[ipxe-devel] uuid mangling patch

Michael Brown mbrown at fensystems.co.uk
Wed Mar 20 00:30:13 UTC 2013

On Tuesday 19 Mar 2013 16:16:10 Michael Brown wrote:
> Looks as though the endianness changed in SMBIOS 2.6, for some unknown
> reason:
>    http://linux.derkeiler.com/Mailing-Lists/Kernel/2011-01/msg07703.html
> This is incredibly annoying to deal with; iPXE treats a UUID (from any
> source) as being an opaque sequence of bytes.  It's only at the point of
> converting to a text string that we care about endianness, and at that
> point we have no knowledge of where the raw data came from.

I've pushed a patch to try to work around this problem:


UUIDs are still treated by iPXE as being in network byte order.  At the point 
of trying to read a UUID from SMBIOS (identified using a heuristic; it won't 
catch all cases but should catch most), we check the SMBIOS version number 
and, if it's 2.6 or newer, byte-swap the relevant fields to pretend that the 
data was stored in network byte order to begin with.

The upshot is that using ${uuid} should perform magical byte-swapping as 
needed, while the raw bytes can still be extracted using e.g. ${uuid:hex}.


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