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

src/trusted/service_runtime/arch/arm/nacl_tls.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/nacl_platform.h"
 #include "native_client/src/include/nacl_macros.h"
 #include "native_client/src/include/portability.h"
 #include "native_client/src/shared/platform/nacl_check.h"
 #include "native_client/src/shared/platform/nacl_sync_checked.h"
 #include "native_client/src/trusted/service_runtime/arch/arm/sel_ldr_arm.h"
 #include "native_client/src/trusted/service_runtime/nacl_app_thread.h"
 #include "native_client/src/trusted/service_runtime/nacl_globals.h"
 #include "native_client/src/trusted/service_runtime/nacl_tls.h"
 #include "native_client/src/trusted/service_runtime/sel_ldr.h"
 #include "native_client/src/trusted/service_runtime/sel_memory.h"
 
 static struct NaClMutex gNaClTlsMu;
 static int gNaClThreadIdxInUse[NACL_THREAD_MAX];  /* bool */
 static size_t const kNumThreads = NACL_ARRAY_SIZE_UNSAFE(gNaClThreadIdxInUse);
 
-/*
- * This holds the index of the current thread.
- * This is also used directly in nacl_syscall.S (NaClSyscallSeg).
- */
-__thread uint32_t gNaClThreadIdx = NACL_TLS_INDEX_INVALID;
+/* May be NULL if the current thread does not host a NaClAppThread. */
+static THREAD struct NaClThreadContext *nacl_current_thread;
 
-uint32_t NaClTlsGetIdx(void) {
-  return gNaClThreadIdx;
+void NaClTlsSetCurrentThread(struct NaClAppThread *natp) {
+  nacl_current_thread = &natp->user;
 }
 
-void NaClTlsSetIdx(uint32_t tls_idx) {
-  gNaClThreadIdx = tls_idx;
+struct NaClAppThread *NaClTlsGetCurrentThread(void) {
+  return NaClAppThreadFromThreadContext(nacl_current_thread);
 }
 
 uint32_t NaClGetThreadIdx(struct NaClAppThread *natp) {
   return natp->user.tls_idx;
 }
 
 
 int NaClTlsInit(void) {
   size_t i;
 
@@ skipping 32 matching lines @@
   if (kNumThreads != i) {
     return i;
   }
 
   NaClLog(LOG_ERROR, "NaClThreadIdxAllocate: no more slots for a thread\n");
   return NACL_TLS_INDEX_INVALID;
 }
 
 
 /*
- * Allocation does not mean we can set gNaClThreadIdx, since we are not
- * that thread.  Setting it must wait until the thread actually launches.
+ * Allocation does not mean we can set nacl_current_thread, since we
+ * are not that thread.  Setting it must wait until the thread
+ * actually launches.
  */
 uint32_t NaClTlsAllocate(struct NaClAppThread *natp) {
   UNREFERENCED_PARAMETER(natp);
 
   return NaClThreadIdxAllocate();
 }
 
 
 void NaClTlsFree(struct NaClAppThread *natp) {
   uint32_t idx = NaClGetThreadIdx(natp);
@@ skipping 19 matching lines @@
 
 
 uint32_t NaClTlsGetTlsValue1(struct NaClAppThread *natp) {
   return natp->user.tls_value1;
 }
 
 
 uint32_t NaClTlsGetTlsValue2(struct NaClAppThread *natp) {
   return natp->user.tls_value2;
 }