1 /* 2 * Copyright (C) 2006 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 dalvik.system; 18 19 import libcore.io.ErrnoException; 20 import libcore.io.Libcore; 21 22 import java.io.File; 23 24 /** 25 * Provides access to the Dalvik "zygote" feature, which allows a VM instance to 26 * be partially initialized and then fork()'d from the partially initialized 27 * state. 28 * 29 * @hide 30 */ 31 public class Zygote { 32 /* 33 * Bit values for "debugFlags" argument. The definitions are duplicated 34 * in the native code. 35 */ 36 /** enable debugging over JDWP */ 37 public static final int DEBUG_ENABLE_DEBUGGER = 1; 38 /** enable JNI checks */ 39 public static final int DEBUG_ENABLE_CHECKJNI = 1 << 1; 40 /** enable Java programming language "assert" statements */ 41 public static final int DEBUG_ENABLE_ASSERT = 1 << 2; 42 /** disable the JIT compiler */ 43 public static final int DEBUG_ENABLE_SAFEMODE = 1 << 3; 44 /** Enable logging of third-party JNI activity. */ 45 public static final int DEBUG_ENABLE_JNI_LOGGING = 1 << 4; 46 47 /** No external storage should be mounted. */ 48 public static final int MOUNT_EXTERNAL_NONE = 0; 49 /** Single-user external storage should be mounted. */ 50 public static final int MOUNT_EXTERNAL_SINGLEUSER = 1; 51 /** Multi-user external storage should be mounted. */ 52 public static final int MOUNT_EXTERNAL_MULTIUSER = 2; 53 /** All multi-user external storage should be mounted. */ 54 public static final int MOUNT_EXTERNAL_MULTIUSER_ALL = 3; 55 56 /** 57 * When set by the system server, all subsequent apps will be launched in 58 * VM safe mode. 59 */ 60 public static boolean systemInSafeMode = false; 61 62 private Zygote() {} 63 64 private static void preFork() { 65 Daemons.stop(); 66 waitUntilAllThreadsStopped(); 67 } 68 69 /** 70 * We must not fork until we're single-threaded again. Wait until /proc shows we're 71 * down to just one thread. 72 */ 73 private static void waitUntilAllThreadsStopped() { 74 File tasks = new File("/proc/self/task"); 75 while (tasks.list().length > 1) { 76 try { 77 // Experimentally, booting and playing about with a stingray, I never saw us 78 // go round this loop more than once with a 10ms sleep. 79 Thread.sleep(10); 80 } catch (InterruptedException ignored) { 81 } 82 } 83 } 84 85 private static void postFork() { 86 Daemons.start(); 87 } 88 89 /** 90 * Forks a new Zygote instance, but does not leave the zygote mode. 91 * The current VM must have been started with the -Xzygote flag. The 92 * new child is expected to eventually call forkAndSpecialize() 93 * 94 * @return 0 if this is the child, pid of the child 95 * if this is the parent, or -1 on error 96 */ 97 public static int fork() { 98 preFork(); 99 int pid = nativeFork(); 100 postFork(); 101 return pid; 102 } 103 104 native public static int nativeFork(); 105 106 /** 107 * Forks a new VM instance. The current VM must have been started 108 * with the -Xzygote flag. <b>NOTE: new instance keeps all 109 * root capabilities. The new process is expected to call capset()</b>. 110 * 111 * @param uid the UNIX uid that the new process should setuid() to after 112 * fork()ing and and before spawning any threads. 113 * @param gid the UNIX gid that the new process should setgid() to after 114 * fork()ing and and before spawning any threads. 115 * @param gids null-ok; a list of UNIX gids that the new process should 116 * setgroups() to after fork and before spawning any threads. 117 * @param debugFlags bit flags that enable debugging features. 118 * @param rlimits null-ok an array of rlimit tuples, with the second 119 * dimension having a length of 3 and representing 120 * (resource, rlim_cur, rlim_max). These are set via the posix 121 * setrlimit(2) call. 122 * @param seInfo null-ok a string specifying SELinux information for 123 * the new process. 124 * @param niceName null-ok a string specifying the process name. 125 * 126 * @return 0 if this is the child, pid of the child 127 * if this is the parent, or -1 on error. 128 */ 129 public static int forkAndSpecialize(int uid, int gid, int[] gids, int debugFlags, 130 int[][] rlimits, int mountExternal, String seInfo, String niceName) { 131 preFork(); 132 int pid = nativeForkAndSpecialize( 133 uid, gid, gids, debugFlags, rlimits, mountExternal, seInfo, niceName); 134 postFork(); 135 return pid; 136 } 137 138 native public static int nativeForkAndSpecialize(int uid, int gid, int[] gids, int debugFlags, 139 int[][] rlimits, int mountExternal, String seInfo, String niceName); 140 141 /** 142 * Special method to start the system server process. In addition to the 143 * common actions performed in forkAndSpecialize, the pid of the child 144 * process is recorded such that the death of the child process will cause 145 * zygote to exit. 146 * 147 * @param uid the UNIX uid that the new process should setuid() to after 148 * fork()ing and and before spawning any threads. 149 * @param gid the UNIX gid that the new process should setgid() to after 150 * fork()ing and and before spawning any threads. 151 * @param gids null-ok; a list of UNIX gids that the new process should 152 * setgroups() to after fork and before spawning any threads. 153 * @param debugFlags bit flags that enable debugging features. 154 * @param rlimits null-ok an array of rlimit tuples, with the second 155 * dimension having a length of 3 and representing 156 * (resource, rlim_cur, rlim_max). These are set via the posix 157 * setrlimit(2) call. 158 * @param permittedCapabilities argument for setcap() 159 * @param effectiveCapabilities argument for setcap() 160 * 161 * @return 0 if this is the child, pid of the child 162 * if this is the parent, or -1 on error. 163 */ 164 public static int forkSystemServer(int uid, int gid, int[] gids, int debugFlags, 165 int[][] rlimits, long permittedCapabilities, long effectiveCapabilities) { 166 preFork(); 167 int pid = nativeForkSystemServer( 168 uid, gid, gids, debugFlags, rlimits, permittedCapabilities, effectiveCapabilities); 169 postFork(); 170 return pid; 171 } 172 173 native public static int nativeForkSystemServer(int uid, int gid, int[] gids, int debugFlags, 174 int[][] rlimits, long permittedCapabilities, long effectiveCapabilities); 175 176 /** 177 * Executes "/system/bin/sh -c <command>" using the exec() system call. 178 * This method throws a runtime exception if exec() failed, otherwise, this 179 * method never returns. 180 * 181 * @param command The shell command to execute. 182 */ 183 public static void execShell(String command) { 184 String[] args = { "/system/bin/sh", "-c", command }; 185 try { 186 Libcore.os.execv(args[0], args); 187 } catch (ErrnoException e) { 188 throw new RuntimeException(e); 189 } 190 } 191 192 /** 193 * Appends quotes shell arguments to the specified string builder. 194 * The arguments are quoted using single-quotes, escaped if necessary, 195 * prefixed with a space, and appended to the command. 196 * 197 * @param command A string builder for the shell command being constructed. 198 * @param args An array of argument strings to be quoted and appended to the command. 199 * @see #execShell(String) 200 */ 201 public static void appendQuotedShellArgs(StringBuilder command, String[] args) { 202 for (String arg : args) { 203 command.append(" '").append(arg.replace("'", "'\\''")).append("'"); 204 } 205 } 206 } 207
