/*
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* Copyright (C) 2017 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 "uevent_listener.h"
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#include <fcntl.h>
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#include <poll.h>
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#include <string.h>
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#include <unistd.h>
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#include <memory>
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#include <android-base/logging.h>
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#include <cutils/uevent.h>
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namespace android {
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namespace init {
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static void ParseEvent(const char* msg, Uevent* uevent) {
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uevent->partition_num = -1;
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uevent->major = -1;
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uevent->minor = -1;
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uevent->action.clear();
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uevent->path.clear();
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uevent->subsystem.clear();
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uevent->firmware.clear();
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uevent->partition_name.clear();
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uevent->device_name.clear();
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uevent->modalias.clear();
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// currently ignoring SEQNUM
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while (*msg) {
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if (!strncmp(msg, "ACTION=", 7)) {
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msg += 7;
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uevent->action = msg;
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} else if (!strncmp(msg, "DEVPATH=", 8)) {
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msg += 8;
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uevent->path = msg;
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} else if (!strncmp(msg, "SUBSYSTEM=", 10)) {
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msg += 10;
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uevent->subsystem = msg;
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} else if (!strncmp(msg, "FIRMWARE=", 9)) {
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msg += 9;
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uevent->firmware = msg;
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} else if (!strncmp(msg, "MAJOR=", 6)) {
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msg += 6;
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uevent->major = atoi(msg);
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} else if (!strncmp(msg, "MINOR=", 6)) {
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msg += 6;
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uevent->minor = atoi(msg);
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} else if (!strncmp(msg, "PARTN=", 6)) {
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msg += 6;
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uevent->partition_num = atoi(msg);
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} else if (!strncmp(msg, "PARTNAME=", 9)) {
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msg += 9;
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uevent->partition_name = msg;
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} else if (!strncmp(msg, "DEVNAME=", 8)) {
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msg += 8;
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uevent->device_name = msg;
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} else if (!strncmp(msg, "MODALIAS=", 9)) {
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msg += 9;
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uevent->modalias = msg;
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}
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// advance to after the next \0
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while (*msg++)
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;
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}
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if (LOG_UEVENTS) {
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LOG(INFO) << "event { '" << uevent->action << "', '" << uevent->path << "', '"
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<< uevent->subsystem << "', '" << uevent->firmware << "', " << uevent->major
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<< ", " << uevent->minor << " }";
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}
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}
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UeventListener::UeventListener(size_t uevent_socket_rcvbuf_size) {
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device_fd_.reset(uevent_open_socket(uevent_socket_rcvbuf_size, true));
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if (device_fd_ == -1) {
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LOG(FATAL) << "Could not open uevent socket";
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}
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fcntl(device_fd_, F_SETFL, O_NONBLOCK);
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}
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bool UeventListener::ReadUevent(Uevent* uevent) const {
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char msg[UEVENT_MSG_LEN + 2];
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int n = uevent_kernel_multicast_recv(device_fd_, msg, UEVENT_MSG_LEN);
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if (n <= 0) {
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if (errno != EAGAIN && errno != EWOULDBLOCK) {
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LOG(ERROR) << "Error reading from Uevent Fd";
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}
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return false;
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}
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if (n >= UEVENT_MSG_LEN) {
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LOG(ERROR) << "Uevent overflowed buffer, discarding";
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// Return true here even if we discard as we may have more uevents pending and we
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// want to keep processing them.
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return true;
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}
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msg[n] = '\0';
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msg[n + 1] = '\0';
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ParseEvent(msg, uevent);
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return true;
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}
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// RegenerateUevents*() walks parts of the /sys tree and pokes the uevent files to cause the kernel
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// to regenerate device add uevents that have already happened. This is particularly useful when
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// starting ueventd, to regenerate all of the uevents that it had previously missed.
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//
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// We drain any pending events from the netlink socket every time we poke another uevent file to
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// make sure we don't overrun the socket's buffer.
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//
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ListenerAction UeventListener::RegenerateUeventsForDir(DIR* d,
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const ListenerCallback& callback) const {
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int dfd = dirfd(d);
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int fd = openat(dfd, "uevent", O_WRONLY);
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if (fd >= 0) {
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write(fd, "add\n", 4);
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close(fd);
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Uevent uevent;
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while (ReadUevent(&uevent)) {
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if (callback(uevent) == ListenerAction::kStop) return ListenerAction::kStop;
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}
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}
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dirent* de;
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while ((de = readdir(d)) != nullptr) {
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if (de->d_type != DT_DIR || de->d_name[0] == '.') continue;
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fd = openat(dfd, de->d_name, O_RDONLY | O_DIRECTORY);
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if (fd < 0) continue;
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std::unique_ptr<DIR, decltype(&closedir)> d2(fdopendir(fd), closedir);
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if (d2 == 0) {
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close(fd);
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} else {
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if (RegenerateUeventsForDir(d2.get(), callback) == ListenerAction::kStop) {
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return ListenerAction::kStop;
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}
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}
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}
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// default is always to continue looking for uevents
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return ListenerAction::kContinue;
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}
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ListenerAction UeventListener::RegenerateUeventsForPath(const std::string& path,
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const ListenerCallback& callback) const {
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std::unique_ptr<DIR, decltype(&closedir)> d(opendir(path.c_str()), closedir);
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if (!d) return ListenerAction::kContinue;
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return RegenerateUeventsForDir(d.get(), callback);
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}
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static const char* kRegenerationPaths[] = {"/sys/class", "/sys/block", "/sys/devices"};
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void UeventListener::RegenerateUevents(const ListenerCallback& callback) const {
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for (const auto path : kRegenerationPaths) {
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if (RegenerateUeventsForPath(path, callback) == ListenerAction::kStop) return;
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}
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}
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void UeventListener::Poll(const ListenerCallback& callback,
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const std::optional<std::chrono::milliseconds> relative_timeout) const {
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using namespace std::chrono;
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pollfd ufd;
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ufd.events = POLLIN;
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ufd.fd = device_fd_;
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auto start_time = steady_clock::now();
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while (true) {
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ufd.revents = 0;
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int timeout_ms = -1;
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if (relative_timeout) {
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auto now = steady_clock::now();
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auto time_elapsed = duration_cast<milliseconds>(now - start_time);
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if (time_elapsed > *relative_timeout) return;
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auto remaining_timeout = *relative_timeout - time_elapsed;
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timeout_ms = remaining_timeout.count();
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}
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int nr = poll(&ufd, 1, timeout_ms);
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if (nr == 0) return;
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if (nr < 0) {
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PLOG(ERROR) << "poll() of uevent socket failed, continuing";
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continue;
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}
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if (ufd.revents & POLLIN) {
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// We're non-blocking, so if we receive a poll event keep processing until
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// we have exhausted all uevent messages.
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Uevent uevent;
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while (ReadUevent(&uevent)) {
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if (callback(uevent) == ListenerAction::kStop) return;
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}
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}
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}
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}
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} // namespace init
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} // namespace android
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