+/* GDT selectors defined by loader.
+ More selectors are defined by userprog/gdt.h. */
+#define SEL_NULL 0x00 /* Null selector. */
+#define SEL_KCSEG 0x08 /* Kernel code selector. */
+#define SEL_KDSEG 0x10 /* Kernel data selector. */
+
+#endif /* threads/loader.h */