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 net/if.h header. */
  55 #if defined(_NET_IF_H) && defined(__USE_MISC)
  56
  57 /* GLIBC headers included first so don't define anything
  58  * that would already be defined. */
  59
  60 #define __UAPI_DEF_IF_IFCONF 0
  61 #define __UAPI_DEF_IF_IFMAP 0
  62 #define __UAPI_DEF_IF_IFNAMSIZ 0
  63 #define __UAPI_DEF_IF_IFREQ 0
  64 /* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
  65 #define __UAPI_DEF_IF_NET_DEVICE_FLAGS 0
  66 /* For the future if glibc adds IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO */
  67 #ifndef __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO
  68 #define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
  69 #endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO */
  70
  71 #else /* _NET_IF_H */
  72
  73 /* Linux headers included first, and we must define everything
  74  * we need. The expectation is that glibc will check the
  75  * __UAPI_DEF_* defines and adjust appropriately. */
  76
  77 #define __UAPI_DEF_IF_IFCONF 1
  78 #define __UAPI_DEF_IF_IFMAP 1
  79 #define __UAPI_DEF_IF_IFNAMSIZ 1
  80 #define __UAPI_DEF_IF_IFREQ 1
  81 /* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
  82 #define __UAPI_DEF_IF_NET_DEVICE_FLAGS 1
  83 /* For the future if glibc adds IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO */
  84 #define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
  85
  86 #endif /* _NET_IF_H */
  87
  88 /* Coordinate with glibc netinet/in.h header. */
  89 #if defined(_NETINET_IN_H)
  90
  91 /* GLIBC headers included first so don't define anything
  92  * that would already be defined. */
  93 #define __UAPI_DEF_IN_ADDR              0
  94 #define __UAPI_DEF_IN_IPPROTO           0
  95 #define __UAPI_DEF_IN_PKTINFO           0
  96 #define __UAPI_DEF_IP_MREQ              0
  97 #define __UAPI_DEF_SOCKADDR_IN          0
  98 #define __UAPI_DEF_IN_CLASS             0
  99
 100 #define __UAPI_DEF_IN6_ADDR             0
 101 /* The exception is the in6_addr macros which must be defined
 102  * if the glibc code didn't define them. This guard matches
 103  * the guard in glibc/inet/netinet/in.h which defines the
 104  * additional in6_addr macros e.g. s6_addr16, and s6_addr32. */
 105 #if defined(__USE_MISC) || defined (__USE_GNU)
 106 #define __UAPI_DEF_IN6_ADDR_ALT         0
 107 #else
 108 #define __UAPI_DEF_IN6_ADDR_ALT         1
 109 #endif
 110 #define __UAPI_DEF_SOCKADDR_IN6         0
 111 #define __UAPI_DEF_IPV6_MREQ            0
 112 #define __UAPI_DEF_IPPROTO_V6           0
 113 #define __UAPI_DEF_IPV6_OPTIONS         0
 114 #define __UAPI_DEF_IN6_PKTINFO          0
 115 #define __UAPI_DEF_IP6_MTUINFO          0
 116
 117 #else
 118
 119 /* Linux headers included first, and we must define everything
 120  * we need. The expectation is that glibc will check the
 121  * __UAPI_DEF_* defines and adjust appropriately. */
 122 #define __UAPI_DEF_IN_ADDR              1
 123 #define __UAPI_DEF_IN_IPPROTO           1
 124 #define __UAPI_DEF_IN_PKTINFO           1
 125 #define __UAPI_DEF_IP_MREQ              1
 126 #define __UAPI_DEF_SOCKADDR_IN          1
 127 #define __UAPI_DEF_IN_CLASS             1
 128
 129 #define __UAPI_DEF_IN6_ADDR             1
 130 /* We unconditionally define the in6_addr macros and glibc must
 131  * coordinate. */
 132 #define __UAPI_DEF_IN6_ADDR_ALT         1
 133 #define __UAPI_DEF_SOCKADDR_IN6         1
 134 #define __UAPI_DEF_IPV6_MREQ            1
 135 #define __UAPI_DEF_IPPROTO_V6           1
 136 #define __UAPI_DEF_IPV6_OPTIONS         1
 137 #define __UAPI_DEF_IN6_PKTINFO          1
 138 #define __UAPI_DEF_IP6_MTUINFO          1
 139
 140 #endif /* _NETINET_IN_H */
 141
 142 /* Definitions for xattr.h */
 143 #if defined(_SYS_XATTR_H)
 144 #define __UAPI_DEF_XATTR                0
 145 #else
 146 #define __UAPI_DEF_XATTR                1
 147 #endif
 148
 149 /* If we did not see any headers from any supported C libraries,
 150  * or we are being included in the kernel, then define everything
 151  * that we need. */
 152 #else /* !defined(__GLIBC__) */
 153
 154 /* Definitions for if.h */
 155 #define __UAPI_DEF_IF_IFCONF 1
 156 #define __UAPI_DEF_IF_IFMAP 1
 157 #define __UAPI_DEF_IF_IFNAMSIZ 1
 158 #define __UAPI_DEF_IF_IFREQ 1
 159 /* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
 160 #define __UAPI_DEF_IF_NET_DEVICE_FLAGS 1
 161 /* For the future if glibc adds IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO */
 162 #define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
 163
 164 /* Definitions for in.h */
 165 #define __UAPI_DEF_IN_ADDR              1
 166 #define __UAPI_DEF_IN_IPPROTO           1
 167 #define __UAPI_DEF_IN_PKTINFO           1
 168 #define __UAPI_DEF_IP_MREQ              1
 169 #define __UAPI_DEF_SOCKADDR_IN          1
 170 #define __UAPI_DEF_IN_CLASS             1
 171
 172 /* Definitions for in6.h */
 173 #define __UAPI_DEF_IN6_ADDR             1
 174 #define __UAPI_DEF_IN6_ADDR_ALT         1
 175 #define __UAPI_DEF_SOCKADDR_IN6         1
 176 #define __UAPI_DEF_IPV6_MREQ            1
 177 #define __UAPI_DEF_IPPROTO_V6           1
 178 #define __UAPI_DEF_IPV6_OPTIONS         1
 179 #define __UAPI_DEF_IN6_PKTINFO          1
 180 #define __UAPI_DEF_IP6_MTUINFO          1
 181
 182 /* Definitions for xattr.h */
 183 #define __UAPI_DEF_XATTR                1
 184
 185 #endif /* __GLIBC__ */
 186
 187 #endif /* _UAPI_LIBC_COMPAT_H */