src/userprog/exception.c

@@ -158,6 +158,16 @@ page_fault (struct intr_frame *f)
 #ifdef VM
   struct thread *t = thread_current ();
   void *upage = pg_round_down (fault_addr);
+
+  /* If the fault address is in a user page that is not present, then it might
+  be an executable file page that needs to be lazily loaded. So, we check the
+  SPT to determine if this is the case, and if so load the page from disk. */
+  if (not_present && is_user_vaddr (upage))
+    {
+      if (try_fetch_page (upage, write))
+        return;
+    }
+
   if (user)
     {
       if (not_present)
@@ -193,15 +203,6 @@ page_fault (struct intr_frame *f)
       f->eax = 0xffffffff;
       return;
     }
-
-  /* If the fault address is in a user page that is not present, then it might
-  just need to be lazily loaded. So, we check our SPT to see if the page
-  is expected to have data loaded in memory. */
-  if (not_present && is_user_vaddr (upage) && upage != NULL)
-    {
-      if (try_fetch_page (upage, write))
-        return;
-    }
 #endif
 
   /* To implement virtual memory, delete the rest of the function