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, index;
 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
 201         /* FIXME: this group shuffle is currently a no-op. */
 202         for (i = num_groups - 1; i > 0; i--) {
 203                 struct partition_group tmp;
 204                 randnum = ranval(prng_state) % (i + 1);
 205                 tmp = size_group[i];
 206                 size_group[i] = size_group[randnum];
 207                 size_group[randnum] = tmp;
 208         }
 209
 210         for (x = 0; x < num_groups; x++) {
 211                 for (index = size_group[x].length - 1; index > 0; index--) {
 212                         tree tmp;
 213
 214                         i = size_group[x].start + index;
 215                         if (DECL_BIT_FIELD_TYPE(newtree[i]))
 216                                 continue;
 217                         randnum = ranval(prng_state) % (index + 1);
 218                         randnum += size_group[x].start;
 219                         // we could handle this case differently if desired
 220                         if (DECL_BIT_FIELD_TYPE(newtree[randnum]))
 221                                 continue;
 222                         tmp = newtree[i];
 223                         newtree[i] = newtree[randnum];
 224                         newtree[randnum] = tmp;
 225                 }
 226         }
 227 }
 228
 229 static void full_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
 230 {
 231         unsigned long i, randnum;
 232
 233         for (i = length - 1; i > 0; i--) {
 234                 tree tmp;
 235                 randnum = ranval(prng_state) % (i + 1);
 236                 tmp = newtree[i];
 237                 newtree[i] = newtree[randnum];
 238                 newtree[randnum] = tmp;
 239         }
 240 }
 241
 242 /* modern in-place Fisher-Yates shuffle */
 243 static void shuffle(const_tree type, tree *newtree, unsigned long length)
 244 {
 245         unsigned long i;
 246         u64 seed[4];
 247         ranctx prng_state;
 248         const unsigned char *structname;
 249
 250         if (length == 0)
 251                 return;
 252
 253         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
 254
 255         structname = ORIG_TYPE_NAME(type);
 256
 257 #ifdef __DEBUG_PLUGIN
 258         fprintf(stderr, "Shuffling struct %s %p\n", (const char *)structname, type);
 259 #ifdef __DEBUG_VERBOSE
 260         debug_tree((tree)type);
 261 #endif
 262 #endif
 263
 264         for (i = 0; i < 4; i++) {
 265                 seed[i] = shuffle_seed[i];
 266                 seed[i] ^= name_hash(structname);
 267         }
 268
 269         raninit(&prng_state, (u64 *)&seed);
 270
 271         if (performance_mode)
 272                 performance_shuffle(newtree, length, &prng_state);
 273         else
 274                 full_shuffle(newtree, length, &prng_state);
 275 }
 276
 277 static bool is_flexible_array(const_tree field)
 278 {
 279         const_tree fieldtype;
 280         const_tree typesize;
 281         const_tree elemtype;
 282         const_tree elemsize;
 283
 284         fieldtype = TREE_TYPE(field);
 285         typesize = TYPE_SIZE(fieldtype);
 286
 287         if (TREE_CODE(fieldtype) != ARRAY_TYPE)
 288                 return false;
 289
 290         elemtype = TREE_TYPE(fieldtype);
 291         elemsize = TYPE_SIZE(elemtype);
 292
 293         /* size of type is represented in bits */
 294
 295         if (typesize == NULL_TREE && TYPE_DOMAIN(fieldtype) != NULL_TREE &&
 296             TYPE_MAX_VALUE(TYPE_DOMAIN(fieldtype)) == NULL_TREE)
 297                 return true;
 298
 299         if (typesize != NULL_TREE &&
 300             (TREE_CONSTANT(typesize) && (!tree_to_uhwi(typesize) ||
 301              tree_to_uhwi(typesize) == tree_to_uhwi(elemsize))))
 302                 return true;
 303
 304         return false;
 305 }
 306
 307 static int relayout_struct(tree type)
 308 {
