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