86 lines
3.2 KiB
C++
86 lines
3.2 KiB
C++
// Copyright (C) 2020 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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#define LOG_TAG "netjniutils"
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#include "netjniutils/netjniutils.h"
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#include <android-modules-utils/sdk_level.h>
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#include <dlfcn.h>
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#include <stdbool.h>
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#include <string.h>
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#include <sys/system_properties.h>
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#include <android/api-level.h>
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#include <android/log.h>
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namespace android {
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namespace netjniutils {
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namespace {
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int GetNativeFileDescriptorWithoutNdk(JNIEnv* env, jobject javaFd) {
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// Prior to Android S, we need to find the descriptor field in the FileDescriptor class. The
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// symbol name has been stable in libcore, but is a private implementation detail.
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// Older libnativehelper_compat_c++ versions had a jniGetFdFromFileDescriptor method, but this
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// was removed in S to replace it with the NDK API in libnativehelper.
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// The code is copied here instead. This code can be removed once R is not supported anymore.
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static const jfieldID descriptorFieldID = [env]() -> jfieldID {
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jclass cls = env->FindClass("java/io/FileDescriptor");
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jfieldID fieldID = env->GetFieldID(cls, "descriptor", "I");
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env->DeleteLocalRef(cls);
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if (fieldID == nullptr) {
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__android_log_print(ANDROID_LOG_FATAL, LOG_TAG, "Failed to get descriptor field.");
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}
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return fieldID;
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}();
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return javaFd != nullptr ? env->GetIntField(javaFd, descriptorFieldID) : -1;
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}
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int GetNativeFileDescriptorWithNdk(JNIEnv* env, jobject javaFd) {
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// Since Android S, there is an NDK API to get a file descriptor present in libnativehelper.so.
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// libnativehelper is loaded into all processes by the zygote since the zygote uses it
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// to load the Android Runtime and is also a public library (because of the NDK API).
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typedef int (*ndkGetFd_t)(JNIEnv*, jobject);
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static const ndkGetFd_t ndkGetFd = []() -> ndkGetFd_t {
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void* handle = dlopen("libnativehelper.so", RTLD_NOLOAD | RTLD_NODELETE);
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auto ndkGetFd = reinterpret_cast<ndkGetFd_t>(dlsym(handle, "AFileDescriptor_getFd"));
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if (ndkGetFd == nullptr) {
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__android_log_print(ANDROID_LOG_FATAL, LOG_TAG,
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"Failed to dlsym(AFileDescriptor_getFd): %s", dlerror());
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dlclose(handle);
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}
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return ndkGetFd;
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}();
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return javaFd != nullptr ? ndkGetFd(env, javaFd) : -1;
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}
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} // namespace
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int GetNativeFileDescriptor(JNIEnv* env, jobject javaFd) {
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static const bool preferNdkFileDescriptorApi = []() -> bool
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{ return android::modules::sdklevel::IsAtLeastS(); }();
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if (preferNdkFileDescriptorApi) {
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return GetNativeFileDescriptorWithNdk(env, javaFd);
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} else {
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return GetNativeFileDescriptorWithoutNdk(env, javaFd);
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}
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}
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} // namespace netjniutils
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} // namespace android
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