diff --git a/mp.c b/mp.c
index 7a0a67632576325b9c3d53f684f1246fa66d943c..59beda3ea7550ed2146fc803fb99912149549d6d 100644
--- a/mp.c
+++ b/mp.c
@@ -196,7 +196,8 @@ mp_bcpu(void)
 
 extern void mpmain(void);
 
-#define APBOOTCODE 0x7000 // XXX hack
+// Write bootstrap code to unused memory at 0x7000.
+#define APBOOTCODE 0x7000
 
 void
 mp_startthem(void)
diff --git a/syscall.c b/syscall.c
index 166bf4b5d068d94833127af6f04bceee019dd5ec..ee22d09bf879e54061f44a926c617e266952af61 100644
--- a/syscall.c
+++ b/syscall.c
@@ -168,7 +168,7 @@ syscall(void)
     break;
   default:
     cprintf("unknown sys call %d\n", num);
-    // XXX fault
+    // Maybe kill the process?
     break;
   }
   cp->tf->eax = ret;