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=-3.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 7F22CC43460 for ; Mon, 3 May 2021 19:38:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5E99C613BC for ; Mon, 3 May 2021 19:38:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229633AbhECTjp (ORCPT ); Mon, 3 May 2021 15:39:45 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:42650 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229472AbhECTjo (ORCPT ); Mon, 3 May 2021 15:39:44 -0400 Received: from in02.mta.xmission.com ([166.70.13.52]) by out01.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1ldeP2-00HDI3-Qv; Mon, 03 May 2021 13:38:48 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=fess.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1ldeOx-00DxKW-Li; Mon, 03 May 2021 13:38:48 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Peter Zijlstra Cc: Marco Elver , Arnd Bergmann , Florian Weimer , "David S. Miller" , Ingo Molnar , Thomas Gleixner , Peter Collingbourne , Dmitry Vyukov , Alexander Potapenko , sparclinux , linux-arch , Linux Kernel Mailing List , Linux API , kasan-dev References: Date: Mon, 03 May 2021 14:38:39 -0500 In-Reply-To: (Peter Zijlstra's message of "Mon, 3 May 2021 14:44:21 +0200") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1ldeOx-00DxKW-Li;;;mid=;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX193P6Zs47y9HH8Pk31Hd8htHGyDNhcJWFA= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH 7/3] signal: Deliver all of the perf_data in si_perf X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org Peter Zijlstra writes: > On Sun, May 02, 2021 at 01:39:16PM -0500, Eric W. Biederman wrote: > >> The one thing that this doesn't do is give you a 64bit field >> on 32bit architectures. >> >> On 32bit builds the layout is: >> >> int si_signo; >> int si_errno; >> int si_code; >> void __user *_addr; >> >> So I believe if the first 3 fields were moved into the _sifields union >> si_perf could define a 64bit field as it's first member and it would not >> break anything else. >> >> Given that the data field is 64bit that seems desirable. > > The data field is fundamentally an address, it is internally a u64 > because the perf ring buffer has u64 alignment and it saves on compat > crap etc. > > So for the 32bit/compat case the high bits will always be 0 and > truncating into an unsigned long is fine. I see why it is fine to truncate the data field into an unsigned long. Other than technical difficulties in extending siginfo_t is there any reason not to define data as a __u64? Eric