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=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS 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 B9C43C33CAF for ; Fri, 13 Dec 2019 20:37:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EF5DF247A0 for ; Fri, 13 Dec 2019 20:37:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="X4Em0CQg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727702AbfLMO2x (ORCPT ); Fri, 13 Dec 2019 09:28:53 -0500 Received: from mail-wm1-f42.google.com ([209.85.128.42]:36828 "EHLO mail-wm1-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725747AbfLMO2w (ORCPT ); Fri, 13 Dec 2019 09:28:52 -0500 Received: by mail-wm1-f42.google.com with SMTP id p17so6778474wma.1; Fri, 13 Dec 2019 06:28:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=6QLZHSUqVyecs2iharIBnV+waYycsRrF0PppbO8VMdc=; b=X4Em0CQg7XPS3z8XGXcRnzQcQadSqmHsHNxwILAXvTkGF1A0285lgDVyCcfmeLJMPj +Tk9WJ2x/6XiFUCTHg0b8xn10ROMgVaTjQnbg+3qy3Gv3aep3BkV8hyVg4Rj0h75Z/oD 35XebvEWDrOknx7OGqgYUi4qMIv+qa9zC1voRXNBH6drGXWrKcVy9HlcS2r/HuYmNAI9 OLcCG+k1GSnn6YvMkJcBCrtfY6FidTIooBhHPKYhYtE5D3BJoBZLsrfJHapK+8InoSks f0UPKA4o/9sHfTcTLWVTfcOsu/7MQOC8y9flklApuHnQ61tarND+8sgZ2yf0UyGiQP7W Yp+g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=6QLZHSUqVyecs2iharIBnV+waYycsRrF0PppbO8VMdc=; b=e1PsduVgWWPPq+XS6OML6AgiNG0pHqizZ+fMSp4k4x5E0WYtf7Q4+spsaIyGb1itu9 BCDr4EpFN+e9OhOIP7KcYBDMP125frdK+ZBn1ozDVFWXnjhltDagnwJj00kQoJImNiON sOnhBEJwbaDR5neVPbqOI+010URVGFCCCJv6x+zo6/We+W3GKpWNU+wQ5oRZwOpzsUzv dJ0Q1gruUC+Rf64ORXL0FM9uuIoddNFZT+gi+2ociGtaU4dcnrUindfy5i8X7xSCGgX9 E8oXwvhnsnxFedLtInHdCoQf36oIsfnUBHH0uZ5l//sCM6grbvMf989H2eg0O1ViAUa/ /SxA== X-Gm-Message-State: APjAAAWSCpmOfllyRJxWc+a3ghTwJo5zJ8B5ATF/LQFep4/rQic+dylm 7bDnAG8hK+EA58J+rPKBXb8= X-Google-Smtp-Source: APXvYqwcogMDfRsO+0kr7L/xFj6Up/8vQMcepDErEiyPT73ffpPLdwealTjrhoiMySzSoGv/hvLbhQ== X-Received: by 2002:a1c:980e:: with SMTP id a14mr9520966wme.76.1576247330116; Fri, 13 Dec 2019 06:28:50 -0800 (PST) Received: from ltop.local ([2a02:a03f:40f6:4600:60b0:6ca6:1eae:3b06]) by smtp.gmail.com with ESMTPSA id h127sm11148048wme.31.2019.12.13.06.28.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Dec 2019 06:28:49 -0800 (PST) Date: Fri, 13 Dec 2019 15:28:46 +0100 From: Luc Van Oostenryck To: Peter Zijlstra Cc: Will Deacon , Linus Torvalds , Michael Ellerman , dja@axtens.net, Linux Kernel Mailing List , linuxppc-dev@lists.ozlabs.org, Christophe Leroy , linux-arch , Mark Rutland , Segher Boessenkool , Arnd Bergmann , Christian Borntraeger Subject: Re: READ_ONCE() + STACKPROTECTOR_STRONG == :/ (was Re: [GIT PULL] Please pull powerpc/linux.git powerpc-5.5-2 tag (topic/kasan-bitops)) Message-ID: <20191213142846.ki2t2fwljnql66lt@ltop.local> References: <20191212100756.GA11317@willie-the-truck> <20191212104610.GW2827@hirez.programming.kicks-ass.net> <20191212180634.GA19020@willie-the-truck> <20191212193401.GB19020@willie-the-truck> <20191212202157.GD11457@worktop.programming.kicks-ass.net> <20191212205338.GB11802@worktop.programming.kicks-ass.net> <20191213104706.xnpqaehmtean3mkd@ltop.local> <20191213125618.GD2844@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191213125618.GD2844@hirez.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 13, 2019 at 01:56:18PM +0100, Peter Zijlstra wrote: > > Excellent! I had to change it to something like: > > #define unqual_typeof(x) typeof(({_Atomic typeof(x) ___x __maybe_unused; ___x; })) > > but that does indeed work! > > Now I suppose we should wrap that in a symbol that indicates our > compiler does indeed support _Atomic, otherwise things will come apart. > > That is, my gcc-4.6 doesn't seem to have it, while gcc-4.8 does, which > is exactly the range that needs the daft READ_ONCE() construct, how > convenient :/ > > Something a little like this perhaps? Yes, this looks good to me. Just a small nit here below. > --- > > diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h > index 7d9cc5ec4971..c389af602da8 100644 > --- a/arch/arm64/include/asm/barrier.h > +++ b/arch/arm64/include/asm/barrier.h > @@ -75,9 +75,9 @@ static inline unsigned long array_index_mask_nospec(unsigned long idx, > > #define __smp_store_release(p, v) \ > do { \ > - typeof(p) __p = (p); \ > - union { typeof(*p) __val; char __c[1]; } __u = \ > - { .__val = (__force typeof(*p)) (v) }; \ > + unqual_typeof(p) __p = (p); \ > + union { unqual_typeof(*p) __val; char __c[1]; } __u = \ > + { .__val = (__force unqual_typeof(*p)) (v) }; \ The 2 two trailing backslashes are now off by one tab. -- Luc