Re: [PATCH 3/5] qmp: Added the helper stamp check.

[Daniel P . Berrangé]

On Tue, Feb 28, 2023 at 08:01:51PM +0100, Toke Høiland-Jørgensen wrote:
> Daniel P. Berrangé <berrange@redhat.com> writes:
> 
> Just to interject a note on this here: the skeleton code is mostly a
> convenience feature used to embed BPF programs into the calling binary.
> It is perfectly possible to just have the BPF object file itself reside
> directly in the file system and just use the regular libbpf APIs to load
> it. Some things get a bit more cumbersome (mostly setting values of
> global variables, if the BPF program uses those).
> 
> So the JSON example above could just be a regular compiled-from-clang
> BPF object file, and the management program can load that, inspect its
> contents using the libbpf APIs and pass the file descriptors on to Qemu.
> It's even possible to embed version information into this so that Qemu
> can check if it understands the format and bail out if it doesn't - just
> stick a version field in the configuration map as the first entry :)

If all you have is the BPF object file is it possible to interrogate
it to get a list of all the maps, and get FDs associated for them ?
I had a look at the libbpf API and wasn't sure about that, it seemed
like you had to know the required maps upfront ?  If it is possible
to auto-discover everything you need, soley from the BPF object file
as input, then just dealing with that in isolation would feel simpler.


With regards,
Daniel
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