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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_IN_ADDR 0
60#define __UAPI_DEF_IN_IPPROTO 0
61#define __UAPI_DEF_IN_PKTINFO 0
62#define __UAPI_DEF_IP_MREQ 0
63#define __UAPI_DEF_SOCKADDR_IN 0
64#define __UAPI_DEF_IN_CLASS 0
65
66#define __UAPI_DEF_IN6_ADDR 0
67/* The exception is the in6_addr macros which must be defined
68 * if the glibc code didn't define them. This guard matches
69 * the guard in glibc/inet/netinet/in.h which defines the
70 * additional in6_addr macros e.g. s6_addr16, and s6_addr32. */
71#if defined(__USE_MISC) || defined (__USE_GNU)
72#define __UAPI_DEF_IN6_ADDR_ALT 0
73#else
74#define __UAPI_DEF_IN6_ADDR_ALT 1
75#endif
76#define __UAPI_DEF_SOCKADDR_IN6 0
77#define __UAPI_DEF_IPV6_MREQ 0
78#define __UAPI_DEF_IPPROTO_V6 0
79#define __UAPI_DEF_IPV6_OPTIONS 0
80#define __UAPI_DEF_IN6_PKTINFO 0
81#define __UAPI_DEF_IP6_MTUINFO 0
82
83#else
84
85/* Linux headers included first, and we must define everything
86 * we need. The expectation is that glibc will check the
87 * __UAPI_DEF_* defines and adjust appropriately. */
88#define __UAPI_DEF_IN_ADDR 1
89#define __UAPI_DEF_IN_IPPROTO 1
90#define __UAPI_DEF_IN_PKTINFO 1
91#define __UAPI_DEF_IP_MREQ 1
92#define __UAPI_DEF_SOCKADDR_IN 1
93#define __UAPI_DEF_IN_CLASS 1
94
95#define __UAPI_DEF_IN6_ADDR 1
96/* We unconditionally define the in6_addr macros and glibc must
97 * coordinate. */
98#define __UAPI_DEF_IN6_ADDR_ALT 1
99#define __UAPI_DEF_SOCKADDR_IN6 1
100#define __UAPI_DEF_IPV6_MREQ 1
101#define __UAPI_DEF_IPPROTO_V6 1
102#define __UAPI_DEF_IPV6_OPTIONS 1
103#define __UAPI_DEF_IN6_PKTINFO 1
104#define __UAPI_DEF_IP6_MTUINFO 1
105
106#endif /* _NETINET_IN_H */
107
108/* Definitions for xattr.h */
109#if defined(_SYS_XATTR_H)
110#define __UAPI_DEF_XATTR 0
111#else
112#define __UAPI_DEF_XATTR 1
113#endif
114
115/* If we did not see any headers from any supported C libraries,
116 * or we are being included in the kernel, then define everything
117 * that we need. */
118#else /* !defined(__GLIBC__) */
119
120/* Definitions for in.h */
121#define __UAPI_DEF_IN_ADDR 1
122#define __UAPI_DEF_IN_IPPROTO 1
123#define __UAPI_DEF_IN_PKTINFO 1
124#define __UAPI_DEF_IP_MREQ 1
125#define __UAPI_DEF_SOCKADDR_IN 1
126#define __UAPI_DEF_IN_CLASS 1
127
128/* Definitions for in6.h */
129#define __UAPI_DEF_IN6_ADDR 1
130#define __UAPI_DEF_IN6_ADDR_ALT 1
131#define __UAPI_DEF_SOCKADDR_IN6 1
132#define __UAPI_DEF_IPV6_MREQ 1
133#define __UAPI_DEF_IPPROTO_V6 1
134#define __UAPI_DEF_IPV6_OPTIONS 1
135#define __UAPI_DEF_IN6_PKTINFO 1
136#define __UAPI_DEF_IP6_MTUINFO 1
137
138/* Definitions for xattr.h */
139#define __UAPI_DEF_XATTR 1
140
141#endif /* __GLIBC__ */
142
143#endif /* _UAPI_LIBC_COMPAT_H */