 309         unsigned long num_fields = (unsigned long)list_length(TYPE_FIELDS(type));
 310         unsigned long shuffle_length = num_fields;
 311         tree field;
 312         tree newtree[num_fields];
 313         unsigned long i;
 314         tree list;
 315         tree variant;
 316         tree main_variant;
 317         expanded_location xloc;
 318         bool has_flexarray = false;
 319
 320         if (TYPE_FIELDS(type) == NULL_TREE)
 321                 return 0;
 322
 323         if (num_fields < 2)
 324                 return 0;
 325
 326         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
 327
 328         gcc_assert(num_fields < INT_MAX);
 329
 330         if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)) ||
 331             lookup_attribute("no_randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))))
 332                 return 0;
 333
 334         /* Workaround for 3rd-party VirtualBox source that we can't modify ourselves */
 335         if (!strcmp((const char *)ORIG_TYPE_NAME(type), "INTNETTRUNKFACTORY") ||
 336             !strcmp((const char *)ORIG_TYPE_NAME(type), "RAWPCIFACTORY"))
 337                 return 0;
 338
 339         /* throw out any structs in uapi */
 340         xloc = expand_location(DECL_SOURCE_LOCATION(TYPE_FIELDS(type)));
 341
 342         if (strstr(xloc.file, "/uapi/"))
 343                 error(G_("attempted to randomize userland API struct %s"), ORIG_TYPE_NAME(type));
 344
 345         for (field = TYPE_FIELDS(type), i = 0; field; field = TREE_CHAIN(field), i++) {
 346                 gcc_assert(TREE_CODE(field) == FIELD_DECL);
 347                 newtree[i] = field;
 348         }
 349
 350         /*
 351          * enforce that we don't randomize the layout of the last
 352          * element of a struct if it's a 0 or 1-length array
 353          * or a proper flexible array
 354          */
 355         if (is_flexible_array(newtree[num_fields - 1])) {
 356                 has_flexarray = true;
 357                 shuffle_length--;
 358         }
 359
 360         shuffle(type, (tree *)newtree, shuffle_length);
 361
 362         /*
 363          * set up a bogus anonymous struct field designed to error out on unnamed struct initializers
 364          * as gcc provides no other way to detect such code
 365          */
 366         list = make_node(FIELD_DECL);
 367         TREE_CHAIN(list) = newtree[0];
 368         TREE_TYPE(list) = void_type_node;
 369         DECL_SIZE(list) = bitsize_zero_node;
 370         DECL_NONADDRESSABLE_P(list) = 1;
 371         DECL_FIELD_BIT_OFFSET(list) = bitsize_zero_node;
 372         DECL_SIZE_UNIT(list) = size_zero_node;
 373         DECL_FIELD_OFFSET(list) = size_zero_node;
 374         DECL_CONTEXT(list) = type;
 375         // to satisfy the constify plugin
 376         TREE_READONLY(list) = 1;
 377
 378         for (i = 0; i < num_fields - 1; i++)
 379                 TREE_CHAIN(newtree[i]) = newtree[i+1];
 380         TREE_CHAIN(newtree[num_fields - 1]) = NULL_TREE;
 381
 382         main_variant = TYPE_MAIN_VARIANT(type);
 383         for (variant = main_variant; variant; variant = TYPE_NEXT_VARIANT(variant)) {
 384                 TYPE_FIELDS(variant) = list;
 385                 TYPE_ATTRIBUTES(variant) = copy_list(TYPE_ATTRIBUTES(variant));
 386                 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("randomize_performed"), NULL_TREE, TYPE_ATTRIBUTES(variant));
 387                 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("designated_init"), NULL_TREE, TYPE_ATTRIBUTES(variant));
 388                 if (has_flexarray)
 389                         TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("has_flexarray"), NULL_TREE, TYPE_ATTRIBUTES(type));
 390         }
 391
 392         /*
 393          * force a re-layout of the main variant
 394          * the TYPE_SIZE for all variants will be recomputed
 395          * by finalize_type_size()
 396          */
 397         TYPE_SIZE(main_variant) = NULL_TREE;
