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
/* 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) //£¨×¢£oê¾ày′úÂëÎa±¾èË/uc1EBOOTÖD·ÖÇøêμÏÖÔ′Â루/uc1WINCE5.0+S3C2440+128MNAND,MBRD′Ôúμú¸ö/uc1BLOCK£¬·Öò»¸ö/uc1BINFS¸ñê½·ÖÇøoíò»¸ö/uc1FAT¸ñê½·ÖÇø£©¡££© 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
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。 Code Snippet
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 Code Snippet
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);。 Code Snippet
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。 Code Snippet
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。 Code Snippet
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。 Code Snippet
/* 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。 Code Snippet
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。 Code Snippet
/* 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。 Code Snippet
Addr LBAtoCHS(FlashInfo *pFlashInfo, Addr lba) { Addr chs; DWORD tmp = pFlashInfo->dwNumBlocks * pFlashInfo->wSectorsPerBlock; chs.type = CHS; chs.chs.cylinder = (WORD)(lba.lba / tmp); // ÖùÃæ,ó|¸Ãê¼ÖÕêÇ tmp = lba.lba % tmp; chs.chs.head = (WORD)(tmp / pFlashInfo->wSectorsPerBlock); // ¿éμØÖ· chs.chs.sector = (WORD)((tmp % pFlashInfo->wSectorsPerBlock) + 1); // éèÇø+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。 Code Snippet
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。 Code Snippet
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
Code Snippet
// end of master boot record contains 4 partition entries typedefstruct _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。 Code Snippet
// 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"); }
引用通告 此日志的引用通告 URL 是:
http://giwawe.spaces.live.com/blog/cns!92AFEF096943066B!260.trak