[轉]NandFlash的分區實現

NandFlash的分區實現

提到分區就需要知道MBR，瞭解分區表。

什麼是MBR

     硬盤的0柱面、0磁頭、1扇區稱爲主引導扇區，NANDFLASH由BLOCK和Sector組成，所以NANDFLASH的第0 BLOCK，第1 Sector爲主引導扇區，FDISK程序寫到該扇區的內容稱爲主引導記錄（MBR）。該記錄佔用512個字節，它用於硬盤啓動時將系統控制權交給用戶指定的，並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，並運行系統引導程序。
• 出錯信息數據區，偏移地址0089H--00E1H爲出錯信息，00E2H--01BDH全爲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字節爲分區項1、分區項2、分區項3、分區項4。
• 結束標誌字，偏移地址01FE--01FF的2個字節值爲結束標誌55AA,如果該標誌錯誤系統就不能啓動。

0000-0088	Master Boot Record 主引導程序	主引導 程序
0089-01BD	出錯信息數據區	數據區
01BE-01CD	分區項1（16字節）	分區表
01CE-01DD	分區項2（16字節）	…
01DE-01ED	分區項3（16字節）	…
01EE-01FD	分區項4（16字節）	…
01FE	55	結束標誌
01FF	AA	…

                             圖6-15 MBR的組成結構圖

MBR中的分區信息結構

     佔用512個字節的MBR中，偏移地址01BEH--01FDH的64個字節，爲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於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

存貯字節位	內容及含義
第1字節	引導標誌。若值爲80H表示活動分區，若值爲00H表示非活動分區。
第2、3、4字節	本分區的起始磁頭號、扇區號、柱面號。其中： 磁頭號——第2字節； 扇區號——第3字節的低6位； 柱面號——爲第3字節高2位+第4字節8位。
第5字節	分區類型符: 00H——表示該分區未用（即沒有指定）； 06H——FAT16基本分區； 0BH——FAT32基本分區； 05H——擴展分區； 07H——NTFS分區； 0FH——（LBA模式）擴展分區（83H爲Linux分區等）。
第6、7、8字節	本分區的結束磁頭號、扇區號、柱面號，其中： 磁頭號——第6字節； 扇區號——第7字節的低6位； 柱面號——第7字節的高2位+第8字節。
第9、10、11、12字節	本分區之前已用了的扇區數
第13、14、15、16字節	本分區的總扇區數

        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。透徹瞭解。然後就是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。

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 爲(NK_START_BLOCK+1)*PAGES_PER_BLOCK，

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

第三個參數分區的格式爲PART_BINFS，即BINFS格式，

第四個參數指示該分區爲活動分區，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。

 

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. }

 

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保存在哪裏，前面說過NANDFLASH的第0 BLOCK，第1 Sector爲主引導扇區，也就是MBR，但是NAND如果被當作啓動芯片，○地址一般被BOOTLOADER代碼佔據，MBR只有放在後面的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。

 

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()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

 

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. }

 

這裏dwBlockNum直接給了個3，因爲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)

然後確定BLOCK是否可使用的BLOCK，最後通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爲0XE9,FD,FF，當然，還有熟悉的結束標誌符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);。

 

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。在函數的最後調用了    CreateMBR();來創建一個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. }

當然。因爲還沒有進行分區，這裏寫入的MBR分區表部分是空的。

 

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()函數中，就寫入了判斷MBR 的一些標誌到BLOCK，    g_pSectorInfoBuf->bOEMReserved &= ~OEM_BLOCK_READONLY;

    g_pSectorInfoBuf->wReserved2 &= ~SECTOR_WRITE_COMPLETED;

    g_pSectorInfoBuf->dwReserved1 = 0;

Wince系統啓動時，具體是NANDFLASH驅動加載成功後，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也寫入成功後就可以開始新建分區了。

 

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. }

 

如果第二個參數爲－1，則視爲將餘下的所有空間劃爲一個分區。LastLogSector();函數獲得最後一個邏輯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之後的所有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。

 

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. }

 

這裏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。

 

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. }

 

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

 

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. }

 

這就是爲什麼系統啓動後，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。最後調用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。

 

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. }

 

重要結構：PARTENTRY

 

Code Snippet

1. // end of master boot record contains 4 partition entries
2. typedef struct _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後面的空間，全部分爲一個FAT格式的分區。

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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