virtio-devices: seccomp: Add seccomp_filter module

This patch added the seccomp_filter module to the virtio-devices crate
by taking reference code from the vmm crate. This patch also adds
allowed-list for the virtio-block worker thread.

Partially fixes: #925

Signed-off-by: Bo Chen <chen.bo@intel.com>

virtio-devices/src/lib.rs

@@ -41,6 +41,7 @@ pub mod net;
 pub mod net_util;
 mod pmem;
 mod rng;
+pub mod seccomp_filters;
 pub mod transport;
 pub mod vhost_user;
 pub mod vsock;
@@ -97,6 +98,8 @@ pub enum ActivateError {
     VhostUserBlkSetup(vhost_user::Error),
     /// Failed to reset vhost-user daemon.
     VhostUserReset(vhost_user::Error),
+    /// Cannot create seccomp filter
+    CreateSeccompFilter(seccomp::SeccompError),
 }
 
 pub type ActivateResult = std::result::Result<(), ActivateError>;