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1/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
2/*
3 * Compatibility interface for userspace libc header coordination:
4 *
5 * Define compatibility macros that are used to control the inclusion or
6 * exclusion of UAPI structures and definitions in coordination with another
7 * userspace C library.
8 *
9 * This header is intended to solve the problem of UAPI definitions that
10 * conflict with userspace definitions. If a UAPI header has such conflicting
11 * definitions then the solution is as follows:
12 *
13 * * Synchronize the UAPI header and the libc headers so either one can be
14 * used and such that the ABI is preserved. If this is not possible then
15 * no simple compatibility interface exists (you need to write translating
16 * wrappers and rename things) and you can't use this interface.
17 *
18 * Then follow this process:
19 *
20 * (a) Include libc-compat.h in the UAPI header.
21 * e.g. #include <linux/libc-compat.h>
22 * This include must be as early as possible.
23 *
24 * (b) In libc-compat.h add enough code to detect that the comflicting
25 * userspace libc header has been included first.
26 *
27 * (c) If the userspace libc header has been included first define a set of
28 * guard macros of the form __UAPI_DEF_FOO and set their values to 1, else
29 * set their values to 0.
30 *
31 * (d) Back in the UAPI header with the conflicting definitions, guard the
32 * definitions with:
33 * #if __UAPI_DEF_FOO
34 * ...
35 * #endif
36 *
37 * This fixes the situation where the linux headers are included *after* the
38 * libc headers. To fix the problem with the inclusion in the other order the
39 * userspace libc headers must be fixed like this:
40 *
41 * * For all definitions that conflict with kernel definitions wrap those
42 * defines in the following:
43 * #if !__UAPI_DEF_FOO
44 * ...
45 * #endif
46 *
47 * This prevents the redefinition of a construct already defined by the kernel.
48 */
49#ifndef _LIBC_COMPAT_H
50#define _LIBC_COMPAT_H
51
52/* We have included glibc headers... */
53#if defined(__GLIBC__)
54
55/* Coordinate with glibc net/if.h header. */
56#if defined(_NET_IF_H) && defined(__USE_MISC)
57
58/* GLIBC headers included first so don't define anything
59 * that would already be defined. */
60
61#define __UAPI_DEF_IF_IFCONF 0
62#define __UAPI_DEF_IF_IFMAP 0
63#define __UAPI_DEF_IF_IFNAMSIZ 0
64#define __UAPI_DEF_IF_IFREQ 0
65/* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
66#define __UAPI_DEF_IF_NET_DEVICE_FLAGS 0
67/* For the future if glibc adds IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO */
68#ifndef __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO
69#define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
70#endif /* __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO */
71
72#else /* _NET_IF_H */
73
74/* Linux headers included first, and we must define everything
75 * we need. The expectation is that glibc will check the
76 * __UAPI_DEF_* defines and adjust appropriately. */
77
78#define __UAPI_DEF_IF_IFCONF 1
79#define __UAPI_DEF_IF_IFMAP 1
80#define __UAPI_DEF_IF_IFNAMSIZ 1
81#define __UAPI_DEF_IF_IFREQ 1
82/* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
83#define __UAPI_DEF_IF_NET_DEVICE_FLAGS 1
84/* For the future if glibc adds IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO */
85#define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
86
87#endif /* _NET_IF_H */
88
89/* Coordinate with glibc netinet/in.h header. */
90#if defined(_NETINET_IN_H)
91
92/* GLIBC headers included first so don't define anything
93 * that would already be defined. */
94#define __UAPI_DEF_IN_ADDR 0
95#define __UAPI_DEF_IN_IPPROTO 0
96#define __UAPI_DEF_IN_PKTINFO 0
97#define __UAPI_DEF_IP_MREQ 0
98#define __UAPI_DEF_SOCKADDR_IN 0
99#define __UAPI_DEF_IN_CLASS 0
100
101#define __UAPI_DEF_IN6_ADDR 0
