tools/objtool/check.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>
   4  */
   5
   6 #include <string.h>
   7 #include <stdlib.h>
   8
   9 #include "builtin.h"
  10 #include "cfi.h"
  11 #include "arch.h"
  12 #include "check.h"
  13 #include "special.h"
  14 #include "warn.h"
  15 #include "arch_elf.h"
  16
  17 #include <linux/hashtable.h>
  18 #include <linux/kernel.h>
  19
  20 #define FAKE_JUMP_OFFSET -1
  21
  22 #define C_JUMP_TABLE_SECTION ".rodata..c_jump_table"
  23
  24 struct alternative {
  25         struct list_head list;
  26         struct instruction *insn;
  27         bool skip_orig;
  28 };
  29
  30 const char *objname;
  31 struct cfi_init_state initial_func_cfi;
  32
  33 struct instruction *find_insn(struct objtool_file *file,
  34                               struct section *sec, unsigned long offset)
  35 {
  36         struct instruction *insn;
  37
  38         hash_for_each_possible(file->insn_hash, insn, hash, sec_offset_hash(sec, offset)) {
  39                 if (insn->sec == sec && insn->offset == offset)
  40                         return insn;
  41         }
  42
  43         return NULL;
  44 }
  45
  46 static struct instruction *next_insn_same_sec(struct objtool_file *file,
  47                                               struct instruction *insn)
  48 {
  49         struct instruction *next = list_next_entry(insn, list);
  50
  51         if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
  52                 return NULL;
  53
  54         return next;
  55 }
  56
  57 static struct instruction *next_insn_same_func(struct objtool_file *file,
  58                                                struct instruction *insn)
  59 {
  60         struct instruction *next = list_next_entry(insn, list);
  61         struct symbol *func = insn->func;
  62
  63         if (!func)
  64                 return NULL;
  65
  66         if (&next->list != &file->insn_list && next->func == func)
  67                 return next;
  68
  69         /* Check if we're already in the subfunction: */
  70         if (func == func->cfunc)
  71                 return NULL;
  72
  73         /* Move to the subfunction: */
  74         return find_insn(file, func->cfunc->sec, func->cfunc->offset);
  75 }
  76
  77 static struct instruction *prev_insn_same_sym(struct objtool_file *file,
  78                                                struct instruction *insn)
  79 {
  80         struct instruction *prev = list_prev_entry(insn, list);
  81
  82         if (&prev->list != &file->insn_list && prev->func == insn->func)
  83                 return prev;
  84
  85         return NULL;
  86 }
  87
  88 #define func_for_each_insn(file, func, insn)                            \
  89         for (insn = find_insn(file, func->sec, func->offset);           \
  90              insn;                                                      \
  91              insn = next_insn_same_func(file, insn))
  92
  93 #define sym_for_each_insn(file, sym, insn)                              \
  94         for (insn = find_insn(file, sym->sec, sym->offset);             \
  95              insn && &insn->list != &file->insn_list &&                 \
  96                 insn->sec == sym->sec &&                                \
  97                 insn->offset < sym->offset + sym->len;                  \
  98              insn = list_next_entry(insn, list))
  99
 100 #define sym_for_each_insn_continue_reverse(file, sym, insn)             \
 101         for (insn = list_prev_entry(insn, list);                        \
 102              &insn->list != &file->insn_list &&                         \
 103                 insn->sec == sym->sec && insn->offset >= sym->offset;   \
 104              insn = list_prev_entry(insn, list))
 105
 106 #define sec_for_each_insn_from(file, insn)                              \
 107         for (; insn; insn = next_insn_same_sec(file, insn))
 108
 109 #define sec_for_each_insn_continue(file, insn)                          \
 110         for (insn = next_insn_same_sec(file, insn); insn;               \
 111              insn = next_insn_same_sec(file, insn))
 112
 113 static bool is_static_jump(struct instruction *insn)
 114 {
 115         return insn->type == INSN_JUMP_CONDITIONAL ||
 116                insn->type == INSN_JUMP_UNCONDITIONAL;
 117 }
 118
 119 static bool is_sibling_call(struct instruction *insn)
 120 {
 121         /* An indirect jump is either a sibling call or a jump to a table. */
 122         if (insn->type == INSN_JUMP_DYNAMIC)
 123                 return list_empty(&insn->alts);
 124
 125         if (!is_static_jump(insn))
 126                 return false;
 127
 128         /* add_jump_destinations() sets insn->call_dest for sibling calls. */
 129         return !!insn->call_dest;
 130 }
 131
 132 /*
 133  * This checks to see if the given function is a "noreturn" function.
 134  *
 135  * For global functions which are outside the scope of this object file, we
 136  * have to keep a manual list of them.
 137  *
 138  * For local functions, we have to detect them manually by simply looking for
 139  * the lack of a return instruction.
 140  */
 141 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 142                                 int recursion)
 143 {
 144         int i;
 145         struct instruction *insn;
 146         bool empty = true;
 147
 148         /*
 149          * Unfortunately these have to be hard coded because the noreturn
 150          * attribute isn't provided in ELF data.
 151          */
 152         static const char * const global_noreturns[] = {
 153                 "__stack_chk_fail",
 154                 "panic",
 155                 "do_exit",
 156                 "do_task_dead",
 157                 "__module_put_and_exit",
 158                 "complete_and_exit",
 159                 "__reiserfs_panic",
 160                 "lbug_with_loc",
 161                 "fortify_panic",
 162                 "usercopy_abort",
 163                 "machine_real_restart",
 164                 "rewind_stack_do_exit",
 165                 "kunit_try_catch_throw",
 166         };
 167
 168         if (!func)
 169                 return false;
 170
 171         if (func->bind == STB_WEAK)
 172                 return false;
 173
 174         if (func->bind == STB_GLOBAL)
 175                 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
 176                         if (!strcmp(func->name, global_noreturns[i]))
 177                                 return true;
 178
 179         if (!func->len)
 180                 return false;
 181
 182         insn = find_insn(file, func->sec, func->offset);
 183         if (!insn->func)
 184                 return false;
 185
 186         func_for_each_insn(file, func, insn) {
 187                 empty = false;
 188
 189                 if (insn->type == INSN_RETURN)
 190                         return false;
 191         }
 192
 193         if (empty)
 194                 return false;
 195
 196         /*
 197          * A function can have a sibling call instead of a return.  In that
 198          * case, the function's dead-end status depends on whether the target
 199          * of the sibling call returns.
 200          */
 201         func_for_each_insn(file, func, insn) {
 202                 if (is_sibling_call(insn)) {
 203                         struct instruction *dest = insn->jump_dest;
 204
 205                         if (!dest)
 206                                 /* sibling call to another file */
 207                                 return false;
 208
 209                         /* local sibling call */
 210                         if (recursion == 5) {
 211                                 /*
 212                                  * Infinite recursion: two functions have
 213                                  * sibling calls to each other.  This is a very
 214                                  * rare case.  It means they aren't dead ends.
 215                                  */
 216                                 return false;
 217                         }
 218
 219                         return __dead_end_function(file, dest->func, recursion+1);
 220                 }
 221         }
 222
 223         return true;
 224 }
 225
 226 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
 227 {
 228         return __dead_end_function(file, func, 0);
 229 }
 230
 231 static void init_cfi_state(struct cfi_state *cfi)
 232 {
 233         int i;
 234
 235         for (i = 0; i < CFI_NUM_REGS; i++) {
 236                 cfi->regs[i].base = CFI_UNDEFINED;
 237                 cfi->vals[i].base = CFI_UNDEFINED;
 238         }
 239         cfi->cfa.base = CFI_UNDEFINED;
 240         cfi->drap_reg = CFI_UNDEFINED;
 241         cfi->drap_offset = -1;
 242 }
 243
 244 static void init_insn_state(struct insn_state *state, struct section *sec)
 245 {
 246         memset(state, 0, sizeof(*state));
 247         init_cfi_state(&state->cfi);
 248
 249         /*
 250          * We need the full vmlinux for noinstr validation, otherwise we can
 251          * not correctly determine insn->call_dest->sec (external symbols do
 252          * not have a section).
 253          */
 254         if (vmlinux && sec)
 255                 state->noinstr = sec->noinstr;
 256 }
 257
 258 /*
 259  * Call the arch-specific instruction decoder for all the instructions and add
 260  * them to the global instruction list.
 261  */
 262 static int decode_instructions(struct objtool_file *file)
 263 {
 264         struct section *sec;
 265         struct symbol *func;
 266         unsigned long offset;
 267         struct instruction *insn;
 268         unsigned long nr_insns = 0;
 269         int ret;
 270
 271         for_each_sec(file, sec) {
 272
 273                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
 274                         continue;
 275
 276                 if (strcmp(sec->name, ".altinstr_replacement") &&
 277                     strcmp(sec->name, ".altinstr_aux") &&
 278                     strncmp(sec->name, ".discard.", 9))
 279                         sec->text = true;
 280
 281                 if (!strcmp(sec->name, ".noinstr.text") ||
 282                     !strcmp(sec->name, ".entry.text"))
 283                         sec->noinstr = true;
 284
 285                 for (offset = 0; offset < sec->len; offset += insn->len) {
 286                         insn = malloc(sizeof(*insn));
 287                         if (!insn) {
 288                                 WARN("malloc failed");
 289                                 return -1;
 290                         }
 291                         memset(insn, 0, sizeof(*insn));
 292                         INIT_LIST_HEAD(&insn->alts);
 293                         INIT_LIST_HEAD(&insn->stack_ops);
 294                         init_cfi_state(&insn->cfi);
 295
 296                         insn->sec = sec;
 297                         insn->offset = offset;
 298
 299                         ret = arch_decode_instruction(file->elf, sec, offset,
 300                                                       sec->len - offset,
 301                                                       &insn->len, &insn->type,
 302                                                       &insn->immediate,
 303                                                       &insn->stack_ops);
 304                         if (ret)
 305                                 goto err;
 306
 307                         hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));
 308                         list_add_tail(&insn->list, &file->insn_list);
 309                         nr_insns++;
 310                 }
 311
 312                 list_for_each_entry(func, &sec->symbol_list, list) {
 313                         if (func->type != STT_FUNC || func->alias != func)
 314                                 continue;
 315
 316                         if (!find_insn(file, sec, func->offset)) {
 317                                 WARN("%s(): can't find starting instruction",
 318                                      func->name);
 319                                 return -1;
 320                         }
 321
 322                         sym_for_each_insn(file, func, insn)
 323                                 insn->func = func;
 324                 }
 325         }
 326
 327         if (stats)
 328                 printf("nr_insns: %lu\n", nr_insns);
 329
 330         return 0;
 331
 332 err:
 333         free(insn);
 334         return ret;
 335 }
 336
 337 static struct instruction *find_last_insn(struct objtool_file *file,
 338                                           struct section *sec)
 339 {
 340         struct instruction *insn = NULL;
 341         unsigned int offset;
 342         unsigned int end = (sec->len > 10) ? sec->len - 10 : 0;
 343
 344         for (offset = sec->len - 1; offset >= end && !insn; offset--)
 345                 insn = find_insn(file, sec, offset);
 346
 347         return insn;
 348 }
 349
 350 /*
 351  * Mark "ud2" instructions and manually annotated dead ends.
 352  */
 353 static int add_dead_ends(struct objtool_file *file)
 354 {
 355         struct section *sec;
 356         struct reloc *reloc;
 357         struct instruction *insn;
 358
 359         /*
 360          * By default, "ud2" is a dead end unless otherwise annotated, because
 361          * GCC 7 inserts it for certain divide-by-zero cases.
 362          */
 363         for_each_insn(file, insn)
 364                 if (insn->type == INSN_BUG)
 365                         insn->dead_end = true;
 366
 367         /*
 368          * Check for manually annotated dead ends.