 398         layout_type(main_variant);
 399         gcc_assert(TYPE_SIZE(main_variant) != NULL_TREE);
 400
 401         return 1;
 402 }
 403
 404 /* from constify plugin */
 405 static const_tree get_field_type(const_tree field)
 406 {
 407         return strip_array_types(TREE_TYPE(field));
 408 }
 409
 410 /* from constify plugin */
 411 static bool is_fptr(const_tree fieldtype)
 412 {
 413         if (TREE_CODE(fieldtype) != POINTER_TYPE)
 414                 return false;
 415
 416         return TREE_CODE(TREE_TYPE(fieldtype)) == FUNCTION_TYPE;
 417 }
 418
 419 /* derived from constify plugin */
 420 static int is_pure_ops_struct(const_tree node)
 421 {
 422         const_tree field;
 423
 424         gcc_assert(TREE_CODE(node) == RECORD_TYPE || TREE_CODE(node) == UNION_TYPE);
 425
 426         for (field = TYPE_FIELDS(node); field; field = TREE_CHAIN(field)) {
 427                 const_tree fieldtype = get_field_type(field);
 428                 enum tree_code code = TREE_CODE(fieldtype);
 429
 430                 if (node == fieldtype)
 431                         continue;
 432
 433                 if (code == RECORD_TYPE || code == UNION_TYPE) {
 434                         if (!is_pure_ops_struct(fieldtype))
 435                                 return 0;
 436                         continue;
 437                 }
 438
 439                 if (!is_fptr(fieldtype))
 440                         return 0;
 441         }
 442
 443         return 1;
 444 }
 445
 446 static void randomize_type(tree type)
 447 {
 448         tree variant;
 449
 450         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
 451
 452         if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
 453                 return;
 454
 455         if (lookup_attribute("randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))) || is_pure_ops_struct(type))
 456                 relayout_struct(type);
 457
 458         for (variant = TYPE_MAIN_VARIANT(type); variant; variant = TYPE_NEXT_VARIANT(variant)) {
 459                 TYPE_ATTRIBUTES(type) = copy_list(TYPE_ATTRIBUTES(type));
 460                 TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("randomize_considered"), NULL_TREE, TYPE_ATTRIBUTES(type));
 461         }
 462 #ifdef __DEBUG_PLUGIN
 463         fprintf(stderr, "Marking randomize_considered on struct %s\n", ORIG_TYPE_NAME(type));
 464 #ifdef __DEBUG_VERBOSE
 465         debug_tree(type);
 466 #endif
 467 #endif
 468 }
 469
 470 static void update_decl_size(tree decl)
 471 {
 472         tree lastval, lastidx, field, init, type, flexsize;
 473         unsigned HOST_WIDE_INT len;
 474
 475         type = TREE_TYPE(decl);
 476
 477         if (!lookup_attribute("has_flexarray", TYPE_ATTRIBUTES(type)))
 478                 return;
 479
 480         init = DECL_INITIAL(decl);
 481         if (init == NULL_TREE || init == error_mark_node)
 482                 return;
 483
 484         if (TREE_CODE(init) != CONSTRUCTOR)
 485                 return;
 486
 487         len = CONSTRUCTOR_NELTS(init);
 488         if (!len)
 489                 return;
 490
 491         lastval = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->value;
 492         lastidx = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->index;
 493
 494         for (field = TYPE_FIELDS(TREE_TYPE(decl)); TREE_CHAIN(field); field = TREE_CHAIN(field))
 495                 ;
 496
 497         if (lastidx != field)
 498                 return;
 499
 500         if (TREE_CODE(lastval) != STRING_CST) {
 501                 error("Only string constants are supported as initializers "
 502                       "for randomized structures with flexible arrays");
 503                 return;
 504         }
 505
 506         flexsize = bitsize_int(TREE_STRING_LENGTH(lastval) *
 507                 tree_to_uhwi(TYPE_SIZE(TREE_TYPE(TREE_TYPE(lastval)))));
 508
 509         DECL_SIZE(decl) = size_binop(PLUS_EXPR, TYPE_SIZE(type), flexsize);
 510
 511         return;
 512 }
