1 //===- Store.cpp - Interface for maps from Locations to Values ------------===//
2 //
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
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file defined the types Store and StoreManager.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "clang/StaticAnalyzer/Core/PathSensitive/Store.h"
14 #include "clang/AST/ASTContext.h"
15 #include "clang/AST/CXXInheritance.h"
16 #include "clang/AST/CharUnits.h"
17 #include "clang/AST/Decl.h"
18 #include "clang/AST/DeclCXX.h"
19 #include "clang/AST/DeclObjC.h"
20 #include "clang/AST/Expr.h"
21 #include "clang/AST/Type.h"
22 #include "clang/Basic/LLVM.h"
23 #include "clang/StaticAnalyzer/Core/PathSensitive/BasicValueFactory.h"
24 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
25 #include "clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h"
26 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
27 #include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h"
28 #include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h"
29 #include "clang/StaticAnalyzer/Core/PathSensitive/StoreRef.h"
30 #include "clang/StaticAnalyzer/Core/PathSensitive/SymExpr.h"
31 #include "llvm/ADT/APSInt.h"
32 #include "llvm/ADT/Optional.h"
33 #include "llvm/ADT/SmallVector.h"
34 #include "llvm/Support/Casting.h"
35 #include "llvm/Support/ErrorHandling.h"
36 #include <cassert>
37 #include <cstdint>
38
39 using namespace clang;
40 using namespace ento;
41
StoreManager(ProgramStateManager & stateMgr)42 StoreManager::StoreManager(ProgramStateManager &stateMgr)
43 : svalBuilder(stateMgr.getSValBuilder()), StateMgr(stateMgr),
44 MRMgr(svalBuilder.getRegionManager()), Ctx(stateMgr.getContext()) {}
45
enterStackFrame(Store OldStore,const CallEvent & Call,const StackFrameContext * LCtx)46 StoreRef StoreManager::enterStackFrame(Store OldStore,
47 const CallEvent &Call,
48 const StackFrameContext *LCtx) {
49 StoreRef Store = StoreRef(OldStore, *this);
50
51 SmallVector<CallEvent::FrameBindingTy, 16> InitialBindings;
52 Call.getInitialStackFrameContents(LCtx, InitialBindings);
53
54 for (const auto &I : InitialBindings)
55 Store = Bind(Store.getStore(), I.first.castAs<Loc>(), I.second);
56
57 return Store;
58 }
59
MakeElementRegion(const SubRegion * Base,QualType EleTy,uint64_t index)60 const ElementRegion *StoreManager::MakeElementRegion(const SubRegion *Base,
61 QualType EleTy,
62 uint64_t index) {
63 NonLoc idx = svalBuilder.makeArrayIndex(index);
64 return MRMgr.getElementRegion(EleTy, idx, Base, svalBuilder.getContext());
65 }
66
GetElementZeroRegion(const SubRegion * R,QualType T)67 const ElementRegion *StoreManager::GetElementZeroRegion(const SubRegion *R,
68 QualType T) {
69 NonLoc idx = svalBuilder.makeZeroArrayIndex();
70 assert(!T.isNull());
71 return MRMgr.getElementRegion(T, idx, R, Ctx);
72 }
73
castRegion(const MemRegion * R,QualType CastToTy)74 Optional<const MemRegion *> StoreManager::castRegion(const MemRegion *R,
75 QualType CastToTy) {
76 ASTContext &Ctx = StateMgr.getContext();
77
78 // Handle casts to Objective-C objects.
79 if (CastToTy->isObjCObjectPointerType())
80 return R->StripCasts();
81
82 if (CastToTy->isBlockPointerType()) {
83 // FIXME: We may need different solutions, depending on the symbol
84 // involved. Blocks can be casted to/from 'id', as they can be treated
85 // as Objective-C objects. This could possibly be handled by enhancing
86 // our reasoning of downcasts of symbolic objects.
87 if (isa<CodeTextRegion>(R) || isa<SymbolicRegion>(R))
88 return R;
89
90 // We don't know what to make of it. Return a NULL region, which
91 // will be interpreted as UnknownVal.
