1/* Initialization code for TLS in statically linked application.
2 Copyright (C) 2002-2020 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
28#ifdef SHARED
29 #error makefile bug, this file is for static only
30#endif
31
32dtv_t _dl_static_dtv[2 + TLS_SLOTINFO_SURPLUS];
33
34
35static struct dtv_slotinfo_list static_slotinfo =
36 {
37 /* Allocate an array of 2 + TLS_SLOTINFO_SURPLUS elements. */
38 .slotinfo = { [array_length (_dl_static_dtv) - 1] = { 0 } },
39 };
40
41/* Highest dtv index currently needed. */
42size_t _dl_tls_max_dtv_idx;
43/* Flag signalling whether there are gaps in the module ID allocation. */
44bool _dl_tls_dtv_gaps;
45/* Information about the dtv slots. */
46struct dtv_slotinfo_list *_dl_tls_dtv_slotinfo_list;
47/* Number of modules in the static TLS block. */
48size_t _dl_tls_static_nelem;
49/* Size of the static TLS block. */
50size_t _dl_tls_static_size;
51/* Size actually allocated in the static TLS block. */
52size_t _dl_tls_static_used;
53/* Alignment requirement of the static TLS block. */
54size_t _dl_tls_static_align;
55/* Size of surplus space in the static TLS area for dynamically
56 loaded modules with IE-model TLS or for TLSDESC optimization.
57 See comments in elf/dl-tls.c where it is initialized. */
58size_t _dl_tls_static_surplus;
59/* Remaining amount of static TLS that may be used for optimizing
60 dynamic TLS access (e.g. with TLSDESC). */
61size_t _dl_tls_static_optional;
62
63/* Generation counter for the dtv. */
64size_t _dl_tls_generation;
65
66
67/* Additional definitions needed by TLS initialization. */
68#ifdef TLS_INIT_HELPER
69TLS_INIT_HELPER
70#endif
71
72static void
73init_slotinfo (void)
74{
75 /* Create the slotinfo list. Note that the type of static_slotinfo
76 has effectively a zero-length array, so we cannot use the size of
77 static_slotinfo to determine the array length. */
78 static_slotinfo.len = array_length (_dl_static_dtv);
79 /* static_slotinfo.next = NULL; -- Already zero. */
80
81 /* The slotinfo list. Will be extended by the code doing dynamic
82 linking. */
83 GL(dl_tls_max_dtv_idx) = 1;
84 GL(dl_tls_dtv_slotinfo_list) = &static_slotinfo;
85}
86
87static void
88init_static_tls (size_t memsz, size_t align)
89{
90 /* That is the size of the TLS memory for this object. */
91 GL(dl_tls_static_size) = roundup (memsz + GLRO(dl_tls_static_surplus),
92 TLS_TCB_ALIGN);
93#if TLS_TCB_AT_TP
94 GL(dl_tls_static_size) += TLS_TCB_SIZE;
95#endif
96 GL(dl_tls_static_used) = memsz;
97 /* The alignment requirement for the static TLS block. */
98 GL(dl_tls_static_align) = align;
99 /* Number of elements in the static TLS block. */
100 GL(dl_tls_static_nelem) = GL(dl_tls_max_dtv_idx);
101}
102
103void
104__libc_setup_tls (void)
105{
106 void *tlsblock;
107 size_t memsz = 0;
108 size_t filesz = 0;
109 void *initimage = NULL;
110 size_t align = 0;
111 size_t max_align = TCB_ALIGNMENT;
112 size_t tcb_offset;
113 const ElfW(Phdr) *phdr;
114
115 struct link_map *main_map = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
116
117 /* Look through the TLS segment if there is any. */
118 if (_dl_phdr != NULL)
119 for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
120 if (phdr->p_type == PT_TLS)
121 {
122 /* Remember the values we need. */
123 memsz = phdr->p_memsz;
124 filesz = phdr->p_filesz;
125 initimage = (void *) phdr->p_vaddr + main_map->l_addr;
126 align = phdr->p_align;
127 if (phdr->p_align > max_align)
128 max_align = phdr->p_align;
129 break;
130 }
131
132 /* Calculate the size of the static TLS surplus, with 0 auditors. */
133 _dl_tls_static_surplus_init (0);
134
135 /* We have to set up the TCB block which also (possibly) contains
136 'errno'. Therefore we avoid 'malloc' which might touch 'errno'.
