Re: [ros-dev] About GDIOBJHDR header changes

[James Tabor]

Hi!
>  From my teams research they say this is still valid for
> xp. If the 
alignment is not correct? It would fubar the rest of the structure
that has be verified as correct for XP. eg DCOBJ.

 typedef struct _BASEOBJECT
{
    HANDLE     hHmgr;              // 0x0 <- xp
    PVOID      pEntry;                 // 0x4 <- No longer a pointer.
    LONG       cExclusiveLock; // 0x8 <- xp
    PW32THREAD Tid;               // 0xc <- xp
} BASEOBJECT, *POBJ;

On Dec 30, 2007 7:52 AM, Alex Ionescu &lt;ionucu(a)videotron.ca&gt; wrote:
>   Let's begin with the GDI Base Object, which is a
> header at the top of every
>  GDI Object. The structure is called _BASEOBJECT (what you refer to as
>  "GDIOBJHDR") and is defined as follows:
>
>  struct _BASEOBJECT
>  {
>      HANDLE hHmgr;
>      ULONG ulShareCount;
>      LONG cExclusiveLock;
>      ULONG BaseFlags;
>      PW32THREAD Tid;
>  };
>
>  The pointer to a _BASEOBJECT is known as a POBJ.
>
>  Now, how to get to this object? Well, dxg and win32k.sys now both implement
>  different Hmhr's (Handle Managers).
>
>  In Win32K land, the handles come from gpentHmgr, and each handle is indexed
>  from it. The resulting structure is called an _ENTRY, and is defined as
>  follows:
>
>  struct _ENTRY
>  {
>      union
>      {
>          POBJ pobj;
>          HANDLE hFree;
>      };
>      union
>      {
>           ULONG ulObj;
>           struct
>           {
>                  USHORT Count:15;
>                  USHORT Lock:1;
>                  HANDLE Pid;
>           };
>      } ObjectOwner;
>      USHORT FullUnique;
>      UCHAR Objt;
>      UCHAR Flags;
>      PVOID pUser;
>  };
>
>  DXG uses a DDENTRY structure, which is similar. Handles are indexed from
>  gpentDdHmgr.
>  
This is correct too. xteam confirms it. I commit an update to our
entry based on their research . Count and lock merged into Count.
FullUnique and Objt are correct.

>   What Greatlord hadn't noticed while reversing is
> that part of the code was
>  dealing with the DD_ENTRY object, and part of it was dereferencing the first
>  member of DD_ENTRY, which is the pObj (and was now dealing with the
>  _BASEOBJECT).
>
>  Objt is where the object type is defined -- you already seem to know the
>  Win32K Objects. Here are the DXG objects:
>
>  DD_MOTIONCOMP_TYPE
>  DD_VIDEOPORT_TYPE
>  D3D_HANDLE_TYPE
>  DD_SURFACE_TYPE
>  DD_DIRECTDRAW_TYPE
>  DD_DEF_TYPE.
>
>  So how exactly then does DdHmgrLock work? Quite similarly to HmgrLock:
>
>
>  POBJ
>  FASTCALL
>  DdHmgLock(HDD_OBJ DdHandle,
>            UCHAR ObjectType,
>            BOOLEAN LockOwned)
>  {
>      POBJ Object = NULL;
>      PDD_ENTRY Entry;
>      ULONG Index;
>
>      //
>      // Acquire the DirectX Handle Manager Lock
>      //
>      if (!LockOwned) DdHmgAcquireHmgrSemaphore();
>
>      //
>      // Get the handle index and validate it
>      //
>      Index = DdHandle & 0x1FFFFF;
>      if (Index < gcMaxDdHmgr)
>      {
>          //
>          // Get the entry
>          //
>          Entry = gpentDdHmgr[Index];
>
>          //
>          // Validate the owner
>          //
>          if ((Entry->ObjectOwner.Pid = PsGetCurrentProcessId() & 0xFFFFFFFC)
>  ||
>              !(Entry->ObjectOwner.Pid))
>          {
>              //
>              // Validate the object type
>              //
>              if (Entry->Objt == ObjectType)
>              {
>                  //
>                  // Validate the handle type
>                  //
>                  if (Entry->FullUnique == ((DdHandle >> 21) & 0x7FF))
>                  {
>                      //
>                      // Get the GDI Object
>                      //
>                      Object = DdEntry->pObj;
>
>                      //
>                      // Make sure we can lock it
>                      //
>                      if (!(Object->cExclusiveLock) ||
>                          (Object->Tid == (PW32THREAD)PsGetCurrentThread()))
>                      {
>                          //
>                          // Acquire the lock
>                          //
>                          InterlockedIncrement(&Object->cExclusiveLock);
>                          Object->Tid = (PW32THREAD)PsGetCurrentThread();
>                      }
>                      else
>                      {
>                          //
>                          // Already locked by someone else
>                          //
>                          Object = NULL;
>                      }
>                  }
>              }
>          }
>      }
>
>      //
>      // Release the lock
>      //
>      if (!LockOwned) DdHmgReleaseHmgrSemaphore();
>
>      //
>      // Return the object
>      //
>      return Object;
>  }
>
>
>  I am looking forward to compatible Hmgr implementation in win32k!
>  
Me too! One of our most needed things todo! 8^) HmgLock anyone?

>   Any questions?
>
>
>
>
>  Best regards,
>  Alex Ionescu
>