1 /* 2 * Copyright 2014-2016 by Open Source Security, Inc., Brad Spengler <[email protected]> 3 * and PaX Team <[email protected]> 4 * Licensed under the GPL v2 5 * 6 * Note: the choice of the license means that the compilation process is 7 * NOT 'eligible' as defined by gcc's library exception to the GPL v3, 8 * but for the kernel it doesn't matter since it doesn't link against 9 * any of the gcc libraries 10 * 11 * Usage: 12 * $ # for 4.5/4.6/C based 4.7 13 * $ gcc -I`gcc -print-file-name=plugin`/include -I`gcc -print-file-name=plugin`/include/c-family -fPIC -shared -O2 -o randomize_layout_plugin.so randomize_layout_plugin.c 14 * $ # for C++ based 4.7/4.8+ 15 * $ g++ -I`g++ -print-file-name=plugin`/include -I`g++ -print-file-name=plugin`/include/c-family -fPIC -shared -O2 -o randomize_layout_plugin.so randomize_layout_plugin.c 16 * $ gcc -fplugin=./randomize_layout_plugin.so test.c -O2 17 */ 18 19 #include "gcc-common.h" 20 #include "randomize_layout_seed.h" 21 22 #if BUILDING_GCC_MAJOR < 4 || (BUILDING_GCC_MAJOR == 4 && BUILDING_GCC_MINOR < 7) 23 #error "The RANDSTRUCT plugin requires GCC 4.7 or newer." 24 #endif 25 26 #define ORIG_TYPE_NAME(node) \ 27 (TYPE_NAME(TYPE_MAIN_VARIANT(node)) != NULL_TREE ? ((const unsigned char *)IDENTIFIER_POINTER(TYPE_NAME(TYPE_MAIN_VARIANT(node)))) : (const unsigned char *)"anonymous") 28 29 #define INFORM(loc, msg, ...) inform(loc, "randstruct: " msg, ##__VA_ARGS__) 30 #define MISMATCH(loc, how, ...) INFORM(loc, "casting between randomized structure pointer types (" how "): %qT and %qT\n", __VA_ARGS__) 31 32 __visible int plugin_is_GPL_compatible; 33 34 static int performance_mode; 35 36 static struct plugin_info randomize_layout_plugin_info = { 37 .version = "201402201816vanilla", 38 .help = "disable\t\t\tdo not activate plugin\n" 39 "performance-mode\tenable cacheline-aware layout randomization\n" 40 }; 41 42 struct whitelist_entry { 43 const char *pathname; 44 const char *lhs; 45 const char *rhs; 46 }; 47 48 static const struct whitelist_entry whitelist[] = { 49 /* walk struct security_hook_heads as an array of struct list_head */ 50 { "security/security.c", "list_head", "security_hook_heads" }, 51 { } 52 }; 53 54 /* from old Linux dcache.h */ 55 static inline unsigned long 56 partial_name_hash(unsigned long c, unsigned long prevhash) 57 { 58 return (prevhash + (c << 4) + (c >> 4)) * 11; 59 } 60 static inline unsigned int 61 name_hash(const unsigned char *name) 62 { 63 unsigned long hash = 0; 64 unsigned int len = strlen((const char *)name); 65 while (len--) 66 hash = partial_name_hash(*name++, hash); 67 return (unsigned int)hash; 68 } 69 70 static tree handle_randomize_layout_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs) 71 { 72 tree type; 73 74 *no_add_attrs = true; 75 if (TREE_CODE(*node) == FUNCTION_DECL) { 76 error("%qE attribute does not apply to functions (%qF)", name, *node); 77 return NULL_TREE; 78 } 79 80 if (TREE_CODE(*node) == PARM_DECL) { 81 error("%qE attribute does not apply to function parameters (%qD)", name, *node); 82 return NULL_TREE; 83 } 84 85 if (TREE_CODE(*node) == VAR_DECL) { 86 error("%qE attribute does not apply to variables (%qD)", name, *node); 87 return NULL_TREE; 88 } 89 90 if (TYPE_P(*node)) { 91 type = *node; 92 } else { 93 gcc_assert(TREE_CODE(*node) == TYPE_DECL); 94 type = TREE_TYPE(*node); 95 } 96 97 if (TREE_CODE(type) != RECORD_TYPE) { 98 error("%qE attribute used on %qT applies to struct types only", name, type); 99 return NULL_TREE; 100 } 101 102 if (lookup_attribute(IDENTIFIER_POINTER(name), TYPE_ATTRIBUTES(type))) { 103 error("%qE attribute is already applied to the type %qT", name, type); 104 return NULL_TREE; 105 } 106 