 513
 514
 515 static void randomize_layout_finish_decl(void *event_data, void *data)
 516 {
 517         tree decl = (tree)event_data;
 518         tree type;
 519
 520         if (decl == NULL_TREE || decl == error_mark_node)
 521                 return;
 522
 523         type = TREE_TYPE(decl);
 524
 525         if (TREE_CODE(decl) != VAR_DECL)
 526                 return;
 527
 528         if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
 529                 return;
 530
 531         if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)))
 532                 return;
 533
 534         DECL_SIZE(decl) = 0;
 535         DECL_SIZE_UNIT(decl) = 0;
 536         SET_DECL_ALIGN(decl, 0);
 537         SET_DECL_MODE (decl, VOIDmode);
 538         SET_DECL_RTL(decl, 0);
 539         update_decl_size(decl);
 540         layout_decl(decl, 0);
 541 }
 542
 543 static void finish_type(void *event_data, void *data)
 544 {
 545         tree type = (tree)event_data;
 546
 547         if (type == NULL_TREE || type == error_mark_node)
 548                 return;
 549
 550         if (TREE_CODE(type) != RECORD_TYPE)
 551                 return;
 552
 553         if (TYPE_FIELDS(type) == NULL_TREE)
 554                 return;
 555
 556         if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
 557                 return;
 558
 559 #ifdef __DEBUG_PLUGIN
 560         fprintf(stderr, "Calling randomize_type on %s\n", ORIG_TYPE_NAME(type));
 561 #endif
 562 #ifdef __DEBUG_VERBOSE
 563         debug_tree(type);
 564 #endif
 565         randomize_type(type);
 566
 567         return;
 568 }
 569
 570 static struct attribute_spec randomize_layout_attr = { };
 571 static struct attribute_spec no_randomize_layout_attr = { };
 572 static struct attribute_spec randomize_considered_attr = { };
 573 static struct attribute_spec randomize_performed_attr = { };
 574
 575 static void register_attributes(void *event_data, void *data)
 576 {
 577         randomize_layout_attr.name              = "randomize_layout";
 578         randomize_layout_attr.type_required     = true;
 579         randomize_layout_attr.handler           = handle_randomize_layout_attr;
 580         randomize_layout_attr.affects_type_identity = true;
 581
 582         no_randomize_layout_attr.name           = "no_randomize_layout";
 583         no_randomize_layout_attr.type_required  = true;
 584         no_randomize_layout_attr.handler        = handle_randomize_layout_attr;
 585         no_randomize_layout_attr.affects_type_identity = true;
 586
 587         randomize_considered_attr.name          = "randomize_considered";
 588         randomize_considered_attr.type_required = true;
 589         randomize_considered_attr.handler       = handle_randomize_considered_attr;
 590
 591         randomize_performed_attr.name           = "randomize_performed";
 592         randomize_performed_attr.type_required  = true;
 593         randomize_performed_attr.handler        = handle_randomize_performed_attr;
 594
 595         register_attribute(&randomize_layout_attr);
 596         register_attribute(&no_randomize_layout_attr);
 597         register_attribute(&randomize_considered_attr);
 598         register_attribute(&randomize_performed_attr);
 599 }
 600
 601 static void check_bad_casts_in_constructor(tree var, tree init)
 602 {
 603         unsigned HOST_WIDE_INT idx;
 604         tree field, val;
 605         tree field_type, val_type;
 606
 607         FOR_EACH_CONSTRUCTOR_ELT(CONSTRUCTOR_ELTS(init), idx, field, val) {
 608                 if (TREE_CODE(val) == CONSTRUCTOR) {
 609                         check_bad_casts_in_constructor(var, val);
 610                         continue;
 611                 }
 612
 613                 /* pipacs' plugin creates franken-arrays that differ from those produced by
 614                    normal code which all have valid 'field' trees. work around this */
 615                 if (field == NULL_TREE)
 616                         continue;
