一、概述
目前Android系统终端的升级主要是通过无线进行的（FOTA，Firmware Over-The-Air），主要流程是通过无线方式将升级包下载到终端，而后调用系统的升级接口进行升级。本文主要分析升级包下载后，调用系统升级接口之后的流程。
1.1 升级包结构
升级包是用make otapackage命令生成的，对于差分包，需要生成两个ota整包，再用系统的编译工具利用这两个整包生成一个差分包。下面是某终端Android9.0版本的ota升级包结构。
├─firmware-update
└─META-INF
└─com
├─android
├─metadata
├─otacert
└─google
└─android
├─update-binary
├─updater-script
├─boot.img
├─system.new.dat.br
├─system.patch.dat
├─system.transfer.list
├─vendor.new.dat.br
├─vendor.patch.dat
├─vendor.transfer.listfirmware-update：目录下主要是一些固件的升级，如mbn、dtbo、vbmeta等
boot.img：更新boot分区所需要的文件，包括kernel+ramdisk
system.new.dat.br：Android8.1镜像后新的压缩格式，为数据部分，里面是system.img数据。
system.transfer.list：数据转换的描述列表。
system.patch.dat：升级时用到，ota包中大小为0。
vendor和system类似。
update-binary：二进制文件，相当于一个脚本解释器，能够识别updater-script中描述的操作，文件的命名由bootable/recovery/install.cpp 中的UPDATE_BINARY_NAME值而定。
updater-script：升级包的升级脚本，文件的命名由bootable/recovery/updater/updater.cpp中的SCRIPT_NAME值而定。
metadata：描述设备信息及环境变量的元数据，主要包括一些编译选项、签名公钥，时间戳以及设备型号等。
otacert：ota签名。
1.2 系统启动模式
Android系统启动主要有两种：
1.组合键
用户通过按下组合键，不同的终端可以定义组合键，进入不同的工作模式，在bootable/bootloader/lk/app/aboot/aboot.c文件中判断，具体有两种：
bootloader模式，可进一步进入fastboot（快速刷机模式）。
Recovery模式，进入这种模式系统会出现一个简单的ui界面，用来提示用户的进一步操作。
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2.正常启动
没有按下任何组合键，正常开机，bootloader会读取启动控制信息块BCB(bootloader control block)，它是一个结构体，存放着启动命令Command。根据不同的命令，系统可以进入三种不同的启动模式。下面是Bootloader Message的定义，通过注释可以了解具体结构体中成员变量的含义。
[->bootloader_message.h]
/* Bootloader Message (2-KiB)
*
* This structure describes the content of a block in flash
* that is used for recovery and the bootloader to talk to
* each other.
*
* The command field is updated by linux when it wants to
* reboot into recovery or to update radio or bootloader firmware.
* It is also updated by the bootloader when firmware update
* is complete (to boot into recovery for any final cleanup)
*
* The status field was used by the bootloader after the completion
* of an "update-radio" or "update-hboot" command, which has been
* deprecated since Froyo.
*
* The recovery field is only written by linux and used
* for the system to send a message to recovery or the
* other way around.
*
* The stage field is written by packages which restart themselves
* multiple times, so that the UI can reflect which invocation of the
* package it is. If the value is of the format "#/#" (eg, "1/3"),
* the UI will add a simple indicator of that status.
*
* We used to have slot_suffix field for A/B boot control metadata in
* this struct, which gets unintentionally cleared by recovery or
* uncrypt. Move it into struct bootloader_message_ab to avoid the
* issue.
*/
struct bootloader_message {
char command[32];
char status[32];
char recovery[768];
// The 'recovery' field used to be 1024 bytes. It has only ever
// been used to store the recovery command line, so 768 bytes
// should be plenty. We carve off the last 256 bytes to store the
// stage string (for multistage packages) and possible future
// expansion.
char stage[32];
// The 'reserved' field used to be 224 bytes when it was initially
// carved off from the 1024-byte recovery field. Bump it up to
// 1184-byte so that the entire bootloader_message struct rounds up
// to 2048-byte.
char reserved[1184];
};二、OTA升级重启前
前面介绍完OTA升级包和系统启动模式，现在看下真正的ota升级的步骤。无论ota包是通过无线下载还是导入到SD卡，最后都会调用到RecoverySystem.installPackage方法，下面分析下这个详细的流程。
2.1 RS.installPackage
[->RecoverySystem.java]
public static void installPackage(Context context, File packageFile, boolean processed)
throws IOException {
synchronized (sRequestLock) {
LOG_FILE.delete();
// Must delete the file in case it was created by system server.
//删除之前的uncrypt file
UNCRYPT_PACKAGE_FILE.delete();
String filename = packageFile.getCanonicalPath();
Log.w(TAG, "!!! REBOOTING TO INSTALL " + filename + " !!!");
// If the package name ends with "_s.zip", it's a security update.
boolean securityUpdate = filename.endsWith("_s.zip");
// If the package is on the /data partition, the package needs to
// be processed (i.e. uncrypt'd). The caller specifies if that has
// been done in 'processed' parameter.
//如果升级包的路径是/data/开始
if (filename.startsWith("/data/")) {
if (processed) {
if (!BLOCK_MAP_FILE.exists()) {
Log.e(TAG, "Package claimed to have been processed but failed to find "
+ "the block map file.");
throw new IOException("Failed to find block map file");
}
} else {
FileWriter uncryptFile = new FileWriter(UNCRYPT_PACKAGE_FILE);
try {
//将路径写入uncryptFile
uncryptFile.write(filename + "/n");
} finally {
uncryptFile.close();
}
// UNCRYPT_PACKAGE_FILE needs to be readable and writable
// by system server.
if (!UNCRYPT_PACKAGE_FILE.setReadable(true, false)
|| !UNCRYPT_PACKAGE_FILE.setWritable(true, false)) {
Log.e(TAG, "Error setting permission for " + UNCRYPT_PACKAGE_FILE);
}
BLOCK_MAP_FILE.delete();
}
// If the package is on the /data partition, use the block map
// file as the package name instead.
filename = "@/cache/recovery/block.map";
}
final String filenameArg = "--update_package=" + filename + "/n";
final String localeArg = "--locale=" + Locale.getDefault().toLanguageTag() + "/n";
final String securityArg = "--security/n";
String command = filenameArg + localeArg;
if (securityUpdate) {
command += securityArg;
}
RecoverySystem rs = (RecoverySystem) context.getSystemService(
Context.RECOVERY_SERVICE);
//向bootloader control block写入命名
if (!rs.setupBcb(command)) {
throw new IOException("Setup BCB failed");
}
// Having set up the BCB (bootloader control block), go ahead and reboot
PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
String reason = PowerManager.REBOOT_RECOVERY_UPDATE;
// On TV, reboot quiescently if the screen is off
if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_LEANBACK)) {
WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
if (wm.getDefaultDisplay().getState() != Display.STATE_ON) {
reason += ",quiescent";
}
}
//重启
pm.reboot(reason);
throw new IOException("Reboot failed (no permissions?)");
}
}private static final File RECOVERY_DIR = new File("/cache/recovery");
public static final File UNCRYPT_PACKAGE_FILE = new File(RECOVERY_DIR, “uncrypt_file”);
这里主要是对ota升级包的处理，由于进入recovery模式后，data分区将不能加载，因此需要将其通过block方式，把ota升级包生成稀疏的描述文件，保存在/cache/recovery/block.map中。升级的命令写入到BCB,重启之后bootloader会读取BCB中的command从而进入升级模式。
2.2 RS.setupBcb
[->RecoverySystem.java]
/**
* Talks to RecoverySystemService via Binder to set up the BCB.
*/
private boolean setupBcb(String command) {
try {
//通过binder调用setupBcb
return mService.setupBcb(command);
} catch (RemoteException unused) {
}
return false;
}2.3 RSS.setupBcb
[->RecoverySystemService.java]
@Override // Binder call
public boolean setupBcb(String command) {
if (DEBUG) Slog.d(TAG, "setupBcb: [" + command + "]");
synchronized (sRequestLock) {
return setupOrClearBcb(true, command);
}
}2.4 RSS.setupOrClearBcb
[->RecoverySystemService.java]
private boolean setupOrClearBcb(boolean isSetup, String command) {
mContext.enforceCallingOrSelfPermission(android.Manifest.permission.RECOVERY, null);
final boolean available = checkAndWaitForUncryptService();
if (!available) {
Slog.e(TAG, "uncrypt service is unavailable.");
return false;
}
//设置ctl.start属性，启动setup-bcb服务
if (isSetup) {
SystemProperties.set("ctl.start", "setup-bcb");
} else {
SystemProperties.set("ctl.start", "clear-bcb");
}
// Connect to the uncrypt service socket.
// 连接uncrypt服务
LocalSocket socket = connectService();
if (socket == null) {
Slog.e(TAG, "Failed to connect to uncrypt socket");
return false;
}
DataInputStream dis = null;
DataOutputStream dos = null;
try {
dis = new DataInputStream(socket.getInputStream());
dos = new DataOutputStream(socket.getOutputStream());
// Send the BCB commands if it's to setup BCB.
// 发送BCB commands
if (isSetup) {
byte[] cmdUtf8 = command.getBytes("UTF-8");
dos.writeInt(cmdUtf8.length);
dos.write(cmdUtf8, 0, cmdUtf8.length);
dos.flush();
}
// Read the status from the socket.
int status = dis.readInt();
// Ack receipt of the status code. uncrypt waits for the ack so
// the socket won't be destroyed before we receive the code.
dos.writeInt(0);
if (status == 100) {
Slog.i(TAG, "uncrypt " + (isSetup ? "setup" : "clear") +
" bcb successfully finished.");
} else {
// Error in /system/bin/uncrypt.
Slog.e(TAG, "uncrypt failed with status: " + status);
return false;
}
} catch (IOException e) {
Slog.e(TAG, "IOException when communicating with uncrypt:", e);
return false;
} finally {
IoUtils.closeQuietly(dis);
IoUtils.closeQuietly(dos);
IoUtils.closeQuietly(socket);
}
return true;
}SystemProperties.set(“ctl.start”, “setup-bcb”)，通过这种方式来启动服务（SystemProperties设置属性的原理详细见文章Android SystemProperties系统属性分析），而后连接服务，向其中发送BCB command。
2.5 PM.reboot
[->PowerManager.java]
public void reboot(String reason) {
try {
mService.reboot(false, reason, true);
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}2.6 PMS.reboot
[->PowerManagerService.java]
/**
* Reboots the device.
*
* @param confirm If true, shows a reboot confirmation dialog.
* @param reason The reason for the reboot, or null if none.
* @param wait If true, this call waits for the reboot to complete and does not return.
*/
@Override // Binder call
public void reboot(boolean confirm, String reason, boolean wait) {
mContext.enforceCallingOrSelfPermission(android.Manifest.permission.REBOOT, null);
if (PowerManager.REBOOT_RECOVERY.equals(reason)
|| PowerManager.REBOOT_RECOVERY_UPDATE.equals(reason)) {
mContext.enforceCallingOrSelfPermission(android.Manifest.permission.RECOVERY, null);
}
final long ident = Binder.clearCallingIdentity();
try {
shutdownOrRebootInternal(HALT_MODE_REBOOT, confirm, reason, wait);
} finally {
Binder.restoreCallingIdentity(ident);
}
}这里传入的参数confirm：false ， reason：REBOOT_RECOVERY_UPDATE = “recovery-update”，wait：true
2.7 PMS.shutdownOrRebootInternal
[->PowerManagerService.java]
private void shutdownOrRebootInternal(final @HaltMode int haltMode, final boolean confirm,
final String reason, boolean wait) {
if (mHandler == null || !mSystemReady) {
if (RescueParty.isAttemptingFactoryReset()) {
// If we're stuck in a really low-level reboot loop, and a
// rescue party is trying to prompt the user for a factory data
// reset, we must GET TO DA CHOPPA!
