ea1a8217b0
If the glibc xattr.h header is included after the uapi header, compilation fails due to an enum re-using a #define from the uapi header. Protect against this by guarding the define and enum inclusions against each other. (See https://lists.debian.org/debian-glibc/2014/03/msg00029.html and https://sourceware.org/glibc/wiki/Synchronizing_Headers for more information.) Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Allan McRae <allan@archlinux.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
112 lines
3.6 KiB
C
112 lines
3.6 KiB
C
/*
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* Compatibility interface for userspace libc header coordination:
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*
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* Define compatibility macros that are used to control the inclusion or
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* exclusion of UAPI structures and definitions in coordination with another
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* userspace C library.
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*
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* This header is intended to solve the problem of UAPI definitions that
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* conflict with userspace definitions. If a UAPI header has such conflicting
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* definitions then the solution is as follows:
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*
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* * Synchronize the UAPI header and the libc headers so either one can be
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* used and such that the ABI is preserved. If this is not possible then
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* no simple compatibility interface exists (you need to write translating
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* wrappers and rename things) and you can't use this interface.
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*
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* Then follow this process:
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*
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* (a) Include libc-compat.h in the UAPI header.
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* e.g. #include <linux/libc-compat.h>
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* This include must be as early as possible.
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*
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* (b) In libc-compat.h add enough code to detect that the comflicting
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* userspace libc header has been included first.
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*
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* (c) If the userspace libc header has been included first define a set of
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* guard macros of the form __UAPI_DEF_FOO and set their values to 1, else
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* set their values to 0.
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*
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* (d) Back in the UAPI header with the conflicting definitions, guard the
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* definitions with:
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* #if __UAPI_DEF_FOO
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* ...
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* #endif
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*
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* This fixes the situation where the linux headers are included *after* the
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* libc headers. To fix the problem with the inclusion in the other order the
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* userspace libc headers must be fixed like this:
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*
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* * For all definitions that conflict with kernel definitions wrap those
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* defines in the following:
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* #if !__UAPI_DEF_FOO
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* ...
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* #endif
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*
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* This prevents the redefinition of a construct already defined by the kernel.
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*/
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#ifndef _UAPI_LIBC_COMPAT_H
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#define _UAPI_LIBC_COMPAT_H
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/* We have included glibc headers... */
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#if defined(__GLIBC__)
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/* Coordinate with glibc netinet/in.h header. */
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#if defined(_NETINET_IN_H)
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/* GLIBC headers included first so don't define anything
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* that would already be defined. */
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#define __UAPI_DEF_IN6_ADDR 0
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/* The exception is the in6_addr macros which must be defined
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* if the glibc code didn't define them. This guard matches
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* the guard in glibc/inet/netinet/in.h which defines the
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* additional in6_addr macros e.g. s6_addr16, and s6_addr32. */
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#if defined(__USE_MISC) || defined (__USE_GNU)
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#define __UAPI_DEF_IN6_ADDR_ALT 0
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#else
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#define __UAPI_DEF_IN6_ADDR_ALT 1
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#endif
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#define __UAPI_DEF_SOCKADDR_IN6 0
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#define __UAPI_DEF_IPV6_MREQ 0
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#define __UAPI_DEF_IPPROTO_V6 0
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#else
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/* Linux headers included first, and we must define everything
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* we need. The expectation is that glibc will check the
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* __UAPI_DEF_* defines and adjust appropriately. */
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#define __UAPI_DEF_IN6_ADDR 1
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/* We unconditionally define the in6_addr macros and glibc must
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* coordinate. */
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#define __UAPI_DEF_IN6_ADDR_ALT 1
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#define __UAPI_DEF_SOCKADDR_IN6 1
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#define __UAPI_DEF_IPV6_MREQ 1
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#define __UAPI_DEF_IPPROTO_V6 1
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#endif /* _NETINET_IN_H */
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/* Definitions for xattr.h */
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#if defined(_SYS_XATTR_H)
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#define __UAPI_DEF_XATTR 0
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#else
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#define __UAPI_DEF_XATTR 1
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#endif
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/* If we did not see any headers from any supported C libraries,
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* or we are being included in the kernel, then define everything
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* that we need. */
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#else /* !defined(__GLIBC__) */
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/* Definitions for in6.h */
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#define __UAPI_DEF_IN6_ADDR 1
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#define __UAPI_DEF_IN6_ADDR_ALT 1
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#define __UAPI_DEF_SOCKADDR_IN6 1
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#define __UAPI_DEF_IPV6_MREQ 1
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#define __UAPI_DEF_IPPROTO_V6 1
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/* Definitions for xattr.h */
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#define __UAPI_DEF_XATTR 1
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#endif /* __GLIBC__ */
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#endif /* _UAPI_LIBC_COMPAT_H */
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