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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 1A3F6C2BA1A for ; Tue, 7 Apr 2020 17:26:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D698E206F7 for ; Tue, 7 Apr 2020 17:26:41 +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="aBj6/lGP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726525AbgDGR0k (ORCPT ); Tue, 7 Apr 2020 13:26:40 -0400 Received: from merlin.infradead.org ([205.233.59.134]:45696 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726421AbgDGR0k (ORCPT ); Tue, 7 Apr 2020 13:26:40 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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; bh=QHtKlTs2KaIESq55FMaA9+K4wJtVD9YC1RoEo72D/Xg=; b=aBj6/lGPkdMbz8tsqagUCQuEfi 4Eaneh2MHE6feFLtR/4iAWcOGiiqFluGWIZRIqTACrSlgc8O9mk2/qQNTsLd/DTb4NmtDhk4WXOmf 3bnc5eybaCrkd8rd8uQokPi7CiRLYr023r5lIDFeJ9cmFGwijaJOX108M15YwEIvCPIwBvxtgBVuw O5Vj+EeEYVYEWTx7a+qc48r3mJMHqTZ6cqXkljDMPRaOXi9L6+shxxaEmavmMNiwwgxqGGUy0p1nv UztOgnaAKZsS268OgV+t90IP2TllJZsXUDxtYoaYI/P/Y/V6tkW9sLeefzxdOwVz4r68s0ZDVxdOo Fh7YDcBw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jLrzd-0005w4-2Y; Tue, 07 Apr 2020 17:26:33 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id B73CB3010C8; Tue, 7 Apr 2020 19:26:30 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id A34D42B0A1247; Tue, 7 Apr 2020 19:26:30 +0200 (CEST) Date: Tue, 7 Apr 2020 19:26:30 +0200 From: Peter Zijlstra To: Alexandre Chartre Cc: Josh Poimboeuf , x86@kernel.org, linux-kernel@vger.kernel.org, jthierry@redhat.com, tglx@linutronix.de Subject: Re: [PATCH V2 9/9] x86/speculation: Remove all ANNOTATE_NOSPEC_ALTERNATIVE directives Message-ID: <20200407172630.GH20730@hirez.programming.kicks-ass.net> References: <20200407073142.20659-1-alexandre.chartre@oracle.com> <20200407073142.20659-10-alexandre.chartre@oracle.com> <20200407132837.GA20730@hirez.programming.kicks-ass.net> <20200407133454.n55u5nx33ruj73gx@treble> <89b10eb8-c030-b954-6be3-8830fc6a8daa@oracle.com> <3eb36fd2-9827-4c1b-681c-9c1d65c7582f@oracle.com> <20200407162838.5hlh6oom4oa45ugt@treble> <06605b1c-c9ae-fd18-bcb1-e4a48f2cb60e@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <06605b1c-c9ae-fd18-bcb1-e4a48f2cb60e@oracle.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 07, 2020 at 07:01:43PM +0200, Alexandre Chartre wrote: > I think that's the case with smap_save: > > static __always_inline unsigned long smap_save(void) > { > unsigned long flags; > > asm volatile (ALTERNATIVE("", "pushf; pop %0; " __ASM_CLAC, > X86_FEATURE_SMAP) > : "=rm" (flags) : : "memory", "cc"); > > return flags; > } > > The alternative does change the stack but objtool won't complain > because it handles the pushf and pop instruction. Oh bugger; indeed! That'll wreck unwinding.