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 #  ifndef IS_IN_rtld
  85 #   define TLS_TCB_SIZE sizeof (struct _pthread_descr_struct)
  86 #  else
  87 #   include <nptl-struct-pthread.h>
  88 #   define TLS_TCB_SIZE \
  89   (sizeof (struct _pthread_descr_struct) > NPTL_STRUCT_PTHREAD_SIZE     \
  90    ? sizeof (struct _pthread_descr_struct) : NPTL_STRUCT_PTHREAD_SIZE)
  91 #  endif
  92
  93 /* Alignment requirements for the TCB.  */
  94 #  define TLS_TCB_ALIGN __alignof__ (struct _pthread_descr_struct)
  95
  96 /* The TCB can have any size and the memory following the address the
  97    thread pointer points to is unspecified.  Allocate the TCB there.  */
  98 #  define TLS_TCB_AT_TP 1
  99
 100
 101 /* Install the dtv pointer.  The pointer passed is to the element with
 102    index -1 which contain the length.  */
 103 #  define INSTALL_DTV(descr, dtvp) \
 104   ((tcbhead_t *) (descr))->dtv = (dtvp) + 1
 105
 106 /* Install new dtv for current thread.  */
 107 #  define INSTALL_NEW_DTV(dtv) \
 108   ({ struct _pthread_descr_struct *__descr;                                   \
 109      THREAD_SETMEM (__descr, p_header.data.dtvp, (dtv)); })
 110
 111 /* Return dtv of given thread descriptor.  */
 112 #  define GET_DTV(descr) \
 113   (((tcbhead_t *) (descr))->dtv)
 114
 115 #  ifdef __PIC__
 116 #   define TLS_EBX_ARG "r"
 117 #   define TLS_LOAD_EBX "xchgl %3, %%ebx\n\t"
 118 #  else
 119 #   define TLS_EBX_ARG "b"
 120 #   define TLS_LOAD_EBX
 121 #  endif
 122
 123 #  if !defined IS_IN_linuxthreads && !defined DO_MODIFY_LDT
 124 #   include "useldt.h"          /* For the structure.  */
 125 #  endif
 126 #  if __ASSUME_LDT_WORKS > 0
 127 #   define TLS_DO_MODIFY_LDT_KERNEL_CHECK(doit) (doit) /* Nothing to check.  */
 128 #  else
 129 #   define TLS_DO_MODIFY_LDT_KERNEL_CHECK(doit)                               \
 130   (__builtin_expect (GLRO(dl_osversion) < 131939, 0)                          \
 131    ? "kernel too old for thread-local storage support\n"                              \
 132    : (doit))
 133 #  endif
 134
 135 #  define TLS_DO_MODIFY_LDT(descr, nr)                                        \
 136 TLS_DO_MODIFY_LDT_KERNEL_CHECK(                                               \
 137 ({                                                                            \
 138   struct modify_ldt_ldt_s ldt_entry =                                         \
 139     { nr, (unsigned long int) (descr), 0xfffff /* 4GB in pages */,            \
 140       1, 0, 0, 1, 0, 1, 0 };                                                  \
 141   int result;                                                                 \
 142   asm volatile (TLS_LOAD_EBX                                                  \
 143                 "int $0x80\n\t"                                               \
 144                 TLS_LOAD_EBX                                                  \
 145                 : "=a" (result)                                               \
 146                 : "0" (__NR_modify_ldt),                                      \
 147                 /* The extra argument with the "m" constraint is necessary    \
 148                    to let the compiler know that we are accessing LDT_ENTRY   \
 149                    here.  */                                                  \
 150                 "m" (ldt_entry), TLS_EBX_ARG (1), "c" (&ldt_entry),           \
 151                 "d" (sizeof (ldt_entry)));                                    \
 152   __builtin_expect (result, 0) == 0                                           \
 153   ? ({ asm ("movw %w0, %%gs" : : "q" ((nr) * 8 + 7)); NULL; })                \
 154   : "cannot set up LDT for thread-local storage\n";                           \
 155 }))
 156
 157 #  define TLS_DO_SET_THREAD_AREA(descr, secondcall)                           \
 158 ({                                                                            \
 159   struct modify_ldt_ldt_s ldt_entry =                                         \
 160     { -1, (unsigned long int) (descr), 0xfffff /* 4GB in pages */,            \
