FatPkg/FatPei/Mbr.c

   1 /** @file
   2   Routines supporting partition discovery and
   3   logical device reading
   4
   5 Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
   6
   7 SPDX-License-Identifier: BSD-2-Clause-Patent
   8
   9 **/
  10
  11 #include <IndustryStandard/Mbr.h>
  12 #include "FatLitePeim.h"
  13
  14 /**
  15   Test to see if the Mbr buffer is a valid MBR
  16
  17   @param[in]  Mbr               Parent Handle
  18   @param[in]  LastLba           Last Lba address on the device.
  19
  20   @retval     TRUE              Mbr is a Valid MBR
  21   @retval     FALSE             Mbr is not a Valid MBR
  22
  23 **/
  24 BOOLEAN
  25 PartitionValidMbr (
  26   IN  MASTER_BOOT_RECORD      *Mbr,
  27   IN  EFI_PEI_LBA             LastLba
  28   )
  29 {
  30   UINT32  StartingLBA;
  31   UINT32  EndingLBA;
  32   UINT32  NewEndingLBA;
  33   INTN    Index1;
  34   INTN    Index2;
  35   BOOLEAN MbrValid;
  36
  37   if (Mbr->Signature != MBR_SIGNATURE) {
  38     return FALSE;
  39   }
  40   //
  41   // The BPB also has this signature, so it can not be used alone.
  42   //
  43   MbrValid = FALSE;
  44   for (Index1 = 0; Index1 < MAX_MBR_PARTITIONS; Index1++) {
  45     if (Mbr->Partition[Index1].OSIndicator == 0x00 || UNPACK_UINT32 (Mbr->Partition[Index1].SizeInLBA) == 0) {
  46       continue;
  47     }
  48
  49     MbrValid    = TRUE;
  50     StartingLBA = UNPACK_UINT32 (Mbr->Partition[Index1].StartingLBA);
  51     EndingLBA   = StartingLBA + UNPACK_UINT32 (Mbr->Partition[Index1].SizeInLBA) - 1;
  52     if (EndingLBA > LastLba) {
  53       //
  54       // Compatibility Errata:
  55       //  Some systems try to hide drive space with their INT 13h driver
  56       //  This does not hide space from the OS driver. This means the MBR
  57       //  that gets created from DOS is smaller than the MBR created from
  58       //  a real OS (NT & Win98). This leads to BlockIo->LastBlock being
  59       //  wrong on some systems FDISKed by the OS.
  60       //
  61       //  return FALSE Because no block devices on a system are implemented
  62       //  with INT 13h
  63       //
  64       return FALSE;
  65     }
  66
  67     for (Index2 = Index1 + 1; Index2 < MAX_MBR_PARTITIONS; Index2++) {
  68       if (Mbr->Partition[Index2].OSIndicator == 0x00 || UNPACK_INT32 (Mbr->Partition[Index2].SizeInLBA) == 0) {
  69         continue;
  70       }
  71
  72       NewEndingLBA = UNPACK_UINT32 (Mbr->Partition[Index2].StartingLBA) + UNPACK_UINT32 (Mbr->Partition[Index2].SizeInLBA) - 1;
  73       if (NewEndingLBA >= StartingLBA && UNPACK_UINT32 (Mbr->Partition[Index2].StartingLBA) <= EndingLBA) {
  74         //
  75         // This region overlaps with the Index1'th region
  76         //
  77         return FALSE;
  78       }
  79     }
  80   }
  81   //
  82   // Non of the regions overlapped so MBR is O.K.
  83   //
  84   return MbrValid;
  85 }
  86
  87 /**
  88   This function finds Mbr partitions. Main algorithm
  89   is ported from DXE partition driver.
  90
  91   @param[in]  PrivateData       The global memory map
  92   @param[in]  ParentBlockDevNo  The parent block device
  93
  94   @retval TRUE              New partitions are detected and logical block devices
  95                             are added to block device array
  96   @retval FALSE             No new partitions are added
  97
  98 **/
  99 BOOLEAN
 100 FatFindMbrPartitions (
 101   IN  PEI_FAT_PRIVATE_DATA *PrivateData,
 102   IN  UINTN                ParentBlockDevNo
 103   )
 104 {
 105   EFI_STATUS            Status;
 106   MASTER_BOOT_RECORD    *Mbr;
 107   UINTN                 Index;
 108   BOOLEAN               Found;
 109   PEI_FAT_BLOCK_DEVICE  *ParentBlockDev;
 110   PEI_FAT_BLOCK_DEVICE  *BlockDev;
 111
 112   if (ParentBlockDevNo > PEI_FAT_MAX_BLOCK_DEVICE - 1) {
 113     return FALSE;
 114   }
 115
 116   ParentBlockDev  = &(PrivateData->BlockDevice[ParentBlockDevNo]);
 117
 118   if (ParentBlockDev->BlockSize > PEI_FAT_MAX_BLOCK_SIZE) {
 119     DEBUG((DEBUG_ERROR, "Device BlockSize %x exceeds FAT_MAX_BLOCK_SIZE\n", ParentBlockDev->BlockSize));
 120     return FALSE;
 121   }
 122
 123   Found           = FALSE;
 124   Mbr             = (MASTER_BOOT_RECORD *) PrivateData->BlockData;
 125
 126   Status = FatReadBlock (
 127             PrivateData,
 128             ParentBlockDevNo,
 129             0,
 130             ParentBlockDev->BlockSize,
 131             Mbr
 132             );
 133
 134   if (EFI_ERROR (Status) || !PartitionValidMbr (Mbr, ParentBlockDev->LastBlock)) {
 135     goto Done;
 136   }
 137   //
 138   // We have a valid mbr - add each partition
 139   //
 140   for (Index = 0; Index < MAX_MBR_PARTITIONS; Index++) {
 141     if (Mbr->Partition[Index].OSIndicator == 0x00 || UNPACK_INT32 (Mbr->Partition[Index].SizeInLBA) == 0) {
 142       //
 143       // Don't use null MBR entries
 144       //
 145       continue;
 146     }
 147     //
 148     // Register this partition
 149     //
 150     if (PrivateData->BlockDeviceCount < PEI_FAT_MAX_BLOCK_DEVICE) {
 151
 152       Found                       = TRUE;
 153
 154       BlockDev                    = &(PrivateData->BlockDevice[PrivateData->BlockDeviceCount]);
 155
 156       BlockDev->BlockSize         = MBR_SIZE;
 157       BlockDev->LastBlock         = UNPACK_INT32 (Mbr->Partition[Index].SizeInLBA) - 1;
 158       BlockDev->IoAlign           = ParentBlockDev->IoAlign;
 159       BlockDev->Logical           = TRUE;
 160       BlockDev->PartitionChecked  = FALSE;
 161       BlockDev->StartingPos = MultU64x32 (
 162                                 UNPACK_INT32 (Mbr->Partition[Index].StartingLBA),
 163                                 ParentBlockDev->BlockSize
 164                                 );
 165       BlockDev->ParentDevNo = ParentBlockDevNo;
 166
 167       PrivateData->BlockDeviceCount++;
 168     }
 169   }
 170
 171 Done:
 172
 173   ParentBlockDev->PartitionChecked = TRUE;
 174   return Found;
 175 }