GDT_ENTRY_BOOT_CS 18 arch/x86/include/asm/segment.h #define __BOOT_CS (GDT_ENTRY_BOOT_CS * 8) GDT_ENTRY_BOOT_CS 20 arch/x86/include/asm/segment.h #define GDT_ENTRY_BOOT_DS (GDT_ENTRY_BOOT_CS + 1) GDT_ENTRY_BOOT_CS 23 arch/x86/include/asm/segment.h #define GDT_ENTRY_BOOT_TSS (GDT_ENTRY_BOOT_CS + 2)