From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Wangnan (F)" Subject: Re: perf call stacks on 32bit ARM v7 Date: Wed, 28 Sep 2016 09:43:25 +0800 Message-ID: <57EB203D.6000603@huawei.com> References: <4233607.GXAFRqVoOG@agathebauer> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from szxga03-in.huawei.com ([119.145.14.66]:14514 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933592AbcI1BrQ (ORCPT ); Tue, 27 Sep 2016 21:47:16 -0400 In-Reply-To: <4233607.GXAFRqVoOG@agathebauer> Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: Milian Wolff , jean.pihet@newoldbits.com Cc: perf group , hekuang 00206996 On 2016/9/28 5:25, Milian Wolff wrote: > Hello Jean, others. > > Can someone please clarify the requirements for getting perf to properly > unwind the call stack on 32bit ARM v7? > > Looking at [1], it seems that I need either (a) frame pointers, or (b) DWARF > debug information. Because (a) is often not available, and (b) is too large > for small flash drives on embedded - how do I use perf with split debug > information files? I.e. I have tries to record on the arm board using DWARF: > > arm-v7$ perf record --call-graph dwarf ... > > Then transferred the perf.data file over to my host machine. Perf archive said > that no build-id's could be found, so I'm not using that. Instead, I try to > ask perf to find the split debug packes using symfs: > > x86-64$ perf report --symfs ... -g graph > > But that does not work and I'm not seeing any backtraces. Stracing the report, > I don't see it even trying to access files - how can I debug this and figure > out what I'm supposed to be using? Unfortunaetly, currently perf only supports corss decoding dwarf for x86_64, x86_32 and arm64. ARM32 is not on the list. Please see: http://www.spinics.net/lists/kernel/msg2266293.html and tools/perf/util/unwind-libunwind.c I think adding ARM32 support should not be very hard on perf side. Add He Kuang to the CC list, he is the author of this patch set. Thank you.