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         install_handler();
  89 }
  90
  91 /** @brief Destructor */
  92 ModelChecker::~ModelChecker()
  93 {
  94         delete scheduler;
  95 }
  96
  97 /** Method to set parameters */
  98 model_params * ModelChecker::getParams() {
  99         return &params;
 100 }
 101
 102 /**
 103  * Restores user program to initial state and resets all model-checker data
 104  * structures.
 105  */
 106 void ModelChecker::reset_to_initial_state()
 107 {
 108
 109         /**
 110          * FIXME: if we utilize partial rollback, we will need to free only
 111          * those pending actions which were NOT pending before the rollback
 112          * point
 113          */
 114         for (unsigned int i = 0;i < get_num_threads();i++)
 115                 delete get_thread(int_to_id(i))->get_pending();
 116
 117         snapshot_roll_back(snapshot);
 118 }
 119
 120 /** @return the number of user threads created during this execution */
 121 unsigned int ModelChecker::get_num_threads() const
 122 {
 123         return execution->get_num_threads();
 124 }
 125
 126 /**
 127  * Must be called from user-thread context (e.g., through the global
 128  * thread_current() interface)
 129  *
 130  * @return The currently executing Thread.
 131  */
 132 Thread * ModelChecker::get_current_thread() const
 133 {
 134         return scheduler->get_current_thread();
 135 }
 136
 137 /**
 138  * @brief Choose the next thread to execute.
 139  *
 140  * This function chooses the next thread that should execute. It can enforce
 141  * execution replay/backtracking or, if the model-checker has no preference
 142  * regarding the next thread (i.e., when exploring a new execution ordering),
 143  * we defer to the scheduler.
 144  *
 145  * @return The next chosen thread to run, if any exist. Or else if the current
 146  * execution should terminate, return NULL.
 147  */
 148 Thread * ModelChecker::get_next_thread()
 149 {
 150
 151         /*
 152          * Have we completed exploring the preselected path? Then let the
 153          * scheduler decide
 154          */
 155         return scheduler->select_next_thread();
 156 }
 157
 158 /**
 159  * @brief Assert a bug in the executing program.
 160  *
 161  * Use this function to assert any sort of bug in the user program. If the
 162  * current trace is feasible (actually, a prefix of some feasible execution),
 163  * then this execution will be aborted, printing the appropriate message. If
 164  * the current trace is not yet feasible, the error message will be stashed and
 165  * printed if the execution ever becomes feasible.
 166  *
 167  * @param msg Descriptive message for the bug (do not include newline char)
 168  * @return True if bug is immediately-feasible
 169  */
 170 void ModelChecker::assert_bug(const char *msg, ...)
 171 {
 172         char str[800];
 173
 174         va_list ap;
 175         va_start(ap, msg);
 176         vsnprintf(str, sizeof(str), msg, ap);
 177         va_end(ap);
 178
 179         execution->assert_bug(str);
 180 }
 181
 182 /**
 183  * @brief Assert a bug in the executing program, asserted by a user thread
 184  * @see ModelChecker::assert_bug
 185  * @param msg Descriptive message for the bug (do not include newline char)
 186  */
 187 void ModelChecker::assert_user_bug(const char *msg)
 188 {
 189         /* If feasible bug, bail out now */
 190         assert_bug(msg);
 191         switch_to_master(NULL);
 192 }
 193
 194 /** @brief Print bug report listing for this execution (if any bugs exist) */
 195 void ModelChecker::print_bugs() const
 196 {
 197         SnapVector<bug_message *> *bugs = execution->get_bugs();
 198
 199         model_print("Bug report: %zu bug%s detected\n",
 200                                                         bugs->size(),
 201                                                         bugs->size() > 1 ? "s" : "");
 202         for (unsigned int i = 0;i < bugs->size();i++)
 203                 (*bugs)[i] -> print();
 204 }
 205
 206 /**
 207  * @brief Record end-of-execution stats
 208  *
 209  * Must be run when exiting an execution. Records various stats.
 210  * @see struct execution_stats
 211  */
 212 void ModelChecker::record_stats()
 213 {
 214         stats.num_total ++;
 215         if (execution->have_bug_reports())
 216                 stats.num_buggy_executions ++;
 217         else if (execution->is_complete_execution())
 218                 stats.num_complete ++;
 219         else {
 220                 //All threads are sleeping
 221                 /**
 222                  * @todo We can violate this ASSERT() when fairness/sleep sets
 223                  * conflict to cause an execution to terminate, e.g. with:
 224                  * Scheduler: [0: disabled][1: disabled][2: sleep][3: current, enabled]
 225                  */
 226                 //ASSERT(scheduler->all_threads_sleeping());
 227         }
 228 }
 229
 230 /** @brief Print execution stats */
 231 void ModelChecker::print_stats() const
 232 {
 233         model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
 234         model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
 235         model_print("Total executions: %d\n", stats.num_total);
 236 }
 237
 238 /**
 239  * @brief End-of-exeuction print
 240  * @param printbugs Should any existing bugs be printed?
