scripts/gcc-plugins/randomize_layout_plugin.c

   1 /*
   2  * Copyright 2014-2016 by Open Source Security, Inc., Brad Spengler <spender@grsecurity.net>
   3  *                   and PaX Team <pageexec@freemail.hu>
   4  * Licensed under the GPL v2
   5  *
   6  * Note: the choice of the license means that the compilation process is
   7  *       NOT 'eligible' as defined by gcc's library exception to the GPL v3,
   8  *       but for the kernel it doesn't matter since it doesn't link against
   9  *       any of the gcc libraries
  10  *
  11  * Usage:
  12  * $ # for 4.5/4.6/C based 4.7
  13  * $ gcc -I`gcc -print-file-name=plugin`/include -I`gcc -print-file-name=plugin`/include/c-family -fPIC -shared -O2 -o randomize_layout_plugin.so randomize_layout_plugin.c
  14  * $ # for C++ based 4.7/4.8+
  15  * $ g++ -I`g++ -print-file-name=plugin`/include -I`g++ -print-file-name=plugin`/include/c-family -fPIC -shared -O2 -o randomize_layout_plugin.so randomize_layout_plugin.c
  16  * $ gcc -fplugin=./randomize_layout_plugin.so test.c -O2
  17  */
  18
  19 #include "gcc-common.h"
  20 #include "randomize_layout_seed.h"
  21
  22 #if BUILDING_GCC_MAJOR < 4 || (BUILDING_GCC_MAJOR == 4 && BUILDING_GCC_MINOR < 7)
  23 #error "The RANDSTRUCT plugin requires GCC 4.7 or newer."
  24 #endif
  25
  26 #define ORIG_TYPE_NAME(node) \
  27         (TYPE_NAME(TYPE_MAIN_VARIANT(node)) != NULL_TREE ? ((const unsigned char *)IDENTIFIER_POINTER(TYPE_NAME(TYPE_MAIN_VARIANT(node)))) : (const unsigned char *)"anonymous")
  28
  29 #define INFORM(loc, msg, ...)   inform(loc, "randstruct: " msg, ##__VA_ARGS__)
  30 #define MISMATCH(loc, how, ...) INFORM(loc, "casting between randomized structure pointer types (" how "): %qT and %qT\n", __VA_ARGS__)
  31
  32 __visible int plugin_is_GPL_compatible;
  33
  34 static int performance_mode;
  35
  36 static struct plugin_info randomize_layout_plugin_info = {
  37         .version        = PLUGIN_VERSION,
  38         .help           = "disable\t\t\tdo not activate plugin\n"
  39                           "performance-mode\tenable cacheline-aware layout randomization\n"
  40 };
  41
  42 /* from old Linux dcache.h */
  43 static inline unsigned long
  44 partial_name_hash(unsigned long c, unsigned long prevhash)
  45 {
  46         return (prevhash + (c << 4) + (c >> 4)) * 11;
  47 }
  48 static inline unsigned int
  49 name_hash(const unsigned char *name)
  50 {
  51         unsigned long hash = 0;
  52         unsigned int len = strlen((const char *)name);
  53         while (len--)
  54                 hash = partial_name_hash(*name++, hash);
  55         return (unsigned int)hash;
  56 }
  57
  58 static tree handle_randomize_layout_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
  59 {
  60         tree type;
  61
  62         *no_add_attrs = true;
  63         if (TREE_CODE(*node) == FUNCTION_DECL) {
  64                 error("%qE attribute does not apply to functions (%qF)", name, *node);
  65                 return NULL_TREE;
  66         }
  67
  68         if (TREE_CODE(*node) == PARM_DECL) {
  69                 error("%qE attribute does not apply to function parameters (%qD)", name, *node);
  70                 return NULL_TREE;
  71         }
  72
  73         if (TREE_CODE(*node) == VAR_DECL) {
  74                 error("%qE attribute does not apply to variables (%qD)", name, *node);
  75                 return NULL_TREE;
  76         }
  77
  78         if (TYPE_P(*node)) {
  79                 type = *node;
  80         } else {
  81                 gcc_assert(TREE_CODE(*node) == TYPE_DECL);
  82                 type = TREE_TYPE(*node);
  83         }
  84
  85         if (TREE_CODE(type) != RECORD_TYPE) {
  86                 error("%qE attribute used on %qT applies to struct types only", name, type);
  87                 return NULL_TREE;
  88         }
  89
  90         if (lookup_attribute(IDENTIFIER_POINTER(name), TYPE_ATTRIBUTES(type))) {
  91                 error("%qE attribute is already applied to the type %qT", name, type);
  92                 return NULL_TREE;
  93         }
  94
  95         *no_add_attrs = false;
  96
  97         return NULL_TREE;
  98 }
  99
 100 /* set on complete types that we don't need to inspect further at all */
 101 static tree handle_randomize_considered_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
 102 {
 103         *no_add_attrs = false;
