scripts/gcc-plugins/latent_entropy_plugin.c

   1 /*
   2  * Copyright 2012-2016 by the PaX Team <pageexec@freemail.hu>
   3  * Copyright 2016 by Emese Revfy <re.emese@gmail.com>
   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  * This gcc plugin helps generate a little bit of entropy from program state,
  12  * used throughout the uptime of the kernel. Here is an instrumentation example:
  13  *
  14  * before:
  15  * void __latent_entropy test(int argc, char *argv[])
  16  * {
  17  *      if (argc <= 1)
  18  *              printf("%s: no command arguments :(\n", *argv);
  19  *      else
  20  *              printf("%s: %d command arguments!\n", *argv, args - 1);
  21  * }
  22  *
  23  * after:
  24  * void __latent_entropy test(int argc, char *argv[])
  25  * {
  26  *      // latent_entropy_execute() 1.
  27  *      unsigned long local_entropy;
  28  *      // init_local_entropy() 1.
  29  *      void *local_entropy_frameaddr;
  30  *      // init_local_entropy() 3.
  31  *      unsigned long tmp_latent_entropy;
  32  *
  33  *      // init_local_entropy() 2.
  34  *      local_entropy_frameaddr = __builtin_frame_address(0);
  35  *      local_entropy = (unsigned long) local_entropy_frameaddr;
  36  *
  37  *      // init_local_entropy() 4.
  38  *      tmp_latent_entropy = latent_entropy;
  39  *      // init_local_entropy() 5.
  40  *      local_entropy ^= tmp_latent_entropy;
  41  *
  42  *      // latent_entropy_execute() 3.
  43  *      if (argc <= 1) {
  44  *              // perturb_local_entropy()
  45  *              local_entropy += 4623067384293424948;
  46  *              printf("%s: no command arguments :(\n", *argv);
  47  *              // perturb_local_entropy()
  48  *      } else {
  49  *              local_entropy ^= 3896280633962944730;
  50  *              printf("%s: %d command arguments!\n", *argv, args - 1);
  51  *      }
  52  *
  53  *      // latent_entropy_execute() 4.
  54  *      tmp_latent_entropy = rol(tmp_latent_entropy, local_entropy);
  55  *      latent_entropy = tmp_latent_entropy;
  56  * }
  57  *
  58  * TODO:
  59  * - add ipa pass to identify not explicitly marked candidate functions
  60  * - mix in more program state (function arguments/return values,
  61  *   loop variables, etc)
  62  * - more instrumentation control via attribute parameters
  63  *
  64  * BUGS:
  65  * - none known
  66  *
  67  * Options:
  68  * -fplugin-arg-latent_entropy_plugin-disable
  69  *
  70  * Attribute: __attribute__((latent_entropy))
  71  *  The latent_entropy gcc attribute can be only on functions and variables.
  72  *  If it is on a function then the plugin will instrument it. If the attribute
  73  *  is on a variable then the plugin will initialize it with a random value.
  74  *  The variable must be an integer, an integer array type or a structure
  75  *  with integer fields.
