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;
 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         for (i = num_groups - 1; i > 0; i--) {
 219                 struct partition_group tmp;
 220                 randnum = ranval(prng_state) % (i + 1);
 221                 tmp = size_group[i];
 222                 size_group[i] = size_group[randnum];
 223                 size_group[randnum] = tmp;
 224         }
 225
 226         for (x = 0; x < num_groups; x++) {
 227                 for (i = size_group[x].start + size_group[x].length - 1; i > size_group[x].start; i--) {
 228                         tree tmp;
 229                         if (DECL_BIT_FIELD_TYPE(newtree[i]))
 230                                 continue;
 231                         randnum = ranval(prng_state) % (i + 1);
 232                         // we could handle this case differently if desired
 233                         if (DECL_BIT_FIELD_TYPE(newtree[randnum]))
 234                                 continue;
 235                         tmp = newtree[i];
 236                         newtree[i] = newtree[randnum];
 237                         newtree[randnum] = tmp;
 238                 }
 239         }
 240 }
 241
 242 static void full_shuffle(tree *newtree, unsigned long length, ranctx *prng_state)
 243 {
 244         unsigned long i, randnum;
 245
 246         for (i = length - 1; i > 0; i--) {
 247                 tree tmp;
 248                 randnum = ranval(prng_state) % (i + 1);
 249                 tmp = newtree[i];
 250                 newtree[i] = newtree[randnum];
 251                 newtree[randnum] = tmp;
 252         }
 253 }
 254
 255 /* modern in-place Fisher-Yates shuffle */
 256 static void shuffle(const_tree type, tree *newtree, unsigned long length)
 257 {
 258         unsigned long i;
 259         u64 seed[4];
 260         ranctx prng_state;
 261         const unsigned char *structname;
 262
 263         if (length == 0)
 264                 return;
 265
 266         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
 267
 268         structname = ORIG_TYPE_NAME(type);
 269
 270 #ifdef __DEBUG_PLUGIN
 271         fprintf(stderr, "Shuffling struct %s %p\n", (const char *)structname, type);
 272 #ifdef __DEBUG_VERBOSE
 273         debug_tree((tree)type);
 274 #endif
 275 #endif
 276
 277         for (i = 0; i < 4; i++) {
 278                 seed[i] = shuffle_seed[i];
 279                 seed[i] ^= name_hash(structname);
 280         }
 281
 282         raninit(&prng_state, (u64 *)&seed);
 283
 284         if (performance_mode)
 285                 performance_shuffle(newtree, length, &prng_state);
 286         else
 287                 full_shuffle(newtree, length, &prng_state);
 288 }
 289
 290 static bool is_flexible_array(const_tree field)
 291 {
 292         const_tree fieldtype;
 293         const_tree typesize;
 294         const_tree elemtype;
 295         const_tree elemsize;
 296
 297         fieldtype = TREE_TYPE(field);
 298         typesize = TYPE_SIZE(fieldtype);
 299
 300         if (TREE_CODE(fieldtype) != ARRAY_TYPE)
 301                 return false;
 302
 303         elemtype = TREE_TYPE(fieldtype);
 304         elemsize = TYPE_SIZE(elemtype);
 305
 306         /* size of type is represented in bits */
 307
 308         if (typesize == NULL_TREE && TYPE_DOMAIN(fieldtype) != NULL_TREE &&
 309             TYPE_MAX_VALUE(TYPE_DOMAIN(fieldtype)) == NULL_TREE)
 310                 return true;
 311
 312         if (typesize != NULL_TREE &&
 313             (TREE_CONSTANT(typesize) && (!tree_to_uhwi(typesize) ||
 314              tree_to_uhwi(typesize) == tree_to_uhwi(elemsize))))
 315                 return true;
 316
 317         return false;
 318 }
 319
 320 static int relayout_struct(tree type)
 321 {
 322         unsigned long num_fields = (unsigned long)list_length(TYPE_FIELDS(type));
 323         unsigned long shuffle_length = num_fields;
