windbg does not show dbgprint messages

Question

Hi all,

I'm running windbg local kernel debugging. Basically I need to check some DbgPrint messages.

My OS: WIndows server 2019 version 1809

Windbg version: 6.9.0003.113 AMD64

I've run below 2 commands to enable local debug

bcdedit /debug on
bcdedit /dbgsettings local

and Enabled Kd_xxx_Mask as,

lkd> dd nt!Kd_NDIS_Mask L1
fffff80622ada4f8 ffffffff lkd> dd nt!Kd_DEFAULT_Mask L1 fffff80622ada544 ffffffff

Then I ran "!dbgprint". I suppose when I load one net driver, I can see a lot of messages from OS kernel.

but in fact I saw some strange characters.

lkd> !dbgprint
õ/X=(@

Can someone help here to let me know any steps I did wrong?

Answer 1

Hi,
You may have to do below settings in registry to enable the debug prints.

Open up the registry.
Go to path, “HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Debug Print Filter”. If "Debug Print Filter" is not present then create it.
Add value “DEFAULT” : REG_DWORD : 0xFFFFFFFF and then reboot.

after windbg attachment, you could restart, without turning off debugger.
https://learn.microsoft.com/en-us/windows-hardware/drivers/debugger/reading-and-filtering-debugging-messages
Hope this helps and please help to accept as Answer if the response is useful.
Best Regards,
Carl

Answer 2

Hi Carl,

I already have that keys created in Registry and verified that by,
lkd> dd nt!Kd_DEFAULT_Mask L1

I meant the value of nt!Kd_DEFAULT_Mask follows the value I set in the registry.
But still I can't see Dbgprint messages from Windebg.

Note: I'm using windbg local debug, not debugging a remote server.

Thanks.