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=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 E4912C433E6 for ; Wed, 10 Feb 2021 17:08:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9B95A64E15 for ; Wed, 10 Feb 2021 17:08:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232014AbhBJRIl (ORCPT ); Wed, 10 Feb 2021 12:08:41 -0500 Received: from www262.sakura.ne.jp ([202.181.97.72]:61123 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232107AbhBJRIK (ORCPT ); Wed, 10 Feb 2021 12:08:10 -0500 Received: from fsav302.sakura.ne.jp (fsav302.sakura.ne.jp [153.120.85.133]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 11AH7QGZ037842; Thu, 11 Feb 2021 02:07:26 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav302.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav302.sakura.ne.jp); Thu, 11 Feb 2021 02:07:26 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav302.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 11AH7QoT037837 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Thu, 11 Feb 2021 02:07:26 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [PATCH 0/3][RESEND] add support for never printing hashed addresses To: Steven Rostedt Cc: Timur Tabi , Petr Mladek , Sergey Senozhatsky , Vlastimil Babka , Andy Shevchenko , Matthew Wilcox , akpm@linux-foundation.org, Linus Torvalds , roman.fietze@magna.com, Kees Cook , John Ogness , akinobu.mita@gmail.com, glider@google.com, Andrey Konovalov , Marco Elver , Rasmus Villemoes , Pavel Machek , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20210210051814.845713-1-timur@kernel.org> <6da0be5a-7cb0-4943-e61f-7c3275e60cb6@i-love.sakura.ne.jp> <20210210111836.2468f10a@gandalf.local.home> <20210210114633.1b755f6e@gandalf.local.home> From: Tetsuo Handa Message-ID: Date: Thu, 11 Feb 2021 02:07:21 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210210114633.1b755f6e@gandalf.local.home> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/02/11 1:46, Steven Rostedt wrote: > On Thu, 11 Feb 2021 01:39:41 +0900 > Tetsuo Handa wrote: > >> On 2021/02/11 1:18, Steven Rostedt wrote: >>> The point of this exercise is to be able to debug the *same* kernel that >>> someone is having issues with. And this is to facilitate that debugging. >> >> That's too difficult to use. If a problem is not reproducible, we will have >> no choice but always specify "never hash pointers" command line option. If a >> problem is reproducible, we can rebuild that kernel with "never hash pointers" >> config option turned on. > > Now the question is, why do you need the unhashed pointer? Because unhashed pointers might give some clue. We can rebuild the same kernel using the same kernel config / compiler etc. and compare unhashed pointers with addresses in System.map / kallsyms files without reproducing the problem. > > Currently, the instruction pointer is what is fine right? You get the > a function and its offset. If there's something that is needed, perhaps we > should look at how to fix that, instead of just unhashing all pointers by > default. I'm not refusing to use kernel command line options. I'm expecting that we can also hardcode using kernel config options. Since boot-time switching via kernel command line options makes the kernel behave differently, less boot-time switching is better for avoiding unexpected problems (e.g. unintended LSM was enabled).