From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: Compat 32-bit syscall entry from 64-bit task!? Date: Mon, 06 Feb 2012 12:30:50 -0800 Message-ID: <4F30387A.9040209@zytor.com> References: <20120116183730.GB21112@redhat.com> <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> <4F173F48.2070604@zytor.com> <4F176605.5020101@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Denys Vlasenko , 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-se To: Roland McGrath Return-path: In-Reply-To: Sender: linux-security-module-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On 01/20/2012 02:40 PM, Roland McGrath wrote: > If you change the size of a regset, then the new full size will be the size > of the core file notes. Existing userland tools will not be expecting > this, they expect a known exact size. If you need to add new stuff, it > really is easier all around to add a new regset flavor. When adding a new > one, you can make it variable-sized from the start so as to be extensible > in the future. We did this for NT_X86_XSTATE, for example. > > Thanks, > Roland Hi Roland, What is needed to make a regset variable-sized? Just declaring that it may change in size in the future, or does one need a length field at the top (I would personally have expected that both notes and ptrace would have out-of-band methods for getting the size?) -hp-a -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755587Ab2BFUeK (ORCPT ); Mon, 6 Feb 2012 15:34:10 -0500 Received: from terminus.zytor.com ([198.137.202.10]:60558 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751016Ab2BFUeH (ORCPT ); Mon, 6 Feb 2012 15:34:07 -0500 Message-ID: <4F30387A.9040209@zytor.com> Date: Mon, 06 Feb 2012 12:30:50 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:9.0) Gecko/20111222 Thunderbird/9.0 MIME-Version: 1.0 To: Roland McGrath CC: Denys Vlasenko , 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> <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> <4F173F48.2070604@zytor.com> <4F176605.5020101@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 01/20/2012 02:40 PM, Roland McGrath wrote: > If you change the size of a regset, then the new full size will be the size > of the core file notes. Existing userland tools will not be expecting > this, they expect a known exact size. If you need to add new stuff, it > really is easier all around to add a new regset flavor. When adding a new > one, you can make it variable-sized from the start so as to be extensible > in the future. We did this for NT_X86_XSTATE, for example. > > Thanks, > Roland Hi Roland, What is needed to make a regset variable-sized? Just declaring that it may change in size in the future, or does one need a length field at the top (I would personally have expected that both notes and ptrace would have out-of-band methods for getting the size?) -hp-a -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.