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_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, offset)
  38                 if (insn->sec == sec && insn->offset == offset)
  39                         return insn;
  40
  41         return NULL;
  42 }
  43
  44 static struct instruction *next_insn_same_sec(struct objtool_file *file,
  45                                               struct instruction *insn)
  46 {
  47         struct instruction *next = list_next_entry(insn, list);
  48
  49         if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
  50                 return NULL;
  51
  52         return next;
  53 }
  54
  55 static struct instruction *next_insn_same_func(struct objtool_file *file,
  56                                                struct instruction *insn)
  57 {
  58         struct instruction *next = list_next_entry(insn, list);
  59         struct symbol *func = insn->func;
  60
  61         if (!func)
  62                 return NULL;
  63
  64         if (&next->list != &file->insn_list && next->func == func)
  65                 return next;
  66
  67         /* Check if we're already in the subfunction: */
  68         if (func == func->cfunc)
  69                 return NULL;
  70
  71         /* Move to the subfunction: */
  72         return find_insn(file, func->cfunc->sec, func->cfunc->offset);
  73 }
  74
  75 #define func_for_each_insn(file, func, insn)                            \
  76         for (insn = find_insn(file, func->sec, func->offset);           \
  77              insn;                                                      \
  78              insn = next_insn_same_func(file, insn))
  79
  80 #define sym_for_each_insn(file, sym, insn)                              \
  81         for (insn = find_insn(file, sym->sec, sym->offset);             \
  82              insn && &insn->list != &file->insn_list &&                 \
  83                 insn->sec == sym->sec &&                                \
  84                 insn->offset < sym->offset + sym->len;                  \
  85              insn = list_next_entry(insn, list))
  86
  87 #define sym_for_each_insn_continue_reverse(file, sym, insn)             \
  88         for (insn = list_prev_entry(insn, list);                        \
  89              &insn->list != &file->insn_list &&                         \
  90                 insn->sec == sym->sec && insn->offset >= sym->offset;   \
  91              insn = list_prev_entry(insn, list))
  92
  93 #define sec_for_each_insn_from(file, insn)                              \
  94         for (; insn; insn = next_insn_same_sec(file, insn))
  95
  96 #define sec_for_each_insn_continue(file, insn)                          \
  97         for (insn = next_insn_same_sec(file, insn); insn;               \
  98              insn = next_insn_same_sec(file, insn))
  99
 100 static bool is_static_jump(struct instruction *insn)
 101 {
 102         return insn->type == INSN_JUMP_CONDITIONAL ||
 103                insn->type == INSN_JUMP_UNCONDITIONAL;
 104 }
 105
 106 static bool is_sibling_call(struct instruction *insn)
 107 {
 108         /* An indirect jump is either a sibling call or a jump to a table. */
 109         if (insn->type == INSN_JUMP_DYNAMIC)
 110                 return list_empty(&insn->alts);
 111
 112         if (!is_static_jump(insn))
 113                 return false;
 114
 115         /* add_jump_destinations() sets insn->call_dest for sibling calls. */
 116         return !!insn->call_dest;
 117 }
 118
 119 /*
 120  * This checks to see if the given function is a "noreturn" function.
 121  *
 122  * For global functions which are outside the scope of this object file, we
 123  * have to keep a manual list of them.
 124  *
 125  * For local functions, we have to detect them manually by simply looking for
 126  * the lack of a return instruction.
 127  */
 128 static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 129                                 int recursion)
 130 {
 131         int i;
 132         struct instruction *insn;
 133         bool empty = true;
 134
 135         /*
 136          * Unfortunately these have to be hard coded because the noreturn
 137          * attribute isn't provided in ELF data.
 138          */
 139         static const char * const global_noreturns[] = {
 140                 "__stack_chk_fail",
 141                 "panic",
 142                 "do_exit",
 143                 "do_task_dead",
 144                 "__module_put_and_exit",
 145                 "complete_and_exit",
 146                 "__reiserfs_panic",
 147                 "lbug_with_loc",
 148                 "fortify_panic",
 149                 "usercopy_abort",
 150                 "machine_real_restart",
 151                 "rewind_stack_do_exit",
 152                 "kunit_try_catch_throw",
 153         };
 154
 155         if (!func)
 156                 return false;
 157
 158         if (func->bind == STB_WEAK)
 159                 return false;
 160
 161         if (func->bind == STB_GLOBAL)
 162                 for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
 163                         if (!strcmp(func->name, global_noreturns[i]))
 164                                 return true;
 165
 166         if (!func->len)
 167                 return false;
 168
 169         insn = find_insn(file, func->sec, func->offset);
 170         if (!insn->func)
 171                 return false;
 172
 173         func_for_each_insn(file, func, insn) {
 174                 empty = false;
 175
 176                 if (insn->type == INSN_RETURN)
 177                         return false;
 178         }
 179
 180         if (empty)
 181                 return false;
 182
 183         /*
 184          * A function can have a sibling call instead of a return.  In that
 185          * case, the function's dead-end status depends on whether the target
 186          * of the sibling call returns.
 187          */
 188         func_for_each_insn(file, func, insn) {
 189                 if (is_sibling_call(insn)) {
 190                         struct instruction *dest = insn->jump_dest;
 191
 192                         if (!dest)
 193                                 /* sibling call to another file */
 194                                 return false;
 195
 196                         /* local sibling call */
 197                         if (recursion == 5) {
 198                                 /*
 199                                  * Infinite recursion: two functions have
 200                                  * sibling calls to each other.  This is a very
 201                                  * rare case.  It means they aren't dead ends.
 202                                  */
 203                                 return false;
 204                         }
 205
 206                         return __dead_end_function(file, dest->func, recursion+1);
 207                 }
 208         }
 209
 210         return true;
 211 }
 212
 213 static bool dead_end_function(struct objtool_file *file, struct symbol *func)
 214 {
 215         return __dead_end_function(file, func, 0);
 216 }
 217
 218 static void clear_insn_state(struct insn_state *state)
 219 {
 220         int i;
 221
 222         memset(state, 0, sizeof(*state));
 223         state->cfa.base = CFI_UNDEFINED;
 224         for (i = 0; i < CFI_NUM_REGS; i++) {
 225                 state->regs[i].base = CFI_UNDEFINED;
 226                 state->vals[i].base = CFI_UNDEFINED;
 227         }
 228         state->drap_reg = CFI_UNDEFINED;
 229         state->drap_offset = -1;
 230 }
 231
 232 /*
 233  * Call the arch-specific instruction decoder for all the instructions and add
 234  * them to the global instruction list.
 235  */
 236 static int decode_instructions(struct objtool_file *file)
 237 {
 238         struct section *sec;
 239         struct symbol *func;
 240         unsigned long offset;
 241         struct instruction *insn;
 242         unsigned long nr_insns = 0;
 243         int ret;
 244
 245         for_each_sec(file, sec) {
 246
 247                 if (!(sec->sh.sh_flags & SHF_EXECINSTR))
 248                         continue;
 249
 250                 if (strcmp(sec->name, ".altinstr_replacement") &&
 251                     strcmp(sec->name, ".altinstr_aux") &&
 252                     strncmp(sec->name, ".discard.", 9))
 253                         sec->text = true;
 254
 255                 for (offset = 0; offset < sec->len; offset += insn->len) {
 256                         insn = malloc(sizeof(*insn));
 257                         if (!insn) {
 258                                 WARN("malloc failed");
 259                                 return -1;
 260                         }
 261                         memset(insn, 0, sizeof(*insn));
 262                         INIT_LIST_HEAD(&insn->alts);
 263                         clear_insn_state(&insn->state);
 264
 265                         insn->sec = sec;
 266                         insn->offset = offset;
 267
 268                         ret = arch_decode_instruction(file->elf, sec, offset,
 269                                                       sec->len - offset,
 270                                                       &insn->len, &insn->type,
 271                                                       &insn->immediate,
 272                                                       &insn->stack_op);
 273                         if (ret)
 274                                 goto err;
 275
 276                         hash_add(file->insn_hash, &insn->hash, insn->offset);
 277                         list_add_tail(&insn->list, &file->insn_list);
 278                         nr_insns++;
 279                 }
 280
 281                 list_for_each_entry(func, &sec->symbol_list, list) {
 282                         if (func->type != STT_FUNC || func->alias != func)
 283                                 continue;
 284
 285                         if (!find_insn(file, sec, func->offset)) {
 286                                 WARN("%s(): can't find starting instruction",
 287                                      func->name);
 288                                 return -1;
 289                         }
 290
 291                         sym_for_each_insn(file, func, insn)
 292                                 insn->func = func;
 293                 }
 294         }
 295
 296         if (stats)
 297                 printf("nr_insns: %lu\n", nr_insns);
 298
 299         return 0;
 300
 301 err:
 302         free(insn);
 303         return ret;
 304 }
 305
 306 /*
 307  * Mark "ud2" instructions and manually annotated dead ends.
 308  */
 309 static int add_dead_ends(struct objtool_file *file)
 310 {
 311         struct section *sec;
 312         struct rela *rela;
 313         struct instruction *insn;
 314         bool found;
 315
 316         /*
 317          * By default, "ud2" is a dead end unless otherwise annotated, because
 318          * GCC 7 inserts it for certain divide-by-zero cases.
 319          */
 320         for_each_insn(file, insn)
 321                 if (insn->type == INSN_BUG)
 322                         insn->dead_end = true;
 323
 324         /*
 325          * Check for manually annotated dead ends.
 326          */
 327         sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
 328         if (!sec)
 329                 goto reachable;
 330
 331         list_for_each_entry(rela, &sec->rela_list, list) {
 332                 if (rela->sym->type != STT_SECTION) {
 333                         WARN("unexpected relocation symbol type in %s", sec->name);
 334                         return -1;
 335                 }
 336                 insn = find_insn(file, rela->sym->sec, rela->addend);
 337                 if (insn)
 338                         insn = list_prev_entry(insn, list);
 339                 else if (rela->addend == rela->sym->sec->len) {
 340                         found = false;
 341                         list_for_each_entry_reverse(insn, &file->insn_list, list) {
 342                                 if (insn->sec == rela->sym->sec) {
 343                                         found = true;
 344                                         break;
 345                                 }
 346                         }
 347
 348                         if (!found) {
 349                                 WARN("can't find unreachable insn at %s+0x%x",
 350                                      rela->sym->sec->name, rela->addend);
 351                                 return -1;
 352                         }
 353                 } else {
 354                         WARN("can't find unreachable insn at %s+0x%x",
 355                              rela->sym->sec->name, rela->addend);
 356                         return -1;
 357                 }
 358
 359                 insn->dead_end = true;
 360         }
 361
 362 reachable:
 363         /*
 364          * These manually annotated reachable checks are needed for GCC 4.4,
 365          * where the Linux unreachable() macro isn't supported.  In that case
 366          * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
 367          * not a dead end.
