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                 if (curr_pred != NULL)  {
  54                         Predicate * selected_branch = NULL;
  55
  56                         if (check_store_visibility(curr_pred, read_inst, inst_act_map, rf_set))
  57                                 selected_branch = selectBranch(tid, curr_pred, read_inst);
  58                         else {
  59                                 // no child of curr_pred matches read_inst, check back edges
  60                                 PredSet * back_edges = curr_pred->get_backedges();
  61                                 PredSetIter * it = back_edges->iterator();
  62
  63                                 while (it->hasNext()) {
  64                                         curr_pred = it->next();
  65                                         if (check_store_visibility(curr_pred, read_inst, inst_act_map, rf_set)) {
  66                                                 selected_branch = selectBranch(tid, curr_pred, read_inst);
  67                                                 break;
  68                                         }
  69                                 }
  70                         }
  71
  72                         prune_writes(tid, selected_branch, rf_set, inst_act_map);
  73                 }
  74
  75                 if (!failed_predicates.isEmpty())
  76                         failed_predicates.reset();
  77
  78                 thrd_last_read_act[thread_id] = read;
  79                 thrd_last_func_inst[thread_id] = read_inst;
  80         }
  81
  82         // No write satisfies the selected predicate, so pause this thread.
  83         while ( rf_set->size() == 0 ) {
  84                 Predicate * selected_branch = get_selected_child_branch(tid);
  85
  86                 //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());
  87
  88                 SnapVector<ModelAction *> * pruned_writes = thrd_pruned_writes[thread_id];
  89                 for (uint i = 0;i < pruned_writes->size();i++) {
  90                         rf_set->push_back( (*pruned_writes)[i] );
  91                 }
  92
  93                 // Reselect a predicate and prune writes
  94                 Predicate * curr_pred = selected_branch->get_parent();
  95                 FuncInst * read_inst = thrd_last_func_inst[thread_id];
  96                 selected_branch = selectBranch(tid, curr_pred, read_inst);
  97
  98                 FuncNode * func_node = history->get_curr_func_node(tid);
  99                 inst_act_map_t * inst_act_map = func_node->get_inst_act_map(tid);
 100                 prune_writes(tid, selected_branch, rf_set, inst_act_map);
 101
 102                 ASSERT(selected_branch);
 103         }
 104
 105         ASSERT(rf_set->size() != 0);
 106         int random_index = random() % rf_set->size();
 107
 108         return random_index;
 109 }
 110
 111 /* For children of curr_pred that matches read_inst.
 112  * If any store in rf_set satisfies the a child's predicate,
 113  * increment the store visibility count for it.
 114  *
 115  * @return False if no child matches read_inst
 116  */
 117 bool NewFuzzer::check_store_visibility(Predicate * curr_pred, FuncInst * read_inst,
 118 inst_act_map_t * inst_act_map, SnapVector<ModelAction *> * rf_set)
 119 {
 120         ASSERT(!rf_set->empty());
 121         if (curr_pred == NULL || read_inst == NULL)
 122                 return false;
 123
 124         ModelVector<Predicate *> * children = curr_pred->get_children();
 125         bool any_child_match = false;
 126
 127         /* Iterate over all predicate children */
 128         for (uint i = 0;i < children->size();i++) {
 129                 Predicate * branch = (*children)[i];
 130
 131                 /* The children predicates may have different FuncInsts */
 132                 if (branch->get_func_inst() == read_inst) {
 133                         PredExprSet * pred_expressions = branch->get_pred_expressions();
 134                         any_child_match = true;
 135
 136                         /* Do not check unset predicates */
