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      1 /*
      2  * Copyright (C) 2010 Google 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 are
      6  * met:
      7  *
      8  *     * Redistributions of source code must retain the above copyright
      9  * notice, this list of conditions and the following disclaimer.
     10  *     * Redistributions in binary form must reproduce the above
     11  * copyright notice, this list of conditions and the following disclaimer
     12  * in the documentation and/or other materials provided with the
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     14  *     * Neither the name of Google Inc. nor the names of its
     15  * contributors may be used to endorse or promote products derived from
     16  * this software without specific prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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     27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29  */
     30 
     31 #ifndef ScriptWrappable_h
     32 #define ScriptWrappable_h
     33 
     34 #include "bindings/v8/UnsafePersistent.h"
     35 #include "bindings/v8/V8Utilities.h"
     36 #include "bindings/v8/WrapperTypeInfo.h"
     37 #include <v8.h>
     38 
     39 // Helper to call webCoreInitializeScriptWrappableForInterface in the global namespace.
     40 template <class C> inline void initializeScriptWrappableHelper(C* object)
     41 {
     42     void webCoreInitializeScriptWrappableForInterface(C*);
     43     webCoreInitializeScriptWrappableForInterface(object);
     44 }
     45 
     46 namespace WebCore {
     47 
     48 class ScriptWrappable {
     49 public:
     50     ScriptWrappable() : m_wrapperOrTypeInfo(0) { }
     51 
     52     // Wrappables need to be initialized with their most derrived type for which
     53     // bindings exist, in much the same way that certain other types need to be
     54     // adopted and so forth. The overloaded initializeScriptWrappableForInterface()
     55     // functions are implemented by the generated V8 bindings code. Declaring the
     56     // extern function in the template avoids making a centralized header of all
     57     // the bindings in the universe. C++11's extern template feature may provide
     58     // a cleaner solution someday.
     59     template <class C> static void init(C* object)
     60     {
     61         initializeScriptWrappableHelper(object);
     62     }
     63 
     64     void setWrapper(v8::Handle<v8::Object> wrapper, v8::Isolate* isolate, const WrapperConfiguration& configuration)
     65     {
     66         ASSERT(!containsWrapper());
     67         if (!*wrapper) {
     68             m_wrapperOrTypeInfo = 0;
     69             return;
     70         }
     71         v8::Persistent<v8::Object> persistent(isolate, wrapper);
     72         configuration.configureWrapper(&persistent, isolate);
     73         persistent.MakeWeak(this, &makeWeakCallback);
     74         m_wrapperOrTypeInfo = reinterpret_cast<uintptr_t>(persistent.ClearAndLeak()) | 1;
     75         ASSERT(containsWrapper());
     76     }
     77 
     78     v8::Local<v8::Object> newLocalWrapper(v8::Isolate* isolate) const
     79     {
     80         return unsafePersistent().newLocal(isolate);
     81     }
     82 
     83     const WrapperTypeInfo* typeInfo()
     84     {
     85         if (containsTypeInfo())
     86             return reinterpret_cast<const WrapperTypeInfo*>(m_wrapperOrTypeInfo);
     87 
     88         if (containsWrapper()) {
     89             return toWrapperTypeInfo(unsafePersistent().deprecatedHandle());
     90         }
     91 
     92         return 0;
     93     }
     94 
     95     void setTypeInfo(const WrapperTypeInfo* info)
     96     {
     97         m_wrapperOrTypeInfo = reinterpret_cast<uintptr_t>(info);
     98         ASSERT(containsTypeInfo());
     99     }
    100 
    101     static bool wrapperCanBeStoredInObject(const void*) { return false; }
    102     static bool wrapperCanBeStoredInObject(const ScriptWrappable*) { return true; }
    103 
    104     static void setWrapperInObject(void*, v8::Handle<v8::Object>, v8::Isolate*, const WrapperConfiguration&)
    105     {
    106         ASSERT_NOT_REACHED();
    107     }
    108 
    109     static void setWrapperInObject(ScriptWrappable* object, v8::Handle<v8::Object> wrapper, v8::Isolate* isolate, const WrapperConfiguration& configuration)
    110     {
    111         object->setWrapper(wrapper, isolate, configuration);
    112     }
    113 
    114     static const WrapperTypeInfo* getTypeInfoFromObject(void* object)
    115     {
    116         ASSERT_NOT_REACHED();
    117         return 0;
    118     }
    119 
    120     static const WrapperTypeInfo* getTypeInfoFromObject(ScriptWrappable* object)
    121     {
    122         return object->typeInfo();
    123     }
    124 
    125     static void setTypeInfoInObject(void* object, const WrapperTypeInfo* info)
    126     {
    127         ASSERT_NOT_REACHED();
    128     }
    129 
    130     static void setTypeInfoInObject(ScriptWrappable* object, const WrapperTypeInfo* info)
    131     {
    132         object->setTypeInfo(info);
    133     }
    134 
    135 protected:
    136     ~ScriptWrappable()
