linux-kernel - Re: [PATCH] net/tls: fix const assignment warning

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Message-ID: <67e50644-c48e-12b7-4d12-b344f2024090@mellanox.com>
Date:   Wed, 8 Apr 2020 21:59:49 +0300
From:   Boris Pismenny <borisp@...lanox.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Aviad Yehezkel <aviadye@...lanox.com>,
        John Fastabend <john.fastabend@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Sitnicki <jakub@...udflare.com>
Cc:     Dirk van der Merwe <dirk.vandermerwe@...ronome.com>,
        Simon Horman <simon.horman@...ronome.com>,
        Davide Caratti <dcaratti@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net/tls: fix const assignment warning


On 08/04/2020 21:54, Arnd Bergmann wrote:
> Building with some experimental patches, I came across a warning
> in the tls code:
> 
> include/linux/compiler.h:215:30: warning: assignment discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
>   215 |  *(volatile typeof(x) *)&(x) = (val);  \
>       |                              ^
> net/tls/tls_main.c:650:4: note: in expansion of macro 'smp_store_release'
>   650 |    smp_store_release(&saved_tcpv4_prot, prot);
> 
> This appears to be a legitimate warning about assigning a const pointer
> into the non-const 'saved_tcpv4_prot' global. Annotate both the ipv4 and
> ipv6 pointers 'const' to make the code internally consistent.
> 
> Fixes: 5bb4c45d466c ("net/tls: Read sk_prot once when building tls proto ops")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  net/tls/tls_main.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
> index 156efce50dbd..0e989005bdc2 100644
> --- a/net/tls/tls_main.c
> +++ b/net/tls/tls_main.c
> @@ -56,9 +56,9 @@ enum {
>  	TLS_NUM_PROTS,
>  };
>  
> -static struct proto *saved_tcpv6_prot;
> +static const struct proto *saved_tcpv6_prot;
>  static DEFINE_MUTEX(tcpv6_prot_mutex);
> -static struct proto *saved_tcpv4_prot;
> +static const struct proto *saved_tcpv4_prot;
>  static DEFINE_MUTEX(tcpv4_prot_mutex);
>  static struct proto tls_prots[TLS_NUM_PROTS][TLS_NUM_CONFIG][TLS_NUM_CONFIG];
>  static struct proto_ops tls_sw_proto_ops;
> 

LGTM