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-Ramoops oops/panic logger
-Sergiu Iordache <>
-Updated: 17 November 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
-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).
-Ramoops also supports software ECC protection of persistent memory regions.
-This might be useful when a hardware reset was used to bring the machine back
-to life (i.e. a watchdog triggered). In such cases, RAM may be somewhat
-corrupt, but usually it is restorable.
-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/pstore_ram.h>
-static struct ramoops_platform_data ramoops_data = {
- .mem_size = <...>,
- .mem_address = <...>,
- .record_size = <...>,
- .dump_oops = <...>,
- .ecc = <...>,
-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 the pstore filesystem. The format for these
-files is "dmesg-ramoops-N", where N is the record number in memory. To delete
-a stored record from RAM, simply unlink the respective pstore file.