/*
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* Copyright (C) 2011 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "jni_env_ext.h"
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#include <algorithm>
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#include <vector>
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#include "android-base/stringprintf.h"
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#include "base/mutex.h"
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#include "base/to_str.h"
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#include "check_jni.h"
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#include "indirect_reference_table.h"
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#include "java_vm_ext.h"
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#include "jni_internal.h"
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#include "lock_word.h"
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#include "mirror/object-inl.h"
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#include "nth_caller_visitor.h"
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#include "scoped_thread_state_change.h"
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#include "thread-current-inl.h"
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#include "thread_list.h"
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namespace art {
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using android::base::StringPrintf;
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static constexpr size_t kMonitorsInitial = 32; // Arbitrary.
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static constexpr size_t kMonitorsMax = 4096; // Arbitrary sanity check.
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const JNINativeInterface* JNIEnvExt::table_override_ = nullptr;
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bool JNIEnvExt::CheckLocalsValid(JNIEnvExt* in) NO_THREAD_SAFETY_ANALYSIS {
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if (in == nullptr) {
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return false;
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}
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return in->locals_.IsValid();
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}
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jint JNIEnvExt::GetEnvHandler(JavaVMExt* vm, /*out*/void** env, jint version) {
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UNUSED(vm);
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// GetEnv always returns a JNIEnv* for the most current supported JNI version,
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// and unlike other calls that take a JNI version doesn't care if you supply
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// JNI_VERSION_1_1, which we don't otherwise support.
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if (JavaVMExt::IsBadJniVersion(version) && version != JNI_VERSION_1_1) {
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return JNI_EVERSION;
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}
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Thread* thread = Thread::Current();
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CHECK(thread != nullptr);
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*env = thread->GetJniEnv();
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return JNI_OK;
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}
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JNIEnvExt* JNIEnvExt::Create(Thread* self_in, JavaVMExt* vm_in, std::string* error_msg) {
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std::unique_ptr<JNIEnvExt> ret(new JNIEnvExt(self_in, vm_in, error_msg));
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if (CheckLocalsValid(ret.get())) {
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return ret.release();
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}
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return nullptr;
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}
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JNIEnvExt::JNIEnvExt(Thread* self_in, JavaVMExt* vm_in, std::string* error_msg)
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: self_(self_in),
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vm_(vm_in),
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local_ref_cookie_(kIRTFirstSegment),
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locals_(kLocalsInitial, kLocal, IndirectReferenceTable::ResizableCapacity::kYes, error_msg),
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monitors_("monitors", kMonitorsInitial, kMonitorsMax),
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critical_(0),
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check_jni_(false),
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runtime_deleted_(false) {
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MutexLock mu(Thread::Current(), *Locks::jni_function_table_lock_);
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check_jni_ = vm_in->IsCheckJniEnabled();
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functions = GetFunctionTable(check_jni_);
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unchecked_functions_ = GetJniNativeInterface();
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}
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void JNIEnvExt::SetFunctionsToRuntimeShutdownFunctions() {
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functions = GetRuntimeShutdownNativeInterface();
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runtime_deleted_ = true;
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}
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JNIEnvExt::~JNIEnvExt() {
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}
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jobject JNIEnvExt::NewLocalRef(mirror::Object* obj) {
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if (obj == nullptr) {
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return nullptr;
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}
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std::string error_msg;
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jobject ref = reinterpret_cast<jobject>(locals_.Add(local_ref_cookie_, obj, &error_msg));
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if (UNLIKELY(ref == nullptr)) {
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// This is really unexpected if we allow resizing local IRTs...
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LOG(FATAL) << error_msg;
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UNREACHABLE();
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}
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return ref;
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}
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void JNIEnvExt::DeleteLocalRef(jobject obj) {
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if (obj != nullptr) {
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locals_.Remove(local_ref_cookie_, reinterpret_cast<IndirectRef>(obj));
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}
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}
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void JNIEnvExt::SetCheckJniEnabled(bool enabled) {
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check_jni_ = enabled;
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MutexLock mu(Thread::Current(), *Locks::jni_function_table_lock_);
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functions = GetFunctionTable(enabled);
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// Check whether this is a no-op because of override.
