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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT 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 40BDFC6778C for ; Tue, 3 Jul 2018 08:15:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E3F2E24D63 for ; Tue, 3 Jul 2018 08:15:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="hd5R6ie6" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E3F2E24D63 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org 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 S932910AbeGCIPj (ORCPT ); Tue, 3 Jul 2018 04:15:39 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:49560 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753560AbeGCIPh (ORCPT ); Tue, 3 Jul 2018 04:15:37 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=ZrYoh/t/fLnf5vc0rVVajIBxjuDvZDIvPUWILNmluxs=; b=hd5R6ie65m1//9JGU7bo1R8hR AX4x563kgxD7Ipq34WRyZLOwxNMN66ipPsrxq7xPdq1IkIJ04h/Z8mIVVJ/lSeY7EI1/Q48blvhK9 9T0VXmNCHUNbLJ7ULCsFa1kTnK4pAA801GqSds9Z8Wo1UYKx3t2QcjiSXZNCp51km38UYTgNpf8HH KCmm574Vsfu23TDwIS4M74DoWOa2x9VFIrT/Jo3vIVLfNM4OKP4/qndX/7BXIG/iNj97CWy8fe4gF LwgaMJquEcboVNMYer1RcZeNpfDe1LXmUHXJup6+WJ+M74CBM33VcfNtY+Iery/E8WlZRraUWE/os fBxWDM7dQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1faGSa-000844-1l; Tue, 03 Jul 2018 08:14:52 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id A21212028932F; Tue, 3 Jul 2018 10:14:49 +0200 (CEST) Date: Tue, 3 Jul 2018 10:14:49 +0200 From: Peter Zijlstra To: Mathieu Desnoyers Cc: Linus Torvalds , 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" , Andi Kleen , Chris Lameter , Ben Maurer , rostedt , Josh Triplett , Catalin Marinas , Will Deacon , Michael Kerrisk , Joel Fernandes , michal.simek@xilinx.com Subject: Re: [RFC PATCH for 4.18] rseq: use __u64 for rseq_cs fields, validate user inputs Message-ID: <20180703081449.GT2494@hirez.programming.kicks-ass.net> References: <20180702223143.4663-1-mathieu.desnoyers@efficios.com> <825871008.10839.1530573419561.JavaMail.zimbra@efficios.com> <1959930320.10843.1530573742647.JavaMail.zimbra@efficios.com> <8B2E4CEB-3080-4602-8B62-774E400892EB@amacapital.net> <459661281.10865.1530580742205.JavaMail.zimbra@efficios.com> <858886246.10882.1530583291379.JavaMail.zimbra@efficios.com> <1776351430.10902.1530585009519.JavaMail.zimbra@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1776351430.10902.1530585009519.JavaMail.zimbra@efficios.com> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 02, 2018 at 10:30:09PM -0400, Mathieu Desnoyers wrote: > > Use "get_user()". It works for 64-bit objects too, and it will be > > atomic in the 32-bit sub-parts on a 32-bit architecture. > > Is it really ? Last time we had this discussion, not all architectures > guaranteed that reading a 64-bit integer would happen in two atomic > 32-bit sub-parts. This was the main motivation for the LINUX_FIELD_u32_u64() > macro as it stands today (rather than using a union). Just state, as a requirement for supporting rseq, that the arch {get,put}_user(u64) on 32bit targets must be exactly 2 u32 loads/stores. We're piece-wise enabling rseq across architectures anyway, and when the relevant maintains do this, they can have a look at their {get,put}_user() implementations and fix them. If you rely on get_user(u64) working, that means microblaze is already broken, but I suppose it already was, since their rseq enablement patch is extremely dodgy. Michal?