  76  */
  77
  78 #include "gcc-common.h"
  79
  80 __visible int plugin_is_GPL_compatible;
  81
  82 static GTY(()) tree latent_entropy_decl;
  83
  84 static struct plugin_info latent_entropy_plugin_info = {
  85         .version        = "201606141920vanilla",
  86         .help           = "disable\tturn off latent entropy instrumentation\n",
  87 };
  88
  89 static unsigned HOST_WIDE_INT deterministic_seed;
  90 static unsigned HOST_WIDE_INT rnd_buf[32];
  91 static size_t rnd_idx = ARRAY_SIZE(rnd_buf);
  92 static int urandom_fd = -1;
  93
  94 static unsigned HOST_WIDE_INT get_random_const(void)
  95 {
  96         if (deterministic_seed) {
  97                 unsigned HOST_WIDE_INT w = deterministic_seed;
  98                 w ^= w << 13;
  99                 w ^= w >> 7;
 100                 w ^= w << 17;
 101                 deterministic_seed = w;
 102                 return deterministic_seed;
 103         }
 104
 105         if (urandom_fd < 0) {
 106                 urandom_fd = open("/dev/urandom", O_RDONLY);
 107                 gcc_assert(urandom_fd >= 0);
 108         }
 109         if (rnd_idx >= ARRAY_SIZE(rnd_buf)) {
 110                 gcc_assert(read(urandom_fd, rnd_buf, sizeof(rnd_buf)) == sizeof(rnd_buf));
 111                 rnd_idx = 0;
 112         }
 113         return rnd_buf[rnd_idx++];
 114 }
 115
 116 static tree tree_get_random_const(tree type)
 117 {
 118         unsigned long long mask;
 119
 120         mask = 1ULL << (TREE_INT_CST_LOW(TYPE_SIZE(type)) - 1);
 121         mask = 2 * (mask - 1) + 1;
 122
 123         if (TYPE_UNSIGNED(type))
 124                 return build_int_cstu(type, mask & get_random_const());
 125         return build_int_cst(type, mask & get_random_const());
 126 }
 127
 128 static tree handle_latent_entropy_attribute(tree *node, tree name,
 129                                                 tree args __unused,
 130                                                 int flags __unused,
 131                                                 bool *no_add_attrs)
 132 {
 133         tree type;
 134 #if BUILDING_GCC_VERSION <= 4007
 135         VEC(constructor_elt, gc) *vals;
 136 #else
 137         vec<constructor_elt, va_gc> *vals;
 138 #endif
 139
 140         switch (TREE_CODE(*node)) {
 141         default:
 142                 *no_add_attrs = true;
 143                 error("%qE attribute only applies to functions and variables",
 144                         name);
 145                 break;
 146
 147         case VAR_DECL:
 148                 if (DECL_INITIAL(*node)) {
 149                         *no_add_attrs = true;
 150                         error("variable %qD with %qE attribute must not be initialized",
 151                                 *node, name);
 152                         break;
 153                 }
 154
 155                 if (!TREE_STATIC(*node)) {
 156                         *no_add_attrs = true;
 157                         error("variable %qD with %qE attribute must not be local",
 158                                 *node, name);
 159                         break;
 160                 }
 161
 162                 type = TREE_TYPE(*node);
 163                 switch (TREE_CODE(type)) {
 164                 default:
 165                         *no_add_attrs = true;
 166                         error("variable %qD with %qE attribute must be an integer or a fixed length integer array type or a fixed sized structure with integer fields",
 167                                 *node, name);
 168                         break;
 169
 170                 case RECORD_TYPE: {
 171                         tree fld, lst = TYPE_FIELDS(type);
 172                         unsigned int nelt = 0;
 173
 174                         for (fld = lst; fld; nelt++, fld = TREE_CHAIN(fld)) {
 175                                 tree fieldtype;
 176
 177                                 fieldtype = TREE_TYPE(fld);
 178                                 if (TREE_CODE(fieldtype) == INTEGER_TYPE)
 179                                         continue;
 180
 181                                 *no_add_attrs = true;
 182                                 error("structure variable %qD with %qE attribute has a non-integer field %qE",
 183                                         *node, name, fld);
 184                                 break;
 185                         }
 186
 187                         if (fld)
 188                                 break;
 189
 190 #if BUILDING_GCC_VERSION <= 4007
 191                         vals = VEC_alloc(constructor_elt, gc, nelt);
 192 #else
 193                         vec_alloc(vals, nelt);
 194 #endif
 195
 196                         for (fld = lst; fld; fld = TREE_CHAIN(fld)) {
 197                                 tree random_const, fld_t = TREE_TYPE(fld);
