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1 //===- ThreadSafety.cpp ----------------------------------------*- C++ --*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // A intra-procedural analysis for thread safety (e.g. deadlocks and race
11 // conditions), based off of an annotation system.
12 //
13 // See http://clang.llvm.org/docs/ThreadSafetyAnalysis.html
14 // for more information.
15 //
16 //===----------------------------------------------------------------------===//
17 
18 #include "clang/AST/Attr.h"
19 #include "clang/AST/DeclCXX.h"
20 #include "clang/AST/ExprCXX.h"
21 #include "clang/AST/StmtCXX.h"
22 #include "clang/AST/StmtVisitor.h"
23 #include "clang/Analysis/Analyses/PostOrderCFGView.h"
24 #include "clang/Analysis/Analyses/ThreadSafety.h"
25 #include "clang/Analysis/Analyses/ThreadSafetyCommon.h"
26 #include "clang/Analysis/Analyses/ThreadSafetyLogical.h"
27 #include "clang/Analysis/Analyses/ThreadSafetyTIL.h"
28 #include "clang/Analysis/Analyses/ThreadSafetyTraverse.h"
29 #include "clang/Analysis/AnalysisContext.h"
30 #include "clang/Analysis/CFG.h"
31 #include "clang/Analysis/CFGStmtMap.h"
32 #include "clang/Basic/OperatorKinds.h"
33 #include "clang/Basic/SourceLocation.h"
34 #include "clang/Basic/SourceManager.h"
35 #include "llvm/ADT/BitVector.h"
36 #include "llvm/ADT/FoldingSet.h"
37 #include "llvm/ADT/ImmutableMap.h"
38 #include "llvm/ADT/PostOrderIterator.h"
39 #include "llvm/ADT/SmallVector.h"
40 #include "llvm/ADT/StringRef.h"
41 #include "llvm/Support/raw_ostream.h"
42 #include <algorithm>
43 #include <ostream>
44 #include <sstream>
45 #include <utility>
46 #include <vector>
47 using namespace clang;
48 using namespace threadSafety;
49 
50 // Key method definition
~ThreadSafetyHandler()51 ThreadSafetyHandler::~ThreadSafetyHandler() {}
52 
53 namespace {
54 class TILPrinter :
55   public til::PrettyPrinter<TILPrinter, llvm::raw_ostream> {};
56 
57 
58 /// Issue a warning about an invalid lock expression
warnInvalidLock(ThreadSafetyHandler & Handler,const Expr * MutexExp,const NamedDecl * D,const Expr * DeclExp,StringRef Kind)59 static void warnInvalidLock(ThreadSafetyHandler &Handler,
60                             const Expr *MutexExp, const NamedDecl *D,
61                             const Expr *DeclExp, StringRef Kind) {
62   SourceLocation Loc;
63   if (DeclExp)
64     Loc = DeclExp->getExprLoc();
65 
66   // FIXME: add a note about the attribute location in MutexExp or D
67   if (Loc.isValid())
68     Handler.handleInvalidLockExp(Kind, Loc);
69 }
70 
71 /// \brief A set of CapabilityInfo objects, which are compiled from the
72 /// requires attributes on a function.
73 class CapExprSet : public SmallVector<CapabilityExpr, 4> {
74 public:
75   /// \brief Push M onto list, but discard duplicates.
push_back_nodup(const CapabilityExpr & CapE)76   void push_back_nodup(const CapabilityExpr &CapE) {
77     iterator It = std::find_if(begin(), end(),
78                                [=](const CapabilityExpr &CapE2) {
79       return CapE.equals(CapE2);
80     });
81     if (It == end())
82       push_back(CapE);
83   }
84 };
85 
86 class FactManager;
87 class FactSet;
88 
89 /// \brief This is a helper class that stores a fact that is known at a
90 /// particular point in program execution.  Currently, a fact is a capability,
91 /// along with additional information, such as where it was acquired, whether
92 /// it is exclusive or shared, etc.
93 ///
94 /// FIXME: this analysis does not currently support either re-entrant
95 /// locking or lock "upgrading" and "downgrading" between exclusive and
96 /// shared.
97 class FactEntry : public CapabilityExpr {
98 private:
99   LockKind          LKind;            ///<  exclusive or shared
100   SourceLocation    AcquireLoc;       ///<  where it was acquired.
101   bool              Asserted;         ///<  true if the lock was asserted
102   bool              Declared;         ///<  true if the lock was declared
103 
104 public:
FactEntry(const CapabilityExpr & CE,LockKind LK,SourceLocation Loc,bool Asrt,bool Declrd=false)105   FactEntry(const CapabilityExpr &CE, LockKind LK, SourceLocation Loc,
106             bool Asrt, bool Declrd = false)
107       : CapabilityExpr(CE), LKind(LK), AcquireLoc(Loc), Asserted(Asrt),
108         Declared(Declrd) {}
109 
~FactEntry()110   virtual ~FactEntry() {}
111 
kind() const112   LockKind          kind()       const { return LKind;      }
loc() const113   SourceLocation    loc()        const { return AcquireLoc; }
asserted() const114   bool              asserted()   const { return Asserted; }
declared() const115   bool              declared()   const { return Declared; }
116 
setDeclared(bool D)117   void setDeclared(bool D) { Declared = D; }
118 
119   virtual void
120   handleRemovalFromIntersection(const FactSet &FSet, FactManager &FactMan,
121                                 SourceLocation JoinLoc, LockErrorKind LEK,
122                                 ThreadSafetyHandler &Handler) const = 0;
123   virtual void handleUnlock(FactSet &FSet, FactManager &FactMan,
124                             const CapabilityExpr &Cp, SourceLocation UnlockLoc,
125                             bool FullyRemove, ThreadSafetyHandler &Handler,
126                             StringRef DiagKind) const = 0;
127 
128   // Return true if LKind >= LK, where exclusive > shared
isAtLeast(LockKind LK)129   bool isAtLeast(LockKind LK) {
130     return  (LKind == LK_Exclusive) || (LK == LK_Shared);
131   }
132 };
133 
134 
135 typedef unsigned short FactID;
136 
137 /// \brief FactManager manages the memory for all facts that are created during
138 /// the analysis of a single routine.
139 class FactManager {
140 private:
141   std::vector<std::unique_ptr<FactEntry>> Facts;
142 
143 public:
newFact(std::unique_ptr<FactEntry> Entry)144   FactID newFact(std::unique_ptr<FactEntry> Entry) {
145     Facts.push_back(std::move(Entry));
146     return static_cast<unsigned short>(Facts.size() - 1);
147   }
148 
operator [](FactID F) const149   const FactEntry &operator[](FactID F) const { return *Facts[F]; }
operator [](FactID F)150   FactEntry &operator[](FactID F) { return *Facts[F]; }
151 };
152 
153 
154 /// \brief A FactSet is the set of facts that are known to be true at a
155 /// particular program point.  FactSets must be small, because they are
156 /// frequently copied, and are thus implemented as a set of indices into a
157 /// table maintained by a FactManager.  A typical FactSet only holds 1 or 2
158 /// locks, so we can get away with doing a linear search for lookup.  Note
159 /// that a hashtable or map is inappropriate in this case, because lookups
160 /// may involve partial pattern matches, rather than exact matches.
161 class FactSet {
162 private:
163   typedef SmallVector<FactID, 4> FactVec;
164 
165   FactVec FactIDs;
166 
167 public:
168   typedef FactVec::iterator       iterator;
169   typedef FactVec::const_iterator const_iterator;
170 
begin()171   iterator       begin()       { return FactIDs.begin(); }
begin() const172   const_iterator begin() const { return FactIDs.begin(); }
173 
end()174   iterator       end()       { return FactIDs.end(); }
end() const175   const_iterator end() const { return FactIDs.end(); }
176 
isEmpty() const177   bool isEmpty() const { return FactIDs.size() == 0; }
178 
179   // Return true if the set contains only negative facts
isEmpty(FactManager & FactMan) const180   bool isEmpty(FactManager &FactMan) const {
181     for (FactID FID : *this) {
182       if (!FactMan[FID].negative())
183         return false;
184     }
185     return true;
186   }
187 
addLockByID(FactID ID)188   void addLockByID(FactID ID) { FactIDs.push_back(ID); }
189 
addLock(FactManager & FM,std::unique_ptr<FactEntry> Entry)190   FactID addLock(FactManager &FM, std::unique_ptr<FactEntry> Entry) {
191     FactID F = FM.newFact(std::move(Entry));
192     FactIDs.push_back(F);
193     return F;
194   }
195 
removeLock(FactManager & FM,const CapabilityExpr & CapE)196   bool removeLock(FactManager& FM, const CapabilityExpr &CapE) {
197     unsigned n = FactIDs.size();
198     if (n == 0)
199       return false;
200 
201     for (unsigned i = 0; i < n-1; ++i) {
202       if (FM[FactIDs[i]].matches(CapE)) {
203         FactIDs[i] = FactIDs[n-1];
204         FactIDs.pop_back();
205         return true;
206       }
207     }
208     if (FM[FactIDs[n-1]].matches(CapE)) {
209       FactIDs.pop_back();
210       return true;
211     }
212     return false;
213   }
214 
findLockIter(FactManager & FM,const CapabilityExpr & CapE)215   iterator findLockIter(FactManager &FM, const CapabilityExpr &CapE) {
216     return std::find_if(begin(), end(), [&](FactID ID) {
217       return FM[ID].matches(CapE);
218     });
219   }
220 
findLock(FactManager & FM,const CapabilityExpr & CapE) const221   FactEntry *findLock(FactManager &FM, const CapabilityExpr &CapE) const {
222     auto I = std::find_if(begin(), end(), [&](FactID ID) {
223       return FM[ID].matches(CapE);
224     });
225     return I != end() ? &FM[*I] : nullptr;
226   }
227 
findLockUniv(FactManager & FM,const CapabilityExpr & CapE) const228   FactEntry *findLockUniv(FactManager &FM, const CapabilityExpr &CapE) const {
229     auto I = std::find_if(begin(), end(), [&](FactID ID) -> bool {
230       return FM[ID].matchesUniv(CapE);
231     });
232     return I != end() ? &FM[*I] : nullptr;
233   }
234 
findPartialMatch(FactManager & FM,const CapabilityExpr & CapE) const235   FactEntry *findPartialMatch(FactManager &FM,
236                               const CapabilityExpr &CapE) const {
237     auto I = std::find_if(begin(), end(), [&](FactID ID) -> bool {
238       return FM[ID].partiallyMatches(CapE);
239     });
240     return I != end() ? &FM[*I] : nullptr;
241   }
242 
containsMutexDecl(FactManager & FM,const ValueDecl * Vd) const243   bool containsMutexDecl(FactManager &FM, const ValueDecl* Vd) const {
244     auto I = std::find_if(begin(), end(), [&](FactID ID) -> bool {
245       return FM[ID].valueDecl() == Vd;
246     });
247     return I != end();
248   }
249 };
250 
251 class ThreadSafetyAnalyzer;
252 } // namespace
253 
254 namespace clang {
255 namespace threadSafety {
256 class BeforeSet {
257 private:
258   typedef SmallVector<const ValueDecl*, 4>  BeforeVect;
259 
260   struct BeforeInfo {
BeforeInfoclang::threadSafety::BeforeSet::BeforeInfo261     BeforeInfo() : Visited(0) {}
BeforeInfoclang::threadSafety::BeforeSet::BeforeInfo262     BeforeInfo(BeforeInfo &&O) : Vect(std::move(O.Vect)), Visited(O.Visited) {}
263 
264     BeforeVect Vect;
265     int Visited;
266   };
267 
268   typedef llvm::DenseMap<const ValueDecl *, std::unique_ptr<BeforeInfo>>
269       BeforeMap;
270   typedef llvm::DenseMap<const ValueDecl*, bool>        CycleMap;
271 
272 public:
BeforeSet()273   BeforeSet() { }
274 
275   BeforeInfo* insertAttrExprs(const ValueDecl* Vd,
276                               ThreadSafetyAnalyzer& Analyzer);
277 
278   BeforeInfo *getBeforeInfoForDecl(const ValueDecl *Vd,
279                                    ThreadSafetyAnalyzer &Analyzer);
280 
281   void checkBeforeAfter(const ValueDecl* Vd,
282                         const FactSet& FSet,
283                         ThreadSafetyAnalyzer& Analyzer,
284                         SourceLocation Loc, StringRef CapKind);
285 
286 private:
287   BeforeMap BMap;
288   CycleMap  CycMap;
289 };
290 } // end namespace threadSafety
291 } // end namespace clang
292 
293 namespace {
294 typedef llvm::ImmutableMap<const NamedDecl*, unsigned> LocalVarContext;
295 class LocalVariableMap;
296 
297 /// A side (entry or exit) of a CFG node.
298 enum CFGBlockSide { CBS_Entry, CBS_Exit };
299 
300 /// CFGBlockInfo is a struct which contains all the information that is
301 /// maintained for each block in the CFG.  See LocalVariableMap for more
302 /// information about the contexts.
303 struct CFGBlockInfo {
304   FactSet EntrySet;             // Lockset held at entry to block
305   FactSet ExitSet;              // Lockset held at exit from block
306   LocalVarContext EntryContext; // Context held at entry to block
307   LocalVarContext ExitContext;  // Context held at exit from block
308   SourceLocation EntryLoc;      // Location of first statement in block
309   SourceLocation ExitLoc;       // Location of last statement in block.
310   unsigned EntryIndex;          // Used to replay contexts later
311   bool Reachable;               // Is this block reachable?
312 
getSet__anon4f66b6dc0811::CFGBlockInfo313   const FactSet &getSet(CFGBlockSide Side) const {
314     return Side == CBS_Entry ? EntrySet : ExitSet;
315   }
getLocation__anon4f66b6dc0811::CFGBlockInfo316   SourceLocation getLocation(CFGBlockSide Side) const {
317     return Side == CBS_Entry ? EntryLoc : ExitLoc;
318   }
319 
320 private:
CFGBlockInfo__anon4f66b6dc0811::CFGBlockInfo321   CFGBlockInfo(LocalVarContext EmptyCtx)
322     : EntryContext(EmptyCtx), ExitContext(EmptyCtx), Reachable(false)
323   { }
324 
325 public:
326   static CFGBlockInfo getEmptyBlockInfo(LocalVariableMap &M);
327 };
328 
329 
330 
331 // A LocalVariableMap maintains a map from local variables to their currently
332 // valid definitions.  It provides SSA-like functionality when traversing the
333 // CFG.  Like SSA, each definition or assignment to a variable is assigned a
334 // unique name (an integer), which acts as the SSA name for that definition.
