From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 29845 invoked by alias); 17 Jan 2012 20:18:44 -0000 Received: (qmail 29834 invoked by uid 22791); 17 Jan 2012 20:18:42 -0000 X-SWARE-Spam-Status: No, hits=-6.4 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_HI,SPF_HELO_PASS,T_RP_MATCHES_RCVD X-Spam-Check-By: sourceware.org Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 17 Jan 2012 20:18:27 +0000 Received: from int-mx12.intmail.prod.int.phx2.redhat.com (int-mx12.intmail.prod.int.phx2.redhat.com [10.5.11.25]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id q0HKIRE6030504 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 17 Jan 2012 15:18:27 -0500 Received: from t510.usersys.redhat.com (dhcp-10-15-1-97.hsv.redhat.com [10.15.1.97]) by int-mx12.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id q0HKIQLL008430 (version=TLSv1/SSLv3 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO) for ; Tue, 17 Jan 2012 15:18:27 -0500 Message-ID: <4F15D792.2050408@redhat.com> Date: Tue, 17 Jan 2012 20:18:00 -0000 From: David Smith User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:9.0) Gecko/20111222 Thunderbird/9.0 MIME-Version: 1.0 To: systemtap@sourceware.org Subject: Re: automated way to find functions that we might want to blacklist References: <84bor03ij9.fsf@sauna.l.org> <20111223211030.GA23631@sli.dy.fi> <20120115214402.GG6309@sli.dy.fi> In-Reply-To: <20120115214402.GG6309@sli.dy.fi> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-IsSubscribed: yes 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: 2012-q1/txt/msg00020.txt.bz2 On 01/15/2012 03:44 PM, Sami Liedes wrote: > Probing any of these functions (eventually) crashes Debian testing's > kernel 3.1.x: A couple of these don't make any sense to me: > * hash_64 > * hash_ptr There is nothing that those 2 functions do that can crash the kernel. Those functions (should be) always inlined. I'd guess the problem isn't those two functions, but the function that is calling them. To test for true function calls, you *shouldn't* do: # stap -e 'probe kernel.function("*") {}' The above probes inlined functions and real function calls. Instead you should do the equivalent of: # stap -e 'probe kernel.function("*").call {}' Another problem I see with your testing methodology is that you are using xen. I don't think we've used xen in a while, but the xen kernel always gave us different results than a regular kernel. I'd test on bare metal or in a kvm instance. I'll make one final comment here. In my mind the blacklist is a semi-temporary thing (although we don't typically remove functions from it). The real fix here is to get the crashing functions marked with '__kprobes' in the upstream kernel. This fixes the problem for all kprobes users, not just systemtap. -- David Smith dsmith@redhat.com Red Hat http://www.redhat.com 256.217.0141 (direct) 256.837.0057 (fax)