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         tmp_branches_storage(),
  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                 FuncInst * read_inst = func_node->get_inst(read);
  52                 inst_act_map_t * inst_act_map = func_node->get_inst_act_map(tid);
  53
  54                 if (curr_pred != NULL)  {
  55                         Predicate * selected_branch = NULL;
  56
  57                         if (check_store_visibility(curr_pred, read_inst, inst_act_map, rf_set))
  58                                 selected_branch = selectBranch(tid, curr_pred, read_inst);
  59                         else {
  60                                 // no child of curr_pred matches read_inst, check back edges
  61                                 PredSet * back_edges = curr_pred->get_backedges();
  62                                 PredSetIter * it = back_edges->iterator();
  63
  64                                 while (it->hasNext()) {
  65                                         curr_pred = it->next();
  66                                         if (check_store_visibility(curr_pred, read_inst, inst_act_map, rf_set)) {
  67                                                 selected_branch = selectBranch(tid, curr_pred, read_inst);
  68                                                 break;
  69                                         }
  70                                 }
  71                         }
  72
  73                         prune_writes(tid, selected_branch, rf_set, inst_act_map);
  74                 }
  75
  76                 if (!failed_predicates.isEmpty())
  77                         failed_predicates.reset();
  78
  79                 thrd_last_read_act[thread_id] = read;
  80                 thrd_last_func_inst[thread_id] = read_inst;
  81         }
  82
  83         // No write satisfies the selected predicate, so pause this thread.
  84         while ( rf_set->size() == 0 ) {
  85                 Predicate * selected_branch = get_selected_child_branch(tid);
  86
  87                 //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());
  88
  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         ASSERT(rf_set->size() != 0);
 107         int random_index = random() % rf_set->size();
 108
 109         return random_index;
 110 }
 111
 112 /* For children of curr_pred that matches read_inst.
 113  * If any store in rf_set satisfies the a child's predicate,
 114  * increment the store visibility count for it.
 115  *
 116  * @return False if no child matches read_inst
 117  */
 118 bool NewFuzzer::check_store_visibility(Predicate * curr_pred, FuncInst * read_inst,
 119 inst_act_map_t * inst_act_map, SnapVector<ModelAction *> * rf_set)
 120 {
 121         ASSERT(!rf_set->empty());
 122         if (curr_pred == NULL || read_inst == NULL)
 123                 return false;
 124
 125         ModelVector<Predicate *> * children = curr_pred->get_children();
 126         bool any_child_match = false;
 127
 128         /* Iterate over all predicate children */
 129         for (uint i = 0;i < children->size();i++) {
 130                 Predicate * branch = (*children)[i];
 131
 132                 /* The children predicates may have different FuncInsts */
 133                 if (branch->get_func_inst() == read_inst) {
 134                         PredExprSet * pred_expressions = branch->get_pred_expressions();
 135                         any_child_match = true;
 136
 137                         /* Do not check unset predicates */
 138                         if (pred_expressions->isEmpty())
 139                                 continue;
 140
 141                         branch->incr_total_checking_count();
 142
 143                         /* Iterate over all write actions */
 144                         for (uint j = 0;j < rf_set->size();j++) {
 145                                 ModelAction * write_act = (*rf_set)[j];
 146                                 uint64_t write_val = write_act->get_write_value();
 147                                 bool dummy = true;
 148                                 bool satisfy_predicate = check_predicate_expressions(pred_expressions, inst_act_map, write_val, &dummy);
 149
 150                                 /* If one write value satisfies the predicate, go to check the next predicate */
