uclibc-ng/ldso/ldso/dl-tls.c

/* vi: set sw=4 ts=4: */
/*
 * Thread-local storage handling in the ELF dynamic linker.
 *
 * Copyright (C) 2005 by Steven J. Hill <sjhill@realitydiluted.com>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. The name of the above contributors may not be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE 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 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.
 */

#include <tls.h>
#include <dl-tls.h>
#include <ldsodefs.h>

void *(*_dl_calloc_function) (size_t __nmemb, size_t __size) = NULL;
void *(*_dl_realloc_function) (void *__ptr, size_t __size) = NULL;
void *(*_dl_memalign_function) (size_t __boundary, size_t __size) = NULL;

void (*_dl_free_function) (void *__ptr);
void *_dl_memalign (size_t __boundary, size_t __size);
struct link_map *_dl_update_slotinfo (unsigned long int req_modid);

/* Round up N to the nearest multiple of P, where P is a power of 2
   --- without using libgcc division routines.  */
#define roundup_pow2(n, p) (((n) + (p) - 1) & ~((p) - 1))

void *
_dl_calloc (size_t __nmemb, size_t __size)
{
	void *result;
	size_t size = (__size * __nmemb);

	if (_dl_calloc_function)
		return (*_dl_calloc_function) (__nmemb, __size);

	if ((result = _dl_malloc(size)) != NULL) {
		_dl_memset(result, 0, size);
	}

	return result;
}

void *
_dl_realloc (void * __ptr, size_t __size)
{
	if (_dl_realloc_function)
		return (*_dl_realloc_function) (__ptr, __size);

	_dl_debug_early("NOT IMPLEMENTED PROPERLY!!!\n");
	return NULL;
}

/* The __tls_get_addr function has two basic forms which differ in the
   arguments.  The IA-64 form takes two parameters, the module ID and
   offset.  The form used, among others, on IA-32 takes a reference to
   a special structure which contain the same information.  The second
   form seems to be more often used (in the moment) so we default to
   it.  Users of the IA-64 form have to provide adequate definitions
   of the following macros.  */
#ifndef GET_ADDR_ARGS
# define GET_ADDR_ARGS		tls_index *ti
#endif
#ifndef GET_ADDR_MODULE
# define GET_ADDR_MODULE	ti->ti_module
#endif
#ifndef GET_ADDR_OFFSET
# define GET_ADDR_OFFSET	ti->ti_offset
#endif

/*
 * Amount of excess space to allocate in the static TLS area
 * to allow dynamic loading of modules defining IE-model TLS data.
 */
#define TLS_STATIC_SURPLUS	64 + DL_NNS * 100

/* Value used for dtv entries for which the allocation is delayed. */
#define TLS_DTV_UNALLOCATED	((void *) -1l)

/*
 * We are trying to perform a static TLS relocation in MAP, but it was
 * dynamically loaded.  This can only work if there is enough surplus in
 * the static TLS area already allocated for each running thread.  If this
 * object's TLS segment is too big to fit, we fail.  If it fits,
 * we set MAP->l_tls_offset and return.
 * This function intentionally does not return any value but signals error
 * directly, as static TLS should be rare and code handling it should
 * not be inlined as much as possible.
 */
void
internal_function __attribute_noinline__
_dl_allocate_static_tls (struct link_map *map)
{
	/* If the alignment requirements are too high fail.  */
	if (map->l_tls_align > _dl_tls_static_align)
	{
fail:
		_dl_dprintf(2, "cannot allocate memory in static TLS block");
		_dl_exit(30);
	}

# ifdef TLS_TCB_AT_TP
	size_t freebytes;
	size_t n;
	size_t blsize;

	freebytes = _dl_tls_static_size - _dl_tls_static_used - TLS_TCB_SIZE;

	blsize = map->l_tls_blocksize + map->l_tls_firstbyte_offset;
	if (freebytes < blsize)
		goto fail;

	n = (freebytes - blsize) & ~(map->l_tls_align - 1);

	size_t offset = _dl_tls_static_used + (freebytes - n
		- map->l_tls_firstbyte_offset);

	map->l_tls_offset = _dl_tls_static_used = offset;
# elif defined(TLS_DTV_AT_TP)
	size_t used;
	size_t check;

	size_t offset = roundup_pow2 (_dl_tls_static_used, map->l_tls_align);
	used = offset + map->l_tls_blocksize;
	check = used;

