1 //===- CastValueChecker - Model implementation of custom RTTIs --*- C++ -*-===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 // This defines CastValueChecker which models casts of custom RTTIs.
12 // - It only allows one succesful cast between two types however in the wild
13 // the object could be casted to multiple types.
14 // - It needs to check the most likely type information from the dynamic type
15 // map to increase precision of dynamic casting.
17 //===----------------------------------------------------------------------===//
19 #include "clang/AST/DeclTemplate.h"
20 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
21 #include "clang/StaticAnalyzer/Core/Checker.h"
22 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
23 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
24 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
25 #include "clang/StaticAnalyzer/Core/PathSensitive/DynamicType.h"
26 #include "llvm/ADT/Optional.h"
29 using namespace clang;
33 class CastValueChecker : public Checker<check::DeadSymbols, eval::Call> {
34 enum class CallKind { Function, Method, InstanceOf };
37 std::function<void(const CastValueChecker *, const CallEvent &Call,
38 DefinedOrUnknownSVal, CheckerContext &)>;
41 // We have five cases to evaluate a cast:
42 // 1) The parameter is non-null, the return value is non-null.
43 // 2) The parameter is non-null, the return value is null.
44 // 3) The parameter is null, the return value is null.
45 // cast: 1; dyn_cast: 1, 2; cast_or_null: 1, 3; dyn_cast_or_null: 1, 2, 3.
47 // 4) castAs: Has no parameter, the return value is non-null.
48 // 5) getAs: Has no parameter, the return value is null or non-null.
50 // We have two cases to check the parameter is an instance of the given type.
51 // 1) isa: The parameter is non-null, returns boolean.
52 // 2) isa_and_nonnull: The parameter is null or non-null, returns boolean.
53 bool evalCall(const CallEvent &Call, CheckerContext &C) const;
54 void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const;
57 // These are known in the LLVM project. The pairs are in the following form:
58 // {{{namespace, call}, argument-count}, {callback, kind}}
59 const CallDescriptionMap<std::pair<CastCheck, CallKind>> CDM = {
60 {{{"llvm", "cast"}, 1},
61 {&CastValueChecker::evalCast, CallKind::Function}},
62 {{{"llvm", "dyn_cast"}, 1},
63 {&CastValueChecker::evalDynCast, CallKind::Function}},
64 {{{"llvm", "cast_or_null"}, 1},
65 {&CastValueChecker::evalCastOrNull, CallKind::Function}},
66 {{{"llvm", "dyn_cast_or_null"}, 1},
67 {&CastValueChecker::evalDynCastOrNull, CallKind::Function}},
68 {{{"clang", "castAs"}, 0},
69 {&CastValueChecker::evalCastAs, CallKind::Method}},
70 {{{"clang", "getAs"}, 0},
71 {&CastValueChecker::evalGetAs, CallKind::Method}},
72 {{{"llvm", "isa"}, 1},
73 {&CastValueChecker::evalIsa, CallKind::InstanceOf}},
74 {{{"llvm", "isa_and_nonnull"}, 1},
75 {&CastValueChecker::evalIsaAndNonNull, CallKind::InstanceOf}}};
77 void evalCast(const CallEvent &Call, DefinedOrUnknownSVal DV,
78 CheckerContext &C) const;
79 void evalDynCast(const CallEvent &Call, DefinedOrUnknownSVal DV,
80 CheckerContext &C) const;
81 void evalCastOrNull(const CallEvent &Call, DefinedOrUnknownSVal DV,
82 CheckerContext &C) const;
83 void evalDynCastOrNull(const CallEvent &Call, DefinedOrUnknownSVal DV,
84 CheckerContext &C) const;
