csu/libc-tls.c

   1 /* Initialization code for TLS in statically linked application.
   2    Copyright (C) 2002-2013 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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <ldsodefs.h>
  21 #include <tls.h>
  22 #include <unistd.h>
  23 #include <stdio.h>
  24 #include <sys/param.h>
  25
  26
  27 #ifdef SHARED
  28  #error makefile bug, this file is for static only
  29 #endif
  30
  31 dtv_t _dl_static_dtv[2 + TLS_SLOTINFO_SURPLUS];
  32
  33
  34 static struct
  35 {
  36   struct dtv_slotinfo_list si;
  37   /* The dtv_slotinfo_list data structure does not include the actual
  38      information since it is defined as an array of size zero.  We define
  39      here the necessary entries.  Note that it is not important whether
  40      there is padding or not since we will always access the information
  41      through the 'si' element.  */
  42   struct dtv_slotinfo info[2 + TLS_SLOTINFO_SURPLUS];
  43 } static_slotinfo;
  44
  45 /* Fake link map for the application.  */
  46 static struct link_map static_map;
  47
  48
  49 /* Highest dtv index currently needed.  */
  50 size_t _dl_tls_max_dtv_idx;
  51 /* Flag signalling whether there are gaps in the module ID allocation.  */
  52 bool _dl_tls_dtv_gaps;
  53 /* Information about the dtv slots.  */
  54 struct dtv_slotinfo_list *_dl_tls_dtv_slotinfo_list;
  55 /* Number of modules in the static TLS block.  */
  56 size_t _dl_tls_static_nelem;
  57 /* Size of the static TLS block.  Giving this initialized value
  58    preallocates some surplus bytes in the static TLS area.  */
  59 size_t _dl_tls_static_size = 2048;
  60 /* Size actually allocated in the static TLS block.  */
  61 size_t _dl_tls_static_used;
  62 /* Alignment requirement of the static TLS block.  */
  63 size_t _dl_tls_static_align;
  64
  65 /* Generation counter for the dtv.  */
  66 size_t _dl_tls_generation;
  67
  68
  69 /* Additional definitions needed by TLS initialization.  */
  70 #ifdef TLS_INIT_HELPER
  71 TLS_INIT_HELPER
  72 #endif
  73
  74 static void
  75 init_slotinfo (void)
  76 {
  77   /* Create the slotinfo list.  */
  78   static_slotinfo.si.len = (((char *) (&static_slotinfo + 1)
  79                              - (char *) &static_slotinfo.si.slotinfo[0])
  80                             / sizeof static_slotinfo.si.slotinfo[0]);
  81   // static_slotinfo.si.next = NULL;    already zero
  82
  83   /* The slotinfo list.  Will be extended by the code doing dynamic
  84      linking.  */
  85   GL(dl_tls_max_dtv_idx) = 1;
  86   GL(dl_tls_dtv_slotinfo_list) = &static_slotinfo.si;
  87 }
  88
  89 static void
  90 init_static_tls (size_t memsz, size_t align)
  91 {
  92   /* That is the size of the TLS memory for this object.  The initialized
  93      value of _dl_tls_static_size is provided by dl-open.c to request some
  94      surplus that permits dynamic loading of modules with IE-model TLS.  */
  95   GL(dl_tls_static_size) = roundup (memsz + GL(dl_tls_static_size),
  96                                     TLS_TCB_ALIGN);
  97 #if TLS_TCB_AT_TP
  98   GL(dl_tls_static_size) += TLS_TCB_SIZE;
  99 #endif
 100   GL(dl_tls_static_used) = memsz;
 101   /* The alignment requirement for the static TLS block.  */
 102   GL(dl_tls_static_align) = align;
 103   /* Number of elements in the static TLS block.  */
 104   GL(dl_tls_static_nelem) = GL(dl_tls_max_dtv_idx);
 105 }
 106
 107 void
 108 __libc_setup_tls (size_t tcbsize, size_t tcbalign)
 109 {
 110   void *tlsblock;
 111   size_t memsz = 0;
 112   size_t filesz = 0;
 113   void *initimage = NULL;
 114   size_t align = 0;
 115   size_t max_align = tcbalign;
 116   size_t tcb_offset;
 117   const ElfW(Phdr) *phdr;
 118
 119   /* Look through the TLS segment if there is any.  */
 120   if (_dl_phdr != NULL)
 121     for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
 122       if (phdr->p_type == PT_TLS)
 123         {
 124           /* Remember the values we need.  */
 125           memsz = phdr->p_memsz;
 126           filesz = phdr->p_filesz;
 127           initimage = (void *) phdr->p_vaddr;
 128           align = phdr->p_align;
 129           if (phdr->p_align > max_align)
 130             max_align = phdr->p_align;
 131           break;
 132         }
 133
 134   /* We have to set up the TCB block which also (possibly) contains
 135      'errno'.  Therefore we avoid 'malloc' which might touch 'errno'.
