mbr.c

来自「EFI BIOS是Intel提出的下一代的BIOS标准。这里上传的Edk源代码是」· C语言 代码 · 共 323 行

/*++

Copyright (c) 2004 - 2006, Intel Corporation                                                         
All rights reserved. This program and the accompanying materials                          
are licensed and made available under the terms and conditions of the BSD License         
which accompanies this distribution.  The full text of the license may be found at        
http://opensource.org/licenses/bsd-license.php                                            
                                                                                          
THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,                     
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.             

Module Name:

  Mbr.c
  
Abstract:

  Decode a hard disk partitioned with the legacy MBR found on most PC's

  MBR - Master Boot Record is in the first sector of a partitioned hard disk.
        The MBR supports four partitions per disk. The MBR also contains legacy
        code that is not run on an EFI system. The legacy code reads the 
        first sector of the active partition into memory and 

  BPB - Bios Parameter Block is in the first sector of a FAT file system. 
        The BPB contains information about the FAT file system. The BPB is 
        always on the first sector of a media. The first sector also contains
        the legacy boot strap code.

--*/

#include "Partition.h"
#include "Mbr.h"

BOOLEAN
PartitionValidMbr (
  IN  MASTER_BOOT_RECORD      *Mbr,
  IN  EFI_LBA                 LastLba
  )
/*++

Routine Description:
  Test to see if the Mbr buffer is a valid MBR

Arguments:       
  Mbr     - Parent Handle 
  LastLba - Last Lba address on the device.

Returns:
  TRUE  - Mbr is a Valid MBR
  FALSE - Mbr is not a Valid MBR

--*/
{
  UINT32  StartingLBA;
  UINT32  EndingLBA;
  UINT32  NewEndingLBA;
  INTN    Index1;
  INTN    Index2;
  BOOLEAN MbrValid;

  if (Mbr->Signature != MBR_SIGNATURE) {
    return FALSE;
  }
  //
  // The BPB also has this signature, so it can not be used alone.
  //
  MbrValid = FALSE;
  for (Index1 = 0; Index1 < MAX_MBR_PARTITIONS; Index1++) {
    if (Mbr->Partition[Index1].OSIndicator == 0x00 || UNPACK_UINT32 (Mbr->Partition[Index1].SizeInLBA) == 0) {
      continue;
    }

    MbrValid    = TRUE;
    StartingLBA = UNPACK_UINT32 (Mbr->Partition[Index1].StartingLBA);
    EndingLBA   = StartingLBA + UNPACK_UINT32 (Mbr->Partition[Index1].SizeInLBA) - 1;
    if (EndingLBA > LastLba) {
      //
      // Compatibility Errata:
      //  Some systems try to hide drive space with their INT 13h driver
      //  This does not hide space from the OS driver. This means the MBR
      //  that gets created from DOS is smaller than the MBR created from
      //  a real OS (NT & Win98). This leads to BlockIo->LastBlock being
      //  wrong on some systems FDISKed by the OS.
      //
      // return FALSE since no block devices on a system are implemented
      // with INT 13h
      //
      return FALSE;
    }

    for (Index2 = Index1 + 1; Index2 < MAX_MBR_PARTITIONS; Index2++) {
      if (Mbr->Partition[Index2].OSIndicator == 0x00 || UNPACK_UINT32 (Mbr->Partition[Index2].SizeInLBA) == 0) {
        continue;
      }

      NewEndingLBA = UNPACK_UINT32 (Mbr->Partition[Index2].StartingLBA) + UNPACK_UINT32 (Mbr->Partition[Index2].SizeInLBA) - 1;
      if (NewEndingLBA >= StartingLBA && UNPACK_UINT32 (Mbr->Partition[Index2].StartingLBA) <= EndingLBA) {
        //
        // This region overlaps with the Index1'th region
        //
        return FALSE;
      }
    }
  }
  //
  // Non of the regions overlapped so MBR is O.K.
  //
  return MbrValid;
}

BOOLEAN
PartitionInstallMbrChildHandles (
  IN  EFI_DRIVER_BINDING_PROTOCOL  *This,
  IN  EFI_HANDLE                   Handle,
  IN  EFI_DISK_IO_PROTOCOL         *DiskIo,
  IN  EFI_BLOCK_IO_PROTOCOL        *BlockIo,
  IN  EFI_DEVICE_PATH_PROTOCOL     *DevicePath
  )
/*++

Routine Description:
  Install child handles if the Handle supports MBR format.

