Re: [OE-core] [PATCH] recipes-kernel: add libbpf

["Matteo Croce" <mcroce@linux.microsoft.com>]

On Mon, Feb 8, 2021 at 9:13 PM Bruce Ashfield <bruce.ashfield@gmail.com> wrote:
>
> On Mon, Feb 8, 2021 at 1:18 PM Matteo Croce <mcroce@linux.microsoft.com> wrote:
> >
> > From: Matteo Croce <mcroce@microsoft.com>
> >
> > Add a recipe to build libbpf from https://github.com/libbpf/libbpf
> > The only patch fixes a build issue, and it's already merged upstream.
>
> Thanks for the submission! I have a few comments / questions.
>
> To get this into oe-core, we should be commenting / documenting why it
> should be in core, versus another layer. The standard criteria is that
> there are enough varied users and that the functionality is common
> enough, that it belongs in core.
>

For sure bcc and bpftrace can use it, and maybe also perf.
In future even iproute2 will use it, as it has been ported to libbpf recently.
Feel free to propose another layer, in case you know a better one.


> There should also be some sort of oe-selftest for the functionality,
> otherwise, it is hard to detect breakages. Some sort of application
> that uses the library and that can be executed in qemu would be
> enough.
>

That's doable.

> What are the kernel requirements ? CONFIG_BPF is selected by other
> kernel configs (it has no menu entry, so it must be), is it that, or
> something else that is the requirement (classic BFP?). If that option
> is now always on, is that true for the reference kernel versions in
> master (5.4 and 5.10).
>

I'd say BPF_SYSCALL, which is the single entry point for al the eBPF routines.

> Finally, does this work across all the supported architectures ? if
> not, we'll need compatibility settings.
>

I tested it only x86 and aarch64, but it should be arch independent.

Thanks!
-- 
per aspera ad upstream