WinDbg - Semaphores, Mutexes and Timers

In this episode of Defrag Tools, Andrew Richards, Chad Beeder and Larry Larsen continue looking at the Debugging Tools for Windows (in particular WinDbg). WinDbg is a debugger that supports user mode debugging of a process, or kernel mode debugging of a computer.

This installment goes over the commands used to diagnose Semaphores, Mutexes and (Waitable) Timers in a user mode application. For timers, we delve deep in to the kernel to gather more information about them. We use these commands:

!handle

!handle <handle> <mask>

!object <name>

!object <addr>

!timer

!timer <addr>

ub @rip

dt nt!_KTHREAD <addr>

Make sure you watch Defrag Tools Episode #1 and Defrag Tools Episode #23 for instructions on how to get the Debugging Tools for Windows and how to set the required environment variables for symbol and source code resolution.