300 lines
11 KiB
C++
300 lines
11 KiB
C++
/*
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* Copyright (C) 2011 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <ctime>
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#include "object.h"
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#include "array-inl.h"
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#include "art_field-inl.h"
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#include "art_field.h"
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#include "class-inl.h"
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#include "class.h"
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#include "class_linker-inl.h"
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#include "dex/descriptors_names.h"
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#include "dex/dex_file-inl.h"
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#include "gc/accounting/card_table-inl.h"
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#include "gc/heap-inl.h"
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#include "handle_scope-inl.h"
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#include "iftable-inl.h"
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#include "monitor.h"
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#include "object-inl.h"
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#include "object-refvisitor-inl.h"
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#include "object_array-inl.h"
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#include "runtime.h"
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#include "throwable.h"
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#include "well_known_classes.h"
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namespace art {
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namespace mirror {
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Atomic<uint32_t> Object::hash_code_seed(987654321U + std::time(nullptr));
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class CopyReferenceFieldsWithReadBarrierVisitor {
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public:
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explicit CopyReferenceFieldsWithReadBarrierVisitor(ObjPtr<Object> dest_obj)
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: dest_obj_(dest_obj) {}
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void operator()(ObjPtr<Object> obj, MemberOffset offset, bool /* is_static */) const
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ALWAYS_INLINE REQUIRES_SHARED(Locks::mutator_lock_) {
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// GetFieldObject() contains a RB.
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ObjPtr<Object> ref = obj->GetFieldObject<Object>(offset);
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// No WB here as a large object space does not have a card table
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// coverage. Instead, cards will be marked separately.
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dest_obj_->SetFieldObjectWithoutWriteBarrier<false, false>(offset, ref);
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}
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void operator()(ObjPtr<mirror::Class> klass, ObjPtr<mirror::Reference> ref) const
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ALWAYS_INLINE REQUIRES_SHARED(Locks::mutator_lock_) {
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// Copy java.lang.ref.Reference.referent which isn't visited in
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// Object::VisitReferences().
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DCHECK(klass->IsTypeOfReferenceClass());
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this->operator()(ref, mirror::Reference::ReferentOffset(), false);
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}
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// Unused since we don't copy class native roots.
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void VisitRootIfNonNull(mirror::CompressedReference<mirror::Object>* root ATTRIBUTE_UNUSED)
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const {}
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void VisitRoot(mirror::CompressedReference<mirror::Object>* root ATTRIBUTE_UNUSED) const {}
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private:
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const ObjPtr<Object> dest_obj_;
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};
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ObjPtr<Object> Object::CopyObject(ObjPtr<mirror::Object> dest,
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ObjPtr<mirror::Object> src,
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size_t num_bytes) {
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// Copy instance data. Don't assume memcpy copies by words (b/32012820).
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{
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const size_t offset = sizeof(Object);
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uint8_t* src_bytes = reinterpret_cast<uint8_t*>(src.Ptr()) + offset;
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uint8_t* dst_bytes = reinterpret_cast<uint8_t*>(dest.Ptr()) + offset;
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num_bytes -= offset;
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DCHECK_ALIGNED(src_bytes, sizeof(uintptr_t));
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DCHECK_ALIGNED(dst_bytes, sizeof(uintptr_t));
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// Use word sized copies to begin.
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while (num_bytes >= sizeof(uintptr_t)) {
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reinterpret_cast<Atomic<uintptr_t>*>(dst_bytes)->store(
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reinterpret_cast<Atomic<uintptr_t>*>(src_bytes)->load(std::memory_order_relaxed),
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std::memory_order_relaxed);
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src_bytes += sizeof(uintptr_t);
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dst_bytes += sizeof(uintptr_t);
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num_bytes -= sizeof(uintptr_t);
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}
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// Copy possible 32 bit word.
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if (sizeof(uintptr_t) != sizeof(uint32_t) && num_bytes >= sizeof(uint32_t)) {
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reinterpret_cast<Atomic<uint32_t>*>(dst_bytes)->store(
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reinterpret_cast<Atomic<uint32_t>*>(src_bytes)->load(std::memory_order_relaxed),
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std::memory_order_relaxed);
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src_bytes += sizeof(uint32_t);
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dst_bytes += sizeof(uint32_t);
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num_bytes -= sizeof(uint32_t);
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}
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// Copy remaining bytes, avoid going past the end of num_bytes since there may be a redzone
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// there.
