{ "schemaVersion": "0.11.0", "canonical": "https://www.pystone.net/notes/android-os-boot-sequence/", "atlas": "https://www.pystone.net/?node=android-os-boot-sequence#knowledge-atlas", "markdown": "https://www.pystone.net/notes/android-os-boot-sequence.md", "context": "https://www.pystone.net/notes/android-os-boot-sequence.context.json", "knowledgeVersion": "224c990773de.5fa8af6e39fa", "build": { "siteCommit": "224c990773de166d23a886306577dd90379529ce", "notesCommit": "5fa8af6e39fa3891d1b9b4832bfa6c4e0ecaaf0a", "builtAt": "1970-01-01T00:00:00.000Z", "version": "224c990773de.5fa8af6e39fa" }, "id": "note:android-os-boot-sequence", "slug": "android-os-boot-sequence", "title": "Android OS 启动流程", "type": "note", "visibility": "public", "idStability": "rename-stable", "author": { "name": "Perrin Yong", "profile": "https://www.pystone.net/profile/" }, "publisher": { "name": "Perrin Yong", "profile": "https://www.pystone.net/profile/" }, "aliases": [], "summary": "Android OS Boot Process ![](assets/image 20250122183537175.png) 图片来源: https://copperhead.co/blog/android boot process/ Android OS 启动流程 发生时间 ：设备加电时。 作用 ： 1. 初始化硬件（CPU、内存等）。 2. 扫描引导介质（如 NAND 或 eMMC）以寻找引导加载程序（Bootloader）…", "contentRole": "unspecified", "isMoc": false, "mocRecognition": "none", "generated": false, "attribution": "unspecified", "domain": "10-计算机、信息技术与工程", "tags": [], "mocs": [], "contentHash": "3457bc1386087f7a8282c6b241dcca71b30ea02b5bb47223c07cb2f3ffc6a5f2", "assets": [ { "reference": "assets/image-20250122183537175.png", "url": "/media/3ea4dc931d1dff105b41.png", "mediaType": "image/png", "contentHash": "3ea4dc931d1dff105b4189f07008880331bbd0b5a2e299f71fef847ec8d344f9", "byteLength": 50714, "width": 735, "height": 628 } ], "headings": [ { "depth": 1, "text": "Android OS 启动流程", "anchor": "android-os-启动流程", "citation": "https://www.pystone.net/notes/android-os-boot-sequence/#android-os-%E5%90%AF%E5%8A%A8%E6%B5%81%E7%A8%8B" }, { "depth": 2, "text": "2. Bootloader（引导加载程序）", "anchor": "2-bootloader引导加载程序", "citation": "https://www.pystone.net/notes/android-os-boot-sequence/#2-bootloader%E5%BC%95%E5%AF%BC%E5%8A%A0%E8%BD%BD%E7%A8%8B%E5%BA%8F" }, { "depth": 2, "text": "3. Linux Kernel（Linux 内核）", "anchor": "3-linux-kernellinux-内核", "citation": "https://www.pystone.net/notes/android-os-boot-sequence/#3-linux-kernellinux-%E5%86%85%E6%A0%B8" }, { "depth": 2, "text": "4. Init Process（初始化进程）", "anchor": "4-init-process初始化进程", "citation": "https://www.pystone.net/notes/android-os-boot-sequence/#4-init-process%E5%88%9D%E5%A7%8B%E5%8C%96%E8%BF%9B%E7%A8%8B" }, { "depth": 2, "text": "初始化和启动属性服务", "anchor": "初始化和启动属性服务", "citation": "https://www.pystone.net/notes/android-os-boot-sequence/#%E5%88%9D%E5%A7%8B%E5%8C%96%E5%92%8C%E5%90%AF%E5%8A%A8%E5%B1%9E%E6%80%A7%E6%9C%8D%E5%8A%A1" }, { "depth": 2, "text": "Init 解析Service", "anchor": "init-解析service", "citation": "https://www.pystone.net/notes/android-os-boot-sequence/#init-%E8%A7%A3%E6%9E%90service" }, { "depth": 2, "text": "init启动Service(包括zygote)", "anchor": "init启动service包括zygote", "citation": "https://www.pystone.net/notes/android-os-boot-sequence/#init%E5%90%AF%E5%8A%A8service%E5%8C%85%E6%8B%ACzygote" }, { "depth": 