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/*
* Copyright (C) 2015 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_CLASS_TABLE_H_
#define ART_RUNTIME_CLASS_TABLE_H_
#include <string>
#include <utility>
#include <vector>
#include "base/allocator.h"
#include "base/hash_set.h"
#include "base/macros.h"
#include "base/mutex.h"
#include "gc_root.h"
#include "obj_ptr.h"
namespace art {
class OatFile;
namespace linker {
class ImageWriter;
} // namespace linker
namespace linker {
class OatWriter;
} // namespace linker
namespace mirror {
class Class;
class ClassLoader;
class Object;
} // namespace mirror
// Each loader has a ClassTable
class ClassTable {
public:
class TableSlot {
public:
TableSlot() : data_(0u) {}
TableSlot(const TableSlot& copy) : data_(copy.data_.load(std::memory_order_relaxed)) {}
explicit TableSlot(ObjPtr<mirror::Class> klass);
TableSlot(ObjPtr<mirror::Class> klass, uint32_t descriptor_hash);
TableSlot& operator=(const TableSlot& copy) {
data_.store(copy.data_.load(std::memory_order_relaxed), std::memory_order_relaxed);
return *this;
}
bool IsNull() const REQUIRES_SHARED(Locks::mutator_lock_);
uint32_t Hash() const {
return MaskHash(data_.load(std::memory_order_relaxed));
}
static uint32_t MaskHash(uint32_t hash) {
return hash & kHashMask;
}
bool MaskedHashEquals(uint32_t other) const {
return MaskHash(other) == Hash();
}
template<ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
ObjPtr<mirror::Class> Read() const REQUIRES_SHARED(Locks::mutator_lock_);
// NO_THREAD_SAFETY_ANALYSIS since the visitor may require heap bitmap lock.
template<typename Visitor>
void VisitRoot(const Visitor& visitor) const NO_THREAD_SAFETY_ANALYSIS;
private:
// Extract a raw pointer from an address.
static ObjPtr<mirror::Class> ExtractPtr(uint32_t data)
REQUIRES_SHARED(Locks::mutator_lock_);
static uint32_t Encode(ObjPtr<mirror::Class> klass, uint32_t hash_bits)
REQUIRES_SHARED(Locks::mutator_lock_);
// Data contains the class pointer GcRoot as well as the low bits of the descriptor hash.
mutable Atomic<uint32_t> data_;
static constexpr uint32_t kHashMask = kObjectAlignment - 1;
};
using DescriptorHashPair = std::pair<const char*, uint32_t>;
class ClassDescriptorHash {
public:
// uint32_t for cross compilation.
uint32_t operator()(const TableSlot& slot) const NO_THREAD_SAFETY_ANALYSIS;
// uint32_t for cross compilation.
uint32_t operator()(const DescriptorHashPair& pair) const NO_THREAD_SAFETY_ANALYSIS;
};
class ClassDescriptorEquals {
public:
// Same class loader and descriptor.
bool operator()(const TableSlot& a, const TableSlot& b) const
NO_THREAD_SAFETY_ANALYSIS;
// Same descriptor.
bool operator()(const TableSlot& a, const DescriptorHashPair& b) const
NO_THREAD_SAFETY_ANALYSIS;
};
class TableSlotEmptyFn {
public:
void MakeEmpty(TableSlot& item) const NO_THREAD_SAFETY_ANALYSIS {
item = TableSlot();
DCHECK(IsEmpty(item));
}
bool IsEmpty(const TableSlot& item) const NO_THREAD_SAFETY_ANALYSIS {
return item.IsNull();
}
};
// Hash set that hashes class descriptor, and compares descriptors and class loaders. Results
// should be compared for a matching class descriptor and class loader.
using ClassSet = HashSet<TableSlot,
TableSlotEmptyFn,
ClassDescriptorHash,
ClassDescriptorEquals,
TrackingAllocator<TableSlot, kAllocatorTagClassTable>>;
ClassTable();
// Freeze the current class tables by allocating a new table and never updating or modifying the
// existing table. This helps prevents dirty pages after caused by inserting after zygote fork.
