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         execution(new ModelExecution(this, scheduler)),
  37         history(new ModelHistory()),
  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);    // L: user_main_wrapper passes the user program
  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         initRaceDetector();
  52 }
  53
  54 /** @brief Destructor */
  55 ModelChecker::~ModelChecker()
  56 {
  57         delete scheduler;
  58 }
  59
  60 /** Method to set parameters */
  61 model_params * ModelChecker::getParams() {
  62         return &params;
  63 }
  64
  65 /**
  66  * Restores user program to initial state and resets all model-checker data
  67  * structures.
  68  */
  69 void ModelChecker::reset_to_initial_state()
  70 {
  71
  72         /**
  73          * FIXME: if we utilize partial rollback, we will need to free only
  74          * those pending actions which were NOT pending before the rollback
  75          * point
  76          */
  77         for (unsigned int i = 0;i < get_num_threads();i++)
  78                 delete get_thread(int_to_id(i))->get_pending();
  79
  80         snapshot_backtrack_before(0);
  81 }
  82
  83 /** @return the number of user threads created during this execution */
  84 unsigned int ModelChecker::get_num_threads() const
  85 {
  86         return execution->get_num_threads();
  87 }
  88
  89 /**
  90  * Must be called from user-thread context (e.g., through the global
  91  * thread_current() interface)
  92  *
  93  * @return The currently executing Thread.
  94  */
  95 Thread * ModelChecker::get_current_thread() const
  96 {
  97         return scheduler->get_current_thread();
  98 }
  99
 100 /**
 101  * @brief Choose the next thread to execute.
 102  *
 103  * This function chooses the next thread that should execute. It can enforce
 104  * execution replay/backtracking or, if the model-checker has no preference
 105  * regarding the next thread (i.e., when exploring a new execution ordering),
 106  * we defer to the scheduler.
 107  *
 108  * @return The next chosen thread to run, if any exist. Or else if the current
 109  * execution should terminate, return NULL.
 110  */
 111 Thread * ModelChecker::get_next_thread()
 112 {
 113
 114         /*
 115          * Have we completed exploring the preselected path? Then let the
 116          * scheduler decide
 117          */
 118         return scheduler->select_next_thread();
 119 }
 120
 121 /**
 122  * @brief Assert a bug in the executing program.
 123  *
 124  * Use this function to assert any sort of bug in the user program. If the
 125  * current trace is feasible (actually, a prefix of some feasible execution),
 126  * then this execution will be aborted, printing the appropriate message. If
 127  * the current trace is not yet feasible, the error message will be stashed and
 128  * printed if the execution ever becomes feasible.
 129  *
 130  * @param msg Descriptive message for the bug (do not include newline char)
 131  * @return True if bug is immediately-feasible
 132  */
 133 bool ModelChecker::assert_bug(const char *msg, ...)
 134 {
 135         char str[800];
 136
 137         va_list ap;
 138         va_start(ap, msg);
 139         vsnprintf(str, sizeof(str), msg, ap);
 140         va_end(ap);
 141
 142         return execution->assert_bug(str);
 143 }
 144
 145 /**
 146  * @brief Assert a bug in the executing program, asserted by a user thread
 147  * @see ModelChecker::assert_bug
 148  * @param msg Descriptive message for the bug (do not include newline char)
 149  */
 150 void ModelChecker::assert_user_bug(const char *msg)
 151 {
 152         /* If feasible bug, bail out now */
 153         if (assert_bug(msg))
 154                 switch_to_master(NULL);
 155 }
 156
 157 /** @brief Print bug report listing for this execution (if any bugs exist) */
 158 void ModelChecker::print_bugs() const
 159 {
 160         SnapVector<bug_message *> *bugs = execution->get_bugs();
 161
 162         model_print("Bug report: %zu bug%s detected\n",
 163                                                         bugs->size(),
 164                                                         bugs->size() > 1 ? "s" : "");
 165         for (unsigned int i = 0;i < bugs->size();i++)
 166                 (*bugs)[i] -> print();
 167 }
 168
 169 /**
 170  * @brief Record end-of-execution stats
 171  *
 172  * Must be run when exiting an execution. Records various stats.
 173  * @see struct execution_stats
 174  */
 175 void ModelChecker::record_stats()
 176 {
 177         stats.num_total ++;
 178         if (!execution->isfeasibleprefix())
 179                 stats.num_infeasible ++;
 180         else if (execution->have_bug_reports())
 181                 stats.num_buggy_executions ++;
 182         else if (execution->is_complete_execution())
 183                 stats.num_complete ++;
 184         else {
 185                 stats.num_redundant ++;
 186
 187                 /**
 188                  * @todo We can violate this ASSERT() when fairness/sleep sets
 189                  * conflict to cause an execution to terminate, e.g. with:
 190                  * Scheduler: [0: disabled][1: disabled][2: sleep][3: current, enabled]
 191                  */
 192                 //ASSERT(scheduler->all_threads_sleeping());
 193         }
 194 }
 195
 196 /** @brief Print execution stats */
 197 void ModelChecker::print_stats() const
 198 {
 199         model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
 200         model_print("Number of redundant executions: %d\n", stats.num_redundant);
 201         model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
 202         model_print("Number of infeasible executions: %d\n", stats.num_infeasible);
 203         model_print("Total executions: %d\n", stats.num_total);
 204 }
 205
 206 /**
 207  * @brief End-of-exeuction print
 208  * @param printbugs Should any existing bugs be printed?
