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        = "201402201816vanilla",
  38         .help           = "disable\t\t\tdo not activate plugin\n"
  39                           "performance-mode\tenable cacheline-aware layout randomization\n"
  40 };
  41
  42 struct whitelist_entry {
  43         const char *pathname;
  44         const char *lhs;
  45         const char *rhs;
  46 };
  47
  48 static const struct whitelist_entry whitelist[] = {
  49         /* NIU overloads mapping with page struct */
  50         { "drivers/net/ethernet/sun/niu.c", "page", "address_space" },
  51         /* unix_skb_parms via UNIXCB() buffer */
  52         { "net/unix/af_unix.c", "unix_skb_parms", "char" },
  53         /* big_key payload.data struct splashing */
  54         { "security/keys/big_key.c", "path", "void *" },
  55         /* walk struct security_hook_heads as an array of struct list_head */
  56         { "security/security.c", "list_head", "security_hook_heads" },
  57         { }
  58 };
  59
  60 /* from old Linux dcache.h */
  61 static inline unsigned long
  62 partial_name_hash(unsigned long c, unsigned long prevhash)
  63 {
  64         return (prevhash + (c << 4) + (c >> 4)) * 11;
  65 }
  66 static inline unsigned int
  67 name_hash(const unsigned char *name)
  68 {
  69         unsigned long hash = 0;
  70         unsigned int len = strlen((const char *)name);
  71         while (len--)
  72                 hash = partial_name_hash(*name++, hash);
  73         return (unsigned int)hash;
  74 }
  75
  76 static tree handle_randomize_layout_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
  77 {
  78         tree type;
  79
  80         *no_add_attrs = true;
  81         if (TREE_CODE(*node) == FUNCTION_DECL) {
  82                 error("%qE attribute does not apply to functions (%qF)", name, *node);
  83                 return NULL_TREE;
  84         }
  85
  86         if (TREE_CODE(*node) == PARM_DECL) {
  87                 error("%qE attribute does not apply to function parameters (%qD)", name, *node);
  88                 return NULL_TREE;
  89         }
  90
  91         if (TREE_CODE(*node) == VAR_DECL) {
  92                 error("%qE attribute does not apply to variables (%qD)", name, *node);
  93                 return NULL_TREE;
  94         }
  95
  96         if (TYPE_P(*node)) {
  97                 type = *node;
  98         } else {
  99                 gcc_assert(TREE_CODE(*node) == TYPE_DECL);
 100                 type = TREE_TYPE(*node);
 101         }
 102
 103         if (TREE_CODE(type) != RECORD_TYPE) {
 104                 error("%qE attribute used on %qT applies to struct types only", name, type);
 105                 return NULL_TREE;
 106         }
 107
 108         if (lookup_attribute(IDENTIFIER_POINTER(name), TYPE_ATTRIBUTES(type))) {
 109                 error("%qE attribute is already applied to the type %qT", name, type);
 110                 return NULL_TREE;
 111         }
 112
 113         *no_add_attrs = false;
 114
 115         return NULL_TREE;
 116 }
 117
 118 /* set on complete types that we don't need to inspect further at all */
 119 static tree handle_randomize_considered_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
 120 {
 121         *no_add_attrs = false;
 122         return NULL_TREE;
 123 }
 124
 125 /*
 126  * set on types that we've performed a shuffle on, to prevent re-shuffling
 127  * this does not preclude us from inspecting its fields for potential shuffles
 128  */
 129 static tree handle_randomize_performed_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
 130 {
 131         *no_add_attrs = false;
 132         return NULL_TREE;
 133 }
 134
 135 /*
 136  * 64bit variant of Bob Jenkins' public domain PRNG
 137  * 256 bits of internal state
 138  */
 139
 140 typedef unsigned long long u64;
 141
 142 typedef struct ranctx { u64 a; u64 b; u64 c; u64 d; } ranctx;
 143
 144 #define rot(x,k) (((x)<<(k))|((x)>>(64-(k))))
 145 static u64 ranval(ranctx *x) {
 146         u64 e = x->a - rot(x->b, 7);
 147         x->a = x->b ^ rot(x->c, 13);
 148         x->b = x->c + rot(x->d, 37);
 149         x->c = x->d + e;
 150         x->d = e + x->a;
 151         return x->d;
 152 }
 153
 154 static void raninit(ranctx *x, u64 *seed) {
 155         int i;
 156
 157         x->a = seed[0];
 158         x->b = seed[1];
 159         x->c = seed[2];
 160         x->d = seed[3];
 161
 162         for (i=0; i < 30; ++i)
 163                 (void)ranval(x);
 164 }
 165
 166 static u64 shuffle_seed[4];
 167
 168 struct partition_group {
 169         tree tree_start;
 170         unsigned long start;
