[bpf-next,v5,02/13] bpf: Generalize finding member offset of struct_ops prog

Commit Message

Amery Hung March 13, 2025, 7:02 p.m. UTC

Generalize prog_ops_moff() so that we can use it to retrieve a struct_ops
program's offset for different ops.

Signed-off-by: Amery Hung <[e-mail]>
Acked-by: Eduard Zingerman <[e-mail]>
---
 include/linux/bpf.h         |  1 +
 kernel/bpf/bpf_struct_ops.c | 13 +++++++++++++
 net/ipv4/bpf_tcp_ca.c       | 23 ++---------------------
 3 files changed, 16 insertions(+), 21 deletions(-)

Patch

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 7d55553de3fc..463e922cb0f5 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1908,6 +1908,7 @@  static inline void bpf_module_put(const void *data, struct module *owner)
 		module_put(owner);
 }
 int bpf_struct_ops_link_create(union bpf_attr *attr);
+u32 bpf_struct_ops_prog_moff(const struct bpf_prog *prog);
 
 #ifdef CONFIG_NET
 /* Define it here to avoid the use of forward declaration */
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index db13ee70d94d..1a5a9dee1e4a 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -1387,3 +1387,16 @@  void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struct bpf_map *map
 
 	info->btf_vmlinux_id = btf_obj_id(st_map->btf);
 }
+
+u32 bpf_struct_ops_prog_moff(const struct bpf_prog *prog)
+{
+	const struct btf_member *m;
+	const struct btf_type *t;
+	u32 midx;
+
+	t = btf_type_by_id(prog->aux->attach_btf, prog->aux->attach_btf_id);
+	midx = prog->expected_attach_type;
+	m = &btf_type_member(t)[midx];
+
+	return __btf_member_bit_offset(t, m) / 8;
+}
diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
index 554804774628..415bd3b18eef 100644
--- a/net/ipv4/bpf_tcp_ca.c
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -16,7 +16,6 @@  static struct bpf_struct_ops bpf_tcp_congestion_ops;
 
 static const struct btf_type *tcp_sock_type;
 static u32 tcp_sock_id, sock_id;
-static const struct btf_type *tcp_congestion_ops_type;
 
 static int bpf_tcp_ca_init(struct btf *btf)
 {
@@ -33,11 +32,6 @@  static int bpf_tcp_ca_init(struct btf *btf)
 	tcp_sock_id = type_id;
 	tcp_sock_type = btf_type_by_id(btf, tcp_sock_id);
 
-	type_id = btf_find_by_name_kind(btf, "tcp_congestion_ops", BTF_KIND_STRUCT);
-	if (type_id < 0)
-		return -EINVAL;
-	tcp_congestion_ops_type = btf_type_by_id(btf, type_id);
-
 	return 0;
 }
 
@@ -135,19 +129,6 @@  static const struct bpf_func_proto bpf_tcp_send_ack_proto = {
 	.arg2_type	= ARG_ANYTHING,
 };
 
-static u32 prog_ops_moff(const struct bpf_prog *prog)
-{
-	const struct btf_member *m;
-	const struct btf_type *t;
-	u32 midx;
-
-	midx = prog->expected_attach_type;
-	t = tcp_congestion_ops_type;
-	m = &btf_type_member(t)[midx];
-
-	return __btf_member_bit_offset(t, m) / 8;
-}
-
 static const struct bpf_func_proto *
 bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id,
 			  const struct bpf_prog *prog)
@@ -166,7 +147,7 @@  bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id,
 		 * setsockopt() to make further changes which
 		 * may potentially allocate new resources.
 		 */
-		if (prog_ops_moff(prog) !=
+		if (bpf_struct_ops_prog_moff(prog) !=
 		    offsetof(struct tcp_congestion_ops, release))
 			return &bpf_sk_setsockopt_proto;
 		return NULL;
@@ -177,7 +158,7 @@  bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id,
 		 * The bpf-tcp-cc already has a more powerful way
 		 * to read tcp_sock from the PTR_TO_BTF_ID.
 		 */
-		if (prog_ops_moff(prog) !=
+		if (bpf_struct_ops_prog_moff(prog) !=
 		    offsetof(struct tcp_congestion_ops, release))
 			return &bpf_sk_getsockopt_proto;
 		return NULL;