From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932135AbbCEIgg (ORCPT ); Thu, 5 Mar 2015 03:36:36 -0500 Received: from mail.skyhub.de ([78.46.96.112]:51113 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932065AbbCEIgd (ORCPT ); Thu, 5 Mar 2015 03:36:33 -0500 Date: Thu, 5 Mar 2015 09:35:19 +0100 From: Borislav Petkov To: Ingo Molnar Cc: X86 ML , Andy Lutomirski , LKML , Linus Torvalds Subject: Re: [PATCH v2 07/15] x86/lib/copy_user_64.S: Convert to ALTERNATIVE_2 Message-ID: <20150305083519.GB3915@pd.tnic> References: <1424776497-3180-1-git-send-email-bp@alien8.de> <1424776497-3180-8-git-send-email-bp@alien8.de> <20150304062552.GA16111@gmail.com> <20150304090038.GB3233@pd.tnic> <20150305003249.GB20449@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20150305003249.GB20449@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 05, 2015 at 01:32:49AM +0100, Ingo Molnar wrote: > We could also do a (limited) relink during early bootup, as part of > the alternatives patching pass in essence: for that we need to stick > the relocation info into a section and put that into the vmlinux. Oh, you want us to do our own asm inlining, so to speak, and save us even a CALL. Well, that would be more involved and saving a single CALL is making me question the effort. Also, with shifted virtual addresses at boot time, debuggability becomes a serious pain because "objdump -D vmlinux" output is worthless all of a sudden. For example, even during doing those patches, I had to go and dump kernel memory to see what actually gets patched in. And without kvm and the monitor console, I would've had a serious hard time. If you change larger portions of the kernel at early boot, that might make the whole endeavor of debugging a serious undertaking. I already dread the moment when I'd have to look at a kaslr'ed splat. We'll see. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. --