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         /* unix_skb_parms via UNIXCB() buffer */
  50         { "net/unix/af_unix.c", "unix_skb_parms", "char" },
  51         /* walk struct security_hook_heads as an array of struct list_head */
  52         { "security/security.c", "list_head", "security_hook_heads" },
  53         { }
  54 };
  55
  56 /* from old Linux dcache.h */
  57 static inline unsigned long
  58 partial_name_hash(unsigned long c, unsigned long prevhash)
  59 {
  60         return (prevhash + (c << 4) + (c >> 4)) * 11;
  61 }
  62 static inline unsigned int
  63 name_hash(const unsigned char *name)
  64 {
  65         unsigned long hash = 0;
  66         unsigned int len = strlen((const char *)name);
  67         while (len--)
  68                 hash = partial_name_hash(*name++, hash);
  69         return (unsigned int)hash;
  70 }
  71
  72 static tree handle_randomize_layout_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
  73 {
  74         tree type;
  75
  76         *no_add_attrs = true;
  77         if (TREE_CODE(*node) == FUNCTION_DECL) {
  78                 error("%qE attribute does not apply to functions (%qF)", name, *node);
  79                 return NULL_TREE;
  80         }
  81
  82         if (TREE_CODE(*node) == PARM_DECL) {
  83                 error("%qE attribute does not apply to function parameters (%qD)", name, *node);
  84                 return NULL_TREE;
  85         }
  86
  87         if (TREE_CODE(*node) == VAR_DECL) {
  88                 error("%qE attribute does not apply to variables (%qD)", name, *node);
  89                 return NULL_TREE;
  90         }
  91
  92         if (TYPE_P(*node)) {
  93                 type = *node;
  94         } else {
  95                 gcc_assert(TREE_CODE(*node) == TYPE_DECL);
  96                 type = TREE_TYPE(*node);
  97         }
  98
  99         if (TREE_CODE(type) != RECORD_TYPE) {
 100                 error("%qE attribute used on %qT applies to struct types only", name, type);
 101                 return NULL_TREE;
 102         }
 103
 104         if (lookup_attribute(IDENTIFIER_POINTER(name), TYPE_ATTRIBUTES(type))) {
 105                 error("%qE attribute is already applied to the type %qT", name, type);
 106                 return NULL_TREE;
 107         }
 108
 109         *no_add_attrs = false;
 110
 111         return NULL_TREE;
 112 }
 113
 114 /* set on complete types that we don't need to inspect further at all */
 115 static tree handle_randomize_considered_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
 116 {
 117         *no_add_attrs = false;
 118         return NULL_TREE;
 119 }
 120
 121 /*
 122  * set on types that we've performed a shuffle on, to prevent re-shuffling
 123  * this does not preclude us from inspecting its fields for potential shuffles
 124  */
 125 static tree handle_randomize_performed_attr(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
 126 {
 127         *no_add_attrs = false;
 128         return NULL_TREE;
 129 }
 130
 131 /*
 132  * 64bit variant of Bob Jenkins' public domain PRNG
 133  * 256 bits of internal state
 134  */
 135
 136 typedef unsigned long long u64;
 137
 138 typedef struct ranctx { u64 a; u64 b; u64 c; u64 d; } ranctx;
 139
 140 #define rot(x,k) (((x)<<(k))|((x)>>(64-(k))))
 141 static u64 ranval(ranctx *x) {
 142         u64 e = x->a - rot(x->b, 7);
 143         x->a = x->b ^ rot(x->c, 13);
 144         x->b = x->c + rot(x->d, 37);
 145         x->c = x->d + e;
 146         x->d = e + x->a;
 147         return x->d;
 148 }
 149
 150 static void raninit(ranctx *x, u64 *seed) {
 151         int i;
 152
 153         x->a = seed[0];
 154         x->b = seed[1];
 155         x->c = seed[2];
 156         x->d = seed[3];
 157
 158         for (i=0; i < 30; ++i)
 159                 (void)ranval(x);
 160 }
 161
 162 static u64 shuffle_seed[4];
 163
 164 struct partition_group {
 165         tree tree_start;
 166         unsigned long start;
 167         unsigned long length;
 168 };
 169
 170 static void partition_struct(tree *fields, unsigned long length, struct partition_group *size_groups, unsigned long *num_groups)
 171 {
 172         unsigned long i;
 173         unsigned long accum_size = 0;
 174         unsigned long accum_length = 0;
 175         unsigned long group_idx = 0;
 176
 177         gcc_assert(length < INT_MAX);
 178
 179         memset(size_groups, 0, sizeof(struct partition_group) * length);
 180
 181         for (i = 0; i < length; i++) {
 182                 if (size_groups[group_idx].tree_start == NULL_TREE) {
 183                         size_groups[group_idx].tree_start = fields[i];
