elf: Make more functions available for binding during dlclose (bug 30425)

Previously, after destructors for a DSO have been invoked, ld.so refused
to bind against that DSO in all cases.  Relax this restriction somewhat
if the referencing object is itself a DSO that is being unloaded.  This
assumes that the symbol reference is not going to be stored anywhere.

The situation in the test case can arise fairly easily with C++ and
objects that are built with different optimization levels and therefore
define different functions with vague linkage.

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

1 files changed, 49 insertions, 0 deletions

diff --git a/elf/tst-dlclose-lazy-mod2.c b/elf/tst-dlclose-lazy-mod2.c
new file mode 100644
index 0000000000..767f69ffdb
--- /dev/null
+++ b/elf/tst-dlclose-lazy-mod2.c
@@ -0,0 +1,49 @@
+/* Lazy binding during dlclose.  Indirectly loaded module.
+   Copyright (C) 2023 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 <stdlib.h>
+
+void
+exported_function (int ignored)
+{
+  /* This function is interposed from tst-dlclose-lazy-mod1.so and
+     thus never called.  */
+  abort ();
+}
+
+static void __attribute__ ((constructor))
+init (void)
+{
+  puts ("info: tst-dlclose-lazy-mod2.so constructor called");
+
+  /* Trigger lazy binding to the definition in
+     tst-dlclose-lazy-mod1.so, but not for
+     lazily_bound_exported_function in that module.  */
+  exported_function (0);
+}
+
+static void __attribute__ ((destructor))
+fini (void)
+{
+  puts ("info: tst-dlclose-lazy-mod2.so destructor called");
+
+  /* Trigger the lazily_bound_exported_function call in
+     exported_function in tst-dlclose-lazy-mod1.so.  */
+  exported_function (1);
+}