nptl_db/td_thr_tlsbase.c

   1 /* Locate TLS data for a thread.
   2    Copyright (C) 2003-2014 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include "thread_dbP.h"
  20
  21 td_err_e
  22 td_thr_tlsbase (const td_thrhandle_t *th,
  23                 unsigned long int modid,
  24                 psaddr_t *base)
  25 {
  26   td_err_e err;
  27   psaddr_t dtv, dtvslot, dtvptr;
  28
  29   if (modid < 1)
  30     return TD_NOTLS;
  31
  32   psaddr_t pd = th->th_unique;
  33   if (pd == 0)
  34     {
  35       /* This is the fake handle for the main thread before libpthread
  36          initialization.  We are using 0 for its th_unique because we can't
  37          trust that its thread register has been initialized.  But we need
  38          a real pointer to have any TLS access work.  In case of dlopen'd
  39          libpthread, initialization might not be for quite some time.  So
  40          try looking up the thread register now.  Worst case, it's nonzero
  41          uninitialized garbage and we get bogus results for TLS access
  42          attempted too early.  Tough.  */
  43
  44       td_thrhandle_t main_th;
  45       err = __td_ta_lookup_th_unique (th->th_ta_p, ps_getpid (th->th_ta_p->ph),
  46                                       &main_th);
  47       if (err == 0)
  48         pd = main_th.th_unique;
  49       if (pd == 0)
  50         return TD_TLSDEFER;
  51     }
  52
  53   /* Get the DTV pointer from the thread descriptor.  */
  54   err = DB_GET_FIELD (dtv, th->th_ta_p, pd, pthread, dtvp, 0);
  55   if (err != TD_OK)
  56     return err;
  57
  58   /* Find the corresponding entry in the DTV.  */
  59   err = DB_GET_FIELD_ADDRESS (dtvslot, th->th_ta_p, dtv, dtv, dtv, modid);
  60   if (err != TD_OK)
  61     return err;
  62
  63   /* Extract the TLS block address from that DTV slot.  */
  64   err = DB_GET_FIELD (dtvptr, th->th_ta_p, dtvslot, dtv_t, pointer_val, 0);
  65   if (err != TD_OK)
  66     return err;
  67
  68   /* It could be that the memory for this module is not allocated for
  69      the given thread.  */
  70   if ((uintptr_t) dtvptr & 1)
  71     return TD_TLSDEFER;
  72
  73   *base = dtvptr;
  74   return TD_OK;
  75 }