contrib/llvm/tools/clang/lib/StaticAnalyzer/Checkers/PthreadLockChecker.cpp

   1 //===--- PthreadLockChecker.cpp - Check for locking problems ---*- C++ -*--===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This defines PthreadLockChecker, a simple lock -> unlock checker.
  11 // Also handles XNU locks, which behave similarly enough to share code.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
  16 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
  17 #include "clang/StaticAnalyzer/Core/Checker.h"
  18 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
  19 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
  20 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
  21
  22 using namespace clang;
  23 using namespace ento;
  24
  25 namespace {
  26
  27 struct LockState {
  28   enum Kind {
  29     Destroyed,
  30     Locked,
  31     Unlocked,
  32     UntouchedAndPossiblyDestroyed,
  33     UnlockedAndPossiblyDestroyed
  34   } K;
  35
  36 private:
  37   LockState(Kind K) : K(K) {}
  38
  39 public:
  40   static LockState getLocked() { return LockState(Locked); }
  41   static LockState getUnlocked() { return LockState(Unlocked); }
  42   static LockState getDestroyed() { return LockState(Destroyed); }
  43   static LockState getUntouchedAndPossiblyDestroyed() {
  44     return LockState(UntouchedAndPossiblyDestroyed);
  45   }
  46   static LockState getUnlockedAndPossiblyDestroyed() {
  47     return LockState(UnlockedAndPossiblyDestroyed);
  48   }
  49
  50   bool operator==(const LockState &X) const {
  51     return K == X.K;
  52   }
  53
  54   bool isLocked() const { return K == Locked; }
  55   bool isUnlocked() const { return K == Unlocked; }
  56   bool isDestroyed() const { return K == Destroyed; }
  57   bool isUntouchedAndPossiblyDestroyed() const {
  58     return K == UntouchedAndPossiblyDestroyed;
  59   }
  60   bool isUnlockedAndPossiblyDestroyed() const {
  61     return K == UnlockedAndPossiblyDestroyed;
  62   }
  63
  64   void Profile(llvm::FoldingSetNodeID &ID) const {
  65     ID.AddInteger(K);
  66   }
  67 };
  68
  69 class PthreadLockChecker
  70     : public Checker<check::PostStmt<CallExpr>, check::DeadSymbols> {
  71   mutable std::unique_ptr<BugType> BT_doublelock;
  72   mutable std::unique_ptr<BugType> BT_doubleunlock;
  73   mutable std::unique_ptr<BugType> BT_destroylock;
  74   mutable std::unique_ptr<BugType> BT_initlock;
  75   mutable std::unique_ptr<BugType> BT_lor;
  76   enum LockingSemantics {
  77     NotApplicable = 0,
  78     PthreadSemantics,
  79     XNUSemantics
  80   };
  81 public:
  82   void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
  83   void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;
  84   void printState(raw_ostream &Out, ProgramStateRef State,
  85                   const char *NL, const char *Sep) const override;
  86
  87   void AcquireLock(CheckerContext &C, const CallExpr *CE, SVal lock,
  88                    bool isTryLock, enum LockingSemantics semantics) const;
  89
  90   void ReleaseLock(CheckerContext &C, const CallExpr *CE, SVal lock) const;
  91   void DestroyLock(CheckerContext &C, const CallExpr *CE, SVal Lock,
  92                    enum LockingSemantics semantics) const;
  93   void InitLock(CheckerContext &C, const CallExpr *CE, SVal Lock) const;
  94   void reportUseDestroyedBug(CheckerContext &C, const CallExpr *CE) const;
  95   ProgramStateRef resolvePossiblyDestroyedMutex(ProgramStateRef state,
  96                                                 const MemRegion *lockR,
  97                                                 const SymbolRef *sym) const;
  98 };
  99 } // end anonymous namespace
 100
 101 // A stack of locks for tracking lock-unlock order.
 102 REGISTER_LIST_WITH_PROGRAMSTATE(LockSet, const MemRegion *)
 103
 104 // An entry for tracking lock states.
 105 REGISTER_MAP_WITH_PROGRAMSTATE(LockMap, const MemRegion *, LockState)
 106
 107 // Return values for unresolved calls to pthread_mutex_destroy().
