android13添加system_server进程的系统服务

在系统system_server中添加一个系统java层服务

基于AOSP 13版本。
实施步骤：

1. 准备系统服务代码DemoSystemService.java和Android.bp文件
2. 将services.jar模块编译依赖新增模块
3. SystemServer.java中启动Demo服务
4. 添加SELINUX规则

1, DemoSystemService代码示例

AOSP/demo/services/src/com/chen/services

package com.chen.services;

import android.content.Context;
import android.os.Binder;
import android.os.Parcel;
import android.os.RemoteException;

import com.android.server.SystemService;

import java.util.concurrent.CountDownLatch;
// 这里的继承Binder，可以改成自己的AIDL.Stub类
public class DemoSystemService extends Binder {
    private Context mContext;

    public DemoSystemService(Context context){
        mContext = context;
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
    }

    public void systemReady() {
        // initSomething();
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
    }

    private void initSomething(){
    }

    @Override
    protected boolean onTransact(int code, Parcel data, Parcel reply, int flags) throws RemoteException {
        return super.onTransact(code, data, reply, flags);
    }

    public static class LifeCycle extends SystemService {

        private DemoSystemService mService;
        private final CountDownLatch mCountDown = new CountDownLatch(1);

        /**
         * Initializes the system service.
         * 

         * Subclasses must define a single argument constructor that accepts the context
         * and passes it to super.
         * 
         *
         * @param context The system server context.
         */
        public LifeCycle(Context context) {
            super(context);
            mService = new DemoSystemService(context);
        }

        @Override
        public void onStart() {
            // 父类的方法
            publishBinderService("demo",mService);
        }

        @Override
        public void onBootPhase(int phase) {
            switch (phase) {
                case SystemService.PHASE_ACTIVITY_MANAGER_READY:
                    mService.systemReady();
                    break;
                default:
                    break;
            }
        }
    }


}

demo/services/src/Android.bp

filegroup {
    name: "demo--system-service-sources",
    srcs: ["com/chen/services/DemoSystemService.java"],
}

2, services.jar模块编译依赖demo服务

修改frameworks/base/services/Android.bp, diff如下：

diff --git a/services/Android.bp b/services/Android.bp
index ccdf7ca06924..d26ffd533292 100644
--- a/services/Android.bp
+++ b/services/Android.bp
@@ -132,7 +132,9 @@ java_library {
         profile: "art-profile",
     },
 
-    srcs: [":services-main-sources"],
+    srcs: [":services-main-sources",
+           ":demo--system-service-sources"
+    ],
 
     // The convention is to name each service module 'services.$(module_name)'
     static_libs: [

3, SystemServer.java中启动Demo服务

修改frameworks/base/services/java/com/android/server/SystemServer.java, 启动DemoSystemService，diff如下：

diff --git a/services/java/com/android/server/SystemServer.java b/services/java/com/android/server/SystemServer.java
index 46141940a907..5d99ebe7842b 100644
--- a/services/java/com/android/server/SystemServer.java
+++ b/services/java/com/android/server/SystemServer.java
@@ -213,6 +213,7 @@ import com.android.server.webkit.WebViewUpdateService;
 import com.android.server.wm.ActivityTaskManagerService;
 import com.android.server.wm.WindowManagerGlobalLock;
 import com.android.server.wm.WindowManagerService;
+import com.chen.services.DemoSystemService;
 
 import dalvik.system.VMRuntime;
 
@@ -2141,6 +2142,10 @@ public final class SystemServer implements Dumpable {
             }
             t.traceEnd();
 
+            t.traceBegin("StartDemoSystemService");
+            mSystemServiceManager.startService(DemoSystemService.LifeCycle.class);
+            t.traceEnd();
+
             t.traceBegin("StartSoundTriggerMiddlewareService");
             mSystemServiceManager.startService(SoundTriggerMiddlewareService.Lifecycle.class);
             t.traceEnd();

4, 添加SELINUX规则

修改system/sepolicy库，添加demo服务的标签和规则，注意添加的服务名称为demo,(publishBinderService(“demo”,mService)
diff如下：

