1 //== DivZeroChecker.cpp - Division by zero checker --------------*- 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 // This defines DivZeroChecker, a builtin check in ExprEngine that performs 11 // checks for division by zeros. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #include "ClangSACheckers.h" 16 #include "clang/StaticAnalyzer/Core/Checker.h" 17 #include "clang/StaticAnalyzer/Core/CheckerManager.h" 18 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" 19 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" 20 21 using namespace clang; 22 using namespace ento; 23 24 namespace { 25 class DivZeroChecker : public Checker< check::PreStmt<BinaryOperator> > { 26 mutable OwningPtr<BuiltinBug> BT; 27 void reportBug(const char *Msg, 28 ProgramStateRef StateZero, 29 CheckerContext &C) const ; 30 public: 31 void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const; 32 }; 33 } // end anonymous namespace 34 35 void DivZeroChecker::reportBug(const char *Msg, 36 ProgramStateRef StateZero, 37 CheckerContext &C) const { 38 if (ExplodedNode *N = C.generateSink(StateZero)) { 39 if (!BT) 40 BT.reset(new BuiltinBug("Division by zero")); 41 42 BugReport *R = 43 new BugReport(*BT, Msg, N); 44 45 R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, 46 bugreporter::GetDenomExpr(N), R)); 47 C.EmitReport(R); 48 } 49 } 50 51 void DivZeroChecker::checkPreStmt(const BinaryOperator *B, 52 CheckerContext &C) const { 53 BinaryOperator::Opcode Op = B->getOpcode(); 54 if (Op != BO_Div && 55 Op != BO_Rem && 56 Op != BO_DivAssign && 57 Op != BO_RemAssign) 58 return; 59 60 if (!B->getRHS()->getType()->isScalarType()) 61 return; 62 63 SVal Denom = C.getState()->getSVal(B->getRHS(), C.getLocationContext()); 64 const DefinedSVal *DV = dyn_cast<DefinedSVal>(&Denom); 65 66 // Divide-by-undefined handled in the generic checking for uses of 67 // undefined values. 68 if (!DV) 69 return; 70 71 // Check for divide by zero. 72 ConstraintManager &CM = C.getConstraintManager(); 73 ProgramStateRef stateNotZero, stateZero; 74 llvm::tie(stateNotZero, stateZero) = CM.assumeDual(C.getState(), *DV); 75 76 if (!stateNotZero) { 77 assert(stateZero); 78 reportBug("Division by zero", stateZero, C); 79 return; 80 } 81 82 bool TaintedD = C.getState()->isTainted(*DV); 83 if ((stateNotZero && stateZero && TaintedD)) { 84 reportBug("Division by a tainted value, possibly zero", stateZero, C); 85 return; 86 } 87 88 // If we get here, then the denom should not be zero. We abandon the implicit 89 // zero denom case for now. 90 C.addTransition(stateNotZero); 91 } 92 93 void ento::registerDivZeroChecker(CheckerManager &mgr) { 94 mgr.registerChecker<DivZeroChecker>(); 95 } 96