wince NandFlash分区实现 MBR创建过程

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

1. /*  BP_OpenPartition
2. *
3. *  Opens/creates a partition depending on the creation flags.  If it is opening
4. *  and the partition has already been opened, then it returns a handle to the
5. *  opened partition.  Otherwise, it loads the state information of that partition
6. *  into memory and returns a handle.
7. *
8. *  ENTRY
9. *      dwStartSector - Logical sector to start the partition.  NEXT_FREE_LOC if none
10. *          specified.  Ignored if opening existing partition.
11. *      dwNumSectors - Number of logical sectors of the partition.  USE_REMAINING_SPACE
12. *          to indicate to take up the rest of the space on the flash for that partition (should
13. *          only be used when creating extended partitions).  This parameter is ignored
14. *          if opening existing partition.
15. *      dwPartType - Type of partition to create/open.
16. *      fActive - TRUE indicates to create/open the active partition.  FALSE for
17. *          inactive.
18. *      dwCreationFlags - PART_CREATE_NEW to create only.  Fail if it already
19. *          exists.  PART_OPEN_EXISTING to open only.  Fail if it doesn't exist.
20. *          PART_OPEN_ALWAYS creates if it does not exist and opens if it
21. *          does exist.
22. *
23. *  EXIT
24. *      Handle to the partition on success.  INVALID_HANDLE_VALUE on error.
25. */
26.  
27. HANDLE BP_OpenPartition(DWORD dwStartSector, DWORD dwNumSectors, DWORD dwPartType, BOOL fActive, DWORD dwCreationFlags)
28. //£¨×¢£ºÊ¾Àý´úÂëΪ±¾ÈË/uc1EBOOTÖзÖÇøʵÏÖÔ´Â루/uc1WINCE5.0+S3C2440+128MNAND,MBRдÔÚµÚ¸ö/uc1BLOCK£¬·ÖÒ»¸ö/uc1BINFS¸ñʽ·ÖÇøºÍÒ»¸ö/uc1FAT¸ñʽ·ÖÇø£©¡££©
29. 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。

Code Snippet

1. HANDLE BP_OpenPartition(DWORD dwStartSector, DWORD dwNumSectors, DWORD dwPartType, BOOL fActive, DWORD dwCreationFlags)
2. {
3.         DWORD dwPartIndex;
4.         BOOL fExists;
5.         ASSERT (g_pbMBRSector);
6.         if (!IsValidMBR()) {
7.             DWORD dwFlags = 0;
8.             //fly
9.              RETAILMSG(1, (TEXT("BP_OpenPartition:: dwStartSector=0x%x ,dwNumSectors= 0x%x.,dwPartType = 0x%x/r/n"), dwStartSector, dwNumSectors,dwPartType));
10.             if (dwCreationFlags == PART_OPEN_EXISTING) {
11.                 RETAILMSG(1, (TEXT("OpenPartition: Invalid MBR.  Cannot open existing partition 0x%x./r/n"), dwPartType));
12.                return INVALID_HANDLE_VALUE;
13.             }
14.             RETAILMSG(1, (TEXT("OpenPartition: Invalid MBR.  Formatting flash./r/n")));
15.             if (g_FlashInfo.flashType == NOR) {
16.                 dwFlags |= FORMAT_SKIP_BLOCK_CHECK;
17.             }
18.             //fly
19.             RETAILMSG(1, (TEXT("BP_LowLevelFormat: g_pbMBRSector=0x%x, g_dwMBRSectorNum= 0x%x./r/n"), *g_pbMBRSector, g_dwMBRSectorNum));
20.             BP_LowLevelFormat (SECTOR_TO_BLOCK(dwStartSector), SECTOR_TO_BLOCK(dwNumSectors), dwFlags);
21.             dwPartIndex = 0;
22.             fExists = FALSE;
23.         }
24.         else {
25.             fExists = GetPartitionTableIndex(dwPartType, fActive, &dwPartIndex);       
26.         }
27.         RETAILMSG(1, (TEXT("OpenPartition: Partition Exists=0x%x for part 0x%x./r/n"), fExists, dwPartType));
28.         if (fExists) {
29.             // Partition was found.
30.             if (dwCreationFlags == PART_CREATE_NEW)
31.                 return INVALID_HANDLE_VALUE;
32.             if (g_partStateTable[dwPartIndex].pPartEntry == NULL) {
33.                 // Open partition.  If this is the boot section partition, then file pointer starts after MBR
34.                 g_partStateTable[dwPartIndex].pPartEntry = (PPARTENTRY)(g_pbMBRSector + PARTTABLE_OFFSET +sizeof(PARTENTRY)*dwPartIndex);
35.                 g_partStateTable[dwPartIndex].dwDataPointer = 0;
36.             }
37.            if ( dwNumSectors > g_partStateTable[dwPartIndex].pPartEntry->Part_TotalSectors )
38.              return CreatePartition (dwStartSector, dwNumSectors, dwPartType, fActive, dwPartIndex);
39.            else         
40.                   return (HANDLE)&g_partStateTable[dwPartIndex];           
41.         }
42.         else {
43.             // If there are already 4 partitions, or creation flag specified OPEN_EXISTING, fail.
44.             if ((dwPartIndex == NUM_PARTS) || (dwCreationFlags == PART_OPEN_EXISTING))
45.                 return INVALID_HANDLE_VALUE;
46.             // Create new partition
47.             return CreatePartition (dwStartSector, dwNumSectors, dwPartType, fActive, dwPartIndex);
48.         }
49.         return INVALID_HANDLE_VALUE;
50. }