PowerManagerService.lowLevelReboot(reason);
} else {
throw new IllegalStateException("Too early to call shutdown() or reboot()");
}
}
//上面传过来的是HALT_MODE_REBOOT
Runnable runnable = new Runnable() {
@Override
public void run() {
synchronized (this) {
if (haltMode == HALT_MODE_REBOOT_SAFE_MODE) {
ShutdownThread.rebootSafeMode(getUiContext(), confirm);
} else if (haltMode == HALT_MODE_REBOOT) {
ShutdownThread.reboot(getUiContext(), reason, confirm);
} else {
ShutdownThread.shutdown(getUiContext(), reason, confirm);
}
}
}
};
// ShutdownThread must run on a looper capable of displaying the UI.
Message msg = Message.obtain(UiThread.getHandler(), runnable);
msg.setAsynchronous(true);
UiThread.getHandler().sendMessage(msg);
// PowerManager.reboot() is documented not to return so just wait for the inevitable.
if (wait) {
synchronized (runnable) {
while (true) {
try {
runnable.wait();
} catch (InterruptedException e) {
}
}
}
}
}2.8 ST.reboot
[->ShutdownThread.java]
public static void reboot(final Context context, String reason, boolean confirm) {
mReboot = true;
mRebootSafeMode = false;
mRebootHasProgressBar = false;
mReason = reason;
shutdownInner(context, confirm);
}2.9 ST.shutdownInner
[->ShutdownThread.java]
private static void shutdownInner(final Context context, boolean confirm) {
// ShutdownThread is called from many places, so best to verify here that the context passed
// in is themed.
context.assertRuntimeOverlayThemable();
// ensure that only one thread is trying to power down.
// any additional calls are just returned
synchronized (sIsStartedGuard) {
if (sIsStarted) {
Log.d(TAG, "Request to shutdown already running, returning.");
return;
}
}
final int longPressBehavior = context.getResources().getInteger(
com.android.internal.R.integer.config_longPressOnPowerBehavior);
final int resourceId = mRebootSafeMode
? com.android.internal.R.string.reboot_safemode_confirm
: (longPressBehavior == 2
? com.android.internal.R.string.shutdown_confirm_question
: com.android.internal.R.string.shutdown_confirm);
Log.d(TAG, "Notifying thread to start shutdown longPressBehavior=" + longPressBehavior);
if (confirm) {
final CloseDialogReceiver closer = new CloseDialogReceiver(context);
if (sConfirmDialog != null) {
sConfirmDialog.dismiss();
}
sConfirmDialog = new AlertDialog.Builder(context)
.setTitle(mRebootSafeMode
? com.android.internal.R.string.reboot_safemode_title
: com.android.internal.R.string.power_off)
.setMessage(resourceId)
.setPositiveButton(com.android.internal.R.string.yes, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
beginShutdownSequence(context);
}
})
.setNegativeButton(com.android.internal.R.string.no, null)
.create();
closer.dialog = sConfirmDialog;
sConfirmDialog.setOnDismissListener(closer);
sConfirmDialog.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG);
sConfirmDialog.show();
} else {
//走这里
beginShutdownSequence(context);
}
}2.10 ST.beginShutdownSequence
[->ShutdownThread.java]
private static void beginShutdownSequence(Context context) {
synchronized (sIsStartedGuard) {
if (sIsStarted) {
Log.d(TAG, "Shutdown sequence already running, returning.");
return;
}
sIsStarted = true;
}
sInstance.mProgressDialog = showShutdownDialog(context);
sInstance.mContext = context;
sInstance.mPowerManager = (PowerManager)context.getSystemService(Context.POWER_SERVICE);
// make sure we never fall asleep again
sInstance.mCpuWakeLock = null;
try {
sInstance.mCpuWakeLock = sInstance.mPowerManager.newWakeLock(
PowerManager.PARTIAL_WAKE_LOCK, TAG + "-cpu");
sInstance.mCpuWakeLock.setReferenceCounted(false);
sInstance.mCpuWakeLock.acquire();
} catch (SecurityException e) {
Log.w(TAG, "No permission to acquire wake lock", e);
sInstance.mCpuWakeLock = null;
}
// also make sure the screen stays on for better user experience
sInstance.mScreenWakeLock = null;
if (sInstance.mPowerManager.isScreenOn()) {
try {
sInstance.mScreenWakeLock = sInstance.mPowerManager.newWakeLock(
PowerManager.FULL_WAKE_LOCK, TAG + "-screen");
sInstance.mScreenWakeLock.setReferenceCounted(false);
sInstance.mScreenWakeLock.acquire();
} catch (SecurityException e) {
Log.w(TAG, "No permission to acquire wake lock", e);
sInstance.mScreenWakeLock = null;
}
}
if (SecurityLog.isLoggingEnabled()) {
SecurityLog.writeEvent(SecurityLog.TAG_OS_SHUTDOWN);
}
// start the thread that initiates shutdown
sInstance.mHandler = new Handler() {
};
//启动线程
sInstance.start();
}2.10.1 ST.showShutdownDialog
[->ShutdownThread.java]
private static ProgressDialog showShutdownDialog(Context context) {
// Throw up a system dialog to indicate the device is rebooting / shutting down.
ProgressDialog pd = new ProgressDialog(context);
// Path 1: Reboot to recovery for update
// Condition: mReason startswith REBOOT_RECOVERY_UPDATE
//
// Path 1a: uncrypt needed
// Condition: if /cache/recovery/uncrypt_file exists but
// /cache/recovery/block.map doesn't.
// UI: determinate progress bar (mRebootHasProgressBar == True)
//
// * Path 1a is expected to be removed once the GmsCore shipped on
// device always calls uncrypt prior to reboot.
//
// Path 1b: uncrypt already done
// UI: spinning circle only (no progress bar)
//
// Path 2: Reboot to recovery for factory reset
// Condition: mReason == REBOOT_RECOVERY
// UI: spinning circle only (no progress bar)
//
// Path 3: Regular reboot / shutdown
// Condition: Otherwise
// UI: spinning circle only (no progress bar)
// mReason could be "recovery-update" or "recovery-update,quiescent".
//传入的是REBOOT_RECOVERY_UPDATE，走这里
if (mReason != null && mReason.startsWith(PowerManager.REBOOT_RECOVERY_UPDATE)) {
// We need the progress bar if uncrypt will be invoked during the
// reboot, which might be time-consuming.
mRebootHasProgressBar = RecoverySystem.UNCRYPT_PACKAGE_FILE.exists()
&& !(RecoverySystem.BLOCK_MAP_FILE.exists());
pd.setTitle(context.getText(com.android.internal.R.string.reboot_to_update_title));
//正常升级模式下，mRebootHasProgressBar = true
if (mRebootHasProgressBar) {
pd.setMax(100);
pd.setProgress(0);
pd.setIndeterminate(false);
pd.setProgressNumberFormat(null);
pd.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
pd.setMessage(context.getText(
com.android.internal.R.string.reboot_to_update_prepare));
} else {
if (showSysuiReboot()) {
return null;
}
pd.setIndeterminate(true);
pd.setMessage(context.getText(
com.android.internal.R.string.reboot_to_update_reboot));
}
} else if (mReason != null && mReason.equals(PowerManager.REBOOT_RECOVERY)) {
if (RescueParty.isAttemptingFactoryReset()) {
// We're not actually doing a factory reset yet; we're rebooting
// to ask the user if they'd like to reset, so give them a less
// scary dialog message.
pd.setTitle(context.getText(com.android.internal.R.string.power_off));
pd.setMessage(context.getText(com.android.internal.R.string.shutdown_progress));
pd.setIndeterminate(true);
} else {
// Factory reset path. Set the dialog message accordingly.
pd.setTitle(context.getText(com.android.internal.R.string.reboot_to_reset_title));
pd.setMessage(context.getText(
com.android.internal.R.string.reboot_to_reset_message));
pd.setIndeterminate(true);
}
} else {
if (showSysuiReboot()) {
return null;
}
pd.setTitle(context.getText(com.android.internal.R.string.power_off));
pd.setMessage(context.getText(com.android.internal.R.string.shutdown_progress));
pd.setIndeterminate(true);
}
pd.setCancelable(false);
pd.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG);
pd.show();
return pd;
}2.11 ST.run
[->ShutdownThread.java]
/**
* Makes sure we handle the shutdown gracefully.
* Shuts off power regardless of radio state if the allotted time has passed.
*/
public void run() {
TimingsTraceLog shutdownTimingLog = newTimingsLog();
shutdownTimingLog.traceBegin("SystemServerShutdown");
metricShutdownStart();
metricStarted(METRIC_SYSTEM_SERVER);
BroadcastReceiver br = new BroadcastReceiver() {
@Override public void onReceive(Context context, Intent intent) {
// We don't allow apps to cancel this, so ignore the result.
actionDone();
}
};
/*
* Write a system property in case the system_server reboots before we
* get to the actual hardware restart. If that happens, we'll retry at
* the beginning of the SystemServer startup.
*/
{
String reason = (mReboot ? "1" : "0") + (mReason != null ? mReason : "");
SystemProperties.set(SHUTDOWN_ACTION_PROPERTY, reason);
}
/*
* If we are rebooting into safe mode, write a system property
* indicating so.
*/
if (mRebootSafeMode) {
SystemProperties.set(REBOOT_SAFEMODE_PROPERTY, "1");
}
metricStarted(METRIC_SEND_BROADCAST);
shutdownTimingLog.traceBegin("SendShutdownBroadcast");
Log.i(TAG, "Sending shutdown broadcast...");
// First send the high-level shut down broadcast.
mActionDone = false;
Intent intent = new Intent(Intent.ACTION_SHUTDOWN);
intent.addFlags(Intent.FLAG_RECEIVER_FOREGROUND | Intent.FLAG_RECEIVER_REGISTERED_ONLY);
mContext.sendOrderedBroadcastAsUser(intent,
UserHandle.ALL, null, br, mHandler, 0, null, null);
final long endTime = SystemClock.elapsedRealtime() + MAX_BROADCAST_TIME;
synchronized (mActionDoneSync) {
while (!mActionDone) {
long delay = endTime - SystemClock.elapsedRealtime();
if (delay <= 0) {
Log.w(TAG, "Shutdown broadcast timed out");
break;
} else if (mRebootHasProgressBar) {
int status = (int)((MAX_BROADCAST_TIME - delay) * 1.0 *
BROADCAST_STOP_PERCENT / MAX_BROADCAST_TIME);
sInstance.setRebootProgress(status, null);
}
try {
mActionDoneSync.wait(Math.min(delay, ACTION_DONE_POLL_WAIT_MS));
} catch (InterruptedException e) {
}
}
}
if (mRebootHasProgressBar) {
sInstance.setRebootProgress(BROADCAST_STOP_PERCENT, null);
}
shutdownTimingLog.traceEnd(); // SendShutdownBroadcast
metricEnded(METRIC_SEND_BROADCAST);
Log.i(TAG, "Shutting down activity manager...");
shutdownTimingLog.traceBegin("ShutdownActivityManager");
metricStarted(METRIC_AM);
final IActivityManager am =
IActivityManager.Stub.asInterface(ServiceManager.checkService("activity"));
if (am != null) {
try {
am.shutdown(MAX_BROADCAST_TIME);
} catch (RemoteException e) {
}
}
if (mRebootHasProgressBar) {
sInstance.setRebootProgress(ACTIVITY_MANAGER_STOP_PERCENT, null);
}
shutdownTimingLog.traceEnd();// ShutdownActivityManager
metricEnded(METRIC_AM);
Log.i(TAG, "Shutting down package manager...");
shutdownTimingLog.traceBegin("ShutdownPackageManager");
metricStarted(METRIC_PM);
final PackageManagerService pm = (PackageManagerService)
ServiceManager.getService("package");
if (pm != null) {
pm.shutdown();
}
if (mRebootHasProgressBar) {
sInstance.setRebootProgress(PACKAGE_MANAGER_STOP_PERCENT, null);
}
shutdownTimingLog.traceEnd(); // ShutdownPackageManager
metricEnded(METRIC_PM);
// Shutdown radios.
