nptl_db/td_thr_tlsbase.c

   1 /* Locate TLS data for a thread.
   2    Copyright (C) 2003-2017 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 #include <link.h>
  21
  22 /* Get the DTV slotinfo list head entry from the dynamic loader state
  23    into *LISTHEAD.  */
  24 static td_err_e
  25 dtv_slotinfo_list (td_thragent_t *ta,
  26                    psaddr_t *listhead)
  27 {
  28   td_err_e err;
  29   psaddr_t head;
  30
  31   if (ta->ta_addr__rtld_global == 0
  32       && td_mod_lookup (ta->ph, LD_SO, SYM__rtld_global,
  33                         &ta->ta_addr__rtld_global) != PS_OK)
  34     ta->ta_addr__rtld_global = (void*)-1;
  35
  36   if (ta->ta_addr__rtld_global != (void*)-1)
  37     {
  38       err = DB_GET_FIELD (head, ta, ta->ta_addr__rtld_global,
  39                           rtld_global, _dl_tls_dtv_slotinfo_list, 0);
  40       if (err != TD_OK)
  41         return err;
  42     }
  43   else
  44     {
  45       if (ta->ta_addr__dl_tls_dtv_slotinfo_list == 0
  46           && td_mod_lookup (ta->ph, NULL, SYM__dl_tls_dtv_slotinfo_list,
  47                             &ta->ta_addr__dl_tls_dtv_slotinfo_list) != PS_OK)
  48         return TD_ERR;
  49
  50       err = _td_fetch_value (ta, ta->ta_var__dl_tls_dtv_slotinfo_list,
  51                              SYM_DESC__dl_tls_dtv_slotinfo_list,
  52                              0, ta->ta_addr__dl_tls_dtv_slotinfo_list, &head);
  53       if (err != TD_OK)
  54         return err;
  55     }
  56
  57   *listhead = head;
  58   return TD_OK;
  59 }
  60
  61 /* Get the address of the DTV slotinfo entry for MODID into
  62    *DTVSLOTINFO.  */
  63 static td_err_e
  64 dtv_slotinfo (td_thragent_t *ta,
  65               unsigned long int modid,
  66               psaddr_t *dtvslotinfo)
  67 {
  68   td_err_e err;
  69   psaddr_t slot, temp;
  70   size_t slbase = 0;
  71
  72   err = dtv_slotinfo_list (ta, &slot);
  73   if (err != TD_OK)
  74     return err;
  75
  76   while (slot)
  77     {
  78       /* Get the number of entries in this list entry's array.  */
  79       err = DB_GET_FIELD (temp, ta, slot, dtv_slotinfo_list, len, 0);
  80       if (err != TD_OK)
  81         return err;
  82       size_t len = (uintptr_t)temp;
  83
  84       /* Did we find the list entry for modid?  */
  85       if (modid < slbase + len)
  86         break;
  87
  88       /* We didn't, so get the next list entry.  */
  89       slbase += len;
  90       err = DB_GET_FIELD (temp, ta, slot, dtv_slotinfo_list,
  91                           next, 0);
  92       if (err != TD_OK)
  93         return err;
  94       slot = temp;
  95     }
  96
  97   /* We reached the end of the list and found nothing.  */
  98   if (!slot)
  99     return TD_ERR;
 100
 101   /* Take the slotinfo for modid from the list entry.  */
 102   err = DB_GET_FIELD_ADDRESS (temp, ta, slot, dtv_slotinfo_list,
 103                               slotinfo, modid - slbase);
 104   if (err != TD_OK)
 105     return err;
 106   slot = temp;
 107
 108   *dtvslotinfo = slot;
 109   return TD_OK;
 110 }
 111
 112 /* Return in *BASE the base address of the TLS block for MODID within
 113    TH.
 114
 115    It should return success and yield the correct pointer in any
 116    circumstance where the TLS block for the module and thread
 117    requested has already been initialized.
