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
  22 ModelChecker *model = NULL;
  23
  24 /** Wrapper to run the user's main function, with appropriate arguments */
  25 void user_main_wrapper(void *)
  26 {
  27         user_main(model->params.argc, model->params.argv);
  28 }
  29
  30 /** @brief Constructor */
  31 ModelChecker::ModelChecker() :
  32         /* Initialize default scheduler */
  33         params(),
  34         restart_flag(false),
  35         scheduler(new Scheduler()),
  36         history(new ModelHistory()),
  37         execution(new ModelExecution(this, scheduler)),
  38         execution_number(1),
  39         trace_analyses(),
  40         inspect_plugin(NULL)
  41 {
  42         memset(&stats,0,sizeof(struct execution_stats));
  43         init_thread = new Thread(execution->get_next_id(), (thrd_t *) model_malloc(sizeof(thrd_t)), &user_main_wrapper, NULL, NULL);
  44 #ifdef TLS
  45         init_thread->setTLS((char *)get_tls_addr());
  46 #endif
  47         execution->add_thread(init_thread);
  48         scheduler->set_current_thread(init_thread);
  49         execution->setParams(&params);
  50         param_defaults(&params);
  51         parse_options(&params);
  52         initRaceDetector();
  53 }
  54
  55 /** @brief Destructor */
  56 ModelChecker::~ModelChecker()
  57 {
  58         delete scheduler;
  59 }
  60
  61 /** Method to set parameters */
  62 model_params * ModelChecker::getParams() {
  63         return &params;
  64 }
  65
  66 /**
  67  * Restores user program to initial state and resets all model-checker data
  68  * structures.
  69  */
  70 void ModelChecker::reset_to_initial_state()
  71 {
  72
  73         /**
  74          * FIXME: if we utilize partial rollback, we will need to free only
  75          * those pending actions which were NOT pending before the rollback
  76          * point
  77          */
  78         for (unsigned int i = 0;i < get_num_threads();i++)
  79                 delete get_thread(int_to_id(i))->get_pending();
  80
  81         snapshot_backtrack_before(0);
  82 }
  83
  84 /** @return the number of user threads created during this execution */
  85 unsigned int ModelChecker::get_num_threads() const
  86 {
  87         return execution->get_num_threads();
  88 }
  89
  90 /**
  91  * Must be called from user-thread context (e.g., through the global
  92  * thread_current() interface)
  93  *
  94  * @return The currently executing Thread.
  95  */
  96 Thread * ModelChecker::get_current_thread() const
  97 {
  98         return scheduler->get_current_thread();
  99 }
 100
 101 /**
 102  * @brief Choose the next thread to execute.
 103  *
 104  * This function chooses the next thread that should execute. It can enforce
 105  * execution replay/backtracking or, if the model-checker has no preference
 106  * regarding the next thread (i.e., when exploring a new execution ordering),
 107  * we defer to the scheduler.
 108  *
 109  * @return The next chosen thread to run, if any exist. Or else if the current
 110  * execution should terminate, return NULL.
 111  */
 112 Thread * ModelChecker::get_next_thread()
 113 {
 114
 115         /*
 116          * Have we completed exploring the preselected path? Then let the
 117          * scheduler decide
 118          */
 119         return scheduler->select_next_thread();
 120 }
 121
 122 /**
 123  * @brief Assert a bug in the executing program.
 124  *
 125  * Use this function to assert any sort of bug in the user program. If the
 126  * current trace is feasible (actually, a prefix of some feasible execution),
 127  * then this execution will be aborted, printing the appropriate message. If
 128  * the current trace is not yet feasible, the error message will be stashed and
 129  * printed if the execution ever becomes feasible.
 130  *
 131  * @param msg Descriptive message for the bug (do not include newline char)
 132  * @return True if bug is immediately-feasible
 133  */
 134 void ModelChecker::assert_bug(const char *msg, ...)
