1 /* Initialization code for TLS in statically linked application.
2 Copyright (C) 2002, 2003, 2004, 2005 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 <errno.h>
20 #include <ldsodefs.h>
21 #include <tls.h>
22 #include <unistd.h>
23 #include <stdio.h>
24 #include <sys/param.h>
25 #include <elf.h>
26 #include <link.h>
27 #include <string.h>
28 #include <stdlib.h>
29 #include <sys/mman.h>
30
31 #ifdef SHARED
32 #error makefile bug, this file is for static only
33 #endif
34
35 #if USE_TLS
36 extern ElfW(Phdr) *_dl_phdr;
37 extern size_t _dl_phnum;
38
39 #ifdef __FDPIC__
40 /* phdr->p_vaddr is not valid in FDPIC mode. To find tdata start we
41 use the linker script defined symbol __tdata_start. */
42 extern int __tdata_start;
43 #endif
44
45 #ifdef SHARED
46 static
47 #endif
48 dtv_t static_dtv[2 + TLS_SLOTINFO_SURPLUS];
49
50
51 static struct
52 {
53 struct dtv_slotinfo_list si;
54 /* The dtv_slotinfo_list data structure does not include the actual
55 information since it is defined as an array of size zero. We define
56 here the necessary entries. Note that it is not important whether
57 there is padding or not since we will always access the information
58 through the 'si' element. */
59 struct dtv_slotinfo info[2 + TLS_SLOTINFO_SURPLUS];
60 } static_slotinfo;
61
62 /* Fake link map for the application. */
63 static struct link_map static_map;
64
65
66 /* Highest dtv index currently needed. */
67 size_t _dl_tls_max_dtv_idx;
68 /* Flag signalling whether there are gaps in the module ID allocation. */
69 bool _dl_tls_dtv_gaps;
70 /* Information about the dtv slots. */
71 struct dtv_slotinfo_list *_dl_tls_dtv_slotinfo_list;
72 /* Number of modules in the static TLS block. */
73 size_t _dl_tls_static_nelem;
74 /* Size of the static TLS block. */
75 size_t _dl_tls_static_size;
76 /* Size actually allocated in the static TLS block. */
77 size_t _dl_tls_static_used;
78 /* Alignment requirement of the static TLS block. */
79 size_t _dl_tls_static_align;
80
81 /* Generation counter for the dtv. */
82 size_t _dl_tls_generation;
83
84
85 /* Additional definitions needed by TLS initialization. */
86 #ifdef TLS_INIT_HELPER
87 TLS_INIT_HELPER
88 #endif
89
90 static inline void
init_slotinfo(void)91 init_slotinfo (void)
92 {
93 /* Create the slotinfo list. */
94 static_slotinfo.si.len = (((char *) (&static_slotinfo + 1)
95 - (char *) &static_slotinfo.si.slotinfo[0])
96 / sizeof static_slotinfo.si.slotinfo[0]);
97 // static_slotinfo.si.next = NULL; already zero
98
99 /* The slotinfo list. Will be extended by the code doing dynamic
100 linking. */
101 GL(dl_tls_max_dtv_idx) = 1;
102 GL(dl_tls_dtv_slotinfo_list) = &static_slotinfo.si;
103 }
104
105 static inline void
init_static_tls(size_t memsz,size_t align)106 init_static_tls (size_t memsz, size_t align)
107 {
108 /* That is the size of the TLS memory for this object. The initialized
109 value of _dl_tls_static_size is provided by dl-open.c to request some
110 surplus that permits dynamic loading of modules with IE-model TLS. */
111 GL(dl_tls_static_size) = roundup (memsz + GL(dl_tls_static_size),
112 TLS_TCB_ALIGN);
113 GL(dl_tls_static_used) = memsz;
114 /* The alignment requirement for the static TLS block. */
115 GL(dl_tls_static_align) = align;
