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 android.system.ErrnoException;
22import android.system.Os;
23import android.os.SystemClock;
24import android.util.Slog;
25
26/** @hide */
27public final class Zygote {
28    private static final String TAG = "Zygote";
29    /*
30    * Bit values for "debugFlags" argument.  The definitions are duplicated
31    * in the native code.
32    */
33
34    /** enable debugging over JDWP */
35    public static final int DEBUG_ENABLE_DEBUGGER   = 1;
36    /** enable JNI checks */
37    public static final int DEBUG_ENABLE_CHECKJNI   = 1 << 1;
38    /** enable Java programming language "assert" statements */
39    public static final int DEBUG_ENABLE_ASSERT     = 1 << 2;
40    /** disable the JIT compiler */
41    public static final int DEBUG_ENABLE_SAFEMODE   = 1 << 3;
42    /** Enable logging of third-party JNI activity. */
43    public static final int DEBUG_ENABLE_JNI_LOGGING = 1 << 4;
44
45    /** No external storage should be mounted. */
46    public static final int MOUNT_EXTERNAL_NONE = 0;
47    /** Single-user external storage should be mounted. */
48    public static final int MOUNT_EXTERNAL_SINGLEUSER = 1;
49    /** Multi-user external storage should be mounted. */
50    public static final int MOUNT_EXTERNAL_MULTIUSER = 2;
51    /** All multi-user external storage should be mounted. */
52    public static final int MOUNT_EXTERNAL_MULTIUSER_ALL = 3;
53
54    private static final ZygoteHooks VM_HOOKS = new ZygoteHooks();
55
56    private Zygote() {}
57
58    /**
59     * Forks a new VM instance.  The current VM must have been started
60     * with the -Xzygote flag. <b>NOTE: new instance keeps all
61     * root capabilities. The new process is expected to call capset()</b>.
62     *
63     * @param uid the UNIX uid that the new process should setuid() to after
64     * fork()ing and and before spawning any threads.
65     * @param gid the UNIX gid that the new process should setgid() to after
66     * fork()ing and and before spawning any threads.
67     * @param gids null-ok; a list of UNIX gids that the new process should
68     * setgroups() to after fork and before spawning any threads.
69     * @param debugFlags bit flags that enable debugging features.
70     * @param rlimits null-ok an array of rlimit tuples, with the second
71     * dimension having a length of 3 and representing
72     * (resource, rlim_cur, rlim_max). These are set via the posix
73     * setrlimit(2) call.
74     * @param seInfo null-ok a string specifying SELinux information for
75     * the new process.
76     * @param niceName null-ok a string specifying the process name.
77     * @param fdsToClose an array of ints, holding one or more POSIX
78     * file descriptor numbers that are to be closed by the child
79     * (and replaced by /dev/null) after forking.  An integer value
80     * of -1 in any entry in the array means "ignore this one".
81     * @param instructionSet null-ok the instruction set to use.
82     * @param appDataDir null-ok the data directory of the app.
83     *
84     * @return 0 if this is the child, pid of the child
85     * if this is the parent, or -1 on error.
86     */
87    public static int forkAndSpecialize(int uid, int gid, int[] gids, int debugFlags,
88          int[][] rlimits, int mountExternal, String seInfo, String niceName, int[] fdsToClose,
89          String instructionSet, String appDataDir) {
90        long startTime = SystemClock.elapsedRealtime();
91        VM_HOOKS.preFork();
92        checkTime(startTime, "Zygote.preFork");
93        int pid = nativeForkAndSpecialize(
94                  uid, gid, gids, debugFlags, rlimits, mountExternal, seInfo, niceName, fdsToClose,
95                  instructionSet, appDataDir);
96        checkTime(startTime, "Zygote.nativeForkAndSpecialize");
97        VM_HOOKS.postForkCommon();
98        checkTime(startTime, "Zygote.postForkCommon");
99        return pid;
100    }
101
102    native private static int nativeForkAndSpecialize(int uid, int gid, int[] gids,int debugFlags,
103          int[][] rlimits, int mountExternal, String seInfo, String niceName, int[] fdsToClose,
104          String instructionSet, String appDataDir);
105
106    /**
107     * Temporary hack: check time since start time and log if over a fixed threshold.
108     *
109     */
110    private static void checkTime(long startTime, String where) {
111        long now = SystemClock.elapsedRealtime();
112        if ((now-startTime) > 1000) {
113            // If we are taking more than a second, log about it.
114            Slog.w(TAG, "Slow operation: " + (now-startTime) + "ms so far, now at " + where);
115        }
116    }
117
118    /**
119     * Special method to start the system server process. In addition to the
120     * common actions performed in forkAndSpecialize, the pid of the child
121     * process is recorded such that the death of the child process will cause
122     * zygote to exit.
123     *
124     * @param uid the UNIX uid that the new process should setuid() to after
125     * fork()ing and and before spawning any threads.
126     * @param gid the UNIX gid that the new process should setgid() to after
127     * fork()ing and and before spawning any threads.
128     * @param gids null-ok; a list of UNIX gids that the new process should
129     * setgroups() to after fork and before spawning any threads.
130     * @param debugFlags bit flags that enable debugging features.
131     * @param rlimits null-ok an array of rlimit tuples, with the second
132     * dimension having a length of 3 and representing
133     * (resource, rlim_cur, rlim_max). These are set via the posix
134     * setrlimit(2) call.
135     * @param permittedCapabilities argument for setcap()
136     * @param effectiveCapabilities argument for setcap()
137     *
138     * @return 0 if this is the child, pid of the child
139     * if this is the parent, or -1 on error.
140     */
141    public static int forkSystemServer(int uid, int gid, int[] gids, int debugFlags,
142            int[][] rlimits, long permittedCapabilities, long effectiveCapabilities) {
143        VM_HOOKS.preFork();
144        int pid = nativeForkSystemServer(
145                uid, gid, gids, debugFlags, rlimits, permittedCapabilities, effectiveCapabilities);
146        VM_HOOKS.postForkCommon();
147        return pid;
148    }
149
150    native private static int nativeForkSystemServer(int uid, int gid, int[] gids, int debugFlags,
151            int[][] rlimits, long permittedCapabilities, long effectiveCapabilities);
152
153    private static void callPostForkChildHooks(int debugFlags, String instructionSet) {
154        long startTime = SystemClock.elapsedRealtime();
155        VM_HOOKS.postForkChild(debugFlags, instructionSet);
156        checkTime(startTime, "Zygote.callPostForkChildHooks");
157    }
158
159
160    /**
161     * Executes "/system/bin/sh -c &lt;command&gt;" using the exec() system call.
162     * This method throws a runtime exception if exec() failed, otherwise, this
163     * method never returns.
164     *
165     * @param command The shell command to execute.
166     */
167    public static void execShell(String command) {
168        String[] args = { "/system/bin/sh", "-c", command };
169        try {
170            Os.execv(args[0], args);
171        } catch (ErrnoException e) {
172            throw new RuntimeException(e);
173        }
174    }
175
176    /**
177     * Appends quotes shell arguments to the specified string builder.
178     * The arguments are quoted using single-quotes, escaped if necessary,
179     * prefixed with a space, and appended to the command.
180     *
181     * @param command A string builder for the shell command being constructed.
182     * @param args An array of argument strings to be quoted and appended to the command.
183     * @see #execShell(String)
184     */
185    public static void appendQuotedShellArgs(StringBuilder command, String[] args) {
186        for (String arg : args) {
187            command.append(" '").append(arg.replace("'", "'\\''")).append("'");
188        }
189    }
190}
191