 104         return NULL_TREE;
 105 }
 106
 107 /*
 108  * set on types that we've performed a shuffle on, to prevent re-shuffling
 109  * this does not preclude us from inspecting its fields for potential shuffles
 110  */
 111 static tree handle_randomize_performed_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  * 64bit variant of Bob Jenkins' public domain PRNG
 119  * 256 bits of internal state
 120  */
 121
 122 typedef unsigned long long u64;
 123
 124 typedef struct ranctx { u64 a; u64 b; u64 c; u64 d; } ranctx;
 125
 126 #define rot(x,k) (((x)<<(k))|((x)>>(64-(k))))
 127 static u64 ranval(ranctx *x) {
 128         u64 e = x->a - rot(x->b, 7);
 129         x->a = x->b ^ rot(x->c, 13);
 130         x->b = x->c + rot(x->d, 37);
 131         x->c = x->d + e;
 132         x->d = e + x->a;
 133         return x->d;
 134 }
 135
 136 static void raninit(ranctx *x, u64 *seed) {
 137         int i;
 138
 139         x->a = seed[0];
 140         x->b = seed[1];
 141         x->c = seed[2];
 142         x->d = seed[3];
 143
 144         for (i=0; i < 30; ++i)
 145                 (void)ranval(x);
 146 }
 147
 148 static u64 shuffle_seed[4];
 149
 150 struct partition_group {
 151         tree tree_start;
 152         unsigned long start;
 153         unsigned long length;
 154 };
 155
 156 static void partition_struct(tree *fields, unsigned long length, struct partition_group *size_groups, unsigned long *num_groups)
 157 {
 158         unsigned long i;
 159         unsigned long accum_size = 0;
 160         unsigned long accum_length = 0;
 161         unsigned long group_idx = 0;
 162
 163         gcc_assert(length < INT_MAX);
 164
 165         memset(size_groups, 0, sizeof(struct partition_group) * length);
 166
 167         for (i = 0; i < length; i++) {
 168                 if (size_groups[group_idx].tree_start == NULL_TREE) {
 169                         size_groups[group_idx].tree_start = fields[i];
 170                         size_groups[group_idx].start = i;
 171                         accum_length = 0;
 172                         accum_size = 0;
 173                 }
 174                 accum_size += (unsigned long)int_size_in_bytes(TREE_TYPE(fields[i]));
 175                 accum_length++;
 176                 if (accum_size >= 64) {
 177                         size_groups[group_idx].length = accum_length;
 178                         accum_length = 0;
 179                         group_idx++;
 180                 }
 181         }
 182
 183         if (size_groups[group_idx].tree_start != NULL_TREE &&
 184             !size_groups[group_idx].length) {
 185                 size_groups[group_idx].length = accum_length;
 186                 group_idx++;
 187         }
 188
 189         *num_groups = group_idx;
 190 }
 191
 192 static void performance_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
 193 {
 194         unsigned long i, x;
 195         struct partition_group size_group[length];
 196         unsigned long num_groups = 0;
 197         unsigned long randnum;
 198
 199         partition_struct(newtree, length, (struct partition_group *)&size_group, &num_groups);
 200         for (i = num_groups - 1; i > 0; i--) {
 201                 struct partition_group tmp;
 202                 randnum = ranval(prng_state) % (i + 1);
 203                 tmp = size_group[i];
 204                 size_group[i] = size_group[randnum];
 205                 size_group[randnum] = tmp;
 206         }
 207
 208         for (x = 0; x < num_groups; x++) {
 209                 for (i = size_group[x].start + size_group[x].length - 1; i > size_group[x].start; i--) {
 210                         tree tmp;
 211                         if (DECL_BIT_FIELD_TYPE(newtree[i]))
 212                                 continue;
 213                         randnum = ranval(prng_state) % (i + 1);
 214                         // we could handle this case differently if desired
 215                         if (DECL_BIT_FIELD_TYPE(newtree[randnum]))
 216                                 continue;
 217                         tmp = newtree[i];
 218                         newtree[i] = newtree[randnum];
 219                         newtree[randnum] = tmp;
 220                 }
 221         }
 222 }
 223
 224 static void full_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
 225 {
 226         unsigned long i, randnum;
 227
