Index: netbsd32.h
===================================================================
RCS file: /cvsroot/src/sys/compat/netbsd32/netbsd32.h,v
retrieving revision 1.118
diff -p -u -u -r1.118 netbsd32.h
--- netbsd32.h	10 May 2018 02:36:07 -0000	1.118
+++ netbsd32.h	11 Aug 2018 03:39:52 -0000
@@ -965,7 +965,7 @@ struct netbsd32_tmpfs_args {
 /* from <fs/cd9660/cd9660_mount.h> */
 struct netbsd32_iso_args {
 	netbsd32_charp fspec;
-	struct export_args30 _pad1;
+	struct netbsd32_export_args30 _pad1;
 	int	flags;
 };
 
@@ -1021,8 +1021,6 @@ struct netbsd32_mountd_exports_list {
 	netbsd32_export_argsp	mel_exports;
 };
 
-/* no struct export_args30 yet */
-
 /* from <nfs/nfsmount,h> */
 struct netbsd32_nfs_args {
 	int32_t		version;	/* args structure version number */
@@ -1060,6 +1058,17 @@ struct netbsd32_msdosfs_args {
 	int	gmtoff;		/* v3: offset from UTC in seconds */
 };
 
+/* from <miscfs/genfs/layer.h> */
+struct netbsd32_layer_args {
+	netbsd32_charp target;		/* Target of loopback  */
+	struct netbsd32_export_args30 _pad1; /* compat with old userland tools */
+};
+
+/* from <miscfs/nullfs/null.h> */
+struct netbsd32_null_args {
+	struct	netbsd32_layer_args	la;	/* generic layerfs args */
+};
+
 struct netbsd32_posix_spawn_file_actions_entry {
 	enum { FAE32_OPEN, FAE32_DUP2, FAE32_CLOSE } fae_action;
 
Index: netbsd32_fs.c
===================================================================
RCS file: /cvsroot/src/sys/compat/netbsd32/netbsd32_fs.c,v
retrieving revision 1.80
diff -p -u -u -r1.80 netbsd32_fs.c
--- netbsd32_fs.c	1 Jun 2017 02:45:08 -0000	1.80
+++ netbsd32_fs.c	11 Aug 2018 03:39:52 -0000
@@ -54,6 +54,7 @@ __KERNEL_RCSID(0, "$NetBSD: netbsd32_fs.
 #include <fs/msdosfs/bpb.h>
 #include <fs/msdosfs/msdosfsmount.h>
 #include <ufs/ufs/ufsmount.h>
+#include <miscfs/nullfs/null.h>
 
 #define NFS_ARGS_ONLY
 #include <nfs/nfsmount.h>
@@ -799,6 +800,7 @@ netbsd32___mount50(struct lwp *l, const 
 		struct netbsd32_nfs_args nfs_args;
 		struct netbsd32_msdosfs_args msdosfs_args;
 		struct netbsd32_tmpfs_args tmpfs_args;
+		struct netbsd32_null_args null_args;
 	} fs_args32;
 	union {
 		struct ufs_args ufs_args;
@@ -807,6 +809,7 @@ netbsd32___mount50(struct lwp *l, const 
 		struct nfs_args nfs_args;
 		struct msdosfs_args msdosfs_args;
 		struct tmpfs_args tmpfs_args;
+		struct null_args null_args;
 	} fs_args;
 	const char *type = SCARG_P32(uap, type);
 	const char *path = SCARG_P32(uap, path);
@@ -953,6 +956,20 @@ netbsd32___mount50(struct lwp *l, const 
 		data_seg = UIO_SYSSPACE;
 		data = &fs_args.nfs_args;
 		data_len = sizeof(fs_args.nfs_args);
+	} else if (strcmp(mtype, MOUNT_NULL) == 0) {
+		if (data_len > sizeof(fs_args32.null_args))
+			return EINVAL;
+		if ((flags & MNT_GETARGS) == 0) {
+			error = copyin(data, &fs_args32.null_args, 
+			    sizeof(fs_args32.null_args));
+			if (error)
+				return error;
+			fs_args.null_args.la.target =
+			    NETBSD32PTR64(fs_args32.null_args.la.target);
+		}
+		data_seg = UIO_SYSSPACE;
+		data = &fs_args.null_args;
+		data_len = sizeof(fs_args.null_args);
 	} else {
 		data_seg = UIO_USERSPACE;
 	}
@@ -1032,6 +1049,13 @@ netbsd32___mount50(struct lwp *l, const 
 			    fs_args.nfs_args.hostname);
 			error = copyout(&fs_args32.nfs_args, data,
 			    sizeof(fs_args32.nfs_args));
+		} else if (strcmp(mtype, MOUNT_NULL) == 0) {
+			if (data_len != sizeof(fs_args.null_args))
+				return EINVAL;
+			NETBSD32PTR32(fs_args32.null_args.la.target,
+			    fs_args.null_args.la.target);
+			error = copyout(&fs_args32.null_args, data, 
+			    sizeof(fs_args32.null_args));
 		}
 	}
 	return error;