 171         unsigned long length;
 172 };
 173
 174 static void partition_struct(tree *fields, unsigned long length, struct partition_group *size_groups, unsigned long *num_groups)
 175 {
 176         unsigned long i;
 177         unsigned long accum_size = 0;
 178         unsigned long accum_length = 0;
 179         unsigned long group_idx = 0;
 180
 181         gcc_assert(length < INT_MAX);
 182
 183         memset(size_groups, 0, sizeof(struct partition_group) * length);
 184
 185         for (i = 0; i < length; i++) {
 186                 if (size_groups[group_idx].tree_start == NULL_TREE) {
 187                         size_groups[group_idx].tree_start = fields[i];
 188                         size_groups[group_idx].start = i;
 189                         accum_length = 0;
 190                         accum_size = 0;
 191                 }
 192                 accum_size += (unsigned long)int_size_in_bytes(TREE_TYPE(fields[i]));
 193                 accum_length++;
 194                 if (accum_size >= 64) {
 195                         size_groups[group_idx].length = accum_length;
 196                         accum_length = 0;
 197                         group_idx++;
 198                 }
 199         }
 200
 201         if (size_groups[group_idx].tree_start != NULL_TREE &&
 202             !size_groups[group_idx].length) {
 203                 size_groups[group_idx].length = accum_length;
 204                 group_idx++;
 205         }
 206
 207         *num_groups = group_idx;
 208 }
 209
 210 static void performance_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
 211 {
 212         unsigned long i, x, index;
 213         struct partition_group size_group[length];
 214         unsigned long num_groups = 0;
 215         unsigned long randnum;
 216
 217         partition_struct(newtree, length, (struct partition_group *)&size_group, &num_groups);
 218
 219         /* FIXME: this group shuffle is currently a no-op. */
 220         for (i = num_groups - 1; i > 0; i--) {
 221                 struct partition_group tmp;
 222                 randnum = ranval(prng_state) % (i + 1);
 223                 tmp = size_group[i];
 224                 size_group[i] = size_group[randnum];
 225                 size_group[randnum] = tmp;
 226         }
 227
 228         for (x = 0; x < num_groups; x++) {
 229                 for (index = size_group[x].length - 1; index > 0; index--) {
 230                         tree tmp;
 231
 232                         i = size_group[x].start + index;
 233                         if (DECL_BIT_FIELD_TYPE(newtree[i]))
 234                                 continue;
 235                         randnum = ranval(prng_state) % (index + 1);
 236                         randnum += size_group[x].start;
 237                         // we could handle this case differently if desired
 238                         if (DECL_BIT_FIELD_TYPE(newtree[randnum]))
 239                                 continue;
 240                         tmp = newtree[i];
 241                         newtree[i] = newtree[randnum];
 242                         newtree[randnum] = tmp;
 243                 }
 244         }
 245 }
 246
 247 static void full_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
 248 {
 249         unsigned long i, randnum;
 250
 251         for (i = length - 1; i > 0; i--) {
 252                 tree tmp;
 253                 randnum = ranval(prng_state) % (i + 1);
 254                 tmp = newtree[i];
 255                 newtree[i] = newtree[randnum];
 256                 newtree[randnum] = tmp;
 257         }
 258 }
 259
 260 /* modern in-place Fisher-Yates shuffle */
 261 static void shuffle(const_tree type, tree *newtree, unsigned long length)
 262 {
 263         unsigned long i;
 264         u64 seed[4];
 265         ranctx prng_state;
 266         const unsigned char *structname;
 267
 268         if (length == 0)
 269                 return;
 270
 271         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
 272
 273         structname = ORIG_TYPE_NAME(type);
 274
 275 #ifdef __DEBUG_PLUGIN
 276         fprintf(stderr, "Shuffling struct %s %p\n", (const char *)structname, type);
 277 #ifdef __DEBUG_VERBOSE
 278         debug_tree((tree)type);
 279 #endif
 280 #endif
 281
 282         for (i = 0; i < 4; i++) {
 283                 seed[i] = shuffle_seed[i];
 284                 seed[i] ^= name_hash(structname);
 285         }
 286
 287         raninit(&prng_state, (u64 *)&seed);
 288
 289         if (performance_mode)
 290                 performance_shuffle(newtree, length, &prng_state);
 291         else
 292                 full_shuffle(newtree, length, &prng_state);
