From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752945Ab2A1PLb (ORCPT ); Sat, 28 Jan 2012 10:11:31 -0500 Received: from mail-yw0-f46.google.com ([209.85.213.46]:36199 "EHLO mail-yw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752715Ab2A1PLa (ORCPT ); Sat, 28 Jan 2012 10:11:30 -0500 Message-ID: <1327763490.16907.1.camel@lappy> Subject: Re: BUG: unable to handle kernel paging request at ffffc7ff81000398 (sys_kexec_load) From: Sasha Levin To: "Eric W. Biederman" Cc: Dave Jones , kexec@lists.infradead.org, linux-kernel Date: Sat, 28 Jan 2012 10:11:30 -0500 In-Reply-To: References: <1327212367.32115.4.camel@lappy> Content-Type: text/plain; charset="us-ascii" X-Mailer: Evolution 3.2.2 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 2012-01-21 at 20:49 -0800, Eric W. Biederman wrote: > Interesting. > > The fact that this happens in native_set_pte would suggest that we are > trying to write to a page table that does not exist. So this might > be a layer below kexec_load that has the problem. > > Do you have the kernel you were testing? A disassembly of the > native_set_pte, machine_kexec_prepare and sys_kexec_load > would be interesting, for attempting to trace this back to what went > wrong. I did some work into investigating it today, looks like it's simple to trigger it using the following code: #include int main(void) { char dummy[4096] = {0}; syscall(246, 0xffffffff81008000, 1, dummy, 2); return 0; } I'll continue trying to figure out whats wrong, but hopefully this lead will help in reproducing it easily. -- Sasha.