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 /*--
  71                 Thread * read_thread = execution->get_thread(tid);
  72                 bool should_reselect_predicate = true;
  73                 bool should_sleep = should_conditional_sleep(selected_branch);
  74                 dist_info_vec.clear();
  75
  76                 if (!find_threads(read)) {
  77                         update_predicate_score(selected_branch, SLEEP_FAIL_TYPE1);
  78                         should_reselect_predicate = true;
  79                 } else if (!should_sleep) {
  80                         update_predicate_score(selected_branch, SLEEP_FAIL_TYPE2);
  81                         should_reselect_predicate = true;
  82                 } else {
  83                         for (uint i = 0; i < dist_info_vec.size(); i++) {
  84                                 struct node_dist_info info = dist_info_vec[i];
  85                                 history->add_waiting_thread(tid, info.tid, info.target, info.dist);
  86                         }
  87
  88                         // reset thread pending action and revert sequence numbers
  89                         read_thread->set_pending(read);
  90                         read->reset_seq_number();
  91                         execution->restore_last_seq_num();
  92
  93                         conditional_sleep(read_thread);
  94                         // Returning -1 stops the while loop of ModelExecution::process_read
  95                         return -1;
  96                 }
  97 */
  98
  99                 SnapVector<ModelAction *> * pruned_writes = thrd_pruned_writes[thread_id];
 100                 for (uint i = 0; i < pruned_writes->size(); i++) {
 101                         rf_set->push_back( (*pruned_writes)[i] );
 102                 }
 103
 104                 // Reselect a predicate and prune writes
 105                 Predicate * curr_pred = selected_branch->get_parent();
 106                 FuncInst * read_inst = thrd_last_func_inst[thread_id];
 107                 selected_branch = selectBranch(tid, curr_pred, read_inst);
 108
 109                 FuncNode * func_node = history->get_curr_func_node(tid);
 110                 inst_act_map_t * inst_act_map = func_node->get_inst_act_map(tid);
 111                 prune_writes(tid, selected_branch, rf_set, inst_act_map);
 112
 113                 ASSERT(selected_branch);
 114         }
 115
 116         ASSERT(rf_set->size() != 0);
 117         int random_index = random() % rf_set->size();
 118
 119         return random_index;
 120 }
 121
 122 void NewFuzzer::check_store_visibility(Predicate * curr_pred, FuncInst * read_inst,
 123         inst_act_map_t * inst_act_map, SnapVector<ModelAction *> * rf_set)
 124 {
 125         ASSERT(!rf_set->empty());
 126         if (curr_pred == NULL || read_inst == NULL)
 127                 return;
 128
 129         ModelVector<Predicate *> * children = curr_pred->get_children();
 130         SnapVector<Predicate *> branches;
 131
 132         /* The children predicates may have different FuncInsts */
 133         for (uint i = 0; i < children->size(); i++) {
 134                 Predicate * child = (*children)[i];
 135                 if (child->get_func_inst() == read_inst) {
 136                         branches.push_back(child);
 137                 }
 138         }
 139
 140         /* Predicate children have not been generated */
 141         if (branches.empty())
 142                 return;
 143
 144         /* Iterate over all predicate children */
 145         for (uint i = 0; i < branches.size(); i++) {
 146                 Predicate * branch = branches[i];
 147                 PredExprSet * pred_expressions = branch->get_pred_expressions();
 148
 149                 /* Do not check unset predicates */
 150                 if (pred_expressions->isEmpty())
 151                         continue;
 152
 153                 branch->incr_total_checking_count();
 154
 155                 /* Iterate over all write actions */
 156                 for (uint j = 0; j < rf_set->size(); j++) {
