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kvm tools: check the cluster boundary in the qcow read code

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The QCOW1 code should always read the data in cluster size. A new function
qcow1_read_cluster() is added to read a cluster wort of data. The current
function to read the data i.e. qcow1_read_sector is modified to use this newly
added function and preserve the cluster boundary.

Signed-off-by: Prasad Joshi <prasadjoshi124@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
This commit is contained in:
Prasad Joshi
2011-04-16 20:40:25 +01:00
committed by Will Deacon
parent 4c0205d09a
commit 3dac48d4a6
1 changed files with 57 additions and 29 deletions
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qcow.c
+57 -29
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@@ -36,68 +36,96 @@ static inline u64 get_cluster_offset(struct qcow *q, u64 offset)
return offset & ((1 << header->cluster_bits)-1);
}
static int qcow1_read_sector(struct disk_image *self, uint64_t sector, void *dst, uint32_t dst_len)
static u32 qcow1_read_cluster(struct qcow *q, u64 offset, void *dst,
u32 dst_len)
{
struct qcow *q = self->priv;
struct qcow1_header *header = q->header;
struct qcow_table *table = &q->table;
u64 l2_table_offset;
u64 l2_table_size;
u64 cluster_size;
u64 clust_offset;
u64 clust_start;
u64 *l2_table = NULL;
u64 l1_idx;
u64 l2_idx;
u64 offset;
u32 length;
offset = sector << SECTOR_SHIFT;
if (offset >= header->size)
length = cluster_size = 1 << header->cluster_bits;
l1_idx = get_l1_index(q, offset);
if (l1_idx >= table->table_size)
goto out_error;
l1_idx = get_l1_index(q, offset);
if (l1_idx >= q->table.table_size)
clust_offset = get_cluster_offset(q, offset);
if (clust_offset >= cluster_size)
goto out_error;
l2_table_offset = q->table.l1_table[l1_idx];
length = cluster_size - clust_offset;
if (length > dst_len)
length = dst_len;
l2_table_offset = table->l1_table[l1_idx];
if (!l2_table_offset)
goto zero_sector;
goto zero_cluster;
l2_table_size = 1 << header->l2_bits;
l2_table = calloc(l2_table_size, sizeof(u64));
l2_table_size = 1 << header->l2_bits;
l2_table = calloc(l2_table_size, sizeof(u64));
if (!l2_table)
goto out_error;
if (pread_in_full(q->fd, l2_table, sizeof(u64) * l2_table_size, l2_table_offset) < 0)
if (pread_in_full(q->fd, l2_table, l2_table_size * sizeof(u64),
l2_table_offset) < 0)
goto out_error;
l2_idx = get_l2_index(q, offset);
l2_idx = get_l2_index(q, offset);
if (l2_idx >= l2_table_size)
goto out_error;
clust_start = be64_to_cpu(l2_table[l2_idx]);
clust_start = be64_to_cpu(l2_table[l2_idx]);
free(l2_table);
if (!clust_start)
goto zero_sector;
goto zero_cluster;
clust_offset = get_cluster_offset(q, offset);
if (pread_in_full(q->fd, dst, dst_len, clust_start + clust_offset) < 0)
if (pread_in_full(q->fd, dst, length, clust_start + clust_offset) < 0)
goto out_error;
return 0;
zero_sector:
memset(dst, 0, dst_len);
return 0;
return length;
zero_cluster:
memset(dst, 0, length);
return length;
out_error:
free(l2_table);
return -1;
}
static int qcow1_read_sector(struct disk_image *self, uint64_t sector,
void *dst, uint32_t dst_len)
{
struct qcow *q = self->priv;
struct qcow1_header *header = q->header;
char *buf = dst;
u64 offset;
u32 length;
u32 nr;
length = 0;
while (length < dst_len) {
offset = sector << SECTOR_SHIFT;
if (offset >= header->size)
goto out_error;
nr = qcow1_read_cluster(q, offset, buf, dst_len - length);
if (!nr)
goto out_error;
length += nr;
buf += nr;
sector += (nr >> SECTOR_SHIFT);
}
return 0;
out_error:
return -1;
}