 209  */
 210 void ModelChecker::print_execution(bool printbugs) const
 211 {
 212         model_print("Program output from execution %d:\n",
 213                                                         get_execution_number());
 214         print_program_output();
 215
 216         if (params.verbose >= 3) {
 217                 print_stats();
 218         }
 219
 220         /* Don't print invalid bugs */
 221         if (printbugs && execution->have_bug_reports()) {
 222                 model_print("\n");
 223                 print_bugs();
 224         }
 225
 226         model_print("\n");
 227         execution->print_summary();
 228 }
 229
 230 /**
 231  * Queries the model-checker for more executions to explore and, if one
 232  * exists, resets the model-checker state to execute a new execution.
 233  *
 234  * @return If there are more executions to explore, return true. Otherwise,
 235  * return false.
 236  */
 237 bool ModelChecker::next_execution()
 238 {
 239         DBG();
 240         /* Is this execution a feasible execution that's worth bug-checking? */
 241         bool complete = execution->isfeasibleprefix() &&
 242                                                                         (execution->is_complete_execution() ||
 243                                                                          execution->have_bug_reports());
 244
 245         /* End-of-execution bug checks */
 246         if (complete) {
 247                 if (execution->is_deadlocked())
 248                         assert_bug("Deadlock detected");
 249
 250                 run_trace_analyses();
 251         }
 252
 253         record_stats();
 254         /* Output */
 255         if ( (complete && params.verbose) || params.verbose>1 || (complete && execution->have_bug_reports()))
 256                 print_execution(complete);
 257         else
 258                 clear_program_output();
 259
 260         if (restart_flag) {
 261                 do_restart();
 262                 return true;
 263         }
 264 // test code
 265         execution_number ++;
 266         reset_to_initial_state();
 267         return false;
 268 }
 269
 270 /** @brief Run trace analyses on complete trace */
 271 void ModelChecker::run_trace_analyses() {
 272         for (unsigned int i = 0;i < trace_analyses.size();i ++)
 273                 trace_analyses[i] -> analyze(execution->get_action_trace());
 274 }
 275
 276 /**
 277  * @brief Get a Thread reference by its ID
 278  * @param tid The Thread's ID
 279  * @return A Thread reference
 280  */
 281 Thread * ModelChecker::get_thread(thread_id_t tid) const
 282 {
 283         return execution->get_thread(tid);
 284 }
 285
 286 /**
 287  * @brief Get a reference to the Thread in which a ModelAction was executed
 288  * @param act The ModelAction
 289  * @return A Thread reference
 290  */
 291 Thread * ModelChecker::get_thread(const ModelAction *act) const
 292 {
 293         return execution->get_thread(act);
 294 }
 295
 296 /**
 297  * Switch from a model-checker context to a user-thread context. This is the
 298  * complement of ModelChecker::switch_to_master and must be called from the
 299  * model-checker context
 300  *
 301  * @param thread The user-thread to switch to
 302  */
 303 void ModelChecker::switch_from_master(Thread *thread)
 304 {
 305         scheduler->set_current_thread(thread);
 306         Thread::swap(&system_context, thread);
 307 }
 308
 309 /**
 310  * Switch from a user-context to the "master thread" context (a.k.a. system
 311  * context). This switch is made with the intention of exploring a particular
 312  * model-checking action (described by a ModelAction object). Must be called
 313  * from a user-thread context.
 314  *
 315  * @param act The current action that will be explored. May be NULL only if
 316  * trace is exiting via an assertion (see ModelExecution::set_assert and
 317  * ModelExecution::has_asserted).
