* H. Peter Anvin <hpa@xxxxxxxxx> wrote: > On 07/01/2011 08:36 AM, Ingo Molnar wrote: > > > > So we could kill multiple birds with the same stone here: > > > > - remove various ugly uses of /dev/mem (including the rootkit usage), > > with or without strict-devmem > > > > - extending it to above-4G for inspection purposes > > > > - allowing to kill /dev/mem access runtime similar to the > > disable_modules lock-down killswitch, for the so inclined. > > > > Would you be interested in modifying your patch-set in such a > > fashion? > > > > There is another use that I have looked at, as well: for testing > purposes, it would be extremely good to be able to dirty and/or > flush an arbitrary physical cache line for testing purposes. > > This is very very similar to /dev/mem usage -- access to an > arbitrary chunk of memory -- and a fully enabled /dev/mem can of > course support this use (just mmap the page with the relevant cache > line). However, it could also be a separate device which could > have looser permissions than /dev/mem; or a set of ioctls on > /dev/mem with a separate kill switch, because no data would ever be > have modified or returned to user space. > > Either way, though, we found that it would share a lot of code with > the /dev/mem implementation, and as such fixing up the underlying > machinery is the sanest way to upstream this. To me that cache flush thing sounds obscure (but still useful) enough to justify a new ioctl over /dev/mem. Not sure it even needs a killswitch, unless there's some real security problem related to it. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html