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_IN6_ADDR 0 60 /* The exception is the in6_addr macros which must be defined 61 * if the glibc code didn't define them. This guard matches 62 * the guard in glibc/inet/netinet/in.h which defines the 63 * additional in6_addr macros e.g. s6_addr16, and s6_addr32. */ 64 #if defined(__USE_MISC) || defined (__USE_GNU) 65 #define __UAPI_DEF_IN6_ADDR_ALT 0 66 #else 67 #define __UAPI_DEF_IN6_ADDR_ALT 1 68 #endif 69 #define __UAPI_DEF_SOCKADDR_IN6 0 70 #define __UAPI_DEF_IPV6_MREQ 0 71 #define __UAPI_DEF_IPPROTO_V6 0 72 #define __UAPI_DEF_IPV6_OPTIONS 0 73 #define __UAPI_DEF_IN6_PKTINFO 0 74 #define __UAPI_DEF_IP6_MTUINFO 0 75 76 #else 77 78 /* Linux headers included first, and we must define everything 79 * we need. The expectation is that glibc will check the 80 * __UAPI_DEF_* defines and adjust appropriately. */ 81 #define __UAPI_DEF_IN6_ADDR 1 82 /* We unconditionally define the in6_addr macros and glibc must 83 * coordinate. */ 84 #define __UAPI_DEF_IN6_ADDR_ALT 1 85 #define __UAPI_DEF_SOCKADDR_IN6 1 86 #define __UAPI_DEF_IPV6_MREQ 1 87 #define __UAPI_DEF_IPPROTO_V6 1 88 #define __UAPI_DEF_IPV6_OPTIONS 1 89 #define __UAPI_DEF_IN6_PKTINFO 1 90 #define __UAPI_DEF_IP6_MTUINFO 1 91 92 #endif /* _NETINET_IN_H */ 93 94 /* Definitions for xattr.h */ 95 #if defined(_SYS_XATTR_H) 96 #define __UAPI_DEF_XATTR 0 97 #else 98 #define __UAPI_DEF_XATTR 1 99 #endif 100 101 /* If we did not see any headers from any supported C libraries, 102 * or we are being included in the kernel, then define everything 103 * that we need. */ 104 #else /* !defined(__GLIBC__) */ 105 106 /* Definitions for in6.h */ 107 #define __UAPI_DEF_IN6_ADDR 1 108 #define __UAPI_DEF_IN6_ADDR_ALT 1 109 #define __UAPI_DEF_SOCKADDR_IN6 1 110 #define __UAPI_DEF_IPV6_MREQ 1 111 #define __UAPI_DEF_IPPROTO_V6 1 112 #define __UAPI_DEF_IPV6_OPTIONS 1 113 #define __UAPI_DEF_IN6_PKTINFO 1 114 #define __UAPI_DEF_IP6_MTUINFO 1 115 116 /* Definitions for xattr.h */ 117 #define __UAPI_DEF_XATTR 1 118 119 #endif /* __GLIBC__ */ 120 121 #endif /* _UAPI_LIBC_COMPAT_H */ 122