Carlos O'Donell | cfd280c | 2013-08-15 17:28:10 +0800 | [diff] [blame] | 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 | |
| 73 | #else |
| 74 | |
| 75 | /* Linux headers included first, and we must define everything |
| 76 | * we need. The expectation is that glibc will check the |
| 77 | * __UAPI_DEF_* defines and adjust appropriately. */ |
| 78 | #define __UAPI_DEF_IN6_ADDR 1 |
| 79 | /* We unconditionally define the in6_addr macros and glibc must |
| 80 | * coordinate. */ |
| 81 | #define __UAPI_DEF_IN6_ADDR_ALT 1 |
| 82 | #define __UAPI_DEF_SOCKADDR_IN6 1 |
| 83 | #define __UAPI_DEF_IPV6_MREQ 1 |
| 84 | #define __UAPI_DEF_IPPROTO_V6 1 |
| 85 | |
| 86 | #endif /* _NETINET_IN_H */ |
| 87 | |
Serge Hallyn | ea1a821 | 2014-04-03 14:48:33 -0700 | [diff] [blame] | 88 | /* Definitions for xattr.h */ |
| 89 | #if defined(_SYS_XATTR_H) |
| 90 | #define __UAPI_DEF_XATTR 0 |
| 91 | #else |
| 92 | #define __UAPI_DEF_XATTR 1 |
| 93 | #endif |
Carlos O'Donell | cfd280c | 2013-08-15 17:28:10 +0800 | [diff] [blame] | 94 | |
| 95 | /* If we did not see any headers from any supported C libraries, |
| 96 | * or we are being included in the kernel, then define everything |
| 97 | * that we need. */ |
| 98 | #else /* !defined(__GLIBC__) */ |
| 99 | |
| 100 | /* Definitions for in6.h */ |
| 101 | #define __UAPI_DEF_IN6_ADDR 1 |
| 102 | #define __UAPI_DEF_IN6_ADDR_ALT 1 |
| 103 | #define __UAPI_DEF_SOCKADDR_IN6 1 |
| 104 | #define __UAPI_DEF_IPV6_MREQ 1 |
| 105 | #define __UAPI_DEF_IPPROTO_V6 1 |
| 106 | |
Serge Hallyn | ea1a821 | 2014-04-03 14:48:33 -0700 | [diff] [blame] | 107 | /* Definitions for xattr.h */ |
| 108 | #define __UAPI_DEF_XATTR 1 |
| 109 | |
Carlos O'Donell | cfd280c | 2013-08-15 17:28:10 +0800 | [diff] [blame] | 110 | #endif /* __GLIBC__ */ |
| 111 | |
| 112 | #endif /* _UAPI_LIBC_COMPAT_H */ |