1/* Hash table for TLS descriptors.
2 Copyright (C) 2005-2021 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Alexandre Oliva <aoliva@redhat.com>
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <https://www.gnu.org/licenses/>. */
19
20#ifndef TLSDESCHTAB_H
21# define TLSDESCHTAB_H 1
22
23#include <atomic.h>
24
25# ifdef SHARED
26
27# include <inline-hashtab.h>
28
29inline static int
30hash_tlsdesc (void *p)
31{
32 struct tlsdesc_dynamic_arg *td = p;
33
34 /* We know all entries are for the same module, so ti_offset is the
35 only distinguishing entry. */
36 return td->tlsinfo.ti_offset;
37}
38
39inline static int
40eq_tlsdesc (void *p, void *q)
41{
42 struct tlsdesc_dynamic_arg *tdp = p, *tdq = q;
43
44 return tdp->tlsinfo.ti_offset == tdq->tlsinfo.ti_offset;
45}
46
47inline static size_t
48map_generation (struct link_map *map)
49{
50 size_t idx = map->l_tls_modid;
51 struct dtv_slotinfo_list *listp = GL(dl_tls_dtv_slotinfo_list);
52
53 /* Find the place in the dtv slotinfo list. */
54 do
55 {
56 /* Does it fit in the array of this list element? */
57 if (idx < listp->len)
58 {
59 /* We should never get here for a module in static TLS, so
60 we can assume that, if the generation count is zero, we
61 still haven't determined the generation count for this
62 module. */
63 if (listp->slotinfo[idx].map == map && listp->slotinfo[idx].gen)
64 return listp->slotinfo[idx].gen;
65 else
66 break;
67 }
68 idx -= listp->len;
69 listp = listp->next;
70 }
71 while (listp != NULL);
72
73 /* If we get to this point, the module still hasn't been assigned an
74 entry in the dtv slotinfo data structures, and it will when we're
75 done with relocations. At that point, the module will get a
76 generation number that is one past the current generation, so
77 return exactly that. */
78 return GL(dl_tls_generation) + 1;
79}
80
81/* Returns the data pointer for a given map and tls offset that is used
82 to fill in one of the GOT entries referenced by a TLSDESC relocation
83 when using dynamic TLS. This requires allocation, returns NULL on
84 allocation failure. */
85void *
86_dl_make_tlsdesc_dynamic (struct link_map *map, size_t ti_offset)
87{
88 struct hashtab *ht;
89 void **entry;
90 struct tlsdesc_dynamic_arg *td, test;
91
92 ht = map->l_mach.tlsdesc_table;
93 if (! ht)
94 {
95 ht = htab_create ();
96 if (! ht)
97 return 0;
98 map->l_mach.tlsdesc_table = ht;
99 }
100
101 test.tlsinfo.ti_module = map->l_tls_modid;
102 test.tlsinfo.ti_offset = ti_offset;
103 entry = htab_find_slot (ht, &test, 1, hash_tlsdesc, eq_tlsdesc);
104 if (! entry)
105 return 0;
106
107 if (*entry)
108 {
109 td = *entry;
110 return td;
111 }
112
113 *entry = td = malloc (sizeof (struct tlsdesc_dynamic_arg));
114 /* This may be higher than the map's generation, but it doesn't
115 matter much. Worst case, we'll have one extra DTV update per
116 thread. */
117 td->gen_count = map_generation (map);
118 td->tlsinfo = test.tlsinfo;
119 return td;
120}
121
122# endif /* SHARED */
123
124#endif
125