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