 228         for (i = length - 1; i > 0; i--) {
 229                 tree tmp;
 230                 randnum = ranval(prng_state) % (i + 1);
 231                 tmp = newtree[i];
 232                 newtree[i] = newtree[randnum];
 233                 newtree[randnum] = tmp;
 234         }
 235 }
 236
 237 /* modern in-place Fisher-Yates shuffle */
 238 static void shuffle(const_tree type, tree *newtree, unsigned long length)
 239 {
 240         unsigned long i;
 241         u64 seed[4];
 242         ranctx prng_state;
 243         const unsigned char *structname;
 244
 245         if (length == 0)
 246                 return;
 247
 248         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
 249
 250         structname = ORIG_TYPE_NAME(type);
 251
 252 #ifdef __DEBUG_PLUGIN
 253         fprintf(stderr, "Shuffling struct %s %p\n", (const char *)structname, type);
 254 #ifdef __DEBUG_VERBOSE
 255         debug_tree((tree)type);
 256 #endif
 257 #endif
 258
 259         for (i = 0; i < 4; i++) {
 260                 seed[i] = shuffle_seed[i];
 261                 seed[i] ^= name_hash(structname);
 262         }
 263
 264         raninit(&prng_state, (u64 *)&seed);
 265
 266         if (performance_mode)
 267                 performance_shuffle(newtree, length, &prng_state);
 268         else
 269                 full_shuffle(newtree, length, &prng_state);
 270 }
 271
 272 static bool is_flexible_array(const_tree field)
 273 {
 274         const_tree fieldtype;
 275         const_tree typesize;
 276         const_tree elemtype;
 277         const_tree elemsize;
 278
 279         fieldtype = TREE_TYPE(field);
 280         typesize = TYPE_SIZE(fieldtype);
 281
 282         if (TREE_CODE(fieldtype) != ARRAY_TYPE)
 283                 return false;
 284
 285         elemtype = TREE_TYPE(fieldtype);
 286         elemsize = TYPE_SIZE(elemtype);
 287
 288         /* size of type is represented in bits */
 289
 290         if (typesize == NULL_TREE && TYPE_DOMAIN(fieldtype) != NULL_TREE &&
 291             TYPE_MAX_VALUE(TYPE_DOMAIN(fieldtype)) == NULL_TREE)
 292                 return true;
 293
 294         if (typesize != NULL_TREE &&
 295             (TREE_CONSTANT(typesize) && (!tree_to_uhwi(typesize) ||
 296              tree_to_uhwi(typesize) == tree_to_uhwi(elemsize))))
 297                 return true;
 298
 299         return false;
 300 }
 301
 302 static int relayout_struct(tree type)
 303 {
 304         unsigned long num_fields = (unsigned long)list_length(TYPE_FIELDS(type));
 305         unsigned long shuffle_length = num_fields;
 306         tree field;
 307         tree newtree[num_fields];
 308         unsigned long i;
 309         tree list;
 310         tree variant;
 311         tree main_variant;
 312         expanded_location xloc;
 313         bool has_flexarray = false;
 314
 315         if (TYPE_FIELDS(type) == NULL_TREE)
 316                 return 0;
 317
 318         if (num_fields < 2)
 319                 return 0;
 320
 321         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
 322
 323         gcc_assert(num_fields < INT_MAX);
 324
 325         if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)) ||
 326             lookup_attribute("no_randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))))
 327                 return 0;
 328
 329         /* Workaround for 3rd-party VirtualBox source that we can't modify ourselves */
 330         if (!strcmp((const char *)ORIG_TYPE_NAME(type), "INTNETTRUNKFACTORY") ||
 331             !strcmp((const char *)ORIG_TYPE_NAME(type), "RAWPCIFACTORY"))
 332                 return 0;
 333
 334         /* throw out any structs in uapi */
 335         xloc = expand_location(DECL_SOURCE_LOCATION(TYPE_FIELDS(type)));
 336
 337         if (strstr(xloc.file, "/uapi/"))
 338                 error(G_("attempted to randomize userland API struct %s"), ORIG_TYPE_NAME(type));
 339
 340         for (field = TYPE_FIELDS(type), i = 0; field; field = TREE_CHAIN(field), i++) {
 341                 gcc_assert(TREE_CODE(field) == FIELD_DECL);
 342                 newtree[i] = field;
 343         }
 344
 345         /*
 346          * enforce that we don't randomize the layout of the last
 347          * element of a struct if it's a 0 or 1-length array
 348          * or a proper flexible array
 349          */
 350         if (is_flexible_array(newtree[num_fields - 1])) {
 351                 has_flexarray = true;