 184                         size_groups[group_idx].start = i;
 185                         accum_length = 0;
 186                         accum_size = 0;
 187                 }
 188                 accum_size += (unsigned long)int_size_in_bytes(TREE_TYPE(fields[i]));
 189                 accum_length++;
 190                 if (accum_size >= 64) {
 191                         size_groups[group_idx].length = accum_length;
 192                         accum_length = 0;
 193                         group_idx++;
 194                 }
 195         }
 196
 197         if (size_groups[group_idx].tree_start != NULL_TREE &&
 198             !size_groups[group_idx].length) {
 199                 size_groups[group_idx].length = accum_length;
 200                 group_idx++;
 201         }
 202
 203         *num_groups = group_idx;
 204 }
 205
 206 static void performance_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
 207 {
 208         unsigned long i, x;
 209         struct partition_group size_group[length];
 210         unsigned long num_groups = 0;
 211         unsigned long randnum;
 212
 213         partition_struct(newtree, length, (struct partition_group *)&size_group, &num_groups);
 214         for (i = num_groups - 1; i > 0; i--) {
 215                 struct partition_group tmp;
 216                 randnum = ranval(prng_state) % (i + 1);
 217                 tmp = size_group[i];
 218                 size_group[i] = size_group[randnum];
 219                 size_group[randnum] = tmp;
 220         }
 221
 222         for (x = 0; x < num_groups; x++) {
 223                 for (i = size_group[x].start + size_group[x].length - 1; i > size_group[x].start; i--) {
 224                         tree tmp;
 225                         if (DECL_BIT_FIELD_TYPE(newtree[i]))
 226                                 continue;
 227                         randnum = ranval(prng_state) % (i + 1);
 228                         // we could handle this case differently if desired
 229                         if (DECL_BIT_FIELD_TYPE(newtree[randnum]))
 230                                 continue;
 231                         tmp = newtree[i];
 232                         newtree[i] = newtree[randnum];
 233                         newtree[randnum] = tmp;
 234                 }
 235         }
 236 }
 237
 238 static void full_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
 239 {
 240         unsigned long i, randnum;
 241
 242         for (i = length - 1; i > 0; i--) {
 243                 tree tmp;
 244                 randnum = ranval(prng_state) % (i + 1);
 245                 tmp = newtree[i];
 246                 newtree[i] = newtree[randnum];
 247                 newtree[randnum] = tmp;
 248         }
 249 }
 250
 251 /* modern in-place Fisher-Yates shuffle */
 252 static void shuffle(const_tree type, tree *newtree, unsigned long length)
 253 {
 254         unsigned long i;
 255         u64 seed[4];
 256         ranctx prng_state;
 257         const unsigned char *structname;
 258
 259         if (length == 0)
 260                 return;
 261
 262         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
 263
 264         structname = ORIG_TYPE_NAME(type);
 265
 266 #ifdef __DEBUG_PLUGIN
 267         fprintf(stderr, "Shuffling struct %s %p\n", (const char *)structname, type);
 268 #ifdef __DEBUG_VERBOSE
 269         debug_tree((tree)type);
 270 #endif
 271 #endif
 272
 273         for (i = 0; i < 4; i++) {
 274                 seed[i] = shuffle_seed[i];
 275                 seed[i] ^= name_hash(structname);
 276         }
 277
 278         raninit(&prng_state, (u64 *)&seed);
 279
 280         if (performance_mode)
 281                 performance_shuffle(newtree, length, &prng_state);
 282         else
 283                 full_shuffle(newtree, length, &prng_state);
 284 }
 285
 286 static bool is_flexible_array(const_tree field)
 287 {
 288         const_tree fieldtype;
 289         const_tree typesize;
 290         const_tree elemtype;
 291         const_tree elemsize;
 292
 293         fieldtype = TREE_TYPE(field);
 294         typesize = TYPE_SIZE(fieldtype);
 295
 296         if (TREE_CODE(fieldtype) != ARRAY_TYPE)
 297                 return false;
 298
 299         elemtype = TREE_TYPE(fieldtype);
 300         elemsize = TYPE_SIZE(elemtype);
 301
 302         /* size of type is represented in bits */
 303
 304         if (typesize == NULL_TREE && TYPE_DOMAIN(fieldtype) != NULL_TREE &&
 305             TYPE_MAX_VALUE(TYPE_DOMAIN(fieldtype)) == NULL_TREE)
 306                 return true;
 307
 308         if (typesize != NULL_TREE &&
 309             (TREE_CONSTANT(typesize) && (!tree_to_uhwi(typesize) ||
