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 /** @brief Constructor */
  30 ModelChecker::ModelChecker() :
  31         /* Initialize default scheduler */
  32         params(),
  33         restart_flag(false),
  34         scheduler(new Scheduler()),
  35         history(new ModelHistory()),
  36         execution(new ModelExecution(this, scheduler)),
  37         execution_number(1),
  38         trace_analyses(),
  39         inspect_plugin(NULL)
  40 {
  41         model_print("C11Tester\n"
  42                                                         "Copyright (c) 2013 and 2019 Regents of the University of California. All rights reserved.\n"
  43                                                         "Distributed under the GPLv2\n"
  44                                                         "Written by Weiyu Luo, Brian Norris, and Brian Demsky\n\n");
  45         memset(&stats,0,sizeof(struct execution_stats));
  46         init_thread = new Thread(execution->get_next_id(), (thrd_t *) model_malloc(sizeof(thrd_t)), &placeholder, NULL, NULL);
  47 #ifdef TLS
  48         init_thread->setTLS((char *)get_tls_addr());
  49 #endif
  50         execution->add_thread(init_thread);
  51         scheduler->set_current_thread(init_thread);
  52         register_plugins();
  53         execution->setParams(&params);
  54         param_defaults(&params);
  55         parse_options(&params);
  56         initRaceDetector();
  57         /* Configure output redirection for the model-checker */
  58         redirect_output();
  59         install_trace_analyses(get_execution());
  60 }
  61
  62 /** @brief Destructor */
  63 ModelChecker::~ModelChecker()
  64 {
  65         delete scheduler;
  66 }
  67
  68 /** Method to set parameters */
  69 model_params * ModelChecker::getParams() {
  70         return &params;
  71 }
  72
  73 /**
  74  * Restores user program to initial state and resets all model-checker data
  75  * structures.
  76  */
  77 void ModelChecker::reset_to_initial_state()
  78 {
  79
  80         /**
  81          * FIXME: if we utilize partial rollback, we will need to free only
  82          * those pending actions which were NOT pending before the rollback
  83          * point
  84          */
  85         for (unsigned int i = 0;i < get_num_threads();i++)
  86                 delete get_thread(int_to_id(i))->get_pending();
  87
  88         snapshot_roll_back(snapshot);
  89 }
  90
  91 /** @return the number of user threads created during this execution */
  92 unsigned int ModelChecker::get_num_threads() const
  93 {
  94         return execution->get_num_threads();
  95 }
  96
  97 /**
  98  * Must be called from user-thread context (e.g., through the global
  99  * thread_current() interface)
 100  *
 101  * @return The currently executing Thread.
 102  */
 103 Thread * ModelChecker::get_current_thread() const
 104 {
 105         return scheduler->get_current_thread();
 106 }
 107
 108 /**
 109  * @brief Choose the next thread to execute.
 110  *
 111  * This function chooses the next thread that should execute. It can enforce
 112  * execution replay/backtracking or, if the model-checker has no preference
 113  * regarding the next thread (i.e., when exploring a new execution ordering),
 114  * we defer to the scheduler.
 115  *
 116  * @return The next chosen thread to run, if any exist. Or else if the current
 117  * execution should terminate, return NULL.
 118  */
 119 Thread * ModelChecker::get_next_thread()
 120 {
 121
 122         /*
 123          * Have we completed exploring the preselected path? Then let the
 124          * scheduler decide
 125          */
 126         return scheduler->select_next_thread();
 127 }
 128
 129 /**
 130  * @brief Assert a bug in the executing program.
 131  *
 132  * Use this function to assert any sort of bug in the user program. If the
 133  * current trace is feasible (actually, a prefix of some feasible execution),
 134  * then this execution will be aborted, printing the appropriate message. If
 135  * the current trace is not yet feasible, the error message will be stashed and
 136  * printed if the execution ever becomes feasible.
 137  *
 138  * @param msg Descriptive message for the bug (do not include newline char)
 139  * @return True if bug is immediately-feasible
 140  */
 141 void ModelChecker::assert_bug(const char *msg, ...)
 142 {
 143         char str[800];
 144
 145         va_list ap;
 146         va_start(ap, msg);
 147         vsnprintf(str, sizeof(str), msg, ap);
 148         va_end(ap);
 149
 150         execution->assert_bug(str);
 151 }
 152
 153 /**
 154  * @brief Assert a bug in the executing program, asserted by a user thread
 155  * @see ModelChecker::assert_bug
 156  * @param msg Descriptive message for the bug (do not include newline char)
 157  */
 158 void ModelChecker::assert_user_bug(const char *msg)
 159 {
 160         /* If feasible bug, bail out now */
 161         assert_bug(msg);
 162         switch_to_master(NULL);
 163 }
 164
 165 /** @brief Print bug report listing for this execution (if any bugs exist) */
 166 void ModelChecker::print_bugs() const
 167 {
 168         SnapVector<bug_message *> *bugs = execution->get_bugs();
 169
 170         model_print("Bug report: %zu bug%s detected\n",
 171                                                         bugs->size(),
 172                                                         bugs->size() > 1 ? "s" : "");
 173         for (unsigned int i = 0;i < bugs->size();i++)
 174                 (*bugs)[i] -> print();
 175 }
 176
 177 /**
 178  * @brief Record end-of-execution stats
 179  *
 180  * Must be run when exiting an execution. Records various stats.
