1/*
2 * Copyright (C) 2009, 2011 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#ifndef MarkStack_h
27#define MarkStack_h
28
29#include "JSValue.h"
30#include "Register.h"
31#include "WriteBarrier.h"
32#include <wtf/HashSet.h>
33#include <wtf/Vector.h>
34#include <wtf/Noncopyable.h>
35#include <wtf/OSAllocator.h>
36
37namespace JSC {
38
39    class ConservativeRoots;
40    class JSGlobalData;
41    class Register;
42
43    enum MarkSetProperties { MayContainNullValues, NoNullValues };
44
45    class MarkStack {
46        WTF_MAKE_NONCOPYABLE(MarkStack);
47    public:
48        MarkStack(void* jsArrayVPtr)
49            : m_jsArrayVPtr(jsArrayVPtr)
50#if !ASSERT_DISABLED
51            , m_isCheckingForDefaultMarkViolation(false)
52            , m_isDraining(false)
53#endif
54        {
55        }
56
57        ~MarkStack()
58        {
59            ASSERT(m_markSets.isEmpty());
60            ASSERT(m_values.isEmpty());
61        }
62
63        void deprecatedAppend(JSCell**);
64        template <typename T> void append(WriteBarrierBase<T>*);
65
66        void appendValues(WriteBarrierBase<Unknown>* barriers, size_t count, MarkSetProperties properties = NoNullValues)
67        {
68            JSValue* values = barriers->slot();
69            if (count)
70                m_markSets.append(MarkSet(values, values + count, properties));
71        }
72
73        void append(ConservativeRoots&);
74
75        bool addOpaqueRoot(void* root) { return m_opaqueRoots.add(root).second; }
76        bool containsOpaqueRoot(void* root) { return m_opaqueRoots.contains(root); }
77        int opaqueRootCount() { return m_opaqueRoots.size(); }
78
79        void drain();
80        void reset();
81
82    private:
83        friend class HeapRootMarker; // Allowed to mark a JSValue* or JSCell** directly.
84        void append(JSValue*);
85        void append(JSValue*, size_t count);
86        void append(JSCell**);
87
88        void internalAppend(JSCell*);
89        void internalAppend(JSValue);
90        void markChildren(JSCell*);
91
92        struct MarkSet {
93            MarkSet(JSValue* values, JSValue* end, MarkSetProperties properties)
94                : m_values(values)
95                , m_end(end)
96                , m_properties(properties)
97            {
98                ASSERT(values);
99            }
100            JSValue* m_values;
101            JSValue* m_end;
102            MarkSetProperties m_properties;
103        };
104
105        static void* allocateStack(size_t size) { return OSAllocator::reserveAndCommit(size); }
106        static void releaseStack(void* addr, size_t size) { OSAllocator::decommitAndRelease(addr, size); }
107
108        static void initializePagesize();
109        static size_t pageSize()
110        {
111            if (!s_pageSize)
112                initializePagesize();
113            return s_pageSize;
114        }
115
116        template <typename T> struct MarkStackArray {
117            MarkStackArray()
118                : m_top(0)
119                , m_allocated(MarkStack::pageSize())
120                , m_capacity(m_allocated / sizeof(T))
121            {
122                m_data = reinterpret_cast<T*>(allocateStack(m_allocated));
123            }
124
125            ~MarkStackArray()
126            {
127                releaseStack(m_data, m_allocated);
128            }
129
130            void expand()
131            {
132                size_t oldAllocation = m_allocated;
133                m_allocated *= 2;
134                m_capacity = m_allocated / sizeof(T);
135                void* newData = allocateStack(m_allocated);
136                memcpy(newData, m_data, oldAllocation);
137                releaseStack(m_data, oldAllocation);
138                m_data = reinterpret_cast<T*>(newData);
139            }
140
141            inline void append(const T& v)
142            {
143                if (m_top == m_capacity)
144                    expand();
145                m_data[m_top++] = v;
146            }
147
148            inline T removeLast()
149            {
150                ASSERT(m_top);
151                return m_data[--m_top];
152            }
153
154            inline T& last()
155            {
156                ASSERT(m_top);
157                return m_data[m_top - 1];
158            }
159
160            inline bool isEmpty()
161            {
162                return m_top == 0;
163            }
164
165            inline size_t size() { return m_top; }
166
167            inline void shrinkAllocation(size_t size)
168            {
169                ASSERT(size <= m_allocated);
170                ASSERT(0 == (size % MarkStack::pageSize()));
171                if (size == m_allocated)
172                    return;
173#if OS(WINDOWS) || OS(SYMBIAN) || PLATFORM(BREWMP)
174                // We cannot release a part of a region with VirtualFree.  To get around this,
175                // we'll release the entire region and reallocate the size that we want.
