From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 1916 invoked by alias); 12 Jan 2007 05:43:24 -0000 Received: (qmail 1909 invoked by uid 22791); 12 Jan 2007 05:43:24 -0000 X-Spam-Status: No, hits=4.3 required=5.0 tests=BAYES_50,DNS_FROM_RFC_ABUSE,DNS_FROM_RFC_POST,DNS_FROM_RFC_WHOIS,NO_REAL_NAME X-Spam-Check-By: sourceware.org Received: from smtp2.vsnl.net (HELO fe2.vsnl.net) (203.200.235.232) by sourceware.org (qpsmtpd/0.31) with ESMTP; Fri, 12 Jan 2007 05:43:19 +0000 Received: from vsnl.net ([172.16.28.40]) by fe2.internal.vsnl.net (vsnl mail server fe2) with ESMTP id <0JBQ0066HQI798C0@fe2.internal.vsnl.net> for systemtap@sources.redhat.com; Fri, 12 Jan 2007 11:12:07 +0530 (IST) Received: from [172.16.28.177] (Forwarded-For: [121.100.32.51]) by store2.internal.vsnl.net (mshttpd); Fri, 12 Jan 2007 10:42:07 +0500 Date: Fri, 12 Jan 2007 05:43:00 -0000 From: rsmadhvesh@vsnl.net Subject: Re: Kprobes Support for ARM arch In-reply-to: <20070112053157.GA7437@in.ibm.com> To: ananth@in.ibm.com Cc: systemtap@sources.redhat.com, madhvesh.s@ap.sony.com, lubna@ap.sony.com, satish.v@ap.sony.com Message-id: MIME-version: 1.0 X-Mailer: Sun Java(tm) System Messenger Express 6.2-6.01 (built Apr 3 2006) Content-type: text/plain; charset=us-ascii Content-language: en Content-transfer-encoding: 7BIT Content-disposition: inline X-Accept-Language: en Priority: normal References: <20070112053157.GA7437@in.ibm.com> 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: 2007-q1/txt/msg00083.txt.bz2 Dear Ananth, Ananth N Mavinakayanahalli wrote on Friday, January 12, 2007 11:02 am > On Thu, Jan 11, 2007 at 07:58:07PM +0500, rsmadhvesh@vsnl.net wrote: > > Hi Madhvesh, > > > Hi All, > > > > Recently we completed the kprobes support for ARM architecture > > targetted at 2.6.16 kernel. I have uploaded these patches in the > > below CELF wiki page along with few test programs. > > This implementation is tested using 2.6.16-24 kernel for > > OMAP5912 OSK reference platform. > > I am not familiar with the ARM architecture details... the following > comments are from a quick glance at the patch. > > > The patch is available in the below CELF wiki page > > http://tree.celinuxforum.org/CelfPubWiki/PatchArchive > > > > The patch can be downloaded directly from here > > > http://tree.celinuxforum.org/CelfPubWiki/PatchArchive?action=AttachFile&do=get&target=kprobes-arm-patches-2.6.16.24.tgz > > > > This implementation supports only kprobes and doesnot > > support any other variants like jprobes, kretprobes etc. > > Also it doesnot support branch/jump instructions probing. > > How are you ensuring that a kprobe register request on a branch/jump > instruction fails? I don't see any profiling done to verify what the > underlying instruction is. We are working out a way to check for branch/jump instructions which can be used to take care of runtime crash if probe is placed for those instructions. > > See arch_prepare_kprobe() from the powerpc port as to how we fail > kproberegistration on certain instructions. Thank you for the pointers, we are trying to address in same fashion. > > > I noticed some discussions regarding ARM kprobes in the > > archive. We are open to suggestions and how this implementation can > > be improved. > > Given that quite a bit of the kprobes code for any platform is > architecture specific, its important that your code gets reviewed > by the > ARM kernel gurus/maintainers, if you intend that the patch be included > in the mainline Linux kernels. > > Also, you may want to port the patch to the latest kernel. There have > been some interface changes: > - kprobe modules are more portable with the addition of in-kernel > symbol lookup. > - The page fault case gets its own notifier so there isn't a > penalty paid > when kprobes aren't in use. It will be interesting to merge to main line kernel, i will ask you if i find any difficulty in porting Thank you very much for your quick feedback Best Regards Madhvesh