/*
* Get a string from userland into (bf). Strip a trailing
* nl character (to allow easy access from the shell).
* The buffer should be *buflenp + 1 chars long. vfs_getuserstr
* will automatically add a nul char at the end.
*
* Returns 0 on success or the following errors
*
* EINVAL: file offset is non-zero.
* EMSGSIZE: message is longer than kernel buffer
* EFAULT: user i/o buffer is not addressable
*/