	/* dl_tls_static_used includes the TCB at the beginning. */
	if (check > _dl_tls_static_size)
		goto fail;

	map->l_tls_offset = offset;
	_dl_tls_static_used = used;
# else
#  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
# endif

	/*
	 * If the object is not yet relocated we cannot initialize the
	 * static TLS region.  Delay it.
	 */
	if (((struct elf_resolve *) map)->init_flag & RELOCS_DONE)
    {
#ifdef SHARED
		/*
		 * Update the slot information data for at least the generation of
		 * the DSO we are allocating data for.
		 */
		if (__builtin_expect (THREAD_DTV()[0].counter != _dl_tls_generation, 0))
			(void) _dl_update_slotinfo (map->l_tls_modid);
#endif
		_dl_init_static_tls (map);
	}
	else
		map->l_need_tls_init = 1;
}

#ifdef SHARED
/* Initialize static TLS area and DTV for current (only) thread.
   libpthread implementations should provide their own hook
   to handle all threads.  */
void
attribute_hidden __attribute_noinline__
_dl_nothread_init_static_tls (struct link_map *map)
{
# ifdef TLS_TCB_AT_TP
	void *dest = (char *) THREAD_SELF - map->l_tls_offset;
# elif defined(TLS_DTV_AT_TP)
	void *dest = (char *) THREAD_SELF + map->l_tls_offset + TLS_PRE_TCB_SIZE;
# else
#  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
# endif

	/* Fill in the DTV slot so that a later LD/GD access will find it.  */
	dtv_t *dtv = THREAD_DTV ();
	if (!(map->l_tls_modid <= dtv[-1].counter)) {
		_dl_dprintf(2, "map->l_tls_modid <= dtv[-1].counter FAILED!\n");
		_dl_exit(30);
	}
	dtv[map->l_tls_modid].pointer.val = dest;
	dtv[map->l_tls_modid].pointer.is_static = true;

	/* Initialize the memory.  */
	_dl_memcpy(dest, map->l_tls_initimage, map->l_tls_initimage_size);
	_dl_memset((dest + map->l_tls_initimage_size), '\0',
		map->l_tls_blocksize - map->l_tls_initimage_size);
}
#endif

/* Taken from glibc/sysdeps/generic/dl-tls.c */
static void
oom (void)
{
	_dl_debug_early("cannot allocate thread-local memory: ABORT\n");
	_dl_exit(30);
}

size_t
internal_function
_dl_next_tls_modid (void)
{
  size_t result;

  if (__builtin_expect (_dl_tls_dtv_gaps, false))
    {
      size_t disp = 0;
      struct dtv_slotinfo_list *runp = _dl_tls_dtv_slotinfo_list;

      /* Note that this branch will never be executed during program
	 start since there are no gaps at that time.  Therefore it
	 does not matter that the dl_tls_dtv_slotinfo is not allocated
	 yet when the function is called for the first times.

	 NB: the offset +1 is due to the fact that DTV[0] is used
	 for something else.  */
      result = _dl_tls_static_nelem + 1;
      if (result <= _dl_tls_max_dtv_idx)
	do
	  {
	    while (result - disp < runp->len)
	      {
		if (runp->slotinfo[result - disp].map == NULL)
		  break;

		++result;
		_dl_assert (result <= _dl_tls_max_dtv_idx + 1);
	      }

	    if (result - disp < runp->len)
	      break;

	    disp += runp->len;
	  }
	while ((runp = runp->next) != NULL);

      if (result > _dl_tls_max_dtv_idx)
	{
	  /* The new index must indeed be exactly one higher than the
	     previous high.  */
	  _dl_assert (result == _dl_tls_max_dtv_idx + 1);
	  /* There is no gap anymore.  */
	  _dl_tls_dtv_gaps = false;

	  goto nogaps;
	}
    }
  else
    {
      /* No gaps, allocate a new entry.  */
    nogaps:

      result = ++_dl_tls_max_dtv_idx;
    }

  return result;
}

void
internal_function
_dl_determine_tlsoffset (void)
{
  size_t max_align = TLS_TCB_ALIGN;
  size_t freetop = 0;
  size_t freebottom = 0;

  /* The first element of the dtv slot info list is allocated.  */
  _dl_assert (_dl_tls_dtv_slotinfo_list != NULL);
  /* There is at this point only one element in the
     dl_tls_dtv_slotinfo_list list.  */
  _dl_assert (_dl_tls_dtv_slotinfo_list->next == NULL);

  struct dtv_slotinfo *slotinfo = _dl_tls_dtv_slotinfo_list->slotinfo;

  /* Determining the offset of the various parts of the static TLS
     block has several dependencies.  In addition we have to work
     around bugs in some toolchains.