116 /* Number of elements in the static TLS block. */
117 GL(dl_tls_static_nelem) = GL(dl_tls_max_dtv_idx);
118 }
119
120 #if !defined(__FDPIC__) && !defined(SHARED) && defined(STATIC_PIE)
121 ElfW(Addr) _dl_load_base;
122 #endif
123
124 void __libc_setup_tls (size_t tcbsize, size_t tcbalign);
125 void
__libc_setup_tls(size_t tcbsize,size_t tcbalign)126 __libc_setup_tls (size_t tcbsize, size_t tcbalign)
127 {
128 void *tlsblock;
129 size_t memsz = 0;
130 size_t filesz = 0;
131 void *initimage = NULL;
132 size_t align = 0;
133 size_t max_align = tcbalign;
134 size_t tcb_offset;
135 ElfW(Phdr) *phdr;
136
137 /* Look through the TLS segment if there is any. */
138 if (_dl_phdr != NULL)
139 for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
140 if (phdr->p_type == PT_TLS)
141 {
142 /* Remember the values we need. */
143 memsz = phdr->p_memsz;
144 filesz = phdr->p_filesz;
145 #ifdef __FDPIC__
146 initimage = (void *) &__tdata_start;
147 #else
148 initimage = (void *) phdr->p_vaddr;
149 #if !defined(SHARED) && defined(STATIC_PIE)
150 initimage += _dl_load_base;
151 #endif
152 #endif
153 align = phdr->p_align;
154 if (phdr->p_align > max_align)
155 max_align = phdr->p_align;
156 break;
157 }
158
159 /* We have to set up the TCB block which also (possibly) contains
160 'errno'. Therefore we avoid 'malloc' which might touch 'errno'.
161 Instead we use 'sbrk' which would only uses 'errno' if it fails.
162 In this case we are right away out of memory and the user gets
163 what she/he deserves.
164
165 The initialized value of _dl_tls_static_size is provided by dl-open.c
166 to request some surplus that permits dynamic loading of modules with
167 IE-model TLS. */
168 /* Use mmap instead of sbrk since this commit disables sbrk area
169 for FDPIC MMU-less platforms:
170 fs/binfmt_elf_fdpic.c: fix brk area overlap with stack on NOMMU
171 https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/fs/binfmt_elf_fdpic.c?id=4ac313111018cb44ecc250445de5ccb93026a980
172 Loading static PIE ELFs on noMMU is possible since the linux kernel commit
173 1bde925d2354 ("fs/binfmt_elf_fdpic.c: provide NOMMU loader for regular ELF binaries")
174 and it is subject to the same brk restriction.
175 */
176 # if defined(TLS_TCB_AT_TP)
177 tcb_offset = roundup (memsz + GL(dl_tls_static_size), tcbalign);
178 # if defined(__FDPIC__) || (!defined(__ARCH_USE_MMU__) && defined(STATIC_PIE))
179 tlsblock = mmap (NULL, tcb_offset + tcbsize + max_align,
180 PROT_READ|PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
181 # else
182 tlsblock = sbrk (tcb_offset + tcbsize + max_align);
183 # endif
184 # elif defined(TLS_DTV_AT_TP)
185 tcb_offset = roundup (tcbsize, align ?: 1);
186 # if defined(__FDPIC__) || (!defined(__ARCH_USE_MMU__) && defined(STATIC_PIE))
187 tlsblock = mmap (NULL, tcb_offset + memsz + max_align + TLS_PRE_TCB_SIZE + GL(dl_tls_static_size),
188 PROT_READ|PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
189 # else
190 tlsblock = sbrk (tcb_offset + memsz + max_align
191 + TLS_PRE_TCB_SIZE + GL(dl_tls_static_size));
192 # endif
193 memset(tlsblock, '\0', tcb_offset + memsz + max_align + TLS_PRE_TCB_SIZE + GL(dl_tls_static_size));
194 tlsblock += TLS_PRE_TCB_SIZE;
195 # else
196 /* In case a model with a different layout for the TCB and DTV
