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Aha! Share was a *red herring* ! Hunt over !!! (Miscellaneous)

posted by cm(R) Homepage E-mail, Düsseldorf, Germany, 15.12.2009, 21:13

> > Installing SHARE.EXE is legitimate under MS-DOS 7.00 and might work with
> a
> > specially written FAT32 SHARE.EXE under MS-DOS 7.10+.
>
> FIXWRAP is executed as a DEVICE= driver installation. The user may well
> INSTALL=SHARE.EXE if s/he likes, we couldn't care less !!!
>
> So evident, we must have been blind.

I don't like this. Say, a user loads FIXWRAP using DEVLOAD. This is of course not what users should do but they are able to. It's just no general solution to find the code segment, even restricting the OS to MS 7+.

I'd suggest you use the far jump at 0:C0 instead (the CP/M "CALL 5" compatibility entry). This either points directly to the DOS code segment or to one of the stubs in the DOS data segment. You can identify the stub and if it's one, you have to retrieve the address that it jumps to in its last instruction; this address points to the DOS code segment. To ensure that this will actually retrieve correct pointers, check that at 0:C0 there is indeed a far jump. You could probably decide where to search for the patch location using the CALL 5 handler instead of the Int27 handler as well.

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l

 

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