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_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
registerBuiltinFunctionChecker(CheckerManager & mgr)99 void ento::registerBuiltinFunctionChecker(CheckerManager &mgr) {
100 mgr.registerChecker<BuiltinFunctionChecker>();
101 }
102