model.cc

   1 #include <stdio.h>
   2 #include <algorithm>
   3 #include <new>
   4 #include <stdarg.h>
   5 #include <string.h>
   6 #include <cstdlib>
   7
   8 #include "model.h"
   9 #include "action.h"
  10 #include "schedule.h"
  11 #include "snapshot-interface.h"
  12 #include "common.h"
  13 #include "datarace.h"
  14 #include "threads-model.h"
  15 #include "output.h"
  16 #include "traceanalysis.h"
  17 #include "execution.h"
  18 #include "history.h"
  19 #include "bugmessage.h"
  20 #include "params.h"
  21 #include "plugins.h"
  22
  23 ModelChecker *model = NULL;
  24
  25 void placeholder(void *) {
  26         ASSERT(0);
  27 }
  28
  29 /** @brief Constructor */
  30 ModelChecker::ModelChecker() :
  31         /* Initialize default scheduler */
  32         params(),
  33         scheduler(new Scheduler()),
  34         history(new ModelHistory()),
  35         execution(new ModelExecution(this, scheduler)),
  36         execution_number(1),
  37         trace_analyses(),
  38         inspect_plugin(NULL)
  39 {
  40         model_print("C11Tester\n"
  41                                                         "Copyright (c) 2013 and 2019 Regents of the University of California. All rights reserved.\n"
  42                                                         "Distributed under the GPLv2\n"
  43                                                         "Written by Weiyu Luo, Brian Norris, and Brian Demsky\n\n");
  44         memset(&stats,0,sizeof(struct execution_stats));
  45         init_thread = new Thread(execution->get_next_id(), (thrd_t *) model_malloc(sizeof(thrd_t)), &placeholder, NULL, NULL);
  46 #ifdef TLS
  47         init_thread->setTLS((char *)get_tls_addr());
  48 #endif
  49         execution->add_thread(init_thread);
  50         scheduler->set_current_thread(init_thread);
  51         register_plugins();
  52         execution->setParams(&params);
  53         param_defaults(&params);
  54         parse_options(&params);
  55         initRaceDetector();
  56         /* Configure output redirection for the model-checker */
  57         redirect_output();
  58         install_trace_analyses(get_execution());
  59 }
  60
  61 /** @brief Destructor */
  62 ModelChecker::~ModelChecker()
  63 {
  64         delete scheduler;
  65 }
  66
  67 /** Method to set parameters */
  68 model_params * ModelChecker::getParams() {
  69         return &params;
  70 }
  71
  72 /**
  73  * Restores user program to initial state and resets all model-checker data
  74  * structures.
  75  */
  76 void ModelChecker::reset_to_initial_state()
  77 {
  78
  79         /**
  80          * FIXME: if we utilize partial rollback, we will need to free only
  81          * those pending actions which were NOT pending before the rollback
  82          * point
  83          */
  84         for (unsigned int i = 0;i < get_num_threads();i++)
  85                 delete get_thread(int_to_id(i))->get_pending();
  86
  87         snapshot_roll_back(snapshot);
  88 }
  89
  90 /** @return the number of user threads created during this execution */
  91 unsigned int ModelChecker::get_num_threads() const
  92 {
  93         return execution->get_num_threads();
  94 }
  95
  96 /**
  97  * Must be called from user-thread context (e.g., through the global
  98  * thread_current() interface)
  99  *
 100  * @return The currently executing Thread.
 101  */
 102 Thread * ModelChecker::get_current_thread() const
 103 {
 104         return scheduler->get_current_thread();
 105 }
 106
 107 /**
 108  * @brief Choose the next thread to execute.
 109  *
 110  * This function chooses the next thread that should execute. It can enforce
 111  * execution replay/backtracking or, if the model-checker has no preference
 112  * regarding the next thread (i.e., when exploring a new execution ordering),
 113  * we defer to the scheduler.
 114  *
 115  * @return The next chosen thread to run, if any exist. Or else if the current
 116  * execution should terminate, return NULL.
 117  */
 118 Thread * ModelChecker::get_next_thread()
 119 {
 120
 121         /*
 122          * Have we completed exploring the preselected path? Then let the
 123          * scheduler decide
 124          */
 125         return scheduler->select_next_thread();
 126 }
 127
 128 /**
 129  * @brief Assert a bug in the executing program.
