From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_NEOMUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DD69DC31E46 for ; Wed, 12 Jun 2019 14:28:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A677A20B1F for ; Wed, 12 Jun 2019 14:28:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2439645AbfFLO1C (ORCPT ); Wed, 12 Jun 2019 10:27:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60032 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2439638AbfFLO1B (ORCPT ); Wed, 12 Jun 2019 10:27:01 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 91C0DC18B2F3; Wed, 12 Jun 2019 14:27:00 +0000 (UTC) Received: from treble (ovpn-120-37.rdu2.redhat.com [10.10.120.37]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BA67519483; Wed, 12 Jun 2019 14:26:54 +0000 (UTC) Date: Wed, 12 Jun 2019 09:26:52 -0500 From: Josh Poimboeuf To: Steven Rostedt Cc: Peter Zijlstra , Kairui Song , Alexei Starovoitov , Song Liu , lkml , Kernel Team , Alexei Starovoitov , Daniel Borkmann , "bpf@vger.kernel.org" Subject: Re: Getting empty callchain from perf_callchain_kernel() Message-ID: <20190612142652.tzrlwduirm4edmtf@treble> References: <20190522174517.pbdopvookggen3d7@treble> <20190522234635.a47bettklcf5gt7c@treble> <20190523133253.tad6ywzzexks6hrp@treble> <20190523152413.m2pbnamihu3s2c5s@treble> <20190524085319.GE2589@hirez.programming.kicks-ass.net> <20190612030501.7tbsjy353g7l74ej@treble> <20190612091023.6bccf262@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190612091023.6bccf262@gandalf.local.home> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Wed, 12 Jun 2019 14:27:01 +0000 (UTC) Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Wed, Jun 12, 2019 at 09:10:23AM -0400, Steven Rostedt wrote: > On Tue, 11 Jun 2019 22:05:01 -0500 > Josh Poimboeuf wrote: > > > Right now, ftrace has a special hook in the ORC unwinder > > (orc_ftrace_find). It would be great if we could get rid of that in > > favor of the "always use frame pointers" approach. I'll hold off on > > doing the kpatch/kprobe trampoline conversions in my patches since it > > would conflict with yours. > > Basically, IIUC, what you are saying is that the ftrace trampoline > should always store the %sp in %rb even when CONFIG_FRAME_POINTER is not > enabled? And this can allow you to remove the ftrace specific code from > the orc unwinder? Basically, yes. Though the frame pointer encoding which Peter is adding to the ftrace/kprobes trampolines might complicate things a bit. -- Josh