1 /*
2  * Copyright (C) 2014 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #ifndef ART_RUNTIME_READ_BARRIER_H_
18 #define ART_RUNTIME_READ_BARRIER_H_
19 
20 #include "base/mutex.h"
21 #include "base/macros.h"
22 #include "gc_root.h"
23 #include "jni.h"
24 #include "mirror/object_reference.h"
25 #include "offsets.h"
26 #include "read_barrier_c.h"
27 
28 // This is a C++ (not C) header file, separate from read_barrier_c.h
29 // which needs to be a C header file for asm_support.h.
30 
31 namespace art {
32 namespace mirror {
33   class Object;
34   template<typename MirrorType> class HeapReference;
35 }  // namespace mirror
36 class ArtMethod;
37 
38 class ReadBarrier {
39  public:
40   // TODO: disable thse flags for production use.
41   // Enable the to-space invariant checks.
42   static constexpr bool kEnableToSpaceInvariantChecks = true;
43   // Enable the read barrier checks.
44   static constexpr bool kEnableReadBarrierInvariantChecks = true;
45 
46   // It's up to the implementation whether the given field gets updated whereas the return value
47   // must be an updated reference unless kAlwaysUpdateField is true.
48   template <typename MirrorType, ReadBarrierOption kReadBarrierOption = kWithReadBarrier,
49             bool kAlwaysUpdateField = false>
50   ALWAYS_INLINE static MirrorType* Barrier(
51       mirror::Object* obj, MemberOffset offset, mirror::HeapReference<MirrorType>* ref_addr)
52       SHARED_REQUIRES(Locks::mutator_lock_);
53 
54   // It's up to the implementation whether the given root gets updated
55   // whereas the return value must be an updated reference.
56   template <typename MirrorType, ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
57   ALWAYS_INLINE static MirrorType* BarrierForRoot(MirrorType** root,
58                                                   GcRootSource* gc_root_source = nullptr)
59       SHARED_REQUIRES(Locks::mutator_lock_);
60 
61   // It's up to the implementation whether the given root gets updated
62   // whereas the return value must be an updated reference.
63   template <typename MirrorType, ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
64   ALWAYS_INLINE static MirrorType* BarrierForRoot(mirror::CompressedReference<MirrorType>* root,
65                                                   GcRootSource* gc_root_source = nullptr)
66       SHARED_REQUIRES(Locks::mutator_lock_);
67 
68   static bool IsDuringStartup();
69 
70   // Without the holder object.
AssertToSpaceInvariant(mirror::Object * ref)71   static void AssertToSpaceInvariant(mirror::Object* ref)
72       SHARED_REQUIRES(Locks::mutator_lock_) {
73     AssertToSpaceInvariant(nullptr, MemberOffset(0), ref);
74   }
75   // With the holder object.
76   static void AssertToSpaceInvariant(mirror::Object* obj, MemberOffset offset,
77                                      mirror::Object* ref)
78       SHARED_REQUIRES(Locks::mutator_lock_);
79   // With GcRootSource.
80   static void AssertToSpaceInvariant(GcRootSource* gc_root_source, mirror::Object* ref)
81       SHARED_REQUIRES(Locks::mutator_lock_);
82 
83   // ALWAYS_INLINE on this caused a performance regression b/26744236.
84   static mirror::Object* Mark(mirror::Object* obj) SHARED_REQUIRES(Locks::mutator_lock_);
85 
WhitePtr()86   static mirror::Object* WhitePtr() {
87     return reinterpret_cast<mirror::Object*>(white_ptr_);
88   }
GrayPtr()89   static mirror::Object* GrayPtr() {
90     return reinterpret_cast<mirror::Object*>(gray_ptr_);
91   }
BlackPtr()92   static mirror::Object* BlackPtr() {
93     return reinterpret_cast<mirror::Object*>(black_ptr_);
94   }
95 
96   ALWAYS_INLINE static bool HasGrayReadBarrierPointer(mirror::Object* obj,
97                                                       uintptr_t* out_rb_ptr_high_bits)
98       SHARED_REQUIRES(Locks::mutator_lock_);
99 
100   // Note: These couldn't be constexpr pointers as reinterpret_cast isn't compatible with them.
101   static constexpr uintptr_t white_ptr_ = 0x0;    // Not marked.
102   static constexpr uintptr_t gray_ptr_ = 0x1;     // Marked, but not marked through. On mark stack.
103   static constexpr uintptr_t black_ptr_ = 0x2;    // Marked through. Used for non-moving objects.
104   static constexpr uintptr_t rb_ptr_mask_ = 0x3;  // The low 2 bits for white|gray|black.
105 };
106 
107 }  // namespace art
108 
109 #endif  // ART_RUNTIME_READ_BARRIER_H_
110