How to use int 13 while BSD is running

[Jason Dictos]

HI John,

	I think I am beginning to understand your original reply to my
email. I think following your suggestions of using our code in a modified
boot loader environment to pull the data we need from a bios addressable
discs is the best idea so far. I wonder what kind of memory restrictions
apply in this mode, our application would have to be stripped down to a
single threaded app, possibly with a custom init flag for this mode, but
then again our kernel would have to be custom compiled for this mode, just
like it is now for dos mode. Now that I think about it, other then being
able to compile in 32 bit mode, I wonder what kind of advantages this mode
would give us from our current dos mode? We still have to seriously shrink
it down and link into custom libraries to support this mode.

-Jason

-----Original Message-----
From: John Baldwin [mailto:jhb at FreeBSD.org] 
Sent: Wednesday, March 10, 2004 2:30 PM
To: Jason Dictos
Cc: 'freebsd-hardware at freebsd.org'
Subject: Re: How to use int 13 while BSD is running

On Wednesday 10 March 2004 01:22 pm, Jason Dictos wrote:
> Thanks for the reply, however I'm looking for a more DMPI style 
> interface while in protected mode. If we didn't need to be in 
> protected mode, then I'd just leave it the way it is-us booting into 
> DR DOS and using inline assembly to access int 13. However what we're 
> trying to do is move to a 32 bit kernel environment, while still 
> retaining access to realmode interrupts.

The loader runs in protected mode.  Basically, BTX is a small kernel that
allows for a single protected mode task.  That task can make BIOS calls, the
real mode interrupt handlers are still used for device interrupts, etc.  For
example, see src/sys/boot/i386/libi386/biosdisk.c to see how it uses int13
to talk to the disks but from within a 32-bit protected mode app written in
C.

> -Jason
>
> -----Original Message-----
> From: John Baldwin [mailto:jhb at FreeBSD.org]
> Sent: Wednesday, March 10, 2004 7:52 AM
> To: Jason Dictos
> Cc: 'freebsd-hardware at freebsd.org'
> Subject: Re: How to use int 13 while BSD is running
>
> On Tuesday 09 March 2004 04:24 pm, Jason Dictos wrote:
> > Hello,
> >
> > 	I'm investigating what resources are out there for accessing bios 
> > addressable devices while BSD is up and running. The situation is 
> > this, currently we licenses Caldera DOS for a program we wrote which 
> > uses the
> > int13 extensions to manipulate the systems hard drive (i.e. to 
> > recover partition tables and what not). This forces our application 
> > to be written in 16 bit mode, but it does allows us to not have to 
> > worry about loading any driver which would be hardware specific to 
> > access the hard drive. Is there any way to write a driver for BSD 
> > which would put the processor into real mode, therefore allowing us 
> > to use the int
> > 13 api of the bios to read and write hard drives? That way we could 
> > package a stripped down BSD kernel which loaded our driver and gave 
> > our application access to hard disks without having to load any 
> > device
>
> driver.
>
> > Apologies in advance if this is the wrong mailing list,
>
> Look at the loader in src/sys/boot.   It is a 32-bit C app that uses BIOS
> calls to access the disk.  It uses a psuedo-kernel called BTX to 
> manage interrupts in vm86 mode and run BIOS code in vm86 mode.  You 
> can probably port your software to being a custom loader that uses 
> boot2 to boot off of a floppy.  You can also use cdboot to boot a 
> loader off of a CD or pxeboot to boot a loader image over the network.  
> The loader uses libstand which provides several useful things like 
> malloc/free, some basic filesystem support, etc.
>
> --
> John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/ 
> "Power Users Use the Power to Serve"  =  http://www.FreeBSD.org
>
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--
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/ "Power
Users Use the Power to Serve"  =  http://www.FreeBSD.org

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