 130  *
 131  * Use this function to assert any sort of bug in the user program. If the
 132  * current trace is feasible (actually, a prefix of some feasible execution),
 133  * then this execution will be aborted, printing the appropriate message. If
 134  * the current trace is not yet feasible, the error message will be stashed and
 135  * printed if the execution ever becomes feasible.
 136  *
 137  * @param msg Descriptive message for the bug (do not include newline char)
 138  * @return True if bug is immediately-feasible
 139  */
 140 void ModelChecker::assert_bug(const char *msg, ...)
 141 {
 142         char str[800];
 143
 144         va_list ap;
 145         va_start(ap, msg);
 146         vsnprintf(str, sizeof(str), msg, ap);
 147         va_end(ap);
 148
 149         execution->assert_bug(str);
 150 }
 151
 152 /**
 153  * @brief Assert a bug in the executing program, asserted by a user thread
 154  * @see ModelChecker::assert_bug
 155  * @param msg Descriptive message for the bug (do not include newline char)
 156  */
 157 void ModelChecker::assert_user_bug(const char *msg)
 158 {
 159         /* If feasible bug, bail out now */
 160         assert_bug(msg);
 161         switch_to_master(NULL);
 162 }
 163
 164 /** @brief Print bug report listing for this execution (if any bugs exist) */
 165 void ModelChecker::print_bugs() const
 166 {
 167         SnapVector<bug_message *> *bugs = execution->get_bugs();
 168
 169         model_print("Bug report: %zu bug%s detected\n",
 170                                                         bugs->size(),
 171                                                         bugs->size() > 1 ? "s" : "");
 172         for (unsigned int i = 0;i < bugs->size();i++)
 173                 (*bugs)[i] -> print();
 174 }
 175
 176 /**
 177  * @brief Record end-of-execution stats
 178  *
 179  * Must be run when exiting an execution. Records various stats.
 180  * @see struct execution_stats
 181  */
 182 void ModelChecker::record_stats()
 183 {
 184         stats.num_total ++;
 185         if (execution->have_bug_reports())
 186                 stats.num_buggy_executions ++;
 187         else if (execution->is_complete_execution())
 188                 stats.num_complete ++;
 189         else {
 190                 //All threads are sleeping
 191                 /**
 192                  * @todo We can violate this ASSERT() when fairness/sleep sets
 193                  * conflict to cause an execution to terminate, e.g. with:
 194                  * Scheduler: [0: disabled][1: disabled][2: sleep][3: current, enabled]
 195                  */
 196                 //ASSERT(scheduler->all_threads_sleeping());
 197         }
 198 }
 199
 200 /** @brief Print execution stats */
 201 void ModelChecker::print_stats() const
 202 {
 203         model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
 204         model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
 205         model_print("Total executions: %d\n", stats.num_total);
 206 }
 207
 208 /**
 209  * @brief End-of-exeuction print
 210  * @param printbugs Should any existing bugs be printed?
 211  */
 212 void ModelChecker::print_execution(bool printbugs) const
 213 {
 214         model_print("Program output from execution %d:\n",
 215                                                         get_execution_number());
 216         print_program_output();
 217
 218         if (params.verbose >= 3) {
 219                 print_stats();
 220         }
 221
 222         /* Don't print invalid bugs */
 223         if (printbugs && execution->have_bug_reports()) {
 224                 model_print("\n");
 225                 print_bugs();
 226         }
 227
 228         model_print("\n");
 229         execution->print_summary();
 230 }
 231
 232 /**
 233  * Queries the model-checker for more executions to explore and, if one
 234  * exists, resets the model-checker state to execute a new execution.
 235  *
 236  * @return If there are more executions to explore, return true. Otherwise,
 237  * return false.