335 // The total set of names is shared among all CFG basic blocks.
336 // Unlike SSA, we do not rewrite expressions to replace local variables declrefs
337 // with their SSA-names.  Instead, we compute a Context for each point in the
338 // code, which maps local variables to the appropriate SSA-name.  This map
339 // changes with each assignment.
340 //
341 // The map is computed in a single pass over the CFG.  Subsequent analyses can
342 // then query the map to find the appropriate Context for a statement, and use
343 // that Context to look up the definitions of variables.
344 class LocalVariableMap {
345 public:
346   typedef LocalVarContext Context;
347 
348   /// A VarDefinition consists of an expression, representing the value of the
349   /// variable, along with the context in which that expression should be
350   /// interpreted.  A reference VarDefinition does not itself contain this
351   /// information, but instead contains a pointer to a previous VarDefinition.
352   struct VarDefinition {
353   public:
354     friend class LocalVariableMap;
355 
356     const NamedDecl *Dec;  // The original declaration for this variable.
357     const Expr *Exp;       // The expression for this variable, OR
358     unsigned Ref;          // Reference to another VarDefinition
359     Context Ctx;           // The map with which Exp should be interpreted.
360 
isReference__anon4f66b6dc0811::LocalVariableMap::VarDefinition361     bool isReference() { return !Exp; }
362 
363   private:
364     // Create ordinary variable definition
VarDefinition__anon4f66b6dc0811::LocalVariableMap::VarDefinition365     VarDefinition(const NamedDecl *D, const Expr *E, Context C)
366       : Dec(D), Exp(E), Ref(0), Ctx(C)
367     { }
368 
369     // Create reference to previous definition
VarDefinition__anon4f66b6dc0811::LocalVariableMap::VarDefinition370     VarDefinition(const NamedDecl *D, unsigned R, Context C)
371       : Dec(D), Exp(nullptr), Ref(R), Ctx(C)
372     { }
373   };
374 
375 private:
376   Context::Factory ContextFactory;
377   std::vector<VarDefinition> VarDefinitions;
378   std::vector<unsigned> CtxIndices;
379   std::vector<std::pair<Stmt*, Context> > SavedContexts;
380 
381 public:
LocalVariableMap()382   LocalVariableMap() {
383     // index 0 is a placeholder for undefined variables (aka phi-nodes).
384     VarDefinitions.push_back(VarDefinition(nullptr, 0u, getEmptyContext()));
385   }
386 
387   /// Look up a definition, within the given context.
lookup(const NamedDecl * D,Context Ctx)388   const VarDefinition* lookup(const NamedDecl *D, Context Ctx) {
389     const unsigned *i = Ctx.lookup(D);
390     if (!i)
391       return nullptr;
392     assert(*i < VarDefinitions.size());
393     return &VarDefinitions[*i];
394   }
395 
396   /// Look up the definition for D within the given context.  Returns
397   /// NULL if the expression is not statically known.  If successful, also
398   /// modifies Ctx to hold the context of the return Expr.
lookupExpr(const NamedDecl * D,Context & Ctx)399   const Expr* lookupExpr(const NamedDecl *D, Context &Ctx) {
400     const unsigned *P = Ctx.lookup(D);
401     if (!P)
402       return nullptr;
403 
404     unsigned i = *P;
405     while (i > 0) {
406       if (VarDefinitions[i].Exp) {
407         Ctx = VarDefinitions[i].Ctx;
408         return VarDefinitions[i].Exp;
409       }
410       i = VarDefinitions[i].Ref;
411     }
412     return nullptr;
413   }
414 
getEmptyContext()415   Context getEmptyContext() { return ContextFactory.getEmptyMap(); }
416 
417   /// Return the next context after processing S.  This function is used by
418   /// clients of the class to get the appropriate context when traversing the
419   /// CFG.  It must be called for every assignment or DeclStmt.
getNextContext(unsigned & CtxIndex,Stmt * S,Context C)420   Context getNextContext(unsigned &CtxIndex, Stmt *S, Context C) {
421     if (SavedContexts[CtxIndex+1].first == S) {
422       CtxIndex++;
423       Context Result = SavedContexts[CtxIndex].second;
424       return Result;
425     }
426     return C;
427   }
428 
dumpVarDefinitionName(unsigned i)429   void dumpVarDefinitionName(unsigned i) {
430     if (i == 0) {
431       llvm::errs() << "Undefined";
432       return;
433     }
434     const NamedDecl *Dec = VarDefinitions[i].Dec;
435     if (!Dec) {
436       llvm::errs() << "<<NULL>>";
437       return;
438     }
439     Dec->printName(llvm::errs());
440     llvm::errs() << "." << i << " " << ((const void*) Dec);
441   }
442 
443   /// Dumps an ASCII representation of the variable map to llvm::errs()
dump()444   void dump() {
445     for (unsigned i = 1, e = VarDefinitions.size(); i < e; ++i) {
446       const Expr *Exp = VarDefinitions[i].Exp;
447       unsigned Ref = VarDefinitions[i].Ref;
448 
449       dumpVarDefinitionName(i);
450       llvm::errs() << " = ";
451       if (Exp) Exp->dump();
452       else {
453         dumpVarDefinitionName(Ref);
454         llvm::errs() << "\n";
455       }
456     }
457   }
458 
459   /// Dumps an ASCII representation of a Context to llvm::errs()
dumpContext(Context C)460   void dumpContext(Context C) {
461     for (Context::iterator I = C.begin(), E = C.end(); I != E; ++I) {
462       const NamedDecl *D = I.getKey();
463       D->printName(llvm::errs());
464       const unsigned *i = C.lookup(D);
465       llvm::errs() << " -> ";
466       dumpVarDefinitionName(*i);
467       llvm::errs() << "\n";
468     }
469   }
470 
471   /// Builds the variable map.
472   void traverseCFG(CFG *CFGraph, const PostOrderCFGView *SortedGraph,
473                    std::vector<CFGBlockInfo> &BlockInfo);
474 
475 protected:
476   // Get the current context index
getContextIndex()477   unsigned getContextIndex() { return SavedContexts.size()-1; }
478 
479   // Save the current context for later replay
saveContext(Stmt * S,Context C)480   void saveContext(Stmt *S, Context C) {
481     SavedContexts.push_back(std::make_pair(S,C));
482   }
483 
484   // Adds a new definition to the given context, and returns a new context.
485   // This method should be called when declaring a new variable.
addDefinition(const NamedDecl * D,const Expr * Exp,Context Ctx)486   Context addDefinition(const NamedDecl *D, const Expr *Exp, Context Ctx) {
487     assert(!Ctx.contains(D));
488     unsigned newID = VarDefinitions.size();
489     Context NewCtx = ContextFactory.add(Ctx, D, newID);
490     VarDefinitions.push_back(VarDefinition(D, Exp, Ctx));
491     return NewCtx;
492   }
493 
494   // Add a new reference to an existing definition.
addReference(const NamedDecl * D,unsigned i,Context Ctx)495   Context addReference(const NamedDecl *D, unsigned i, Context Ctx) {
496     unsigned newID = VarDefinitions.size();
497     Context NewCtx = ContextFactory.add(Ctx, D, newID);
498     VarDefinitions.push_back(VarDefinition(D, i, Ctx));
499     return NewCtx;
500   }
501 
502   // Updates a definition only if that definition is already in the map.
503   // This method should be called when assigning to an existing variable.
updateDefinition(const NamedDecl * D,Expr * Exp,Context Ctx)504   Context updateDefinition(const NamedDecl *D, Expr *Exp, Context Ctx) {
505     if (Ctx.contains(D)) {
506       unsigned newID = VarDefinitions.size();
507       Context NewCtx = ContextFactory.remove(Ctx, D);
508       NewCtx = ContextFactory.add(NewCtx, D, newID);
509       VarDefinitions.push_back(VarDefinition(D, Exp, Ctx));
510       return NewCtx;
511     }
512     return Ctx;
513   }
514 
515   // Removes a definition from the context, but keeps the variable name
516   // as a valid variable.  The index 0 is a placeholder for cleared definitions.
clearDefinition(const NamedDecl * D,Context Ctx)517   Context clearDefinition(const NamedDecl *D, Context Ctx) {
518     Context NewCtx = Ctx;
519     if (NewCtx.contains(D)) {
520       NewCtx = ContextFactory.remove(NewCtx, D);
521       NewCtx = ContextFactory.add(NewCtx, D, 0);
522     }
523     return NewCtx;
524   }
525 
526   // Remove a definition entirely frmo the context.
removeDefinition(const NamedDecl * D,Context Ctx)527   Context removeDefinition(const NamedDecl *D, Context Ctx) {
528     Context NewCtx = Ctx;
529     if (NewCtx.contains(D)) {
530       NewCtx = ContextFactory.remove(NewCtx, D);
531     }
532     return NewCtx;
533   }
534 
535   Context intersectContexts(Context C1, Context C2);
536   Context createReferenceContext(Context C);
537   void intersectBackEdge(Context C1, Context C2);
538 
539   friend class VarMapBuilder;
540 };
541 
542 
543 // This has to be defined after LocalVariableMap.
getEmptyBlockInfo(LocalVariableMap & M)544 CFGBlockInfo CFGBlockInfo::getEmptyBlockInfo(LocalVariableMap &M) {
545   return CFGBlockInfo(M.getEmptyContext());
546 }
547 
548 
549 /// Visitor which builds a LocalVariableMap
550 class VarMapBuilder : public StmtVisitor<VarMapBuilder> {
551 public:
552   LocalVariableMap* VMap;
553   LocalVariableMap::Context Ctx;
554 
VarMapBuilder(LocalVariableMap * VM,LocalVariableMap::Context C)555   VarMapBuilder(LocalVariableMap *VM, LocalVariableMap::Context C)
556     : VMap(VM), Ctx(C) {}
557 
558   void VisitDeclStmt(DeclStmt *S);
559   void VisitBinaryOperator(BinaryOperator *BO);
560 };
561 
562 
563 // Add new local variables to the variable map
VisitDeclStmt(DeclStmt * S)564 void VarMapBuilder::VisitDeclStmt(DeclStmt *S) {
565   bool modifiedCtx = false;
566   DeclGroupRef DGrp = S->getDeclGroup();
567   for (const auto *D : DGrp) {
568     if (const auto *VD = dyn_cast_or_null<VarDecl>(D)) {
569       const Expr *E = VD->getInit();
570 
571       // Add local variables with trivial type to the variable map
572       QualType T = VD->getType();
573       if (T.isTrivialType(VD->getASTContext())) {
574         Ctx = VMap->addDefinition(VD, E, Ctx);
575         modifiedCtx = true;
576       }
577     }
578   }
579   if (modifiedCtx)
580     VMap->saveContext(S, Ctx);
581 }
582 
583 // Update local variable definitions in variable map
VisitBinaryOperator(BinaryOperator * BO)584 void VarMapBuilder::VisitBinaryOperator(BinaryOperator *BO) {
585   if (!BO->isAssignmentOp())
586     return;
587 
588   Expr *LHSExp = BO->getLHS()->IgnoreParenCasts();
589 
590   // Update the variable map and current context.
591   if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(LHSExp)) {
592     ValueDecl *VDec = DRE->getDecl();
593     if (Ctx.lookup(VDec)) {
594       if (BO->getOpcode() == BO_Assign)
595         Ctx = VMap->updateDefinition(VDec, BO->getRHS(), Ctx);
596       else
597         // FIXME -- handle compound assignment operators
598         Ctx = VMap->clearDefinition(VDec, Ctx);
599       VMap->saveContext(BO, Ctx);
600     }
601   }
602 }
603 
604 
605 // Computes the intersection of two contexts.  The intersection is the
606 // set of variables which have the same definition in both contexts;
607 // variables with different definitions are discarded.
608 LocalVariableMap::Context
intersectContexts(Context C1,Context C2)609 LocalVariableMap::intersectContexts(Context C1, Context C2) {
610   Context Result = C1;
611   for (const auto &P : C1) {
612     const NamedDecl *Dec = P.first;
613     const unsigned *i2 = C2.lookup(Dec);
614     if (!i2)             // variable doesn't exist on second path
615       Result = removeDefinition(Dec, Result);
616     else if (*i2 != P.second)  // variable exists, but has different definition
617       Result = clearDefinition(Dec, Result);
618   }
619   return Result;
620 }
621 
622 // For every variable in C, create a new variable that refers to the
623 // definition in C.  Return a new context that contains these new variables.
624 // (We use this for a naive implementation of SSA on loop back-edges.)
createReferenceContext(Context C)625 LocalVariableMap::Context LocalVariableMap::createReferenceContext(Context C) {
626   Context Result = getEmptyContext();
627   for (const auto &P : C)
628     Result = addReference(P.first, P.second, Result);
629   return Result;
630 }
631 
632 // This routine also takes the intersection of C1 and C2, but it does so by
633 // altering the VarDefinitions.  C1 must be the result of an earlier call to
634 // createReferenceContext.
intersectBackEdge(Context C1,Context C2)635 void LocalVariableMap::intersectBackEdge(Context C1, Context C2) {
636   for (const auto &P : C1) {
637     unsigned i1 = P.second;
638     VarDefinition *VDef = &VarDefinitions[i1];
639     assert(VDef->isReference());
640 
641     const unsigned *i2 = C2.lookup(P.first);
642     if (!i2 || (*i2 != i1))
643       VDef->Ref = 0;    // Mark this variable as undefined
644   }
645 }
646 
647 
648 // Traverse the CFG in topological order, so all predecessors of a block
649 // (excluding back-edges) are visited before the block itself.  At
650 // each point in the code, we calculate a Context, which holds the set of
651 // variable definitions which are visible at that point in execution.
652 // Visible variables are mapped to their definitions using an array that
653 // contains all definitions.
654 //
655 // At join points in the CFG, the set is computed as the intersection of
656 // the incoming sets along each edge, E.g.