85 void evalCastAs(const CallEvent &Call, DefinedOrUnknownSVal DV,
86 CheckerContext &C) const;
87 void evalGetAs(const CallEvent &Call, DefinedOrUnknownSVal DV,
88 CheckerContext &C) const;
89 void evalIsa(const CallEvent &Call, DefinedOrUnknownSVal DV,
90 CheckerContext &C) const;
91 void evalIsaAndNonNull(const CallEvent &Call, DefinedOrUnknownSVal DV,
92 CheckerContext &C) const;
96 static bool isInfeasibleCast(const DynamicCastInfo *CastInfo,
101 return CastSucceeds ? CastInfo->fails() : CastInfo->succeeds();
104 static const NoteTag *getNoteTag(CheckerContext &C,
105 const DynamicCastInfo *CastInfo,
106 QualType CastToTy, const Expr *Object,
107 bool CastSucceeds, bool IsKnownCast) {
108 std::string CastToName =
109 CastInfo ? CastInfo->to()->getPointeeCXXRecordDecl()->getNameAsString()
110 : CastToTy->getPointeeCXXRecordDecl()->getNameAsString();
111 Object = Object->IgnoreParenImpCasts();
114 [=]() -> std::string {
115 SmallString<128> Msg;
116 llvm::raw_svector_ostream Out(Msg);
121 if (const auto *DRE = dyn_cast<DeclRefExpr>(Object)) {
122 Out << '\'' << DRE->getDecl()->getNameAsString() << '\'';
123 } else if (const auto *ME = dyn_cast<MemberExpr>(Object)) {
124 Out << (IsKnownCast ? "Field '" : "field '")
125 << ME->getMemberDecl()->getNameAsString() << '\'';
127 Out << (IsKnownCast ? "The object" : "the object");
130 Out << ' ' << (CastSucceeds ? "is a" : "is not a") << " '" << CastToName
133 return std::string(Out.str());
135 /*IsPrunable=*/true);
138 //===----------------------------------------------------------------------===//
139 // Main logic to evaluate a cast.
140 //===----------------------------------------------------------------------===//
142 static QualType alignReferenceTypes(QualType toAlign, QualType alignTowards,
144 if (alignTowards->isLValueReferenceType() &&
145 alignTowards.isConstQualified()) {
147 return ACtx.getLValueReferenceType(toAlign);
148 } else if (alignTowards->isLValueReferenceType())
149 return ACtx.getLValueReferenceType(toAlign);
150 else if (alignTowards->isRValueReferenceType())
151 return ACtx.getRValueReferenceType(toAlign);
153 llvm_unreachable("Must align towards a reference type!");
156 static void addCastTransition(const CallEvent &Call, DefinedOrUnknownSVal DV,
157 CheckerContext &C, bool IsNonNullParam,
158 bool IsNonNullReturn,
159 bool IsCheckedCast = false) {
160 ProgramStateRef State = C.getState()->assume(DV, IsNonNullParam);
166 QualType CastToTy = Call.getResultType();
168 if (Call.getNumArgs() > 0) {
169 Object = Call.getArgExpr(0);
170 CastFromTy = Call.parameters()[0]->getType();
172 Object = cast<CXXInstanceCall>(&Call)->getCXXThisExpr();
173 CastFromTy = Object->getType();
174 if (CastToTy->isPointerType()) {
175 if (!CastFromTy->isPointerType())
178 if (!CastFromTy->isReferenceType())
181 CastFromTy = alignReferenceTypes(CastFromTy, CastToTy, C.getASTContext());
185 const MemRegion *MR = DV.getAsRegion();
186 const DynamicCastInfo *CastInfo =
187 getDynamicCastInfo(State, MR, CastFromTy, CastToTy);
189 // We assume that every checked cast succeeds.
190 bool CastSucceeds = IsCheckedCast || CastFromTy == CastToTy;
193 CastSucceeds = IsNonNullReturn && CastInfo->succeeds();
195 CastSucceeds = IsNonNullReturn;
198 // Check for infeasible casts.
199 if (isInfeasibleCast(CastInfo, CastSucceeds)) {
200 C.generateSink(State, C.getPredecessor());
204 // Store the type and the cast information.
