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491 lines
13 KiB
491 lines
13 KiB
/*++
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Copyright (c) 1992 Microsoft Corporation
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Module Name:
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fat_rec.c
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Abstract:
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This module contains the mini-file system recognizer for FAT.
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Author:
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Darryl E. Havens (darrylh) 8-dec-1992
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Environment:
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Kernel mode, local to I/O system
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Revision History:
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--*/
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#include "fs_rec.h"
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#include "fat_rec.h"
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#ifdef ALLOC_PRAGMA
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#pragma alloc_text(PAGE,FatRecFsControl)
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#pragma alloc_text(PAGE,IsFatVolume)
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#pragma alloc_text(PAGE,FatReadBlock)
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#pragma alloc_text(PAGE,UnpackBiosParameterBlock)
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#endif // ALLOC_PRAGMA
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NTSTATUS
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FatRecFsControl(
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IN PDEVICE_OBJECT DeviceObject,
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IN PIRP Irp
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)
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/*++
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Routine Description:
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This function performs the mount and driver reload functions for this mini-
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file system recognizer driver.
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Arguments:
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DeviceObject - Pointer to this driver's device object.
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Irp - Pointer to the I/O Request Packet (IRP) representing the function to
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be performed.
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Return Value:
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The function value is the final status of the operation.
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--*/
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{
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NTSTATUS status;
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PIO_STACK_LOCATION irpSp;
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PDEVICE_EXTENSION deviceExtension;
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PDEVICE_OBJECT targetDevice;
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PPACKED_BOOT_SECTOR buffer;
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LARGE_INTEGER byteOffset;
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UNICODE_STRING driverName;
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NTSTATUS extStatus;
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PAGED_CODE();
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//
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// Begin by determining what function that is to be performed.
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//
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deviceExtension = (PDEVICE_EXTENSION) DeviceObject->DeviceExtension;
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irpSp = IoGetCurrentIrpStackLocation( Irp );
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switch ( irpSp->MinorFunction ) {
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case IRP_MN_MOUNT_VOLUME:
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//
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// Attempt to mount a volume: Determine whether or not the volume in
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// question is a FAT volume and, if so, let the I/O system know that it
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// is by returning a special status code so that this driver can get
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// called back to load the FAT file system.
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//
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//
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// Begin by making a special case test to determine whether or not this
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// driver has ever recognized a volume as being a FAT volume and the
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// attempt to load the driver failed. If so, then simply complete the
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// request with an error, indicating that the volume is not recognized
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// so that it gets mounted by the RAW file system.
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//
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status = STATUS_UNRECOGNIZED_VOLUME;
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if (deviceExtension->RealFsLoadFailed || irpSp->Flags) {
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break;
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}
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//
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// Attempt to determine whether or not the target volume being mounted
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// is a FAT volume. Note that if an error occurs, and this is a floppy
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// drive, and the error occurred on the actual read from the device,
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// then the FAT file system will actually be loaded to handle the
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// problem since this driver is a place holder and does not need to
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// know all of the protocols for handling floppy errors.
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//
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targetDevice = irpSp->Parameters.MountVolume.DeviceObject;
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byteOffset.QuadPart = 0;
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if (FatReadBlock( targetDevice, &byteOffset, 512, &extStatus, &buffer )) {
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if (IsFatVolume( buffer )) {
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status = STATUS_FS_DRIVER_REQUIRED;
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}
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ExFreePool( buffer );
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} else {
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if (!NT_SUCCESS( extStatus )) {
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if (targetDevice->Characteristics & FILE_FLOPPY_DISKETTE) {
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status = STATUS_FS_DRIVER_REQUIRED;
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}
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}
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}
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break;
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case IRP_MN_LOAD_FILE_SYSTEM:
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//
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// Attempt to load the FAT file system: A volume has been found that
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// appears to be a FAT volume, so attempt to load the FAT file system.
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// If it successfully loads, then
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//
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RtlInitUnicodeString( &driverName, L"\\Registry\\Machine\\System\\CurrentControlSet\\Services\\Fastfat" );
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status = ZwLoadDriver( &driverName );
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if (!NT_SUCCESS( status )) {
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if (status != STATUS_IMAGE_ALREADY_LOADED) {
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deviceExtension->RealFsLoadFailed = TRUE;
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}
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} else {
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IoUnregisterFileSystem( DeviceObject );
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}
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break;
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default:
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status = STATUS_INVALID_DEVICE_REQUEST;
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}
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//
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// Finally, complete the request and return the same status code to the
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// caller.
