提到分区就不得不提到MBR，不得不提到分区表。
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。
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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。
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
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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。
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主要函数。
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HANDLE BP_OpenPartition(DWORD dwStartSector,DWORD dwNumSectors,DWORD dwPartType,BOOL fActive,DWORD dwCreationFlags)
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注：示例代码为本人EBOOT中分区实现源码（WINCE5.0+S3C2440+128MNAND,MBR写在第4个BLOCK，分一个BINFS格式分区和一个FAT格式分区）。
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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_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。
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HANDLE BP_OpenPartition(DWORD dwStartSector,DWORD dwCreationFlags)
{
??????? DWORD dwPartIndex;
??????? BOOL fExists;
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??????? 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"),dwPartType));
??????????????? 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);???????
??????? }
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??????? RETAILMSG(1,(TEXT("OpenPartition: Partition Exists=0x%x for part 0x%x./r/n"),fExists,dwPartType));
??????? 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 {
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??????????? // 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;
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??????????? // Create new partition
??????????? return CreatePartition (dwStartSector,dwPartIndex);
??????? }
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??????? 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();???????
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??? RETAILMSG (1,(TEXT("IsValidMBR: MBR sector = 0x%x/r/n"),g_dwMBRSectorNum));
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??? 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) {
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??????? if (!IS_BLOCK_UNUSABLE (dwBlockNum)) {
??????????? dwSector = dwBlockNum * g_FlashInfo.wSectorsPerBlock;
???????????
??????????? if (!FMD_ReadSector (dwSector,&si,1)) {
??????????????? 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;
??????????? }
??????? }
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??????? dwBlockNum++;
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??? }
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??? 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。
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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);。
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BOOL BP_LowLevelFormat(DWORD dwStartBlock,DWORD dwNumBlocks,DWORD dwFlags)
{
??? dwNumBlocks = min (dwNumBlocks,g_FlashInfo.dwNumBlocks);
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??? RETAILMSG(1,(TEXT("fly::Enter LowLevelFormat [0x%x,0x%x]./r/n"),dwStartBlock,dwNumBlocks));// dwStartBlock + dwNumBlocks - 1));
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??? // Erase all the flash blocks.
??? if (!EraseBlocks(dwStartBlock,dwNumBlocks,dwFlags))
??????? return(FALSE);
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??? // Determine first good starting block
??? while (IS_BLOCK_UNUSABLE (dwStartBlock) && dwStartBlock < g_FlashInfo.dwNumBlocks) {
??????? dwStartBlock++;
??? }
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??? if (dwStartBlock >= g_FlashInfo.dwNumBlocks) {
??????? RETAILMSG(1,(TEXT("BP_LowLevelFormat: no good blocks/r/n")));???????
??????? return FALSE;
??? }
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??? // MBR goes in the first sector of the starting block.? This will be logical sector 0.
??? g_dwMBRSectorNum = dwStartBlock * g_FlashInfo.wSectorsPerBlock;
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??? RETAILMSG(1,(TEXT("fly:g_dwMBRSectorNum=%d/r/n"),g_dwMBRSectorNum));
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??? // 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.
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??? 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;
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??? // Zero out partition table so that mspart treats entries as empty.
??? memset (g_pbMBRSector+PARTTABLE_OFFSET,sizeof(PARTENTRY) * NUM_PARTS);
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??? return WriteMBR();
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}? 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;
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??? //dwMBRBlockNum = 1 ;
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??? RETAILMSG(1,(TEXT("WriteMBR: MBR block = 0x%x,g_dwMBRSectorNum = 0x%x./r/n"),dwMBRBlockNum,g_dwMBRSectorNum));
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??? 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);
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??? if (!FMD_EraseBlock (dwMBRBlockNum)) {
??????? RETAILMSG (1,(TEXT("CreatePartition: error erasing block 0x%x/r/n"),dwMBRBlockNum));
??????? return FALSE;
??? }
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??? 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;
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??? RETAILMSG(1,(TEXT("fly::WriteMBR: MBR block = 0x%x./r/n"),dwMBRBlockNum));
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??? if (!WriteBlock (dwMBRBlockNum,g_pSectorInfoBuf)) {
??????? RETAILMSG (1,(TEXT("CreatePartition: could not write to block 0x%x/r/n"),dwMBRBlockNum));
??????? return FALSE;
??? }
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??? 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。
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static HANDLE CreatePartition (DWORD dwStartSector,DWORD dwPartIndex)
{
??? DWORD dwBootInd = 0;
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??? RETAILMSG(1,(TEXT("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;???
