wince NandFlash分区实现 MBR创建过程

发布时间：2020-12-15 18:19:15 所属栏目：百科来源：网络整理

导读：在网站上看到这篇文章，讲解的比较有逻辑性，转载了留着进一步研究！！ ?复制网址： http://blog.csdn.net/paul73022/article/details/6092897 NandFlash的分区实现提到分区就需要知道MBR，了解分区表。什么是MBR ???? 硬盘的0柱面、0磁头、1扇区称为主引

在网站上看到这篇文章，讲解的比较有逻辑性，转载了留着进一步研究！！

?复制网址： http://blog.csdn.net/paul73022/article/details/6092897

NandFlash的分区实现

提到分区就需要知道MBR，了解分区表。

什么是MBR

???? 硬盘的0柱面、0磁头、1扇区称为主引导扇区，NANDFLASH由BLOCK和Sector组成，所以NANDFLASH的第0 BLOCK，第1 Sector为主引导扇区，FDISK程序写到该扇区的内容称为主引导记录（MBR）。该记录占用512个字节，它用于硬盘启动时将系统控制权交给用户指定的，并在分区表中登记了的某个操作系统区。

MBR的组成

一个扇区的硬盘主引导记录MBR由如图6-15所示的4个部分组成。

主引导程序（偏移地址0000H—0088H），它负责从活动分区中装载，并运行系统引导程序。
出错信息数据区，偏移地址0089H--00E1H为出错信息，00E2H--01BDH全为0字节。
分区表（DPT,Disk Partition Table）含4个分区项，偏移地址01BEH--01FDH,每个分区表项长16个字节，共64字节为分区项1、分区项2、分区项3、分区项4。
结束标志字，偏移地址01FE--01FF的2个字节值为结束标志55AA,如果该标志错误系统就不能启动。

0000-0088
Master Boot Record

主引导程序

主引导

程序

0089-01BD 出错信息数据区数据区

01BE-01CD

分区项1（16字节）

分区表

01CE-01DD

分区项2（16字节）
…

01DE-01ED

分区项3（16字节）
…

01EE-01FD

分区项4（16字节）
…

01FE

55
结束标志

01FF

AA
…

???????????????????????????? 图6-15 MBR的组成结构图

MBR中的分区信息结构

???? 占用512个字节的MBR中，偏移地址01BEH--01FDH的64个字节，为4个分区项内容（分区信息表）。它是由磁盘介质类型及用户在使用 FDISK定义分区说确定的。在实际应用中，FDISK对一个磁盘划分的主分区可少于4个，但最多不超过4个。每个分区表的项目是16个字节，其内容含义如表6-19所示。
表6-19 分区项表（16字节）内容及含义

存贮字节位内容及含义

第1字节引导标志。若值为80H表示活动分区，若值为00H表示非活动分区。

第2、3、4字节
本分区的起始磁头号、扇区号、柱面号。其中：

磁头号——第2字节；

扇区号——第3字节的低6位；

柱面号——为第3字节高2位+第4字节8位。

第5字节
分区类型符:

00H——表示该分区未用（即没有指定）；

06H——FAT16基本分区；

0BH——FAT32基本分区；

05H——扩展分区；

07H——NTFS分区；

0FH——（LBA模式）扩展分区（83H为Linux分区等）。

第6、7、8字节
本分区的结束磁头号、扇区号、柱面号，其中：

磁头号——第6字节；

扇区号——第7字节的低6位；

柱面号——第7字节的高2位+第8字节。

第9、10、11、12字节本分区之前已用了的扇区数

第13、14、15、16字节本分区的总扇区数

??????? EBOOT中对NAND分区主要代码，eboot目录下的fmd.cpp文件，与NAND驱动基本相同，所以，要对NAND进行分区，就得对NAND驱动非常熟悉。透彻了解。然后就是E:/WINCE500/PUBLIC/COMMON/OAK/DRIVERS/ETHDBG/BOOTPART/bootpart.cpp文件了。该文件主要通过调用NANDFLASH的读写操作来写入MBR，也是今天主要的分析对象。

主要函数。

 
     Code Snippet 
    
 
     /*? BP_OpenPartition
*
*? Opens/creates a partition depending on the creation flags.? If it is opening
*? and the partition has already been opened,then it returns a handle to the
*? opened partition.? Otherwise,it loads the state information of that partition
*? into memory and returns a handle.
* 
*? ENTRY
*????? dwStartSector - Logical sector to start the partition.? NEXT_FREE_LOC if none
*????????? specified.? Ignored if opening existing partition.
*????? dwNumSectors - Number of logical sectors of the partition.? USE_REMAINING_SPACE
*????????? to indicate to take up the rest of the space on the flash for that partition (should
*????????? only be used when creating extended partitions).? This parameter is ignored
*????????? if opening existing partition.
*????? dwPartType - Type of partition to create/open.
*????? fActive - TRUE indicates to create/open the active partition.? FALSE for
*????????? inactive.
*????? dwCreationFlags - PART_CREATE_NEW to create only.? Fail if it already
*????????? exists.? PART_OPEN_EXISTING to open only.? Fail if it doesn't exist.
*????????? PART_OPEN_ALWAYS creates if it does not exist and opens if it
*????????? does exist.
*