Arguments:       
  This       - Calling context.
  Handle     - Parent Handle 
  DiskIo     - Parent DiskIo interface
  BlockIo    - Parent BlockIo interface
  DevicePath - Parent Device Path

Returns:
  EFI_SUCCESS - If a child handle was added
  other       - A child handle was not added

--*/
{
  EFI_STATUS                Status;
  MASTER_BOOT_RECORD        *Mbr;
  UINT32                    ExtMbrStartingLba;
  UINTN                     Index;
  HARDDRIVE_DEVICE_PATH     HdDev;
  HARDDRIVE_DEVICE_PATH     ParentHdDev;
  BOOLEAN                   Found;
  UINT32                    PartitionNumber;
  EFI_DEVICE_PATH_PROTOCOL  *DevicePathNode;
  EFI_DEVICE_PATH_PROTOCOL  *LastDevicePathNode;

  Mbr             = NULL;
  Found           = FALSE;

  Mbr             = EfiLibAllocatePool (BlockIo->Media->BlockSize);
  if (Mbr == NULL) {
    goto Done;
  }

  Status = BlockIo->ReadBlocks (
                      BlockIo,
                      BlockIo->Media->MediaId,
                      0,
                      BlockIo->Media->BlockSize,
                      Mbr
                      );
  if (EFI_ERROR (Status) || !PartitionValidMbr (Mbr, BlockIo->Media->LastBlock)) {
    goto Done;
  }
  //
  // We have a valid mbr - add each partition
  //
  //
  // Get starting and ending LBA of the parent block device.
  //
  LastDevicePathNode = NULL;
  EfiZeroMem (&ParentHdDev, sizeof (ParentHdDev));
  DevicePathNode = DevicePath;
  while (!EfiIsDevicePathEnd (DevicePathNode)) {
    LastDevicePathNode  = DevicePathNode;
    DevicePathNode      = EfiNextDevicePathNode (DevicePathNode);
  }

  if (LastDevicePathNode != NULL) {
    if (DevicePathType (LastDevicePathNode) == MEDIA_DEVICE_PATH &&
        DevicePathSubType (LastDevicePathNode) == MEDIA_HARDDRIVE_DP
        ) {
      gBS->CopyMem (&ParentHdDev, LastDevicePathNode, sizeof (ParentHdDev));
    } else {
      LastDevicePathNode = NULL;
    }
  }

  PartitionNumber = 1;

  EfiZeroMem (&HdDev, sizeof (HdDev));
  HdDev.Header.Type     = MEDIA_DEVICE_PATH;
  HdDev.Header.SubType  = MEDIA_HARDDRIVE_DP;
  SetDevicePathNodeLength (&HdDev.Header, sizeof (HdDev));
  HdDev.MBRType         = MBR_TYPE_PCAT;
  HdDev.SignatureType   = SIGNATURE_TYPE_MBR;

  if (LastDevicePathNode == NULL) {
    //
    // This is a MBR, add each partition
    //
    for (Index = 0; Index < MAX_MBR_PARTITIONS; Index++) {
      if (Mbr->Partition[Index].OSIndicator == 0x00 || UNPACK_UINT32 (Mbr->Partition[Index].SizeInLBA) == 0) {
        //
        // Don't use null MBR entries
        //
        continue;
      }

      if (Mbr->Partition[Index].OSIndicator == PMBR_GPT_PARTITION) {
        //
        // This is the guard MBR for the GPT. If you ever see a GPT disk with zero partitions you can get here.
        //  We can not produce an MBR BlockIo for this device as the MBR spans the GPT headers. So formating 
        //  this BlockIo would corrupt the GPT structures and require a recovery that would corrupt the format
        //  that corrupted the GPT partition. 
        //
        continue;
      }

