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 /* 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 { } 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 for (field = TYPE_FIELDS(node); field; field = TREE_CHAIN(field)) { 438 const_tree fieldtype = get_field_type(field); 439 enum tree_code code = TREE_CODE(fieldtype); 440 441 if (node == fieldtype) 442 continue; 443 444 if (code == RECORD_TYPE || code == UNION_TYPE) { 445 if (!is_pure_ops_struct(fieldtype)) 446 return 0; 447 continue; 448 } 449 450 if (!is_fptr(fieldtype)) 451 return 0; 452 } 453 454 return 1; 455 } 456 457 static void randomize_type(tree type) 458 { 459 tree variant; 460 461 gcc_assert(TREE_CODE(type) == RECORD_TYPE); 462 463 if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type))) 464 return; 465 466 if (lookup_attribute("randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))) || is_pure_ops_struct(type)) 467 relayout_struct(type); 468 469 for (variant = TYPE_MAIN_VARIANT(type); variant; variant = TYPE_NEXT_VARIANT(variant)) { 470 TYPE_ATTRIBUTES(type) = copy_list(TYPE_ATTRIBUTES(type)); 471 TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("randomize_considered"), NULL_TREE, TYPE_ATTRIBUTES(type)); 472 } 473 #ifdef __DEBUG_PLUGIN 474 fprintf(stderr, "Marking randomize_considered on struct %s\n", ORIG_TYPE_NAME(type)); 475 #ifdef __DEBUG_VERBOSE 476 debug_tree(type); 477 #endif 478 #endif 479 } 480 481 static void update_decl_size(tree decl) 482 { 483 tree lastval, lastidx, field, init, type, flexsize; 484 unsigned HOST_WIDE_INT len; 485 486 type = TREE_TYPE(decl); 487 488 if (!lookup_attribute("has_flexarray", TYPE_ATTRIBUTES(type))) 489 return; 490 491 init = DECL_INITIAL(decl); 492 if (init == NULL_TREE || init == error_mark_node) 493 return; 494 495 if (TREE_CODE(init) != CONSTRUCTOR) 496 return; 497 498 len = CONSTRUCTOR_NELTS(init); 499 if (!len) 500 return; 501 502 lastval = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->value; 503 lastidx = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->index; 504 505 for (field = TYPE_FIELDS(TREE_TYPE(decl)); TREE_CHAIN(field); field = TREE_CHAIN(field)) 506 ; 507 508 if (lastidx != field) 509 return; 510 511 if (TREE_CODE(lastval) != STRING_CST) { 512 error("Only string constants are supported as initializers " 513 "for randomized structures with flexible arrays"); 514 return; 515 } 516 517 flexsize = bitsize_int(TREE_STRING_LENGTH(lastval) * 518 tree_to_uhwi(TYPE_SIZE(TREE_TYPE(TREE_TYPE(lastval))))); 519 520 DECL_SIZE(decl) = size_binop(PLUS_EXPR, TYPE_SIZE(type), flexsize); 521 522 return; 523 } 524 525 526 static void randomize_layout_finish_decl(void *event_data, void *data) 527 { 528 tree decl = (tree)event_data; 529 tree type; 530 531 if (decl == NULL_TREE || decl == error_mark_node) 532 return; 533 534 type = TREE_TYPE(decl); 535 536 if (TREE_CODE(decl) != VAR_DECL) 537 return; 538 539 if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE) 540 return; 541 542 if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type))) 543 return; 544 545 DECL_SIZE(decl) = 0; 546 DECL_SIZE_UNIT(decl) = 0; 547 SET_DECL_ALIGN(decl, 0); 548 SET_DECL_MODE (decl, VOIDmode); 549 SET_DECL_RTL(decl, 0); 550 update_decl_size(decl); 551 layout_decl(decl, 0); 552 } 553 554 static void finish_type(void *event_data, void *data) 555 { 556 tree type = (tree)event_data; 557 558 if (type == NULL_TREE || type == error_mark_node) 559 return; 560 561 if (TREE_CODE(type) != RECORD_TYPE) 562 return; 563 564 if (TYPE_FIELDS(type) == NULL_TREE) 565 return; 566 567 if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type))) 568 return; 569 570 #ifdef __DEBUG_PLUGIN 571 fprintf(stderr, "Calling randomize_type on %s\n", ORIG_TYPE_NAME(type)); 572 #endif 573 #ifdef __DEBUG_VERBOSE 574 debug_tree(type); 575 #endif 576 randomize_type(type); 577 578 return; 579 } 580 581 static struct attribute_spec randomize_layout_attr = { }; 582 static struct attribute_spec