 151                                 if (satisfy_predicate) {
 152                                         branch->incr_store_visible_count();
 153                                         break;
 154                                 }
 155                         }
 156                 }
 157         }
 158
 159         return any_child_match;
 160 }
 161
 162
 163 /* Select a random branch from the children of curr_pred
 164  * @return The selected branch
 165  */
 166 Predicate * NewFuzzer::selectBranch(thread_id_t tid, Predicate * curr_pred, FuncInst * read_inst)
 167 {
 168         int thread_id = id_to_int(tid);
 169         if ( thrd_selected_child_branch.size() <= (uint) thread_id)
 170                 thrd_selected_child_branch.resize(thread_id + 1);
 171
 172         if (curr_pred == NULL || read_inst == NULL) {
 173                 thrd_selected_child_branch[thread_id] = NULL;
 174                 return NULL;
 175         }
 176
 177         ModelVector<Predicate *> * children = curr_pred->get_children();
 178         tmp_branches_storage.clear();
 179
 180         for (uint i = 0; i < children->size(); i++) {
 181                 Predicate * child = (*children)[i];
 182                 if (child->get_func_inst() == read_inst && !failed_predicates.contains(child)) {
 183                         tmp_branches_storage.push_back(child);
 184                 }
 185         }
 186
 187         // predicate children have not been generated
 188         if (tmp_branches_storage.size() == 0) {
 189                 thrd_selected_child_branch[thread_id] = NULL;
 190                 return NULL;
 191         }
 192
 193         int index = choose_index(&tmp_branches_storage, 0);
 194         Predicate * random_branch = tmp_branches_storage[ index ];
 195         thrd_selected_child_branch[thread_id] = random_branch;
 196
 197         return random_branch;
 198 }
 199
 200 /**
 201  * @brief Select a branch from the given predicate branches based
 202  * on their exploration counts.
 203  *
 204  * Let b_1, ..., b_n be branches with exploration counts c_1, ..., c_n
 205  * M := max(c_1, ..., c_n) + 1
 206  * Factor f_i := M / (c_i + 1)
 207  * The probability p_i that branch b_i is selected:
 208  *      p_i := f_i / (f_1 + ... + f_n)
 209  *           = \fraction{ 1/(c_i + 1) }{ 1/(c_1 + 1) + ... + 1/(c_n + 1) }
 210  *
 211  * Note: (1) c_i + 1 is used because counts may be 0.
 212  *       (2) The numerator of f_i is chosen to reduce the effect of underflow
 213  *
 214  * @param numerator is M defined above
 215  */
 216 int NewFuzzer::choose_index(SnapVector<Predicate *> * branches, uint32_t numerator)
 217 {
 218         return random() % branches->size();
 219 /*--
 220         if (branches->size() == 1)
 221                 return 0;
 222
 223         double total_factor = 0;
 224         SnapVector<double> factors = SnapVector<double>( branches->size() + 1 );
 225         for (uint i = 0; i < branches->size(); i++) {
 226                 Predicate * branch = (*branches)[i];
 227                 double factor = (double) numerator / (branch->get_expl_count() + 5 * branch->get_fail_count() + 1);
 228                 total_factor += factor;
 229                 factors.push_back(factor);
 230         }
 231
 232         double prob = (double) random() / RAND_MAX;
 233         double prob_sum = 0;
 234         int index = 0;
 235
 236         for (uint i = 0; i < factors.size(); i++) {
 237                 index = i;
 238                 prob_sum += (double) (factors[i] / total_factor);
 239                 if (prob_sum > prob) {
 240                         break;
 241                 }
 242         }
 243
 244         return index;
 245  */
 246 }
 247
 248 Predicate * NewFuzzer::get_selected_child_branch(thread_id_t tid)
 249 {
 250         int thread_id = id_to_int(tid);
 251         if (thrd_selected_child_branch.size() <= (uint) thread_id)
 252                 return NULL;
 253
 254         return thrd_selected_child_branch[thread_id];
 255 }
 256
 257 /* Remove writes from the rf_set that do not satisfie the selected predicate,
 258  * and store them in thrd_pruned_writes
 259  *
 260  * @return true if rf_set is pruned
 261  */
 262 bool NewFuzzer::prune_writes(thread_id_t tid, Predicate * pred,
 263 SnapVector<ModelAction *> * rf_set, inst_act_map_t * inst_act_map)
 264 {
 265         if (pred == NULL)
