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_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 A440BC282E0 for ; Fri, 19 Apr 2019 19:12:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 789AC2064A for ; Fri, 19 Apr 2019 19:12:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729455AbfDSTMe (ORCPT ); Fri, 19 Apr 2019 15:12:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45626 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726075AbfDSTMb (ORCPT ); Fri, 19 Apr 2019 15:12:31 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 25709307E055; Fri, 19 Apr 2019 10:55:35 +0000 (UTC) Received: from localhost (ovpn-12-186.pek2.redhat.com [10.72.12.186]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7C6B160BE2; Fri, 19 Apr 2019 10:55:32 +0000 (UTC) Date: Fri, 19 Apr 2019 18:55:29 +0800 From: Baoquan He To: Borislav Petkov Cc: Kairui Song , Thomas Gleixner , linux-kernel@vger.kernel.org, Junichi Nomura , Dave Young , Chao Fan , "x86@kernel.org" , "kexec@lists.infradead.org" Subject: Re: [RFC PATCH] kexec, x86/boot: map systab region in identity mapping before accessing it Message-ID: <20190419105529.GF11060@MiWiFi-R3L-srv> References: <20190419101733.GA10324@zn.tnic> <20190419105014.GE11060@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190419105014.GE11060@MiWiFi-R3L-srv> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Fri, 19 Apr 2019 10:55:35 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/19/19 at 06:50pm, Baoquan He wrote: > On 04/19/19 at 12:17pm, Borislav Petkov wrote: > > Breaking thread because this one got too big. > > > > On Fri, Apr 19, 2019 at 04:34:58PM +0800, Kairui Song wrote: > > > There are two approach to fix it, detect if the systab is mapped, and > > > avoid reading it if not. > > > > Ok, so tglx and I discussed this situation which is slowly getting out > > of hand with all the tinkering. > > > > So, here's what we should do - scream loudly now if some of this doesn't > > make any sense. > > > > 1. Junichi's patch should get the systab check above added and sent to > > 5.1 so that at least some EFI kexecing can work with 5.1 > > Talked with Kairui privately just now. Seems Junichi's patch need add > this systab mapping. Since the systab region is not mapped on some > machines. Those machine don't have this issue because they got systab > region luckily coverred by 1 GB page mapping in 1st kernel before > kexec jumping. > > This issue should happen whether it is KASLR kernel or not KASLR kernel. > > > > > 2. Then, the fact whether the kernel has been kexec'ed and which > > addresses it should use early, should all be passed through boot_params > > which is either setup by kexec(1) or by the first kernel itself, in the > > kexec_file_load() case. > > Seems no better way to check if it's kexec-ed kernel, except of the > setup data checking of kexec-ed kernel. > > It may happen in both kexec_load or kexec_file_load, since we build > ident mapping of kexec for RAM in 1st kernel. > > > > > > the systab region is not mapped by the identity mapping provided by > > > kexec. > > > > 3. Then that needs to be fixed in the first kernel as it is a > > shortcoming of us starting to parse systab very early. It is the kexec > > setup code's problem not the early compressed stage's problem that the > > EFI systab is not mapped. > > Yeah, adding the systab mapping looks good. Kairui put it in ^ in 1st kernel > decompressing stage just because he wants to cover the case in which the > old kernel kexec jumping to 2nd kernel. Now it seems not very > reasonable, we also have the new kernel kexec jumping to old 2nd kernel. > > Thanks > Baoquan