sysdeps/mach/hurd/i386/tls.h

   1 /* Definitions for thread-local data handling.  Hurd/i386 version.
   2    Copyright (C) 2003-2014 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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _I386_TLS_H
  20 #define _I386_TLS_H
  21
  22
  23 /* Some things really need not be machine-dependent.  */
  24 #include <sysdeps/mach/hurd/tls.h>
  25
  26 /* The TCB can have any size and the memory following the address the
  27    thread pointer points to is unspecified.  Allocate the TCB there.  */
  28 #define TLS_TCB_AT_TP   1
  29
  30 #ifndef __ASSEMBLER__
  31
  32 /* Use i386-specific RPCs to arrange that %gs segment register prefix
  33    addresses the TCB in each thread.  */
  34 # include <mach/i386/mach_i386.h>
  35
  36 # ifndef HAVE_I386_SET_GDT
  37 #  define __i386_set_gdt(thr, sel, desc) ((void) (thr), (void) (sel), (void) (desc), MIG_BAD_ID)
  38 # endif
  39
  40 # include <errno.h>
  41 # include <assert.h>
  42
  43 # define HURD_TLS_DESC_DECL(desc, tcb)                                        \
  44   struct descriptor desc =                                                    \
  45     {                           /* low word: */                               \
  46       0xffff                    /* limit 0..15 */                             \
  47       | (((unsigned int) (tcb)) << 16) /* base 0..15 */                       \
  48       ,                         /* high word: */                              \
  49       ((((unsigned int) (tcb)) >> 16) & 0xff) /* base 16..23 */               \
  50       | ((0x12 | 0x60 | 0x80) << 8) /* access = ACC_DATA_W|ACC_PL_U|ACC_P */  \
  51       | (0xf << 16)             /* limit 16..19 */                            \
  52       | ((4 | 8) << 20)         /* granularity = SZ_32|SZ_G */                \
  53       | (((unsigned int) (tcb)) & 0xff000000) /* base 24..31 */               \
  54     }
  55
  56
  57 static inline const char * __attribute__ ((unused))
  58 _hurd_tls_init (tcbhead_t *tcb, int secondcall)
  59 {
  60   HURD_TLS_DESC_DECL (desc, tcb);
  61
  62   if (!secondcall)
  63     {
  64       /* This field is used by TLS accesses to get our "thread pointer"
  65          from the TLS point of view.  */
  66       tcb->tcb = tcb;
  67
  68       /* Cache our thread port.  */
  69       tcb->self = __mach_thread_self ();
  70
  71       /* Get the first available selector.  */
  72       int sel = -1;
  73       error_t err = __i386_set_gdt (tcb->self, &sel, desc);
  74       if (err == MIG_BAD_ID)
  75         {
  76           /* Old kernel, use a per-thread LDT.  */
  77           sel = 0x27;
  78           err = __i386_set_ldt (tcb->self, sel, &desc, 1);
  79           assert_perror (err);
  80           if (err)
  81             return "i386_set_ldt failed";
  82         }
  83       else if (err)
  84         {
  85           assert_perror (err); /* Separate from above with different line #. */
  86           return "i386_set_gdt failed";
  87         }
  88
  89       /* Now install the new selector.  */
  90       asm volatile ("mov %w0, %%gs" :: "q" (sel));
  91     }
  92   else
  93     {
  94       /* Fetch the selector set by the first call.  */
  95       int sel;
  96       asm ("mov %%gs, %w0" : "=q" (sel) : "0" (0));
  97       if (__builtin_expect (sel, 0x50) & 4) /* LDT selector */
  98         {
  99           error_t err = __i386_set_ldt (tcb->self, sel, &desc, 1);
 100           assert_perror (err);
 101           if (err)
 102             return "i386_set_ldt failed";
 103         }
 104       else
 105         {
 106           error_t err = __i386_set_gdt (tcb->self, &sel, desc);
 107           assert_perror (err);
 108           if (err)
 109             return "i386_set_gdt failed";
 110         }
 111     }
 112
 113   return 0;
 114 }
 115
 116 /* Code to initially initialize the thread pointer.  This might need
 117    special attention since 'errno' is not yet available and if the
 118    operation can cause a failure 'errno' must not be touched.  */
 119 # define TLS_INIT_TP(descr, secondcall) \
 120     _hurd_tls_init ((tcbhead_t *) (descr), (secondcall))
 121
 122 /* Return the TCB address of the current thread.  */
 123 # define THREAD_SELF                                                          \
 124   ({ tcbhead_t *__tcb;                                                        \
 125      __asm__ ("movl %%gs:%c1,%0" : "=r" (__tcb)                               \
 126               : "i" (offsetof (tcbhead_t, tcb)));                             \
 127      __tcb;})
 128
 129 /* Install new dtv for current thread.  */
 130 # define INSTALL_NEW_DTV(dtvp)                                                \
 131   ({ asm volatile ("movl %0,%%gs:%P1"                                         \
 132                    : : "ir" (dtvp), "i" (offsetof (tcbhead_t, dtv))); })
 133
 134 /* Return the address of the dtv for the current thread.  */
 135 # define THREAD_DTV()                                                         \
 136   ({ dtv_t *_dtv;                                                             \
 137      asm ("movl %%gs:%P1,%0" : "=q" (_dtv) : "i" (offsetof (tcbhead_t, dtv)));\
 138      _dtv; })
 139
 140 # include <mach/machine/thread_status.h>
 141
 142 /* Set up TLS in the new thread of a fork child, copying from our own.  */
 143 static inline error_t __attribute__ ((unused))
 144 _hurd_tls_fork (thread_t child, struct i386_thread_state *state)
 145 {
 146   /* Fetch the selector set by _hurd_tls_init.  */
 147   int sel;
 148   asm ("mov %%gs, %w0" : "=q" (sel) : "0" (0));
 149   if (sel == state->ds)         /* _hurd_tls_init was never called.  */
 150     return 0;
 151
 152   tcbhead_t *const tcb = THREAD_SELF;
 153   HURD_TLS_DESC_DECL (desc, tcb);
 154   error_t err;
 155
 156   if (__builtin_expect (sel, 0x50) & 4) /* LDT selector */
 157     err = __i386_set_ldt (child, sel, &desc, 1);
 158   else
 159     err = __i386_set_gdt (child, &sel, desc);
 160
 161   state->gs = sel;
 162   return err;
 163 }
 164
 165 #endif  /* !__ASSEMBLER__ */
 166
 167 #endif  /* i386/tls.h */