 324         tree field;
 325         tree newtree[num_fields];
 326         unsigned long i;
 327         tree list;
 328         tree variant;
 329         tree main_variant;
 330         expanded_location xloc;
 331         bool has_flexarray = false;
 332
 333         if (TYPE_FIELDS(type) == NULL_TREE)
 334                 return 0;
 335
 336         if (num_fields < 2)
 337                 return 0;
 338
 339         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
 340
 341         gcc_assert(num_fields < INT_MAX);
 342
 343         if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)) ||
 344             lookup_attribute("no_randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))))
 345                 return 0;
 346
 347         /* Workaround for 3rd-party VirtualBox source that we can't modify ourselves */
 348         if (!strcmp((const char *)ORIG_TYPE_NAME(type), "INTNETTRUNKFACTORY") ||
 349             !strcmp((const char *)ORIG_TYPE_NAME(type), "RAWPCIFACTORY"))
 350                 return 0;
 351
 352         /* throw out any structs in uapi */
 353         xloc = expand_location(DECL_SOURCE_LOCATION(TYPE_FIELDS(type)));
 354
 355         if (strstr(xloc.file, "/uapi/"))
 356                 error(G_("attempted to randomize userland API struct %s"), ORIG_TYPE_NAME(type));
 357
 358         for (field = TYPE_FIELDS(type), i = 0; field; field = TREE_CHAIN(field), i++) {
 359                 gcc_assert(TREE_CODE(field) == FIELD_DECL);
 360                 newtree[i] = field;
 361         }
 362
 363         /*
 364          * enforce that we don't randomize the layout of the last
 365          * element of a struct if it's a 0 or 1-length array
 366          * or a proper flexible array
 367          */
 368         if (is_flexible_array(newtree[num_fields - 1])) {
 369                 has_flexarray = true;
 370                 shuffle_length--;
 371         }
 372
 373         shuffle(type, (tree *)newtree, shuffle_length);
 374
 375         /*
 376          * set up a bogus anonymous struct field designed to error out on unnamed struct initializers
 377          * as gcc provides no other way to detect such code
 378          */
 379         list = make_node(FIELD_DECL);
 380         TREE_CHAIN(list) = newtree[0];
 381         TREE_TYPE(list) = void_type_node;
 382         DECL_SIZE(list) = bitsize_zero_node;
 383         DECL_NONADDRESSABLE_P(list) = 1;
 384         DECL_FIELD_BIT_OFFSET(list) = bitsize_zero_node;
 385         DECL_SIZE_UNIT(list) = size_zero_node;
 386         DECL_FIELD_OFFSET(list) = size_zero_node;
 387         DECL_CONTEXT(list) = type;
 388         // to satisfy the constify plugin
 389         TREE_READONLY(list) = 1;
 390
 391         for (i = 0; i < num_fields - 1; i++)
 392                 TREE_CHAIN(newtree[i]) = newtree[i+1];
 393         TREE_CHAIN(newtree[num_fields - 1]) = NULL_TREE;
 394
 395         main_variant = TYPE_MAIN_VARIANT(type);
 396         for (variant = main_variant; variant; variant = TYPE_NEXT_VARIANT(variant)) {
 397                 TYPE_FIELDS(variant) = list;
 398                 TYPE_ATTRIBUTES(variant) = copy_list(TYPE_ATTRIBUTES(variant));
 399                 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("randomize_performed"), NULL_TREE, TYPE_ATTRIBUTES(variant));
 400                 TYPE_ATTRIBUTES(variant) = tree_cons(get_identifier("designated_init"), NULL_TREE, TYPE_ATTRIBUTES(variant));
 401                 if (has_flexarray)
 402                         TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("has_flexarray"), NULL_TREE, TYPE_ATTRIBUTES(type));
 403         }
 404
 405         /*
 406          * force a re-layout of the main variant
 407          * the TYPE_SIZE for all variants will be recomputed
 408          * by finalize_type_size()
 409          */
 410         TYPE_SIZE(main_variant) = NULL_TREE;
 411         layout_type(main_variant);