 352                 shuffle_length--;
 353         }
 354
 355         shuffle(type, (tree *)newtree, shuffle_length);
 356
 357         /*
 358          * set up a bogus anonymous struct field designed to error out on unnamed struct initializers
 359          * as gcc provides no other way to detect such code
 360          */
 361         list = make_node(FIELD_DECL);
 362         TREE_CHAIN(list) = newtree[0];
 363         TREE_TYPE(list) = void_type_node;
 364         DECL_SIZE(list) = bitsize_zero_node;
 365         DECL_NONADDRESSABLE_P(list) = 1;
 366         DECL_FIELD_BIT_OFFSET(list) = bitsize_zero_node;
 367         DECL_SIZE_UNIT(list) = size_zero_node;
 368         DECL_FIELD_OFFSET(list) = size_zero_node;
 369         DECL_CONTEXT(list) = type;
 370         // to satisfy the constify plugin
 371         TREE_READONLY(list) = 1;
 372
 373         for (i = 0; i < num_fields - 1; i++)
 374                 TREE_CHAIN(newtree[i]) = newtree[i+1];
 375         TREE_CHAIN(newtree[num_fields - 1]) = NULL_TREE;
 376
 377         main_variant = TYPE_MAIN_VARIANT(type);
 378         for (variant = main_variant; variant; variant = TYPE_NEXT_VARIANT(variant)) {
 379                 TYPE_FIELDS(variant) = list;
 380                 TYPE_ATTRIBUTES(variant) = copy_list(TYPE_ATTRIBUTES(variant));
 381                 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("randomize_performed"), NULL_TREE, TYPE_ATTRIBUTES(variant));
 382                 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("designated_init"), NULL_TREE, TYPE_ATTRIBUTES(variant));
 383                 if (has_flexarray)
 384                         TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("has_flexarray"), NULL_TREE, TYPE_ATTRIBUTES(type));
 385         }
 386
 387         /*
 388          * force a re-layout of the main variant
 389          * the TYPE_SIZE for all variants will be recomputed
 390          * by finalize_type_size()
 391          */
 392         TYPE_SIZE(main_variant) = NULL_TREE;
 393         layout_type(main_variant);
 394         gcc_assert(TYPE_SIZE(main_variant) != NULL_TREE);
 395
 396         return 1;
 397 }
 398
 399 /* from constify plugin */
 400 static const_tree get_field_type(const_tree field)
 401 {
 402         return strip_array_types(TREE_TYPE(field));
 403 }
 404
 405 /* from constify plugin */
 406 static bool is_fptr(const_tree fieldtype)
 407 {
 408         if (TREE_CODE(fieldtype) != POINTER_TYPE)
 409                 return false;
 410
 411         return TREE_CODE(TREE_TYPE(fieldtype)) == FUNCTION_TYPE;
 412 }
 413
 414 /* derived from constify plugin */
 415 static int is_pure_ops_struct(const_tree node)
 416 {
 417         const_tree field;
 418
 419         gcc_assert(TREE_CODE(node) == RECORD_TYPE || TREE_CODE(node) == UNION_TYPE);
 420
 421         for (field = TYPE_FIELDS(node); field; field = TREE_CHAIN(field)) {
 422                 const_tree fieldtype = get_field_type(field);
 423                 enum tree_code code = TREE_CODE(fieldtype);
 424
 425                 if (node == fieldtype)
 426                         continue;
 427
 428                 if (code == RECORD_TYPE || code == UNION_TYPE) {
 429                         if (!is_pure_ops_struct(fieldtype))
 430                                 return 0;
 431                         continue;
 432                 }
 433
 434                 if (!is_fptr(fieldtype))
 435                         return 0;
 436         }
 437
 438         return 1;
 439 }
 440
 441 static void randomize_type(tree type)
 442 {
 443         tree variant;
 444
 445         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
 446
 447         if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
 448                 return;
 449
 450         if (lookup_attribute("randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))) || is_pure_ops_struct(type))
 451                 relayout_struct(type);
 452
 453         for (variant = TYPE_MAIN_VARIANT(type); variant; variant = TYPE_NEXT_VARIANT(variant)) {
 454                 TYPE_ATTRIBUTES(type) = copy_list(TYPE_ATTRIBUTES(type));
 455                 TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("randomize_considered"), NULL_TREE, TYPE_ATTRIBUTES(type));
 456         }
 457 #ifdef __DEBUG_PLUGIN
 458         fprintf(stderr, "Marking randomize_considered on struct %s\n", ORIG_TYPE_NAME(type));
