elf: Change TLS static surplus default back to 1664

Make the computation in elf/dl-tls.c more transparent, and add
an explicit test for the historic value.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

1 files changed, 42 insertions, 0 deletions

diff --git a/elf/tst-tls-surplus.c b/elf/tst-tls-surplus.c
new file mode 100644
index 0000000000..b0dea0b5ee
--- /dev/null
+++ b/elf/tst-tls-surplus.c
@@ -0,0 +1,42 @@
+/* Test size of the static TLS surplus reservation for backwards compatibility.
+   Copyright (C) 2020 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 <stdio.h>
+#include <support/check.h>
+#include <support/xdlfcn.h>
+
+static int do_test (void);
+#include <support/test-driver.c>
+
+/* This hack results in a definition of struct rtld_global_ro.  Do
+   this after all the other header inclusions, to minimize the
+   impact.  */
+#define SHARED
+#include <ldsodefs.h>
+
+static
+int do_test (void)
+{
+  /* Avoid introducing a copy relocation due to the hidden alias in
+     ld.so.  */
+  struct rtld_global_ro *glro = xdlsym (NULL, "_rtld_global_ro");
+  printf ("info: _dl_tls_static_surplus: %zu\n", glro->_dl_tls_static_surplus);
+  /* Hisoric value: 16 * 100 + 64.  */
+  TEST_VERIFY (glro->_dl_tls_static_surplus >= 1664);
+  return 0;
+}