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。
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。
/* 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)
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 ）。
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。
HANDLE BP_OpenPartition(DWORD dwStartSector, DWORD dwNumSectors, DWORD dwPartType, BOOL fActive, 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"), 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);
}
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, dwNumSectors, dwPartType, fActive, 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, dwNumSectors, dwPartType, fActive, 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, NULL, &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;
}
}
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), SECTOR_TO_BLOCK(dwNumSectors), dwFlags); 再创建分区，CreatePartition (dwStartSector, dwNumSectors, dwPartType, fActive, 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;
RETAILMSG(1,(TEXT("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, dwNumBlocks, 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, 0, 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,g_dwMBRSectorNum));
memset (g_pbBlock, 0xff, g_dwDataBytesPerBlock);
memset (g_pSectorInfoBuf, 0xff, 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));
return FALSE;
}
memcpy (g_pbBlock + (g_dwMBRSectorNum % g_FlashInfo.wSectorsPerBlock) * g_FlashInfo.wDataBytesPerSector, g_pbMBRSector, g_FlashInfo.wDataBytesPerSector);
g_pSectorInfoBuf->bOEMReserved &= ~OEM_BLOCK_READONLY;
g_pSectorInfoBuf->wReserved2 &= ~SECTOR_WRITE_COMPLETED;
g_pSectorInfoBuf->dwReserved1 = 0;
RETAILMSG(1, (TEXT("fly::WriteMBR: MBR block = 0x%x./r/n"), dwMBRBlockNum));
if (!WriteBlock (dwMBRBlockNum, g_pbBlock, 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 dwNumSectors, DWORD dwPartType, BOOL fActive, DWORD dwPartIndex)
{
DWORD dwBootInd = 0;
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;
// 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)){
RETAILMSG (1, (TEXT("fly:::::CreatePartition: sectors [0x%x, 0x%x] requested are out of range or taken by another partition/r/n"), dwStartSector, dwNumSectors));
return INVALID_HANDLE_VALUE;
}
RETAILMSG(1, (TEXT("CreatePartition: Start = 0x%x, Num = 0x%x./r/n"), dwStartSector, dwNumSectors));
AddPartitionTableEntry (dwPartIndex, dwStartSector, dwNumSectors, (BYTE)dwPartType, (BYTE)dwBootInd);
if (dwBootInd & PART_IND_READ_ONLY) {
if (!WriteLogicalNumbers (dwStartSector, dwNumSectors, TRUE)) {
RETAILMSG(1, (TEXT("CreatePartition: can't mark sector info./r/n")));
return INVALID_HANDLE_VALUE;
}
}
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, dwStartSector, dwNumSectors, (BYTE)dwPartType, (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.
*
* EXIT
*/
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); // 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, DWORD dwNumSectors, 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, 0xff, g_dwDataBytesPerBlock);
memset (g_pSectorInfoBuf, 0xff, sizeof(SectorInfo) * g_FlashInfo.wSectorsPerBlock);
// No need to check return, since a failed read means data hasn't been written yet.
ReadBlock (dwBlockNum, g_pbBlock, 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_pbBlock, 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, fActive, &dwPartIndex); 获得分区表。和dwPartIndex 分区表的索引号。
static BOOL GetPartitionTableIndex (DWORD dwPartType, BOOL fActive, 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/wu_ye_zhou/archive/2010/06/12/5667136.aspx