;
4582         if (size <= 0) {
4583                 WARN("objdump string size calculation failed");
4584                 return -1;
4585         }
4586
4587         cmd = malloc(size);
4588
4589         /* real snprintf() */
4590         snprintf(cmd, size, objdump_str, cross_compile, objname, funcs);
4591         ret = system(cmd);
4592         if (ret) {
4593                 WARN("disassembly failed: %d", ret);
4594                 return -1;
4595         }
4596
4597         return 0;
4598 }
4599
4600 static int disas_warned_funcs(struct objtool_file *file)
4601 {
4602         struct symbol *sym;
4603         char *funcs = NULL, *tmp;
4604
4605         for_each_sym(file, sym) {
4606                 if (sym->warned) {
4607                         if (!funcs) {
4608                                 funcs = malloc(strlen(sym->name) + 1);
4609                                 strcpy(funcs, sym->name);
4610                         } else {
4611                                 tmp = malloc(strlen(funcs) + strlen(sym->name) + 2);
4612                                 sprintf(tmp, "%s %s", funcs, sym->name);
4613                                 free(funcs);
4614                                 funcs = tmp;
4615                         }
4616                 }
4617         }
4618
4619         if (funcs)
4620                 disas_funcs(funcs);
4621
4622         return 0;
4623 }
4624
4625 struct insn_chunk {
4626         void *addr;
4627         struct insn_chunk *next;
4628 };
4629
4630 /*
4631  * Reduce peak RSS usage by freeing insns memory before writing the ELF file,
4632  * which can trigger more allocations for .debug_* sections whose data hasn't
4633  * been read yet.
4634  */
4635 static void free_insns(struct objtool_file *file)
4636 {
4637         struct instruction *insn;
4638         struct insn_chunk *chunks = NULL, *chunk;
4639
4640         for_each_insn(file, insn) {
4641                 if (!insn->idx) {
4642                         chunk = malloc(sizeof(*chunk));
4643                         chunk->addr = insn;
4644                         chunk->next = chunks;
4645                         chunks = chunk;
4646                 }
4647         }
4648
4649         for (chunk = chunks; chunk; chunk = chunk->next)
4650                 free(chunk->addr);
4651 }
4652
4653 int check(struct objtool_file *file)
4654 {
4655         int ret, warnings = 0;
4656
4657         arch_initial_func_cfi_state(&initial_func_cfi);
4658         init_cfi_state(&init_cfi);
4659         init_cfi_state(&func_cfi);
4660         set_func_state(&func_cfi);
4661         init_cfi_state(&force_undefined_cfi);
4662         force_undefined_cfi.force_undefined = true;
4663
4664         if (!cfi_hash_alloc(1UL << (file->elf->symbol_bits - 3)))
4665                 goto out;
4666
4667         cfi_hash_add(&init_cfi);
4668         cfi_hash_add(&func_cfi);
4669
4670         ret = decode_sections(file);
4671         if (ret < 0)
4672                 goto out;
4673
4674         warnings += ret;
4675
4676         if (!nr_insns)
4677                 goto out;
4678
4679         if (opts.retpoline) {
4680                 ret = validate_retpoline(file);
4681                 if (ret < 0)
4682                         return ret;
4683                 warnings += ret;
4684         }
4685
4686         if (opts.stackval || opts.orc || opts.uaccess) {
4687                 ret = validate_functions(file);
4688                 if (ret < 0)
4689                         goto out;
4690                 warnings += ret;
4691
4692                 ret = validate_unwind_hints(file, NULL);
4693                 if (ret < 0)
4694                         goto out;
4695                 warnings += ret;
4696
4697                 if (!warnings) {
4698                         ret = validate_reachable_instructions(file);
4699                         if (ret < 0)
4700                                 goto out;
4701                         warnings += ret;
4702                 }
4703
4704         } else if (opts.noinstr) {
4705                 ret = validate_noinstr_sections(file);
4706                 if (ret < 0)
4707                         goto out;
4708                 warnings += ret;
4709         }
4710
4711         if (opts.unret) {
4712                 /*
4713                  * Must be after validate_branch() and friends, it plays
4714                  * further games with insn->visited.
4715                  */
4716                 ret = validate_unrets(file);
4717                 if (ret < 0)
4718                         return ret;
4719                 warnings += ret;
4720         }
4721
4722         if (opts.ibt) {
4723                 ret = validate_ibt(file);
4724                 if (ret < 0)
4725                         goto out;
4726                 warnings += ret;
4727         }
4728
4729         if (opts.sls) {
4730                 ret = validate_sls(file);
4731                 if (ret < 0)
4732                         goto out;
4733                 warnings += ret;
4734         }
4735
4736         if (opts.static_call) {
4737                 ret = create_static_call_sections(file);
4738                 if (ret < 0)
4739                         goto out;
4740                 warnings += ret;
4741         }
4742
4743         if (opts.retpoline) {
4744                 ret = create_retpoline_sites_sections(file);
4745                 if (ret < 0)
4746                         goto out;
4747                 warnings += ret;
4748         }
4749
4750         if (opts.cfi) {
4751                 ret = create_cfi_sections(file);
4752                 if (ret < 0)
4753                         goto out;
4754                 warnings += ret;
4755         }
4756
4757         if (opts.rethunk) {
4758                 ret = create_return_sites_sections(file);
4759                 if (ret < 0)
4760                         goto out;
4761                 warnings += ret;
4762
4763                 if (opts.hack_skylake) {
4764                         ret = create_direct_call_sections(file);
4765                         if (ret < 0)
4766                                 goto out;
4767                         warnings += ret;
4768                 }
4769         }
4770
4771         if (opts.mcount) {
4772                 ret = create_mcount_loc_sections(file);
4773                 if (ret < 0)
4774                         goto out;
4775                 warnings += ret;
4776         }
4777
4778         if (opts.prefix) {
4779                 ret = add_prefix_symbols(file);
4780                 if (ret < 0)
4781                         return ret;
4782                 warnings += ret;
4783         }
4784
4785         if (opts.ibt) {
4786                 ret = create_ibt_endbr_seal_sections(file);
4787                 if (ret < 0)
4788                         goto out;
4789                 warnings += ret;
4790         }
4791
4792         if (opts.orc && nr_insns) {
4793                 ret = orc_create(file);
4794                 if (ret < 0)
4795                         goto out;
4796                 warnings += ret;
4797         }
4798
4799         free_insns(file);
4800
4801         if (opts.verbose)
4802                 disas_warned_funcs(file);
4803
4804         if (opts.stats) {
4805                 printf("nr_insns_visited: %ld\n", nr_insns_visited);
4806                 printf("nr_cfi: %ld\n", nr_cfi);
4807                 printf("nr_cfi_reused: %ld\n", nr_cfi_reused);
4808                 printf("nr_cfi_cache: %ld\n", nr_cfi_cache);
4809         }
4810
4811 out:
4812         /*
4813          *  For now, don't fail the kernel build on fatal warnings.  These
4814          *  errors are still fairly common due to the growing matrix of
4815          *  supported toolchains and their recent pace of change.
4816          */
4817         return 0;
4818 }