diff --git a/prebuilts/api/33.0/private/compat/32.0/32.0.ignore.cil b/prebuilts/api/33.0/private/compat/32.0/32.0.ignore.cil
index 076d642e2..f7733c4d9 100644
--- a/prebuilts/api/33.0/private/compat/32.0/32.0.ignore.cil
+++ b/prebuilts/api/33.0/private/compat/32.0/32.0.ignore.cil
@@ -82,4 +82,5 @@
     vendor_vm_file
     virtual_device_service
     wallpaper_effects_generation_service
+    demo_service
 ))
diff --git a/prebuilts/api/33.0/private/service_contexts b/prebuilts/api/33.0/private/service_contexts
index 72fa16629..6cdb000eb 100644
--- a/prebuilts/api/33.0/private/service_contexts
+++ b/prebuilts/api/33.0/private/service_contexts
@@ -324,6 +324,7 @@ statscompanion                            u:object_r:statscompanion_service:s0
 statsmanager                              u:object_r:statsmanager_service:s0
 soundtrigger                              u:object_r:voiceinteraction_service:s0
 soundtrigger_middleware                   u:object_r:soundtrigger_middleware_service:s0
+demo                   u:object_r:demo_service:s0
 statusbar                                 u:object_r:statusbar_service:s0
 storaged                                  u:object_r:storaged_service:s0
 storaged_pri                              u:object_r:storaged_service:s0
diff --git a/prebuilts/api/33.0/public/service.te b/prebuilts/api/33.0/public/service.te
index e862b405f..fdc84c1a0 100644
--- a/prebuilts/api/33.0/public/service.te
+++ b/prebuilts/api/33.0/public/service.te
@@ -218,6 +218,7 @@ type system_config_service, system_api_service, system_server_service, service_m
 type system_server_dumper_service, system_api_service, system_server_service, service_manager_type;
 type system_update_service, system_server_service, service_manager_type;
 type soundtrigger_middleware_service, system_server_service, service_manager_type;
+type demo_service, system_server_service, service_manager_type;
 type speech_recognition_service, app_api_service, ephemeral_app_api_service, system_server_service, service_manager_type;
 type tare_service, app_api_service, system_server_service, service_manager_type;
 type task_service, system_server_service, service_manager_type;
diff --git a/private/compat/32.0/32.0.ignore.cil b/private/compat/32.0/32.0.ignore.cil
index 076d642e2..f7733c4d9 100644
--- a/private/compat/32.0/32.0.ignore.cil
+++ b/private/compat/32.0/32.0.ignore.cil
@@ -82,4 +82,5 @@
     vendor_vm_file
     virtual_device_service
     wallpaper_effects_generation_service
+    demo_service
 ))
diff --git a/private/service_contexts b/private/service_contexts
index 72fa16629..6cdb000eb 100644
--- a/private/service_contexts
+++ b/private/service_contexts
@@ -324,6 +324,7 @@ statscompanion                            u:object_r:statscompanion_service:s0
 statsmanager                              u:object_r:statsmanager_service:s0
 soundtrigger                              u:object_r:voiceinteraction_service:s0
 soundtrigger_middleware                   u:object_r:soundtrigger_middleware_service:s0
+demo                   u:object_r:demo_service:s0
 statusbar                                 u:object_r:statusbar_service:s0
 storaged                                  u:object_r:storaged_service:s0
 storaged_pri                              u:object_r:storaged_service:s0
diff --git a/public/service.te b/public/service.te
index e862b405f..fdc84c1a0 100644
--- a/public/service.te
+++ b/public/service.te
@@ -218,6 +218,7 @@ type system_config_service, system_api_service, system_server_service, service_m
 type system_server_dumper_service, system_api_service, system_server_service, service_manager_type;
 type system_update_service, system_server_service, service_manager_type;
 type soundtrigger_middleware_service, system_server_service, service_manager_type;
+type demo_service, system_server_service, service_manager_type;
 type speech_recognition_service, app_api_service, ephemeral_app_api_service, system_server_service, service_manager_type;
 type tare_service, app_api_service, system_server_service, service_manager_type;
 type task_service, system_server_service, service_manager_type;

总结：

经过上面的修改，编译运行时，system_server进程就可以找到DemoSystemService类，并且在启动服务时赋予此服务对应的SE身份。

在模拟器里，可以查看到新添加的demo服务：
emulator_car_x86_64:/ $ dumpsys -l |grep demo
  demo

可改进：

1，demo库可以改为java_library_static形式，可参考：
frameworks/base/services/searchui/Android.bp

filegroup {
    name: "services.searchui-sources",
    srcs: ["java/**/*.java"],
    path: "java",
    visibility: ["//frameworks/base/services"],
}

java_library_static {
    name: "services.searchui",
    defaults: ["platform_service_defaults"],
    srcs: [":services.searchui-sources"],
    libs: ["services.core"],
}

2，services依赖此模块，可以参考如下，通过static_libs方式引用：
/home/chen/disk1/work/projects/aosp/android-13.0.0_r41/frameworks/base/services/Android.bp

java_library {
    name: "services",
    defaults: ["services_java_defaults"],
    installable: true,

    dex_preopt: {
        app_image: true,
        profile: "art-profile",
    },

    srcs: [":services-main-sources",
           ":demo--system-service-sources"
    ],

    // The convention is to name each service module 'services.$(module_name)'
    static_libs: [
        "services.core",
        "services.accessibility",
        "services.appprediction",
        "services.appwidget",
        "services.autofill",
        "services.backup",
        "services.companion",
        "services.contentcapture",
        "services.contentsuggestions",
        "services.coverage",
        "services.devicepolicy",
        "services.midi",
        "services.musicsearch",
        "services.net",
        "services.people",
        "services.print",
        "services.profcollect",
        "services.restrictions",
        "services.searchui",//参考此处
        ......