 318  * @return Return the value returned by the current action
 319  */
 320 uint64_t ModelChecker::switch_to_master(ModelAction *act)
 321 {
 322         if (modellock) {
 323                 static bool fork_message_printed = false;
 324
 325                 if (!fork_message_printed) {
 326                         model_print("Fork handler or dead thread trying to call into model checker...\n");
 327                         fork_message_printed = true;
 328                 }
 329                 delete act;
 330                 return 0;
 331         }
 332         DBG();
 333         Thread *old = thread_current();
 334         scheduler->set_current_thread(NULL);
 335         ASSERT(!old->get_pending());
 336
 337         if (inspect_plugin != NULL) {
 338                 inspect_plugin->inspectModelAction(act);
 339         }
 340
 341         old->set_pending(act);
 342         if (Thread::swap(old, &system_context) < 0) {
 343                 perror("swap threads");
 344                 exit(EXIT_FAILURE);
 345         }
 346         return old->get_return_value();
 347 }
 348
 349 static void runChecker() {
 350         model->run();
 351         delete model;
 352 }
 353
 354 void ModelChecker::startChecker() {
 355         startExecution(get_system_context(), runChecker);
 356         snapshot_stack_init();
 357         snapshot_record(0);
 358 }
 359
 360 bool ModelChecker::should_terminate_execution()
 361 {
 362         /* Infeasible -> don't take any more steps */
 363         if (execution->is_infeasible())
 364                 return true;
 365         else if (execution->isfeasibleprefix() && execution->have_fatal_bug_reports()) {
 366                 execution->set_assert();
 367                 return true;
 368         } else if (execution->isFinished()) {
 369                 return true;
 370         }
 371         return false;
 372 }
 373
 374 /** @brief Restart ModelChecker upon returning to the run loop of the
 375  *      model checker. */
 376 void ModelChecker::restart()
 377 {
 378         restart_flag = true;
 379 }
 380
 381 void ModelChecker::do_restart()
 382 {
 383         restart_flag = false;
 384         reset_to_initial_state();
 385         memset(&stats,0,sizeof(struct execution_stats));
 386         execution_number = 1;
 387 }
 388
 389 void ModelChecker::startMainThread() {
 390         init_thread->set_state(THREAD_RUNNING);
 391         scheduler->set_current_thread(init_thread);
 392         main_thread_startup();
 393 }
 394
 395 /** @brief Run ModelChecker for the user program */
 396 void ModelChecker::run()
 397 {
 398         //Need to initial random number generator state to avoid resets on rollback
 399         char random_state[256];
 400         initstate(423121, random_state, sizeof(random_state));
 401
 402         for(int exec = 0;exec < params.maxexecutions;exec++) {
 403                 Thread * t = init_thread;
 404
 405                 do {
 406                         /*
 407                          * Stash next pending action(s) for thread(s). There
 408                          * should only need to stash one thread's action--the
 409                          * thread which just took a step--plus the first step
 410                          * for any newly-created thread
 411                          */
 412                         for (unsigned int i = 0;i < get_num_threads();i++) {
 413                                 thread_id_t tid = int_to_id(i);
 414                                 Thread *thr = get_thread(tid);
 415                                 if (!thr->is_model_thread() && !thr->is_complete() && (!thr->get_pending())) {
 416                                         switch_from_master(thr);        // L: context swapped, and action type of thr changed.
 417                                         if (thr->is_waiting_on(thr))
 418                                                 assert_bug("Deadlock detected (thread %u)", i);
 419                                 }
 420                         }
 421
 422                         /* Don't schedule threads which should be disabled */
 423                         for (unsigned int i = 0;i < get_num_threads();i++) {
 424                                 Thread *th = get_thread(int_to_id(i));
 425                                 ModelAction *act = th->get_pending();
 426                                 if (act && execution->is_enabled(th) && !execution->check_action_enabled(act)) {
 427                                         scheduler->sleep(th);
 428                                 }
 429                         }
 430
 431                         for (unsigned int i = 1;i < get_num_threads();i++) {
 432                                 Thread *th = get_thread(int_to_id(i));
 433                                 ModelAction *act = th->get_pending();
 434                                 if (act && execution->is_enabled(th) && (th->get_state() != THREAD_BLOCKED) ) {
 435                                         if (act->is_write()) {
 436                                                 std::memory_order order = act->get_mo();
 437                                                 if (order == std::memory_order_relaxed || \
 438                                                                 order == std::memory_order_release) {
 439                                                         t = th;
 440                                                         break;
 441                                                 }
 442                                         } else if (act->get_type() == THREAD_CREATE || \
 443                                                                                  act->get_type() == PTHREAD_CREATE || \
 444                                                                                  act->get_type() == THREAD_START || \
 445                                                                                  act->get_type() == THREAD_FINISH) {
 446                                                 t = th;
 447                                                 break;
 448                                         }
 449                                 }
 450                         }
 451
 452                         /* Catch assertions from prior take_step or from
 453                         * between-ModelAction bugs (e.g., data races) */
 454
 455                         if (execution->has_asserted())
 456                                 break;
 457                         if (!t)
 458                                 t = get_next_thread();
 459                         if (!t || t->is_model_thread())
 460                                 break;
 461
 462                         /* Consume the next action for a Thread */
 463                         ModelAction *curr = t->get_pending();
 464                         t->set_pending(NULL);
 465                         t = execution->take_step(curr);
 466                 } while (!should_terminate_execution());
 467                 next_execution();
 468                 //restore random number generator state after rollback
 469                 setstate(random_state);
 470         }
 471
 472         model_print("******* Model-checking complete: *******\n");
 473         print_stats();
 474
 475         /* Have the trace analyses dump their output. */
 476         for (unsigned int i = 0;i < trace_analyses.size();i++)
 477                 trace_analyses[i]->finish();
 478
 479         /* unlink tmp file created by last child process */
 480         char filename[256];
 481         snprintf_(filename, sizeof(filename), "C11FuzzerTmp%d", getpid());
 482         unlink(filename);
 483 }