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         curr_thread_num(1),
  69         trace_analyses(),
  70         inspect_plugin(NULL)
  71 {
  72         model_print("C11Tester\n"
  73                                                         "Copyright (c) 2013 and 2019 Regents of the University of California. All rights reserved.\n"
  74                                                         "Distributed under the GPLv2\n"
  75                                                         "Written by Weiyu Luo, Brian Norris, and Brian Demsky\n\n");
  76         memset(&stats,0,sizeof(struct execution_stats));
  77         init_thread = new Thread(execution->get_next_id(), (thrd_t *) model_malloc(sizeof(thrd_t)), &placeholder, NULL, NULL);
  78 #ifdef TLS
  79         init_thread->setTLS((char *)get_tls_addr());
  80 #endif
  81         execution->add_thread(init_thread);
  82         scheduler->set_current_thread(init_thread);
  83         register_plugins();
  84         execution->setParams(&params);
  85         param_defaults(&params);
  86         parse_options(&params);
  87         initRaceDetector();
  88         /* Configure output redirection for the model-checker */
  89         install_handler();
  90 }
  91
  92 /** @brief Destructor */
  93 ModelChecker::~ModelChecker()
  94 {
  95         delete scheduler;
  96 }
  97
  98 /** Method to set parameters */
  99 model_params * ModelChecker::getParams() {
 100         return &params;
 101 }
 102
 103 /**
 104  * Restores user program to initial state and resets all model-checker data
 105  * structures.
 106  */
 107 void ModelChecker::reset_to_initial_state()
 108 {
 109
 110         /**
 111          * FIXME: if we utilize partial rollback, we will need to free only
 112          * those pending actions which were NOT pending before the rollback
 113          * point
 114          */
 115         for (unsigned int i = 0;i < get_num_threads();i++)
 116                 delete get_thread(int_to_id(i))->get_pending();
 117
 118         snapshot_roll_back(snapshot);
 119 }
 120
 121 /** @return the number of user threads created during this execution */
 122 unsigned int ModelChecker::get_num_threads() const
 123 {
 124         return execution->get_num_threads();
 125 }
 126
 127 /**
 128  * Must be called from user-thread context (e.g., through the global
 129  * thread_current() interface)
 130  *
 131  * @return The currently executing Thread.
 132  */
 133 Thread * ModelChecker::get_current_thread() const
 134 {
 135         return scheduler->get_current_thread();
 136 }
 137
 138 /**
 139  * Must be called from user-thread context (e.g., through the global
 140  * thread_current_id() interface)
 141  *
 142  * @return The id of the currently executing Thread.
 143  */
 144 thread_id_t ModelChecker::get_current_thread_id() const
 145 {
 146         ASSERT(int_to_id(curr_thread_num) == get_current_thread()->get_id());
 147         return int_to_id(curr_thread_num);
 148 }
 149
 150 /**
 151  * @brief Choose the next thread to execute.
 152  *
 153  * This function chooses the next thread that should execute. It can enforce
 154  * execution replay/backtracking or, if the model-checker has no preference
 155  * regarding the next thread (i.e., when exploring a new execution ordering),
 156  * we defer to the scheduler.
 157  *
 158  * @return The next chosen thread to run, if any exist. Or else if the current
 159  * execution should terminate, return NULL.
 160  */
 161 Thread * ModelChecker::get_next_thread()
 162 {
 163
 164         /*
 165          * Have we completed exploring the preselected path? Then let the
 166          * scheduler decide
 167          */
 168         return scheduler->select_next_thread();
 169 }
 170
 171 /**
 172  * @brief Assert a bug in the executing program.
 173  *
 174  * Use this function to assert any sort of bug in the user program. If the
 175  * current trace is feasible (actually, a prefix of some feasible execution),
 176  * then this execution will be aborted, printing the appropriate message. If
 177  * the current trace is not yet feasible, the error message will be stashed and
 178  * printed if the execution ever becomes feasible.
