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 /** @brief Constructor */
  25 ModelChecker::ModelChecker() :
  26         /* Initialize default scheduler */
  27         params(),
  28         restart_flag(false),
  29         scheduler(new Scheduler()),
  30         history(new ModelHistory()),
  31         execution(new ModelExecution(this, scheduler)),
  32         execution_number(1),
  33         trace_analyses(),
  34         inspect_plugin(NULL)
  35 {
  36         printf("C11Tester\n"
  37                "Copyright (c) 2013 and 2019 Regents of the University of California. All rights reserved.\n"
  38                "Distributed under the GPLv2\n"
  39                "Written by Weiyu Luo, Brian Norris, and Brian Demsky\n\n");
  40         memset(&stats,0,sizeof(struct execution_stats));
  41         init_thread = new Thread(execution->get_next_id(), (thrd_t *) model_malloc(sizeof(thrd_t)), NULL, NULL, NULL);
  42 #ifdef TLS
  43         init_thread->setTLS((char *)get_tls_addr());
  44 #endif
  45         execution->add_thread(init_thread);
  46         scheduler->set_current_thread(init_thread);
  47         register_plugins();
  48         execution->setParams(&params);
  49         param_defaults(&params);
  50         parse_options(&params);
  51         initRaceDetector();
  52         /* Configure output redirection for the model-checker */
  53         redirect_output();
  54         install_trace_analyses(model->get_execution());
  55 }
  56
  57 /** @brief Destructor */
  58 ModelChecker::~ModelChecker()
  59 {
  60         delete scheduler;
  61 }
  62
  63 /** Method to set parameters */
  64 model_params * ModelChecker::getParams() {
  65         return &params;
  66 }
  67
  68 /**
  69  * Restores user program to initial state and resets all model-checker data
  70  * structures.
  71  */
  72 void ModelChecker::reset_to_initial_state()
  73 {
  74
  75         /**
  76          * FIXME: if we utilize partial rollback, we will need to free only
  77          * those pending actions which were NOT pending before the rollback
  78          * point
  79          */
  80         for (unsigned int i = 0;i < get_num_threads();i++)
  81                 delete get_thread(int_to_id(i))->get_pending();
  82
  83         snapshot_backtrack_before(0);
  84 }
  85
  86 /** @return the number of user threads created during this execution */
  87 unsigned int ModelChecker::get_num_threads() const
  88 {
  89         return execution->get_num_threads();
  90 }
  91
  92 /**
  93  * Must be called from user-thread context (e.g., through the global
  94  * thread_current() interface)
  95  *
  96  * @return The currently executing Thread.
  97  */
  98 Thread * ModelChecker::get_current_thread() const
  99 {
 100         return scheduler->get_current_thread();
 101 }
 102
 103 /**
 104  * @brief Choose the next thread to execute.
 105  *
 106  * This function chooses the next thread that should execute. It can enforce
 107  * execution replay/backtracking or, if the model-checker has no preference
 108  * regarding the next thread (i.e., when exploring a new execution ordering),
 109  * we defer to the scheduler.
 110  *
 111  * @return The next chosen thread to run, if any exist. Or else if the current
 112  * execution should terminate, return NULL.
 113  */
 114 Thread * ModelChecker::get_next_thread()
 115 {
 116
 117         /*
 118          * Have we completed exploring the preselected path? Then let the
 119          * scheduler decide
 120          */
 121         return scheduler->select_next_thread();
 122 }
 123
 124 /**
 125  * @brief Assert a bug in the executing program.
 126  *
 127  * Use this function to assert any sort of bug in the user program. If the
 128  * current trace is feasible (actually, a prefix of some feasible execution),
 129  * then this execution will be aborted, printing the appropriate message. If
 130  * the current trace is not yet feasible, the error message will be stashed and
 131  * printed if the execution ever becomes feasible.
 132  *
 133  * @param msg Descriptive message for the bug (do not include newline char)
 134  * @return True if bug is immediately-feasible
 135  */
 136 void ModelChecker::assert_bug(const char *msg, ...)
