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Date: Sun, 3 Dec 2017 14:28:25 +0300
From: "Dmitry V. Levin" <ldv@...linux.org>
To: Felix Janda <felix.janda@...teo.de>
Cc: linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
musl@...ts.openwall.com, Hauke Mehrtens <hauke@...ke-m.de>,
"David S. Miller" <davem@...emloft.net>,
Carlos O'Donell <carlos@...hat.com>,
Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCHv3 resend] uapi libc compat: add fallback for unsupported
libcs
Hi,
On Sun, Nov 12, 2017 at 01:30:17PM -0500, Felix Janda wrote:
> libc-compat.h aims to prevent symbol collisions between uapi and libc
> headers for each supported libc. This requires continuous coordination
> between them.
>
> The goal of this commit is to improve the situation for libcs (such as
> musl) which are not yet supported and/or do not wish to be explicitly
> supported, while not affecting supported libcs. More precisely, with
> this commit, unsupported libcs can request the suppression of any
> specific uapi definition by defining the correspondings _UAPI_DEF_*
> macro as 0. This can fix symbol collisions for them, as long as the
> libc headers are included before the uapi headers. Inclusion in the
> other order is outside the scope of this commit.
>
> All infrastructure in order to enable this fallback for unsupported
> libcs is already in place, except that libc-compat.h unconditionally
> defines all _UAPI_DEF_* macros to 1 for all unsupported libcs so that
> any previous definitions are ignored. In order to fix this, this commit
> merely makes these definitions conditional.
>
> This commit together with the musl libc commit
>
> http://git.musl-libc.org/cgit/musl/commit/?id=04983f2272382af92eb8f8838964ff944fbb8258
>
> fixes for example the following compiler errors when <linux/in6.h> is
> included after musl's <netinet/in.h>:
>
> ./linux/in6.h:32:8: error: redefinition of 'struct in6_addr'
> ./linux/in6.h:49:8: error: redefinition of 'struct sockaddr_in6'
> ./linux/in6.h:59:8: error: redefinition of 'struct ipv6_mreq'
>
> Signed-off-by: Felix Janda <felix.janda@...teo.de>
> Reviewed-by: Hauke Mehrtens <hauke@...ke-m.de>
> ---
> v3: Fix typos, add a comment to the file and use #ifndef.
> v2: The only change to the previous version is the commit title and
> message.
> ---
> include/uapi/linux/libc-compat.h | 55 +++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 54 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/libc-compat.h b/include/uapi/linux/libc-compat.h
> index 44b8a6bd5fe1..65db6b26d790 100644
> --- a/include/uapi/linux/libc-compat.h
> +++ b/include/uapi/linux/libc-compat.h
> @@ -167,46 +167,99 @@
>
> /* If we did not see any headers from any supported C libraries,
> * or we are being included in the kernel, then define everything
> - * that we need. */
> + * that we need. Check for previous __UAPI_* definitions to give
> + * unsupported C libraries a way to opt out of any kernel definition. */
> #else /* !defined(__GLIBC__) */
>
> /* Definitions for if.h */
> +#ifndef __UAPI_DEF_IF_IFCONF
> #define __UAPI_DEF_IF_IFCONF 1
> +#endif
> +#ifndef __UAPI_DEF_IF_IFMAP
> #define __UAPI_DEF_IF_IFMAP 1
> +#endif
> +#ifndef __UAPI_DEF_IF_IFNAMSIZ
> #define __UAPI_DEF_IF_IFNAMSIZ 1
> +#endif
> +#ifndef __UAPI_DEF_IF_IFREQ
> #define __UAPI_DEF_IF_IFREQ 1
> +#endif
> /* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
> +#ifndef __UAPI_DEF_IF_NET_DEVICE_FLAGS
> #define __UAPI_DEF_IF_NET_DEVICE_FLAGS 1
> +#endif
> /* For the future if glibc adds IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO */
> +#ifndef __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO
> #define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
> +#endif
Please double-check that mentioning glibc in comments
of this !__GLIBC__ section is relevant.
>
> /* Definitions for in.h */
> +#ifndef __UAPI_DEF_IN_ADDR
> #define __UAPI_DEF_IN_ADDR 1
> +#endif
> +#ifndef __UAPI_DEF_IN_IPPROTO
> #define __UAPI_DEF_IN_IPPROTO 1
> +#endif
> +#ifndef __UAPI_DEF_IN_PKTINFO
> #define __UAPI_DEF_IN_PKTINFO 1
> +#endif
> +#ifndef __UAPI_DEF_IP_MREQ
> #define __UAPI_DEF_IP_MREQ 1
> +#endif
> +#ifndef __UAPI_DEF_SOCKADDR_IN
> #define __UAPI_DEF_SOCKADDR_IN 1
> +#endif
> +#ifndef __UAPI_DEF_IN_CLASS
> #define __UAPI_DEF_IN_CLASS 1
> +#endif
>
> /* Definitions for in6.h */
> +#ifndef __UAPI_DEF_IN6_ADDR
> #define __UAPI_DEF_IN6_ADDR 1
> +#endif
> +#ifndef __UAPI_DEF_IN6_ADDR_ALT
> #define __UAPI_DEF_IN6_ADDR_ALT 1
> +#endif
> +#ifndef __UAPI_DEF_SOCKADDR_IN6
> #define __UAPI_DEF_SOCKADDR_IN6 1
> +#endif
> +#ifndef __UAPI_DEF_IPV6_MREQ
> #define __UAPI_DEF_IPV6_MREQ 1
> +#endif
> +#ifndef __UAPI_DEF_IPPROTO_V6
> #define __UAPI_DEF_IPPROTO_V6 1
> +#endif
> +#ifndef __UAPI_DEF_IPV6_OPTIONS
> #define __UAPI_DEF_IPV6_OPTIONS 1
> +#endif
> +#ifndef __UAPI_DEF_IN6_PKTINFO
> #define __UAPI_DEF_IN6_PKTINFO 1
> +#endif
> +#ifndef __UAPI_DEF_IP6_MTUINFO
> #define __UAPI_DEF_IP6_MTUINFO 1
> +#endif
>
> /* Definitions for ipx.h */
> +#ifndef __UAPI_DEF_SOCKADDR_IPX
> #define __UAPI_DEF_SOCKADDR_IPX 1
> +#endif
> +#ifndef __UAPI_DEF_IPX_ROUTE_DEFINITION
> #define __UAPI_DEF_IPX_ROUTE_DEFINITION 1
> +#endif
> +#ifndef __UAPI_DEF_IPX_INTERFACE_DEFINITION
> #define __UAPI_DEF_IPX_INTERFACE_DEFINITION 1
> +#endif
> +#ifndef __UAPI_DEF_IPX_CONFIG_DATA
> #define __UAPI_DEF_IPX_CONFIG_DATA 1
> +#endif
> +#ifndef __UAPI_DEF_IPX_ROUTE_DEF
> #define __UAPI_DEF_IPX_ROUTE_DEF 1
> +#endif
>
> /* Definitions for xattr.h */
> +#ifndef __UAPI_DEF_XATTR
> #define __UAPI_DEF_XATTR 1
> +#endif
>
> #endif /* __GLIBC__ */
As most of affected macros are related to networking (in fact, all except
__UAPI_DEF_XATTR affect uapi/linux/{if.h,in.h,in6.h,ipv6.h,ipx.h} only),
I think this patch should be submitted to netdev.
--
ldv
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