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_assume: { 45 assert (CE->arg_begin() != CE->arg_end()); 46 SVal ArgSVal = state->getSVal(CE->getArg(0), LCtx); 47 if (ArgSVal.isUndef()) 48 return true; // Return true to model purity. 49 50 state = state->assume(ArgSVal.castAs<DefinedOrUnknownSVal>(), true); 51 // FIXME: do we want to warn here? Not right now. The most reports might 52 // come from infeasible paths, thus being false positives. 53 if (!state) 54 return true; 55 56 C.addTransition(state); 57 return true; 58 } 59 60 case Builtin::BI__builtin_unpredictable: 61 case Builtin::BI__builtin_expect: 62 case Builtin::BI__builtin_assume_aligned: 63 case Builtin::BI__builtin_addressof: { 64 // For __builtin_unpredictable, __builtin_expect, and 65 // __builtin_assume_aligned, just return the value of the subexpression. 66 // __builtin_addressof is going from a reference to a pointer, but those 67 // are represented the same way in the analyzer. 68 assert (CE->arg_begin() != CE->arg_end()); 69 SVal X = state->getSVal(*(CE->arg_begin()), LCtx); 70 C.addTransition(state->BindExpr(CE, LCtx, X)); 71 return true; 72 } 73 74 case Builtin::BI__builtin_alloca_with_align: 75 case Builtin::BI__builtin_alloca: { 76 // FIXME: Refactor into StoreManager itself? 77 MemRegionManager& RM = C.getStoreManager().getRegionManager(); 78 const AllocaRegion* R = 79 RM.getAllocaRegion(CE, C.blockCount(), C.getLocationContext()); 80 81 // Set the extent of the region in bytes. This enables us to use the 82 // SVal of the argument directly. If we save the extent in bits, we 83 // cannot represent values like symbol*8. 84 DefinedOrUnknownSVal Size = 85 state->getSVal(*(CE->arg_begin()), LCtx).castAs<DefinedOrUnknownSVal>(); 86 87 SValBuilder& svalBuilder = C.getSValBuilder(); 88 DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder); 89 DefinedOrUnknownSVal extentMatchesSizeArg = 90 svalBuilder.evalEQ(state, Extent, Size); 91 state = state->assume(extentMatchesSizeArg, true); 92 assert(state && "The region should not have any previous constraints"); 93 94 C.addTransition(state->BindExpr(CE, LCtx, loc::MemRegionVal(R))); 95 return true; 96 } 97 98 case Builtin::BI__builtin_object_size: { 99 // This must be resolvable at compile time, so we defer to the constant 100 // evaluator for a value. 101 SVal V = UnknownVal(); 102 llvm::APSInt Result; 103 if (CE->EvaluateAsInt(Result, C.getASTContext(), Expr::SE_NoSideEffects)) { 104 // Make sure the result has the correct type. 105 SValBuilder &SVB = C.getSValBuilder(); 106 BasicValueFactory &BVF = SVB.getBasicValueFactory(); 107 BVF.getAPSIntType(CE->getType()).apply(Result); 108 V = SVB.makeIntVal(Result); 109 } 110 111 C.addTransition(state->BindExpr(CE, LCtx, V)); 112 return true; 113 } 114 } 115 } 116 117 void ento::registerBuiltinFunctionChecker(CheckerManager &mgr) { 118 mgr.registerChecker<BuiltinFunctionChecker>(); 119 } 120