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  • crashing when attempting to dismount

    I'm running into a situation where the CLI is unable to dismount all mounted disks (-a -t file) on a specific endpoint.
    ' -D -m G:' results in the process crashing; the same behavior occurs with the -d switch. The UI (osfmount.exe) is able to correctly dismount the disks on this endpoint.

    Below is the -l output after the disk was mounted:

    PS C:\SupportData> & 'C:\Program Files\OSFMount\' -l -m G:
    Mount point: G:
    Image file:
    \??\C:\Users\xxxxx.xxxx\Documents\Virtual Machines\TEW137\TEW137_System.vmdk
    Image file offset: 63866667008 bytes
    Size: 555745280 bytes (530 MB), ReadOnly, File Type Virtual Disk, HDD.

    Below is the Windows Error Report (WER) log from the app crash:

    Stopped working
    ‎1/‎9/‎2023 5:58 PM
    Report sent
    Faulting Application Path: C:\Program Files\OSFMount\
    Problem signature
    Problem Event Name: APPCRASH
    Application Name:
    Application Version:
    Application Timestamp: 629e44f3
    Fault Module Name:
    Fault Module Version:
    Fault Module Timestamp: 629e44f3
    Exception Code: c000001d
    Exception Offset: 000000000003a985
    OS Version: 10.0.19045.
    Locale ID: 1033
    Additional Information 1: 3e47
    Additional Information 2: 3e475b4949b1225cdec91f4166870ced
    Additional Information 3: bfd9
    Additional Information 4: bfd9e6fa8c1cdf2772e30722430d26fb
    Extra information about the problem
    Bucket ID: b16ec0928624f194ab1d3945ef48d957 (1953780785878718807)​
    Please let me know if ProcMon logs, userdump of the process crashing, MSInfo32, or any other data would be useful.

    This only happens on one of the four test machines I'm using, but it also happens to be the only physical device (the other three are VMs).

    OSFMount 3.1.1001.0 on Windows 10 22H2 x64 Enterprise (en-US)

  • #2
    Yes, if you can EMail us the crash dump, that might help.

    Any chance of getting the TEW137_System.vmdk file?


    • #3
      Thanks for the crash dump.

      It crashed with an illegal instruction (Exception Code: c000001d).

      The illegal instruction in question was this innocent looking instruction
      popcnt  rbx,rax
      This instruction has an interesting history. And it seems it was only (re?)introduced into x86 land with the SSE4.2 collection of instructions.

      It looks like you are trying to run OSFMount on a rather old Intel E8400 CPU from the year 2008. I am suspecting that this old CPU doesn't support this instruction set & instead crashes.

      Now we could rewrite / recompile OSFMount to make it work. But it might be easier to just update the system requirements to state that SSE4.2 is required (i.e. anything newer that around 2010).


      • #4
        Updating pre-reqs is very doable. I often repurpose old hardware for testing and clearly this "savings" has its own challenges.

        Thanks for the quick response and detail!