     Each TLS block from the objects available at link time has a size
     and an alignment requirement.  The GNU ld computes the alignment
     requirements for the data at the positions *in the file*, though.
     I.e, it is not simply possible to allocate a block with the size
     of the TLS program header entry.  The data is layed out assuming
     that the first byte of the TLS block fulfills

       p_vaddr mod p_align == &TLS_BLOCK mod p_align

     This means we have to add artificial padding at the beginning of
     the TLS block.  These bytes are never used for the TLS data in
     this module but the first byte allocated must be aligned
     according to mod p_align == 0 so that the first byte of the TLS
     block is aligned according to p_vaddr mod p_align.  This is ugly
     and the linker can help by computing the offsets in the TLS block
     assuming the first byte of the TLS block is aligned according to
     p_align.

     The extra space which might be allocated before the first byte of
     the TLS block need not go unused.  The code below tries to use
     that memory for the next TLS block.  This can work if the total
     memory requirement for the next TLS block is smaller than the
     gap.  */

# ifdef TLS_TCB_AT_TP
  /* We simply start with zero.  */
  size_t cnt, offset = 0;

  for (cnt = 1; slotinfo[cnt].map != NULL; ++cnt)
    {
      _dl_assert (cnt < _dl_tls_dtv_slotinfo_list->len);

      size_t firstbyte = (-slotinfo[cnt].map->l_tls_firstbyte_offset
			  & (slotinfo[cnt].map->l_tls_align - 1));
      size_t off;
      max_align = MAX (max_align, slotinfo[cnt].map->l_tls_align);

      if (freebottom - freetop >= slotinfo[cnt].map->l_tls_blocksize)
	{
	  off = roundup_pow2 (freetop + slotinfo[cnt].map->l_tls_blocksize
                          - firstbyte, slotinfo[cnt].map->l_tls_align)
		+ firstbyte;
	  if (off <= freebottom)
	    {
	      freetop = off;

	      /* XXX For some architectures we perhaps should store the
		 negative offset.  */
	      slotinfo[cnt].map->l_tls_offset = off;
	      continue;
	    }
	}

      off = roundup_pow2 (offset + slotinfo[cnt].map->l_tls_blocksize
                          - firstbyte, slotinfo[cnt].map->l_tls_align)
            + firstbyte;
      if (off > offset + slotinfo[cnt].map->l_tls_blocksize
		+ (freebottom - freetop))
	{
	  freetop = offset;
	  freebottom = off - slotinfo[cnt].map->l_tls_blocksize;
	}
      offset = off;

      /* XXX For some architectures we perhaps should store the
	 negative offset.  */
      slotinfo[cnt].map->l_tls_offset = off;
    }

  _dl_tls_static_used = offset;
  _dl_tls_static_size = (roundup_pow2 (offset + TLS_STATIC_SURPLUS, max_align)
			    + TLS_TCB_SIZE);
# elif defined(TLS_DTV_AT_TP)
  /* The TLS blocks start right after the TCB.  */
  size_t offset = TLS_TCB_SIZE;
  size_t cnt;

  for (cnt = 1; slotinfo[cnt].map != NULL; ++cnt)
    {
      _dl_assert (cnt < _dl_tls_dtv_slotinfo_list->len);

      size_t firstbyte = (-slotinfo[cnt].map->l_tls_firstbyte_offset
			  & (slotinfo[cnt].map->l_tls_align - 1));
      size_t off;
      max_align = MAX (max_align, slotinfo[cnt].map->l_tls_align);

      if (slotinfo[cnt].map->l_tls_blocksize <= freetop - freebottom)
	{
	  off = roundup_pow2 (freebottom, slotinfo[cnt].map->l_tls_align);
	  if (off - freebottom < firstbyte)
	    off += slotinfo[cnt].map->l_tls_align;
	  if (off + slotinfo[cnt].map->l_tls_blocksize - firstbyte <= freetop)
	    {
	      slotinfo[cnt].map->l_tls_offset = off - firstbyte;
	      freebottom = (off + slotinfo[cnt].map->l_tls_blocksize
			    - firstbyte);
	      continue;
	    }
	}

      off = roundup_pow2 (offset, slotinfo[cnt].map->l_tls_align);
      if (off - offset < firstbyte)
	off += slotinfo[cnt].map->l_tls_align;

      slotinfo[cnt].map->l_tls_offset = off - firstbyte;
      if (off - firstbyte - offset > freetop - freebottom)
	{
	  freebottom = offset;
	  freetop = off - firstbyte;
	}

      offset = off + slotinfo[cnt].map->l_tls_blocksize - firstbyte;
    }

  _dl_tls_static_used = offset;
  _dl_tls_static_size = roundup_pow2 (offset + TLS_STATIC_SURPLUS,
                                      TLS_TCB_ALIGN);
# else
#  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
# endif