 198
 199                                 random_const = tree_get_random_const(fld_t);
 200                                 CONSTRUCTOR_APPEND_ELT(vals, fld, random_const);
 201                         }
 202
 203                         /* Initialize the fields with random constants */
 204                         DECL_INITIAL(*node) = build_constructor(type, vals);
 205                         break;
 206                 }
 207
 208                 /* Initialize the variable with a random constant */
 209                 case INTEGER_TYPE:
 210                         DECL_INITIAL(*node) = tree_get_random_const(type);
 211                         break;
 212
 213                 case ARRAY_TYPE: {
 214                         tree elt_type, array_size, elt_size;
 215                         unsigned int i, nelt;
 216                         HOST_WIDE_INT array_size_int, elt_size_int;
 217
 218                         elt_type = TREE_TYPE(type);
 219                         elt_size = TYPE_SIZE_UNIT(TREE_TYPE(type));
 220                         array_size = TYPE_SIZE_UNIT(type);
 221
 222                         if (TREE_CODE(elt_type) != INTEGER_TYPE || !array_size
 223                                 || TREE_CODE(array_size) != INTEGER_CST) {
 224                                 *no_add_attrs = true;
 225                                 error("array variable %qD with %qE attribute must be a fixed length integer array type",
 226                                         *node, name);
 227                                 break;
 228                         }
 229
 230                         array_size_int = TREE_INT_CST_LOW(array_size);
 231                         elt_size_int = TREE_INT_CST_LOW(elt_size);
 232                         nelt = array_size_int / elt_size_int;
 233
 234 #if BUILDING_GCC_VERSION <= 4007
 235                         vals = VEC_alloc(constructor_elt, gc, nelt);
 236 #else
 237                         vec_alloc(vals, nelt);
 238 #endif
 239
 240                         for (i = 0; i < nelt; i++) {
 241                                 tree cst = size_int(i);
 242                                 tree rand_cst = tree_get_random_const(elt_type);
 243
 244                                 CONSTRUCTOR_APPEND_ELT(vals, cst, rand_cst);
 245                         }
 246
 247                         /*
 248                          * Initialize the elements of the array with random
 249                          * constants
 250                          */
 251                         DECL_INITIAL(*node) = build_constructor(type, vals);
 252                         break;
 253                 }
 254                 }
 255                 break;
 256
 257         case FUNCTION_DECL:
 258                 break;
 259         }
 260
 261         return NULL_TREE;
 262 }
 263
 264 static struct attribute_spec latent_entropy_attr = { };
 265
 266 static void register_attributes(void *event_data __unused, void *data __unused)
 267 {
 268         latent_entropy_attr.name                = "latent_entropy";
 269         latent_entropy_attr.decl_required       = true;
 270         latent_entropy_attr.handler             = handle_latent_entropy_attribute;
 271
 272         register_attribute(&latent_entropy_attr);
 273 }
 274
 275 static bool latent_entropy_gate(void)
 276 {
 277         tree list;
 278
 279         /* don't bother with noreturn functions for now */
 280         if (TREE_THIS_VOLATILE(current_function_decl))
 281                 return false;
 282
 283         /* gcc-4.5 doesn't discover some trivial noreturn functions */
 284         if (EDGE_COUNT(EXIT_BLOCK_PTR_FOR_FN(cfun)->preds) == 0)
 285                 return false;
 286
 287         list = DECL_ATTRIBUTES(current_function_decl);
 288         return lookup_attribute("latent_entropy", list) != NULL_TREE;
 289 }
 290
 291 static tree create_var(tree type, const char *name)
 292 {
 293         tree var;
 294
 295         var = create_tmp_var(type, name);
 296         add_referenced_var(var);
 297         mark_sym_for_renaming(var);
 298         return var;
 299 }
 300
 301 /*
 302  * Set up the next operation and its constant operand to use in the latent
 303  * entropy PRNG. When RHS is specified, the request is for perturbing the
 304  * local latent entropy variable, otherwise it is for perturbing the global
 305  * latent entropy variable where the two operands are already given by the
 306  * local and global latent entropy variables themselves.
 307  *
 308  * The operation is one of add/xor/rol when instrumenting the local entropy
 309  * variable and one of add/xor when perturbing the global entropy variable.
 310  * Rotation is not used for the latter case because it would transmit less
 311  * entropy to the global variable than the other two operations.
