On Sun, Apr 28, 2013 at 05:58:55PM +0800, Fam Zheng wrote:
> 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.
>
Yes, you are correct - I will add that in for v3.
> > +
> > + 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
