1 //===--- PthreadLockChecker.cpp - Check for locking problems ---*- C++ -*--===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This defines PthreadLockChecker, a simple lock -> unlock checker.
11 // Also handles XNU locks, which behave similarly enough to share code.
13 //===----------------------------------------------------------------------===//
15 #include "ClangSACheckers.h"
16 #include "clang/StaticAnalyzer/Core/Checker.h"
17 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
18 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
19 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
20 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
21 #include "llvm/ADT/ImmutableList.h"
23 using namespace clang;
27 class PthreadLockChecker : public Checker< check::PostStmt<CallExpr> > {
28 mutable OwningPtr<BugType> BT_doublelock;
29 mutable OwningPtr<BugType> BT_lor;
30 enum LockingSemantics {
36 void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
38 void AcquireLock(CheckerContext &C, const CallExpr *CE, SVal lock,
39 bool isTryLock, enum LockingSemantics semantics) const;
41 void ReleaseLock(CheckerContext &C, const CallExpr *CE, SVal lock) const;
43 } // end anonymous namespace
45 // GDM Entry for tracking lock state.
46 namespace { class LockSet {}; }
49 template <> struct ProgramStateTrait<LockSet> :
50 public ProgramStatePartialTrait<llvm::ImmutableList<const MemRegion*> > {
51 static void *GDMIndex() { static int x = 0; return &x; }
53 } // end of ento (ProgramState) namespace
54 } // end clang namespace
57 void PthreadLockChecker::checkPostStmt(const CallExpr *CE,
58 CheckerContext &C) const {
59 ProgramStateRef state = C.getState();
60 const LocationContext *LCtx = C.getLocationContext();
61 StringRef FName = C.getCalleeName(CE);
65 if (CE->getNumArgs() != 1)
68 if (FName == "pthread_mutex_lock" ||
69 FName == "pthread_rwlock_rdlock" ||
70 FName == "pthread_rwlock_wrlock")
71 AcquireLock(C, CE, state->getSVal(CE->getArg(0), LCtx),
72 false, PthreadSemantics);
73 else if (FName == "lck_mtx_lock" ||
74 FName == "lck_rw_lock_exclusive" ||
75 FName == "lck_rw_lock_shared")
76 AcquireLock(C, CE, state->getSVal(CE->getArg(0), LCtx),
78 else if (FName == "pthread_mutex_trylock" ||
79 FName == "pthread_rwlock_tryrdlock" ||
80 FName == "pthread_rwlock_tryrwlock")
81 AcquireLock(C, CE, state->getSVal(CE->getArg(0), LCtx),
82 true, PthreadSemantics);
83 else if (FName == "lck_mtx_try_lock" ||
84 FName == "lck_rw_try_lock_exclusive" ||
85 FName == "lck_rw_try_lock_shared")
86 AcquireLock(C, CE, state->getSVal(CE->getArg(0), LCtx),
88 else if (FName == "pthread_mutex_unlock" ||
89 FName == "pthread_rwlock_unlock" ||
90 FName == "lck_mtx_unlock" ||
91 FName == "lck_rw_done")
92 ReleaseLock(C, CE, state->getSVal(CE->getArg(0), LCtx));
95 void PthreadLockChecker::AcquireLock(CheckerContext &C, const CallExpr *CE,
96 SVal lock, bool isTryLock,
97 enum LockingSemantics semantics) const {
99 const MemRegion *lockR = lock.getAsRegion();
103 ProgramStateRef state = C.getState();
105 SVal X = state->getSVal(CE, C.getLocationContext());
106 if (X.isUnknownOrUndef())
109 DefinedSVal retVal = cast<DefinedSVal>(X);
111 if (state->contains<LockSet>(lockR)) {
113 BT_doublelock.reset(new BugType("Double locking", "Lock checker"));
114 ExplodedNode *N = C.generateSink();
117 BugReport *report = new BugReport(*BT_doublelock,
118 "This lock has already "
120 report->addRange(CE->getArg(0)->getSourceRange());
121 C.EmitReport(report);
125 ProgramStateRef lockSucc = state;
127 // Bifurcate the state, and allow a mode where the lock acquisition fails.
128 ProgramStateRef lockFail;
130 case PthreadSemantics:
131 llvm::tie(lockFail, lockSucc) = state->assume(retVal);
134 llvm::tie(lockSucc, lockFail) = state->assume(retVal);
137 llvm_unreachable("Unknown tryLock locking semantics");
139 assert(lockFail && lockSucc);
140 C.addTransition(lockFail);
142 } else if (semantics == PthreadSemantics) {
143 // Assume that the return value was 0.
144 lockSucc = state->assume(retVal, false);
148 // XNU locking semantics return void on non-try locks
149 assert((semantics == XNUSemantics) && "Unknown locking semantics");
153 // Record that the lock was acquired.
154 lockSucc = lockSucc->add<LockSet>(lockR);
155 C.addTransition(lockSucc);
158 void PthreadLockChecker::ReleaseLock(CheckerContext &C, const CallExpr *CE,
161 const MemRegion *lockR = lock.getAsRegion();
165 ProgramStateRef state = C.getState();
166 llvm::ImmutableList<const MemRegion*> LS = state->get<LockSet>();
168 // FIXME: Better analysis requires IPA for wrappers.
169 // FIXME: check for double unlocks
173 const MemRegion *firstLockR = LS.getHead();
174 if (firstLockR != lockR) {
176 BT_lor.reset(new BugType("Lock order reversal", "Lock checker"));
177 ExplodedNode *N = C.generateSink();
180 BugReport *report = new BugReport(*BT_lor,
181 "This was not the most "
182 "recently acquired lock. "
183 "Possible lock order "
185 report->addRange(CE->getArg(0)->getSourceRange());
186 C.EmitReport(report);
190 // Record that the lock was released.
191 state = state->set<LockSet>(LS.getTail());
192 C.addTransition(state);
196 void ento::registerPthreadLockChecker(CheckerManager &mgr) {
197 mgr.registerChecker<PthreadLockChecker>();