 108 REGISTER_MAP_WITH_PROGRAMSTATE(DestroyRetVal, const MemRegion *, SymbolRef)
 109
 110 void PthreadLockChecker::checkPostStmt(const CallExpr *CE,
 111                                        CheckerContext &C) const {
 112   StringRef FName = C.getCalleeName(CE);
 113   if (FName.empty())
 114     return;
 115
 116   if (CE->getNumArgs() != 1 && CE->getNumArgs() != 2)
 117     return;
 118
 119   if (FName == "pthread_mutex_lock" ||
 120       FName == "pthread_rwlock_rdlock" ||
 121       FName == "pthread_rwlock_wrlock")
 122     AcquireLock(C, CE, C.getSVal(CE->getArg(0)), false, PthreadSemantics);
 123   else if (FName == "lck_mtx_lock" ||
 124            FName == "lck_rw_lock_exclusive" ||
 125            FName == "lck_rw_lock_shared")
 126     AcquireLock(C, CE, C.getSVal(CE->getArg(0)), false, XNUSemantics);
 127   else if (FName == "pthread_mutex_trylock" ||
 128            FName == "pthread_rwlock_tryrdlock" ||
 129            FName == "pthread_rwlock_trywrlock")
 130     AcquireLock(C, CE, C.getSVal(CE->getArg(0)),
 131                 true, PthreadSemantics);
 132   else if (FName == "lck_mtx_try_lock" ||
 133            FName == "lck_rw_try_lock_exclusive" ||
 134            FName == "lck_rw_try_lock_shared")
 135     AcquireLock(C, CE, C.getSVal(CE->getArg(0)), true, XNUSemantics);
 136   else if (FName == "pthread_mutex_unlock" ||
 137            FName == "pthread_rwlock_unlock" ||
 138            FName == "lck_mtx_unlock" ||
 139            FName == "lck_rw_done")
 140     ReleaseLock(C, CE, C.getSVal(CE->getArg(0)));
 141   else if (FName == "pthread_mutex_destroy")
 142     DestroyLock(C, CE, C.getSVal(CE->getArg(0)), PthreadSemantics);
 143   else if (FName == "lck_mtx_destroy")
 144     DestroyLock(C, CE, C.getSVal(CE->getArg(0)), XNUSemantics);
 145   else if (FName == "pthread_mutex_init")
 146     InitLock(C, CE, C.getSVal(CE->getArg(0)));
 147 }
 148
 149 // When a lock is destroyed, in some semantics(like PthreadSemantics) we are not
 150 // sure if the destroy call has succeeded or failed, and the lock enters one of
 151 // the 'possibly destroyed' state. There is a short time frame for the
 152 // programmer to check the return value to see if the lock was successfully
 153 // destroyed. Before we model the next operation over that lock, we call this
 154 // function to see if the return value was checked by now and set the lock state
 155 // - either to destroyed state or back to its previous state.
 156
 157 // In PthreadSemantics, pthread_mutex_destroy() returns zero if the lock is
 158 // successfully destroyed and it returns a non-zero value otherwise.
 159 ProgramStateRef PthreadLockChecker::resolvePossiblyDestroyedMutex(
 160     ProgramStateRef state, const MemRegion *lockR, const SymbolRef *sym) const {
 161   const LockState *lstate = state->get<LockMap>(lockR);
 162   // Existence in DestroyRetVal ensures existence in LockMap.
 163   // Existence in Destroyed also ensures that the lock state for lockR is either
 164   // UntouchedAndPossiblyDestroyed or UnlockedAndPossiblyDestroyed.
 165   assert(lstate->isUntouchedAndPossiblyDestroyed() ||
 166          lstate->isUnlockedAndPossiblyDestroyed());
 167
 168   ConstraintManager &CMgr = state->getConstraintManager();
 169   ConditionTruthVal retZero = CMgr.isNull(state, *sym);
 170   if (retZero.isConstrainedFalse()) {
 171     if (lstate->isUntouchedAndPossiblyDestroyed())
 172       state = state->remove<LockMap>(lockR);
 173     else if (lstate->isUnlockedAndPossiblyDestroyed())
 174       state = state->set<LockMap>(lockR, LockState::getUnlocked());
 175   } else
 176     state = state->set<LockMap>(lockR, LockState::getDestroyed());
 177
 178   // Removing the map entry (lockR, sym) from DestroyRetVal as the lock state is
 179   // now resolved.
