Re: load of in-place relocation addend in AArch64

[Nick Clifton <nickc@redhat.com>]

Hi Frédéric,

> My compiler generates REL relocations with an in-place addend but the addend is not taken into account for computing the final relocated symbol address (S+A).

Is there any particular reason for this ?

Ie, if your compiler generated RELA relocations then all of your problems
with the binutils should go away...

> So it seems the that I'm the first one that generates REL relocations for AArch64 target.

True.

> However, I don't see any limitation on using REL relocations in the AARCH64 ABI.

Correct.  There are - in theory - allowed.

> I would appreciate any comment/feedback that would help me understanding the reasons behind that.

As a general rule RELA relocations are preferable in that they
are simpler - it is easier to extract the addend - and in theory
they have the possibility to express a wider range of addends
than would be available to REL relocations.

Have you tried modifying the AArch64 code in the BFD library to
support REL relocations ?  In theory all that you need to do is
to change a few lines in bfd/elfnn-aarch64.c:

   #define elf_backend_may_use_rel_p      0

and maybe:

   #define elf_backend_may_use_rela_p     1
   #define elf_backend_default_use_rela_p 1
   #define elf_backend_rela_normal	 1

In practice I am pretty sure that there will be assumptions of RELA
relocs elsewhere in the AArch64 specific code, so I doubt it will be
as simple as I have suggested.

Cheers
   Nick