 369          */
 370         sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
 371         if (!sec)
 372                 goto reachable;
 373
 374         list_for_each_entry(reloc, &sec->reloc_list, list) {
 375                 if (reloc->sym->type != STT_SECTION) {
 376                         WARN("unexpected relocation symbol type in %s", sec->name);
 377                         return -1;
 378                 }
 379                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 380                 if (insn)
 381                         insn = list_prev_entry(insn, list);
 382                 else if (reloc->addend == reloc->sym->sec->len) {
 383                         insn = find_last_insn(file, reloc->sym->sec);
 384                         if (!insn) {
 385                                 WARN("can't find unreachable insn at %s+0x%x",
 386                                      reloc->sym->sec->name, reloc->addend);
 387                                 return -1;
 388                         }
 389                 } else {
 390                         WARN("can't find unreachable insn at %s+0x%x",
 391                              reloc->sym->sec->name, reloc->addend);
 392                         return -1;
 393                 }
 394
 395                 insn->dead_end = true;
 396         }
 397
 398 reachable:
 399         /*
 400          * These manually annotated reachable checks are needed for GCC 4.4,
 401          * where the Linux unreachable() macro isn't supported.  In that case
 402          * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
 403          * not a dead end.
 404          */
 405         sec = find_section_by_name(file->elf, ".rela.discard.reachable");
 406         if (!sec)
 407                 return 0;
 408
 409         list_for_each_entry(reloc, &sec->reloc_list, list) {
 410                 if (reloc->sym->type != STT_SECTION) {
 411                         WARN("unexpected relocation symbol type in %s", sec->name);
 412                         return -1;
 413                 }
 414                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 415                 if (insn)
 416                         insn = list_prev_entry(insn, list);
 417                 else if (reloc->addend == reloc->sym->sec->len) {
 418                         insn = find_last_insn(file, reloc->sym->sec);
 419                         if (!insn) {
 420                                 WARN("can't find reachable insn at %s+0x%x",
 421                                      reloc->sym->sec->name, reloc->addend);
 422                                 return -1;
 423                         }
 424                 } else {
 425                         WARN("can't find reachable insn at %s+0x%x",
 426                              reloc->sym->sec->name, reloc->addend);
 427                         return -1;
 428                 }
 429
 430                 insn->dead_end = false;
 431         }
 432
 433         return 0;
 434 }
 435
 436 /*
 437  * Warnings shouldn't be reported for ignored functions.
 438  */
 439 static void add_ignores(struct objtool_file *file)
 440 {
 441         struct instruction *insn;
 442         struct section *sec;
 443         struct symbol *func;
 444         struct reloc *reloc;
 445
 446         sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
 447         if (!sec)
 448                 return;
 449
 450         list_for_each_entry(reloc, &sec->reloc_list, list) {
 451                 switch (reloc->sym->type) {
 452                 case STT_FUNC:
 453                         func = reloc->sym;
 454                         break;
 455
 456                 case STT_SECTION:
 457                         func = find_func_by_offset(reloc->sym->sec, reloc->addend);
 458                         if (!func)
 459                                 continue;
 460                         break;
 461
 462                 default:
 463                         WARN("unexpected relocation symbol type in %s: %d", sec->name, reloc->sym->type);
 464                         continue;
 465                 }
 466
 467                 func_for_each_insn(file, func, insn)
 468                         insn->ignore = true;
 469         }
 470 }
 471
 472 /*
 473  * This is a whitelist of functions that is allowed to be called with AC set.
 474  * The list is meant to be minimal and only contains compiler instrumentation
 475  * ABI and a few functions used to implement *_{to,from}_user() functions.
 476  *
 477  * These functions must not directly change AC, but may PUSHF/POPF.
 478  */
 479 static const char *uaccess_safe_builtin[] = {
 480         /* KASAN */
 481         "kasan_report",
 482         "check_memory_region",
 483         /* KASAN out-of-line */
 484         "__asan_loadN_noabort",
 485         "__asan_load1_noabort",
 486         "__asan_load2_noabort",
 487         "__asan_load4_noabort",
 488         "__asan_load8_noabort",
 489         "__asan_load16_noabort",
 490         "__asan_storeN_noabort",
 491         "__asan_store1_noabort",
 492         "__asan_store2_noabort",
 493         "__asan_store4_noabort",
 494         "__asan_store8_noabort",
 495         "__asan_store16_noabort",
 496         /* KASAN in-line */
 497         "__asan_report_load_n_noabort",
 498         "__asan_report_load1_noabort",
 499         "__asan_report_load2_noabort",
 500         "__asan_report_load4_noabort",
 501         "__asan_report_load8_noabort",
 502         "__asan_report_load16_noabort",
 503         "__asan_report_store_n_noabort",
 504         "__asan_report_store1_noabort",
 505         "__asan_report_store2_noabort",
 506         "__asan_report_store4_noabort",
 507         "__asan_report_store8_noabort",
 508         "__asan_report_store16_noabort",
 509         /* KCSAN */
 510         "__kcsan_check_access",
 511         "kcsan_found_watchpoint",
 512         "kcsan_setup_watchpoint",
 513         "kcsan_check_scoped_accesses",
 514         "kcsan_disable_current",
 515         "kcsan_enable_current_nowarn",
 516         /* KCSAN/TSAN */
 517         "__tsan_func_entry",
 518         "__tsan_func_exit",
 519         "__tsan_read_range",
 520         "__tsan_write_range",
 521         "__tsan_read1",
 522         "__tsan_read2",
 523         "__tsan_read4",
 524         "__tsan_read8",
 525         "__tsan_read16",
 526         "__tsan_write1",
 527         "__tsan_write2",
 528         "__tsan_write4",
 529         "__tsan_write8",
 530         "__tsan_write16",
 531         /* KCOV */
 532         "write_comp_data",
 533         "check_kcov_mode",
 534         "__sanitizer_cov_trace_pc",
 535         "__sanitizer_cov_trace_const_cmp1",
 536         "__sanitizer_cov_trace_const_cmp2",
 537         "__sanitizer_cov_trace_const_cmp4",
 538         "__sanitizer_cov_trace_const_cmp8",
 539         "__sanitizer_cov_trace_cmp1",
 540         "__sanitizer_cov_trace_cmp2",
 541         "__sanitizer_cov_trace_cmp4",
 542         "__sanitizer_cov_trace_cmp8",
 543         "__sanitizer_cov_trace_switch",
 544         /* UBSAN */
 545         "ubsan_type_mismatch_common",
 546         "__ubsan_handle_type_mismatch",
 547         "__ubsan_handle_type_mismatch_v1",
 548         "__ubsan_handle_shift_out_of_bounds",
 549         /* misc */
 550         "csum_partial_copy_generic",
 551         "__memcpy_mcsafe",
 552         "mcsafe_handle_tail",
 553         "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
 554         NULL
 555 };
 556
 557 static void add_uaccess_safe(struct objtool_file *file)
 558 {
 559         struct symbol *func;
 560         const char **name;
 561
 562         if (!uaccess)
 563                 return;
 564
 565         for (name = uaccess_safe_builtin; *name; name++) {
 566                 func = find_symbol_by_name(file->elf, *name);
 567                 if (!func)
 568                         continue;
 569
 570                 func->uaccess_safe = true;
 571         }
 572 }
 573
 574 /*
 575  * FIXME: For now, just ignore any alternatives which add retpolines.  This is
 576  * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
 577  * But it at least allows objtool to understand the control flow *around* the
 578  * retpoline.
 579  */
 580 static int add_ignore_alternatives(struct objtool_file *file)
 581 {
 582         struct section *sec;
 583         struct reloc *reloc;
 584         struct instruction *insn;
 585
 586         sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
 587         if (!sec)
 588                 return 0;
 589
 590         list_for_each_entry(reloc, &sec->reloc_list, list) {
 591                 if (reloc->sym->type != STT_SECTION) {
 592                         WARN("unexpected relocation symbol type in %s", sec->name);
 593                         return -1;
 594                 }
 595
 596                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
 597                 if (!insn) {
 598                         WARN("bad .discard.ignore_alts entry");
 599                         return -1;
 600                 }
 601
 602                 insn->ignore_alts = true;
 603         }
 604
 605         return 0;
 606 }
 607
 608 /*
 609  * Find the destination instructions for all jumps.
 610  */
 611 static int add_jump_destinations(struct objtool_file *file)
 612 {
 613         struct instruction *insn;
 614         struct reloc *reloc;
 615         struct section *dest_sec;
 616         unsigned long dest_off;
 617
 618         for_each_insn(file, insn) {
 619                 if (!is_static_jump(insn))
 620                         continue;
 621
 622                 if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET)
 623                         continue;
 624
 625                 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
 626                                                insn->offset, insn->len);
 627                 if (!reloc) {
 628                         dest_sec = insn->sec;
 629                         dest_off = arch_jump_destination(insn);
 630                 } else if (reloc->sym->type == STT_SECTION) {
 631                         dest_sec = reloc->sym->sec;
 632                         dest_off = arch_dest_reloc_offset(reloc->addend);
 633                 } else if (reloc->sym->sec->idx) {
 634                         dest_sec = reloc->sym->sec;
 635                         dest_off = reloc->sym->sym.st_value +
 636                                    arch_dest_reloc_offset(reloc->addend);
 637                 } else if (strstr(reloc->sym->name, "_indirect_thunk_")) {
 638                         /*
 639                          * Retpoline jumps are really dynamic jumps in
 640                          * disguise, so convert them accordingly.
 641                          */
 642                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
 643                                 insn->type = INSN_JUMP_DYNAMIC;
 644                         else
 645                                 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
 646
 647                         insn->retpoline_safe = true;
 648                         continue;
 649                 } else {
 650                         /* external sibling call */
 651                         insn->call_dest = reloc->sym;
 652                         continue;
 653                 }
 654
 655                 insn->jump_dest = find_insn(file, dest_sec, dest_off);
 656                 if (!insn->jump_dest) {
 657
 658                         /*
 659                          * This is a special case where an alt instruction
 660                          * jumps past the end of the section.  These are
 661                          * handled later in handle_group_alt().
 662                          */
 663                         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
 664                                 continue;
 665
 666                         WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
 667                                   insn->sec, insn->offset, dest_sec->name,
 668                                   dest_off);
 669                         return -1;
 670                 }
 671
 672                 /*
 673                  * Cross-function jump.
 674                  */
 675                 if (insn->func && insn->jump_dest->func &&
 676                     insn->func != insn->jump_dest->func) {
 677
 678                         /*
 679                          * For GCC 8+, create parent/child links for any cold
 680                          * subfunctions.  This is _mostly_ redundant with a
 681                          * similar initialization in read_symbols().
 682                          *
 683                          * If a function has aliases, we want the *first* such
 684                          * function in the symbol table to be the subfunction's
 685                          * parent.  In that case we overwrite the
 686                          * initialization done in read_symbols().
 687                          *
 688                          * However this code can't completely replace the
 689                          * read_symbols() code because this doesn't detect the
 690                          * case where the parent function's only reference to a
 691                          * subfunction is through a jump table.
 692                          */
 693                         if (!strstr(insn->func->name, ".cold.") &&
 694                             strstr(insn->jump_dest->func->name, ".cold.")) {
 695                                 insn->func->cfunc = insn->jump_dest->func;
 696                                 insn->jump_dest->func->pfunc = insn->func;
 697
 698                         } else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
 699                                    insn->jump_dest->offset == insn->jump_dest->func->offset) {
 700
 701                                 /* internal sibling call */
 702                                 insn->call_dest = insn->jump_dest->func;
 703                         }
 704                 }
 705         }
 706
 707         return 0;
 708 }
 709
 710 static void remove_insn_ops(struct instruction *insn)
 711 {
 712         struct stack_op *op, *tmp;
 713
 714         list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) {
 715                 list_del(&op->list);
 716                 free(op);
 717         }
 718 }
 719
 720 /*
 721  * Find the destination instructions for all calls.
