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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 99757C3A5A5 for ; Thu, 5 Sep 2019 13:23:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9D534206CD for ; Thu, 5 Sep 2019 13:23:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732933AbfIENXv (ORCPT ); Thu, 5 Sep 2019 09:23:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56044 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731733AbfIENXv (ORCPT ); Thu, 5 Sep 2019 09:23:51 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0B66B190C10E; Thu, 5 Sep 2019 13:23:51 +0000 (UTC) Received: from treble (ovpn-120-170.rdu2.redhat.com [10.10.120.170]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 51A725D9E1; Thu, 5 Sep 2019 13:23:47 +0000 (UTC) Date: Thu, 5 Sep 2019 08:23:44 -0500 From: Josh Poimboeuf To: Jiri Kosina Cc: Petr Mladek , Joe Lawrence , Miroslav Benes , linux-kernel@vger.kernel.org, live-patching@vger.kernel.org Subject: Re: [RFC PATCH 2/2] livepatch: Clear relocation targets on a module removal Message-ID: <20190905132344.byfybt6s42cajtfz@treble> References: <20190822223649.ptg6e7qyvosrljqx@treble> <20190823081306.kbkm7b4deqrare2v@pathway.suse.cz> <20190826145449.wyo7avwpqyriem46@treble> <5c649320-a9bf-ae7f-5102-483bc34d219f@redhat.com> <20190904084932.gndrtewubqiaxmzy@pathway.suse.cz> <20190905025055.36loaatxtkhdo4q5@treble> <20190905110955.wl4lwjbnpqybhkcn@pathway.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.70]); Thu, 05 Sep 2019 13:23:51 +0000 (UTC) Sender: live-patching-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On Thu, Sep 05, 2019 at 01:19:06PM +0200, Jiri Kosina wrote: > On Thu, 5 Sep 2019, Petr Mladek wrote: > > > > I don't have a number, but it's very common to patch a function which > > > uses jump labels or alternatives. > > > > Really? My impression is that both alternatives and jump_labels > > are used in hot paths. I would expect them mostly in core code > > that is always loaded. > > > > Alternatives are often used in assembly that we are not able > > to livepatch anyway. > > > > Or are they spread widely via some macros or inlined functions? > > All the indirect jumps are turned into alternatives when retpolines are in > place. Actually in C code those are done by the compiler as calls/jumps to __x86_indirect_thunk_*. But there are still a bunch of paravirt patched instructions and alternatives used throughout the kernel. -- Josh