Two basic PMode questions 
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 Two basic PMode questions

I've only just started to code a little in on my own pmode server
and I've got a few basic questions:

1. To call a realmode interrupt, do I have to enter realmode,
restore IDT, stack and all that?

2. The IRQs generated. If I want to redirect them to their realmode
handlers. Do I have to enter realmode then?

I've been looking on some pmode-server code. The documentation
says the IRQs are refirected to their default RM handlers but
I can't see that the CPU-mode is changed in the code...

Please help me sort things out.

Johan Levin             Sweden
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Fri, 28 May 1999 03:00:00 GMT  
 Two basic PMode questions

Quote:
> I've only just started to code a little in on my own pmode server
> and I've got a few basic questions:
> 1. To call a realmode interrupt, do I have to enter realmode,
> restore IDT, stack and all that?For 286 systems, yes. For i386+ systems you can simulate the interrupt

using a V86 task. This way to stay in protected mode.

Quote:
> 2. The IRQs generated. If I want to redirect them to their realmode
> handlers. Do I have to enter realmode then?Same answer as for 1.
> I've been looking on some pmode-server code. The documentation
> says the IRQs are refirected to their default RM handlers but
> I can't see that the CPU-mode is changed in the code...If you like, I can send my own protected mode header (D32). It uses

a V86 task (actually it 'morphs' your task to a V86 task) to simulate
the interrupt. For this you have to set up a V86 stack frame, a V86
stack (the real mode stack) and set the virtual mode bit in the EFLAGS.

Herman



Mon, 31 May 1999 03:00:00 GMT  
 
 [ 2 post ] 

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