shutdownTimingLog.traceBegin("ShutdownRadios");
metricStarted(METRIC_RADIOS);
shutdownRadios(MAX_RADIO_WAIT_TIME);
if (mRebootHasProgressBar) {
sInstance.setRebootProgress(RADIO_STOP_PERCENT, null);
}
shutdownTimingLog.traceEnd(); // ShutdownRadios
metricEnded(METRIC_RADIOS);
//为true，将执行uncrypt操作
if (mRebootHasProgressBar) {
sInstance.setRebootProgress(MOUNT_SERVICE_STOP_PERCENT, null);
// If it's to reboot to install an update and uncrypt hasn't been
// done yet, trigger it now.
uncrypt();
}
shutdownTimingLog.traceEnd(); // SystemServerShutdown
metricEnded(METRIC_SYSTEM_SERVER);
saveMetrics(mReboot, mReason);
// Remaining work will be done by init, including vold shutdown
rebootOrShutdown(mContext, mReboot, mReason);
}2.12 ST.uncrypt
[->ShutdownThread.java]
private void uncrypt() {
Log.i(TAG, "Calling uncrypt and monitoring the progress...");
final RecoverySystem.ProgressListener progressListener =
new RecoverySystem.ProgressListener() {
@Override
public void onProgress(int status) {
if (status >= 0 && status < 100) {
// Scale down to [MOUNT_SERVICE_STOP_PERCENT, 100).
status = (int)(status * (100.0 - MOUNT_SERVICE_STOP_PERCENT) / 100);
status += MOUNT_SERVICE_STOP_PERCENT;
CharSequence msg = mContext.getText(
com.android.internal.R.string.reboot_to_update_package);
sInstance.setRebootProgress(status, msg);
} else if (status == 100) {
CharSequence msg = mContext.getText(
com.android.internal.R.string.reboot_to_update_reboot);
sInstance.setRebootProgress(status, msg);
} else {
// Ignored
}
}
};
final boolean[] done = new boolean[1];
done[0] = false;
Thread t = new Thread() {
@Override
public void run() {
RecoverySystem rs = (RecoverySystem) mContext.getSystemService(
Context.RECOVERY_SERVICE);
String filename = null;
try {
filename = FileUtils.readTextFile(RecoverySystem.UNCRYPT_PACKAGE_FILE, 0, null);
rs.processPackage(mContext, new File(filename), progressListener);
} catch (IOException e) {
Log.e(TAG, "Error uncrypting file", e);
}
done[0] = true;
}
};
t.start();
try {
t.join(MAX_UNCRYPT_WAIT_TIME);
} catch (InterruptedException unused) {
}
if (!done[0]) {
Log.w(TAG, "Timed out waiting for uncrypt.");
final int uncryptTimeoutError = 100;
String timeoutMessage = String.format("uncrypt_time: %d/n" + "uncrypt_error: %d/n",
MAX_UNCRYPT_WAIT_TIME / 1000, uncryptTimeoutError);
try {
FileUtils.stringToFile(RecoverySystem.UNCRYPT_STATUS_FILE, timeoutMessage);
} catch (IOException e) {
Log.e(TAG, "Failed to write timeout message to uncrypt status", e);
}
}
}2.13 RS.processPackage
[->RecoverySystem.java]
public static void processPackage(Context context,
File packageFile,
final ProgressListener listener,
final Handler handler)
throws IOException {
String filename = packageFile.getCanonicalPath();
if (!filename.startsWith("/data/")) {
return;
}
RecoverySystem rs = (RecoverySystem) context.getSystemService(Context.RECOVERY_SERVICE);
IRecoverySystemProgressListener progressListener = null;
if (listener != null) {
final Handler progressHandler;
if (handler != null) {
progressHandler = handler;
} else {
progressHandler = new Handler(context.getMainLooper());
}
progressListener = new IRecoverySystemProgressListener.Stub() {
int lastProgress = 0;
long lastPublishTime = System.currentTimeMillis();
@Override
public void onProgress(final int progress) {
final long now = System.currentTimeMillis();
progressHandler.post(new Runnable() {
@Override
public void run() {
if (progress > lastProgress &&
now - lastPublishTime > PUBLISH_PROGRESS_INTERVAL_MS) {
lastProgress = progress;
lastPublishTime = now;
listener.onProgress(progress);
}
}
});
}
};
}
//通过progressListener传递进度到界面
if (!rs.uncrypt(filename, progressListener)) {
throw new IOException("process package failed");
}
}2.14 RS.uncrypt
[->RecoverySystem.java]
/**
* Talks to RecoverySystemService via Binder to trigger uncrypt.
*/
private boolean uncrypt(String packageFile, IRecoverySystemProgressListener listener) {
try {
return mService.uncrypt(packageFile, listener);
} catch (RemoteException unused) {
}
return false;
}2.15 RSS.uncrypt
[->RecoverySystemService.java]
public boolean uncrypt(String filename, IRecoverySystemProgressListener listener) {
if (DEBUG) Slog.d(TAG, "uncrypt: " + filename);
synchronized (sRequestLock) {
mContext.enforceCallingOrSelfPermission(android.Manifest.permission.RECOVERY, null);
final boolean available = checkAndWaitForUncryptService();
if (!available) {
Slog.e(TAG, "uncrypt service is unavailable.");
return false;
}
// Write the filename into UNCRYPT_PACKAGE_FILE to be read by
// uncrypt.
RecoverySystem.UNCRYPT_PACKAGE_FILE.delete();
try (FileWriter uncryptFile = new FileWriter(RecoverySystem.UNCRYPT_PACKAGE_FILE)) {
uncryptFile.write(filename + "/n");
} catch (IOException e) {
Slog.e(TAG, "IOException when writing /"" +
RecoverySystem.UNCRYPT_PACKAGE_FILE + "/":", e);
return false;
}
// Trigger uncrypt via init.
//通过设置ctl.start属性，开启uncrypt服务
SystemProperties.set("ctl.start", "uncrypt");
// Connect to the uncrypt service socket.
//连接服务
LocalSocket socket = connectService();
if (socket == null) {
Slog.e(TAG, "Failed to connect to uncrypt socket");
return false;
}
// Read the status from the socket.
DataInputStream dis = null;
DataOutputStream dos = null;
try {
dis = new DataInputStream(socket.getInputStream());
dos = new DataOutputStream(socket.getOutputStream());
int lastStatus = Integer.MIN_VALUE;
while (true) {
// 读取进度
int status = dis.readInt();
// Avoid flooding the log with the same message.
if (status == lastStatus && lastStatus != Integer.MIN_VALUE) {
continue;
}
lastStatus = status;
if (status >= 0 && status <= 100) {
// Update status
Slog.i(TAG, "uncrypt read status: " + status);
if (listener != null) {
try {
listener.onProgress(status);
} catch (RemoteException ignored) {
Slog.w(TAG, "RemoteException when posting progress");
}
}
if (status == 100) {
Slog.i(TAG, "uncrypt successfully finished.");
// Ack receipt of the final status code. uncrypt
// waits for the ack so the socket won't be
// destroyed before we receive the code.
dos.writeInt(0);
break;
}
} else {
// Error in /system/bin/uncrypt.
Slog.e(TAG, "uncrypt failed with status: " + status);
// Ack receipt of the final status code. uncrypt waits
// for the ack so the socket won't be destroyed before
// we receive the code.
dos.writeInt(0);
return false;
}
}
} catch (IOException e) {
Slog.e(TAG, "IOException when reading status: ", e);
return false;
} finally {
IoUtils.closeQuietly(dis);
IoUtils.closeQuietly(dos);
IoUtils.closeQuietly(socket);
}
return true;
}
}SystemProperties.set(“ctl.start”, “uncrypt”);这个操作主要是通过init（启动的Properties服务）进行,而后启动uncrypt服务，通过socket方式systemserver和uncrypt进行通信。
[->uncrypt.rc]
service uncrypt /system/bin/uncrypt
class main
socket uncrypt stream 600 system system
disabled
oneshot
service setup-bcb /system/bin/uncrypt --setup-bcb
class main
socket uncrypt stream 600 system system
disabled
oneshot
service clear-bcb /system/bin/uncrypt --clear-bcb
class main
socket uncrypt stream 600 system system
disabled
oneshot2.16 uncrypt.main
[->uncrypt.cpp]
//
// If the filesystem is using an encrypted block device, it will also
// read the file and rewrite it to the same blocks of the underlying
// (unencrypted) block device, so the file contents can be read
// without the need for the decryption key.
//
// The output of this program is a "block map" which looks like this:
//
// /dev/block/platform/msm_sdcc.1/by-name/userdata # block device
// 49652 4096 # file size in bytes, block size
// 3 # count of block ranges
// 1000 1008 # block range 0
// 2100 2102 # ... block range 1
// 30 33 # ... block range 2
//
// Each block range represents a half-open interval; the line "30 33"
// reprents the blocks [30, 31, 32].
//
// Recovery can take this block map file and retrieve the underlying
// file data to use as an update package.
/**
* In addition to the uncrypt work, uncrypt also takes care of setting and
* clearing the bootloader control block (BCB) at /misc partition.
*
* uncrypt is triggered as init services on demand. It uses socket to
* communicate with its caller (i.e. system_server). The socket is managed by
* init (i.e. created prior to the service starts, and destroyed when uncrypt
* exits).
*
* Below is the uncrypt protocol.
*
* a. caller b. init c. uncrypt
* --------------- ------------ --------------
* a1. ctl.start:
* setup-bcb /
* clear-bcb /
* uncrypt
*
* b2. create socket at
* /dev/socket/uncrypt
*
* c3. listen and accept
*
* a4. send a 4-byte int
* (message length)
* c5. receive message length
* a6. send message
* c7. receive message
* c8. <do the work; may send
* the progress>
* a9. <may handle progress>
* c10. <upon finishing>
* send "100" or "-1"
*
* a11. receive status code
* a12. send a 4-byte int to
* ack the receive of the
* final status code
* c13. receive and exit
*
* b14. destroy the socket
*
* Note that a12 and c13 are necessary to ensure a11 happens before the socket
* gets destroyed in b14.
*/
int main(int argc, char** argv) {
enum { UNCRYPT, SETUP_BCB, CLEAR_BCB, UNCRYPT_DEBUG } action;
const char* input_path = nullptr;
const char* map_file = CACHE_BLOCK_MAP.c_str();
//解析参数
if (argc == 2 && strcmp(argv[1], "--clear-bcb") == 0) {
action = CLEAR_BCB;
} else if (argc == 2 && strcmp(argv[1], "--setup-bcb") == 0) {
action = SETUP_BCB;
} else if (argc == 1) {
action = UNCRYPT;
} else if (argc == 3) {
input_path = argv[1];
map_file = argv[2];
action = UNCRYPT_DEBUG;
} else {
usage(argv[0]);
return 2;
}
if ((fstab = read_fstab()) == nullptr) {
log_uncrypt_error_code(kUncryptFstabReadError);
return 1;
}
if (action == UNCRYPT_DEBUG) {
LOG(INFO) << "uncrypt called in debug mode, skip socket communication";
bool success = uncrypt_wrapper(input_path, map_file, -1);
if (success) {
LOG(INFO) << "uncrypt succeeded";
} else{
LOG(INFO) << "uncrypt failed";
}
return success ? 0 : 1;
}
// c3. The socket is created by init when starting the service. uncrypt
// will use the socket to communicate with its caller.
android::base::unique_fd service_socket(android_get_control_socket(UNCRYPT_SOCKET.c_str()));
if (service_socket == -1) {
PLOG(ERROR) << "failed to open socket /"" << UNCRYPT_SOCKET << "/"";
log_uncrypt_error_code(kUncryptSocketOpenError);
return 1;
}
fcntl(service_socket, F_SETFD, FD_CLOEXEC);
if (listen(service_socket, 1) == -1) {
PLOG(ERROR) << "failed to listen on socket " << service_socket.get();
log_uncrypt_error_code(kUncryptSocketListenError);
return 1;
}
android::base::unique_fd socket_fd(accept4(service_socket, nullptr, nullptr, SOCK_CLOEXEC));
if (socket_fd == -1) {
PLOG(ERROR) << "failed to accept on socket " << service_socket.get();
log_uncrypt_error_code(kUncryptSocketAcceptError);
return 1;
}
bool success = false;
switch (action) {
//UNCRYPT操作
case UNCRYPT:
success = uncrypt_wrapper(input_path, map_file, socket_fd);
break;
case SETUP_BCB:
success = setup_bcb(socket_fd);
break;
case CLEAR_BCB:
success = clear_bcb(socket_fd);
break;
default: // Should never happen.
