Am 01.08.2013 um 05:23 hat Jeff Cody geschrieben:
> 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 | 157
> +++++++++++++++++++++++++++++++++++++++++++++++++++-
> block/vhdx.h | 12 +++-
> configure | 13 +++++
> 4 files changed, 180 insertions(+), 4 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..9b50442 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 + 4));
sizeof(crc) for consistency.
> +
> + 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 +242,24 @@ 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).
> + *
> + * We can do this with uuid_generate if uuid.h is present,
> + * however not all systems have uuid and the generation is
> + * pretty straightforward for the DCE + random usage case
> + *
> + */
> +void vhdx_guid_generate(MSGUID *guid)
> +{
> + uuid_t uuid;
> + assert(guid != NULL);
> +
> + uuid_generate(uuid);
> + memcpy(guid, uuid, 16);
> +}
Should MSGUID be QEMU_PACKED to make sure that this works? Also
sizeof(guid) instead of 16?
> +
> +/*
> * 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 +297,107 @@ 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);
> +
> + memcpy(&new_h->file_write_guid, &orig_h->file_write_guid,
> sizeof(MSGUID));
> + memcpy(&new_h->data_write_guid, &orig_h->data_write_guid,
> sizeof(MSGUID));
> + memcpy(&new_h->log_guid, &orig_h->log_guid,
> sizeof(MSGUID));
Can we avoid memcpy? I think this should work:
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
> rw)
> +{
> + 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 generate before any file write, including
> + * headers */
> + memcpy(&inactive_header->file_write_guid, &s->session_guid,
> + sizeof(MSGUID));
Here a simple assignment should do as well.
> +
> + /* a new data guid only needs to be generate before any guest-visible
> + * writes, so update it if the image is opened r/w. */
> + if (rw) {
> + 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, 4);
> + vhdx_header_le_export(inactive_header, &header_le);
> + bdrv_pwrite_sync(bs->file, header_offset, &header_le,
> sizeof(VHDXHeader));
> + s->curr_header = hdr_idx;
> +
> +exit:
> + qemu_vfree(buffer);
> + return ret;
> +}
Kevin
