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335 lines
11 KiB
335 lines
11 KiB
//===--- PthreadLockChecker.cpp - Check for locking problems ---*- C++ -*--===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This defines PthreadLockChecker, a simple lock -> unlock checker.
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// Also handles XNU locks, which behave similarly enough to share code.
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//
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//===----------------------------------------------------------------------===//
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#include "ClangSACheckers.h"
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#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
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#include "clang/StaticAnalyzer/Core/Checker.h"
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#include "clang/StaticAnalyzer/Core/CheckerManager.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
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#include "llvm/ADT/ImmutableList.h"
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using namespace clang;
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using namespace ento;
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namespace {
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struct LockState {
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enum Kind { Destroyed, Locked, Unlocked } K;
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private:
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LockState(Kind K) : K(K) {}
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public:
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static LockState getLocked() { return LockState(Locked); }
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static LockState getUnlocked() { return LockState(Unlocked); }
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static LockState getDestroyed() { return LockState(Destroyed); }
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bool operator==(const LockState &X) const {
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return K == X.K;
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}
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bool isLocked() const { return K == Locked; }
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bool isUnlocked() const { return K == Unlocked; }
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bool isDestroyed() const { return K == Destroyed; }
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void Profile(llvm::FoldingSetNodeID &ID) const {
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ID.AddInteger(K);
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}
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};
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class PthreadLockChecker : public Checker< check::PostStmt<CallExpr> > {
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mutable std::unique_ptr<BugType> BT_doublelock;
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mutable std::unique_ptr<BugType> BT_doubleunlock;
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mutable std::unique_ptr<BugType> BT_destroylock;
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mutable std::unique_ptr<BugType> BT_initlock;
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mutable std::unique_ptr<BugType> BT_lor;
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enum LockingSemantics {
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NotApplicable = 0,
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PthreadSemantics,
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XNUSemantics
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};
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public:
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void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
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void AcquireLock(CheckerContext &C, const CallExpr *CE, SVal lock,
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bool isTryLock, enum LockingSemantics semantics) const;
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void ReleaseLock(CheckerContext &C, const CallExpr *CE, SVal lock) const;
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void DestroyLock(CheckerContext &C, const CallExpr *CE, SVal Lock) const;
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void InitLock(CheckerContext &C, const CallExpr *CE, SVal Lock) const;
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void reportUseDestroyedBug(CheckerContext &C, const CallExpr *CE) const;
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};
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} // end anonymous namespace
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// GDM Entry for tracking lock state.
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REGISTER_LIST_WITH_PROGRAMSTATE(LockSet, const MemRegion *)
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REGISTER_MAP_WITH_PROGRAMSTATE(LockMap, const MemRegion *, LockState)
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void PthreadLockChecker::checkPostStmt(const CallExpr *CE,
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CheckerContext &C) const {
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ProgramStateRef state = C.getState();
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const LocationContext *LCtx = C.getLocationContext();
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StringRef FName = C.getCalleeName(CE);
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if (FName.empty())
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return;
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if (CE->getNumArgs() != 1 && CE->getNumArgs() != 2)
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return;
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if (FName == "pthread_mutex_lock" ||
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FName == "pthread_rwlock_rdlock" ||
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FName == "pthread_rwlock_wrlock")
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AcquireLock(C, CE, state->getSVal(CE->getArg(0), LCtx),
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false, PthreadSemantics);
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else if (FName == "lck_mtx_lock" ||
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FName == "lck_rw_lock_exclusive" ||
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FName == "lck_rw_lock_shared")
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AcquireLock(C, CE, state->getSVal(CE->getArg(0), LCtx),
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false, XNUSemantics);
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else if (FName == "pthread_mutex_trylock" ||
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FName == "pthread_rwlock_tryrdlock" ||
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FName == "pthread_rwlock_trywrlock")
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AcquireLock(C, CE, state->getSVal(CE->getArg(0), LCtx),
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true, PthreadSemantics);
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else if (FName == "lck_mtx_try_lock" ||
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FName == "lck_rw_try_lock_exclusive" ||
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FName == "lck_rw_try_lock_shared")
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AcquireLock(C, CE, state->getSVal(CE->getArg(0), LCtx),
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true, XNUSemantics);
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else if (FName == "pthread_mutex_unlock" ||
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FName == "pthread_rwlock_unlock" ||
