Re: [PATCH v2 02/14] elf: Add a DTV setup test [BZ #27136]

[Szabolcs Nagy <szabolcs.nagy@arm.com>]

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The 04/14/2021 15:06, Adhemerval Zanella wrote:
> On 13/04/2021 05:18, Szabolcs Nagy via Libc-alpha wrote:
> > The test dlopens a large number of modules with TLS, they are reused
> > from an existing test.
> > 
> > The test relies on the reuse of slotinfo entries after dlclose, without
> > bug 27135 fixed this needs a failing dlopen. With a slotinfo list that
> > has non-monotone increasing generation counters, bug 27136 can trigger.
> > 
> > --
> > v2:
> > - moved from nptl/ to elf/
> > - dlopen a different set of existing modules.
> > - code style fixes (!= NULL etc).
> > - moved after bug fix patch
> 
> LGTM, with just a small suggestion below?
> 
> Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

thanks

> > +{
> > +  char buf[100];
> > +  snprintf (buf, sizeof buf, "tst-tls-manydynamic%02dmod.so", i);
> > +  mod[i] = xdlopen (buf, RTLD_LAZY);
> > +}
> 
> Maybe xasprintf here?  

committed with this change, but made a mistake

committed patches are attached.

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From 52290d8c04569615fb011ee286d52dc5147afbd7 Mon Sep 17 00:00:00 2001
From: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date: Thu, 15 Apr 2021 09:57:10 +0100
Subject: [PATCH] elf: Fix missing include in test case [BZ #27136]

Broken test was introduced in

  commit 8f85075a2e9c26ff7486d4bbaf358999807d215c
  elf: Add a DTV setup test [BZ #27136]
---
 elf/tst-tls20.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/elf/tst-tls20.c b/elf/tst-tls20.c
index ac5f8c8d39..9977ec8032 100644
--- a/elf/tst-tls20.c
+++ b/elf/tst-tls20.c
@@ -21,6 +21,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <support/check.h>
+#include <support/support.h>
 #include <support/xdlfcn.h>
 #include <support/xthread.h>
 
-- 
2.17.1


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From 8f85075a2e9c26ff7486d4bbaf358999807d215c Mon Sep 17 00:00:00 2001
From: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date: Thu, 31 Dec 2020 12:24:38 +0000
Subject: [PATCH] elf: Add a DTV setup test [BZ #27136]

The test dlopens a large number of modules with TLS, they are reused
from an existing test.

The test relies on the reuse of slotinfo entries after dlclose, without
bug 27135 fixed this needs a failing dlopen. With a slotinfo list that
has non-monotone increasing generation counters, bug 27136 can trigger.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
---
 elf/Makefile           | 10 ++++-
 elf/tst-tls20.c        | 98 ++++++++++++++++++++++++++++++++++++++++++
 elf/tst-tls20mod-bad.c |  2 +
 3 files changed, 109 insertions(+), 1 deletion(-)
 create mode 100644 elf/tst-tls20.c
 create mode 100644 elf/tst-tls20mod-bad.c

diff --git a/elf/Makefile b/elf/Makefile
index de659655dc..c531470ede 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -222,7 +222,8 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
 	 tst-audit14 tst-audit15 tst-audit16 \
 	 tst-single_threaded tst-single_threaded-pthread \
 	 tst-tls-ie tst-tls-ie-dlmopen argv0test \
-	 tst-glibc-hwcaps tst-glibc-hwcaps-prepend tst-glibc-hwcaps-mask
+	 tst-glibc-hwcaps tst-glibc-hwcaps-prepend tst-glibc-hwcaps-mask \
+	 tst-tls20
 #	 reldep9
 tests-internal += loadtest unload unload2 circleload1 \
 	 neededtest neededtest2 neededtest3 neededtest4 \
@@ -344,6 +345,7 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
 		libmarkermod2-1 libmarkermod2-2 \
 		libmarkermod3-1 libmarkermod3-2 libmarkermod3-3 \
 		libmarkermod4-1 libmarkermod4-2 libmarkermod4-3 libmarkermod4-4 \
+		tst-tls20mod-bad
 
 # Most modules build with _ISOMAC defined, but those filtered out
 # depend on internal headers.
@@ -1922,3 +1924,9 @@ $(objpfx)tst-rtld-help.out: $(objpfx)ld.so
 	fi; \
 	(exit $$status); \
 	$(evaluate-test)
+
+# Reuses tst-tls-many-dynamic-modules
+tst-tls20mod-bad.so-no-z-defs = yes
+$(objpfx)tst-tls20: $(libdl) $(shared-thread-library)
+$(objpfx)tst-tls20.out: $(objpfx)tst-tls20mod-bad.so \
+			$(tst-tls-many-dynamic-modules:%=$(objpfx)%.so)
diff --git a/elf/tst-tls20.c b/elf/tst-tls20.c
new file mode 100644
index 0000000000..ac5f8c8d39
--- /dev/null
+++ b/elf/tst-tls20.c
@@ -0,0 +1,98 @@
+/* Test dtv setup if entries don't have monotone 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-tls20mod-bad.so", RTLD_NOW);
+  if (m != NULL)
+    FAIL_EXIT1 ("dlopen of tst-tls20mod-bad.so succeeded\n");
+}
+
+static void
+load_mod (int i)
+{
+  char *buf = xasprintf ("tst-tls-manydynamic%02dmod.so", i);
+  mod[i] = xdlopen (buf, RTLD_LAZY);
+  free (buf);
+}
+
+static void
+unload_mod (int i)
+{
+  if (mod[i] != NULL)
+    xdlclose (mod[i]);
+  mod[i] = NULL;
+}
+
+static void
+access (int i)
+{
+  char *buf = xasprintf ("tls_global_%02d", i);
+  dlerror ();
+  int *p = dlsym (mod[i], buf);
+  printf ("mod[%d]: &tls = %p\n", i, p);
+  if (p == NULL)
+    FAIL_EXIT1 ("dlsym failed: %s\n", dlerror ());
+  ++*p;
+  free (buf);
+}
+
+static void *
+start (void *a)
+{
+  for (int i = 0; i < NMOD; i++)
+    if (mod[i] != NULL)
+      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/elf/tst-tls20mod-bad.c b/elf/tst-tls20mod-bad.c
new file mode 100644
index 0000000000..c1aed8ea7d
--- /dev/null
+++ b/elf/tst-tls20mod-bad.c
@@ -0,0 +1,2 @@
+void missing_symbol (void);
+void f (void) {missing_symbol ();}
-- 
2.17.1