From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from hrndva-omtalb.mail.rr.com (hrndva-omtalb.mail.rr.com [71.74.56.122]) by ozlabs.org (Postfix) with ESMTP id 50FF4B6F06 for ; Tue, 17 May 2011 03:03:47 +1000 (EST) Subject: Re: [PATCH 3/5] v2 seccomp_filters: Enable ftrace-based system call filtering From: Steven Rostedt To: Ingo Molnar In-Reply-To: <20110516165249.GB10929@elte.hu> References: <1305289146.2466.8.camel@twins> <20110513122646.GA3924@elte.hu> <1305290370.2466.14.camel@twins> <1305290612.2466.17.camel@twins> <20110513125452.GD3924@elte.hu> <1305292132.2466.26.camel@twins> <20110513131800.GA7883@elte.hu> <1305294935.2466.64.camel@twins> <20110513145737.GC32688@elte.hu> <1305563026.5456.19.camel@gandalf.stny.rr.com> <20110516165249.GB10929@elte.hu> Content-Type: text/plain; charset="ISO-8859-15" Date: Mon, 16 May 2011 13:03:42 -0400 Message-ID: <1305565422.5456.21.camel@gandalf.stny.rr.com> Mime-Version: 1.0 Cc: linux-mips@linux-mips.org, linux-sh@vger.kernel.org, Peter Zijlstra , Frederic Weisbecker , Heiko Carstens , Oleg Nesterov , David Howells , Paul Mackerras , Ralf Baechle , "H. Peter Anvin" , sparclinux@vger.kernel.org, Jiri Slaby , linux-s390@vger.kernel.org, Russell King , x86@kernel.org, James Morris , Linus Torvalds , Ingo Molnar , linux-arm-kernel , kees.cook@canonical.com, "Serge E. Hallyn" , Martin Schwidefsky , Thomas Gleixner , Roland McGrath , Michal Marek , Michal Simek , Will Drewry , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Eric Paris , Paul Mundt , Tejun Heo , linux390@de.ibm.com, Andrew Morton , agl@chromium.org, "David S. Miller" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, 2011-05-16 at 18:52 +0200, Ingo Molnar wrote: > * Steven Rostedt wrote: > > > I'm a bit nervous about the 'active' role of (trace_)events, because of the > > way multiple callbacks can be registered. How would: > > > > err = event_x(); > > if (err == -EACCESS) { > > > > be handled? [...] > > The default behavior would be something obvious: to trigger all callbacks and > use the first non-zero return value. But how do we know which callback that was from? There's no ordering of what callbacks are called first. > > > [...] Would we need a way to prioritize which call back gets the return > > value? One way I guess would be to add a check_event option, where you pass > > in an ENUM of the event you want: > > > > event_x(); > > err = check_event_x(MYEVENT); > > > > If something registered itself as "MYEVENT" to event_x, then you get the > > return code of MYEVENT. If the MYEVENT was not registered, a -ENODEV or > > something could be returned. I'm sure we could even optimize it such a way if > > no active events have been registered to event_x, that check_event_x() will > > return -ENODEV without any branches. > > I would keep it simple and extensible - that way we can complicate it when the > need arises! :) The above is rather trivial to implement. I don't think it complicates anything. -- Steve