Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264708AbTI2U0P (ORCPT ); Mon, 29 Sep 2003 16:26:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264709AbTI2U0P (ORCPT ); Mon, 29 Sep 2003 16:26:15 -0400 Received: from nevyn.them.org ([66.93.172.17]:46976 "EHLO nevyn.them.org") by vger.kernel.org with ESMTP id S264708AbTI2U0L (ORCPT ); Mon, 29 Sep 2003 16:26:11 -0400 Date: Mon, 29 Sep 2003 16:26:04 -0400 From: Daniel Jacobowitz To: Mikulas Patocka Cc: Arjan van de Ven , Linus Torvalds , Brian Gerst , Linux-Kernel Subject: Re: -mregparm=3 (was Re: [PATCH] i386 do_machine_check() is redundant. Message-ID: <20030929202604.GA23344@nevyn.them.org> Mail-Followup-To: Mikulas Patocka , Arjan van de Ven , Linus Torvalds , Brian Gerst , Linux-Kernel References: <1064775868.5045.4.camel@laptop.fenrus.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 29, 2003 at 10:20:45PM +0200, Mikulas Patocka wrote: > > > > Use machine_check_vector in the entry code instead. > > > > > > This is wrong. You just lost the "asmlinkage" thing, which means that it > > > breaks when asmlinkage matters. > > > > > > And yes, asmlinkage _can_ matter, even on x86. It disasbles regparm, for > > > one thing, so it makes a huge difference if the kernel is compiled with > > > -mregparm=3 (which used to work, and which I'd love to do, but gcc has > > > often been a tad fragile). > > > > gcc 3.2 and later are supposed to be ok (eg during 3.2 development a > > long standing bug with regparm was fixed and now is believed to work)... > > since our makefiles check gcc version already... this can be made gcc > > version dependent as well for sure.. > > They are still buggy. gcc 3.3.1 miscompiles itself with -mregparm=3 > (without -O or -O2 it works). (I am too lazy to spend several days trying > to find exactly which function in gcc was miscompiled, maybe I do it one > day). gcc 2.95.3 compiles gcc 3.3.1 with -mregparm=3 -O2 correctly. > gcc 3.4 doesn't seem to be better. > > gcc 2.7.2.3 has totally broken -mregparm=3, even quite simple programs > fail. You can't build GCC with -mregparm=3. It changes the interface to system functions. So unless your libc happened to be built with -mregparm=3, and extensively hacked to expect arguments in registers to the assembly stubs, it can't work. It's interesting for kernel code, whole distributions, or things which are careful to have a glue layer. -- Daniel Jacobowitz MontaVista Software Debian GNU/Linux Developer - 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/