1. init进程
2. zygote进程
2.1 AndroidRuntime
2.2 ZygoteInit
3. system_server进程
3.1 init1阶段
3.2 init2阶段
接着Linux启动部分 http://blog.csdn.net/qianjin0703/article/details/6881107
1. init进程
系统在内核空间初始化进程,内存,文件系统,驱动模块之后,调用init_post()函数,开启第一个用户进程init,进入用户空间。
/kernel/init/main.c (仅截取部分重要代码)
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static noinline int init_post(void)
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{
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run_init_process("/sbin/init");
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run_init_process("/etc/init");
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run_init_process("/bin/init");
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run_init_process("/bin/sh");
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}
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static noinline int init_post(void)
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{
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run_init_process("/sbin/init");
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run_init_process("/etc/init");
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run_init_process("/bin/init");
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run_init_process("/bin/sh");
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}
终端下查看1号进程,
可见,init是系统守护进程和zygote的父进程。
/system/core/init/init.c
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int main(int argc, char **argv)
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{
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mkdir("/dev", 0755);
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mkdir("/proc", 0755);
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mkdir("/sys", 0755);
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mount("devpts", "/dev/pts", "devpts", 0, NULL);
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mount("proc", "/proc", "proc", 0, NULL);
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mount("sysfs", "/sys", "sysfs", 0, NULL);
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open_devnull_stdio();
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klog_init();
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property_init();
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get_hardware_name(hardware, &revision);
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process_kernel_cmdline();
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init_parse_config_file("/init.rc");
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action_for_each_trigger("early-init", action_add_queue_tail);
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queue_builtin_action(wait_for_coldboot_done_action, "wait_for_coldboot_done");
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queue_builtin_action(keychord_init_action, "keychord_init");
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queue_builtin_action(console_init_action, "console_init");
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action_for_each_trigger("init", action_add_queue_tail);
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for(;;) {
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execute_one_command();
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restart_processes();
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nr = poll(ufds, fd_count, timeout);
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for (i = 0; i < fd_count; i++) {
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if (ufds[i].revents == POLLIN) {
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if (ufds[i].fd == get_property_set_fd())
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handle_property_set_fd();
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else if (ufds[i].fd == get_keychord_fd())
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handle_keychord();
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else if (ufds[i].fd == get_signal_fd())
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handle_signal();
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}
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}
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}
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return 0;
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}
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int main(int argc, char **argv)
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{
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mkdir("/dev", 0755);
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mkdir("/proc", 0755);
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mkdir("/sys", 0755);
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mount("devpts", "/dev/pts", "devpts", 0, NULL);
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mount("proc", "/proc", "proc", 0, NULL);
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mount("sysfs", "/sys", "sysfs", 0, NULL);
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open_devnull_stdio();
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klog_init();
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property_init();
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get_hardware_name(hardware, &revision);
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process_kernel_cmdline();
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init_parse_config_file("/init.rc");
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action_for_each_trigger("early-init", action_add_queue_tail);
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queue_builtin_action(wait_for_coldboot_done_action, "wait_for_coldboot_done");
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queue_builtin_action(keychord_init_action, "keychord_init");
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queue_builtin_action(console_init_action, "console_init");
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action_for_each_trigger("init", action_add_queue_tail);
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for(;;) {
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execute_one_command();
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restart_processes();
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nr = poll(ufds, fd_count, timeout);
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for (i = 0; i < fd_count; i++) {
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if (ufds[i].revents == POLLIN) {
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if (ufds[i].fd == get_property_set_fd())
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handle_property_set_fd();
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else if (ufds[i].fd == get_keychord_fd())
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handle_keychord();
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else if (ufds[i].fd == get_signal_fd())
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handle_signal();
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}
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}
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}
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return 0;
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}
init进程归纳如下
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解析init.rc和init.*.rc
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挂载文件系统,建立文件夹和文件,设置权限,为一些文件写入初值
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初始化property属性
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启动系统守护进程如adbd, vold, rild等
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启动zygote进程
2. zygote进程
zygote既是Android系统创建java世界的盘古,又是繁殖system_server和所有应用程序的女娲。
终端下查看zygote进程,
2.1 AndroidRuntime
/frameworks/base/cmds/app_process/app_main.cpp
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int main(int argc, const char* const argv[])
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{
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AppRuntime runtime;
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if (zygote) {
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runtime.start("com.android.internal.os.ZygoteInit",
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startSystemServer ? "start-system-server" : "");