137 Instead we use 'sbrk' which would only uses 'errno' if it fails.
138 In this case we are right away out of memory and the user gets
139 what she/he deserves. */
140#if TLS_TCB_AT_TP
141 /* Align the TCB offset to the maximum alignment, as
142 _dl_allocate_tls_storage (in elf/dl-tls.c) does using __libc_memalign
143 and dl_tls_static_align. */
144 tcb_offset = roundup (memsz + GLRO(dl_tls_static_surplus), max_align);
145 tlsblock = __sbrk (tcb_offset + TLS_INIT_TCB_SIZE + max_align);
146#elif TLS_DTV_AT_TP
147 tcb_offset = roundup (TLS_INIT_TCB_SIZE, align ?: 1);
148 tlsblock = __sbrk (tcb_offset + memsz + max_align
149 + TLS_PRE_TCB_SIZE + GLRO(dl_tls_static_surplus));
150 tlsblock += TLS_PRE_TCB_SIZE;
151#else
152 /* In case a model with a different layout for the TCB and DTV
153 is defined add another #elif here and in the following #ifs. */
154# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
155#endif
156
157 /* Align the TLS block. */
158 tlsblock = (void *) (((uintptr_t) tlsblock + max_align - 1)
159 & ~(max_align - 1));
160
161 /* Initialize the dtv. [0] is the length, [1] the generation counter. */
162 _dl_static_dtv[0].counter = (sizeof (_dl_static_dtv) / sizeof (_dl_static_dtv[0])) - 2;
163 // _dl_static_dtv[1].counter = 0; would be needed if not already done
164
165 /* Initialize the TLS block. */
166#if TLS_TCB_AT_TP
167 _dl_static_dtv[2].pointer.val = ((char *) tlsblock + tcb_offset
168 - roundup (memsz, align ?: 1));
169 main_map->l_tls_offset = roundup (memsz, align ?: 1);
170#elif TLS_DTV_AT_TP
171 _dl_static_dtv[2].pointer.val = (char *) tlsblock + tcb_offset;
172 main_map->l_tls_offset = tcb_offset;
173#else
174# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
175#endif
176 _dl_static_dtv[2].pointer.to_free = NULL;
177 /* sbrk gives us zero'd memory, so we don't need to clear the remainder. */
178 memcpy (_dl_static_dtv[2].pointer.val, initimage, filesz);
179
180 /* Install the pointer to the dtv. */
181
182 /* Initialize the thread pointer. */
183#if TLS_TCB_AT_TP
184 INSTALL_DTV ((char *) tlsblock + tcb_offset, _dl_static_dtv);
185
186 const char *lossage = TLS_INIT_TP ((char *) tlsblock + tcb_offset);
187#elif TLS_DTV_AT_TP
188 INSTALL_DTV (tlsblock, _dl_static_dtv);
189 const char *lossage = TLS_INIT_TP (tlsblock);
190#else
191# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
192#endif
193 if (__builtin_expect (lossage != NULL, 0))
194 _startup_fatal (lossage);
195
196 /* Update the executable's link map with enough information to make
197 the TLS routines happy. */
198 main_map->l_tls_align = align;
199 main_map->l_tls_blocksize = memsz;
200 main_map->l_tls_initimage = initimage;
201 main_map->l_tls_initimage_size = filesz;
202 main_map->l_tls_modid = 1;
203
204 init_slotinfo ();
205 /* static_slotinfo.slotinfo[1].gen = 0; -- Already zero. */
206 static_slotinfo.slotinfo[1].map = main_map;
207
208 memsz = roundup (memsz, align ?: 1);
209
210#if TLS_DTV_AT_TP
211 memsz += tcb_offset;
212#endif
213
214 init_static_tls (memsz, MAX (TLS_TCB_ALIGN, max_align));
215}
216