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obtrace and DEVICE_OBJECT

Aleh_KazakevichAleh_Kazakevich Member Posts: 86

Is it possible to use the 'Object Reference Tracing' (!obtrace) for a DEVICE_OBJECT?
I tried several times with different 'gflags' settings, but with no success.

When I set a process name filter (gflags /i) the tracing is working for Key,
File and some other object types, but not for DEVICE_OBJECT:

kd> !obtrace address
Unable to find object in table.

The address of a device object is 100% valid (this can be verified,
for example, by the '!devobj' and '!devstack' commands).

It seems that a 'gflags /i' filter does not apply for the objects created
in the system process context, like a driver objects or a device objects.

When I set a tag names (gflags /t + Dflt, tlfD or any other custom tag)
the tracing does not working at all and I see the message again: "Unable to
find object in table".

Some additional information:

- Windows 7, Windows 8.1 (both x64);

- gflags settings (!gflag):

Current NtGlobalFlag contents: 0x01007400
ptg - Enable pool tagging
ust - Create user mode stack trace database
kst - Create kernel mode stack trace database
otl - Maintain a list of objects for each type
eot - Enable object handle type tagging

- "C:\Program Files\Windows Kits\8.1\Debuggers\x64\gflags.exe" /ro

Boot Registry Settings :
Object Ref Tracing Enabled
Permanent Traces
Pool Tags: Dflt;tlfD;ABCD;DCBA
Process Name: All Processes
(and system was rebooted).




  • Scott_Noone_(OSR)Scott_Noone_(OSR) Administrator Posts: 3,473
    I just ran a quick test on Win7 x86 Checked and it worked fine. I don't
    *think* it's a checked build only thing, but I don't have a Win7 Free
    already installed to play with at the moment.

    Steps were:

    1. Copy gflags.exe and gflagsui.dll to the target machine

    2. Under Object Reference Tracing tick the Enable box

    3. In Pool Tags put: Devi

    4. Click OK, reboot

    kd> !obtrace 8d359830
    Object: 8d359830
    Image: System
    Sequence (+/-) Tag Stack
    -------- ----- ---- ---------------------------------------------------
    41d7 +1 Dflt nt!ObCreateObject+1ab



  • Aleh_KazakevichAleh_Kazakevich Member Posts: 86
    Excellent! It's working!

    My mistake was that I specified invalid tag value ('Dflt', for example).
    Thanks, Scott.
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