RE: [patch] --filter option in ld: srcfix

[PODOPLELOV Andrei <Andrei.PODOPLELOV@3ds.com>]

Hi Florian,

Responding to your idea about filtering...
I just checked the filtering. It does work as expected, means, I cannot build main.c using some new symbol, defined only in filtee.c, but not in filter.c. So the runtime won't use the full set of filtee's symbols, but just a subset, defined in the filter.

You can check my sample, attached to the previous email. Easy to use. Just rename build.txt to build.sh, and put the usual  #!/bin/bash on the top to build it. Then run "./prog".

I am completely open to change my wording.

Thanks,
Andrei

-----Original Message-----
From: Florian Weimer <fweimer@redhat.com>
Sent: Wednesday, December 8, 2021 1:08 PM
To: PODOPLELOV Andrei <Andrei.PODOPLELOV@3ds.com>
Cc: mtk.manpages@gmail.com; linux-man@vger.kernel.org; alx.manpages@gmail.com
Subject: Re: [patch] --filter option in ld: srcfix

* PODOPLELOV Andrei:

> I believe it would be beneficial to change it to something like:
>
>        --filter=name
>            When creating an ELF shared object (a "filter"), set the
>            internal DT_FILTER field to the specified name - another
>            ELF shared object (a "filtee"). This tells the dynamic linker
>            that the symbol table of the "filter" should be used to
>            select a subset of the symbols provided by the "filtee".
>
>            When you link a program against this "filter" and run it,
>            the dynamic linker will see the DT_FILTER field and resolve
>            symbols according to the symbol table of the "filter" object
>            as usual. However, when a certain symbol of the "filter" is
>            also present in "filtee", it will actually link to the
>            definition in the "filtee".

I think that's still misleading because to my knowledge, glibc does not implement any filtering.  Only the symbol search order is changed (what you describe in the second paragraph).

Thanks,
Florian

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