 368          */
 369         sec = find_section_by_name(file->elf, ".rela.discard.reachable");
 370         if (!sec)
 371                 return 0;
 372
 373         list_for_each_entry(rela, &sec->rela_list, list) {
 374                 if (rela->sym->type != STT_SECTION) {
 375                         WARN("unexpected relocation symbol type in %s", sec->name);
 376                         return -1;
 377                 }
 378                 insn = find_insn(file, rela->sym->sec, rela->addend);
 379                 if (insn)
 380                         insn = list_prev_entry(insn, list);
 381                 else if (rela->addend == rela->sym->sec->len) {
 382                         found = false;
 383                         list_for_each_entry_reverse(insn, &file->insn_list, list) {
 384                                 if (insn->sec == rela->sym->sec) {
 385                                         found = true;
 386                                         break;
 387                                 }
 388                         }
 389
 390                         if (!found) {
 391                                 WARN("can't find reachable insn at %s+0x%x",
 392                                      rela->sym->sec->name, rela->addend);
 393                                 return -1;
 394                         }
 395                 } else {
 396                         WARN("can't find reachable insn at %s+0x%x",
 397                              rela->sym->sec->name, rela->addend);
 398                         return -1;
 399                 }
 400
 401                 insn->dead_end = false;
 402         }
 403
 404         return 0;
 405 }
 406
 407 /*
 408  * Warnings shouldn't be reported for ignored functions.
 409  */
 410 static void add_ignores(struct objtool_file *file)
 411 {
 412         struct instruction *insn;
 413         struct section *sec;
 414         struct symbol *func;
 415         struct rela *rela;
 416
 417         sec = find_section_by_name(file->elf, ".rela.discard.func_stack_frame_non_standard");
 418         if (!sec)
 419                 return;
 420
 421         list_for_each_entry(rela, &sec->rela_list, list) {
 422                 switch (rela->sym->type) {
 423                 case STT_FUNC:
 424                         func = rela->sym;
 425                         break;
 426
 427                 case STT_SECTION:
 428                         func = find_func_by_offset(rela->sym->sec, rela->addend);
 429                         if (!func)
 430                                 continue;
 431                         break;
 432
 433                 default:
 434                         WARN("unexpected relocation symbol type in %s: %d", sec->name, rela->sym->type);
 435                         continue;
 436                 }
 437
 438                 func_for_each_insn(file, func, insn)
 439                         insn->ignore = true;
 440         }
 441 }
 442
 443 /*
 444  * This is a whitelist of functions that is allowed to be called with AC set.
 445  * The list is meant to be minimal and only contains compiler instrumentation
 446  * ABI and a few functions used to implement *_{to,from}_user() functions.
 447  *
 448  * These functions must not directly change AC, but may PUSHF/POPF.
 449  */
 450 static const char *uaccess_safe_builtin[] = {
 451         /* KASAN */
 452         "kasan_report",
 453         "check_memory_region",
 454         /* KASAN out-of-line */
 455         "__asan_loadN_noabort",
 456         "__asan_load1_noabort",
 457         "__asan_load2_noabort",
 458         "__asan_load4_noabort",
 459         "__asan_load8_noabort",
 460         "__asan_load16_noabort",
 461         "__asan_storeN_noabort",
 462         "__asan_store1_noabort",
 463         "__asan_store2_noabort",
 464         "__asan_store4_noabort",
 465         "__asan_store8_noabort",
 466         "__asan_store16_noabort",
 467         /* KASAN in-line */
 468         "__asan_report_load_n_noabort",
 469         "__asan_report_load1_noabort",
 470         "__asan_report_load2_noabort",
 471         "__asan_report_load4_noabort",
 472         "__asan_report_load8_noabort",
 473         "__asan_report_load16_noabort",
 474         "__asan_report_store_n_noabort",
 475         "__asan_report_store1_noabort",
 476         "__asan_report_store2_noabort",
 477         "__asan_report_store4_noabort",
 478         "__asan_report_store8_noabort",
 479         "__asan_report_store16_noabort",
 480         /* KCSAN */
 481         "__kcsan_check_access",
 482         "kcsan_found_watchpoint",
 483         "kcsan_setup_watchpoint",
 484         "kcsan_check_scoped_accesses",
 485         "kcsan_disable_current",
 486         "kcsan_enable_current_nowarn",
 487         /* KCSAN/TSAN */
 488         "__tsan_func_entry",
 489         "__tsan_func_exit",
 490         "__tsan_read_range",
 491         "__tsan_write_range",
 492         "__tsan_read1",
 493         "__tsan_read2",
 494         "__tsan_read4",
 495         "__tsan_read8",
 496         "__tsan_read16",
 497         "__tsan_write1",
 498         "__tsan_write2",
 499         "__tsan_write4",
 500         "__tsan_write8",
 501         "__tsan_write16",
 502         /* KCOV */
 503         "write_comp_data",
 504         "__sanitizer_cov_trace_pc",
 505         "__sanitizer_cov_trace_const_cmp1",
 506         "__sanitizer_cov_trace_const_cmp2",
 507         "__sanitizer_cov_trace_const_cmp4",
 508         "__sanitizer_cov_trace_const_cmp8",
 509         "__sanitizer_cov_trace_cmp1",
 510         "__sanitizer_cov_trace_cmp2",
 511         "__sanitizer_cov_trace_cmp4",
 512         "__sanitizer_cov_trace_cmp8",
 513         "__sanitizer_cov_trace_switch",
 514         /* UBSAN */
 515         "ubsan_type_mismatch_common",
 516         "__ubsan_handle_type_mismatch",
 517         "__ubsan_handle_type_mismatch_v1",
 518         "__ubsan_handle_shift_out_of_bounds",
 519         /* misc */
 520         "csum_partial_copy_generic",
 521         "__memcpy_mcsafe",
 522         "mcsafe_handle_tail",
 523         "ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
 524         NULL
 525 };
 526
 527 static void add_uaccess_safe(struct objtool_file *file)
 528 {
 529         struct symbol *func;
 530         const char **name;
 531
 532         if (!uaccess)
 533                 return;
 534
 535         for (name = uaccess_safe_builtin; *name; name++) {
 536                 func = find_symbol_by_name(file->elf, *name);
 537                 if (!func)
 538                         continue;
 539
 540                 func->uaccess_safe = true;
 541         }
 542 }
 543
 544 /*
 545  * FIXME: For now, just ignore any alternatives which add retpolines.  This is
 546  * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
 547  * But it at least allows objtool to understand the control flow *around* the
 548  * retpoline.
 549  */
 550 static int add_ignore_alternatives(struct objtool_file *file)
 551 {
 552         struct section *sec;
 553         struct rela *rela;
 554         struct instruction *insn;
 555
 556         sec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
 557         if (!sec)
 558                 return 0;
 559
 560         list_for_each_entry(rela, &sec->rela_list, list) {
 561                 if (rela->sym->type != STT_SECTION) {
 562                         WARN("unexpected relocation symbol type in %s", sec->name);
 563                         return -1;
 564                 }
 565
 566                 insn = find_insn(file, rela->sym->sec, rela->addend);
 567                 if (!insn) {
 568                         WARN("bad .discard.ignore_alts entry");
 569                         return -1;
 570                 }
 571
 572                 insn->ignore_alts = true;
 573         }
 574
 575         return 0;
 576 }
 577
 578 /*
 579  * Find the destination instructions for all jumps.
 580  */
 581 static int add_jump_destinations(struct objtool_file *file)
 582 {
 583         struct instruction *insn;
 584         struct rela *rela;
 585         struct section *dest_sec;
 586         unsigned long dest_off;
 587
 588         for_each_insn(file, insn) {
 589                 if (!is_static_jump(insn))
 590                         continue;
 591
 592                 if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET)
 593                         continue;
 594
 595                 rela = find_rela_by_dest_range(file->elf, insn->sec,
 596                                                insn->offset, insn->len);
 597                 if (!rela) {
 598                         dest_sec = insn->sec;
 599                         dest_off = insn->offset + insn->len + insn->immediate;
 600                 } else if (rela->sym->type == STT_SECTION) {
 601                         dest_sec = rela->sym->sec;
 602                         dest_off = rela->addend + 4;
 603                 } else if (rela->sym->sec->idx) {
 604                         dest_sec = rela->sym->sec;
 605                         dest_off = rela->sym->sym.st_value + rela->addend + 4;
 606                 } else if (strstr(rela->sym->name, "_indirect_thunk_")) {
 607                         /*
 608                          * Retpoline jumps are really dynamic jumps in
 609                          * disguise, so convert them accordingly.
 610                          */
 611                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
 612                                 insn->type = INSN_JUMP_DYNAMIC;
 613                         else
 614                                 insn->type = INSN_JUMP_DYNAMIC_CONDITIONAL;
 615
 616                         insn->retpoline_safe = true;
 617                         continue;
 618                 } else {
 619                         /* external sibling call */
 620                         insn->call_dest = rela->sym;
 621                         continue;
 622                 }
 623
 624                 insn->jump_dest = find_insn(file, dest_sec, dest_off);
 625                 if (!insn->jump_dest) {
 626
 627                         /*
 628                          * This is a special case where an alt instruction
 629                          * jumps past the end of the section.  These are
 630                          * handled later in handle_group_alt().
 631                          */
 632                         if (!strcmp(insn->sec->name, ".altinstr_replacement"))
 633                                 continue;
 634
 635                         WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
 636                                   insn->sec, insn->offset, dest_sec->name,
 637                                   dest_off);
 638                         return -1;
 639                 }
 640
 641                 /*
 642                  * Cross-function jump.
 643                  */
 644                 if (insn->func && insn->jump_dest->func &&
 645                     insn->func != insn->jump_dest->func) {
 646
 647                         /*
 648                          * For GCC 8+, create parent/child links for any cold
 649                          * subfunctions.  This is _mostly_ redundant with a
 650                          * similar initialization in read_symbols().
 651                          *
 652                          * If a function has aliases, we want the *first* such
 653                          * function in the symbol table to be the subfunction's
 654                          * parent.  In that case we overwrite the
 655                          * initialization done in read_symbols().
 656                          *
 657                          * However this code can't completely replace the
 658                          * read_symbols() code because this doesn't detect the
 659                          * case where the parent function's only reference to a
 660                          * subfunction is through a jump table.
