glibc/sysdeps/generic/dl-tls.c

/* Thread-local storage handling in the ELF dynamic linker.  Generic version.
   Copyright (C) 2002 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   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, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <assert.h>

#include <tls.h>

/* We don't need any of this if TLS is not supported.  */
#ifdef USE_TLS

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

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


size_t
internal_function
_dl_next_tls_modid (void)
{
  size_t result;

  if (__builtin_expect (GL(dl_tls_dtv_gaps), false))
    {
      /* XXX If this method proves too costly we can optimize
	 it to use a constant time method.  But I don't think
	 it's a problem.  */
      struct link_map *runp = GL(dl_initimage_list);
      bool used[GL(dl_tls_max_dtv_idx)];

      assert (runp != NULL);
      do
	{
	  assert (runp->l_tls_modid > 0
		  && runp->l_tls_modid <= GL(dl_tls_max_dtv_idx));
	  used[runp->l_tls_modid - 1] = true;
	}
      while ((runp = runp->l_tls_nextimage) != GL(dl_initimage_list));

      result = 0;
      do
	/* The information about the gaps is pessimistic.  It might be
	   there are actually none.  */
	if (result >= GL(dl_tls_max_dtv_idx))
	  {
	    /* Now we know there is actually no gap.  Bump the maximum
	       ID number and remember that there are no gaps.  */
	    result = ++GL(dl_tls_max_dtv_idx);
	    GL(dl_tls_dtv_gaps) = false;
	    break;
	  }
      while (used[result++]);
    }
  else
    /* No gaps, allocate a new entry.  */
    result = ++GL(dl_tls_max_dtv_idx);

  return result;
}


void
internal_function
_dl_determine_tlsoffset (struct link_map *firstp)
{
  struct link_map *runp = firstp;
  size_t max_align = 0;
  size_t offset;

# if TLS_TCB_AT_TP
  /* We simply start with zero.  */
  offset = 0;

  do
    {
      max_align = MAX (max_align, runp->l_tls_align);

      /* Compute the offset of the next TLS block.  */
      offset = roundup (offset + runp->l_tls_blocksize, runp->l_tls_align);

      /* XXX For some architectures we perhaps should store the
	 negative offset.  */
      runp->l_tls_offset = offset;
    }
  while ((runp = runp->l_tls_nextimage) != firstp);

  /* The thread descriptor (pointed to by the thread pointer) has its
     own alignment requirement.  Adjust the static TLS size
     and TLS offsets appropriately.  */
  if (offset % TLS_TCB_ALIGN != 0)
    {
      size_t add = TLS_TCB_ALIGN - offset % TLS_TCB_ALIGN;

      /* XXX If the offset stored is negative we must subtract here.  */
      offset += add;

      runp = firstp;
      do
	runp->l_tls_offset += add;
      while ((runp = runp->l_tls_nextimage) != firstp);
    }

  GL(dl_tls_static_size) = offset + TLS_TCB_SIZE;
# elif TLS_DTV_AT_TP
  struct link_map *lastp;

  /* The first block starts right after the TCB.  */
  offset = TLS_TCB_SIZE;
  max_align = runp->l_tls_align;
  runp->l_tls_offset = offset;
  lastp = runp;

  while ((runp = runp->l_tls_nextimage) != firstp)
    {
      max_align = MAX (max_align, runp->l_tls_align);

      /* Compute the offset of the next TLS block.  */
      offset = roundup (offset + lastp->l_tls_blocksize, runp->l_tls_align);

      runp->l_tls_offset = offset;

      lastp = runp;
    }

  GL(dl_tls_static_size) = offset + lastp->l_tls_blocksize;
# else
#  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
# endif

  /* The alignment requirement for the static TLS block.  */
  GL(dl_tls_static_align) = MAX (TLS_TCB_ALIGN, max_align);
}


/* 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


void *
__tls_get_addr (GET_ADDR_ARGS)
{
  dtv_t *dtv = THREAD_DTV ();

  if (dtv[GET_ADDR_MODULE].pointer == TLS_DTV_UNALLOCATE)
    /* XXX */;

  return (char *) dtv[GET_ADDR_MODULE].pointer + GET_ADDR_OFFSET;
}

#endif	/* use TLS */