Remove nacl_user[] array lookup from syscall code path on x86-64 and MIPS

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 52 matching lines @@
 }
 
 
 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,
+ * This TLS variable mirrors nacl_current_thread 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;
+static THREAD struct NaClThreadContext *nacl_current_thread;
 
-void NaClTlsSetIdx(uint32_t tls_idx) {
-  nacl_thread_index = tls_idx;
+void NaClTlsSetCurrentThread(struct NaClAppThread *natp) {
+  nacl_current_thread = &natp->user;
 }
 
-uint32_t NaClTlsGetIdx(void) {
-  return nacl_thread_index;
+struct NaClAppThread *NaClTlsGetCurrentThread(void) {
+  return NaClAppThreadFromThreadContext(nacl_current_thread);
 }
 
 #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);
+void NaClTlsSetCurrentThread(struct NaClAppThread *natp) {
+  UNREFERENCED_PARAMETER(natp);
 }
 
 #endif