 412         gcc_assert(TYPE_SIZE(main_variant) != NULL_TREE);
 413
 414         return 1;
 415 }
 416
 417 /* from constify plugin */
 418 static const_tree get_field_type(const_tree field)
 419 {
 420         return strip_array_types(TREE_TYPE(field));
 421 }
 422
 423 /* from constify plugin */
 424 static bool is_fptr(const_tree fieldtype)
 425 {
 426         if (TREE_CODE(fieldtype) != POINTER_TYPE)
 427                 return false;
 428
 429         return TREE_CODE(TREE_TYPE(fieldtype)) == FUNCTION_TYPE;
 430 }
 431
 432 /* derived from constify plugin */
 433 static int is_pure_ops_struct(const_tree node)
 434 {
 435         const_tree field;
 436
 437         gcc_assert(TREE_CODE(node) == RECORD_TYPE || TREE_CODE(node) == UNION_TYPE);
 438
 439         for (field = TYPE_FIELDS(node); field; field = TREE_CHAIN(field)) {
 440                 const_tree fieldtype = get_field_type(field);
 441                 enum tree_code code = TREE_CODE(fieldtype);
 442
 443                 if (node == fieldtype)
 444                         continue;
 445
 446                 if (!is_fptr(fieldtype))
 447                         return 0;
 448
 449                 if (code != RECORD_TYPE && code != UNION_TYPE)
 450                         continue;
 451
 452                 if (!is_pure_ops_struct(fieldtype))
 453                         return 0;
 454         }
 455
 456         return 1;
 457 }
 458
 459 static void randomize_type(tree type)
 460 {
 461         tree variant;
 462
 463         gcc_assert(TREE_CODE(type) == RECORD_TYPE);
 464
 465         if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
 466                 return;
 467
 468         if (lookup_attribute("randomize_layout", TYPE_ATTRIBUTES(TYPE_MAIN_VARIANT(type))) || is_pure_ops_struct(type))
 469                 relayout_struct(type);
 470
 471         for (variant = TYPE_MAIN_VARIANT(type); variant; variant = TYPE_NEXT_VARIANT(variant)) {
 472                 TYPE_ATTRIBUTES(type) = copy_list(TYPE_ATTRIBUTES(type));
 473                 TYPE_ATTRIBUTES(type) = tree_cons(get_identifier("randomize_considered"), NULL_TREE, TYPE_ATTRIBUTES(type));
 474         }
 475 #ifdef __DEBUG_PLUGIN
 476         fprintf(stderr, "Marking randomize_considered on struct %s\n", ORIG_TYPE_NAME(type));
 477 #ifdef __DEBUG_VERBOSE
 478         debug_tree(type);
 479 #endif
 480 #endif
 481 }
 482
 483 static void update_decl_size(tree decl)
 484 {
 485         tree lastval, lastidx, field, init, type, flexsize;
 486         unsigned HOST_WIDE_INT len;
 487
 488         type = TREE_TYPE(decl);
 489
 490         if (!lookup_attribute("has_flexarray", TYPE_ATTRIBUTES(type)))
 491                 return;
 492
 493         init = DECL_INITIAL(decl);
 494         if (init == NULL_TREE || init == error_mark_node)
 495                 return;
 496
 497         if (TREE_CODE(init) != CONSTRUCTOR)
 498                 return;
 499
 500         len = CONSTRUCTOR_NELTS(init);
 501         if (!len)
 502                 return;
 503
 504         lastval = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->value;
 505         lastidx = CONSTRUCTOR_ELT(init, CONSTRUCTOR_NELTS(init) - 1)->index;
 506
 507         for (field = TYPE_FIELDS(TREE_TYPE(decl)); TREE_CHAIN(field); field = TREE_CHAIN(field))
 508                 ;
 509
 510         if (lastidx != field)
 511                 return;
 512
 513         if (TREE_CODE(lastval) != STRING_CST) {
 514                 error("Only string constants are supported as initializers "
 515                       "for randomized structures with flexible arrays");
 516                 return;
 517         }
 518
 519         flexsize = bitsize_int(TREE_STRING_LENGTH(lastval) *
 520                 tree_to_uhwi(TYPE_SIZE(TREE_TYPE(TREE_TYPE(lastval)))));
 521
 522         DECL_SIZE(decl) = size_binop(PLUS_EXPR, TYPE_SIZE(type), flexsize);
 523
 524         return;
 525 }
 526
 527
