2 * Copyright (c) 2004 Doug Rabson
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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
26 * $FreeBSD: src/lib/libc/gen/tls.c,v 1.7 2005/03/01 23:42:00 davidxu Exp $
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.
37 #include <machine/tls.h>
46 #include "libc_private.h"
48 __weak_reference(__libc_allocate_tls, _rtld_allocate_tls);
49 __weak_reference(__libc_free_tls, _rtld_free_tls);
50 __weak_reference(__libc_call_init, _rtld_call_init);
52 __weak_reference(___libc_tls_get_addr, ___tls_get_addr);
54 __weak_reference(__libc_tls_get_addr, __tls_get_addr);
55 __weak_reference(__libc_tls_get_addr_tcb, __tls_get_addr_tcb);
56 __weak_reference(_libc_init_tls, _init_tls);
58 struct tls_tcb *__libc_allocate_tls(void);
59 void __libc_free_tls(struct tls_tcb *tcb);
61 #if !defined(RTLD_STATIC_TLS_VARIANT_II)
62 #error "Unsupported TLS layout"
67 #define round(size, align) \
68 (((size) + (align) - 1) & ~((align) - 1))
70 static size_t tls_static_space;
71 static size_t tls_init_size;
72 static void *tls_init;
73 static struct tls_tcb *initial_tcb;
80 void *___libc_tls_get_addr(void *ti) __attribute__((__regparm__(1)));
82 __attribute__((__regparm__(1)))
84 ___libc_tls_get_addr(void *ti __unused)
91 void *__libc_tls_get_addr(void *ti);
92 void *__libc_tls_get_addr_tcb(struct tls_tcb *, void *);
95 __libc_tls_get_addr(void *ti __unused)
101 __libc_tls_get_addr_tcb(struct tls_tcb *tcb __unused, void *got_ptr __unused)
109 * Free Static TLS, weakly bound to _rtld_free_tls()
112 __libc_free_tls(struct tls_tcb *tcb)
116 data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) &
117 ~RTLD_STATIC_TLS_ALIGN_MASK;
119 if (tcb == initial_tcb) {
120 /* initial_tcb was allocated with sbrk(), cannot call free() */
122 free((char *)tcb - data_size);
127 * Allocate Static TLS, weakly bound to _rtld_allocate_tls()
129 * NOTE! There is a chicken-and-egg problem here because no TLS exists
130 * on the first call into this function.
133 __libc_allocate_tls(void)
139 data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) &
140 ~RTLD_STATIC_TLS_ALIGN_MASK;
143 * Allocate space. malloc() may require a working TLS segment
144 * so we use sbrk() for main's TLS.
146 if (initial_tcb == NULL)
147 tcb = sbrk(data_size + sizeof(*tcb) + 3 * sizeof(*dtv));
149 tcb = malloc(data_size + sizeof(*tcb) + 3 * sizeof(*dtv));
151 tcb = (struct tls_tcb *)((char *)tcb + data_size);
152 dtv = (Elf_Addr *)(tcb + 1);
154 memset(tcb, 0, sizeof(*tcb));
155 #ifdef RTLD_TCB_HAS_SELF_POINTER
161 * Dummy-up the module array. A static binary has only one. This
162 * allows us to support the generic __tls_get_addr compiler ABI
163 * function. However, if there is no RTLD linked in, nothing in
164 * the program should ever call __tls_get_addr (and our version
165 * of it doesn't do anything).
169 dtv[2] = (Elf_Addr)((char *)tcb - tls_static_space);
171 memcpy((char *)tcb - tls_static_space,
172 tls_init, tls_init_size);
173 memset((char *)tcb - tls_static_space + tls_init_size,
174 0, tls_static_space - tls_init_size);
177 * Activate the initial TCB
179 if (initial_tcb == NULL) {
189 __libc_allocate_tls(void)
195 __libc_free_tls(struct tls_tcb *tcb __unused)
202 __libc_call_init(void)
206 extern char **environ;
215 * If this is a static binary there is no RTLD and so we have not
216 * yet calculated the static space requirement. Do so now.
219 Elf_Auxinfo *aux, *auxp;
224 sp = (Elf_Addr *) environ;
227 aux = (Elf_Auxinfo *) sp;
230 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) {
231 switch (auxp->a_type) {
233 phdr = auxp->a_un.a_ptr;
237 phent = auxp->a_un.a_val;
241 phnum = auxp->a_un.a_val;
245 if (phdr == NULL || phent != sizeof(Elf_Phdr) || phnum == 0)
248 for (i = 0; (unsigned)i < phnum; i++) {
249 if (phdr[i].p_type == PT_TLS) {
250 tls_static_space = round(phdr[i].p_memsz,
252 tls_init_size = phdr[i].p_filesz;
253 tls_init = (void*) phdr[i].p_vaddr;
259 * Allocate the initial TLS segment. The TLS has not been set up
260 * yet for either the static or dynamic linked case (RTLD no longer
261 * sets up an initial TLS segment for us).
263 tcb = _libc_allocate_tls();
269 * Allocate a standard TLS. This function is called by libc and by
270 * thread libraries to create a new TCB with libc-related fields properly
271 * initialized (whereas _rtld_allocate_tls() is unable to completely set
274 * Note that this is different from __libc_allocate_tls which is the
275 * weakly bound symbol that handles the case where _rtld_allocate_tls
279 _libc_allocate_tls(void)
283 tcb = _rtld_allocate_tls();
286 #if defined(__thread)
288 tcb->tcb_errno_p = &errno;
290 /* TLS libc dynamically linked */
291 tcb->tcb_errno_p = __tls_get_addr_tcb(tcb, __get_errno_GOT_ptr());
293 /* TLS libc (threaded or unthreaded) */
294 tcb->tcb_errno_p = (void *)((char *)tcb + __get_errno_GS_offset());