sysdeps/mach/hurd/i386/tls.h

   1 /* Definitions for thread-local data handling.  Hurd/i386 version.
   2    Copyright (C) 2003, 2004, 2006, 2007 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 /* The TCB can have any size and the memory following the address the
  29    thread pointer points to is unspecified.  Allocate the TCB there.  */
  30 # define TLS_TCB_AT_TP  1
  31
  32 # ifndef __ASSEMBLER__
  33
  34 /* Use i386-specific RPCs to arrange that %gs segment register prefix
  35    addresses the TCB in each thread.  */
  36 # include <mach/i386/mach_i386.h>
  37
  38 # ifndef HAVE_I386_SET_GDT
  39 #  define __i386_set_gdt(thr, sel, desc) ((void) (thr), (void) (sel), (void) (desc), MIG_BAD_ID)
  40 # endif
  41
  42 # include <errno.h>
  43 # include <assert.h>
  44
  45 #define HURD_TLS_DESC_DECL(desc, tcb)                                         \
  46   struct descriptor desc =                                                    \
  47     {                           /* low word: */                               \
  48       0xffff                    /* limit 0..15 */                             \
  49       | (((unsigned int) (tcb)) << 16) /* base 0..15 */                       \
  50       ,                         /* high word: */                              \
  51       ((((unsigned int) (tcb)) >> 16) & 0xff) /* base 16..23 */               \
  52       | ((0x12 | 0x60 | 0x80) << 8) /* access = ACC_DATA_W|ACC_PL_U|ACC_P */  \
  53       | (0xf << 16)             /* limit 16..19 */                            \
  54       | ((4 | 8) << 20)         /* granularity = SZ_32|SZ_G */                \
  55       | (((unsigned int) (tcb)) & 0xff000000) /* base 24..31 */               \
  56     }
  57
  58
  59 static inline const char * __attribute__ ((unused))
  60 _hurd_tls_init (tcbhead_t *tcb, int secondcall)
  61 {
  62   HURD_TLS_DESC_DECL (desc, tcb);
  63
  64   if (!secondcall)
  65     {
  66       /* This field is used by TLS accesses to get our "thread pointer"
  67          from the TLS point of view.  */
  68       tcb->tcb = tcb;
  69
  70       /* Cache our thread port.  */
  71       tcb->self = __mach_thread_self ();
  72
  73       /* Get the first available selector.  */
  74       int sel = -1;
  75       error_t err = __i386_set_gdt (tcb->self, &sel, desc);
  76       if (err == MIG_BAD_ID)
  77         {
  78           /* Old kernel, use a per-thread LDT.  */
  79           sel = 0x27;
  80           err = __i386_set_ldt (tcb->self, sel, &desc, 1);
  81           assert_perror (err);
  82           if (err)
  83             return "i386_set_ldt failed";
  84         }
  85       else if (err)
  86         {
  87           assert_perror (err); /* Separate from above with different line #. */
  88           return "i386_set_gdt failed";
  89         }
  90
  91       /* Now install the new selector.  */
  92       asm volatile ("mov %w0, %%gs" :: "q" (sel));
  93     }
  94   else
  95     {
  96       /* Fetch the selector set by the first call.  */
  97       int sel;
  98       asm ("mov %%gs, %w0" : "=q" (sel) : "0" (0));
  99       if (__builtin_expect (sel, 0x50) & 4) /* LDT selector */
 100         {
 101           error_t err = __i386_set_ldt (tcb->self, sel, &desc, 1);
 102           assert_perror (err);
 103           if (err)
 104             return "i386_set_ldt failed";
 105         }
 106       else
 107         {
 108           error_t err = __i386_set_gdt (tcb->self, &sel, desc);
 109           assert_perror (err);
 110           if (err)
 111             return "i386_set_gdt failed";
 112         }
 113     }
 114
 115   return 0;
 116 }
 117
 118 /* Code to initially initialize the thread pointer.  This might need
 119    special attention since 'errno' is not yet available and if the
 120    operation can cause a failure 'errno' must not be touched.  */
 121 # define TLS_INIT_TP(descr, secondcall) \
 122     _hurd_tls_init ((tcbhead_t *) (descr), (secondcall))
 123 # define TLS_INIT_TP_EXPENSIVE 1
 124
 125 /* Return the TCB address of the current thread.  */
 126 # define THREAD_SELF                                                          \
 127   ({ tcbhead_t *__tcb;                                                        \
 128      __asm__ ("movl %%gs:%c1,%0" : "=r" (__tcb)                               \
 129               : "i" (offsetof (tcbhead_t, tcb)));                             \
 130      __tcb;})
 131
 132 /* Install new dtv for current thread.  */
 133 # define INSTALL_NEW_DTV(dtvp)                                                \
 134   ({ asm volatile ("movl %0,%%gs:%P1"                                         \
 135                    : : "ir" (dtvp), "i" (offsetof (tcbhead_t, dtv))); })
 136
 137 /* Return the address of the dtv for the current thread.  */
 138 # define THREAD_DTV()                                                         \
 139   ({ dtv_t *_dtv;                                                             \
 140      asm ("movl %%gs:%P1,%0" : "=q" (_dtv) : "i" (offsetof (tcbhead_t, dtv)));\
 141      _dtv; })
 142
 143 #include <mach/machine/thread_status.h>
 144
 145 /* Set up TLS in the new thread of a fork child, copying from our own.  */
 146 static inline error_t __attribute__ ((unused))
 147 _hurd_tls_fork (thread_t child, struct i386_thread_state *state)
 148 {
 149   /* Fetch the selector set by _hurd_tls_init.  */
 150   int sel;
 151   asm ("mov %%gs, %w0" : "=q" (sel) : "0" (0));
 152   if (sel == state->ds)         /* _hurd_tls_init was never called.  */
 153     return 0;
 154
 155   tcbhead_t *const tcb = THREAD_SELF;
 156   HURD_TLS_DESC_DECL (desc, tcb);
 157   error_t err;
 158
 159   if (__builtin_expect (sel, 0x50) & 4) /* LDT selector */
 160     err = __i386_set_ldt (child, sel, &desc, 1);
 161   else
 162     err = __i386_set_gdt (child, &sel, desc);
 163
 164   state->gs = sel;
 165   return err;
 166 }
 167
 168 # endif /* !__ASSEMBLER__ */
 169 #endif /* HAVE_TLS_SUPPORT */
 170
 171 #endif  /* i386/tls.h */