 179  *
 180  * @param msg Descriptive message for the bug (do not include newline char)
 181  * @return True if bug is immediately-feasible
 182  */
 183 void ModelChecker::assert_bug(const char *msg, ...)
 184 {
 185         char str[800];
 186
 187         va_list ap;
 188         va_start(ap, msg);
 189         vsnprintf(str, sizeof(str), msg, ap);
 190         va_end(ap);
 191
 192         execution->assert_bug(str);
 193 }
 194
 195 /**
 196  * @brief Assert a bug in the executing program, asserted by a user thread
 197  * @see ModelChecker::assert_bug
 198  * @param msg Descriptive message for the bug (do not include newline char)
 199  */
 200 void ModelChecker::assert_user_bug(const char *msg)
 201 {
 202         /* If feasible bug, bail out now */
 203         assert_bug(msg);
 204         switch_thread(NULL);
 205 }
 206
 207 /** @brief Print bug report listing for this execution (if any bugs exist) */
 208 void ModelChecker::print_bugs() const
 209 {
 210         SnapVector<bug_message *> *bugs = execution->get_bugs();
 211
 212         model_print("Bug report: %zu bug%s detected\n",
 213                                                         bugs->size(),
 214                                                         bugs->size() > 1 ? "s" : "");
 215         for (unsigned int i = 0;i < bugs->size();i++)
 216                 (*bugs)[i] -> print();
 217 }
 218
 219 /**
 220  * @brief Record end-of-execution stats
 221  *
 222  * Must be run when exiting an execution. Records various stats.
 223  * @see struct execution_stats
 224  */
 225 void ModelChecker::record_stats()
 226 {
 227         stats.num_total ++;
 228         if (execution->have_bug_reports())
 229                 stats.num_buggy_executions ++;
 230         else if (execution->is_complete_execution())
 231                 stats.num_complete ++;
 232         else {
 233                 //All threads are sleeping
 234                 /**
 235                  * @todo We can violate this ASSERT() when fairness/sleep sets
 236                  * conflict to cause an execution to terminate, e.g. with:
 237                  * Scheduler: [0: disabled][1: disabled][2: sleep][3: current, enabled]
 238                  */
 239                 //ASSERT(scheduler->all_threads_sleeping());
 240         }
 241 }
 242
 243 /** @brief Print execution stats */
 244 void ModelChecker::print_stats() const
 245 {
 246         model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
 247         model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
 248         model_print("Total executions: %d\n", stats.num_total);
 249 }
 250
 251 /**
 252  * @brief End-of-exeuction print
 253  * @param printbugs Should any existing bugs be printed?
 254  */
 255 void ModelChecker::print_execution(bool printbugs) const
 256 {
 257         model_print("Program output from execution %d:\n",
 258                                                         get_execution_number());
 259         print_program_output();
 260
 261         if (params.verbose >= 3) {
 262                 print_stats();
 263         }
 264
 265         /* Don't print invalid bugs */
 266         if (printbugs && execution->have_bug_reports()) {
 267                 model_print("\n");
 268                 print_bugs();
 269         }
 270
 271         model_print("\n");
 272         execution->print_summary();
 273 }
 274
 275 /**
 276  * Queries the model-checker for more executions to explore and, if one
 277  * exists, resets the model-checker state to execute a new execution.
 278  *
 279  * @return If there are more executions to explore, return true. Otherwise,
 280  * return false.