 661                          */
 662                         if (!strstr(insn->func->name, ".cold.") &&
 663                             strstr(insn->jump_dest->func->name, ".cold.")) {
 664                                 insn->func->cfunc = insn->jump_dest->func;
 665                                 insn->jump_dest->func->pfunc = insn->func;
 666
 667                         } else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
 668                                    insn->jump_dest->offset == insn->jump_dest->func->offset) {
 669
 670                                 /* internal sibling call */
 671                                 insn->call_dest = insn->jump_dest->func;
 672                         }
 673                 }
 674         }
 675
 676         return 0;
 677 }
 678
 679 /*
 680  * Find the destination instructions for all calls.
 681  */
 682 static int add_call_destinations(struct objtool_file *file)
 683 {
 684         struct instruction *insn;
 685         unsigned long dest_off;
 686         struct rela *rela;
 687
 688         for_each_insn(file, insn) {
 689                 if (insn->type != INSN_CALL)
 690                         continue;
 691
 692                 rela = find_rela_by_dest_range(file->elf, insn->sec,
 693                                                insn->offset, insn->len);
 694                 if (!rela) {
 695                         dest_off = insn->offset + insn->len + insn->immediate;
 696                         insn->call_dest = find_func_by_offset(insn->sec, dest_off);
 697                         if (!insn->call_dest)
 698                                 insn->call_dest = find_symbol_by_offset(insn->sec, dest_off);
 699
 700                         if (insn->ignore)
 701                                 continue;
 702
 703                         if (!insn->call_dest) {
 704                                 WARN_FUNC("unsupported intra-function call",
 705                                           insn->sec, insn->offset);
 706                                 if (retpoline)
 707                                         WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");
 708                                 return -1;
 709                         }
 710
 711                         if (insn->func && insn->call_dest->type != STT_FUNC) {
 712                                 WARN_FUNC("unsupported call to non-function",
 713                                           insn->sec, insn->offset);
 714                                 return -1;
 715                         }
 716
 717                 } else if (rela->sym->type == STT_SECTION) {
 718                         insn->call_dest = find_func_by_offset(rela->sym->sec,
 719                                                               rela->addend+4);
 720                         if (!insn->call_dest) {
 721                                 WARN_FUNC("can't find call dest symbol at %s+0x%x",
 722                                           insn->sec, insn->offset,
 723                                           rela->sym->sec->name,
 724                                           rela->addend + 4);
 725                                 return -1;
 726                         }
 727                 } else
 728                         insn->call_dest = rela->sym;
 729         }
 730
 731         return 0;
 732 }
 733
 734 /*
 735  * The .alternatives section requires some extra special care, over and above
 736  * what other special sections require:
 737  *
 738  * 1. Because alternatives are patched in-place, we need to insert a fake jump
 739  *    instruction at the end so that validate_branch() skips all the original
 740  *    replaced instructions when validating the new instruction path.
 741  *
 742  * 2. An added wrinkle is that the new instruction length might be zero.  In
 743  *    that case the old instructions are replaced with noops.  We simulate that
 744  *    by creating a fake jump as the only new instruction.
 745  *
 746  * 3. In some cases, the alternative section includes an instruction which
 747  *    conditionally jumps to the _end_ of the entry.  We have to modify these
 748  *    jumps' destinations to point back to .text rather than the end of the
 749  *    entry in .altinstr_replacement.
 750  */
 751 static int handle_group_alt(struct objtool_file *file,
 752                             struct special_alt *special_alt,
 753                             struct instruction *orig_insn,
 754                             struct instruction **new_insn)
 755 {
 756         struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
 757         unsigned long dest_off;
 758
 759         last_orig_insn = NULL;
 760         insn = orig_insn;
 761         sec_for_each_insn_from(file, insn) {
 762                 if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
 763                         break;
 764
 765                 insn->alt_group = true;
 766                 last_orig_insn = insn;
 767         }
 768
 769         if (next_insn_same_sec(file, last_orig_insn)) {
 770                 fake_jump = malloc(sizeof(*fake_jump));
 771                 if (!fake_jump) {
 772                         WARN("malloc failed");
 773                         return -1;
 774                 }
 775                 memset(fake_jump, 0, sizeof(*fake_jump));
 776                 INIT_LIST_HEAD(&fake_jump->alts);
 777                 clear_insn_state(&fake_jump->state);
 778
 779                 fake_jump->sec = special_alt->new_sec;
 780                 fake_jump->offset = FAKE_JUMP_OFFSET;
 781                 fake_jump->type = INSN_JUMP_UNCONDITIONAL;
 782                 fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
 783                 fake_jump->func = orig_insn->func;
 784         }
 785
 786         if (!special_alt->new_len) {
 787                 if (!fake_jump) {
 788                         WARN("%s: empty alternative at end of section",
 789                              special_alt->orig_sec->name);
 790                         return -1;
 791                 }
 792
 793                 *new_insn = fake_jump;
 794                 return 0;
 795         }
 796
 797         last_new_insn = NULL;
 798         insn = *new_insn;
 799         sec_for_each_insn_from(file, insn) {
 800                 if (insn->offset >= special_alt->new_off + special_alt->new_len)
 801                         break;
 802
 803                 last_new_insn = insn;
 804
 805                 insn->ignore = orig_insn->ignore_alts;
 806                 insn->func = orig_insn->func;
 807
 808                 /*
 809                  * Since alternative replacement code is copy/pasted by the
 810                  * kernel after applying relocations, generally such code can't
 811                  * have relative-address relocation references to outside the
 812                  * .altinstr_replacement section, unless the arch's
 813                  * alternatives code can adjust the relative offsets
 814                  * accordingly.
 815                  *
 816                  * The x86 alternatives code adjusts the offsets only when it
 817                  * encounters a branch instruction at the very beginning of the
 818                  * replacement group.
 819                  */
 820                 if ((insn->offset != special_alt->new_off ||
 821                     (insn->type != INSN_CALL && !is_static_jump(insn))) &&
 822                     find_rela_by_dest_range(file->elf, insn->sec, insn->offset, insn->len)) {
 823
 824                         WARN_FUNC("unsupported relocation in alternatives section",
 825                                   insn->sec, insn->offset);
 826                         return -1;
 827                 }
 828
 829                 if (!is_static_jump(insn))
 830                         continue;
 831
 832                 if (!insn->immediate)
 833                         continue;
 834
 835                 dest_off = insn->offset + insn->len + insn->immediate;
 836                 if (dest_off == special_alt->new_off + special_alt->new_len) {
 837                         if (!fake_jump) {
 838                                 WARN("%s: alternative jump to end of section",
 839                                      special_alt->orig_sec->name);
 840                                 return -1;
 841                         }
 842                         insn->jump_dest = fake_jump;
 843                 }
 844
 845                 if (!insn->jump_dest) {
 846                         WARN_FUNC("can't find alternative jump destination",
 847                                   insn->sec, insn->offset);
 848                         return -1;
 849                 }
 850         }
 851
 852         if (!last_new_insn) {
 853                 WARN_FUNC("can't find last new alternative instruction",
 854                           special_alt->new_sec, special_alt->new_off);
 855                 return -1;
 856         }
 857
 858         if (fake_jump)
 859                 list_add(&fake_jump->list, &last_new_insn->list);
 860
 861         return 0;
 862 }
 863
 864 /*
 865  * A jump table entry can either convert a nop to a jump or a jump to a nop.
 866  * If the original instruction is a jump, make the alt entry an effective nop
 867  * by just skipping the original instruction.
 868  */
 869 static int handle_jump_alt(struct objtool_file *file,
 870                            struct special_alt *special_alt,
 871                            struct instruction *orig_insn,
 872                            struct instruction **new_insn)
 873 {
 874         if (orig_insn->type == INSN_NOP)
 875                 return 0;
 876
 877         if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
 878                 WARN_FUNC("unsupported instruction at jump label",
 879                           orig_insn->sec, orig_insn->offset);
 880                 return -1;
 881         }
 882
 883         *new_insn = list_next_entry(orig_insn, list);
 884         return 0;
 885 }
 886
 887 /*
 888  * Read all the special sections which have alternate instructions which can be
 889  * patched in or redirected to at runtime.  Each instruction having alternate
 890  * instruction(s) has them added to its insn->alts list, which will be
 891  * traversed in validate_branch().
 892  */
 893 static int add_special_section_alts(struct objtool_file *file)
 894 {
 895         struct list_head special_alts;
 896         struct instruction *orig_insn, *new_insn;
 897         struct special_alt *special_alt, *tmp;
 898         struct alternative *alt;
 899         int ret;
 900
 901         ret = special_get_alts(file->elf, &special_alts);
 902         if (ret)
 903                 return ret;
 904
 905         list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
 906
 907                 orig_insn = find_insn(file, special_alt->orig_sec,
 908                                       special_alt->orig_off);
 909                 if (!orig_insn) {
 910                         WARN_FUNC("special: can't find orig instruction",
 911                                   special_alt->orig_sec, special_alt->orig_off);
 912                         ret = -1;
 913                         goto out;
 914                 }
 915
 916                 new_insn = NULL;
 917                 if (!special_alt->group || special_alt->new_len) {
 918                         new_insn = find_insn(file, special_alt->new_sec,
 919                                              special_alt->new_off);
 920                         if (!new_insn) {
 921                                 WARN_FUNC("special: can't find new instruction",
 922                                           special_alt->new_sec,
 923                                           special_alt->new_off);
 924                                 ret = -1;
 925                                 goto out;
 926                         }
 927                 }
 928
 929                 if (special_alt->group) {
 930                         ret = handle_group_alt(file, special_alt, orig_insn,
 931                                                &new_insn);
 932                         if (ret)
 933                                 goto out;
 934                 } else if (special_alt->jump_or_nop) {
 935                         ret = handle_jump_alt(file, special_alt, orig_insn,
 936                                               &new_insn);
 937                         if (ret)
 938                                 goto out;
 939                 }
 940
 941                 alt = malloc(sizeof(*alt));
 942                 if (!alt) {
 943                         WARN("malloc failed");
 944                         ret = -1;
 945                         goto out;
 946                 }
 947
 948                 alt->insn = new_insn;
 949                 alt->skip_orig = special_alt->skip_orig;
 950                 orig_insn->ignore_alts |= special_alt->skip_alt;
 951                 list_add_tail(&alt->list, &orig_insn->alts);
 952
 953                 list_del(&special_alt->list);
 954                 free(special_alt);
 955         }
 956
 957 out:
 958         return ret;
 959 }
 960
 961 static int add_jump_table(struct objtool_file *file, struct instruction *insn,
 962                             struct rela *table)
 963 {
 964         struct rela *rela = table;
 965         struct instruction *dest_insn;
 966         struct alternative *alt;
 967         struct symbol *pfunc = insn->func->pfunc;
 968         unsigned int prev_offset = 0;
 969
 970         /*
 971          * Each @rela is a switch table relocation which points to the target
 972          * instruction.
