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

["H.J. Lu via Libc-alpha" <libc-alpha@sourceware.org>]

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           |  2 ++
 Makerules            |  1 +
 elf/Makefile         |  7 +++++++
 elf/tst-global2.c    | 32 ++++++++++++++++++++++++++++++++
 elf/tst-globalmod2.c | 41 +++++++++++++++++++++++++++++++++++++++++
 5 files changed, 83 insertions(+)
 create mode 100644 elf/tst-global2.c
 create mode 100644 elf/tst-globalmod2.c

diff --git a/Makeconfig b/Makeconfig
index 06f1cca320..02a0afb9c2 100644
--- a/Makeconfig
+++ b/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) \
diff --git a/Makerules b/Makerules
index 9a56cbdead..37c29758ee 100644
--- a/Makerules
+++ b/Makerules
@@ -591,6 +591,7 @@ $(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
 
diff --git a/elf/Makefile b/elf/Makefile
index 8eb7e6e5d9..bbca0b21bc 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -279,6 +279,7 @@ tests += \
   tst-glibc-hwcaps-mask \
   tst-glibc-hwcaps-prepend \
   tst-global1 \
+  tst-global2 \
   tst-initfinilazyfail \
   tst-initorder \
   tst-initorder2 \
@@ -535,6 +536,7 @@ modules-names = \
   tst-filterobj-filtee \
   tst-filterobj-flt \
   tst-finilazyfailmod \
+  tst-globalmod2 \
   tst-initlazyfailmod \
   tst-initorder2a \
   tst-initorder2b \
@@ -1624,6 +1626,11 @@ 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 $< -) > $@; \
diff --git a/elf/tst-global2.c b/elf/tst-global2.c
new file mode 100644
index 0000000000..e929f526f4
--- /dev/null
+++ b/elf/tst-global2.c
@@ -0,0 +1,32 @@
+/* Test BZ #28455.
+   Copyright (C) 2021 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>
diff --git a/elf/tst-globalmod2.c b/elf/tst-globalmod2.c
new file mode 100644
index 0000000000..6fd70a72a8
--- /dev/null
+++ b/elf/tst-globalmod2.c
@@ -0,0 +1,41 @@
+/* Test BZ #28455.
+   Copyright (C) 2021 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;
+}
-- 
2.33.1