 238  */
 239 void ModelChecker::finish_execution(bool more_executions)
 240 {
 241         DBG();
 242         /* Is this execution a feasible execution that's worth bug-checking? */
 243         bool complete = (execution->is_complete_execution() ||
 244                                                                          execution->have_bug_reports());
 245
 246         /* End-of-execution bug checks */
 247         if (complete) {
 248                 if (execution->is_deadlocked())
 249                         assert_bug("Deadlock detected");
 250
 251                 run_trace_analyses();
 252         }
 253
 254         record_stats();
 255         /* Output */
 256         if ( (complete && params.verbose) || params.verbose>1 || (complete && execution->have_bug_reports()))
 257                 print_execution(complete);
 258         else
 259                 clear_program_output();
 260
 261 // test code
 262         execution_number ++;
 263         if (more_executions)
 264                 reset_to_initial_state();
 265         history->set_new_exec_flag();
 266 }
 267
 268 /** @brief Run trace analyses on complete trace */
 269 void ModelChecker::run_trace_analyses() {
 270         for (unsigned int i = 0;i < trace_analyses.size();i ++)
 271                 trace_analyses[i] -> analyze(execution->get_action_trace());
 272 }
 273
 274 /**
 275  * @brief Get a Thread reference by its ID
 276  * @param tid The Thread's ID
 277  * @return A Thread reference
 278  */
 279 Thread * ModelChecker::get_thread(thread_id_t tid) const
 280 {
 281         return execution->get_thread(tid);
 282 }
 283
 284 /**
 285  * @brief Get a reference to the Thread in which a ModelAction was executed
 286  * @param act The ModelAction
 287  * @return A Thread reference
 288  */
 289 Thread * ModelChecker::get_thread(const ModelAction *act) const
 290 {
 291         return execution->get_thread(act);
 292 }
 293
 294 /**
 295  * Switch from a model-checker context to a user-thread context. This is the
 296  * complement of ModelChecker::switch_to_master and must be called from the
 297  * model-checker context
 298  *
 299  * @param thread The user-thread to switch to
 300  */
 301 void ModelChecker::switch_from_master(Thread *thread)
 302 {
 303         scheduler->set_current_thread(thread);
 304         Thread::swap(&system_context, thread);
 305 }
 306
 307 /**
 308  * Switch from a user-context to the "master thread" context (a.k.a. system
 309  * context). This switch is made with the intention of exploring a particular
 310  * model-checking action (described by a ModelAction object). Must be called
 311  * from a user-thread context.
 312  *
 313  * @param act The current action that will be explored. May be NULL only if
 314  * trace is exiting via an assertion (see ModelExecution::set_assert and
 315  * ModelExecution::has_asserted).
 316  * @return Return the value returned by the current action
 317  */
 318 uint64_t ModelChecker::switch_to_master(ModelAction *act)
 319 {
 320         if (modellock) {
 321                 static bool fork_message_printed = false;
 322
 323                 if (!fork_message_printed) {
 324                         model_print("Fork handler or dead thread trying to call into model checker...\n");
 325                         fork_message_printed = true;
 326                 }
 327                 delete act;
 328                 return 0;
 329         }
 330         DBG();
 331         Thread *old = thread_current();
 332         scheduler->set_current_thread(NULL);
 333         ASSERT(!old->get_pending());
 334
 335         if (inspect_plugin != NULL) {
 336                 inspect_plugin->inspectModelAction(act);
 337         }
 338
 339         old->set_pending(act);
 340         if (Thread::swap(old, &system_context) < 0) {
 341                 perror("swap threads");
 342                 exit(EXIT_FAILURE);
 343         }
 344         return old->get_return_value();
 345 }
 346
 347 void ModelChecker::continueRunExecution(Thread *old)
 348 {
 349
 350         if (params.traceminsize != 0 &&
 351                         execution->get_curr_seq_num() > checkfree) {
 352                 checkfree += params.checkthreshold;
 353                 execution->collectActions();
 354         }
 355
 356         thread_chosen = false;
 357         curr_thread_num = 1;
 358         Thread *thr = getNextThread();
 359         if (thr != nullptr) {
 360                 scheduler->set_current_thread(thr);
 361                 if (Thread::swap(old, thr) < 0) {
 362                         perror("swap threads");
 363                         exit(EXIT_FAILURE);
 364                 }
 365         } else
 366                 handleChosenThread(old);
 367 }
 368
 369 void ModelChecker::startRunExecution(ucontext_t *old)
 370 {
 371
 372         if (params.traceminsize != 0 &&
 373                         execution->get_curr_seq_num() > checkfree) {
 374                 checkfree += params.checkthreshold;
 375                 execution->collectActions();
