Techwiki:Win32k/HEAD

Head structures.

typedef struct _HEAD
{
  HANDLE h;
  DWORD  cLockObj;
} HEAD, *PHEAD;

typedef struct _THROBJHEAD
{
   HEAD;
   PTHREADINFO pti;
} THROBJHEAD, *PTHROBJHEAD;
//
typedef struct _THRDESKHEAD
{
   THROBJHEAD;
   PDESKTOP    rpdesk;
   PVOID       pSelf;   // points to the kernel mode address
} THRDESKHEAD, *PTHRDESKHEAD;

typedef struct _PROCOBJHEAD
{
   HEAD;
   DWORD hTaskWow;
} PROCOBJHEAD, *PPROCOBJHEAD;
//
typedef struct _PROCDESKHEAD
{
   PROCOBJHEAD;
   PDESKTOP    rpdesk;
   PVOID       pSelf;
} PROCDESKHEAD, *PPROCDESKHEAD;

References

• http://chpie.tistory.com/entry/Blocking-Global-message-hook
• http://blog.csdn.net/norsd/archive/2006/08/01/1007583.aspx
• Windows Symbol files, userkdx.dll, !dso, W7U symbols