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                 FuncInst * read_inst = func_node->get_inst(read);
  51                 Predicate * selected_branch = selectBranch(tid, curr_pred, read_inst);
  52
  53                 inst_act_map_t * inst_act_map = func_node->get_inst_act_map(tid);
  54                 prune_writes(tid, selected_branch, rf_set, inst_act_map);
  55
  56                 if (!failed_predicates.isEmpty())
  57                         failed_predicates.reset();
  58
  59                 thrd_last_read_act[thread_id] = read;
  60                 thrd_last_func_inst[thread_id] = read_inst;
  61         }
  62
  63         // No write satisfies the selected predicate, so pause this thread.
  64         while ( rf_set->size() == 0 ) {
  65                 Thread * read_thread = execution->get_thread(tid);
  66                 //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());
  67
  68                 if (find_threads(read)) {
  69                         // reset thread pending action and revert sequence numbers
  70                         read_thread->set_pending(read);
  71                         read->reset_seq_number();
  72                         execution->restore_last_seq_num();
  73
  74                         conditional_sleep(read_thread);
  75
  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 //                      selected_branch->incr_count();
  81                         failed_predicates.put(selected_branch, true);
  82
  83                         SnapVector<ModelAction *> * pruned_writes = thrd_pruned_writes[thread_id];
  84                         for (uint i = 0; i < pruned_writes->size(); i++) {
  85                                 rf_set->push_back( (*pruned_writes)[i] );
  86                         }
  87
  88                         // Reselect a predicate and prune writes
  89                         Predicate * curr_pred = selected_branch->get_parent();
  90                         FuncInst * read_inst = thrd_last_func_inst[thread_id];
  91                         selected_branch = selectBranch(tid, curr_pred, read_inst);
  92
  93                         FuncNode * func_node = history->get_curr_func_node(tid);
  94                         inst_act_map_t * inst_act_map = func_node->get_inst_act_map(tid);
  95                         prune_writes(tid, selected_branch, rf_set, inst_act_map);
  96
  97                         ASSERT(selected_branch);
  98                 }
  99         }
 100
 101         ASSERT(rf_set->size() != 0);
 102         int random_index = random() % rf_set->size();
 103
 104         return random_index;
 105 }
 106
 107 /* Select a random branch from the children of curr_pred
 108  * @return The selected branch
 109  */
 110 Predicate * NewFuzzer::selectBranch(thread_id_t tid, Predicate * curr_pred, FuncInst * read_inst)
 111 {
 112         int thread_id = id_to_int(tid);
 113         if ( thrd_selected_child_branch.size() <= (uint) thread_id)
 114                 thrd_selected_child_branch.resize(thread_id + 1);
 115
 116         if (curr_pred == NULL || read_inst == NULL) {
 117                 thrd_selected_child_branch[thread_id] = NULL;
 118                 return NULL;
 119         }
 120
 121         ModelVector<Predicate *> * children = curr_pred->get_children();
 122         SnapVector<Predicate *> branches;
 123         uint32_t numerator = 1;
 124
 125         for (uint i = 0; i < children->size(); i++) {
 126                 Predicate * child = (*children)[i];
 127                 if (child->get_func_inst() == read_inst && !failed_predicates.contains(child)) {
 128                         branches.push_back(child);
 129
 130                         // max of (exploration counts + 1)
 131                         if (child->get_count() + 1 > numerator)
 132                                 numerator = child->get_count() + 1;
 133                 }
 134         }
 135
 136         // predicate children have not been generated
 137         if (branches.size() == 0) {
 138                 thrd_selected_child_branch[thread_id] = NULL;
 139                 return NULL;
 140         }
 141
 142         // randomly select a branch
 143         // int random_index = random() % branches.size();
 144         // Predicate * random_branch = branches[ random_index ];
 145
 146         int index = choose_index(&branches, numerator);
 147         Predicate * random_branch = branches[ index ];
 148         thrd_selected_child_branch[thread_id] = random_branch;
 149
 150         return random_branch;
 151 }
 152
 153 /**
 154  * @brief Select a branch from the given predicate branches based
 155  * on their exploration counts.
 156  *
 157  * Let b_1, ..., b_n be branches with exploration counts c_1, ..., c_n
 158  * M := max(c_1, ..., c_n) + 1
 159  * Factor f_i := M / (c_i + 1)
 160  * The probability p_i that branch b_i is selected:
 161  *      p_i := f_i / (f_1 + ... + f_n)
 162  *           = \fraction{ 1/(c_i + 1) }{ 1/(c_1 + 1) + ... + 1/(c_n + 1) }
 163  *
 164  * Note: (1) c_i + 1 is used because counts may be 0.