657 //
658 //                       { Context                 | VarDefinitions }
659 //   int x = 0;          { x -> x1                 | x1 = 0 }
660 //   int y = 0;          { x -> x1, y -> y1        | y1 = 0, x1 = 0 }
661 //   if (b) x = 1;       { x -> x2, y -> y1        | x2 = 1, y1 = 0, ... }
662 //   else   x = 2;       { x -> x3, y -> y1        | x3 = 2, x2 = 1, ... }
663 //   ...                 { y -> y1  (x is unknown) | x3 = 2, x2 = 1, ... }
664 //
665 // This is essentially a simpler and more naive version of the standard SSA
666 // algorithm.  Those definitions that remain in the intersection are from blocks
667 // that strictly dominate the current block.  We do not bother to insert proper
668 // phi nodes, because they are not used in our analysis; instead, wherever
669 // a phi node would be required, we simply remove that definition from the
670 // context (E.g. x above).
671 //
672 // The initial traversal does not capture back-edges, so those need to be
673 // handled on a separate pass.  Whenever the first pass encounters an
674 // incoming back edge, it duplicates the context, creating new definitions
675 // that refer back to the originals.  (These correspond to places where SSA
676 // might have to insert a phi node.)  On the second pass, these definitions are
677 // set to NULL if the variable has changed on the back-edge (i.e. a phi
678 // node was actually required.)  E.g.
679 //
680 //                       { Context           | VarDefinitions }
681 //   int x = 0, y = 0;   { x -> x1, y -> y1  | y1 = 0, x1 = 0 }
682 //   while (b)           { x -> x2, y -> y1  | [1st:] x2=x1; [2nd:] x2=NULL; }
683 //     x = x+1;          { x -> x3, y -> y1  | x3 = x2 + 1, ... }
684 //   ...                 { y -> y1           | x3 = 2, x2 = 1, ... }
685 //
traverseCFG(CFG * CFGraph,const PostOrderCFGView * SortedGraph,std::vector<CFGBlockInfo> & BlockInfo)686 void LocalVariableMap::traverseCFG(CFG *CFGraph,
687                                    const PostOrderCFGView *SortedGraph,
688                                    std::vector<CFGBlockInfo> &BlockInfo) {
689   PostOrderCFGView::CFGBlockSet VisitedBlocks(CFGraph);
690 
691   CtxIndices.resize(CFGraph->getNumBlockIDs());
692 
693   for (const auto *CurrBlock : *SortedGraph) {
694     int CurrBlockID = CurrBlock->getBlockID();
695     CFGBlockInfo *CurrBlockInfo = &BlockInfo[CurrBlockID];
696 
697     VisitedBlocks.insert(CurrBlock);
698 
699     // Calculate the entry context for the current block
700     bool HasBackEdges = false;
701     bool CtxInit = true;
702     for (CFGBlock::const_pred_iterator PI = CurrBlock->pred_begin(),
703          PE  = CurrBlock->pred_end(); PI != PE; ++PI) {
704       // if *PI -> CurrBlock is a back edge, so skip it
705       if (*PI == nullptr || !VisitedBlocks.alreadySet(*PI)) {
706         HasBackEdges = true;
707         continue;
708       }
709 
710       int PrevBlockID = (*PI)->getBlockID();
711       CFGBlockInfo *PrevBlockInfo = &BlockInfo[PrevBlockID];
712 
713       if (CtxInit) {
714         CurrBlockInfo->EntryContext = PrevBlockInfo->ExitContext;
715         CtxInit = false;
716       }
717       else {
718         CurrBlockInfo->EntryContext =
719           intersectContexts(CurrBlockInfo->EntryContext,
720                             PrevBlockInfo->ExitContext);
721       }
722     }
723 
724     // Duplicate the context if we have back-edges, so we can call
725     // intersectBackEdges later.
726     if (HasBackEdges)
727       CurrBlockInfo->EntryContext =
728         createReferenceContext(CurrBlockInfo->EntryContext);
729 
730     // Create a starting context index for the current block
731     saveContext(nullptr, CurrBlockInfo->EntryContext);
732     CurrBlockInfo->EntryIndex = getContextIndex();
733 
734     // Visit all the statements in the basic block.
735     VarMapBuilder VMapBuilder(this, CurrBlockInfo->EntryContext);
736     for (CFGBlock::const_iterator BI = CurrBlock->begin(),
737          BE = CurrBlock->end(); BI != BE; ++BI) {
738       switch (BI->getKind()) {
739         case CFGElement::Statement: {
740           CFGStmt CS = BI->castAs<CFGStmt>();
741           VMapBuilder.Visit(const_cast<Stmt*>(CS.getStmt()));
742           break;
743         }
744         default:
745           break;
746       }
747     }
748     CurrBlockInfo->ExitContext = VMapBuilder.Ctx;
749 
750     // Mark variables on back edges as "unknown" if they've been changed.
751     for (CFGBlock::const_succ_iterator SI = CurrBlock->succ_begin(),
752          SE  = CurrBlock->succ_end(); SI != SE; ++SI) {
753       // if CurrBlock -> *SI is *not* a back edge
754       if (*SI == nullptr || !VisitedBlocks.alreadySet(*SI))
755         continue;
756 
757       CFGBlock *FirstLoopBlock = *SI;
758       Context LoopBegin = BlockInfo[FirstLoopBlock->getBlockID()].EntryContext;
759       Context LoopEnd   = CurrBlockInfo->ExitContext;
760       intersectBackEdge(LoopBegin, LoopEnd);
761     }
762   }
763 
764   // Put an extra entry at the end of the indexed context array
765   unsigned exitID = CFGraph->getExit().getBlockID();
766   saveContext(nullptr, BlockInfo[exitID].ExitContext);
767 }
768 
769 /// Find the appropriate source locations to use when producing diagnostics for
770 /// each block in the CFG.
findBlockLocations(CFG * CFGraph,const PostOrderCFGView * SortedGraph,std::vector<CFGBlockInfo> & BlockInfo)771 static void findBlockLocations(CFG *CFGraph,
772                                const PostOrderCFGView *SortedGraph,
773                                std::vector<CFGBlockInfo> &BlockInfo) {
774   for (const auto *CurrBlock : *SortedGraph) {
775     CFGBlockInfo *CurrBlockInfo = &BlockInfo[CurrBlock->getBlockID()];
776 
777     // Find the source location of the last statement in the block, if the
778     // block is not empty.
779     if (const Stmt *S = CurrBlock->getTerminator()) {
780       CurrBlockInfo->EntryLoc = CurrBlockInfo->ExitLoc = S->getLocStart();
781     } else {
782       for (CFGBlock::const_reverse_iterator BI = CurrBlock->rbegin(),
783            BE = CurrBlock->rend(); BI != BE; ++BI) {
784         // FIXME: Handle other CFGElement kinds.
785         if (Optional<CFGStmt> CS = BI->getAs<CFGStmt>()) {
786           CurrBlockInfo->ExitLoc = CS->getStmt()->getLocStart();
787           break;
788         }
789       }
790     }
791 
792     if (CurrBlockInfo->ExitLoc.isValid()) {
793       // This block contains at least one statement. Find the source location
794       // of the first statement in the block.
795       for (CFGBlock::const_iterator BI = CurrBlock->begin(),
796            BE = CurrBlock->end(); BI != BE; ++BI) {
797         // FIXME: Handle other CFGElement kinds.
798         if (Optional<CFGStmt> CS = BI->getAs<CFGStmt>()) {
799           CurrBlockInfo->EntryLoc = CS->getStmt()->getLocStart();
800           break;
801         }
802       }
803     } else if (CurrBlock->pred_size() == 1 && *CurrBlock->pred_begin() &&
804                CurrBlock != &CFGraph->getExit()) {
805       // The block is empty, and has a single predecessor. Use its exit
806       // location.
807       CurrBlockInfo->EntryLoc = CurrBlockInfo->ExitLoc =
808           BlockInfo[(*CurrBlock->pred_begin())->getBlockID()].ExitLoc;
809     }
810   }
811 }
812 
813 class LockableFactEntry : public FactEntry {
814 private:
815   bool Managed; ///<  managed by ScopedLockable object
816 
817 public:
LockableFactEntry(const CapabilityExpr & CE,LockKind LK,SourceLocation Loc,bool Mng=false,bool Asrt=false)818   LockableFactEntry(const CapabilityExpr &CE, LockKind LK, SourceLocation Loc,
819                     bool Mng = false, bool Asrt = false)
820       : FactEntry(CE, LK, Loc, Asrt), Managed(Mng) {}
821 
822   void
handleRemovalFromIntersection(const FactSet & FSet,FactManager & FactMan,SourceLocation JoinLoc,LockErrorKind LEK,ThreadSafetyHandler & Handler) const823   handleRemovalFromIntersection(const FactSet &FSet, FactManager &FactMan,
824                                 SourceLocation JoinLoc, LockErrorKind LEK,
825                                 ThreadSafetyHandler &Handler) const override {
826     if (!Managed && !asserted() && !negative() && !isUniversal()) {
827       Handler.handleMutexHeldEndOfScope("mutex", toString(), loc(), JoinLoc,
828                                         LEK);
829     }
830   }
831 
handleUnlock(FactSet & FSet,FactManager & FactMan,const CapabilityExpr & Cp,SourceLocation UnlockLoc,bool FullyRemove,ThreadSafetyHandler & Handler,StringRef DiagKind) const832   void handleUnlock(FactSet &FSet, FactManager &FactMan,
833                     const CapabilityExpr &Cp, SourceLocation UnlockLoc,
834                     bool FullyRemove, ThreadSafetyHandler &Handler,
835                     StringRef DiagKind) const override {
836     FSet.removeLock(FactMan, Cp);
837     if (!Cp.negative()) {
838       FSet.addLock(FactMan, llvm::make_unique<LockableFactEntry>(
839                                 !Cp, LK_Exclusive, UnlockLoc));
840     }
841   }
842 };
843 
844 class ScopedLockableFactEntry : public FactEntry {
845 private:
846   SmallVector<const til::SExpr *, 4> UnderlyingMutexes;
847 
848 public:
ScopedLockableFactEntry(const CapabilityExpr & CE,SourceLocation Loc,const CapExprSet & Excl,const CapExprSet & Shrd)849   ScopedLockableFactEntry(const CapabilityExpr &CE, SourceLocation Loc,
850                           const CapExprSet &Excl, const CapExprSet &Shrd)
851       : FactEntry(CE, LK_Exclusive, Loc, false) {
852     for (const auto &M : Excl)
853       UnderlyingMutexes.push_back(M.sexpr());
854     for (const auto &M : Shrd)
855       UnderlyingMutexes.push_back(M.sexpr());
856   }
857 
858   void
handleRemovalFromIntersection(const FactSet & FSet,FactManager & FactMan,SourceLocation JoinLoc,LockErrorKind LEK,ThreadSafetyHandler & Handler) const859   handleRemovalFromIntersection(const FactSet &FSet, FactManager &FactMan,
860                                 SourceLocation JoinLoc, LockErrorKind LEK,
861                                 ThreadSafetyHandler &Handler) const override {
862     for (const til::SExpr *UnderlyingMutex : UnderlyingMutexes) {
863       if (FSet.findLock(FactMan, CapabilityExpr(UnderlyingMutex, false))) {
864         // If this scoped lock manages another mutex, and if the underlying
865         // mutex is still held, then warn about the underlying mutex.
866         Handler.handleMutexHeldEndOfScope(
867             "mutex", sx::toString(UnderlyingMutex), loc(), JoinLoc, LEK);
868       }
869     }
870   }
871 
handleUnlock(FactSet & FSet,FactManager & FactMan,const CapabilityExpr & Cp,SourceLocation UnlockLoc,bool FullyRemove,ThreadSafetyHandler & Handler,StringRef DiagKind) const872   void handleUnlock(FactSet &FSet, FactManager &FactMan,
873                     const CapabilityExpr &Cp, SourceLocation UnlockLoc,
874                     bool FullyRemove, ThreadSafetyHandler &Handler,
875                     StringRef DiagKind) const override {
876     assert(!Cp.negative() && "Managing object cannot be negative.");
877     for (const til::SExpr *UnderlyingMutex : UnderlyingMutexes) {
878       CapabilityExpr UnderCp(UnderlyingMutex, false);
879       auto UnderEntry = llvm::make_unique<LockableFactEntry>(
880           !UnderCp, LK_Exclusive, UnlockLoc);
881 
882       if (FullyRemove) {
883         // We're destroying the managing object.
884         // Remove the underlying mutex if it exists; but don't warn.
885         if (FSet.findLock(FactMan, UnderCp)) {
886           FSet.removeLock(FactMan, UnderCp);
887           FSet.addLock(FactMan, std::move(UnderEntry));
888         }
889       } else {
890         // We're releasing the underlying mutex, but not destroying the
891         // managing object.  Warn on dual release.
892         if (!FSet.findLock(FactMan, UnderCp)) {
893           Handler.handleUnmatchedUnlock(DiagKind, UnderCp.toString(),
894                                         UnlockLoc);
895         }
896         FSet.removeLock(FactMan, UnderCp);
897         FSet.addLock(FactMan, std::move(UnderEntry));
898       }
899     }
900     if (FullyRemove)
901       FSet.removeLock(FactMan, Cp);
902   }
903 };
904 
905 /// \brief Class which implements the core thread safety analysis routines.
