From a6e4656398da974972d22052d670b4fc3a599e7a Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Mon, 10 Feb 2020 13:11:42 -0800 Subject: [PATCH] UPSTREAM: dynamic_debug: allow to work if debugfs is disabled 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. Bug: 145162121 Reported-by: many different companies Cc: Jason Baron Acked-by: Will Deacon Link: https://lore.kernel.org/r/20200210211142.GB1373304@kroah.com Signed-off-by: Greg Kroah-Hartman (cherry picked from commit 239a5791ffd5559f51815df442c4dbbe7fc21ade) Signed-off-by: Greg Kroah-Hartman Change-Id: Icd892ea823af6254726847700fd9c251d13b556b --- .../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..0dc2eb8e44e5 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 be +found in ``/proc/dynamic_debug/control``. + Viewing Dynamic Debug Behaviour =============================== diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 93d97f9b0157..5bcf9380e469 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. + 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 @@ out_err: early_initcall(dynamic_debug_init); /* Debugfs setup must be done later */ -fs_initcall(dynamic_debug_init_debugfs); +fs_initcall(dynamic_debug_init_control);