 459 #ifdef __DEBUG_VERBOSE
 460         debug_tree(type);
 461 #endif
 462 #endif
 463 }
 464
 465 static void update_decl_size(tree decl)
 466 {
 467         tree lastval, lastidx, field, init, type, flexsize;
 468         unsigned HOST_WIDE_INT len;
 469
 470         type = TREE_TYPE(decl);
 471
 472         if (!lookup_attribute("has_flexarray", TYPE_ATTRIBUTES(type)))
 473                 return;
 474
 475         init = DECL_INITIAL(decl);
 476         if (init == NULL_TREE || init == error_mark_node)
 477                 return;
 478
 479         if (TREE_CODE(init) != CONSTRUCTOR)
 480                 return;
 481
 482         len = CONSTRUCTOR_NELTS(init);
 483         if (!len)
 484                 return;
 485
 486         lastval = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->value;
 487         lastidx = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->index;
 488
 489         for (field = TYPE_FIELDS(TREE_TYPE(decl)); TREE_CHAIN(field); field = TREE_CHAIN(field))
 490                 ;
 491
 492         if (lastidx != field)
 493                 return;
 494
 495         if (TREE_CODE(lastval) != STRING_CST) {
 496                 error("Only string constants are supported as initializers "
 497                       "for randomized structures with flexible arrays");
 498                 return;
 499         }
 500
 501         flexsize = bitsize_int(TREE_STRING_LENGTH(lastval) *
 502                 tree_to_uhwi(TYPE_SIZE(TREE_TYPE(TREE_TYPE(lastval)))));
 503
 504         DECL_SIZE(decl) = size_binop(PLUS_EXPR, TYPE_SIZE(type), flexsize);
 505
 506         return;
 507 }
 508
 509
 510 static void randomize_layout_finish_decl(void *event_data, void *data)
 511 {
 512         tree decl = (tree)event_data;
 513         tree type;
 514
 515         if (decl == NULL_TREE || decl == error_mark_node)
 516                 return;
 517
 518         type = TREE_TYPE(decl);
 519
 520         if (TREE_CODE(decl) != VAR_DECL)
 521                 return;
 522
 523         if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
 524                 return;
 525
 526         if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)))
 527                 return;
 528
 529         DECL_SIZE(decl) = 0;
 530         DECL_SIZE_UNIT(decl) = 0;
 531         SET_DECL_ALIGN(decl, 0);
 532         SET_DECL_MODE (decl, VOIDmode);
 533         SET_DECL_RTL(decl, 0);
 534         update_decl_size(decl);
 535         layout_decl(decl, 0);
 536 }
 537
 538 static void finish_type(void *event_data, void *data)
 539 {
 540         tree type = (tree)event_data;
 541
 542         if (type == NULL_TREE || type == error_mark_node)
 543                 return;
 544
 545         if (TREE_CODE(type) != RECORD_TYPE)
 546                 return;
 547
 548         if (TYPE_FIELDS(type) == NULL_TREE)
 549                 return;
 550
 551         if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
 552                 return;
 553
 554 #ifdef __DEBUG_PLUGIN
 555         fprintf(stderr, "Calling randomize_type on %s\n", ORIG_TYPE_NAME(type));
 556 #endif
 557 #ifdef __DEBUG_VERBOSE
 558         debug_tree(type);
 559 #endif
 560         randomize_type(type);
 561
 562         return;
 563 }
 564
 565 static struct attribute_spec randomize_layout_attr = { };
 566 static struct attribute_spec no_randomize_layout_attr = { };
 567 static struct attribute_spec randomize_considered_attr = { };
 568 static struct attribute_spec randomize_performed_attr = { };
 569
 570 static void register_attributes(void *event_data, void *data)
 571 {
 572         randomize_layout_attr.name              = "randomize_layout";
 573         randomize_layout_attr.type_required     = true;
 574         randomize_layout_attr.handler           = handle_randomize_layout_attr;
 575         randomize_layout_attr.affects_type_identity = true;
 576
 577         no_randomize_layout_attr.name           = "no_randomize_layout";
 578         no_randomize_layout_attr.type_required  = true;
 579         no_randomize_layout_attr.handler        = handle_randomize_layout_attr;
 580         no_randomize_layout_attr.affects_type_identity = true;
 581
 582         randomize_considered_attr.name          = "randomize_considered";
 583         randomize_considered_attr.type_required = true;
 584         randomize_considered_attr.handler       = handle_randomize_considered_attr;
 585