 312  */
 313 static enum tree_code get_op(tree *rhs)
 314 {
 315         static enum tree_code op;
 316         unsigned HOST_WIDE_INT random_const;
 317
 318         random_const = get_random_const();
 319
 320         switch (op) {
 321         case BIT_XOR_EXPR:
 322                 op = PLUS_EXPR;
 323                 break;
 324
 325         case PLUS_EXPR:
 326                 if (rhs) {
 327                         op = LROTATE_EXPR;
 328                         /*
 329                          * This code limits the value of random_const to
 330                          * the size of a long for the rotation
 331                          */
 332                         random_const %= TYPE_PRECISION(long_unsigned_type_node);
 333                         break;
 334                 }
 335
 336         case LROTATE_EXPR:
 337         default:
 338                 op = BIT_XOR_EXPR;
 339                 break;
 340         }
 341         if (rhs)
 342                 *rhs = build_int_cstu(long_unsigned_type_node, random_const);
 343         return op;
 344 }
 345
 346 static gimple create_assign(enum tree_code code, tree lhs, tree op1,
 347                                 tree op2)
 348 {
 349         return gimple_build_assign_with_ops(code, lhs, op1, op2);
 350 }
 351
 352 static void perturb_local_entropy(basic_block bb, tree local_entropy)
 353 {
 354         gimple_stmt_iterator gsi;
 355         gimple assign;
 356         tree rhs;
 357         enum tree_code op;
 358
 359         op = get_op(&rhs);
 360         assign = create_assign(op, local_entropy, local_entropy, rhs);
 361         gsi = gsi_after_labels(bb);
 362         gsi_insert_before(&gsi, assign, GSI_NEW_STMT);
 363         update_stmt(assign);
 364 }
 365
 366 static void __perturb_latent_entropy(gimple_stmt_iterator *gsi,
 367                                         tree local_entropy)
 368 {
 369         gimple assign;
 370         tree temp;
 371         enum tree_code op;
 372
 373         /* 1. create temporary copy of latent_entropy */
 374         temp = create_var(long_unsigned_type_node, "temp_latent_entropy");
 375
 376         /* 2. read... */
 377         add_referenced_var(latent_entropy_decl);
 378         mark_sym_for_renaming(latent_entropy_decl);
 379         assign = gimple_build_assign(temp, latent_entropy_decl);
 380         gsi_insert_before(gsi, assign, GSI_NEW_STMT);
 381         update_stmt(assign);
 382
 383         /* 3. ...modify... */
 384         op = get_op(NULL);
 385         assign = create_assign(op, temp, temp, local_entropy);
 386         gsi_insert_after(gsi, assign, GSI_NEW_STMT);
 387         update_stmt(assign);
 388
 389         /* 4. ...write latent_entropy */
 390         assign = gimple_build_assign(latent_entropy_decl, temp);
 391         gsi_insert_after(gsi, assign, GSI_NEW_STMT);
 392         update_stmt(assign);
 393 }
 394
 395 static bool handle_tail_calls(basic_block bb, tree local_entropy)
 396 {
 397         gimple_stmt_iterator gsi;
 398
 399         for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
 400                 gcall *call;
 401                 gimple stmt = gsi_stmt(gsi);
 402
 403                 if (!is_gimple_call(stmt))
 404                         continue;
 405
 406                 call = as_a_gcall(stmt);
 407                 if (!gimple_call_tail_p(call))
 408                         continue;
 409
 410                 __perturb_latent_entropy(&gsi, local_entropy);
 411                 return true;
 412         }
 413
 414         return false;
 415 }
 416
 417 static void perturb_latent_entropy(tree local_entropy)
 418 {
 419         edge_iterator ei;
 420         edge e, last_bb_e;
 421         basic_block last_bb;
 422
 423         gcc_assert(single_pred_p(EXIT_BLOCK_PTR_FOR_FN(cfun)));
 424         last_bb_e = single_pred_edge(EXIT_BLOCK_PTR_FOR_FN(cfun));
 425
 426         FOR_EACH_EDGE(e, ei, last_bb_e->src->preds) {
 427                 if (ENTRY_BLOCK_PTR_FOR_FN(cfun) == e->src)
 428                         continue;
 429                 if (EXIT_BLOCK_PTR_FOR_FN(cfun) == e->src)
 430                         continue;
 431
 432                 handle_tail_calls(e->src, local_entropy);
 433         }
 434