107 *no_add_attrs = false; 108 109 return NULL_TREE; 110 } 111 112 /* set on complete types that we don't need to inspect further at all */ 113 static tree handle_randomize_considered_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs) 114 { 115 *no_add_attrs = false; 116 return NULL_TREE; 117 } 118 119 /* 120 * set on types that we've performed a shuffle on, to prevent re-shuffling 121 * this does not preclude us from inspecting its fields for potential shuffles 122 */ 123 static tree handle_randomize_performed_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs) 124 { 125 *no_add_attrs = false; 126 return NULL_TREE; 127 } 128 129 /* 130 * 64bit variant of Bob Jenkins' public domain PRNG 131 * 256 bits of internal state 132 */ 133 134 typedef unsigned long long u64; 135 136 typedef struct ranctx { u64 a; u64 b; u64 c; u64 d; } ranctx; 137 138 #define rot(x,k) (((x)<<(k))|((x)>>(64-(k)))) 139 static u64 ranval(ranctx *x) { 140 u64 e = x->a - rot(x->b, 7); 141 x->a = x->b ^ rot(x->c, 13); 142 x->b = x->c + rot(x->d, 37); 143 x->c = x->d + e; 144 x->d = e + x->a; 145 return x->d; 146 } 147 148 static void raninit(ranctx *x, u64 *seed) { 149 int i; 150 151 x->a = seed[0]; 152 x->b = seed[1]; 153 x->c = seed[2]; 154 x->d = seed[3]; 155 156 for (i=0; i < 30; ++i) 157 (void)ranval(x); 158 } 159 160 static u64 shuffle_seed[4]; 161 162 struct partition_group { 163 tree tree_start; 164 unsigned long start; 165 unsigned long length; 166 }; 167 168 static void partition_struct(tree *fields, unsigned long length, struct partition_group *size_groups, unsigned long *num_groups) 169 { 170 unsigned long i; 171 unsigned long accum_size = 0; 172 unsigned long accum_length = 0; 173 unsigned long group_idx = 0; 174 175 gcc_assert(length < INT_MAX); 176 177 memset(size_groups, 0, sizeof(struct partition_group) * length); 178 179 for (i = 0; i < length; i++) { 180 if (size_groups[group_idx].tree_start == NULL_TREE) { 181 size_groups[group_idx].tree_start = fields[i]; 182 size_groups[group_idx].start = i; 183 accum_length = 0; 184 accum_size = 0; 185 } 186 accum_size += (unsigned long)int_size_in_bytes(TREE_TYPE(fields[i])); 187 accum_length++; 188 if (accum_size >= 64) { 189 size_groups[group_idx].length = accum_length; 190 accum_length = 0; 191 group_idx++; 192 } 193 } 194 195 if (size_groups[group_idx].tree_start != NULL_TREE && 196 !size_groups[group_idx].length) { 197 size_groups[group_idx].length = accum_length; 198 group_idx++; 199 } 200 201 *num_groups = group_idx; 202 } 203 204 static void performance_shuffle(tree *newtree, unsigned long length, ranctx *prng_state) 205 { 206 unsigned long i, x; 207 struct partition_group size_group[length]; 208 unsigned long num_groups = 0; 209 unsigned long randnum; 210 211 partition_struct(newtree, length, (struct partition_group *)&size_group, &num_groups); 212 for (i = num_groups - 1; i > 0; i--) { 213 struct partition_group tmp; 214 randnum = ranval(prng_state) % (i + 1); 215 tmp = size_group[i]; 216 size_group[i] = size_group[randnum]; 217 size_group[randnum] = tmp; 218 } 219 220 for (x = 0; x < num_groups; x++) { 221 for (i = size_group[x].start + size_group[x].length - 1; i > size_group[x].start; i--) { 222 tree tmp; 223 if (DECL_BIT_FIELD_TYPE(newtree[i])) 224 continue; 225 randnum = ranval(prng_state) % (i + 1); 226 // we could handle this case differently if desired 227 if (DECL_BIT_FIELD_TYPE(newtree[randnum])) 228 continue; 229 tmp = newtree[i]; 230 newtree[i] = newtree[randnum]; 231 newtree[randnum] = tmp; 232 } 233 } 234 } 235 236 static void full_shuffle(tree *newtree, unsigned long length, ranctx *prng_state) 237 { 238 unsigned long i, randnum; 239 240 for (i = length - 1; i > 0; i--) { 241 tree tmp; 242 randnum = ranval(prng_state) % (i + 1); 243 tmp = newtree[i]; 244 newtree[i] = newtree[randnum]; 245 newtree[randnum] = tmp; 246 } 247 } 248 249 /* modern in-place Fisher-Yates shuffle */ 250 static void shuffle(const_tree type, tree *newtree, unsigned long length) 251 { 252 unsigned long i; 253 u64 seed[4]; 254 ranctx prng_state; 255 const unsigned char *structname; 256 257 if (length == 0) 258 return; 259 260 gcc_assert(TREE_CODE(type) == RECORD_TYPE); 261 262 structname = ORIG_TYPE_NAME(type); 263 264 #ifdef __DEBUG_PLUGIN 265 fprintf(stderr, "Shuffling struct %s %p\n", (const char *)structname, type); 266 #ifdef __DEBUG_VERBOSE 267 debug_tree((tree)type); 268 #endif 269 #endif 270 271 for (i = 0; i < 4; i++) { 272 seed[i] = shuffle_seed[i]; 273 seed[i] ^= name_hash(structname); 274 } 275 276 raninit(&prng_state, (u64 *)&seed); 277 278 if (performance_mode) 279 performance_shuffle(newtree, length, &prng_state); 280 else 281 full_shuffle(newtree, length, &prng_state); 282 } 283 284 static bool is_flexible_array(const_tree field) 285 { 286 const_tree fieldtype; 287 const_tree typesize; 288 const_tree elemtype; 289 const_tree elemsize; 290 291 fieldtype = TREE_TYPE(field); 292 typesize = TYPE_SIZE(fieldtype); 293 294 if (TREE_CODE(fieldtype) != ARRAY_TYPE) 295 return false; 296 297 elemtype = TREE_TYPE(fieldtype); 298 elemsize = TYPE_SIZE(elemtype); 299 300 /* size of type is represented in bits */ 301 302 if (typesize == NULL_TREE && TYPE_DOMAIN(fieldtype) != NULL_TREE && 303 TYPE_MAX_VALUE(TYPE_DOMAIN(fieldtype)) == NULL_TREE) 304 return true; 305 306 if (typesize != NULL_TREE && 307 (TREE_CONSTANT(typesize) && (!tree_to_uhwi(typesize) || 308 tree_to_uhwi(typesize) == tree_to_uhwi(elemsize)))) 309 return true; 310 311 return false; 312 } 313 314 static int relayout_struct(tree type) 315 { 316 unsigned long num_fields = (unsigned long)list_length(TYPE_FIELDS(type)); 317 unsigned long shuffle_length = num_fields; 318 tree field; 319 tree newtree[num_fields]; 320 unsigned long i; 321 tree list; 322 tree variant; 323 tree main_variant; 324 expanded_location xloc; 325 bool has_flexarray = false; 326 327 if (TYPE_FIELDS(type) == NULL_TREE) 328 return 0; 329 330 if (num_fields < 2) 331 return 0; 332 333 gcc_assert(TREE_CODE(type) == RECORD_TYPE); 334 335 gcc_assert(num_fields < INT_MAX); 336 337 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)) || 338 lookup_attribute("no_randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type)))) 339 return 0; 340 341 /* Workaround for 3rd-party VirtualBox source that we can't modify ourselves */ 342 if (!strcmp((const char *)ORIG_TYPE_NAME(type), "INTNETTRUNKFACTORY") || 343 !strcmp((const char *)ORIG_TYPE_NAME(type), "RAWPCIFACTORY")) 344 return 0; 345 346 /* throw out any structs in uapi */ 347 xloc = expand_location(DECL_SOURCE_LOCATION(TYPE_FIELDS(type))); 348 349 if (strstr(xloc.file, "/uapi/")) 350 error(G_("attempted to randomize userland API struct %s"), ORIG_TYPE_NAME(type)); 351 352 for (field = TYPE_FIELDS(type), i = 0; field; field = TREE_CHAIN(field), i++) { 353 gcc_assert(TREE_CODE(field) == FIELD_DECL); 354 newtree[i] = field; 355 } 356 357 /* 358 * enforce that we don't randomize the layout of the last 359 * element of a struct if it's a 0 or 1-length array 360 * or a proper flexible array 361 */ 362 if (is_flexible_array(newtree[num_fields - 1])) { 363 has_flexarray = true; 364 shuffle_length--; 365 } 366 367 shuffle(type, (tree *)newtree, shuffle_length); 368 369 /* 370 * set up a bogus anonymous struct field designed to error out on unnamed struct initializers 371 * as gcc provides no other way to detect such code 