 722  */
 723 static int add_call_destinations(struct objtool_file *file)
 724 {
 725         struct instruction *insn;
 726         unsigned long dest_off;
 727         struct reloc *reloc;
 728
 729         for_each_insn(file, insn) {
 730                 if (insn->type != INSN_CALL)
 731                         continue;
 732
 733                 reloc = find_reloc_by_dest_range(file->elf, insn->sec,
 734                                                insn->offset, insn->len);
 735                 if (!reloc) {
 736                         dest_off = arch_jump_destination(insn);
 737                         insn->call_dest = find_func_by_offset(insn->sec, dest_off);
 738                         if (!insn->call_dest)
 739                                 insn->call_dest = find_symbol_by_offset(insn->sec, dest_off);
 740
 741                         if (insn->ignore)
 742                                 continue;
 743
 744                         if (!insn->call_dest) {
 745                                 WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);
 746                                 return -1;
 747                         }
 748
 749                         if (insn->func && insn->call_dest->type != STT_FUNC) {
 750                                 WARN_FUNC("unsupported call to non-function",
 751                                           insn->sec, insn->offset);
 752                                 return -1;
 753                         }
 754
 755                 } else if (reloc->sym->type == STT_SECTION) {
 756                         dest_off = arch_dest_reloc_offset(reloc->addend);
 757                         insn->call_dest = find_func_by_offset(reloc->sym->sec,
 758                                                               dest_off);
 759                         if (!insn->call_dest) {
 760                                 WARN_FUNC("can't find call dest symbol at %s+0x%lx",
 761                                           insn->sec, insn->offset,
 762                                           reloc->sym->sec->name,
 763                                           dest_off);
 764                                 return -1;
 765                         }
 766                 } else
 767                         insn->call_dest = reloc->sym;
 768
 769                 /*
 770                  * Many compilers cannot disable KCOV with a function attribute
 771                  * so they need a little help, NOP out any KCOV calls from noinstr
 772                  * text.
 773                  */
 774                 if (insn->sec->noinstr &&
 775                     !strncmp(insn->call_dest->name, "__sanitizer_cov_", 16)) {
 776                         if (reloc) {
 777                                 reloc->type = R_NONE;
 778                                 elf_write_reloc(file->elf, reloc);
 779                         }
 780
 781                         elf_write_insn(file->elf, insn->sec,
 782                                        insn->offset, insn->len,
 783                                        arch_nop_insn(insn->len));
 784                         insn->type = INSN_NOP;
 785                 }
 786
 787                 /*
 788                  * Whatever stack impact regular CALLs have, should be undone
 789                  * by the RETURN of the called function.
 790                  *
 791                  * Annotated intra-function calls retain the stack_ops but
 792                  * are converted to JUMP, see read_intra_function_calls().
 793                  */
 794                 remove_insn_ops(insn);
 795         }
 796
 797         return 0;
 798 }
 799
 800 /*
 801  * The .alternatives section requires some extra special care, over and above
 802  * what other special sections require:
 803  *
 804  * 1. Because alternatives are patched in-place, we need to insert a fake jump
 805  *    instruction at the end so that validate_branch() skips all the original
 806  *    replaced instructions when validating the new instruction path.
 807  *
 808  * 2. An added wrinkle is that the new instruction length might be zero.  In
 809  *    that case the old instructions are replaced with noops.  We simulate that
 810  *    by creating a fake jump as the only new instruction.
 811  *
 812  * 3. In some cases, the alternative section includes an instruction which
 813  *    conditionally jumps to the _end_ of the entry.  We have to modify these
 814  *    jumps' destinations to point back to .text rather than the end of the
 815  *    entry in .altinstr_replacement.
 816  */
 817 static int handle_group_alt(struct objtool_file *file,
 818                             struct special_alt *special_alt,
 819                             struct instruction *orig_insn,
 820                             struct instruction **new_insn)
 821 {
 822         static unsigned int alt_group_next_index = 1;
 823         struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
 824         unsigned int alt_group = alt_group_next_index++;
 825         unsigned long dest_off;
 826
 827         last_orig_insn = NULL;
 828         insn = orig_insn;
 829         sec_for_each_insn_from(file, insn) {
 830                 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
 831                         break;
 832
 833                 insn->alt_group = alt_group;
 834                 last_orig_insn = insn;
 835         }
 836
 837         if (next_insn_same_sec(file, last_orig_insn)) {
 838                 fake_jump = malloc(sizeof(*fake_jump));
 839                 if (!fake_jump) {
 840                         WARN("malloc failed");
 841                         return -1;
 842                 }
 843                 memset(fake_jump, 0, sizeof(*fake_jump));
 844                 INIT_LIST_HEAD(&fake_jump->alts);
 845                 INIT_LIST_HEAD(&fake_jump->stack_ops);
 846                 init_cfi_state(&fake_jump->cfi);
 847
 848                 fake_jump->sec = special_alt->new_sec;
 849                 fake_jump->offset = FAKE_JUMP_OFFSET;
 850                 fake_jump->type = INSN_JUMP_UNCONDITIONAL;
 851                 fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
 852                 fake_jump->func = orig_insn->func;
 853         }
 854
 855         if (!special_alt->new_len) {
 856                 if (!fake_jump) {
 857                         WARN("%s: empty alternative at end of section",
 858                              special_alt->orig_sec->name);
 859                         return -1;
 860                 }
 861
 862                 *new_insn = fake_jump;
 863                 return 0;
 864         }
 865
 866         last_new_insn = NULL;
 867         alt_group = alt_group_next_index++;
 868         insn = *new_insn;
 869         sec_for_each_insn_from(file, insn) {
 870                 if (insn->offset >= special_alt->new_off + special_alt->new_len)
 871                         break;
 872
 873                 last_new_insn = insn;
 874
 875                 insn->ignore = orig_insn->ignore_alts;
 876                 insn->func = orig_insn->func;
 877                 insn->alt_group = alt_group;
 878
 879                 /*
 880                  * Since alternative replacement code is copy/pasted by the
 881                  * kernel after applying relocations, generally such code can't
 882                  * have relative-address relocation references to outside the
 883                  * .altinstr_replacement section, unless the arch's
 884                  * alternatives code can adjust the relative offsets
 885                  * accordingly.
 886                  *
 887                  * The x86 alternatives code adjusts the offsets only when it
 888                  * encounters a branch instruction at the very beginning of the
 889                  * replacement group.
 890                  */
 891                 if ((insn->offset != special_alt->new_off ||
 892                     (insn->type != INSN_CALL && !is_static_jump(insn))) &&
 893                     find_reloc_by_dest_range(file->elf, insn->sec, insn->offset, insn->len)) {
 894
 895                         WARN_FUNC("unsupported relocation in alternatives section",
 896                                   insn->sec, insn->offset);
 897                         return -1;
 898                 }
 899
 900                 if (!is_static_jump(insn))
 901                         continue;
 902
 903                 if (!insn->immediate)
 904                         continue;
 905
 906                 dest_off = arch_jump_destination(insn);
 907                 if (dest_off == special_alt->new_off + special_alt->new_len) {
 908                         if (!fake_jump) {
 909                                 WARN("%s: alternative jump to end of section",
 910                                      special_alt->orig_sec->name);
 911                                 return -1;
 912                         }
 913                         insn->jump_dest = fake_jump;
 914                 }
 915
 916                 if (!insn->jump_dest) {
 917                         WARN_FUNC("can't find alternative jump destination",
 918                                   insn->sec, insn->offset);
 919                         return -1;
 920                 }
 921         }
 922
 923         if (!last_new_insn) {
 924                 WARN_FUNC("can't find last new alternative instruction",
 925                           special_alt->new_sec, special_alt->new_off);
 926                 return -1;
 927         }
 928
 929         if (fake_jump)
 930                 list_add(&fake_jump->list, &last_new_insn->list);
 931
 932         return 0;
 933 }
 934
 935 /*
 936  * A jump table entry can either convert a nop to a jump or a jump to a nop.
 937  * If the original instruction is a jump, make the alt entry an effective nop
 938  * by just skipping the original instruction.
 939  */
 940 static int handle_jump_alt(struct objtool_file *file,
 941                            struct special_alt *special_alt,
 942                            struct instruction *orig_insn,
 943                            struct instruction **new_insn)
 944 {
 945         if (orig_insn->type == INSN_NOP)
 946                 return 0;
 947
 948         if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
 949                 WARN_FUNC("unsupported instruction at jump label",
 950                           orig_insn->sec, orig_insn->offset);
 951                 return -1;
 952         }
 953
 954         *new_insn = list_next_entry(orig_insn, list);
 955         return 0;
 956 }
 957
 958 /*
 959  * Read all the special sections which have alternate instructions which can be
 960  * patched in or redirected to at runtime.  Each instruction having alternate
 961  * instruction(s) has them added to its insn->alts list, which will be
 962  * traversed in validate_branch().
 963  */
 964 static int add_special_section_alts(struct objtool_file *file)
 965 {
 966         struct list_head special_alts;
 967         struct instruction *orig_insn, *new_insn;
 968         struct special_alt *special_alt, *tmp;
 969         struct alternative *alt;
 970         int ret;
 971
 972         ret = special_get_alts(file->elf, &special_alts);
 973         if (ret)
 974                 return ret;
 975
 976         list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
 977
 978                 orig_insn = find_insn(file, special_alt->orig_sec,
 979                                       special_alt->orig_off);
 980                 if (!orig_insn) {
 981                         WARN_FUNC("special: can't find orig instruction",
 982                                   special_alt->orig_sec, special_alt->orig_off);
 983                         ret = -1;
 984                         goto out;
 985                 }
 986
 987                 new_insn = NULL;
 988                 if (!special_alt->group || special_alt->new_len) {
 989                         new_insn = find_insn(file, special_alt->new_sec,
 990                                              special_alt->new_off);
 991                         if (!new_insn) {
 992                                 WARN_FUNC("special: can't find new instruction",
 993                                           special_alt->new_sec,
 994                                           special_alt->new_off);
 995                                 ret = -1;
 996                                 goto out;
 997                         }
 998                 }
 999
1000                 if (special_alt->group) {
1001                         if (!special_alt->orig_len) {
1002                                 WARN_FUNC("empty alternative entry",
1003                                           orig_insn->sec, orig_insn->offset);
1004                                 continue;
1005                         }
1006
1007                         ret = handle_group_alt(file, special_alt, orig_insn,
1008                                                &new_insn);
1009                         if (ret)
1010                                 goto out;
1011                 } else if (special_alt->jump_or_nop) {
1012                         ret = handle_jump_alt(file, special_alt, orig_insn,
1013                                               &new_insn);
1014                         if (ret)
1015                                 goto out;
1016                 }
1017
1018                 alt = malloc(sizeof(*alt));
1019                 if (!alt) {
1020                         WARN("malloc failed");
1021                         ret = -1;
1022                         goto out;
1023                 }
1024
1025                 alt->insn = new_insn;
1026                 alt->skip_orig = special_alt->skip_orig;
1027                 orig_insn->ignore_alts |= special_alt->skip_alt;
1028                 list_add_tail(&alt->list, &orig_insn->alts);
1029
1030                 list_del(&special_alt->list);
1031                 free(special_alt);
1032         }
1033
1034 out:
1035         return ret;
1036 }
1037
1038 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
1039                             struct reloc *table)
1040 {
1041         struct reloc *reloc = table;
1042         struct instruction *dest_insn;
1043         struct alternative *alt;
1044         struct symbol *pfunc = insn->func->pfunc;
1045         unsigned int prev_offset = 0;
1046
1047         /*
1048          * Each @reloc is a switch table relocation which points to the target
1049          * instruction.
