Init
init进程被赋予了很多重要工作，init进程启动主要分为两个阶段：
第一个阶段主要完成：
1.环境变量设置
2.挂载部分文件系统并创建目录，创建设备节点
3.初始化日志输出等
4.启用SELinux安全策略
5.开启第二阶段流程
第二个阶段主要完成：
1.初始化属性区
2.执行SELinux第二阶段
3.新建epoll并初始化子进程终止信号处理函数
4.解析系统属性文件，并开启属性服务
5.拉起subcontext
6.加载rc脚本，开其脚本解析，执行对应流程
main()：
build\sa6125-car-r600\android\system\core\init\main.cpp
using namespace android::init;
int main(int argc, char** argv) {
#if __has_feature(address_sanitizer)
__asan_set_error_report_callback(AsanReportCallback);
#endif
if (!strcmp(basename(argv[0]), "ueventd")) { // ueventd跳转
return ueventd_main(argc, argv);
}
if (argc > 1) {
if (!strcmp(argv[1], "subcontext")) { // 拉起subcontext
android::base::InitLogging(argv, &android::base::KernelLogger);
const BuiltinFunctionMap function_map;
return SubcontextMain(argc, argv, &function_map);
}
if (!strcmp(argv[1], "selinux_setup")) { // 启动SELinux服务
return SetupSelinux(argv);
}
if (!strcmp(argv[1], "second_stage")) { // 启动Init进程第二阶段，启动熟悉服务，加载进程
return SecondStageMain(argc, argv);
}
}
return FirstStageMain(argc, argv);
}
ueventd_main()：
build\android\system\core\init\ueventd.cpp
负责节点创建，Android中的ueventd是一个守护进程，它通过netlink scoket监听内核生成的uevent消息，当ueventd收到这样的消息时，它通过采取适当的行动来处理它，通常是在/dev中创建设备节点，设置文件权限，设置selinux标签等。ueventd的启动和之前的selinux、subcontext不一样。ueventd时在init.rc中定义service，被second_stage_init创建出来的
ueventd通过两种方式创建设备节点文件分别是冷启动和热启动: 1.冷启动:通俗讲就是已经设定好的,比如 cpu频率，统一创建好的文件节点。 2.执启动:诵俗讲就是动态创建的比加 ush插拔等节占
int ueventd_main(int argc, char** argv) {
/*
* init sets the umask to 077 for forked processes. We need to
* create files with exact permissions, without modification by
* the umask.
*/
umask(000); // 清除系统默认权限，保证新建目录的访问权限由mkdir
android::base::InitLogging(argv, &android::base::KernelLogger);
LOG(INFO) << "ueventd started!";
SelinuxSetupKernelLogging();
SelabelInitialize();
std::vector<std::unique_ptr<UeventHandler>> uevent_handlers;
// Keep the current product name base configuration so we remain backwards compatible and
// allow it to override everything.
// TODO: cleanup platform ueventd.rc to remove vendor specific device node entries (b/34968103)
auto hardware = android::base::GetProperty("ro.hardware", "");
auto ueventd_configuration = ParseConfig({"/ueventd.rc", "/vendor/ueventd.rc",
"/odm/ueventd.rc", "/ueventd." + hardware + ".rc"});
uevent_handlers.emplace_back(std::make_unique<DeviceHandler>(
std::move(ueventd_configuration.dev_permissions),
std::move(ueventd_configuration.sysfs_permissions),
std::move(ueventd_configuration.subsystems), android::fs_mgr::GetBootDevices(), true));
uevent_handlers.emplace_back(std::make_unique<FirmwareHandler>(
std::move(ueventd_configuration.firmware_directories)));
if (ueventd_configuration.enable_modalias_handling) {
uevent_handlers.emplace_back(std::make_unique<ModaliasHandler>());
}
UeventListener uevent_listener(ueventd_configuration.uevent_socket_rcvbuf_size);
if (access(COLDBOOT_DONE, F_OK) != 0) {
ColdBoot cold_boot(uevent_listener, uevent_handlers);
cold_boot.Run();
}
for (auto& uevent_handler : uevent_handlers) {
uevent_handler->ColdbootDone();
}
// We use waitpid() in ColdBoot, so we can't ignore SIGCHLD until now.