 435         last_bb = single_pred(EXIT_BLOCK_PTR_FOR_FN(cfun));
 436         if (!handle_tail_calls(last_bb, local_entropy)) {
 437                 gimple_stmt_iterator gsi = gsi_last_bb(last_bb);
 438
 439                 __perturb_latent_entropy(&gsi, local_entropy);
 440         }
 441 }
 442
 443 static void init_local_entropy(basic_block bb, tree local_entropy)
 444 {
 445         gimple assign, call;
 446         tree frame_addr, rand_const, tmp, fndecl, udi_frame_addr;
 447         enum tree_code op;
 448         unsigned HOST_WIDE_INT rand_cst;
 449         gimple_stmt_iterator gsi = gsi_after_labels(bb);
 450
 451         /* 1. create local_entropy_frameaddr */
 452         frame_addr = create_var(ptr_type_node, "local_entropy_frameaddr");
 453
 454         /* 2. local_entropy_frameaddr = __builtin_frame_address() */
 455         fndecl = builtin_decl_implicit(BUILT_IN_FRAME_ADDRESS);
 456         call = gimple_build_call(fndecl, 1, integer_zero_node);
 457         gimple_call_set_lhs(call, frame_addr);
 458         gsi_insert_before(&gsi, call, GSI_NEW_STMT);
 459         update_stmt(call);
 460
 461         udi_frame_addr = fold_convert(long_unsigned_type_node, frame_addr);
 462         assign = gimple_build_assign(local_entropy, udi_frame_addr);
 463         gsi_insert_after(&gsi, assign, GSI_NEW_STMT);
 464         update_stmt(assign);
 465
 466         /* 3. create temporary copy of latent_entropy */
 467         tmp = create_var(long_unsigned_type_node, "temp_latent_entropy");
 468
 469         /* 4. read the global entropy variable into local entropy */
 470         add_referenced_var(latent_entropy_decl);
 471         mark_sym_for_renaming(latent_entropy_decl);
 472         assign = gimple_build_assign(tmp, latent_entropy_decl);
 473         gsi_insert_after(&gsi, assign, GSI_NEW_STMT);
 474         update_stmt(assign);
 475
 476         /* 5. mix local_entropy_frameaddr into local entropy */
 477         assign = create_assign(BIT_XOR_EXPR, local_entropy, local_entropy, tmp);
 478         gsi_insert_after(&gsi, assign, GSI_NEW_STMT);
 479         update_stmt(assign);
 480
 481         rand_cst = get_random_const();
 482         rand_const = build_int_cstu(long_unsigned_type_node, rand_cst);
 483         op = get_op(NULL);
 484         assign = create_assign(op, local_entropy, local_entropy, rand_const);
 485         gsi_insert_after(&gsi, assign, GSI_NEW_STMT);
 486         update_stmt(assign);
 487 }
 488
 489 static bool create_latent_entropy_decl(void)
 490 {
 491         varpool_node_ptr node;
 492
 493         if (latent_entropy_decl != NULL_TREE)
 494                 return true;
 495
 496         FOR_EACH_VARIABLE(node) {
 497                 tree name, var = NODE_DECL(node);
 498
 499                 if (DECL_NAME_LENGTH(var) < sizeof("latent_entropy") - 1)
 500                         continue;
 501
 502                 name = DECL_NAME(var);
 503                 if (strcmp(IDENTIFIER_POINTER(name), "latent_entropy"))
 504                         continue;
 505
 506                 latent_entropy_decl = var;
 507                 break;
 508         }
 509
 510         return latent_entropy_decl != NULL_TREE;
 511 }
 512
 513 static unsigned int latent_entropy_execute(void)
 514 {
 515         basic_block bb;
 516         tree local_entropy;
 517
 518         if (!create_latent_entropy_decl())
 519                 return 0;
 520
 521         /* prepare for step 2 below */
 522         gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
 523         bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
 524         if (!single_pred_p(bb)) {
 525                 split_edge(single_succ_edge(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
 526                 gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
 527                 bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
 528         }
 529
 530         /* 1. create the local entropy variable */
 531         local_entropy = create_var(long_unsigned_type_node, "local_entropy");
 532
 533         /* 2. initialize the local entropy variable */
 534         init_local_entropy(bb, local_entropy);
 535
 536         bb = bb->next_bb;
 537
 538         /*
 539          * 3. instrument each BB with an operation on the
