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
 110 __libc_setup_tls (size_t tcbsize, size_t tcbalign)
 111 {
 112   void *tlsblock;
 113   size_t memsz = 0;
 114   size_t filesz = 0;
 115   void *initimage = NULL;
 116   size_t align = 0;
 117   size_t max_align = tcbalign;
 118   size_t tcb_offset;
 119   ElfW(Phdr) *phdr;
 120
 121   /* Look through the TLS segment if there is any.  */
 122   if (_dl_phdr != NULL)
 123     for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
 124       if (phdr->p_type == PT_TLS)
 125         {
 126           /* Remember the values we need.  */
 127           memsz = phdr->p_memsz;
 128           filesz = phdr->p_filesz;
 129           initimage = (void *) phdr->p_vaddr;
 130           align = phdr->p_align;
 131           if (phdr->p_align > max_align)
 132             max_align = phdr->p_align;
 133           break;
 134         }
 135
 136   /* We have to set up the TCB block which also (possibly) contains
 137      'errno'.  Therefore we avoid 'malloc' which might touch 'errno'.
 138      Instead we use 'sbrk' which would only uses 'errno' if it fails.
 139      In this case we are right away out of memory and the user gets
 140      what she/he deserves.
 141
 142      The initialized value of _dl_tls_static_size is provided by dl-open.c
 143      to request some surplus that permits dynamic loading of modules with
 144      IE-model TLS.  */
 145 #if TLS_TCB_AT_TP
 146   tcb_offset = roundup (memsz + GL(dl_tls_static_size), tcbalign);
 147   tlsblock = __sbrk (tcb_offset + tcbsize + max_align);
 148 #elif TLS_DTV_AT_TP
 149   tcb_offset = roundup (tcbsize, align ?: 1);
 150   tlsblock = __sbrk (tcb_offset + memsz + max_align
 151                      + TLS_PRE_TCB_SIZE + GL(dl_tls_static_size));
 152   tlsblock += TLS_PRE_TCB_SIZE;
 153 #else
 154   /* In case a model with a different layout for the TCB and DTV
 155      is defined add another #elif here and in the following #ifs.  */
 156 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 157 #endif
 158
 159   /* Align the TLS block.  */
 160   tlsblock = (void *) (((uintptr_t) tlsblock + max_align - 1)
 161                        & ~(max_align - 1));
 162
 163   /* Initialize the dtv.  [0] is the length, [1] the generation counter.  */
 164   static_dtv[0].counter = (sizeof (static_dtv) / sizeof (static_dtv[0])) - 2;
 165   // static_dtv[1].counter = 0;         would be needed if not already done
 166
 167   /* Initialize the TLS block.  */
 168 #if TLS_TCB_AT_TP
 169   static_dtv[2].pointer.val = ((char *) tlsblock + tcb_offset
 170                                - roundup (memsz, align ?: 1));
 171   static_map.l_tls_offset = roundup (memsz, align ?: 1);
 172 #elif TLS_DTV_AT_TP
 173   static_dtv[2].pointer.val = (char *) tlsblock + tcb_offset;
 174   static_map.l_tls_offset = tcb_offset;
 175 #else
 176 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 177 #endif
 178   static_dtv[2].pointer.is_static = true;
 179   /* sbrk gives us zero'd memory, so we don't need to clear the remainder.  */
 180   memcpy (static_dtv[2].pointer.val, initimage, filesz);
 181
 182   /* Install the pointer to the dtv.  */
 183
 184   /* Initialize the thread pointer.  */
 185 #if TLS_TCB_AT_TP
 186   INSTALL_DTV ((char *) tlsblock + tcb_offset, static_dtv);
 187
 188   const char *lossage = TLS_INIT_TP ((char *) tlsblock + tcb_offset, 0);
 189 #elif TLS_DTV_AT_TP
 190   INSTALL_DTV (tlsblock, static_dtv);
 191   const char *lossage = TLS_INIT_TP (tlsblock, 0);
 192 #else
 193 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 194 #endif
 195   if (__builtin_expect (lossage != NULL, 0))
 196     __libc_fatal (lossage);
 197
 198   /* We have to create a fake link map which normally would be created
 199      by the dynamic linker.  It just has to have enough information to
 200      make the TLS routines happy.  */
 201   static_map.l_tls_align = align;
 202   static_map.l_tls_blocksize = memsz;
 203   static_map.l_tls_initimage = initimage;
 204   static_map.l_tls_initimage_size = filesz;
 205   static_map.l_type = lt_executable;
 206   static_map.l_tls_modid = 1;
 207
 208   init_slotinfo ();
 209   // static_slotinfo.si.slotinfo[1].gen = 0; already zero
 210   static_slotinfo.si.slotinfo[1].map = &static_map;
 211
 212   memsz = roundup (memsz, align ?: 1);
 213
 214 #if TLS_TCB_AT_TP
 215   memsz += tcbsize;
 216 #elif TLS_DTV_AT_TP
 217   memsz += tcb_offset;
 218 #endif
 219
 220   init_static_tls (memsz, MAX (TLS_TCB_ALIGN, max_align));
 221 }
 222
 223 /* This is called only when the data structure setup was skipped at startup,
 224    when there was no need for it then.  Now we have dynamically loaded
 225    something needing TLS, or libpthread needs it.  */
 226 int
 227 internal_function
 228 _dl_tls_setup (void)
 229 {
 230   init_slotinfo ();
 231   init_static_tls (
 232 #if TLS_TCB_AT_TP
 233                    TLS_TCB_SIZE,
 234 #else
 235                    0,
 236 #endif
 237                    TLS_TCB_ALIGN);
 238   return 0;
 239 }
 240
 241
 242 /* This is the minimal initialization function used when libpthread is
 243    not used.  */
 244 void
 245 __attribute__ ((weak))
 246 __pthread_initialize_minimal (void)
 247 {
 248   __libc_setup_tls (TLS_INIT_TCB_SIZE, TLS_INIT_TCB_ALIGN);
 249 }