LOG(ERROR) << "Invalid uncrypt action code: " << action;
return 1;
}
// c13. Read a 4-byte code from the client before uncrypt exits. This is to
// ensure the client to receive the last status code before the socket gets
// destroyed.
int code;
if (android::base::ReadFully(socket_fd, &code, 4)) {
LOG(INFO) << " received " << code << ", exiting now";
} else {
PLOG(ERROR) << "failed to read the code";
}
return success ? 0 : 1;
}通过文件头的注释，可以知道具体的通信方式。
2.17 uncrypt.uncrypt_wrapper
[->uncrypt.cpp]
static bool uncrypt_wrapper(const char* input_path, const char* map_file, const int socket) {
// Initialize the uncrypt error to kUncryptErrorPlaceholder.
log_uncrypt_error_code(kUncryptErrorPlaceholder);
std::string package;
if (input_path == nullptr) {
if (!find_uncrypt_package(UNCRYPT_PATH_FILE, &package)) {
write_status_to_socket(-1, socket);
// Overwrite the error message.
log_uncrypt_error_code(kUncryptPackageMissingError);
return false;
}
input_path = package.c_str();
}
CHECK(map_file != nullptr);
auto start = std::chrono::system_clock::now();
//执行uncrypt操作
int status = uncrypt(input_path, map_file, socket);
std::chrono::duration<double> duration = std::chrono::system_clock::now() - start;
int count = static_cast<int>(duration.count());
std::string uncrypt_message = android::base::StringPrintf("uncrypt_time: %d/n", count);
if (status != 0) {
// Log the time cost and error code if uncrypt fails.
uncrypt_message += android::base::StringPrintf("uncrypt_error: %d/n", status);
if (!android::base::WriteStringToFile(uncrypt_message, UNCRYPT_STATUS)) {
PLOG(WARNING) << "failed to write to " << UNCRYPT_STATUS;
}
write_status_to_socket(-1, socket);
return false;
}
if (!android::base::WriteStringToFile(uncrypt_message, UNCRYPT_STATUS)) {
PLOG(WARNING) << "failed to write to " << UNCRYPT_STATUS;
}
//通过socket方式通知进度
write_status_to_socket(100, socket);
return true;
}2.18 uncrypt.uncrypt
[->uncrypt.cpp]
static int uncrypt(const char* input_path, const char* map_file, const int socket) {
LOG(INFO) << "update package is /"" << input_path << "/"";
// Turn the name of the file we're supposed to convert into an absolute path, so we can find
// what filesystem it's on.
char path[PATH_MAX+1];
if (realpath(input_path, path) == nullptr) {
PLOG(ERROR) << "failed to convert /"" << input_path << "/" to absolute path";
return kUncryptRealpathFindError;
}
bool encryptable;
bool encrypted;
bool f2fs_fs;
const char* blk_dev = find_block_device(path, &encryptable, &encrypted, &f2fs_fs);
if (blk_dev == nullptr) {
LOG(ERROR) << "failed to find block device for " << path;
return kUncryptBlockDeviceFindError;
}
// If the filesystem it's on isn't encrypted, we only produce the
// block map, we don't rewrite the file contents (it would be
// pointless to do so).
LOG(INFO) << "encryptable: " << (encryptable ? "yes" : "no");
LOG(INFO) << " encrypted: " << (encrypted ? "yes" : "no");
// Recovery supports installing packages from 3 paths: /cache,
// /data, and /sdcard. (On a particular device, other locations
// may work, but those are three we actually expect.)
//
// On /data we want to convert the file to a block map so that we
// can read the package without mounting the partition. On /cache
// and /sdcard we leave the file alone.
if (strncmp(path, "/data/", 6) == 0) {
LOG(INFO) << "writing block map " << map_file;
//生成blockmap
return produce_block_map(path, map_file, blk_dev, encrypted, f2fs_fs, socket);
}
return 0;
}2.19 uncrypt.produce_block_map
[->uncrypt.cpp]
static int produce_block_map(const char* path, const char* map_file, const char* blk_dev,
bool encrypted, bool f2fs_fs, int socket) {
std::string err;
if (!android::base::RemoveFileIfExists(map_file, &err)) {
LOG(ERROR) << "failed to remove the existing map file " << map_file << ": " << err;
return kUncryptFileRemoveError;
}
std::string tmp_map_file = std::string(map_file) + ".tmp";
android::base::unique_fd mapfd(open(tmp_map_file.c_str(),
O_WRONLY | O_CREAT, S_IRUSR | S_IWUSR));
if (mapfd == -1) {
PLOG(ERROR) << "failed to open " << tmp_map_file;
return kUncryptFileOpenError;
}
// Make sure we can write to the socket.
if (!write_status_to_socket(0, socket)) {
LOG(ERROR) << "failed to write to socket " << socket;
return kUncryptSocketWriteError;
}
struct stat sb;
if (stat(path, &sb) != 0) {
LOG(ERROR) << "failed to stat " << path;
return kUncryptFileStatError;
}
LOG(INFO) << " block size: " << sb.st_blksize << " bytes";
int blocks = ((sb.st_size-1) / sb.st_blksize) + 1;
LOG(INFO) << " file size: " << sb.st_size << " bytes, " << blocks << " blocks";
std::vector<int> ranges;
std::string s = android::base::StringPrintf("%s/n%" PRId64 " %" PRId64 "/n",
blk_dev, static_cast<int64_t>(sb.st_size),
static_cast<int64_t>(sb.st_blksize));
if (!android::base::WriteStringToFd(s, mapfd)) {
PLOG(ERROR) << "failed to write " << tmp_map_file;
return kUncryptWriteError;
}
std::vector<std::vector<unsigned char>> buffers;
/*
* buffers大小为5，static constexpr int WINDOW_SIZE = 5;
*/
if (encrypted) {
buffers.resize(WINDOW_SIZE, std::vector<unsigned char>(sb.st_blksize));
}
int head_block = 0;
int head = 0, tail = 0;
android::base::unique_fd fd(open(path, O_RDONLY));
if (fd == -1) {
PLOG(ERROR) << "failed to open " << path << " for reading";
return kUncryptFileOpenError;
}
android::base::unique_fd wfd;
if (encrypted) {
wfd.reset(open(blk_dev, O_WRONLY));
if (wfd == -1) {
PLOG(ERROR) << "failed to open " << blk_dev << " for writing";
return kUncryptBlockOpenError;
}
}
#ifndef F2FS_IOC_SET_DONTMOVE
#ifndef F2FS_IOCTL_MAGIC
#define F2FS_IOCTL_MAGIC 0xf5
#endif
#define F2FS_IOC_SET_DONTMOVE _IO(F2FS_IOCTL_MAGIC, 13)
#endif
if (f2fs_fs && ioctl(fd, F2FS_IOC_SET_DONTMOVE) < 0) {
PLOG(ERROR) << "Failed to set non-movable file for f2fs: " << path << " on " << blk_dev;
return kUncryptIoctlError;
}
off64_t pos = 0;
int last_progress = 0;
while (pos < sb.st_size) {
// Update the status file, progress must be between [0, 99].
int progress = static_cast<int>(100 * (double(pos) / double(sb.st_size)));
if (progress > last_progress) {
last_progress = progress;
write_status_to_socket(progress, socket);
}
if ((tail+1) % WINDOW_SIZE == head) {
// write out head buffer
int block = head_block;
if (ioctl(fd, FIBMAP, &block) != 0) {
PLOG(ERROR) << "failed to find block " << head_block;
return kUncryptIoctlError;
}
if (block == 0) {
LOG(ERROR) << "failed to find block " << head_block << ", retrying";
int error = retry_fibmap(fd, path, &block, head_block);
if (error != kUncryptNoError) {
return error;
}
}
add_block_to_ranges(ranges, block);
//data分区是否加密
if (encrypted) {
if (write_at_offset(buffers[head].data(), sb.st_blksize, wfd,
static_cast<off64_t>(sb.st_blksize) * block) != 0) {
return kUncryptWriteError;
}
}
head = (head + 1) % WINDOW_SIZE;
++head_block;
}
// read next block to tail
// data分区加密
if (encrypted) {
size_t to_read = static_cast<size_t>(
std::min(static_cast<off64_t>(sb.st_blksize), sb.st_size - pos));
if (!android::base::ReadFully(fd, buffers[tail].data(), to_read)) {
PLOG(ERROR) << "failed to read " << path;
return kUncryptReadError;
}
pos += to_read;
} else {
// If we're not encrypting; we don't need to actually read
// anything, just skip pos forward as if we'd read a
// block.
pos += sb.st_blksize;
}
tail = (tail+1) % WINDOW_SIZE;
}
while (head != tail) {
// write out head buffer
int block = head_block;
if (ioctl(fd, FIBMAP, &block) != 0) {
PLOG(ERROR) << "failed to find block " << head_block;
return kUncryptIoctlError;
}
if (block == 0) {
LOG(ERROR) << "failed to find block " << head_block << ", retrying";
int error = retry_fibmap(fd, path, &block, head_block);
if (error != kUncryptNoError) {
return error;
}
}
add_block_to_ranges(ranges, block);
//data分区是否加密
if (encrypted) {
if (write_at_offset(buffers[head].data(), sb.st_blksize, wfd,
static_cast<off64_t>(sb.st_blksize) * block) != 0) {
return kUncryptWriteError;
}
}
head = (head + 1) % WINDOW_SIZE;
++head_block;
}
if (!android::base::WriteStringToFd(
android::base::StringPrintf("%zu/n", ranges.size() / 2), mapfd)) {
PLOG(ERROR) << "failed to write " << tmp_map_file;
return kUncryptWriteError;
}
for (size_t i = 0; i < ranges.size(); i += 2) {
if (!android::base::WriteStringToFd(
android::base::StringPrintf("%d %d/n", ranges[i], ranges[i+1]), mapfd)) {
PLOG(ERROR) << "failed to write " << tmp_map_file;
return kUncryptWriteError;
}
}
if (fsync(mapfd) == -1) {
PLOG(ERROR) << "failed to fsync /"" << tmp_map_file << "/"";
return kUncryptFileSyncError;
}
if (close(mapfd.release()) == -1) {
PLOG(ERROR) << "failed to close " << tmp_map_file;
return kUncryptFileCloseError;
}
if (encrypted) {
if (fsync(wfd) == -1) {
PLOG(ERROR) << "failed to fsync /"" << blk_dev << "/"";
return kUncryptFileSyncError;
}
if (close(wfd.release()) == -1) {
PLOG(ERROR) << "failed to close " << blk_dev;
return kUncryptFileCloseError;
}
}
if (rename(tmp_map_file.c_str(), map_file) == -1) {
PLOG(ERROR) << "failed to rename " << tmp_map_file << " to " << map_file;
return kUncryptFileRenameError;
}
// Sync dir to make rename() result written to disk.