 528 static void randomize_layout_finish_decl(void *event_data, void *data)
 529 {
 530         tree decl = (tree)event_data;
 531         tree type;
 532
 533         if (decl == NULL_TREE || decl == error_mark_node)
 534                 return;
 535
 536         type = TREE_TYPE(decl);
 537
 538         if (TREE_CODE(decl) != VAR_DECL)
 539                 return;
 540
 541         if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
 542                 return;
 543
 544         if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(type)))
 545                 return;
 546
 547         DECL_SIZE(decl) = 0;
 548         DECL_SIZE_UNIT(decl) = 0;
 549         SET_DECL_ALIGN(decl, 0);
 550         SET_DECL_MODE (decl, VOIDmode);
 551         SET_DECL_RTL(decl, 0);
 552         update_decl_size(decl);
 553         layout_decl(decl, 0);
 554 }
 555
 556 static void finish_type(void *event_data, void *data)
 557 {
 558         tree type = (tree)event_data;
 559
 560         if (type == NULL_TREE || type == error_mark_node)
 561                 return;
 562
 563         if (TREE_CODE(type) != RECORD_TYPE)
 564                 return;
 565
 566         if (TYPE_FIELDS(type) == NULL_TREE)
 567                 return;
 568
 569         if (lookup_attribute("randomize_considered", TYPE_ATTRIBUTES(type)))
 570                 return;
 571
 572 #ifdef __DEBUG_PLUGIN
 573         fprintf(stderr, "Calling randomize_type on %s\n", ORIG_TYPE_NAME(type));
 574 #endif
 575 #ifdef __DEBUG_VERBOSE
 576         debug_tree(type);
 577 #endif
 578         randomize_type(type);
 579
 580         return;
 581 }
 582
 583 static struct attribute_spec randomize_layout_attr = {
 584         .name           = "randomize_layout",
 585         // related to args
 586         .min_length     = 0,
 587         .max_length     = 0,
 588         .decl_required  = false,
 589         // need type declaration
 590         .type_required  = true,
 591         .function_type_required = false,
 592         .handler                = handle_randomize_layout_attr,
 593 #if BUILDING_GCC_VERSION >= 4007
 594         .affects_type_identity  = true
 595 #endif
 596 };
 597
 598 static struct attribute_spec no_randomize_layout_attr = {
 599         .name           = "no_randomize_layout",
 600         // related to args
 601         .min_length     = 0,
 602         .max_length     = 0,
 603         .decl_required  = false,
 604         // need type declaration
 605         .type_required  = true,
 606         .function_type_required = false,
 607         .handler                = handle_randomize_layout_attr,
 608 #if BUILDING_GCC_VERSION >= 4007
 609         .affects_type_identity  = true
 610 #endif
 611 };
 612
 613 static struct attribute_spec randomize_considered_attr = {
 614         .name           = "randomize_considered",
 615         // related to args
 616         .min_length     = 0,
 617         .max_length     = 0,
 618         .decl_required  = false,
 619         // need type declaration
 620         .type_required  = true,
 621         .function_type_required = false,
 622         .handler                = handle_randomize_considered_attr,
 623 #if BUILDING_GCC_VERSION >= 4007
 624         .affects_type_identity  = false
 625 #endif
 626 };
 627
 628 static struct attribute_spec randomize_performed_attr = {
 629         .name           = "randomize_performed",
 630         // related to args
 631         .min_length     = 0,
 632         .max_length     = 0,
 633         .decl_required  = false,
 634         // need type declaration
 635         .type_required  = true,
 636         .function_type_required = false,
 637         .handler                = handle_randomize_performed_attr,
 638 #if BUILDING_GCC_VERSION >= 4007
 639         .affects_type_identity  = false
 640 #endif
 641 };
 642
 643 static void register_attributes(void *event_data, void *data)
 644 {
 645         register_attribute(&randomize_layout_attr);