 157                         ModelAction * write_act = (*rf_set)[j];
 158                         uint64_t write_val = write_act->get_write_value();
 159                         bool dummy = true;
 160                         bool satisfy_predicate = check_predicate_expressions(pred_expressions, inst_act_map, write_val, &dummy);
 161
 162                         /* If one write value satisfies the predicate, go to check the next predicate */
 163                         if (satisfy_predicate) {
 164                                 branch->incr_store_visible_count();
 165                                 break;
 166                         }
 167                 }
 168         }
 169 }
 170
 171
 172 /* Select a random branch from the children of curr_pred
 173  * @return The selected branch
 174  */
 175 Predicate * NewFuzzer::selectBranch(thread_id_t tid, Predicate * curr_pred, FuncInst * read_inst)
 176 {
 177         int thread_id = id_to_int(tid);
 178         if ( thrd_selected_child_branch.size() <= (uint) thread_id)
 179                 thrd_selected_child_branch.resize(thread_id + 1);
 180
 181         if (curr_pred == NULL || read_inst == NULL) {
 182                 thrd_selected_child_branch[thread_id] = NULL;
 183                 return NULL;
 184         }
 185
 186         ModelVector<Predicate *> * children = curr_pred->get_children();
 187         SnapVector<Predicate *> branches;
 188
 189         for (uint i = 0; i < children->size(); i++) {
 190                 Predicate * child = (*children)[i];
 191                 if (child->get_func_inst() == read_inst && !failed_predicates.contains(child)) {
 192                         branches.push_back(child);
 193
 194                         /*-- max of (exploration counts + 1)
 195                         if (child->get_expl_count() + 1 > numerator)
 196                                 numerator = child->get_expl_count() + 1;
 197                         */
 198                 }
 199         }
 200
 201         // predicate children have not been generated
 202         if (branches.size() == 0) {
 203                 thrd_selected_child_branch[thread_id] = NULL;
 204                 return NULL;
 205         }
 206
 207         int index = choose_index(&branches, 0);
 208         Predicate * random_branch = branches[ index ];
 209         thrd_selected_child_branch[thread_id] = random_branch;
 210
 211         // Update predicate tree position
 212         FuncNode * func_node = history->get_curr_func_node(tid);
 213         func_node->set_predicate_tree_position(tid, random_branch);
 214
 215         return random_branch;
 216 }
 217
 218 /**
 219  * @brief Select a branch from the given predicate branches based
 220  * on their exploration counts.
 221  *
 222  * Let b_1, ..., b_n be branches with exploration counts c_1, ..., c_n
 223  * M := max(c_1, ..., c_n) + 1
 224  * Factor f_i := M / (c_i + 1)
 225  * The probability p_i that branch b_i is selected:
 226  *      p_i := f_i / (f_1 + ... + f_n)
 227  *           = \fraction{ 1/(c_i + 1) }{ 1/(c_1 + 1) + ... + 1/(c_n + 1) }
 228  *
 229  * Note: (1) c_i + 1 is used because counts may be 0.
 230  *       (2) The numerator of f_i is chosen to reduce the effect of underflow
 231  *
 232  * @param numerator is M defined above
 233  */
 234 int NewFuzzer::choose_index(SnapVector<Predicate *> * branches, uint32_t numerator)
 235 {
 236         return random() % branches->size();
 237 /*--
 238         if (branches->size() == 1)
 239                 return 0;
 240
 241         double total_factor = 0;
 242         SnapVector<double> factors = SnapVector<double>( branches->size() + 1 );
 243         for (uint i = 0; i < branches->size(); i++) {
 244                 Predicate * branch = (*branches)[i];
 245                 double factor = (double) numerator / (branch->get_expl_count() + 5 * branch->get_fail_count() + 1);
 246                 total_factor += factor;
 247                 factors.push_back(factor);
 248         }
 249
 250         double prob = (double) random() / RAND_MAX;
 251         double prob_sum = 0;
 252         int index = 0;
