Re: [PATCH bpf-next v3 2/3] bpf: btf: Add BTF_KFUNCS_START/END macro pair

From: Lorenz Bauer <lorenz.bauer@isovalent.com>
To: Daniel Xu <dxu@dxuuu.xyz>
Cc: andrii@kernel.org, ast@kernel.org, daniel@iogearbox.net,
	 martin.lau@linux.dev, alexei.starovoitov@gmail.com,
	olsajiri@gmail.com,  quentin@isovalent.com,
	alan.maguire@oracle.com, memxor@gmail.com,  song@kernel.org,
	yonghong.song@linux.dev, john.fastabend@gmail.com,
	 kpsingh@kernel.org, sdf@google.com, haoluo@google.com,
	jolsa@kernel.org,  bpf@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH bpf-next v3 2/3] bpf: btf: Add BTF_KFUNCS_START/END macro pair
Date: Mon, 8 Jan 2024 10:14:13 +0100	[thread overview]
Message-ID: <CAN+4W8isJzy=J_CciNqwUa5o7wu+RQ1_cvPYXt7_OkgjPycsDw@mail.gmail.com> (raw)
In-Reply-To: <ae0a144d9ade8bf096317cc86367ed1f5468af25.1704565248.git.dxu@dxuuu.xyz>

On Sat, Jan 6, 2024 at 7:25 PM Daniel Xu <dxu@dxuuu.xyz> wrote:
>
> This macro pair is functionally equivalent to BTF_SET8_START/END, except
> with BTF_SET8_KFUNCS flag set in the btf_id_set8 flags field. The next
> commit will codemod all kfunc set8s to this new variant such that all
> kfuncs are tagged as such in .BTF_ids section.
>
> Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
> ---
>  include/linux/btf_ids.h | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
> index dca09b7f21dc..0fe4f1cd1918 100644
> --- a/include/linux/btf_ids.h
> +++ b/include/linux/btf_ids.h
> @@ -8,6 +8,9 @@ struct btf_id_set {
>         u32 ids[];
>  };
>
> +/* This flag implies BTF_SET8 holds kfunc(s) */
> +#define BTF_SET8_KFUNCS                (1 << 0)

Nit: could this be an enum so that the flag is discoverable via BTF?
Also, isn't this UAPI if pahole interprets this flag?