372 */ 373 list = make_node(FIELD_DECL); 374 TREE_CHAIN(list) = newtree[0]; 375 TREE_TYPE(list) = void_type_node; 376 DECL_SIZE(list) = bitsize_zero_node; 377 DECL_NONADDRESSABLE_P(list) = 1; 378 DECL_FIELD_BIT_OFFSET(list) = bitsize_zero_node; 379 DECL_SIZE_UNIT(list) = size_zero_node; 380 DECL_FIELD_OFFSET(list) = size_zero_node; 381 DECL_CONTEXT(list) = type; 382 // to satisfy the constify plugin 383 TREE_READONLY(list) = 1; 384 385 for (i = 0; i < num_fields - 1; i++) 386 TREE_CHAIN(newtree[i]) = newtree[i+1]; 387 TREE_CHAIN(newtree[num_fields - 1]) = NULL_TREE; 388 389 main_variant = TYPE_MAIN_VARIANT(type); 390 for (variant = main_variant; variant; variant = TYPE_NEXT_VARIANT(variant)) { 391 TYPE_FIELDS(variant) = list; 392 TYPE_ATTRIBUTES(variant) = copy_list(TYPE_ATTRIBUTES(variant)); 393 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("randomize_performed"), NULL_TREE, TYPE_ATTRIBUTES(variant)); 394 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("designated_init"), NULL_TREE, TYPE_ATTRIBUTES(variant)); 395 if (has_flexarray) 396 TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("has_flexarray"), NULL_TREE, TYPE_ATTRIBUTES(type)); 397 } 398 399 /* 400 * force a re-layout of the main variant 401 * the TYPE_SIZE for all variants will be recomputed 402 * by finalize_type_size() 403 */ 404 TYPE_SIZE(main_variant) = NULL_TREE; 405 layout_type(main_variant); 406 gcc_assert(TYPE_SIZE(main_variant) != NULL_TREE); 407 408 return 1; 409 } 410 411 /* from constify plugin */ 412 static const_tree get_field_type(const_tree field) 413 { 414 return strip_array_types(TREE_TYPE(field)); 415 } 416 417 /* from constify plugin */ 418 static bool is_fptr(const_tree fieldtype) 419 { 420 if (TREE_CODE(fieldtype) != POINTER_TYPE) 421 return false; 422 423 return TREE_CODE(TREE_TYPE(fieldtype)) == FUNCTION_TYPE; 424 } 425 426 /* derived from constify plugin */ 427 static int is_pure_ops_struct(const_tree node) 428 { 429 const_tree field; 430 431 gcc_assert(TREE_CODE(node) == RECORD_TYPE || TREE_CODE(node) == UNION_TYPE); 432 433 /* XXX: Do not apply randomization to all-ftpr structs yet. */ 434 return 0; 435 436 for (field = TYPE_FIELDS(node); field; field = TREE_CHAIN(field)) { 437 const_tree fieldtype = get_field_type(field); 438 enum tree_code code = TREE_CODE(fieldtype); 439 440 if (node == fieldtype) 441 continue; 442 443 if (!is_fptr(fieldtype)) 444 return 0; 445 446 if (code != RECORD_TYPE && code != UNION_TYPE) 447 continue; 448 449 if (!is_pure_ops_struct(fieldtype)) 450 return 0; 451 } 452 453 return 1; 454 } 455 456 static void randomize_type(tree type) 457 { 458 tree variant; 459 460 gcc_assert(TREE_CODE(type) == RECORD_TYPE); 461 462 if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type))) 463 return; 464 465 if (lookup_attribute("randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))) || is_pure_ops_struct(type)) 466 relayout_struct(type); 467 468 for (variant = TYPE_MAIN_VARIANT(type); variant; variant = TYPE_NEXT_VARIANT(variant)) { 469 TYPE_ATTRIBUTES(type) = copy_list(TYPE_ATTRIBUTES(type)); 470 TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("randomize_considered"), NULL_TREE, TYPE_ATTRIBUTES(type)); 471 } 472 #ifdef __DEBUG_PLUGIN 473 fprintf(stderr, "Marking randomize_considered on struct %s\n", ORIG_TYPE_NAME(type)); 474 #ifdef __DEBUG_VERBOSE 475 debug_tree(type); 476 #endif 477 #endif 478 } 479 480 static void update_decl_size(tree decl) 481 { 482 tree lastval, lastidx, field, init, type, flexsize; 483 unsigned HOST_WIDE_INT len; 484 485 type = TREE_TYPE(decl); 486 487 if (!lookup_attribute("has_flexarray", TYPE_ATTRIBUTES(type))) 488 return; 489 490 init = DECL_INITIAL(decl); 