x86: segment selector macros

This copies into asm-x86/segment_64.h some macros from asm-x86/segment_32.h
for dissecting segment selectors.  This lets other code use these macros
uniformly on 32/64-bit rather than duplicating the constants elsewhere.
Signed-off-by: NRoland McGrath <roland@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

include/asm-x86/segment_64.h

@@ -50,4 +50,15 @@
 #define GDT_SIZE (GDT_ENTRIES * 8)
 #define TLS_SIZE (GDT_ENTRY_TLS_ENTRIES * 8) 
 
+/* Bottom two bits of selector give the ring privilege level */
+#define SEGMENT_RPL_MASK	0x3
+/* Bit 2 is table indicator (LDT/GDT) */
+#define SEGMENT_TI_MASK		0x4
+
+/* User mode is privilege level 3 */
+#define USER_RPL		0x3
+/* LDT segment has TI set, GDT has it cleared */
+#define SEGMENT_LDT		0x4
+#define SEGMENT_GDT		0x0
+
 #endif