Zygote.java revision 973b4663b0b5ee62006522bf4742af076096e548 
1/*
2 * Copyright (C) 2014 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
19
20import dalvik.system.ZygoteHooks;
21import libcore.io.ErrnoException;
22import libcore.io.Libcore;
23
24/** @hide */
25public final class Zygote {
26    /*
27    * Bit values for "debugFlags" argument.  The definitions are duplicated
28    * in the native code.
29    */
30
31    /** enable debugging over JDWP */
32    public static final int DEBUG_ENABLE_DEBUGGER   = 1;
33    /** enable JNI checks */
34    public static final int DEBUG_ENABLE_CHECKJNI   = 1 << 1;
35    /** enable Java programming language "assert" statements */
36    public static final int DEBUG_ENABLE_ASSERT     = 1 << 2;
37    /** disable the JIT compiler */
38    public static final int DEBUG_ENABLE_SAFEMODE   = 1 << 3;
39    /** Enable logging of third-party JNI activity. */
40    public static final int DEBUG_ENABLE_JNI_LOGGING = 1 << 4;
41
42    /** No external storage should be mounted. */
43    public static final int MOUNT_EXTERNAL_NONE = 0;
44    /** Single-user external storage should be mounted. */
45    public static final int MOUNT_EXTERNAL_SINGLEUSER = 1;
46    /** Multi-user external storage should be mounted. */
47    public static final int MOUNT_EXTERNAL_MULTIUSER = 2;
48    /** All multi-user external storage should be mounted. */
49    public static final int MOUNT_EXTERNAL_MULTIUSER_ALL = 3;
50
51    private static final ZygoteHooks VM_HOOKS = new ZygoteHooks();
52
53    private Zygote() {}
54
55    /**
56     * Forks a new VM instance.  The current VM must have been started
57     * with the -Xzygote flag. <b>NOTE: new instance keeps all
58     * root capabilities. The new process is expected to call capset()</b>.
59     *
60     * @param uid the UNIX uid that the new process should setuid() to after
61     * fork()ing and and before spawning any threads.
62     * @param gid the UNIX gid that the new process should setgid() to after
63     * fork()ing and and before spawning any threads.
64     * @param gids null-ok; a list of UNIX gids that the new process should
65     * setgroups() to after fork and before spawning any threads.
66     * @param debugFlags bit flags that enable debugging features.
67     * @param rlimits null-ok an array of rlimit tuples, with the second
68     * dimension having a length of 3 and representing
69     * (resource, rlim_cur, rlim_max). These are set via the posix
70     * setrlimit(2) call.
71     * @param seInfo null-ok a string specifying SELinux information for
72     * the new process.
73     * @param niceName null-ok a string specifying the process name.
74     * @param fdsToClose an array of ints, holding one or more POSIX
75     * file descriptor numbers that are to be closed by the child
76     * (and replaced by /dev/null) after forking.  An integer value
77     * of -1 in any entry in the array means "ignore this one".
78     *
79     * @return 0 if this is the child, pid of the child
80     * if this is the parent, or -1 on error.
81     */
82    public static int forkAndSpecialize(int uid, int gid, int[] gids, int debugFlags,
83          int[][] rlimits, int mountExternal, String seInfo, String niceName, int[] fdsToClose) {
84        VM_HOOKS.preFork();
85        int pid = nativeForkAndSpecialize(
86                  uid, gid, gids, debugFlags, rlimits, mountExternal, seInfo, niceName, fdsToClose);
87        VM_HOOKS.postForkCommon();
88        return pid;
89    }
90
91    native private static int nativeForkAndSpecialize(int uid, int gid, int[] gids,int debugFlags,
92          int[][] rlimits, int mountExternal, String seInfo, String niceName, int[] fdsToClose);
93
94    /**
95     * Special method to start the system server process. In addition to the
96     * common actions performed in forkAndSpecialize, the pid of the child
97     * process is recorded such that the death of the child process will cause
98     * zygote to exit.
99     *
100     * @param uid the UNIX uid that the new process should setuid() to after
101     * fork()ing and and before spawning any threads.
102     * @param gid the UNIX gid that the new process should setgid() to after
103     * fork()ing and and before spawning any threads.
104     * @param gids null-ok; a list of UNIX gids that the new process should
105     * setgroups() to after fork and before spawning any threads.
106     * @param debugFlags bit flags that enable debugging features.
107     * @param rlimits null-ok an array of rlimit tuples, with the second
108     * dimension having a length of 3 and representing
109     * (resource, rlim_cur, rlim_max). These are set via the posix
110     * setrlimit(2) call.
111     * @param permittedCapabilities argument for setcap()
112     * @param effectiveCapabilities argument for setcap()
113     *
114     * @return 0 if this is the child, pid of the child
115     * if this is the parent, or -1 on error.
116     */
117    public static int forkSystemServer(int uid, int gid, int[] gids, int debugFlags,
118            int[][] rlimits, long permittedCapabilities, long effectiveCapabilities) {
119        VM_HOOKS.preFork();
120        int pid = nativeForkSystemServer(
121                uid, gid, gids, debugFlags, rlimits, permittedCapabilities, effectiveCapabilities);
122        VM_HOOKS.postForkCommon();
123        return pid;
124    }
125
126    native private static int nativeForkSystemServer(int uid, int gid, int[] gids, int debugFlags,
127            int[][] rlimits, long permittedCapabilities, long effectiveCapabilities);
128
129    private static void callPostForkChildHooks(int debugFlags) {
130        VM_HOOKS.postForkChild(debugFlags);
131    }
132
133
134    /**
135     * Executes "/system/bin/sh -c &lt;command&gt;" using the exec() system call.
136     * This method throws a runtime exception if exec() failed, otherwise, this
137     * method never returns.
138     *
139     * @param command The shell command to execute.
140     */
141    public static void execShell(String command) {
142        String[] args = { "/system/bin/sh", "-c", command };
143        try {
144            Libcore.os.execv(args[0], args);
145        } catch (ErrnoException e) {
146            throw new RuntimeException(e);
147        }
148    }
149
150    /**
151     * Appends quotes shell arguments to the specified string builder.
152     * The arguments are quoted using single-quotes, escaped if necessary,
153     * prefixed with a space, and appended to the command.
154     *
155     * @param command A string builder for the shell command being constructed.
156     * @param args An array of argument strings to be quoted and appended to the command.
157     * @see #execShell(String)
158     */
159    public static void appendQuotedShellArgs(StringBuilder command, String[] args) {
160        for (String arg : args) {
161            command.append(" '").append(arg.replace("'", "'\\''")).append("'");
162        }
163    }
164}
165