| //===- ThreadSafety.cpp ----------------------------------------*- C++ --*-===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // A intra-procedural analysis for thread safety (e.g. deadlocks and race |
| // conditions), based off of an annotation system. |
| // |
| // See http://clang.llvm.org/docs/LanguageExtensions.html#threadsafety for more |
| // information. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "clang/Analysis/Analyses/ThreadSafety.h" |
| #include "clang/Analysis/AnalysisContext.h" |
| #include "clang/Analysis/CFG.h" |
| #include "clang/Analysis/CFGStmtMap.h" |
| #include "clang/AST/DeclCXX.h" |
| #include "clang/AST/ExprCXX.h" |
| #include "clang/AST/StmtCXX.h" |
| #include "clang/AST/StmtVisitor.h" |
| #include "clang/Basic/SourceManager.h" |
| #include "clang/Basic/SourceLocation.h" |
| #include "llvm/ADT/BitVector.h" |
| #include "llvm/ADT/FoldingSet.h" |
| #include "llvm/ADT/ImmutableMap.h" |
| #include "llvm/ADT/PostOrderIterator.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/ADT/StringRef.h" |
| #include <algorithm> |
| #include <vector> |
| |
| using namespace clang; |
| using namespace thread_safety; |
| |
| // Key method definition |
| ThreadSafetyHandler::~ThreadSafetyHandler() {} |
| |
| namespace { |
| |
| /// \brief Implements a set of CFGBlocks using a BitVector. |
| /// |
| /// This class contains a minimal interface, primarily dictated by the SetType |
| /// template parameter of the llvm::po_iterator template, as used with external |
| /// storage. We also use this set to keep track of which CFGBlocks we visit |
| /// during the analysis. |
| class CFGBlockSet { |
| llvm::BitVector VisitedBlockIDs; |
| |
| public: |
| // po_iterator requires this iterator, but the only interface needed is the |
| // value_type typedef. |
| struct iterator { |
| typedef const CFGBlock *value_type; |
| }; |
| |
| CFGBlockSet() {} |
| CFGBlockSet(const CFG *G) : VisitedBlockIDs(G->getNumBlockIDs(), false) {} |
| |
| /// \brief Set the bit associated with a particular CFGBlock. |
| /// This is the important method for the SetType template parameter. |
| bool insert(const CFGBlock *Block) { |
| // Note that insert() is called by po_iterator, which doesn't check to make |
| // sure that Block is non-null. Moreover, the CFGBlock iterator will |
| // occasionally hand out null pointers for pruned edges, so we catch those |
| // here. |
| if (Block == 0) |
| return false; // if an edge is trivially false. |
| if (VisitedBlockIDs.test(Block->getBlockID())) |
| return false; |
| VisitedBlockIDs.set(Block->getBlockID()); |
| return true; |
| } |
| |
| /// \brief Check if the bit for a CFGBlock has been already set. |
| /// This method is for tracking visited blocks in the main threadsafety loop. |
| /// Block must not be null. |
| bool alreadySet(const CFGBlock *Block) { |
| return VisitedBlockIDs.test(Block->getBlockID()); |
| } |
| }; |
| |
| |
| /// \brief We create a helper class which we use to iterate through CFGBlocks in |
| /// the topological order. |
| class TopologicallySortedCFG { |
| typedef llvm::po_iterator<const CFG*, CFGBlockSet, true> po_iterator; |
| |
| std::vector<const CFGBlock*> Blocks; |
| |
| public: |
| typedef std::vector<const CFGBlock*>::reverse_iterator iterator; |
| |
| TopologicallySortedCFG(const CFG *CFGraph) { |
| Blocks.reserve(CFGraph->getNumBlockIDs()); |
| CFGBlockSet BSet(CFGraph); |
| |
| for (po_iterator I = po_iterator::begin(CFGraph, BSet), |
| E = po_iterator::end(CFGraph, BSet); I != E; ++I) { |
| Blocks.push_back(*I); |
| } |
| } |
| |
| iterator begin() { |
| return Blocks.rbegin(); |
| } |
| |
| iterator end() { |
| return Blocks.rend(); |
| } |
| |
| bool empty() { |
| return begin() == end(); |
| } |
| }; |
| |
| |
| /// \brief A MutexID object uniquely identifies a particular mutex, and |
| /// is built from an Expr* (i.e. calling a lock function). |
| /// |
| /// Thread-safety analysis works by comparing lock expressions. Within the |
| /// body of a function, an expression such as "x->foo->bar.mu" will resolve to |
| /// a particular mutex object at run-time. Subsequent occurrences of the same |
| /// expression (where "same" means syntactic equality) will refer to the same |
| /// run-time object if three conditions hold: |
| /// (1) Local variables in the expression, such as "x" have not changed. |
| /// (2) Values on the heap that affect the expression have not changed. |
| /// (3) The expression involves only pure function calls. |