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。

Code Snippet

1. static BOOL IsValidMBR()
2. {
3.     // Check to see if the MBR is valid
4.     // MBR block is always located at logical sector 0
5.     g_dwMBRSectorNum = GetMBRSectorNum();       
6.     RETAILMSG (1, (TEXT("IsValidMBR: MBR sector = 0x%x/r/n"), g_dwMBRSectorNum));
7.     if ((g_dwMBRSectorNum == INVALID_ADDR) || !FMD_ReadSector (g_dwMBRSectorNum, g_pbMBRSector, NULL, 1)) {
8.        RETAILMSG (1, (TEXT("IsValidMBR-----return FALSE-------------------/r/n")));
9.         return FALSE;
10.     }   
11.     return ((g_pbMBRSector[0] == 0xE9) &&
12.          (g_pbMBRSector[1] == 0xfd) &&
13.          (g_pbMBRSector[2] == 0xff) &&
14.          (g_pbMBRSector[SECTOR_SIZE_FS-2] == 0x55) &&
15.          (g_pbMBRSector[SECTOR_SIZE_FS-1] == 0xAA));
16. }

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

Code Snippet

1. static DWORD GetMBRSectorNum ()
2. {
3.     DWORD dwBlockNum = 3, dwSector = 0;
4.     SectorInfo si;
5.     
6.     while (dwBlockNum < g_FlashInfo.dwNumBlocks) {
7.         if (!IS_BLOCK_UNUSABLE (dwBlockNum)) {
8.             dwSector = dwBlockNum * g_FlashInfo.wSectorsPerBlock;
9.             if (!FMD_ReadSector (dwSector, NULL, &si, 1)) {
10.                 RETAILMSG(1, (TEXT("GetMBRSectorNum: Could not read sector 0x%x./r/n"), dwSector));
11.                 return INVALID_ADDR;
12.             }
13.             // Check to see if logical sector number is 0
14.             if (si.dwReserved1 == 0) {
15.               //RETAILMSG(1,(TEXT("dwBlockNum=%d/r/n"),dwBlockNum));
16.                return dwSector;
17.             }
18.         }
19.         dwBlockNum++;
20.     }
21.     return INVALID_ADDR;
22. }