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while (num_bytes > 0) {
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reinterpret_cast<Atomic<uint8_t>*>(dst_bytes)->store(
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reinterpret_cast<Atomic<uint8_t>*>(src_bytes)->load(std::memory_order_relaxed),
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std::memory_order_relaxed);
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src_bytes += sizeof(uint8_t);
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dst_bytes += sizeof(uint8_t);
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num_bytes -= sizeof(uint8_t);
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}
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}
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if (kUseReadBarrier) {
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// We need a RB here. After copying the whole object above, copy references fields one by one
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// again with a RB to make sure there are no from space refs. TODO: Optimize this later?
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CopyReferenceFieldsWithReadBarrierVisitor visitor(dest);
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src->VisitReferences(visitor, visitor);
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}
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// Perform write barriers on copied object references.
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ObjPtr<Class> c = src->GetClass();
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if (c->IsArrayClass()) {
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if (!c->GetComponentType()->IsPrimitive()) {
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ObjPtr<ObjectArray<Object>> array = dest->AsObjectArray<Object>();
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WriteBarrier::ForArrayWrite(dest, 0, array->GetLength());
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}
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} else {
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WriteBarrier::ForEveryFieldWrite(dest);
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}
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return dest;
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}
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// An allocation pre-fence visitor that copies the object.
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class CopyObjectVisitor {
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public:
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CopyObjectVisitor(Handle<Object>* orig, size_t num_bytes)
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: orig_(orig), num_bytes_(num_bytes) {}
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void operator()(ObjPtr<Object> obj, size_t usable_size ATTRIBUTE_UNUSED) const
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REQUIRES_SHARED(Locks::mutator_lock_) {
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Object::CopyObject(obj, orig_->Get(), num_bytes_);
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}
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private:
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Handle<Object>* const orig_;
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const size_t num_bytes_;
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DISALLOW_COPY_AND_ASSIGN(CopyObjectVisitor);
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};
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ObjPtr<Object> Object::Clone(Handle<Object> h_this, Thread* self) {
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CHECK(!h_this->IsClass()) << "Can't clone classes.";
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// Object::SizeOf gets the right size even if we're an array. Using c->AllocObject() here would
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// be wrong.
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gc::Heap* heap = Runtime::Current()->GetHeap();
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size_t num_bytes = h_this->SizeOf();
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CopyObjectVisitor visitor(&h_this, num_bytes);
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ObjPtr<Object> copy = heap->IsMovableObject(h_this.Get())
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? heap->AllocObject(self, h_this->GetClass(), num_bytes, visitor)
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: heap->AllocNonMovableObject(self, h_this->GetClass(), num_bytes, visitor);
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if (h_this->GetClass()->IsFinalizable()) {
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heap->AddFinalizerReference(self, ©);
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}
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return copy;
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}
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uint32_t Object::GenerateIdentityHashCode() {
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uint32_t expected_value, new_value;
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do {
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expected_value = hash_code_seed.load(std::memory_order_relaxed);
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new_value = expected_value * 1103515245 + 12345;
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} while (!hash_code_seed.CompareAndSetWeakRelaxed(expected_value, new_value) ||
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(expected_value & LockWord::kHashMask) == 0);
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return expected_value & LockWord::kHashMask;
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}
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void Object::SetHashCodeSeed(uint32_t new_seed) {
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hash_code_seed.store(new_seed, std::memory_order_relaxed);
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}
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int32_t Object::IdentityHashCode() {
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ObjPtr<Object> current_this = this; // The this pointer may get invalidated by thread suspension.
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while (true) {
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LockWord lw = current_this->GetLockWord(false);
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switch (lw.GetState()) {
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case LockWord::kUnlocked: {
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// Try to compare and swap in a new hash, if we succeed we will return the hash on the next
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// loop iteration.
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LockWord hash_word = LockWord::FromHashCode(GenerateIdentityHashCode(), lw.GCState());
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DCHECK_EQ(hash_word.GetState(), LockWord::kHashCode);
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// Use a strong CAS to prevent spurious failures since these can make the boot image
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// non-deterministic.