906 class ThreadSafetyAnalyzer {
907   friend class BuildLockset;
908   friend class threadSafety::BeforeSet;
909 
910   llvm::BumpPtrAllocator Bpa;
911   threadSafety::til::MemRegionRef Arena;
912   threadSafety::SExprBuilder SxBuilder;
913 
914   ThreadSafetyHandler       &Handler;
915   const CXXMethodDecl       *CurrentMethod;
916   LocalVariableMap          LocalVarMap;
917   FactManager               FactMan;
918   std::vector<CFGBlockInfo> BlockInfo;
919 
920   BeforeSet* GlobalBeforeSet;
921 
922 public:
ThreadSafetyAnalyzer(ThreadSafetyHandler & H,BeforeSet * Bset)923   ThreadSafetyAnalyzer(ThreadSafetyHandler &H, BeforeSet* Bset)
924      : Arena(&Bpa), SxBuilder(Arena), Handler(H), GlobalBeforeSet(Bset) {}
925 
926   bool inCurrentScope(const CapabilityExpr &CapE);
927 
928   void addLock(FactSet &FSet, std::unique_ptr<FactEntry> Entry,
929                StringRef DiagKind, bool ReqAttr = false);
930   void removeLock(FactSet &FSet, const CapabilityExpr &CapE,
931                   SourceLocation UnlockLoc, bool FullyRemove, LockKind Kind,
932                   StringRef DiagKind);
933 
934   template <typename AttrType>
935   void getMutexIDs(CapExprSet &Mtxs, AttrType *Attr, Expr *Exp,
936                    const NamedDecl *D, VarDecl *SelfDecl = nullptr);
937 
938   template <class AttrType>
939   void getMutexIDs(CapExprSet &Mtxs, AttrType *Attr, Expr *Exp,
940                    const NamedDecl *D,
941                    const CFGBlock *PredBlock, const CFGBlock *CurrBlock,
942                    Expr *BrE, bool Neg);
943 
944   const CallExpr* getTrylockCallExpr(const Stmt *Cond, LocalVarContext C,
945                                      bool &Negate);
946 
947   void getEdgeLockset(FactSet &Result, const FactSet &ExitSet,
948                       const CFGBlock* PredBlock,
949                       const CFGBlock *CurrBlock);
950 
951   void intersectAndWarn(FactSet &FSet1, const FactSet &FSet2,
952                         SourceLocation JoinLoc,
953                         LockErrorKind LEK1, LockErrorKind LEK2,
954                         bool Modify=true);
955 
intersectAndWarn(FactSet & FSet1,const FactSet & FSet2,SourceLocation JoinLoc,LockErrorKind LEK1,bool Modify=true)956   void intersectAndWarn(FactSet &FSet1, const FactSet &FSet2,
957                         SourceLocation JoinLoc, LockErrorKind LEK1,
958                         bool Modify=true) {
959     intersectAndWarn(FSet1, FSet2, JoinLoc, LEK1, LEK1, Modify);
960   }
961 
962   void runAnalysis(AnalysisDeclContext &AC);
963 };
964 } // namespace
965 
966 /// Process acquired_before and acquired_after attributes on Vd.
insertAttrExprs(const ValueDecl * Vd,ThreadSafetyAnalyzer & Analyzer)967 BeforeSet::BeforeInfo* BeforeSet::insertAttrExprs(const ValueDecl* Vd,
968     ThreadSafetyAnalyzer& Analyzer) {
969   // Create a new entry for Vd.
970   BeforeInfo *Info = nullptr;
971   {
972     // Keep InfoPtr in its own scope in case BMap is modified later and the
973     // reference becomes invalid.
974     std::unique_ptr<BeforeInfo> &InfoPtr = BMap[Vd];
975     if (!InfoPtr)
976       InfoPtr.reset(new BeforeInfo());
977     Info = InfoPtr.get();
978   }
979 
980   for (Attr* At : Vd->attrs()) {
981     switch (At->getKind()) {
982       case attr::AcquiredBefore: {
983         auto *A = cast<AcquiredBeforeAttr>(At);
984 
985         // Read exprs from the attribute, and add them to BeforeVect.
986         for (const auto *Arg : A->args()) {
987           CapabilityExpr Cp =
988             Analyzer.SxBuilder.translateAttrExpr(Arg, nullptr);
989           if (const ValueDecl *Cpvd = Cp.valueDecl()) {
990             Info->Vect.push_back(Cpvd);
991             auto It = BMap.find(Cpvd);
992             if (It == BMap.end())
993               insertAttrExprs(Cpvd, Analyzer);
994           }
995         }
996         break;
997       }
998       case attr::AcquiredAfter: {
999         auto *A = cast<AcquiredAfterAttr>(At);
1000 
1001         // Read exprs from the attribute, and add them to BeforeVect.
1002         for (const auto *Arg : A->args()) {
1003           CapabilityExpr Cp =
1004             Analyzer.SxBuilder.translateAttrExpr(Arg, nullptr);
1005           if (const ValueDecl *ArgVd = Cp.valueDecl()) {
1006             // Get entry for mutex listed in attribute
1007             BeforeInfo *ArgInfo = getBeforeInfoForDecl(ArgVd, Analyzer);
1008             ArgInfo->Vect.push_back(Vd);
1009           }
1010         }
1011         break;
1012       }
1013       default:
1014         break;
1015     }
1016   }
1017 
1018   return Info;
1019 }
1020 
1021 BeforeSet::BeforeInfo *
getBeforeInfoForDecl(const ValueDecl * Vd,ThreadSafetyAnalyzer & Analyzer)1022 BeforeSet::getBeforeInfoForDecl(const ValueDecl *Vd,
1023                                 ThreadSafetyAnalyzer &Analyzer) {
1024   auto It = BMap.find(Vd);
1025   BeforeInfo *Info = nullptr;
1026   if (It == BMap.end())
1027     Info = insertAttrExprs(Vd, Analyzer);
1028   else
1029     Info = It->second.get();
1030   assert(Info && "BMap contained nullptr?");
1031   return Info;
1032 }
1033 
1034 /// Return true if any mutexes in FSet are in the acquired_before set of Vd.
checkBeforeAfter(const ValueDecl * StartVd,const FactSet & FSet,ThreadSafetyAnalyzer & Analyzer,SourceLocation Loc,StringRef CapKind)1035 void BeforeSet::checkBeforeAfter(const ValueDecl* StartVd,
1036                                  const FactSet& FSet,
1037                                  ThreadSafetyAnalyzer& Analyzer,
1038                                  SourceLocation Loc, StringRef CapKind) {
1039   SmallVector<BeforeInfo*, 8> InfoVect;
1040 
1041   // Do a depth-first traversal of Vd.
1042   // Return true if there are cycles.
1043   std::function<bool (const ValueDecl*)> traverse = [&](const ValueDecl* Vd) {
1044     if (!Vd)
1045       return false;
1046 
1047     BeforeSet::BeforeInfo *Info = getBeforeInfoForDecl(Vd, Analyzer);
1048 
1049     if (Info->Visited == 1)
1050       return true;
1051 
1052     if (Info->Visited == 2)
1053       return false;
1054 
1055     if (Info->Vect.empty())
1056       return false;
1057 
1058     InfoVect.push_back(Info);
1059     Info->Visited = 1;
1060     for (auto *Vdb : Info->Vect) {
1061       // Exclude mutexes in our immediate before set.
1062       if (FSet.containsMutexDecl(Analyzer.FactMan, Vdb)) {
1063         StringRef L1 = StartVd->getName();
1064         StringRef L2 = Vdb->getName();
1065         Analyzer.Handler.handleLockAcquiredBefore(CapKind, L1, L2, Loc);
1066       }
1067       // Transitively search other before sets, and warn on cycles.
1068       if (traverse(Vdb)) {
1069         if (CycMap.find(Vd) == CycMap.end()) {
1070           CycMap.insert(std::make_pair(Vd, true));
1071           StringRef L1 = Vd->getName();
1072           Analyzer.Handler.handleBeforeAfterCycle(L1, Vd->getLocation());
1073         }
1074       }
1075     }
1076     Info->Visited = 2;
1077     return false;
1078   };
1079 
1080   traverse(StartVd);
1081 
1082   for (auto* Info : InfoVect)
1083     Info->Visited = 0;
1084 }
1085 
1086 
1087 
1088 /// \brief Gets the value decl pointer from DeclRefExprs or MemberExprs.
getValueDecl(const Expr * Exp)1089 static const ValueDecl *getValueDecl(const Expr *Exp) {
1090   if (const auto *CE = dyn_cast<ImplicitCastExpr>(Exp))
1091     return getValueDecl(CE->getSubExpr());
1092 
1093   if (const auto *DR = dyn_cast<DeclRefExpr>(Exp))
1094     return DR->getDecl();
1095 
1096   if (const auto *ME = dyn_cast<MemberExpr>(Exp))
1097     return ME->getMemberDecl();
1098 
1099   return nullptr;
1100 }
1101 
1102 namespace {
1103 template <typename Ty>
1104 class has_arg_iterator_range {
1105   typedef char yes[1];
1106   typedef char no[2];
1107 
1108   template <typename Inner>
1109   static yes& test(Inner *I, decltype(I->args()) * = nullptr);
1110 
1111   template <typename>
1112   static no& test(...);
1113 
1114 public:
1115   static const bool value = sizeof(test<Ty>(nullptr)) == sizeof(yes);
1116 };
1117 } // namespace
1118 
ClassifyDiagnostic(const CapabilityAttr * A)1119 static StringRef ClassifyDiagnostic(const CapabilityAttr *A) {
1120   return A->getName();
1121 }
1122 
ClassifyDiagnostic(QualType VDT)1123 static StringRef ClassifyDiagnostic(QualType VDT) {
1124   // We need to look at the declaration of the type of the value to determine
1125   // which it is. The type should either be a record or a typedef, or a pointer
1126   // or reference thereof.
1127   if (const auto *RT = VDT->getAs<RecordType>()) {
1128     if (const auto *RD = RT->getDecl())
1129       if (const auto *CA = RD->getAttr<CapabilityAttr>())
1130         return ClassifyDiagnostic(CA);
1131   } else if (const auto *TT = VDT->getAs<TypedefType>()) {
1132     if (const auto *TD = TT->getDecl())
1133       if (const auto *CA = TD->getAttr<CapabilityAttr>())
1134         return ClassifyDiagnostic(CA);
1135   } else if (VDT->isPointerType() || VDT->isReferenceType())
1136     return ClassifyDiagnostic(VDT->getPointeeType());
1137 
1138   return "mutex";
1139 }
1140 
ClassifyDiagnostic(const ValueDecl * VD)1141 static StringRef ClassifyDiagnostic(const ValueDecl *VD) {
1142   assert(VD && "No ValueDecl passed");
1143 
1144   // The ValueDecl is the declaration of a mutex or role (hopefully).
1145   return ClassifyDiagnostic(VD->getType());
1146 }
1147 
1148 template <typename AttrTy>
1149 static typename std::enable_if<!has_arg_iterator_range<AttrTy>::value,
1150                                StringRef>::type
ClassifyDiagnostic(const AttrTy * A)1151 ClassifyDiagnostic(const AttrTy *A) {
1152   if (const ValueDecl *VD = getValueDecl(A->getArg()))
1153     return ClassifyDiagnostic(VD);
1154   return "mutex";
1155 }
1156 
1157 template <typename AttrTy>
1158 static typename std::enable_if<has_arg_iterator_range<AttrTy>::value,
1159                                StringRef>::type
ClassifyDiagnostic(const AttrTy * A)1160 ClassifyDiagnostic(const AttrTy *A) {
1161   for (const auto *Arg : A->args()) {
1162     if (const ValueDecl *VD = getValueDecl(Arg))
1163       return ClassifyDiagnostic(VD);
1164   }
1165   return "mutex";
1166 }
1167 
1168 
inCurrentScope(const CapabilityExpr & CapE)1169 inline bool ThreadSafetyAnalyzer::inCurrentScope(const CapabilityExpr &CapE) {
1170   if (!CurrentMethod)
1171       return false;
1172   if (auto *P = dyn_cast_or_null<til::Project>(CapE.sexpr())) {
1173     auto *VD = P->clangDecl();
1174     if (VD)
1175       return VD->getDeclContext() == CurrentMethod->getDeclContext();
1176   }
1177   return false;
1178 }
1179 
1180 
1181 /// \brief Add a new lock to the lockset, warning if the lock is already there.
1182 /// \param ReqAttr -- true if this is part of an initial Requires attribute.
addLock(FactSet & FSet,std::unique_ptr<FactEntry> Entry,StringRef DiagKind,bool ReqAttr)1183 void ThreadSafetyAnalyzer::addLock(FactSet &FSet,
1184                                    std::unique_ptr<FactEntry> Entry,
1185                                    StringRef DiagKind, bool ReqAttr) {
1186   if (Entry->shouldIgnore())
1187     return;
1188 
1189   if (!ReqAttr && !Entry->negative()) {
1190     // look for the negative capability, and remove it from the fact set.
1191     CapabilityExpr NegC = !*Entry;
1192     FactEntry *Nen = FSet.findLock(FactMan, NegC);
1193     if (Nen) {
1194       FSet.removeLock(FactMan, NegC);
1195     }
1196     else {
1197       if (inCurrentScope(*Entry) && !Entry->asserted())
1198         Handler.handleNegativeNotHeld(DiagKind, Entry->toString(),
1199                                       NegC.toString(), Entry->loc());
1200     }
1201   }
1202 
1203   // Check before/after constraints
1204   if (Handler.issueBetaWarnings() &&
1205       !Entry->asserted() && !Entry->declared()) {
1206     GlobalBeforeSet->checkBeforeAfter(Entry->valueDecl(), FSet, *this,
1207                                       Entry->loc(), DiagKind);
1208   }
1209 
1210   // FIXME: Don't always warn when we have support for reentrant locks.
1211   if (FSet.findLock(FactMan, *Entry)) {
1212     if (!Entry->asserted())
1213       Handler.handleDoubleLock(DiagKind, Entry->toString(), Entry->loc());
1214   } else {
1215     FSet.addLock(FactMan, std::move(Entry));
1216   }
1217 }
1218 
1219 
1220 /// \brief Remove a lock from the lockset, warning if the lock is not there.
1221 /// \param UnlockLoc The source location of the unlock (only used in error msg)
removeLock(FactSet & FSet,const CapabilityExpr & Cp,SourceLocation UnlockLoc,bool FullyRemove,LockKind ReceivedKind,StringRef DiagKind)1222 void ThreadSafetyAnalyzer::removeLock(FactSet &FSet, const CapabilityExpr &Cp,
1223                                       SourceLocation UnlockLoc,
1224                                       bool FullyRemove, LockKind ReceivedKind,
1225                                       StringRef DiagKind) {
1226   if (Cp.shouldIgnore())
1227     return;
1228 
1229   const FactEntry *LDat = FSet.findLock(FactMan, Cp);
1230   if (!LDat) {
1231     Handler.handleUnmatchedUnlock(DiagKind, Cp.toString(), UnlockLoc);
1232     return;
1233   }
1234 
1235   // Generic lock removal doesn't care about lock kind mismatches, but
1236   // otherwise diagnose when the lock kinds are mismatched.