 617                 field_type = TREE_TYPE(field);
 618                 val_type = TREE_TYPE(val);
 619
 620                 if (TREE_CODE(field_type) != POINTER_TYPE || TREE_CODE(val_type) != POINTER_TYPE)
 621                         continue;
 622
 623                 if (field_type == val_type)
 624                         continue;
 625
 626                 field_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(field_type))));
 627                 val_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(val_type))));
 628
 629                 if (field_type == void_type_node)
 630                         continue;
 631                 if (field_type == val_type)
 632                         continue;
 633                 if (TREE_CODE(val_type) != RECORD_TYPE)
 634                         continue;
 635
 636                 if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(val_type)))
 637                         continue;
 638                 MISMATCH(DECL_SOURCE_LOCATION(var), "constructor\n", TYPE_MAIN_VARIANT(field_type), TYPE_MAIN_VARIANT(val_type));
 639         }
 640 }
 641
 642 /* derived from the constify plugin */
 643 static void check_global_variables(void *event_data, void *data)
 644 {
 645         struct varpool_node *node;
 646         tree init;
 647
 648         FOR_EACH_VARIABLE(node) {
 649                 tree var = NODE_DECL(node);
 650                 init = DECL_INITIAL(var);
 651                 if (init == NULL_TREE)
 652                         continue;
 653
 654                 if (TREE_CODE(init) != CONSTRUCTOR)
 655                         continue;
 656
 657                 check_bad_casts_in_constructor(var, init);
 658         }
 659 }
 660
 661 static bool dominated_by_is_err(const_tree rhs, basic_block bb)
 662 {
 663         basic_block dom;
 664         gimple dom_stmt;
 665         gimple call_stmt;
 666         const_tree dom_lhs;
 667         const_tree poss_is_err_cond;
 668         const_tree poss_is_err_func;
 669         const_tree is_err_arg;
 670
 671         dom = get_immediate_dominator(CDI_DOMINATORS, bb);
 672         if (!dom)
 673                 return false;
 674
 675         dom_stmt = last_stmt(dom);
 676         if (!dom_stmt)
 677                 return false;
 678
 679         if (gimple_code(dom_stmt) != GIMPLE_COND)
 680                 return false;
 681
 682         if (gimple_cond_code(dom_stmt) != NE_EXPR)
 683                 return false;
 684
 685         if (!integer_zerop(gimple_cond_rhs(dom_stmt)))
 686                 return false;
 687
 688         poss_is_err_cond = gimple_cond_lhs(dom_stmt);
 689
 690         if (TREE_CODE(poss_is_err_cond) != SSA_NAME)
 691                 return false;
 692
 693         call_stmt = SSA_NAME_DEF_STMT(poss_is_err_cond);
 694
 695         if (gimple_code(call_stmt) != GIMPLE_CALL)
 696                 return false;
 697
 698         dom_lhs = gimple_get_lhs(call_stmt);
 699         poss_is_err_func = gimple_call_fndecl(call_stmt);
 700         if (!poss_is_err_func)
 701                 return false;
 702         if (dom_lhs != poss_is_err_cond)
 703                 return false;
 704         if (strcmp(DECL_NAME_POINTER(poss_is_err_func), "IS_ERR"))
 705                 return false;
 706
 707         is_err_arg = gimple_call_arg(call_stmt, 0);
 708         if (!is_err_arg)
 709                 return false;
 710
 711         if (is_err_arg != rhs)
 712                 return false;
 713
 714         return true;
 715 }
 716
 717 static void handle_local_var_initializers(void)
 718 {
 719         tree var;
 720         unsigned int i;
 721
 722         FOR_EACH_LOCAL_DECL(cfun, i, var) {
 723                 tree init = DECL_INITIAL(var);
 724                 if (!init)
 725                         continue;
 726                 if (TREE_CODE(init) != CONSTRUCTOR)
 727                         continue;
 728                 check_bad_casts_in_constructor(var, init);
 729         }
 730 }
 731
 732 /*
