Thread suspension: Implement for Linux

src/trusted/service_runtime/arch/x86_32/nacl_tls_32.c

 /*
  * Copyright (c) 2012 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "native_client/src/include/portability.h"
 
 #include "native_client/src/shared/platform/nacl_check.h"
 #include "native_client/src/trusted/service_runtime/arch/x86/nacl_ldt_x86.h"
@@ skipping 40 matching lines @@
                                              0,
                                              base_addr,
                                              4);
 }
 
 
 uint32_t NaClGetThreadIdx(struct NaClAppThread *natp) {
   return natp->user.gs >> 3;
 }
 
+#if NACL_LINUX
+
+/*
+ * This TLS variable mirrors nacl_thread_index in the x86-64 sandbox,
+ * except that, on x86-32, we only use it for getting the identity of
+ * the interrupted thread in a signal handler in the Linux
+ * implementation of thread suspension.
+ *
+ * We should not enable this code on Windows because TLS variables do
+ * not work inside dynamically-loaded DLLs -- such as chrome.dll -- on
+ * Windows XP.
+ */
+THREAD uint32_t nacl_thread_index;
+
+void NaClTlsSetIdx(uint32_t tls_idx) {
+  nacl_thread_index = tls_idx;
+}
+
+uint32_t NaClTlsGetIdx(void) {
+  return nacl_thread_index;
+}
+
+#else
+
 /*
  * This is a NOOP, since TLS (or TSD) is not used to keep the thread
  * index on the x86-32.  We use segmentation (%gs) to provide access
  * to the per-thread data, and the segment selector itself tells us
  * the thread's identity.
  */
 void NaClTlsSetIdx(uint32_t tls_idx) {
   UNREFERENCED_PARAMETER(tls_idx);
 }
+
+#endif