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 | |
32 | dtv_t _dl_static_dtv[2 + TLS_SLOTINFO_SURPLUS]; |
33 | |
34 | |
35 | static 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. */ |
42 | size_t _dl_tls_max_dtv_idx; |
43 | /* Flag signalling whether there are gaps in the module ID allocation. */ |
44 | bool _dl_tls_dtv_gaps; |
45 | /* Information about the dtv slots. */ |
46 | struct dtv_slotinfo_list *_dl_tls_dtv_slotinfo_list; |
47 | /* Number of modules in the static TLS block. */ |
48 | size_t _dl_tls_static_nelem; |
49 | /* Size of the static TLS block. Giving this initialized value |
50 | preallocates some surplus bytes in the static TLS area. */ |
51 | size_t _dl_tls_static_size = 2048; |
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 | |
57 | /* Generation counter for the dtv. */ |
58 | size_t _dl_tls_generation; |
59 | |
60 | |
61 | /* Additional definitions needed by TLS initialization. */ |
62 | #ifdef TLS_INIT_HELPER |
63 | TLS_INIT_HELPER |
64 | #endif |
65 | |
66 | static void |
67 | init_slotinfo (void) |
68 | { |
69 | /* Create the slotinfo list. Note that the type of static_slotinfo |
70 | has effectively a zero-length array, so we cannot use the size of |
71 | static_slotinfo to determine the array length. */ |
72 | static_slotinfo.len = array_length (_dl_static_dtv); |
73 | /* static_slotinfo.next = NULL; -- Already zero. */ |
74 | |
75 | /* The slotinfo list. Will be extended by the code doing dynamic |
76 | linking. */ |
77 | GL(dl_tls_max_dtv_idx) = 1; |
78 | GL(dl_tls_dtv_slotinfo_list) = &static_slotinfo; |
79 | } |
80 | |
81 | static void |
82 | init_static_tls (size_t memsz, size_t align) |
83 | { |
84 | /* That is the size of the TLS memory for this object. The initialized |
85 | value of _dl_tls_static_size is provided by dl-open.c to request some |
86 | surplus that permits dynamic loading of modules with IE-model TLS. */ |
87 | GL(dl_tls_static_size) = roundup (memsz + GL(dl_tls_static_size), |
88 | TLS_TCB_ALIGN); |
89 | #if TLS_TCB_AT_TP |
90 | GL(dl_tls_static_size) += TLS_TCB_SIZE; |
91 | #endif |
92 | GL(dl_tls_static_used) = memsz; |
93 | /* The alignment requirement for the static TLS block. */ |
94 | GL(dl_tls_static_align) = align; |
95 | /* Number of elements in the static TLS block. */ |
96 | GL(dl_tls_static_nelem) = GL(dl_tls_max_dtv_idx); |
97 | } |
98 | |
99 | void |
100 | __libc_setup_tls (void) |
101 | { |
102 | void *tlsblock; |
103 | size_t memsz = 0; |
104 | size_t filesz = 0; |
105 | void *initimage = NULL; |
106 | size_t align = 0; |
107 | size_t max_align = TCB_ALIGNMENT; |
108 | size_t tcb_offset; |
109 | const ElfW(Phdr) *phdr; |
110 | |
111 | struct link_map *main_map = GL(dl_ns)[LM_ID_BASE]._ns_loaded; |
112 | |
113 | /* Look through the TLS segment if there is any. */ |
114 | if (_dl_phdr != NULL) |
115 | for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr) |
116 | if (phdr->p_type == PT_TLS) |
117 | { |
118 | /* Remember the values we need. */ |
119 | memsz = phdr->p_memsz; |
120 | filesz = phdr->p_filesz; |
121 | initimage = (void *) phdr->p_vaddr + main_map->l_addr; |
122 | align = phdr->p_align; |
123 | if (phdr->p_align > max_align) |
124 | max_align = phdr->p_align; |
125 | break; |
126 | } |
127 | |
128 | /* We have to set up the TCB block which also (possibly) contains |
129 | 'errno'. Therefore we avoid 'malloc' which might touch 'errno'. |
130 | Instead we use 'sbrk' which would only uses 'errno' if it fails. |