no_randomize_layout_attr = { }; 583 static struct attribute_spec randomize_considered_attr = { }; 584 static struct attribute_spec randomize_performed_attr = { }; 585 586 static void register_attributes(void *event_data, void *data) 587 { 588 randomize_layout_attr.name = "randomize_layout"; 589 randomize_layout_attr.type_required = true; 590 randomize_layout_attr.handler = handle_randomize_layout_attr; 591 randomize_layout_attr.affects_type_identity = true; 592 593 no_randomize_layout_attr.name = "no_randomize_layout"; 594 no_randomize_layout_attr.type_required = true; 595 no_randomize_layout_attr.handler = handle_randomize_layout_attr; 596 no_randomize_layout_attr.affects_type_identity = true; 597 598 randomize_considered_attr.name = "randomize_considered"; 599 randomize_considered_attr.type_required = true; 600 randomize_considered_attr.handler = handle_randomize_considered_attr; 601 602 randomize_performed_attr.name = "randomize_performed"; 603 randomize_performed_attr.type_required = true; 604 randomize_performed_attr.handler = handle_randomize_performed_attr; 605 606 register_attribute(&randomize_layout_attr); 607 register_attribute(&no_randomize_layout_attr); 608 register_attribute(&randomize_considered_attr); 609 register_attribute(&randomize_performed_attr); 610 } 611 612 static void check_bad_casts_in_constructor(tree var, tree init) 613 { 614 unsigned HOST_WIDE_INT idx; 615 tree field, val; 616 tree field_type, val_type; 617 618 FOR_EACH_CONSTRUCTOR_ELT(CONSTRUCTOR_ELTS(init), idx, field, val) { 619 if (TREE_CODE(val) == CONSTRUCTOR) { 620 check_bad_casts_in_constructor(var, val); 621 continue; 622 } 623 624 /* pipacs' plugin creates franken-arrays that differ from those produced by 625 normal code which all have valid 'field' trees. work around this */ 626 if (field == NULL_TREE) 627 continue; 628 field_type = TREE_TYPE(field); 629 val_type = TREE_TYPE(val); 630 631 if (TREE_CODE(field_type) != POINTER_TYPE || TREE_CODE(val_type) != POINTER_TYPE) 632 continue; 633 634 if (field_type == val_type) 635 continue; 636 637 field_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(field_type)))); 638 val_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(val_type)))); 639 640 if (field_type == void_type_node) 641 continue; 642 if (field_type == val_type) 643 continue; 644 if (TREE_CODE(val_type) != RECORD_TYPE) 645 continue; 646 647 if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(val_type))) 648 continue; 649 MISMATCH(DECL_SOURCE_LOCATION(var), "constructor\n", TYPE_MAIN_VARIANT(field_type), TYPE_MAIN_VARIANT(val_type)); 650 } 651 } 652 653 /* derived from the constify plugin */ 654 static void check_global_variables(void *event_data, void *data) 655 { 656 struct varpool_node *node; 657 tree init; 658 659 FOR_EACH_VARIABLE(node) { 660 tree var = NODE_DECL(node); 661 init = DECL_INITIAL(var); 662 if (init == NULL_TREE) 663 continue; 664 665 if (TREE_CODE(init) != CONSTRUCTOR) 666 continue; 667 668 check_bad_casts_in_constructor(var, init); 669 } 670 } 671 672 static bool dominated_by_is_err(const_tree rhs, basic_block bb) 673 { 674 basic_block dom; 675 gimple dom_stmt; 676 gimple call_stmt; 677 const_tree dom_lhs; 678 const_tree poss_is_err_cond; 679 const_tree poss_is_err_func; 680 const_tree is_err_arg; 681 682 dom = get_immediate_dominator(CDI_DOMINATORS, bb); 683 if (!dom) 684 return false; 685 686 dom_stmt = last_stmt(dom); 687 if (!dom_stmt) 688 return false; 689 690 if (gimple_code(dom_stmt) != GIMPLE_COND) 691 return false; 692 693 if (gimple_cond_code(dom_stmt) != NE_EXPR) 694 return false; 695 696 if (!integer_zerop(gimple_cond_rhs(dom_stmt))) 697 return false; 698 699 poss_is_err_cond = gimple_cond_lhs(dom_stmt); 700 701 if (TREE_CODE(poss_is_err_cond) != SSA_NAME) 702 return false; 703 704 call_stmt = SSA_NAME_DEF_STMT(poss_is_err_cond); 705 706 if (gimple_code(call_stmt) != GIMPLE_CALL) 707 return false; 708 709 dom_lhs = gimple_get_lhs(call_stmt); 