 376         }
 377
 378         thread_chosen = false;
 379         curr_thread_num = 1;
 380         Thread *thr = getNextThread();
 381         if (thr != nullptr) {
 382                 scheduler->set_current_thread(thr);
 383                 if (Thread::swap(old, thr) < 0) {
 384                         perror("swap threads");
 385                         exit(EXIT_FAILURE);
 386                 }
 387         } else
 388                 handleChosenThread(old);
 389 }
 390
 391 Thread* ModelChecker::getNextThread()
 392 {
 393         Thread *nextThread = nullptr;
 394         for (unsigned int i = curr_thread_num; i < get_num_threads(); i++) {
 395                 thread_id_t tid = int_to_id(i);
 396                 Thread *thr = get_thread(tid);
 397
 398                 if (!thr->is_complete() && !thr->get_pending()) {
 399                         curr_thread_num = i;
 400                         nextThread = thr;
 401                         break;
 402                 }
 403                 ModelAction *act = thr->get_pending();
 404
 405                 if (act && execution->is_enabled(thr) && !execution->check_action_enabled(act)) {
 406                         scheduler->sleep(thr);
 407                 }
 408
 409         chooseThread(act, thr);
 410         }
 411         return nextThread;
 412 }
 413
 414 void ModelChecker::finishRunExecution(Thread *old)
 415 {
 416         scheduler->set_current_thread(NULL);
 417         if (Thread::swap(old, &system_context) < 0) {
 418                 perror("swap threads");
 419                 exit(EXIT_FAILURE);
 420         }
 421 }
 422
 423 void ModelChecker::finishRunExecution(ucontext_t *old)
 424 {
 425         scheduler->set_current_thread(NULL);
 426         break_execution = true;
 427 }
 428
 429 void ModelChecker::consumeAction()
 430 {
 431         ModelAction *curr = chosen_thread->get_pending();
 432         Thread * th = thread_current();
 433         if (curr->get_type() == THREAD_FINISH && th != NULL)  {
 434                 // Thread finish must be consumed in the master context
 435                 scheduler->set_current_thread(NULL);
 436                 if (Thread::swap(th, &system_context) < 0) {
 437                         perror("swap threads");
 438                         exit(EXIT_FAILURE);
 439                 }
 440         } else {
 441                 chosen_thread->set_pending(NULL);
 442                 chosen_thread = execution->take_step(curr);
 443         }
 444 }
 445
 446 void ModelChecker::chooseThread(ModelAction *act, Thread *thr)
 447 {
 448         if (!thread_chosen && act && execution->is_enabled(thr) && (thr->get_state() != THREAD_BLOCKED) ) {
 449                 if (act->is_write()) {
 450                         std::memory_order order = act->get_mo();
 451                         if (order == std::memory_order_relaxed || \
 452                                         order == std::memory_order_release) {
 453                                 chosen_thread = thr;
 454                                 thread_chosen = true;
 455                         }
 456                 } else if (act->get_type() == THREAD_CREATE || \
 457                                                         act->get_type() == PTHREAD_CREATE || \
 458                                                         act->get_type() == THREAD_START || \
 459                                                         act->get_type() == THREAD_FINISH) {
 460                         chosen_thread = thr;
 461                         thread_chosen = true;
 462                 }
 463         }
 464 }
 465
 466 uint64_t ModelChecker::switch_thread(ModelAction *act)
 467 {
 468         if (modellock) {
 469                 static bool fork_message_printed = false;
 470
 471                 if (!fork_message_printed) {
 472                         model_print("Fork handler or dead thread trying to call into model checker...\n");
 473                         fork_message_printed = true;
 474                 }
 475                 delete act;
 476                 return 0;
 477         }
 478         DBG();
 479         Thread *old = thread_current();
 480         ASSERT(!old->get_pending());
 481
 482         if (inspect_plugin != NULL) {
 483                 inspect_plugin->inspectModelAction(act);
 484         }
 485
 486         old->set_pending(act);
 487
 488         if (old->is_waiting_on(old))
 489                 assert_bug("Deadlock detected (thread %u)", curr_thread_num);
 490
 491         if (act && execution->is_enabled(old) && !execution->check_action_enabled(act)) {
 492                 scheduler->sleep(old);
 493         }
 494         chooseThread(act, old);
 495
 496         curr_thread_num++;
 497         Thread* next = getNextThread();
 498         if (next != nullptr)
 499                 handleNewValidThread(old, next);
 500         else {
 501                 old->set_state(THREAD_READY);   // Just to avoid the first ASSERT in ModelExecution::take_step