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);。

Code Snippet

1. BOOL BP_LowLevelFormat(DWORD dwStartBlock, DWORD dwNumBlocks, DWORD dwFlags)
2. {
3.     dwNumBlocks = min (dwNumBlocks, g_FlashInfo.dwNumBlocks);
4.     RETAILMSG(1,(TEXT("fly::Enter LowLevelFormat [0x%x, 0x%x]./r/n"), dwStartBlock,dwNumBlocks));// dwStartBlock + dwNumBlocks - 1));
5.     // Erase all the flash blocks.
6.     if (!EraseBlocks(dwStartBlock, dwNumBlocks, dwFlags))
7.         return(FALSE);
8.     // Determine first good starting block
9.     while (IS_BLOCK_UNUSABLE (dwStartBlock) && dwStartBlock < g_FlashInfo.dwNumBlocks) {
10.         dwStartBlock++;
11.     }
12.     if (dwStartBlock >= g_FlashInfo.dwNumBlocks) {
13.         RETAILMSG(1,(TEXT("BP_LowLevelFormat: no good blocks/r/n")));       
14.         return FALSE;
15.     }
16.     // MBR goes in the first sector of the starting block.  This will be logical sector 0.
17.     g_dwMBRSectorNum = dwStartBlock * g_FlashInfo.wSectorsPerBlock;
18.     RETAILMSG(1,(TEXT("fly:g_dwMBRSectorNum=%d/r/n"),g_dwMBRSectorNum));
19.     // Create an MBR.
20.     CreateMBR();
21.     return(TRUE);
22. }

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。

Code Snippet

1. static BOOL CreateMBR()
2. {
3.     // This, plus a valid partition table, is all the CE partition manager needs to recognize
4.     // the MBR as valid. It does not contain boot code.
5.     memset (g_pbMBRSector, 0xff, g_FlashInfo.wDataBytesPerSector);
6.     g_pbMBRSector[0] = 0xE9;
7.     g_pbMBRSector[1] = 0xfd;
8.     g_pbMBRSector[2] = 0xff;
9.     g_pbMBRSector[SECTOR_SIZE_FS-2] = 0x55;
10.     g_pbMBRSector[SECTOR_SIZE_FS-1] = 0xAA;
11.     // Zero out partition table so that mspart treats entries as empty.
12.     memset (g_pbMBRSector+PARTTABLE_OFFSET, 0,sizeof(PARTENTRY) * NUM_PARTS);
13.     return WriteMBR();
14. }

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。

Code Snippet

1. static BOOL WriteMBR()
2. {
3.     DWORD dwMBRBlockNum = g_dwMBRSectorNum / g_FlashInfo.wSectorsPerBlock;
4.     //dwMBRBlockNum = 1 ;
5.     RETAILMSG(1, (TEXT("WriteMBR: MBR block = 0x%x,g_dwMBRSectorNum = 0x%x./r/n"), dwMBRBlockNum,g_dwMBRSectorNum));
6.     memset (g_pbBlock, 0xff, g_dwDataBytesPerBlock);
7.     memset (g_pSectorInfoBuf, 0xff, sizeof(SectorInfo) * g_FlashInfo.wSectorsPerBlock);
8.     // No need to check return, since a failed read means data hasn't been written yet.
9.     ReadBlock (dwMBRBlockNum, g_pbBlock, g_pSectorInfoBuf);
10.     if (!FMD_EraseBlock (dwMBRBlockNum)) {
11.         RETAILMSG (1, (TEXT("CreatePartition: error erasing block 0x%x/r/n"), dwMBRBlockNum));
12.         return FALSE;
13.     }
14.     memcpy (g_pbBlock + (g_dwMBRSectorNum % g_FlashInfo.wSectorsPerBlock) * g_FlashInfo.wDataBytesPerSector, g_pbMBRSector, g_FlashInfo.wDataBytesPerSector);
15.     g_pSectorInfoBuf->bOEMReserved &= ~OEM_BLOCK_READONLY;
16.     g_pSectorInfoBuf->wReserved2 &= ~SECTOR_WRITE_COMPLETED;
17.     g_pSectorInfoBuf->dwReserved1 = 0;
18.     RETAILMSG(1, (TEXT("fly::WriteMBR: MBR block = 0x%x./r/n"), dwMBRBlockNum));
19.     if (!WriteBlock (dwMBRBlockNum, g_pbBlock, g_pSectorInfoBuf)) {
20.         RETAILMSG (1, (TEXT("CreatePartition: could not write to block 0x%x/r/n"), dwMBRBlockNum));
21.         return FALSE;
22.     }
23.     return TRUE;
24. }