      HdDev.PartitionNumber = PartitionNumber ++;
      HdDev.PartitionStart  = UNPACK_UINT32 (Mbr->Partition[Index].StartingLBA);
      HdDev.PartitionSize   = UNPACK_UINT32 (Mbr->Partition[Index].SizeInLBA);
      EfiCopyMem (HdDev.Signature, &(Mbr->UniqueMbrSignature[0]), sizeof (UINT32));

      Status = PartitionInstallChildHandle (
                This,
                Handle,
                DiskIo,
                BlockIo,
                DevicePath,
                (EFI_DEVICE_PATH_PROTOCOL *) &HdDev,
                HdDev.PartitionStart,
                HdDev.PartitionStart + HdDev.PartitionSize - 1,
                MBR_SIZE,
                (BOOLEAN) (Mbr->Partition[Index].OSIndicator == EFI_PARTITION)
                );

      if (!EFI_ERROR (Status)) {
        Found = TRUE;
      }
    }
  } else {
    //
    // It's an extended partition. Follow the extended partition
    // chain to get all the logical drives
    //
    ExtMbrStartingLba = 0;

    do {

      Status = BlockIo->ReadBlocks (
                          BlockIo,
                          BlockIo->Media->MediaId,
                          ExtMbrStartingLba,
                          BlockIo->Media->BlockSize,
                          Mbr
                          );
      if (EFI_ERROR (Status)) {
        goto Done;
      }

      if (Mbr->Partition[0].OSIndicator == 0) {
        break;
      }

      if ((Mbr->Partition[0].OSIndicator == EXTENDED_DOS_PARTITION) ||
          (Mbr->Partition[0].OSIndicator == EXTENDED_WINDOWS_PARTITION)) {
        ExtMbrStartingLba = UNPACK_UINT32 (Mbr->Partition[0].StartingLBA);
        continue;
      }

      HdDev.PartitionNumber = PartitionNumber ++;
      HdDev.PartitionStart  = UNPACK_UINT32 (Mbr->Partition[0].StartingLBA) + ExtMbrStartingLba + ParentHdDev.PartitionStart;
      HdDev.PartitionSize   = UNPACK_UINT32 (Mbr->Partition[0].SizeInLBA);
      if (HdDev.PartitionStart + HdDev.PartitionSize - 1 >=
            ParentHdDev.PartitionStart + ParentHdDev.PartitionSize) {
        break;
      }

      //
      // The signature in EBR(Extended Boot Record) should always be 0.
      //
      *((UINT32 *) &HdDev.Signature[0]) = 0;

      Status = PartitionInstallChildHandle (
                This,
                Handle,
                DiskIo,
                BlockIo,
                DevicePath,
                (EFI_DEVICE_PATH_PROTOCOL *) &HdDev,
                HdDev.PartitionStart - ParentHdDev.PartitionStart,
                HdDev.PartitionStart - ParentHdDev.PartitionStart + HdDev.PartitionSize - 1,
                MBR_SIZE,
                (BOOLEAN) (Mbr->Partition[0].OSIndicator == EFI_PARTITION)
                );
      if (!EFI_ERROR (Status)) {
        Found = TRUE;
      }

      if ((Mbr->Partition[1].OSIndicator != EXTENDED_DOS_PARTITION) &&
          (Mbr->Partition[1].OSIndicator != EXTENDED_WINDOWS_PARTITION)) {
        break;
      }

      ExtMbrStartingLba = UNPACK_UINT32 (Mbr->Partition[1].StartingLBA);
      //
      // Don't allow partition to be self referencing
      //
      if (ExtMbrStartingLba == 0) {
        break;
      }
    } while (ExtMbrStartingLba  < ParentHdDev.PartitionSize);
  }

Done:
  gBS->FreePool (Mbr);

  return Found;
}