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Digging Into Android System Services
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Dave Smith
September 16, 2016
Programming
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Digging Into Android System Services
Walkthrough of the architecture that the Android platform uses to expose services to applications.
Dave Smith
September 16, 2016
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Transcript
Digging Into Android System Services Dave Smith, PE @devunwired
Why Are You Here? Trace AOSP Code Learn Platform Internals
Discover App Impact
Linux Kernel Hardware Abstraction Layer Native Services Runtime Application Framework
Applications
Linux Kernel Hardware Abstraction Layer Native Services Runtime Application Framework
Applications
Application System Server Manager Service
Application System Server Manager Service Application Manager Application Manager Application
Manager
Context.getSystemService(SERVICE_NAME)
ContextImpl SystemServiceRegistry Context AlarmManager NotificationManager LocationManager PowerManager Context.getSystemService(SERVICE_NAME)
package android.app; final class SystemServiceRegistry { ... static
{ ... registerService(Context.ACCOUNT_SERVICE, AccountManager.class, new CachedServiceFetcher<AccountManager>() { @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<AlarmManager>() { @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
package android.app; final class SystemServiceRegistry { ... static
{ ... registerService(Context.ACCOUNT_SERVICE, AccountManager.class, new CachedServiceFetcher<AccountManager>() { @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<AlarmManager>() { @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
Application System Server Manager Service
Binder IPC Application System Server Service Manager
Application System Server Manager Service Binder IPC AIDL Proxy Stub
Application System Server AlarmManager AlarmManagerService IAlarmManager IAlarmManager.Stub Binder IPC
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(); ... }
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(); ... }
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(); ... }
Binder IPC Application Service Object
Binder IPC Application Service Object Object
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) { ... } ... }
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) { ... } ... }
Application System Server Manager Service
Application System Server Manager Service Service Manager Stub Stub
Application System Server Manager Service Service Manager IBinder Stub IBinder
Application System Server Manager Service Service Manager Proxy Stub IBinder
$ 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] ...
package android.app; final class SystemServiceRegistry { ... static
{ ... registerService(Context.ACCOUNT_SERVICE, AccountManager.class, new CachedServiceFetcher<AccountManager>() { @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<AlarmManager>() { @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
package android.app; final class SystemServiceRegistry { ... static
{ ... registerService(Context.ACCOUNT_SERVICE, AccountManager.class, new CachedServiceFetcher<AccountManager>() { @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<AlarmManager>() { @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
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
@devunwired +DaveSmithDev milehighandroid.com wiresareobsolete.com