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 /* unix_skb_parms via UNIXCB() buffer */ 50 { "net/unix/af_unix.c", "unix_skb_parms", "char" }, 51 /* big_key payload.data struct splashing */ 52 { "security/keys/big_key.c", "path", "void *" }, 53 /* walk struct security_hook_heads as an array of struct list_head */ 54 { "security/security.c", "list_head", "security_hook_heads" }, 55 { } 56 }; 57 58 /* from old Linux dcache.h */ 59 static inline unsigned long 60 partial_name_hash(unsigned long c, unsigned long prevhash) 61 { 62 return (prevhash + (c << 4) + (c >> 4)) * 11; 63 } 64 static inline unsigned int 65 name_hash(const unsigned char *name) 66 { 67 unsigned long hash = 0; 68 unsigned int len = strlen((const char *)name); 69 while (len--) 70 hash = partial_name_hash(*name++, hash); 71 return (unsigned int)hash; 72 } 73 74 static tree handle_randomize_layout_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs) 75 { 76 tree type; 77 78 *no_add_attrs = true; 79 if (TREE_CODE(*node) == FUNCTION_DECL) { 80 error("%qE attribute does not apply to functions (%qF)", name, *node); 81 return NULL_TREE; 82 } 83 84 if (TREE_CODE(*node) == PARM_DECL) { 85 error("%qE attribute does not apply to function parameters (%qD)", name, *node); 86 return NULL_TREE; 87 } 88 89 if (TREE_CODE(*node) == VAR_DECL) { 90 error("%qE attribute does not apply to variables (%qD)", name, *node); 91 return NULL_TREE; 92 } 93 94 if (TYPE_P(*node)) { 95 type = *node; 96 } else { 97 gcc_assert(TREE_CODE(*node) == TYPE_DECL); 98 type = TREE_TYPE(*node); 99 } 100 101 if (TREE_CODE(type) != RECORD_TYPE) { 102 error("%qE attribute used on %qT applies to struct types only", name, type); 103 return NULL_TREE; 104 } 105 106 if (lookup_attribute(IDENTIFIER_POINTER(name), TYPE_ATTRIBUTES(type))) { 107 error("%qE attribute is already applied to the type %qT", name, type); 108 return NULL_TREE; 109 } 110 111 *no_add_attrs = false; 112 113 return NULL_TREE; 114 } 115 116 /* set on complete types that we don't need to inspect further at all */ 117 static tree handle_randomize_considered_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs) 118 { 119 *no_add_attrs = false; 120 return NULL_TREE; 121 } 122 123 /* 124 * set on types that we've performed a shuffle on, to prevent re-shuffling 125 * this does not preclude us from inspecting its fields for potential shuffles 126 */ 127 static tree handle_randomize_performed_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs) 128 { 129 *no_add_attrs = false; 130 return NULL_TREE; 131 } 132 133 /* 134 * 64bit variant of Bob Jenkins' public domain PRNG 135 * 256 bits of internal state 136 */ 137 138 typedef unsigned long long u64; 139 140 typedef struct ranctx { u64 a; u64 b; u64 c; u64 d; } ranctx; 141 142 #define rot(x,k) (((x)<<(k))|((x)>>(64-(k)))) 143 static u64 ranval(ranctx *x) { 144 u64 e = x->a - rot(x->b, 7); 145 x->a = x->b ^ rot(x->c, 13); 146 x->b = x->c + rot(x->d, 37); 147 x->c = x->d + e; 148 x->d = e + x->a; 149 return x->d; 150 } 151 152 static void raninit(ranctx *x, u64 *seed) { 153 int i; 154 155 x->a = seed[0]; 156 x->b = seed[1]; 157 x->c = seed[2]; 158 x->d = seed[3]; 159 160 for (i=0; i < 30; ++i) 161 (void)ranval(x); 162 } 163 164 static u64 shuffle_seed[4]; 165 166 struct partition_group { 167 tree tree_start; 168 unsigned long start; 169 unsigned long length; 170 }; 171 172 static void partition_struct(tree *fields, unsigned long length, struct partition_group *size_groups, unsigned long *num_groups) 173 { 174 unsigned long i; 175 unsigned long accum_size = 0; 176 unsigned long accum_length = 0; 177 unsigned long group_idx = 0; 178 179 gcc_assert(length < INT_MAX); 180 181 memset(size_groups, 0, sizeof(struct partition_group) * length); 182 183 for (i = 0; i < length; i++) { 184 if (size_groups[group_idx].tree_start == NULL_TREE) { 185 size_groups[group_idx].tree_start = fields[i]; 186 size_groups[group_idx].start = i; 187 accum_length = 0; 188 accum_size = 0; 189 } 190 accum_size += (unsigned long)int_size_in_bytes(TREE_TYPE(fields[i])); 191 accum_length++; 192 if (accum_size >= 64) { 193 size_groups[group_idx].length = accum_length; 194 accum_length = 0; 195 group_idx++; 196 } 197 } 198 199 if (size_groups[group_idx].tree_start != NULL_TREE && 200 !size_groups[group_idx].length) { 201 size_groups[group_idx].length = accum_length; 202 group_idx++; 203 } 204 205 *num_groups = group_idx; 206 } 207 208 static void performance_shuffle(tree *newtree, unsigned long length, ranctx *prng_state) 209 { 210 unsigned long i, x; 211 struct partition_group size_group[length]; 212 unsigned long num_groups = 0; 213 unsigned long randnum; 214 215 partition_struct(newtree, length, (struct partition_group *)&size_group, &num_groups); 216 for (i = num_groups - 1; i > 0; i--) { 217 struct partition_group tmp; 218 randnum = ranval(prng_state) % (i + 1); 219 tmp = size_group[i]; 220 size_group[i] = size_group[randnum]; 221 size_group[randnum] = tmp; 222 } 223 224 for (x = 0; x < num_groups; x++) { 225 for (i = size_group[x].start + size_group[x].length - 1; i > size_group[x].start; i--) { 226 tree tmp; 227 if (DECL_BIT_FIELD_TYPE(newtree[i])) 228 continue; 229 randnum = ranval(prng_state) % (i + 1); 230 // we could handle this case differently if desired 231 if (DECL_BIT_FIELD_TYPE(newtree[randnum])) 232 continue; 233 tmp = newtree[i]; 234 newtree[i] = newtree[randnum]; 235 newtree[randnum] = tmp; 236 } 237 } 238 } 239 240 static void full_shuffle(tree *newtree, unsigned long length, ranctx *prng_state) 241 { 242 unsigned long i, randnum; 243 244 for (i = length - 1; i > 0; i--) { 245 tree tmp; 246 randnum = ranval(prng_state) % (i + 1); 247 tmp = newtree[i]; 248 newtree[i] = newtree[randnum]; 249 newtree[randnum] = tmp; 250 } 251 } 252 253 /* modern in-place Fisher-Yates shuffle */ 254 static void shuffle(const_tree type, tree *newtree, unsigned long length) 255 { 256 unsigned long i; 257 u64 seed[4]; 258 ranctx prng_state; 259 const unsigned char *structname; 260 261 if (length == 0) 262 return; 263 264 gcc_assert(TREE_CODE(type) == RECORD_TYPE); 265 266 structname = ORIG_TYPE_NAME(type); 267 268 #ifdef __DEBUG_PLUGIN 269 fprintf(stderr, "Shuffling struct %s %p\n", (const char *)structname, type); 270 #ifdef __DEBUG_VERBOSE 271 debug_tree((tree)type); 272 #endif 273 #endif 274 275 for (i = 0; i < 4; i++) { 276 seed[i] = shuffle_seed[i]; 277 seed[i] ^= name_hash(structname); 278 } 279 280 raninit(&prng_state, (u64 *)&seed); 281 282 if (performance_mode) 283 performance_shuffle(newtree, length, &prng_state); 284 else 285 full_shuffle(newtree, length, &prng_state); 286 } 287 288 static bool is_flexible_array(const_tree field) 289 { 290 const_tree fieldtype; 291 const_tree typesize; 292 const_tree elemtype; 293 const_tree elemsize; 294 295 fieldtype = TREE_TYPE(field); 296 typesize = TYPE_SIZE(fieldtype); 297 298 if (TREE_CODE(fieldtype) != ARRAY_TYPE) 299 return false; 300 