sysdeps/generic/libc-tls.c

   1 /* Initialization code for TLS in statically linked application.
   2    Copyright (C) 2002, 2003 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 #ifdef USE_TLS
  33 extern ElfW(Phdr) *_dl_phdr;
  34 extern size_t _dl_phnum;
  35
  36
  37 /* DTV with just one element plus overhead.  */
  38 static dtv_t static_dtv[3];
  39
  40
  41 static struct
  42 {
  43   struct dtv_slotinfo_list si;
  44   /* The dtv_slotinfo_list data structure does not include the actual
  45      information since it is defined as an array of size zero.  We define
  46      here the necessary entries.  Note that it is not important whether
  47      there is padding or not since we will always access the information
  48      through the 'si' element.  */
  49   struct dtv_slotinfo info[2 + TLS_SLOTINFO_SURPLUS];
  50 } static_slotinfo;
  51
  52 /* Fake link map for the application.  */
  53 static struct link_map static_map;
  54
  55
  56 /* Highest dtv index currently needed.  */
  57 size_t _dl_tls_max_dtv_idx;
  58 /* Flag signalling whether there are gaps in the module ID allocation.  */
  59 bool _dl_tls_dtv_gaps;
  60 /* Information about the dtv slots.  */
  61 struct dtv_slotinfo_list *_dl_tls_dtv_slotinfo_list;
  62 /* Number of modules in the static TLS block.  */
  63 size_t _dl_tls_static_nelem;
  64 /* Size of the static TLS block.  */
  65 size_t _dl_tls_static_size;
  66 /* Size actually allocated in the static TLS block.  */
  67 size_t _dl_tls_static_used;
  68 /* Alignment requirement of the static TLS block.  */
  69 size_t _dl_tls_static_align;
  70
  71 /* Generation counter for the dtv.  */
  72 size_t _dl_tls_generation;
  73
  74
  75 /* Additional definitions needed by TLS initialization.  */
  76 #ifdef TLS_INIT_HELPER
  77 TLS_INIT_HELPER
  78 #endif
  79
  80 static inline void
  81 init_slotinfo (void)
  82 {
  83   /* Create the slotinfo list.  */
  84   static_slotinfo.si.len = (((char *) (&static_slotinfo + 1)
  85                              - (char *) &static_slotinfo.si.slotinfo[0])
  86                             / sizeof static_slotinfo.si.slotinfo[0]);
  87   // static_slotinfo.si.next = NULL;    already zero
  88
  89   /* The slotinfo list.  Will be extended by the code doing dynamic
  90      linking.  */
  91   GL(dl_tls_max_dtv_idx) = 1;
  92   GL(dl_tls_dtv_slotinfo_list) = &static_slotinfo.si;
  93 }
  94
  95 static inline void
  96 init_static_tls (size_t memsz, size_t align)
  97 {
  98   /* That is the size of the TLS memory for this object.  The initialized
  99      value of _dl_tls_static_size is provided by dl-open.c to request some
 100      surplus that permits dynamic loading of modules with IE-model TLS.  */
 101   GL(dl_tls_static_size) = roundup (memsz + GL(dl_tls_static_size),
 102                                     TLS_TCB_ALIGN);
 103   GL(dl_tls_static_used) = memsz;
 104   /* The alignment requirement for the static TLS block.  */
 105   GL(dl_tls_static_align) = align;
 106   /* Number of elements in the static TLS block.  */
 107   GL(dl_tls_static_nelem) = GL(dl_tls_max_dtv_idx);
 108 }
 109
 110 void
 111 __libc_setup_tls (size_t tcbsize, size_t tcbalign)
 112 {
 113   void *tlsblock;
 114   size_t memsz = 0;
 115   size_t filesz = 0;
 116   void *initimage = NULL;
 117   size_t align = 0;
 118   size_t max_align = tcbalign;
 119   size_t tcb_offset;
 120   ElfW(Phdr) *phdr;
 121
 122   /* Look through the TLS segment if there is any.  */
 123   if (_dl_phdr != NULL)
 124     for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
 125       if (phdr->p_type == PT_TLS)
 126         {
 127           /* Remember the values we need.  */
 128           memsz = phdr->p_memsz;
 129           filesz = phdr->p_filesz;
 130           initimage = (void *) phdr->p_vaddr;
 131           align = phdr->p_align;
 132           if (phdr->p_align > max_align)
 133             max_align = phdr->p_align;
 134           break;
 135         }
 136
 137 #ifdef TLS_INIT_TP_EXPENSIVE
 138   if (memsz == 0 && tcbsize <= TLS_INIT_TCB_SIZE)
 139     {
 140       /* We do not need a TLS block and no thread descriptor.  */
 141 # ifdef NONTLS_INIT_TP
 142       NONTLS_INIT_TP;
 143 # endif
 144       return;
 145     }
 146 #endif
 147
 148   /* We have to set up the TCB block which also (possibly) contains
 149      'errno'.  Therefore we avoid 'malloc' which might touch 'errno'.
