Re: large copy_to_user fills only one page?

[Ingo Oeser]

Hi Emmanuel,

On Thu, May 30, 2002 at 04:36:22PM +0200, Emmanuel Michon wrote:
> I'm working with linux-2.4.18, and writing some
> trivial code to get from kernel a grabbed image working this way:
> What I get actually is only 4K filled in userland, but copy_to_user
> returns IMSIZE!

copy_to_user() returns the number of bytes NOT copied.
same for copy_from_user().

This is a common mistake and your code using this functions should
look like this:

if (copy_from_user(to,uptr,size)) {
   return -EFAULT;
}

/* Do some processing */

if (copy_to_user(uptr,from,size)) {
   return -EFAULT;
}

PS: CC'ed linux-kernel, that you will not get 1000 answers ;-)

Regards

Ingo Oeser
-- 
Science is what we can tell a computer. Art is everything else. --- D.E.Knuth