linux-kernel - [PATCH bpf-next 5/9] bpf: Allow registration of const cfi

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Message-Id: <20241127-bpf-const-ops-v1-5-a698b8d58680@weissschuh.net>
Date: Wed, 27 Nov 2024 20:15:24 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: "David S. Miller" <davem@...emloft.net>, 
 David Ahern <dsahern@...nel.org>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Simon Horman <horms@...nel.org>, Martin KaFai Lau <martin.lau@...nel.org>, 
 Kui-Feng Lee <thinker.li@...il.com>, Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, 
 John Fastabend <john.fastabend@...il.com>, 
 Andrii Nakryiko <andrii@...nel.org>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 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>, Jiri Kosina <jikos@...nel.org>, 
 Benjamin Tissoires <bentiss@...nel.org>, Tejun Heo <tj@...nel.org>, 
 David Vernet <void@...ifault.com>, Ingo Molnar <mingo@...hat.com>, 
 Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>, 
 Vincent Guittot <vincent.guittot@...aro.org>, 
 Dietmar Eggemann <dietmar.eggemann@....com>, 
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, 
 Mel Gorman <mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 bpf@...r.kernel.org, linux-input@...r.kernel.org, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH bpf-next 5/9] bpf: Allow registration of const cfi_stubs

The BPF core does not need to modify the cfi_stubs.
Reflect this in the API so users can move their structures into
read-only memory.

Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
 include/linux/bpf.h         | 2 +-
 kernel/bpf/bpf_struct_ops.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index a9267af9671b2bc8961cde24d2f79f473ab227d7..fbe5ae7c2b380fdb624ea1f04fdf56e4f6710f14 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1795,7 +1795,7 @@ struct bpf_struct_ops {
 	void (*unreg)(void *kdata, struct bpf_link *link);
 	int (*update)(void *kdata, void *old_kdata, struct bpf_link *link);
 	int (*validate)(void *kdata);
-	void *cfi_stubs;
+	const void *cfi_stubs;
 	struct module *owner;
 	const char *name;
 };
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index 967f0914d473fcde4a6ce3bb6ac976345daf8e88..2a9b9c39f1e7c2c22dc83ad68766b522117f3979 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -778,7 +778,7 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
 		trampoline_start = image_off;
 		err = bpf_struct_ops_prepare_trampoline(tlinks, link,
 						&st_ops_desc->func_models[i],
-						*(void **)(st_ops->cfi_stubs + moff),
+						*(void *const *)(st_ops->cfi_stubs + moff),
 						&image, &image_off,
 						st_map->image_pages_cnt < MAX_TRAMP_IMAGE_PAGES);
 		if (err)

-- 
2.47.1