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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 9C362C352A4 for ; Sun, 9 Feb 2020 12:57:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 721632081E for ; Sun, 9 Feb 2020 12:57:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581253036; bh=6sX0Ip+mK3tsK8D8/OZZvuROxHkWLqF6ytnpDiTpDsc=; h=Date:From:To:Cc:Subject:In-Reply-To:List-ID:From; b=Cglnb22RY7dtYwoFdZj7uPCgFxmb55CxH9dVjvKQeFIA+aJFwtMDg57mcljrlRG1R K578K5Q1ggmsttJ1Hk8qCl+/ILQr4L9pZpX8JXLKTC5zKOia5SO+/SfAFh5O6qqRFs 5CnfVVz17rqc0VlWMNDmRE6cHJXSBfybyqV0XP2o= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727848AbgBIM5P (ORCPT ); Sun, 9 Feb 2020 07:57:15 -0500 Received: from mail.kernel.org ([198.145.29.99]:45064 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727631AbgBIM5P (ORCPT ); Sun, 9 Feb 2020 07:57:15 -0500 Received: from localhost (unknown [38.98.37.135]) (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 BD3C620733; Sun, 9 Feb 2020 12:57:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581253034; bh=6sX0Ip+mK3tsK8D8/OZZvuROxHkWLqF6ytnpDiTpDsc=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=uSxZe6b/ilcxBYyy5/bKvhjr7cQ9Ksm4h7zu5SBIPM+dw5YWlfJQkbJeGY3LwRLj0 cdVypdKUJmaw12ip8kq0HQOgkiYxOtubI4lvvt0hMDgJlMTM7B9KdjyE4HGLtxaDaG HiFCNoAPNqKYPRb2357mo+LpyTQFACsKkIqGNa8M= Date: Sun, 9 Feb 2020 12:05:49 +0100 From: Greg Kroah-Hartman To: "Theodore Y. Ts'o" , Jonathan Corbet , Saravana Kannan , Jason Baron , Will Deacon Cc: linux-kernel@vger.kernel.org, kernel-team@android.com, Randy Dunlap Subject: [PATCH v5] dynamic_debug: allow to work if debugfs is disabled Message-ID: <20200209110549.GA1621867@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200123093628.GA18991@willie-the-truck> <20200123085015.GA436361@kroah.com> <20200125101130.449a8e4d@lwn.net> <20200125014231.GI147870@mit.edu> <20200123155340.GD147870@mit.edu> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org With the realization that having debugfs enabled on "production" systems is generally not a good idea, debugfs is being disabled from more and more platforms over time. However, the functionality of dynamic debugging still is needed at times, and since it relies on debugfs for its user api, having debugfs disabled also forces dynamic debug to be disabled. To get around this, also create the "control" file for dynamic_debug in procfs. This allows people turn on debugging as needed at runtime for individual driverfs and subsystems. Reported-by: many different companies Cc: Jason Baron Signed-off-by: Greg Kroah-Hartman --- v5: as many people asked for it, now enable the control file in both debugfs and procfs at the same time. v4: tweaks to the .rst text thanks to Randy's review v3: rename init function as it is now no longer just for debugfs, thanks to Jason for the review. Fix build warning for debugfs_initialized call. v2: Fix up octal permissions and add procfs reference to the Kconfig entry, thanks to Will for the review. .../admin-guide/dynamic-debug-howto.rst | 3 +++ lib/Kconfig.debug | 7 ++++--- lib/dynamic_debug.c | 20 ++++++++++++++----- 3 files changed, 22 insertions(+), 8 deletions(-) diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst index 252e5ef324e5..585451d12608 100644 --- a/Documentation/admin-guide/dynamic-debug-howto.rst +++ b/Documentation/admin-guide/dynamic-debug-howto.rst @@ -54,6 +54,9 @@ If you make a mistake with the syntax, the write will fail thus:: /dynamic_debug/control -bash: echo: write error: Invalid argument +Note, for systems without 'debugfs' enabled, the control file can also +be found in ``/proc/dynamic_debug/control``. + Viewing Dynamic Debug Behaviour =============================== diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 69def4a9df00..a15dde66dc4c 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -98,7 +98,7 @@ config DYNAMIC_DEBUG bool "Enable dynamic printk() support" default n depends on PRINTK - depends on DEBUG_FS + depends on (DEBUG_FS || PROC_FS) help Compiles debug level messages into the kernel, which would not @@ -116,8 +116,9 @@ config DYNAMIC_DEBUG Usage: Dynamic debugging is controlled via the 'dynamic_debug/control' file, - which is contained in the 'debugfs' filesystem. Thus, the debugfs - filesystem must first be mounted before making use of this feature. + which is contained in the 'debugfs' filesystem or procfs if + debugfs is not present. Thus, the debugfs or procfs filesystem + must first be mounted before making use of this feature. We refer the control file as: /dynamic_debug/control. This file contains a list of the debug statements that can be enabled. The format for each line of the file is: diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c index c60409138e13..c220c1891729 100644 --- a/lib/dynamic_debug.c +++ b/lib/dynamic_debug.c @@ -991,15 +991,25 @@ static void ddebug_remove_all_tables(void) static __initdata int ddebug_init_success; -static int __init dynamic_debug_init_debugfs(void) +static int __init dynamic_debug_init_control(void) { - struct dentry *dir; + struct proc_dir_entry *procfs_dir; + struct dentry *debugfs_dir; if (!ddebug_init_success) return -ENODEV; - dir = debugfs_create_dir("dynamic_debug", NULL); - debugfs_create_file("control", 0644, dir, NULL, &ddebug_proc_fops); + /* Create the control file in debugfs if it is enabled */ + if (debugfs_initialized()) { + debugfs_dir = debugfs_create_dir("dynamic_debug", NULL); + debugfs_create_file("control", 0644, debugfs_dir, NULL, + &ddebug_proc_fops); + } + + /* Also create the control file in procfs */ + procfs_dir = proc_mkdir("dynamic_debug", NULL); + if (procfs_dir) + proc_create("control", 0644, procfs_dir, &ddebug_proc_fops); return 0; } @@ -1077,4 +1087,4 @@ static int __init dynamic_debug_init(void) early_initcall(dynamic_debug_init); /* Debugfs setup must be done later */ -fs_initcall(dynamic_debug_init_debugfs); +fs_initcall(dynamic_debug_init_control); -- 2.25.0