92 return None;
93 }
94
95 // Now assume we are casting from pointer to pointer. Other cases should
96 // already be handled.
97 QualType PointeeTy = CastToTy->getPointeeType();
98 QualType CanonPointeeTy = Ctx.getCanonicalType(PointeeTy);
99
100 // Handle casts to void*. We just pass the region through.
101 if (CanonPointeeTy.getLocalUnqualifiedType() == Ctx.VoidTy)
102 return R;
103
104 // Handle casts from compatible types.
105 if (R->isBoundable())
106 if (const auto *TR = dyn_cast<TypedValueRegion>(R)) {
107 QualType ObjTy = Ctx.getCanonicalType(TR->getValueType());
108 if (CanonPointeeTy == ObjTy)
109 return R;
110 }
111
112 // Process region cast according to the kind of the region being cast.
113 switch (R->getKind()) {
114 case MemRegion::CXXThisRegionKind:
115 case MemRegion::CodeSpaceRegionKind:
116 case MemRegion::StackLocalsSpaceRegionKind:
117 case MemRegion::StackArgumentsSpaceRegionKind:
118 case MemRegion::HeapSpaceRegionKind:
119 case MemRegion::UnknownSpaceRegionKind:
120 case MemRegion::StaticGlobalSpaceRegionKind:
121 case MemRegion::GlobalInternalSpaceRegionKind:
122 case MemRegion::GlobalSystemSpaceRegionKind:
123 case MemRegion::GlobalImmutableSpaceRegionKind: {
124 llvm_unreachable("Invalid region cast");
125 }
126
127 case MemRegion::FunctionCodeRegionKind:
128 case MemRegion::BlockCodeRegionKind:
129 case MemRegion::BlockDataRegionKind:
130 case MemRegion::StringRegionKind:
131 // FIXME: Need to handle arbitrary downcasts.
132 case MemRegion::SymbolicRegionKind:
133 case MemRegion::AllocaRegionKind:
134 case MemRegion::CompoundLiteralRegionKind:
135 case MemRegion::FieldRegionKind:
136 case MemRegion::ObjCIvarRegionKind:
137 case MemRegion::ObjCStringRegionKind:
138 case MemRegion::NonParamVarRegionKind:
139 case MemRegion::ParamVarRegionKind:
140 case MemRegion::CXXTempObjectRegionKind:
141 case MemRegion::CXXBaseObjectRegionKind:
142 case MemRegion::CXXDerivedObjectRegionKind:
143 return MakeElementRegion(cast<SubRegion>(R), PointeeTy);
144
145 case MemRegion::ElementRegionKind: {
146 // If we are casting from an ElementRegion to another type, the
147 // algorithm is as follows:
148 //
149 // (1) Compute the "raw offset" of the ElementRegion from the
150 // base region. This is done by calling 'getAsRawOffset()'.
151 //
152 // (2a) If we get a 'RegionRawOffset' after calling
153 // 'getAsRawOffset()', determine if the absolute offset
154 // can be exactly divided into chunks of the size of the
155 // casted-pointee type. If so, create a new ElementRegion with
156 // the pointee-cast type as the new ElementType and the index
157 // being the offset divded by the chunk size. If not, create
158 // a new ElementRegion at offset 0 off the raw offset region.
159 //
160 // (2b) If we don't a get a 'RegionRawOffset' after calling
161 // 'getAsRawOffset()', it means that we are at offset 0.
162 //
163 // FIXME: Handle symbolic raw offsets.
164
165 const ElementRegion *elementR = cast<ElementRegion>(R);
166 const RegionRawOffset &rawOff = elementR->getAsArrayOffset();
167 const MemRegion *baseR = rawOff.getRegion();
168
169 // If we cannot compute a raw offset, throw up our hands and return
170 // a NULL MemRegion*.
171 if (!baseR)
172 return None;
173
174 CharUnits off = rawOff.getOffset();
175
176 if (off.isZero()) {
177 // Edge case: we are at 0 bytes off the beginning of baseR. We
178 // check to see if type we are casting to is the same as the base
179 // region. If so, just return the base region.
