newfuzzer.cc

   1 #include "newfuzzer.h"
   2 #include "threads-model.h"
   3 #include "action.h"
   4 #include "history.h"
   5 #include "funcnode.h"
   6 #include "funcinst.h"
   7 #include "concretepredicate.h"
   8 #include "waitobj.h"
   9
  10 #include "model.h"
  11 #include "schedule.h"
  12 #include "execution.h"
  13
  14 NewFuzzer::NewFuzzer() :
  15         thrd_last_read_act(),
  16         thrd_last_func_inst(),
  17         thrd_selected_child_branch(),
  18         thrd_pruned_writes(),
  19         paused_thread_list(),
  20         paused_thread_table(128),
  21         failed_predicates(32),
  22         dist_info_vec()
  23 {}
  24
  25 /**
  26  * @brief Register the ModelHistory and ModelExecution engine
  27  */
  28 void NewFuzzer::register_engine(ModelHistory * history, ModelExecution *execution)
  29 {
  30         this->history = history;
  31         this->execution = execution;
  32 }
  33
  34 int NewFuzzer::selectWrite(ModelAction *read, SnapVector<ModelAction *> * rf_set)
  35 {
  36         return random() % rf_set->size();
  37
  38         thread_id_t tid = read->get_tid();
  39         int thread_id = id_to_int(tid);
  40
  41         if (thrd_last_read_act.size() <= (uint) thread_id) {
  42                 thrd_last_read_act.resize(thread_id + 1);
  43                 thrd_last_func_inst.resize(thread_id + 1);
  44         }
  45
  46         // A new read action is encountered, select a random child branch of current predicate
  47         if (read != thrd_last_read_act[thread_id]) {
  48                 FuncNode * func_node = history->get_curr_func_node(tid);
  49                 Predicate * curr_pred = func_node->get_predicate_tree_position(tid);
  50                 FuncInst * read_inst = func_node->get_inst(read);
  51                 inst_act_map_t * inst_act_map = func_node->get_inst_act_map(tid);
  52
  53                 check_store_visibility(curr_pred, read_inst, inst_act_map, rf_set);
  54                 Predicate * selected_branch = selectBranch(tid, curr_pred, read_inst);
  55                 prune_writes(tid, selected_branch, rf_set, inst_act_map);
  56
  57                 if (!failed_predicates.isEmpty())
  58                         failed_predicates.reset();
  59
  60                 thrd_last_read_act[thread_id] = read;
  61                 thrd_last_func_inst[thread_id] = read_inst;
  62         }
  63
  64         // No write satisfies the selected predicate, so pause this thread.
  65         while ( rf_set->size() == 0 ) {
  66                 Predicate * selected_branch = get_selected_child_branch(tid);
  67
  68                 //model_print("the %d read action of thread %d at %p is unsuccessful\n", read->get_seq_number(), read_thread->get_id(), read->get_location());
  69
  70                 SnapVector<ModelAction *> * pruned_writes = thrd_pruned_writes[thread_id];
  71                 for (uint i = 0; i < pruned_writes->size(); i++) {
  72                         rf_set->push_back( (*pruned_writes)[i] );
  73                 }
  74
  75                 // Reselect a predicate and prune writes
  76                 Predicate * curr_pred = selected_branch->get_parent();
  77                 FuncInst * read_inst = thrd_last_func_inst[thread_id];
  78                 selected_branch = selectBranch(tid, curr_pred, read_inst);
  79
  80                 FuncNode * func_node = history->get_curr_func_node(tid);
  81                 inst_act_map_t * inst_act_map = func_node->get_inst_act_map(tid);
  82                 prune_writes(tid, selected_branch, rf_set, inst_act_map);
  83
  84                 ASSERT(selected_branch);
  85         }
  86
  87         ASSERT(rf_set->size() != 0);
  88         int random_index = random() % rf_set->size();
  89
  90         return random_index;
  91 }
  92
  93 void NewFuzzer::check_store_visibility(Predicate * curr_pred, FuncInst * read_inst,
  94         inst_act_map_t * inst_act_map, SnapVector<ModelAction *> * rf_set)
  95 {
  96         ASSERT(!rf_set->empty());
