From: Christian Taedcke <christian.taed...@weidmueller.com> This fixes an issue where the FAT type (FAT12, FAT16) is not correctly detected, e.g. when the BPB field BS_FilSysType contains the valid value "FAT ".
According to the FAT spec the field BS_FilSysType has only informational character and does not determine the FAT type. The logic of this code is based on the linux kernel implementation from the file fs/fat/inode.c function fat_fill_super(). For details about FAT see http://elm-chan.org/docs/fat_e.html Signed-off-by: Christian Taedcke <christian.taed...@weidmueller.com> --- fs/fat/fat.c | 58 +++++++++++++++++++++++----------------- include/fat.h | 6 ----- test/image/spl_load_fs.c | 2 +- 3 files changed, 35 insertions(+), 31 deletions(-) diff --git a/fs/fat/fat.c b/fs/fat/fat.c index 8a0f4e4e6c..9179257ff2 100644 --- a/fs/fat/fat.c +++ b/fs/fat/fat.c @@ -27,6 +27,9 @@ #define FATU8ARRAY2CPU16(x) (((x)[1] << 8) + (x)[0]) +/* maximum number of clusters for FAT12 */ +#define MAX_FAT12 0xFF4 + /* * Convert a string to lowercase. Converts at most 'len' characters, * 'len' may be larger than the length of 'str' if 'str' is NULL @@ -485,6 +488,32 @@ static __u8 mkcksum(struct nameext *nameext) return ret; } +/* + * Determine the FAT type + * + * Based on fat_fill_super() from the Linux kernel's fs/fat/inode.c + */ +static int +determine_fat_bits(const boot_sector *bs) +{ + if (!bs->fat_length && bs->fat32_length) { + return 32; + } else { + u16 fat_start = bs->reserved; + u32 dir_start = fat_start + bs->fats * bs->fat_length; + u32 rootdir_sectors = FATU8ARRAY2CPU16(bs->dir_entries) * + sizeof(dir_entry) / + FATU8ARRAY2CPU16(bs->sector_size); + u32 data_start = dir_start + rootdir_sectors; + u16 sectors = FATU8ARRAY2CPU16(bs->sectors); + u32 total_sectors = sectors ? sectors : bs->total_sect; + u32 total_clusters = (total_sectors - data_start) / + bs->cluster_size; + + return (total_clusters > MAX_FAT12) ? 16 : 12; + } +} + /* * Read boot sector and volume info from a FAT filesystem */ @@ -493,7 +522,6 @@ read_bootsectandvi(boot_sector *bs, volume_info *volinfo, int *fatsize) { __u8 *block; volume_info *vistart; - int ret = 0; if (cur_dev == NULL) { debug("Error: no device selected\n"); @@ -508,7 +536,8 @@ read_bootsectandvi(boot_sector *bs, volume_info *volinfo, int *fatsize) if (disk_read(0, 1, block) < 0) { debug("Error: reading block\n"); - goto fail; + free(block); + return -1; } memcpy(bs, block, sizeof(boot_sector)); @@ -527,33 +556,15 @@ read_bootsectandvi(boot_sector *bs, volume_info *volinfo, int *fatsize) bs->info_sector = FAT2CPU16(bs->info_sector); bs->backup_boot = FAT2CPU16(bs->backup_boot); vistart = (volume_info *)(block + sizeof(boot_sector)); - *fatsize = 32; } else { vistart = (volume_info *)&(bs->fat32_length); - *fatsize = 0; } memcpy(volinfo, vistart, sizeof(volume_info)); - if (*fatsize == 32) { - if (strncmp(FAT32_SIGN, vistart->fs_type, SIGNLEN) == 0) - goto exit; - } else { - if (strncmp(FAT12_SIGN, vistart->fs_type, SIGNLEN) == 0) { - *fatsize = 12; - goto exit; - } - if (strncmp(FAT16_SIGN, vistart->fs_type, SIGNLEN) == 0) { - *fatsize = 16; - goto exit; - } - } + *fatsize = determine_fat_bits(bs); - debug("Error: broken fs_type sign\n"); -fail: - ret = -1; -exit: free(block); - return ret; + return 0; } static int get_fs_info(fsdata *mydata) @@ -1158,9 +1169,8 @@ int file_fat_detectfs(void) memcpy(vol_label, volinfo.volume_label, 11); vol_label[11] = '\0'; - volinfo.fs_type[5] = '\0'; - printf("Filesystem: %s \"%s\"\n", volinfo.fs_type, vol_label); + printf("Filesystem: FAT%d \"%s\"\n", fatsize, vol_label); return 0; } diff --git a/include/fat.h b/include/fat.h index a9756fb4cd..3dce99a23c 100644 --- a/include/fat.h +++ b/include/fat.h @@ -34,12 +34,6 @@ struct disk_partition; /* Maximum number of entry for long file name according to spec */ #define MAX_LFN_SLOT 20 -/* Filesystem identifiers */ -#define FAT12_SIGN "FAT12 " -#define FAT16_SIGN "FAT16 " -#define FAT32_SIGN "FAT32 " -#define SIGNLEN 8 - /* File attributes */ #define ATTR_RO 1 #define ATTR_HIDDEN 2 diff --git a/test/image/spl_load_fs.c b/test/image/spl_load_fs.c index 297ab08a82..90e640b5de 100644 --- a/test/image/spl_load_fs.c +++ b/test/image/spl_load_fs.c @@ -220,7 +220,7 @@ static size_t create_fat(void *dst, size_t size, const char *filename, bs->root_cluster = cpu_to_le32(root_sector); vi->ext_boot_sign = 0x29; - memcpy(vi->fs_type, FAT32_SIGN, sizeof(vi->fs_type)); + memcpy(vi->fs_type, "FAT32 ", sizeof(vi->fs_type)); memcpy(dst + 0x1fe, "\x55\xAA", 2); -- 2.34.1