180 if (const auto *TR = dyn_cast<TypedValueRegion>(baseR)) {
181 QualType ObjTy = Ctx.getCanonicalType(TR->getValueType());
182 QualType CanonPointeeTy = Ctx.getCanonicalType(PointeeTy);
183 if (CanonPointeeTy == ObjTy)
184 return baseR;
185 }
186
187 // Otherwise, create a new ElementRegion at offset 0.
188 return MakeElementRegion(cast<SubRegion>(baseR), PointeeTy);
189 }
190
191 // We have a non-zero offset from the base region. We want to determine
192 // if the offset can be evenly divided by sizeof(PointeeTy). If so,
193 // we create an ElementRegion whose index is that value. Otherwise, we
194 // create two ElementRegions, one that reflects a raw offset and the other
195 // that reflects the cast.
196
197 // Compute the index for the new ElementRegion.
198 int64_t newIndex = 0;
199 const MemRegion *newSuperR = nullptr;
200
201 // We can only compute sizeof(PointeeTy) if it is a complete type.
202 if (!PointeeTy->isIncompleteType()) {
203 // Compute the size in **bytes**.
204 CharUnits pointeeTySize = Ctx.getTypeSizeInChars(PointeeTy);
205 if (!pointeeTySize.isZero()) {
206 // Is the offset a multiple of the size? If so, we can layer the
207 // ElementRegion (with elementType == PointeeTy) directly on top of
208 // the base region.
209 if (off % pointeeTySize == 0) {
210 newIndex = off / pointeeTySize;
211 newSuperR = baseR;
212 }
213 }
214 }
215
216 if (!newSuperR) {
217 // Create an intermediate ElementRegion to represent the raw byte.
218 // This will be the super region of the final ElementRegion.
219 newSuperR = MakeElementRegion(cast<SubRegion>(baseR), Ctx.CharTy,
220 off.getQuantity());
221 }
222
223 return MakeElementRegion(cast<SubRegion>(newSuperR), PointeeTy, newIndex);
224 }
225 }
226
227 llvm_unreachable("unreachable");
228 }
229
regionMatchesCXXRecordType(SVal V,QualType Ty)230 static bool regionMatchesCXXRecordType(SVal V, QualType Ty) {
231 const MemRegion *MR = V.getAsRegion();
232 if (!MR)
233 return true;
234
235 const auto *TVR = dyn_cast<TypedValueRegion>(MR);
236 if (!TVR)
237 return true;
238
239 const CXXRecordDecl *RD = TVR->getValueType()->getAsCXXRecordDecl();
240 if (!RD)
241 return true;
242
243 const CXXRecordDecl *Expected = Ty->getPointeeCXXRecordDecl();
244 if (!Expected)
245 Expected = Ty->getAsCXXRecordDecl();
246
247 return Expected->getCanonicalDecl() == RD->getCanonicalDecl();
248 }
249
evalDerivedToBase(SVal Derived,const CastExpr * Cast)250 SVal StoreManager::evalDerivedToBase(SVal Derived, const CastExpr *Cast) {
251 // Sanity check to avoid doing the wrong thing in the face of
252 // reinterpret_cast.
253 if (!regionMatchesCXXRecordType(Derived, Cast->getSubExpr()->getType()))
254 return UnknownVal();
255
256 // Walk through the cast path to create nested CXXBaseRegions.
257 SVal Result = Derived;
258 for (CastExpr::path_const_iterator I = Cast->path_begin(),
259 E = Cast->path_end();
260 I != E; ++I) {
261 Result = evalDerivedToBase(Result, (*I)->getType(), (*I)->isVirtual());
262 }
263 return Result;
264 }
265
evalDerivedToBase(SVal Derived,const CXXBasePath & Path)266 SVal StoreManager::evalDerivedToBase(SVal Derived, const CXXBasePath &Path) {
267 // Walk through the path to create nested CXXBaseRegions.
