On Tue, 04/23 10:24, Jeff Cody wrote:
> +/* opens the specified header block from the VHDX file header section */
> +static int vhdx_parse_header(BlockDriverState *bs, BDRVVHDXState *s)
> +{
> + int ret = 0;
> + vhdx_header *header1;
> + vhdx_header *header2;
> + uint64_t h1_seq = 0;
> + uint64_t h2_seq = 0;
> + uint8_t *buffer;
> +
> + header1 = qemu_blockalign(bs, sizeof(vhdx_header));
> + header2 = qemu_blockalign(bs, sizeof(vhdx_header));
> +
> + buffer = qemu_blockalign(bs, VHDX_HEADER_SIZE);
> +
> + s->headers[0] = header1;
> + s->headers[1] = header2;
> +
Logic for header1 and header2 are completely the same, IMO it might be
better to avoid code with a loop.
> + /* We have to read the whole VHDX_HEADER_SIZE instead of
> + * sizeof(vhdx_header), because the checksum is over the whole
> + * region */
> + ret = bdrv_pread(bs->file, VHDX_HEADER1_OFFSET, buffer,
> VHDX_HEADER_SIZE);
> + if (ret < 0) {
> + goto fail;
> + }
> + /* copy over just the relevant portion that we need */
> + memcpy(header1, buffer, sizeof(vhdx_header));
> + vhdx_header_le_import(header1);
> +
> + if (vhdx_checksum_is_valid(buffer, VHDX_HEADER_SIZE, 4) &&
> + header1->signature == VHDX_HDR_MAGIC) {
> + h1_seq = header1->sequence_number;
> + }
Do we need to check the version here? As the specification page 15 says:
The Version field specifies the version of the VHDX format used
within the VHDX file. This field must be set to 1. If it is not, a
parser must not attempt to parse the file using the details from
this format specification.
> +
> + ret = bdrv_pread(bs->file, VHDX_HEADER2_OFFSET, buffer,
> VHDX_HEADER_SIZE);
> + if (ret < 0) {
> + goto fail;
> + }
> + /* copy over just the relevant portion that we need */
> + memcpy(header2, buffer, sizeof(vhdx_header));
> + vhdx_header_le_import(header2);
> +
> + if (vhdx_checksum_is_valid(buffer, VHDX_HEADER_SIZE, 4) &&
> + header2->signature == VHDX_HDR_MAGIC) {
> + h2_seq = header2->sequence_number;
> + }
Same as above.
> +
> + if (h1_seq > h2_seq) {
> + s->curr_header = 0;
> + } else if (h2_seq > h1_seq) {
> + s->curr_header = 1;
> + } else {
> + printf("NO VALID HEADER\n");
> + ret = -EINVAL;
> + goto fail;
> + }
> +
> + ret = 0;
> +
> + goto exit;
> +
> +fail:
> + qemu_vfree(header1);
> + qemu_vfree(header2);
> + s->headers[0] = NULL;
> + s->headers[1] = NULL;
> +exit:
> + qemu_vfree(buffer);
> + return ret;
> +}
--
Fam