 181  * @see struct execution_stats
 182  */
 183 void ModelChecker::record_stats()
 184 {
 185         stats.num_total ++;
 186         if (execution->have_bug_reports())
 187                 stats.num_buggy_executions ++;
 188         else if (execution->is_complete_execution())
 189                 stats.num_complete ++;
 190         else {
 191                 //All threads are sleeping
 192                 /**
 193                  * @todo We can violate this ASSERT() when fairness/sleep sets
 194                  * conflict to cause an execution to terminate, e.g. with:
 195                  * Scheduler: [0: disabled][1: disabled][2: sleep][3: current, enabled]
 196                  */
 197                 //ASSERT(scheduler->all_threads_sleeping());
 198         }
 199 }
 200
 201 /** @brief Print execution stats */
 202 void ModelChecker::print_stats() const
 203 {
 204         model_print("Number of complete, bug-free executions: %d\n", stats.num_complete);
 205         model_print("Number of buggy executions: %d\n", stats.num_buggy_executions);
 206         model_print("Total executions: %d\n", stats.num_total);
 207 }
 208
 209 /**
 210  * @brief End-of-exeuction print
 211  * @param printbugs Should any existing bugs be printed?
 212  */
 213 void ModelChecker::print_execution(bool printbugs) const
 214 {
 215         model_print("Program output from execution %d:\n",
 216                                                         get_execution_number());
 217         print_program_output();
 218
 219         if (params.verbose >= 3) {
 220                 print_stats();
 221         }
 222
 223         /* Don't print invalid bugs */
 224         if (printbugs && execution->have_bug_reports()) {
 225                 model_print("\n");
 226                 print_bugs();
 227         }
 228
 229         model_print("\n");
 230         execution->print_summary();
 231 }
 232
 233 /**
 234  * Queries the model-checker for more executions to explore and, if one
 235  * exists, resets the model-checker state to execute a new execution.
 236  *
 237  * @return If there are more executions to explore, return true. Otherwise,
 238  * return false.
 239  */
 240 bool ModelChecker::next_execution()
 241 {
 242         DBG();
 243         /* Is this execution a feasible execution that's worth bug-checking? */
 244         bool complete = (execution->is_complete_execution() ||
 245                                                                          execution->have_bug_reports());
 246
 247         /* End-of-execution bug checks */
 248         if (complete) {
 249                 if (execution->is_deadlocked())
 250                         assert_bug("Deadlock detected");
 251
 252                 run_trace_analyses();
 253         }
 254
 255         record_stats();
 256         /* Output */
 257         if ( (complete && params.verbose) || params.verbose>1 || (complete && execution->have_bug_reports()))
 258                 print_execution(complete);
 259         else
 260                 clear_program_output();
 261
 262         if (restart_flag) {
 263                 do_restart();
 264                 return true;
 265         }
 266 // test code
 267         execution_number ++;
 268         reset_to_initial_state();
 269         history->set_new_exec_flag();
 270         return false;
 271 }
 272
 273 /** @brief Run trace analyses on complete trace */
 274 void ModelChecker::run_trace_analyses() {
 275         for (unsigned int i = 0;i < trace_analyses.size();i ++)
 276                 trace_analyses[i] -> analyze(execution->get_action_trace());
 277 }
 278
 279 /**
 280  * @brief Get a Thread reference by its ID
 281  * @param tid The Thread's ID
 282  * @return A Thread reference
 283  */
 284 Thread * ModelChecker::get_thread(thread_id_t tid) const
 285 {
 286         return execution->get_thread(tid);
 287 }
 288
 289 /**
 290  * @brief Get a reference to the Thread in which a ModelAction was executed
 291  * @param act The ModelAction
 292  * @return A Thread reference
 293  */
 294 Thread * ModelChecker::get_thread(const ModelAction *act) const
 295 {
 296         return execution->get_thread(act);
 297 }
 298
 299 /**
 300  * Switch from a model-checker context to a user-thread context. This is the
 301  * complement of ModelChecker::switch_to_master and must be called from the
 302  * model-checker context
 303  *
 304  * @param thread The user-thread to switch to
 305  */
 306 void ModelChecker::switch_from_master(Thread *thread)
 307 {
 308         scheduler->set_current_thread(thread);
 309         Thread::swap(&system_context, thread);
 310 }
 311
 312 /**
 313  * Switch from a user-context to the "master thread" context (a.k.a. system
 314  * context). This switch is made with the intention of exploring a particular
 315  * model-checking action (described by a ModelAction object). Must be called
 316  * from a user-thread context.
