534 lines
19 KiB
C++
534 lines
19 KiB
C++
// SValBuilder.cpp - Basic class for all SValBuilder implementations -*- 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 file defines SValBuilder, the base class for all (complete) SValBuilder
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// implementations.
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//
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//===----------------------------------------------------------------------===//
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#include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h"
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#include "clang/AST/DeclCXX.h"
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#include "clang/AST/ExprCXX.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/BasicValueFactory.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
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#include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h"
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using namespace clang;
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using namespace ento;
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//===----------------------------------------------------------------------===//
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// Basic SVal creation.
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//===----------------------------------------------------------------------===//
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void SValBuilder::anchor() { }
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DefinedOrUnknownSVal SValBuilder::makeZeroVal(QualType type) {
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if (Loc::isLocType(type))
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return makeNull();
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if (type->isIntegralOrEnumerationType())
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return makeIntVal(0, type);
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// FIXME: Handle floats.
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// FIXME: Handle structs.
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return UnknownVal();
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}
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NonLoc SValBuilder::makeNonLoc(const SymExpr *lhs, BinaryOperator::Opcode op,
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const llvm::APSInt& rhs, QualType type) {
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// The Environment ensures we always get a persistent APSInt in
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// BasicValueFactory, so we don't need to get the APSInt from
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// BasicValueFactory again.
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assert(lhs);
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assert(!Loc::isLocType(type));
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return nonloc::SymbolVal(SymMgr.getSymIntExpr(lhs, op, rhs, type));
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}
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NonLoc SValBuilder::makeNonLoc(const llvm::APSInt& lhs,
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BinaryOperator::Opcode op, const SymExpr *rhs,
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QualType type) {
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assert(rhs);
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assert(!Loc::isLocType(type));
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return nonloc::SymbolVal(SymMgr.getIntSymExpr(lhs, op, rhs, type));
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}
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NonLoc SValBuilder::makeNonLoc(const SymExpr *lhs, BinaryOperator::Opcode op,
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const SymExpr *rhs, QualType type) {
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assert(lhs && rhs);
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assert(!Loc::isLocType(type));
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return nonloc::SymbolVal(SymMgr.getSymSymExpr(lhs, op, rhs, type));
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}
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NonLoc SValBuilder::makeNonLoc(const SymExpr *operand,
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QualType fromTy, QualType toTy) {
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assert(operand);
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assert(!Loc::isLocType(toTy));
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return nonloc::SymbolVal(SymMgr.getCastSymbol(operand, fromTy, toTy));
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}
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SVal SValBuilder::convertToArrayIndex(SVal val) {
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if (val.isUnknownOrUndef())
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return val;
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// Common case: we have an appropriately sized integer.
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if (Optional<nonloc::ConcreteInt> CI = val.getAs<nonloc::ConcreteInt>()) {
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const llvm::APSInt& I = CI->getValue();
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if (I.getBitWidth() == ArrayIndexWidth && I.isSigned())
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return val;
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}
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return evalCastFromNonLoc(val.castAs<NonLoc>(), ArrayIndexTy);
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}
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nonloc::ConcreteInt SValBuilder::makeBoolVal(const CXXBoolLiteralExpr *boolean){
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return makeTruthVal(boolean->getValue());
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}
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DefinedOrUnknownSVal
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SValBuilder::getRegionValueSymbolVal(const TypedValueRegion* region) {
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QualType T = region->getValueType();
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if (!SymbolManager::canSymbolicate(T))
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return UnknownVal();
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SymbolRef sym = SymMgr.getRegionValueSymbol(region);
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if (Loc::isLocType(T))
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return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
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return nonloc::SymbolVal(sym);
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}
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DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const void *SymbolTag,
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const Expr *Ex,
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const LocationContext *LCtx,
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unsigned Count) {
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QualType T = Ex->getType();
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// Compute the type of the result. If the expression is not an R-value, the
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// result should be a location.
