Add and use link-test-modules-rpath-link [BZ #28455]

DT_RUNPATH is only used to find the immediate dependencies of the
executable or shared object containing the DT_RUNPATH entry:

1. Define link-test-modules-rpath-link if $(build-hardcoded-path-in-tests)
is yes.
2. Use $(link-test-modules-rpath-link) in build-module-helper so that
test modules can dlopen modules with DT_RUNPATH.
3. Add a test to show why link-test-modules-rpath-link is needed.

This partially fixes BZ #28455.

Makeconfig

@@ -575,8 +575,10 @@ link-libc-rpath-link = -Wl,-rpath-link=$(rpath-link)
 # build-hardcoded-path-in-tests.
 ifeq (yes,$(build-hardcoded-path-in-tests))
 link-libc-tests-rpath-link = $(link-libc-rpath)
+link-test-modules-rpath-link = $(link-libc-rpath)
 else
 link-libc-tests-rpath-link = $(link-libc-rpath-link)
+link-test-modules-rpath-link =
 endif  # build-hardcoded-path-in-tests
 
 link-libc-between-gnulib = $(common-objpfx)libc.so$(libc.so-version) \

Makerules

@@ -597,6 +597,7 @@ $(LINK.o) -shared -static-libgcc $(sysdep-LDFLAGS) $(rtld-LDFLAGS) \
 	  $(if $($(@F)-no-z-defs)$(no-z-defs),,-Wl,-z,defs) \
 	  -B$(csu-objpfx) $(load-map-file) \
 	  $(LDFLAGS.so) $(LDFLAGS-$(@F:%.so=%).so) \
+	  $(link-test-modules-rpath-link) \
 	  -L$(subst :, -L,$(rpath-link)) -Wl,-rpath-link=$(rpath-link)
 endef
 

elf/Makefile

@@ -402,6 +402,7 @@ tests += \
   tst-glibc-hwcaps-mask \
   tst-glibc-hwcaps-prepend \
   tst-global1 \
+  tst-global2 \
   tst-initfinilazyfail \
   tst-initorder \
   tst-initorder2 \
@@ -716,6 +717,7 @@ modules-names = \
   tst-filterobj-filtee \
   tst-filterobj-flt \
   tst-finilazyfailmod \
+  tst-globalmod2 \
   tst-initlazyfailmod \
   tst-initorder2a \
   tst-initorder2b \
@@ -1863,6 +1865,11 @@ tst-audit8-ENV = LD_AUDIT=$(objpfx)tst-auditmod1.so
 
 $(objpfx)tst-global1.out: $(objpfx)testobj6.so $(objpfx)testobj2.so
 
+$(objpfx)tst-global2: $(objpfx)tst-globalmod2.so
+$(objpfx)tst-global2.out: $(objpfx)reldepmod1.so $(objpfx)reldepmod4.so
+LDFLAGS-tst-global2 = -Wl,--enable-new-dtags
+LDFLAGS-tst-globalmod2.so = -Wl,--enable-new-dtags
+
 $(objpfx)order2.out: $(objpfx)order2mod1.so $(objpfx)order2mod2.so
 $(objpfx)order2-cmp.out: $(objpfx)order2.out
 	(echo "12345" | cmp $< -) > $@; \

elf/tst-global2.c

@@ -0,0 +1,32 @@
+/* Test BZ #28455.
+   Copyright (C) 2022 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/>.  */
+
+/* In glibc configured with --enable-hardcoded-path-in-tests, a test
+   program built with -Wl,--enable-new-dtags, which adds DT_RUNPATH,
+   instead of DT_RPATH, can call a function in a shared library, which
+   dlopens another shared library.  */
+
+extern int test (void);
+
+static int
+do_test (void)
+{
+  return test ();
+}
+
+#include <support/test-driver.c>

elf/tst-globalmod2.c

@@ -0,0 +1,41 @@
+/* Test BZ #28455.
+   Copyright (C) 2022 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/>.  */
+
+/* In glibc configured with --enable-hardcoded-path-in-tests, a test
+   program built with -Wl,--enable-new-dtags, which adds DT_RUNPATH,
+   instead of DT_RPATH, can call a function in a shared library, which
+   dlopens another shared library.  */
+
+#include <dlfcn.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+extern int test (void);
+
+int
+test (void)
+{
+  (void) dlopen ("reldepmod4.so", RTLD_LAZY | RTLD_GLOBAL);
+  if (dlsym (RTLD_DEFAULT, "call_me") != NULL)
+    {
+      puts ("found \"call_me\"");
+      return EXIT_SUCCESS;
+    }
+  puts ("didn't find \"call_me\"");
+  return EXIT_FAILURE;
+}