*? EXIT  
*????? Handle to the partition on success.? INVALID_HANDLE_VALUE on error.
*/ 
? 
HANDLE BP_OpenPartition(DWORD dwStartSector,DWORD dwNumSectors,DWORD dwPartType,BOOL fActive,DWORD dwCreationFlags)
//￡¨×￠￡oê?ày′ú???a±?è?/uc1EBOOT?D·???êμ???′??￡¨/uc1WINCE5.0+S3C2440+128MNAND,MBRD′?úμú??/uc1BLOCK￡?·?ò???/uc1BINFS??ê?·???oíò???/uc1FAT??ê?·???￡??￡￡?
BOOL WriteRegionsToBootMedia(DWORD dwImageStart,DWORD dwImageLength,DWORD dwLaunchAddr)

在把SDRAM中的NK烧写到NAND中去之前，先创建一个BINFS分区。

hPart = BP_OpenPartition( (NK_START_BLOCK+1)PAGES_PER_BLOCK,? // next block of MBR???? BINFS_BLOCKPAGES_PER_BLOCK,//SECTOR_TO_BLOCK_SIZE(FILE_TO_SECTOR_SIZE(dwBINFSPartLength))*PAGES_PER_BLOCK,? //align to block

????????????????????????????? PART_BINFS,

????????????????????????????? TRUE,

????????????????????????????? PART_OPEN_ALWAYS);

第一个参数分区的起始sector 为(NK_START_BLOCK+1)*PAGES_PER_BLOCK，

第二个参数分区的结束 sector为BINFS_BLOCK*PAGES_PER_BLOCK，

第三个参数分区的格式为PART_BINFS，即BINFS格式，

第四个参数指示该分区为活动分区，fActive = TURE，

第五个参数PART_OPEN_ALWAYS指示如果分区不存在就创建该分区，存在就OPEN该分区，返回分区句柄。

HANDLE BP_OpenPartition(DWORD dwStartSector,DWORD dwCreationFlags)

{

??????? DWORD dwPartIndex;

??????? BOOL fExists;

??????? ASSERT (g_pbMBRSector);

??????? if (!IsValidMBR()) {

??????????? DWORD dwFlags = 0;

??????????? //fly

???????????? RETAILMSG(1,(TEXT("BP_OpenPartition:: dwStartSector=0x%x,dwNumSectors= 0x%x.,dwPartType = 0x%x/r/n"),dwStartSector,dwNumSectors,dwPartType));

??????????? if (dwCreationFlags == PART_OPEN_EXISTING) {

??????????????? RETAILMSG(1,(TEXT("OpenPartition: Invalid MBR.? Cannot open existing partition 0x%x./r/n"),243)">???????????????return INVALID_HANDLE_VALUE;

??????????? }

??????????? RETAILMSG(1,(TEXT("OpenPartition: Invalid MBR.? Formatting flash./r/n")));

??????????? if (g_FlashInfo.flashType == NOR) {

??????????????? dwFlags |= FORMAT_SKIP_BLOCK_CHECK;

??????????? }

??????????? //fly

??????????? RETAILMSG(1,(TEXT("BP_LowLevelFormat: g_pbMBRSector=0x%x,g_dwMBRSectorNum= 0x%x./r/n"),*g_pbMBRSector,g_dwMBRSectorNum));

??????????? BP_LowLevelFormat (SECTOR_TO_BLOCK(dwStartSector),SECTOR_TO_BLOCK(dwNumSectors),dwFlags);

??????????? dwPartIndex = 0;

??????????? fExists = FALSE;

??????? }

??????? else {

??????????? fExists = GetPartitionTableIndex(dwPartType,fActive,&dwPartIndex);???????

??????? }

??????? RETAILMSG(1,(TEXT("OpenPartition: Partition Exists=0x%x for part 0x%x./r/n"),fExists,243)">??????? if (fExists) {

??????????? // Partition was found.

??????????? if (dwCreationFlags == PART_CREATE_NEW)

??????????????? return INVALID_HANDLE_VALUE;

??????????? if (g_partStateTable[dwPartIndex].pPartEntry == NULL) {

??????????????? // Open partition.? If this is the boot section partition,then file pointer starts after MBR

??????????????? g_partStateTable[dwPartIndex].pPartEntry = (PPARTENTRY)(g_pbMBRSector + PARTTABLE_OFFSET +sizeof(PARTENTRY)*dwPartIndex);

??????????????? g_partStateTable[dwPartIndex].dwDataPointer = 0;

??????????? }

?????????? if ( dwNumSectors > g_partStateTable[dwPartIndex].pPartEntry->Part_TotalSectors )

?????????????return CreatePartition (dwStartSector,dwPartType,dwPartIndex);

?????????? else?????????

??????????????????return (HANDLE)&g_partStateTable[dwPartIndex];???????????

??????? }

??????? else {

??????????? // If there are already 4 partitions,or creation flag specified OPEN_EXISTING,fail.

??????????? if ((dwPartIndex == NUM_PARTS) || (dwCreationFlags == PART_OPEN_EXISTING))

??????????????? return INVALID_HANDLE_VALUE;

??????????? // Create new partition

??????????? return CreatePartition (dwStartSector,dwPartIndex);

??????? }

??????? return INVALID_HANDLE_VALUE;

}

进入函数，首先做的事就是检测MBR的有效性。通过函数IsValidMBR（）实现。

检测MBR的有效性，首先要知道MBR保存在哪里，前面说过NANDFLASH的第0 BLOCK，第1 Sector为主引导扇区，也就是MBR，但是NAND如果被当作启动芯片，○地址一般被BOOTLOADER代码占据，MBR只有放在后面的BLOCK中。所以我把第0 个BLOCK放NBOOT，第1个BLOCK放TOC，第2个BLOCK放EBOOT，第3个BLOCK保留，第4个BLOCK就放MBR。

static BOOL IsValidMBR()

{

??? // Check to see if the MBR is valid

??? // MBR block is always located at logical sector 0

??? g_dwMBRSectorNum = GetMBRSectorNum();???????

