From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752527Ab1HMTfZ (ORCPT ); Sat, 13 Aug 2011 15:35:25 -0400 Received: from oproxy4-pub.bluehost.com ([69.89.21.11]:45719 "HELO oproxy4-pub.bluehost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752025Ab1HMTfW (ORCPT ); Sat, 13 Aug 2011 15:35:22 -0400 Date: Sat, 13 Aug 2011 12:34:56 -0700 From: Randy Dunlap To: lkml Cc: torvalds , Sergiu Iordache Subject: [PATCH 6/8] Documentation: add Ramoops usage description Message-Id: <20110813123456.6efef5ce.rdunlap@xenotime.net> In-Reply-To: <20110813122200.8e2fc879.rdunlap@xenotime.net> References: <20110813122200.8e2fc879.rdunlap@xenotime.net> Organization: YPO4 X-Mailer: Sylpheed 2.7.1 (GTK+ 2.16.6; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Identified-User: {1807:box742.bluehost.com:xenotime:xenotime.net} {sentby:smtp auth 50.53.38.135 authed with rdunlap@xenotime.net} Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Sergiu Iordache Add a documentation file describing the usage of Ramoops Signed-off-by: Sergiu Iordache Signed-off-by: Randy Dunlap --- Documentation/00-INDEX | 2 Documentation/ramoops.txt | 76 ++++++++++++++++++++++++++++++++++++ 2 files changed, 78 insertions(+) create mode 100644 Documentation/ramoops.txt --- lnx-31-rc1-git7.orig/Documentation/00-INDEX +++ lnx-31-rc1-git7/Documentation/00-INDEX @@ -272,6 +272,8 @@ printk-formats.txt - how to get printk format specifiers right prio_tree.txt - info on radix-priority-search-tree use for indexing vmas. +ramoops.txt + - documentation of the ramoops oops/panic logging module. rbtree.txt - info on what red-black trees are and what they are for. robust-futex-ABI.txt --- /dev/null +++ lnx-31-rc1-git7/Documentation/ramoops.txt @@ -0,0 +1,76 @@ +Ramoops oops/panic logger +========================= + +Sergiu Iordache + +Updated: 8 August 2011 + +0. Introduction + +Ramoops is an oops/panic logger that writes its logs to RAM before the system +crashes. It works by logging oopses and panics in a circular buffer. Ramoops +needs a system with persistent RAM so that the content of that area can +survive after a restart. + +1. Ramoops concepts + +Ramoops uses a predefined memory area to store the dump. The start and size of +the memory area are set using two variables: + * "mem_address" for the start + * "mem_size" for the size. The memory size will be rounded down to a + power of two. + +The memory area is divided into "record_size" chunks (also rounded down to +power of two) and each oops/panic writes a "record_size" chunk of +information. + +Dumping both oopses and panics can be done by setting 1 in the "dump_oops" +variable while setting 0 in that variable dumps only the panics. + +The module uses a counter to record multiple dumps but the counter gets reset +on restart (i.e. new dumps after the restart will overwrite old ones). + +2. Setting the parameters + +Setting the ramoops parameters can be done in 2 different manners: + 1. Use the module parameters (which have the names of the variables described + as before). + 2. Use a platform device and set the platform data. The parameters can then + be set through that platform data. An example of doing that is: + +#include +[...] + +static struct ramoops_platform_data ramoops_data = { + .mem_size = <...>, + .mem_address = <...>, + .record_size = <...>, + .dump_oops = <...>, +}; + +static struct platform_device ramoops_dev = { + .name = "ramoops", + .dev = { + .platform_data = &ramoops_data, + }, +}; + +[... inside a function ...] +int ret; + +ret = platform_device_register(&ramoops_dev); +if (ret) { + printk(KERN_ERR "unable to register platform device\n"); + return ret; +} + +3. Dump format + +The data dump begins with a header, currently defined as "====" followed by a +timestamp and a new line. The dump then continues with the actual data. + +4. Reading the data + +The dump data can be read from memory (through /dev/mem or other means). +Getting the module parameters, which are needed in order to parse the data, can +be done through /sys/module/ramoops/parameters/* .