From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753192Ab2ARV41 (ORCPT ); Wed, 18 Jan 2012 16:56:27 -0500 Received: from terminus.zytor.com ([198.137.202.10]:33037 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753016Ab2ARV4Z (ORCPT ); Wed, 18 Jan 2012 16:56:25 -0500 Message-ID: <4F173F48.2070604@zytor.com> Date: Wed, 18 Jan 2012 13:53:12 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:8.0) Gecko/20111115 Thunderbird/8.0 MIME-Version: 1.0 To: Roland McGrath CC: Linus Torvalds , Indan Zupancic , Andi Kleen , Jamie Lokier , Andrew Lutomirski , Oleg Nesterov , Will Drewry , linux-kernel@vger.kernel.org, keescook@chromium.org, john.johansen@canonical.com, serge.hallyn@canonical.com, coreyb@linux.vnet.ibm.com, pmoore@redhat.com, eparis@redhat.com, djm@mindrot.org, segoon@openwall.com, rostedt@goodmis.org, jmorris@namei.org, scarybeasts@gmail.com, avi@redhat.com, penberg@cs.helsinki.fi, viro@zeniv.linux.org.uk, mingo@elte.hu, akpm@linux-foundation.org, khilman@ti.com, borislav.petkov@amd.com, amwang@redhat.com, ak@linux.intel.com, eric.dumazet@gmail.com, gregkh@suse.de, dhowells@redhat.com, daniel.lezcano@free.fr, linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, olofj@chromium.org, mhalcrow@google.com, dlaor@redhat.com Subject: Re: Compat 32-bit syscall entry from 64-bit task!? References: <20120116183730.GB21112@redhat.com> <20120117170512.GB17070@redhat.com> <49017bd7edab7010cd9ac767e39d99e4.squirrel@webmail.greenhost.nl> <20120118015013.GR11715@one.firstfloor.org> <20120118020453.GL7180@jl-vm1.vm.bytemark.co.uk> <20120118022217.GS11715@one.firstfloor.org> <4F1731C1.4050007@zytor.com> <4F1733DF.7040905@zytor.com> <4F1737C9.3070905@zytor.com> In-Reply-To: X-Enigmail-Version: 1.3.4 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 01/18/2012 01:51 PM, Roland McGrath wrote: > > There are all the concerns about obscure ABI compatibility with > expectations of existing debuggers and so forth, which Linus has mentioned. > For that I can accept his point that things today so mishandle the > int80-from-64 case that something like a new meaning for high bits of > orig_ax or whatnot in just that case would not be actually problematic. > When you and I were discussing a more general feature of distinguishing > int80 from sysenter from syscall from traps from asynchronous interrupts, > that was of more concern. > > I do feel strongly that any new means of exposing bona fide user state > ought to be done via the user_regset mechanism. (i.e., either overloading > some existing user_regs_struct bits if that truly is harmless to > compatibility, or adding a new regset flavor.) That way it is > automatically recorded in core files, accessible with PTRACE_GETREGSET, > etc. (But I'm not really working on this stuff any more, so I'm out of the > business of arguing strenuously about such opinions.) > I think we can obviously agree that regsets is the only way to go for any kind of new state. -hpa