Why my kernel Written in C doesn't work,while Assembly dose?
Posted: Mon Aug 08, 2005 4:32 am
I am trying to write a small experimental OS.But I encountered some questions.Hope you can help me.
My bootloader works very well.It can load the kernel to the right position .At first I wrote my small kernel in asm,it works well.Later I changed my kernel to asm-C mixed one.Then it doesn't work.
I will show you my codes:
My KernelBuild.bat looks like this:
The following is the kernel.
PS.My work Enviroment:
Bochs ,WindowsXP,DJGPP(with gcc,ld,nasm in it),Hex Workshop(Binary file editor)
I think the problem is caused by the following command.
gcc -c c.c -o c.o
nasm -f aout tl.asm -o tl.o
ld -Ttext=0x10000 -e begin tl.o c.o
rename a.out krnl.bin
But I don't know where and why.
Do any one know what's the matter with this?Lots of thanks!
All the code can be found in the attach file.
My bootloader works very well.It can load the kernel to the right position .At first I wrote my small kernel in asm,it works well.Later I changed my kernel to asm-C mixed one.Then it doesn't work.
I will show you my codes:
Code: Select all
----------------------------------------------
;BOOTLOADER.asm
; myboot.asm bootstrap for real mode image or loader
;Aug,01,2005
%define IMAGE_SEG 0x1000
org 0x7C00
entry:
jmp short begin
nop
;reserved as my own param area
times 0x3B db 0
begin:
xor ax, ax
mov ds, ax
cli
mov ss, ax
mov sp, 0x7C00
mov bp, sp
sti
call read
eof:
mov ax,sucmsg ;Leaving boot
mov si,ax
call disps
jmp IMAGE_SEG:0
error:
mov ax,errmsg ;Leaving boot
mov si,ax
call disps
xor ah, ah
int 16h ;Wait for a key
int 19h ;Try to reboot
read:
mov ax,loadmsg ;Leaving boot
mov si,ax
call disps
mov ch,0
mov cl,2 ;we write our kernel to disk start from sector two
mov dh,0
mov dl,0 ;DL = Drive number
xor bx,bx
mov ax,IMAGE_SEG ;ES:BX = address
mov es,ax ; =1000:0000
mov al,0x5 ;read 5 sectors
mov ah, 2 ;AH = Read command
int 13h ;Do it
jc error
ret
;In: DS:SI points to the string to be displayed.
;Out: None
disps:
mov ax, 0x0e0D
mov bh ,0x00
mov bl,7
.1 int 10h
lodsb
test al,al
jnz .1
ret
errmsg db 10,"Error Executing bootsector",13
db 10,"Press any key to reboot",13,10,0
loadmsg db 10,"Loading kernel...",13,10,0
sucmsg db 10,"Ready to jump to kernel",13,10,0
size equ $ - entry
%if size+11+2 > 512
%error "code is too large for boot sector"
%endif
times (512 - size - 2) db 0
db 0x55, 0xAA ;2 byte boot signature
----------------------------------------------------
Code: Select all
gcc -c c.c -o c.o
nasm -f aout tl.asm -o tl.o
ld -Ttext=0x10000 -e begin tl.o c.o
rename a.out krnl.bin
Code: Select all
/* TL.asm (TestLoader) ,this part is also works well,if I deleted the part written in C */
;TL.asm Test the loader
;Aug,01,2005
[global begin]
[extern _main]
begin:
mov ax, cs
mov ds,ax
mov ax,showmsg
mov si,ax
call disps
mov ax,rbtmsg
mov si,ax
call disps
call _main ;written in C
xor ah, ah
int 16h ;Wait for a key
int 19h ;Try to reboot
disp:
mov ah, 0x0e
mov bh ,0x00
mov bl,7
int 10h
ret
disps:
mov ax, 0x0e0D
mov bh ,0x00 ;
mov bl,7
.1 int 10h
lodsb
test al,al
jnz .1
ret
showmsg db 10,"Hello World!",13,10,0
rbtmsg db 10,"Mission End!",13,"Press any key to exit",13,10,0
times (512*40) db 0
Code: Select all
/*C.c written in C,this part doesn't work correctly : ( */
char* msg = "Kernel loaded and Start Running Now..." ;
int main()
{
unsigned char* videomem = ( unsigned char* )0xb8000 ;
while( *msg != '\0' ){
*videomem++ = *msg++ ;
*videomem++ = 0x1b ; }
for(;;);
return 0;
}
Bochs ,WindowsXP,DJGPP(with gcc,ld,nasm in it),Hex Workshop(Binary file editor)
I think the problem is caused by the following command.
gcc -c c.c -o c.o
nasm -f aout tl.asm -o tl.o
ld -Ttext=0x10000 -e begin tl.o c.o
rename a.out krnl.bin
But I don't know where and why.
Do any one know what's the matter with this?Lots of thanks!
All the code can be found in the attach file.