??? RETAILMSG (1,(TEXT("IsValidMBR: MBR sector = 0x%x/r/n"),g_dwMBRSectorNum));

??? if ((g_dwMBRSectorNum == INVALID_ADDR) || !FMD_ReadSector (g_dwMBRSectorNum,g_pbMBRSector,NULL,1)) {

?????? RETAILMSG (1,(TEXT("IsValidMBR-----return FALSE-------------------/r/n")));

??????? return FALSE;

??? }???

??? return ((g_pbMBRSector[0] == 0xE9) &&

???????? (g_pbMBRSector[1] == 0xfd) &&

???????? (g_pbMBRSector[2] == 0xff) &&

???????? (g_pbMBRSector[SECTOR_SIZE_FS-2] == 0x55) &&

???????? (g_pbMBRSector[SECTOR_SIZE_FS-1] == 0xAA));

}

IsValidMBR()实现的第一行就是给全局变量g_dwMBRSectorNum 赋值，显而易见，g_dwMBRSectorNum就是指示保存MBR的那个Sector了。

g_dwMBRSectorNum = GetMBRSectorNum();?? //是获得保存MBR的那个Sector

static DWORD GetMBRSectorNum ()

{

??? DWORD dwBlockNum = 3,dwSector = 0;

??? SectorInfo si;

????

??? while (dwBlockNum < g_FlashInfo.dwNumBlocks) {

??????? if (!IS_BLOCK_UNUSABLE (dwBlockNum)) {

??????????? dwSector = dwBlockNum * g_FlashInfo.wSectorsPerBlock;

??????????? if (!FMD_ReadSector (dwSector,&si,243)">??????????????? RETAILMSG(1,(TEXT("GetMBRSectorNum: Could not read sector 0x%x./r/n"),dwSector));

??????????????? return INVALID_ADDR;

??????????? }

??????????? // Check to see if logical sector number is 0

??????????? if (si.dwReserved1 == 0) {

????????????? //RETAILMSG(1,(TEXT("dwBlockNum=%d/r/n"),dwBlockNum));

???????????????return dwSector;

??????????? }

??????? }

??????? dwBlockNum++;

??? }

??? return INVALID_ADDR;

}

这里dwBlockNum直接给了个3，因为NBOOT，TOC，EBOOT已经把前三个BLOCK用了。所以MBR的选择直接排除了前三个BLOCK了。

#define IS_BLOCK_UNUSABLE(blockID) ((FMD_GetBlockStatus (blockID) & (BLOCK_STATUS_BAD|BLOCK_STATUS_RESERVED)) > 0)

然后确定BLOCK是否可使用的BLOCK，最后通si.dwReserved1 == 0来判断是不是选择这个Sector来保存MBR。

IsValidMBR（）中还有一个重要的结构就是g_pbMBRSector数组，它就是MBR了。

函数返回时，MBR必须符合下列记录。

???

return ((g_pbMBRSector[0] == 0xE9) &&

???????? (g_pbMBRSector[1] == 0xfd) &&

???????? (g_pbMBRSector[2] == 0xff) &&

???????? (g_pbMBRSector[SECTOR_SIZE_FS-2] == 0x55) &&

???????? (g_pbMBRSector[SECTOR_SIZE_FS-1] == 0xAA));

可以看到只有开始三个字节为0XE9,FD,FF，当然，还有熟悉的结束标志符0X55AA。

如果没有检测到MBR，则先对NANDFLASH进行低级格式化。BP_LowLevelFormat (SECTOR_TO_BLOCK(dwStartSector),dwFlags);再创建分区，CreatePartition (dwStartSector,dwPartIndex);。

BOOL BP_LowLevelFormat(DWORD dwStartBlock,DWORD dwNumBlocks,DWORD dwFlags)

{

??? dwNumBlocks = min (dwNumBlocks,g_FlashInfo.dwNumBlocks);

??? RETAILMSG(1,(TEXT("fly::Enter LowLevelFormat [0x%x,0x%x]./r/n"),dwStartBlock,dwNumBlocks));// dwStartBlock + dwNumBlocks - 1));

??? // Erase all the flash blocks.

??? if (!EraseBlocks(dwStartBlock,dwNumBlocks,dwFlags))

??????? return(FALSE);

??? // Determine first good starting block

??? while (IS_BLOCK_UNUSABLE (dwStartBlock) && dwStartBlock < g_FlashInfo.dwNumBlocks) {

??????? dwStartBlock++;

??? }

??? if (dwStartBlock >= g_FlashInfo.dwNumBlocks) {

??????? RETAILMSG(1,(TEXT("BP_LowLevelFormat: no good blocks/r/n")));???????

??????? return FALSE;

??? }

??? // MBR goes in the first sector of the starting block.? This will be logical sector 0.

??? g_dwMBRSectorNum = dwStartBlock * g_FlashInfo.wSectorsPerBlock;

"fly:g_dwMBRSectorNum=%d/r/n"),g_dwMBRSectorNum));

??? // Create an MBR.