  /* The alignment requirement for the static TLS block.  */
  _dl_tls_static_align = max_align;
}

/* This is called only when the data structure setup was skipped at startup,
   when there was no need for it then.  Now we have dynamically loaded
   something needing TLS, or libpthread needs it.  */
rtld_hidden_proto(_dl_tls_setup)
int
internal_function
_dl_tls_setup (void)
{
  _dl_assert (_dl_tls_dtv_slotinfo_list == NULL);
  _dl_assert (_dl_tls_max_dtv_idx == 0);

  const size_t nelem = 2 + TLS_SLOTINFO_SURPLUS;

  _dl_tls_dtv_slotinfo_list
    = _dl_calloc (1, (sizeof (struct dtv_slotinfo_list)
		  + nelem * sizeof (struct dtv_slotinfo)));
  if (_dl_tls_dtv_slotinfo_list == NULL)
    return -1;

  _dl_tls_dtv_slotinfo_list->len = nelem;

  /* Number of elements in the static TLS block.  It can't be zero
     because of various assumptions.  The one element is null.  */
  _dl_tls_static_nelem = _dl_tls_max_dtv_idx = 1;

  /* This initializes more variables for us.  */
  _dl_determine_tlsoffset ();

  return 0;
}
rtld_hidden_def (_dl_tls_setup)

static void *
internal_function
allocate_dtv (void *result)
{
  dtv_t *dtv;
  size_t dtv_length;

  /* We allocate a few more elements in the dtv than are needed for the
     initial set of modules.  This should avoid in most cases expansions
     of the dtv.  */
  dtv_length = _dl_tls_max_dtv_idx + DTV_SURPLUS;
  dtv = _dl_calloc (dtv_length + 2, sizeof (dtv_t));
  if (dtv != NULL)
    {
      /* This is the initial length of the dtv.  */
      dtv[0].counter = dtv_length;

      /* The rest of the dtv (including the generation counter) is
	 Initialize with zero to indicate nothing there.  */

      /* Add the dtv to the thread data structures.  */
      INSTALL_DTV (result, dtv);
    }
  else
    result = NULL;

  return result;
}

/* Get size and alignment requirements of the static TLS block.  */
void
internal_function
_dl_get_tls_static_info (size_t *sizep, size_t *alignp)
{
  *sizep = _dl_tls_static_size;
  *alignp = _dl_tls_static_align;
}

void *
internal_function
_dl_allocate_tls_storage (void)
{
  void *result;
  size_t size = _dl_tls_static_size;

# if defined(TLS_DTV_AT_TP)
  /* Memory layout is:
     [ TLS_PRE_TCB_SIZE ] [ TLS_TCB_SIZE ] [ TLS blocks ]
			  ^ This should be returned.  */
  size += (TLS_PRE_TCB_SIZE + _dl_tls_static_align - 1)
	  & ~(_dl_tls_static_align - 1);
# endif

  /* Allocate a correctly aligned chunk of memory.  */
  result = _dl_memalign (_dl_tls_static_align, size);
  if (__builtin_expect (result != NULL, 1))
    {
      /* Allocate the DTV.  */
      void *allocated = result;

# ifdef TLS_TCB_AT_TP
      /* The TCB follows the TLS blocks.  */
      result = (char *) result + size - TLS_TCB_SIZE;

      /* Clear the TCB data structure.  We can't ask the caller (i.e.
	 libpthread) to do it, because we will initialize the DTV et al.  */
      _dl_memset (result, '\0', TLS_TCB_SIZE);
# elif defined(TLS_DTV_AT_TP)
      result = (char *) result + size - _dl_tls_static_size;

