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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 autolearn=ham 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 9BD85C43603 for ; Wed, 4 Dec 2019 14:21:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 72FB62073C for ; Wed, 4 Dec 2019 14:21:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727956AbfLDOVS (ORCPT ); Wed, 4 Dec 2019 09:21:18 -0500 Received: from mail.kernel.org ([198.145.29.99]:56982 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727828AbfLDOVS (ORCPT ); Wed, 4 Dec 2019 09:21:18 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3CE58206DF; Wed, 4 Dec 2019 14:21:17 +0000 (UTC) Date: Wed, 4 Dec 2019 09:21:15 -0500 From: Steven Rostedt To: Antonio Borneo Cc: Ingo Molnar , Joel Fernandes , Joel Fernandes , , Subject: Re: [PATCH] tracing: Fix printing ptrs in preempt/irq enable/disable events Message-ID: <20191204092115.30ef75c9@gandalf.local.home> In-Reply-To: <20191127154428.191095-1-antonio.borneo@st.com> References: <20191127154428.191095-1-antonio.borneo@st.com> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Joel, Any comments on this patch? -- Steve On Wed, 27 Nov 2019 16:44:28 +0100 Antonio Borneo wrote: > This tracing event class is the only instance in kernel that logs > in the trace buffer the instruction pointer as offset to _stext, > instead of logging the full pointer. > This looks like a nice optimization for 64 bits platforms, where a > 32 bit offset can take less space than a full 64 bits pointer. But > the symbol _stext is incorrectly resolved as zero in the expansion > of TP_printk(), which then prints only the hex offset instead of > the name of the caller function. Plus, on arm arch the kernel > modules are loaded at address lower than _stext, causing the u32 > offset arithmetics to overflow and wrap at 32 bits. > I did not identified a 64 bit arch where the modules are loaded at > offset from _stext that exceed u32 range, but I also did not > identified any constraint to feel safe with a u32 offset. > > Log directly the instruction pointer instead of the offset to > _stext. > > Signed-off-by: Antonio Borneo > Fixes: d59158162e03 ("tracing: Add support for preempt and irq enable/disable events") > --- > include/trace/events/preemptirq.h | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/include/trace/events/preemptirq.h b/include/trace/events/preemptirq.h > index 95fba0471e5b..d548a6aafa18 100644 > --- a/include/trace/events/preemptirq.h > +++ b/include/trace/events/preemptirq.h > @@ -18,18 +18,18 @@ DECLARE_EVENT_CLASS(preemptirq_template, > TP_ARGS(ip, parent_ip), > > TP_STRUCT__entry( > - __field(u32, caller_offs) > - __field(u32, parent_offs) > + __field(unsigned long, caller_ip) > + __field(unsigned long, parent_ip) > ), > > TP_fast_assign( > - __entry->caller_offs = (u32)(ip - (unsigned long)_stext); > - __entry->parent_offs = (u32)(parent_ip - (unsigned long)_stext); > + __entry->caller_ip = ip; > + __entry->parent_ip = parent_ip; > ), > > TP_printk("caller=%pS parent=%pS", > - (void *)((unsigned long)(_stext) + __entry->caller_offs), > - (void *)((unsigned long)(_stext) + __entry->parent_offs)) > + (void *)__entry->caller_ip, > + (void *)__entry->parent_ip) > ); > > #ifdef CONFIG_TRACE_IRQFLAGS