??? CreateMBR();

??? return(TRUE);

}

在对NANDFLASH进行低格时，主要对坏块的处理。if (!EraseBlocks(dwStartBlock,dwFlags))检测每一个Sector，每个BLOCK只要有一个Sector不能读写这个块都会被处理成坏块，这样才能保证系统的稳定性。在函数的最后调用了??? CreateMBR();来创建一个MBR。

static BOOL CreateMBR()

{

??? // This,plus a valid partition table,is all the CE partition manager needs to recognize

??? // the MBR as valid. It does not contain boot code.

??? memset (g_pbMBRSector,0xff,g_FlashInfo.wDataBytesPerSector);

??? g_pbMBRSector[0] = 0xE9;

??? g_pbMBRSector[1] = 0xfd;

??? g_pbMBRSector[2] = 0xff;

??? g_pbMBRSector[SECTOR_SIZE_FS-2] = 0x55;

??? g_pbMBRSector[SECTOR_SIZE_FS-1] = 0xAA;

??? // Zero out partition table so that mspart treats entries as empty.

??? memset (g_pbMBRSector+PARTTABLE_OFFSET,sizeof(PARTENTRY) * NUM_PARTS);

??? return WriteMBR();

}

当然。因为还没有进行分区，这里写入的MBR分区表部分是空的。

static BOOL WriteMBR()

{

??? DWORD dwMBRBlockNum = g_dwMBRSectorNum / g_FlashInfo.wSectorsPerBlock;

??? //dwMBRBlockNum = 1 ;

??? RETAILMSG(1,(TEXT("WriteMBR: MBR block = 0x%x,g_dwMBRSectorNum = 0x%x./r/n"),dwMBRBlockNum,243)">??? memset (g_pbBlock,g_dwDataBytesPerBlock);

??? memset (g_pSectorInfoBuf, sizeof(SectorInfo) * g_FlashInfo.wSectorsPerBlock);

??? // No need to check return,since a failed read means data hasn't been written yet.

??? ReadBlock (dwMBRBlockNum,g_pbBlock,g_pSectorInfoBuf);

??? if (!FMD_EraseBlock (dwMBRBlockNum)) {

??????? RETAILMSG (1,(TEXT("CreatePartition: error erasing block 0x%x/r/n"),dwMBRBlockNum));

??? memcpy (g_pbBlock + (g_dwMBRSectorNum % g_FlashInfo.wSectorsPerBlock) * g_FlashInfo.wDataBytesPerSector,g_FlashInfo.wDataBytesPerSector);

??? g_pSectorInfoBuf->bOEMReserved &= ~OEM_BLOCK_READONLY;

??? g_pSectorInfoBuf->wReserved2 &= ~SECTOR_WRITE_COMPLETED;

??? g_pSectorInfoBuf->dwReserved1 = 0;

"fly::WriteMBR: MBR block = 0x%x./r/n"),dwMBRBlockNum));

??? if (!WriteBlock (dwMBRBlockNum,g_pSectorInfoBuf)) {

??????? RETAILMSG (1,(TEXT("CreatePartition: could not write to block 0x%x/r/n"),dwMBRBlockNum));

??????? return FALSE;

??? }

??? return TRUE;

}

在WriteMBR()函数中，就写入了判断MBR 的一些标志到BLOCK，??? g_pSectorInfoBuf->bOEMReserved &= ~OEM_BLOCK_READONLY;

??? g_pSectorInfoBuf->wReserved2 &= ~SECTOR_WRITE_COMPLETED;

??? g_pSectorInfoBuf->dwReserved1 = 0;

Wince系统启动时，具体是NANDFLASH驱动加载成功后，MOUNT文件系统到NANDFLASH之前，也会通过读取这些SectorInfo来得到MBR 保存的BLOCK，进而读取MBR，获得分区信息，从而把各分区MOUNT到相应文件系统。格式化完成，MBR也写入成功后就可以开始新建分区了。

/*? CreatePartition

*? Creates a new partition.? If it is a boot section partition,then it formats

*? flash.

*? ENTRY

*????? dwStartSector - Logical sector to start the partition.? NEXT_FREE_LOC if

*????????? none specified.

*????? dwNumSectors - Number of logical sectors of the partition.? USE_REMAINING_SPACE

*????????? to indicate to take up the rest of the space on the flash for that partition.

*????? dwPartType - Type of partition to create.

*????? fActive - TRUE indicates to create the active partition.? FALSE for

*????????? inactive.

*????? dwPartIndex - Index of the partition entry on the MBR

*? EXIT

*????? Handle to the partition on success.? INVALID_HANDLE_VALUE on error.

static HANDLE CreatePartition (DWORD dwStartSector,DWORD dwPartIndex)

{

??? DWORD dwBootInd = 0;

"CreatePartition: Enter CreatePartition for 0x%x./r/n"),dwPartType));

??? if (fActive)

??????? dwBootInd |= PART_IND_ACTIVE;

??? if (dwPartType == PART_BOOTSECTION || dwPartType == PART_BINFS || dwPartType == PART_XIP)

??????? dwBootInd |= PART_IND_READ_ONLY;???

???? // If start sector is invalid,it means find next free sector

??? if (dwStartSector == NEXT_FREE_LOC) {???????

