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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C48EFCDB474 for ; Mon, 23 Oct 2023 11:45:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234413AbjJWLp3 (ORCPT ); Mon, 23 Oct 2023 07:45:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50022 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234390AbjJWLpN (ORCPT ); Mon, 23 Oct 2023 07:45:13 -0400 Received: from mgamail.intel.com (mgamail.intel.com [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 04BDEDB; Mon, 23 Oct 2023 04:45:11 -0700 (PDT) X-IronPort-AV: E=McAfee;i="6600,9927,10871"; a="385701223" X-IronPort-AV: E=Sophos;i="6.03,244,1694761200"; d="scan'208";a="385701223" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Oct 2023 04:45:11 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10871"; a="874681317" X-IronPort-AV: E=Sophos;i="6.03,244,1694761200"; d="scan'208";a="874681317" Received: from smile.fi.intel.com ([10.237.72.54]) by fmsmga002.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Oct 2023 04:45:08 -0700 Received: from andy by smile.fi.intel.com with local (Exim 4.97-RC2) (envelope-from ) id 1qutMn-00000007vRG-3QFa; Mon, 23 Oct 2023 14:45:05 +0300 Date: Mon, 23 Oct 2023 14:45:05 +0300 From: Andy Shevchenko To: Kees Cook Cc: Jan Kara , Baokun Li , Josh Poimboeuf , Nathan Chancellor , Nick Desaulniers , Kees Cook , Ferry Toth , linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org Subject: Re: [GIT PULL] ext2, quota, and udf fixes for 6.6-rc1 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Sat, Oct 21, 2023 at 04:36:19PM -0700, Kees Cook wrote: > On October 20, 2023 1:36:36 PM PDT, andy.shevchenko@gmail.com wrote: > >That said, if you or anyone has ideas how to debug futher, I'm all ears! > > I don't think this has been tried yet: > > When I've had these kind of hard-to-find glitches I've used manual > built-binary bisection. Assuming you have a source tree that works when built > with Clang and not with GCC: > - build the tree with Clang with, say, O=build-clang > - build the tree with GCC, O=build-gcc > - make a new tree for testing: cp -a build-clang build-test > - pick a suspect .o file (or files) to copy from build-gcc into build-test > - perform a relink: "make O=build-test" should DTRT since the copied-in .o > files should be newer than the .a and other targets > - test for failure, repeat > > Once you've isolated it to (hopefully) a single .o file, then comes the > byte-by-byte analysis or something similar... > > I hope that helps! These kinds of bugs are super frustrating. I'm sorry, but I can't see how this is not an error prone approach. If it's a timing issue then the arbitrary object change may help and it doesn't prove anything. As earlier I tried to comment out the error message, and it worked with GCC as well. The difference is so little (according to Linus) that it may not be suspectible. Maybe I am missing the point... -- With Best Regards, Andy Shevchenko