 253
 254         for (uint i = 0; i < factors.size(); i++) {
 255                 index = i;
 256                 prob_sum += (double) (factors[i] / total_factor);
 257                 if (prob_sum > prob) {
 258                         break;
 259                 }
 260         }
 261
 262         return index;
 263 */
 264 }
 265
 266 Predicate * NewFuzzer::get_selected_child_branch(thread_id_t tid)
 267 {
 268         int thread_id = id_to_int(tid);
 269         if (thrd_selected_child_branch.size() <= (uint) thread_id)
 270                 return NULL;
 271
 272         return thrd_selected_child_branch[thread_id];
 273 }
 274
 275 /* Remove writes from the rf_set that do not satisfie the selected predicate,
 276  * and store them in thrd_pruned_writes
 277  *
 278  * @return true if rf_set is pruned
 279  */
 280 bool NewFuzzer::prune_writes(thread_id_t tid, Predicate * pred,
 281         SnapVector<ModelAction *> * rf_set, inst_act_map_t * inst_act_map)
 282 {
 283         if (pred == NULL)
 284                 return false;
 285
 286         PredExprSet * pred_expressions = pred->get_pred_expressions();
 287         if (pred_expressions->getSize() == 0)   // unset predicates
 288                 return false;
 289
 290         int thread_id = id_to_int(tid);
 291         uint old_size = thrd_pruned_writes.size();
 292         if (thrd_pruned_writes.size() <= (uint) thread_id) {
 293                 uint new_size = thread_id + 1;
 294                 thrd_pruned_writes.resize(new_size);
 295                 for (uint i = old_size; i < new_size; i++)
 296                         thrd_pruned_writes[i] = new SnapVector<ModelAction *>();
 297         }
 298         SnapVector<ModelAction *> * pruned_writes = thrd_pruned_writes[thread_id];
 299         pruned_writes->clear(); // clear the old pruned_writes set
 300
 301         bool pruned = false;
 302         uint index = 0;
 303
 304         while ( index < rf_set->size() ) {
 305                 ModelAction * write_act = (*rf_set)[index];
 306                 uint64_t write_val = write_act->get_write_value();
 307                 bool no_predicate = false;
 308                 bool satisfy_predicate = check_predicate_expressions(pred_expressions, inst_act_map, write_val, &no_predicate);
 309
 310                 if (no_predicate)
 311                         return false;
 312
 313                 if (!satisfy_predicate) {
 314                         ASSERT(rf_set != NULL);
 315                         (*rf_set)[index] = rf_set->back();
 316                         rf_set->pop_back();
 317                         pruned_writes->push_back(write_act);
 318                         pruned = true;
 319                 } else
 320                         index++;
 321         }
 322
 323         return pruned;
 324 }
 325
 326 /* @brief Put a thread to sleep because no writes in rf_set satisfies the selected predicate.
 327  *
 328  * @param thread A thread whose last action is a read
 329  */
 330 void NewFuzzer::conditional_sleep(Thread * thread)
 331 {
 332         int index = paused_thread_list.size();
 333
 334         model->getScheduler()->add_sleep(thread);
 335         paused_thread_list.push_back(thread);
 336         paused_thread_table.put(thread, index); // Update table
 337
 338         /* Add the waiting condition to ModelHistory */
 339         ModelAction * read = thread->get_pending();
 340         thread_id_t tid = thread->get_id();
 341         FuncNode * func_node = history->get_curr_func_node(tid);
 342         inst_act_map_t * inst_act_map = func_node->get_inst_act_map(tid);
 343
 344         Predicate * selected_branch = get_selected_child_branch(tid);
 345         ConcretePredicate * concrete = selected_branch->evaluate(inst_act_map, tid);
 346         concrete->set_location(read->get_location());
 347
 348         history->add_waiting_write(concrete);
 349         /* history->add_waiting_thread is already called in find_threads */
 350 }
 351
 352 /**
 353  * Decides whether a thread should condition sleep based on
 354  * the sleep score of the chosen predicate.
