csu/libc-tls.c

   1 /* Initialization code for TLS in statically linked application.
   2    Copyright (C) 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <errno.h>
  21 #include <ldsodefs.h>
  22 #include <tls.h>
  23 #include <unistd.h>
  24 #include <stdio.h>
  25 #include <sys/param.h>
  26
  27
  28 #ifdef SHARED
  29  #error makefile bug, this file is for static only
  30 #endif
  31
  32 extern ElfW(Phdr) *_dl_phdr;
  33 extern size_t _dl_phnum;
  34
  35
  36 static dtv_t static_dtv[2 + TLS_SLOTINFO_SURPLUS];
  37
  38
  39 static struct
  40 {
  41   struct dtv_slotinfo_list si;
  42   /* The dtv_slotinfo_list data structure does not include the actual
  43      information since it is defined as an array of size zero.  We define
  44      here the necessary entries.  Note that it is not important whether
  45      there is padding or not since we will always access the information
  46      through the 'si' element.  */
  47   struct dtv_slotinfo info[2 + TLS_SLOTINFO_SURPLUS];
  48 } static_slotinfo;
  49
  50 /* Fake link map for the application.  */
  51 static struct link_map static_map;
  52
  53
  54 /* Highest dtv index currently needed.  */
  55 size_t _dl_tls_max_dtv_idx;
  56 /* Flag signalling whether there are gaps in the module ID allocation.  */
  57 bool _dl_tls_dtv_gaps;
  58 /* Information about the dtv slots.  */
  59 struct dtv_slotinfo_list *_dl_tls_dtv_slotinfo_list;
  60 /* Number of modules in the static TLS block.  */
  61 size_t _dl_tls_static_nelem;
  62 /* Size of the static TLS block.  Giving this initialized value
  63    preallocates some surplus bytes in the static TLS area.  */
  64 size_t _dl_tls_static_size = 2048;
  65 /* Size actually allocated in the static TLS block.  */
  66 size_t _dl_tls_static_used;
  67 /* Alignment requirement of the static TLS block.  */
  68 size_t _dl_tls_static_align;
  69
  70 /* Generation counter for the dtv.  */
  71 size_t _dl_tls_generation;
  72
  73
  74 /* Additional definitions needed by TLS initialization.  */
  75 #ifdef TLS_INIT_HELPER
  76 TLS_INIT_HELPER
  77 #endif
  78
  79 static inline void
  80 init_slotinfo (void)
  81 {
  82   /* Create the slotinfo list.  */
  83   static_slotinfo.si.len = (((char *) (&static_slotinfo + 1)
  84                              - (char *) &static_slotinfo.si.slotinfo[0])
  85                             / sizeof static_slotinfo.si.slotinfo[0]);
  86   // static_slotinfo.si.next = NULL;    already zero
  87
  88   /* The slotinfo list.  Will be extended by the code doing dynamic
  89      linking.  */
  90   GL(dl_tls_max_dtv_idx) = 1;
  91   GL(dl_tls_dtv_slotinfo_list) = &static_slotinfo.si;
  92 }
  93
  94 static inline void
  95 init_static_tls (size_t memsz, size_t align)
  96 {
  97   /* That is the size of the TLS memory for this object.  The initialized
  98      value of _dl_tls_static_size is provided by dl-open.c to request some
  99      surplus that permits dynamic loading of modules with IE-model TLS.  */
 100   GL(dl_tls_static_size) = roundup (memsz + GL(dl_tls_static_size),
 101                                     TLS_TCB_ALIGN);
 102   GL(dl_tls_static_used) = memsz;
 103   /* The alignment requirement for the static TLS block.  */
 104   GL(dl_tls_static_align) = align;
 105   /* Number of elements in the static TLS block.  */
 106   GL(dl_tls_static_nelem) = GL(dl_tls_max_dtv_idx);
 107 }
 108
 109 void *__tls_template_start;
 110 void *__tls_template_tdata_end;
 111 void *__tls_template_end;
 112
 113 void
 114 __libc_setup_tls (size_t tcbsize, size_t tcbalign)
 115 {
 116   void *tlsblock;
 117   size_t memsz = 0;
 118   size_t filesz = 0;
 119   void *initimage = NULL;
 120   size_t align = 0;
 121   size_t max_align = tcbalign;
 122   size_t tcb_offset;
 123   ElfW(Phdr) *phdr;
 124
 125 #if 0
 126   /* Look through the TLS segment if there is any.  */
 127   if (_dl_phdr != NULL)
 128     for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
 129       if (phdr->p_type == PT_TLS)
 130         {
 131           /* Remember the values we need.  */
 132           memsz = phdr->p_memsz;
 133           filesz = phdr->p_filesz;
 134           initimage = (void *) phdr->p_vaddr;
 135           align = phdr->p_align;
 136           if (phdr->p_align > max_align)
 137             max_align = phdr->p_align;
 138           break;
 139         }
 140 #endif
 141   initimage = (void *) &__tls_template_start;
 142   memsz = (size_t) &__tls_template_end - (size_t) &__tls_template_start;
 143   filesz = (size_t) &__tls_template_tdata_end - (size_t) &__tls_template_start;
 144   align = 4;
 145
 146   /* We have to set up the TCB block which also (possibly) contains
 147      'errno'.  Therefore we avoid 'malloc' which might touch 'errno'.