 293 }
 294
 295 static bool is_flexible_array(const_tree field)
 296 {
 297         const_tree fieldtype;
 298         const_tree typesize;
 299         const_tree elemtype;
 300         const_tree elemsize;
 301
 302         fieldtype = TREE_TYPE(field);
 303         typesize = TYPE_SIZE(fieldtype);
 304
 305         if (TREE_CODE(fieldtype) != ARRAY_TYPE)
 306                 return false;
 307
 308         elemtype = TREE_TYPE(fieldtype);
 309         elemsize = TYPE_SIZE(elemtype);
 310
 311         /* size of type is represented in bits */
 312
 313         if (typesize == NULL_TREE && TYPE_DOMAIN(fieldtype) != NULL_TREE &&
 314             TYPE_MAX_VALUE(TYPE_DOMAIN(fieldtype)) == NULL_TREE)
 315                 return true;
 316
 317         if (typesize != NULL_TREE &&
 318             (TREE_CONSTANT(typesize) && (!tree_to_uhwi(typesize) ||
 319              tree_to_uhwi(typesize) == tree_to_uhwi(elemsize))))
 320                 return true;
 321
 322         return false;
 323 }
 324
 325 static int relayout_struct(tree type)
 326 {
 327         unsigned long num_fields = (unsigned long)list_length(TYPE_FIELDS(type));
 328         unsigned long shuffle_length = num_fields;
 329         tree field;
 330         tree newtree[num_fields];
 331         unsigned long i;
 332         tree list;
 333         tree variant;
 334         tree main_variant;
 335         expanded_location xloc;
 336         bool has_flexarray = false;
 337
 338         if (TYPE_FIELDS(type) == NULL_TREE)
 339                 return 0;
 340
 341         if (num_fields < 2)
 342                 return 0;
 343
 344         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
 345
 346         gcc_assert(num_fields < INT_MAX);
 347
 348         if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)) ||
 349             lookup_attribute("no_randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))))
 350                 return 0;
 351
 352         /* Workaround for 3rd-party VirtualBox source that we can't modify ourselves */
 353         if (!strcmp((const char *)ORIG_TYPE_NAME(type), "INTNETTRUNKFACTORY") ||
 354             !strcmp((const char *)ORIG_TYPE_NAME(type), "RAWPCIFACTORY"))
 355                 return 0;
 356
 357         /* throw out any structs in uapi */
 358         xloc = expand_location(DECL_SOURCE_LOCATION(TYPE_FIELDS(type)));
 359
 360         if (strstr(xloc.file, "/uapi/"))
 361                 error(G_("attempted to randomize userland API struct %s"), ORIG_TYPE_NAME(type));
 362
 363         for (field = TYPE_FIELDS(type), i = 0; field; field = TREE_CHAIN(field), i++) {
 364                 gcc_assert(TREE_CODE(field) == FIELD_DECL);
 365                 newtree[i] = field;
 366         }
 367
 368         /*
 369          * enforce that we don't randomize the layout of the last
 370          * element of a struct if it's a 0 or 1-length array
 371          * or a proper flexible array
 372          */
 373         if (is_flexible_array(newtree[num_fields - 1])) {
 374                 has_flexarray = true;
 375                 shuffle_length--;
 376         }
 377
 378         shuffle(type, (tree *)newtree, shuffle_length);
 379
 380         /*
 381          * set up a bogus anonymous struct field designed to error out on unnamed struct initializers
 382          * as gcc provides no other way to detect such code
 383          */
 384         list = make_node(FIELD_DECL);
 385         TREE_CHAIN(list) = newtree[0];
 386         TREE_TYPE(list) = void_type_node;
 387         DECL_SIZE(list) = bitsize_zero_node;
 388         DECL_NONADDRESSABLE_P(list) = 1;
 389         DECL_FIELD_BIT_OFFSET(list) = bitsize_zero_node;
 390         DECL_SIZE_UNIT(list) = size_zero_node;
 391         DECL_FIELD_OFFSET(list) = size_zero_node;
 392         DECL_CONTEXT(list) = type;
 393         // to satisfy the constify plugin
 394         TREE_READONLY(list) = 1;
 395
 396         for (i = 0; i < num_fields - 1; i++)
 397                 TREE_CHAIN(newtree[i]) = newtree[i+1];
 398         TREE_CHAIN(newtree[num_fields - 1]) = NULL_TREE;
 399
 400         main_variant = TYPE_MAIN_VARIANT(type);
 401         for (variant = main_variant; variant; variant = TYPE_NEXT_VARIANT(variant)) {
 402                 TYPE_FIELDS(variant) = list;
 403                 TYPE_ATTRIBUTES(variant) = copy_list(TYPE_ATTRIBUTES(variant));
 404                 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("randomize_performed"), NULL_TREE, TYPE_ATTRIBUTES(variant));
 405                 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("designated_init"), NULL_TREE, TYPE_ATTRIBUTES(variant));
