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Index > OS Construction > Generic Boot and then 2nd file execute with FLOPPY or CD.

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janequorzar



Joined: 11 Sep 2010
Posts: 60
janequorzar
This is an example of boot and second file that you can use with FASM and PARTCOPY. You can also take the FLOPPY IMAGE and use PowerISO to make your own Boot CD with this code. Its the most basics of basics without any attachment to ANY other Operating System. So with this you can write your own OS from scratch.

I even included info so you can copy both files to a floppy image :

partcopy BootUp.bin 0 200 -f0 0
partcopy mycode.bin 0 FFFF -f0 200

Make sure to read the text file.

Enjoy.


Description: My Generic OS Boot source code from scratch with instructions on how to put it onto floppy and CD.
Download
Filename: GenericOS.zip
Filesize: 6.34 KB
Downloaded: 155 Time(s)

Post 23 Sep 2010, 19:37
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janequorzar



Joined: 11 Sep 2010
Posts: 60
janequorzar
UPDATE : I meant to also say that in the 2nd file you can setup your GDT and trasnfer to Pmode ( protected mode ) because now you have the room to do it right.
Post 23 Sep 2010, 19:42
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baldr



Joined: 19 Mar 2008
Posts: 1651
baldr
janequorzar,

Your method for calculating boot code size is somewhat unusual. size = stophere + bootstart would give rather unexpected result. Wink

This boot sector will load only first 1024 bytes of mycode.bin. It can be misleading, since you've made mycode.bin 65535 bytes in size. Even if someone manage to load entire file in memory, there are two problems (at least Wink):
  1. Last 4095 bytes of mycode.bin will be off-limit for segment 0 (you're loading it at 0x1000).
  2. It will overwrite boot sector code during loading (though this can be used for implicit control transfer, see below).
Code:
; This is CHS 0/0/1
        org     0x7C00
        mov     ax, 0x0201
        mov     cx, 0x0002      ; CHS: 0/0/2
        mov     dh, 0           ; dl is from BIOS Boot Specification/BAID
        mov     bx, $$
        push    cs
        pop     es
        int     0x13
int13ret:                       ; control will return here, or it seems so
        rb      $$+510-$
        dw      0xAA55

; This is CHS 0/0/2
        org     0x7C00
message db      "Hello world!", 13, 10, 0; Overlays boot up to int 0x13
        rb      int13ret-$      ; need this for shorter messages
; This is entry point, believe it or not
        mov     si, message
        push    cs
        pop     ds
        mov     ah, 0x0E
        xor     bh, bh
next:   lodsb
        test    al, al
        je      done
        int     0x10
        jmp     next
done:   xor     ah, ah
        int     0x16
        int     0x19    
As a sidenote, you can edit your messages instead of double-posting.
Post 24 Sep 2010, 07:19
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egos



Joined: 10 Feb 2009
Posts: 144
egos
Code:
; This is CHS 0/0/1
        org     0x7C00
        mov     ax, 0x0201
        mov     cx, 0x0002      ; CHS: 0/0/2
        mov     dh, 0           ; dl is from BIOS Boot Specification/BAID
        mov     bx, $$
        push    cs
        pop     es
        int     0x13
int13ret:                       ; control will return here, or it seems so
        rb      $$+510-$
        dw      0xAA55

; This is CHS 0/0/2
        org     0x7C00
message db      "Hello world!", 13, 10, 0; Overlays boot up to int 0x13
        rb      int13ret-$      ; need this for shorter messages
; This is entry point, believe it or not    
It's crazy method. And why does need preloader code if it loads only one sector at 0x7C00?
Post 24 Sep 2010, 09:05
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janequorzar



Joined: 11 Sep 2010
Posts: 60
janequorzar
baldr wrote:
janequorzar,

Your method for calculating boot code size is somewhat unusual. size = stophere + bootstart would give rather unexpected result. Wink