??????? dwStartSector = FindFreeSector();

??????? if (dwStartSector == INVALID_ADDR) {

??????????? RETAILMSG(1,(TEXT("CreatePartition: can't find free sector./r/n")));

??????????? return INVALID_HANDLE_VALUE;

??????? }

??????? // Start extended partition on a block boundary

??????? if ((dwPartType == PART_EXTENDED) && (dwStartSector % g_FlashInfo.wSectorsPerBlock)) {

??????????? dwStartSector = (dwStartSector / g_FlashInfo.wSectorsPerBlock + 1) * g_FlashInfo.wSectorsPerBlock;

??????? }

??? }

??? // If num sectors is invalid,fill the rest of the space up

??? if (dwNumSectors == USE_REMAINING_SPACE) {

??????? DWORD dwLastLogSector = LastLogSector();

??????? if (dwLastLogSector == INVALID_ADDR)

??????????? return INVALID_HANDLE_VALUE;

??????? // Determine the number of blocks to reserve for the FAL compaction when creating an extended partition.

??????? DWORD dwReservedBlocks = g_FlashInfo.dwNumBlocks / PERCENTAGE_OF_MEDIA_TO_RESERVE;

??????? if((dwReservedBlocks = g_FlashInfo.dwNumBlocks / PERCENTAGE_OF_MEDIA_TO_RESERVE) < MINIMUM_FLASH_BLOCKS_TO_RESERVE) {

??????????? dwReservedBlocks = MINIMUM_FLASH_BLOCKS_TO_RESERVE;

??????? }

??????? dwNumSectors = dwLastLogSector - dwStartSector + 1 - dwReservedBlocks * g_FlashInfo.wSectorsPerBlock;

??? }

??? if (!AreSectorsFree (dwStartSector,dwNumSectors)){

"fly:::::CreatePartition: sectors [0x%x,0x%x] requested are out of range or taken by another partition/r/n"),dwNumSectors));

??????? return INVALID_HANDLE_VALUE;

??? }

??? RETAILMSG(1,(TEXT("CreatePartition: Start = 0x%x,Num = 0x%x./r/n"),dwNumSectors));

??? AddPartitionTableEntry (dwPartIndex,(BYTE)dwPartType,(BYTE)dwBootInd);

??? if (dwBootInd & PART_IND_READ_ONLY) {

??????? if (!WriteLogicalNumbers (dwStartSector,TRUE)) {

??????????? RETAILMSG(1,(TEXT("CreatePartition: can't mark sector info./r/n")));

??? }

??? if (!WriteMBR())

??????? return INVALID_HANDLE_VALUE;

??? g_partStateTable[dwPartIndex].pPartEntry = (PPARTENTRY)(g_pbMBRSector + PARTTABLE_OFFSET +sizeof(PARTENTRY)*dwPartIndex);

??? g_partStateTable[dwPartIndex].dwDataPointer = 0;

??? return (HANDLE)&g_partStateTable[dwPartIndex];???????????

}

如果第二个参数为－1，则视为将余下的所有空间划为一个分区。LastLogSector();函数获得最后一个逻辑Sector。

static DWORD LastLogSector()

{

??? if (g_dwLastLogSector) {

?????? return g_dwLastLogSector;

??? }

??? DWORD dwMBRBlock = g_dwMBRSectorNum / g_FlashInfo.wSectorsPerBlock;

??? DWORD dwUnusableBlocks = dwMBRBlock;

??? for (DWORD i = dwMBRBlock; i < g_FlashInfo.dwNumBlocks; i++) {

??????? if (IS_BLOCK_UNUSABLE (i))

??????????? dwUnusableBlocks++;

??? }

??? g_dwLastLogSector = (g_FlashInfo.dwNumBlocks - dwUnusableBlocks) * g_FlashInfo.wSectorsPerBlock - 1;

??? RETAILMSG(1,(TEXT("fly:::LastLogSector: Last log sector is: 0x%x./r/n"),g_dwLastLogSector));

??? return g_dwLastLogSector;

}

即g_dwLastLogSector = (g_FlashInfo.dwNumBlocks - dwUnusableBlocks) * g_FlashInfo.wSectorsPerBlock - 1;//（NAND 的BLOCK总数 – MBR保存的那个BLOCK）* 每个BLOCK的Sector数 – 保存MBR的那个Sector。得到的就是从MBR那个Sector之后的所有Sector，即逻辑大小。

AreSectorsFree (dwStartSector,dwNumSectors)函数判断参数提供的起始Sector和个数有没有超出来NAND的界限，或者逻辑分区的界限。

重头戏开始了。通过AddPartitionTableEntry (dwPartIndex,(BYTE)dwBootInd); 准备分区信息写入分区表。

/*? AddPartitionTableEntry

*? Generates the partition entry for the partition table and copies the entry

*? into the MBR that is stored in memory.

