linux-kernel - Re: [PATCH linux-next v2] mpls: don't build sysctl related code when sysctl is disabled

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Message-ID: <ea97df59-481b-3f05-476c-33e733b5c4ba@gmail.com>
Date:   Fri, 7 Jun 2019 11:14:41 -0600
From:   David Ahern <dsahern@...il.com>
To:     Matteo Croce <mcroce@...hat.com>, netdev@...r.kernel.org,
        linux-next@...r.kernel.org, akpm@...ux-foundation.org,
        Randy Dunlap <rdunlap@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH linux-next v2] mpls: don't build sysctl related code when
 sysctl is disabled

On 6/6/19 6:36 PM, Matteo Croce wrote:
> Some sysctl related code and data structures is never referenced
> when CONFIG_SYSCTL is not set.
> While this is usually harmless, it produces a build failure since sysctl
> shared variables exists, due to missing sysctl_vals symbol:
> 
>     ld: net/mpls/af_mpls.o: in function `mpls_platform_labels':
>     af_mpls.c:(.text+0x162a): undefined reference to `sysctl_vals'
>     ld: net/mpls/af_mpls.o:(.rodata+0x830): undefined reference to `sysctl_vals'
>     ld: net/mpls/af_mpls.o:(.rodata+0x838): undefined reference to `sysctl_vals'
>     ld: net/mpls/af_mpls.o:(.rodata+0x870): undefined reference to `sysctl_vals'
> 
> Fix this by moving all sysctl related code under #ifdef CONFIG_SYSCTL
> 
> Reported-by: Randy Dunlap <rdunlap@...radead.org>
> Signed-off-by: Matteo Croce <mcroce@...hat.com>
> ---
> 
> v1 -> v2: fix a crash on netns destroy
> 
>  net/mpls/af_mpls.c | 393 ++++++++++++++++++++++++---------------------
>  1 file changed, 207 insertions(+), 186 deletions(-)
> 

As I recall you need to set platform_labels for the mpls code to even
work, so building mpls_router without sysctl is pointless.