 310              tree_to_uhwi(typesize) == tree_to_uhwi(elemsize))))
 311                 return true;
 312
 313         return false;
 314 }
 315
 316 static int relayout_struct(tree type)
 317 {
 318         unsigned long num_fields = (unsigned long)list_length(TYPE_FIELDS(type));
 319         unsigned long shuffle_length = num_fields;
 320         tree field;
 321         tree newtree[num_fields];
 322         unsigned long i;
 323         tree list;
 324         tree variant;
 325         tree main_variant;
 326         expanded_location xloc;
 327         bool has_flexarray = false;
 328
 329         if (TYPE_FIELDS(type) == NULL_TREE)
 330                 return 0;
 331
 332         if (num_fields < 2)
 333                 return 0;
 334
 335         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
 336
 337         gcc_assert(num_fields < INT_MAX);
 338
 339         if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)) ||
 340             lookup_attribute("no_randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))))
 341                 return 0;
 342
 343         /* Workaround for 3rd-party VirtualBox source that we can't modify ourselves */
 344         if (!strcmp((const char *)ORIG_TYPE_NAME(type), "INTNETTRUNKFACTORY") ||
 345             !strcmp((const char *)ORIG_TYPE_NAME(type), "RAWPCIFACTORY"))
 346                 return 0;
 347
 348         /* throw out any structs in uapi */
 349         xloc = expand_location(DECL_SOURCE_LOCATION(TYPE_FIELDS(type)));
 350
 351         if (strstr(xloc.file, "/uapi/"))
 352                 error(G_("attempted to randomize userland API struct %s"), ORIG_TYPE_NAME(type));
 353
 354         for (field = TYPE_FIELDS(type), i = 0; field; field = TREE_CHAIN(field), i++) {
 355                 gcc_assert(TREE_CODE(field) == FIELD_DECL);
 356                 newtree[i] = field;
 357         }
 358
 359         /*
 360          * enforce that we don't randomize the layout of the last
 361          * element of a struct if it's a 0 or 1-length array
 362          * or a proper flexible array
 363          */
 364         if (is_flexible_array(newtree[num_fields - 1])) {
 365                 has_flexarray = true;
 366                 shuffle_length--;
 367         }
 368
 369         shuffle(type, (tree *)newtree, shuffle_length);
 370
 371         /*
 372          * set up a bogus anonymous struct field designed to error out on unnamed struct initializers
 373          * as gcc provides no other way to detect such code
 374          */
 375         list = make_node(FIELD_DECL);
 376         TREE_CHAIN(list) = newtree[0];
 377         TREE_TYPE(list) = void_type_node;
 378         DECL_SIZE(list) = bitsize_zero_node;
 379         DECL_NONADDRESSABLE_P(list) = 1;
 380         DECL_FIELD_BIT_OFFSET(list) = bitsize_zero_node;
 381         DECL_SIZE_UNIT(list) = size_zero_node;
 382         DECL_FIELD_OFFSET(list) = size_zero_node;
 383         DECL_CONTEXT(list) = type;
 384         // to satisfy the constify plugin
 385         TREE_READONLY(list) = 1;
 386
 387         for (i = 0; i < num_fields - 1; i++)
 388                 TREE_CHAIN(newtree[i]) = newtree[i+1];
 389         TREE_CHAIN(newtree[num_fields - 1]) = NULL_TREE;
 390
 391         main_variant = TYPE_MAIN_VARIANT(type);
 392         for (variant = main_variant; variant; variant = TYPE_NEXT_VARIANT(variant)) {
 393                 TYPE_FIELDS(variant) = list;
 394                 TYPE_ATTRIBUTES(variant) = copy_list(TYPE_ATTRIBUTES(variant));
 395                 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("randomize_performed"), NULL_TREE, TYPE_ATTRIBUTES(variant));
 396                 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("designated_init"), NULL_TREE, TYPE_ATTRIBUTES(variant));
 397                 if (has_flexarray)
 398                         TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("has_flexarray"), NULL_TREE, TYPE_ATTRIBUTES(type));
 399         }
 400
 401         /*
 402          * force a re-layout of the main variant
 403          * the TYPE_SIZE for all variants will be recomputed
 404          * by finalize_type_size()
 405          */
 406         TYPE_SIZE(main_variant) = NULL_TREE;
 407         layout_type(main_variant);
 408         gcc_assert(TYPE_SIZE(main_variant) != NULL_TREE);
 409
 410         return 1;
 411 }
 412
 413 /* from constify plugin */
 414 static const_tree get_field_type(const_tree field)
 415 {
 416         return strip_array_types(TREE_TYPE(field));
 417 }
 418
 419 /* from constify plugin */
 420 static bool is_fptr(const_tree fieldtype)
 421 {
