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Date: Sat, 6 Jul 2002 02:28:35 -0700
From: David Schultz <dschultz@uclink.Berkeley.EDU>
To: David Xu <bsddiy@yahoo.com>
Cc: Jonathan Lemon <jlemon@flugsvamp.com>, current@FreeBSD.ORG
Subject: Re: i386 trap code
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	Jonathan Lemon <jlemon@flugsvamp.com>, current@FreeBSD.ORG
References: <200207060557.g665vhm16951@prism.flugsvamp.com> <20020706090701.37865.qmail@web20906.mail.yahoo.com>
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Thus spake David Xu <bsddiy@yahoo.com>:
> I don't know if FreeBSD can run DOS program, if it can, then one CPU running
> DOS program can confuse another CPU which is running BIOS code because of this
> global flags. 
> 
> my current patch does not remove vm86_lock, it is still there, my orginal
> purpose is while CPU in VM86 mode, when hardware interrupt occurs, still
> allow interrupt thread to run.

FreeBSD can run DOS programs, but it does so by emulating all of
the common DOS and BIOS calls.  You can't safely give untrusted
userland programs direct access to the BIOS, and even if you
could, the BIOS calls wouldn't work as the DOS programs expected
them to.  See doscmd(1).

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