SMRAM SMM Driver

Hi
I need to save few bytes by custom SMM Driver. I know almost nothing about it.
If I try to call to get IP for own data section the mobo going to brick. Seems like the stack is non setup yet. I tried to setup it temporary on Save State but Windows freezing on load

Code:

use16
org 0
start:
        DefineStack:
        mov     ebx,[cs:0xFF84]
        mov     eax,[cs:0xFF84+4]
        mov     [cs:0xFF84],ss
        mov     [cs:0xFF84+4],esp
        mov     cx,cs
        mov     ss,cx
        mov     edx,[cs:0xFF7C]
        mov     ecx,[cs:0xFF7C+4]
        mov     esp,0xFF84
;       call    getIP
;       jmp     RestoreStack
;       DataOffset      dw 0x07EB
;                       dw 0
;                       dw 0
;                       dw 0
;       getIP:
;       ret
        RestoreStack:
        mov     ss,[cs:0xFF84]
        mov     esp,[cs:0xFF84+4]
        mov     [cs:0xFF84+4],eax
        mov     [cs:0xFF84],ebx
        mov     ebx,[cs:0xFF7C+4]       ;DataOffset
        mov     [cs:0xFF7C+4],ecx
        mov     [cs:0xFF7C],edx

Where can I use some few bytes in SMRAM (or anywhere else)?
Or maybe some example how to setup SMM Driver via DXE. It will be fine too as I'll be happy to configure SMM at DXE stage.