FS4412中uboot对emmc的分区解析
时间：2017-11-27 来源：未知
Author：runner 2017.10.15
声明
平台： fs4412 （Samsung exynos4412）
u-boot版本： u-boot-2010.03-FS4412
简述
在FS4412的开发中，uboot通过movi、fdisk、fastboot等命令对emmc做了相应的分区操作，这里主要分析，这些命令是如何对emmc进行分区的，每条命令使用的分区之间有什么联系和区别。
uboot对emmc分区分析
整个u-boot源码的入口是在u-boot-2010.03-FS4412/cpu/arm_cortexa9/start.S，对于该文件中所做的具体工作，我们这里进行分析，主要看该文件中调用emmc初始化的位置：
图中提示的start_armboot函数的实现是在u-boot-2010.03-FS4412/lib_arm/board.c中；当然我们的目的肯定不是只简单的找到这个函数就够了，我们需要了解这个函数中还调用了一个关键的函数接口去初始化emmc，如下：
这里的mmc_initialize函数的具体实现是在u-boot-2010.03-FS4412/drivers/mmc/mmc.c中；那么该函数的主要目的实际上是调用mmc_init，mmc_init又是如何实现的？我们接着往下追，mmc_init函数的实现还是在这个文件中。我们的目的是找到mmc被分区的部分为大家解读，所以对于这个函数其它部分就不做赘述，这里只看该函数后调用的mmc_startup,如下：
mmc_startup函数的实现也是在上述文件中，该函数调用init_raw_area_table接口实现对emmc的分区操作：
init_raw_area_table函数的实现是在u-boot-2010.03-FS4412/common/cmd_movi.c中。具体实现如下：
C++ Code
int init_raw_area_table (block_dev_desc_t *dev_desc)
{
struct mmc *host = find_mmc_device(dev_desc->dev);
/* when last block does not have raw_area definition. */
if (raw_area_control.magic_number != MAGIC_NUMBER_MOVI)
{
int i = 0;
member_t *image;
u32 capacity;
dbg("The host name is %s\n", host->name);
if(host->high_capacity)
{
capacity = host->capacity;
}
else
{
capacity = host->capacity * (host->read_bl_len / MOVI_BLKSIZE);
}
dbg("Warning: cannot find the raw area table(%p) %08x\n",
&raw_area_control, raw_area_control.magic_number);
/* add magic number */
raw_area_control.magic_number = MAGIC_NUMBER_MOVI;
/* init raw_area will be 16MB */
raw_area_control.start_blk = 16 * 1024 * 1024 / MOVI_BLKSIZE;
raw_area_control.total_blk = capacity;
raw_area_control.next_raw_area = 0;
strcpy(raw_area_control.description, "initial raw table");
image = raw_area_control.image;
/* image 0 should be fwbl1 */
if(strcmp(host->name, "S5P_MSHC4") == 0)
image[0].start_blk = 0;
else
image[0].start_blk = (eFUSE_SIZE / MOVI_BLKSIZE);
image[0].used_blk = MOVI_FWBL1_BLKCNT;
image[0].size = FWBL1_SIZE;
image[0].attribute = 0x0;
strcpy(image[0].description, "fwbl1");
dbg("fwbl1: %d\n", image[0].start_blk);
/* image 1 should be bl2 */
image[1].start_blk = image[0].start_blk + image[0].used_blk;
image[1].used_blk = MOVI_BL2_BLKCNT;
image[1].size = BL2_SIZE;
image[1].attribute = 0x3;
strcpy(image[1].description, "bl2");
dbg("bl2: %d\n", image[1].start_blk);
#if 0
/* image 2 should be uboot */
image[2].start_blk = image[1].start_blk + image[1].used_blk;
image[2].used_blk = MOVI_UBOOT_BLKCNT;
image[2].size = PART_SIZE_UBOOT;
image[2].attribute = 0x2;
strcpy(image[2].description, "bootloader");
dbg("u-boot: %d\n", image[2].start_blk);
#else
/*BL1,BL2,u-boot have been combined together when compiling for EMMC*/
if(strcmp(host->name, "S5P_MSHC4") == 0)
image[2].start_blk = 0;
else
image[2].start_blk = (eFUSE_SIZE / MOVI_BLKSIZE);
image[2].used_blk = MOVI_FWBL1_BLKCNT + MOVI_UBOOT_BLKCNT + MOVI_BL2_BLKCNT;