| /// |
| /// The current implementation assumes, but does not verify, that multiple uses |
| /// of the same lock expression satisfies these criteria. |
| /// |
| /// Clang introduces an additional wrinkle, which is that it is difficult to |
| /// derive canonical expressions, or compare expressions directly for equality. |
| /// Thus, we identify a mutex not by an Expr, but by the set of named |
| /// declarations that are referenced by the Expr. In other words, |
| /// x->foo->bar.mu will be a four element vector with the Decls for |
| /// mu, bar, and foo, and x. The vector will uniquely identify the expression |
| /// for all practical purposes. |
| /// |
| /// Note we will need to perform substitution on "this" and function parameter |
| /// names when constructing a lock expression. |
| /// |
| /// For example: |
| /// class C { Mutex Mu; void lock() EXCLUSIVE_LOCK_FUNCTION(this->Mu); }; |
| /// void myFunc(C *X) { ... X->lock() ... } |
| /// The original expression for the mutex acquired by myFunc is "this->Mu", but |
| /// "X" is substituted for "this" so we get X->Mu(); |
| /// |
| /// For another example: |
| /// foo(MyList *L) EXCLUSIVE_LOCKS_REQUIRED(L->Mu) { ... } |
| /// MyList *MyL; |
| /// foo(MyL); // requires lock MyL->Mu to be held |
| class MutexID { |
| SmallVector<NamedDecl*, 2> DeclSeq; |
| |
| /// Build a Decl sequence representing the lock from the given expression. |
| /// Recursive function that terminates on DeclRefExpr. |
| /// Note: this function merely creates a MutexID; it does not check to |
| /// ensure that the original expression is a valid mutex expression. |
| void buildMutexID(Expr *Exp, Expr *Parent, int NumArgs, |
| const NamedDecl **FunArgDecls, Expr **FunArgs) { |
| if (!Exp) { |
| DeclSeq.clear(); |
| return; |
| } |
| |
| if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Exp)) { |
| if (FunArgDecls) { |
| // Substitute call arguments for references to function parameters |
| for (int i = 0; i < NumArgs; ++i) { |
| if (DRE->getDecl() == FunArgDecls[i]) { |
| buildMutexID(FunArgs[i], 0, 0, 0, 0); |
| return; |
| } |
| } |
| } |
| NamedDecl *ND = cast<NamedDecl>(DRE->getDecl()->getCanonicalDecl()); |
| DeclSeq.push_back(ND); |
| } else if (MemberExpr *ME = dyn_cast<MemberExpr>(Exp)) { |
| NamedDecl *ND = ME->getMemberDecl(); |
| DeclSeq.push_back(ND); |
| buildMutexID(ME->getBase(), Parent, NumArgs, FunArgDecls, FunArgs); |
| } else if (isa<CXXThisExpr>(Exp)) { |
| if (Parent) |
| buildMutexID(Parent, 0, 0, 0, 0); |
| else |
| return; // mutexID is still valid in this case |
| } else if (UnaryOperator *UOE = dyn_cast<UnaryOperator>(Exp)) |
| buildMutexID(UOE->getSubExpr(), Parent, NumArgs, FunArgDecls, FunArgs); |
| else if (CastExpr *CE = dyn_cast<CastExpr>(Exp)) |
| buildMutexID(CE->getSubExpr(), Parent, NumArgs, FunArgDecls, FunArgs); |
| else |
| DeclSeq.clear(); // Mark as invalid lock expression. |
| } |
| |
| /// \brief Construct a MutexID from an expression. |
| /// \param MutexExp The original mutex expression within an attribute |
| /// \param DeclExp An expression involving the Decl on which the attribute |
| /// occurs. |
| /// \param D The declaration to which the lock/unlock attribute is attached. |
| void buildMutexIDFromExp(Expr *MutexExp, Expr *DeclExp, const NamedDecl *D) { |
| Expr *Parent = 0; |
| unsigned NumArgs = 0; |
| Expr **FunArgs = 0; |
| SmallVector<const NamedDecl*, 8> FunArgDecls; |
| |
| // If we are processing a raw attribute expression, with no substitutions. |
| if (DeclExp == 0) { |
| buildMutexID(MutexExp, 0, 0, 0, 0); |
| return; |
| } |
| |
| // Examine DeclExp to find Parent and FunArgs, which are used to substitute |
| // for formal parameters when we call buildMutexID later. |
| if (MemberExpr *ME = dyn_cast<MemberExpr>(DeclExp)) { |
| Parent = ME->getBase(); |
| } else if (CXXMemberCallExpr *CE = dyn_cast<CXXMemberCallExpr>(DeclExp)) { |
| Parent = CE->getImplicitObjectArgument(); |
| NumArgs = CE->getNumArgs(); |
| FunArgs = CE->getArgs(); |
| } else if (CXXConstructExpr *CE = dyn_cast<CXXConstructExpr>(DeclExp)) { |
| Parent = 0; // FIXME -- get the parent from DeclStmt |
| NumArgs = CE->getNumArgs(); |
| FunArgs = CE->getArgs(); |
| } |
| |
| // If the attribute has no arguments, then assume the argument is "this". |
| if (MutexExp == 0) { |
| buildMutexID(Parent, 0, 0, 0, 0); |
| return; |
| } |
| |
| // FIXME: handle default arguments |
| if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D)) { |