 733  * iterate over all statements to find "bad" casts:
 734  * those where the address of the start of a structure is cast
 735  * to a pointer of a structure of a different type, or a
 736  * structure pointer type is cast to a different structure pointer type
 737  */
 738 static unsigned int find_bad_casts_execute(void)
 739 {
 740         basic_block bb;
 741
 742         handle_local_var_initializers();
 743
 744         FOR_EACH_BB_FN(bb, cfun) {
 745                 gimple_stmt_iterator gsi;
 746
 747                 for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
 748                         gimple stmt;
 749                         const_tree lhs;
 750                         const_tree lhs_type;
 751                         const_tree rhs1;
 752                         const_tree rhs_type;
 753                         const_tree ptr_lhs_type;
 754                         const_tree ptr_rhs_type;
 755                         const_tree op0;
 756                         const_tree op0_type;
 757                         enum tree_code rhs_code;
 758
 759                         stmt = gsi_stmt(gsi);
 760
 761 #ifdef __DEBUG_PLUGIN
 762 #ifdef __DEBUG_VERBOSE
 763                         debug_gimple_stmt(stmt);
 764                         debug_tree(gimple_get_lhs(stmt));
 765 #endif
 766 #endif
 767
 768                         if (gimple_code(stmt) != GIMPLE_ASSIGN)
 769                                 continue;
 770
 771 #ifdef __DEBUG_PLUGIN
 772 #ifdef __DEBUG_VERBOSE
 773                         debug_tree(gimple_assign_rhs1(stmt));
 774 #endif
 775 #endif
 776
 777
 778                         rhs_code = gimple_assign_rhs_code(stmt);
 779
 780                         if (rhs_code != ADDR_EXPR && rhs_code != SSA_NAME)
 781                                 continue;
 782
 783                         lhs = gimple_get_lhs(stmt);
 784                         lhs_type = TREE_TYPE(lhs);
 785                         rhs1 = gimple_assign_rhs1(stmt);
 786                         rhs_type = TREE_TYPE(rhs1);
 787
 788                         if (TREE_CODE(rhs_type) != POINTER_TYPE ||
 789                             TREE_CODE(lhs_type) != POINTER_TYPE)
 790                                 continue;
 791
 792                         ptr_lhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(lhs_type))));
 793                         ptr_rhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(rhs_type))));
 794
 795                         if (ptr_rhs_type == void_type_node)
 796                                 continue;
 797
 798                         if (ptr_lhs_type == void_type_node)
 799                                 continue;
 800
 801                         if (dominated_by_is_err(rhs1, bb))
 802                                 continue;
 803
 804                         if (TREE_CODE(ptr_rhs_type) != RECORD_TYPE) {
 805 #ifndef __DEBUG_PLUGIN
 806                                 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_lhs_type)))
 807 #endif
 808                                 MISMATCH(gimple_location(stmt), "rhs", ptr_lhs_type, ptr_rhs_type);
 809                                 continue;
 810                         }
 811
 812                         if (rhs_code == SSA_NAME && ptr_lhs_type == ptr_rhs_type)
 813                                 continue;
 814
 815                         if (rhs_code == ADDR_EXPR) {
 816                                 op0 = TREE_OPERAND(rhs1, 0);
 817
 818                                 if (op0 == NULL_TREE)
 819                                         continue;
 820
 821                                 if (TREE_CODE(op0) != VAR_DECL)
 822                                         continue;
 823
 824                                 op0_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(op0))));
 825                                 if (op0_type == ptr_lhs_type)
 826                                         continue;
 827
 828 #ifndef __DEBUG_PLUGIN
