global ivt
ivt: dd 0x00000000

global gdt_desc
gdt_desc:
    dw gdt_end - gdt
    dd gdt
gdt:
gdt_null: dq 0
gdt_code: dw 0xFFFF, 0     ; bits 0-15 limit (4GB), bits 0-15 base address
          db 0             ; bits 16-23 base address
          db 10011010b     ; access byte
          db 11001111b     ; bits 16-19 limit (4GB), 4 bits flags
          db 0 ; bits 24-31 base address
gdt_data: dw 0xFFFF, 0     ; bits 0-15 limit (4GB), bits 0-15 base address
          db 0             ; bits 16-23 base address
          db 10010010b     ; access byte
          db 11001111b     ; bits 16-19 limit (4GB), 4 bits flags
          db 0 ; bits 24-31 base address
gdt_r3code: dw 0xFFFF, 0     ; bits 0-15 limit (4GB), bits 0-15 base address
          db 0             ; bits 16-23 base address
          db 0xFA     ; access byte
          db 11001111b     ; bits 16-19 limit (4GB), 4 bits flags
          db 0 ; bits 24-31 base address
gdt_r3data: dw 0xFFFF, 0     ; bits 0-15 limit (4GB), bits 0-15 base address
          db 0             ; bits 16-23 base address
          db 0xF2     ; access byte
          db 11001111b     ; bits 16-19 limit (4GB), 4 bits flags
          db 0 ; bits 24-31 base address
gdt_tss:  dw 0x2080, 0x0000;26*4, tss_data     ; bits 0-15 limit (4GB), bits 0-15 base address
          db 0x20            ; bits 16-23 base address
          db 0x89     ; access byte
          db 00000000b     ; bits 16-19 limit (4GB), 4 bits flags
          db 0 ; bits 24-31 base address
gdt_end: