Fix: mbox output

kernel/Start.S

@@ -17,13 +17,9 @@ _start:
 	mov     sp, x1
 
 	// clear bss
-	ldr     x1, =__bss_start
-	ldr     w2, =__bss_size
-3:  
-	cbz     w2, 4f
-	str     xzr, [x1], #8
-	sub     w2, w2, #1
-	cbnz    w2, 3b
+	adr x0, __bss_start
+	adr x1, __bss_end
+	bl memzero
 
 4:
 	// jump to C code, should not return