 266                 return false;
 267
 268         PredExprSet * pred_expressions = pred->get_pred_expressions();
 269         if (pred_expressions->getSize() == 0)   // unset predicates
 270                 return false;
 271
 272         int thread_id = id_to_int(tid);
 273         uint old_size = thrd_pruned_writes.size();
 274         if (thrd_pruned_writes.size() <= (uint) thread_id) {
 275                 uint new_size = thread_id + 1;
 276                 thrd_pruned_writes.resize(new_size);
 277                 for (uint i = old_size;i < new_size;i++)
 278                         thrd_pruned_writes[i] = new SnapVector<ModelAction *>();
 279         }
 280         SnapVector<ModelAction *> * pruned_writes = thrd_pruned_writes[thread_id];
 281         pruned_writes->clear(); // clear the old pruned_writes set
 282
 283         bool pruned = false;
 284         uint index = 0;
 285
 286         while ( index < rf_set->size() ) {
 287                 ModelAction * write_act = (*rf_set)[index];
 288                 uint64_t write_val = write_act->get_write_value();
 289                 bool no_predicate = false;
 290                 bool satisfy_predicate = check_predicate_expressions(pred_expressions, inst_act_map, write_val, &no_predicate);
 291
 292                 if (no_predicate)
 293                         return false;
 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 bool NewFuzzer::has_paused_threads()
 335 {
 336         return paused_thread_list.size() != 0;
 337 }
 338
 339 Thread * NewFuzzer::selectThread(int * threadlist, int numthreads)
 340 {
 341         if (numthreads == 0 && has_paused_threads()) {
 342                 wake_up_paused_threads(threadlist, &numthreads);
 343                 //model_print("list size: %d, active t id: %d\n", numthreads, threadlist[0]);
 344         }
 345
 346         int random_index = random() % numthreads;
 347         int thread = threadlist[random_index];
 348         thread_id_t curr_tid = int_to_id(thread);
 349         return execution->get_thread(curr_tid);
 350 }
 351
 352 /* Force waking up one of threads paused by Fuzzer, because otherwise
 353  * the Fuzzer is not making progress
 354  */
 355 void NewFuzzer::wake_up_paused_threads(int * threadlist, int * numthreads)
 356 {
 357         int random_index = random() % paused_thread_list.size();
 358         Thread * thread = paused_thread_list[random_index];
 359         model->getScheduler()->remove_sleep(thread);
 360
 361         Thread * last_thread = paused_thread_list.back();
 362         paused_thread_list[random_index] = last_thread;
 363         paused_thread_list.pop_back();
 364         paused_thread_table.put(last_thread, random_index);     // Update table
 365         paused_thread_table.remove(thread);
 366
 367         thread_id_t tid = thread->get_id();
 368         history->remove_waiting_write(tid);
 369         history->remove_waiting_thread(tid);
 370
 371         threadlist[*numthreads] = tid;
 372         (*numthreads)++;
 373
 374 /*--
 375         Predicate * selected_branch = get_selected_child_branch(tid);
 376         update_predicate_score(selected_branch, SLEEP_FAIL_TYPE3);
 377  */
 378
 379         model_print("thread %d is woken up\n", tid);
 380 }
 381
 382 /* Wake up conditional sleeping threads if the desired write is available */
 383 void NewFuzzer::notify_paused_thread(Thread * thread)
 384 {
 385         ASSERT(paused_thread_table.contains(thread));
 386
 387         int index = paused_thread_table.get(thread);
 388         model->getScheduler()->remove_sleep(thread);
 389
 390         Thread * last_thread = paused_thread_list.back();
 391         paused_thread_list[index] = last_thread;
 392         paused_thread_list.pop_back();
 393         paused_thread_table.put(last_thread, index);    // Update table
 394         paused_thread_table.remove(thread);
 395
 396         thread_id_t tid = thread->get_id();
 397         history->remove_waiting_write(tid);
 398         history->remove_waiting_thread(tid);
 399
 400 /*--
 401         Predicate * selected_branch = get_selected_child_branch(tid);
 402         update_predicate_score(selected_branch, SLEEP_SUCCESS);
 403  */
 404
 405         model_print("** thread %d is woken up\n", tid);
 406 }
 407
 408 /* Find threads that may write values that the pending read action is waiting for.
