libc-compat.h (7288B) - Raw
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 _LIBC_COMPAT_H 50 #define _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 /* _LIBC_COMPAT_H */