Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750993AbVKJO63 (ORCPT ); Thu, 10 Nov 2005 09:58:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751002AbVKJO63 (ORCPT ); Thu, 10 Nov 2005 09:58:29 -0500 Received: from mailout1.vmware.com ([65.113.40.130]:18949 "EHLO mailout1.vmware.com") by vger.kernel.org with ESMTP id S1750985AbVKJO62 (ORCPT ); Thu, 10 Nov 2005 09:58:28 -0500 Message-ID: <43736011.7060902@vmware.com> Date: Thu, 10 Nov 2005 06:58:25 -0800 From: Zachary Amsden User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.2) Gecko/20040803 X-Accept-Language: en-us, en MIME-Version: 1.0 To: prasanna@in.ibm.com Cc: Ingo Molnar , Andi Kleen , virtualization@lists.osdl.org, Andrew Morton , Chris Wright , Linus Torvalds , Linux Kernel Mailing List , "H. Peter Anvin" , Zwane Mwaikambo , Martin Bligh , Pratap Subrahmanyam , Christopher Li , "Eric W. Biederman" , ananth@in.ibm.com, anil.s.keshavamurthy@intel.com, davem@davemloft.net Subject: Re: [PATCH 19/21] i386 Kprobes semaphore fix References: <200511080439.jA84diI6009951@zach-dev.vmware.com> <200511081412.05285.ak@suse.de> <4370A9F5.4060103@vmware.com> <200511091438.11848.ak@suse.de> <437227FD.6040905@vmware.com> <20051109165804.GA15481@elte.hu> <43723768.2060103@vmware.com> <20051110180954.GD8514@in.ibm.com> In-Reply-To: <20051110180954.GD8514@in.ibm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 10 Nov 2005 14:58:27.0323 (UTC) FILETIME=[34B2F4B0:01C5E607] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2074 Lines: 70 Prasanna S Panchamukhi wrote: >On Wed, Nov 09, 2005 at 09:52:40AM -0800, Zachary Amsden wrote: > > >>Ingo Molnar wrote: >> >> >> >>>* Zachary Amsden wrote: >>> >>> >>> >>> >>> >>>>>I believe user space kprobes are being worked on by some IBM India folks >>>>>yes. >>>>> >>>>> >>>>> >>>>> >>>>I'm convinced this is pointless. What does it buy you over a ptrace >>>>based debugger? Why would you want extra code running in the kernel >>>>that can be done perfectly well in userspace? >>>> >>>> >>>> >>>> >>>kprobes are not just for 'debuggers', they are also used for tracing and >>>other dynamic instrumentation in projects like systemtap. Ptrace is way >>>too slow and limited for things like that. >>> >>> >>> >>> >>Well, if there is a justification for it, that means we really should >>handle all the nasty EIP conversion cases due to segmentation and v8086 >>mode in the kprobes code. I was hoping that might not be the case. >> >> >> > >As Ingo mentioned above, Systemtap uses kprobes infrastructure to provide >dynamic kernel instrumentation. Using which user can add lots of probes >easily, so we need to take care of this fast path. > >Instead of calling convert_eip_to_linear() for all cases, you can >just check if it is in kernel mode and calculate the address directly > > if (kernel mode) > addr = regs->eip - sizeof(kprobe_opcode_t); > else > addr = convert_eip_to_linear(..); > >there by avoiding call to convert_eip_to_linear () for every kernel probes. > >As Andi mentioned user space probes support is in progress and >this address conversion will help in case of user space probes as well. > I like this better. I have to rework that patch anyways, since it no longer applies cleanly. Zach - 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/