/*
* Copyright (C) 2014 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 com.android.internal.os;
import dalvik.system.ZygoteHooks;
import android.system.ErrnoException;
import android.system.Os;
import android.os.SystemClock;
import android.util.Slog;
/** @hide */
public final class Zygote {
private static final String TAG = "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;
private static final ZygoteHooks VM_HOOKS = new ZygoteHooks();
private Zygote() {}
/**
* 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.
* @param fdsToClose an array of ints, holding one or more POSIX
* file descriptor numbers that are to be closed by the child
* (and replaced by /dev/null) after forking. An integer value
* of -1 in any entry in the array means "ignore this one".
* @param instructionSet null-ok the instruction set to use.
* @param appDataDir null-ok the data directory of the app.
*
* @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, int[] fdsToClose,
String instructionSet, String appDataDir) {
long startTime = SystemClock.elapsedRealtime();
VM_HOOKS.preFork();
checkTime(startTime, "Zygote.preFork");
int pid = nativeForkAndSpecialize(
uid, gid, gids, debugFlags, rlimits, mountExternal, seInfo, niceName, fdsToClose,
instructionSet, appDataDir);
checkTime(startTime, "Zygote.nativeForkAndSpecialize");
VM_HOOKS.postForkCommon();
checkTime(startTime, "Zygote.postForkCommon");
return pid;
}
native private static int nativeForkAndSpecialize(int uid, int gid, int[] gids,int debugFlags,
int[][] rlimits, int mountExternal, String seInfo, String niceName, int[] fdsToClose,
String instructionSet, String appDataDir);
/**
* Temporary hack: check time since start time and log if over a fixed threshold.
*
*/
private static void checkTime(long startTime, String where) {
long now = SystemClock.elapsedRealtime();
if ((now-startTime) > 1000) {
// If we are taking more than a second, log about it.
Slog.w(TAG, "Slow operation: " + (now-startTime) + "ms so far, now at " + where);
}
}
/**
* 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) {
VM_HOOKS.preFork();
int pid = nativeForkSystemServer(
uid, gid, gids, debugFlags, rlimits, permittedCapabilities, effectiveCapabilities);
VM_HOOKS.postForkCommon();
return pid;
}
native private static int nativeForkSystemServer(int uid, int gid, int[] gids, int debugFlags,
int[][] rlimits, long permittedCapabilities, long effectiveCapabilities);
private static void callPostForkChildHooks(int debugFlags, String instructionSet) {
long startTime = SystemClock.elapsedRealtime();
VM_HOOKS.postForkChild(debugFlags, instructionSet);
checkTime(startTime, "Zygote.callPostForkChildHooks");
}
/**
* 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 {
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("'");
}
}
}
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