 165  *       (2) The numerator of f_i is chosen to reduce the effect of underflow
 166  *
 167  * @param numerator is M defined above
 168  */
 169 int NewFuzzer::choose_index(SnapVector<Predicate *> * branches, uint32_t numerator)
 170 {
 171         if (branches->size() == 1)
 172                 return 0;
 173
 174         double total_factor = 0;
 175         SnapVector<double> factors = SnapVector<double>( branches->size() );
 176         for (uint i = 0; i < branches->size(); i++) {
 177                 Predicate * branch = (*branches)[i];
 178                 double factor = (double) numerator / (branch->get_count() + 1);
 179                 total_factor += factor;
 180                 factors[i] = factor;
 181         }
 182
 183         double prob = (double) random() / RAND_MAX;
 184         double prob_sum = 0;
 185         int index = 0;
 186
 187         for (uint i = 0; i < factors.size(); i++) {
 188                 prob_sum += (double) factors[i] / total_factor;
 189                 if (prob_sum > prob) {
 190                         index = i;
 191                         break;
 192                 }
 193         }
 194
 195         return index;
 196 }
 197
 198 Predicate * NewFuzzer::get_selected_child_branch(thread_id_t tid)
 199 {
 200         int thread_id = id_to_int(tid);
 201         if (thrd_selected_child_branch.size() <= (uint) thread_id)
 202                 return NULL;
 203
 204         return thrd_selected_child_branch[thread_id];
 205 }
 206
 207 /* Remove writes from the rf_set that do not satisfie the selected predicate,
 208  * and store them in thrd_pruned_writes
 209  *
 210  * @return true if rf_set is pruned
 211  */
 212 bool NewFuzzer::prune_writes(thread_id_t tid, Predicate * pred,
 213         SnapVector<ModelAction *> * rf_set, inst_act_map_t * inst_act_map)
 214 {
 215         if (pred == NULL)
 216                 return false;
 217
 218         PredExprSet * pred_expressions = pred->get_pred_expressions();
 219         if (pred_expressions->getSize() == 0)   // unset predicates
 220                 return false;
 221
 222         int thread_id = id_to_int(tid);
 223         uint old_size = thrd_pruned_writes.size();
 224         if (thrd_pruned_writes.size() <= (uint) thread_id) {
 225                 uint new_size = thread_id + 1;
 226                 thrd_pruned_writes.resize(new_size);
 227                 for (uint i = old_size; i < new_size; i++)
 228                         thrd_pruned_writes[i] = new SnapVector<ModelAction *>();
 229         }
 230         SnapVector<ModelAction *> * pruned_writes = thrd_pruned_writes[thread_id];
 231         pruned_writes->clear(); // clear the old pruned_writes set
 232
 233         bool pruned = false;
 234         uint index = 0;
 235
 236         while ( index < rf_set->size() ) {
 237                 ModelAction * write_act = (*rf_set)[index];
 238                 uint64_t write_val = write_act->get_write_value();
 239                 bool satisfy_predicate = true;
 240
 241                 PredExprSetIter * pred_expr_it = pred_expressions->iterator();
 242                 while (pred_expr_it->hasNext()) {
 243                         struct pred_expr * expression = pred_expr_it->next();
 244                         bool equality;
 245
 246                         switch (expression->token) {
 247                                 case NOPREDICATE:
 248                                         return false;
 249                                 case EQUALITY:
 250                                         FuncInst * to_be_compared;
 251                                         ModelAction * last_act;
 252                                         uint64_t last_read;
 253
 254                                         to_be_compared = expression->func_inst;
 255                                         last_act = inst_act_map->get(to_be_compared);
 256                                         last_read = last_act->get_reads_from_value();
 257
 258                                         equality = (write_val == last_read);
 259                                         if (equality != expression->value)
 260                                                 satisfy_predicate = false;
 261                                         break;
 262                                 case NULLITY:
 263                                         equality = ((void*)write_val == NULL);
 264                                         if (equality != expression->value)
 265                                                 satisfy_predicate = false;
 266                                         break;
 267                                 default:
 268                                         model_print("unknown predicate token\n");
 269                                         break;
 270                         }
 271
 272                         if (!satisfy_predicate)
 273                                 break;
 274                 }
 275
 276                 if (!satisfy_predicate) {
 277                         ASSERT(rf_set != NULL);
 278                         (*rf_set)[index] = rf_set->back();
 279                         rf_set->pop_back();
 280                         pruned_writes->push_back(write_act);
 281                         pruned = true;
 282                 } else
 283                         index++;
 284         }
 285
 286         return pruned;
 287 }
 288
 289 /* @brief Put a thread to sleep because no writes in rf_set satisfies the selected predicate.