*? ENTRY

*????? entry - index into partition table

*????? startSector - starting logical sector

*????? totalSectors - total logical sectors

*????? fileSystem - type of partition

*????? bootInd - byte in partition entry that stores various flags such as

*????????? active and read-only status.

static void AddPartitionTableEntry(DWORD entry,DWORD startSector,DWORD totalSectors,BYTE fileSystem,BYTE bootInd)

{

??? PARTENTRY partentry = {0};

??? Addr startAddr;

??? Addr endAddr;

??? ASSERT(entry < 4);

??? // no checking with disk info and start/total sectors because we allow

??? // bogus partitions for testing purposes

??? // initially known partition table entry

??? partentry.Part_BootInd = bootInd;

??? partentry.Part_FileSystem = fileSystem;

??? partentry.Part_StartSector = startSector;

??? partentry.Part_TotalSectors = totalSectors;

??? // logical block addresses for the first and final sector (start on the second head)

??? startAddr.type = LBA;

??? startAddr.lba = partentry.Part_StartSector;

??? endAddr.type = LBA;

??? endAddr.lba = partentry.Part_StartSector + partentry.Part_TotalSectors-1;

??? // translate the LBA addresses to CHS addresses

??? startAddr = LBAtoCHS(&g_FlashInfo,startAddr);

??? endAddr = LBAtoCHS(&g_FlashInfo,endAddr);

??? // starting address

??? partentry.Part_FirstTrack = (BYTE)(startAddr.chs.cylinder & 0xFF);

??? partentry.Part_FirstHead = (BYTE)(startAddr.chs.head & 0xFF);

??? // lower 6-bits == sector,upper 2-bits = cylinder upper 2-bits of 10-bit cylinder #

??? partentry.Part_FirstSector = (BYTE)((startAddr.chs.sector & 0x3F) | ((startAddr.chs.cylinder & 0x0300) >> 2));

??? // ending address:

??? partentry.Part_LastTrack = (BYTE)(endAddr.chs.cylinder & 0xFF);

??? partentry.Part_LastHead = (BYTE)(endAddr.chs.head & 0xFF);

??? // lower 6-bits == sector,upper 2-bits = cylinder upper 2-bits of 10-bit cylinder #

??? partentry.Part_LastSector = (BYTE)((endAddr.chs.sector & 0x3F) | ((endAddr.chs.cylinder & 0x0300) >> 2));

??? memcpy(g_pbMBRSector+PARTTABLE_OFFSET+(sizeof(PARTENTRY)*entry),&partentry,sizeof(PARTENTRY));

}

这里面的地址信息是一种叫CHS(Cyinder/Head/Sector)的地址。eboot中有将逻辑地址LBS(Logical Block Addr)与这种地址互相转换的函数LBAtoCHS,CHSToLBA。

Addr LBAtoCHS(FlashInfo *pFlashInfo,Addr lba)

{

??? Addr chs;

??? DWORD tmp = pFlashInfo->dwNumBlocks * pFlashInfo->wSectorsPerBlock;

??? chs.type = CHS;

??? chs.chs.cylinder = (WORD)(lba.lba / tmp);?????????????????????????????// ?ù??,ó|??ê???ê?

??? tmp = lba.lba % tmp;

??? chs.chs.head = (WORD)(tmp / pFlashInfo->wSectorsPerBlock);????????????// ?éμ??·

??? chs.chs.sector = (WORD)((tmp % pFlashInfo->wSectorsPerBlock) + 1);????// éè??+1

??? return chs;

}

Addr CHStoLBA(FlashInfo *pFlashInfo,Addr chs)

{

??? Addr lba;

??? lba.type = LBA;

??? lba.lba = ((chs.chs.cylinder * pFlashInfo->dwNumBlocks + chs.chs.head)

??????? * pFlashInfo->wSectorsPerBlock)+ chs.chs.sector - 1;

??? return lba;

}

如果分区的格式有只读属性，则通过WriteLogicalNumbers（）函数写分区的Sectorinfo，把这部分空间保护起来。

static BOOL WriteLogicalNumbers (DWORD dwStartSector,BOOL fReadOnly)

{

??? DWORD dwNumSectorsWritten = 0;

??? DWORD dwPhysSector = Log2Phys (dwStartSector);

??? DWORD dwBlockNum = dwPhysSector / g_FlashInfo.wSectorsPerBlock;

??? DWORD dwOffset = dwPhysSector % g_FlashInfo.wSectorsPerBlock;

??? while (dwNumSectorsWritten < dwNumSectors) {

??????? // If bad block,move to the next block

??????? if (IS_BLOCK_UNUSABLE (dwBlockNum)) {

??????????? dwBlockNum++;

??????????? continue;

??????? }

??????? memset (g_pbBlock,g_dwDataBytesPerBlock);

??????? memset (g_pSectorInfoBuf,sizeof(SectorInfo) * g_FlashInfo.wSectorsPerBlock);

??????? // No need to check return,since a failed read means data hasn't been written yet.

??????? ReadBlock (dwBlockNum,g_pSectorInfoBuf);

??????? if (!FMD_EraseBlock (dwBlockNum)) {

??????????? return FALSE;

??????? }

??????? DWORD dwSectorsToWrite = g_FlashInfo.wSectorsPerBlock - dwOffset;

??????? PSectorInfo pSectorInfo = g_pSectorInfoBuf + dwOffset;

??????? // If this is the last block,then calculate sectors to write if there isn't a full block to update

??????? if ((dwSectorsToWrite + dwNumSectorsWritten) > dwNumSectors)

??????????? dwSectorsToWrite = dwNumSectors - dwNumSectorsWritten;

??????? for (DWORD iSector = 0; iSector < dwSectorsToWrite; iSector++,pSectorInfo++,dwNumSectorsWritten++) {

??????????? // Assert read only by setting bit to 0 to prevent wear-leveling by FAL

??????????? if (fReadOnly)

??????????????? pSectorInfo->bOEMReserved &= ~OEM_BLOCK_READONLY;

??????????? // Set to write completed so FAL can map the sector

??????????? pSectorInfo->wReserved2 &= ~SECTOR_WRITE_COMPLETED;???????

