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