| for (unsigned i = 0, ni = FD->getNumParams(); i < ni && i < NumArgs; ++i) { |
| FunArgDecls.push_back(FD->getParamDecl(i)); |
| } |
| } |
| buildMutexID(MutexExp, Parent, NumArgs, &FunArgDecls.front(), FunArgs); |
| } |
| |
| public: |
| /// \param MutexExp The original mutex expression within an attribute |
| /// \param DeclExp An expression involving the Decl on which the attribute |
| /// occurs. |
| /// \param D The declaration to which the lock/unlock attribute is attached. |
| /// Caller must check isValid() after construction. |
| MutexID(Expr* MutexExp, Expr *DeclExp, const NamedDecl* D) { |
| buildMutexIDFromExp(MutexExp, DeclExp, D); |
| } |
| |
| /// Return true if this is a valid decl sequence. |
| /// Caller must call this by hand after construction to handle errors. |
| bool isValid() const { |
| return !DeclSeq.empty(); |
| } |
| |
| /// Issue a warning about an invalid lock expression |
| static void warnInvalidLock(ThreadSafetyHandler &Handler, Expr* MutexExp, |
| Expr *DeclExp, const NamedDecl* D) { |
| SourceLocation Loc; |
| if (DeclExp) |
| Loc = DeclExp->getExprLoc(); |
| |
| // FIXME: add a note about the attribute location in MutexExp or D |
| if (Loc.isValid()) |
| Handler.handleInvalidLockExp(Loc); |
| } |
| |
| bool operator==(const MutexID &other) const { |
| return DeclSeq == other.DeclSeq; |
| } |
| |
| bool operator!=(const MutexID &other) const { |
| return !(*this == other); |
| } |
| |
| // SmallVector overloads Operator< to do lexicographic ordering. Note that |
| // we use pointer equality (and <) to compare NamedDecls. This means the order |
| // of MutexIDs in a lockset is nondeterministic. In order to output |
| // diagnostics in a deterministic ordering, we must order all diagnostics to |
| // output by SourceLocation when iterating through this lockset. |
| bool operator<(const MutexID &other) const { |
| return DeclSeq < other.DeclSeq; |
| } |
| |
| /// \brief Returns the name of the first Decl in the list for a given MutexID; |
| /// e.g. the lock expression foo.bar() has name "bar". |
| /// The caret will point unambiguously to the lock expression, so using this |
| /// name in diagnostics is a way to get simple, and consistent, mutex names. |
| /// We do not want to output the entire expression text for security reasons. |
| StringRef getName() const { |
| assert(isValid()); |
| return DeclSeq.front()->getName(); |
| } |
| |
| void Profile(llvm::FoldingSetNodeID &ID) const { |
| for (SmallVectorImpl<NamedDecl*>::const_iterator I = DeclSeq.begin(), |
| E = DeclSeq.end(); I != E; ++I) { |
| ID.AddPointer(*I); |
| } |
| } |
| }; |
| |
| |
| /// \brief This is a helper class that stores info about the most recent |
| /// accquire of a Lock. |
| /// |
| /// The main body of the analysis maps MutexIDs to LockDatas. |
| struct LockData { |
| SourceLocation AcquireLoc; |
| |
| /// \brief LKind stores whether a lock is held shared or exclusively. |
| /// Note that this analysis does not currently support either re-entrant |
| /// locking or lock "upgrading" and "downgrading" between exclusive and |
| /// shared. |
| /// |
| /// FIXME: add support for re-entrant locking and lock up/downgrading |
| LockKind LKind; |
| |
| LockData(SourceLocation AcquireLoc, LockKind LKind) |
| : AcquireLoc(AcquireLoc), LKind(LKind) {} |
| |
| bool operator==(const LockData &other) const { |
| return AcquireLoc == other.AcquireLoc && LKind == other.LKind; |
| } |
| |
| bool operator!=(const LockData &other) const { |
| return !(*this == other); |
| } |
| |
| void Profile(llvm::FoldingSetNodeID &ID) const { |
| ID.AddInteger(AcquireLoc.getRawEncoding()); |
| ID.AddInteger(LKind); |
| } |
| }; |
| |
| |
| /// A Lockset maps each MutexID (defined above) to information about how it has |
| /// been locked. |
| typedef llvm::ImmutableMap<MutexID, LockData> Lockset; |
| |
| /// \brief We use this class to visit different types of expressions in |
| /// CFGBlocks, and build up the lockset. |
| /// An expression may cause us to add or remove locks from the lockset, or else |
| /// output error messages related to missing locks. |
| /// FIXME: In future, we may be able to not inherit from a visitor. |
| class BuildLockset : public StmtVisitor<BuildLockset> { |
| friend class ThreadSafetyAnalyzer; |
| |
| ThreadSafetyHandler &Handler; |
| Lockset LSet; |
| Lockset::Factory &LocksetFactory; |
| |
| // Helper functions |
| void removeLock(SourceLocation UnlockLoc, MutexID &Mutex); |