2, "text": "AppRuntime启动Zygote", "anchor": "appruntime启动zygote", "citation": "https://www.pystone.net/notes/android-os-boot-sequence/#appruntime%E5%90%AF%E5%8A%A8zygote" }, { "depth": 2, "text": "Zygote Init", "anchor": "zygote-init", "citation": "https://www.pystone.net/notes/android-os-boot-sequence/#zygote-init" }, { "depth": 2, "text": "6. System Services（系统服务）", "anchor": "6-system-services系统服务", "citation": "https://www.pystone.net/notes/android-os-boot-sequence/#6-system-services%E7%B3%BB%E7%BB%9F%E6%9C%8D%E5%8A%A1" }, { "depth": 2, "text": "SyetemServer进程的启动", "anchor": "syetemserver进程的启动", "citation": "https://www.pystone.net/notes/android-os-boot-sequence/#syetemserver%E8%BF%9B%E7%A8%8B%E7%9A%84%E5%90%AF%E5%8A%A8" }, { "depth": 2, "text": "SyetemServer进程的工作", "anchor": "syetemserver进程的工作", "citation": "https://www.pystone.net/notes/android-os-boot-sequence/#syetemserver%E8%BF%9B%E7%A8%8B%E7%9A%84%E5%B7%A5%E4%BD%9C" }, { "depth": 2, "text": "7. Boot Completed（启动完成）", "anchor": "7-boot-completed启动完成", "citation": "https://www.pystone.net/notes/android-os-boot-sequence/#7-boot-completed%E5%90%AF%E5%8A%A8%E5%AE%8C%E6%88%90" }, { "depth": 2, "text": "Launcher", "anchor": "launcher", "citation": "https://www.pystone.net/notes/android-os-boot-sequence/#launcher" }, { "depth": 2, "text": "Thanks", "anchor": "thanks", "citation": "https://www.pystone.net/notes/android-os-boot-sequence/#thanks" } ], "claims": [], "outgoing": [], "incoming": [ { "id": "note:application-and-cloud-engineering", "title": "应用开发与云端工程", "url": "https://www.pystone.net/notes/application-and-cloud-engineering/", "atlas": "https://www.pystone.net/?node=application-and-cloud-engineering#knowledge-atlas", "label": "应用开发与云端工程", "origin": "explicit", "humanReviewed": true, "context": "Android开发中的“Android OS 启动流程”导航项", "citation": "https://www.pystone.net/notes/application-and-cloud-engineering/#android%E5%BC%80%E5%8F%91" } ], "contentMarkdown": "Android OS Boot Process\n![](assets/image-20250122183537175.png)\n图片来源: https://copperhead.co/blog/android-boot-process/\n# Android OS 启动流程\n- **发生时间**：设备加电时。\n- **作用**：\n 1. 初始化硬件（CPU、内存等）。\n 2. 扫描引导介质（如 NAND 或 eMMC）以寻找引导加载程序（Bootloader）。\n 3. 将引导加载程序复制到内存中，并开始执行。\n- **类似功能**：类似于电脑的 BIOS，完成最基本的硬件初始化。\n\n---\n\n## **2. Bootloader（引导加载程序）**\n\n- **发生时间**：ROM代码执行后。\n- **功能**：\n - 引导加载程序不是 Android 系统的一部分，主要由设备制造商定制，负责加载 Android 系统。\n - 分为两个阶段：\n 1. **初始程序加载（IPL）**：\n - 设置外部 RAM。\n - 将第二阶段程序（SPL）复制到 RAM 并开始执行。\n 2. **第二程序加载（SPL）**：\n - 加载 Android 系统核心（Linux Kernel）。\n - 初始化硬件（如显示、文件系统等）。\n - 提供进入其他模式（如 fastboot 和 recovery）的选项。\n - 将 Linux Kernel 从引导介质复制到内存中并执行。\n\n---\n\n## **3. Linux Kernel（Linux 内核）**\n\n- **发生时间**：Bootloader 将控制权交给内核时。\n- **功能**：\n 1. 设置缓存、内存保护、调度机制。\n 2. 加载必要的驱动程序（设备驱动、显示驱动等）。\n 3. 初始化硬件（电源管理、存储等）。\n 4. 查找并启动 `init` 进程。\n- **区别于普通 Linux 内核的功能**：\n - **Binder**：Android 专用的进程间通信（IPC）机制。\n - **ASHMEM**：高效共享内存管理。\n - **Wake Locks**：管理设备在空闲时的电源状态。\n - **Logger**：支持 Android 的 logcat 日志工具。\n - **Paranoid Networking**：基于进程组的网络权限控制。\n\n---\n\n## **4. Init Process（初始化进程）**\ninit进程是Android系统中用户空间的第一个进程\n\n\n- **发生时间**：内核加载完成后。\n- **功能**：\n 1. 