Hi everyone,
For some research reason, I need to log all property access to Blink in v8.
Since all the property load information is passed to Blink through class
`FunctionCallbackInfo`, I tried to add a pointer field in this class to
hold the property name (represented as std::string) like follow:
V8_INLINE FunctionCallbackInfo(internal::Address* implicit_args,
internal::Address* values, int length);
internal::Address* implicit_args_;
internal::Address* values_;
int length_;
std::string* property_info_; // The field I add.
}
The `property_info_` field is initialized in the constructor function
through c++ `new`.
I also added a const setter function for the `property_info_` field. The
setter function like follow:
void FunctionCallbackInfo<T>::SetPropertyInfo(::std::string s) const {
*property_info_ = s;
}
In Blink, I modified the template file to set this field every time an
attribute in Blink is visited.
In code snips I write by myself, it works well. However, when I try to run
the code on some real-world websites, I found that the value of the field
property_info_ is set to a strange value 0x38, so the pointer to the string
is overlapped by some other value.
I tried to mark the property_info_ field as private and even moved it to
class `ReturnValue<T>`, the overlapping case still happens:
template<typename T>
class ReturnValue {
public:
template <class S> V8_INLINE ReturnValue(const ReturnValue<S>& that)
: value_(that.value_) {
TYPE_CHECK(T, S);
}
// Local setters
template <typename S>
V8_INLINE void Set(const Global<S>& handle);
template <typename S>
V8_INLINE void Set(const TracedGlobal<S>& handle);
template <typename S>
V8_INLINE void Set(const Local<S> handle);
// Fast primitive setters
V8_INLINE void Set(bool value);
V8_INLINE void Set(double i);
V8_INLINE void Set(int32_t i);
V8_INLINE void Set(uint32_t i);
// Fast JS primitive setters
V8_INLINE void SetNull();
V8_INLINE void SetUndefined();
V8_INLINE void SetEmptyString();
// Convenience getter for Isolate
V8_INLINE Isolate* GetIsolate() const;
// Pointer setter: Uncompilable to prevent inadvertent misuse.
template <typename S>
V8_INLINE void Set(S* whatever);
// Getter. Creates a new Local<> so it comes with a certain performance
// hit. If the ReturnValue was not yet set, this will return the undefined
// value.
V8_INLINE Local<Value> Get() const;
// use for taint map by n0b0dy
V8_INLINE internal::Address GetValueAddr() const;
V8_INLINE void SetProperty(std::string) const; // The setter function I
add
private:
template<class F> friend class ReturnValue;
template<class F> friend class FunctionCallbackInfo;
template<class F> friend class PropertyCallbackInfo;
template <class F, class G, class H>
friend class PersistentValueMapBase;
V8_INLINE void SetInternal(internal::Address value) { *value_ = value; }
V8_INLINE internal::Address GetDefaultValue();
V8_INLINE explicit ReturnValue(internal::Address* slot);
internal::Address* value_;
internal::Address* property_info_; // the field I add
};
I read the in
https://source.chromium.org/chromium/chromium/src/+/master:v8/src/builtins/x64/builtins-x64.cc;drc=34ad93361f96ad875bf350ced27e15b7aa126113;bpv=1;bpt=1;l=3317
and found that v8 will arrange the stack frame with its own call
convention, But I didn't find why the pointer value is still overlapped in
class ReturnValue.
Does anyone have ideas about what should I do?
Thanks a lot!
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