linux-kernel - Re: [PATCH] perf lookup of ppc64 symbols

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Message-ID: <20100617151705.GD4217@ghostprotocols.net>
Date:	Thu, 17 Jun 2010 12:17:05 -0300
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Anton Blanchard <anton@...ba.org>
Cc:	Eric B Munson <ebmunson@...ibm.com>, mingo@...e.hu,
	a.p.zijlstra@...llo.nl, paulus@...ba.org,
	linux-kernel@...r.kernel.org, amodra@...il.com
Subject: Re: [PATCH] perf lookup of ppc64 symbols

Em Fri, Jun 18, 2010 at 12:46:08AM +1000, Anton Blanchard escreveu:
> 
> Hi,
> 
> > Currently symbol resolution does not work for 64-bit programs
> > using perf.  For this to work perf needs to lookup symbol names in
> > the OPD.  This patch adds this functionality.  The OPD data is
> > used to find symbol names when available.
> 
> To clarify, this is an issue with 64bit architectures that use function
> descriptors (eg ppc64). The problem is that a symbol doesn't point to a text
> address, it points to a data area that contains (amongst other things) a
> pointer to the text address.
> 
> We look for a section called ".opd" which is the function descriptor
> area. To create the full symbol table, when we see a symbol in the function
> descriptor section we load the first pointer and use that as the text
> address. The only tricky part here is working out which section the
> text address is in. Right now we have a loop which is sub optimal:

I'll update the comment in Eric's patch and apply this to perf/core, for
.36, we can optimize this later, correctness first :-)

- Arnaldo
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