netdev - Re: [PATCH bpf-next v4 00/12] install libbpf headers when using the library

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Message-ID: <CACdoK4KaaV_OZJdUz30VyQYyJNeseV=7LX+akeeXpFhQe6Zh6w@mail.gmail.com>
Date:   Sat, 9 Oct 2021 22:03:27 +0100
From:   Quentin Monnet <quentin@...valent.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v4 00/12] install libbpf headers when using the library

On Fri, 8 Oct 2021 at 20:13, Andrii Nakryiko <andrii.nakryiko@...il.com> wrote:

> Tons of ungrateful work, thank you! Applied to bpf-next.
>
> I did a few clean ups (from my POV), see comments on relevant patches.

Thanks for that. I don't mind the clean ups. There are several of them
I considered before sending but wasn't sure about, so it's a good
thing that you did it :).

> Also in a bunch of Makefiles I've moved `| $(LIBBPF_OUTPUT)` to the
> same line if the line wasn't overly long. 80 characters is not a law,
> and I preferred single-line Makefile target definitions, if possible.

No particular preference on my side, so OK.

>
> There is one problem in bpftool's Makefile, but it works with a
> limited case of single file today. Please follow up with a proper fix.

Right, good catch. I'm sending the fix.

>
> Btw, running make in bpftool's directory, I'm getting:
>
> make[1]: Entering directory '/data/users/andriin/linux/tools/lib/bpf'
> make[1]: Entering directory '/data/users/andriin/linux/tools/lib/bpf'
> make[1]: Nothing to be done for 'install_headers'.
> make[1]: Leaving directory '/data/users/andriin/linux/tools/lib/bpf'
> make[1]: Leaving directory '/data/users/andriin/linux/tools/lib/bpf'
>
> Not sure how useful those are, might be better to disable that.

I had a look for bpftool, this is because we always descend into
libbpf's directory (FORCE target). Removing this FORCE target as I did
in samples/bpf/ avoids the descent and clears the output. I'll send a
patch.

>
> When running libbpf's make, we constantly getting this annoying warning:
>
> Warning: Kernel ABI header at 'tools/include/uapi/linux/netlink.h'
> differs from latest version at 'include/uapi/linux/netlink.h'
> Warning: Kernel ABI header at 'tools/include/uapi/linux/if_link.h'
> differs from latest version at 'include/uapi/linux/if_link.h'
>
> If you will get a chance, maybe you can get rid of that as well? I
> don't think we need to stay up to date with netlink.h and if_link.h,
> so this seems like just a noise.

I can look into that. Are you sure you want the warnings removed? Or
would it be cleaner to simply update the headers?

>
> There was also
>
> make[4]: Nothing to be done for 'install_headers'.
>
> when building the kernel. It probably is coming from either
> bpf_preload or iterators, but maybe also resolve_btfids, I didn't try
> to narrow this down. Also seems like a noise, tbh. There are similar
> useless notifications when building selftests/bpf. If it doesn't take
> too much time to clean all that up, I'd greatly appreciate that!

I haven't looked into it yet, but I can do as a follow-up. I'll post
the patches for bpftool first because I prefer to submit the fix for
bpftool's Makefile as soon as possible, and will look at this next.

Thanks,
Quentin