Re: [PATCH 1/3] elf: Allow dlopen of filter object to work [BZ #16272]

[Florian Weimer <fweimer at redhat dot com>]

* David Kilroy:

>> Florian Weimer 
>> * David Kilroy:
>> 
>> >> The Solaris documentation does not mention symbol filtering
>> (constraining
>> >> the set of exported symbols) at run time.  This kind of filtering is
>> achieved at
>> >> run time because the link editor only looks at symbols in the filter and
>> does
>> >> not consult the filtee.
>> >
>> > My assumption was that on Solaris only the symbols mentioned in the
>> filter
>> > actually get bound at runtime. I haven't looked at what would have to be
>> done
>> > to support that behaviour. I'm sounds non-trivial :)
>> 
>> I expected that based on the name of the feature, but the Solaris
>> documentation does not support that.  It's only clear that they filter
>> at link time.
>
> [I just wanted to respond to this part of your email here. I'll
> respond to the rest via Szabolcs email.]
>
> The web page does say "The runtime linker uses the filtee to resolve
> any symbols defined by filter.so.1. If the filtee is not found, or a
> filter symbol is not found in the filtee, the filter is skipped for
> this symbol lookup."

It says “not found in the filtee”.  I think this means that the filter
is never used for symbol lookup (something we do not implement in
glibc), not that the symbol set of the filtee is restricted to that of
the filter (not implemented either).  It is possible that there was a
typo here in and the roles of filter and filtee are swapped in this
documentation paragraph, though.

Thanks,
Florian