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                         selected_branch->incr_fail_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_expl_count() + 1 > numerator)
 132                                 numerator = child->get_expl_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         // Update predicate tree position
 151         FuncNode * func_node = history->get_curr_func_node(tid);
 152         func_node->set_predicate_tree_position(tid, random_branch);
 153
 154         return random_branch;
 155 }
 156
 157 /**
 158  * @brief Select a branch from the given predicate branches based
 159  * on their exploration counts.
 160  *
 161  * Let b_1, ..., b_n be branches with exploration counts c_1, ..., c_n
 162  * M := max(c_1, ..., c_n) + 1
 163  * Factor f_i := M / (c_i + 1)
 164  * The probability p_i that branch b_i is selected:
 165  *      p_i := f_i / (f_1 + ... + f_n)
 166  *           = \fraction{ 1/(c_i + 1) }{ 1/(c_1 + 1) + ... + 1/(c_n + 1) }
 167  *
 168  * Note: (1) c_i + 1 is used because counts may be 0.
 169  *       (2) The numerator of f_i is chosen to reduce the effect of underflow
 170  *
 171  * @param numerator is M defined above
 172  */
 173 int NewFuzzer::choose_index(SnapVector<Predicate *> * branches, uint32_t numerator)
 174 {
 175         if (branches->size() == 1)
 176                 return 0;
 177
 178         double total_factor = 0;
 179         SnapVector<double> factors = SnapVector<double>( branches->size() + 1 );
 180         for (uint i = 0; i < branches->size(); i++) {
 181                 Predicate * branch = (*branches)[i];
 182                 double factor = (double) numerator / (branch->get_expl_count() + 5 * branch->get_fail_count() + 1);
 183                 total_factor += factor;
 184                 factors.push_back(factor);
 185         }
 186
 187         double prob = (double) random() / RAND_MAX;
 188         double prob_sum = 0;
 189         int index = 0;
 190
 191         for (uint i = 0; i < factors.size(); i++) {
 192                 index = i;
 193                 prob_sum += (double) (factors[i] / total_factor);
 194                 if (prob_sum > prob) {
 195                         break;
 196                 }
 197         }
 198
 199         return index;
 200 }
 201
 202 Predicate * NewFuzzer::get_selected_child_branch(thread_id_t tid)
 203 {
 204         int thread_id = id_to_int(tid);
 205         if (thrd_selected_child_branch.size() <= (uint) thread_id)
 206                 return NULL;
 207
 208         return thrd_selected_child_branch[thread_id];
 209 }
 210
 211 /* Remove writes from the rf_set that do not satisfie the selected predicate,
 212  * and store them in thrd_pruned_writes
 213  *
 214  * @return true if rf_set is pruned
 215  */
 216 bool NewFuzzer::prune_writes(thread_id_t tid, Predicate * pred,
 217         SnapVector<ModelAction *> * rf_set, inst_act_map_t * inst_act_map)
 218 {
 219         if (pred == NULL)
 220                 return false;
 221
 222         PredExprSet * pred_expressions = pred->get_pred_expressions();
 223         if (pred_expressions->getSize() == 0)   // unset predicates
 224                 return false;
 225
 226         int thread_id = id_to_int(tid);
 227         uint old_size = thrd_pruned_writes.size();
 228         if (thrd_pruned_writes.size() <= (uint) thread_id) {
 229                 uint new_size = thread_id + 1;
 230                 thrd_pruned_writes.resize(new_size);
 231                 for (uint i = old_size; i < new_size; i++)
 232                         thrd_pruned_writes[i] = new SnapVector<ModelAction *>();
 233         }
 234         SnapVector<ModelAction *> * pruned_writes = thrd_pruned_writes[thread_id];
 235         pruned_writes->clear(); // clear the old pruned_writes set
 236
 237         bool pruned = false;
 238         uint index = 0;
 239
 240         while ( index < rf_set->size() ) {
 241                 ModelAction * write_act = (*rf_set)[index];
 242                 uint64_t write_val = write_act->get_write_value();
 243                 bool satisfy_predicate = true;
 244
 245                 PredExprSetIter * pred_expr_it = pred_expressions->iterator();
 246                 while (pred_expr_it->hasNext()) {
 247                         struct pred_expr * expression = pred_expr_it->next();
 248                         bool equality;
 249
 250                         switch (expression->token) {
 251                                 case NOPREDICATE:
 252                                         return false;
 253                                 case EQUALITY:
 254                                         FuncInst * to_be_compared;
 255                                         ModelAction * last_act;
 256                                         uint64_t last_read;
 257
 258                                         to_be_compared = expression->func_inst;
 259                                         last_act = inst_act_map->get(to_be_compared);
 260                                         last_read = last_act->get_reads_from_value();
 261
 262                                         equality = (write_val == last_read);
 263                                         if (equality != expression->value)
 264                                                 satisfy_predicate = false;
 265                                         break;
 266                                 case NULLITY:
 267                                         equality = ((void*)write_val == NULL);
 268                                         if (equality != expression->value)
 269                                                 satisfy_predicate = false;
 270                                         break;
 271                                 default:
 272                                         model_print("unknown predicate token\n");
 273                                         break;
 274                         }
 275
 276                         if (!satisfy_predicate)
 277                                 break;
 278                 }
 279
 280                 if (!satisfy_predicate) {
 281                         ASSERT(rf_set != NULL);
 282                         (*rf_set)[index] = rf_set->back();
 283                         rf_set->pop_back();
 284                         pruned_writes->push_back(write_act);
 285                         pruned = true;
 286                 } else
 287                         index++;
 288         }
 289
 290         return pruned;
 291 }
 292
 293 /* @brief Put a thread to sleep because no writes in rf_set satisfies the selected predicate.