signal(SIGCHLD, SIG_IGN);
// Reap and pending children that exited between the last call to waitpid() and setting SIG_IGN
// for SIGCHLD above.
while (waitpid(-1, nullptr, WNOHANG) > 0) {
}
uevent_listener.Poll([&uevent_handlers](const Uevent& uevent) {
for (auto& uevent_handler : uevent_handlers) {
uevent_handler->HandleUevent(uevent);
}
return ListenerAction::kContinue;
});
return 0;
}
FirstStageMain()：
build\android\system\core\init\first_stage_main.cpp
umask(0)：清除系统默认权限，保证新建目录的访问权限由mkdir设置。 使用mkdir/mount/chmod指令来创建基本文件系统目录并挂载相关的文件系统。Android系统挂载了tmpfs、devpts、proc、sysfs这四类文件系统。其中，/dev是设备目录，所有外部设备和虚拟设备都在该目录下；/proc是存储当前系统内核运行信息的文件目录，/sys存储了硬件设备在内核上的映射。 SetStdioToDevNull()：关闭/stdin/stdout/stderr的fd，重定向到/dev/null。 InitKernelLogging()：初始化kernel日志，输出到/dev/kmsg。 load内核各模块。 第一阶段做完后，再次调用main()进入SetupSelinux阶段
int FirstStageMain(int argc, char** argv) {
if (REBOOT_BOOTLOADER_ON_PANIC) {
InstallRebootSignalHandlers();
}
boot_clock::time_point start_time = boot_clock::now();
std::vector<std::pair<std::string, int>> errors;
#define CHECKCALL(x) \
if (x != 0) errors.emplace_back(#x " failed", errno);
// Clear the umask.
umask(0); // 清除系统默认权限，保证新建目录的访问权限由mkdir设置
CHECKCALL(clearenv()); // 虚拟文件挂载
CHECKCALL(setenv("PATH", _PATH_DEFPATH, 1));
// Get the basic filesystem setup we need put together in the initramdisk
// on / and then we'll let the rc file figure out the rest.
CHECKCALL(mount("tmpfs", "/dev", "tmpfs", MS_NOSUID, "mode=0755")); // dev是设备目录，所有外部设备和虚拟设备都在该目录下
CHECKCALL(mkdir("/dev/pts", 0755));
CHECKCALL(mkdir("/dev/socket", 0755));
CHECKCALL(mount("devpts", "/dev/pts", "devpts", 0, NULL));
#define MAKE_STR(x) __STRING(x)
CHECKCALL(mount("proc", "/proc", "proc", 0, "hidepid=2,gid=" MAKE_STR(AID_READPROC))); // proc是存储当前系统内核运行信息的文件目录
#undef MAKE_STR
// Don't expose the raw commandline to unprivileged processes.
CHECKCALL(chmod("/proc/cmdline", 0440));
gid_t groups[] = {AID_READPROC};
CHECKCALL(setgroups(arraysize(groups), groups));
CHECKCALL(mount("sysfs", "/sys", "sysfs", 0, NULL)); // sys存储了硬件设备在内核上的映射
CHECKCALL(mount("selinuxfs", "/sys/fs/selinux", "selinuxfs", 0, NULL));
CHECKCALL(mknod("/dev/kmsg", S_IFCHR | 0600, makedev(1, 11)));
if constexpr (WORLD_WRITABLE_KMSG) {
CHECKCALL(mknod("/dev/kmsg_debug", S_IFCHR | 0622, makedev(1, 11)));
}
CHECKCALL(mknod("/dev/random", S_IFCHR | 0666, makedev(1, 8)));
CHECKCALL(mknod("/dev/urandom", S_IFCHR | 0666, makedev(1, 9)));
// This is needed for log wrapper, which gets called before ueventd runs.
