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.
35 #include <sys/param.h>
38 #include <machine/tls.h>
47 #include "libc_private.h"
49 __weak_reference(__libc_allocate_tls, _rtld_allocate_tls);
50 __weak_reference(__libc_free_tls, _rtld_free_tls);
51 __weak_reference(__libc_call_init, _rtld_call_init);
52 __weak_reference(__libc_tls_get_addr, __tls_get_addr);
53 __weak_reference(__libc_tls_get_addr_tcb, __tls_get_addr_tcb);
54 __weak_reference(_libc_init_tls, _init_tls);
56 struct tls_tcb *__libc_allocate_tls(void);
57 void __libc_free_tls(struct tls_tcb *tcb);
59 #if !defined(RTLD_STATIC_TLS_VARIANT_II)
60 #error "Unsupported TLS layout"
65 static size_t tls_static_space;
66 static size_t tls_init_size;
67 static void *tls_init;
68 static struct tls_tcb *initial_tcb;
71 void *__libc_tls_get_addr(void *ti);
72 void *__libc_tls_get_addr_tcb(struct tls_tcb *, void *);
75 __libc_tls_get_addr(void *ti __unused)
81 __libc_tls_get_addr_tcb(struct tls_tcb *tcb __unused, void *got_ptr __unused)
89 * Free Static TLS, weakly bound to _rtld_free_tls()
92 __libc_free_tls(struct tls_tcb *tcb)
96 data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) &
97 ~RTLD_STATIC_TLS_ALIGN_MASK;
99 if (tcb == initial_tcb) {
100 /* initial_tcb was allocated with sbrk(), cannot call free() */
102 free((char *)tcb - data_size);
107 * Allocate Static TLS, weakly bound to _rtld_allocate_tls()
109 * NOTE! There is a chicken-and-egg problem here because no TLS exists
110 * on the first call into this function.
113 __libc_allocate_tls(void)
119 data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) &
120 ~RTLD_STATIC_TLS_ALIGN_MASK;
123 * Allocate space. malloc() may require a working TLS segment
124 * so we use sbrk() for main's TLS.
126 if (initial_tcb == NULL)
127 tcb = sbrk(data_size + sizeof(*tcb) + 3 * sizeof(*dtv));
129 tcb = malloc(data_size + sizeof(*tcb) + 3 * sizeof(*dtv));
131 tcb = (struct tls_tcb *)((char *)tcb + data_size);
132 dtv = (Elf_Addr *)(tcb + 1);
134 memset(tcb, 0, sizeof(*tcb));
135 #ifdef RTLD_TCB_HAS_SELF_POINTER
141 * Dummy-up the module array. A static binary has only one. This
142 * allows us to support the generic __tls_get_addr compiler ABI
143 * function. However, if there is no RTLD linked in, nothing in
144 * the program should ever call __tls_get_addr (and our version
145 * of it doesn't do anything).
149 dtv[2] = (Elf_Addr)((char *)tcb - tls_static_space);
151 memcpy((char *)tcb - tls_static_space,
152 tls_init, tls_init_size);
153 memset((char *)tcb - tls_static_space + tls_init_size,
154 0, tls_static_space - tls_init_size);
157 * Activate the initial TCB
159 if (initial_tcb == NULL) {
169 __libc_allocate_tls(void)
175 __libc_free_tls(struct tls_tcb *tcb __unused)
182 __libc_call_init(void)
186 extern char **environ;
195 * If this is a static binary there is no RTLD and so we have not
196 * yet calculated the static space requirement. Do so now.
199 Elf_Auxinfo *aux, *auxp;
204 sp = (Elf_Addr *) environ;
207 aux = (Elf_Auxinfo *) sp;
210 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) {
211 switch (auxp->a_type) {
213 phdr = auxp->a_un.a_ptr;
217 phent = auxp->a_un.a_val;
221 phnum = auxp->a_un.a_val;
225 if (phdr == NULL || phent != sizeof(Elf_Phdr) || phnum == 0)
228 for (i = 0; (unsigned)i < phnum; i++) {
229 if (phdr[i].p_type == PT_TLS) {
230 tls_static_space = roundup2(phdr[i].p_memsz,
232 tls_init_size = phdr[i].p_filesz;
233 tls_init = (void*) phdr[i].p_vaddr;
239 * Allocate the initial TLS segment. The TLS has not been set up
240 * yet for either the static or dynamic linked case (RTLD no longer
241 * sets up an initial TLS segment for us).
243 tcb = _libc_allocate_tls();
249 * Allocate a standard TLS. This function is called by libc and by
250 * thread libraries to create a new TCB with libc-related fields properly
251 * initialized (whereas _rtld_allocate_tls() is unable to completely set
254 * Note that this is different from __libc_allocate_tls which is the
255 * weakly bound symbol that handles the case where _rtld_allocate_tls
259 _libc_allocate_tls(void)
263 tcb = _rtld_allocate_tls();
266 #if defined(__thread)
268 tcb->tcb_errno_p = &errno;
270 /* TLS libc dynamically linked */
271 tcb->tcb_errno_p = __tls_get_addr_tcb(tcb, __get_errno_GOT_ptr());
273 /* TLS libc (threaded or unthreaded) */
274 tcb->tcb_errno_p = (void *)((char *)tcb + __get_errno_GS_offset());