# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1206638017 0
# Node ID 17e30b91b9e2a6607d7b2a7db011ac2a4f11d1d1
# Parent a819cf758b8cf5624214ba59bc0c13172b3c7f05
tapdisk: Fix L1 table endianess of qcow images
Fix tapdisk to use big endian L1 tables as used by qemu/ioemu. Old
tapdisk images with native endianess are automagically converted to
big endian when the image file is opened for the first time.
Signed-off-by: Kevin Wolf <kwolf@xxxxxxx>
---
tools/blktap/drivers/block-qcow.c | 68 ++++++++++++++++++++++++++++++++------
1 files changed, 59 insertions(+), 9 deletions(-)
diff -r a819cf758b8c -r 17e30b91b9e2 tools/blktap/drivers/block-qcow.c
--- a/tools/blktap/drivers/block-qcow.c Thu Mar 27 16:20:25 2008 +0000
+++ b/tools/blktap/drivers/block-qcow.c Thu Mar 27 17:13:37 2008 +0000
@@ -76,6 +76,7 @@
#define QCOW_OFLAG_COMPRESSED (1LL << 63)
#define SPARSE_FILE 0x01
+#define EXTHDR_L1_BIG_ENDIAN 0x02
#ifndef O_BINARY
#define O_BINARY 0
@@ -147,19 +148,30 @@ static int decompress_cluster(struct tdq
static uint32_t gen_cksum(char *ptr, int len)
{
+ int i;
unsigned char *md;
uint32_t ret;
md = malloc(MD5_DIGEST_LENGTH);
if(!md) return 0;
-
- if (MD5((unsigned char *)ptr, len, md) != md) {
- free(md);
- return 0;
- }
-
- memcpy(&ret, md, sizeof(uint32_t));
+
+ /* Convert L1 table to big endian */
+ for(i = 0; i < len / sizeof(uint64_t); i++) {
+ cpu_to_be64s(&((uint64_t*) ptr)[i]);
+ }
+
+ /* Generate checksum */
+ if (MD5((unsigned char *)ptr, len, md) != md)
+ ret = 0;
+ else
+ memcpy(&ret, md, sizeof(uint32_t));
+
+ /* Convert L1 table back to native endianess */
+ for(i = 0; i < len / sizeof(uint64_t); i++) {
+ be64_to_cpus(&((uint64_t*) ptr)[i]);
+ }
+
free(md);
return ret;
}
@@ -354,7 +366,8 @@ static uint64_t get_cluster_offset(struc
int n_start, int n_end)
{
int min_index, i, j, l1_index, l2_index, l2_sector, l1_sector;
- char *tmp_ptr, *tmp_ptr2, *l2_ptr, *l1_ptr;
+ char *tmp_ptr2, *l2_ptr, *l1_ptr;
+ uint64_t *tmp_ptr;
uint64_t l2_offset, *l2_table, cluster_offset, tmp;
uint32_t min_count;
int new_l2_table;
@@ -400,6 +413,11 @@ static uint64_t get_cluster_offset(struc
DPRINTF("ERROR allocating memory for L1 table\n");
}
memcpy(tmp_ptr, l1_ptr, 4096);
+
+ /* Convert block to write to big endian */
+ for(i = 0; i < 4096 / sizeof(uint64_t); i++) {
+ cpu_to_be64s(&tmp_ptr[i]);
+ }
/*
* Issue non-asynchronous L1 write.
@@ -777,7 +795,7 @@ int tdqcow_open (struct disk_driver *dd,
goto fail;
for(i = 0; i < s->l1_size; i++) {
- //be64_to_cpus(&s->l1_table[i]);
+ be64_to_cpus(&s->l1_table[i]);
//DPRINTF("L1[%d] => %llu\n", i, s->l1_table[i]);
if (s->l1_table[i] > final_cluster)
final_cluster = s->l1_table[i];
@@ -810,6 +828,38 @@ int tdqcow_open (struct disk_driver *dd,
be32_to_cpus(&exthdr->xmagic);
if(exthdr->xmagic != XEN_MAGIC)
goto end_xenhdr;
+
+ /* Try to detect old tapdisk images. They have to be fixed
because
+ * they don't use big endian but native endianess for the L1
table */
+ if ((exthdr->flags & EXTHDR_L1_BIG_ENDIAN) == 0) {
+
+ /*
+ The image is broken. Fix it. The L1 table has
already been
+ byte-swapped, so we can write it to the image file
as it is
+ currently in memory. Then swap it back to native
endianess
+ for operation.
+ */
+
+ DPRINTF("qcow: Converting image to big endian L1
table\n");
+
+ lseek(fd, s->l1_table_offset, SEEK_SET);
+ if (write(fd, s->l1_table, l1_table_size) !=
l1_table_size) {
+ DPRINTF("qcow: Failed to write new L1 table\n");
+ goto fail;
+ }
+
+ for(i = 0;i < s->l1_size; i++) {
+ cpu_to_be64s(&s->l1_table[i]);
+ }
+
+ /* Write the big endian flag to the extended header */
+ exthdr->flags |= EXTHDR_L1_BIG_ENDIAN;
+
+ if (write(fd, buf, 512) != 512) {
+ DPRINTF("qcow: Failed to write extended
header\n");
+ goto fail;
+ }
+ }
/*Finally check the L1 table cksum*/
be32_to_cpus(&exthdr->cksum);
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