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 #include <signal.h>
  30
  31 #define SIGSTACKSIZE 65536
  32 static void mprot_handle_pf(int sig, siginfo_t *si, void *unused)
  33 {
  34         model_print("Segmentation fault at %p\n", si->si_addr);
  35         model_print("For debugging, place breakpoint at: %s:%d\n",
  36                                                         __FILE__, __LINE__);
  37         print_trace();  // Trace printing may cause dynamic memory allocation
  38         while(1)
  39                 ;
  40 }
  41
  42 void install_handler() {
  43         stack_t ss;
  44         ss.ss_sp = model_malloc(SIGSTACKSIZE);
  45         ss.ss_size = SIGSTACKSIZE;
  46         ss.ss_flags = 0;
  47         sigaltstack(&ss, NULL);
  48         struct sigaction sa;
  49         sa.sa_flags = SA_SIGINFO | SA_NODEFER | SA_RESTART | SA_ONSTACK;
  50         sigemptyset(&sa.sa_mask);
  51         sa.sa_sigaction = mprot_handle_pf;
  52
  53         if (sigaction(SIGSEGV, &sa, NULL) == -1) {
  54                 perror("sigaction(SIGSEGV)");
  55                 exit(EXIT_FAILURE);
  56         }
  57
  58 }
  59
  60 /** @brief Constructor */
  61 ModelChecker::ModelChecker() :
  62         /* Initialize default scheduler */
  63         params(),
  64         scheduler(new Scheduler()),
  65         history(new ModelHistory()),
  66         execution(new ModelExecution(this, scheduler)),
  67         execution_number(1),
  68         trace_analyses(),
  69         inspect_plugin(NULL)
  70 {
  71         model_print("C11Tester\n"
  72                                                         "Copyright (c) 2013 and 2019 Regents of the University of California. All rights reserved.\n"
  73                                                         "Distributed under the GPLv2\n"
  74                                                         "Written by Weiyu Luo, Brian Norris, and Brian Demsky\n\n");
  75         memset(&stats,0,sizeof(struct execution_stats));
  76         init_thread = new Thread(execution->get_next_id(), (thrd_t *) model_malloc(sizeof(thrd_t)), &placeholder, NULL, NULL);
  77 #ifdef TLS
  78         init_thread->setTLS((char *)get_tls_addr());
  79 #endif
  80         execution->add_thread(init_thread);
  81         scheduler->set_current_thread(init_thread);
  82         register_plugins();
  83         execution->setParams(&params);
  84         param_defaults(&params);
  85         parse_options(&params);
  86         initRaceDetector();
  87         /* Configure output redirection for the model-checker */
  88         redirect_output();
  89         install_trace_analyses(get_execution());
  90         install_handler();
  91 }
  92
  93 /** @brief Destructor */
  94 ModelChecker::~ModelChecker()
  95 {
  96         delete scheduler;
  97 }
  98
  99 /** Method to set parameters */
 100 model_params * ModelChecker::getParams() {
 101         return &params;
 102 }
 103
 104 /**
 105  * Restores user program to initial state and resets all model-checker data
 106  * structures.
 107  */
 108 void ModelChecker::reset_to_initial_state()
 109 {
 110
 111         /**
 112          * FIXME: if we utilize partial rollback, we will need to free only
 113          * those pending actions which were NOT pending before the rollback
 114          * point
 115          */
 116         for (unsigned int i = 0;i < get_num_threads();i++)
 117                 delete get_thread(int_to_id(i))->get_pending();
 118
 119         snapshot_roll_back(snapshot);
 120 }
 121
 122 /** @return the number of user threads created during this execution */
 123 unsigned int ModelChecker::get_num_threads() const
 124 {
 125         return execution->get_num_threads();
 126 }
 127
 128 /**
 129  * Must be called from user-thread context (e.g., through the global
 130  * thread_current() interface)
 131  *
 132  * @return The currently executing Thread.
 133  */
 134 Thread * ModelChecker::get_current_thread() const
 135 {
 136         return scheduler->get_current_thread();
 137 }
 138
 139 /**
 140  * @brief Choose the next thread to execute.