 137 {
 138         char str[800];
 139
 140         va_list ap;
 141         va_start(ap, msg);
 142         vsnprintf(str, sizeof(str), msg, ap);
 143         va_end(ap);
 144
 145         execution->assert_bug(str);
 146 }
 147
 148 /**
 149  * @brief Assert a bug in the executing program, asserted by a user thread
 150  * @see ModelChecker::assert_bug
 151  * @param msg Descriptive message for the bug (do not include newline char)
 152  */
 153 void ModelChecker::assert_user_bug(const char *msg)
 154 {
 155         /* If feasible bug, bail out now */
 156         assert_bug(msg);
 157         switch_to_master(NULL);
 158 }
 159
 160 /** @brief Print bug report listing for this execution (if any bugs exist) */
 161 void ModelChecker::print_bugs() const
 162 {
 163         SnapVector<bug_message *> *bugs = execution->get_bugs();
 164
 165         model_print("Bug report: %zu bug%s detected\n",
 166                                                         bugs->size(),
 167                                                         bugs->size() > 1 ? "s" : "");
 168         for (unsigned int i = 0;i < bugs->size();i++)
 169                 (*bugs)[i] -> print();
 170 }
 171
 172 /**
 173  * @brief Record end-of-execution stats
 174  *
 175  * Must be run when exiting an execution. Records various stats.
 176  * @see struct execution_stats
 177  */
 178 void ModelChecker::record_stats()
 179 {
 180         stats.num_total ++;
 181         if (execution->have_bug_reports())
 182                 stats.num_buggy_executions ++;
 183         else if (execution->is_complete_execution())
 184                 stats.num_complete ++;
 185         else {
 186                 //All threads are sleeping
 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 buggy executions: %d\n", stats.num_buggy_executions);
 201         model_print("Total executions: %d\n", stats.num_total);
 202 }
 203
 204 /**
 205  * @brief End-of-exeuction print
 206  * @param printbugs Should any existing bugs be printed?
 207  */
 208 void ModelChecker::print_execution(bool printbugs) const
 209 {
 210         model_print("Program output from execution %d:\n",
 211                                                         get_execution_number());
 212         print_program_output();
 213
 214         if (params.verbose >= 3) {
 215                 print_stats();
 216         }
 217
 218         /* Don't print invalid bugs */
 219         if (printbugs && execution->have_bug_reports()) {
 220                 model_print("\n");
 221                 print_bugs();
 222         }
 223
 224         model_print("\n");
 225         execution->print_summary();
 226 }
 227
 228 /**
 229  * Queries the model-checker for more executions to explore and, if one
 230  * exists, resets the model-checker state to execute a new execution.
 231  *
 232  * @return If there are more executions to explore, return true. Otherwise,
 233  * return false.
 234  */
 235 bool ModelChecker::next_execution()
 236 {
 237         DBG();
 238         /* Is this execution a feasible execution that's worth bug-checking? */
 239         bool complete = (execution->is_complete_execution() ||
 240                                                                          execution->have_bug_reports());
 241
 242         /* End-of-execution bug checks */
 243         if (complete) {
 244                 if (execution->is_deadlocked())
 245                         assert_bug("Deadlock detected");
 246
 247                 run_trace_analyses();
 248         }
 249
 250         record_stats();
 251         /* Output */
 252         if ( (complete && params.verbose) || params.verbose>1 || (complete && execution->have_bug_reports()))
 253                 print_execution(complete);
 254         else
 255                 clear_program_output();
 256
 257         if (restart_flag) {
 258                 do_restart();
 259                 return true;
 260         }
 261 // test code
 262         execution_number ++;
 263         reset_to_initial_state();
 264         history->set_new_exec_flag();
 265         return false;
 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 static void runChecker() {
 348         model->run();
 349         delete model;
 350 }
 351
 352 void ModelChecker::startChecker() {
 353         startExecution(get_system_context(), runChecker);
 354         snapshot_stack_init();
 355         snapshot_record(0);
 356 }
 357
 358 bool ModelChecker::should_terminate_execution()
 359 {
 360         if (execution->have_bug_reports()) {
 361                 execution->set_assert();
 362                 return true;
 363         } else if (execution->isFinished()) {
 364                 return true;
 365         }
 366         return false;
 367 }
 368
 369 /** @brief Restart ModelChecker upon returning to the run loop of the
 370  *      model checker. */
 371 void ModelChecker::restart()
 372 {
 373         restart_flag = true;
 374 }
 375
 376 void ModelChecker::do_restart()
 377 {
 378         restart_flag = false;
 379         reset_to_initial_state();
 380         memset(&stats,0,sizeof(struct execution_stats));
 381         execution_number = 1;
 382 }
 383
 384 void ModelChecker::startMainThread() {
 385         init_thread->set_state(THREAD_RUNNING);
 386         scheduler->set_current_thread(init_thread);
 387         main_thread_startup();
 388 }
 389
 390 /** @brief Run ModelChecker for the user program */