 180   state = state->remove<DestroyRetVal>(lockR);
 181   return state;
 182 }
 183
 184 void PthreadLockChecker::printState(raw_ostream &Out, ProgramStateRef State,
 185                                     const char *NL, const char *Sep) const {
 186   LockMapTy LM = State->get<LockMap>();
 187   if (!LM.isEmpty()) {
 188     Out << Sep << "Mutex states:" << NL;
 189     for (auto I : LM) {
 190       I.first->dumpToStream(Out);
 191       if (I.second.isLocked())
 192         Out << ": locked";
 193       else if (I.second.isUnlocked())
 194         Out << ": unlocked";
 195       else if (I.second.isDestroyed())
 196         Out << ": destroyed";
 197       else if (I.second.isUntouchedAndPossiblyDestroyed())
 198         Out << ": not tracked, possibly destroyed";
 199       else if (I.second.isUnlockedAndPossiblyDestroyed())
 200         Out << ": unlocked, possibly destroyed";
 201       Out << NL;
 202     }
 203   }
 204
 205   LockSetTy LS = State->get<LockSet>();
 206   if (!LS.isEmpty()) {
 207     Out << Sep << "Mutex lock order:" << NL;
 208     for (auto I: LS) {
 209       I->dumpToStream(Out);
 210       Out << NL;
 211     }
 212   }
 213
 214   // TODO: Dump destroyed mutex symbols?
 215 }
 216
 217 void PthreadLockChecker::AcquireLock(CheckerContext &C, const CallExpr *CE,
 218                                      SVal lock, bool isTryLock,
 219                                      enum LockingSemantics semantics) const {
 220
 221   const MemRegion *lockR = lock.getAsRegion();
 222   if (!lockR)
 223     return;
 224
 225   ProgramStateRef state = C.getState();
 226   const SymbolRef *sym = state->get<DestroyRetVal>(lockR);
 227   if (sym)
 228     state = resolvePossiblyDestroyedMutex(state, lockR, sym);
 229
 230   SVal X = C.getSVal(CE);
 231   if (X.isUnknownOrUndef())
 232     return;
 233
 234   DefinedSVal retVal = X.castAs<DefinedSVal>();
 235
 236   if (const LockState *LState = state->get<LockMap>(lockR)) {
 237     if (LState->isLocked()) {
 238       if (!BT_doublelock)
 239         BT_doublelock.reset(new BugType(this, "Double locking",
 240                                         "Lock checker"));
 241       ExplodedNode *N = C.generateErrorNode();
 242       if (!N)
 243         return;
 244       auto report = llvm::make_unique<BugReport>(
 245           *BT_doublelock, "This lock has already been acquired", N);
 246       report->addRange(CE->getArg(0)->getSourceRange());
 247       C.emitReport(std::move(report));
 248       return;
 249     } else if (LState->isDestroyed()) {
 250       reportUseDestroyedBug(C, CE);
 251       return;
 252     }
 253   }
 254
 255   ProgramStateRef lockSucc = state;
 256   if (isTryLock) {
 257     // Bifurcate the state, and allow a mode where the lock acquisition fails.
 258     ProgramStateRef lockFail;
 259     switch (semantics) {
 260     case PthreadSemantics:
 261       std::tie(lockFail, lockSucc) = state->assume(retVal);
 262       break;
 263     case XNUSemantics:
 264       std::tie(lockSucc, lockFail) = state->assume(retVal);
 265       break;
 266     default:
 267       llvm_unreachable("Unknown tryLock locking semantics");
 268     }
 269     assert(lockFail && lockSucc);
 270     C.addTransition(lockFail);
 271
 272   } else if (semantics == PthreadSemantics) {
 273     // Assume that the return value was 0.
