Index: kern_synch.c
===================================================================
RCS file: /cvs/src/sys/kern/kern_synch.c,v
retrieving revision 1.135
diff -u -p -r1.135 kern_synch.c
--- kern_synch.c	13 Sep 2016 08:32:44 -0000	1.135
+++ kern_synch.c	23 Jan 2017 06:37:31 -0000
@@ -635,6 +635,68 @@ sys___thrwakeup(struct proc *p, void *v,
 	return (0);
 }
 
+struct rwlock sys_cas_lock = RWLOCK_INITIALIZER("cas");
+
+int
+sys_cas_uint(struct proc *p, void *v, register_t *retval)
+{
+	struct sys_cas_uint_args /* {
+		syscallarg(unsigned int *) p;
+		syscallarg(unsigned int) e;
+		syscallarg(unsigned int) n;
+	} */ *uap = v;
+	unsigned int *uip = SCARG(uap, p);
+	unsigned int n, o = 0;
+	int error;
+
+	rw_enter_write(&sys_cas_lock);
+	error = copyin(uip, &o, sizeof(*uip));
+	if (error == 0 && o == SCARG(uap, e)) {
+		n = SCARG(uap, n);
+		error = copyout(&n, uip, sizeof(*uip));
+	}
+	rw_exit_write(&sys_cas_lock);
+
+	if (error) {
+		KERNEL_LOCK();
+		psignal(p, SIGSEGV);
+		KERNEL_UNLOCK();
+	}
+
+	*retval = o;
+	return (error);
+}
+
+int
+sys_cas_ulong(struct proc *p, void *v, register_t *retval)
+{
+	struct sys_cas_ulong_args /* {
+		syscallarg(u_long *) p;
+		syscallarg(u_long) e;
+		syscallarg(u_long) n;
+	} */ *uap = v;
+	u_long *uip = SCARG(uap, p);
+	u_long n, o = 0;
+	int error;
+
+	rw_enter_write(&sys_cas_lock);
+	error = copyin(uip, &o, sizeof(*uip));
+	if (error == 0 && o == SCARG(uap, e)) {
+		n = SCARG(uap, n);
+		error = copyout(&n, uip, sizeof(*uip));
+	}
+	rw_exit_write(&sys_cas_lock);
+
+	if (error) {
+		KERNEL_LOCK();
+		psignal(p, SIGSEGV);
+		KERNEL_UNLOCK();
+	}
+
+	*retval = o;
+	return (error);
+}
+
 void
 refcnt_init(struct refcnt *r)
 {
Index: syscalls.master
===================================================================
RCS file: /cvs/src/sys/kern/syscalls.master,v
retrieving revision 1.174
diff -u -p -r1.174 syscalls.master
--- syscalls.master	4 Sep 2016 17:22:40 -0000	1.174
+++ syscalls.master	23 Jan 2017 06:37:31 -0000
@@ -299,8 +299,10 @@
 156	OBSOL		ogetdirentries
 157	OBSOL		statfs25
 158	OBSOL		fstatfs25
-159	UNIMPL
-160	UNIMPL
+159	STD NOLOCK	{ u_int sys_cas_uint(u_int *p, u_int e, \
+			    u_int n); }
+160	STD NOLOCK	{ u_long sys_cas_ulong(u_long *p, u_long e, \
+			    u_long n); }
 161	STD		{ int sys_getfh(const char *fname, fhandle_t *fhp); }
 162	OBSOL		ogetdomainname
 163	OBSOL		osetdomainname