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Re: [patch] Resolve ppc64 func descriptors as .func (via .opd)
- From: Mark Wielaard <mjw at redhat dot com>
- To: elfutils-devel at lists dot fedorahosted dot org
- Date: Wed, 05 Dec 2012 17:30:35 +0100
- Subject: Re: [patch] Resolve ppc64 func descriptors as .func (via .opd)
On Wed, 2012-12-05 at 16:54 +0100, Jan Kratochvil wrote:
> On Wed, 05 Dec 2012 16:04:11 +0100, Mark Wielaard wrote:
> > No. Lets keep the shndxp/sym.shndx values as they are.
> I do not mind, OK, I do not see what is shndxp/sym.shndx for the caller good
Good. Lets drop munging the shndxp/sym.shndx.
> Although the only idea of its use I have is that an application may have
> general logic for translation of ELF symbols from .opd section, in this case
> it would then try to double-translate such symbol (which would fortunately
> fail as VMA is then not from the .opd section anymore).
Could you give an example of what you have in mind here? If you think it
is relevant and/or might help me understand your use case.
> > Because then we change the contract of the function even more. Just
> > changing the st_value can be seen as how the function already works (we
> > consider resolving the function descriptor address just like adjusting
> > the st_value for the module location), but stretching it to do other
> > things too means we really should look into a new function for new
> > functionality.
> I really do not mind any function contracts.
But keeping a sane/simple interface is important.
> I look only what is needed by the caller.
Then maybe you do need a completely different function after all?
> Caller needs a function which works universally for any address, returning any
> type of matching symbol, including resolving of function descriptors.
OK, I think we can provide that through dwfl_module_addrsym () if we let
the backend detect function descriptor symbols and return that
symbol/name if the address matches. That is what I propose you
> And I already tried to explain multiple times why the code symbols need to be
> differently named and that such different name is already defined by ppc64 ABI.
Indeed, I still don't see why this is relevant. The address will match
the function descriptor symbol and name. Not some synthetic code symbol.
As far as I can see the returned name and symbol information is what the
> If we have not found an agreement on that part then the next step is to get an
> approval from IBM. I would find very unfriendly to break their ABI standard
> in common standard package without even letting them know.
Please do ask if you think that is helpful. I might be missing why it is
relevant/important. Having more opinions will certainly be welcome.
But I think just returning what is in the symbol table and not trying to
munch the returned values from what we already have is good enough.