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。

Code Snippet

1. /*  CreatePartition
2. *
3. *  Creates a new partition.  If it is a boot section partition, then it formats
4. *  flash.
5. *
6. *  ENTRY
7. *      dwStartSector - Logical sector to start the partition.  NEXT_FREE_LOC if
8. *          none specified.
9. *      dwNumSectors - Number of logical sectors of the partition.  USE_REMAINING_SPACE
10. *          to indicate to take up the rest of the space on the flash for that partition.
11. *      dwPartType - Type of partition to create.
12. *      fActive - TRUE indicates to create the active partition.  FALSE for
13. *          inactive.
14. *      dwPartIndex - Index of the partition entry on the MBR
15. *
16. *  EXIT
17. *      Handle to the partition on success.  INVALID_HANDLE_VALUE on error.
18. */
19. static HANDLE CreatePartition (DWORD dwStartSector, DWORD dwNumSectors, DWORD dwPartType, BOOL fActive, DWORD dwPartIndex)
20. {
21.     DWORD dwBootInd = 0;
22.     RETAILMSG(1, (TEXT("CreatePartition: Enter CreatePartition for 0x%x./r/n"), dwPartType));
23.     if (fActive)
24.         dwBootInd |= PART_IND_ACTIVE;
25.     if (dwPartType == PART_BOOTSECTION || dwPartType == PART_BINFS || dwPartType == PART_XIP)
26.         dwBootInd |= PART_IND_READ_ONLY;   
27.      // If start sector is invalid, it means find next free sector
28.     if (dwStartSector == NEXT_FREE_LOC) {       
29.         dwStartSector = FindFreeSector();
30.         if (dwStartSector == INVALID_ADDR) {
31.             RETAILMSG(1, (TEXT("CreatePartition: can't find free sector./r/n")));
32.             return INVALID_HANDLE_VALUE;
33.         }
34.         // Start extended partition on a block boundary
35.         if ((dwPartType == PART_EXTENDED) && (dwStartSector % g_FlashInfo.wSectorsPerBlock)) {
36.             dwStartSector = (dwStartSector / g_FlashInfo.wSectorsPerBlock + 1) * g_FlashInfo.wSectorsPerBlock;
37.         }
38.     }
39.     // If num sectors is invalid, fill the rest of the space up
40.     if (dwNumSectors == USE_REMAINING_SPACE) {
41.         DWORD dwLastLogSector = LastLogSector();
42.         if (dwLastLogSector == INVALID_ADDR)
43.             return INVALID_HANDLE_VALUE;
44.         // Determine the number of blocks to reserve for the FAL compaction when creating an extended partition.
45.         DWORD dwReservedBlocks = g_FlashInfo.dwNumBlocks / PERCENTAGE_OF_MEDIA_TO_RESERVE;
46.         if((dwReservedBlocks = g_FlashInfo.dwNumBlocks / PERCENTAGE_OF_MEDIA_TO_RESERVE) < MINIMUM_FLASH_BLOCKS_TO_RESERVE) {
47.             dwReservedBlocks = MINIMUM_FLASH_BLOCKS_TO_RESERVE;
48.         }
49.         dwNumSectors = dwLastLogSector - dwStartSector + 1 - dwReservedBlocks * g_FlashInfo.wSectorsPerBlock;
50.     }
51.     if (!AreSectorsFree (dwStartSector, dwNumSectors)){
52.         RETAILMSG (1, (TEXT("fly:::::CreatePartition: sectors [0x%x, 0x%x] requested are out of range or taken by another partition/r/n"), dwStartSector, dwNumSectors));
53.         return INVALID_HANDLE_VALUE;
54.     }
55.     RETAILMSG(1, (TEXT("CreatePartition: Start = 0x%x, Num = 0x%x./r/n"), dwStartSector, dwNumSectors));
56.     AddPartitionTableEntry (dwPartIndex, dwStartSector, dwNumSectors, (BYTE)dwPartType, (BYTE)dwBootInd);
57.     if (dwBootInd & PART_IND_READ_ONLY) {
58.         if (!WriteLogicalNumbers (dwStartSector, dwNumSectors, TRUE)) {
59.             RETAILMSG(1, (TEXT("CreatePartition: can't mark sector info./r/n")));
60.             return INVALID_HANDLE_VALUE;
61.         }
62.     }
63.     if (!WriteMBR())
64.         return INVALID_HANDLE_VALUE;
65.     g_partStateTable[dwPartIndex].pPartEntry = (PPARTENTRY)(g_pbMBRSector + PARTTABLE_OFFSET +sizeof(PARTENTRY)*dwPartIndex);
66.     g_partStateTable[dwPartIndex].dwDataPointer = 0;
67.     return (HANDLE)&g_partStateTable[dwPartIndex];           
68. }

