Date: Mon, 10 Mar 1997 08:21:39 GMT
Message-Id: <199703100821.IAA17465@bryggen.bgnett.no>
From: Gisle Vanem <giva AT bgnett DOT no>
To: djgpp AT delorie DOT com
Cc: giva AT bbb DOT no
Subject: Re: RMCB Help

Andrew Crabtree <71223 DOT 3315 AT CompuServe DOT COM> wrote:

> ..into the ARP handler, and that crashed too ( I'm just trying to verify it gets
> to my routine OK).  It sometimes reports the page fault, and sometimes just
> exits without any message.  If no arps go out (I'm controlling them fron a
> traffic generator) then no problems.
...
> __dpmi_allocate_real_mode_callback(&ARPPacketHandler,&arpRegs,&arpSeg)

OTOH, this function requires that ARPPacketHandler() returns with a "retf".
Instead I would use:

  _go32_dpmi_seginfo rm_cb;

  rm_cb.pm_offset = (unsigned long) &ARPPacketHandler;
  _go32_dpmi_allocate_real_mode_callback_retf (&rm_cb,&arpRegs);

Look at the info page for this function for an example.

>   /* es:di - pointer to our function */
>   regs.x.es = arpSeg.segment;
>   regs.x.di = arpSeg.offset16;
         ^^
This would become:
  regs.x.es  = rm_cb.rm_segment;
  regs.d.edi = rm_cb.rm_offset;
       ^^

It's safer to fill all 32-bits; One never knows if the packet-driver
ignores high-words or not.

Gisle V.