1.FirstStageMain 

//android10\system\core\init\first_stage_init.cpp

int FirstStageMain(int argc, char** argv) {
    const char* path = "/system/bin/init";
    const char* args[] = {path, "selinux_setup", nullptr};
    execv(path, const_cast<char**>(args));
}

 2.main

//android10\system\core\init\main.cpp
int main(int argc, char** argv) {

    if (argc > 1) {

        if (!strcmp(argv[1], "selinux_setup")) {
            return SetupSelinux(argv);
        }
    }
}

3.SetupSelinux

//android10\system\core\init\selinux.cpp

int SetupSelinux(char** argv) {
    InitKernelLogging(argv); //为啥调用多次

    // Set up SELinux, loading the SELinux policy.
    SelinuxSetupKernelLogging();
    SelinuxInitialize();

    const char* path = "/system/bin/init";
    const char* args[] = {path, "second_stage", nullptr};//4.second_stage
    execv(path, const_cast<char**>(args));
}