Re: [PATCH 1/3] Kprobes: Make kprobe modules more portable

From: Paulo Marques
Date: Tue Aug 08 2006 - 13:26:12 EST

Christoph Hellwig wrote:
On Tue, Aug 08, 2006 at 09:34:00AM -0700, Stephen Hemminger wrote:
Okay, does this makes kprobe's the first reflective kernel interface.

Actually kallsyms_lookup_name was the first interface like that. And lots
of external kprobes used it like that - in fact tcp_probe.c is the first
one I've seen doing it differently. But kallsyms_lookup_name is a really
awkward lowlevel buildingblock that's almost impossible to use correctly,
so this patch hides it behind the proper kprobes interface.

Just one side note: kallsyms_lookup_name is _really_ inefficient. The kallsyms structure is tailored so that kallsyms_lookup (the most frequently used function) is really fast. Doing it the other way around involves a O(N) search, uncompressing every symbol name as it goes :P

I don't think this is really a performance problem for users like kprobes, but I just wanted people to keep in mind that there is a penalty involved in calling kallsyms_lookup_name.

Paulo Marques -

"The face of a child can say it all, especially the
mouth part of the face."
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