This adds the ability to update the headers in a VHDX image, including
generating a new MS-compatible GUID.
As VHDX depends on uuid.h, VHDX is now a configurable build option. If
VHDX support is enabled, that will also enable uuid as well. The
default is to have VHDX enabled.
To enable/disable VHDX: --enable-vhdx, --disable-vhdx
Signed-off-by: Jeff Cody <jc...@redhat.com>
---
block/Makefile.objs | 2 +-
block/vhdx.c | 161 +++++++++++++++++++++++++++++++++++++++++++++++++++-
block/vhdx.h | 14 ++++-
configure | 24 ++++++++
4 files changed, 196 insertions(+), 5 deletions(-)
diff --git a/block/Makefile.objs b/block/Makefile.objs
index 4cf9aa4..e5e54e6 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -2,7 +2,7 @@ block-obj-y += raw.o cow.o qcow.o vdi.o vmdk.o cloop.o dmg.o
bochs.o vpc.o vvfat
block-obj-y += qcow2.o qcow2-refcount.o qcow2-cluster.o qcow2-snapshot.o
qcow2-cache.o
block-obj-y += qed.o qed-gencb.o qed-l2-cache.o qed-table.o qed-cluster.o
block-obj-y += qed-check.o
-block-obj-y += vhdx.o
+block-obj-$(CONFIG_VHDX) += vhdx.o
block-obj-y += parallels.o blkdebug.o blkverify.o
block-obj-y += snapshot.o qapi.o
block-obj-$(CONFIG_WIN32) += raw-win32.o win32-aio.o
diff --git a/block/vhdx.c b/block/vhdx.c
index 56bc88e..7bd7c12 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -21,6 +21,7 @@
#include "qemu/crc32c.h"
#include "block/vhdx.h"
+#include <uuid/uuid.h>
/* Several metadata and region table data entries are identified by
* guids in a MS-specific GUID format. */
@@ -156,11 +157,40 @@ typedef struct BDRVVHDXState {
VHDXBatEntry *bat;
uint64_t bat_offset;
+ MSGUID session_guid;
+
+
VHDXParentLocatorHeader parent_header;
VHDXParentLocatorEntry *parent_entries;
} BDRVVHDXState;
+/* Calculates new checksum.
+ *
+ * Zero is substituted during crc calculation for the original crc field
+ * crc_offset: byte offset in buf of the buffer crc
+ * buf: buffer pointer
+ * size: size of buffer (must be > crc_offset+4)
+ *
+ * Note: The resulting checksum is in the CPU endianness, not necessarily
+ * in the file format endianness (LE). Any header export to disk should
+ * make sure that vhdx_header_le_export() is used to convert to the
+ * correct endianness
+ */
+uint32_t vhdx_update_checksum(uint8_t *buf, size_t size, int crc_offset)
+{
+ uint32_t crc;
+
+ assert(buf != NULL);
+ assert(size > (crc_offset + sizeof(crc)));
+
+ memset(buf + crc_offset, 0, sizeof(crc));
+ crc = crc32c(0xffffffff, buf, size);
+ memcpy(buf + crc_offset, &crc, sizeof(crc));
+
+ return crc;
+}
+
uint32_t vhdx_checksum_calc(uint32_t crc, uint8_t *buf, size_t size,
int crc_offset)
{
@@ -212,6 +242,19 @@ bool vhdx_checksum_is_valid(uint8_t *buf, size_t size, int
crc_offset)
/*
+ * This generates a UUID that is compliant with the MS GUIDs used
+ * in the VHDX spec (and elsewhere).
