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