197 is defined add another #elif here and in the following #ifs. */
198 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
199 # endif
200
201 /* Align the TLS block. */
202 tlsblock = (void *) (((uintptr_t) tlsblock + max_align - 1)
203 & ~(max_align - 1));
204
205 /* Initialize the dtv. [0] is the length, [1] the generation counter. */
206 static_dtv[0].counter = (sizeof (static_dtv) / sizeof (static_dtv[0])) - 2;
207 // static_dtv[1].counter = 0; would be needed if not already done
208
209 /* Initialize the TLS block. */
210 # if defined(TLS_TCB_AT_TP)
211 static_dtv[2].pointer.val = ((char *) tlsblock + tcb_offset
212 - roundup (memsz, align ?: 1));
213 static_map.l_tls_offset = roundup (memsz, align ?: 1);
214 # elif defined(TLS_DTV_AT_TP)
215 static_dtv[2].pointer.val = (char *) tlsblock + tcb_offset;
216 static_map.l_tls_offset = tcb_offset;
217 # else
218 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
219 # endif
220 static_dtv[2].pointer.is_static = true;
221 /* sbrk gives us zero'd memory, so we don't need to clear the remainder. */
222 memcpy (static_dtv[2].pointer.val, initimage, filesz);
223
224 /* Install the pointer to the dtv. */
225
226 /* Initialize the thread pointer. */
227 # if defined(TLS_TCB_AT_TP)
228 INSTALL_DTV ((char *) tlsblock + tcb_offset, static_dtv);
229
230 const char *lossage = TLS_INIT_TP ((char *) tlsblock + tcb_offset, 0);
231 # elif defined(TLS_DTV_AT_TP)
232 INSTALL_DTV (tlsblock, static_dtv);
233 const char *lossage = (char *)TLS_INIT_TP (tlsblock, 0);
234 # else
235 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
236 # endif
237 if (__builtin_expect (lossage != NULL, 0))
238 abort();
239
240 /* We have to create a fake link map which normally would be created
241 by the dynamic linker. It just has to have enough information to
242 make the TLS routines happy. */
243 static_map.l_tls_align = align;
244 static_map.l_tls_blocksize = memsz;
245 static_map.l_tls_initimage = initimage;
246 static_map.l_tls_initimage_size = filesz;
247 static_map.l_tls_modid = 1;
248
249 init_slotinfo ();
250 // static_slotinfo.si.slotinfo[1].gen = 0; already zero
251 static_slotinfo.si.slotinfo[1].map = &static_map;
252
253 memsz = roundup (memsz, align ?: 1);
254
255 # if defined(TLS_TCB_AT_TP)
256 memsz += tcbsize;
257 # elif defined(TLS_DTV_AT_TP)
258 memsz += tcb_offset;
259 # endif
260
261 init_static_tls (memsz, MAX (TLS_TCB_ALIGN, max_align));
262 }
263
264 /* This is called only when the data structure setup was skipped at startup,
265 when there was no need for it then. Now we have dynamically loaded
266 something needing TLS, or libpthread needs it. */
267 int
268 internal_function
_dl_tls_setup(void)269 _dl_tls_setup (void)
270 {
271 init_slotinfo ();
272 init_static_tls (
273 # if defined(TLS_TCB_AT_TP)
274 TLS_TCB_SIZE,
275 # else
276 0,
277 # endif
278 TLS_TCB_ALIGN);
279 return 0;
280 }
281
282 extern void __pthread_initialize_minimal(void) __attribute__((weak));
283
284 /* This is the minimal initialization function used when libpthread is
285 not used. */
286 void
287 __attribute__ ((weak))
__pthread_initialize_minimal(void)288 __pthread_initialize_minimal (void)
289 {
290 __libc_setup_tls (TLS_INIT_TCB_SIZE, TLS_INIT_TCB_ALIGN);
291 }
292
293 #endif
294