 973          */
 974         list_for_each_entry_from(rela, &table->sec->rela_list, list) {
 975
 976                 /* Check for the end of the table: */
 977                 if (rela != table && rela->jump_table_start)
 978                         break;
 979
 980                 /* Make sure the table entries are consecutive: */
 981                 if (prev_offset && rela->offset != prev_offset + 8)
 982                         break;
 983
 984                 /* Detect function pointers from contiguous objects: */
 985                 if (rela->sym->sec == pfunc->sec &&
 986                     rela->addend == pfunc->offset)
 987                         break;
 988
 989                 dest_insn = find_insn(file, rela->sym->sec, rela->addend);
 990                 if (!dest_insn)
 991                         break;
 992
 993                 /* Make sure the destination is in the same function: */
 994                 if (!dest_insn->func || dest_insn->func->pfunc != pfunc)
 995                         break;
 996
 997                 alt = malloc(sizeof(*alt));
 998                 if (!alt) {
 999                         WARN("malloc failed");
1000                         return -1;
1001                 }
1002
1003                 alt->insn = dest_insn;
1004                 list_add_tail(&alt->list, &insn->alts);
1005                 prev_offset = rela->offset;
1006         }
1007
1008         if (!prev_offset) {
1009                 WARN_FUNC("can't find switch jump table",
1010                           insn->sec, insn->offset);
1011                 return -1;
1012         }
1013
1014         return 0;
1015 }
1016
1017 /*
1018  * find_jump_table() - Given a dynamic jump, find the switch jump table in
1019  * .rodata associated with it.
1020  *
1021  * There are 3 basic patterns:
1022  *
1023  * 1. jmpq *[rodata addr](,%reg,8)
1024  *
1025  *    This is the most common case by far.  It jumps to an address in a simple
1026  *    jump table which is stored in .rodata.
1027  *
1028  * 2. jmpq *[rodata addr](%rip)
1029  *
1030  *    This is caused by a rare GCC quirk, currently only seen in three driver
1031  *    functions in the kernel, only with certain obscure non-distro configs.
1032  *
1033  *    As part of an optimization, GCC makes a copy of an existing switch jump
1034  *    table, modifies it, and then hard-codes the jump (albeit with an indirect
1035  *    jump) to use a single entry in the table.  The rest of the jump table and
1036  *    some of its jump targets remain as dead code.
1037  *
1038  *    In such a case we can just crudely ignore all unreachable instruction
1039  *    warnings for the entire object file.  Ideally we would just ignore them
1040  *    for the function, but that would require redesigning the code quite a
1041  *    bit.  And honestly that's just not worth doing: unreachable instruction
1042  *    warnings are of questionable value anyway, and this is such a rare issue.
1043  *
1044  * 3. mov [rodata addr],%reg1
1045  *    ... some instructions ...
1046  *    jmpq *(%reg1,%reg2,8)
1047  *
1048  *    This is a fairly uncommon pattern which is new for GCC 6.  As of this
1049  *    writing, there are 11 occurrences of it in the allmodconfig kernel.
1050  *
1051  *    As of GCC 7 there are quite a few more of these and the 'in between' code
1052  *    is significant. Esp. with KASAN enabled some of the code between the mov
1053  *    and jmpq uses .rodata itself, which can confuse things.
1054  *
1055  *    TODO: Once we have DWARF CFI and smarter instruction decoding logic,
1056  *    ensure the same register is used in the mov and jump instructions.
1057  *
1058  *    NOTE: RETPOLINE made it harder still to decode dynamic jumps.
1059  */
1060 static struct rela *find_jump_table(struct objtool_file *file,
1061                                       struct symbol *func,
1062                                       struct instruction *insn)
1063 {
1064         struct rela *text_rela, *table_rela;
1065         struct instruction *dest_insn, *orig_insn = insn;
1066         struct section *table_sec;
1067         unsigned long table_offset;
1068
1069         /*
1070          * Backward search using the @first_jump_src links, these help avoid
1071          * much of the 'in between' code. Which avoids us getting confused by
1072          * it.
1073          */
1074         for (;
1075              &insn->list != &file->insn_list &&
1076              insn->sec == func->sec &&
1077              insn->offset >= func->offset;
1078
1079              insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {
1080
1081                 if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
1082                         break;
1083
1084                 /* allow small jumps within the range */
1085                 if (insn->type == INSN_JUMP_UNCONDITIONAL &&
1086                     insn->jump_dest &&
1087                     (insn->jump_dest->offset <= insn->offset ||
1088                      insn->jump_dest->offset > orig_insn->offset))
1089                     break;
1090
1091                 /* look for a relocation which references .rodata */
1092                 text_rela = find_rela_by_dest_range(file->elf, insn->sec,
1093                                                     insn->offset, insn->len);
1094                 if (!text_rela || text_rela->sym->type != STT_SECTION ||
1095                     !text_rela->sym->sec->rodata)
1096                         continue;
1097
1098                 table_offset = text_rela->addend;
1099                 table_sec = text_rela->sym->sec;
1100
1101                 if (text_rela->type == R_X86_64_PC32)
1102                         table_offset += 4;
1103
1104                 /*
1105                  * Make sure the .rodata address isn't associated with a
1106                  * symbol.  GCC jump tables are anonymous data.
1107                  *
1108                  * Also support C jump tables which are in the same format as
1109                  * switch jump tables.  For objtool to recognize them, they
1110                  * need to be placed in the C_JUMP_TABLE_SECTION section.  They
1111                  * have symbols associated with them.
1112                  */
1113                 if (find_symbol_containing(table_sec, table_offset) &&
1114                     strcmp(table_sec->name, C_JUMP_TABLE_SECTION))
1115                         continue;
1116
1117                 /*
1118                  * Each table entry has a rela associated with it.  The rela
1119                  * should reference text in the same function as the original
1120                  * instruction.
1121                  */
1122                 table_rela = find_rela_by_dest(file->elf, table_sec, table_offset);
1123                 if (!table_rela)
1124                         continue;
1125                 dest_insn = find_insn(file, table_rela->sym->sec, table_rela->addend);
1126                 if (!dest_insn || !dest_insn->func || dest_insn->func->pfunc != func)
1127                         continue;
1128
1129                 /*
1130                  * Use of RIP-relative switch jumps is quite rare, and
1131                  * indicates a rare GCC quirk/bug which can leave dead code
1132                  * behind.
1133                  */
1134                 if (text_rela->type == R_X86_64_PC32)
1135                         file->ignore_unreachables = true;
1136
1137                 return table_rela;
1138         }
1139
1140         return NULL;
1141 }
1142
1143 /*
1144  * First pass: Mark the head of each jump table so that in the next pass,
1145  * we know when a given jump table ends and the next one starts.
1146  */
1147 static void mark_func_jump_tables(struct objtool_file *file,
1148                                     struct symbol *func)
1149 {
1150         struct instruction *insn, *last = NULL;
1151         struct rela *rela;
1152
1153         func_for_each_insn(file, func, insn) {
1154                 if (!last)
1155                         last = insn;
1156
1157                 /*
1158                  * Store back-pointers for unconditional forward jumps such
1159                  * that find_jump_table() can back-track using those and
1160                  * avoid some potentially confusing code.
1161                  */
1162                 if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
1163                     insn->offset > last->offset &&
1164                     insn->jump_dest->offset > insn->offset &&
1165                     !insn->jump_dest->first_jump_src) {
1166
1167                         insn->jump_dest->first_jump_src = insn;
1168                         last = insn->jump_dest;
1169                 }
1170
1171                 if (insn->type != INSN_JUMP_DYNAMIC)
1172                         continue;
1173
1174                 rela = find_jump_table(file, func, insn);
1175                 if (rela) {
1176                         rela->jump_table_start = true;
1177                         insn->jump_table = rela;
1178                 }
1179         }
1180 }
1181
1182 static int add_func_jump_tables(struct objtool_file *file,
1183                                   struct symbol *func)
1184 {
1185         struct instruction *insn;
1186         int ret;
1187
1188         func_for_each_insn(file, func, insn) {
1189                 if (!insn->jump_table)
1190                         continue;
1191
1192                 ret = add_jump_table(file, insn, insn->jump_table);
1193                 if (ret)
1194                         return ret;
1195         }
1196
1197         return 0;
1198 }
1199
1200 /*
1201  * For some switch statements, gcc generates a jump table in the .rodata
1202  * section which contains a list of addresses within the function to jump to.
1203  * This finds these jump tables and adds them to the insn->alts lists.