301 elemtype = TREE_TYPE(fieldtype); 302 elemsize = TYPE_SIZE(elemtype); 303 304 /* size of type is represented in bits */ 305 306 if (typesize == NULL_TREE && TYPE_DOMAIN(fieldtype) != NULL_TREE && 307 TYPE_MAX_VALUE(TYPE_DOMAIN(fieldtype)) == NULL_TREE) 308 return true; 309 310 if (typesize != NULL_TREE && 311 (TREE_CONSTANT(typesize) && (!tree_to_uhwi(typesize) || 312 tree_to_uhwi(typesize) == tree_to_uhwi(elemsize)))) 313 return true; 314 315 return false; 316 } 317 318 static int relayout_struct(tree type) 319 { 320 unsigned long num_fields = (unsigned long)list_length(TYPE_FIELDS(type)); 321 unsigned long shuffle_length = num_fields; 322 tree field; 323 tree newtree[num_fields]; 324 unsigned long i; 325 tree list; 326 tree variant; 327 tree main_variant; 328 expanded_location xloc; 329 bool has_flexarray = false; 330 331 if (TYPE_FIELDS(type) == NULL_TREE) 332 return 0; 333 334 if (num_fields < 2) 335 return 0; 336 337 gcc_assert(TREE_CODE(type) == RECORD_TYPE); 338 339 gcc_assert(num_fields < INT_MAX); 340 341 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)) || 342 lookup_attribute("no_randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type)))) 343 return 0; 344 345 /* Workaround for 3rd-party VirtualBox source that we can't modify ourselves */ 346 if (!strcmp((const char *)ORIG_TYPE_NAME(type), "INTNETTRUNKFACTORY") || 347 !strcmp((const char *)ORIG_TYPE_NAME(type), "RAWPCIFACTORY")) 348 return 0; 349 350 /* throw out any structs in uapi */ 351 xloc = expand_location(DECL_SOURCE_LOCATION(TYPE_FIELDS(type))); 352 353 if (strstr(xloc.file, "/uapi/")) 354 error(G_("attempted to randomize userland API struct %s"), ORIG_TYPE_NAME(type)); 355 356 for (field = TYPE_FIELDS(type), i = 0; field; field = TREE_CHAIN(field), i++) { 357 gcc_assert(TREE_CODE(field) == FIELD_DECL); 358 newtree[i] = field; 359 } 360 361 /* 362 * enforce that we don't randomize the layout of the last 363 * element of a struct if it's a 0 or 1-length array 364 * or a proper flexible array 365 */ 366 if (is_flexible_array(newtree[num_fields - 1])) { 367 has_flexarray = true; 368 shuffle_length--; 369 } 370 371 shuffle(type, (tree *)newtree, shuffle_length); 372 373 /* 374 * set up a bogus anonymous struct field designed to error out on unnamed struct initializers 375 * as gcc provides no other way to detect such code 376 */ 377 list = make_node(FIELD_DECL); 378 TREE_CHAIN(list) = newtree[0]; 379 TREE_TYPE(list) = void_type_node; 380 DECL_SIZE(list) = bitsize_zero_node; 381 DECL_NONADDRESSABLE_P(list) = 1; 382 DECL_FIELD_BIT_OFFSET(list) = bitsize_zero_node; 383 DECL_SIZE_UNIT(list) = size_zero_node; 384 DECL_FIELD_OFFSET(list) = size_zero_node; 385 DECL_CONTEXT(list) = type; 386 // to satisfy the constify plugin 387 TREE_READONLY(list) = 1; 388 389 for (i = 0; i < num_fields - 1; i++) 390 TREE_CHAIN(newtree[i]) = newtree[i+1]; 391 TREE_CHAIN(newtree[num_fields - 1]) = NULL_TREE; 392 393 main_variant = TYPE_MAIN_VARIANT(type); 394 for (variant = main_variant; variant; variant = TYPE_NEXT_VARIANT(variant)) { 395 TYPE_FIELDS(variant) = list; 396 TYPE_ATTRIBUTES(variant) = copy_list(TYPE_ATTRIBUTES(variant)); 397 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("randomize_performed"), NULL_TREE, TYPE_ATTRIBUTES(variant)); 398 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("designated_init"), NULL_TREE, TYPE_ATTRIBUTES(variant)); 399 if (has_flexarray) 400 TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("has_flexarray"), NULL_TREE, TYPE_ATTRIBUTES(type)); 401 } 402 403 /* 404 * force a re-layout of the main variant 405 * the TYPE_SIZE for all variants will be recomputed 406 * by finalize_type_size() 407 */ 408 TYPE_SIZE(main_variant) = NULL_TREE; 409 layout_type(main_variant); 410 gcc_assert(TYPE_SIZE(main_variant) != NULL_TREE); 411 412 return 1; 413 } 414 415 /* from constify plugin */ 416 static const_tree get_field_type(const_tree field) 417 { 418 return strip_array_types(TREE_TYPE(field)); 419 } 420 421 /* from constify plugin */ 422 static bool is_fptr(const_tree fieldtype) 423 { 424 if (TREE_CODE(fieldtype) != POINTER_TYPE) 425 return false; 426 427 return TREE_CODE(TREE_TYPE(fieldtype)) == FUNCTION_TYPE; 428 } 429 430 /* derived from constify plugin */ 431 static int is_pure_ops_struct(const_tree node) 432 { 433 const_tree field; 434 435 gcc_assert(TREE_CODE(node) == RECORD_TYPE || TREE_CODE(node) == UNION_TYPE); 436 437 /* XXX: Do not apply randomization to all-ftpr structs yet. */ 438 return 0; 439 440 for (field = TYPE_FIELDS(node); field; field = TREE_CHAIN(field)) { 441 const_tree fieldtype = get_field_type(field); 442 enum tree_code code = TREE_CODE(fieldtype); 443 444 if (node == fieldtype) 445 continue; 446 447 if (!is_fptr(fieldtype)) 448 return 0; 449 450 if (code != RECORD_TYPE && code != UNION_TYPE) 451 continue; 452 453 if (!is_pure_ops_struct(fieldtype)) 454 return 0; 455 } 456 457 return 1; 458 } 459 460 static void randomize_type(tree type) 461 { 462 tree variant; 463 464 gcc_assert(TREE_CODE(type) == RECORD_TYPE); 465 466 if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type))) 467 return; 468 469 if (lookup_attribute("randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))) || is_pure_ops_struct(type)) 470 relayout_struct(type); 471 472 for (variant = TYPE_MAIN_VARIANT(type); variant; variant = TYPE_NEXT_VARIANT(variant)) { 473 TYPE_ATTRIBUTES(type) = copy_list(TYPE_ATTRIBUTES(type)); 474 TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("randomize_considered"), NULL_TREE, TYPE_ATTRIBUTES(type)); 475 } 476 #ifdef __DEBUG_PLUGIN 477 fprintf(stderr, "Marking randomize_considered on struct %s\n", ORIG_TYPE_NAME(type)); 478 #ifdef __DEBUG_VERBOSE 479 debug_tree(type); 480 #endif 481 #endif 482 } 483 484 static void update_decl_size(tree decl) 485 { 486 tree lastval, lastidx, field, init, type, flexsize; 487 unsigned HOST_WIDE_INT len; 488 489 type = TREE_TYPE(decl); 490 491 if (!lookup_attribute("has_flexarray", TYPE_ATTRIBUTES(type))) 492 return; 493 494 init = DECL_INITIAL(decl); 495 if (init == NULL_TREE || init == error_mark_node) 496 return; 497 498 if (TREE_CODE(init) != CONSTRUCTOR) 499 return; 500 501 len = CONSTRUCTOR_NELTS(init); 502 if (!len) 503 return; 504 505 lastval = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->value; 506 lastidx = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->index; 507 508 for (field = TYPE_FIELDS(TREE_TYPE(decl)); TREE_CHAIN(field); field = TREE_CHAIN(field)) 509 ; 510 511 if (lastidx != field) 512 return; 513 514 if (TREE_CODE(lastval) != STRING_CST) { 515 error("Only string constants are supported as initializers " 516 "for randomized structures with flexible arrays"); 517 return; 518 } 519 520 flexsize = bitsize_int(TREE_STRING_LENGTH(lastval) * 521 tree_to_uhwi(TYPE_SIZE(TREE_TYPE(TREE_TYPE(lastval))))); 522 523 DECL_SIZE(decl) = size_binop(PLUS_EXPR, TYPE_SIZE(type), flexsize); 524 525 return; 