include/uapi/linux/libc-compat.h

   1 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
   2 /*
   3  * Compatibility interface for userspace libc header coordination:
   4  *
   5  * Define compatibility macros that are used to control the inclusion or
   6  * exclusion of UAPI structures and definitions in coordination with another
   7  * userspace C library.
   8  *
   9  * This header is intended to solve the problem of UAPI definitions that
  10  * conflict with userspace definitions. If a UAPI header has such conflicting
  11  * definitions then the solution is as follows:
  12  *
  13  * * Synchronize the UAPI header and the libc headers so either one can be
  14  *   used and such that the ABI is preserved. If this is not possible then
  15  *   no simple compatibility interface exists (you need to write translating
  16  *   wrappers and rename things) and you can't use this interface.
  17  *
  18  * Then follow this process:
  19  *
  20  * (a) Include libc-compat.h in the UAPI header.
  21  *      e.g. #include <linux/libc-compat.h>
  22  *     This include must be as early as possible.
  23  *
  24  * (b) In libc-compat.h add enough code to detect that the comflicting
  25  *     userspace libc header has been included first.
  26  *
  27  * (c) If the userspace libc header has been included first define a set of
  28  *     guard macros of the form __UAPI_DEF_FOO and set their values to 1, else
  29  *     set their values to 0.
  30  *
  31  * (d) Back in the UAPI header with the conflicting definitions, guard the
  32  *     definitions with:
  33  *     #if __UAPI_DEF_FOO
  34  *       ...
  35  *     #endif
  36  *
  37  * This fixes the situation where the linux headers are included *after* the
  38  * libc headers. To fix the problem with the inclusion in the other order the
  39  * userspace libc headers must be fixed like this:
  40  *
  41  * * For all definitions that conflict with kernel definitions wrap those
  42  *   defines in the following:
  43  *   #if !__UAPI_DEF_FOO
  44  *     ...
  45  *   #endif
  46  *
  47  * This prevents the redefinition of a construct already defined by the kernel.
  48  */
  49 #ifndef _UAPI_LIBC_COMPAT_H
  50 #define _UAPI_LIBC_COMPAT_H
  51
  52 /* We have included glibc headers... */
  53 #if defined(__GLIBC__)
  54
  55 /* Coordinate with glibc net/if.h header. */
  56 #if defined(_NET_IF_H) && defined(__USE_MISC)
  57
  58 /* GLIBC headers included first so don't define anything
  59  * that would already be defined. */
  60
  61 #define __UAPI_DEF_IF_IFCONF 0
  62 #define __UAPI_DEF_IF_IFMAP 0
  63 #define __UAPI_DEF_IF_IFNAMSIZ 0
  64 #define __UAPI_DEF_IF_IFREQ 0
  65 /* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
  66 #define __UAPI_DEF_IF_NET_DEVICE_FLAGS 0
  67 /* For the future if glibc adds IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO */
  68 #ifndef __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO
  69 #define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
  70 #endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO */
  71
  72 #else /* _NET_IF_H */
  73
  74 /* Linux headers included first, and we must define everything
  75  * we need. The expectation is that glibc will check the
  76  * __UAPI_DEF_* defines and adjust appropriately. */
  77
  78 #define __UAPI_DEF_IF_IFCONF 1
  79 #define __UAPI_DEF_IF_IFMAP 1
  80 #define __UAPI_DEF_IF_IFNAMSIZ 1
  81 #define __UAPI_DEF_IF_IFREQ 1
  82 /* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
  83 #define __UAPI_DEF_IF_NET_DEVICE_FLAGS 1
  84 /* For the future if glibc adds IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO */
  85 #define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
  86
  87 #endif /* _NET_IF_H */
  88
  89 /* Coordinate with glibc netinet/in.h header. */
  90 #if defined(_NETINET_IN_H)
  91
  92 /* GLIBC headers included first so don't define anything
  93  * that would already be defined. */
  94 #define __UAPI_DEF_IN_ADDR              0
  95 #define __UAPI_DEF_IN_IPPROTO           0
  96 #define __UAPI_DEF_IN_PKTINFO           0
  97 #define __UAPI_DEF_IP_MREQ              0
  98 #define __UAPI_DEF_SOCKADDR_IN          0
  99 #define __UAPI_DEF_IN_CLASS             0
 100
 101 #define __UAPI_DEF_IN6_ADDR             0
 102 /* The exception is the in6_addr macros which must be defined
 103  * if the glibc code didn't define them. This guard matches
