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partitions: dos: parse extended partition 

DOS MBRs might contain an extended partition that holds several logical
partitions. Add these to the partitions of the block device.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
This commit is contained in:
Uwe Kleine-König 2013-11-08 11:13:41 +01:00 committed by Sascha Hauer
parent 8ddf910d2f
commit 6fecd2aaca
1 changed files with 75 additions and 1 deletions
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76
common/partitions/dos.c
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@ -116,12 +116,64 @@ static int dos_get_disk_signature(struct param_d *p, void *_priv)
return 0;
}
static void dos_extended_partition(struct block_device *blk, struct partition_desc *pd,
struct partition *partition)
{
uint8_t *buf = dma_alloc(SECTOR_SIZE);
uint32_t ebr_sector = partition->first_sec;
struct partition_entry *table = (struct partition_entry *)&buf[0x1be];
while (pd->used_entries < ARRAY_SIZE(pd->parts)) {
int rc, i;
int n = pd->used_entries;
dev_dbg(blk->dev, "expect EBR in sector %x\n", ebr_sector);
rc = block_read(blk, buf, ebr_sector, 1);
if (rc != 0) {
dev_err(blk->dev, "Cannot read EBR partition table\n");
goto out;
}
/* sanity checks */
if (buf[0x1fe] != 0x55 || buf[0x1ff] != 0xaa) {
dev_err(blk->dev, "sector %x doesn't contain an EBR signature\n", ebr_sector);
goto out;
}
for (i = 0x1de; i < 0x1fe; ++i)
if (buf[i]) {
dev_err(blk->dev, "EBR's third or fourth partition non-empty\n");
goto out;
}
/* /sanity checks */
/* the first entry defines the extended partition */
pd->parts[n].first_sec = ebr_sector +
get_unaligned_le32(&table[0].partition_start);
pd->parts[n].size = get_unaligned_le32(&table[0].partition_size);
pd->parts[n].dos_partition_type = table[0].type;
pd->used_entries++;
/* the second entry defines the start of the next ebr if != 0 */
if (get_unaligned_le32(&table[1].partition_start))
ebr_sector = partition->first_sec +
get_unaligned_le32(&table[1].partition_start);
else
break;
}
out:
dma_free(buf);
return;
}
/**
* Check if a DOS like partition describes this block device
* @param blk Block device to register to
* @param pd Where to store the partition information
*
* It seems at least on ARM this routine canot use temp. stack space for the
* It seems at least on ARM this routine cannot use temp. stack space for the
* sector. So, keep the malloc/free.
*/
static void dos_partition(void *buf, struct block_device *blk,
@ -129,6 +181,7 @@ static void dos_partition(void *buf, struct block_device *blk,
{
struct partition_entry *table;
struct partition pentry;
struct partition *extended_partition = NULL;
uint8_t *buffer = buf;
int i;
struct disk_signature_priv *dsp;
@ -150,11 +203,32 @@ static void dos_partition(void *buf, struct block_device *blk,
pd->parts[n].size = pentry.size;
pd->parts[n].dos_partition_type = pentry.dos_partition_type;
pd->used_entries++;
/*
* Partitions of type 0x05 and 0x0f (and some more)
* contain extended partitions. Only check for type 0x0f
* here as this is the easiest to parse and common
* enough.
*/
if (pentry.dos_partition_type == 0x0f) {
if (!extended_partition)
extended_partition = &pd->parts[n];
else
/*
* An DOS MBR must only contain a single
* extended partition. Just ignore all
* but the first.
*/
dev_warn(blk->dev, "Skipping additional extended partition\n");
}
} else {
dev_dbg(blk->dev, "Skipping empty partition %d\n", i);
}
}
if (extended_partition)
dos_extended_partition(blk, pd, extended_partition);
dsp = xzalloc(sizeof(*dsp));
dsp->blk = blk;