268 SVal Result = Derived;
269 for (const auto &I : Path)
270 Result = evalDerivedToBase(Result, I.Base->getType(),
271 I.Base->isVirtual());
272 return Result;
273 }
274
evalDerivedToBase(SVal Derived,QualType BaseType,bool IsVirtual)275 SVal StoreManager::evalDerivedToBase(SVal Derived, QualType BaseType,
276 bool IsVirtual) {
277 const MemRegion *DerivedReg = Derived.getAsRegion();
278 if (!DerivedReg)
279 return Derived;
280
281 const CXXRecordDecl *BaseDecl = BaseType->getPointeeCXXRecordDecl();
282 if (!BaseDecl)
283 BaseDecl = BaseType->getAsCXXRecordDecl();
284 assert(BaseDecl && "not a C++ object?");
285
286 if (const auto *AlreadyDerivedReg =
287 dyn_cast<CXXDerivedObjectRegion>(DerivedReg)) {
288 if (const auto *SR =
289 dyn_cast<SymbolicRegion>(AlreadyDerivedReg->getSuperRegion()))
290 if (SR->getSymbol()->getType()->getPointeeCXXRecordDecl() == BaseDecl)
291 return loc::MemRegionVal(SR);
292
293 DerivedReg = AlreadyDerivedReg->getSuperRegion();
294 }
295
296 const MemRegion *BaseReg = MRMgr.getCXXBaseObjectRegion(
297 BaseDecl, cast<SubRegion>(DerivedReg), IsVirtual);
298
299 return loc::MemRegionVal(BaseReg);
300 }
301
302 /// Returns the static type of the given region, if it represents a C++ class
303 /// object.
304 ///
305 /// This handles both fully-typed regions, where the dynamic type is known, and
306 /// symbolic regions, where the dynamic type is merely bounded (and even then,
307 /// only ostensibly!), but does not take advantage of any dynamic type info.
getCXXRecordType(const MemRegion * MR)308 static const CXXRecordDecl *getCXXRecordType(const MemRegion *MR) {
309 if (const auto *TVR = dyn_cast<TypedValueRegion>(MR))
310 return TVR->getValueType()->getAsCXXRecordDecl();
311 if (const auto *SR = dyn_cast<SymbolicRegion>(MR))
312 return SR->getSymbol()->getType()->getPointeeCXXRecordDecl();
313 return nullptr;
314 }
315
attemptDownCast(SVal Base,QualType TargetType,bool & Failed)316 SVal StoreManager::attemptDownCast(SVal Base, QualType TargetType,
317 bool &Failed) {
318 Failed = false;
319
320 const MemRegion *MR = Base.getAsRegion();
321 if (!MR)
322 return UnknownVal();
323
324 // Assume the derived class is a pointer or a reference to a CXX record.
325 TargetType = TargetType->getPointeeType();
326 assert(!TargetType.isNull());
327 const CXXRecordDecl *TargetClass = TargetType->getAsCXXRecordDecl();
328 if (!TargetClass && !TargetType->isVoidType())
329 return UnknownVal();
330
331 // Drill down the CXXBaseObject chains, which represent upcasts (casts from
332 // derived to base).
333 while (const CXXRecordDecl *MRClass = getCXXRecordType(MR)) {
334 // If found the derived class, the cast succeeds.
335 if (MRClass == TargetClass)
336 return loc::MemRegionVal(MR);
337
338 // We skip over incomplete types. They must be the result of an earlier
339 // reinterpret_cast, as one can only dynamic_cast between types in the same
340 // class hierarchy.
341 if (!TargetType->isVoidType() && MRClass->hasDefinition()) {
342 // Static upcasts are marked as DerivedToBase casts by Sema, so this will
343 // only happen when multiple or virtual inheritance is involved.
344 CXXBasePaths Paths(/*FindAmbiguities=*/false, /*RecordPaths=*/true,
345 /*DetectVirtual=*/false);
346 if (MRClass->isDerivedFrom(TargetClass, Paths))
347 return evalDerivedToBase(loc::MemRegionVal(MR), Paths.front());
348 }
349
350 if (const auto *BaseR = dyn_cast<CXXBaseObjectRegion>(MR)) {
351 // Drill down the chain to get the derived classes.