 422         if (TREE_CODE(fieldtype) != POINTER_TYPE)
 423                 return false;
 424
 425         return TREE_CODE(TREE_TYPE(fieldtype)) == FUNCTION_TYPE;
 426 }
 427
 428 /* derived from constify plugin */
 429 static int is_pure_ops_struct(const_tree node)
 430 {
 431         const_tree field;
 432
 433         gcc_assert(TREE_CODE(node) == RECORD_TYPE || TREE_CODE(node) == UNION_TYPE);
 434
 435         /* XXX: Do not apply randomization to all-ftpr structs yet. */
 436         return 0;
 437
 438         for (field = TYPE_FIELDS(node); field; field = TREE_CHAIN(field)) {
 439                 const_tree fieldtype = get_field_type(field);
 440                 enum tree_code code = TREE_CODE(fieldtype);
 441
 442                 if (node == fieldtype)
 443                         continue;
 444
 445                 if (!is_fptr(fieldtype))
 446                         return 0;
 447
 448                 if (code != RECORD_TYPE && code != UNION_TYPE)
 449                         continue;
 450
 451                 if (!is_pure_ops_struct(fieldtype))
 452                         return 0;
 453         }
 454
 455         return 1;
 456 }
 457
 458 static void randomize_type(tree type)
 459 {
 460         tree variant;
 461
 462         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
 463
 464         if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
 465                 return;
 466
 467         if (lookup_attribute("randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))) || is_pure_ops_struct(type))
 468                 relayout_struct(type);
 469
 470         for (variant = TYPE_MAIN_VARIANT(type); variant; variant = TYPE_NEXT_VARIANT(variant)) {
 471                 TYPE_ATTRIBUTES(type) = copy_list(TYPE_ATTRIBUTES(type));
 472                 TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("randomize_considered"), NULL_TREE, TYPE_ATTRIBUTES(type));
 473         }
 474 #ifdef __DEBUG_PLUGIN
 475         fprintf(stderr, "Marking randomize_considered on struct %s\n", ORIG_TYPE_NAME(type));
 476 #ifdef __DEBUG_VERBOSE
 477         debug_tree(type);
 478 #endif
 479 #endif
 480 }
 481
 482 static void update_decl_size(tree decl)
 483 {
 484         tree lastval, lastidx, field, init, type, flexsize;
 485         unsigned HOST_WIDE_INT len;
 486
 487         type = TREE_TYPE(decl);
 488
 489         if (!lookup_attribute("has_flexarray", TYPE_ATTRIBUTES(type)))
 490                 return;
 491
 492         init = DECL_INITIAL(decl);
 493         if (init == NULL_TREE || init == error_mark_node)
 494                 return;
 495
 496         if (TREE_CODE(init) != CONSTRUCTOR)
 497                 return;
 498
 499         len = CONSTRUCTOR_NELTS(init);
 500         if (!len)
 501                 return;
 502
 503         lastval = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->value;
 504         lastidx = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->index;
 505
 506         for (field = TYPE_FIELDS(TREE_TYPE(decl)); TREE_CHAIN(field); field = TREE_CHAIN(field))
 507                 ;
 508
 509         if (lastidx != field)
 510                 return;
 511
 512         if (TREE_CODE(lastval) != STRING_CST) {
 513                 error("Only string constants are supported as initializers "
 514                       "for randomized structures with flexible arrays");
 515                 return;
 516         }
 517
 518         flexsize = bitsize_int(TREE_STRING_LENGTH(lastval) *
 519                 tree_to_uhwi(TYPE_SIZE(TREE_TYPE(TREE_TYPE(lastval)))));
 520
 521         DECL_SIZE(decl) = size_binop(PLUS_EXPR, TYPE_SIZE(type), flexsize);
 522
 523         return;
 524 }
 525
 526
 527 static void randomize_layout_finish_decl(void *event_data, void *data)
 528 {
 529         tree decl = (tree)event_data;
 530         tree type;
 531
 532         if (decl == NULL_TREE || decl == error_mark_node)
 533                 return;
 534
 535         type = TREE_TYPE(decl);
 536
 537         if (TREE_CODE(decl) != VAR_DECL)
 538                 return;
 539
 540         if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
 541                 return;
 542
 543         if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)))
 544                 return;
 545
 546         DECL_SIZE(decl) = 0;
 547         DECL_SIZE_UNIT(decl) = 0;
 548         SET_DECL_ALIGN(decl, 0);
 549         SET_DECL_MODE (decl, VOIDmode);
 550         SET_DECL_RTL(decl, 0);
 551         update_decl_size(decl);
 552         layout_decl(decl, 0);
 553 }
 554
 555 static void finish_type(void *event_data, void *data)
 556 {
 557         tree type = (tree)event_data;
 558
