sysdeps/mach/hurd/i386/tls.h

   1 /* Definitions for thread-local data handling.  Hurd/i386 version.
   2    Copyright (C) 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 _I386_TLS_H
  21 #define _I386_TLS_H
  22
  23 #if defined HAVE_TLS_SUPPORT
  24
  25 /* Some things really need not be machine-dependent.  */
  26 # include <sysdeps/mach/hurd/tls.h>
  27
  28 /* Indiciate that TLS support is available.  */
  29 # define USE_TLS        1
  30
  31 /* The TCB can have any size and the memory following the address the
  32    thread pointer points to is unspecified.  Allocate the TCB there.  */
  33 # define TLS_TCB_AT_TP  1
  34
  35 # ifndef ASSEMBLER
  36
  37 /* Use i386-specific RPCs to arrange that %gs segment register prefix
  38    addresses the TCB in each thread.  */
  39 # include <mach/i386/mach_i386.h>
  40
  41 # ifndef HAVE_I386_SET_GDT
  42 #  define __i386_set_gdt(thr, sel, desc) ((thr), (sel), (desc), MIG_BAD_ID)
  43 # endif
  44
  45 # include <errno.h>
  46 # include <assert.h>
  47
  48 static inline const char * __attribute__ ((unused))
  49 _hurd_tls_init (tcbhead_t *tcb, int secondcall)
  50 {
  51   const unsigned int base = (unsigned int) tcb;
  52   struct descriptor desc =
  53     {                           /* low word: */
  54       0xffff                    /* limit 0..15 */
  55       | (base << 16)            /* base 0..15 */
  56       ,                         /* high word: */
  57       ((base >> 16) & 0xff)     /* base 16..23 */
  58       | ((0x12 | 0x60 | 0x80) << 8) /* access = ACC_DATA_W|ACC_PL_U|ACC_P */
  59       | (0xf << 16)             /* limit 16..19 */
  60       | ((4 | 8) << 20)         /* granularity = SZ_32|SZ_G */
  61       | (base & 0xff000000)     /* base 24..31 */
  62     };
  63
  64   if (!secondcall)
  65     {
  66       /* Cache our thread port.  */
  67       tcb->self = __mach_thread_self ();
  68
  69       /* Get the first available selector.  */
  70       int sel = -1;
  71       error_t err = __i386_set_gdt (tcb->self, &sel, desc);
  72       if (err == MIG_BAD_ID)
  73         {
  74           /* Old kernel, use a per-thread LDT.  */
  75           sel = 0x27;
  76           err = __i386_set_ldt (tcb->self, sel, &desc, 1);
  77           assert_perror (err);
  78           return "i386_set_ldt failed";
  79         }
  80       else
  81         {
  82           assert_perror (err); /* Separate from above with different line #. */
  83           return "i386_set_gdt failed";
  84         }
  85
  86       /* Now install the new selector.  */
  87       asm volatile ("mov %w0, %%gs" :: "q" (sel));
  88     }
  89   else
  90     {
  91       /* Fetch the selector set by the first call.  */
  92       int sel;
  93       asm ("mov %%gs, %w0" : "=q" (sel));
  94       if (__builtin_expect (sel, 0x50) & 4) /* LDT selector */
  95         {
  96           error_t err = __i386_set_ldt (tcb->self, sel, &desc, 1);
  97           assert_perror (err);
  98           return "i386_set_ldt failed";
  99         }
 100       else
 101         {
 102           error_t err = __i386_set_gdt (tcb->self, &sel, desc);
 103           assert_perror (err);
 104           return "i386_set_gdt failed";
 105         }
 106     }
 107
 108   return 0;
 109 }
 110
 111 /* Code to initially initialize the thread pointer.  This might need
 112    special attention since 'errno' is not yet available and if the
 113    operation can cause a failure 'errno' must not be touched.  */
 114 # define TLS_INIT_TP(descr, secondcall) \
 115     _hurd_tls_init ((tcbhead_t *) (descr), (secondcall))
 116 # define TLS_INIT_TP_EXPENSIVE 1
 117
 118 /* Return the TCB address of the current thread.  */
 119 # define THREAD_SELF                                                          \
 120   ({ tcbhead_t *__tcb;                                                        \
 121      __asm__ ("movl %%gs:%c1,%0" : "=r" (__tcb)                               \
 122               : "i" (offsetof (tcbhead_t, tcb)));                             \
 123      __tcb;})
 124
 125 /* Install new dtv for current thread.  */
 126 # define INSTALL_NEW_DTV(dtvp)                                                \
 127   ({ asm volatile ("movl %0,%%gs:%P1"                                         \
 128                    : : "ir" (dtvp), "i" (offsetof (tcbhead_t, dtv))); })
 129
 130 /* Return the address of the dtv for the current thread.  */
 131 # define THREAD_DTV()                                                         \
 132   ({ void *_dtv;                                                              \
 133      asm ("movl %%gs:%P1,%0" : "=q" (_dtv) : "i" (offsetof (tcbhead_t, dtv)));\
 134      _dtv; })
 135
 136 # endif /* !ASSEMBLER */
 137 #endif /* HAVE_TLS_SUPPORT */
 138
 139 #endif  /* i386/tls.h */