From: Maxim Kammerer <mk@dee.su>
To: linux-mm@kvack.org
Cc: tails-dev@boum.org
Subject: PROBLEM: memtest tests only LOWMEM
Date: Mon, 26 Dec 2011 04:18:29 +0200 [thread overview]
Message-ID: <CAHsXYDCWJSCOe3DkK2kkR4Yvie6WW2DYCi=h_CAwjotwNZWihg@mail.gmail.com> (raw)
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)
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next reply other threads:[~2011-12-26 2:18 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-26 2:18 Maxim Kammerer [this message]
2012-01-12 20:27 ` Maxim Kammerer
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