/*
* Copyright (C) 2006 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package dalvik.system;
import libcore.io.ErrnoException;
import libcore.io.Libcore;
import java.io.File;
/**
* Provides access to the Dalvik "zygote" feature, which allows a VM instance to
* be partially initialized and then fork()'d from the partially initialized
* state.
*
* @hide
*/
public class Zygote {
/*
* Bit values for "debugFlags" argument. The definitions are duplicated
* in the native code.
*/
/** enable debugging over JDWP */
public static final int DEBUG_ENABLE_DEBUGGER = 1;
/** enable JNI checks */
public static final int DEBUG_ENABLE_CHECKJNI = 1 << 1;
/** enable Java programming language "assert" statements */
public static final int DEBUG_ENABLE_ASSERT = 1 << 2;
/** disable the JIT compiler */
public static final int DEBUG_ENABLE_SAFEMODE = 1 << 3;
/** Enable logging of third-party JNI activity. */
public static final int DEBUG_ENABLE_JNI_LOGGING = 1 << 4;
/** No external storage should be mounted. */
public static final int MOUNT_EXTERNAL_NONE = 0;
/** Single-user external storage should be mounted. */
public static final int MOUNT_EXTERNAL_SINGLEUSER = 1;
/** Multi-user external storage should be mounted. */
public static final int MOUNT_EXTERNAL_MULTIUSER = 2;
/** All multi-user external storage should be mounted. */
public static final int MOUNT_EXTERNAL_MULTIUSER_ALL = 3;
/**
* When set by the system server, all subsequent apps will be launched in
* VM safe mode.
*/
public static boolean systemInSafeMode = false;
private Zygote() {}
private static void preFork() {
Daemons.stop();
waitUntilAllThreadsStopped();
}
/**
* We must not fork until we're single-threaded again. Wait until /proc shows we're
* down to just one thread.
*/
private static void waitUntilAllThreadsStopped() {
File tasks = new File("/proc/self/task");
while (tasks.list().length > 1) {
try {
// Experimentally, booting and playing about with a stingray, I never saw us
// go round this loop more than once with a 10ms sleep.
Thread.sleep(10);
} catch (InterruptedException ignored) {
}
}
}
private static void postFork() {
Daemons.start();
}
/**
* Forks a new Zygote instance, but does not leave the zygote mode.
* The current VM must have been started with the -Xzygote flag. The
* new child is expected to eventually call forkAndSpecialize()
*
* @return 0 if this is the child, pid of the child
* if this is the parent, or -1 on error
*/
public static int fork() {
preFork();
int pid = nativeFork();
postFork();
return pid;
}
native public static int nativeFork();
/**
* Forks a new VM instance. The current VM must have been started
* with the -Xzygote flag. <b>NOTE: new instance keeps all
* root capabilities. The new process is expected to call capset()</b>.
*
* @param uid the UNIX uid that the new process should setuid() to after
* fork()ing and and before spawning any threads.
* @param gid the UNIX gid that the new process should setgid() to after
* fork()ing and and before spawning any threads.
* @param gids null-ok; a list of UNIX gids that the new process should
* setgroups() to after fork and before spawning any threads.
* @param debugFlags bit flags that enable debugging features.
* @param rlimits null-ok an array of rlimit tuples, with the second
* dimension having a length of 3 and representing
* (resource, rlim_cur, rlim_max). These are set via the posix
* setrlimit(2) call.
* @param seInfo null-ok a string specifying SELinux information for
* the new process.
* @param niceName null-ok a string specifying the process name.
*
* @return 0 if this is the child, pid of the child
* if this is the parent, or -1 on error.
*/
public static int forkAndSpecialize(int uid, int gid, int[] gids, int debugFlags,
int[][] rlimits, int mountExternal, String seInfo, String niceName) {
preFork();
int pid = nativeForkAndSpecialize(
uid, gid, gids, debugFlags, rlimits, mountExternal, seInfo, niceName);
postFork();
return pid;
}
native public static int nativeForkAndSpecialize(int uid, int gid, int[] gids, int debugFlags,
int[][] rlimits, int mountExternal, String seInfo, String niceName);
/**
* Special method to start the system server process. In addition to the
* common actions performed in forkAndSpecialize, the pid of the child
* process is recorded such that the death of the child process will cause
* zygote to exit.
*
* @param uid the UNIX uid that the new process should setuid() to after
* fork()ing and and before spawning any threads.
* @param gid the UNIX gid that the new process should setgid() to after
* fork()ing and and before spawning any threads.
* @param gids null-ok; a list of UNIX gids that the new process should
* setgroups() to after fork and before spawning any threads.
* @param debugFlags bit flags that enable debugging features.
* @param rlimits null-ok an array of rlimit tuples, with the second
* dimension having a length of 3 and representing
* (resource, rlim_cur, rlim_max). These are set via the posix
* setrlimit(2) call.
* @param permittedCapabilities argument for setcap()
* @param effectiveCapabilities argument for setcap()
*
* @return 0 if this is the child, pid of the child
* if this is the parent, or -1 on error.
*/
public static int forkSystemServer(int uid, int gid, int[] gids, int debugFlags,
int[][] rlimits, long permittedCapabilities, long effectiveCapabilities) {
preFork();
int pid = nativeForkSystemServer(
uid, gid, gids, debugFlags, rlimits, permittedCapabilities, effectiveCapabilities);
postFork();
return pid;
}
native public static int nativeForkSystemServer(int uid, int gid, int[] gids, int debugFlags,
int[][] rlimits, long permittedCapabilities, long effectiveCapabilities);
/**
* Executes "/system/bin/sh -c <command>" using the exec() system call.
* This method throws a runtime exception if exec() failed, otherwise, this
* method never returns.
*
* @param command The shell command to execute.
*/
public static void execShell(String command) {
String[] args = { "/system/bin/sh", "-c", command };
try {
Libcore.os.execv(args[0], args);
} catch (ErrnoException e) {
throw new RuntimeException(e);
}
}
/**
* Appends quotes shell arguments to the specified string builder.
* The arguments are quoted using single-quotes, escaped if necessary,
* prefixed with a space, and appended to the command.
*
* @param command A string builder for the shell command being constructed.
* @param args An array of argument strings to be quoted and appended to the command.
* @see #execShell(String)
*/
public static void appendQuotedShellArgs(StringBuilder command, String[] args) {
for (String arg : args) {
command.append(" '").append(arg.replace("'", "'\\''")).append("'");
}
}
}