build-sys: check for openat() and linux for switch_root

Signed-off-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/configure.ac b/configure.ac
index ac5fecd6a923df0710b1331fb11619638db35f40..8ea831aa496cdeb1d52083fda687ad9f6320dc47 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -145,6 +145,8 @@ AC_CHECK_FUNCS(
        rpmatch])
 AC_FUNC_FSEEKO
 
+AC_CHECK_FUNCS([openat fstatat unlinkat], [have_openat=yes], [have_openat=no])
+
 AC_CHECK_MEMBER(struct sockaddr.sa_len,
                AC_DEFINE_UNQUOTED(HAVE_SA_LEN,1,[Define if struct sockaddr contains sa_len]),,
        [#include <sys/types.h>
@@ -630,9 +632,27 @@ AM_CONDITIONAL(BUILD_CRAMFS, test "x$build_cramfs" = xyes)
 
 AC_ARG_ENABLE([switch_root],
   AS_HELP_STRING([--disable-switch_root], [do not build switch_root]),
-  [], enable_switch_root=no
+  [], enable_switch_root=check
 )
-AM_CONDITIONAL(BUILD_SWITCH_ROOT, test "x$enable_switch_root" = xyes)
+
+if test "x$enable_switch_root" = xno; then
+  build_switch_root=no
+else
+  build_switch_root=yes
+  case $enable_switch_root:$linux_os in
+  yes:no) AC_MSG_ERROR([switch_root selected for non-linux system]);;
+  check:no) AC_MSG_WARN([non-linux system; do not build switch_root])
+            build_switch_root=no;;
+  esac
+  if test "x$build_switch_root" = xyes; then
+    case $enable_switch_root:$have_openat in
+    yes:no) AC_MSG_ERROR([switch_root selected but openat() function not found]);;
+    check:no) AC_MSG_WARN([openat() function not found; do not build switch_root])
+              build_switch_root=no;;
+    esac
+  fi
+fi
+AM_CONDITIONAL(BUILD_SWITCH_ROOT, test "x$build_switch_root" = xyes)
 
 
 AC_ARG_ENABLE([elvtune],