 406                 if (has_flexarray)
 407                         TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("has_flexarray"), NULL_TREE, TYPE_ATTRIBUTES(type));
 408         }
 409
 410         /*
 411          * force a re-layout of the main variant
 412          * the TYPE_SIZE for all variants will be recomputed
 413          * by finalize_type_size()
 414          */
 415         TYPE_SIZE(main_variant) = NULL_TREE;
 416         layout_type(main_variant);
 417         gcc_assert(TYPE_SIZE(main_variant) != NULL_TREE);
 418
 419         return 1;
 420 }
 421
 422 /* from constify plugin */
 423 static const_tree get_field_type(const_tree field)
 424 {
 425         return strip_array_types(TREE_TYPE(field));
 426 }
 427
 428 /* from constify plugin */
 429 static bool is_fptr(const_tree fieldtype)
 430 {
 431         if (TREE_CODE(fieldtype) != POINTER_TYPE)
 432                 return false;
 433
 434         return TREE_CODE(TREE_TYPE(fieldtype)) == FUNCTION_TYPE;
 435 }
 436
 437 /* derived from constify plugin */
 438 static int is_pure_ops_struct(const_tree node)
 439 {
 440         const_tree field;
 441
 442         gcc_assert(TREE_CODE(node) == RECORD_TYPE || TREE_CODE(node) == UNION_TYPE);
 443
 444         for (field = TYPE_FIELDS(node); field; field = TREE_CHAIN(field)) {
 445                 const_tree fieldtype = get_field_type(field);
 446                 enum tree_code code = TREE_CODE(fieldtype);
 447
 448                 if (node == fieldtype)
 449                         continue;
 450
 451                 if (code == RECORD_TYPE || code == UNION_TYPE) {
 452                         if (!is_pure_ops_struct(fieldtype))
 453                                 return 0;
 454                         continue;
 455                 }
 456
 457                 if (!is_fptr(fieldtype))
 458                         return 0;
 459         }
 460
 461         return 1;
 462 }
 463
 464 static void randomize_type(tree type)
 465 {
 466         tree variant;
 467
 468         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
 469
 470         if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
 471                 return;
 472
 473         if (lookup_attribute("randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))) || is_pure_ops_struct(type))
 474                 relayout_struct(type);
 475
 476         for (variant = TYPE_MAIN_VARIANT(type); variant; variant = TYPE_NEXT_VARIANT(variant)) {
 477                 TYPE_ATTRIBUTES(type) = copy_list(TYPE_ATTRIBUTES(type));
 478                 TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("randomize_considered"), NULL_TREE, TYPE_ATTRIBUTES(type));
 479         }
 480 #ifdef __DEBUG_PLUGIN
 481         fprintf(stderr, "Marking randomize_considered on struct %s\n", ORIG_TYPE_NAME(type));
 482 #ifdef __DEBUG_VERBOSE
 483         debug_tree(type);
 484 #endif
 485 #endif
 486 }
 487
 488 static void update_decl_size(tree decl)
 489 {
 490         tree lastval, lastidx, field, init, type, flexsize;
 491         unsigned HOST_WIDE_INT len;
 492
 493         type = TREE_TYPE(decl);
 494
 495         if (!lookup_attribute("has_flexarray", TYPE_ATTRIBUTES(type)))
 496                 return;
 497
 498         init = DECL_INITIAL(decl);
 499         if (init == NULL_TREE || init == error_mark_node)
 500                 return;
 501
 502         if (TREE_CODE(init) != CONSTRUCTOR)
 503                 return;
 504
 505         len = CONSTRUCTOR_NELTS(init);
 506         if (!len)
 507                 return;
 508
 509         lastval = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->value;
 510         lastidx = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->index;
 511
 512         for (field = TYPE_FIELDS(TREE_TYPE(decl)); TREE_CHAIN(field); field = TREE_CHAIN(field))
 513                 ;
 514
 515         if (lastidx != field)
 516                 return;
 517
 518         if (TREE_CODE(lastval) != STRING_CST) {
 519                 error("Only string constants are supported as initializers "
 520                       "for randomized structures with flexible arrays");
 521                 return;
 522         }
 523
 524         flexsize = bitsize_int(TREE_STRING_LENGTH(lastval) *
 525                 tree_to_uhwi(TYPE_SIZE(TREE_TYPE(TREE_TYPE(lastval)))));
 526
 527         DECL_SIZE(decl) = size_binop(PLUS_EXPR, TYPE_SIZE(type), flexsize);
 528
 529         return;
 530 }
 531
 532
 533 static void randomize_layout_finish_decl(void *event_data, void *data)
 534 {
 535         tree decl = (tree)event_data;
 536         tree type;
 537
 538         if (decl == NULL_TREE || decl == error_mark_node)
