From 222e2a7620e6520ffaf4fc4e69d79c18da31542e Mon Sep 17 00:00:00 2001 From: "Zancanaro; Carlo" Date: Mon, 24 Sep 2012 09:58:17 +1000 Subject: Add the clang library to the repo (with some of my changes, too). --- .../lib/StaticAnalyzer/Checkers/VLASizeChecker.cpp | 162 +++++++++++++++++++++ 1 file changed, 162 insertions(+) create mode 100644 clang/lib/StaticAnalyzer/Checkers/VLASizeChecker.cpp (limited to 'clang/lib/StaticAnalyzer/Checkers/VLASizeChecker.cpp') diff --git a/clang/lib/StaticAnalyzer/Checkers/VLASizeChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/VLASizeChecker.cpp new file mode 100644 index 0000000..38c9cc1 --- /dev/null +++ b/clang/lib/StaticAnalyzer/Checkers/VLASizeChecker.cpp @@ -0,0 +1,162 @@ +//=== VLASizeChecker.cpp - Undefined dereference checker --------*- C++ -*-===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This defines VLASizeChecker, a builtin check in ExprEngine that +// performs checks for declaration of VLA of undefined or zero size. +// In addition, VLASizeChecker is responsible for defining the extent +// of the MemRegion that represents a VLA. +// +//===----------------------------------------------------------------------===// + +#include "ClangSACheckers.h" +#include "clang/StaticAnalyzer/Core/Checker.h" +#include "clang/StaticAnalyzer/Core/CheckerManager.h" +#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" +#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" +#include "clang/AST/CharUnits.h" +#include "llvm/ADT/SmallString.h" +#include "llvm/ADT/STLExtras.h" + +using namespace clang; +using namespace ento; + +namespace { +class VLASizeChecker : public Checker< check::PreStmt > { + mutable OwningPtr BT; + enum VLASize_Kind { VLA_Garbage, VLA_Zero, VLA_Tainted }; + + void reportBug(VLASize_Kind Kind, + const Expr *SizeE, + ProgramStateRef State, + CheckerContext &C) const; +public: + void checkPreStmt(const DeclStmt *DS, CheckerContext &C) const; +}; +} // end anonymous namespace + +void VLASizeChecker::reportBug(VLASize_Kind Kind, + const Expr *SizeE, + ProgramStateRef State, + CheckerContext &C) const { + // Generate an error node. + ExplodedNode *N = C.generateSink(State); + if (!N) + return; + + if (!BT) + BT.reset(new BuiltinBug("Dangerous variable-length array (VLA) declaration")); + + SmallString<256> buf; + llvm::raw_svector_ostream os(buf); + os << "Declared variable-length array (VLA) "; + switch (Kind) { + case VLA_Garbage: + os << "uses a garbage value as its size"; + break; + case VLA_Zero: + os << "has zero size"; + break; + case VLA_Tainted: + os << "has tainted size"; + break; + } + + BugReport *report = new BugReport(*BT, os.str(), N); + report->addRange(SizeE->getSourceRange()); + report->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, SizeE, + report)); + C.EmitReport(report); + return; +} + +void VLASizeChecker::checkPreStmt(const DeclStmt *DS, CheckerContext &C) const { + if (!DS->isSingleDecl()) + return; + + const VarDecl *VD = dyn_cast(DS->getSingleDecl()); + if (!VD) + return; + + ASTContext &Ctx = C.getASTContext(); + const VariableArrayType *VLA = Ctx.getAsVariableArrayType(VD->getType()); + if (!VLA) + return; + + // FIXME: Handle multi-dimensional VLAs. + const Expr *SE = VLA->getSizeExpr(); + ProgramStateRef state = C.getState(); + SVal sizeV = state->getSVal(SE, C.getLocationContext()); + + if (sizeV.isUndef()) { + reportBug(VLA_Garbage, SE, state, C); + return; + } + + // See if the size value is known. It can't be undefined because we would have + // warned about that already. + if (sizeV.isUnknown()) + return; + + // Check if the size is tainted. + if (state->isTainted(sizeV)) { + reportBug(VLA_Tainted, SE, 0, C); + return; + } + + // Check if the size is zero. + DefinedSVal sizeD = cast(sizeV); + + ProgramStateRef stateNotZero, stateZero; + llvm::tie(stateNotZero, stateZero) = state->assume(sizeD); + + if (stateZero && !stateNotZero) { + reportBug(VLA_Zero, SE, stateZero, C); + return; + } + + // From this point on, assume that the size is not zero. + state = stateNotZero; + + // VLASizeChecker is responsible for defining the extent of the array being + // declared. We do this by multiplying the array length by the element size, + // then matching that with the array region's extent symbol. + + // Convert the array length to size_t. + SValBuilder &svalBuilder = C.getSValBuilder(); + QualType SizeTy = Ctx.getSizeType(); + NonLoc ArrayLength = cast(svalBuilder.evalCast(sizeD, SizeTy, + SE->getType())); + + // Get the element size. + CharUnits EleSize = Ctx.getTypeSizeInChars(VLA->getElementType()); + SVal EleSizeVal = svalBuilder.makeIntVal(EleSize.getQuantity(), SizeTy); + + // Multiply the array length by the element size. + SVal ArraySizeVal = svalBuilder.evalBinOpNN(state, BO_Mul, ArrayLength, + cast(EleSizeVal), SizeTy); + + // Finally, assume that the array's extent matches the given size. + const LocationContext *LC = C.getLocationContext(); + DefinedOrUnknownSVal Extent = + state->getRegion(VD, LC)->getExtent(svalBuilder); + DefinedOrUnknownSVal ArraySize = cast(ArraySizeVal); + DefinedOrUnknownSVal sizeIsKnown = + svalBuilder.evalEQ(state, Extent, ArraySize); + state = state->assume(sizeIsKnown, true); + + // Assume should not fail at this point. + assert(state); + + // Remember our assumptions! + C.addTransition(state); +} + +void ento::registerVLASizeChecker(CheckerManager &mgr) { + mgr.registerChecker(); +} -- cgit v1.2.3