[PATCH bpf-next v1 1/3] bpf: add bpf_features enum

[Eduard Zingerman <eddyz87@xxxxxxxxx>]

This commit adds a kernel side enum for use in conjucntion with BTF
CO-RE bpf_core_enum_value_exists. The goal of the enum is to assist
with available BPF features detection. Intended usage looks as
follows:

  if (bpf_core_enum_value_exists(enum bpf_features, BPF_FEAT_<f>))
     ... use feature f ...

Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
---
 kernel/bpf/verifier.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 279a64933262..71de4c9487d5 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -44,6 +44,10 @@ static const struct bpf_verifier_ops * const bpf_verifier_ops[] = {
 #undef BPF_LINK_TYPE
 };
 
+enum bpf_features {
+	__MAX_BPF_FEAT = 0,
+};
+
 struct bpf_mem_alloc bpf_global_percpu_ma;
 static bool bpf_global_percpu_ma_set;
 
@@ -24388,6 +24392,8 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
 	u32 log_true_size;
 	bool is_priv;
 
+	BTF_TYPE_EMIT(enum bpf_features);
+
 	/* no program is valid */
 	if (ARRAY_SIZE(bpf_verifier_ops) == 0)
 		return -EINVAL;
-- 
2.47.1