Downstream-only patch to enhance CPU detection.  Review thread:

  <https://sourceware.org/pipermail/libc-alpha/2021-May/125916.html>

Author: Florian Weimer <fweimer@redhat.com>
Date:   Thu May 6 11:58:02 2021 +0200

    s390x: Check HWCAP bits against compiler flags
    
    When compiled with GCC 11.1 and -march=z14 -O3 build flags, running
    ld.so (or any dynamically linked program) prints:
    
    Fatal glibc error: CPU lacks VXE support (z14 or later required)
    
    Co-Authored-By: Stefan Liebler <stli@linux.ibm.com>

diff --git a/sysdeps/s390/s390-64/dl-hwcap-check.h b/sysdeps/s390/s390-64/dl-hwcap-check.h
new file mode 100644
index 0000000000000000..87e18be6bd0c512b
--- /dev/null
+++ b/sysdeps/s390/s390-64/dl-hwcap-check.h
@@ -0,0 +1,40 @@
+/* Check for hardware capabilities after HWCAP parsing.  S390 version.
+   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/>.  */
+
+#ifndef _DL_HWCAP_CHECK_H
+#define _DL_HWCAP_CHECK_H
+
+#include <ldsodefs.h>
+
+static inline void
+dl_hwcap_check (void)
+{
+#if defined __ARCH__
+# if __ARCH__ >= 13
+  if (!(GLRO(dl_hwcap) & HWCAP_S390_VXRS_EXT2))
+    _dl_fatal_printf ("\
+Fatal glibc error: CPU lacks VXRS_EXT2 support (z15 or later required)\n");
+# elif __ARCH__ >= 12
+  if (!(GLRO(dl_hwcap) & HWCAP_S390_VXE))
+    _dl_fatal_printf ("\
+Fatal glibc error: CPU lacks VXE support (z14 or later required)\n");
+# endif
+#endif /* __ARCH__ */
+}
+
+#endif /* _DL_HWCAP_CHECK_H */