netdev - Re: [PATCH bpf-next 4/4] selftests/bpf: Remove tests for prologue/epilogue with kfuncs

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Message-ID: <4423cc78-ec0c-4171-bf34-cc9b6596fa5a@linux.dev>
Date: Wed, 21 Jan 2026 11:13:29 -0800
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Jakub Sitnicki <jakub@...udflare.com>
Cc: Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 John Fastabend <john.fastabend@...il.com>,
 Andrii Nakryiko <andrii@...nel.org>, Eduard Zingerman <eddyz87@...il.com>,
 Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>,
 KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>,
 Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
 Amery Hung <ameryhung@...il.com>, netdev@...r.kernel.org,
 kernel-team@...udflare.com, bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next 4/4] selftests/bpf: Remove tests for
 prologue/epilogue with kfuncs

On 1/21/26 1:49 AM, Jakub Sitnicki wrote:
> On Tue, Jan 20, 2026 at 03:48 PM -08, Martin KaFai Lau wrote:
>> On 1/19/26 11:53 AM, Jakub Sitnicki wrote:
>>> Remove pro_epilogue_with_kfunc test program and its supporting code in
>>> bpf_testmod. This test exercised calling kfuncs from prologue and epilogue,
>>> which is no longer supported after the switch to direct helper calls.
>>
>> Is it easy to change it to test calling helper in pro/epilogue?
> 
> I gave it a shot and the obstacle is that bpf_cgroup_from_id and
> bpf_cgroup_release are not exported symbols, so they can't be referred
> to from bpf_testmod. We'd have to move the whole thing to lib/test_bpf
> so it's a built-in.

I was thinking of creating a helper in bpf_testmod.c but then noticed it 
may fail in the JIT that needs bpf_jit_supports_far_kfunc_call(). A 
cleaner way could be to use the existing pro/epilogue in bpf_qdisc ops. 
I was wondering if the __xlated test here could be quickly adapted in 
patch 4 but it seems that's not the case. The existing bpf_qdisc is 
testing it quietly without the __xlated, so no need to hold up this set.

For patch 3 and 4,

Acked-by: Martin KaFai Lau <martin.lau@...nel.org>