| void addLock(SourceLocation LockLoc, MutexID &Mutex, LockKind LK); |
| |
| template <class AttrType> |
| void addLocksToSet(LockKind LK, AttrType *Attr, Expr *Exp, NamedDecl *D); |
| void removeLocksFromSet(UnlockFunctionAttr *Attr, |
| Expr *Exp, NamedDecl* FunDecl); |
| |
| const ValueDecl *getValueDecl(Expr *Exp); |
| void warnIfMutexNotHeld (const NamedDecl *D, Expr *Exp, AccessKind AK, |
| Expr *MutexExp, ProtectedOperationKind POK); |
| void checkAccess(Expr *Exp, AccessKind AK); |
| void checkDereference(Expr *Exp, AccessKind AK); |
| void handleCall(Expr *Exp, NamedDecl *D); |
| |
| /// \brief Returns true if the lockset contains a lock, regardless of whether |
| /// the lock is held exclusively or shared. |
| bool locksetContains(const MutexID &Lock) const { |
| return LSet.lookup(Lock); |
| } |
| |
| /// \brief Returns true if the lockset contains a lock with the passed in |
| /// locktype. |
| bool locksetContains(const MutexID &Lock, LockKind KindRequested) const { |
| const LockData *LockHeld = LSet.lookup(Lock); |
| return (LockHeld && KindRequested == LockHeld->LKind); |
| } |
| |
| /// \brief Returns true if the lockset contains a lock with at least the |
| /// passed in locktype. So for example, if we pass in LK_Shared, this function |
| /// returns true if the lock is held LK_Shared or LK_Exclusive. If we pass in |
| /// LK_Exclusive, this function returns true if the lock is held LK_Exclusive. |
| bool locksetContainsAtLeast(const MutexID &Lock, |
| LockKind KindRequested) const { |
| switch (KindRequested) { |
| case LK_Shared: |
| return locksetContains(Lock); |
| case LK_Exclusive: |
| return locksetContains(Lock, KindRequested); |
| } |
| llvm_unreachable("Unknown LockKind"); |
| } |
| |
| public: |
| BuildLockset(ThreadSafetyHandler &Handler, Lockset LS, Lockset::Factory &F) |
| : StmtVisitor<BuildLockset>(), Handler(Handler), LSet(LS), |
| LocksetFactory(F) {} |
| |
| Lockset getLockset() { |
| return LSet; |
| } |
| |
| void VisitUnaryOperator(UnaryOperator *UO); |
| void VisitBinaryOperator(BinaryOperator *BO); |
| void VisitCastExpr(CastExpr *CE); |
| void VisitCXXMemberCallExpr(CXXMemberCallExpr *Exp); |
| void VisitCXXConstructExpr(CXXConstructExpr *Exp); |
| }; |
| |
| /// \brief Add a new lock to the lockset, warning if the lock is already there. |
| /// \param LockLoc The source location of the acquire |
| /// \param LockExp The lock expression corresponding to the lock to be added |
| void BuildLockset::addLock(SourceLocation LockLoc, MutexID &Mutex, |
| LockKind LK) { |
| // FIXME: deal with acquired before/after annotations. We can write a first |
| // pass that does the transitive lookup lazily, and refine afterwards. |
| LockData NewLock(LockLoc, LK); |
| |
| // FIXME: Don't always warn when we have support for reentrant locks. |
| if (locksetContains(Mutex)) |
| Handler.handleDoubleLock(Mutex.getName(), LockLoc); |
| else |
| LSet = LocksetFactory.add(LSet, Mutex, NewLock); |
| } |
| |
| /// \brief Remove a lock from the lockset, warning if the lock is not there. |
| /// \param LockExp The lock expression corresponding to the lock to be removed |
| /// \param UnlockLoc The source location of the unlock (only used in error msg) |
| void BuildLockset::removeLock(SourceLocation UnlockLoc, MutexID &Mutex) { |
| Lockset NewLSet = LocksetFactory.remove(LSet, Mutex); |
| if(NewLSet == LSet) |
| Handler.handleUnmatchedUnlock(Mutex.getName(), UnlockLoc); |
| else |
| LSet = NewLSet; |
| } |
| |
| /// \brief This function, parameterized by an attribute type, is used to add a |
| /// set of locks specified as attribute arguments to the lockset. |
| template <typename AttrType> |
| void BuildLockset::addLocksToSet(LockKind LK, AttrType *Attr, |
| Expr *Exp, NamedDecl* FunDecl) { |
| typedef typename AttrType::args_iterator iterator_type; |
| |
| SourceLocation ExpLocation = Exp->getExprLoc(); |
| |
| if (Attr->args_size() == 0) { |
| // The mutex held is the "this" object. |
| MutexID Mutex(0, Exp, FunDecl); |
| if (!Mutex.isValid()) |
| MutexID::warnInvalidLock(Handler, 0, Exp, FunDecl); |
| else |
| addLock(ExpLocation, Mutex, LK); |
| return; |
| } |
| |
| for (iterator_type I=Attr->args_begin(), E=Attr->args_end(); I != E; ++I) { |
| MutexID Mutex(*I, Exp, FunDecl); |
| if (!Mutex.isValid()) |
| MutexID::warnInvalidLock(Handler, *I, Exp, FunDecl); |
| else |
| addLock(ExpLocation, Mutex, LK); |
| } |
| } |
| |
| /// \brief This function removes a set of locks specified as attribute |
