stringio.asm

.DATA
    IMAGE DQ ?
    SYSTEMTABLE DQ ?
    INDEX DQ ?
    CONIN DQ ?
    WAITFORKEY DQ ?
    WAITFOREVENT DQ ?
    CONOUT DQ ?
    OUTPUTSTRING DQ ?
    BOOTSERVICES DQ ?
    HELLOMESSAGE DW "H", "E", "L", "L", "O", " ", "U", "E", "F", "I", 10, 13, 0

.CODE
EFI_MAIN PROC
    MOV IMAGE, RCX
    MOV SYSTEMTABLE, RDX

    MOV RAX, QWORD PTR [RDX + 030H]
    MOV CONIN, RAX
    MOV RBX, QWORD PTR [RAX + 10H]
    MOV WAITFORKEY
    MOV RAX, QWORD PTR [RDX + 040H]
    MOV CONOUT, RAX
    MOV RBX, QWORD PTR [RAX + 08H]
    MOV OUTPUTSTRING, RBX
    MOV RAX, QWORD PTR [RDX + 60H]
    MOV BOOYSERVICES, RAX
    MOV RBX, QWORD PTR [RAX + 60H]
    MOV WAITFOREVENT, RBX


    MOV RCX, CONOUT
    LEA RDX, [HELLOMESSAGE] 
    CALL OUTPUTSTRING

    MOV RCX, 01H
    LEA RDX, [WAITFORKEY]
    LEA R8, [INDEX]
    CALL WAITFOREVENT

    RET

EFI_MAIN ENDP
END