This boot sector will load only first 1024 bytes of mycode.bin. It can be misleading, since you've made mycode.bin 65535 bytes in size. Even if someone manage to load entire file in memory, there are two problems (at least Wink):
  1. Last 4095 bytes of mycode.bin will be off-limit for segment 0 (you're loading it at 0x1000).
  2. It will overwrite boot sector code during loading (though this can be used for implicit control transfer, see below).
Code:
; This is CHS 0/0/1
        org     0x7C00
        mov     ax, 0x0201
        mov     cx, 0x0002      ; CHS: 0/0/2
        mov     dh, 0           ; dl is from BIOS Boot Specification/BAID
        mov     bx, $$
        push    cs
        pop     es
        int     0x13
int13ret:                       ; control will return here, or it seems so
        rb      $$+510-$
        dw      0xAA55

; This is CHS 0/0/2
        org     0x7C00
message db      "Hello world!", 13, 10, 0; Overlays boot up to int 0x13
        rb      int13ret-$      ; need this for shorter messages
; This is entry point, believe it or not
        mov     si, message
        push    cs
        pop     ds
        mov     ah, 0x0E
        xor     bh, bh
next:   lodsb
        test    al, al
        je      done
        int     0x10
        jmp     next
done:   xor     ah, ah
        int     0x16
        int     0x19    
As a sidenote, you can edit your messages instead of double-posting.


Actually, I been doing it this way for 10 years and never had a problem of any kind. Smile Remember, this is transferring to the next file, it does not need the BootUp.bin file once it gets past it. And as far as memory, this is for presetting up before you get to the Kernel anyhow, at least this way you have more room to play in. The 65535 was there to show that it could transfer the file with partcopy for those who didn't know it could do it. Your focusing on an area that probably never get used and not on what the code is actually doing. Smile Remember, if you put into the 2nd file a reset of the memory you will have the full 64 K at your disposal.. This is just basic startup transfer FROM the boot code example. The point is not the limits, but what you gain from this. You do not need a Pre-Loading message or anything in the bootup.bin file when you can do all that with freedom in the 2nd file. And on top of that, the reason for the 0x1000 is so that you do not overwrite the bootup.bin file while its trying to access the 2nd file position on the current drive. Remember, you have to FIND the drive and sometimes people put thier code on a floppy disk, which in turn means you have to wait for the motor to give you access, so it is written this way to keep searching until it finds it in the bootup file. Once it finds it, boom, 1000 here I come.. lol THEN you can clear your previous space and setup to utilize the full 64K like you wish you could with the original boot code. But thats all up to you now how you do it, which is why you now have more freedom. Smile


Last edited by janequorzar on 24 Sep 2010, 13:19; edited 3 times in total
Post 24 Sep 2010, 12:54
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baldr



Joined: 19 Mar 2008
Posts: 1651
baldr
egos,

Overwriting return address for int 0x13 in BIOS stack — that's what I would call crazy method.

As for one sector — most BIOSes support multitrack operations (some of them handle 64 KiB DMA boundaries too), thus one-byte modification of mov ax, 0x0201 allows loading many sectors at once. That was simple demonstration of trick.

----8<----
janequorzar,

That wasn't critique, just some things to be noted.
Post 24 Sep 2010, 20:26
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janequorzar



Joined: 11 Sep 2010
Posts: 60
janequorzar
hey total agreement of the 201. minus one number would be 200.. remember 0 counts as a number from the beginning. Smile
Post 25 Sep 2010, 03:33
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luke77



Joined: 14 May 2010
Posts: 18
luke77
What would be neat would be a floppy program that could access and write to NTFS disks.

I have a lot of older code that I would still like to use.

My BIOS is ten years old, so I don't think I can use a bootable USB drive with it.

I have a second disk that I only use for backup.
I would be willing to convert it back to Fat32 if I knew I could access and write to it from a boot floppy.

Take care,
Andy
Post 25 Sep 2010, 04:43
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baldr



Joined: 19 Mar 2008
Posts: 1651
baldr
janequorzar wrote:
hey total agreement of the 201. minus one number would be 200.. remember 0 counts as a number from the beginning. Smile
Yep, and 65535 bytes are numbered 0…65534.

----8<----
luke77,

FAT32 can be accessed using MS-DOS 7.1+ (Win95 OSR2+) boot disk, LFNs can be supported too (DOSLFN).
Post 25 Sep 2010, 05:28
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egos



Joined: 10 Feb 2009
Posts: 144
egos
Quote:
Overwriting return address for int 0x13 in BIOS stack — that's what I would call crazy method.