 539                 return;
 540
 541         type = TREE_TYPE(decl);
 542
 543         if (TREE_CODE(decl) != VAR_DECL)
 544                 return;
 545
 546         if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
 547                 return;
 548
 549         if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)))
 550                 return;
 551
 552         DECL_SIZE(decl) = 0;
 553         DECL_SIZE_UNIT(decl) = 0;
 554         SET_DECL_ALIGN(decl, 0);
 555         SET_DECL_MODE (decl, VOIDmode);
 556         SET_DECL_RTL(decl, 0);
 557         update_decl_size(decl);
 558         layout_decl(decl, 0);
 559 }
 560
 561 static void finish_type(void *event_data, void *data)
 562 {
 563         tree type = (tree)event_data;
 564
 565         if (type == NULL_TREE || type == error_mark_node)
 566                 return;
 567
 568         if (TREE_CODE(type) != RECORD_TYPE)
 569                 return;
 570
 571         if (TYPE_FIELDS(type) == NULL_TREE)
 572                 return;
 573
 574         if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
 575                 return;
 576
 577 #ifdef __DEBUG_PLUGIN
 578         fprintf(stderr, "Calling randomize_type on %s\n", ORIG_TYPE_NAME(type));
 579 #endif
 580 #ifdef __DEBUG_VERBOSE
 581         debug_tree(type);
 582 #endif
 583         randomize_type(type);
 584
 585         return;
 586 }
 587
 588 static struct attribute_spec randomize_layout_attr = { };
 589 static struct attribute_spec no_randomize_layout_attr = { };
 590 static struct attribute_spec randomize_considered_attr = { };
 591 static struct attribute_spec randomize_performed_attr = { };
 592
 593 static void register_attributes(void *event_data, void *data)
 594 {
 595         randomize_layout_attr.name              = "randomize_layout";
 596         randomize_layout_attr.type_required     = true;
 597         randomize_layout_attr.handler           = handle_randomize_layout_attr;
 598 #if BUILDING_GCC_VERSION >= 4007
 599         randomize_layout_attr.affects_type_identity = true;
 600 #endif
 601
 602         no_randomize_layout_attr.name           = "no_randomize_layout";
 603         no_randomize_layout_attr.type_required  = true;
 604         no_randomize_layout_attr.handler        = handle_randomize_layout_attr;
 605 #if BUILDING_GCC_VERSION >= 4007
 606         no_randomize_layout_attr.affects_type_identity = true;
 607 #endif
 608
 609         randomize_considered_attr.name          = "randomize_considered";
 610         randomize_considered_attr.type_required = true;
 611         randomize_considered_attr.handler       = handle_randomize_considered_attr;
 612
 613         randomize_performed_attr.name           = "randomize_performed";
 614         randomize_performed_attr.type_required  = true;
 615         randomize_performed_attr.handler        = handle_randomize_performed_attr;
 616
 617         register_attribute(&randomize_layout_attr);
 618         register_attribute(&no_randomize_layout_attr);
 619         register_attribute(&randomize_considered_attr);
 620         register_attribute(&randomize_performed_attr);
 621 }
 622
 623 static void check_bad_casts_in_constructor(tree var, tree init)
 624 {
 625         unsigned HOST_WIDE_INT idx;
 626         tree field, val;
 627         tree field_type, val_type;
 628
 629         FOR_EACH_CONSTRUCTOR_ELT(CONSTRUCTOR_ELTS(init), idx, field, val) {
 630                 if (TREE_CODE(val) == CONSTRUCTOR) {
 631                         check_bad_casts_in_constructor(var, val);
 632                         continue;
 633                 }
 634
 635                 /* pipacs' plugin creates franken-arrays that differ from those produced by
 636                    normal code which all have valid 'field' trees. work around this */
 637                 if (field == NULL_TREE)
 638                         continue;
 639                 field_type = TREE_TYPE(field);
 640                 val_type = TREE_TYPE(val);
 641
 642                 if (TREE_CODE(field_type) != POINTER_TYPE || TREE_CODE(val_type) != POINTER_TYPE)
 643                         continue;
 644
 645                 if (field_type == val_type)
 646                         continue;
 647
 648                 field_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(field_type))));
 649                 val_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(val_type))));
 650
 651                 if (field_type == void_type_node)
 652                         continue;
 653                 if (field_type == val_type)
 654                         continue;
 655                 if (TREE_CODE(val_type) != RECORD_TYPE)
