Re: [Xen-devel] [PATCH v7 04/11] public: xen.h: add definitions for UUID handling

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Oct 05, 2017 at 12:00:20AM +0300, Volodymyr Babchuk wrote:
> Added type xen_uuid_t. This type represents UUID as an array of 16
> bytes in big endian format.
> 
> Added macro XEN_DEFINE_UUID that constructs UUID in the usual way:
> 
>  XEN_DEFINE_UUID(0x00112233, 0x4455, 0x6677, 0x8899,
>               0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff)
> 
> will construct UUID 00112233-4455-6677-8899-aabbccddeeff presented as
>  {0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88,
>   0x99, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff}
> 
> NB: This is compatible with Linux kernel and with libuuid, but it is not
> compatible with Microsoft, as they use mixed-endian encoding (some
> components are little-endian, some are big-endian).

Oh boy. What a mess.

Do we care about Microsoft for this or is this more for information
purpose?
> 
> Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
> ---
> 
> * Fixed example for XEN_DEFINE_UUID() usage. Was
>   XEN_DEFINE_UUID(0x00112233, 0x4455, 0x6677, 0x8899, 0xaabbccddeeff)
> 
> * Added comment to xen.h
> 
> * Used
>   #if defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
>   instead of
>   #if defined(__GNUC__) && !defined(__STRICT_ANSI__)
> 
> * Used generic macro XEN_DEFINE_UUID_
> 
> ---
> xen/include/public/xen.h | 33 +++++++++++++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
> 
> diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
> index 2ac6b1e..1a6255f 100644
> --- a/xen/include/public/xen.h
> +++ b/xen/include/public/xen.h
> @@ -930,6 +930,39 @@ __DEFINE_XEN_GUEST_HANDLE(uint16, uint16_t);
>  __DEFINE_XEN_GUEST_HANDLE(uint32, uint32_t);
>  __DEFINE_XEN_GUEST_HANDLE(uint64, uint64_t);
>  
> +typedef struct
> +{
> +    uint8_t a[16];
> +} xen_uuid_t;
> +
> +/*
> + * XEN_DEFINE_UUID(0x00112233, 0x4455, 0x6677, 0x8899,
> + *                 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff)
> + * will construct UUID 00112233-4455-6677-8899-aabbccddeeff presented as
> + * {0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88,
> + * 0x99, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff};
> + *
> + * NB: This is compatible with Linux kernel and with libuuid, but it is not
> + * compatible with Microsoft, as they use mixed-endian encoding (some
> + * components are little-endian, some are big-endian).
> + */
> +#define XEN_DEFINE_UUID_(a, b, c, d, e1, e2, e3, e4, e5, e6)            \
> +    {{((a) >> 24) & 0xFF, ((a) >> 16) & 0xFF,                           \
> +      ((a) >>  8) & 0xFF, ((a) >>  0) & 0xFF,                           \
> +      ((b) >>  8) & 0xFF, ((b) >>  0) & 0xFF,                           \
> +      ((c) >>  8) & 0xFF, ((c) >>  0) & 0xFF,                           \
> +      ((d) >>  8) & 0xFF, ((d) >>  0) & 0xFF,                           \
> +                e1, e2, e3, e4, e5, e6}}
> +
> +/* Compound literals are supported in C99 and later. */
> +#if defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
> +#define XEN_DEFINE_UUID(a, b, c, d, e1, e2, e3, e4, e5, e6)             \
> +    (xen_uuid_t)XEN_DEFINE_UUID_(a, b, c, d, e1, e2, e3, e4, e5, e6)
> +#else
> +#define XEN_DEFINE_UUID(a, b, c, d, e1, e2, e3, e4, e5, e6)             \
> +    XEN_DEFINE_UUID_(a, b, c, d, e1, e2, e3, e4, e5, e6)
> +#endif /* defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L */
> +
>  #endif /* !__ASSEMBLY__ */
>  
>  /* Default definitions for macros used by domctl/sysctl. */
> -- 
> 2.7.4
> 
> 
> _______________________________________________
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