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      1 //=== CastSizeChecker.cpp ---------------------------------------*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // CastSizeChecker checks when casting a malloc'ed symbolic region to type T,
     11 // whether the size of the symbolic region is a multiple of the size of T.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 #include "ClangSACheckers.h"
     15 #include "clang/AST/CharUnits.h"
     16 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
     17 #include "clang/StaticAnalyzer/Core/Checker.h"
     18 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
     19 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
     20 
     21 using namespace clang;
     22 using namespace ento;
     23 
     24 namespace {
     25 class CastSizeChecker : public Checker< check::PreStmt<CastExpr> > {
     26   mutable OwningPtr<BuiltinBug> BT;
     27 public:
     28   void checkPreStmt(const CastExpr *CE, CheckerContext &C) const;
     29 };
     30 }
     31 
     32 void CastSizeChecker::checkPreStmt(const CastExpr *CE,CheckerContext &C) const {
     33   const Expr *E = CE->getSubExpr();
     34   ASTContext &Ctx = C.getASTContext();
     35   QualType ToTy = Ctx.getCanonicalType(CE->getType());
     36   const PointerType *ToPTy = dyn_cast<PointerType>(ToTy.getTypePtr());
     37 
     38   if (!ToPTy)
     39     return;
     40 
     41   QualType ToPointeeTy = ToPTy->getPointeeType();
     42 
     43   // Only perform the check if 'ToPointeeTy' is a complete type.
     44   if (ToPointeeTy->isIncompleteType())
     45     return;
     46 
     47   ProgramStateRef state = C.getState();
     48   const MemRegion *R = state->getSVal(E, C.getLocationContext()).getAsRegion();
     49   if (R == 0)
     50     return;
     51 
     52   const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R);
     53   if (SR == 0)
     54     return;
     55 
     56   SValBuilder &svalBuilder = C.getSValBuilder();
     57   SVal extent = SR->getExtent(svalBuilder);
     58   const llvm::APSInt *extentInt = svalBuilder.getKnownValue(state, extent);
     59   if (!extentInt)
     60     return;
     61 
     62   CharUnits regionSize = CharUnits::fromQuantity(extentInt->getSExtValue());
     63   CharUnits typeSize = C.getASTContext().getTypeSizeInChars(ToPointeeTy);
     64 
     65   // Ignore void, and a few other un-sizeable types.
     66   if (typeSize.isZero())
     67     return;
     68 
     69   if (regionSize % typeSize != 0) {
     70     if (ExplodedNode *errorNode = C.generateSink()) {
     71       if (!BT)
     72         BT.reset(new BuiltinBug("Cast region with wrong size.",
     73                             "Cast a region whose size is not a multiple of the"
     74                             " destination type size."));
     75       BugReport *R = new BugReport(*BT, BT->getDescription(),
     76                                                errorNode);
     77       R->addRange(CE->getSourceRange());
     78       C.emitReport(R);
     79     }
     80   }
     81 }
     82 
     83 
     84 void ento::registerCastSizeChecker(CheckerManager &mgr) {
     85   mgr.registerChecker<CastSizeChecker>();
     86 }
     87