Help Making an Operating System.

[AeroASM]

I got Bochs, but I do not think I will use it. Is there no simple way to just load a flat .bin file into memory and execute it?

[thomasantony]

Yes there is. Rename the file to .COM and put an ORG 100h instead of any other ORG instruction in the source. And go into DOS  mode (not DOS shell, select Restart in MSDOS mode in Shutdown menu). Go to whatever directory you have the program and run it. I think making a Bochs image file and running it is much easier than this. Making an image is very simple. If you use NASM put the following in a file (empty.asm, dummy.asm bullsh*t.asm anything..)

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times 1474560-(your_bin_file_size) db 0

Now assemble the file to get dummy.bin
Now do the following DOS command

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copy /B your_bin_file.bin+dummy.bin a.img

There you have your image file. You can put all the assembling and other things into a batch file to make it easy

Thomas

[roticv]

For OS coding, I use fasm which can output binary. I use winimage to create the floppy disk image and use vmware/virtual pc to test it.

[Farabi]

I have the code for set flat real mode, but unfortunately this computer cannot open a .zip file. Maybe you can get use of it. Or if you can, please check my post titled "Courious about Opcode?".

[pbrennick]

AeroASM,

http://www.emu8086.com/ is a nice Visual Microprocessor Emulator.  It also has its own Assembler as well as sample code for creating a tiny OS.  When you load the source code you can copy it to a virtual floppy (memory) and test it there.  It is a nifty tool as it can emulate a lot of stuff.

Paul

[AeroASM]

I have got that but it is no use for Protected Mode

[thomasantony]

Hi roticv,
     Isn't it a pain in the a** if you have to use WinImage every time you have to check out a small change you made to the prog. I use the following batch file for tesing my FAT12 OS. It copies the files and copies some 100k into an image file so that it contains the FAT structures, the file data etc. Then I add a dummy file at the end.

@echo off
nasm -fbin -o boot.com boot.asm
if errorlevel 1 goto exit
nasm -fbin -o oskernel.com oskernel.asm
if errorlevel 1 goto exit
nasm -fbin -o dummy.bin dummy.asm
copy logo.txt a:
debug boot.com < debugops.ini
copy oskernel.com a:
:partcopy -f0 0 3E800 os.bin
partcopy -f0 0 19000 os.bin
copy /b os.bin+dummy.bin a.img
\bochs\bochs -q
:\bochs\bochsdbg -q
del dummy.bin
del os.bin
:exit

debugops.ini contians:

w 100 0 0 1
q

  So I can test my OS simply by running this batch file.
Thomas :U

[rea]

By the way, there is a way that you can "delete" a step in your work ;) or a workaround..

Files:

1) boot.asm
1) kernel.asm
2) img.asm

img.asm:

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incbin "boot.bin"
incbin  "kernel.bin"
;%assign addition FSIZE
;%error Size of boot.bin+kernel.bin = s
times 1474560- (FSIZE) db 0


compile it with:

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nasmw -fbin -oimg.img -DFSIZE=15 img.asm


Sure, before you should know the size of the kernel.bin and boot.bin, and sure you can use -DFSIZE 15+30 if you dont whant to make the adition ;), yiu can uncomment the lines if you whant to check them ;).

-------------------------------------------

[FIX]
Ops, I was missing a operator in a previous try, now I have remembered another one, then it can be reduced more ;)

img.asm:

incbin "boot.bin" incbin  "kernel.bin" times 1474560- ($-$$) db 0

or

start_here: incbin "boot.bin" incbin  "kernel.bin" end_here: times 1474560- (end_here-start_here) db 0

compile it with:

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nasmw -fbin -oimg.img img.asm


And dont need to add :P, I was failing because I was only using times "1474560- $ db 0", that dosent work ;).
[/FIX]

I do another sugestion.. because $$ signal the start of the segment then is the same than the second one way...

[thomasantony]

Hi,
  Should have got this before. I think I can still use it by 'incbinning' the FAT data read from the disk.

Thomas :U

[Polizei]

AeroASM: You do not need a PHYSICAL floppy drive, you can emulate it by using VMware WorkStation (I use 5.0 for my boot tests) ;))