CHECKCALL(mknod("/dev/ptmx", S_IFCHR | 0666, makedev(5, 2)));
CHECKCALL(mknod("/dev/null", S_IFCHR | 0666, makedev(1, 3)));
// These below mounts are done in first stage init so that first stage mount can mount
// subdirectories of /mnt/{vendor,product}/. Other mounts, not required by first stage mount,
// should be done in rc files.
// Mount staging areas for devices managed by vold
// See storage config details at http://source.android.com/devices/storage/
CHECKCALL(mount("tmpfs", "/mnt", "tmpfs", MS_NOEXEC | MS_NOSUID | MS_NODEV,
"mode=0755,uid=0,gid=1000"));
// /mnt/vendor is used to mount vendor-specific partitions that can not be
// part of the vendor partition, e.g. because they are mounted read-write.
CHECKCALL(mkdir("/mnt/vendor", 0755));
// /mnt/product is used to mount product-specific partitions that can not be
// part of the product partition, e.g. because they are mounted read-write.
CHECKCALL(mkdir("/mnt/product", 0755));
// /apex is used to mount APEXes
CHECKCALL(mount("tmpfs", "/apex", "tmpfs", MS_NOEXEC | MS_NOSUID | MS_NODEV,
"mode=0755,uid=0,gid=0"));
// /debug_ramdisk is used to preserve additional files from the debug ramdisk
CHECKCALL(mount("tmpfs", "/debug_ramdisk", "tmpfs", MS_NOEXEC | MS_NOSUID | MS_NODEV,
"mode=0755,uid=0,gid=0"));
#undef CHECKCALL
SetStdioToDevNull(argv); // 关闭/stdin/stdout/stderr的fd，重定向到/dev/null
// Now that tmpfs is mounted on /dev and we have /dev/kmsg, we can actually
// talk to the outside world...
InitKernelLogging(argv); // 初始化kernel日志，输出到/dev/kmsg
if (!errors.empty()) {
for (const auto& [error_string, error_errno] : errors) {
LOG(ERROR) << error_string << " " << strerror(error_errno);
}
LOG(FATAL) << "Init encountered errors starting first stage, aborting";
}
LOG(INFO) << "init first stage started!";
auto old_root_dir = std::unique_ptr<DIR, decltype(&closedir)>{opendir("/"), closedir};
if (!old_root_dir) {
PLOG(ERROR) << "Could not opendir("/"), not freeing ramdisk";
}
struct stat old_root_info;
if (stat("/", &old_root_info) != 0) {
PLOG(ERROR) << "Could not stat("/"), not freeing ramdisk";
old_root_dir.reset();
}
if (ForceNormalBoot()) {
mkdir("/first_stage_ramdisk", 0755);
// SwitchRoot() must be called with a mount point as the target, so we bind mount the
// target directory to itself here.
if (mount("/first_stage_ramdisk", "/first_stage_ramdisk", nullptr, MS_BIND, nullptr) != 0) {
LOG(FATAL) << "Could not bind mount /first_stage_ramdisk to itself";
}
SwitchRoot("/first_stage_ramdisk");
}
// If this file is present, the second-stage init will use a userdebug sepolicy
// and load adb_debug.prop to allow adb root, if the device is unlocked.
if (access("/force_debuggable", F_OK) == 0) {
std::error_code ec; // to invoke the overloaded copy_file() that won't throw.
if (!fs::copy_file("/adb_debug.prop", kDebugRamdiskProp, ec) ||
!fs::copy_file("/userdebug_plat_sepolicy.cil", kDebugRamdiskSEPolicy, ec)) {
LOG(ERROR) << "Failed to setup debug ramdisk";
} else {
// setenv for second-stage init to read above kDebugRamdisk* files.
