From patchwork Tue Apr 9 19:15:48 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Jesse Larrew X-Patchwork-Id: 235191 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id CCC862C00BD for ; Wed, 10 Apr 2013 05:23:28 +1000 (EST) Received: from localhost ([::1]:33512 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UPe8c-0005GA-Mf for incoming@patchwork.ozlabs.org; Tue, 09 Apr 2013 15:23:26 -0400 Received: from eggs.gnu.org ([208.118.235.92]:41560) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UPe8K-0005Em-Hm for qemu-devel@nongnu.org; Tue, 09 Apr 2013 15:23:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UPe8J-0005Y1-Gy for qemu-devel@nongnu.org; Tue, 09 Apr 2013 15:23:08 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:44832) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UPe8J-0005Xr-A8 for qemu-devel@nongnu.org; Tue, 09 Apr 2013 15:23:07 -0400 Received: from /spool/local by e33.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Tue, 9 Apr 2013 13:16:21 -0600 Received: from d03relay02.boulder.ibm.com (d03relay02.boulder.ibm.com [9.17.195.227]) by d03dlp01.boulder.ibm.com (Postfix) with ESMTP id 4DC861FF0051; Tue, 9 Apr 2013 13:11:13 -0600 (MDT) Received: from d03av06.boulder.ibm.com (d03av06.boulder.ibm.com [9.17.195.245]) by d03relay02.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r39JG2oT034238; Tue, 9 Apr 2013 13:16:03 -0600 Received: from d03av06.boulder.ibm.com (loopback [127.0.0.1]) by d03av06.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r39JIaf8009086; Tue, 9 Apr 2013 13:18:36 -0600 Received: from jlarrew.austin.ibm.com (jlarrew.austin.ibm.com [9.41.149.149]) by d03av06.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id r39JIZlZ009022; Tue, 9 Apr 2013 13:18:35 -0600 Message-ID: <516468E4.7020007@linux.vnet.ibm.com> Date: Tue, 09 Apr 2013 14:15:48 -0500 From: Jesse Larrew User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130311 Thunderbird/17.0.4 MIME-Version: 1.0 To: li guang References: <1365474461-17474-1-git-send-email-lig.fnst@cn.fujitsu.com> <51639ACE.8020505@linux.vnet.ibm.com> <1365483900.9553.8.camel@liguang.fnst.cn.fujitsu.com> In-Reply-To: <1365483900.9553.8.camel@liguang.fnst.cn.fujitsu.com> X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13040919-2398-0000-0000-0000131A96A3 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.4.x-2.6.x [generic] X-Received-From: 32.97.110.151 Cc: qemu-trivial@nongnu.org, Stefan Hajnoczi , Anthony Liguori , qemu-devel@nongnu.org Subject: Re: [Qemu-devel] [PATCH v3] hw/i386/pc: prompt not multboot or morden kernel image X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org On 04/09/2013 12:05 AM, li guang wrote: > 在 2013-04-08一的 23:36 -0500，Jesse Larrew写道： >> On 04/08/2013 09:27 PM, liguang wrote: >>> if head magic is missing or wrong unexpectedly, we'd >>> better to prompt memssage for this. >>> e.g. >>> I make a mistake to boot a vmlinuz for MIPS(which >>> I think it's for x86) like this: >>> qemu-system-x86_64 -kernel vmlinuz -initrd demord >>> then qemu report: >>> "qemu: linux kernel too old to load a ram disk" >>> that's misleading. >>> >> >> Yes, that message would definitely be misleading in this case. >> >>> Signed-off-by: liguang >>> --- >>> hw/i386/pc.c | 2 ++ >>> 1 files changed, 2 insertions(+), 0 deletions(-) >>> >>> diff --git a/hw/i386/pc.c b/hw/i386/pc.c >>> index ebbf059..6b29c3f 100644 >>> --- a/hw/i386/pc.c >>> +++ b/hw/i386/pc.c >>> @@ -686,6 +686,8 @@ static void load_linux(void *fw_cfg, >>> if (load_multiboot(fw_cfg, f, kernel_filename, initrd_filename, >>> kernel_cmdline, kernel_size, header)) { >>> return; >>> + } else { >>> + fprintf(stderr, "warn: invalid multiboot or modern kernel image\n"); >>> } >>> protocol = 0; >>> } >>> >> >> My impression from reading through the code is that this branch can be >> legitimately triggered by an older kernel (protocol < 0x200). > > right. > >> In that case,the error message above would also be misleading. > > the warning message is saying: hey, we prefer modern kernel image > or multiboot, but you specify neither, what are you doing? > do you want to boot an old(obsolete) kernel? > > or, add a line like fprintf(stderr, "do you boot an old kernel?\n") :-) > Ah, I understand now. Thanks for explaining that. :) >> >> I think a better solution might be to simply validate that the arch >> specified in the ELF header matches the arch that qemu is emulating. >> I'll look into this more tomorrow morning. :) > > that's fine > Looking at Documentation/x86/boot.txt in the kernel source, it looks like there is a separate word of header magic that all x86 kernels should have -- even the oldest images. Adding a separate check for that magic might be a more complete solution: --- hw/i386/pc.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/hw/i386/pc.c b/hw/i386/pc.c index 8d75b34..e120427 100644 --- a/hw/i386/pc.c +++ b/hw/i386/pc.c @@ -686,6 +686,14 @@ static void load_linux(void *fw_cfg, if (load_multiboot(fw_cfg, f, kernel_filename, initrd_filename, kernel_cmdline, kernel_size, header)) { return; + } else { + /* This is the closest thing old Linux kernels have to a + magic number. */ + if (lduw_p(header+0x01FE) != 0xAA55) { + fprintf(stderr, "qemu: '%s' is not an x86 kernel image.\n", + kernel_filename); + exit(1); + } } protocol = 0; }