 656                         continue;
 657
 658                 if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(val_type)))
 659                         continue;
 660                 MISMATCH(DECL_SOURCE_LOCATION(var), "constructor\n", TYPE_MAIN_VARIANT(field_type), TYPE_MAIN_VARIANT(val_type));
 661         }
 662 }
 663
 664 /* derived from the constify plugin */
 665 static void check_global_variables(void *event_data, void *data)
 666 {
 667         struct varpool_node *node;
 668         tree init;
 669
 670         FOR_EACH_VARIABLE(node) {
 671                 tree var = NODE_DECL(node);
 672                 init = DECL_INITIAL(var);
 673                 if (init == NULL_TREE)
 674                         continue;
 675
 676                 if (TREE_CODE(init) != CONSTRUCTOR)
 677                         continue;
 678
 679                 check_bad_casts_in_constructor(var, init);
 680         }
 681 }
 682
 683 static bool dominated_by_is_err(const_tree rhs, basic_block bb)
 684 {
 685         basic_block dom;
 686         gimple dom_stmt;
 687         gimple call_stmt;
 688         const_tree dom_lhs;
 689         const_tree poss_is_err_cond;
 690         const_tree poss_is_err_func;
 691         const_tree is_err_arg;
 692
 693         dom = get_immediate_dominator(CDI_DOMINATORS, bb);
 694         if (!dom)
 695                 return false;
 696
 697         dom_stmt = last_stmt(dom);
 698         if (!dom_stmt)
 699                 return false;
 700
 701         if (gimple_code(dom_stmt) != GIMPLE_COND)
 702                 return false;
 703
 704         if (gimple_cond_code(dom_stmt) != NE_EXPR)
 705                 return false;
 706
 707         if (!integer_zerop(gimple_cond_rhs(dom_stmt)))
 708                 return false;
 709
 710         poss_is_err_cond = gimple_cond_lhs(dom_stmt);
 711
 712         if (TREE_CODE(poss_is_err_cond) != SSA_NAME)
 713                 return false;
 714
 715         call_stmt = SSA_NAME_DEF_STMT(poss_is_err_cond);
 716
 717         if (gimple_code(call_stmt) != GIMPLE_CALL)
 718                 return false;
 719
 720         dom_lhs = gimple_get_lhs(call_stmt);
 721         poss_is_err_func = gimple_call_fndecl(call_stmt);
 722         if (!poss_is_err_func)
 723                 return false;
 724         if (dom_lhs != poss_is_err_cond)
 725                 return false;
 726         if (strcmp(DECL_NAME_POINTER(poss_is_err_func), "IS_ERR"))
 727                 return false;
 728
 729         is_err_arg = gimple_call_arg(call_stmt, 0);
 730         if (!is_err_arg)
 731                 return false;
 732
 733         if (is_err_arg != rhs)
 734                 return false;
 735
 736         return true;
 737 }
 738
 739 static void handle_local_var_initializers(void)
 740 {
 741         tree var;
 742         unsigned int i;
 743
 744         FOR_EACH_LOCAL_DECL(cfun, i, var) {
 745                 tree init = DECL_INITIAL(var);
 746                 if (!init)
 747                         continue;
 748                 if (TREE_CODE(init) != CONSTRUCTOR)
 749                         continue;
 750                 check_bad_casts_in_constructor(var, init);
 751         }
 752 }
 753
 754 static bool type_name_eq(gimple stmt, const_tree type_tree, const char *wanted_name)
 755 {
 756         const char *type_name;
 757
 758         if (type_tree == NULL_TREE)
 759                 return false;
 760
 761         switch (TREE_CODE(type_tree)) {
 762         case RECORD_TYPE:
 763                 type_name = TYPE_NAME_POINTER(type_tree);
 764                 break;
 765         case INTEGER_TYPE:
 766                 if (TYPE_PRECISION(type_tree) == CHAR_TYPE_SIZE)
 767                         type_name = "char";
 768                 else {
 769                         INFORM(gimple_location(stmt), "found non-char INTEGER_TYPE cast comparison: %qT\n", type_tree);
 770                         debug_tree(type_tree);
 771                         return false;
 772                 }
 773                 break;
 774         case POINTER_TYPE:
 775                 if (TREE_CODE(TREE_TYPE(type_tree)) == VOID_TYPE) {
 776                         type_name = "void *";
 777                         break;
 778                 } else {
 779                         INFORM(gimple_location(stmt), "found non-void POINTER_TYPE cast comparison %qT\n", type_tree);
 780                         debug_tree(type_tree);
 781                         return false;
 782                 }
 783         default:
 784                 INFORM(gimple_location(stmt), "unhandled cast comparison: %qT\n", type_tree);
 785                 debug_tree(type_tree);
