glibc/linuxthreads/sysdeps/i386/tls.h

/* Definition for thread-local data handling.  linuxthreads/i386 version.
   Copyright (C) 2002 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 _TLS_H
#define _TLS_H

# include <pt-machine.h>

#ifndef __ASSEMBLER__
# include <stddef.h>

/* Type for the dtv.  */
typedef union dtv
{
  size_t counter;
  void *pointer;
} dtv_t;


typedef struct
{
  void *tcb;		/* Pointer to the TCB.  Not necessary the
			   thread descriptor used by libpthread.  */
  dtv_t *dtv;
  void *self;		/* Pointer to the thread descriptor.  */
} tcbhead_t;
#endif


/* We can support TLS only if the floating-stack support is available.  */
#if defined FLOATING_STACKS && defined HAVE_TLS_SUPPORT

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

# ifndef __ASSEMBLER__
/* Get system call information.  */
#  include <sysdep.h>


/* Get the thread descriptor definition.  */
#  include <linuxthreads/descr.h>

/* This is the size of the initial TCB.  */
#  define TLS_INIT_TCB_SIZE sizeof (tcbhead_t)

/* Alignment requirements for the initial TCB.  */
#  define TLS_INIT_TCB_ALIGN __alignof__ (tcbhead_t)

/* This is the size of the TCB.  */
#  define TLS_TCB_SIZE sizeof (struct _pthread_descr_struct)

/* Alignment requirements for the TCB.  */
#  define TLS_TCB_ALIGN __alignof__ (struct _pthread_descr_struct)

/* The TCB can have any size and the memory following the address the
   thread pointer points to is unspecified.  Allocate the TCB there.  */
#  define TLS_TCB_AT_TP	1


/* Install the dtv pointer.  The pointer passed is to the element with
   index -1 which contain the length.  */
#  define INSTALL_DTV(descr, dtvp) \
  ((tcbhead_t *) (descr))->dtv = (dtvp) + 1

/* Install new dtv for current thread.  */
#  define INSTALL_NEW_DTV(dtv) \
  ({ struct _pthread_descr_struct *__descr;				      \
     THREAD_SETMEM (__descr, p_header.data.dtvp, (dtv)); })

/* Return dtv of given thread descriptor.  */
#  define GET_DTV(descr) \
  (((tcbhead_t *) (descr))->dtv)

#  ifdef __PIC__
#   define TLS_EBX_ARG "r"
#   define TLS_LOAD_EBX "xchgl %3, %%ebx\n\t"
#  else
#   define TLS_EBX_ARG "b"
#   define TLS_LOAD_EBX
#  endif

#  define TLS_DO_MODIFY_LDT(descr, nr)					      \
({									      \
  struct modify_ldt_ldt_s ldt_entry =					      \
    { nr, (unsigned long int) (descr), sizeof (struct _pthread_descr_struct), \
      1, 0, 0, 0, 0, 1, 0 };						      \
  int result;								      \
  asm volatile (TLS_LOAD_EBX						      \
		"int $0x80\n\t"						      \
		TLS_LOAD_EBX						      \
		: "=a" (result)						      \
		: "0" (__NR_modify_ldt),				      \
		/* The extra argument with the "m" constraint is necessary    \
		   to let the compiler know that we are accessing LDT_ENTRY   \
		   here.  */						      \
		"m" (ldt_entry), TLS_EBX_ARG (1), "c" (&ldt_entry),	      \
		"d" (sizeof (ldt_entry)));				      \
  __builtin_expect (result, 0) != 0 ? -1 : nr * 8 + 7;			      \
})

#  define TLS_DO_SET_THREAD_AREA(descr)					      \
({									      \
  struct modify_ldt_ldt_s ldt_entry =					      \
    { -1, (unsigned long int) (descr), sizeof (struct _pthread_descr_struct), \
      1, 0, 0, 0, 0, 1, 0 };						      \
  int result;								      \
  asm volatile (TLS_LOAD_EBX						      \
		"int $0x80\n\t"						      \
		TLS_LOAD_EBX						      \
		: "=a" (result), "=m" (ldt_entry.entry_number)		      \
		: "0" (__NR_set_thread_area),				      \
		/* The extra argument with the "m" constraint is necessary    \
		   to let the compiler know that we are accessing LDT_ENTRY   \
		   here.  */						      \
		TLS_EBX_ARG (&ldt_entry), "m" (ldt_entry));		      \
    __builtin_expect (result, 0) == 0 ? ldt_entry.entry_number * 8 + 3 : -1;  \
})

#  ifdef __ASSUME_SET_THREAD_AREA_SYSCALL
#   define TLS_SETUP_GS_SEGMENT(descr) TLS_DO_SET_THREAD_AREA (descr)
#  elif defined __NR_set_thread_area
#   define TLS_SETUP_GS_SEGMENT(descr) \
  ({ int __seg = TLS_DO_SET_THREAD_AREA (descr); \
     __seg == -1 ? TLS_DO_MODIFY_LDT (descr, 0) : __seg; })
#  else
#   define TLS_SETUP_GS_SEGMENT(descr) TLS_DO_MODIFY_LDT ((descr), 0)
#  endif

/* 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)						      \
  ({									      \
    void *_descr = (descr);						      \
    tcbhead_t *head = _descr;						      \
    int __gs;								      \
									      \
    head->tcb = _descr;							      \
    /* For now the thread descriptor is at the same address.  */	      \
    head->self = _descr;						      \
									      \
    __gs = TLS_SETUP_GS_SEGMENT (_descr);				      \
    if (__builtin_expect (__gs, 7) != -1)				      \
      {									      \
	asm ("movw %w0, %%gs" : : "q" (__gs));				      \
	__gs = 0;							      \
      }									      \
    __gs;								      \
  })


/* Return the address of the dtv for the current thread.  */
#  define THREAD_DTV() \
  ({ struct _pthread_descr_struct *__descr;				      \
     THREAD_GETMEM (__descr, p_header.data.dtvp); })

# endif	/* FLOATING_STACKS && HAVE_TLS_SUPPORT */
#endif /* __ASSEMBLER__ */

#endif	/* tls.h */