Re: [PATCH v4 1/1] ArmPkg/OpteeLib: Add APIs to communicate with OP-TEE

[Leif Lindholm <leif.lindholm@linaro.org>]

On Thu, Oct 18, 2018 at 12:59:32PM +0530, Sumit Garg wrote:
> > So, looking at the OpTee sources, TEE_UUID is defined as a struct, to
> > exactly the same layout as the EFI_GUID type (which is a typedef of
> > the GUID struct). Could we add a OPTEE_UUID typedef for the same
> > struct in OpteeLib.h?
> >
> > Since it comes in as an OPTEE_MESSAGE_PARAM_VALUE, alignment is
> > already guaranteed to be 64-bit.
> >
> > (This also deserves a comment explaining how EFI_GUID basically
> > follows rfc4122, but uses little-endian for the timestamp fields.)
> 
> Actually, OP-TEE also uses little-endian format for timestamp fields.
> You can refer to [1] for conversion from network byte order (octets)
> to little-endian and vice-versa.
> 
> So for communications among secure world and non-secure world it uses
> network byte order for UUID/GUID to comply with rfc4122.
> 
> [1] https://github.com/OP-TEE/optee_os/blob/master/core/tee/uuid.c

Huh, ok. That's good to know.
It does however not change my comments. Since we're dealing with data
structures of a known layout, I am not a fan of treating them as byte
arrays.

/
    Leif