Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932748Ab0HDMvT (ORCPT ); Wed, 4 Aug 2010 08:51:19 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:50414 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932619Ab0HDMvS (ORCPT ); Wed, 4 Aug 2010 08:51:18 -0400 Date: Wed, 4 Aug 2010 18:18:22 +0530 From: Srikar Dronamraju To: Peter Zijlstra Cc: Christoph Hellwig , Ingo Molnar , Steven Rostedt , Randy Dunlap , Arnaldo Carvalho de Melo , Linus Torvalds , Masami Hiramatsu , Ananth N Mavinakayanahalli , Oleg Nesterov , Mark Wielaard , Mathieu Desnoyers , LKML , Naren A Devaiah , Jim Keniston , Frederic Weisbecker , "Frank Ch. Eigler" , Andrew Morton , "Paul E. McKenney" Subject: Re: [PATCHv9 2.6.35-rc4-tip 2/13] uprobes: Breakpoint insertion/removal in user space applications. Message-ID: <20100804124822.GC28212@linux.vnet.ibm.com> Reply-To: Srikar Dronamraju References: <20100712103214.27491.15142.sendpatchset@localhost6.localdomain6> <20100712103235.27491.293.sendpatchset@localhost6.localdomain6> <20100720042814.GA13624@infradead.org> <20100720072202.GB19375@linux.vnet.ibm.com> <1280923528.1923.1058.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <1280923528.1923.1058.camel@laptop> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2597 Lines: 59 * Peter Zijlstra [2010-08-04 14:05:28]: > On Tue, 2010-07-20 at 12:52 +0530, Srikar Dronamraju wrote: > > > Just wondering why these are function pointers. Do we exepect an > > > architecture to provide different versions of these for say 32 vs 64-bit > > > binaries? If not just making these arch provided helpers might be a lot > > > simpler. Especially in the current version where only very few of these > > > are overriden by the architecture at all. > > > > > > > Some of these functions are purely optional example being > > validate_address. > > > > Some of these functions need not be defined by the architecture in > > which case we default to the functions defined in common code. > > examples being: read_opcode, set_bkpt, and set_orig_insn. > > > > Some of these functions are architecture mode specific, for example > > there is a architecture specific pre_xol needed for x86_64. However > > generic pre_xol for x86_32 would suffice for x86_32. > > > > Some of these functions need to be mandatorily defined by the > > architecture. example being set_ip and analyze_insn. > > > > Apart from the above flexibilities and enforcements that we can make > > when we use function pointers, its would be handy to incorporate > > more enhancements like return probes and booster. > > Still not sure why you're using this vector though, why not use weak > function for optionals and defaults and no implementation for mandatory > functions (and if the implementations fails to provide it, that will > result in a link error). Yes, we can certainly use weak functions instead of pointers. One another reason why we had these as function pointers in a structure was that it would easy be for a person porting uprobes to a new architecture. i.e person porting to a new architecture knows in one place(structure) which all functions need to be provided. However I would go with your suggestion and make the changes to use weak functions in the next version of the patchset. > > Are there likely to be multiple different versions of this method vector > around on a running kernel? No for a running kernel, there will be only one method vector. Also wanted to check with if you had tried perf probes and had comments/suggestions on any of the other patches in the patchset. -- Thanks and Regards Srikar -- 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/