 317  *
 318  * @param act The current action that will be explored. May be NULL only if
 319  * trace is exiting via an assertion (see ModelExecution::set_assert and
 320  * ModelExecution::has_asserted).
 321  * @return Return the value returned by the current action
 322  */
 323 uint64_t ModelChecker::switch_to_master(ModelAction *act)
 324 {
 325         if (modellock) {
 326                 static bool fork_message_printed = false;
 327
 328                 if (!fork_message_printed) {
 329                         model_print("Fork handler or dead thread trying to call into model checker...\n");
 330                         fork_message_printed = true;
 331                 }
 332                 delete act;
 333                 return 0;
 334         }
 335         DBG();
 336         Thread *old = thread_current();
 337         scheduler->set_current_thread(NULL);
 338         ASSERT(!old->get_pending());
 339
 340         if (inspect_plugin != NULL) {
 341                 inspect_plugin->inspectModelAction(act);
 342         }
 343
 344         old->set_pending(act);
 345         if (Thread::swap(old, &system_context) < 0) {
 346                 perror("swap threads");
 347                 exit(EXIT_FAILURE);
 348         }
 349         return old->get_return_value();
 350 }
 351
 352 static void runChecker() {
 353         model->run();
 354         delete model;
 355 }
 356
 357 void ModelChecker::startChecker() {
 358         startExecution(get_system_context(), runChecker);
 359         snapshot = take_snapshot();
 360         initMainThread();
 361 }
 362
 363 bool ModelChecker::should_terminate_execution()
 364 {
 365         if (execution->have_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 /** @brief Run ModelChecker for the user program */
 390 void ModelChecker::run()
 391 {
 392         //Need to initial random number generator state to avoid resets on rollback
 393         char random_state[256];
 394         initstate(423121, random_state, sizeof(random_state));
 395
 396         for(int exec = 0;exec < params.maxexecutions;exec++) {
 397                 Thread * t = init_thread;
 398
 399                 do {
 400                         /*
 401                          * Stash next pending action(s) for thread(s). There
 402                          * should only need to stash one thread's action--the
 403                          * thread which just took a step--plus the first step
 404                          * for any newly-created thread
 405                          */
 406                         for (unsigned int i = 0;i < get_num_threads();i++) {
 407                                 thread_id_t tid = int_to_id(i);
 408                                 Thread *thr = get_thread(tid);
 409                                 if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
 410                                         switch_from_master(thr);
 411                                         if (thr->is_waiting_on(thr))
 412                                                 assert_bug("Deadlock detected (thread %u)", i);
 413                                 }
 414                         }
 415
 416                         /* Don't schedule threads which should be disabled */
 417                         for (unsigned int i = 0;i < get_num_threads();i++) {
 418                                 Thread *th = get_thread(int_to_id(i));
 419                                 ModelAction *act = th->get_pending();
 420                                 if (act && execution->is_enabled(th) && !execution->check_action_enabled(act)) {
 421                                         scheduler->sleep(th);
 422                                 }
 423                         }
 424
 425                         for (unsigned int i = 1;i < get_num_threads();i++) {
 426                                 Thread *th = get_thread(int_to_id(i));
 427                                 ModelAction *act = th->get_pending();
 428                                 if (act && execution->is_enabled(th) && (th->get_state() != THREAD_BLOCKED) ) {
 429                                         if (act->is_write()) {
 430                                                 std::memory_order order = act->get_mo();
 431                                                 if (order == std::memory_order_relaxed || \
 432                                                                 order == std::memory_order_release) {
 433                                                         t = th;
 434                                                         break;
 435                                                 }
 436                                         } else if (act->get_type() == THREAD_CREATE || \
 437                                                                                  act->get_type() == PTHREAD_CREATE || \
 438                                                                                  act->get_type() == THREAD_START || \
 439                                                                                  act->get_type() == THREAD_FINISH) {
 440                                                 t = th;
 441                                                 break;
 442                                         }
 443                                 }
 444                         }
 445
 446                         /* Catch assertions from prior take_step or from
 447                         * between-ModelAction bugs (e.g., data races) */
 448
 449                         if (execution->has_asserted())
 450                                 break;
 451                         if (!t)
 452                                 t = get_next_thread();
 453                         if (!t || t->is_model_thread())
 454                                 break;
 455                         if (t->just_woken_up()) {
 456                                 t->set_wakeup_state(false);
 457                                 t->set_pending(NULL);
 458                                 t = NULL;
 459                                 continue;       // Allow this thread to stash the next pending action
 460                         }
 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 }