 141  *
 142  * This function chooses the next thread that should execute. It can enforce
 143  * execution replay/backtracking or, if the model-checker has no preference
 144  * regarding the next thread (i.e., when exploring a new execution ordering),
 145  * we defer to the scheduler.
 146  *
 147  * @return The next chosen thread to run, if any exist. Or else if the current
 148  * execution should terminate, return NULL.
 149  */
 150 Thread * ModelChecker::get_next_thread()
 151 {
 152
 153         /*
 154          * Have we completed exploring the preselected path? Then let the
 155          * scheduler decide
 156          */
 157         return scheduler->select_next_thread();
 158 }
 159
 160 /**
 161  * @brief Assert a bug in the executing program.
 162  *
 163  * Use this function to assert any sort of bug in the user program. If the
 164  * current trace is feasible (actually, a prefix of some feasible execution),
 165  * then this execution will be aborted, printing the appropriate message. If
 166  * the current trace is not yet feasible, the error message will be stashed and
 167  * printed if the execution ever becomes feasible.
 168  *
 169  * @param msg Descriptive message for the bug (do not include newline char)
 170  * @return True if bug is immediately-feasible
 171  */
 172 void ModelChecker::assert_bug(const char *msg, ...)
 173 {
 174         char str[800];
 175
 176         va_list ap;
 177         va_start(ap, msg);
 178         vsnprintf(str, sizeof(str), msg, ap);
 179         va_end(ap);
 180
 181         execution->assert_bug(str);
 182 }
 183
 184 /**
 185  * @brief Assert a bug in the executing program, asserted by a user thread
 186  * @see ModelChecker::assert_bug
 187  * @param msg Descriptive message for the bug (do not include newline char)
 188  */
 189 void ModelChecker::assert_user_bug(const char *msg)
 190 {
 191         /* If feasible bug, bail out now */
 192         assert_bug(msg);
 193         switch_to_master(NULL);
 194 }
 195
 196 /** @brief Print bug report listing for this execution (if any bugs exist) */
 197 void ModelChecker::print_bugs() const
 198 {
 199         SnapVector<bug_message *> *bugs = execution->get_bugs();
 200
 201         model_print("Bug report: %zu bug%s detected\n",
 202                                                         bugs->size(),
 203                                                         bugs->size() > 1 ? "s" : "");
 204         for (unsigned int i = 0;i < bugs->size();i++)
 205                 (*bugs)[i] -> print();
 206 }
 207
 208 /**
 209  * @brief Record end-of-execution stats
 210  *
 211  * Must be run when exiting an execution. Records various stats.
 212  * @see struct execution_stats
 213  */
 214 void ModelChecker::record_stats()
 215 {
 216         stats.num_total ++;
 217         if (execution->have_bug_reports())
 218                 stats.num_buggy_executions ++;
 219         else if (execution->is_complete_execution())
 220                 stats.num_complete ++;
 221         else {
 222                 //All threads are sleeping
 223                 /**
 224                  * @todo We can violate this ASSERT() when fairness/sleep sets
 225                  * conflict to cause an execution to terminate, e.g. with:
 226                  * Scheduler: [0: disabled][1: disabled][2: sleep][3: current, enabled]
 227                  */
 228                 //ASSERT(scheduler->all_threads_sleeping());
 229         }
 230 }
 231
 232 /** @brief Print execution stats */
 233 void ModelChecker::print_stats() const
 234 {
 235         model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
 236         model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
 237         model_print("Total executions: %d\n", stats.num_total);
 238 }
 239
 240 /**
 241  * @brief End-of-exeuction print
 242  * @param printbugs Should any existing bugs be printed?
 243  */
 244 void ModelChecker::print_execution(bool printbugs) const
 245 {
 246         model_print("Program output from execution %d:\n",
 247                                                         get_execution_number());
 248         print_program_output();
 249
 250         if (params.verbose >= 3) {
 251                 print_stats();
 252         }
 253
 254         /* Don't print invalid bugs */
 255         if (printbugs && execution->have_bug_reports()) {
 256                 model_print("\n");
 257                 print_bugs();
 258         }
 259
 260         model_print("\n");
 261         execution->print_summary();
 262 }
 263
 264 /**
 265  * Queries the model-checker for more executions to explore and, if one
 266  * exists, resets the model-checker state to execute a new execution.
