linux-user: Support the epoll syscalls

Support the epoll family of syscalls: epoll_create(), epoll_create1(),
epoll_ctl(), epoll_wait() and epoll_pwait(). Note that epoll_create1()
and epoll_pwait() are later additions, so we have to test separately
in configure for their presence.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@nokia.com>
diff --git a/configure b/configure
index a3f5345..cb72ced 100755
--- a/configure
+++ b/configure
@@ -2142,6 +2142,51 @@
   dup3=yes
 fi
 
+# check for epoll support
+epoll=no
+cat > $TMPC << EOF
+#include <sys/epoll.h>
+
+int main(void)
+{
+    epoll_create(0);
+    return 0;
+}
+EOF
+if compile_prog "$ARCH_CFLAGS" "" ; then
+  epoll=yes
+fi
+
+# epoll_create1 and epoll_pwait are later additions
+# so we must check separately for their presence
+epoll_create1=no
+cat > $TMPC << EOF
+#include <sys/epoll.h>
+
+int main(void)
+{
+    epoll_create1(0);
+    return 0;
+}
+EOF
+if compile_prog "$ARCH_CFLAGS" "" ; then
+  epoll_create1=yes
+fi
+
+epoll_pwait=no
+cat > $TMPC << EOF
+#include <sys/epoll.h>
+
+int main(void)
+{
+    epoll_pwait(0, 0, 0, 0, 0);
+    return 0;
+}
+EOF
+if compile_prog "$ARCH_CFLAGS" "" ; then
+  epoll_pwait=yes
+fi
+
 # Check if tools are available to build documentation.
 if test "$docs" != "no" ; then
   if has makeinfo && has pod2man; then
@@ -2674,6 +2719,15 @@
 if test "$dup3" = "yes" ; then
   echo "CONFIG_DUP3=y" >> $config_host_mak
 fi
+if test "$epoll" = "yes" ; then
+  echo "CONFIG_EPOLL=y" >> $config_host_mak
+fi
+if test "$epoll_create1" = "yes" ; then
+  echo "CONFIG_EPOLL_CREATE1=y" >> $config_host_mak
+fi
+if test "$epoll_pwait" = "yes" ; then
+  echo "CONFIG_EPOLL_PWAIT=y" >> $config_host_mak
+fi
 if test "$inotify" = "yes" ; then
   echo "CONFIG_INOTIFY=y" >> $config_host_mak
 fi