include/uapi/linux/libc-compat.h

   1 /*
   2  * Compatibility interface for userspace libc header coordination:
   3  *
   4  * Define compatibility macros that are used to control the inclusion or
   5  * exclusion of UAPI structures and definitions in coordination with another
   6  * userspace C library.
   7  *
   8  * This header is intended to solve the problem of UAPI definitions that
   9  * conflict with userspace definitions. If a UAPI header has such conflicting
  10  * definitions then the solution is as follows:
  11  *
  12  * * Synchronize the UAPI header and the libc headers so either one can be
  13  *   used and such that the ABI is preserved. If this is not possible then
  14  *   no simple compatibility interface exists (you need to write translating
  15  *   wrappers and rename things) and you can't use this interface.
  16  *
  17  * Then follow this process:
  18  *
  19  * (a) Include libc-compat.h in the UAPI header.
  20  *      e.g. #include <linux/libc-compat.h>
  21  *     This include must be as early as possible.
  22  *
  23  * (b) In libc-compat.h add enough code to detect that the comflicting
  24  *     userspace libc header has been included first.
  25  *
  26  * (c) If the userspace libc header has been included first define a set of
  27  *     guard macros of the form __UAPI_DEF_FOO and set their values to 1, else
  28  *     set their values to 0.
  29  *
  30  * (d) Back in the UAPI header with the conflicting definitions, guard the
  31  *     definitions with:
  32  *     #if __UAPI_DEF_FOO
  33  *       ...
  34  *     #endif
  35  *
  36  * This fixes the situation where the linux headers are included *after* the
  37  * libc headers. To fix the problem with the inclusion in the other order the
  38  * userspace libc headers must be fixed like this:
  39  *
  40  * * For all definitions that conflict with kernel definitions wrap those
  41  *   defines in the following:
  42  *   #if !__UAPI_DEF_FOO
  43  *     ...
  44  *   #endif
  45  *
  46  * This prevents the redefinition of a construct already defined by the kernel.
  47  */
  48 #ifndef _UAPI_LIBC_COMPAT_H
  49 #define _UAPI_LIBC_COMPAT_H
  50
  51 /* We have included glibc headers... */
  52 #if defined(__GLIBC__)
  53
  54 /* Coordinate with glibc netinet/in.h header. */
  55 #if defined(_NETINET_IN_H)
  56
  57 /* GLIBC headers included first so don't define anything
  58  * that would already be defined. */
  59 #define __UAPI_DEF_IN_ADDR              0
  60 #define __UAPI_DEF_IN_IPPROTO           0
  61 #define __UAPI_DEF_IN_PKTINFO           0
  62 #define __UAPI_DEF_IP_MREQ              0
  63 #define __UAPI_DEF_SOCKADDR_IN          0
  64 #define __UAPI_DEF_IN_CLASS             0
  65
  66 #define __UAPI_DEF_IN6_ADDR             0
  67 /* The exception is the in6_addr macros which must be defined
  68  * if the glibc code didn't define them. This guard matches
  69  * the guard in glibc/inet/netinet/in.h which defines the
  70  * additional in6_addr macros e.g. s6_addr16, and s6_addr32. */
  71 #if defined(__USE_MISC) || defined (__USE_GNU)
  72 #define __UAPI_DEF_IN6_ADDR_ALT         0
  73 #else
  74 #define __UAPI_DEF_IN6_ADDR_ALT         1
  75 #endif
  76 #define __UAPI_DEF_SOCKADDR_IN6         0
  77 #define __UAPI_DEF_IPV6_MREQ            0
  78 #define __UAPI_DEF_IPPROTO_V6           0
  79 #define __UAPI_DEF_IPV6_OPTIONS         0
  80 #define __UAPI_DEF_IN6_PKTINFO          0
  81 #define __UAPI_DEF_IP6_MTUINFO          0
  82
  83 #else
  84
  85 /* Linux headers included first, and we must define everything
  86  * we need. The expectation is that glibc will check the
  87  * __UAPI_DEF_* defines and adjust appropriately. */
  88 #define __UAPI_DEF_IN_ADDR              1
  89 #define __UAPI_DEF_IN_IPPROTO           1
  90 #define __UAPI_DEF_IN_PKTINFO           1
  91 #define __UAPI_DEF_IP_MREQ              1
  92 #define __UAPI_DEF_SOCKADDR_IN          1
  93 #define __UAPI_DEF_IN_CLASS             1
  94
  95 #define __UAPI_DEF_IN6_ADDR             1
  96 /* We unconditionally define the in6_addr macros and glibc must
  97  * coordinate. */
  98 #define __UAPI_DEF_IN6_ADDR_ALT         1
  99 #define __UAPI_DEF_SOCKADDR_IN6         1
 100 #define __UAPI_DEF_IPV6_MREQ            1
 101 #define __UAPI_DEF_IPPROTO_V6           1
 102 #define __UAPI_DEF_IPV6_OPTIONS         1
 103 #define __UAPI_DEF_IN6_PKTINFO          1
 104 #define __UAPI_DEF_IP6_MTUINFO          1
 105
 106 #endif /* _NETINET_IN_H */
 107
 108 /* Definitions for xattr.h */
 109 #if defined(_SYS_XATTR_H)
 110 #define __UAPI_DEF_XATTR                0
 111 #else
 112 #define __UAPI_DEF_XATTR                1
 113 #endif
 114
 115 /* If we did not see any headers from any supported C libraries,
 116  * or we are being included in the kernel, then define everything
 117  * that we need. */
 118 #else /* !defined(__GLIBC__) */
 119
 120 /* Definitions for in.h */
 121 #define __UAPI_DEF_IN_ADDR              1
 122 #define __UAPI_DEF_IN_IPPROTO           1
 123 #define __UAPI_DEF_IN_PKTINFO           1
 124 #define __UAPI_DEF_IP_MREQ              1
 125 #define __UAPI_DEF_SOCKADDR_IN          1
 126 #define __UAPI_DEF_IN_CLASS             1
 127
 128 /* Definitions for in6.h */
 129 #define __UAPI_DEF_IN6_ADDR             1
 130 #define __UAPI_DEF_IN6_ADDR_ALT         1
 131 #define __UAPI_DEF_SOCKADDR_IN6         1
 132 #define __UAPI_DEF_IPV6_MREQ            1
 133 #define __UAPI_DEF_IPPROTO_V6           1
 134 #define __UAPI_DEF_IPV6_OPTIONS         1
 135 #define __UAPI_DEF_IN6_PKTINFO          1
 136 #define __UAPI_DEF_IP6_MTUINFO          1
 137
 138 /* Definitions for xattr.h */
 139 #define __UAPI_DEF_XATTR                1
 140
 141 #endif /* __GLIBC__ */
 142
 143 #endif /* _UAPI_LIBC_COMPAT_H */