setenv("INIT_FORCE_DEBUGGABLE", "true", 1);
}
}
if (!DoFirstStageMount()) { // 获取system，vendor等重要分区信息并挂载
LOG(FATAL) << "Failed to mount required partitions early ...";
}
struct stat new_root_info;
if (stat("/", &new_root_info) != 0) {
PLOG(ERROR) << "Could not stat("/"), not freeing ramdisk";
old_root_dir.reset();
}
if (old_root_dir && old_root_info.st_dev != new_root_info.st_dev) {
FreeRamdisk(old_root_dir.get(), old_root_info.st_dev);
}
SetInitAvbVersionInRecovery();
static constexpr uint32_t kNanosecondsPerMillisecond = 1e6;
uint64_t start_ms = start_time.time_since_epoch().count() / kNanosecondsPerMillisecond;
setenv("INIT_STARTED_AT", std::to_string(start_ms).c_str(), 1);
const char* path = "/system/bin/init"; //启动selinux setup命令
const char* args[] = {path, "selinux_setup", nullptr};
execv(path, const_cast<char**>(args));
// execv() only returns if an error happened, in which case we
// panic and never fall through this conditional.
PLOG(FATAL) << "execv("" << path << "") failed";
return 1;
}
SetupSelinux() ：
build\android\system\core\init\selinux.cpp
初始化selinux，加载SELinux规则;
(2)、配置SELinux相关log输出；
(3)、启动init第二阶段主流程
Selinux启动完后会再次携带参数调用main()进入SecondStageMain阶段
void SelinuxInitialize() {
Timer t;
LOG(INFO) << "Loading SELinux policy";
if (!LoadPolicy()) {
LOG(FATAL) << "Unable to load SELinux policy";
}
bool kernel_enforcing = (security_getenforce() == 1);
bool is_enforcing = IsEnforcing();
if (kernel_enforcing != is_enforcing) {
if (security_setenforce(is_enforcing)) {
PLOG(FATAL) << "security_setenforce(%s) failed" << (is_enforcing ? "true" : "false");
}
}
if (auto result = WriteFile("/sys/fs/selinux/checkreqprot", "0"); !result) {
LOG(FATAL) << "Unable to write to /sys/fs/selinux/checkreqprot: " << result.error();
}
// init's first stage can't set properties, so pass the time to the second stage.
setenv("INIT_SELINUX_TOOK", std::to_string(t.duration().count()).c_str(), 1);
}
int SetupSelinux(char** argv) {
InitKernelLogging(argv);
if (REBOOT_BOOTLOADER_ON_PANIC) {
InstallRebootSignalHandlers();
}
// Set up SELinux, loading the SELinux policy.
SelinuxSetupKernelLogging();
SelinuxInitialize();
// We're in the kernel domain and want to transition to the init domain. File systems that
// store SELabels in their xattrs, such as ext4 do not need an explicit restorecon here,
// but other file systems do. In particular, this is needed for ramdisks such as the
// recovery image for A/B devices.
if (selinux_android_restorecon("/system/bin/init", 0) == -1) {
PLOG(FATAL) << "restorecon failed of /system/bin/init failed";
}
const char* path = "/system/bin/init";
const char* args[] = {path, "second_stage", nullptr};
execv(path, const_cast<char**>(args));
// execv() only returns if an error happened, in which case we
// panic and never return from this function.
PLOG(FATAL) << "execv("" << path << "") failed";
return 1;
}
// selinux_android_file_context_handle() takes on the order of 10+ms to run, so we want to cache
// its value. selinux_android_restorecon() also needs an sehandle for file context look up. It
// will create and store its own copy, but selinux_android_set_sehandle() can be used to provide
// one, thus eliminating an extra call to selinux_android_file_context_handle().
void SelabelInitialize() {
sehandle = selinux_android_file_context_handle();
selinux_android_set_sehandle(sehandle);
}
// A C++ wrapper around selabel_lookup() using the cached sehandle.
// If sehandle is null, this returns success with an empty context.
bool SelabelLookupFileContext(const std::string& key, int type, std::string* result) {
result->clear();
if (!sehandle) return true;
char* context;
if (selabel_lookup(sehandle, &context, key.c_str(), type) != 0) {
return false;
}
*result = context;
free(context);
return true;
}
// A C++ wrapper around selabel_lookup_best_match() using the cached sehandle.
