android9.0 系统默认时间修改

一. 问题：最近项目出现未联网的机器默认时间从2009-01-01 00:00 开始计时，桌面显示2009-01-01 03:00，需求是2019-01-01 8:00 开始计时

二.问题分析：

1. 通过分析代码，frameworks\base\services\java\com\android\server\SystemServer.java

private static final long EARLIEST_SUPPORTED_TIME = 86400 * 1000;

private void run()中

// If a device's clock is before 1970 (before 0), a lot of
// APIs crash dealing with negative numbers, notably
// java.io.File#setLastModified, so instead we fake it and
// hope that time from cell towers or NTP fixes it shortly.
if (System.currentTimeMillis() < EARLIEST_SUPPORTED_TIME) {
Slog.w(TAG, "System clock is before 1970; setting to 1970.");
SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);
}

// Here we go!
Slog.i(TAG, "Entered the Android system server!");
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_SYSTEM_RUN, SystemClock.uptimeMillis());

此处判断的是1970年

2. 抓取log：

01-01 08:04:37.768 3524 3524 D SystemServerTiming: StartConsumerIrService took to complete: 3ms
01-01 08:04:37.769 3524 3524 I SystemServer: StartAlarmManagerService
01-01 08:04:37.769 3524 3524 I SystemServiceManager: Starting com.android.server.AlarmManagerService
01-01 08:04:37.773 3524 3524 I AlarmManager: Current time only 277773, advancing to build time 1230739200000
01-01 00:00:00.008 3524 3524 D SystemServerTiming: StartAlarmManagerService took to complete: 13ms
01-01 00:00:00.008 3524 3524 I SystemServer: InitWatchdog
01-01 00:00:00.009 3524 3524 D SystemServerTiming: InitWatchdog took to complete: 0ms
01-01 00:00:00.009 3524 3524 I SystemServer: StartInputManagerService
01-01 00:00:00.010 3524 3524 I InputManager: Initializing input manager, mUseDevInputEventForAudioJack=false
01-01 00:00:00.011 3524 3524 D SystemServerTiming: StartInputManagerService took to complete: 2ms
01-01 00:00:00.011 3524 3524 I SystemServer: StartWindowManagerService

追查源码：frameworks\base\services\core\java\com\android\server\AlarmManagerService.java

发现以下设置，对比当前系统时间和system 文件夹时间

// We have to set current TimeZone info to kernel
// because kernel doesn't keep this after reboot
setTimeZoneImpl(SystemProperties.get(TIMEZONE_PROPERTY));

// Also sure that we're booting with a halfway sensible current time
if (mNativeData != 0) {
final long systemBuildTime = Environment.getRootDirectory().lastModified();
if (System.currentTimeMillis() < systemBuildTime) {
Slog.i(TAG, "Current time only " + System.currentTimeMillis()
+ ", advancing to build time " + systemBuildTime);
setKernelTime(mNativeData, systemBuildTime);
}
}

发现系统时间早于文件夹时间，将系统时间设置为文件夹时间

drwxr-xr-x 14 root root 4096 2009-01-01 00:00 system
-rw-r--r-- 1 root root 5272 2009-01-01 00:00 ueventd.rc
drwxr-xr-x 13 root root 4096 2009-01-01 00:00 vendor

三.解决方案：

修改默认时间

方法1，在原有的时间设置 frameworks\base\services\java\com\android\server\SystemServer.java

if (System.currentTimeMillis() < EARLIEST_SUPPORTED_TIME) {
Slog.w(TAG, "System clock is before 1970; setting to 1970.");
SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);
}

设置：EARLIEST_SUPPORTED_TIME=1546300800000L，发现不起作用，需要在以下代码出设置：

private static final long EARLIEST_SUPPORTED_TIME_DH= 1546300800000L;

// Start services.
try {
traceBeginAndSlog("StartServices");
startBootstrapServices();
startCoreServices();
startOtherServices();
//begin 201901010800
if (System.currentTimeMillis() < EARLIEST_SUPPORTED_TIME_DH) {
Slog.w(TAG, "Start services System clock is before 201901010800; setting to 201901010800.");
SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME_HR);
}
//end
SystemServerInitThreadPool.shutdown();
} catch (Throwable ex) {
Slog.e("System", "******************************************");
Slog.e("System", "************ Failure starting system services", ex);
throw ex;
} finally {
traceEnd();
}

方法二 frameworks\base\services\core\java\com\android\server\AlarmManagerService.java

private static final long DEFAULT_SUPPORTED_TIME_DH= 1546300800000L;

public void onStart() 方法中：

// We have to set current TimeZone info to kernel
// because kernel doesn't keep this after reboot
setTimeZoneImpl(SystemProperties.get(TIMEZONE_PROPERTY));

//begin 201901010800

if (mNativeData != 0) {

if (System.currentTimeMillis() < DEFAULT_SUPPORTED_TIME_DH) {
Slog.i(TAG, "Current time only " + System.currentTimeMillis()
+ ", advancing to time " + DEFAULT_SUPPORTED_TIME_DH);
setKernelTime(mNativeData, DEFAULT_SUPPORTED_TIME_DH);
}

}

//end 201901010800

// Also sure that we're booting with a halfway sensible current time
if (mNativeData != 0) {
final long systemBuildTime = Environment.getRootDirectory().lastModified();
if (System.currentTimeMillis() < systemBuildTime) {
Slog.i(TAG, "Current time only " + System.currentTimeMillis()
+ ", advancing to build time " + systemBuildTime);
setKernelTime(mNativeData, systemBuildTime);
}
}

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