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windows-nt/Source/XPSP1/NT/base/fsrec/fat_rec.c

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/*++
Copyright (c) 1992 Microsoft Corporation
Module Name:
fat_rec.c
Abstract:
This module contains the mini-file system recognizer for FAT.
Author:
Darryl E. Havens (darrylh) 8-dec-1992
Environment:
Kernel mode, local to I/O system
Revision History:
--*/
#include "fs_rec.h"
#include "fat_rec.h"
//
// The local debug trace level
//
#define Dbg (FSREC_DEBUG_LEVEL_FAT)
#ifdef ALLOC_PRAGMA
#pragma alloc_text(PAGE,FatRecFsControl)
#pragma alloc_text(PAGE,IsFatVolume)
#pragma alloc_text(PAGE,UnpackBiosParameterBlock)
#endif // ALLOC_PRAGMA
NTSTATUS
FatRecFsControl(
IN PDEVICE_OBJECT DeviceObject,
IN PIRP Irp
)
/*++
Routine Description:
This function performs the mount and driver reload functions for this mini-
file system recognizer driver.
Arguments:
DeviceObject - Pointer to this driver's device object.
Irp - Pointer to the I/O Request Packet (IRP) representing the function to
be performed.
Return Value:
The function value is the final status of the operation.
--*/
{
NTSTATUS status;
PIO_STACK_LOCATION irpSp;
PDEVICE_EXTENSION deviceExtension;
PDEVICE_OBJECT targetDevice;
PPACKED_BOOT_SECTOR buffer;
LARGE_INTEGER byteOffset;
UNICODE_STRING driverName;
ULONG bytesPerSector;
BOOLEAN isDeviceFailure = FALSE;
PAGED_CODE();
//
// Begin by determining what function that is to be performed.
//
deviceExtension = (PDEVICE_EXTENSION) DeviceObject->DeviceExtension;
irpSp = IoGetCurrentIrpStackLocation( Irp );
switch ( irpSp->MinorFunction ) {
case IRP_MN_MOUNT_VOLUME:
//
// Attempt to mount a volume: Determine whether or not the volume in
// question is a FAT volume and, if so, let the I/O system know that it
// is by returning a special status code so that this driver can get
// called back to load the FAT file system.
//
status = STATUS_UNRECOGNIZED_VOLUME;
//
// Attempt to determine whether or not the target volume being mounted
// is a FAT volume. Note that if an error occurs, and this is a floppy
// drive, and the error occurred on the actual read from the device,
// then the FAT file system will actually be loaded to handle the
// problem since this driver is a place holder and does not need to
// know all of the protocols for handling floppy errors.
//
targetDevice = irpSp->Parameters.MountVolume.DeviceObject;
//
// First retrieve the sector size for this media.
//
if (FsRecGetDeviceSectorSize( targetDevice,
&bytesPerSector )) {
byteOffset.QuadPart = 0;
buffer = NULL;
if (FsRecReadBlock( targetDevice,
&byteOffset,
512,
bytesPerSector,
&buffer,
&isDeviceFailure ) &&
IsFatVolume( buffer )) {
status = STATUS_FS_DRIVER_REQUIRED;
}
if (buffer != NULL) {
ExFreePool( buffer );
}
} else {
//
// Devices that can't get us this much ...
//
isDeviceFailure = TRUE;
}
//
// See if we should make the real filesystem take a shot at a wacky floppy.
//
if (isDeviceFailure) {
if (targetDevice->Characteristics & FILE_FLOPPY_DISKETTE) {
status = STATUS_FS_DRIVER_REQUIRED;
}
}
break;
case IRP_MN_LOAD_FILE_SYSTEM:
status = FsRecLoadFileSystem( DeviceObject,
L"\\Registry\\Machine\\System\\CurrentControlSet\\Services\\Fastfat" );
break;
default:
status = STATUS_INVALID_DEVICE_REQUEST;
}
//
// Finally, complete the request and return the same status code to the
// caller.
//
Irp->IoStatus.Status = status;
IoCompleteRequest( Irp, IO_NO_INCREMENT );
return status;
}
BOOLEAN
IsFatVolume(
IN PPACKED_BOOT_SECTOR Buffer
)
/*++
Routine Description:
This routine looks at the buffer passed in which contains the FAT boot
sector and determines whether or not it represents an actual FAT boot
sector.
Arguments:
Buffer - Pointer to buffer containing potential boot block.
Return Value:
The function returns TRUE if the buffer contains a recognizable FAT boot
sector, otherwise it returns FALSE.
