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Digging Into Android System Services Dave Smith, PE @devunwired

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Why Are You Here? Trace AOSP Code Learn Platform Internals Discover App Impact

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Linux Kernel Hardware Abstraction Layer Native Services Runtime Application Framework Applications

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Linux Kernel Hardware Abstraction Layer Native Services Runtime Application Framework Applications

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Application System Server Manager Service

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Application System Server Manager Service Application Manager Application Manager Application Manager

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Context.getSystemService(SERVICE_NAME)

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ContextImpl SystemServiceRegistry Context AlarmManager NotificationManager LocationManager PowerManager Context.getSystemService(SERVICE_NAME)

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package android.app;
 
 final class SystemServiceRegistry {
 ...
 
 static {
 ...
 registerService(Context.ACCOUNT_SERVICE, AccountManager.class,
 new CachedServiceFetcher() {
 @Override
 public AccountManager createService(ContextImpl ctx) {
 IBinder b = ServiceManager.getService(Context.ACCOUNT_SERVICE);
 IAccountManager service = IAccountManager.Stub.asInterface(b);
 return new AccountManager(ctx, service);
 }
 });
 ...
 registerService(Context.ALARM_SERVICE, AlarmManager.class,
 new CachedServiceFetcher() {
 @Override
 public AlarmManager createService(ContextImpl ctx) {
 IBinder b = ServiceManager.getService(Context.ALARM_SERVICE);
 IAlarmManager service = IAlarmManager.Stub.asInterface(b);
 return new AlarmManager(service, ctx);
 }
 });
 ...
 }
 } SystemServiceRegistry.java

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package android.app;
 
 final class SystemServiceRegistry {
 ...
 
 static {
 ...
 registerService(Context.ACCOUNT_SERVICE, AccountManager.class,
 new CachedServiceFetcher() {
 @Override
 public AccountManager createService(ContextImpl ctx) {
 IBinder b = ServiceManager.getService(Context.ACCOUNT_SERVICE);
 IAccountManager service = IAccountManager.Stub.asInterface(b);
 return new AccountManager(ctx, service);
 }
 });
 ...
 registerService(Context.ALARM_SERVICE, AlarmManager.class,
 new CachedServiceFetcher() {
 @Override
 public AlarmManager createService(ContextImpl ctx) {
 IBinder b = ServiceManager.getService(Context.ALARM_SERVICE);
 IAlarmManager service = IAlarmManager.Stub.asInterface(b);
 return new AlarmManager(service, ctx);
 }
 });
 ...
 }
 } SystemServiceRegistry.java

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Application System Server Manager Service

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Binder IPC Application System Server Service Manager

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Application System Server Manager Service Binder IPC AIDL Proxy Stub

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Application System Server AlarmManager AlarmManagerService IAlarmManager IAlarmManager.Stub Binder IPC

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IAlarmManager.aidl AlarmManager.java package android.app;
 
 ...
 
 public class AlarmManager {
 private final IAlarmManager mService;
 ...
 
 public void setTime(long millis) {
 try {
 mService.setTime(millis);
 } catch (RemoteException ex) {
 throw ex.rethrowFromSystemServer();
 }
 }
 
 public void setTimeZone(String timeZone) {
 ...
 
 try {
 mService.setTimeZone(timeZone);
 } catch (RemoteException ex) {
 throw ex.rethrowFromSystemServer();
 }
 }
 } package android.app;
 
 interface IAlarmManager {
 void set(...);
 boolean setTime(long millis);
 void setTimeZone(String zone);
 void remove(...);
 long getNextWakeFromIdleTime();
 ...
 }

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IAlarmManager.aidl AlarmManager.java package android.app;
 
 ...
 
 public class AlarmManager {
 private final IAlarmManager mService;
 ...
 
 public void setTime(long millis) {
 try {
 mService.setTime(millis);
 } catch (RemoteException ex) {
 throw ex.rethrowFromSystemServer();
 }
 }
 
 public void setTimeZone(String timeZone) {
 ...
 
 try {
 mService.setTimeZone(timeZone);
 } catch (RemoteException ex) {
 throw ex.rethrowFromSystemServer();
 }
 }
 } package android.app;
 
 interface IAlarmManager {
 void set(...);
 boolean setTime(long millis);
 void setTimeZone(String zone);
 void remove(...);
 long getNextWakeFromIdleTime();
 ...
 }

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package com.android.server;
 
 public class AlarmManagerService extends SystemService {
 ... 
 private final IBinder mService = new IAlarmManager.Stub() { 
 @Override
 public boolean setTime(long millis) {
 getContext().enforceCallingOrSelfPermission(
 "android.permission.SET_TIME",
 "setTime");
 ...
 } 
 @Override
 public void setTimeZone(String tz) {
 getContext().enforceCallingOrSelfPermission(
 "android.permission.SET_TIME_ZONE",
 "setTimeZone");
 ...
 }
 }; 
 } AlarmManagerService.java IAlarmManager.aidl package android.app;
 
 interface IAlarmManager {
 void set(...);
 boolean setTime(long millis);
 void setTimeZone(String zone);
 void remove(...);
 long getNextWakeFromIdleTime();
 ...
 }

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Binder IPC Application Service Object

