gdtr_operand = make_gdtr_operand (sizeof gdt - 1, gdt);
asm volatile ("lgdt %0" :: "m" (gdtr_operand));
asm volatile ("ltr %w0" :: "r" (SEL_TSS));
gdtr_operand = make_gdtr_operand (sizeof gdt - 1, gdt);
asm volatile ("lgdt %0" :: "m" (gdtr_operand));
asm volatile ("ltr %w0" :: "r" (SEL_TSS));