挂载关键目录：`/sys`、`/dev`、`/proc`。\n 2. 调用start_property_service启动属性服务,\n 3. 运行 `init.rc` 脚本：\n - 配置系统属性。\n - 启动关键守护进程。\n - 加载 Zygote 进程。\n- **位置**：\n - `init` 源码路径：`/system/core/init`\n - `init.rc` 路径：`/system/core/rootdir`\n\n**system/core/init/init.cpp**\n\n```cpp\nint main(int argc, char** argv) {\n if (!strcmp(basename(argv[0]), \"ueventd\")) {\n return ueventd_main(argc, argv);\n }\n if (!strcmp(basename(argv[0]), \"watchdogd\")) {\n return watchdogd_main(argc, argv);\n }\n umask(0);\n add_environment(\"PATH\", _PATH_DEFPATH);\n bool is_first_stage = (argc == 1) || (strcmp(argv[1], \"--second-stage\") != 0);\n //创建文件并挂载\n if (is_first_stage) {\n mount(\"tmpfs\", \"/dev\", \"tmpfs\", MS_NOSUID, \"mode=0755\");\n mkdir(\"/dev/pts\", 0755);\n mkdir(\"/dev/socket\", 0755);\n mount(\"devpts\", \"/dev/pts\", \"devpts\", 0, NULL);\n #define MAKE_STR(x) __STRING(x)\n mount(\"proc\", \"/proc\", \"proc\", 0, \"hidepid=2,gid=\" MAKE_STR(AID_READPROC));\n mount(\"sysfs\", \"/sys\", \"sysfs\", 0, NULL);\n }\n open_devnull_stdio();\n klog_init();\n klog_set_level(KLOG_NOTICE_LEVEL);\n NOTICE(\"init %s started!\\n\", is_first_stage ? \"first stage\" : \"second stage\");\n if (!is_first_stage) {\n // Indicate that booting is in progress to background fw loaders, etc.\n close(open(\"/dev/.booting\", O_WRONLY | O_CREAT | O_CLOEXEC, 0000));\n //初始化属性相关资源\n property_init();//1\n process_kernel_dt();\n process_kernel_cmdline();\n export_kernel_boot_props();\n }\n ...\n //启动属性服务\n start_property_service();//2\n const BuiltinFunctionMap function_map;\n Action::set_function_map(&function_map);\n Parser& parser = Parser::GetInstance();\n parser.AddSectionParser(\"service\",std::make_unique());\n parser.AddSectionParser(\"on\", std::make_unique());\n parser.AddSectionParser(\"import\", std::make_unique());\n //解析init.rc配置文件\n parser.ParseConfig(\"/init.rc\");//3\n ...\n while (true) {\n if (!waiting_for_exec) {\n am.ExecuteOneCommand();\n restart_processes();\n }\n int timeout = -1;\n if (process_needs_restart) {\n timeout = (process_needs_restart - gettime()) * 1000;\n if (timeout < 0)\n timeout = 0;\n }\n if (am.HasMoreCommands()) {\n timeout = 0;\n }\n bootchart_sample(&timeout);\n epoll_event ev;\n int nr = TEMP_FAILURE_RETRY(epoll_wait(epoll_fd, &ev, 1, timeout));\n if (nr == -1) {\n ERROR(\"epoll_wait failed: %s\\n\", strerror(errno));\n } else if (nr == 1) {\n ((void (*)()) ev.data.ptr)();\n }\n }\n return 0;\n}\n\n```\n\n\n---\n\n**system/core/rootdir/init.zygote64.rc**\n```bash\nservice zygote /system/bin/app_process64 -Xzygote /system/bin --zygote --start-system-server\n class main\n socket zygote stream 660 root system\n onrestart write /sys/android_power/request_state wake\n onrestart write /sys/power/state on\n onrestart restart audioserver\n onrestart restart cameraserver\n onrestart restart media\n onrestart restart netd\n writepid /dev/cpuset/foreground/tasks /dev/stune/foreground/tasks\n\n```\n\n## 初始化和启动属性服务\n property_init 对属性进行初始化\n start_property_service启动属性服务\n\nWindows平台上有一个注册表管理器，注册表的内容采用键值对的形式来记录用户、软件的一些使用信息。即使系统或者软件重启，它还是能够根据之前在注册表中的记录，进行相应的初始化工作。Android也提供了一个类似的机制，叫做属性服务。