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???? // 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;
??????? }
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??????? // Start extended partition on a block boundary
??????? if ((dwPartType == PART_EXTENDED) && (dwStartSector % g_FlashInfo.wSectorsPerBlock)) {
??????????? dwStartSector = (dwStartSector / g_FlashInfo.wSectorsPerBlock + 1) * g_FlashInfo.wSectorsPerBlock;
??????? }
??? }
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??? // If num sectors is invalid,fill the rest of the space up
??? if (dwNumSectors == USE_REMAINING_SPACE) {
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??????? DWORD dwLastLogSector = LastLogSector();
??????? if (dwLastLogSector == INVALID_ADDR)
??????????? return INVALID_HANDLE_VALUE;
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??????? // 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)){
??????? RETAILMSG (1,(TEXT("fly:::::CreatePartition: sectors [0x%x,0x%x] requested are out of range or taken by another partition/r/n"),dwNumSectors));
??????? return INVALID_HANDLE_VALUE;
??? }
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??? RETAILMSG(1,(TEXT("CreatePartition: Start = 0x%x,Num = 0x%x./r/n"),dwNumSectors));
???
??? AddPartitionTableEntry (dwPartIndex,(BYTE)dwPartType,(BYTE)dwBootInd);
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??? if (dwBootInd & PART_IND_READ_ONLY) {
??????? if (!WriteLogicalNumbers (dwStartSector,TRUE)) {
??????????? RETAILMSG(1,(TEXT("CreatePartition: can't mark sector info./r/n")));
??????????? return INVALID_HANDLE_VALUE;
??????? }
??? }
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??? if (!WriteMBR())
??????? return INVALID_HANDLE_VALUE;
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??? g_partStateTable[dwPartIndex].pPartEntry = (PPARTENTRY)(g_pbMBRSector + PARTTABLE_OFFSET + sizeof(PARTENTRY)*dwPartIndex);
??? g_partStateTable[dwPartIndex].dwDataPointer = 0;
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??? 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;
??? }
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??? DWORD dwMBRBlock = g_dwMBRSectorNum / g_FlashInfo.wSectorsPerBlock;
??? DWORD dwUnusableBlocks = dwMBRBlock;
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??? 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;
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??? 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。
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static void AddPartitionTableEntry(DWORD entry,DWORD startSector,DWORD totalSectors,BYTE fileSystem,BYTE bootInd)
{
??? PARTENTRY partentry = {0};
??? Addr startAddr;
??? Addr endAddr;
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??? ASSERT(entry < 4);
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??? // no checking with disk info and start/total sectors because we allow
??? // bogus partitions for testing purposes
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??? // initially known partition table entry
??? partentry.Part_BootInd = bootInd;
??? partentry.Part_FileSystem = fileSystem;
??? partentry.Part_StartSector = startSector;
??? partentry.Part_TotalSectors = totalSectors;
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??? // 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;
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??? // translate the LBA addresses to CHS addresses
??? startAddr = LBAtoCHS(&g_FlashInfo,startAddr);
??? endAddr = LBAtoCHS(&g_FlashInfo,endAddr);
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??? // 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));
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??? // 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));
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??? 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);????????????????????????????????????? // 柱面,应该始终是0
??? tmp = lba.lba % tmp;
??? chs.chs.head = (WORD)(tmp / pFlashInfo->wSectorsPerBlock);???????????????????? // 块地址
??? chs.chs.sector = (WORD)((tmp % pFlashInfo->wSectorsPerBlock) + 1);???? // 扇区+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;
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??? 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;
??????? }
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??????? 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++;
??? }
??? return TRUE;
}
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;
??????? }
??? }
?
??? return FALSE;
}
?
重要结构：PARTENTRY
// end of master boot record contains 4 partition entries
typedef struct _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");
??? }
?
本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/hugohong/archive/2009/05/20/4204700.aspx
