Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757685Ab1EXXhN (ORCPT ); Tue, 24 May 2011 19:37:13 -0400 Received: from terminus.zytor.com ([198.137.202.10]:37540 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754753Ab1EXXhL (ORCPT ); Tue, 24 May 2011 19:37:11 -0400 Message-ID: <4DDC4107.5060006@zytor.com> Date: Tue, 24 May 2011 16:36:39 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc14 Thunderbird/3.1.10 MIME-Version: 1.0 To: Dan Rosenberg CC: Tony Luck , linux-kernel@vger.kernel.org, davej@redhat.com, kees.cook@canonical.com, davem@davemloft.net, eranian@google.com, torvalds@linux-foundation.org, adobriyan@gmail.com, penberg@kernel.org, Arjan van de Ven , Andrew Morton , Valdis.Kletnieks@vt.edu, Ingo Molnar , pageexec@freemail.hu Subject: Re: [RFC][PATCH] Randomize kernel base address on boot References: <1306269105.21443.20.camel@dan> <4DDC31DF.5010303@zytor.com> <1306278296.1921.10.camel@dan> <4DDC3A1A.6030006@zytor.com> <1306280089.1921.18.camel@dan> In-Reply-To: <1306280089.1921.18.camel@dan> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1554 Lines: 39 On 05/24/2011 04:34 PM, Dan Rosenberg wrote: > On Tue, 2011-05-24 at 16:07 -0700, H. Peter Anvin wrote: >> On 05/24/2011 04:04 PM, Dan Rosenberg wrote: >>> >>>> 2. Not introduce a performance regression (we avoid locating in the >>>> bottom 16 MiB for performance reasons, except on very small systems); >>> >>> I altered the boot code so that it uses CONFIG_PHYSICAL_START, which >>> defaults to 16 MiB, as a lower bound on location. So nothing will ever >>> get loaded below there, and I still can take advantage of higher >>> alignment granularity. Are there other problems I'm not anticipating? >>> >> >> Please look at the discussion as to what led us to do things this way. >> > > Would you be able to point me to said discussion? The only thing I can > find is this: > > http://marc.info/?l=linux-kernel&m=124173552516435&w=2 > > This set PHYSICAL_START at 16 MB and alignment at 2/4 MB. Then, three > days later, this was committed: > > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=ceefccc93932b920a8ec6f35f596db05202a12fe > > This sets the alignment to 16 MB, with the only justification being that > relocatable kernels also need to start above 16 MB. > I think those patches came after the discussion were already over. I'll try to look for it. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/