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addes3 17 Aug 2011, 00:52
Hi folks, I'm making a simple real-mode OS called AXOS.
Currently all it does is load the kernel and set an interrupt, but I'm hoping I'll be able to extend it to support I/O, Files, etc. I've been skimming through OSDev.org and http://www.brokenthorn.com/Resources/OSDev1.html I've recently had a problem when running on bare hardware with a 1.44MB floppy. Currently AXOS prints 'A' when resetting the floppy, 'B' when loading the kernel, 'C' at the start of the kernel, set's int 50h in the IVT, then calls int 50h which prints 'D'. This is what happens in Bochs. The floppy currently prints 'ABC' then freezes. I use PartCopy to put the image on the floppy, like so: partcopy axos.img 0 400 -f0 Here's the code: x_boot.asm: Code: format binary
use16
org 7c00h
jmp start
nop
OEM: db "adamsxos"
bpbBytesPerSector: dw 512
bpbSectorsPerCluster: db 1
bpbReservedSectors: dw 2
bpbNumberOfFATs: db 2
bpbRootEntries: dw 224
bpbTotalSectors: dw 2880
bpbMedia: db 0F0h
bpbSectorsPerFAT: dw 9
bpbSectorsPerTrack: dw 18
bpbHeadsPerCylinder: dw 2
bpbHiddenSectors: dd 0
bpbTotalSectorsBig: dd 0
bsDriveNumber: db 0
bsUnused: db 0
bsExtBootSignature: db 29h
bsSerialNumber: dd 0
bsVolumeLabel: db "X "
bsFileSystem: db "FAT12 "
start:
reset_floppy: ;reset the floppy drive
mov ax,0e41h
xor bx,bx
int 10h
mov ah,00h
int 13h
jc reset_floppy
read_floppy:
mov ax,0e42h
xor bx,bx
int 10h
mov ax,0000h
mov es,ax
mov bx,1000h
mov ah,2
mov al,1
mov ch,0
mov cl,2
mov dh,0
int 13h ;read 1 sector from floppy drive
jc read_floppy ;if error, try again
jmp 0000:1000h
times 510 - ($-$$) nop
dw 0aa55h x_kernel.asm: Code: format binary
use16
org 1000h
start:
mov ax,0e43h
xor bx,bx
int 10h
mov dword [320],0000+interrupt
mov [boot_drive],dl
int 50h
cli
hlt
interrupt:
mov ax,0e44h
xor bx,bx
sti
int 10h
cli
iret
boot_drive db 0
times 512 - ($-$$) nop Here's what I use to make the image: Code: format binary as 'img' file 'x_boot.bin' file 'x_kernel.bin' |
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17 Aug 2011, 00:52 |
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me239 17 Aug 2011, 02:07
nice job. Have you seen my xOS? It's a realmode OS with FAT12 support with source included if you wanted to take a look.
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17 Aug 2011, 02:07 |
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typedef 17 Aug 2011, 03:32
me239, where is it. I'd like to take a look at it please
 |
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17 Aug 2011, 03:32 |
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me239 17 Aug 2011, 04:02
typedef wrote: me239, where is it. I'd like to take a look at it please |
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17 Aug 2011, 04:02 |
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DJ Mauretto 17 Aug 2011, 07:30
Quote: I've recently had a problem when running on bare hardware with a 1.44MB floppy. Hello, you must set the stack and the data segment in early stage of your bootloader 
you are making too many wrong assumptions  _________________ Nil Volentibus Arduum  |
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17 Aug 2011, 07:30 |
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addes3 17 Aug 2011, 21:17
Thank you
 Works now.