std::string file_name = map_file;
std::string dir_name = dirname(&file_name[0]);
android::base::unique_fd dfd(open(dir_name.c_str(), O_RDONLY | O_DIRECTORY));
if (dfd == -1) {
PLOG(ERROR) << "failed to open dir " << dir_name;
return kUncryptFileOpenError;
}
if (fsync(dfd) == -1) {
PLOG(ERROR) << "failed to fsync " << dir_name;
return kUncryptFileSyncError;
}
if (close(dfd.release()) == -1) {
PLOG(ERROR) << "failed to close " << dir_name;
return kUncryptFileCloseError;
}
return 0;
}这里将ota升级包生成block.map，如果升级包在的分区data是加密，那么每次获得每个block实际索引时，读取解密后的block数据到buffer，每当有5个block数据时，然后把buffer数据写入到实际的对应索引block中。
执行完成uncrypt操作，接着2.11节，执行重启的操作。
如果要测试uncrypt的功能，可以在adb shell环境下测试，将ota包推到data目录下，直接执行uncrypt命名。
# uncrypt /data/ota.zip /cache/recovery/block.map
# cat /cache/recovery/block.map
/dev/block/bootdevice/by-name/userdata //block device
1189005639 4096 //文件大小，block块大小
2 //block块的个数
440320 524288 //第一个block块的范围区间
561152 767469 //第二个block块的范围区间2.20 ST.rebootOrShutdown
接着2.11中run方法继续。
[->ShutdownThread.java]
public static void rebootOrShutdown(final Context context, boolean reboot, String reason) {
// 传过来reboot为true
if (reboot) {
Log.i(TAG, "Rebooting, reason: " + reason);
PowerManagerService.lowLevelReboot(reason);
Log.e(TAG, "Reboot failed, will attempt shutdown instead");
reason = null;
} else if (SHUTDOWN_VIBRATE_MS > 0 && context != null) {
// vibrate before shutting down
Vibrator vibrator = new SystemVibrator(context);
try {
vibrator.vibrate(SHUTDOWN_VIBRATE_MS, VIBRATION_ATTRIBUTES);
} catch (Exception e) {
// Failure to vibrate shouldn't interrupt shutdown. Just log it.
Log.w(TAG, "Failed to vibrate during shutdown.", e);
}
// vibrator is asynchronous so we need to wait to avoid shutting down too soon.
try {
Thread.sleep(SHUTDOWN_VIBRATE_MS);
} catch (InterruptedException unused) {
}
}
// Shutdown power
Log.i(TAG, "Performing low-level shutdown...");
PowerManagerService.lowLevelShutdown(reason);
}2.20.1 PWS.lowLevelReboot
[->PowerManagerService.java]
/**
* Low-level function to reboot the device. On success, this
* function doesn't return. If more than 20 seconds passes from
* the time a reboot is requested, this method returns.
*
* @param reason code to pass to the kernel (e.g. "recovery"), or null.
*/
public static void lowLevelReboot(String reason) {
if (reason == null) {
reason = "";
}
// If the reason is "quiescent", it means that the boot process should proceed
// without turning on the screen/lights.
// The "quiescent" property is sticky, meaning that any number
// of subsequent reboots should honor the property until it is reset.
if (reason.equals(PowerManager.REBOOT_QUIESCENT)) {
sQuiescent = true;
reason = "";
} else if (reason.endsWith("," + PowerManager.REBOOT_QUIESCENT)) {
sQuiescent = true;
reason = reason.substring(0,
reason.length() - PowerManager.REBOOT_QUIESCENT.length() - 1);
}
if (reason.equals(PowerManager.REBOOT_RECOVERY)
|| reason.equals(PowerManager.REBOOT_RECOVERY_UPDATE)) {
reason = "recovery";
}
if (sQuiescent) {
// Pass the optional "quiescent" argument to the bootloader to let it know
// that it should not turn the screen/lights on.
reason = reason + ",quiescent";
}
//重启操作
SystemProperties.set("sys.powerctl", "reboot," + reason);
try {
Thread.sleep(20 * 1000L);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
Slog.wtf(TAG, "Unexpected return from lowLevelReboot!");
}2.20.2 PWS.lowLevelReboot
public static void lowLevelShutdown(String reason) {
if (reason == null) {
reason = "";
}
//关机
SystemProperties.set("sys.powerctl", "shutdown," + reason);
}2.21 小结
OTA升级重启前，主要的操作是对升级包进行处理的过程，对升级包提前处理的原因是因为在进入recovery模式进行升级时无法加载升级包所在的分区。在重启前的主要操作如下：
1.通过SystemProperties设置属性(setup-bcb)，向BCB中设置升级的Command；
2.通过SystemProperties设置属性(uncrypt)，开启uncrypt服务，将升级包生成一系列的block块，recovery可以读取block.map文件并获取这个文件的数据作为升级包；
3.uncrypt完成后，重启。
三、OTA升级重启后
终端重启后，加载bootloader过程中，由于之前写入的recovery的command，则将进入recovery模式.
3.1 aboot.aboot_init
[->aboot.c]
void aboot_init(const struct app_descriptor *app)
{
unsigned reboot_mode = 0;
int boot_err_type = 0;
int boot_slot = INVALID;
/* Initialise wdog to catch early lk crashes */
#if WDOG_SUPPORT
msm_wdog_init();
#endif
/* Setup page size information for nv storage */
if (target_is_emmc_boot())
{
page_size = mmc_page_size();
page_mask = page_size - 1;
mmc_blocksize = mmc_get_device_blocksize();
mmc_blocksize_mask = mmc_blocksize - 1;
}
else
{
page_size = flash_page_size();
page_mask = page_size - 1;
}
ASSERT((MEMBASE + MEMSIZE) > MEMBASE);
read_device_info(&device);
read_allow_oem_unlock(&device);
/* Detect multi-slot support */
if (partition_multislot_is_supported())
{
boot_slot = partition_find_active_slot();
if (boot_slot == INVALID)
{
boot_into_fastboot = true;
dprintf(INFO, "Active Slot: (INVALID)/n");
}
else
{
/* Setting the state of system to boot active slot */
partition_mark_active_slot(boot_slot);
dprintf(INFO, "Active Slot: (%s)/n", SUFFIX_SLOT(boot_slot));
}
}
/* Display splash screen if enabled */
#if DISPLAY_SPLASH_SCREEN
#if NO_ALARM_DISPLAY
if (!check_alarm_boot()) {
#endif
dprintf(SPEW, "Display Init: Start/n");
#if DISPLAY_HDMI_PRIMARY
if (!strlen(device.display_panel))
strlcpy(device.display_panel, DISPLAY_PANEL_HDMI,
sizeof(device.display_panel));
#endif
#if ENABLE_WBC
/* Wait if the display shutdown is in progress */
while(pm_app_display_shutdown_in_prgs());
if (!pm_appsbl_display_init_done())
target_display_init(device.display_panel);
else
display_image_on_screen();
#else
target_display_init(device.display_panel);
#endif
dprintf(SPEW, "Display Init: Done/n");
#if NO_ALARM_DISPLAY
}
#endif
#endif
target_serialno((unsigned char *) sn_buf);
dprintf(SPEW,"serial number: %s/n",sn_buf);
memset(display_panel_buf, '/0', MAX_PANEL_BUF_SIZE);
/*
* Check power off reason if user force reset,
* if yes phone will do normal boot.
*/
if (is_user_force_reset())
goto normal_boot;
/* Check if we should do something other than booting up */
if (keys_get_state(KEY_VOLUMEUP) && keys_get_state(KEY_VOLUMEDOWN))
{
dprintf(ALWAYS,"dload mode key sequence detected/n");
reboot_device(EMERGENCY_DLOAD);
dprintf(CRITICAL,"Failed to reboot into dload mode/n");
boot_into_fastboot = true;
}
if (!boot_into_fastboot)
{
if (keys_get_state(KEY_HOME) || keys_get_state(KEY_VOLUMEUP))
boot_into_recovery = 1;
if (!boot_into_recovery &&
(keys_get_state(KEY_BACK) || keys_get_state(KEY_VOLUMEDOWN)))
boot_into_fastboot = true;
}
#if NO_KEYPAD_DRIVER
if (fastboot_trigger())
boot_into_fastboot = true;
#endif
#if USE_PON_REBOOT_REG
reboot_mode = check_hard_reboot_mode();
#else
reboot_mode = check_reboot_mode();
#endif
if (reboot_mode == RECOVERY_MODE)
{
boot_into_recovery = 1;
}
else if(reboot_mode == FASTBOOT_MODE)
{
boot_into_fastboot = true;
}
else if(reboot_mode == ALARM_BOOT)
{
boot_reason_alarm = true;
}
#if VERIFIED_BOOT || VERIFIED_BOOT_2
else if (VB_M <= target_get_vb_version())
{
if (reboot_mode == DM_VERITY_ENFORCING)
{
device.verity_mode = 1;
write_device_info(&device);
}
#if ENABLE_VB_ATTEST
else if (reboot_mode == DM_VERITY_EIO)
#else
else if (reboot_mode == DM_VERITY_LOGGING)
#endif
{
device.verity_mode = 0;
write_device_info(&device);
}
else if (reboot_mode == DM_VERITY_KEYSCLEAR)
{
if(send_delete_keys_to_tz())
ASSERT(0);
}
}
#endif
normal_boot:
if (!boot_into_fastboot)
{
if (target_is_emmc_boot())
{
if(emmc_recovery_init())
dprintf(ALWAYS,"error in emmc_recovery_init/n");
if(target_use_signed_kernel())
{
if((device.is_unlocked) || (device.is_tampered))
{
#ifdef TZ_TAMPER_FUSE
set_tamper_fuse_cmd(HLOS_IMG_TAMPER_FUSE);
#endif
#if USE_PCOM_SECBOOT
set_tamper_flag(device.is_tampered);
#endif
}
}
retry_boot:
/* Trying to boot active partition */
if (partition_multislot_is_supported())
{
boot_slot = partition_find_boot_slot();
partition_mark_active_slot(boot_slot);
if (boot_slot == INVALID)
goto fastboot;
}
boot_err_type = boot_linux_from_mmc();
switch (boot_err_type)
{
case ERR_INVALID_PAGE_SIZE:
case ERR_DT_PARSE:
case ERR_ABOOT_ADDR_OVERLAP:
case ERR_INVALID_BOOT_MAGIC:
if(partition_multislot_is_supported())
{
/*
* Deactivate current slot, as it failed to
* boot, and retry next slot.
*/
partition_deactivate_slot(boot_slot);
goto retry_boot;
}
else
break;
default:
break;
/* going to fastboot menu */
}
}
else
{
//见3.2节
recovery_init();
#if USE_PCOM_SECBOOT
if((device.is_unlocked) || (device.is_tampered))
set_tamper_flag(device.is_tampered);
#endif
boot_linux_from_flash();
}
dprintf(CRITICAL, "ERROR: Could not do normal boot. Reverting "
"to fastboot mode./n");
}
fastboot:
/* We are here means regular boot did not happen. Start fastboot. */
/* register aboot specific fastboot commands */
aboot_fastboot_register_commands();
/* dump partition table for debug info */
partition_dump();
/* initialize and start fastboot */
#if !VERIFIED_BOOT_2
fastboot_init(target_get_scratch_address(), target_get_max_flash_size());
#else
/* Add salt buffer offset at start of image address to copy VB salt */
fastboot_init(ADD_SALT_BUFF_OFFSET(target_get_scratch_address()),
SUB_SALT_BUFF_OFFSET(target_get_max_flash_size()));
#endif
#if FBCON_DISPLAY_MSG
display_fastboot_menu();
#endif
}aboot执行后读取bootloader中command命令，执行recovery_init.
