Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750897AbVIWMBY (ORCPT ); Fri, 23 Sep 2005 08:01:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750898AbVIWMBX (ORCPT ); Fri, 23 Sep 2005 08:01:23 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:60119 "EHLO e32.co.us.ibm.com") by vger.kernel.org with ESMTP id S1750896AbVIWMBX (ORCPT ); Fri, 23 Sep 2005 08:01:23 -0400 Date: Fri, 23 Sep 2005 17:31:07 +0530 From: Vivek Goyal To: "Eric W. Biederman" Cc: Dave Anderson , Morton Andrew Morton , Fastboot mailing list , linux kernel mailing list , fastboot-bounces@lists.osdl.org Subject: Re: [Fastboot] [PATCH] Kdump(x86): add note type NT_KDUMPINFO tokernelcore dumps Message-ID: <20050923120107.GB7440@in.ibm.com> Reply-To: vgoyal@in.ibm.com References: <4332FD56.2F5256F5@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2241 Lines: 56 On Fri, Sep 23, 2005 at 01:12:23AM -0600, Eric W. Biederman wrote: > Dave Anderson writes: > > > So does elf_core_dump() as well, but to gdb it's useless AFAICT... > > We can always post_process things when generating a core dump > if we have enough information. > > > Hey -- I wasn't even aware of the "crashing_cpu" variable. > > That would work just fine. > > > > Still a "panic_task", and perhaps even a "crash_page_size" variable > > would be nice as well. No additional notes required... > > To avoid defining an ABI that we need to maintain there is some > benefit in simply using static variables. But the form of the > information really isn't the concern. > > Where we capture the information and how reliable is that capture > is the concern. > > To capture page size the easiest and most reliable way I can see > to do is to modify vmlinux.lds.S to contain something like: > > _page_shift = PAGE_SHIFT; > Giving you an absolute symbol _page_shift in vmlinux that > contains the value you need, without overhead in the running > kernel. That's a cool idea. I just tested it. [vivek@vivegoya linux]$ readelf -s vmlinux | grep __page_shift 28865: 0000000c 0 NOTYPE GLOBAL DEFAULT ABS __page_shift > > crashing_cpu makes sense to capture in some form, we definitely > need to compute something that will allow us to write to > a per cpu area on an SMP system. > > The big concern at this point is that the code has not undergone > a serious stability audit. So it is the expectation that there > is still code we can remove and modify to increase the likely hood > of getting a crash dump. > > Currently we know that stack overflows sometimes happen and that > they are a source of kernel crashes. It would be good if we could > take a crash dump despite them. To do that requires code more > robust than we have today. Quite likely it means that we will > not be able to reliably capture the task_struct of the crashing cpu. > Agreed. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/