\n\n## Init 解析Service\n\n\n**system/core/init/service.cpp**\n\n```c\nbool ServiceParser::ParseSection(const std::vector& args,\n std::string* err) {\n if (args.size() < 3) {\n *err = \"services must have a name and a program\";\n return false;\n }\n const std::string& name = args[1];\n if (!IsValidName(name)) {\n *err = StringPrintf(\"invalid service name '%s'\", name.c_str());\n return false;\n }\n std::vector str_args(args.begin() + 2, args.end());\n service_ = std::make_unique(name, \"default\", str_args);//1\n return true;\n}\n\nbool ServiceParser::ParseLineSection(const std::vector& args,\n const std::string& filename, int line,\n std::string* err) const {\n return service_ ? service_->HandleLine(args, err) : false;\n}\n\nvoid ServiceParser::EndSection() {\n if (service_) {\n ServiceManager::GetInstance().AddService(std::move(service_));\n }\n}\n\nvoid ServiceManager::AddService(std::unique_ptr service) {\n Service* old_service = FindServiceByName(service->name());\n if (old_service) {\n ERROR(\"ignored duplicate definition of service '%s'\",\n service->name().c_str());\n return;\n }\n services_.emplace_back(std::move(service));//1\n}\n\n```\n\n根据参数创建出service对象，然后根据选项域的内容填充service对象，最后将service对象加入到vector类型的services链表中。\n\n## init启动Service(包括zygote)\n\n**system/core/rootdir/init.rc**\n```bash\n...\non nonencrypted\n # A/B update verifier that marks a successful boot.\n exec - root -- /system/bin/update_verifier nonencrypted\n class_start main\n class_start late_start\n...\n```\n\nclass_start 对应的函数是 do_class_start\n```cpp\nstatic int do_class_start(const std::vector& args) {\n /* Starting a class does not start services\n * which are explicitly disabled. They must\n * be started individually.\n */\n ServiceManager::GetInstance().\n ForEachServiceInClass(args[1], [] (Service* s) { s->StartIfNotDisabled(); });\n return 0;\n}\n```\n\n**system/core/init/service.cpp**\n```cpp\nbool Service::StartIfNotDisabled() {\n if (!(flags_ & SVC_DISABLED)) {\n return Start();\n } else {\n flags_ |= SVC_DISABLED_START;\n }\n return true;\n}\n```\n\n```cpp\nbool Service::Start() {\n flags_ &= (~(SVC_DISABLED|SVC_RESTARTING|SVC_RESET|SVC_RESTART|SVC_DISABLED_START));\n time_started_ = 0;\n if (flags_ & SVC_RUNNING) {//如果Service已经运行，则不启动\n return false;\n }\n bool needs_console = (flags_ & SVC_CONSOLE);\n if (needs_console && !have_console) {\n ERROR(\"service '%s' requires console\\n\", name_.c_str());\n flags_ |= SVC_DISABLED;\n return false;\n }\n //判断需要启动的Service的对应的执行文件是否存在，不存在则不启动该Service\n struct stat sb;\n if (stat(args_[0].c_str(), &sb) == -1) {\n ERROR(\"cannot find '%s' (%s), disabling '%s'\\n\",\n args_[0].c_str(), strerror(errno), name_.c_str());\n flags_ |= SVC_DISABLED;\n return false;\n }\n\n...\n pid_t pid = fork();//1.fork函数创建子进程\n if (pid == 0) {//运行在子进程中\n umask(077);\n for (const auto& ei : envvars_) {\n add_environment(ei.name.c_str(), ei.value.c_str());\n }\n for (const auto& si : sockets_) {\n int socket_type = ((si.type == \"stream\" ? SOCK_STREAM :\n (si.type == \"dgram\" ? SOCK_DGRAM :\n SOCK_SEQPACKET)));\n const char* socketcon =\n !si.socketcon.empty() ? si.socketcon.c_str() : scon.c_str();\n\n int s = create_socket(si.name.c_str(), socket_type, si.perm,\n si.uid, si.gid, socketcon);\n if (s >= 0) {\n PublishSocket(si.name, s);\n }\n }\n...