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
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17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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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>
39 #include <machine/tls.h>
48 #include "libc_private.h"
50 struct tls_tcb *__libc_allocate_tls(void);
51 void __libc_free_tls(struct tls_tcb *tcb);
52 void __libc_call_init(void);
54 #if !defined(RTLD_STATIC_TLS_VARIANT_II)
55 #error "Unsupported TLS layout"
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;
66 void *__libc_tls_get_addr(void *ti);
67 void *__libc_tls_get_addr_tcb(struct tls_tcb *, void *);
70 __libc_tls_get_addr(void *ti __unused)
76 __libc_tls_get_addr_tcb(struct tls_tcb *tcb __unused, void *got_ptr __unused)
84 * Free Static TLS, weakly bound to _rtld_free_tls()
87 __libc_free_tls(struct tls_tcb *tcb)
91 data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) &
92 ~RTLD_STATIC_TLS_ALIGN_MASK;
94 if (tcb == initial_tcb) {
95 /* initial_tcb was allocated with mmap(), cannot call free() */
97 free((char *)tcb - data_size);
102 * Allocate Static TLS, weakly bound to _rtld_allocate_tls()
104 * NOTE! There is a chicken-and-egg problem here because no TLS exists
105 * on the first call into this function.
108 __libc_allocate_tls(void)
114 data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) &
115 ~RTLD_STATIC_TLS_ALIGN_MASK;
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().
123 if (initial_tcb == NULL) {
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,
133 tcb = malloc(data_size + sizeof(*tcb) + 3 * sizeof(*dtv));
136 tcb = (struct tls_tcb *)((char *)tcb + data_size);
137 dtv = (Elf_Addr *)(tcb + 1);
139 memset(tcb, 0, sizeof(*tcb));
140 #ifdef RTLD_TCB_HAS_SELF_POINTER
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).
154 dtv[2] = (Elf_Addr)((char *)tcb - tls_static_space);
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);
162 * Activate the initial TCB
164 if (initial_tcb == NULL) {
174 __libc_allocate_tls(void)
180 __libc_free_tls(struct tls_tcb *tcb __unused)
187 __libc_call_init(void)
191 extern char **environ;
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.
204 Elf_Auxinfo *aux, *auxp;
209 sp = (Elf_Addr *) environ;
212 aux = (Elf_Auxinfo *) sp;
215 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) {
216 switch (auxp->a_type) {
218 phdr = auxp->a_un.a_ptr;
222 phent = auxp->a_un.a_val;
226 phnum = auxp->a_un.a_val;
230 if (phdr == NULL || phent != sizeof(Elf_Phdr) || phnum == 0)
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,
237 tls_init_size = phdr[i].p_filesz;
238 tls_init = (void*) phdr[i].p_vaddr;
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).
248 tcb = _libc_allocate_tls();
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
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
264 _libc_allocate_tls(void)
268 tcb = _rtld_allocate_tls();
271 #if defined(__thread)
273 tcb->tcb_errno_p = &errno;
275 /* TLS libc dynamically linked */
276 tcb->tcb_errno_p = __tls_get_addr_tcb(tcb, __get_errno_GOT_ptr());
278 /* TLS libc (threaded or unthreaded) */
279 tcb->tcb_errno_p = (void *)((char *)tcb + __get_errno_GS_offset());
285 __weak_reference(__libc_allocate_tls, _rtld_allocate_tls);
286 __weak_reference(__libc_free_tls, _rtld_free_tls);
287 __weak_reference(__libc_call_init, _rtld_call_init);
288 __weak_reference(__libc_tls_get_addr, __tls_get_addr);
289 __weak_reference(__libc_tls_get_addr_tcb, __tls_get_addr_tcb);
290 __weak_reference(_libc_init_tls, _init_tls);