 540          *    local entropy variable
 541          */
 542         while (bb != EXIT_BLOCK_PTR_FOR_FN(cfun)) {
 543                 perturb_local_entropy(bb, local_entropy);
 544                 bb = bb->next_bb;
 545         };
 546
 547         /* 4. mix local entropy into the global entropy variable */
 548         perturb_latent_entropy(local_entropy);
 549         return 0;
 550 }
 551
 552 static void latent_entropy_start_unit(void *gcc_data __unused,
 553                                         void *user_data __unused)
 554 {
 555         tree type, id;
 556         int quals;
 557
 558         if (in_lto_p)
 559                 return;
 560
 561         /* extern volatile unsigned long latent_entropy */
 562         quals = TYPE_QUALS(long_unsigned_type_node) | TYPE_QUAL_VOLATILE;
 563         type = build_qualified_type(long_unsigned_type_node, quals);
 564         id = get_identifier("latent_entropy");
 565         latent_entropy_decl = build_decl(UNKNOWN_LOCATION, VAR_DECL, id, type);
 566
 567         TREE_STATIC(latent_entropy_decl) = 1;
 568         TREE_PUBLIC(latent_entropy_decl) = 1;
 569         TREE_USED(latent_entropy_decl) = 1;
 570         DECL_PRESERVE_P(latent_entropy_decl) = 1;
 571         TREE_THIS_VOLATILE(latent_entropy_decl) = 1;
 572         DECL_EXTERNAL(latent_entropy_decl) = 1;
 573         DECL_ARTIFICIAL(latent_entropy_decl) = 1;
 574         lang_hooks.decls.pushdecl(latent_entropy_decl);
 575 }
 576
 577 #define PASS_NAME latent_entropy
 578 #define PROPERTIES_REQUIRED PROP_gimple_leh | PROP_cfg
 579 #define TODO_FLAGS_FINISH TODO_verify_ssa | TODO_verify_stmts | TODO_dump_func \
 580         | TODO_update_ssa
 581 #include "gcc-generate-gimple-pass.h"
 582
 583 __visible int plugin_init(struct plugin_name_args *plugin_info,
 584                           struct plugin_gcc_version *version)
 585 {
 586         bool enabled = true;
 587         const char * const plugin_name = plugin_info->base_name;
 588         const int argc = plugin_info->argc;
 589         const struct plugin_argument * const argv = plugin_info->argv;
 590         int i;
 591
 592         /*
 593          * Call get_random_seed() with noinit=true, so that this returns
 594          * 0 in the case where no seed has been passed via -frandom-seed.
 595          */
 596         deterministic_seed = get_random_seed(true);
 597
 598         static const struct ggc_root_tab gt_ggc_r_gt_latent_entropy[] = {
 599                 {
 600                         .base = &latent_entropy_decl,
 601                         .nelt = 1,
 602                         .stride = sizeof(latent_entropy_decl),
 603                         .cb = &gt_ggc_mx_tree_node,
 604                         .pchw = &gt_pch_nx_tree_node
 605                 },
 606                 LAST_GGC_ROOT_TAB
 607         };
 608
 609         PASS_INFO(latent_entropy, "optimized", 1, PASS_POS_INSERT_BEFORE);
 610
 611         if (!plugin_default_version_check(version, &gcc_version)) {
 612                 error(G_("incompatible gcc/plugin versions"));
 613                 return 1;
 614         }
 615
 616         for (i = 0; i < argc; ++i) {
 617                 if (!(strcmp(argv[i].key, "disable"))) {
 618                         enabled = false;
 619                         continue;
 620                 }
 621                 error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
 622         }
 623
 624         register_callback(plugin_name, PLUGIN_INFO, NULL,
 625                                 &latent_entropy_plugin_info);
 626         if (enabled) {
 627                 register_callback(plugin_name, PLUGIN_START_UNIT,
 628                                         &latent_entropy_start_unit, NULL);
 629                 register_callback(plugin_name, PLUGIN_REGISTER_GGC_ROOTS,
 630                                   NULL, (void *)&gt_ggc_r_gt_latent_entropy);
 631                 register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,
 632                                         &latent_entropy_pass_info);
 633         }
 634         register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes,
 635                                 NULL);
 636
 637         return 0;
 638 }