 829                                 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(op0_type)))
 830 #endif
 831                                 MISMATCH(gimple_location(stmt), "op0", ptr_lhs_type, op0_type);
 832                         } else {
 833                                 const_tree ssa_name_var = SSA_NAME_VAR(rhs1);
 834                                 /* skip bogus type casts introduced by container_of */
 835                                 if (ssa_name_var != NULL_TREE && DECL_NAME(ssa_name_var) &&
 836                                     !strcmp((const char *)DECL_NAME_POINTER(ssa_name_var), "__mptr"))
 837                                         continue;
 838 #ifndef __DEBUG_PLUGIN
 839                                 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_rhs_type)))
 840 #endif
 841                                 MISMATCH(gimple_location(stmt), "ssa", ptr_lhs_type, ptr_rhs_type);
 842                         }
 843
 844                 }
 845         }
 846         return 0;
 847 }
 848
 849 #define PASS_NAME find_bad_casts
 850 #define NO_GATE
 851 #define TODO_FLAGS_FINISH TODO_dump_func
 852 #include "gcc-generate-gimple-pass.h"
 853
 854 __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
 855 {
 856         int i;
 857         const char * const plugin_name = plugin_info->base_name;
 858         const int argc = plugin_info->argc;
 859         const struct plugin_argument * const argv = plugin_info->argv;
 860         bool enable = true;
 861         int obtained_seed = 0;
 862         struct register_pass_info find_bad_casts_pass_info;
 863
 864         find_bad_casts_pass_info.pass                   = make_find_bad_casts_pass();
 865         find_bad_casts_pass_info.reference_pass_name    = "ssa";
 866         find_bad_casts_pass_info.ref_pass_instance_number       = 1;
 867         find_bad_casts_pass_info.pos_op                 = PASS_POS_INSERT_AFTER;
 868
 869         if (!plugin_default_version_check(version, &gcc_version)) {
 870                 error(G_("incompatible gcc/plugin versions"));
 871                 return 1;
 872         }
 873
 874         if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
 875                 inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
 876                 enable = false;
 877         }
 878
 879         for (i = 0; i < argc; ++i) {
 880                 if (!strcmp(argv[i].key, "disable")) {
 881                         enable = false;
 882                         continue;
 883                 }
 884                 if (!strcmp(argv[i].key, "performance-mode")) {
 885                         performance_mode = 1;
 886                         continue;
 887                 }
 888                 error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
 889         }
 890
 891         if (strlen(randstruct_seed) != 64) {
 892                 error(G_("invalid seed value supplied for %s plugin"), plugin_name);
 893                 return 1;
 894         }
 895         obtained_seed = sscanf(randstruct_seed, "%016llx%016llx%016llx%016llx",
 896                 &shuffle_seed[0], &shuffle_seed[1], &shuffle_seed[2], &shuffle_seed[3]);
 897         if (obtained_seed != 4) {
 898                 error(G_("Invalid seed supplied for %s plugin"), plugin_name);
 899                 return 1;
 900         }
 901
 902         register_callback(plugin_name, PLUGIN_INFO, NULL, &randomize_layout_plugin_info);
 903         if (enable) {
 904                 register_callback(plugin_name, PLUGIN_ALL_IPA_PASSES_START, check_global_variables, NULL);
 905                 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &find_bad_casts_pass_info);
 906                 register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
 907                 register_callback(plugin_name, PLUGIN_FINISH_DECL, randomize_layout_finish_decl, NULL);
 908         }
 909         register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);
 910
 911         return 0;
 912 }