 355  *
 356  * sleep_score = 0: never sleeps
 357  * sleep_score = 100: always sleeps
 358  **/
 359 bool NewFuzzer::should_conditional_sleep(Predicate * predicate)
 360 {
 361         return false;
 362         /*
 363         int sleep_score = predicate->get_sleep_score();
 364         int random_num = random() % 100;
 365
 366         // should sleep if random_num falls within [0, sleep_score)
 367         if (random_num < sleep_score)
 368                 return true;
 369
 370         return false;
 371         */
 372 }
 373
 374 bool NewFuzzer::has_paused_threads()
 375 {
 376         return paused_thread_list.size() != 0;
 377 }
 378
 379 Thread * NewFuzzer::selectThread(int * threadlist, int numthreads)
 380 {
 381         if (numthreads == 0 && has_paused_threads()) {
 382                 wake_up_paused_threads(threadlist, &numthreads);
 383                 //model_print("list size: %d, active t id: %d\n", numthreads, threadlist[0]);
 384         }
 385
 386         int random_index = random() % numthreads;
 387         int thread = threadlist[random_index];
 388         thread_id_t curr_tid = int_to_id(thread);
 389         return execution->get_thread(curr_tid);
 390 }
 391
 392 /* Force waking up one of threads paused by Fuzzer, because otherwise
 393  * the Fuzzer is not making progress
 394  */
 395 void NewFuzzer::wake_up_paused_threads(int * threadlist, int * numthreads)
 396 {
 397         int random_index = random() % paused_thread_list.size();
 398         Thread * thread = paused_thread_list[random_index];
 399         model->getScheduler()->remove_sleep(thread);
 400
 401         Thread * last_thread = paused_thread_list.back();
 402         paused_thread_list[random_index] = last_thread;
 403         paused_thread_list.pop_back();
 404         paused_thread_table.put(last_thread, random_index);     // Update table
 405         paused_thread_table.remove(thread);
 406
 407         thread_id_t tid = thread->get_id();
 408         history->remove_waiting_write(tid);
 409         history->remove_waiting_thread(tid);
 410
 411         threadlist[*numthreads] = tid;
 412         (*numthreads)++;
 413
 414 /*--
 415         Predicate * selected_branch = get_selected_child_branch(tid);
 416         update_predicate_score(selected_branch, SLEEP_FAIL_TYPE3);
 417 */
 418
 419         model_print("thread %d is woken up\n", tid);
 420 }
 421
 422 /* Wake up conditional sleeping threads if the desired write is available */
 423 void NewFuzzer::notify_paused_thread(Thread * thread)
 424 {
 425         ASSERT(paused_thread_table.contains(thread));
 426
 427         int index = paused_thread_table.get(thread);
 428         model->getScheduler()->remove_sleep(thread);
 429
 430         Thread * last_thread = paused_thread_list.back();
 431         paused_thread_list[index] = last_thread;
 432         paused_thread_list.pop_back();
 433         paused_thread_table.put(last_thread, index);    // Update table
 434         paused_thread_table.remove(thread);
 435
 436         thread_id_t tid = thread->get_id();
 437         history->remove_waiting_write(tid);
 438         history->remove_waiting_thread(tid);
 439
 440 /*--
 441         Predicate * selected_branch = get_selected_child_branch(tid);
 442         update_predicate_score(selected_branch, SLEEP_SUCCESS);
 443 */
 444
 445         model_print("** thread %d is woken up\n", tid);
 446 }
 447
 448 /* Find threads that may write values that the pending read action is waiting for.