 137                         if (pred_expressions->isEmpty())
 138                                 continue;
 139
 140                         branch->incr_total_checking_count();
 141
 142                         /* Iterate over all write actions */
 143                         for (uint j = 0;j < rf_set->size();j++) {
 144                                 ModelAction * write_act = (*rf_set)[j];
 145                                 uint64_t write_val = write_act->get_write_value();
 146                                 bool dummy = true;
 147                                 bool satisfy_predicate = check_predicate_expressions(pred_expressions, inst_act_map, write_val, &dummy);
 148
 149                                 /* If one write value satisfies the predicate, go to check the next predicate */
 150                                 if (satisfy_predicate) {
 151                                         branch->incr_store_visible_count();
 152                                         break;
 153                                 }
 154                         }
 155                 }
 156         }
 157
 158         return any_child_match;
 159 }
 160
 161
 162 /* Select a random branch from the children of curr_pred
 163  * @return The selected branch
 164  */
 165 Predicate * NewFuzzer::selectBranch(thread_id_t tid, Predicate * curr_pred, FuncInst * read_inst)
 166 {
 167         int thread_id = id_to_int(tid);
 168         if ( thrd_selected_child_branch.size() <= (uint) thread_id)
 169                 thrd_selected_child_branch.resize(thread_id + 1);
 170
 171         if (curr_pred == NULL || read_inst == NULL) {
 172                 thrd_selected_child_branch[thread_id] = NULL;
 173                 return NULL;
 174         }
 175
 176         ModelVector<Predicate *> * children = curr_pred->get_children();
 177         SnapVector<Predicate *> branches;
 178
 179         for (uint i = 0; i < children->size(); i++) {
 180                 Predicate * child = (*children)[i];
 181                 if (child->get_func_inst() == read_inst && !failed_predicates.contains(child)) {
 182                         branches.push_back(child);
 183                 }
 184         }
 185
 186         // predicate children have not been generated
 187         if (branches.size() == 0) {
 188                 thrd_selected_child_branch[thread_id] = NULL;
 189                 return NULL;
 190         }
 191
 192         int index = choose_index(&branches, 0);
 193         Predicate * random_branch = branches[ index ];
 194         thrd_selected_child_branch[thread_id] = random_branch;
 195
 196         return random_branch;
 197 }
 198
 199 /**
 200  * @brief Select a branch from the given predicate branches based
 201  * on their exploration counts.
 202  *
 203  * Let b_1, ..., b_n be branches with exploration counts c_1, ..., c_n
 204  * M := max(c_1, ..., c_n) + 1
 205  * Factor f_i := M / (c_i + 1)
 206  * The probability p_i that branch b_i is selected:
 207  *      p_i := f_i / (f_1 + ... + f_n)
 208  *           = \fraction{ 1/(c_i + 1) }{ 1/(c_1 + 1) + ... + 1/(c_n + 1) }
 209  *
 210  * Note: (1) c_i + 1 is used because counts may be 0.
 211  *       (2) The numerator of f_i is chosen to reduce the effect of underflow
 212  *
 213  * @param numerator is M defined above
 214  */
 215 int NewFuzzer::choose_index(SnapVector<Predicate *> * branches, uint32_t numerator)
 216 {
 217         return random() % branches->size();
 218 /*--
 219         if (branches->size() == 1)
 220                 return 0;
 221
 222         double total_factor = 0;
 223         SnapVector<double> factors = SnapVector<double>( branches->size() + 1 );
 224         for (uint i = 0; i < branches->size(); i++) {
 225                 Predicate * branch = (*branches)[i];
 226                 double factor = (double) numerator / (branch->get_expl_count() + 5 * branch->get_fail_count() + 1);
 227                 total_factor += factor;
 228                 factors.push_back(factor);
 229         }
 230
 231         double prob = (double) random() / RAND_MAX;
 232         double prob_sum = 0;
