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 B87CCC433EF for ; Mon, 30 May 2022 09:31:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234773AbiE3Jb3 (ORCPT ); Mon, 30 May 2022 05:31:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53744 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233729AbiE3Jb2 (ORCPT ); Mon, 30 May 2022 05:31:28 -0400 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B032A6CAB1 for ; Mon, 30 May 2022 02:31:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1653903086; x=1685439086; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version; bh=RNo1VFn9TNhcSAwdGqSc/kbrNGzlnlE99QCowyLqR4c=; b=QdzTZAuWxkmY5K5sRLkwYkYQyUGYKwdw1FeqZL61F4y0z+n4iUE1Vdny Wv6S/nHg7FAstK1OthiSUzBQRDQp1/QiDxTX1OJWVhD3jUQpYQrY240yb mPREj2jEJYJwC0vujhKFkvPhgY1NWzi4sgcoPxO4cW1LjXbiaIGS4bSJn BusZOOH21ABLDJPIQcHcs4bRCh708KB9ySwXLpeujwlnCoMo5RYrmPtlB pu9GjLSC82cgmADg6gAkYIYe76pEi/g8w0hps53omrH+4YICgHkgj+8A7 UOH7PypfYUvg9br8yC32tLQBdyRps7Lg14rJkGwfJkXiOp4U4Xs1Gfo11 g==; X-IronPort-AV: E=McAfee;i="6400,9594,10362"; a="255438074" X-IronPort-AV: E=Sophos;i="5.91,262,1647327600"; d="scan'208";a="255438074" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 May 2022 02:31:26 -0700 X-IronPort-AV: E=Sophos;i="5.91,262,1647327600"; d="scan'208";a="706083847" Received: from jkuna-mobl.ger.corp.intel.com (HELO localhost) ([10.249.150.228]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 May 2022 02:31:20 -0700 From: Jani Nikula To: Linus Torvalds , Arnd Bergmann Cc: Sudip Mukherjee , Russell King , Viresh Kumar , Shiraz Hashim , Ville =?utf-8?B?U3lyasOkbMOk?= , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , dri-devel , Linux Kernel Mailing List , Linux ARM , SoC Team Subject: Re: mainline build failure due to f1e4c916f97f ("drm/edid: add EDID block count and size helpers") In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: Date: Mon, 30 May 2022 12:31:17 +0300 Message-ID: <87a6aztli2.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 28 May 2022, Linus Torvalds wrote: > On Sat, May 28, 2022 at 11:59 AM Arnd Bergmann wrote: >> >> It's CONFIG_ARM_AEABI, which is normally set everywhere. Without this >> option, you the kernel is built for the old 'OABI' that forces all non-packed >> struct members to be at least 16-bit aligned. > > Looks like forced word (32 bit) alignment to me. > > I wonder how many other structures that messes up, but I committed the > EDID fix for now. Thanks for the fix, and the thorough commit message! > This has presumably been broken for a long time, but maybe the > affected targets don't typically use EDID and kernel modesetting, and > only use some fixed display setup instead. > > Those structure definitions go back a _loong_ time (from a quick 'git > blame' I see November 2008). > > But despite that, I did not mark my fix 'cc:stable' because I don't > know if any of those machines affected by this bad arm ABI issue could > possibly care. > > At least my tree hopefully now builds on them, with the BUILD_BUG_ON() > that uncovered this. Indeed the bug is ancient. I just threw in the BUILD_BUG_ON() on a whim as an extra sanity check when doing pointer arithmetics on struct edid *. If there are affected machines, buffer overflows are the real danger due to edid->extensions indicating the number of extensions. BR, Jani. -- Jani Nikula, Intel Open Source Graphics Center