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=-7.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS 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 B65E4C2D0A3 for ; Thu, 12 Nov 2020 05:51:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4EE5B20825 for ; Thu, 12 Nov 2020 05:51:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="gLQTpc2O" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726457AbgKLFvG (ORCPT ); Thu, 12 Nov 2020 00:51:06 -0500 Received: from mail.kernel.org ([198.145.29.99]:36062 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726291AbgKLFu7 (ORCPT ); Thu, 12 Nov 2020 00:50:59 -0500 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C7330208FE; Thu, 12 Nov 2020 05:50:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605160258; bh=sUnEyP4i6nDSMic8kwaWeggT//BLpHV2h10fY8zdYd8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=gLQTpc2Om076jzZ2cdtYFaQ+4osWtLdUGUcdj7ojc9LF4srcwRlNtfD6iPUZGJ9D8 din+LaswQmwYc9PwMCkj2/dgnJYZ/LRBr4nbOp1y+DMveSFP7eSNLRztfc7A5sR6ov +Lva9Sr0QZvzV+5ppr2DaNqrjnDinoL+fbLFsLs0= Date: Thu, 12 Nov 2020 14:50:55 +0900 From: Masami Hiramatsu To: Chen Yu Cc: Linux Kernel Mailing List , Chen Yu Subject: Re: bootconfig length parse error in kernel Message-Id: <20201112145055.0029e5ca5973618a6cf2d887@kernel.org> In-Reply-To: References: <20201111183742.e7c90597216343d9d2ffcb4e@kernel.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Chen, On Thu, 12 Nov 2020 12:34:36 +0800 Chen Yu wrote: > Hi Masami, > > On Wed, Nov 11, 2020 at 5:37 PM Masami Hiramatsu wrote: > > > > Hi Chen, > > > > On Tue, 10 Nov 2020 23:39:53 +0800 > > Chen Yu wrote: > > > > > Hi Masami, > > > Thanks for writing bootconfig and it is useful for boot up trace event > > > debugging. > > > > Thanks for testing! > > > > > However it was found that on 5.10-rc2 the bootconfig does not work and it shows > > > "'bootconfig' found on command line, but no bootconfig found" > > > And the reason for this is the kernel found the magic number to be incorrect. > > > I've added some hack in kernel to dump the first 12 bytes, it shows: > > > "OTCONFIG". So printed more content ahead we can find > > > "#BOOTCONFIG" ahead. So it looks that there is some alignment during > > > initrd load, and get_boot_config_from_initrd() might also deal with it. That is > > > to say: > > > data = (char *)initrd_end - BOOTCONFIG_MAGIC_LEN; > > > might do some alignment? > > > > Hrm, interesting. So initrd_end might be aligned. Could you print out the > > actuall address of initrd_end? > I've done some investigation, it looks like this issue is not related > to alignment, but related to > the bootloader that has provided an inaccurate ramdisk size via > boot_params.hdr.ramdisk_size. Yeah, it seems to happen. bootloader can pass wrong (bigger) size to kernel. BTW, what bootloader would you use? > The actual size of initrd is: > ls /boot/initrd.img-5.10.0-rc3-e1000e-hw+ -l > -rw-r--r-- 1 root root 48689230 11月 12 00:08 > /boot/initrd.img-5.10.0-rc3-e1000e-hw+ > while the ramdisk size provided by bootloader via > boot_params.hdr.ramdisk_size is > 48689232, which is 2 bytes bigger than the actual size, and this is > why the initrd_end > is bigger than expected and causing the missmatch of magic number. OK. It seems that the bootloader might cut it up to 16 bytes aligned. (But I think that's wrong behavior, there is no reason to do it) > Since there is no guarantee that bootloader provides the accurate > ramdisk size, an compromised > proposal might be that to search for the magic number a little ahead. If the bootloader does such wrong behavior, there is no guarantee that the size is "a little" bigger. IOW, it can be aligned to the page size (4KB-) > For example, the > following patch works for me: > diff --git a/init/main.c b/init/main.c > index 130376ec10ba..60fb125d44f4 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -273,7 +273,10 @@ static void * __init > get_boot_config_from_initrd(u32 *_size, u32 *_csum) > if (!initrd_end) > return NULL; > > - data = (char *)initrd_end - BOOTCONFIG_MAGIC_LEN; > + data = memchr((char *)initrd_end - 2 * BOOTCONFIG_MAGIC_LEN, > + '#', BOOTCONFIG_MAGIC_LEN); > + if (!data) > + return NULL; So this also does not guarantee that we can find "#" in BOOTCONFIG_MAGIC_LEN. We need to find actual code in the bootloader, what it does. > if (memcmp(data, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN)) > return NULL; > > > > And could you tell me which platform are you tested? > > > It is HP ZHAN 99 Mobile Workstation G1 with i5-8300H, Ubuntu 20.04. Hmm, this means x86 Grub2 does this change. Let me check it. Thank you, -- Masami Hiramatsu