1204  */
1205 static int add_jump_table_alts(struct objtool_file *file)
1206 {
1207         struct section *sec;
1208         struct symbol *func;
1209         int ret;
1210
1211         if (!file->rodata)
1212                 return 0;
1213
1214         for_each_sec(file, sec) {
1215                 list_for_each_entry(func, &sec->symbol_list, list) {
1216                         if (func->type != STT_FUNC)
1217                                 continue;
1218
1219                         mark_func_jump_tables(file, func);
1220                         ret = add_func_jump_tables(file, func);
1221                         if (ret)
1222                                 return ret;
1223                 }
1224         }
1225
1226         return 0;
1227 }
1228
1229 static int read_unwind_hints(struct objtool_file *file)
1230 {
1231         struct section *sec, *relasec;
1232         struct rela *rela;
1233         struct unwind_hint *hint;
1234         struct instruction *insn;
1235         struct cfi_reg *cfa;
1236         int i;
1237
1238         sec = find_section_by_name(file->elf, ".discard.unwind_hints");
1239         if (!sec)
1240                 return 0;
1241
1242         relasec = sec->rela;
1243         if (!relasec) {
1244                 WARN("missing .rela.discard.unwind_hints section");
1245                 return -1;
1246         }
1247
1248         if (sec->len % sizeof(struct unwind_hint)) {
1249                 WARN("struct unwind_hint size mismatch");
1250                 return -1;
1251         }
1252
1253         file->hints = true;
1254
1255         for (i = 0; i < sec->len / sizeof(struct unwind_hint); i++) {
1256                 hint = (struct unwind_hint *)sec->data->d_buf + i;
1257
1258                 rela = find_rela_by_dest(file->elf, sec, i * sizeof(*hint));
1259                 if (!rela) {
1260                         WARN("can't find rela for unwind_hints[%d]", i);
1261                         return -1;
1262                 }
1263
1264                 insn = find_insn(file, rela->sym->sec, rela->addend);
1265                 if (!insn) {
1266                         WARN("can't find insn for unwind_hints[%d]", i);
1267                         return -1;
1268                 }
1269
1270                 cfa = &insn->state.cfa;
1271
1272                 if (hint->type == UNWIND_HINT_TYPE_SAVE) {
1273                         insn->save = true;
1274                         continue;
1275
1276                 } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
1277                         insn->restore = true;
1278                         insn->hint = true;
1279                         continue;
1280                 }
1281
1282                 insn->hint = true;
1283
1284                 switch (hint->sp_reg) {
1285                 case ORC_REG_UNDEFINED:
1286                         cfa->base = CFI_UNDEFINED;
1287                         break;
1288                 case ORC_REG_SP:
1289                         cfa->base = CFI_SP;
1290                         break;
1291                 case ORC_REG_BP:
1292                         cfa->base = CFI_BP;
1293                         break;
1294                 case ORC_REG_SP_INDIRECT:
1295                         cfa->base = CFI_SP_INDIRECT;
1296                         break;
1297                 case ORC_REG_R10:
1298                         cfa->base = CFI_R10;
1299                         break;
1300                 case ORC_REG_R13:
1301                         cfa->base = CFI_R13;
1302                         break;
1303                 case ORC_REG_DI:
1304                         cfa->base = CFI_DI;
1305                         break;
1306                 case ORC_REG_DX:
1307                         cfa->base = CFI_DX;
1308                         break;
1309                 default:
1310                         WARN_FUNC("unsupported unwind_hint sp base reg %d",
1311                                   insn->sec, insn->offset, hint->sp_reg);
1312                         return -1;
1313                 }
1314
1315                 cfa->offset = hint->sp_offset;
1316                 insn->state.type = hint->type;
1317                 insn->state.end = hint->end;
1318         }
1319
1320         return 0;
1321 }
1322
1323 static int read_retpoline_hints(struct objtool_file *file)
1324 {
1325         struct section *sec;
1326         struct instruction *insn;
1327         struct rela *rela;
1328
1329         sec = find_section_by_name(file->elf, ".rela.discard.retpoline_safe");
1330         if (!sec)
1331                 return 0;
1332
1333         list_for_each_entry(rela, &sec->rela_list, list) {
1334                 if (rela->sym->type != STT_SECTION) {
1335                         WARN("unexpected relocation symbol type in %s", sec->name);
1336                         return -1;
1337                 }
1338
1339                 insn = find_insn(file, rela->sym->sec, rela->addend);
1340                 if (!insn) {
1341                         WARN("bad .discard.retpoline_safe entry");
1342                         return -1;
1343                 }
1344
1345                 if (insn->type != INSN_JUMP_DYNAMIC &&
1346                     insn->type != INSN_CALL_DYNAMIC) {
1347                         WARN_FUNC("retpoline_safe hint not an indirect jump/call",
1348                                   insn->sec, insn->offset);
1349                         return -1;
1350                 }
1351
1352                 insn->retpoline_safe = true;
1353         }
1354
1355         return 0;
1356 }
1357
1358 static void mark_rodata(struct objtool_file *file)
1359 {
1360         struct section *sec;
1361         bool found = false;
1362
1363         /*
1364          * Search for the following rodata sections, each of which can
1365          * potentially contain jump tables:
1366          *
1367          * - .rodata: can contain GCC switch tables
1368          * - .rodata.<func>: same, if -fdata-sections is being used
1369          * - .rodata..c_jump_table: contains C annotated jump tables
1370          *
1371          * .rodata.str1.* sections are ignored; they don't contain jump tables.
1372          */
1373         for_each_sec(file, sec) {
1374                 if ((!strncmp(sec->name, ".rodata", 7) && !strstr(sec->name, ".str1.")) ||
1375                     !strcmp(sec->name, C_JUMP_TABLE_SECTION)) {
1376                         sec->rodata = true;
1377                         found = true;
1378                 }
1379         }
1380
1381         file->rodata = found;
1382 }
1383
1384 static int decode_sections(struct objtool_file *file)
1385 {
1386         int ret;
1387
1388         mark_rodata(file);
1389
1390         ret = decode_instructions(file);
1391         if (ret)
1392                 return ret;
1393
1394         ret = add_dead_ends(file);
1395         if (ret)
1396                 return ret;
1397
1398         add_ignores(file);
1399         add_uaccess_safe(file);
1400
1401         ret = add_ignore_alternatives(file);
1402         if (ret)
1403                 return ret;
1404
1405         ret = add_jump_destinations(file);
1406         if (ret)
1407                 return ret;
1408
1409         ret = add_special_section_alts(file);
1410         if (ret)
1411                 return ret;
1412
1413         ret = add_call_destinations(file);
1414         if (ret)
1415                 return ret;
1416
1417         ret = add_jump_table_alts(file);
1418         if (ret)
1419                 return ret;
1420
1421         ret = read_unwind_hints(file);
1422         if (ret)
1423                 return ret;
1424
1425         ret = read_retpoline_hints(file);
1426         if (ret)
1427                 return ret;
1428
1429         return 0;
1430 }
1431
1432 static bool is_fentry_call(struct instruction *insn)
1433 {
1434         if (insn->type == INSN_CALL &&
1435             insn->call_dest->type == STT_NOTYPE &&
1436             !strcmp(insn->call_dest->name, "__fentry__"))
1437                 return true;
1438
1439         return false;
1440 }
1441
1442 static bool has_modified_stack_frame(struct insn_state *state)
1443 {
1444         int i;
1445
1446         if (state->cfa.base != initial_func_cfi.cfa.base ||
1447             state->cfa.offset != initial_func_cfi.cfa.offset ||
1448             state->stack_size != initial_func_cfi.cfa.offset ||
1449             state->drap)
1450                 return true;
1451
1452         for (i = 0; i < CFI_NUM_REGS; i++)
1453                 if (state->regs[i].base != initial_func_cfi.regs[i].base ||
1454                     state->regs[i].offset != initial_func_cfi.regs[i].offset)
1455                         return true;
1456
1457         return false;
1458 }
1459
1460 static bool has_valid_stack_frame(struct insn_state *state)
1461 {
1462         if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
1463             state->regs[CFI_BP].offset == -16)
1464                 return true;
1465
1466         if (state->drap && state->regs[CFI_BP].base == CFI_BP)
1467                 return true;
1468
1469         return false;
1470 }
1471
1472 static int update_insn_state_regs(struct instruction *insn, struct insn_state *state)
1473 {
1474         struct cfi_reg *cfa = &state->cfa;
1475         struct stack_op *op = &insn->stack_op;
1476
1477         if (cfa->base != CFI_SP)
1478                 return 0;
1479
1480         /* push */
1481         if (op->dest.type == OP_DEST_PUSH || op->dest.type == OP_DEST_PUSHF)
1482                 cfa->offset += 8;
1483
1484         /* pop */
1485         if (op->src.type == OP_SRC_POP || op->src.type == OP_SRC_POPF)
1486                 cfa->offset -= 8;
1487
1488         /* add immediate to sp */
1489         if (op->dest.type == OP_DEST_REG && op->src.type == OP_SRC_ADD &&
1490             op->dest.reg == CFI_SP && op->src.reg == CFI_SP)
1491                 cfa->offset -= op->src.offset;
1492
1493         return 0;
1494 }
1495
1496 static void save_reg(struct insn_state *state, unsigned char reg, int base,
1497                      int offset)
1498 {
1499         if (arch_callee_saved_reg(reg) &&
1500             state->regs[reg].base == CFI_UNDEFINED) {
1501                 state->regs[reg].base = base;
1502                 state->regs[reg].offset = offset;
1503         }
1504 }
1505
1506 static void restore_reg(struct insn_state *state, unsigned char reg)
1507 {
1508         state->regs[reg].base = CFI_UNDEFINED;
1509         state->regs[reg].offset = 0;
1510 }
1511
1512 /*
1513  * A note about DRAP stack alignment:
1514  *
1515  * GCC has the concept of a DRAP register, which is used to help keep track of
1516  * the stack pointer when aligning the stack.  r10 or r13 is used as the DRAP
1517  * register.  The typical DRAP pattern is:
1518  *
1519  *   4c 8d 54 24 08             lea    0x8(%rsp),%r10
1520  *   48 83 e4 c0                and    $0xffffffffffffffc0,%rsp
1521  *   41 ff 72 f8                pushq  -0x8(%r10)
1522  *   55                         push   %rbp
1523  *   48 89 e5                   mov    %rsp,%rbp
1524  *                              (more pushes)
1525  *   41 52                      push   %r10
1526  *                              ...
1527  *   41 5a                      pop    %r10
1528  *                              (more pops)
1529  *   5d                         pop    %rbp
1530  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1531  *   c3                         retq
1532  *
1533  * There are some variations in the epilogues, like:
1534  *
1535  *   5b                         pop    %rbx
1536  *   41 5a                      pop    %r10
1537  *   41 5c                      pop    %r12
1538  *   41 5d                      pop    %r13
1539  *   41 5e                      pop    %r14
1540  *   c9                         leaveq
1541  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1542  *   c3                         retq
1543  *
1544  * and:
1545  *
1546  *   4c 8b 55 e8                mov    -0x18(%rbp),%r10
1547  *   48 8b 5d e0                mov    -0x20(%rbp),%rbx
1548  *   4c 8b 65 f0                mov    -0x10(%rbp),%r12
1549  *   4c 8b 6d f8                mov    -0x8(%rbp),%r13
1550  *   c9                         leaveq
1551  *   49 8d 62 f8                lea    -0x8(%r10),%rsp
1552  *   c3                         retq
1553  *
1554  * Sometimes r13 is used as the DRAP register, in which case it's saved and
1555  * restored beforehand:
1556  *
1557  *   41 55                      push   %r13
1558  *   4c 8d 6c 24 10             lea    0x10(%rsp),%r13
1559  *   48 83 e4 f0                and    $0xfffffffffffffff0,%rsp
1560  *                              ...
