Re: [Qemu-devel] [PATCH v2 2/2] vmdk: Read footer for streamOptimized images

[Jeff Cody <jcody@redhat.com>]

On 08/16/2012 05:50 AM, Kevin Wolf wrote:
> The footer takes precedence over the header when it exists. It contains
> the real grain directory offset that is missing in the header. Without
> this patch, streamOptimized images with a footer cannot be read.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
> v2:
> - Enough footer sanity checks, I hope? :-)
> 
>  block/vmdk.c |   56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 56 insertions(+), 0 deletions(-)
> 
> diff --git a/block/vmdk.c b/block/vmdk.c
> index 9648398..bba4c61 100644
> --- a/block/vmdk.c
> +++ b/block/vmdk.c
> @@ -35,6 +35,7 @@
>  #define VMDK4_FLAG_RGD (1 << 1)
>  #define VMDK4_FLAG_COMPRESS (1 << 16)
>  #define VMDK4_FLAG_MARKER (1 << 17)
> +#define VMDK4_GD_AT_END 0xffffffffffffffffULL
>  
>  typedef struct {
>      uint32_t version;
> @@ -115,6 +116,13 @@ typedef struct VmdkGrainMarker {
>      uint8_t  data[0];
>  } VmdkGrainMarker;
>  
> +enum {
> +    MARKER_END_OF_STREAM    = 0,
> +    MARKER_GRAIN_TABLE      = 1,
> +    MARKER_GRAIN_DIRECTORY  = 2,
> +    MARKER_FOOTER           = 3,
> +};
> +
>  static int vmdk_probe(const uint8_t *buf, int buf_size, const char *filename)
>  {
>      uint32_t magic;
> @@ -451,6 +459,54 @@ static int vmdk_open_vmdk4(BlockDriverState *bs,
>      if (header.capacity == 0 && header.desc_offset) {
>          return vmdk_open_desc_file(bs, flags, header.desc_offset << 9);
>      }
> +
> +    if (le64_to_cpu(header.gd_offset) == VMDK4_GD_AT_END) {
> +        /*
> +         * The footer takes precedence over the header, so read it in. The
> +         * footer starts at offset -1024 from the end: One sector for the
> +         * footer, and another one for the end-of-stream marker.
> +         */
> +        struct {
> +            struct {
> +                uint64_t val;
> +                uint32_t size;
> +                uint32_t type;
> +                uint8_t pad[512 - 16];
> +            } QEMU_PACKED footer_marker;
> +
> +            uint32_t magic;
> +            VMDK4Header header;
> +            uint8_t pad[512 - 4 - sizeof(VMDK4Header)];
> +
> +            struct {
> +                uint64_t val;
> +                uint32_t size;
> +                uint32_t type;
> +                uint8_t pad[512 - 16];
> +            } QEMU_PACKED eos_marker;
> +        } QEMU_PACKED footer;
> +
> +        ret = bdrv_pread(file,
> +            bs->file->total_sectors * 512 - 1536,
> +            &footer, sizeof(footer));
> +        if (ret < 0) {
> +            return ret;
> +        }
> +
> +        /* Some sanity checks for the footer */
> +        if (be32_to_cpu(footer.magic) != VMDK4_MAGIC ||
> +            le32_to_cpu(footer.footer_marker.size) != 0  ||
> +            le32_to_cpu(footer.footer_marker.type) != MARKER_FOOTER ||
> +            le64_to_cpu(footer.eos_marker.val) != 0  ||
> +            le32_to_cpu(footer.eos_marker.size) != 0  ||
> +            le32_to_cpu(footer.eos_marker.type) != MARKER_END_OF_STREAM)
> +        {
> +            return -EINVAL;
> +        }
> +
> +        header = footer.header;
> +    }
> +
>      l1_entry_sectors = le32_to_cpu(header.num_gtes_per_gte)
>                          * le64_to_cpu(header.granularity);
>      if (l1_entry_sectors == 0) {
> 

Reviewed-by: Jeff Cody <jcody@redhat.com>