 409  * Side effect: waiting thread related info are stored in dist_info_vec
 410  *
 411  * @return True if any thread is found
 412  */
 413 bool NewFuzzer::find_threads(ModelAction * pending_read)
 414 {
 415         ASSERT(pending_read->is_read());
 416
 417         void * location = pending_read->get_location();
 418         thread_id_t self_id = pending_read->get_tid();
 419         bool finds_waiting_for = false;
 420
 421         SnapVector<FuncNode *> * func_node_list = history->getWrFuncNodes(location);
 422         for (uint i = 0;i < func_node_list->size();i++) {
 423                 FuncNode * target_node = (*func_node_list)[i];
 424                 for (uint i = 1;i < execution->get_num_threads();i++) {
 425                         thread_id_t tid = int_to_id(i);
 426                         if (tid == self_id)
 427                                 continue;
 428
 429                         FuncNode * node = history->get_curr_func_node(tid);
 430                         /* It is possible that thread tid is not in any FuncNode */
 431                         if (node == NULL)
 432                                 continue;
 433
 434                         int distance = node->compute_distance(target_node);
 435                         if (distance != -1) {
 436                                 finds_waiting_for = true;
 437                                 //model_print("thread: %d; distance from node %d to node %d: %d\n", tid, node->get_func_id(), target_node->get_func_id(), distance);
 438
 439                                 dist_info_vec.push_back(node_dist_info(tid, target_node, distance));
 440                         }
 441                 }
 442         }
 443
 444         return finds_waiting_for;
 445 }
 446
 447 bool NewFuzzer::check_predicate_expressions(PredExprSet * pred_expressions,
 448 inst_act_map_t * inst_act_map, uint64_t write_val, bool * no_predicate)
 449 {
 450         bool satisfy_predicate = true;
 451
 452         PredExprSetIter * pred_expr_it = pred_expressions->iterator();
 453         while (pred_expr_it->hasNext()) {
 454                 struct pred_expr * expression = pred_expr_it->next();
 455                 bool equality;
 456
 457                 switch (expression->token) {
 458                         case NOPREDICATE:
 459                                 *no_predicate = true;
 460                                 break;
 461                         case EQUALITY:
 462                                 FuncInst * to_be_compared;
 463                                 ModelAction * last_act;
 464                                 uint64_t last_read;
 465
 466                                 to_be_compared = expression->func_inst;
 467                                 last_act = inst_act_map->get(to_be_compared);
 468                                 last_read = last_act->get_reads_from_value();
 469
 470                                 equality = (write_val == last_read);
 471                                 if (equality != expression->value)
 472                                         satisfy_predicate = false;
 473                                 break;
 474                         case NULLITY:
 475                                 // TODO: implement likely to be null
 476                                 equality = ((void*) (write_val & 0xffffffff) == NULL);
 477                                 if (equality != expression->value)
 478                                         satisfy_predicate = false;
 479                                 break;
 480                         default:
 481                                 model_print("unknown predicate token\n");
 482                                 break;
 483                 }
 484
 485                 if (!satisfy_predicate)
 486                         break;
 487         }
 488
 489         return satisfy_predicate;
 490 }
 491
 492 bool NewFuzzer::shouldWait(const ModelAction * act)
 493 {
 494         return random() & 1;
 495 }