On 10/23/17 1:52 PM, Daniel Borkmann wrote:
On 10/23/2017 07:58 PM, Yonghong Song wrote:
[...]
__this_cpu_dec(bpf_prog_active);
@@ -741,3 +754,63 @@ const struct bpf_verifier_ops
perf_event_verifier_ops = {
const struct bpf_prog_ops perf_event_prog_ops = {
};
+
+static DEFINE_MUTEX(bpf_event_mutex);
+
+int perf_event_attach_bpf_prog(struct perf_event *event,
+ struct bpf_prog *prog)
+{
+ struct bpf_prog_array __rcu *old_array;
+ struct bpf_prog_array *new_array;
+ int ret;
+
+ mutex_lock(&bpf_event_mutex);
+
+ if (event->prog)
+ return -EEXIST;
Needs to go to out here, otherwise deadlock.
Thanks for catching this! Will fix this and the below one as well in the
new revision.
+
+ old_array = rcu_dereference_protected(event->tp_event->prog_array,
+ lockdep_is_held(&bpf_event_mutex));
+ ret = bpf_prog_array_copy(old_array, NULL, prog, &new_array);
+ if (ret < 0)
+ goto out;
+
+ /* set the new array to event->tp_event and set event->prog */
+ event->prog = prog;
+ rcu_assign_pointer(event->tp_event->prog_array, new_array);
+
+ if (old_array)
+ bpf_prog_array_free(old_array);
+
+out:
+ mutex_unlock(&bpf_event_mutex);
+ return ret;
+}
+
+void perf_event_detach_bpf_prog(struct perf_event *event)
+{
+ struct bpf_prog_array __rcu *old_array;
+ struct bpf_prog_array *new_array;
+ int ret;
+
+ mutex_lock(&bpf_event_mutex);
+
+ if (!event->prog)
+ return;
Ditto.
+
+ old_array = rcu_dereference_protected(event->tp_event->prog_array,
+ lockdep_is_held(&bpf_event_mutex));
+
+ ret = bpf_prog_array_copy(old_array, event->prog, NULL, &new_array);
+ if (ret < 0) {
+ bpf_prog_array_delete_safe(old_array, event->prog);
+ } else {
+ rcu_assign_pointer(event->tp_event->prog_array, new_array);
+ bpf_prog_array_free(old_array);
+ }
+
+ bpf_prog_put(event->prog);
+ event->prog = NULL;
+
+ mutex_unlock(&bpf_event_mutex);
+}
[...]
