Copy large memory regions from & to userspace

[Clemens Kolbitsch <clemens.kol@gmx.at>]

Hi!
Just a short question: What is the correct method of copying large areas of 
memory from userspace into userspace when running in kernel-mode?

According to just about any type of documentation out there something like

unsigned long *from = 0x08000000;
unsigned long *to = 0x09000000;
memcpy(to, from, 0x1000);

should be avoided as copy_from_user, put_user, etc. should be used instead...

Is there a third set of functions for direct from-userspace-to-userspace 
copying or is it legitimate to assure that the first bytes in the from & to 
memory areas are available and then just do the plain memcpy?

Maybe there is a simple "just use the xxx function-set" answer to that, that i 
just have not ran into yet :-)

Thanks!