1237   if (ReceivedKind != LK_Generic && LDat->kind() != ReceivedKind) {
1238     Handler.handleIncorrectUnlockKind(DiagKind, Cp.toString(),
1239                                       LDat->kind(), ReceivedKind, UnlockLoc);
1240   }
1241 
1242   LDat->handleUnlock(FSet, FactMan, Cp, UnlockLoc, FullyRemove, Handler,
1243                      DiagKind);
1244 }
1245 
1246 
1247 /// \brief Extract the list of mutexIDs from the attribute on an expression,
1248 /// and push them onto Mtxs, discarding any duplicates.
1249 template <typename AttrType>
getMutexIDs(CapExprSet & Mtxs,AttrType * Attr,Expr * Exp,const NamedDecl * D,VarDecl * SelfDecl)1250 void ThreadSafetyAnalyzer::getMutexIDs(CapExprSet &Mtxs, AttrType *Attr,
1251                                        Expr *Exp, const NamedDecl *D,
1252                                        VarDecl *SelfDecl) {
1253   if (Attr->args_size() == 0) {
1254     // The mutex held is the "this" object.
1255     CapabilityExpr Cp = SxBuilder.translateAttrExpr(nullptr, D, Exp, SelfDecl);
1256     if (Cp.isInvalid()) {
1257        warnInvalidLock(Handler, nullptr, D, Exp, ClassifyDiagnostic(Attr));
1258        return;
1259     }
1260     //else
1261     if (!Cp.shouldIgnore())
1262       Mtxs.push_back_nodup(Cp);
1263     return;
1264   }
1265 
1266   for (const auto *Arg : Attr->args()) {
1267     CapabilityExpr Cp = SxBuilder.translateAttrExpr(Arg, D, Exp, SelfDecl);
1268     if (Cp.isInvalid()) {
1269        warnInvalidLock(Handler, nullptr, D, Exp, ClassifyDiagnostic(Attr));
1270        continue;
1271     }
1272     //else
1273     if (!Cp.shouldIgnore())
1274       Mtxs.push_back_nodup(Cp);
1275   }
1276 }
1277 
1278 
1279 /// \brief Extract the list of mutexIDs from a trylock attribute.  If the
1280 /// trylock applies to the given edge, then push them onto Mtxs, discarding
1281 /// any duplicates.
1282 template <class AttrType>
getMutexIDs(CapExprSet & Mtxs,AttrType * Attr,Expr * Exp,const NamedDecl * D,const CFGBlock * PredBlock,const CFGBlock * CurrBlock,Expr * BrE,bool Neg)1283 void ThreadSafetyAnalyzer::getMutexIDs(CapExprSet &Mtxs, AttrType *Attr,
1284                                        Expr *Exp, const NamedDecl *D,
1285                                        const CFGBlock *PredBlock,
1286                                        const CFGBlock *CurrBlock,
1287                                        Expr *BrE, bool Neg) {
1288   // Find out which branch has the lock
1289   bool branch = false;
1290   if (CXXBoolLiteralExpr *BLE = dyn_cast_or_null<CXXBoolLiteralExpr>(BrE))
1291     branch = BLE->getValue();
1292   else if (IntegerLiteral *ILE = dyn_cast_or_null<IntegerLiteral>(BrE))
1293     branch = ILE->getValue().getBoolValue();
1294 
1295   int branchnum = branch ? 0 : 1;
1296   if (Neg)
1297     branchnum = !branchnum;
1298 
1299   // If we've taken the trylock branch, then add the lock
1300   int i = 0;
1301   for (CFGBlock::const_succ_iterator SI = PredBlock->succ_begin(),
1302        SE = PredBlock->succ_end(); SI != SE && i < 2; ++SI, ++i) {
1303     if (*SI == CurrBlock && i == branchnum)
1304       getMutexIDs(Mtxs, Attr, Exp, D);
1305   }
1306 }
1307 
getStaticBooleanValue(Expr * E,bool & TCond)1308 static bool getStaticBooleanValue(Expr *E, bool &TCond) {
1309   if (isa<CXXNullPtrLiteralExpr>(E) || isa<GNUNullExpr>(E)) {
1310     TCond = false;
1311     return true;
1312   } else if (CXXBoolLiteralExpr *BLE = dyn_cast<CXXBoolLiteralExpr>(E)) {
1313     TCond = BLE->getValue();
1314     return true;
1315   } else if (IntegerLiteral *ILE = dyn_cast<IntegerLiteral>(E)) {
1316     TCond = ILE->getValue().getBoolValue();
1317     return true;
1318   } else if (ImplicitCastExpr *CE = dyn_cast<ImplicitCastExpr>(E)) {
1319     return getStaticBooleanValue(CE->getSubExpr(), TCond);
1320   }
1321   return false;
1322 }
1323 
1324 
1325 // If Cond can be traced back to a function call, return the call expression.
1326 // The negate variable should be called with false, and will be set to true
1327 // if the function call is negated, e.g. if (!mu.tryLock(...))
getTrylockCallExpr(const Stmt * Cond,LocalVarContext C,bool & Negate)1328 const CallExpr* ThreadSafetyAnalyzer::getTrylockCallExpr(const Stmt *Cond,
1329                                                          LocalVarContext C,
1330                                                          bool &Negate) {
1331   if (!Cond)
1332     return nullptr;
1333 
1334   if (const CallExpr *CallExp = dyn_cast<CallExpr>(Cond)) {
1335     return CallExp;
1336   }
1337   else if (const ParenExpr *PE = dyn_cast<ParenExpr>(Cond)) {
1338     return getTrylockCallExpr(PE->getSubExpr(), C, Negate);
1339   }
1340   else if (const ImplicitCastExpr *CE = dyn_cast<ImplicitCastExpr>(Cond)) {
1341     return getTrylockCallExpr(CE->getSubExpr(), C, Negate);
1342   }
1343   else if (const ExprWithCleanups* EWC = dyn_cast<ExprWithCleanups>(Cond)) {
1344     return getTrylockCallExpr(EWC->getSubExpr(), C, Negate);
1345   }
1346   else if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Cond)) {
1347     const Expr *E = LocalVarMap.lookupExpr(DRE->getDecl(), C);
1348     return getTrylockCallExpr(E, C, Negate);
1349   }
1350   else if (const UnaryOperator *UOP = dyn_cast<UnaryOperator>(Cond)) {
1351     if (UOP->getOpcode() == UO_LNot) {
1352       Negate = !Negate;
1353       return getTrylockCallExpr(UOP->getSubExpr(), C, Negate);
1354     }
1355     return nullptr;
1356   }
1357   else if (const BinaryOperator *BOP = dyn_cast<BinaryOperator>(Cond)) {
1358     if (BOP->getOpcode() == BO_EQ || BOP->getOpcode() == BO_NE) {
1359       if (BOP->getOpcode() == BO_NE)
1360         Negate = !Negate;
1361 
1362       bool TCond = false;
1363       if (getStaticBooleanValue(BOP->getRHS(), TCond)) {
1364         if (!TCond) Negate = !Negate;
1365         return getTrylockCallExpr(BOP->getLHS(), C, Negate);
1366       }
1367       TCond = false;
1368       if (getStaticBooleanValue(BOP->getLHS(), TCond)) {
1369         if (!TCond) Negate = !Negate;
1370         return getTrylockCallExpr(BOP->getRHS(), C, Negate);
1371       }
1372       return nullptr;
1373     }
1374     if (BOP->getOpcode() == BO_LAnd) {
1375       // LHS must have been evaluated in a different block.
1376       return getTrylockCallExpr(BOP->getRHS(), C, Negate);
1377     }
1378     if (BOP->getOpcode() == BO_LOr) {
1379       return getTrylockCallExpr(BOP->getRHS(), C, Negate);
1380     }
1381     return nullptr;
1382   }
1383   return nullptr;
1384 }
1385 
1386 
1387 /// \brief Find the lockset that holds on the edge between PredBlock
1388 /// and CurrBlock.  The edge set is the exit set of PredBlock (passed
1389 /// as the ExitSet parameter) plus any trylocks, which are conditionally held.
getEdgeLockset(FactSet & Result,const FactSet & ExitSet,const CFGBlock * PredBlock,const CFGBlock * CurrBlock)1390 void ThreadSafetyAnalyzer::getEdgeLockset(FactSet& Result,
1391                                           const FactSet &ExitSet,
1392                                           const CFGBlock *PredBlock,
1393                                           const CFGBlock *CurrBlock) {
1394   Result = ExitSet;
1395 
1396   const Stmt *Cond = PredBlock->getTerminatorCondition();
1397   if (!Cond)
1398     return;
1399 
1400   bool Negate = false;
1401   const CFGBlockInfo *PredBlockInfo = &BlockInfo[PredBlock->getBlockID()];
1402   const LocalVarContext &LVarCtx = PredBlockInfo->ExitContext;
1403   StringRef CapDiagKind = "mutex";
1404 
1405   CallExpr *Exp =
1406     const_cast<CallExpr*>(getTrylockCallExpr(Cond, LVarCtx, Negate));
1407   if (!Exp)
1408     return;
1409 
1410   NamedDecl *FunDecl = dyn_cast_or_null<NamedDecl>(Exp->getCalleeDecl());
1411   if(!FunDecl || !FunDecl->hasAttrs())
1412     return;
1413 
1414   CapExprSet ExclusiveLocksToAdd;
1415   CapExprSet SharedLocksToAdd;
1416 
1417   // If the condition is a call to a Trylock function, then grab the attributes
1418   for (auto *Attr : FunDecl->attrs()) {
1419     switch (Attr->getKind()) {
1420       case attr::ExclusiveTrylockFunction: {
1421         ExclusiveTrylockFunctionAttr *A =
1422           cast<ExclusiveTrylockFunctionAttr>(Attr);
1423         getMutexIDs(ExclusiveLocksToAdd, A, Exp, FunDecl,
1424                     PredBlock, CurrBlock, A->getSuccessValue(), Negate);
1425         CapDiagKind = ClassifyDiagnostic(A);
1426         break;
1427       }
1428       case attr::SharedTrylockFunction: {
1429         SharedTrylockFunctionAttr *A =
1430           cast<SharedTrylockFunctionAttr>(Attr);
1431         getMutexIDs(SharedLocksToAdd, A, Exp, FunDecl,
1432                     PredBlock, CurrBlock, A->getSuccessValue(), Negate);
1433         CapDiagKind = ClassifyDiagnostic(A);
1434         break;
1435       }
1436       default:
1437         break;
1438     }
1439   }
1440 
1441   // Add and remove locks.
1442   SourceLocation Loc = Exp->getExprLoc();
1443   for (const auto &ExclusiveLockToAdd : ExclusiveLocksToAdd)
1444     addLock(Result, llvm::make_unique<LockableFactEntry>(ExclusiveLockToAdd,
1445                                                          LK_Exclusive, Loc),
1446             CapDiagKind);
1447   for (const auto &SharedLockToAdd : SharedLocksToAdd)
1448     addLock(Result, llvm::make_unique<LockableFactEntry>(SharedLockToAdd,
1449                                                          LK_Shared, Loc),
1450             CapDiagKind);
1451 }
1452 
1453 namespace {
1454 /// \brief We use this class to visit different types of expressions in
1455 /// CFGBlocks, and build up the lockset.
1456 /// An expression may cause us to add or remove locks from the lockset, or else
1457 /// output error messages related to missing locks.
1458 /// FIXME: In future, we may be able to not inherit from a visitor.
1459 class BuildLockset : public StmtVisitor<BuildLockset> {
1460   friend class ThreadSafetyAnalyzer;
1461 
1462   ThreadSafetyAnalyzer *Analyzer;
1463   FactSet FSet;
1464   LocalVariableMap::Context LVarCtx;
1465   unsigned CtxIndex;
1466 
1467   // helper functions
1468   void warnIfMutexNotHeld(const NamedDecl *D, const Expr *Exp, AccessKind AK,
1469                           Expr *MutexExp, ProtectedOperationKind POK,
1470                           StringRef DiagKind, SourceLocation Loc);
1471   void warnIfMutexHeld(const NamedDecl *D, const Expr *Exp, Expr *MutexExp,
1472                        StringRef DiagKind);
1473 
1474   void checkAccess(const Expr *Exp, AccessKind AK,
1475                    ProtectedOperationKind POK = POK_VarAccess);
1476   void checkPtAccess(const Expr *Exp, AccessKind AK,
1477                      ProtectedOperationKind POK = POK_VarAccess);
1478 
1479   void handleCall(Expr *Exp, const NamedDecl *D, VarDecl *VD = nullptr);
1480 
1481 public:
BuildLockset(ThreadSafetyAnalyzer * Anlzr,CFGBlockInfo & Info)1482   BuildLockset(ThreadSafetyAnalyzer *Anlzr, CFGBlockInfo &Info)
1483     : StmtVisitor<BuildLockset>(),
1484       Analyzer(Anlzr),
1485       FSet(Info.EntrySet),
1486       LVarCtx(Info.EntryContext),
1487       CtxIndex(Info.EntryIndex)
1488   {}
1489 
1490   void VisitUnaryOperator(UnaryOperator *UO);
1491   void VisitBinaryOperator(BinaryOperator *BO);
1492   void VisitCastExpr(CastExpr *CE);
1493   void VisitCallExpr(CallExpr *Exp);
1494   void VisitCXXConstructExpr(CXXConstructExpr *Exp);
1495   void VisitDeclStmt(DeclStmt *S);
1496 };
1497 } // namespace
1498 
1499 /// \brief Warn if the LSet does not contain a lock sufficient to protect access
1500 /// of at least the passed in AccessKind.
warnIfMutexNotHeld(const NamedDecl * D,const Expr * Exp,AccessKind AK,Expr * MutexExp,ProtectedOperationKind POK,StringRef DiagKind,SourceLocation Loc)1501 void BuildLockset::warnIfMutexNotHeld(const NamedDecl *D, const Expr *Exp,
1502                                       AccessKind AK, Expr *MutexExp,
1503                                       ProtectedOperationKind POK,
1504                                       StringRef DiagKind, SourceLocation Loc) {
1505   LockKind LK = getLockKindFromAccessKind(AK);
1506 
1507   CapabilityExpr Cp = Analyzer->SxBuilder.translateAttrExpr(MutexExp, D, Exp);
1508   if (Cp.isInvalid()) {
1509     warnInvalidLock(Analyzer->Handler, MutexExp, D, Exp, DiagKind);
1510     return;
1511   } else if (Cp.shouldIgnore()) {
1512     return;
1513   }
1514 
1515   if (Cp.negative()) {
1516     // Negative capabilities act like locks excluded
1517     FactEntry *LDat = FSet.findLock(Analyzer->FactMan, !Cp);
1518     if (LDat) {
1519       Analyzer->Handler.handleFunExcludesLock(
1520           DiagKind, D->getNameAsString(), (!Cp).toString(), Loc);
1521       return;
1522     }
1523 
1524     // If this does not refer to a negative capability in the same class,
1525     // then stop here.
