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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"
using namespace clang;
using namespace ento;
namespace {
struct LockState {
enum Kind {
Destroyed,
Locked,
Unlocked,
UntouchedAndPossiblyDestroyed,
UnlockedAndPossiblyDestroyed
} K;
private:
LockState(Kind K) : K(K) {}
public:
static LockState getLocked() { return LockState(Locked); }
static LockState getUnlocked() { return LockState(Unlocked); }
static LockState getDestroyed() { return LockState(Destroyed); }
static LockState getUntouchedAndPossiblyDestroyed() {
return LockState(UntouchedAndPossiblyDestroyed);
}
static LockState getUnlockedAndPossiblyDestroyed() {
return LockState(UnlockedAndPossiblyDestroyed);
}
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; }
bool isUntouchedAndPossiblyDestroyed() const {
return K == UntouchedAndPossiblyDestroyed;
}
bool isUnlockedAndPossiblyDestroyed() const {
return K == UnlockedAndPossiblyDestroyed;
}
void Profile(llvm::FoldingSetNodeID &ID) const {
ID.AddInteger(K);
}
};
class PthreadLockChecker
: public Checker<check::PostStmt<CallExpr>, check::DeadSymbols> {
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 checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;
void printState(raw_ostream &Out, ProgramStateRef State,
const char *NL, const char *Sep) const override;
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,
enum LockingSemantics semantics) const;
void InitLock(CheckerContext &C, const CallExpr *CE, SVal Lock) const;
void reportUseDestroyedBug(CheckerContext &C, const CallExpr *CE) const;
ProgramStateRef resolvePossiblyDestroyedMutex(ProgramStateRef state,
const MemRegion *lockR,
const SymbolRef *sym) const;
};
} // end anonymous namespace
// A stack of locks for tracking lock-unlock order.
REGISTER_LIST_WITH_PROGRAMSTATE(LockSet, const MemRegion *)
// An entry for tracking lock states.
REGISTER_MAP_WITH_PROGRAMSTATE(LockMap, const MemRegion *, LockState)
// Return values for unresolved calls to pthread_mutex_destroy().
REGISTER_MAP_WITH_PROGRAMSTATE(DestroyRetVal, const MemRegion *, SymbolRef)
void PthreadLockChecker::checkPostStmt(const CallExpr *CE,
CheckerContext &C) const {
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, C.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, C.getSVal(CE->getArg(0)), false, XNUSemantics);
else if (FName == "pthread_mutex_trylock" ||
FName == "pthread_rwlock_tryrdlock" ||
FName == "pthread_rwlock_trywrlock")
AcquireLock(C, CE, C.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, C.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, C.getSVal(CE->getArg(0)));
else if (FName == "pthread_mutex_destroy")
DestroyLock(C, CE, C.getSVal(CE->getArg(0)), PthreadSemantics);
else if (FName == "lck_mtx_destroy")
DestroyLock(C, CE, C.getSVal(CE->getArg(0)), XNUSemantics);
else if (FName == "pthread_mutex_init")
InitLock(C, CE, C.getSVal(CE->getArg(0)));
}
// When a lock is destroyed, in some semantics(like PthreadSemantics) we are not
// sure if the destroy call has succeeded or failed, and the lock enters one of
// the 'possibly destroyed' state. There is a short time frame for the
// programmer to check the return value to see if the lock was successfully
// destroyed. Before we model the next operation over that lock, we call this
// function to see if the return value was checked by now and set the lock state
// - either to destroyed state or back to its previous state.
// In PthreadSemantics, pthread_mutex_destroy() returns zero if the lock is
// successfully destroyed and it returns a non-zero value otherwise.
ProgramStateRef PthreadLockChecker::resolvePossiblyDestroyedMutex(
ProgramStateRef state, const MemRegion *lockR, const SymbolRef *sym) const {
const LockState *lstate = state->get<LockMap>(lockR);
// Existence in DestroyRetVal ensures existence in LockMap.
// Existence in Destroyed also ensures that the lock state for lockR is either
// UntouchedAndPossiblyDestroyed or UnlockedAndPossiblyDestroyed.
assert(lstate->isUntouchedAndPossiblyDestroyed() ||
lstate->isUnlockedAndPossiblyDestroyed());
ConstraintManager &CMgr = state->getConstraintManager();
ConditionTruthVal retZero = CMgr.isNull(state, *sym);
if (retZero.isConstrainedFalse()) {
if (lstate->isUntouchedAndPossiblyDestroyed())
state = state->remove<LockMap>(lockR);
else if (lstate->isUnlockedAndPossiblyDestroyed())
state = state->set<LockMap>(lockR, LockState::getUnlocked());
} else
state = state->set<LockMap>(lockR, LockState::getDestroyed());
// Removing the map entry (lockR, sym) from DestroyRetVal as the lock state is
// now resolved.
