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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/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
#include "llvm/ADT/ImmutableList.h"
using namespace clang;
using namespace ento;
namespace {
class PthreadLockChecker : public Checker< check::PostStmt<CallExpr> > {
mutable OwningPtr<BugType> BT_doublelock;
mutable OwningPtr<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;
};
} // end anonymous namespace
// GDM Entry for tracking lock state.
REGISTER_LIST_WITH_PROGRAMSTATE(LockSet, const MemRegion *)
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)
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_tryrwlock")
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));
}
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 = cast<DefinedSVal>(X);
if (state->contains<LockSet>(lockR)) {
if (!BT_doublelock)
BT_doublelock.reset(new BugType("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;
}
ProgramStateRef lockSucc = state;
if (isTryLock) {
// Bifurcate the state, and allow a mode where the lock acquisition fails.
ProgramStateRef lockFail;
switch (semantics) {
case PthreadSemantics:
llvm::tie(lockFail, lockSucc) = state->assume(retVal);
break;
case XNUSemantics:
llvm::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);
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();
LockSetTy LS = state->get<LockSet>();
// FIXME: Better analysis requires IPA for wrappers.
// FIXME: check for double unlocks
if (LS.isEmpty())
return;
const MemRegion *firstLockR = LS.getHead();
if (firstLockR != lockR) {
if (!BT_lor)
BT_lor.reset(new BugType("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());
C.addTransition(state);
}
void ento::registerPthreadLockChecker(CheckerManager &mgr) {
mgr.registerChecker<PthreadLockChecker>();
}
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