libpthread/nptl/sysdeps/generic/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, 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 #include <elf.h>
  26 #include <link.h>
  27 #include <string.h>
  28 #include <stdlib.h>
  29 #include <sys/mman.h>
  30
  31 #ifdef SHARED
  32  #error makefile bug, this file is for static only
  33 #endif
  34
  35 #if USE_TLS
  36 extern ElfW(Phdr) *_dl_phdr;
  37 extern size_t _dl_phnum;
  38
  39 #ifdef __FDPIC__
  40 /* phdr->p_vaddr is not valid in FDPIC mode. To find tdata start we
  41    use the linker script defined symbol __tdata_start.  */
  42 extern int __tdata_start;
  43 #endif
  44
  45 static dtv_t static_dtv[2 + TLS_SLOTINFO_SURPLUS];
  46
  47
  48 static struct
  49 {
  50   struct dtv_slotinfo_list si;
  51   /* The dtv_slotinfo_list data structure does not include the actual
  52      information since it is defined as an array of size zero.  We define
  53      here the necessary entries.  Note that it is not important whether
  54      there is padding or not since we will always access the information
  55      through the 'si' element.  */
  56   struct dtv_slotinfo info[2 + TLS_SLOTINFO_SURPLUS];
  57 } static_slotinfo;
  58
  59 /* Fake link map for the application.  */
  60 static struct link_map static_map;
  61
  62
  63 /* Highest dtv index currently needed.  */
  64 size_t _dl_tls_max_dtv_idx;
  65 /* Flag signalling whether there are gaps in the module ID allocation.  */
  66 bool _dl_tls_dtv_gaps;
  67 /* Information about the dtv slots.  */
  68 struct dtv_slotinfo_list *_dl_tls_dtv_slotinfo_list;
  69 /* Number of modules in the static TLS block.  */
  70 size_t _dl_tls_static_nelem;
  71 /* Size of the static TLS block.  */
  72 size_t _dl_tls_static_size;
  73 /* Size actually allocated in the static TLS block.  */
  74 size_t _dl_tls_static_used;
  75 /* Alignment requirement of the static TLS block.  */
  76 size_t _dl_tls_static_align;
  77
  78 /* Generation counter for the dtv.  */
  79 size_t _dl_tls_generation;
  80
  81
  82 /* Additional definitions needed by TLS initialization.  */
  83 #ifdef TLS_INIT_HELPER
  84 TLS_INIT_HELPER
  85 #endif
  86
  87 static inline void
  88 init_slotinfo (void)
  89 {
  90   /* Create the slotinfo list.  */
  91   static_slotinfo.si.len = (((char *) (&static_slotinfo + 1)
  92                              - (char *) &static_slotinfo.si.slotinfo[0])
  93                             / sizeof static_slotinfo.si.slotinfo[0]);
  94   // static_slotinfo.si.next = NULL;    already zero
  95
  96   /* The slotinfo list.  Will be extended by the code doing dynamic
  97      linking.  */
  98   GL(dl_tls_max_dtv_idx) = 1;
  99   GL(dl_tls_dtv_slotinfo_list) = &static_slotinfo.si;
 100 }
 101
 102 static inline void
 103 init_static_tls (size_t memsz, size_t align)
 104 {
 105   /* That is the size of the TLS memory for this object.  The initialized
 106      value of _dl_tls_static_size is provided by dl-open.c to request some
 107      surplus that permits dynamic loading of modules with IE-model TLS.  */
 108   GL(dl_tls_static_size) = roundup (memsz + GL(dl_tls_static_size),
 109                                     TLS_TCB_ALIGN);
 110   GL(dl_tls_static_used) = memsz;
 111   /* The alignment requirement for the static TLS block.  */
 112   GL(dl_tls_static_align) = align;
 113   /* Number of elements in the static TLS block.  */
 114   GL(dl_tls_static_nelem) = GL(dl_tls_max_dtv_idx);
 115 }
 116
 117 void __libc_setup_tls (size_t tcbsize, size_t tcbalign);
 118 void
 119 __libc_setup_tls (size_t tcbsize, size_t tcbalign)
 120 {
 121   void *tlsblock;
 122   size_t memsz = 0;
 123   size_t filesz = 0;
 124   void *initimage = NULL;
 125   size_t align = 0;
 126   size_t max_align = tcbalign;
 127   size_t tcb_offset;
 128   ElfW(Phdr) *phdr;
 129
 130   /* Look through the TLS segment if there is any.  */
 131   if (_dl_phdr != NULL)
 132     for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
 133       if (phdr->p_type == PT_TLS)
 134         {
 135           /* Remember the values we need.  */
 136           memsz = phdr->p_memsz;
 137           filesz = phdr->p_filesz;
 138 #ifdef __FDPIC__
 139           initimage = (void *) &__tdata_start;
 140 #else
 141           initimage = (void *) phdr->p_vaddr;
 142 #endif
 143           align = phdr->p_align;
 144           if (phdr->p_align > max_align)
 145             max_align = phdr->p_align;
 146           break;
 147         }
 148
 149   /* We have to set up the TCB block which also (possibly) contains
 150      'errno'.  Therefore we avoid 'malloc' which might touch 'errno'.
 151      Instead we use 'sbrk' which would only uses 'errno' if it fails.
 152      In this case we are right away out of memory and the user gets
 153      what she/he deserves.