 161       1, 0, 0, 1, 0, 1, 0 };                                                  \
 162   int result;                                                                 \
 163   if (secondcall)                                                             \
 164     ldt_entry.entry_number = ({ int _gs;                                      \
 165                                 asm ("movw %%gs, %w0" : "=q" (_gs));          \
 166                                 (_gs & 0xffff) >> 3; });                      \
 167   asm volatile (TLS_LOAD_EBX                                                  \
 168                 "int $0x80\n\t"                                               \
 169                 TLS_LOAD_EBX                                                  \
 170                 : "=a" (result), "=m" (ldt_entry.entry_number)                \
 171                 : "0" (__NR_set_thread_area),                                 \
 172                 /* The extra argument with the "m" constraint is necessary    \
 173                    to let the compiler know that we are accessing LDT_ENTRY   \
 174                    here.  */                                                  \
 175                 TLS_EBX_ARG (&ldt_entry), "m" (ldt_entry));                   \
 176   if (__builtin_expect (result, 0) == 0)                                      \
 177     asm ("movw %w0, %%gs" : : "q" (ldt_entry.entry_number * 8 + 3));          \
 178   result;                                                                     \
 179 })
 180
 181 #  ifdef __ASSUME_SET_THREAD_AREA_SYSCALL
 182 #   define TLS_SETUP_GS_SEGMENT(descr, secondcall)                            \
 183   (TLS_DO_SET_THREAD_AREA (descr, secondcall)                                 \
 184    ? "set_thread_area failed when setting up thread-local storage\n" : NULL)
 185 #  elif defined __NR_set_thread_area
 186 #   define TLS_SETUP_GS_SEGMENT(descr, secondcall) \
 187   (TLS_DO_SET_THREAD_AREA (descr, secondcall)                                 \
 188    ? TLS_DO_MODIFY_LDT (descr, 0) : NULL)
 189 #  else
 190 #   define TLS_SETUP_GS_SEGMENT(descr, secondcall) \
 191   TLS_DO_MODIFY_LDT ((descr), 0)
 192 #  endif
 193
 194 #if defined NEED_DL_SYSINFO
 195 # define INIT_SYSINFO \
 196   head->sysinfo = GLRO(dl_sysinfo)
 197 #else
 198 # define INIT_SYSINFO
 199 #endif
 200
 201 /* Code to initially initialize the thread pointer.  This might need
 202    special attention since 'errno' is not yet available and if the
 203    operation can cause a failure 'errno' must not be touched.
 204
 205    The value of this macro is null if successful, or an error string.  */
 206 #  define TLS_INIT_TP(descr, secondcall)                                      \
 207   ({                                                                          \
 208     void *_descr = (descr);                                                   \
 209     tcbhead_t *head = _descr;                                                 \
 210                                                                               \
 211     head->tcb = _descr;                                                       \
 212     /* For now the thread descriptor is at the same address.  */              \
 213     head->self = _descr;                                                      \
 214                                                                               \
 215     INIT_SYSINFO;                                                             \
 216     TLS_SETUP_GS_SEGMENT (_descr, secondcall);                                \
 217   })
 218
 219 /* Indicate that dynamic linker shouldn't try to initialize TLS even
 220    when no PT_TLS segments are found in the program and libraries
 221    it is linked against.  */
 222 #  define TLS_INIT_TP_EXPENSIVE 1
 223
 224 /* Return the address of the dtv for the current thread.  */
 225 #  define THREAD_DTV() \
 226   ({ struct _pthread_descr_struct *__descr;                                   \
 227      THREAD_GETMEM (__descr, p_header.data.dtvp); })
 228
 229 # endif /* HAVE_TLS_SUPPORT && (FLOATING_STACKS || !IS_IN_libpthread) */
 230 #endif /* __ASSEMBLER__ */
 231
 232 #endif  /* tls.h */