 233         int index = 0;
 234
 235         for (uint i = 0; i < factors.size(); i++) {
 236                 index = i;
 237                 prob_sum += (double) (factors[i] / total_factor);
 238                 if (prob_sum > prob) {
 239                         break;
 240                 }
 241         }
 242
 243         return index;
 244  */
 245 }
 246
 247 Predicate * NewFuzzer::get_selected_child_branch(thread_id_t tid)
 248 {
 249         int thread_id = id_to_int(tid);
 250         if (thrd_selected_child_branch.size() <= (uint) thread_id)
 251                 return NULL;
 252
 253         return thrd_selected_child_branch[thread_id];
 254 }
 255
 256 /* Remove writes from the rf_set that do not satisfie the selected predicate,
 257  * and store them in thrd_pruned_writes
 258  *
 259  * @return true if rf_set is pruned
 260  */
 261 bool NewFuzzer::prune_writes(thread_id_t tid, Predicate * pred,
 262 SnapVector<ModelAction *> * rf_set, inst_act_map_t * inst_act_map)
 263 {
 264         if (pred == NULL)
 265                 return false;
 266
 267         PredExprSet * pred_expressions = pred->get_pred_expressions();
 268         if (pred_expressions->getSize() == 0)   // unset predicates
 269                 return false;
 270
 271         int thread_id = id_to_int(tid);
 272         uint old_size = thrd_pruned_writes.size();
 273         if (thrd_pruned_writes.size() <= (uint) thread_id) {
 274                 uint new_size = thread_id + 1;
 275                 thrd_pruned_writes.resize(new_size);
 276                 for (uint i = old_size;i < new_size;i++)
 277                         thrd_pruned_writes[i] = new SnapVector<ModelAction *>();
 278         }
 279         SnapVector<ModelAction *> * pruned_writes = thrd_pruned_writes[thread_id];
 280         pruned_writes->clear(); // clear the old pruned_writes set
 281
 282         bool pruned = false;
 283         uint index = 0;
 284
 285         while ( index < rf_set->size() ) {
 286                 ModelAction * write_act = (*rf_set)[index];
 287                 uint64_t write_val = write_act->get_write_value();
 288                 bool no_predicate = false;
 289                 bool satisfy_predicate = check_predicate_expressions(pred_expressions, inst_act_map, write_val, &no_predicate);
 290
 291                 if (no_predicate)
 292                         return false;
 293
 294                 if (!satisfy_predicate) {
 295                         ASSERT(rf_set != NULL);
 296                         (*rf_set)[index] = rf_set->back();
 297                         rf_set->pop_back();
 298                         pruned_writes->push_back(write_act);
 299                         pruned = true;
 300                 } else
 301                         index++;
 302         }
 303
 304         return pruned;
 305 }
 306
 307 /* @brief Put a thread to sleep because no writes in rf_set satisfies the selected predicate.
 308  *
 309  * @param thread A thread whose last action is a read
 310  */
 311 void NewFuzzer::conditional_sleep(Thread * thread)
 312 {
 313         int index = paused_thread_list.size();
 314
 315         model->getScheduler()->add_sleep(thread);
 316         paused_thread_list.push_back(thread);
 317         paused_thread_table.put(thread, index); // Update table
 318
 319         /* Add the waiting condition to ModelHistory */
 320         ModelAction * read = thread->get_pending();
 321         thread_id_t tid = thread->get_id();
 322         FuncNode * func_node = history->get_curr_func_node(tid);
 323         inst_act_map_t * inst_act_map = func_node->get_inst_act_map(tid);
 324
 325         Predicate * selected_branch = get_selected_child_branch(tid);
 326         ConcretePredicate * concrete = selected_branch->evaluate(inst_act_map, tid);
 327         concrete->set_location(read->get_location());
 328
 329         history->add_waiting_write(concrete);
 330         /* history->add_waiting_thread is already called in find_threads */
 331 }
 332
 333 /**
 334  * Decides whether a thread should condition sleep based on
 335  * the sleep score of the chosen predicate.
