From:	"Groman" <groman AT thehelm DOT com>
Newsgroups:	alt.os.development,alt.lang.asm,comp.os.msdos.djgpp,alt.os.assembly
Subject:	Having troubles with IDT/IRQ0
Lines:	65
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Message-ID:	<CXMe4.467$YK4.12132@nnrp3-w.snfc21.pbi.net>
Date:	Tue, 11 Jan 2000 13:06:55 -0800
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To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

Could somebody please tell me if the following bits and pieces are correct
and do what I want(99% chance the problem is elseware, but I want to make
sure
these pieces are which work)
I've been starring into this code for about 16 hours now, and I think I am
missing something obvious:
The computer reboots as soon as I enable the interrupts(IRQs are shifted to
0x20 and are all masked but 0x2 and 0x0(code from Linux 2.0 source))

Bochs panics saying
interrupt(): gate descriptor is not valid sys seg



I am using djgpp with nasm...


is this a correct IDT entry?
struct IDTDesc
{
 unsigned short  OffSet1 _pack;    // Offset
 unsigned short  Selector1 _pack;  // Segment selector
 unsigned short  Flags _pack;      // Flags
 unsigned short  OffSet2 _pack;    // Rest of the offset
} _pack;

is this the correct way to setup the IDT(statically)

IDTDesc IDT[256];


is this the correct way to change interrupt 0x20 to handler IRQ0Handler:

 unsigned long int offset = (unsigned int)(void *)&IRQ0Handler;
 DisableInt();

 IDT[0x20].OffSet1 = (offset&0xFFFF);
 IDT[0x20].OffSet2 = (offset>>16);
 IDT[0x20].Flags   =  0x8E00;
 IDT[0x20].Selector1 = 0x8;

will this work as an interrupt handler?

_IRQ0Handler:
 push eax
 push edx


 mov dx,0x20
 mov al,0x20
 out dx,al

 inc word [0xb8000]

 pop edx
 pop eax
 iret

sincerely, groman

thank you in advance.

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