 786                 return false;
 787         }
 788
 789         return strcmp(type_name, wanted_name) == 0;
 790 }
 791
 792 static bool whitelisted_cast(gimple stmt, const_tree lhs_tree, const_tree rhs_tree)
 793 {
 794         const struct whitelist_entry *entry;
 795         expanded_location xloc = expand_location(gimple_location(stmt));
 796
 797         for (entry = whitelist; entry->pathname; entry++) {
 798                 if (!strstr(xloc.file, entry->pathname))
 799                         continue;
 800
 801                 if (type_name_eq(stmt, lhs_tree, entry->lhs) && type_name_eq(stmt, rhs_tree, entry->rhs))
 802                         return true;
 803         }
 804
 805         return false;
 806 }
 807
 808 /*
 809  * iterate over all statements to find "bad" casts:
 810  * those where the address of the start of a structure is cast
 811  * to a pointer of a structure of a different type, or a
 812  * structure pointer type is cast to a different structure pointer type
 813  */
 814 static unsigned int find_bad_casts_execute(void)
 815 {
 816         basic_block bb;
 817
 818         handle_local_var_initializers();
 819
 820         FOR_EACH_BB_FN(bb, cfun) {
 821                 gimple_stmt_iterator gsi;
 822
 823                 for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
 824                         gimple stmt;
 825                         const_tree lhs;
 826                         const_tree lhs_type;
 827                         const_tree rhs1;
 828                         const_tree rhs_type;
 829                         const_tree ptr_lhs_type;
 830                         const_tree ptr_rhs_type;
 831                         const_tree op0;
 832                         const_tree op0_type;
 833                         enum tree_code rhs_code;
 834
 835                         stmt = gsi_stmt(gsi);
 836
 837 #ifdef __DEBUG_PLUGIN
 838 #ifdef __DEBUG_VERBOSE
 839                         debug_gimple_stmt(stmt);
 840                         debug_tree(gimple_get_lhs(stmt));
 841 #endif
 842 #endif
 843
 844                         if (gimple_code(stmt) != GIMPLE_ASSIGN)
 845                                 continue;
 846
 847 #ifdef __DEBUG_PLUGIN
 848 #ifdef __DEBUG_VERBOSE
 849                         debug_tree(gimple_assign_rhs1(stmt));
 850 #endif
 851 #endif
 852
 853
 854                         rhs_code = gimple_assign_rhs_code(stmt);
 855
 856                         if (rhs_code != ADDR_EXPR && rhs_code != SSA_NAME)
 857                                 continue;
 858
 859                         lhs = gimple_get_lhs(stmt);
 860                         lhs_type = TREE_TYPE(lhs);
 861                         rhs1 = gimple_assign_rhs1(stmt);
 862                         rhs_type = TREE_TYPE(rhs1);
 863
 864                         if (TREE_CODE(rhs_type) != POINTER_TYPE ||
 865                             TREE_CODE(lhs_type) != POINTER_TYPE)
 866                                 continue;
 867
 868                         ptr_lhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(lhs_type))));
 869                         ptr_rhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(rhs_type))));
 870
 871                         if (ptr_rhs_type == void_type_node)
 872                                 continue;
 873
 874                         if (ptr_lhs_type == void_type_node)
 875                                 continue;
 876
 877                         if (dominated_by_is_err(rhs1, bb))
 878                                 continue;
 879
 880                         if (TREE_CODE(ptr_rhs_type) != RECORD_TYPE) {
 881 #ifndef __DEBUG_PLUGIN
 882                                 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_lhs_type)))
 883 #endif
 884                                 {
 885                                         if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
 886                                                 MISMATCH(gimple_location(stmt), "rhs", ptr_lhs_type, ptr_rhs_type);
 887                                 }
 888                                 continue;
 889                         }
 890
 891                         if (rhs_code == SSA_NAME && ptr_lhs_type == ptr_rhs_type)
 892                                 continue;
 893
 894                         if (rhs_code == ADDR_EXPR) {
 895                                 op0 = TREE_OPERAND(rhs1, 0);
 896
 897                                 if (op0 == NULL_TREE)
 898                                         continue;
 899
 900                                 if (TREE_CODE(op0) != VAR_DECL)
 901                                         continue;
 902
