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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 357B9C6778A for ; Tue, 3 Jul 2018 18:15:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DB878248F3 for ; Tue, 3 Jul 2018 18:15:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="O5+DhWuM" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DB878248F3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=efficios.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 S934462AbeGCSPh (ORCPT ); Tue, 3 Jul 2018 14:15:37 -0400 Received: from mail.efficios.com ([167.114.142.138]:60090 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934392AbeGCSPf (ORCPT ); Tue, 3 Jul 2018 14:15:35 -0400 Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id DA52E230F94; Tue, 3 Jul 2018 14:15:34 -0400 (EDT) Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10032) with ESMTP id asVSSc4ZTi03; Tue, 3 Jul 2018 14:15:34 -0400 (EDT) Received: from localhost (ip6-localhost [IPv6:::1]) by mail.efficios.com (Postfix) with ESMTP id 73ED3230F8E; Tue, 3 Jul 2018 14:15:34 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.efficios.com 73ED3230F8E DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=default; t=1530641734; bh=rdz9WjrHPD9GSxSAZqqRfxyGetqyWoYbu7XLqefShzw=; h=Date:From:To:Message-ID:MIME-Version; b=O5+DhWuMXJ3tApQzkATWJ3xS6NfcwV3q+cMkl4ww4BEGrSQOdQhhL+DeVwL/XVwsH 5k9OFF+sIdV7HWp2JW82Z0LvYUZSsQpjPSanXf90X7I425C+BOq8fBmUG0R8LcG8jg wMyjFWzcDXJxs4LS/sAXl5k59bDNZWXOQpfIh19J4MJmWl+0K1kbDkl5O+8St/Pv0z pptF4vrBCATW6TsW6TogM5FfodKE5WQrkEItgcXOoXjNP9WrSHvAkcW2JhaBeE9b4n Xs7hdTnMW6mugaG7k7JZYD2PqhsvXPxl0ayYAq68vAztuWpo4dglsGrYFZEUEhuMCp lukmOZAvPe42A== X-Virus-Scanned: amavisd-new at efficios.com Received: from mail.efficios.com ([IPv6:::1]) by localhost (mail02.efficios.com [IPv6:::1]) (amavisd-new, port 10026) with ESMTP id hv1mUjqXn0ZK; Tue, 3 Jul 2018 14:15:34 -0400 (EDT) Received: from mail02.efficios.com (mail02.efficios.com [167.114.142.138]) by mail.efficios.com (Postfix) with ESMTP id 5662B230F87; Tue, 3 Jul 2018 14:15:34 -0400 (EDT) Date: Tue, 3 Jul 2018 14:15:34 -0400 (EDT) From: Mathieu Desnoyers To: Peter Zijlstra Cc: Linus Torvalds , Andi Kleen , heiko carstens , Andy Lutomirski , Thomas Gleixner , linux-kernel , linux-api , "Paul E. McKenney" , Boqun Feng , Dave Watson , Paul Turner , Andrew Morton , Russell King , Ingo Molnar , "H. Peter Anvin" , Chris Lameter , Ben Maurer , rostedt , Josh Triplett , Catalin Marinas , Will Deacon , Michael Kerrisk , Joel Fernandes , Michal Simek , schwidefsky , gor Message-ID: <1708848118.11868.1530641734202.JavaMail.zimbra@efficios.com> In-Reply-To: <20180703181143.GB2494@hirez.programming.kicks-ass.net> References: <858886246.10882.1530583291379.JavaMail.zimbra@efficios.com> <20180703164048.i2te5gjemcafqzwf@two.firstfloor.org> <20180703173451.GX2494@hirez.programming.kicks-ass.net> <399697782.11820.1530639539750.JavaMail.zimbra@efficios.com> <20180703174833.GZ2494@hirez.programming.kicks-ass.net> <1048940999.11846.1530640717837.JavaMail.zimbra@efficios.com> <20180703181143.GB2494@hirez.programming.kicks-ass.net> Subject: Re: [RFC PATCH for 4.18] rseq: use __u64 for rseq_cs fields, validate user inputs MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [167.114.142.138] X-Mailer: Zimbra 8.8.8_GA_2096 (ZimbraWebClient - FF52 (Linux)/8.8.8_GA_1703) Thread-Topic: rseq: use __u64 for rseq_cs fields, validate user inputs Thread-Index: qpFjzL0ilmYomLVPp7bOS76dHloPpw== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- On Jul 3, 2018, at 2:11 PM, Peter Zijlstra peterz@infradead.org wrote: > On Tue, Jul 03, 2018 at 01:58:37PM -0400, Mathieu Desnoyers wrote: >> I can modify the ABI to put the cpu_id_start and cpu_id fields inside >> a union, and update it with a single store. >> >> Thoughts ? > > Let's keep them for now, we can always frob this later, they are aligned > and proper, no need to expose that union to userspace. Isn't it weird to change the API of an exposed public uapi header ? What if userspace chooses to do sizeof(__rseq_abi.cpu_id) ? We would break this unless we use a transparent union, which puts constraints I would hope not to have on compilers supporting transparent unions (I recall C++ had issues with this). I'd prefer to expose the union right away if it's fine with you. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com