??????????? // Write the logical sector number

??????????? pSectorInfo->dwReserved1 = dwStartSector + dwNumSectorsWritten;???????????

??????? }

??????? if (!WriteBlock (dwBlockNum,g_pSectorInfoBuf))

??????????? return FALSE;

??????? dwOffset = 0;

??????? dwBlockNum++;

}

这就是为什么系统启动后，我们无法写入文件的BINFS文件系统格式分区的原因了。而FAT格式就可以。最后调用WriteMBR()完全MBR的写入，分区完毕。

让我们继续回到BP_OpenPartition函数中，如果从一开始IsValidMBR()就检测到有效的MBR，GetPartitionTableIndex(dwPartType,&dwPartIndex);获得分区表。和dwPartIndex分区表的索引号。

static BOOL GetPartitionTableIndex (DWORD dwPartType,PDWORD pdwIndex)

{

??? PPARTENTRY pPartEntry = (PPARTENTRY)(g_pbMBRSector + PARTTABLE_OFFSET);

??? DWORD iEntry = 0;

??? for (iEntry = 0; iEntry < NUM_PARTS; iEntry++,pPartEntry++) {

??????? if ((pPartEntry->Part_FileSystem == dwPartType) && (((pPartEntry->Part_BootInd & PART_IND_ACTIVE) != 0) == fActive)) {

??????????? *pdwIndex = iEntry;

??????????? return TRUE;

??????? }

??????? if (!IsValidPart (pPartEntry)) {

??????????? *pdwIndex = iEntry;

??? }

??? return FALSE;

}

重要结构：PARTENTRY

// end of master boot record contains 4 partition entries

typedefstruct _PARTENTRY {

??????? BYTE??????????? Part_BootInd;?????????? // If 80h means this is boot partition

??????? BYTE??????????? Part_FirstHead;????????// Partition starting head based 0

??????? BYTE??????????? Part_FirstSector;?????? // Partition starting sector based 1

??????? BYTE??????????? Part_FirstTrack;???????// Partition starting track based 0

??????? BYTE??????????? Part_FileSystem;??????? // Partition type signature field

??????? BYTE??????????? Part_LastHead;?????????// Partition ending head based 0

??????? BYTE??????????? Part_LastSector;??????? // Partition ending sector based 1

??????? BYTE??????????? Part_LastTrack;????????// Partition ending track based 0

??????? DWORD?????????? Part_StartSector;?????? // Logical starting sector based 0

??????? DWORD?????????? Part_TotalSectors;?????// Total logical sectors in partition

} PARTENTRY;

分区表就是通过这个结构写入MBR，起始地址，分区大小，分区格式，对应结构写入MBR所在的Sector就可以了。在检测有效分区时static BOOL IsValidPart (PPARTENTRY pPartEntry)

{

??? return (pPartEntry->Part_FileSystem != 0xff) && (pPartEntry->Part_FileSystem != 0);

}

就是通过对分区表文件系统格式的判断了。

把NAND后面的空间，全部分为一个FAT格式的分区。

// create extended partition in whatever is left

hPartEx = BP_OpenPartition( (NK_START_BLOCK+1+BINFS_BLOCK) * PAGES_PER_BLOCK,

??????????????????????????? NEXT_FREE_LOC,?? // (1024 - (NK_START_BLOCK+1+SECTOR_TO_BLOCK_SIZE(FILE_TO_SECTOR_SIZE(dwBINFSPartLength)))) * PAGES_PER_BLOCK,

??????????????????????????? PART_DOS32,

??????????????????????????? TRUE,

??????????????????????????? PART_OPEN_ALWAYS);

if (hPartEx == INVALID_HANDLE_VALUE )

{

??? EdbgOutputDebugString("*** WARN: StoreImageToBootMedia: Failed to open/create Extended partition ***/r/n");

}

引用通告

此日志的引用通告 URL 是：

http://giwawe.spaces.live.com/blog/cns!92AFEF096943066B!260.trak

引用此项的网络日志

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wince NandFlash分区实现 MBR创建过程

NandFlash的分区实现

提到分区就需要知道MBR，了解分区表。

什么是MBR

一个扇区的硬盘主引导记录MBR由如图6-15所示的4个部分组成。

Master Boot Record

主引导程序

主引导

程序

01BE-01CD

分区项1（16字节）

分区表

01CE-01DD

分区项2（16字节）

01DE-01ED

分区项3（16字节）

01EE-01FD

分区项4（16字节）

01FE

55

01FF

AA

???????????????????????????? 图6-15 MBR的组成结构图

本分区的起始磁头号、扇区号、柱面号。其中：

磁头号——第2字节；

扇区号——第3字节的低6位；

柱面号——为第3字节高2位+第4字节8位。

分区类型符:

00H——表示该分区未用（即没有指定）；

06H——FAT16基本分区；

0BH——FAT32基本分区；

05H——扩展分区；

07H——NTFS分区；

0FH——（LBA模式）扩展分区（83H为Linux分区等）。

本分区的结束磁头号、扇区号、柱面号，其中：

磁头号——第6字节；

扇区号——第7字节的低6位；

柱面号——第7字节的高2位+第8字节。

主要函数。

在把SDRAM中的NK烧写到NAND中去之前，先创建一个BINFS分区。

hPart = BP_OpenPartition( (NK_START_BLOCK+1)*PAGES_PER_BLOCK,? // next block of MBR???? BINFS_BLOCK*PAGES_PER_BLOCK,//SECTOR_TO_BLOCK_SIZE(FILE_TO_SECTOR_SIZE(dwBINFSPartLength))*PAGES_PER_BLOCK,? //align to block

