From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758642AbYC0JrV (ORCPT ); Thu, 27 Mar 2008 05:47:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755373AbYC0JrN (ORCPT ); Thu, 27 Mar 2008 05:47:13 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:54556 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755232AbYC0JrM (ORCPT ); Thu, 27 Mar 2008 05:47:12 -0400 Date: Thu, 27 Mar 2008 10:46:48 +0100 From: Ingo Molnar To: Paul Jackson Cc: ying.huang@intel.com, hpa@zytor.com, andi@firstfloor.org, mingo@redhat.com, tglx@linutronix.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH -mm 0/4] x86_64 boot: Add linked listof struct setup_data to boot protocol Message-ID: <20080327094648.GA5056@elte.hu> References: <1206601743.3067.20.camel@caritas-dev.intel.com> <20080327083221.GD15626@elte.hu> <20080327040216.99dcde7b.pj@sgi.com> <20080327090925.GC30918@elte.hu> <20080327042147.15f7ce28.pj@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080327042147.15f7ce28.pj@sgi.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0002] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Paul Jackson wrote: > Ingo wrote: > > stupidly shortsighted limit ... > > Eh ... I don't think all that shortsighted ... that 4096 limit has > probably been around longer than Linux. Linus or hpa or others would > know the history better than I do. the limit for boot parameters is 2048 bytes - the BUILD_WARN_ON() checks for the sum of the two boot parameter areas. We used empty_zero_page for boot parameter passing for a near eternity - 2K for the command line (which used to be clipped - recently upped to true 2048), and 2K for the boot parameters. As a historic/nostalgic sidenote: the 2048 limit is not as old as Linux, version 0.11 of Linux had 512 bytes of special area for boot parameters, at 0x90000-0x901FF. having fixed-length 2K buffering ABI between two historically rather inflexible pieces of software (the bootloader and the kernel), at a very fragile and under-capable junction of our bootstrap (very early during bootup) _is_ shortsighted. Granted, it's a difficult area to change but still it's a nasty limit - as you have found it out first-hand ;-) Ingo