526 } 527 528 529 static void randomize_layout_finish_decl(void *event_data, void *data) 530 { 531 tree decl = (tree)event_data; 532 tree type; 533 534 if (decl == NULL_TREE || decl == error_mark_node) 535 return; 536 537 type = TREE_TYPE(decl); 538 539 if (TREE_CODE(decl) != VAR_DECL) 540 return; 541 542 if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE) 543 return; 544 545 if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type))) 546 return; 547 548 DECL_SIZE(decl) = 0; 549 DECL_SIZE_UNIT(decl) = 0; 550 SET_DECL_ALIGN(decl, 0); 551 SET_DECL_MODE (decl, VOIDmode); 552 SET_DECL_RTL(decl, 0); 553 update_decl_size(decl); 554 layout_decl(decl, 0); 555 } 556 557 static void finish_type(void *event_data, void *data) 558 { 559 tree type = (tree)event_data; 560 561 if (type == NULL_TREE || type == error_mark_node) 562 return; 563 564 if (TREE_CODE(type) != RECORD_TYPE) 565 return; 566 567 if (TYPE_FIELDS(type) == NULL_TREE) 568 return; 569 570 if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type))) 571 return; 572 573 #ifdef __DEBUG_PLUGIN 574 fprintf(stderr, "Calling randomize_type on %s\n", ORIG_TYPE_NAME(type)); 575 #endif 576 #ifdef __DEBUG_VERBOSE 577 debug_tree(type); 578 #endif 579 randomize_type(type); 580 581 return; 582 } 583 584 static struct attribute_spec randomize_layout_attr = { 585 .name = "randomize_layout", 586 // related to args 587 .min_length = 0, 588 .max_length = 0, 589 .decl_required = false, 590 // need type declaration 591 .type_required = true, 592 .function_type_required = false, 593 .handler = handle_randomize_layout_attr, 594 #if BUILDING_GCC_VERSION >= 4007 595 .affects_type_identity = true 596 #endif 597 }; 598 599 static struct attribute_spec no_randomize_layout_attr = { 600 .name = "no_randomize_layout", 601 // related to args 602 .min_length = 0, 603 .max_length = 0, 604 .decl_required = false, 605 // need type declaration 606 .type_required = true, 607 .function_type_required = false, 608 .handler = handle_randomize_layout_attr, 609 #if BUILDING_GCC_VERSION >= 4007 610 .affects_type_identity = true 611 #endif 612 }; 613 614 static struct attribute_spec randomize_considered_attr = { 615 .name = "randomize_considered", 616 // related to args 617 .min_length = 0, 618 .max_length = 0, 619 .decl_required = false, 620 // need type declaration 621 .type_required = true, 622 .function_type_required = false, 623 .handler = handle_randomize_considered_attr, 624 #if BUILDING_GCC_VERSION >= 4007 625 .affects_type_identity = false 626 #endif 627 }; 628 629 static struct attribute_spec randomize_performed_attr = { 630 .name = "randomize_performed", 631 // related to args 632 .min_length = 0, 633 .max_length = 0, 634 .decl_required = false, 635 // need type declaration 636 .type_required = true, 637 .function_type_required = false, 638 .handler = handle_randomize_performed_attr, 639 #if BUILDING_GCC_VERSION >= 4007 640 .affects_type_identity = false 641 #endif 642 }; 643 644 static void register_attributes(void *event_data, void *data) 645 { 646 register_attribute(&randomize_layout_attr); 647 register_attribute(&no_randomize_layout_attr); 648 register_attribute(&randomize_considered_attr); 649 register_attribute(&randomize_performed_attr); 650 } 651 652 static void check_bad_casts_in_constructor(tree var, tree init) 653 { 654 unsigned HOST_WIDE_INT idx; 655 tree field, val; 656 tree field_type, val_type; 657 658 FOR_EACH_CONSTRUCTOR_ELT(CONSTRUCTOR_ELTS(init), idx, field, val) { 