// If sehandle is null, this returns success with an empty context.
bool SelabelLookupFileContextBestMatch(const std::string& key,
const std::vector<std::string>& aliases, int type,
std::string* result) {
result->clear();
if (!sehandle) return true;
std::vector<const char*> c_aliases;
for (const auto& alias : aliases) {
c_aliases.emplace_back(alias.c_str());
}
c_aliases.emplace_back(nullptr);
char* context;
if (selabel_lookup_best_match(sehandle, &context, key.c_str(), &c_aliases[0], type) != 0) {
return false;
}
*result = context;
free(context);
return true;
}
SecondStageMain()：
1.系统熟悉模块初始化
property_init();//属性共享内存区域初始化
property_load_boot_defaults(load_debug_prop);//加载系统属性配置文件
StartPropertyService(&epoll);//启动属性服务
2.解析内核信息
process_kernel_dt();//解析DT
process_kernel_cmdline();//解析cmeline
export_kernel_boot_props();//设置内核boot属性
3.Subcontext是Android9.0才出现的，用来进一步隔离vendor与system权限而引入的。下面代码是subcontext的初始化函数入口 ：
subcontexts = InitializeSubcontexts();
4.设置init进程和其fork()的子进程的oom_adj。oom_adj主要用在lowmemorykiller机制中，每一类别的进程会有其oom_adj的范围，oom_adj值越大表示进程越不重要，当lowmemory时，会优先kill oom_adj高的进程
5.最后解析init.rc脚本，建立rc文件中定义的action 、service，按照脚本执行动作，进入无限循环，进行子进程实时监控
SecondStageMain()：
int SecondStageMain(int argc, char** argv) {
if (REBOOT_BOOTLOADER_ON_PANIC) {
InstallRebootSignalHandlers();
}
SetStdioToDevNull(argv);
InitKernelLogging(argv);
LOG(INFO) << "init second stage started!";
if (DeferOverlayfsMount()) {
Fstab fstab;
if (ReadDefaultFstab(&fstab)) {
fstab.erase(std::remove_if(fstab.begin(), fstab.end(),
[](const auto& entry) {
return !entry.fs_mgr_flags.first_stage_mount;
}),
fstab.end());
LOG(INFO) << "Running deferred mounting of overlayfs";
fs_mgr_overlayfs_mount_all(&fstab);
}
}
// Set init and its forked children's oom_adj.
if (auto result = WriteFile("/proc/1/oom_score_adj", "-1000"); !result) {
LOG(ERROR) << "Unable to write -1000 to /proc/1/oom_score_adj: " << result.error();
}
// Enable seccomp if global boot option was passed (otherwise it is enabled in zygote).
GlobalSeccomp();
// Set up a session keyring that all processes will have access to. It
// will hold things like FBE encryption keys. No process should override
// its session keyring.
keyctl_get_keyring_ID(KEY_SPEC_SESSION_KEYRING, 1);
// Indicate that booting is in progress to background fw loaders, etc.
close(open("/dev/.booting", O_WRONLY | O_CREAT | O_CLOEXEC, 0000));
property_init(); // 属性共享内存区域初始化
// If arguments are passed both on the command line and in DT,
// properties set in DT always have priority over the command-line ones.
process_kernel_dt(); // 解析内核信息，解析DT
process_kernel_cmdline(); // 解析cmeline
// Propagate the kernel variables to internal variables
// used by init as well as the current required properties.
export_kernel_boot_props(); // 设置内核boot属性
// Make the time that init started available for bootstat to log.
property_set("ro.boottime.init", getenv("INIT_STARTED_AT"));
property_set("ro.boottime.init.selinux", getenv("INIT_SELINUX_TOOK"));
// Set libavb version for Framework-only OTA match in Treble build.
const char* avb_version = getenv("INIT_AVB_VERSION");
if (avb_version) property_set("ro.boot.avb_version", avb_version);
// See if need to load debug props to allow adb root, when the device is unlocked.
