Re: [PATCH] Fix MIPS ELF64 relocation howtos

[Thiemo Seufer <ica2_ts@csv.ica.uni-stuttgart.de>]

H . J . Lu wrote:
[snip]
> > This means to use the specification as a guide as long as it's
> > reasonable for Linux. That's my intention, too. 
> 
> Good. While we are on it, here are things I'd like to see in the new
> `traditional 64bit MIPS ELF ABI':
> 
> 1. Make gp callee-saved.

Ok. We should also use the rest of the NewABI calling conventions.

> 2. Use RELA relocation if all possible.

My private patch does so already, and since the ABI draft claims some
essential relocations to be unsupported for REL, this should be used
for all MIPS ELF64 variants. It's the only sane way AFAICS.

> 3. Use relocations in the SGI 64bit ABI when make senses to us.

Ok. I made some steps towards this in my private patch for the
_HIGHER and _HIGHEST relocations.

> 4. Drop support for the MIPS/SGI quickstart.

Since there is no support for quickstart in binutils: already done. :-)

> 5. Add support for the glibc prelink.

This will be an issue when we can do PIC.

> #1 is a gcc only issue.

No, we need to handle .cpsetup, .cpreturn and possibly .cplocal
as well as the resulting relocations. Even if we rely on gcc to
expand these .cp*, we have to handle %gp_rel() and %neg().

> I think the change to gcc is minimum. That is
> we make sure that we don't use o64 for gcc. #2, #3, #4 and #5 will
> affect binutils.

I doubt anybody actually uses o64. I found several places in
binutils where it is broken or only partially implemented.


Thiemo