elf/tlsdeschtab.h

   1 /* Hash table for TLS descriptors.
   2    Copyright (C) 2005-2023 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    <https://www.gnu.org/licenses/>.  */
  18
  19 #ifndef TLSDESCHTAB_H
  20 # define TLSDESCHTAB_H 1
  21
  22 #include <atomic.h>
  23
  24 # ifdef SHARED
  25
  26 #  include <inline-hashtab.h>
  27
  28 inline static int
  29 hash_tlsdesc (void *p)
  30 {
  31   struct tlsdesc_dynamic_arg *td = p;
  32
  33   /* We know all entries are for the same module, so ti_offset is the
  34      only distinguishing entry.  */
  35   return td->tlsinfo.ti_offset;
  36 }
  37
  38 inline static int
  39 eq_tlsdesc (void *p, void *q)
  40 {
  41   struct tlsdesc_dynamic_arg *tdp = p, *tdq = q;
  42
  43   return tdp->tlsinfo.ti_offset == tdq->tlsinfo.ti_offset;
  44 }
  45
  46 inline static size_t
  47 map_generation (struct link_map *map)
  48 {
  49   size_t idx = map->l_tls_modid;
  50   struct dtv_slotinfo_list *listp = GL(dl_tls_dtv_slotinfo_list);
  51
  52   /* Find the place in the dtv slotinfo list.  */
  53   do
  54     {
  55       /* Does it fit in the array of this list element?  */
  56       if (idx < listp->len)
  57         {
  58           /* We should never get here for a module in static TLS, so
  59              we can assume that, if the generation count is zero, we
  60              still haven't determined the generation count for this
  61              module.  */
  62           if (listp->slotinfo[idx].map == map && listp->slotinfo[idx].gen)
  63             return listp->slotinfo[idx].gen;
  64           else
  65             break;
  66         }
  67       idx -= listp->len;
  68       listp = listp->next;
  69     }
  70   while (listp != NULL);
  71
  72   /* If we get to this point, the module still hasn't been assigned an
  73      entry in the dtv slotinfo data structures, and it will when we're
  74      done with relocations.  At that point, the module will get a
  75      generation number that is one past the current generation, so
  76      return exactly that.  */
  77   return GL(dl_tls_generation) + 1;
  78 }
  79
  80 /* Returns the data pointer for a given map and tls offset that is used
  81    to fill in one of the GOT entries referenced by a TLSDESC relocation
  82    when using dynamic TLS.  This requires allocation, returns NULL on
  83    allocation failure.  */
  84 void *
  85 _dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset)
  86 {
  87   struct hashtab *ht;
  88   void **entry;
  89   struct tlsdesc_dynamic_arg *td, test;
  90
  91   ht = map->l_mach.tlsdesc_table;
  92   if (! ht)
  93     {
  94       ht = htab_create ();
  95       if (! ht)
  96         return 0;
  97       map->l_mach.tlsdesc_table = ht;
  98     }
  99
 100   test.tlsinfo.ti_module = map->l_tls_modid;
 101   test.tlsinfo.ti_offset = ti_offset;
 102   entry = htab_find_slot (ht, &test, 1, hash_tlsdesc, eq_tlsdesc);
 103   if (! entry)
 104     return 0;
 105
 106   if (*entry)
 107     {
 108       td = *entry;
 109       return td;
 110     }
 111
 112   *entry = td = malloc (sizeof (struct tlsdesc_dynamic_arg));
 113   if (! td)
 114     return 0;
 115   /* This may be higher than the map's generation, but it doesn't
 116      matter much.  Worst case, we'll have one extra DTV update per
 117      thread.  */
 118   td->gen_count = map_generation (map);
 119   td->tlsinfo = test.tlsinfo;
 120   return td;
 121 }
 122
 123 # endif /* SHARED */
 124
 125 #endif