1561  *   49 8d 65 f0                lea    -0x10(%r13),%rsp
1562  *   41 5d                      pop    %r13
1563  *   c3                         retq
1564  */
1565 static int update_insn_state(struct instruction *insn, struct insn_state *state)
1566 {
1567         struct stack_op *op = &insn->stack_op;
1568         struct cfi_reg *cfa = &state->cfa;
1569         struct cfi_reg *regs = state->regs;
1570
1571         /* stack operations don't make sense with an undefined CFA */
1572         if (cfa->base == CFI_UNDEFINED) {
1573                 if (insn->func) {
1574                         WARN_FUNC("undefined stack state", insn->sec, insn->offset);
1575                         return -1;
1576                 }
1577                 return 0;
1578         }
1579
1580         if (state->type == ORC_TYPE_REGS || state->type == ORC_TYPE_REGS_IRET)
1581                 return update_insn_state_regs(insn, state);
1582
1583         switch (op->dest.type) {
1584
1585         case OP_DEST_REG:
1586                 switch (op->src.type) {
1587
1588                 case OP_SRC_REG:
1589                         if (op->src.reg == CFI_SP && op->dest.reg == CFI_BP &&
1590                             cfa->base == CFI_SP &&
1591                             regs[CFI_BP].base == CFI_CFA &&
1592                             regs[CFI_BP].offset == -cfa->offset) {
1593
1594                                 /* mov %rsp, %rbp */
1595                                 cfa->base = op->dest.reg;
1596                                 state->bp_scratch = false;
1597                         }
1598
1599                         else if (op->src.reg == CFI_SP &&
1600                                  op->dest.reg == CFI_BP && state->drap) {
1601
1602                                 /* drap: mov %rsp, %rbp */
1603                                 regs[CFI_BP].base = CFI_BP;
1604                                 regs[CFI_BP].offset = -state->stack_size;
1605                                 state->bp_scratch = false;
1606                         }
1607
1608                         else if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1609
1610                                 /*
1611                                  * mov %rsp, %reg
1612                                  *
1613                                  * This is needed for the rare case where GCC
1614                                  * does:
1615                                  *
1616                                  *   mov    %rsp, %rax
1617                                  *   ...
1618                                  *   mov    %rax, %rsp
1619                                  */
1620                                 state->vals[op->dest.reg].base = CFI_CFA;
1621                                 state->vals[op->dest.reg].offset = -state->stack_size;
1622                         }
1623
1624                         else if (op->src.reg == CFI_BP && op->dest.reg == CFI_SP &&
1625                                  cfa->base == CFI_BP) {
1626
1627                                 /*
1628                                  * mov %rbp, %rsp
1629                                  *
1630                                  * Restore the original stack pointer (Clang).
1631                                  */
1632                                 state->stack_size = -state->regs[CFI_BP].offset;
1633                         }
1634
1635                         else if (op->dest.reg == cfa->base) {
1636
1637                                 /* mov %reg, %rsp */
1638                                 if (cfa->base == CFI_SP &&
1639                                     state->vals[op->src.reg].base == CFI_CFA) {
1640
1641                                         /*
1642                                          * This is needed for the rare case
1643                                          * where GCC does something dumb like:
1644                                          *
1645                                          *   lea    0x8(%rsp), %rcx
1646                                          *   ...
1647                                          *   mov    %rcx, %rsp
1648                                          */
1649                                         cfa->offset = -state->vals[op->src.reg].offset;
1650                                         state->stack_size = cfa->offset;
1651
1652                                 } else {
1653                                         cfa->base = CFI_UNDEFINED;
1654                                         cfa->offset = 0;
1655                                 }
1656                         }
1657
1658                         break;
1659
1660                 case OP_SRC_ADD:
1661                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
1662
1663                                 /* add imm, %rsp */
1664                                 state->stack_size -= op->src.offset;
1665                                 if (cfa->base == CFI_SP)
1666                                         cfa->offset -= op->src.offset;
1667                                 break;
1668                         }
1669
1670                         if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
1671
1672                                 /* lea disp(%rbp), %rsp */
1673                                 state->stack_size = -(op->src.offset + regs[CFI_BP].offset);
1674                                 break;
1675                         }
1676
1677                         if (op->src.reg == CFI_SP && cfa->base == CFI_SP) {
1678
1679                                 /* drap: lea disp(%rsp), %drap */
1680                                 state->drap_reg = op->dest.reg;
1681
1682                                 /*
1683                                  * lea disp(%rsp), %reg
1684                                  *
1685                                  * This is needed for the rare case where GCC
1686                                  * does something dumb like:
1687                                  *
1688                                  *   lea    0x8(%rsp), %rcx
1689                                  *   ...
1690                                  *   mov    %rcx, %rsp
1691                                  */
1692                                 state->vals[op->dest.reg].base = CFI_CFA;
1693                                 state->vals[op->dest.reg].offset = \
1694                                         -state->stack_size + op->src.offset;
1695
1696                                 break;
1697                         }
1698
1699                         if (state->drap && op->dest.reg == CFI_SP &&
1700                             op->src.reg == state->drap_reg) {
1701
1702                                  /* drap: lea disp(%drap), %rsp */
1703                                 cfa->base = CFI_SP;
1704                                 cfa->offset = state->stack_size = -op->src.offset;
1705                                 state->drap_reg = CFI_UNDEFINED;
1706                                 state->drap = false;
1707                                 break;
1708                         }
1709
1710                         if (op->dest.reg == state->cfa.base) {
1711                                 WARN_FUNC("unsupported stack register modification",
1712                                           insn->sec, insn->offset);
1713                                 return -1;
1714                         }
1715
1716                         break;
1717
1718                 case OP_SRC_AND:
1719                         if (op->dest.reg != CFI_SP ||
1720                             (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
1721                             (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
1722                                 WARN_FUNC("unsupported stack pointer realignment",
1723                                           insn->sec, insn->offset);
1724                                 return -1;
1725                         }
1726
1727                         if (state->drap_reg != CFI_UNDEFINED) {
1728                                 /* drap: and imm, %rsp */
1729                                 cfa->base = state->drap_reg;
1730                                 cfa->offset = state->stack_size = 0;
1731                                 state->drap = true;
1732                         }
1733
1734                         /*
1735                          * Older versions of GCC (4.8ish) realign the stack
1736                          * without DRAP, with a frame pointer.
1737                          */
1738
1739                         break;
1740
1741                 case OP_SRC_POP:
1742                 case OP_SRC_POPF:
1743                         if (!state->drap && op->dest.type == OP_DEST_REG &&
1744                             op->dest.reg == cfa->base) {
1745
1746                                 /* pop %rbp */
1747                                 cfa->base = CFI_SP;
1748                         }
1749
1750                         if (state->drap && cfa->base == CFI_BP_INDIRECT &&
1751                             op->dest.type == OP_DEST_REG &&
1752                             op->dest.reg == state->drap_reg &&
1753                             state->drap_offset == -state->stack_size) {
1754
1755                                 /* drap: pop %drap */
1756                                 cfa->base = state->drap_reg;
1757                                 cfa->offset = 0;
1758                                 state->drap_offset = -1;
1759
1760                         } else if (regs[op->dest.reg].offset == -state->stack_size) {
1761
1762                                 /* pop %reg */
1763                                 restore_reg(state, op->dest.reg);
1764                         }
1765
1766                         state->stack_size -= 8;
1767                         if (cfa->base == CFI_SP)
1768                                 cfa->offset -= 8;
1769
1770                         break;
1771
1772                 case OP_SRC_REG_INDIRECT:
1773                         if (state->drap && op->src.reg == CFI_BP &&
1774                             op->src.offset == state->drap_offset) {
1775
1776                                 /* drap: mov disp(%rbp), %drap */
1777                                 cfa->base = state->drap_reg;
1778                                 cfa->offset = 0;
1779                                 state->drap_offset = -1;
1780                         }
1781
1782                         if (state->drap && op->src.reg == CFI_BP &&
1783                             op->src.offset == regs[op->dest.reg].offset) {
1784
1785                                 /* drap: mov disp(%rbp), %reg */
1786                                 restore_reg(state, op->dest.reg);
1787
1788                         } else if (op->src.reg == cfa->base &&
1789                             op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
1790
1791                                 /* mov disp(%rbp), %reg */
1792                                 /* mov disp(%rsp), %reg */
1793                                 restore_reg(state, op->dest.reg);
1794                         }
1795
1796                         break;
1797
1798                 default:
1799                         WARN_FUNC("unknown stack-related instruction",
1800                                   insn->sec, insn->offset);
1801                         return -1;
1802                 }
1803
1804                 break;
1805
1806         case OP_DEST_PUSH:
1807         case OP_DEST_PUSHF:
1808                 state->stack_size += 8;
1809                 if (cfa->base == CFI_SP)
1810                         cfa->offset += 8;
1811
1812                 if (op->src.type != OP_SRC_REG)
1813                         break;
1814
1815                 if (state->drap) {
1816                         if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1817
1818                                 /* drap: push %drap */
1819                                 cfa->base = CFI_BP_INDIRECT;
1820                                 cfa->offset = -state->stack_size;