 281  */
 282 void ModelChecker::finish_execution(bool more_executions)
 283 {
 284         DBG();
 285         /* Is this execution a feasible execution that's worth bug-checking? */
 286         bool complete = (execution->is_complete_execution() ||
 287                                                                          execution->have_bug_reports());
 288
 289         /* End-of-execution bug checks */
 290         if (complete) {
 291                 if (execution->is_deadlocked())
 292                         assert_bug("Deadlock detected");
 293
 294                 run_trace_analyses();
 295         }
 296
 297         record_stats();
 298         /* Output */
 299         if ( (complete && params.verbose) || params.verbose>1 || (complete && execution->have_bug_reports()))
 300                 print_execution(complete);
 301         else
 302                 clear_program_output();
 303
 304         execution_number ++;
 305         history->set_new_exec_flag();
 306
 307         if (more_executions)
 308                 reset_to_initial_state();
 309 }
 310
 311 /** @brief Run trace analyses on complete trace */
 312 void ModelChecker::run_trace_analyses() {
 313         for (unsigned int i = 0;i < trace_analyses.size();i ++)
 314                 trace_analyses[i] -> analyze(execution->get_action_trace());
 315 }
 316
 317 /**
 318  * @brief Get a Thread reference by its ID
 319  * @param tid The Thread's ID
 320  * @return A Thread reference
 321  */
 322 Thread * ModelChecker::get_thread(thread_id_t tid) const
 323 {
 324         return execution->get_thread(tid);
 325 }
 326
 327 /**
 328  * @brief Get a reference to the Thread in which a ModelAction was executed
 329  * @param act The ModelAction
 330  * @return A Thread reference
 331  */
 332 Thread * ModelChecker::get_thread(const ModelAction *act) const
 333 {
 334         return execution->get_thread(act);
 335 }
 336
 337 void ModelChecker::startRunExecution(Thread *old) {
 338         while (true) {
 339                 if (params.traceminsize != 0 &&
 340                                 execution->get_curr_seq_num() > checkfree) {
 341                         checkfree += params.checkthreshold;
 342                         execution->collectActions();
 343                 }
 344
 345                 thread_chosen = false;
 346                 curr_thread_num = 1;
 347                 Thread *thr = getNextThread(old);
 348                 if (thr != nullptr) {
 349                         scheduler->set_current_thread(thr);
 350
 351                         if (Thread::swap(old, thr) < 0) {
 352                                 perror("swap threads");
 353                                 exit(EXIT_FAILURE);
 354                         }
 355                         return;
 356                 }
 357
 358                 if (!handleChosenThread(old)) {
 359                         return;
 360                 }
 361         }
 362 }
 363
 364 Thread* ModelChecker::getNextThread(Thread *old)
 365 {
 366         Thread *nextThread = nullptr;
 367         for (unsigned int i = curr_thread_num;i < get_num_threads();i++) {
 368                 thread_id_t tid = int_to_id(i);
 369                 Thread *thr = get_thread(tid);
 370
 371                 if (!thr->is_complete()) {
 372                         if (!thr->get_pending()) {
 373                                 curr_thread_num = i;
 374                                 nextThread = thr;
 375                                 break;
 376                         }
 377                 } else if (thr != old && !thr->is_freed()) {
 378                         thr->freeResources();
 379                 }
 380
 381                 ModelAction *act = thr->get_pending();
 382                 if (act && execution->is_enabled(tid)){
 383                         /* Don't schedule threads which should be disabled */
 384                         if (!execution->check_action_enabled(act)) {
 385                                 scheduler->sleep(thr);
 386                         }
 387
 388                         /* Allow pending relaxed/release stores or thread actions to perform first */
 389                         else if (!thread_chosen) {
 390                                 if (act->is_write()) {
 391                                         std::memory_order order = act->get_mo();
 392                                         if (order == std::memory_order_relaxed || \
 393                                                         order == std::memory_order_release) {
 394                                                 chosen_thread = thr;
 395                                                 thread_chosen = true;
 396                                         }
 397                                 } else if (act->get_type() == THREAD_CREATE || \
 398                                                                          act->get_type() == PTHREAD_CREATE || \
 399                                                                          act->get_type() == THREAD_START || \
