Async-signal safe TLS.

ChangeLog:

2014-01-03  Andrew Hunter  <ahh@google.com>

	* elf/dl-open.c (): New comment.
	* elf/dl-reloc.c (_dl_try_allocate_static_tls): Use
	atomic_compare_and_exchange_bool_acq
	(_dl_allocate_static_tls): Block signals.
	* elf/dl-tls.c (allocate_and_init): Return void.
	(_dl_update_slotinfo): Block signals, use atomic update.

nptl/ChangeLog:

2014-01-03  Andrew Hunter  <ahh@google.com>

	* nptl/Makefile (tst-tls7): New test.
	* nptl/tst-tls7.c: New file.
	* nptl/tst-tls7mod.c: New file.
	* nptl/allocatestack.c (init_one_static_tls): Use atomic barrier.

5 files changed, 190 insertions, 7 deletions

diff --git a/nptl/ChangeLog b/nptl/ChangeLog
index c27ace4..3c7675e 100644
--- a/nptl/ChangeLog
+++ b/nptl/ChangeLog
@@ -1,4 +1,11 @@
-2011-12-12  Adhemerval Zanella  <azanella@linux.vnet.ibm.com>
+2014-01-03  Andrew Hunter  <ahh@google.com>
+
+	* nptl/Makefile (tst-tls7): New test.
+	* nptl/tst-tls7.c: New file.
+	* nptl/tst-tls7mod.c: New file.
+	* nptl/allocatestack.c (init_one_static_tls): Use atomic barrier.
+
+2013-12-12  Adhemerval Zanella  <azanella@linux.vnet.ibm.com>
 
 	* sysdeps/powerpc/tls.h (struct tcbhead_t): Add DSO and TAR fields.
 	* nptl/sysdeps/powerpc/tcb-offsets.sym: Likewise.
diff --git a/nptl/Makefile b/nptl/Makefile
index 57cc8c6..a43e740 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -293,7 +293,7 @@ tests += tst-cancelx2 tst-cancelx3 tst-cancelx4 tst-cancelx5 \
 	 tst-oncex3 tst-oncex4
 endif
 ifeq ($(build-shared),yes)
-tests += tst-atfork2 tst-tls3 tst-tls4 tst-tls5 tst-_res1 tst-fini1 \
+tests += tst-atfork2 tst-tls3 tst-tls4 tst-tls5 tst-tls7 tst-_res1 tst-fini1 \
 	 tst-stackguard1
 tests-nolibpthread += tst-fini1
 ifeq ($(have-z-execstack),yes)
@@ -304,7 +304,8 @@ endif
 modules-names = tst-atfork2mod tst-tls3mod tst-tls4moda tst-tls4modb \
 		tst-tls5mod tst-tls5moda tst-tls5modb tst-tls5modc \
 		tst-tls5modd tst-tls5mode tst-tls5modf \
-		tst-_res1mod1 tst-_res1mod2 tst-execstack-mod tst-fini1mod
+		tst-_res1mod1 tst-_res1mod2 tst-execstack-mod tst-fini1mod \
+		tst-tls7mod
 extra-test-objs += $(addsuffix .os,$(strip $(modules-names))) tst-cleanup4aux.o
 test-extras += $(modules-names) tst-cleanup4aux
 test-modules = $(addprefix $(objpfx),$(addsuffix .so,$(modules-names)))
@@ -318,6 +319,7 @@ tst-tls5modc.so-no-z-defs = yes
 tst-tls5modd.so-no-z-defs = yes
 tst-tls5mode.so-no-z-defs = yes
 tst-tls5modf.so-no-z-defs = yes
+tst-tls7mod.so-no-z-defs = yes
 
 ifeq ($(build-shared),yes)
 # Build all the modules even when not actually running test programs.
@@ -480,6 +482,12 @@ $(objpfx)tst-tls5: $(objpfx)tst-tls5mod.so $(shared-thread-library)
 LDFLAGS-tst-tls5 = $(no-as-needed)
 LDFLAGS-tst-tls5mod.so = -Wl,-soname,tst-tls5mod.so
 
+# ensure free(malloc()) isn't optimized out
+CFLAGS-tst-tls7.c = -fno-builtin-malloc -fno-builtin-free
+$(objpfx)tst-tls7: $(libdl) $(shared-thread-library)
+$(objpfx)tst-tls7.out: $(objpfx)tst-tls7mod.so
+$(objpfx)tst-tls7mod.so: $(shared-thread-library)
+
 ifeq ($(build-shared),yes)
 ifeq ($(run-built-tests),yes)
 tests: $(objpfx)tst-tls6.out
diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
index 7f6094e..2a5ac22 100644
--- a/nptl/allocatestack.c
+++ b/nptl/allocatestack.c
@@ -1173,13 +1173,18 @@ init_one_static_tls (struct pthread *curp, struct link_map *map)
 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 # endif
 
