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aosp12/art/runtime/mirror/object_reference.h

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/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ART_RUNTIME_MIRROR_OBJECT_REFERENCE_H_
#define ART_RUNTIME_MIRROR_OBJECT_REFERENCE_H_
#include <array>
#include <string_view>
#include "base/atomic.h"
#include "base/locks.h" // For Locks::mutator_lock_.
#include "heap_poisoning.h"
#include "obj_ptr.h"
#include "runtime_globals.h"
namespace art {
namespace mirror {
class Object;
// Classes shared with the managed side of the world need to be packed so that they don't have
// extra platform specific padding.
#define MANAGED PACKED(4)
#define MIRROR_CLASS(desc) \
static_assert(::art::mirror::IsMirroredDescriptor(desc), \
desc " is not a known mirror class. Please update" \
" IsMirroredDescriptor to include it!")
constexpr bool IsMirroredDescriptor(std::string_view desc) {
if (desc[0] != 'L') {
// All primitives and arrays are mirrored
return true;
}
#define MIRROR_DESCRIPTORS(vis) \
vis("Ljava/lang/Class;") \
vis("Ljava/lang/ClassLoader;") \
vis("Ljava/lang/ClassNotFoundException;") \
vis("Ljava/lang/DexCache;") \
vis("Ljava/lang/Object;") \
vis("Ljava/lang/StackTraceElement;") \
vis("Ljava/lang/String;") \
vis("Ljava/lang/Throwable;") \
vis("Ljava/lang/invoke/ArrayElementVarHandle;") \
vis("Ljava/lang/invoke/ByteArrayViewVarHandle;") \
vis("Ljava/lang/invoke/ByteBufferViewVarHandle;") \
vis("Ljava/lang/invoke/CallSite;") \
vis("Ljava/lang/invoke/FieldVarHandle;") \
vis("Ljava/lang/invoke/MethodHandle;") \
vis("Ljava/lang/invoke/MethodHandleImpl;") \
vis("Ljava/lang/invoke/MethodHandles$Lookup;") \
vis("Ljava/lang/invoke/MethodType;") \
vis("Ljava/lang/invoke/VarHandle;") \
vis("Ljava/lang/ref/FinalizerReference;") \
vis("Ljava/lang/ref/Reference;") \
vis("Ljava/lang/reflect/AccessibleObject;") \
vis("Ljava/lang/reflect/Constructor;") \
vis("Ljava/lang/reflect/Executable;") \
vis("Ljava/lang/reflect/Field;") \
vis("Ljava/lang/reflect/Method;") \
vis("Ljava/lang/reflect/Proxy;") \
vis("Ldalvik/system/ClassExt;") \
vis("Ldalvik/system/EmulatedStackFrame;")
// TODO: Once we are C++ 20 we can just have a constexpr array and std::find.
// constexpr std::array<std::string_view, 28> kMirrorTypes{
// // Fill in
// };
// return std::find(kMirrorTypes.begin(), kMirrorTypes.end(), desc) != kMirrorTypes.end();
#define CHECK_DESCRIPTOR(descriptor) \
if (std::string_view(descriptor) == desc) { \
return true; \
}
MIRROR_DESCRIPTORS(CHECK_DESCRIPTOR)
#undef CHECK_DESCRIPTOR
return false;
#undef MIRROR_DESCRIPTORS
}
template<bool kPoisonReferences, class MirrorType>
class PtrCompression {
public:
// Compress reference to its bit representation.
static uint32_t Compress(MirrorType* mirror_ptr) {
uintptr_t as_bits = reinterpret_cast<uintptr_t>(mirror_ptr);
return static_cast<uint32_t>(kPoisonReferences ? -as_bits : as_bits);
}
// Uncompress an encoded reference from its bit representation.
static MirrorType* Decompress(uint32_t ref) {
uintptr_t as_bits = kPoisonReferences ? -ref : ref;
return reinterpret_cast<MirrorType*>(as_bits);
}
// Convert an ObjPtr to a compressed reference.
static uint32_t Compress(ObjPtr<MirrorType> ptr) REQUIRES_SHARED(Locks::mutator_lock_);
};
// Value type representing a reference to a mirror::Object of type MirrorType.
template<bool kPoisonReferences, class MirrorType>
class MANAGED ObjectReference {
private:
using Compression = PtrCompression<kPoisonReferences, MirrorType>;
public:
/*
* Returns a pointer to the mirror of the managed object this reference is for.