131 | In this case we are right away out of memory and the user gets |
132 | what she/he deserves. |
133 | |
134 | The initialized value of _dl_tls_static_size is provided by dl-open.c |
135 | to request some surplus that permits dynamic loading of modules with |
136 | IE-model TLS. */ |
137 | #if TLS_TCB_AT_TP |
138 | /* Align the TCB offset to the maximum alignment, as |
139 | _dl_allocate_tls_storage (in elf/dl-tls.c) does using __libc_memalign |
140 | and dl_tls_static_align. */ |
141 | tcb_offset = roundup (memsz + GL(dl_tls_static_size), max_align); |
142 | tlsblock = __sbrk (tcb_offset + TLS_INIT_TCB_SIZE + max_align); |
143 | #elif TLS_DTV_AT_TP |
144 | tcb_offset = roundup (TLS_INIT_TCB_SIZE, align ?: 1); |
145 | tlsblock = __sbrk (tcb_offset + memsz + max_align |
146 | + TLS_PRE_TCB_SIZE + GL(dl_tls_static_size)); |
147 | tlsblock += TLS_PRE_TCB_SIZE; |
148 | #else |
149 | /* In case a model with a different layout for the TCB and DTV |
150 | is defined add another #elif here and in the following #ifs. */ |
151 | # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined" |
152 | #endif |
153 | |
154 | /* Align the TLS block. */ |
155 | tlsblock = (void *) (((uintptr_t) tlsblock + max_align - 1) |
156 | & ~(max_align - 1)); |
157 | |
158 | /* Initialize the dtv. [0] is the length, [1] the generation counter. */ |
159 | _dl_static_dtv[0].counter = (sizeof (_dl_static_dtv) / sizeof (_dl_static_dtv[0])) - 2; |
160 | // _dl_static_dtv[1].counter = 0; would be needed if not already done |
161 | |
162 | /* Initialize the TLS block. */ |
163 | #if TLS_TCB_AT_TP |
164 | _dl_static_dtv[2].pointer.val = ((char *) tlsblock + tcb_offset |
165 | - roundup (memsz, align ?: 1)); |
166 | main_map->l_tls_offset = roundup (memsz, align ?: 1); |
167 | #elif TLS_DTV_AT_TP |
168 | _dl_static_dtv[2].pointer.val = (char *) tlsblock + tcb_offset; |
169 | main_map->l_tls_offset = tcb_offset; |
170 | #else |
171 | # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined" |
172 | #endif |
173 | _dl_static_dtv[2].pointer.to_free = NULL; |
174 | /* sbrk gives us zero'd memory, so we don't need to clear the remainder. */ |
175 | memcpy (_dl_static_dtv[2].pointer.val, initimage, filesz); |
176 | |
177 | /* Install the pointer to the dtv. */ |
178 | |
179 | /* Initialize the thread pointer. */ |
180 | #if TLS_TCB_AT_TP |
181 | INSTALL_DTV ((char *) tlsblock + tcb_offset, _dl_static_dtv); |
182 | |
183 | const char *lossage = TLS_INIT_TP ((char *) tlsblock + tcb_offset); |
184 | #elif TLS_DTV_AT_TP |
185 | INSTALL_DTV (tlsblock, _dl_static_dtv); |
186 | const char *lossage = TLS_INIT_TP (tlsblock); |
187 | #else |
188 | # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined" |
189 | #endif |
190 | if (__builtin_expect (lossage != NULL, 0)) |
191 | _startup_fatal (lossage); |
192 | |
193 | /* Update the executable's link map with enough information to make |
194 | the TLS routines happy. */ |
195 | main_map->l_tls_align = align; |
196 | main_map->l_tls_blocksize = memsz; |
197 | main_map->l_tls_initimage = initimage; |
198 | main_map->l_tls_initimage_size = filesz; |
199 | main_map->l_tls_modid = 1; |
200 | |
201 | init_slotinfo (); |
202 | /* static_slotinfo.slotinfo[1].gen = 0; -- Already zero. */ |
203 | static_slotinfo.slotinfo[1].map = main_map; |
204 | |
205 | memsz = roundup (memsz, align ?: 1); |
206 | |
207 | #if TLS_DTV_AT_TP |
208 | memsz += tcb_offset; |
209 | #endif |
210 | |
211 | init_static_tls (memsz, MAX (TLS_TCB_ALIGN, max_align)); |
212 | } |
213 | |