1050          */
1051         list_for_each_entry_from(reloc, &table->sec->reloc_list, list) {
1052
1053                 /* Check for the end of the table: */
1054                 if (reloc != table && reloc->jump_table_start)
1055                         break;
1056
1057                 /* Make sure the table entries are consecutive: */
1058                 if (prev_offset && reloc->offset != prev_offset + 8)
1059                         break;
1060
1061                 /* Detect function pointers from contiguous objects: */
1062                 if (reloc->sym->sec == pfunc->sec &&
1063                     reloc->addend == pfunc->offset)
1064                         break;
1065
1066                 dest_insn = find_insn(file, reloc->sym->sec, reloc->addend);
1067                 if (!dest_insn)
1068                         break;
1069
1070                 /* Make sure the destination is in the same function: */
1071                 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
1072                         break;
1073
1074                 alt = malloc(sizeof(*alt));
1075                 if (!alt) {
1076                         WARN("malloc failed");
1077                         return -1;
1078                 }
1079
1080                 alt->insn = dest_insn;
1081                 list_add_tail(&alt->list, &insn->alts);
1082                 prev_offset = reloc->offset;
1083         }
1084
1085         if (!prev_offset) {
1086                 WARN_FUNC("can't find switch jump table",
1087                           insn->sec, insn->offset);
1088                 return -1;
1089         }
1090
1091         return 0;
1092 }
1093
1094 /*
1095  * find_jump_table() - Given a dynamic jump, find the switch jump table in
1096  * .rodata associated with it.
1097  *
1098  * There are 3 basic patterns:
1099  *
1100  * 1. jmpq *[rodata addr](,%reg,8)
1101  *
1102  *    This is the most common case by far.  It jumps to an address in a simple
1103  *    jump table which is stored in .rodata.
1104  *
1105  * 2. jmpq *[rodata addr](%rip)
1106  *
1107  *    This is caused by a rare GCC quirk, currently only seen in three driver
1108  *    functions in the kernel, only with certain obscure non-distro configs.
1109  *
1110  *    As part of an optimization, GCC makes a copy of an existing switch jump
1111  *    table, modifies it, and then hard-codes the jump (albeit with an indirect
1112  *    jump) to use a single entry in the table.  The rest of the jump table and
1113  *    some of its jump targets remain as dead code.
1114  *
1115  *    In such a case we can just crudely ignore all unreachable instruction
1116  *    warnings for the entire object file.  Ideally we would just ignore them
1117  *    for the function, but that would require redesigning the code quite a
1118  *    bit.  And honestly that's just not worth doing: unreachable instruction
1119  *    warnings are of questionable value anyway, and this is such a rare issue.
1120  *
1121  * 3. mov [rodata addr],%reg1
1122  *    ... some instructions ...
1123  *    jmpq *(%reg1,%reg2,8)
1124  *
1125  *    This is a fairly uncommon pattern which is new for GCC 6.  As of this
1126  *    writing, there are 11 occurrences of it in the allmodconfig kernel.
1127  *
1128  *    As of GCC 7 there are quite a few more of these and the 'in between' code
1129  *    is significant. Esp. with KASAN enabled some of the code between the mov
1130  *    and jmpq uses .rodata itself, which can confuse things.
1131  *
1132  *    TODO: Once we have DWARF CFI and smarter instruction decoding logic,
1133  *    ensure the same register is used in the mov and jump instructions.
1134  *
1135  *    NOTE: RETPOLINE made it harder still to decode dynamic jumps.
1136  */
1137 static struct reloc *find_jump_table(struct objtool_file *file,
1138                                       struct symbol *func,
1139                                       struct instruction *insn)
1140 {
1141         struct reloc *text_reloc, *table_reloc;
1142         struct instruction *dest_insn, *orig_insn = insn;
1143         struct section *table_sec;
1144         unsigned long table_offset;
1145
1146         /*
1147          * Backward search using the @first_jump_src links, these help avoid
1148          * much of the 'in between' code. Which avoids us getting confused by
1149          * it.
1150          */
1151         for (;
1152              insn && insn->func && insn->func->pfunc == func;
1153              insn = insn->first_jump_src ?: prev_insn_same_sym(file, insn)) {
1154
1155                 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1156                         break;
1157
1158                 /* allow small jumps within the range */
1159                 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1160                     insn->jump_dest &&
1161                     (insn->jump_dest->offset <= insn->offset ||
1162                      insn->jump_dest->offset > orig_insn->offset))
1163                     break;
1164
1165                 /* look for a relocation which references .rodata */
1166                 text_reloc = find_reloc_by_dest_range(file->elf, insn->sec,
1167                                                     insn->offset, insn->len);
1168                 if (!text_reloc || text_reloc->sym->type != STT_SECTION ||
1169                     !text_reloc->sym->sec->rodata)
1170                         continue;
1171
1172                 table_offset = text_reloc->addend;
1173                 table_sec = text_reloc->sym->sec;
1174
1175                 if (text_reloc->type == R_X86_64_PC32)
1176                         table_offset += 4;
1177
1178                 /*
1179                  * Make sure the .rodata address isn't associated with a
1180                  * symbol.  GCC jump tables are anonymous data.
1181                  *
1182                  * Also support C jump tables which are in the same format as
1183                  * switch jump tables.  For objtool to recognize them, they
1184                  * need to be placed in the C_JUMP_TABLE_SECTION section.  They
1185                  * have symbols associated with them.
1186                  */
1187                 if (find_symbol_containing(table_sec, table_offset) &&
1188                     strcmp(table_sec->name, C_JUMP_TABLE_SECTION))
1189                         continue;
1190
1191                 /*
1192                  * Each table entry has a reloc associated with it.  The reloc
1193                  * should reference text in the same function as the original
1194                  * instruction.
1195                  */
1196                 table_reloc = find_reloc_by_dest(file->elf, table_sec, table_offset);
1197                 if (!table_reloc)
1198                         continue;
1199                 dest_insn = find_insn(file, table_reloc->sym->sec, table_reloc->addend);
1200                 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1201                         continue;
1202
1203                 /*
1204                  * Use of RIP-relative switch jumps is quite rare, and
1205                  * indicates a rare GCC quirk/bug which can leave dead code
1206                  * behind.
1207                  */
1208                 if (text_reloc->type == R_X86_64_PC32)
1209                         file->ignore_unreachables = true;
1210
1211                 return table_reloc;
1212         }
1213
1214         return NULL;
1215 }
1216
1217 /*
1218  * First pass: Mark the head of each jump table so that in the next pass,
1219  * we know when a given jump table ends and the next one starts.
1220  */
1221 static void mark_func_jump_tables(struct objtool_file *file,
1222                                     struct symbol *func)
1223 {
1224         struct instruction *insn, *last = NULL;
1225         struct reloc *reloc;
1226
1227         func_for_each_insn(file, func, insn) {
1228                 if (!last)
1229                         last = insn;
1230
1231                 /*
1232                  * Store back-pointers for unconditional forward jumps such
1233                  * that find_jump_table() can back-track using those and
1234                  * avoid some potentially confusing code.
1235                  */
1236                 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1237                     insn->offset > last->offset &&
1238                     insn->jump_dest->offset > insn->offset &&
1239                     !insn->jump_dest->first_jump_src) {
1240
1241                         insn->jump_dest->first_jump_src = insn;
1242                         last = insn->jump_dest;
1243                 }
1244
1245                 if (insn->type != INSN_JUMP_DYNAMIC)
1246                         continue;
1247
1248                 reloc = find_jump_table(file, func, insn);
1249                 if (reloc) {
1250                         reloc->jump_table_start = true;
1251                         insn->jump_table = reloc;
1252                 }
1253         }
1254 }
1255
1256 static int add_func_jump_tables(struct objtool_file *file,
1257                                   struct symbol *func)
1258 {
1259         struct instruction *insn;
1260         int ret;
1261
1262         func_for_each_insn(file, func, insn) {
1263                 if (!insn->jump_table)
1264                         continue;
1265
1266                 ret = add_jump_table(file, insn, insn->jump_table);
1267                 if (ret)
1268                         return ret;
1269         }
1270
1271         return 0;
1272 }
1273
1274 /*
1275  * For some switch statements, gcc generates a jump table in the .rodata
1276  * section which contains a list of addresses within the function to jump to.
1277  * This finds these jump tables and adds them to the insn->alts lists.
1278  */
1279 static int add_jump_table_alts(struct objtool_file *file)
1280 {
1281         struct section *sec;
1282         struct symbol *func;
1283         int ret;
1284
1285         if (!file->rodata)
1286                 return 0;
1287
1288         for_each_sec(file, sec) {
1289                 list_for_each_entry(func, &sec->symbol_list, list) {
1290                         if (func->type != STT_FUNC)
1291                                 continue;
1292
1293                         mark_func_jump_tables(file, func);
1294                         ret = add_func_jump_tables(file, func);
1295                         if (ret)
1296                                 return ret;
1297                 }
1298         }
1299
1300         return 0;
1301 }
1302
1303 static int read_unwind_hints(struct objtool_file *file)
1304 {
1305         struct section *sec, *relocsec;
1306         struct reloc *reloc;
1307         struct unwind_hint *hint;
1308         struct instruction *insn;
1309         struct cfi_reg *cfa;
1310         int i;
1311
1312         sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1313         if (!sec)
1314                 return 0;
1315
1316         relocsec = sec->reloc;
1317         if (!relocsec) {
1318                 WARN("missing .rela.discard.unwind_hints section");
1319                 return -1;
1320         }
1321
1322         if (sec->len % sizeof(struct unwind_hint)) {
1323                 WARN("struct unwind_hint size mismatch");
1324                 return -1;
1325         }
1326
1327         file->hints = true;
1328
1329         for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
1330                 hint = (struct unwind_hint *)sec->data->d_buf + i;
1331
1332                 reloc = find_reloc_by_dest(file->elf, sec, i * sizeof(*hint));
1333                 if (!reloc) {
1334                         WARN("can't find reloc for unwind_hints[%d]", i);
1335                         return -1;
1336                 }
1337
1338                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1339                 if (!insn) {
1340                         WARN("can't find insn for unwind_hints[%d]", i);
1341                         return -1;
1342                 }
1343
1344                 cfa = &insn->cfi.cfa;
1345
1346                 if (hint->type == UNWIND_HINT_TYPE_RET_OFFSET) {
1347                         insn->ret_offset = hint->sp_offset;
1348                         continue;
1349                 }
1350
1351                 insn->hint = true;
1352
1353                 switch (hint->sp_reg) {
1354                 case ORC_REG_UNDEFINED:
1355                         cfa->base = CFI_UNDEFINED;
1356                         break;
1357                 case ORC_REG_SP:
1358                         cfa->base = CFI_SP;
1359                         break;
1360                 case ORC_REG_BP:
1361                         cfa->base = CFI_BP;
1362                         break;
1363                 case ORC_REG_SP_INDIRECT:
1364                         cfa->base = CFI_SP_INDIRECT;
1365                         break;
1366                 case ORC_REG_R10:
1367                         cfa->base = CFI_R10;
1368                         break;
1369                 case ORC_REG_R13:
1370                         cfa->base = CFI_R13;
1371                         break;
1372                 case ORC_REG_DI:
1373                         cfa->base = CFI_DI;
1374                         break;
1375                 case ORC_REG_DX:
1376                         cfa->base = CFI_DX;
1377                         break;
1378                 default:
1379                         WARN_FUNC("unsupported unwind_hint sp base reg %d",
1380                                   insn->sec, insn->offset, hint->sp_reg);
1381                         return -1;
1382                 }
1383
1384                 cfa->offset = hint->sp_offset;
1385                 insn->cfi.type = hint->type;
1386                 insn->cfi.end = hint->end;
1387         }
1388
1389         return 0;
1390 }
1391
1392 static int read_retpoline_hints(struct objtool_file *file)
1393 {
1394         struct section *sec;
1395         struct instruction *insn;
1396         struct reloc *reloc;
1397
1398         sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1399         if (!sec)
1400                 return 0;
1401
1402         list_for_each_entry(reloc, &sec->reloc_list, list) {
1403                 if (reloc->sym->type != STT_SECTION) {
1404                         WARN("unexpected relocation symbol type in %s", sec->name);
1405                         return -1;
1406                 }
1407
1408                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1409                 if (!insn) {
1410                         WARN("bad .discard.retpoline_safe entry");
1411                         return -1;
1412                 }
1413
1414                 if (insn->type != INSN_JUMP_DYNAMIC &&
1415                     insn->type != INSN_CALL_DYNAMIC) {
1416                         WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1417                                   insn->sec, insn->offset);
1418                         return -1;
1419                 }
1420
1421                 insn->retpoline_safe = true;
1422         }
1423
1424         return 0;
1425 }
1426
1427 static int read_instr_hints(struct objtool_file *file)
1428 {
1429         struct section *sec;
1430         struct instruction *insn;
1431         struct reloc *reloc;
1432
1433         sec = find_section_by_name(file->elf, ".rela.discard.instr_end");
1434         if (!sec)
1435                 return 0;
1436
1437         list_for_each_entry(reloc, &sec->reloc_list, list) {
1438                 if (reloc->sym->type != STT_SECTION) {
1439                         WARN("unexpected relocation symbol type in %s", sec->name);
1440                         return -1;
1441                 }
1442
1443                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1444                 if (!insn) {
1445                         WARN("bad .discard.instr_end entry");
1446                         return -1;
1447                 }
1448
1449                 insn->instr--;
1450         }
1451
1452         sec = find_section_by_name(file->elf, ".rela.discard.instr_begin");
1453         if (!sec)
1454                 return 0;
1455
1456         list_for_each_entry(reloc, &sec->reloc_list, list) {
1457                 if (reloc->sym->type != STT_SECTION) {
1458                         WARN("unexpected relocation symbol type in %s", sec->name);
1459                         return -1;
1460                 }
1461
1462                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1463                 if (!insn) {
1464                         WARN("bad .discard.instr_begin entry");
1465                         return -1;
1466                 }
1467
1468                 insn->instr++;
1469         }
1470
1471         return 0;
1472 }
1473
1474 static int read_intra_function_calls(struct objtool_file *file)
1475 {
1476         struct instruction *insn;
1477         struct section *sec;
1478         struct reloc *reloc;
1479
1480         sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");
1481         if (!sec)
1482                 return 0;
1483
1484         list_for_each_entry(reloc, &sec->reloc_list, list) {
1485                 unsigned long dest_off;
1486
1487                 if (reloc->sym->type != STT_SECTION) {
1488                         WARN("unexpected relocation symbol type in %s",
1489                              sec->name);
1490                         return -1;
1491                 }
1492
1493                 insn = find_insn(file, reloc->sym->sec, reloc->addend);
1494                 if (!insn) {
1495                         WARN("bad .discard.intra_function_call entry");
1496                         return -1;
1497                 }
1498
1499                 if (insn->type != INSN_CALL) {
1500                         WARN_FUNC("intra_function_call not a direct call",
1501                                   insn->sec, insn->offset);
1502                         return -1;
1503                 }
1504
1505                 /*
1506                  * Treat intra-function CALLs as JMPs, but with a stack_op.