 135 {
 136         char str[800];
 137
 138         va_list ap;
 139         va_start(ap, msg);
 140         vsnprintf(str, sizeof(str), msg, ap);
 141         va_end(ap);
 142
 143         execution->assert_bug(str);
 144 }
 145
 146 /**
 147  * @brief Assert a bug in the executing program, asserted by a user thread
 148  * @see ModelChecker::assert_bug
 149  * @param msg Descriptive message for the bug (do not include newline char)
 150  */
 151 void ModelChecker::assert_user_bug(const char *msg)
 152 {
 153         /* If feasible bug, bail out now */
 154         assert_bug(msg);
 155         switch_to_master(NULL);
 156 }
 157
 158 /** @brief Print bug report listing for this execution (if any bugs exist) */
 159 void ModelChecker::print_bugs() const
 160 {
 161         SnapVector<bug_message *> *bugs = execution->get_bugs();
 162
 163         model_print("Bug report: %zu bug%s detected\n",
 164                                                         bugs->size(),
 165                                                         bugs->size() > 1 ? "s" : "");
 166         for (unsigned int i = 0;i < bugs->size();i++)
 167                 (*bugs)[i] -> print();
 168 }
 169
 170 /**
 171  * @brief Record end-of-execution stats
 172  *
 173  * Must be run when exiting an execution. Records various stats.
 174  * @see struct execution_stats
 175  */
 176 void ModelChecker::record_stats()
 177 {
 178         stats.num_total ++;
 179         if (execution->have_bug_reports())
 180                 stats.num_buggy_executions ++;
 181         else if (execution->is_complete_execution())
 182                 stats.num_complete ++;
 183         else {
 184                 //All threads are sleeping
 185                 /**
 186                  * @todo We can violate this ASSERT() when fairness/sleep sets
 187                  * conflict to cause an execution to terminate, e.g. with:
 188                  * Scheduler: [0: disabled][1: disabled][2: sleep][3: current, enabled]
 189                  */
 190                 //ASSERT(scheduler->all_threads_sleeping());
 191         }
 192 }
 193
 194 /** @brief Print execution stats */
 195 void ModelChecker::print_stats() const
 196 {
 197         model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
 198         model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
 199         model_print("Total executions: %d\n", stats.num_total);
 200 }
 201
 202 /**
 203  * @brief End-of-exeuction print
 204  * @param printbugs Should any existing bugs be printed?
 205  */
 206 void ModelChecker::print_execution(bool printbugs) const
 207 {
 208         model_print("Program output from execution %d:\n",
 209                                                         get_execution_number());
 210         print_program_output();
 211
 212         if (params.verbose >= 3) {
 213                 print_stats();
 214         }
 215
 216         /* Don't print invalid bugs */
 217         if (printbugs && execution->have_bug_reports()) {
 218                 model_print("\n");
 219                 print_bugs();
 220         }
 221
 222         model_print("\n");
 223         execution->print_summary();
 224 }
 225
 226 /**
 227  * Queries the model-checker for more executions to explore and, if one
 228  * exists, resets the model-checker state to execute a new execution.
 229  *
 230  * @return If there are more executions to explore, return true. Otherwise,
 231  * return false.