    137     {
    138         ASSERT(m_wrapperOrTypeInfo);  // Assert initialization via init() even if not subsequently wrapped.
    139         m_wrapperOrTypeInfo = 0;      // Break UAF attempts to wrap.
    140     }
    141 
    142 private:
    143     // For calling unsafePersistent and getWrapperFromObject.
    144     friend class MinorGCWrapperVisitor;
    145     friend class DOMDataStore;
    146 
    147     UnsafePersistent<v8::Object> unsafePersistent() const
    148     {
    149         v8::Object* object = containsWrapper() ? reinterpret_cast<v8::Object*>(m_wrapperOrTypeInfo & ~1) : 0;
    150         return UnsafePersistent<v8::Object>(object);
    151     }
    152 
    153     static UnsafePersistent<v8::Object> getUnsafeWrapperFromObject(void*)
    154     {
    155         ASSERT_NOT_REACHED();
    156         return UnsafePersistent<v8::Object>();
    157     }
    158 
    159     static UnsafePersistent<v8::Object> getUnsafeWrapperFromObject(ScriptWrappable* object)
    160     {
    161         return object->unsafePersistent();
    162     }
    163 
    164     inline bool containsWrapper() const { return (m_wrapperOrTypeInfo & 1) == 1; }
    165     inline bool containsTypeInfo() const { return m_wrapperOrTypeInfo && (m_wrapperOrTypeInfo & 1) == 0; }
    166 
    167     inline void disposeWrapper(v8::Persistent<v8::Object>* value, const WrapperTypeInfo* info)
    168     {
    169         ASSERT(containsWrapper());
    170         ASSERT(*reinterpret_cast<uintptr_t*>(value) == (m_wrapperOrTypeInfo & ~1));
    171         value->Dispose();
    172         setTypeInfo(info);
    173     }
    174 
    175     // If zero, then this contains nothing, otherwise:
    176     //   If the bottom bit it set, then this contains a pointer to a wrapper object in the remainging bits.
    177     //   If the bottom bit is clear, then this contains a pointer to the wrapper type info in the remaining bits.
    178     uintptr_t m_wrapperOrTypeInfo;
    179 
    180     static void makeWeakCallback(v8::Isolate* isolate, v8::Persistent<v8::Object>* wrapper, ScriptWrappable* key)
    181     {
    182         ASSERT(key->unsafePersistent().deprecatedHandle() == *wrapper);
    183 
    184         // Note: |object| might not be equal to |key|, e.g., if ScriptWrappable isn't a left-most base class.
    185         void* object = toNative(*wrapper);
    186         WrapperTypeInfo* info = toWrapperTypeInfo(*wrapper);
    187         ASSERT(info->derefObjectFunction);
    188 
    189         key->disposeWrapper(wrapper, info);
    190         // FIXME: I noticed that 50%~ of minor GC cycle times can be consumed
    191         // inside key->deref(), which causes Node destructions. We should
    192         // make Node destructions incremental.
    193         info->derefObject(object);
    194     }
    195 };
    196 
    197 } // namespace WebCore
    198 
    199 #endif // ScriptWrappable_h
    200