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}
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int main(int argc, const char* const argv[])
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{
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AppRuntime runtime;
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if (zygote) {
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runtime.start("com.android.internal.os.ZygoteInit",
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startSystemServer ? "start-system-server" : "");
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}
AppRuntime是从AndroidRuntime类派生的,最后由runtime.start()进入Java世界。
/frameworks/base/core/jni/AndroidRuntime.cpp
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void AndroidRuntime::start(const char* className, const char* options)
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{
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JNIEnv* env;
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if (startVm(&mJavaVM, &env) != 0) {
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return;
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}
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onVmCreated(env);
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if (startReg(env) < 0) {
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ALOGE("Unable to register all android natives\n");
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return;
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}
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char* slashClassName = toSlashClassName(className);
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jclass startClass = env->FindClass(slashClassName);
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jmethodID startMeth = env->GetStaticMethodID(startClass, "main",
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"([Ljava/lang/String;)V");
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env->CallStaticVoidMethod(startClass, startMeth, strArray);
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}
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void AndroidRuntime::start(const char* className, const char* options)
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{
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JNIEnv* env;
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if (startVm(&mJavaVM, &env) != 0) {
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return;
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}
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onVmCreated(env);
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-
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if (startReg(env) < 0) {
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ALOGE("Unable to register all android natives\n");
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return;
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}
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char* slashClassName = toSlashClassName(className);
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jclass startClass = env->FindClass(slashClassName);
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jmethodID startMeth = env->GetStaticMethodID(startClass, "main",
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"([Ljava/lang/String;)V");
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env->CallStaticVoidMethod(startClass, startMeth, strArray);
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}
-> 创建虚拟机
注意这里会设置虚拟机的heapsize,默认16M,一般32M,不能太小,否则在操作大尺寸图片时无法分配所需内存。
-> 注册jni函数
这里注册了本地方法,这些方法最终被编译进动态链接库libandroid_runtime.so,供上层Java调用。
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static const RegJNIRec gRegJNI[] = {
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REG_JNI(register_android_debug_JNITest),
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REG_JNI(register_com_android_internal_os_RuntimeInit),
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REG_JNI(register_android_os_SystemClock),
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REG_JNI(register_android_util_Log),
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REG_JNI(register_android_os_Process),
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REG_JNI(register_android_os_SystemProperties),
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REG_JNI(register_android_os_Binder),
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REG_JNI(register_android_view_Display),
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REG_JNI(register_android_graphics_Bitmap),
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REG_JNI(register_android_graphics_Camera),
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REG_JNI(register_android_database_SQLiteDatabase),
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REG_JNI(register_android_os_Power),
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REG_JNI(register_android_os_StatFs),
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REG_JNI(register_android_net_NetworkUtils),
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REG_JNI(register_android_nfc_NdefMessage),
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REG_JNI(register_com_android_internal_os_ZygoteInit),
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REG_JNI(register_android_hardware_Camera),
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REG_JNI(register_android_hardware_SensorManager),
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REG_JNI(register_android_hardware_UsbDevice),
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REG_JNI(register_android_media_AudioRecord),
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REG_JNI(register_android_media_AudioSystem),
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REG_JNI(register_android_media_AudioTrack),
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REG_JNI(register_android_opengl_classes),
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REG_JNI(register_android_bluetooth_BluetoothSocket),
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REG_JNI(register_android_server_BluetoothService),
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REG_JNI(register_android_app_ActivityThread),
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REG_JNI(register_android_app_NativeActivity),
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REG_JNI(register_android_view_InputChannel),
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REG_JNI(register_android_view_InputQueue),
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REG_JNI(register_android_view_KeyEvent),
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REG_JNI(register_android_view_MotionEvent),
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REG_JNI(register_android_view_PointerIcon),
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};
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static const RegJNIRec gRegJNI[] = {
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REG_JNI(register_android_debug_JNITest),
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REG_JNI(register_com_android_internal_os_RuntimeInit),
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REG_JNI(register_android_os_SystemClock),
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REG_JNI(register_android_util_Log),
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REG_JNI(register_android_os_Process),
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REG_JNI(register_android_os_SystemProperties),
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REG_JNI(register_android_os_Binder),
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REG_JNI(register_android_view_Display),
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REG_JNI(register_android_graphics_Bitmap),
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REG_JNI(register_android_graphics_Camera),
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REG_JNI(register_android_database_SQLiteDatabase),
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REG_JNI(register_android_os_Power),
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REG_JNI(register_android_os_StatFs),