-  /* Fill in the DTV slot so that a later LD/GD access will find it.  */
-  dtv[map->l_tls_modid].pointer.val = dest;
-  dtv[map->l_tls_modid].pointer.is_static = true;
-
   /* Initialize the memory.  */
   memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size),
 	  '\0', map->l_tls_blocksize - map->l_tls_initimage_size);
+
+  /* Fill in the DTV slot so that a later LD/GD access will find it.  */
+  dtv[map->l_tls_modid].pointer.is_static = true;
+  /* Pairs against the read barrier in tls_get_attr_tail, guaranteeing
+     any thread waiting for an update to pointer.val sees the
+     initimage write.  */
+  atomic_write_barrier ();
+  dtv[map->l_tls_modid].pointer.val = dest;
+
 }
 
 void
diff --git a/nptl/tst-tls7.c b/nptl/tst-tls7.c
new file mode 100644
index 0000000..3bb3f7d
--- /dev/null
+++ b/nptl/tst-tls7.c
@@ -0,0 +1,120 @@
+/* Copyright (C) 2013 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/>.  */
+
+
+/* This test checks that TLS in a dlopened object works when first accessed
+   from a signal handler.  */
+
+#include <dlfcn.h>
+#include <pthread.h>
+#include <semaphore.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+void *
+spin (void *ignored)
+{
+  while (1)
+    {
+      /* busywork */
+      free (malloc (128));
+    }
+
+  /* never reached */
+  return NULL;
+}
+
+int
+do_test (void)
+{
+  pthread_t th[10];
+
+  for (int i = 0; i < 10; ++i)
+    {
+      if (pthread_create (&th[i], NULL, spin, NULL))
+        {
+          puts ("pthread_create failed");
+          exit (1);
+        }
+    }
+#define NITERS 75
+
+  for (int i = 0; i < NITERS; ++i)
+    {
+      void *h = dlopen ("tst-tls7mod.so", RTLD_LAZY);
+      if (h == NULL)
+        {
+          puts ("dlopen failed");
+          exit (1);
+        }
+
+      void (*action) (int, siginfo_t *, void *) = dlsym (h, "action");
+      if (action == NULL)
+        {
+          puts ("dlsym for action failed");
+          exit (1);
+        }
+
+      struct sigaction sa;
+      sa.sa_sigaction = action;
+      sigemptyset (&sa.sa_mask);
+      sa.sa_flags = SA_SIGINFO;
+      if (sigaction (SIGUSR1, &sa, NULL))
+        {
+          puts ("sigaction failed");
+          exit (1);
+        }
+
+      sem_t sem;
+      if (sem_init (&sem, 0, 0))
+        {
+          puts ("sem_init failed");
+        }
+
+      sigval_t val;
+      val.sival_ptr = &sem;
+      for (int i = 0; i < 10; ++i)
+        {
+          if (pthread_sigqueue (th[i], SIGUSR1, val))
+            {
+              puts ("pthread_sigqueue failed");
+            }
+        }
+
+
+      for (int i = 0; i < 10; ++i)
+        {
+          if (sem_wait (&sem))
+          {
+            puts ("sem_wait failed");
+          }
+        }
+
+      if (dlclose (h))
+        {
+          puts ("dlclose failed");
+          exit (1);
+        }
+    }
+  return 0;
+}
+
+#define TIMEOUT 4
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
diff --git a/nptl/tst-tls7mod.c b/nptl/tst-tls7mod.c
new file mode 100644
index 0000000..aff29b9
--- /dev/null
+++ b/nptl/tst-tls7mod.c
@@ -0,0 +1,43 @@
+/* Copyright (C) 2013 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/>.  */
+
+/* Dynamic module with TLS to be accessed by a signal handler to check safety
+   of that mode. */
+
+#include <semaphore.h>
+#include <signal.h>
+#include <unistd.h>
+
+/* This is an unlikely value to see in incorrectly initialized TLS
+   block -- make sure we're initialized properly. */
+static __thread intptr_t tls_data = 0xdeadbeef;
+
+void
+action (int signo, siginfo_t *info, void *ignored)
+{
+  sem_t *sem = info->si_value.sival_ptr;
+  if (tls_data != 0xdeadbeef)
+    {
+      write (STDOUT_FILENO, "wrong TLS value\n", 17);
+      _exit (1);
+    }
+
+  /* arbitrary choice, just write something unique-ish. */
+  tls_data = (intptr_t) info;
+
+  sem_post (sem);
+}