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if (enabled && JNIEnvExt::table_override_ != nullptr) {
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LOG(WARNING) << "Enabling CheckJNI after a JNIEnv function table override is not functional.";
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}
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}
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void JNIEnvExt::DumpReferenceTables(std::ostream& os) {
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locals_.Dump(os);
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monitors_.Dump(os);
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}
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void JNIEnvExt::PushFrame(int capacity) {
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DCHECK_GE(locals_.FreeCapacity(), static_cast<size_t>(capacity));
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stacked_local_ref_cookies_.push_back(local_ref_cookie_);
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local_ref_cookie_ = locals_.GetSegmentState();
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}
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void JNIEnvExt::PopFrame() {
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locals_.SetSegmentState(local_ref_cookie_);
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local_ref_cookie_ = stacked_local_ref_cookies_.back();
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stacked_local_ref_cookies_.pop_back();
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}
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// Note: the offset code is brittle, as we can't use OFFSETOF_MEMBER or offsetof easily. Thus, there
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// are tests in jni_internal_test to match the results against the actual values.
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// This is encoding the knowledge of the structure and layout of JNIEnv fields.
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static size_t JNIEnvSize(size_t pointer_size) {
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// A single pointer.
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return pointer_size;
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}
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Offset JNIEnvExt::SegmentStateOffset(size_t pointer_size) {
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size_t locals_offset = JNIEnvSize(pointer_size) +
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2 * pointer_size + // Thread* self + JavaVMExt* vm.
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4 + // local_ref_cookie.
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(pointer_size - 4); // Padding.
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size_t irt_segment_state_offset =
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IndirectReferenceTable::SegmentStateOffset(pointer_size).Int32Value();
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return Offset(locals_offset + irt_segment_state_offset);
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}
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Offset JNIEnvExt::LocalRefCookieOffset(size_t pointer_size) {
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return Offset(JNIEnvSize(pointer_size) +
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2 * pointer_size); // Thread* self + JavaVMExt* vm
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}
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Offset JNIEnvExt::SelfOffset(size_t pointer_size) {
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return Offset(JNIEnvSize(pointer_size));
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}
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// Use some defining part of the caller's frame as the identifying mark for the JNI segment.
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static uintptr_t GetJavaCallFrame(Thread* self) REQUIRES_SHARED(Locks::mutator_lock_) {
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NthCallerVisitor zeroth_caller(self, 0, false);
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zeroth_caller.WalkStack();
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if (zeroth_caller.caller == nullptr) {
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// No Java code, must be from pure native code.
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return 0;
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} else if (zeroth_caller.GetCurrentQuickFrame() == nullptr) {
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// Shadow frame = interpreter. Use the actual shadow frame's address.
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DCHECK(zeroth_caller.GetCurrentShadowFrame() != nullptr);
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return reinterpret_cast<uintptr_t>(zeroth_caller.GetCurrentShadowFrame());
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} else {
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// Quick frame = compiled code. Use the bottom of the frame.
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return reinterpret_cast<uintptr_t>(zeroth_caller.GetCurrentQuickFrame());
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}
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}
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void JNIEnvExt::RecordMonitorEnter(jobject obj) {
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locked_objects_.push_back(std::make_pair(GetJavaCallFrame(self_), obj));
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}
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static std::string ComputeMonitorDescription(Thread* self,
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jobject obj) REQUIRES_SHARED(Locks::mutator_lock_) {
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ObjPtr<mirror::Object> o = self->DecodeJObject(obj);
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if ((o->GetLockWord(false).GetState() == LockWord::kThinLocked) &&
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Locks::mutator_lock_->IsExclusiveHeld(self)) {
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// Getting the identity hashcode here would result in lock inflation and suspension of the
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// current thread, which isn't safe if this is the only runnable thread.
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return StringPrintf("<@addr=0x%" PRIxPTR "> (a %s)",
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reinterpret_cast<intptr_t>(o.Ptr()),
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o->PrettyTypeOf().c_str());
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} else {
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// IdentityHashCode can cause thread suspension, which would invalidate o if it moved. So
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// we get the pretty type before we call IdentityHashCode.
