elf: Add ld.so test with non-existing program name

None of the existing tests seem to cover the case where
_dl_signal_error is called without an active error handler.
The new elf/tst-rtld-does-not-exist test triggers such a
_dl_signal_error call from _dl_map_object.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

elf/Makefile

@@ -621,6 +621,13 @@ $(objpfx)tst-valgrind-smoke.out: tst-valgrind-smoke.sh $(objpfx)ld.so $(objpfx)v
 		'$(run-program-env)' '$(rpath-link)' $(objpfx)valgrind-test \
 		'$(valgrind-suppressions-tst-valgrind-smoke)' > $@; $(evaluate-test)
 
+ifeq ($(run-built-tests),yes)
+tests-special += $(objpfx)tst-rtld-does-not-exist.out
+endif
+$(objpfx)tst-rtld-does-not-exist.out: tst-rtld-does-not-exist.sh $(objpfx)ld.so
+	$(SHELL) $< $(objpfx)ld.so > $@; \
+	$(evaluate-test)
+
 tests += $(tests-execstack-$(have-z-execstack))
 ifeq ($(run-built-tests),yes)
 tests-special += \

elf/tst-rtld-does-not-exist.sh

@@ -0,0 +1,39 @@
+#!/bin/sh
+# Check that running ld.so with a non-existing file prints an error.
+# Copyright (C) 2024 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/>.
+
+export LC_ALL=C
+
+rtld="$1"
+tmp_out="$(mktemp)"
+
+$rtld program-does-not-exist 2>"$tmp_out"
+status=$?
+echo "$rtld exit status: $status"
+echo "output (with expected error):"
+cat "$tmp_out"
+
+if test $status -eq 127 \
+	&& grep -q "^program-does-not-exist: error while loading shared libraries: program-does-not-exist: cannot open shared object file$" "$tmp_out" \
+	&& test "$(wc -l < "$tmp_out")" -eq 1 ; then
+    status=0
+else
+    status=1
+fi
+rm "$tmp_out"
+exit $status