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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED, 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 E5258C43381 for ; Sat, 23 Feb 2019 08:39:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A83C9206A3 for ; Sat, 23 Feb 2019 08:39:51 +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="osAqe5/F" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726631AbfBWIju (ORCPT ); Sat, 23 Feb 2019 03:39:50 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:38240 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726177AbfBWIjt (ORCPT ); Sat, 23 Feb 2019 03:39:49 -0500 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=xtvmSIA5GbdSg1LeBhZQEUzLKD0LVlVHfuS0/yyCVQc=; b=osAqe5/FaW4bURfQr3hPT8Jpe FdVmSZRddqnJen24pYVOA8/ztVvJHGnslt4wEQvYMKJaehGoFHPElqGyEZIHEqzqkyKfufGxZC8yg MoRggCXCoMRP4hLnSjdNNQ55rxwWOlqZ6U2SZwoUTarnjHFXKWzjCHobNGaxU0vf8Smo1oP7ky8rg wto8tQIA3URds4tRDrzC+yByOAEterXlqKTB27+yb2gG3PD7arLyTZf/y+JLJakGpbPbEAVqdR7hR n336N5LQ7XJB7fzjt1gR2XYuRao9ooa4rlJpAZ9siTgnS7x7hW1RjjN5pNWNEKKp1Btj8nPf1TPYw 3DuaqqPXw==; 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 1gxSqW-00059i-Pl; Sat, 23 Feb 2019 08:39:44 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 0185F20259708; Sat, 23 Feb 2019 09:39:42 +0100 (CET) Date: Sat, 23 Feb 2019 09:39:42 +0100 From: Peter Zijlstra To: hpa@zytor.com Cc: Thomas Gleixner , Linus Torvalds , Julien Thierry , Will Deacon , Andy Lutomirski , Ingo Molnar , Linux List Kernel Mailing , "linux-alpha@vger.kernel.org" , Ingo Molnar , Catalin Marinas , James Morse , valentin.schneider@arm.com, Brian Gerst , Josh Poimboeuf , Andrew Lutomirski , Borislav Petkov , Denys Vlasenko Subject: Re: [RFC][PATCH] objtool: STAC/CLAC validation Message-ID: <20190223083942.GF32477@hirez.programming.kicks-ass.net> References: <9e037d68-75e7-1beb-0c9c-33a7ffeced1b@zytor.com> <20190219090409.GW32494@hirez.programming.kicks-ass.net> <20190219124808.GG8501@fuggles.cambridge.arm.com> <20190222222635.GK14054@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 22, 2019 at 03:39:48PM -0800, hpa@zytor.com wrote: > Objtool could also detect CLAC-STAC or STAC-CLAC sequences without > memory operations and remove them; don't know how often that happens, > but I know it *does* happen. Objtool doesn't know about memops; that'd be a lot of work. Also, objtool doesn't actually rewrite the text, at best it could warn about such occurences.