From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758672AbYEELbV (ORCPT ); Mon, 5 May 2008 07:31:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758265AbYEELbA (ORCPT ); Mon, 5 May 2008 07:31:00 -0400 Received: from tomts40.bellnexxia.net ([209.226.175.97]:62049 "EHLO tomts40-srv.bellnexxia.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1758245AbYEELa7 (ORCPT ); Mon, 5 May 2008 07:30:59 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AjMFAEuNHkhMROPA/2dsb2JhbACBU6g8 Date: Mon, 5 May 2008 07:30:57 -0400 From: Mathieu Desnoyers To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, systemtap@sources.redhat.com, "Frank Ch. Eigler" Subject: Re: System call instrumentation Message-ID: <20080505113057.GA28070@Krystal> References: <20080504134838.GA21487@Krystal> <20080505065559.GD3350@elte.hu> <20080505105915.GA26444@Krystal> <20080505111029.GA9948@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <20080505111029.GA9948@elte.hu> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 07:25:29 up 66 days, 7:36, 5 users, load average: 1.13, 0.81, 0.77 User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Ingo Molnar (mingo@elte.hu) wrote: > > * Mathieu Desnoyers wrote: > > > > hm, i'm not sure about this. I've implemented system call tracing in > > > -rt [embedded in the latency tracer] and it only needed changes in > > > entry.S, not in every system call site. Now, granted, that tracer > > > was simpler than what LTTng tries to do, but do we _really_ need > > > more complexity? A trace point that simply expresses: > > > > > > sys_call_event(int sysno, long param1, long param2, long param3, > > > long param4, long param5, long param6); > > > > > > > That would work for all system calls that doesn't have parameters like > > "const char __user *filename". > > what's the problem with them? Do you want to follow those parameters? > > Ingo Ideally, I'd like to have this kind of high-level information : event name : kernel syscall syscall name : open arg1 (%s) : "somefile" <----- arg2 (%d) : flags arg3 (%d) : mode However, "somefile" has to be read from userspace. With the protection involved, it would cause a performance impact to read it a second time rather than tracing the string once it's been copied to kernel-space. Mathieu -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68