csu/libc-tls.c

   1 /* Initialization code for TLS in statically linked application.
   2    Copyright (C) 2002-2006, 2009 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 #if TLS_TCB_AT_TP
 103   GL(dl_tls_static_size) += TLS_TCB_SIZE;
 104 #endif
 105   GL(dl_tls_static_used) = memsz;
 106   /* The alignment requirement for the static TLS block.  */
 107   GL(dl_tls_static_align) = align;
 108   /* Number of elements in the static TLS block.  */
 109   GL(dl_tls_static_nelem) = GL(dl_tls_max_dtv_idx);
 110 }
 111
 112 void
 113 __libc_setup_tls (size_t tcbsize, size_t tcbalign)
 114 {
 115   void *tlsblock;
 116   size_t memsz = 0;
 117   size_t filesz = 0;
 118   void *initimage = NULL;
 119   size_t align = 0;
 120   size_t max_align = tcbalign;
 121   size_t tcb_offset;
 122   ElfW(Phdr) *phdr;
 123
 124   /* Look through the TLS segment if there is any.  */
 125   if (_dl_phdr != NULL)
 126     for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
 127       if (phdr->p_type == PT_TLS)
 128         {
 129           /* Remember the values we need.  */
 130           memsz = phdr->p_memsz;
 131           filesz = phdr->p_filesz;
 132           initimage = (void *) phdr->p_vaddr;
 133           align = phdr->p_align;
 134           if (phdr->p_align > max_align)
 135             max_align = phdr->p_align;
 136           break;
 137         }
 138
 139   /* We have to set up the TCB block which also (possibly) contains
 140      'errno'.  Therefore we avoid 'malloc' which might touch 'errno'.
 141      Instead we use 'sbrk' which would only uses 'errno' if it fails.
 142      In this case we are right away out of memory and the user gets
 143      what she/he deserves.
 144
 145      The initialized value of _dl_tls_static_size is provided by dl-open.c
 146      to request some surplus that permits dynamic loading of modules with
 147      IE-model TLS.  */
 148 #if TLS_TCB_AT_TP
 149   tcb_offset = roundup (memsz + GL(dl_tls_static_size), tcbalign);
 150   tlsblock = __sbrk (tcb_offset + tcbsize + max_align);
 151 #elif TLS_DTV_AT_TP
 152   tcb_offset = roundup (tcbsize, align ?: 1);
 153   tlsblock = __sbrk (tcb_offset + memsz + max_align
 154                      + TLS_PRE_TCB_SIZE + GL(dl_tls_static_size));
 155   tlsblock += TLS_PRE_TCB_SIZE;
 156 #else
 157   /* In case a model with a different layout for the TCB and DTV
 158      is defined add another #elif here and in the following #ifs.  */
 159 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 160 #endif
 161
 162   /* Align the TLS block.  */
 163   tlsblock = (void *) (((uintptr_t) tlsblock + max_align - 1)
 164                        & ~(max_align - 1));
 165
 166   /* Initialize the dtv.  [0] is the length, [1] the generation counter.  */
 167   static_dtv[0].counter = (sizeof (static_dtv) / sizeof (static_dtv[0])) - 2;
 168   // static_dtv[1].counter = 0;         would be needed if not already done
 169
 170   /* Initialize the TLS block.  */
 171 #if TLS_TCB_AT_TP
 172   static_dtv[2].pointer.val = ((char *) tlsblock + tcb_offset
 173                                - roundup (memsz, align ?: 1));
 174   static_map.l_tls_offset = roundup (memsz, align ?: 1);
 175 #elif TLS_DTV_AT_TP
 176   static_dtv[2].pointer.val = (char *) tlsblock + tcb_offset;
 177   static_map.l_tls_offset = tcb_offset;
 178 #else
 179 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 180 #endif
 181   static_dtv[2].pointer.is_static = true;
 182   /* sbrk gives us zero'd memory, so we don't need to clear the remainder.  */
 183   memcpy (static_dtv[2].pointer.val, initimage, filesz);
 184
 185   /* Install the pointer to the dtv.  */
 186
 187   /* Initialize the thread pointer.  */
 188 #if TLS_TCB_AT_TP
 189   INSTALL_DTV ((char *) tlsblock + tcb_offset, static_dtv);
 190
 191   const char *lossage = TLS_INIT_TP ((char *) tlsblock + tcb_offset, 0);
 192 #elif TLS_DTV_AT_TP
 193   INSTALL_DTV (tlsblock, static_dtv);
 194   const char *lossage = TLS_INIT_TP (tlsblock, 0);
 195 #else
 196 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 197 #endif
 198   if (__builtin_expect (lossage != NULL, 0))
 199     __libc_fatal (lossage);
 200
 201   /* We have to create a fake link map which normally would be created
 202      by the dynamic linker.  It just has to have enough information to
 203      make the TLS routines happy.  */
 204   static_map.l_tls_align = align;
 205   static_map.l_tls_blocksize = memsz;
 206   static_map.l_tls_initimage = initimage;
 207   static_map.l_tls_initimage_size = filesz;
 208   static_map.l_type = lt_executable;
 209   static_map.l_tls_modid = 1;
 210
 211   init_slotinfo ();
 212   // static_slotinfo.si.slotinfo[1].gen = 0; already zero
 213   static_slotinfo.si.slotinfo[1].map = &static_map;
 214
 215   memsz = roundup (memsz, align ?: 1);
 216
 217 #if 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 }