From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759664AbZANO1U (ORCPT ); Wed, 14 Jan 2009 09:27:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753530AbZANO1K (ORCPT ); Wed, 14 Jan 2009 09:27:10 -0500 Received: from mx2.redhat.com ([66.187.237.31]:46453 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752770AbZANO1I (ORCPT ); Wed, 14 Jan 2009 09:27:08 -0500 Date: Wed, 14 Jan 2009 09:25:46 -0500 From: Jason Baron To: Lai Jiangshan Cc: Ingo Molnar , Steven Rostedt , Linux Kernel Mailing List Subject: Re: [PATCH 4/5] ftrace: show ftrace_bprintk()'s formats Message-ID: <20090114142546.GA3141@redhat.com> References: <495ADF57.8030008@cn.fujitsu.com> <20090113231617.GD3210@redhat.com> <496D52D4.70202@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <496D52D4.70202@cn.fujitsu.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 14, 2009 at 10:49:56AM +0800, Lai Jiangshan wrote: > Jason Baron wrote: > > On Wed, Dec 31, 2008 at 10:56:23AM +0800, Lai Jiangshan wrote: > >> Impact: let user knows the format > >> > >> Create a file on /tracing/ to show ftrace_bprintk()'s formats. > >> > >> This formats will help for these condition: > >> 1) User get binary data from core file.(formats are backup before coredump) > >> 2) User splice ring_buffer to a file. > >> User can use formats for parsing the binary data in userspace. > >> > > > > When I 'cat' trace_bprintk_formats on my system the file is empty. This > > seems to be b/c 'ftrace_bprintk' is not being used in this patchset. It > > can't be used in patch #5 during marker register b/c the format wouldn't > > be known at runtime. Thus, as it currently stands this patch, patch 4/5, > > isn't adding much? > > If you don't use ftrace_bprintk(), the file trace_bprintk_formats is empty. > This file record all formats which ftrace_bprintk() uses. > > You can use ftrace_bprintk() everywhere as another printk(). > > Patch #5 enables binary printk for markers, this is another additional tool > for tracing markers. > > > > > A thought on how this might be resolved would be to have the core marker > > code pass us its address so this could be recorded in the trace buffer. > > Then, also add some debug file that displays the markers and maps marker > > addresses with format strings. > > > > Patch#5 does it as you said. > > > hmm...i'm still not clear on this. in patch #5 you have: +static void marker_bprintk_probe(void *probe_private, void *call_private, + const char *fmt, va_list *args) +{ + struct marker_bprintk_struct *p = probe_private; + + if (p->fmt_state == MARKER_FMT_LACK) { + int flen = strlen(fmt); + if (p->fmt - p->name + flen < MARKER_NAME_FMT_LEN) { + memcpy(p->fmt, fmt, flen + 1); + p->fmt_state = MARKER_FMT_OK; + } else + p->fmt_state = MARKER_FMT_INVALID; + } + + if (p->fmt_state == MARKER_FMT_OK) + trace_vbprintk(0, p->name, *args); +} + trace_vbprintk first argument is 'ip'. So I don't see how we are associating instruction pointers with each 'ftrace' record? Aren't we just recording each entry with '0' for the 'ip'? thanks, -Jason