From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 24C84C3E8C5 for ; Sun, 29 Nov 2020 03:29:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D672120825 for ; Sun, 29 Nov 2020 03:29:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726067AbgK2D3W (ORCPT ); Sat, 28 Nov 2020 22:29:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36684 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725616AbgK2D3W (ORCPT ); Sat, 28 Nov 2020 22:29:22 -0500 Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [IPv6:2002:c35c:fd02::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 241CFC0613D1 for ; Sat, 28 Nov 2020 19:28:42 -0800 (PST) Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kjDNv-00FCcT-VO; Sun, 29 Nov 2020 03:28:24 +0000 Date: Sun, 29 Nov 2020 03:28:23 +0000 From: Al Viro To: Walt Drummond Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, brgerst@gmail.com, linux@dominikbrodowski.net, gustavoars@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/signals: Fix save/restore signal stack to correctly support sigset_t Message-ID: <20201129032823.GA3579531@ZenIV.linux.org.uk> References: <20201119221132.1515696-1-walt@drummond.us> <20201128052317.GY3576660@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: Al Viro Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Nov 28, 2020 at 06:19:31PM -0800, Walt Drummond wrote: > Thanks Al. I want to understand the nuance, so please bear with me as I > reason this out. The cast in stone nature of this is due to both the need > to keep userspace and kernel space in sync (ie, you'd have to coordinate > libc and kernel changes super tightly to pull this off), and any change in > the size of struct rt_sigframe would break backwards compatibility with > older binaries, is that correct? Pretty much so. I would expect gdb and friends to be very unhappy about that, for starters, along with a bunch of fun stuff like JVM, etc. Ask the userland folks (libc, gdb, etc.) how would they feel about such changes. I'm fairly sure that it's _not_ going to be a matter of changing _NSIG, rebuilding the kernel and living happily ever after.