csu/libc-tls.c

   1 /* Initialization code for TLS in statically linked application.
   2    Copyright (C) 2002, 2003, 2004, 2005 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 static dtv_t static_dtv[2 + TLS_SLOTINFO_SURPLUS];
  38
  39
  40 static struct
  41 {
  42   struct dtv_slotinfo_list si;
  43   /* The dtv_slotinfo_list data structure does not include the actual
  44      information since it is defined as an array of size zero.  We define
  45      here the necessary entries.  Note that it is not important whether
  46      there is padding or not since we will always access the information
  47      through the 'si' element.  */
  48   struct dtv_slotinfo info[2 + TLS_SLOTINFO_SURPLUS];
  49 } static_slotinfo;
  50
  51 /* Fake link map for the application.  */
  52 static struct link_map static_map;
  53
  54
  55 /* Highest dtv index currently needed.  */
  56 size_t _dl_tls_max_dtv_idx;
  57 /* Flag signalling whether there are gaps in the module ID allocation.  */
  58 bool _dl_tls_dtv_gaps;
  59 /* Information about the dtv slots.  */
  60 struct dtv_slotinfo_list *_dl_tls_dtv_slotinfo_list;
  61 /* Number of modules in the static TLS block.  */
  62 size_t _dl_tls_static_nelem;
  63 /* Size of the static TLS block.  Giving this initialized value
  64    preallocates some surplus bytes in the static TLS area.  */
  65 size_t _dl_tls_static_size = 2048;
  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   /* We have to set up the TCB block which also (possibly) contains
 138      'errno'.  Therefore we avoid 'malloc' which might touch 'errno'.
 139      Instead we use 'sbrk' which would only uses 'errno' if it fails.
 140      In this case we are right away out of memory and the user gets
 141      what she/he deserves.
 142
 143      The initialized value of _dl_tls_static_size is provided by dl-open.c
 144      to request some surplus that permits dynamic loading of modules with
 145      IE-model TLS.  */
 146 # if TLS_TCB_AT_TP
 147   tcb_offset = roundup (memsz + GL(dl_tls_static_size), tcbalign);
 148   tlsblock = __sbrk (tcb_offset + tcbsize + max_align);
 149 # elif TLS_DTV_AT_TP
 150   tcb_offset = roundup (tcbsize, align ?: 1);
 151   tlsblock = __sbrk (tcb_offset + memsz + max_align
 152                      + TLS_PRE_TCB_SIZE + GL(dl_tls_static_size));
 153   tlsblock += TLS_PRE_TCB_SIZE;
 154 # else
 155   /* In case a model with a different layout for the TCB and DTV
 156      is defined add another #elif here and in the following #ifs.  */
 157 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 158 # endif
 159
 160   /* Align the TLS block.  */
 161   tlsblock = (void *) (((uintptr_t) tlsblock + max_align - 1)
 162                        & ~(max_align - 1));
 163
 164   /* Initialize the dtv.  [0] is the length, [1] the generation counter.  */
 165   static_dtv[0].counter = (sizeof (static_dtv) / sizeof (static_dtv[0])) - 2;
 166   // static_dtv[1].counter = 0;         would be needed if not already done
 167
 168   /* Initialize the TLS block.  */
 169 # if TLS_TCB_AT_TP
 170   static_dtv[2].pointer.val = ((char *) tlsblock + tcb_offset
 171                                - roundup (memsz, align ?: 1));
 172   static_map.l_tls_offset = roundup (memsz, align ?: 1);
 173 # elif TLS_DTV_AT_TP
 174   static_dtv[2].pointer.val = (char *) tlsblock + tcb_offset;
 175   static_map.l_tls_offset = tcb_offset;
 176 # else
 177 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 178 # endif
 179   static_dtv[2].pointer.is_static = true;
 180   /* sbrk gives us zero'd memory, so we don't need to clear the remainder.  */
 181   memcpy (static_dtv[2].pointer.val, initimage, filesz);
 182
 183   /* Install the pointer to the dtv.  */
 184
 185   /* Initialize the thread pointer.  */
 186 # if TLS_TCB_AT_TP
 187   INSTALL_DTV ((char *) tlsblock + tcb_offset, static_dtv);
 188
 189   const char *lossage = TLS_INIT_TP ((char *) tlsblock + tcb_offset, 0);
 190 # elif TLS_DTV_AT_TP
 191   INSTALL_DTV (tlsblock, static_dtv);
 192   const char *lossage = TLS_INIT_TP (tlsblock, 0);
 193 # else
 194 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 195 # endif
 196   if (__builtin_expect (lossage != NULL, 0))
 197     __libc_fatal (lossage);
 198
 199   /* We have to create a fake link map which normally would be created
 200      by the dynamic linker.  It just has to have enough information to
 201      make the TLS routines happy.  */
 202   static_map.l_tls_align = align;
 203   static_map.l_tls_blocksize = memsz;
 204   static_map.l_tls_initimage = initimage;
 205   static_map.l_tls_initimage_size = filesz;
 206   static_map.l_type = lt_executable;
 207   static_map.l_tls_modid = 1;
 208
 209   init_slotinfo ();
 210   // static_slotinfo.si.slotinfo[1].gen = 0; already zero
 211   static_slotinfo.si.slotinfo[1].map = &static_map;
 212
 213   memsz = roundup (memsz, align ?: 1);
 214
 215 # if TLS_TCB_AT_TP
 216   memsz += tcbsize;
 217 # elif TLS_DTV_AT_TP
 218   memsz += tcb_offset;
 219 # endif
 220
 221   init_static_tls (memsz, MAX (TLS_TCB_ALIGN, max_align));
 222 }
 223
 224 /* This is called only when the data structure setup was skipped at startup,
 225    when there was no need for it then.  Now we have dynamically loaded
 226    something needing TLS, or libpthread needs it.  */
 227 int
 228 internal_function
 229 _dl_tls_setup (void)
 230 {
 231   init_slotinfo ();
 232   init_static_tls (
 233 # if TLS_TCB_AT_TP
 234                    TLS_TCB_SIZE,
 235 # else
 236                    0,
 237 # endif
 238                    TLS_TCB_ALIGN);
 239   return 0;
 240 }
 241
 242
 243 /* This is the minimal initialization function used when libpthread is
 244    not used.  */
 245 void
 246 __attribute__ ((weak))
 247 __pthread_initialize_minimal (void)
 248 {
 249   __libc_setup_tls (TLS_INIT_TCB_SIZE, TLS_INIT_TCB_ALIGN);
 250 }
 251
 252 #elif defined NONTLS_INIT_TP
 253
 254 /* This is the minimal initialization function used when libpthread is
 255    not used.  */
 256 void
 257 __attribute__ ((weak))
 258 __pthread_initialize_minimal (void)
 259 {
 260   NONTLS_INIT_TP;
 261 }
 262
 263 #endif