 391 void ModelChecker::run()
 392 {
 393         //Need to initial random number generator state to avoid resets on rollback
 394         char random_state[256];
 395         initstate(423121, random_state, sizeof(random_state));
 396
 397         for(int exec = 0;exec < params.maxexecutions;exec++) {
 398                 Thread * t = init_thread;
 399
 400                 do {
 401                         /*
 402                          * Stash next pending action(s) for thread(s). There
 403                          * should only need to stash one thread's action--the
 404                          * thread which just took a step--plus the first step
 405                          * for any newly-created thread
 406                          */
 407                         for (unsigned int i = 0;i < get_num_threads();i++) {
 408                                 thread_id_t tid = int_to_id(i);
 409                                 Thread *thr = get_thread(tid);
 410                                 if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
 411                                         switch_from_master(thr);
 412                                         if (thr->is_waiting_on(thr))
 413                                                 assert_bug("Deadlock detected (thread %u)", i);
 414                                 }
 415                         }
 416
 417                         /* Don't schedule threads which should be disabled */
 418                         for (unsigned int i = 0;i < get_num_threads();i++) {
 419                                 Thread *th = get_thread(int_to_id(i));
 420                                 ModelAction *act = th->get_pending();
 421                                 if (act && execution->is_enabled(th) && !execution->check_action_enabled(act)) {
 422                                         scheduler->sleep(th);
 423                                 }
 424                         }
 425
 426                         for (unsigned int i = 1;i < get_num_threads();i++) {
 427                                 Thread *th = get_thread(int_to_id(i));
 428                                 ModelAction *act = th->get_pending();
 429                                 if (act && execution->is_enabled(th) && (th->get_state() != THREAD_BLOCKED) ) {
 430                                         if (act->is_write()) {
 431                                                 std::memory_order order = act->get_mo();
 432                                                 if (order == std::memory_order_relaxed || \
 433                                                                 order == std::memory_order_release) {
 434                                                         t = th;
 435                                                         break;
 436                                                 }
 437                                         } else if (act->get_type() == THREAD_CREATE || \
 438                                                                                  act->get_type() == PTHREAD_CREATE || \
 439                                                                                  act->get_type() == THREAD_START || \
 440                                                                                  act->get_type() == THREAD_FINISH) {
 441                                                 t = th;
 442                                                 break;
 443                                         }
 444                                 }
 445                         }
 446
 447                         /* Catch assertions from prior take_step or from
 448                         * between-ModelAction bugs (e.g., data races) */
 449
 450                         if (execution->has_asserted())
 451                                 break;
 452                         if (!t)
 453                                 t = get_next_thread();
 454                         if (!t || t->is_model_thread())
 455                                 break;
 456                         if (t->just_woken_up()) {
 457                                 t->set_wakeup_state(false);
 458                                 t->set_pending(NULL);
 459                                 t = NULL;
 460                                 continue;       // Allow this thread to stash the next pending action
 461                         }
 462
 463                         /* Consume the next action for a Thread */
 464                         ModelAction *curr = t->get_pending();
 465                         t->set_pending(NULL);
 466                         t = execution->take_step(curr);
 467                 } while (!should_terminate_execution());
 468                 next_execution();
 469                 //restore random number generator state after rollback
 470                 setstate(random_state);
 471         }
 472
 473         model_print("******* Model-checking complete: *******\n");
 474         print_stats();
 475
 476         /* Have the trace analyses dump their output. */
 477         for (unsigned int i = 0;i < trace_analyses.size();i++)
 478                 trace_analyses[i]->finish();
 479
 480         /* unlink tmp file created by last child process */
 481         char filename[256];
 482         snprintf_(filename, sizeof(filename), "C11FuzzerTmp%d", getpid());
 483         unlink(filename);
 484 }