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 27731C61082 for ; Mon, 8 Jul 2019 04:11:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EEE3C20659 for ; Mon, 8 Jul 2019 04:11:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725905AbfGHELL (ORCPT ); Mon, 8 Jul 2019 00:11:11 -0400 Received: from linux.microsoft.com ([13.77.154.182]:48100 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725781AbfGHELL (ORCPT ); Mon, 8 Jul 2019 00:11:11 -0400 Received: from [192.168.1.8] (c-67-168-100-174.hsd1.wa.comcast.net [67.168.100.174]) by linux.microsoft.com (Postfix) with ESMTPSA id 72B8820B7185; Sun, 7 Jul 2019 21:11:10 -0700 (PDT) Subject: Re: [PATCH] tpm: Document UEFI event log quirks To: Jarkko Sakkinen , linux-kernel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-doc@vger.kernel.org Cc: tweek@google.com, matthewgarrett@google.com, Jonathan Corbet References: <20190703161109.22935-1-jarkko.sakkinen@linux.intel.com> From: Jordan Hand Message-ID: <33ff21e2-1e27-cc85-0ea3-5127cb2598ba@linux.microsoft.com> Date: Sun, 7 Jul 2019 21:10:48 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On 7/5/19 3:26 AM, Jarkko Sakkinen wrote: > On Wed, 2019-07-03 at 10:08 -0700, Jordan Hand wrote: >>> +This introduces another problem: nothing guarantees that it is not >>> +called before the stub gets to run. Thus, it needs to copy the final >>> +events table preboot size to the custom configuration table so that >>> +kernel offset it later on. >> >> This doesn't really explain what the size will be used for. Matthew's >> patch description for "tpm: Don't duplicate events from the final event >> log in the TCG2 log" outlines this well. You could maybe word it >> differently but I think the information is necessary: >> >> "We can avoid this problem by looking at the size of the Final Event Log >> just before we call ExitBootServices() and exporting this to the main >> kernel. The kernel can then skip over all events that occured before >> ExitBootServices() and only append events that were not also logged to >> the main log." > > Not exactly sure what is missing from my paragraph. The way I see it has > more information as it states what is used at as the vessel for > exportation (the custom configuration table). > > Maybe something like: > > "Thus, it nees to save the final events table size at the time to the > custom configuration table so that the TPM driver can later on skip the > events generated during the preboot time." > Yes, that sounds more clear to me. Thanks, Jordan