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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 BD9C6C3A5A5 for ; Thu, 5 Sep 2019 11:32:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8DB4322CEC for ; Thu, 5 Sep 2019 11:32:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567683151; bh=Y+myvtaL/wVtidX/HGF2iJ5MxtkmherpGfkJw9XyNpI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=02t5OgI3zqfDswTfSqQS+oJ8zhgjNJ1w76d/C07BZJBjabzWD3UcezWJ/7yF6mLnn pCt+oftLk+lcYJ3XqmI5kYdjznirS8SlKLZefU2GHUp3fpSfO2w4aiLU8lJcD1UCP4 RttNQfu3KEBCEoC4NtqQlm4lVJ2jj9M0h/P27tkk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388549AbfIELca (ORCPT ); Thu, 5 Sep 2019 07:32:30 -0400 Received: from mail.kernel.org ([198.145.29.99]:35538 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733226AbfIELca (ORCPT ); Thu, 5 Sep 2019 07:32:30 -0400 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (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 9A0B92070C; Thu, 5 Sep 2019 11:32:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567683149; bh=Y+myvtaL/wVtidX/HGF2iJ5MxtkmherpGfkJw9XyNpI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=fQ2pxKWhksD2CMPVfQNcHYobKtpPfkh2PKa4YujwIMyaCVYwLoqBvhennaA8SVflm R9qs0Vv7rIyRfbig0j3hXq/kINB3MvWzLvOzxi68MnM/ekvP7JK/QJJ7LLKSiIBvt5 2XV21+pxjeh1LIhtWyY4qv3ZlRFs2OtjL6I20LdA= Date: Thu, 5 Sep 2019 20:32:24 +0900 From: Masami Hiramatsu To: Andrew Cooper Cc: Ingo Molnar , Juergen Gross , "Stefano Stabellini" , Peter Zijlstra , Randy Dunlap , , , Borislav Petkov , "Josh Poimboeuf" , , "Boris Ostrovsky" Subject: Re: [Xen-devel] [PATCH -tip 0/2] x86: Prohibit kprobes on XEN_EMULATE_PREFIX Message-Id: <20190905203224.e41d7f3dfbf918c5031f9766@kernel.org> In-Reply-To: <1372ce73-e2d8-6144-57df-a98429587826@citrix.com> References: <156759754770.24473.11832897710080799131.stgit@devnote2> <20190905104937.60aa03f699a9c0fbf1b651b9@kernel.org> <1372ce73-e2d8-6144-57df-a98429587826@citrix.com> X-Mailer: Sylpheed 3.5.1 (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 Thu, 5 Sep 2019 08:54:17 +0100 Andrew Cooper wrote: > On 05/09/2019 02:49, Masami Hiramatsu wrote: > > On Wed, 4 Sep 2019 12:54:55 +0100 > > Andrew Cooper wrote: > > > >> On 04/09/2019 12:45, Masami Hiramatsu wrote: > >>> Hi, > >>> > >>> These patches allow x86 instruction decoder to decode > >>> xen-cpuid which has XEN_EMULATE_PREFIX, and prohibit > >>> kprobes to probe on it. > >>> > >>> Josh reported that the objtool can not decode such special > >>> prefixed instructions, and I found that we also have to > >>> prohibit kprobes to probe on such instruction. > >>> > >>> This series can be applied on -tip master branch which > >>> has merged Josh's objtool/perf sharing common x86 insn > >>> decoder series. > >> The paravirtualised xen-cpuid is were you'll see it most in a regular > >> kernel, but be aware that it is also used for testing purposes in other > >> circumstances, and there is an equivalent KVM prefix which is used for > >> KVM testing. > > Good catch! I didn't notice that. Is that really same sequance or KVM uses > > another sequence of instructions for KVM prefix? > > I don't know if you've spotted, but the prefix is a ud2a instruction > followed by 'xen' in ascii. > > The KVM version was added in c/s 6c86eedc206dd1f9d37a2796faa8e6f2278215d2 > Ah, OK. I see it. But it seems that another ud0/ud1 can be used by other (new) virtualization. So at this moment I will just add a sequence as a pattern of prefix. Not use a fixed ud2 + sig. Thank you, > > > >> It might be better to generalise the decode support to "virtualisation > >> escape prefix" or something slightly more generic. > > Agreed, it is easy to expand it, we can switch the prefix template. > > Could you tell me where I should look? I will add it. > > These are the only two I'm aware of. > > ~Andrew -- Masami Hiramatsu