 646         register_attribute(&no_randomize_layout_attr);
 647         register_attribute(&randomize_considered_attr);
 648         register_attribute(&randomize_performed_attr);
 649 }
 650
 651 static void check_bad_casts_in_constructor(tree var, tree init)
 652 {
 653         unsigned HOST_WIDE_INT idx;
 654         tree field, val;
 655         tree field_type, val_type;
 656
 657         FOR_EACH_CONSTRUCTOR_ELT(CONSTRUCTOR_ELTS(init), idx, field, val) {
 658                 if (TREE_CODE(val) == CONSTRUCTOR) {
 659                         check_bad_casts_in_constructor(var, val);
 660                         continue;
 661                 }
 662
 663                 /* pipacs' plugin creates franken-arrays that differ from those produced by
 664                    normal code which all have valid 'field' trees. work around this */
 665                 if (field == NULL_TREE)
 666                         continue;
 667                 field_type = TREE_TYPE(field);
 668                 val_type = TREE_TYPE(val);
 669
 670                 if (TREE_CODE(field_type) != POINTER_TYPE || TREE_CODE(val_type) != POINTER_TYPE)
 671                         continue;
 672
 673                 if (field_type == val_type)
 674                         continue;
 675
 676                 field_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(field_type))));
 677                 val_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(val_type))));
 678
 679                 if (field_type == void_type_node)
 680                         continue;
 681                 if (field_type == val_type)
 682                         continue;
 683                 if (TREE_CODE(val_type) != RECORD_TYPE)
 684                         continue;
 685
 686                 if (!lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(val_type)))
 687                         continue;
 688                 MISMATCH(DECL_SOURCE_LOCATION(var), "constructor\n", TYPE_MAIN_VARIANT(field_type), TYPE_MAIN_VARIANT(val_type));
 689         }
 690 }
 691
 692 /* derived from the constify plugin */
 693 static void check_global_variables(void *event_data, void *data)
 694 {
 695         struct varpool_node *node;
 696         tree init;
 697
 698         FOR_EACH_VARIABLE(node) {
 699                 tree var = NODE_DECL(node);
 700                 init = DECL_INITIAL(var);
 701                 if (init == NULL_TREE)
 702                         continue;
 703
 704                 if (TREE_CODE(init) != CONSTRUCTOR)
 705                         continue;
 706
 707                 check_bad_casts_in_constructor(var, init);
 708         }
 709 }
 710
 711 static bool dominated_by_is_err(const_tree rhs, basic_block bb)
 712 {
 713         basic_block dom;
 714         gimple dom_stmt;
 715         gimple call_stmt;
 716         const_tree dom_lhs;
 717         const_tree poss_is_err_cond;
 718         const_tree poss_is_err_func;
 719         const_tree is_err_arg;
 720
 721         dom = get_immediate_dominator(CDI_DOMINATORS, bb);
 722         if (!dom)
 723                 return false;
 724
 725         dom_stmt = last_stmt(dom);
 726         if (!dom_stmt)
 727                 return false;
 728
 729         if (gimple_code(dom_stmt) != GIMPLE_COND)
 730                 return false;
 731
 732         if (gimple_cond_code(dom_stmt) != NE_EXPR)
 733                 return false;
 734
 735         if (!integer_zerop(gimple_cond_rhs(dom_stmt)))
 736                 return false;
 737
 738         poss_is_err_cond = gimple_cond_lhs(dom_stmt);
 739
 740         if (TREE_CODE(poss_is_err_cond) != SSA_NAME)
 741                 return false;
 742
 743         call_stmt = SSA_NAME_DEF_STMT(poss_is_err_cond);
 744
 745         if (gimple_code(call_stmt) != GIMPLE_CALL)
 746                 return false;
 747
 748         dom_lhs = gimple_get_lhs(call_stmt);
 749         poss_is_err_func = gimple_call_fndecl(call_stmt);