 336  *
 337  * sleep_score = 0: never sleeps
 338  * sleep_score = 100: always sleeps
 339  **/
 340 bool NewFuzzer::should_conditional_sleep(Predicate * predicate)
 341 {
 342         return false;
 343         /*
 344            int sleep_score = predicate->get_sleep_score();
 345            int random_num = random() % 100;
 346
 347            // should sleep if random_num falls within [0, sleep_score)
 348            if (random_num < sleep_score)
 349                 return true;
 350
 351            return false;
 352          */
 353 }
 354
 355 bool NewFuzzer::has_paused_threads()
 356 {
 357         return paused_thread_list.size() != 0;
 358 }
 359
 360 Thread * NewFuzzer::selectThread(int * threadlist, int numthreads)
 361 {
 362         if (numthreads == 0 && has_paused_threads()) {
 363                 wake_up_paused_threads(threadlist, &numthreads);
 364                 //model_print("list size: %d, active t id: %d\n", numthreads, threadlist[0]);
 365         }
 366
 367         int random_index = random() % numthreads;
 368         int thread = threadlist[random_index];
 369         thread_id_t curr_tid = int_to_id(thread);
 370         return execution->get_thread(curr_tid);
 371 }
 372
 373 /* Force waking up one of threads paused by Fuzzer, because otherwise
 374  * the Fuzzer is not making progress
 375  */
 376 void NewFuzzer::wake_up_paused_threads(int * threadlist, int * numthreads)
 377 {
 378         int random_index = random() % paused_thread_list.size();
 379         Thread * thread = paused_thread_list[random_index];
 380         model->getScheduler()->remove_sleep(thread);
 381
 382         Thread * last_thread = paused_thread_list.back();
 383         paused_thread_list[random_index] = last_thread;
 384         paused_thread_list.pop_back();
 385         paused_thread_table.put(last_thread, random_index);     // Update table
 386         paused_thread_table.remove(thread);
 387
 388         thread_id_t tid = thread->get_id();
 389         history->remove_waiting_write(tid);
 390         history->remove_waiting_thread(tid);
 391
 392         threadlist[*numthreads] = tid;
 393         (*numthreads)++;
 394
 395 /*--
 396         Predicate * selected_branch = get_selected_child_branch(tid);
 397         update_predicate_score(selected_branch, SLEEP_FAIL_TYPE3);
 398  */
 399
 400         model_print("thread %d is woken up\n", tid);
 401 }
 402
 403 /* Wake up conditional sleeping threads if the desired write is available */
 404 void NewFuzzer::notify_paused_thread(Thread * thread)
 405 {
 406         ASSERT(paused_thread_table.contains(thread));
 407
 408         int index = paused_thread_table.get(thread);
 409         model->getScheduler()->remove_sleep(thread);
 410
 411         Thread * last_thread = paused_thread_list.back();
 412         paused_thread_list[index] = last_thread;
 413         paused_thread_list.pop_back();
 414         paused_thread_table.put(last_thread, index);    // Update table
 415         paused_thread_table.remove(thread);
 416
 417         thread_id_t tid = thread->get_id();
 418         history->remove_waiting_write(tid);
 419         history->remove_waiting_thread(tid);
 420
 421 /*--
 422         Predicate * selected_branch = get_selected_child_branch(tid);
 423         update_predicate_score(selected_branch, SLEEP_SUCCESS);
 424  */
 425
 426         model_print("** thread %d is woken up\n", tid);
 427 }
 428
 429 /* Find threads that may write values that the pending read action is waiting for.
