csu/libc-tls.c

   1 /* Initialization code for TLS in statically linked application.
   2    Copyright (C) 2002-2012 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 extern ElfW(Phdr) *_dl_phdr;
  32 extern size_t _dl_phnum;
  33
  34
  35 dtv_t _dl_static_dtv[2 + TLS_SLOTINFO_SURPLUS];
  36
  37
  38 static struct
  39 {
  40   struct dtv_slotinfo_list si;
  41   /* The dtv_slotinfo_list data structure does not include the actual
  42      information since it is defined as an array of size zero.  We define
  43      here the necessary entries.  Note that it is not important whether
  44      there is padding or not since we will always access the information
  45      through the 'si' element.  */
  46   struct dtv_slotinfo info[2 + TLS_SLOTINFO_SURPLUS];
  47 } static_slotinfo;
  48
  49 /* Fake link map for the application.  */
  50 static struct link_map static_map;
  51
  52
  53 /* Highest dtv index currently needed.  */
  54 size_t _dl_tls_max_dtv_idx;
  55 /* Flag signalling whether there are gaps in the module ID allocation.  */
  56 bool _dl_tls_dtv_gaps;
  57 /* Information about the dtv slots.  */
  58 struct dtv_slotinfo_list *_dl_tls_dtv_slotinfo_list;
  59 /* Number of modules in the static TLS block.  */
  60 size_t _dl_tls_static_nelem;
  61 /* Size of the static TLS block.  Giving this initialized value
  62    preallocates some surplus bytes in the static TLS area.  */
  63 size_t _dl_tls_static_size = 2048;
  64 /* Size actually allocated in the static TLS block.  */
  65 size_t _dl_tls_static_used;
  66 /* Alignment requirement of the static TLS block.  */
  67 size_t _dl_tls_static_align;
  68
  69 /* Generation counter for the dtv.  */
  70 size_t _dl_tls_generation;
  71
  72
  73 /* Additional definitions needed by TLS initialization.  */
  74 #ifdef TLS_INIT_HELPER
  75 TLS_INIT_HELPER
  76 #endif
  77
  78 static inline void
  79 init_slotinfo (void)
  80 {
  81   /* Create the slotinfo list.  */
  82   static_slotinfo.si.len = (((char *) (&static_slotinfo + 1)
  83                              - (char *) &static_slotinfo.si.slotinfo[0])
  84                             / sizeof static_slotinfo.si.slotinfo[0]);
  85   // static_slotinfo.si.next = NULL;    already zero
  86
  87   /* The slotinfo list.  Will be extended by the code doing dynamic
  88      linking.  */
  89   GL(dl_tls_max_dtv_idx) = 1;
  90   GL(dl_tls_dtv_slotinfo_list) = &static_slotinfo.si;
  91 }
  92
  93 static inline void
  94 init_static_tls (size_t memsz, size_t align)
  95 {
  96   /* That is the size of the TLS memory for this object.  The initialized
  97      value of _dl_tls_static_size is provided by dl-open.c to request some
  98      surplus that permits dynamic loading of modules with IE-model TLS.  */
  99   GL(dl_tls_static_size) = roundup (memsz + GL(dl_tls_static_size),
 100                                     TLS_TCB_ALIGN);
 101 #if TLS_TCB_AT_TP
 102   GL(dl_tls_static_size) += TLS_TCB_SIZE;
 103 #endif
 104   GL(dl_tls_static_used) = memsz;
 105   /* The alignment requirement for the static TLS block.  */
 106   GL(dl_tls_static_align) = align;
 107   /* Number of elements in the static TLS block.  */
 108   GL(dl_tls_static_nelem) = GL(dl_tls_max_dtv_idx);
 109 }
 110
 111 void
 112 __libc_setup_tls (size_t tcbsize, size_t tcbalign)
 113 {
 114   void *tlsblock;
 115   size_t memsz = 0;
 116   size_t filesz = 0;
 117   void *initimage = NULL;
 118   size_t align = 0;
 119   size_t max_align = tcbalign;
 120   size_t tcb_offset;
 121   ElfW(Phdr) *phdr;
 122
 123   /* Look through the TLS segment if there is any.  */
 124   if (_dl_phdr != NULL)
 125     for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
 126       if (phdr->p_type == PT_TLS)
 127         {
 128           /* Remember the values we need.  */
 129           memsz = phdr->p_memsz;
 130           filesz = phdr->p_filesz;
 131           initimage = (void *) phdr->p_vaddr;
 132           align = phdr->p_align;
 133           if (phdr->p_align > max_align)
 134             max_align = phdr->p_align;
 135           break;
 136         }
 137
 138   /* We have to set up the TCB block which also (possibly) contains
 139      'errno'.  Therefore we avoid 'malloc' which might touch 'errno'.
