Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934252AbYCFRfz (ORCPT ); Thu, 6 Mar 2008 12:35:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932272AbYCFRes (ORCPT ); Thu, 6 Mar 2008 12:34:48 -0500 Received: from vaxjo.synopsys.com ([198.182.60.75]:33554 "EHLO vaxjo.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932166AbYCFRer (ORCPT ); Thu, 6 Mar 2008 12:34:47 -0500 Date: Thu, 6 Mar 2008 09:34:38 -0800 From: Joe Buck To: Richard Guenther Cc: Andi Kleen , Andrew Haley , Aurelien Jarno , "H. Peter Anvin" , Michael Matz , linux-kernel@vger.kernel.org, gcc@gcc.gnu.org Subject: Re: Linux doesn't follow x86/x86-64 ABI wrt direction flag Message-ID: <20080306173438.GH17267@synopsys.com> References: <20080305153020.GA24631@volta.aurel32.net> <47CEC3AA.6080709@zytor.com> <20080305195834.GA17267@synopsys.com> <20080305202319.GA17053@volta.aurel32.net> <47CF0627.2070200@zytor.com> <47CF07FE.10200@aurel32.net> <47CFBF28.4060309@redhat.com> <871w6ogjnu.fsf@basil.nowhere.org> <84fc9c000803060406u7dfa0d38ve8af3154bf5064f9@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <84fc9c000803060406u7dfa0d38ve8af3154bf5064f9@mail.gmail.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1630 Lines: 34 On Thu, Mar 06, 2008 at 01:06:17PM +0100, Richard Guenther wrote: > On 06 Mar 2008 12:45:57 +0100, Andi Kleen wrote: > > Andrew Haley writes: > > > > > > I suppose one could apply the precautionary principle, but those systems that > > > don't update kernels won't update gcc either, so the solution won't work. > > > > You seem to assume that running a gcc 4.3 compiled binary requires a > > gcc update. That is not necessarily true. > > It (sometimes) requires a libgcc and libstdc++ update. "Sometimes" is correct; many users commonly run newer compilers on older distros, with LD_LIBRARY_PATH set to pick up the correct C++ support library. This is particularly common on servers, where you don't want to mess with a working system but you might need to run newer code. So, we've been arguing for a while, so the question is what to do. Using a principle based on the old IETF concept of being liberal in what you accept, and conservative in what you send, I think that both the Linux kernel and gcc should fix the problem. The kernel should fix the information leak, and gcc should remove the assumption that the direction flag is set in a given direction on function entry. The gcc patch will be too late for 4.3.0, but it would be on the 4.3 branch, and we would recommend that distros pick it up for any compilers they ship. -- 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/