 430  * Side effect: waiting thread related info are stored in dist_info_vec
 431  *
 432  * @return True if any thread is found
 433  */
 434 bool NewFuzzer::find_threads(ModelAction * pending_read)
 435 {
 436         ASSERT(pending_read->is_read());
 437
 438         void * location = pending_read->get_location();
 439         thread_id_t self_id = pending_read->get_tid();
 440         bool finds_waiting_for = false;
 441
 442         SnapVector<FuncNode *> * func_node_list = history->getWrFuncNodes(location);
 443         for (uint i = 0;i < func_node_list->size();i++) {
 444                 FuncNode * target_node = (*func_node_list)[i];
 445                 for (uint i = 1;i < execution->get_num_threads();i++) {
 446                         thread_id_t tid = int_to_id(i);
 447                         if (tid == self_id)
 448                                 continue;
 449
 450                         FuncNode * node = history->get_curr_func_node(tid);
 451                         /* It is possible that thread tid is not in any FuncNode */
 452                         if (node == NULL)
 453                                 continue;
 454
 455                         int distance = node->compute_distance(target_node);
 456                         if (distance != -1) {
 457                                 finds_waiting_for = true;
 458                                 //model_print("thread: %d; distance from node %d to node %d: %d\n", tid, node->get_func_id(), target_node->get_func_id(), distance);
 459
 460                                 dist_info_vec.push_back(node_dist_info(tid, target_node, distance));
 461                         }
 462                 }
 463         }
 464
 465         return finds_waiting_for;
 466 }
 467
 468 /* Update predicate counts and scores (asynchronous) when the read value is not available
 469  *
 470  * @param type
 471  *        type 1: find_threads return false
 472  *        type 2: find_threads return true, but the fuzzer decides that that thread shall not sleep based on sleep score
 473  *        type 3: threads are put to sleep but woken up before the waited value appears
 474  *        type 4: threads are put to sleep and the waited vaule appears (success)
 475  */
 476
 477 /*--
 478    void NewFuzzer::update_predicate_score(Predicate * predicate, sleep_result_t type)
 479    {
 480         switch (type) {
 481                 case SLEEP_FAIL_TYPE1:
 482                         predicate->incr_fail_count();
 483
 484                         // Do not choose this predicate when reselecting a new branch
 485                         failed_predicates.put(predicate, true);
 486                         break;
 487                 case SLEEP_FAIL_TYPE2:
 488                         predicate->incr_fail_count();
 489                         predicate->incr_sleep_score(1);
 490                         failed_predicates.put(predicate, true);
 491                         break;
 492                 case SLEEP_FAIL_TYPE3:
 493                         predicate->incr_fail_count();
 494                         predicate->decr_sleep_score(10);
 495                         break;
 496                 case SLEEP_SUCCESS:
 497                         predicate->incr_sleep_score(10);
 498                         break;
 499                 default:
 500                         model_print("unknown predicate result type.\n");
 501                         break;
 502         }
 503    }
 504  */
 505
 506 bool NewFuzzer::check_predicate_expressions(PredExprSet * pred_expressions,
 507 inst_act_map_t * inst_act_map, uint64_t write_val, bool * no_predicate)
 508 {
 509         bool satisfy_predicate = true;
 510
 511         PredExprSetIter * pred_expr_it = pred_expressions->iterator();
 512         while (pred_expr_it->hasNext()) {
 513                 struct pred_expr * expression = pred_expr_it->next();
 514                 bool equality;
 515
 516                 switch (expression->token) {
 517                         case NOPREDICATE:
 518                                 *no_predicate = true;
 519                                 break;
 520                         case EQUALITY:
 521                                 FuncInst * to_be_compared;
 522                                 ModelAction * last_act;
 523                                 uint64_t last_read;
 524
 525                                 to_be_compared = expression->func_inst;
 526                                 last_act = inst_act_map->get(to_be_compared);
 527                                 last_read = last_act->get_reads_from_value();
 528
 529                                 equality = (write_val == last_read);
 530                                 if (equality != expression->value)
 531                                         satisfy_predicate = false;
 532                                 break;
 533                         case NULLITY:
 534                                 // TODO: implement likely to be null
 535                                 equality = ((void*) (write_val & 0xffffffff) == NULL);
 536                                 if (equality != expression->value)
 537                                         satisfy_predicate = false;
 538                                 break;
 539                         default:
 540                                 model_print("unknown predicate token\n");
 541                                 break;
 542                 }
 543
 544                 if (!satisfy_predicate)
 545                         break;
 546         }
 547
 548         return satisfy_predicate;
 549 }
 550
 551 bool NewFuzzer::shouldWait(const ModelAction * act)
 552 {
 553         return random() & 1;
 554 }