710 poss_is_err_func = gimple_call_fndecl(call_stmt); 711 if (!poss_is_err_func) 712 return false; 713 if (dom_lhs != poss_is_err_cond) 714 return false; 715 if (strcmp(DECL_NAME_POINTER(poss_is_err_func), "IS_ERR")) 716 return false; 717 718 is_err_arg = gimple_call_arg(call_stmt, 0); 719 if (!is_err_arg) 720 return false; 721 722 if (is_err_arg != rhs) 723 return false; 724 725 return true; 726 } 727 728 static void handle_local_var_initializers(void) 729 { 730 tree var; 731 unsigned int i; 732 733 FOR_EACH_LOCAL_DECL(cfun, i, var) { 734 tree init = DECL_INITIAL(var); 735 if (!init) 736 continue; 737 if (TREE_CODE(init) != CONSTRUCTOR) 738 continue; 739 check_bad_casts_in_constructor(var, init); 740 } 741 } 742 743 static bool type_name_eq(gimple stmt, const_tree type_tree, const char *wanted_name) 744 { 745 const char *type_name; 746 747 if (type_tree == NULL_TREE) 748 return false; 749 750 switch (TREE_CODE(type_tree)) { 751 case RECORD_TYPE: 752 type_name = TYPE_NAME_POINTER(type_tree); 753 break; 754 case INTEGER_TYPE: 755 if (TYPE_PRECISION(type_tree) == CHAR_TYPE_SIZE) 756 type_name = "char"; 757 else { 758 INFORM(gimple_location(stmt), "found non-char INTEGER_TYPE cast comparison: %qT\n", type_tree); 759 debug_tree(type_tree); 760 return false; 761 } 762 break; 763 case POINTER_TYPE: 764 if (TREE_CODE(TREE_TYPE(type_tree)) == VOID_TYPE) { 765 type_name = "void *"; 766 break; 767 } else { 768 INFORM(gimple_location(stmt), "found non-void POINTER_TYPE cast comparison %qT\n", type_tree); 769 debug_tree(type_tree); 770 return false; 771 } 772 default: 773 INFORM(gimple_location(stmt), "unhandled cast comparison: %qT\n", type_tree); 774 debug_tree(type_tree); 775 return false; 776 } 777 778 return strcmp(type_name, wanted_name) == 0; 779 } 780 781 static bool whitelisted_cast(gimple stmt, const_tree lhs_tree, const_tree rhs_tree) 782 { 783 const struct whitelist_entry *entry; 784 expanded_location xloc = expand_location(gimple_location(stmt)); 785 786 for (entry = whitelist; entry->pathname; entry++) { 787 if (!strstr(xloc.file, entry->pathname)) 788 continue; 789 790 if (type_name_eq(stmt, lhs_tree, entry->lhs) && type_name_eq(stmt, rhs_tree, entry->rhs)) 791 return true; 792 } 793 794 return false; 795 } 796 797 /* 798 * iterate over all statements to find "bad" casts: 799 * those where the address of the start of a structure is cast 800 * to a pointer of a structure of a different type, or a 801 * structure pointer type is cast to a different structure pointer type 802 */ 803 static unsigned int find_bad_casts_execute(void) 804 { 805 basic_block bb; 806 807 handle_local_var_initializers(); 808 809 FOR_EACH_BB_FN(bb, cfun) { 810 gimple_stmt_iterator gsi; 811 812 for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) { 813 gimple stmt; 814 const_tree lhs; 815 const_tree lhs_type; 816 const_tree rhs1; 817 const_tree rhs_type; 818 const_tree ptr_lhs_type; 819 const_tree ptr_rhs_type; 820 const_tree op0; 821 const_tree op0_type; 822 enum tree_code rhs_code; 823 824 stmt = gsi_stmt(gsi); 825 826 #ifdef __DEBUG_PLUGIN 827 #ifdef __DEBUG_VERBOSE 828 debug_gimple_stmt(stmt); 829 debug_tree(gimple_get_lhs(stmt)); 830 #endif 831 #endif 832 833 if (gimple_code(stmt) != GIMPLE_ASSIGN) 834 continue; 835 836 #ifdef __DEBUG_PLUGIN 837 #ifdef __DEBUG_VERBOSE 838 debug_tree(gimple_assign_rhs1(stmt)); 839 #endif 840 #endif 841 842 843 rhs_code = gimple_assign_rhs_code(stmt); 844 845 if (rhs_code != ADDR_EXPR && rhs_code != SSA_NAME) 846 continue; 847 848 lhs = gimple_get_lhs(stmt); 849 lhs_type = TREE_TYPE(lhs); 850 rhs1 = gimple_assign_rhs1(stmt); 851 rhs_type = TREE_TYPE(rhs1); 852 853 if (TREE_CODE(rhs_type) != POINTER_TYPE || 854 TREE_CODE(lhs_type) != POINTER_TYPE) 855 continue; 856 857 ptr_lhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(lhs_type)))); 858 ptr_rhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(rhs_type)))); 859 860 if (ptr_rhs_type == void_type_node) 861 