Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751356AbVK2N1o (ORCPT ); Tue, 29 Nov 2005 08:27:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751355AbVK2N1o (ORCPT ); Tue, 29 Nov 2005 08:27:44 -0500 Received: from e32.co.us.ibm.com ([32.97.110.150]:14985 "EHLO e32.co.us.ibm.com") by vger.kernel.org with ESMTP id S1751356AbVK2N1n (ORCPT ); Tue, 29 Nov 2005 08:27:43 -0500 Date: Tue, 29 Nov 2005 18:57:30 +0530 From: Vivek Goyal To: "Eric W. Biederman" Cc: Fernando Luis Vazquez Cao , fastboot@lists.osdl.org, linux-kernel@vger.kernel.org Subject: Re: [Fastboot] Re: [PATCH & RFC] kdump and stack overflows Message-ID: <20051129132730.GA3803@in.ibm.com> Reply-To: vgoyal@in.ibm.com References: <1133183463.2327.96.camel@localhost.localdomain> <1133200815.2425.98.camel@localhost.localdomain> 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: 1790 Lines: 46 On Mon, Nov 28, 2005 at 11:29:29AM -0700, Eric W. Biederman wrote: > Fernando Luis Vazquez Cao writes: > > > On Mon, 2005-11-28 at 06:39 -0700, Eric W. Biederman wrote: > >> Fernando Luis Vazquez Cao writes: > > > Regarding the stack overflow audit of the nmi path, we have the problem > > that both nmi_enter and nmi_exit in do_nmi (see code below) make heavy > > use of "current" indirectly (specially through the kernel preemption > > code). > > Ok. I wonder if it would be saner to simply replace the nmi trap > handler on the crash dump path? > Sounds interesting. > >> I believe we have a separate interrupt stack that > >> should help but.. > > Yes, when using 4K stacks we have a separate interrupt stack that should > > help, but I am afraid that crash dumping is about being paranoid. > > Oh I agree. If we had a private 4K stack for the nmi handler we > would not need to worry about overflow in that case. Having private 4K stack makes sense as crash_nmi_callback() itself requires quite some space on stack. If one has enabled CONFIG_4KSTACKS, then we use separate interrupt stack and we are probably safe from stack overflows but otherwise we need it. > (baring > nmi happening during nmis) Hmm. Is there anything to keep > us doing something bad in that case? > > I guess as long as we don't clear the high bit of port 0x70 we > should be reasonably safe from the nmi firing multiple times. Are you referring to port 0x23 for IMCR register. Thanks Vivek - 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/