elf: Smoke-test ldconfig -p against system /etc/ld.so.cache

The test is sufficient to detect the ldconfig bug fixed in
commit 9fe6f63638 ("elf: Fix 64 time_t
support for installed statically binaries").

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

elf/Makefile

@@ -626,6 +626,7 @@ ifeq ($(run-built-tests),yes)
 tests-special += \
   $(objpfx)noload-mem.out \
   $(objpfx)tst-ldconfig-X.out \
+  $(objpfx)tst-ldconfig-p.out \
   $(objpfx)tst-leaks1-mem.out \
   $(objpfx)tst-rtld-help.out \
   # tests-special
@@ -2396,6 +2397,11 @@ $(objpfx)tst-ldconfig-X.out : tst-ldconfig-X.sh $(objpfx)ldconfig
 		 '$(run-program-env)' > $@; \
 	$(evaluate-test)
 
+$(objpfx)tst-ldconfig-p.out : tst-ldconfig-p.sh $(objpfx)ldconfig
+	$(SHELL) $< '$(common-objpfx)' '$(test-wrapper-env)' \
+		 '$(run-program-env)' > $@; \
+	$(evaluate-test)
+
 # Test static linking of all the libraries we can possibly link
 # together.  Note that in some configurations this may be less than the
 # complete list of libraries we build but we try to maxmimize this list.

elf/tst-ldconfig-p.sh

@@ -0,0 +1,77 @@
+#!/bin/sh
+# Test that ldconfig -p prints something useful.
+# 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/>.
+
+# Check that the newly built ldconfig -p can dump the system
+# /etc/ld.so.cache file.  This should always work even if the ABIs are
+# not compatible, except in a cross-endian build (that presumably
+# involves emulation when running ldconfig).
+
+common_objpfx=$1
+test_wrapper_env=$2
+run_program_env=$3
+
+if ! test -r /etc/ld.so.cache; then
+    echo "warning: /etc/ld.so.cache does not exist, test skipped"
+    exit 77
+fi
+
+testout="${common_objpfx}elf/tst-ldconfig-p.out"
+# Truncate file.
+: > "$testout"
+
+${test_wrapper_env} \
+${run_program_env} \
+${common_objpfx}elf/ldconfig -p \
+  $testroot/lib >>"$testout" 2>>"$testout"
+status=$?
+echo "info: ldconfig exit status: $status" >>"$testout"
+
+errors=0
+case $status in
+    (0)
+	if head -n 1 "$testout" | \
+		grep -q "libs found in cache \`/etc/ld.so.cache'\$" ; then
+	    echo "info: initial string found" >>"$testout"
+	else
+	    echo "error: initial string not found" >>"$testout"
+	    errors=1
+	fi
+	if grep -q "^	libc\.so\..* => " "$testout"; then
+	    echo "info: libc.so.* string found" >>"$testout"
+	else
+	    echo "error: libc.so.* string not found" >>"$testout"
+	    errors=1
+	fi
+	;;
+    (1)
+	if head -n 1 "$testout" | \
+		grep -q ": Cache file has wrong endianness\.$" ; then
+	    echo "info: cache file has wrong endianess" >> "$testout"
+	else
+	    echo "error: unexpected ldconfig error message" >> "$testout"
+	    errors=1
+	fi
+	;;
+    (*)
+	echo "error: unexpected exit status" >> "$testout"
+	errors=1
+	;;
+esac
+
+exit $errors