      /* Clear the TCB data structure and TLS_PRE_TCB_SIZE bytes before it.
	 We can't ask the caller (i.e. libpthread) to do it, because we will
	 initialize the DTV et al.  */
      _dl_memset ((char *) result - TLS_PRE_TCB_SIZE, '\0',
	      TLS_PRE_TCB_SIZE + TLS_TCB_SIZE);
# endif

      result = allocate_dtv (result);
      if (result == NULL)
	_dl_free (allocated);
    }

  return result;
}

void *
internal_function
_dl_allocate_tls_init (void *result)
{
  if (result == NULL)
    /* The memory allocation failed.  */
    return NULL;

  dtv_t *dtv = GET_DTV (result);
  struct dtv_slotinfo_list *listp;
  size_t total = 0;
  size_t maxgen = 0;

  /* We have to prepare the dtv for all currently loaded modules using
     TLS.  For those which are dynamically loaded we add the values
     indicating deferred allocation.  */
  listp = _dl_tls_dtv_slotinfo_list;
  while (1)
    {
      size_t cnt;

      for (cnt = total == 0 ? 1 : 0; cnt < listp->len; ++cnt)
	{
	  struct link_map *map;
	  void *dest;

	  /* Check for the total number of used slots.  */
	  if (total + cnt > _dl_tls_max_dtv_idx)
	    break;

	  map = listp->slotinfo[cnt].map;
	  if (map == NULL)
	    /* Unused entry.  */
	    continue;

	  /* Keep track of the maximum generation number.  This might
	     not be the generation counter.  */
	  maxgen = MAX (maxgen, listp->slotinfo[cnt].gen);

	  if (map->l_tls_offset == NO_TLS_OFFSET)
	    {
	      /* For dynamically loaded modules we simply store
		 the value indicating deferred allocation.  */
	      dtv[map->l_tls_modid].pointer.val = TLS_DTV_UNALLOCATED;
	      dtv[map->l_tls_modid].pointer.is_static = false;
	      continue;
	    }

	  _dl_assert (map->l_tls_modid == cnt);
	  _dl_assert (map->l_tls_blocksize >= map->l_tls_initimage_size);
# ifdef TLS_TCB_AT_TP
	  _dl_assert ((size_t) map->l_tls_offset >= map->l_tls_blocksize);
	  dest = (char *) result - map->l_tls_offset;
# elif defined(TLS_DTV_AT_TP)
	  dest = (char *) result + map->l_tls_offset;
# else
#  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
# endif

	  /* Copy the initialization image and clear the BSS part.  */
	  dtv[map->l_tls_modid].pointer.val = dest;
	  dtv[map->l_tls_modid].pointer.is_static = true;
	  _dl_memcpy(dest, map->l_tls_initimage, map->l_tls_initimage_size);
	  _dl_memset((dest + map->l_tls_initimage_size), '\0',
		  map->l_tls_blocksize - map->l_tls_initimage_size);

	}

      total += cnt;
      if (total >= _dl_tls_max_dtv_idx)
	break;

      listp = listp->next;
      _dl_assert (listp != NULL);
    }

  /* The DTV version is up-to-date now.  */
  dtv[0].counter = maxgen;

  return result;
}

void *
internal_function
_dl_allocate_tls (void *mem)
{
  return _dl_allocate_tls_init (mem == NULL
				? _dl_allocate_tls_storage ()
				: allocate_dtv (mem));
}

void
internal_function
_dl_deallocate_tls (void *tcb, bool dealloc_tcb)
{
  dtv_t *dtv = GET_DTV (tcb);
  size_t cnt;

  /* We need to free the memory allocated for non-static TLS.  */
  for (cnt = 0; cnt < dtv[-1].counter; ++cnt)
    if (! dtv[1 + cnt].pointer.is_static
	&& dtv[1 + cnt].pointer.val != TLS_DTV_UNALLOCATED)
      _dl_free (dtv[1 + cnt].pointer.val);

  /* The array starts with dtv[-1].  */
  if (dtv != _dl_initial_dtv)
    _dl_free (dtv - 1);

  if (dealloc_tcb)
    {
# ifdef TLS_TCB_AT_TP
      /* The TCB follows the TLS blocks.  Back up to free the whole block.  */
      tcb -= _dl_tls_static_size - TLS_TCB_SIZE;
# elif defined(TLS_DTV_AT_TP)
      /* Back up the TLS_PRE_TCB_SIZE bytes.  */
      tcb -= (TLS_PRE_TCB_SIZE + _dl_tls_static_align - 1)
	     & ~(_dl_tls_static_align - 1);
# endif
      _dl_free (tcb);
    }
}

static void *
allocate_and_init (struct link_map *map)
{
	void *newp;

	newp = _dl_memalign (map->l_tls_align, map->l_tls_blocksize);
	if (newp == NULL)
	{
		_dl_dprintf(2, "%s:%d: Out of memory!!!\n", __FUNCTION__, __LINE__);
		_dl_exit(1);
	}