 750         if (!poss_is_err_func)
 751                 return false;
 752         if (dom_lhs != poss_is_err_cond)
 753                 return false;
 754         if (strcmp(DECL_NAME_POINTER(poss_is_err_func), "IS_ERR"))
 755                 return false;
 756
 757         is_err_arg = gimple_call_arg(call_stmt, 0);
 758         if (!is_err_arg)
 759                 return false;
 760
 761         if (is_err_arg != rhs)
 762                 return false;
 763
 764         return true;
 765 }
 766
 767 static void handle_local_var_initializers(void)
 768 {
 769         tree var;
 770         unsigned int i;
 771
 772         FOR_EACH_LOCAL_DECL(cfun, i, var) {
 773                 tree init = DECL_INITIAL(var);
 774                 if (!init)
 775                         continue;
 776                 if (TREE_CODE(init) != CONSTRUCTOR)
 777                         continue;
 778                 check_bad_casts_in_constructor(var, init);
 779         }
 780 }
 781
 782 static bool type_name_eq(gimple stmt, const_tree type_tree, const char *wanted_name)
 783 {
 784         const char *type_name;
 785
 786         if (type_tree == NULL_TREE)
 787                 return false;
 788
 789         switch (TREE_CODE(type_tree)) {
 790         case RECORD_TYPE:
 791                 type_name = TYPE_NAME_POINTER(type_tree);
 792                 break;
 793         case INTEGER_TYPE:
 794                 if (TYPE_PRECISION(type_tree) == CHAR_TYPE_SIZE)
 795                         type_name = "char";
 796                 else {
 797                         INFORM(gimple_location(stmt), "found non-char INTEGER_TYPE cast comparison: %qT\n", type_tree);
 798                         debug_tree(type_tree);
 799                         return false;
 800                 }
 801                 break;
 802         case POINTER_TYPE:
 803                 if (TREE_CODE(TREE_TYPE(type_tree)) == VOID_TYPE) {
 804                         type_name = "void *";
 805                         break;
 806                 } else {
 807                         INFORM(gimple_location(stmt), "found non-void POINTER_TYPE cast comparison %qT\n", type_tree);
 808                         debug_tree(type_tree);
 809                         return false;
 810                 }
 811         default:
 812                 INFORM(gimple_location(stmt), "unhandled cast comparison: %qT\n", type_tree);
 813                 debug_tree(type_tree);
 814                 return false;
 815         }
 816
 817         return strcmp(type_name, wanted_name) == 0;
 818 }
 819
 820 static bool whitelisted_cast(gimple stmt, const_tree lhs_tree, const_tree rhs_tree)
 821 {
 822         const struct whitelist_entry *entry;
 823         expanded_location xloc = expand_location(gimple_location(stmt));
 824
 825         for (entry = whitelist; entry->pathname; entry++) {
 826                 if (!strstr(xloc.file, entry->pathname))
 827                         continue;
 828
 829                 if (type_name_eq(stmt, lhs_tree, entry->lhs) && type_name_eq(stmt, rhs_tree, entry->rhs))
 830                         return true;
 831         }
 832
 833         return false;
 834 }
 835
 836 /*
 837  * iterate over all statements to find "bad" casts:
 838  * those where the address of the start of a structure is cast
 839  * to a pointer of a structure of a different type, or a
 840  * structure pointer type is cast to a different structure pointer type
 841  */
 842 static unsigned int find_bad_casts_execute(void)
 843 {
 844         basic_block bb;
 845
 846         handle_local_var_initializers();
 847
 848         FOR_EACH_BB_FN(bb, cfun) {
 849                 gimple_stmt_iterator gsi;
 850
 851                 for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
 852                         gimple stmt;
 853                         const_tree lhs;
 854                         const_tree lhs_type;