 232  */
 233 bool ModelChecker::next_execution()
 234 {
 235         DBG();
 236         /* Is this execution a feasible execution that's worth bug-checking? */
 237         bool complete = (execution->is_complete_execution() ||
 238                                                                          execution->have_bug_reports());
 239
 240         /* End-of-execution bug checks */
 241         if (complete) {
 242                 if (execution->is_deadlocked())
 243                         assert_bug("Deadlock detected");
 244
 245                 run_trace_analyses();
 246         }
 247
 248         record_stats();
 249         /* Output */
 250         if ( (complete && params.verbose) || params.verbose>1 || (complete && execution->have_bug_reports()))
 251                 print_execution(complete);
 252         else
 253                 clear_program_output();
 254
 255         if (restart_flag) {
 256                 do_restart();
 257                 return true;
 258         }
 259 // test code
 260         execution_number ++;
 261         reset_to_initial_state();
 262         history->set_new_exec_flag();
 263         return false;
 264 }
 265
 266 /** @brief Run trace analyses on complete trace */
 267 void ModelChecker::run_trace_analyses() {
 268         for (unsigned int i = 0;i < trace_analyses.size();i ++)
 269                 trace_analyses[i] -> analyze(execution->get_action_trace());
 270 }
 271
 272 /**
 273  * @brief Get a Thread reference by its ID
 274  * @param tid The Thread's ID
 275  * @return A Thread reference
 276  */
 277 Thread * ModelChecker::get_thread(thread_id_t tid) const
 278 {
 279         return execution->get_thread(tid);
 280 }
 281
 282 /**
 283  * @brief Get a reference to the Thread in which a ModelAction was executed
 284  * @param act The ModelAction
 285  * @return A Thread reference
 286  */
 287 Thread * ModelChecker::get_thread(const ModelAction *act) const
 288 {
 289         return execution->get_thread(act);
 290 }
 291
 292 /**
 293  * Switch from a model-checker context to a user-thread context. This is the
 294  * complement of ModelChecker::switch_to_master and must be called from the
 295  * model-checker context
 296  *
 297  * @param thread The user-thread to switch to
 298  */
 299 void ModelChecker::switch_from_master(Thread *thread)
 300 {
 301         scheduler->set_current_thread(thread);
 302         Thread::swap(&system_context, thread);
 303 }
 304
 305 /**
 306  * Switch from a user-context to the "master thread" context (a.k.a. system
 307  * context). This switch is made with the intention of exploring a particular
 308  * model-checking action (described by a ModelAction object). Must be called
 309  * from a user-thread context.
 310  *
 311  * @param act The current action that will be explored. May be NULL only if
 312  * trace is exiting via an assertion (see ModelExecution::set_assert and
 313  * ModelExecution::has_asserted).
 314  * @return Return the value returned by the current action
 315  */
 316 uint64_t ModelChecker::switch_to_master(ModelAction *act)
 317 {
 318         if (modellock) {
 319                 static bool fork_message_printed = false;
 320
 321                 if (!fork_message_printed) {
 322                         model_print("Fork handler or dead thread trying to call into model checker...\n");
 323                         fork_message_printed = true;
 324                 }
 325                 delete act;
 326                 return 0;
 327         }
 328         DBG();
 329         Thread *old = thread_current();
 330         scheduler->set_current_thread(NULL);
 331         ASSERT(!old->get_pending());
 332
 333         if (inspect_plugin != NULL) {
 334                 inspect_plugin->inspectModelAction(act);
 335         }
 336
 337         old->set_pending(act);
 338         if (Thread::swap(old, &system_context) < 0) {
 339                 perror("swap threads");
 340                 exit(EXIT_FAILURE);
 341         }
 342         return old->get_return_value();
 343 }
 344
 345 static void runChecker() {
 346         model->run();
 347         delete model;
 348 }
 349
 350 void ModelChecker::startChecker() {
 351         startExecution(get_system_context(), runChecker);
 352         snapshot_stack_init();
 353         snapshot_record(0);
 354 }
 355
 356 bool ModelChecker::should_terminate_execution()
 357 {
 358         if (execution->have_bug_reports()) {
 359                 execution->set_assert();
 360                 return true;
 361         } else if (execution->isFinished()) {
 362                 return true;
 363         }
 364         return false;
 365 }
 366
 367 /** @brief Restart ModelChecker upon returning to the run loop of the
 368  *      model checker. */
 369 void ModelChecker::restart()
 370 {
 371         restart_flag = true;
 372 }
 373
 374 void ModelChecker::do_restart()
 375 {
 376         restart_flag = false;
 377         reset_to_initial_state();
 378         memset(&stats,0,sizeof(struct execution_stats));
 379         execution_number = 1;
 380 }
 381
 382 void ModelChecker::startMainThread() {
 383         init_thread->set_state(THREAD_RUNNING);
 384         scheduler->set_current_thread(init_thread);
 385         main_thread_startup();
 386 }
 387
 388 /** @brief Run ModelChecker for the user program */
 389 void ModelChecker::run()
