drivers/filesystems/fs_rec/fat.c

   1 /*
   2  * COPYRIGHT:        See COPYING in the top level directory
   3  * PROJECT:          ReactOS File System Recognizer
   4  * FILE:             drivers/filesystems/fs_rec/fat.c
   5  * PURPOSE:          FAT Recognizer
   6  * PROGRAMMER:       Alex Ionescu (alex.ionescu@reactos.org)
   7  *                   Eric Kohl
   8  */
   9
  10 /* INCLUDES *****************************************************************/
  11
  12 #include "fs_rec.h"
  13 #define NDEBUG
  14 #include <debug.h>
  15
  16 /* FUNCTIONS ****************************************************************/
  17
  18 BOOLEAN
  19 NTAPI
  20 FsRecIsFatVolume(IN PPACKED_BOOT_SECTOR PackedBootSector)
  21 {
  22     BIOS_PARAMETER_BLOCK Bpb;
  23     BOOLEAN Result = TRUE;
  24     PAGED_CODE();
  25
  26     RtlZeroMemory(&Bpb, sizeof(BIOS_PARAMETER_BLOCK));
  27
  28     /* Unpack the BPB and do a small fix up */
  29     FatUnpackBios(&Bpb, &PackedBootSector->PackedBpb);
  30     if (Bpb.Sectors) Bpb.LargeSectors = 0;
  31
  32     /* Recognize jump */
  33     if ((PackedBootSector->Jump[0] != 0x49) &&
  34         (PackedBootSector->Jump[0] != 0xE9) &&
  35         (PackedBootSector->Jump[0] != 0xEB))
  36     {
  37         /* Fail */
  38         Result = FALSE;
  39     }
  40     else if ((Bpb.BytesPerSector != 128) &&
  41              (Bpb.BytesPerSector != 256) &&
  42              (Bpb.BytesPerSector != 512) &&
  43              (Bpb.BytesPerSector != 1024) &&
  44              (Bpb.BytesPerSector != 2048) &&
  45              (Bpb.BytesPerSector != 4096))
  46     {
  47         /* Fail */
  48         Result = FALSE;
  49     }
  50     else if ((Bpb.SectorsPerCluster != 1) &&
  51              (Bpb.SectorsPerCluster != 2) &&
  52              (Bpb.SectorsPerCluster != 4) &&
  53              (Bpb.SectorsPerCluster != 8) &&
  54              (Bpb.SectorsPerCluster != 16) &&
  55              (Bpb.SectorsPerCluster != 32) &&
  56              (Bpb.SectorsPerCluster != 64) &&
  57              (Bpb.SectorsPerCluster != 128))
  58     {
  59         /* Fail */
  60         Result = FALSE;
  61     }
  62     else if (!Bpb.ReservedSectors)
  63     {
  64         /* Fail */
  65         Result = FALSE;
  66     }
  67     else if (!(Bpb.Sectors) && !(Bpb.LargeSectors))
  68     {
  69         /* Fail */
  70         Result = FALSE;
  71     }
  72     else if ((Bpb.Media != 0x00) &&
  73              (Bpb.Media != 0x01) &&
  74              (Bpb.Media != 0xf0) &&
  75              (Bpb.Media != 0xf8) &&
  76              (Bpb.Media != 0xf9) &&
  77              (Bpb.Media != 0xfa) &&
  78              (Bpb.Media != 0xfb) &&
  79              (Bpb.Media != 0xfc) &&
  80              (Bpb.Media != 0xfd) &&
  81              (Bpb.Media != 0xfe) &&
  82              (Bpb.Media != 0xff))
  83     {
  84         /* Fail */
  85         Result = FALSE;
  86     }
  87     else if ((Bpb.SectorsPerFat) && !(Bpb.RootEntries))
  88     {
  89         /* Fail */
  90         Result = FALSE;
  91     }
  92
  93     /* Return the result */
  94     return Result;
  95 }
  96
  97 NTSTATUS
  98 NTAPI
  99 FsRecVfatFsControl(IN PDEVICE_OBJECT DeviceObject,
 100                    IN PIRP Irp)
 101 {
 102     PIO_STACK_LOCATION Stack;
 103     NTSTATUS Status;
 104     PDEVICE_OBJECT MountDevice;
 105     PPACKED_BOOT_SECTOR Bpb = NULL;
 106     ULONG SectorSize;
 107     LARGE_INTEGER Offset = {{0, 0}};
 108     BOOLEAN DeviceError = FALSE;
 109     PAGED_CODE();
 110
 111     /* Get the I/O Stack and check the function type */
 112     Stack = IoGetCurrentIrpStackLocation(Irp);
 113     switch (Stack->MinorFunction)
 114     {
 115         case IRP_MN_MOUNT_VOLUME:
 116
 117             /* Assume failure */
 118             Status = STATUS_UNRECOGNIZED_VOLUME;
 119
 120             /* Get the device object and request the sector size */
 121             MountDevice = Stack->Parameters.MountVolume.DeviceObject;
 122             if (FsRecGetDeviceSectorSize(MountDevice, &SectorSize))
 123             {
 124                 /* Try to read the BPB */
 125                 if (FsRecReadBlock(MountDevice,
 126                                    &Offset,
 127                                    512,
 128                                    SectorSize,
 129                                    (PVOID)&Bpb,
 130                                    &DeviceError))
 131                 {
 132                     /* Check if it's an actual FAT volume */
 133                     if (FsRecIsFatVolume(Bpb))
 134                     {
 135                         /* It is! */
 136                         Status = STATUS_FS_DRIVER_REQUIRED;
 137                     }
 138                 }
 139
 140                 /* Free the boot sector if we have one */
 141                 ExFreePool(Bpb);
 142             }
 143             else
 144             {
 145                 /* We have some sort of failure in the storage stack */
 146                 DeviceError = TRUE;
 147             }
 148
 149             /* Check if we have an error on the stack */
 150             if (DeviceError)
 151             {
 152                 /* Was this because of a floppy? */
 153                 if (MountDevice->Characteristics & FILE_FLOPPY_DISKETTE)
 154                 {
 155                     /* Let the FS try anyway */
 156                     Status = STATUS_FS_DRIVER_REQUIRED;
 157                 }
 158             }
 159
 160             break;
 161
 162         case IRP_MN_LOAD_FILE_SYSTEM:
 163
 164             /* Load the file system */
 165             Status = FsRecLoadFileSystem(DeviceObject,
 166                                          L"\\Registry\\Machine\\System\\CurrentControlSet\\Services\\fastfat");
 167             break;
 168
 169         default:
 170
 171             /* Invalid request */
 172             Status = STATUS_INVALID_DEVICE_REQUEST;
 173     }
 174
 175     /* Return Status */
 176     return Status;
 177 }
 178
 179 /* EOF */