 294  *
 295  * @param thread A thread whose last action is a read
 296  */
 297 void NewFuzzer::conditional_sleep(Thread * thread)
 298 {
 299         int index = paused_thread_list.size();
 300
 301         model->getScheduler()->add_sleep(thread);
 302         paused_thread_list.push_back(thread);
 303         paused_thread_table.put(thread, index); // Update table
 304
 305         /* Add the waiting condition to ModelHistory */
 306         ModelAction * read = thread->get_pending();
 307         thread_id_t tid = thread->get_id();
 308         FuncNode * func_node = history->get_curr_func_node(tid);
 309         inst_act_map_t * inst_act_map = func_node->get_inst_act_map(tid);
 310
 311         Predicate * selected_branch = get_selected_child_branch(tid);
 312         ConcretePredicate * concrete = selected_branch->evaluate(inst_act_map, tid);
 313         concrete->set_location(read->get_location());
 314
 315         history->add_waiting_write(concrete);
 316         /* history->add_waiting_thread is already called in find_threads */
 317 }
 318
 319 bool NewFuzzer::has_paused_threads()
 320 {
 321         return paused_thread_list.size() != 0;
 322 }
 323
 324 Thread * NewFuzzer::selectThread(int * threadlist, int numthreads)
 325 {
 326         if (numthreads == 0 && has_paused_threads()) {
 327                 wake_up_paused_threads(threadlist, &numthreads);
 328                 //model_print("list size: %d, active t id: %d\n", numthreads, threadlist[0]);
 329         }
 330
 331         int random_index = random() % numthreads;
 332         int thread = threadlist[random_index];
 333         thread_id_t curr_tid = int_to_id(thread);
 334         return execution->get_thread(curr_tid);
 335 }
 336
 337 /* Force waking up one of threads paused by Fuzzer, because otherwise
 338  * the Fuzzer is not making progress
 339  */
 340 void NewFuzzer::wake_up_paused_threads(int * threadlist, int * numthreads)
 341 {
 342         int random_index = random() % paused_thread_list.size();
 343         Thread * thread = paused_thread_list[random_index];
 344         model->getScheduler()->remove_sleep(thread);
 345
 346         Thread * last_thread = paused_thread_list.back();
 347         paused_thread_list[random_index] = last_thread;
 348         paused_thread_list.pop_back();
 349         paused_thread_table.put(last_thread, random_index);     // Update table
 350         paused_thread_table.remove(thread);
 351
 352         thread_id_t tid = thread->get_id();
 353         history->remove_waiting_write(tid);
 354         history->remove_waiting_thread(tid);
 355
 356         threadlist[*numthreads] = tid;
 357         (*numthreads)++;
 358
 359         Predicate * selected_branch = get_selected_child_branch(tid);
 360         selected_branch->incr_fail_count();
 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         model_print("** thread %d is woken up\n", tid);
 383 }
 384
 385 /* Find threads that may write values that the pending read action is waiting for
 386  * @return True if any thread is found
 387  */
 388 bool NewFuzzer::find_threads(ModelAction * pending_read)
 389 {
 390         ASSERT(pending_read->is_read());
 391
 392         void * location = pending_read->get_location();
 393         thread_id_t self_id = pending_read->get_tid();
 394         bool finds_waiting_for = false;
 395
 396         SnapVector<FuncNode *> * func_node_list = history->getWrFuncNodes(location);
 397         for (uint i = 0; i < func_node_list->size(); i++) {
 398                 FuncNode * target_node = (*func_node_list)[i];
 399                 for (uint i = 1; i < execution->get_num_threads(); i++) {
 400                         thread_id_t tid = int_to_id(i);
 401                         if (tid == self_id)
 402                                 continue;
 403
 404                         FuncNode * node = history->get_curr_func_node(tid);
 405                         /* It is possible that thread tid is not in any FuncNode */
 406                         if (node == NULL)
 407                                 continue;
 408
 409                         int distance = node->compute_distance(target_node);
 410                         if (distance != -1) {
 411                                 history->add_waiting_thread(self_id, tid, target_node, distance);
 412                                 finds_waiting_for = true;
 413                                 //model_print("thread: %d; distance from node %d to node %d: %d\n", tid, node->get_func_id(), target_node->get_func_id(), distance);
 414                         }
 415                 }
 416         }
 417
 418         return finds_waiting_for;
 419 }
 420
 421 bool NewFuzzer::shouldWait(const ModelAction * act)
 422 {
 423         return random() & 1;
 424 }