From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx157.postini.com [74.125.245.157]) by kanga.kvack.org (Postfix) with SMTP id EC8D46B004F for ; Sun, 25 Dec 2011 21:18:50 -0500 (EST) Received: by obcwo8 with SMTP id wo8so8178514obc.14 for ; Sun, 25 Dec 2011 18:18:50 -0800 (PST) MIME-Version: 1.0 From: Maxim Kammerer Date: Mon, 26 Dec 2011 04:18:29 +0200 Message-ID: Subject: PROBLEM: memtest tests only LOWMEM Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: tails-dev@boum.org 1. On 32-bit x86, memtest=3Dn 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 Libert=E9 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=3D646361. 3. Keywords: memtest, highmem, mm, security 4. Kernel version: 3.0.4-hardened-r5 (Gentoo) x86 32-bit with PAE --=20 Maxim Kammerer Libert=E9 Linux (discussion / support: http://dee.su/liberte-contribute) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org