 855                         const_tree rhs1;
 856                         const_tree rhs_type;
 857                         const_tree ptr_lhs_type;
 858                         const_tree ptr_rhs_type;
 859                         const_tree op0;
 860                         const_tree op0_type;
 861                         enum tree_code rhs_code;
 862
 863                         stmt = gsi_stmt(gsi);
 864
 865 #ifdef __DEBUG_PLUGIN
 866 #ifdef __DEBUG_VERBOSE
 867                         debug_gimple_stmt(stmt);
 868                         debug_tree(gimple_get_lhs(stmt));
 869 #endif
 870 #endif
 871
 872                         if (gimple_code(stmt) != GIMPLE_ASSIGN)
 873                                 continue;
 874
 875 #ifdef __DEBUG_PLUGIN
 876 #ifdef __DEBUG_VERBOSE
 877                         debug_tree(gimple_assign_rhs1(stmt));
 878 #endif
 879 #endif
 880
 881
 882                         rhs_code = gimple_assign_rhs_code(stmt);
 883
 884                         if (rhs_code != ADDR_EXPR && rhs_code != SSA_NAME)
 885                                 continue;
 886
 887                         lhs = gimple_get_lhs(stmt);
 888                         lhs_type = TREE_TYPE(lhs);
 889                         rhs1 = gimple_assign_rhs1(stmt);
 890                         rhs_type = TREE_TYPE(rhs1);
 891
 892                         if (TREE_CODE(rhs_type) != POINTER_TYPE ||
 893                             TREE_CODE(lhs_type) != POINTER_TYPE)
 894                                 continue;
 895
 896                         ptr_lhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(lhs_type))));
 897                         ptr_rhs_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(rhs_type))));
 898
 899                         if (ptr_rhs_type == void_type_node)
 900                                 continue;
 901
 902                         if (ptr_lhs_type == void_type_node)
 903                                 continue;
 904
 905                         if (dominated_by_is_err(rhs1, bb))
 906                                 continue;
 907
 908                         if (TREE_CODE(ptr_rhs_type) != RECORD_TYPE) {
 909 #ifndef __DEBUG_PLUGIN
 910                                 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_lhs_type)))
 911 #endif
 912                                 {
 913                                         if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
 914                                                 MISMATCH(gimple_location(stmt), "rhs", ptr_lhs_type, ptr_rhs_type);
 915                                 }
 916                                 continue;
 917                         }
 918
 919                         if (rhs_code == SSA_NAME && ptr_lhs_type == ptr_rhs_type)
 920                                 continue;
 921
 922                         if (rhs_code == ADDR_EXPR) {
 923                                 op0 = TREE_OPERAND(rhs1, 0);
 924
 925                                 if (op0 == NULL_TREE)
 926                                         continue;
 927
 928                                 if (TREE_CODE(op0) != VAR_DECL)
 929                                         continue;
 930
 931                                 op0_type = TYPE_MAIN_VARIANT(strip_array_types(TYPE_MAIN_VARIANT(TREE_TYPE(op0))));
 932                                 if (op0_type == ptr_lhs_type)
 933                                         continue;
 934
 935 #ifndef __DEBUG_PLUGIN
 936                                 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(op0_type)))
 937 #endif
 938                                 {
 939                                         if (!whitelisted_cast(stmt, ptr_lhs_type, op0_type))
 940                                                 MISMATCH(gimple_location(stmt), "op0", ptr_lhs_type, op0_type);
 941                                 }
 942                         } else {
