Print Screen/Sys Rq Button

WINDBG
1

I discovered yesterday that while remote debugging (WindBg) the kernel the Print Screen/System request key on my target will “crash” my code; that is stop at a break point in my driver code to detect a failure.

I believe that the System Request is designed to do this.

However when I try to run the target machine without the debugger Sys Rq will still “crash” my code (I the code stops after TraceView shows the tracing errors in that the DPC is not receiving IO requests to terminate).

Adding a value named BreakOnSysRq, and set it equal to DWORD 0x0 in

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\i8042prt\Parameters

And rebooting has no effect.

I tried pressing Sys Rq on other machines running our code and the code continues to run with no TraceView errors i.e. the DPC is receiving IO requests in a timely fashion.

So my question is does kernel debugging in WindBg leave the target with the SysRq key in a state that causes it to try to interrupt the kernel even after the kernel, on the target, is up and running without WindBg?

We are using Windows 10 IoT Enterprise build 1809.

2

I guess I just proved this to be the case by performing the same actions on a second development machine.

Is there any way to get Print Screen/Sys Rq key to act only as a print screen key after using kernel debugger?

3

To be fair I uninstalled then reinstalled the drivers and the problem seems to have gone away.