GDT:
.nd db  0   ;limit 7:0
    db  0   ;limit 15:8
    db  0   ;base 7:0
    db  0   ;base 15:8
    db  0   ;base 23:16
    db  0   ;access rights
    db  0   ;granularity, op-size, limit 19:16
    db  0   ;base 31:24

.cs db  0xFF    ;limit 0xFFFF
    db  0xFF
    db  0   ;base 0
    db  0
    db  0
    db  0x9A    ;present, ring 0, code, ?, readable
    db  0xCF    ;granularity=4k, 32-bit, limit=0xFF
    db  0
.ds db  0xFF    ;limit 0xFFFF
    db  0xFF
    db  0   ;base 0
    db  0
    db  0
    db  0x92    ;present, ring 0, data, up, writable
    db  0xCF    ;granularity=4k, 32-bit, limit=0xFF
    db  0

.ss db  0   ;limit 0
    db  0
    db  0   ;base 0
    db  0
    db  0
    db  0x96    ;present, ring 0, data, down, writable
    db  0xC0    ;granularity=4k, 32-bit, limit=0
    db  0
.end: