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      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 
     55   static Offset LocalRefCookieOffset() {
     56     return Offset(OFFSETOF_MEMBER(JNIEnvExt, local_ref_cookie));
     57   }
     58 
     59   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:
    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 
    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