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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 D7AF0C43441 for ; Wed, 10 Oct 2018 18:56:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9DB702087D for ; Wed, 10 Oct 2018 18:56:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9DB702087D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.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 S1727152AbeJKCTj (ORCPT ); Wed, 10 Oct 2018 22:19:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:40062 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726734AbeJKCTj (ORCPT ); Wed, 10 Oct 2018 22:19:39 -0400 Received: from gandalf.local.home (cpe-66-24-56-78.stny.res.rr.com [66.24.56.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8F9C32085B; Wed, 10 Oct 2018 18:56:10 +0000 (UTC) Date: Wed, 10 Oct 2018 14:56:08 -0400 From: Steven Rostedt To: Josh Poimboeuf Cc: Andy Lutomirski , Peter Zijlstra , LKML , Linus Torvalds , Ingo Molnar , Andrew Morton , Thomas Gleixner , Masami Hiramatsu , Mathieu Desnoyers , Matthew Helsley , "Rafael J. Wysocki" , David Woodhouse , Paolo Bonzini , Jason Baron , Jiri Kosina , Ard Biesheuvel , Andrew Lutomirski Subject: Re: [POC][RFC][PATCH 1/2] jump_function: Addition of new feature "jump_function" Message-ID: <20181010145608.2094d254@gandalf.local.home> In-Reply-To: <20181010183330.ootwmz6deazg2k2n@treble> References: <20181006093905.46276505@vmware.local.home> <20181008072134.GB5663@hirez.programming.kicks-ass.net> <20181008155757.GC5663@hirez.programming.kicks-ass.net> <20181009021710.qwt5hpntyeps44h3@treble> <20181008235750.59da83ae@gandalf.local.home> <20181010175237.e7m3sldcu2maoqcq@treble> <20181010181605.arsyjxwdztztrjih@treble> <20181010183330.ootwmz6deazg2k2n@treble> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 10 Oct 2018 13:33:30 -0500 Josh Poimboeuf wrote: > Re-reading your suggestion, I may have misunderstood what you're > suggesting here, but I'm thinking about doing something like what you > proposed earlier: > > GLOBAL(tramp) > jmp *current_func(%rip) > ENDPROC(tramp) > > That is, doing an indirect jump instead of the above direct jump, so > that any previous references to the trampoline would still work (and it > would also work during early boot). > > Though it should probably be a retpoline instead of an indirect jump. But do we care, as it only takes place during text_poke_bp() right? I don't think we need to worry about training trampoline branch prediction that can only be hit when something enables the jump. -- Steve