GDT_ENTRY_PERCPU
# define __KERNEL_PERCPU (GDT_ENTRY_PERCPU*8)
[GDT_ENTRY_PERCPU] = GDT_ENTRY_INIT(DESC_DATA32, 0, 0xfffff),
write_gdt_entry(get_cpu_gdt_rw(cpu), GDT_ENTRY_PERCPU, &d, DESCTYPE_S);