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From: | "Dijkstra" <pepitek AT gmail DOT com> |
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Subject: | Re: Need to hook INT 21h from a DJGPP TSR |
Date: | 8 Oct 2005 10:03:15 -0700 |
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Hi Rod! Thanks for your examples. I'm also experimenting with other extenders, namely DOS32A and WDOSX. The DOS32A is interesting since it seems much more understandable (from my poor assembler perspective :-) From the source code of DOS32A you can see it hooks INT 21h internally, so unless I deeply modify the DOS32A source code, it's a bad idea to hook it again. It can lead to many undesirable "PM" -> "RM" -> "PM Again" chain loops. So, I'm heading now into a diferent direction. I give up on the idea of chaining INT 2Fh and 21h and make some kind of installable driver instead. I will hook INT AFh and A1h (2Fh or 80h, 21h or 80h). They will be real mode callbacks (_go32_dpmi_allocate_real_mode_callback_iret) so that I could call them from real mode. Then, I will code an additional pure real mode tiny TSR that will be forwarding INT 21h and 2Fh safely from there. I don't know if all this mess will work, but it will be a good research work. :-) Cheers, Jose Miguel.
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