 140      Instead we use 'sbrk' which would only uses 'errno' if it fails.
 141      In this case we are right away out of memory and the user gets
 142      what she/he deserves.
 143
 144      The initialized value of _dl_tls_static_size is provided by dl-open.c
 145      to request some surplus that permits dynamic loading of modules with
 146      IE-model TLS.  */
 147 #if TLS_TCB_AT_TP
 148   tcb_offset = roundup (memsz + GL(dl_tls_static_size), tcbalign);
 149   tlsblock = __sbrk (tcb_offset + tcbsize + max_align);
 150 #elif TLS_DTV_AT_TP
 151   tcb_offset = roundup (tcbsize, align ?: 1);
 152   tlsblock = __sbrk (tcb_offset + memsz + max_align
 153                      + TLS_PRE_TCB_SIZE + GL(dl_tls_static_size));
 154   tlsblock += TLS_PRE_TCB_SIZE;
 155 #else
 156   /* In case a model with a different layout for the TCB and DTV
 157      is defined add another #elif here and in the following #ifs.  */
 158 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 159 #endif
 160
 161   /* Align the TLS block.  */
 162   tlsblock = (void *) (((uintptr_t) tlsblock + max_align - 1)
 163                        & ~(max_align - 1));
 164
 165   /* Initialize the dtv.  [0] is the length, [1] the generation counter.  */
 166   _dl_static_dtv[0].counter = (sizeof (_dl_static_dtv) / sizeof (_dl_static_dtv[0])) - 2;
 167   // _dl_static_dtv[1].counter = 0;             would be needed if not already done
 168
 169   /* Initialize the TLS block.  */
 170 #if TLS_TCB_AT_TP
 171   _dl_static_dtv[2].pointer.val = ((char *) tlsblock + tcb_offset
 172                                - roundup (memsz, align ?: 1));
 173   static_map.l_tls_offset = roundup (memsz, align ?: 1);
 174 #elif TLS_DTV_AT_TP
 175   _dl_static_dtv[2].pointer.val = (char *) tlsblock + tcb_offset;
 176   static_map.l_tls_offset = tcb_offset;
 177 #else
 178 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 179 #endif
 180   _dl_static_dtv[2].pointer.is_static = true;
 181   /* sbrk gives us zero'd memory, so we don't need to clear the remainder.  */
 182   memcpy (_dl_static_dtv[2].pointer.val, initimage, filesz);
 183
 184   /* Install the pointer to the dtv.  */
 185
 186   /* Initialize the thread pointer.  */
 187 #if TLS_TCB_AT_TP
 188   INSTALL_DTV ((char *) tlsblock + tcb_offset, _dl_static_dtv);
 189
 190   const char *lossage = TLS_INIT_TP ((char *) tlsblock + tcb_offset, 0);
 191 #elif TLS_DTV_AT_TP
 192   INSTALL_DTV (tlsblock, _dl_static_dtv);
 193   const char *lossage = TLS_INIT_TP (tlsblock, 0);
 194 #else
 195 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 196 #endif
 197   if (__builtin_expect (lossage != NULL, 0))
 198     __libc_fatal (lossage);
 199
 200   /* We have to create a fake link map which normally would be created
 201      by the dynamic linker.  It just has to have enough information to
 202      make the TLS routines happy.  */
 203   static_map.l_tls_align = align;
 204   static_map.l_tls_blocksize = memsz;
 205   static_map.l_tls_initimage = initimage;
 206   static_map.l_tls_initimage_size = filesz;
 207   static_map.l_type = lt_executable;
 208   static_map.l_tls_modid = 1;
 209
 210   init_slotinfo ();
 211   // static_slotinfo.si.slotinfo[1].gen = 0; already zero
 212   static_slotinfo.si.slotinfo[1].map = &static_map;
 213
 214   memsz = roundup (memsz, align ?: 1);
 215
 216 #if 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 }