1821
1822                                 /* save drap so we know when to restore it */
1823                                 state->drap_offset = -state->stack_size;
1824
1825                         } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
1826
1827                                 /* drap: push %rbp */
1828                                 state->stack_size = 0;
1829
1830                         } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1831
1832                                 /* drap: push %reg */
1833                                 save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
1834                         }
1835
1836                 } else {
1837
1838                         /* push %reg */
1839                         save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
1840                 }
1841
1842                 /* detect when asm code uses rbp as a scratch register */
1843                 if (!no_fp && insn->func && op->src.reg == CFI_BP &&
1844                     cfa->base != CFI_BP)
1845                         state->bp_scratch = true;
1846                 break;
1847
1848         case OP_DEST_REG_INDIRECT:
1849
1850                 if (state->drap) {
1851                         if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
1852
1853                                 /* drap: mov %drap, disp(%rbp) */
1854                                 cfa->base = CFI_BP_INDIRECT;
1855                                 cfa->offset = op->dest.offset;
1856
1857                                 /* save drap offset so we know when to restore it */
1858                                 state->drap_offset = op->dest.offset;
1859                         }
1860
1861                         else if (regs[op->src.reg].base == CFI_UNDEFINED) {
1862
1863                                 /* drap: mov reg, disp(%rbp) */
1864                                 save_reg(state, op->src.reg, CFI_BP, op->dest.offset);
1865                         }
1866
1867                 } else if (op->dest.reg == cfa->base) {
1868
1869                         /* mov reg, disp(%rbp) */
1870                         /* mov reg, disp(%rsp) */
1871                         save_reg(state, op->src.reg, CFI_CFA,
1872                                  op->dest.offset - state->cfa.offset);
1873                 }
1874
1875                 break;
1876
1877         case OP_DEST_LEAVE:
1878                 if ((!state->drap && cfa->base != CFI_BP) ||
1879                     (state->drap && cfa->base != state->drap_reg)) {
1880                         WARN_FUNC("leave instruction with modified stack frame",
1881                                   insn->sec, insn->offset);
1882                         return -1;
1883                 }
1884
1885                 /* leave (mov %rbp, %rsp; pop %rbp) */
1886
1887                 state->stack_size = -state->regs[CFI_BP].offset - 8;
1888                 restore_reg(state, CFI_BP);
1889
1890                 if (!state->drap) {
1891                         cfa->base = CFI_SP;
1892                         cfa->offset -= 8;
1893                 }
1894
1895                 break;
1896
1897         case OP_DEST_MEM:
1898                 if (op->src.type != OP_SRC_POP && op->src.type != OP_SRC_POPF) {
1899                         WARN_FUNC("unknown stack-related memory operation",
1900                                   insn->sec, insn->offset);
1901                         return -1;
1902                 }
1903
1904                 /* pop mem */
1905                 state->stack_size -= 8;
1906                 if (cfa->base == CFI_SP)
1907                         cfa->offset -= 8;
1908
1909                 break;
1910
1911         default:
1912                 WARN_FUNC("unknown stack-related instruction",
1913                           insn->sec, insn->offset);
1914                 return -1;
1915         }
1916
1917         return 0;
1918 }
1919
1920 static bool insn_state_match(struct instruction *insn, struct insn_state *state)
1921 {
1922         struct insn_state *state1 = &insn->state, *state2 = state;
1923         int i;
1924
1925         if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
1926                 WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
1927                           insn->sec, insn->offset,
1928                           state1->cfa.base, state1->cfa.offset,
1929                           state2->cfa.base, state2->cfa.offset);
1930
1931         } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
1932                 for (i = 0; i < CFI_NUM_REGS; i++) {
1933                         if (!memcmp(&state1->regs[i], &state2->regs[i],
1934                                     sizeof(struct cfi_reg)))
1935                                 continue;
1936
1937                         WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
1938                                   insn->sec, insn->offset,
1939                                   i, state1->regs[i].base, state1->regs[i].offset,
1940                                   i, state2->regs[i].base, state2->regs[i].offset);
1941                         break;
1942                 }
1943
1944         } else if (state1->type != state2->type) {
1945                 WARN_FUNC("stack state mismatch: type1=%d type2=%d",
1946                           insn->sec, insn->offset, state1->type, state2->type);
1947
1948         } else if (state1->drap != state2->drap ||
1949                  (state1->drap && state1->drap_reg != state2->drap_reg) ||
1950                  (state1->drap && state1->drap_offset != state2->drap_offset)) {
1951                 WARN_FUNC("stack state mismatch: drap1=%d(%d,%d) drap2=%d(%d,%d)",
1952                           insn->sec, insn->offset,
1953                           state1->drap, state1->drap_reg, state1->drap_offset,
1954                           state2->drap, state2->drap_reg, state2->drap_offset);
1955
1956         } else
1957                 return true;
1958
1959         return false;
1960 }
1961
1962 static inline bool func_uaccess_safe(struct symbol *func)
1963 {
1964         if (func)
1965                 return func->uaccess_safe;
1966
1967         return false;
1968 }
1969
1970 static inline const char *call_dest_name(struct instruction *insn)
1971 {
1972         if (insn->call_dest)
1973                 return insn->call_dest->name;
1974
1975         return "{dynamic}";
1976 }
1977
1978 static int validate_call(struct instruction *insn, struct insn_state *state)
1979 {
1980         if (state->uaccess && !func_uaccess_safe(insn->call_dest)) {
1981                 WARN_FUNC("call to %s() with UACCESS enabled",
1982                                 insn->sec, insn->offset, call_dest_name(insn));
1983                 return 1;
1984         }
1985
1986         if (state->df) {
1987                 WARN_FUNC("call to %s() with DF set",
1988                                 insn->sec, insn->offset, call_dest_name(insn));
1989                 return 1;
1990         }
1991
1992         return 0;
1993 }
1994
1995 static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
1996 {
1997         if (has_modified_stack_frame(state)) {
1998                 WARN_FUNC("sibling call from callable instruction with modified stack frame",
1999                                 insn->sec, insn->offset);
2000                 return 1;
2001         }
2002
2003         return validate_call(insn, state);
2004 }
2005
2006 static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state)
2007 {
2008         if (state->uaccess && !func_uaccess_safe(func)) {
2009                 WARN_FUNC("return with UACCESS enabled",
2010                           insn->sec, insn->offset);
2011                 return 1;
2012         }
2013
2014         if (!state->uaccess && func_uaccess_safe(func)) {
2015                 WARN_FUNC("return with UACCESS disabled from a UACCESS-safe function",
2016                           insn->sec, insn->offset);
2017                 return 1;
2018         }
2019
2020         if (state->df) {
2021                 WARN_FUNC("return with DF set",
2022                           insn->sec, insn->offset);
2023                 return 1;
2024         }
2025
2026         if (func && has_modified_stack_frame(state)) {
2027                 WARN_FUNC("return with modified stack frame",
2028                           insn->sec, insn->offset);
2029                 return 1;
2030         }
2031
2032         if (state->bp_scratch) {
2033                 WARN("%s uses BP as a scratch register",
2034                      func->name);
2035                 return 1;
2036         }
2037
2038         return 0;
2039 }
2040
2041 /*
2042  * Follow the branch starting at the given instruction, and recursively follow
2043  * any other branches (jumps).  Meanwhile, track the frame pointer state at
2044  * each instruction and validate all the rules described in
2045  * tools/objtool/Documentation/stack-validation.txt.
2046  */
2047 static int validate_branch(struct objtool_file *file, struct symbol *func,
2048                            struct instruction *first, struct insn_state state)
2049 {
2050         struct alternative *alt;
2051         struct instruction *insn, *next_insn;
2052         struct section *sec;
2053         u8 visited;
2054         int ret;
2055
2056         insn = first;
2057         sec = insn->sec;
2058
2059         if (insn->alt_group && list_empty(&insn->alts)) {
2060                 WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
2061                           sec, insn->offset);
2062                 return 1;
2063         }
2064
2065         while (1) {
2066                 next_insn = next_insn_same_sec(file, insn);
2067
2068                 if (file->c_file && func && insn->func && func != insn->func->pfunc) {
2069                         WARN("%s() falls through to next function %s()",
2070                              func->name, insn->func->name);
2071                         return 1;
2072                 }
2073
2074                 if (func && insn->ignore) {
2075                         WARN_FUNC("BUG: why am I validating an ignored function?",
2076                                   sec, insn->offset);
2077                         return 1;
2078                 }
2079
2080                 visited = 1 << state.uaccess;
2081                 if (insn->visited) {
2082                         if (!insn->hint && !insn_state_match(insn, &state))
2083                                 return 1;
2084
2085                         if (insn->visited & visited)
2086                                 return 0;
2087                 }
2088
2089                 if (insn->hint) {
2090                         if (insn->restore) {
2091                                 struct instruction *save_insn, *i;
2092
2093                                 i = insn;
2094                                 save_insn = NULL;
2095                                 sym_for_each_insn_continue_reverse(file, func, i) {
2096                                         if (i->save) {
2097                                                 save_insn = i;
2098                                                 break;
2099                                         }
2100                                 }
2101
2102                                 if (!save_insn) {
2103                                         WARN_FUNC("no corresponding CFI save for CFI restore",
2104                                                   sec, insn->offset);
2105                                         return 1;
2106                                 }
2107
2108                                 if (!save_insn->visited) {
2109                                         /*
2110                                          * Oops, no state to copy yet.
2111                                          * Hopefully we can reach this
2112                                          * instruction from another branch
2113                                          * after the save insn has been
2114                                          * visited.