 586         randomize_performed_attr.name           = "randomize_performed";
 587         randomize_performed_attr.type_required  = true;
 588         randomize_performed_attr.handler        = handle_randomize_performed_attr;
 589
 590         register_attribute(&randomize_layout_attr);
 591         register_attribute(&no_randomize_layout_attr);
 592         register_attribute(&randomize_considered_attr);
 593         register_attribute(&randomize_performed_attr);
 594 }
 595
 596 static void check_bad_casts_in_constructor(tree var, tree init)
 597 {
 598         unsigned HOST_WIDE_INT idx;
 599         tree field, val;
 600         tree field_type, val_type;
 601
 602         FOR_EACH_CONSTRUCTOR_ELT(CONSTRUCTOR_ELTS(init), idx, field, val) {
 603                 if (TREE_CODE(val) == CONSTRUCTOR) {
 604                         check_bad_casts_in_constructor(var, val);
 605                         continue;
 606                 }
 607
 608                 /* pipacs' plugin creates franken-arrays that differ from those produced by
 609                    normal code which all have valid 'field' trees. work around this */
 610                 if (field == NULL_TREE)
 611                         continue;
 612                 field_type = TREE_TYPE(field);
 613                 val_type = TREE_TYPE(val);
 614
 615                 if (TREE_CODE(field_type) != POINTER_TYPE || TREE_CODE(val_type) != POINTER_TYPE)
 616                         continue;
 617
 618                 if (field_type == val_type)
 619                         continue;
 620
 621                 field_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(field_type))));
 622                 val_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(val_type))));
 623
 624                 if (field_type == void_type_node)
 625                         continue;
 626                 if (field_type == val_type)
 627                         continue;
 628                 if (TREE_CODE(val_type) != RECORD_TYPE)
 629                         continue;
 630
 631                 if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(val_type)))
 632                         continue;
 633                 MISMATCH(DECL_SOURCE_LOCATION(var), "constructor\n", TYPE_MAIN_VARIANT(field_type), TYPE_MAIN_VARIANT(val_type));
 634         }
 635 }
 636
 637 /* derived from the constify plugin */
 638 static void check_global_variables(void *event_data, void *data)
 639 {
 640         struct varpool_node *node;
 641         tree init;
 642
 643         FOR_EACH_VARIABLE(node) {
 644                 tree var = NODE_DECL(node);
 645                 init = DECL_INITIAL(var);
 646                 if (init == NULL_TREE)
 647                         continue;
 648
 649                 if (TREE_CODE(init) != CONSTRUCTOR)
 650                         continue;
 651
 652                 check_bad_casts_in_constructor(var, init);
 653         }
 654 }
 655
 656 static bool dominated_by_is_err(const_tree rhs, basic_block bb)
 657 {
 658         basic_block dom;
 659         gimple dom_stmt;
 660         gimple call_stmt;
 661         const_tree dom_lhs;
 662         const_tree poss_is_err_cond;
 663         const_tree poss_is_err_func;
 664         const_tree is_err_arg;
 665
 666         dom = get_immediate_dominator(CDI_DOMINATORS, bb);
 667         if (!dom)
 668                 return false;
 669
 670         dom_stmt = last_stmt(dom);
 671         if (!dom_stmt)
 672                 return false;
 673
 674         if (gimple_code(dom_stmt) != GIMPLE_COND)
 675                 return false;
 676
 677         if (gimple_cond_code(dom_stmt) != NE_EXPR)
 678                 return false;
 679
 680         if (!integer_zerop(gimple_cond_rhs(dom_stmt)))
 681                 return false;
 682
 683         poss_is_err_cond = gimple_cond_lhs(dom_stmt);
 684
 685         if (TREE_CODE(poss_is_err_cond) != SSA_NAME)
 686                 return false;
 687
 688         call_stmt = SSA_NAME_DEF_STMT(poss_is_err_cond);
 689
 690         if (gimple_code(call_stmt) != GIMPLE_CALL)
 691                 return false;
 692
 693         dom_lhs = gimple_get_lhs(call_stmt);
 694         poss_is_err_func = gimple_call_fndecl(call_stmt);
 695         if (!poss_is_err_func)
 696                 return false;
 697         if (dom_lhs != poss_is_err_cond)
 698                 return false;
