SecondStageMain函数实现是在system/core/init/init.cpp中，该阶段主要做的事情是初始化property系统，解析init.rc。
然后再执行early init action，执行init action, 执行 early-boot and boot actions。
其中/init.rc是主要的.rc文件，由init可执行文件在开始执行时加载。它负责系统的初始设置。
在加载主目录/init.rc后, init立即加载包含在/{system,vendor,odm}/etc/init/目录中的所有文件。

int SecondStageMain(int argc, char** argv) {
    PropertyInit();
    ...
    // Now set up SELinux for second stage.
    SelinuxSetupKernelLogging();
    SelabelInitialize();
    SelinuxRestoreContext();
    ...
    StartPropertyService(&property_fd);
    ...
    ActionManager& am = ActionManager::GetInstance();
    ServiceList& sm = ServiceList::GetInstance();

    LoadBootScripts(am, sm);
    ...
    am.QueueEventTrigger("early-init");
    ...
    am.QueueEventTrigger("init");

    // 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");
    }
}

static void LoadBootScripts(ActionManager& action_manager, ServiceList& service_list) {
    Parser parser = CreateParser(action_manager, service_list);

    std::string bootscript = GetProperty("ro.boot.init_rc", "");
    if (bootscript.empty()) {
        parser.ParseConfig("/system/etc/init/hw/init.rc");
        if (!parser.ParseConfig("/system/etc/init")) {
            late_import_paths.emplace_back("/system/etc/init");
        }
        // late_import is available only in Q and earlier release. As we don't
        // have system_ext in those versions, skip late_import for system_ext.
        parser.ParseConfig("/system_ext/etc/init");
        if (!parser.ParseConfig("/vendor/etc/init")) {
            late_import_paths.emplace_back("/vendor/etc/init");
        }
        if (!parser.ParseConfig("/odm/etc/init")) {
            late_import_paths.emplace_back("/odm/etc/init");
        }
        if (!parser.ParseConfig("/product/etc/init")) {
            late_import_paths.emplace_back("/product/etc/init");
        }
    } else {
        parser.ParseConfig(bootscript);
    }
}