x86: use get_desc_base

This changes a couple of places to use the get_desc_base function.
They were duplicating the same calculation with different equivalent code.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index aa9414e..9ea1d75 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -464,11 +464,7 @@
 
 static inline u32 read_32bit_tls(struct task_struct *t, int tls)
 {
-	struct desc_struct *desc = (void *)t->thread.tls_array;
-	desc += tls;
-	return desc->base0 | 
-		(((u32)desc->base1) << 16) | 
-		(((u32)desc->base2) << 24);
+	return get_desc_base(&t->thread.tls_array[tls]);
 }
 
 /*