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linux-next/include/uapi/linux/libc-compat.h
Hauke Mehrtens da360299b6 uapi/if_ether.h: move __UAPI_DEF_ETHHDR libc define 
This fixes a compile problem of some user space applications by not
including linux/libc-compat.h in uapi/if_ether.h.

linux/libc-compat.h checks which "features" the header files, included
from the libc, provide to make the Linux kernel uapi header files only
provide no conflicting structures and enums. If a user application mixes
kernel headers and libc headers it could happen that linux/libc-compat.h
gets included too early where not all other libc headers are included
yet. Then the linux/libc-compat.h would not prevent all the
redefinitions and we run into compile problems.
This patch removes the include of linux/libc-compat.h from
uapi/if_ether.h to fix the recently introduced case, but not all as this
is more or less impossible.

It is no problem to do the check directly in the if_ether.h file and not
in libc-compat.h as this does not need any fancy glibc header detection
as glibc never provided struct ethhdr and should define
__UAPI_DEF_ETHHDR by them self when they will provide this.

The following test program did not compile correctly any more:

#include <linux/if_ether.h>
#include <netinet/in.h>
#include <linux/in.h>

int main(void)
{
	return 0;
}

Fixes: 6926e041a8 ("uapi/if_ether.h: prevent redefinition of struct ethhdr")
Reported-by: Guillaume Nault <g.nault@alphalink.fr>
Cc: <stable@vger.kernel.org> # 4.15
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-02-13 11:23:24 -05:00

