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) ((void) (thr), (void) (sel), (void) (desc), MIG_BAD_ID)
  43 # endif
  44
  45 # include <errno.h>
  46 # include <assert.h>
  47
  48 #define HURD_TLS_DESC_DECL(desc, tcb)                                         \
  49   struct descriptor desc =                                                    \
  50     {                           /* low word: */                               \
  51       0xffff                    /* limit 0..15 */                             \
  52       | (((unsigned int) (tcb)) << 16) /* base 0..15 */                       \
  53       ,                         /* high word: */                              \
  54       ((((unsigned int) (tcb)) >> 16) & 0xff) /* base 16..23 */               \
  55       | ((0x12 | 0x60 | 0x80) << 8) /* access = ACC_DATA_W|ACC_PL_U|ACC_P */  \
  56       | (0xf << 16)             /* limit 16..19 */                            \
  57       | ((4 | 8) << 20)         /* granularity = SZ_32|SZ_G */                \
  58       | (((unsigned int) (tcb)) & 0xff000000) /* base 24..31 */               \
  59     }
  60
  61
  62 static inline const char * __attribute__ ((unused))
  63 _hurd_tls_init (tcbhead_t *tcb, int secondcall)
  64 {
  65   HURD_TLS_DESC_DECL (desc, tcb);
  66
  67   if (!secondcall)
  68     {
  69       /* This field is used by TLS accesses to get our "thread pointer"
  70          from the TLS point of view.  */
  71       tcb->tcb = tcb;
  72
  73       /* Cache our thread port.  */
  74       tcb->self = __mach_thread_self ();
  75
  76       /* Get the first available selector.  */
  77       int sel = -1;
  78       error_t err = __i386_set_gdt (tcb->self, &sel, desc);
  79       if (err == MIG_BAD_ID)
  80         {
  81           /* Old kernel, use a per-thread LDT.  */
  82           sel = 0x27;
  83           err = __i386_set_ldt (tcb->self, sel, &desc, 1);
  84           assert_perror (err);
  85           if (err)
  86             return "i386_set_ldt failed";
  87         }
  88       else if (err)
  89         {
  90           assert_perror (err); /* Separate from above with different line #. */
  91           return "i386_set_gdt failed";
  92         }
  93
  94       /* Now install the new selector.  */
  95       asm volatile ("mov %w0, %%gs" :: "q" (sel));
  96     }
  97   else
  98     {
  99       /* Fetch the selector set by the first call.  */
 100       int sel;
 101       asm ("mov %%gs, %w0" : "=q" (sel));
 102       if (__builtin_expect (sel, 0x50) & 4) /* LDT selector */
 103         {
 104           error_t err = __i386_set_ldt (tcb->self, sel, &desc, 1);
 105           assert_perror (err);
 106           if (err)
 107             return "i386_set_ldt failed";
 108         }
 109       else
 110         {
 111           error_t err = __i386_set_gdt (tcb->self, &sel, desc);
 112           assert_perror (err);
 113           if (err)
 114             return "i386_set_gdt failed";
 115         }
 116     }
 117
 118   return 0;
 119 }
 120
 121 /* Code to initially initialize the thread pointer.  This might need
 122    special attention since 'errno' is not yet available and if the
 123    operation can cause a failure 'errno' must not be touched.  */
 124 # define TLS_INIT_TP(descr, secondcall) \
 125     _hurd_tls_init ((tcbhead_t *) (descr), (secondcall))
 126 # define TLS_INIT_TP_EXPENSIVE 1
 127
 128 /* Return the TCB address of the current thread.  */
 129 # define THREAD_SELF                                                          \
 130   ({ tcbhead_t *__tcb;                                                        \
 131      __asm__ ("movl %%gs:%c1,%0" : "=r" (__tcb)                               \
 132               : "i" (offsetof (tcbhead_t, tcb)));                             \
 133      __tcb;})
 134
 135 /* Install new dtv for current thread.  */
 136 # define INSTALL_NEW_DTV(dtvp)                                                \
 137   ({ asm volatile ("movl %0,%%gs:%P1"                                         \
 138                    : : "ir" (dtvp), "i" (offsetof (tcbhead_t, dtv))); })
 139
 140 /* Return the address of the dtv for the current thread.  */
 141 # define THREAD_DTV()                                                         \
 142   ({ dtv_t *_dtv;                                                             \
 143      asm ("movl %%gs:%P1,%0" : "=q" (_dtv) : "i" (offsetof (tcbhead_t, dtv)));\
 144      _dtv; })
 145
 146 #include <mach/machine/thread_status.h>
 147
 148 /* Set up TLS in the new thread of a fork child, copying from our own.  */
 149 static inline error_t __attribute__ ((unused))
 150 _hurd_tls_fork (thread_t child, struct i386_thread_state *state)
 151 {
 152   /* Fetch the selector set by _hurd_tls_init.  */
 153   int sel;
 154   asm ("mov %%gs, %w0" : "=q" (sel));
 155   if (sel == state->ds)         /* _hurd_tls_init was never called.  */
 156     return 0;
 157
 158   tcbhead_t *const tcb = THREAD_SELF;
 159   HURD_TLS_DESC_DECL (desc, tcb);
 160   error_t err;
 161
 162   if (__builtin_expect (sel, 0x50) & 4) /* LDT selector */
 163     err = __i386_set_ldt (child, sel, &desc, 1);
 164   else
 165     err = __i386_set_gdt (child, &sel, desc);
 166
 167   state->gs = sel;
 168   return err;
 169 }
 170
 171 # endif /* !ASSEMBLER */
 172 #endif /* HAVE_TLS_SUPPORT */
 173
 174 #endif  /* i386/tls.h */