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