1526     if (!Analyzer->inCurrentScope(Cp))
1527       return;
1528 
1529     // Otherwise the negative requirement must be propagated to the caller.
1530     LDat = FSet.findLock(Analyzer->FactMan, Cp);
1531     if (!LDat) {
1532       Analyzer->Handler.handleMutexNotHeld("", D, POK, Cp.toString(),
1533                                            LK_Shared, Loc);
1534     }
1535     return;
1536   }
1537 
1538   FactEntry* LDat = FSet.findLockUniv(Analyzer->FactMan, Cp);
1539   bool NoError = true;
1540   if (!LDat) {
1541     // No exact match found.  Look for a partial match.
1542     LDat = FSet.findPartialMatch(Analyzer->FactMan, Cp);
1543     if (LDat) {
1544       // Warn that there's no precise match.
1545       std::string PartMatchStr = LDat->toString();
1546       StringRef   PartMatchName(PartMatchStr);
1547       Analyzer->Handler.handleMutexNotHeld(DiagKind, D, POK, Cp.toString(),
1548                                            LK, Loc, &PartMatchName);
1549     } else {
1550       // Warn that there's no match at all.
1551       Analyzer->Handler.handleMutexNotHeld(DiagKind, D, POK, Cp.toString(),
1552                                            LK, Loc);
1553     }
1554     NoError = false;
1555   }
1556   // Make sure the mutex we found is the right kind.
1557   if (NoError && LDat && !LDat->isAtLeast(LK)) {
1558     Analyzer->Handler.handleMutexNotHeld(DiagKind, D, POK, Cp.toString(),
1559                                          LK, Loc);
1560   }
1561 }
1562 
1563 /// \brief Warn if the LSet contains the given lock.
warnIfMutexHeld(const NamedDecl * D,const Expr * Exp,Expr * MutexExp,StringRef DiagKind)1564 void BuildLockset::warnIfMutexHeld(const NamedDecl *D, const Expr *Exp,
1565                                    Expr *MutexExp, StringRef DiagKind) {
1566   CapabilityExpr Cp = Analyzer->SxBuilder.translateAttrExpr(MutexExp, D, Exp);
1567   if (Cp.isInvalid()) {
1568     warnInvalidLock(Analyzer->Handler, MutexExp, D, Exp, DiagKind);
1569     return;
1570   } else if (Cp.shouldIgnore()) {
1571     return;
1572   }
1573 
1574   FactEntry* LDat = FSet.findLock(Analyzer->FactMan, Cp);
1575   if (LDat) {
1576     Analyzer->Handler.handleFunExcludesLock(
1577         DiagKind, D->getNameAsString(), Cp.toString(), Exp->getExprLoc());
1578   }
1579 }
1580 
1581 /// \brief Checks guarded_by and pt_guarded_by attributes.
1582 /// Whenever we identify an access (read or write) to a DeclRefExpr that is
1583 /// marked with guarded_by, we must ensure the appropriate mutexes are held.
1584 /// Similarly, we check if the access is to an expression that dereferences
1585 /// a pointer marked with pt_guarded_by.
checkAccess(const Expr * Exp,AccessKind AK,ProtectedOperationKind POK)1586 void BuildLockset::checkAccess(const Expr *Exp, AccessKind AK,
1587                                ProtectedOperationKind POK) {
1588   Exp = Exp->IgnoreParenCasts();
1589 
1590   SourceLocation Loc = Exp->getExprLoc();
1591 
1592   // Local variables of reference type cannot be re-assigned;
1593   // map them to their initializer.
1594   while (const auto *DRE = dyn_cast<DeclRefExpr>(Exp)) {
1595     const auto *VD = dyn_cast<VarDecl>(DRE->getDecl()->getCanonicalDecl());
1596     if (VD && VD->isLocalVarDecl() && VD->getType()->isReferenceType()) {
1597       if (const auto *E = VD->getInit()) {
1598         Exp = E;
1599         continue;
1600       }
1601     }
1602     break;
1603   }
1604 
1605   if (const UnaryOperator *UO = dyn_cast<UnaryOperator>(Exp)) {
1606     // For dereferences
1607     if (UO->getOpcode() == clang::UO_Deref)
1608       checkPtAccess(UO->getSubExpr(), AK, POK);
1609     return;
1610   }
1611 
1612   if (const ArraySubscriptExpr *AE = dyn_cast<ArraySubscriptExpr>(Exp)) {
1613     checkPtAccess(AE->getLHS(), AK, POK);
1614     return;
1615   }
1616 
1617   if (const MemberExpr *ME = dyn_cast<MemberExpr>(Exp)) {
1618     if (ME->isArrow())
1619       checkPtAccess(ME->getBase(), AK, POK);
1620     else
1621       checkAccess(ME->getBase(), AK, POK);
1622   }
1623 
1624   const ValueDecl *D = getValueDecl(Exp);
1625   if (!D || !D->hasAttrs())
1626     return;
1627 
1628   if (D->hasAttr<GuardedVarAttr>() && FSet.isEmpty(Analyzer->FactMan)) {
1629     Analyzer->Handler.handleNoMutexHeld("mutex", D, POK, AK, Loc);
1630   }
1631 
1632   for (const auto *I : D->specific_attrs<GuardedByAttr>())
1633     warnIfMutexNotHeld(D, Exp, AK, I->getArg(), POK,
1634                        ClassifyDiagnostic(I), Loc);
1635 }
1636 
1637 
1638 /// \brief Checks pt_guarded_by and pt_guarded_var attributes.
1639 /// POK is the same  operationKind that was passed to checkAccess.
checkPtAccess(const Expr * Exp,AccessKind AK,ProtectedOperationKind POK)1640 void BuildLockset::checkPtAccess(const Expr *Exp, AccessKind AK,
1641                                  ProtectedOperationKind POK) {
1642   while (true) {
1643     if (const ParenExpr *PE = dyn_cast<ParenExpr>(Exp)) {
1644       Exp = PE->getSubExpr();
1645       continue;
1646     }
1647     if (const CastExpr *CE = dyn_cast<CastExpr>(Exp)) {
1648       if (CE->getCastKind() == CK_ArrayToPointerDecay) {
1649         // If it's an actual array, and not a pointer, then it's elements
1650         // are protected by GUARDED_BY, not PT_GUARDED_BY;
1651         checkAccess(CE->getSubExpr(), AK, POK);
1652         return;
1653       }
1654       Exp = CE->getSubExpr();
1655       continue;
1656     }
1657     break;
1658   }
1659 
1660   // Pass by reference warnings are under a different flag.
1661   ProtectedOperationKind PtPOK = POK_VarDereference;
1662   if (POK == POK_PassByRef) PtPOK = POK_PtPassByRef;
1663 
1664   const ValueDecl *D = getValueDecl(Exp);
1665   if (!D || !D->hasAttrs())
1666     return;
1667 
1668   if (D->hasAttr<PtGuardedVarAttr>() && FSet.isEmpty(Analyzer->FactMan))
1669     Analyzer->Handler.handleNoMutexHeld("mutex", D, PtPOK, AK,
1670                                         Exp->getExprLoc());
1671 
1672   for (auto const *I : D->specific_attrs<PtGuardedByAttr>())
1673     warnIfMutexNotHeld(D, Exp, AK, I->getArg(), PtPOK,
1674                        ClassifyDiagnostic(I), Exp->getExprLoc());
1675 }
1676 
1677 /// \brief Process a function call, method call, constructor call,
1678 /// or destructor call.  This involves looking at the attributes on the
1679 /// corresponding function/method/constructor/destructor, issuing warnings,
1680 /// and updating the locksets accordingly.
1681 ///
1682 /// FIXME: For classes annotated with one of the guarded annotations, we need
1683 /// to treat const method calls as reads and non-const method calls as writes,
1684 /// and check that the appropriate locks are held. Non-const method calls with
1685 /// the same signature as const method calls can be also treated as reads.
1686 ///
handleCall(Expr * Exp,const NamedDecl * D,VarDecl * VD)1687 void BuildLockset::handleCall(Expr *Exp, const NamedDecl *D, VarDecl *VD) {
1688   SourceLocation Loc = Exp->getExprLoc();
1689   CapExprSet ExclusiveLocksToAdd, SharedLocksToAdd;
1690   CapExprSet ExclusiveLocksToRemove, SharedLocksToRemove, GenericLocksToRemove;
1691   CapExprSet ScopedExclusiveReqs, ScopedSharedReqs;
1692   StringRef CapDiagKind = "mutex";
1693 
1694   // Figure out if we're calling the constructor of scoped lockable class
1695   bool isScopedVar = false;
1696   if (VD) {
1697     if (const CXXConstructorDecl *CD = dyn_cast<const CXXConstructorDecl>(D)) {
1698       const CXXRecordDecl* PD = CD->getParent();
1699       if (PD && PD->hasAttr<ScopedLockableAttr>())
1700         isScopedVar = true;
1701     }
1702   }
1703 
1704   for(Attr *Atconst : D->attrs()) {
1705     Attr* At = const_cast<Attr*>(Atconst);
1706     switch (At->getKind()) {
1707       // When we encounter a lock function, we need to add the lock to our
1708       // lockset.
1709       case attr::AcquireCapability: {
1710         auto *A = cast<AcquireCapabilityAttr>(At);
1711         Analyzer->getMutexIDs(A->isShared() ? SharedLocksToAdd
1712                                             : ExclusiveLocksToAdd,
1713                               A, Exp, D, VD);
1714 
1715         CapDiagKind = ClassifyDiagnostic(A);
1716         break;
1717       }
1718 
1719       // An assert will add a lock to the lockset, but will not generate
1720       // a warning if it is already there, and will not generate a warning
1721       // if it is not removed.
1722       case attr::AssertExclusiveLock: {
1723         AssertExclusiveLockAttr *A = cast<AssertExclusiveLockAttr>(At);
1724 
1725         CapExprSet AssertLocks;
1726         Analyzer->getMutexIDs(AssertLocks, A, Exp, D, VD);
1727         for (const auto &AssertLock : AssertLocks)
1728           Analyzer->addLock(FSet,
1729                             llvm::make_unique<LockableFactEntry>(
1730                                 AssertLock, LK_Exclusive, Loc, false, true),
1731                             ClassifyDiagnostic(A));
1732         break;
1733       }
1734       case attr::AssertSharedLock: {
1735         AssertSharedLockAttr *A = cast<AssertSharedLockAttr>(At);
1736 
1737         CapExprSet AssertLocks;
1738         Analyzer->getMutexIDs(AssertLocks, A, Exp, D, VD);
1739         for (const auto &AssertLock : AssertLocks)
1740           Analyzer->addLock(FSet, llvm::make_unique<LockableFactEntry>(
1741                                       AssertLock, LK_Shared, Loc, false, true),
1742                             ClassifyDiagnostic(A));
1743         break;
1744       }
1745 
1746       // When we encounter an unlock function, we need to remove unlocked
1747       // mutexes from the lockset, and flag a warning if they are not there.
1748       case attr::ReleaseCapability: {
1749         auto *A = cast<ReleaseCapabilityAttr>(At);
1750         if (A->isGeneric())
1751           Analyzer->getMutexIDs(GenericLocksToRemove, A, Exp, D, VD);
1752         else if (A->isShared())
1753           Analyzer->getMutexIDs(SharedLocksToRemove, A, Exp, D, VD);
1754         else
1755           Analyzer->getMutexIDs(ExclusiveLocksToRemove, A, Exp, D, VD);
1756 
1757         CapDiagKind = ClassifyDiagnostic(A);
1758         break;
1759       }
1760 
1761       case attr::RequiresCapability: {
1762         RequiresCapabilityAttr *A = cast<RequiresCapabilityAttr>(At);
1763         for (auto *Arg : A->args()) {
1764           warnIfMutexNotHeld(D, Exp, A->isShared() ? AK_Read : AK_Written, Arg,
1765                              POK_FunctionCall, ClassifyDiagnostic(A),
1766                              Exp->getExprLoc());
1767           // use for adopting a lock
1768           if (isScopedVar) {
1769             Analyzer->getMutexIDs(A->isShared() ? ScopedSharedReqs
1770                                                 : ScopedExclusiveReqs,
1771                                   A, Exp, D, VD);
1772           }
1773         }
1774         break;
1775       }
1776 
1777       case attr::LocksExcluded: {
1778         LocksExcludedAttr *A = cast<LocksExcludedAttr>(At);
1779         for (auto *Arg : A->args())
1780           warnIfMutexHeld(D, Exp, Arg, ClassifyDiagnostic(A));
1781         break;
1782       }
1783 
1784       // Ignore attributes unrelated to thread-safety
1785       default:
1786         break;
1787     }
1788   }
1789 
1790   // Add locks.
1791   for (const auto &M : ExclusiveLocksToAdd)
1792     Analyzer->addLock(FSet, llvm::make_unique<LockableFactEntry>(
1793                                 M, LK_Exclusive, Loc, isScopedVar),
1794                       CapDiagKind);
1795   for (const auto &M : SharedLocksToAdd)
1796     Analyzer->addLock(FSet, llvm::make_unique<LockableFactEntry>(
1797                                 M, LK_Shared, Loc, isScopedVar),
1798                       CapDiagKind);
1799 
1800   if (isScopedVar) {
1801     // Add the managing object as a dummy mutex, mapped to the underlying mutex.
1802     SourceLocation MLoc = VD->getLocation();
1803     DeclRefExpr DRE(VD, false, VD->getType(), VK_LValue, VD->getLocation());
1804     // FIXME: does this store a pointer to DRE?
1805     CapabilityExpr Scp = Analyzer->SxBuilder.translateAttrExpr(&DRE, nullptr);
1806 
1807     std::copy(ScopedExclusiveReqs.begin(), ScopedExclusiveReqs.end(),
1808               std::back_inserter(ExclusiveLocksToAdd));
1809     std::copy(ScopedSharedReqs.begin(), ScopedSharedReqs.end(),
1810               std::back_inserter(SharedLocksToAdd));
1811     Analyzer->addLock(FSet,
1812                       llvm::make_unique<ScopedLockableFactEntry>(
1813                           Scp, MLoc, ExclusiveLocksToAdd, SharedLocksToAdd),
1814                       CapDiagKind);
1815   }
1816 
1817   // Remove locks.