 502                 handleChosenThread(old);
 503         }
 504
 505         return old->get_return_value();
 506 }
 507
 508 void ModelChecker::handleNewValidThread(Thread *old, Thread *next)
 509 {
 510         scheduler->set_current_thread(next);
 511
 512         if (Thread::swap(old, next) < 0) {
 513                 perror("swap threads");
 514                 exit(EXIT_FAILURE);
 515         }
 516 }
 517
 518 void ModelChecker::handleChosenThread(Thread *old)
 519 {
 520         if (execution->has_asserted())
 521                 finishRunExecution(old);
 522         if (!chosen_thread)
 523                 chosen_thread = get_next_thread();
 524         if (!chosen_thread || chosen_thread->is_model_thread())
 525                 finishRunExecution(old);
 526         if (chosen_thread->just_woken_up()) {
 527                 chosen_thread->set_wakeup_state(false);
 528                 chosen_thread->set_pending(NULL);
 529                 chosen_thread = NULL;
 530                 // Allow this thread to stash the next pending action
 531                 if (should_terminate_execution())
 532                         finishRunExecution(old);
 533                 else
 534                         continueRunExecution(old);
 535         } else {
 536                 /* Consume the next action for a Thread */
 537                 consumeAction();
 538
 539                 if (should_terminate_execution())
 540                         finishRunExecution(old);
 541                 else
 542                         continueRunExecution(old);
 543         }
 544 }
 545
 546 void ModelChecker::handleChosenThread(ucontext_t *old)
 547 {
 548         if (execution->has_asserted()) {
 549                 finishRunExecution(old);
 550                 return;
 551         }
 552         if (!chosen_thread)
 553                 chosen_thread = get_next_thread();
 554         if (!chosen_thread || chosen_thread->is_model_thread()) {
 555                 finishRunExecution(old);
 556                 return;
 557         }
 558         if (chosen_thread->just_woken_up()) {
 559                 chosen_thread->set_wakeup_state(false);
 560                 chosen_thread->set_pending(NULL);
 561                 chosen_thread = NULL;
 562                 // Allow this thread to stash the next pending action
 563                 if (should_terminate_execution())
 564                         finishRunExecution(old);
 565                 else
 566                         startRunExecution(old);
 567         } else {
 568                 /* Consume the next action for a Thread */
 569                 consumeAction();
 570
 571                 if (should_terminate_execution())
 572                         finishRunExecution(old);
 573                 else
 574                         startRunExecution(old);
 575         }
 576 }
 577
 578
 579 static void runChecker() {
 580         model->run();
 581         delete model;
 582 }
 583
 584 void ModelChecker::startChecker() {
 585         startExecution(get_system_context(), runChecker);
 586         snapshot = take_snapshot();
 587         initMainThread();
 588 }
 589
 590 bool ModelChecker::should_terminate_execution()
 591 {
 592         if (execution->have_bug_reports()) {
 593                 execution->set_assert();
 594                 return true;
 595         } else if (execution->isFinished()) {
 596                 return true;
 597         }
 598         return false;
 599 }
 600
 601 /** @brief Run ModelChecker for the user program */
 602 void ModelChecker::run()
 603 {
 604         //Need to initial random number generator state to avoid resets on rollback
 605         char random_state[256];
 606         initstate(423121, random_state, sizeof(random_state));
 607         checkfree = params.checkthreshold;
 608         for(int exec = 0;exec < params.maxexecutions;exec++) {
 609                 chosen_thread = init_thread;
 610                 break_execution = false;
 611                 do {
 612                         if (break_execution)
 613                                 break;
 614
 615                         thread_chosen = false;
 616                         curr_thread_num = 1;
 617                         startRunExecution(&system_context);
 618                 } while (!should_terminate_execution());
 619
 620                 finish_execution((exec+1) < params.maxexecutions);
 621                 //restore random number generator state after rollback
 622                 setstate(random_state);
 623         }
 624
 625         model_print("******* Model-checking complete: *******\n");
 626         print_stats();
 627
 628         /* Have the trace analyses dump their output. */
 629         for (unsigned int i = 0;i < trace_analyses.size();i++)
 630                 trace_analyses[i]->finish();
 631
 632         /* unlink tmp file created by last child process */
 633         char filename[256];
 634         snprintf_(filename, sizeof(filename), "C11FuzzerTmp%d", getpid());
 635         unlink(filename);
 636 }