+ */
+void vhdx_guid_generate(MSGUID *guid)
+{
+ uuid_t uuid;
+ assert(guid != NULL);
+
+ uuid_generate(uuid);
+ memcpy(guid, uuid, sizeof(MSGUID));
+}
+
+/*
* Per the MS VHDX Specification, for every VHDX file:
* - The header section is fixed size - 1 MB
* - The header section is always the first "object"
@@ -249,6 +292,113 @@ static void vhdx_header_le_import(VHDXHeader *h)
le64_to_cpus(&h->log_offset);
}
+/* All VHDX structures on disk are little endian */
+static void vhdx_header_le_export(VHDXHeader *orig_h, VHDXHeader *new_h)
+{
+ assert(orig_h != NULL);
+ assert(new_h != NULL);
+
+ new_h->signature = cpu_to_le32(orig_h->signature);
+ new_h->checksum = cpu_to_le32(orig_h->checksum);
+ new_h->sequence_number = cpu_to_le64(orig_h->sequence_number);
+
+ new_h->file_write_guid = orig_h->file_write_guid;
+ new_h->data_write_guid = orig_h->data_write_guid;
+ new_h->log_guid = orig_h->log_guid;
+
+ cpu_to_leguids(&new_h->file_write_guid);
+ cpu_to_leguids(&new_h->data_write_guid);
+ cpu_to_leguids(&new_h->log_guid);
+
+ new_h->log_version = cpu_to_le16(orig_h->log_version);
+ new_h->version = cpu_to_le16(orig_h->version);
+ new_h->log_length = cpu_to_le32(orig_h->log_length);
+ new_h->log_offset = cpu_to_le64(orig_h->log_offset);
+}
+
+/* Update the VHDX headers
+ *
+ * This follows the VHDX spec procedures for header updates.
+ *
+ * - non-current header is updated with largest sequence number
+ */
+static int vhdx_update_header(BlockDriverState *bs, BDRVVHDXState *s,
+ bool generate_data_write_guid)
+{
+ int ret = 0;
+ int hdr_idx = 0;
+ uint64_t header_offset = VHDX_HEADER1_OFFSET;
+
+ VHDXHeader *active_header;
+ VHDXHeader *inactive_header;
+ VHDXHeader header_le;
+ uint8_t *buffer;
+
+ /* operate on the non-current header */
+ if (s->curr_header == 0) {
+ hdr_idx = 1;
+ header_offset = VHDX_HEADER2_OFFSET;
+ }
+
+ active_header = s->headers[s->curr_header];
+ inactive_header = s->headers[hdr_idx];
+
+ inactive_header->sequence_number = active_header->sequence_number + 1;
+
+ /* a new file guid must be generated before any file write, including
+ * headers */
+ inactive_header->file_write_guid = s->session_guid;
+
+ /* a new data guid only needs to be generated before any guest-visible
+ * writes (i.e. something observable via virtual disk read) */
+ if (generate_data_write_guid) {
+ vhdx_guid_generate(&inactive_header->data_write_guid);
+ }
+
+ /* the header checksum is not over just the packed size of VHDXHeader,
+ * but rather over the entire 'reserved' range for the header, which is
+ * 4KB (VHDX_HEADER_SIZE). */
+
+ buffer = qemu_blockalign(bs, VHDX_HEADER_SIZE);
+ /* we can't assume the extra reserved bytes are 0 */
+ ret = bdrv_pread(bs->file, header_offset, buffer, VHDX_HEADER_SIZE);
+ if (ret < 0) {
+ goto exit;
+ }
+ /* overwrite the actual VHDXHeader portion */
+ memcpy(buffer, inactive_header, sizeof(VHDXHeader));
+ inactive_header->checksum =
+ vhdx_update_checksum(buffer, VHDX_HEADER_SIZE,
+ offsetof(VHDXHeader, checksum));
+ vhdx_header_le_export(inactive_header, &header_le);
+ ret = bdrv_pwrite_sync(bs->file, header_offset, &header_le,
+ sizeof(VHDXHeader));
+ if (ret < 0) {
+ goto exit;
+ }
+ s->curr_header = hdr_idx;
+
+exit:
+ qemu_vfree(buffer);
+ return ret;
+}
+
+/*
+ * The VHDX spec calls for header updates to be performed twice, so that both
+ * the current and non-current header have valid info
+ */
+static int vhdx_update_headers(BlockDriverState *bs, BDRVVHDXState *s,
+ bool generate_data_write_guid)
+{
+ int ret;
+
+ ret = vhdx_update_header(bs, s, generate_data_write_guid);
+ if (ret < 0) {
+ return ret;
+ }
+ ret = vhdx_update_header(bs, s, generate_data_write_guid);
+ return ret;
+}
/* opens the specified header block from the VHDX file header section */
static int vhdx_parse_header(BlockDriverState *bs, BDRVVHDXState *s)
@@ -739,6 +889,11 @@ static int vhdx_open(BlockDriverState *bs, QDict *options,
int flags)
goto fail;
}
+ /* This is used for any header updates, for the file_write_guid.