 290  *
 291  * @param thread A thread whose last action is a read
 292  */
 293 void NewFuzzer::conditional_sleep(Thread * thread)
 294 {
 295         int index = paused_thread_list.size();
 296
 297         model->getScheduler()->add_sleep(thread);
 298         paused_thread_list.push_back(thread);
 299         paused_thread_table.put(thread, index); // Update table
 300
 301         /* Add the waiting condition to ModelHistory */
 302         ModelAction * read = thread->get_pending();
 303         thread_id_t tid = thread->get_id();
 304         FuncNode * func_node = history->get_curr_func_node(tid);
 305         inst_act_map_t * inst_act_map = func_node->get_inst_act_map(tid);
 306
 307         Predicate * selected_branch = get_selected_child_branch(tid);
 308         ConcretePredicate * concrete = selected_branch->evaluate(inst_act_map, tid);
 309         concrete->set_location(read->get_location());
 310
 311         history->add_waiting_write(concrete);
 312         /* history->add_waiting_thread is already called in find_threads */
 313 }
 314
 315 bool NewFuzzer::has_paused_threads()
 316 {
 317         return paused_thread_list.size() != 0;
 318 }
 319
 320 Thread * NewFuzzer::selectThread(int * threadlist, int numthreads)
 321 {
 322         if (numthreads == 0 && has_paused_threads()) {
 323                 wake_up_paused_threads(threadlist, &numthreads);
 324                 //model_print("list size: %d, active t id: %d\n", numthreads, threadlist[0]);
 325         }
 326
 327         int random_index = random() % numthreads;
 328         int thread = threadlist[random_index];
 329         thread_id_t curr_tid = int_to_id(thread);
 330         return execution->get_thread(curr_tid);
 331 }
 332
 333 /* Force waking up one of threads paused by Fuzzer, because otherwise
 334  * the Fuzzer is not making progress
 335  */
 336 void NewFuzzer::wake_up_paused_threads(int * threadlist, int * numthreads)
 337 {
 338         int random_index = random() % paused_thread_list.size();
 339         Thread * thread = paused_thread_list[random_index];
 340         model->getScheduler()->remove_sleep(thread);
 341
 342         Thread * last_thread = paused_thread_list.back();
 343         paused_thread_list[random_index] = last_thread;
 344         paused_thread_list.pop_back();
 345         paused_thread_table.put(last_thread, random_index);     // Update table
 346         paused_thread_table.remove(thread);
 347
 348         thread_id_t tid = thread->get_id();
 349         history->remove_waiting_write(tid);
 350         history->remove_waiting_thread(tid);
 351
 352         //model_print("thread %d is woken up\n", tid);
 353         threadlist[*numthreads] = tid;
 354         (*numthreads)++;
 355 }
 356
 357 /* Wake up conditional sleeping threads if the desired write is available */
 358 void NewFuzzer::notify_paused_thread(Thread * thread)
 359 {
 360         ASSERT(paused_thread_table.contains(thread));
 361
 362         int index = paused_thread_table.get(thread);
 363         model->getScheduler()->remove_sleep(thread);
 364
 365         Thread * last_thread = paused_thread_list.back();
 366         paused_thread_list[index] = last_thread;
 367         paused_thread_list.pop_back();
 368         paused_thread_table.put(last_thread, index);    // Update table
 369         paused_thread_table.remove(thread);
 370
 371         thread_id_t tid = thread->get_id();
 372         history->remove_waiting_write(tid);
 373         history->remove_waiting_thread(tid);
 374 }
 375
 376 /* Find threads that may write values that the pending read action is waiting for
 377  * @return True if any thread is found
 378  */
 379 bool NewFuzzer::find_threads(ModelAction * pending_read)
 380 {
 381         ASSERT(pending_read->is_read());
 382
 383         void * location = pending_read->get_location();
 384         thread_id_t self_id = pending_read->get_tid();
 385         bool finds_waiting_for = false;
 386
 387         SnapVector<FuncNode *> * func_node_list = history->getWrFuncNodes(location);
 388         for (uint i = 0; i < func_node_list->size(); i++) {
 389                 FuncNode * target_node = (*func_node_list)[i];
 390                 for (uint i = 1; i < execution->get_num_threads(); i++) {
 391                         thread_id_t tid = int_to_id(i);
 392                         if (tid == self_id)
 393                                 continue;
 394
 395                         FuncNode * node = history->get_curr_func_node(tid);
 396                         /* It is possible that thread tid is not in any FuncNode */
 397                         if (node == NULL)
 398                                 continue;
 399
 400                         int distance = node->compute_distance(target_node);
 401                         if (distance != -1) {
 402                                 history->add_waiting_thread(self_id, tid, target_node, distance);
 403                                 finds_waiting_for = true;
 404                                 //model_print("thread: %d; distance from node %d to node %d: %d\n", tid, node->get_func_id(), target_node->get_func_id(), distance);
 405                         }
 406                 }
 407         }
 408
 409         return finds_waiting_for;
 410 }
 411
 412 bool NewFuzzer::shouldWait(const ModelAction * act)
 413 {
 414         return random() & 1;
 415 }