xref: /linux/include/uapi/linux/libc-compat.h (revision 9410645520e9b820069761f3450ef6661418e279)
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 _UAPI_LIBC_COMPAT_H
50 #define _UAPI_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 /* _UAPI_LIBC_COMPAT_H */
232