????????????????????????????? PART_BINFS,

????????????????????????????? TRUE,

????????????????????????????? PART_OPEN_ALWAYS);

第一个参数分区的起始sector 为(NK_START_BLOCK+1)*PAGES_PER_BLOCK，

第二个参数分区的结束 sector为BINFS_BLOCK*PAGES_PER_BLOCK，

第三个参数分区的格式为PART_BINFS，即BINFS格式，

第四个参数指示该分区为活动分区，fActive = TURE，

第五个参数PART_OPEN_ALWAYS指示如果分区不存在就创建该分区，存在就OPEN该分区，返回分区句柄。

进入函数，首先做的事就是检测MBR的有效性。通过函数IsValidMBR（）实现。

IsValidMBR()实现的第一行就是给全局变量g_dwMBRSectorNum 赋值，显而易见，g_dwMBRSectorNum就是指示保存MBR的那个Sector了。

g_dwMBRSectorNum = GetMBRSectorNum();?? //是获得保存MBR的那个Sector

这里dwBlockNum直接给了个3，因为NBOOT，TOC，EBOOT已经把前三个BLOCK用了。所以MBR的选择直接排除了前三个BLOCK了。

#define IS_BLOCK_UNUSABLE(blockID) ((FMD_GetBlockStatus (blockID) & (BLOCK_STATUS_BAD|BLOCK_STATUS_RESERVED)) > 0)

然后确定BLOCK是否可使用的BLOCK，最后通si.dwReserved1 == 0来判断是不是选择这个Sector来保存MBR。

IsValidMBR（）中还有一个重要的结构就是g_pbMBRSector数组，它就是MBR了。

函数返回时，MBR必须符合下列记录。

???

return ((g_pbMBRSector[0] == 0xE9) &&

???????? (g_pbMBRSector[1] == 0xfd) &&

???????? (g_pbMBRSector[2] == 0xff) &&

???????? (g_pbMBRSector[SECTOR_SIZE_FS-2] == 0x55) &&

???????? (g_pbMBRSector[SECTOR_SIZE_FS-1] == 0xAA));

可以看到只有开始三个字节为0XE9,FD,FF，当然，还有熟悉的结束标志符0X55AA。

如果没有检测到MBR，则先对NANDFLASH进行低级格式化。BP_LowLevelFormat (SECTOR_TO_BLOCK(dwStartSector),dwFlags);再创建分区，CreatePartition (dwStartSector,dwPartIndex);。

当然。因为还没有进行分区，这里写入的MBR分区表部分是空的。

在WriteMBR()函数中，就写入了判断MBR 的一些标志到BLOCK，??? g_pSectorInfoBuf->bOEMReserved &= ~OEM_BLOCK_READONLY;

??? g_pSectorInfoBuf->wReserved2 &= ~SECTOR_WRITE_COMPLETED;

??? g_pSectorInfoBuf->dwReserved1 = 0;

如果第二个参数为－1，则视为将余下的所有空间划为一个分区。LastLogSector();函数获得最后一个逻辑Sector。

即g_dwLastLogSector = (g_FlashInfo.dwNumBlocks - dwUnusableBlocks) * g_FlashInfo.wSectorsPerBlock - 1;//（NAND 的BLOCK总数 – MBR保存的那个BLOCK）* 每个BLOCK的Sector数 – 保存MBR的那个Sector。得到的就是从MBR那个Sector之后的所有Sector，即逻辑大小。

AreSectorsFree (dwStartSector,dwNumSectors)函数判断参数提供的起始Sector和个数有没有超出来NAND的界限，或者逻辑分区的界限。

重头戏开始了。通过AddPartitionTableEntry (dwPartIndex,(BYTE)dwBootInd); 准备分区信息写入分区表。

这里面的地址信息是一种叫CHS(Cyinder/Head/Sector)的地址。eboot中有将逻辑地址LBS(Logical Block Addr)与这种地址互相转换的函数LBAtoCHS,CHSToLBA。

如果分区的格式有只读属性，则通过WriteLogicalNumbers（）函数写分区的Sectorinfo，把这部分空间保护起来。

这就是为什么系统启动后，我们无法写入文件的BINFS文件系统格式分区的原因了。而FAT格式就可以。最后调用WriteMBR()完全MBR的写入，分区完毕。

让我们继续回到BP_OpenPartition函数中，如果从一开始IsValidMBR()就检测到有效的MBR，GetPartitionTableIndex(dwPartType,&dwPartIndex);获得分区表。和dwPartIndex分区表的索引号。

重要结构：PARTENTRY

分区表就是通过这个结构写入MBR，起始地址，分区大小，分区格式，对应结构写入MBR所在的Sector就可以了。在检测有效分区时static BOOL IsValidPart (PPARTENTRY pPartEntry)

{

hPart = BP_OpenPartition( (NK_START_BLOCK+1)PAGES_PER_BLOCK,? // next block of MBR???? BINFS_BLOCKPAGES_PER_BLOCK,//SECTOR_TO_BLOCK_SIZE(FILE_TO_SECTOR_SIZE(dwBINFSPartLength))*PAGES_PER_BLOCK,? //align to block