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From 7d61af935fdc0e18519a6f907d4b3b0aa05b5972 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Wed, 22 Jan 2020 08:39:32 +0100
Subject: [PATCH] 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.
Reported-by: many different companies
Cc: Jason Baron <jbaron@akamai.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
Documentation/admin-guide/dynamic-debug-howto.rst | 3 +++
lib/Kconfig.debug | 7 ++++---
lib/dynamic_debug.c | 20 +++++++++++++++-----
3 files changed, 22 insertions(+), 8 deletions(-)
--- 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, t
<debugfs>/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
===============================
--- 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: <debugfs>/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:
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -991,15 +991,25 @@ static void ddebug_remove_all_tables(voi
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);
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