2115                                          */
2116                                         if (insn == first)
2117                                                 return 0;
2118
2119                                         WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo",
2120                                                   sec, insn->offset);
2121                                         return 1;
2122                                 }
2123
2124                                 insn->state = save_insn->state;
2125                         }
2126
2127                         state = insn->state;
2128
2129                 } else
2130                         insn->state = state;
2131
2132                 insn->visited |= visited;
2133
2134                 if (!insn->ignore_alts) {
2135                         bool skip_orig = false;
2136
2137                         list_for_each_entry(alt, &insn->alts, list) {
2138                                 if (alt->skip_orig)
2139                                         skip_orig = true;
2140
2141                                 ret = validate_branch(file, func, alt->insn, state);
2142                                 if (ret) {
2143                                         if (backtrace)
2144                                                 BT_FUNC("(alt)", insn);
2145                                         return ret;
2146                                 }
2147                         }
2148
2149                         if (skip_orig)
2150                                 return 0;
2151                 }
2152
2153                 switch (insn->type) {
2154
2155                 case INSN_RETURN:
2156                         return validate_return(func, insn, &state);
2157
2158                 case INSN_CALL:
2159                 case INSN_CALL_DYNAMIC:
2160                         ret = validate_call(insn, &state);
2161                         if (ret)
2162                                 return ret;
2163
2164                         if (!no_fp && func && !is_fentry_call(insn) &&
2165                             !has_valid_stack_frame(&state)) {
2166                                 WARN_FUNC("call without frame pointer save/setup",
2167                                           sec, insn->offset);
2168                                 return 1;
2169                         }
2170
2171                         if (dead_end_function(file, insn->call_dest))
2172                                 return 0;
2173
2174                         break;
2175
2176                 case INSN_JUMP_CONDITIONAL:
2177                 case INSN_JUMP_UNCONDITIONAL:
2178                         if (func && is_sibling_call(insn)) {
2179                                 ret = validate_sibling_call(insn, &state);
2180                                 if (ret)
2181                                         return ret;
2182
2183                         } else if (insn->jump_dest) {
2184                                 ret = validate_branch(file, func,
2185                                                       insn->jump_dest, state);
2186                                 if (ret) {
2187                                         if (backtrace)
2188                                                 BT_FUNC("(branch)", insn);
2189                                         return ret;
2190                                 }
2191                         }
2192
2193                         if (insn->type == INSN_JUMP_UNCONDITIONAL)
2194                                 return 0;
2195
2196                         break;
2197
2198                 case INSN_JUMP_DYNAMIC:
2199                 case INSN_JUMP_DYNAMIC_CONDITIONAL:
2200                         if (func && is_sibling_call(insn)) {
2201                                 ret = validate_sibling_call(insn, &state);
2202                                 if (ret)
2203                                         return ret;
2204                         }
2205
2206                         if (insn->type == INSN_JUMP_DYNAMIC)
2207                                 return 0;
2208
2209                         break;
2210
2211                 case INSN_CONTEXT_SWITCH:
2212                         if (func && (!next_insn || !next_insn->hint)) {
2213                                 WARN_FUNC("unsupported instruction in callable function",
2214                                           sec, insn->offset);
2215                                 return 1;
2216                         }
2217                         return 0;
2218
2219                 case INSN_STACK:
2220                         if (update_insn_state(insn, &state))
2221                                 return 1;
2222
2223                         if (insn->stack_op.dest.type == OP_DEST_PUSHF) {
2224                                 if (!state.uaccess_stack) {
2225                                         state.uaccess_stack = 1;
2226                                 } else if (state.uaccess_stack >> 31) {
2227                                         WARN_FUNC("PUSHF stack exhausted", sec, insn->offset);
2228                                         return 1;
2229                                 }
2230                                 state.uaccess_stack <<= 1;
2231                                 state.uaccess_stack  |= state.uaccess;
2232                         }
2233
2234                         if (insn->stack_op.src.type == OP_SRC_POPF) {
2235                                 if (state.uaccess_stack) {
2236                                         state.uaccess = state.uaccess_stack & 1;
2237                                         state.uaccess_stack >>= 1;
2238                                         if (state.uaccess_stack == 1)
2239                                                 state.uaccess_stack = 0;
2240                                 }
2241                         }
2242
2243                         break;
2244
2245                 case INSN_STAC:
2246                         if (state.uaccess) {
2247                                 WARN_FUNC("recursive UACCESS enable", sec, insn->offset);
2248                                 return 1;
2249                         }
2250
2251                         state.uaccess = true;
2252                         break;
2253
2254                 case INSN_CLAC:
2255                         if (!state.uaccess && func) {
2256                                 WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
2257                                 return 1;
2258                         }
2259
2260                         if (func_uaccess_safe(func) && !state.uaccess_stack) {
2261                                 WARN_FUNC("UACCESS-safe disables UACCESS", sec, insn->offset);
2262                                 return 1;
2263                         }
2264
2265                         state.uaccess = false;
2266                         break;
2267
2268                 case INSN_STD:
2269                         if (state.df)
2270                                 WARN_FUNC("recursive STD", sec, insn->offset);
2271
2272                         state.df = true;
2273                         break;
2274
2275                 case INSN_CLD:
2276                         if (!state.df && func)
2277                                 WARN_FUNC("redundant CLD", sec, insn->offset);
2278
2279                         state.df = false;
2280                         break;
2281
2282                 default:
2283                         break;
2284                 }
2285
2286                 if (insn->dead_end)
2287                         return 0;
2288
2289                 if (!next_insn) {
2290                         if (state.cfa.base == CFI_UNDEFINED)
2291                                 return 0;
2292                         WARN("%s: unexpected end of section", sec->name);
2293                         return 1;
2294                 }
2295
2296                 insn = next_insn;
2297         }
2298
2299         return 0;
2300 }
2301
2302 static int validate_unwind_hints(struct objtool_file *file)
2303 {
2304         struct instruction *insn;
2305         int ret, warnings = 0;
2306         struct insn_state state;
2307
2308         if (!file->hints)
2309                 return 0;
2310
2311         clear_insn_state(&state);
2312
2313         for_each_insn(file, insn) {
2314                 if (insn->hint && !insn->visited) {
2315                         ret = validate_branch(file, insn->func, insn, state);
2316                         if (ret && backtrace)
2317                                 BT_FUNC("<=== (hint)", insn);
2318                         warnings += ret;
2319                 }
2320         }
2321
2322         return warnings;
2323 }
2324
2325 static int validate_retpoline(struct objtool_file *file)
2326 {
2327         struct instruction *insn;
2328         int warnings = 0;
2329
2330         for_each_insn(file, insn) {
2331                 if (insn->type != INSN_JUMP_DYNAMIC &&
2332                     insn->type != INSN_CALL_DYNAMIC)
2333                         continue;
2334
2335                 if (insn->retpoline_safe)
2336                         continue;
2337
2338                 /*
2339                  * .init.text code is ran before userspace and thus doesn't
2340                  * strictly need retpolines, except for modules which are
2341                  * loaded late, they very much do need retpoline in their
2342                  * .init.text
2343                  */
2344                 if (!strcmp(insn->sec->name, ".init.text") && !module)
2345                         continue;
2346
2347                 WARN_FUNC("indirect %s found in RETPOLINE build",
2348                           insn->sec, insn->offset,
2349                           insn->type == INSN_JUMP_DYNAMIC ? "jump" : "call");
2350
2351                 warnings++;
2352         }
2353
2354         return warnings;
2355 }
2356
2357 static bool is_kasan_insn(struct instruction *insn)
2358 {
2359         return (insn->type == INSN_CALL &&
2360                 !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
2361 }
2362
2363 static bool is_ubsan_insn(struct instruction *insn)
2364 {
2365         return (insn->type == INSN_CALL &&
2366                 !strcmp(insn->call_dest->name,
2367                         "__ubsan_handle_builtin_unreachable"));
2368 }
2369
2370 static bool ignore_unreachable_insn(struct instruction *insn)
2371 {
2372         int i;
2373
2374         if (insn->ignore || insn->type == INSN_NOP)
2375                 return true;
2376
2377         /*
2378          * Ignore any unused exceptions.  This can happen when a whitelisted
2379          * function has an exception table entry.
2380          *
2381          * Also ignore alternative replacement instructions.  This can happen
2382          * when a whitelisted function uses one of the ALTERNATIVE macros.
2383          */
2384         if (!strcmp(insn->sec->name, ".fixup") ||
2385             !strcmp(insn->sec->name, ".altinstr_replacement") ||
2386             !strcmp(insn->sec->name, ".altinstr_aux"))
2387                 return true;
2388
2389         /*
2390          * Check if this (or a subsequent) instruction is related to
2391          * CONFIG_UBSAN or CONFIG_KASAN.
2392          *
2393          * End the search at 5 instructions to avoid going into the weeds.
2394          */
2395         if (!insn->func)
2396                 return false;
2397         for (i = 0; i < 5; i++) {
2398
2399                 if (is_kasan_insn(insn) || is_ubsan_insn(insn))
2400                         return true;
2401
2402                 if (insn->type == INSN_JUMP_UNCONDITIONAL) {
2403                         if (insn->jump_dest &&
2404                             insn->jump_dest->func == insn->func) {
2405                                 insn = insn->jump_dest;
2406                                 continue;
2407                         }
2408
2409                         break;
2410                 }
2411
2412                 if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
2413                         break;
2414
2415                 insn = list_next_entry(insn, list);
2416         }
2417
2418         return false;
2419 }
2420
2421 static int validate_section(struct objtool_file *file, struct section *sec)
2422 {
2423         struct symbol *func;
2424         struct instruction *insn;
2425         struct insn_state state;
2426         int ret, warnings = 0;
2427
2428         clear_insn_state(&state);
2429
2430         state.cfa = initial_func_cfi.cfa;
2431         memcpy(&state.regs, &initial_func_cfi.regs,
2432                CFI_NUM_REGS * sizeof(struct cfi_reg));
2433         state.stack_size = initial_func_cfi.cfa.offset;
2434
2435         list_for_each_entry(func, &sec->symbol_list, list) {
2436                 if (func->type != STT_FUNC)
2437                         continue;
2438
2439                 if (!func->len) {
2440                         WARN("%s() is missing an ELF size annotation",
2441                              func->name);
2442                         warnings++;
2443                 }
2444
2445                 if (func->pfunc != func || func->alias != func)
2446                         continue;
2447
2448                 insn = find_insn(file, sec, func->offset);
2449                 if (!insn || insn->ignore || insn->visited)
2450                         continue;
2451
2452                 state.uaccess = func->uaccess_safe;
2453
2454                 ret = validate_branch(file, func, insn, state);
2455                 if (ret && backtrace)
2456                         BT_FUNC("<=== (func)", insn);
2457                 warnings += ret;
2458         }
2459
2460         return warnings;
2461 }
2462
2463 static int validate_functions(struct objtool_file *file)
2464 {
2465         struct section *sec;
2466         int warnings = 0;
2467
2468         for_each_sec(file, sec)
2469                 warnings += validate_section(file, sec);
2470
2471         return warnings;
2472 }
2473
2474 static int validate_reachable_instructions(struct objtool_file *file)
2475 {
2476         struct instruction *insn;
2477
2478         if (file->ignore_unreachables)
2479                 return 0;
2480
2481         for_each_insn(file, insn) {
2482                 if (insn->visited || ignore_unreachable_insn(insn))
2483                         continue;
2484
2485                 WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
2486                 return 1;
2487         }
2488
2489         return 0;
2490 }
2491
2492 static struct objtool_file file;
2493
2494 int check(const char *_objname, bool orc)
2495 {
2496         int ret, warnings = 0;
2497
2498         objname = _objname;
2499
2500         file.elf = elf_read(objname, orc ? O_RDWR : O_RDONLY);
2501         if (!file.elf)
2502                 return 1;
2503
2504         INIT_LIST_HEAD(&file.insn_list);
2505         hash_init(file.insn_hash);
2506         file.c_file = find_section_by_name(file.elf, ".comment");
2507         file.ignore_unreachables = no_unreachable;
2508         file.hints = false;
2509
2510         arch_initial_func_cfi_state(&initial_func_cfi);
2511
2512         ret = decode_sections(&file);
2513         if (ret < 0)
2514                 goto out;
2515         warnings += ret;
2516
2517         if (list_empty(&file.insn_list))
2518                 goto out;
2519
2520         if (retpoline) {
2521                 ret = validate_retpoline(&file);
2522                 if (ret < 0)
2523                         return ret;
2524                 warnings += ret;
2525         }
2526
2527         ret = validate_functions(&file);
2528         if (ret < 0)
2529                 goto out;
2530         warnings += ret;
2531
2532         ret = validate_unwind_hints(&file);
2533         if (ret < 0)
2534                 goto out;
2535         warnings += ret;
2536
2537         if (!warnings) {
2538                 ret = validate_reachable_instructions(&file);
2539                 if (ret < 0)
2540                         goto out;
2541                 warnings += ret;
2542         }
2543
2544         if (orc) {
2545                 ret = create_orc(&file);
2546                 if (ret < 0)
2547                         goto out;
2548
2549                 ret = create_orc_sections(&file);
2550                 if (ret < 0)
2551                         goto out;
2552
2553                 ret = elf_write(file.elf);
2554                 if (ret < 0)
2555                         goto out;
2556         }
2557
2558 out:
2559         if (ret < 0) {
2560                 /*
2561                  *  Fatal error.  The binary is corrupt or otherwise broken in
2562                  *  some way, or objtool itself is broken.  Fail the kernel
2563                  *  build.
2564                  */
2565                 return ret;
2566         }
2567
2568         return 0;
2569 }