linux-kernel - [PATCH -v4 0/2] printk.devkmsg: Ratelimit it by default

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Date:	Fri,  8 Jul 2016 11:18:48 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, Franck Bui <fbui@...e.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Subject: [PATCH -v4 0/2] printk.devkmsg: Ratelimit it by default

From: Borislav Petkov <bp@...e.de>

Hi all,

sorry for spamming so quickly again and not waiting for a week before
resubmitting but I believe the stuff is ready for 4.8.

So here's v4 with all the minor review comments addressed.

Changelog:
----------

v3:

here's v3 integrating Ingo's comments. The thing is called
printk.devkmsg= or printk_devkmsg now, depending on cmdline option or
sysctl.

v2:

here's v2 with the requested sysctl option kernel.printk_kmsg and
locking of the setting when printk.kmsg= is supplied on the command
line.

Patch 1 is unchanged.

Patch 2 has grown the sysctl addition.

v1:

Rostedt is busy so I took Linus' old patch and Steven's last v2 and
split and extended them with the comments people had on the last thread:

https://lkml.kernel.org/r/20160425145606.598329f2@gandalf.local.home

I hope, at least.

So it is ratelimiting by default, with "on" and "off" cmdline options. I
called the option somewhat a bit shorter too: "printk.kmsg"

The current use cases of this and of which I'm aware are:

* debug the kernel and thus shut up all interfering input from
userspace, i.e. boot with "printk.kmsg=off"

* debug userspace (and by that I mean systemd) by booting with
"printk.kmsg=on" so that the ratelimiting is disabled and the kernel log
gets all the spew.

Thoughts?

Please queue,
thanks.

Borislav Petkov (2):
  ratelimit: Extend to print suppressed messages on release
  printk: Add kernel parameter to control writes to /dev/kmsg

 Documentation/kernel-parameters.txt |  6 +++
 Documentation/sysctl/kernel.txt     | 14 ++++++
 include/linux/printk.h              |  7 +++
 include/linux/ratelimit.h           | 38 +++++++++++++---
 kernel/printk/printk.c              | 86 +++++++++++++++++++++++++++++++++----
 kernel/sysctl.c                     |  9 ++++
 lib/ratelimit.c                     | 10 +++--
 7 files changed, 153 insertions(+), 17 deletions(-)

-- 
2.7.3