 400                                                                          act->get_type() == THREAD_FINISH) {
 401                                         chosen_thread = thr;
 402                                         thread_chosen = true;
 403                                 }
 404                         }
 405                 }
 406         }
 407         return nextThread;
 408 }
 409
 410 /* Swap back to system_context and terminate this execution */
 411 void ModelChecker::finishRunExecution(Thread *old)
 412 {
 413         scheduler->set_current_thread(NULL);
 414
 415         /** Reset curr_thread_num to initial value for next execution. */
 416         curr_thread_num = 1;
 417
 418         /** If we have more executions, we won't make it past this call. */
 419         finish_execution(execution_number < params.maxexecutions);
 420
 421
 422         /** We finished the final execution.  Print stuff and exit. */
 423         model_print("******* Model-checking complete: *******\n");
 424         print_stats();
 425
 426         /* Have the trace analyses dump their output. */
 427         for (unsigned int i = 0;i < trace_analyses.size();i++)
 428                 trace_analyses[i]->finish();
 429
 430         /* unlink tmp file created by last child process */
 431         char filename[256];
 432         snprintf_(filename, sizeof(filename), "C11FuzzerTmp%d", getpid());
 433         unlink(filename);
 434
 435         /* Exit. */
 436         _Exit(0);
 437 }
 438
 439 uint64_t ModelChecker::switch_thread(ModelAction *act)
 440 {
 441         if (modellock) {
 442                 static bool fork_message_printed = false;
 443
 444                 if (!fork_message_printed) {
 445                         model_print("Fork handler or dead thread trying to call into model checker...\n");
 446                         fork_message_printed = true;
 447                 }
 448                 delete act;
 449                 return 0;
 450         }
 451         DBG();
 452         Thread *old = thread_current();
 453         old->set_state(THREAD_READY);
 454
 455         ASSERT(!old->get_pending());
 456
 457         if (inspect_plugin != NULL) {
 458                 inspect_plugin->inspectModelAction(act);
 459         }
 460
 461         old->set_pending(act);
 462
 463         if (old->is_waiting_on(old))
 464                 assert_bug("Deadlock detected (thread %u)", curr_thread_num);
 465
 466         Thread* next = getNextThread(old);
 467         if (next != nullptr) {
 468                 scheduler->set_current_thread(next);
 469                 if (Thread::swap(old, next) < 0) {
 470                         perror("swap threads");
 471                         exit(EXIT_FAILURE);
 472                 }
 473         } else {
 474                 if (handleChosenThread(old)) {
 475                         startRunExecution(old);
 476                 }
 477         }
 478         return old->get_return_value();
 479 }
 480
 481 bool ModelChecker::handleChosenThread(Thread *old)
 482 {
 483         if (execution->has_asserted()) {
 484                 finishRunExecution(old);
 485                 return false;
 486         }
 487         if (!chosen_thread) {
 488                 chosen_thread = get_next_thread();
 489         }
 490         if (!chosen_thread || chosen_thread->is_model_thread()) {
 491                 finishRunExecution(old);
 492                 return false;
 493         }
 494         if (chosen_thread->just_woken_up()) {
 495                 chosen_thread->set_wakeup_state(false);
 496                 chosen_thread->set_pending(NULL);
 497                 chosen_thread = NULL;
 498                 // Allow this thread to stash the next pending action
 499                 return true;
 500         }
 501
 502         // Consume the next action for a Thread
 503         ModelAction *curr = chosen_thread->get_pending();
 504         chosen_thread->set_pending(NULL);
 505         chosen_thread = execution->take_step(curr);
 506
 507         if (should_terminate_execution()) {
 508                 finishRunExecution(old);
 509                 return false;
 510         } else {
 511                 return true;
 512         }
 513 }
 514
 515 void ModelChecker::startChecker() {
 516         startExecution();
 517         //Need to initial random number generator state to avoid resets on rollback
 518         initstate(423121, random_state, sizeof(random_state));
 519
 520         snapshot = take_snapshot();
 521
 522         //reset random number generator state
 523         setstate(random_state);
 524
 525         install_trace_analyses(get_execution());
 526         redirect_output();
 527         initMainThread();
 528 }
 529
 530 bool ModelChecker::should_terminate_execution()
 531 {
 532         if (execution->have_bug_reports()) {
 533                 execution->set_assert();
 534                 return true;
 535         } else if (execution->isFinished()) {
 536                 return true;
 537         }
 538         return false;
 539 }