DOS ain't dead

Device drivers: Changing the attribute word at install time? (Developers)

posted by ecm  , Düsseldorf, Germany, 03.10.2023, 20:56

> The sentence says the driver install routine is called first, and then the
> attributes are evaluated. Which makes sense as there is no need to worry
> about driver chains or attributes if the install routine in the driver
> errors out.

UPX sources indicate that "OpenDOS" wants the interrupt field untouched by the packer, that is it may read it before running the unpacker (strategy entrypoint).

https://github.com/upx/upx/blob/7f9d381c7b594ecf7d...f3c0f16527599/src/stub/src/i086-dos16.sys.S#L42

https://github.com/upx/upx/blob/7f9d381c7b594ecf7d...f3c0f16527599/src/stub/src/i086-dos16.exe.S#L34

section         DEVICEENTRY
                .long   -1
                .short  attribute
                .short  strategy        /* .sys header */
                .short  interrupt       /* opendos wants this field untouched */

Here's this part in EDR-DOS, an OpenDOS derivative: https://hg.pushbx.org/ecm/edrdos/file/e1dbcad5136e/drbio/config.a86#l556


        mov     ax,es:DH_STRATEGY[di]   ; Set up the STRATEGY Entry Point
        mov     strategy_off,ax
        mov     strategy_seg,es

        mov     ax,es:DH_INTERRUPT[di]  ; Set up the INTERRUPT Entry Point
        mov     interrupt_off,ax
        mov     interrupt_seg,es
        call    init_static_request

Evidently it does read both entrypoint offsets before calling the strategy during device initialisation.

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l

Complete thread:

• Device drivers: Changing the attribute word at install time? - mbbrutman, 02.10.2023, 23:47 (Developers)
  • Device drivers: Changing the attribute word at install time? - glennmcc, 03.10.2023, 03:43
  • Device drivers: Changing the attribute word at install time? - mbbrutman, 03.10.2023, 20:21
    • Device drivers: Changing the attribute word at install time? - ecm, 03.10.2023, 20:56
      • Device drivers: Changing the attribute word at install time? - mbbrutman, 03.10.2023, 21:26
        • Device drivers: Changing the attribute word at install time? - tkchia, 03.10.2023, 21:32
          • Device drivers: Changing the attribute word at install time? - mbbrutman, 03.10.2023, 22:48
          • Device drivers: Changing the attribute word at install time? - tom, 04.10.2023, 23:43
  • Device drivers: Changing the attribute word at install time? - tkchia, 03.10.2023, 21:28
    • Device drivers: Changing the attribute word at install time? - mbbrutman, 03.10.2023, 22:51
      • Device drivers: Changing the attribute word at install time? - bretjohn, 06.10.2023, 21:35
        • Device drivers: Changing the attribute word at install time? - mbbrutman, 07.10.2023, 20:42
          • Device drivers: Changing the attribute word at install time? - bretjohn, 09.10.2023, 19:17
            • Device drivers: Changing the attribute word at install time? - mbbrutman, 02.11.2023, 19:39
  • Device drivers: Changing the attribute word at install time? - Rugxulo, 23.11.2023, 22:15