 943                                 const_tree ssa_name_var = SSA_NAME_VAR(rhs1);
 944                                 /* skip bogus type casts introduced by container_of */
 945                                 if (ssa_name_var != NULL_TREE && DECL_NAME(ssa_name_var) &&
 946                                     !strcmp((const char *)DECL_NAME_POINTER(ssa_name_var), "__mptr"))
 947                                         continue;
 948 #ifndef __DEBUG_PLUGIN
 949                                 if (lookup_attribute("randomize_performed", TYPE_ATTRIBUTES(ptr_rhs_type)))
 950 #endif
 951                                 {
 952                                         if (!whitelisted_cast(stmt, ptr_lhs_type, ptr_rhs_type))
 953                                                 MISMATCH(gimple_location(stmt), "ssa", ptr_lhs_type, ptr_rhs_type);
 954                                 }
 955                         }
 956
 957                 }
 958         }
 959         return 0;
 960 }
 961
 962 #define PASS_NAME find_bad_casts
 963 #define NO_GATE
 964 #define TODO_FLAGS_FINISH TODO_dump_func
 965 #include "gcc-generate-gimple-pass.h"
 966
 967 __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
 968 {
 969         int i;
 970         const char * const plugin_name = plugin_info->base_name;
 971         const int argc = plugin_info->argc;
 972         const struct plugin_argument * const argv = plugin_info->argv;
 973         bool enable = true;
 974         int obtained_seed = 0;
 975         struct register_pass_info find_bad_casts_pass_info;
 976
 977         find_bad_casts_pass_info.pass                   = make_find_bad_casts_pass();
 978         find_bad_casts_pass_info.reference_pass_name    = "ssa";
 979         find_bad_casts_pass_info.ref_pass_instance_number       = 1;
 980         find_bad_casts_pass_info.pos_op                 = PASS_POS_INSERT_AFTER;
 981
 982         if (!plugin_default_version_check(version, &gcc_version)) {
 983                 error(G_("incompatible gcc/plugin versions"));
 984                 return 1;
 985         }
 986
 987         if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
 988                 inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
 989                 enable = false;
 990         }
 991
 992         for (i = 0; i < argc; ++i) {
 993                 if (!strcmp(argv[i].key, "disable")) {
 994                         enable = false;
 995                         continue;
 996                 }
 997                 if (!strcmp(argv[i].key, "performance-mode")) {
 998                         performance_mode = 1;
 999                         continue;
1000                 }
1001                 error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
1002         }
1003
1004         if (strlen(randstruct_seed) != 64) {
1005                 error(G_("invalid seed value supplied for %s plugin"), plugin_name);
1006                 return 1;
1007         }
1008         obtained_seed = sscanf(randstruct_seed, "%016llx%016llx%016llx%016llx",
1009                 &shuffle_seed[0], &shuffle_seed[1], &shuffle_seed[2], &shuffle_seed[3]);
1010         if (obtained_seed != 4) {
1011                 error(G_("Invalid seed supplied for %s plugin"), plugin_name);
1012                 return 1;
1013         }
1014
1015         register_callback(plugin_name, PLUGIN_INFO, NULL, &randomize_layout_plugin_info);
1016         if (enable) {
1017                 register_callback(plugin_name, PLUGIN_ALL_IPA_PASSES_START, check_global_variables, NULL);
1018                 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &find_bad_casts_pass_info);
1019                 register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
1020                 register_callback(plugin_name, PLUGIN_FINISH_DECL, randomize_layout_finish_decl, NULL);
1021         }
1022         register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);
1023
1024         return 0;
1025 }