+ * The spec dictates that a new value should be used for the first
+ * header update */
+ vhdx_guid_generate(&s->session_guid);
+
ret = vhdx_parse_header(bs, s);
if (ret) {
goto fail;
@@ -801,8 +956,10 @@ static int vhdx_open(BlockDriverState *bs, QDict *options,
int flags)
}
if (flags & BDRV_O_RDWR) {
- ret = -ENOTSUP;
- goto fail;
+ ret = vhdx_update_headers(bs, s, false);
+ if (ret < 0) {
+ goto fail;
+ }
}
/* TODO: differencing files, write */
diff --git a/block/vhdx.h b/block/vhdx.h
index 9eb6b97..403f766 100644
--- a/block/vhdx.h
+++ b/block/vhdx.h
@@ -67,7 +67,7 @@ typedef struct VHDXFileIdentifier {
* Microsoft is not just 16 bytes though - it is a structure that is defined,
* so we need to follow it here so that endianness does not trip us up */
-typedef struct MSGUID {
+typedef struct QEMU_PACKED MSGUID {
uint32_t data1;
uint16_t data2;
uint16_t data3;
@@ -309,17 +309,27 @@ typedef struct QEMU_PACKED VHDXParentLocatorEntry {
/* ----- END VHDX SPECIFICATION STRUCTURES ---- */
+void vhdx_guid_generate(MSGUID *guid);
+
+uint32_t vhdx_update_checksum(uint8_t *buf, size_t size, int crc_offset);
uint32_t vhdx_checksum_calc(uint32_t crc, uint8_t *buf, size_t size,
int crc_offset);
bool vhdx_checksum_is_valid(uint8_t *buf, size_t size, int crc_offset);
-static void leguid_to_cpus(MSGUID *guid)
+static inline void leguid_to_cpus(MSGUID *guid)
{
le32_to_cpus(&guid->data1);
le16_to_cpus(&guid->data2);
le16_to_cpus(&guid->data3);
}
+static inline void cpu_to_leguids(MSGUID *guid)
+{
+ cpu_to_le32s(&guid->data1);
+ cpu_to_le16s(&guid->data2);
+ cpu_to_le16s(&guid->data3);
+}
+
#endif
diff --git a/configure b/configure
index 18fa608..d02488d 100755
--- a/configure
+++ b/configure
@@ -243,6 +243,7 @@ gtk=""
gtkabi="2.0"
tpm="no"
libssh2=""
+vhdx=""
# parse CC options first
for opt do
@@ -945,6 +946,10 @@ for opt do
;;
--enable-libssh2) libssh2="yes"
;;
+ --enable-vhdx) vhdx="yes"
+ ;;
+ --disable-vhdx) vhdx="no"
+ ;;
*) echo "ERROR: unknown option $opt"; show_help="yes"
;;
esac
@@ -1159,6 +1164,8 @@ echo " --gcov=GCOV use specified gcov
[$gcov_tool]"
echo " --enable-tpm enable TPM support"
echo " --disable-libssh2 disable ssh block device support"
echo " --enable-libssh2 enable ssh block device support"
+echo " --disable-vhdx disables support for the Microsoft VHDX image
format"
+echo " --enable-vhdx enable support for the Microsoft VHDX image
format"
echo ""
echo "NOTE: The object files are built at the place where configure is
launched"
exit 1
@@ -1970,6 +1977,18 @@ EOF
fi
fi
+if test "$vhdx" = "yes" ; then
+ if test "$uuid" = "no" ; then
+ error_exit "uuid required for VHDX support"
+ fi
+elif test "$vhdx" != "no" ; then
+ if test "$uuid" = "yes" ; then
+ vhdx=yes
+ else
+ vhdx=no
+ fi
+fi
+
##########################################
# xfsctl() probe, used for raw-posix
if test "$xfs" != "no" ; then
@@ -3613,6 +3632,7 @@ echo "TPM support $tpm"
echo "libssh2 support $libssh2"
echo "TPM passthrough $tpm_passthrough"
echo "QOM debugging $qom_cast_debug"
+echo "vhdx $vhdx"
if test "$sdl_too_old" = "yes"; then
echo "-> Your SDL version is too old - please upgrade to have SDL support"
@@ -4003,6 +4023,10 @@ if test "$virtio_blk_data_plane" = "yes" ; then
echo 'CONFIG_VIRTIO_BLK_DATA_PLANE=$(CONFIG_VIRTIO)' >> $config_host_mak
fi
+if test "$vhdx" = "yes" ; then
+ echo "CONFIG_VHDX=y" >> $config_host_mak
+fi
+
# USB host support
case "$usb" in
linux)
--
1.8.1.4
