linux-kernel - Re: [PATCH] tcp: don't use __constant_cpu_to

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Message-ID: <20190318163208.GC7431@mini-arch.hsd1.ca.comcast.net>
Date:   Mon, 18 Mar 2019 09:32:08 -0700
From:   Stanislav Fomichev <sdf@...ichev.me>
To:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tcp: don't use __constant_cpu_to_be32

On 03/16, Sergey Senozhatsky wrote:
> On (03/16/19 14:19), Sergey Senozhatsky wrote:
> > # define __bpf_ntohs(x)                 __builtin_bswap16(x)
> > # define __bpf_htons(x)                 __builtin_bswap16(x)
> > 
> > So I sort of suspect that what should have been done was that
> > __HAVE_BUILTIN_BSWAP16__ ifdef, just like what include/uapi/linux/swab.h
> > does.
> 
> E.g. use uapi __swab16/__swab32 in selftests/bpf/bpf_endian.h?
> 
> -=-=-=-=-=-
> 
>  tools/testing/selftests/bpf/bpf_endian.h | 32 ++++++++------------------------
>  1 file changed, 8 insertions(+), 24 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/bpf_endian.h b/tools/testing/selftests/bpf/bpf_endian.h
> index b25595ea4a78..68789b4c7ef0 100644
> --- a/tools/testing/selftests/bpf/bpf_endian.h
> +++ b/tools/testing/selftests/bpf/bpf_endian.h
> @@ -20,38 +20,22 @@
>   * use different targets.
>   */
>  #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
> -# define __bpf_ntohs(x)			__builtin_bswap16(x)
> -# define __bpf_htons(x)			__builtin_bswap16(x)
> -# define __bpf_constant_ntohs(x)	___constant_swab16(x)
> -# define __bpf_constant_htons(x)	___constant_swab16(x)
> -# define __bpf_ntohl(x)			__builtin_bswap32(x)
> -# define __bpf_htonl(x)			__builtin_bswap32(x)
> -# define __bpf_constant_ntohl(x)	___constant_swab32(x)
> -# define __bpf_constant_htonl(x)	___constant_swab32(x)
> +# define __bpf_ntohs(x)			__swab16(x)
> +# define __bpf_htons(x)			__swab16(x)
> +# define __bpf_ntohl(x)			__swab32(x)
> +# define __bpf_htonl(x)			__swab32(x)
>  #elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
>  # define __bpf_ntohs(x)			(x)
>  # define __bpf_htons(x)			(x)
> -# define __bpf_constant_ntohs(x)	(x)
> -# define __bpf_constant_htons(x)	(x)
>  # define __bpf_ntohl(x)			(x)
>  # define __bpf_htonl(x)			(x)
> -# define __bpf_constant_ntohl(x)	(x)
> -# define __bpf_constant_htonl(x)	(x)
>  #else
>  # error "Fix your compiler's __BYTE_ORDER__?!"
>  #endif
>  
> -#define bpf_htons(x)				\
> -	(__builtin_constant_p(x) ?		\
> -	 __bpf_constant_htons(x) : __bpf_htons(x))
> -#define bpf_ntohs(x)				\
> -	(__builtin_constant_p(x) ?		\
> -	 __bpf_constant_ntohs(x) : __bpf_ntohs(x))
> -#define bpf_htonl(x)				\
> -	(__builtin_constant_p(x) ?		\
> -	 __bpf_constant_htonl(x) : __bpf_htonl(x))
> -#define bpf_ntohl(x)				\
> -	(__builtin_constant_p(x) ?		\
> -	 __bpf_constant_ntohl(x) : __bpf_ntohl(x))
> +#define bpf_htons(x)	__bpf_htons((x))
> +#define bpf_ntohs(x)	__bpf_ntohs((x))
> +#define bpf_htonl(x)	__bpf_htonl((x))
> +#define bpf_ntohl(x)	__bpf_ntohl((x))
At this point we can probably drop __bpf_xxx as well?
Care to resend with proper description when bpf-next opens?

>  
>  #endif /* __BPF_ENDIAN__ */