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, 34 insertions, 0 deletions

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 51bee695d32c..0048cb24ba7b 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1272,6 +1272,37 @@ static int bpf_prog_detach(const union bpf_attr *attr)
         return ret;
 }
 
+#define BPF_PROG_QUERY_LAST_FIELD query.prog_cnt
+
+static int bpf_prog_query(const union bpf_attr *attr,
+                          union bpf_attr __user *uattr)
+{
+        struct cgroup *cgrp;
+        int ret;
+
+        if (!capable(CAP_NET_ADMIN))
+                return -EPERM;
+        if (CHECK_ATTR(BPF_PROG_QUERY))
+                return -EINVAL;
+        if (attr->query.query_flags & ~BPF_F_QUERY_EFFECTIVE)
+                return -EINVAL;
+
+        switch (attr->query.attach_type) {
+        case BPF_CGROUP_INET_INGRESS:
+        case BPF_CGROUP_INET_EGRESS:
+        case BPF_CGROUP_INET_SOCK_CREATE:
+        case BPF_CGROUP_SOCK_OPS:
+                break;
+        default:
+                return -EINVAL;
+        }
+        cgrp = cgroup_get_from_fd(attr->query.target_fd);
+        if (IS_ERR(cgrp))
+                return PTR_ERR(cgrp);
+        ret = cgroup_bpf_query(cgrp, attr, uattr);
+        cgroup_put(cgrp);
+        return ret;
+}
 #endif /* CONFIG_CGROUP_BPF */
 
 #define BPF_PROG_TEST_RUN_LAST_FIELD test.duration
@@ -1568,6 +1599,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
         case BPF_PROG_DETACH:
                 err = bpf_prog_detach(&attr);
                 break;
+        case BPF_PROG_QUERY:
+                err = bpf_prog_query(&attr, uattr);
+                break;
 #endif
         case BPF_PROG_TEST_RUN:
                 err = bpf_prog_test_run(&attr, uattr);