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const std::string pretty_type(o->PrettyTypeOf());
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return StringPrintf("<0x%08x> (a %s)", o->IdentityHashCode(), pretty_type.c_str());
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}
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}
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static void RemoveMonitors(Thread* self,
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uintptr_t frame,
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ReferenceTable* monitors,
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std::vector<std::pair<uintptr_t, jobject>>* locked_objects)
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REQUIRES_SHARED(Locks::mutator_lock_) {
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auto kept_end = std::remove_if(
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locked_objects->begin(),
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locked_objects->end(),
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[self, frame, monitors](const std::pair<uintptr_t, jobject>& pair)
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REQUIRES_SHARED(Locks::mutator_lock_) {
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if (frame == pair.first) {
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ObjPtr<mirror::Object> o = self->DecodeJObject(pair.second);
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monitors->Remove(o);
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return true;
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}
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return false;
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});
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locked_objects->erase(kept_end, locked_objects->end());
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}
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void JNIEnvExt::CheckMonitorRelease(jobject obj) {
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uintptr_t current_frame = GetJavaCallFrame(self_);
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std::pair<uintptr_t, jobject> exact_pair = std::make_pair(current_frame, obj);
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auto it = std::find(locked_objects_.begin(), locked_objects_.end(), exact_pair);
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bool will_abort = false;
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if (it != locked_objects_.end()) {
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locked_objects_.erase(it);
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} else {
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// Check whether this monitor was locked in another JNI "session."
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ObjPtr<mirror::Object> mirror_obj = self_->DecodeJObject(obj);
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for (std::pair<uintptr_t, jobject>& pair : locked_objects_) {
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if (self_->DecodeJObject(pair.second) == mirror_obj) {
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std::string monitor_descr = ComputeMonitorDescription(self_, pair.second);
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vm_->JniAbortF("<JNI MonitorExit>",
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"Unlocking monitor that wasn't locked here: %s",
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monitor_descr.c_str());
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will_abort = true;
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break;
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}
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}
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}
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// When we abort, also make sure that any locks from the current "session" are removed from
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// the monitors table, otherwise we may visit local objects in GC during abort (which won't be
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// valid anymore).
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if (will_abort) {
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RemoveMonitors(self_, current_frame, &monitors_, &locked_objects_);
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}
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}
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void JNIEnvExt::CheckNoHeldMonitors() {
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// The locked_objects_ are grouped by their stack frame component, as this enforces structured
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// locking, and the groups form a stack. So the current frame entries are at the end. Check
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// whether the vector is empty, and when there are elements, whether the last element belongs
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// to this call - this signals that there are unlocked monitors.
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if (!locked_objects_.empty()) {
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uintptr_t current_frame = GetJavaCallFrame(self_);
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std::pair<uintptr_t, jobject>& pair = locked_objects_[locked_objects_.size() - 1];
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if (pair.first == current_frame) {
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std::string monitor_descr = ComputeMonitorDescription(self_, pair.second);
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vm_->JniAbortF("<JNI End>",
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"Still holding a locked object on JNI end: %s",
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monitor_descr.c_str());
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// When we abort, also make sure that any locks from the current "session" are removed from
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// the monitors table, otherwise we may visit local objects in GC during abort.
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RemoveMonitors(self_, current_frame, &monitors_, &locked_objects_);
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} else if (kIsDebugBuild) {
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// Make sure there are really no other entries and our checking worked as expected.
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for (std::pair<uintptr_t, jobject>& check_pair : locked_objects_) {
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CHECK_NE(check_pair.first, current_frame);
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}
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}
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}
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// Ensure critical locks aren't held when returning to Java.
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if (critical_ > 0) {
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vm_->JniAbortF("<JNI End>",
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"Critical lock held when returning to Java on thread %s",
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ToStr<Thread>(*self_).c_str());
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}
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}
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static void ThreadResetFunctionTable(Thread* thread, void* arg ATTRIBUTE_UNUSED)
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REQUIRES(Locks::jni_function_table_lock_) {
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JNIEnvExt* env = thread->GetJniEnv();
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bool check_jni = env->IsCheckJniEnabled();
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env->functions = JNIEnvExt::GetFunctionTable(check_jni);
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}
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void JNIEnvExt::SetTableOverride(const JNINativeInterface* table_override) {
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MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
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MutexLock mu2(Thread::Current(), *Locks::jni_function_table_lock_);
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JNIEnvExt::table_override_ = table_override;
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// See if we have a runtime. Note: we cannot run other code (like JavaVMExt's CheckJNI install
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// code), as we'd have to recursively lock the mutex.
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Runtime* runtime = Runtime::Current();
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if (runtime != nullptr) {
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runtime->GetThreadList()->ForEach(ThreadResetFunctionTable, nullptr);
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}
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}
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const JNINativeInterface* JNIEnvExt::GetFunctionTable(bool check_jni) {
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const JNINativeInterface* override = JNIEnvExt::table_override_;
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if (override != nullptr) {
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return override;
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}
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return check_jni ? GetCheckJniNativeInterface() : GetJniNativeInterface();
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}
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} // namespace art
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