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QualType ExType = Ex->getType();
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if (Ex->isGLValue())
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T = LCtx->getAnalysisDeclContext()->getASTContext().getPointerType(ExType);
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return conjureSymbolVal(SymbolTag, Ex, LCtx, T, Count);
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}
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DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const void *symbolTag,
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const Expr *expr,
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const LocationContext *LCtx,
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QualType type,
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unsigned count) {
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if (!SymbolManager::canSymbolicate(type))
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return UnknownVal();
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SymbolRef sym = SymMgr.conjureSymbol(expr, LCtx, type, count, symbolTag);
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if (Loc::isLocType(type))
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return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
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return nonloc::SymbolVal(sym);
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}
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DefinedOrUnknownSVal SValBuilder::conjureSymbolVal(const Stmt *stmt,
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const LocationContext *LCtx,
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QualType type,
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unsigned visitCount) {
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if (!SymbolManager::canSymbolicate(type))
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return UnknownVal();
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SymbolRef sym = SymMgr.conjureSymbol(stmt, LCtx, type, visitCount);
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if (Loc::isLocType(type))
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return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
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return nonloc::SymbolVal(sym);
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}
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DefinedOrUnknownSVal
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SValBuilder::getConjuredHeapSymbolVal(const Expr *E,
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const LocationContext *LCtx,
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unsigned VisitCount) {
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QualType T = E->getType();
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assert(Loc::isLocType(T));
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assert(SymbolManager::canSymbolicate(T));
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SymbolRef sym = SymMgr.conjureSymbol(E, LCtx, T, VisitCount);
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return loc::MemRegionVal(MemMgr.getSymbolicHeapRegion(sym));
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}
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DefinedSVal SValBuilder::getMetadataSymbolVal(const void *symbolTag,
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const MemRegion *region,
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const Expr *expr, QualType type,
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unsigned count) {
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assert(SymbolManager::canSymbolicate(type) && "Invalid metadata symbol type");
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SymbolRef sym =
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SymMgr.getMetadataSymbol(region, expr, type, count, symbolTag);
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if (Loc::isLocType(type))
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return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
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return nonloc::SymbolVal(sym);
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}
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DefinedOrUnknownSVal
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SValBuilder::getDerivedRegionValueSymbolVal(SymbolRef parentSymbol,
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const TypedValueRegion *region) {
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QualType T = region->getValueType();
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if (!SymbolManager::canSymbolicate(T))
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return UnknownVal();
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SymbolRef sym = SymMgr.getDerivedSymbol(parentSymbol, region);
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if (Loc::isLocType(T))
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return loc::MemRegionVal(MemMgr.getSymbolicRegion(sym));
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return nonloc::SymbolVal(sym);
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}
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DefinedSVal SValBuilder::getFunctionPointer(const FunctionDecl *func) {
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return loc::MemRegionVal(MemMgr.getFunctionTextRegion(func));
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}
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DefinedSVal SValBuilder::getBlockPointer(const BlockDecl *block,
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CanQualType locTy,
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const LocationContext *locContext,
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unsigned blockCount) {
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const BlockTextRegion *BC =
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MemMgr.getBlockTextRegion(block, locTy, locContext->getAnalysisDeclContext());
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const BlockDataRegion *BD = MemMgr.getBlockDataRegion(BC, locContext,
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blockCount);
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return loc::MemRegionVal(BD);
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}
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/// Return a memory region for the 'this' object reference.
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loc::MemRegionVal SValBuilder::getCXXThis(const CXXMethodDecl *D,
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const StackFrameContext *SFC) {
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return loc::MemRegionVal(getRegionManager().
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getCXXThisRegion(D->getThisType(getContext()), SFC));
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}
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/// Return a memory region for the 'this' object reference.
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loc::MemRegionVal SValBuilder::getCXXThis(const CXXRecordDecl *D,
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const StackFrameContext *SFC) {
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const Type *T = D->getTypeForDecl();
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QualType PT = getContext().getPointerType(QualType(T, 0));
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return loc::MemRegionVal(getRegionManager().getCXXThisRegion(PT, SFC));
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}
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Optional<SVal> SValBuilder::getConstantVal(const Expr *E) {
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E = E->IgnoreParens();
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switch (E->getStmtClass()) {
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// Handle expressions that we treat differently from the AST's constant
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// evaluator.
