From: Anton Blanchard <anton@samba.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
Paul Mackerras <paulus@samba.org>,
Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
emunson@mgebm.net, linux-kernel@vger.kernel.org,
amodra@gmail.com
Subject: Re: [PATCH] perf: Fix symbol resolution on old ppc64 ABI
Date: Mon, 25 Jul 2011 20:48:59 +1000 [thread overview]
Message-ID: <20110725204859.51e50611@kryten> (raw)
In-Reply-To: <20110725062542.GA694@elte.hu>
Hi Ingo,
> > 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.)
It would cover most cases. There would be an issue with functions that
are less than 24 bytes in length (ie 6 instructions). Tiny functions
are probably rare enough that we can live with it.
Anton
next prev parent reply other threads:[~2011-07-25 10:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-25 4:23 [PATCH] perf: Fix symbol resolution on old ppc64 ABI Anton Blanchard
2011-07-25 6:25 ` Ingo Molnar
2011-07-25 10:48 ` Anton Blanchard [this message]
2011-07-25 10:50 ` Ingo Molnar
2011-07-25 12:32 ` Anton Blanchard
2011-07-25 12:36 ` Ingo Molnar
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