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//
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Irp->IoStatus.Status = status;
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IoCompleteRequest( Irp, IO_NO_INCREMENT );
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return status;
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}
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BOOLEAN
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IsFatVolume(
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IN PPACKED_BOOT_SECTOR Buffer
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)
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/*++
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Routine Description:
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This routine looks at the buffer passed in which contains the FAT boot
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sector and determines whether or not it represents an actual FAT boot
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sector.
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Arguments:
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Buffer - Pointer to buffer containing potential boot block.
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Return Value:
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The function returns TRUE if the buffer contains a recognizable FAT boot
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sector, otherwise it returns FALSE.
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--*/
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{
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BIOS_PARAMETER_BLOCK bios;
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BOOLEAN result;
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PAGED_CODE();
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//
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// Begin by unpacking the Bios Parameter Block that is packed in the boot
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// sector so that it can be examined without incurring alignment faults.
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//
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UnpackBiosParameterBlock( &Buffer->PackedBpb, &bios );
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//
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// Assume that the sector represents a FAT boot block and then determine
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// whether or not it really does.
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//
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result = TRUE;
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if (bios.Sectors) {
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bios.LargeSectors = 0;
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}
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// FMR Jul.11.1994 NaokiM - Fujitsu -
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// FMR boot sector has 'IPL1' string at the beginnig.
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if (Buffer->Jump[0] != 0x49 && /* FMR */
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Buffer->Jump[0] != 0xe9 &&
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Buffer->Jump[0] != 0xeb) {
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result = FALSE;
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// FMR Jul.11.1994 NaokiM - Fujitsu -
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// Sector size of FMR partition is 2048.
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} else if (bios.BytesPerSector != 128 &&
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bios.BytesPerSector != 256 &&
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bios.BytesPerSector != 512 &&
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bios.BytesPerSector != 1024 &&
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bios.BytesPerSector != 2048 && /* FMR */
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bios.BytesPerSector != 4096) {
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result = FALSE;
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} else if (bios.SectorsPerCluster != 1 &&
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bios.SectorsPerCluster != 2 &&
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bios.SectorsPerCluster != 4 &&
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bios.SectorsPerCluster != 8 &&
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bios.SectorsPerCluster != 16 &&
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bios.SectorsPerCluster != 32 &&
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bios.SectorsPerCluster != 64 &&
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bios.SectorsPerCluster != 128) {
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result = FALSE;
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} else if (!bios.ReservedSectors) {
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result = FALSE;
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} else if (!bios.Fats) {
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result = FALSE;
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} else if (!bios.RootEntries) {
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result = FALSE;
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//
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// Prior to DOS 3.2 might contains value in both of Sectors and
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// Sectors Large.
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//
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} else if (!bios.Sectors && !bios.LargeSectors) {
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result = FALSE;
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} else if (!bios.SectorsPerFat) {
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result = FALSE;
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// FMR Jul.11.1994 NaokiM - Fujitsu -
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// 1. Media descriptor of FMR partitions is 0xfa.
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// 2. Media descriptor of partitions formated by FMR OS/2 is 0x00.
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// 3. Media descriptor of floppy disks formated by FMR DOS is 0x01.
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} else if (bios.Media != 0x00 && /* FMR */
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bios.Media != 0x01 && /* FMR */
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bios.Media != 0xf0 &&
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bios.Media != 0xf8 &&
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bios.Media != 0xf9 &&
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bios.Media != 0xfa && /* FMR */
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bios.Media != 0xfb &&
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bios.Media != 0xfc &&
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bios.Media != 0xfd &&
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bios.Media != 0xfe &&
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bios.Media != 0xff) {
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result = FALSE;
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}
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return result;
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}
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BOOLEAN
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FatReadBlock(
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IN PDEVICE_OBJECT DeviceObject,
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IN PLARGE_INTEGER ByteOffset,
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IN ULONG MinimumBytes,
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OUT PNTSTATUS ExtendedStatus,
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OUT PPACKED_BOOT_SECTOR *Buffer
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)
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/*++
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Routine Description:
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This routine reads a minimum numbers of bytes into a buffer starting at
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the byte offset from the base of the device represented by the device
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object.
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Arguments:
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DeviceObject - Pointer to the device object from which to read.
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ByteOffset - Pointer to a 64-bit byte offset from the base of the device
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from which to start the read.
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MinimumBytes - Supplies the minimum number of bytes to be read.
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ExtendedStatus - Variable to receive extended status information about
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any I/O errors that occurred.
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Buffer - Variable to receive a pointer to the allocated buffer containing
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the bytes read.
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Return Value:
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The function value is TRUE if the bytes were read, otherwise FALSE.
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--*/
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{
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#define RoundUp( x, y ) ( ((x + (y-1)) / y) * y )
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DISK_GEOMETRY diskGeometry;
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IO_STATUS_BLOCK ioStatus;
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KEVENT event;
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PIRP irp;
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NTSTATUS status;
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PAGED_CODE();
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//
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// Begin by getting the disk geometry so that the number of bytes required
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// for a single read can be determined.
