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* Copyright (C) 2011 The Android Open Source Project
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <jni.h>
#include "base/macros.h"
#include "base/mutex.h"
#include "indirect_reference_table.h"
#include "obj_ptr.h"
#include "reference_table.h"
namespace art {
class JavaVMExt;
namespace mirror {
class Object;
} // namespace mirror
// Number of local references in the indirect reference table. The value is arbitrary but
// low enough that it forces sanity checks.
static constexpr size_t kLocalsInitial = 512;
class JNIEnvExt : public JNIEnv {
// Creates a new JNIEnvExt. Returns null on error, in which case error_msg
// will contain a description of the error.
static JNIEnvExt* Create(Thread* self, JavaVMExt* vm, std::string* error_msg);
static Offset SegmentStateOffset(size_t pointer_size);
static Offset LocalRefCookieOffset(size_t pointer_size);
static Offset SelfOffset(size_t pointer_size);
static jint GetEnvHandler(JavaVMExt* vm, /*out*/void** out, jint version);
void DumpReferenceTables(std::ostream& os)
void SetCheckJniEnabled(bool enabled) REQUIRES(!Locks::jni_function_table_lock_);
void PushFrame(int capacity) REQUIRES_SHARED(Locks::mutator_lock_);
void PopFrame() REQUIRES_SHARED(Locks::mutator_lock_);
template<typename T>
T AddLocalReference(ObjPtr<mirror::Object> obj)
void UpdateLocal(IndirectRef iref, ObjPtr<mirror::Object> obj) REQUIRES_SHARED(Locks::mutator_lock_) {
locals_.Update(iref, obj);
jobject NewLocalRef(mirror::Object* obj) REQUIRES_SHARED(Locks::mutator_lock_);
void DeleteLocalRef(jobject obj) REQUIRES_SHARED(Locks::mutator_lock_);
void TrimLocals() REQUIRES_SHARED(Locks::mutator_lock_) {
void AssertLocalsEmpty() REQUIRES_SHARED(Locks::mutator_lock_) {
size_t GetLocalsCapacity() REQUIRES_SHARED(Locks::mutator_lock_) {
return locals_.Capacity();
IRTSegmentState GetLocalRefCookie() const { return local_ref_cookie_; }
void SetLocalRefCookie(IRTSegmentState new_cookie) { local_ref_cookie_ = new_cookie; }
IRTSegmentState GetLocalsSegmentState() const REQUIRES_SHARED(Locks::mutator_lock_) {
return locals_.GetSegmentState();
void SetLocalSegmentState(IRTSegmentState new_state) REQUIRES_SHARED(Locks::mutator_lock_) {
void VisitJniLocalRoots(RootVisitor* visitor, const RootInfo& root_info)
REQUIRES_SHARED(Locks::mutator_lock_) {
locals_.VisitRoots(visitor, root_info);
Thread* GetSelf() const { return self_; }
uint32_t GetCritical() const { return critical_; }
void SetCritical(uint32_t new_critical) { critical_ = new_critical; }
uint64_t GetCriticalStartUs() const { return critical_start_us_; }
void SetCriticalStartUs(uint64_t new_critical_start_us) {
critical_start_us_ = new_critical_start_us;
const JNINativeInterface* GetUncheckedFunctions() const {
return unchecked_functions_;
JavaVMExt* GetVm() const { return vm_; }
bool IsRuntimeDeleted() const { return runtime_deleted_; }
bool IsCheckJniEnabled() const { return check_jni_; }
// Functions to keep track of monitor lock and unlock operations. Used to ensure proper locking
// rules in CheckJNI mode.