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。

Code Snippet

1. static DWORD LastLogSector()
2. {
3.     if (g_dwLastLogSector) {
4.        return g_dwLastLogSector;
5.     }
6.     DWORD dwMBRBlock = g_dwMBRSectorNum / g_FlashInfo.wSectorsPerBlock;
7.     DWORD dwUnusableBlocks = dwMBRBlock;
8.     for (DWORD i = dwMBRBlock; i < g_FlashInfo.dwNumBlocks; i++) {
9.         if (IS_BLOCK_UNUSABLE (i))
10.             dwUnusableBlocks++;
11.     }
12.     g_dwLastLogSector = (g_FlashInfo.dwNumBlocks - dwUnusableBlocks) * g_FlashInfo.wSectorsPerBlock - 1;
13.     RETAILMSG(1, (TEXT("fly:::LastLogSector: Last log sector is: 0x%x./r/n"), g_dwLastLogSector));
14.     return g_dwLastLogSector;
15. }

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。

Code Snippet

1. /*  AddPartitionTableEntry
2. *
3. *  Generates the partition entry for the partition table and copies the entry
4. *  into the MBR that is stored in memory.
5. *
6. *
7. *  ENTRY
8. *      entry - index into partition table
9. *      startSector - starting logical sector
10. *      totalSectors - total logical sectors
11. *      fileSystem - type of partition
12. *      bootInd - byte in partition entry that stores various flags such as
13. *          active and read-only status.
14. *
15. *  EXIT
16. */
17. static void AddPartitionTableEntry(DWORD entry, DWORD startSector, DWORD totalSectors, BYTE fileSystem, BYTE bootInd)
18. {
19.     PARTENTRY partentry = {0};
20.     Addr startAddr;
21.     Addr endAddr;
22.     ASSERT(entry < 4);
23.     // no checking with disk info and start/total sectors because we allow
24.     // bogus partitions for testing purposes
25.     // initially known partition table entry
26.     partentry.Part_BootInd = bootInd;
27.     partentry.Part_FileSystem = fileSystem;
28.     partentry.Part_StartSector = startSector;
29.     partentry.Part_TotalSectors = totalSectors;
30.     // logical block addresses for the first and final sector (start on the second head)
31.     startAddr.type = LBA;
32.     startAddr.lba = partentry.Part_StartSector;
33.     endAddr.type = LBA;
34.     endAddr.lba = partentry.Part_StartSector + partentry.Part_TotalSectors-1;
35.     // translate the LBA addresses to CHS addresses
36.     startAddr = LBAtoCHS(&g_FlashInfo, startAddr);
37.     endAddr = LBAtoCHS(&g_FlashInfo, endAddr);
38.     // starting address
39.     partentry.Part_FirstTrack = (BYTE)(startAddr.chs.cylinder & 0xFF);
40.     partentry.Part_FirstHead = (BYTE)(startAddr.chs.head & 0xFF);
41.     // lower 6-bits == sector, upper 2-bits = cylinder upper 2-bits of 10-bit cylinder #
42.     partentry.Part_FirstSector = (BYTE)((startAddr.chs.sector & 0x3F) | ((startAddr.chs.cylinder & 0x0300) >> 2));
43.     // ending address:
44.     partentry.Part_LastTrack = (BYTE)(endAddr.chs.cylinder & 0xFF);
45.     partentry.Part_LastHead = (BYTE)(endAddr.chs.head & 0xFF);
46.     // lower 6-bits == sector, upper 2-bits = cylinder upper 2-bits of 10-bit cylinder #
47.     partentry.Part_LastSector = (BYTE)((endAddr.chs.sector & 0x3F) | ((endAddr.chs.cylinder & 0x0300) >> 2));
48.     memcpy(g_pbMBRSector+PARTTABLE_OFFSET+(sizeof(PARTENTRY)*entry), &partentry,sizeof(PARTENTRY));
49. }