352 MR = BaseR->getSuperRegion();
353 continue;
354 }
355
356 // If this is a cast to void*, return the region.
357 if (TargetType->isVoidType())
358 return loc::MemRegionVal(MR);
359
360 // Strange use of reinterpret_cast can give us paths we don't reason
361 // about well, by putting in ElementRegions where we'd expect
362 // CXXBaseObjectRegions. If it's a valid reinterpret_cast (i.e. if the
363 // derived class has a zero offset from the base class), then it's safe
364 // to strip the cast; if it's invalid, -Wreinterpret-base-class should
365 // catch it. In the interest of performance, the analyzer will silently
366 // do the wrong thing in the invalid case (because offsets for subregions
367 // will be wrong).
368 const MemRegion *Uncasted = MR->StripCasts(/*IncludeBaseCasts=*/false);
369 if (Uncasted == MR) {
370 // We reached the bottom of the hierarchy and did not find the derived
371 // class. We must be casting the base to derived, so the cast should
372 // fail.
373 break;
374 }
375
376 MR = Uncasted;
377 }
378
379 // If we're casting a symbolic base pointer to a derived class, use
380 // CXXDerivedObjectRegion to represent the cast. If it's a pointer to an
381 // unrelated type, it must be a weird reinterpret_cast and we have to
382 // be fine with ElementRegion. TODO: Should we instead make
383 // Derived{TargetClass, Element{SourceClass, SR}}?
384 if (const auto *SR = dyn_cast<SymbolicRegion>(MR)) {
385 QualType T = SR->getSymbol()->getType();
386 const CXXRecordDecl *SourceClass = T->getPointeeCXXRecordDecl();
387 if (TargetClass && SourceClass && TargetClass->isDerivedFrom(SourceClass))
388 return loc::MemRegionVal(
389 MRMgr.getCXXDerivedObjectRegion(TargetClass, SR));
390 return loc::MemRegionVal(GetElementZeroRegion(SR, TargetType));
391 }
392
393 // We failed if the region we ended up with has perfect type info.
394 Failed = isa<TypedValueRegion>(MR);
395 return UnknownVal();
396 }
397
getLValueFieldOrIvar(const Decl * D,SVal Base)398 SVal StoreManager::getLValueFieldOrIvar(const Decl *D, SVal Base) {
399 if (Base.isUnknownOrUndef())
400 return Base;
401
402 Loc BaseL = Base.castAs<Loc>();
403 const SubRegion* BaseR = nullptr;
404
405 switch (BaseL.getSubKind()) {
406 case loc::MemRegionValKind:
407 BaseR = cast<SubRegion>(BaseL.castAs<loc::MemRegionVal>().getRegion());
408 break;
409
410 case loc::GotoLabelKind:
411 // These are anormal cases. Flag an undefined value.
412 return UndefinedVal();
413
414 case loc::ConcreteIntKind:
415 // While these seem funny, this can happen through casts.
416 // FIXME: What we should return is the field offset, not base. For example,
417 // add the field offset to the integer value. That way things
418 // like this work properly: &(((struct foo *) 0xa)->f)
419 // However, that's not easy to fix without reducing our abilities
420 // to catch null pointer dereference. Eg., ((struct foo *)0x0)->f = 7
421 // is a null dereference even though we're dereferencing offset of f
422 // rather than null. Coming up with an approach that computes offsets
423 // over null pointers properly while still being able to catch null
424 // dereferences might be worth it.
425 return Base;
426
427 default:
428 llvm_unreachable("Unhandled Base.");
429 }
430
431 // NOTE: We must have this check first because ObjCIvarDecl is a subclass
432 // of FieldDecl.