const char* force_debuggable_env = getenv("INIT_FORCE_DEBUGGABLE");
if (force_debuggable_env && AvbHandle::IsDeviceUnlocked()) {
load_debug_prop = "true"s == force_debuggable_env;
}
// Set memcg property based on kernel cmdline argument
bool memcg_enabled = android::base::GetBoolProperty("ro.boot.memcg",false);
if (memcg_enabled) {
// root memory control cgroup
mkdir("/dev/memcg", 0755);
chown("/dev/memcg",AID_SYSTEM,AID_SYSTEM);
mount("none", "/dev/memcg", "cgroup", 0, "memory");
// app mem cgroups, used by activity manager, lmkd and zygote
mkdir("/dev/memcg/apps/",0755);
chown("/dev/memcg/apps/",AID_SYSTEM,AID_SYSTEM);
mkdir("/dev/memcg/system",0550);
chown("/dev/memcg/system",AID_SYSTEM,AID_SYSTEM);
if (auto result = WriteFile("/dev/memcg/memory.swappiness", "100"); !result) {
LOG(ERROR) << "Unable to write 100 to /dev/memcg/memory.swappiness" << result.error();
}
if (auto result = WriteFile("/dev/memcg/apps/memory.swappiness", "100"); !result) {
LOG(ERROR) << "Unable to write 100 to /dev/memcg/memory.swappiness" << result.error();
}
if (auto result = WriteFile("/dev/memcg/system/memory.swappiness", "100"); !result) {
LOG(ERROR) << "Unable to write 100 to /dev/memcg/memory.swappiness" << result.error();
}
}
// Clean up our environment.
unsetenv("INIT_STARTED_AT");
unsetenv("INIT_SELINUX_TOOK");
unsetenv("INIT_AVB_VERSION");
unsetenv("INIT_FORCE_DEBUGGABLE");
// Now set up SELinux for second stage.
SelinuxSetupKernelLogging();
SelabelInitialize();
SelinuxRestoreContext();
Epoll epoll;
if (auto result = epoll.Open(); !result) {
PLOG(FATAL) << result.error();
}
InstallSignalFdHandler(&epoll);
property_load_boot_defaults(load_debug_prop); // 加载系统属性配置文件
UmountDebugRamdisk();
fs_mgr_vendor_overlay_mount_all();
export_oem_lock_status();
StartPropertyService(&epoll); // 启动属性服务
MountHandler mount_handler(&epoll);
set_usb_controller();
const BuiltinFunctionMap function_map;
Action::set_function_map(&function_map);
if (!SetupMountNamespaces()) {
PLOG(FATAL) << "SetupMountNamespaces failed";
}
subcontexts = InitializeSubcontexts(); // sub初始化函数入口，用来进一步隔离vendor和system权限而引入的
ActionManager& am = ActionManager::GetInstance(); // 解析rc脚本，建立文件中定义的action，service，按照脚本执行动作
ServiceList& sm = ServiceList::GetInstance(); // 获取ActionManager实例和ServiceList实例
LoadBootScripts(am, sm);
// Turning this on and letting the INFO logging be discarded adds 0.2s to
// Nexus 9 boot time, so it's disabled by default.
if (false) DumpState();
// Make the GSI status available before scripts start running.
if (android::gsi::IsGsiRunning()) {
property_set("ro.gsid.image_running", "1");
} else {
property_set("ro.gsid.image_running", "0");
}
am.QueueBuiltinAction(SetupCgroupsAction, "SetupCgroups");
am.QueueBuiltinAction(SetKptrRestrictAction, "SetKptrRestrict");
am.QueueEventTrigger("early-init");
// Queue an action that waits for coldboot done so we know ueventd has set up all of /dev...
am.QueueBuiltinAction(wait_for_coldboot_done_action, "wait_for_coldboot_done");
// ... so that we can start queuing up actions that require stuff from /dev.
am.QueueBuiltinAction(MixHwrngIntoLinuxRngAction, "MixHwrngIntoLinuxRng");
am.QueueBuiltinAction(SetMmapRndBitsAction, "SetMmapRndBits");
Keychords keychords;
am.QueueBuiltinAction(
[&epoll, &keychords](const BuiltinArguments& args) -> Result<Success> {
for (const auto& svc : ServiceList::GetInstance()) {
keychords.Register(svc->keycodes());
}
keychords.Start(&epoll, HandleKeychord);
return Success();
},
"KeychordInit");
am.QueueBuiltinAction(console_init_action, "console_init");
// Trigger all the boot actions to get us started.