 241  */
 242 void ModelChecker::print_execution(bool printbugs) const
 243 {
 244         model_print("Program output from execution %d:\n",
 245                                                         get_execution_number());
 246         print_program_output();
 247
 248         if (params.verbose >= 3) {
 249                 print_stats();
 250         }
 251
 252         /* Don't print invalid bugs */
 253         if (printbugs && execution->have_bug_reports()) {
 254                 model_print("\n");
 255                 print_bugs();
 256         }
 257
 258         model_print("\n");
 259         execution->print_summary();
 260 }
 261
 262 /**
 263  * Queries the model-checker for more executions to explore and, if one
 264  * exists, resets the model-checker state to execute a new execution.
 265  *
 266  * @return If there are more executions to explore, return true. Otherwise,
 267  * return false.
 268  */
 269 void ModelChecker::finish_execution(bool more_executions)
 270 {
 271         DBG();
 272         /* Is this execution a feasible execution that's worth bug-checking? */
 273         bool complete = (execution->is_complete_execution() ||
 274                                                                          execution->have_bug_reports());
 275
 276         /* End-of-execution bug checks */
 277         if (complete) {
 278                 if (execution->is_deadlocked())
 279                         assert_bug("Deadlock detected");
 280
 281                 run_trace_analyses();
 282         }
 283
 284         record_stats();
 285         /* Output */
 286         if ( (complete && params.verbose) || params.verbose>1 || (complete && execution->have_bug_reports()))
 287                 print_execution(complete);
 288         else
 289                 clear_program_output();
 290
 291 // test code
 292         execution_number ++;
 293         if (more_executions)
 294                 reset_to_initial_state();
 295
 296         history->set_new_exec_flag();
 297 }
 298
 299 /** @brief Run trace analyses on complete trace */
 300 void ModelChecker::run_trace_analyses() {
 301         for (unsigned int i = 0;i < trace_analyses.size();i ++)
 302                 trace_analyses[i] -> analyze(execution->get_action_trace());
 303 }
 304
 305 /**
 306  * @brief Get a Thread reference by its ID
 307  * @param tid The Thread's ID
 308  * @return A Thread reference
 309  */
 310 Thread * ModelChecker::get_thread(thread_id_t tid) const
 311 {
 312         return execution->get_thread(tid);
 313 }
 314
 315 /**
 316  * @brief Get a reference to the Thread in which a ModelAction was executed
 317  * @param act The ModelAction
 318  * @return A Thread reference
 319  */
 320 Thread * ModelChecker::get_thread(const ModelAction *act) const
 321 {
 322         return execution->get_thread(act);
 323 }
 324
 325 /**
 326  * Switch from a model-checker context to a user-thread context. This is the
 327  * complement of ModelChecker::switch_to_master and must be called from the
 328  * model-checker context
 329  *
 330  * @param thread The user-thread to switch to
 331  */
 332 void ModelChecker::switch_from_master(Thread *thread)
 333 {
 334         scheduler->set_current_thread(thread);
 335         Thread::swap(&system_context, thread);
 336 }
 337
 338 /**
 339  * Switch from a user-context to the "master thread" context (a.k.a. system
 340  * context). This switch is made with the intention of exploring a particular
 341  * model-checking action (described by a ModelAction object). Must be called
 342  * from a user-thread context.
 343  *
 344  * @param act The current action that will be explored. May be NULL only if
 345  * trace is exiting via an assertion (see ModelExecution::set_assert and
 346  * ModelExecution::has_asserted).
