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