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 #include "llvm/ADT/STLExtras.h" 21 22 using namespace clang; 23 using namespace ento; 24 25 namespace { 26 class DivZeroChecker : public Checker< check::PreStmt<BinaryOperator> > { 27 mutable llvm::OwningPtr<BuiltinBug> BT; 28 void reportBug(const char *Msg, 29 ProgramStateRef StateZero, 30 CheckerContext &C) const ; 31 public: 32 void checkPreStmt(const BinaryOperator *B, CheckerContext &C) const; 33 }; 34 } // end anonymous namespace 35 36 void DivZeroChecker::reportBug(const char *Msg, 37 ProgramStateRef StateZero, 38 CheckerContext &C) const { 39 if (ExplodedNode *N = C.generateSink(StateZero)) { 40 if (!BT) 41 BT.reset(new BuiltinBug("Division by zero")); 42 43 BugReport *R = 44 new BugReport(*BT, Msg, N); 45 46 R->addVisitor(bugreporter::getTrackNullOrUndefValueVisitor(N, 47 bugreporter::GetDenomExpr(N))); 48 49 C.EmitReport(R); 50 } 51 } 52 53 void DivZeroChecker::checkPreStmt(const BinaryOperator *B, 54 CheckerContext &C) const { 55 BinaryOperator::Opcode Op = B->getOpcode(); 56 if (Op != BO_Div && 57 Op != BO_Rem && 58 Op != BO_DivAssign && 59 Op != BO_RemAssign) 60 return; 61 62 if (!B->getRHS()->getType()->isIntegerType() || 63 !B->getRHS()->getType()->isScalarType()) 64 return; 65 66 SVal Denom = C.getState()->getSVal(B->getRHS(), C.getLocationContext()); 67 const DefinedSVal *DV = dyn_cast<DefinedSVal>(&Denom); 68 69 // Divide-by-undefined handled in the generic checking for uses of 70 // undefined values. 71 if (!DV) 72 return; 73 74 // Check for divide by zero. 75 ConstraintManager &CM = C.getConstraintManager(); 76 ProgramStateRef stateNotZero, stateZero; 77 llvm::tie(stateNotZero, stateZero) = CM.assumeDual(C.getState(), *DV); 78 79 if (!stateNotZero) { 80 assert(stateZero); 81 reportBug("Division by zero", stateZero, C); 82 return; 83 } 84 85 bool TaintedD = C.getState()->isTainted(*DV); 86 if ((stateNotZero && stateZero && TaintedD)) { 87 reportBug("Division by a tainted value, possibly zero", stateZero, C); 88 return; 89 } 90 91 // If we get here, then the denom should not be zero. We abandon the implicit 92 // zero denom case for now. 93 C.addTransition(stateNotZero); 94 } 95 96 void ento::registerDivZeroChecker(CheckerManager &mgr) { 97 mgr.registerChecker<DivZeroChecker>(); 98 } 99