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      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 
     37 namespace 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