 154
 155      The initialized value of _dl_tls_static_size is provided by dl-open.c
 156      to request some surplus that permits dynamic loading of modules with
 157      IE-model TLS.  */
 158   /* Use mmap instead of sbrk since this commit disables sbrk area
 159      for FDPIC MMU-less platforms:
 160      fs/binfmt_elf_fdpic.c: fix brk area overlap with stack on NOMMU
 161      https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/fs/binfmt_elf_fdpic.c?id=4ac313111018cb44ecc250445de5ccb93026a980
 162    */
 163 # if defined(TLS_TCB_AT_TP)
 164   tcb_offset = roundup (memsz + GL(dl_tls_static_size), tcbalign);
 165 #  if defined(__FDPIC__)
 166   tlsblock = mmap (NULL, tcb_offset + tcbsize + max_align,
 167                    PROT_READ|PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 168 #  else
 169   tlsblock = sbrk (tcb_offset + tcbsize + max_align);
 170 #  endif
 171 # elif defined(TLS_DTV_AT_TP)
 172   tcb_offset = roundup (tcbsize, align ?: 1);
 173 #  if defined(__FDPIC__)
 174   tlsblock = mmap (NULL, tcb_offset + memsz + max_align + TLS_PRE_TCB_SIZE + GL(dl_tls_static_size),
 175                    PROT_READ|PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 176 #  else
 177   tlsblock = sbrk (tcb_offset + memsz + max_align
 178                      + TLS_PRE_TCB_SIZE + GL(dl_tls_static_size));
 179 #  endif
 180   memset(tlsblock, '\0', tcb_offset + memsz + max_align + TLS_PRE_TCB_SIZE + GL(dl_tls_static_size));
 181   tlsblock += TLS_PRE_TCB_SIZE;
 182 # else
 183   /* In case a model with a different layout for the TCB and DTV
 184      is defined add another #elif here and in the following #ifs.  */
 185 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 186 # endif
 187
 188   /* Align the TLS block.  */
 189   tlsblock = (void *) (((uintptr_t) tlsblock + max_align - 1)
 190                        & ~(max_align - 1));
 191
 192   /* Initialize the dtv.  [0] is the length, [1] the generation counter.  */
 193   static_dtv[0].counter = (sizeof (static_dtv) / sizeof (static_dtv[0])) - 2;
 194   // static_dtv[1].counter = 0;         would be needed if not already done
 195
 196   /* Initialize the TLS block.  */
 197 # if defined(TLS_TCB_AT_TP)
 198   static_dtv[2].pointer.val = ((char *) tlsblock + tcb_offset
 199                                - roundup (memsz, align ?: 1));
 200   static_map.l_tls_offset = roundup (memsz, align ?: 1);
 201 # elif defined(TLS_DTV_AT_TP)
 202   static_dtv[2].pointer.val = (char *) tlsblock + tcb_offset;
 203   static_map.l_tls_offset = tcb_offset;
 204 # else
 205 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 206 # endif
 207   static_dtv[2].pointer.is_static = true;
 208   /* sbrk gives us zero'd memory, so we don't need to clear the remainder.  */
 209   memcpy (static_dtv[2].pointer.val, initimage, filesz);
 210
 211   /* Install the pointer to the dtv.  */
 212
 213   /* Initialize the thread pointer.  */
 214 # if defined(TLS_TCB_AT_TP)
 215   INSTALL_DTV ((char *) tlsblock + tcb_offset, static_dtv);
 216
 217   const char *lossage = TLS_INIT_TP ((char *) tlsblock + tcb_offset, 0);
 218 # elif defined(TLS_DTV_AT_TP)
 219   INSTALL_DTV (tlsblock, static_dtv);
 220   const char *lossage = (char *)TLS_INIT_TP (tlsblock, 0);
 221 # else
 222 #  error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
 223 # endif
 224   if (__builtin_expect (lossage != NULL, 0))
 225     abort();
 226
 227   /* We have to create a fake link map which normally would be created
 228      by the dynamic linker.  It just has to have enough information to
 229      make the TLS routines happy.  */
 230   static_map.l_tls_align = align;
 231   static_map.l_tls_blocksize = memsz;
 232   static_map.l_tls_initimage = initimage;
 233   static_map.l_tls_initimage_size = filesz;
 234   static_map.l_tls_modid = 1;
 235
 236   init_slotinfo ();
 237   // static_slotinfo.si.slotinfo[1].gen = 0; already zero
 238   static_slotinfo.si.slotinfo[1].map = &static_map;
 239
 240   memsz = roundup (memsz, align ?: 1);
 241
 242 # if defined(TLS_TCB_AT_TP)
 243   memsz += tcbsize;
 244 # elif defined(TLS_DTV_AT_TP)
 245   memsz += tcb_offset;
 246 # endif
 247
 248   init_static_tls (memsz, MAX (TLS_TCB_ALIGN, max_align));
 249 }
 250
 251 /* This is called only when the data structure setup was skipped at startup,
 252    when there was no need for it then.  Now we have dynamically loaded
 253    something needing TLS, or libpthread needs it.  */
 254 int
 255 internal_function
 256 _dl_tls_setup (void)
 257 {
 258   init_slotinfo ();
 259   init_static_tls (
 260 # if defined(TLS_TCB_AT_TP)
 261                    TLS_TCB_SIZE,
 262 # else
 263                    0,
 264 # endif
 265                    TLS_TCB_ALIGN);
 266   return 0;
 267 }
 268
 269 extern void __pthread_initialize_minimal(void) __attribute__((weak));
 270
 271 /* This is the minimal initialization function used when libpthread is
 272    not used.  */
 273 void
 274 __attribute__ ((weak))
 275 __pthread_initialize_minimal (void)
 276 {
 277   __libc_setup_tls (TLS_INIT_TCB_SIZE, TLS_INIT_TCB_ALIGN);
 278 }
 279
 280 #endif