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 6b49e1991ae7..eba966c09053 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;