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。

Code Snippet

1. Addr LBAtoCHS(FlashInfo *pFlashInfo, Addr lba)
2. {
3.     Addr chs;
4.     DWORD tmp = pFlashInfo->dwNumBlocks * pFlashInfo->wSectorsPerBlock;
5.     chs.type = CHS;
6.     chs.chs.cylinder = (WORD)(lba.lba / tmp);                             // ÖùÃæ,Ó¦¸ÃʼÖÕÊÇ
7.     tmp = lba.lba % tmp;
8.     chs.chs.head = (WORD)(tmp / pFlashInfo->wSectorsPerBlock);            // ¿éµØÖ·
9.     chs.chs.sector = (WORD)((tmp % pFlashInfo->wSectorsPerBlock) + 1);    // ÉÈÇø+1
10.     return chs;
11. }
12. Addr CHStoLBA(FlashInfo *pFlashInfo, Addr chs)
13. {
14.     Addr lba;
15.     lba.type = LBA;
16.     lba.lba = ((chs.chs.cylinder * pFlashInfo->dwNumBlocks + chs.chs.head)
17.         * pFlashInfo->wSectorsPerBlock)+ chs.chs.sector - 1;
18.     return lba;
19. }

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。

Code Snippet

1. static BOOL WriteLogicalNumbers (DWORD dwStartSector, DWORD dwNumSectors, BOOL fReadOnly)
2. {
3.     DWORD dwNumSectorsWritten = 0;
4.     DWORD dwPhysSector = Log2Phys (dwStartSector);
5.     DWORD dwBlockNum = dwPhysSector / g_FlashInfo.wSectorsPerBlock;
6.     DWORD dwOffset = dwPhysSector % g_FlashInfo.wSectorsPerBlock;
7.     while (dwNumSectorsWritten < dwNumSectors) {
8.         // If bad block, move to the next block
9.         if (IS_BLOCK_UNUSABLE (dwBlockNum)) {
10.             dwBlockNum++;
11.             continue;
12.         }
13.         memset (g_pbBlock, 0xff, g_dwDataBytesPerBlock);
14.         memset (g_pSectorInfoBuf, 0xff,sizeof(SectorInfo) * g_FlashInfo.wSectorsPerBlock);
15.         // No need to check return, since a failed read means data hasn't been written yet.
16.         ReadBlock (dwBlockNum, g_pbBlock, g_pSectorInfoBuf);
17.         if (!FMD_EraseBlock (dwBlockNum)) {
18.             return FALSE;
19.         }
20.         DWORD dwSectorsToWrite = g_FlashInfo.wSectorsPerBlock - dwOffset;
21.         PSectorInfo pSectorInfo = g_pSectorInfoBuf + dwOffset;
22.         // If this is the last block, then calculate sectors to write if there isn't a full block to update
23.         if ((dwSectorsToWrite + dwNumSectorsWritten) > dwNumSectors)
24.             dwSectorsToWrite = dwNumSectors - dwNumSectorsWritten;
25.         for (DWORD iSector = 0; iSector < dwSectorsToWrite; iSector++, pSectorInfo++, dwNumSectorsWritten++) {
26.             // Assert read only by setting bit to 0 to prevent wear-leveling by FAL
27.             if (fReadOnly)
28.                 pSectorInfo->bOEMReserved &= ~OEM_BLOCK_READONLY;
29.             // Set to write completed so FAL can map the sector
30.             pSectorInfo->wReserved2 &= ~SECTOR_WRITE_COMPLETED;       
