Re: [Tails-dev] PROBLEM: memtest tests only LOWMEM

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Autor: Maxim Kammerer
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Para: The Tails public development discussion list
Assunto: Re: [Tails-dev] PROBLEM: memtest tests only LOWMEM
Well, it seems that even with the reminder sent about 8 days ago, no
one on the linux-mm mailing list cares. I tried OFTC/#mm several times
as well, but never saw any response. I think I will stay with the
32/64-bit KEXEC split in the meanwhile. Will also ask memtest86+
author about the difficulties of adapting it for the task.

Best regards,
Maxim

On Mon, Dec 26, 2011 at 04:18, Maxim Kammerer <mk@???> wrote:
> 1. On 32-bit x86, memtest=n tests only LOWMEM memory (~ 895 MiB),
> HIGHMEM is ignored
>
> 2. On 3.0.4-hardened-r5, HIGHMEM memory (HIGHMEM64G in my tests) is
> apparently ignored during memtest. Looking at arch/x86/mm/memtest.c,
> no special mapping is performed (kmap/kunmap?), so it seems that at
> most ~895 MiB can be tested in 32-bit x86 kernels. This might not
> appear like an important issue (as there are other memory testing
> tools available), but memtest is extremely useful for anti-forensic
> memory wiping on shutdown/reboot in security-oriented distributions
> like Liberté Linux and Tails, and there is no other good substitute.
> See, for instance, some background in Debian bug
> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=646361.
>
> 3. Keywords: memtest, highmem, mm, security
>
> 4. Kernel version: 3.0.4-hardened-r5 (Gentoo) x86 32-bit with PAE


--
Maxim Kammerer
Liberté Linux (discussion / support: http://dee.su/liberte-contribute)