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