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, 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 static dtv_t 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 /* Initial dtv of the main thread, not allocated with normal malloc.  */
  69 void *_dl_initial_dtv = &static_dtv[1];
  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 #if TLS_TCB_AT_TP
 104   GL(dl_tls_static_size) += TLS_TCB_SIZE;
 105 #endif
 106   GL(dl_tls_static_used) = memsz;
 107   /* The alignment requirement for the static TLS block.  */
 108   GL(dl_tls_static_align) = align;
 109   /* Number of elements in the static TLS block.  */
 110   GL(dl_tls_static_nelem) = GL(dl_tls_max_dtv_idx);
 111 }
 112
 113 void
 114 __libc_setup_tls (size_t tcbsize, size_t tcbalign)
 115 {
 116   void *tlsblock;
 117   size_t memsz = 0;
 118   size_t filesz = 0;
 119   void *initimage = NULL;
 120   size_t align = 0;
 121   size_t max_align = tcbalign;
 122   size_t tcb_offset;
 123   ElfW(Phdr) *phdr;
 124
 125   /* Look through the TLS segment if there is any.  */
 126   if (_dl_phdr != NULL)
 127     for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
 128       if (phdr->p_type == PT_TLS)
 129         {
 130           /* Remember the values we need.  */
 131           memsz = phdr->p_memsz;
 132           filesz = phdr->p_filesz;
 133           initimage = (void *) phdr->p_vaddr;
 134           align = phdr->p_align;
 135           if (phdr->p_align > max_align)
 136             max_align = phdr->p_align;
 137           break;
 138         }
 139
 140   /* We have to set up the TCB block which also (possibly) contains
 141      'errno'.  Therefore we avoid 'malloc' which might touch 'errno'.
 142      Instead we use 'sbrk' which would only uses 'errno' if it fails.
 143      In this case we are right away out of memory and the user gets
 144      what she/he deserves.
 145
 146      The initialized value of _dl_tls_static_size is provided by dl-open.c
 147      to request some surplus that permits dynamic loading of modules with
 148      IE-model TLS.  */
 149 #if TLS_TCB_AT_TP
 150   tcb_offset = roundup (memsz + GL(dl_tls_static_size), tcbalign);
 151   tlsblock = __sbrk (tcb_offset + tcbsize + max_align);
 152 #elif TLS_DTV_AT_TP
 153   tcb_offset = roundup (tcbsize, align ?: 1);
 154   tlsblock = __sbrk (tcb_offset + memsz + max_align
 155                      + TLS_PRE_TCB_SIZE + GL(dl_tls_static_size));
 156   tlsblock += TLS_PRE_TCB_SIZE;
 157 #else
 158   /* In case a model with a different layout for the TCB and DTV
 159      is defined add another #elif here and in the following #ifs.  */
 160 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 161 #endif
 162
 163   /* Align the TLS block.  */
 164   tlsblock = (void *) (((uintptr_t) tlsblock + max_align - 1)
 165                        & ~(max_align - 1));
 166
 167   /* Initialize the dtv.  [0] is the length, [1] the generation counter.  */
 168   static_dtv[0].counter = (sizeof (static_dtv) / sizeof (static_dtv[0])) - 2;
 169   // static_dtv[1].counter = 0;         would be needed if not already done
 170
 171   /* Initialize the TLS block.  */
 172 #if TLS_TCB_AT_TP
 173   static_dtv[2].pointer.val = ((char *) tlsblock + tcb_offset
 174                                - roundup (memsz, align ?: 1));
 175   static_map.l_tls_offset = roundup (memsz, align ?: 1);
 176 #elif TLS_DTV_AT_TP
 177   static_dtv[2].pointer.val = (char *) tlsblock + tcb_offset;
 178   static_map.l_tls_offset = tcb_offset;
 179 #else
 180 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 181 #endif
 182   static_dtv[2].pointer.is_static = true;
 183   /* sbrk gives us zero'd memory, so we don't need to clear the remainder.  */
 184   memcpy (static_dtv[2].pointer.val, initimage, filesz);
 185
 186   /* Install the pointer to the dtv.  */
 187
 188   /* Initialize the thread pointer.  */
 189 #if TLS_TCB_AT_TP
 190   INSTALL_DTV ((char *) tlsblock + tcb_offset, static_dtv);
 191
 192   const char *lossage = TLS_INIT_TP ((char *) tlsblock + tcb_offset, 0);
 193 #elif TLS_DTV_AT_TP
 194   INSTALL_DTV (tlsblock, static_dtv);
 195   const char *lossage = TLS_INIT_TP (tlsblock, 0);
 196 #else
 197 # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 198 #endif
 199   if (__builtin_expect (lossage != NULL, 0))
 200     __libc_fatal (lossage);
 201
 202   /* We have to create a fake link map which normally would be created
 203      by the dynamic linker.  It just has to have enough information to
 204      make the TLS routines happy.  */
 205   static_map.l_tls_align = align;
 206   static_map.l_tls_blocksize = memsz;
 207   static_map.l_tls_initimage = initimage;
 208   static_map.l_tls_initimage_size = filesz;
 209   static_map.l_type = lt_executable;
 210   static_map.l_tls_modid = 1;
 211
 212   init_slotinfo ();
 213   // static_slotinfo.si.slotinfo[1].gen = 0; already zero
 214   static_slotinfo.si.slotinfo[1].map = &static_map;
 215
 216   memsz = roundup (memsz, align ?: 1);
 217
 218 #if TLS_DTV_AT_TP
 219   memsz += tcb_offset;
 220 #endif
 221
 222   init_static_tls (memsz, MAX (TLS_TCB_ALIGN, max_align));
 223 }
 224
 225 /* This is called only when the data structure setup was skipped at startup,
 226    when there was no need for it then.  Now we have dynamically loaded
 227    something needing TLS, or libpthread needs it.  */
 228 int
 229 internal_function
 230 _dl_tls_setup (void)
 231 {
 232   init_slotinfo ();
 233   init_static_tls (
 234 #if TLS_TCB_AT_TP
 235                    TLS_TCB_SIZE,
 236 #else
 237                    0,
 238 #endif
 239                    TLS_TCB_ALIGN);
 240   return 0;
 241 }
 242
 243
 244 /* This is the minimal initialization function used when libpthread is
 245    not used.  */
 246 void
 247 __attribute__ ((weak))
 248 __pthread_initialize_minimal (void)
 249 {
 250   __libc_setup_tls (TLS_INIT_TCB_SIZE, TLS_INIT_TCB_ALIGN);
 251 }