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if (current_this->CasLockWord(lw, hash_word, CASMode::kStrong, std::memory_order_relaxed)) {
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return hash_word.GetHashCode();
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}
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break;
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}
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case LockWord::kThinLocked: {
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// Inflate the thin lock to a monitor and stick the hash code inside of the monitor. May
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// fail spuriously.
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Thread* self = Thread::Current();
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StackHandleScope<1> hs(self);
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Handle<mirror::Object> h_this(hs.NewHandle(current_this));
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Monitor::InflateThinLocked(self, h_this, lw, GenerateIdentityHashCode());
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// A GC may have occurred when we switched to kBlocked.
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current_this = h_this.Get();
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break;
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}
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case LockWord::kFatLocked: {
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// Already inflated, return the hash stored in the monitor.
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Monitor* monitor = lw.FatLockMonitor();
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DCHECK(monitor != nullptr);
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return monitor->GetHashCode();
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}
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case LockWord::kHashCode: {
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return lw.GetHashCode();
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}
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default: {
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LOG(FATAL) << "Invalid state during hashcode " << lw.GetState();
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UNREACHABLE();
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}
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}
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}
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}
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void Object::CheckFieldAssignmentImpl(MemberOffset field_offset, ObjPtr<Object> new_value) {
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ObjPtr<Class> c = GetClass();
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Runtime* runtime = Runtime::Current();
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if (runtime->GetClassLinker() == nullptr || !runtime->IsStarted() ||
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!runtime->GetHeap()->IsObjectValidationEnabled() || !c->IsResolved()) {
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return;
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}
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for (ObjPtr<Class> cur = c; cur != nullptr; cur = cur->GetSuperClass()) {
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for (ArtField& field : cur->GetIFields()) {
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if (field.GetOffset().Int32Value() == field_offset.Int32Value()) {
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CHECK_NE(field.GetTypeAsPrimitiveType(), Primitive::kPrimNot);
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// TODO: resolve the field type for moving GC.
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ObjPtr<mirror::Class> field_type =
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kMovingCollector ? field.LookupResolvedType() : field.ResolveType();
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if (field_type != nullptr) {
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CHECK(field_type->IsAssignableFrom(new_value->GetClass()));
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}
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return;
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}
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}
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}
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if (c->IsArrayClass()) {
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// Bounds and assign-ability done in the array setter.
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return;
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}
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if (IsClass()) {
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for (ArtField& field : AsClass()->GetSFields()) {
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if (field.GetOffset().Int32Value() == field_offset.Int32Value()) {
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CHECK_NE(field.GetTypeAsPrimitiveType(), Primitive::kPrimNot);
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// TODO: resolve the field type for moving GC.
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ObjPtr<mirror::Class> field_type =
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kMovingCollector ? field.LookupResolvedType() : field.ResolveType();
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if (field_type != nullptr) {
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CHECK(field_type->IsAssignableFrom(new_value->GetClass()));
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}
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return;
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}
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}
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}
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LOG(FATAL) << "Failed to find field for assignment to " << reinterpret_cast<void*>(this)
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<< " of type " << c->PrettyDescriptor() << " at offset " << field_offset;
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UNREACHABLE();
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}
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ArtField* Object::FindFieldByOffset(MemberOffset offset) {
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return IsClass() ? ArtField::FindStaticFieldWithOffset(AsClass(), offset.Uint32Value())
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: ArtField::FindInstanceFieldWithOffset(GetClass(), offset.Uint32Value());
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}
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std::string Object::PrettyTypeOf(ObjPtr<mirror::Object> obj) {
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return (obj == nullptr) ? "null" : obj->PrettyTypeOf();
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}
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std::string Object::PrettyTypeOf() {
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// From-space version is the same as the to-space version since the dex file never changes.
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// Avoiding the read barrier here is important to prevent recursive AssertToSpaceInvariant
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// issues.
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ObjPtr<mirror::Class> klass = GetClass<kDefaultVerifyFlags, kWithoutReadBarrier>();
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if (klass == nullptr) {
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return "(raw)";
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}
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std::string temp;
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std::string result(PrettyDescriptor(klass->GetDescriptor(&temp)));
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if (klass->IsClassClass()) {
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result += "<" + PrettyDescriptor(AsClass()->GetDescriptor(&temp)) + ">";
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}
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return result;
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}
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} // namespace mirror
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} // namespace art
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