Index: libgo/configure.ac
===================================================================
--- libgo/configure.ac	(revision 180345)
+++ libgo/configure.ac	(working copy)
@@ -505,6 +505,28 @@ CFLAGS="$CFLAGS -D_LARGEFILE_SOURCE -D_L
 AC_CHECK_TYPES(off64_t)
 CFLAGS=$CFLAGS_hold
 
+dnl Work out the size of the epoll_events struct on GNU/Linux.
+AC_CACHE_CHECK([epoll_event size],
+[libgo_cv_c_epoll_event_size],
+[AC_COMPUTE_INT(libgo_cv_c_epoll_event_size,
+[sizeof (struct epoll_event)],
+[#include <sys/epoll.h>],
+[libgo_cv_c_epoll_event_size=0])])
+SIZEOF_STRUCT_EPOLL_EVENT=${libgo_cv_c_epoll_event_size}
+AC_SUBST(SIZEOF_STRUCT_EPOLL_EVENT)
+
+dnl Work out the offset of the fd field in the epoll_events struct on
+dnl GNU/Linux.
+AC_CACHE_CHECK([epoll_event data.fd offset],
+[libgo_cv_c_epoll_event_fd_offset],
+[AC_COMPUTE_INT(libgo_cv_c_epoll_event_fd_offset,
+[offsetof (struct epoll_event, data.fd)],
+[#include <stddef.h>
+#include <sys/epoll.h>],
+[libgo_cv_c_epoll_event_fd_offset=0])])
+STRUCT_EPOLL_EVENT_FD_OFFSET=${libgo_cv_c_epoll_event_fd_offset}
+AC_SUBST(STRUCT_EPOLL_EVENT_FD_OFFSET)
+
 AC_CACHE_SAVE
 
 if test ${multilib} = yes; then
Index: libgo/go/syscall/socket_linux.go
===================================================================
--- libgo/go/syscall/socket_linux.go	(revision 180552)
+++ libgo/go/syscall/socket_linux.go	(working copy)
@@ -164,15 +164,6 @@ func anyToSockaddrOS(rsa *RawSockaddrAny
 	return nil, EAFNOSUPPORT
 }
 
-// We don't take this type directly from the header file because it
-// uses a union.  FIXME.
-
-type EpollEvent struct {
-	Events uint32
-	Fd int32
-	Pad int32
-}
-
 //sysnb	EpollCreate(size int) (fd int, errno int)
 //epoll_create(size int) int
 
Index: libgo/Makefile.am
===================================================================
--- libgo/Makefile.am	(revision 180552)
+++ libgo/Makefile.am	(working copy)
@@ -1498,7 +1498,7 @@ endif # !LIBGO_IS_LINUX
 
 # Define socket sizes and types.
 if LIBGO_IS_LINUX
-syscall_socket_file = go/syscall/socket_linux.go
+syscall_socket_file = go/syscall/socket_linux.go epoll.go
 else
 if LIBGO_IS_SOLARIS
 syscall_socket_file = go/syscall/socket_solaris.go
@@ -1582,6 +1582,34 @@ s-sysinfo: $(srcdir)/mksysinfo.sh config
 	$(SHELL) $(srcdir)/../move-if-change tmp-sysinfo.go sysinfo.go
 	$(STAMP) $@
 
+# The epoll struct has an embedded union and is packed on x86_64,
+# which is too complicated for mksysinfo.sh.  We find the offset of
+# the only field we care about in configure.ac, and generate the
+# struct here.
+epoll.go: s-epoll; @true
+s-epoll: Makefile
+	rm -f epoll.go.tmp
+	echo 'package syscall' > epoll.go.tmp
+	echo 'type EpollEvent struct {' >> epoll.go.tmp
+	echo '	Events uint32' >> epoll.go.tmp
+	case "$(SIZEOF_STRUCT_EPOLL_EVENT),$(STRUCT_EPOLL_EVENT_FD_OFFSET)" in \
+	0,0) echo 1>&2 "*** struct epoll_event data.fd offset unknown"; \
+	   exit 1; ;; \
+	8,4) echo '	Fd int32' >> epoll.go.tmp; ;; \
+	12,4) echo '	Fd int32' >> epoll.go.tmp; \
+	   echo '	Pad [4]byte' >> epoll.go.tmp; ;; \
+	12,8) echo '	Pad [4]byte' >> epoll.go.tmp; \
+	   echo '	Fd int32' >> epoll.go.tmp; ;; \
+	16,8) echo '	Pad [4]byte' >> epoll.go.tmp; \
+	   echo '	Fd int32' >> epoll.go.tmp; \
+	   echo '	Pad2 [4]byte' >> epoll.go.tmp; ;; \
+	*) echo 1>&2 "*** struct epoll_event unsupported"; \
+	   exit 1; ;; \
+	esac
+	echo '}' >> epoll.go.tmp
+	$(SHELL) $(srcdir)/../move-if-change epoll.go.tmp epoll.go
+	$(STAMP) $@
+
 if LIBGO_IS_LINUX
 # os_lib_inotify_lo = os/inotify.lo
 os_lib_inotify_lo =