Add a DTV setup test [BZ #27136]

The test relies on reusing slotinfo entries after dlclose which
can result in non-monotonic increasing generation counters in
the slotinfo list. It can trigger bug 27136.

The test requires large number of modules with TLS so the
modules of tst-tls7 are used instead of duplicating them.

3 files changed, 106 insertions, 2 deletions

diff --git a/nptl/Makefile b/nptl/Makefile
index 208629876d..a11b598efd 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -354,7 +354,7 @@ LDFLAGS-pthread.so = -Wl,--enable-new-dtags,-z,nodelete,-z,initfirst
 tests += tst-cancelx7 tst-cancelx17 tst-cleanupx4
 
 ifeq ($(build-shared),yes)
-tests += tst-compat-forwarder tst-audit-threads
+tests += tst-compat-forwarder tst-audit-threads tst-tls8
 tests-internal += tst-tls3 tst-tls3-malloc tst-tls5 tst-stackguard1 tst-tls7
 ifeq ($(have-z-execstack),yes)
 tests += tst-execstack
@@ -371,7 +371,7 @@ modules-names = tst-tls3mod \
 		tst-execstack-mod \
 		tst-compat-forwarder-mod tst-audit-threads-mod1 \
 		tst-audit-threads-mod2 \
-		tst-tls7mod tst-tls7mod-dep
+		tst-tls7mod tst-tls7mod-dep tst-tls8mod-bad
 extra-test-objs += $(addsuffix .os,$(strip $(modules-names))) \
 		   tst-cleanup4aux.o tst-cleanupx4aux.o $(tst-tls7mod-deps)
 test-extras += tst-cleanup4aux tst-cleanupx4aux
@@ -528,6 +528,12 @@ $(objpfx)tst-tls7mod.so: $(tst-tls7mod-deps:%=$(objpfx)%)
 $(tst-tls7mod-deps:%=$(objpfx)%): $(objpfx)tst-tls7mod-dep.so
 	cp -f $< $@
 
+# Reuse tst-tls7mod-dep*.so.
+tst-tls8mod-bad.so-no-z-defs = yes
+$(objpfx)tst-tls8: $(libdl) $(shared-thread-library)
+$(objpfx)tst-tls8.out: $(objpfx)tst-tls8mod-bad.so \
+		       $(tst-tls7mod-deps:%=$(objpfx)%)
+
 $(objpfx)tst-dlsym1: $(libdl) $(shared-thread-library)
 
 ifeq (yes,$(build-shared))
diff --git a/nptl/tst-tls8.c b/nptl/tst-tls8.c
new file mode 100644
index 0000000000..be7b64c9be
--- /dev/null
+++ b/nptl/tst-tls8.c
@@ -0,0 +1,96 @@
+/* Test dtv setup if entries don't have monoton increasing generation.
+   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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <dlfcn.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <support/xdlfcn.h>
+#include <support/xthread.h>
+
+#define NMOD 100
+static void *mod[NMOD];
+
+static void
+load_fail (void)
+{
+  /* Expected to fail because of a missing symbol.  */
+  void *m = dlopen ("tst-tls8mod-bad.so", RTLD_NOW);
+  if (m != NULL)
+    FAIL_EXIT1 ("dlopen of tst-tls8mod-bad.so succeeded\n");
+}
+
+static void
+load_mod (int i)
+{
+  char buf[100];
+  sprintf (buf, "tst-tls7mod-dep-%02d.so", i);
+  mod[i] = xdlopen (buf, RTLD_LAZY);
+}
+
+static void
+unload_mod (int i)
+{
+  if (mod[i])
+    xdlclose (mod[i]);
+  mod[i] = 0;
+}
+
+static void
+access (int i)
+{
+  dlerror ();
+  int *p = dlsym (mod[i], "x");
+  printf ("mod[%d]: &x = %p\n", i, p);
+  if (p == NULL)
+    FAIL_EXIT1 ("dlsym failed: %s\n", dlerror ());
+  ++*p;
+}
+
+static void *
+start (void *a)
+{
+  for (int i = 0; i < NMOD; i++)
+    if (mod[i])
+      access (i);
+  return 0;
+}
+
+static int
+do_test (void)
+{
+  int i;
+
+  for (i = 0; i < NMOD; i++)
+    {
+      load_mod (i);
+      /* Bump the generation of mod[0] without using new dtv slot.  */
+      unload_mod (0);
+      load_fail (); /* Ensure GL(dl_tls_dtv_gaps) is true: see bug 27135.  */
+      load_mod (0);
+      /* Access TLS in all loaded modules.  */
+      pthread_t t = xpthread_create (0, start, 0);
+      xpthread_join (t);
+    }
+  for (i = 0; i < NMOD; i++)
+    unload_mod (i);
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/nptl/tst-tls8mod-bad.c b/nptl/tst-tls8mod-bad.c
new file mode 100644
index 0000000000..c1aed8ea7d
--- /dev/null
+++ b/nptl/tst-tls8mod-bad.c
@@ -0,0 +1,2 @@
+void missing_symbol (void);
+void f (void) {missing_symbol ();}