1/* Initialization code for TLS in statically linked application.
2 Copyright (C) 2002-2021 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#include <startup.h>
20#include <errno.h>
21#include <ldsodefs.h>
22#include <tls.h>
23#include <unistd.h>
24#include <stdio.h>
25#include <sys/param.h>
26#include <array_length.h>
27#include <list.h>
28
29#ifdef SHARED
30 #error makefile bug, this file is for static only
31#endif
32
33dtv_t _dl_static_dtv[2 + TLS_SLOTINFO_SURPLUS];
34
35
36static struct dtv_slotinfo_list static_slotinfo =
37 {
38 /* Allocate an array of 2 + TLS_SLOTINFO_SURPLUS elements. */
39 .slotinfo = { [array_length (_dl_static_dtv) - 1] = { 0 } },
40 };
41
42/* Highest dtv index currently needed. */
43size_t _dl_tls_max_dtv_idx;
44/* Flag signalling whether there are gaps in the module ID allocation. */
45bool _dl_tls_dtv_gaps;
46/* Information about the dtv slots. */
47struct dtv_slotinfo_list *_dl_tls_dtv_slotinfo_list;
48/* Number of modules in the static TLS block. */
49size_t _dl_tls_static_nelem;
50/* Size of the static TLS block. */
51size_t _dl_tls_static_size;
52/* Size actually allocated in the static TLS block. */
53size_t _dl_tls_static_used;
54/* Alignment requirement of the static TLS block. */
55size_t _dl_tls_static_align;
56/* Size of surplus space in the static TLS area for dynamically
57 loaded modules with IE-model TLS or for TLSDESC optimization.
58 See comments in elf/dl-tls.c where it is initialized. */
59size_t _dl_tls_static_surplus;
60/* Remaining amount of static TLS that may be used for optimizing
61 dynamic TLS access (e.g. with TLSDESC). */
62size_t _dl_tls_static_optional;
63
64/* Generation counter for the dtv. */
65size_t _dl_tls_generation;
66
67
68/* Additional definitions needed by TLS initialization. */
69#ifdef TLS_INIT_HELPER
70TLS_INIT_HELPER
71#endif
72
73static void
74init_slotinfo (void)
75{
76 /* Create the slotinfo list. Note that the type of static_slotinfo
77 has effectively a zero-length array, so we cannot use the size of
78 static_slotinfo to determine the array length. */
79 static_slotinfo.len = array_length (_dl_static_dtv);
80 /* static_slotinfo.next = NULL; -- Already zero. */
81
82 /* The slotinfo list. Will be extended by the code doing dynamic
83 linking. */
84 GL(dl_tls_max_dtv_idx) = 1;
85 GL(dl_tls_dtv_slotinfo_list) = &static_slotinfo;
86}
87
88static void
89init_static_tls (size_t memsz, size_t align)
90{
91 /* That is the size of the TLS memory for this object. */
92 GL(dl_tls_static_size) = roundup (memsz + GLRO(dl_tls_static_surplus),
93 TLS_TCB_ALIGN);
94#if TLS_TCB_AT_TP
95 GL(dl_tls_static_size) += TLS_TCB_SIZE;
96#endif
97 GL(dl_tls_static_used) = memsz;
98 /* The alignment requirement for the static TLS block. */
99 GL(dl_tls_static_align) = align;
100 /* Number of elements in the static TLS block. */
101 GL(dl_tls_static_nelem) = GL(dl_tls_max_dtv_idx);
102}
103
104void
105__libc_setup_tls (void)
106{
107 void *tlsblock;
108 size_t memsz = 0;
109 size_t filesz = 0;
110 void *initimage = NULL;
111 size_t align = 0;
112 size_t max_align = TCB_ALIGNMENT;
113 size_t tcb_offset;
114 const ElfW(Phdr) *phdr;
115
116 struct link_map *main_map = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
117
118 /* Look through the TLS segment if there is any. */
119 if (_dl_phdr != NULL)
120 for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
121 if (phdr->p_type == PT_TLS)
122 {
123 /* Remember the values we need. */
124 memsz = phdr->p_memsz;
125 filesz = phdr->p_filesz;
126 initimage = (void *) phdr->p_vaddr + main_map->l_addr;
127 align = phdr->p_align;
128 if (phdr->p_align > max_align)
129 max_align = phdr->p_align;
130 break;
131 }
132
133 /* Calculate the size of the static TLS surplus, with 0 auditors. */
134 _dl_tls_static_surplus_init (0);
135
136 /* We have to set up the TCB block which also (possibly) contains
137 'errno'. Therefore we avoid 'malloc' which might touch 'errno'.