	/* Initialize the memory.  */
	_dl_memcpy (newp, map->l_tls_initimage, map->l_tls_initimage_size);
	_dl_memset ((newp + map->l_tls_initimage_size), '\0',
		map->l_tls_blocksize - map->l_tls_initimage_size);

	return newp;
}

struct link_map *
_dl_update_slotinfo (unsigned long int req_modid)
{
  struct link_map *the_map = NULL;
  dtv_t *dtv = THREAD_DTV ();

  /* The global dl_tls_dtv_slotinfo array contains for each module
     index the generation counter current when the entry was created.
     This array never shrinks so that all module indices which were
     valid at some time can be used to access it.  Before the first
     use of a new module index in this function the array was extended
     appropriately.  Access also does not have to be guarded against
     modifications of the array.  It is assumed that pointer-size
     values can be read atomically even in SMP environments.  It is
     possible that other threads at the same time dynamically load
     code and therefore add to the slotinfo list.  This is a problem
     since we must not pick up any information about incomplete work.
     The solution to this is to ignore all dtv slots which were
     created after the one we are currently interested.  We know that
     dynamic loading for this module is completed and this is the last
     load operation we know finished.  */
  unsigned long int idx = req_modid;
  struct dtv_slotinfo_list *listp = _dl_tls_dtv_slotinfo_list;

  _dl_debug_early ("Updating slotinfo for module %d\n", req_modid);

  while (idx >= listp->len)
    {
      idx -= listp->len;
      listp = listp->next;
    }

  if (dtv[0].counter < listp->slotinfo[idx].gen)
    {
      /* The generation counter for the slot is higher than what the
	 current dtv implements.  We have to update the whole dtv but
	 only those entries with a generation counter <= the one for
	 the entry we need.  */
      size_t new_gen = listp->slotinfo[idx].gen;
      size_t total = 0;

      /* We have to look through the entire dtv slotinfo list.  */
      listp =  _dl_tls_dtv_slotinfo_list;
      do
	{
	  size_t cnt;

	  for (cnt = total == 0 ? 1 : 0; cnt < listp->len; ++cnt)
	    {
	      size_t gen = listp->slotinfo[cnt].gen;

	      if (gen > new_gen)
		/* This is a slot for a generation younger than the
		   one we are handling now.  It might be incompletely
		   set up so ignore it.  */
		continue;

	      /* If the entry is older than the current dtv layout we
		 know we don't have to handle it.  */
	      if (gen <= dtv[0].counter)
		continue;

	      /* If there is no map this means the entry is empty.  */
	      struct link_map *map = listp->slotinfo[cnt].map;
	      if (map == NULL)
		{
		  /* If this modid was used at some point the memory
		     might still be allocated.  */
		  if (! dtv[total + cnt].pointer.is_static
		      && dtv[total + cnt].pointer.val != TLS_DTV_UNALLOCATED)
		    {
		      _dl_free (dtv[total + cnt].pointer.val);
		      dtv[total + cnt].pointer.val = TLS_DTV_UNALLOCATED;
		    }

		  continue;
		}

	      /* Check whether the current dtv array is large enough.  */
	      size_t modid = map->l_tls_modid;
	      _dl_assert (total + cnt == modid);
	      if (dtv[-1].counter < modid)
		{
		  /* Reallocate the dtv.  */
		  dtv_t *newp;
		  size_t newsize = _dl_tls_max_dtv_idx + DTV_SURPLUS;
		  size_t oldsize = dtv[-1].counter;

		  _dl_assert (map->l_tls_modid <= newsize);

		  if (dtv == _dl_initial_dtv)
		    {
		      /* This is the initial dtv that was allocated
			 during rtld startup using the dl-minimal.c
			 malloc instead of the real malloc.  We can't
			 free it, we have to abandon the old storage.  */

		      newp = _dl_malloc ((2 + newsize) * sizeof (dtv_t));
		      if (newp == NULL)
			oom ();
		      _dl_memcpy (newp, &dtv[-1], oldsize * sizeof (dtv_t));
		    }
		  else
		    {
		      newp = _dl_realloc (&dtv[-1],
				      (2 + newsize) * sizeof (dtv_t));
		      if (newp == NULL)
			oom ();
		    }

		  newp[0].counter = newsize;