1507                  * See add_call_destinations(), which strips stack_ops from
1508                  * normal CALLs.
1509                  */
1510                 insn->type = INSN_JUMP_UNCONDITIONAL;
1511
1512                 dest_off = insn->offset + insn->len + insn->immediate;
1513                 insn->jump_dest = find_insn(file, insn->sec, dest_off);
1514                 if (!insn->jump_dest) {
1515                         WARN_FUNC("can't find call dest at %s+0x%lx",
1516                                   insn->sec, insn->offset,
1517                                   insn->sec->name, dest_off);
1518                         return -1;
1519                 }
1520         }
1521
1522         return 0;
1523 }
1524
1525 static void mark_rodata(struct objtool_file *file)
1526 {
1527         struct section *sec;
1528         bool found = false;
1529
1530         /*
1531          * Search for the following rodata sections, each of which can
1532          * potentially contain jump tables:
1533          *
1534          * - .rodata: can contain GCC switch tables
1535          * - .rodata.<func>: same, if -fdata-sections is being used
1536          * - .rodata..c_jump_table: contains C annotated jump tables
1537          *
1538          * .rodata.str1.* sections are ignored; they don't contain jump tables.
1539          */
1540         for_each_sec(file, sec) {
1541                 if (!strncmp(sec->name, ".rodata", 7) &&
1542                     !strstr(sec->name, ".str1.")) {
1543                         sec->rodata = true;
1544                         found = true;
1545                 }
1546         }
1547
1548         file->rodata = found;
1549 }
1550
1551 static int decode_sections(struct objtool_file *file)
1552 {
1553         int ret;
1554
1555         mark_rodata(file);
1556
1557         ret = decode_instructions(file);
1558         if (ret)
1559                 return ret;
1560
1561         ret = add_dead_ends(file);
1562         if (ret)
1563                 return ret;
1564
1565         add_ignores(file);
1566         add_uaccess_safe(file);
1567
1568         ret = add_ignore_alternatives(file);
1569         if (ret)
1570                 return ret;
1571
1572         ret = add_jump_destinations(file);
1573         if (ret)
1574                 return ret;
1575
1576         ret = add_special_section_alts(file);
1577         if (ret)
1578                 return ret;
1579
1580         ret = read_intra_function_calls(file);
1581         if (ret)
1582                 return ret;
1583
1584         ret = add_call_destinations(file);
1585         if (ret)
1586                 return ret;
1587
1588         ret = add_jump_table_alts(file);
1589         if (ret)
1590                 return ret;
1591
1592         ret = read_unwind_hints(file);
1593         if (ret)
1594                 return ret;
1595
1596         ret = read_retpoline_hints(file);
1597         if (ret)
1598                 return ret;
1599
1600         ret = read_instr_hints(file);
1601         if (ret)
1602                 return ret;
1603
1604         return 0;
1605 }
1606
1607 static bool is_fentry_call(struct instruction *insn)
1608 {
1609         if (insn->type == INSN_CALL && insn->call_dest &&
1610             insn->call_dest->type == STT_NOTYPE &&
1611             !strcmp(insn->call_dest->name, "__fentry__"))
1612                 return true;
1613
1614         return false;
1615 }
1616
1617 static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
1618 {
1619         u8 ret_offset = insn->ret_offset;
1620         struct cfi_state *cfi = &state->cfi;
1621         int i;
1622
1623         if (cfi->cfa.base != initial_func_cfi.cfa.base || cfi->drap)
1624                 return true;
1625
1626         if (cfi->cfa.offset != initial_func_cfi.cfa.offset + ret_offset)
1627                 return true;
1628
1629         if (cfi->stack_size != initial_func_cfi.cfa.offset + ret_offset)
1630                 return true;
1631
1632         /*
1633          * If there is a ret offset hint then don't check registers
1634          * because a callee-saved register might have been pushed on
1635          * the stack.
1636          */
1637         if (ret_offset)
1638                 return false;
1639
1640         for (i = 0; i < CFI_NUM_REGS; i++) {
1641                 if (cfi->regs[i].base != initial_func_cfi.regs[i].base ||
1642                     cfi->regs[i].offset != initial_func_cfi.regs[i].offset)
1643                         return true;
1644         }
1645
1646         return false;
1647 }
1648
1649 static bool has_valid_stack_frame(struct insn_state *state)
1650 {
1651         struct cfi_state *cfi = &state->cfi;
1652
1653         if (cfi->cfa.base == CFI_BP && cfi->regs[CFI_BP].base == CFI_CFA &&
1654             cfi->regs[CFI_BP].offset == -16)
1655                 return true;
1656
1657         if (cfi->drap && cfi->regs[CFI_BP].base == CFI_BP)
1658                 return true;
1659
1660         return false;
1661 }
1662
1663 static int update_cfi_state_regs(struct instruction *insn,
1664                                   struct cfi_state *cfi,
1665                                   struct stack_op *op)
1666 {
1667         struct cfi_reg *cfa = &cfi->cfa;
1668
1669         if (cfa->base != CFI_SP && cfa->base != CFI_SP_INDIRECT)
1670                 return 0;
1671
1672         /* push */
1673         if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
1674                 cfa->offset += 8;
1675
1676         /* pop */
1677         if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
1678                 cfa->offset -= 8;
1679
1680         /* add immediate to sp */
1681         if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1682             op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1683                 cfa->offset -= op->src.offset;
1684
1685         return 0;
1686 }
1687
1688 static void save_reg(struct cfi_state *cfi, unsigned char reg, int base, int offset)
1689 {
1690         if (arch_callee_saved_reg(reg) &&
1691             cfi->regs[reg].base == CFI_UNDEFINED) {
1692                 cfi->regs[reg].base = base;
1693                 cfi->regs[reg].offset = offset;
1694         }
1695 }
1696
1697 static void restore_reg(struct cfi_state *cfi, unsigned char reg)
1698 {
1699         cfi->regs[reg].base = initial_func_cfi.regs[reg].base;
1700         cfi->regs[reg].offset = initial_func_cfi.regs[reg].offset;
1701 }
1702
1703 /*
1704  * A note about DRAP stack alignment:
1705  *
1706  * GCC has the concept of a DRAP register, which is used to help keep track of
1707  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
1708  * register.  The typical DRAP pattern is:
1709  *
1710  *   4c 8d 54 24 08             lea    0x8(%rsp),%r10
1711  *   48 83 e4 c0                and    $0xffffffffffffffc0,%rsp
1712  *   41 ff 72 f8                pushq  -0x8(%r10)
1713  *   55                         push   %rbp
1714  *   48 89 e5                   mov    %rsp,%rbp
1715  *                              (more pushes)
1716  *   41 52                      push   %r10
1717  *                              ...
1718  *   41 5a                      pop    %r10
1719  *                              (more pops)
1720  *   5d                         pop    %rbp
1721  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1722  *   c3                         retq
1723  *
1724  * There are some variations in the epilogues, like:
1725  *
1726  *   5b                         pop    %rbx
1727  *   41 5a                      pop    %r10
1728  *   41 5c                      pop    %r12
1729  *   41 5d                      pop    %r13
1730  *   41 5e                      pop    %r14
1731  *   c9                         leaveq
1732  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1733  *   c3                         retq
1734  *
1735  * and:
1736  *
1737  *   4c 8b 55 e8                mov    -0x18(%rbp),%r10
1738  *   48 8b 5d e0                mov    -0x20(%rbp),%rbx
1739  *   4c 8b 65 f0                mov    -0x10(%rbp),%r12
1740  *   4c 8b 6d f8                mov    -0x8(%rbp),%r13
1741  *   c9                         leaveq
1742  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1743  *   c3                         retq
1744  *
1745  * Sometimes r13 is used as the DRAP register, in which case it's saved and
1746  * restored beforehand:
1747  *
1748  *   41 55                      push   %r13
1749  *   4c 8d 6c 24 10             lea    0x10(%rsp),%r13
1750  *   48 83 e4 f0                and    $0xfffffffffffffff0,%rsp
1751  *                              ...
