Date: Wed, 23 Sep 1998 14:14:38 +0300 (IDT)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: Doug Gale <dgale AT mailexcite DOT com>
cc: Endlisnis <s257m AT unb DOT ca>, djgpp AT delorie DOT com
Subject: Re: FW: Inline ASM
In-Reply-To: <BLOMHPCJOFLBAAAA@mailexcite.com>
Message-ID: <Pine.SUN.3.91.980923141353.1392N-100000@is>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Precedence: bulk


On Mon, 21 Sep 1998, Doug Gale wrote:

> If you say it works, I guess it works (ok, ok, I AM wrong :). Have
> you tested this under more than one DPMI server (eg. Windows,
> CWSDPMI, novell's dpmi server, QEMM, etc)?

INT instructions should be (and are) reflected to real mode under all
DPMI providers.  Int 2Fh has some problem on certain versions of
Windows 95, but that's a bug in Windows.

> I wonder what the official DPMI spec has to say about this?

Here's what it says:

             3.2 Default Interrupt Reflection


            DPMI hosts  provide interrupt  vectors  for  all  100h  (256
            decimal) interrupts  for protected  mode clients.   When the
            DPMI client initializes, all interrupt vectors will point to
            code that  will automatically  reflect the interrupt to real
            mode (except  for Int  31h and  Int 21h,  AH=4Ch).   When  a
            default interrupt  reflection handler  is executed  it  will
            switch to real mode, preserving the EAX, EBX, ECX, EDX, ESI,
            EDI, and  EBP registers and flags, and reflect the interrupt
            in real  mode.   When the  real mode  interrupt returns, the
            default  interrupt  reflection  code  will  switch  back  to
            protected mode  and return  with the modified values of EAX,
            EBX, ECX,  EDX, ESI, EDI, EBP, and flags.  Segment registers
            and the  stack pointer  will not  be passed  between  modes.
            Therefore, any  API that  passes pointers  or information in
            segment registers  will need  to  be  translated  by  a  DOS
            extender.