From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751144AbdGNVoa (ORCPT ); Fri, 14 Jul 2017 17:44:30 -0400 Received: from mail.kernel.org ([198.145.29.99]:36794 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751049AbdGNVo3 (ORCPT ); Fri, 14 Jul 2017 17:44:29 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9EB8C22CAF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Fri, 14 Jul 2017 17:44:25 -0400 From: Steven Rostedt To: Pratyush Anand Cc: Felipe Balbi , Alexander Shishkin , Ingo Molnar , Linux USB , linux-kernel@vger.kernel.org, Chunyan Zhang Subject: Re: [PATCH] usb: gadget: functions: add ftrace export over USB Message-ID: <20170714174425.715ad62f@gandalf.local.home> In-Reply-To: <78398669-55b1-a4be-4864-9a3a4ed0707c@redhat.com> References: <20170609061327.17899-1-felipe.balbi@linux.intel.com> <87mv9hqwt8.fsf@linux.intel.com> <78398669-55b1-a4be-4864-9a3a4ed0707c@redhat.com> X-Mailer: Claws Mail 3.14.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 14 Jul 2017 11:22:51 +0530 Pratyush Anand wrote: > Hi Felipe, > > On Friday 09 June 2017 03:58 PM, Felipe Balbi wrote: > > Felipe Balbi writes: > > > >> Allow for ftrace data to be exported over a USB Gadget > >> Controller. With this, we have a potentially very fast pipe for > >> transmitting ftrace data to a Host PC for further analysis. > >> > >> Note that in order to decode the data, one needs access to kernel > >> symbols in order to convert binary data into function names and what > >> not. > >> > >> Signed-off-by: Felipe Balbi > >> --- > >> > >> I wanted to take this through the gadget tree, but there is a > >> dependency with a previous patch of mine adding and extra argument to > >> the ->write() function. Hoping someone else will take it. > > > > just as an extra note here. In order for this to be really useful, it > > would be nice to be able to control what is going to be traced over USB > > Probably you will also need to export *atleast* symbol information. In future, > if this framework is extended to export tracepoint/kprobe/uprobe event data, > then the information like event format etc will also need to be exported. > > What tool do you use on host machine in order to extract information from this > exported target ring buffer data? > IMHO, standard tools like trace-cmd will not be able to use it as it is. > Have you looked at how trace-cmd does network transfers? Perhaps this can do something similar. I'm also working on having trace-cmd work through sockets for guest to host tracing. See trace-cmd listen. -- Steve