// Record locking of a monitor.
void RecordMonitorEnter(jobject obj) REQUIRES_SHARED(Locks::mutator_lock_);
// Check the release, that is, that the release is performed in the same JNI "segment."
void CheckMonitorRelease(jobject obj) REQUIRES_SHARED(Locks::mutator_lock_);
// Check that no monitors are held that have been acquired in this JNI "segment."
void CheckNoHeldMonitors() REQUIRES_SHARED(Locks::mutator_lock_);
void VisitMonitorRoots(RootVisitor* visitor, const RootInfo& root_info)
REQUIRES_SHARED(Locks::mutator_lock_) {
monitors_.VisitRoots(visitor, root_info);
// Set the functions to the runtime shutdown functions.
void SetFunctionsToRuntimeShutdownFunctions();
// Set the function table override. This will install the override (or original table, if null)
// to all threads.
// Note: JNI function table overrides are sensitive to the order of operations wrt/ CheckJNI.
// After overriding the JNI function table, CheckJNI toggling is ignored.
static void SetTableOverride(const JNINativeInterface* table_override)
REQUIRES(!Locks::thread_list_lock_, !Locks::jni_function_table_lock_);
// Return either the regular, or the CheckJNI function table. Will return table_override_ instead
// if it is not null.
static const JNINativeInterface* GetFunctionTable(bool check_jni)
// Checking "locals" requires the mutator lock, but at creation time we're
// really only interested in validity, which isn't changing. To avoid grabbing
// the mutator lock, factored out and tagged with NO_THREAD_SAFETY_ANALYSIS.
static bool CheckLocalsValid(JNIEnvExt* in) NO_THREAD_SAFETY_ANALYSIS;
// Override of function tables. This applies to both default as well as instrumented (CheckJNI)
// function tables.
static const JNINativeInterface* table_override_ GUARDED_BY(Locks::jni_function_table_lock_);
// The constructor should not be called directly. It may leave the object in an erroneous state,
// and the result needs to be checked.
JNIEnvExt(Thread* self, JavaVMExt* vm, std::string* error_msg)
// Link to Thread::Current().
Thread* const self_;
// The invocation interface JavaVM.
JavaVMExt* const vm_;
// Cookie used when using the local indirect reference table.
IRTSegmentState local_ref_cookie_;
// JNI local references.
IndirectReferenceTable locals_ GUARDED_BY(Locks::mutator_lock_);
// Stack of cookies corresponding to PushLocalFrame/PopLocalFrame calls.
// TODO: to avoid leaks (and bugs), we need to clear this vector on entry (or return)
// to a native method.
std::vector<IRTSegmentState> stacked_local_ref_cookies_;
// Entered JNI monitors, for bulk exit on thread detach.
ReferenceTable monitors_;
// Used by -Xcheck:jni.
const JNINativeInterface* unchecked_functions_;
// All locked objects, with the (Java caller) stack frame that locked them. Used in CheckJNI
// to ensure that only monitors locked in this native frame are being unlocked, and that at
// the end all are unlocked.
std::vector<std::pair<uintptr_t, jobject>> locked_objects_;
// Start time of "critical" JNI calls to ensure that their use doesn't
// excessively block the VM with CheckJNI.
uint64_t critical_start_us_;
// How many nested "critical" JNI calls are we in? Used by CheckJNI to ensure that criticals are
uint32_t critical_;
// Frequently-accessed fields cached from JavaVM.
bool check_jni_;
// If we are a JNI env for a daemon thread with a deleted runtime.
bool runtime_deleted_;
friend class JNI;
friend class ScopedJniEnvLocalRefState;
friend class Thread;
ART_FRIEND_TEST(JniInternalTest, JNIEnvExtOffsets);
// Used to save and restore the JNIEnvExt state when not going through code created by the JNI
// compiler.
class ScopedJniEnvLocalRefState {
explicit ScopedJniEnvLocalRefState(JNIEnvExt* env) :
saved_local_ref_cookie_(env->local_ref_cookie_) {
env->local_ref_cookie_ = env->locals_.GetSegmentState();
~ScopedJniEnvLocalRefState() {
env_->local_ref_cookie_ = saved_local_ref_cookie_;
JNIEnvExt* const env_;
const IRTSegmentState saved_local_ref_cookie_;
} // namespace art