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FName == "lck_mtx_unlock" ||
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FName == "lck_rw_done")
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ReleaseLock(C, CE, state->getSVal(CE->getArg(0), LCtx));
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else if (FName == "pthread_mutex_destroy" ||
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FName == "lck_mtx_destroy")
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DestroyLock(C, CE, state->getSVal(CE->getArg(0), LCtx));
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else if (FName == "pthread_mutex_init")
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InitLock(C, CE, state->getSVal(CE->getArg(0), LCtx));
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}
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void PthreadLockChecker::AcquireLock(CheckerContext &C, const CallExpr *CE,
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SVal lock, bool isTryLock,
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enum LockingSemantics semantics) const {
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const MemRegion *lockR = lock.getAsRegion();
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if (!lockR)
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return;
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ProgramStateRef state = C.getState();
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SVal X = state->getSVal(CE, C.getLocationContext());
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if (X.isUnknownOrUndef())
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return;
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DefinedSVal retVal = X.castAs<DefinedSVal>();
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if (const LockState *LState = state->get<LockMap>(lockR)) {
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if (LState->isLocked()) {
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if (!BT_doublelock)
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BT_doublelock.reset(new BugType(this, "Double locking",
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"Lock checker"));
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ExplodedNode *N = C.generateErrorNode();
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if (!N)
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return;
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auto report = llvm::make_unique<BugReport>(
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*BT_doublelock, "This lock has already been acquired", N);
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report->addRange(CE->getArg(0)->getSourceRange());
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C.emitReport(std::move(report));
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return;
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} else if (LState->isDestroyed()) {
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reportUseDestroyedBug(C, CE);
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return;
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}
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}
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ProgramStateRef lockSucc = state;
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if (isTryLock) {
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// Bifurcate the state, and allow a mode where the lock acquisition fails.
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ProgramStateRef lockFail;
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switch (semantics) {
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case PthreadSemantics:
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std::tie(lockFail, lockSucc) = state->assume(retVal);
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break;
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case XNUSemantics:
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std::tie(lockSucc, lockFail) = state->assume(retVal);
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break;
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default:
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llvm_unreachable("Unknown tryLock locking semantics");
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}
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assert(lockFail && lockSucc);
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C.addTransition(lockFail);
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} else if (semantics == PthreadSemantics) {
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// Assume that the return value was 0.
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lockSucc = state->assume(retVal, false);
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assert(lockSucc);
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} else {
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// XNU locking semantics return void on non-try locks
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assert((semantics == XNUSemantics) && "Unknown locking semantics");
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lockSucc = state;
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}
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// Record that the lock was acquired.
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lockSucc = lockSucc->add<LockSet>(lockR);
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lockSucc = lockSucc->set<LockMap>(lockR, LockState::getLocked());
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C.addTransition(lockSucc);
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}
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void PthreadLockChecker::ReleaseLock(CheckerContext &C, const CallExpr *CE,
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SVal lock) const {
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const MemRegion *lockR = lock.getAsRegion();
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if (!lockR)
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return;
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ProgramStateRef state = C.getState();
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if (const LockState *LState = state->get<LockMap>(lockR)) {
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if (LState->isUnlocked()) {
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if (!BT_doubleunlock)
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BT_doubleunlock.reset(new BugType(this, "Double unlocking",
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"Lock checker"));
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ExplodedNode *N = C.generateErrorNode();
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if (!N)
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return;
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auto Report = llvm::make_unique<BugReport>(
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*BT_doubleunlock, "This lock has already been unlocked", N);
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Report->addRange(CE->getArg(0)->getSourceRange());
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C.emitReport(std::move(Report));
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return;
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} else if (LState->isDestroyed()) {
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reportUseDestroyedBug(C, CE);
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return;
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}
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}
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LockSetTy LS = state->get<LockSet>();
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// FIXME: Better analysis requires IPA for wrappers.
