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llvm-project/clang/lib/StaticAnalyzer/Checkers/PthreadLockChecker.cpp

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