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 llvm::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))); 47 48 C.EmitReport(R); 49 } 50 } 51 52 void DivZeroChecker::checkPreStmt(const BinaryOperator *B, 53 CheckerContext &C) const { 54 BinaryOperator::Opcode Op = B->getOpcode(); 55 if (Op != BO_Div && 56 Op != BO_Rem && 57 Op != BO_DivAssign && 58 Op != BO_RemAssign) 59 return; 60 61 if (!B->getRHS()->getType()->isIntegerType() || 62 !B->getRHS()->getType()->isScalarType()) 63 return; 64 65 SVal Denom = C.getState()->getSVal(B->getRHS(), C.getLocationContext()); 66 const DefinedSVal *DV = dyn_cast<DefinedSVal>(&Denom); 67 68 // Divide-by-undefined handled in the generic checking for uses of 69 // undefined values. 70 if (!DV) 71 return; 72 73 // Check for divide by zero. 74 ConstraintManager &CM = C.getConstraintManager(); 75 ProgramStateRef stateNotZero, stateZero; 76 llvm::tie(stateNotZero, stateZero) = CM.assumeDual(C.getState(), *DV); 77 78 if (!stateNotZero) { 79 assert(stateZero); 80 reportBug("Division by zero", stateZero, C); 81 return; 82 } 83 84 bool TaintedD = C.getState()->isTainted(*DV); 85 if ((stateNotZero && stateZero && TaintedD)) { 86 reportBug("Division by a tainted value, possibly zero", stateZero, C); 87 return; 88 } 89 90 // If we get here, then the denom should not be zero. We abandon the implicit 91 // zero denom case for now. 92 C.addTransition(stateNotZero); 93 } 94 95 void ento::registerDivZeroChecker(CheckerManager &mgr) { 96 mgr.registerChecker<DivZeroChecker>(); 97 } 98