*
* This does NOT return the current object (which isn't derived from, and
* therefor cannot be a mirror::Object) as a mirror pointer. Instead, this
* returns a pointer to the mirror of the managed object this refers to.
*
* TODO (chriswailes): Rename to GetPtr().
*/
MirrorType* AsMirrorPtr() const {
return Compression::Decompress(reference_);
}
void Assign(MirrorType* other) {
reference_ = Compression::Compress(other);
}
void Assign(ObjPtr<MirrorType> ptr) REQUIRES_SHARED(Locks::mutator_lock_);
void Clear() {
reference_ = 0;
DCHECK(IsNull());
}
bool IsNull() const {
return reference_ == 0;
}
uint32_t AsVRegValue() const {
return reference_;
}
static ObjectReference<kPoisonReferences, MirrorType> FromMirrorPtr(MirrorType* mirror_ptr)
REQUIRES_SHARED(Locks::mutator_lock_) {
return ObjectReference<kPoisonReferences, MirrorType>(mirror_ptr);
}
protected:
explicit ObjectReference(MirrorType* mirror_ptr) REQUIRES_SHARED(Locks::mutator_lock_)
: reference_(Compression::Compress(mirror_ptr)) {
}
// The encoded reference to a mirror::Object.
uint32_t reference_;
};
// References between objects within the managed heap.
// Similar API to ObjectReference, but not a value type. Supports atomic access.
template<class MirrorType>
class MANAGED HeapReference {
private:
using Compression = PtrCompression<kPoisonHeapReferences, MirrorType>;
public:
HeapReference() REQUIRES_SHARED(Locks::mutator_lock_) : HeapReference(nullptr) {}
template <bool kIsVolatile = false>
MirrorType* AsMirrorPtr() const REQUIRES_SHARED(Locks::mutator_lock_) {
return Compression::Decompress(
kIsVolatile ? reference_.load(std::memory_order_seq_cst) : reference_.LoadJavaData());
}
template <bool kIsVolatile = false>
void Assign(MirrorType* other) REQUIRES_SHARED(Locks::mutator_lock_) {
if (kIsVolatile) {
reference_.store(Compression::Compress(other), std::memory_order_seq_cst);
} else {
reference_.StoreJavaData(Compression::Compress(other));
}
}
template <bool kIsVolatile = false>
void Assign(ObjPtr<MirrorType> ptr) REQUIRES_SHARED(Locks::mutator_lock_);
void Clear() {
reference_.StoreJavaData(0);
DCHECK(IsNull());
}
bool IsNull() const {
return reference_.LoadJavaData() == 0;
}
static HeapReference<MirrorType> FromMirrorPtr(MirrorType* mirror_ptr)
REQUIRES_SHARED(Locks::mutator_lock_) {
return HeapReference<MirrorType>(mirror_ptr);
}
bool CasWeakRelaxed(MirrorType* old_ptr, MirrorType* new_ptr)
REQUIRES_SHARED(Locks::mutator_lock_);
private:
explicit HeapReference(MirrorType* mirror_ptr) REQUIRES_SHARED(Locks::mutator_lock_)
: reference_(Compression::Compress(mirror_ptr)) {}
// The encoded reference to a mirror::Object. Atomically updateable.
Atomic<uint32_t> reference_;
};
static_assert(sizeof(mirror::HeapReference<mirror::Object>) == kHeapReferenceSize,
"heap reference size does not match");
// Standard compressed reference used in the runtime. Used for StackReference and GC roots.
template<class MirrorType>
class MANAGED CompressedReference : public mirror::ObjectReference<false, MirrorType> {
public:
CompressedReference<MirrorType>() REQUIRES_SHARED(Locks::mutator_lock_)
: mirror::ObjectReference<false, MirrorType>(nullptr) {}
static CompressedReference<MirrorType> FromMirrorPtr(MirrorType* p)
REQUIRES_SHARED(Locks::mutator_lock_) {
return CompressedReference<MirrorType>(p);
}
private:
explicit CompressedReference(MirrorType* p) REQUIRES_SHARED(Locks::mutator_lock_)
: mirror::ObjectReference<false, MirrorType>(p) {}
};
} // namespace mirror
} // namespace art
#endif // ART_RUNTIME_MIRROR_OBJECT_REFERENCE_H_
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