DOS ain't dead

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

posted by Ninho , 15.12.2009, 22:32

> 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+.


> Say, a user loads FIXWRAP using DEVLOAD. This is of
> course not what users should do but they are able to.

Your user is a vicious type, I assume s/he also loaded SHARE.EXE before trying to DEVLOAD FIXWRAP.SYS ? Let'm get what they deserve !


> It's just no general
> solution to find the code segment, even restricting the OS to MS 7+.

I find it good enough, until offered a better one, so let's read on :

> I'd suggest you use the far jump at 0:C0 instead (the CP/M "CALL 5"
> compatibility entry).

Oh! CP/M to the rescue! No, I don't think so


> 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.

Those stubs are NOT used and the segment therein is bogus whenever DOS=LOW and no XMS is loaded. Excuse me, I understand you are proud of your gimmick but so am I with mine own. Your method arrives at the same point as mine through more detours. And what if the motherf^cker of a user you have in mind (the one who devloads FIXWRAP) also messes with int 30 ? This is not serious !

To appease your fears, FIXWRAP could check whether it is being initiated by DOS or whether by a DEVLoader, it is not very difficult.

> the patch location using the CALL 5 handler instead of the Int27 handler
> as well.

I chose int 27 because it leads us almost right to the point of interest !

Cheers

---
Ninho

Complete thread:

• new HACKWRAP fix for MS-DOS7+, aka smashing the bug - Ninho, 11.12.2009, 00:17 (Miscellaneous)
  • new HACKWRAP fix for MS-DOS7+, aka smashing the bug - ecm, 11.12.2009, 15:02
    • new *FIXWRAP* for MS-DOS7+, aka smashing the bug - Ninho, 12.12.2009, 01:12
  • FIXWRAP technical thread. News - Ninho, 12.12.2009, 16:05
    • CM's questions, answered - Ninho, 12.12.2009, 18:22
      • CM's questions, answered - ecm, 12.12.2009, 22:40
        • CM's questions, answered - Ninho, 13.12.2009, 00:10
          • CM's questions, answered - ecm, 13.12.2009, 00:51
            • CM's questions, answered - Ninho, 13.12.2009, 10:32
      • CM's questions, answered - geoffchappell, 14.12.2009, 10:42
        • CM's questions, answered - Ninho, 14.12.2009, 12:19
  • new HACKWRAP fix for MS-DOS7+, aka smashing the bug - geoffchappell, 14.12.2009, 10:41
    • new HACKWRAP fix for MS-DOS7+, aka smashing the bug - Ninho, 14.12.2009, 11:49
      • new HACKWRAP fix for MS-DOS7+, aka smashing the bug - geoffchappell, 15.12.2009, 16:55
        • new HACKWRAP fix for MS-DOS7+, aka smashing the bug - Ninho, 15.12.2009, 19:08
        • new HACKWRAP fix for MS-DOS7+, aka smashing the bug - Ninho, 17.12.2009, 16:35
  • the DOS code segment hunt, results/questions - Ninho, 14.12.2009, 20:37
    • the DOS code segment hunt, results/questions - ecm, 14.12.2009, 23:30
      • the DOS code segment hunt, results/questions - Ninho, 15.12.2009, 00:59
      • Aha! Share was a *red herring* ! Hunt over !!! - Ninho, 15.12.2009, 10:32
        • Aha! Share was a *red herring* ! Hunt over !!! - ecm, 15.12.2009, 21:13
          • Aha! Share was a *red herring* ! Hunt over !!! - Ninho, 15.12.2009, 22:32
            • Aha! Share was a *red herring* ! Hunt over !!! - ecm, 15.12.2009, 23:05
      • the DOS code segment hunt, results/questions - geoffchappell, 15.12.2009, 16:56
        • the DOS code segment hunt, results/questions - ecm, 15.12.2009, 21:19
          • the DOS code segment hunt, results/questions - Ninho, 15.12.2009, 22:38
            • the DOS code segment hunt, results/questions - ecm, 15.12.2009, 23:06
              • the DOS code segment hunt, results/questions - Ninho, 16.12.2009, 09:22
        • the DOS code segment hunt, results/questions - Ninho, 16.12.2009, 20:24
          • the DOS code segment hunt, results/questions - Ninho, 30.12.2009, 10:50
    • the algorithm, sketched for review. Nitpicks ? - Ninho, 16.12.2009, 19:51
      • the algorithm, sketched for review. Nitpicks ? - ecm, 17.12.2009, 16:19
        • the algorithm, sketched for review. Nitpicks ? - Ninho, 17.12.2009, 17:14
          • the algorithm, sketched for review. Nitpicks ? - ecm, 17.12.2009, 20:32
            • the algorithm, sketched for review. Nitpicks ? - Ninho, 17.12.2009, 21:05
              • the algorithm, sketched for review. Nitpicks ? - ecm, 17.12.2009, 21:13
                • the algorithm, sketched for review. Nitpicks ? - Ninho, 17.12.2009, 23:16
                • digression : MSDOS 7 and SHARE.EXE revisited - Ninho, 18.12.2009, 13:04
                  • digression : MSDOS 7 and SHARE.EXE revisited - ecm, 18.12.2009, 14:31
                    • digression : MSDOS 7 and SHARE.EXE revisited - Ninho, 18.12.2009, 17:19
                      • digression : MSDOS 7 and SHARE.EXE revisited - ecm, 18.12.2009, 18:19
                        • digression : MSDOS 7 and SHARE.EXE revisited - Ninho, 18.12.2009, 18:55
  • HACKWRAP.SYS news, testing - Ninho, 20.12.2009, 02:44
    • FIXWRAP.SYS 0.5 beta - released - please try it ! - Ninho, 23.12.2009, 00:07