Debugging techniques inside kernel

[Valdis.Kletnieks at vt.edu]

On Mon, 08 Jul 2013 11:22:16 +0900, manty kuma said:

> For ex : *CONFIG_SLUB_DEBUG_ON, *CONFIG_DMA_API_DEBUG
> I am just told to use these configs and check. Not sure how to use them
> effectively. Please share if you are aware of these kind of configs and how
> to use them. To have them at one place it would be useful for debugging
> beginners like me.

Most _DEBUG config options are set-and-forget - you turn them on and
there's no further configuration needed. They enable additional code
that does additional sanity checking and if it finds a problem, it issues
a printk() or a stack dump or similar which shows up in dmesg.

If you're chasing memory corruption, it may be useful to use netconsole
or a serial console to send out all the printk() output in real time, as
often an error will be detected but the system will panic()/crash/hang
in a way that your local syslog daemon is unable to write the message to
disk.  (I'm told that on newer UEFI based systems, you can use pstore in
a similar fashion, but have not tried it myself yet).

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