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REG_JNI(register_android_net_NetworkUtils),
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REG_JNI(register_android_nfc_NdefMessage),
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REG_JNI(register_com_android_internal_os_ZygoteInit),
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REG_JNI(register_android_hardware_Camera),
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REG_JNI(register_android_hardware_SensorManager),
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REG_JNI(register_android_hardware_UsbDevice),
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REG_JNI(register_android_media_AudioRecord),
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REG_JNI(register_android_media_AudioSystem),
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REG_JNI(register_android_media_AudioTrack),
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REG_JNI(register_android_opengl_classes),
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REG_JNI(register_android_bluetooth_BluetoothSocket),
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REG_JNI(register_android_server_BluetoothService),
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REG_JNI(register_android_app_ActivityThread),
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REG_JNI(register_android_app_NativeActivity),
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REG_JNI(register_android_view_InputChannel),
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REG_JNI(register_android_view_InputQueue),
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REG_JNI(register_android_view_KeyEvent),
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REG_JNI(register_android_view_MotionEvent),
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REG_JNI(register_android_view_PointerIcon),
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};
2.2 ZygoteInit
/frameworks/base/core/java/com/android/internal/os/ZygoteInit.java
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public static void main(String argv[]) {
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try {
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SamplingProfilerIntegration.start();
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registerZygoteSocket();
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preload();
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SamplingProfilerIntegration.writeZygoteSnapshot();
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if (argv[1].equals("start-system-server")) {
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startSystemServer();
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}
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runSelectLoopMode();
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closeServerSocket();
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}
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}
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public static void main(String argv[]) {
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try {
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SamplingProfilerIntegration.start();
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registerZygoteSocket();
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preload();
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SamplingProfilerIntegration.writeZygoteSnapshot();
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if (argv[1].equals("start-system-server")) {
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startSystemServer();
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}
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runSelectLoopMode();
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closeServerSocket();
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}
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}
-> 建立服务端Socket
zygote及系统中其他程序的通信没有使用Binder,而是采用了基于AF_UNIX类型的Socket.
-> 预加载类和资源
预加载的类可以在 /frameworks/base/preloaded-classes 查看。预加载的资源生成framewrok-res.apk,主要是一些图标,刷机达人经常修改它。
-> 启动system_server进程
zygote进程fork出system_server子进程,把任务繁重的系统服务全部托管出去,自己负责循环监听所有应用程序的请求。
-> 等待应用程序的请求
zygote通过runSelectLoopMode()处理应用程序客户端的请求,由ZygoteConnection的runOnce()孵化出新的应用程序。
综上所述,zygote进程归纳如下
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创建虚拟机
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注册jni函数
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预加载类和资源
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启动system_server进程
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监听应用程序请求
3. system_server进程
/frameworks/base/services/java/com/android/SystemServer.java
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public static void main(String[] args) {
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System.loadLibrary("android_servers");
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init1(args);
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}
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public static void main(String[] args) {
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System.loadLibrary("android_servers");
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init1(args);
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}
3.1 init1阶段
加载libandriod_server.so库,实现init1
/frameworks/base/cmds/system_server/library/system_init.cpp
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extern "C" status_t system_init()
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{
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sp grim = new GrimReaper();
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sm->asBinder()->linkToDeath(grim, grim.get(), 0);
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char propBuf[PROPERTY_VALUE_MAX];
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property_get("system_init.startsurfaceflinger", propBuf, "1");
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if (strcmp(propBuf, "1") == 0) {
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SurfaceFlinger::instantiate();
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}
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property_get("system_init.startsensorservice", propBuf, "1");
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if (strcmp(propBuf, "1") == 0) {
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SensorService::instantiate();
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}
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AndroidRuntime* runtime = AndroidRuntime::getRuntime();
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jclass clazz = env->FindClass("com/android/server/SystemServer");
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jmethodID methodId = env->GetStaticMethodID(clazz, "init2", "()V");
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env->CallStaticVoidMethod(clazz, methodId);
-
-
return NO_ERROR;
-
}
-
extern "C" status_t system_init()
-
{
-
-
sp grim = new GrimReaper();
-
sm->asBinder()->linkToDeath(grim, grim.get(), 0);
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-
char propBuf[PROPERTY_VALUE_MAX];
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property_get("system_init.startsurfaceflinger", propBuf, "1");
-
if (strcmp(propBuf, "1") == 0) {
-
-
SurfaceFlinger::instantiate();
-
}
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property_get("system_init.startsensorservice", propBuf, "1");
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if (strcmp(propBuf, "1") == 0) {
-
-
SensorService::instantiate();
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}
-
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AndroidRuntime* runtime = AndroidRuntime::getRuntime();
-
-
jclass clazz = env->FindClass("com/android/server/SystemServer");
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jmethodID methodId = env->GetStaticMethodID(clazz, "init2", "()V");
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env->CallStaticVoidMethod(clazz, methodId);
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-
return NO_ERROR;
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}
3.2 init2阶段
init2回到Java层,启动一个ServerThread线程,启动系统的各项服务。
http://blog.csdn.net/leerobin83/article/details/7306177
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