1818   // FIXME -- should only fully remove if the attribute refers to 'this'.
1819   bool Dtor = isa<CXXDestructorDecl>(D);
1820   for (const auto &M : ExclusiveLocksToRemove)
1821     Analyzer->removeLock(FSet, M, Loc, Dtor, LK_Exclusive, CapDiagKind);
1822   for (const auto &M : SharedLocksToRemove)
1823     Analyzer->removeLock(FSet, M, Loc, Dtor, LK_Shared, CapDiagKind);
1824   for (const auto &M : GenericLocksToRemove)
1825     Analyzer->removeLock(FSet, M, Loc, Dtor, LK_Generic, CapDiagKind);
1826 }
1827 
1828 
1829 /// \brief For unary operations which read and write a variable, we need to
1830 /// check whether we hold any required mutexes. Reads are checked in
1831 /// VisitCastExpr.
VisitUnaryOperator(UnaryOperator * UO)1832 void BuildLockset::VisitUnaryOperator(UnaryOperator *UO) {
1833   switch (UO->getOpcode()) {
1834     case clang::UO_PostDec:
1835     case clang::UO_PostInc:
1836     case clang::UO_PreDec:
1837     case clang::UO_PreInc: {
1838       checkAccess(UO->getSubExpr(), AK_Written);
1839       break;
1840     }
1841     default:
1842       break;
1843   }
1844 }
1845 
1846 /// For binary operations which assign to a variable (writes), we need to check
1847 /// whether we hold any required mutexes.
1848 /// FIXME: Deal with non-primitive types.
VisitBinaryOperator(BinaryOperator * BO)1849 void BuildLockset::VisitBinaryOperator(BinaryOperator *BO) {
1850   if (!BO->isAssignmentOp())
1851     return;
1852 
1853   // adjust the context
1854   LVarCtx = Analyzer->LocalVarMap.getNextContext(CtxIndex, BO, LVarCtx);
1855 
1856   checkAccess(BO->getLHS(), AK_Written);
1857 }
1858 
1859 
1860 /// Whenever we do an LValue to Rvalue cast, we are reading a variable and
1861 /// need to ensure we hold any required mutexes.
1862 /// FIXME: Deal with non-primitive types.
VisitCastExpr(CastExpr * CE)1863 void BuildLockset::VisitCastExpr(CastExpr *CE) {
1864   if (CE->getCastKind() != CK_LValueToRValue)
1865     return;
1866   checkAccess(CE->getSubExpr(), AK_Read);
1867 }
1868 
1869 
VisitCallExpr(CallExpr * Exp)1870 void BuildLockset::VisitCallExpr(CallExpr *Exp) {
1871   bool ExamineArgs = true;
1872   bool OperatorFun = false;
1873 
1874   if (CXXMemberCallExpr *CE = dyn_cast<CXXMemberCallExpr>(Exp)) {
1875     MemberExpr *ME = dyn_cast<MemberExpr>(CE->getCallee());
1876     // ME can be null when calling a method pointer
1877     CXXMethodDecl *MD = CE->getMethodDecl();
1878 
1879     if (ME && MD) {
1880       if (ME->isArrow()) {
1881         if (MD->isConst()) {
1882           checkPtAccess(CE->getImplicitObjectArgument(), AK_Read);
1883         } else {  // FIXME -- should be AK_Written
1884           checkPtAccess(CE->getImplicitObjectArgument(), AK_Read);
1885         }
1886       } else {
1887         if (MD->isConst())
1888           checkAccess(CE->getImplicitObjectArgument(), AK_Read);
1889         else     // FIXME -- should be AK_Written
1890           checkAccess(CE->getImplicitObjectArgument(), AK_Read);
1891       }
1892     }
1893   } else if (CXXOperatorCallExpr *OE = dyn_cast<CXXOperatorCallExpr>(Exp)) {
1894     OperatorFun = true;
1895 
1896     auto OEop = OE->getOperator();
1897     switch (OEop) {
1898       case OO_Equal: {
1899         ExamineArgs = false;
1900         const Expr *Target = OE->getArg(0);
1901         const Expr *Source = OE->getArg(1);
1902         checkAccess(Target, AK_Written);
1903         checkAccess(Source, AK_Read);
1904         break;
1905       }
1906       case OO_Star:
1907       case OO_Arrow:
1908       case OO_Subscript: {
1909         const Expr *Obj = OE->getArg(0);
1910         checkAccess(Obj, AK_Read);
1911         if (!(OEop == OO_Star && OE->getNumArgs() > 1)) {
1912           // Grrr.  operator* can be multiplication...
1913           checkPtAccess(Obj, AK_Read);
1914         }
1915         break;
1916       }
1917       default: {
1918         // TODO: get rid of this, and rely on pass-by-ref instead.
1919         const Expr *Obj = OE->getArg(0);
1920         checkAccess(Obj, AK_Read);
1921         break;
1922       }
1923     }
1924   }
1925 
1926   if (ExamineArgs) {
1927     if (FunctionDecl *FD = Exp->getDirectCallee()) {
1928 
1929       // NO_THREAD_SAFETY_ANALYSIS does double duty here.  Normally it
1930       // only turns off checking within the body of a function, but we also
1931       // use it to turn off checking in arguments to the function.  This
1932       // could result in some false negatives, but the alternative is to
1933       // create yet another attribute.
1934       //
1935       if (!FD->hasAttr<NoThreadSafetyAnalysisAttr>()) {
1936         unsigned Fn = FD->getNumParams();
1937         unsigned Cn = Exp->getNumArgs();
1938         unsigned Skip = 0;
1939 
1940         unsigned i = 0;
1941         if (OperatorFun) {
1942           if (isa<CXXMethodDecl>(FD)) {
1943             // First arg in operator call is implicit self argument,
1944             // and doesn't appear in the FunctionDecl.
1945             Skip = 1;
1946             Cn--;
1947           } else {
1948             // Ignore the first argument of operators; it's been checked above.
1949             i = 1;
1950           }
1951         }
1952         // Ignore default arguments
1953         unsigned n = (Fn < Cn) ? Fn : Cn;
1954 
1955         for (; i < n; ++i) {
1956           ParmVarDecl* Pvd = FD->getParamDecl(i);
1957           Expr* Arg = Exp->getArg(i+Skip);
1958           QualType Qt = Pvd->getType();
1959           if (Qt->isReferenceType())
1960             checkAccess(Arg, AK_Read, POK_PassByRef);
1961         }
1962       }
1963     }
1964   }
1965 
1966   NamedDecl *D = dyn_cast_or_null<NamedDecl>(Exp->getCalleeDecl());
1967   if(!D || !D->hasAttrs())
1968     return;
1969   handleCall(Exp, D);
1970 }
1971 
VisitCXXConstructExpr(CXXConstructExpr * Exp)1972 void BuildLockset::VisitCXXConstructExpr(CXXConstructExpr *Exp) {
1973   const CXXConstructorDecl *D = Exp->getConstructor();
1974   if (D && D->isCopyConstructor()) {
1975     const Expr* Source = Exp->getArg(0);
1976     checkAccess(Source, AK_Read);
1977   }
1978   // FIXME -- only handles constructors in DeclStmt below.
1979 }
1980 
VisitDeclStmt(DeclStmt * S)1981 void BuildLockset::VisitDeclStmt(DeclStmt *S) {
1982   // adjust the context
1983   LVarCtx = Analyzer->LocalVarMap.getNextContext(CtxIndex, S, LVarCtx);
1984 
1985   for (auto *D : S->getDeclGroup()) {
1986     if (VarDecl *VD = dyn_cast_or_null<VarDecl>(D)) {
1987       Expr *E = VD->getInit();
1988       // handle constructors that involve temporaries
1989       if (ExprWithCleanups *EWC = dyn_cast_or_null<ExprWithCleanups>(E))
1990         E = EWC->getSubExpr();
1991 
1992       if (CXXConstructExpr *CE = dyn_cast_or_null<CXXConstructExpr>(E)) {
1993         NamedDecl *CtorD = dyn_cast_or_null<NamedDecl>(CE->getConstructor());
1994         if (!CtorD || !CtorD->hasAttrs())
1995           return;
1996         handleCall(CE, CtorD, VD);
1997       }
1998     }
1999   }
2000 }
2001 
2002 
2003 
2004 /// \brief Compute the intersection of two locksets and issue warnings for any
2005 /// locks in the symmetric difference.
2006 ///
2007 /// This function is used at a merge point in the CFG when comparing the lockset
2008 /// of each branch being merged. For example, given the following sequence:
2009 /// A; if () then B; else C; D; we need to check that the lockset after B and C
2010 /// are the same. In the event of a difference, we use the intersection of these
2011 /// two locksets at the start of D.
2012 ///
2013 /// \param FSet1 The first lockset.
2014 /// \param FSet2 The second lockset.
2015 /// \param JoinLoc The location of the join point for error reporting
2016 /// \param LEK1 The error message to report if a mutex is missing from LSet1
2017 /// \param LEK2 The error message to report if a mutex is missing from Lset2
intersectAndWarn(FactSet & FSet1,const FactSet & FSet2,SourceLocation JoinLoc,LockErrorKind LEK1,LockErrorKind LEK2,bool Modify)2018 void ThreadSafetyAnalyzer::intersectAndWarn(FactSet &FSet1,
2019                                             const FactSet &FSet2,
2020                                             SourceLocation JoinLoc,
2021                                             LockErrorKind LEK1,
2022                                             LockErrorKind LEK2,
2023                                             bool Modify) {
2024   FactSet FSet1Orig = FSet1;
2025 
2026   // Find locks in FSet2 that conflict or are not in FSet1, and warn.
2027   for (const auto &Fact : FSet2) {
2028     const FactEntry *LDat1 = nullptr;
2029     const FactEntry *LDat2 = &FactMan[Fact];
2030     FactSet::iterator Iter1  = FSet1.findLockIter(FactMan, *LDat2);
2031     if (Iter1 != FSet1.end()) LDat1 = &FactMan[*Iter1];
2032 
2033     if (LDat1) {
2034       if (LDat1->kind() != LDat2->kind()) {
2035         Handler.handleExclusiveAndShared("mutex", LDat2->toString(),
2036                                          LDat2->loc(), LDat1->loc());
2037         if (Modify && LDat1->kind() != LK_Exclusive) {
2038           // Take the exclusive lock, which is the one in FSet2.
2039           *Iter1 = Fact;
2040         }
2041       }
2042       else if (Modify && LDat1->asserted() && !LDat2->asserted()) {
2043         // The non-asserted lock in FSet2 is the one we want to track.
2044         *Iter1 = Fact;
2045       }
2046     } else {
2047       LDat2->handleRemovalFromIntersection(FSet2, FactMan, JoinLoc, LEK1,
2048                                            Handler);
2049     }
2050   }
2051 
2052   // Find locks in FSet1 that are not in FSet2, and remove them.
2053   for (const auto &Fact : FSet1Orig) {
2054     const FactEntry *LDat1 = &FactMan[Fact];
2055     const FactEntry *LDat2 = FSet2.findLock(FactMan, *LDat1);
2056 
2057     if (!LDat2) {
2058       LDat1->handleRemovalFromIntersection(FSet1Orig, FactMan, JoinLoc, LEK2,
2059                                            Handler);
2060       if (Modify)
2061         FSet1.removeLock(FactMan, *LDat1);
2062     }
2063   }
2064 }
2065 
2066 
2067 // Return true if block B never continues to its successors.
neverReturns(const CFGBlock * B)2068 static bool neverReturns(const CFGBlock *B) {
2069   if (B->hasNoReturnElement())
2070     return true;
2071   if (B->empty())
2072     return false;
2073 
2074   CFGElement Last = B->back();
2075   if (Optional<CFGStmt> S = Last.getAs<CFGStmt>()) {
2076     if (isa<CXXThrowExpr>(S->getStmt()))
2077       return true;
2078   }
2079   return false;
2080 }
2081 
2082 
2083 /// \brief Check a function's CFG for thread-safety violations.
2084 ///
2085 /// We traverse the blocks in the CFG, compute the set of mutexes that are held
2086 /// at the end of each block, and issue warnings for thread safety violations.
2087 /// Each block in the CFG is traversed exactly once.
runAnalysis(AnalysisDeclContext & AC)2088 void ThreadSafetyAnalyzer::runAnalysis(AnalysisDeclContext &AC) {
2089   // TODO: this whole function needs be rewritten as a visitor for CFGWalker.
2090   // For now, we just use the walker to set things up.
2091   threadSafety::CFGWalker walker;
2092   if (!walker.init(AC))
2093     return;
2094 
2095   // AC.dumpCFG(true);
2096   // threadSafety::printSCFG(walker);
2097 
2098   CFG *CFGraph = walker.getGraph();
2099   const NamedDecl *D = walker.getDecl();
2100   const FunctionDecl *CurrentFunction = dyn_cast<FunctionDecl>(D);
2101   CurrentMethod = dyn_cast<CXXMethodDecl>(D);
2102 
2103   if (D->hasAttr<NoThreadSafetyAnalysisAttr>())
2104     return;
2105 
2106   // FIXME: Do something a bit more intelligent inside constructor and
2107   // destructor code.  Constructors and destructors must assume unique access
2108   // to 'this', so checks on member variable access is disabled, but we should
2109   // still enable checks on other objects.
2110   if (isa<CXXConstructorDecl>(D))
2111     return;  // Don't check inside constructors.
2112   if (isa<CXXDestructorDecl>(D))
2113     return;  // Don't check inside destructors.
2114 
2115   Handler.enterFunction(CurrentFunction);
2116 
2117   BlockInfo.resize(CFGraph->getNumBlockIDs(),
2118     CFGBlockInfo::getEmptyBlockInfo(LocalVarMap));
2119 
2120   // We need to explore the CFG via a "topological" ordering.
2121   // That way, we will be guaranteed to have information about required
2122   // predecessor locksets when exploring a new block.