31.             // Write the logical sector number
32.             pSectorInfo->dwReserved1 = dwStartSector + dwNumSectorsWritten;           
33.         }
34.         if (!WriteBlock (dwBlockNum, g_pbBlock, g_pSectorInfoBuf))
35.             return FALSE;
36.         dwOffset = 0;
37.         dwBlockNum++;
38.     }
39.     return TRUE;
40. }

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。

Code Snippet

1. static BOOL GetPartitionTableIndex (DWORD dwPartType, BOOL fActive, PDWORD pdwIndex)
2. {
3.     PPARTENTRY pPartEntry = (PPARTENTRY)(g_pbMBRSector + PARTTABLE_OFFSET);
4.     DWORD iEntry = 0;
5.     for (iEntry = 0; iEntry < NUM_PARTS; iEntry++, pPartEntry++) {
6.         if ((pPartEntry->Part_FileSystem == dwPartType) && (((pPartEntry->Part_BootInd & PART_IND_ACTIVE) != 0) == fActive)) {
7.             *pdwIndex = iEntry;
8.             return TRUE;
9.         }
10.         if (!IsValidPart (pPartEntry)) {
11.             *pdwIndex = iEntry;
12.             return FALSE;
13.         }
14.     }
15.     return FALSE;
16. }

重要结构：PARTENTRY

Code Snippet

1. // end of master boot record contains 4 partition entries
2. typedefstruct _PARTENTRY {
3.         BYTE            Part_BootInd;           // If 80h means this is boot partition
4.         BYTE            Part_FirstHead;        // Partition starting head based 0
5.         BYTE            Part_FirstSector;       // Partition starting sector based 1
6.         BYTE            Part_FirstTrack;       // Partition starting track based 0
7.         BYTE            Part_FileSystem;        // Partition type signature field
8.         BYTE            Part_LastHead;         // Partition ending head based 0
9.         BYTE            Part_LastSector;        // Partition ending sector based 1
10.         BYTE            Part_LastTrack;        // Partition ending track based 0
11.         DWORD           Part_StartSector;       // Logical starting sector based 0
12.         DWORD           Part_TotalSectors;     // Total logical sectors in partition
13. } 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。

Code Snippet

1. // create extended partition in whatever is left
2. hPartEx = BP_OpenPartition( (NK_START_BLOCK+1+BINFS_BLOCK) * PAGES_PER_BLOCK,
3.                             NEXT_FREE_LOC,   // (1024 - (NK_START_BLOCK+1+SECTOR_TO_BLOCK_SIZE(FILE_TO_SECTOR_SIZE(dwBINFSPartLength)))) * PAGES_PER_BLOCK,
4.                             PART_DOS32,
5.                             TRUE,
6.                             PART_OPEN_ALWAYS);
7. if (hPartEx == INVALID_HANDLE_VALUE )
8. {
9.     EdbgOutputDebugString("*** WARN: StoreImageToBootMedia: Failed to open/create Extended partition ***/r/n");
10. }

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