491 if (init == NULL_TREE || init == error_mark_node) 492 return; 493 494 if (TREE_CODE(init) != CONSTRUCTOR) 495 return; 496 497 len = CONSTRUCTOR_NELTS(init); 498 if (!len) 499 return; 500 501 lastval = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->value; 502 lastidx = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->index; 503 504 for (field = TYPE_FIELDS(TREE_TYPE(decl)); TREE_CHAIN(field); field = TREE_CHAIN(field)) 505 ; 506 507 if (lastidx != field) 508 return; 509 510 if (TREE_CODE(lastval) != STRING_CST) { 511 error("Only string constants are supported as initializers " 512 "for randomized structures with flexible arrays"); 513 return; 514 } 515 516 flexsize = bitsize_int(TREE_STRING_LENGTH(lastval) * 517 tree_to_uhwi(TYPE_SIZE(TREE_TYPE(TREE_TYPE(lastval))))); 518 519 DECL_SIZE(decl) = size_binop(PLUS_EXPR, TYPE_SIZE(type), flexsize); 520 521 return; 522 } 523 524 525 static void randomize_layout_finish_decl(void *event_data, void *data) 526 { 527 tree decl = (tree)event_data; 528 tree type; 529 530 if (decl == NULL_TREE || decl == error_mark_node) 531 return; 532 533 type = TREE_TYPE(decl); 534 535 if (TREE_CODE(decl) != VAR_DECL) 536 return; 537 538 if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE) 539 return; 540 541 if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type))) 542 return; 543 544 DECL_SIZE(decl) = 0; 545 DECL_SIZE_UNIT(decl) = 0; 546 SET_DECL_ALIGN(decl, 0); 547 SET_DECL_MODE (decl, VOIDmode); 548 SET_DECL_RTL(decl, 0); 549 update_decl_size(decl); 550 layout_decl(decl, 0); 551 } 552 553 static void finish_type(void *event_data, void *data) 554 { 555 tree type = (tree)event_data; 556 557 if (type == NULL_TREE || type == error_mark_node) 558 return; 559 560 if (TREE_CODE(type) != RECORD_TYPE) 561 return; 562 563 if (TYPE_FIELDS(type) == NULL_TREE) 564 return; 565 566 if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type))) 567 return; 568 569 #ifdef __DEBUG_PLUGIN 570 fprintf(stderr, "Calling randomize_type on %s\n", ORIG_TYPE_NAME(type)); 571 #endif 572 #ifdef __DEBUG_VERBOSE 573 debug_tree(type); 574 #endif 575 randomize_type(type); 576 577 return; 578 } 579 580 static struct attribute_spec randomize_layout_attr = { 581 .name = "randomize_layout", 582 // related to args 583 .min_length = 0, 584 .max_length = 0, 585 .decl_required = false, 586 // need type declaration 587 .type_required = true, 588 .function_type_required = false, 589 .handler = handle_randomize_layout_attr, 590 #if BUILDING_GCC_VERSION >= 4007 591 .affects_type_identity = true 592 #endif 593 }; 594 595 static struct attribute_spec no_randomize_layout_attr = { 596 .name = "no_randomize_layout", 597 // related to args 598 .min_length = 0, 599 .max_length = 0, 600 .decl_required = false, 601 // need type declaration 602 .type_required = true, 603 .function_type_required = false, 604 .handler = handle_randomize_layout_attr, 605 #if BUILDING_GCC_VERSION >= 4007 606 .affects_type_identity = true 607 #endif 608 }; 609 610 static struct attribute_spec randomize_considered_attr = { 611 .name = "randomize_considered", 612 // related to args 613 .min_length = 0, 614 .max_length = 0, 615 .decl_required = false, 616 // need type declaration 617 .type_required = true, 618 .function_type_required = false, 619 .handler = handle_randomize_considered_attr, 620 #if BUILDING_GCC_VERSION >= 4007 621 .affects_type_identity = false 622 #endif 623 }; 624 625 static struct attribute_spec randomize_performed_attr = { 626 .name = "randomize_performed", 627 // related to args 628 .min_length = 0, 629 .max_length = 0, 630 .decl_required = false, 631 // need type declaration 632 .type_required = true, 633 .function_type_required = false, 634 .handler = handle_randomize_performed_attr, 635 #if BUILDING_GCC_VERSION >= 4007 636 .affects_type_identity = false 637 #endif 638 }; 639 640 static void register_attributes(void *event_data, void *data) 641 { 642 register_attribute(&randomize_layout_attr); 643 register_attribute(&no_randomize_layout_attr); 644 register_attribute(&randomize_considered_attr); 645 register_attribute(&randomize_performed_attr); 646 } 647 648 static void check_bad_casts_in_constructor(tree var, tree init) 649 { 650 unsigned HOST_WIDE_INT idx; 651 tree field, val; 652 tree field_type, val_type; 653 654 FOR_EACH_CONSTRUCTOR_ELT(CONSTRUCTOR_ELTS(init), idx, field, val) { 655 if (TREE_CODE(val) == CONSTRUCTOR) { 656 check_bad_casts_in_constructor(var, val); 657 continue; 658 } 659 660 /* pipacs' plugin creates franken-arrays that differ from those produced by 661 normal code which all have valid 'field' trees. work around this */ 662 if (field == NULL_TREE) 663 continue; 664 field_type = TREE_TYPE(field); 665 val_type = TREE_TYPE(val); 666 667 if (TREE_CODE(field_type) != POINTER_TYPE || TREE_CODE(val_type) != POINTER_TYPE) 668 continue; 669 670 if (field_type == val_type) 671 continue; 672 673 field_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(field_type)))); 674 val_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(val_type)))); 675 676 if (field_type == void_type_node) 677 continue; 678 if (field_type == val_type) 679 continue; 680 if (TREE_CODE(val_type) != RECORD_TYPE) 681 continue; 682 683 if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(val_type))) 684 continue; 685 MISMATCH(DECL_SOURCE_LOCATION(var), "constructor\n", TYPE_MAIN_VARIANT(field_type), TYPE_MAIN_VARIANT(val_type)); 686 } 687 } 688 689 /* derived from the constify plugin */ 690 static void check_global_variables(void *event_data, void *data) 691 { 692 struct varpool_node *node; 693 tree init; 694 695 FOR_EACH_VARIABLE(node) { 696 tree var = NODE_DECL(node); 697 init = DECL_INITIAL(var); 698 if (init == NULL_TREE) 699 continue; 700 701 if (TREE_CODE(init) != CONSTRUCTOR) 702 continue; 703 704 check_bad_casts_in_constructor(var, init); 705 } 706 } 707 708 static bool dominated_by_is_err(const_tree rhs, basic_block bb) 709 { 710 basic_block dom; 711 gimple dom_stmt; 712 gimple call_stmt; 713 const_tree dom_lhs; 714 const_tree poss_is_err_cond; 715 const_tree poss_is_err_func; 716 const_tree is_err_arg; 717 718 dom = get_immediate_dominator(CDI_DOMINATORS, bb); 719 if (!dom) 720 return false; 721 722 dom_stmt = last_stmt(dom); 723 if (!dom_stmt) 724 return false; 725 726 if (gimple_code(dom_stmt) != GIMPLE_COND) 727 return false; 728 729 if (gimple_cond_code(dom_stmt) != NE_EXPR) 730 return false; 731 732 if (!integer_zerop(gimple_cond_rhs(dom_stmt))) 733 return false; 734 735 poss_is_err_cond = gimple_cond_lhs(dom_stmt); 736 737 if (TREE_CODE(poss_is_err_cond) != SSA_NAME) 738 return false; 739 740 call_stmt = SSA_NAME_DEF_STMT(poss_is_err_cond); 741 742 if (gimple_code(call_stmt) != GIMPLE_CALL) 743 return false; 744 745 dom_lhs = gimple_get_lhs(call_stmt); 746 poss_is_err_func = gimple_call_fndecl(call_stmt); 747 if (!poss_is_err_func) 748 return false; 749 if (dom_lhs != poss_is_err_cond) 750 return false; 751 if (strcmp(DECL_NAME_POINTER(poss_is_err_func), "IS_ERR")) 752 return false; 753 754 is_err_arg = gimple_call_arg(call_stmt, 0); 755 if (!is_err_arg) 756 return false; 757 758 if (is_err_arg != rhs) 759 return false; 760 761 return true; 762 } 763 764 static void handle_local_var_initializers(void) 765 { 766 tree var; 767 unsigned int i; 768 769 FOR_EACH_LOCAL_DECL(cfun, i, var) { 770 tree init = DECL_INITIAL(var); 