1752  *   49 8d 65 f0                lea    -0x10(%r13),%rsp
1753  *   41 5d                      pop    %r13
1754  *   c3                         retq
1755  */
1756 static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi,
1757                              struct stack_op *op)
1758 {
1759         struct cfi_reg *cfa = &cfi->cfa;
1760         struct cfi_reg *regs = cfi->regs;
1761
1762         /* stack operations don't make sense with an undefined CFA */
1763         if (cfa->base == CFI_UNDEFINED) {
1764                 if (insn->func) {
1765                         WARN_FUNC("undefined stack state", insn->sec, insn->offset);
1766                         return -1;
1767                 }
1768                 return 0;
1769         }
1770
1771         if (cfi->type == ORC_TYPE_REGS || cfi->type == ORC_TYPE_REGS_IRET)
1772                 return update_cfi_state_regs(insn, cfi, op);
1773
1774         switch (op->dest.type) {
1775
1776         case OP_DEST_REG:
1777                 switch (op->src.type) {
1778
1779                 case OP_SRC_REG:
1780                         if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
1781                             cfa->base == CFI_SP &&
1782                             regs[CFI_BP].base == CFI_CFA &&
1783                             regs[CFI_BP].offset == -cfa->offset) {
1784
1785                                 /* mov %rsp, %rbp */
1786                                 cfa->base = op->dest.reg;
1787                                 cfi->bp_scratch = false;
1788                         }
1789
1790                         else if (op->src.reg == CFI_SP &&
1791                                  op->dest.reg == CFI_BP && cfi->drap) {
1792
1793                                 /* drap: mov %rsp, %rbp */
1794                                 regs[CFI_BP].base = CFI_BP;
1795                                 regs[CFI_BP].offset = -cfi->stack_size;
1796                                 cfi->bp_scratch = false;
1797                         }
1798
1799                         else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1800
1801                                 /*
1802                                  * mov %rsp, %reg
1803                                  *
1804                                  * This is needed for the rare case where GCC
1805                                  * does:
1806                                  *
1807                                  *   mov    %rsp, %rax
1808                                  *   ...
1809                                  *   mov    %rax, %rsp
1810                                  */
1811                                 cfi->vals[op->dest.reg].base = CFI_CFA;
1812                                 cfi->vals[op->dest.reg].offset = -cfi->stack_size;
1813                         }
1814
1815                         else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
1816                                  cfa->base == CFI_BP) {
1817
1818                                 /*
1819                                  * mov %rbp, %rsp
1820                                  *
1821                                  * Restore the original stack pointer (Clang).
1822                                  */
1823                                 cfi->stack_size = -cfi->regs[CFI_BP].offset;
1824                         }
1825
1826                         else if (op->dest.reg == cfa->base) {
1827
1828                                 /* mov %reg, %rsp */
1829                                 if (cfa->base == CFI_SP &&
1830                                     cfi->vals[op->src.reg].base == CFI_CFA) {
1831
1832                                         /*
1833                                          * This is needed for the rare case
1834                                          * where GCC does something dumb like:
1835                                          *
1836                                          *   lea    0x8(%rsp), %rcx
1837                                          *   ...
1838                                          *   mov    %rcx, %rsp
1839                                          */
1840                                         cfa->offset = -cfi->vals[op->src.reg].offset;
1841                                         cfi->stack_size = cfa->offset;
1842
1843                                 } else {
1844                                         cfa->base = CFI_UNDEFINED;
1845                                         cfa->offset = 0;
1846                                 }
1847                         }
1848
1849                         break;
1850
1851                 case OP_SRC_ADD:
1852                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
1853
1854                                 /* add imm, %rsp */
1855                                 cfi->stack_size -= op->src.offset;
1856                                 if (cfa->base == CFI_SP)
1857                                         cfa->offset -= op->src.offset;
1858                                 break;
1859                         }
1860
1861                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
1862
1863                                 /* lea disp(%rbp), %rsp */
1864                                 cfi->stack_size = -(op->src.offset + regs[CFI_BP].offset);
1865                                 break;
1866                         }
1867
1868                         if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1869
1870                                 /* drap: lea disp(%rsp), %drap */
1871                                 cfi->drap_reg = op->dest.reg;
1872
1873                                 /*
1874                                  * lea disp(%rsp), %reg
1875                                  *
1876                                  * This is needed for the rare case where GCC
1877                                  * does something dumb like:
1878                                  *
1879                                  *   lea    0x8(%rsp), %rcx
1880                                  *   ...
1881                                  *   mov    %rcx, %rsp
1882                                  */
1883                                 cfi->vals[op->dest.reg].base = CFI_CFA;
1884                                 cfi->vals[op->dest.reg].offset = \
1885                                         -cfi->stack_size + op->src.offset;
1886
1887                                 break;
1888                         }
1889
1890                         if (cfi->drap && op->dest.reg == CFI_SP &&
1891                             op->src.reg == cfi->drap_reg) {
1892
1893                                  /* drap: lea disp(%drap), %rsp */
1894                                 cfa->base = CFI_SP;
1895                                 cfa->offset = cfi->stack_size = -op->src.offset;
1896                                 cfi->drap_reg = CFI_UNDEFINED;
1897                                 cfi->drap = false;
1898                                 break;
1899                         }
1900
1901                         if (op->dest.reg == cfi->cfa.base) {
1902                                 WARN_FUNC("unsupported stack register modification",
1903                                           insn->sec, insn->offset);
1904                                 return -1;
1905                         }
1906
1907                         break;
1908
1909                 case OP_SRC_AND:
1910                         if (op->dest.reg != CFI_SP ||
1911                             (cfi->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
1912                             (cfi->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
1913                                 WARN_FUNC("unsupported stack pointer realignment",
1914                                           insn->sec, insn->offset);
1915                                 return -1;
1916                         }
1917
1918                         if (cfi->drap_reg != CFI_UNDEFINED) {
1919                                 /* drap: and imm, %rsp */
1920                                 cfa->base = cfi->drap_reg;
1921                                 cfa->offset = cfi->stack_size = 0;
1922                                 cfi->drap = true;
1923                         }
1924
1925                         /*
1926                          * Older versions of GCC (4.8ish) realign the stack
1927                          * without DRAP, with a frame pointer.
1928                          */
1929
1930                         break;
1931
1932                 case OP_SRC_POP:
1933                 case OP_SRC_POPF:
1934                         if (!cfi->drap && op->dest.reg == cfa->base) {
1935
1936                                 /* pop %rbp */
1937                                 cfa->base = CFI_SP;
1938                         }
1939
1940                         if (cfi->drap && cfa->base == CFI_BP_INDIRECT &&
1941                             op->dest.reg == cfi->drap_reg &&
1942                             cfi->drap_offset == -cfi->stack_size) {
1943
1944                                 /* drap: pop %drap */
1945                                 cfa->base = cfi->drap_reg;
1946                                 cfa->offset = 0;
1947                                 cfi->drap_offset = -1;
1948
1949                         } else if (regs[op->dest.reg].offset == -cfi->stack_size) {
1950
1951                                 /* pop %reg */
1952                                 restore_reg(cfi, op->dest.reg);
1953                         }
1954
1955                         cfi->stack_size -= 8;
1956                         if (cfa->base == CFI_SP)
1957                                 cfa->offset -= 8;
1958
1959                         break;
1960
1961                 case OP_SRC_REG_INDIRECT:
1962                         if (cfi->drap && op->src.reg == CFI_BP &&
1963                             op->src.offset == cfi->drap_offset) {
1964
1965                                 /* drap: mov disp(%rbp), %drap */
1966                                 cfa->base = cfi->drap_reg;
1967                                 cfa->offset = 0;
1968                                 cfi->drap_offset = -1;
1969                         }
1970
1971                         if (cfi->drap && op->src.reg == CFI_BP &&
1972                             op->src.offset == regs[op->dest.reg].offset) {
1973
1974                                 /* drap: mov disp(%rbp), %reg */
1975                                 restore_reg(cfi, op->dest.reg);
1976
1977                         } else if (op->src.reg == cfa->base &&
1978                             op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
1979
1980                                 /* mov disp(%rbp), %reg */
1981                                 /* mov disp(%rsp), %reg */
1982                                 restore_reg(cfi, op->dest.reg);
1983                         }
1984
1985                         break;
1986
1987                 default:
1988                         WARN_FUNC("unknown stack-related instruction",
1989                                   insn->sec, insn->offset);
1990                         return -1;
1991                 }
1992
1993                 break;
1994
1995         case OP_DEST_PUSH:
1996         case OP_DEST_PUSHF:
1997                 cfi->stack_size += 8;
1998                 if (cfa->base == CFI_SP)
1999                         cfa->offset += 8;
2000
2001                 if (op->src.type != OP_SRC_REG)
2002                         break;
2003
2004                 if (cfi->drap) {
2005                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2006
2007                                 /* drap: push %drap */
2008                                 cfa->base = CFI_BP_INDIRECT;
2009                                 cfa->offset = -cfi->stack_size;
2010
2011                                 /* save drap so we know when to restore it */
2012                                 cfi->drap_offset = -cfi->stack_size;
2013
2014                         } else if (op->src.reg == CFI_BP && cfa->base == cfi->drap_reg) {
2015
2016                                 /* drap: push %rbp */
2017                                 cfi->stack_size = 0;
2018
2019                         } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
2020
2021                                 /* drap: push %reg */
2022                                 save_reg(cfi, op->src.reg, CFI_BP, -cfi->stack_size);
2023                         }
2024
2025                 } else {
2026
2027                         /* push %reg */
2028                         save_reg(cfi, op->src.reg, CFI_CFA, -cfi->stack_size);
2029                 }
2030
2031                 /* detect when asm code uses rbp as a scratch register */
2032                 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
2033                     cfa->base != CFI_BP)
2034                         cfi->bp_scratch = true;
2035                 break;
2036
2037         case OP_DEST_REG_INDIRECT:
2038
2039                 if (cfi->drap) {
2040                         if (op->src.reg == cfa->base && op->src.reg == cfi->drap_reg) {
2041
2042                                 /* drap: mov %drap, disp(%rbp) */
2043                                 cfa->base = CFI_BP_INDIRECT;
2044                                 cfa->offset = op->dest.offset;
2045
2046                                 /* save drap offset so we know when to restore it */
2047                                 cfi->drap_offset = op->dest.offset;
2048                         }
2049
2050                         else if (regs[op->src.reg].base == CFI_UNDEFINED) {
2051
2052                                 /* drap: mov reg, disp(%rbp) */
2053                                 save_reg(cfi, op->src.reg, CFI_BP, op->dest.offset);
2054                         }
2055
2056                 } else if (op->dest.reg == cfa->base) {
2057
2058                         /* mov reg, disp(%rbp) */
2059                         /* mov reg, disp(%rsp) */
2060                         save_reg(cfi, op->src.reg, CFI_CFA,
2061                                  op->dest.offset - cfi->cfa.offset);
2062                 }
2063
2064                 break;
2065
2066         case OP_DEST_LEAVE:
2067                 if ((!cfi->drap && cfa->base != CFI_BP) ||
2068                     (cfi->drap && cfa->base != cfi->drap_reg)) {
2069                         WARN_FUNC("leave instruction with modified stack frame",
2070                                   insn->sec, insn->offset);
2071                         return -1;
2072                 }
2073
2074                 /* leave (mov %rbp, %rsp; pop %rbp) */
2075