		  /* Clear the newly allocated part.  */
		  _dl_memset (newp + 2 + oldsize, '\0',
			  (newsize - oldsize) * sizeof (dtv_t));

		  /* Point dtv to the generation counter.  */
		  dtv = &newp[1];

		  /* Install this new dtv in the thread data
		     structures.  */
		  INSTALL_NEW_DTV (dtv);
		}

	      /* If there is currently memory allocate for this
		 dtv entry free it.  */
	      /* XXX Ideally we will at some point create a memory
		 pool.  */
	      if (! dtv[modid].pointer.is_static
		  && dtv[modid].pointer.val != TLS_DTV_UNALLOCATED)
		/* Note that free is called for NULL is well.  We
		   deallocate even if it is this dtv entry we are
		   supposed to load.  The reason is that we call
		   memalign and not malloc.  */
		_dl_free (dtv[modid].pointer.val);

	      /* This module is loaded dynamically- We defer memory
		 allocation.  */
	      dtv[modid].pointer.is_static = false;
	      dtv[modid].pointer.val = TLS_DTV_UNALLOCATED;

	      if (modid == req_modid)
		the_map = map;
	    }

	  total += listp->len;
	}
      while ((listp = listp->next) != NULL);

      /* This will be the new maximum generation counter.  */
      dtv[0].counter = new_gen;
    }

  return the_map;
}


/* The generic dynamic and local dynamic model cannot be used in
   statically linked applications.  */
void *
__tls_get_addr (GET_ADDR_ARGS)
{
  dtv_t *dtv = THREAD_DTV ();
  struct link_map *the_map = NULL;
  void *p;

  if (__builtin_expect (dtv[0].counter != _dl_tls_generation, 0))
    {
      the_map = _dl_update_slotinfo (GET_ADDR_MODULE);
      dtv = THREAD_DTV ();
    }

  p = dtv[GET_ADDR_MODULE].pointer.val;

  if (__builtin_expect (p == TLS_DTV_UNALLOCATED, 0))
    {
      /* The allocation was deferred.  Do it now.  */
      if (the_map == NULL)
	{
	  /* Find the link map for this module.  */
	  size_t idx = GET_ADDR_MODULE;
	  struct dtv_slotinfo_list *listp = _dl_tls_dtv_slotinfo_list;

	  while (idx >= listp->len)
	    {
	      idx -= listp->len;
	      listp = listp->next;
	    }

	  the_map = listp->slotinfo[idx].map;
	}

      p = dtv[GET_ADDR_MODULE].pointer.val = allocate_and_init (the_map);
      dtv[GET_ADDR_MODULE].pointer.is_static = false;
    }

  return (char *) p + GET_ADDR_OFFSET;
}

void
_dl_add_to_slotinfo (struct link_map  *l)
{
  /* Now that we know the object is loaded successfully add
     modules containing TLS data to the dtv info table.  We
     might have to increase its size.  */
  struct dtv_slotinfo_list *listp;
  struct dtv_slotinfo_list *prevp;
  size_t idx = l->l_tls_modid;

  _dl_debug_early("Adding to slotinfo for %s\n", l->l_name);

  /* Find the place in the dtv slotinfo list.  */
  listp = _dl_tls_dtv_slotinfo_list;
  prevp = NULL;		/* Needed to shut up gcc.  */
  do
    {
      /* Does it fit in the array of this list element?  */
      if (idx < listp->len)
	break;
      idx -= listp->len;
      prevp = listp;
      listp = listp->next;
    }
  while (listp != NULL);

  if (listp == NULL)
    {
      /* When we come here it means we have to add a new element
	 to the slotinfo list.  And the new module must be in
	 the first slot.  */
      _dl_assert (idx == 0);

      listp = prevp->next = (struct dtv_slotinfo_list *)
	_dl_malloc (sizeof (struct dtv_slotinfo_list)
		+ TLS_SLOTINFO_SURPLUS * sizeof (struct dtv_slotinfo));
      if (listp == NULL)
	{
	  /* We ran out of memory.  We will simply fail this
	     call but don't undo anything we did so far.  The
	     application will crash or be terminated anyway very
	     soon.  */

