linuxthreads/sysdeps/i386/tls.h

   1 /* Definition for thread-local data handling.  linuxthreads/i386 version.
   2    Copyright (C) 2002, 2003, 2004 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 #ifndef _TLS_H
  21 #define _TLS_H
  22
  23 # include <dl-sysdep.h>
  24 # include <pt-machine.h>
  25
  26 #ifndef __ASSEMBLER__
  27 # include <stddef.h>
  28 # include <stdint.h>
  29
  30 /* Type for the dtv.  */
  31 typedef union dtv
  32 {
  33   size_t counter;
  34   void *pointer;
  35 } dtv_t;
  36
  37
  38 typedef struct
  39 {
  40   void *tcb;            /* Pointer to the TCB.  Not necessary the
  41                            thread descriptor used by libpthread.  */
  42   dtv_t *dtv;
  43   void *self;           /* Pointer to the thread descriptor.  */
  44   int multiple_threads;
  45 #ifdef NEED_DL_SYSINFO
  46   uintptr_t sysinfo;
  47 #endif
  48 } tcbhead_t;
  49
  50 #else /* __ASSEMBLER__ */
  51 # include <tcb-offsets.h>
  52 #endif
  53
  54 /* We can support TLS only if the floating-stack support is available.
  55    However, we want to compile in the support and test at runtime whether
  56    the running kernel can support it or not.  To avoid bothering with the
  57    TLS support code at all, use configure --without-tls.
  58
  59    We need USE_TLS to be consistently defined, for ldsodefs.h conditionals.
  60    But some of the code below can cause problems in building libpthread
  61    (e.g. useldt.h will defined FLOATING_STACKS when it shouldn't).  */
  62
  63 #if defined HAVE_TLS_SUPPORT \
  64     && (defined FLOATING_STACKS || !defined IS_IN_libpthread)
  65
  66 /* Signal that TLS support is available.  */
  67 # define USE_TLS        1
  68
  69 # ifndef __ASSEMBLER__
  70 /* Get system call information.  */
  71 #  include <sysdep.h>
  72
  73
  74 /* Get the thread descriptor definition.  */
  75 #  include <linuxthreads/descr.h>
  76
  77 /* This is the size of the initial TCB.  */
  78 #  define TLS_INIT_TCB_SIZE sizeof (tcbhead_t)
  79
  80 /* Alignment requirements for the initial TCB.  */
  81 #  define TLS_INIT_TCB_ALIGN __alignof__ (tcbhead_t)
  82
  83 /* This is the size of the TCB.  */
  84 #  define TLS_TCB_SIZE sizeof (struct _pthread_descr_struct)
  85
  86 /* Alignment requirements for the TCB.  */
  87 #  define TLS_TCB_ALIGN __alignof__ (struct _pthread_descr_struct)
  88
  89 /* The TCB can have any size and the memory following the address the
  90    thread pointer points to is unspecified.  Allocate the TCB there.  */
  91 #  define TLS_TCB_AT_TP 1
  92
  93
  94 /* Install the dtv pointer.  The pointer passed is to the element with
  95    index -1 which contain the length.  */
  96 #  define INSTALL_DTV(descr, dtvp) \
  97   ((tcbhead_t *) (descr))->dtv = (dtvp) + 1
  98
  99 /* Install new dtv for current thread.  */
 100 #  define INSTALL_NEW_DTV(dtv) \
 101   ({ struct _pthread_descr_struct *__descr;                                   \
 102      THREAD_SETMEM (__descr, p_header.data.dtvp, (dtv)); })
 103
 104 /* Return dtv of given thread descriptor.  */
 105 #  define GET_DTV(descr) \
 106   (((tcbhead_t *) (descr))->dtv)
 107
 108 #  ifdef __PIC__
 109 #   define TLS_EBX_ARG "r"
 110 #   define TLS_LOAD_EBX "xchgl %3, %%ebx\n\t"
 111 #  else
 112 #   define TLS_EBX_ARG "b"
 113 #   define TLS_LOAD_EBX
 114 #  endif
 115
 116 #  if !defined IS_IN_linuxthreads && !defined DO_MODIFY_LDT
 117 #   include "useldt.h"          /* For the structure.  */
 118 #  endif
 119 #  if __ASSUME_LDT_WORKS > 0
 120 #   define TLS_DO_MODIFY_LDT_KERNEL_CHECK(doit) (doit) /* Nothing to check.  */
 121 #  else
 122 #   define TLS_DO_MODIFY_LDT_KERNEL_CHECK(doit)                               \
 123   (__builtin_expect (GLRO(dl_osversion) < 131939, 0)                          \
 124    ? "kernel too old for thread-local storage support\n"                              \
 125    : (doit))
 126 #  endif
 127
 128 #  define TLS_DO_MODIFY_LDT(descr, nr)                                        \
 129 TLS_DO_MODIFY_LDT_KERNEL_CHECK(                                               \
 130 ({                                                                            \
 131   struct modify_ldt_ldt_s ldt_entry =                                         \
 132     { nr, (unsigned long int) (descr), 0xfffff /* 4GB in pages */,            \
 133       1, 0, 0, 1, 0, 1, 0 };                                                  \
 134   int result;                                                                 \
 135   asm volatile (TLS_LOAD_EBX                                                  \
 136                 "int $0x80\n\t"                                               \
 137                 TLS_LOAD_EBX                                                  \
 138                 : "=a" (result)                                               \
 139                 : "0" (__NR_modify_ldt),                                      \
 140                 /* The extra argument with the "m" constraint is necessary    \
 141                    to let the compiler know that we are accessing LDT_ENTRY   \