659 if (TREE_CODE(val) == CONSTRUCTOR) { 660 check_bad_casts_in_constructor(var, val); 661 continue; 662 } 663 664 /* pipacs' plugin creates franken-arrays that differ from those produced by 665 normal code which all have valid 'field' trees. work around this */ 666 if (field == NULL_TREE) 667 continue; 668 field_type = TREE_TYPE(field); 669 val_type = TREE_TYPE(val); 670 671 if (TREE_CODE(field_type) != POINTER_TYPE || TREE_CODE(val_type) != POINTER_TYPE) 672 continue; 673 674 if (field_type == val_type) 675 continue; 676 677 field_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(field_type)))); 678 val_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(val_type)))); 679 680 if (field_type == void_type_node) 681 continue; 682 if (field_type == val_type) 683 continue; 684 if (TREE_CODE(val_type) != RECORD_TYPE) 685 continue; 686 687 if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(val_type))) 688 continue; 689 MISMATCH(DECL_SOURCE_LOCATION(var), "constructor\n", TYPE_MAIN_VARIANT(field_type), TYPE_MAIN_VARIANT(val_type)); 690 } 691 } 692 693 /* derived from the constify plugin */ 694 static void check_global_variables(void *event_data, void *data) 695 { 696 struct varpool_node *node; 697 tree init; 698 699 FOR_EACH_VARIABLE(node) { 700 tree var = NODE_DECL(node); 701 init = DECL_INITIAL(var); 702 if (init == NULL_TREE) 703 continue; 704 705 if (TREE_CODE(init) != CONSTRUCTOR) 706 continue; 707 708 check_bad_casts_in_constructor(var, init); 709 } 710 } 711 712 static bool dominated_by_is_err(const_tree rhs, basic_block bb) 713 { 714 basic_block dom; 715 gimple dom_stmt; 716 gimple call_stmt; 717 const_tree dom_lhs; 718 const_tree poss_is_err_cond; 719 const_tree poss_is_err_func; 720 const_tree is_err_arg; 721 722 dom = get_immediate_dominator(CDI_DOMINATORS, bb); 723 if (!dom) 724 return false; 725 726 dom_stmt = last_stmt(dom); 727 if (!dom_stmt) 728 return false; 729 730 if (gimple_code(dom_stmt) != GIMPLE_COND) 731 return false; 732 733 if (gimple_cond_code(dom_stmt) != NE_EXPR) 734 return false; 735 736 if (!integer_zerop(gimple_cond_rhs(dom_stmt))) 737 return false; 738 739 poss_is_err_cond = gimple_cond_lhs(dom_stmt); 740 741 if (TREE_CODE(poss_is_err_cond) != SSA_NAME) 742 return false; 743 744 call_stmt = SSA_NAME_DEF_STMT(poss_is_err_cond); 745 746 if (gimple_code(call_stmt) != GIMPLE_CALL) 747 return false; 748 749 dom_lhs = gimple_get_lhs(call_stmt); 750 poss_is_err_func = gimple_call_fndecl(call_stmt); 751 if (!poss_is_err_func) 752 return false; 753 if (dom_lhs != poss_is_err_cond) 754 return false; 755 if (strcmp(DECL_NAME_POINTER(poss_is_err_func), "IS_ERR")) 756 return false; 757 758 is_err_arg = gimple_call_arg(call_stmt, 0); 759 if (!is_err_arg) 760 return false; 761 762 if (is_err_arg != rhs) 763 return false; 764 765 return true; 766 } 767 768 static void handle_local_var_initializers(void) 769 { 770 tree var; 771 unsigned int i; 772 773 FOR_EACH_LOCAL_DECL(cfun, i, var) { 774 tree init = DECL_INITIAL(var); 775 if (!init) 776 continue; 777 if (TREE_CODE(init) != CONSTRUCTOR) 778 continue; 779 check_bad_casts_in_constructor(var, init); 780 } 781 } 782 783 static bool type_name_eq(gimple stmt, const_tree type_tree, const char *wanted_name) 784 { 785 const char *type_name; 786 787 if (type_tree == NULL_TREE) 788 return false; 789 790 switch (TREE_CODE(type_tree)) { 791 case RECORD_TYPE: 792 type_name = TYPE_NAME_POINTER(type_tree); 793 break; 