netdev - Re: [PATCH bpf-next v8 04/11] bpf: support fsession for bpf_session_is

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Message-ID: <CAADnVQLj4c-nc6gLbBiaT24KXWEpG3AzFT=P1tszu_akXhyD=Q@mail.gmail.com>
Date: Fri, 9 Jan 2026 18:40:22 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Menglong Dong <menglong8.dong@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>, Andrii Nakryiko <andrii@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Martin KaFai Lau <martin.lau@...ux.dev>, Eduard <eddyz87@...il.com>, 
	Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, 
	John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	"David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, jiang.biao@...ux.dev, 
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, X86 ML <x86@...nel.org>, 
	"H. Peter Anvin" <hpa@...or.com>, bpf <bpf@...r.kernel.org>, 
	Network Development <netdev@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next v8 04/11] bpf: support fsession for bpf_session_is_return

On Wed, Jan 7, 2026 at 6:25 PM Menglong Dong <menglong8.dong@...il.com> wrote:
>
> +       } else if (func_id == special_kfunc_list[KF_bpf_session_is_return]) {
> +               if (prog->expected_attach_type == BPF_TRACE_FSESSION)
> +                       addr = (unsigned long)bpf_fsession_is_return;

...

> +bool bpf_fsession_is_return(void *ctx)
> +{
> +       /* This helper call is inlined by verifier. */
> +       return !!(((u64 *)ctx)[-1] & (1 << BPF_TRAMP_M_IS_RETURN));
> +}
> +

Why do this specialization and introduce a global function
that will never be called, since it will be inlined anyway?

Remove the first hunk and make the 2nd a comment instead of a real function?