771 if (!init) 772 continue; 773 if (TREE_CODE(init) != CONSTRUCTOR) 774 continue; 775 check_bad_casts_in_constructor(var, init); 776 } 777 } 778 779 static bool type_name_eq(gimple stmt, const_tree type_tree, const char *wanted_name) 780 { 781 const char *type_name; 782 783 if (type_tree == NULL_TREE) 784 return false; 785 786 switch (TREE_CODE(type_tree)) { 787 case RECORD_TYPE: 788 type_name = TYPE_NAME_POINTER(type_tree); 789 break; 790 case INTEGER_TYPE: 791 if (TYPE_PRECISION(type_tree) == CHAR_TYPE_SIZE) 792 type_name = "char"; 793 else { 794 INFORM(gimple_location(stmt), "found non-char INTEGER_TYPE cast comparison: %qT\n", type_tree); 795 debug_tree(type_tree); 796 return false; 797 } 798 break; 799 case POINTER_TYPE: 800 if (TREE_CODE(TREE_TYPE(type_tree)) == VOID_TYPE) { 801 type_name = "void *"; 802 break; 803 } else { 804 INFORM(gimple_location(stmt), "found non-void POINTER_TYPE cast comparison %qT\n", type_tree); 805 debug_tree(type_tree); 806 return false; 807 } 808 default: 809 INFORM(gimple_location(stmt), "unhandled cast comparison: %qT\n", type_tree); 810 debug_tree(type_tree); 811 return false; 812 } 813 814 return strcmp(type_name, wanted_name) == 0; 815 } 816 817 static bool whitelisted_cast(gimple stmt, const_tree lhs_tree, const_tree rhs_tree) 818 { 819 const struct whitelist_entry *entry; 820 expanded_location xloc = expand_location(gimple_location(stmt)); 821 822 for (entry = whitelist; entry->pathname; entry++) { 823 if (!strstr(xloc.file, entry->pathname)) 824 continue; 825 826 if (type_name_eq(stmt, lhs_tree, entry->lhs) && type_name_eq(stmt, rhs_tree, entry->rhs)) 827 return true; 828 } 829 830 return false; 831 } 832 833 /* 834 * iterate over all statements to find "bad" casts: 835 * those where the address of the start of a structure is cast 836 * to a pointer of a structure of a different type, or a 837 * structure pointer type is cast to a different structure pointer type 838 */ 839 static unsigned int find_bad_casts_execute(void) 840 { 841 basic_block bb; 842 843 handle_local_var_initializers(); 844 845 FOR_EACH_BB_FN(bb, cfun) { 846 gimple_stmt_iterator gsi; 847 848 for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) { 849 gimple stmt; 850 const_tree lhs; 851 const_tree lhs_type; 852 const_tree rhs1; 853 const_tree rhs_type; 854 const_tree ptr_lhs_type; 855 const_tree ptr_rhs_type; 856 const_tree op0; 857 const_tree op0_type; 858 enum tree_code rhs_code; 859 860 stmt = gsi_stmt(gsi); 861 862 #ifdef __DEBUG_PLUGIN 863 #ifdef __DEBUG_VERBOSE 864 debug_gimple_stmt(stmt); 865 debug_tree(gimple_get_lhs(stmt)); 866 #endif 867 #endif 868 869 if (gimple_code(stmt) != GIMPLE_ASSIGN) 870 continue; 871 872 #ifdef __DEBUG_PLUGIN 873 #ifdef __DEBUG_VERBOSE 874 debug_tree(gimple_assign_rhs1(stmt)); 875 #endif 876 #endif 877 878 879 rhs_code = gimple_assign_rhs_code(stmt); 880 881 if (rhs_code != ADDR_EXPR && rhs_code != SSA_NAME) 882 continue; 883 884 lhs = gimple_get_lhs(stmt); 885 lhs_type = TREE_TYPE(lhs); 886 rhs1 = gimple_assign_rhs1(stmt); 887 rhs_type = TREE_TYPE(rhs1); 888 889 if (TREE_CODE(rhs_type) != POINTER_TYPE || 890 TREE_CODE(lhs_type) != POINTER_TYPE) 891 continue; 892 893 ptr_lhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(lhs_type)))); 894 ptr_rhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(rhs_type)))); 895 896 if (ptr_rhs_type == void_type_node) 897 continue; 898 899 if (ptr_lhs_type == void_type_node) 900 continue; 901 902 if (dominated_by_is_err(rhs1, bb)) 903 continue; 904 905 if (TREE_CODE(ptr_rhs_type) != RECORD_TYPE) { 906 #ifndef __DEBUG_PLUGIN 907 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_lhs_type))) 908 #endif 909 { 910 