sysdeps/generic/tls.h

   1 /* Definition for thread-local data handling.  Generic version.
   2    Copyright (C) 2002-2017 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 /* An architecture-specific version of this file has to defined a
  20    number of symbols:
  21
  22      TLS_TCB_AT_TP  or  TLS_DTV_AT_TP
  23
  24      The presence of one of these symbols signals which variant of
  25      the TLS ABI is used.  There are in the moment two variants
  26      available:
  27
  28      * the thread pointer points to a thread control block
  29
  30      * the thread pointer points to the dynamic thread vector
  31
  32
  33      TLS_TCB_SIZE
  34
  35      This is the size of the thread control block structure.  How
  36      this is actually defined depends on the ABI.  The thread control
  37      block could be internal descriptor of the thread library or
  38      just a data structure which allows finding the DTV.
  39
  40      TLS_INIT_TCB_SIZE
  41
  42      Similarly, but this value is only used at startup and in the
  43      dynamic linker itself.  There are no threads in use at that time.
  44
  45
  46      TLS_TCB_ALIGN
  47
  48      Alignment requirements for the TCB structure.
  49
  50      TLS_INIT_TCB_ALIGN
  51
  52      Similarly, but for the structure used at startup time.
  53
  54
  55      INSTALL_DTV(tcb, init_dtv)
  56
  57      This macro must install the given initial DTV into the thread control
  58      block TCB.  The normal runtime functionality must then be able to
  59      use the value.
  60
  61
  62      TLS_INIT_TP(tcb)
  63
  64      This macro must initialize the thread pointer to enable normal TLS
  65      operation.  The parameter is a pointer to the thread control block.
  66      ld.so calls this macro once.
  67
  68
  69      THREAD_DTV()
  70
  71      This macro returns the address of the DTV of the current thread.
  72      This normally is done using the thread register which points
  73      to the dtv or the TCB (from which the DTV can found).
  74   */