	  /* We have to do this since some entries in the dtv
	     slotinfo array might already point to this
	     generation.  */
	  ++_dl_tls_generation;

	  _dl_dprintf (_dl_debug_file,
			"cannot create TLS data structures: ABORT\n");
	  _dl_exit (127);
	}

      listp->len = TLS_SLOTINFO_SURPLUS;
      listp->next = NULL;
      _dl_memset (listp->slotinfo, '\0',
	      TLS_SLOTINFO_SURPLUS * sizeof (struct dtv_slotinfo));
    }

  /* Add the information into the slotinfo data structure.  */
  listp->slotinfo[idx].map = l;
  listp->slotinfo[idx].gen = _dl_tls_generation + 1;
  /* ??? ideally this would be done once per call to dlopen.  However there's
     no easy way to indicate whether a library used TLS, so do it here
	 instead. */
  /* Bump the TLS generation number.  */
  _dl_tls_generation++;
}

/* Taken from glibc/elf/rtld.c */
static bool tls_init_tp_called;

/* _dl_error_catch_tsd points to this for the single-threaded case.
   It's reset by the thread library for multithreaded programs.  */
void ** __attribute__ ((const))
_dl_initial_error_catch_tsd (void)
{
	static void *data;
	return &data;
}

#ifdef SHARED
void*
internal_function
init_tls (void);

rtld_hidden_proto(init_tls)
void *
internal_function
init_tls (void)
{
	/* Number of elements in the static TLS block.  */
	_dl_tls_static_nelem = _dl_tls_max_dtv_idx;

	/* Do not do this twice.  The audit interface might have required
	   the DTV interfaces to be set up early.  */
	if (_dl_initial_dtv != NULL)
		return NULL;

	/* Allocate the array which contains the information about the
	   dtv slots.  We allocate a few entries more than needed to
	   avoid the need for reallocation.  */
	size_t nelem = _dl_tls_max_dtv_idx + 1 + TLS_SLOTINFO_SURPLUS;

	/* Allocate.  */
	_dl_assert (_dl_tls_dtv_slotinfo_list == NULL);
	_dl_tls_dtv_slotinfo_list = (struct dtv_slotinfo_list *)
		_dl_calloc (sizeof (struct dtv_slotinfo_list)
			+ nelem * sizeof (struct dtv_slotinfo), 1);
	/* No need to check the return value.  If memory allocation failed
	   the program would have been terminated.  */

	struct dtv_slotinfo *slotinfo = _dl_tls_dtv_slotinfo_list->slotinfo;
	_dl_tls_dtv_slotinfo_list->len = nelem;
	_dl_tls_dtv_slotinfo_list->next = NULL;

	/* Fill in the information from the loaded modules.  No namespace
	   but the base one can be filled at this time.  */
	int i = 0;
	struct link_map *l;
	for (l =  (struct link_map *) _dl_loaded_modules; l != NULL; l = l->l_next)
		if (l->l_tls_blocksize != 0)
		{
			/* This is a module with TLS data.  Store the map reference.
			   The generation counter is zero.  */

			/* Skeep slot[0]: it will be never used */
			slotinfo[++i].map = l;
		}
	_dl_assert (i == _dl_tls_max_dtv_idx);

	/* Compute the TLS offsets for the various blocks.  */
	_dl_determine_tlsoffset ();

	/* Construct the static TLS block and the dtv for the initial
	   thread.  For some platforms this will include allocating memory
	   for the thread descriptor.  The memory for the TLS block will
	   never be freed.  It should be allocated accordingly.  The dtv
	   array can be changed if dynamic loading requires it.  */
	void *tcbp = _dl_allocate_tls_storage ();
	if (tcbp == NULL) {
		_dl_debug_early("\ncannot allocate TLS data structures for initial thread");
		_dl_exit(30);
	}

	/* Store for detection of the special case by __tls_get_addr
	   so it knows not to pass this dtv to the normal realloc.  */
	_dl_initial_dtv = GET_DTV (tcbp);

	/* And finally install it for the main thread.  If ld.so itself uses
	   TLS we know the thread pointer was initialized earlier.  */
	const char *lossage = (char *)TLS_INIT_TP (tcbp, USE___THREAD);
	if(__builtin_expect (lossage != NULL, 0)) {
		_dl_debug_early("cannot set up thread-local storage: %s\n", lossage);
		_dl_exit(30);
	}
	tls_init_tp_called = true;

	return tcbp;
}
rtld_hidden_def (init_tls)
#endif