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From: lbr@holos0.uucp (Len Reed)
Newsgroups: comp.os.msdos.programmer
Subject: Re: stealing an interrupt
Message-ID: <1990Dec19.174902.6122@holos0.uucp>
Date: 19 Dec 90 17:49:02 GMT
References: <90351.150210TOMIII@MTUS5.BITNET> <1990Dec18.163810.21268@jato.jpl.nasa.gov>
Organization: Holos Software, Inc., Atlanta, GA
Lines: 21

In article <1990Dec18.163810.21268@jato.jpl.nasa.gov> schmidt@mars.UUCP (Kevin Schmidt) writes:

>Everything looks fine except that the last jump (jmp [old_int]) has two
>problems.  First the jump must include a segment override so that the
>data segment (ds) is not used in calculating the address of old_int.
>Second you must insure that it is a far jump.  Thus the line should read:
>
>   jmp far cs:[old_int]

Elsewhere I've noted that you should change the assumes.  Overriding the
segment is fine, too, if you wish.  You don't need to tell the assembler
that this is a far jump, though, since it knows this because old_int is
doubleword.  If you wish to make everything explicit, though, the above
form is incorrect.  Try

	jmp cs:dword ptr [old_int]	; far jump indirect to saved handler
-- 
Len Reed
Holos Software, Inc.
Voice: (404) 496-1358
UUCP: ...!gatech!holos0!lbr