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Binder IPC Application Service Object Object

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public class MainActivity extends Activity implements LocationListener {
 
 @Override
 protected void onResume() {
 super.onResume();
 
 LocationManager manager = (LocationManager) getSystemService(LOCATION_SERVICE);
 manager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
 }
 
 @Override
 protected void onPause() {
 super.onPause();
 
 LocationManager manager = (LocationManager) getSystemService(LOCATION_SERVICE);
 manager.removeUpdates(this);
 }
 
 @Override
 public void onLocationChanged(Location location) {
 ...
 }
 
 ...
 }

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public class MainActivity extends Activity implements LocationListener {
 
 @Override
 protected void onResume() {
 super.onResume();
 
 LocationManager manager = (LocationManager) getSystemService(LOCATION_SERVICE);
 manager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
 }
 
 @Override
 protected void onPause() {
 super.onPause();
 
 LocationManager manager = (LocationManager) getSystemService(LOCATION_SERVICE);
 manager.removeUpdates(this);
 }
 
 @Override
 public void onLocationChanged(Location location) {
 ...
 }
 
 ...
 }

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Application System Server Manager Service

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Application System Server Manager Service Service Manager Stub Stub

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Application System Server Manager Service Service Manager IBinder Stub IBinder

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Application System Server Manager Service Service Manager Proxy Stub IBinder

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$ adb shell service list Found 116 services: 0 carrier_config: [com.android.internal.telephony.ICarrierConfigLoader] 1 phone: [com.android.internal.telephony.ITelephony] 2 isms: [com.android.internal.telephony.ISms] 3 iphonesubinfo: [com.android.internal.telephony.IPhoneSubInfo] 4 simphonebook: [com.android.internal.telephony.IIccPhoneBook] 5 isub: [com.android.internal.telephony.ISub] 6 telecom: [com.android.internal.telecom.ITelecomService] 7 contexthub_service: [android.hardware.location.IContextHubService] 8 dns_listener: [android.net.metrics.IDnsEventListener] 9 connectivity_metrics_logger: [android.net.IConnectivityMetricsLogger] 10 imms: [com.android.internal.telephony.IMms] 11 media_projection: [android.media.projection.IMediaProjectionManager] 12 launcherapps: [android.content.pm.ILauncherApps] 13 shortcut: [android.content.pm.IShortcutService] 14 fingerprint: [android.hardware.fingerprint.IFingerprintService] 15 trust: [android.app.trust.ITrustManager] 16 media_router: [android.media.IMediaRouterService] 17 media_session: [android.media.session.ISessionManager] 18 restrictions: [android.content.IRestrictionsManager] 19 print: [android.print.IPrintManager] 20 graphicsstats: [android.view.IGraphicsStats] ...

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package android.app;
 
 final class SystemServiceRegistry {
 ...
 
 static {
 ...
 registerService(Context.ACCOUNT_SERVICE, AccountManager.class,
 new CachedServiceFetcher() {
 @Override
 public AccountManager createService(ContextImpl ctx) {
 IBinder b = ServiceManager.getService(Context.ACCOUNT_SERVICE);
 IAccountManager service = IAccountManager.Stub.asInterface(b);
 return new AccountManager(ctx, service);
 }
 });
 ...
 registerService(Context.ALARM_SERVICE, AlarmManager.class,
 new CachedServiceFetcher() {
 @Override
 public AlarmManager createService(ContextImpl ctx) {
 IBinder b = ServiceManager.getService(Context.ALARM_SERVICE);
 IAlarmManager service = IAlarmManager.Stub.asInterface(b);
 return new AlarmManager(service, ctx);
 }
 });
 ...
 }
 } SystemServiceRegistry.java

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package android.app;
 
 final class SystemServiceRegistry {
 ...
 
 static {
 ...
 registerService(Context.ACCOUNT_SERVICE, AccountManager.class,
 new CachedServiceFetcher() {
 @Override
 public AccountManager createService(ContextImpl ctx) {
 IBinder b = ServiceManager.getService(Context.ACCOUNT_SERVICE);
 IAccountManager service = IAccountManager.Stub.asInterface(b);
 return new AccountManager(ctx, service);
 }
 });
 ...
 registerService(Context.ALARM_SERVICE, AlarmManager.class,
 new CachedServiceFetcher() {
 @Override
 public AlarmManager createService(ContextImpl ctx) {
 IBinder b = ServiceManager.getService(Context.ALARM_SERVICE);
 IAlarmManager service = IAlarmManager.Stub.asInterface(b);
 return new AlarmManager(service, ctx);
 }
 });
 ...
 }
 } SystemServiceRegistry.java

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package com.android.server;
 
 import android.content.Context;
 
 public final class SystemServer {
 ...
 ConnectivityServicer connectivity = new ConnectivityService(
 context, networkManagement, networkStats, networkPolicy);
 ServiceManager.addService(Context.CONNECTIVITY_SERVICE, connectivity); 
 ...
 LocationManagerService location = new LocationManagerService(context);
 ServiceManager.addService(Context.LOCATION_SERVICE, location);
 ...
 } SystemServer.java

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@devunwired +DaveSmithDev milehighandroid.com wiresareobsolete.com