[syslinux] Syslinux DOS-based installer in FreeDOS

[perditionc at gmail.com]

On Sat, May 24, 2014 at 11:22 PM, H. Peter Anvin <hpa at zytor.com> wrote:

> On 05/24/2014 01:58 PM, Ady wrote:
> >
> > My guess is that if this was a bug in FreeDOS (as in "something" that
> > has nothing to do with the syslinux.com command) then it would be
> > somehow triggered by other DOS programs trying to write to the MBR.
> > Considering that there are several (open source) DOS programs that
> > are capable of successfully writing to the MBR under FreeDOS, I would
> > tend to think that there is some interaction issue.
> >
>
> There are a few different ways to do this.  I suspect programs like
> FDISK use direct BIOS accesses, because they have to also create
> partitions.
>
> Syslinux uses INT 21, AX=440D, CH=08/48 CL=41/61 which to the best of my
> understanding is supposed to read the absolute sectors corresponding to
> a target device, and I just verified under MS-DOS 6.22 behaves that way,
> and that FreeDOS 1.1 does not -- which by definition means it is a bug
> in FreeDOS.
>
>         -hpa
>
>
Thank you both, for finding the bug and narrowing down to the specific
calls at fault.
I have posted a preliminary fix (see
https://sourceforge.net/p/freedos/bugs/121/ ).

Kenneth J. Davis