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      1 /*
      2  * Copyright (C) 2012 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.server.os;
     18 
     19 import android.content.pm.PackageManager;
     20 import android.os.Binder;
     21 import android.os.ISchedulingPolicyService;
     22 import android.os.Process;
     23 import android.util.Log;
     24 
     25 /**
     26  * The implementation of the scheduling policy service interface.
     27  *
     28  * @hide
     29  */
     30 public class SchedulingPolicyService extends ISchedulingPolicyService.Stub {
     31 
     32     private static final String TAG = "SchedulingPolicyService";
     33 
     34     // Minimum and maximum values allowed for requestPriority parameter prio
     35     private static final int PRIORITY_MIN = 1;
     36     private static final int PRIORITY_MAX = 3;
     37 
     38     public SchedulingPolicyService() {
     39     }
     40 
     41     // TODO(b/35196900) We should pass the period in time units, rather
     42     // than a fixed priority number.
     43     public int requestPriority(int pid, int tid, int prio, boolean isForApp) {
     44         //Log.i(TAG, "requestPriority(pid=" + pid + ", tid=" + tid + ", prio=" + prio + ")");
     45 
     46         // Verify that the caller uid is permitted, priority is in range,
     47         // and that the callback thread specified by app belongs to the app that
     48         // called mediaserver or audioserver.
     49         // Once we've verified that the caller uid is permitted, we can trust the pid but
     50         // we can't trust the tid.  No need to explicitly check for pid == 0 || tid == 0,
     51         // since if not the case then the getThreadGroupLeader() test will also fail.
     52         if (!isPermitted() || prio < PRIORITY_MIN ||
     53                 prio > PRIORITY_MAX || Process.getThreadGroupLeader(tid) != pid) {
     54            return PackageManager.PERMISSION_DENIED;
     55         }
     56         if (Binder.getCallingUid() != Process.BLUETOOTH_UID) {
     57             try {
     58                 // make good use of our CAP_SYS_NICE capability
     59                 Process.setThreadGroup(tid, !isForApp ?
     60                   Process.THREAD_GROUP_AUDIO_SYS : Process.THREAD_GROUP_RT_APP);
     61             } catch (RuntimeException e) {
     62                 Log.e(TAG, "Failed setThreadGroup: " + e);
     63                 return PackageManager.PERMISSION_DENIED;
     64            }
     65         }
     66         try {
     67             // must be in this order or it fails the schedulability constraint
     68             Process.setThreadScheduler(tid, Process.SCHED_FIFO | Process.SCHED_RESET_ON_FORK,
     69                                        prio);
     70         } catch (RuntimeException e) {
     71             Log.e(TAG, "Failed setThreadScheduler: " + e);
     72             return PackageManager.PERMISSION_DENIED;
     73         }
     74         return PackageManager.PERMISSION_GRANTED;
     75     }
     76 
     77     private boolean isPermitted() {
     78         // schedulerservice hidl
     79         if (Binder.getCallingPid() == Process.myPid()) {
     80             return true;
     81         }
     82 
     83         switch (Binder.getCallingUid()) {
     84         case Process.AUDIOSERVER_UID: // fastcapture, fastmixer
     85         case Process.CAMERASERVER_UID: // camera high frame rate recording
     86         case Process.BLUETOOTH_UID: // Bluetooth audio playback
     87             return true;
     88         default:
     89             return false;
     90         }
     91     }
     92 }
     93