Messages in this thread | | | Subject | Re: [PATCH v2] dynamic_debug: allow to work if debugfs is disabled | From | Jason Baron <> | Date | Wed, 22 Jan 2020 13:56:48 -0500 |
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On 1/22/20 8:53 AM, Greg Kroah-Hartman wrote: > > 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, move the "control" file for dynamic_debug to procfs IFF > debugfs is disabled. This lets people turn on debugging as needed at runtime > for individual driverfs and subsystems. >
Hi Greg,
Thanks for updating this. Just a comment below.
> Reported-by: many different companies > Cc: Jason Baron <jbaron@akamai.com> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > --- > 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 | 17 ++++++++++++++--- > 3 files changed, 21 insertions(+), 6 deletions(-) > > diff --git a/Documentation/admin-guide/dynamic-debug-howto.rst b/Documentation/admin-guide/dynamic-debug-howto.rst > index 252e5ef324e5..41f43a373a6a 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:: > <debugfs>/dynamic_debug/control > -bash: echo: write error: Invalid argument > > +Note, for systems without 'debugfs' enabled, the control file can be > +also found in ``/proc/dynamic_debug/control``. > + > Viewing Dynamic Debug Behaviour > =============================== > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 5ffe144c9794..49980eb8c18e 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: <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: > diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c > index c60409138e13..0f1b26f10fb2 100644 > --- a/lib/dynamic_debug.c > +++ b/lib/dynamic_debug.c > @@ -993,13 +993,24 @@ static __initdata int ddebug_init_success; > > static int __init dynamic_debug_init_debugfs(void) > {
The naming now is a little confusing - dynamic_debug_init_control ?
> - struct dentry *dir; > + struct dentry *debugfs_dir; > + struct proc_dir_entry *procfs_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); > + return 0; > + } > + > + /* No debugfs so put it in procfs instead */ > + procfs_dir = proc_mkdir("dynamic_debug", NULL); > + if (procfs_dir) > + proc_create("control", 0644, procfs_dir, &ddebug_proc_fops); > > return 0; > } >
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