 699         if (strcmp(DECL_NAME_POINTER(poss_is_err_func), "IS_ERR"))
 700                 return false;
 701
 702         is_err_arg = gimple_call_arg(call_stmt, 0);
 703         if (!is_err_arg)
 704                 return false;
 705
 706         if (is_err_arg != rhs)
 707                 return false;
 708
 709         return true;
 710 }
 711
 712 static void handle_local_var_initializers(void)
 713 {
 714         tree var;
 715         unsigned int i;
 716
 717         FOR_EACH_LOCAL_DECL(cfun, i, var) {
 718                 tree init = DECL_INITIAL(var);
 719                 if (!init)
 720                         continue;
 721                 if (TREE_CODE(init) != CONSTRUCTOR)
 722                         continue;
 723                 check_bad_casts_in_constructor(var, init);
 724         }
 725 }
 726
 727 /*
 728  * iterate over all statements to find "bad" casts:
 729  * those where the address of the start of a structure is cast
 730  * to a pointer of a structure of a different type, or a
 731  * structure pointer type is cast to a different structure pointer type
 732  */
 733 static unsigned int find_bad_casts_execute(void)
 734 {
 735         basic_block bb;
 736
 737         handle_local_var_initializers();
 738
 739         FOR_EACH_BB_FN(bb, cfun) {
 740                 gimple_stmt_iterator gsi;
 741
 742                 for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
 743                         gimple stmt;
 744                         const_tree lhs;
 745                         const_tree lhs_type;
 746                         const_tree rhs1;
 747                         const_tree rhs_type;
 748                         const_tree ptr_lhs_type;
 749                         const_tree ptr_rhs_type;
 750                         const_tree op0;
 751                         const_tree op0_type;
 752                         enum tree_code rhs_code;
 753
 754                         stmt = gsi_stmt(gsi);
 755
 756 #ifdef __DEBUG_PLUGIN
 757 #ifdef __DEBUG_VERBOSE
 758                         debug_gimple_stmt(stmt);
 759                         debug_tree(gimple_get_lhs(stmt));
 760 #endif
 761 #endif
 762
 763                         if (gimple_code(stmt) != GIMPLE_ASSIGN)
 764                                 continue;
 765
 766 #ifdef __DEBUG_PLUGIN
 767 #ifdef __DEBUG_VERBOSE
 768                         debug_tree(gimple_assign_rhs1(stmt));
 769 #endif
 770 #endif
 771
 772
 773                         rhs_code = gimple_assign_rhs_code(stmt);
 774
 775                         if (rhs_code != ADDR_EXPR && rhs_code != SSA_NAME)
 776                                 continue;
 777
 778                         lhs = gimple_get_lhs(stmt);
 779                         lhs_type = TREE_TYPE(lhs);
 780                         rhs1 = gimple_assign_rhs1(stmt);
 781                         rhs_type = TREE_TYPE(rhs1);
 782
 783                         if (TREE_CODE(rhs_type) != POINTER_TYPE ||
 784                             TREE_CODE(lhs_type) != POINTER_TYPE)
 785                                 continue;
 786
 787                         ptr_lhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(lhs_type))));
 788                         ptr_rhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(rhs_type))));
 789
 790                         if (ptr_rhs_type == void_type_node)
 791                                 continue;
 792
 793                         if (ptr_lhs_type == void_type_node)
 794                                 continue;
 795
 796                         if (dominated_by_is_err(rhs1, bb))
 797                                 continue;
 798
 799                         if (TREE_CODE(ptr_rhs_type) != RECORD_TYPE) {
 800 #ifndef __DEBUG_PLUGIN
 801                                 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_lhs_type)))
 802 #endif
 803                                 MISMATCH(gimple_location(stmt), "rhs", ptr_lhs_type, ptr_rhs_type);
 804                                 continue;
 805                         }
 806
 807                         if (rhs_code == SSA_NAME && ptr_lhs_type == ptr_rhs_type)
 808                                 continue;
 809
 810                         if (rhs_code == ADDR_EXPR) {
 811                                 op0 = TREE_OPERAND(rhs1, 0);
 812
 813                                 if (op0 == NULL_TREE)
 814                                         continue;
