Re: [RFC] prevent "dd if=/dev/mem" crash

Matt Chapman
2003-10-18T02:01:52Z

On Fri, Oct 17, 2003 at 06:48:33PM -0700, David Mosberger wrote:
> >>>>> On Fri, 17 Oct 2003 17:49:55 -0700, Andrew Morton <akpm@osdl.org> said:
>
> Andrew> We _want_ to be able to read mmio ranges via /dev/mem, don't
> Andrew> we? I guess it has never come up because everyone uses
> Andrew> kmem.
>
> I just don't see how making a "dd if=/dev/mem" safe and allowing
> access to arbitrary physical memory can go to together. Given that
> /dev/mem _is_ being used for accessing mmio space, is it really worth
> bothering trying to make such a "dd" safe?

Usually people who want to access MMIO devices would use mmap rather
than read/write.

But I do agree that the current semantics are not unreasonable and the
user should think about what they're doing before accessing random parts
of /dev/mem.

Matt