Unable to call 'C' functions at boot time

[zak100]

Hi,
I want to call 'C' functions through my assembly language code at boot time.
But its not working.

;---------bootmz.asm
%define bootseg 0
%define bootoff 7C00h

%define loadoff 7E00h




ORG 7c00h      ;Because BIOS loades the OS at 
                       ; address 0:7C00h so ORG 7C00h 
                       ; makes that the refrence to date 
                       ; are with the right offset (7c00h).


                       
   ; CS = 0 / IP = 7C00h // SS = ? / SP = ?
   ; You are now at address 7c00.
jmp start   ;Here we start the, BIOS gave us now the control.



;///////////////////////////////////////////
;//Here goes all the data of the program.
;///////////////////////////////////////////

xCursor db 0
yCursor db 0


nSector db 0
nTrack  db 0
nSide   db 0
nDrive  db 0

nTrays  db 0

;
szReady                db 'Are You Ready to start Loading the OS...',0
szErrorReadingDrive    db 'Error Reading Drive, Press any Key to
reboot...',0
;//Done Reading a track.
szPlaceMarker          db  '~~~~',0
szDone                 db  'Done',0

pOS                    dw   loadoff
;//Points to where to download the Operating System. 

;/////////////////////////////////
;//Here the program starts.
;/////////////////////////////////


start:

    CLI     ;Clear Interupt Flag so while setting 
        ;up the stack any interrupt would not be fired.
;----------------STACK
        mov AX,7B0h    ;lets have the stack start at 7c00h-256 = 7B00h
        mov SS,ax      ;SS:SP = 7B0h:256 = 7B00h:256
        mov SP,256     ;Lets make the stack 256 bytes.
        
        XOR AX,AX      ;Makes AX=0.
        MOV ES,AX      ;Make ES=0
        mov DS,ax


    STI     ;Set Back the Interupt Flag after 
        ;we finished setting a stack frame.
       
        Call ClearScreen       ;ClearScreen()
        LEA AX,[szReady]         ;Get Address of szReady.
        CALL PrintMessage      ;Call PrintfMessage()
        CALL GetKey                    ;Call GetKey()
        
    mov bp, 1 ; sectors to load
        CALL DownloadOS
;        CALL GetKey                    ;Call GetKey()
        CALL GiveControlToOS  ;Give Control To OS.

;/////////////////////////////////////
;//Prints a message to the screen.
;/////////////////////////////////////
PrintMessage:

        mov DI,AX      ;AX holds the address of the string to Display.
        Mov byte [xCursor],1  ;Column.
        
ContinuPrinting:

        cmp byte [DI],0    ;Did we get to the End of String.
        JE EndPrintingMessage  ;if you get to the end of the string return.
        
        mov AH,2               ;Move Cursor
        mov DH,[yCursor]         ;row.
        mov DL,[xCursor]         ;column.
        mov BH,0               ;page number.
        INT 10h
        INC byte [xCursor]
        
        mov AH,0Ah             ;Display Character Function.
        mov AL,[DI]            ;character to display.
        mov BH,0               ;page number.
        mov CX,1               ;number of times to write character
        INT 10h
               
        INC DI                 ;Go to next character.
        
        JMP ContinuPrinting    ;go to Print Next Character.
               
EndPrintingMessage:
        
        Inc byte [yCursor]            ;So Next time the message would
                               ;be printed in the second line.
        
        cmp byte [yCursor],25
        JNE dontMoveCorsurToBegin 
        Mov byte [yCursor],0
        
dontMoveCorsurToBegin:
        ret
        
               
;PrintMessage EndP 
;//////////////////////////////////////
;//Waits for the user to press a key.
;//////////////////////////////////////
GetKey: ; PROC

        mov ah,0
        int 16h ;Wait for a key press.
        Ret
        
;///////////////////////////////////////////
;//Gives Control To Second Part Loader.
;///////////////////////////////////////////
GiveControlToOS:

        LEA AX,[szDone]
        Call PrintMessage
        CALL GetKey

        jmp 7E0h:40h

        mov ax, [loadoff + 18h]

        push 7E0h
        push ax
        retf

;///////////////////////////////////
;//Clear Screen.
;///////////////////////////////////
ClearScreen:

        mov ax,0600h   ;//Scroll All Screen UP to Clear Screen.
        mov bh,07
        mov cx,0
        mov dx,184fh   
        int 10h
        
        Mov byte [xCursor],0  ;//Set Cursor Position So next 
                        ;//write would start in 
                        ;//the beginning of screen.
        Mov byte [yCursor],0

        Ret
        
;/////////////////////////////////
;//PrintPlaceMarker.
;/////////////////////////////////
PrintPlaceMarker:

        LEA AX,[szPlaceMarker]
        CALL PrintMessage  ;Call PrintfMessage()
;        CALL GetKey        ;Call GetKey()
        ret
        
;///////////////////////////////////
;//DownloadOS
;///////////////////////////////////
DownloadOS:

        mov byte [nDrive],0
        mov byte [nSide],0
        mov byte [nTrack],0
        mov byte [nSector],1 ; desired sector - 1!
        