 347  * @return Return the value returned by the current action
 348  */
 349 uint64_t ModelChecker::switch_to_master(ModelAction *act)
 350 {
 351         if (modellock) {
 352                 static bool fork_message_printed = false;
 353
 354                 if (!fork_message_printed) {
 355                         model_print("Fork handler or dead thread trying to call into model checker...\n");
 356                         fork_message_printed = true;
 357                 }
 358                 delete act;
 359                 return 0;
 360         }
 361         DBG();
 362         Thread *old = thread_current();
 363         scheduler->set_current_thread(NULL);
 364         ASSERT(!old->get_pending());
 365
 366         if (inspect_plugin != NULL) {
 367                 inspect_plugin->inspectModelAction(act);
 368         }
 369
 370         old->set_pending(act);
 371         if (Thread::swap(old, &system_context) < 0) {
 372                 perror("swap threads");
 373                 exit(EXIT_FAILURE);
 374         }
 375         return old->get_return_value();
 376 }
 377
 378 static void runChecker() {
 379         model->run();
 380         delete model;
 381 }
 382
 383 void ModelChecker::startChecker() {
 384         startExecution(get_system_context(), runChecker);
 385         snapshot = take_snapshot();
 386
 387         install_trace_analyses(get_execution());
 388         redirect_output();
 389         initMainThread();
 390 }
 391
 392 bool ModelChecker::should_terminate_execution()
 393 {
 394         if (execution->have_bug_reports()) {
 395                 execution->set_assert();
 396                 return true;
 397         } else if (execution->isFinished()) {
 398                 return true;
 399         }
 400         return false;
 401 }
 402
 403 /** @brief Run ModelChecker for the user program */
 404 void ModelChecker::run()
 405 {
 406         //Need to initial random number generator state to avoid resets on rollback
 407         char random_state[256];
 408         initstate(423121, random_state, sizeof(random_state));
 409         modelclock_t checkfree = params.checkthreshold;
 410         for(int exec = 0;exec < params.maxexecutions;exec++) {
 411                 Thread * t = init_thread;
 412
 413                 do {
 414                         /* Check whether we need to free model actions. */
 415
 416                         if (params.traceminsize != 0 &&
 417                                         execution->get_curr_seq_num() > checkfree) {
 418                                 checkfree += params.checkthreshold;
 419                                 execution->collectActions();
 420                         }
 421
 422                         /*
 423                          * Stash next pending action(s) for thread(s). There
 424                          * should only need to stash one thread's action--the
 425                          * thread which just took a step--plus the first step
 426                          * for any newly-created thread
 427                          */
 428                         for (unsigned int i = 0;i < get_num_threads();i++) {
 429                                 thread_id_t tid = int_to_id(i);
 430                                 Thread *thr = get_thread(tid);
 431                                 if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
 432                                         switch_from_master(thr);
 433                                         if (thr->is_waiting_on(thr))
 434                                                 assert_bug("Deadlock detected (thread %u)", i);
 435                                 }
 436                         }
 437
 438                         /* Don't schedule threads which should be disabled */
 439                         for (unsigned int i = 0;i < get_num_threads();i++) {
 440                                 Thread *th = get_thread(int_to_id(i));
 441                                 ModelAction *act = th->get_pending();
 442                                 if (act && execution->is_enabled(th) && !execution->check_action_enabled(act)) {
 443                                         scheduler->sleep(th);
 444                                 }
 445                         }
 446
 447                         for (unsigned int i = 1;i < get_num_threads();i++) {
 448                                 Thread *th = get_thread(int_to_id(i));
 449                                 ModelAction *act = th->get_pending();
 450                                 if (act && execution->is_enabled(th) && (th->get_state() != THREAD_BLOCKED) ) {
 451                                         if (act->is_write()) {
 452                                                 std::memory_order order = act->get_mo();
 453                                                 if (order == std::memory_order_relaxed || \
 454                                                                 order == std::memory_order_release) {
 455                                                         t = th;
 456                                                         break;
 457                                                 }
 458                                         } else if (act->get_type() == THREAD_CREATE || \
 459                                                                                  act->get_type() == PTHREAD_CREATE || \
 460                                                                                  act->get_type() == THREAD_START || \
 461                                                                                  act->get_type() == THREAD_FINISH) {
 462                                                 t = th;
 463                                                 break;
 464                                         }
 465                                 }
 466                         }
 467
 468                         /* Catch assertions from prior take_step or from
 469                         * between-ModelAction bugs (e.g., data races) */
 470
 471                         if (execution->has_asserted())
 472                                 break;
 473                         if (!t)
 474                                 t = get_next_thread();
 475                         if (!t || t->is_model_thread())
 476                                 break;
 477                         if (t->just_woken_up()) {
 478                                 t->set_wakeup_state(false);
 479                                 t->set_pending(NULL);
 480                                 t = NULL;
 481                                 continue;       // Allow this thread to stash the next pending action
 482                         }
 483
 484                         /* Consume the next action for a Thread */
 485                         ModelAction *curr = t->get_pending();
 486                         t->set_pending(NULL);
 487                         t = execution->take_step(curr);
 488                 } while (!should_terminate_execution());
 489                 finish_execution((exec+1) < params.maxexecutions);
 490                 //restore random number generator state after rollback
 491                 setstate(random_state);
 492         }
 493
 494         model_print("******* Model-checking complete: *******\n");
 495         print_stats();
 496
 497         /* Have the trace analyses dump their output. */
 498         for (unsigned int i = 0;i < trace_analyses.size();i++)
 499                 trace_analyses[i]->finish();
 500
 501         /* unlink tmp file created by last child process */
 502         char filename[256];
 503         snprintf_(filename, sizeof(filename), "C11FuzzerTmp%d", getpid());
 504         unlink(filename);
 505 }