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 <pthreadP.h>
28
29 #ifdef SHARED
30 #error makefile bug, this file is for static only
31 #endif
32
33 dtv_t _dl_static_dtv[2 + TLS_SLOTINFO_SURPLUS];
34
35
36 static 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. */
43 size_t _dl_tls_max_dtv_idx;
44 /* Flag signalling whether there are gaps in the module ID allocation. */
45 bool _dl_tls_dtv_gaps;
46 /* Information about the dtv slots. */
47 struct dtv_slotinfo_list *_dl_tls_dtv_slotinfo_list;
48 /* Number of modules in the static TLS block. */
49 size_t _dl_tls_static_nelem;
50 /* Size of the static TLS block. */
51 size_t _dl_tls_static_size;
52 /* Size actually allocated in the static TLS block. */
53 size_t _dl_tls_static_used;
54 /* Alignment requirement of the static TLS block. */
55 size_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. */
59 size_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). */
62 size_t _dl_tls_static_optional;
63
64 /* Generation counter for the dtv. */
65 size_t _dl_tls_generation;
66
67
68 /* Additional definitions needed by TLS initialization. */
69 #ifdef TLS_INIT_HELPER
70 TLS_INIT_HELPER
71 #endif
72
73 static void
init_slotinfo(void)74 init_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
88 static void
init_static_tls(size_t memsz,size_t align)89 init_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 TCB_ALIGNMENT);
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
104 void
__libc_setup_tls(void)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 __tls_pre_init_tp ();
119
120 /* Look through the TLS segment if there is any. */
121 if (_dl_phdr != NULL)
122 for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
123 if (phdr->p_type == PT_TLS)
124 {
125 /* Remember the values we need. */
126 memsz = phdr->p_memsz;
127 filesz = phdr->p_filesz;
128 initimage = (void *) phdr->p_vaddr + main_map->l_addr;
129 align = phdr->p_align;
130 if (phdr->p_align > max_align)
131 max_align = phdr->p_align;
132 break;
133 }
134
135 /* Calculate the size of the static TLS surplus, with 0 auditors. */
136 _dl_tls_static_surplus_init (0);
137
138 /* We have to set up the TCB block which also (possibly) contains
139 'errno'. Therefore we avoid 'malloc' which might touch 'errno'.
140 Instead we use 'sbrk' which would only uses 'errno' if it fails.
141 In this case we are right away out of memory and the user gets
142 what she/he deserves. */
143 #if TLS_TCB_AT_TP
144 /* Align the TCB offset to the maximum alignment, as
145 _dl_allocate_tls_storage (in elf/dl-tls.c) does using __libc_memalign
146 and dl_tls_static_align. */
147 tcb_offset = roundup (memsz + GLRO(dl_tls_static_surplus), max_align);
148 tlsblock = __sbrk (tcb_offset + TLS_INIT_TCB_SIZE + max_align);
149 #elif TLS_DTV_AT_TP
150 tcb_offset = roundup (TLS_INIT_TCB_SIZE, align ?: 1);
151 tlsblock = __sbrk (tcb_offset + memsz + max_align
152 + TLS_PRE_TCB_SIZE + GLRO(dl_tls_static_surplus));
153 tlsblock += TLS_PRE_TCB_SIZE;
154 #else
155 /* In case a model with a different layout for the TCB and DTV
156 is defined add another #elif here and in the following #ifs. */
157 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
158 #endif
159
160 /* Align the TLS block. */
161 tlsblock = (void *) (((uintptr_t) tlsblock + max_align - 1)
162 & ~(max_align - 1));
163
164 /* Initialize the dtv. [0] is the length, [1] the generation counter. */
165 _dl_static_dtv[0].counter = (sizeof (_dl_static_dtv) / sizeof (_dl_static_dtv[0])) - 2;
166 // _dl_static_dtv[1].counter = 0; would be needed if not already done
167
168 /* Initialize the TLS block. */
169 #if TLS_TCB_AT_TP
170 _dl_static_dtv[2].pointer.val = ((char *) tlsblock + tcb_offset
171 - roundup (memsz, align ?: 1));
172 main_map->l_tls_offset = roundup (memsz, align ?: 1);
173 #elif TLS_DTV_AT_TP
174 _dl_static_dtv[2].pointer.val = (char *) tlsblock + tcb_offset;
175 main_map->l_tls_offset = tcb_offset;
176 #else
177 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
178 #endif
179 _dl_static_dtv[2].pointer.to_free = NULL;
180 /* sbrk gives us zero'd memory, so we don't need to clear the remainder. */
181 memcpy (_dl_static_dtv[2].pointer.val, initimage, filesz);
182
183 /* Install the pointer to the dtv. */
184
185 /* Initialize the thread pointer. */
186 #if TLS_TCB_AT_TP
187 INSTALL_DTV ((char *) tlsblock + tcb_offset, _dl_static_dtv);
188
189 const char *lossage = TLS_INIT_TP ((char *) tlsblock + tcb_offset);
190 #elif TLS_DTV_AT_TP
191 INSTALL_DTV (tlsblock, _dl_static_dtv);
192 const char *lossage = TLS_INIT_TP (tlsblock);
193 #else
194 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
195 #endif
196 if (__builtin_expect (lossage != NULL, 0))
197 _startup_fatal (lossage);
198 __tls_init_tp ();
199
200 /* Update the executable's link map with enough information to make
201 the TLS routines happy. */
202 main_map->l_tls_align = align;
203 main_map->l_tls_blocksize = memsz;
204 main_map->l_tls_initimage = initimage;
205 main_map->l_tls_initimage_size = filesz;
206 main_map->l_tls_modid = 1;
207
208 init_slotinfo ();
209 /* static_slotinfo.slotinfo[1].gen = 0; -- Already zero. */
210 static_slotinfo.slotinfo[1].map = main_map;
211
212 memsz = roundup (memsz, align ?: 1);
213
214 #if TLS_DTV_AT_TP
215 memsz += tcb_offset;
216 #endif
217
218 init_static_tls (memsz, MAX (TCB_ALIGNMENT, max_align));
219 }
220