 142                    here.  */                                                  \
 143                 "m" (ldt_entry), TLS_EBX_ARG (1), "c" (&ldt_entry),           \
 144                 "d" (sizeof (ldt_entry)));                                    \
 145   __builtin_expect (result, 0) == 0                                           \
 146   ? ({ asm ("movw %w0, %%gs" : : "q" ((nr) * 8 + 7)); NULL; })                \
 147   : "cannot set up LDT for thread-local storage\n";                           \
 148 }))
 149
 150 #  define TLS_DO_SET_THREAD_AREA(descr, secondcall)                           \
 151 ({                                                                            \
 152   struct modify_ldt_ldt_s ldt_entry =                                         \
 153     { -1, (unsigned long int) (descr), 0xfffff /* 4GB in pages */,            \
 154       1, 0, 0, 1, 0, 1, 0 };                                                  \
 155   int result;                                                                 \
 156   if (secondcall)                                                             \
 157     ldt_entry.entry_number = ({ int _gs;                                      \
 158                                 asm ("movw %%gs, %w0" : "=q" (_gs));          \
 159                                 (_gs & 0xffff) >> 3; });                      \
 160   asm volatile (TLS_LOAD_EBX                                                  \
 161                 "int $0x80\n\t"                                               \
 162                 TLS_LOAD_EBX                                                  \
 163                 : "=a" (result), "=m" (ldt_entry.entry_number)                \
 164                 : "0" (__NR_set_thread_area),                                 \
 165                 /* The extra argument with the "m" constraint is necessary    \
 166                    to let the compiler know that we are accessing LDT_ENTRY   \
 167                    here.  */                                                  \
 168                 TLS_EBX_ARG (&ldt_entry), "m" (ldt_entry));                   \
 169   if (__builtin_expect (result, 0) == 0)                                      \
 170     asm ("movw %w0, %%gs" : : "q" (ldt_entry.entry_number * 8 + 3));          \
 171   result;                                                                     \
 172 })
 173
 174 #  ifdef __ASSUME_SET_THREAD_AREA_SYSCALL
 175 #   define TLS_SETUP_GS_SEGMENT(descr, secondcall)                            \
 176   (TLS_DO_SET_THREAD_AREA (descr, secondcall)                                 \
 177    ? "set_thread_area failed when setting up thread-local storage\n" : NULL)
 178 #  elif defined __NR_set_thread_area
 179 #   define TLS_SETUP_GS_SEGMENT(descr, secondcall) \
 180   (TLS_DO_SET_THREAD_AREA (descr, secondcall)                                 \
 181    ? TLS_DO_MODIFY_LDT (descr, 0) : NULL)
 182 #  else
 183 #   define TLS_SETUP_GS_SEGMENT(descr, secondcall) \
 184   TLS_DO_MODIFY_LDT ((descr), 0)
 185 #  endif
 186
 187 #if defined NEED_DL_SYSINFO
 188 # define INIT_SYSINFO \
 189   head->sysinfo = GLRO(dl_sysinfo)
 190 #else
 191 # define INIT_SYSINFO
 192 #endif
 193
 194 /* Code to initially initialize the thread pointer.  This might need
 195    special attention since 'errno' is not yet available and if the
 196    operation can cause a failure 'errno' must not be touched.
 197
 198    The value of this macro is null if successful, or an error string.  */
 199 #  define TLS_INIT_TP(descr, secondcall)                                      \
 200   ({                                                                          \
 201     void *_descr = (descr);                                                   \
 202     tcbhead_t *head = _descr;                                                 \
 203                                                                               \
 204     head->tcb = _descr;                                                       \
 205     /* For now the thread descriptor is at the same address.  */              \
 206     head->self = _descr;                                                      \
 207                                                                               \
 208     INIT_SYSINFO;                                                             \
 209     TLS_SETUP_GS_SEGMENT (_descr, secondcall);                                \
 210   })
 211
 212 /* Indicate that dynamic linker shouldn't try to initialize TLS even
 213    when no PT_TLS segments are found in the program and libraries
 214    it is linked against.  */
 215 #  define TLS_INIT_TP_EXPENSIVE 1
 216
 217 /* Return the address of the dtv for the current thread.  */
 218 #  define THREAD_DTV() \
 219   ({ struct _pthread_descr_struct *__descr;                                   \
 220      THREAD_GETMEM (__descr, p_header.data.dtvp); })
 221
 222 # endif /* HAVE_TLS_SUPPORT && (FLOATING_STACKS || !IS_IN_libpthread) */
 223 #endif /* __ASSEMBLER__ */
 224
 225 #endif  /* tls.h */