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