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