 559         if (type == NULL_TREE || type == error_mark_node)
 560                 return;
 561
 562         if (TREE_CODE(type) != RECORD_TYPE)
 563                 return;
 564
 565         if (TYPE_FIELDS(type) == NULL_TREE)
 566                 return;
 567
 568         if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
 569                 return;
 570
 571 #ifdef __DEBUG_PLUGIN
 572         fprintf(stderr, "Calling randomize_type on %s\n", ORIG_TYPE_NAME(type));
 573 #endif
 574 #ifdef __DEBUG_VERBOSE
 575         debug_tree(type);
 576 #endif
 577         randomize_type(type);
 578
 579         return;
 580 }
 581
 582 static struct attribute_spec randomize_layout_attr = {
 583         .name           = "randomize_layout",
 584         // related to args
 585         .min_length     = 0,
 586         .max_length     = 0,
 587         .decl_required  = false,
 588         // need type declaration
 589         .type_required  = true,
 590         .function_type_required = false,
 591         .handler                = handle_randomize_layout_attr,
 592 #if BUILDING_GCC_VERSION >= 4007
 593         .affects_type_identity  = true
 594 #endif
 595 };
 596
 597 static struct attribute_spec no_randomize_layout_attr = {
 598         .name           = "no_randomize_layout",
 599         // related to args
 600         .min_length     = 0,
 601         .max_length     = 0,
 602         .decl_required  = false,
 603         // need type declaration
 604         .type_required  = true,
 605         .function_type_required = false,
 606         .handler                = handle_randomize_layout_attr,
 607 #if BUILDING_GCC_VERSION >= 4007
 608         .affects_type_identity  = true
 609 #endif
 610 };
 611
 612 static struct attribute_spec randomize_considered_attr = {
 613         .name           = "randomize_considered",
 614         // related to args
 615         .min_length     = 0,
 616         .max_length     = 0,
 617         .decl_required  = false,
 618         // need type declaration
 619         .type_required  = true,
 620         .function_type_required = false,
 621         .handler                = handle_randomize_considered_attr,
 622 #if BUILDING_GCC_VERSION >= 4007
 623         .affects_type_identity  = false
 624 #endif
 625 };
 626
 627 static struct attribute_spec randomize_performed_attr = {
 628         .name           = "randomize_performed",
 629         // related to args
 630         .min_length     = 0,
 631         .max_length     = 0,
 632         .decl_required  = false,
 633         // need type declaration
 634         .type_required  = true,
 635         .function_type_required = false,
 636         .handler                = handle_randomize_performed_attr,
 637 #if BUILDING_GCC_VERSION >= 4007
 638         .affects_type_identity  = false
 639 #endif
 640 };
 641
 642 static void register_attributes(void *event_data, void *data)
 643 {
 644         register_attribute(&randomize_layout_attr);
 645         register_attribute(&no_randomize_layout_attr);
 646         register_attribute(&randomize_considered_attr);
 647         register_attribute(&randomize_performed_attr);
 648 }
 649
 650 static void check_bad_casts_in_constructor(tree var, tree init)
 651 {
 652         unsigned HOST_WIDE_INT idx;
 653         tree field, val;
 654         tree field_type, val_type;
 655
 656         FOR_EACH_CONSTRUCTOR_ELT(CONSTRUCTOR_ELTS(init), idx, field, val) {
 657                 if (TREE_CODE(val) == CONSTRUCTOR) {
 658                         check_bad_casts_in_constructor(var, val);
 659                         continue;
 660                 }
 661
 662                 /* pipacs' plugin creates franken-arrays that differ from those produced by
 663                    normal code which all have valid 'field' trees. work around this */
 664                 if (field == NULL_TREE)
 665                         continue;
 666                 field_type = TREE_TYPE(field);
 667                 val_type = TREE_TYPE(val);
 668
 669                 if (TREE_CODE(field_type) != POINTER_TYPE || TREE_CODE(val_type) != POINTER_TYPE)
 670                         continue;
 671
 672                 if (field_type == val_type)
 673                         continue;
 674
 675                 field_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(field_type))));
 676                 val_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(val_type))));
 677
 678                 if (field_type == void_type_node)
 679                         continue;
 680                 if (field_type == val_type)
 681                         continue;
 682                 if (TREE_CODE(val_type) != RECORD_TYPE)