 390 {
 391         //Need to initial random number generator state to avoid resets on rollback
 392         char random_state[256];
 393         initstate(423121, random_state, sizeof(random_state));
 394
 395         for(int exec = 0;exec < params.maxexecutions;exec++) {
 396                 Thread * t = init_thread;
 397
 398                 do {
 399                         /*
 400                          * Stash next pending action(s) for thread(s). There
 401                          * should only need to stash one thread's action--the
 402                          * thread which just took a step--plus the first step
 403                          * for any newly-created thread
 404                          */
 405                         for (unsigned int i = 0;i < get_num_threads();i++) {
 406                                 thread_id_t tid = int_to_id(i);
 407                                 Thread *thr = get_thread(tid);
 408                                 if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
 409                                         switch_from_master(thr);
 410                                         if (thr->is_waiting_on(thr))
 411                                                 assert_bug("Deadlock detected (thread %u)", i);
 412                                 }
 413                         }
 414
 415                         /* Don't schedule threads which should be disabled */
 416                         for (unsigned int i = 0;i < get_num_threads();i++) {
 417                                 Thread *th = get_thread(int_to_id(i));
 418                                 ModelAction *act = th->get_pending();
 419                                 if (act && execution->is_enabled(th) && !execution->check_action_enabled(act)) {
 420                                         scheduler->sleep(th);
 421                                 }
 422                         }
 423
 424                         for (unsigned int i = 1;i < get_num_threads();i++) {
 425                                 Thread *th = get_thread(int_to_id(i));
 426                                 ModelAction *act = th->get_pending();
 427                                 if (act && execution->is_enabled(th) && (th->get_state() != THREAD_BLOCKED) ) {
 428                                         if (act->is_write()) {
 429                                                 std::memory_order order = act->get_mo();
 430                                                 if (order == std::memory_order_relaxed || \
 431                                                                 order == std::memory_order_release) {
 432                                                         t = th;
 433                                                         break;
 434                                                 }
 435                                         } else if (act->get_type() == THREAD_CREATE || \
 436                                                                                  act->get_type() == PTHREAD_CREATE || \
 437                                                                                  act->get_type() == THREAD_START || \
 438                                                                                  act->get_type() == THREAD_FINISH) {
 439                                                 t = th;
 440                                                 break;
 441                                         }
 442                                 }
 443                         }
 444
 445                         /* Catch assertions from prior take_step or from
 446                         * between-ModelAction bugs (e.g., data races) */
 447
 448                         if (execution->has_asserted())
 449                                 break;
 450                         if (!t)
 451                                 t = get_next_thread();
 452                         if (!t || t->is_model_thread())
 453                                 break;
 454                         if (t->just_woken_up()) {
 455                                 t->set_wakeup_state(false);
 456                                 t->set_pending(NULL);
 457                                 t = NULL;
 458                                 continue;       // Allow this thread to stash the next pending action
 459                         }
 460
 461                         /* Consume the next action for a Thread */
 462                         ModelAction *curr = t->get_pending();
 463                         t->set_pending(NULL);
 464                         t = execution->take_step(curr);
 465                 } while (!should_terminate_execution());
 466                 next_execution();
 467                 //restore random number generator state after rollback
 468                 setstate(random_state);
 469         }
 470
 471         model_print("******* Model-checking complete: *******\n");
 472         print_stats();
 473
 474         /* Have the trace analyses dump their output. */
 475         for (unsigned int i = 0;i < trace_analyses.size();i++)
 476                 trace_analyses[i]->finish();
 477
 478         /* unlink tmp file created by last child process */
 479         char filename[256];
 480         snprintf_(filename, sizeof(filename), "C11FuzzerTmp%d", getpid());
 481         unlink(filename);
 482 }