 150      Instead we use 'sbrk' which would only uses 'errno' if it fails.
 151      In this case we are right away out of memory and the user gets
 152      what she/he deserves.
 153
 154      The initialized value of _dl_tls_static_size is provided by dl-open.c
 155      to request some surplus that permits dynamic loading of modules with
 156      IE-model TLS.  */
 157 # if TLS_TCB_AT_TP
 158   tcb_offset = roundup (memsz + GL(dl_tls_static_size), tcbalign);
 159   tlsblock = __sbrk (tcb_offset + tcbsize + max_align);
 160 # elif TLS_DTV_AT_TP
 161   tcb_offset = roundup (tcbsize, align ?: 1);
 162   tlsblock = __sbrk (tcb_offset + memsz + max_align
 163                      + TLS_PRE_TCB_SIZE + GL(dl_tls_static_size));
 164   tlsblock += TLS_PRE_TCB_SIZE;
 165 # else
 166   /* In case a model with a different layout for the TCB and DTV
 167      is defined add another #elif here and in the following #ifs.  */
 168 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 169 # endif
 170
 171   /* Align the TLS block.  */
 172   tlsblock = (void *) (((uintptr_t) tlsblock + max_align - 1)
 173                        & ~(max_align - 1));
 174
 175   /* Initialize the dtv.  [0] is the length, [1] the generation counter.  */
 176   static_dtv[0].counter = 1;
 177   // static_dtv[1].counter = 0;         would be needed if not already done
 178
 179   /* Initialize the TLS block.  */
 180 # if TLS_TCB_AT_TP
 181   static_dtv[2].pointer = ((char *) tlsblock + tcb_offset
 182                            - roundup (memsz, align ?: 1));
 183   static_map.l_tls_offset = roundup (memsz, align ?: 1);
 184 # elif TLS_DTV_AT_TP
 185   static_dtv[2].pointer = (char *) tlsblock + tcb_offset;
 186   static_map.l_tls_offset = tcb_offset;
 187 # else
 188 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 189 # endif
 190   /* sbrk gives us zero'd memory, so we don't need to clear the remainder.  */
 191   memcpy (static_dtv[2].pointer, initimage, filesz);
 192
 193   /* Install the pointer to the dtv.  */
 194
 195   /* Initialize the thread pointer.  */
 196 # if TLS_TCB_AT_TP
 197   INSTALL_DTV ((char *) tlsblock + tcb_offset, static_dtv);
 198
 199   const char *lossage = TLS_INIT_TP ((char *) tlsblock + tcb_offset, 0);
 200 # elif TLS_DTV_AT_TP
 201   INSTALL_DTV (tlsblock, static_dtv);
 202   const char *lossage = TLS_INIT_TP (tlsblock, 0);
 203 # else
 204 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 205 # endif
 206   if (__builtin_expect (lossage != NULL, 0))
 207     __libc_fatal (lossage);
 208
 209   /* We have to create a fake link map which normally would be created
 210      by the dynamic linker.  It just has to have enough information to
 211      make the TLS routines happy.  */
 212   static_map.l_tls_align = align;
 213   static_map.l_tls_blocksize = memsz;
 214   static_map.l_tls_initimage = initimage;
 215   static_map.l_tls_initimage_size = filesz;
 216   static_map.l_type = lt_executable;
 217   static_map.l_tls_modid = 1;
 218
 219   init_slotinfo ();
 220   // static_slotinfo.si.slotinfo[1].gen = 0; already zero
 221   static_slotinfo.si.slotinfo[1].map = &static_map;
 222
 223   memsz = roundup (memsz, align ?: 1);
 224
 225 # if TLS_TCB_AT_TP
 226   memsz += tcbsize;
 227 # elif TLS_DTV_AT_TP
 228   memsz += tcb_offset;
 229 # endif
 230
 231   init_static_tls (memsz, MAX (TLS_TCB_ALIGN, max_align));
 232 }
 233
 234 /* This is called only when the data structure setup was skipped at startup,
 235    when there was no need for it then.  Now we have dynamically loaded
 236    something needing TLS, or libpthread needs it.  */
 237 int
 238 internal_function
 239 _dl_tls_setup (void)
 240 {
 241   init_slotinfo ();
 242   init_static_tls (
 243 # if TLS_TCB_AT_TP
 244                    TLS_TCB_SIZE,
 245 # else
 246                    0,
 247 # endif
 248                    TLS_TCB_ALIGN);
 249   return 0;
 250 }
 251
 252
 253 /* This is the minimal initialization function used when libpthread is
 254    not used.  */
 255 void
 256 __attribute__ ((weak))
 257 __pthread_initialize_minimal (void)
 258 {
 259   __libc_setup_tls (TLS_INIT_TCB_SIZE, TLS_INIT_TCB_ALIGN);
 260 }
 261
 262 #elif defined NONTLS_INIT_TP
 263
 264 /* This is the minimal initialization function used when libpthread is
 265    not used.  */
 266 void
 267 __attribute__ ((weak))
 268 __pthread_initialize_minimal (void)
 269 {
 270   NONTLS_INIT_TP;
 271 }
 272
 273 #endif