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Eboot 中给nandflash分区实现

發布時間：2025/4/16 编程问答 45 豆豆

生活随笔收集整理的這篇文章主要介紹了 Eboot 中给nandflash分区实现小編覺得挺不錯的,現在分享給大家,幫大家做個參考.

提到分區就不得不提到MBR，不得不提到分區表。

什么是MBR

硬盤的0柱面、0磁頭、1扇區稱為主引導扇區，NANDFLASH由BLOCK和Sector組成，所以NANDFLASH的第0 BLOCK，第1 Sector為主引導扇區，FDISK程序寫到該扇區的內容稱為主引導記錄（MBR）。該記錄占用512個字節，它用于硬盤啟動時將系統控制權交給用戶指定的，并在分區表中登記了的某個操作系統區。

MBR的組成
一個扇區的硬盤主引導記錄MBR由如圖6-15所示的4個部分組成。
·主引導程序（偏移地址0000H--0088H），它負責從活動分區中裝載，并運行系統引導程序。
·出錯信息數據區，偏移地址0089H--00E1H為出錯信息，00E2H--01BDH全為0字節。
·分區表（DPT,Disk Partition Table）含4個分區項，偏移地址01BEH--01FDH,每個分區表項長16個字節，共64字節為分區項1、分區項2、分區項3、分區項4。
·結束標志字，偏移地址01FE--01FF的2個字節值為結束標志55AA,如果該標志錯誤系統就不能啟動。

圖6-15 MBR的組成結構圖

MBR中的分區信息結構

??? 占用512個字節的MBR中，偏移地址01BEH--01FDH的64個字節，為4個分區項內容（分區信息表）。它是由磁盤介質類型及用戶在使用 FDISK定義分區說確定的。在實際應用中，FDISK對一個磁盤劃分的主分區可少于4個，但最多不超過4個。每個分區表的項目是16個字節，其內容含義如表6-19所示。
表6-19 分區項表（16字節）內容及含義

EBOOT中對NAND分區主要代碼，eboot目錄下的fmd.cpp文件，與NAND驅動基本相同，所以，要對NAND進行分區，就得對NAND驅動非常熟悉。透徹了解。然后就是
E:/WINCE500/PUBLIC/COMMON/OAK/DRIVERS/ETHDBG/BOOTPART/bootpart.cpp文件了。該文件主要通過調用NANDFLASH的讀寫操作來寫入MBR，也是今天主要的分析對象。

主要函數。

/*? 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：示例代碼為本人EBOOT中分區實現源碼（WINCE5.0+S3C2440+128MNAND,MBR寫在第4個BLOCK，分一個BINFS格式分區和一個FAT格式分區）。

BOOL WriteRegionsToBootMedia(DWORD dwImageStart, DWORD dwImageLength, DWORD dwLaunchAddr)

在把SDRAM中的NK燒寫到NAND中去之前，先創建一個BINFS分區。

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);

第一個參數分區的起始sector 為(NK_START_BLOCK+1)*PAGES_PER_BLOCK，

第二個參數分區的結束 sector為BINFS_BLOCK*PAGES_PER_BLOCK，

第三個參數分區的格式為PART_BINFS，即BINFS格式，

第四個參數指示該分區為活動分區，fActive = TURE，

第五個參數PART_OPEN_ALWAYS指示如果分區不存在就創建該分區，存在就OPEN該分區，返回分區句柄。

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;

???????

}

進入函數，首先做的事就是檢測MBR的有效性。通過函數IsValidMBR（）實現。

檢測MBR的有效性，首先要知道MBR保存在哪里，前面說過NANDFLASH的第0 BLOCK，第1 Sector為主引導扇區，也就是MBR，但是NAND如果被當作啟動芯片，○地址一般被BOOTLOADER代碼占據，MBR只有放在后面的BLOCK中。所以我把第0 個BLOCK放NBOOT，第1個BLOCK放TOC，第2個BLOCK放EBOOT，第3個BLOCK保留，第4個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()實現的第一行就是給全局變量g_dwMBRSectorNum 賦值，顯而易見，g_dwMBRSectorNum就是指示保存MBR的那個Sector了。

g_dwMBRSectorNum = GetMBRSectorNum();?? //是獲得保存MBR的那個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;

