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