Re: [PATCH 00/10] Enhance /dev/mem to allow read/write of arbitrary

Ingo Molnar
2011-07-03T19:46:18Z

* Petr Tesarik <ptesarik@suse.cz> wrote:

> > Do you expect distros to enable this boot option by default? I.e.
> > would SuSE be willing to ship with a restrictive /dev/mem by
> > default? That's really the wider goal we want to work towards.
>
> I'm not really the decision-maker on this, but even though I don't
> need it for crash, there are several other users which would have
> to be fixed:
>
> 1. hwinfo (EFI, MPTABLE and ACPI table parsing, analyzing video BIOS)
> 2. dmidecode (SMBIOS, DMI)
> 3. possibly others

But those tables wont be in regular RAM (they will be in ROM or in
RAM marked non-RAM in a special way in the e820 tables).

dmidecode certainly works on Fedora.

> > Hm, why would the ability "dirty and/or flush an arbitrary
> > physical cache line for testing purposes" be a DoS?
>
> Effectively switching off CPU caches can slow things down quite a
> bit... especially on a large SMP system. ;)

Flushing a cacheline isnt switching it off. You can already 'flush'
the cache from user-space as well, by trashing it for example. So i
don't see the DoS angle.

Thanks,

Ingo