| /// arguments from the lockset. |
| void BuildLockset::removeLocksFromSet(UnlockFunctionAttr *Attr, |
| Expr *Exp, NamedDecl* FunDecl) { |
| SourceLocation ExpLocation; |
| if (Exp) ExpLocation = Exp->getExprLoc(); |
| |
| if (Attr->args_size() == 0) { |
| // The mutex held is the "this" object. |
| MutexID Mu(0, Exp, FunDecl); |
| if (!Mu.isValid()) |
| MutexID::warnInvalidLock(Handler, 0, Exp, FunDecl); |
| else |
| removeLock(ExpLocation, Mu); |
| return; |
| } |
| |
| for (UnlockFunctionAttr::args_iterator I = Attr->args_begin(), |
| E = Attr->args_end(); I != E; ++I) { |
| MutexID Mutex(*I, Exp, FunDecl); |
| if (!Mutex.isValid()) |
| MutexID::warnInvalidLock(Handler, *I, Exp, FunDecl); |
| else |
| removeLock(ExpLocation, Mutex); |
| } |
| } |
| |
| /// \brief Gets the value decl pointer from DeclRefExprs or MemberExprs |
| const ValueDecl *BuildLockset::getValueDecl(Expr *Exp) { |
| if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Exp)) |
| return DR->getDecl(); |
| |
| if (const MemberExpr *ME = dyn_cast<MemberExpr>(Exp)) |
| return ME->getMemberDecl(); |
| |
| return 0; |
| } |
| |
| /// \brief Warn if the LSet does not contain a lock sufficient to protect access |
| /// of at least the passed in AccessKind. |
| void BuildLockset::warnIfMutexNotHeld(const NamedDecl *D, Expr *Exp, |
| AccessKind AK, Expr *MutexExp, |
| ProtectedOperationKind POK) { |
| LockKind LK = getLockKindFromAccessKind(AK); |
| |
| MutexID Mutex(MutexExp, Exp, D); |
| if (!Mutex.isValid()) |
| MutexID::warnInvalidLock(Handler, MutexExp, Exp, D); |
| else if (!locksetContainsAtLeast(Mutex, LK)) |
| Handler.handleMutexNotHeld(D, POK, Mutex.getName(), LK, Exp->getExprLoc()); |
| } |
| |
| /// \brief This method identifies variable dereferences and checks pt_guarded_by |
| /// and pt_guarded_var annotations. Note that we only check these annotations |
| /// at the time a pointer is dereferenced. |
| /// FIXME: We need to check for other types of pointer dereferences |
| /// (e.g. [], ->) and deal with them here. |
| /// \param Exp An expression that has been read or written. |
| void BuildLockset::checkDereference(Expr *Exp, AccessKind AK) { |
| UnaryOperator *UO = dyn_cast<UnaryOperator>(Exp); |
| if (!UO || UO->getOpcode() != clang::UO_Deref) |
| return; |
| Exp = UO->getSubExpr()->IgnoreParenCasts(); |
| |
| const ValueDecl *D = getValueDecl(Exp); |
| if(!D || !D->hasAttrs()) |
| return; |
| |
| if (D->getAttr<PtGuardedVarAttr>() && LSet.isEmpty()) |
| Handler.handleNoMutexHeld(D, POK_VarDereference, AK, Exp->getExprLoc()); |
| |
| const AttrVec &ArgAttrs = D->getAttrs(); |
| for(unsigned i = 0, Size = ArgAttrs.size(); i < Size; ++i) |
| if (PtGuardedByAttr *PGBAttr = dyn_cast<PtGuardedByAttr>(ArgAttrs[i])) |
| warnIfMutexNotHeld(D, Exp, AK, PGBAttr->getArg(), POK_VarDereference); |
| } |
| |
| /// \brief Checks guarded_by and guarded_var attributes. |
| /// Whenever we identify an access (read or write) of a DeclRefExpr or |
| /// MemberExpr, we need to check whether there are any guarded_by or |
| /// guarded_var attributes, and make sure we hold the appropriate mutexes. |
| void BuildLockset::checkAccess(Expr *Exp, AccessKind AK) { |
| const ValueDecl *D = getValueDecl(Exp); |
| if(!D || !D->hasAttrs()) |
| return; |
| |
| if (D->getAttr<GuardedVarAttr>() && LSet.isEmpty()) |
| Handler.handleNoMutexHeld(D, POK_VarAccess, AK, Exp->getExprLoc()); |
| |
| const AttrVec &ArgAttrs = D->getAttrs(); |
| for(unsigned i = 0, Size = ArgAttrs.size(); i < Size; ++i) |
| if (GuardedByAttr *GBAttr = dyn_cast<GuardedByAttr>(ArgAttrs[i])) |
| warnIfMutexNotHeld(D, Exp, AK, GBAttr->getArg(), POK_VarAccess); |
| } |
| |
| /// \brief Process a function call, method call, constructor call, |
| /// or destructor call. This involves looking at the attributes on the |
| /// corresponding function/method/constructor/destructor, issuing warnings, |
| /// and updating the locksets accordingly. |
| /// |
| /// FIXME: For classes annotated with one of the guarded annotations, we need |
| /// to treat const method calls as reads and non-const method calls as writes, |
| /// and check that the appropriate locks are held. Non-const method calls with |
| /// the same signature as const method calls can be also treated as reads. |
| /// |
| /// FIXME: We need to also visit CallExprs to catch/check global functions. |
| /// |
| /// FIXME: Do not flag an error for member variables accessed in constructors/ |
| /// destructors |