 104  * the guard in glibc/inet/netinet/in.h which defines the
 105  * additional in6_addr macros e.g. s6_addr16, and s6_addr32. */
 106 #if defined(__USE_MISC) || defined (__USE_GNU)
 107 #define __UAPI_DEF_IN6_ADDR_ALT         0
 108 #else
 109 #define __UAPI_DEF_IN6_ADDR_ALT         1
 110 #endif
 111 #define __UAPI_DEF_SOCKADDR_IN6         0
 112 #define __UAPI_DEF_IPV6_MREQ            0
 113 #define __UAPI_DEF_IPPROTO_V6           0
 114 #define __UAPI_DEF_IPV6_OPTIONS         0
 115 #define __UAPI_DEF_IN6_PKTINFO          0
 116 #define __UAPI_DEF_IP6_MTUINFO          0
 117
 118 #else
 119
 120 /* Linux headers included first, and we must define everything
 121  * we need. The expectation is that glibc will check the
 122  * __UAPI_DEF_* defines and adjust appropriately. */
 123 #define __UAPI_DEF_IN_ADDR              1
 124 #define __UAPI_DEF_IN_IPPROTO           1
 125 #define __UAPI_DEF_IN_PKTINFO           1
 126 #define __UAPI_DEF_IP_MREQ              1
 127 #define __UAPI_DEF_SOCKADDR_IN          1
 128 #define __UAPI_DEF_IN_CLASS             1
 129
 130 #define __UAPI_DEF_IN6_ADDR             1
 131 /* We unconditionally define the in6_addr macros and glibc must
 132  * coordinate. */
 133 #define __UAPI_DEF_IN6_ADDR_ALT         1
 134 #define __UAPI_DEF_SOCKADDR_IN6         1
 135 #define __UAPI_DEF_IPV6_MREQ            1
 136 #define __UAPI_DEF_IPPROTO_V6           1
 137 #define __UAPI_DEF_IPV6_OPTIONS         1
 138 #define __UAPI_DEF_IN6_PKTINFO          1
 139 #define __UAPI_DEF_IP6_MTUINFO          1
 140
 141 #endif /* _NETINET_IN_H */
 142
 143 /* Definitions for xattr.h */
 144 #if defined(_SYS_XATTR_H)
 145 #define __UAPI_DEF_XATTR                0
 146 #else
 147 #define __UAPI_DEF_XATTR                1
 148 #endif
 149
 150 /* If we did not see any headers from any supported C libraries,
 151  * or we are being included in the kernel, then define everything
 152  * that we need. Check for previous __UAPI_* definitions to give
 153  * unsupported C libraries a way to opt out of any kernel definition. */
 154 #else /* !defined(__GLIBC__) */
 155
 156 /* Definitions for if.h */
 157 #ifndef __UAPI_DEF_IF_IFCONF
 158 #define __UAPI_DEF_IF_IFCONF 1
 159 #endif
 160 #ifndef __UAPI_DEF_IF_IFMAP
 161 #define __UAPI_DEF_IF_IFMAP 1
 162 #endif
 163 #ifndef __UAPI_DEF_IF_IFNAMSIZ
 164 #define __UAPI_DEF_IF_IFNAMSIZ 1
 165 #endif
 166 #ifndef __UAPI_DEF_IF_IFREQ
 167 #define __UAPI_DEF_IF_IFREQ 1
 168 #endif
 169 /* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
 170 #ifndef __UAPI_DEF_IF_NET_DEVICE_FLAGS
 171 #define __UAPI_DEF_IF_NET_DEVICE_FLAGS 1
 172 #endif
 173 /* For the future if glibc adds IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO */
 174 #ifndef __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO
 175 #define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
 176 #endif
 177
 178 /* Definitions for in.h */
 179 #ifndef __UAPI_DEF_IN_ADDR
 180 #define __UAPI_DEF_IN_ADDR              1
 181 #endif
 182 #ifndef __UAPI_DEF_IN_IPPROTO
 183 #define __UAPI_DEF_IN_IPPROTO           1
 184 #endif
 185 #ifndef __UAPI_DEF_IN_PKTINFO
 186 #define __UAPI_DEF_IN_PKTINFO           1
 187 #endif
 188 #ifndef __UAPI_DEF_IP_MREQ
 189 #define __UAPI_DEF_IP_MREQ              1
 190 #endif
 191 #ifndef __UAPI_DEF_SOCKADDR_IN
 192 #define __UAPI_DEF_SOCKADDR_IN          1
 193 #endif
 194 #ifndef __UAPI_DEF_IN_CLASS
 195 #define __UAPI_DEF_IN_CLASS             1
 196 #endif
 197
 198 /* Definitions for in6.h */
 199 #ifndef __UAPI_DEF_IN6_ADDR
 200 #define __UAPI_DEF_IN6_ADDR             1
 201 #endif
 202 #ifndef __UAPI_DEF_IN6_ADDR_ALT
 203 #define __UAPI_DEF_IN6_ADDR_ALT         1
 204 #endif
 205 #ifndef __UAPI_DEF_SOCKADDR_IN6
 206 #define __UAPI_DEF_SOCKADDR_IN6         1
 207 #endif
 208 #ifndef __UAPI_DEF_IPV6_MREQ
 209 #define __UAPI_DEF_IPV6_MREQ            1
 210 #endif
 211 #ifndef __UAPI_DEF_IPPROTO_V6
 212 #define __UAPI_DEF_IPPROTO_V6           1
 213 #endif
 214 #ifndef __UAPI_DEF_IPV6_OPTIONS
 215 #define __UAPI_DEF_IPV6_OPTIONS         1
 216 #endif
 217 #ifndef __UAPI_DEF_IN6_PKTINFO
 218 #define __UAPI_DEF_IN6_PKTINFO          1
 219 #endif
 220 #ifndef __UAPI_DEF_IP6_MTUINFO
 221 #define __UAPI_DEF_IP6_MTUINFO          1
 222 #endif
 223
 224 /* Definitions for xattr.h */
 225 #ifndef __UAPI_DEF_XATTR
 226 #define __UAPI_DEF_XATTR                1
 227 #endif
 228
 229 #endif /* __GLIBC__ */
 230
 231 #endif /* _UAPI_LIBC_COMPAT_H */