 148      Instead we use 'sbrk' which would only uses 'errno' if it fails.
 149      In this case we are right away out of memory and the user gets
 150      what she/he deserves.
 151
 152      The initialized value of _dl_tls_static_size is provided by dl-open.c
 153      to request some surplus that permits dynamic loading of modules with
 154      IE-model TLS.  */
 155 #if TLS_TCB_AT_TP
 156   tcb_offset = roundup (memsz + GL(dl_tls_static_size), tcbalign);
 157   tlsblock = __sbrk (tcb_offset + tcbsize + max_align);
 158 #elif TLS_DTV_AT_TP
 159   tcb_offset = roundup (tcbsize, align ?: 1);
 160   tlsblock = __sbrk (tcb_offset + memsz + max_align
 161                      + TLS_PRE_TCB_SIZE + GL(dl_tls_static_size));
 162   tlsblock += TLS_PRE_TCB_SIZE;
 163 #else
 164   /* In case a model with a different layout for the TCB and DTV
 165      is defined add another #elif here and in the following #ifs.  */
 166 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 167 #endif
 168
 169   /* Align the TLS block.  */
 170   tlsblock = (void *) (((uintptr_t) tlsblock + max_align - 1)
 171                        & ~(max_align - 1));
 172
 173   /* Initialize the dtv.  [0] is the length, [1] the generation counter.  */
 174   static_dtv[0].counter = (sizeof (static_dtv) / sizeof (static_dtv[0])) - 2;
 175   // static_dtv[1].counter = 0;         would be needed if not already done
 176
 177   /* Initialize the TLS block.  */
 178 #if TLS_TCB_AT_TP
 179   static_dtv[2].pointer.val = ((char *) tlsblock + tcb_offset
 180                                - roundup (memsz, align ?: 1));
 181   static_map.l_tls_offset = roundup (memsz, align ?: 1);
 182 #elif TLS_DTV_AT_TP
 183   static_dtv[2].pointer.val = (char *) tlsblock + tcb_offset;
 184   static_map.l_tls_offset = tcb_offset;
 185 #else
 186 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 187 #endif
 188   static_dtv[2].pointer.is_static = true;
 189   /* sbrk gives us zero'd memory, so we don't need to clear the remainder.  */
 190   memcpy (static_dtv[2].pointer.val, initimage, filesz);
 191
 192   /* Install the pointer to the dtv.  */
 193
 194   /* Initialize the thread pointer.  */
 195 #if TLS_TCB_AT_TP
 196   INSTALL_DTV ((char *) tlsblock + tcb_offset, static_dtv);
 197
 198   const char *lossage = TLS_INIT_TP ((char *) tlsblock + tcb_offset, 0);
 199 #elif TLS_DTV_AT_TP
 200   INSTALL_DTV (tlsblock, static_dtv);
 201   const char *lossage = TLS_INIT_TP (tlsblock, 0);
 202 #else
 203 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 204 #endif
 205   if (__builtin_expect (lossage != NULL, 0))
 206     __libc_fatal (lossage);
 207
 208   /* We have to create a fake link map which normally would be created
 209      by the dynamic linker.  It just has to have enough information to
 210      make the TLS routines happy.  */
 211   static_map.l_tls_align = align;
 212   static_map.l_tls_blocksize = memsz;
 213   static_map.l_tls_initimage = initimage;
 214   static_map.l_tls_initimage_size = filesz;
 215   static_map.l_type = lt_executable;
 216   static_map.l_tls_modid = 1;
 217
 218   init_slotinfo ();
 219   // static_slotinfo.si.slotinfo[1].gen = 0; already zero
 220   static_slotinfo.si.slotinfo[1].map = &static_map;
 221
 222   memsz = roundup (memsz, align ?: 1);
 223
 224 #if TLS_TCB_AT_TP
 225   memsz += tcbsize;
 226 #elif TLS_DTV_AT_TP
 227   memsz += tcb_offset;
 228 #endif
 229
 230   init_static_tls (memsz, MAX (TLS_TCB_ALIGN, max_align));
 231 }
 232
 233 /* This is called only when the data structure setup was skipped at startup,
 234    when there was no need for it then.  Now we have dynamically loaded
 235    something needing TLS, or libpthread needs it.  */
 236 int
 237 internal_function
 238 _dl_tls_setup (void)
 239 {
 240   init_slotinfo ();
 241   init_static_tls (
 242 #if TLS_TCB_AT_TP
 243                    TLS_TCB_SIZE,
 244 #else
 245                    0,
 246 #endif
 247                    TLS_TCB_ALIGN);
 248   return 0;
 249 }
 250
 251
 252 /* This is the minimal initialization function used when libpthread is
 253    not used.  */
 254 void
 255 __attribute__ ((weak))
 256 __pthread_initialize_minimal (void)
 257 {
 258   __libc_setup_tls (TLS_INIT_TCB_SIZE, TLS_INIT_TCB_ALIGN);
 259 }