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

5 files changed, 21 insertions, 73 deletions

diff --git a/libc/bionic/ThreadLocalBuffer.h b/libc/bionic/ThreadLocalBuffer.h
deleted file mode 100644
index 99acdba17..000000000
--- a/libc/bionic/ThreadLocalBuffer.h
+++ /dev/null
@@ -1,59 +0,0 @@
-/*
- * 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 name ## _once; \
-  static pthread_key_t name ## _key; \
-  static void name ## _key_destroy(void* buffer) { \
-    free(buffer); \
-  } \
-  static void name ## _key_init() { \
-    pthread_key_create(&name ## _key, name ## _key_destroy); \
-  }
-
-// Leaves "name_buffer" and "name_byte_count" defined and initialized.
-#define LOCAL_INIT_THREAD_LOCAL_BUFFER(type, name, byte_count) \
-  pthread_once(&name ## _once, name ## _key_init); \
-  type name ## _buffer = reinterpret_cast<type>(pthread_getspecific(name ## _key)); \
-  if (name ## _buffer == NULL) { \
-    name ## _buffer = reinterpret_cast<type>(malloc(byte_count)); \
-    pthread_setspecific(name ## _key, name ## _buffer); \
-  } \
-  const size_t name ## _buffer_size = byte_count
-
-#endif // _BIONIC_THREAD_LOCAL_BUFFER_H_included
diff --git a/libc/bionic/pthread.c b/libc/bionic/pthread.c
index da3a55152..719bc83b5 100644
--- a/libc/bionic/pthread.c
+++ b/libc/bionic/pthread.c
@@ -163,20 +163,20 @@ __get_stack_base(int  *p_stack_size)
 }
 
 
-void  __init_tls(void**  tls, void*  thread)
-{
-    int  nn;
+void  __init_tls(void** tls, void* thread) {
+  ((pthread_internal_t*) thread)->tls = tls;
 
-    ((pthread_internal_t*)thread)->tls = tls;
+  // Zero-initialize all the slots.
+  for (size_t i = 0; i < BIONIC_TLS_SLOTS; ++i) {
+    tls[i] = NULL;
+  }
 
-    // slot 0 must point to the tls area, this is required by the implementation
-    // of the x86 Linux kernel thread-local-storage
-    tls[TLS_SLOT_SELF]      = (void*)tls;
-    tls[TLS_SLOT_THREAD_ID] = thread;
-    for (nn = TLS_SLOT_ERRNO; nn < BIONIC_TLS_SLOTS; nn++)
-       tls[nn] = 0;
+  // Slot 0 must point to the tls area, this is required by the implementation
+  // of the x86 Linux kernel thread-local-storage.
+  tls[TLS_SLOT_SELF]      = (void*) tls;
+  tls[TLS_SLOT_THREAD_ID] = thread;
 
-    __set_tls( (void*)tls );
+  __set_tls((void*) tls);
 }
 
 
diff --git a/libc/bionic/pthread_internal.h b/libc/bionic/pthread_internal.h
index 58a809a26..4bc81efe4 100644
--- a/libc/bionic/pthread_internal.h
+++ b/libc/bionic/pthread_internal.h
@@ -45,6 +45,13 @@ typedef struct pthread_internal_t
     int                         internal_flags;
     __pthread_cleanup_t*        cleanup_stack;
     void**                      tls;         /* thread-local storage area */
+
+    /*
+     * The dynamic linker implements dlerror(3), which makes it hard for us to implement this
+     * per-thread buffer by simply using malloc(3) and free(3).
+     */
+#define __BIONIC_DLERROR_BUFFER_SIZE 512
+    char dlerror_buffer[__BIONIC_DLERROR_BUFFER_SIZE];
 } pthread_internal_t;
 
 int _init_thread(pthread_internal_t* thread, pid_t kernel_id, pthread_attr_t* attr,
diff --git a/libc/bionic/strerror.cpp b/libc/bionic/strerror.cpp
index 455dc5234..a50c99fe8 100644
--- a/libc/bionic/strerror.cpp
+++ b/libc/bionic/strerror.cpp
@@ -41,6 +41,6 @@ char* strerror(int error_number) {
   }
 
   LOCAL_INIT_THREAD_LOCAL_BUFFER(char*, strerror, NL_TEXTMAX);
-  strerror_r(error_number, strerror_buffer, strerror_buffer_size);
-  return strerror_buffer;
+  strerror_r(error_number, strerror_tls_buffer, strerror_tls_buffer_size);
+  return strerror_tls_buffer;
 }
diff --git a/libc/bionic/strsignal.cpp b/libc/bionic/strsignal.cpp
index 9b046d4f2..c549e74ce 100644
--- a/libc/bionic/strsignal.cpp
+++ b/libc/bionic/strsignal.cpp
@@ -42,5 +42,5 @@ char* strsignal(int signal_number) {
   }
 
   LOCAL_INIT_THREAD_LOCAL_BUFFER(char*, strsignal, NL_TEXTMAX);
-  return const_cast<char*>(__strsignal(signal_number, strsignal_buffer, strsignal_buffer_size));
+  return const_cast<char*>(__strsignal(signal_number, strsignal_tls_buffer, strsignal_tls_buffer_size));
 }