102/* The exception is the in6_addr macros which must be defined
103 * if the glibc code didn't define them. This guard matches
104 * the guard in glibc/inet/netinet/in.h which defines the
105 * additional in6_addr macros e.g. s6_addr16, and s6_addr32. */
106#if defined(__USE_MISC) || defined (__USE_GNU)
107#define __UAPI_DEF_IN6_ADDR_ALT 0
108#else
109#define __UAPI_DEF_IN6_ADDR_ALT 1
110#endif
111#define __UAPI_DEF_SOCKADDR_IN6 0
112#define __UAPI_DEF_IPV6_MREQ 0
113#define __UAPI_DEF_IPPROTO_V6 0
114#define __UAPI_DEF_IPV6_OPTIONS 0
115#define __UAPI_DEF_IN6_PKTINFO 0
116#define __UAPI_DEF_IP6_MTUINFO 0
117
118#else
119
120/* Linux headers included first, and we must define everything
121 * we need. The expectation is that glibc will check the
122 * __UAPI_DEF_* defines and adjust appropriately. */
123#define __UAPI_DEF_IN_ADDR 1
124#define __UAPI_DEF_IN_IPPROTO 1
125#define __UAPI_DEF_IN_PKTINFO 1
126#define __UAPI_DEF_IP_MREQ 1
127#define __UAPI_DEF_SOCKADDR_IN 1
128#define __UAPI_DEF_IN_CLASS 1
129
130#define __UAPI_DEF_IN6_ADDR 1
131/* We unconditionally define the in6_addr macros and glibc must
132 * coordinate. */
133#define __UAPI_DEF_IN6_ADDR_ALT 1
134#define __UAPI_DEF_SOCKADDR_IN6 1
135#define __UAPI_DEF_IPV6_MREQ 1
136#define __UAPI_DEF_IPPROTO_V6 1
137#define __UAPI_DEF_IPV6_OPTIONS 1
138#define __UAPI_DEF_IN6_PKTINFO 1
139#define __UAPI_DEF_IP6_MTUINFO 1
140
141#endif /* _NETINET_IN_H */
142
143/* Definitions for xattr.h */
144#if defined(_SYS_XATTR_H)
145#define __UAPI_DEF_XATTR 0
146#else
147#define __UAPI_DEF_XATTR 1
148#endif
149
150/* If we did not see any headers from any supported C libraries,
151 * or we are being included in the kernel, then define everything
152 * that we need. Check for previous __UAPI_* definitions to give
153 * unsupported C libraries a way to opt out of any kernel definition. */
154#else /* !defined(__GLIBC__) */
155
156/* Definitions for if.h */
157#ifndef __UAPI_DEF_IF_IFCONF
158#define __UAPI_DEF_IF_IFCONF 1
159#endif
160#ifndef __UAPI_DEF_IF_IFMAP
161#define __UAPI_DEF_IF_IFMAP 1
162#endif
163#ifndef __UAPI_DEF_IF_IFNAMSIZ
164#define __UAPI_DEF_IF_IFNAMSIZ 1
165#endif
166#ifndef __UAPI_DEF_IF_IFREQ
167#define __UAPI_DEF_IF_IFREQ 1
168#endif
169/* Everything up to IFF_DYNAMIC, matches net/if.h until glibc 2.23 */
170#ifndef __UAPI_DEF_IF_NET_DEVICE_FLAGS
171#define __UAPI_DEF_IF_NET_DEVICE_FLAGS 1
172#endif
173/* For the future if glibc adds IFF_LOWER_UP, IFF_DORMANT and IFF_ECHO */
174#ifndef __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO
175#define __UAPI_DEF_IF_NET_DEVICE_FLAGS_LOWER_UP_DORMANT_ECHO 1
176#endif
177
178/* Definitions for in.h */
179#ifndef __UAPI_DEF_IN_ADDR
180#define __UAPI_DEF_IN_ADDR 1
181#endif
182#ifndef __UAPI_DEF_IN_IPPROTO
183#define __UAPI_DEF_IN_IPPROTO 1
184#endif
185#ifndef __UAPI_DEF_IN_PKTINFO
186#define __UAPI_DEF_IN_PKTINFO 1
187#endif
188#ifndef __UAPI_DEF_IP_MREQ
189#define __UAPI_DEF_IP_MREQ 1
190#endif
191#ifndef __UAPI_DEF_SOCKADDR_IN
192#define __UAPI_DEF_SOCKADDR_IN 1
193#endif
194#ifndef __UAPI_DEF_IN_CLASS
195#define __UAPI_DEF_IN_CLASS 1
196#endif
197
198/* Definitions for in6.h */
199#ifndef __UAPI_DEF_IN6_ADDR
200#define __UAPI_DEF_IN6_ADDR 1
201#endif
202#ifndef __UAPI_DEF_IN6_ADDR_ALT
203#define __UAPI_DEF_IN6_ADDR_ALT 1
204#endif
205#ifndef __UAPI_DEF_SOCKADDR_IN6
206#define __UAPI_DEF_SOCKADDR_IN6 1
207#endif
208#ifndef __UAPI_DEF_IPV6_MREQ
209#define __UAPI_DEF_IPV6_MREQ 1
210#endif
211#ifndef __UAPI_DEF_IPPROTO_V6
212#define __UAPI_DEF_IPPROTO_V6 1
213#endif
214#ifndef __UAPI_DEF_IPV6_OPTIONS
215#define __UAPI_DEF_IPV6_OPTIONS 1
216#endif
217#ifndef __UAPI_DEF_IN6_PKTINFO
218#define __UAPI_DEF_IN6_PKTINFO 1
219#endif
220#ifndef __UAPI_DEF_IP6_MTUINFO
221#define __UAPI_DEF_IP6_MTUINFO 1
222#endif
223
224/* Definitions for xattr.h */
225#ifndef __UAPI_DEF_XATTR
226#define __UAPI_DEF_XATTR 1
227#endif
228
229#endif /* __GLIBC__ */
230
231#endif /* _LIBC_COMPAT_H */