| void BuildLockset::handleCall(Expr *Exp, NamedDecl *D) { |
| AttrVec &ArgAttrs = D->getAttrs(); |
| for(unsigned i = 0; i < ArgAttrs.size(); ++i) { |
| Attr *Attr = ArgAttrs[i]; |
| switch (Attr->getKind()) { |
| // When we encounter an exclusive lock function, we need to add the lock |
| // to our lockset with kind exclusive. |
| case attr::ExclusiveLockFunction: { |
| ExclusiveLockFunctionAttr *A = cast<ExclusiveLockFunctionAttr>(Attr); |
| addLocksToSet(LK_Exclusive, A, Exp, D); |
| break; |
| } |
| |
| // When we encounter a shared lock function, we need to add the lock |
| // to our lockset with kind shared. |
| case attr::SharedLockFunction: { |
| SharedLockFunctionAttr *A = cast<SharedLockFunctionAttr>(Attr); |
| addLocksToSet(LK_Shared, A, Exp, D); |
| break; |
| } |
| |
| // When we encounter an unlock function, we need to remove unlocked |
| // mutexes from the lockset, and flag a warning if they are not there. |
| case attr::UnlockFunction: { |
| UnlockFunctionAttr *UFAttr = cast<UnlockFunctionAttr>(Attr); |
| removeLocksFromSet(UFAttr, Exp, D); |
| break; |
| } |
| |
| case attr::ExclusiveLocksRequired: { |
| ExclusiveLocksRequiredAttr *ELRAttr = |
| cast<ExclusiveLocksRequiredAttr>(Attr); |
| |
| for (ExclusiveLocksRequiredAttr::args_iterator |
| I = ELRAttr->args_begin(), E = ELRAttr->args_end(); I != E; ++I) |
| warnIfMutexNotHeld(D, Exp, AK_Written, *I, POK_FunctionCall); |
| break; |
| } |
| |
| case attr::SharedLocksRequired: { |
| SharedLocksRequiredAttr *SLRAttr = cast<SharedLocksRequiredAttr>(Attr); |
| |
| for (SharedLocksRequiredAttr::args_iterator I = SLRAttr->args_begin(), |
| E = SLRAttr->args_end(); I != E; ++I) |
| warnIfMutexNotHeld(D, Exp, AK_Read, *I, POK_FunctionCall); |
| break; |
| } |
| |
| case attr::LocksExcluded: { |
| LocksExcludedAttr *LEAttr = cast<LocksExcludedAttr>(Attr); |
| for (LocksExcludedAttr::args_iterator I = LEAttr->args_begin(), |
| E = LEAttr->args_end(); I != E; ++I) { |
| MutexID Mutex(*I, Exp, D); |
| if (!Mutex.isValid()) |
| MutexID::warnInvalidLock(Handler, *I, Exp, D); |
| else if (locksetContains(Mutex)) |
| Handler.handleFunExcludesLock(D->getName(), Mutex.getName(), |
| Exp->getExprLoc()); |
| } |
| break; |
| } |
| |
| // Ignore other (non thread-safety) attributes |
| default: |
| break; |
| } |
| } |
| } |
| |
| /// \brief For unary operations which read and write a variable, we need to |
| /// check whether we hold any required mutexes. Reads are checked in |
| /// VisitCastExpr. |
| void BuildLockset::VisitUnaryOperator(UnaryOperator *UO) { |
| switch (UO->getOpcode()) { |
| case clang::UO_PostDec: |
| case clang::UO_PostInc: |
| case clang::UO_PreDec: |
| case clang::UO_PreInc: { |
| Expr *SubExp = UO->getSubExpr()->IgnoreParenCasts(); |
| checkAccess(SubExp, AK_Written); |
| checkDereference(SubExp, AK_Written); |
| break; |
| } |
| default: |
| break; |
| } |
| } |
| |
| /// For binary operations which assign to a variable (writes), we need to check |
| /// whether we hold any required mutexes. |
| /// FIXME: Deal with non-primitive types. |
| void BuildLockset::VisitBinaryOperator(BinaryOperator *BO) { |
| if (!BO->isAssignmentOp()) |
| return; |
| Expr *LHSExp = BO->getLHS()->IgnoreParenCasts(); |
| checkAccess(LHSExp, AK_Written); |
| checkDereference(LHSExp, AK_Written); |
| } |
| |
| /// Whenever we do an LValue to Rvalue cast, we are reading a variable and |
| /// need to ensure we hold any required mutexes. |
| /// FIXME: Deal with non-primitive types. |
| void BuildLockset::VisitCastExpr(CastExpr *CE) { |
| if (CE->getCastKind() != CK_LValueToRValue) |
| return; |
| Expr *SubExp = CE->getSubExpr()->IgnoreParenCasts(); |
| checkAccess(SubExp, AK_Read); |
| checkDereference(SubExp, AK_Read); |
| } |
| |
| |
| void BuildLockset::VisitCXXMemberCallExpr(CXXMemberCallExpr *Exp) { |
| NamedDecl *D = dyn_cast_or_null<NamedDecl>(Exp->getCalleeDecl()); |
| if(!D || !D->hasAttrs()) |
| return; |
| handleCall(Exp, D); |
| } |
| |
| void BuildLockset::VisitCXXConstructExpr(CXXConstructExpr *Exp) { |
| NamedDecl *D = cast<NamedDecl>(Exp->getConstructor()); |
| if(!D || !D->hasAttrs()) |
| return; |
| handleCall(Exp, D); |
| } |
| |
| |
| /// \brief Class which implements the core thread safety analysis routines. |
| class ThreadSafetyAnalyzer { |
| ThreadSafetyHandler &Handler; |
| Lockset::Factory LocksetFactory; |
| |
| public: |
| ThreadSafetyAnalyzer(ThreadSafetyHandler &H) : Handler(H) {} |
| |