\n //2.通过execve执行程序\n if (execve(args_[0].c_str(), (char**) &strs[0], (char**) ENV) < 0) {\n ERROR(\"cannot execve('%s'): %s\\n\", args_[0].c_str(), strerror(errno));\n }\n\n _exit(127);\n }\n...\n return true;\n}\n\n```\n调用fork函数来创建子进程\n在子进程中调用execve执行system/bin/app_process\n**frameworks/base/cmds/app_process/app_main.cpp**\n```cpp\nint main(int argc, char* const argv[])\n{\n ...\n if (zygote) {\n runtime.start(\"com.android.internal.os.ZygoteInit\", args, zygote);//1\n } else if (className) {\n runtime.start(\"com.android.internal.os.RuntimeInit\", args, zygote);\n } else {\n fprintf(stderr, \"Error: no class name or --zygote supplied.\\n\");\n app_usage();\n LOG_ALWAYS_FATAL(\"app_process: no class name or --zygote supplied.\");\n return 10;\n }\n}\n\n```\n\n调用runtime(AppRuntime)的start来启动zygote。\n\n## AppRuntime启动Zygote\n\n\ninit启动zygote时主要是调用app_main.cpp的main函数中的AppRuntime的start来启动zygote进程\n\n**frameworks/base/cmds/app_process/app_main.cpp**\n```cpp\nint main(int argc, char* const argv[])\n{\n...\n\n AppRuntime runtime(argv[0], computeArgBlockSize(argc, argv));\n ...\n Vector args;\n if (!className.isEmpty()) {\n args.add(application ? String8(\"application\") : String8(\"tool\"));\n runtime.setClassNameAndArgs(className, argc - i, argv + i);\n } else {\n // We're in zygote mode.\n maybeCreateDalvikCache();\n if (startSystemServer) {\n args.add(String8(\"start-system-server\"));//1\n }\n char prop[PROP_VALUE_MAX];\n if (property_get(ABI_LIST_PROPERTY, prop, NULL) == 0) {\n LOG_ALWAYS_FATAL(\"app_process: Unable to determine ABI list from property %s.\",\n ABI_LIST_PROPERTY);\n return 11;\n }\n String8 abiFlag(\"--abi-list=\");\n abiFlag.append(prop);\n args.add(abiFlag);\n for (; i < argc; ++i) {\n args.add(String8(argv[i]));\n }\n }\n if (!niceName.isEmpty()) {\n runtime.setArgv0(niceName.string());\n set_process_name(niceName.string());\n }\n if (zygote) {\n runtime.start(\"com.android.internal.os.ZygoteInit\", args, zygote);//2\n } else if (className) {\n runtime.start(\"com.android.internal.os.RuntimeInit\", args, zygote);\n } else {\n fprintf(stderr, \"Error: no class name or --zygote supplied.\\n\");\n app_usage();\n LOG_ALWAYS_FATAL(\"app_process: no class name or --zygote supplied.\");\n return 10;\n }\n}\n\n```\n\nruntime指的就是AppRuntime，AppRuntime声明也在app_main.cpp中，它继承AndroidRuntime\n调用start其实是调用AndroidRuntime的start函数\n\n**frameworks/base/core/jni/AndroidRuntime.cpp**\n```cpp\nvoid AndroidRuntime::start(const char* className, const Vector& options, bool zygote)\n{\n ...