1 /*-
2 * Copyright (c) 2004 Doug Rabson
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
26 * $FreeBSD: src/lib/libc/gen/tls.c,v 1.7 2005/03/01 23:42:00 davidxu Exp $
27 */
28
29 /*
30 * Define stubs for TLS internals so that programs and libraries can
31 * link. These functions will be replaced by functional versions at
32 * runtime from ld-elf.so.1.
33 */
34
35 #include <sys/param.h>
36 #include <sys/tls.h>
37 #include <sys/mman.h>
38
39 #include <machine/tls.h>
40
41 #include <stdlib.h>
42 #include <string.h>
43 #include <elf.h>
44 #include <assert.h>
45 #include <errno.h>
46 #include <unistd.h>
47
48 #include "libc_private.h"
49
50 struct tls_tcb *__libc_allocate_tls(void);
51 void __libc_free_tls(struct tls_tcb *tcb);
52 void __libc_call_init(void);
53
54 #if !defined(RTLD_STATIC_TLS_VARIANT_II)
55 #error "Unsupported TLS layout"
56 #endif
57
58 #ifndef PIC
59
60 static size_t tls_static_space;
61 static size_t tls_init_size;
62 static void *tls_init;
63 static struct tls_tcb *initial_tcb;
64 #endif
65
66 void *__libc_tls_get_addr(void *ti);
67 void *__libc_tls_get_addr_tcb(struct tls_tcb *, void *);
68
69 void *
__libc_tls_get_addr(void * ti __unused)70 __libc_tls_get_addr(void *ti __unused)
71 {
72 return (NULL);
73 }
74
75 void *
__libc_tls_get_addr_tcb(struct tls_tcb * tcb __unused,void * got_ptr __unused)76 __libc_tls_get_addr_tcb(struct tls_tcb *tcb __unused, void *got_ptr __unused)
77 {
78 return (NULL);
79 }
80
81 #ifndef PIC
82
83 /*
84 * Free Static TLS, weakly bound to _rtld_free_tls()
85 */
86 void
__libc_free_tls(struct tls_tcb * tcb)87 __libc_free_tls(struct tls_tcb *tcb)
88 {
89 size_t data_size;
90
91 data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) &
92 ~RTLD_STATIC_TLS_ALIGN_MASK;
93
94 if (tcb == initial_tcb) {
95 /* initial_tcb was allocated with mmap(), cannot call free() */
96 } else {
97 free((char *)tcb - data_size);
98 }
99 }
100
101 /*
102 * Allocate Static TLS, weakly bound to _rtld_allocate_tls()
103 *
104 * NOTE! There is a chicken-and-egg problem here because no TLS exists
105 * on the first call into this function.
106 */
107 struct tls_tcb *
__libc_allocate_tls(void)108 __libc_allocate_tls(void)
109 {
110 size_t data_size;
111 struct tls_tcb *tcb;
112 Elf_Addr *dtv;
113
114 data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) &
115 ~RTLD_STATIC_TLS_ALIGN_MASK;
116
117 /*
118 * Allocate space. malloc() may require a working TLS segment
119 * so we use sbrk() for main's TLS. Oops, but in order to be
120 * compatible with older kernels we cannot use sbrk() because it
121 * will generate an errno (which needs the TLS), so use mmap().
122 */
123 if (initial_tcb == NULL) {
124 size_t bytes;
125
126 bytes = data_size + sizeof(*tcb) + 3 * sizeof(*dtv);
127 bytes = (bytes + PAGE_MASK) & ~(size_t)PAGE_MASK;
128 tcb = mmap((void *)1, bytes,
129 PROT_READ | PROT_WRITE,
130 MAP_PRIVATE | MAP_ANON,
131 -1, 0);
132 } else {
133 tcb = malloc(data_size + sizeof(*tcb) + 3 * sizeof(*dtv));
134 }
135
136 tcb = (struct tls_tcb *)((char *)tcb + data_size);
137 dtv = (Elf_Addr *)(tcb + 1);
138
139 memset(tcb, 0, sizeof(*tcb));
140 #ifdef RTLD_TCB_HAS_SELF_POINTER
141 tcb->tcb_self = tcb;
142 #endif
143 tcb->tcb_dtv = dtv;
144
145 /*
146 * Dummy-up the module array. A static binary has only one. This
147 * allows us to support the generic __tls_get_addr compiler ABI
148 * function. However, if there is no RTLD linked in, nothing in
149 * the program should ever call __tls_get_addr (and our version
150 * of it doesn't do anything).