@me239: Sounds cool, I'll look it up. |
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17 Aug 2011, 21:17 |
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me239 18 Aug 2011, 04:15
addes3 wrote: Thank you http://board.flatassembler.net/topic.php?t=13249 |
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18 Aug 2011, 04:15 |
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addes3 18 Aug 2011, 22:48
Here's an updated version. Currently no file support, though.
x_boot.asm: Code: format binary
use16
org 7c00h
jmp start
nop
OEM: db "ADAMS OS"
bpbBytesPerSector: dw 512
bpbSectorsPerCluster: db 1
bpbReservedSectors: dw 2880
bpbNumberOfFATs: db 2
bpbRootEntries: dw 224
bpbTotalSectors: dw 2880
bpbMedia: db 0F0h
bpbSectorsPerFAT: dw 9
bpbSectorsPerTrack: dw 18
bpbHeadsPerCylinder: dw 2
bpbHiddenSectors: dd 0
bpbTotalSectorsBig: dd 0
bsDriveNumber: db 0
bsUnused: db 0
bsExtBootSignature: db 29h
bsSerialNumber: dd 0
bsVolumeLabel: db "AXOS "
bsFileSystem: db "FAT12 "
start:
cli ;set up the segments and stack
xor ax,ax
mov ds,ax
mov es,ax
mov fs,ax
mov gs,ax
mov ax,0fffh
mov ss,ax
mov sp,0ffffh
mov bp,sp
sti
reset_floppy: ;reset the floppy drive
mov ah,00h
int 13h
jc reset_floppy
read_kernel:
mov ax,0000h
mov es,ax
mov bx,1000h
mov ah,2
mov al,1
mov ch,0
mov cl,2
mov dh,0
int 13h ;read 1 sector from floppy drive
jc read_kernel ;if error, try again
jmp 0000:1000h
times 510 - ($-$$) nop
dw 0aa55h x_kernel.asm: Code: format binary
use16
org 1000h
crlf equ 0dh,0ah
macro mov p1,p2 {
if p2 eqtype ''
local ..string,..skip
jmp ..skip
..string db p2,0
..skip:
mov p1,..string
else
mov p1,p2
end if
}
start:
mov ax,0e43h
xor bx,bx
int 10h
mov dword [320],0000+interrupt
mov [boot_drive],dl
mov ax,0003h
int 10h
mov si,.msg
mov ah,01h
int 50h
mov di,.input
mov dx,19h
mov ah,03h
int 50h
mov si,new_line
mov ah,01h
int 50h
mov si,.input
mov ah,01h
int 50h
cli
hlt
.msg db 'AXOS V0.01',0dh,0ah,'>',0
.input rb 20h
error:
mov si,.msg
mov ah,01h
int 50h
cli
hlt
.msg db 'WHOOPS: AXOS ERROR!',0
interrupt:
or ah,ah
jz terminate_program
cmp ah,01h
je print_string
cmp ah,02h
je clear_screen
cmp ah,03h
je get_string
cmp ah,04h
je wait_enter
cmp ah,05h
jmp error
terminate_program:
cli ;set up the segments and stack
xor ax,ax
mov ds,ax
mov es,ax
mov fs,ax
mov gs,ax
mov ax,0fffh
mov ss,ax
mov sp,0ffffh
mov bp,sp
sti
jmp 2000h
;prints a zero-terminated, ds:si pointed string
print_string:
push ax
@@:
lodsb
or al,al
jz .ret
mov ah,0eh
int 10h
jmp @b
.ret:
pop ax
iret
;clears the screen, no args or returns
clear_screen:
push ax di es dx
mov ax,0b800h
mov es,ax
xor di,di
@@:
mov byte [es:di],0
add di,2
cmp di,4000
jne @b
mov ah,02h
mov dx,0000h
int 10h
.ret:
pop dx es di ax
iret
;gets a string from the keyboard, es:di points to the reserved memory, dx holds maximum characters to collect
;returns: es:di string, dx = 0 or bytes of memory not used
get_string:
push ax
dec dx
@@:
xor ah,ah
int 16h
or al,al
jz .extended
cmp al,0ah
je .ret
cmp al,0dh
je .ret
mov ah,0eh
int 10h
.store:
stosb
dec dx
or dx,dx
jz .ret
jmp @b
.extended:
shr ax,8
jmp .store
.ret:
mov al,0
stosb
pop ax
iret
;waits until return key is pressed
wait_enter:
push ax
@@:
xor ah,ah
int 16h
cmp ah,0ah
jne @b
.ret:
pop ax
iret
boot_drive db 0
new_line db crlf,0
times 200h - ($-$$) nop |
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18 Aug 2011, 22:48 |
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me239 19 Aug 2011, 01:43
addes3 wrote: Here's an updated version. Currently no file support, though |
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19 Aug 2011, 01:43 |
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