Re: booting Linux from a dos box in win3.1

Albert Cahalan (albert@ccs.neu.edu)
Tue, 3 Sep 1996 19:26:08 -0400 (EDT)

> From: Hans Lermen <lermen@elserv.ffm.fgan.de>
> On Mon, 2 Sep 1996, 0xdeadbeef wrote:
>
>> ... basically, i need to know if it's at all possible to boot
>> Linux from a Windows 3.1 DOS box without exiting Windows.
>
> Without 'exiting Windows': NO !
>
> The DOS-Box runs in VM86 mode, out of this you can't enter neither
> '_real_ realmode' nor 'ring0 protected mode'. Loadlin can overcome this
> restriction when a VCPI-Server is available: it first enters VCPI, then
> returns to realmode, then jumps back to arch/i386/boot/setup.S code.
> However, Windows (may be 3.1 or '95) don't supply a VCPI-Server,
> so any attempt to enter ring0 protected mode will be refused.

I think a Windows program can request that some other program
will run when Windows quits. Some game programs do that, even
under Windows 3.1. (it is easy with Windows 95)

For Windows NT, I think a VxD would be needed. They run in kernel
mode, so they can shut down all the services and then just start
the Linux code directly. That would work for all platforms I think,
and it would mean the real-mode code could be eliminated for i386.