3.2 recovery.recovery_init
[->recovery.c]
/* Bootloader / Recovery Flow
*
* On every boot, the bootloader will read the recovery_message
* from flash and check the command field. The bootloader should
* deal with the command field not having a 0 terminator correctly
* (so as to not crash if the block is invalid or corrupt).
*
* The bootloader will have to publish the partition that contains
* the recovery_message to the linux kernel so it can update it.
*
* if command == "boot-recovery" -> boot recovery.img
* else if command == "update-radio" -> update radio image (below)
* else -> boot boot.img (normal boot)
*
* Radio Update Flow
* 1. the bootloader will attempt to load and validate the header
* 2. if the header is invalid, status="invalid-update", goto #8
* 3. display the busy image on-screen
* 4. if the update image is invalid, status="invalid-radio-image", goto #8
* 5. attempt to update the firmware (depending on the command)
* 6. if successful, status="okay", goto #8
* 7. if failed, and the old image can still boot, status="failed-update"
* 8. write the recovery_message, leaving the recovery field
* unchanged, updating status, and setting command to
* "boot-recovery"
* 9. reboot
*
* The bootloader will not modify or erase the cache partition.
* It is recovery's responsibility to clean up the mess afterwards.
*/
int recovery_init (void)
{
struct recovery_message msg;
char partition_name[32];
unsigned valid_command = 0;
int update_status = 0;
// get recovery message
if (get_recovery_message(&msg))
return -1;
msg.command[sizeof(msg.command)-1] = '/0'; //Ensure termination
if (msg.command[0] != 0 && msg.command[0] != 255) {
dprintf(INFO,"Recovery command: %d %s/n",
sizeof(msg.command), msg.command);
}
if (!strcmp("boot-recovery",msg.command))
{
if(!strcmp("RADIO",msg.status))
{
/* We're now here due to radio update, so check for update status */
int ret = get_boot_info_apps(UPDATE_STATUS, (unsigned int *) &update_status);
if(!ret && (update_status & 0x01))
{
dprintf(INFO,"radio update success/n");
strlcpy(msg.status, "OKAY", sizeof(msg.status));
}
else
{
dprintf(INFO,"radio update failed/n");
strlcpy(msg.status, "failed-update", sizeof(msg.status));
}
strlcpy(msg.command, "", sizeof(msg.command)); // clearing recovery command
set_recovery_message(&msg); // send recovery message
boot_into_recovery = 1; // Boot in recovery mode
return 0;
}
boot_into_recovery = 1; // Boot in recovery mode
return 0;
}
if (!strcmp("update-radio",msg.command)) {
dprintf(INFO,"start radio update/n");
valid_command = 1;
strlcpy(partition_name, "FOTA", sizeof(partition_name));
}
//Todo: Add support for bootloader update too.
if(!valid_command) {
//We need not to do anything
return 0; // Boot in normal mode
}
if (set_ssd_radio_update(partition_name)) {
/* If writing to FOTA partition fails */
strlcpy(msg.command, "", sizeof(msg.command));
strlcpy(msg.status, "failed-update", sizeof(msg.status));
goto SEND_RECOVERY_MSG;
}
else {
/* Setting this to check the radio update status */
strlcpy(msg.command, "boot-recovery", sizeof(msg.command));
strlcpy(msg.status, "RADIO", sizeof(msg.status));
goto SEND_RECOVERY_MSG;
}
strlcpy(msg.status, "OKAY", sizeof(msg.status));
SEND_RECOVERY_MSG:
set_recovery_message(&msg); // send recovery message
boot_into_recovery = 1; // Boot in recovery mode
reboot_device(0);
return 0;
}参照代码前注释boot recovery.img之后，将会执行recovery.cpp中的main方法。
3.3 recovery.main
[->recovery.cpp]
/*
* The recovery tool communicates with the main system through /cache files.
* /cache/recovery/command - INPUT - command line for tool, one arg per line
* /cache/recovery/log - OUTPUT - combined log file from recovery run(s)
*
* The arguments which may be supplied in the recovery.command file:
* --update_package=path - verify install an OTA package file
* --wipe_data - erase user data (and cache), then reboot
* --prompt_and_wipe_data - prompt the user that data is corrupt,
* with their consent erase user data (and cache), then reboot
* --wipe_cache - wipe cache (but not user data), then reboot
* --set_encrypted_filesystem=on|off - enables / diasables encrypted fs
* --just_exit - do nothing; exit and reboot
*
* After completing, we remove /cache/recovery/command and reboot.
* Arguments may also be supplied in the bootloader control block (BCB).
* These important scenarios must be safely restartable at any point:
*
* FACTORY RESET
* 1. user selects "factory reset"
* 2. main system writes "--wipe_data" to /cache/recovery/command
* 3. main system reboots into recovery
* 4. get_args() writes BCB with "boot-recovery" and "--wipe_data"
* -- after this, rebooting will restart the erase --
* 5. erase_volume() reformats /data
* 6. erase_volume() reformats /cache
* 7. finish_recovery() erases BCB
* -- after this, rebooting will restart the main system --
* 8. main() calls reboot() to boot main system
*
* OTA INSTALL
* 1. main system downloads OTA package to /cache/some-filename.zip
* 2. main system writes "--update_package=/cache/some-filename.zip"
* 3. main system reboots into recovery
* 4. get_args() writes BCB with "boot-recovery" and "--update_package=..."
* -- after this, rebooting will attempt to reinstall the update --
* 5. install_package() attempts to install the update
* NOTE: the package install must itself be restartable from any point
* 6. finish_recovery() erases BCB
* -- after this, rebooting will (try to) restart the main system --
* 7. ** if install failed **
* 7a. prompt_and_wait() shows an error icon and waits for the user
* 7b. the user reboots (pulling the battery, etc) into the main system
*/
int main(int argc, char **argv) {
// We don't have logcat yet under recovery; so we'll print error on screen and
// log to stdout (which is redirected to recovery.log) as we used to do.
android::base::InitLogging(argv, &UiLogger);
// Take last pmsg contents and rewrite it to the current pmsg session.
static const char filter[] = "recovery/";
// Do we need to rotate?
bool doRotate = false;
__android_log_pmsg_file_read(LOG_ID_SYSTEM, ANDROID_LOG_INFO, filter, logbasename, &doRotate);
// Take action to refresh pmsg contents
__android_log_pmsg_file_read(LOG_ID_SYSTEM, ANDROID_LOG_INFO, filter, logrotate, &doRotate);
// If this binary is started with the single argument "--adbd",
// instead of being the normal recovery binary, it turns into kind
// of a stripped-down version of adbd that only supports the
// 'sideload' command. Note this must be a real argument, not
// anything in the command file or bootloader control block; the
// only way recovery should be run with this argument is when it
// starts a copy of itself from the apply_from_adb() function.
if (argc == 2 && strcmp(argv[1], "--adbd") == 0) {
minadbd_main();
return 0;
}
time_t start = time(nullptr);
// redirect_stdio should be called only in non-sideload mode. Otherwise
// we may have two logger instances with different timestamps.
redirect_stdio(TEMPORARY_LOG_FILE);
printf("Starting recovery (pid %d) on %s", getpid(), ctime(&start));
load_volume_table();
has_cache = volume_for_mount_point(CACHE_ROOT) != nullptr;
std::vector<std::string> args = get_args(argc, argv);
std::vector<char*> args_to_parse(args.size());
std::transform(args.cbegin(), args.cend(), args_to_parse.begin(),
[](const std::string& arg) { return const_cast<char*>(arg.c_str()); });
const char* update_package = nullptr;
bool should_wipe_data = false;
bool should_prompt_and_wipe_data = false;
bool should_wipe_cache = false;
bool should_wipe_ab = false;
size_t wipe_package_size = 0;
bool show_text = false;
bool sideload = false;
bool sideload_auto_reboot = false;
bool just_exit = false;
bool shutdown_after = false;
int retry_count = 0;
bool security_update = false;
int status = INSTALL_SUCCESS;
bool mount_required = true;
if (has_cache && ensure_path_mounted(CACHE_ROOT) == 0) {
//Create /cache/recovery specifically if it is not created
//As in cases where device is booted into recovery directly after
//flashing recovery folder is not created in init
mkdir_recursively(CACHE_LOG_DIR, 0777, false, sehandle);
}
int arg;
int option_index;
//解析参数
while ((arg = getopt_long(args_to_parse.size(), args_to_parse.data(), "", OPTIONS,
&option_index)) != -1) {
switch (arg) {
case 'n':
android::base::ParseInt(optarg, &retry_count, 0);
break;
case 'u':
update_package = optarg;
break;
case 'w':
should_wipe_data = true;
break;
case 'c':
should_wipe_cache = true;
break;
case 't':
show_text = true;
break;
case 's':
sideload = true;
break;
case 'a':
sideload = true;
sideload_auto_reboot = true;
break;
case 'x':
just_exit = true;
break;
case 'l':
locale = optarg;
break;
case 'p':
shutdown_after = true;
break;
case 'r':
reason = optarg;
break;
case 'e':
security_update = true;
break;
case 0: {
std::string option = OPTIONS[option_index].name;
if (option == "wipe_ab") {
should_wipe_ab = true;
} else if (option == "wipe_package_size") {
android::base::ParseUint(optarg, &wipe_package_size);
} else if (option == "prompt_and_wipe_data") {
should_prompt_and_wipe_data = true;
}
break;
}
case '?':
LOG(ERROR) << "Invalid command argument";
continue;
}
}
if (locale.empty()) {
if (has_cache) {
locale = load_locale_from_cache();
}
if (locale.empty()) {
locale = DEFAULT_LOCALE;
}
}
printf("locale is [%s]/n", locale.c_str());
printf("stage is [%s]/n", stage.c_str());
printf("reason is [%s]/n", reason);
Device* device = make_device();
if (android::base::GetBoolProperty("ro.boot.quiescent", false)) {
printf("Quiescent recovery mode./n");
ui = new StubRecoveryUI();
} else {
ui = device->GetUI();
if (!ui->Init(locale)) {
printf("Failed to initialize UI, use stub UI instead./n");
ui = new StubRecoveryUI();
}
}
// Set background string to "installing security update" for security update,
// otherwise set it to "installing system update".
ui->SetSystemUpdateText(security_update);
int st_cur, st_max;
if (!stage.empty() && sscanf(stage.c_str(), "%d/%d", &st_cur, &st_max) == 2) {
ui->SetStage(st_cur, st_max);
}
ui->SetBackground(RecoveryUI::NONE);
if (show_text) ui->ShowText(true);
sehandle = selinux_android_file_context_handle();
selinux_android_set_sehandle(sehandle);
if (!sehandle) {
ui->Print("Warning: No file_contexts/n");
}
device->StartRecovery();
printf("Command:");
for (const auto& arg : args) {
printf(" /"%s/"", arg.c_str());
}
printf("/n/n");
if (update_package) {
if (!strncmp("/sdcard", update_package, 7)) {
//If this is a UFS device lets mount the sdcard ourselves.Depending
//on if the device is UFS or EMMC based the path to the sdcard
//device changes so we cannot rely on the block dev path from
//recovery.fstab file
if (is_ufs_dev()) {
if(do_sdcard_mount_for_ufs() != 0) {
status = INSTALL_ERROR;
goto error;
}
mount_required = false;
} else {
ui->Print("Update via sdcard on EMMC dev. Using path from fstab/n");
}
}
}
property_list(print_property, nullptr);
printf("/n");
ui->Print("Supported API: %d/n", kRecoveryApiVersion);
if (update_package != nullptr) {
// It's not entirely true that we will modify the flash. But we want
// to log the update attempt since update_package is non-NULL.
modified_flash = true;
if (!is_battery_ok()) {
ui->Print("battery capacity is not enough for installing package, needed is %d%%/n",
BATTERY_OK_PERCENTAGE);
// Log the error code to last_install when installation skips due to
// low battery.