 815
 816                                 if (TREE_CODE(op0) != VAR_DECL)
 817                                         continue;
 818
 819                                 op0_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(op0))));
 820                                 if (op0_type == ptr_lhs_type)
 821                                         continue;
 822
 823 #ifndef __DEBUG_PLUGIN
 824                                 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(op0_type)))
 825 #endif
 826                                 MISMATCH(gimple_location(stmt), "op0", ptr_lhs_type, op0_type);
 827                         } else {
 828                                 const_tree ssa_name_var = SSA_NAME_VAR(rhs1);
 829                                 /* skip bogus type casts introduced by container_of */
 830                                 if (ssa_name_var != NULL_TREE && DECL_NAME(ssa_name_var) &&
 831                                     !strcmp((const char *)DECL_NAME_POINTER(ssa_name_var), "__mptr"))
 832                                         continue;
 833 #ifndef __DEBUG_PLUGIN
 834                                 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_rhs_type)))
 835 #endif
 836                                 MISMATCH(gimple_location(stmt), "ssa", ptr_lhs_type, ptr_rhs_type);
 837                         }
 838
 839                 }
 840         }
 841         return 0;
 842 }
 843
 844 #define PASS_NAME find_bad_casts
 845 #define NO_GATE
 846 #define TODO_FLAGS_FINISH TODO_dump_func
 847 #include "gcc-generate-gimple-pass.h"
 848
 849 __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
 850 {
 851         int i;
 852         const char * const plugin_name = plugin_info->base_name;
 853         const int argc = plugin_info->argc;
 854         const struct plugin_argument * const argv = plugin_info->argv;
 855         bool enable = true;
 856         int obtained_seed = 0;
 857         struct register_pass_info find_bad_casts_pass_info;
 858
 859         find_bad_casts_pass_info.pass                   = make_find_bad_casts_pass();
 860         find_bad_casts_pass_info.reference_pass_name    = "ssa";
 861         find_bad_casts_pass_info.ref_pass_instance_number       = 1;
 862         find_bad_casts_pass_info.pos_op                 = PASS_POS_INSERT_AFTER;
 863
 864         if (!plugin_default_version_check(version, &gcc_version)) {
 865                 error(G_("incompatible gcc/plugin versions"));
 866                 return 1;
 867         }
 868
 869         if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
 870                 inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
 871                 enable = false;
 872         }
 873
 874         for (i = 0; i < argc; ++i) {
 875                 if (!strcmp(argv[i].key, "disable")) {
 876                         enable = false;
 877                         continue;
 878                 }
 879                 if (!strcmp(argv[i].key, "performance-mode")) {
 880                         performance_mode = 1;
 881                         continue;
 882                 }
 883                 error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
 884         }
 885
 886         if (strlen(randstruct_seed) != 64) {
 887                 error(G_("invalid seed value supplied for %s plugin"), plugin_name);
 888                 return 1;
 889         }
 890         obtained_seed = sscanf(randstruct_seed, "%016llx%016llx%016llx%016llx",
 891                 &shuffle_seed[0], &shuffle_seed[1], &shuffle_seed[2], &shuffle_seed[3]);
 892         if (obtained_seed != 4) {
 893                 error(G_("Invalid seed supplied for %s plugin"), plugin_name);
 894                 return 1;
 895         }
 896
 897         register_callback(plugin_name, PLUGIN_INFO, NULL, &randomize_layout_plugin_info);
 898         if (enable) {
 899                 register_callback(plugin_name, PLUGIN_ALL_IPA_PASSES_START, check_global_variables, NULL);
 900                 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &find_bad_casts_pass_info);
 901                 register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
 902                 register_callback(plugin_name, PLUGIN_FINISH_DECL, randomize_layout_finish_decl, NULL);
 903         }
 904         register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);
 905
 906         return 0;
 907 }