image[2].size = PART_SIZE_UBOOT + FWBL1_SIZE + BL2_SIZE;
image[2].attribute = 0x2;
strcpy(image[2].description, "bootloader");
dbg("u-boot: %d\n", image[2].start_blk);
#endif
/* image 3 should be environment */
image[3].start_blk = (544 * 1024) / MOVI_BLKSIZE;
image[3].used_blk = MOVI_ENV_BLKCNT;
image[3].size = CONFIG_ENV_SIZE;
image[3].attribute = 0x10;
strcpy(image[3].description, "environment");
dbg("env: %d\n", image[3].start_blk);
/* image 4 should be kernel */
image[4].start_blk = image[3].start_blk + image[3].used_blk;
image[4].used_blk = MOVI_ZIMAGE_BLKCNT;
image[4].size = PART_SIZE_KERNEL;
image[4].attribute = 0x4;
strcpy(image[4].description, "kernel");
dbg("knl: %d\n", image[4].start_blk);
/* image 5 should be RFS */
image[5].start_blk = image[4].start_blk + image[4].used_blk;
image[5].used_blk = MOVI_ROOTFS_BLKCNT;
image[5].size = PART_SIZE_ROOTFS;
image[5].attribute = 0x8;
strcpy(image[5].description, "ramdisk");
dbg("rfs: %d\n", image[5].start_blk);
#ifdef CONFIG_RECOVERY
/* image 6 should be Recovery */
image[6].start_blk = image[5].start_blk + image[5].used_blk;
image[6].used_blk = RAW_AREA_SIZE / MOVI_BLKSIZE - image[5].start_blk;
image[6].size = image[6].used_blk * MOVI_BLKSIZE;
image[6].attribute = 0x6;
strcpy(image[6].description, "Recovery");
dbg("recovery: %d\n", image[6].start_blk);
#endif
/* image 7 should be disk */
image[7].start_blk = RAW_AREA_SIZE / MOVI_BLKSIZE;
image[7].size = capacity - RAW_AREA_SIZE;
image[7].used_blk = image[7].size / MOVI_BLKSIZE;
image[7].attribute = 0xff;
strcpy(image[7].description, "disk");
dbg("disk: %d\n", image[7].start_blk);
for (i = 8; i < 15; i++)
{
raw_area_control.image[i].start_blk = 0;
raw_area_control.image[i].used_blk = 0;
}
}
return 0;
}
可以看到：
image[0] 存放的是BL1，start_blk = 0 / 1,used_blk = (8*1024)/512
image[1] 存放的是BL2，start_blk = image[0].start_blk + image[0].used_blk; used_blk = (16*1024)/512
image[2] 存放的是Bootloader,
image[3] 存放的是environment（环境变量）
image[4] 存放的是kernel
image[5] 存放的是ramdisk
image[6] 存放的是Recovery
image[7] 存放的是disk（即文件系统）
后面的几个分区的起始地址和使用地址，都是通过上面一一偏移得到的，有兴趣的同学可以自己查阅源码进行计算。这样的话，我们就知道了平时烧写的kernel镜像或者ramdisk镜像在emmc中存放的地址空间了。
fdisk命令分区分析
我们知道使用fdisk命令对emmc 分区时，命令格式如下：
fdisk -c 0 300 1024 300
或者使用fdisk命令查询分区大小：
fdisk -p 0
那么这四个分区分别代表什么意思呢？要搞清楚这个问题，我们就要去看fdisk命令的实现过程了，fdisk命令在uboot源码中实现的位置是在common/cmd_mmc_fdisk.c中。在该文件中对于这个命令其它实现的部分我不做赘述，直接看具体分区的操作，函数名称为：make_mmc_partition , 实现如下：
C++ Code
int make_mmc_partition(int total_block_count, unsigned char *mbr, int flag, char *argv[])
{
unsigned int block_start = 0, block_offset;
SDInfo sdInfo;
PartitionInfo partInfo[4];
///////////////////////////////////////////////////////////
memset((unsigned char *)&sdInfo, 0x00, sizeof(SDInfo));
///////////////////////////////////////////////////////////
get_SDInfo(total_block_count, &sdInfo);
///////////////////////////////////////////////////////////
// ??? Unit??§?????????
