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