mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-27 11:45:01 +07:00
77 lines
2.3 KiB
Plaintext
77 lines
2.3 KiB
Plaintext
|
Ramoops oops/panic logger
|
||
|
|
=========================
|
||
|
|
|
||
|
|
Sergiu Iordache <sergiu@chromium.org>
|
||
|
|
|
||
|
|
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 <linux/ramoops.h>
|
||
|
|
[...]
|
||
|
|
|
||
|
|
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/* .
|