 274     lockSucc = state->assume(retVal, false);
 275     assert(lockSucc);
 276
 277   } else {
 278     // XNU locking semantics return void on non-try locks
 279     assert((semantics == XNUSemantics) && "Unknown locking semantics");
 280     lockSucc = state;
 281   }
 282
 283   // Record that the lock was acquired.
 284   lockSucc = lockSucc->add<LockSet>(lockR);
 285   lockSucc = lockSucc->set<LockMap>(lockR, LockState::getLocked());
 286   C.addTransition(lockSucc);
 287 }
 288
 289 void PthreadLockChecker::ReleaseLock(CheckerContext &C, const CallExpr *CE,
 290                                      SVal lock) const {
 291
 292   const MemRegion *lockR = lock.getAsRegion();
 293   if (!lockR)
 294     return;
 295
 296   ProgramStateRef state = C.getState();
 297   const SymbolRef *sym = state->get<DestroyRetVal>(lockR);
 298   if (sym)
 299     state = resolvePossiblyDestroyedMutex(state, lockR, sym);
 300
 301   if (const LockState *LState = state->get<LockMap>(lockR)) {
 302     if (LState->isUnlocked()) {
 303       if (!BT_doubleunlock)
 304         BT_doubleunlock.reset(new BugType(this, "Double unlocking",
 305                                           "Lock checker"));
 306       ExplodedNode *N = C.generateErrorNode();
 307       if (!N)
 308         return;
 309       auto Report = llvm::make_unique<BugReport>(
 310           *BT_doubleunlock, "This lock has already been unlocked", N);
 311       Report->addRange(CE->getArg(0)->getSourceRange());
 312       C.emitReport(std::move(Report));
 313       return;
 314     } else if (LState->isDestroyed()) {
 315       reportUseDestroyedBug(C, CE);
 316       return;
 317     }
 318   }
 319
 320   LockSetTy LS = state->get<LockSet>();
 321
 322   // FIXME: Better analysis requires IPA for wrappers.
 323
 324   if (!LS.isEmpty()) {
 325     const MemRegion *firstLockR = LS.getHead();
 326     if (firstLockR != lockR) {
 327       if (!BT_lor)
 328         BT_lor.reset(new BugType(this, "Lock order reversal", "Lock checker"));
 329       ExplodedNode *N = C.generateErrorNode();
 330       if (!N)
 331         return;
 332       auto report = llvm::make_unique<BugReport>(
 333           *BT_lor, "This was not the most recently acquired lock. Possible "
 334                    "lock order reversal", N);
 335       report->addRange(CE->getArg(0)->getSourceRange());
 336       C.emitReport(std::move(report));
 337       return;
 338     }
 339     // Record that the lock was released.
 340     state = state->set<LockSet>(LS.getTail());
 341   }
 342
 343   state = state->set<LockMap>(lockR, LockState::getUnlocked());
 344   C.addTransition(state);
 345 }
 346
 347 void PthreadLockChecker::DestroyLock(CheckerContext &C, const CallExpr *CE,
 348                                      SVal Lock,
 349                                      enum LockingSemantics semantics) const {
 350
 351   const MemRegion *LockR = Lock.getAsRegion();
 352   if (!LockR)
 353     return;
 354
 355   ProgramStateRef State = C.getState();
 356
 357   const SymbolRef *sym = State->get<DestroyRetVal>(LockR);
 358   if (sym)
 359     State = resolvePossiblyDestroyedMutex(State, LockR, sym);
 360
 361   const LockState *LState = State->get<LockMap>(LockR);
 362   // Checking the return value of the destroy method only in the case of
 363   // PthreadSemantics
 364   if (semantics == PthreadSemantics) {
 365     if (!LState || LState->isUnlocked()) {
 366       SymbolRef sym = C.getSVal(CE).getAsSymbol();
 367       if (!sym) {
 368         State = State->remove<LockMap>(LockR);
 369         C.addTransition(State);
 370         return;
 371       }
 372       State = State->set<DestroyRetVal>(LockR, sym);
 373       if (LState && LState->isUnlocked())
 374         State = State->set<LockMap>(
 375             LockR, LockState::getUnlockedAndPossiblyDestroyed());
 376       else
