Make dlerror(3) thread-safe.

I gave up trying to use the usual thread-local buffer idiom; calls to
calloc(3) and free(3) from any of the "dl" functions -- which live in
the dynamic linker -- end up resolving to the dynamic linker's stubs.
I tried to work around that, but was just making things more complicated.
This alternative costs us a well-known TLS slot (instead of the
dynamically-allocated TLS slot we'd have used otherwise, so no difference
there), plus an extra buffer inside every pthread_internal_t.

Bug: 5404023
Change-Id: Ie9614edd05b6d1eeaf7bf9172792d616c6361767

1 files changed, 60 insertions, 0 deletions

diff --git a/libc/private/ThreadLocalBuffer.h b/libc/private/ThreadLocalBuffer.h
new file mode 100644
index 000000000..1c5e3f48a
--- /dev/null
+++ b/libc/private/ThreadLocalBuffer.h
@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef _BIONIC_THREAD_LOCAL_BUFFER_H_included
+#define _BIONIC_THREAD_LOCAL_BUFFER_H_included
+
+#include <malloc.h>
+#include <pthread.h>
+
+// libstdc++ currently contains __cxa_guard_acquire and __cxa_guard_release,
+// so we make do with macros instead of a C++ class.
+// TODO: move __cxa_guard_acquire and __cxa_guard_release into libc.
+
+#define GLOBAL_INIT_THREAD_LOCAL_BUFFER(name) \
+  static pthread_once_t __bionic_tls_ ## name ## _once; \
+  static pthread_key_t __bionic_tls_ ## name ## _key; \
+  static void __bionic_tls_ ## name ## _key_destroy(void* buffer) { \
+    free(buffer); \
+  } \
+  static void __bionic_tls_ ## name ## _key_init() { \
+    pthread_key_create(&__bionic_tls_ ## name ## _key, __bionic_tls_ ## name ## _key_destroy); \
+  }
+
+// Leaves "name_tls_buffer" and "name_tls_buffer_size" defined and initialized.
+#define LOCAL_INIT_THREAD_LOCAL_BUFFER(type, name, byte_count) \
+  pthread_once(&__bionic_tls_ ## name ## _once, __bionic_tls_ ## name ## _key_init); \
+  type name ## _tls_buffer = \
+      reinterpret_cast<type>(pthread_getspecific(__bionic_tls_ ## name ## _key)); \
+  if (name ## _tls_buffer == NULL) { \
+    name ## _tls_buffer = reinterpret_cast<type>(calloc(1, byte_count)); \
+    pthread_setspecific(__bionic_tls_ ## name ## _key, name ## _tls_buffer); \
+  } \
+  const size_t name ## _tls_buffer_size __attribute__((unused)) = byte_count
+
+#endif // _BIONIC_THREAD_LOCAL_BUFFER_H_included