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=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 E285BC2D0C3 for ; Sat, 21 Dec 2019 23:47:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B4FE9206C3 for ; Sat, 21 Dec 2019 23:47:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="BtXPVluI" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726828AbfLUXrn (ORCPT ); Sat, 21 Dec 2019 18:47:43 -0500 Received: from mail-pj1-f68.google.com ([209.85.216.68]:34955 "EHLO mail-pj1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726066AbfLUXrn (ORCPT ); Sat, 21 Dec 2019 18:47:43 -0500 Received: by mail-pj1-f68.google.com with SMTP id s7so5794370pjc.0 for ; Sat, 21 Dec 2019 15:47:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=fXy9xPSzwrsW14AMvNrH3dau8w//YzJTAr3l1Saqoig=; b=BtXPVluI1WJZfcKt5Lud61D40VYwvpo6G9Kp/Zsin1sj39dw2Dx681RY9uOB4Vqs28 JWjDIAY4lEvhH95dllicpVB7VvOZflG+nvB9i8ly9SVnTnh8T8+NDo+HmIZwRePTp1jS jmtmCvrpP5x12TX5TYu5W4Vk+6pEm5t36iekU= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=fXy9xPSzwrsW14AMvNrH3dau8w//YzJTAr3l1Saqoig=; b=UM1T2qYGuXFg/oc8ZJ3QeZcIammvIjUccmD6BCiFM9Rg0VLr4iqbw4jNNep7wmjEZ7 jT6QHsS3T0vFDtduOoaYLlu9rJ63Ucf7zgeVmZyxAFcbRD5dMlS7upqQdForOy18fhOC 3eEfANviaCyY6v85JC/PKuvjwC7+J4hLiNZgxkNUEOViZ8w00WQ9CNj8QL9OlB0SMuMi kijK55Ef64eej63TvJZEAjXvXy3Uga/FGN3Sk8/vaLPX9NNZ4WFgDrKqD90jm2Itn/ex ekllPi4TPlMPX6ZlyTpnvzR3HvpkyfMwfZ7xf5FH9UFNfOSD/r9ONojByGy46cPaMws2 OugQ== X-Gm-Message-State: APjAAAV8EOBB35yRtMReAPtDkn1IfZjO5TuqXlISRXyEi1MyUOu9MTsr IJCjCNOxe2ghI0Wo51rPj9kqEQ== X-Google-Smtp-Source: APXvYqzqzkp+eh1lKWYNwRToIgvfbaM/icchIpqxyrT/W118lizYV6091XMmfU8VB14/yYGANC8/Ew== X-Received: by 2002:a17:902:8bc9:: with SMTP id r9mr22866985plo.48.1576972062452; Sat, 21 Dec 2019 15:47:42 -0800 (PST) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id 133sm18161268pfy.14.2019.12.21.15.47.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 21 Dec 2019 15:47:42 -0800 (PST) Date: Sat, 21 Dec 2019 18:47:41 -0500 From: Joel Fernandes To: Steven Rostedt Cc: Antonio Borneo , Ingo Molnar , linux-kernel@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com Subject: Re: [PATCH] tracing: Fix printing ptrs in preempt/irq enable/disable events Message-ID: <20191221234741.GA116648@google.com> References: <20191127154428.191095-1-antonio.borneo@st.com> <20191204092115.30ef75c9@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191204092115.30ef75c9@gandalf.local.home> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 04, 2019 at 09:21:15AM -0500, Steven Rostedt wrote: > > Joel, > > Any comments on this patch? Steve, it looks like this issue happens with trace-cmd not knowing what _stext is. If I do cat trace_pipe , then I don't see the issue as _stext is looked up correctly but the reporter of the bug is using trace-cmd. Is there a way to solve this within trace-cmd? Not knowing much about trace-cmd internals, I will have to defer to you on this though.. Other than this, I need to make the offset to _stext as s32 instead of u32 type so that the problem of the symbol location being before _stext does not cause overflow. Lastly, I am not super convinced that we need to store the full pointer just to handle a case where the offset of the symbol might be more than +-2G from _stext. Once we see such issue, then we can handle it. But right now the size of the trace buffer is utilized better by just storing the offset IMHO. thanks, - Joel > > -- 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 >