 683                         continue;
 684
 685                 if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(val_type)))
 686                         continue;
 687                 MISMATCH(DECL_SOURCE_LOCATION(var), "constructor\n", TYPE_MAIN_VARIANT(field_type), TYPE_MAIN_VARIANT(val_type));
 688         }
 689 }
 690
 691 /* derived from the constify plugin */
 692 static void check_global_variables(void *event_data, void *data)
 693 {
 694         struct varpool_node *node;
 695         tree init;
 696
 697         FOR_EACH_VARIABLE(node) {
 698                 tree var = NODE_DECL(node);
 699                 init = DECL_INITIAL(var);
 700                 if (init == NULL_TREE)
 701                         continue;
 702
 703                 if (TREE_CODE(init) != CONSTRUCTOR)
 704                         continue;
 705
 706                 check_bad_casts_in_constructor(var, init);
 707         }
 708 }
 709
 710 static bool dominated_by_is_err(const_tree rhs, basic_block bb)
 711 {
 712         basic_block dom;
 713         gimple dom_stmt;
 714         gimple call_stmt;
 715         const_tree dom_lhs;
 716         const_tree poss_is_err_cond;
 717         const_tree poss_is_err_func;
 718         const_tree is_err_arg;
 719
 720         dom = get_immediate_dominator(CDI_DOMINATORS, bb);
 721         if (!dom)
 722                 return false;
 723
 724         dom_stmt = last_stmt(dom);
 725         if (!dom_stmt)
 726                 return false;
 727
 728         if (gimple_code(dom_stmt) != GIMPLE_COND)
 729                 return false;
 730
 731         if (gimple_cond_code(dom_stmt) != NE_EXPR)
 732                 return false;
 733
 734         if (!integer_zerop(gimple_cond_rhs(dom_stmt)))
 735                 return false;
 736
 737         poss_is_err_cond = gimple_cond_lhs(dom_stmt);
 738
 739         if (TREE_CODE(poss_is_err_cond) != SSA_NAME)
 740                 return false;
 741
 742         call_stmt = SSA_NAME_DEF_STMT(poss_is_err_cond);
 743
 744         if (gimple_code(call_stmt) != GIMPLE_CALL)
 745                 return false;
 746
 747         dom_lhs = gimple_get_lhs(call_stmt);
 748         poss_is_err_func = gimple_call_fndecl(call_stmt);
 749         if (!poss_is_err_func)
 750                 return false;
 751         if (dom_lhs != poss_is_err_cond)
 752                 return false;
 753         if (strcmp(DECL_NAME_POINTER(poss_is_err_func), "IS_ERR"))
 754                 return false;
 755
 756         is_err_arg = gimple_call_arg(call_stmt, 0);
 757         if (!is_err_arg)
 758                 return false;
 759
 760         if (is_err_arg != rhs)
 761                 return false;
 762
 763         return true;
 764 }
 765
 766 static void handle_local_var_initializers(void)
 767 {
 768         tree var;
 769         unsigned int i;
 770
 771         FOR_EACH_LOCAL_DECL(cfun, i, var) {
 772                 tree init = DECL_INITIAL(var);
 773                 if (!init)
 774                         continue;
 775                 if (TREE_CODE(init) != CONSTRUCTOR)
 776                         continue;
 777                 check_bad_casts_in_constructor(var, init);
 778         }
 779 }
 780
 781 static bool type_name_eq(gimple stmt, const_tree type_tree, const char *wanted_name)
 782 {
 783         const char *type_name;
 784
 785         if (type_tree == NULL_TREE)
 786                 return false;
 787
 788         switch (TREE_CODE(type_tree)) {
 789         case RECORD_TYPE:
 790                 type_name = TYPE_NAME_POINTER(type_tree);
 791                 break;
 792         case INTEGER_TYPE:
 793                 if (TYPE_PRECISION(type_tree) == CHAR_TYPE_SIZE)
 794                         type_name = "char";
 795                 else {
 796                         INFORM(gimple_location(stmt), "found non-char INTEGER_TYPE cast comparison: %qT\n", type_tree);
 797                         debug_tree(type_tree);
 798                         return false;
 799                 }
 800                 break;
 801         case POINTER_TYPE:
 802                 if (TREE_CODE(TREE_TYPE(type_tree)) == VOID_TYPE) {
 803                         type_name = "void *";
 804                         break;
 805                 } else {
 806                         INFORM(gimple_location(stmt), "found non-void POINTER_TYPE cast comparison %qT\n", type_tree);
 807                         debug_tree(type_tree);
 808                         return false;
 809                 }
 810         default:
 811                 INFORM(gimple_location(stmt), "unhandled cast comparison: %qT\n", type_tree);
 812                 debug_tree(type_tree);
