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Core Dumps Rock

April 17, 2011 3 comments

So it’s been a while since my last post, and I find myself thinking about core dumps lately.

I won’t be wowing you with my awesome knowledge or teaching obscure implementation details regarding core dumps… I guess my bottom line message is “core dumps rock.”

Some of the more hard-core guys like Linus don’t believe in debuggers (real men don’t need ’em, eh?) but for the rest of us mere mortals debuggers are vital tools. And while I agree with Linus’s reasoning against debuggers, especially in the kernel — I guess I’m a pragmatist at heart. Use whatever tool helps you get the job done…

Anyways, core dumps are awesome. Especially if any of the following are true:
– you’re chasing an intermittent bug that only happens once in N runs or doesn’t reproduce with a debugger attached
– your code is running on an embedded device and there’s no JTAG (hence no realtime debugging/debugger)
– you want to save a snapshot of the system/app/problem for debugging later

Core dumps (and what triggers them) vary from OS to OS, but they generally contain some/all of the following:
– the page tables/memory for the crashing process, or a full RAM dump on some embedded targets
– the processor registers, including MMU configuration and other hardware configuration/state info

This info can be loaded into a debugger later on to construct a backtrace, examine variables, and can go a long ways towards solving the crash at hand.

I’ve used core dumps several times recently and it’s been a real lifesaver. The exact mechanics of using core dumps are already documented ad nauseum elsewhere, so I won’t repeat that info here. Just wanted to put in a plug for core dumps… Because when you need ’em, they… Rock.

Atto

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