Index: sys/arm64/arm64/copyinout.S
===================================================================
--- sys/arm64/arm64/copyinout.S
+++ sys/arm64/arm64/copyinout.S
@@ -52,6 +52,9 @@
  */
 ENTRY(copyout)
 	cbz	x2, 1f
+	mov	x3, (VM_MAXUSER_ADDRESS - VM_MINUSER_ADDRESS)
+	cmp	x2, x3
+	b.hi	copyio_fault_nopcb
 	add	x3, x1, x2
 	ldr	x4, =VM_MAXUSER_ADDRESS
 	cmp	x3, x4
@@ -71,6 +74,9 @@
  */
 ENTRY(copyin)
 	cbz	x2, 1f
+	mov	x3, (VM_MAXUSER_ADDRESS - VM_MINUSER_ADDRESS)
+	cmp	x2, x3
+	b.hi	copyio_fault_nopcb
 	add	x3, x0, x2
 	ldr	x4, =VM_MAXUSER_ADDRESS
 	cmp	x3, x4
@@ -92,11 +98,11 @@
 	mov	x5, xzr		/* count = 0 */
 	mov	w4, #1		/* If zero return faulure */
 	cbz	x2, 3f		/* If len == 0 then skip loop */
-	ldr	x7, =VM_MAXUSER_ADDRESS
 
 	adr	x6, copyio_fault /* Get the handler address */
 	SET_FAULT_HANDLER(x6, x7) /* Set the handler */
 
+	ldr	x7, =VM_MAXUSER_ADDRESS
 1:	cmp	x0, x7
 	b.cs	copyio_fault
 	ldrb	w4, [x0], #1	/* Load from uaddr */
Index: sys/arm64/arm64/genassym.c
===================================================================
--- sys/arm64/arm64/genassym.c
+++ sys/arm64/arm64/genassym.c
@@ -39,6 +39,7 @@
 
 ASSYM(KERNBASE, KERNBASE);
 ASSYM(VM_MAXUSER_ADDRESS, VM_MAXUSER_ADDRESS);
+ASSYM(VM_MINUSER_ADDRESS, VM_MINUSER_ADDRESS);
 
 ASSYM(TDF_ASTPENDING, TDF_ASTPENDING);
 ASSYM(TDF_NEEDRESCHED, TDF_NEEDRESCHED);