log_failure_code(kLowBattery, update_package);
status = INSTALL_SKIPPED;
} else if (bootreason_in_blacklist()) {
// Skip update-on-reboot when bootreason is kernel_panic or similar
ui->Print("bootreason is in the blacklist; skip OTA installation/n");
log_failure_code(kBootreasonInBlacklist, update_package);
status = INSTALL_SKIPPED;
} else {
// It's a fresh update. Initialize the retry_count in the BCB to 1; therefore we can later
// identify the interrupted update due to unexpected reboots.
if (retry_count == 0) {
set_retry_bootloader_message(retry_count + 1, args);
}
//见3.4节，安装升级包
status = install_package(update_package, &should_wipe_cache, TEMPORARY_INSTALL_FILE, mount_required,
retry_count);
if (status == INSTALL_SUCCESS && should_wipe_cache) {
wipe_cache(false, device);
}
if (status != INSTALL_SUCCESS) {
ui->Print("Installation aborted./n");
// When I/O error happens, reboot and retry installation RETRY_LIMIT
// times before we abandon this OTA update.
if (status == INSTALL_RETRY && retry_count < RETRY_LIMIT) {
copy_logs();
retry_count += 1;
set_retry_bootloader_message(retry_count, args);
// Print retry count on screen.
ui->Print("Retry attempt %d/n", retry_count);
// Reboot and retry the update
if (!reboot("reboot,recovery")) {
ui->Print("Reboot failed/n");
} else {
while (true) {
pause();
}
}
}
// If this is an eng or userdebug build, then automatically
// turn the text display on if the script fails so the error
// message is visible.
if (is_ro_debuggable()) {
ui->ShowText(true);
}
}
}
} else if (should_wipe_data) {
if (!wipe_data(device)) {
status = INSTALL_ERROR;
}
} else if (should_prompt_and_wipe_data) {
ui->ShowText(true);
ui->SetBackground(RecoveryUI::ERROR);
if (!prompt_and_wipe_data(device)) {
status = INSTALL_ERROR;
}
ui->ShowText(false);
} else if (should_wipe_cache) {
if (!wipe_cache(false, device)) {
status = INSTALL_ERROR;
}
} else if (should_wipe_ab) {
if (!wipe_ab_device(wipe_package_size)) {
status = INSTALL_ERROR;
}
} else if (sideload) {
// 'adb reboot sideload' acts the same as user presses key combinations
// to enter the sideload mode. When 'sideload-auto-reboot' is used, text
// display will NOT be turned on by default. And it will reboot after
// sideload finishes even if there are errors. Unless one turns on the
// text display during the installation. This is to enable automated
// testing.
if (!sideload_auto_reboot) {
ui->ShowText(true);
}
status = apply_from_adb(&should_wipe_cache, TEMPORARY_INSTALL_FILE);
if (status == INSTALL_SUCCESS && should_wipe_cache) {
if (!wipe_cache(false, device)) {
status = INSTALL_ERROR;
}
}
ui->Print("/nInstall from ADB complete (status: %d)./n", status);
if (sideload_auto_reboot) {
ui->Print("Rebooting automatically./n");
}
} else if (!just_exit) {
// If this is an eng or userdebug build, automatically turn on the text display if no command
// is specified. Note that this should be called before setting the background to avoid
// flickering the background image.
if (is_ro_debuggable()) {
ui->ShowText(true);
}
status = INSTALL_NONE; // No command specified
ui->SetBackground(RecoveryUI::NO_COMMAND);
}
error:
if (status == INSTALL_ERROR || status == INSTALL_CORRUPT) {
ui->SetBackground(RecoveryUI::ERROR);
if (!ui->IsTextVisible()) {
sleep(5);
}
}
Device::BuiltinAction after = shutdown_after ? Device::SHUTDOWN : Device::REBOOT;
// 1. If the recovery menu is visible, prompt and wait for commands.
// 2. If the state is INSTALL_NONE, wait for commands. (i.e. In user build, manually reboot into
// recovery to sideload a package.)
// 3. sideload_auto_reboot is an option only available in user-debug build, reboot the device
// without waiting.
// 4. In all other cases, reboot the device. Therefore, normal users will observe the device
// reboot after it shows the "error" screen for 5s.
if ((status == INSTALL_NONE && !sideload_auto_reboot) || ui->IsTextVisible()) {
Device::BuiltinAction temp = prompt_and_wait(device, status);
if (temp != Device::NO_ACTION) {
after = temp;
}
}
// Save logs and clean up before rebooting or shutting down.
// 见3.8节
finish_recovery();
switch (after) {
case Device::SHUTDOWN:
ui->Print("Shutting down.../n");
android::base::SetProperty(ANDROID_RB_PROPERTY, "shutdown,");
break;
case Device::REBOOT_BOOTLOADER:
ui->Print("Rebooting to bootloader.../n");
android::base::SetProperty(ANDROID_RB_PROPERTY, "reboot,bootloader");
break;
default:
ui->Print("Rebooting.../n");
reboot("reboot,");
break;
}
while (true) {
pause();
}
// Should be unreachable.
return EXIT_SUCCESS;
}获取参数后，根据相应的参数执行相应的操作，这里是执行OTA INSTALL的流程，install_package完成之执行finish_recovery操作，之后正式完成升级的操作。
3.4 install.install_package
[->install.cpp]
int install_package(const std::string& path, bool* wipe_cache, const std::string& install_file,
bool needs_mount, int retry_count) {
CHECK(!path.empty());
CHECK(!install_file.empty());
CHECK(wipe_cache != nullptr);
modified_flash = true;
auto start = std::chrono::system_clock::now();
int start_temperature = GetMaxValueFromThermalZone();
int max_temperature = start_temperature;
int result = 0;
std::vector<std::string> log_buffer;
if (needs_mount == true)
result = setup_install_mounts();
if (result != 0 ) {
LOG(ERROR) << "failed to set up expected mounts for install; aborting";
result = INSTALL_ERROR;
} else {
//见3.5节
result = really_install_package(path, wipe_cache, needs_mount, &log_buffer, retry_count,
&max_temperature);
}
// Measure the time spent to apply OTA update in seconds.
std::chrono::duration<double> duration = std::chrono::system_clock::now() - start;
int time_total = static_cast<int>(duration.count());
bool has_cache = volume_for_mount_point("/cache") != nullptr;
// Skip logging the uncrypt_status on devices without /cache.
if (has_cache) {
static constexpr const char* UNCRYPT_STATUS = "/cache/recovery/uncrypt_status";
if (ensure_path_mounted(UNCRYPT_STATUS) != 0) {
LOG(WARNING) << "Can't mount " << UNCRYPT_STATUS;
} else {
std::string uncrypt_status;
if (!android::base::ReadFileToString(UNCRYPT_STATUS, &uncrypt_status)) {
PLOG(WARNING) << "failed to read uncrypt status";
} else if (!android::base::StartsWith(uncrypt_status, "uncrypt_")) {
LOG(WARNING) << "corrupted uncrypt_status: " << uncrypt_status;
} else {
log_buffer.push_back(android::base::Trim(uncrypt_status));
}
}
}
// The first two lines need to be the package name and install result.
std::vector<std::string> log_header = {
path,
result == INSTALL_SUCCESS ? "1" : "0",
"time_total: " + std::to_string(time_total),
"retry: " + std::to_string(retry_count),
};
int end_temperature = GetMaxValueFromThermalZone();
max_temperature = std::max(end_temperature, max_temperature);
if (start_temperature > 0) {
log_buffer.push_back("temperature_start: " + std::to_string(start_temperature));
}
if (end_temperature > 0) {
log_buffer.push_back("temperature_end: " + std::to_string(end_temperature));
}
if (max_temperature > 0) {
log_buffer.push_back("temperature_max: " + std::to_string(max_temperature));
}
std::string log_content =
android::base::Join(log_header, "/n") + "/n" + android::base::Join(log_buffer, "/n") + "/n";
if (!android::base::WriteStringToFile(log_content, install_file)) {
PLOG(ERROR) << "failed to write " << install_file;
}
// Write a copy into last_log.
LOG(INFO) << log_content;
return result;
}3.5 install.really_install_package
[->install.cpp]
static int really_install_package(const std::string& path, bool* wipe_cache, bool needs_mount,
std::vector<std::string>* log_buffer, int retry_count,
int* max_temperature) {
//ui显示
ui->SetBackground(RecoveryUI::INSTALLING_UPDATE);
ui->Print("Finding update package.../n");
// Give verification half the progress bar...
ui->SetProgressType(RecoveryUI::DETERMINATE);
ui->ShowProgress(VERIFICATION_PROGRESS_FRACTION, VERIFICATION_PROGRESS_TIME);
LOG(INFO) << "Update location: " << path;
// Map the update package into memory.
ui->Print("Opening update package.../n");
if (needs_mount) {
if (path[0] == '@') {
ensure_path_mounted(path.substr(1).c_str());
} else {
ensure_path_mounted(path.c_str());
}
}
MemMapping map;
if (!map.MapFile(path)) {
LOG(ERROR) << "failed to map file";
log_buffer->push_back(android::base::StringPrintf("error: %d", kMapFileFailure));
return INSTALL_CORRUPT;
}
// Verify package.
// 校验升级包
if (!verify_package(map.addr, map.length)) {
log_buffer->push_back(android::base::StringPrintf("error: %d", kZipVerificationFailure));
return INSTALL_CORRUPT;
}
// Try to open the package.
ZipArchiveHandle zip;
int err = OpenArchiveFromMemory(map.addr, map.length, path.c_str(), &zip);
if (err != 0) {
LOG(ERROR) << "Can't open " << path << " : " << ErrorCodeString(err);
log_buffer->push_back(android::base::StringPrintf("error: %d", kZipOpenFailure));
CloseArchive(zip);
return INSTALL_CORRUPT;
}
// Additionally verify the compatibility of the package.
if (!verify_package_compatibility(zip)) {
log_buffer->push_back(android::base::StringPrintf("error: %d", kPackageCompatibilityFailure));
CloseArchive(zip);
return INSTALL_CORRUPT;
}
// Verify and install the contents of the package.
ui->Print("Installing update.../n");
if (retry_count > 0) {
ui->Print("Retry attempt: %d/n", retry_count);
}
ui->SetEnableReboot(false);
//见3.6节
int result = try_update_binary(path, zip, wipe_cache, log_buffer, retry_count, max_temperature);
ui->SetEnableReboot(true);
ui->Print("/n");
CloseArchive(zip);
return result;
}3.6 install.try_update_binary
[->install.cpp]
static int try_update_binary(const std::string& package, ZipArchiveHandle zip, bool* wipe_cache,
std::vector<std::string>* log_buffer, int retry_count,
int* max_temperature) {
read_source_target_build(zip, log_buffer);
int pipefd[2];
pipe(pipefd);
std::vector<std::string> args;
#ifdef AB_OTA_UPDATER
//执行update_binary_command操作，见3.7节
int ret = update_binary_command(package, zip, "/sbin/update_engine_sideload", retry_count,
pipefd[1], &args);
#else
int ret = update_binary_command(package, zip, "/tmp/update-binary", retry_count, pipefd[1],
&args);
#endif
if (ret) {
close(pipefd[0]);
close(pipefd[1]);
log_buffer->push_back(android::base::StringPrintf("error: %d", kUpdateBinaryCommandFailure));
return ret;
}
// When executing the update binary contained in the package, the
// arguments passed are:
//
// - the version number for this interface
//
// - an FD to which the program can write in order to update the
// progress bar. The program can write single-line commands:
//
// progress <frac> <secs>
// fill up the next <frac> part of of the progress bar
// over <secs> seconds. If <secs> is zero, use
// set_progress commands to manually control the
// progress of this segment of the bar.
