Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750734AbWIUGyk (ORCPT ); Thu, 21 Sep 2006 02:54:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750743AbWIUGyk (ORCPT ); Thu, 21 Sep 2006 02:54:40 -0400 Received: from mtagate6.uk.ibm.com ([195.212.29.139]:15577 "EHLO mtagate6.uk.ibm.com") by vger.kernel.org with ESMTP id S1750734AbWIUGyj (ORCPT ); Thu, 21 Sep 2006 02:54:39 -0400 In-Reply-To: <20060920234517.GA29171@Krystal> Subject: Re: [PATCH] Linux Markers 0.4 (+dynamic probe loader) for 2.6.17 To: Mathieu Desnoyers Cc: Andrew Morton , Alan Cox , "Frank Ch. Eigler" , Greg Kroah-Hartman , Christoph Hellwig , Jes Sorensen , Paul Mundt , linux-kernel , ltt-dev@shafik.org, Masami Hiramatsu , Mathieu Desnoyers , Martin Bligh , Michel Dagenais , Ingo Molnar , prasanna@in.ibm.com, systemtap@sources.redhat.com, systemtap-owner@sourceware.org, Thomas Gleixner , William Cohen , Tom Zanussi X-Mailer: Lotus Notes Release 7.0.1 July 07, 2006 Message-ID: From: Richard J Moore Date: Thu, 21 Sep 2006 07:54:31 +0100 X-MIMETrack: Serialize by Router on D06ML065/06/M/IBM(Release 6.5.5HF607 | June 26, 2006) at 21/09/2006 07:56:50 MIME-Version: 1.0 Content-type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1435 Lines: 27 Matthieu, are you aware of the work done on generalized RAS hooks for linux? It was used in dprpbes, LTT and LKST at one time. That in its own way dealt with some of the issues you're trying to solve. I'm not saying it's the correct solution, but it shares a lot of common ground. Check out "kernel hooks" aka ghki. We used it to dynamically remove dprobes from the pagefault code path when no user probes were active. It was also used to instrument tracepoints for different facilities that needed to share instrumentation point. There was also a /proc interface that showed which hooks were installed and their status. We have generic mechanisms that would work across most architectures and optimized ones for specific architectures. One thing we tried to do was to make sure that affect on data cache was minimized or eliminated. We achieved that on IA32 by making the hook mechanism a test following a load of a literal into a register. The hook was activated and deactivated by moving 1 or 0 into a register - i.e. by editing the literal in the instruction. (changing mov eax,0 to mov eax,1) You might as well see whether there are any bone on that carcass worth picking. Richard - 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/