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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_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 | ||
88 | ||
89 | /* If we did not see any headers from any supported C libraries, | |
90 | * or we are being included in the kernel, then define everything | |
91 | * that we need. */ | |
92 | #else /* !defined(__GLIBC__) */ | |
93 | ||
94 | /* Definitions for in6.h */ | |
95 | #define __UAPI_DEF_IN6_ADDR 1 | |
96 | #define __UAPI_DEF_IN6_ADDR_ALT 1 | |
97 | #define __UAPI_DEF_SOCKADDR_IN6 1 | |
98 | #define __UAPI_DEF_IPV6_MREQ 1 | |
99 | #define __UAPI_DEF_IPPROTO_V6 1 | |
100 | ||
101 | #endif /* __GLIBC__ */ | |
102 | ||
103 | #endif /* _UAPI_LIBC_COMPAT_H */ |