Mastering Embedded Linux Programming - Second Edition

Preserving the Oops

Decoding an Oops is only possible if you can capture it in the first place. If the system crashes during boot before the console is enabled, or after a suspend, you won't see it. There are mechanisms to log kernel Oops and messages to an MTD partition or to persistent memory, but here is a simple technique that works in many cases and needs little prior thought.

So long as the contents of memory are not corrupted during a reset (and usually they are not), you can reboot into the bootloader and use it to display memory. You need to know the location of the kernel log buffer, remembering that it is a simple ring buffer of text messages. The symbol is __log_buf. Look this up in System.map for the kernel:

$ grep __log_buf ...