From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750832AbVKKPyM (ORCPT ); Fri, 11 Nov 2005 10:54:12 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750833AbVKKPyM (ORCPT ); Fri, 11 Nov 2005 10:54:12 -0500 Received: from mx1.suse.de ([195.135.220.2]:4792 "EHLO mx1.suse.de") by vger.kernel.org with ESMTP id S1750832AbVKKPyL (ORCPT ); Fri, 11 Nov 2005 10:54:11 -0500 From: Andi Kleen To: discuss@x86-64.org Subject: Re: [discuss] Re: [PATCH] x86-64: adjust ia32entry.S Date: Fri, 11 Nov 2005 16:53:52 +0100 User-Agent: KMail/1.8 Cc: "Jan Beulich" , linux-kernel@vger.kernel.org References: <4370AFF0.76F0.0078.0@novell.com> <200511111634.44871.ak@suse.de> <4374CBE9.76F0.0078.0@novell.com> In-Reply-To: <4374CBE9.76F0.0078.0@novell.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200511111653.52341.ak@suse.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Friday 11 November 2005 16:50, Jan Beulich wrote: > >>> Andi Kleen 11.11.05 16:34:44 >>> > > > >On Wednesday 09 November 2005 17:10, Jan Beulich wrote: > >> IA32 compatibility entry points needlessly played with extended > >> registers. Additionally, frame unwind information was still > > incorrect > > >> for ia32_ptregs_common (sorry, my fault). > > > >What do you mean with needlessly played? That it didn't initialize > >all on the stack frame? That was more a feature than a bug. > >Did it cause you problems? > > It saved and restored R12-R15, even though these registers have no > meaning (and are architecturally undefined) when coming from/going to > 32-bit mode. Problems? No, except that without the extra loads (stores > don't matter that much I believe) performance is better... int 0x80 can be called from long mode too. We especially kept this option to allow JITs like valgrind to run a 32bit process in a 64bit image. In this case we shouldn't leak kernel registers. You're right they normally shouldn't be leaked anyways because the C ABI will save/restore it. I will think about it. > > >In general I'm weary of making the asm macros more complex > >(adding more arguments etc.) Please keep it simple. > > Then ignore this, perhaps with the exception of the unwind info > adjustment. Can you please resubmit that as a separate patch? -Andi