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case Stmt::AddrLabelExprClass:
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return makeLoc(cast<AddrLabelExpr>(E));
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case Stmt::CXXScalarValueInitExprClass:
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case Stmt::ImplicitValueInitExprClass:
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return makeZeroVal(E->getType());
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case Stmt::ObjCStringLiteralClass: {
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const ObjCStringLiteral *SL = cast<ObjCStringLiteral>(E);
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return makeLoc(getRegionManager().getObjCStringRegion(SL));
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}
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case Stmt::StringLiteralClass: {
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const StringLiteral *SL = cast<StringLiteral>(E);
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return makeLoc(getRegionManager().getStringRegion(SL));
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}
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// Fast-path some expressions to avoid the overhead of going through the AST's
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// constant evaluator
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case Stmt::CharacterLiteralClass: {
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const CharacterLiteral *C = cast<CharacterLiteral>(E);
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return makeIntVal(C->getValue(), C->getType());
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}
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case Stmt::CXXBoolLiteralExprClass:
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return makeBoolVal(cast<CXXBoolLiteralExpr>(E));
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case Stmt::TypeTraitExprClass: {
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const TypeTraitExpr *TE = cast<TypeTraitExpr>(E);
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return makeTruthVal(TE->getValue(), TE->getType());
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}
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case Stmt::IntegerLiteralClass:
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return makeIntVal(cast<IntegerLiteral>(E));
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case Stmt::ObjCBoolLiteralExprClass:
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return makeBoolVal(cast<ObjCBoolLiteralExpr>(E));
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case Stmt::CXXNullPtrLiteralExprClass:
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return makeNull();
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case Stmt::ImplicitCastExprClass: {
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const CastExpr *CE = cast<CastExpr>(E);
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if (CE->getCastKind() == CK_ArrayToPointerDecay) {
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Optional<SVal> ArrayVal = getConstantVal(CE->getSubExpr());
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if (!ArrayVal)
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return None;
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return evalCast(*ArrayVal, CE->getType(), CE->getSubExpr()->getType());
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}
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// FALLTHROUGH
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}
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// If we don't have a special case, fall back to the AST's constant evaluator.
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default: {
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// Don't try to come up with a value for materialized temporaries.
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if (E->isGLValue())
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return None;
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ASTContext &Ctx = getContext();
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llvm::APSInt Result;
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if (E->EvaluateAsInt(Result, Ctx))
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return makeIntVal(Result);
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if (Loc::isLocType(E->getType()))
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if (E->isNullPointerConstant(Ctx, Expr::NPC_ValueDependentIsNotNull))
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return makeNull();
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return None;
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}
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}
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}
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//===----------------------------------------------------------------------===//
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SVal SValBuilder::makeSymExprValNN(ProgramStateRef State,
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BinaryOperator::Opcode Op,
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NonLoc LHS, NonLoc RHS,
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QualType ResultTy) {
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if (!State->isTainted(RHS) && !State->isTainted(LHS))
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return UnknownVal();
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const SymExpr *symLHS = LHS.getAsSymExpr();
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const SymExpr *symRHS = RHS.getAsSymExpr();
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// TODO: When the Max Complexity is reached, we should conjure a symbol
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// instead of generating an Unknown value and propagate the taint info to it.
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const unsigned MaxComp = 10000; // 100000 28X
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if (symLHS && symRHS &&
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(symLHS->computeComplexity() + symRHS->computeComplexity()) < MaxComp)
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return makeNonLoc(symLHS, Op, symRHS, ResultTy);
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if (symLHS && symLHS->computeComplexity() < MaxComp)
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if (Optional<nonloc::ConcreteInt> rInt = RHS.getAs<nonloc::ConcreteInt>())
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return makeNonLoc(symLHS, Op, rInt->getValue(), ResultTy);
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if (symRHS && symRHS->computeComplexity() < MaxComp)
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if (Optional<nonloc::ConcreteInt> lInt = LHS.getAs<nonloc::ConcreteInt>())
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return makeNonLoc(lInt->getValue(), Op, symRHS, ResultTy);
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return UnknownVal();
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}
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SVal SValBuilder::evalBinOp(ProgramStateRef state, BinaryOperator::Opcode op,
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SVal lhs, SVal rhs, QualType type) {
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if (lhs.isUndef() || rhs.isUndef())
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return UndefinedVal();
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if (lhs.isUnknown() || rhs.isUnknown())
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return UnknownVal();
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if (Optional<Loc> LV = lhs.getAs<Loc>()) {
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if (Optional<Loc> RV = rhs.getAs<Loc>())
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return evalBinOpLL(state, op, *LV, *RV, type);
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return evalBinOpLN(state, op, *LV, rhs.castAs<NonLoc>(), type);
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}
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if (Optional<Loc> RV = rhs.getAs<Loc>()) {
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// Support pointer arithmetic where the addend is on the left
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// and the pointer on the right.
