csu/libc-tls.c

   1 /* Initialization code for TLS in statically linked application.
   2    Copyright (C) 2002-2015 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
  46 /* Highest dtv index currently needed.  */
  47 size_t _dl_tls_max_dtv_idx;
  48 /* Flag signalling whether there are gaps in the module ID allocation.  */
  49 bool _dl_tls_dtv_gaps;
  50 /* Information about the dtv slots.  */
  51 struct dtv_slotinfo_list *_dl_tls_dtv_slotinfo_list;
  52 /* Number of modules in the static TLS block.  */
  53 size_t _dl_tls_static_nelem;
  54 /* Size of the static TLS block.  Giving this initialized value
  55    preallocates some surplus bytes in the static TLS area.  */
  56 size_t _dl_tls_static_size = 2048;
  57 /* Size actually allocated in the static TLS block.  */
  58 size_t _dl_tls_static_used;
  59 /* Alignment requirement of the static TLS block.  */
  60 size_t _dl_tls_static_align;
  61
  62 /* Generation counter for the dtv.  */
  63 size_t _dl_tls_generation;
  64
  65
  66 /* Additional definitions needed by TLS initialization.  */
  67 #ifdef TLS_INIT_HELPER
  68 TLS_INIT_HELPER
  69 #endif
  70
  71 static void
  72 init_slotinfo (void)
  73 {
  74   /* Create the slotinfo list.  */
  75   static_slotinfo.si.len = (((char *) (&static_slotinfo + 1)
  76                              - (char *) &static_slotinfo.si.slotinfo[0])
  77                             / sizeof static_slotinfo.si.slotinfo[0]);
  78   // static_slotinfo.si.next = NULL;    already zero
  79
  80   /* The slotinfo list.  Will be extended by the code doing dynamic
  81      linking.  */
  82   GL(dl_tls_max_dtv_idx) = 1;
  83   GL(dl_tls_dtv_slotinfo_list) = &static_slotinfo.si;
  84 }
  85
  86 static void
  87 init_static_tls (size_t memsz, size_t align)
  88 {
  89   /* That is the size of the TLS memory for this object.  The initialized
  90      value of _dl_tls_static_size is provided by dl-open.c to request some
  91      surplus that permits dynamic loading of modules with IE-model TLS.  */
  92   GL(dl_tls_static_size) = roundup (memsz + GL(dl_tls_static_size),
  93                                     TLS_TCB_ALIGN);
  94 #if TLS_TCB_AT_TP
  95   GL(dl_tls_static_size) += TLS_TCB_SIZE;
  96 #endif
  97   GL(dl_tls_static_used) = memsz;
  98   /* The alignment requirement for the static TLS block.  */
  99   GL(dl_tls_static_align) = align;
 100   /* Number of elements in the static TLS block.  */
 101   GL(dl_tls_static_nelem) = GL(dl_tls_max_dtv_idx);
 102 }
 103
 104 void
 105 __libc_setup_tls (size_t tcbsize, size_t tcbalign)
 106 {
 107   void *tlsblock;
 108   size_t memsz = 0;
 109   size_t filesz = 0;
 110   void *initimage = NULL;
 111   size_t align = 0;
 112   size_t max_align = tcbalign;
 113   size_t tcb_offset;
 114   const ElfW(Phdr) *phdr;
 115
 116   /* Look through the TLS segment if there is any.  */
 117   if (_dl_phdr != NULL)
 118     for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
 119       if (phdr->p_type == PT_TLS)
 120         {
 121           /* Remember the values we need.  */
 122           memsz = phdr->p_memsz;
 123           filesz = phdr->p_filesz;
 124           initimage = (void *) phdr->p_vaddr;
 125           align = phdr->p_align;
 126           if (phdr->p_align > max_align)
 127             max_align = phdr->p_align;
 128           break;
 129         }
 130
 131   /* We have to set up the TCB block which also (possibly) contains
 132      'errno'.  Therefore we avoid 'malloc' which might touch 'errno'.
 133      Instead we use 'sbrk' which would only uses 'errno' if it fails.
 134      In this case we are right away out of memory and the user gets
 135      what she/he deserves.
 136
 137      The initialized value of _dl_tls_static_size is provided by dl-open.c
 138      to request some surplus that permits dynamic loading of modules with
 139      IE-model TLS.  */
 140 #if TLS_TCB_AT_TP
 141   /* Align the TCB offset to the maximum alignment, as
 142      _dl_allocate_tls_storage (in elf/dl-tls.c) does using __libc_memalign
 143      and dl_tls_static_align.  */
 144   tcb_offset = roundup (memsz + GL(dl_tls_static_size), max_align);
 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   struct link_map *main_map = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
 166
 167   /* Initialize the TLS block.  */
 168 #if TLS_TCB_AT_TP
 169   _dl_static_dtv[2].pointer.val = ((char *) tlsblock + tcb_offset
 170                                - roundup (memsz, align ?: 1));
 171   main_map->l_tls_offset = roundup (memsz, align ?: 1);
 172 #elif TLS_DTV_AT_TP
 173   _dl_static_dtv[2].pointer.val = (char *) tlsblock + tcb_offset;
 174   main_map->l_tls_offset = tcb_offset;
 175 #else
 176 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 177 #endif
 178   _dl_static_dtv[2].pointer.is_static = true;
 179   /* sbrk gives us zero'd memory, so we don't need to clear the remainder.  */
 180   memcpy (_dl_static_dtv[2].pointer.val, initimage, filesz);
 181
 182   /* Install the pointer to the dtv.  */
 183
 184   /* Initialize the thread pointer.  */
 185 #if TLS_TCB_AT_TP
 186   INSTALL_DTV ((char *) tlsblock + tcb_offset, _dl_static_dtv);
 187
 188   const char *lossage = TLS_INIT_TP ((char *) tlsblock + tcb_offset);
 189 #elif TLS_DTV_AT_TP
 190   INSTALL_DTV (tlsblock, _dl_static_dtv);
 191   const char *lossage = TLS_INIT_TP (tlsblock);
 192 #else
 193 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 194 #endif
 195   if (__builtin_expect (lossage != NULL, 0))
 196     __libc_fatal (lossage);
 197
 198   /* Update the executable's link map with enough information to make
 199      the TLS routines happy.  */
 200   main_map->l_tls_align = align;
 201   main_map->l_tls_blocksize = memsz;
 202   main_map->l_tls_initimage = initimage;
 203   main_map->l_tls_initimage_size = filesz;
 204   main_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 = main_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 }