1/*
2 * Copyright (C) 2011, 2016 Apple Inc. All rights reserved.
3 *
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation; either
7 * version 2 of the License, or (at your option) any later version.
8 *
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Lesser General Public License for more details.
13 *
14 * You should have received a copy of the GNU Lesser General Public
15 * License along with this library; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17 *
18 */
19
20#pragma once
21
22#include "CallFrame.h"
23#include "GetVM.h"
24#include "VMInlines.h"
25#include <wtf/StackStats.h>
26
27namespace JSC {
28
29class StringRecursionChecker {
30 WTF_MAKE_NONCOPYABLE(StringRecursionChecker);
31
32public:
33 StringRecursionChecker(JSGlobalObject*, JSObject* thisObject);
34 ~StringRecursionChecker();
35
36 JSValue earlyReturnValue() const; // 0 if everything is OK, value to return for failure cases
37
38private:
39 JSValue throwStackOverflowError();
40 JSValue emptyString();
41 JSValue performCheck();
42
43 JSGlobalObject* m_globalObject;
44 JSObject* m_thisObject;
45 JSValue m_earlyReturnValue;
46
47 StackStats::CheckPoint stackCheckpoint;
48};
49
50inline JSValue StringRecursionChecker::performCheck()
51{
52 VM& vm = getVM(m_globalObject);
53 if (UNLIKELY(!vm.isSafeToRecurseSoft()))
54 return throwStackOverflowError();
55
56 bool alreadyVisited = false;
57 if (!vm.stringRecursionCheckFirstObject)
58 vm.stringRecursionCheckFirstObject = m_thisObject;
59 else if (vm.stringRecursionCheckFirstObject == m_thisObject)
60 alreadyVisited = true;
61 else
62 alreadyVisited = !vm.stringRecursionCheckVisitedObjects.add(m_thisObject).isNewEntry;
63
64 if (alreadyVisited)
65 return emptyString(); // Return empty string to avoid infinite recursion.
66 return JSValue(); // Indicate success.
67}
68
69inline StringRecursionChecker::StringRecursionChecker(JSGlobalObject* globalObject, JSObject* thisObject)
70 : m_globalObject(globalObject)
71 , m_thisObject(thisObject)
72 , m_earlyReturnValue(performCheck())
73{
74}
75
76inline JSValue StringRecursionChecker::earlyReturnValue() const
77{
78 return m_earlyReturnValue;
79}
80
81inline StringRecursionChecker::~StringRecursionChecker()
82{
83 if (m_earlyReturnValue)
84 return;
85
86 VM& vm = getVM(m_globalObject);
87 if (vm.stringRecursionCheckFirstObject == m_thisObject)
88 vm.stringRecursionCheckFirstObject = nullptr;
89 else {
90 ASSERT(vm.stringRecursionCheckVisitedObjects.contains(m_thisObject));
91 vm.stringRecursionCheckVisitedObjects.remove(m_thisObject);
92 }
93}
94
95} // namespace JSC
96