glibc/sysdeps/mach/hurd/i386/tls.h

/* Definitions for thread-local data handling.  Hurd/i386 version.
   Copyright (C) 2003 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#ifndef _I386_TLS_H
#define _I386_TLS_H

#if defined HAVE_TLS_SUPPORT

/* Some things really need not be machine-dependent.  */
# include <sysdeps/mach/hurd/tls.h>

/* Indiciate that TLS support is available.  */
# define USE_TLS	1

/* Use i386-specific RPCs to arrange that %gs segment register prefix
   addresses the TCB in each thread.  */
# include <mach/i386/mach_i386.h>

#ifndef HAVE_I386_SET_GDT
# define __i386_set_gdt(thr, sel, desc) ((thr), (sel), (desc), MIG_BAD_ID)
#endif

static inline int _hurd_tls_init (tcbhead_t *, int secondcall)
     __attribute__ ((unused));

static inline const char *
_hurd_tls_init (tcbhead_t *tcb, int secondcall)
{
  const unsigned int base = (unsigned int) tcb;
  const struct descriptor desc =
    {				/* low word: */
      0xffff			/* limit 0..15 */
      | (base << 16)		/* base 0..15 */
      ,				/* high word: */
      ((base >> 16) & 0xff)	/* base 16..23 */
      | ((0x12 | 0x60 | 0x80) << 8) /* access = ACC_DATA_W|ACC_PL_U|ACC_P */
      | (0xf << 16)		/* limit 16..19 */
      | ((4 | 8) << 20)		/* granularity = SZ_32|SZ_G */
      | (base & 0xff000000)	/* base 24..31 */
    };

  if (!secondcall)
    {
      /* Cache our thread port.  */
      tcb->self = __mach_thread_self ();

      /* Get the first available selector.  */
      int sel = -1;
      error_t err = __i386_set_gdt (tcb->self, &sel, &desc);
      if (err == MIG_BAD_ID)
	{
	  /* Old kernel, use a per-thread LDT.  */
	  sel = 0x27;
	  err = __i386_set_ldt (tcb->self, sel, &desc, 1);
	  assert_perror (err);
	  return "i386_set_ldt failed";
	}
      else
	{
	  assert_perror (err); /* Separate from above with different line #. */
	  return "i386_set_gdt failed";
	}

      /* Now install the new selector.  */
      asm volatile ("mov %w0, %%gs" :: "q" (sel));
    }
  else
    {
      /* Fetch the selector set by the first call.  */
      int sel;
      asm ("mov %%gs, %w0" : "=q" (sel));
      if (__builtin_expect (sel, 0x50) & 4) /* LDT selector */
	{
	  error_t err = __i386_set_ldt (tcb->self, sel, &desc, 1);
	  assert_perror (err);
	  return "i386_set_ldt failed";
	}
      else
	{
	  error_t err = __i386_set_gdt (tcb->self, &sel, &desc);
	  assert_perror (err);
	  return "i386_set_gdt failed";
	}
    }

  return 0;
}

/* Code to initially initialize the thread pointer.  This might need
   special attention since 'errno' is not yet available and if the
   operation can cause a failure 'errno' must not be touched.  */
# define TLS_INIT_TP(descr, secondcall) \
    _hurd_tls_init ((tcbhead_t *) (descr), (secondcall))

/* Install new dtv for current thread.  */
# define INSTALL_NEW_DTV(dtv) \
  ({ __asm__ ("movl %0, %%gs:0" : : "r" (dtv)); })

/* Return the address of the dtv for the current thread.  */
# define THREAD_DTV() \
  ({ void *_dtv; __asm__ ("movl %%gs:0, %0" : "=r" (_dtv)); _dtv; })


#endif /* HAVE_TLS_SUPPORT */

#endif	/* i386/tls.h */