}

這里dwBlockNum直接給了個3，因為NBOOT，TOC，EBOOT已經把前三個BLOCK用了。所以MBR的選擇直接排除了前三個BLOCK了。

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

然后確定BLOCK是否可使用的BLOCK，最后通si.dwReserved1 == 0來判斷是不是選擇這個Sector來保存MBR。

IsValidMBR（）中還有一個重要的結構就是g_pbMBRSector數組，它就是MBR了。

函數返回時，MBR必須符合下列記錄。

??? 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));

可以看到只有開始三個字節為0XE9,FD,FF，當然，還有熟悉的結束標志符0X55AA。

如果沒有檢測到MBR，則先對NANDFLASH進行低級格式化。BP_LowLevelFormat (SECTOR_TO_BLOCK(dwStartSector), SECTOR_TO_BLOCK(dwNumSectors), dwFlags);再創建分區，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);

}

在對NANDFLASH進行低格時，主要對壞塊的處理。if (!EraseBlocks(dwStartBlock, dwNumBlocks, dwFlags))檢測每一個Sector，每個BLOCK只要有一個Sector不能讀寫這個塊都會被處理成壞塊，這樣才能保證系統的穩定性。在函數的最后調用了??? CreateMBR();來創建一個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();

}? 當然。因為還沒有進行分區，這里寫入的MBR分區表部分是空的。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()函數中，就寫入了判斷MBR 的一些標志到BLOCK，??? g_pSectorInfoBuf->bOEMReserved &= ~OEM_BLOCK_READONLY;

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

??? g_pSectorInfoBuf->dwReserved1 = 0;

Wince系統啟動時，具體是NANDFLASH驅動加載成功后，MOUNT文件系統到NANDFLASH之前，也會通過讀取這些SectorInfo來得到MBR 保存的BLOCK，進而讀取MBR，獲得分區信息，從而把各分區MOUNT到相應文件系統。格式化完成，MBR也寫入成功后就可以開始新建分區了。

/*? 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];???????????

}

如果第二個參數為－1，則視為將余下的所有空間劃為一個分區。LastLogSector();函數獲得最后一個邏輯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總數 – MBR保存的那個BLOCK）* 每個BLOCK的Sector數 – 保存MBR的那個Sector。得到的就是從MBR那個Sector之后的所有Sector，即邏輯大小。

AreSectorsFree (dwStartSector, dwNumSectors)函數判斷參數提供的起始Sector和個數有沒有超出來NAND的界限，或者邏輯分區的界限。???

重頭戲開始了。通過AddPartitionTableEntry (dwPartIndex, dwStartSector, dwNumSectors, (BYTE)dwPartType, (BYTE)dwBootInd); 準備分區信息寫入分區表。

/*? 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));

}

這里面的地址信息是一種叫CHS(Cyinder/Head/Sector)的地址。eboot中有將邏輯地址LBS(Logical Block Addr)與這種地址互相轉換的函數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,應該始終是0
??? tmp = lba.lba % tmp;
??? chs.chs.head = (WORD)(tmp / pFlashInfo->wSectorsPerBlock);???????????????????? // 塊地址
??? chs.chs.sector = (WORD)((tmp % pFlashInfo->wSectorsPerBlock) + 1);???? // 扇區+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;
}

如果分區的格式有只讀屬性，則通過WriteLogicalNumbers（）函數寫分區的Sectorinfo，把這部分空間保護起來。

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;

}

這就是為什么系統啟動后，我們無法寫入文件的BINFS文件系統格式分區的原因了。而FAT格式就可以。最后調用WriteMBR()完全MBR的寫入，分區完畢。

讓我們繼續回到BP_OpenPartition函數中，如果從一開始IsValidMBR()就檢測到有效的MBR，GetPartitionTableIndex(dwPartType, fActive, &dwPartIndex);獲得分區表。和dwPartIndex分區表的索引號。

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;

}

重要結構：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;

分區表就是通過這個結構寫入MBR，起始地址，分區大小，分區格式，對應結構寫入MBR所在的Sector就可以了。在檢測有效分區時static BOOL IsValidPart (PPARTENTRY pPartEntry)

{

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

}

就是通過對分區表文件系統格式的判斷了。

把NAND后面的空間，全部分為一個FAT格式的分區。

??? //

??? // 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");

??? }

本文來自CSDN博客，轉載請標明出處：http://blog.csdn.net/hugohong/archive/2009/05/20/4204700.aspx

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