151 */
152 dtv[0] = 1;
153 dtv[1] = 1;
154 dtv[2] = (Elf_Addr)((char *)tcb - tls_static_space);
155
156 memcpy((char *)tcb - tls_static_space,
157 tls_init, tls_init_size);
158 memset((char *)tcb - tls_static_space + tls_init_size,
159 0, tls_static_space - tls_init_size);
160
161 /*
162 * Activate the initial TCB
163 */
164 if (initial_tcb == NULL) {
165 initial_tcb = tcb;
166 tls_set_tcb(tcb);
167 }
168 return (tcb);
169 }
170
171 #else
172
173 struct tls_tcb *
__libc_allocate_tls(void)174 __libc_allocate_tls(void)
175 {
176 return (NULL);
177 }
178
179 void
__libc_free_tls(struct tls_tcb * tcb __unused)180 __libc_free_tls(struct tls_tcb *tcb __unused)
181 {
182 }
183
184 #endif /* PIC */
185
186 void
__libc_call_init(void)187 __libc_call_init(void)
188 {
189 }
190
191 extern char **environ;
192
193 struct tls_tcb *
_libc_init_tls(void)194 _libc_init_tls(void)
195 {
196 struct tls_tcb *tcb;
197
198 #ifndef PIC
199 /*
200 * If this is a static binary there is no RTLD and so we have not
201 * yet calculated the static space requirement. Do so now.
202 */
203 Elf_Addr *sp;
204 Elf_Auxinfo *aux, *auxp;
205 Elf_Phdr *phdr;
206 size_t phent, phnum;
207 int i;
208
209 sp = (Elf_Addr *) environ;
210 while (*sp++ != 0)
211 ;
212 aux = (Elf_Auxinfo *) sp;
213 phdr = NULL;
214 phent = phnum = 0;
215 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) {
216 switch (auxp->a_type) {
217 case AT_PHDR:
218 phdr = auxp->a_un.a_ptr;
219 break;
220
221 case AT_PHENT:
222 phent = auxp->a_un.a_val;
223 break;
224
225 case AT_PHNUM:
226 phnum = auxp->a_un.a_val;
227 break;
228 }
229 }
230 if (phdr == NULL || phent != sizeof(Elf_Phdr) || phnum == 0)
231 return(NULL);
232
233 for (i = 0; (unsigned)i < phnum; i++) {
234 if (phdr[i].p_type == PT_TLS) {
235 tls_static_space = roundup2(phdr[i].p_memsz,
236 phdr[i].p_align);
237 tls_init_size = phdr[i].p_filesz;
238 tls_init = (void*) phdr[i].p_vaddr;
239 }
240 }
241 #endif
242
243 /*
244 * Allocate the initial TLS segment. The TLS has not been set up
245 * yet for either the static or dynamic linked case (RTLD no longer
246 * sets up an initial TLS segment for us).
247 */
248 tcb = _libc_allocate_tls();
249 tls_set_tcb(tcb);
250 return(tcb);
251 }
252
253 /*
254 * Allocate a standard TLS. This function is called by libc and by
255 * thread libraries to create a new TCB with libc-related fields properly
256 * initialized (whereas _rtld_allocate_tls() is unable to completely set
257 * up the TCB).
258 *
259 * Note that this is different from __libc_allocate_tls which is the
260 * weakly bound symbol that handles the case where _rtld_allocate_tls
261 * does not exist.
262 */
263 struct tls_tcb *
_libc_allocate_tls(void)264 _libc_allocate_tls(void)
265 {
266 struct tls_tcb *tcb;
267
268 tcb = _rtld_allocate_tls();
269 return(tcb);
270 }
271
272 __weak_reference(__libc_allocate_tls, _rtld_allocate_tls);
273 __weak_reference(__libc_free_tls, _rtld_free_tls);
274 __weak_reference(__libc_call_init, _rtld_call_init);
275 __weak_reference(__libc_tls_get_addr, __tls_get_addr);
276 __weak_reference(__libc_tls_get_addr_tcb, __tls_get_addr_tcb);
277 __weak_reference(_libc_init_tls, _init_tls);
278