From: Egbert Eich eich@suse.com
Devices that used to have a whole disk FAT filesystem but got then partitioned will most likely still have a FAT or FAT32 signature in the first sector as this sector does not get overwritten by a partitioning tool (otherwise the tool would risk to kill the mbr).
The current partition search algorithm will erronously detect such a device as a raw FAT device.
Instead of looking for the FAT or FAT32 signatures immediately we use the same algorithm as used by the Linux kernel and first check for a valid boot indicator flag on each of the 4 partitions. If the value of this flag is invalid for the first entry we then do the raw partition check. If the flag for any higher partition is wrong we assume the device is neiter a MBR nor PBR device.
v2: Coding style cleanup.
Signed-off-by: Egbert Eich eich@suse.com --- disk/part_dos.c | 18 +++++++++++++++--- 1 files changed, 15 insertions(+), 3 deletions(-)
diff --git a/disk/part_dos.c b/disk/part_dos.c index 37087a6..3fc8564 100644 --- a/disk/part_dos.c +++ b/disk/part_dos.c @@ -74,13 +74,25 @@ static void print_one_part(dos_partition_t *p, int ext_part_sector,
static int test_block_type(unsigned char *buffer) { + int slot; + struct dos_partition *p; + if((buffer[DOS_PART_MAGIC_OFFSET + 0] != 0x55) || (buffer[DOS_PART_MAGIC_OFFSET + 1] != 0xaa) ) { return (-1); } /* no DOS Signature at all */ - if (strncmp((char *)&buffer[DOS_PBR_FSTYPE_OFFSET],"FAT",3)==0 || - strncmp((char *)&buffer[DOS_PBR32_FSTYPE_OFFSET],"FAT32",5)==0) { - return DOS_PBR; /* is PBR */ + p = (struct dos_partition *)&buffer[DOS_PART_TBL_OFFSET]; + for (slot = 0; slot < 3; slot++) { + if (p->boot_ind != 0 && p->boot_ind != 0x80) { + if (!slot && + (strncmp((char *)&buffer[DOS_PBR_FSTYPE_OFFSET], + "FAT", 3) == 0 || + strncmp((char *)&buffer[DOS_PBR32_FSTYPE_OFFSET], + "FAT32", 5) == 0)) { + return DOS_PBR; /* is PBR */ + } else + return -1; + } } return DOS_MBR; /* Is MBR */ }