state = state->remove<DestroyRetVal>(lockR);
return state;
}
void PthreadLockChecker::printState(raw_ostream &Out, ProgramStateRef State,
const char *NL, const char *Sep) const {
LockMapTy LM = State->get<LockMap>();
if (!LM.isEmpty()) {
Out << Sep << "Mutex states:" << NL;
for (auto I : LM) {
I.first->dumpToStream(Out);
if (I.second.isLocked())
Out << ": locked";
else if (I.second.isUnlocked())
Out << ": unlocked";
else if (I.second.isDestroyed())
Out << ": destroyed";
else if (I.second.isUntouchedAndPossiblyDestroyed())
Out << ": not tracked, possibly destroyed";
else if (I.second.isUnlockedAndPossiblyDestroyed())
Out << ": unlocked, possibly destroyed";
Out << NL;
}
}
LockSetTy LS = State->get<LockSet>();
if (!LS.isEmpty()) {
Out << Sep << "Mutex lock order:" << NL;
for (auto I: LS) {
I->dumpToStream(Out);
Out << NL;
}
}
// TODO: Dump destroyed mutex symbols?
}
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();
const SymbolRef *sym = state->get<DestroyRetVal>(lockR);
if (sym)
state = resolvePossiblyDestroyedMutex(state, lockR, sym);
SVal X = C.getSVal(CE);
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.generateErrorNode();
if (!N)
return;
auto report = llvm::make_unique<BugReport>(
*BT_doublelock, "This lock has already been acquired", N);
report->addRange(CE->getArg(0)->getSourceRange());
C.emitReport(std::move(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();
const SymbolRef *sym = state->get<DestroyRetVal>(lockR);
if (sym)
state = resolvePossiblyDestroyedMutex(state, lockR, sym);
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.generateErrorNode();
if (!N)
return;
auto Report = llvm::make_unique<BugReport>(
*BT_doubleunlock, "This lock has already been unlocked", N);
Report->addRange(CE->getArg(0)->getSourceRange());
C.emitReport(std::move(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.generateErrorNode();
if (!N)
return;
auto report = llvm::make_unique<BugReport>(
*BT_lor, "This was not the most recently acquired lock. Possible "
"lock order reversal", N);
report->addRange(CE->getArg(0)->getSourceRange());
C.emitReport(std::move(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,
enum LockingSemantics semantics) const {
const MemRegion *LockR = Lock.getAsRegion();
if (!LockR)
return;
ProgramStateRef State = C.getState();
const SymbolRef *sym = State->get<DestroyRetVal>(LockR);
if (sym)
State = resolvePossiblyDestroyedMutex(State, LockR, sym);
const LockState *LState = State->get<LockMap>(LockR);
// Checking the return value of the destroy method only in the case of
// PthreadSemantics
if (semantics == PthreadSemantics) {
if (!LState || LState->isUnlocked()) {
SymbolRef sym = C.getSVal(CE).getAsSymbol();
if (!sym) {
State = State->remove<LockMap>(LockR);
C.addTransition(State);
return;
}
State = State->set<DestroyRetVal>(LockR, sym);
if (LState && LState->isUnlocked())
State = State->set<LockMap>(
LockR, LockState::getUnlockedAndPossiblyDestroyed());
else
State = State->set<LockMap>(
LockR, LockState::getUntouchedAndPossiblyDestroyed());
C.addTransition(State);
return;
}
} else {
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.generateErrorNode();
if (!N)
return;
auto Report = llvm::make_unique<BugReport>(*BT_destroylock, Message, N);
Report->addRange(CE->getArg(0)->getSourceRange());
C.emitReport(std::move(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 SymbolRef *sym = State->get<DestroyRetVal>(LockR);
if (sym)
State = resolvePossiblyDestroyedMutex(State, LockR, sym);
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.generateErrorNode();
if (!N)
return;
auto Report = llvm::make_unique<BugReport>(*BT_initlock, Message, N);
Report->addRange(CE->getArg(0)->getSourceRange());
C.emitReport(std::move(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.generateErrorNode();
if (!N)
return;
auto Report = llvm::make_unique<BugReport>(
*BT_destroylock, "This lock has already been destroyed", N);
Report->addRange(CE->getArg(0)->getSourceRange());
C.emitReport(std::move(Report));
}
void PthreadLockChecker::checkDeadSymbols(SymbolReaper &SymReaper,
CheckerContext &C) const {
ProgramStateRef State = C.getState();
// TODO: Clean LockMap when a mutex region dies.
DestroyRetValTy TrackedSymbols = State->get<DestroyRetVal>();
for (DestroyRetValTy::iterator I = TrackedSymbols.begin(),
E = TrackedSymbols.end();
I != E; ++I) {
const SymbolRef Sym = I->second;
const MemRegion *lockR = I->first;
bool IsSymDead = SymReaper.isDead(Sym);
// Remove the dead symbol from the return value symbols map.
if (IsSymDead)
State = resolvePossiblyDestroyedMutex(State, lockR, &Sym);
}
C.addTransition(State);
}
void ento::registerPthreadLockChecker(CheckerManager &mgr) {
mgr.registerChecker<PthreadLockChecker>();
}
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