205 bool IsKnownCast = CastInfo || IsCheckedCast || CastFromTy == CastToTy;
206 if (!IsKnownCast || IsCheckedCast)
207 State = setDynamicTypeAndCastInfo(State, MR, CastFromTy, CastToTy,
210 SVal V = CastSucceeds ? C.getSValBuilder().evalCast(DV, CastToTy, CastFromTy)
211 : C.getSValBuilder().makeNull();
213 State->BindExpr(Call.getOriginExpr(), C.getLocationContext(), V, false),
214 getNoteTag(C, CastInfo, CastToTy, Object, CastSucceeds, IsKnownCast));
217 static void addInstanceOfTransition(const CallEvent &Call,
218 DefinedOrUnknownSVal DV,
219 ProgramStateRef State, CheckerContext &C,
221 const FunctionDecl *FD = Call.getDecl()->getAsFunction();
222 QualType CastFromTy = Call.parameters()[0]->getType();
223 QualType CastToTy = FD->getTemplateSpecializationArgs()->get(0).getAsType();
224 if (CastFromTy->isPointerType())
225 CastToTy = C.getASTContext().getPointerType(CastToTy);
226 else if (CastFromTy->isReferenceType())
227 CastToTy = alignReferenceTypes(CastToTy, CastFromTy, C.getASTContext());
231 const MemRegion *MR = DV.getAsRegion();
232 const DynamicCastInfo *CastInfo =
233 getDynamicCastInfo(State, MR, CastFromTy, CastToTy);
237 CastSucceeds = IsInstanceOf && CastInfo->succeeds();
239 CastSucceeds = IsInstanceOf || CastFromTy == CastToTy;
241 if (isInfeasibleCast(CastInfo, CastSucceeds)) {
242 C.generateSink(State, C.getPredecessor());
246 // Store the type and the cast information.
247 bool IsKnownCast = CastInfo || CastFromTy == CastToTy;
249 State = setDynamicTypeAndCastInfo(State, MR, CastFromTy, CastToTy,
253 State->BindExpr(Call.getOriginExpr(), C.getLocationContext(),
254 C.getSValBuilder().makeTruthVal(CastSucceeds)),
255 getNoteTag(C, CastInfo, CastToTy, Call.getArgExpr(0), CastSucceeds,
259 //===----------------------------------------------------------------------===//
260 // Evaluating cast, dyn_cast, cast_or_null, dyn_cast_or_null.
261 //===----------------------------------------------------------------------===//
263 static void evalNonNullParamNonNullReturn(const CallEvent &Call,
264 DefinedOrUnknownSVal DV,
266 bool IsCheckedCast = false) {
267 addCastTransition(Call, DV, C, /*IsNonNullParam=*/true,
268 /*IsNonNullReturn=*/true, IsCheckedCast);
271 static void evalNonNullParamNullReturn(const CallEvent &Call,
272 DefinedOrUnknownSVal DV,
274 addCastTransition(Call, DV, C, /*IsNonNullParam=*/true,
275 /*IsNonNullReturn=*/false);
278 static void evalNullParamNullReturn(const CallEvent &Call,
279 DefinedOrUnknownSVal DV,
281 if (ProgramStateRef State = C.getState()->assume(DV, false))
282 C.addTransition(State->BindExpr(Call.getOriginExpr(),
283 C.getLocationContext(),
284 C.getSValBuilder().makeNull(), false),
285 C.getNoteTag("Assuming null pointer is passed into cast",
286 /*IsPrunable=*/true));
289 void CastValueChecker::evalCast(const CallEvent &Call, DefinedOrUnknownSVal DV,
290 CheckerContext &C) const {
291 evalNonNullParamNonNullReturn(Call, DV, C, /*IsCheckedCast=*/true);
294 void CastValueChecker::evalDynCast(const CallEvent &Call,
295 DefinedOrUnknownSVal DV,
296 CheckerContext &C) const {
297 evalNonNullParamNonNullReturn(Call, DV, C);
298 evalNonNullParamNullReturn(Call, DV, C);
301 void CastValueChecker::evalCastOrNull(const CallEvent &Call,
302 DefinedOrUnknownSVal DV,
303 CheckerContext &C) const {
304 evalNonNullParamNonNullReturn(Call, DV, C);
305 evalNullParamNullReturn(Call, DV, C);
308 void CastValueChecker::evalDynCastOrNull(const CallEvent &Call,
309 DefinedOrUnknownSVal DV,
310 CheckerContext &C) const {
311 evalNonNullParamNonNullReturn(Call, DV, C);
312 evalNonNullParamNullReturn(Call, DV, C);
313 evalNullParamNullReturn(Call, DV, C);
316 //===----------------------------------------------------------------------===//
317 // Evaluating castAs, getAs.
