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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/GRStateTrait.h"
#include "llvm/ADT/ImmutableList.h"
using namespace clang;
using namespace ento;
namespace {
class PthreadLockChecker : public Checker< check::PostStmt<CallExpr> > {
mutable llvm::OwningPtr<BugType> BT_doublelock;
mutable llvm::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.
namespace { class LockSet {}; }
namespace clang {
namespace ento {
template <> struct GRStateTrait<LockSet> :
public GRStatePartialTrait<llvm::ImmutableList<const MemRegion*> > {
static void* GDMIndex() { static int x = 0; return &x; }
};
} // end GR namespace
} // end clang namespace
void PthreadLockChecker::checkPostStmt(const CallExpr *CE,
CheckerContext &C) const {
const GRState *state = C.getState();
const Expr *Callee = CE->getCallee();
const FunctionDecl *FD = state->getSVal(Callee).getAsFunctionDecl();
if (!FD)
return;
// Get the name of the callee.
IdentifierInfo *II = FD->getIdentifier();
if (!II) // if no identifier, not a simple C function
return;
llvm::StringRef FName = II->getName();
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)), 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)), false, XNUSemantics);
else if (FName == "pthread_mutex_trylock" ||
FName == "pthread_rwlock_tryrdlock" ||
FName == "pthread_rwlock_tryrwlock")
AcquireLock(C, CE, state->getSVal(CE->getArg(0)), 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)), 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)));
}
void PthreadLockChecker::AcquireLock(CheckerContext &C, const CallExpr *CE,
SVal lock, bool isTryLock,
enum LockingSemantics semantics) const {
const MemRegion *lockR = lock.getAsRegion();
if (!lockR)
return;
const GRState *state = C.getState();
SVal X = state->getSVal(CE);
if (X.isUnknownOrUndef())
return;
DefinedSVal retVal = cast<DefinedSVal>(X);
llvm::ImmutableList<const MemRegion*> LS = state->get<LockSet>();
if (state->contains<LockSet>(lockR)) {
if (!BT_doublelock)
BT_doublelock.reset(new BugType("Double locking", "Lock checker"));
ExplodedNode *N = C.generateSink();
if (!N)
return;
EnhancedBugReport *report = new EnhancedBugReport(*BT_doublelock,
"This lock has already "
"been acquired", N);
report->addRange(CE->getArg(0)->getSourceRange());
C.EmitReport(report);
return;
}
const GRState *lockSucc = state;
if (isTryLock) {
// Bifurcate the state, and allow a mode where the lock acquisition fails.
const GRState *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");
break;
}
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;
const GRState *state = C.getState();
llvm::ImmutableList<const MemRegion*> 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;
EnhancedBugReport *report = new EnhancedBugReport(*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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