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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 F1A20C04EB9 for ; Sat, 1 Dec 2018 13:41:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C0AF320834 for ; Sat, 1 Dec 2018 13:41:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C0AF320834 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=xmission.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726801AbeLBAyM (ORCPT ); Sat, 1 Dec 2018 19:54:12 -0500 Received: from out02.mta.xmission.com ([166.70.13.232]:45665 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726619AbeLBAyL (ORCPT ); Sat, 1 Dec 2018 19:54:11 -0500 Received: from in01.mta.xmission.com ([166.70.13.51]) by out02.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1gT5Wa-0002pT-JH; Sat, 01 Dec 2018 06:41:36 -0700 Received: from ip68-227-174-240.om.om.cox.net ([68.227.174.240] helo=x220.xmission.com) by in01.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1gT5WZ-000754-JT; Sat, 01 Dec 2018 06:41:36 -0700 From: ebiederm@xmission.com (Eric W. Biederman) To: Andy Lutomirski Cc: Arnd Bergmann , Christian Brauner , Florian Weimer , LKML , "Serge E. Hallyn" , Jann Horn , Andrew Morton , Oleg Nesterov , Aleksa Sarai , Al Viro , Linux FS Devel , Linux API , Daniel Colascione , Tim Murray , linux-man , Kees Cook References: <20181120105124.14733-1-christian@brauner.io> <87in0g5aqo.fsf@oldenburg.str.redhat.com> <36323361-90BD-41AF-AB5B-EE0D7BA02C21@amacapital.net> <993B98AC-51DF-4131-AF7F-7DA2A7F485F1@brauner.io> <20181129195551.woe2bl3z3yaysqb6@brauner.io> <6E21165F-2C76-4877-ABD9-0C86D55FD6AA@amacapital.net> <87y39b2lm2.fsf@xmission.com> <20181130065606.kmilbbq46oeycjp5@brauner.io> Date: Sat, 01 Dec 2018 07:41:30 -0600 In-Reply-To: (Andy Lutomirski's message of "Fri, 30 Nov 2018 08:35:45 -0800") Message-ID: <87va4d1i0l.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1gT5WZ-000754-JT;;;mid=<87va4d1i0l.fsf@xmission.com>;;;hst=in01.mta.xmission.com;;;ip=68.227.174.240;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1849rd1zGyAih2l8kAX++Rg5ToGYkIpqPU= X-SA-Exim-Connect-IP: 68.227.174.240 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH v2] signal: add procfd_signal() syscall X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andy Lutomirski writes: > On Fri, Nov 30, 2018 at 3:41 AM Arnd Bergmann wrote: >> siginfo_t as it is now still has a number of other downsides, and Andy in >> particular didn't like the idea of having three new variants on x86 >> (depending on how you count). His alternative suggestion of having >> a single syscall entry point that takes a 'signfo_t __user *' but interprets >> it as compat_siginfo depending on in_compat_syscall()/in_x32_syscall() >> should work correctly, but feels wrong to me, or at least inconsistent >> with how we do this elsewhere. > > BTW, do we consider siginfo_t to be extensible? If so, and if we pass > in a pointer, presumably we should pass a length as well. siginfo is extensible in the sense that the structure is 128 bytes and we use at most 48 bytes. siginfo gets embedded in stack frames when signals get delivered so a size change upwards is non-trivial, and is possibly and ABI break so I believe a length field would be pointless. Eric