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 22:20 +0800, cheng long wrote:
> > because it may be swapped out to disk ...
> > you need a special function that can deal with that (and swaps it right
> > back in)
> Why can't we use the "page fault handler" like in user space to swap
> the page back in?

that's a lot more tricky than it sounds ;)
(for example... how would you deliver SIGBUS to the kernel?)

to make this practical, there is a special copy operation that does do
this... but it's not generic.
(it's also a really easy way to get security holes; by copying at least
you get a snapshot of the data that the user cannot meddle with from
another thread)


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