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  */
  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
  53 #if !defined(RTLD_STATIC_TLS_VARIANT_II)
  54 #error "Unsupported TLS layout"
  55 #endif
  56
  57 #ifndef PIC
  58
  59 static size_t tls_static_space;
  60 static size_t tls_init_size;
  61 static void *tls_init;
  62 static struct tls_tcb *initial_tcb;
  63 #endif
  64
  65 void *__libc_tls_get_addr(void *ti);
  66 void *__libc_tls_get_addr_tcb(struct tls_tcb *, void *);
  67
  68 void *
  69 __libc_tls_get_addr(void *ti __unused)
  70 {
  71         return (NULL);
  72 }
  73
  74 void *
  75 __libc_tls_get_addr_tcb(struct tls_tcb *tcb __unused, void *got_ptr __unused)
  76 {
  77         return (NULL);
  78 }
  79
  80 #ifndef PIC
  81
  82 /*
  83  * Free Static TLS, weakly bound to _rtld_free_tls()
  84  */
  85 void
  86 __libc_free_tls(struct tls_tcb *tcb)
  87 {
  88         size_t data_size;
  89
  90         data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) &
  91                     ~RTLD_STATIC_TLS_ALIGN_MASK;
  92
  93         if (tcb == initial_tcb) {
  94                 /* initial_tcb was allocated with mmap(), cannot call free() */
  95         } else {
  96                 free((char *)tcb - data_size);
  97         }
  98 }
  99
 100 /*
 101  * Allocate Static TLS, weakly bound to _rtld_allocate_tls()
 102  *
 103  * NOTE!  There is a chicken-and-egg problem here because no TLS exists
 104  * on the first call into this function.
 105  */
 106 struct tls_tcb *
 107 __libc_allocate_tls(void)
 108 {
 109         size_t data_size;
 110         struct tls_tcb *tcb;
 111         Elf_Addr *dtv;
 112
 113         data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) &
 114                     ~RTLD_STATIC_TLS_ALIGN_MASK;
 115
 116         /*
 117          * Allocate space.  malloc() may require a working TLS segment
 118          * so we use sbrk() for main's TLS.  Oops, but in order to be
 119          * compatible with older kernels we cannot use sbrk() because it
 120          * will generate an errno (which needs the TLS), so use mmap().
 121          */
 122         if (initial_tcb == NULL) {
 123                 size_t bytes;
 124
 125                 bytes = data_size + sizeof(*tcb) + 3 * sizeof(*dtv);
 126                 bytes = (bytes + PAGE_MASK) & ~(size_t)PAGE_MASK;
 127                 tcb = mmap((void *)1, bytes,
 128                            PROT_READ | PROT_WRITE,
 129                            MAP_PRIVATE | MAP_ANON,
 130                            -1, 0);
 131         } else {
 132                 tcb = malloc(data_size + sizeof(*tcb) + 3 * sizeof(*dtv));
 133         }
 134
 135         tcb = (struct tls_tcb *)((char *)tcb + data_size);
 136         dtv = (Elf_Addr *)(tcb + 1);
 137
 138         memset(tcb, 0, sizeof(*tcb));
 139 #ifdef RTLD_TCB_HAS_SELF_POINTER
 140         tcb->tcb_self = tcb;
 141 #endif
 142         tcb->tcb_dtv = dtv;
 143
 144         /*
 145          * Dummy-up the module array.  A static binary has only one.  This
 146          * allows us to support the generic __tls_get_addr compiler ABI
 147          * function.  However, if there is no RTLD linked in, nothing in
 148          * the program should ever call __tls_get_addr (and our version
 149          * of it doesn't do anything).
