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/** @file
Routines supporting partition discovery and
logical device reading
Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#include <IndustryStandard/Mbr.h>
#include "FatLitePeim.h"
/**
Test to see if the Mbr buffer is a valid MBR
@param[in] Mbr Parent Handle
@param[in] LastLba Last Lba address on the device.
@retval TRUE Mbr is a Valid MBR
@retval FALSE Mbr is not a Valid MBR
**/
BOOLEAN
PartitionValidMbr (
IN MASTER_BOOT_RECORD *Mbr,
IN EFI_PEI_LBA LastLba
)
{
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 Because 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_INT32 (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;
}
/**
This function finds Mbr partitions. Main algorithm
is ported from DXE partition driver.
@param[in] PrivateData The global memory map
@param[in] ParentBlockDevNo The parent block device
@retval TRUE New partitions are detected and logical block devices
are added to block device array
@retval FALSE No new partitions are added
**/
BOOLEAN
FatFindMbrPartitions (
IN PEI_FAT_PRIVATE_DATA *PrivateData,
IN UINTN ParentBlockDevNo
)
{
EFI_STATUS Status;
MASTER_BOOT_RECORD *Mbr;
UINTN Index;
BOOLEAN Found;
PEI_FAT_BLOCK_DEVICE *ParentBlockDev;
PEI_FAT_BLOCK_DEVICE *BlockDev;
if (ParentBlockDevNo > PEI_FAT_MAX_BLOCK_DEVICE - 1) {
return FALSE;
}
ParentBlockDev = &(PrivateData->BlockDevice[ParentBlockDevNo]);
if (ParentBlockDev->BlockSize > PEI_FAT_MAX_BLOCK_SIZE) {
DEBUG((DEBUG_ERROR, "Device BlockSize %x exceeds FAT_MAX_BLOCK_SIZE\n", ParentBlockDev->BlockSize));
return FALSE;
}
Found = FALSE;
Mbr = (MASTER_BOOT_RECORD *) PrivateData->BlockData;
Status = FatReadBlock (
PrivateData,
ParentBlockDevNo,
0,
ParentBlockDev->BlockSize,
Mbr
);
if (EFI_ERROR (Status) || !PartitionValidMbr (Mbr, ParentBlockDev->LastBlock)) {
goto Done;
}
//
// We have a valid mbr - add each partition
//
for (Index = 0; Index < MAX_MBR_PARTITIONS; Index++) {
if (Mbr->Partition[Index].OSIndicator == 0x00 || UNPACK_INT32 (Mbr->Partition[Index].SizeInLBA) == 0) {
//
// Don't use null MBR entries
//
continue;
}
//
// Register this partition
//
if (PrivateData->BlockDeviceCount < PEI_FAT_MAX_BLOCK_DEVICE) {
Found = TRUE;
BlockDev = &(PrivateData->BlockDevice[PrivateData->BlockDeviceCount]);
BlockDev->BlockSize = MBR_SIZE;
BlockDev->LastBlock = UNPACK_INT32 (Mbr->Partition[Index].SizeInLBA) - 1;
BlockDev->IoAlign = ParentBlockDev->IoAlign;
BlockDev->Logical = TRUE;
BlockDev->PartitionChecked = FALSE;
BlockDev->StartingPos = MultU64x32 (
UNPACK_INT32 (Mbr->Partition[Index].StartingLBA),
ParentBlockDev->BlockSize
);
BlockDev->ParentDevNo = ParentBlockDevNo;
PrivateData->BlockDeviceCount++;
}
}
Done:
ParentBlockDev->PartitionChecked = TRUE;
return Found;
}
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