 377         State = State->set<LockMap>(
 378             LockR, LockState::getUntouchedAndPossiblyDestroyed());
 379       C.addTransition(State);
 380       return;
 381     }
 382   } else {
 383     if (!LState || LState->isUnlocked()) {
 384       State = State->set<LockMap>(LockR, LockState::getDestroyed());
 385       C.addTransition(State);
 386       return;
 387     }
 388   }
 389   StringRef Message;
 390
 391   if (LState->isLocked()) {
 392     Message = "This lock is still locked";
 393   } else {
 394     Message = "This lock has already been destroyed";
 395   }
 396
 397   if (!BT_destroylock)
 398     BT_destroylock.reset(new BugType(this, "Destroy invalid lock",
 399                                      "Lock checker"));
 400   ExplodedNode *N = C.generateErrorNode();
 401   if (!N)
 402     return;
 403   auto Report = llvm::make_unique<BugReport>(*BT_destroylock, Message, N);
 404   Report->addRange(CE->getArg(0)->getSourceRange());
 405   C.emitReport(std::move(Report));
 406 }
 407
 408 void PthreadLockChecker::InitLock(CheckerContext &C, const CallExpr *CE,
 409                                   SVal Lock) const {
 410
 411   const MemRegion *LockR = Lock.getAsRegion();
 412   if (!LockR)
 413     return;
 414
 415   ProgramStateRef State = C.getState();
 416
 417   const SymbolRef *sym = State->get<DestroyRetVal>(LockR);
 418   if (sym)
 419     State = resolvePossiblyDestroyedMutex(State, LockR, sym);
 420
 421   const struct LockState *LState = State->get<LockMap>(LockR);
 422   if (!LState || LState->isDestroyed()) {
 423     State = State->set<LockMap>(LockR, LockState::getUnlocked());
 424     C.addTransition(State);
 425     return;
 426   }
 427
 428   StringRef Message;
 429
 430   if (LState->isLocked()) {
 431     Message = "This lock is still being held";
 432   } else {
 433     Message = "This lock has already been initialized";
 434   }
 435
 436   if (!BT_initlock)
 437     BT_initlock.reset(new BugType(this, "Init invalid lock",
 438                                   "Lock checker"));
 439   ExplodedNode *N = C.generateErrorNode();
 440   if (!N)
 441     return;
 442   auto Report = llvm::make_unique<BugReport>(*BT_initlock, Message, N);
 443   Report->addRange(CE->getArg(0)->getSourceRange());
 444   C.emitReport(std::move(Report));
 445 }
 446
 447 void PthreadLockChecker::reportUseDestroyedBug(CheckerContext &C,
 448                                                const CallExpr *CE) const {
 449   if (!BT_destroylock)
 450     BT_destroylock.reset(new BugType(this, "Use destroyed lock",
 451                                      "Lock checker"));
 452   ExplodedNode *N = C.generateErrorNode();
 453   if (!N)
 454     return;
 455   auto Report = llvm::make_unique<BugReport>(
 456       *BT_destroylock, "This lock has already been destroyed", N);
 457   Report->addRange(CE->getArg(0)->getSourceRange());
 458   C.emitReport(std::move(Report));
 459 }
 460
 461 void PthreadLockChecker::checkDeadSymbols(SymbolReaper &SymReaper,
 462                                           CheckerContext &C) const {
 463   ProgramStateRef State = C.getState();
 464
 465   // TODO: Clean LockMap when a mutex region dies.
 466
 467   DestroyRetValTy TrackedSymbols = State->get<DestroyRetVal>();
 468   for (DestroyRetValTy::iterator I = TrackedSymbols.begin(),
 469                                  E = TrackedSymbols.end();
 470        I != E; ++I) {
 471     const SymbolRef Sym = I->second;
 472     const MemRegion *lockR = I->first;
 473     bool IsSymDead = SymReaper.isDead(Sym);
 474     // Remove the dead symbol from the return value symbols map.
 475     if (IsSymDead)
 476       State = resolvePossiblyDestroyedMutex(State, lockR, &Sym);
 477   }
 478   C.addTransition(State);
 479 }
 480
 481 void ento::registerPthreadLockChecker(CheckerManager &mgr) {
 482   mgr.registerChecker<PthreadLockChecker>();
 483 }