linux-kernel - [PATCH bpf-next] bpf: Add comment about helper freeze

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Message-Id: <20250204-bpf-helper-freeze-v1-1-46efd9ff20dc@outlook.com>
Date: Tue, 04 Feb 2025 10:00:21 +0800
From: Levi Zim via B4 Relay <devnull+rsworktech.outlook.com@...nel.org>
To: Andrii Nakryiko <andrii@...nel.org>, 
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 Eduard Zingerman <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>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Levi Zim <rsworktech@...look.com>
Subject: [PATCH bpf-next] bpf: Add comment about helper freeze

From: Levi Zim <rsworktech@...look.com>

Put a comment after the bpf helper list in uapi bpf.h to prevent people
from trying to add new helpers there and direct them to kfuncs.

Link: https://lore.kernel.org/bpf/CAEf4BzZvQF+QQ=oip4vdz5A=9bd+OmN-CXk5YARYieaipK9s+A@mail.gmail.com/
Link: https://lore.kernel.org/bpf/20221231004213.h5fx3loccbs5hyzu@macbook-pro-6.dhcp.thefacebook.com/
Suggested-by: Andrii Nakryiko <andrii@...nel.org>
Signed-off-by: Levi Zim <rsworktech@...look.com>
---
Put a comment after the bpf helper list in uapi bpf.h to prevent people
from trying to add new helpers there and direct them to kfuncs.
---
 include/uapi/linux/bpf.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 2acf9b33637174bd16b1d12ccc6410c5f55a7ea9..fff6cdb8d11a2c211a6205ae2937b2bdf593cd42 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -6019,7 +6019,10 @@ union bpf_attr {
 	FN(user_ringbuf_drain, 209, ##ctx)		\
 	FN(cgrp_storage_get, 210, ##ctx)		\
 	FN(cgrp_storage_delete, 211, ##ctx)		\
-	/* */
+	/* This helper list is effectively frozen. If you are trying to	\
+	 * add a new helper, you should add a kfunc instead which has	\
+	 * less stability guarantees. See Documentation/bpf/kfuncs.rst	\
+	 */
 
 /* backwards-compatibility macros for users of __BPF_FUNC_MAPPER that don't
  * know or care about integer value that is now passed as second argument

---
base-commit: 03f3aa4a6b664270d502c7fb44c634cbe250261e
change-id: 20250204-bpf-helper-freeze-cf3e0b29fb63

Best regards,
-- 
Levi Zim <rsworktech@...look.com>