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
evalCall(const CallExpr * CE,CheckerContext & C) const32 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_addressof: {
46 // For __builtin_expect, just return the value of the subexpression.
47 // __builtin_addressof is going from a reference to a pointer, but those
48 // are represented the same way in the analyzer.
49 assert (CE->arg_begin() != CE->arg_end());
50 SVal X = state->getSVal(*(CE->arg_begin()), LCtx);
51 C.addTransition(state->BindExpr(CE, LCtx, X));
52 return true;
53 }
54
55 case Builtin::BI__builtin_alloca: {
56 // FIXME: Refactor into StoreManager itself?
57 MemRegionManager& RM = C.getStoreManager().getRegionManager();
58 const AllocaRegion* R =
59 RM.getAllocaRegion(CE, C.blockCount(), C.getLocationContext());
60
61 // Set the extent of the region in bytes. This enables us to use the
62 // SVal of the argument directly. If we save the extent in bits, we
63 // cannot represent values like symbol*8.
64 DefinedOrUnknownSVal Size =
65 state->getSVal(*(CE->arg_begin()), LCtx).castAs<DefinedOrUnknownSVal>();
66
67 SValBuilder& svalBuilder = C.getSValBuilder();
68 DefinedOrUnknownSVal Extent = R->getExtent(svalBuilder);
69 DefinedOrUnknownSVal extentMatchesSizeArg =
70 svalBuilder.evalEQ(state, Extent, Size);
71 state = state->assume(extentMatchesSizeArg, true);
72 assert(state && "The region should not have any previous constraints");
73
74 C.addTransition(state->BindExpr(CE, LCtx, loc::MemRegionVal(R)));
75 return true;
76 }
77
78 case Builtin::BI__builtin_object_size: {
79 // This must be resolvable at compile time, so we defer to the constant
80 // evaluator for a value.
81 SVal V = UnknownVal();
82 llvm::APSInt Result;
83 if (CE->EvaluateAsInt(Result, C.getASTContext(), Expr::SE_NoSideEffects)) {
84 // Make sure the result has the correct type.
85 SValBuilder &SVB = C.getSValBuilder();
86 BasicValueFactory &BVF = SVB.getBasicValueFactory();
87 BVF.getAPSIntType(CE->getType()).apply(Result);
88 V = SVB.makeIntVal(Result);
89 }
90
91 C.addTransition(state->BindExpr(CE, LCtx, V));
92 return true;
93 }
94 }
95 }
96
registerBuiltinFunctionChecker(CheckerManager & mgr)97 void ento::registerBuiltinFunctionChecker(CheckerManager &mgr) {
98 mgr.registerChecker<BuiltinFunctionChecker>();
99 }
100