433 if (const auto *ID = dyn_cast<ObjCIvarDecl>(D))
434 return loc::MemRegionVal(MRMgr.getObjCIvarRegion(ID, BaseR));
435
436 return loc::MemRegionVal(MRMgr.getFieldRegion(cast<FieldDecl>(D), BaseR));
437 }
438
getLValueIvar(const ObjCIvarDecl * decl,SVal base)439 SVal StoreManager::getLValueIvar(const ObjCIvarDecl *decl, SVal base) {
440 return getLValueFieldOrIvar(decl, base);
441 }
442
getLValueElement(QualType elementType,NonLoc Offset,SVal Base)443 SVal StoreManager::getLValueElement(QualType elementType, NonLoc Offset,
444 SVal Base) {
445 // If the base is an unknown or undefined value, just return it back.
446 // FIXME: For absolute pointer addresses, we just return that value back as
447 // well, although in reality we should return the offset added to that
448 // value. See also the similar FIXME in getLValueFieldOrIvar().
449 if (Base.isUnknownOrUndef() || Base.getAs<loc::ConcreteInt>())
450 return Base;
451
452 if (Base.getAs<loc::GotoLabel>())
453 return UnknownVal();
454
455 const SubRegion *BaseRegion =
456 Base.castAs<loc::MemRegionVal>().getRegionAs<SubRegion>();
457
458 // Pointer of any type can be cast and used as array base.
459 const auto *ElemR = dyn_cast<ElementRegion>(BaseRegion);
460
461 // Convert the offset to the appropriate size and signedness.
462 Offset = svalBuilder.convertToArrayIndex(Offset).castAs<NonLoc>();
463
464 if (!ElemR) {
465 // If the base region is not an ElementRegion, create one.
466 // This can happen in the following example:
467 //
468 // char *p = __builtin_alloc(10);
469 // p[1] = 8;
470 //
471 // Observe that 'p' binds to an AllocaRegion.
472 return loc::MemRegionVal(MRMgr.getElementRegion(elementType, Offset,
473 BaseRegion, Ctx));
474 }
475
476 SVal BaseIdx = ElemR->getIndex();
477
478 if (!BaseIdx.getAs<nonloc::ConcreteInt>())
479 return UnknownVal();
480
481 const llvm::APSInt &BaseIdxI =
482 BaseIdx.castAs<nonloc::ConcreteInt>().getValue();
483
484 // Only allow non-integer offsets if the base region has no offset itself.
485 // FIXME: This is a somewhat arbitrary restriction. We should be using
486 // SValBuilder here to add the two offsets without checking their types.
487 if (!Offset.getAs<nonloc::ConcreteInt>()) {
488 if (isa<ElementRegion>(BaseRegion->StripCasts()))
489 return UnknownVal();
490
491 return loc::MemRegionVal(MRMgr.getElementRegion(
492 elementType, Offset, cast<SubRegion>(ElemR->getSuperRegion()), Ctx));
493 }
494
495 const llvm::APSInt& OffI = Offset.castAs<nonloc::ConcreteInt>().getValue();
496 assert(BaseIdxI.isSigned());
497
498 // Compute the new index.
499 nonloc::ConcreteInt NewIdx(svalBuilder.getBasicValueFactory().getValue(BaseIdxI +
500 OffI));
501
502 // Construct the new ElementRegion.
503 const SubRegion *ArrayR = cast<SubRegion>(ElemR->getSuperRegion());
504 return loc::MemRegionVal(MRMgr.getElementRegion(elementType, NewIdx, ArrayR,
505 Ctx));
506 }
507
508 StoreManager::BindingsHandler::~BindingsHandler() = default;
509
HandleBinding(StoreManager & SMgr,Store store,const MemRegion * R,SVal val)510 bool StoreManager::FindUniqueBinding::HandleBinding(StoreManager& SMgr,
511 Store store,
512 const MemRegion* R,
513 SVal val) {
514 SymbolRef SymV = val.getAsLocSymbol();
515 if (!SymV || SymV != Sym)
516 return true;
517
518 if (Binding) {
519 First = false;
520 return false;
521 }
522 else
523 Binding = R;
524
525 return true;
526 }
527