sysdeps/generic/libc-tls.c

   1 /* Initialization code for TLS in statically linked application.
   2    Copyright (C) 2002 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
  25
  26 #ifdef USE_TLS
  27 extern ElfW(Phdr) *_dl_phdr;
  28 extern size_t _dl_phnum;
  29
  30
  31 /* DTV with just one element plus overhead.  */
  32 static dtv_t static_dtv[3];
  33
  34
  35 static struct
  36 {
  37   struct dtv_slotinfo_list si;
  38   /* The dtv_slotinfo_list data structure does not include the actual
  39      informatin since it is defined as an array of size zero.  We
  40      define here the necessary entries.  Not that it is not important
  41      whether there is padding or not since we will always access the
  42      informatin through the 'si' element.  */
  43   struct dtv_slotinfo info[2 + TLS_SLOTINFO_SURPLUS];
  44 } static_slotinfo;
  45
  46 /* Fake link map for the application.  */
  47 static struct link_map static_map;
  48
  49
  50 /* Additional definitions needed by TLS initialization.  */
  51 #ifdef TLS_INIT_HELPER
  52 TLS_INIT_HELPER
  53 #endif
  54
  55
  56 void
  57 __libc_setup_tls (size_t tcbsize, size_t tcbalign)
  58 {
  59   void *tlsblock;
  60   size_t memsz = 0;
  61   size_t filesz = 0;
  62   void *initimage = NULL;
  63   size_t align = 0;
  64   size_t max_align = tcbalign;
  65   size_t tcb_offset;
  66   ElfW(Phdr) *phdr;
  67
  68   /* Look through the TLS segment if there is any.  */
  69   if (_dl_phdr != NULL)
  70     for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
  71       if (phdr->p_type == PT_TLS)
  72         {
  73           /* Remember the values we need.  */
  74           memsz = phdr->p_memsz;
  75           filesz = phdr->p_filesz;
  76           initimage = (void *) phdr->p_vaddr;
  77           align = phdr->p_align;
  78           if (phdr->p_align > max_align)
  79             max_align = phdr->p_align;
  80           break;
  81         }
  82
  83   if (memsz == 0 && tcbsize == 0)
  84     /* We do not need a TLS block and no thread descriptor.  */
  85     return;
  86
  87   /* We have to set up the TCB block which also (possibly) contains
  88      'errno'.  Therefore we avoid 'malloc' which might touch 'errno'.
  89      Instead we use 'sbrk' which would only uses 'errno' if it fails.
  90      In this case we are right away out of memory and the user gets
  91      what she/he deserves.  */
  92 # if TLS_TCB_AT_TP
  93   tlsblock = __sbrk (roundup (memsz, tcbalign) + tcbsize + max_align);
  94 # elif TLS_DTV_AT_TP
  95   tlsblock = __sbrk (roundup (tcbsize, align) + memsz + max_align);
  96 # else
  97   /* In case a model with a different layout for the TCB and DTV
  98      is defined add another #elif here and in the following #ifs.  */
  99 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 100 # endif
 101
 102   /* Align the TLS block.  */
 103   tlsblock = (void *) (((uintptr_t) tlsblock + max_align - 1)
 104                        & ~(max_align - 1));
 105
 106   /* Initialize the dtv.  [0] is the length, [1] the generation counter.  */
 107   static_dtv[0].counter = 1;
 108   // static_dtv[1].counter = 0;         would be needed if not already done
 109
 110   /* Initialize the TLS block.  */
 111 # if TLS_TCB_AT_TP
 112   static_dtv[2].pointer = tlsblock;
 113 # elif TLS_DTV_AT_TP
 114   tcb_offset = roundup (tcbsize, align);
 115   static_dtv[2].pointer = (char *) tlsblock + tcb_offset;
 116 # else
 117 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 118 # endif
 119   memset (__mempcpy (static_dtv[2].pointer, initimage, filesz),
 120           '\0', memsz - filesz);
 121
 122   /* Install the pointer to the dtv.  */
 123
 124   /* Initialize the thread pointer.  */
 125 # if TLS_TCB_AT_TP
 126   tcb_offset = roundup (memsz, tcbalign);
 127
 128   INSTALL_DTV ((char *) tlsblock + tcb_offset, static_dtv);
 129
 130   TLS_INIT_TP ((char *) tlsblock + tcb_offset, 0);
 131 # elif TLS_DTV_AT_TP
 132   INSTALL_DTV (tlsblock, static_dtv);
 133   TLS_INIT_TP (tlsblock, 0);
 134 # else
 135 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 136 # endif
 137
 138   /* We have to create a fake link map which normally would be created
 139      by the dynamic linker.  It just has to have enough information to
 140      make the TLS routines happy.  */
 141   static_map.l_tls_align = align;
 142   static_map.l_tls_blocksize = memsz;
 143   static_map.l_tls_initimage_size = filesz;
 144   static_map.l_tls_offset = tcb_offset;
 145   static_map.l_type = lt_executable;
 146   static_map.l_tls_modid = 1;
 147
 148   /* Create the slotinfo list.  */
 149   static_slotinfo.si.len = 1;   /* Only one element.  */
 150   // static_slotinfo.si.next = NULL;    already zero
 151
 152   static_slotinfo.si.slotinfo[1].gen = 0;
 153   static_slotinfo.si.slotinfo[1].map = &static_map;
 154
 155   /* The slotinfo list.  Will be extended by the code doing dynamic
 156      linking.  */
 157   GL(dl_tls_max_dtv_idx) = 1;
 158   GL(dl_tls_dtv_slotinfo_list) = &static_slotinfo.si;
 159
 160   /* That is the size of the TLS memory for this object.  */
 161   GL(dl_tls_static_size) = (roundup (memsz, align ?: 1)
 162 # if TLS_TCB_AT_TP
 163                             + tcbsize
 164 # endif
 165                             );
 166   /* The alignment requirement for the static TLS block.  */
 167   GL(dl_tls_static_align) = MAX (TLS_TCB_ALIGN, max_align);
 168   /* Number of elements in the static TLS block.  */
 169   GL(dl_tls_static_nelem) = GL(dl_tls_max_dtv_idx);
 170 }
 171
 172
 173 /* This is the minimal initialization function used when libpthread is
 174    not used.  */
 175 void
 176 __attribute__ ((weak))
 177 __pthread_initialize_minimal (void)
 178 {
 179   __libc_setup_tls (TLS_INIT_TCB_SIZE, TLS_INIT_TCB_ALIGN);
 180 }
 181 #endif