1 /*
2  * Copyright (C) 2011 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_JNI_ENV_EXT_H_
18 #define ART_RUNTIME_JNI_ENV_EXT_H_
19 
20 #include <jni.h>
21 
22 #include "base/macros.h"
23 #include "base/mutex.h"
24 #include "indirect_reference_table.h"
25 #include "object_callbacks.h"
26 #include "reference_table.h"
27 
28 namespace art {
29 
30 class JavaVMExt;
31 
32 // Maximum number of local references in the indirect reference table. The value is arbitrary but
33 // low enough that it forces sanity checks.
34 static constexpr size_t kLocalsMax = 512;
35 
36 struct JNIEnvExt : public JNIEnv {
37   static JNIEnvExt* Create(Thread* self, JavaVMExt* vm);
38 
39   ~JNIEnvExt();
40 
41   void DumpReferenceTables(std::ostream& os)
42       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
43 
44   void SetCheckJniEnabled(bool enabled);
45 
46   void PushFrame(int capacity);
47   void PopFrame();
48 
49   template<typename T>
50   T AddLocalReference(mirror::Object* obj)
51       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
52 
53   static Offset SegmentStateOffset();
54 
LocalRefCookieOffsetJNIEnvExt55   static Offset LocalRefCookieOffset() {
56     return Offset(OFFSETOF_MEMBER(JNIEnvExt, local_ref_cookie));
57   }
58 
SelfOffsetJNIEnvExt59   static Offset SelfOffset() {
60     return Offset(OFFSETOF_MEMBER(JNIEnvExt, self));
61   }
62 
63   jobject NewLocalRef(mirror::Object* obj) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
64   void DeleteLocalRef(jobject obj) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
65 
66   Thread* const self;
67   JavaVMExt* const vm;
68 
69   // Cookie used when using the local indirect reference table.
70   uint32_t local_ref_cookie;
71 
72   // JNI local references.
73   IndirectReferenceTable locals GUARDED_BY(Locks::mutator_lock_);
74 
75   // Stack of cookies corresponding to PushLocalFrame/PopLocalFrame calls.
76   // TODO: to avoid leaks (and bugs), we need to clear this vector on entry (or return)
77   // to a native method.
78   std::vector<uint32_t> stacked_local_ref_cookies;
79 
80   // Frequently-accessed fields cached from JavaVM.
81   bool check_jni;
82 
83   // How many nested "critical" JNI calls are we in?
84   int critical;
85 
86   // Entered JNI monitors, for bulk exit on thread detach.
87   ReferenceTable monitors;
88 
89   // Used by -Xcheck:jni.
90   const JNINativeInterface* unchecked_functions;
91 
92  private:
93   // The constructor should not be called directly. It may leave the object in an erronuous state,
94   // and the result needs to be checked.
95   JNIEnvExt(Thread* self, JavaVMExt* vm);
96 };
97 
98 // Used to save and restore the JNIEnvExt state when not going through code created by the JNI
99 // compiler.
100 class ScopedJniEnvLocalRefState {
101  public:
ScopedJniEnvLocalRefState(JNIEnvExt * env)102   explicit ScopedJniEnvLocalRefState(JNIEnvExt* env) : env_(env) {
103     saved_local_ref_cookie_ = env->local_ref_cookie;
104     env->local_ref_cookie = env->locals.GetSegmentState();
105   }
106 
~ScopedJniEnvLocalRefState()107   ~ScopedJniEnvLocalRefState() {
108     env_->locals.SetSegmentState(env_->local_ref_cookie);
109     env_->local_ref_cookie = saved_local_ref_cookie_;
110   }
111 
112  private:
113   JNIEnvExt* const env_;
114   uint32_t saved_local_ref_cookie_;
115 
116   DISALLOW_COPY_AND_ASSIGN(ScopedJniEnvLocalRefState);
117 };
118 
119 }  // namespace art
120 
121 #endif  // ART_RUNTIME_JNI_ENV_EXT_H_
122