x86: modify get_desc_base

This patch makes get_desc_base() receive a struct desc_struct,
and then uses its internal fields to compute the base address.
This is done at both i386 and x86_64, and then it is moved
to common header

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>

arch/x86/kernel/tls.c

@@ -112,7 +112,7 @@ int do_get_thread_area(struct task_struct *p, int idx,
 
 	memset(&info, 0, sizeof(struct user_desc));
 	info.entry_number = idx;
-	info.base_addr = get_desc_base((void *)desc);
+	info.base_addr = get_desc_base((struct desc_struct *)desc);
 	info.limit = GET_LIMIT(desc);
 	info.seg_32bit = GET_32BIT(desc);
 	info.contents = GET_CONTENTS(desc);

arch/x86/mm/fault_32.c

@@ -115,7 +115,7 @@ static inline unsigned long get_segment_eip(struct pt_regs *regs,
 	}
 
 	/* Decode the code segment base from the descriptor */
-	base = get_desc_base((unsigned long *)desc);
+	base = get_desc_base((struct desc_struct *)desc);
 
 	if (seg & (1<<2)) { 
 		mutex_unlock(&current->mm->context.lock);

include/asm-x86/desc.h

@@ -69,6 +69,11 @@ static inline void load_LDT(mm_context_t *pc)
 	preempt_enable();
 }
 
+static inline unsigned long get_desc_base(struct desc_struct *desc)
+{
+	return desc->base0 | ((desc->base1) << 16) | ((desc->base2) << 24);
+}
+
 #else
 /*
  * GET_DESC_BASE reads the descriptor base of the specified segment.

include/asm-x86/desc_32.h

@@ -168,14 +168,6 @@ static inline void __set_tss_desc(unsigned int cpu, unsigned int entry, const vo
 
 #define set_tss_desc(cpu,addr) __set_tss_desc(cpu, GDT_ENTRY_TSS, addr)
 
-static inline unsigned long get_desc_base(unsigned long *desc)
-{
-	unsigned long base;
-	base = ((desc[0] >> 16)  & 0x0000ffff) |
-		((desc[1] << 16) & 0x00ff0000) |
-		(desc[1] & 0xff000000);
-	return base;
-}
 #endif /* !__ASSEMBLY__ */
 
 #endif

include/asm-x86/desc_64.h

@@ -156,15 +156,6 @@ static inline void load_TLS(struct thread_struct *t, unsigned int cpu)
 		gdt[i] = t->tls_array[i];
 }
 
-static inline unsigned long get_desc_base(const void *ptr)
-{
-	const u32 *desc = ptr;
-	unsigned long base;
-	base = ((desc[0] >> 16)  & 0x0000ffff) |
-		((desc[1] << 16) & 0x00ff0000) |
-		(desc[1] & 0xff000000);
-	return base;
-}
 #endif /* !__ASSEMBLY__ */
 
 #endif