continue; 862 863 if (ptr_lhs_type == void_type_node) 864 continue; 865 866 if (dominated_by_is_err(rhs1, bb)) 867 continue; 868 869 if (TREE_CODE(ptr_rhs_type) != RECORD_TYPE) { 870 #ifndef __DEBUG_PLUGIN 871 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_lhs_type))) 872 #endif 873 { 874 if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type)) 875 MISMATCH(gimple_location(stmt), "rhs", ptr_lhs_type, ptr_rhs_type); 876 } 877 continue; 878 } 879 880 if (rhs_code == SSA_NAME && ptr_lhs_type == ptr_rhs_type) 881 continue; 882 883 if (rhs_code == ADDR_EXPR) { 884 op0 = TREE_OPERAND(rhs1, 0); 885 886 if (op0 == NULL_TREE) 887 continue; 888 889 if (TREE_CODE(op0) != VAR_DECL) 890 continue; 891 892 op0_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(op0)))); 893 if (op0_type == ptr_lhs_type) 894 continue; 895 896 #ifndef __DEBUG_PLUGIN 897 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(op0_type))) 898 #endif 899 { 900 if (!whitelisted_cast(stmt, ptr_lhs_type, op0_type)) 901 MISMATCH(gimple_location(stmt), "op0", ptr_lhs_type, op0_type); 902 } 903 } else { 904 const_tree ssa_name_var = SSA_NAME_VAR(rhs1); 905 /* skip bogus type casts introduced by container_of */ 906 if (ssa_name_var != NULL_TREE && DECL_NAME(ssa_name_var) && 907 !strcmp((const char *)DECL_NAME_POINTER(ssa_name_var), "__mptr")) 908 continue; 909 #ifndef __DEBUG_PLUGIN 910 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_rhs_type))) 911 #endif 912 { 913 if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type)) 914 MISMATCH(gimple_location(stmt), "ssa", ptr_lhs_type, ptr_rhs_type); 915 } 916 } 917 918 } 919 } 920 return 0; 921 } 922 923 #define PASS_NAME find_bad_casts 924 #define NO_GATE 925 #define TODO_FLAGS_FINISH TODO_dump_func 926 #include "gcc-generate-gimple-pass.h" 927 928 __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version) 929 { 930 int i; 931 const char * const plugin_name = plugin_info->base_name; 932 const int argc = plugin_info->argc; 933 const struct plugin_argument * const argv = plugin_info->argv; 934 bool enable = true; 935 int obtained_seed = 0; 936 struct register_pass_info find_bad_casts_pass_info; 937 938 find_bad_casts_pass_info.pass = make_find_bad_casts_pass(); 939 find_bad_casts_pass_info.reference_pass_name = "ssa"; 940 find_bad_casts_pass_info.ref_pass_instance_number = 1; 941 find_bad_casts_pass_info.pos_op = PASS_POS_INSERT_AFTER; 942 943 if (!plugin_default_version_check(version, &gcc_version)) { 944 error(G_("incompatible gcc/plugin versions")); 945 return 1; 946 } 947 948 if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) { 949 inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name); 950 enable = false; 951 } 952 953 for (i = 0; i < argc; ++i) { 954 if (!strcmp(argv[i].key, "disable")) { 955 enable = false; 956 continue; 957 } 958 if (!strcmp(argv[i].key, "performance-mode")) { 959 performance_mode = 1; 960 continue; 961 } 962 error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key); 963 } 964 965 if (strlen(randstruct_seed) != 64) { 966 error(G_("invalid seed value supplied for %s plugin"), plugin_name); 967 return 1; 968 } 969 obtained_seed = sscanf(randstruct_seed, "%016llx%016llx%016llx%016llx", 970 &shuffle_seed[0], &shuffle_seed[1], &shuffle_seed[2], &shuffle_seed[3]); 971 if (obtained_seed != 4) { 972 error(G_("Invalid seed supplied for %s plugin"), plugin_name); 973 return 1; 974 } 975 976 register_callback(plugin_name, PLUGIN_INFO, NULL, &randomize_layout_plugin_info); 977 if (enable) { 978 register_callback(plugin_name, PLUGIN_ALL_IPA_PASSES_START, check_global_variables, NULL); 979 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &find_bad_casts_pass_info); 980 register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL); 981 register_callback(plugin_name, PLUGIN_FINISH_DECL, randomize_layout_finish_decl, NULL); 982 } 983 register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL); 984 985 return 0; 986 } 987