Re: [Bpf] IETF BPF working group draft charter

[David Vernet <void@manifault.com>]

On Thu, May 18, 2023 at 07:42:11PM +0000, Dave Thaler wrote:
> Jose E. Marchesi <jemarch@gnu.org> wrote:
> > I would think that the way the x86_64, aarch64, risc-v, sparc, mips, powerpc
> > architectures, along with their variants, handle their ELF extensions and
> > psABI, ensures interoperability good enough for the problem at hand, but ok.
> > I'm definitely not an expert in these matters.
> 
> I am not familiar enough with those to make any comment about that.

Hi Dave,

Taking a step back here, perhaps we need to think about all of this more
generically as "ABI", rather than ELF "extensions", "bindings", etc.  In
my opinion this would include, at a minimum, the following items from
the current proposed WG charter:

* the eBPF bindings for the ELF executable file format,

* the platform support ABI, including calling convention, linker
  requirements, and relocations,

As far as I know (please correct me if I'm wrong), there isn't really a
precedence for standardizing ABIs like this. For example, x86 calling
conventions are not standardized.  Solaris, Linux, FreeBSD, macOS, etc
all follow the System V AMD64 ABI, but Microsoft of course does not. As
Jose pointed out, such standards extensions do not exist for psABI ELF
extensions for various architectures either.

While it may be that we do end up needing to standardize these ABIs for
BPF, I'm beginning to think that we should just remove them from the
current WG charter, and consider standardizing them at a later time if
it's clear that it's actually necessary. I think this is especially true
given that we don't seem to be getting any closer to having consensus,
and that we're very short on time given that Erik is going to be
proposing the charter to the rest of the ADs in just two days on 5/25.

Thanks,
David