  97         if (curr_pred == NULL || read_inst == NULL)
  98                 return;
  99
 100         ModelVector<Predicate *> * children = curr_pred->get_children();
 101
 102         /* Iterate over all predicate children */
 103         for (uint i = 0; i < children->size(); i++) {
 104                 Predicate * branch = (*children)[i];
 105
 106                 /* The children predicates may have different FuncInsts */
 107                 if (branch->get_func_inst() == read_inst) {
 108                         PredExprSet * pred_expressions = branch->get_pred_expressions();
 109
 110                         /* Do not check unset predicates */
 111                         if (pred_expressions->isEmpty())
 112                                 continue;
 113
 114                         branch->incr_total_checking_count();
 115
 116                         /* Iterate over all write actions */
 117                         for (uint j = 0; j < rf_set->size(); j++) {
 118                                 ModelAction * write_act = (*rf_set)[j];
 119                                 uint64_t write_val = write_act->get_write_value();
 120                                 bool dummy = true;
 121                                 bool satisfy_predicate = check_predicate_expressions(pred_expressions, inst_act_map, write_val, &dummy);
 122
 123                                 /* If one write value satisfies the predicate, go to check the next predicate */
 124                                 if (satisfy_predicate) {
 125                                         branch->incr_store_visible_count();
 126                                         break;
 127                                 }
 128                         }
 129                 }
 130
 131         }
 132 }
 133
 134
 135 /* Select a random branch from the children of curr_pred
 136  * @return The selected branch
 137  */
 138 Predicate * NewFuzzer::selectBranch(thread_id_t tid, Predicate * curr_pred, FuncInst * read_inst)
 139 {
 140         int thread_id = id_to_int(tid);
 141         if ( thrd_selected_child_branch.size() <= (uint) thread_id)
 142                 thrd_selected_child_branch.resize(thread_id + 1);
 143
 144         if (curr_pred == NULL || read_inst == NULL) {
 145                 thrd_selected_child_branch[thread_id] = NULL;
 146                 return NULL;
 147         }
 148
 149         ModelVector<Predicate *> * children = curr_pred->get_children();
 150         SnapVector<Predicate *> branches;
 151
 152         for (uint i = 0; i < children->size(); i++) {
 153                 Predicate * child = (*children)[i];
 154                 if (child->get_func_inst() == read_inst && !failed_predicates.contains(child)) {
 155                         branches.push_back(child);
 156                 }
 157         }
 158
 159         // predicate children have not been generated
 160         if (branches.size() == 0) {
 161                 thrd_selected_child_branch[thread_id] = NULL;
 162                 return NULL;
 163         }
 164
 165         int index = choose_index(&branches, 0);
 166         Predicate * random_branch = branches[ index ];
 167         thrd_selected_child_branch[thread_id] = random_branch;
 168
 169         // Update predicate tree position
 170         FuncNode * func_node = history->get_curr_func_node(tid);
 171         func_node->set_predicate_tree_position(tid, random_branch);
 172
 173         return random_branch;
 174 }
 175
 176 /**
 177  * @brief Select a branch from the given predicate branches based
 178  * on their exploration counts.
 179  *
 180  * Let b_1, ..., b_n be branches with exploration counts c_1, ..., c_n
 181  * M := max(c_1, ..., c_n) + 1
 182  * Factor f_i := M / (c_i + 1)
 183  * The probability p_i that branch b_i is selected:
 184  *      p_i := f_i / (f_1 + ... + f_n)
 185  *           = \fraction{ 1/(c_i + 1) }{ 1/(c_1 + 1) + ... + 1/(c_n + 1) }
 186  *
 187  * Note: (1) c_i + 1 is used because counts may be 0.