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//
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*ExtendedStatus = STATUS_SUCCESS;
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KeInitializeEvent( &event, SynchronizationEvent, FALSE );
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irp = IoBuildDeviceIoControlRequest( IOCTL_DISK_GET_DRIVE_GEOMETRY,
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DeviceObject,
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(PVOID) NULL,
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0,
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&diskGeometry,
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sizeof( diskGeometry ),
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FALSE,
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&event,
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&ioStatus );
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if (!irp) {
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return FALSE;
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}
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status = IoCallDriver( DeviceObject, irp );
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if (status == STATUS_PENDING) {
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(VOID) KeWaitForSingleObject( &event,
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Executive,
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KernelMode,
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FALSE,
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(PLARGE_INTEGER) NULL );
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status = ioStatus.Status;
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}
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if (!NT_SUCCESS( status )) {
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*ExtendedStatus = status;
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return FALSE;
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}
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//
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// Ensure that the drive actually knows how many bytes there are per
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// sector. Floppy drives do not know if the media is unformatted.
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//
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if (!diskGeometry.BytesPerSector) {
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return FALSE;
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}
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//
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// Set the minimum number of bytes to read to the maximum of the bytes that
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// the caller wants to read, and the number of bytes in a sector.
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//
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if (MinimumBytes < diskGeometry.BytesPerSector) {
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MinimumBytes = diskGeometry.BytesPerSector;
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} else {
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MinimumBytes = RoundUp( MinimumBytes, diskGeometry.BytesPerSector );
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}
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//
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// Allocate a buffer large enough to contain the bytes required, round the
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// request to a page boundary to solve any alignment requirements.
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//
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*Buffer = ExAllocatePool( NonPagedPool,
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(MinimumBytes + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1) );
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if (!*Buffer) {
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return FALSE;
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}
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//
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// Read the actual bytes off of the disk.
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//
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KeResetEvent( &event );
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irp = IoBuildSynchronousFsdRequest( IRP_MJ_READ,
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DeviceObject,
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*Buffer,
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MinimumBytes,
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ByteOffset,
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&event,
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&ioStatus );
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if (!irp) {
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return FALSE;
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}
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status = IoCallDriver( DeviceObject, irp );
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if (status == STATUS_PENDING) {
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(VOID) KeWaitForSingleObject( &event,
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Executive,
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KernelMode,
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FALSE,
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(PLARGE_INTEGER) NULL );
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status = ioStatus.Status;
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}
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if (!NT_SUCCESS( status )) {
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*ExtendedStatus = status;
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ExFreePool( *Buffer );
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return FALSE;
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}
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return TRUE;
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}
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VOID
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UnpackBiosParameterBlock(
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IN PPACKED_BIOS_PARAMETER_BLOCK Bios,
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OUT PBIOS_PARAMETER_BLOCK UnpackedBios
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)
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/*++
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Routine Description:
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This routine copies a packed Bios Parameter Block to an unpacked Bios
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Parameter Block.
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Arguments:
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Bios - Pointer to the packed Bios Parameter Block.
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UnpackedBios - Pointer to the unpacked Bios Parameter Block.
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Return Value:
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None.
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--*/
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{
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PAGED_CODE();
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//
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// Unpack the Bios Parameter Block.
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//
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CopyUchar2( &UnpackedBios->BytesPerSector, &Bios->BytesPerSector[0] );
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CopyUchar2( &UnpackedBios->BytesPerSector, &Bios->BytesPerSector[0] );
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CopyUchar1( &UnpackedBios->SectorsPerCluster, &Bios->SectorsPerCluster[0] );
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CopyUchar2( &UnpackedBios->ReservedSectors, &Bios->ReservedSectors[0] );
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CopyUchar1( &UnpackedBios->Fats, &Bios->Fats[0] );
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CopyUchar2( &UnpackedBios->RootEntries, &Bios->RootEntries[0] );
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CopyUchar2( &UnpackedBios->Sectors, &Bios->Sectors[0] );
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CopyUchar1( &UnpackedBios->Media, &Bios->Media[0] );
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CopyUchar2( &UnpackedBios->SectorsPerFat, &Bios->SectorsPerFat[0] );
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CopyUchar2( &UnpackedBios->SectorsPerTrack, &Bios->SectorsPerTrack[0] );
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CopyUchar2( &UnpackedBios->Heads, &Bios->Heads[0] );
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CopyUchar4( &UnpackedBios->HiddenSectors, &Bios->HiddenSectors[0] );
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CopyUchar4( &UnpackedBios->LargeSectors, &Bios->LargeSectors[0] );
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}
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