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