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if (!LS.isEmpty()) {
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const MemRegion *firstLockR = LS.getHead();
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if (firstLockR != lockR) {
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if (!BT_lor)
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BT_lor.reset(new BugType(this, "Lock order reversal", "Lock checker"));
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ExplodedNode *N = C.generateErrorNode();
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if (!N)
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return;
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auto report = llvm::make_unique<BugReport>(
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*BT_lor, "This was not the most recently acquired lock. Possible "
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"lock order reversal", N);
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report->addRange(CE->getArg(0)->getSourceRange());
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C.emitReport(std::move(report));
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return;
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}
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// Record that the lock was released.
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state = state->set<LockSet>(LS.getTail());
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}
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state = state->set<LockMap>(lockR, LockState::getUnlocked());
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C.addTransition(state);
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}
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void PthreadLockChecker::DestroyLock(CheckerContext &C, const CallExpr *CE,
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SVal Lock) const {
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const MemRegion *LockR = Lock.getAsRegion();
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if (!LockR)
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return;
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ProgramStateRef State = C.getState();
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const LockState *LState = State->get<LockMap>(LockR);
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if (!LState || LState->isUnlocked()) {
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State = State->set<LockMap>(LockR, LockState::getDestroyed());
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C.addTransition(State);
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return;
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}
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StringRef Message;
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if (LState->isLocked()) {
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Message = "This lock is still locked";
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} else {
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Message = "This lock has already been destroyed";
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}
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if (!BT_destroylock)
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BT_destroylock.reset(new BugType(this, "Destroy invalid lock",
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"Lock checker"));
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ExplodedNode *N = C.generateErrorNode();
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if (!N)
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return;
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auto Report = llvm::make_unique<BugReport>(*BT_destroylock, Message, N);
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Report->addRange(CE->getArg(0)->getSourceRange());
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C.emitReport(std::move(Report));
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}
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void PthreadLockChecker::InitLock(CheckerContext &C, const CallExpr *CE,
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SVal Lock) const {
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const MemRegion *LockR = Lock.getAsRegion();
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if (!LockR)
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return;
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ProgramStateRef State = C.getState();
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const struct LockState *LState = State->get<LockMap>(LockR);
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if (!LState || LState->isDestroyed()) {
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State = State->set<LockMap>(LockR, LockState::getUnlocked());
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C.addTransition(State);
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return;
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}
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StringRef Message;
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if (LState->isLocked()) {
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Message = "This lock is still being held";
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} else {
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Message = "This lock has already been initialized";
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}
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if (!BT_initlock)
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BT_initlock.reset(new BugType(this, "Init invalid lock",
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"Lock checker"));
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ExplodedNode *N = C.generateErrorNode();
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if (!N)
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return;
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auto Report = llvm::make_unique<BugReport>(*BT_initlock, Message, N);
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Report->addRange(CE->getArg(0)->getSourceRange());
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C.emitReport(std::move(Report));
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}
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void PthreadLockChecker::reportUseDestroyedBug(CheckerContext &C,
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const CallExpr *CE) const {
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if (!BT_destroylock)
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BT_destroylock.reset(new BugType(this, "Use destroyed lock",
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"Lock checker"));
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ExplodedNode *N = C.generateErrorNode();
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if (!N)
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return;
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auto Report = llvm::make_unique<BugReport>(
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*BT_destroylock, "This lock has already been destroyed", N);
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Report->addRange(CE->getArg(0)->getSourceRange());
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C.emitReport(std::move(Report));
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}
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void ento::registerPthreadLockChecker(CheckerManager &mgr) {
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mgr.registerChecker<PthreadLockChecker>();
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}
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