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32-bit MSDOS (Announce)

posted by marcov, 30.06.2021, 22:47

> > I do not know where you get the idea that DPMI applications demand "that
> a
> > segment register be set a certain way",
>
> http://dos32a.narechk.net/manual/index.html
>
> ES = 32-bit data selector with base=PSP and limit=256 bytes
>
>
> That's what DOS32A executables require. The
> caller needs the privilege requires to set the
> ES register. In some environments I am interested
> in, that is not possible.
And how is that related to DPMI ? E.g. DJGPP go32v2 programs afaik assume es to be simply equal to ds. (so that rep movsb can be used to copy)

We also map the first 1MB of memory to the FS selector for easy dos access, but that is also not related to DPMI, and since your OS would be an independent target/OS anyway, that is not relevant.


> > or that they cannot run unprivileged.
>
> It is the caller who needs to be privileged in
> order to set segment registers and interrupt
> vectors. In an environment I am interested in
> (interested in running Win32 executables), I
> will not be privileged.
You can work around entry requirements in the privileged program loader. Doesn't have to mean that the binary itself must run privileged.

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