bpf: Add mptcp_sched_ops CFI

'''
The cfi_stubs pointer is added in the commit 2cd3e37 ("x86/cfi,bpf:
Fix bpf_struct_ops CFI"), this patch initializes it as dummy stubs
__bpf_mptcp_sched_ops.
'''

Note:

BPF tests on export branch fail with this error:

 BUG: kernel NULL pointer dereference, address: 0000000000000000
 #PF: supervisor read access in kernel mode
 #PF: error_code(0x0000) - not-present page
 PGD 0 P4D 0
 Oops: 0000 [#1] PREEMPT SMP PTI
 CPU: 3 PID: 1512 Comm: test_progs Tainted: G        W IOE      6.7.0-rc5 torvalds#37
 Hardware name: LENOVO 4180PG2/4180PG2, BIOS 83ET76WW (1.46 ) 07/05/2013
 RIP: 0010:bpf_struct_ops_map_update_elem+0x4ee/0x610

This patch fixes this error. It can be applied after the commit
"bpf: Add bpf_mptcp_sched_ops"

Signed-off-by: Geliang Tang <[email protected]>

net/mptcp/bpf.c

@@ -147,6 +147,19 @@ static int bpf_mptcp_sched_init(struct btf *btf)
 	return 0;
 }
 
+static void __bpf_mptcp_sched_init(struct mptcp_sock *msk)
+{
+}
+
+static void __bpf_mptcp_sched_release(struct mptcp_sock *msk)
+{
+}
+
+static struct mptcp_sched_ops __bpf_mptcp_sched_ops = {
+	.init		= __bpf_mptcp_sched_init,
+	.release	= __bpf_mptcp_sched_release,
+};
+
 struct bpf_struct_ops bpf_mptcp_sched_ops = {
 	.verifier_ops	= &bpf_mptcp_sched_verifier_ops,
 	.reg		= bpf_mptcp_sched_reg,
@@ -155,6 +168,7 @@ struct bpf_struct_ops bpf_mptcp_sched_ops = {
 	.init_member	= bpf_mptcp_sched_init_member,
 	.init		= bpf_mptcp_sched_init,
 	.name		= "mptcp_sched_ops",
+	.cfi_stubs	= &__bpf_mptcp_sched_ops,
 };
 #endif /* CONFIG_BPF_JIT */