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
28inline static int
29hash_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
38inline static int
39eq_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
46inline static size_t
47map_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. */
84void *
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
126