 136      Instead we use 'sbrk' which would only uses 'errno' if it fails.
 137      In this case we are right away out of memory and the user gets
 138      what she/he deserves.
 139
 140      The initialized value of _dl_tls_static_size is provided by dl-open.c
 141      to request some surplus that permits dynamic loading of modules with
 142      IE-model TLS.  */
 143 #if TLS_TCB_AT_TP
 144   tcb_offset = roundup (memsz + GL(dl_tls_static_size), tcbalign);
 145   tlsblock = __sbrk (tcb_offset + tcbsize + max_align);
 146 #elif TLS_DTV_AT_TP
 147   tcb_offset = roundup (tcbsize, align ?: 1);
 148   tlsblock = __sbrk (tcb_offset + memsz + max_align
 149                      + TLS_PRE_TCB_SIZE + GL(dl_tls_static_size));
 150   tlsblock += TLS_PRE_TCB_SIZE;
 151 #else
 152   /* In case a model with a different layout for the TCB and DTV
 153      is defined add another #elif here and in the following #ifs.  */
 154 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 155 #endif
 156
 157   /* Align the TLS block.  */
 158   tlsblock = (void *) (((uintptr_t) tlsblock + max_align - 1)
 159                        & ~(max_align - 1));
 160
 161   /* Initialize the dtv.  [0] is the length, [1] the generation counter.  */
 162   _dl_static_dtv[0].counter = (sizeof (_dl_static_dtv) / sizeof (_dl_static_dtv[0])) - 2;
 163   // _dl_static_dtv[1].counter = 0;             would be needed if not already done
 164
 165   /* Initialize the TLS block.  */
 166 #if TLS_TCB_AT_TP
 167   _dl_static_dtv[2].pointer.val = ((char *) tlsblock + tcb_offset
 168                                - roundup (memsz, align ?: 1));
 169   static_map.l_tls_offset = roundup (memsz, align ?: 1);
 170 #elif TLS_DTV_AT_TP
 171   _dl_static_dtv[2].pointer.val = (char *) tlsblock + tcb_offset;
 172   static_map.l_tls_offset = tcb_offset;
 173 #else
 174 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 175 #endif
 176   _dl_static_dtv[2].pointer.is_static = true;
 177   /* sbrk gives us zero'd memory, so we don't need to clear the remainder.  */
 178   memcpy (_dl_static_dtv[2].pointer.val, initimage, filesz);
 179
 180   /* Install the pointer to the dtv.  */
 181
 182   /* Initialize the thread pointer.  */
 183 #if TLS_TCB_AT_TP
 184   INSTALL_DTV ((char *) tlsblock + tcb_offset, _dl_static_dtv);
 185
 186   const char *lossage = TLS_INIT_TP ((char *) tlsblock + tcb_offset, 0);
 187 #elif TLS_DTV_AT_TP
 188   INSTALL_DTV (tlsblock, _dl_static_dtv);
 189   const char *lossage = TLS_INIT_TP (tlsblock, 0);
 190 #else
 191 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 192 #endif
 193   if (__builtin_expect (lossage != NULL, 0))
 194     __libc_fatal (lossage);
 195
 196   /* We have to create a fake link map which normally would be created
 197      by the dynamic linker.  It just has to have enough information to
 198      make the TLS routines happy.  */
 199   static_map.l_tls_align = align;
 200   static_map.l_tls_blocksize = memsz;
 201   static_map.l_tls_initimage = initimage;
 202   static_map.l_tls_initimage_size = filesz;
 203   static_map.l_type = lt_executable;
 204   static_map.l_tls_modid = 1;
 205
 206   init_slotinfo ();
 207   // static_slotinfo.si.slotinfo[1].gen = 0; already zero
 208   static_slotinfo.si.slotinfo[1].map = &static_map;
 209
 210   memsz = roundup (memsz, align ?: 1);
 211
 212 #if TLS_DTV_AT_TP
 213   memsz += tcb_offset;
 214 #endif
 215
 216   init_static_tls (memsz, MAX (TLS_TCB_ALIGN, max_align));
 217 }
 218
 219 /* This is called only when the data structure setup was skipped at startup,
 220    when there was no need for it then.  Now we have dynamically loaded
 221    something needing TLS, or libpthread needs it.  */
 222 int
 223 internal_function
 224 _dl_tls_setup (void)
 225 {
 226   init_slotinfo ();
 227   init_static_tls (
 228 #if TLS_TCB_AT_TP
 229                    TLS_TCB_SIZE,
 230 #else
 231                    0,
 232 #endif
 233                    TLS_TCB_ALIGN);
 234   return 0;
 235 }
 236
 237
 238 /* This is the minimal initialization function used when libpthread is
 239    not used.  */
 240 void
 241 __attribute__ ((weak))
 242 __pthread_initialize_minimal (void)
 243 {
 244   __libc_setup_tls (TLS_INIT_TCB_SIZE, TLS_INIT_TCB_ALIGN);
 245 }