\n /* start the virtual machine */\n JniInvocation jni_invocation;\n jni_invocation.Init(NULL);\n JNIEnv* env;\n if (startVm(&mJavaVM, &env, zygote) != 0) {//1\n return;\n }\n onVmCreated(env);\n if (startReg(env) < 0) {//2\n ALOGE(\"Unable to register all android natives\\n\");\n return;\n }\n jclass stringClass;\n jobjectArray strArray;\n jstring classNameStr;\n\n stringClass = env->FindClass(\"java/lang/String\");\n assert(stringClass != NULL);\n //创建数组\n strArray = env->NewObjectArray(options.size() + 1, stringClass, NULL);\n assert(strArray != NULL);\n //从app_main的main函数得知className为com.android.internal.os.ZygoteInit\n classNameStr = env->NewStringUTF(className);\n assert(classNameStr != NULL);\n env->SetObjectArrayElement(strArray, 0, classNameStr);\n\n for (size_t i = 0; i < options.size(); ++i) {\n jstring optionsStr = env->NewStringUTF(options.itemAt(i).string());\n assert(optionsStr != NULL);\n env->SetObjectArrayElement(strArray, i + 1, optionsStr);\n }\n char* slashClassName = toSlashClassName(className);\n jclass startClass = env->FindClass(slashClassName);\n if (startClass == NULL) {\n ALOGE(\"JavaVM unable to locate class '%s'\\n\", slashClassName);\n /* keep going */\n } else {\n //找到ZygoteInit的main函数\n jmethodID startMeth = env->GetStaticMethodID(startClass, \"main\",\n \"([Ljava/lang/String;)V\");//3\n if (startMeth == NULL) {\n ALOGE(\"JavaVM unable to find main() in '%s'\\n\", className);\n /* keep going */\n } else {\n //通过JNI调用ZygoteInit的main函数\n env->CallStaticVoidMethod(startClass, startMeth, strArray);//4\n\n#if 0\n if (env->ExceptionCheck())\n threadExitUncaughtException(env);\n#endif\n }\n }\n ...\n}\n\n```\n\n调用startVm函数来创建JavaVm\n调用startReg函数用来为JavaVm注册JNI\n找到ZygoteInit的main函数\nstartClass从app_main的main函数得知为com.android.internal.os.ZygoteInit\n通过JNI调用ZygoteInit的main函数\n\n通过JNI调用ZygoteInit的main函数后，Zygote便进入了Java框架层，此前没有任何代码进入过Java框架层，换句换说**Zygote开创了Java框架层**。\n\n## Zygote Init\n在Android系统中，JavaVM(Java虚拟机)、应用程序进程以及运行系统的关键服务的SystemServer进程都是由Zygote进程来创建的，我们也将它称为孵化器。\n\n通过fock(复制进程)的形式来创建应用程序进程和SystemServer进程\n由于Zygote进程在启动时会创建JavaVM，因此通过fock而创建的应用程序进程和SystemServer进程可以在内部获取一个JavaVM的实例拷贝。\n\n\n- **发生时间**：`init` 进程启动后。\n- **功能**：\n 1. Zygote 是一个特殊的虚拟机进程，负责预加载系统核心库和资源。\n 2. 提供共享内存机制，支持应用快速启动，减少资源消耗。\n 3. 启动时完成以下步骤：\n - 加载 `ZygoteInit` 类（源码路径：`/frameworks/base/core/java/com/android/internal/os/ZygoteInit.java`）。\n - 注册 Zygote 套接字（用于接收命令）。\n - 预加载类文件（`/frameworks/base` 下的预加载列表）。\n - 预加载资源（如主题、布局等）。\n 4. 启动系统服务。\n\n\n**frameworks/base/core/java/com/android/internal/os/ZygoteInit.java**\n```java\n public static void main(String argv[]) {\n ...\n try {\n ...\n //注册Zygote用的Socket\n registerZygoteSocket(socketName);//1\n ...\n //预加载类和资源\n preload();//2\n ...\n if (startSystemServer) {\n //启动SystemServer进程\n startSystemServer(abiList, socketName);//3\n }\n Log.i(TAG, \"Accepting command socket connections\");\n //等待客户端请求\n runSelectLoop(abiList);//4\n closeServerSocket();\n } catch (MethodAndArgsCaller caller) {\n caller.run();\n } catch (RuntimeException ex) {\n Log.e(TAG, \"Zygote died with exception\", ex);\n closeServerSocket();\n throw ex;\n }\n }\n\n```\n\n通过registerZygoteSocket函数来创建一个Server端的Socket，这个Socket用来等待ActivityManagerService来请求Zygote来创建新的应用程序进程\n预加载类和资源\n启动SystemServer进程，这样系统的关键服务也会由SystemServer进程启动起来\n调用runSelectLoop函数来等待客户端请求\n\n## **6. System Services（系统服务）**\n## SyetemServer进程的启动\nZygote进程启动了SyetemServer进程\n```java\n private static boolean startSystemServer(String abiList, String socketName)\n throws MethodAndArgsCaller, RuntimeException {\n ...