bpf: introduce BPF_PROG_QUERY command

introduce BPF_PROG_QUERY command to retrieve a set of either
attached programs to given cgroup or a set of effective programs
that will execute for events within a cgroup

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
for cgroup bits
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 38 insertions, 0 deletions

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 6b49e19..eba966c 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1412,6 +1412,44 @@ void bpf_prog_array_free(struct bpf_prog_array __rcu *progs)
 	kfree_rcu(progs, rcu);
 }
 
+int bpf_prog_array_length(struct bpf_prog_array __rcu *progs)
+{
+	struct bpf_prog **prog;
+	u32 cnt = 0;
+
+	rcu_read_lock();
+	prog = rcu_dereference(progs)->progs;
+	for (; *prog; prog++)
+		cnt++;
+	rcu_read_unlock();
+	return cnt;
+}
+
+int bpf_prog_array_copy_to_user(struct bpf_prog_array __rcu *progs,
+				__u32 __user *prog_ids, u32 cnt)
+{
+	struct bpf_prog **prog;
+	u32 i = 0, id;
+
+	rcu_read_lock();
+	prog = rcu_dereference(progs)->progs;
+	for (; *prog; prog++) {
+		id = (*prog)->aux->id;
+		if (copy_to_user(prog_ids + i, &id, sizeof(id))) {
+			rcu_read_unlock();
+			return -EFAULT;
+		}
+		if (++i == cnt) {
+			prog++;
+			break;
+		}
+	}
+	rcu_read_unlock();
+	if (*prog)
+		return -ENOSPC;
+	return 0;
+}
+
 static void bpf_prog_free_deferred(struct work_struct *work)
 {
 	struct bpf_prog_aux *aux;