if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type)) 911 MISMATCH(gimple_location(stmt), "rhs", ptr_lhs_type, ptr_rhs_type); 912 } 913 continue; 914 } 915 916 if (rhs_code == SSA_NAME && ptr_lhs_type == ptr_rhs_type) 917 continue; 918 919 if (rhs_code == ADDR_EXPR) { 920 op0 = TREE_OPERAND(rhs1, 0); 921 922 if (op0 == NULL_TREE) 923 continue; 924 925 if (TREE_CODE(op0) != VAR_DECL) 926 continue; 927 928 op0_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(op0)))); 929 if (op0_type == ptr_lhs_type) 930 continue; 931 932 #ifndef __DEBUG_PLUGIN 933 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(op0_type))) 934 #endif 935 { 936 if (!whitelisted_cast(stmt, ptr_lhs_type, op0_type)) 937 MISMATCH(gimple_location(stmt), "op0", ptr_lhs_type, op0_type); 938 } 939 } else { 940 const_tree ssa_name_var = SSA_NAME_VAR(rhs1); 941 /* skip bogus type casts introduced by container_of */ 942 if (ssa_name_var != NULL_TREE && DECL_NAME(ssa_name_var) && 943 !strcmp((const char *)DECL_NAME_POINTER(ssa_name_var), "__mptr")) 944 continue; 945 #ifndef __DEBUG_PLUGIN 946 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_rhs_type))) 947 #endif 948 { 949 if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type)) 950 MISMATCH(gimple_location(stmt), "ssa", ptr_lhs_type, ptr_rhs_type); 951 } 952 } 953 954 } 955 } 956 return 0; 957 } 958 959 #define PASS_NAME find_bad_casts 960 #define NO_GATE 961 #define TODO_FLAGS_FINISH TODO_dump_func 962 #include "gcc-generate-gimple-pass.h" 963 964 __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version) 965 { 966 int i; 967 const char * const plugin_name = plugin_info->base_name; 968 const int argc = plugin_info->argc; 969 const struct plugin_argument * const argv = plugin_info->argv; 970 bool enable = true; 971 int obtained_seed = 0; 972 struct register_pass_info find_bad_casts_pass_info; 973 974 find_bad_casts_pass_info.pass = make_find_bad_casts_pass(); 975 find_bad_casts_pass_info.reference_pass_name = "ssa"; 976 find_bad_casts_pass_info.ref_pass_instance_number = 1; 977 find_bad_casts_pass_info.pos_op = PASS_POS_INSERT_AFTER; 978 979 if (!plugin_default_version_check(version, &gcc_version)) { 980 error(G_("incompatible gcc/plugin versions")); 981 return 1; 982 } 983 984 if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) { 985 inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name); 986 enable = false; 987 } 988 989 for (i = 0; i < argc; ++i) { 990 if (!strcmp(argv[i].key, "disable")) { 991 enable = false; 992 continue; 993 } 994 if (!strcmp(argv[i].key, "performance-mode")) { 995 performance_mode = 1; 996 continue; 997 } 998 error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key); 999 } 1000 1001 if (strlen(randstruct_seed) != 64) { 1002 error(G_("invalid seed value supplied for %s plugin"), plugin_name); 1003 return 1; 1004 } 1005 obtained_seed = sscanf(randstruct_seed, "%016llx%016llx%016llx%016llx", 1006 &shuffle_seed[0], &shuffle_seed[1], &shuffle_seed[2], &shuffle_seed[3]); 1007 if (obtained_seed != 4) { 1008 error(G_("Invalid seed supplied for %s plugin"), plugin_name); 1009 return 1; 1010 } 1011 1012 register_callback(plugin_name, PLUGIN_INFO, NULL, &randomize_layout_plugin_info); 1013 if (enable) { 1014 register_callback(plugin_name, PLUGIN_ALL_IPA_PASSES_START, check_global_variables, NULL); 1015 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &find_bad_casts_pass_info); 1016 register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL); 1017 register_callback(plugin_name, PLUGIN_FINISH_DECL, randomize_layout_finish_decl, NULL); 1018 } 1019 register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL); 1020 1021 return 0; 1022 } 1023