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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /include/uapi/linux/libc-compat.h
Initial import
Diffstat (limited to 'include/uapi/linux/libc-compat.h')
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diff --git a/include/uapi/linux/libc-compat.h b/include/uapi/linux/libc-compat.h
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+++ b/include/uapi/linux/libc-compat.h
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+/*
+ * 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
+#define __UAPI_DEF_IPV6_OPTIONS 0
+#define __UAPI_DEF_IN6_PKTINFO 0
+#define __UAPI_DEF_IP6_MTUINFO 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
+#define __UAPI_DEF_IPV6_OPTIONS 1
+#define __UAPI_DEF_IN6_PKTINFO 1
+#define __UAPI_DEF_IP6_MTUINFO 1
+
+#endif /* _NETINET_IN_H */
+
+/* Definitions for xattr.h */
+#if defined(_SYS_XATTR_H)
+#define __UAPI_DEF_XATTR 0
+#else
+#define __UAPI_DEF_XATTR 1
+#endif
+
+/* 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
+#define __UAPI_DEF_IPV6_OPTIONS 1
+#define __UAPI_DEF_IN6_PKTINFO 1
+#define __UAPI_DEF_IP6_MTUINFO 1
+
+/* Definitions for xattr.h */
+#define __UAPI_DEF_XATTR 1
+
+#endif /* __GLIBC__ */
+
+#endif /* _UAPI_LIBC_COMPAT_H */