linux-kernel - Re: [PATCH] perf: Fix symbol resolution on old ppc64 ABI

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Message-ID: <20110725062542.GA694@elte.hu>
Date:	Mon, 25 Jul 2011 08:25:42 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Anton Blanchard <anton@...ba.org>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	emunson@...bm.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf: Fix symbol resolution on old ppc64 ABI


* Anton Blanchard <anton@...ba.org> wrote:

> The synthetic symbol creation code has an issue with the old ppc64 
> ABI. We end up with duplicate symbols of different sizes that 
> overlap.
> 
> To fix this, walk all of the symbols and remove any duplicates that 
> are the length of a function descriptor.

> I'd prefer not to add a ppc64 specific hack here, but I'm not sure 
> how we can fix this in a simpler way.

Symbol space problems are common on other architectures as well.

We could use a heuristic: when symbols are overlapping then we could 
throw away the one that is smaller. This would implicitly cover the 
ppc64 case, right?

I'd also suggest we warn somewhere that a symbol has been thrown 
away, if verbosity is turned off. (i.e. don't warn by default.)

Thanks,

	Ingo
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