As for one sector — most BIOSes support multitrack operations (some of them handle 64 KiB DMA boundaries too), thus one-byte modification of mov ax, 0x0201 allows loading many sectors at once. That was simple demonstration of trick.
What is necessity to overwrite boot code? What if error occurred during function execution. Loading of whole module at one disk operation is bad practice.
Post 25 Sep 2010, 10:42
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janequorzar



Joined: 11 Sep 2010
Posts: 60
janequorzar
egos wrote:
Quote:
Overwriting return address for int 0x13 in BIOS stack — that's what I would call crazy method.

As for one sector — most BIOSes support multitrack operations (some of them handle 64 KiB DMA boundaries too), thus one-byte modification of mov ax, 0x0201 allows loading many sectors at once. That was simple demonstration of trick.
What is necessity to overwrite boot code? What if error occurred during function execution. Loading of whole module at one disk operation is bad practice.


Exactly why this demo is here. This works, it has for all my students too, thats the beauty of it. The key thing here is that it doesn't require you to have to have anything from Microsoft or Linux to make it call another file. Thats the whole point of this demo. It goes to show you CAN do it. As I tell everyone, an OS is not limited to just the BIG WIGS out there. You can make your own from scratch.

I am currently doing that. I writing my own routines that doesn't require the Interrupts and does not require any support from other OSs. This is a complete project from scratch that I am working on, and it works. Once this is to a point that I can show the public, you'll get your free copy.. Smile

And FASM is the compiler I chose to make this. Cool
Post 25 Sep 2010, 13:53
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baldr



Joined: 19 Mar 2008
Posts: 1651
baldr
egos wrote:
What is necessity to overwrite boot code? What if error occurred during function execution. Loading of whole module at one disk operation is bad practice.
I repeat again: that code was shown just to demonstrate what will happen when read buffer overlaps code that reads in it. Just a trick.

If read error occurs, in most cases it's permanent (I'm talking about FDD/HDD).

Loadind part of module is pointless (if it's module).

----8<----
janequorzar,

Your code works, unquestionably. I was simply pointing to some flaws that are inherent to its design (due to simplicity). There are boot sectors (with source) that can load real file from FAT12/16 FS, though (partcopy will be needed only once).
Post 25 Sep 2010, 14:35
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janequorzar



Joined: 11 Sep 2010
Posts: 60
janequorzar
baldr wrote:
egos wrote:
What is necessity to overwrite boot code? What if error occurred during function execution. Loading of whole module at one disk operation is bad practice.
I repeat again: that code was shown just to demonstrate what will happen when read buffer overlaps code that reads in it. Just a trick.

If read error occurs, in most cases it's permanent (I'm talking about FDD/HDD).

Loadind part of module is pointless (if it's module).

----8<----
janequorzar,

Your code works, unquestionably. I was simply pointing to some flaws that are inherent to its design (due to simplicity). There are boot sectors (with source) that can load real file from FAT12/16 FS, though (partcopy will be needed only once).


Ok but thats my exact point. Using the FATx system means your using Microsoft's stuff. If you ever were to sell your OS you couldn't unless you pay Microsoft to do it. Or just don't use their FAT x system. To read from another file is up to HOW you do it.. The reason for the Partcopy to copy two files is because for you to transfer a file in windows to another disk / hard drive means you have to have that OS file table on the target drive. To get around that you use partcopy to work your way up. That way, you are not using MS stuff. Read the Terms of Service by MS and it says you are NOT allowed by any means to use their software to make an OS unless its for educational purposes.

Their FAT system is patented. Scroll down.

http://en.wikipedia.org/wiki/File_Allocation_Table

So my demo I made as a way to show HOW it can be done. Of course there are flaws.. not the point. That can be fixed. But we WANT people to consider how to do it and I am showing they can.

Hope that clarifies the intention here. Its all good.. If anything, your making my code work even better in the explanation as to why its there in the first place. So keep it up.. Smile
Post 25 Sep 2010, 15:18
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baldr



Joined: 19 Mar 2008
Posts: 1651
baldr
janequorzar,

Those patents seem to be related to LFNs.

