How is the bthkd extension library used under WinDbg?

Toni Nguyen

New member

Aug 23, 2022

I am trying to use the !bthtree command to dump the complete Bluetooth device tree as specified from the !bthhelp command.
WinDbg is running and is attached to a svchost.exe process that imports several Bluetooth DLLs:

- svchost.exe (1808) | DLL | C:\Windows\System32\bthserv.dll
- svchost.exe (1808) | DLL | C:\Windows\System32\BthTelemetry.dll
- svchost.exe (1808) | DLL | C:\Windows\System32\Microsoft.Bluetooth.Service.dll
- svchost.exe (1808) | DLL | C:\Windows\System32\Microsoft.Bluetooth.Proxy.dll
- svchost.exe (1808) | DLL | C:\Windows\System32\Windows.Internal.Devices.Bluetooth.dll

Using the !bthkd.bthtree command results in the following message:

Controller:
Failed to read list of device objects.
BTHENUM:
Error: Unable to read BTHENUM!BthEnumGlobals
Unable to find driver object
RFCOMM:
00000000: Unable to get value of ObpRootDirectoryObject
Error: Unable to read rfcomm!g_DriverObject
ENUMERATED DEVICES:
Error: Unable to read BTHENUM!BthEnumGlobals
Unable to find driver object

Sadly other [/ICODE]!bthkd[/ICODE] commands (such as !hcicmd, !bthenuminfo) also fail in a similar manner. WinDbg is debugging the target process locally.
Unfortunately, the documentation (https://docs.microsoft.com/en-us/windows-hardware/drivers/debugger/bluetooh-extensions--bthkd-dll-) does not really provide much additional information on how to use the bthkd extension.

Does anyone have experience in using extension libraries for WinDbg? I would greatly appreciate any input on that topic.