From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 13246 invoked by alias); 18 Sep 2008 08:01:06 -0000 Received: (qmail 13226 invoked by uid 22791); 18 Sep 2008 08:01:05 -0000 X-Spam-Status: No, hits=-1.9 required=5.0 tests=AWL,BAYES_00,SPF_SOFTFAIL X-Spam-Check-By: sourceware.org Received: from mtagate1.uk.ibm.com (HELO mtagate1.uk.ibm.com) (194.196.100.161) by sourceware.org (qpsmtpd/0.31) with ESMTP; Thu, 18 Sep 2008 08:00:23 +0000 Received: from d06nrmr1407.portsmouth.uk.ibm.com (d06nrmr1407.portsmouth.uk.ibm.com [9.149.38.185]) by mtagate1.uk.ibm.com (8.13.1/8.13.1) with ESMTP id m8I80JFO030493 for ; Thu, 18 Sep 2008 08:00:19 GMT Received: from d06av02.portsmouth.uk.ibm.com (d06av02.portsmouth.uk.ibm.com [9.149.37.228]) by d06nrmr1407.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v9.1) with ESMTP id m8I80HuZ3502204 for ; Thu, 18 Sep 2008 09:00:17 +0100 Received: from d06av02.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av02.portsmouth.uk.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m8I80HTi027333 for ; Thu, 18 Sep 2008 09:00:17 +0100 Received: from richardm.t43p.ibm.com ([9.12.233.159]) by d06av02.portsmouth.uk.ibm.com (8.12.11.20060308/8.12.11) with ESMTP id m8I80FW3027263 for ; Thu, 18 Sep 2008 09:00:16 +0100 Message-ID: <48D20A8F.4060307@uk.ibm.com> Date: Thu, 18 Sep 2008 08:01:00 -0000 From: "R. J. Moore" User-Agent: Thunderbird 2.0.0.14 (X11/20080515) MIME-Version: 1.0 To: systemtap@sources.redhat.com Subject: Re: kernel summit session on systemtap Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org X-SW-Source: 2008-q3/txt/msg00691.txt.bz2 I don't know whether it is possible with the latest code, but for debugging purposes, I would be happy if SystemTap could operate on external names and relative addresses - i.e. without the need to have any symbolic information. This is the way I used ancestors to systemtap for shooting very difficult kernel problems in the field. Generally I started with a crashdump. Determined that I needed some extra info in a particular code path. Looked at the underlying assembler and plugged in a probepoint at the required location as a relative address to the beginning of the load module. I used this technique 100s and 100s of times to shoot those bugs that would only show in live environment with a complex work load patterns. I admit that this is extreme debugging, but if system tap won't even operate without a ton of extra junk present then I see its application as being very limited indeed. Not everyone will want to work at the assembler level, but if System Tap can, then tools can be built that do code analysis to help generate and divine probepoints. Much can be done knowing that nearly 100% of the code we probe is generated by the one tool - gcc. In theory, what is generated is deterministic, or the reverse engineering of it is. We should not ignore System Tap efficacy when being used to complement core dumps, crash dumps, kernel and application debuggers. Richard -- Richard J Moore Tel: (44) 1962-817072 Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU