Hi,
I am using kernel code in which I have put he 'C' functions. This code is being loaded to the sector 2 after creating the bin file using exe2bin. I am also creating a stack but its not detected by the linker.
D:\nasm prog>alink -o kernel.exe test_kernel2.obj main1.o
ALINK v1.6 (C) Copyright 1998-9 Anthony A.J. Williams.
All Rights Reserved
Loading file test_kernel2.obj
Loading file main1.o
matched Externs
matched ComDefs
Warning - no stack
D:\nasm prog>
The complete kernel code is given below:
; call c function
extern _K_main
;--- test kernel.bin---
; push cs
; push cs
; pop ds
; pop es
..start: mov ax, 7E0H
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:
mov cx,1000
Delay: Loop Delay
call _K_main; this is in main.c
hlt
jmp blackhole
msg db 'Welcome to the Kernel!', 0
times 0x200-($-$$) db 0
The loader for this kernel is:
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 7E00h
;//Points to where to download the Operating System.
;//Disk Paremeter Table.
StepRateAndHeadUnloadTime db 0DFh
HeadLoadTimeAndDMAModeFlag db 2h
DelayForMotorTurnOff db 25h
;// (1 = 256) //(2 = 512 bytes)
BytesPerSector db 2h
;// 18 sectors in a track.
SectorsPerTrack db 18
IntersectorGapLength db 1Bh
DataLength db 0FFh
IntersectorGapLengthDuringFormat db 54h
FormatByteValue db 0F6h
HeadSettlingTime db 0Fh
DelayUntilMotorAtNormalSpeed db 8h
DisketteSectorAddress_as_LBA_OfTheDataArea db 0
CylinderNumberToReadFrom db 0
SectorNumberToReadFrom db 0
DisketteSectorAddress_as_LBA_OfTheRootDirectory db 0
;/////////////////////////////////
;//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.
; Mov ax,CS ;Set the data segment = CS = 0
; suggest you use 0 here!
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()
; CALL SetNewDisketteParameterTable
;SetNewDisketteParameterTable()
mov bp, 1 ; sectors to load
CALL DownloadOS
CALL GetKey ;Call GetKey()
CALL GiveControlToOS ;Give Control To OS.
;ret
;/////////////////////////////////////
;//Prints a message to the screen.
;/////////////////////////////////////
PrintMessage: ; PROC
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
;GetKey EndP
;///////////////////////////////////////////
;//Gives Control To Second Part Loader.
;///////////////////////////////////////////
GiveControlToOS: ; PROC
LEA AX,[szDone]
Call PrintMessage
CALL GetKey
; db 0e9h ;Far JMP op code.
; dw 512 ;JMP 512 bytes ahead
;jmp 0:7E00h;-----------------------------------At this point we are going to Kernel code; for including C prog:test_kernel2.asm
jmp 7D0h:100h
; jmp 0:7D00h
; POP AX ;//Another why to make
;the CPU jump to a new place.
; POP AX
; Push 7E0h ;Push New CS address.
; Push 0 ;Push New IP address.
;The address that comes out is 7E00:0000.
; comment does not match code!
;(512 bytes Higher from were BIOS Put us.)
retf
; you'd want "retf" here.
;GiveControlToOS EndP
;///////////////////////////////////
;//Clear Screen.
;///////////////////////////////////
ClearScreen: ; PROC
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
;ClearScreen EndP
;/////////////////////////////////
;//PrintPlaceMarker.
;/////////////////////////////////
PrintPlaceMarker: ; PROC
LEA AX,[szPlaceMarker]
CALL PrintMessage ;Call PrintfMessage()
CALL GetKey ;Call GetKey()
ret
;PrintPlaceMarker EndP
;/////////////////////////////////////////
;//Set New Disk Parameter Table
;/////////////////////////////////////////
SetNewDisketteParameterTable: ; PROC
LEA DX,[StepRateAndHeadUnloadTime]
;//Get the address of the Disk Parameters Block.
;//Int 1E (that is in address 0:78h)
;//holds the address of the disk parametrs
;//block, so now change it to
;//our parametr black.
;//DX holds the address of our Parameters block.
MOV WORD [CS:0078h],DX
MOV WORD [CS:007Ah],0000
; these should have labels on 'em. Where is this supposed to be???
;Reset Drive To Update the DisketteParameterTable.
MOV AH,0
INT 13H
ret
;SetNewDisketteParameterTable EndP
;///////////////////////////////////
;//DownloadOS
;///////////////////////////////////
DownloadOS: ;PROC
mov byte [nDrive],0
mov byte [nSide],0
mov byte [nTrack],0
mov byte [nSector],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
;now 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
;DownloadOS EndP
;////////////////////////////////////////
;//Read Sector.
;////////////////////////////////////////
ReadSector: ; PROC
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
CMP AH,0 ;Int 13 return Code is in AH.
JE EndReadSector ;if 'Sucsess' (AH = 0) End function.
mov AH,0 ;Else Reset Drive . And Try Again...
INT 13h
cmp byte [nTrays],3 ;Chack 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
;ReadSector EndP
;////////////////////////////////////
;//
;////////////////////////////////////
times 510 - ($ - $$) db 0
db 55h, 0AAh
;-------------------
And the 'C' prog file is:
#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++;
vidmem=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=*message;
*message++;
i++;
vidmem=WHITE_TXT;
i++;
}
}
return 1;
}
Can somebody plz help me with this prob.
Zulfi.