 188  *       (2) The numerator of f_i is chosen to reduce the effect of underflow
 189  *
 190  * @param numerator is M defined above
 191  */
 192 int NewFuzzer::choose_index(SnapVector<Predicate *> * branches, uint32_t numerator)
 193 {
 194         return random() % branches->size();
 195 /*--
 196         if (branches->size() == 1)
 197                 return 0;
 198
 199         double total_factor = 0;
 200         SnapVector<double> factors = SnapVector<double>( branches->size() + 1 );
 201         for (uint i = 0; i < branches->size(); i++) {
 202                 Predicate * branch = (*branches)[i];
 203                 double factor = (double) numerator / (branch->get_expl_count() + 5 * branch->get_fail_count() + 1);
 204                 total_factor += factor;
 205                 factors.push_back(factor);
 206         }
 207
 208         double prob = (double) random() / RAND_MAX;
 209         double prob_sum = 0;
 210         int index = 0;
 211
 212         for (uint i = 0; i < factors.size(); i++) {
 213                 index = i;
 214                 prob_sum += (double) (factors[i] / total_factor);
 215                 if (prob_sum > prob) {
 216                         break;
 217                 }
 218         }
 219
 220         return index;
 221 */
 222 }
 223
 224 Predicate * NewFuzzer::get_selected_child_branch(thread_id_t tid)
 225 {
 226         int thread_id = id_to_int(tid);
 227         if (thrd_selected_child_branch.size() <= (uint) thread_id)
 228                 return NULL;
 229
 230         return thrd_selected_child_branch[thread_id];
 231 }
 232
 233 /* Remove writes from the rf_set that do not satisfie the selected predicate,
 234  * and store them in thrd_pruned_writes
 235  *
 236  * @return true if rf_set is pruned
 237  */
 238 bool NewFuzzer::prune_writes(thread_id_t tid, Predicate * pred,
 239         SnapVector<ModelAction *> * rf_set, inst_act_map_t * inst_act_map)
 240 {
 241         if (pred == NULL)
 242                 return false;
 243
 244         PredExprSet * pred_expressions = pred->get_pred_expressions();
 245         if (pred_expressions->getSize() == 0)   // unset predicates
 246                 return false;
 247
 248         int thread_id = id_to_int(tid);
 249         uint old_size = thrd_pruned_writes.size();
 250         if (thrd_pruned_writes.size() <= (uint) thread_id) {
 251                 uint new_size = thread_id + 1;
 252                 thrd_pruned_writes.resize(new_size);
 253                 for (uint i = old_size; i < new_size; i++)
 254                         thrd_pruned_writes[i] = new SnapVector<ModelAction *>();
 255         }
 256         SnapVector<ModelAction *> * pruned_writes = thrd_pruned_writes[thread_id];
 257         pruned_writes->clear(); // clear the old pruned_writes set
 258
 259         bool pruned = false;
 260         uint index = 0;
 261
 262         while ( index < rf_set->size() ) {
 263                 ModelAction * write_act = (*rf_set)[index];
 264                 uint64_t write_val = write_act->get_write_value();
 265                 bool no_predicate = false;
 266                 bool satisfy_predicate = check_predicate_expressions(pred_expressions, inst_act_map, write_val, &no_predicate);
 267
 268                 if (no_predicate)
 269                         return false;
 270
 271                 if (!satisfy_predicate) {
 272                         ASSERT(rf_set != NULL);
 273                         (*rf_set)[index] = rf_set->back();
 274                         rf_set->pop_back();
 275                         pruned_writes->push_back(write_act);
 276                         pruned = true;
 277                 } else
 278                         index++;
 279         }
 280
 281         return pruned;
 282 }
 283
 284 /* @brief Put a thread to sleep because no writes in rf_set satisfies the selected predicate.
 285  *
 286  * @param thread A thread whose last action is a read
 287  */
 288 void NewFuzzer::conditional_sleep(Thread * thread)
 289 {
 290         int index = paused_thread_list.size();
 291
 292         model->getScheduler()->add_sleep(thread);
 293         paused_thread_list.push_back(thread);
 294         paused_thread_table.put(thread, index); // Update table
 295
 296         /* Add the waiting condition to ModelHistory */
 297         ModelAction * read = thread->get_pending();
 298         thread_id_t tid = thread->get_id();
 299         FuncNode * func_node = history->get_curr_func_node(tid);
 300         inst_act_map_t * inst_act_map = func_node->get_inst_act_map(tid);
 301
 302         Predicate * selected_branch = get_selected_child_branch(tid);
 303         ConcretePredicate * concrete = selected_branch->evaluate(inst_act_map, tid);
 304         concrete->set_location(read->get_location());
 305
 306         history->add_waiting_write(concrete);
 307         /* history->add_waiting_thread is already called in find_threads */
 308 }
 309
 310 /**
 311  * Decides whether a thread should condition sleep based on
 312  * the sleep score of the chosen predicate.
