diff --git a/sdk/xtdk/i686/ketypes.h b/sdk/xtdk/i686/ketypes.h
index 5192f6f..1327d91 100644
--- a/sdk/xtdk/i686/ketypes.h
+++ b/sdk/xtdk/i686/ketypes.h
@@ -13,6 +13,48 @@
 #include <xttypes.h>
 
 
+/* Selector masks */
+#define MODE_MASK                         0x0001
+#define RPL_MASK                          0x0003
+
+/* GDT selector names */
+#define KGDT_NULL                         0x0000
+#define KGDT_R0_CODE                      0x0008
+#define KGDT_R0_DATA                      0x0010
+#define KGDT_R3_CODE                      0x0018
+#define KGDT_R3_DATA                      0x0020
+#define KGDT_SYS_TSS                      0x0028
+#define KGDT_R0_PCR                       0x0030
+#define KGDT_R3_TEB                       0x0038
+#define KGDT_VDM_TILE                     0x0040
+#define KGDT_R0_LDT                       0x0048
+#define KGDT_DF_TSS                       0x0050
+#define KGDT_NMI_TSS                      0x0058
+
+/* GDT descriptor privilege levels */
+#define KGDT_DPL_SYSTEM                   0
+#define KGDT_DPL_USER                     3
+
+/* GDT descriptor properties */
+#define KGDT_DESCRIPTOR_ACCESSED          0x01
+#define KGDT_DESCRIPTOR_READ_WRITE        0x02
+#define KGDT_DESCRIPTOR_EXECUTE_READ      0x02
+#define KGDT_DESCRIPTOR_EXPAND_DOWN       0x04
+#define KGDT_DESCRIPTOR_CONFORMING        0x04
+#define KGDT_DESCRIPTOR_CODE              0x08
+
+/* GDT descriptor type codes */
+#define KGDT_TYPE_CODE                    (0x10 | KGDT_DESCRIPTOR_CODE | KGDT_DESCRIPTOR_EXECUTE_READ)
+#define KGDT_TYPE_DATA                    (0x10 | KGDT_DESCRIPTOR_READ_WRITE)
+
+/* I686 Segment Types */
+#define I686_TASK_GATE                    0x5
+#define I686_TSS                          0x9
+#define I686_ACTIVE_TSS                   0xB
+#define I686_CALL_GATE                    0xC
+#define I686_INTERRUPT_GATE               0xE
+#define I686_TRAP_GATE                    0xF
+
 /* IOPM Definitions */
 #define IOPM_COUNT                        1
 #define IOPM_SIZE                         8192