Checking an Event's Signaled State in KM w/ WinDBG

I've talked about debugging events in the past in UM in simple terms.  !handle works great, and although is use is slightly different in UM vs KM it provides a lot of good information, but lets say you are in KD and want to know if your event is signaled or not.  !handle will not tell you that.  This is how you do it.  Note: you need to have a KD to look at the kernel's objects.

1. Find the index of handle


1: kd> dt g_hMyEvent
my_bin!g_hMyEvent
0x00001218
Void

2. Use !handle to get the address of the event object.

1: kd> !handle 0x00001218 f -1 Event

Searching for handles of type Event

PROCESS 845f4b40  SessionId: 0  Cid: 040c    Peb: 7fbb4000  ParentCid: 023c
    DirBase: 7ffea200  ObjectTable: a194d280  HandleCount: 1071.
    Image: svchost.exe

Handle table at a194d280 with 1071 entries in use

1218: Object: aa934288  GrantedAccess: 001f0003 Entry: bb591430
Object: aa934288  Type: (845692b8) Event
    ObjectHeader: aa934270 (new version)
        HandleCount: 1  PointerCount: 62

3. Cast that pointer to the dispatch header it is

1: kd> ?? (PDISPATCHER_HEADER)0xaa934288

PDISPATCHER_HEADER 0xaa934288

   +0x000 Type             : 0 ''

   +0x001 TimerControlFlags : 0 ''

   +0x001 Absolute         : 0y0

   +0x001 Wake             : 0y0

   +0x001 EncodedTolerableDelay : 0y000000 (0)

   +0x001 Abandoned        : 0 ''

   +0x001 Signalling       : 0 ''

   +0x002 ThreadControlFlags : 0x4 ''

   +0x002 CycleProfiling   : 0y0

   +0x002 CounterProfiling : 0y0

   +0x002 GroupScheduling  : 0y1

   +0x002 AffinitySet      : 0y0

   +0x002 Reserved         : 0y0000

   +0x002 Hand             : 0x4 ''

   +0x002 Size             : 0x4 ''

   +0x003 TimerMiscFlags   : 0 ''

   +0x003 Index            : 0y0

   +0x003 Processor        : 0y00000 (0)

   +0x003 Inserted         : 0y0

   +0x003 Expired          : 0y0

   +0x003 DebugActive      : 0 ''

   +0x003 DpcActive        : 0 ''

   +0x000 Lock             : 0n262144

   +0x000 LockNV           : 0n262144

   +0x004 SignalState      : 0n1

   +0x008 WaitListHead     : _LIST_ENTRY [ 0xaa934290 - 0xaa934290 ]

There you go, you can see this event is in a signaled state.

By the way, the member Type 0 means event notification.  Other common values:

    EventNotificationObject = 0,
    EventSynchronizationObject = 1,
    MutantObject = 2,
    ProcessObject = 3,
    QueueObject = 4,
    SemaphoreObject = 5,
    ThreadObject = 6,