====== 참고 ======

  * https://coherentmusings.wordpress.com/2014/06/10/implementing-mmap-for-transferring-data-from-user-space-to-kernel-space/
  * http://blog.naver.com/PostView.nhn?blogId=sysganda&logNo=30173573554&parentCategoryNo=&categoryNo=20&viewDate=&isShowPopularPosts=false&from=postView