From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753069AbcFOCCN (ORCPT ); Tue, 14 Jun 2016 22:02:13 -0400 Received: from mail.kernel.org ([198.145.29.136]:52220 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752738AbcFOCCM (ORCPT ); Tue, 14 Jun 2016 22:02:12 -0400 Date: Wed, 15 Jun 2016 11:02:01 +0900 From: Masami Hiramatsu To: Arnaldo Carvalho de Melo Cc: Linux Kernel Mailing List Subject: Re: perf probe issues Message-Id: <20160615110201.c2838ec2291cd9caaaa93ce4@kernel.org> In-Reply-To: <20160614170504.GD3978@kernel.org> References: <20160614170504.GD3978@kernel.org> X-Mailer: Sylpheed 3.4.3 (GTK+ 2.24.28; x86_64-redhat-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 Tue, 14 Jun 2016 14:05:04 -0300 Arnaldo Carvalho de Melo wrote: > Hi Masami, > > While investigating a problem in the annotation code reported by > Linus, with "kaslr" on the kernel command line and this in .config: > > [root@jouet ~]# egrep 'CONFIG_(RANDOMIZE_BASE|DEBUG_INFO)' ~acme/git/build/v4.7.0-rc3/.config > CONFIG_RANDOMIZE_BASE=y > # CONFIG_DEBUG_INFO is not set > [root@jouet ~]# > > [root@jouet ~]# grep -w vfs_write /proc/kallsyms > ffffffffac2404c0 T vfs_write > [root@jouet ~]# perf probe vfs_write > vfs_write is out of .text, skip it. > Error: Failed to add events. > [root@jouet ~]# perf probe -v vfs_write > probe-definition(0): vfs_write > symbol:vfs_write file:(null) line:0 offset:0 return:0 lazy:(null) > 0 arguments > Looking at the vmlinux_path (8 entries long) > Using /lib/modules/4.7.0-rc3/build/vmlinux for symbols > Could not open debuginfo. Try to use symbols. > vfs_write is out of .text, skip it. > Error: Failed to add events. Reason: No such file or directory (Code: -2) > [root@jouet ~]# > > Can you try to test with this config to investigate this problem? Yes, I guess it missed to get start_text because of KASLR... > > We need to improve the error messages, for instance: > > "Could not open debuginfo. Try to use symbols." > > I think should be rewritten as: "Trying to use kallsyms", no? I.e. if it > doesn't manage to find a vmlinux file, it will try to use kallsyms as a > fallback, is that what is happening here? Let me check that the perf symbol/map object uses kallsyms for kernel. Anyway, if the target is not the kernel, do we change the message as "trying to use symbols"? > > - Arnaldo -- Masami Hiramatsu