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the DOS code segment hunt, results/questions (Miscellaneous)

posted by Ninho(R) E-mail, 15.12.2009, 00:59
(edited by Ninho on 15.12.2009, 01:20)

>> 2: :-| DOSDATA:90h. There are 15 far pointers who seem to point to
>> DOSCODE always. I could use that, the infortune is I cannot find reference
>> data about them. They don't seem to appear in Ralf's list.

> Look for SHARE.EXE hooks; they're listed in the Int21.52 (DOS data)
> description. These hooks are either addressed with fixed offsets or by
> finding the first SFT container (segment must be the DOS data segment).
> The latter's offset is 0CCh, and just in front of it are the SHARE.EXE
> hooks.

Ah, right you are ! I was working by my partial compilation, hand written on paper after Ralf's tables, unfortunately at the position of these pointers I had retained only "DWORD pointer to FAR routine for ???", forgetting to note the relation to SHARE.EXE.

> 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+. (Microsoft simply
> omitted SHARE.EXE from MS-DOS 7.10 and never provided a FAT32 version.)
> Therefore, all of these pointers could be hooked by SHARE.EXE pointing to
> its segment instead of the DOS code segment.

Thank you Christian; I'll load SHARE and see the look of the routines therein, it might be feasible to trace back from there to the original ones in the kernel.

> I'd say you should try working with method 3; MS-DOS 7.00 probably stores
> the code segment somewhere around there as did earlier and later versions.

Method 3 was taking DOS CS from Word [70:3]. Unfortunately in MSDOS 7.0 it has the DOS DATA segment instead. Doesn't work out.

> Method 2 might not be reliable especially with MS-DOS 7.00 due to SHARE.EXE
> being provided by Microsoft there.

IIRC from way back, SHARE was not installed by default in Win 95 "A" install,
it mifht even not have been present on the installation media (at that time, most often *floppies*). Rather it was part of supplemental files that people could download from Microsoft's or others' BBS (Internet? B.Gates hadn't heard of the internet yet...) Hence the number of users still running 95 "A", /and/ loading SHARE at that, must be quicly approaching zero ;=)



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