TSS examples

; Example GDT entry for a TSS

; TSS for transitioning between rings, 1-byte gran, base=tss, limit=TSS_SIZE-1
gdt_tss:
    dw TSS_SIZE-1      ; segment length, bits 0-15
    dw tss             ; segment base, bits 0-15
    db 0x0             ; segment base, bits 16-23
    db 10001001b       ; access flags (8 bits)
    db 00000000b       ; flags (4 bits) + segment length, bits 16-19
    db 0x0             ; segment base, bits 24-31


; Example TSS structure

tss:
    dd 0x0
    dd 0x4000 ;esp0
    dd 0x10 ;ss0
    TIMES 22 dd 0x0
    dw 0x0
    dw TSS_SIZE        ;IOPB offset
;    dd 0x0            ; SSP: If not using a shadow stack (CET disabled)
                       ; this can be removed
tssend:
TSS_SIZE equ tssend - tss