x86: Remove GDR related magic numbers

--
Changes for v2:
 - Use an enum
 - Add defined for GDT size (previously added in patch 7)
 - Use X86_ namespace (as per Linux headers)

arch/x86/cpu/cpu.c

@@ -63,13 +63,13 @@ static void reload_gdt(void)
 	 */
 	static const u64 boot_gdt[] __attribute__((aligned(16))) = {
 		/* CS: code, read/execute, 4 GB, base 0 */
-		[GDT_ENTRY_32BIT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff),
+		[X86_GDT_ENTRY_32BIT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff),
 		/* DS: data, read/write, 4 GB, base 0 */
-		[GDT_ENTRY_32BIT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff),
+		[X86_GDT_ENTRY_32BIT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff),
 		/* 16-bit CS: code, read/execute, 64 kB, base 0 */
-		[GDT_ENTRY_16BIT_CS] = GDT_ENTRY(0x109b, 0, 0x0ffff),
+		[X86_GDT_ENTRY_16BIT_CS] = GDT_ENTRY(0x109b, 0, 0x0ffff),
 		/* 16-bit DS: data, read/write, 64 kB, base 0 */
-		[GDT_ENTRY_16BIT_DS] = GDT_ENTRY(0x1093, 0, 0x0ffff),
+		[X86_GDT_ENTRY_16BIT_DS] = GDT_ENTRY(0x1093, 0, 0x0ffff),
 	};
 	static struct gdt_ptr gdt;
 

arch/x86/cpu/start.S

@@ -29,6 +29,7 @@
 #include <config.h>
 #include <version.h>
 #include <asm/global_data.h>
+#include <asm/processor.h>
 #include <asm/processor-flags.h>
 #include <generated/asm-offsets.h>
 
@@ -58,7 +59,7 @@ _start:
 	/* This is the 32-bit cold-reset entry point */
 
 	/* Load the segement registes to match the gdt loaded in start16.S */
-	movl	$0x18, %eax
+	movl	$(X86_GDT_ENTRY_32BIT_DS * X86_GDT_ENTRY_SIZE), %eax
 	movw	%ax, %fs
 	movw	%ax, %ds
 	movw	%ax, %gs

arch/x86/include/asm/processor.h

@@ -24,9 +24,24 @@
 #ifndef __ASM_PROCESSOR_H_
 #define __ASM_PROCESSOR_H_ 1
 
-#define GDT_ENTRY_32BIT_CS	2
-#define GDT_ENTRY_32BIT_DS	(GDT_ENTRY_32BIT_CS + 1)
-#define GDT_ENTRY_16BIT_CS	(GDT_ENTRY_32BIT_DS + 1)
-#define GDT_ENTRY_16BIT_DS	(GDT_ENTRY_16BIT_CS + 1)
+#define X86_GDT_ENTRY_SIZE	8
+
+#ifndef __ASSEMBLY__
+
+enum {
+	X86_GDT_ENTRY_NULL = 0,
+	X86_GDT_ENTRY_UNUSED,
+	X86_GDT_ENTRY_32BIT_CS,
+	X86_GDT_ENTRY_32BIT_DS,
+	X86_GDT_ENTRY_16BIT_CS,
+	X86_GDT_ENTRY_16BIT_DS,
+	X86_GDT_NUM_ENTRIES
+};
+#else
+/* NOTE: If the above enum is modified, this define must be checked */
+#define X86_GDT_ENTRY_32BIT_DS	3
+#endif
+
+#define X86_GDT_SIZE		(X86_GDT_NUM_ENTRIES * X86_GDT_ENTRY_SIZE)
 
 #endif