Re: [SeaBIOS] [PATCH] biostables: Support SMBIOS 2.6+ UUID format

[Kevin O'Connor]

On Tue, Jan 12, 2016 at 02:22:41PM -0500, Cole Robinson wrote:
> SMBIOS 2.6+ stores the UUID in a different format, with the first 3
> fields in little endian format. This is what modern qemu delivers
> and what dmidecode also handles, so let's follow suit too. More
> info at this thread:
>
> http://www.seabios.org/pipermail/seabios/2015-November/010031.html
>
> The only place this affects is when reporting the UUID at startup.
> https://bugzilla.redhat.com/show_bug.cgi?id=1284259
>
> src/fw/biostables.c | 51 ++++++++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 40 insertions(+), 11 deletions(-)
>
> diff --git a/src/fw/biostables.c b/src/fw/biostables.c
> index cb74396..2e15f82 100644
> --- a/src/fw/biostables.c
> +++ b/src/fw/biostables.c
> @@ -306,17 +306,46 @@ display_uuid(void)
>              if (memcmp(uuid, empty_uuid, sizeof(empty_uuid)) == 0)
>                  return;
>        printf("Machine UUID"
>               " %02x%02x%02x%02x"
>               "-%02x%02x"
>               "-%02x%02x"
>               "-%02x%02x"
>               "-%02x%02x%02x%02x%02x%02x\n"
>               , uuid[ 0], uuid[ 1], uuid[ 2], uuid[ 3]
>               , uuid[ 4], uuid[ 5]
>               , uuid[ 6], uuid[ 7]
>               , uuid[ 8], uuid[ 9]
>               , uuid[10], uuid[11], uuid[12], uuid[13], uuid[14], uuid[15]);
>        /*
>        * comment borrowed from dmidecode:
>        *
>        * As of version 2.6 of the SMBIOS specification, the first 3
>        * fields of the UUID are supposed to be encoded on little-endian.
>        * The specification says that this is the defacto standard,
>        * however I've seen systems following RFC 4122 instead and use
>        * network byte order, so I am reluctant to apply the byte-swapping
>        * for older versions.
>        */

I find this comment confusing - how about something like:

According to SMBIOS v2.6 the first three fields are encoded in
little-endian format.  Versions prior to v2.6 did not specify the
encoding, but we follow dmidecode and assume big-endian encoding.
>        if (SMBiosAddr->smbios_major_version > 2 ||
>            (SMBiosAddr->smbios_major_version == 2 &&
>             SMBiosAddr->smbios_minor_version >= 6)) {
>            printf("Machine UUID"
>                   " %02x%02x%02x%02x"
>                   "-%02x%02x"
>                   "-%02x%02x"
>                   "-%02x%02x"
>                   "-%02x%02x%02x%02x%02x%02x\n"
>                   , uuid[ 3], uuid[ 2], uuid[ 1], uuid[ 0]
>                   , uuid[ 5], uuid[ 4]
>                   , uuid[ 7], uuid[ 6]
>                   , uuid[ 8], uuid[ 9]
>                   , uuid[10], uuid[11], uuid[12]
>                   , uuid[13], uuid[14], uuid[15]);
>        } else {
>            printf("Machine UUID"
>                   " %02x%02x%02x%02x"
>                   "-%02x%02x"
>                   "-%02x%02x"
>                   "-%02x%02x"
>                   "-%02x%02x%02x%02x%02x%02x\n"
>                   , uuid[ 0], uuid[ 1], uuid[ 2], uuid[ 3]
>                   , uuid[ 4], uuid[ 5]
>                   , uuid[ 6], uuid[ 7]
>                   , uuid[ 8], uuid[ 9]
>                   , uuid[10], uuid[11], uuid[12]
>                   , uuid[13], uuid[14], uuid[15]);
>        }

The above is okay to me, but I'd like to get Gerd's comments as well,
as I think he had some concerns the last time it came up.

-Kevin