2123   const PostOrderCFGView *SortedGraph = walker.getSortedGraph();
2124   PostOrderCFGView::CFGBlockSet VisitedBlocks(CFGraph);
2125 
2126   // Mark entry block as reachable
2127   BlockInfo[CFGraph->getEntry().getBlockID()].Reachable = true;
2128 
2129   // Compute SSA names for local variables
2130   LocalVarMap.traverseCFG(CFGraph, SortedGraph, BlockInfo);
2131 
2132   // Fill in source locations for all CFGBlocks.
2133   findBlockLocations(CFGraph, SortedGraph, BlockInfo);
2134 
2135   CapExprSet ExclusiveLocksAcquired;
2136   CapExprSet SharedLocksAcquired;
2137   CapExprSet LocksReleased;
2138 
2139   // Add locks from exclusive_locks_required and shared_locks_required
2140   // to initial lockset. Also turn off checking for lock and unlock functions.
2141   // FIXME: is there a more intelligent way to check lock/unlock functions?
2142   if (!SortedGraph->empty() && D->hasAttrs()) {
2143     const CFGBlock *FirstBlock = *SortedGraph->begin();
2144     FactSet &InitialLockset = BlockInfo[FirstBlock->getBlockID()].EntrySet;
2145 
2146     CapExprSet ExclusiveLocksToAdd;
2147     CapExprSet SharedLocksToAdd;
2148     StringRef CapDiagKind = "mutex";
2149 
2150     SourceLocation Loc = D->getLocation();
2151     for (const auto *Attr : D->attrs()) {
2152       Loc = Attr->getLocation();
2153       if (const auto *A = dyn_cast<RequiresCapabilityAttr>(Attr)) {
2154         getMutexIDs(A->isShared() ? SharedLocksToAdd : ExclusiveLocksToAdd, A,
2155                     nullptr, D);
2156         CapDiagKind = ClassifyDiagnostic(A);
2157       } else if (const auto *A = dyn_cast<ReleaseCapabilityAttr>(Attr)) {
2158         // UNLOCK_FUNCTION() is used to hide the underlying lock implementation.
2159         // We must ignore such methods.
2160         if (A->args_size() == 0)
2161           return;
2162         // FIXME -- deal with exclusive vs. shared unlock functions?
2163         getMutexIDs(ExclusiveLocksToAdd, A, nullptr, D);
2164         getMutexIDs(LocksReleased, A, nullptr, D);
2165         CapDiagKind = ClassifyDiagnostic(A);
2166       } else if (const auto *A = dyn_cast<AcquireCapabilityAttr>(Attr)) {
2167         if (A->args_size() == 0)
2168           return;
2169         getMutexIDs(A->isShared() ? SharedLocksAcquired
2170                                   : ExclusiveLocksAcquired,
2171                     A, nullptr, D);
2172         CapDiagKind = ClassifyDiagnostic(A);
2173       } else if (isa<ExclusiveTrylockFunctionAttr>(Attr)) {
2174         // Don't try to check trylock functions for now
2175         return;
2176       } else if (isa<SharedTrylockFunctionAttr>(Attr)) {
2177         // Don't try to check trylock functions for now
2178         return;
2179       }
2180     }
2181 
2182     // FIXME -- Loc can be wrong here.
2183     for (const auto &Mu : ExclusiveLocksToAdd) {
2184       auto Entry = llvm::make_unique<LockableFactEntry>(Mu, LK_Exclusive, Loc);
2185       Entry->setDeclared(true);
2186       addLock(InitialLockset, std::move(Entry), CapDiagKind, true);
2187     }
2188     for (const auto &Mu : SharedLocksToAdd) {
2189       auto Entry = llvm::make_unique<LockableFactEntry>(Mu, LK_Shared, Loc);
2190       Entry->setDeclared(true);
2191       addLock(InitialLockset, std::move(Entry), CapDiagKind, true);
2192     }
2193   }
2194 
2195   for (const auto *CurrBlock : *SortedGraph) {
2196     int CurrBlockID = CurrBlock->getBlockID();
2197     CFGBlockInfo *CurrBlockInfo = &BlockInfo[CurrBlockID];
2198 
2199     // Use the default initial lockset in case there are no predecessors.
2200     VisitedBlocks.insert(CurrBlock);
2201 
2202     // Iterate through the predecessor blocks and warn if the lockset for all
2203     // predecessors is not the same. We take the entry lockset of the current
2204     // block to be the intersection of all previous locksets.
2205     // FIXME: By keeping the intersection, we may output more errors in future
2206     // for a lock which is not in the intersection, but was in the union. We
2207     // may want to also keep the union in future. As an example, let's say
2208     // the intersection contains Mutex L, and the union contains L and M.
2209     // Later we unlock M. At this point, we would output an error because we
2210     // never locked M; although the real error is probably that we forgot to
2211     // lock M on all code paths. Conversely, let's say that later we lock M.
2212     // In this case, we should compare against the intersection instead of the
2213     // union because the real error is probably that we forgot to unlock M on
2214     // all code paths.
2215     bool LocksetInitialized = false;
2216     SmallVector<CFGBlock *, 8> SpecialBlocks;
2217     for (CFGBlock::const_pred_iterator PI = CurrBlock->pred_begin(),
2218          PE  = CurrBlock->pred_end(); PI != PE; ++PI) {
2219 
2220       // if *PI -> CurrBlock is a back edge
2221       if (*PI == nullptr || !VisitedBlocks.alreadySet(*PI))
2222         continue;
2223 
2224       int PrevBlockID = (*PI)->getBlockID();
2225       CFGBlockInfo *PrevBlockInfo = &BlockInfo[PrevBlockID];
2226 
2227       // Ignore edges from blocks that can't return.
2228       if (neverReturns(*PI) || !PrevBlockInfo->Reachable)
2229         continue;
2230 
2231       // Okay, we can reach this block from the entry.
2232       CurrBlockInfo->Reachable = true;
2233 
2234       // If the previous block ended in a 'continue' or 'break' statement, then
2235       // a difference in locksets is probably due to a bug in that block, rather
2236       // than in some other predecessor. In that case, keep the other
2237       // predecessor's lockset.
2238       if (const Stmt *Terminator = (*PI)->getTerminator()) {
2239         if (isa<ContinueStmt>(Terminator) || isa<BreakStmt>(Terminator)) {
2240           SpecialBlocks.push_back(*PI);
2241           continue;
2242         }
2243       }
2244 
2245       FactSet PrevLockset;
2246       getEdgeLockset(PrevLockset, PrevBlockInfo->ExitSet, *PI, CurrBlock);
2247 
2248       if (!LocksetInitialized) {
2249         CurrBlockInfo->EntrySet = PrevLockset;
2250         LocksetInitialized = true;
2251       } else {
2252         intersectAndWarn(CurrBlockInfo->EntrySet, PrevLockset,
2253                          CurrBlockInfo->EntryLoc,
2254                          LEK_LockedSomePredecessors);
2255       }
2256     }
2257 
2258     // Skip rest of block if it's not reachable.
2259     if (!CurrBlockInfo->Reachable)
2260       continue;
2261 
2262     // Process continue and break blocks. Assume that the lockset for the
2263     // resulting block is unaffected by any discrepancies in them.
2264     for (const auto *PrevBlock : SpecialBlocks) {
2265       int PrevBlockID = PrevBlock->getBlockID();
2266       CFGBlockInfo *PrevBlockInfo = &BlockInfo[PrevBlockID];
2267 
2268       if (!LocksetInitialized) {
2269         CurrBlockInfo->EntrySet = PrevBlockInfo->ExitSet;
2270         LocksetInitialized = true;
2271       } else {
2272         // Determine whether this edge is a loop terminator for diagnostic
2273         // purposes. FIXME: A 'break' statement might be a loop terminator, but
2274         // it might also be part of a switch. Also, a subsequent destructor
2275         // might add to the lockset, in which case the real issue might be a
2276         // double lock on the other path.
2277         const Stmt *Terminator = PrevBlock->getTerminator();
2278         bool IsLoop = Terminator && isa<ContinueStmt>(Terminator);
2279 
2280         FactSet PrevLockset;
2281         getEdgeLockset(PrevLockset, PrevBlockInfo->ExitSet,
2282                        PrevBlock, CurrBlock);
2283 
2284         // Do not update EntrySet.
2285         intersectAndWarn(CurrBlockInfo->EntrySet, PrevLockset,
2286                          PrevBlockInfo->ExitLoc,
2287                          IsLoop ? LEK_LockedSomeLoopIterations
2288                                 : LEK_LockedSomePredecessors,
2289                          false);
2290       }
2291     }
2292 
2293     BuildLockset LocksetBuilder(this, *CurrBlockInfo);
2294 
2295     // Visit all the statements in the basic block.
2296     for (CFGBlock::const_iterator BI = CurrBlock->begin(),
2297          BE = CurrBlock->end(); BI != BE; ++BI) {
2298       switch (BI->getKind()) {
2299         case CFGElement::Statement: {
2300           CFGStmt CS = BI->castAs<CFGStmt>();
2301           LocksetBuilder.Visit(const_cast<Stmt*>(CS.getStmt()));
2302           break;
2303         }
2304         // Ignore BaseDtor, MemberDtor, and TemporaryDtor for now.
2305         case CFGElement::AutomaticObjectDtor: {
2306           CFGAutomaticObjDtor AD = BI->castAs<CFGAutomaticObjDtor>();
2307           CXXDestructorDecl *DD = const_cast<CXXDestructorDecl *>(
2308               AD.getDestructorDecl(AC.getASTContext()));
2309           if (!DD->hasAttrs())
2310             break;
2311 
2312           // Create a dummy expression,
2313           VarDecl *VD = const_cast<VarDecl*>(AD.getVarDecl());
2314           DeclRefExpr DRE(VD, false, VD->getType().getNonReferenceType(),
2315                           VK_LValue, AD.getTriggerStmt()->getLocEnd());
2316           LocksetBuilder.handleCall(&DRE, DD);
2317           break;
2318         }
2319         default:
2320           break;
2321       }
2322     }
2323     CurrBlockInfo->ExitSet = LocksetBuilder.FSet;
2324 
2325     // For every back edge from CurrBlock (the end of the loop) to another block
2326     // (FirstLoopBlock) we need to check that the Lockset of Block is equal to
2327     // the one held at the beginning of FirstLoopBlock. We can look up the
2328     // Lockset held at the beginning of FirstLoopBlock in the EntryLockSets map.
2329     for (CFGBlock::const_succ_iterator SI = CurrBlock->succ_begin(),
2330          SE  = CurrBlock->succ_end(); SI != SE; ++SI) {
2331 
2332       // if CurrBlock -> *SI is *not* a back edge
2333       if (*SI == nullptr || !VisitedBlocks.alreadySet(*SI))
2334         continue;
2335 
2336       CFGBlock *FirstLoopBlock = *SI;
2337       CFGBlockInfo *PreLoop = &BlockInfo[FirstLoopBlock->getBlockID()];
2338       CFGBlockInfo *LoopEnd = &BlockInfo[CurrBlockID];
2339       intersectAndWarn(LoopEnd->ExitSet, PreLoop->EntrySet,
2340                        PreLoop->EntryLoc,
2341                        LEK_LockedSomeLoopIterations,
2342                        false);
2343     }
2344   }
2345 
2346   CFGBlockInfo *Initial = &BlockInfo[CFGraph->getEntry().getBlockID()];
2347   CFGBlockInfo *Final   = &BlockInfo[CFGraph->getExit().getBlockID()];
2348 
2349   // Skip the final check if the exit block is unreachable.
2350   if (!Final->Reachable)
2351     return;
2352 
2353   // By default, we expect all locks held on entry to be held on exit.
2354   FactSet ExpectedExitSet = Initial->EntrySet;
2355 
2356   // Adjust the expected exit set by adding or removing locks, as declared
2357   // by *-LOCK_FUNCTION and UNLOCK_FUNCTION.  The intersect below will then
2358   // issue the appropriate warning.
2359   // FIXME: the location here is not quite right.
2360   for (const auto &Lock : ExclusiveLocksAcquired)
2361     ExpectedExitSet.addLock(FactMan, llvm::make_unique<LockableFactEntry>(
2362                                          Lock, LK_Exclusive, D->getLocation()));
2363   for (const auto &Lock : SharedLocksAcquired)
2364     ExpectedExitSet.addLock(FactMan, llvm::make_unique<LockableFactEntry>(
2365                                          Lock, LK_Shared, D->getLocation()));
2366   for (const auto &Lock : LocksReleased)
2367     ExpectedExitSet.removeLock(FactMan, Lock);
2368 
2369   // FIXME: Should we call this function for all blocks which exit the function?
2370   intersectAndWarn(ExpectedExitSet, Final->ExitSet,
2371                    Final->ExitLoc,
2372                    LEK_LockedAtEndOfFunction,
2373                    LEK_NotLockedAtEndOfFunction,
2374                    false);
2375 
2376   Handler.leaveFunction(CurrentFunction);
2377 }
2378 
2379 
2380 /// \brief Check a function's CFG for thread-safety violations.
2381 ///
2382 /// We traverse the blocks in the CFG, compute the set of mutexes that are held
2383 /// at the end of each block, and issue warnings for thread safety violations.
2384 /// Each block in the CFG is traversed exactly once.
runThreadSafetyAnalysis(AnalysisDeclContext & AC,ThreadSafetyHandler & Handler,BeforeSet ** BSet)2385 void threadSafety::runThreadSafetyAnalysis(AnalysisDeclContext &AC,
2386                                            ThreadSafetyHandler &Handler,
2387                                            BeforeSet **BSet) {
2388   if (!*BSet)
2389     *BSet = new BeforeSet;
2390   ThreadSafetyAnalyzer Analyzer(Handler, *BSet);
2391   Analyzer.runAnalysis(AC);
2392 }
2393 
threadSafetyCleanup(BeforeSet * Cache)2394 void threadSafety::threadSafetyCleanup(BeforeSet *Cache) { delete Cache; }
2395 
2396 /// \brief Helper function that returns a LockKind required for the given level
2397 /// of access.
getLockKindFromAccessKind(AccessKind AK)2398 LockKind threadSafety::getLockKindFromAccessKind(AccessKind AK) {
2399   switch (AK) {
2400     case AK_Read :
2401       return LK_Shared;
2402     case AK_Written :
2403       return LK_Exclusive;
2404   }
2405   llvm_unreachable("Unknown AccessKind");
2406 }
2407