138 Instead we use 'sbrk' which would only uses 'errno' if it fails.
139 In this case we are right away out of memory and the user gets
140 what she/he deserves. */
141#if TLS_TCB_AT_TP
142 /* Align the TCB offset to the maximum alignment, as
143 _dl_allocate_tls_storage (in elf/dl-tls.c) does using __libc_memalign
144 and dl_tls_static_align. */
145 tcb_offset = roundup (memsz + GLRO(dl_tls_static_surplus), max_align);
146 tlsblock = __sbrk (tcb_offset + TLS_INIT_TCB_SIZE + max_align);
147#elif TLS_DTV_AT_TP
148 tcb_offset = roundup (TLS_INIT_TCB_SIZE, align ?: 1);
149 tlsblock = __sbrk (tcb_offset + memsz + max_align
150 + TLS_PRE_TCB_SIZE + GLRO(dl_tls_static_surplus));
151 tlsblock += TLS_PRE_TCB_SIZE;
152#else
153 /* In case a model with a different layout for the TCB and DTV
154 is defined add another #elif here and in the following #ifs. */
155# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
156#endif
157
158 /* Align the TLS block. */
159 tlsblock = (void *) (((uintptr_t) tlsblock + max_align - 1)
160 & ~(max_align - 1));
161
162 /* Initialize the dtv. [0] is the length, [1] the generation counter. */
163 _dl_static_dtv[0].counter = (sizeof (_dl_static_dtv) / sizeof (_dl_static_dtv[0])) - 2;
164 // _dl_static_dtv[1].counter = 0; would be needed if not already done
165
166 /* Initialize the TLS block. */
167#if TLS_TCB_AT_TP
168 _dl_static_dtv[2].pointer.val = ((char *) tlsblock + tcb_offset
169 - roundup (memsz, align ?: 1));
170 main_map->l_tls_offset = roundup (memsz, align ?: 1);
171#elif TLS_DTV_AT_TP
172 _dl_static_dtv[2].pointer.val = (char *) tlsblock + tcb_offset;
173 main_map->l_tls_offset = tcb_offset;
174#else
175# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
176#endif
177 _dl_static_dtv[2].pointer.to_free = NULL;
178 /* sbrk gives us zero'd memory, so we don't need to clear the remainder. */
179 memcpy (_dl_static_dtv[2].pointer.val, initimage, filesz);
180
181 /* Install the pointer to the dtv. */
182
183 /* Initialize the thread pointer. */
184#if TLS_TCB_AT_TP
185 INSTALL_DTV ((char *) tlsblock + tcb_offset, _dl_static_dtv);
186
187 const char *lossage = TLS_INIT_TP ((char *) tlsblock + tcb_offset);
188#elif TLS_DTV_AT_TP
189 INSTALL_DTV (tlsblock, _dl_static_dtv);
190 const char *lossage = TLS_INIT_TP (tlsblock);
191#else
192# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
193#endif
194 if (__builtin_expect (lossage != NULL, 0))
195 _startup_fatal (lossage);
196
197#if THREAD_GSCOPE_IN_TCB
198 INIT_LIST_HEAD (&_dl_stack_used);
199 INIT_LIST_HEAD (&_dl_stack_user);
200 list_add (&THREAD_SELF->list, &_dl_stack_user);
201#endif
202
203 /* Update the executable's link map with enough information to make
204 the TLS routines happy. */
205 main_map->l_tls_align = align;
206 main_map->l_tls_blocksize = memsz;
207 main_map->l_tls_initimage = initimage;
208 main_map->l_tls_initimage_size = filesz;
209 main_map->l_tls_modid = 1;
210
211 init_slotinfo ();
212 /* static_slotinfo.slotinfo[1].gen = 0; -- Already zero. */
213 static_slotinfo.slotinfo[1].map = main_map;
214
215 memsz = roundup (memsz, align ?: 1);
216
217#if TLS_DTV_AT_TP
218 memsz += tcb_offset;
219#endif
220
221 init_static_tls (memsz, MAX (TLS_TCB_ALIGN, max_align));
222}
223