RE: [Bpf] IETF BPF working group draft charter

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> -----Original Message-----
> From: David Vernet <void@xxxxxxxxxxxxx>
> Sent: Tuesday, May 23, 2023 9:32 AM
> To: Dave Thaler <dthaler@xxxxxxxxxxxxx>
> Cc: Jose E. Marchesi <jemarch@xxxxxxx>; bpf@xxxxxxxx; bpf
> <bpf@xxxxxxxxxxxxxxx>; Erik Kline <ek.ietf@xxxxxxxxx>; Suresh Krishnan
> (sureshk) <sureshk@xxxxxxxxx>; Christoph Hellwig <hch@xxxxxxxxxxxxx>;
> Alexei Starovoitov <ast@xxxxxxxxxx>
> Subject: Re: [Bpf] IETF BPF working group draft charter
> 
> On Thu, May 18, 2023 at 07:42:11PM +0000, Dave Thaler wrote:
> > Jose E. Marchesi <jemarch@xxxxxxx> 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

I can tell you it's very important to those who work on the ebpf-for-windows project that the ELF format is common between Linux and Windows so that tools like
llvm-objdump and bpftool and other BPF-specific ELF parsing tools work for both
Linux and Windows.   We don't want Windows to diverge.

As such, I feel strongly that it is a requirement to be standardized right away.
Hence I would not want this removed from the charter unless there's an effort
to do it somewhere else right away, which would seem to increase the coordination
burden.

Dave





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