 903                                 op0_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(op0))));
 904                                 if (op0_type == ptr_lhs_type)
 905                                         continue;
 906
 907 #ifndef __DEBUG_PLUGIN
 908                                 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(op0_type)))
 909 #endif
 910                                 {
 911                                         if (!whitelisted_cast(stmt, ptr_lhs_type, op0_type))
 912                                                 MISMATCH(gimple_location(stmt), "op0", ptr_lhs_type, op0_type);
 913                                 }
 914                         } else {
 915                                 const_tree ssa_name_var = SSA_NAME_VAR(rhs1);
 916                                 /* skip bogus type casts introduced by container_of */
 917                                 if (ssa_name_var != NULL_TREE && DECL_NAME(ssa_name_var) &&
 918                                     !strcmp((const char *)DECL_NAME_POINTER(ssa_name_var), "__mptr"))
 919                                         continue;
 920 #ifndef __DEBUG_PLUGIN
 921                                 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_rhs_type)))
 922 #endif
 923                                 {
 924                                         if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
 925                                                 MISMATCH(gimple_location(stmt), "ssa", ptr_lhs_type, ptr_rhs_type);
 926                                 }
 927                         }
 928
 929                 }
 930         }
 931         return 0;
 932 }
 933
 934 #define PASS_NAME find_bad_casts
 935 #define NO_GATE
 936 #define TODO_FLAGS_FINISH TODO_dump_func
 937 #include "gcc-generate-gimple-pass.h"
 938
 939 __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
 940 {
 941         int i;
 942         const char * const plugin_name = plugin_info->base_name;
 943         const int argc = plugin_info->argc;
 944         const struct plugin_argument * const argv = plugin_info->argv;
 945         bool enable = true;
 946         int obtained_seed = 0;
 947         struct register_pass_info find_bad_casts_pass_info;
 948
 949         find_bad_casts_pass_info.pass                   = make_find_bad_casts_pass();
 950         find_bad_casts_pass_info.reference_pass_name    = "ssa";
 951         find_bad_casts_pass_info.ref_pass_instance_number       = 1;
 952         find_bad_casts_pass_info.pos_op                 = PASS_POS_INSERT_AFTER;
 953
 954         if (!plugin_default_version_check(version, &gcc_version)) {
 955                 error(G_("incompatible gcc/plugin versions"));
 956                 return 1;
 957         }
 958
 959         if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
 960                 inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
 961                 enable = false;
 962         }
 963
 964         for (i = 0; i < argc; ++i) {
 965                 if (!strcmp(argv[i].key, "disable")) {
 966                         enable = false;
 967                         continue;
 968                 }
 969                 if (!strcmp(argv[i].key, "performance-mode")) {
 970                         performance_mode = 1;
 971                         continue;
 972                 }
 973                 error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
 974         }
 975
 976         if (strlen(randstruct_seed) != 64) {
 977                 error(G_("invalid seed value supplied for %s plugin"), plugin_name);
 978                 return 1;
 979         }
 980         obtained_seed = sscanf(randstruct_seed, "%016llx%016llx%016llx%016llx",
 981                 &shuffle_seed[0], &shuffle_seed[1], &shuffle_seed[2], &shuffle_seed[3]);
 982         if (obtained_seed != 4) {
 983                 error(G_("Invalid seed supplied for %s plugin"), plugin_name);
 984                 return 1;
 985         }
 986
 987         register_callback(plugin_name, PLUGIN_INFO, NULL, &randomize_layout_plugin_info);
 988         if (enable) {
 989                 register_callback(plugin_name, PLUGIN_ALL_IPA_PASSES_START, check_global_variables, NULL);
 990                 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &find_bad_casts_pass_info);
 991                 register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
 992                 register_callback(plugin_name, PLUGIN_FINISH_DECL, randomize_layout_finish_decl, NULL);
 993         }
 994         register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);
 995
 996         return 0;
 997 }