I have a problem with some code. It's a part of my own OS that I want to build in the future and share on SourceForge. I have two assembly files:
gdos.asm, the kernel. And...vga.asm, my own VGA driver.
Everything works correctly in DOSBox.
But when I run it on normal MS-DOS on my external drive, it's causing this error:
Memory allocation error:
Failed load COMMAND.COM. System halted
This problem may be related to the code where I allocate extra memory to the program by resizing it. The complete source code is:
First file: GDOS.ASM:
format MZ
stack 4096
entry GDOS_MAINSEG:GDOS_KERNEL_START
segment GDOS_MAINSEG
GDOS_KERNEL_START: ; Punkt startowy jĄdra / Kernel start point
push cs
pop ds
push cs
pop es
mov ax,GDOS_KERNEL_END ;Autoalokacja do konkretnego rozmiaru / Autoallocation for concrete size
shr ax,4
inc ax
init: ;Inicjujemy GDOS
mov bx,ax
mov ah,0x4a
int 0x21
mov dx,DrvString0
call far GDOS_MAINSEG:gdosLoadDriverDOS
call far GDOS_MAINSEG:gdosSetModeByID
mov ax,0x4c00
int 0x21
GDOS_KERNEL_DATA:
DrvString0 : db 'VGA.BIN',0 ;Nazwa pliku dla sterownika VGA / Filename for VGA driver
GraphicsDriver: dw 0x0
g3:
dw 0,0
dw 0,0
DriverDeletionBuffer: TIMES 16 db 0
RecommendedDriverPosition: db 0
GDOS_KERNEL_FUNC:
gdosLoadDriverDOS: ;Funkcja adujĄca sterownik za pomocĄ DOS-a / Function loading driver with DOS
push ds
push es
mov ax,0x3d00
mov cl,0x0
int 0x21
jc end_gdosLoadDriverDOS
mov si,ax ;Zapisz uchwyt / Save handle
mov ah,0x48
mov bx,1
int 0x21
jc end_gdosLoadDriverDOS
mov es,ax
mov ds,ax
mov ah,0x3f
mov cx,16
mov bx,si
mov dx,0
int 0x21
jc end_gdosLoadDriverDOS
mov ah,0x42
mov al,0x00
mov cx,0
mov dx,0
int 0x21
jc end_gdosLoadDriverDOS
mov bx,[0x2]
mov cx,bx
shr bx,4
inc bx
mov ah,0x4a
int 0x21
mov bx,si
mov dx,0
mov ah,0x3f
int 0x21
mov [0x2],es
mov bp,0x0
call far [es:bp]
push cs
pop ds
mov bp,g3
mov [bp+2],es
end_gdosLoadDriverDOS:
pop es
pop ds
retf
gdosSetModeByID:
push es
push ds
push cs
pop ds
mov bp,g3
mov ax,[GraphicsDriver]
shl ax,2
add bp,ax
mov di,[bp+2]
mov es,di
mov di,[es:11]
sub sp,4
mov bp,sp
mov [ss:bp],di
mov [ss:bp+2],es
call far [ss:bp]
add sp,4
pop ds
pop es
retf
GDOS_KERNEL_END:
Second file: VGA.ASM
GDOS_DRIVER_START:
GDOS_SECTION_DRIVER_HEADER:
gEntry: dw vgaEntry ;Punkt wejścia sterownika / Driver entry
gDriverSize: dw GDOS_DRIVER_END ;Rozmiar sterownika w bajtach / Driver size in bytes
gDriverType: db 1 ;0x1 - Sterownik grafiki / 0x1 - Graphics driver
gPortsData: dw vgaPorts
gMemData: dw vgaMem
gShared: dw vgaShared ;Lista sterowników dla których zasoby są udostępnione
gBasicFunc: dw vgaChangeModeID
gBasicPtrs: dw vgaPtrs
GDOS_SECTION_DRIVER_DATA:
vgaIDString: db 'vga-drv$',0 ;SĹ‚uĹĽy do wyszukiwania sterownika przez GDOS / It's for GDOS driver search
vgaShared0: db 'svga-drv',0
vgaEntry:
retf
vgaPorts:
db 0x1
db 2
dw 0x3c8,0x3c9
db 0x0
vgaMem:
db 0x1
db 2
dd 0x0000A000,0x0000BFFF
db 0x0
vgaShared:
db 0x1
dw vgaShared0
db 0x0
vgaPtrs:
dw vgaModes
vgaModes:
vgaFunc:
dw vgaChangeModeID
vgaMisc_Common db 0x63
R_W256 db 0x00
R_W320 db 0x00
R_W360 db 0x04
R_W376 db 0x04
R_W400 db 0x04
R_H200 db 0x00
R_H224 db 0x80
R_H240 db 0x80
R_H256 db 0x80
R_H270 db 0x80
R_H300 db 0x80
R_H360 db 0x00
R_H400 db 0x00
R_H480 db 0x80
R_H564 db 0x80
R_H600 db 0x80
HOR_REGS db 0x0,0x1,0x2,0x3,0x4,0x5,0x13
VER_REGS db 0x6,0x7,0x9,0x10,0x11,0x12,0x15,0x16
W256: db 0x5f,0x3f,0x40,0x82,0x4a,0x9a,0x20
vgaChangeModeID: ;TEST
push ds
push cs
pop ds
mov ah,9
mov dx,vgaIDString
int 0x21
pop ds
retf
GDOS_DRIVER_END:
To assemble the files into GDOS.EXE and VGA.BIN I use the commands:
fasm GDOS.ASM
fasm VGA.ASM
When the program is run I expect it to display the following and then exit back to the DOS prompt:
vga-drv