| Lockset intersectAndWarn(const Lockset LSet1, const Lockset LSet2, |
| LockErrorKind LEK); |
| |
| Lockset addLock(Lockset &LSet, Expr *MutexExp, const NamedDecl *D, |
| LockKind LK, SourceLocation Loc); |
| |
| void runAnalysis(AnalysisContext &AC); |
| }; |
| |
| /// \brief Compute the intersection of two locksets and issue warnings for any |
| /// locks in the symmetric difference. |
| /// |
| /// This function is used at a merge point in the CFG when comparing the lockset |
| /// of each branch being merged. For example, given the following sequence: |
| /// A; if () then B; else C; D; we need to check that the lockset after B and C |
| /// are the same. In the event of a difference, we use the intersection of these |
| /// two locksets at the start of D. |
| Lockset ThreadSafetyAnalyzer::intersectAndWarn(const Lockset LSet1, |
| const Lockset LSet2, |
| LockErrorKind LEK) { |
| Lockset Intersection = LSet1; |
| for (Lockset::iterator I = LSet2.begin(), E = LSet2.end(); I != E; ++I) { |
| const MutexID &LSet2Mutex = I.getKey(); |
| const LockData &LSet2LockData = I.getData(); |
| if (const LockData *LD = LSet1.lookup(LSet2Mutex)) { |
| if (LD->LKind != LSet2LockData.LKind) { |
| Handler.handleExclusiveAndShared(LSet2Mutex.getName(), |
| LSet2LockData.AcquireLoc, |
| LD->AcquireLoc); |
| if (LD->LKind != LK_Exclusive) |
| Intersection = LocksetFactory.add(Intersection, LSet2Mutex, |
| LSet2LockData); |
| } |
| } else { |
| Handler.handleMutexHeldEndOfScope(LSet2Mutex.getName(), |
| LSet2LockData.AcquireLoc, LEK); |
| } |
| } |
| |
| for (Lockset::iterator I = LSet1.begin(), E = LSet1.end(); I != E; ++I) { |
| if (!LSet2.contains(I.getKey())) { |
| const MutexID &Mutex = I.getKey(); |
| const LockData &MissingLock = I.getData(); |
| Handler.handleMutexHeldEndOfScope(Mutex.getName(), |
| MissingLock.AcquireLoc, LEK); |
| Intersection = LocksetFactory.remove(Intersection, Mutex); |
| } |
| } |
| return Intersection; |
| } |
| |
| Lockset ThreadSafetyAnalyzer::addLock(Lockset &LSet, Expr *MutexExp, |
| const NamedDecl *D, |
| LockKind LK, SourceLocation Loc) { |
| MutexID Mutex(MutexExp, 0, D); |
| if (!Mutex.isValid()) { |
| MutexID::warnInvalidLock(Handler, MutexExp, 0, D); |
| return LSet; |
| } |
| LockData NewLock(Loc, LK); |
| return LocksetFactory.add(LSet, Mutex, NewLock); |
| } |
| |
| /// \brief Check a function's CFG for thread-safety violations. |
| /// |
| /// We traverse the blocks in the CFG, compute the set of mutexes that are held |
| /// at the end of each block, and issue warnings for thread safety violations. |
| /// Each block in the CFG is traversed exactly once. |
| void ThreadSafetyAnalyzer::runAnalysis(AnalysisContext &AC) { |
| CFG *CFGraph = AC.getCFG(); |
| if (!CFGraph) return; |
| const NamedDecl *D = dyn_cast_or_null<NamedDecl>(AC.getDecl()); |
| |
| if (!D) |
| return; // Ignore anonymous functions for now. |
| if (D->getAttr<NoThreadSafetyAnalysisAttr>()) |
| return; |
| |
| // FIXME: Switch to SmallVector? Otherwise improve performance impact? |
| std::vector<Lockset> EntryLocksets(CFGraph->getNumBlockIDs(), |
| LocksetFactory.getEmptyMap()); |
| std::vector<Lockset> ExitLocksets(CFGraph->getNumBlockIDs(), |
| LocksetFactory.getEmptyMap()); |
| |
| // We need to explore the CFG via a "topological" ordering. |
| // That way, we will be guaranteed to have information about required |
| // predecessor locksets when exploring a new block. |
| TopologicallySortedCFG SortedGraph(CFGraph); |
| CFGBlockSet VisitedBlocks(CFGraph); |
| |
| // Add locks from exclusive_locks_required and shared_locks_required |
| // to initial lockset. |
| if (!SortedGraph.empty() && D->hasAttrs()) { |
| const CFGBlock *FirstBlock = *SortedGraph.begin(); |
| Lockset &InitialLockset = EntryLocksets[FirstBlock->getBlockID()]; |
| const AttrVec &ArgAttrs = D->getAttrs(); |
| for(unsigned i = 0; i < ArgAttrs.size(); ++i) { |
| Attr *Attr = ArgAttrs[i]; |
| SourceLocation AttrLoc = Attr->getLocation(); |
| if (SharedLocksRequiredAttr *SLRAttr |
| = dyn_cast<SharedLocksRequiredAttr>(Attr)) { |
| for (SharedLocksRequiredAttr::args_iterator |
| SLRIter = SLRAttr->args_begin(), |
| SLREnd = SLRAttr->args_end(); SLRIter != SLREnd; ++SLRIter) |
| InitialLockset = addLock(InitialLockset, |
| *SLRIter, D, LK_Shared, |
| AttrLoc); |
| } else if (ExclusiveLocksRequiredAttr *ELRAttr |
| = dyn_cast<ExclusiveLocksRequiredAttr>(Attr)) { |
| for (ExclusiveLocksRequiredAttr::args_iterator |
| ELRIter = ELRAttr->args_begin(), |
