lib/libc/gen/tls.c

   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  *      $DragonFly: src/lib/libc/gen/tls.c,v 1.10 2005/11/19 22:32:53 swildner Exp $
  28  */
  29
  30 /*
  31  * Define stubs for TLS internals so that programs and libraries can
  32  * link. These functions will be replaced by functional versions at
  33  * runtime from ld-elf.so.1.
  34  */
  35
  36 #include <sys/cdefs.h>
  37 #include <sys/tls.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 __weak_reference(__libc_allocate_tls, _rtld_allocate_tls);
  51 __weak_reference(__libc_free_tls, _rtld_free_tls);
  52 __weak_reference(__libc_call_init, _rtld_call_init);
  53 #ifdef __i386__
  54 __weak_reference(___libc_tls_get_addr, ___tls_get_addr);
  55 #endif
  56 __weak_reference(__libc_tls_get_addr, __tls_get_addr);
  57 __weak_reference(__libc_tls_get_addr_tcb, __tls_get_addr_tcb);
  58 __weak_reference(_libc_init_tls, _init_tls);
  59
  60 struct tls_tcb *__libc_allocate_tls(void);
  61 void __libc_free_tls(struct tls_tcb *tcb);
  62
  63 #if !defined(RTLD_STATIC_TLS_VARIANT_II)
  64 #error "Unsupported TLS layout"
  65 #endif
  66
  67 #ifndef PIC
  68
  69 #define round(size, align) \
  70         (((size) + (align) - 1) & ~((align) - 1))
  71
  72 static size_t tls_static_space;
  73 static size_t tls_init_size;
  74 static void *tls_init;
  75 static struct tls_tcb *initial_tcb;
  76 #endif
  77
  78 #ifdef __i386__
  79
  80 /* GNU ABI */
  81
  82 void *___libc_tls_get_addr(void *ti) __attribute__((__regparm__(1)));
  83
  84 __attribute__((__regparm__(1)))
  85 void *
  86 ___libc_tls_get_addr(void *ti __unused)
  87 {
  88         return (0);
  89 }
  90
  91 #endif
  92
  93 void *__libc_tls_get_addr(void *ti);
  94 void *__libc_tls_get_addr_tcb(struct tls_tcb *, void *);
  95
  96 void *
  97 __libc_tls_get_addr(void *ti __unused)
  98 {
  99         return (NULL);
 100 }
 101
 102 void *
 103 __libc_tls_get_addr_tcb(struct tls_tcb *tcb __unused, void *got_ptr __unused)
 104 {
 105         return (NULL);
 106 }
 107
 108 #ifndef PIC
 109
 110 /*
 111  * Free Static TLS, weakly bound to _rtld_free_tls()
 112  */
 113 void
 114 __libc_free_tls(struct tls_tcb *tcb)
 115 {
 116         size_t data_size;
 117
 118         data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) &
 119                     ~RTLD_STATIC_TLS_ALIGN_MASK;
 120
 121         if (tcb == initial_tcb) {
 122                 /* initial_tcb was allocated with sbrk(), cannot call free() */
 123         } else {
 124                 free((char *)tcb - data_size);
 125         }
 126 }
 127
 128 /*
 129  * Allocate Static TLS, weakly bound to _rtld_allocate_tls()
 130  *
 131  * NOTE!  There is a chicken-and-egg problem here because no TLS exists
 132  * on the first call into this function.
 133  */
 134 struct tls_tcb *
 135 __libc_allocate_tls(void)
 136 {
 137         size_t data_size;
 138         struct tls_tcb *tcb;
 139         Elf_Addr *dtv;
 140
 141         data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) &
 142                     ~RTLD_STATIC_TLS_ALIGN_MASK;
 143
 144         /*
 145          * Allocate space.  malloc() may require a working TLS segment
 146          * so we use sbrk() for main's TLS.
 147          */
 148         if (initial_tcb == NULL)
 149                 tcb = sbrk(data_size + sizeof(*tcb) + 3 * sizeof(Elf_Addr));
 150         else
 151                 tcb = malloc(data_size + sizeof(*tcb));
 152
 153         tcb = (struct tls_tcb *)((char *)tcb + data_size);
 154         dtv = (Elf_Addr *)(tcb + 1);
 155
 156         memset(tcb, 0, sizeof(*tcb));
 157 #ifdef RTLD_TCB_HAS_SELF_POINTER
 158         tcb->tcb_self = tcb;
 159 #endif
 160         tcb->tcb_dtv = dtv;
 161
 162         /*
 163          * Dummy-up the module array.  A static binary has only one.  This
 164          * allows us to support the generic __tls_get_addr compiler ABI
 165          * function.  However, if there is no RTLD linked in, nothing in
 166          * the program should ever call __tls_get_addr (and our version
 167          * of it doesn't do anything).
