[PATCH bpf-next 2/3] bpf: Show precise rejected function when attaching to __btf_id functions

[KaFai Wan <mannkafai@gmail.com>]

Show the precise rejected function name when attaching tracing to
__btf_id functions.

$ ./fentry
libbpf: prog 'migrate_disable': BPF program load failed: -EINVAL
libbpf: prog 'migrate_disable': -- BEGIN PROG LOAD LOG --
Attaching tracing to __btf_id function 'migrate_disable' is rejected.

Signed-off-by: KaFai Wan <mannkafai@gmail.com>
---
 kernel/bpf/verifier.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 275d82fb1a1a..2779d63e1f8b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -23938,6 +23938,8 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 			return ret;
 	} else if (prog->type == BPF_PROG_TYPE_TRACING &&
 		   btf_id_set_contains(&btf_id_deny, btf_id)) {
+		verbose(env, "Attaching tracing to __btf_id function '%s' is rejected.\n",
+			tgt_info.tgt_name);
 		return -EINVAL;
 	} else if ((prog->expected_attach_type == BPF_TRACE_FEXIT ||
 		   prog->expected_attach_type == BPF_MODIFY_RETURN) &&
-- 
2.43.0