[NTOSKRNL] Implement support for device maps in ObpLookupObjectName

This allows getting rid of the ?? hack in the kernel but this doesn't
allow enabling LUID device maps as ReactOS can no longer open a
session with them enabled. So, we must remain with device maps at
root

CORE-16114

ntoskrnl/include/internal/ob.h

@@ -443,6 +443,12 @@ ObIsLUIDDeviceMapsEnabled(
     VOID
 );
 
+PDEVICE_MAP
+NTAPI
+ObpReferenceDeviceMap(
+    VOID
+);
+
 //
 // Security descriptor cache functions
 //

ntoskrnl/ob/obname.c

@@ -214,26 +214,6 @@ ObpCreateDosDevicesDirectory(VOID)
     if (!NT_SUCCESS(Status))
         goto done;
 
-    /*********************************************\
-    |*** HACK until we support device mappings ***|
-    |*** Add a symlink \??\ <--> \GLOBAL??\    ***|
-    \*********************************************/
-    RtlInitUnicodeString(&LinkName, L"\\??");
-    InitializeObjectAttributes(&ObjectAttributes,
-                               &LinkName,
-                               OBJ_PERMANENT,
-                               NULL,
-                               &DosDevicesSD);
-    Status = NtCreateSymbolicLinkObject(&SymHandle,
-                                        SYMBOLIC_LINK_ALL_ACCESS,
-                                        &ObjectAttributes,
-                                        &RootName);
-    if (NT_SUCCESS(Status)) NtClose(SymHandle);
-    /*********************************************\
-    \*********************************************/
-
-    // FIXME: Create a device mapping for the global \?? directory
-
     /*
      * Initialize the \??\GLOBALROOT symbolic link
      * pointing to the root directory \ .
@@ -490,6 +470,8 @@ ObpLookupObjectName(IN HANDLE RootHandle OPTIONAL,
     PWCHAR NewName;
     POBJECT_HEADER_NAME_INFO ObjectNameInfo;
     ULONG MaxReparse = 30;
+    PDEVICE_MAP DeviceMap = NULL;
+    UNICODE_STRING LocalName;
     PAGED_CODE();
     OBTRACE(OB_NAMESPACE_DEBUG,
             "%s - Finding Object: %wZ. Expecting: %p\n",
@@ -642,6 +624,8 @@ ObpLookupObjectName(IN HANDLE RootHandle OPTIONAL,
             *FoundObject = Object;
             return Status;
         }
+
+        LocalName = *ObjectName;
     }
     else
     {
@@ -695,7 +679,14 @@ ObpLookupObjectName(IN HANDLE RootHandle OPTIONAL,
         else
         {
 ParseFromRoot:
-            /* FIXME: Check if we have a device map */
+            LocalName = *ObjectName;
+
+            /* Deference the device map if we already have one */
+            if (DeviceMap != NULL)
+            {
+                ObfDereferenceDeviceMap(DeviceMap);
+                DeviceMap = NULL;
+            }
 
             /* Check if this is a possible DOS name */
             if (!((ULONG_PTR)(ObjectName->Buffer) & 7))
@@ -713,7 +704,17 @@ ParseFromRoot:
                     (*(PULONGLONG)(ObjectName->Buffer) ==
                      ObpDosDevicesShortNamePrefix.Alignment.QuadPart))
                 {
-                    /* FIXME! */
+                    DeviceMap = ObpReferenceDeviceMap();
+                    /* We have a local mapping, drop the ?? prefix */
+                    if (DeviceMap != NULL && DeviceMap->DosDevicesDirectory != NULL)
+                    {
+                        LocalName.Length -= ObpDosDevicesShortName.Length;
+                        LocalName.MaximumLength -= ObpDosDevicesShortName.Length;
+                        LocalName.Buffer += (ObpDosDevicesShortName.Length / sizeof(WCHAR));
+
+                        /* We'll browse that local directory */
+                        Directory = DeviceMap->DosDevicesDirectory;
+                    }
                 }
                 else if ((ObjectName->Length == ObpDosDevicesShortName.Length -
                                                 sizeof(WCHAR)) &&
@@ -722,7 +723,23 @@ ParseFromRoot:
                          (*((PWCHAR)(ObjectName->Buffer) + 2) ==
                           (WCHAR)(ObpDosDevicesShortNameRoot.Alignment.HighPart)))
                 {
-                    /* FIXME! */
+                    DeviceMap = ObpReferenceDeviceMap();
+
+                    /* Caller is looking for the directory itself */
+                    if (DeviceMap != NULL && DeviceMap->DosDevicesDirectory != NULL)
+                    {
+                        Status = ObReferenceObjectByPointer(DeviceMap->DosDevicesDirectory,
+                                                            0,
+                                                            ObjectType,
+                                                            AccessMode);
+                        if (NT_SUCCESS(Status))
+                        {
+                            *FoundObject = DeviceMap->DosDevicesDirectory;
+                        }
+
+                        ObfDereferenceDeviceMap(DeviceMap);
+                        return Status;
+                    }
                 }
             }
         }
@@ -740,7 +757,7 @@ ParseFromRoot:
     while (Reparse && MaxReparse)
     {
         /* Get the name */
-        RemainingName = *ObjectName;
+        RemainingName = LocalName;
 
         /* Disable reparsing again */
         Reparse = FALSE;
@@ -1149,7 +1166,7 @@ ReparseObject:
     }
 
     /* Check if we have a device map and dereference it if so */
-    //if (DeviceMap) ObfDereferenceDeviceMap(DeviceMap);
+    if (DeviceMap) ObfDereferenceDeviceMap(DeviceMap);
 
     /* Check if we have a referenced directory and dereference it if so */
     if (ReferencedDirectory) ObDereferenceObject(ReferencedDirectory);