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 "jni.h"
23 #include "mirror/object_reference.h"
24 #include "offsets.h"
25 #include "read_barrier_c.h"
26 
27 // This is a C++ (not C) header file, separate from read_barrier_c.h
28 // which needs to be a C header file for asm_support.h.
29 
30 namespace art {
31 namespace mirror {
32   class Object;
33   template<typename MirrorType> class HeapReference;
34 }  // namespace mirror
35 class ArtMethod;
36 
37 class ReadBarrier {
38  public:
39   // TODO: disable thse flags for production use.
40   // Enable the to-space invariant checks.
41   static constexpr bool kEnableToSpaceInvariantChecks = true;
42   // Enable the read barrier checks.
43   static constexpr bool kEnableReadBarrierInvariantChecks = true;
44 
45   // It's up to the implementation whether the given field gets
46   // updated whereas the return value must be an updated reference.
47   template <typename MirrorType, ReadBarrierOption kReadBarrierOption = kWithReadBarrier,
48             bool kMaybeDuringStartup = false>
49   ALWAYS_INLINE static MirrorType* Barrier(
50       mirror::Object* obj, MemberOffset offset, mirror::HeapReference<MirrorType>* ref_addr)
51       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
52 
53   // It's up to the implementation whether the given root gets updated
54   // whereas the return value must be an updated reference.
55   template <typename MirrorType, ReadBarrierOption kReadBarrierOption = kWithReadBarrier,
56             bool kMaybeDuringStartup = false>
57   ALWAYS_INLINE static MirrorType* BarrierForRoot(MirrorType** root)
58       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
59 
60   // It's up to the implementation whether the given root gets updated
61   // whereas the return value must be an updated reference.
62   template <typename MirrorType, ReadBarrierOption kReadBarrierOption = kWithReadBarrier,
63             bool kMaybeDuringStartup = false>
64   ALWAYS_INLINE static MirrorType* BarrierForRoot(mirror::CompressedReference<MirrorType>* root)
65       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
66 
67   static bool IsDuringStartup();
68 
69   // Without the holder object.
AssertToSpaceInvariant(mirror::Object * ref)70   static void AssertToSpaceInvariant(mirror::Object* ref)
71       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
72     AssertToSpaceInvariant(nullptr, MemberOffset(0), ref);
73   }
74   // With the holder object.
75   static void AssertToSpaceInvariant(mirror::Object* obj, MemberOffset offset,
76                                      mirror::Object* ref)
77       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
78 
79   static mirror::Object* Mark(mirror::Object* obj) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
80 
WhitePtr()81   static mirror::Object* WhitePtr() {
82     return reinterpret_cast<mirror::Object*>(white_ptr_);
83   }
GrayPtr()84   static mirror::Object* GrayPtr() {
85     return reinterpret_cast<mirror::Object*>(gray_ptr_);
86   }
BlackPtr()87   static mirror::Object* BlackPtr() {
88     return reinterpret_cast<mirror::Object*>(black_ptr_);
89   }
90 
91   ALWAYS_INLINE static bool HasGrayReadBarrierPointer(mirror::Object* obj,
92                                                       uintptr_t* out_rb_ptr_high_bits)
93       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
94 
95   // Note: These couldn't be constexpr pointers as reinterpret_cast isn't compatible with them.
96   static constexpr uintptr_t white_ptr_ = 0x0;    // Not marked.
97   static constexpr uintptr_t gray_ptr_ = 0x1;     // Marked, but not marked through. On mark stack.
98   static constexpr uintptr_t black_ptr_ = 0x2;    // Marked through. Used for non-moving objects.
99   static constexpr uintptr_t rb_ptr_mask_ = 0x3;  // The low 2 bits for white|gray|black.
100 };
101 
102 }  // namespace art
103 
104 #endif  // ART_RUNTIME_READ_BARRIER_H_
105