Provided by:
linux-doc-2.6.15_2.6.15-23.39_all 
NAME
strncpy_from_user - Copy a NUL terminated string from userspace.
SYNOPSIS
long strncpy_from_user (char * dst, const char __user * src,
long count);
ARGUMENTS
dst Destination address, in kernel space. This buffer must be at
least count bytes long.
src Source address, in user space.
count Maximum number of bytes to copy, including the trailing NUL.
DESCRIPTION
Copies a NUL-terminated string from userspace to kernel space.
On success, returns the length of the string (not including the
trailing NUL).
If access to userspace fails, returns -EFAULT (some data may have been
copied).
If count is smaller than the length of the string, copies count bytes
and returns count.