https://source.android.com/security/selinux/device-policy
http://www.cnblogs.com/Ph-one/p/5708836.html
https://blog.csdn.net/lqxandroid2012/article/details/53087305
https://blog.csdn.net/fantasy_wxe/article/details/52013922
http://www.xuebuyuan.com/2121833.html