1 //=== BuiltinFunctionChecker.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 // This checker evaluates clang builtin functions. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "ClangSACheckers.h" 15 #include "clang/Basic/Builtins.h" 16 #include "clang/StaticAnalyzer/Core/Checker.h" 17 #include "clang/StaticAnalyzer/Core/CheckerManager.h" 18 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" 19 20 using namespace clang; 21 using namespace ento; 22 23 namespace { 24 25 class BuiltinFunctionChecker : public Checker<eval::Call> { 26 public: 27 bool evalCall(const CallExpr *CE, CheckerContext &C) const; 28 }; 29 30 } 31 32 bool BuiltinFunctionChecker::evalCall(const CallExpr *CE, 33 CheckerContext &C) const { 34 ProgramStateRef state = C.getState(); 35 const FunctionDecl *FD = C.getCalleeDecl(CE); 36 const LocationContext *LCtx = C.getLocationContext(); 37 if (!FD) 38 return false; 39 40 switch (FD->getBuiltinID()) { 41 default: 42 return false; 43 44 case Builtin::BI__builtin_expect: 45 case Builtin::BI__builtin_assume_aligned: 46 case Builtin::BI__builtin_addressof: { 47 // For __builtin_expect and __builtin_assume_aligned, just return the value 48 // of the subexpression. 49 // __builtin_addressof is going from a reference to a pointer, but those 50 // are represented the same way in the analyzer. 51 assert (CE->arg_begin() != CE->arg_end()); 52 SVal X = state->getSVal(*(CE->arg_begin()), LCtx); 53 C.addTransition(state->BindExpr(CE, LCtx, X)); 54 return true; 55 } 56 57 case Builtin::BI__builtin_alloca: { 58 // FIXME: Refactor into StoreManager itself? 59 MemRegionManager& RM = C.getStoreManager().getRegionManager(); 60 const AllocaRegion* R = 61 RM.getAllocaRegion(CE, C.blockCount(), C.getLocationContext()); 62 63 // Set the extent of the region in bytes. This enables us to use the 64 // SVal of the argument directly. If we save the extent in bits, we 65 // cannot represent values like symbol*8. 66 DefinedOrUnknownSVal Size = 67 state->getSVal(*(CE->arg_begin()), LCtx).castAs<DefinedOrUnknownSVal>(); 68 69 SValBuilder& svalBuilder = C.getSValBuilder(); 70 DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder); 71 DefinedOrUnknownSVal extentMatchesSizeArg = 72 svalBuilder.evalEQ(state, Extent, Size); 73 state = state->assume(extentMatchesSizeArg, true); 74 assert(state && "The region should not have any previous constraints"); 75 76 C.addTransition(state->BindExpr(CE, LCtx, loc::MemRegionVal(R))); 77 return true; 78 } 79 80 case Builtin::BI__builtin_object_size: { 81 // This must be resolvable at compile time, so we defer to the constant 82 // evaluator for a value. 83 SVal V = UnknownVal(); 84 llvm::APSInt Result; 85 if (CE->EvaluateAsInt(Result, C.getASTContext(), Expr::SE_NoSideEffects)) { 86 // Make sure the result has the correct type. 87 SValBuilder &SVB = C.getSValBuilder(); 88 BasicValueFactory &BVF = SVB.getBasicValueFactory(); 89 BVF.getAPSIntType(CE->getType()).apply(Result); 90 V = SVB.makeIntVal(Result); 91 } 92 93 C.addTransition(state->BindExpr(CE, LCtx, V)); 94 return true; 95 } 96 } 97 } 98 99 void ento::registerBuiltinFunctionChecker(CheckerManager &mgr) { 100 mgr.registerChecker<BuiltinFunctionChecker>(); 101 } 102