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_unpredictable: 45 case Builtin::BI__builtin_expect: 46 case Builtin::BI__builtin_assume_aligned: 47 case Builtin::BI__builtin_addressof: { 48 // For __builtin_unpredictable, __builtin_expect, and 49 // __builtin_assume_aligned, just return the value of the subexpression. 50 // __builtin_addressof is going from a reference to a pointer, but those 51 // are represented the same way in the analyzer. 52 assert (CE->arg_begin() != CE->arg_end()); 53 SVal X = state->getSVal(*(CE->arg_begin()), LCtx); 54 C.addTransition(state->BindExpr(CE, LCtx, X)); 55 return true; 56 } 57 58 case Builtin::BI__builtin_alloca_with_align: 59 case Builtin::BI__builtin_alloca: { 60 // FIXME: Refactor into StoreManager itself? 61 MemRegionManager& RM = C.getStoreManager().getRegionManager(); 62 const AllocaRegion* R = 63 RM.getAllocaRegion(CE, C.blockCount(), C.getLocationContext()); 64 65 // Set the extent of the region in bytes. This enables us to use the 66 // SVal of the argument directly. If we save the extent in bits, we 67 // cannot represent values like symbol*8. 68 DefinedOrUnknownSVal Size = 69 state->getSVal(*(CE->arg_begin()), LCtx).castAs<DefinedOrUnknownSVal>(); 70 71 SValBuilder& svalBuilder = C.getSValBuilder(); 72 DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder); 73 DefinedOrUnknownSVal extentMatchesSizeArg = 74 svalBuilder.evalEQ(state, Extent, Size); 75 state = state->assume(extentMatchesSizeArg, true); 76 assert(state && "The region should not have any previous constraints"); 77 78 C.addTransition(state->BindExpr(CE, LCtx, loc::MemRegionVal(R))); 79 return true; 80 } 81 82 case Builtin::BI__builtin_object_size: { 83 // This must be resolvable at compile time, so we defer to the constant 84 // evaluator for a value. 85 SVal V = UnknownVal(); 86 llvm::APSInt Result; 87 if (CE->EvaluateAsInt(Result, C.getASTContext(), Expr::SE_NoSideEffects)) { 88 // Make sure the result has the correct type. 89 SValBuilder &SVB = C.getSValBuilder(); 90 BasicValueFactory &BVF = SVB.getBasicValueFactory(); 91 BVF.getAPSIntType(CE->getType()).apply(Result); 92 V = SVB.makeIntVal(Result); 93 } 94 95 C.addTransition(state->BindExpr(CE, LCtx, V)); 96 return true; 97 } 98 } 99 } 100 101 void ento::registerBuiltinFunctionChecker(CheckerManager &mgr) { 102 mgr.registerChecker<BuiltinFunctionChecker>(); 103 } 104