From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754059AbcGDOZH (ORCPT ); Mon, 4 Jul 2016 10:25:07 -0400 Received: from mail.skyhub.de ([78.46.96.112]:59450 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750734AbcGDOZD (ORCPT ); Mon, 4 Jul 2016 10:25:03 -0400 From: Borislav Petkov To: LKML Cc: Andrew Morton , Franck Bui , Greg Kroah-Hartman , Ingo Molnar , Linus Torvalds , Peter Zijlstra , Steven Rostedt , =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= Subject: [PATCH -v3 0/2] printk.devkmsg: Ratelimit it by default Date: Mon, 4 Jul 2016 16:24:50 +0200 Message-Id: <1467642292-15671-1-git-send-email-bp@alien8.de> X-Mailer: git-send-email 2.7.3 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Borislav Petkov Hi all, here's v3 integrating Ingo's comments. The thing is called printk.devkmsg= or printk_devkmsg now, depending on cmdline option or sysctl. Changelog: ---------- 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? 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 | 36 +++++++++++++--- kernel/printk/printk.c | 83 +++++++++++++++++++++++++++++++++---- kernel/sysctl.c | 9 ++++ lib/ratelimit.c | 6 ++- 7 files changed, 146 insertions(+), 15 deletions(-) -- 2.7.3