forked from OSchip/llvm-project
136 lines
4.6 KiB
C++
136 lines
4.6 KiB
C++
//=== VLASizeChecker.cpp - Undefined dereference checker --------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This defines VLASizeChecker, a builtin check in GRExprEngine that
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// performs checks for declaration of VLA of undefined or zero size.
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// In addition, VLASizeChecker is responsible for defining the extent
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// of the MemRegion that represents a VLA.
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//
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//===----------------------------------------------------------------------===//
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#include "GRExprEngineInternalChecks.h"
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#include "clang/AST/CharUnits.h"
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#include "clang/Checker/BugReporter/BugType.h"
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#include "clang/Checker/PathSensitive/CheckerVisitor.h"
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#include "clang/Checker/PathSensitive/GRExprEngine.h"
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using namespace clang;
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namespace {
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class VLASizeChecker : public CheckerVisitor<VLASizeChecker> {
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BugType *BT_zero;
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BugType *BT_undef;
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public:
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VLASizeChecker() : BT_zero(0), BT_undef(0) {}
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static void *getTag() { static int tag = 0; return &tag; }
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void PreVisitDeclStmt(CheckerContext &C, const DeclStmt *DS);
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};
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} // end anonymous namespace
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void clang::RegisterVLASizeChecker(GRExprEngine &Eng) {
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Eng.registerCheck(new VLASizeChecker());
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}
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void VLASizeChecker::PreVisitDeclStmt(CheckerContext &C, const DeclStmt *DS) {
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if (!DS->isSingleDecl())
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return;
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const VarDecl *VD = dyn_cast<VarDecl>(DS->getSingleDecl());
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if (!VD)
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return;
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ASTContext &Ctx = C.getASTContext();
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const VariableArrayType *VLA = Ctx.getAsVariableArrayType(VD->getType());
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if (!VLA)
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return;
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// FIXME: Handle multi-dimensional VLAs.
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const Expr* SE = VLA->getSizeExpr();
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const GRState *state = C.getState();
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SVal sizeV = state->getSVal(SE);
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if (sizeV.isUndef()) {
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// Generate an error node.
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ExplodedNode *N = C.GenerateSink();
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if (!N)
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return;
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if (!BT_undef)
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BT_undef = new BuiltinBug("Declared variable-length array (VLA) uses a "
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"garbage value as its size");
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EnhancedBugReport *report =
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new EnhancedBugReport(*BT_undef, BT_undef->getName(), N);
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report->addRange(SE->getSourceRange());
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report->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue, SE);
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C.EmitReport(report);
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return;
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}
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// See if the size value is known. It can't be undefined because we would have
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// warned about that already.
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if (sizeV.isUnknown())
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return;
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// Check if the size is zero.
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DefinedSVal sizeD = cast<DefinedSVal>(sizeV);
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const GRState *stateNotZero, *stateZero;
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llvm::tie(stateNotZero, stateZero) = state->Assume(sizeD);
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if (stateZero && !stateNotZero) {
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ExplodedNode* N = C.GenerateSink(stateZero);
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if (!BT_zero)
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BT_zero = new BuiltinBug("Declared variable-length array (VLA) has zero "
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"size");
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EnhancedBugReport *report =
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new EnhancedBugReport(*BT_zero, BT_zero->getName(), N);
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report->addRange(SE->getSourceRange());
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report->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue, SE);
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C.EmitReport(report);
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return;
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}
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// From this point on, assume that the size is not zero.
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state = stateNotZero;
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// VLASizeChecker is responsible for defining the extent of the array being
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// declared. We do this by multiplying the array length by the element size,
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// then matching that with the array region's extent symbol.
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// Convert the array length to size_t.
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ValueManager &ValMgr = C.getValueManager();
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SValuator &SV = ValMgr.getSValuator();
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QualType SizeTy = Ctx.getSizeType();
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NonLoc ArrayLength = cast<NonLoc>(SV.EvalCast(sizeD, SizeTy, SE->getType()));
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// Get the element size.
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CharUnits EleSize = Ctx.getTypeSizeInChars(VLA->getElementType());
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SVal EleSizeVal = ValMgr.makeIntVal(EleSize.getQuantity(), SizeTy);
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// Multiply the array length by the element size.
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SVal ArraySizeVal = SV.EvalBinOpNN(state, BO_Mul, ArrayLength,
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cast<NonLoc>(EleSizeVal), SizeTy);
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// Finally, Assume that the array's extent matches the given size.
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const LocationContext *LC = C.getPredecessor()->getLocationContext();
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DefinedOrUnknownSVal Extent = state->getRegion(VD, LC)->getExtent(ValMgr);
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DefinedOrUnknownSVal ArraySize = cast<DefinedOrUnknownSVal>(ArraySizeVal);
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DefinedOrUnknownSVal SizeIsKnown = SV.EvalEQ(state, Extent, ArraySize);
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state = state->Assume(SizeIsKnown, true);
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// Assume should not fail at this point.
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assert(state);
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// Remember our assumptions!
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C.addTransition(state);
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}
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