794 case INTEGER_TYPE: 795 if (TYPE_PRECISION(type_tree) == CHAR_TYPE_SIZE) 796 type_name = "char"; 797 else { 798 INFORM(gimple_location(stmt), "found non-char INTEGER_TYPE cast comparison: %qT\n", type_tree); 799 debug_tree(type_tree); 800 return false; 801 } 802 break; 803 case POINTER_TYPE: 804 if (TREE_CODE(TREE_TYPE(type_tree)) == VOID_TYPE) { 805 type_name = "void *"; 806 break; 807 } else { 808 INFORM(gimple_location(stmt), "found non-void POINTER_TYPE cast comparison %qT\n", type_tree); 809 debug_tree(type_tree); 810 return false; 811 } 812 default: 813 INFORM(gimple_location(stmt), "unhandled cast comparison: %qT\n", type_tree); 814 debug_tree(type_tree); 815 return false; 816 } 817 818 return strcmp(type_name, wanted_name) == 0; 819 } 820 821 static bool whitelisted_cast(gimple stmt, const_tree lhs_tree, const_tree rhs_tree) 822 { 823 const struct whitelist_entry *entry; 824 expanded_location xloc = expand_location(gimple_location(stmt)); 825 826 for (entry = whitelist; entry->pathname; entry++) { 827 if (!strstr(xloc.file, entry->pathname)) 828 continue; 829 830 if (type_name_eq(stmt, lhs_tree, entry->lhs) && type_name_eq(stmt, rhs_tree, entry->rhs)) 831 return true; 832 } 833 834 return false; 835 } 836 837 /* 838 * iterate over all statements to find "bad" casts: 839 * those where the address of the start of a structure is cast 840 * to a pointer of a structure of a different type, or a 841 * structure pointer type is cast to a different structure pointer type 842 */ 843 static unsigned int find_bad_casts_execute(void) 844 { 845 basic_block bb; 846 847 handle_local_var_initializers(); 848 849 FOR_EACH_BB_FN(bb, cfun) { 850 gimple_stmt_iterator gsi; 851 852 for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) { 853 gimple stmt; 854 const_tree lhs; 855 const_tree lhs_type; 856 const_tree rhs1; 857 const_tree rhs_type; 858 const_tree ptr_lhs_type; 859 const_tree ptr_rhs_type; 860 const_tree op0; 861 const_tree op0_type; 862 enum tree_code rhs_code; 863 864 stmt = gsi_stmt(gsi); 865 866 #ifdef __DEBUG_PLUGIN 867 #ifdef __DEBUG_VERBOSE 868 debug_gimple_stmt(stmt); 869 debug_tree(gimple_get_lhs(stmt)); 870 #endif 871 #endif 872 873 if (gimple_code(stmt) != GIMPLE_ASSIGN) 874 continue; 875 876 #ifdef __DEBUG_PLUGIN 877 #ifdef __DEBUG_VERBOSE 878 debug_tree(gimple_assign_rhs1(stmt)); 879 #endif 880 #endif 881 882 883 rhs_code = gimple_assign_rhs_code(stmt); 884 885 if (rhs_code != ADDR_EXPR && rhs_code != SSA_NAME) 886 continue; 887 888 lhs = gimple_get_lhs(stmt); 889 lhs_type = TREE_TYPE(lhs); 890 rhs1 = gimple_assign_rhs1(stmt); 891 rhs_type = TREE_TYPE(rhs1); 892 893 if (TREE_CODE(rhs_type) != POINTER_TYPE || 894 TREE_CODE(lhs_type) != POINTER_TYPE) 895 continue; 896 897 ptr_lhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(lhs_type)))); 898 ptr_rhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(rhs_type)))); 899 900 if (ptr_rhs_type == void_type_node) 901 continue; 902 903 if (ptr_lhs_type == void_type_node) 904 continue; 905 906 if (dominated_by_is_err(rhs1, bb)) 907 continue; 908 909 if (TREE_CODE(ptr_rhs_type) != RECORD_TYPE) { 910 #ifndef __DEBUG_PLUGIN 911 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_lhs_type))) 912 #endif 913 { 914 if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type)) 915 MISMATCH(gimple_location(stmt), "rhs", ptr_lhs_type, ptr_rhs_type); 916 } 917 continue; 918 } 919 920 if (rhs_code == SSA_NAME && ptr_lhs_type == ptr_rhs_type) 