Re: [PATCH v2] elf: Remove ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA

[Florian Weimer <fweimer@redhat.com>]

* Szabolcs Nagy via Libc-alpha:

> but that's not true: the exe (or a shared lib) can now
> interpose a protected variable by another one with the
> same name (and no copy relocs).

That's not desirable at all, I think.  It's certainly very surprising.

> i originally thought that warning/rejecting copy relocs in
> ld is enough to get sane behaviour for protected symbols,
> but when multiple definitions are present the behaviour
> will depend on ld's decision to use GOT or not.
>
> i think the removed logic tried to ensure that GOT relocs
> resolve to the definition within the same shared lib for
> protected data. (i.e. ld's decision does not matter.)
>
> if we want to allow ld to not use GOT then i think we need
> to keep the logic that makes GOT behave consistently with
> that future.

I agree.  I have this mental model that protected symbols behave like
-Bsymbolic.  The ELF specification also seems to require that the symbol
cannot be preempted.

Thanks,
Florian