318 //===----------------------------------------------------------------------===//
320 static void evalZeroParamNonNullReturn(const CallEvent &Call,
321 DefinedOrUnknownSVal DV,
323 bool IsCheckedCast = false) {
324 addCastTransition(Call, DV, C, /*IsNonNullParam=*/true,
325 /*IsNonNullReturn=*/true, IsCheckedCast);
328 static void evalZeroParamNullReturn(const CallEvent &Call,
329 DefinedOrUnknownSVal DV,
331 addCastTransition(Call, DV, C, /*IsNonNullParam=*/true,
332 /*IsNonNullReturn=*/false);
335 void CastValueChecker::evalCastAs(const CallEvent &Call,
336 DefinedOrUnknownSVal DV,
337 CheckerContext &C) const {
338 evalZeroParamNonNullReturn(Call, DV, C, /*IsCheckedCast=*/true);
341 void CastValueChecker::evalGetAs(const CallEvent &Call, DefinedOrUnknownSVal DV,
342 CheckerContext &C) const {
343 evalZeroParamNonNullReturn(Call, DV, C);
344 evalZeroParamNullReturn(Call, DV, C);
347 //===----------------------------------------------------------------------===//
348 // Evaluating isa, isa_and_nonnull.
349 //===----------------------------------------------------------------------===//
351 void CastValueChecker::evalIsa(const CallEvent &Call, DefinedOrUnknownSVal DV,
352 CheckerContext &C) const {
353 ProgramStateRef NonNullState, NullState;
354 std::tie(NonNullState, NullState) = C.getState()->assume(DV);
357 addInstanceOfTransition(Call, DV, NonNullState, C, /*IsInstanceOf=*/true);
358 addInstanceOfTransition(Call, DV, NonNullState, C, /*IsInstanceOf=*/false);
362 C.generateSink(NullState, C.getPredecessor());
366 void CastValueChecker::evalIsaAndNonNull(const CallEvent &Call,
367 DefinedOrUnknownSVal DV,
368 CheckerContext &C) const {
369 ProgramStateRef NonNullState, NullState;
370 std::tie(NonNullState, NullState) = C.getState()->assume(DV);
373 addInstanceOfTransition(Call, DV, NonNullState, C, /*IsInstanceOf=*/true);
374 addInstanceOfTransition(Call, DV, NonNullState, C, /*IsInstanceOf=*/false);
378 addInstanceOfTransition(Call, DV, NullState, C, /*IsInstanceOf=*/false);
382 //===----------------------------------------------------------------------===//
383 // Main logic to evaluate a call.
384 //===----------------------------------------------------------------------===//
386 bool CastValueChecker::evalCall(const CallEvent &Call,
387 CheckerContext &C) const {
388 const auto *Lookup = CDM.lookup(Call);
392 const CastCheck &Check = Lookup->first;
393 CallKind Kind = Lookup->second;
395 Optional<DefinedOrUnknownSVal> DV;
398 case CallKind::Function: {
399 // We only model casts from pointers to pointers or from references
400 // to references. Other casts are most likely specialized and we
401 // cannot model them.
402 QualType ParamT = Call.parameters()[0]->getType();
403 QualType ResultT = Call.getResultType();
404 if (!(ParamT->isPointerType() && ResultT->isPointerType()) &&
405 !(ParamT->isReferenceType() && ResultT->isReferenceType()))
408 DV = Call.getArgSVal(0).getAs<DefinedOrUnknownSVal>();
411 case CallKind::InstanceOf: {
412 // We need to obtain the only template argument to determinte the type.
413 const FunctionDecl *FD = Call.getDecl()->getAsFunction();
414 if (!FD || !FD->getTemplateSpecializationArgs())
417 DV = Call.getArgSVal(0).getAs<DefinedOrUnknownSVal>();
420 case CallKind::Method:
421 const auto *InstanceCall = dyn_cast<CXXInstanceCall>(&Call);
425 DV = InstanceCall->getCXXThisVal().getAs<DefinedOrUnknownSVal>();
432 Check(this, Call, *DV, C);
436 void CastValueChecker::checkDeadSymbols(SymbolReaper &SR,
437 CheckerContext &C) const {
438 C.addTransition(removeDeadCasts(C.getState(), SR));
441 void ento::registerCastValueChecker(CheckerManager &Mgr) {
442 Mgr.registerChecker<CastValueChecker>();
445 bool ento::shouldRegisterCastValueChecker(const CheckerManager &mgr) {