 150          */
 151         dtv[0] = 1;
 152         dtv[1] = 1;
 153         dtv[2] = (Elf_Addr)((char *)tcb - tls_static_space);
 154
 155         memcpy((char *)tcb - tls_static_space,
 156                 tls_init, tls_init_size);
 157         memset((char *)tcb - tls_static_space + tls_init_size,
 158                 0, tls_static_space - tls_init_size);
 159
 160         /*
 161          * Activate the initial TCB
 162          */
 163         if (initial_tcb == NULL) {
 164                 initial_tcb = tcb;
 165                 tls_set_tcb(tcb);
 166         }
 167         return (tcb);
 168 }
 169
 170 #else
 171
 172 struct tls_tcb *
 173 __libc_allocate_tls(void)
 174 {
 175         return (NULL);
 176 }
 177
 178 void
 179 __libc_free_tls(struct tls_tcb *tcb __unused)
 180 {
 181 }
 182
 183 #endif /* PIC */
 184
 185 void
 186 __libc_call_init(void)
 187 {
 188 }
 189
 190 extern char **environ;
 191
 192 struct tls_tcb *
 193 _libc_init_tls(void)
 194 {
 195         struct tls_tcb *tcb;
 196
 197 #ifndef PIC
 198         /*
 199          * If this is a static binary there is no RTLD and so we have not
 200          * yet calculated the static space requirement.  Do so now.
 201          */
 202         Elf_Addr *sp;
 203         Elf_Auxinfo *aux, *auxp;
 204         Elf_Phdr *phdr;
 205         size_t phent, phnum;
 206         int i;
 207
 208         sp = (Elf_Addr *) environ;
 209         while (*sp++ != 0)
 210                 ;
 211         aux = (Elf_Auxinfo *) sp;
 212         phdr = NULL;
 213         phent = phnum = 0;
 214         for (auxp = aux; auxp->a_type != AT_NULL; auxp++) {
 215                 switch (auxp->a_type) {
 216                 case AT_PHDR:
 217                         phdr = auxp->a_un.a_ptr;
 218                         break;
 219
 220                 case AT_PHENT:
 221                         phent = auxp->a_un.a_val;
 222                         break;
 223
 224                 case AT_PHNUM:
 225                         phnum = auxp->a_un.a_val;
 226                         break;
 227                 }
 228         }
 229         if (phdr == NULL || phent != sizeof(Elf_Phdr) || phnum == 0)
 230                 return(NULL);
 231
 232         for (i = 0; (unsigned)i < phnum; i++) {
 233                 if (phdr[i].p_type == PT_TLS) {
 234                         tls_static_space = roundup2(phdr[i].p_memsz,
 235                             phdr[i].p_align);
 236                         tls_init_size = phdr[i].p_filesz;
 237                         tls_init = (void*) phdr[i].p_vaddr;
 238                 }
 239         }
 240 #endif
 241
 242         /*
 243          * Allocate the initial TLS segment.  The TLS has not been set up
 244          * yet for either the static or dynamic linked case (RTLD no longer
 245          * sets up an initial TLS segment for us).
 246          */
 247         tcb = _libc_allocate_tls();
 248         tls_set_tcb(tcb);
 249         return(tcb);
 250 }
 251
 252 /*
 253  * Allocate a standard TLS.  This function is called by libc and by
 254  * thread libraries to create a new TCB with libc-related fields properly
 255  * initialized (whereas _rtld_allocate_tls() is unable to completely set
 256  * up the TCB).
 257  *
 258  * Note that this is different from __libc_allocate_tls which is the
 259  * weakly bound symbol that handles the case where _rtld_allocate_tls
 260  * does not exist.
 261  */
 262 struct tls_tcb *
 263 _libc_allocate_tls(void)
 264 {
 265         struct tls_tcb *tcb;
 266
 267         tcb = _rtld_allocate_tls();
 268
 269 #if 0
 270 #if defined(__thread)
 271         /* non-TLS libc */
 272         tcb->tcb_errno_p = &errno;
 273 #elif defined(PIC)
 274         /* TLS libc dynamically linked */
 275         tcb->tcb_errno_p = __tls_get_addr_tcb(tcb, __get_errno_GOT_ptr());
 276 #else
 277         /* TLS libc (threaded or unthreaded) */
 278         tcb->tcb_errno_p = (void *)((char *)tcb + __get_errno_GS_offset());
 279 #endif
 280 #endif
 281         return(tcb);
 282 }
 283
 284 __weak_reference(__libc_allocate_tls, _rtld_allocate_tls);
 285 __weak_reference(__libc_free_tls, _rtld_free_tls);
 286 __weak_reference(__libc_call_init, _rtld_call_init);
 287 __weak_reference(__libc_tls_get_addr, __tls_get_addr);
 288 __weak_reference(__libc_tls_get_addr_tcb, __tls_get_addr_tcb);
 289 __weak_reference(_libc_init_tls, _init_tls);