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