[LSF/MM/BPF TOPIC] Compiled BPF

[LSF/MM/BPF TOPIC] Compiled BPF

[Jose E. Marchesi]

Hello people!

[Turns out I forgot to send the topic proposal to the mailing list once
 the topic was proposed (in time) via the google form.  But better late
 than never..]

Work on GCC BPF (also binutils, etc) is progressing at a good pace and
there are a lot of updates and topics that would benefit from having
some face-to-face discussion with the kernel hackers.

Some of these updates and topics are:

- Dealing with some pending differences in behavior between GCC and
  clang/llvm.

- Support of "optional" but important BPF features such as quick calls
  which are currently not supported by GCC.  We are preparing an
  exhaustive support matrix to track this, kees-style.

- Documentation and maintenance of the ABI in general, and some specific
  ABI issues in particular that need agreement and definition at this
  point.

- We are finally ready to add -fverifiable, aiming at GCC 17 (GCC 16 is
  now in stage 4) and we would like to get feedback on some of the
  details.

- Handling CO-RE limitations and corner cases at compile time.  The
  compilers should emit proper diagnostics and behave the same way.

- Testing: we have finally upstreamed the infrastructure that allows
  loading and running GCC BPF tests in kernel.  Along with the support
  for building the kernel BPF selftests, the idea is to have strong
  coverage to detect regressions ASAP in both kernel and compiler side.

- More upstream BPF projects are adding support for using GCC BPF, and
  support in distros is improving.

- We recently got an important reinforcement for the developmet of GCC
  BPF, thanks to Meta: Vineet Gupta, an experienced GCC hacker, has
  joined the party and is already doing great work, speeding up the
  development.

It would be useful if we could have some time during LSFMMBPF to
dedicate to these topics, if possible.

Salud!

[LSF/MM/BPF TOPIC] Compiled BPF

[Jose E. Marchesi]

Hello.

I would like to propose an activity for the BPF track at LSFMMBPF.

As in previous editions, the purpose of the activity is to do a quick
recap of the current BPF support in both GCC and clang/LLVM and where we
stand, to discuss and clarify any particular issue that may be relevant
to either compiler, and to collect and address comments, requirements
and other feedback from the kernel hackers present.

On the GCC BPF side we would like to pay special attention to the topic
of divergences, as we are nowadays being bugged not so much by missing
features anymore, as it used to be, but by divergences in the support of
certain features between GCC and clang.  Some of these divergences are
trivial to fix just by following clang's behavior as they are found, but
others require discussion and agreement.  Also, we would like to expand
a bit the scope of the discussion to cover a few topics related to the
"environment" where the compiled BPF programs are built.  Examples of
the later are external linking and the inclusion of host standard
headers by BPF programs.

Thanks!

[LSF/MM/BPF TOPIC] Compiled BPF

[Jose E. Marchesi]

[Resending because I don't think the message reached bpf@vger]

Hello.

I would like to propose an activity for the BPF track at LSFMMBPF.

As in previous editions, the purpose of the activity is to do a quick
recap of the current BPF support in both GCC and clang/LLVM and where we
stand, to discuss and clarify any particular issue that may be relevant
to either compiler, and to collect and address comments, requirements
and other feedback from the kernel hackers present.

On the GCC BPF side we would like to pay special attention to the topic
of divergences, as we are nowadays being bugged not so much by missing
features anymore, as it used to be, but by divergences in the support of
certain features between GCC and clang.  Some of these divergences are
trivial to fix just by following clang's behavior as they are found, but
others require discussion and agreement.  Also, we would like to expand
a bit the scope of the discussion to cover a few topics related to the
"environment" where the compiled BPF programs are built.  Examples of
the later are external linking and the inclusion of host standard
headers by BPF programs.

Thanks!