[roland/tls-init] Start cleaning up TLS initial value for pthread_create.

--- a/nptl/sysdeps/i386/tls.h
+++ b/nptl/sysdeps/i386/tls.h
@@ -192,6 +192,26 @@  union user_desc_init
 # endif
 #endif
 
+static inline void __attribute__ ((unused, always_inline))
+tls_fill_user_desc (union user_desc_init *desc,
+                    unsigned int entry_number,
+                    void *pd)
+{
+  desc->vals[0] = entry_number;
+  /* The 'base_addr' field.  Pointer to the TCB.  */
+  desc->vals[1] = (unsigned long int) pd;
+  /* The 'limit' field.  We use 4GB which is 0xfffff pages.  */
+  desc->vals[2] = 0xfffff;
+  /* Collapsed value of the bitfield:
+     .seg_32bit = 1
+     .contents = 0
+     .read_exec_only = 0
+     .limit_in_pages = 1
+     .seg_not_present = 0
+     .useable = 1 */
+  desc->vals[3] = 0x51;
+}
+
 /* Code to initially initialize the thread pointer.  This might need
    special attention since 'errno' is not yet available and if the
    operation can cause a failure 'errno' must not be touched.  */
@@ -207,20 +227,8 @@  union user_desc_init
      /* New syscall handling support.  */				      \
      INIT_SYSINFO;							      \
 									      \
-     /* The 'entry_number' field.  Let the kernel pick a value.  */	      \
-     _segdescr.vals[0] = -1;						      \
-     /* The 'base_addr' field.  Pointer to the TCB.  */			      \
-     _segdescr.vals[1] = (unsigned long int) _thrdescr;			      \
-     /* The 'limit' field.  We use 4GB which is 0xfffff pages.  */	      \
-     _segdescr.vals[2] = 0xfffff;					      \
-     /* Collapsed value of the bitfield:				      \
-	  .seg_32bit = 1						      \
-	  .contents = 0							      \
-	  .read_exec_only = 0						      \
-	  .limit_in_pages = 1						      \
-	  .seg_not_present = 0						      \
-	  .useable = 1 */						      \
-     _segdescr.vals[3] = 0x51;						      \
+     /* Let the kernel pick a value for the 'entry_number' field.  */	      \
+     tls_fill_user_desc (&_segdescr, -1, _thrdescr);			      \
 									      \
      /* Install the TLS.  */						      \
      asm volatile (TLS_LOAD_EBX						      \
@@ -244,6 +252,15 @@  union user_desc_init
      _result == 0 ? NULL						      \
      : "set_thread_area failed when setting up thread-local storage\n"; })
 
+# define TLS_DEFINE_INIT_TP(tp, pd)					      \
+  union user_desc_init _segdescr;					      \
+  /* Find the 'entry_number' field that the kernel selected in TLS_INIT_TP.   \
+     The first three bits of the segment register value select the GDT,	      \
+     ignore them.  We get the index from the value of the %gs register in     \
+     the current thread.  */						      \
+  tls_fill_user_desc (&_segdescr, TLS_GET_GS () >> 3, pd);		      \
+  const struct user_desc *tp = &_segdescr.desc
+
 
 /* Return the address of the dtv for the current thread.  */
 # define THREAD_DTV() \
--- a/nptl/sysdeps/pthread/createthread.c
+++ b/nptl/sysdeps/pthread/createthread.c
@@ -30,10 +30,18 @@ 
 
 #define CLONE_SIGNAL		(CLONE_SIGHAND | CLONE_THREAD)
 
-/* Unless otherwise specified, the thread "register" is going to be
-   initialized with a pointer to the TCB.  */
-#ifndef TLS_VALUE
-# define TLS_VALUE pd
+/* The <tls.h> header should define the macro TLS_DEFINE_INIT_TP such that:
+	TLS_DEFINE_INIT_TP (VAR, PD);
+   Declares and initializes a variable VAR with the value that should
+   be passed to the OS thread creation function (e.g. clone) to initialize
+   its TLS state for the 'struct pthread *' PD.  */
+#ifndef TLS_DEFINE_INIT_TP
+/* For a transitional period while all the <tls.h> implementations are
+   getting updated, we define it using the old TLS_VALUE macro.  */
+# define TLS_DEFINE_INIT_TP(tp, pd) void *tp = TLS_VALUE
+# ifndef TLS_VALUE
+#  define TLS_VALUE pd
+# endif
 #endif
 
 #ifndef ARCH_CLONE
@@ -52,9 +60,7 @@  do_clone (struct pthread *pd, const struct pthread_attr *attr,
 	  int clone_flags, int (*fct) (void *), STACK_VARIABLES_PARMS,
 	  int stopped)
 {
-#ifdef PREPARE_CREATE
-  PREPARE_CREATE;
-#endif
+  TLS_DEFINE_INIT_TP (tp, pd);
 
   if (__glibc_unlikely (stopped != 0))
     /* We make sure the thread does not run far by forcing it to get a
@@ -73,7 +79,7 @@  do_clone (struct pthread *pd, const struct pthread_attr *attr,
   atomic_increment (&__nptl_nthreads);
 
   int rc = ARCH_CLONE (fct, STACK_VARIABLES_ARGS, clone_flags,
-		       pd, &pd->tid, TLS_VALUE, &pd->tid);
+		       pd, &pd->tid, tp, &pd->tid);
 
   if (__glibc_unlikely (rc == -1))
     {
--- a/nptl/sysdeps/x86_64/tls.h
+++ b/nptl/sysdeps/x86_64/tls.h
@@ -164,6 +164,8 @@  typedef struct
     _result ? "cannot set %fs base address for thread-local storage" : 0;     \
   })
 
+# define TLS_DEFINE_INIT_TP(tp, pd) void *tp = (pd)
+
 
 /* Return the address of the dtv for the current thread.  */
 # define THREAD_DTV() \
--- a/sysdeps/unix/sysv/linux/i386/createthread.c
+++ /dev/null
@@ -1,48 +0,0 @@ 
-/* Copyright (C) 2002-2014 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-   Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <http://www.gnu.org/licenses/>.  */
-
-/* The "thread register" gets initialized from a segment descriptor.
-   Initialize such a descriptor first.  */
-#define PREPARE_CREATE \
-  union user_desc_init desc;						      \
-									      \
-  /* Describe the thread-local storage segment.  */			      \
-									      \
-  /* The 'entry_number' field.  The first three bits of the segment	      \
-     register value select the GDT, ignore them.  We get the index	      \
-     from the value of the %gs register in the current thread.  */	      \
-  desc.vals[0] = TLS_GET_GS () >> 3;					      \
-  /* The 'base_addr' field.  Pointer to the TCB.  */			      \
-  desc.vals[1] = (unsigned long int) pd;				      \
-  /* The 'limit' field.  We use 4GB which is 0xfffff pages.  */		      \
-  desc.vals[2] = 0xfffff;						      \
-  /* Collapsed value of the bitfield:					      \
-       .seg_32bit = 1							      \
-       .contents = 0							      \
-       .read_exec_only = 0						      \
-       .limit_in_pages = 1						      \
-       .seg_not_present = 0						      \
-       .useable = 1 */							      \
-  desc.vals[3] = 0x51
-
-/* Value passed to 'clone' for initialization of the thread register.  */
-#define TLS_VALUE &desc.desc
-
-
-/* Get the real implementation.  */
-#include <nptl/sysdeps/pthread/createthread.c>