To stay on topic: do you think boot sector can contain layout of kernel (let it be the placement of binary to load, sector-wise) as a part of it? I mean, on different disks (with different kernel placement) boot sector can be different too?
Post 25 Sep 2010, 15:58
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janequorzar



Joined: 11 Sep 2010
Posts: 60
janequorzar
baldr wrote:
janequorzar,

Those patents seem to be related to LFNs.

To stay on topic: do you think boot sector can contain layout of kernel (let it be the placement of binary to load, sector-wise) as a part of it? I mean, on different disks (with different kernel placement) boot sector can be different too?


Ok, try this experiment. Make a Boot.bin ( or use mine ) without Microsoft's FAT table or code.. Take it completely out. Then partcopy the boot to that floppy disk.

THEN in windows, copy a file to the disk. You wont be able too. The way Windows works is it looks for the boot sector table. If it is within Microsoft parameters, it will allow you to transfer a file to it. Without that table, Windows has no clue what to do. Partcopy, doesn't need to worry about that. Hence the reason to copy both files with it and create a TABLE of your own with it. Its tricky, but it does work. This is where you can write another piece of software in windows that formats and puts a bootsector on the floppy. And keep in mind, the OS determines what sector you have the TABLE on.. Not the computer. So you are free to put your own "fat" type of table in the 2nd sector. This is what I call, thinking outside the box. Out of "big brothers" reach. Smile
Post 25 Sep 2010, 16:55
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janequorzar



Joined: 11 Sep 2010
Posts: 60
janequorzar
On another note, I am actually writing an Operating System from scratch. The first time I made an OS, I learned all these lessons the hard way. Needless to say, my original OS from back in 2000 didn't go anywhere. But now, since I have some education on this that is way advanced compared to where I was, now I can do it right this time. And it is paying off. People are seeing my OS already and they didn't know you could do it this way. What I shown you here, is only a small demo of not having to conform to any one pattern of thinking. Being creative is what I do this for.

I actually am writing TWO OSs. The reason is because one of them is from the famous TV show Star Trek. I am making an OS based off their LCARS interface just like I did back in 2000. LCARS is one of my favorite Graphical designs. My other OS is one with an original design and can be sold commercially if I so choose. Both with original code and not taken from anywhere else. So far, its working. No problems. Its why I mentioned earlier, that you will all have a copy of my OS when I get it ready for the public. Very Happy
Post 25 Sep 2010, 17:04
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baldr



Joined: 19 Mar 2008
Posts: 1651
baldr
janequorzar wrote:
THEN in windows, copy a file to the disk. You wont be able too.
Why should I expect Windows to recognize volume with unknown file system (or without FS at all)? Wink

Direct media access is somewhat straightforward (though I like the way FORTH keeps external storage access simple). Named (and probably non-contiguous) entities we know as files require some housekeeping to exist. Moreso, some sort of hierarchical/tagged approach can simplify proper classification of such entities.

Looks like I've been driven off-topic again.
Post 25 Sep 2010, 18:21
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janequorzar



Joined: 11 Sep 2010
Posts: 60
janequorzar
baldr wrote:
janequorzar wrote:
THEN in windows, copy a file to the disk. You wont be able too.
Why should I expect Windows to recognize volume with unknown file system (or without FS at all)? Wink

Direct media access is somewhat straightforward (though I like the way FORTH keeps external storage access simple). Named (and probably non-contiguous) entities we know as files require some housekeeping to exist. Moreso, some sort of hierarchical/tagged approach can simplify proper classification of such entities.

Looks like I've been driven off-topic again.


I'm in total agreement here. And yes Direct Media access can be setup anyway you want it for your own OS, the way you see fit. Gotta love creativity. Cool
Post 25 Sep 2010, 22:04
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edfed



Joined: 20 Feb 2006
Posts: 4242
Location: 2018
edfed
direct drive acess is the low level layer of the file system.
even under windows, you can make it. it is up to the programmer to do what he wants to do.
Post 25 Sep 2010, 22:09
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janequorzar



Joined: 11 Sep 2010
Posts: 60
janequorzar
edfed wrote:
direct drive acess is the low level layer of the file system.
even under windows, you can make it. it is up to the programmer to do what he wants to do.


Exactly Very Happy
Post 25 Sep 2010, 22:11
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