//
// set_progress <frac>
// <frac> should be between 0.0 and 1.0; sets the
// progress bar within the segment defined by the most
// recent progress command.
//
// ui_print <string>
// display <string> on the screen.
//
// wipe_cache
// a wipe of cache will be performed following a successful
// installation.
//
// clear_display
// turn off the text display.
//
// enable_reboot
// packages can explicitly request that they want the user
// to be able to reboot during installation (useful for
// debugging packages that don't exit).
//
// retry_update
// updater encounters some issue during the update. It requests
// a reboot to retry the same package automatically.
//
// log <string>
// updater requests logging the string (e.g. cause of the
// failure).
//
// - the name of the package zip file.
//
// - an optional argument "retry" if this update is a retry of a failed
// update attempt.
//
// Convert the vector to a NULL-terminated char* array suitable for execv.
const char* chr_args[args.size() + 1];
chr_args[args.size()] = nullptr;
for (size_t i = 0; i < args.size(); i++) {
chr_args[i] = args[i].c_str();
}
pid_t pid = fork();
if (pid == -1) {
close(pipefd[0]);
close(pipefd[1]);
PLOG(ERROR) << "Failed to fork update binary";
log_buffer->push_back(android::base::StringPrintf("error: %d", kForkUpdateBinaryFailure));
return INSTALL_ERROR;
}
if (pid == 0) {
umask(022);
close(pipefd[0]);
execv(chr_args[0], const_cast<char**>(chr_args));
// Bug: 34769056
// We shouldn't use LOG/PLOG in the forked process, since they may cause
// the child process to hang. This deadlock results from an improperly
// copied mutex in the ui functions.
fprintf(stdout, "E:Can't run %s (%s)/n", chr_args[0], strerror(errno));
_exit(EXIT_FAILURE);
}
close(pipefd[1]);
std::atomic<bool> logger_finished(false);
std::thread temperature_logger(log_max_temperature, max_temperature, std::ref(logger_finished));
*wipe_cache = false;
bool retry_update = false;
char buffer[1024];
FILE* from_child = fdopen(pipefd[0], "r");
while (fgets(buffer, sizeof(buffer), from_child) != nullptr) {
std::string line(buffer);
size_t space = line.find_first_of(" /n");
std::string command(line.substr(0, space));
if (command.empty()) continue;
// Get rid of the leading and trailing space and/or newline.
std::string args = space == std::string::npos ? "" : android::base::Trim(line.substr(space));
if (command == "progress") {
std::vector<std::string> tokens = android::base::Split(args, " ");
double fraction;
int seconds;
if (tokens.size() == 2 && android::base::ParseDouble(tokens[0].c_str(), &fraction) &&
android::base::ParseInt(tokens[1], &seconds)) {
ui->ShowProgress(fraction * (1 - VERIFICATION_PROGRESS_FRACTION), seconds);
} else {
LOG(ERROR) << "invalid /"progress/" parameters: " << line;
}
} else if (command == "set_progress") {
std::vector<std::string> tokens = android::base::Split(args, " ");
double fraction;
if (tokens.size() == 1 && android::base::ParseDouble(tokens[0].c_str(), &fraction)) {
ui->SetProgress(fraction);
} else {
LOG(ERROR) << "invalid /"set_progress/" parameters: " << line;
}
} else if (command == "ui_print") {
ui->PrintOnScreenOnly("%s/n", args.c_str());
fflush(stdout);
} else if (command == "wipe_cache") {
*wipe_cache = true;
} else if (command == "clear_display") {
ui->SetBackground(RecoveryUI::NONE);
} else if (command == "enable_reboot") {
// packages can explicitly request that they want the user
// to be able to reboot during installation (useful for
// debugging packages that don't exit).
ui->SetEnableReboot(true);
} else if (command == "retry_update") {
retry_update = true;
} else if (command == "log") {
if (!args.empty()) {
// Save the logging request from updater and write to last_install later.
log_buffer->push_back(args);
} else {
LOG(ERROR) << "invalid /"log/" parameters: " << line;
}
} else {
LOG(ERROR) << "unknown command [" << command << "]";
}
}
fclose(from_child);
int status;
waitpid(pid, &status, 0);
logger_finished.store(true);
finish_log_temperature.notify_one();
temperature_logger.join();
if (retry_update) {
return INSTALL_RETRY;
}
if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
LOG(ERROR) << "Error in " << package << " (Status " << WEXITSTATUS(status) << ")";
return INSTALL_ERROR;
}
return INSTALL_SUCCESS;
}3.7 install.update_binary_command
[->install.cpp]
int update_binary_command(const std::string& package, ZipArchiveHandle zip,
const std::string& binary_path, int retry_count, int status_fd,
std::vector<std::string>* cmd) {
CHECK(cmd != nullptr);
// On traditional updates we extract the update binary from the package.
static constexpr const char* UPDATE_BINARY_NAME = "META-INF/com/google/android/update-binary";
ZipString binary_name(UPDATE_BINARY_NAME);
ZipEntry binary_entry;
if (FindEntry(zip, binary_name, &binary_entry) != 0) {
LOG(ERROR) << "Failed to find update binary " << UPDATE_BINARY_NAME;
return INSTALL_CORRUPT;
}
unlink(binary_path.c_str());
int fd = open(binary_path.c_str(), O_CREAT | O_WRONLY | O_TRUNC | O_CLOEXEC, 0755);
if (fd == -1) {
PLOG(ERROR) << "Failed to create " << binary_path;
return INSTALL_ERROR;
}
int32_t error = ExtractEntryToFile(zip, &binary_entry, fd);
close(fd);
if (error != 0) {
LOG(ERROR) << "Failed to extract " << UPDATE_BINARY_NAME << ": " << ErrorCodeString(error);
return INSTALL_ERROR;
}
*cmd = {
binary_path,
std::to_string(kRecoveryApiVersion),
std::to_string(status_fd),
package,
};
if (retry_count > 0) {
cmd->push_back("retry");
}
return 0;
}前面介绍到update-binary相当于一个脚本解释器，能够识别updater-script中描述的操作。来看下updater-script中的内容：
...
show_progress(0.650000, 0);
ui_print("Patching system image unconditionally...");
block_image_update("/dev/block/bootdevice/by-name/system", package_extract_file("system.transfer.list"), "system.new.dat.br", "system.patch.dat") ||
abort("E1001: Failed to update system image.");
show_progress(0.100000, 0);
ui_print("Patching vendor image unconditionally...");
block_image_update("/dev/block/bootdevice/by-name/vendor", package_extract_file("vendor.transfer.list"), "vendor.new.dat.br", "vendor.patch.dat") ||
abort("E2001: Failed to update vendor image.");
show_progress(0.050000, 5);
package_extract_file("boot.img", "/dev/block/bootdevice/by-name/boot");
show_progress(0.200000, 10);
...调用的是block_image_update，传入的是升级包里面的system.transfer.list和system.new.dat.br来实现升级。
block_image_update在bootable/recovery/updater/blockimg.cpp中，具体的实现PerformBlockImageUpdate函数中，这里不再详细展开。
void RegisterBlockImageFunctions() {
RegisterFunction("block_image_verify", BlockImageVerifyFn);
RegisterFunction("block_image_update", BlockImageUpdateFn);
RegisterFunction("block_image_recover", BlockImageRecoverFn);
RegisterFunction("check_first_block", CheckFirstBlockFn);
RegisterFunction("range_sha1", RangeSha1Fn);
}来system.transfer.list中的内容：
4
583603
0
0
erase 6,1020,7774,524808,527824,580432,773491
new 6,0,207,222,508,8286,8817
new 2,8817,9841
new 2,9841,10865
...
zero 6,524360,524808,527824,528336,579920,579984
zero 6,579984,580432,773491,774003,786268,786332
zero 2,786332,786431其中
4：为transfer的版本，目前支持1-4版本
583603：为总共new的block数量
0：stash slots没有使用，所以这里两个都是0
erase：需要擦除的block块范围数
new: 需要写入的block块范围数
zero: 需要填充0的block块范围数
3.8 recovery.finish_recovery
[->recovery.cpp]
static void finish_recovery() {
// Save the locale to cache, so if recovery is next started up without a '--locale' argument
// (e.g., directly from the bootloader) it will use the last-known locale.
if (!locale.empty() && has_cache) {
LOG(INFO) << "Saving locale /"" << locale << "/"";
if (ensure_path_mounted(LOCALE_FILE) != 0) {
LOG(ERROR) << "Failed to mount " << LOCALE_FILE;
} else if (!android::base::WriteStringToFile(locale, LOCALE_FILE)) {
PLOG(ERROR) << "Failed to save locale to " << LOCALE_FILE;
}
}
copy_logs();
// Reset to normal system boot so recovery won't cycle indefinitely.
std::string err;
if (!clear_bootloader_message(&err)) {
LOG(ERROR) << "Failed to clear BCB message: " << err;
}
// Remove the command file, so recovery won't repeat indefinitely.
if (has_cache) {
if (ensure_path_mounted(COMMAND_FILE) != 0 || (unlink(COMMAND_FILE) && errno != ENOENT)) {
LOG(WARNING) << "Can't unlink " << COMMAND_FILE;
}
ensure_path_unmounted(CACHE_ROOT);
}
sync(); // For good measure.
}完成升级后，清除BCB操作。
3.9 小结
ota升级重启后，主要的操作如下:
1.加载bootloader，读取bootloader中的command命令
2.读取到升级的命令后，boot recovery.img，recovery.cpp中的main函数执行。
3.执行install_package操作，这里会解析ota包中的内容（block.map的形式），执行相应的升级包中脚本操作，同时会同步进行一些ui的显示操作。
4.install_package操作完成后，最后finish_recovery，完成升级的操作。
四、总结
[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-9Dk2eqWs-1577705272566)(https://skytoby.github.io/2019/Android%20OTA%E5%8D%87%E7%BA%A7%E6%B5%81%E7%A8%8B%E5%88%86%E6%9E%90/OTA.jpg)]
本文分析Android终端ota升级的全过程。从介绍ota升级包的格式和系统启动模式开始作为基础，后面详细分析了从升级重启前到重启后的详细流程，其中升级重启前的流程如下：
[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-zInb41pn-1577704943833)(/Android OTA升级流程分析/OTA.jpg)]
OTA升级重启前，主要的操作是对升级包进行处理的过程，对升级包提前处理的原因是因为在进入recovery模式进行升级时无法加载升级包所在的分区。在重启前的主要操作如下：
1.通过SystemProperties设置属性(setup-bcb)，向BCB中设置升级的Command；
2.通过SystemProperties设置属性(uncrypt)，开启uncrypt服务，将升级包生成一系列的block块，recovery可以读取block.map文件并获取这个文件的数据作为升级包；
3.uncrypt完成后，重启。
ota升级重启后，主要的操作如下:
1.加载bootloader，读取bootloader中的command命令
2.读取到升级的命令后，boot recovery.img，recovery.cpp中的main函数执行。
3.执行install_package操作，这里会解析ota包中的内容（block.map的形式），执行相应的升级包中脚本操作，同时会同步进行一些ui的显示操作。
4.install_package操作完成后，最后finish_recovery，完成升级的操作。
附录
源码路径
frameworks/base/core/java/android/os/RecoverySystem.java
frameworks/base/services/core/java/com/android/server/RecoverySystemService.java
frameworks/base/core/java/android/os/PowerManager.java
frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java
frameworks/base/services/core/java/com/android/server/power/ShutdownThread.java
bootable/recovery/uncrypt/uncrypt.cpp
bootable/recovery/uncrypt/uncrypt.rc
bootable/bootloader/lk/app/aboot/aboot.c
bootable/bootloader/lk/app/aboot/recovery.c
bootable/recovery/updater/install.cpp
bootable/recovery/install.cpp
bootable/recovery/bootloader_message/include/bootloader_message/bootloader_message.h
bootable/recovery/updater/blockimg.cpp
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