| ELREnd = ELRAttr->args_end(); ELRIter != ELREnd; ++ELRIter) |
| InitialLockset = addLock(InitialLockset, |
| *ELRIter, D, LK_Exclusive, |
| AttrLoc); |
| } |
| } |
| } |
| |
| for (TopologicallySortedCFG::iterator I = SortedGraph.begin(), |
| E = SortedGraph.end(); I!= E; ++I) { |
| const CFGBlock *CurrBlock = *I; |
| int CurrBlockID = CurrBlock->getBlockID(); |
| |
| VisitedBlocks.insert(CurrBlock); |
| |
| // Use the default initial lockset in case there are no predecessors. |
| Lockset &Entryset = EntryLocksets[CurrBlockID]; |
| Lockset &Exitset = ExitLocksets[CurrBlockID]; |
| |
| // Iterate through the predecessor blocks and warn if the lockset for all |
| // predecessors is not the same. We take the entry lockset of the current |
| // block to be the intersection of all previous locksets. |
| // FIXME: By keeping the intersection, we may output more errors in future |
| // for a lock which is not in the intersection, but was in the union. We |
| // may want to also keep the union in future. As an example, let's say |
| // the intersection contains Mutex L, and the union contains L and M. |
| // Later we unlock M. At this point, we would output an error because we |
| // never locked M; although the real error is probably that we forgot to |
| // lock M on all code paths. Conversely, let's say that later we lock M. |
| // In this case, we should compare against the intersection instead of the |
| // union because the real error is probably that we forgot to unlock M on |
| // all code paths. |
| bool LocksetInitialized = false; |
| for (CFGBlock::const_pred_iterator PI = CurrBlock->pred_begin(), |
| PE = CurrBlock->pred_end(); PI != PE; ++PI) { |
| |
| // if *PI -> CurrBlock is a back edge |
| if (*PI == 0 || !VisitedBlocks.alreadySet(*PI)) |
| continue; |
| |
| int PrevBlockID = (*PI)->getBlockID(); |
| if (!LocksetInitialized) { |
| Entryset = ExitLocksets[PrevBlockID]; |
| LocksetInitialized = true; |
| } else { |
| Entryset = intersectAndWarn(Entryset, ExitLocksets[PrevBlockID], |
| LEK_LockedSomePredecessors); |
| } |
| } |
| |
| BuildLockset LocksetBuilder(Handler, Entryset, LocksetFactory); |
| for (CFGBlock::const_iterator BI = CurrBlock->begin(), |
| BE = CurrBlock->end(); BI != BE; ++BI) { |
| if (const CFGStmt *CfgStmt = dyn_cast<CFGStmt>(&*BI)) |
| LocksetBuilder.Visit(const_cast<Stmt*>(CfgStmt->getStmt())); |
| } |
| Exitset = LocksetBuilder.getLockset(); |
| |
| // For every back edge from CurrBlock (the end of the loop) to another block |
| // (FirstLoopBlock) we need to check that the Lockset of Block is equal to |
| // the one held at the beginning of FirstLoopBlock. We can look up the |
| // Lockset held at the beginning of FirstLoopBlock in the EntryLockSets map. |
| for (CFGBlock::const_succ_iterator SI = CurrBlock->succ_begin(), |
| SE = CurrBlock->succ_end(); SI != SE; ++SI) { |
| |
| // if CurrBlock -> *SI is *not* a back edge |
| if (*SI == 0 || !VisitedBlocks.alreadySet(*SI)) |
| continue; |
| |
| CFGBlock *FirstLoopBlock = *SI; |
| Lockset PreLoop = EntryLocksets[FirstLoopBlock->getBlockID()]; |
| Lockset LoopEnd = ExitLocksets[CurrBlockID]; |
| intersectAndWarn(LoopEnd, PreLoop, LEK_LockedSomeLoopIterations); |
| } |
| } |
| |
| Lockset InitialLockset = EntryLocksets[CFGraph->getEntry().getBlockID()]; |
| Lockset FinalLockset = ExitLocksets[CFGraph->getExit().getBlockID()]; |
| |
| // FIXME: Should we call this function for all blocks which exit the function? |
| intersectAndWarn(InitialLockset, FinalLockset, LEK_LockedAtEndOfFunction); |
| } |
| |
| } // end anonymous namespace |
| |
| |
| namespace clang { |
| namespace thread_safety { |
| |
| /// \brief Check a function's CFG for thread-safety violations. |
| /// |
| /// We traverse the blocks in the CFG, compute the set of mutexes that are held |
| /// at the end of each block, and issue warnings for thread safety violations. |
| /// Each block in the CFG is traversed exactly once. |
| void runThreadSafetyAnalysis(AnalysisContext &AC, |
| ThreadSafetyHandler &Handler) { |
| ThreadSafetyAnalyzer Analyzer(Handler); |
| Analyzer.runAnalysis(AC); |
| } |
| |
| /// \brief Helper function that returns a LockKind required for the given level |
| /// of access. |
| LockKind getLockKindFromAccessKind(AccessKind AK) { |
| switch (AK) { |
| case AK_Read : |
| return LK_Shared; |
| case AK_Written : |
| return LK_Exclusive; |
| } |
| llvm_unreachable("Unknown AccessKind"); |
| } |
| |
| }} // end namespace clang::thread_safety |