 267  *
 268  * @return If there are more executions to explore, return true. Otherwise,
 269  * return false.
 270  */
 271 void ModelChecker::finish_execution(bool more_executions)
 272 {
 273         DBG();
 274         /* Is this execution a feasible execution that's worth bug-checking? */
 275         bool complete = (execution->is_complete_execution() ||
 276                                                                          execution->have_bug_reports());
 277
 278         /* End-of-execution bug checks */
 279         if (complete) {
 280                 if (execution->is_deadlocked())
 281                         assert_bug("Deadlock detected");
 282
 283                 run_trace_analyses();
 284         }
 285
 286         record_stats();
 287         /* Output */
 288         if ( (complete && params.verbose) || params.verbose>1 || (complete && execution->have_bug_reports()))
 289                 print_execution(complete);
 290         else
 291                 clear_program_output();
 292
 293 // test code
 294         execution_number ++;
 295         if (more_executions)
 296                 reset_to_initial_state();
 297         history->set_new_exec_flag();
 298 }
 299
 300 /** @brief Run trace analyses on complete trace */
 301 void ModelChecker::run_trace_analyses() {
 302         for (unsigned int i = 0;i < trace_analyses.size();i ++)
 303                 trace_analyses[i] -> analyze(execution->get_action_trace());
 304 }
 305
 306 /**
 307  * @brief Get a Thread reference by its ID
 308  * @param tid The Thread's ID
 309  * @return A Thread reference
 310  */
 311 Thread * ModelChecker::get_thread(thread_id_t tid) const
 312 {
 313         return execution->get_thread(tid);
 314 }
 315
 316 /**
 317  * @brief Get a reference to the Thread in which a ModelAction was executed
 318  * @param act The ModelAction
 319  * @return A Thread reference
 320  */
 321 Thread * ModelChecker::get_thread(const ModelAction *act) const
 322 {
 323         return execution->get_thread(act);
 324 }
 325
 326 /**
 327  * Switch from a model-checker context to a user-thread context. This is the
 328  * complement of ModelChecker::switch_to_master and must be called from the
 329  * model-checker context
 330  *
 331  * @param thread The user-thread to switch to
 332  */
 333 void ModelChecker::switch_from_master(Thread *thread)
 334 {
 335         scheduler->set_current_thread(thread);
 336         Thread::swap(&system_context, thread);
 337 }
 338
 339 /**
 340  * Switch from a user-context to the "master thread" context (a.k.a. system
 341  * context). This switch is made with the intention of exploring a particular
 342  * model-checking action (described by a ModelAction object). Must be called
 343  * from a user-thread context.
 344  *
 345  * @param act The current action that will be explored. May be NULL only if
 346  * trace is exiting via an assertion (see ModelExecution::set_assert and
 347  * ModelExecution::has_asserted).
 348  * @return Return the value returned by the current action
 349  */
 350 uint64_t ModelChecker::switch_to_master(ModelAction *act)
 351 {
 352         if (modellock) {
 353                 static bool fork_message_printed = false;
 354
 355                 if (!fork_message_printed) {
 356                         model_print("Fork handler or dead thread trying to call into model checker...\n");
 357                         fork_message_printed = true;
 358                 }
 359                 delete act;
 360                 return 0;
 361         }
 362         DBG();
 363         Thread *old = thread_current();
 364         scheduler->set_current_thread(NULL);
 365         ASSERT(!old->get_pending());
 366
 367         if (inspect_plugin != NULL) {
 368                 inspect_plugin->inspectModelAction(act);
 369         }
 370
 371         old->set_pending(act);
 372         if (Thread::swap(old, &system_context) < 0) {
 373                 perror("swap threads");
 374                 exit(EXIT_FAILURE);
 375         }
 376         return old->get_return_value();
 377 }
 378
 379 static void runChecker() {
 380         model->run();
 381         delete model;
 382 }
 383
 384 void ModelChecker::startChecker() {
 385         startExecution(get_system_context(), runChecker);
 386         snapshot = take_snapshot();
 387         initMainThread();
 388 }
 389
 390 bool ModelChecker::should_terminate_execution()
 391 {
 392         if (execution->have_bug_reports()) {
 393                 execution->set_assert();
 394                 return true;
 395         } else if (execution->isFinished()) {
 396                 return true;
 397         }
 398         return false;
 399 }
 400
 401 /** @brief Run ModelChecker for the user program */
 402 void ModelChecker::run()
 403 {
 404         //Need to initial random number generator state to avoid resets on rollback
 405         char random_state[256];
 406         initstate(423121, random_state, sizeof(random_state));
 407         modelclock_t checkfree = params.checkthreshold;
 408         for(int exec = 0;exec < params.maxexecutions;exec++) {
 409                 Thread * t = init_thread;
 410
 411                 do {
 412                         /* Check whether we need to free model actions. */
 413
 414                         if (params.traceminsize != 0 &&
 415                                         execution->get_curr_seq_num() > checkfree) {
 416                                 checkfree += params.checkthreshold;
 417                                 execution->collectActions();
 418                         }
 419
 420                         /*
 421                          * Stash next pending action(s) for thread(s). There
 422                          * should only need to stash one thread's action--the
 423                          * thread which just took a step--plus the first step
 424                          * for any newly-created thread
 425                          */
 426                         for (unsigned int i = 0;i < get_num_threads();i++) {
 427                                 thread_id_t tid = int_to_id(i);
 428                                 Thread *thr = get_thread(tid);
 429                                 if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
 430                                         switch_from_master(thr);
 431                                         if (thr->is_waiting_on(thr))
 432                                                 assert_bug("Deadlock detected (thread %u)", i);
 433                                 }
 434                         }
 435
 436                         /* Don't schedule threads which should be disabled */
 437                         for (unsigned int i = 0;i < get_num_threads();i++) {
 438                                 Thread *th = get_thread(int_to_id(i));
 439                                 ModelAction *act = th->get_pending();
 440                                 if (act && execution->is_enabled(th) && !execution->check_action_enabled(act)) {
 441                                         scheduler->sleep(th);
 442                                 }
 443                         }
 444
 445                         for (unsigned int i = 1;i < get_num_threads();i++) {
 446                                 Thread *th = get_thread(int_to_id(i));
 447                                 ModelAction *act = th->get_pending();
 448                                 if (act && execution->is_enabled(th) && (th->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                                                         t = th;
 454                                                         break;
 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                                                 t = th;
 461                                                 break;
 462                                         }
 463                                 }
 464                         }
 465
 466                         /* Catch assertions from prior take_step or from
 467                         * between-ModelAction bugs (e.g., data races) */
 468
 469                         if (execution->has_asserted())
 470                                 break;
 471                         if (!t)
 472                                 t = get_next_thread();
 473                         if (!t || t->is_model_thread())
 474                                 break;
 475                         if (t->just_woken_up()) {
 476                                 t->set_wakeup_state(false);
 477                                 t->set_pending(NULL);
 478                                 t = NULL;
 479                                 continue;       // Allow this thread to stash the next pending action
 480                         }
 481
 482                         /* Consume the next action for a Thread */
 483                         ModelAction *curr = t->get_pending();
 484                         t->set_pending(NULL);
 485                         t = execution->take_step(curr);
 486                 } while (!should_terminate_execution());
 487                 finish_execution((exec+1) < params.maxexecutions);
 488                 //restore random number generator state after rollback
 489                 setstate(random_state);
 490         }
 491
 492         model_print("******* Model-checking complete: *******\n");
 493         print_stats();
 494
 495         /* Have the trace analyses dump their output. */
 496         for (unsigned int i = 0;i < trace_analyses.size();i++)
 497                 trace_analyses[i]->finish();
 498
 499         /* unlink tmp file created by last child process */
 500         char filename[256];
 501         snprintf_(filename, sizeof(filename), "C11FuzzerTmp%d", getpid());
 502         unlink(filename);
 503 }