 813                 return false;
 814         }
 815
 816         return strcmp(type_name, wanted_name) == 0;
 817 }
 818
 819 static bool whitelisted_cast(gimple stmt, const_tree lhs_tree, const_tree rhs_tree)
 820 {
 821         const struct whitelist_entry *entry;
 822         expanded_location xloc = expand_location(gimple_location(stmt));
 823
 824         for (entry = whitelist; entry->pathname; entry++) {
 825                 if (!strstr(xloc.file, entry->pathname))
 826                         continue;
 827
 828                 if (type_name_eq(stmt, lhs_tree, entry->lhs) && type_name_eq(stmt, rhs_tree, entry->rhs))
 829                         return true;
 830         }
 831
 832         return false;
 833 }
 834
 835 /*
 836  * iterate over all statements to find "bad" casts:
 837  * those where the address of the start of a structure is cast
 838  * to a pointer of a structure of a different type, or a
 839  * structure pointer type is cast to a different structure pointer type
 840  */
 841 static unsigned int find_bad_casts_execute(void)
 842 {
 843         basic_block bb;
 844
 845         handle_local_var_initializers();
 846
 847         FOR_EACH_BB_FN(bb, cfun) {
 848                 gimple_stmt_iterator gsi;
 849
 850                 for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
 851                         gimple stmt;
 852                         const_tree lhs;
 853                         const_tree lhs_type;
 854                         const_tree rhs1;
 855                         const_tree rhs_type;
 856                         const_tree ptr_lhs_type;
 857                         const_tree ptr_rhs_type;
 858                         const_tree op0;
 859                         const_tree op0_type;
 860                         enum tree_code rhs_code;
 861
 862                         stmt = gsi_stmt(gsi);
 863
 864 #ifdef __DEBUG_PLUGIN
 865 #ifdef __DEBUG_VERBOSE
 866                         debug_gimple_stmt(stmt);
 867                         debug_tree(gimple_get_lhs(stmt));
 868 #endif
 869 #endif
 870
 871                         if (gimple_code(stmt) != GIMPLE_ASSIGN)
 872                                 continue;
 873
 874 #ifdef __DEBUG_PLUGIN
 875 #ifdef __DEBUG_VERBOSE
 876                         debug_tree(gimple_assign_rhs1(stmt));
 877 #endif
 878 #endif
 879
 880
 881                         rhs_code = gimple_assign_rhs_code(stmt);
 882
 883                         if (rhs_code != ADDR_EXPR && rhs_code != SSA_NAME)
 884                                 continue;
 885
 886                         lhs = gimple_get_lhs(stmt);
 887                         lhs_type = TREE_TYPE(lhs);
 888                         rhs1 = gimple_assign_rhs1(stmt);
 889                         rhs_type = TREE_TYPE(rhs1);
 890
 891                         if (TREE_CODE(rhs_type) != POINTER_TYPE ||
 892                             TREE_CODE(lhs_type) != POINTER_TYPE)
 893                                 continue;
 894
 895                         ptr_lhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(lhs_type))));
 896                         ptr_rhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(rhs_type))));
 897
 898                         if (ptr_rhs_type == void_type_node)
 899                                 continue;
 900
 901                         if (ptr_lhs_type == void_type_node)
 902                                 continue;
 903
 904                         if (dominated_by_is_err(rhs1, bb))
 905                                 continue;
 906
 907                         if (TREE_CODE(ptr_rhs_type) != RECORD_TYPE) {
 908 #ifndef __DEBUG_PLUGIN
 909                                 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_lhs_type)))
 910 #endif
 911                                 {
 912                                         if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
 913                                                 MISMATCH(gimple_location(stmt), "rhs", ptr_lhs_type, ptr_rhs_type);
 914                                 }
 915                                 continue;
 916                         }
 917
 918                         if (rhs_code == SSA_NAME && ptr_lhs_type == ptr_rhs_type)
 919                                 continue;
 920
 921                         if (rhs_code == ADDR_EXPR) {
 922                                 op0 = TREE_OPERAND(rhs1, 0);
 923
 924                                 if (op0 == NULL_TREE)
 925                                         continue;
 926
 927                                 if (TREE_CODE(op0) != VAR_DECL)
 928                                         continue;