--*/
{
BIOS_PARAMETER_BLOCK bios;
BOOLEAN result;
PAGED_CODE();
//
// Begin by unpacking the Bios Parameter Block that is packed in the boot
// sector so that it can be examined without incurring alignment faults.
//
UnpackBiosParameterBlock( &Buffer->PackedBpb, &bios );
//
// Assume that the sector represents a FAT boot block and then determine
// whether or not it really does.
//
result = TRUE;
if (bios.Sectors) {
bios.LargeSectors = 0;
}
// FMR Jul.11.1994 NaokiM - Fujitsu -
// FMR boot sector has 'IPL1' string at the beginnig.
if (Buffer->Jump[0] != 0x49 && /* FMR */
Buffer->Jump[0] != 0xe9 &&
Buffer->Jump[0] != 0xeb) {
result = FALSE;
// FMR Jul.11.1994 NaokiM - Fujitsu -
// Sector size of FMR partition is 2048.
} else if (bios.BytesPerSector != 128 &&
bios.BytesPerSector != 256 &&
bios.BytesPerSector != 512 &&
bios.BytesPerSector != 1024 &&
bios.BytesPerSector != 2048 && /* FMR */
bios.BytesPerSector != 4096) {
result = FALSE;
} else if (bios.SectorsPerCluster != 1 &&
bios.SectorsPerCluster != 2 &&
bios.SectorsPerCluster != 4 &&
bios.SectorsPerCluster != 8 &&
bios.SectorsPerCluster != 16 &&
bios.SectorsPerCluster != 32 &&
bios.SectorsPerCluster != 64 &&
bios.SectorsPerCluster != 128) {
result = FALSE;
} else if (!bios.ReservedSectors) {
result = FALSE;
} else if (!bios.Fats) {
result = FALSE;
//
// Prior to DOS 3.2 might contains value in both of Sectors and
// Sectors Large.
//
} else if (!bios.Sectors && !bios.LargeSectors) {
result = FALSE;
// FMR Jul.11.1994 NaokiM - Fujitsu -
// 1. Media descriptor of FMR partitions is 0xfa.
// 2. Media descriptor of partitions formated by FMR OS/2 is 0x00.
// 3. Media descriptor of floppy disks formated by FMR DOS is 0x01.
} else if (bios.Media != 0x00 && /* FMR */
bios.Media != 0x01 && /* FMR */
bios.Media != 0xf0 &&
bios.Media != 0xf8 &&
bios.Media != 0xf9 &&
bios.Media != 0xfa && /* FMR */
bios.Media != 0xfb &&
bios.Media != 0xfc &&
bios.Media != 0xfd &&
bios.Media != 0xfe &&
bios.Media != 0xff) {
result = FALSE;
} else if (bios.SectorsPerFat != 0 && bios.RootEntries == 0) {
result = FALSE;
}
return result;
}
VOID
UnpackBiosParameterBlock(
IN PPACKED_BIOS_PARAMETER_BLOCK Bios,
OUT PBIOS_PARAMETER_BLOCK UnpackedBios
)
/*++
Routine Description:
This routine copies a packed Bios Parameter Block to an unpacked Bios
Parameter Block.
Arguments:
Bios - Pointer to the packed Bios Parameter Block.
UnpackedBios - Pointer to the unpacked Bios Parameter Block.
Return Value:
None.
--*/
{
PAGED_CODE();
//
// Unpack the Bios Parameter Block.
//
CopyUchar2( &UnpackedBios->BytesPerSector, &Bios->BytesPerSector[0] );
CopyUchar2( &UnpackedBios->BytesPerSector, &Bios->BytesPerSector[0] );
CopyUchar1( &UnpackedBios->SectorsPerCluster, &Bios->SectorsPerCluster[0] );
CopyUchar2( &UnpackedBios->ReservedSectors, &Bios->ReservedSectors[0] );
CopyUchar1( &UnpackedBios->Fats, &Bios->Fats[0] );
CopyUchar2( &UnpackedBios->RootEntries, &Bios->RootEntries[0] );
CopyUchar2( &UnpackedBios->Sectors, &Bios->Sectors[0] );
CopyUchar1( &UnpackedBios->Media, &Bios->Media[0] );
CopyUchar2( &UnpackedBios->SectorsPerFat, &Bios->SectorsPerFat[0] );
CopyUchar2( &UnpackedBios->SectorsPerTrack, &Bios->SectorsPerTrack[0] );
CopyUchar2( &UnpackedBios->Heads, &Bios->Heads[0] );
CopyUchar4( &UnpackedBios->HiddenSectors, &Bios->HiddenSectors[0] );
CopyUchar4( &UnpackedBios->LargeSectors, &Bios->LargeSectors[0] );
}
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