centos man page for __copy_to_user

__COPY_TO_USER(9)					    Memory Management in Linux						 __COPY_TO_USER(9)

NAME
       __copy_to_user - Copy a block of data into user space, with less checking.

SYNOPSIS
       unsigned long __copy_to_user(void __user * to, const void * from, unsigned long n);

ARGUMENTS
       to
	   Destination address, in user space.

       from
	   Source address, in kernel space.

       n
	   Number of bytes to copy.

CONTEXT
       User context only. This function may sleep.

DESCRIPTION
       Copy data from kernel space to user space. Caller must check the specified block with access_ok before calling this function.

       Returns number of bytes that could not be copied. On success, this will be zero.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014							 __COPY_TO_USER(9)