2076                 cfi->stack_size = -cfi->regs[CFI_BP].offset - 8;
2077                 restore_reg(cfi, CFI_BP);
2078
2079                 if (!cfi->drap) {
2080                         cfa->base = CFI_SP;
2081                         cfa->offset -= 8;
2082                 }
2083
2084                 break;
2085
2086         case OP_DEST_MEM:
2087                 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
2088                         WARN_FUNC("unknown stack-related memory operation",
2089                                   insn->sec, insn->offset);
2090                         return -1;
2091                 }
2092
2093                 /* pop mem */
2094                 cfi->stack_size -= 8;
2095                 if (cfa->base == CFI_SP)
2096                         cfa->offset -= 8;
2097
2098                 break;
2099
2100         default:
2101                 WARN_FUNC("unknown stack-related instruction",
2102                           insn->sec, insn->offset);
2103                 return -1;
2104         }
2105
2106         return 0;
2107 }
2108
2109 static int handle_insn_ops(struct instruction *insn, struct insn_state *state)
2110 {
2111         struct stack_op *op;
2112
2113         list_for_each_entry(op, &insn->stack_ops, list) {
2114                 struct cfi_state old_cfi = state->cfi;
2115                 int res;
2116
2117                 res = update_cfi_state(insn, &state->cfi, op);
2118                 if (res)
2119                         return res;
2120
2121                 if (insn->alt_group && memcmp(&state->cfi, &old_cfi, sizeof(struct cfi_state))) {
2122                         WARN_FUNC("alternative modifies stack", insn->sec, insn->offset);
2123                         return -1;
2124                 }
2125
2126                 if (op->dest.type == OP_DEST_PUSHF) {
2127                         if (!state->uaccess_stack) {
2128                                 state->uaccess_stack = 1;
2129                         } else if (state->uaccess_stack >> 31) {
2130                                 WARN_FUNC("PUSHF stack exhausted",
2131                                           insn->sec, insn->offset);
2132                                 return 1;
2133                         }
2134                         state->uaccess_stack <<= 1;
2135                         state->uaccess_stack  |= state->uaccess;
2136                 }
2137
2138                 if (op->src.type == OP_SRC_POPF) {
2139                         if (state->uaccess_stack) {
2140                                 state->uaccess = state->uaccess_stack & 1;
2141                                 state->uaccess_stack >>= 1;
2142                                 if (state->uaccess_stack == 1)
2143                                         state->uaccess_stack = 0;
2144                         }
2145                 }
2146         }
2147
2148         return 0;
2149 }
2150
2151 static bool insn_cfi_match(struct instruction *insn, struct cfi_state *cfi2)
2152 {
2153         struct cfi_state *cfi1 = &insn->cfi;
2154         int i;
2155
2156         if (memcmp(&cfi1->cfa, &cfi2->cfa, sizeof(cfi1->cfa))) {
2157
2158                 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
2159                           insn->sec, insn->offset,
2160                           cfi1->cfa.base, cfi1->cfa.offset,
2161                           cfi2->cfa.base, cfi2->cfa.offset);
2162
2163         } else if (memcmp(&cfi1->regs, &cfi2->regs, sizeof(cfi1->regs))) {
2164                 for (i = 0; i < CFI_NUM_REGS; i++) {
2165                         if (!memcmp(&cfi1->regs[i], &cfi2->regs[i],
2166                                     sizeof(struct cfi_reg)))
2167                                 continue;
2168
2169                         WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
2170                                   insn->sec, insn->offset,
2171                                   i, cfi1->regs[i].base, cfi1->regs[i].offset,
2172                                   i, cfi2->regs[i].base, cfi2->regs[i].offset);
2173                         break;
2174                 }
2175
2176         } else if (cfi1->type != cfi2->type) {
2177
2178                 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
2179                           insn->sec, insn->offset, cfi1->type, cfi2->type);
2180
2181         } else if (cfi1->drap != cfi2->drap ||
2182                    (cfi1->drap && cfi1->drap_reg != cfi2->drap_reg) ||
2183                    (cfi1->drap && cfi1->drap_offset != cfi2->drap_offset)) {
2184
2185                 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
2186                           insn->sec, insn->offset,
2187                           cfi1->drap, cfi1->drap_reg, cfi1->drap_offset,
2188                           cfi2->drap, cfi2->drap_reg, cfi2->drap_offset);
2189
2190         } else
2191                 return true;
2192
2193         return false;
2194 }
2195
2196 static inline bool func_uaccess_safe(struct symbol *func)
2197 {
2198         if (func)
2199                 return func->uaccess_safe;
2200
2201         return false;
2202 }
2203
2204 static inline const char *call_dest_name(struct instruction *insn)
2205 {
2206         if (insn->call_dest)
2207                 return insn->call_dest->name;
2208
2209         return "{dynamic}";
2210 }
2211
2212 static inline bool noinstr_call_dest(struct symbol *func)
2213 {
2214         /*
2215          * We can't deal with indirect function calls at present;
2216          * assume they're instrumented.
2217          */
2218         if (!func)
2219                 return false;
2220
2221         /*
2222          * If the symbol is from a noinstr section; we good.
2223          */
2224         if (func->sec->noinstr)
2225                 return true;
2226
2227         /*
2228          * The __ubsan_handle_*() calls are like WARN(), they only happen when
2229          * something 'BAD' happened. At the risk of taking the machine down,
2230          * let them proceed to get the message out.
2231          */
2232         if (!strncmp(func->name, "__ubsan_handle_", 15))
2233                 return true;
2234
2235         return false;
2236 }
2237
2238 static int validate_call(struct instruction *insn, struct insn_state *state)
2239 {
2240         if (state->noinstr && state->instr <= 0 &&
2241             !noinstr_call_dest(insn->call_dest)) {
2242                 WARN_FUNC("call to %s() leaves .noinstr.text section",
2243                                 insn->sec, insn->offset, call_dest_name(insn));
2244                 return 1;
2245         }
2246
2247         if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
2248                 WARN_FUNC("call to %s() with UACCESS enabled",
2249                                 insn->sec, insn->offset, call_dest_name(insn));
2250                 return 1;
2251         }
2252
2253         if (state->df) {
2254                 WARN_FUNC("call to %s() with DF set",
2255                                 insn->sec, insn->offset, call_dest_name(insn));
2256                 return 1;
2257         }
2258
2259         return 0;
2260 }
2261
2262 static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
2263 {
2264         if (has_modified_stack_frame(insn, state)) {
2265                 WARN_FUNC("sibling call from callable instruction with modified stack frame",
2266                                 insn->sec, insn->offset);
2267                 return 1;
2268         }
2269
2270         return validate_call(insn, state);
2271 }
2272
2273 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
2274 {
2275         if (state->noinstr && state->instr > 0) {
2276                 WARN_FUNC("return with instrumentation enabled",
2277                           insn->sec, insn->offset);
2278                 return 1;
2279         }
2280
2281         if (state->uaccess && !func_uaccess_safe(func)) {
2282                 WARN_FUNC("return with UACCESS enabled",
2283                           insn->sec, insn->offset);
2284                 return 1;
2285         }
2286
2287         if (!state->uaccess && func_uaccess_safe(func)) {
2288                 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
2289                           insn->sec, insn->offset);
2290                 return 1;
2291         }
2292
2293         if (state->df) {
2294                 WARN_FUNC("return with DF set",
2295                           insn->sec, insn->offset);
2296                 return 1;
2297         }
2298
2299         if (func && has_modified_stack_frame(insn, state)) {
2300                 WARN_FUNC("return with modified stack frame",
2301                           insn->sec, insn->offset);
2302                 return 1;
2303         }
2304
2305         if (state->cfi.bp_scratch) {
2306                 WARN_FUNC("BP used as a scratch register",
2307                           insn->sec, insn->offset);
2308                 return 1;
2309         }
2310
2311         return 0;
2312 }
2313
2314 /*
2315  * Alternatives should not contain any ORC entries, this in turn means they
2316  * should not contain any CFI ops, which implies all instructions should have
2317  * the same same CFI state.
2318  *
2319  * It is possible to constuct alternatives that have unreachable holes that go
2320  * unreported (because they're NOPs), such holes would result in CFI_UNDEFINED
2321  * states which then results in ORC entries, which we just said we didn't want.
2322  *
2323  * Avoid them by copying the CFI entry of the first instruction into the whole
2324  * alternative.
2325  */
2326 static void fill_alternative_cfi(struct objtool_file *file, struct instruction *insn)
2327 {
2328         struct instruction *first_insn = insn;
2329         int alt_group = insn->alt_group;
2330
2331         sec_for_each_insn_continue(file, insn) {
2332                 if (insn->alt_group != alt_group)
2333                         break;
2334                 insn->cfi = first_insn->cfi;
2335         }
2336 }
2337
2338 /*
2339  * Follow the branch starting at the given instruction, and recursively follow
2340  * any other branches (jumps).  Meanwhile, track the frame pointer state at
2341  * each instruction and validate all the rules described in
2342  * tools/objtool/Documentation/stack-validation.txt.
2343  */
2344 static int validate_branch(struct objtool_file *file, struct symbol *func,
2345                            struct instruction *insn, struct insn_state state)
2346 {
2347         struct alternative *alt;
2348         struct instruction *next_insn;
2349         struct section *sec;
2350         u8 visited;
2351         int ret;
2352
2353         sec = insn->sec;
2354
2355         while (1) {
2356                 next_insn = next_insn_same_sec(file, insn);
2357
2358                 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
2359                         WARN("%s() falls through to next function %s()",
2360                              func->name, insn->func->name);
2361                         return 1;
2362                 }
2363
2364                 if (func && insn->ignore) {
2365                         WARN_FUNC("BUG: why am I validating an ignored function?",
2366                                   sec, insn->offset);
2367                         return 1;
2368                 }
2369
2370                 visited = 1 << state.uaccess;
2371                 if (insn->visited) {
2372                         if (!insn->hint && !insn_cfi_match(insn, &state.cfi))
2373                                 return 1;
2374
2375                         if (insn->visited & visited)
2376                                 return 0;
2377                 }
2378
2379                 if (state.noinstr)
2380                         state.instr += insn->instr;
2381
2382                 if (insn->hint)
2383                         state.cfi = insn->cfi;
2384                 else
2385                         insn->cfi = state.cfi;
2386
2387                 insn->visited |= visited;
2388
2389                 if (!insn->ignore_alts && !list_empty(&insn->alts)) {
2390                         bool skip_orig = false;
2391
2392                         list_for_each_entry(alt, &insn->alts, list) {
2393                                 if (alt->skip_orig)
2394                                         skip_orig = true;
2395
2396                                 ret = validate_branch(file, func, alt->insn, state);
2397                                 if (ret) {
2398                                         if (backtrace)
2399                                                 BT_FUNC("(alt)", insn);
2400                                         return ret;
2401                                 }
2402                         }
2403
2404                         if (insn->alt_group)
2405                                 fill_alternative_cfi(file, insn);
2406
2407                         if (skip_orig)
2408                                 return 0;
2409                 }
2410
2411                 if (handle_insn_ops(insn, &state))
2412                         return 1;
2413
2414                 switch (insn->type) {
2415
2416                 case INSN_RETURN:
2417                         return validate_return(func, insn, &state);
2418
2419                 case INSN_CALL:
2420                 case INSN_CALL_DYNAMIC:
2421                         ret = validate_call(insn, &state);
2422                         if (ret)
2423                                 return ret;
2424
2425                         if (!no_fp && func && !is_fentry_call(insn) &&
2426                             !has_valid_stack_frame(&state)) {
2427                                 WARN_FUNC("call without frame pointer save/setup",
2428                                           sec, insn->offset);
2429                                 return 1;
2430                         }
2431
2432                         if (dead_end_function(file, insn->call_dest))
2433                                 return 0;
2434
2435                         break;
2436
2437                 case INSN_JUMP_CONDITIONAL:
2438                 case INSN_JUMP_UNCONDITIONAL:
2439                         if (func && is_sibling_call(insn)) {
2440                                 ret = validate_sibling_call(insn, &state);
2441                                 if (ret)
2442                                         return ret;
2443
2444                         } else if (insn->jump_dest) {
2445                                 ret = validate_branch(file, func,
2446                                                       insn->jump_dest, state);
2447                                 if (ret) {