 168          */
 169         dtv[0] = 1;
 170         dtv[1] = 1;
 171         dtv[2] = (Elf_Addr)((char *)tcb - tls_static_space);
 172
 173         memcpy((char *)tcb - tls_static_space,
 174                 tls_init, tls_init_size);
 175         memset((char *)tcb - tls_static_space + tls_init_size,
 176                 0, tls_static_space - tls_init_size);
 177
 178         /*
 179          * Activate the initial TCB
 180          */
 181         if (initial_tcb == NULL) {
 182                 initial_tcb = tcb;
 183                 tls_set_tcb(tcb);
 184         }
 185         return (tcb);
 186 }
 187
 188 #else
 189
 190 struct tls_tcb *
 191 __libc_allocate_tls(void)
 192 {
 193         return (NULL);
 194 }
 195
 196 void
 197 __libc_free_tls(struct tls_tcb *tcb __unused)
 198 {
 199 }
 200
 201 #endif /* PIC */
 202
 203 void
 204 __libc_call_init(void)
 205 {
 206 }
 207
 208 extern char **environ;
 209
 210 struct tls_tcb *
 211 _libc_init_tls(void)
 212 {
 213         struct tls_tcb *tcb;
 214
 215 #ifndef PIC
 216         /*
 217          * If this is a static binary there is no RTLD and so we have not
 218          * yet calculated the static space requirement.  Do so now.
 219          */
 220         Elf_Addr *sp;
 221         Elf_Auxinfo *aux, *auxp;
 222         Elf_Phdr *phdr;
 223         size_t phent, phnum;
 224         int i;
 225
 226         sp = (Elf_Addr *) environ;
 227         while (*sp++ != 0)
 228                 ;
 229         aux = (Elf_Auxinfo *) sp;
 230         phdr = 0;
 231         phent = phnum = 0;
 232         for (auxp = aux; auxp->a_type != AT_NULL; auxp++) {
 233                 switch (auxp->a_type) {
 234                 case AT_PHDR:
 235                         phdr = auxp->a_un.a_ptr;
 236                         break;
 237
 238                 case AT_PHENT:
 239                         phent = auxp->a_un.a_val;
 240                         break;
 241
 242                 case AT_PHNUM:
 243                         phnum = auxp->a_un.a_val;
 244                         break;
 245                 }
 246         }
 247         if (phdr == 0 || phent != sizeof(Elf_Phdr) || phnum == 0)
 248                 return(NULL);
 249
 250         for (i = 0; (unsigned)i < phnum; i++) {
 251                 if (phdr[i].p_type == PT_TLS) {
 252                         tls_static_space = round(phdr[i].p_memsz,
 253                             phdr[i].p_align);
 254                         tls_init_size = phdr[i].p_filesz;
 255                         tls_init = (void*) phdr[i].p_vaddr;
 256                 }
 257         }
 258 #endif
 259
 260         /*
 261          * Allocate the initial TLS segment.  The TLS has not been set up
 262          * yet for either the static or dynamic linked case (RTLD no longer
 263          * sets up an initial TLS segment for us).
 264          */
 265         tcb = _libc_allocate_tls();
 266         tls_set_tcb(tcb);
 267         return(tcb);
 268 }
 269
 270 /*
 271  * Allocate a standard TLS.  This function is called by libc and by
 272  * thread libraries to create a new TCB with libc-related fields properly
 273  * initialized (whereas _rtld_allocate_tls() is unable to completely set
 274  * up the TCB).
 275  *
 276  * Note that this is different from __libc_allocate_tls which is the
 277  * weakly bound symbol that handles the case where _rtld_allocate_tls
 278  * does not exist.
 279  */
 280 struct tls_tcb *
 281 _libc_allocate_tls(void)
 282 {
 283         struct tls_tcb *tcb;
 284
 285         tcb = _rtld_allocate_tls();
 286
 287 #if 0
 288 #if defined(__thread)
 289         /* non-TLS libc */
 290         tcb->tcb_errno_p = &errno;
 291 #elif defined(PIC)
 292         /* TLS libc dynamically linked */
 293         tcb->tcb_errno_p = __tls_get_addr_tcb(tcb, __get_errno_GOT_ptr());
 294 #else
 295         /* TLS libc (threaded or unthreaded) */
 296         tcb->tcb_errno_p = (void *)((char *)tcb + __get_errno_GS_offset());
 297 #endif
 298 #endif
 299         return(tcb);
 300 }
 301