ZygoteServer.java revision b9679dc1fad508a001e30a941148e1bdc3fe953f 
1/*
2 * Copyright (C) 2007 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
17package com.android.internal.os;
18
19import static android.system.OsConstants.POLLIN;
20
21import android.net.LocalServerSocket;
22import android.system.Os;
23import android.system.ErrnoException;
24import android.system.StructPollfd;
25import android.util.Log;
26
27import java.io.IOException;
28import java.io.FileDescriptor;
29import java.util.ArrayList;
30
31/**
32 * Server socket class for zygote processes.
33 *
34 * Provides functions to wait for commands on a UNIX domain socket, and fork
35 * off child processes that inherit the initial state of the VM.%
36 *
37 * Please see {@link ZygoteConnection.Arguments} for documentation on the
38 * client protocol.
39 */
40class ZygoteServer {
41    public static final String TAG = "ZygoteServer";
42
43    private static final String ANDROID_SOCKET_PREFIX = "ANDROID_SOCKET_";
44
45    private LocalServerSocket mServerSocket;
46
47    ZygoteServer() {
48    }
49
50    /**
51     * Registers a server socket for zygote command connections
52     *
53     * @throws RuntimeException when open fails
54     */
55    void registerServerSocket(String socketName) {
56        if (mServerSocket == null) {
57            int fileDesc;
58            final String fullSocketName = ANDROID_SOCKET_PREFIX + socketName;
59            try {
60                String env = System.getenv(fullSocketName);
61                fileDesc = Integer.parseInt(env);
62            } catch (RuntimeException ex) {
63                throw new RuntimeException(fullSocketName + " unset or invalid", ex);
64            }
65
66            try {
67                FileDescriptor fd = new FileDescriptor();
68                fd.setInt$(fileDesc);
69                mServerSocket = new LocalServerSocket(fd);
70            } catch (IOException ex) {
71                throw new RuntimeException(
72                        "Error binding to local socket '" + fileDesc + "'", ex);
73            }
74        }
75    }
76
77    /**
78     * Waits for and accepts a single command connection. Throws
79     * RuntimeException on failure.
80     */
81    private ZygoteConnection acceptCommandPeer(String abiList) {
82        try {
83            return new ZygoteConnection(mServerSocket.accept(), abiList);
84        } catch (IOException ex) {
85            throw new RuntimeException(
86                    "IOException during accept()", ex);
87        }
88    }
89
90    /**
91     * Close and clean up zygote sockets. Called on shutdown and on the
92     * child's exit path.
93     */
94    void closeServerSocket() {
95        try {
96            if (mServerSocket != null) {
97                FileDescriptor fd = mServerSocket.getFileDescriptor();
98                mServerSocket.close();
99                if (fd != null) {
100                    Os.close(fd);
101                }
102            }
103        } catch (IOException ex) {
104            Log.e(TAG, "Zygote:  error closing sockets", ex);
105        } catch (ErrnoException ex) {
106            Log.e(TAG, "Zygote:  error closing descriptor", ex);
107        }
108
109        mServerSocket = null;
110    }
111
112    /**
113     * Return the server socket's underlying file descriptor, so that
114     * ZygoteConnection can pass it to the native code for proper
115     * closure after a child process is forked off.
116     */
117
118    FileDescriptor getServerSocketFileDescriptor() {
119        return mServerSocket.getFileDescriptor();
120    }
121
122    /**
123     * Runs the zygote process's select loop. Accepts new connections as
124     * they happen, and reads commands from connections one spawn-request's
125     * worth at a time.
126     *
127     * @throws Zygote.MethodAndArgsCaller in a child process when a main()
128     * should be executed.
129     */
130    void runSelectLoop(String abiList) throws Zygote.MethodAndArgsCaller {
131        ArrayList<FileDescriptor> fds = new ArrayList<FileDescriptor>();
132        ArrayList<ZygoteConnection> peers = new ArrayList<ZygoteConnection>();
133
134        fds.add(mServerSocket.getFileDescriptor());
135        peers.add(null);
136
137        while (true) {
138            StructPollfd[] pollFds = new StructPollfd[fds.size()];
139            for (int i = 0; i < pollFds.length; ++i) {
140                pollFds[i] = new StructPollfd();
141                pollFds[i].fd = fds.get(i);
142                pollFds[i].events = (short) POLLIN;
143            }
144            try {
145                Os.poll(pollFds, -1);
146            } catch (ErrnoException ex) {
147                throw new RuntimeException("poll failed", ex);
148            }
149            for (int i = pollFds.length - 1; i >= 0; --i) {
150                if ((pollFds[i].revents & POLLIN) == 0) {
151                    continue;
152                }
153                if (i == 0) {
154                    ZygoteConnection newPeer = acceptCommandPeer(abiList);
155                    peers.add(newPeer);
156                    fds.add(newPeer.getFileDesciptor());
157                } else {
158                    boolean done = peers.get(i).runOnce(this);
159                    if (done) {
160                        peers.remove(i);
161                        fds.remove(i);
162                    }
163                }
164            }
165        }
166    }
167}
168