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assert(op == BO_Add);
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// Commute the operands.
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return evalBinOpLN(state, op, *RV, lhs.castAs<NonLoc>(), type);
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}
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return evalBinOpNN(state, op, lhs.castAs<NonLoc>(), rhs.castAs<NonLoc>(),
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type);
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}
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DefinedOrUnknownSVal SValBuilder::evalEQ(ProgramStateRef state,
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DefinedOrUnknownSVal lhs,
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DefinedOrUnknownSVal rhs) {
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return evalBinOp(state, BO_EQ, lhs, rhs, getConditionType())
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.castAs<DefinedOrUnknownSVal>();
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}
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/// Recursively check if the pointer types are equal modulo const, volatile,
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/// and restrict qualifiers. Also, assume that all types are similar to 'void'.
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/// Assumes the input types are canonical.
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static bool shouldBeModeledWithNoOp(ASTContext &Context, QualType ToTy,
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QualType FromTy) {
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while (Context.UnwrapSimilarPointerTypes(ToTy, FromTy)) {
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Qualifiers Quals1, Quals2;
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ToTy = Context.getUnqualifiedArrayType(ToTy, Quals1);
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FromTy = Context.getUnqualifiedArrayType(FromTy, Quals2);
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// Make sure that non-cvr-qualifiers the other qualifiers (e.g., address
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// spaces) are identical.
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Quals1.removeCVRQualifiers();
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Quals2.removeCVRQualifiers();
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if (Quals1 != Quals2)
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return false;
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}
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// If we are casting to void, the 'From' value can be used to represent the
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// 'To' value.
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if (ToTy->isVoidType())
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return true;
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if (ToTy != FromTy)
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return false;
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return true;
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}
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// FIXME: should rewrite according to the cast kind.
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SVal SValBuilder::evalCast(SVal val, QualType castTy, QualType originalTy) {
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castTy = Context.getCanonicalType(castTy);
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originalTy = Context.getCanonicalType(originalTy);
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if (val.isUnknownOrUndef() || castTy == originalTy)
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return val;
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if (castTy->isBooleanType()) {
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if (val.isUnknownOrUndef())
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return val;
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if (val.isConstant())
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return makeTruthVal(!val.isZeroConstant(), castTy);
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if (!Loc::isLocType(originalTy) &&
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!originalTy->isIntegralOrEnumerationType() &&
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!originalTy->isMemberPointerType())
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return UnknownVal();
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if (SymbolRef Sym = val.getAsSymbol(true)) {
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BasicValueFactory &BVF = getBasicValueFactory();
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// FIXME: If we had a state here, we could see if the symbol is known to
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// be zero, but we don't.
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return makeNonLoc(Sym, BO_NE, BVF.getValue(0, Sym->getType()), castTy);
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}
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// Loc values are not always true, they could be weakly linked functions.
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if (Optional<Loc> L = val.getAs<Loc>())
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return evalCastFromLoc(*L, castTy);
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Loc L = val.castAs<nonloc::LocAsInteger>().getLoc();
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return evalCastFromLoc(L, castTy);
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}
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// For const casts, casts to void, just propagate the value.
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if (!castTy->isVariableArrayType() && !originalTy->isVariableArrayType())
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if (shouldBeModeledWithNoOp(Context, Context.getPointerType(castTy),
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Context.getPointerType(originalTy)))
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return val;
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// Check for casts from pointers to integers.