 449  * Side effect: waiting thread related info are stored in dist_info_vec
 450  *
 451  * @return True if any thread is found
 452  */
 453 bool NewFuzzer::find_threads(ModelAction * pending_read)
 454 {
 455         ASSERT(pending_read->is_read());
 456
 457         void * location = pending_read->get_location();
 458         thread_id_t self_id = pending_read->get_tid();
 459         bool finds_waiting_for = false;
 460
 461         SnapVector<FuncNode *> * func_node_list = history->getWrFuncNodes(location);
 462         for (uint i = 0; i < func_node_list->size(); i++) {
 463                 FuncNode * target_node = (*func_node_list)[i];
 464                 for (uint i = 1; i < execution->get_num_threads(); i++) {
 465                         thread_id_t tid = int_to_id(i);
 466                         if (tid == self_id)
 467                                 continue;
 468
 469                         FuncNode * node = history->get_curr_func_node(tid);
 470                         /* It is possible that thread tid is not in any FuncNode */
 471                         if (node == NULL)
 472                                 continue;
 473
 474                         int distance = node->compute_distance(target_node);
 475                         if (distance != -1) {
 476                                 finds_waiting_for = true;
 477                                 //model_print("thread: %d; distance from node %d to node %d: %d\n", tid, node->get_func_id(), target_node->get_func_id(), distance);
 478
 479                                 dist_info_vec.push_back(node_dist_info(tid, target_node, distance));
 480                         }
 481                 }
 482         }
 483
 484         return finds_waiting_for;
 485 }
 486
 487 /* Update predicate counts and scores (asynchronous) when the read value is not available
 488  *
 489  * @param type
 490  *        type 1: find_threads return false
 491  *        type 2: find_threads return true, but the fuzzer decides that that thread shall not sleep based on sleep score
 492  *        type 3: threads are put to sleep but woken up before the waited value appears
 493  *        type 4: threads are put to sleep and the waited vaule appears (success)
 494  */
 495
 496 /*--
 497 void NewFuzzer::update_predicate_score(Predicate * predicate, sleep_result_t type)
 498 {
 499         switch (type) {
 500                 case SLEEP_FAIL_TYPE1:
 501                         predicate->incr_fail_count();
 502
 503                         // Do not choose this predicate when reselecting a new branch
 504                         failed_predicates.put(predicate, true);
 505                         break;
 506                 case SLEEP_FAIL_TYPE2:
 507                         predicate->incr_fail_count();
 508                         predicate->incr_sleep_score(1);
 509                         failed_predicates.put(predicate, true);
 510                         break;
 511                 case SLEEP_FAIL_TYPE3:
 512                         predicate->incr_fail_count();
 513                         predicate->decr_sleep_score(10);
 514                         break;
 515                 case SLEEP_SUCCESS:
 516                         predicate->incr_sleep_score(10);
 517                         break;
 518                 default:
 519                         model_print("unknown predicate result type.\n");
 520                         break;
 521         }
 522 }
 523 */
 524
 525 bool NewFuzzer::check_predicate_expressions(PredExprSet * pred_expressions,
 526         inst_act_map_t * inst_act_map, uint64_t write_val, bool * no_predicate)
 527 {
 528         bool satisfy_predicate = true;
 529
 530         PredExprSetIter * pred_expr_it = pred_expressions->iterator();
 531         while (pred_expr_it->hasNext()) {
 532                 struct pred_expr * expression = pred_expr_it->next();
 533                 bool equality;
 534
 535                 switch (expression->token) {
 536                         case NOPREDICATE:
 537                                 *no_predicate = true;
 538                                 break;
 539                         case EQUALITY:
 540                                 FuncInst * to_be_compared;
 541                                 ModelAction * last_act;
 542                                 uint64_t last_read;
 543
 544                                 to_be_compared = expression->func_inst;
 545                                 last_act = inst_act_map->get(to_be_compared);
 546                                 last_read = last_act->get_reads_from_value();
 547
 548                                 equality = (write_val == last_read);
 549                                 if (equality != expression->value)
 550                                         satisfy_predicate = false;
 551                                 break;
 552                         case NULLITY:
 553                                 equality = ((void*)write_val == NULL);
 554                                 if (equality != expression->value)
 555                                         satisfy_predicate = false;
 556                                 break;
 557                         default:
 558                                 model_print("unknown predicate token\n");
 559                                 break;
 560                 }
 561
 562                 if (!satisfy_predicate)
 563                         break;
 564         }
 565
 566         return satisfy_predicate;
 567 }
 568
 569 bool NewFuzzer::shouldWait(const ModelAction * act)
 570 {
 571         return random() & 1;
 572 }