268 lines
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/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
/*
* Compatibility interface for userspace libc header coordination:
*
* Define compatibility macros that are used to control the inclusion or
* exclusion of UAPI structures and definitions in coordination with another
* userspace C library.
*
* This header is intended to solve the problem of UAPI definitions that
* conflict with userspace definitions. If a UAPI header has such conflicting
* definitions then the solution is as follows:
*
* * Synchronize the UAPI header and the libc headers so either one can be
* used and such that the ABI is preserved. If this is not possible then
* no simple compatibility interface exists (you need to write translating
* wrappers and rename things) and you can't use this interface.
*
* Then follow this process:
*
* (a) Include libc-compat.h in the UAPI header.
* e.g. #include <linux/libc-compat.h>
* This include must be as early as possible.
*
* (b) In libc-compat.h add enough code to detect that the comflicting
* userspace libc header has been included first.
*
* (c) If the userspace libc header has been included first define a set of
* guard macros of the form __UAPI_DEF_FOO and set their values to 1, else
* set their values to 0.
*
* (d) Back in the UAPI header with the conflicting definitions, guard the
* definitions with:
* #if __UAPI_DEF_FOO
* ...
* #endif
*
* This fixes the situation where the linux headers are included *after* the
* libc headers. To fix the problem with the inclusion in the other order the
* userspace libc headers must be fixed like this:
*
* * For all definitions that conflict with kernel definitions wrap those
* defines in the following:
* #if !__UAPI_DEF_FOO
* ...
* #endif
*
* This prevents the redefinition of a construct already defined by the kernel.
*/
#ifndef _UAPI_LIBC_COMPAT_H
#define _UAPI_LIBC_COMPAT_H
/* We have included glibc headers... */
#if defined(__GLIBC__)
/* Coordinate with glibc net/if.h header. */
#if defined(_NET_IF_H) && defined(__USE_MISC)
/* GLIBC headers included first so don't define anything
* that would already be defined. */
#define __UAPI_DEF_IF_IFCONF 0
#define __UAPI_DEF_IF_IFMAP 0
#define __UAPI_DEF_IF_IFNAMSIZ 0
#define __UAPI_DEF_IF_IFREQ 0
/* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
#define __UAPI_DEF_IF_NET_DEVICE_FLAGS 0
/* 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 /* __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO */
#else /* _NET_IF_H */
/* Linux headers included first, and we must define everything
* we need. The expectation is that glibc will check the
* __UAPI_DEF_* defines and adjust appropriately. */
#define __UAPI_DEF_IF_IFCONF 1
#define __UAPI_DEF_IF_IFMAP 1
#define __UAPI_DEF_IF_IFNAMSIZ 1
#define __UAPI_DEF_IF_IFREQ 1
/* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
#define __UAPI_DEF_IF_NET_DEVICE_FLAGS 1
/* For the future if glibc adds IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO */
#define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
#endif /* _NET_IF_H */
/* Coordinate with glibc netinet/in.h header. */
#if defined(_NETINET_IN_H)
/* GLIBC headers included first so don't define anything
* that would already be defined. */
#define __UAPI_DEF_IN_ADDR 0
#define __UAPI_DEF_IN_IPPROTO 0
#define __UAPI_DEF_IN_PKTINFO 0
#define __UAPI_DEF_IP_MREQ 0
#define __UAPI_DEF_SOCKADDR_IN 0
#define __UAPI_DEF_IN_CLASS 0
#define __UAPI_DEF_IN6_ADDR 0
/* The exception is the in6_addr macros which must be defined
* if the glibc code didn't define them. This guard matches
* the guard in glibc/inet/netinet/in.h which defines the
* additional in6_addr macros e.g. s6_addr16, and s6_addr32. */
#if defined(__USE_MISC) || defined (__USE_GNU)
#define __UAPI_DEF_IN6_ADDR_ALT 0
#else
#define __UAPI_DEF_IN6_ADDR_ALT 1
#endif
#define __UAPI_DEF_SOCKADDR_IN6 0
#define __UAPI_DEF_IPV6_MREQ 0
#define __UAPI_DEF_IPPROTO_V6 0
#define __UAPI_DEF_IPV6_OPTIONS 0
#define __UAPI_DEF_IN6_PKTINFO 0
#define __UAPI_DEF_IP6_MTUINFO 0
#else
/* Linux headers included first, and we must define everything
* we need. The expectation is that glibc will check the
* __UAPI_DEF_* defines and adjust appropriately. */
#define __UAPI_DEF_IN_ADDR 1
#define __UAPI_DEF_IN_IPPROTO 1
#define __UAPI_DEF_IN_PKTINFO 1
#define __UAPI_DEF_IP_MREQ 1
#define __UAPI_DEF_SOCKADDR_IN 1
#define __UAPI_DEF_IN_CLASS 1
#define __UAPI_DEF_IN6_ADDR 1
/* We unconditionally define the in6_addr macros and glibc must
* coordinate. */
#define __UAPI_DEF_IN6_ADDR_ALT 1
#define __UAPI_DEF_SOCKADDR_IN6 1
#define __UAPI_DEF_IPV6_MREQ 1
#define __UAPI_DEF_IPPROTO_V6 1
#define __UAPI_DEF_IPV6_OPTIONS 1
#define __UAPI_DEF_IN6_PKTINFO 1
#define __UAPI_DEF_IP6_MTUINFO 1
#endif /* _NETINET_IN_H */
/* Coordinate with glibc netipx/ipx.h header. */
#if defined(__NETIPX_IPX_H)
#define __UAPI_DEF_SOCKADDR_IPX 0
#define __UAPI_DEF_IPX_ROUTE_DEFINITION 0
#define __UAPI_DEF_IPX_INTERFACE_DEFINITION 0
#define __UAPI_DEF_IPX_CONFIG_DATA 0
#define __UAPI_DEF_IPX_ROUTE_DEF 0
#else /* defined(__NETIPX_IPX_H) */
#define __UAPI_DEF_SOCKADDR_IPX 1
#define __UAPI_DEF_IPX_ROUTE_DEFINITION 1
#define __UAPI_DEF_IPX_INTERFACE_DEFINITION 1
#define __UAPI_DEF_IPX_CONFIG_DATA 1
#define __UAPI_DEF_IPX_ROUTE_DEF 1
#endif /* defined(__NETIPX_IPX_H) */
/* Definitions for xattr.h */
#if defined(_SYS_XATTR_H)
#define __UAPI_DEF_XATTR 0
#else
#define __UAPI_DEF_XATTR 1
#endif
/* 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. 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
/* 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__ */
#endif /* _UAPI_LIBC_COMPAT_H */
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