am.QueueEventTrigger("init");
// Starting the BoringSSL self test, for NIAP certification compliance.
am.QueueBuiltinAction(StartBoringSslSelfTest, "StartBoringSslSelfTest");
// Repeat mix_hwrng_into_linux_rng in case /dev/hw_random or /dev/random
// wasn't ready immediately after wait_for_coldboot_done
am.QueueBuiltinAction(MixHwrngIntoLinuxRngAction, "MixHwrngIntoLinuxRng");
// Initialize binder before bringing up other system services
am.QueueBuiltinAction(InitBinder, "InitBinder");
// Don't mount filesystems or start core system services in charger mode.
std::string bootmode = GetProperty("ro.bootmode", "");
if (bootmode == "charger") {
am.QueueEventTrigger("charger");
} else {
am.QueueEventTrigger("late-init");
}
// Run all property triggers based on current state of the properties.
am.QueueBuiltinAction(queue_property_triggers_action, "queue_property_triggers");
while (true) {
// By default, sleep until something happens.
auto epoll_timeout = std::optional<std::chrono::milliseconds>{};
if (do_shutdown && !shutting_down) {
do_shutdown = false;
if (HandlePowerctlMessage(shutdown_command)) {
shutting_down = true;
}
}
if (!(waiting_for_prop || Service::is_exec_service_running())) {
am.ExecuteOneCommand();
}
if (!(waiting_for_prop || Service::is_exec_service_running())) {
if (!shutting_down) {
auto next_process_action_time = HandleProcessActions();
// If there's a process that needs restarting, wake up in time for that.
if (next_process_action_time) {
epoll_timeout = std::chrono::ceil<std::chrono::milliseconds>(
*next_process_action_time - boot_clock::now());
if (*epoll_timeout < 0ms) epoll_timeout = 0ms;
}
}
// If there's more work to do, wake up again immediately.
if (am.HasMoreCommands()) epoll_timeout = 0ms;
}
if (auto result = epoll.Wait(epoll_timeout); !result) {
LOG(ERROR) << result.error();
}
}
return 0;
}
init.rc：
on init
sysclktz 0 //将时区设置为0
...
# Start logd before any other services run to ensure we capture all of their logs.
start logd
# Start essential services.
start servicemanager // 开启服务管理
start hwservicemanager
start vndservicemanager
触发 late-init，会启动各种fs，Zygote、early-boot、boot等。所以servicemanager进程比zygote启动更早。
# Mount filesystems and start core system services.
on late-ini
trigger early-fs
trigger fs
trigger post-fs.
trigger late-fs
trigger post-fs-data
trigger load_persist_props_action
trigger load_bpf_programs
#触发启动zygote // 触发启动zygote
trigger zygote-start
trigger firmware_mounts_complete
trigger early-boot
trigger boot
on early-fs
# Once metadata has been mounted, we'll need vold to deal with userdata checkpointing
start vold
on post-fs
exec - system system -- /system/bin/vdc checkpoint markBootAttempt
mount rootfs rootfs / remount bind ro nodev
# Mount default storage into root namespace
mount none /mnt/user/0 /storage bind rec
mount none none /storage slave rec
chown system cache /cache
chmod 0770 /cache
restorecon_recursive /cache
mkdir /cache/recovery 0770 system cache
chown root system /proc/kmsg
chmod 0440 /proc/kmsg
# It is recommended to put unnecessary data/ initialization from post-fs-data
# to start-zygote in device's init.rc to unblock zygote start.
on zygote-start && property:ro.crypto.state=unencrypted
wait_for_prop odsign.verification.done 1
# A/B update verifier that marks a successful boot.
exec_start update_verifier_nonencrypted
start statsd
start netd
start zygote
start zygote_secondary