ContinueDownload:
        
        INC byte [nSector]            ;Read Next Sector.
        cmp byte [nSector],19         ;Did we get to end of track.
        JNE StayInTrack

        CALL PrintPlaceMarker  ;Print now '~~~~' so the user would 
                               ;know that we finished reading a track
        INC byte [nTrack]             ;If we get to end of track Move to
next track.
        mov byte [nSector],1          ;And Read Next Sector.
        CMP byte [nTrack],5           ;Read 5 Tracks (Modify this value 
                                   ;to how much Tracks you want to read).
        JE      EndDownloadingOS
        
StayInTrack:
        
        ;ReadSector();
        Call ReadSector
    dec bp
    jz EndDownloadingOS
        
        
        JMP     ContinueDownload
        ;If didn't yet finish Loading OS.
        
EndDownloadingOS:

        ret
        
;////////////////////////////////////////
;//Read Sector.
;////////////////////////////////////////
ReadSector:

        mov byte [nTrays],0
        
TryAgain:

        mov AH,2               ;//Read Function.
        mov AL,1               ;//1 Sector.
        mov CH,[nTrack]
        mov CL,[nSector]         ;//Remember: Sectors start with 1, not 0.
        mov DH,[nSide]
        mov DL,[nDrive]
        Mov BX,[pOS]             ;//ES:BX points to the address 
                               ;to were to store the sector.
        INT 13h
        
    jnc EndReadSector

        mov AH,0               ;Else Reset Drive . And Try Again...
        INT 13h
        cmp byte [nTrays],3           ;Check if you tryed reading 
                               ;more then 3 times.
        
        JE DisplayError        ; if tryed 3 Times Display Error.
        
        INC byte [nTrays]
        
        jmp TryAgain       ;Try Reading again.
        
DisplayError:
        LEA AX,[szErrorReadingDrive]
        Call PrintMessage
        Call GetKey
        mov AH,0                       ;Reboot Computer.
        INT 19h
        

EndReadSector:
        ADD WORD [pOS],512  ;//Move the pointer 
                               ;(ES:BX = ES:pOS = 0:pOS) 512 bytes.
                               ;//Here you set the varible 
                               ;pOS (pOS points to were BIOS 
                               ;//Would load the Next Sector).
        Ret
        
;////////////////////////////////////
;//
;////////////////////////////////////

times 510 - ($ - $$) db 0
db 55h, 0AAh
;-------------------

;Kernel code calling 'C' language function
;test_k.asm


global _Test
extern _K_main
segment code
;--- test kernel.bin---

segment code
_Test:

    mov ds,ax
    mov es,ax
    mov si, msg

    mov ah, 0Eh
    mov bx, 7
top:
    lodsb
    cmp al, 0
    jz blackhole
    int 10h
    jmp short top

blackhole:
    
    
    call _K_main; this is in main1.c
    hlt
    jmp blackhole
    ret

msg db 'Welcome to the Kernel!', 0

times 0x200-($-$$) db 0
      
;-----------------------------

;C program, main1.c
#define WHITE_TXT 0x07
void K_clear_screen();
unsigned int K_printf(char *message, unsigned int line);
//void update_cursor(int row, int col);

K_main(){
K_clear_screen();
K_printf("Hi\n How is this for a starter OS?",0);
}

void K_clear_screen() {
char *vidmem=(char*) 0xb8000;
unsigned int i=0;
while(i<(80*25*2))
{
vidmem[i]=' ';
i++;
vidmem[i]=WHITE_TXT;
}
}

unsigned int K_printf(char *message, unsigned int line){
char *vidmem=(char *) 0xb8000;
unsigned int i=0;
i=(line*80*2);
while(*message!=0)
{
if(*message=='\n')
{
line++;
i=(line*80*2);
*message++;
}

else {
vidmem[i]=*message;
*message++;
i++;
vidmem[i]=WHITE_TXT;
i++;
}
}
return 1;
}



;-------------compiling infor

nasm -f bin bootmz.asm -o boot.bin

nasm -f obj test_k.asm
gcc -c main1.c


alink -oEXE test_k.obj main1.o


copy /b boot.bin+test_k.exe image.bin
partcopy image.bin 0 323 -f0


Can somebody plz help me with this?

Zulfi.
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