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,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 EEE00C43381 for ; Fri, 8 Mar 2019 21:34:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BF19C20652 for ; Fri, 8 Mar 2019 21:34:32 +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="r5fmDJPb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726687AbfCHVeb (ORCPT ); Fri, 8 Mar 2019 16:34:31 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:47678 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726388AbfCHVea (ORCPT ); Fri, 8 Mar 2019 16:34:30 -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=CxB8s96WjghhiesOt5ydVNCuiwaAMnUIxwjNAKFzIeQ=; b=r5fmDJPb2lVy/CXQoQTgE8OdX rsD8rfaVhOJXNDqQxsWQv7aN95BTuUTrAFRCrVTKif+pfd8HMmDKFqf8pXei/116oLGklmoRHptLf Ds/RlzO8MViDL3tzGVmQp0c1qxXI/i+Q2kL8KW2PB9IGkArKQpLCWsWWufnxlw+ND/NIQji6pOjo8 sddRitabkt0R2J5W/Tk6RaktvEc40upTuXSwjahZuxqtgVcrpomHPnkow79jUhhGimYyFOXQRXrCs fYU8qPjCgjGmEoq3VYwiGkzuK58waJMbenl6R2PA9PtHZFbX8277e36bCQbtDp9nwpFvglNwm42e0 N5wXo4QEw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1h2N8H-00027H-0R; Fri, 08 Mar 2019 21:34:21 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id D4112981BBE; Fri, 8 Mar 2019 22:34:18 +0100 (CET) Date: Fri, 8 Mar 2019 22:34:18 +0100 From: Peter Zijlstra To: Josh Poimboeuf Cc: torvalds@linux-foundation.org, tglx@linutronix.de, hpa@zytor.com, julien.thierry@arm.com, will.deacon@arm.com, luto@amacapital.net, mingo@kernel.org, catalin.marinas@arm.com, james.morse@arm.com, valentin.schneider@arm.com, brgerst@gmail.com, luto@kernel.org, bp@alien8.de, dvlasenk@redhat.com, linux-kernel@vger.kernel.org, dvyukov@google.com, rostedt@goodmis.org Subject: Re: [PATCH 16/20] objtool: Rewrite alt->skip_orig Message-ID: <20190308213418.GF2482@worktop.programming.kicks-ass.net> References: <20190307114511.870090179@infradead.org> <20190307115200.515578829@infradead.org> <20190308201510.4luzked52x3sdezg@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190308201510.4luzked52x3sdezg@treble> 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, Mar 08, 2019 at 02:15:56PM -0600, Josh Poimboeuf wrote: > On Thu, Mar 07, 2019 at 12:45:27PM +0100, Peter Zijlstra wrote: > > Really skip the original instruction flow, instead of letting it > > continue with NOPs. > > > > Since the alternative code flow already continues after the original > > instructions, only the alt-original is skipped. > > I like this approach. I wonder if we can do something similar to get > rid of the nasty fake jumps. This actually hard relies on those fake jumps. Or am I missing the point?