linux-kernel - [PATCH bpf-next 2/9] bpf: Move func_models from bpf_struct_ops to bpf_struct_ops

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Message-Id: <20241127-bpf-const-ops-v1-2-a698b8d58680@weissschuh.net>
Date: Wed, 27 Nov 2024 20:15:21 +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 2/9] bpf: Move func_models from bpf_struct_ops to
 bpf_struct_ops_desc

The func_models are the only member of struct bpf_struct_ops which are
modified by the BPF core.
Moving it into bpf_struct_ops_desc allows the static definitions of
bpf_struct_ops throughout the tree being moved into read-only memory.

The dummy ops don't have access to a bpf_struct_ops_desc.
For them declare a dedicated static variable for the func_members.

Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
 include/linux/bpf.h            | 4 ++--
 kernel/bpf/bpf_struct_ops.c    | 4 ++--
 net/bpf/bpf_dummy_struct_ops.c | 4 ++--
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 3ace0d6227e3cb70dd75bdc6afa52870dee250f1..b734543b7a2b48e717d4f1be765e0198114b4f0a 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1779,7 +1779,6 @@ struct btf_member;
  * @type: BTF type.
  * @value_type: Value type.
  * @name: The name of the struct bpf_struct_ops object.
- * @func_models: Func models
  * @type_id: BTF type id.
  * @value_id: BTF value id.
  */
@@ -1799,7 +1798,6 @@ struct bpf_struct_ops {
 	void *cfi_stubs;
 	struct module *owner;
 	const char *name;
-	struct btf_func_model func_models[BPF_STRUCT_OPS_MAX_NR_MEMBERS];
 };

 /* Every member of a struct_ops type has an instance even a member is not
@@ -1825,6 +1823,8 @@ struct bpf_struct_ops_desc {

 	/* Collection of argument information for each member */
 	struct bpf_struct_ops_arg_info *arg_info;
+
+	struct btf_func_model func_models[BPF_STRUCT_OPS_MAX_NR_MEMBERS];
 };

 enum bpf_struct_ops_state {
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index 606efe32485a985b854aa7e96e1a7f7cfd5057d3..7ee7c25d21d480d46b40b23ff8aec9d12ea81f68 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -397,7 +397,7 @@ int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,

 		if (btf_distill_func_proto(log, btf,
 					   func_proto, mname,
-					   &st_ops->func_models[i])) {
+					   &st_ops_desc->func_models[i])) {
 			pr_warn("Error in parsing func ptr %s in struct %s\n",
 				mname, st_ops->name);
 			err = -EINVAL;
@@ -777,7 +777,7 @@ 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->func_models[i],
+						&st_ops_desc->func_models[i],
 						*(void **)(st_ops->cfi_stubs + moff),
 						&image, &image_off,
 						st_map->image_pages_cnt < MAX_TRAMP_IMAGE_PAGES);
diff --git a/net/bpf/bpf_dummy_struct_ops.c b/net/bpf/bpf_dummy_struct_ops.c
index f71f67c6896b3de862a556d6f1e959a378cbda96..3a675227074e546e6a02e80db3841ed72d5bbff8 100644
--- a/net/bpf/bpf_dummy_struct_ops.c
+++ b/net/bpf/bpf_dummy_struct_ops.c
@@ -129,7 +129,7 @@ extern const struct bpf_link_ops bpf_struct_ops_link_lops;
 int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,
 			    union bpf_attr __user *uattr)
 {
-	const struct bpf_struct_ops *st_ops = &bpf_bpf_dummy_ops;
+	static typeof_member(struct bpf_struct_ops_desc, func_models) func_models;
 	const struct btf_type *func_proto;
 	struct bpf_dummy_ops_test_args *args;
 	struct bpf_tramp_links *tlinks = NULL;
@@ -175,7 +175,7 @@ int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,

 	op_idx = prog->expected_attach_type;
 	err = bpf_struct_ops_prepare_trampoline(tlinks, link,
-						&st_ops->func_models[op_idx],
+						&func_models[op_idx],
 						&dummy_ops_test_ret_function,
 						&image, &image_off,
 						true);

-- 
2.47.1