Re: Why can't we use the user-space pointer in kernel mode?

[Arjan van de Ven <arjan@xxxxxxxxxxxxx>]

On Wed, 2006-05-03 at 18:56 +0800, cheng long wrote:
> Hi, all
> 
> Since the progress in kernel mode can access the whole address space,
> why we must copy the user-space data into kernel space?
> Why  can't we dereference the user-space pointer directly?

because it may be swapped out to disk ... 
you need a special function that can deal with that (and swaps it right
back in)


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