1/* Initialization code for TLS in statically linked application.
2 Copyright (C) 2002-2018 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 <http://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
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
36{
37 struct dtv_slotinfo_list si;
38 /* The dtv_slotinfo_list data structure does not include the actual
39 information since it is defined as an array of size zero. We define
40 here the necessary entries. Note that it is not important whether
41 there is padding or not since we will always access the information
42 through the 'si' element. */
43 struct dtv_slotinfo info[2 + TLS_SLOTINFO_SURPLUS];
44} static_slotinfo;
45
46
47/* Highest dtv index currently needed. */
48size_t _dl_tls_max_dtv_idx;
49/* Flag signalling whether there are gaps in the module ID allocation. */
50bool _dl_tls_dtv_gaps;
51/* Information about the dtv slots. */
52struct dtv_slotinfo_list *_dl_tls_dtv_slotinfo_list;
53/* Number of modules in the static TLS block. */
54size_t _dl_tls_static_nelem;
55/* Size of the static TLS block. Giving this initialized value
56 preallocates some surplus bytes in the static TLS area. */
57size_t _dl_tls_static_size = 2048;
58/* Size actually allocated in the static TLS block. */
59size_t _dl_tls_static_used;
60/* Alignment requirement of the static TLS block. */
61size_t _dl_tls_static_align;
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. */
76 static_slotinfo.si.len = (((char *) (&static_slotinfo + 1)
77 - (char *) &static_slotinfo.si.slotinfo[0])
78 / sizeof static_slotinfo.si.slotinfo[0]);
79 // static_slotinfo.si.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.si;
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. The initialized
91 value of _dl_tls_static_size is provided by dl-open.c to request some
92 surplus that permits dynamic loading of modules with IE-model TLS. */
93 GL(dl_tls_static_size) = roundup (memsz + GL(dl_tls_static_size),
94 TLS_TCB_ALIGN);
95#if TLS_TCB_AT_TP
96 GL(dl_tls_static_size) += TLS_TCB_SIZE;
97#endif
98 GL(dl_tls_static_used) = memsz;
99 /* The alignment requirement for the static TLS block. */
100 GL(dl_tls_static_align) = align;
101 /* Number of elements in the static TLS block. */
102 GL(dl_tls_static_nelem) = GL(dl_tls_max_dtv_idx);
103}
104
105void
106__libc_setup_tls (void)
107{
108 void *tlsblock;
109 size_t memsz = 0;
110 size_t filesz = 0;
111 void *initimage = NULL;
112 size_t align = 0;
113 size_t max_align = TCB_ALIGNMENT;
114 size_t tcb_offset;
115 const ElfW(Phdr) *phdr;
116
117 struct link_map *main_map = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
118
119 /* Look through the TLS segment if there is any. */
120 if (_dl_phdr != NULL)
121 for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
122 if (phdr->p_type == PT_TLS)
123 {
124 /* Remember the values we need. */
125 memsz = phdr->p_memsz;
126 filesz = phdr->p_filesz;
127 initimage = (void *) phdr->p_vaddr + main_map->l_addr;
128 align = phdr->p_align;
129 if (phdr->p_align > max_align)
130 max_align = phdr->p_align;
131 break;
132 }
133
134 /* We have to set up the TCB block which also (possibly) contains
135 'errno'. Therefore we avoid 'malloc' which might touch 'errno'.
136 Instead we use 'sbrk' which would only uses 'errno' if it fails.
137 In this case we are right away out of memory and the user gets
138 what she/he deserves.
139
140 The initialized value of _dl_tls_static_size is provided by dl-open.c
141 to request some surplus that permits dynamic loading of modules with
142 IE-model TLS. */
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 + GL(dl_tls_static_size), 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 + GL(dl_tls_static_size));
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
199 /* Update the executable's link map with enough information to make
200 the TLS routines happy. */
201 main_map->l_tls_align = align;
202 main_map->l_tls_blocksize = memsz;
203 main_map->l_tls_initimage = initimage;
204 main_map->l_tls_initimage_size = filesz;
205 main_map->l_tls_modid = 1;
206
207 init_slotinfo ();
208 // static_slotinfo.si.slotinfo[1].gen = 0; already zero
209 static_slotinfo.si.slotinfo[1].map = main_map;
210
211 memsz = roundup (memsz, align ?: 1);
212
213#if TLS_DTV_AT_TP
214 memsz += tcb_offset;
215#endif
216
217 init_static_tls (memsz, MAX (TLS_TCB_ALIGN, max_align));
218}
219