 118
 119    It should fail with TD_TLSDEFER only when the thread could not
 120    possibly have observed any values in that TLS block.  That way, the
 121    debugger can fall back to showing initial values from the PT_TLS
 122    segment (and refusing attempts to mutate) for the TD_TLSDEFER case,
 123    and never fail to make the values the program will actually see
 124    available to the user of the debugger.  */
 125 td_err_e
 126 td_thr_tlsbase (const td_thrhandle_t *th,
 127                 unsigned long int modid,
 128                 psaddr_t *base)
 129 {
 130   td_err_e err;
 131   psaddr_t dtv, dtvslot, dtvptr, temp;
 132
 133   if (modid < 1)
 134     return TD_NOTLS;
 135
 136   psaddr_t pd = th->th_unique;
 137   if (pd == 0)
 138     {
 139       /* This is the fake handle for the main thread before libpthread
 140          initialization.  We are using 0 for its th_unique because we can't
 141          trust that its thread register has been initialized.  But we need
 142          a real pointer to have any TLS access work.  In case of dlopen'd
 143          libpthread, initialization might not be for quite some time.  So
 144          try looking up the thread register now.  Worst case, it's nonzero
 145          uninitialized garbage and we get bogus results for TLS access
 146          attempted too early.  Tough.  */
 147
 148       td_thrhandle_t main_th;
 149       err = __td_ta_lookup_th_unique (th->th_ta_p, ps_getpid (th->th_ta_p->ph),
 150                                       &main_th);
 151       if (err == 0)
 152         pd = main_th.th_unique;
 153       if (pd == 0)
 154         return TD_TLSDEFER;
 155     }
 156
 157   err = dtv_slotinfo (th->th_ta_p, modid, &temp);
 158   if (err != TD_OK)
 159     return err;
 160
 161   psaddr_t slot;
 162   err = DB_GET_STRUCT (slot, th->th_ta_p, temp, dtv_slotinfo);
 163   if (err != TD_OK)
 164     return err;
 165
 166   /* Take the link_map from the slotinfo.  */
 167   psaddr_t map;
 168   err = DB_GET_FIELD_LOCAL (map, th->th_ta_p, slot, dtv_slotinfo, map, 0);
 169   if (err != TD_OK)
 170     return err;
 171   if (!map)
 172     return TD_ERR;
 173
 174   /* Ok, the modid is good, now find out what DTV generation it
 175      requires.  */
 176   err = DB_GET_FIELD_LOCAL (temp, th->th_ta_p, slot, dtv_slotinfo, gen, 0);
 177   if (err != TD_OK)
 178     return err;
 179   size_t modgen = (uintptr_t)temp;
 180
 181   /* Get the DTV pointer from the thread descriptor.  */
 182   err = DB_GET_FIELD (dtv, th->th_ta_p, pd, pthread, dtvp, 0);
 183   if (err != TD_OK)
 184     return err;
 185
 186   psaddr_t dtvgenloc;
 187   /* Get the DTV generation count at dtv[0].counter.  */
 188   err = DB_GET_FIELD_ADDRESS (dtvgenloc, th->th_ta_p, dtv, dtv, dtv, 0);
 189   if (err != TD_OK)
 190     return err;
 191   err = DB_GET_FIELD (temp, th->th_ta_p, dtvgenloc, dtv_t, counter, 0);
 192   if (err != TD_OK)
 193     return err;
 194   size_t dtvgen = (uintptr_t)temp;
 195
 196   /* Is the DTV current enough?  */
 197   if (dtvgen < modgen)
 198     {
 199     try_static_tls:
 200       /* If the module uses Static TLS, we're still good.  */
 201       err = DB_GET_FIELD (temp, th->th_ta_p, map, link_map, l_tls_offset, 0);
 202       if (err != TD_OK)
 203         return err;
 204       ptrdiff_t tlsoff = (uintptr_t)temp;
 205
 206       if (tlsoff != FORCED_DYNAMIC_TLS_OFFSET
 207           && tlsoff != NO_TLS_OFFSET)
 208         {
 209           psaddr_t tp = pd;
 210
 211 #if TLS_TCB_AT_TP
 212           dtvptr = tp - tlsoff;
 213 #elif TLS_DTV_AT_TP
 214           dtvptr = tp + tlsoff + TLS_PRE_TCB_SIZE;
 215 #else
 216 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 217 #endif
 218
 219           *base = dtvptr;
 220           return TD_OK;
 221         }
 222
 223       return TD_TLSDEFER;
 224     }
 225
 226   /* Find the corresponding entry in the DTV.  */
 227   err = DB_GET_FIELD_ADDRESS (dtvslot, th->th_ta_p, dtv, dtv, dtv, modid);
 228   if (err != TD_OK)
 229     return err;
 230
 231   /* Extract the TLS block address from that DTV slot.  */
 232   err = DB_GET_FIELD (dtvptr, th->th_ta_p, dtvslot, dtv_t, pointer_val, 0);
 233   if (err != TD_OK)
 234     return err;
 235
 236   /* It could be that the memory for this module is not allocated for
 237      the given thread.  */
 238   if ((uintptr_t) dtvptr & 1)
 239     goto try_static_tls;
 240
 241   *base = dtvptr;
 242   return TD_OK;
 243 }