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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 463BBC55186 for ; Wed, 22 Apr 2020 10:45:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2D2D720787 for ; Wed, 22 Apr 2020 10:45:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731887AbgDVKpi (ORCPT ); Wed, 22 Apr 2020 06:45:38 -0400 Received: from mx2.suse.de ([195.135.220.15]:41066 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729907AbgDVKpg (ORCPT ); Wed, 22 Apr 2020 06:45:36 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 2C486ABD6; Wed, 22 Apr 2020 10:45:33 +0000 (UTC) Subject: Re: [PATCH 5.6 096/166] x86/xen: Make the boot CPU idle task reliable To: Greg Kroah-Hartman , linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org, Miroslav Benes , Sasha Levin References: <20200422095047.669225321@linuxfoundation.org> <20200422095059.319186761@linuxfoundation.org> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: <48afe770-83c3-03c0-c21f-334ab2056ea3@suse.com> Date: Wed, 22 Apr 2020 12:45:32 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200422095059.319186761@linuxfoundation.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22.04.20 11:57, Greg Kroah-Hartman wrote: > From: Miroslav Benes > > [ Upstream commit 2f62f36e62daec43aa7b9633ef7f18e042a80bed ] > > The unwinder reports the boot CPU idle task's stack on XEN PV as > unreliable, which affects at least live patching. There are two reasons > for this. First, the task does not follow the x86 convention that its > stack starts at the offset right below saved pt_regs. It allows the > unwinder to easily detect the end of the stack and verify it. Second, > startup_xen() function does not store the return address before jumping > to xen_start_kernel() which confuses the unwinder. > > Amend both issues by moving the starting point of initial stack in > startup_xen() and storing the return address before the jump, which is > exactly what call instruction does. > > Signed-off-by: Miroslav Benes > Reviewed-by: Juergen Gross > Signed-off-by: Juergen Gross > Signed-off-by: Sasha Levin You'll need upstream d6f34f4c6b4a96 ("x86/xen: fix booting 32-bit pv guest"), too. Juergen