S390: Don't test nanoseconds in io/tst-stat.c

Both new tests io/tst-stat and io/tst-stat-lfs (_FILE_OFFSET_BITS=64)
are comparing the nanosecond fields with the statx result.  Unfortunately
on s390(31bit) those fields are always zero if old KABI with non-LFS
support is used.  With _FILE_OFFSET_BITS=64 stat is using statx internally.

As suggested by Adhemerval this patch disables the nanosecond check for
s390(31bit).
Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

3 files changed, 35 insertions, 0 deletions

diff --git a/support/Makefile b/support/Makefile
index fc9f493..900e17f 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -71,6 +71,7 @@ libsupport-routines = \
   support_set_small_thread_stack_size \
   support_shared_allocate \
   support_small_stack_thread_attribute \
+  support_stat_nanoseconds \
   support_subprocess \
   support_test_compare_blob \
   support_test_compare_failure \
diff --git a/support/support.h b/support/support.h
index 2e477c9..90f3ff9 100644
--- a/support/support.h
+++ b/support/support.h
@@ -134,6 +134,9 @@ extern ssize_t support_copy_file_range (int, off64_t *, int, off64_t *,
    operations (such as fstatat or utimensat).  */
 extern bool support_path_support_time64 (const char *path);
 
+/* Return true if stat supports nanoseconds resolution.  */
+extern bool support_stat_nanoseconds (void);
+
 __END_DECLS
 
 #endif /* SUPPORT_H */
diff --git a/support/support_stat_nanoseconds.c b/support/support_stat_nanoseconds.c
new file mode 100644
index 0000000..c0d5b2c
--- /dev/null
+++ b/support/support_stat_nanoseconds.c
@@ -0,0 +1,31 @@
+/* Check if stat supports nanosecond resolution.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stdbool.h>
+
+bool
+support_stat_nanoseconds (void)
+{
+  /* s390 stat64 compat symbol does not support nanoseconds resolution
+     and it used on non-LFS [f,l]stat[at] implementations.  */
+#if defined __linux__ && !defined __s390x__ && defined __s390__
+  return false;
+#else
+  return true;
+#endif
+}