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