921 continue; 922 923 if (rhs_code == ADDR_EXPR) { 924 op0 = TREE_OPERAND(rhs1, 0); 925 926 if (op0 == NULL_TREE) 927 continue; 928 929 if (TREE_CODE(op0) != VAR_DECL) 930 continue; 931 932 op0_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(op0)))); 933 if (op0_type == ptr_lhs_type) 934 continue; 935 936 #ifndef __DEBUG_PLUGIN 937 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(op0_type))) 938 #endif 939 { 940 if (!whitelisted_cast(stmt, ptr_lhs_type, op0_type)) 941 MISMATCH(gimple_location(stmt), "op0", ptr_lhs_type, op0_type); 942 } 943 } else { 944 const_tree ssa_name_var = SSA_NAME_VAR(rhs1); 945 /* skip bogus type casts introduced by container_of */ 946 if (ssa_name_var != NULL_TREE && DECL_NAME(ssa_name_var) && 947 !strcmp((const char *)DECL_NAME_POINTER(ssa_name_var), "__mptr")) 948 continue; 949 #ifndef __DEBUG_PLUGIN 950 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_rhs_type))) 951 #endif 952 { 953 if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type)) 954 MISMATCH(gimple_location(stmt), "ssa", ptr_lhs_type, ptr_rhs_type); 955 } 956 } 957 958 } 959 } 960 return 0; 961 } 962 963 #define PASS_NAME find_bad_casts 964 #define NO_GATE 965 #define TODO_FLAGS_FINISH TODO_dump_func 966 #include "gcc-generate-gimple-pass.h" 967 968 __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version) 969 { 970 int i; 971 const char * const plugin_name = plugin_info->base_name; 972 const int argc = plugin_info->argc; 973 const struct plugin_argument * const argv = plugin_info->argv; 974 bool enable = true; 975 int obtained_seed = 0; 976 struct register_pass_info find_bad_casts_pass_info; 977 978 find_bad_casts_pass_info.pass = make_find_bad_casts_pass(); 979 find_bad_casts_pass_info.reference_pass_name = "ssa"; 980 find_bad_casts_pass_info.ref_pass_instance_number = 1; 981 find_bad_casts_pass_info.pos_op = PASS_POS_INSERT_AFTER; 982 983 if (!plugin_default_version_check(version, &gcc_version)) { 984 error(G_("incompatible gcc/plugin versions")); 985 return 1; 986 } 987 988 if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) { 989 inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name); 990 enable = false; 991 } 992 993 for (i = 0; i < argc; ++i) { 994 if (!strcmp(argv[i].key, "disable")) { 995 enable = false; 996 continue; 997 } 998 if (!strcmp(argv[i].key, "performance-mode")) { 999 performance_mode = 1; 1000 continue; 1001 } 1002 error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key); 1003 } 1004 1005 if (strlen(randstruct_seed) != 64) { 1006 error(G_("invalid seed value supplied for %s plugin"), plugin_name); 1007 return 1; 1008 } 1009 obtained_seed = sscanf(randstruct_seed, "%016llx%016llx%016llx%016llx", 1010 &shuffle_seed[0], &shuffle_seed[1], &shuffle_seed[2], &shuffle_seed[3]); 1011 if (obtained_seed != 4) { 1012 error(G_("Invalid seed supplied for %s plugin"), plugin_name); 1013 return 1; 1014 } 1015 1016 register_callback(plugin_name, PLUGIN_INFO, NULL, &randomize_layout_plugin_info); 1017 if (enable) { 1018 register_callback(plugin_name, PLUGIN_ALL_IPA_PASSES_START, check_global_variables, NULL); 1019 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &find_bad_casts_pass_info); 1020 register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL); 1021 register_callback(plugin_name, PLUGIN_FINISH_DECL, randomize_layout_finish_decl, NULL); 1022 } 1023 register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL); 1024 1025 return 0; 1026 } 1027