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