X86_VENDOR_UNKNOWN = 0xff
 };
 
+/* Global descriptor table (GDT) bits */
+enum {
+       GDT_4KB                 = 1ULL << 55,
+       GDT_32BIT               = 1ULL << 54,
+       GDT_LONG                = 1ULL << 53,
+       GDT_PRESENT             = 1ULL << 47,
+       GDT_NOTSYS              = 1ULL << 44,
+       GDT_CODE                = 1ULL << 43,
+       GDT_LIMIT_LOW_SHIFT     = 0,
+       GDT_LIMIT_LOW_MASK      = 0xffff,
+       GDT_LIMIT_HIGH_SHIFT    = 48,
+       GDT_LIMIT_HIGH_MASK     = 0xf,
+       GDT_BASE_LOW_SHIFT      = 16,
+       GDT_BASE_LOW_MASK       = 0xffff,
+       GDT_BASE_HIGH_SHIFT     = 56,
+       GDT_BASE_HIGH_MASK      = 0xf,
+};
+
 struct cpuid_result {
        uint32_t eax;
        uint32_t ebx;