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 */ 188