2448                                         if (backtrace)
2449                                                 BT_FUNC("(branch)", insn);
2450                                         return ret;
2451                                 }
2452                         }
2453
2454                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
2455                                 return 0;
2456
2457                         break;
2458
2459                 case INSN_JUMP_DYNAMIC:
2460                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
2461                         if (func && is_sibling_call(insn)) {
2462                                 ret = validate_sibling_call(insn, &state);
2463                                 if (ret)
2464                                         return ret;
2465                         }
2466
2467                         if (insn->type == INSN_JUMP_DYNAMIC)
2468                                 return 0;
2469
2470                         break;
2471
2472                 case INSN_CONTEXT_SWITCH:
2473                         if (func && (!next_insn || !next_insn->hint)) {
2474                                 WARN_FUNC("unsupported instruction in callable function",
2475                                           sec, insn->offset);
2476                                 return 1;
2477                         }
2478                         return 0;
2479
2480                 case INSN_STAC:
2481                         if (state.uaccess) {
2482                                 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
2483                                 return 1;
2484                         }
2485
2486                         state.uaccess = true;
2487                         break;
2488
2489                 case INSN_CLAC:
2490                         if (!state.uaccess && func) {
2491                                 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
2492                                 return 1;
2493                         }
2494
2495                         if (func_uaccess_safe(func) && !state.uaccess_stack) {
2496                                 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
2497                                 return 1;
2498                         }
2499
2500                         state.uaccess = false;
2501                         break;
2502
2503                 case INSN_STD:
2504                         if (state.df)
2505                                 WARN_FUNC("recursive STD", sec, insn->offset);
2506
2507                         state.df = true;
2508                         break;
2509
2510                 case INSN_CLD:
2511                         if (!state.df && func)
2512                                 WARN_FUNC("redundant CLD", sec, insn->offset);
2513
2514                         state.df = false;
2515                         break;
2516
2517                 default:
2518                         break;
2519                 }
2520
2521                 if (insn->dead_end)
2522                         return 0;
2523
2524                 if (!next_insn) {
2525                         if (state.cfi.cfa.base == CFI_UNDEFINED)
2526                                 return 0;
2527                         WARN("%s: unexpected end of section", sec->name);
2528                         return 1;
2529                 }
2530
2531                 insn = next_insn;
2532         }
2533
2534         return 0;
2535 }
2536
2537 static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
2538 {
2539         struct instruction *insn;
2540         struct insn_state state;
2541         int ret, warnings = 0;
2542
2543         if (!file->hints)
2544                 return 0;
2545
2546         init_insn_state(&state, sec);
2547
2548         if (sec) {
2549                 insn = find_insn(file, sec, 0);
2550                 if (!insn)
2551                         return 0;
2552         } else {
2553                 insn = list_first_entry(&file->insn_list, typeof(*insn), list);
2554         }
2555
2556         while (&insn->list != &file->insn_list && (!sec || insn->sec == sec)) {
2557                 if (insn->hint && !insn->visited) {
2558                         ret = validate_branch(file, insn->func, insn, state);
2559                         if (ret && backtrace)
2560                                 BT_FUNC("<=== (hint)", insn);
2561                         warnings += ret;
2562                 }
2563
2564                 insn = list_next_entry(insn, list);
2565         }
2566
2567         return warnings;
2568 }
2569
2570 static int validate_retpoline(struct objtool_file *file)
2571 {
2572         struct instruction *insn;
2573         int warnings = 0;
2574
2575         for_each_insn(file, insn) {
2576                 if (insn->type != INSN_JUMP_DYNAMIC &&
2577                     insn->type != INSN_CALL_DYNAMIC)
2578                         continue;
2579
2580                 if (insn->retpoline_safe)
2581                         continue;
2582
2583                 /*
2584                  * .init.text code is ran before userspace and thus doesn't
2585                  * strictly need retpolines, except for modules which are
2586                  * loaded late, they very much do need retpoline in their
2587                  * .init.text
2588                  */
2589                 if (!strcmp(insn->sec->name, ".init.text") && !module)
2590                         continue;
2591
2592                 WARN_FUNC("indirect %s found in RETPOLINE build",
2593                           insn->sec, insn->offset,
2594                           insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
2595
2596                 warnings++;
2597         }
2598
2599         return warnings;
2600 }
2601
2602 static bool is_kasan_insn(struct instruction *insn)
2603 {
2604         return (insn->type == INSN_CALL &&
2605                 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
2606 }
2607
2608 static bool is_ubsan_insn(struct instruction *insn)
2609 {
2610         return (insn->type == INSN_CALL &&
2611                 !strcmp(insn->call_dest->name,
2612                         "__ubsan_handle_builtin_unreachable"));
2613 }
2614
2615 static bool ignore_unreachable_insn(struct instruction *insn)
2616 {
2617         int i;
2618
2619         if (insn->ignore || insn->type == INSN_NOP)
2620                 return true;
2621
2622         /*
2623          * Ignore any unused exceptions.  This can happen when a whitelisted
2624          * function has an exception table entry.
2625          *
2626          * Also ignore alternative replacement instructions.  This can happen
2627          * when a whitelisted function uses one of the ALTERNATIVE macros.
2628          */
2629         if (!strcmp(insn->sec->name, ".fixup") ||
2630             !strcmp(insn->sec->name, ".altinstr_replacement") ||
2631             !strcmp(insn->sec->name, ".altinstr_aux"))
2632                 return true;
2633
2634         if (!insn->func)
2635                 return false;
2636
2637         /*
2638          * CONFIG_UBSAN_TRAP inserts a UD2 when it sees
2639          * __builtin_unreachable().  The BUG() macro has an unreachable() after
2640          * the UD2, which causes GCC's undefined trap logic to emit another UD2
2641          * (or occasionally a JMP to UD2).
2642          */
2643         if (list_prev_entry(insn, list)->dead_end &&
2644             (insn->type == INSN_BUG ||
2645              (insn->type == INSN_JUMP_UNCONDITIONAL &&
2646               insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
2647                 return true;
2648
2649         /*
2650          * Check if this (or a subsequent) instruction is related to
2651          * CONFIG_UBSAN or CONFIG_KASAN.
2652          *
2653          * End the search at 5 instructions to avoid going into the weeds.
2654          */
2655         for (i = 0; i < 5; i++) {
2656
2657                 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
2658                         return true;
2659
2660                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
2661                         if (insn->jump_dest &&
2662                             insn->jump_dest->func == insn->func) {
2663                                 insn = insn->jump_dest;
2664                                 continue;
2665                         }
2666
2667                         break;
2668                 }
2669
2670                 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
2671                         break;
2672
2673                 insn = list_next_entry(insn, list);
2674         }
2675
2676         return false;
2677 }
2678
2679 static int validate_symbol(struct objtool_file *file, struct section *sec,
2680                            struct symbol *sym, struct insn_state *state)
2681 {
2682         struct instruction *insn;
2683         int ret;
2684
2685         if (!sym->len) {
2686                 WARN("%s() is missing an ELF size annotation", sym->name);
2687                 return 1;
2688         }
2689
2690         if (sym->pfunc != sym || sym->alias != sym)
2691                 return 0;
2692
2693         insn = find_insn(file, sec, sym->offset);
2694         if (!insn || insn->ignore || insn->visited)
2695                 return 0;
2696
2697         state->uaccess = sym->uaccess_safe;
2698
2699         ret = validate_branch(file, insn->func, insn, *state);
2700         if (ret && backtrace)
2701                 BT_FUNC("<=== (sym)", insn);
2702         return ret;
2703 }
2704
2705 static int validate_section(struct objtool_file *file, struct section *sec)
2706 {
2707         struct insn_state state;
2708         struct symbol *func;
2709         int warnings = 0;
2710
2711         list_for_each_entry(func, &sec->symbol_list, list) {
2712                 if (func->type != STT_FUNC)
2713                         continue;
2714
2715                 init_insn_state(&state, sec);
2716                 state.cfi.cfa = initial_func_cfi.cfa;
2717                 memcpy(&state.cfi.regs, &initial_func_cfi.regs,
2718                        CFI_NUM_REGS * sizeof(struct cfi_reg));
2719                 state.cfi.stack_size = initial_func_cfi.cfa.offset;
2720
2721                 warnings += validate_symbol(file, sec, func, &state);
2722         }
2723
2724         return warnings;
2725 }
2726
2727 static int validate_vmlinux_functions(struct objtool_file *file)
2728 {
2729         struct section *sec;
2730         int warnings = 0;
2731
2732         sec = find_section_by_name(file->elf, ".noinstr.text");
2733         if (sec) {
2734                 warnings += validate_section(file, sec);
2735                 warnings += validate_unwind_hints(file, sec);
2736         }
2737
2738         sec = find_section_by_name(file->elf, ".entry.text");
2739         if (sec) {
2740                 warnings += validate_section(file, sec);
2741                 warnings += validate_unwind_hints(file, sec);
2742         }
2743
2744         return warnings;
2745 }
2746
2747 static int validate_functions(struct objtool_file *file)
2748 {
2749         struct section *sec;
2750         int warnings = 0;
2751
2752         for_each_sec(file, sec) {
2753                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
2754                         continue;
2755
2756                 warnings += validate_section(file, sec);
2757         }
2758
2759         return warnings;
2760 }
2761
2762 static int validate_reachable_instructions(struct objtool_file *file)
2763 {
2764         struct instruction *insn;
2765
2766         if (file->ignore_unreachables)
2767                 return 0;
2768
2769         for_each_insn(file, insn) {
2770                 if (insn->visited || ignore_unreachable_insn(insn))
2771                         continue;
2772
2773                 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
2774                 return 1;
2775         }
2776
2777         return 0;
2778 }
2779
2780 static struct objtool_file file;
2781
2782 int check(const char *_objname, bool orc)
2783 {
2784         int ret, warnings = 0;
2785
2786         objname = _objname;
2787
2788         file.elf = elf_open_read(objname, O_RDWR);
2789         if (!file.elf)
2790                 return 1;
2791
2792         INIT_LIST_HEAD(&file.insn_list);
2793         hash_init(file.insn_hash);
2794         file.c_file = !vmlinux && find_section_by_name(file.elf, ".comment");
2795         file.ignore_unreachables = no_unreachable;
2796         file.hints = false;
2797
2798         arch_initial_func_cfi_state(&initial_func_cfi);
2799
2800         ret = decode_sections(&file);
2801         if (ret < 0)
2802                 goto out;
2803         warnings += ret;
2804
2805         if (list_empty(&file.insn_list))
2806                 goto out;
2807
2808         if (vmlinux && !validate_dup) {
2809                 ret = validate_vmlinux_functions(&file);
2810                 if (ret < 0)
2811                         goto out;
2812
2813                 warnings += ret;
2814                 goto out;
2815         }
2816
2817         if (retpoline) {
2818                 ret = validate_retpoline(&file);
2819                 if (ret < 0)
2820                         return ret;
2821                 warnings += ret;
2822         }
2823
2824         ret = validate_functions(&file);
2825         if (ret < 0)
2826                 goto out;
2827         warnings += ret;
2828
2829         ret = validate_unwind_hints(&file, NULL);
2830         if (ret < 0)
2831                 goto out;
2832         warnings += ret;
2833
2834         if (!warnings) {
2835                 ret = validate_reachable_instructions(&file);
2836                 if (ret < 0)
2837                         goto out;
2838                 warnings += ret;
2839         }
2840
2841         if (orc) {
2842                 ret = create_orc(&file);
2843                 if (ret < 0)
2844                         goto out;
2845
2846                 ret = create_orc_sections(&file);
2847                 if (ret < 0)
2848                         goto out;
2849         }
2850
2851         if (file.elf->changed) {
2852                 ret = elf_write(file.elf);
2853                 if (ret < 0)
2854                         goto out;
2855         }
2856
2857 out:
2858         if (ret < 0) {
2859                 /*
2860                  *  Fatal error.  The binary is corrupt or otherwise broken in
2861                  *  some way, or objtool itself is broken.  Fail the kernel
2862                  *  build.
2863                  */
2864                 return ret;
2865         }
2866
2867         return 0;
2868 }