시스템 초기화 시kernel시스템 초기화를 완성하기 위해 내장 상태에서 프로그램을 만들고 실행합니다.

/* This is a non __init function. Force it to be noinline otherwise gcc
 736 * makes it inline to init() and it becomes part of init.text section
 737 */
 738static noinline int init_post(void)
 739{
 740        /* need to finish all async __init code before freeing the memory */
 741        async_synchronize_full();
 742        free_initmem();
 743        mark_rodata_ro();
 744        system_state = SYSTEM_RUNNING;
 745        numa_default_policy();
 746
 747
 748        current->signal->flags |= SIGNAL_UNKILLABLE;
 749
 750        if (ramdisk_execute_command) {
 751                run_init_process(ramdisk_execute_command);
 752                printk(KERN_WARNING "Failed to execute %s
",
 753                                ramdisk_execute_command);
 754        }
 755
 756        /*
 757         * We try each of these until one succeeds.
 758         *
 759         * The Bourne shell can be used instead of init if we are
 760         * trying to recover a really broken machine.

 761         */
 762        if (execute_command) {
 763                run_init_process(execute_command);
 764                printk(KERN_WARNING "Failed to execute %s.  Attempting "
 765                                        "defaults...
", execute_command);
 766        }
 767        run_init_process("/sbin/init");
 768        run_init_process("/etc/init");
 769        run_init_process("/bin/init");
 770        run_init_process("/bin/sh");
 771
 772        panic("No init found.  Try passing init= option to kernel. "
 773              "See Linux Documentation/init.txt for guidance.");
 774}

 105static inline int
 106call_usermodehelper(char *path, char **argv, char **envp, enum umh_wait wait)
 107{
 108        return call_usermodehelper_fns(path, argv, envp, wait,
 109                                       NULL, NULL, NULL);
 110}
 111


  50enum umh_wait {
  51        UMH_NO_WAIT = -1,       /* don't wait at all */
  52        UMH_WAIT_EXEC = 0,      /* wait for the exec, but not the process */
  53        UMH_WAIT_PROC = 1,      /* wait for the process to complete */
  54};
  55
  56struct subprocess_info {
  57        struct work_struct work;
  58        struct completion *complete;
  59        char *path;
  60        char **argv;
  61        char **envp;
  62        enum umh_wait wait;
  63        int retval;
  64        int (*init)(struct subprocess_info *info);
  65        void (*cleanup)(struct subprocess_info *info);
  66        void *data;
  67};
  68

kernel/kmod.c    

377/**
 378 * call_usermodehelper_exec - start a usermode application
 379 * @sub_info: information about the subprocessa        
 380 * @wait: wait for the application to finish and return status.            ，     。
 381 *        when -1 don't wait at all, but you get no useful error back when
 382 *        the program couldn't be exec'ed. This makes it safe to call
 383 *        from interrupt context.

 384 *
 385 * Runs a user-space application.  The application is started
 386 * asynchronously if wait is not set, and runs as a child of keventd.
 387 * (ie. it runs with full root capabilities).

 388 */
 389int call_usermodehelper_exec(struct subprocess_info *sub_info,
 390                             enum umh_wait wait)
 391{
 392        DECLARE_COMPLETION_ONSTACK(done);
 393        int retval = 0;
 394
 395        helper_lock();
 396        if (sub_info->path[0] == '\0')
 397                goto out;
 398
 399        if (!khelper_wq || usermodehelper_disabled) {
 400                retval = -EBUSY;
 401                goto out;
 402        }
 403
 404        sub_info->complete = &done;
 405        sub_info->wait = wait;
 406                 。
 407        queue_work(khelper_wq, &sub_info->work);
 408        if (wait == UMH_NO_WAIT)        /* task has freed sub_info */
 409                goto unlock;

410        wait_for_completion(&done);
 411        retval = sub_info->retval;
 412
 413out:
 414        call_usermodehelper_freeinfo(sub_info);
 415unlock:
 416        helper_unlock();
 417        return retval;
 418}
 419EXPORT_SYMBOL(call_usermodehelper_exec);
 420
 421void __init usermodehelper_init(void)
 422{
 423        khelper_wq = create_singlethread_workqueue("khelper");
 424        BUG_ON(!khelper_wq);
 425}

#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
//#include<linux/config.h>

#include <linux/kernel.h>/*printk()*/
#include <linux/sched.h>

MODULE_LICENSE("GPL");


static __init int test_driver_init(void)
{
    int result = 0;
    char cmd_path[] = "/usr/bin/touch";
    char* cmd_argv[] = {cmd_path,"/touchX.txt",NULL};
    char* cmd_envp[] = {"HOME=/", "PATH=/sbin:/bin:/usr/bin", NULL};

    result = call_usermodehelper(cmd_path, cmd_argv, cmd_envp, UMH_WAIT_PROC);
    printk(KERN_DEBUG "test driver init exec! there result of call_usermodehelper is %d
", result);
    printk(KERN_DEBUG "test driver init exec! the process is \"%s\", pid is %d.
",current->comm, current->pid);
    return result;
}


static __exit void test_driver_exit(void)
{
    int result = 0;
    char cmd_path[] = "/bin/rm";
    char* cmd_argv[] = {cmd_path,"/touchX.txt",NULL};
    char* cmd_envp[] = {"HOME=/", "PATH=/sbin:/bin:/usr/bin", NULL};

    result = call_usermodehelper(cmd_path, cmd_argv, cmd_envp, UMH_WAIT_PROC);
    printk(KERN_DEBUG "test driver exit exec! the result of call_usermodehelper is %d
", result);
    printk(KERN_DEBUG "test driver exit exec! the process is \"%s\",pidis %d 
", current->comm, current->pid);
}

module_init(test_driver_init);
module_exit(test_driver_exit);