176                releaseStack(m_data, m_allocated);
177                m_data = reinterpret_cast<T*>(allocateStack(size));
178#else
179                releaseStack(reinterpret_cast<char*>(m_data) + size, m_allocated - size);
180#endif
181                m_allocated = size;
182                m_capacity = m_allocated / sizeof(T);
183            }
184
185        private:
186            size_t m_top;
187            size_t m_allocated;
188            size_t m_capacity;
189            T* m_data;
190        };
191
192        void* m_jsArrayVPtr;
193        MarkStackArray<MarkSet> m_markSets;
194        MarkStackArray<JSCell*> m_values;
195        static size_t s_pageSize;
196        HashSet<void*> m_opaqueRoots; // Handle-owning data structures not visible to the garbage collector.
197
198#if !ASSERT_DISABLED
199    public:
200        bool m_isCheckingForDefaultMarkViolation;
201        bool m_isDraining;
202#endif
203    };
204
205    inline void MarkStack::append(JSValue* slot, size_t count)
206    {
207        if (!count)
208            return;
209        m_markSets.append(MarkSet(slot, slot + count, NoNullValues));
210    }
211
212    template <typename T> inline void MarkStack::append(WriteBarrierBase<T>* slot)
213    {
214        internalAppend(*slot->slot());
215    }
216
217    ALWAYS_INLINE void MarkStack::deprecatedAppend(JSCell** value)
218    {
219        ASSERT(value);
220        internalAppend(*value);
221    }
222
223    ALWAYS_INLINE void MarkStack::append(JSValue* value)
224    {
225        ASSERT(value);
226        internalAppend(*value);
227    }
228
229    ALWAYS_INLINE void MarkStack::append(JSCell** value)
230    {
231        ASSERT(value);
232        internalAppend(*value);
233    }
234
235    ALWAYS_INLINE void MarkStack::internalAppend(JSValue value)
236    {
237        ASSERT(value);
238        if (value.isCell())
239            internalAppend(value.asCell());
240    }
241
242    // Privileged class for marking JSValues directly. It is only safe to use
243    // this class to mark direct heap roots that are marked during every GC pass.
244    // All other references should be wrapped in WriteBarriers and marked through
245    // the MarkStack.
246    class HeapRootMarker {
247    private:
248        friend class Heap;
249        HeapRootMarker(MarkStack&);
250
251    public:
252        void mark(JSValue*);
253        void mark(JSValue*, size_t);
254        void mark(JSString**);
255        void mark(JSCell**);
256
257        MarkStack& markStack();
258
259    private:
260        MarkStack& m_markStack;
261    };
262
263    inline HeapRootMarker::HeapRootMarker(MarkStack& markStack)
264        : m_markStack(markStack)
265    {
266    }
267
268    inline void HeapRootMarker::mark(JSValue* slot)
269    {
270        m_markStack.append(slot);
271    }
272
273    inline void HeapRootMarker::mark(JSValue* slot, size_t count)
274    {
275        m_markStack.append(slot, count);
276    }
277
278    inline void HeapRootMarker::mark(JSString** slot)
279    {
280        m_markStack.append(reinterpret_cast<JSCell**>(slot));
281    }
282
283    inline void HeapRootMarker::mark(JSCell** slot)
284    {
285        m_markStack.append(slot);
286    }
287
288    inline MarkStack& HeapRootMarker::markStack()
289    {
290        return m_markStack;
291    }
292
293} // namespace JSC
294
295#endif
296