 929
 930                                 op0_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(op0))));
 931                                 if (op0_type == ptr_lhs_type)
 932                                         continue;
 933
 934 #ifndef __DEBUG_PLUGIN
 935                                 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(op0_type)))
 936 #endif
 937                                 {
 938                                         if (!whitelisted_cast(stmt, ptr_lhs_type, op0_type))
 939                                                 MISMATCH(gimple_location(stmt), "op0", ptr_lhs_type, op0_type);
 940                                 }
 941                         } else {
 942                                 const_tree ssa_name_var = SSA_NAME_VAR(rhs1);
 943                                 /* skip bogus type casts introduced by container_of */
 944                                 if (ssa_name_var != NULL_TREE && DECL_NAME(ssa_name_var) &&
 945                                     !strcmp((const char *)DECL_NAME_POINTER(ssa_name_var), "__mptr"))
 946                                         continue;
 947 #ifndef __DEBUG_PLUGIN
 948                                 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_rhs_type)))
 949 #endif
 950                                 {
 951                                         if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
 952                                                 MISMATCH(gimple_location(stmt), "ssa", ptr_lhs_type, ptr_rhs_type);
 953                                 }
 954                         }
 955
 956                 }
 957         }
 958         return 0;
 959 }
 960
 961 #define PASS_NAME find_bad_casts
 962 #define NO_GATE
 963 #define TODO_FLAGS_FINISH TODO_dump_func
 964 #include "gcc-generate-gimple-pass.h"
 965
 966 __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
 967 {
 968         int i;
 969         const char * const plugin_name = plugin_info->base_name;
 970         const int argc = plugin_info->argc;
 971         const struct plugin_argument * const argv = plugin_info->argv;
 972         bool enable = true;
 973         int obtained_seed = 0;
 974         struct register_pass_info find_bad_casts_pass_info;
 975
 976         find_bad_casts_pass_info.pass                   = make_find_bad_casts_pass();
 977         find_bad_casts_pass_info.reference_pass_name    = "ssa";
 978         find_bad_casts_pass_info.ref_pass_instance_number       = 1;
 979         find_bad_casts_pass_info.pos_op                 = PASS_POS_INSERT_AFTER;
 980
 981         if (!plugin_default_version_check(version, &gcc_version)) {
 982                 error(G_("incompatible gcc/plugin versions"));
 983                 return 1;
 984         }
 985
 986         if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
 987                 inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
 988                 enable = false;
 989         }
 990
 991         for (i = 0; i < argc; ++i) {
 992                 if (!strcmp(argv[i].key, "disable")) {
 993                         enable = false;
 994                         continue;
 995                 }
 996                 if (!strcmp(argv[i].key, "performance-mode")) {
 997                         performance_mode = 1;
 998                         continue;
 999                 }
1000                 error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
1001         }
1002
1003         if (strlen(randstruct_seed) != 64) {
1004                 error(G_("invalid seed value supplied for %s plugin"), plugin_name);
1005                 return 1;
1006         }
1007         obtained_seed = sscanf(randstruct_seed, "%016llx%016llx%016llx%016llx",
1008                 &shuffle_seed[0], &shuffle_seed[1], &shuffle_seed[2], &shuffle_seed[3]);
1009         if (obtained_seed != 4) {
1010                 error(G_("Invalid seed supplied for %s plugin"), plugin_name);
1011                 return 1;
1012         }
1013
1014         register_callback(plugin_name, PLUGIN_INFO, NULL, &randomize_layout_plugin_info);
1015         if (enable) {
1016                 register_callback(plugin_name, PLUGIN_ALL_IPA_PASSES_START, check_global_variables, NULL);
1017                 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &find_bad_casts_pass_info);
1018                 register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
1019                 register_callback(plugin_name, PLUGIN_FINISH_DECL, randomize_layout_finish_decl, NULL);
1020         }
1021         register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);
1022
1023         return 0;
1024 }