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if (castTy->isIntegralOrEnumerationType() && Loc::isLocType(originalTy))
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return evalCastFromLoc(val.castAs<Loc>(), castTy);
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// Check for casts from integers to pointers.
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if (Loc::isLocType(castTy) && originalTy->isIntegralOrEnumerationType()) {
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if (Optional<nonloc::LocAsInteger> LV = val.getAs<nonloc::LocAsInteger>()) {
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if (const MemRegion *R = LV->getLoc().getAsRegion()) {
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StoreManager &storeMgr = StateMgr.getStoreManager();
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R = storeMgr.castRegion(R, castTy);
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return R ? SVal(loc::MemRegionVal(R)) : UnknownVal();
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}
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return LV->getLoc();
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}
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return dispatchCast(val, castTy);
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}
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// Just pass through function and block pointers.
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if (originalTy->isBlockPointerType() || originalTy->isFunctionPointerType()) {
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assert(Loc::isLocType(castTy));
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return val;
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}
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// Check for casts from array type to another type.
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if (const ArrayType *arrayT =
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dyn_cast<ArrayType>(originalTy.getCanonicalType())) {
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// We will always decay to a pointer.
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QualType elemTy = arrayT->getElementType();
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val = StateMgr.ArrayToPointer(val.castAs<Loc>(), elemTy);
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// Are we casting from an array to a pointer? If so just pass on
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// the decayed value.
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if (castTy->isPointerType() || castTy->isReferenceType())
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return val;
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// Are we casting from an array to an integer? If so, cast the decayed
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// pointer value to an integer.
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assert(castTy->isIntegralOrEnumerationType());
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// FIXME: Keep these here for now in case we decide soon that we
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// need the original decayed type.
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// QualType elemTy = cast<ArrayType>(originalTy)->getElementType();
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// QualType pointerTy = C.getPointerType(elemTy);
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return evalCastFromLoc(val.castAs<Loc>(), castTy);
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}
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// Check for casts from a region to a specific type.
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if (const MemRegion *R = val.getAsRegion()) {
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// Handle other casts of locations to integers.
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if (castTy->isIntegralOrEnumerationType())
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return evalCastFromLoc(loc::MemRegionVal(R), castTy);
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// FIXME: We should handle the case where we strip off view layers to get
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// to a desugared type.
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|
if (!Loc::isLocType(castTy)) {
|
|
// FIXME: There can be gross cases where one casts the result of a function
|
|
// (that returns a pointer) to some other value that happens to fit
|
|
// within that pointer value. We currently have no good way to
|
|
// model such operations. When this happens, the underlying operation
|
|
// is that the caller is reasoning about bits. Conceptually we are
|
|
// layering a "view" of a location on top of those bits. Perhaps
|
|
// we need to be more lazy about mutual possible views, even on an
|
|
// SVal? This may be necessary for bit-level reasoning as well.
|
|
return UnknownVal();
|
|
}
|
|
|
|
// We get a symbolic function pointer for a dereference of a function
|
|
// pointer, but it is of function type. Example:
|
|
|
|
// struct FPRec {
|
|
// void (*my_func)(int * x);
|
|
// };
|
|
//
|
|
// int bar(int x);
|
|
//
|
|
// int f1_a(struct FPRec* foo) {
|
|
// int x;
|
|
// (*foo->my_func)(&x);
|
|
// return bar(x)+1; // no-warning
|
|
// }
|
|
|
|
assert(Loc::isLocType(originalTy) || originalTy->isFunctionType() ||
|
|
originalTy->isBlockPointerType() || castTy->isReferenceType());
|
|
|
|
StoreManager &storeMgr = StateMgr.getStoreManager();
|
|
|
|
// Delegate to store manager to get the result of casting a region to a
|
|
// different type. If the MemRegion* returned is NULL, this expression
|
|
// Evaluates to UnknownVal.
|
|
R = storeMgr.castRegion(R, castTy);
|
|
return R ? SVal(loc::MemRegionVal(R)) : UnknownVal();
|
|
}
|
|
|
|
return dispatchCast(val, castTy);
|
|
}
|