Re: [PATCH v2] RISC-V: Fix IFUNC resolver cannot access gp pointer

[Florian Weimer <fweimer@redhat.com>]

* Kito Cheng:

> Hi Florian:
>
> Thanks for your explanation! one more question around the
> HIDDEN_VAR_NEEDS_DYNAMIC_RELOC,
> RISC-V don't set that to 1 but seems to work well so far...?
> Is it because the GP register is limited to executable so that we are
> safe without that?

Yes, exactly.  The dynamic linker doesn't use the GP register for its
own purposes, and it doesn't impact code generation for the dynamic
linker itself.

However, the way GP setup is currently handled is highly problematic
because the ABI does not give us a proper way to set it up correctly.
The use of a dynamic symbol is too fragile and seems to have been added
as an afterthought.  This should be a dynamic tag in the main
executable.  If we had that, we could set GP in all relevant calls to
application code (of course this assumes that applications do not use GP
as a global register variable for a different purpose, but hopefully
that's not the case).

Thanks,
Florian