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Diffstat (limited to 'include/uapi/linux/libc-compat.h')
| -rw-r--r-- | include/uapi/linux/libc-compat.h | 103 |
1 files changed, 103 insertions, 0 deletions
diff --git a/include/uapi/linux/libc-compat.h b/include/uapi/linux/libc-compat.h new file mode 100644 index 000000000000..335e8a7cad39 --- /dev/null +++ b/include/uapi/linux/libc-compat.h @@ -0,0 +1,103 @@ +/* + * Compatibility interface for userspace libc header coordination: + * + * Define compatibility macros that are used to control the inclusion or + * exclusion of UAPI structures and definitions in coordination with another + * userspace C library. + * + * This header is intended to solve the problem of UAPI definitions that + * conflict with userspace definitions. If a UAPI header has such conflicting + * definitions then the solution is as follows: + * + * * Synchronize the UAPI header and the libc headers so either one can be + * used and such that the ABI is preserved. If this is not possible then + * no simple compatibility interface exists (you need to write translating + * wrappers and rename things) and you can't use this interface. + * + * Then follow this process: + * + * (a) Include libc-compat.h in the UAPI header. + * e.g. #include <linux/libc-compat.h> + * This include must be as early as possible. + * + * (b) In libc-compat.h add enough code to detect that the comflicting + * userspace libc header has been included first. + * + * (c) If the userspace libc header has been included first define a set of + * guard macros of the form __UAPI_DEF_FOO and set their values to 1, else + * set their values to 0. + * + * (d) Back in the UAPI header with the conflicting definitions, guard the + * definitions with: + * #if __UAPI_DEF_FOO + * ... + * #endif + * + * This fixes the situation where the linux headers are included *after* the + * libc headers. To fix the problem with the inclusion in the other order the + * userspace libc headers must be fixed like this: + * + * * For all definitions that conflict with kernel definitions wrap those + * defines in the following: + * #if !__UAPI_DEF_FOO + * ... + * #endif + * + * This prevents the redefinition of a construct already defined by the kernel. + */ +#ifndef _UAPI_LIBC_COMPAT_H +#define _UAPI_LIBC_COMPAT_H + +/* We have included glibc headers... */ +#if defined(__GLIBC__) + +/* Coordinate with glibc netinet/in.h header. */ +#if defined(_NETINET_IN_H) + +/* GLIBC headers included first so don't define anything + * that would already be defined. */ +#define __UAPI_DEF_IN6_ADDR 0 +/* The exception is the in6_addr macros which must be defined + * if the glibc code didn't define them. This guard matches + * the guard in glibc/inet/netinet/in.h which defines the + * additional in6_addr macros e.g. s6_addr16, and s6_addr32. */ +#if defined(__USE_MISC) || defined (__USE_GNU) +#define __UAPI_DEF_IN6_ADDR_ALT 0 +#else +#define __UAPI_DEF_IN6_ADDR_ALT 1 +#endif +#define __UAPI_DEF_SOCKADDR_IN6 0 +#define __UAPI_DEF_IPV6_MREQ 0 +#define __UAPI_DEF_IPPROTO_V6 0 + +#else + +/* Linux headers included first, and we must define everything + * we need. The expectation is that glibc will check the + * __UAPI_DEF_* defines and adjust appropriately. */ +#define __UAPI_DEF_IN6_ADDR 1 +/* We unconditionally define the in6_addr macros and glibc must + * coordinate. */ +#define __UAPI_DEF_IN6_ADDR_ALT 1 +#define __UAPI_DEF_SOCKADDR_IN6 1 +#define __UAPI_DEF_IPV6_MREQ 1 +#define __UAPI_DEF_IPPROTO_V6 1 + +#endif /* _NETINET_IN_H */ + + +/* If we did not see any headers from any supported C libraries, + * or we are being included in the kernel, then define everything + * that we need. */ +#else /* !defined(__GLIBC__) */ + +/* Definitions for in6.h */ +#define __UAPI_DEF_IN6_ADDR 1 +#define __UAPI_DEF_IN6_ADDR_ALT 1 +#define __UAPI_DEF_SOCKADDR_IN6 1 +#define __UAPI_DEF_IPV6_MREQ 1 +#define __UAPI_DEF_IPPROTO_V6 1 + +#endif /* __GLIBC__ */ + +#endif /* _UAPI_LIBC_COMPAT_H */ |