 313  *
 314  * sleep_score = 0: never sleeps
 315  * sleep_score = 100: always sleeps
 316  **/
 317 bool NewFuzzer::should_conditional_sleep(Predicate * predicate)
 318 {
 319         return false;
 320         /*
 321         int sleep_score = predicate->get_sleep_score();
 322         int random_num = random() % 100;
 323
 324         // should sleep if random_num falls within [0, sleep_score)
 325         if (random_num < sleep_score)
 326                 return true;
 327
 328         return false;
 329         */
 330 }
 331
 332 bool NewFuzzer::has_paused_threads()
 333 {
 334         return paused_thread_list.size() != 0;
 335 }
 336
 337 Thread * NewFuzzer::selectThread(int * threadlist, int numthreads)
 338 {
 339         if (numthreads == 0 && has_paused_threads()) {
 340                 wake_up_paused_threads(threadlist, &numthreads);
 341                 //model_print("list size: %d, active t id: %d\n", numthreads, threadlist[0]);
 342         }
 343
 344         int random_index = random() % numthreads;
 345         int thread = threadlist[random_index];
 346         thread_id_t curr_tid = int_to_id(thread);
 347         return execution->get_thread(curr_tid);
 348 }
 349
 350 /* Force waking up one of threads paused by Fuzzer, because otherwise
 351  * the Fuzzer is not making progress
 352  */
 353 void NewFuzzer::wake_up_paused_threads(int * threadlist, int * numthreads)
 354 {
 355         int random_index = random() % paused_thread_list.size();
 356         Thread * thread = paused_thread_list[random_index];
 357         model->getScheduler()->remove_sleep(thread);
 358
 359         Thread * last_thread = paused_thread_list.back();
 360         paused_thread_list[random_index] = last_thread;
 361         paused_thread_list.pop_back();
 362         paused_thread_table.put(last_thread, random_index);     // Update table
 363         paused_thread_table.remove(thread);
 364
 365         thread_id_t tid = thread->get_id();
 366         history->remove_waiting_write(tid);
 367         history->remove_waiting_thread(tid);
 368
 369         threadlist[*numthreads] = tid;
 370         (*numthreads)++;
 371
 372 /*--
 373         Predicate * selected_branch = get_selected_child_branch(tid);
 374         update_predicate_score(selected_branch, SLEEP_FAIL_TYPE3);
 375 */
 376
 377         model_print("thread %d is woken up\n", tid);
 378 }
 379
 380 /* Wake up conditional sleeping threads if the desired write is available */
 381 void NewFuzzer::notify_paused_thread(Thread * thread)
 382 {
 383         ASSERT(paused_thread_table.contains(thread));
 384
 385         int index = paused_thread_table.get(thread);
 386         model->getScheduler()->remove_sleep(thread);
 387
 388         Thread * last_thread = paused_thread_list.back();
 389         paused_thread_list[index] = last_thread;
 390         paused_thread_list.pop_back();
 391         paused_thread_table.put(last_thread, index);    // Update table
 392         paused_thread_table.remove(thread);
 393
 394         thread_id_t tid = thread->get_id();
 395         history->remove_waiting_write(tid);
 396         history->remove_waiting_thread(tid);
 397
 398 /*--
 399         Predicate * selected_branch = get_selected_child_branch(tid);
 400         update_predicate_score(selected_branch, SLEEP_SUCCESS);
 401 */
 402
 403         model_print("** thread %d is woken up\n", tid);
 404 }
 405
 406 /* Find threads that may write values that the pending read action is waiting for.
