[UDFS] Change service group to Boot File System

drivers/filesystems/fs_rec/fs_rec.h

@@ -137,6 +137,9 @@ typedef struct BIOS_PARAMETER_BLOCK
     USHORT BackupBootSector;
 } BIOS_PARAMETER_BLOCK, *PBIOS_PARAMETER_BLOCK;
 
+/* UDFS Tag Identifier for Anchor Volume Descriptor Pointer (ECMA-167 7.2) */
+#define UDFS_TAG_ID_AVDP  0x0002
+
 /* UDFS Structures */
 #include <pshpack1.h>
 typedef struct _TAG

drivers/filesystems/fs_rec/udfs.c

@@ -29,7 +29,12 @@ FsRecIsUdfsVolume(IN PDEVICE_OBJECT DeviceObject,
     int i;
     PAGED_CODE();
 
-    Offset.QuadPart = 16 * SectorSize;
+    /* Per ECMA-167 section 8.4.1, the Volume Recognition Sequence starts at
+     * a fixed byte offset of 32768, regardless of the physical sector size.
+     * Using 16 * SectorSize is only correct for 2048-byte sectors (CD-ROM);
+     * for 512-byte sector devices (e.g. VHDs) it gives 8192 instead of 32768,
+     * causing the VRS to be missed entirely. */
+    Offset.QuadPart = UDFS_VRS_START_OFFSET;
     for (i = 0; i < 16; i++)
     {
         if (!FsRecReadBlock(DeviceObject,
@@ -55,6 +60,7 @@ FsRecIsUdfsVolume(IN PDEVICE_OBJECT DeviceObject,
         {
             DPRINT("NSR03 found\n");
             ret = TRUE;
+            break;
         }
 
         if (!strncmp((const char*)VolumeStructDesc->Ident,
@@ -63,6 +69,7 @@ FsRecIsUdfsVolume(IN PDEVICE_OBJECT DeviceObject,
         {
             DPRINT("NSR02 found\n");
             ret = TRUE;
+            break;
         }
 
         if (!strncmp((const char*)VolumeStructDesc->Ident,
@@ -98,6 +105,34 @@ FsRecIsUdfsVolume(IN PDEVICE_OBJECT DeviceObject,
 
     if (VolumeStructDesc)
         ExFreePool(VolumeStructDesc);
+
+    /* If the VRS scan did not find an NSR descriptor, fall back to checking
+     * for the Anchor Volume Descriptor Pointer at sector 256. This covers
+     * disks where the VRS is absent or could not be read, and mirrors the
+     * detection approach used by the UDFS driver itself. */
+    if (!ret)
+    {
+        PAVDP AnchorVDP = NULL;
+
+        Offset.QuadPart = (LONGLONG)UDFS_AVDP_SECTOR * SectorSize;
+        if (FsRecReadBlock(DeviceObject,
+                           &Offset,
+                           sizeof(AVDP),
+                           SectorSize,
+                           (PVOID *)&AnchorVDP,
+                           NULL))
+        {
+            /* Tag identifier 2 = Anchor Volume Descriptor Pointer (ECMA-167 7.2) */
+            if (AnchorVDP->DescriptorTag.Identifier == UDFS_TAG_ID_AVDP &&
+                AnchorVDP->DescriptorTag.Location == UDFS_AVDP_SECTOR)
+            {
+                DPRINT("AVDP found at sector 256\n");
+                ret = TRUE;
+            }
+            ExFreePool(AnchorVDP);
+        }
+    }
+
     return ret;
 }
 

drivers/filesystems/udfs/udfs_reg.inf

@@ -1,7 +1,7 @@
 ; UDF Filesystem driver
 [AddReg]
 HKLM,"SYSTEM\CurrentControlSet\Services\Udfs","ErrorControl",0x00010001,0x00000001
-HKLM,"SYSTEM\CurrentControlSet\Services\Udfs","Group",0x00000000,"File System"
+HKLM,"SYSTEM\CurrentControlSet\Services\Udfs","Group",0x00000000,"Boot File System"
 HKLM,"SYSTEM\CurrentControlSet\Services\Udfs","ImagePath",0x00020000,"system32\drivers\udfs.sys"
-HKLM,"SYSTEM\CurrentControlSet\Services\Udfs","Start",0x00010001,0x00000001
+HKLM,"SYSTEM\CurrentControlSet\Services\Udfs","Start",0x00010001,0x00000003
 HKLM,"SYSTEM\CurrentControlSet\Services\Udfs","Type",0x00010001,0x00000002