x86: introduce fill_ldt

This patch introduces fill_ldt(), which populates a ldt descriptor
from a user_desc in once, instead of relying in the LDT_entry_a and
LDT_entry_b macros

Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/kernel/tls.c b/arch/x86/kernel/tls.c
index 67a3776..74d2b65 100644
--- a/arch/x86/kernel/tls.c
+++ b/arch/x86/kernel/tls.c
@@ -67,10 +67,9 @@
 	if (LDT_empty(&info)) {
 		desc[0] = 0;
 		desc[1] = 0;
-	} else {
-		desc[0] = LDT_entry_a(&info);
-		desc[1] = LDT_entry_b(&info);
-	}
+	} else
+		fill_ldt((struct desc_struct *)desc, &info);
+
 	if (t == &current->thread)
 		load_TLS(t, cpu);