From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753905Ab2KUA2q (ORCPT ); Tue, 20 Nov 2012 19:28:46 -0500 Received: from terminus.zytor.com ([198.137.202.10]:45503 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752254Ab2KUA2p (ORCPT ); Tue, 20 Nov 2012 19:28:45 -0500 Message-ID: <50AC2022.5030207@zytor.com> Date: Tue, 20 Nov 2012 16:28:18 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121029 Thunderbird/16.0.2 MIME-Version: 1.0 To: Yinghai Lu CC: Thomas Gleixner , Ingo Molnar , "Eric W. Biederman" , linux-kernel@vger.kernel.org, Matt Fleming Subject: Re: [PATCH v2 03/13] x86: Add macro for 64bit entry startup_64 References: <1353222571-31544-1-git-send-email-yinghai@kernel.org> <1353222571-31544-4-git-send-email-yinghai@kernel.org> <50AAB5E8.5070807@zytor.com> <50AABD15.1050809@zytor.com> <41603b4d-cd34-4c6e-9e1f-ac78816b5097@email.android.com> <23b6f8fe-37cd-4cbb-9c90-511dab4e5b5b@email.android.com> <50ABF23A.7020305@zytor.com> In-Reply-To: X-Enigmail-Version: 1.4.6 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 On 11/20/2012 04:20 PM, Yinghai Lu wrote: > > So will have > Bit 1 (read): LOADED_ABOVE_4G > - If 1, code, boot_param, cmdline, ramdisk could be loaded above 4G, > > will update the patches accordingly. > No, read the below. >> >> On the other hand, the read flags in loadflags has not been modified for a >> very long time, and there is a serious risk that some broken bootloader >> might be doing a full byte comparison. >> >> relocatable_kernel really should have been a flag, but it is now defined as >> a comparison with zero. As such, and in an effort to minimize the growth of >> struct setup_header (it is limited to little over 128 bytes long) I suggest >> we redefine the 16-byte field at offset 0x236 as a new flags field. We >> still only need one flag, though. >> >> Backwards compatibility is so much fun. > > yes. try to make it ready for future is fun too. > > are you going to have pointer for ext_header ? > No, it doesn't help us much. Overall, we need to keep growth of struct setup_header under some control. The highest usable offset is 0x280. -hpa