 407  * Side effect: waiting thread related info are stored in dist_info_vec
 408  *
 409  * @return True if any thread is found
 410  */
 411 bool NewFuzzer::find_threads(ModelAction * pending_read)
 412 {
 413         ASSERT(pending_read->is_read());
 414
 415         void * location = pending_read->get_location();
 416         thread_id_t self_id = pending_read->get_tid();
 417         bool finds_waiting_for = false;
 418
 419         SnapVector<FuncNode *> * func_node_list = history->getWrFuncNodes(location);
 420         for (uint i = 0; i < func_node_list->size(); i++) {
 421                 FuncNode * target_node = (*func_node_list)[i];
 422                 for (uint i = 1; i < execution->get_num_threads(); i++) {
 423                         thread_id_t tid = int_to_id(i);
 424                         if (tid == self_id)
 425                                 continue;
 426
 427                         FuncNode * node = history->get_curr_func_node(tid);
 428                         /* It is possible that thread tid is not in any FuncNode */
 429                         if (node == NULL)
 430                                 continue;
 431
 432                         int distance = node->compute_distance(target_node);
 433                         if (distance != -1) {
 434                                 finds_waiting_for = true;
 435                                 //model_print("thread: %d; distance from node %d to node %d: %d\n", tid, node->get_func_id(), target_node->get_func_id(), distance);
 436
 437                                 dist_info_vec.push_back(node_dist_info(tid, target_node, distance));
 438                         }
 439                 }
 440         }
 441
 442         return finds_waiting_for;
 443 }
 444
 445 /* Update predicate counts and scores (asynchronous) when the read value is not available
 446  *
 447  * @param type
 448  *        type 1: find_threads return false
 449  *        type 2: find_threads return true, but the fuzzer decides that that thread shall not sleep based on sleep score
 450  *        type 3: threads are put to sleep but woken up before the waited value appears
 451  *        type 4: threads are put to sleep and the waited vaule appears (success)
 452  */
 453
 454 /*--
 455 void NewFuzzer::update_predicate_score(Predicate * predicate, sleep_result_t type)
 456 {
 457         switch (type) {
 458                 case SLEEP_FAIL_TYPE1:
 459                         predicate->incr_fail_count();
 460
 461                         // Do not choose this predicate when reselecting a new branch
 462                         failed_predicates.put(predicate, true);
 463                         break;
 464                 case SLEEP_FAIL_TYPE2:
 465                         predicate->incr_fail_count();
 466                         predicate->incr_sleep_score(1);
 467                         failed_predicates.put(predicate, true);
 468                         break;
 469                 case SLEEP_FAIL_TYPE3:
 470                         predicate->incr_fail_count();
 471                         predicate->decr_sleep_score(10);
 472                         break;
 473                 case SLEEP_SUCCESS:
 474                         predicate->incr_sleep_score(10);
 475                         break;
 476                 default:
 477                         model_print("unknown predicate result type.\n");
 478                         break;
 479         }
 480 }
 481 */
 482
 483 bool NewFuzzer::check_predicate_expressions(PredExprSet * pred_expressions,
 484         inst_act_map_t * inst_act_map, uint64_t write_val, bool * no_predicate)
 485 {
 486         bool satisfy_predicate = true;
 487
 488         PredExprSetIter * pred_expr_it = pred_expressions->iterator();
 489         while (pred_expr_it->hasNext()) {
 490                 struct pred_expr * expression = pred_expr_it->next();
 491                 bool equality;
 492
 493                 switch (expression->token) {
 494                         case NOPREDICATE:
 495                                 *no_predicate = true;
 496                                 break;
 497                         case EQUALITY:
 498                                 FuncInst * to_be_compared;
 499                                 ModelAction * last_act;
 500                                 uint64_t last_read;
 501
 502                                 to_be_compared = expression->func_inst;
 503                                 last_act = inst_act_map->get(to_be_compared);
 504                                 last_read = last_act->get_reads_from_value();
 505
 506                                 equality = (write_val == last_read);
 507                                 if (equality != expression->value)
 508                                         satisfy_predicate = false;
 509                                 break;
 510                         case NULLITY:
 511                                 equality = ((void*)write_val == NULL);
 512                                 if (equality != expression->value)
 513                                         satisfy_predicate = false;
 514                                 break;
 515                         default:
 516                                 model_print("unknown predicate token\n");
 517                                 break;
 518                 }
 519
 520                 if (!satisfy_predicate)
 521                         break;
 522         }
 523
 524         return satisfy_predicate;
 525 }
 526
 527 bool NewFuzzer::shouldWait(const ModelAction * act)
 528 {
 529         return random() & 1;
 530 }