block_start = calc_unit(DISK_START, sdInfo);
block_offset = calc_unit(SYSTEM_PART_SIZE, sdInfo);
/* modify by cym 20131206 */
#if 0
block_offset = calc_unit(SYSTEM_PART_SIZE, sdInfo);
printf("block_start = %d, block_offset = %d\n", block_start, block_offset);
#else
if (flag)
block_offset = calc_unit((unsigned long long)
simple_strtoul(argv[3], NULL, 0) * 1024 * 1024, sdInfo);
else
block_offset = calc_unit(SYSTEM_PART_SIZE, sdInfo);
#endif
/* end modify */
partInfo[0].bootable = 0x00;
partInfo[0].partitionId = 0x83;
make_partitionInfo(block_start, block_offset, sdInfo, &partInfo[0]);
///////////////////////////////////////////////////////////
block_start += block_offset;
/* modify by cym 20131206 */
#if 0
if (strcmp(argv[2], "1") == 0)// TF card
block_offset = calc_unit(_300MB, sdInfo);
else
block_offset = calc_unit(USER_DATA_PART_SIZE, sdInfo);
#else
if (flag)
block_offset = calc_unit((unsigned long long)
simple_strtoul(argv[4], NULL, 0) * 1024 * 1024, sdInfo);
else
{
if (strcmp(argv[2], "1") == 0)// TF card
block_offset = calc_unit(_300MB, sdInfo);
else
block_offset = calc_unit(USER_DATA_PART_SIZE, sdInfo);
}
#endif
/* end modify */
partInfo[1].bootable = 0x00;
partInfo[1].partitionId = 0x83;
make_partitionInfo(block_start, block_offset, sdInfo, &partInfo[1]);
///////////////////////////////////////////////////////////
block_start += block_offset;
/* modify by cym 20131206 */
#if 0
block_offset = calc_unit(CACHE_PART_SIZE, sdInfo);
#else
if(flag)
block_offset =
calc_unit((unsigned long long)
simple_strtoul(argv[5], NULL, 0) * 1024 * 1024, sdInfo);
else
block_offset = calc_unit(CACHE_PART_SIZE, sdInfo);
#endif
/* end modify */
partInfo[2].bootable = 0x00;
partInfo[2].partitionId = 0x83;
make_partitionInfo(block_start, block_offset, sdInfo, &partInfo[2]);
///////////////////////////////////////////////////////////
block_start += block_offset;
block_offset = BLOCK_END;
partInfo[3].bootable = 0x00;
partInfo[3].partitionId = 0x0C;
make_partitionInfo(block_start, block_offset, sdInfo, &partInfo[3]);
///////////////////////////////////////////////////////////
memset(mbr, 0x00, sizeof(*mbr) * 512); // liang, clean the mem again
mbr[510] = 0x55;
mbr[511] = 0xAA;
encode_partitionInfo(partInfo[0], &mbr[0x1CE]);
encode_partitionInfo(partInfo[1], &mbr[0x1DE]);
encode_partitionInfo(partInfo[2], &mbr[0x1EE]);
encode_partitionInfo(partInfo[3], &mbr[0x1BE]);
return 0;
}
从上述代码中我们可以看到，在执行fdisk命令时打印的四个分区实际上就是partInfo的四个元素，partInfo[0]代表的是system分区，partInfo[1]代表的是userdata分区， partInfo[2]代表的是cache分区，剩下的partInfo[3]是fat分区。所以在fdisk命令执行完成后，出现的四个分区1、2、3、4依次为fat、system、userdata、cache。
fastboot命令分析
我们在uboot状态下执行fastboot命令的时候显示的8个分区信息，跟前面咱们看到几个分区又是什么样的关系呢？实际上这里的bootloader、kernel、ramdisk、Recovery就是前面提到的那几个分区，由uboot在启动时调用mmc_init实现的。而后面的system、userdata、cache、fat四个分区统称为disk分区，同样也是fdisk命令实现的分区信息。