\n if (pid == 0) {\n if (hasSecondZygote(abiList)) {\n waitForSecondaryZygote(socketName);\n }\n handleSystemServerProcess(parsedArgs);\n }\n return true;\n }\n\n```\n\n在startSystemServer函数中调用handleSystemServerProcess来启动SystemServer进程。\n```java\n private static void handleSystemServerProcess(\n ZygoteConnection.Arguments parsedArgs)\n throws ZygoteInit.MethodAndArgsCaller {\n closeServerSocket();//1\n ...\n if (parsedArgs.invokeWith != null) {\n ...\n } else {\n ClassLoader cl = null;\n if (systemServerClasspath != null) {\n cl = createSystemServerClassLoader(systemServerClasspath,\n parsedArgs.targetSdkVersion);\n Thread.currentThread().setContextClassLoader(cl);\n }\n RuntimeInit.zygoteInit(parsedArgs.targetSdkVersion, parsedArgs.remainingArgs, cl);//2\n }\n }\n\n```\n- SystemServer进程是复制了Zygote进程的地址空间，因此也会得到Zygote进程创建的Socket，这个Socket对于SyetemServer进程没有用处，因此，需要注释1处的代码来关闭该Socket。\n**frameworks/base/core/java/com/android/internal/os/RuntimeInit.java**\n```java\npublic static final void zygoteInit(int targetSdkVersion, String[] argv, ClassLoader classLoader)\n throws ZygoteInit.MethodAndArgsCaller {\n if (DEBUG) Slog.d(TAG, \"RuntimeInit: Starting application from zygote\");\n Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, \"RuntimeInit\");\n redirectLogStreams();\n commonInit();\n nativeZygoteInit();//1\n applicationInit(targetSdkVersion, argv, classLoader);//2\n }\n\n```\n\n\n## SyetemServer进程的工作\n1.启动Binder线程池，这样就可以与其他进程进行通信。\n2.创建SystemServiceManager用于对系统的服务进行创建、启动和生命周期管理。\n3.启动各种系统服务。\n\n- 核心服务：\n\t1. **Activity Manager**：管理应用生命周期。\n\t2. **Package Manager**：管理应用安装和卸载。\n\t3. **Power Manager**：管理设备电源状态。\n\t4. **Window Manager**：负责窗口和视图的渲染。\n\t5. **Sensor Service**：管理传感器。\n- 其他服务：\n\t- 蓝牙服务、通知管理、剪贴板服务、音频服务等。\n\n\n## **7. Boot Completed（启动完成）**\n\n- **发生时间**：系统服务全部启动后。\n- **功能**：\n - 系统广播 `ACTION_BOOT_COMPLETED` 通知其他进程和应用启动完成。\n - 设备显示主屏（Home Screen），用户可以开始交互。\n\n---\n\n## Launcher\n最后一步是启动一个Home应用程序, 叫做Launcher.\n\n显示系统中已经安装的应用程序, 用户可以通过点击这些快捷图标来启动相应的应用程序\n\n> 请求PackageManagerService返回系统中已经安装的应用程序的信息，并将这些信息封装成一个快捷图标列表显示在系统屏幕上\n\nSyetemServer进程在启动的过程中会启动PackageManagerService，PackageManagerService启动后会将系统中的应用程序安装完成。在此前已经启动的ActivityManagerService会将Launcher启动起来。\n\n**frameworks/base/services/java/com/android/server/SystemServer.java**\n```java\n private void startOtherServices() {\n ...\n mActivityManagerService.systemReady(new Runnable() {\n @Override\n public void run() {\n Slog.i(TAG, \"Making services ready\");\n mSystemServiceManager.startBootPhase(\n SystemService.PHASE_ACTIVITY_MANAGER_READY);\n\n...\n}\n...\n}\n\n```\n**frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java**\n```java\npublic void systemReady(final Runnable goingCallback) {\n...\nsynchronized (this) {\n ...\n mStackSupervisor.resumeFocusedStackTopActivityLocked();\n mUserController.sendUserSwitchBroadcastsLocked(-1, currentUserId);\n }\n }\n\n```\n\n详细的Launcher启动过程见: https://juejin.cn/post/6844903471645196302#heading-2\n## Thanks\nhttps://copperhead.co/blog/android-boot-process/\nhttps://juejin.cn/post/6844903470634369032\nhttps://juejin.cn/post/6844903470881832968\nhttps://juejin.cn/post/6844903471146074126\nhttps://juejin.cn/post/6844903471645196302\n\nChatGPT\n" }