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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 23FC0C433E0 for ; Wed, 31 Mar 2021 11:54:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BBC6D61990 for ; Wed, 31 Mar 2021 11:54:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235253AbhCaLxt (ORCPT ); Wed, 31 Mar 2021 07:53:49 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:19904 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235284AbhCaLxT (ORCPT ); Wed, 31 Mar 2021 07:53:19 -0400 Received: from pps.filterd (m0187473.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 12VBXdoa166180; Wed, 31 Mar 2021 07:52:52 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=date : from : to : cc : subject : message-id : mime-version : content-type; s=pp1; bh=/V7yWWNxYngIC7wyYWbeATuXW63w4vjLjmXFFb6sRso=; b=OB+QZSWfadHU9JeKkgyjq8Q8lYiOnSOXXHSQ3gM02s947l02FUplMR+qPNm2PyTH+dwA oaz3wKZDBYJbHgD0PKvOirJHWN0DqE0Wiq5o+VvePWn+8XQad5xAFuTVlu3OrQhDe6eF eKC0hq8SI0uzv9OzDceLOD7gmBowWTb0Mx4yNQGdTe13lukDLCkXycyTe27oBnlCEXgo rEAT092CxDkPqK1XOEVJuIymXsvNNuUJ5xGusV8kpdAmprM52IKdJkvPen8Oys2o6M/h LIwixMb0hovpKnjo/AxztUiS3hK4DRQ7PmhrYNjPx7p8Xm4y0WtnDYhNZ/SRVZBPe6oJ zA== Received: from ppma06ams.nl.ibm.com (66.31.33a9.ip4.static.sl-reverse.com [169.51.49.102]) by mx0a-001b2d01.pphosted.com with ESMTP id 37mnfswa4w-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 31 Mar 2021 07:52:52 -0400 Received: from pps.filterd (ppma06ams.nl.ibm.com [127.0.0.1]) by ppma06ams.nl.ibm.com (8.16.0.43/8.16.0.43) with SMTP id 12VBq8c4006263; Wed, 31 Mar 2021 11:52:50 GMT Received: from b06cxnps3074.portsmouth.uk.ibm.com (d06relay09.portsmouth.uk.ibm.com [9.149.109.194]) by ppma06ams.nl.ibm.com with ESMTP id 37matt0hgx-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 31 Mar 2021 11:52:49 +0000 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 12VBqlDp37945762 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 31 Mar 2021 11:52:47 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id AA8D1A4060; Wed, 31 Mar 2021 11:52:47 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6AE48A405B; Wed, 31 Mar 2021 11:52:47 +0000 (GMT) Received: from localhost (unknown [9.171.83.5]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Wed, 31 Mar 2021 11:52:47 +0000 (GMT) Date: Wed, 31 Mar 2021 13:52:45 +0200 From: Vasily Gorbik To: Steven Rostedt Cc: Josef Bacik , linux-kernel@vger.kernel.org Subject: User stacktrace garbage when USER_STACKTRACE_SUPPORT is not enabled Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-TM-AS-GCONF: 00 X-Proofpoint-GUID: sDrSpfMaK1BgUhd-7ygtTgiQWv4YnO5R X-Proofpoint-ORIG-GUID: sDrSpfMaK1BgUhd-7ygtTgiQWv4YnO5R X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369,18.0.761 definitions=2021-03-31_03:2021-03-30,2021-03-31 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 priorityscore=1501 spamscore=0 malwarescore=0 impostorscore=0 bulkscore=0 mlxlogscore=817 clxscore=1011 suspectscore=0 adultscore=0 phishscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2103300000 definitions=main-2103310085 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Steven, At least on s390 since commit cbc3b92ce037 ("tracing: Set kernel_stack's caller size properly") kernel stack trace contains 8 garbage values in the end. I assume those are supposed to be filled by ftrace_trace_userstack, which is only implemented on x86. sshd-804 [050] 1997.252608: kernel_stack: => trampoline_probe_handler (549628c94) => kprobe_handler (549629260) => kprobe_exceptions_notify (549629370) => notify_die (549686e5e) => illegal_op (54960d440) => __do_pgm_check (54a106b08) => pgm_check_handler (54a112cc8) => kretprobe_trampoline (549629438) => kretprobe_trampoline (549629436) => do_syscall (549611ee6) => __do_syscall (54a106ccc) => system_call (54a112b5a) => 769010000000322 => 22125e4d8 => 22125e8f8 => e000054100040100 => _end (3220000000c) => 2 => 20f892ec00000002 => 20f898b800000002 kernel/trace/trace_entries.h: 159 #define FTRACE_STACK_ENTRIES 8 160 161 FTRACE_ENTRY(kernel_stack, stack_entry, 162 163 TRACE_STACK, 164 165 F_STRUCT( 166 __field( int, size ) 167 __array( unsigned long, caller, FTRACE_STACK_ENTRIES ) 168 ), Is there any reason to keep those 8 extra values in the caller array if CONFIG_USER_STACKTRACE_SUPPORT is not enabled? Any advice how to fix that gracefully? It seems to work if I simply set FTRACE_STACK_ENTRIES to 0 when CONFIG_USER_STACKTRACE_SUPPORT is not enabled.