void FreezeSnapshot()
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Returns the number of classes in previous snapshots defined by `defining_loader`.
size_t NumZygoteClasses(ObjPtr<mirror::ClassLoader> defining_loader) const
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Returns all off the classes in the lastest snapshot defined by `defining_loader`.
size_t NumNonZygoteClasses(ObjPtr<mirror::ClassLoader> defining_loader) const
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Returns the number of classes in previous snapshots no matter the defining loader.
size_t NumReferencedZygoteClasses() const
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Returns all off the classes in the lastest snapshot no matter the defining loader.
size_t NumReferencedNonZygoteClasses() const
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Update a class in the table with the new class. Returns the existing class which was replaced.
ObjPtr<mirror::Class> UpdateClass(const char* descriptor,
ObjPtr<mirror::Class> new_klass,
size_t hash)
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// NO_THREAD_SAFETY_ANALYSIS for object marking requiring heap bitmap lock.
template<class Visitor>
void VisitRoots(Visitor& visitor)
NO_THREAD_SAFETY_ANALYSIS
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
template<class Visitor>
void VisitRoots(const Visitor& visitor)
NO_THREAD_SAFETY_ANALYSIS
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Stops visit if the visitor returns false.
template <ReadBarrierOption kReadBarrierOption = kWithReadBarrier, typename Visitor>
bool Visit(Visitor& visitor)
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
template <ReadBarrierOption kReadBarrierOption = kWithReadBarrier, typename Visitor>
bool Visit(const Visitor& visitor)
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Return the first class that matches the descriptor. Returns null if there are none.
ObjPtr<mirror::Class> Lookup(const char* descriptor, size_t hash)
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Return the first class that matches the descriptor of klass. Returns null if there are none.
// Used for tests and debug-build checks.
ObjPtr<mirror::Class> LookupByDescriptor(ObjPtr<mirror::Class> klass)
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
void Insert(ObjPtr<mirror::Class> klass)
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
void InsertWithHash(ObjPtr<mirror::Class> klass, size_t hash)
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Return true if we inserted the strong root, false if it already exists.
bool InsertStrongRoot(ObjPtr<mirror::Object> obj)
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Return true if we inserted the oat file, false if it already exists.
bool InsertOatFile(const OatFile* oat_file)
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Read a table from ptr and put it at the front of the class set.
size_t ReadFromMemory(uint8_t* ptr)
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Add a class set to the front of classes.
void AddClassSet(ClassSet&& set)
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Clear strong roots (other than classes themselves).
void ClearStrongRoots()
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Filter strong roots (other than classes themselves).
template <typename Filter>
void RemoveStrongRoots(const Filter& filter)
REQUIRES(!lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
ReaderWriterMutex& GetLock() {
return lock_;
}
private:
size_t CountDefiningLoaderClasses(ObjPtr<mirror::ClassLoader> defining_loader,
const ClassSet& set) const
REQUIRES(lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Return true if we inserted the oat file, false if it already exists.
bool InsertOatFileLocked(const OatFile* oat_file)
REQUIRES(lock_)
REQUIRES_SHARED(Locks::mutator_lock_);
// Lock to guard inserting and removing.
mutable ReaderWriterMutex lock_;
// We have a vector to help prevent dirty pages after the zygote forks by calling FreezeSnapshot.
std::vector<ClassSet> classes_ GUARDED_BY(lock_);
// Extra strong roots that can be either dex files or dex caches. Dex files used by the class
// loader which may not be owned by the class loader must be held strongly live. Also dex caches
// are held live to prevent them being unloading once they have classes in them.
std::vector<GcRoot<mirror::Object>> strong_roots_ GUARDED_BY(lock_);
// Keep track of oat files with GC roots associated with dex caches in `strong_roots_`.
std::vector<const OatFile*> oat_files_ GUARDED_BY(lock_);
friend class linker::ImageWriter; // for InsertWithoutLocks.
};
} // namespace art
#endif // ART_RUNTIME_CLASS_TABLE_H_