From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754112AbYIYIxz (ORCPT ); Thu, 25 Sep 2008 04:53:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752215AbYIYIxq (ORCPT ); Thu, 25 Sep 2008 04:53:46 -0400 Received: from terminus.zytor.com ([198.137.202.10]:42564 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751969AbYIYIxp (ORCPT ); Thu, 25 Sep 2008 04:53:45 -0400 Message-ID: <48DB5186.8060502@zytor.com> Date: Thu, 25 Sep 2008 01:53:26 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Ingo Molnar CC: Vegard Nossum , x86@kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner Subject: Re: v2.6.27-rc7: x86: #GP on panic? References: <19f34abd0809241209l3a69d607v153549ee43e085e9@mail.gmail.com> <20080925080417.GB27048@elte.hu> In-Reply-To: <20080925080417.GB27048@elte.hu> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ingo Molnar wrote: > * Vegard Nossum wrote: > >> Hi, >> >> With 2.6.27-rc7 on qemu-x86_64, it seems that panic will trigger a >> General Protection Fault. I haven't seen it before. > >> [ 4.523641] Code: eb fd 55 48 89 e5 53 51 83 3d 25 e8 78 00 00 75 >> 1a 31 d2 31 f6 48 c7 c7 e1 9c 01 81 e8 f7 a4 03 00 9c 5b fa e8 94 09 >> 00 00 53 9d <5a> 5b c9 c3 55 31 c0 48 89 e5 89 04 25 b0 c0 5f ff 65 83 >> 04 25 > > hm, 0x5a is a simple pop %rdx. A #GP there means the stack segment is > bust? > No, that would be #SS (and segments don't really exist in 64-bit mode anyway.) In 32-bit mode it could mean a code segment overrun. *However*... [ 4.523477] general protection fault: fff2 [1] SMP There is an error code attached to the #GP, which is supposed to mean that somehow a segment selector was involved. This doesn't look like a very valid segment selector at all. > hm: > >> ffffffff8101a6b9 >> ffffffff81019d25: 53 push %rbx >> ffffffff81019d26: 9d popfq >> ffffffff81019d27: 5a pop %rdx > > so it's preceded by a popfq and on the next instruction we #GP. > > but the stack and flags state looks good: > > [ 4.523641] RSP: 0018:ffff880007867d70 EFLAGS: 00000286 > My guess is that the popfq enables interrupts, and we try to take an interrupt through an IDT entry which isn't set up correctly. -hpa